JP3064956B2 - Auto tensioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic tensioner for automatically applying an appropriate tension to transmission members such as an endless annular flat belt, V belt, toothed belt, and chain.

[0002]

2. Description of the Related Art As a conventional auto-tensioner, one disclosed in Japanese Patent Publication No. 2-500210 is known. 10 and 11 show a structure described in the publication, in which a V-belt 1 is wound around a pulley 2 and a play pulley 3. FIG. The play pulley 3 is rotatably attached to the tip of the arm 4,
The base end of the arm 4 is swingably attached to the shaft 5. A hydraulic auto tensioner 5 is provided at the center of the arm 4.
0 is linked.

An auto-tensioner 50 includes a bottomed cylindrical casing 51, a cylinder 52 fitted in the casing 51, and a cylinder 52 through an open end of the casing 51.
A plunger 55 having a piston portion 53 which slides into and out of the casing 51 and a seal ring 54 provided at an open end of the casing 51 and in sliding contact with the plunger 55 are provided.

[0004] A mounting portion 56 formed on the lower surface of the casing 51 and a mounting portion 5 formed on the upper end of the plunger 55.
7 are provided with mounting holes 58, respectively. A cylindrical resin dry bearing (bushing) 59 is inserted into the inner periphery of each mounting hole 58 with almost no interference, and a cylindrical metal collar 60 is inserted into the inner periphery of the dry bearing 59.
Is inserted with almost no interference. Therefore,
The sliding rotation can also occur between the mounting hole 58 and the dry bearing 59, but the dry bearing 5 having a small sliding area can be used.
9 and the collar 60 are more likely to occur. Casing 5
The collar 60 on one side is connected to, for example, the immovable part 6 in FIG. 10, and the collar 60 on the plunger 55 side is connected to, for example, the arm 4 in FIG.

[0005]

As described above, the dry bearing 59 and the collar 60 have almost no interference.
Muddy water and the like easily penetrate between them, and the penetrated muddy water and the like promote abrasion of the sliding surfaces of the dry bearing 59 and the collar 60, so that there is a possibility that rattling or abnormal noise may occur during use.

SUMMARY OF THE INVENTION An object of the present invention is to provide an auto tensioner which solves the above-mentioned problems and prevents infiltration of muddy water or the like between a dry bearing and a collar, thereby reducing wear and preventing backlash and abnormal noise. It is in.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a casing and a plunger which enters and exits the casing, and a mounting hole is formed in each mounting portion of the casing or the plunger. In an auto tensioner in which a cylindrical dry bearing is inserted into the inner periphery of the mounting hole, and a cylindrical collar is inserted into the inner periphery of the dry bearing, inner diameters are formed at both ends of the inner peripheral surface of the dry bearing. Is provided with a seal protrusion smaller than the outer diameter of the collar by the protrusion margin, and the collar is press-fitted into the inner periphery of both seal protrusions with the protrusion margin, and both ends of the outer peripheral surface of the collar at both seal protrusions. Is sealed.

As described above, when the collar is press-fitted into the dry bearing, sliding between the mounting hole and the dry bearing may become a problem. In that case, a press-fit portion whose outer diameter is larger than the inner diameter of the mounting hole by the press-fit portion interference margin is provided on the outer peripheral surface of the dry bearing, and the press-fit portion is press-fitted to the inner periphery of the mounting hole with the press-fit portion interference margin. Press-fit part tightening
Set the margin and area, and the margin and area of the seal projection.
By constant, it is preferable that the frictional force between the mounting hole and the dry bearings larger than the frictional force between the dry bearing and color. As a result, sliding rotation mainly occurs between the dry bearing and the collar, rather than between the mounting hole and the dry bearing, and both seal projections seal both ends of the outer peripheral surface of the collar.

Further, in the above case, a relief groove having a groove bottom deeper than the inner diameter of the mounting hole is provided on the outer peripheral surface of the dry bearing.
It is preferable that deformation of the dry bearing when the press-fitting portion is press-fitted into the mounting hole is released to the escape groove and absorbed.

Here, the "press-fit portion" and the "escape groove portion"
Any arrangement may be made on the outer peripheral surface of the dry bearing.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an auto tensioner according to the present invention will be described 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 auto-tensioner 10 and the transmission member is not particularly limited, and can be used in place of the conventional auto-tensioner 50, for example, as shown in FIG.

The auto-tensioner 10 of the first embodiment shown in FIGS. 1 to 5 has a bottomed cylindrical casing 11. Mounting part 12 integrally formed on the lower surface of casing 11
A mounting hole 26 is provided through the mounting hole 26, and a cylindrical resin dry bearing (bushing) 14 is inserted into the inner circumference of the mounting hole 26, and a cylindrical metal collar 13 is inserted into the inner circumference of the dry bearing 14. Is inserted.

As shown in FIGS. 4 and 5, at both ends of the dry bearing 14, an insertion-side flange portion 27 and an abutment-side flange portion 28 which are engaged with both ends of the mounting hole 26 are integrally formed. Is inserted into the mounting hole 26 from the insertion side flange portion 27 having a chamfer. As shown in FIG. 4 (a), an annular press-fit portion 29 whose outer diameter is larger than the inner diameter of the mounting hole 26 by the press-fit portion interference Ta is integrally formed at both ends of the outer peripheral surface of the dry bearing 14, At the center of the outer peripheral surface of the bearing 14, there is provided an annular relief groove 31 having a V-shaped cross section whose groove bottom is deeper than the inner diameter of the mounting hole 26. At the time of insertion shown in FIG. 4B, the two press-fitting portions 29 are press-fitted into the inner periphery of the mounting hole 26 with the press-fitting portion interference Ta.
At least a part of the deformation of the dry bearing 14 at the time of press-fitting (particularly, the diameter reduction deformation of the press-fitting portion 29) is released to the escape groove portion 31 (transition to the deformation of the escape groove portion 31) and absorbed.

As shown in FIG. 4A, the inner diameter of the collar 13 is set at both ends of the inner peripheral surface of the dry bearing 14.
Seal protrusion 35 smaller than the outer diameter of the protrusion by the protrusion interference Tb.
Are integrally formed. At the time of insertion shown in FIG.
A collar 13 is provided on the inner periphery of both seal protrusions 35 so that the protrusion interference Tb is provided.
, And both ends of the outer peripheral surface of the collar 13 are sealed by the two seal projections 35. Therefore, intrusion of muddy water or the like between the dry bearing 14 and the collar 13 can be prevented, thereby reducing abrasion and preventing backlash and abnormal noise. At least a part of the deformation of the seal projection 35 at the time of press-fitting of the collar 13 is at least partially released into the escape groove 31 and absorbed.

Here, by properly setting the interference Ta and the area of the press-fit part 29 of the press-fit part 29 and the interference Tb and the area of the protrusion of the seal protrusion 35, the distance between the mounting hole 26 and the dry bearing 14 is reduced. The frictional force between them is larger than the frictional force between the dry bearing 14 and the collar 13. Thus, the sliding rotation mainly occurs between the dry bearing 14 and the collar 13 than between the mounting hole 26 and the dry bearing 14. Therefore, wear between the mounting hole 26 and the dry bearing 14 does not matter.

A press-fitted portion 15 having a reduced diameter is provided in the lower portion of the inner periphery of the casing 11, and an oil groove 16 is formed in the inner peripheral surface of the press-fitted portion 15 and the inner bottom surface of the casing 11.

A bottomed cylindrical cylinder 1 having an outer diameter 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). A mounting hole 26 is provided through the mounting portion 19 at the upper end of the plunger 8, similarly to the mounting portion 12, and a dry bearing 14 is inserted into the inner periphery of the mounting hole 26. A collar 13 is inserted around the circumference. The collar 13 is connected to, for example, the arm 4 shown in FIG. The structure and mutual relationship of the mounting hole 26, the dry bearing 14 and the collar 13 are the same as those in the mounting portion 12. Therefore, intrusion of muddy water or the like between the dry bearing 14 and the collar 13 can be prevented, thereby reducing abrasion and rattling and abnormal noise.

Above the plunger 8 and 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 in a compressed state between the lower surface of the ceiling portion of the spring cover 41 and the spring seat 40 installed on the upper surface of the press-fitted portion 15, and moves the plunger 8 in the retreating direction (upward in the figure). It is energizing. Casing 11
The stepped portion on the inner periphery of the open end of the
A seal ring 20 slidingly in contact with the outer cylinder 41a is mounted together with a ring fitting 21, and the seal ring 20 is locked from below onto a stopper ring 22 fitted in a groove on the inner periphery of the opening end so as not to come off. ing.

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 in which the hydraulic oil 7 is stored. The high-pressure chamber 23 and the low-pressure chamber 24 communicate 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 connected to the cylinder 17 and the piston unit 1.
The hydraulic oil 7 can also leak from the high-pressure chamber 23 to the low-pressure chamber 24 via the clearance 30 through the clearance 30 between the hydraulic oils 7.

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. Further, in the present embodiment, the cylindrical portion 33 and the casing 1
The outer peripheral surface of the casing 11 is provided with a step 48 so that the gap with the casing 1 is narrow (gap 46) on the opening end side of the casing 11 and wide (gap 47) on the opening end side of the cylindrical portion 33. Therefore, the above effect is further enhanced.

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. 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.

When the auto tensioner 10 configured as described above is used, for example, as shown in FIG. 10, the plunger 8 urged upward by the elastic force of the return spring 44 causes the arm 4 to tilt upward. , Play pulley 3
Accordingly, an appropriate tension can be applied to the V belt 1. In addition, at the time of overload, the hydraulic oil 7 in the high-pressure chamber 23 leaks from the clearance 30 to the low-pressure chamber 24, so that the piston portion 18 can enter the cylinder 17 deeply.
Changes in belt length can be absorbed (automatically adjusted).

Next, a second embodiment shown in FIGS. 6 and 7 is an example in which the relief groove 31 of the dry bearing 14 is an annular groove having a uniform depth. Others are common to the first embodiment.

The third embodiment shown in FIGS. 8 and 9 is similar to the third embodiment shown in FIGS.
1 is an example in which a plurality of strip-shaped press-fit portions 29 and relief groove portions 31 are alternately arranged in the circumferential direction. Others are common to the first embodiment.

The present invention is not limited to the above-described embodiment, but may be embodied with appropriate modifications without departing from the spirit of the invention, for example, as described below.

(1) In the first or second embodiment, two or more annular escape grooves 31 are provided. (2) The width of the seal projection 35 is appropriately increased or decreased.

[0029]

As described in detail above, according to the auto-tensioner according to the present invention, it is possible to prevent intrusion of muddy water and the like between the dry bearing and the collar, thereby reducing the wear between the dry bearing and the collar, thereby reducing backlash and noise. Can be prevented , and mounting holes and
This has an excellent effect that wear between the bearing and the bearing does not matter .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an auto tensioner according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 shows a mounting portion, a dry bearing, and a collar of the auto tensioner, wherein (a) is a cross-sectional view before press-fitting, and (b).
Is a sectional view after press-fitting.

FIG. 5 is a perspective view of the dry bearing.

FIG. 6 is a sectional view showing a dry bearing according to a second embodiment of the present invention.

FIG. 7 is a perspective view of the dry bearing.

FIG. 8 is a sectional view showing a dry bearing according to a third embodiment of the present invention.

FIG. 9 is a perspective view of the dry bearing.

FIG. 10 is a schematic view showing an example of use of an auto tensioner.

FIG. 11 is a partially cutaway front view showing a conventional auto tensioner.

[Explanation of symbols]

 Reference Signs List 8 Plunger 10 Auto tensioner 11 Casing 12 Attachment part 13 Collar 14 Dry bearing 19 Attachment part 26 Attachment hole 27 Insertion side flange part 28 Contact side flange part 29 Press-in part 31 Relief groove part 35 Seal projection Ta Press-in part tightening allowance Tb Projection Deadline

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16H 7/12

Claims (2)

(57) [Claims] 1. A casing (11) and a plunger (8) which enters and exits the casing, and a mounting hole (26) penetrates through each mounting portion (12, 19) of the casing or the plunger. And an auto-tensioner having a cylindrical dry bearing (14) inserted into the inner periphery of the mounting hole and a cylindrical collar (13) inserted into the inner periphery of the dry bearing. At both ends of the inner peripheral surface, seal projections (35) whose inner diameters are smaller than the outer diameter of the collar (13) by the protrusion interference (Tb) are provided, and collars (35) are provided on the inner periphery of both seal projections (35). 13) with the protrusion interference (T
b) press-fitted with a seals the ends of the outer peripheral surface of the collar (13) in both the sealing projection (35), wherein an outer diameter taken on the outer circumferential surface of the dry bearing (14)
Larger than the inner diameter of the perforated hole (26) by the press-fit part interference (Ta)
A press-fitting portion (29), and an inner periphery of the mounting hole (26).
Press fitting part (29) with the press fitting part interference (Ta)
Press-fitting, press-fitting part interference (Ta) and area of the press-fitting part (29)
Projection interference (Tb) and area of the seal projection (35)
Setting, the mounting hole (26) and the dry bearing
(14) to the dry bearing (1)
4) An auto-tensioner characterized in that the frictional force is larger than the frictional force between the collar and the collar . 2. A relief groove (31) whose groove bottom is deeper than the inner diameter of the mounting hole (26) is provided on the outer peripheral surface of the dry bearing (14), and a press-fit portion (29) is inserted into the mounting hole (26).
Claim and adapted to absorb escaping the groove portion (31) escape deformation of dry bearing (14) when press-fitting the 1
Auto tensioner as described.