In recent years, there has been developed a scroll compressor which includes a fixed scroll member having a fixed spiral wrap erected on one face of a fixed end plate, and an orbiting scroll member having an orbiting spiral wrap erected on one face of an orbiting end plate and assembled in a manner capable of orbiting, while being blocked from rotation, with respect to the fixed scroll member. The fixed scroll member and the orbiting scroll member individually include step portions on the leading end faces and the bottom faces of their individual spiral wraps such that the spiral wraps have a higher wrap height on the outer circumference side than that on the inner circumference side. The scroll compressor is enabled to perform three-dimensional compressions capable of compressing in the circumferential direction of the spiral wraps and in the wrap height direction.
The aforementioned scroll compressor is featured in that the compression ratio can be increased to improve the compression performance without enlarging the external diameter of the compressor.
With the scroll compressor, in connection with the setting of such a tip clearance between the leading end face of the spiral wrap and the bottom face as influences the gas leakage at a compression process to vary a compression efficiency, it has been proposed (as referred to Patent Documents 1 and 2) by considering the level of the thermal expansions of the paired scroll members that the tip clearance on the inner circumference side with respect to the step portion of the spiral wrap is made larger than the tip clearance on the outer circumference side with respect to the step portion.
[Patent Document 1] JP-A-2002-5052
[Patent Document 2] JP-A-2003-035285
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