JPH0735207A - Chain guide - Google Patents

Abstract

PURPOSE:To suppress forced displacement fluctuation which occurs in a chain on the occasion of transition between linear track and curved track so that vibration application force is not input in a chain guide. CONSTITUTION:A contact face 10A of a chain guide in contact with a chain is constituted by a curved track forming section 10a and linear track forming sections 10b, 10c adjacent to its start point S and end point E. The linear track forming sections 10b, 10c are offset in parallel by a distance epsilon represented by an equation, epsilon=(R+d/2)-{(R+d/2)<2>-(L/2)<2>}<1/2>, in the direction in which they are apart from a center of curvature 0 of the curved track forming section 10a from a tangent line 20 at the start point S or a tangent line at the end point E.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chain guide for contacting a chain wound around a plurality of sprockets and running, for example, to apply tension to the chain, prevent the chain from swaying, set a chain track, and the like. Especially, it is designed so that the vibration exciting force is not input from the chain to the chain guide.

[0002]

2. Description of the Related Art FIG. 5 is a front view of a conventional chain drive device 11 for rotating a camshaft of a DOHC engine, which is one type of vehicle engine, at a predetermined timing. That is, in the chain drive device 11, the chain 2 is wound around the crank side sprocket 1 and the sprocket 3 that are directly connected to the crankshaft of the engine, and the sprocket 4 that is coaxial with the sprocket 3 and is integrally provided in the rotation direction. And the chain 5 is wound around the cam side sprockets 6 and 6 directly connected to the cam shaft. Therefore, the rotational driving force of the crankshaft of the engine is first transmitted to the crank side sprocket 1,
From there, it is transmitted to the sprocket 3 and the sprocket 4 via the chain 2, then to the cam side sprockets 6 and 6 via the chain 5, and finally to the crankshaft.

Further, the chain drive device 11 includes a chain 2, which is in a track between the sprockets 1, 3, 4, and 6.
By properly contacting the chain 5, the chain guides 7 for predetermining the orbits of the chains 2, 5, preventing the chains 2, 5 from fluttering, applying tension to the chains 2, 5, etc.
It is equipped with 8, 9, and 10.

[0004]

Certainly, with the structure shown in FIG. 5, the rotational driving force of the crankshaft can be transmitted to the camshaft, and the chain guides 7 to 10 are provided. It is possible to run the chains 2 and 5 along a desired track to prevent the chains 2 and 5 from fluttering and to apply a desired tension to the chains 2 and 5.
There is a problem that the vibrational excitation force is input to 10, and this is particularly remarkable in the case where the chain guide has a curved track and the track has a small radius of curvature like the chain guide 10.

The reason why the vibration exciting force is generated will be described by taking the chain 5 and the chain guide 10 as an example.
As shown in FIG. 6, when the chain 5 moves from the straight orbit on the air or the chain guide 10 to the curved orbit on the chain guide 10, and vice versa, there are many Since the chain 5 connecting the links of 1 always forms a polygonal trajectory on the curved trajectory, the chain 5 repeats the forced displacement variation of the distance ε, and the reaction of the chain inertial force generated by the forced displacement variation causes The chain guide 10 receives the vibration exciting force.

Then, the vibration excitation force is propagated to, for example, the engine main body which supports the chain guides 7 to 10, vibrates the engine block and is radiated as a part of the engine noise, and the noise in the vehicle interior is deteriorated. I was invited. Conventional techniques for solving such a problem include those disclosed in Japanese Utility Model Publication No. 55-93753, Japanese Utility Model Publication No. 63-82851, and the like. In these conventional techniques, chain guides are used. Although the problematic vibration was insulated by supporting the contact surface with the chain of the with an elastic body, it is necessary to absorb the vibration in the elastic body that supports the contact surface, so a sufficient vibration isolation effect In order to obtain the above, it is necessary to use a flexible elastic body, which causes another problem that durability against wear etc. is reduced and the life of the chain guide itself is shortened.

The present invention has been made by paying attention to the unsolved problems of the prior art as described above. Even if an elastic body or the like, which is problematic in terms of durability, is not used, vibration is applied from the chain. It is intended to provide a chain guide that is hard to input force.

[0008]

In order to achieve the above object, the present invention provides a chain guide which contacts a chain wound around a plurality of sprockets, in which the orbit of the contact surface with the chain has a radius of curvature R And a linear trajectory adjacent to the curved trajectory, and the linear trajectory has a tangent at the end point of the curved trajectory in a direction away from the center of curvature of the curved trajectory according to the following equation (1). This is an orbit existing on a straight line that has moved in parallel over the required distance ε.

Ε = (R + d / 2)-{(R + d / 2) ^2- (L / 2) ² } ^1/2 (1) However, in the above formula (1), L is the pitch of the chain,
d is the height of the links forming the chain.

[0010]

When the chain passes through a curved track, it draws a polygonal track instead of a perfect circular track. Therefore, the distance ε expressed by the above equation (1) near the boundary between the curved track and the straight track. However, since the linear trajectory is offset in parallel by the distance ε or more, such forced displacement fluctuation cannot occur.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an embodiment of the present invention, and is an enlarged view of a contact portion between a chain 5 and a chain guide 10. Since the entire structure of the chain drive device is the same as that of the conventional structure shown in FIG. 5, its illustration and description are omitted.

That is, the chain guide 1 in this embodiment
0 is different from the conventional chain guide in the shape of the contact surface 10A that contacts the chain 5, and the contact surface 10A
Is composed of a curved track forming part 10a and straight track forming parts 10b and 10c which are continuous at both ends thereof. As shown in FIG. 2, the curved track forming part 10a has a radius of curvature R and a starting point. It is formed so as to draw an arc from (end point) S to end point (end point) E. Since the shape of the contact surface 10A is symmetrical between the start point S side and the end point E side with the center line C therebetween, the following description will be given only on the start point S side.

On the other hand, the linear trajectory forming section 1 adjacent to the starting point S
0b is a tangent line 2 at the starting point S of the curved track forming portion 10a.
0 is formed so as to exist on the straight line 21 that is translated in the direction away from the center of curvature O of the curved track forming portion 10a by the distance ε represented by the above formula (1). The starting point S and the end of the linear trajectory forming portion 10a are spaced by a distance D. The distance D is half the pitch L of the chain 5 (see FIG. 3) L / 2. It is desirable to be longer than. However, if the distance D is made extremely long, the desired effect cannot be exerted, so the distance D is L
Optimally, slightly larger than / 2, at least L
Larger than should be avoided. That is, the distance D is actually set within the range of L / 2 ≦ D ≦ L (2).

Here, the chain 5 is the chain guide 10
When moving on the curved track forming portion 10a, since each link 5a forming the chain 5 draws a polygonal track, the center 5b of the link 5a is, as shown in FIG.
The distance ε expressed by the above equation (1) rather than the complete arc trajectory t
Only the inner orbit will be passed. Incidentally, the above equation (1) expressing the distance ε can be easily derived by applying the Pythagorean theorem to each dimensional relationship of FIG.

For this reason, each link 5a tends to generate the forced displacement variation of the distance ε when the straight track is changed to the curved track and when the curve track is changed to the straight track. If so, the linear trajectory forming portions 10b, 1
Since 0c is offset by the distance ε, there is no margin for the above-mentioned forced displacement fluctuation, and since the distance D satisfies the equation (2), it floats in the air on the chain guide 10. Since there is no link 5a that ends up, the orbit of the chain 5 changes continuously, as shown in FIG. Therefore, the vibration exciting force that is conventionally input from the chain 5 to the chain guide 10 is not generated due to such forced displacement variation, so that the vibration level is reduced.

In the above embodiment, the chain guide 1
The case where the present invention is applied to 0 has been described.
The present invention is naturally applicable to the other chain guides 7 to 9 shown in FIG. Further, in the above embodiment, the curved track forming portion 10a and the linear track forming portions 10b and 10c.
Although the and are connected in a stepwise manner, the connection is not limited to this, and may be connected smoothly as shown in FIG. 4, for example. However, also in this case, it is necessary to set the distance D so as to satisfy the above expression (2).

Further, in the above embodiment, the linear trajectory forming portion 10b is configured to be translated from the tangent line 20 by a distance ε, but the translation may be longer than the distance ε. However, if the translation distance is extremely long,
Link 5a floating in the air on the chain guide 10
It is only within the range that does not occur because there will be.

Further, in the above embodiment, both the linear trajectory forming portion 10b on the start point S side and the linear trajectory forming portion 10c on the end point E side are offset by the distance ε, but only one of them is offset. Even in this case, the vibration level can be reduced as compared with the conventional case. The chain drive device to which the present invention can be applied is not limited to the vehicle engine.

[0019]

As described above, according to the present invention,
Since the straight track adjacent to the curved track is offset parallel to the tangent at the end point of the curved track by the distance ε represented by the above formula (1), the chain track on the chain guide is continuous. Therefore, the forced displacement fluctuation that has conventionally occurred does not occur. Therefore, since the vibration excitation force does not occur, the vibration level can be reduced.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is an explanatory diagram of a contact surface shape of a chain guide.

FIG. 3 is an explanatory diagram of a relationship between a chain link and a contact surface.

FIG. 4 is an explanatory view of a main part of a contact surface shape of another embodiment.

FIG. 5 is a front view of a general chain drive device.

FIG. 6 is a conceptual diagram showing a configuration of a conventional chain guide.

[Explanation of symbols]

 1 Crank side sprocket 2,5 Chain 3,4 Sprocket 6 Cam side sprocket 7,8,9,10 Chain guide 10A Contact surface 10a Curved track forming part 10b, 10c Straight track forming part 11 Chain drive device 20 Tangent line 21 Straight line S Starting point (End point) E End point (End point)

Claims (1)

[Claims] 1. A chain guide for contacting a chain wound around a plurality of sprockets, wherein a trajectory of a contact surface with the chain includes a curved trajectory having a radius of curvature R and a linear trajectory adjacent to the curved trajectory. And, the linear trajectory is a trajectory that exists on a straight line that is parallel to the tangent line at the end point of the curved trajectory in a direction away from the center of curvature of the curved trajectory by a distance ε obtained by the following formula. A characteristic chain guide. ε = (R + d / 2)-{(R + d / 2) ^2- (L / 2)
² } ^{1/2 where} L is the pitch of the chain and d is the height of the links forming the chain.