JPH10141453A - Hydraulic auto tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic auto tensioner which corresponds to a tensioner for high tensile force and is compact and increase the sealing property so as to prevent and reduce wear of a slide part thereof. SOLUTION: This hydraulic auto tensioner is constituted in such a manner that a high pressure chamber 23 and a low pressure chamber 24 are formed in the inside and outside of a cylinder 17, a piston part 18 of a plunger 8 advances into the high pressure chamber 23, and the plunger 8 is energized in the direction of retraction by a return spring 44 provided in the low pressure chamber 24. In this case, a spring cover 41 provided with an outer cylinder 41a which can cross over an end part of an opening of a casing 11 from the low pressure chamber 24 and can be extended is fixed on the plunger 8, a seal ring 20 which comes into slide-contact with outer periphery of the outer cylinder 41a is provided in the end part of the opening of the casing 11, and a return spring 44 is arranged between the outer cylinder 41a and the plunger 8. Moreover, a dust cover 32 is attached to the plunger 8 so that it moves together with the plunger 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic auto-tensioner for automatically applying appropriate tension to transmission members such as endless annular flat belts, V-belts, toothed belts and chains.

[0002]

2. Description of the Related Art As a conventional hydraulic auto-tensioner, one disclosed in Japanese Patent Application Publication No. Hei 2-500210 is known. 7 and 8 show the structure described in the publication, and FIG.
A belt 1 is wrapped around a pulley 2 and a play pulley 3.
The idler pulley 3 is rotatably attached to the distal end of the arm 4, and the base end of the arm 4 is attached to the shaft 5 so as to be swingable. A hydraulic auto tensioner 50 is connected to the center of the arm 4.

A hydraulic auto-tensioner 50 includes a bottomed cylindrical casing 51, a cylinder 52 fitted into the casing 51, and a piston 53 slidably inserted into the cylinder 52 through an open end of the casing 51. And a seal ring 54 provided at the open end of the casing 51 and slidably in contact with the piston 53. The upper end of the piston 53 is connected to the arm 4. A high-pressure chamber 55 in the cylinder 52 and a low-pressure chamber 56 between the cylinder 52 and the casing 51
Communicates with a check valve 57 at a lower portion of the cylinder 52 and a passage 58, and passes through the passage 58 from the low pressure chamber 56 to the high pressure chamber 5.
5 and also communicates through a clearance 59 between the cylinder 52 and the piston 53, and the hydraulic oil flows from the high-pressure chamber 55 to the low-pressure chamber 56 via the clearance 59.

[0004] In the middle of the piston 53, an engagement ring 6 is provided.
0 is fitted, and the spring seat upper 61 that engages with the engagement ring 60 is loosely fitted from below.
The spring seat upper 61 is in contact with a lid 62 fixed to the opening end of the casing 51 by caulking so as not to come off. The seal ring 54 is attached to the inner periphery of the lid 62. In the low pressure chamber 56,
A return spring 64 is mounted between a spring seat lower 63 integrally formed below the cylinder 52 and the spring seat upper 61, and the return spring 64 is connected to the spring seat upper 61 and the engagement ring 60.
Urges the piston 53 in the cylinder retreating direction (upward in the figure).

[0005]

However, the hydraulic auto-tensioner 50 has the following problems. A return spring 64 is provided below the seal ring 54.
Is provided, the height of the return spring 64 is restricted, so that a long return spring that exerts a high load cannot be used, and it is difficult to use a tensioner for high tension. If the height of the entire tensioner is increased, the height at which the return spring is mounted can be increased. Since the seal ring 54 and the piston 53 are exposed to the outside, dust, water, etc.
The problem of wear between the piston 53 and the seal ring 54 easily occurs between the piston 53 and the piston 53 rusting. This abrasion causes the hydraulic oil to flow out due to a decrease in sealing performance, and causes a loss of the tensioner function.

[0006] A first object of the present invention is to solve the above-mentioned problem and to use a long return spring which exerts a high load without increasing the height of the entire tensioner, and to cope with a tensioner for high tension. An object of the present invention is to provide a compact hydraulic auto tensioner. A second object of the present invention is to
An object of the present invention is to provide a highly reliable hydraulic auto-tensioner that can solve the above-mentioned problems and can prevent and reduce abrasion of a sliding portion by improving sealing performance. A third object of the present invention is to provide a hydraulic auto-tensioner that can achieve both the first and second objects.

[0007]

According to a first aspect of the present invention, a cylindrical cylinder is provided inside a bottomed cylindrical casing, and a high-pressure chamber and a high-pressure chamber are provided inside and outside the cylinder. In a hydraulic auto tensioner in which a low pressure chamber is formed, a plunger of a plunger enters the high pressure chamber from an open end of the casing, and a plunger is urged in a retreating direction by a return spring provided in the low pressure chamber, A spring cover having an outer cylinder that can extend beyond the opening end of the casing from the casing is fixed to the plunger, and a seal ring that slides on the outer periphery of the outer cylinder is provided at the opening end of the casing. A return spring is arranged between the two.

According to a second aspect of the present invention, a cylindrical cylinder is provided inside a bottomed cylindrical casing, and a high-pressure chamber and a low-pressure chamber are formed inside and outside the cylinder. In a hydraulic auto-tensioner in which the plunger piston enters the high-pressure chamber and the plunger is urged in the retreating direction by a return spring provided in the low-pressure chamber, the opening end of the casing is covered from the plunger to the outer periphery of the casing. Dust cover
It is characterized in that it is attached to the plunger so as to move with the plunger.

According to a third aspect of the present invention, a cylindrical cylinder is provided inside a bottomed cylindrical casing, and a high-pressure chamber and a low-pressure chamber are formed inside and outside the cylinder. In a hydraulic auto-tensioner in which a piston portion of a plunger enters a high-pressure chamber and a plunger is urged in a retreating direction by a return spring provided in the low-pressure chamber, the plunger can extend from the low-pressure chamber beyond the opening end of the casing. A spring cover having an outer cylinder is fixed to the plunger, a seal ring that slides on the outer circumference of the outer cylinder is provided at an open end of the casing, and a return spring is arranged between the outer cylinder and the plunger. Move the dust cover, which covers the sliding part between the cover and the seal ring, to the outer periphery of the casing, so that the dust cover moves with the plunger. Characterized in that the installed.

[0010] In the second or third invention, it is preferable to further configure as (1) and (2) below. (1) The dust cover is formed of resin or rubber, and the lip portion that is in sliding contact with the outer periphery of the casing without any gap is integrally formed with the cylindrical portion of the dust cover disposed on the outer periphery of the casing with the resin or rubber. In this case, it is preferable to provide the dust cover with a bellows portion that expands and contracts in the direction of movement of the plunger to absorb the vibration of the plunger.

(2) The casing of the casing is arranged such that the gap between the casing and the casing of the dust cover arranged on the outer periphery of the casing is narrow at the opening end of the casing and wide at the opening end of the casing. The outer peripheral surface or the inner peripheral surface of the cylindrical portion has a stepped structure.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic auto tensioner of the present invention will be described below with reference to the drawings. The hydraulic auto tensioner 10 is a general-purpose product for automatically applying appropriate tension to transmission members such as an endless annular flat belt, V belt, toothed belt, and chain. The structure between the hydraulic auto tensioner 10 and the transmission member is not particularly limited, and can be used in place of the conventional hydraulic auto tensioner 50 as shown in FIG. 7, for example.

A hydraulic auto-tensioner 10 according to a first embodiment shown in FIGS. 1 to 3 includes a bottomed cylindrical casing 11 and a mounting portion 12 integrally formed on the lower surface of the casing 11.
, An annular collar 13 is rotatably provided via a dry bearing 14. A press-fitted portion 15 having a reduced diameter is provided at a lower portion of the inner periphery of the casing 11.
An oil groove 16 is formed in the inner peripheral surface of the casing 11 and the inner bottom surface of the casing 11.

A bottomed cylindrical cylinder 1 having an outer diameter that is slightly smaller than the inner diameter of the casing 11 is provided in the casing 11.
7 is inserted, and its lower end is press-fitted and fixed to the press-fitted portion 15. From the open end of the casing 11 to the cylinder 17
A rod-shaped piston portion 18 at the lower end of the plunger 8 is slidably moved up and down with a predetermined clearance 30 into the inside (high-pressure chamber 23 described later). An annular collar 13 is rotatably provided on a mounting portion 19 at the upper end of the plunger 8 via a dry bearing 14.
Are connected, for example, to the arm 4 of FIG.

Above the plunger 8 but below the mounting portion 19, a longer outer cylinder 41a which has entered the opening of the casing 11, a shorter inner cylinder which is press-fitted to the outer periphery of the plunger 8, and upper ends of both cylinders A spring cover 41 integrally formed with a ceiling portion closing the portion is press-fitted and fixed. A return spring 44 is mounted between the lower surface of the ceiling portion of the spring cover 41 and the upper surface of the press-fitted portion 15 in a compressed state,
The plunger 8 is urged in the retreating direction (upward in the figure). A seal ring 20 slidably in contact with an outer cylinder 41a of a spring cover 41 is attached to a stepped portion on the inner periphery of the open end of the casing 11 together with a ring fitting 21, and the seal ring 20 is fitted into a groove on the inner periphery of the open end. The stopper ring 22 is locked from below so as not to come off.

Thus, the outer cylinder 4 of the spring cover 41
1a is configured to extend upward from a low-pressure chamber 24 to be described later beyond the opening end of the casing 11, and a return spring 4a is provided between the outer cylinder 41a and the plunger 8.
Since the tension springs 4 are provided, the height of the return springs 44 can be secured to the maximum without increasing the height of the entire tensioner. Therefore, a long return spring 4 that exhibits high load while being compact
4 can be used, and corresponds to a tensioner for high tension (for example, a belt transmission member of a four-cylinder engine or a diesel engine with a high fluctuation torque).

A high-pressure chamber 23 is formed between the inner peripheral surface of the cylinder 17 and the lower end surface of the piston 18. A low-pressure chamber 24 is formed between the outer peripheral surface of the cylinder 17, the inner peripheral surface of the casing 11, and the spring cover 41, and has a structure for storing hydraulic oil. High pressure chamber 23 and low pressure chamber 2
4 communicates in one direction via a check valve 25 provided on the bottom wall of the cylinder 17 and the oil groove 16. The high-pressure chamber 23 and the low-pressure chamber 24 are formed by the cylinder 17 and the piston 18
Hydraulic oil can also leak from the high-pressure chamber 23 to the low-pressure chamber 24 via the clearance 30 through the clearance 30 therebetween.

An upper portion of the plunger 8 and a lower portion of the mounting portion 19, a rubber covering the open end of the casing 11 (particularly the spring cover 41 and the seal ring 20) from the plunger 8 to the outer periphery of the casing 11. A dust cover 32 is attached, and the dust cover 32 moves up and down together with the plunger 8. The dust cover 32 is provided on the cylindrical portion 3
3 and a plate-shaped lid portion 34 for closing the upper end of the cylindrical portion 33 are integrally formed. The inner peripheral edge of the lid portion 34 is sandwiched between the flange portion 9 integrally formed on the upper portion of the plunger 8 and the upper surface of the ceiling portion of the spring cover 41 with an interference, and is securely sealed.

As described above, since the dust cover 32 covers the sliding portion between the spring cover 41 and the seal ring 20, dust, water and the like may enter the sliding portion and the spring cover 41 may rust. Can be prevented and reduced, and wear of the sliding portion can be prevented and reduced, and the tensioner function can be maintained. In the present embodiment, the same effect is further enhanced by configuring the tubular portion 33 as follows.

The cylindrical portion 33 is provided at an intermediate portion between the upper end and the lower end thereof, and is provided with a bellows portion 35 which expands and contracts in the direction of movement of the plunger 8. The lip portion 36 that slides on the outer periphery of the eleventh without gap is integrally formed of rubber. And the cylinder part 33 is
At the position where the piston is most retracted, it is still long enough to cover the open end of the casing 11 and to keep the lip portion 36 in sliding contact with the outer periphery of the casing 11.

The bellows portion 35 is formed to be thinner than other portions of the cylindrical portion 33 so as to be easily expanded and contracted. The inner diameter of the constricted portion 35a of the bellows portion 35 is the lip portion 36.
As shown in FIG. 3, the constricted portion 35 a does not protrude inward from the inner diameter of the cylindrical portion 33 when the bellows 35 is retracted, as shown in FIG. 3. Therefore, the constricted portion 35a does not interfere with the casing 11 to prevent the plunger 8 from moving forward and backward.

The lip portion 36 is an upper and lower double ridge provided around the inner periphery of the cylindrical portion 33, and the ridge is formed by the casing 11.
It is formed so as to become thinner toward the tip so as to minimize friction with the outer periphery. The lip portion 36 closes the gap between the dust cover 32 and the casing 11 to prevent dust and water from entering between the spring cover 41 and the seal ring 20 and prevent the piston portion 18 from being rusted. I have. Further, by making the ridges double up and down, the sealing inside the dust cover 32 is further enhanced. Therefore, the reliability against abrasion is improved,
The sealing property is maintained, and the tensioner function can be maintained.

In a normal use state of the hydraulic auto tensioner 10, the plunger 8 moves forward and backward with a small stroke with respect to the casing 11. Then, the lid 34 of the dust cover 32 is also moved up and down accordingly, but the vibration caused by the movement is absorbed by the elastic action of the lid 34 and the bellows 35 and is not transmitted to the lip 36. . Therefore, in a normal use state, even if the plunger 8 moves forward and backward, the lip portion 36 does not move up and down, and the lip portion 36 does not wear.

When the hydraulic auto-tensioner 10 is assembled or removed, or when the belt length changes due to long-term use, the plunger 8 moves back and forth with respect to the casing 11 with a large stroke. It slides and responds to the forward / backward movement. Since this sliding is rare, it does not relate to the wear of the lip portion 36.

Next, in the hydraulic auto-tensioner 10 of the second embodiment shown in FIGS. 4 to 6, the cylindrical portion 33 of the dust cover disposed on the outer periphery of the casing 11 is formed straight. Instead of forming the bellows portion 35 and the lip portion 36, the gap between the cylindrical portion 33 and the casing 11 is narrow at the open end side of the casing 11 (gap 46) and wide at the open end side of the cylindrical portion 33 (gap 47). Thus, the present embodiment differs from the first embodiment in that the outer peripheral surface of the casing 11 has a stepped structure.

If the gap between the cylindrical portion 33 and the casing 11 is only a wide gap, the effect of preventing intrusion of dust, water, etc. is reduced. On the other hand, if the gap is only a narrow gap, muddy water is accumulated under the gap 46 due to surface tension. Will not fall. In the present embodiment, the narrow gap 46 on the opening end side of the casing 11 exhibits an effect of preventing intrusion of dust, water, and the like, and the wide gap 47 on the opening end side of the cylindrical portion 33 drops muddy water without accumulating. , Sealability and tensioner function can be maintained.

In this embodiment, a spring seat 40 for receiving a return spring 44 is interposed on the upper surface of the press-fitted portion 15. Other members and parts are basically common to the first embodiment, and are denoted by common reference numerals and description thereof is omitted.

It should be noted that the present invention is not limited to the above-described embodiment, and can be embodied by appropriately changing the scope of the invention as follows, for example, as follows.

(1) In the dust cover 32 of the first embodiment, a soft resin is used for the bellows portion 35 and the lip portion 36 and a hard resin is used for the other portions. Or use rubber. (2) Increasing or decreasing the number of ridges of the lip portion 36 of the first embodiment. (3) In the second embodiment, the same narrow gap 46 and wide gap 47 as described above are realized by making the outer peripheral surface of the casing 11 stepless and making the inner peripheral surface of the cylindrical portion 33 stepped. .

[0030]

As described in detail above, according to the hydraulic auto tensioner of the first aspect of the present invention, a long return spring that exerts a high load can be used without increasing the height of the entire tensioner. It is compatible with tensioners for high tension while being compact.

According to the hydraulic auto-tensioner according to the second aspect of the present invention, the sealing performance can be improved, the wear of the sliding portion can be prevented or reduced, and the reliability can be improved.

According to the hydraulic auto-tensioner according to the third aspect of the present invention, a long return spring that exerts a high load can be used without increasing the height of the entire tensioner. Can be used for tensioners. In addition, it is possible to prevent or reduce the wear of the sliding portion by enhancing the sealing property, and to enhance the reliability.

In addition to the above effects, the hydraulic auto-tensioner according to the fourth, fifth or sixth aspect of the present invention can further enhance the sealing performance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a hydraulic auto-tensioner according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway front view of a dust cover of the hydraulic auto tensioner.

FIG. 3 is a partially cutaway front view showing the dust cover in a retracted state.

FIG. 4 is a cross-sectional view showing a hydraulic auto tensioner according to a second embodiment of the present invention.

FIG. 5 is a sectional view taken along line VV of FIG. 4;

FIG. 6 is a sectional view taken along line VI-VI of FIG. 4;

FIG. 7 is a schematic view showing an example of use of a hydraulic auto tensioner.

FIG. 8 is a partially broken front view showing a conventional hydraulic auto tensioner.

[Explanation of symbols]

 8 Plunger 10 Hydraulic auto tensioner 11 Casing 17 Cylinder 18 Piston section 20 Seal ring 23 High pressure chamber 24 Low pressure chamber 32 Dust cover 33 Tube section 34 Cover 35 Bellows section 36 Lip section 41 Spring cover 41a Outer pipe 44 Return spring 46 Narrow gap 47 wide gap 48 steps

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tomiho Hirano 10 Hamadashita, Nakahata-cho, Nishio-shi, Aichi Pref.

Claims (6)

[Claims] 1. A high-pressure chamber and a low-pressure chamber are formed inside and outside a cylinder provided in a bottomed cylindrical casing, and a plunger is inserted into the high-pressure chamber from an opening end of the casing. In a hydraulic auto-tensioner configured to allow a piston portion to enter and urge a plunger in a retreating direction by a return spring provided in the low-pressure chamber, an outer cylinder that can extend from the low-pressure chamber beyond an opening end of a casing. A hydraulic cover, wherein a spring cover provided is fixed to a plunger, a seal ring slidingly contacting the outer periphery of the outer cylinder is provided at an opening end of the casing, and a return spring is arranged between the outer cylinder and the plunger. Auto tensioner. 2. A high-pressure chamber and a low-pressure chamber are formed inside and outside a cylinder provided in a bottomed cylindrical casing, and a plunger is inserted into the high-pressure chamber from an open end of the casing. A hydraulic auto tensioner in which a piston portion is made to enter and a plunger is urged in a retreating direction by a return spring provided in the low-pressure chamber, wherein the plunger covers an opening end of the casing, and is arranged from the plunger to the outer periphery of the casing. A hydraulic dust cover having a dust cover attached to the plunger so as to move with the plunger. 3. A high-pressure chamber and a low-pressure chamber are formed inside and outside a cylinder provided in a bottomed cylindrical casing, and a plunger is inserted into the high-pressure chamber from an open end of the casing. In a hydraulic auto-tensioner configured to allow a piston portion to enter and urge a plunger in a retreating direction by a return spring provided in the low-pressure chamber, an outer cylinder that can extend from the low-pressure chamber beyond an opening end of a casing. A spring cover provided is fixed to the plunger, a seal ring slidably contacting the outer periphery of the outer cylinder is provided at an open end of the casing, and a return spring is arranged between the outer cylinder and the plunger. A dust cover covering the sliding portion with the seal ring and extending to the outer periphery of the casing is moved by the plunger so as to move together with the plunger. Hydraulic auto-tensioner, characterized in that attached to. 4. The dust cover is formed of resin or rubber, and a lip portion which is in sliding contact with a cylindrical portion of the dust cover disposed on the outer periphery of the casing without any gap on the outer periphery of the casing is formed integrally with the resin or rubber. Item 4. The hydraulic auto tensioner according to item 2 or 3. 5. The hydraulic auto-tensioner according to claim 4, wherein a bellows portion is provided on the dust cover so as to expand and contract in the direction of movement of the plunger and absorb vibration of the plunger. 6. The casing of the casing such that a gap between the casing and the casing of the dust cover disposed on the outer periphery of the casing is narrow at the opening end of the casing and wide at the opening end of the casing. 4. The hydraulic auto-tensioner according to claim 2, wherein the outer peripheral surface or the inner peripheral surface of the cylindrical portion has a stepped structure.