JPH05272606A - Belt tension adjusting device - Google Patents

Abstract

PURPOSE:To provide a belt tension adjusting device, having large damper capacity in a compact shape without using a hydraulic damper. CONSTITUTION:A parallel spline 10 and a helical spline 11 are formed on the hole part 2 of a pulley arm 1 and a fulcrum shaft 6 respectively, and a nut 12 is fitted between the splines 10 and 11 to be pressed in the shaft direction by a compression spring 13. The movement of the nut 12 in the direction to contract the compression spring 13 causes both the splines 10 and 11 to form wedge angles to lock the nut 12, stopping the rotation of the pulley arm 1.

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 used for adjusting the tension of an engine timing belt or the like.

[0002]

2. Description of the Related Art As a belt tension adjusting device of this type, a fulcrum shaft is fitted in a hole provided at an eccentric position of a pulley shaft, and the fulcrum shaft is disclosed in Japanese Utility Model Laid-Open No. 62-188652. It has been proposed to fill the space between the hole and the hole with oil exhibiting a damper effect.

However, in the above apparatus, the amount of movement of the pulley shaft is determined only by the amount of eccentricity of the fulcrum shaft, so there are cases where the movement of the pulley cannot cope with large changes in belt length. The viscosity of oil has a small damper capacity, and there is a problem that the variable load from the belt cannot be sufficiently absorbed.

On the other hand, in Japanese Utility Model Publication No. 63-29964, a pulley is attached to the tip of an oscillating arm, and the oscillating arm is oscillated by a hydraulic direct acting damper having a large damper capacity. A device has been proposed.

However, in the above-mentioned device, the pulley part and the damper part are separated from each other, so that there is a problem that the device becomes large, and the hydraulic direct-acting damper has a large number of parts and a complicated structure. There is a drawback.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide a belt tension adjusting device capable of exerting a large damper capacity with a simple structure and a compact shape. ..

[0007]

In order to solve the above-mentioned problems, the present invention fits a fulcrum shaft standing on a fixing member into a hole provided in a pulley arm, and the fulcrum shaft and the hole face each other. Splines that are relatively inclined in the axial direction are formed on the surface, and a nut that engages with each of the splines and a pressing unit that presses the nut in the axial direction are provided between the fulcrum shaft and the hole. , The inclination angle formed by both splines,
It is set to be smaller than the friction angle between each spline and the nut.

[0008]

In the above structure, when the pulley arm is rotated by the load from the belt, the nut is moved in the axial direction by the guide of both splines. When the moving direction of the nut is in a direction in which the pressing force of the pressing means is strengthened, both of the inclined splines form a wedge angle with respect to the nut, and a large frictional resistance is generated on the contact surface between the spline and the nut. Therefore, the nut is locked and the rotation of the pulley arm is stopped.

On the contrary, when the nut moves in the direction of weakening the pressing force, both splines do not form a wedge angle, so that the nut moves smoothly and the pulley arm rotates. By setting the direction in which the pulley arm rotates to a direction in which the tension of the belt increases, the tension of the belt can be kept constant.

When the angle formed by both splines is larger than the friction angle between each spline and the nut, the nut is not locked by the spline and moves instantly.
The above-mentioned one-way damper characteristic of the pulley arm cannot be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIGS. 1 to 3, the pulley arm 1 has a boss 3 having a hole 2 on the inner side formed at one end and a tension pulley 4 pressed against the belt A at the other end. It is rotatably attached by 5.

A fulcrum shaft 6 standing on a fixing member such as an engine block is fitted in the hole 2. The fulcrum shaft 6 is composed of a collar 7 having a flange 7a at its lower end and a tightening bolt 8 inserted through the inside of the collar 7. A detent pin 9 serving as a positioning reference for the device is attached to the lower surface of the collar 7. Has been.

On the inner peripheral surface of the hole 2 of the pulley arm 1, there are formed three parallel splines 10 parallel to the axis, and on the outer peripheral surface of the collar 7 of the fulcrum shaft 6 which faces the parallel splines 10, an axial line is formed. On the other hand, three helical splines 11 that are twisted at a constant angle are formed. Further, between the pulley arm 1 and the fulcrum shaft 6, a nut 12 whose outer peripheral surface and inner peripheral surface engage with the parallel spline 10 and the helical spline 11, respectively, is attached.
A compression spring 13 that presses the nut 12 upward in the axial direction is incorporated on the lower side of the shaft 2.

In the above structure, when the pulley arm 1 is rotated right and left, the nut 22 is axially moved by the guide of the parallel spline 10 and the helical spline 11, and the compression spring 13 is expanded and contracted. In this case, the moving direction of the nut 12 is determined by the inclination (twisting direction) of the helical spline 11.

The inclination of the helical spline 11 is such that when the pulley arm 1 receives the tension from the belt A and rotates counterclockwise in the figure, the nut 12 is pushed into the bottom of the hole 2.
The compression spring 13 is set so as to be contracted. In addition, the helix angle α of the helical spline 11 with respect to the parallel spline 11 is such that both the splines 10 and 11 and the nut 1
It is set to be smaller than the friction angle on the sliding surface of No. 2.

A ring 14 whose inner peripheral surface conforms to the shape of the helical spline 11 is press-fitted into the upper end portion of the fulcrum shaft 6, and between the outer peripheral surface of the ring 14 and the inner peripheral surface of the hole portion 2, A plain bearing 15 is provided which receives a radial load. A sliding bearing 16 with a collar is provided between the lower end of the fulcrum shaft 6 and the inner peripheral surface of the hole 2.
It is designed to receive radial load and thrust load.

The plain bearings 15 and 16 and the nut 12 described above.
It is desirable to use a material that is free from fretting corrosion in a non-lubricated state. For example, it is formed by injection molding a self-lubricating synthetic resin such as polyimide or polyether ether ketone (PEEK). On the other hand, the pulley arm 1 and the collar 7 of the fulcrum shaft 6 are made of aluminum alloy.

In the belt tension adjusting device of the embodiment having the above-mentioned structure, the tension pulley 4 is fixed to the engine block or the like by the tightening bolts 8 which pass through the fulcrum shaft 6, and the tension pulley 4 is pressed against the belt A to be mounted.

As described above, when the pulley is pressed against the belt, the nut 12 stops moving when the spring force of the deforming compression spring 13 that tries to restore and the reaction force from the belt A are balanced, so that the nut 12 does not move to a certain extent. Tension is applied.

When the tension of the belt increases from the above-mentioned balanced state and the pulley arm 1 rotates counterclockwise, the nut 1
2 is pushed, but in this case, the helical spline 11 and the parallel spline 10 form a wedge angle with respect to the nut 12, and the frictional resistance of the sliding surface between the nut 12 and both splines 10 and 11 is significantly increased. Therefore, the movement of the nut 12 is locked, and the rotation of the pulley arm 1 is stopped.

On the contrary, when the tension of the belt decreases from the above-mentioned balanced state and the pulley arm 1 rotates clockwise, the nut 12 projects, but in this case, the spring force of the compression spring 13 assists the movement of the nut 12. , Hercules Spline 11
Since the parallel spline 10 does not form a wedge angle with the nut 12, the nut 12 moves smoothly. Therefore, the pulley arm 1 quickly rotates toward the slackened belt to keep the belt tension constant.

As described above, the belt tension adjusting device of the embodiment operates only in the projecting direction of the nut 12 with respect to the load applied instantaneously, and the movement is locked in the pushing direction.
Functions as a one-way damper.

On the other hand, when a high-frequency fluctuating load is applied from the belt with the nut 12 locked, the nut 12
When the contact surfaces of the splines 10 and 11 are gradually loosened, the nut 12 is gradually moved and pushed. Therefore, for changes in tension such as changes in temperature slowly,
Since the pulley arm 1 is gradually rotated, the belt tension can be kept constant while exhibiting a large rigidity with respect to the load from the belt. The helical spline 11 for controlling the movement of the nut 12 as described above
The twist angle α of is preferably set in such a range that the slack of the spline and the nut can occur in response to a high-frequency load change in a range smaller than the friction angle between the nut 12 and the splines 10 and 11, It is desirable to set the angle range of 5 to 15 degrees.

FIG. 4 shows another embodiment of the pulley arm 1.
Between the pulley 4 and the boss 3 of the tension coil spring 17
Is attached to give a spring force to the belt A to the pulley arm 1. Further, in the example of FIG. 5, one end of the grip coil spring 18 is connected to the pulley arm 1 and the other end is connected to the collar 7 of the fulcrum shaft 6, respectively, to give the pulley arm 1 a twisting force in a rotating direction. In this way, in addition to the compression spring 13,
By attaching the tension coil spring 17 and the torsion coil spring 18, the tension applied to the belt can be increased.

Although the helical spline 11 is formed on the fulcrum shaft 6 in the above embodiment, the helical spline 11 may be formed on the pulley arm 1 and the parallel spline 10 may be formed on the fulcrum shaft 6. In addition, a helical spline is formed on both the pulley arm 1 and the fulcrum shaft 6,
The twist angle of each spline may be different.

Although the compression spring 13 is shown as the pressing means for the nut 12, a disc spring, a rubber material or the like may be used instead.

[0027]

As described above, according to the present invention, the wedge effect is generated by the two inclined splines, and the movement of the nut is mechanically locked to stop the rotation of the pulley arm. It is possible to obtain a one-way damper characteristic having the above, and it is possible to reliably absorb the fluctuating load of the belt.

Further, since the fulcrum shaft and the nut are simply incorporated into the inside of the pulley arm, there is an effect that the structure can be greatly simplified and the shape can be made compact as compared with the hydraulic linear motion damper.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing a belt tension adjusting device of an embodiment.

FIG. 2 is a sectional view showing a spline of the same.

FIG. 3 is a partial cross-sectional plan view taken along the line III-III in FIG.

FIG. 4 is a plan view showing another embodiment.

FIG. 5 is a vertical sectional front view showing another embodiment.

[Explanation of symbols]

 1 Pulley Arm 2 Hole 4 Tension Pulley 6 Support Shaft 7 Collar 10 Parallel Spline 11 Helical Spline 12 Nut 13 Compression Spring

Claims (1)

[Claims] 1. A fulcrum shaft erected on a fixing member is fitted into a hole provided in a pulley arm, and a spline inclined relative to the axial direction is formed on a surface facing the fulcrum shaft and the hole. , Between the fulcrum shaft and the hole, a nut that engages with each spline and a pressing means that presses the nut in the axial direction are provided, and the inclination angle formed by the both splines is set between each spline and the nut. Belt tension adjustment device that is set smaller than the friction angle.