JP2003120767A - Automatic tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce generation of uncomfortable noise in a rod return prohibiting mechanism in an automatic tensioner. SOLUTION: This automatic tensioner is provided with the rod return prohibiting mechanism 29 comprising a collar 43 having a taper surface 42 developed in an advance direction of a push rod 10, a plurality of balls 47 disposed between the taper surface 42 and an outer circumferential surface of the push rod 10, a retainer 45 to retain the balls 47, and a retainer coil spring (retainer energizing means) 48 to energize the retainer 45 to apply the balls 47 to the taper surface 42. The collar 43 is formed as a separate body from a tensioner body 9, and it is engaged inside a collar engagement hole 22 in the tensioner body 9 having a prescribed diametric gap C1 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a predetermined tension to an endless body of a winding transmission mechanism such as an engine cam chain or a timing belt in a tension direction to automatically absorb looseness. More specifically, the present invention relates to an automatic tensioner provided with a rod return blocking mechanism using a ball.

[0002]

2. Description of the Related Art FIG. 4 shows an automatic tensioner for a cam chain of an engine having a conventional ball-type rod return blocking mechanism. The automatic tensioner includes a tensioner body 101 having a rod support hole 114 and a rod support hole 114.
A push rod 102 supported by the cam chain 10 so as to be movable in the axial direction of the rod.
Coil spring 10 for tension urging to 4 side (front side)
5 and a ball-type rod return blocking mechanism 110 that blocks the backward movement of the push rod 102.

The push rod 102 has a rod support hole 11
4 protrudes forward from the front end P1 of No. 4 in a cantilever manner and abuts on the rod receiving portion 108a of the guide shoe 108. The guide shoe 108 is formed in an arcuate shape, and the end portion on the side opposite to the cam chain moving direction A is rotatably supported by the engine via a support shaft 109 and slidably contacts the cam chain 104 with a constant pressure. .

The rod return blocking mechanism 110 includes a plurality of balls 120 arranged on the outer periphery of the push rod 102,
The retainer 121 holds the ball 120 movably in the rod radial direction, and a collar 123 having a tapered surface 122 on the inner circumference. The collar 123 is press-fitted and fixed to the front half cylinder portion of the tensioner body 101. Retainer 1
21 is biased rearward by the tension coil spring 105 and brings the ball 120 into contact with the tapered surface 122 to provide an environment in which a backward blocking force can always be generated. That is, when the push rod 102 receives a moving force in the backward direction, the ball 120 interlocks with the push rod 102 and immediately gets caught between the taper surface 122 and the push rod outer peripheral surface, and the push rod 102 moves by the wedge action. It is designed to prevent backward movement.

[0005]

While the engine is operating, the guide shoe 108 vibrates in a direction substantially perpendicular to the chain moving direction A (rod axial center direction) due to a change in tension acting on the cam chain 104, and at the same time, the above force is applied. Changes in the curvature of the bow, which causes the rod receiver 108
The position a also vibrates in the direction A. Further, it is repeatedly pulled in the chain moving direction A by friction with the cam chain 104 and vibrates in the chain moving direction A due to the radial gap in the support shaft 109. The vibration of the guide shoe 108 in the chain moving direction A is generated by the rod receiving portion 1.
Vibration of the push rod 102 in the radial direction of the rod is generated via 08a, which may cause an unpleasant sound in the rod return blocking mechanism 110.

(1) However, as shown in FIG. 4, the collar 123 having the tapered surface 122 is attached to the tensioner body 101.
In the case of adopting a structure that is fixed to the rigid, the rod support hole 114 and the outer periphery of the push rod 102 are absorbed in order to absorb the deviation between the center of the rod axis and the retainer and the center of the tapered surface 122 caused by manufacturing error. Surface gap C4
Of the push rod 102 in the rod radial direction with respect to the tensioner body 101 becomes large, which causes an increase in the generation of the unpleasant sound. On the other hand, if the gap C4 is suppressed to a small value, the manufacturing error and the collar 12 will be reduced during assembly.
Since it is impossible to absorb the deviation between the center of the rod shaft and the retainer and the center of the tapered surface 122 due to the fixation of No. 3, it becomes difficult to maintain high assembly accuracy, and it is difficult to uniformly press all the balls 120 by the tapered surface 122. become.

(2) Further, as shown in FIG. 4, the rod support hole 1
14 is formed rearward of the rod return blocking mechanism 110, and the push rod 102 has a rod support hole 114.
In the structure that cantileveredly projects from the front end P1 of
The bending moment length of the push rod 102 becomes large, which also promotes the radial vibration of the push rod 102 and causes an unpleasant sound.
Further, when the amount of forward protrusion of the push rod 102 changes, the support length L3 of the push rod 102 in the axial direction also changes.

[0008]

An object of the present invention is to make it possible to equalize the rod return blocking force by the wedge action of the ball over the entire circumference regardless of manufacturing errors, and to transmit the rod radial direction from the endless body side to the push rod. The purpose is to reduce the vibration of the rod and eliminate the generation of unpleasant sound in the rod return blocking mechanism.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 is a push rod supported by a tensioner body so as to be movable in the rod axis direction, and the push rod is wound around a transmission mechanism. In an automatic tensioner equipped with a biasing mechanism that biases the endless body and a ball-type rod return prevention mechanism that prevents the push rod from moving backward, the rod return prevention mechanism expands in the forward direction of the push rod. A collar having a tapered surface, a plurality of balls arranged between the tapered surface and the outer peripheral surface of the push rod, a retainer for holding the balls, and a retainer for biasing the balls into contact with the tapered surface. The collar is formed separately from the tensioner body and has a diameter inside the collar fitting hole of the tensioner body. It is fitted with a predetermined gap direction.

Thus, the center line of the taper surface, the axial center line of the push rod, and the center line of the retainer can be automatically matched at the time of assembly regardless of manufacturing errors and the like, and all balls of the rod return prevention mechanism can be made. It is possible to press uniformly by the tapered surface, and it is possible to reduce the generation of unpleasant sound in the return blocking mechanism.

According to a second aspect of the present invention, a push rod movably supported by the tensioner body in the axial direction of the rod, urging means for urging the push rod toward the endless body of the winding transmission mechanism, and the push rod. In the automatic tensioner equipped with a ball-type rod return prevention mechanism for preventing the backward movement of the rod, the cylindrical rod support hole of the tensioner body that supports the push rod is connected to the endless body side in the rod axis direction relative to the rod return prevention mechanism. And extends to near the tip of the push rod.

As a result, the supporting range of the push rod in the axial direction of the rod can be widened, and the cantilevered projection amount of the push rod can be shortened to the necessary minimum, so that the vibration of the push rod in the radial direction can be achieved. Can be suppressed, and the generation of unpleasant sound in the return blocking mechanism can be reduced.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION [Arrangement of Automatic Tensioner] FIG. 3 is an example in which an automatic tensioner T according to the present invention is installed in a cam drive winding transmission mechanism of an engine.
An endless cam chain 1 is wound around the crankshaft 2 and a pair of camshafts 3 and 4, and is moved in the direction of arrow A by the rotation of the crankshaft 2. A guide shoe 7 for an automatic tensioner is in sliding contact with the cam chain 1, the guide shoe 7 is formed in an arch shape, and the end portion on the side opposite to the moving direction A of the cam chain is the support shaft 1.
It is rotatably supported by the engine via 1.

The automatic tensioner T includes a tensioner body 9 fixed to a wall 8 forming a part of an engine body (cylinder, etc.) and a push rod supported in the tensioner body 9 so as to be slidable in the rod axis direction. It is composed of 10 parts.

[Structure of Automatic Tensioner] (Structure of Tensioner Body) FIG. 1 is an enlarged vertical sectional view of the automatic tensioner T, and the endless body side (guide shoe side) in the rod axis direction will be described as the front side. The tensioner body 9 is composed of a pair of front and rear body members 9a and 9b. The front body member 9a is formed with a cylindrical rod support hole 14 penetrating in the front-rear direction, and a flange 15 and a cylindrical mounting part 16 are formed at the rear end of the rod support hole 14. A spring housing hole 18 is formed on the rear side through an annular step surface 17. The rear body member 9b has a bottom wall 9c formed at a rear end thereof and a flange 20 formed at a front end thereof, and a rod insertion hole 36 is formed at an inner periphery of a rear half portion thereof, and a rod insertion hole 36 is formed at a front side of the rod insertion hole 36. A cylindrical collar fitting hole 22 is formed through an annular step surface 21, and the collar fitting hole 22 has a front surface opened. Also,
A screw 25 for temporarily fixing a rod is screwed into the outer peripheral wall of the rear half of the rear body member 9b, and a hook 23 for temporarily assembling the body members 9a and 9b is formed on the outer peripheral end of the front end flange 20. Has been done. Both body members 9a, 9
As a means for temporarily assembling b, a screwing structure using bolts or the like may be adopted instead of the hook 23.

The rod support hole 14 of the front body member 9a extends to near the front end of the push rod 10, and the front end P1 of the rod support hole 14 is located near the front end of the push rod 10. The radial gap C3 between the rod support hole 14 and the push rod 10 is set small enough to allow the push rod 10 to move in the axial direction but not to allow radial play. On the other hand, the inner diameter of the rod insertion hole 36 of the rear body member 9b is larger than the inner diameter of the rod support hole 14, and a radial clearance C2 is ensured so that the push rod 10 can move with almost no frictional resistance. ing.

The brazing part 16 of the front body member 9a is fitted into the collar fitting hole 22 of the rear body member 9b, so that the shaft centers of both body members 9a and 9b are aligned. Flange 15, 20 of both body members 9a, 9b
Overlap with each other through the O-ring 27, the front body member 9a is inserted into the mounting hole 33 of the wall 8, and each flange 1
It is fixed to the mounting surface 34 of the wall 8 by a common bolt 32 that is inserted through the bolt insertion holes 30 and 31 of 5, 20.

(Structure of Push Rod) The push rod 10 is fitted and supported in the rod support hole 14 of the front body member 9a so as to be slidable in the front-rear direction.
A rear end opening-shaped spring accommodating shaft core hole 35 is formed in the shaft core part of the above, and an annular groove 37 for temporarily fixing the rod is formed on the outer periphery of the rear end part. The rear portion of the push rod 10 passes through the collar fitting hole 22 of the rear side body member 9b and passes through the rod insertion hole 36.
It has reached inside.

A washer 39 is provided between the front end surface of the axial core hole 35 of the push rod 10 and the bottom wall 9c of the rear body member 9b.
The tension coil spring 40 is contracted via the coil spring 40, and by pushing the push rod 10 forward by the coil spring 40, the front end of the push rod 10 applies a predetermined load to the rod receiving portion 7a of the guide shoe 7. Abuts on.

(Rod Return Blocking Mechanism) As the rod return blocking mechanism 29, the collar fitting hole 22 and the push rod 10 are provided.
A collar 43 having an inner peripheral tapered surface 42, a retainer 45 having a ball insertion hole 44, and a plurality of balls (steel balls) inserted in the ball insertion hole 44
47 is arranged, and a retainer coil spring 48 is arranged in the spring housing hole 18.

The taper surface 42 of the collar 43 is formed so as to expand toward the front in the axial direction of the rod, and is hardened by carburizing and quenching. The outer peripheral surface of the collar 43 is fitted with the collar. The hole 22 is fitted with a predetermined radial clearance C1. The gap C1 is ensured so that the maximum manufacturing error in the radial direction can be absorbed. The retainer 45 is fitted to the outer peripheral surface of the push rod 10 so as to be slidable in the axial direction,
The retainer coil spring 48 is contracted between the front surface of the retainer 45 and the step surface 17 of the front body member 9a, and the retainer 45 is biased rearward by the retainer coil spring 48 to move the ball 47 to the tapered surface 42. Abutting.
The load of the retainer coil spring 48 is such that the ball 47 is lightly pressed against the tapered surface 42,
This provides an environment in which the wedge action of the ball 47 can be immediately exhibited when the moving force of the push rod 10 in the backward direction is applied. The load of the retainer coil spring 48 can be adjusted to an arbitrary value, but it is preferable that the load is such that it is lightly pressed against the tapered surface 42 as described above.

For example, as shown in FIG. 2, eight ball insertion holes 44 of the retainer 45 are formed at equal intervals in the circumferential direction, and balls 47 are inserted into each ball insertion hole 44 so as to be movable in the radial direction. ing.

[0023]

[Assembly and Installation Method] With the rear body member 9b facing upward, the tension coil spring 40 and the push rod 10 are inserted into the rear body member 9b, and the temporary fixing screw 25
The push rod 10 is temporarily fixed by engaging with the annular groove 37 of the push rod 10.

The collar 43, the retainer 45 holding the balls 47, and the retainer coil spring 48 are sequentially fitted to the outer peripheral side of the push rod 10 and the collar fitting hole 22 is provided.
Then, the O-ring 27 is inserted into the front body member 9a, and the brazing part 16 of the front body member 9a is fitted into the collar fitting hole 22 by the brazing. At this time, both body members 9
a and 9b are relatively displaced around the rod axis,
After the coil spring 48 is compressed and then returned to the normal relative rotation position, the hook 23 of the rear body member 9b is engaged with the flange 15 of the front body member 9a. As a result, the two body members 9a and 9b are temporarily connected to each other, the front body member 9a is inserted into the mounting hole 33, and the common bolt 32 fastens both body members 9a and 9b to the mounting surface 34. In this manner, the common bolt 32 allows both body members 9a and 9b to be joined together and attached to the wall 8 at the same time, the number of parts for assembly can be reduced, and the assembling work can be facilitated.

After attaching the tensioner body 9 to the wall 8, the push rod 10 is unlocked (temporarily fixed) by loosening the temporary set screw 25, and the push rod 10 is moved forward by the elastic force of the tension coil spring 40. And is brought into contact with the rod receiving portion 7a of the guide shoe 7.

Since the retainer coil spring 48 and the tension coil spring 40 are assembled independently during the above-mentioned assembly, it is possible to set the loads suitable for tension and biasing the retainer, respectively, and to use them during use. They do not affect each other.

[Automatic alignment of rod return prevention mechanism] Due to manufacturing errors and the like, the center of the collar fitting hole 22 and the anchor portion 1
6 and the center of the rod support hole 14 are displaced from each other, and as a result, the axial center of the push rod 10 and the center of the collar fitting hole 22 are displaced from each other, the outer peripheral surface of the collar 43 and the collar fitting hole 22 are separated from each other. Since a predetermined gap C1 that can absorb the maximum manufacturing error is secured between the gaps, the gap C1 absorbs the misalignment, and the tapered surface 42, the retainer 45, and the push rod 10 are automatically aligned. . That is, after assembly, the center of the tapered surface 42 of the collar 43 is at the center of the retainer 45.
And the axial center of the push rod 10, and even if there is a manufacturing error as described above, the tapered surface 4 of the collar 43
2 presses all the balls 47 evenly, and all the balls 47 uniformly exert the wedge action on the push rod 10 over the entire circumference, so that the push rod 10 can be gripped.

[0028]

[Operation of Tensioner] By pushing the push rod 10 forward by the tension coil spring 40, the guide shoe 7 is pressed by the cam chain 1 with a predetermined load, whereby a constant tension is applied to the cam chain 1. Is given.

[Operation of Rod Return Blocking Mechanism] While the engine is operating, a backward reaction force is applied to the push rod 10 from the cam chain 1 via the guide shoe 7, but the ball 4
7 interlocks with the push rod 10 and bites into the tapered surface 42 and the push rod outer peripheral surface, and the wedge action of the ball 47 prevents the push rod 10 from returning (retracting movement). On the other hand, with respect to loosening due to the extension of the cam chain 1, the pushing force of the coil spring 40 causes the push rod 10 to gradually move forward in accordance with the amount of looseness of the cam chain 1 and maintain an appropriate tension. In this case, the ball 4
7 is pulled forward by the push rod 10, the pressure on the push rod 10 is released, and the push rod 10 can move forward.

During operation, the guide shoe 7 vibrates in the direction substantially perpendicular to the chain moving direction A due to the change in the tension acting on the cam chain 1 as in the contents described in the above-mentioned problems of the prior art, and at the same time, the above force is applied. Changes in the curvature of the bow, and the position of the rod receiving portion 7a also vibrates in the substantially A direction. Further, it is repeatedly pulled in the chain moving direction A due to friction with the cam chain 1, and vibrates in the chain moving direction A due to the radial gap in the support shaft 11. In response to such radial vibration, in the structure of FIG. 1, the entire length L1 of the rod support hole 14 is formed to be long, and the front end P1 of the rod support hole 14 is located near the front end of the push rod 10. Forward protrusion amount L
2 is limited to a short length, and since the push rod 10 is fitted in the rod support hole 14 with almost no radial play, vibration in the push rod 10 radial direction is suppressed. The rod support length L1 does not change even if the protrusion amount L2 of the push rod 10 changes.

Since the radial movement of the push rod 10 is suppressed as described above, the radial movements of the retainer 45 and the ball 47 are naturally suppressed, and the generation of unpleasant sound in the rod return prevention mechanism 29 is suppressed. To be done.

Since the retainer coil spring 48 is provided, even if the ball 47 is separated from the taper surface 42 or the outer peripheral surface of the push rod 10 by the vibration of the push rod 10 in the axial direction, the ball 47 quickly comes into contact with the ball 47. Can be returned to the state. Moreover, since the retainer coil spring 48 is provided independently of the tension coil spring 40, the retainer 4 is independent of the tension setting load.
The set load of 5 can be freely set, and the operability of the rod return blocking mechanism 29 can be improved. Further, the retainer coil spring 48 is formed as a separate member from the tension coil spring 40 that presses the push rod 10, thereby suppressing the vibration and load fluctuation of the retainer coil spring 48 due to the vibration of the push rod 10. You can Furthermore, the amount of protrusion L of the push rod 10 due to use
Even if 2 is changed, the load of the retainer coil spring 48 does not change, and the posture of the retainer 45 of the rod return blocking mechanism 29 can always be kept constant.

Further, since the front end of the coil spring 48 is supported by the step surface 17 of the front body member 9a via a washer or the like, the stability of the load of the coil spring 48 is maintained.

[0034]

Other Embodiments (1) As an endless body of a winding transmission mechanism to which the present invention is applied, it can be used not only for a cam chain but also for a timing belt or the like.

(2) The present invention is not limited to motorcycle engines, but can be applied to various vehicle engines or other engines.

(3) The number of balls 47 is 8 as shown in FIG.
Although it is desirable that the number is about four, it is possible to use four or six, and at least three or more are required.

[0037]

As described above, according to the present invention, the push rod 10 supported by the tensioner body 9 so as to be movable in the rod axis direction, and the tension for urging the push rod 10 toward the endless body of the winding transmission mechanism. Coil spring 40
The following advantages are provided in the automatic tensioner including the urging means such as the above and the ball type rod return blocking mechanism 29 for blocking the backward movement of the push rod 10.

(1) The invention according to claim 1 is arranged between the collar 43 having the tapered surface 42 that expands in the forward direction of the push rod 10, and between the tapered surface 42 and the outer peripheral surface of the push rod 10. Multiple balls 47
And a retainer 45 that holds the ball 47, and the ball 4
Retainer 45 so that 7 contacts the tapered surface 42.
A rod return preventing mechanism 29 including a retainer coil spring (retainer urging means) 48 for urging the retainer, the collar 43 is formed separately from the tensioner body 9, and the collar fitting hole of the tensioner body 9 is formed. Since it is fitted with a predetermined radial gap C1 inside 22, the shaft fitting of the push rod 10 and the collar fitting hole 2 due to manufacturing errors or the like.
Even if the center of 2 is deviated, during assembly, misalignment is absorbed by the radial clearance C1 between the collar fitting hole 22 and the outer peripheral surface of the collar 43, and after assembly, the tapered surface 42 is made up of all the balls 4
The push rod 10 can be pressed against the entire circumference of the push rod 10 with a uniform load due to the uniform wedge action of all the balls 47.

(2) Since the gap C1 between the collar fitting hole 22 and the collar 43 absorbs a manufacturing error as described above, the rod support hole 1 of the tensioner body 9 is prevented.
The radial distance C3 between the push rod 10 and the push rod 10 can be suppressed to a minimum size required for the movement of the push rod 10 in the axial direction.
The vibration of 0 in the radial direction of the rod is suppressed, and the generation of unpleasant sound in the rod return blocking mechanism 29 can be reduced.

(3) According to the second aspect of the present invention, the cylindrical rod support hole 14 of the tensioner body 9 supporting the push rod 10 is provided on the cam chain side of the rod return blocking mechanism 29 in the axial direction of the rod axis. If the push rod 10 is formed on the (endless body side) and extends to the vicinity of the front end of the push rod 10, the support range of the push rod 10 in the rod axis direction can be widened and the cantilevered projection amount of the push rod 10 can be increased. It can be shortened to the required minimum.
As a result, radial vibration of the push rod 10 can be suppressed, and generation of unpleasant sound in the rod return blocking mechanism 29 can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an automatic tensioner to which the present invention is applied.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a schematic front view showing a state where the automatic tensioner of the present invention is provided in a cam chain of an engine.

FIG. 4 is a vertical sectional view of a conventional example.

[Explanation of symbols]

1 Cam Chain (Endless Body) 7 Guide Shoe 9 Tensioner Body 14 Rod Support Hole 22 Collar Fitting Hole 40 Tension Coil Spring (Biasing Means for Tension) 42 Tapered Surface 43 Collar 44 Ball Insertion Hole 45 Retainer 47 Ball 48 Retainer Coil spring (biasing means for retainer)

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Claims (2)

[Claims] 1. A push rod supported by a tensioner body so as to be movable in the rod axis direction, a biasing means for biasing the push rod toward an endless body of a winding transmission mechanism, and a backward movement of the push rod. In an automatic tensioner equipped with a ball-type rod return prevention mechanism, the rod return prevention mechanism includes a collar having a tapered surface that expands in the forward direction of the push rod, and a gap between the tapered surface and the outer peripheral surface of the push rod. A plurality of balls arranged on the retainer, a retainer for holding the balls, and retainer urging means for urging the retainer so that the balls come into contact with the tapered surface, and the collar is provided separately from the tensioner body. The automatic tensioner is formed and is fitted into the collar fitting hole of the tensioner body with a predetermined radial gap. Na. 2. A push rod supported by a tensioner body so as to be movable in the rod axis direction, a biasing means for biasing the push rod toward the endless body of the winding transmission mechanism, and a backward movement of the push rod. In the automatic tensioner equipped with a ball-type rod return prevention mechanism, the cylindrical rod support hole of the tensioner body supporting the push rod is formed on the endless body side in the axial direction of the rod axis with respect to the rod return prevention mechanism. An automatic tensioner characterized by being extended to the vicinity of the tip.