PURPOSE: To enable a cam to be easily press fitted onto a rotor shaft by forming a hole in a yoke above a ball bearing mounted on the cam and attaching a diaphragm pump section to the hole to make the yoke integral with a pump body.

CONSTITUTION: A pump body 14 has the surface A worked at a right angle to a follower 11, and a pump body 14 is inserted into a yoke 1 mounting hole 26 to attach the surface A closely to the upper surface of a U-shaped plate 27 welded to the outer surface of the yoke 1. The upper surface of the U-shaped plate 27 is formed to be parallel to the center of the yoke 1. Thus, by such assemblage, the lower end of the follower 11 easily contacts vertically the outer ring surface of a ball bearing 10 so that the follower 11 are vertically smoothly driven.