Patent Application
20080295535
This invention relates generally to thermal management systems and, more particularly, to liquid cooled thermal management systems for vehicles.
Electric vehicles and hybrid electric vehicles may be equipped with power sources such as high voltage batteries and/or fuel cells. These power sources can generate a great deal of heat during their operation. High output demand from drivers can increase the amount of heat generated by the power source. Generally, batteries and fuel cells must operate within a predetermined temperature range. Heat generated from the power source can build up within a compartment where the power source is stored. As a result, the devices must be cooled so that they may continue to operate within their acceptable operating temperature.
Additionally, electric vehicles and hybrid electric vehicles are equipped with high voltage electronics (HVE) such as power converters, power inverters, powertrain controllers and the like. Like the power sources, the HVE may also need to operate within a predetermined temperature range. Additionally, like the power sources, the HVE can generate heat during their operation.
A thermal management system for vehicles includes a refrigerant circuit, a coolant circuit, and a heat exchanger. The refrigerant circuit contains at least one evaporator for receiving cooled refrigerant and for providing conditioned air to a passenger compartment of the vehicle. The coolant circuit circulates coolant to cool an electric power source and high voltage electronics powered by the electric power source. The heat exchanger is communicated with the refrigerant circuit and the coolant circuit for transferring heat from the coolant to the refrigerant in the refrigerant circuit.
In another implementation, the thermal management system includes a refrigerant loop in which refrigerant is circulated for conditioning air in a passenger compartment of the vehicle. The system also includes a coolant loop in which liquid coolant circulates, the coolant loop includes an electric power source cooled by the coolant, high voltage electronics cooled by the coolant, and a heat, exchanger coupled with the coolant loop and the refrigerant loop to transfer heat from the coolant to the refrigerant to control the temperature of the electric power source and the high voltage electronics.
In yet another implementation, the thermal management system includes a refrigerant loop circulating refrigerant for conditioning air in a passenger compartment of the vehicle. The system also includes a power supply cooling loop, a high voltage electronics cooling loop, and a heat exchanger. The power supply cooling loop circulates liquid coolant for controlling the temperature of an electric power source. The high voltage electronics cooling loop circulates liquid coolant shared with the power supply cooling loop for controlling the temperature of high voltage electronics. The heat exchanger is coupled with the power supply cooling loop, the high voltage electronics cooling loop, and the refrigerant loop to transfer heat from the liquid coolant to the refrigerant.
The following detailed description of preferred embodiments and best mode will be set forth with regard to the accompanying drawings in which:
Referring in more detail to the drawings,
The coolant loop 16 includes the high voltage power source 12, the high voltage electronics 14, the liquid-to-liquid heat exchanger 20, and a pump 22 for circulating liquid coolant near, across, or through the high voltage power source and HVE to absorb heat from the devices and allow them to operate within their normal operating temperature. The liquid coolant can be any suitable coolant such as a glycol-based coolant such as Ethylene Glycol, Propylene Glycol, or the like.
The high voltage power source 12 may include one or more electrical power sources. For example, the high voltage power source 12 may include one or more high voltage batteries, fuel cells, etc., or a combination thereof. The high voltage power source 12 may generate a great deal of heat as current is drawn from it and/or when the power source retrieves or stores electrical energy through chemical reactions occurring in the power source. The amount of heat generated by the high voltage power source 12 may increase as the driver demands more power from the power source to drive the vehicle, such as during vehicle acceleration. The high voltage power source 12 may require cooling for it to continue operating within its normal operating range to compensate for the heat it generates.
Like the high voltage power source 12, the HVE 14 receives coolant in the coolant circuit 16. The HVE 14 includes electronics for use with the high voltage power source 12. For example, the HVE 14 may include an inverter for converting power from a DC voltage to an AC voltage or vice versa, a power converter such as a DC to DC converter or a transformer for converting a voltage from one voltage level to another voltage level, an electric motor control module for controlling one or more electric motors, a transmission controller for controlling a transmission, or the like. The HVE 14 may also include other electronic components that utilize power from the high voltage power source 12 or other electrical power sources in the vehicle. For example, the HVE 14 may include sensors powered by a low voltage power source. Like the high voltage power source 12, the HVE 14 generates heat during its operation. The HVE 14 may have an operating range beyond that of the high voltage power source 12, however. For example, some HVEs may have a normal operating range approximately 25 degrees C. higher than a common high voltage power source 12. The HVE 14 may be housed within a storage area shared with the high voltage power source 12 or may be located outside of the storage area for the high voltage power source.
As shown in
It may be advantageous to plumb the high voltage power source 12 in the cooling loop 16 after the liquid-to-liquid heat exchanger 20 and before the HVE 14 because the high voltage power source 12 may be generally has a lower operating temperature than the HVE 14. Placing the high voltage power source 12 in the cooling loop 16 after the liquid-to-liquid heat exchanger 20 and before the HVE 14 may maximize the amount of heat the coolant can absorb from the high voltage power source 12. The coolant has its lowest temperature at any point in the cooling loop 16 when it exits the liquid-to-liquid heat exchanger 20 because both the high voltage power source 12 and the HVE 14 heat the coolant as the coolant passes near the devices.
The liquid-to-liquid heat exchanger 20 transfers heat from the coolant in the coolant loop 16 to a second coolant used in the refrigerant loop 18. In one implementation, the coolant in the refrigerant loop is a high-pressure refrigerant such as a refrigerant that may be evaporated and condensed back into a liquid. For example, the refrigerant may be R134A, R12, or the like.
The refrigerant loop 18 may contain components commonly found in vehicle systems for conditioning the air of the passenger compartment of a vehicle. For example, the refrigerant loop 18 may include a compressor 30, a condenser 32, and an evaporator 34. The compressor 30 compresses the refrigerant gas causing it to become a hot high-pressure gas. The gas passes through the condenser 32 where it condenses into a cold liquid. Out of the condenser 32, the liquid refrigerant passes through the evaporator 34 where it evaporates to become a low-pressure gas. Air is blown over the evaporator 34 and into the passenger compartment for cooling the passenger compartment of the vehicle. The evaporator 34 may be connected in the refrigerant loop via a valve 36. The valve 36 may be responsive to a temperature signal, such as from a temperature sensor (not shown), to control the flow rate of refrigerant to the evaporator 34. The valve 36 may be a thermal expansion valve, a bi-metal strip valve, a solenoid, or the like. The temperature sensor may measure the temperature of the passenger compartment and control the amount of refrigerant passing through the evaporator 34 depending upon the amount of cooling needed for the passenger compartment. Alternatively, the valve 36 may include an optional three-way valve to act as a bypass for the evaporator 34 when cooling is not necessary for the passenger compartment.
The refrigerant loop 18 may be coupled with, the coolant loop 16 via the liquid-to-liquid heat exchanger 20. Because the liquid-to-liquid heat exchanger 20 allows refrigerant passing through the heat exchanger to absorb heat from the coolant loop, the liquid-to-liquid heat exchanger 20 enables the coolant loop 16 to use the cooling capabilities of the refrigerant loop 18 to cool both the high voltage power source 12 and the HVE 14.
A valve 38 coupled with the liquid-to-liquid heat exchanger 20 and plumbed into the refrigerant loop 18 may control a variable amount of refrigerant to pass through the liquid-to-liquid heat exchanger. The valve 38 may vary the amount of refrigerant passing through the liquid-to-liquid heat exchanger 20 based upon the amount of cooling needed to cool the high voltage power source 12 and/or the HVE 14. The valve 38 may be responsive to one or more temperature signals, such as from a temperature sensor, to vary the amount of refrigerant, passing through the liquid-to-liquid heat exchanger 20. The valve 38 may be a thermal expansion-valve, a bi-metal strip valve, a solenoid-valve, or the like. The valve may also cut off the flow of refrigerant through the liquid-to-liquid heat exchanger 20 when cooling is unnecessary for the high voltage power source 12 and the HVE 14. In one implementation, the valve 38 is a thermal expansion valve having a shutdown mode to close the valve and cut off the flow of refrigerant through the liquid-to-liquid heat exchanger. Alternatively, the valve 38 may be coupled with an optional three-way valve to provide a cutoff for the flow of refrigerant to the liquid-to-liquid heat exchanger 20. The valve 38 may also utilize one or more temperature sensors for measuring the temperature of the coolant in the coolant loop 16, the high voltage power source 12, the HVE 14, or a combination thereof when regulating the flow of the refrigerant.
Valves 50, 52 coupled in the front evaporator loop 40 and the rear evaporator loop 44 may provide full flow-through, partial flow-through, or no flow-through of the refrigerant through each of the loops. The valves 50, 52 for the from evaporator loop 40 and the rear evaporator loop 44 may include three-way valves, proportioning valves, and the like. In one implementation, the valves 50, 52 may be thermal expansion valves including a shutdown mode. The shutdown mode allows the thermal expansion valve to prevent refrigerant from flowing through the loops without the use of a separate three-way valve. The thermal expansion valves 50, 52 also enable the front evaporator 42 and the rear evaporator 46 to receive an amount of refrigerant needed based upon the temperature of the front and rear of the passenger compartment cooled by the front evaporator 42 and rear evaporator 46.
Several loops have also been added to the coolant circuit in
Similar to the power source bypass loop 60,
Another optional feature shown in
In one implementation, the proportioning valve 76 may cut off the flow of coolant through one of the heat exchangers and allow the coolant to flow through the other heat exchanger. For example, if the ambient air temperature is below a particular threshold, all of the coolant may be directed to the ambient air heat exchanger 72 and all coolant flow may be cut off to the liquid-to-liquid heat exchanger 20. In this case, the threshold must be set at a temperature sufficiently low so that the ambient air heat exchanger 72 is able to transfer enough heat from the coolant to the ambient air to maintain the desired operating temperatures of the high voltage power source 12 and the HVE 14. Moreover, in the case where all coolant flows through the ambient air loop 74, valve 38 (connecting the liquid-to-liquid heat exchanger 20 with the refrigerant loop 18) may be placed in shutdown mode to prevent refrigerant from flowing through the liquid-to-liquid heat exchanger 20 when the refrigerant is not required to transfer heat from the coolant. For example, the shutdown mode of valve 38 may prevent refrigerant from flowing through the liquid-to-liquid heat exchanger 20 in tire refrigerant loop 18 when no coolant is flowing through the liquid-to-liquid heat exchanger in the coolant circuit 16. Moreover, when all coolant flows through the ambient air loop 74, the refrigerant loop 18 is not required for cooling the high voltage power source 12 and the HVE 14. Therefore, assuming that the refrigerant loop 18 is not currently being used to cool the passenger compartment, the compressor 30 may be shut off to save several hundred kilowatts of electrical power and/or reduce mechanical drag on the vehicle's engine.
Alternatively, if the ambient air temperature is below one threshold but above a second threshold, the proportioning valve 76 may control the amount of coolant through both the ambient air heat exchanger 72 and the liquid-to-liquid heat exchanger 20 to allow both heat exchangers to absorb heat from the coolant. The valve 76 may adjust the amount of coolant flowing through each of the heat exchangers 20, 72 based upon the amount of heat needed to be absorbed from the coolant and the temperature of the ambient air. In one implementation, the more heat required to be absorbed from the coolant the higher the proportion of coolant may be directed through the liquid-to-liquid heat exchanger 20, assuming that the refrigerant has a higher capacity to absorb heat from the coolant than the ambient air. Likewise, the valves may direct all of the coolant through the liquid-to-liquid heat exchanger 20 and cut off the flow of coolant through the ambient air heat exchanger 72 if the ambient air temperature is too high.
Another feature shown in
Another module introduced in
As can be seen, the thermal management system 10, 10′ is able to control the temperature of the high voltage power source 12 and the HVE 14. Moreover, the thermal management system 10, 10′ incorporates a standard passenger compartment air conditioning refrigerant loop currently found in vehicles with a cooling circuit containing both the high voltage power source and HVE. Thus, the thermal management system ensures that a high voltage battery and/or a fuel cell along with high voltage electronics are able to operate even when high demand is placed on the devices.
While certain preferred embodiments have been shown and described, persons of ordinary skill in this art will readily recognize that the preceding description has been set forth in terms of description rather than limitation, and that various modifications and substitutions can be made without departing from the spirit and scope of the invention. The invention is defined by the following claims.
