To increase the pressure difference necessary for opening and closing a differential pressure regulating valve in proportion to the discharging pressure by transmitting the discharging pressure as the pressure on the discharging chamber side to the differential pressure regulating valve, and increasing the pressure difference necessary for opening and closing the differential pressure valve when the discharging pressure of the discharging chamber is increased.

A diameter of a valve chamber 103 is reduced in comparison with that of a spring supporting portion 105 to be used as a stopper 107 on the way of the valve chamber 103. An oblique cut 108 is formed for flowing the crank chamber gas to an inlet side even when the spring supporting portion 105 is brought into contact with the stopper 107. Accordingly a groove or the like is formed to the oblique cut 108 so that the crank chamber gas flows therein when the spring supporting portion 105 is brought into contact with the oblique cut 108. By properly varying the valve opening pressure difference condition by the discharging pressure, the controllability and the seizing resistance can be improved, and a differential pressure valve structure can be easily designed and manufactured because it is a mechanical structure.