Patent ID: 8117836

Claim:
A scroll type fluid machine comprising: one scroll including a spiral wrap portion extending from a surface of an end plate; the other scroll which is opposed to said one scroll, including a spiral wrap portion extending from a surface of an end plate, said wrap portion of said other scroll overlapping said wrap portion of said one scroll to define a compression chamber; a thrust receiving mechanism which is provided on a back surface of at least one of said one scroll and said other scroll, which permits a gap in a thrust direction between said end plate and said wrap portion to vary by a predetermined amount and supports said end plate in the thrust direction; a discharge port which is provided on a radially inner side of at least one of said one scroll and said other scroll, and which discharges compressed fluid which is compressed by the compression chamber; and a pressure keeping mechanism provided downstream of said discharge port, the pressure keeping mechanism increasing a pressure in said compression chamber right after operation starts so as to push said scroll on a side where said thrust receiving mechanism is provided at its back toward the thrust receiving mechanism, wherein a flow path area of said pressure keeping mechanism can be changed to at least two levels, a small flow path area is set until a pressure upstream of said pressure keeping mechanism reaches a predetermined upstream pressure after a compressing operation is started, and the flow path area is permitted to be changed to a large flow path area after the pressure exceeds said predetermined upstream pressure.