Hydraulic autotensioner

A hydraulic autotensioner comprising a cylinder having a closed bottom end;

• a sleeve mounted in said cylinder;
• a plunger slidably mounted in said sleeve to define a reservoir chamber and a pressure chamber, said plunger being formed with a passage through which said reservoir chamber and said pressure chamber communicate with each other;
• a check valve provided in said passage for closing said passage if a pressure of hydraulic oil in said pressure chamber increases above the pressure of hydraulic oil in said reservoir chamber;
• a rod axially movable together with said plunger;
• a return spring for biasing said rod in such a direction as to have said rod protrude from an upper opening in said cylinder, said return spring being mounted in a space defined between the outer peripheral surface of said sleeve and the inner peripheral surface of said cylinder;
• and wherein said plunger has a cylindrical outer surface and has at bottom thereof that faces said pressure chamber a tapered surface connecting with said cylindrical outer surface and an arcuate surface smoothly connecting with said tapered surface, said tapered surface being at an angle of 5-20 degrees with respect to said cylindrical outer surface.

A hydraulic autotensioner comprising a cylinder having a closed bottom end;

• a sleeve mounted in said cylinder to define a reservoir chamber and a pressure chamber;
• a plunger being formed with a passage through which said reservoir chamber and said pressure chamber communicate with each other;
• a check valve provided in said passage for closing said passage if a pressure of hydraulic oil in said pressure chamber increases above a pressure of hydraulic oil in said reservoir chamber;
• a rod axially movable together with said plunger;
• a return spring for biasing said rod in such a direction as to protrude from an upper opening in said cylinder;
• and a wear ring having a hole through which hydraulic oil flows and mounted on said rod so as to be guided along an inner peripheral surface of said cylinder;
• a spring mounting space being defined between an outer peripheral surface of said sleeve and the inner peripheral surface of said cylinder, said return spring being mounted in said spring mounting space;
• said wear ring having an outer diameter larger than an outer diameter of said sleeve;
• and wherein said plunger has a cylindrical outer surface and has a bottom thereof that faces said pressure chamber, a tapered surface connecting with said cylindrical outer surface and an arcuate surface smoothly connecting with said tapered surface, said tapered surface being at an angle of 5-20 degrees with respect to said cylindrical outer surface.