JPH0777252A - Auto tensioner - Google Patents

Abstract

PURPOSE:To generate a large sliding frictional force between a spring support and a boss part by shortening a distance between the rotational center and the turning axial center of a torsion coil spring and constituting the pressing force of this torsion coil spring against the spring support so as to be increased. CONSTITUTION:This auto tensioner supports a turning member 2 turnably on a fixed member 1 to be locked to, for example, an automobile angine or the like, and interposes a torsion coil spring 3 between both these members 1 and 2. This torsion coil spring 3 is formed in a state that a base end 3a at the side being seated on a spring support 13 is projected in the axial center from a body, and this base end 3a is engaged into a base end engaged hole 5 of the side circumferential part of a rear cup part 1a of the fixed member 1. On the other hand, a tip 3b is engaged into a tip engaged hole 12 in the radial direction, installed on the side circumferential part of a front cup part 2a of the turning member 2 as well. In a state that both these end s 3a and 3b are engaged tight, the body operatesin a direction where its diameter is expanded, whereby the turning member 2 is turned around in the specified direction.

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 As an automatic tensioner of this type, for example, the one disclosed in U.S. Pat. No. 4,473,362 is generally known, and between belt pulleys wound between a drive pulley and a plurality of driven pulleys. It is used to press the span to transfer the rotational force of the drive pulley to all driven pulleys.

Specifically, as shown in FIGS. 3 and 4,
It has a bottomed cylindrical rear cup part b having a base end locking hole a formed in the side peripheral part, and a shaft part c extending axially from the bottom part of the rear cup part b is provided. A fixed member A fixed to the fixed body, a bottomed cylindrical front cup portion e having an opening portion facing the opening portion of the rear cup portion b and a tip locking hole d formed in the side peripheral portion are provided. A boss portion g extending in the axial direction from the bottom portion of the front cup portion e and rotatably fitted to the shaft portion c of the fixing member A via a cylindrical insert bearing f, Further, on the outer periphery of the front cup portion e, an arm portion i is provided projecting at the tip thereof, which rotatably supports a pulley h around an axis Q parallel to the rotation axis P of the boss g,
The rotating member B rotatably supported by the fixed member A at the boss portion g, and the inner peripheral surface of the rotating member B, which is disposed on the outer peripheral side of the boss portion g and fixed to the fixed member A side. A cylindrical spring support C having a surface capable of slidingly contacting the outer peripheral surface of the boss portion g, and a base end disposed in the outer peripheral side of the spring support C and having a base end in the base end locking hole a of the fixing member A. A torsion coil whose tips are respectively locked in the tip locking holes d of the rotating member B to urge the rotating member B to rotate in a predetermined direction (counterclockwise direction in FIG. 3) with respect to the fixed member A. And a spring D. The rotating biasing force of the rotating member B presses the belt t against the pulley h to apply a predetermined tension, and the damping force due to sliding friction is changed according to the change in the tension. There is.

One of the mechanisms for generating the damping force is sliding friction between the inner peripheral surface of the spring support C and the outer peripheral surface of the boss portion g of the rotating member B. That is, when the rotating member B is rotated in the direction opposite to the rotating biasing direction (clockwise direction in FIG. 3), the torsion coil spring D is attached to the base end locking portion a of the fixing member A. A rotation operation is performed with the end locked portion as the rotation center R, and the spring support C is pressed against the boss portion g of the rotating member B with a predetermined pressing force F at the portion indicated by S in FIG. As a result, sliding friction is generated between the spring support C and the boss portion g to dampen the rotation of the rotating member B.

[0005]

In the meanwhile, as automobile engines are being diversified and diversified, there is a demand for variable damping characteristics of auto tensioners mounted on such engines. In particular, in the case of an engine with a small number of cylinders such as four cylinders and three cylinders, since the fluctuation of the belt tension increases as the fluctuation of rotation increases, it is necessary to generate a larger damping force. Is required to be changed to a high damping side.

However, the magnitude of friction generated between the spring support C on the fixed member A side and the boss portion g of the rotating member B is the same when the contact area and the sliding surface characteristics are the same. Has a correlation with the torque characteristic of the torsion coil spring C, so that in the conventional auto tensioner described above, a large damping force can be obtained without changing the torque characteristic, that is, without changing the torsion coil spring C. The problem is that it is difficult.

The present invention has been made in view of the above problems, and an object thereof is to rotate a spring support fixed to a fixed member side by friction generated by a torsion coil spring pressing against a boss portion of a rotating member. In an auto tensioner designed to dampen the rotation of the moving member, the pressing force against the spring support is increased without changing the torque characteristics of the torsion coil spring so that a large frictional force can be obtained. It is to be able to change to a high damping side.

[0008]

In order to achieve the above object, according to the invention of claim 1, the portion where the base end of the torsion coil spring is locked to the base end locking portion of the fixing member is the center of rotation. When the torsion coil spring rotates to press the spring support against the boss portion, paying attention to the fact that the pressing force against the spring support depends on the distance between the rotation center and the rotation axis, By shortening the distance between the center and the rotation axis, the pressing force is increased without changing the torque characteristics of the torsion coil spring.

Specifically, in the present invention, a fixing member having a shaft portion and a base end locking portion and fixed to a fixed body, and a boss portion rotatably fitted on the shaft portion of the fixing member. And a rotating member having a pulley and a tip locking portion that are rotatable around an axis parallel to the rotating axis and a boss portion outer peripheral side of the rotating member, and fixed to the fixing member side. The spring support, the inner peripheral surface of which is slidably in contact with the outer peripheral surface of the boss portion, and the base end of the fixing member is provided on the outer peripheral side of the spring support. And a torsion coil spring whose front ends are respectively locked to the front end locking portions of the rotary member to bias the rotary member in a predetermined direction with respect to the fixed member. The belt is pressed to apply a predetermined tension, and when the tension fluctuates, the rotating member moves in the direction opposite to the rotational biasing direction. When it is rotated in the direction, the torsion coil spring rotates about a portion where the proximal end of the torsion coil spring is locked to the proximal locking portion of the fixing member, and the torsion coil spring performs a predetermined rotational movement of the spring support. It is premised on an autotensioner that is pressed against a boss portion of a rotating member by a pressing force to generate sliding friction between the spring support and the boss portion to dampen the rotation of the rotating member.

The base end of the torsion coil spring is provided so as to protrude from the main body of the torsion coil spring in the axial direction, while the base end locking portion of the fixing member is provided at the bottom of the fixing member. The torsion coil spring is provided with the base end thereof locked to the base end locking portion of the bottom portion of the fixing member to bring the rotation center of the torsion coil spring close to the rotation axis, and the rotation center and the rotation axis. The distance between them is shortened to increase the pressing force against the spring support.

[0011]

With the above construction, in the invention of claim 1, when the rotating member of the auto tensioner is rotated in the direction opposite to the rotational biasing direction, the torsion coil spring locks the base end of the fixing member. Rotation is performed around the base end portion locked to the portion as the center of rotation, whereby the spring support is pressed against the boss portion of the rotating member. Then, sliding friction is generated between the spring support and the boss portion, and the rotation of the rotating member is damped by the sliding friction. At this time, since the base end of the torsion coil spring is locked to the base end locking portion of the bottom portion of the fixing member in a state of protruding from the main body of the torsion coil spring in the axial direction, the torsion coil spring is The portion of the base end of which is locked to the fixing member, that is, the center of rotation when the torsion coil spring performs a rotating operation, is directed radially inward from the conventional fixing member side peripheral portion to the bottom portion of the fixing member. This means that the center of rotation of the torsion coil spring has moved closer to the rotation axis, and the distance between the two has been shortened. Therefore, the pressing force against the spring support increases by the shortened amount, and the damping force can be changed to the high damping side without changing the torque characteristic of the torsion coil spring.

[0012]

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.
And a rotating member 2, and a torsion coil spring 3 for compressing the rotating member 2 in a predetermined direction (counterclockwise direction in FIG. 1) with respect to the fixed member 1 is provided. .

The fixing member 1 has a bottomed cylindrical rear cup portion 1a having an opening on the front side (upper side in FIG. 2) and a shaft portion 4 extending in the axial direction from the center of the bottom portion of the rear cup portion 1a. Then, it is configured to be fixed to a fixed body at a mounting portion (not shown). Further, a base end locking hole 5 as a base end locking portion is formed in the bottom portion of the rear cup portion 1a.

The rotating member 2 has a front cup portion 2a whose opening faces the opening of the rear cup portion 1a,
Outer fitting is performed on the shaft portion 4 of the fixed member 1 from the center of the bottom portion of the front cup portion 2a and from the tip end side thereof through an insert bearing 6 as a cylindrical sliding member made of synthetic resin. And a boss portion 7 that is formed on the outer periphery of the front cup portion 2a.
At the tip thereof, there is provided an arm portion 9 on which a pulley 8 is rotatably supported around an axis Q parallel to the rotation axis P of the boss portion 7. The rotating member 2 is rotatably supported by the fixed member 1 at the boss portion 7, and is not shown in the drawing through the thrust washer 10 made of synthetic resin and the metal front plate 11 at the tip of the shaft portion 4 of the fixed member 1. It is prevented by the retaining means. A belt t, such as a V-belt for driving accessories in an automobile engine, to which a predetermined tension is to be applied, is wound around the pulley 8 as indicated by a phantom line in FIG. Further, a tip locking hole 12 is formed in the side peripheral portion of the front cup portion 2a so as to penetrate the side peripheral portion in the radial direction.

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 semi-cylindrical spring support 13 with a flange made of synthetic resin is interposed between the base end side of the torsion coil spring 3 and the boss portion 7. 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.

As a feature of the present invention, the base end 3a of the torsion coil spring 3 is formed so as to project from the main body in the axial direction. Specifically, the main body of the torsion coil spring 3 is left-handed, and the tip 3b is formed so as to project radially outward from the main body. Then, the base end 3a
Is axially engaged with the base end locking hole 5 in the peripheral portion of the fixed member 1 on the rear cup portion 1a side, and the tip 3b is the front end locking hole 1 in the peripheral portion of the rotating member 2 on the front cup portion 2a side.
Each of the end portions 3a and 3b is restricted from moving in the circumferential direction by being penetrated in the radial direction 2 and locked. Then, by operating the main body in a direction in which the diameter of the main body expands with the both end portions 3a and 3b being locked, the rotary member 2 is biased to rotate in a predetermined direction.

In the torsion coil spring 3, the inward flange 13a of the spring support 3 is pressed against the bottom surface of the rear cup portion 1a by the urging force in the axial direction of the spring support 13, and the spring support 13 is fixed.
It is designed to be fixed to the side. In the fixed state, the rotation member 2 is in a direction opposite to the rotation biasing direction (see FIG. 1).
When it is rotated clockwise, the torsion coil spring 3
Rotates about the portion of the base end 3a locked in the base end locking hole 5 of the fixing member 1 in the clockwise direction in the figure as the center of rotation R. Then, in the figure of the spring support 13, S
The portion indicated by is pressed by the torsion coil spring 13 toward the rotation axis P and pressed against the boss portion 7 of the rotation member 2, so that sliding friction is generated between the spring support 13 and the boss portion 7. However, the rotation of the rotating member 2 is damped by the sliding friction.

Therefore, according to this embodiment, when the belt t is wound around the pulley 8 of the auto tensioner,
Between the insert bearing 6 and the boss 7 of the rotating member 2 in the auto tensioner, and between the boss 7 and the spring support 13, the belt force and the urging force of the torsion coil spring 3 are combined to cause friction. A damping force is generated by the above, and when the tension of the belt t is reduced in this state, the damping force is reduced due to the reduction 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, and thus, the tension decrease of the belt t can be promptly prevented. 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 makes it possible to apply a large resistance force to the pulley 8 and prevent the flapping of the belt t.

The tension of the belt t increases and the rotating member 2
When is rotated in the direction opposite to the rotation urging direction, the torsion coil spring 3 rotates about the base end 3a locked in the base end locking hole 5 of the fixing member 1 as the rotation center R. Do the action,
As a result, the spring support 13 is pressed against the boss portion 7 of the rotating member 2. Then, sliding friction is generated between the spring support 13 and the boss portion 7, and the rotation of the rotating member 2 is damped by the sliding friction. At this time, the base end 3a of the torsion coil spring 3 is locked in the base end locking hole 5 at the bottom of the fixing member 1 in a state of protruding from the main body of the torsion coil spring 3 toward the axial direction. ,
The portion where the base end 3a is locked to the fixing member 1 is shown in FIG.
This means that it is moved inward in the radial direction from the peripheral portion of the conventional fixing member A shown in (4), whereby the rotation center R of the torsion coil spring 3 approaches the rotation axis P and both R, The distance between P is shortened. Therefore, the pressing force F against the spring support 13 is increased by the shortened amount, and the damping force can be changed to the high damping side without changing the torque characteristic of the torsion coil spring 3.

That is, the pressing force F1 in the conventional auto tensioner is, as can be seen from FIG. 3, F1 = T / x1 (where T: torque of torsion coil spring, x: center of rotation-
The distance between the rotation axes). On the other hand, the pressing force F2 of the auto tensioner according to the above embodiment is F2 = T / x2, as can be seen from FIG. Then, since x2 <x1, F2> F1. Therefore, when the torque characteristics of the torsion coil spring 3 are the same, between the rotation center R and the rotation axis P of the torsion coil spring 3. Pressing force F by shortening the distance x
It turns out that can be increased.

Although the tip 3b of the torsion coil spring 3 is projected outward in the radial direction from the main body in the above embodiment, it may be projected in the axial direction from the main body in the same manner as the base end 3a. Good.

[0023]

As described above, according to the first aspect of the present invention, the base end of the torsion coil spring is fixed when the rotating member is rotated in the direction opposite to the rotating biasing direction. The torsion coil spring rotates about the portion locked to the base end locking portion of the member to press the spring support against the boss portion of the rotating member, and between the spring support and the boss portion. In an automatic tensioner configured to generate sliding friction to damp the rotation of a rotating member, the base end of the torsion coil spring is projected from the main body of the torsion coil spring in the axial direction, while the fixing member is fixed. A base end locking portion for locking the base end is provided at the bottom of the, and the distance between the rotation center of the torsion coil spring and the rotation axis is shortened to press the torsion coil spring against the spring support. Was made larger Therefore, a large sliding frictional force can be generated between the spring support and the boss portion without changing the torque characteristic of the torsion coil spring, and the damping force with respect to the rotation of the rotating member is changed to the high damping side. be able to.

[Brief description of drawings]

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

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

FIG. 3 is a view corresponding to FIG. 1 showing a conventional auto tensioner.

FIG. 4 is a view corresponding to FIG. 2 showing a conventional auto tensioner.

[Explanation of symbols]

 1 Fixed Member 2 Rotating Member 3 Torsion Coil Spring 3a Base End 3b Tip 4 Shaft 5 Base End Locking Hole (Base End Locking Part) 7 Boss 8 Pulley 12 Tip Locking Hole 13 Spring Support P Rotating Shaft Center R rotation center x distance between the rotation axis and rotation center F pressing force t belt

Claims (1)

[Claims] 1. A fixing member which has a shaft portion and a base end locking portion and can be fixed to a fixed body, and a boss portion rotatably fitted outside the shaft portion of the fixing member.
A rotating member having a pulley and a tip locking portion rotatable about an axis parallel to the rotating axis, and a state in which the rotating member is arranged on the outer peripheral side of the boss portion of the rotating member and fixed to the fixing member side. A spring support whose inner peripheral surface is in slidable contact with the outer peripheral surface of the boss portion, and a spring support which is disposed on the outer peripheral side of the spring support, has a base end at a base end locking portion of a fixing member, and a tip end engaging member of a rotating member. And a torsion coil spring whose front end is locked to the stopper to bias the rotary member in a predetermined direction with respect to the fixed member, and the belt is pressed against the pulley by the rotary biasing force of the rotary member. To give a predetermined tension, and when the rotating member is rotated in the direction opposite to the rotating biasing direction when the tension changes, the base end of the torsion coil spring is fixed to the base of the fixing member. The torsion coil spring rotates about the part locked by the end locking part as the center of rotation. The auto tensioner is configured to press the spring support against the boss portion of the rotating member with a predetermined pressing force to generate sliding friction between the spring support and the boss portion to dampen the rotation of the rotating member. The base end of the torsion coil spring is provided so as to project from the main body of the torsion coil spring in the axial direction, while the base end locking portion of the fixing member is provided at the bottom of the fixing member. The torsion coil spring is provided with the base end of the torsion coil spring locked to the base end locking portion of the bottom of the fixing member so that the rotation center of the torsion coil spring is close to the rotation axis. The auto tensioner is configured so that the distance between the two is shortened and the pressing force against the spring support is increased.