Variable angle wobble plate type compressor which maintains the crankcase pressure at a predetermined value

A variable displacement wobble plate type compressor including a suction chamber for a refrigerant to be compressed, a discharge chamber for a compressed refrigerant, a plurality of cylinder bores in which associated reciprocatory pistons are disposed so as to draw the refrigerant from the suction chamber and then to discharge the refrigerant after compression to the discharge chamber, a closed crankcase for an assembly of wobble and drive plates to drive the reciprocatory pistons and a control means for changing an angle of wobble of the wobble plate in association with a pressure difference between a suction pressure in the suction chamber and a crankcase interior pressure thereby changing a compressor displacement, wherein said control means comprises:

• built-in pressure detecting means for detecting a change in said crankcase interior pressure with respect to a predetermined pressure value including a casing member fitted in a cavity formed in a head in which said suction chamber is defined,
• a bellows member arranged inside said casing so as to define an atmospheric pressure chamber and a valve chamber separated from one another, and
• a spring member accommodated in said bellows member and having a preselected spring constant permitting said bellows member to be collapsed when said crankcase interior pressure introduced into said valve chamber via said passageway means approaches said predetermined pressure value;
• passageway means for providing a fluid communication between said suction chamber and said crankcase interior and;
• a valve mechanism arranged in a portion of said passageway means and having a valve element operable to open said fluid communication between said suction chamber and said crankcase interior in response to a signal from the pressure detecting means indicating a rise in said crankcase interior pressure from the predetermined pressure value and to close said fluid communication in response to a signal indicating a drop in said crankcase interior pressure from the predetermined pressure value, thereby maintaining said crankcase interior at the predetermined pressure value, the predetermined pressure of said crankcase interior working on said pistons behind compression chambers of said cylinder bores to effect a decrease in the angle of wobble of said wobble plate.