JPH06193694A - Chain tensioner - Google Patents

Abstract

PURPOSE:To provide a chain tensioner which is able to control a chain vibration by means of a mechanical damper mechanism and carry out the adjustment for the increase or decrease of tension. CONSTITUTION:A cylindrical case 6 coming into contact with a chain guide 1 is fitted in a fixed shaft 5, and a wedgy interspace 12 is formed in an interval between a cam surface 11 installed in the fixed shaft 5 and an inner surface of the case 6. The same form friction member 13 and a spring member 14 are built in each wedgy interspace 12, and a tension imparting spring 18, pressing the chain guide to the side where a chain is stretched, is connected to the chain guide 1. When chain tension grows larger, the friction member 13 is thrust in a narrow part of the wedgy interspace 12, checking any rocking motion in the chain guide 1 by dint of frictional force. When the chain tension goes down, the friction member 13 is extruded to a widening part, of the interspace 12, whereby the chain guide 1 is rapidly rocked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chain tensioner for adjusting the tension of a valve train timing chain of an engine to be constant.

[0002]

2. Description of the Related Art As a chain tensioner of this type, there has been known a hydraulic tensioner in which engine oil is introduced into a cylinder and a hydraulic pressure of the engine oil actuates a plunger in the cylinder.

However, in the above hydraulic tensioner, if foreign matter such as dust or metal powder enters the cylinder together with the engine oil, malfunction of the check valve or the plunger may occur. Further, when air is mixed into the engine oil due to rotation of the crankshaft and the mixed oil is introduced into the cylinder, there is a problem that the damping characteristic of the tensioner is deteriorated.

On the other hand, a tensioner that adjusts the tension of the chain by a mechanical structure is disclosed in Japanese Utility Model Laid-Open No. 62-132.
No. 57 is proposed.

In this tensioner, as shown in FIG. 5, a tension rod 32 inserted in a case 31 is biased in a pop-out direction by a coil spring 33, and a support shaft 35 of a ratchet pawl 34 meshing with the tension rod 32 is attached to the case. The ratchet pawl 34 is fitted in the long hole 36 of the armature 31 so that the engaging position of the pawl can be changed.

However, in the above tensioner, the tension rod 32 freely projects in the direction in which the chain is loosened, but the return direction of the tension rod 32 is restricted by the ratchet pawl 34, and the pawl support shaft 35 has the elongated hole 36. Prevents the chain from being overtensioned within the range of retracting. For this reason,
There is a problem that the amount of return of the tension rod 32 that is excessively projected due to chain vibration or the like is reduced by the regulation of the ratchet pawl 34 and the long hole 36.

Further, the structure proposed above does not have the function of absorbing the vibration of the chain, so that the fluttering of the chain cannot be prevented, and there is a problem that noise is likely to occur.

Therefore, an object of the present invention is to provide a tensioner capable of adjusting the tension of the chain to be constant in both the slack side and the tension side by a mechanical structure.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, a cylindrical case that abuts a swingable chain guide is fitted rotatably around a fixed shaft, and the cylinder is formed. A wedge-shaped space that becomes narrow in the circumferential direction is formed between the opposed surfaces of the cylindrical case and the fixed shaft, and a friction member that makes surface contact with the opposed surfaces of the cylindrical case and the fixed shaft at the same time is formed in the wedge-shaped space. And a pressing member that presses the friction member toward the narrow portion of the wedge-shaped space, and a tension applying means for urging the cylindrical case and the chain guide in the chain tension direction on the chain guide and the cylindrical case. The friction member is connected to the narrow portion of the wedge-shaped space by the contact between the tubular case and the fixed shaft when the tubular case is rotated by increasing the tension of the chain.

[0010]

[Operation] When the chain tension increases and the force acting on the chain guide increases, the tubular case rotates around the fixed shaft toward the slack side of the chain, and the friction member contacts the tubular case with the surface of the fixed shaft. It is pushed toward the narrow part of the wedge-shaped space. As a result, the frictional force with respect to the cylindrical case increases, and the swing of the chain guide in the chain slack direction is suppressed.

On the other hand, when the chain tension is reduced and the tubular case tries to rotate toward the tension side of the chain due to the swing of the chain guide due to the urging of the tension applying means, the friction member wedges due to the contact with the tubular case. It is pushed out to the wide part of the shape space, and the frictional force on the tubular case is reduced.
Therefore, the chain guide rapidly swings to keep the tension of the chain constant.

[0012]

1 to 3 show a chain tensioner of an embodiment. As shown in the figure, the chain guide 1
The guide surface 2 of the chain B is provided on the outer surface of the arc-shaped plate material. The chain guide 1 is swingably attached to a fixed member A such as an engine block at a swing fulcrum 3 provided at one end.

The swing fulcrum 3 of the chain guide 1
A protrusion 7 for connection is provided at a position away from, and the damper means 4 and the tension applying spring 18 are connected to the protrusion 7.

The damper means 4 has a fixed shaft 5 fixed to the fixing member A by a bolt 15 and a cylindrical case 6 rotatably fitted to the fixed shaft 5. An arm 8 protruding radially from the outer peripheral surface is in contact with a protrusion 7 of the chain guide 1.

The cylindrical case 6 is sandwiched between the flange 5a at the lower end of the fixed shaft 5 and the thrust plate 16 attached to the upper end of the bolt 15 via thrust washers 17, 17 respectively, and the thrust washer 17, 1
It is supported by a slide guide 7 so as to be freely rotatable relative to the fixed shaft 5.

The case 6 has a cylindrical hole 9 coaxial with the fixed shaft 5, and a friction generating mechanism 10 is incorporated between the cylindrical hole 9 and the fixed shaft 5.

In this friction generating mechanism 10, a plurality of cam surfaces 11 projecting in the radial direction are provided on the outer periphery of the fixed shaft 5 opposed to the cylindrical hole 9 at required intervals in the circumferential direction. A wedge-shaped space 12 is formed between the surface of the hole 9 and the surface. Further, a friction member 13 having substantially the same shape as that of the wedge-shaped space 12 is incorporated in each wedge-shaped space 12, and each of the friction members 13 is pressed by the spring member 14 toward the narrow portion of the wedge-shaped space 12. I have to.

A cam surface 1 forming the wedge-shaped space 12
The cross-sectional shape of 1 is formed in a spiral shape or an eccentric arc shape having a center at an eccentric position with respect to the axial center of the fixed shaft 5, and the wedge angle α is all contact surfaces in the circumferential direction with the friction member 13. It is set to be almost constant. Further, the wedge angle α is formed at an angle equal to or larger than the angle at which the friction member 13 is completely locked, and is set under the condition that the friction member 13 can slide.

Here, the friction member 13 is formed of a synthetic resin having excellent wear resistance and heat resistance, or a metal material of a type different from that of the cylindrical boss 6.

On the other hand, the tension applying spring 18 is provided on the fixed shaft 5.
It is composed of a torsion coil spring that is wound around the arm 6, one end of which is engaged with the arm 8 of the case 6 and the other end of which is engaged with the pin 19 projecting from the engine block A. The guide surface 2 of the guide is pressed against the chain B by rotating the chain tension side.

The chain tensioner of this embodiment has the structure as described above. When the tension of the chain B increases and the force acting on the chain guide 1 increases, the cylindrical case 6 moves around the fixed shaft 5 in FIG. Turn left. As a result, when the chain guide 1 tries to retract from the chain,
The friction member 13 is pushed toward the narrow portion of the wedge-shaped space 12 due to the contact with the cylindrical hole portion 9, the frictional force with respect to the case 6 increases, and the swing of the chain guide 1 in the chain slack direction is suppressed.

On the other hand, when the tension of the chain decreases and the force acting on the chain guide 1 decreases, the spring force of the tension applying spring 18 causes the chain guide 1 to rotate rightward toward the chain. Contact causes the friction member 13 to be pushed out to the wide portion of the wedge-shaped space 12 and the frictional force on the case 6 is reduced, and the chain guide 1 rapidly swings to keep the tension of the chain constant.

As described above, the chain tensioner of the embodiment has the characteristic of a one-way damper in which the swing resistance of the chain guide 1 is large on the left rotation direction side and small on the right rotation direction side. The function to keep the chain tension constant while suppressing the vibration of the chain due to the tension fluctuation. Further, when the tension is reduced, the chain guide 1 quickly rotates rightward, and the minimum value of the tension fluctuation and the tension applying spring 1
Since it moves to a state in which it is in balance with the spring force of 8, the change in tension during acceleration / deceleration of the engine can be satisfactorily followed, and the slack of the chain during low temperature starting can be promptly eliminated.

FIG. 4 shows another embodiment. In this example, a spring receiving screw 21 is provided so as to face the protrusion 7 provided on the chain guide 1, and a tension adjusting spring 22 composed of a compression coil spring is provided between the screw 21 and the protrusion 7.
And the spring force exerts a pressing force for rocking the case 6 and the chain guide 1 toward the chain tension side.

Since other structures and operations are the same as those of the above-mentioned embodiment, the same parts are designated by the same reference numerals and the description thereof will be omitted.

[0026]

As described above, according to the present invention, since the chain tension is adjusted by using the one-way damper utilizing the mechanical frictional force, the chain vibration is surely suppressed and the tension increase / decrease of the chain is appropriately followed. It is possible to adjust the tension and improve the life of the chain and reduce vibration.

Also, since the chain guide can be swung quickly to adjust the tension irrespective of changes in the properties of the engine oil, stable tension adjustment and noise reduction can be realized.

Further, as compared with the hydraulic tensioner, an oil passage for introducing engine oil is not required, and the number of parts can be reduced, which is advantageous in that it can be formed at low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional plan view showing a chain tensioner of an embodiment.

FIG. 2 is a vertical sectional front view of a portion of the above.

FIG. 3 is an enlarged sectional view showing the damper means of the above.

FIG. 4 is a cross-sectional plan view showing another embodiment.

FIG. 5 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chain guide 3 Swinging fulcrum 4 Damper means 5 Fixed shaft 9 Cylindrical hole 10 Friction generating mechanism 11 Cam surface 12 Wedge-shaped space 13 Friction member 14 Spring member 18, 22 Tensioning spring

Claims (1)

[Claims] 1. A cylindrical case that abuts a swingable chain guide is rotatably fitted around a fixed shaft, and is narrowed in the circumferential direction between the facing surfaces of the cylindrical case and the fixed shaft. Forming a wedge-shaped space, and a friction member that simultaneously makes surface contact with the opposing surfaces of the cylindrical case and the fixed shaft in the wedge-shaped space, and presses the friction member toward the narrow portion of the wedge-shaped space. When a pressing member is provided, and the chain guide and the tubular case are connected to a tension applying means for urging the tubular case and the chain guide in the direction in which the chain is stretched, when the tubular case rotates due to the increase in the tension of the chain. A chain tensioner configured such that the friction member is pushed into a narrow portion of the wedge-shaped space by contact with the tubular case and the fixed shaft.