Patent ID: 6890163

Claim:
A scroll compressor provided with a housing; a shaft having a crank part, which is offset, wherein said shaft is rotatably and axially supported by said housing; a movable scroll, which has a spiral shaped blade and an end plate and is driven to orbit by the crank part; and a fixed scroll, which has a spiral shaped blade that meshes with the movable scroll and an end plate and is fixed to said housing, such that, when said movable scroll is driven to orbit by the crank part of said shaft, a plurality of working chambers formed between the blade of said movable scroll and the blade of said fixed scroll move toward the center, and the volumes of the working chambers are successively reduced and fluid is compressed in the working chambers, said scroll compressor comprising: a middle housing provided as part of said housing behind said movable scroll for supporting a thrust load in an axial direction of said shaft acting on said movable scroll along with the rise in the compression pressure of the fluid in the working chambers; at least one ring-shaped groove forming a backpressure chamber in one of a back surface of the end plate of said movable scroll and a front surface of said middle housing facing and supporting the same; a passage for introducing high-pressure fluid into said ring-shaped groove; and at least one ring-shaped seal ring fitted movably in said ring-shaped groove, wherein the sectional shape of said at least one ring-shaped seal ring is such that said seal ring slightly inclines in said ring-shaped groove, wherein said at least one seal ring includes a first seal ring fit along an outer circumference of said ring-shaped groove and a second seal ring fit along an inner circumference of said ring-shaped groove, each fabricated from rubber, plastic, or metal having wear resistance, oil resistance, and elasticity; said first seal ring forms a ring-shaped projection having an outer diameter larger than an outer circumference diameter of said ring-shaped groove in a no-load state before being fit in said backpressure chamber at a portion facing a portion close to the bottom surface of said ring-shaped groove in the outer circumference of said groove; and said second seal ring forms a ring-shaped projection having an inner diameter smaller than an inner circumference diameter of said ring-shaped groove in said no-load state at a portion facing a portion close to the bottom surface of said ring-shaped groove in the inner circumference of said groove.