JPH0932895A - Belt tensioner - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a belt tensioner having high reliability, in which a damping band can exert rocking resistance for a long period of time. [Structure] The tensioner arm is swingably attached to the opening of the tensioner cup, and the damping band 3 is attached to the tensioner arm.
Attach 2. The snap ring 33 is attached to the inner peripheral side of the damping band 32. The damping band 32 is pressed by the snap ring 33 and slidably contacts the inner peripheral surface of the tensioner cup. The damping band 32 has a substantially annular shape cut at one place. Damping band 32
The plate thickness in the radial direction gradually increases in the circumferential direction from both ends 32c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a belt tensioner used for a belt drive mechanism of an automobile engine, for example.

[0002]

2. Description of the Related Art A belt tensioner is used in a transmission device for transmitting a driving force to a plurality of devices by a single belt in order to prevent the belt from slacking and to reliably transmit the driving force. Such a belt tensioner is disclosed in, for example, Japanese Utility Model Laid-Open No. 5-67854.

A conventional belt tensioner (auto tensioner) as disclosed in this publication allows a tensioner arm (swinging arm) to swing in a tensioner cup (fixing case) fixed to a predetermined portion such as an engine block. The tensioner arm is mounted and a pulley is rotatably provided on the tensioner arm. A torsion spring is installed between the tensioner cup and the tensioner arm to urge the tensioner arm in the direction of tensioning the belt.

A C-shaped snap ring is attached to the inner circumferential surface of a damping band (friction member) attached to the tensioner arm in a radially compressed state, and the damping band is pressed and urged toward the tensioner cup side. There is. The outer peripheral surface of the damping band is in sliding contact with the inner peripheral surface of the tensioner arm, and when the tensioner arm is rotated, a damping force (friction force) is generated between the damping band and the tensioner cup, and it swings against the tensioner arm. Adds dynamic resistance.

[0005]

In the above-mentioned conventional belt tensioner, the outer peripheral surface of the damping band is worn by sliding contact with the inner peripheral surface of the tensioner arm.
On the other hand, the snap ring ideally produces a uniform stress distribution along the peripheral surface, but in reality, the stress distribution is not uniform, and for example, in the part away from both ends of the snap ring. A large pressing force acts as compared with other parts. Due to this large pressing force, the amount of wear at the corresponding portion of the damping band advances faster than at other portions. If this amount of wear becomes too large, the tensioner arm will not be able to exert sufficient swing resistance, and it will not be possible to apply an appropriate tension to the belt.

An object of the present invention is to provide a belt tensioner in which a damping band can exert rocking resistance for a long period of time and which has high reliability.

[0007]

A belt tensioner according to the present invention includes a tensioner cup, a tensioner arm swingably attached to an opening of the tensioner cup and a pulley attached to a swing end, and the tensioner arm. A damping band attached to the arm and slidingly contacting the peripheral surface near the opening of the tensioner cup,
The damping band is provided with a spring means for urging the damping band almost all around and pressing the damping band against the tensioner cup, and the damping band has a substantially annular shape cut at one place, and the base part is separated from both ends thereof. In the above, the plate thickness in the radial direction is formed to be larger than other portions.

The thickness of the damping band in the radial direction may be gradually increased from both ends thereof in the circumferential direction. In this case, it is preferable that the center of curvature of the outer peripheral surface of the damping band deviates from the center of curvature of the inner peripheral surface.

The thickness of the damping band in the radial direction may be larger in the vicinity of both ends thereof than in the portion between the base and both ends.

The spring means is, for example, a substantially annular snap ring cut at one place, and both ends of this snap ring and both ends of the damping band are set at positions corresponding to each other. In this case, the outer peripheral surface of the damping band slidably contacts the inner peripheral surface of the tensioner cup, and the snap ring contacts the inner peripheral surface of the damping band in a compressed state. The thickness of the snap ring in the radial direction may be gradually increased from both ends in the circumferential direction. In this case, the center of curvature of the outer peripheral surface of the snap ring deviates from the center of curvature of the inner peripheral surface. Preferably.

[0011]

Embodiments of the present invention will be described below. The belt tensioner of the present embodiment is shown in FIG.
It is used in belt systems for automobile engines as shown in. This belt system includes a drive pulley 1 attached to an output shaft of an engine, driven pulleys 2, 3 and 4 for an air conditioner, a power steering device and an alternator, and idler pulleys 5 and 6,
A belt tensioner 10 is provided, and a single drive belt 7 is suspended between the pulleys.

The belt tensioner 10 includes a fixed portion 20 fixed to the engine block, and a tensioner pulley 40 rotatably provided with respect to the fixed portion 20 about a pivot bolt 23 which is a swing shaft. ing. The tensioner pulley 40 is biased upward in the drawing by a biasing means provided in the fixed portion 20, and the biasing force causes the drive belt 7 to be tensioned. Further, when the drive belt 7 is attached, the tensioner pulley 40 is attached in a state where the tensioner pulley 40 is rotated to the position shown by the broken line in the figure.

Next, a schematic structure of the belt tensioner 10 of the embodiment will be described with reference to FIGS. The fixing portion 20 includes a mounting portion 21 having two mounting holes 21a into which bolts (not shown) for fixing to the engine block are inserted, and a tensioner having a torsion spring 50 (FIG. 5). And a cup 22. The tensioner arm 30 is attached to the tensioner cup 22, and the pivot bolt 2 which is the swing shaft thereof.
It is provided so as to be able to swing about 3. The tensioner pulley 40 is a pulley bolt 4 which is a rotation shaft parallel to the swing shaft.
It is rotatably provided to the tensioner arm 30 via 1. A damping band 32, which is a friction member, is attached to the tensioner arm 30, and the outer peripheral surface of the damping band 32 is in sliding contact with the inner peripheral surface of the tensioner cup 22 from the inside.

FIG. 5 is a sectional view taken along the line VV of FIG.
FIG. 6 is a sectional view taken along line VI-VI in FIG. The tensioner arm 30 has a lid portion 30b and a pulley attachment portion 30c. The lid portion 30b is swingably attached to the opening portion of the tensioner cup 22, and the pulley attachment portion 30c.
A tensioner pulley 40 is rotatably attached to the. A damping band 32 is fixed to the lid portion 30b, and the damping band 32 is used for the tensioner cup 22.
Slidingly contacts the peripheral surface in the vicinity of the opening.

At the center of the bottom surface of the tensioner cup 22,
A bolt engaging portion 22a that rises toward the inside of the cup is formed, and a pivot bolt 23 is screwed into the bolt engaging portion 22a. The pivot bolt 23 has a stepped shape in which a screw portion 23a and a pilot portion 23b are formed at the tip, and is fixed to the tensioner cup 22 by screwing the screw portion 23a into the bolt engaging portion 22a. .

A column portion 23c is provided above the screw portion 23a of the pivot bolt 23, and a bolt head portion 23d is provided above the column portion 23c. Column part 23c
Is inserted into the pivot bushing 31 fitted in the hole 30h of the lid portion 30b of the tensioner arm 30. The axial movement of the pivot bushing 31 is restricted by the bolt head 23d of the pivot bolt 23, and the pivot bushing 31 can slide in the rotational direction with a predetermined frictional resistance. That is, the tensioner arm 30 can swing with respect to the fixed portion 20.

One end of the torsion spring 50 (not shown)
Is fixed to the bottom of the tensioner cup 22, and the other end 52
Is fixed to the tensioner arm 30. The torsion spring 50 is interposed in a compressed state between the tensioner cup 22 and the tensioner arm 30 in an appropriately twisted state, and in this state, a direction in which a drive belt (not shown) suspended on the tensioner pulley 40 is tensioned. The tensioner arm 30 is biased in the rotating direction.

The tensioner pulley 40 is rotatably attached to the pulley attachment portion 30c of the tensioner arm 30 by a pulley bolt 41 via a ball bearing 42. A dust shield 43 that prevents dust from entering is provided between the head of the pulley bolt 41 and the ball bearing 42.

Damping band 32 as a friction member
Is attached to the tensioner arm 30. The damping band 32 is formed of an elastic member such as resin or rubber. For example, polyacetal, a polymer material such as nylon containing molybdenum to provide self-lubricating property, glass fiber reinforced nylon and carbon fiber reinforced plastic having excellent strength are used. Used.

The damping band 32 has three protrusions 32a which protrude inward from the inner peripheral surface near the opening periphery.
Is projected. The width of the protrusion 32a in the circumferential direction is substantially the same as the width of the recess 30a formed in the tensioner arm 30, and the protrusion 32a fits into the recess 30a with substantially no space, so that the damping band 3 is formed.
The relative movement of the two in the rotating direction with respect to the tensioner arm 30 is restricted. Since the plurality of protrusions 32a are provided, the rotational biasing force of the tensioner arm 30 is distributed to the protrusions 32a, whereby the protrusions 32a are formed.
Problems such as breakage are less likely to occur.

The outer peripheral surface 32b of the damping band 32 is in sliding contact with the inner peripheral surface of the tensioner cup 22, and a C-shaped snap ring 33 is in contact with the inner peripheral surface of the damping band 32 in a compressed state. The outer peripheral surface of the snap ring 33 contacts the inner peripheral surface of the damping band 32 over substantially the entire circumference, and the action of the snap ring 33 presses the damping band 32 against the tensioner cup 22. As a result, when the tensioner cup 22 swings, a damping force due to a frictional force is generated in the sliding contact portion.

FIG. 7 shows the snap ring 33.
As the snap ring 33, for example, a "retaining ring" used for fixing a ball bearing in a pipe is used. The snap ring 33 has a substantially annular shape that is cut at one place, that is, a C shape. Snap ring 33
Extends from both end portions 33a over an angular range of about 330 degrees, and the center of curvature of the outer peripheral surface thereof is deviated from the center of curvature of the inner peripheral surface. That is, the radial plate thickness b of the snap ring 33 gradually becomes thicker than the cut portion 33a along the circumferential direction. Further, the both ends 33a have holes 33 into which a jig used to bend the snap ring 33 inward when assembled in the tensioner cup 22 can be engaged.
b is formed.

The biasing force of the snap ring 33 is set appropriately according to the required damping force. Also, a plurality of snap rings 33 may be provided according to the required damping force.

FIG. 8 is a plan view of the damping band 32, and FIG. 9 is a sectional view taken along line IX-IX of FIG. The damping band 32 has a substantially annular shape that is cut at one place, and the cut portion, that is, the gap between both end portions 32 c functions as a drainage portion for draining water that has entered the tensioner cup 22.

Three protrusions 32a are formed in the left and right directions and opposite directions from both ends 32c of the damping band 32. Each protrusion 32 a projects inward from the inner peripheral surface of the upper part of the damping band 32. Damping band 32
The slits 32 extending in the axial direction are provided between the respective protrusions 32a.
g is formed. The both ends 32c and the slit 32g absorb the deformation of the damping band 32 due to heat and abrasion.

A support portion 32d and a stopper 32e are formed on the inner peripheral surface of the damping band 32. Support part 3
A plurality of 2d are provided along the circumferential direction, and as shown in FIG. 10, the support portion 32d holds the snap ring 33 from above and below. The stopper 32e is provided near both ends 32c and extends along the circumferential direction. The stopper 32e is bent at both ends 32c and extends downward, and the bent portion functions as a rotation preventing portion of the snap ring 33 in the circumferential direction.

FIG. 11 is a view of the damping band 32 to which the snap ring 33 is attached as seen from the tensioner cup side. In the figure, the plate thickness and the like are exaggerated for the sake of explanation. Also, the snap ring 33 is shown with diagonal lines.

The snap ring 33 has both ends 33a.
Are attached so as to be determined at positions corresponding to both ends 32c of the damping band 32. The center of curvature of the outer peripheral surface of the damping band 32 is deviated from the center of curvature of the inner peripheral surface. More specifically, the outer peripheral reference line A1 including the center of curvature of the outer peripheral surface of the damping band 32 is the damping band 3
The inner peripheral reference line A2 is located away from the inner peripheral reference line A2 including the center of curvature of the inner peripheral surface of the inner peripheral surface 2.

That is, the radial plate thickness of the damping band 32 gradually increases in the circumferential direction from both end portions 32c, and the plate thickness c1 at the base portion 32f distant from the both end portions 32c is larger than that at other portions. large. In other words, the plate thickness is relatively thick where the stress of the snap ring 33 is relatively large, and the plate thickness of the damping band 32 is relatively thin where the stress of the snap ring 33 is relatively small. As an example, the plate thickness c1 is formed to be about 10% thicker than the plate thickness c2 near the cut portion 32c. For example, when the plate thickness c2 is 2 mm, the plate thickness c1 is 2.2 mm.

According to the belt tensioner of this embodiment, the tensioner arm 30 is rotationally biased by the biasing force of the torsion spring 50 to tension the drive belt 7, and the tensioner arm 30 is swung by the vibration of the drive belt or the like. In doing so, a damping force (friction force) is generated by the urging force of the snap ring 33 at the sliding contact portion where the outer peripheral surface 32b of the damping band 32 and the inner peripheral surface of the tensioner cup 22 are in sliding contact, and this causes the tensioner arm 30 to move. Vibration is dampened.

Since the damping force is generated by the snap ring 33 different from the torsion spring 50, the damping force is kept substantially constant regardless of the rotation angle of the tensioner arm 30. Further, since the damping force generated by the snap ring 33 can be set independently of the turning torque generated by the torsion spring 50, the respective values can be freely combined and easily fulfilled for various requirements. Can respond to.

During the use of this belt tensioner, the outer peripheral surface 32b of the damping band 32 comes into sliding contact with the inner peripheral surface of the tensioner cup 22 and wears. At this time, the amount of wear at each portion of the outer peripheral surface 32b of the damping band 32 differs depending on the stress distribution of the snap ring 33. For example, the cutting portion 3 where the biasing force of the snap ring 33 is relatively large.
The wear of the damping band 32 is significantly increased at the portion contacting the opposite portion facing 3a. However, in the present embodiment, the plate thickness c1 of the damping band 32, which is in contact with the portion of the snap ring 33 where a relatively large stress acts and is significantly worn, is formed larger than the other portions. Therefore, the durability of the damping band 32 is improved, and swing resistance can be imparted for a longer period of time than a damping band having a substantially uniform plate thickness, and a belt tensioner having high reliability can be obtained.

FIG. 12 shows a damping band used in another embodiment. The stress generated in the snap ring 133 is relatively large not only in the portion corresponding to the base portion 132f of the damping band 132 but also in the portion corresponding to both end portions 133a. Therefore, in the damping band 132 of this embodiment, in addition to the plate thickness c1 of the portion corresponding to the base portion 132f being relatively large, the plate thickness c2 near both end portions 132c is also relatively large. That is, the thickness of the damping band 132 in the radial direction is such that the base 132f is located near both ends 132c.
Is larger than the portion between both ends 132c. Totensioner.

According to such a damping band 132, the diameter of the damping band 132 is slightly larger than that of the damping band 32 shown in FIG. 11, but the plate thickness of the portion where the damping band 132 is significantly worn is surely thick. As a result, the durability of the damping band is further improved.

[0035]

As described above, according to the present invention, since the damping band can exert the swing resistance for a long period of time, a belt tensioner having high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a front view showing a belt system of an automobile engine.

FIG. 2 is a plan view showing the appearance of a belt tensioner that is an embodiment of the present invention.

FIG. 3 is a side view showing the appearance of the belt tensioner of FIG.

FIG. 4 is a front view showing the appearance of the belt tensioner of FIG.

5 is a sectional view taken along line VV of the belt tensioner of FIG.

6 is a plan view of the tensioner arm of FIG. 5 as seen from below along line VI-VI.

FIG. 7 is a plan view of a C-shaped snap ring.

FIG. 8 is a plan view of a damping band.

9 is a cross-sectional view taken along line IX-IX of the damping band of FIG.

FIG. 10 is a partial perspective view of a damping band and a C-shaped snap ring.

FIG. 11 is a bottom view of the damping band and the C-shaped snap ring.

FIG. 12 is a bottom view of a damping band and a C-shaped snap ring according to another embodiment.

[Explanation of symbols]

 10 Belt Tensioner 22 Tensioner Cup 30 Tensioner Arm 32 Damping Band 33 Snap Ring 40 Tensioner Pulley

Claims (9)

[Claims] 1. A tensioner cup, a tensioner arm swingably attached to an opening of the tensioner cup, and a pulley attached to a swing end, and a tensioner arm attached to the tensioner arm. The damping band is slidably in contact with the peripheral surface in the vicinity, and spring means for biasing the damping band over substantially the entire circumference and pressing the damping band against the tensioner cup are provided, and the damping band is cut at one place. A belt tensioner, which has a substantially annular shape, and is formed such that a plate portion in the radial direction is formed to have a larger thickness in the radial direction at a base portion apart from both end portions thereof. 2. The belt tensioner according to claim 1, wherein a radial plate thickness of the damping band gradually increases in the circumferential direction from both ends thereof. 3. The belt tensioner according to claim 2, wherein the center of curvature of the outer peripheral surface of the damping band is displaced from the center of curvature of the inner peripheral surface. 4. The belt tensioner according to claim 1, wherein a radial plate thickness of the damping band is larger in the vicinity of both ends thereof than in a portion between the base and both ends. . 5. The spring means is a substantially annular snap ring cut at one place, and both ends of the snap ring and both ends of the damping band are defined at positions corresponding to each other. The belt tensioner according to claim 1. 6. The outer peripheral surface of the damping band is slidably in contact with the inner peripheral surface of the tensioner cup, and the snap ring is in contact with the inner peripheral surface of the damping band in a compressed state. Belt tensioner. 7. The radial plate thickness of the snap ring is
The belt tensioner according to claim 5, wherein the belt tensioner gradually increases from both ends thereof in the circumferential direction. 8. The belt tensioner according to claim 7, wherein the center of curvature of the outer peripheral surface of the snap ring is displaced from the center of curvature of the inner peripheral surface. 9. A tensioner cup, a tensioner arm swingably attached to an opening of the tensioner cup, and a pulley attached to a swing end, and a tensioner arm attached to the tensioner arm. An annular damping band that slidably contacts a peripheral surface in the vicinity and spring means that urges the damping band over substantially the entire circumference and presses the damping band against the tensioner cup are provided, and the damping band includes the spring means. A belt tensioner characterized in that a portion corresponding to a portion where a large amount of stress is generated has a larger radial plate thickness.