PURPOSE: To increase the containment capacity by making first inner teeth and first outer teeth differ by one in the number of teeth, making second outer teeth and second outer teeth differ by at least two in the number of teeth, and connecting a rotary collector of a control part to a piton via an arc gear having the same number of teeth.

CONSTITUTION: When an inlet 19 has high pump pressure and an outlet 20 has atmospheric pressure, a piston 5 is rotated around the contact 27 of a casing 4 through inner teeth 4, 6 which differ by one in the number of teeth in a state where it is hermetically sealed by an arc gear having the same number of teeth through control slits 12, 13 of a rotary collector 11 of a control part 2. Moreover, the piston 5 rotates a drive shaft 9 through inner teeth 7 and outer teeth 8 which differ by at least two in the number of teeth. Therefore, the containment capacity can be increased, and parts can be manufactured by a rational method, for example, by sintering.