Hydraulic auto-tensioner

Patent metadata

Field	Value
Publication number	US-9982759-B2
Application number	US-201214370067-A
Country	US
Kind code	B2
Filing date	Dec 21, 2012
Priority date	Jan 6, 2012
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

A hydraulic auto-tensioner includes a sleeve having its bottom end press-fitted in a sleeve fitting hole in the bottom surface of a cylinder, a rod having its bottom end slidably fitted in the sleeve, and a return spring mounted between a spring support at the upper portion of the rod and the bottom surface of the cylinder. A pressure chamber communicates with a reservoir chamber through a passage formed between fitting surfaces of the sleeve fitting hole and the sleeve. The passage has a check valve. The rod has a valve fitting hole and a communication passage through which the valve fitting hole communicates with the reservoir chamber. The valve fitting hole has a relief valve. An orifice is formed between a valve hole formed in a valve seat of the relief valve and a valve body to prevent a sharp drop in pressure in the pressure chamber.

First claim

What is claimed is:

1. A hydraulic auto-tensioner comprising:
a cylinder containing hydraulic oil and having an inner bottom surface formed with a sleeve fitting hole,
a sleeve having a bottom end portion fitted in the sleeve fitting hole,
a rod having a bottom end portion slidably inserted in the sleeve so as to define a pressure chamber in the sleeve,
a spring support provided at an upper portion of the rod,
a return spring mounted between the spring support and the inner bottom surface of the cylinder and configured to bias the cylinder and the rod in a direction in which the rod protrudes from the cylinder, a reservoir chamber having a top opening being defined between the cylinder and the sleeve, with the top opening of the reservoir chamber closed, a passage being defined between fitting surfaces of the sleeve and the sleeve fitting hole such that the reservoir chamber communicates with the pressure chamber through the passage,
a check valve mounted in the passage and configured to close the passage when a pressure in the pressure chamber exceeds a pressure in the reservoir chamber, the rod being formed with a valve fitting hole having an opening at a bottom end surface of the rod, the rod further being formed with a communication passage through which an upper portion of the valve fitting hole communicates with the reservoir chamber, and
a relief valve mounted in the valve fitting hole and configured to be opened if the pressure in the pressure chamber exceeds a set pressure so as to release the pressure in the pressure chamber into the reservoir chamber through the communication passage formed in the rod, the relief valve including:
a valve seat press-fitted in the valve fitting hole and formed with a valve hole,
a spherical valve body configured to open and close the valve hole from inside the valve fitting hole, wherein the valve body has an outer diameter D, and the orifice has an inner diameter d, and wherein the outer diameter D and the inner diameter d satisfy a relation d=0.05 D to 0.25 D, and
a valve spring biasing the valve body toward the valve hole,

wherein the valve seat is formed with an orifice disposed between the valve hole and a seating surface formed on an upper portion of the valve seat such that the valve body can be seated on the seating surface, the orifice being configured to restrict an amount of oil that passes through the valve hole; and
wherein the seating surface is a tapered surface inclined at an angle of 25° to 85° relative to a center axis of the tapered surface.

2. The hydraulic auto-tensioner of claim 1 , wherein the seating surface has a contact portion to be brought into contact with the valve body, wherein the contact portion is a curved portion having a convex curved section having a radius of curvature of 1 mm to 7 mm.

3. The hydraulic auto-tensioner of claim 1 , wherein the valve hole has an inner surface formed as a vertical mirror image of the seating surface.

4. The hydraulic auto-tensioner of claim 1 , wherein the seating surface has a convex circular arc-shaped section having a radius of curvature of not more than 1 mm.

5. The hydraulic auto-tensioner of claim 1 , wherein the valve fitting hole has a large-diameter hole portion at a bottom end portion of the valve fitting hole, the valve seat being press-fitted in the large-diameter hole portion, the relief valve further including a spring seat mounted in the large-diameter hole portion so as to be slidable along a radially inner surface of the large-diameter hole portion, a shoulder being formed at a top end of the large-diameter hole portion, the shoulder and the spring seat being arranged such that the shoulder restricts a movement of the spring seat by abutting the spring seat, and the spring seat restricts a movement of the valve body so as to restrict a degree of opening of the relief valve, and the spring seat being formed with an oil passage through which oil can flow from a bottom surface of the spring seat to a top surface of the spring seat.

6. A hydraulic auto-tensioner comprising:
a cylinder containing hydraulic oil and having an inner bottom surface formed with a sleeve fitting hole,
a sleeve having a bottom end portion fitted in the sleeve fitting hole,
a rod having a bottom end portion slidably inserted in the sleeve so as to define a pressure chamber in the sleeve,
a spring support provided at an upper portion of the rod,
a return spring mounted between the spring support and the inner bottom surface of the cylinder and configured to bias the cylinder and the rod in a direction in which the rod protrudes from the cylinder, a reservoir chamber having a top opening being defined between the cylinder and the sleeve, with the top opening of the reservoir chamber closed, a passage being defined between fitting surfaces of the sleeve and the sleeve fitting hole such that the reservoir chamber communicates with the pressure chamber through the passage,
a check valve mounted in the passage and configured to close the passage when a pressure in the pressure chamber exceeds a pressure in the reservoir chamber, the rod being formed with a valve fitting hole having an opening at a bottom end surface of the rod, the rod further being formed with a communication passage through which an upper portion of the valve fitting hole communicates with the reservoir chamber, and
a relief valve mounted in the valve fitting hole and configured to be opened if the pressure in the pressure chamber exceeds a set pressure so as to release the pressure in the pressure chamber into the reservoir chamber through the communication passage formed in the rod, the relief valve including:
a valve seat press-fitted in the valve fitting hole and formed with a valve hole,
a spherical valve body configured to open and close the valve hole from inside the valve fitting hole, and
a valve spring biasing the valve body toward the valve hole,

wherein the valve seat is formed with an orifice disposed between the valve hole and a seating surface formed on an upper portion of the valve seat such that the valve body can be seated on the seating surface, the orifice being configured to restrict an amount of oil that passes through the valve hole; and
wherein the valve body has an outer diameter D, and the orifice has an inner diameter d, and the outer diameter D and the inner diameter d satisfy a relation d=0.05 D to 0.25 D.

7. The hydraulic auto-tensioner of claim 6 , wherein the valve fitting hole has a large-diameter hole portion at a bottom end portion of the valve fitting hole, the valve seat being press-fitted in the large-diameter hole portion, the relief valve further including a spring seat mounted in the large-diameter hole portion so as to be slidable along a radially inner surface of the large-diameter hole portion, a shoulder being formed at a top end of the large-diameter hole portion, the shoulder and the spring seat being arranged such that the shoulder restricts a movement of the spring seat by abutting the spring seat, and the spring seat restricts a movement of the valve body so as to restrict a degree of opening of the relief valve, and the spring seat being formed with an oil passage through which oil can flow from a bottom surface of the spring seat to a top surface of the spring seat.

8. A hydraulic auto-tensioner comprising:
a cylinder containing hydraulic oil and having an inner bottom surface formed with a sleeve fitting hole,
a sleeve having a bottom end portion fitted in the sleeve fitting hole,
a rod having a bottom end portion slidably inserted in the sleeve so as to define a pressure chamber in the sleeve,
a spring support provided at an upper portion of the rod,
a return spring mounted between the spring support and the inner bottom

Assignees

• Tanaka Tadahisa
• Kitano Satoshi
• Takano Takehiro
• Ntn Toyo Bearing Co Ltd

Inventors

• Tanaka Tadahisa
• Kitano Satoshi
• Takano Takehiro

Classifications

• F16H2007/0859

  Check valves · CPC title

• F16H7/1236 Primary

  of the fluid and restriction type, e.g. dashpot · CPC title

• F16H2007/0893

  Circular path · CPC title

• F16H2007/0814

  with valves opening on surplus pressure · CPC title

• F16H2007/0806

  Compression coil springs · CPC title