Slant plate type compressor with variable capacity mechanism with improved cooling characteristics

Claim 1

In a slant plate type refrigerant compressor for use in a refrigeration circuit, said compressor including a compressor housing having a central portion, a front end plate at one end and a rear end plate at its other end, said housing having a cylinder block provided with a plurality of cylinders and a crank chamber adjacent said cylinder block, a piston slidably fitted within each of said cylinders, a drive mechanism coupled to said pistons to reciprocate said pistons within said cylinders, said drive mechanism including a drive shaft rotatably supported in said housing, a rotor coupled to said drive shaft and rotatable therewith, and coupling means for drivingly coupling said rotor to said pistons such that the rotary motion of said rotor is converted into reciprocating motion of said pistons, said coupling means including a member having a surface disposed at an incline angle relative to said drive shaft, said incline angle of said member being adjustable in response to changes in the crank chamber pressure to vary the stroke length of said pistons and the capacity of the compressor, said rear end plate having a suction chamber and a discharge chamber, a passageway connected between said crank chamber and said suction chamber, and variable capacity control means for controlling the closing and opening of said passageway to control communication between said suction and said crank chambers to vary the capacity of said compressor by adjusting the incline angle, said variable capacity control means including a valve element to directly open and close said passageway, the improvement comprising: said variable capacity control means further comprising first valve control means for controlling movement of said valve element to open and close said passageway in response to changes of refrigerant pressure in the compressor; and second valve control means coupled to said first valve control means for opening said passageway and operating said compressor at high capacity despite movement of said first valve control means which would otherwise cause said compressor to operate at a lower capacity.