Patent ID: 7331774

Claim:
A scroll compressor comprising a closed shell partitioned into a refrigerant compression chamber including a fixed scroll and an orbiting scroll and a drive chamber including a motor with a main frame held therebetween; a cylindrical thrust ring arranged between a back surface of an end plate of the orbiting scroll and the main frame; and a first back pressure chamber into which a discharge pressure is introduced on an inside of the thrust ring, wherein the main frame is provided with a first inner peripheral surface with a smaller diameter, a second inner peripheral surface with a larger diameter, and a third inner peripheral surface having a diameter smaller than that of the first inner peripheral surface, which are coaxial and have different diameters, a first height difference surface formed between the first inner peripheral surface and the second inner peripheral surface, and a second height difference surface formed between the first inner peripheral surface and the third inner peripheral surface; and the thrust ring has an inside diameter larger than a turning range of an eccentric shaft of the motor, first and second seal surfaces which are brought into close contact with the first and second inner peripheral surfaces, respectively, and an opposed surface which is arranged so as to be opposed to the first height difference surface and forms an independent second back pressure chamber between the opposed surface and the first height difference surface; said scroll compressor further comprising pressure introducing means for introducing a medium pressure between a suction pressure and the discharge pressure into the second back pressure chamber, and regulating means for regulating movement of the thrust ring, formed by making a lower end surface of the thrust ring abut on the second height difference surface.