Slant plate type compressor with variable displacement mechanism

In a slant plate type compressor for use in a refrigeration circuit, said compressor including a compressor housing having a cylinder block provided with a plurality of cylinders a front end plate disposed on one end of said cylinder block and enclosing a crank chamber within said cylinder block, a piston slidably fitted within each of said cylinders, each piston having at least one piston ring thereon, 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 plate having a surface disposed at a slant angle relative to said drive shaft, said slant angle changing in response to a change in pressure in said crank chamber to change the capacity of said compressor, a rear end plate disposed on the opposite side of said cylinder block from said front end plate and defining a suction chamber and a discharge chamber therein, a communication path linking said crank chamber with said suction chamber, and a valve control means for controlling the opening and closing of said communication path to cause in pressure in said crank chamber, an improvement comprising:

• means for compensating for a reduction in blow by gas due to swollen piston rings;
• wherein said compensating means comprises flow control means formed in said cylinder block for controlling the flow of refrigerant gas from said discharge chamber to said crank chamber, said flow control means providing continuous communication between said discharge chamber and said crank chamber and further including throttling means for throttling refrigerant gas flowing therethrough so as to reduce the pressure of refrigerant gas which flows from said discharge chamber to said crank chamber in order to generate a pressure within said crank chamber which controls the slant angle of said plate, said throttling means continuously throttling said discharge pressure to said crank chamber regardless of the amount of pressure in said discharge chamber.