Patent ID: 6899650

Claim:
A hydraulic automatic tensioner for adjusting tension of an endless transmission member included in a power transmitting mechanism for transmitting power to engine accessories of an internal combustion engine through the transmission member, said hydraulic automatic tensioner comprising: a first member; a piston formed integrally with the first member; a second member coaxially combined with the first member so as to be axially movable relative to the first member, said second member defining a fluid-reservoir chamber together with the first member and provided with a leak passage; a cylinder formed integrally with the second member and axially slidably receiving the piston so as to form a pressure chamber filled with a hydraulic fluid; an elastic member pushing the first and the second member away from each other; a control valve placed in the leak passage to normally prevent flow of the hydraulic fluid from the pressure chamber through the leak passage into the fluid-reservoir chamber; and a control device for changing over the control valve between a normal position that prevents flow of the hydraulic fluid from the pressure chamber into the fluid-reservoir chamber and an other position that makes normal function of the control valve ineffective to permit flow of the hydraulic fluid from the pressure chamber into the fluid-reservoir chamber.