Tensioner

Abstract

An object of the present invention is to provide a tensioner capable of keeping the oil pressure in an oil pressure chamber stable in a favorable manner. Provided is a tensioner wherein a relief mechanism includes a partition part, a valve member at least partly positioned inside an internal relief hole such as to be able to approach and separate from an oil pressure chamber, a valve biasing unit, and an external relief hole. A movement restricting part that restricts movement of the valve member toward the oil pressure chamber is formed in the partition part. An oil passing groove is formed in at least one of an outer circumferential surface of the valve member and an inner circumferential surface of the internal relief hole, the outer circumferential surface and the inner circumferential surface facing each other.

Claims

1. A tensioner comprising: a plunger having a plunger hole that is open on a rear side; a housing having a plunger bore that is open on a front side and accommodates the plunger; a main biasing unit that is accommodated so as to freely expand and contract inside an oil pressure chamber formed between the plunger and the plunger bore and that biases the plunger toward the front side; and a relief mechanism that releases oil inside the oil pressure chamber to outside of the plunger when oil pressure in the oil pressure chamber rises, wherein the relief mechanism includes a partition part that partitions an interior of the plunger hole into the oil pressure chamber and a relief space and that has an internal relief hole connecting the oil pressure chamber with the relief space, a valve member at least partly positioned inside the internal relief hole such as to be able to approach and separate from the oil pressure chamber, a valve biasing unit biasing the valve member toward the oil pressure chamber, and an external relief hole formed in the plunger and connecting the relief space with outside of the plunger, a movement restricting part that restricts movement of the valve member toward the oil pressure chamber is formed in the partition part, an oil passing groove is formed in at least one of an outer circumferential surface of the valve member and an inner circumferential surface of the internal relief hole, the outer circumferential surface and the inner circumferential surface facing each other, and the valve member and the internal relief hole are formed such that, as the valve member moves away from the oil pressure chamber, an area where the outer circumferential surface of the valve member and the inner circumferential surface of the internal relief hole face each other decreases along a moving direction of the valve member.

2. The tensioner according to claim 1, wherein the oil passing groove is formed in the outer circumferential surface of the valve member.

3. The tensioner according to claim 1, wherein the plunger includes a plunger body having the plunger hole, and a cap member attached to a front end of the plunger body, and the partition part is formed integrally on an inner circumferential wall of the plunger hole.

4. The tensioner according to claim 1, wherein the valve member includes a columnar valve body, and the internal relief hole is cylindrical.

5. A tensioner comprising: a plunger having a plunger hole that is open on a rear side; a housing having a plunger bore that is open on a front side and accommodates the plunger; a main biasing unit that is accommodated so as to freely expand and contract inside an oil pressure chamber formed between the plunger and the plunger bore and that biases the plunger toward the front side; and a relief mechanism that releases oil inside the oil pressure chamber to outside of the plunger when oil pressure in the oil pressure chamber rises, wherein the relief mechanism includes a partition part that partitions an interior of the plunger hole into the oil pressure chamber and a relief space and that has an internal relief hole connecting the oil pressure chamber with the relief space, a valve member at least partly positioned inside the internal relief hole such as to be able to approach and separate from the oil pressure chamber, a valve biasing unit biasing the valve member toward the oil pressure chamber, and an external relief hole formed in the plunger and connecting the relief space with outside of the plunger, a movement restricting part that restricts movement of the valve member toward the oil pressure chamber is formed in the partition part, an oil passing groove is formed in at least one of an outer circumferential surface of the valve member and an inner circumferential surface of the internal relief hole, the outer circumferential surface and the inner circumferential surface facing each other, and the oil passing groove is formed in the outer circumferential surface of the valve member.

6. A tensioner comprising: a plunger having a plunger hole that is open on a rear side; a housing having a plunger bore that is open on a front side and accommodates the plunger; a main biasing unit that is accommodated so as to freely expand and contract inside an oil pressure chamber formed between the plunger and the plunger bore and that biases the plunger toward the front side; and a relief mechanism that releases oil inside the oil pressure chamber to outside of the plunger when oil pressure in the oil pressure chamber rises, wherein the relief mechanism includes a partition part that partitions an interior of the plunger hole into the oil pressure chamber and a relief space and that has an internal relief hole connecting the oil pressure chamber with the relief space, a valve member at least partly positioned inside the internal relief hole such as to be able to approach and separate from the oil pressure chamber, a valve biasing unit biasing the valve member toward the oil pressure chamber, and an external relief hole formed in the plunger and connecting the relief space with outside of the plunger, a movement restricting part that restricts movement of the valve member toward the oil pressure chamber is formed in the partition part, an oil passing groove is formed in at least one of an outer circumferential surface of the valve member and an inner circumferential surface of the internal relief hole, the outer circumferential surface and the inner circumferential surface facing each other, the plunger includes a plunger body having the plunger hole, and a cap member attached to a front end of the plunger body, and the partition part is formed integrally on an inner circumferential wall of the plunger hole.

7. A tensioner comprising: a plunger having a plunger hole that is open on a rear side; a housing having a plunger bore that is open on a front side and accommodates the plunger; a main biasing unit that is accommodated so as to freely expand and contract inside an oil pressure chamber formed between the plunger and the plunger bore and that biases the plunger toward the front side; and a relief mechanism that releases oil inside the oil pressure chamber to outside of the plunger when oil pressure in the oil pressure chamber rises, wherein the relief mechanism includes a partition part that partitions an interior of the plunger hole into the oil pressure chamber and a relief space and that has an internal relief hole connecting the oil pressure chamber with the relief space, a valve member at least partly positioned inside the internal relief hole such as to be able to approach and separate from the oil pressure chamber, a valve biasing unit biasing the valve member toward the oil pressure chamber, and an external relief hole formed in the plunger and connecting the relief space with outside of the plunger, a movement restricting part that restricts movement of the valve member toward the oil pressure chamber is formed in the partition part, an oil passing groove is formed in at least one of an outer circumferential surface of the valve member and an inner circumferential surface of the internal relief hole, the outer circumferential surface and the inner circumferential surface facing each other, the valve member includes a columnar valve body, and the internal relief hole is cylindrical.

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. 3A is a perspective view illustrating a valve member;

(4) FIG. 3B is a perspective view illustrating the valve member;

(5) FIG. 4 is a cross-sectional view illustrating a state of a relief mechanism in normal operation;

(6) FIG. 5 is a cross-sectional view illustrating a state of the relief mechanism when oil pressure rises;

(7) FIG. 6 is a cross-sectional view illustrating a variation example of the relief mechanism; and

(8) FIG. 7 is a cross-sectional view illustrating a tensioner of related art.

DESCRIPTION OF THE PREFERRED EMBODIMENT

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

(10) First, the tensioner 10 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 drive chain CH passing over a plurality of sprockets S1 to S3 via a tensioner lever G to reduce vibration during the drive.

(11) The tensioner 10 includes, as shown in FIG. 2, a plunger 20 having a plunger hole 21a that is open on a rear side, a housing 30 having a plunger bore 31 that is open on a front side for accommodating the plunger 20, a check valve 40 disposed on the bottom part 32 side of the housing 30, a relief mechanism 50 that releases oil from the oil pressure chamber 11 to the outside of the plunger 20 when the oil pressure in the oil pressure chamber 11 rises, and a main spring (main biasing unit) 60 that is accommodated so as to freely expand and contract inside the oil pressure chamber 11 formed between the plunger 20 and the plunger bore 31 and that biases the plunger 20 toward the front side.

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

(13) The plunger 20 is made up of a cylindrical plunger body 21 having the plunger hole 21a, and a cap member 22 attached to the front end of the plunger body 21, as shown in FIG. 2 and FIG. 4. The plunger body 21 is made of metal such as iron, while the cap member 22 is made of synthetic resin, metal or the like.

(14) The plunger body 21 has a partition part 21b that is integrally formed on the inner circumferential wall of the plunger hole 21a and divides the interior of the plunger hole 21a into the oil pressure chamber 11 on the rear side and a relief space 12 on the front side, as shown in FIG. 2 and FIG. 4.

(15) The partition part 21b has a cylindrical internal relief hole 21c in a central part thereof that extends through in the front to back direction to connect the oil pressure chamber 11 with the relief space 12 as shown in FIG. 4.

(16) Further, an annular movement restricting part 21d, which restricts rearward movement (toward the oil pressure chamber 11) of the valve member 51 disposed in the internal relief hole 21c, protrudes radially inward from the inner circumferential surface of the internal relief hole 21c in the partition part 21b.

(17) The cap member 22 configures a bottom part at the front end of the plunger hole 21a as shown in FIG. 2 and FIG. 4. The cap member 22 is provided with an external relief hole 22a that connects the relief space 12 with the outside of the plunger 20.

(18) The housing 30 includes, as shown in FIG. 1 and FIG. 2, a cylindrical plunger bore 31 that is open on the front side, a bottom part 32 formed on the rear side, an oil supply hole 33 formed in the bottom part 32 to extend through the outer wall of the housing 30 to the plunger bore 31, and a mounting part 34 for fixedly attaching the housing 30 to an engine block.

(19) The check valve 40 allows the oil to flow into the oil pressure chamber 11 from the outside through the oil supply hole 33, and stops the oil from flowing out from the oil supply hole 33.

(20) The check valve 40 is made up of, as shown in FIG. 2, a ball seat 41 disposed in tight contact with the front face of the bottom part 32 of the housing 30, a spherical check ball 42 that can be seated on the ball seat 41 in tight contact therewith, and a retainer 43 arranged on the front side of the check ball 42 to restrict the movement of the check ball 42. A ball spring that biases the check ball 42 toward the ball seat 41 may be disposed between the check ball 42 and the retainer 43.

(21) The main spring 60 is disposed such that, as shown in FIG. 2, its front end is arranged on the rear face of the partition part 21b while its rear end is arranged on the front face of a flange part of the retainer 43. Thus the main spring 60 presses the ball seat 41 and retainer 43 against the bottom part 32 of the housing 30.

(22) As shown in FIG. 2 and FIG. 4, the relief mechanism 50 is made up of the partition part 21b described above, a valve member 51, a valve spring (valve biasing unit) 52 that biases the valve member 51 toward the oil pressure chamber 11, and the external relief hole 22a mentioned above.

(23) The valve member 51 is at least partly positioned inside the internal relief hole 21c such as to be able to move back and forth (to approach and separate from the oil pressure chamber 11).

(24) As shown in FIG. 3A, FIG. 3B, and FIG. 4, the valve member 51 includes a columnar valve body 51a, a lip 51b formed on the outer peripheral edge of the front end face of the valve body 51a, a taper 51c formed on the outer peripheral edge of the rear end face of the valve body 51a, and a plurality of oil passing grooves 51d formed in the outer circumferential surface of the valve body 51a.

(25) As shown in FIG. 3A and FIG. 3B, the oil passing grooves 51d are each formed as a V groove extending straight from the rear end to the front end of the valve body 51a along the front to back direction and circumferentially spaced (at 90 in this embodiment).

(26) The taper 51c is formed such as to decrease in diameter from the front side to the rear side.

(27) As shown in FIG. 4, the valve spring 52 has its front end disposed on the rear face of the bottom at the front end of the plunger hole 21a (cap member 22), and its rear end disposed on the front face of the valve member 51.

(28) In normal operation of the tensioner 10 of this embodiment configured as described above, the rear end face (end face on the oil pressure chamber 11 side) of the valve body 51a is in contact with the movement restricting part 21d by the biasing force of the valve spring 52 as shown in FIG. 4, whereby a seal is formed between the rear end face of the valve body 51a and the movement restricting part 21d so that the oil in the oil pressure chamber 11 is prevented from leaking into the relief space 12.

(29) When the oil pressure in the oil pressure chamber 11 builds up, the valve member 51 is pushed and moves forward by the rising oil pressure in the oil pressure chamber 11 as shown in FIG. 5. As the rear end face of the valve body 51a and the movement restricting part 21d separate from each other, the seal between the valve member 51 and the movement restricting part 21d is removed, and the oil is released from the oil pressure chamber 11 into the relief space 12 through between the rear end face of the valve body 51a and the movement restricting part 21d, and through the oil passing grooves 51d formed in the outer circumferential surface of the valve member 51.

(30) The valve member 51 and internal relief hole 21c are formed such that, as the valve member 51 moves away from the oil pressure chamber 11, the area where the outer circumferential surface of the valve member 51 and the inner circumferential surface of the internal relief hole 21c face each other decreases along the moving direction of the valve member 51 (front to back direction). Therefore, as the valve member 51 moves forward (away from the oil pressure chamber 11), the flow resistance of the oil passage formed between the valve member 51 and the partition part 21b is reduced, so that the amount of released oil can be increased gradually. Thus the oil pressure in the oil pressure chamber 11 can be made stable in a favorable manner.

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

(32) For example, while the tensioner 10 was described as a component to be incorporated in a timing system of a car engine in the embodiment described above, the purpose of use of the tensioner 10 is not limited to this specific application.

(33) Also, while the tensioner 10 was described as a component that applies tension to a drive chain CH with a tensioner lever G in the embodiment described above, the plunger 20 can directly guide the drive chain CH slidably with a distal end thereof to apply tension to the drive chain CH.

(34) The tensioner may not necessarily be applied to a transmission mechanism with a drive chain CH 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.

(35) While the housing 30 accommodating the plunger 20 is described as the component known as a tensioner body that is attached to an engine block or the like in the embodiment described above, the housing 30 is not limited to the specific form described above and may be a cylindrical component known as a sleeve inserted into a body hole formed in the tensioner body.

(36) In the embodiment described above, the oil passing grooves 51d are formed as grooves that extend straight along the front to back direction. The oil passing groove 51d is not limited to the specific form described above. For example, the oil passing groove 51d may be formed in a helical shape on the outer circumferential surface of the valve body 51a (spiral shape formed around the center axis of the valve body 51a that extends in the front to back direction).

(37) In the embodiment described above, the oil passing groove 51d is formed in the valve member 51. Alternatively, oil passing grooves 21e may be formed only in the inner circumferential surface of the internal relief hole 21c that is arranged opposite the outer circumferential surface of the valve member 51 as shown in FIG. 6. Also, the oil passing grooves 21e and 51d may be formed in both of the outer circumferential surface of the valve member 51 and the inner circumferential surface of the internal relief hole 21c.

(38) In the embodiment described above, the oil passing grooves 51d extend from the rear end to the front end of the valve body 51a as shown in FIG. 3A, FIG. 3B, or FIG. 4. When the oil passing grooves 51d are formed to the valve body 51a, they only need to reach at least the rear end of the valve body 51a. When the oil passing grooves 51d are formed to the internal relief hole 21c, they only need to reach at least the front end of the internal relief hole 21c.

(39) In the embodiment described above, the oil passing groove 51d is formed such that its cross-sectional area (width or depth) does not change along the front to back direction. Alternatively, the oil passing groove 51d may be formed such that its cross-sectional area (width or depth) changes along the front to back direction.

(40) In the embodiment described above, the partition part 21b that divides the interior of the plunger hole 21a into the oil pressure chamber 11 and relief space 12 is integrally formed on the inner circumferential wall of the plunger hole 21a. The partition part 21b is not limited to this specific form. For example, the partition part 21b may be formed separately from the plunger 20, and disposed in the plunger hole 21a.

(41) In the embodiment described above, the plunger 20 is made up of two components, the plunger body 21 and cap member 22. The plunger 20 is not limited to this specific form. For example, when the partition part 21b is formed separately from the plunger 20 as mentioned above, the plunger 20 could be configured as a single component.

(42) In the embodiment described above, the valve body 51a is columnar and the internal relief hole 21c is cylindrical. These components are not limited to these specific forms. For example, the valve body 51a and the internal relief hole 21c may respectively be formed in a polygonal column and polygonal cylinder.