Control of compressor outlet pressure based on temperature of thermal load cooled by coolant in electric vehicle

1. A method of operating a thermal management system of a vehicle having an electric traction motor, the method comprising:

circulating coolant through a first thermal load;

circulating refrigerant through a refrigerant circuit including a condenser and a compressor to cool at least one second thermal load;

receiving signals from a sensor that are indicative of a temperature of the first thermal load;

determining if a threshold temperature is exceeded based on the signals received from the sensor;

substantially preventing the outlet pressure of the compressor from exceeding a second maximum outlet threshold pressure if the threshold temperature is determined not to be exceeded; and

substantially preventing the outlet pressure of the compressor from exceeding a second maximum outlet threshold pressure if the threshold temperature is determined to be exceed, wherein the second maximum outlet threshold pressure is lower than the first maximum outlet threshold pressure.

2. The method as claimed in claim 1 , wherein a radiator is operable to cool the coolant, and wherein the radiator is positioned adjacent the condenser and receives an airflow passing through the condenser from a vehicle air inlet.

3. The method as claimed in claim 1 , wherein the steps of substantially preventing the outlet pressure of the compressor from exceeding a first maximum outlet threshold pressure and substantially preventing the outlet pressure of the compressor from exceeding a second maximum outlet threshold pressure each includes controlling the speed of the compressor to control the outlet pressure of the compressor.

4. The method as claimed in claim a, wherein the first thermal load includes at least one component selected from the electric traction motor, and a transmission control module configured for controlling current flow to the electric traction motor.

5. The method as claimed in claim 4 , wherein the sensor is a vehicle speed sensor for the vehicle.

6. The method as claimed in claim 4 , wherein the at least one second thermal load includes at least one of: a battery pack for storing power for use by the electric traction motor and a passenger cabin of the vehicle.

7. A method as claimed in claim 4 , wherein the at least one second thermal load includes a battery pack for storing power for use by the electric traction motor and a passenger cabin of the vehicle, and wherein the method further comprises:

receiving signals from a second sensor that are indicative of a temperature of the battery pack; and

preferentially sending refrigerant from the condenser to cool the battery pack and restricting the flow of refrigerant to cool the passenger cabin if the signals received from the second sensor are indicative of a temperature that exceeds a battery pack threshold temperature.

8. The method as claimed in claim 1 , wherein the sensor is a temperature sensor that is positioned to sense the temperature of the coolant.

9. A thermal management system for a vehicle having an electric traction motor, the system comprising:

a coolant system configured to convey coolant through a first thermal load;

a refrigerant circuit including a compressor configured to compress refrigerant and a condenser, wherein the refrigerant circuit is configured to cool at least one second thermal load; a control system; and

a sensor configured to send signals to the control system that are indicative of a temperature of the first thermal load, wherein the control system is configured to:

determine if a threshold temperature is exceeded based on the signals,

b) substantially prevent the outlet pressure of the compressor from exceeding a first maximum outlet threshold pressure if the threshold temperature is determined not to be exceeded, and

c) substantially prevent the outlet pressure of the compressor from exceeding a second maximum outlet threshold pressure if the threshold temperature is determined to be exceeded and wherein the second maximum outlet threshold pressure is lower than the first maximum outlet threshold pressure.

10. The system as claimed in claim 9 , further comprising a radiator that is operable to cool the coolant, and wherein the radiator is positioned adjacent the condenser and receives an airflow passing through the condenser from a vehicle air inlet.

11. The system as claimed in claim 9 , wherein the control system is configured to control the speed of the compressor to control the outlet pressure of the compressor.

12. The system as claimed in claim 9 , wherein the first thermal load includes at least one component selected from the electric traction motor, and a transmission control module configured for controlling current flow to the electric traction motor.

13. The system as claimed in claim 12 , wherein the sensor is a vehicle speed sensor for the vehicle.

14. The system as claimed in claim 12 , wherein the at least one second thermal load includes at least one of: a battery pack for storing power for use by the electric traction motor and a passenger cabin of the vehicle.

15. The system as claimed in claim 12 , wherein the at least one second thermal load includes a battery pack for storing power for use by the electric traction motor and a passenger cabin of the vehicle, and wherein the control system is further configured to:

d) receive signals from a second sensor that are indicative of a temperature of the battery pack; and

e) preferentially send refrigerant from the condenser to cool the battery pack and restrict the flow of refrigerant to cool the passenger cabin if, during step c) the signals received in step d) are indicative of a temperature that exceeds a battery pack threshold temperature.

16. The system as claimed in claim 9 , wherein the sensor is a temperature sensor that is positioned to sense the temperature of the coolant.

17. A method of operating a thermal management system of a vehicle having an electric traction motor, the method comprising:

circulating coolant through a coolant circuit to cool a first thermal load including at least one of the electric traction motor and a transmission control module configured for controlling current flow to the electric traction motor;

circulating refrigerant through a refrigerant circuit having a condenser and a compressor configured to cool a second thermal load including at least one of a battery pack storing power for use by the electric traction motor and a passenger compartment of the vehicle;

receiving signals from a sensor that are indicative of a temperature of the first thermal load;

determining if a threshold temperature is exceeded based on the signals received by the sensor;

controlling the compressor to prevent a refrigerant outlet pressure from exceeding a first maximum outlet threshold pressure if the threshold temperature is determined not to be exceeded; and

controlling the compressor to prevent the refrigerant outlet pressure from exceeding a second maximum outlet threshold pressure if the threshold temperature is determined to be exceeded, wherein the second maximum outlet threshold pressure is lower than the first maximum outlet threshold pressure.

18. The method as claimed in claim 17 wherein the sensor is a temperature sensor positioned to sense the temperature of the coolant, and wherein the method further comprises receiving signals from a second temperature sensor that are indicative of a temperature of the battery pack, and preferentially sending refrigerant from the condenser to cool the battery pack and restricting the flow of refrigerant to cool the passenger cabin when the signals received from the second temperature sensor are indicative of a temperature that exceeds a battery pack threshold temperature.