TENSIONER

摘要

The present invention is directed to decrease the impact sound of the ratchet mechanism generated at the time of piston retraction. The tensioner includes a piston 3 slidable in the piston bore 2a of the housing 2 and an expandable circlip member 5 engageable with the engagement groove 3a of the piston 3. The piston bore 2a has a guide groove 20 formed therein that has front and rear stop surfaces 20a, 20b adapted to contact the circlip member 5. The engagement groove 3a is formed by a round seat portion S<SUB>0</SUB> that the circlip member 5 is adapted to seat, a piston-retraction restricting portion S<SUB>0</SUB>S<SUB>1</SUB> that is formed on the front side of the round seat portion S<SUB>0</SUB> and a piston-advance permitting portion S<SUB>0</SUB>S<SUB>2</SUB> that is formed on the front side of the round seat portion S<SUB>0</SUB>. The piston-retraction restricting portion S<SUB>0</SUB>S<SUB>1</SUB> permits the circlip member 5 to travel a short distance toward the front side along the rear side stop surface 20b to allow for an enlargement of the circlip member 5 and to restrict retraction of the piston 3 when the piston 3 retracts and the circlip member 5 contacts the rear side stop surface 20b of the guide groove 20.