PURPOSE: To correctly switch fluid discharge capacity according to fluid temperature by fitting a main rotor with low discharge capacity and a sub-rotor with high discharge capacity on a common pump shaft and connecting the main rotor to the sub-rotor through a clutch device which is switched according to temperature.

CONSTITUTION: In a cold state of an engine directly after starting the engine, a shape memory alloy made engaging spring 33 is contracted, and the clutch section 30 of a clutch disk 31 is separated from the clutch section 29 of a main rotor 16 due to the spring force of a returning spring 32. For this reason, a sub-rotor 17 is in a relative rotation state to a pump shaft 13 through a collar 20, and cooling water is discharged only by the rotation of the main rotor 16. On the other hand, when the engine is warmed up, increasing the temperature of the cooling water, the engaging spring 33 is extended, and both of the clutches 29 and 30 engaged due to wedge work, transmitting the torque of the pump shaft 13 to the main rotor 16 and the sub-rotor 17. As a result, a lot of cooling water is discharged.