Tensioner

Abstract

Provided is a simple-structured tensioner that can reduce processing and assembling workload as well as increase the degree of design freedom. A tensioner 10 includes an oil supply hole 33 formed in a sleeve bottom 32 and a check valve 50 disposed on a front face of the sleeve bottom 32. The check valve 50 includes a check ball 51 and a retainer 52. The sleeve bottom 32 includes a ball seat 34 which protrudes in a cylindrical shape toward the front side integrally with and continuously from the edge of the oil supply hole 33 and on which the check ball 51 is seated.

Claims

1. A tensioner comprising: a sleeve having a sleeve bottom on a rear side; a plunger inserted in the sleeve so as to be able to move forward and backward along an axial direction of the sleeve; and a biasing unit that is accommodated so as to be able to expand and contract inside an oil pressure chamber formed between a rear end of the sleeve and a rear end of the plunger and that biases the plunger toward a front side, wherein an oil supply hole is formed in the sleeve bottom, a check valve for preventing oil from flowing out from the oil supply hole is disposed on a front face of the sleeve bottom, the check valve includes a check ball, and a retainer disposed on the front face of the sleeve bottom and restricting movement of the check ball, the sleeve bottom includes a ball seat which protrudes in a cylindrical shape toward the front side integrally with and continuously from an edge of the oil supply hole and on which the check ball is seated, the sleeve including the ball seat is an unitary single piece, and a tapered portion with a diameter increasing from the front side toward the rear side is formed on a rear side of an inner periphery of the oil supply hole.

2. The tensioner according to claim 1, wherein the retainer includes a top disposed on the front side of the check ball, and a skirt extending vertically downward toward the rear side from a peripheral edge of the top and disposed on a radially outer side of the ball seat, the ball seat and the skirt decreasing in diameter from the front side toward the rear side.

3. The tensioner according to claim 2, wherein the skirt includes a plurality of circumferentially arranged slits extending from a rear end of the skirt toward the front side.

4. The tensioner according to claim 1, wherein the ball seat, the oil supply hole, and the tapered portion are plastically deformed by drawing on the sleeve bottom.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an illustrative diagram showing a timing system in which a tensioner according to one embodiment of the present invention is incorporated;

(2) FIG. 2 is a cross-sectional view illustrating the tensioner;

(3) FIG. 3 is a cross-sectional perspective view illustrating the rear end of a sleeve;

(4) FIG. 4 is a cross-sectional view illustrating a conventional tensioner; and

(5) FIG. 5 is a cross-sectional view illustrating an example of a tensioner for reference.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) A tensioner 10 according to one embodiment of the present invention will be described with reference to the drawings.

(7) First, the tensioner 10 of this embodiment is incorporated in a chain transmission used in a timing system or the like of a car engine. As shown in FIG. 1, the tensioner is attached to an engine block (not shown) to apply appropriate tension to the slack side of a transmission chain CH passing over a plurality of sprockets S1 to S3 via a tensioner lever G to reduce vibration during the drive.

(8) The tensioner 10 includes, as shown in FIG. 1 to FIG. 3, a tensioner body 20 having a body hole 21, a sleeve 30 inserted in the body hole 21, a plunger 40 inserted in the sleeve 30 so as to be able to move forward and backward along the axial direction of the sleeve 30, a check valve 50, and a coil spring 60 as a biasing unit that is accommodated so as to be able to expand and contract inside an oil pressure chamber 11 formed between the rear end of the sleeve 30 and the rear end of the plunger 40 and that biases the plunger 40 toward a front side (protruding side).

(9) Hereinafter, various constituent elements of the tensioner 10 will be described with reference to the drawings.

(10) The tensioner body 20 is made from an aluminum alloy, synthetic resin, and the like, and includes, as shown in FIG. 1, the body hole 21 that is open, on one (front) end, an oil supply hole 22 that extends through an outer wall of the tensioner body 20 to the body hole 21, and a mounting part 23 having a mounting hole for a bolt or the like to be passed through to secure the tensioner body 20 to an engine block.

(11) The sleeve 30 is made from a metal such as iron or the like and includes the cylindrical sleeve body 31, and a sleeve bottom 32 formed integrally at the rear end of the sleeve body 31, as shown in FIG. 2 and FIG. 3.

(12) As shown in FIG. 2 and FIG. 3, an oil supply hole 33 is formed in the sleeve bottom 32 for supplying oil into the oil pressure chamber 11 from the outside. This oil supply hole 33 communicates with the oil supply hole 22 of the tensioner body 20 with the sleeve 30 being disposed in the tensioner body 20.

(13) In the sleeve bottom 32 is also formed, as shown in FIG. 2 and FIG. 3, a ball seat 34 protruding in a cylindrical shape toward the front side integrally with and continuously from the edge of the oil supply hole 33. This ball seat 34 functions as a seat for the check ball 51 of a check valve 50 which will sit on the front end thereof. The ball seat 34 is formed by a drawing process wherein the sleeve bottom 32 is pressed from the rear face toward the front face, and as a result of this drawing process, a tapered portion 33a with its diameter increasing from the front side toward the rear side is formed on the rear side of the oil supply hole 33. The ball seat 34 decreases in diameter from the front side toward the rear side.

(14) The plunger 40 is made from a metal such as iron or the like and has a plunger hole 41 inside, which is open on the rear side as shown in FIG. 2 and FIG. 3.

(15) The check valve 50 allows the oil to flow in from the outside through the oil supply holes 22 and 33 into the oil pressure chamber 11, and prevents the oil from flowing out from the oil supply holes 22 and 33. As shown in FIG. 2 and FIG. 3, the check valve is disposed on the front face of the sleeve bottom 32.

(16) As shown in FIG. 2 and FIG. 3, the check valve 50 is made up of a spherical check ball 51 that is seated on the front end of the ball seat 34 to be capable of tightly contacting therewith, a retainer 52 attached on the front face of the sleeve bottom 32 to restrict the movement of the check ball 51, and a ball spring (not shown) disposed between the check ball 51 and the retainer 52. The ball spring (not shown) is provided to bias the check ball 51 toward the ball seat 34, but the ball spring (not shown) may not necessarily be provided. The check ball 51 and the retainer 52 are made of metal.

(17) The retainer 52 includes, as shown in FIG. 2 and FIG. 3, a substantially disc-like top 52a disposed on the front side of the check ball 51, a skirt 52b extending vertically downward toward the rear side from the peripheral edge of the top 52a and arranged on the radially outer side of the ball seat 34, and a plurality of flanges 52c extending radially outward from the rear end of the skirt 52b. The skirt 52b decreases in diameter from the front side toward the rear side, and includes a plurality of circumferentially arranged slits 52d extending from the rear end toward the front side (front end) of the skirt 52b.

(18) The coil spring 60 is disposed such that its front end is in contact with the bottom of the plunger hole 41 of the plunger 40 while its rear end is in contact with the front face of the flanges 52c of the retainer 52, and configured to bias the plunger 40 toward the front side, as shown in FIG. 2 and FIG. 3.

(19) While the coil spring 60 is disposed such that its rear end is in contact with the flanges 52c of the retainer 52 in this embodiment, the way how the rear end of the coil spring 60 is disposed is not limited to the example described above. For example, the rear end of the coil spring 60 may be disposed on the radially outer side of the flanges 52c without making contact therewith.

(20) While embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments and may be carried out with various design changes without departing from the scope of the present invention set forth in the claims.

(21) For example, while the tensioner was described as a component to be incorporated in a timing system of a car engine in the embodiments above, the purpose of use of the tensioner is not limited to this specific application.

(22) Also, while the tensioner was described as a component that applies tension to a transmission chain with a tensioner lever in the embodiments above, the plunger can directly guide the transmission chain slidably with a distal end thereof to apply tension to the transmission chain.

(23) The tensioner may not necessarily be applied to a transmission mechanism with a transmission chain but can also be used for similar transmission mechanisms that use belts, ropes and the like, and can be applied in a variety of industrial fields where it is required to apply tension to an elongated component.

(24) In the embodiment described above, the sleeve is disposed inside the tensioner body that is attached to a part in the surroundings of the tensioner such as an engine block or the like. Instead, the sleeve may be directly attached to the engine block or the like.