Hydraulic automatic tensioner and power transmitting mechanism

Abstract

A hydraulic automatic tensioner for adjusting the tension of an endless belt in a power transmitting mechanism for transmitting power to engine accessories of an internal combustion engine through the belt comprises: a fixed first member (11), a piston (PS) formed integrally with the first member (11), a movable second member (12) coaxially combined with the first member (11) so as to be axially movable relative to the first member (11), a cylinder (CY) formed integrally with the second member (12), defining a fluid-reservoir chamber (R) for storing a hydraulic fluid together with the first member (11), and provided with a leak passage (20), axially slidably receiving the piston (PS), a spring (S) pushing the first and the second member (11, 12) away from each other. The piston (PS) and the cylinder (CY) form a pressure chamber (P) filled with the hydraulic fluid. The second member (12) is provided with a leak passage ((20) through which the hydraulic fluid flows from the pressure chamber (P) into the fluid-reservoir chamber (R). A control valve (V) is placed in the leak passage (20) and inhibits the flow of the hydraulic fluid from the pressure chamber (P) through the leak passage (20) into the fluid-reservoir chamber (R). A control device (13) makes the function of the control valve (V) effective to close the leak passage (20) when activated and makes the function of the control valve (V) ineffective when deactivated so that the pressure chamber (P) is able to communicate with the fluid-reservoir chamber (R) by means of the leak passage (20). The tensioner is capable of properly coping with the sudden change of the tension of the belt to ensure that power is always surely transmitted.

Dependencies are inferred from the claim text.