JPH09250613A - Belt tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a belt tensioner compact which has the function making such management that belt tension may be constant according to the rise and drop changes in ambient temperature. SOLUTION: The belt tensioner is equipped with a shaft 1 fixed to a stationary part, an eccentric sleeve 2 provided on the outer periphery of the shaft 1 in the eccentric state so that it can be relatively rotated, a tension pulley 3 rotatably provided on the outer periphery of the eccentric sleeve 2, and tension management means 11, 22, and 6 provided between the shaft 1 and the eccentric pulley 2 and managing the tension of a belt B to be constant by rotating the eccentric sleeve 2 by necessary angles according to the changes of the ambient temperatures. The tension management means are provided between the shaft 1 arranged axially inside and outside of the inner periphery of the tension pulley 3 and the eccentric sleeve 2, so that the outside dimension such as width becomes small compared with the conventional belt tensioner using a fixed bracket with arm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt tensioner that applies a required tension to a rotating belt. Examples of the target belt include a timing belt of an automobile engine.

[0002]

2. Description of the Related Art Conventionally, as a belt tensioner,
For example, a fixed type that allows the operator to adjust the belt tension by correcting the position in consideration of the time-dependent elongation of the belt, or a belt tension that automatically becomes constant according to the time-dependent elongation of the belt. Automatic type to manage (Actual development 52-1
No. 8384), or one in which the belt tension is automatically maintained constant according to changes in the ambient temperature.
No. 36758) has been proposed.

In particular, belt tensioners of the above type are of interest here. This type of belt tensioner, particularly the belt tensioner disclosed in Japanese Utility Model Laid-Open No. 55-36758, has a structure in which a tension pulley is supported on the tip of an arm of a fixed bracket, and the arm of the fixed bracket has two types of materials having different linear expansion coefficients. The position of the tension pulley is displaced by changing the length of the arm according to the change in the ambient temperature.

[0004]

By the way, it is pointed out that the conventional belt tensioner described above uses a fixed bracket with an arm, so that the overall external dimensions such as lateral width are increased.

Therefore, an object of the present invention is to make a belt tensioner compact, which has a function of keeping the belt tension constant according to changes in the ambient temperature.

[0006]

A first belt tensioner of the present invention includes a shaft fixed to a fixed portion, an eccentric sleeve eccentrically provided on an outer periphery of the shaft so as to be relatively rotatable, and an eccentric sleeve. A tension pulley rotatably provided on the outer periphery, and a tension management means provided between the shaft and the eccentric sleeve, for controlling the belt tension constant by rotating the eccentric sleeve by a required angle in accordance with a change in ambient temperature. I have it.

A second belt tensioner of the present invention is provided with a shaft fixed to a fixed portion, an eccentric sleeve eccentrically provided on the outer periphery of the shaft so as to be relatively rotatable, and rotatably provided on the outer periphery of the eccentric sleeve. Tension pulley,
A first tension managing means, which is provided between the shaft and the eccentric sleeve and rotates the eccentric sleeve by a required angle in accordance with a change in the ambient temperature to keep the belt tension constant, and an eccentric sleeve according to the elongation of the belt. It is provided with a second tension managing means for rotating the belt by a required angle so as to keep the belt tension constant.

In the belt tensioner described above,
The tension management means or the first tension management means is a wedge-shaped convex portion fixedly provided on the outer periphery of the shaft and a relative displacement in the circumferential direction with respect to the wedge-shaped convex portion provided on the inner periphery of the eccentric sleeve. A concave cam surface that is engageable with the concave cam surface, and an elastic biasing member that elastically biases the eccentric sleeve to rotate so as to rotate the eccentric sleeve toward the side where the engagement between the concave cam surface and the wedge-shaped convex portion is deepened. The part where the cam surface exists is made of a material having a larger linear expansion coefficient than the wedge-shaped convex part, and the eccentric sleeve is required by reducing or expanding the inner hole of the eccentric sleeve according to the change in ambient temperature. The engagement position of the concave cam surface with respect to the wedge-shaped convex portion is changed by rotating the wedge-shaped convex portion.

Further, the above-mentioned second tension control means is composed of a torsion spring whose both ends are hooked by the fixed portion and the eccentric sleeve to elastically urge the eccentric sleeve to rotate toward the high tension side of the belt.

Further, in the above-mentioned second tension control means, both ends are hooked by the fixed portion and the eccentric sleeve to elastically urge the eccentric sleeve to rotate toward the high tension side of the belt, and a wedge-shaped convex. And a one-way clutch that allows relative rotation of the section relative to the shaft only to the side where the belt tension is high.

In the above invention, the tension managing means for constantly controlling the belt tension according to the change in the ambient temperature is arranged between the shaft arranged radially inside and outside the inner circumference of the tension pulley and the eccentric sleeve. Since it is devised to do so, it becomes possible to reduce the external size such as the width.

As the tension control means, the eccentric sleeve is rotated by the change in the ambient temperature to keep the belt tension constant. That is, when the concave cam surface of the eccentric sleeve expands or contracts in the radial direction according to the change in the ambient temperature, the eccentric sleeve is rotated so as to change the belt tension to the large side or the small side,
The degree of engagement between the concave cam surface and the wedge-shaped convex portion becomes deeper or shallower. In this state, the engagement between the wedge-shaped convex portion and the concave cam surface is elastically urged toward the deepening side by the tension of the belt and the compression spring, so that the eccentric sleeve is prevented from retreating.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the embodiments shown in FIGS.

1 to 3 relate to a first embodiment of the present invention, FIG. 1 is a front view of a belt tensioner, and FIG. 2 is FIG.
(2)-(2) sectional view taken along the line of FIG.
(3) It is an arrow view of a line cross section.

The belt tensioner A in the illustrated example is used in a state of being fixedly attached to a fixed portion C such as an engine block via a bolt D in order to give a required tension to the belt B. In the embodiment, the tension of the belt B is automatically controlled to be constant according to the change of the ambient temperature.

The belt tensioner A is mainly composed of a shaft 1, an eccentric sleeve 2, a pulley-integrated ball bearing 3, and a torsion spring 4.

The shaft 1 is formed in a hollow shape, and a fixing bolt D is inserted into the hollow portion to be fixed to the fixed portion C in a non-rotating state. 18 in the axial center of this shaft 1
Wedge-shaped protrusions 11 and 11 that are outward in the radial direction are integrally provided at two locations facing each other by 0 degree. The wedge-shaped convex portions 11 and 11 gradually protrude outward in the radial direction from one end side in the circumferential direction toward the other end side, and the outer surfaces thereof are formed in a partial arc shape.

The eccentric sleeve 2 is attached to the outer periphery of the shaft 1 via a rolling bearing 5 such as a deep groove type ball bearing so as to be relatively rotatable by a required angle. The eccentric sleeve 2 is formed in a cylindrical shape, and the inner hole 21 is formed eccentrically at a position deviated from the center. In the inner hole 21 of the eccentric sleeve 2, concave cam surfaces 22 and 22 that engage with the wedge-shaped convex portions 11 and 11 are provided at two positions opposite to each other by 180 degrees. This concave cam surface 22,
22 is formed in a shape that matches the wedge-shaped protrusions 11, 11, and the engagement positions with the wedge-shaped protrusions 11, 11 are displaced by a required amount in the circumferential direction.
Is formed longer in the circumferential direction. This concave cam surface 2
2,22 and the play gap between the wedge-shaped protrusions 11 and 11,
The compression springs 6, 6 are inserted to elastically urge the wedge-shaped convex portions 11, 11 toward the side where the concave cam surfaces 22, 22 bite. That is, the eccentric pulley 2 can be relatively rotated 360 degrees with respect to the shaft 1 by the rolling bearing 5.
The presence of the wedge-shaped convex portions 11 and 11 and the concave cam surfaces 22 and 22 enables relative rotation only at a required angle.

The pulley-integrated ball bearing 3 comprises an eccentric sleeve 2
Is fixedly attached in a state of being biased to almost half of the outer circumference of the inner ring 31, which is press-fitted onto the eccentric sleeve 2, and the outer ring 32 also serves as a pulley around which the belt B is wound, and the inner and outer ring 31. , 32, a crown-shaped cage 34 for holding the balls 33, and oil seals 3 provided on both sides in the axial direction between the inner and outer rings 31, 32.
5, 35 and. As the outer ring 32, a wide one having a projecting portion projecting to both sides in the axial direction of the inner ring 31 is used.

The torsion spring 4 is arranged in the space between the fixed portion C and the pulley-integrated ball bearing 3, and has one end fixed to the fixed portion C and the other end to the pin 7 planted in the eccentric sleeve 2. The eccentric sleeve 2 is hooked and elastically biases the eccentric sleeve 2 in the direction of arrow X in FIGS. 1 and 3.

By the way, the wedge-shaped protrusions 11 and 1 described above are used.
The shaft 1 having 1 and the eccentric sleeve 2 having the concave cam surfaces 22 and 22, and the compression springs 6 and 6 correspond to the tension managing means and the first tension managing means described in claims. The shaft 1 and the eccentric pulley 2 are made of materials having different linear expansion coefficients. For example, the linear expansion coefficient of the eccentric pulley 2 is set to be larger than the linear expansion coefficient of the shaft 1. Specifically, the shaft 1 is made of metal (cast iron, carbon steel, aluminum, etc.)
The eccentric pulley 2 is made of synthetic resin (polyacetal resin, polybutylene terephthalate resin, nylon resin, etc.). Therefore, when the temperature rises, the expansion of the inner hole 21 of the eccentric pulley 2 becomes larger than the expansion of the outer diameter of the shaft 1, and there is a relationship that a gap is formed on the fitting surfaces of the both. Further, the torsion spring 4 corresponds to the second tension management means described in the claims.

Next, the operation will be described. First, in use, when the ambient temperature is a low temperature (required temperature range), the initial position of the belt tensioner A is set so as to apply proper tension to the belt B. That is, with the bolt D temporarily fixed, the hexagonal hole 23 provided in the eccentric pulley 2
1 is attached with an L-shaped hexagon wrench as shown by the phantom line in FIG. 1, the belt tensioner A is pressed against the belt B by this hexagon wrench, and the bolt D is tightened at an appropriate position to keep the belt tensioner A stationary. And This position is arbitrarily set according to the tension applied to the belt B.

In the installed state as described above, when the ambient temperature of the belt tensioner A rises, the tension of the belt B increases due to the expansion of the fixed portion C, but the tension of the belt B becomes constant by the following operation. Managed by. That is, as the temperature rises, the inner hole 21 of the eccentric pulley 2 of the belt tensioner A expands and the wedge-shaped convex portions 11 and 11 expand, but the linear expansion coefficient of the eccentric pulley 2 is set to the wedge-shaped convex portion 1.
Since it is set to be larger than the linear expansion coefficient of 1 and 11,
The expansion of the inner hole 21 of the eccentric pulley 2 is larger than the expansion of the shaft 1. That is, since there is a required gap between the concave cam surfaces 22 and 22 and the wedge-shaped convex portions 11 and 11, the force from the belt B and the compression springs 6 and 6.
The eccentric pulley 2 having the concave cam surfaces 22, 22 is rotated by a required angle in the direction of the arrow Y in FIGS. 1 and 3, that is, on the side of weakening the tension of the belt B, and the tension of the belt B changes with temperature. It will be kept constant regardless of.

In the above-mentioned state, when the ambient temperature decreases, the tension of the belt B decreases due to the contraction of the fixed portion C, but the tension of the belt B is controlled to be constant by the following operation. That is, as the temperature decreases, the eccentric pulley 2
Both the wedge-shaped convex portions 11 and 11 contract, but the eccentric pulley 2 contracts more than the wedge-shaped convex portions 11 and 11, so that the concave cam surfaces 22 and 22 of the eccentric pulley 2 contract. While compressing the compression springs 6 and 6, the compression springs 6 and 6 can be rotated by a required angle in the direction of the arrow X in FIGS. 1 and 3, that is, in the direction of increasing the tension of the belt B, so that the tension can be kept constant regardless of temperature changes. Become.

In all the above states, when momentary vibration or impact is applied from the belt B, the concave cam surfaces 22, 22 and the wedge-shaped convex portions 11, 11 bite in one direction, Since the eccentric pulley 2 and the pulley-integrated ball bearing 3 cannot rotate to the side of the belt B having a small tension (the direction of the arrow Y in FIGS. 1 and 3), it is possible to avoid the occurrence of the loosening or fluttering phenomenon of the belt B.

4 and 5 relate to the second embodiment of the present invention. FIG. 4 is a view corresponding to FIG. 2 and FIG. 5 is a view corresponding to FIG.

In the second embodiment, a one-way clutch 8 is added to the structure of the first embodiment to have a function of automatically maintaining the tension of the belt B constant according to the elongation of the belt B over time. I am making it.

Specifically, the wedge-shaped convex portions 11, 11 are separated from the shaft 1 in the first embodiment, and the one-way clutch 8 is interposed between the shaft 1 and the eccentric sleeve 2.

The one-way clutch 8 has an outer ring 81, a plurality of rollers 82, and a retainer 83. In particular, the wedge-shaped convex portions 11 and 11 described above are opposed to each other by 180 degrees on the outer periphery of the outer ring 81. It is integrated in two places.

The one-way clutch 8 is assembled so as to be locked in the direction of arrow Y in FIG. 5 and free in the direction of arrow X. That is, as the operation, when the belt B stretches over time, the torsion spring 4 elastically biases the eccentric sleeve 2 to rotate in the arrow X direction, and in the elastic biasing direction, the one-way clutch is operated. 8
Is in a free state, the elastic urging force of the torsion spring 4 causes the eccentric sleeve 2 to rotate eccentrically in the arrow X direction at an angle corresponding to the extension of the belt B, which causes the pulley-integrated ball bearing 3 to rotate. It will be pressed against B. When the tension of the belt B and the elastic biasing force of the torsion spring 4 are balanced, the rotation of the eccentric pulley 2 is stopped. At this time, since the reaction force from the belt B acts on the one-way clutch 8, the one-way clutch 8 is locked, and the concave cam surfaces 22 and 22 and the wedge-shaped convex portions 11 and 11 move in one direction. The eccentric sleeve 2 is prevented from retracting due to the biting action of.

The present invention is not limited to the above-described embodiments, but various applications and modifications are conceivable.
For example, the rolling bearing and the pulley may be separately provided without using the pulley-integrated ball bearing 3 as in the above-described embodiment.

[0032]

According to the present invention, since the belt tension control means is devised so as to be provided between the eccentric sleeve and the shaft arranged radially inward and outward on the inner circumference of the tension pulley, a conventional arm with an arm is provided. Compared to the one using a fixed bracket, the external dimensions such as the width can be greatly reduced, and the size can be made compact. Therefore, since it can contribute to the reduction of the occupied space at the installation location, the degree of freedom in design such as arrangement is increased and the usability is improved.

[Brief description of drawings]

FIG. 1 is a front view of a belt tensioner according to a first embodiment of the present invention.

FIG. 2 is an arrow view of a cross section taken along line (2)-(2) of FIG.

FIG. 3 is an arrow view of a cross section taken along line (3)-(3) of FIG.

FIG. 4 is a diagram corresponding to FIG. 2 in a second embodiment of the present invention.

FIG. 5 is a diagram corresponding to FIG. 3 in the second embodiment.

[Explanation of symbols]

 A Belt tensioner B Belt C Fixed part D Bolt 1 Shaft 11 Shaft-shaped convex portion of shaft 2 Eccentric sleeve 21 Inner hole of eccentric sleeve 22 Concave cam surface of eccentric sleeve 3 Pulley integrated ball bearing 4 Torsion spring 6 Compression spring

Claims (5)

[Claims] 1. A shaft fixed to a fixed portion, an eccentric sleeve eccentrically provided on the outer periphery of the shaft so as to be rotatable relative to each other, a tension pulley rotatably provided on the outer periphery of the eccentric sleeve, and the shaft and the eccentricity. A belt tensioner, which is provided between the sleeve and a tension management means for rotating the eccentric sleeve by a required angle in accordance with a change in ambient temperature to maintain the belt tension constant. 2. A shaft fixed to a fixed portion, an eccentric sleeve eccentrically provided on the outer periphery of the shaft so as to be relatively rotatable, a tension pulley rotatably provided on the outer periphery of the eccentric sleeve, and the shaft and the eccentricity. First tension management means provided between the sleeve and the eccentric sleeve for rotating the eccentric sleeve by a required angle in accordance with a change in the ambient temperature to keep the belt tension constant, and rotating the eccentric sleeve by a required angle in accordance with the elongation of the belt. A belt tensioner, comprising: a second tension managing means for controlling the belt tension to be constant. 3. The tension managing means or the first tension managing means has a wedge-shaped convex portion fixedly provided on an outer circumference of the shaft and a wedge-shaped convex portion provided on an inner circumference of the eccentric sleeve. A concave cam surface engaged so as to be relatively displaceable in the circumferential direction, and an elastic urging member for elastically urging the eccentric sleeve to rotate so as to deepen the engagement between the concave cam surface and the wedge-shaped convex portion. And the portion where the concave cam surface is present is
It is made of a material with a coefficient of linear expansion larger than that of the wedge-shaped convex portion, and the inner diameter of the eccentric sleeve is reduced or expanded according to changes in the ambient temperature, and the wedge-shaped convex portion is rotated by the required angle. The belt tensioner according to claim 1, wherein an engagement position of the concave cam surface with respect to the portion is changed. 4. The second tension management means is composed of a torsion spring whose both ends are hooked by a fixed portion and an eccentric sleeve and elastically urges the eccentric sleeve to rotate toward the high tension side of the belt. The belt tensioner according to Item 2 or 3. 5. The second tension control means includes a torsion spring having both ends hooked by a fixed portion and an eccentric sleeve to elastically urge the eccentric sleeve to rotate to a higher tension side of the belt, and a wedge-shaped convex portion. The belt tensioner according to claim 2 or 3, wherein the belt tensioner is configured to be relatively rotatable with respect to the shaft only on the side where the belt tension is large.