Water pump having a clutch

A water pump for a vehicle, comprising:

• a power transmission member driven and rotated by an external power;
• a driven shaft driven to be rotatable independently from the power transmission member;
• an impeller to which a rotation of the driven shaft is transmitted;
• an arm member including a pressing portion which presses an inner circumferential surface of the power transmission member and being contactable to the power transmission member for transmitting a rotation of the power transmission member to the driven shaft;
• a control member controlling the arm member so that the arm member and the power transmission member come in contact with each other or come out of contact from each other and so that a contact state between the arm member and the power transmission member is variable, the control member including a magnetically-attractable portion provided with a joint portion which is joined to the arm member;
• and
• a biasing member provided at the control member for biasing the arm member toward the power transmission member, wherein
• the control member changes a rotational phase between the power transmission member and the arm member so that the arm member and the power transmission member come in contact with each other or come out of contact from each other and so that the contact state between the arm member and the power transmission member is controlled,
• the joint portion includes a long hole provided at one of the magnetically-attractable portion and the arm member and a pin provided at the other one of the magnetically-attractable portion and the arm member, and
• a distance between a center of the pin and a center of the driven shaft when the pin is positioned at a first end portion of the long hole and a distance between the center of the pin and the center of the driven shaft when the pin is positioned at a second end portion of the long hole differ from each other.