Abstract:
An integrated cooling system having two separate evaporator coils is provided. Each evaporator coil has its own shutoff, thereby allowing for individual control over the cooling of each of two vehicle spaces. The evaporator coils may be disposed within the vehicle to cool the passenger compartment and a battery compartment, respectively. The separate control afforded by the cooling system provides the flexibility of shutting off cooling to the vehicle passenger compartment for the comfort of the vehicle occupants, while still providing cooling to the battery, as needed. The cooling system includes a number of control features which provide for automatically shutting off cooling to one or more of the evaporator coils based on parameters such as air temperature and refrigerant pressure.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a vehicle cooling system, and more particularly, a system for separately cooling more than one vehicle space.  
         [0003]     2. Background Art  
         [0004]     There are a variety of vehicles today which utilize electricity, and in particular an electric motor, to at least assist in powering the vehicle. For example, there are electric vehicles, which are powered exclusively by an electric motor; hybrid electric vehicles (HEV), which may be selectively powered by an internal combustion engine or an electric motor; and fuel cell vehicles, or hybrid fuel cell vehicles, just to name a few. The electric motor used in such vehicles may have an electrical power source such as a fuel cell or a battery.  
         [0005]     In the case of a battery used to provide power to an electric motor to drive a vehicle, the temperature of the battery can increase significantly when the motor is used for extended periods of time. The increase in battery temperature may be compounded when the battery is confined to a relatively small, enclosed space. If the increase in battery temperature is left unchecked, the battery life may be reduced. Thus, it is desirable to provide a system for cooling a battery, or batteries, in a vehicle to keep the battery temperature low enough that the battery life is not reduced.  
         [0006]     In addition to the added requirement of keeping the battery cool in a hybrid electric vehicle, there is also a need to provide a cooling system for the vehicle passenger compartment, just as in a conventional vehicle. Although separate systems may be used to provide cool air to the battery and the vehicle passenger compartment, an integrated, or at least partially integrated, cooling system can be used. One attempt to provide an integrated cooling system for both a battery and a vehicle passenger compartment, is described in U.S. Pat. No. 6,138,466 issued to Lake et al. on Oct. 31, 2000.  
         [0007]     Lake et al. discusses the use of a cooling system having an inside heat exchanger for adjusting the temperature of air flowing into the passenger compartment, and a zone-control heat exchanger which may be used for cooling a battery assembly. Lake et al. does not describe a mechanism for detecting the temperature of the air at each heat exchanger, and automatically stopping the flow of cooling fluid to a heat exchanger when the detected temperature falls below a predetermined temperature. Lake et al. does describe disabling operation of the inside heat exchanger when the ambient air temperature outside the vehicle is low, but this does not account for local temperatures near the heat exchanger, nor does it protect the zone-control heat exchanger from icing. In addition, Lake et al. does not describe a mechanism for providing fresh air directly across the battery. This may lead to unnecessary energy consumption, when the temperature of the ambient air outside the vehicle is low enough to cool the battery without the use of a heat exchanger.  
         [0008]     Thus, a need still exists for a vehicle cooling system that at least partially integrates passenger compartment cooling and vehicle battery cooling, and includes a mechanism for automatically shutting off the flow of coolant to an individual heat exchanger when the temperature of that heat exchanger becomes too low, thereby helping to prevent icing on the heat exchanger. In addition, there exists a need for a vehicle cooling system that at least partially integrates passenger compartment cooling and vehicle battery cooling, and provides a fresh air intake directly connected to the vehicle battery, so that at least a portion of the vehicle cooling system can be shut down when the temperature of the ambient air outside the vehicle is low enough to adequately cool the battery without the use of the cooling system.  
       SUMMARY OF INVENTION  
       [0009]     Therefore, a cooling system for a vehicle having first and second spaces to be cooled is provided. The cooling system includes first and second heat exchangers for respectively cooling air flowing into the first and second vehicle spaces. A conduit system is in communication with the first and second heat exchangers, and is configured to provide a fluid flow path to and from the heat exchangers. A pump is selectively operable for moving fluid through the conduit system, and first and second valves are in communication with the conduit system. A first sensor is configured to measure a first temperature, and to output a signal related to the first temperature. The first temperature is indicative of the temperature of air exiting the first heat exchanger. A second sensor is configured to measure a second temperature, and to output a signal related to the second temperature. The second temperature is indicative of the temperature of air exiting the second heat exchanger. A controller is in communication with the first and second sensors, and with at least one of the pump and the first and second valves. The controller is configured to effect a stoppage of fluid flow to the first heat exchanger when the first temperature is below a predetermined temperature. The controller is also configured to effect a stoppage of fluid flow to the second heat exchanger when the second temperature is below the predetermined temperature.  
         [0010]     The invention also provides a cooling system as described above, further including a duct system having at least a portion of the second heat exchanger disposed therein. The duct system is configured to selectively provide fluid communication between a battery and an ambient environment outside the vehicle.  
         [0011]     The invention further provides a cooling system for a vehicle having first and second spaces to be cooled. The cooling system includes first and second heat exchangers for respectively cooling air flowing into the first and second vehicle spaces. A conduit system is in communication with the first and second heat exchangers, and is configured to provide a fluid flow path to and from the heat exchangers. A pump is selectively operable for moving fluid through the conduit system; the pump includes an inlet and an outlet. First and second valves are in communication with the conduit system. A switch is disposed between one of the heat exchangers and the pump inlet. The switch is configured to determine a fluid pressure in the conduit system, and to effect shutdown of the pump when the determined fluid pressure is below a predetermined pressure.  
         [0012]     The invention also provides a vehicle having a passenger compartment and a battery. The vehicle includes a cooling system having first and second heat exchangers. The first heat exchanger is disposed in relation to the passenger compartment for selectively cooling air flowing into the passenger compartment. The second heat exchanger is disposed in relation to the battery for selectively cooling air flowing across the battery. A conduit system is in communication with the first and second heat exchangers, and is configured to provide a fluid flow path to and from the heat exchangers. First and second valves communicate with the conduit system. The first valve is configured to selectively inhibit fluid flow to the first heat exchanger. The second valve is configured to selectively inhibit fluid flow to the second heat exchanger. The cooling system also has first and second sensors. The first sensor is configured to measure a first temperature indicative of the temperature of air exiting of the first heat exchanger; the first sensor is also configured to output a signal related to the first temperature. The second sensor is configured to measure a second temperature indicative of the temperature of air exiting the second heat exchanger, and is further configured to output a signal related to the second temperature. A controller is in communication with the first and second sensors, and at least one of the pump and the first and second valves. The controller is configured to effect a stoppage of fluid to the first heat exchanger when the first temperature is below a predetermined temperature. The controller is further configured to effect a stoppage of fluid flow to the second heat exchanger when the second temperature is below the predetermined temperature. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]      FIG. 1  is a schematic representation of a cooling system in accordance with the present invention;  
         [0014]      FIG. 2  is a graphical illustration of the zones of operation of a cooling system that does not have a separate shutoff valve for each of two evaporator coils;  
         [0015]      FIG. 3  is a graphical illustration of the zones of operation of a cooling system in accordance with the present invention;  
         [0016]      FIG. 4  is a partial fragmentary perspective view of a portion of the cooling system shown in  FIG. 1 ; and  
         [0017]      FIG. 5  is a perspective view of a portion of a vehicle and a portion of the cooling system shown in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0018]      FIG. 1  shows a cooling system  10  for a vehicle having a first space to be cooled, such as a passenger compartment  12 , and a second space to be cooled, such as a battery compartment  14 . Inside the battery compartment  14  is a traction battery  16  used to power a motor (not shown) used to propel the vehicle. Of course, a cooling system, such as the cooling system  10 , can be used to cool vehicle spaces other than a passenger compartment and a battery compartment.  
         [0019]     The cooling system  10  includes a first heat exchanger, or front evaporator coil  18 , which is disposed in relation to the passenger compartment  12  for selectively cooling the air flowing into the passenger compartment  12 . The cooling system  10  also includes a second heat exchanger, or rear evaporator coil  20 . The rear evaporator coil  20  is disposed in relation to the battery compartment  14  for selectively cooling the air flowing into the battery compartment  14  and across the battery  16 . A first fan  22  cooperates with a front duct system  24  for moving air through the front evaporator coil  18  and into the passenger compartment  12 . A second fan  26  cooperates with a rear duct system  28  for moving air through the rear evaporator coil  20 , into the battery compartment  14 , and across the battery  16 . As seen in  FIG. 1 , the rear evaporator coil  20  is disposed within the rear duct system  28 .  
         [0020]     A conduit system  30  is in communication with the front and rear evaporator coils  18 ,  20 , and is configured to provide a fluid flow path to and from the evaporator coils  18 ,  20 . In particular, a pump, or compressor  32 , is selectively operable to move a fluid such as a refrigerant through the conduit system  30 . The compressor  32  includes an inlet  34  and an outlet  36 .  
         [0021]     A first valve  38  communicates with the conduit system  30 , and is configured to selectively inhibit the flow of refrigerant through the front evaporator coil  18 . Similarly, a second valve  40  communicates with the conduit system  30 , and is configured to selectively inhibit the flow of refrigerant to the rear evaporator coil  20 . Because separate valves  38 ,  40  are used to control the flow of refrigerant to the front and rear evaporator coils  18 ,  20 , the cooling system  10  can be used to provide cooling to a single vehicle space. That is, if cooling is desired in the passenger compartment only, the second valve  40  can be closed such that refrigerant does not flow through the rear evaporator coil  20 . Similarly, if the battery  16  needs to be cooled, but the passenger compartment  12  does not, the first valve  38  can be closed, such that refrigerant flows through only the rear evaporator coil  20 .  
         [0022]     Providing separate valves  38 ,  40  for the front and rear evaporator coils  18 ,  20  provides an improvement over vehicle cooling systems that do not have separate shutoff valves for each evaporator coil. Without a separate shutoff valve for each evaporator coil, refrigerant will flow through both evaporator coils even if only one of the two vehicle spaces is calling for cooling. This may lead to undesirably cool air flowing into the vehicle space that did not request cooling.  
         [0023]      FIGS. 2 and 3  graphically illustrate an advantage of having separate shutoff valves, such as the valves  38 ,  40  in the cooling system  10 . When separate evaporator coils are used in a single cooling system, there are four possible zones of operation: 1) both the front and rear evaporator coils are on; 2) the front evaporator coil is on, but the rear evaporator coil is off; 3) both the front and rear evaporator coils are off; and 4) the front evaporator coil is off, but the rear evaporator coil is on.  
         [0024]      FIG. 2  illustrates the situation found in vehicles having a cooling system with front and rear evaporator coils which respectively cool front and rear portions of a large passenger compartment. In such a system, where a separate shutoff valve is not provided for the front evaporator coil, priority is given to the front passengers. In zones  1  and  3 , the front and rear passengers are presumably in agreement, since both evaporator coils are either on or off. In zones  2  and  4 , however, the rear passengers have different demands.  
         [0025]     For example,  FIG. 2  shows that the rear evaporator coil is off in zone  2 ; nonetheless, refrigerant will continue to flow through the coil because the front evaporator coil is calling for cooling. Thus, the rear passengers may experience undesirably cool air which results from the lack of a separate shutoff valve to stop the flow of refrigerant to the rear evaporator coil. Similarly, in zone  4  the front evaporator coil is off, which stops the flow of refrigerant through the entire system. Therefore, even though the rear evaporator coil is on, and the rear passengers may desire cool air, no refrigerant flows through the rear evaporator coil. This is not the case for a cooling system, such as the cooling system  10 , which is operational in all four zones, since each evaporator coil has its own shutoff valve—see  FIG. 3 . Thus, the battery compartment  14  can continued to receive cool air even when the passenger compartment  12  does not.  
         [0026]     Returning to  FIG. 1 , it is seen that the cooling system  10  includes a first sensor, or thermistor  42 , which is configured to measure the temperature of the air exiting the front evaporator coil  18 , and to output a signal related to the measured temperature. A second sensor, or thermistor  44 , is configured to measure the temperature of the air exiting the rear evaporator coil  20 , and to output a signal related to the measured temperature. A controller, or powertrain control module (PCM)  46 , is in communication with various components of the cooling system  10 . For example, the PCM  46  is capable of controlling the compressor  32  to start and stop the flow of refrigerant through the conduit system  30 .  
         [0027]     The compressor  32  includes an on/off clutch for starting and stopping the flow of refrigerant through the conduit system  30 . Of course, other types of compressors may be used, for example, a variable displacement compressor without a clutch. Such a compressor would control the flow of fluid through the conduit system  30  by modulating the displacement of the compressor, as needed. Alternatively, a high voltage, integrated electric motor driven compressor could be used.  
         [0028]     The PCM  46  is in communication with the thermistors  42 ,  44  to receive signals related to their respective measured air temperatures. The PCM  46  also communicates with the valves  38 ,  40 , such that the PCM  46  can effect a stoppage of refrigerant flow to either evaporator coil  18 ,  20  by closing the appropriate valve  38 ,  40 . Although the PCM  46  is shown in  FIG. 1  as a single controller communicating directly with various elements of the cooling system  10 , other controller configurations may also be used. For example, individual elements of the cooling system  10  such as the compressor  32  and the valves  38 ,  40  may have individual controllers, each of which would then be connected to a central controller, such as the PCM  46 .  
         [0029]     The cooling system  10  also includes a third heat exchanger, or condenser  48 , which communicates with the conduit system  30 , and is disposed between the pump outlet  36  and the front and rear evaporator coils  18 ,  20 . The condenser  48  receives hot, high-pressure vapor refrigerant from the compressor  32 . Fans  50 ,  52  move air across the condenser  48  to cool and condense the refrigerant as it moves from condenser inlet  54  to condenser outlet  56 .  
         [0030]     The cooling system  10  also includes a first throttling device, or orifice tube  58 , and a second throttling device, or thermal expansion valve (TXV)  60 . The orifice tube  58  and the TXV  60  each communicate with the conduit system  30 , and are configured to effect a reduction in pressure of the refrigerant before it reaches the front and rear evaporator coils  18 ,  20 , respectively. A cooling system, such as the cooling system  10 , may have a different configuration of throttling devices—e.g., two orifice tubes or two TXVs.  
         [0031]     A number of considerations may be important when choosing the type of throttling device to use with a cooling system, such as the cooling system  10 . For example, a TXV may be more expensive than an orifice tube; however, use of an orifice tube may require a reservoir, such as an accumulator  62 , which requires additional space. The accumulator  62  communicates with the conduit system  30 , and is configured to temporarily store at least some of the refrigerant flowing in the conduit system  30 . The accumulator  32  separates the liquid refrigerant from the liquid and vapor mixture exiting the front evaporator coil  18 . This helps to ensure that most of the refrigerant reaches the compressor  32  in a gaseous state. The compressor  32  also receives a small amount of liquid from the bottom of the accumulator  62 ; this liquid lubricates the compressor  32 .  
         [0032]     The cooling system  10  also includes two switches  64 ,  66 , each of which is in communication with the PCM  46 . As described below, the switches are pressure sensitive devices. Of course, a cooling system, such as the cooling system  10 , may employ other types of pressure sensitive devices, such as pressure transducers. The first switch  64  is disposed between the compressor outlet  36  and the orifice tube  58 . Thus, it may be referred to as a high pressure switch. Conversely, the switch  66  is disposed between the front evaporator coil  18  and the compressor inlet  34 , and thus, may be referred to as a low pressure switch.  
         [0033]     The high pressure switch  64  is configured to determine the pressure of the refrigerant in a conduit system  30 , and to effect shutdown of the compressor  32  when the refrigerant pressure gets above a predetermined pressure. This helps to ensure that the pressure of the refrigerant in a conduit system  30  will never get high enough to damage any of the components of the cooling system  10 , or to vent refrigerant into the atmosphere. The compressor outlet  36  includes a pressure relief valve (not shown) that allows refrigerant to be released when the pressure reaches a predetermined level.  
         [0034]     The high pressure switch  64  performs a second function, and thus, may be referred to as a dual function switch. In addition to effecting a shutdown of the compressor  32  when the refrigerant pressure gets too high, the high pressure switch  64  also signals the PCM  46  to operate the fans  50 ,  52 . This provides a mechanism to reduce the refrigerant pressure prior to the pressure reaching the level where the compressor  32  is shut down. When the switch  64  detects that the refrigerant pressure needs to be reduced, it will signal the PCM  46  to start the fans  50 ,  52  if they are off, and to increase their speed if they are already running. This provides additional cooling for the refrigerant as it flows through the third heat exchanger  48 , which may effect a pressure reduction so that a shutdown of the compressor  32  is not required.  
         [0035]     Similarly, the low pressure switch  66  is configured to determine the pressure of the refrigerant in the conduit system  30  and to effect a shut down of the compressor  32  when the refrigerant pressure is below a predetermined pressure. This helps to ensure that enough refrigerant is flowing into the compressor  32  to cool and lubricate the internal mechanisms of the compressor  32 . The switches  64 ,  66  are connected to the compressor  32  such that they directly effect shutdown of the compressor  32  when the pressure of the refrigerant and the conduit system  32  gets too high or too low. Alternatively, switches, such as the switches  64 ,  66 , can be configured to communicate with the PCM  46 . In such an embodiment the switches  64 ,  66  would signal the PCM  46  when the refrigerant pressure is too high or too low, and the PCM  46  would effect a shutdown of the compressor  32 .  
         [0036]     As discussed above, the thermistors  42 ,  44  communicate with the PCM  46 , and are configured to provide signals to the PCM  46  indicative of the air temperature exiting the front and rear evaporator coils  18 ,  20 , respectively. The PCM  46  is configured to effect a stoppage of refrigerant flow to the front evaporator coil  18  when the first temperature, as measured by the thermistor  42 , is below a predetermined temperature. Similarly, the PCM  46  is configured to effect a stoppage of refrigerant flow to the rear evaporator coil  20  when the second temperature, as measured by the thermistor  44 , is below the predetermined temperature. This helps to prevent damage to the evaporator coils  18 ,  20 , and helps to ensure that they do not get so cold that ice forms on the coils, thereby reducing the efficiency of the cooling system  10 .  
         [0037]     Similarly, the PCM  46  is configured to effect a stoppage of refrigerant flow to either evaporator coil  18 ,  20  when the cooling of the respective vehicle space is not required. The PCM  46  can effect a stoppage of refrigerant flow in a number of different ways. For example, the PCM  46  can close the valves  38 ,  40  individually, thereby stopping refrigerant flow to only one evaporator coil. The PCM  46  can also shutdown the compressor  32 , thereby stopping refrigerant flow to both evaporator coils  18 ,  20 . Alternatively, the PCM  46  can close either or both valves  38 ,  40 , and simultaneously shutdown the compressor  32 .  
         [0038]     As shown in  FIG. 1 , the rear evaporator coil  20  can be used to provide cool air to a battery, such as the battery  16 . The air flowing through either evaporator coil  18 ,  20  can be fresh air, or recirculated. A number of configurations can be used to provide fresh or recirculated air to a battery compartment, such as the battery compartment  14 . An example of such a system is described in copending U.S. patent application Ser. No. ______, entitled “Cooling System For A Vehicle Battery,” Attorney Docket No. 202-1580, filed on Sep. 12, 2003, and incorporated herein by reference.  
         [0039]      FIG. 4  shows one configuration of how the evaporator coil  20  can be used to provide air to cool the battery  16 . As seen in  FIG. 4 , the rear evaporator coil  20  is disposed within the rear duct system  28 . The rear duct system  28  includes an air intake  68  which communicates with a vehicle air intake  70 . The vehicle air intake  70  is attached to a rear quarter window  72  to provide an inlet for ambient air from outside the vehicle into the duct system  28 . Having a fresh air intake for a battery cooling system, particularly one that is located high-up on a vehicle, may have a number of benefits. Such an air intake is described in copending U.S. patent application Ser. No. ______, entitled “Fresh Air Intake For A Vehicle,” Attorney Docket No. 202-1080, filed on Sep. 12, 2003, and incorporated herein by reference. As seen in  FIG. 4 , the duct system  28  provides an air flow path from outside the vehicle through the evaporator coil  20  to the battery  16 , as indicated by the direction arrow. The duct system  28  also provides an air flow path back from the battery  16 , such that the air may be recirculated through the evaporator coil  20 , or exhausted outside the vehicle through an air extractor  74 .  
         [0040]     As seen in  FIG. 5 , the configuration of the rear evaporator coil  20  and the rear duct system  28  may be conveniently located in a vehicle  76  so as to minimize the amount of space taken from the passenger compartment  12 . For example, a first portion  78  of the rear duct system  28  may be disposed along one side  80  of the vehicle  76 . A second portion  82  of the rear duct system  28  may be disposed beneath a load floor  84  so as to come into close proximity to the battery  16 , while not taking up space in the vehicle passenger compartment  12 .  
         [0041]     While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.