Abstract:
A vehicle heating and cooling system having a first coolant loop selectively connecting an engine cooling system with a heater core or a first coolant/refrigerant heat exchanger, a second coolant loop connecting a second coolant/refrigerant heat exchanger and the heater core to warm a passenger compartment of the vehicle. The system also includes a refrigerant loop that provides for conventional cooling of the passenger compartment of the vehicle, as well as operating as a heat pump, together with the coolant loops, to provide heat to the vehicle passenger compartment.

Description:
BACKGROUND OF INVENTION 
     The present invention relates to heating, ventilation and air conditioning systems for vehicles, and in particular to such systems having dual modes for providing heat to passenger compartments of the vehicles. 
     In a conventional automotive vehicle employing an internal combustion engine, the heating of the passenger compartment is accomplished by running engine coolant, typically a mix of water and glycol (antifreeze), through a heater core in the passenger compartment, and then blowing air over the heater core and onto the passengers. The drawback with this is that the heater core will not provide heat until the engine has caused the coolant to warm up. For most conventional engines, this time to warm up the coolant is sufficiently short to satisfy the vehicle passengers. 
     Now, however, newer engines and powertrain arrangements are being developed where the engine does not produce as much excess heat for the coolant to absorb. Some examples are a direct injection engine and a hybrid (engine/motor) powertrain. For these types of powertrains, the temperature of the coolant can take a very long time to rise to a level where it will allow for adequate heating of the passenger compartment when using a conventional heating system. 
     Most automotive vehicles today also include an air conditioning system for cooling the air in the passenger compartment. The air conditioning system can begin to operate almost as soon as the vehicle is started. Some, then, have recognized that the components of the air conditioning system can be employed to operate in a heat pump mode, and so the conventional coolant based heating system is replace with heat from the heat pump operation. But these systems become less and less efficient for heating as the ambient air temperature becomes colder. Consequently, they have not proven efficient enough to provide an adequate heating function to replace the current type of heating system. 
     Thus, it is desirable to have a vehicle heating and cooling system that overcomes the drawbacks of conventional vehicle heating, and heat pump systems in order to warm a vehicle passenger compartment more quickly. 
     SUMMARY OF INVENTION 
     In its embodiments, the present invention contemplates a heating and cooling system for a vehicle having an engine and a passenger compartment. The heating and cooling system includes a first coolant loop having a coolant outlet line and a coolant inlet line adapted to couple to the engine, a heater core, a first heat exchanger, and a coolant valve for selectively directing flow of a coolant from the coolant outlet line to the coolant inlet line through one of the heater core and the first heat exchanger. The system also includes a second coolant loop having a pump for selectively circulating the coolant through a first coolant/refrigerant heat exchanger, the heater core, and back to the pump. There is also a refrigerant loop having a compressor with an inlet and an outlet, a first refrigerant valve for selectively directing the flow of a refrigerant from the compressor outlet to one of a condenser and the first coolant/refrigerant heat exchanger, a refrigerant passage for directing the flow of the refrigerant through an evaporator, and a refrigerant line for returning the refrigerant to the compressor inlet. 
     The present invention further contemplates a method of providing heating and cooling to a passenger compartment of a vehicle having an engine, the method comprising the steps of: selectively circulating a coolant from the engine, through one of a heater core located in the passenger compartment and a first coolant/refrigerant heat exchanger, and back to the engine; selectively circulating the coolant from a pump, through a second coolant/refrigerant heat exchanger, and back to the pump; selectively circulating a refrigerant from a compressor and back to the compressor through one of a first refrigerant path, having a condenser, and evaporator, and an expansion valve between the condenser and the evaporator, and a second refrigerant path, having the second coolant/refrigerant heat exchanger, the first coolant/refrigerant heat exchanger, and the expansion valve between the second coolant/refrigerant heat exchanger and the first coolant/refrigerant heat exchanger. 
     An advantage of the present invention is that the vehicle heating and cooling system can operate in a conventional air conditioning mode, with cooling efficiencies essentially as good as with a conventional air conditioning system, and yet still operate in a heat pump mode to provide supplemental heating when the conventional heating system is not up to an efficient operating temperature. 
     Another advantage of the present invention is that, in the heat pump mode of operation, the coolant absorbs heat from the refrigerant in the heat pump system, which is more efficient than absorbing heat from the ambient air. 
     A further advantage of the present invention is that the heating and cooling system can operate in all three modes with a minimum of heat exchangers, valves and other system components, thus minimizing the cost of the system. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a schematic diagram of a portion of a heating and cooling system that is located in a passenger compartment of a vehicle, in accordance with the present invention; 
     FIG. 2 is a schematic diagram of the vehicle heating and cooling system, illustrating the direction of fluid flow during a cooling cycle, in accordance with the present invention; and 
     FIG. 3 is a schematic diagram similar to FIG. 2, but illustrating the direction of fluid flow during a heat pump cycle. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1-3 illustrate a vehicle heating and cooling system  20  that is partially located behind an instrument panel  22  in a vehicle passenger compartment  24 , and partially in a vehicle engine compartment  26 . The system  20  includes a blower  30 , driven by a motor  29 , and mounted in an air passage  31  in the passenger compartment  24 . The blower  30  is located adjacent to an external air inlet  32 , an internal air inlet  34 , and an air mixing damper  36  that can be moved to partially or fully block off the external air inlet  32  or the internal air inlet  34  from the air passage  31 . 
     Also located in the air passage  31 , near the blower  30 , is an evaporator  38 . The evaporator  38  includes a pair of refrigerant lines  40  and  42  for directing refrigerant into and out of the it. The refrigerant in the lines  40 ,  42  may be any type of refrigerant found in air conditioning or refrigeration systems, such as, for example, R134a. A heater core  44  is located in the air passage  31 , as well as a second air mixing damper  46 , which can be moved to allow air flow through the heater core  44 , block air flow from the heater core  44 , or allow for a partial flow. An engine coolant intake line  43  and an engine coolant outlet line  45  connect to the heater core  44 . The engine coolant in these lines  43 ,  45  may be any type of coolant found in engine cooling systems, such as, for example, a mixture of water and glycol. The heater core  44 , then, is an air/coolant heat exchanger. 
     The air passage  31  also includes three air outlets  48 ,  50  and  52 , with three corresponding dampers  54 ,  56  and  58  that can be adjusted to vary the flow through each of the air outlets  48 ,  50 ,  52 . These air outlets may be, for example, an outlet  48  directed toward a vehicle windshield (not shown) for defrosting, an outlet  50  directed toward the bodies of vehicle occupants (not shown), and an outlet  52  directed toward the feet of vehicle occupants. 
     The heating and cooling system  20  includes three main loops—there is a refrigerant loop  60 , a first coolant loop  62 , and a second coolant loop  61 . The first coolant loop  62  includes an outlet line  63  coming from an engine  64  and leading to a coolant three-way valve  65 . The three-way valve  65  also connects to the coolant intake line  43  of the heater core  44 , and to an intake line  66  to coolant passages in a first coolant/refrigerant heat exchanger  67 . The coolant outlet line  45  from the heater core  44  connects to a coolant three-way valve  94 , which then connects to a coolant outlet line  68  from the heat exchanger  67 . The coolant line  68  connects to a coolant inlet line  69  running back to the engine  64 . The coolant is pumped through the coolant loop  62  with a conventional water pump (not shown), which is part of a conventional engine cooling system (not shown) including a radiator, fan, etc. 
     The second coolant loop  61  includes a second coolant/refrigerant heat exchanger  70  which connects to a coolant line  49 , which, in turn, connects to the coolant intake line  43 . The second heat exchanger  70  also connects to a coolant line  71 . The other end of the coolant line.  71  connects to the outlet of a water pump  92 . The inlet to the water pump  92  connects a coolant line  47 , which connects to coolant line  45  via three-way valve  94 . The water pump  92  can be electrically or mechanically powered, and only needs to operate when the heating and cooling system  20  is in a heat pump mode, as will be discussed in more detail below. 
     The refrigerant loop  60  includes a compressor  72 . The compressor  72  may be any one of several different types (for example, piston, swash plate, scroll), it may be driven by the engine  64  or by a separate motor, and it may have a clutch to disconnect it from the engine or motor or-it may be a variable capacity type, as may be desired depending upon the particular vehicle and engine. The compressor  72  connects to a compressor outlet line- 73  which leads to a first refrigerant three-way valve  74 . The three-way valve  74  also connects to a condenser inlet line  75  that leads to a condenser  76 , and to a refrigerant line  77  that leads to refrigerant tubes in the second coolant/refrigerant heat exchanger  70 . The second coolant/refrigerant heat exchanger  70  also connects to a refrigerant outlet line  87 , which connects to a refrigerant three-way valve  95 . The three-way valve  95  also connects to the inlet of a receiver/drier  79  via refrigerant line  99 . The condenser connects to a refrigerant outlet line  78 , which connects to three-way valve  95 . The receiver/drier  79  connects to an expansion valve  80 , via a refrigerant line  81 , and the expansion valve  80 , in turn, connects to a second refrigerant three-way valve  83 , via refrigerant line  82 . The second three-way valve  83  can direct refrigerant to the evaporator  38 , via refrigerant line  40 , or to the first coolant/refrigerant heat exchanger  67 , via refrigerant line  59 . Refrigerant line  91  connects the outlet of the first coolant/refrigerant heat exchanger  67  to a three-way valve  96 . Three-way valve  96  connects to the inlet to the compressor  72  via refrigerant line  84 . The refrigerant line  42  also connects the outlet from the evaporator  38  to the three-way valve  96 . 
     The operation of the first embodiment, illustrated in FIGS. 1-3, will now be discussed. There are three different modes of operation for the heating and cooling system  20 . The first mode is the cooling (air conditioning) mode. The flow of the refrigerant and the coolant for this mode is illustrated by the arrows in FIG.  2 . 
     The refrigerant is compressed by the compressor  72  and flows into the first refrigerant three-way valve  74 , which directs it into the condenser  76  via condenser inlet line  75 . The three-way valve  74  is closed to line  77 . The action of the compressor  72  in compressing the refrigerant causes the refrigerant temperature to rise. Ambient air flowing through the condenser  76  will absorb heat from the refrigerant. The refrigerant will then flow through the condenser outlet line  78 , through three-way valve  95 , and through the receiver/drier  79 . The refrigerant then flows, via refrigerant line  81 , into the expansion valve  80 . The expansion valve  80  will regulate the pressure of the refrigerant, and thus, the temperature of the refrigerant leaving the expansion valve  80 . This refrigerant will pass through outlet line  82 , the second refrigerant three-way valve  83 , through the refrigerant line  40  and into the evaporator  38 . The second three-way valve  83  will be closed to refrigerant line  59 . The blower  30  forces air across the evaporator  38 , which will absorb heat from the air before the air flows into the passenger compartment  24 . The refrigerant will flow out of the evaporator  38 , via refrigerant lines  42  and  84 , and back to the compressor  72 . Three-way valve  96  will block refrigerant flow into line  91 . So in the cooling mode, the system  20  operates essentially the same as with a conventional vehicle air conditioning system. 
     In the first mode of operation, the engine coolant in the first coolant loop  62  flows from the engine  64 , through the outlet line  63 , through the coolant three-way valve  65 , through coolant intake line  43  and into the heater core  44 . The coolant three-way valve  65  is closed to line  66 . While the blower  30  will create air flow within the air passage  31 , the damper  46  is closed and so the air entering the passenger compartment  24  will not pass over the heater core  44 . Thus, the coolant will have only a vary negligible effect on the temperature of the air flowing into the passenger compartment  24 . From the heater core  44 , the coolant flows through coolant outlet line  45 , through three-way valve  94 , through a portion of coolant line  68 , through coolant engine inlet line  69 , and back to the engine. The coolant flow within the engine  64  and radiator (not shown) will not be discussed since it is conventional. In the second coolant loop  61 , the water pump  92  is preferably off, and so no coolant will flow. 
     The second mode of operation is the heat pump mode. The direction of flow of refrigerant and coolant for this mode is illustrated in FIG.  3 . This mode is employed when the engine and coolant is still cool, but the passenger compartment  24  needs to be warmed. In this mode, the refrigerant flows through the compressor  72 , where it is compressed, and to three-way valve  74  via compressor outlet line  73 . The three-way valve  74  directs the refrigerant into refrigerant line  77 , and blocks the flow into condenser inlet line  75 . The compressed refrigerant then flows into the second coolant/refrigerant heat exchanger  70 . The refrigerant, being at a higher temperature than the coolant in the second coolant loop  61 , will transfer heat to the coolant. The second coolant/refrigerant heat exchanger  70 , in effect, acts as a condenser. The refrigerant then flows through three-way valve  95 , through the receiver/drier  79  and the expansion valve  80  before it passes through the second refrigerant three-way valve  83 . The three-way valve  95  is closed to line  78 . The second three-way valve  83  directs the refrigerant into the first coolant/refrigerant heat exchanger  67 , but blocks the flow to the evaporator  38 . Since the refrigerant will now generally be at a lower temperature than the coolant in the first coolant loop  62 , it will absorb heat before leaving the first coolant/refrigerant heat exchanger  67 , flowing through three-way valve  96 , and back to the compressor  72 . The three-way valve  96  is closed to line  42 . 
     In this heat pump mode of operation, the coolant flows in the first coolant loop  62  from the engine  64 , through the coolant outlet line  63  and into the coolant three-way valve  65 . The three-way valve  65  directs the flow of coolant into heat exchanger intake line  66 , but blocks it from flowing into coolant intake line  43 . The coolant then flows through the coolant/refrigerant heat exchanger  67 . As mentioned above, as the coolant flows through this heat exchanger it will give off heat to the refrigerant. The coolant then flows through coolant line  68 , through the coolant line  69  and back to the engine. 
     In this heat pump mode of operation, coolant also flows in the second coolant loop  61 . The water pump  92  is activated and pumps coolant through coolant line  71  and into the second coolant/refrigerant heat exchanger  70 . As mentioned above, since the refrigerant is at a higher temperature, the coolant will absorb heat from the refrigerant. This coolant, now warmed, then flows through coolant line  49 , through coolant line  43 , and into the heater core  44  in the passenger compartment  24 . The blower  30  forces air through the heater core  44 , warming the air before it flows into the passenger compartment  24 . So in this heat pump mode, the heater core  44  gives off the heat absorbed by the coolant from the refrigerant in the second, coolant/refrigerant heat exchanger  70 . 
     The third mode of operation is a conventional heating mode. This mode occurs when the coolant in the engine is hot and it is desired to add heat to the passenger compartment  24 . In this mode, the compressor  72  is not operating, so the refrigerant is not flowing. Also, the water pump  92  is off, so the coolant in the second coolant loop  61  is not flowing. The coolant in the first coolant loop  62  flows the same as in the cooling mode, as discussed above. But the damper  46  is now open, so air flowing through the passage  31  will pass through the heater core  44  and be warmed before it enters the passenger compartment. 
     While certain embodiments of the present invention have 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.