Tensioner

A tensioner comprising:

• a plunger having a plunger hole that is open on a rear side;
• a housing having a plunger housing hole that is open on a front side in order to house the plunger;
• a check valve that divides a space between the housing and the plunger into a pressure oil chamber and an interior space and allows oil to flow into the pressure oil chamber while preventing oil from flowing back into the interior space;
• a main biasing unit that is housed in the pressure oil chamber to be free to expand and contract and that biases the plunger toward the front side;
• an oil supply passage for supplying oil from an outside of the housing to an oil storage chamber in the interior space;
• and
• a pressure adjustment mechanism that adjusts an oil pressure in the oil storage chamber, wherein
• the oil supply passage includes a housing oil supply hole that penetrates from the outside of the housing to an inner peripheral surface of the plunger housing hole, a plunger oil supply hole that penetrates from an outer peripheral surface of the plunger to an inner peripheral surface of the plunger hole, and a communication adjustment groove formed in one or both of the inner peripheral surface of the plunger housing hole and the outer peripheral surface of the plunger,
• the pressure adjustment mechanism includes a cylinder portion and a piston that is disposed in the cylinder portion so as to be capable of moving in a front-rear direction and that divides the interior space into the oil storage chamber and an adjustment space, and
• a liquid-tight state is maintained between the cylinder portion and the piston in all positions between a position of the piston where the piston has moved closest to the oil storage chamber side and a position of the piston where the piston has moved closest to the adjustment space side.