JP2567594Y2 - Belt tension adjustment device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt tension adjusting device.

[0002]

2. Description of the Related Art A belt tension adjusting device used for an accessory drive belt of an automobile engine has a built-in damper mechanism in the pulley arm to prevent the pulley arm from resonating due to a minute vibration applied from the belt. The structure to control is taken.

FIG. 6 shows a conventional belt tension adjusting device proposed by Japanese Utility Model Laid-Open No. 63-28949. In this device, a hole 34 provided in a pulley arm 33 is rotatably fitted to a fulcrum shaft 32 erected on a fixed member 31,
A damper 35 is incorporated between the fulcrum shaft 32 and the hole 34. The bolt 35 is attached to the fulcrum shaft 32 via a guide means 36 comprising a key groove and a key so as to be movable in the axial direction.
8 between the bolt 37 and the upper wall of the pulley arm 33 to press the bolt 37 downward.
9 is incorporated.

[0004] One end of a tension adjusting spring 40 disposed outside the pulley arm 33 is connected to the pulley arm 33 and the other end is connected to the fixing member 31.

In the above structure, a constant belt tension is applied to the pulley 41 attached to the pulley arm 33 by the spring force of the tension adjusting spring 40, and the frictional force generated on the screw surface of the damper bolt 37 by the spring force of the compression coil spring 39. Thus, a damper effect for buffering the rotation of the pulley arm 33 is provided.

[0006]

In the above-described belt tension adjusting device, in order to provide the damper 35 with a one-way damper characteristic with good responsiveness, the bolt 37 and the thread 38 of the hole 34 have a large helix angle. It is necessary to use a screw, but if such a screw is provided around the entire circumference of the bolt 37, the total length of the bolt 37 and the screw thread 38 becomes longer,
There is a problem that the device becomes large. However, if the screw is not provided on the entire circumference of the bolt 37 or the hole 34, the frictional force generated in the bolt is biased, and stable damper characteristics cannot be obtained.

On the other hand, if the screws of the bolt 37 and the thread 38 are multi-threaded, it is possible to form a screw around the entire circumference of the bolt with a short thread length. However,
Such a multi-threaded screw is difficult to form at the same time when the pulley arm 33 formed of an aluminum alloy or the like is die-cast because a plurality of screws overlap in the axial direction. Threads must be formed by processing. However, since this screw processing needs to be performed at a deep position inside the hole 34, the processing is troublesome and there is a problem that the working efficiency is deteriorated.

Therefore, the present invention aims to provide a structure which can obtain a stable damper characteristic with a short screw thread length and can simultaneously form a screw thread at the time of die-casting a pulley arm.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention forms a thread of a hole of a pulley arm with a multi-threaded screw, and does not superimpose each of the multi-threaded screws in the axial direction. They are arranged as follows.

[0010]

In the above structure, since the threads of the multi-start thread do not overlap in the axial direction, the thread can be formed simultaneously with the die casting by dividing the pulley arm molding die in the axial direction. .

The forming angle range θ of each screw of the above-mentioned multi-start thread
Is given by an equation of θ ≦ 360 ° / n, where n is the number of screws.

[0012]

1 to 3 show a belt tension adjusting device according to an embodiment. The pulley arm 1 has a tension pulley 3 rotatably mounted at one end via a bearing 2, and a guide wall 5 having a hole 4 on the inside at the other end serving as a rotation fulcrum. I have.

The fixing member 6 fixed to the engine block or the like comprises a base 7 and a hollow fulcrum shaft 8 erected at the center thereof, and a fastening bolt 9 is provided inside the fulcrum shaft 8.
Is inserted. As shown in FIG. 1, the fixing member 6 has a guide wall 5 of the pulley arm 1 fitted around the fulcrum shaft 8, and a fastening bolt 9 inserted through the fulcrum shaft 8 is screwed into an engine block or the like. The pin 10 on the seating surface of the fixing member 6 positions the fixing member 6 between the pin 10 and the fastening bolt 9.

The pulley arm 1 and the fixing member 6 are each die-cast from an aluminum alloy.

The base of the fulcrum shaft 8 is a spline 11 composed of a number of axial grooves.
A damper bolt 12 is fitted into the boss. The inner diameter surface of the damper bolt 12 is formed in a groove shape corresponding to the spline 11, and the guide of the spline 11 causes the damper bolt 12 to move in the axial direction of the fulcrum shaft 8, but the rotation is stopped.

On the other hand, on the inner peripheral surface of the hole 4 of the pulley arm 1, a thread 13 composed of two threads 14, 15 is formed, and each of the threads 14, 15 of the thread 13 has an outer periphery of the damper bolt 12. Screws 16 and 17 formed on the surface are screwed together. As shown in FIGS. 4A and 4B, the screws 14 and 15 are formed at an angle range of 180 ° or less on opposing inner peripheral surfaces of the hole 4 so that they do not overlap in the axial direction. It has become. Further, each of the screws 14 and 15 and the bolt 1
The helix angles of the second screws 16, 17 are formed so as to be in the range of 10 to 15 degrees.

The thread 13 of the pulley arm 1 divides the die for die-casting the pulley arm 1 in the axial direction of the hole 4 because the screws 14 and 15 do not overlap in the axial direction.
By releasing the mold in the axial direction, the screws 14 and 15 can be formed simultaneously with the die casting of the pulley arm.

A collar member 18 is press-fitted into the upper end of the fulcrum shaft 8, and a coil spring 19 is incorporated between the collar member 18 and the damper bolt 12. This coil spring 1
Numeral 9 is assembled in a compressed state, and applies a pressing force in the axial direction (downward direction in FIG. 1) to the damper bolt 12 by the spring force.

Further, both ends of the fulcrum shaft 8, ie, between the collar member 18 and the peripheral surface of the hole 4, and the base 8a of the fulcrum shaft 8
Bearing members 20 and 21 constituting a radial bearing are incorporated between the bearing and the peripheral surface of the hole 4. On the other hand, between the lower end of the guide wall 5 of the pulley arm 1 and the upper surface of the base 7, a bearing member 22 constituting a thrust bearing is incorporated.
For each of the bearing members 20, 21, and 22, a sliding bearing material having a small surface friction such as a synthetic resin is used.

A tension adjusting spring 23 composed of a coil spring is disposed outside the guide wall 5. One end of the tension adjusting spring 23 is connected to the pulley arm 1 and the other end is connected to the base 7 of the fixing member 6. Have been combined.

In the belt tension adjusting device of the embodiment having the above structure, the fixing member 6 is fixed to an engine block or the like, and the tension pulley 3 is pressed against the belt to pull the pulley arm 1.
Is rotated by a predetermined angle, the tension adjusting spring 23 is compressed and twisted, and a constant tension is applied to the belt by the spring force of the tension adjusting spring 23 that attempts to restore.

When the tension of the belt increases from the above balance state and the pulley arm 1 rotates, the damper bolt 12
Moves upward, and the coil spring 19 is compressed and contracted. For this reason, the pressing force of the coil spring 19 increases and a large frictional resistance is generated between the damper bolt 12 and the threaded surface of the hole 4, and a large resistance force acts on the rotation of the pulley arm 1.

Conversely, when the belt tension decreases from the above balance state and the pulley arm 1 rotates in the opposite direction to the above, the damper bolt 12 moves downward and the coil spring 19
Is stretched. For this reason, the pressing force applied to the damper bolt 12 from the coil spring 19 acts in a direction that assists the rotation of the pulley arm 1, and the pulley arm 1 can rotate with a small resistance.

In the above structure, the thread 1 of the hole 4
Since 3 is formed with two threads, the entire circumference of the screw of the tapping bolt 12 can be screwed with a shorter thread length as compared with the case where the thread is a single thread. ,
The height of the device can be made compact.

FIGS. 5A and 5B show another embodiment.
The thread 13 of the pulley arm 1 is replaced with three threads 24, 25,
26. In this case, each screw 24, 2
The holes 4 and 5 are provided with holes 4 so that they do not axially overlap each other.
Are formed symmetrically on the inner peripheral surface within a range of 120 degrees or less.

On the other hand, when the thread of the pulley arm has four or more threads, the forming angle range of each screw can be set by using the equation shown in the section of [Action] described above. .

[0027]

[Effect] As described above, in the present invention, since the thread of the pulley arm is a multi-start thread, uniform engagement of the damper bolt can be obtained with a short thread length, and the device can be made compact. Can be. In addition, since the threads of the multi-start thread are not overlapped in the axial direction, the thread can be formed at the same time when the pulley arm is die-cast, and the production efficiency can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a partially longitudinal front view showing an embodiment.

FIG. 2 is a sectional view showing a mounting portion of the above damper bolt.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

4A is a cross-sectional view showing a thread of a hole, and FIG. 4B is a plan view taken along line III-III in FIG.

FIG. 5 (a) is a sectional view showing another embodiment of the thread;
(B) is a plan view taken along line VI-VI of (a).

FIG. 6 is a sectional view showing a conventional example.

[Explanation of symbols]

 Reference Signs List 1 pulley arm 4 hole 6 fixing member 8 fulcrum shaft 11 spline 12 damper bolt 13 screw thread 14, 15 screw 23 tension adjusting spring

Claims (1)

(57) [Scope of request for utility model registration] 1. A fulcrum shaft erected on a fixing member is fitted into a hole provided in a pulley arm, and a bolt is attached to the fulcrum shaft via guide means allowing movement only in the axial direction. Is screwed into a screw thread provided in the hole, and an elastic member that applies an axial spring force to the bolt is incorporated into the hole, and tension is applied to the pulley arm to apply belt tension to the pulley attached thereto. In a belt tension adjusting device to which a spring is connected, a thread of a hole of the pulley arm is formed by a multi-thread screw, and each screw of the multi-thread screw is arranged so as not to overlap in the axial direction. Tension adjustment device.