Chain tensioner

A chain tensioner comprising a housing having a cylinder chamber, a rod member having a rear end thereof inserted in said cylinder chamber, a tension adjusting spring biasing said rod member outwardly of said housing, an oil supply type hydraulic damper for damping axial dynamic load applied to said rod member from the chain by utilizing as a damping medium a hydraulic oil supplied into a closed end of said cylinder chamber through an oil supply passage formed in said housing and a check valve, and a thread engagement means for preventing said rod member from retracting under an axial static load applied to said rod member, said check valve comprising a cylindrical valve seat inserted in an oil outlet of said oil supply passage and having a flange formed on the outer periphery thereof so as to abut the closed end of said cylinder chamber, a check ball provided to be movable into and out of contact with an oil outlet of said valve seat, and a retainer having its mounting position restrained by coming into abutment with said flange for restricting the movement of said check ball.