Slant plate type compressor with variable displacement mechanism

Claim 1

In a slant plate type 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 the 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 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 valve means for controlling the closing and opening of said passageway to vary the capacity of the compressor by adjusting the incline angle, the improvement comprising said valve means including a valve to directly close and open said passageway, first valve control means for controlling the movement of said valve to open and close said passageway in response to changes in refrigerant pressure in said compressor, said first valve control means comprising a bellows element for applying a biasing force in a direction toward the closed position of said valve, and second valve control means coupled to said first valve control means for changing the operating point of said first valve control means in response to an external condition, said second valve control means including means for applying an adjustable negative pressure force to said bellows element to adjustably reduce the biasing force of said first valve control means, said means for applying the negative pressure force including a conduit for coupling to a source of variable negative pressure.