Compressor having release valve mechanism including valve seat ring with specially-designbed curved face

In a compressor having a discharge valve mechanism, the valve seat ring (36) having a curved surface (53b), the flexible plate toward the discharge valve (33) movable portion (33b) and spaced between, but also limiting the movement of the movable portion. In a first direction parallel to the valve plate (A1), the movable part from the fixed valve plate (31) extending from the outlet end of the fixed portion (33a) so as to face the discharge hole (42) of the valve plate. A plurality of curved surface having a radius of curvature different from each other in a second portion of the valve plate and parallel to the direction perpendicular to the first direction.