Variable displacement compressor

Claim 1

An axial piston, variable displacement, wobble plate compressor comprising: means defining a plurality of gas working spaces including suction and discharge ports in each space, and a corresponding plurality of pistons, each positioned in one of said spaces to compress a fluid therein; a drive shaft having a central, cylindrical portion disposed along a longitudinal axis, said cylindrical portion defining an annular slot in proximity to said gas working spaces, and at least one thrust flange member extending radially from said cylindrical portion, which thrust flange member defines a shoulder at the junction with said cylindrical portion and rearwardly extending flanges; a drive plate assembly defining a surface which acts as a cam mechanism driven by said drive shaft, a lug means affixed to said mechanism and having a portion in spaced juxtaposition with said rearwardly extending flanges on said thrust flange member; a wobble plate having a hub assembly and driven by said cam mechanism in a nutating path about the drive shaft axis; a hinge ball insertable in said hub assembly and defining a bore to receive the drive shaft and be slidable thereon; means operably connected between said wobble plate and the pistons to impart reciprocating drive to said pistons, the length of the piston stroke being a function of the angle at which said wobble plate is supported relative to the drive shaft axis; pivot links having two ends and positioned between said rearwardly extending flange member and lug means, one of which ends is attached to said rearwardly extending flange members and the other end being attached to said lug means, which lug means is spaced from the drive shaft axis such that said cam mechanism is pivoted about the hinge ball at a point not coincident with said drive shaft axis, with no driving connection between said drive shaft and cam mechanism along said drive shaft axis, all torque being transmitted from said drive shaft to said cam mechanism through said lug means and pivot links; wherein the improvement comprises a snap ring positioned in said drive shaft annular slot, a piston-stroke-increasing bias spring positioned about said drive shaft between said snap ring and said hinge ball, and a piston-stroke-decreasing spring mounted on said drive shaft between said hinge ball and said shoulder at the junction of said thrust flange member and the cylindrical portion of said drive shaft, which stroke-increasing spring and stroke-decreasing spring cooperate to maintain said wobble plate and hinge ball position to provide a predetermined piston stroke at an equilibrium position.