A variable capacity fluid pump that can be controlled independently of the rotation of the engine is provided. The fluid pump comprises a planetary gear mechanism having a first gear, second gears and a third gear. The second gears are connected to a crankshaft of the engine and transmits a rotational force of the crankshaft. The third gear is connected to the fluid pump. The fluid pump further comprises braking means connected to the first gear. The breaking means generates a braking force upon the first gear. The fluid pump further comprises a one-way clutch provided between the second gears and the third gear. The braking means controls a rotational speed of the first gear so that a rotational speed of the fluid pump is controlled independently of a rotational speed of the crankshaft of the engine.