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'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.