JP2002174306A - Auto-tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an auto-tensioner capable of properly suppressing oscillation or the like of an arm by a simple structure. SOLUTION: This auto-tensioner has a fixed spindle part 12, the arm 2 elastically energized in one rotating direction in a state that a boss part 21 of a one end side is rotatably fitted and supported on the spindle part 12, and tension pulley 3 rotatably supported on another end side of the arm 2. A torsion coil spring 4 elastically energizing the arm 2 in a certain rotating direction is provided between the spindle part 12 and the arm 2 along a rotational axis of the arm 2. A frictional member 7 and the arm 2 are arranged so as to mutually and frictionally contact in a diametral outer side of the torsion coil spring 4. An outer circumference part of the torsion coil spring 4 presses the frictional member 7 and the arm 2 so that mutual contact friction forces increase following expansion of an outer diameter of the torsion coil spring 4 from relaxation by rotation of the arm 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto tensioner for automatically maintaining a proper belt tension of a belt transmission device used as a power transmission means in a vehicle or the like, and more particularly, to a fixed support shaft portion. An arm that is elastically biased in one rotation direction in a state where the boss portion on one end side is rotatably fitted and supported on the support shaft portion, and rotatably supported on the other end side of the arm The present invention relates to an auto tensioner having a tension pulley to be used.

[0002]

2. Description of the Related Art Conventionally, in this type of auto tensioner, for example, as shown in FIG. 4, a base end as one end side of an arm 2 is slidingly supported with respect to a support shaft 11 forming a support shaft portion. Which are externally fitted via a resin bush 7 as the above.

In this conventional auto tensioner, a friction pressing plate 6 fixed to the tip of a support shaft 11 and a friction holding plate 6 as a restricting means for restricting the arm 2 from reciprocating and swinging due to a change in belt tension. A friction plate 5 provided so as to be able to make frictional contact with the friction holding plate 6, and a compression coil spring S that applies an elastic biasing force to the base end of the arm 2 so as to press the friction plate 5 toward the friction holding plate 6. It had been.

[0004]

However, in the above-mentioned conventional auto tensioner, the bush 7 may be formed of a resin having excellent wear resistance and low friction characteristics. It can be said that the impact resistance is insufficient, such as being damaged when a load is applied.

In particular, as shown in FIG. 4, in an auto tensioner of the type that offsets the tension pulley 3,
Due to the belt load acting on the tension pulley 3, the tip of the arm 2 is moved around the center O of the shaft support portion of the arm 2.
A moment M acts to rotate the arm 2 on the side approaching the pivot axis P of the arm.

Therefore, conventionally, as shown in FIG. 4, the moment M causes the support shaft 1 to be fitted to the end of the bush 7 at the place where the base end of the arm 2 is fitted to the support shaft 11. , The bush 7 is apt to be worn at the end, that is, to be liable to be unevenly worn.

[0007] As a result of uneven wear of the bush 7, rattling occurs between the base end of the arm 2 and the support shaft 1, and the rattling becomes severe, and the arm 2 is unduly tilted. There was a fear.

In the conventional auto-tensioner, the regulating means always elastically urges the friction plate 5 with the coil spring S against the friction plate pressing plate 6 integral with the support shaft 11, so that the friction plate 5 And the frictional force between the friction plate pressing plate 6 and the friction plate 5 and thus between the arm 2 and the support shaft 11 is made relatively high so that the arm is steep due to a change in belt tension. 2, the elastic biasing force is concentrated on the friction plate 5 so that the friction plate 5 is liable to be worn, and the friction plate 5 is constantly brought into frictional contact. There is a problem that the swing of the arm 2 becomes heavy to swing the arm 2 to follow the fluctuation of the tension.

In view of this, instead of the above-described regulating means using a bush structure, a friction plate, or the like, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Publication No. 166602, a boss of an arm and a boss on a support shaft side are disposed radially outward of a position where a torsion coil spring elastically biases the arm toward one direction of rotation with respect to the support shaft. A structure has been proposed in which a structure is provided in which the arms can be fitted to each other, and the inclination of the arm is received at a position relatively distant from the axis in the radial direction so that the receiving load can be reduced. As the fitting structure of the bosses, a tapered structure with a tapered structure, such as a wedge, is fitted to one of the bosses, and the boss acts on the torsion coil spring with the fluctuation of the belt tension. The coil spring and one of the bosses are linked to each other so as to shift to a side where the engagement between the two bosses is tight by force, thereby restricting the swing of the arm.

As a result, even if the belt tension fluctuates and the arm attempts to swing unjustly, the frictional force between the bosses is increased so as to restrict the swing.

However, in such a structure, there is provided a mechanism for converting a change in the urging force acting on the torsion coil spring into a force for moving one boss to a side which is strongly fitted to the other boss. It is structurally complicated because it needs to be provided.

The present invention has been made in view of the above circumstances, and provides an automatic tensioner which has a simple structure and which can appropriately suppress the occurrence of swinging or tilting of an arm due to a change in belt tension. With the goal.

[0013]

According to a first aspect of the present invention, there is provided an auto tensioner in which a fixed support shaft and a boss at one end are rotatably fitted to and supported by the support shaft. In an auto tensioner having an arm elastically biased in one rotation direction in a state and a tension pulley rotatably supported on the other end of the arm, a torsion coil spring elastically biases the arm in a constant rotation direction. Is provided between the support shaft portion and the arm in a state along the rotation axis of the arm, and a friction member and the arm are disposed radially outside the torsion coil spring so as to be in frictional contact with each other, As the outer diameter of the torsion coil spring expands due to the relaxation caused by the rotation of the arm, the outer peripheral portion of the torsion coil spring pushes the friction member and the arm such that the contact friction force between them increases. It is characterized configure that the construction of.

According to the structure of the first aspect of the present invention, when the arm swings due to the fluctuation of the belt tension and the torsion coil spring acts so as to relax, the outer peripheral portion of the torsion coil spring accompanies the relaxation. The outer diameter of the expanded torsion coil spring presses the friction member and the arm so as to increase the contact friction force between the friction member and the arm. Swing is suppressed.

Further, since a frictional force for restricting the rotation of the arm is provided at a position radially away from the axis, a torque for providing a resistance to the rotation of the arm due to the fluctuation of the belt tension can be increased. Even if the outer peripheral portion of the torsion coil spring has a relatively small pressing force outward due to the expansion of the diameter of the torsion coil spring, it is possible to sufficiently control the unreasonable swing of the arm and to prevent the arm from tilting moment. Since the receiving load of the inclination can be received in a state where the receiving load can be reduced, uneven wear at the supporting position of the arm can be sufficiently suppressed.

According to a second aspect of the present invention, in the auto-tensioner according to the first aspect, the friction member and the arm are separated from each other by an outer peripheral portion of an intermediate region in the axial direction of the torsion coil spring. And presses the contact frictional force to the side where the contact frictional force increases.

According to the second aspect of the present invention, the outer peripheral portion of the intermediate region in the axial direction of the torsion coil spring can have a larger displacement amount at the time of relaxation than the both ends in the axial direction, and can have a larger displacement amount. , Since the pressing range in the axial direction can be set large, it is easy to easily configure a structure that presses the friction member and the arm to the side where the contact friction force between them increases, and the pressing force is large. There is an advantage that it is easy to do.

According to a third aspect of the present invention, there is provided an auto tensioner according to the first or second aspect, wherein the friction member and the arm are connected to the radially outer portion of the torsion coil spring at a required circumferential position. On the other hand, it is characterized in that it is configured to press against the side where the contact frictional force between them increases.

According to the configuration of the third aspect of the present invention, of the radially outer portion of the torsion coil spring, the friction member and the arm are pressed against the friction member and the arm at the required position on the side where the mutual friction force increases. By doing so, as compared with the case where the friction member or the arm is pressed in the circumferential direction, a change in the shape that increases the contact friction force of the friction member or the arm is more likely to occur than in the case where the friction member or the arm is pressed against the entire circumference. The contact frictional force is relatively easy to increase, and the undue swinging of the arm can be more properly regulated.

According to a fourth aspect of the present invention, there is provided an auto-tensioner according to the third aspect, wherein a radially outer portion of the torsion coil spring is circumferentially separated from the pressing position at a required circumferential position. At a position, a spring receiving portion for receiving a reaction force against the torsion coil spring caused by the pressing is provided.

According to the fourth aspect of the present invention, the torsion coil spring can be expanded in diameter by the spring receiving portion, so that the pressing force with respect to the required circumferential position can be further concentrated, and the friction member and the frictional member can be concentrated. The contact frictional force with the arm can be further increased, and the undesired swing of the arm can be more appropriately restricted.

According to a fifth aspect of the present invention, in the auto-tensioner according to any one of the first to fourth aspects, the pressure on the friction member and the arm accompanying the diameter expansion of the torsion coil spring is reduced. It is configured to be performed indirectly via a support member.

According to the configuration of claim 5 of the present invention, the outer peripheral portion of the torsion coil spring whose diameter is to be expanded first comes into contact with the support member and presses the support member outward. The pressure on the friction member and the arm is
As compared with the case where there is no support member, the operation can be performed at an earlier timing, and the improper rotation of the arm can be quickly restricted.

Further, since the spring outer diameter portion does not directly contact the arm and is pressed, even if the arm is made of a relatively soft member such as aluminum, the arm is not damaged and the durability is enhanced.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a developed sectional view in side view showing an example of an auto tensioner according to the present invention. FIG. 2 is a vertical sectional front view of the auto tensioner. In the drawing, A indicates the entire auto tensioner, 1 is a fixed case having a support shaft portion 12, 2 is an arm, 3 is a tension pulley, and 4 is a torsion coil spring. B is a belt wound around the outer periphery of the tension pulley 3.

The auto-tensioner A has a base end as one end of the arm 2 (having a fitting cylinder 21 as a boss as described later) with respect to the support shaft 12 in the axial direction. A structure in which the center O1 of the shaft support range and the center O2 of the shaft support portion of the tension pulley 3 in the arm 2 in the axial direction are offset in the axial direction, in other words, the tension pulley 3 is connected to the support shaft portion 12 or the The structure is such that it is arranged at a position protruding forward (to the right in FIG. 1) from the tip of the protruding shaft 11.

The automatic tensioner A allows the tension pulley 3 to attenuate the vibration and impact from the belt B while allowing the movement of the tension pulley 3 accompanying the swing of the arm 2 in accordance with the fluctuation in the tension of the belt B. 3 has a function of restricting the movement.

That is, when the tension of the belt B gradually decreases, the arm 2 and the tension pulley 3 tilt to the left in FIGS. 2 and 3 due to the torsion restoring force (elastic urging force acting in the circumferential direction) of the torsion coil spring 4. Thus, the tension of the belt B is kept constant. On the other hand, when the tension of the belt B gradually increases, the arm 2 and the tension pulley 3 tilt rightward in FIGS. 2 and 3 against the torsion restoring force of the torsion coil spring 4 to keep the tension of the belt B constant. keep.

When the belt tension suddenly increases due to strong vibration or impact from the belt B to the auto tensioner A, a fitting cylinder as a boss of the arm 2 supporting the tension pulley 3 is used. The vibrations and shocks are transmitted to the portion 21. As will be described in detail later, the shocks and the like are urged toward the belt tension side from the no-load state. On the other hand, since the torsion acts to relax, the outer peripheral portion of the torsion coil spring 4 expands in diameter, and the outer peripheral portion of the torsion coil spring 4 extends the fitting cylinder 21 of the arm 2 outward. Pressing increases the frictional contact force with the bush 7 as a friction member, thereby restricting sudden swing of the arm 2.

Further, a friction plate 5 interposed between a friction member pressing plate 6 and an arm 2 provided at a distal end of a protruding shaft 11 protruding in the axial direction at the center of the fixed case 1 and a disc spring 1
6, the vibration and shock of the arm 2 due to the sudden swing of the arm 2 are absorbed and attenuated. Movement is suppressed. As a result, the position of the tension pulley 3 can be prevented from largely changing, and the tension with respect to the belt B is kept constant. The operation of the auto-tensioner A according to the present invention will be described in detail later.

Hereinafter, each component of the auto tensioner A will be specifically described.

The fixed case 1 is fixed to a mounting object on which a belt transmission (not shown) is provided. The fixed case 1 has a protruding shaft 11 for fixing the frictional member pressing plate 6 to the tip, and a support having a cylindrical boss structure. The vehicle includes a shaft portion 12 and an attachment portion (not shown) to the engine.

The entire outer peripheral shape of the projecting shaft 11 is substantially cylindrical. The support shaft portion 12 is formed in a bottomed cylindrical shape extending radially outward from the base end side of the protrusion shaft 11 and surrounding the outer periphery of the arm protrusion shaft 11. Protruding shaft 11 and support shaft 1
The reference numeral 2 designates a common axis P1 as the center. Here, the fixed case 1 includes the protruding shaft 11 and the support shaft 1.
2 is a die-cast molded product of an aluminum alloy or the like integrally formed.

The arm 2 is rotatably supported around the shaft center P1 with respect to the support shaft portion 12, and has a base end on one end side thereof for fitting to the support shaft portion 12. A cylindrical portion 21 is formed, and the tension pulley 3 is connected to the shaft center P1 at the distal end.
A pulley supporting portion 22 is formed to rotatably support about an axis P2 parallel to the pulley.

Further, the fitting cylinder 21 and the pulley support 2
2, a flange portion 10 protruding inward is formed and provided at an intermediate position between the two. The flange portion 10 serves as a restricting side wall on one end side in the axial direction of the torsion coil spring 4 described later, and a restricting side wall of a disc spring 16 described later on a front side opposite to the restricting side wall.

The fitting tube portion 21 is a cylindrical portion extending at the base end of the arm 2 in a direction opposite to the side from which the pulley support portion 22 extends, as shown in FIG. The bush 7 is slidably fitted to the inner peripheral surface of the cylindrical bush 7 slidably fitted to the inner peripheral surface of the support shaft portion 12. The bush 7 forms a sliding bearing made of a resin material that guides the fitting tubular portion 21 to slide with respect to the support shaft portion 12.

Further, as shown in FIG. 1, the bush 7 has a cylindrical portion which is sandwiched between the support shaft portion 12 and the fitting tube portion 21 in the radial direction about the axis P1, and a support shaft portion. 12 and a flange-like portion sandwiched between a side surface portion a of a step formed on the outer periphery of the fitting tubular portion 21. In the tubular portion, the support shaft portion 12 is arranged in a radial direction with respect to the axis P1. To support the fitting cylinder 21. The bush 7 constitutes the friction member according to the first aspect.

The tension pulley 3 is rotatably supported by a pulley support 22 of the arm 2 via a rolling ball bearing 9 and is manufactured by press molding. The tension pulley 3 is attached by a bolt 8a and a nut 8c fastened to a pulley support 22 of the arm 2. The above-mentioned rolling ball bearing 9 is fitted to the inner peripheral surface of the tension pulley 3 and the outer peripheral surface of the pulley support 22 of the arm 2.

Hereinafter, a configuration which is a feature of the present invention will be described in detail. The torsion coil spring 4 is normally in a non-contact and torsion-compressed state in an annular space between the outer peripheral surface of the projecting shaft 11 and the inner peripheral surfaces of the support shaft portion 12 and the fitting cylindrical portion 21 without contacting the respective surfaces. It is arranged in.

Both ends of the torsion coil spring 4 are bent portions 41 and 42 bent outward in the radial direction, respectively, and the bent portions 41 are fitted into engagement recesses provided in the arm 2 as shown in FIG. The bent portion 42 is engaged with the engaging concave portion provided in the fixed case 1.

The torsion coil spring 4 is set in a state where it is biased in advance to the side where the outer diameter is reduced.
The arm 2 is rotated in one rotation direction by the torsional restoring force (FIG. 2,
In FIG. 3, the belt B having an endless belt shape is elastically biased in a counterclockwise direction to apply tension outward. In addition,
The torsion coil spring 4 is provided between the inner wall of the fixed case 1 and the flange portion 10 of the arm 2 in the axial direction when the support shaft portion 12 and the fitting tube portion 21 are fitted through the bush 7. It is deployed with almost no compression or expansion.

The arm 2 when the belt load is increased
The rotation of the torsion coil spring 4 against the elastic force of the torsion coil spring 4 (clockwise rotation in FIGS. 2 and 3) relaxes the torsion coil spring 4 and expands the outer circumference of the torsion coil spring 4, thereby forming a fitting cylinder. The outer peripheral portion of the torsion coil spring 4 presses the fitting tube portion 21 outward via a spring support 14 as a support member disposed on the inner peripheral surface of the portion 21.

The spring support 14 is fitted to the fitting cylinder 21
2, it is integrally fixed (at least in the circumferential direction), and as shown in FIG. 2, a required range in the circumferential direction about the axis P1 (in this embodiment, the center is about the axis P1). (In the range of about 90 degrees in terms of angle). In addition, the spring support 14 is located substantially opposite to the axis P1 with respect to the tension pulley 3, as shown in FIG.

On the inner peripheral surface of the fitting tube portion 21 on the opposite side to the axis P1 from the side where the spring support 14 is located, spring receiving portions 17 and 18 projecting inward in the radial direction are provided on the shaft. The torsion coil spring 4 is provided so as to be able to receive the outer peripheral portion within a required range along the center direction.

As a result, the arm 2 swings due to the fluctuation of the belt tension toward the side where the belt tension increases, and the torsion coil spring 4
When the diameter of the spring support 14 is increased, the outer peripheral portion thereof abuts against the spring support 14 and presses the fitting tube portion 21 located outside the spring support 14 outward.

Since the spring support 14 is provided only in a required range in the circumferential direction, the torsion coil spring 4 is provided.
When the diameter is increased, the outer peripheral portion comes into contact only with the spring support 14 and the spring receiving portions 17 and 18.

As a result, the bush 7 sandwiched between the fitting tube portion 21 and the support shaft portion 12 is strongly sandwiched at the pressing portion, and the contact friction force between the bush 7 and the fitting tube portion 21 is increased. To increase.

That is, the outer peripheral portion of the expanding torsion coil spring 4 is regulated in a substantially linear contact state along the axial direction with respect to the spring receiving portions 17 and 18, and on the side opposite to the regulated side, the expanded portion. The outer peripheral portion of the torsion coil spring 4 having a diameter presses the spring support 14.

Therefore, the pressing force against the spring support 14 due to the expansion of the diameter of the torsion coil spring 4 is applied to the spring support 1.
4 also acts on the fitting cylinder 21, and the fitting cylinder 21, which has been elastically deformed so as to spread out somewhat by the pressing force, presses the bush 7.

As a result, since the outside of the bush 7 is restricted by the support shaft portion 12, the bush 7 sandwiched between the support shaft portion 12 and the fitting tube portion 21 and the fitting tube portion 2 are held.
1, the contact frictional force between the bushing 7 and the support shaft 12 is braked, and the arm 2 swings. You'll brake trying.

The braking effect can be increased by concentrating the contact friction force between the bush 7 and the fitting tube 21 only in the circumferential direction where the spring support 14 is installed.
There is less force distribution than when the outer peripheral portion of the torsion coil spring 4 whose diameter is enlarged over the entire circumference comes into contact with the fitting tube portion 21, and the swing of the arm 2 can be more reliably braked.

The outer peripheral portion of the torsion coil spring 4 which comes into contact with the spring support 14 contacts only the intermediate portion in the direction of the axis P1 with the spring support 14, and the torsion coil spring 4 contacts at both ends thereof. Not done.

The means for increasing the frictional force between the bush 7 and the fitting tubular portion 21 by expanding the diameter due to the relaxation of the torsion coil spring 4 and braking the brakes constitutes the first tension fluctuation regulating means for regulating the fluctuation of the belt tension. are doing.

When the sudden increase in the belt load is eliminated, the torsion coil spring 4 returns to its reduced diameter side, so that the pressing against the fitting tube 21 and the bush 7 is stopped. Thus, the deformation of the fitting tube 21 due to the pressing is eliminated, and the contact friction force between the fitting tube 21 and the bush 7 is reduced.

Next, a description will be given of a sub second tension fluctuation restricting means which assists the first tension fluctuation restricting means.
As shown in FIG. 1, the friction plate pressing plate 6 is fixed while being caulked to the tip of the protrusion 11.

The disk-shaped friction plate 5 and the disc spring 16 are sandwiched between the friction plate pressing plate 6 and the front surface 15 of the flange portion 10 and loosely fitted to the protruding portion 11. A disc spring guide 19 is provided.

The friction plate 5, the disc spring 16, the disc spring guide 19, and the friction holding plate 6 constitute a second tension fluctuation regulating means. As shown in FIG. 1, the disc spring guide 19 is provided with an inner brim on the inner peripheral edge of the inner peripheral edge thereof,
An outer flange is provided on the outer diameter edge over the entire circumference, and the inner collar is locked to the inner circumference of the friction plate 5, and the outer collar is locked to the outer circumference of the disc spring 16. .

When the friction holding plate 16 is pressed at a required pressure by the disc spring 16 via the disc spring guide 19 and the friction plate 5, the gap between the fitting cylinder 21 and the bush 7 is eliminated, and the friction plate is pressed. 5 and friction member holding plate 6
Between them and the rotation resistance.

Therefore, even if the arm 2 tries to swing around the axis P1 due to a sudden change in the belt tension, the swing of the arm 2 is regulated together with the first tension variation regulating means.

Here, in the figure, K is the friction member holding plate 6
Is a caulked portion of the protruding shaft 11 which is caulked so as to prevent the shaft from coming off.

The friction member pressing plate 6 is formed of, for example, an annular plate manufactured by press-forming a rolled steel plate for a structure, and is fixed to the protruding shaft 11 so as not to rotate. ing.

Accordingly, with the above configuration, as shown in FIG. 3, when the belt load F suddenly increases, the arm 2 opposes the elastic biasing force of the torsion coil spring 4 so that the auto tensioner A 2 and 3, the torsion coil spring 4 expands in diameter, and the outer peripheral portion of the torsion coil spring 4 is urged through the spring support 14 into the fitting cylindrical portion. 21, the bush 7 is pressed to increase the contact friction force between the fitting tube 21 and the bush 7.

The increase in the contact frictional force acts as a damping of the swing of the arm 2, and even if the arm 2 is inclined by the moment M about the base end side of the arm 2, the arm 2 is inclined radially outward from the axis P 1. Since the support shaft portion 12 and the fitting tube portion 21 are fitted over a required range in the axial direction at a relatively large distance from the arm 2, the arm 2
Is regulated.

Even if the bush 7 is slightly worn due to the inclination of the arm 2, there is a possibility that the uneven wear may occur between the bush 7 and the spindle 12 or the fitting cylinder 21. This gap is eliminated when the fixed case 1 and the arm 2 are pressed by the disc spring 16 toward the side closer to the axial direction.

In the above-described embodiment, the regulation of the tension fluctuation is shared by the first tension fluctuation restricting means and the second tension fluctuation restricting means. As compared with the above-described method, a small torsion coil spring or disc spring can be adopted, and the overall structure can be made compact.

In the above embodiment, the arm is rotatably supported by the arm via the bush outside the torsion coil spring with respect to the fixed case. The boss portion on one end side of the arm may be externally fitted to the surface, and the boss portion on one end side of the arm may be externally fitted to the bush that is externally fitted. In this case, a torsion coil spring is provided so as to be jacketed around the boss of the arm,
A friction member may be provided on the side of the cylindrical structure portion formed at one end of the arm so as to protrude from the boss portion at a predetermined radial distance outward from the outer peripheral portion of the torsion coil spring.

In the above embodiment, as the second tension fluctuation restricting means, the illegal rotation of the arm is restricted by utilizing the frictional force generated between the frictional member and the frictional member pressing plate caused by pressing by the disc spring. However, a structure without the second tension fluctuation restricting means may be adopted. In addition, in the case of this structure, when the torsion coil spring is assembled so as to have a property of elastically biasing in the axial direction, the shaft is supported in the same axial direction as the disc spring of the second tension variation restricting means. The urging force on the side that brings the fitting cylindrical portion close to the portion can be constantly applied.

Further, as the second tension fluctuation restricting means, a sliding bearing structure such as a bush provided on the projecting portion 11 or the like separately from the bush 7 in the above embodiment may be used instead of the friction plate 5.

[0070]

According to the first to fifth aspects of the present invention, when the arm swings due to the fluctuation of the belt tension and the torsion coil spring acts to relax, the torsion coil spring accompanies the relaxation. The outer peripheral portion of the torsion coil spring expands, and the outer peripheral portion of the torsion coil spring presses the friction member and the arm so that the contact friction force between them increases, so that the swing of the arm is braked. And the swing of the arm is suppressed.

Further, since a frictional force for restricting the rotation of the arm is given at a position radially away from the axis, a torque for giving a resistance to the rotation of the arm due to the fluctuation of the belt tension can be increased. Even if the outer peripheral portion of the torsion coil spring has a relatively small pressing force outward due to the expansion of the diameter of the torsion coil spring, it is possible to sufficiently control the unreasonable swing of the arm and to cope with the moment when the arm is tilted. Since the receiving load of the inclination can be received in a state where the load can be reduced, uneven wear at the supporting position of the arm can be sufficiently suppressed.

In particular, according to the configuration of the second aspect of the present invention, the outer peripheral portion of the intermediate region in the axial direction of the torsion coil spring has a larger displacement amount of the diameter expansion at the time of relaxation than both ends in the axial direction. And the pressing range in the axial direction can be set large, so that it is easy to easily construct a structure that presses the friction member and the arm to the side where the contact friction force between them increases, and the pressing force is also low. There is an advantage that it can be easily made large.

According to the third aspect of the present invention, the radially outer portion of the torsion coil spring is located on the side where the frictional force between the frictional member and the arm increases at a required circumferential position. By pressing, a change in shape that increases the contact frictional force of the frictional member or the arm due to the pressing is more likely to occur than in the case of contacting and pressing over substantially the entire circumference in the circumferential direction. Therefore, the contact frictional force can be relatively easily increased, and the undue swinging of the arm can be more appropriately regulated.

According to the structure of the fourth aspect of the present invention, the spring receiving portion allows the torsion coil spring to expand its diameter, thereby further concentrating the pressing force on the required circumferential position. The contact frictional force with the arm can be further increased, and the undesired swing of the arm can be more appropriately restricted.

According to the fifth aspect of the present invention, the outer peripheral portion of the torsion coil spring whose diameter is to be expanded first comes into contact with the support member, and the support member is pressed outward. The pressure on the friction member and the arm is
As compared with the case where there is no support member, the operation can be performed at an earlier timing, and the improper rotation of the arm can be quickly restricted.

Further, since the spring outer diameter portion does not come into direct contact with the arm and is pressed, even if the arm is made of a relatively soft member such as aluminum, the arm is not damaged and the durability is increased.

[Brief description of the drawings]

FIG. 1 is a developed sectional view showing an example of an auto tensioner of the present invention.

FIG. 2 is a longitudinal sectional front view showing an example of the auto tensioner of the present invention.

FIG. 3 is a partially cutaway front view showing the auto-tensioner with a belt wound therearound;

FIG. 4 is a developed sectional view showing an example of a conventional auto tensioner.

[Explanation of symbols]

 Reference Signs List A auto tensioner 2 arm 3 tension pulley 4 torsion coil spring 7 friction member (bush) 12 support shaft portion 14 support portion P1 rotation axis

Claims (5)

[Claims] An arm that is elastically biased in one rotation direction with a fixed support shaft portion, a boss portion on one end side fitted and supported rotatably with respect to the support shaft portion, and the arm; An auto-tensioner having a tension pulley rotatably supported at the other end of the arm, wherein a torsion coil spring for elastically urging the arm in a constant rotation direction is provided along the rotation axis of the arm. And the arm, and a friction member and the arm are arranged radially outside of the torsion coil spring so as to be able to make frictional contact with each other, and the outer diameter of the torsion coil spring is expanded by relaxation by rotation of the arm. An outer peripheral portion of the torsion coil spring presses the friction member and the arm so as to increase a contact friction force therebetween. 2. The auto-tensioner according to claim 1, wherein an outer peripheral portion of the intermediate region in the axial direction of the torsion coil spring increases a contact friction force between the friction member and the arm. An auto-tensioner configured to press against 3. The auto-tensioner according to claim 1, wherein a contact friction force between the friction member and the arm increases at a required circumferential position in a radially outer portion of the torsion coil spring. An auto-tensioner configured to be pressed to the side. 4. The auto-tensioner according to claim 3, wherein the torsion associated with the pressing is located at another position in a circumferential direction with respect to the pressing position at a required circumferential position in a radially outer portion of the torsion coil spring. An automatic tensioner having a spring receiving portion for receiving a reaction force against a coil spring. 5. The auto-tensioner according to claim 1, wherein the friction member is pressed indirectly via a support member when the diameter of the torsion coil spring is increased. It is characterized by having.