Autotensioner

摘要

An autotensioner includes a cylinder having its bottom closed and filled with a hydraulic oil and air, an oil seal mounted in the cylinder to seal the hydraulic oil and air, a rod slidably extending through the oil seal, and a piston slidably mounted in the cylinder with its top end abutting the bottom of the rod. The interior of the cylinder is separated into an upper reservoir chamber and a lower pressure chamber by the piston. Both chambers communicate with each other through a channel formed in the piston. The rod is biased by a spring mounted in the reservoir chamber in such a direction as to protrude from the cylinder. A check valve is provided in the pressure chamber near the bottom of the piston to open the channel in the piston only when the pressure in the pressure chamber is lower than the pressure in the reservoir chamber. The cylinder may have an outer casing and an inner sleeve so that the piston can slide on the inner surface of the sleeve.