PURPOSE: To control a swash plate through a simple mechanism by a method wherein a rotor with a vane contained in a housing is coupled to the one end of a trunnion shaft on which the swash plate is mounted, and the feed and discharge of working fluid to and from pressure chambers partitioned by means of a vane are controlled.

CONSTITUTION: In a variable capacity type pump, a swash plate 5 for regulating reciprocating movement of a piston 6 engaged with a cylinder block 3 rotated by a drive shaft 2 in a casing 1 is secured on a trunnion shaft 4 supported to the casing 1 through a bearing, and by rotating the trunnion shaft 4, the increase and the decrease of a delivery amount are controlled. In this case, a shaft part 14 coupled to the trunnion shaft 4 is inserted in a housing 13 secured to the casing 1, and a rotor 18 having a vane 16a is mounted on the shaft part 14. Pressure chambers 22 and 23 partitioned from each other by means of the vane 16a in the housing 13 are communicated to a fluid feed passage 20 or a fluid discharge passage 21 through through-holes P, T, A, and B formed in the shaft part 14 to rotate the rotor 18.