JP2001165253A - Auto-tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control variation in tension of a belt more effectively in an auto- tensioner for holding the tension of the belt constantly. SOLUTION: An elastic body 12 is wound along outer circumference of a bush 7. One end part of this elastic body 12 is fixed on the bush 7 and the other end part is fixed on the oscillating member 10, respectively. When the oscillating member 10 oscillates to one direction, the elastic body 12 tightens the bush 7 to increase oscillating resistance of the oscillating member 10. When the oscillating member 10 oscillates to the opposite direction, the tightening of the bush 7 is released to decrease the oscillating resistance.

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 applying a predetermined tension to a belt wound around a pulley.

[0002]

2. Description of the Related Art Heretofore, there has been provided an automobile engine in which a timing belt is wound between a crankshaft and a camshaft to rotate both synchronously. In this case, the distance between the shafts of the crankshaft and the camshaft changes depending on the temperature and the like, and the belt itself expands and contracts due to the temperature change, and elongation occurs due to long-term use. For this reason, there is a possibility that the synchronous rotation cannot be maintained satisfactorily due to the fluctuation of the belt tension. Therefore, the tension of the belt is kept constant by an auto tensioner.

As this auto-tensioner, a support shaft is mounted on a fixed bed such as an engine block, and the swing member is eccentrically fitted to the support shaft via a bush while being eccentric. A pulley on which a belt is hung on the outer periphery of the member is rotatably supported via a bearing mechanism, and a tension spring is stretched between the fixed bed and the swing member, and the swing member is biased by the tension spring. Then, there is provided an apparatus in which the tension of the belt is adjusted by swinging the pulley while pressing the belt against the belt about the support shaft.

In this type of auto tensioner, when the belt tension fluctuates slowly, the fluctuation of the belt tension can be easily absorbed by the urging force of a tension spring. However, when the belt tension fluctuates rapidly with the vibration of the belt, the swinging member vibrates violently together with the belt, so that the fluctuation of the belt tension can be effectively absorbed depending on the urging force of the tension spring. It is difficult. Therefore, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-184357, a friction member is interposed between a swinging member and an immovable portion such as a fixed bed, and the friction member is urged toward the immovable portion. Attach the compression spring to the swing member,
By pressing the friction member against the immovable portion with an appropriate pressing force that does not hinder the movement of the rocking member by the compression spring, a predetermined rocking resistance is given to the rocking member. Vibration is attenuated.

[0005]

In order to attenuate the vibration transmitted from the belt as described above, the conventional auto-tensioner presses the friction member against the fixed bed by means of a compression spring so that the predetermined tension is applied to the swing member. In this case, the magnitude of the swing resistance is the same regardless of whether the swing member swings in one direction or the opposite direction. There is no direction. For this reason, it is still insufficient to effectively suppress the belt tension fluctuation.

That is, against a sudden increase in belt tension during belt vibration, the swing resistance of the swing member holding the pulley is made relatively large, and the belt tension is effectively reduced. There is a need. On the other hand, with respect to a sudden decrease in the tension of the belt, it is desirable to reduce the swing resistance of the swing member and make the pulley follow the belt quickly so that the pressing force against the belt can be maintained. However,
In the prior art, since the magnitude of the swing resistance acting on the swing member when the belt tension increases and decreases, the pulley follows the belt when the belt tension sharply decreases. As a result, there is a problem that the function of pressing the belt is reduced, and the vibration cannot be rapidly attenuated. The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an automatic tensioner that can more effectively suppress fluctuations in belt tension.

[0007]

According to an aspect of the present invention, there is provided an auto-tensioner, comprising: a swinging member for rotatably supporting a pulley to be brought into contact with a belt; In an auto-tensioner that presses a friction member having a sliding surface perpendicular to the axis of the support shaft to the friction surface by the urging force of an elastic member, and imparts a swing resistance to the swing member, one end of the auto-tensioner is connected to the bush. It is wound around the outer periphery of the bush while the other end is locked to the swing member, and the bush is tightened by swinging in one direction of the swing member, and the bush is tightened by swinging in the opposite direction. An elastic body for releasing the state is provided (claim 1).

According to this automatic tensioner, when the belt tension increases rapidly, the swinging member swings in one direction (a direction in which the belt tension is reduced), and at the same time, the friction member and the friction surface are separated. Sliding reduces the belt tension.
At this time, since the elastic body tightens the bush, the sliding resistance between the bush and the support shaft increases, the swing resistance of the swing member increases, and the belt tension can be more effectively reduced. In addition, when the belt tension suddenly decreases, the swinging member moves in the opposite direction (the direction in which the belt tension increases).
As the elastic body releases the tightened state of the bush, the sliding resistance between the bush and the support shaft decreases, the swing resistance of the swing member decreases, and the pulley Swings quickly following For this reason, the belt can always be pressed by the pulley.

In the automatic tensioner according to the present invention, the elastic body may be constituted by a leaf spring (claim 2). In this case, the swing to be imparted to the swing member has a very simple structure. It is possible to give directionality to the magnitude of the resistance.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 is a front view of an auto-tensioner according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line XX of FIG. 1, FIG. 3 is a cross-sectional view of a main part taken along line YY of FIG. FIG. 4 is a sectional view taken along the line ZZ in FIG. Auto tensioner 1 of this embodiment
For example, the support shaft 3 is fixed to the fixed bed 2 of the engine block.
Is attached.

The support shaft 3 is composed of a fixing bolt 4 and a sleeve 5 fitted outside the shaft 4a of the fixing bolt 4. The sleeve 5 includes a cylindrical shaft portion 5a and a flange portion 5 formed at an end of the shaft portion 5a on the fixed bed 2 side.
b, one surface of the flange portion 5b is seated on the fixed bed 2 and the other surface is a friction surface 5 for pressing a friction member 26 described later.
c. The fixing bolt 4 is screwed into the fixing bed 2 so that the sleeve 5 is fixed to the fixing bolt 4.
Between the fixed head 2 and the fixed head 2.

A cylindrical bush 7 made of synthetic resin is fitted around the outer periphery of the shaft portion 5a of the sleeve 5 in order to reduce friction between metals. The bush 7 has its peripheral wall divided by a slit 7a extending along the axial direction, so that the diameter can be reduced and expanded (see FIG. 4). A flange 7b is formed at the end of the bush 7 on the head 4b side of the fixing bolt 4, and a washer 7c is interposed between the flange 7b and the head 4b of the fixing bolt 4. A swing member 10 having a circular outer periphery is swingably fitted to the outer periphery of the bush 7 while being eccentric with respect to the support shaft 3. An eccentric hole 10 a having an inner diameter slightly larger than the outer diameter of the bush 7 is formed in the swing member 10 concentrically with the support shaft 3. A leaf spring 12 as an elastic body is interposed between the eccentric hole 10a of the swing member 10 and the bush 7.

As shown in FIG. 4, the leaf spring 12 has a cylindrical shape in which one portion of a peripheral wall is separated, and has a circular cross-section 12a wound around the outer periphery of the bush 7 and in the circumferential direction. Both ends 12b and 12c of the bush 7 are bent into an L shape so that the slit 7a of the bush 7 and the swing member 1
0 are respectively engaged with the inner peripheral grooves. Accordingly, when the swinging member 10 swings clockwise in FIG. 4, the bush 7 is tightened by the leaf spring 12,
The sliding resistance between the bush 7 and the support shaft 3 increases. Also,
When the swing member 10 swings counterclockwise, the leaf spring 1
2 is released, and the sliding resistance between the bush 7 and the support shaft 3 is reduced. The gap between the eccentric hole 10a of the swing member 10 and the bush 7 is
The size is set so as to be a minimum size within a range in which the sliding of the leaf spring 12 is allowed, thereby preventing the swing member 10 from inclining with respect to the axis L of the support shaft 3 as much as possible. .

A pulley 9 on which a belt V is hung is rotatably mounted on the outer periphery of the swing member 10 via a bearing mechanism 8. In this bearing mechanism 8, a plurality of balls 83 are interposed between an inner ring 81 pressed into the outer periphery of the end of the swing member 10 and an outer ring 82 formed integrally with the pulley 9. Are held at predetermined intervals by a holder 84. A cylindrical portion 10 concentric with the support shaft 3 is provided at an end of the swing member 10 on the fixed bed 2 side.
An annular spring hook 22 is press-fitted and fixed to the outer periphery of the cylindrical portion 10b. A tension coil spring 2 is provided between the spring hook 22 and the fixed bed 2.
3, the pulley 9 is pressed toward the belt V by the elastic force of the tension coil spring 23 (see FIG. 1).

A spring loading hole 10c is formed at the end of the rocking member 10 on the fixed bed 2 side of the cylindrical portion 10b (see FIG. 3). The location where the spring loading hole 10c is formed is a position where the inclination of the swing member 10 due to the belt load can be suppressed,
Specifically, the spring is formed at a position on the opposite side of the load point P of the belt V across the support shaft 3 and on a circumference centered on the axis L of the support shaft 3. Mounting hole 10c
Open end faces the friction surface 5c of the flange portion 5b of the sleeve 5.

A compression coil spring 25 and a friction member 26 are inserted into the spring mounting hole 10c, and the friction member 26 is moved by the urging force of the compression coil spring 25 so that the friction surface 5c of the flange portion 5b of the sleeve 5 is formed. Is pressed with an appropriate pressing force that does not hinder the movement of the swinging member 10. Thereby, a constant swing resistance is always applied to the swing member 10, and the vibration energy transmitted from the belt V can be absorbed. As a material of the friction member 26, a super engineering plastic such as PES having excellent wear resistance is used.

In the auto tensioner 1 having the above-described structure, when the tension of the belt V suddenly increases due to vibration or the like, the swinging member 10 moves in the direction of decreasing the tension (clockwise in FIGS. 1 and 4). However, accompanying this, the leaf spring 12 tightens the bush 7, so that the sliding resistance between the bush 7 and the support shaft 3 increases. As a result, the swing member 10
Oscillating resistance increases, and the tension of the belt V can be reduced more effectively. On the other hand, when the tension of the belt V suddenly decreases, the swinging member moves in the direction of increasing the tension (counterclockwise in FIGS. 1 and 4). 7 is released, the sliding resistance between the bush 7 and the support shaft 3 is reduced. As a result, the swing resistance of the swing member 10 holding the pulley 9 is reduced, and the pulley 9 swings at a high response speed so as to maintain the pressing force on the belt V. Accordingly, it is possible to effectively suppress a large fluctuation in the tension of the belt V, such as being separated from the pulley 9 and fluttering.

Further, the swing member 10 and the bush 7 are
Since it is indirectly connected via the leaf spring 12, when the swing member 10 swings, sliding always occurs between the sleeve 5 of the support shaft 3 and the bush 7. Since the sliding portion is specified in this manner, an auxiliary vibration damping action can be stably obtained. That is, when the swing member swings, the conventional auto-tensioner slides between the support shaft and the bush, slides between the bush and the swing member, or slides between the support shaft and the bush, and the bush and the swing member. Are sliding, and the sliding position is not specified, so that the auxiliary vibration damping effect on the belt due to the sliding resistance is likely to be unstable. Is specified, the auxiliary vibration damping action can be stably obtained.

In the above embodiment, the swing member 1
Although the leaf spring 12 is used as the elastic body interposed between the zero and the bush 7, a torsion coil spring may be wound around the bush 7 instead of the leaf spring 12. . Thus, when the swing member 10 swings in one direction, the torsion coil spring acts to tighten the bush 7, so that the magnitude of the swing resistance 10 can be given a direction, and at the same time, the swing member 10 can be urged to rotate in a predetermined direction, so that the tension coil spring 23 can be omitted. The auto tensioner 1 of the present invention can be widely applied not only for the timing belt of an automobile engine but also for adjusting the tension of various other belts.

[0020]

As described above, according to the auto-tensioner according to the first aspect, when the tension of the belt suddenly increases, the elastic body tightens the bush and increases the sliding resistance between the bush and the support shaft. The swing resistance of the swing member increases, and the tension of the belt can be effectively reduced.
On the other hand, when the tension of the belt suddenly decreases, the tightened state of the bush by the elastic body is released, so that the sliding resistance between the bush and the support shaft is reduced, and the rocking resistance of the rocking member is reduced. As a result, the pulley moves quickly following the belt, and the pressed state can be maintained. Therefore, fluctuations in belt tension can be effectively suppressed.

According to the auto tensioner of the present invention, since the leaf spring is used as the elastic body, the direction of the magnitude of the swing resistance to be imparted to the swing member can be increased with a very simple configuration. It becomes possible to have the nature.

[Brief description of the drawings]

FIG. 1 is a front view of an auto tensioner according to an embodiment of the present invention.

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

FIG. 3 is a cross-sectional view of a main part taken along line YY of FIG. 1;

FIG. 4 is a sectional view taken along the line ZZ in FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 auto tensioner 2 fixed bed 3 support shaft 7 bush 9 pulley 10 swing member 12 leaf spring (elastic body) 12b, 12c end portion 25 compression coil spring (elastic member) 26 friction member V belt

Claims (2)

[Claims] An oscillating member rotatably supporting a pulley to be brought into contact with a belt is slidably fitted to a support shaft, and a friction member having a sliding surface perpendicular to the axis of the support shaft is elastically fixed. In an auto-tensioner for applying a swing resistance to a swinging member by pressing against a friction surface by a biasing force of a member, the bushing with the one end locked to the bush and the other end locked to the swinging member, respectively. Wound around the outer periphery, tightening the bush by swinging in one direction of the swing member,
An auto-tensioner comprising an elastic body that releases a tightened state of a bush by swinging in a reverse direction. 2. The auto-tensioner according to claim 1, wherein said elastic body comprises a leaf spring.