To provide a hydraulic automatic tensioner capable of smoothly oscillating a pulley shaft supporting a tension pulley.
A fulcrum shaft 3 with a head part is fixed to an engine block 1. The tension pulley 10 is freely rotatably supported by the pulley shaft 6 which is supported so as to be capable of oscillating around the fulcrum shaft 3. The tension pulley 10 is pressed to a belt by imparting elastic force of a tension adjusting spring to the pulley shaft 6. A hydraulic damper device 11, which buffers the pressing force to be applied from the belt to the pulley shaft 6 via the tension pulley 10, is provided between the pulley shaft 6 and the engine block 1. A washer 14 made of a resin is incorporated between the end faces of the head part 5 of the fulcrum shaft 3 and the pulley shaft 6. As a result, the reduction of friction resistance can be realized by oscillating the pulley shaft 6 in a state of being in contact with the washer 14. The smooth oscillation of the pulley shaft 6 can be realized.
Higashio Masahiro
Torii Kazuhisa
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