Multiplex transmission apparatus

When it is detected that the state of an electrical component connected to a communication node has not changed in the OFF state of an ignition key switch, it is determined that a vehicle equipped with the multiplex transmission apparatus is in a parking state, and the communication node is forcibly shifted to a sleep state, thereby preventing consumption of battery power due to a dark current supplied to the communication node in the sleep state.

What is claimed is:

1. A multiplex transmission apparatus which comprises a plurality of communication nodes connected to each other via a multiplex transmission path, and a plurality of electrical components to be controlled by the plurality of communication nodes, each of the plurality of communication nodes being set in one of an operative state, an inoperative state, and an operable state, comprising:

first detection means for detecting an ON/OFF state of an ignition key switch;

means for monitoring operative/inoperative states of the electrical components;

means for setting a predetermined reference time in accordance with the monitoring result;

second detection means for detecting a change in state of the electrical components within the reference time; and

control means for, when the ignition key switch is in an OFF state, and it is detected that the state of the electrical components has not changed within the reference time, setting the communication node associated with control of the electrical components in the inoperative state.

2. The apparatus according to claim 1, wherein said control means sets the electrical components in the inoperative state when the ignition key switch is in the OFF state, and when said second detection means detects that the electrical components are in the operative state over the reference time.

3. The apparatus according to claim 1, wherein said reference time includes a first reference time corresponding to a case wherein all of the plurality of electrical components are in the inoperative state, and a second reference time corresponding to a case wherein at least one of the plurality of electrical components is in the operative state, and the first reference time is set to be shorter than the second reference time.

4. The apparatus according to claim 1, wherein a plurality of types of said reference time are prepared, and one of the plurality of types of said reference time is selected in correspondence with the number of said electrical components which are in the operative state.

5. The apparatus according to claim 4, wherein said plurality of types of said reference time are set to become shorter as the number of said electrical components which are in the operative state increases.

6. The apparatus according to claim 4, wherein said plurality of types of said reference time are set to become shorter as the number of said electrical components which are in the operative state decreases.

7. The apparatus according to claim 4, further comprising:

means for calculating the amount of power dissipated by said electrical components which are in the operative state, and

wherein said reference time is set on the basis of a predetermined correspondence between the amount of power consumption and a reference time.

8. The apparatus according to claim 1, further comprising:

means for detecting whether the communication node is in the operable state when the ignition key switch is in the OFF state; and

means for outputting a signal indicating that said communication node is in the operable state, and

wherein said control means stops outputting said signal when said communication node associated with control of said electrical components is set in the inoperative state.

9. The apparatus according to claim 8, wherein said signal is periodically output at a predetermined period.

10. A multiplex transmission apparatus which comprises a plurality of communication nodes connected to each other via a multiplex transmission path, and a plurality of electrical components to be controlled by the plurality of communication nodes, each of the plurality of communication nodes being set in one of an operative state, an inoperative state, and an operable state, comprising:

means for monitoring operative/inoperative states of the electrical components;

means for setting one of a plurality of predetermined reference times in accordance with the monitoring result;

detection means for detecting a change in state of the electrical components within the predetermined reference time; and

control means for, when an ignition key switch is in an OFF state, and it is detected that the state of the electrical components has not changed within the predetermined reference time, setting the communication node associated with control of the electrical components in the inoperative state, wherein the predetermined reference time is set in correspondence with the number of said electrical components which are in the operative state.

11. The apparatus according to claim 10, wherein said control means sets the electrical components in the inoperative state when the ignition key switch is in the OFF state, and when said detection means detects that the electrical components are in the operative state during the predetermined reference time.

12. The apparatus according to claim 10, wherein said plurality of predetermined reference times include a first reference time corresponding to a case wherein all of the plurality of electrical components are in the inoperative state, and a second reference time corresponding to a case wherein at least one of the plurality of electrical components is in the operative state, said first reference time being shorter than the second reference time.

13. The apparatus according to claim 10, wherein said plurality of predetermined reference times are set to become shorter as the number of said electrical components which are in the operative state increases.

14. The apparatus according to claim 10, wherein said plurality of predetermined reference times are set to become shorter as the number of said electrical components which are in the operative state decreases.

15. The apparatus according to claim 10, further comprising:

means for calculating an amount of power consumed by said electrical components which are in the operative state,

wherein said reference time is set on the basis of a predetermined correspondence between the amount of power consumption and a reference time.

16. The apparatus according to claim 10, further comprising:

means for detecting whether the communication node is in the operable state when the ignition key switch is in the OFF state; and

means for outputting a signal indicating that said communication node is in the operable state,

wherein said control means stops outputting said signal when said communication node associated with control of said electrical components is set in the inoperative state.

17. The apparatus according to claim 16, wherein said signal is periodically output at a predetermined period.