JPH1061737A - Automatic tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic tensioner which can impede retraction of a rod pressing an endless transmission body without a backlash and prevent retraction of the rod against generation of vibration and impulse. SOLUTION: A rod 8 movably fitted in the axial direction to a body 1 is pressed to an endless transmission body 28 by a head part 13 forwardly protruded from the body 1. In a storage hole 4, 7 of the rod 8 in the body 1, a first tapered surface 9 spread toward the front concentrically to the rod 8 is formed. In the periphery of the rod 8, a second tapered surface 10 spread toward the front to have a gradient smaller than the first tapered surface 9 is formed. Between the first/second tapered surfaces 9, 10, a ball 12 is made to bite in. By a spring unit 17 provided between the ball 12 and the rod 8, the ball 12 is pressed in the biting direction, also the rod 8 is pressed to the front.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission that applies a predetermined tension to an intangible transmission by automatically absorbing looseness by pressing an intangible transmission such as a cam chain or a belt of an engine in a tensioning direction. It is about a tensioner.

[0002]

2. Description of the Related Art Generally, an automatic tensioner of this type is configured so that a rod movably held by a body is urged by a spring to press the rod against a bodyless transmission in a direction of its tension. Such an automatic tensioner is strong against the moving force of the rod in the backward direction so that the rod does not move in the backward direction due to the tension of the infinite body when a load in the return direction is applied to the infinite body. High drag is required. Conventionally, in order to obtain such anti-backup drag,
Means for providing a ratchet mechanism between the rod and a fixed part (body) holding the rod, and a method in which a plurality of balls are engaged between the tapered surface of the body and the outer surface of the rod in conjunction with the retreating movement of the rod. For generating wedge action
No. 6-53139).

[0003]

The means for preventing the rod from retreating by the former ratchet mechanism has the advantage that the retraction of the rod can be prevented within a range of one pitch of the ratchet.
There is a maximum backlash of one pitch of the ratchet, and the rod rattles and loosens the endless transmission until immediately before the engagement position of the ratchet is switched, which may cause noise. In order to solve this, it is conceivable to reduce the pitch of the ratchet. However, as the ratchet pitch becomes smaller, the ratchet teeth also become smaller, so that its workability and durability may be inferior, and it may not be possible to prevent the rod from retracting due to the load of the intangible transmission.

On the other hand, in the latter means of preventing the rod from retreating by the ball type mechanism, since the rod is prevented from retreating in a stepless manner, the rattling of the rod unlike the ratchet mechanism does not occur. However, when a large impact or vibration occurs, the ball may be momentarily separated while floating from the tapered surface of the body or the outer surface of the rod. In such a case, the bite between the tapered surface of the ball and the rod is released, so that the rod instantaneously rotates or slides on the ball under the reaction force of the bodyless transmission. May retreat.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an automatic tensioner capable of preventing back of a rod pressing a bodyless transmission without backlash and preventing the back of the rod against occurrence of vibration or impact. It is assumed that.

[0006]

In order to achieve the above object, an automatic tensioner of the present invention is an automatic tensioner for pressing an endless transmission such as a chain or a belt in a tensioning direction. A rod that is fitted movably in the axial direction and that presses the endless transmission by a head that protrudes forward from the body; and a rod that is formed in a housing hole for the rod in the body and that is concentric with the rod and that moves forward. An expanding first tapered surface, a second tapered surface formed on the outer periphery of the rod and expanding forward and having a smaller gradient than the first tapered surface, and a portion between the first tapered surface and the second tapered surface. And a spring provided between the ball and the rod and pressing the ball in the biting direction and pressing the rod forward by a reaction force of the pressing. Eteiru.

In the automatic tensioner having the above structure, the head of the rod, which protrudes forward from the body, is pressed forward by the spring body and pressed against the intangible transmission. The rod is moved forward by the pressing force of the spring body following the slack accompanying the operation of the intangible transmission, and automatically absorbs the slack in the intangible transmission to give a predetermined tension. When a pressing force in the retreating direction is received from the moved position by the reaction force of the intangible transmission body, the ball that is engaged between the first tapered surface of the body and the second tapered surface of the rod by the spring body causes the rod to move. Receiving the force for retreating, it more strongly bites between the two tapered surfaces to prevent the rod from moving in the retreating direction. Therefore, since the rod is prevented from retreating steplessly by the ball functioning as a wedge member, the rod is held without play against the reaction force of the endless transmission.

When an impact or vibration occurs, the ball spreads forward in the rod, that is, moves forward along the slope of the second tapered surface having a large diameter toward the front. Because it is difficult, it does not separate from the first and second tapered surfaces even momentarily.
As a result, even when an impact or vibration occurs, the retraction preventing force of the rod by the ball is not released, and the rod does not retreat.

In a preferred embodiment of the present invention, the second
The slope of the tapered surface is set to 0.2 ° or more and 1 ° or less. In a further preferred embodiment, the gradient of the second tapered surface is set to 0.3 ° or more and 0.7 ° or less. According to these embodiments, the second tapered surface prevents the ball from displacing by generating a required frictional force with the ball within a range where the length of the rod in the axial direction does not increase. I do.

[0010] In the above invention, a rear end of the second tapered surface may be connected to a rear portion of the rod having a larger diameter through a step. As a result, the diameter of the rear portion of the rod is maintained as large as that of the conventional tensioner, so that the rod can be stably supported on the body.

[0011]

Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a use state of an automatic tensioner according to one embodiment of the present invention. The automatic tensioner T1 applies a constant tension to a timing chain (or belt) 28 as an indefinite power transmission in a tensioning direction. The chain 28 includes, for example, a crankshaft, a camshaft, and an idle shaft of an engine. And is forwarded in the direction of arrow A during operation of the engine. The automatic tensioner T1 is fixed to a mounting portion 30 provided on a part of an engine such as a cylinder in a state where the automatic tensioner T1 faces a chain guide 29 provided along a portion between a chain shaft and a camshaft of the chain 28, for example. Is done. The chain guide 29 is rotatably supported by a cylinder or the like via a support shaft 31 and includes a pad 32 for receiving a pressing force of a rod 8 described later.

The body 1 which forms the main body of the automatic tensioner T1
Is composed of a body main body 2 having a substantially cylindrical shape with a bottom and a cylindrical collar 3 press-fitted and fixed to the outer peripheral surface of the opening of the body main body 2. And a second storage hole 7 inside the body 2.
A rod 8 is slidably fitted in and held in the second storage hole 7 in the body 1 in the body 1. A first tapered surface 9 which is concentric with the rod 8 and expands forward (to the left in the drawing) is formed on the inner periphery of the outer end 3a of the collar 3. A second tapered surface 10 expanding forward is formed on the outer periphery of the intermediate portion.

The second tapered surface 10 of the rod 8
Is connected to a rod rear portion having the same diameter as the rod front portion via a step portion 15. Thus, the rod 8 is provided with the second tapered surface 10 in the middle part, but the diameter of the rear part is maintained as large as the conventional automatic tensioner, so that the rod 8 is stably supported by the body 1. . The second tapered surface 10 is formed with a smaller gradient than the first tapered surface 9, which will be described later. Double taper surface 9,1
0 opposes each other when the automatic tensioner T1 is operated while being fixed to the mounting portion 30.

A plurality of balls 12 rotatably held by a retainer 11 are interposed between the opposed tapered surfaces 9, 10. Are biased rightward in the figure by a compression coil spring (an example of a spring body) 17 interposed between the spring seat 14 and the retainer 11 provided inside (the right side in the figure) of the first and second parts. It bites between the tapered surfaces 9 and 10.
At this time, the rod 8 is urged by the compression coil spring 17 in a direction to protrude forward, and its head 13 presses the chain 28 via the pad 32. Therefore,
The ball 12 allows the rod 8 to move in the forward direction without engaging at all, and receives the pressing force from the rod 8 when the rod 8 tries to move in the retreating direction. The rod 8 engages between the two tapered surfaces 9 and 10 to function as a wedge member, and prevents the rod 8 from retracting.

A mounting cylinder portion 18 having a screw hole 19 is integrally formed with a part of the body main body 2 of the body 1 and a stopper for temporarily fixing the rod 8 is provided in the screw hole 19. A screw 20 is screwed through a packing 21. On the other hand, the rod 8 has a cut surface 22 for escape of the stopper screw 20 and a locking step 23 interposed between the cut surface 22 and the outer peripheral surface of the rod 8. As will be described later, the stopper screw 20 is screwed in, and the distal end face thereof is pressed against the locking step portion 23 to thereby form the rod 8.
Can be temporarily fixed in a state of being inserted behind the body 1. Further, a pin insertion hole 24 is bored in a radial direction at a position near the tip of the rod 8. The stopper screw 20 and the pin insertion hole 24 will be described later.

Next, the operation of the automatic tensioner T1 will be described. The rod 8 is a timing chain 28
Of the compression coil spring 17
When it is moved in the forward direction by the elastic force of the above and receives a pressing force in the backward direction from the moved position by the reaction force of the timing chain 28, the compression coil spring 17 bites between both tapered surfaces 9, 10. The ball 12 is
Receiving the pressing force in the retreating direction from the rod 8, it is further strongly engaged between the tapered surfaces 9 and 10. The wedge action of the ball 12 prevents the rod 8 from retracting.

That is, the rod 8 and the ball 12
The automatic tensioner T1 has a second tapered surface 10 that expands forward on the outer periphery of the rod 8, as shown in FIG. Assuming that the pressing force (rearward) of the compression coil spring 17 on the ball 12 is F1, a component force F parallel to the second tapered surface 10 of the pressing force F1.
A frictional force proportional to 11 acts on the rod 8, and this frictional force is directed radially inward of the rod 8. Further, a component force F12 orthogonal to the second tapered surface 10 acts as a pressing force against the rod 8. Thus, the ball 12 bites between the rod 8 and the ball 12 by the wedge action. Moreover, when the rod 8 tries to retreat, the ball 12 is pushed up along the slope of the second tapered surface 10 and
Is strongly pressed against the first tapered surface 9. As a result, the retraction of the rod 8 is prevented.

As described above, since the rod 8 is continuously stopped by the ball 12 functioning as a wedge member,
The timing belt 28 is held without rattling against the reaction force. Therefore, the noise caused by the loosening of the timing belt 28 is hardly generated, and the rod 8 does not rattle in the moving direction.
8 is smoothly transmitted.

On the other hand, the ball 12
When an external force F2 acting to advance in the direction toward the timing chain 28 is applied, as shown in FIG.
The frictional force proportional to the component force F21 parallel to the second tapered surface 10 in the external force F2 acts between the ball 12 and the second tapered surface 10, and is orthogonal to the second tapered surface 10. The ball 12 is moved to the second tapered surface 1 by the component force F22.
Pressed to zero. Therefore, even when the ball 12 receives a considerably large external force F2, it becomes difficult for the ball 12 to get over the second tapered surface 10 by the frictional force and the pressing force. Thus, the rod 12 does not retreat even when an impact or vibration occurs.

The first and second tapered surfaces 9 and 10 are set at the following angles θ1 and θ2. If the angle θ1 of the first tapered surface 9 is too large, the biting force of the ball 12 due to the urging force of the compression coil spring 17 becomes small. Conversely, if the angle θ1 is too small, the axial length of the first tapered surface 9 becomes large. There is a need to. Therefore, the angle θ1 of the first tapered surface 9 is suitably about 8 °.

On the other hand, when the angle θ2 of the second tapered surface 10 is larger than 1 ° because the angle θ1 of the first tapered surface 9 is about 8 °, the two tapered surfaces 9 and 10 shown in FIG. The space angle θ3 is reduced, and both tapered surfaces 9,
10 becomes longer in the axial direction, and the automatic tensioner T1 becomes larger. That is, the distances D1 and D2 between both ends of each of the tapered surfaces 9 and 10 are determined by the size of the ball 12, so that as the space angle θ3 increases, the axial length L of the tapered surfaces 9 and 10 increases. I will. Therefore, the second of FIG.
The angle θ2 of the tapered surface 10 is preferably set in the range of 0.2 ° or more and 1 ° or less, and more preferably 0. It is good to set it in the range of 3 ° or more and 0.7 or less. In this example, the angle θ2 of the second tapered surface 10 is 0.4
It is set to 6 °.

The procedure for assembling and mounting the automatic tensioner T1 will be described. As shown in FIG. 4, the locking pin 25 is inserted into the pin insertion hole 24 while the compression coil spring 17 is compressed, and the compression coil spring 17 and the ball 12 are inserted between the spring seat 14 and the locking pin 25. And a retainer 11 holding the same. On the other hand, the stopper screw 20
Is moved upward in the drawing until the lower end of the rod 8 comes out of the first storage hole 4, and then the rod 8 is moved to the engagement step 23.
Until the body faces the lower end of the stopper screw 20.
Insert inside. Subsequently, the rod 8 is temporarily stopped so as not to move forward by screwing the stopper screw 20 until its distal end surface presses against the engaging step 23 as shown in the figure.

Next, the automatic tensioner T in the above state
1 is fixed to a mounting portion 30 provided in an engine cylinder or the like, but before that, the locking pin 25 is pulled out. As a result, the retainer 11 is pushed rearward by the restoring force of the compression coil spring 17, and the ball 12 abuts on the first tapered surface 9 and the outer peripheral surface of the rod 3 closer to the front than the second tapered surface 10. The fixing of the automatic tensioner T1 is performed by attaching a mounting piece (not shown) provided so that the head 13 of the rod 8 faces the pad 32 of the chain guide 29 in FIG. This is performed by applying a bolt to the mounting portion 30 with the gasket 27 interposed therebetween, inserting a bolt through an insertion hole provided in the mounting piece, and screwing the bolt into a screw hole provided in the mounting portion 30.

Subsequently, when the stopper screw 20 is loosened, the rod 8 moves forward under the urging force of the compression coil spring 17, and the head 13 presses the timing chain to apply a predetermined tension to the timing chain. By the forward movement of the rod 8, the second tapered surface 10 of the rod 8 advances to a position facing the first tapered surface 9, so that the ball 12 receives the urging force of the compression coil spring 17 and the two tapered surfaces 9,
Biting between 10 Finally, when the stopper screw 20 is screwed again and fixed to the body 1, the operation state shown in FIG. 1 is obtained.

FIG. 5 is a longitudinal sectional view showing an automatic tensioner T2 according to another embodiment. In the figure, a male body 34a of a cap-shaped holding body 34 is screwed into a female body 33a formed in the rear part of a cylindrical body 33 having a larger inner diameter at the rear part (right side in the figure). A holding body 34 is attached to 33 via a gasket 37. The holding body 34 has a first tapered surface 38 that expands forward and is formed on the inner periphery of the tip (left end in the figure). On the other hand, at the rear of the rod 39 fitted movably in the axial direction of the body 33, a loading hole 4 opened rearward is provided.
0 is provided, and the rear portion of the rod 39 is
4 and inserted into the loading hole 40 and the insertion hole 42.
A compression coil spring (an example of a spring body) 41 is interposed in the space defined by the above. The rod 39 is urged in a forward direction toward a chain guide (not shown) by the elastic force of the compression coil spring 41.

A second tapered surface 43 is formed on the rod 39 at a position facing the first tapered surface 38 during operation. The first and second tapered surfaces 38 and 43 are used as the first and second tapered surfaces 9 and 10 in the automatic tensioner T1.
It is formed at the same angle as. The two tapered surfaces 38,
43, a ball 12 rotatably held by a retainer 11 similar to the automatic tensioner T1 is interposed between the retainer 11 and the body 3.
3 is urged rightward in the figure by a compression coil spring 44 interposed therebetween. The compression coil spring 44 has a spring force weaker than that of the compression coil spring 41.
Press between them so that they are slightly in contact with each other. In addition, rod 3
The rear end of the second tapered surface 43 at 9 is connected to the rear end of the large-diameter rod via the step 47.

As a means for preventing the rod 39 from retreating, a ratchet mechanism 48 is provided in addition to the structure including the two tapered surfaces 38 and 43 and the ball 12 that is engaged between them.
The ratchet mechanism 48 is attached to the body 3 by a support pin 49.
3, a ratchet tooth 51 formed on the rod 39 opposed to the claw 50, and a compression coil spring 52 for applying a rotational force to the claw 50 in a direction in which the ratchet tooth 51 meshes. It is composed of

In this automatic tensioner T2, the rod 39
Moves in the forward direction by the amount of extension of the timing chain due to the elastic force of the compression coil spring 41, and receives a pressing force in the backward direction from the moved position by the reaction force of the timing chain. The retraction of the rod 39 is prevented by a wedge effect in which a ball that is always in light contact with the tapered surfaces 38, 43 bites between the tapered surfaces 38, 43. That is, also in this automatic tensioner T2, the rod 39 is
Since the ball 12 that functions as a strong wedge member that bites between the pins 8 and 43 is prevented from retreating in a stepless manner, it is held without rattling against the reaction force of the Kaiming chain.

On the other hand, the ball 12
When an external force acts to move the ball 12 forward, similarly to the automatic tensioner T1, the ball 12 is prevented from being displaced by the tapered surfaces 38, 43 which are both expanded forward, and the two tapered surfaces 38, 43. , 43, even if it is momentary. Even if the ball 12 is separated from the two tapered surfaces 38 and 43 so as to float instantaneously, the rod 39 tries to retreat greatly by releasing the retreat preventing function of the ball 12, When the ratchet mechanism 48 engages within a range of one pitch, the backward movement is prevented.

[0030]

As described above, according to the automatic tensioner of the present invention, in addition to the first tapered surface of the body, a second tapered surface is formed on the rod, and the ball is engaged between the two tapered surfaces. As the ball is prevented from retreating, when the rod receives the force to retreat, the ball is strongly engaged between the two tapered surfaces by the wedge action to move the rod in the retreating direction. Since the rod is blocked, the rod is steplessly blocked by the ball, and can be held without play against the reaction force of the endless transmission. Further, even if an external force is applied to move the ball forward due to generation of vibration or impact, the ball cannot climb over the second tapered surface, so that the retraction preventing function of the rod is not released. Thus, the rod does not retract even when a large vibration or impact occurs.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an attached state of an automatic tensioner according to an embodiment of the present invention.

FIG. 2 is an operation explanatory view of the above.

FIG. 3 is an explanatory diagram of angles of first and second tapered surfaces according to the first embodiment.

FIG. 4 is a longitudinal sectional view showing an attachment process of the above.

FIG. 5 is a longitudinal sectional view showing an automatic tensioner according to another embodiment of the present invention.

[Explanation of symbols]

T1, T2: Automatic tensioner, 1, 33: Body, 4,
7, 42: storage hole, 8, 39: rod, 9, 38: tapered surface, 10, 43: second tapered surface, 12: ball, 1
3 head, 15, 47 step, 17, 42, 44 compression coil spring (spring), 28 timing belt (endless transmission).

Claims (4)

[Claims] 1. An automatic tensioner for pressing an endless transmission such as a chain or a belt in a tensioning direction, comprising: a body; and a head protruding forward from the body which is fitted movably in the axial direction to the body. A rod for pressing the endless transmission; a first tapered surface formed in a housing hole of the rod in the body and extending concentrically with the rod and extending forward; formed on an outer periphery of the rod and facing forward spread,
A second tapered surface having a gradient smaller than that of the first tapered surface; a ball engaged between the first tapered surface and the second tapered surface; and a ball provided between the ball and the rod for engaging the ball. And a spring that presses the rod forward by a reaction force of the pressing. 2. The automatic tensioner according to claim 1, wherein a gradient of the second tapered surface is 0.2 ° or more and 1 ° or less. 3. The automatic tensioner according to claim 1, wherein a gradient of the second tapered surface is 0.3 ° or more and 0.7 ° or less. 4. The automatic tensioner according to claim 1, wherein a rear end of the second tapered surface is connected to a rear portion of a rod having a larger diameter through a step.