Yasohara, Masahiro; Takada, Kazuyuki; Fujisaki, Yoshihiro;

Protection apparatus for brushless motor

A protection apparatus used in a brushless motor is arranged by a brushless motor; a commutation signal detecting unit for detecting a position of a movable member of the brushless motor; a speed detecting unit for detecting a rotation speed of the movable member of the brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from the commutation signal detecting unit; and a drive circuit for producing a commutation signal used to drive the movable member of the brushless motor in response to the detection signal outputted from the commutation signal detecting unit and for driving the brushless motor based upon the commutation signal. The protection apparatus is further constructed of an output voltage instructing unit for supplying to the drive circuit, an output voltage instruction signal for instructing an output voltage of the drive circuit, which constitutes a drive voltage when the brushless motor is driven; a voltage limit level setting unit for setting an upper limit value of the output voltage of the drive circuit; and a voltage limiter unit for limiting the output signal of the output voltage instructing unit based on the setting value of the voltage limit level setting unit to thereby limit an upper limit value of the output voltage of the drive circuit.

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What is claimed is:

1. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit; and

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value.

2. A protection apparatus of a brushless motor as claimed in claim 1, wherein:

the setting value of said voltage limit level setting means is corrected in such a manner that a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor are grasped based upon the drive current of the brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor.

3. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

4. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit; and

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit;

normal rotation limiter means for detecting as to whether or not the rotation speed of said brushless motor reaches a preset maximum limit level based upon the detection signal of said speed detecting means, and for outputting a first power supply interrupting signal when said rotation speed reaches said preset maximum limit level; and

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; and also when said first power supply interrupting signal outputted from said normal rotation limiter means is produced, or said second power supply interrupting signal outputted from said reverse rotation limiter means is produced, said drive circuit is electrically opened from said brushless motor.

5. A protection apparatus for a brushless motor as claimed in claim 4 wherein:

said normal rotation limiter means includes hysteresis means operable in such a manner that the first power supply interrupting signal is outputted when the rotation speed of the brushless motor reaches the preset maximum limit level; outputting of said first power supply interrupting signal is maintained during a time period such that after said first power supply interrupting signal is outputted, the rotation speed of said brushless motor reaches a power supply interrupting signal release level equal to a rotation speed slightly lower than said maximum limit level; outputting of said first power supply interrupting signal is released when the rotation speed of said brushless motor reaches said power supply interrupting signal release level; and thereafter said first power supply interrupting signal is not outputted until the rotation speed of said brushless motor reaches said maximum limit level.

6. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

normal rotation limiter means for detecting as to whether or not the rotation speed of said brushless motor reaches a preset maximum limit level based upon the detection signal of said speed detecting means, and for outputting a first power supply interrupting signal when said rotation speed reaches said preset maximum limit level;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level; in which when said first power supply interrupting signal outputted from said normal rotation limiter means or said second power supply interrupting signal outputted from said reverse rotation limiter means is produced, said drive circuit is electrically opened from said brushless motor;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

7. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit;

normal rotation limiter means for detecting as to whether or not the rotation speed of said brushless motor reaches a preset maximum limit level based upon the detection signal of said speed detecting means, and for outputting a first power supply interrupting signal when said rotation speed reaches said preset maximum limit level;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level; and low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; and also when said first power supply interrupting signal outputted from said normal rotation limiter means, said second power supply interrupting signal outputted from said reverse rotation limiter means, or said third power supply interrupting signal outputted from said low speed overload detecting means is produced, said drive circuit is electrically opened from said brushless motor.

8. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

normal rotation limiter means for detecting as to whether or not the rotation speed of said brushless motor reaches a preset maximum limit level based upon the detection signal of said speed detecting means, and for outputting a first power supply interrupting signal when said rotation speed reaches said preset maximum limit level;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detecting signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level;

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor, in which when said first power supply interrupting signal outputted from said normal rotation limiter means, said second power supply interrupting signal outputted from said reverse rotation limiter means, or the third power supply interrupting signal outputted from said low speed overload detecting means is produced, said drive circuit is electrically opened from said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

9. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit, and also for limiting the output signal of said output voltage instructing means based upon the setting value of said voltage lower limit level setting means to thereby limit the lower limit value of the output voltage of said drive circuit; and

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level; wherein,

when said second power supply interrupting signal outputted from said reverse rotation limiter means is produced, the connection between said drive circuit and said brushless motor is electrically opened, and also the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value and further the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value is such a value lower than the setting value of said voltage limit level setting means, and also such a value higher than a value corresponding to an induced voltage internally produced from said brushless motor.

10. A protection apparatus of a brushless motor as claimed in claim 9, wherein:

either one or both the setting value of said voltage limit level setting means and said setting value of said voltage lower limit level setting means is corrected in such a manner that a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor are grasped based upon the drive current of the brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor.

11. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detectiong means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage linit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set inaccordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset value;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, the setting value of said voltage lower limit level setting means being set in response to the output signal of said speed detecting means in such a manner that said setting value fo this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means and also a value higher than a value corresponding to the induced voltage internally produced from said brushless motor;

voltage limiter means for limiting the output signal of said output voltage instucting means based on the setting value of said voltage limit level setting means and the setting value of said voltage lower limit level setting means to thereby supply said output voltage instruction signal to said drive circuit, and for limiting the upper limit value and the lower limit value of the output voltage of said drive circuit;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limiter means is produced, the connection between said drive circuit and said brushless motor is electrically opened;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon anyd one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

12. A protection apparatus of a brushless motor as claimed in claim 11 wherein:

either one or both the setting value of said voltage limit level setting means and said setting value of said voltage lower limit level setting means is corrected in such a manner that both a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor, or a variation contained in the output voltage of said DC main power supply is grasped based upon either the output current of said DC main power supply, or the drive current of said brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor, or the variation contained in the output voltage of said DC main power supply.

13. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit, and also for limiting the output signal of said output voltage instructing signal based on the setting value of said voltage lower limit level setting means to thereby limit the lower limit value of the output voltage of said drive circuit;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level; and

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means, and also a value higher than a value corresponding to the induced voltage internally produced from the brushless motor; and also;

when said second power supply interrupting signal outputted from said reverse rotation limiter means, or said third power supply interrupting signal outputted from said reverse rotation limiter means is produced, said drive circuit is electrically opened from said brushless motor.

14. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, in which the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means, and also becomes a value higher than a value corresponding to the induced voltage internally produced from the brushless motor;

voltage limiter means for limiting the output signal of said output voltage instructing means based upon the setting value of said voltage limit level setting means and the setting value of said voltage lower limit level setting means to thereby supply said output voltage instruction signal to said drive circuit;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detecting signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level;

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period, in which when said second power supply interrupting signal outputted from said reverse rotation limiter means, or said third power supply interrupting signal outputted from said low speed overload detecting means is produced, said drive circuit is electrically opened from said brushless motor;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

15. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit; and

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level; wherein

when said second power supply interrupting signal outputted from said reverse rotation limiter means is produced, the connection between said drive circuit and said brushless motor is electrically opened,

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value, and

the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value is such a value lower than the setting value of said voltage limit level setting means, and also such a value higher than a value corresponding to an induced voltage internally produced from said brushless motor, when the output voltage of said output voltage instructing means reaches the setting value of said voltage lower level setting means, the connection between said drive circuit and said brushless motor is electrically opened.

16. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, the setting value of said voltage lower limit level setting means being set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means and also a value higher than a value corresponding to the induced voltage internally produced from said brushless motor;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means and the setting value of said voltage lower limit level setting means to thereby supply said output voltage instruction signal to said drive circuit, and for limiting the upper limit value and the lower limit value of the output voltage of said drive circuit;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level, in which when said second power supply interrupting signal outputted from said reverse rotation limiter means is produced, the connection between said drive circuit and said brushless motor is electrically opened;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

17. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, in which the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means, and also becomes a value higher than a value corresponding to the induced voltage internally produced from the brushless motor, and further when the output signal of said output voltage instructing means reaches the setting value of said voltage lower limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level, in which when said second power supply interrupting signal outputted from said reverse rotation limiter means is produced, the connection between said drive circuit and said brushless motor is electrically opened;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

18. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit vale of the output voltage of said drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level; and

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means and also becomes a value higher than such a value corresponding to the induced voltage internally produced from said brushless motor; and when the output signal of said output voltage instructing means reaches the setting value of said voltage lower limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened; and

when said second power supply interrupting signal outputted by said reverse rotation speed limiter means, or said third power supply interrupting signal outputted by said low speed overload detecting means is produced, the connection between said drive circuit and said brushless motor is electrically opened.

19. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, in which the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means and also becomes a value higher than such a value corresponding to the induced voltage internally produced from said brushless motor; and when the output signal of said output voltage instructing means reaches the setting value of said voltage lower limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detecting signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level;

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor, said second power supply interrupting signal outputted from said reverse rotation limiter means, or said third power supply interrupting signal outputted from said low speed overload detecting means is produced, said drive circuit is electrically opened from said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

20. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

speed upper limit level setting means for setting an upper limit value of the rotation speed of said brushless motor;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit; and

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

wherein:

when said second power supply interrupting signal outputted by said reverse rotation limiter means is produced, the connection between said drive circuit and said brushless motor is electrically interrupted;

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; and

the setting value of said speed upper limit level setting means is set in response to the output signal of said output voltage instructing means, equal to a value corresponding to a maximum rotation speed of said brushless motor in which the induced voltage internally produced by said brushless motor can become lower than the output voltage of said drive circuit when the output signal of said output voltage instructing means is supplied as said output voltage instruction signal to said drive circuit, and further when the output signal of said speed detecting means reaches the setting value of said speed upper limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened.

21. A protection apparatus for a brushless motor as claimed in claim 20, wherein:

said protection apparatus is comprised of hysteresis means such that after the output signal of the speed detecting means reaches the setting value of said speed upper limit level setting means to thereby electrically open the connection between the drive circuit and the brushless motor, until the output signal of said speed detecting means becomes a value slightly lower than the setting value of said speed upper limit level setting means, said drive circuit is electrically and continuously opened from said brushless motor; when the output signal of said speed detecting means becomes such a value slightly lower than the setting value of said speed upper limit level setting means, electric opening of said drive circuit with said brushless motor is released; and thereafter the connection between said drive circuit and said brushless motor is not electrically opened until the output signal of said speed detecting means reaches the setting value of said speed upper level setting means.

22. A protection apparatus of a brushless motor as claimed in claim 20 wherein:

either one or both the setting value of said voltage limit level setting means and said setting value of said speed upper limit level setting means is corrected in such a manner that a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor are grasped based upon the drive current of the brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor.

23. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

speed upper limit level setting means for setting an upper limit value of the rotation speed of said brushless motor, in which the setting value of said speed upper limit level setting means is set in response to the output signal of said output voltage instructing means, equal to a value corresponding to a maximum rotation speed of said brushless motor in which the induced voltage internally produced by said brushless motor can become lower than the output voltage of said drive circuit when the output signal of said output voltage instructing means is supplied as said output voltage instruction signal to said drive circuit, and further when the output signal of said speed detecting means reaches the setting value of said speed upper limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level; in which when said second power supply interrupting signal outputted from said reverse rotation limiter means is produced, said drive circuit is electrically opened from said brushless motor;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

24. A protection apparatus of a brushless motor as claimed in claim 23 wherein:

either one or both the setting value of said voltage limit level setting means and said setting value of said speed upper limit level setting means is corrected in such a manner that both a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor, or a variation of said DC main power supply is grasped based upon either the output current of said DC main power supply or the drive current of said brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor, or the variation contained in the output voltage of said DC main power supply.

25. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

speed upper limit level setting means for setting an upper limit value of the rotation speed of said brushless motor;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detection signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level; and

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

the setting value of said speed upper limit level setting means is set in response to the output signal of said output voltage instructing means, equal to a value corresponding to a maximum rotation speed of said brushless motor in which the induced voltage internally produced by said brushless motor can become lower than the output voltage of said drive circuit when the output signal of said output voltage instructing means is supplied as said output voltage instruction signal to said drive circuit; and further when the output signal of said speed detecting means reaches the setting value of said speed upper limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened; and

when said second power supply interrupting signal outputted from said reverse rotation limiter means, or said third power supply interrupting signal outputted from said low speed overload detecting means is produced, the drive circuit is electrically opened from said brushless motor.

26. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

speed upper limit level setting means for setting an upper limit value of the rotation speed of said brushless motor, the setting value of said speed upper limit level setting means is set in response to the output signal of said output voltage instructing means, equal to a value corresponding to a maximum rotation speed of said brushless motor in which the induced voltage internally produced by said brushless motor can become lower than the output voltage of said drive circuit when the output signal of said output voltage instructing means is supplied as said output voltage instruction signal to said drive circuit; and further when the output signal of said speed detecting means reaches the setting value of said speed upper limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened;

reverse rotation limiter means for detecting as to whether or not a reverse rotation speed of said brushless motor reaches a preset reverse rotation limit level based upon the detecting signal of said speed detecting means, and for outputting a second power supply interrupting signal when said reverse rotation speed reaches said preset reverse rotation limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level;

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period, in which when either said second power supply interrupting signal outputted by said reverse rotation limier means or said third power supply interrupting signal outputted by said low speed overload detecting means is produced, the connection between said drive circuit and said brushless motor is electrically opened;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

27. A protection apparatus of a brushless motor as claimed in claim 3, 6, 8, 23 or 26, wherein:

the setting value of said voltage limit level setting means is corrected in such a manner that both a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor, or a variation contained in the output voltage of said DC main power supply is grasped based upon either the output current of said DC main power supply of the drive current of said brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor, or the variation contained in the output voltage of said DC main power supply.

28. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit; and

normal rotation limiter means for detecting as to whether or not the rotation speed of said brushless motor reaches a preset maximum limit level based upon the detection signal of said speed detecting means, and for outputting a first power supply interrupting signal when said rotation speed reaches said preset maximum limit level; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; and

when said first power supply interrupting signal outputted from said normal rotation limiter means is produced, said drive circuit is electrically opened from said brushless motor.

29. A protection apparatus for a brushless motor as claimed in claim 28 wherein:

said normal rotation limiter means includes hysteresis means operable in such a manner that the first power supply interrupting signal is outputted when the rotation speed of the brushless motor reaches the preset maximum limit level; outputting of said first power supply interrupting signal is maintained during a time period such that after said first power supply interrupting signal is outputted, the rotation speed of said brushless motor reaches a power supply interrupting signal release level equal to a rotation speed slightly lower than said maximum limit level; outputting of said first power supply interrupting signal is released when the rotation speed of said brushless motor reaches said power supply interrupting signal release level; and thereafter said first power supply interrupting signal is not outputted until the rotation speed of said brushless motor reaches said maximum limit level.

30. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

normal rotation limiter means for detecting as to whether or not the rotation speed of said brushless motor reaches a preset maximum limit level based upon the detection signal of said speed detecting means, and for outputting a first power supply interrupting signal when said rotation speed reaches said preset maximum limit level, in which when said first power supply interrupting signal outputted from said normal rotation limiter means is produced, said drive circuit is electrically opened from said brushless motor;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

31. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushiess motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit;

normal rotation limiter means for detecting as to whether or not the rotation speed of said brushless motor reaches a preset maximum limit level based upon the detection signal of said speed detecting means, and for outputting a first power supply interrupting signal when said rotation speed reaches said preset maximum limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level; and

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means is continued for a predetermined time period; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; and

when said first power supply interrupting signal outputted from said normal rotation limiter means is produced, or said third power supply interrupting signal outputted from said low speed overload detecting means is produced, said drive circuit is electrically opened from said brushless motor.

32. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

normal rotation limiter means for detecting as to whether or not the rotation speed of said brushless motor reaches a preset maximum limit level based upon the detection signal of said speed detecting means, and for outputting a first power supply interrupting signal when said rotation speed reaches said preset maximum limit level;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level;

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means from said reverse rotation limiter means is continued for a predetermined time period, in which when said first power supply interrupting signal outputted from said normal rotation limiter means, or said third power supply interrupting signal outputted from said low speed overload detecting means is produced, said drive circuit is electrically opened from said brushless motor;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

33. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit; and

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit, and also for limiting the output signal of said output voltage instructing means based upon the setting value of said voltage lower limit level setting means to thereby limit the lower limit value of the output voltage of said drive circuit;

wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; and

the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value is such a value lower than the setting value of said voltage limit level setting means, and also such a value higher than a value corresponding to an induced voltage internally produced from said brushless motor.

34. A protection apparatus of a brushless motor as claimed in claim 33, wherein:

either one or both the setting value of said voltage limit level setting means and said setting value of said voltage lower limit level setting means is corrected in such a manner that a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor are grasped based upon the drive current of the brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor.

35. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, the setting value of said voltage lower limit level setting means being set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means and also a value higher than a value corresponding to the induced voltage internally produced from said brushless motor;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means and the setting value of said voltage lower limit level setting means to thereby supply said output voltage instruction signal to said drive circuit, and for limiting the upper limit value and the lower limit value of the output voltage of said drive circuit;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

36. A protection apparatus of a brushless motor as claimed in claim 35, wherein:

either one or both the setting value of said voltage limit level setting means and said setting value of said voltage lower limit level setting means is corrected in such a manner that both a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor, or a variation contained in the output voltage of said DC main power supply is grasped based upon either the output current of said DC main power supply, or the drive current of said brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor, or the variation contained in the output voltage of said DC main power supply.

37. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of the drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit, and also for limiting the output signal of said output voltage instructing signal based on the setting value of said voltage lower limit level setting means to thereby limit the lower limit value of the output voltage of said drive circuit;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level; and

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means and also said second power supply interrupting signal is not outputted from said reverse rotation limiter means is continued for a predetermined time period; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means, and also a value higher than a value corresponding to the induced voltage internally produced from the brushless motor; and

when said third power supply interrupting signal outputted from said reverse rotation limiter means is produced, said drive circuit is electrically opened from said brushless motor.

38. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, in which the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means, and also becomes a value higher than a value corresponding to the induced voltage internally produced from the brushless motor;

voltage limiter means for limiting the output signal of said output voltage instructing means based upon the setting value of said voltage limit level setting means and the setting value of said voltage lower limit level setting means to thereby supply said output voltage instruction signal to said drive circuit;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level;

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means is continued for a predetermined time period, in which when said third power supply interrupting signal outputted from said low speed overload detecting means is produced, said drive circuit is electrically opened from said brushless motor;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

39. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit; and

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; and

the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value is such a value lower than the setting value of said voltage limit level setting means, and also such a value higher than a value corresponding to an induced voltage internally produced from said brushless motor, when the output voltage of said output voltage instructing means reaches the setting value of said voltage lower level setting means, the connection between said drive circuit and said brushless motor is electrically opened.

40. A protection apparatus of a brushless motor as claimed in claim 39 wherein:

said protection apparatus is comprised of hysteresis means such that during a time period defined by that after the output signal of the output voltage instructing means reaches the setting value of the voltage lower limit level setting means set in response to the output signal of said speed detecting means to thereby electrically open the connection between the drive circuit and the brushless motor, until the setting value of said voltage lower limit level setting means becomes a value slightly lower than the output signal of said output voltage instructing means, said drive circuit is electrically and continuously opened from said brushless motor; when the setting value of said voltage lower limit level setting means becomes such a value slightly lower than the output signal of said output voltage instructing means, electric opening of said drive circuit with said brushless motor is released; and thereafter the connection between said drive circuit and said brushless motor is not electrically opened until the output signal of said output voltage instructing means reaches the setting value of said voltage lower level setting means.

41. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, in which the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means, and also becomes a value higher than a value corresponding to the induced voltage internally produced from the brushless motor, and further when the output signal of said output voltage instructing means reaches the setting value of said voltage lower limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

42. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit vale of the output voltage of said drive circuit;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level; and

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means is continued for a predetermined time period; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means and also becomes a value higher than such a value corresponding to the induced voltage internally produced from said brushless motor; and when the output signal of said output voltage instructing means reaches the setting value of said voltage lower limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened; and

when said third power supply interrupting signal outputted by said low speed overload detecting means is produced, the connection between said drive circuit and said brushless motor is electrically opened.

43. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

voltage lower limit level setting means for setting a lower limit value of the output voltage of said drive circuit, in which the setting value of said voltage lower limit level setting means is set in response to the output signal of said speed detecting means in such a manner that said setting value of this voltage lower limit level setting means becomes a value lower than the setting value of said voltage limit level setting means and also becomes a value higher than such a value corresponding to the induced voltage internally produced from said brushless motor; and when the output signal of said output voltage instructing means reaches the setting value of said voltage lower limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level;

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means is continued for a predetermined time period, and said third power supply interrupting signal outputted from said low speed overload detecting means is produced, said drive circuit is electrically opened from said brushless motor;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor, said second power supply interrupting signal outputted from said reverse rotation limiter means; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

44. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

speed upper limit level setting means for setting an upper limit value of the rotation speed of said brushless motor; and

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; and

the setting value of said speed upper limit level setting means is set in response to the output signal of said output voltage instructing means, equal to a value corresponding to a maximum rotation speed of said brushless motor in which the induced voltage internally produced by said brushless motor can become lower than the output voltage of said drive circuit when the output signal of said output voltage instructing means is supplied as said output voltage instruction signal to said drive circuit, and further when the output signal of said speed detecting means reaches the setting value of said speed upper limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened.

45. A protection apparatus for a brushless motor as claimed in claim 44 wherein:

said protection apparatus is comprised of hysteresis means such that after the output signal of the speed detecting means reaches the setting value of said speed upper limit level setting means to thereby electrically open the connection between the drive circuit and the brushless motor, until the output signal of said speed detecting means becomes a value slightly lower than the setting value of said speed upper limit level setting means, said drive circuit is electrically and continuously opened from said brushless motor; when the output signal of said speed detecting means becomes such a value slightly lower than the setting value of said speed upper limit level setting means, electric opening of said drive circuit with said brushless motor is released; and thereafter the connection between said drive circuit and said brushless motor is not electrically opened until the output signal of said speed detecting means reaches the setting value of said speed upper level setting means.

46. A protection apparatus of a brushless motor as claimed in claim 44 wherein:

either one or both the setting value of said voltage limit level setting means and said setting value of said speed upper limit level setting means is corrected in such a manner that a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor are grasped based upon the drive current of the brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor.

47. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

speed upper limit level setting means for setting an upper limit value of the rotation speed of said brushless motor, in which the setting value of said speed upper limit level setting means is set in response to the output signal of said output voltage instructing means, equal to a value corresponding to a maximum rotation speed of said brushless motor in which the induced voltage internally produced by said brushless motor can become lower than the output voltage of said drive circuit when the output signal of said output voltage instructing means is supplied as said output voltage instruction signal to said drive circuit, and further when the output signal of said speed detecting means reaches the setting value of said speed upper limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

48. A protection apparatus of a brushless motor as claimed in claim 47 wherein:

either one or both the setting value of said voltage limit level setting means and said setting value of said speed upper limit level setting means is corrected in such a manner that both a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor, or a variation of said DC main power supply is grasped based upon either the output current of said DC main power supply or the drive current of said brushless motor in order to compensate for the fluctuation and the variation contained in the induced voltage of said brushless motor, or the variation contained in the output voltage of said DC main power supply.

49. A protection apparatus of a brushless motor comprising:

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal;

output voltage instructing means for supplying to said drive circuit, an output voltage instruction signal for instructing an output voltage of said drive circuit, which constitutes a drive voltage when said brushless motor is driven;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit;

speed upper limit level setting means for setting an upper limit value of the rotation speed of said brushless motor;

voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby limit an upper limit value of the output voltage of said drive circuit;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level; and

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means is continued for a predetermined time period; wherein:

the setting value of said voltage limit level setting means is set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value;

the setting value of said speed upper limit level setting means is set in response to the output signal of said output voltage instructing means, equal to a value corresponding to a maximum rotation speed of said brushless motor in which the induced voltage internally produced by said brushless motor can become lower than the output voltage of said drive circuit when the output signal of said output voltage instructing means is supplied as said output voltage instruction signal to said drive circuit; and further when the output signal of said speed detecting means reaches the setting value of said speed upper limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened; and

when said third power supply interrupting signal outputted from said low speed overload detecting means is produced, the drive circuit is electrically opened from said brushless motor.

50. A protection apparatus of a brushless motor comprising:

a DC (direct current) main power supply;

a brushless motor;

commutation signal detecting means for detecting a position of a movable member of said brushless motor;

speed detecting means for detecting a rotation speed of the movable member of said brushless motor, involving a rotation direction thereof, in response to the detection signal outputted from said commutation signal detecting means;

a drive circuit for producing a commutation signal used to drive the movable member of said brushless motor in response to the detection signal outputted from said commutation signal detecting means and for driving said brushless motor based upon said commutation signal, said drive circuit outputting the output voltage of said DC main power supply in a ratio responding to an output voltage instruction signal as a drive voltage used when said brushless motor is driven;

output voltage instructing means for supplying said output voltage instruction signal to said drive circuit;

voltage limit level setting means for setting an upper limit value of the output voltage of said drive circuit, the setting value of said voltage limit level setting means being set in accordance with the detecting signal outputted from said speed detecting means in such a manner that the higher the rotation speed of the movable member of said brushless motor, said setting value becomes a large value; the lower the rotation speed of the movable member of said brushless motor, said setting value becomes a small value; and when the rotation speed becomes near zero and the rotation direction is reversed, said setting value becomes a preset constant value; voltage limiter means for limiting the output signal of said output voltage instructing means based on the setting value of said voltage limit level setting means to thereby supply the limited output signal to said drive circuit and limit an upper limit value of the output voltage of said drive circuit;

speed upper limit level setting means for setting an upper limit value of the rotation speed of said brushless motor, the setting value of said speed upper limit level setting means is set in response to the output signal of said output voltage instructing means, equal to a value corresponding to a maximum rotation speed of said brushless motor in which the induced voltage internally produced by said brushless motor can become lower than the output voltage of said drive circuit when the output signal of said output voltage instructing means is supplied as said output voltage instruction signal to said drive circuit; and further when the output signal of said speed detecting means reaches the setting value of said speed upper limit level setting means, the connection between said drive circuit and said brushless motor is electrically opened;

low speed failure detecting means for detecting as to whether or not the rotation speed of said brushless motor becomes below a preset low speed failure sensing level, and for outputting a low speed failure signal when said rotation speed becomes below said preset low speed failure sensing level;

low speed overload detecting means containing said low speed failure sensing means, for latch-processing a third power supply interrupting signal to thereby output the latch-processed third power supply interrupting signal in the case that such a condition that said low speed failure signal is outputted from said low speed failure sensing means is continued for a predetermined time period, in which when said third power supply interrupting signal outputted by said low speed overload detecting means is produced, the connection between said drive circuit and said brushless motor is electrically opened;

voltage variation detecting means for detecting a variation contained in the output voltage of said DC main power supply in a direct manner, or based upon any one of an output current of said DC main power supply and a drive current of said brushless motor; and

voltage correcting means for applying said output voltage instruction signal to said drive circuit by conversely changing the output signal of said voltage limiter means in order to compensate for the variation contained in the output voltage of said DC main power supply based upon the detection output from said voltage variation detecting means.

51. A protection apparatus of a brushless motor as claimed in claim 1, 28, 31, 44 or 49, wherein:

the setting value of said voltage limit level setting means is corrected in such a manner that a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor are grasped based upon the drive current of the brushless motor in order to compensate for the fluctuation and variation contained in the induced voltage of said brushless motor.

52. A protection apparatus of a brushless motor as claimed in claim 3, 30, 32, 47 or 50, wherein:

the setting value of said voltage limit level setting means is corrected in such a manner that both a fluctuation and a variation contained in the induced voltage internally produced from said brushless motor, or a variation contained in the output voltage of said DC main power supply is grasped based upon either the output current of said DC main power supply or the drive current of said brushless motor in order to compensate for the fluctuation and variation contained in the induced voltage of said brushless motor, or the variation contained in the output voltage of said DC main power supply.