Abstract:
An air cycle air conditioning system for treating air contained within a passenger compartment of a vehicle. The system includes a compressor for receiving air from the passenger compartment and compressing the air, thereby producing charged air. Further, an expander is provided selectively coupled to the compressor for expanding the air and cooling the air communicated to the passenger compartment. The system further includes an air-to-air heat exchanger that cools the air received by the compressor-and supplies cooled charged air to the vehicle&#39;s engine.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to air cycle air conditioning systems and to systems that also deliver charged air to an automobile engine.  
         BACKGROUND  
         [0002]    Conventional air conditioning systems for conditioning air within a passenger compartment of a vehicle include a cooling and a heating system. The cooling system is typically a refrigerant based vapor compression system. The system includes a compressor, a condenser, an expansion device, an evaporator and a refrigerant supply. In operation, air in the vehicle passenger compartment is cooled by blowing the air over the evaporator and thereby transferring heat from the air to the refrigerant. The refrigerant is then cycled back to the compressor and compressed, cooled in the condenser, expanded by the expansion device and then routed back to the evaporator to complete the cycle.  
           [0003]    The air heating system is also a closed system, however, it is not pressurized. Typically, liquid coolant from the engine cooling system is pumped to a heat exchanger called a heater core. The vehicle passenger compartment air to be heated is blown over the heater core transferring the heat from the liquid coolant in the heater core to the passenger compartment air.  
           [0004]    Air cycle air conditioning systems are also well known, especially in airplanes. Air cycle air conditioning systems operate based off the compression and expansion of air. For example, an airplane has a ready supply of compressed air from the airplane&#39;s jet engine compressor. The compressed air may be expanded in a cooling turbine to provide chilled air for cooling and pressurization of the airplane&#39;s passenger compartment.  
           [0005]    Therefore, it would be desirable to provide an air cycle air conditioning system for an automobile.  
         SUMMARY  
         [0006]    In an aspect of the present invention, an air cycle air conditioning system for treating air contained within a passenger compartment of a vehicle is provided. The system includes a compressor for receiving air from the passenger compartment and compressing the air, thereby producing charged air. An expander selectively coupled to the compressor for expanding the air, thereby cooling the air communicated to the passenger compartment. The system includes an air-to-air heat exchanger that cools the air received by the compressor and supplies the cooled charged air to the vehicle&#39;s engine as well as to the expander.  
           [0007]    In another aspect of the present invention, the system includes an air-to-air heat exchanger having a water separator for removing a portion of water from the air passing through the heat exchanger.  
           [0008]    In another aspect of the present invention, the system includes a clutch for selectively coupling and decoupling the compressor from the expander.  
           [0009]    In yet another aspect of the present invention, the system includes a valve located between the heat exchanger and the expander for reducing air flow to the expander.  
           [0010]    In still another aspect of the present invention, the system includes a bleed tube that connects an inlet of the expander to an outlet of the expander.  
           [0011]    In still another aspect of the present invention, the expander is a positive displacement expander and a variable displacement expander.  
           [0012]    In yet another aspect of the present invention, the variable displacement expander is a reciprocating type of expander in which a stroke of the expander may be adjusted to vary a displacement of the expander.  
           [0013]    In yet another aspect of the present invention, the variable displacement expander is a screw type expander wherein an inlet point is varied to change a displacement of the expander.  
           [0014]    In still another aspect of the present invention, a method for treating air contained within a passenger compartment of a vehicle using an air cycle air conditioning system is provided. The method includes receiving air from the passenger compartment and compressing the air, thereby producing charged air using a compressor, expanding the air using an expander selectively coupled to the compressor, thereby cooling the air communicated to the passenger compartment, cooling the air received by the compressor, and supplying the cooled charged air to the vehicle&#39;s engine using an air-to-air heat exchanger.  
           [0015]    These and other aspects and advantages of the present invention will become apparent upon reading the following detailed description of the invention in combination with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0016]    [0016]FIG. 1 is a schematic diagram of an air cycle air conditioning system for a vehicle, in accordance with the present invention; and  
         [0017]    [0017]FIG. 2 is a schematic diagram of an air cycle air conditioning system for a vehicle having a bleed line connecting an inlet of expander to an outlet of expander, in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0018]    Referring now to FIG. 1, an air cycle air conditioning system  10  for selectively cooling or heating a passenger compartment of a vehicle is provided, in accordance with the present invention. System  10  includes a compressor  12  coupled to a vehicle engine  14  through a pulley and belt drive arrangement  16 . Compressor  12  is an air cycle compressor and would replace a conventional automotive air conditioning compressor. Further, system  10  includes an expander  18 , an intercooler  20 , a water separator  22 , a fan  24  and a heater core  26 .  
         [0019]    Expander  18  expands the air in system  10  which lowers the temperature of the air, lowers the pressure of the air to sub-atmospheric pressure, and condenses a portion of water vapor contained in the air. Expander  18  is connected to compressor  12  through shafts  28  and  30  which are in turn coupled to a clutch mechanism  32 . Clutch mechanism  32  is an electromagnetic clutch used in prior art A/C systems for engaging and disengaging the A/C compressor. However, the present invention contemplates using any other suitable clutch mechanism for engaging and disengaging expander  18  from compressor  12 . Further, the present invention contemplates other means and arrangements for selectively coupling compressor  12  to expander  18 . For example, a pulley and belt arrangement may be employed where a first pulley is fixedly and rotatably coupled to the compressor  12  and a second pulley is fixedly and rotatably coupled to expander  18  and a belt engages the pulleys to transmit a driving torque therebetween. Additionally, in this pulley and belt arrangement, clutch mechanism  32  could be located within one of the pulleys. In operation, the clutch would be engaged to transmit driving torque from the pulley to an input shaft of the expander and disengaged to remove the driving torque form the expander.  
         [0020]    During selective operation, work done by the expanding air within expander  18  may be directed back to compressor  12  to increase the overall efficiency of system  10 . Alternatively, expander  18  may be decoupled from compressor  12  to prevent the expander from acting like a vacuum pump.  
         [0021]    An air to air heat exchanger or intercooler  20  is provided in communication with compressor  12  for lowering the temperature of hot compressed air exiting compressor  12 . Typically, intercooler  20  includes a water separator for removing water condensing in the intercooler. At an exit of intercooler  20  a portion of the cold and charged air is thereafter provided to engine  14 . Thus, system  10  of the present invention provides supercharging of engine  14 . Intercooler  20  exchanges heat contained in the pressurized air with the ambient air. Thus, cold air is received by expander  18  and the air is expanded to a point or the temperature may drop below freezing.  
         [0022]    Water separator  22  is provided in communication with expander  18  therefore further eliminating water from the system. Cold air from expander  18  may then be mixed with outside air by an air mixer  34  before reaching the vehicle&#39;s passenger compartment  36 . Air is then re-circulated and may be mixed with outside air by another air mixer  38  before being received by compressor  12  of system  10 .  
         [0023]    Clutch  32  operates to decouple compressor  12  from expander  18  during selected operating conditions. This is a critical feature in a positive displacement system such as the present invention. The flow rate of the compressor  12  is defined largely by the speed of the compressor. The flow rate of the engine is a function of the intake air boost pressure (supplied by intercooler  20 ) and the engine speed. To balance the mass flow rate, the inlet pressure to the expander must be reduced. Disadvantageously, the flow through the expander is actually heated. Unchecked the temperature of the air exiting the expander rises to an unacceptable condition for the vehicle occupants.  
         [0024]    In an embodiment of the present invention a method for balancing the mass flow rate in system  10  is provided. The method of the instant embodiment contemplates deactivating the expansion process by decoupling expander  18  from compressor  12 . Expander  18  may be decoupled from compressor  12 , for example, by controlling clutch  32 . That is, by causing clutch  32  to disengage.  
         [0025]    In another embodiment of the invention, a method for balancing the mass flow rate is provided. The inlet pressure to the expander is reduced by controlling valve  40 . More specifically, the method of the present invention specifies closing valve  40  to balance the mass flow rate in system  10 . Thus, the work of expansion is eliminated.  
         [0026]    In yet another embodiment of the present invention, an alternate method for balancing the mass flow rate in system  10  and avoiding the potential heat build up in the expander  18  is to close valve  40  and deactivate the expansion process. The in-built positive displacement process can only occur if the working volume is completely contained. Thus, as shown in FIG. 2, the expansion process may be deactivated by allowing atmospheric air to bleed back to the expander inlet and the to the expansion chamber itself. In the present embodiment, the atmospheric air is bleed back to the expander inlet  52  and the to the expansion chamber by a bleed line  50 . Although, the air in system  10  is likely to heat up, due to the inefficiencies of the compressor, the air will be sufficiently lower so that high heat will not be generated during average engine boosting periods. Advantageously, a relatively smooth transition for the air flow into the cabin is provided by the method of the present invention, as compared with the instantaneous effect of activating clutch  32 .  
         [0027]    In still another embodiment of the present invention, an alternate embodiment of a method for balancing the mass flow rate in system  10  and avoiding the potential heat build up in the expander  18  is provided. The method of the instant embodiment includes varying the capacity of the expander. In a reciprocating type expander, varying the capacity is most effectively achieved by varying the stroke. In a screw type of expander, varying the capacity is most effectively achieved by changing the inlet point of the variable pitch expander. However, care must be taken to keep the in-built expansion ratio at the appropriate level. In the case of a screw type expander the inlet point as well as the outlet point would need to be controlled.  
         [0028]    The present invention has many advantages and benefits over the prior art. For example, the present invention provides an air cycle air conditioning system that also serves as an engine boosting mechanism and further provides a mechanism whereby the flow capacity of the expander may be reduced. Moreover the present invention provides a simple to control and simple to implement clutch mechanism to control the flow capacity of the expander. In other embodiments of the present invention flow valves are activated to balance the mass air flow in system  10  and avoid the potential heat build up in the expander.  
         [0029]    As any person skilled in the art of air cycle air conditioning systems and to systems that also delivery charged air to an automobile engine will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.