JPH09229149A - Tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a belt tensioner light and small while the function to give a proper tension to a belt is well maintained. SOLUTION: A twist coil spring 7a to give a resilience to a supporting cylinder 3 and press a pulley 5 supported by the cylinder 3 to a belt is composed of a swing side locking part 10a and a stationary side locking part 11a. The two locking parts 10a, 11a are positioned approx. identically in the circumferential direction and installed in such an arrangement that the swing center of the cylinder 3 is in eccentricity from the axes of the pulley 5 and cylinder 3. This configuration lowers the supporting rigidity over the radial direction of the coil part 9 of the twist coil spring 7a, and displacement of the supporting cylinder 3 will never be hindered even though the internal circumferential edge of the coil part 9 is buffered with respect to the outside surface of the cylinder 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The tensioner according to the present invention is used, for example, in a state in which it is mounted on the front surface of a cylinder block constituting the engine in order to apply proper tension to the timing belt of the engine.

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG.
5 or a tensioner as shown in FIGS. 6 to 7 is used. In each of these tensioners, a support cylinder 3 is supported and fixed to this front surface by a bolt 2 screwed to the front surface of a cylinder block 1 which is a fixed portion. That is, the support cylinder 3 is formed with a through hole 4 in a portion eccentric to the central axis of the support cylinder 3, and the bolt 2 is formed in the through hole 4.
Is inserted. The pulley 5 is rotatably supported by the bearing 6 such as a deep groove type ball bearing on the outer peripheral surface of the distal end portion of the support cylinder 3. Further, a torsion coil spring 7 is provided between the cylinder block 1 and the support cylinder 3 to support the support cylinder 3
In addition, the elastic force is applied in the direction of pressing the pulley 5 against the belt 8.

The torsion coil spring 7 has a coil portion 9 and
A swing side locking portion 10 provided at one end (left end in FIGS. 5 and 7) of the coil portion 9 and locked to a part of the support cylinder 3,
A fixed side locking portion 11 provided at the other end of the coil portion 9 (right end in FIGS. 5 and 7) and locked to the cylinder block 1.
And The first structure of the conventional structure shown in FIGS.
In the case of the example, the coil portion 9 is loosely fitted inside the support cylinder 3, and in the case of the second example of the conventional structure shown in FIGS. 6 to 7, the coil portion 9 is loosely fitted outside the support cylinder 3. doing.

When a predetermined tension is applied to the belt 8 by the tensioner as described above, first, as shown in FIGS. 5 and 7, the support cylinder 3 is supported on the front surface of the cylinder block 11 by the bolt 2. Then, with the bolt 2 loosened, the support cylinder 3 is swung about the bolt 2 by the elastic force of the torsion coil spring 7, and the pulley 5 is pressed against the belt 8. In this state, the above-mentioned torsion coil spring 7 is attached to the belt 8.
Tension is applied according to the elasticity of. Therefore, the bolt 2 is tightened to fix the support cylinder 3 to the cylinder block 1. In this state, appropriate tension corresponding to the elastic force of the torsion coil spring 7 remains applied to the belt 8.

[0005]

In the conventional structure shown in FIGS. 4 to 7, it is possible to secure the stroke of the pulley 5 (the amount of displacement of the pulley 5 when applying a proper tension to the belt 8) and to reduce the size and weight. It is difficult to achieve both. The reason for this is as follows. (1) In the case of the structure of the first example shown in FIGS. 4 to 5, in order to secure the above stroke, it is necessary to increase the eccentricity δ of the bolt 2 with respect to the central axis of the support cylinder 3. On the other hand, when this eccentricity amount δ is increased, the minimum dimension d of the gap 12 between the outer peripheral surface of the bolt 2 and the inner peripheral surface of the support cylinder 3 becomes smaller. This minimum dimension d cannot be made smaller than the wire diameter of the spring material forming the torsion coil spring 7 because the coil portion 9 of the torsion coil spring 7 needs to be provided.
For this reason, it is difficult to achieve both the above-mentioned stroke ensuring and the reduction in size and weight. (2) In the case of the structure of the second example shown in FIGS. 6 to 7, the support cylinder 3 swings in the direction of the arrow α in FIG. 6 when the belt 8 is applied with an appropriate tension. On the other hand, in the case of the conventional structure, the rocking side locking portion 10 and the fixed side locking portion 11 are
The coil portion 9 is provided at a position displaced in the circumferential direction.
High support rigidity in the radial direction. Therefore, in order to allow the support cylinder 3 to be smoothly displaced in the direction of the arrow α, the coil portion 9 is arranged so that the outer peripheral surface of the support cylinder 3 does not interfere with the inner peripheral edge of the coil portion 9. The inner diameter of the must be large enough. If they interfere with each other, the force pressing the pulley 5 against the belt 8 becomes small, and it becomes impossible to apply a desired tension to the belt 8. For this reason, it is difficult to achieve both the above-mentioned stroke ensuring and the reduction in size and weight. In view of such circumstances, the present invention has been invented in order to achieve both of the above-mentioned securing of stroke and reduction in size and weight.

[0006]

The tensioner of the present invention comprises:
Similar to the conventional tensioner described above, a fixed shaft, a support cylinder that supports a portion eccentric to the center axis by the fixed shaft, and a pulley that is rotatably supported by bearings on the outer peripheral surface of the support cylinder. And a torsion coil spring provided between the support cylinder and the fixed portion in order to press the pulley against the belt to which tension is applied. The torsion coil spring includes a coil portion loosely fitted to the support cylinder, a swing side locking portion provided at one end of the coil portion and locked to a part of the support cylinder, and A fixed side locking portion which is provided at the other end of the coil portion and is locked to the fixed portion is provided. Particularly, in the tensioner of the present invention, the rocking side locking portion and the fixed side locking portion are provided at substantially the same position in the circumferential direction of the coil portion and with respect to the central axis of the support cylinder. The fixed shaft is provided at a position substantially coincident with the eccentric direction.

[0007]

The tensioner of the present invention constructed as described above,
The action itself when the support cylinder is swung around the fixed shaft by the elastic force of the torsion coil spring, and the pulley rotatably supported on the outer peripheral surface of the support cylinder is pressed against the belt to give a predetermined elasticity to the belt. Is similar to the conventional tensioner described above. In particular, in the case of the tensioner of the present invention, the rocking side locking portion and the fixed side locking portion are fixed at substantially the same position in the circumferential direction of the coil portion and to the center axis of the support cylinder. Since the shaft is provided at a position substantially coincident with the eccentric direction, the supporting rigidity of the coil portion in the radial direction is low. Therefore, even if the inner peripheral edge of the coil part interferes with the outer peripheral surface of the support cylinder, the coil part is lightly displaced along with the support cylinder in the radial direction. As a result, it is possible to secure the stroke of the pulley and apply the appropriate tension to the belt without making the inner diameter of the coil portion particularly large, and it is possible to reduce the size and weight of the tensioner. Further, the displacement amount of the rocking side locking portion can be small regardless of the rocking displacement of the support cylinder due to the application of the proper tension to the belt. Therefore, the tension fluctuation of the torsion coil spring based on this swing displacement is small, and the fluctuation of the tension applied to the belt is small.

[0008]

1 to 3 show an example of an embodiment of the present invention. The feature of the present invention is that the positions of the rocking side locking portion 10a and the fixed side locking portion 11a provided at both ends of the coil portion 9 constituting the torsion coil spring 7a are set for the purpose of reducing the size and weight of the tensioner. There is a point to devise. Since the structure and operation of the other parts are the same as those of the second example of the conventional structure shown in FIGS. 6 to 7 described above, a part of the illustration and description will be omitted or simplified, and the characteristic part of the present invention will be described below. I will explain mainly.

The rocking side locking portions 10a and the fixed side locking portions 11a provided at both ends of the coil portion 9 constituting the torsion coil spring 7a are provided at substantially the same position in the circumferential direction of the coil portion 9. ing. Also, with the torsion coil spring 7a assembled between the front surface of the cylinder block 1 of the engine and the support cylinder 3 constituting the tensioner, the both locking portions 10a and 11a are connected to the support cylinder 3 and the pulley 5 respectively. The bolt 2 (see FIGS. 5 and 7; not shown in FIGS. 1 to 3), which is the fixed shaft, is substantially eccentric with respect to the central axis O of FIG. It is provided.

That is, as shown in FIG. 2 (A), one end of the wire forming the torsion coil spring 7a is bent inward in the diametrical direction to form the rocking side locking portion 10a.
Similarly, the other end of the wire is bent at the same position in the circumferential direction as the rocking side locking portion 10a in the semicircular shape outward in the diametrical direction of the coil portion 9 to form the fixed side locking portion 11a. . Then, the rocking side locking portion 10a is attached to the support cylinder 3
The fixing side locking portion 11a is locked to the locking pin 13 fixed to the front surface of the cylinder block 1 while being inserted from the outside in the diametrical direction into the locking hole formed in a part of the cylinder block 1. There is. 2A shows the coil portion 9 elastically deformed in order to assemble the torsion coil spring 7a to the tensioner. Therefore, as described above, the rocking side locking portion 10a is supported on the support cylinder 3, the fixed side locking portion 11a is locked on the locking pin 13, and is supported by the support cylinder 3 in the locked state. Elasticity is applied in the direction of pressing the pulley 5 thus pressed against the belt 8.

In the case of the tensioner of the present invention constructed as described above, the swing side locking portion 10a and the fixed side locking portion 11 are provided.
a at substantially the same position in the circumferential direction of the coil portion 9, and
Since the bolt 2 is provided at a position that substantially coincides with the center axis of the support cylinder 3 in the eccentric direction, the support rigidity of the coil portion 9 in the radial direction is low. Therefore,
Even if the inner peripheral edge of the coil portion 9 and the outer peripheral surface of the support cylinder 3 interfere with each other, the coil portion 9 is lightly displaced along with the support cylinder 3 in the radial direction. As a result, the stroke of the pulley 5 can be secured and proper tension can be applied to the belt 8 (see FIGS. 4 and 6; not shown in FIGS. 1 to 3) without increasing the inner diameter of the coil portion 9. As a result, the tensioner can be made smaller and lighter.

On the other hand, as shown in FIG. 2B, when the rocking side locking portion 10a and the fixed side locking portion 11a are provided at positions opposite to each other in the circumferential direction of the coil portion 9, Increases the support rigidity of the coil portion 9 in the radial direction. Therefore, unless the inner diameter of the coil portion 9 is increased to prevent interference between the inner peripheral edge of the coil portion 9 and the outer peripheral surface of the support tube 3, proper tension cannot be applied to the belt 8.

Further, in the case of the tensioner of the present invention, even when the support cylinder 3 swings around the bolt 2 which is the fixed shaft as the tension of the belt 8 fluctuates, the swing side engagement is also performed. The amount of displacement of the stopper 10a is small. That is, considering the case where the pulley 5 (and the support cylinder 3 supporting the pulley 5) is displaced from the neutral position shown by the solid line a in FIG. 3 to the positions shown by the chain lines b and c in FIG. In the case of the tensioner No. 2, the swinging side locking portion 10a moves from the point a'to the points b'and c'in the figure. As is clear from the distances between these points a ', b', and c ', the displacement of the rocking side locking portion 10a due to the displacement of the pulley 5 is slight. In this way, the displacement of the rocking side locking portion 10a is small, which means that the elastic change of the torsion coil spring 7a accompanying the displacement of the pulley 5 is small.
It also leads to easier installation of the tensioner. On the other hand, as shown in FIG. 2B, when the swing-side locking portion 10a and the fixed-side locking portion 11a are provided at positions opposite to each other in the circumferential direction of the coil portion 9, With the displacement of the pulley 5, the swinging side locking portion 10a moves from point A to point B and point C in FIG. As is clear from the distances between the points a, b, and c, the rocking side locking portion 10a associated with the displacement of the pulley 5 is apparent.
Becomes large, and the action and effect obtained by the present invention as described above cannot be obtained.

The illustrated example is a case where the present invention is applied to a tensioner having a structure in which the support cylinder 3 is fixed to a fixed portion such as the cylinder block 1 while the pulley 5 is pressed against the belt 8. Shows. However, the present invention is not limited to the tensioner having such a fixed structure, but can be applied to a tensioner having a structure in which the pulley 5 follows the fluctuation of the tension of the belt 8 (so-called automatic tensioner). In this case,
A swing member corresponding to the support cylinder 3 is swingably supported about the fixed shaft around a fixed shaft fixed to the front surface of the cylinder block 1 by the bolt 2. Then, the torsion coil spring applies an elastic force to the swing member in a direction of pressing the pulley 5 against the belt 8. With this configuration, the same action and effect as when the present invention is applied to the tensioner having the fixed structure can be obtained.

[0015]

Since the tensioner of the present invention is constructed and operates as described above, it is possible to reduce the size and weight while ensuring the function of applying proper tension to the belt.

[Brief description of drawings]

FIG. 1 is a front view showing an example of an embodiment of the present invention with a fixed shaft omitted.

FIG. 2 is a front view of a torsion coil spring, in which (A) shows a shape belonging to the present invention and (B) shows a shape deviating from the present invention.

FIG. 3 is a schematic front view for explaining the operation of the present invention.

FIG. 4 is a front view similar to FIG. 1, showing a first example of a conventional structure.

FIG. 5 is a sectional view taken along line AA of FIG. 4;

FIG. 6 is a front view similar to FIG. 1, showing a second example of the conventional structure.

FIG. 7 is a sectional view taken along line BB of FIG. 6;

[Explanation of symbols]

 1 Cylinder Block 2 Bolt 3 Support Cylinder 4 Through Hole 5 Pulley 6 Bearing 7, 7a Torsion Coil Spring 8 Belt 9 Coil Part 10, 10a Swing Side Locking Part 11, 11a Fixed Side Locking Part 12 Gap 13 Locking Pin

Claims (1)

[Claims] 1. A fixed shaft, a support cylinder supported by the fixed shaft at a portion eccentric to the central axis, a pulley rotatably supported by a bearing on an outer peripheral surface of the support cylinder, and a pulley. Is provided on the belt to be tensioned, a torsion coil spring provided between the support cylinder and a fixed portion is provided, and the torsion coil spring is a coil portion loosely fitted on the support cylinder. A rocking side locking portion provided at one end of the coil portion and locked to a part of the support cylinder, and a fixed portion provided at the other end of the coil portion and locked to the fixed portion. In a tensioner having a side locking part, the swinging side locking part and the fixed side locking part are provided at substantially the same position in the circumferential direction of the coil part and at the same time of the support cylinder. Provided at a position that is approximately coincident with the direction in which the fixed shaft is eccentric with respect to the central axis Tensioner featuring things.