Compressor modulation delay valve for variable capacity compressor

In a control arrangement for an automotive air conditioning system including a variable capacity compressor, a condenser, evaporator and fluid conduit means connecting said compressor, condenser and evaporator in a refrigerant circuit, a housing for said compressor including refrigerant gas suction and discharge chambers formed therein, hydraulically operated modulating means for varying the pumping capacity of said compressor between minimum and maximum, pump means for continuously supplying hydraulic control fluid at a predetermined high pressure to said modulating means, a pressure operated hydraulic control valve assembly formed in said housing controlling said compressor modulating means including a pressure control cell and movable operator means, passage means in said housing adapted to communicate system pressure in said suction chamber to said control cell, a pressure responsive element in said control cell operative at a cell predetermined control pressure for moving said operator means from a closed to an open position when the system pressure in said suction chamber is less than said cell predetermined control pressure, thereby permitting the flow of hydraulic control fluid to said modulating means to reduce the pumping capacity of said compressor, the improvement comprising;

• a modulation delay valve associated with said control arrangement for delaying the movement of said movable operator from its closed position to its open position to prevent premature reduction of pumping capacity of said compressor, said modulation delay valve including a bore in said housing with three spaced-apart ports formed therein, the first one of said ports being an inlet port connected to said discharge chamber, the second one of said ports being an inlet port connected to said suction chamber, and the third one of said ports being an outlet port connected to said pressure control cell, a valve element reciprocally mounted in said bore for opening and closing communication between said second and third ports, means in said bore on one side of said valve element forming a discharge pressure cavity at one end of said bore connected to said first inlet port and a suction pressure cavity at the opposite end of said bore connected to said second inlet port and adapted by movement of said valve element for communication with said third outlet port, and resilient means exerting a force on said valve element in one direction opposing the force exerted by refrigerant gas in said discharge pressure cavity when said pump is operating, the compressed gas in said discharge pressure cavity when said compressor is operating at maximum pump capacity being above a predetermined reference pressure whereby to exert a force on said valve element in the opposite direction causing said valve element to overcome said resilient means closing communication between said second and third ports and trapping refrigerant gas within said pressure control cell at a pressure greater than said predetermined cell control pressure, thereby keeping said movable operator means closed so as to cause said compressor to continue to operate at its maximum pumping capacity, and whereby upon the compressor discharge chamber pressure falling below said reference pressure the delay valve discharge cavity pressure correspondingly falls, allowing said delay valve resilient means to move said valve element in said one direction opening communication between said second and third ports, thereby connecting said pressure control cell to said compressor suction chamber to modulate the capacity of said compressor while obviating premature reduction of maximum pumping capacity of said compressor by said control valve assembly.