JPH0749108Y2 - Auto tensioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an autotensioner used for a relatively long belt such as what is called a serpentine belt.

<Prior Art> A conventional auto tensioner of this type will be described with reference to FIG.

In the illustrated automatic tensioner, a tension arm 2 having a tension pulley 3 at one end is swingably fitted onto a support shaft 6 of a base 1, and a boss portion 2a protruding from the tension arm 2 for a swing fulcrum. One end 5a of the coil spring 5 mounted on the outer periphery of the coil spring 5 is locked and fixed to the base 1, and the other end 5b of the coil spring 5 is locked to the pin 10 of the tension arm 2 to move the tension arm 2 to the coil spring 5. It is configured so as to be urged to swing in a constant direction (direction of arrow A) by a torsion restoring force.

By the way, in the above-mentioned conventional autotensioner, the other end 5b of the coil spring 5 is twisted and compressed from the position (a) to the position (b) in the figure, and is locked to the pin 10 of the tension arm 2 so that the tensioner 2 can swing. Although it will gain power, the coil spring 5 buckles during this torsional compression,
The first winding portion and the final winding portion on the base side are deformed toward the center side as shown by the phantom line in the figure and come into contact with the outer peripheral surface of the boss portion 2a. The contact pressure on the outer peripheral surface of the boss increases as the other end 5b of the coil spring 5 is twisted and compressed toward the winding side.

As a result, frictional resistance is given to the rotation of the boss portion 2a accompanying the swing of the tension arm 2, and the characteristic of the torsional torque given to the tension arm 2 by the coil spring 5 is the eighth.
As shown in the figure.

That is, there is a difference in the frictional resistance due to the change in the contact pressure between the twisting deformation of the coil spring 5 on the winding side and the twisting deformation on the unwinding side. The required spring characteristics cannot be obtained. If such a large hysteresis occurs in the torsional torque characteristic, there arises a problem that the function of suppressing belt vibration is deteriorated. In addition, the boss portion 2a may be locally worn due to the friction of the coil spring 5.

The present applicant has proposed the auto tensioner disclosed in Japanese Patent Application No. 1-47786 for the purpose of solving such a problem.

In this auto tensioner, the coil spring 5 has a spring receiving portion that receives a part or all of the inner peripheral portion in the range from the one end 5a locked to the base 1 to the 180-degree phase angle portion.
11 and 11a are provided on the base 1 to prevent contact with the boss portion 2a due to buckling of the coil spring 5 mounted in a torsionally compressed state.

<Problems to be Solved by the Invention> By the way, even the above-mentioned auto tensioner has the following disadvantages.

In other words, since only a part of the first winding portion of the coil spring 5 mounted in the torsionally compressed state is received by the spring receiving portions 11 and 11a, the first winding portion of the coil spring 5 received by the spring receiving portion is in tension. Although the contact with the boss portion 2a of the arm 2 can be prevented, since the final winding portion of the coil spring 5 is not received, the buckling of the coil spring 5 causes the inner circumference of the final winding portion to move. The boss 2a of the tension arm 2 will come into contact.

Moreover, when the spring receiving portion 11 is a partially arcuate wall, the coil spring 5 is mounted in a torsionally compressed state,
The inner peripheral portion of the coil spring 5 may come into contact with only the both end corners of the spring receiving portion 11, and in extreme cases, the both end corners of the spring receiving portion 11 are chipped, and the function as the spring receiving portion 11 cannot be fulfilled. .

The present invention was devised in view of such circumstances, and an object thereof is to stably support a coil spring and to exert a stable tension function by optimizing a torsion torque characteristic of the coil spring. .

<Means for Solving the Problem> In order to achieve the above-mentioned object, the present invention supports a tension arm equipped with a tension pulley on a base so that the tension arm can swing, and a swing fulcrum projecting on the tension arm is provided. While fixing one end of the coil spring mounted on the boss to the base and locking the other end of the coil spring to the tension arm, the tension arm is urged to swing in a certain direction by the torsion restoring force of the coil spring. The autotensioner configured as described above has the following configuration.

According to the autotensioner of the present invention, one end and the other end of the coil spring are respectively locked to the base and the tension arm at substantially the same phase angle position on the circumference, and the coil is fixed to the base from one end to 90 °. The first spring receiving portion that receives the inner peripheral portion of the range up to the phase angle portion of one degree at one point is provided, and the tension arm extends from the other end portion of the coil spring to the phase angle portion of 90 degrees. It is characterized in that a second spring receiving portion for receiving the inner peripheral portion of the above at one point is provided.

<Operation> According to the above configuration, even if the coil spring mounted in the torsionally compressed state tries to buckle, the first winding portion is the first spring receiving portion provided on the base, and the final winding portion is the tension arm. Since the springs are respectively received by the provided second spring receiving portions, buckling is prevented, and the coil spring does not come into contact with the boss portion of the tension arm. Therefore, local wear of the boss is avoided, and the torsional torque characteristic of the coil spring is excellent with extremely small hysteresis.

Further, since the coil spring comes into point contact with the first and second spring receiving portions, it is possible to avoid occurrence of chipping of the end portion such as a wall-shaped one which has a surface contact as in the conventional case.

<Embodiment> An embodiment of the present invention will be described below in detail with reference to the drawings.

1 to 6 show an embodiment of the present invention.
The auto-tensioner T in the illustrated example includes a base 1 fixed to a wall surface of a mechanical device in which a belt is transmitted by bolts, a tension arm 2 swingably supported by the base 1, and a tip end of the tension arm 2. A tension pulley 3 supported freely and a coil spring 5 for applying a swinging biasing force to the tension arm 2 in a certain direction (arrow A direction) so as to press and bias the tension pulley 3 against the belt 4.

A support shaft 6 is provided at the center of the front surface of the base 1,
A boss portion 2a for swinging fulcrum protruding from the tension arm 2 toward the base side is externally fitted to the support shaft 6, and the boss portion 2A is connected to the support shaft 6 by a stopper ring 7 and a circlip 8. It has been stopped. The coil spring 5 is housed in an annular space formed between the cylindrical portion 1a provided on the front surface of the base 1 and the boss portion 2a. And
The coil spring 5 is inserted into the locking hole 9 formed at a predetermined position of the tubular portion 1a.
One end 5a of the coil spring 5a is engaged and supported, and the other end 5b of the coil spring 5a is locked to a locking pin 10 embedded in the tension arm 2.

As shown in FIG. 3, a coil spring 5 is provided at the bottom of the tubular portion 1a.
A partial arcuate first spring receiving portion 11 is provided so as to extend from the one end portion 5a to the 90-degree phase angle portion. A bulged portion 11a that bulges outward in the radial direction is provided on the outer peripheral surface near the one end of the first spring receiving portion 11. That is, in the first spring receiving portion 11, the raised portion 11a can receive the first winding portion of the coil spring 5 at one point.

As shown in FIG. 4, the boss portion 2a of the tension arm 2 has a hump-shaped second spring which bulges outward in the radial direction within the range from the other end 5b of the coil spring 5 to the phase angle portion of 90 degrees. A receiving portion 2c is provided. The second spring receiving portion 2c is adapted to receive the final winding portion of the coil spring 5 at one point at the top thereof.

A friction body 12 which is spring-biased toward the base side is provided at the tip of the boss portion 2a of the tension arm 2, and the tension arm 2 has a proper frictional resistance between the base 1 and the friction body 12. It has become possible to suppress wobbling. Further, a stopper bolt screwed to the base 1 in a notch 13 formed in the boss portion 2a of the tension arm 2.
14 is engaged, and the swing range of the tension arm 2 is restricted.

In the automatic tensioner T having such a structure, the inner peripheral portion of the first winding portion of the coil spring 5 is received by the first spring receiving portion 11 of the base 1, and the inner peripheral portion of the final winding portion of the coil spring 5 is a tension arm. Since it is received by the second spring receiving portion 2c, the buckling of the coil spring 5 itself can be prevented, and eventually the contact of the tension arm 2 with the outer peripheral surface of the boss portion 2a can be avoided.
Therefore, there is no frictional resistance of the coil spring 5 with respect to the rotation of the boss portion 2a, and the torsion torque characteristic of the coil spring 5 has extremely little hysteresis as shown in FIG. Moreover, the coil spring 5 for the first and second spring receiving portions 11 and 2c
Since the contact state of No. 1 is point contact, especially both ends of the first spring receiving portion 11 formed on the partially arcuate wall need not be chipped.

Further, in the case of adjusting the tension of the belt 4 in the auto tensioner of the illustrated example, as shown in FIG. 6, the wrench 19 is attached to the nut 18 that is screwed into the bolt 17 that serves as the rotation center of the tension pulley 3. , The wrench 19 is pushed in the direction of the arrow, but because the pushing direction of this wrench 19 is the direction to tighten the nut 18 against the bolt 17, the nut 18
In addition to the increase in the tightening force, the rotation resistance of the tension pulley 3 increases, and the tension arm 2 formed of aluminum or the like may be crushed by the nut 18. Therefore, in this embodiment, a fixing agent is applied to the thread portion of the bolt 17, and the nut for the bolt 17 is applied.
After properly adjusting the tightening force of 18, tighten the bolt 17 with the nut.
By fixing 18 to each other, it is devised so as to prevent the occurrence of troubles when the belt tension is adjusted.

Incidentally, the first and second spring receiving portions 11, 2c in the above embodiment
May have a pin shape standing upright at a phase angle position that is deviated by 90 degrees from the locking position of the one end 5a or the other end 5b of the coil spring 5, and the shape thereof is not particularly limited.

<Effect of the Invention> As described above, in the present invention, the buckling of the coil spring is prevented by the first spring receiving portion on the base side and the second spring receiving portion on the tension arm side, and the coil spring is tensioned. Since the arm is not brought into contact with the boss, the tension arm can be oscillated and urged in the predetermined direction with the required torsional torque characteristics with extremely little hysteresis, and also local wear of the boss is prevented. Will be able to. Moreover, the first of the coil springs,
Since the contact state with the second spring receiving portion is set to the point contact, it is possible to avoid the occurrence of chipping of the end portion such as the spring receiving portion formed of the partially arcuate wall which is the surface contact as in the conventional example. Become.

As described above, the auto tensioner of the present invention can exert a stable tension function and effectively suppress the belt vibration.

[Brief description of drawings]

1 to 6 relate to an embodiment of the present invention.
The figure is a partially cutaway front view of the auto tensioner, Fig. 2 is a sectional view taken along the line II-II in Fig. 1, Fig. 3 is a sectional view taken along the line III-III in Fig. 2, and Fig. 4 is IV- in Figure 2
IV line cross-section arrow view, FIG. 5 is a diagram showing a torsion torque characteristic,
FIG. 6 is an operation explanatory view when adjusting the tension of the belt. Further, FIG. 7 is a vertical sectional front view of a main part of a conventional structure, and FIG. 8 is a diagram showing a torsion torque characteristic in a conventional auto tensioner. 1 ... Base, 2 ... Tension arm 2a ... Boss part, 2c ... 2nd spring receiving part 3 ... Tension pulley 5 ... Coil spring, 5a ... One end part 5b ... Other end part, 11 ... No. 1 spring receiving part

Claims (1)

[Scope of utility model registration request] 1. A tension arm provided with a tension pulley is swingably supported by a base, and one end of a coil spring, which is externally mounted on a boss for a swing fulcrum protruding from the tension arm, is locked to the base. An auto tensioner configured to fix and to oscillate the tension arm in a certain direction by a torsion restoring force of the coil spring while locking the other end of the coil spring to the tension arm. Part and the other end are respectively locked to the base and the tension arm at substantially the same phase angle position on the circumference, and on the base, the inner circumference in the range from one end of the coil spring to the phase angle part of 90 degrees. A first spring receiving portion for receiving the portion at one point is provided, and the tension arm is provided from the other end portion of the coil spring to a phase angle portion of 90 degrees. Auto tensioner, wherein the second spring receiving portion for receiving the inner peripheral portion of the circumference at one point are provided.