Hydraulic autotensioner

• US 5,482,262 A
• Filed: 09/23/1994
• Issued: 01/09/1996
• Est. Priority Date: 12/20/1991
• Status: Expired due to Term

• Current Assignee: Elonex Technologies, Inc.
• Original Assignee: NTN Corporation
• Inventors: Yamamoto, Ken, Yamazaki, Norio, Kitano, Satoshi, Hayakawa, Hisashi, Kawashima, Kazuki
• Primary Examiner(s): BALLATO, JOSIE
• Application Number:
  US08/310,994
• Time in Patent Office: 473 Days
• Field of Search: 267/220, 267/221, 267/223, 267/224, 267/226, 188/322.22, 188/315, 188/311, 188/316, 188/317, 474/104, 474/110, 474/138
• US Class Current: 267/226
• CPC Class Codes: F16H 2007/0806 Compression coil springs
• CPC Class Codes: F16H 2007/0859 Check valves
• CPC Class Codes: F16H 2007/0891 Linear path
• CPC Class Codes: F16H 7/1236 of the fluid and restriction type, e.g. dashpot

Abstract

A hydraulic autotensioner has a cylinder having a closed bottom end, a sleeve mounted in the cylinder and a plunger slidably mounted in the sleeve. The interior of the cylinder is divided into a reservoir chamber and a pressure chamber by the plunger which is formed with a passage through which the reservoir chamber and the pressure chamber communicate with each other. A check valve is provided in the passage to close the passage if the pressure of hydraulic oil in the pressure chamber increases above the pressure of hydraulic oil in the reservoir chamber. A return spring is mounted in the cylinder to bias a rod which is axially movable together with the plunger in such a direction as to protrude from an upper opening of the cylinder. The return spring is mounted in a space formed between the outer peripheral surface of the sleeve and the inner peripheral surface of the cylinder.

Claims

1. 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 when the 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 protrude from an upper opening of said cylinder, a wear ring having a hole which allows the passage of hydraulic oil therethrough and mounted on said rod so as to be guided along an inner peripheral surface of said cylinder, said return spring being mounted in a spring mounting space defined between the outer peripheral surface of said sleeve and the inner peripheral surface of said cylinder, said wear ring having a larger outer diameter than the outer diameter of said sleeve, said spring mounting space extending downward beyond said passage.

2. A hydraulic autotensioner as claimed in claim 1 wherein said wear ring comprises an annular plate formed with said hole, a guide sheath provided at the outer periphery of said annular plate so as to be guided along the inner peripheral surface of said cylinder, and a boss provided at the inner periphery of said annular plate for supporting said rod.

3. 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.

4. An autotensioner as claimed in claim 3 further comprising a wear ring that allows the passage of hydraulic oil therethrough and mounted on said rod so as to be guided along the inner peripheral surface of said cylinder, said wear ring comprising an annular plate having a through hole which allows the passage of hydraulic oil, a guide sheath provided at the outer periphery of said annular plate so as to be guided along the inner peripheral surface of said cylinder, and a boss provided at the inner periphery of said annular plate for supporting said rod.

5. 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.