Tensioner

A tensioner comprising:

• a plunger having a plunger hole that is open on a rear side;
• a housing having a plunger accommodating hole that is open on a front side and accommodates the plunger;
• a main biaser that is accommodated inside an oil pressure chamber and that is formed between the plunger and the plunger accommodating hole so as to expand and contract, and urging the plunger toward the front side;
• and a pressure adjusting mechanism adjusting oil pressure in the oil pressure chamber,
• the pressure adjusting mechanism including a cylinder part, a piston unit set inside the cylinder part so as to be able to approach and separate from the oil pressure chamber and partitioning a space formed between the plunger and the housing into the oil pressure chamber and an adjustment space, and a piston biaser biasing the piston unit toward the oil pressure chamber,
• between the cylinder part and the piston unit a liquid tight condition being kept at any place between a position where the piston unit has moved closest to the oil pressure chamber and a position where the piston unit has moved closest to the adjustment space,
• wherein the pressure adjusting mechanism includes an inner sleeve set inside the plunger accommodating hole, a piston spring as the piston biaser is set in the inner sleeve, and the inner sleeve is fitted with the piston unit, and
• wherein the inner sleeve includes a sleeve through hole that extends from an inner circumferential surface to an outer circumferential surface thereof.