Patent ID: 8002656

Claim:
A tensioner for an endless transmission belt, comprising: a plunger body having a hole; a plunger movably provided in the hole of the plunger body; a plunger spring disposed between the plunger and the plunger body to push the plunger toward the endless transmission belt to press the endless transmission belt; a pressure chamber provided between the plunger and the plunger body and configured to store hydraulic oil supplied from an oil pump; a check valve provided in the plunger body and configured to be opened to supply the hydraulic oil to the pressure chamber when a pressure in the pressure chamber is lower than an oil pressure of the hydraulic oil supplied from the oil pump and to be closed when the pressure in the pressure chamber is higher than the oil pressure; and a relief valve provided in the plunger body within a width of the plunger in a direction orthogonal to a longitudinal direction of the plunger and configured to discharge the hydraulic oil in the pressure chamber when the pressure in the pressure chamber exceeds a predetermined value, wherein the relief valve is disposed at a portion that is farther away from the endless transmission belt than the check valve, and wherein the relief valve is disposed coaxially with an axis of the hole.