Patent ID: 8549985

Claim:
A wabble plate type variable displacement compressor having pistons inserted reciprocally into cylinder bores, a swash plate rotated together with a rotational main shaft and supported changeably in angle relative to said main shaft, a wabble plate which is connected to said pistons, in which a rotational movement of said swash plate is converted into a wabble movement of said wabble plate, and which transmits said wabble movement to said pistons to reciprocate said pistons, and a rotation preventing mechanism of said wabble plate, characterized in that said rotation preventing mechanism comprises (a) an inner ring provided in a housing movably in an axial direction although rotation is prevented, supporting said rotational main shaft via a bearing at an inner diameter portion to rotate relatively and to move relatively in an axial direction and having a plurality of guide grooves for guiding a plurality of balls provided for power transmission, (b) a sleeve functioning as a wabble central member of said wabble movement of said wabble plate, provided on said rotational main shaft to rotate relatively thereto and to move in an axial direction and engaged with said inner ring movably in an axial direction together with said inner ring, (c) an outer ring having a plurality of guide grooves for guiding said balls at positions opposing respective guide grooves of said inner ring, supported on said sleeve wabblingly, and connected with said wabble plate fixedly on an outer periphery of said outer ring, and (d) a plurality of balls held by said guide grooves formed in said inner ring and said outer ring at a condition of opposing each other and performing power transmission by being compressed between said guide grooves, a relative shape difference in axial cross-sectional profile is provided between a substantially concave spherical surface formed in an inner periphery of said outer ring functioning as a wabble member for wabblingly connecting said wabble plate in said rotation preventing mechanism and a substantially convex spherical surface formed on an outer periphery of said sleeve functioning as said wabble central member, and said shape difference is set such that the closer to axial opposite ends of a contact portion between said substantially concave spherical surface and said substantially convex spherical surface a position of said contact portion is located, the greater a clearance between both surfaces becomes.