Patent ID: 8545191

Claim:
A water pump for a vehicle, comprising: a power transmitting member rotationally driven by an external force; a driven shaft driven to be rotatable independently from the power transmitting member; an impeller to which a rotation of the driven shaft is transmitted; a biasing member which presses an inner circumferential surface of the power transmitting member so as to be contactable and for rotating in order to transmit a rotation of the power transmitting member to the driven shaft when the biasing member contacts the inner circumferential surface of the power transmitting member, the biasing member being formed so as to be wound in a circumferential direction of the power transmitting member; a control member which allows the power transmitting member and the biasing member to come in contact with each other or to come out of contact from each other and for controlling a contacting state between the power transmitting member and the biasing member; the control member including a driver connected to a first end portion of the biasing member and the driven shaft, a magnetically-attracted portion to which a second end portion of the biasing member is connected, and a driving portion which attracts the magnetically-attracted portion by magnetic force, the driving portion controlling a length of the biasing member in a radial direction of the biasing member by attracting the magnetically-attracted portion; a plate spring positioned between the magnetically-attracted portion and the driver, the plate spring biasing the magnetically-attracted portion away from the driving portion so that an air gap exists between the magnetically-attracted portion and an acting surface of the driving portion; and the driving portion attracting the magnetically-attracted portion by the magnetic force so that the magnetically-attracted portion contacts the acting surface of the driving portion.