Chain tensioner

A chain tensioner comprising:

• a tensioner body having a cylindrical plunger holding hole, one side of which is open,
• a cylindrical plunger slidably inserted into the plunger holding hole, and
• urging means that is telescopically accommodated in a pressure oil chamber formed by the plunger holding hole and the plunger and urges the plunger to a protruding direction on a front side, wherein
• the plunger holding hole has a plunger holding wall directly sliding with the inserted plunger and a plunger holding bottom-surface part at a position opposed to an open side of the plunger holding hole;
• a cylindrical oil storing chamber is provided on an outer periphery side of the plunger holding wall;
• on an end part on the plunger holding bottom-surface part side of the plunger holding hole, a check valve unit that connects the pressure oil chamber and the oil storing chamber capable of being opened/closed is provided;
• the plunger holding wall is constituted by a sleeve that is a separate body from the tensioner body;
• the sleeve has an outer-peripheral blocking plug that blocks the open side of the plunger holding hole in the oil storing chamber;
• and
• an area between an outer periphery of the plunger and the plunger holding wall is uniformly formed up to an opening end of the plunger holding hole.