WATER PUMP

PROBLEM TO BE SOLVED: To provide a water pump capable of being downsized by disposing a clutch mechanism at the circumference of a pump chamber in a pump housing.SOLUTION: A water pump includes: a drive shaft 6 rotatably supported in a pump chamber 3 disposed inside of a pump housing 2; and an impeller 7 accommodated in the pump chamber, having a small-diameter shaft portion 6a and a fixing portion 6c at one end side of the drive shaft, while pressing and fixing a drive ring 14 to the fixing portion, and relatively rotatably disposed on the small-diameter shaft portion through a bearing portion 15 and a driven ring 16. A clutch spring 20 is disposed over outer peripheral faces of the drive ring and the driven ring, a control member 21 for controlling the clutch spring to be deformed while reducing its diameter or expanding its diameter, at an outer peripheral side of the clutch spring, and the control member is slidably retained by an inner peripheral face of a retaining hole 7c of the impeller and an outer peripheral face of an annular projecting portion 14c of the drive ring, and kept into contact with a regulation flange portion 14b of the drive ring at its inner face.