Silent chain transmission

Abstract

To provide a silent chain transmission device capable of suppressing strength deterioration of a link plate and reducing abrasion thereof, and capable of suppressing chain floating to improve power transmission efficiency.SOLUTION: A silent chain transmission device comprises a silent chain 100 of an inner thigh engagement and inner thigh seating type, and a sprocket 130 (140) having sprocket teeth 131 (141). In a state where a plurality of link plates 110 in the silent chain 100 is wound around the silent chain 100 so as to mesh with all the sprocket teeth 131 (141), only an inside flank surface 113 of each of a pair of tooth parts 112a, 112b in the link plate 110 is configured to contact the sprocket teeth 131 (141).SELECTED DRAWING: Figure 5A

Description

Technical Field

[0001] The present invention relates to a silent chain transmission device in which a silent chain starts meshing with a sprocket tooth on the inner flank surface of the tooth portion in the link plate and then seats on the inner flank surface of the tooth portion to transmit power.

Background Art

[0002] As a chain transmission device, one using a silent chain wound around a plurality of sprockets is well-known and widely used for applications such as transmission of driving force, synchronization of rotation timing, change of rotational speed and torque, etc.

[0003] A silent chain is generally constituted by connecting a number of link plates each having a pair of tooth portions and a pair of pin holes bendably with a connecting pin inserted into each pin hole. In a silent chain transmission device, there are various meshing methods depending on the shape of the tooth portion of the link plate. For example, a so-called inside engagement and inside seating type silent chain transmission device in which the link plate starts meshing with the sprocket tooth on the inner flank surface of the tooth portion and seats on the inner flank surface of the tooth portion is known (see, for example, Patent Document 1).

[0004] In an inside engagement and inside seating type silent chain transmission device, since there is no transition between the outer flank surface and the inner flank surface at the meshing point of the tooth portion of the link plate with the sprocket tooth, it is possible to reduce the noise generated during meshing and seating with the sprocket.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] However, in conventional silent chain transmission systems with inward-groove meshing and inward-groove seating, if the seating point of the link plate on the sprocket teeth is located at the tip of the tooth, the distance from the grooved curve between the pair of teeth acting as a pivot point to the seating point becomes large, which causes stress to concentrate in the grooved curve and leads to a decrease in strength.

[0007] For these reasons, conventional silent chain transmission systems are generally configured as an in-toe meshing / out-toe seating type. However, silent chain transmission systems with an inward-to-outward meshing / outward-to-outer seating system had a problem: because the sprockets were designed to be small to improve wrapping, chain lifting occurred, worsening the tooth load distribution.

[0008] Furthermore, in silent chains, as the bending angle increases, the teeth of other link plates adjacent to the link plate in the chain width direction protrude relative to the inner flank surface of one link plate. For this reason, in silent chain transmission systems with inward-to-outward meshing and outward-to-outward seating, there have been significant constraints on the sprocket configuration, such as the need to design the sprocket teeth to be thin.

[0009] The present invention has been made based on the above circumstances, and aims to provide a silent chain transmission device that can suppress the reduction in strength and wear of the link plates, and can also suppress chain lifting to improve power transmission efficiency. [Means for solving the problem]

[0010] The present invention provides a silent chain transmission device comprising a silent chain formed by overlapping a plurality of link plates, each having a pair of front and rear teeth, in the chain width direction and connecting them alternately by connecting pins so as to be bendable, and a sprocket having a plurality of sprocket teeth that the silent chain can mesh with, wherein the silent chain transmits power by starting to mesh with the sprocket teeth on the inner flank surface of the tooth on the front side of the pair of teeth in the direction of chain travel, and then seating on the inner flank surfaces of each of the pair of teeth, wherein the plurality of link plates are configured such that, when the silent chain is wound around the sprocket so as to mesh with all of the sprocket teeth, only the inner flank surfaces of each of the pair of teeth contact the sprocket teeth, thereby solving the above problem. [Effects of the Invention]

[0011] According to the invention of claim 1, when the multiple link plates are wrapped around the silent chain so as to mesh with all the sprocket teeth of the sprocket, only the inner flank surfaces of each pair of teeth are in contact with the sprocket teeth, thereby suppressing chain lift and enabling an in-tooth meshing and in-tooth seating meshing method. Furthermore, because the tooth load can be evenly distributed across all link plates, and the tooth load can be reduced linearly after the link plate seats onto the sprocket teeth, it is possible to suppress the reduction in strength of the link plates and reduce wear. Moreover, by improving the balance of the tooth load distribution ratio, it is possible to improve the power transmission efficiency.

[0012] According to the configuration of claim 2, it is possible to suppress a decrease in strength by preventing stress concentration in the splinter-shaped curved portion between the pair of teeth, and to reduce wear. Furthermore, by reducing the contact force between the pair of teeth on the link plate and the sprocket teeth, it is possible to suppress energy loss and prevent a decrease in power transmission efficiency. Moreover, since the deviation of the contact position due to manufacturing tolerances between the link plate and the sprocket can be minimized, it is possible to reduce variations in the strength of the link plate and variations in NV (noise and vibration) performance.

[0013] According to the configuration of claim 3, even when the bending angle of the silent chain is large, the teeth of other link plates adjacent to the link plate in the chain width direction do not protrude outwards from the inner flank surface of one link plate, and an inward-to-inward meshing and seating method can be realized regardless of the number of sprocket teeth. According to the configuration of claim 4, it is possible to reliably avoid the outer flank surface of the tooth portion of the link plate coming into contact with the sprocket teeth. [Brief explanation of the drawing]

[0014] [Figure 1] This figure schematically shows the configuration of an example of the silent chain transmission device of the present invention. [Figure 2] This is a plan view showing an example of the configuration of a link plate in a silent chain. [Figure 3A] This diagram schematically shows the state in which the silent chain begins to mesh with the sprocket teeth. [Figure 3B] This diagram schematically shows the state in which the silent chain has engaged with the sprocket teeth. [Figure 3C] This diagram schematically shows the silent chain seated against the sprocket teeth. [Figure 4]It is a diagram schematically showing a state where a silent chain is wound around a sprocket so as to mesh with all sprocket teeth. [Figure 5A] It is a diagram schematically showing a meshing state between a link plate belonging to one guide row and sprocket teeth. [Figure 5B] It is a diagram schematically showing a meshing state between a link plate belonging to one guide row and a link plate belonging to another guide row adjacent in the chain width direction and sprocket teeth. [Figure 6] It is a diagram showing a change over time of tooth load from the start of meshing to disengagement of one link plate in the silent chain according to the present invention with respect to sprocket teeth. [Figure 7] It is a diagram showing a load sharing ratio of a tooth portion of a link plate in the silent chain according to the present invention. [Figure 8] It is a diagram schematically showing a configuration in another example of the silent chain transmission device according to the present invention. [Figure 9] It is a diagram showing a change over time of tooth load from the start of meshing to disengagement of one link plate in the silent chain transmission device shown in FIG. 8 with respect to sprocket teeth. [Figure 10] It is a diagram showing a load sharing ratio of a tooth portion of a link plate in the silent chain transmission device shown in FIG. 8.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, a silent chain transmission device according to an embodiment of the present invention will be described based on the drawings.

[0016] FIG. 1 is a diagram schematically showing a configuration in an example of the silent chain transmission device of the present invention. This silent chain transmission device includes a silent chain 100, and large sprockets 130 and small sprockets 140 having sprocket teeth with which the silent chain 100 can mesh and having different numbers of sprocket teeth and diameters.

[0017] The silent chain 100 is constructed by overlapping multiple link plates 110 in the chain width direction and connecting them alternately with connecting pins 125 so that they can be bent. In Figure 1, reference numeral 120 denotes a guide plate that is positioned on the outermost side in the chain width direction and loosely fitted into the link plate 110. This guide plate is used to press-fit and secure both ends of the connecting pin 125 to prevent it from coming loose.

[0018] As shown in Figure 2, the link plate 110 has shoulder portions 111 formed as curved surfaces on both the front and rear sides in the direction of chain progression, a pair of front and rear teeth portions 112a and 112b formed in a bifurcated shape, and a pair of front and rear pin holes 118. Each of the pair of teeth portions 112a and 112b has a planar inner flank surface 113 and a planar outer flank surface 114. In the silent chain 100 according to this embodiment, the connecting pin 125 is composed of, for example, a rocker joint pin consisting of a rocker pin 126 and a joint pin 127, but the connecting pin may be composed of a round pin.

[0019] The engagement method of this silent chain 100 with the large sprocket 130 and the small sprocket 140 is a so-called in-crotch engagement / in-crotch seating type. That is, as shown in Figure 3A, the silent chain 100 starts engaging with the sprocket teeth 131 of the large sprocket 130 and the sprocket teeth 141 of the small sprocket 140 at the inner flank surface 113 of the tooth portion 112a on the forward side in the direction of chain travel. Then, as shown in Figure 3B, the engagement point moves along the inner flank surface 113 toward the crotch-shaped curved portion 115 between the pair of tooth portions 112a and 112b as the engagement progresses, and finally, as shown in Figure 3C, it is configured to seat on the inner flank surface 113 of each of the pair of tooth portions 112a and 112b. In other words, the outer flank surfaces 114 of each of the pair of tooth portions 112a and 112b do not participate in the engagement.

[0020] Thus, as shown in Figure 4, the silent chain 100 can be wrapped around the sprocket so as to mesh with all of its teeth, regardless of the number of teeth on the sprocket. This allows for an inward-to-inward meshing / seating mechanism to be achieved with both the sprocket teeth 131 of the large sprocket 130 and the sprocket teeth 141 of the small sprocket 140, where the bending angle θ of the silent chain 100 is larger.

[0021] To explain in more detail, as shown in Figure 2, the link plate 110 in this silent chain 100 has a relief portion 116 on the outer flank surface 114 of each of the pair of teeth 112a and 112b to avoid contact with the sprocket teeth 131 and 141. The relief portion 116 is formed to curve inward with respect to the tangent T to the shoulder portion 111 and the teeth portions 112a and 112b, so that when the link plate 110 in the silent chain 100 is seated on the sprocket teeth 131 (141) of the large sprocket 130 (small sprocket 140), it is positioned inward in the front-rear direction from the inner flank surface 113 of the teeth portions 112a and 112b of other link plates 110 adjacent in the chain width direction.

[0022] Therefore, as shown in Figure 5A, when the silent chain 100 is wrapped around the large sprocket 130 or small sprocket 140 so as to engage with all the sprocket teeth 131(141), each of the multiple link plates 110a belonging to a single guide row aligned in the direction of chain progression has a gap formed between the outer flank surface 114a of each pair of teeth 112a, 112b and the sprocket teeth 131(141), so that only the inner flank surface 113a of each pair of teeth 112a, 112b contacts the sprocket teeth 131(141). Furthermore, in each of the multiple link plates 110b that are aligned in the direction of chain progression and belong to one guide row and other guide rows adjacent in the chain width direction, as shown in Figure 5B, a gap is formed between the outer flank surface 114b of each pair of teeth 112a, 112b and the sprocket teeth 131(141), so that only the inner flank surface 113b of each pair of teeth 112a, 112b is in contact with the sprocket teeth 131(141).

[0023] When D1 is the diameter of the circle PC1 that circumscribing the pitch line of the silent chain 100 wrapped around the sprocket (chain PCD), and D2 is the diameter of the circle PC2 that connects the seating points of the link plate 110 on the silent chain 100 with respect to the sprocket teeth 131 (141), then it is preferable that D2 / D1 be within the range of, for example, 0.9 or more and less than 1. If the seating point is set such that D2 / D1 is less than 0.9, the distance from the crotch-shaped curved portion 115, which acts as a pivot point, to the seating point becomes large, causing stress to concentrate on the crotch-shaped curved portion 115 and reducing the strength of the link plate 110. As a result, wear on the inner flank surface 113 of the link plate 110 and the sprocket teeth 131 and 141 becomes more likely, and the power transmission efficiency decreases.

[0024] Thus, with the silent chain transmission device described above, as shown by the solid curve in Figure 6, it is possible to significantly reduce the tooth load (contact force) acting on the teeth 112a and 112b of the link plate 110 when meshing with the sprocket teeth 131 (141), and to make the change in tooth load over time from the start of meshing to disengagement more gradual. Furthermore, in conventional silent chain transmission devices with inward-to-outward meshing and outward-to-outward seating, chain lift (load fluctuation indicated by α) occurs during the winding process, as shown by the dashed line in Figure 6. However, with the silent chain transmission device according to this embodiment, chain lift does not occur during the winding process, and the tooth load can be linearly reduced after the link plate 110 has seated on the sprocket teeth 131 (141). Furthermore, even for the small sprocket 140, which has a larger bending angle for the silent chain 100, it is possible to distribute the tooth load evenly across all the link plates 110 that mesh with the sprocket teeth 141, as shown by the solid curve in Figure 7. In Figure 7, the horizontal axis represents the sequence number of sprocket teeth relative to sprocket tooth t1 at the start of engagement, and the values ​​on the vertical axis represent the load sharing ratio of sprocket teeth t1 to t10.

[0025] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design modifications can be made without departing from the present invention as described in the claims.

[0026] For example, although the above embodiment described a silent chain transmission device having a speed ratio, as shown in Figure 8, a silent chain transmission device without a speed ratio may also be used, in which the silent chain 100 is wrapped around sprockets 150 having the same number of sprocket teeth and outer diameter. In the silent chain transmission device according to this embodiment, as shown by the solid curve in Figure 9, it is possible to reduce the tooth load acting on the teeth of the link plate 110 when meshing with the sprocket teeth, and to make the change in tooth load over time from the start of meshing to disengagement smoother. Furthermore, chain lifting does not occur during winding, and the tooth load can be reduced linearly after the link plate 110 has seated on the sprocket teeth. And, as shown by the solid curve in Figure 10, it is possible to distribute the tooth load evenly across all link plates 110 that mesh with the sprocket teeth. In Figures 9 and 10, the dashed curves represent the results of a conventional in-tooth meshing / out-tooth seating type silent chain transmission device, and the tooth load fluctuation indicated by α in Figure 9 is due to chain lifting. In Figure 10, the horizontal axis represents the sprocket tooth sequence number based on sprocket tooth t1 at the start of meshing, and the values ​​on the vertical axis represent the load sharing ratio of sprocket teeth t1 to t23. [Explanation of symbols]

[0027] 100 ··· Silent Chain 110 ··· Link Plate 110a ··· Link Plate 110b ··· Link Plate 111...Shoulder 112a ··· Teeth 112b ··· Teeth 113 ··· Inner flank surface 113a ··· Inner flank surface 113b ··· Inner flank surface 114 ··· Outer flank surface 114a ··· Outer flank surface 114b ··· Outer flank surface 115 ··· Crotch-shaped curve 116 ··· Escape Department 118... Pinhole 120 ··· Guide Plate 125... Connecting pin 126... Rocker pins 127 ··· Joint pin 130... Large sprocket 131... Sprocket teeth 140... Small sprocket 141... Sprocket teeth 150... Sprocket

Claims

1. A silent chain transmission device comprising a silent chain formed by overlapping a plurality of link plates, each having a pair of front and rear teeth, in the chain width direction and connecting them alternately by connecting pins so as to be bendable, and a sprocket having a plurality of sprocket teeth that the silent chain can mesh with, wherein the silent chain begins to mesh with the sprocket teeth at the inner flank surface of the tooth on the front side in the chain direction of the pair of teeth, and then seats at the inner flank surfaces of each of the pair of teeth to transmit power, A silent chain transmission device characterized in that, when the plurality of link plates are wound so as to mesh with all the sprocket teeth of the sprocket, only the inner flank surfaces of each of the pair of teeth contact the sprocket teeth.

2. The silent chain transmission device according to claim 1, characterized in that when D1 is the diameter of the circle circumscribing the pitch line of the silent chain wrapped around the sprocket, and D2 is the diameter of the circle connecting the seating points of the link plates in the silent chain with respect to the sprocket teeth on the sprocket, D2 / D1 is in the range of 0.9 or more and less than 1.

3. The silent chain transmission device according to claim 1, characterized in that the plurality of link plates each have a relief portion on the outer flank surface of the pair of teeth that avoids contact with the sprocket teeth.

4. The silent chain transmission device according to claim 3, characterized in that the relief portion is formed such that, when the link plate in the silent chain is seated on the sprocket teeth of the sprocket, it is positioned inward in the front-rear direction from the inner flank surface of the teeth of another link plate adjacent in the chain width direction.

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