Engine temperature control system

The operating temperature of an internal combustion engine is maintained within desired limits by employing a single coolant temperature sensor for controlling and coordinating the operation of three different temperature control devices for the engine coolant. When the sensed coolant temperature is in a relatively low range a flow control valve controls the amount of coolant diverted from the engine jacket to a radiator to dissipate heat absorbed by the coolant from the engine. If the coolant temperature exceeds that low range, even though the control valve is fully open and all of the coolant is circulated through the radiator, the sensor then effects the opening of radiator shutters to cause ram air to impinge on the radiator to increase the cooling of the coolant. If the temperature still continues to rise after the shutters are fully open, the coolant sensor causes operation of a variable speed fan drive to blow a sufficient amount of air through the radiator to cool the coolant back down to the desired operating range. Such sequential operation of the three control devices provides close temperature control within a relatively narrow range despite wide variations of external conditions and load on the engine, resulting in higher efficiency and longer engine life.

What is claimed is:

1. An engine temperature control system for maintaining the temperature of coolant, in the engine jacket of an internal combustion engine, within desired narrow limits regardless of external conditions and load on the engine, comprising:

a radiator through which the coolant may be circulated from the engine jacket to effect cooling of the coolant;

a temperature sensor for sensing the temperature of the coolant in the engine jacket;

means responsive to said temperature sensor for producing a controlled fluid pressure which is a function of and represents the sensed temperature;

a coolant flow control valve which responds to the fluid pressure, when the sensed coolant temperature is in a relatively low temperature range, to vary the amount of coolant diverted to and flowing through the radiator;

radiator shutters controlled by the fluid pressure, when the sensed temperature is in a medium temperature range above the low temperature range, for adjusting the amount of ram air impinging on the radiator;

and a variable speed fan drive responsive to the fluid pressure, when the sensed coolant temperature is in a relatively high temperature range above the medium range, for blowing a controlled amount of air through the radiator.

2. An engine temperature control system according to claim 1 wherein the controlled fluid pressure is directly proportional to the sensed temperature of the coolant.

3. An engine temperature control system according to claim 1 wherein the controlled fluid pressure is inversely proportional to the sensed temperature of the coolant.

4. An engine temperature control system according to claim 1 and including a pulse width modulation circuit for producing, in response to said temperature sensor, a pulse width modulated signal having a duty cycle which is proportional to the sensed coolant temperature, the pulse width modulated signal being utilized to provide the controlled fluid pressure.

5. An engine temperature control system according to claim 4 and including means responsive to said temperature sensor for providing a temperature signal having an amplitude proportional to the sensed temperature, and wherein said pulse width modulated signal is developed in response to the temperature signal.

6. An engine temperature control system according to claim 5 wherein said temperature signal is applied to a comparator which also receives a triangular shaped signal, said pulse width modulated signal being produced at the output of said comparator.

7. An engine temperature control system according to claim 4 wherein the controlled fluid pressure is proportional to the duty cycle of said pulse width modulated signal and is produced by supplying pressurized fluid to a solenoid off-on valve operated by the pulse width modulated signal, the effective opening of the solenoid valve and the pressure drop thereacross being proportional to the duty cycle of the pulse width modulated signal.

8. An engine temperature control system according to claim 7 wherein the pressurized fluid is pressurized oil which flows through an oil circuit from a pressurized oil supply through said solenoid off-on valve and then through a fixed orifice and finally back to the oil supply, the controlled fluid pressure being directly proportional to the sensed temperature of the coolant and being developed at the junction in the oil circuit between the output of the solenoid valve and the input to the fixed orifice.

9. An engine temperature control system according to claim 7 wherein the pressurized fluid is pressurized oil which flows through an oil circuit from a pressurized oil supply through a fixed orifice and then through said solenoid off-on valve and finally back to the oil supply, the controlled fluid pressure being inversely proportional to the sensed temperature of the coolant and being developed at the junction in the oil circuit between the output of the fixed orifice and the input to the solenoid valve.

10. An engine temperature control system for maintaining the temperature of coolant, in the engine jacket of an internal combustion engine, within desired narrow limits despite wide variations of external conditions and load on the engine, where a flow control valve controls the coolant flow from the engine jacket to a radiator having controllable shutters for varying the amount of ram air striking the radiator, and where a variable speed fan drive controls the amount of air blown through the radiator, said engine temperature control system comprising:

a temperature sensor for sensing the temperature of the coolant in the engine jacket;

means responsive to said temperature sensor for producing a controlled fluid pressure which is a function of and represents the sensed temperature;

and means, responsive to the fluid pressure, for sequentially operating the flow control valve, radiator shutters and variable speed fan drive as the sensed coolant temperature rises through predetermined low, medium and high temperature ranges,

the flow control valve increasing the amount of coolant circulating through the radiator as the sensed temperature increases in the low temperature range, the radiator shutters increasing the amount of ram air impinging on the radiator as the sensed temperature increases in the medium temperature range, and the fan drive increasing the amount of air pulled through the radiator as the temperature increases in the high temperature range.

11. An engine temperature control system for controlling the temperature of coolant in the engine jacket of an internal combustion engine, where the coolant may be circulated, via a flow control valve, around the engine jacket and through a radiator having controllable shutters for varying the amount of ram air that may impinge on the radiator, a variable speed fan drive being provided to control the amount of air blown through the radiator, said engine temperature control system comprising:

a temperature sensor for sensing the temperature of the coolant in the engine jacket;

means responsive to said temperature sensor for producing a pulse width modulated signal having a duty cycle which is proportional to the sensed temperature;

a source of pressurized fluid;

means, coupled to said source of pressurized fluid and responsive to said pulse width modulated signal, for producing a controlled fluid pressure which is proportional to the sensed temperature;

means for utilizing said controlled fluid pressure, when the sensed coolant temperature is in a relatively low temperature range, for controlling the position of the coolant flow control valve to vary the amount of coolant diverted to and flowing through the radiator, the flow control valve being fully open to circulate all of the coolant through the radiator when the sensed coolant temperature is at the high end of the low temperature range;

means for utilizing said controlled fluid pressure, when the sensed coolant temperature is in a medium temperature range above the low temperature range, for adjusting the position of the radiator shutters to vary the amount of ram air striking the radiator, the shutters being fully open to maximize the amount of ram air when the sensed coolant temperature is at the high end of the medium temperature range;

and means for utilizing said controlled fluid pressure, when the sensed coolant temperature is in a relatively high temperature range above the medium temperature range, for varying the speed of the fan drive to control the amount of air pulled through the radiator, thereby to maintain the coolant temperature within desired narrow temperature limits regardless of external conditions and load on the engine.