JP2002349675A - Sprocket for silent chain and silent chain transmitting device for internal combustion engine using the sprocket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent gearing noise and partial wearing from occurring, owing to the interference with a guide link plate 6 resulting from inclination of a sprocket 2 due to chain tension. SOLUTION: A silent chain 1 is composed of overlapping and connecting a plurality of main link plates and guide link plates 6 successively. The sprocket 2 provides chamfered parts 7a, 7b at both sides of tooth end, a chamfered part 7b is larger, compared with the other chamfered part 7a, corresponding to that a gearing point is displaced to an end of the axial direction followed by inclination of the sprocket 2. For this reason, even if the sprocket 2 is inclined temporarily, this will not interfere with the guide link plate 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silent chain type transmission device used for a valve train of an internal combustion engine, and more particularly to an improvement of a sprocket thereof.

[0002]

2. Description of the Related Art For example, in a valve train of an internal combustion engine,
In recent years, there has been a tendency to employ more and more silent chain type transmission devices that are more reliable than timing belts and more quiet than roller chains at the same time (for example, see JP-A-2000-27109). .

FIGS. 9 and 10 show the structure of a general silent chain 1. As shown, the silent chain 1 includes a plurality of main link plates 4 that mesh with teeth 3 on the outer periphery of a sprocket 2. The connecting pins 5 are alternately connected in the longitudinal direction. Each main link plate 4 basically has the same shape.
A valley is formed between the pair of peaks, and a through hole through which the connection pin 5 penetrates is provided at the position of each peak. On both sides of the silent chain 1 in which a plurality of main link plates 4 are stacked, guide link plates 6 each having a shape without a valley are arranged. 5
Are linked by As shown in the drawing, the inner space between the pair of guide link plates 6 is set to be slightly larger than the tooth width of the teeth 3 of the sprocket 2. 6
Are opposed to each other. By the guide link plate 6, the silent chain 1 is correctly guided with respect to the sprocket 2, and the silent chain 1
Is prevented in the tooth width direction, and the sprocket 2 is prevented from falling off.

Further, since the guide link plate 6 is provided as described above, in order to avoid interference between the tip of the teeth 3 and the guide link plate 6 when the silent chain 1 and the sprocket 2 are engaged with each other. As shown, appropriate chamfers 7 are formed on both sides of the tooth tip.

[0005]

When the chamfers 7 are cut out on both sides of the teeth 3 as described above, the substantial meshing contact area between the sprocket 2 and the silent chain 1 is reduced by that amount. This is not preferable in that the contact pressure at the time of contact increases. However, on the other hand, if the chamfered portion 7 is too small, the interference between the tooth tip side surface and the guide link plate 6 may occur transiently.

For example, in a configuration in which a sprocket 2 provided on a camshaft of an internal combustion engine is driven by a silent chain 1, the sprocket 2 is attached to a front end of a camshaft protruding forward from a bearing portion of a cylinder head. The sprocket 2 is tilted toward the inner circumference side of the silent chain 1 due to the tension of the silent chain 1 because it is supported in the holding state. In particular, since the silent chain 1 is subject to the rotational fluctuation of the internal combustion engine and the driving torque of the camshaft, the tension always fluctuates greatly. With this fluctuation, the clearance of the bearing portion and the bending of the camshaft are bent. Due to the deformation, the sprocket 2 transiently tilts relatively largely. When the sprocket 2 is inclined in this way, as shown in FIG. 11, the outer periphery of the sprocket 2 is obliquely offset with respect to the running path of the silent chain 1, and one of the guide link plates 6 and the tooth tip Will interfere with one side. In the drawing, the interference area is shown by hatching.

Since the direction of inclination of the sprocket 2 due to the tension of the silent chain 1 is fixed, the above-described interference between the guide link plate 6 and the tooth tip always occurs on one side of the sprocket 2. Therefore, uneven wear of the sprocket 2 and the guide link plate 6 becomes a problem. Further, in a situation where such interference occurs, a loud noise is generated at the time of meshing.

[0008]

Therefore, according to the present invention, the size of the chamfer of the tooth tip of the sprocket is made asymmetric in consideration of the inclination of the sprocket due to tension.

More specifically, the invention according to claim 1 is a silent chain sprocket in which a silent chain having guide link plates disposed on both sides of a plurality of main link plates is wound around the tooth link. Each chamfer is provided to avoid interference with the guide link plate, and the sprocket is tilted due to the tension of the silent chain.
One of the chamfers on the same side as the axial displacement direction of the outer periphery of the sprocket at the point of engagement with the silent chain is formed to be larger than the other chamfer.

[0010] The chamfered portion can be formed in an appropriate shape such as a tapered straight line, an arc having an appropriate curvature, and a more complicated curve. The section is larger than the other chamfer. More specifically, when assuming a smaller chamfer and a symmetric chamfer, all of the virtual chamfers are included, and one of the chamfers is assumed to be larger than this. Is provided.

When the sprocket is inclined by the tension of the silent chain, the outer peripheral portion of the sprocket is displaced in the axial direction with the inclination. In other words, it is displaced forward at a certain point in the circumferential direction, and displaced rearward at a point 180 ° away from the point on the opposite side. At this time, paying attention to the point of engagement with the silent chain, if this point of engagement is displaced forward, for example, the silent chain trying to travel to the normal position will interfere with the guide link plate located in front of it. Is more likely to occur. Therefore, in such a case, interference is avoided by forming a large chamfered portion on the front side. Conversely, if the meshing point is displaced rearward, interference with the guide link plate located behind the silent chain that tends to run at the normal position is likely to occur. In such a case, interference can be avoided by forming a large chamfered portion on the rear side.

The invention according to claim 2 relates to a silent chain type transmission device for an internal combustion engine using such a sprocket, wherein the sprocket according to claim 1 is provided as a driven sprocket.
A silent chain is wound around another driving sprocket. In such a configuration, the sprocket to be driven is inclined toward the inner peripheral side of the chain due to the tension of the silent chain, but interference can be avoided by making the chamfered portion asymmetric in consideration of the inclination.

[0013] The invention according to claim 3 is, for example, a DO
In order to be suitable for an HC type valve gear or a V type internal combustion engine, two driven sprockets are provided, and a silent chain is wound around the three driven sprockets. . In such a configuration, the sprockets to be driven are each tilted toward the inner circumferential side of the chain due to the tension of the silent chain, but interference is caused by making the chamfered portion asymmetrical in consideration of the tilt at each meshing point. Can be avoided.

In a more specific aspect of the present invention,
The driven sprockets are respectively attached to the tips of two rotating shafts rotatably supported so as to protrude from the main body of the internal combustion engine, and the chamfers on the front side of these sprockets have rear faces respectively. It is formed larger than the chamfer on the side.

Further, in the silent chain type transmission device for an internal combustion engine according to claim 5, the silent chain is such that the guide link plate on one side corresponding to a relatively large chamfered portion is connected to the other guide link plate. In comparison, it is formed longer toward the inner peripheral side of the sprocket. That is, when the chamfered portion is enlarged, the gap between the tooth side surface at the beginning of the engagement is increased. In addition, in a state where the sprocket is inclined by the tension, on the side having the large chamfered portion, the depth of engagement between the teeth and the silent chain becomes relatively shallow with the inclination. In response to such a phenomenon, by extending the guide link plate as in the present invention, it is possible to reliably guide the silent chain even when the sprocket is inclined.

[0016]

According to the present invention, the chamfered portion of the tooth tip of the sprocket is asymmetrical in advance corresponding to the inclination direction at the meshing point of the sprocket due to the chain tension, thereby accommodating the formation of the chamfered portion. The interference with the guide link plate due to the inclination of the sprocket can be reliably avoided while minimizing the decrease in the meshing contact area. Therefore, it is possible to prevent the generation of the meshing noise and the uneven wear of the guide link plate due to the interference.

Further, by extending the guide link plate having the larger chamfered portion, the running stability of the chain can be ensured even when the sprocket is inclined. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a main part of a sprocket 2 according to the present invention, together with a silent chain 1. In particular, a state where the sprocket 2 is inclined by the chain tension is shown. Note that the silent chain 1 is configured by overlapping and linking a plurality of main link plates as described above, but FIG. 1 schematically illustrates only the entire outer shape.

As shown, the teeth 3 of the sprocket 2
Is provided with chamfered portions 7a and 7b on both sides of the tooth tip. In the present invention, these chamfered portions 7a and 7b are asymmetric, and the chamfered portions 7a and 7b are 7b is larger. Specifically, the chamfered portion 7a is formed of an arc having a radius Ra in contact with the tooth base side surface 8, and the cutout amount at the tooth tip is d. In addition, the chamfered portion 7b has a tooth base side surface 8
, And the notch amount at the tooth tip is e. Then, Ra <Rb and d <e.

In this example, when the sprocket 2 is inclined by the tension, the outer peripheral portion of the sprocket 2 at the meshing point is displaced downward as shown in the figure. However, as described above, by setting the chamfered portion 7b large in advance, interference with the guide link plate 6 shown in the lower part of the figure is reliably avoided.

FIG. 2 shows a different embodiment of the chamfer 7b. The chamfered portion 7b is formed of an arc having a radius Rc in contact with the tooth base portion side surface 8, and the notch amount at the tooth tip is d equal to the notch amount of the small chamfered portion 7a. And
There is a relationship of Ra <Rc. Incidentally, it is desirable that Ra <Rb <Rc when compared with the embodiment of FIG. Even in such a configuration, the chamfered portion 7b is connected to the other chamfered portion 7b.
It occupies a larger area than that in which a is symmetric.

FIG. 3 shows an embodiment in which the silent chain 1 combined with the sprocket 2 constructed as described above is improved. The guide link plate 6b on the chamfered portion 7b side is connected to the other side. The guide link plate 6a extends longer toward the inner peripheral side of the sprocket 2. FIG. 4 shows each guide link plate 6a,
6b is shown in comparison. By forming the guide link plate 6b to be long in this manner, excessive play does not occur even with the large chamfered portion 7b, and the running stability of the silent chain 1 is improved. Further, even when the sprocket 2 is inclined by the tension, the silent chain 1 is reliably guided.

FIG. 5 shows an example of guide link plates 6a and 6b used in the silent chain 1 in which sprockets are meshed on both the inner and outer peripheral sides. The guide link plate 6b on the side of the portion 7b is
It is formed longer toward the inner circumference of the chain than a. A ridge 9 and a valley 10 for meshing with a sprocket on the outer peripheral side of the chain are formed on the outer peripheral side of the chain, that is, on the rear side of each guide link plate 6a.

Next, FIG. 6 shows an embodiment in which the present invention is applied to a silent chain type transmission device in a valve train of an internal combustion engine. In this transmission device, a crank sprocket 11, which is a driving sprocket, is located below, and a pair of cam sprockets 2, which are driven sprockets, are arranged above, and between these three members,
A silent chain 1 is wound. Note that the crank sprocket 11 rotates clockwise in the drawing, and accordingly, the silent chain 1 runs along the rotation direction. A chain guide 1 is provided between the crank sprocket 11 and the cam sprocket 2.
2 and 13 are provided, and a chain guide 14 is provided between the pair of cam sprockets 2. Note that the chain guide 12 on the loose side of the chain
Is of a movable type, and is provided with a hydraulic tensioner 15 at an upper portion so as to apply an appropriate tension. In such a chain arrangement, the engagement points of the cam sprocket 2 are point A and point B, respectively.

The cam sprocket 2 is attached to the front end of a camshaft (not shown), and projects from the bearing of the camshaft in a so-called cantilever manner. As a result, as shown by the arrow F in FIG.

FIG. 7 shows the inclined state of the cam sprocket 2 at the mesh point A from the lower left side indicated by the arrow X in FIG. 6, more specifically, from the direction perpendicular to the running direction of the silent chain 1 at the mesh point A. Shown as seen. Accordingly, the right side of FIG. 7 is the front of the engine.
Here, the engagement point A due to the inclination of the cam sprocket 2
Focusing on the axial displacement of, as is clear from the figure,
It is displaced to the right in FIG. In other words, in a general configuration in which the chain winding angle with respect to the cam sprocket 2 does not exceed 180 °, the position where the meshing point A is included within the range of 180 ° to be displaced forward in the engine along the direction of the force F. Because of the relationship, the meshing point A
Will always be displaced forward of the engine. Therefore, when such an inclination due to the tension occurs, there is a possibility that the tooth tip and the guide link plate 6 may interfere with each other on the front surface 2a side of the sprocket 2. Therefore, the cam sprocket 2 (the cam sprocket 2 on the left side in FIG. 6) corresponding to the point A which is the first meshing point along the rotation direction of the silent chain 1
With regard to (1), the chamfer on the front surface 2a side needs to be formed relatively larger than the chamfer on the rear surface 2b side. In addition, the line L in the figure shows the traveling center line of the silent chain 1.

FIG. 8 shows the inclined state of the cam sprocket 2 at the mesh point B as viewed from above indicated by the arrow Y in FIG. 6, that is, from the direction perpendicular to the running direction of the silent chain 1 at the mesh point B. As shown. Therefore, the lower part of FIG. 8 is the front of the engine. Focusing on the axial displacement of the mesh point B due to the inclination of the cam sprocket 2, the mesh point B located at the uppermost portion of the cam sprocket 2 is displaced downward in FIG. Therefore, when the inclination due to the tension occurs, there is a possibility that the tooth tip and the guide link plate 6 may interfere with each other on the front surface 2a side of the sprocket 2. Therefore,
As for the cam sprocket 2 corresponding to the meshing point B (the cam sprocket 2 on the right side in FIG. 6), the chamfer on the front surface 2a needs to be formed relatively larger than the chamfer on the rear surface 2b. In addition, the line L in the figure shows the traveling center line of the silent chain 1.

Here, the cam sprocket 2 on the left side and the cam sprocket 2 on the right side in FIG. It is more desirable to set the sizes of the chamfered portions of the entire surface 2a and the rear surface 2b in consideration of the degree of the influence of the inclination in the above.

The present invention is applicable not only to the valve operating mechanism for directly driving the cam sprocket from the crank sprocket as described above, but also to a two-stage type valve operating mechanism for sequentially transmitting the driving force via an intermediate sprocket. It is possible to apply. Further, the present invention can be applied to a transmission device for driving an auxiliary machine other than the valve operating mechanism.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a main part of a sprocket according to the present invention, together with a silent chain.

FIG. 2 is an enlarged view of a main part, similar to FIG. 1, showing an embodiment in which the shape of a chamfer is changed.

FIG. 3 is a sectional view of a chain showing an embodiment in which one guide link plate is elongated.

FIG. 4 is a plan view showing the respective guide link plates in comparison.

FIG. 5 is a plan view similar to FIG. 4, showing an example of a guide link plate used for a silent chain that also meshes on the outer peripheral side.

FIG. 6 is a front view of the entire silent chain type transmission device used for the valve mechanism of the internal combustion engine.

FIG. 7 is an explanatory view showing the meshing point A viewed from the direction of arrow X in FIG. 6;

FIG. 8 is an explanatory diagram showing the meshing point B as viewed from the direction of arrow Y in FIG. 6;

FIG. 9 is a plan view of a general silent chain.

FIG. 10 is a sectional view of the same.

FIG. 11 is an explanatory diagram of interference caused by the inclination of the sprocket.

[Explanation of symbols]

 1: Silent chain 2: Sprocket 6, 6a, 6b: Guide link plate 7, 7a, 7b: Chamfer

Claims (5)

[Claims] 1. A silent chain sprocket in which a silent chain having guide link plates disposed on both sides of a plurality of main link plates is wound around, and interference with the guide link plates on both sides of a tooth tip is avoided. One of the chamfers is provided on the same side as the axial displacement direction of the outer periphery of the sprocket at the point of engagement with the silent chain with respect to the inclination of the sprocket due to the tension of the silent chain. Is formed larger than the other chamfered portion. 2. A silent chain for an internal combustion engine, wherein the sprocket according to claim 1 is provided as a driven sprocket, and a silent chain is wound between the sprocket and another driving sprocket. Type transmission device. 3. The apparatus according to claim 2, further comprising two driven sprockets,
3. A silent chain is wound around the drive sprocket and the other drive sprocket.
4. The silent chain type transmission device for an internal combustion engine according to claim 1. 4. The driven sprockets are respectively attached to the tips of two rotating shafts rotatably supported so as to protrude from the main body of the internal combustion engine, and the front faces of these sprockets are provided. The silent chain type transmission device for an internal combustion engine according to claim 3, wherein each of the chamfers is formed larger than a chamfer on the rear surface side. 5. The silent chain according to claim 1, wherein the guide link plate on one side corresponding to the relatively large chamfered portion is formed longer on the inner circumferential side of the sprocket than the other guide link plate. The silent chain type transmission device for an internal combustion engine according to any one of claims 2 to 4, characterized in that: