Vehicle cabin thermal management system and control methods

1. A thermal management system for a passenger cabin of a hybrid vehicle, the thermal management system having a refrigerant loop in fluid communication with a compressor, a condenser, and a chiller, comprising:

a main cabin evaporator in fluid communication with the refrigerant loop;

a first valve configured to regulate refrigerant flow through the main cabin evaporator;

a temperature sensor disposed at the main cabin evaporator and configured to output a signal indicative of a main cabin evaporator temperature;

an auxiliary evaporator in fluid communication with the refrigerant loop;

a second valve configured to regulate refrigerant flow through the auxiliary evaporator; and

a controller programmed to, in response to the main cabin evaporator temperature being less than a first temperature threshold while the main cabin evaporator is operated with the second valve closed and the compressor operating at less than a predetermined operating speed, open the second valve to cycle refrigerant through the auxiliary evaporator to cause an increase in the main cabin evaporator temperature.

2. The thermal management system of claim 1 wherein the controller is further programmed to close the second valve in response to the main cabin evaporator temperature increasing to greater than a second temperature threshold while the second valve is open.

3. The thermal management system of claim 2 wherein the second temperature threshold is 2-5 degrees greater than the first temperature threshold.

4. The thermal management system of claim 1 wherein the controller is further programmed to close the second valve in response to a predetermined time duration having elapsed.

5. The thermal management system of claim 1 wherein first temperature threshold is based on a predetermined buffer greater than a sensed ambient temperature.

6. The thermal management system of claim 5 wherein the predetermined buffer is varied from 0.1 degrees Celsius for a 15 degrees Celsius ambient temperature to 1 degree Celsius for a 5 degrees Celsius ambient temperature.

7. A method of controlling a thermal management system having a plurality of evaporators, the method comprising:

operating a compressor to cycle refrigerant through a refrigerant loop;

opening a first valve to allow refrigerant to flow through a main cabin evaporator;

closing a second valve to prevent refrigerant to flow through an auxiliary evaporator;

sensing a temperature indicative of a main cabin evaporator temperature;

in response to the main cabin evaporator temperature being less than a first temperature threshold while the second valve is closed, opening the second valve to cycle refrigerant through the auxiliary evaporator to cause an increase in the main cabin evaporator temperature; and

in response to the main cabin evaporator temperature increasing to greater than a second temperature threshold while the second valve is open, closing the second valve.

8. The method of claim 7 further comprising, closing the second valve in response to refrigerant cycled through the auxiliary evaporator for a predetermined time duration.

9. The method of claim 7 wherein first temperature threshold is based on a buffer temperature greater than a sensed ambient temperature.

10. The method of claim 7 wherein the second temperature threshold is 2-5 degrees greater than the first temperature threshold.

11. A vehicle comprising:

a compressor in fluid communication with a refrigerant loop and operable to generate a refrigerant pressure increase causing flow through the refrigerant loop;

a main cabin evaporator in fluid communication with the refrigerant loop to provide cooling for a first vehicle cabin zone;

a first valve configured to regulate refrigerant flow through the main cabin evaporator;

a temperature sensor disposed at the main cabin evaporator and configured to output a signal indicative of a main cabin evaporator temperature;

an auxiliary evaporator in fluid communication with the refrigerant loop to provide cooling for a second vehicle cabin zone;

a second valve configured to regulate refrigerant flow through the auxiliary evaporator; and

a controller programmed to,

open the first valve and close the second valve in response to a cooling request corresponding to the first vehicle cabin zone to cycle refrigerant through the main cabin evaporator, and

in response to the main cabin evaporator temperature being less than a first temperature threshold while the main cabin evaporator is operated with the second valve closed, open the second valve to cycle refrigerant through the auxiliary evaporator to cause an increase in the main cabin evaporator temperature.

12. The vehicle of claim 11 wherein the controller is further configured to open the second valve in response to the main cabin evaporator temperature being less than the first temperature threshold while the compressor is operated at less than a predetermined operating speed.

13. The vehicle of claim 11 wherein the controller is further programmed to close the second valve in response to the main cabin evaporator temperature increasing to greater than a second temperature threshold while the second valve is open.

14. The vehicle of claim 13 wherein the second temperature threshold is 2-5 degrees greater than the first temperature threshold.

15. The vehicle of claim 11 wherein the controller is further programmed to close the second valve in response to a predetermined time duration having elapsed.

16. The vehicle of claim 11 wherein first temperature threshold is based on a predetermined buffer greater than a sensed ambient temperature.

17. The vehicle of claim 11 wherein the first temperature threshold is varied from 0.1 degrees Celsius greater than ambient for a 15 degrees Celsius ambient temperature to 1 degree Celsius greater than ambient for a 5 degrees Celsius ambient temperature.