JPH07103297A - Auto tensioner - Google Patents

Abstract

PURPOSE:To generate large damping force with an arm part prevented from being locked, by forming the second thick wall part which discontinuously-faces the first thick wall part in one prescribed range of an insert bearing in the other range. CONSTITUTION:In clockwise-rotating a rotating member 2 which decreases the diameter of the main body of a torsion coil spring 3 in an auto tensioner, a sliding-contact area to a boss part 7 is increased by the first and second thick wall parts 31, 32 of an insert bearing 6 which face each other on the basic end side of a shaft part 4. As a result, frictional force against the boss part 7 increases, so it is possible to provide larger damping force. The rotating shaft center (m) of the boss part 7 at the time of rotating a rotating member 2 which increases the diameter of the main body of the torsion coil spring 3 counterclockwise is made eccentric to the first thick wall part 31 on the top end side of the shaft part 4 in the direction of gaps 33, 33 provided between thick wall parts 31, 32. It is thus possible to provide smooth rotation for the rotating member 2, and surely prevent the arm part 9 from being locked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to apply a predetermined tension to a V-belt or the like for driving an auxiliary machine by an automobile engine and to automatically change the damping force according to the variation of the tension. Automatic tensioner, especially measures for increasing its damping force.

[0002]

2. Description of the Related Art An autotensioner of this type is generally known, for example, as shown in U.S. Pat. No. 4,473,362, and a span between pulleys of a belt wound between a drive pulley and a plurality of driven pulleys is known. Press
It is used to transfer the rotational force of the drive pulley to all driven pulleys.

Specifically, as illustrated in FIG. 6, a metal fixing member b having a shaft portion a and fixed to a fixed body such as an automobile engine, and a shaft portion a of the fixing member b. Has a boss portion c rotatably fitted to the outside, and an arm portion e for rotatably supporting the pulley d is provided at the tip of the boss portion so as to rotate about an axis parallel to the axis of the boss portion c. A metal rotating member f rotatably supported by a fixed member b at c
And a torsion coil spring g that is compressed between the two members b and f and biases the rotating member f in a predetermined direction with respect to the fixed member b. A substantially cylindrical insert bearing h is provided between the shaft portion a of the fixed member b and the boss portion c of the rotating member f, and a substantially cylindrical shape is formed on the outer peripheral side of the boss portion c of the rotating member f. The spring supports i are each provided as a damping member.

In the above automatic tensioner, not only the pulley d is pressed against the belt (not shown) by the rotation biasing force of the rotation member f to apply a predetermined tension, but also a damping force is applied according to the fluctuation of the tension. Is designed to change,
It is a tensioner with high added value. That is, when the belt is wound around the pulley d, the belt force (reaction force applied from the belt to the pulley d) is generated between the insert bearing h and the spring support i and the boss portion c of the rotating member f. And the biasing force of the torsion coil spring g combine to generate a damping force due to friction. And
In this state, when the tension of the belt fluctuates in the decreasing direction, the damping force becomes smaller in accordance with the decrease of the belt force, so that the followability of the pulley d to the belt becomes higher and the tension decrease of the belt is prevented. To be done. On the other hand, with respect to the tension of the belt, the damping force also increases due to the increase of the belt force, which gives a large resistance force to the pulley d and prevents the belt from fluttering.

[0005]

By the way, in an automobile engine with a small displacement, since the number of cylinders is small and the fluctuation of the belt tension increases as the fluctuation of the rotation increases, it is necessary to generate a larger damping force. There is.

In this case, the insert bearing is thicker radially outward than the radial thickness of the remaining area of 180 ° or more in the circumferential direction of the insert bearing in a predetermined area less than 180 ° in the circumferential direction. A thick portion is provided, and when the rotating member is urged to rotate in a predetermined direction by the torsion coil spring, it is located in the center of the shaft portion of the fixing member between the shaft portion of the fixing member and the boss portion of the rotating member. On the other hand, the rotation shaft center of the boss portion of the rotation member is eccentric to the thick-walled portion side so that the rotation member can be smoothly rotated in a predetermined direction, and the lock of the arm portion is surely avoided. I have to. Therefore, in an autotensioner that needs to generate a large damping force, the eccentricity of the rotating member causes the torsion coil spring, which reduces its diameter by rotating the rotating member in a direction opposite to the predetermined direction, to reduce the thickness of the boss and the insert bearing. The frictional force with the meat part was small, and it was necessary to improve the auto tensioner in order to obtain a large damping force.

The present invention has been made in view of the above points, and an object thereof is to provide an auto tensioner capable of generating a large damping force while avoiding the locking of the arm portion.

[0008]

[Means for Solving the Problems] To achieve the above object, a solution means provided by the invention according to claim 1 is a fixing member which has a shaft portion and can be fixed to a fixed body, and a shaft of the fixing member. A boss is rotatably fitted to the boss, and a rotative member having a pulley rotatable around an axis parallel to the rotative axis and the fixed member and the rotative member are compressed. And a torsion coil spring for urging the rotating member to rotate in a predetermined direction with respect to the fixed member, and a damping for damping the rotation of the rotating member interposed between the fixed member and the rotating member. It is assumed that an auto tensioner is provided with a member for applying a predetermined tension by pressing the belt to the pulley by the rotational biasing force of the rotating member and changing the damping force according to the fluctuation of the tension. And the damping member, the shaft portion of the fixing member, The cylindrical member is interposed between the rotating member and the boss portion and generates a frictional force between the rotating member and the inner peripheral surface of the boss member according to the fluctuation of the belt tension when the rotating member rotates. It is composed of insert bearings. Then, in the predetermined region of less than 180 ° in the circumferential direction of the insert bearing, the first region is thicker radially outward than the radial thickness of the remaining region of 180 ° or more in the circumferential direction of the insert bearing.
A thick wall portion that is provided with a thick wall portion and bulges outward in the radial direction of the insert bearing in a remaining region of less than 180 ° in the circumferential direction of the insert bearing that discontinuously faces the first thick wall portion of the predetermined region. The second thick portion is provided.

Further, the solution means taken by the invention according to claim 2 specifies the second thick portion of the invention according to claim 1,
The structure is provided in a step shape on one side of the remaining region located on the base end side of the shaft portion with respect to the axially approximately half position of the insert bearing.

Further, the solution means taken by the invention of claim 3 specifies the first thick wall portion of the invention of claim 2,
It is configured such that it is provided in a stepped manner on the other side of a predetermined region located on the tip end side of the shaft portion with respect to the axially approximately half position of the insert bearing.

Further, the solution means taken by the invention of claim 4 is that the first thick part of the invention of claim 1, claim 2 or claim 3 has a radial thickness and a second thickness. The thicknesses of the flesh portions in the radial direction are specified so that they are substantially matched with each other.

[0012]

With the above construction, in the invention according to claim 1,
Thickness that bulges outward in the radial direction of the insert bearing in the remaining area of less than 180 ° in the circumferential direction of the insert bearing that is discontinuously opposed to the first thick part in a predetermined area of less than 180 ° in the circumferential direction of the insert bearing. Since the thick second thick portion is provided, when the rotating member for reducing the diameter of the torsion coil spring is rotated in the opposite predetermined direction, it is provided between the shaft portion of the fixed member and the boss portion of the rotating member. The boss portion of the rotating member is prevented from being eccentric to the first thick-walled portion side with respect to the center of the shaft portion of the fixed member, and is rotated by the first and second thick-walled portions facing each other. The sliding contact area of the moving member with respect to the boss portion increases, and the frictional force with respect to the boss portion of the rotating member increases.

Moreover, since the thick portions are discontinuous with each other and provided in a region of less than 180 ° in the circumferential direction of the insert bearing, when the rotating member is urged to rotate in a predetermined direction by the torsion coil spring, The rotation axis of the boss can be eccentric in the direction of the gap provided between the thick portions, the rotation of the rotation member can be smoothly performed, and the locking of the arm can be avoided.

Further, according to the second aspect of the invention, the second thick portion is provided in a step shape on one side of the remaining region on the base end side of the shaft portion with respect to the axial bearing substantially half position of the insert bearing. During rotation of the rotating member in the opposite direction, between the shaft portion of the fixed member and the boss portion of the rotating member, rotation of the boss portion on the base end side of the shaft portion during rotation of the rotating member is performed. The eccentricity of the moving shaft center toward the first thick-walled portion is prevented, and the sliding contact area of the rotating member with respect to the boss portion is increased by the first and second thick-walled portions facing each other on the base end side of the shaft portion. The frictional force on the boss of the moving member is also large.

Moreover, the circumferential direction 180 of the insert bearing in which the thick portions are discontinuous with each other only at the base end side of the shaft portion
Since it is provided on one side of the remaining area of less than °, when the rotating member is rotated in the predetermined direction, the rotation axis center of the boss part is the gap direction and the axis provided between the thick parts. The tip end side of the part can be eccentric to the first thick part side, the turning of the turning member can be performed more smoothly, and the locking of the arm part is reliably avoided.

According to the third aspect of the present invention, the first thick portion is provided in a stepped shape on the other side of the predetermined region on the tip end side of the shaft bearing with respect to the axially half position of the insert bearing. The rotation shaft of the boss portion, which is provided on one side of the remaining region on the base end side of the shaft portion, in combination with the second thick portion diagonally positioned with respect to the shaft portion, when the rotation member rotates in the counter predetermined direction. The eccentricity of the core toward the first thick portion is prevented by the second thick portion, while the eccentricity of the rotation axis of the boss portion toward the second thick portion is prevented by the first thick portion, The first and second thick-walled portions facing each other at a diagonal position with respect to the shaft portion effectively increase the sliding contact area of the rotating member with respect to the boss portion, and the frictional force of the rotating member with respect to the boss portion is also increased. It will be big.

Moreover, since the thick portions face each other at diagonal positions with respect to the shaft portion, the pivot axis of the boss portion when the pivot member pivots in the predetermined direction is located between the thick portions. The eccentricity can be made with respect to the gap direction provided on the first thick wall portion side of the shaft portion distal end side and the second thick wall portion side of the shaft portion proximal end side, so that the rotating member can be rotated more smoothly. As a result, the lock of the arm portion is reliably avoided.

Further, in the invention according to claim 4, since the radial thickness of the first thick portion and the radial thickness of the second thick portion are substantially equal to each other, the first thick portion Also, the frictional force of the second thick portion against the boss portion of the rotating member becomes uniform.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an auto tensioner according to this embodiment. The auto tensioner is fixed to a fixing member 1 made of a metal such as an aluminum alloy that can be fixed to a fixing body such as an automobile engine, and is assembled to the fixing member 1. And a fixed member 1 which is made of metal and is rotatably supported.
A torsion coil spring 3 that is compressed between the rotating member 2 and the rotating member 2 and biases the rotating member 2 with respect to the fixed member 1 in a predetermined direction.

The fixing member 1 has a bottomed cylindrical rear cup portion 1a having an opening on the front side (upper side in FIG. 1) and a shaft portion 4 extending from the center of the bottom portion of the rear cup portion 1a in the axial center m direction. It has it, and it is made to be fixed to a fixed body in a mounting part not shown. Further, a base end side locking hole 5 is formed in the peripheral wall portion of the rear cup portion 1a so as to penetrate the peripheral wall portion in the radial direction.

The rotating member 2 has a front cup portion 2a whose opening faces the opening of the rear cup portion 1a,
A boss portion 7 that extends from the center of the bottom portion of the front cup portion 2a in the axial center m direction and is externally fitted to the shaft portion 4 of the fixed member 1 from the tip end side thereof through an insert bearing 6 that is a cylindrical damping member. And the outer periphery of the front cup portion 2a is projected outward in the radial direction, and the boss portion 7 is provided at the tip.
And an arm portion 9 on which the pulley 8 is rotatably supported by an axis n parallel to the axis m. The rotating member 2 is rotatably supported by the fixed member 1 at the boss portion 7 and is not shown in the drawing at the tip of the shaft portion 4 of the fixed member 1 via a thrust washer 10 made of synthetic resin and a front plate 11 made of metal. It is prevented by the retaining means. And
A belt t, such as a V-belt for driving auxiliaries in an automobile engine, to which a predetermined tension is to be applied, is wound around the pulley 8 as shown by an imaginary line in FIG. A front end side locking hole 12 is formed in the peripheral wall portion of the front cup portion 2a so as to penetrate the peripheral wall portion in the radial direction.

The main body of the torsion coil spring 3 is left-handed, and each of the end portions 3a and 3b on the base end side and the tip end side protrudes radially outward from the main body.
The proximal end 3a is fixed to the proximal locking hole 5 in the peripheral wall of the rear cup 1a of the fixing member 1, and the distal end 3b is locked to the distal end of the peripheral wall of the front cup 2a of the rotating member 2. Each of the end portions 3a and 3b is restricted from moving in the circumferential direction by being penetrated and locked in the hole 12 in the radial direction. Then, by operating in the direction in which the main body expands with the both ends 3a and 3b locked,
The rotating member 2 is configured to urge the rotating member 2 to rotate counterclockwise in FIG.

Both the inner and outer peripheral surfaces of the insert bearing 6 are formed to have a tapered cross-section with a small diameter on the tip side, and accordingly, the outer peripheral surface of the shaft portion 4 and the inner peripheral surface of the boss portion 7 are both formed. It has a similar sectional taper shape. Further, the insert bearing 6 is prevented from rotating on the side of the shaft portion 4 of the fixing member 1 by a rotation preventing means (not shown).

Further, a cylindrical spring support 13, which is a damping member, is interposed between the boss portion 7 and the proximal end side of the torsion coil spring 3. The inner peripheral surface of the spring support 13 can be slidably contacted with the outer peripheral surface of the boss portion 7. Further, an outward flange 13a that contacts the bottom surface of the rear cup portion 1a is formed at the opening edge of the spring support 13 on the base end side. Then, the outward flange 13a is pressed against the bottom surface of the rear cup portion 1a by the pressing force in the axial direction of the torsion coil spring 3, whereby the spring support 13 is fixed to the fixing member 1 side. Further, when the front cup portion 2a is rotated clockwise in FIG. 2 in this fixed state, the diameter of the main body of the torsion coil spring 3 is reduced, so that the spring support 13 is tightened and its inner peripheral surface is bossed. It comes into pressure contact with the outer peripheral surface of 7, so that a damping force with respect to the rotation of the rotating member 2 is generated.

The operation of the auto tensioner will now be described. The operation of the auto tensioner when the belt t is wound around the pulley 8 will be described. The bosses of the insert bearing 6 and the rotating member 2 in the auto tensioner will be described. Between each of the inner peripheral surface of the portion 7 and the inner peripheral surface of the spring support 13 and the outer peripheral surface of the boss portion 7, the belt force and the biasing force of the torsion coil spring 3 are combined to generate a damping force. When the tension of the belt t decreases, the damping force decreases due to the decrease of the belt force. Then, the rotating member 2 is easily rotated, and the followability of the pulley 8 with respect to the belt t is increased.
The decrease in the tension of the belt t can be prevented quickly.

On the other hand, with respect to the tension of the belt t, the damping force also increases due to the increase of the belt force, which gives a large resistance force to the pulley 8 and prevents the flapping of the belt t.

As a characteristic part of the present invention, as shown in FIGS. 3 and 4, the insert bearing 6 is used.
In a predetermined region A (for example, about 150 °) of less than 180 ° in the circumferential direction, the diameter is larger than the radial thickness of the remaining region B (for example, about 240 °) of 180 ° or more in the circumferential direction of the insert bearing 6. First thick part 3 which is approximately twice as thick outward in the direction
1 is provided. The first thick portion 31 is provided over the entire length of the insert bearing 6 in the axial center m direction. Further, on the large diameter side (other side) of the remaining region B located on the base end side (lower side in the figure) of the shaft portion 4 with respect to the approximately half position of the insert bearing 6 in the axial center m direction, the diameter of the insert bearing 6 is A thick second thick portion 32 is provided which bulges outward in the direction of a step. The second thick portion 32 has a remaining region B of less than 180 ° in the circumferential direction of the insert bearing 6 which is discontinuously opposed to the first thick portion 31 of the predetermined region A.
And is formed to have a wall thickness that substantially matches the first thick wall portion 31. The second thick portion 32 is, for example, about 30 ° on both sides in the circumferential direction so as to face the first thick portion 31 with the axial center m of the boss portion 7 in between at the center position of the remaining region B. It is formed so as to bulge in the range of about 150 ° with the gaps 33, 33 present. In this case, the first thick portion 31
The area of the second thick portion 32 that is less than 180 ° in the circumferential direction of the insert bearing 6 is set so that the torsion torque of the torsion coil spring 3 that acts on the torsion coil spring 3 from the belt t side and the torsion coil spring 3 are set. It is adapted to be appropriately changed based on the frictional force generated between the insert bearing 6 and the boss portion 7 by the deformation in the diameter reducing direction.

Therefore, in the above-described embodiment, the first portion of the predetermined area A of less than 180 ° in the circumferential direction of the insert bearing 6 is used.
In the radial direction toward the large diameter side of the remaining region B on the base end side of the shaft portion 4 which is discontinuously opposed to the thick portion 31 with the gaps 33, 33 and which is approximately half the position in the axial direction of the insert bearing 6. Since the thick second thick portion 32 that bulges outward in the shape of a step is provided, the shaft portion 4 of the fixed member 1 and the boss portion 7 of the rotating member 2 are provided.
And the rotation of the rotating member for reducing the diameter of the main body of the torsion coil spring 3 in the clockwise direction, and the rotation of the rotating member 2, the rotation of the boss portion 7 on the base end side of the shaft portion 4. Eccentricity of the moving shaft center m toward the first thick-walled portion 31 side is prevented, and the first and second thick-walled portions 31 and 32 facing each other at the base end side of the shaft portion 4 with respect to the boss portion 7 of the rotating member 2. The sliding contact area is increased and the frictional force of the rotating member 2 with respect to the boss portion 7 is increased, so that a large damping force can be obtained.

Moreover, the thick portions 31, 32 are provided on the large diameter side of the remaining region B of less than 180 ° in the circumferential direction of the insert bearing 6 discontinuous with each other by the gaps 33, 33 only on the base end side of the shaft portion 4. Therefore, the rotation axis m of the boss portion 7 when the rotation member for expanding the diameter of the main body of the torsion coil spring 3 is rotated in the counterclockwise direction is between the thick portions 31 and 32. The gaps 33, 33 provided and the first thick portion 31 side at the tip end side of the shaft portion 4 can be eccentric, and the rotation member 2 can be smoothly rotated, so that the arm portion 9 can be securely locked. Can be avoided.

In addition, the radial thickness of the first thick portion 31 and the radial thickness of the second thick portion 32 are substantially equal to each other, and the radial thickness of the insert bearing 6 is equal to each other. Since the regions of the thick-walled portions 31 and 32 substantially match, the frictional force of the first and second thick-walled portions 31 and 32 with respect to the boss portion 7 of the rotating member 2 is made uniform, and the thick-walled portions 31 and 32 are made uniform. , 32 can also be improved in wear resistance.

The present invention is not limited to the above embodiment, but includes various other modifications.
For example, in the above embodiment, the first thick portion 31 is provided over the entire length of the insert bearing 6 in the axial center m direction.
As shown in FIG. 4, the first thick portion 41 is provided in a stepped manner on the small diameter side of the predetermined region A located on the tip end side (upper side in the figure) of the shaft bearing in the axial center substantially half position of the insert bearing 6. You can In this case, the first thick portion 41 on the other side of the predetermined area provided on the tip end side of the shaft portion with respect to the axially approximately half position of the insert bearing, and on the one side of the remaining area on the base end side of the shaft portion, Second thick-walled portion 3 at a diagonal position with respect to the shaft portion
2 causes the eccentricity of the rotation axis of the boss portion toward the first thick portion 41 when the rotation member rotates clockwise.
While being prevented by the thick portion 32, eccentricity of the rotation axis of the boss portion toward the second thick portion 32 side is prevented by the first thick portion 41, and the boss portion is opposed to the shaft portion at a diagonal position. First to do
The second thick portions 41 and 32 effectively increase the sliding contact area of the rotating member with respect to the boss portion, and the frictional force of the rotating member with respect to the boss portion is similarly increased. Moreover, since the thick-walled portions 41 and 32 face each other at a diagonal position with respect to the shaft portion, the rotation axis centers of the boss portions 7 when the rotation member rotates in the counterclockwise direction are mutually thickened. Part 41,
The gaps 33, 33 provided between 32, the first thick portion 41 side on the tip side of the shaft portion and the second portion on the base end side of the shaft portion.
The thick portion 32 can be eccentric with respect to the side, and the rotation of the rotating member can be performed more smoothly, so that the locking of the arm 9 can be reliably avoided.

Further, in the above embodiment, the second thick portion 32 is provided on the large diameter side of the remaining region B on the base end side of the shaft portion, but the first thick portion extends over the entire axial length of the insert bearing. In this case, the rotation axis of the boss portion is closer to the first thick portion with respect to the center of the shaft portion of the fixed member when the rotation member rotates in the clockwise direction. The eccentricity is prevented, and the first and second thick portions facing each other increase the sliding contact area of the rotating member with respect to the boss portion, thereby increasing the frictional force of the rotating member with respect to the boss portion. On the other hand, when the rotating member rotates counterclockwise, the rotating shaft center of the boss can be eccentric with respect to the gap between the thick portions, so that the rotating member can be smoothly rotated. The lock of the part is surely avoided.

[0033]

As described above, according to the autotensioner of the first aspect of the present invention, the thick second thick portion that discontinuously faces the first thick portion in the predetermined region of the insert bearing is provided. Since the rotation member is provided in the remaining area, the rotation axis of the boss portion can be eccentric only with respect to the gap when the rotation member is rotated about the predetermined direction, and the arm portion is prevented from being locked, while the rotation member is not rotated in the predetermined direction. The frictional force can be increased and a large damping force can be obtained by increasing the sliding contact area with the boss portion when rotating around the direction.

Further, according to the autotensioner of the second aspect of the invention, the second thick portion is provided stepwise on one side of the remaining area of the base end side of the shaft portion of the insert bearing.
When the rotating member rotates about a predetermined direction, the rotation axis of the boss is eccentric to the gap direction and the first thick-walled side of the tip of the shaft to more reliably avoid the locking of the arm while rotating. A large damping force can be obtained by a large frictional force with respect to the boss portion when the moving member rotates around the opposite direction.

According to the auto tensioner of the third aspect of the invention, since the first thick portion is provided stepwise on the other side of the predetermined region on the tip end side of the insert bearing,
When the rotating member rotates about a predetermined direction, the rotation axis of the boss portion is eccentric to the first thick portion on the tip side of the shaft and the second thick portion on the base end side of the shaft. In addition to more reliably avoiding the locking of the portion, the sliding contact area with respect to the boss portion when the rotating member rotates in the counter predetermined direction in combination with the second thick portion diagonally positioned with respect to the shaft portion is effective. It can be increased to obtain a large damping force.

Further, according to the autotensioner of the invention as set forth in claim 4, since the radial thicknesses of the first and second thick portions are made substantially equal to each other, the first and second thick portions of the first and second thick portions are made substantially equal to each other. The frictional force with respect to the boss portion can be made uniform to improve the wear resistance of each thick portion.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view taken along the line I-I of FIG.

FIG. 2 is a plan view of the auto tensioner according to the embodiment.

FIG. 3 is a perspective view of an insert bearing according to an embodiment.

FIG. 4 is a plan view of the insert bearing according to the embodiment.

5 is a view corresponding to FIG. 3 according to a modified example.

FIG. 6 is a view corresponding to FIG. 1 according to a conventional example.

[Explanation of symbols]

 1 Fixed Member 2 Rotating Member 3 Torsion Coil Spring 4 Shaft Part 6 Insert Bearing (Damping Member) 7 Boss Part 8 Pulley 31, 41 First Thick Part 32 Second Thick Part A Predetermined Area B Remaining Area m Boss Part Shaft center n Pulley shaft center t Belt

Claims (4)

[Claims] 1. A fixing member that has a shaft portion and can be fixed to a fixed body, and a boss portion is rotatably fitted outside the shaft portion of the fixing member.
A rotating member having a pulley rotatable about an axis parallel to the rotating axis, and a rotating member that is compressed between the fixing member and the rotating member and rotates the rotating member with respect to the fixing member in a predetermined direction. A torsion coil spring that urges the rotating member, and a damping member that is interposed between the fixed member and the rotating member and that damps the rotation of the rotating member. An automatic tensioner that presses the belt against the pulley to apply a predetermined tension and changes the damping force according to the fluctuation of the tension, wherein the damping member is a shaft portion of the fixing member. A substantially tubular shape which is interposed between the rotating member and the boss portion and generates a frictional force between the inner peripheral surface of the boss portion and the inner peripheral surface of the boss portion when the rotating member rotates. It consists of the insert bearing of In a predetermined area of less than 180 ° in the circumferential direction of the ring, a first thick portion that is thicker in the radial direction than the radial thickness of the remaining area of 180 ° or more in the circumferential direction of the insert bearing is provided. In the remaining region of the insert bearing, which is discontinuously opposed to the first thick portion in the predetermined region and is less than 180 ° in the circumferential direction, a thick wall that bulges outward in the radial direction of the insert bearing is provided. An automatic tensioner having a second thick portion. 2. The second thick portion is provided stepwise on the other side of the remaining region located on the base end side of the shaft portion with respect to the axially substantially half position of the insert bearing. The auto tensioner described in 1. 3. The first thick-walled portion is provided in a stepped shape on the other side of a predetermined region located closer to the tip end side of the shaft portion than the half position in the axial direction of the insert bearing. Auto tensioner described. 4. The radial thickness of the first thick wall portion and the second wall thickness.
The automatic tensioner according to claim 1, 2, or 3, wherein the thicknesses of the thick portions in the radial direction are substantially the same.