Check valve unit

A check valve unit installed in a plunger of a high-pressure relief valve of a tensioner, the check valve unit comprising:

• a seat relief that contains a check valve and that is inserted into a plunger bore formed in the plunger;
• and
• a cap member fitted onto an engaging part of the seat relief at one end thereof in a direction in which the seat relief is inserted into the plunger bore,
• the plunger including an outlet relief hole in an attachment part of the plunger bore for communication between inside and outside of the plunger,
• the cap member including a flat cap top, an oil flow portion that is a hole extending through the cap top, and a skirt wall that extends down from the cap top,
• the skirt wall including a plurality of outwardly raised contact surfaces protruding radially outwards and a plurality of inwardly raised contact surfaces protruding radially inwards,
• the plurality of outwardly raised contact surfaces having a circumscribed circle with a radius that is larger than an inside radius of the attachment part of the plunger bore before the check valve unit is installed in the plunger,
• the plurality of inwardly raised contact surfaces having an inscribed circle with a radius that is smaller than an outside radius of the engaging part before the cap member is fitted onto the engaging part.