Patent ID: 8206138

Claim:
A scroll fluid machine comprising: a casing; a fixed scroll provided in the casing and having a spiral wrap portion provided upright on an end plate; an orbiting scroll having a wrap portion provided upright on an end plate and performing an orbiting motion in such a state that the wrap portion is overlapped with the wrap portion of the fixed scroll, thereby to compress or expand a fluid in a fluid chamber between these wrap portions; and a rotation prevention mechanism provided between the orbiting scroll and the casing side and preventing the rotation of the orbiting scroll, wherein the rotation prevention mechanism is constituted of: a first ball coupling mechanism, which includes a pair of load supporting members provided so that ball support surfaces are opposed to each other between the orbiting scroll and the casing side, and a load supporting ball provided between the pair of load supporting members and supporting a load in a thrust direction, the ball support surfaces of the load supporting members comprising an annular-shaped groove formed to have a circular arc-shaped cross section, and a second ball coupling mechanism, which includes a pair of rotation prevention supporting members provided so that ball support surfaces are opposed to each other between the orbiting scroll and the casing side and a rotation prevention ball provided between the pair of rotation prevention supporting members and preventing the rotation of the orbiting scroll, the ball support surfaces of the rotation prevention supporting members comprising an annular-shaped peripheral wall protruding in an axial direction.