sprocket

Abstract

The present application provides a chain wheel with high strength and light weight. One embodiment of the present application relates to a chain wheel provided with a plurality of mounting holes 20, a plurality of chain wheel teeth 30, a first opening 40, and a second opening 50. The mounting holes 20 are formed at equal intervals in the circumferential direction. The chain wheel teeth 30 are arranged on the outer periphery. The first opening 40 is formed in a substantially triangular shape, two corners of which respectively face the mounting holes 20, and the remaining corner is arranged on the outer periphery. The second opening 50 is formed in a substantially triangular shape, one corner of which faces the mounting hole 20, and the remaining two corners are arranged on the outer periphery. A first grid 70, in which the driving force and the load reaction force are opposite, and a second grid 80, in which the driving force and the load reaction force are opposite, are defined between the second opening 50 and the first opening 40.

Description

TECHNICAL FIELD

[0001] The present application relates to a sprocket. BACKGROUND

[0002] A mechanism that uses a chain and a sprocket to transmit a rotational force (a driving force or a braking force) is widely used in, for example, two-wheeled motor vehicles and the like. For a sprocket, there are two opposing demands of strength and light weight. Therefore, in, for example, Patent Literature 1, a technique of forming an opening for achieving light weight on a sprocket to the extent that the strength is not impaired is described.

[0003] PATENT LITERATURE

[0004] Patent Literature 1: Japanese Utility Model Registration No. 3224267 SUMMARY

[0005] In Patent Literature 1, although a circular opening is formed, in order to more greatly improve the strength and achieve light weight, the shape and arrangement of the opening need to be designed. The present application aims to provide a sprocket that is both strong and light in weight.

[0006] One embodiment of the present application relates to a sprocket that includes mounting holes, a plurality of sprocket teeth, a first opening, and a second opening, the mounting holes are formed at equal intervals in the circumferential direction, the sprocket teeth are provided on the outer periphery, the first opening is formed in a substantially triangular shape, two of the corners thereof face the mounting holes, respectively, and the remaining one corner is arranged on the outer periphery side, the second opening is formed in a substantially triangular shape, one of the corners thereof faces the mounting hole, and the remaining two corners are arranged on the outer periphery side, and a first grid that opposes a driving force and a load reaction force and a second grid that opposes the driving force and the load reaction force are defined between the second opening and the first opening.

[0007] In the sprocket of the above-described embodiment, the inclination angle of the center line of the portion of the first grid having the smallest width with respect to the radial direction can be smaller than the inclination angle of the center line of the portion of the second grid having the smallest width with respect to the radial direction.

[0008] In the sprocket of the above-described embodiment, the intersection of a first reference line that passes through the center of the mounting hole and is parallel to the center line of the portion of the first grid having the smallest width and a second reference line that passes through the center of the mounting hole and is parallel to the center line of the portion of the second grid having the smallest width can be located near the addendum circle of the sprocket teeth.

[0009] In the sprocket of the above-described embodiment, the ratio of the angle from the intersection to the mounting hole on the first grid side with respect to the angle between the two adjacent mounting holes can be 0.20 or more and 0.45 or less.

[0010] In the sprocket of the above embodiment, the minimum width of the first grid bar can be larger than the minimum width of the second grid bar.

[0011] In the sprocket of the above embodiment, the tangent line of the side edge of the first opening side at the portion of the first grid bar where the width is the smallest can pass through the rotation center side of the mounting hole, the tangent line of the side edge of the second opening side at the portion of the first grid bar where the width is the smallest can pass through the outer periphery side of the mounting hole, the tangent line of the side edge of the first opening side at the portion of the second grid bar where the width is the smallest can pass through the mounting hole, and the tangent line of the side edge of the second opening side at the portion of the second grid bar where the width is the smallest can pass through the outer periphery side of the mounting hole.

[0012] According to the present application, a sprocket with high strength and light weight can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 FIG. 1 is a plan view of a sprocket according to an embodiment of the present application.

[0014] Figure 2 FIG. 4 is a partial enlarged view of a detailed shape of the sprocket. Figure 1

[0015] Figure 3 FIG. 6 is a view showing a model shape of the sprocket according to the embodiment. DETAILED DESCRIPTION

[0016] Hereinafter, an embodiment of the present application will be described with reference to the drawings. Figure 1 FIG. 1 is a plan view of a sprocket 1 according to an embodiment of the present application (a view as seen from the direction of the rotation axis). Figure 2 FIG. 2 is a partial enlarged plan view of a detailed shape of the sprocket 1.

[0017] Figure 1 The sprocket 1 is a driven sprocket that is driven by a chain not shown and that is used to drive a rotation shaft not shown that is fixed to the sprocket 1. The sprocket 1 rotates in the counterclockwise direction. That is, the outer periphery of the sprocket 1 is driven by the chain, and a torque in the counterclockwise direction is transmitted.

[0018] The sprocket 1 is formed in a substantially circular plate shape, and has a central opening 10, a plurality of mounting holes 20, a plurality of sprocket teeth 30, a plurality of first openings 40, and a plurality of second openings 50. The first openings 40 and the second openings 50 are alternately formed in the circumferential direction as seen from the rotation center Cs of the sprocket 1.

[0019] ​In the sprocket 1, a connecting bar 60 connecting between portions forming the mounting hole 20 is defined between the central opening 10 and the first opening 40. A first bar 70 opposite in driving force and load reaction force, and a second bar 80 opposite in driving force and load reaction force are defined between the second opening 50 and the first opening 40. An outer peripheral bar 90 supporting the sprocket teeth 30 is defined radially outward of the mounting hole 20. Note that "opposite in driving force and load reaction force" means that the driving force and the load reaction force acting on the bar as a whole act in the compression direction, and "opposite in driving force and load reaction force" means that the driving force and the load reaction force acting on the bar as a whole act in the tensile direction.

[0020] In the sprocket 1, torque is mainly transmitted by the first bar 70, and the second bar 80 maintains the inclination angle of the first bar 70 and suppresses stress concentration due to deformation of the first bar 70. In the driven sprocket, the first bar 70 extends obliquely from the mounting hole 20 toward the outer periphery to the rear side in the rotation direction, and the second bar 80 extends obliquely from the mounting hole 20 toward the outer periphery to the front side in the rotation direction. In the driving sprocket, the rotation direction is reversed.

[0021] The central opening 10 is formed in the center of the sprocket 1, and it forms a space in which a rotation shaft is disposed. Further, the central opening 10 is advantageous in lightening the sprocket 1. The size of the central opening 10 can be defined according to the required specifications.

[0022] The mounting hole 20 is formed equidistantly in the circumferential direction in the vicinity of the central opening 10, and a bolt for mounting the sprocket 1 to a not-shown hub fixed to the rotation shaft is inserted. The distance between the mounting hole 20 and the central opening 10 can be set to a distance that can ensure a minimum area required for fastening the bolt. In order to achieve fastening by the bolt, an auxiliary structure such as a counterbore 21 can also be formed on the outside of the mounting hole 20. The size, number, radial position, etc. of the mounting hole 20 can be defined according to the required specifications.

[0023] The sprocket teeth 30 are formed in the outer periphery of the sprocket 1 in a specified shape and at a specified pitch to engage with a chain. The shape and number of the sprocket teeth 30 can be defined according to the required specifications. Therefore, the outer diameter of the sprocket 1 can be determined according to the required specifications of the sprocket teeth 30.

[0024] The first opening 40 is formed in a substantially triangular shape, and in this embodiment, in a triangular shape with the corners chamfered. Two corners of the first opening 40 face the mounting hole 20, and the remaining one corner of the first opening 40 is disposed on the outer periphery side and faces the sprocket tooth 30. Note that the "substantially triangular shape" refers to a shape having three sides with relatively small curvature and three corners with relatively large curvature, and more specifically, refers to a shape having three corners defined as regions in which the angle difference between the tangents of the points on the outer edge of the triangle, as viewed from the center of gravity, is 10° or more. That is, each side of the first opening 40 can be a curved line with relatively small curvature compared to the corners, and the chamfered shape of each corner of the first opening 40 can be curved in multiple segments with a portion having relatively large curvature. In particular, the side connecting the two corners of the first opening 40 that face the mounting hole 20 is preferably a circular arc concentric with the central opening 10 so as to substantially fix the width of the connection lattice 60. On the other hand, in order to increase the area of the first opening 40 and ensure the strength of the first lattice 70 and the second lattice 80, the remaining two sides of the first opening 40 are preferably formed at least partially in a straight line. Furthermore, the corner "facing" the mounting hole refers to the corner closest to the mounting hole among the corners.

[0025] The second opening 50 is formed in a substantially triangular shape. One corner of the second opening 50 faces the mounting hole 20, and the remaining two corners of the second opening 50 are disposed on the outer periphery side and face the sprocket tooth 30. Each side of the second opening 50 can also be a curved line, and in particular, the side connecting the two corners disposed on the outer periphery side is preferably a circular arc concentric with the central opening 10 so as to define the outer periphery lattice 90 having a fixed width that supports the sprocket tooth 30. On the other hand, in order to increase the area of the second opening 50 and ensure the strength of the first lattice 70 and the second lattice 80, the remaining two sides of the second opening 50 are preferably formed in a straight line that is at least partially parallel to the side edge on the first opening 40 side of the first lattice 70 and the second lattice 80, respectively.

[0026] The minimum width of the first lattice 70 is preferably greater than the minimum width of the second lattice 80. That is, in order to obtain strength, the width of the first lattice 70, which mainly transmits torque, is preferably relatively large, and in order to reduce weight, the width of the second lattice 80, which assists the first lattice 70, is preferably relatively small.

[0027] The tangent line L71 of the side edge on the first opening 40 side of the portion of the first lattice 70 having the smallest width is preferably located on the rotation center Cs side of the mounting hole 20. Furthermore, the tangent line L72 of the side edge on the second opening 50 side of the portion of the first lattice 70 having the smallest width is preferably located on the outer periphery side of the mounting hole 20. That is, the minimum width of the first lattice 70 is preferably greater than the diameter of the mounting hole 20 having a size in which a bolt having a cross-sectional area necessary for the torque to be transmitted can be inserted.

[0028] Further, the center line Lcl of the portion of the first lattice bar 70 having the smallest width preferably passes through the mounting hole 20. Note that the center line Lcl is a center line of a line segment (a line segment connecting between the closest points) indicating the shortest distance between the first opening 40 and the second opening 50. According to the above-described structure, torque transmitted from the chain via the first lattice bar 70 can be efficiently transmitted to the hub of the sprocket 1 mounted with the mounting hole 20.

[0029] The tangent line L81 of the side edge of the portion of the second lattice bar 80 having the smallest width on the first opening 40 side preferably passes through the mounting hole 20, more preferably the center Ch of the mounting hole 20. Further, the tangent line L82 of the side edge of the portion of the second lattice bar 80 having the smallest width on the second opening 50 side is preferably located on the outer peripheral side of the mounting hole 20. Further, the center line Lc2 of the portion of the second lattice bar 80 having the smallest width preferably passes through the mounting hole 20. According to the above-described structure, the sprocket 1 can be made as light as possible, and deformation of the first lattice bar 70 can be suppressed to increase the strength of the sprocket 1. In particular, the tangent line L81 of the side edge of the portion of the second lattice bar 80 having the smallest width on the first opening 40 side passes through the mounting hole 20, thereby enhancing the effect of increasing the first opening 40 and making the sprocket 1 light.

[0030] The inclination angle a of the center line Lcl of the first lattice bar 70 with respect to the radial direction of the sprocket 1 is preferably smaller than the inclination angle β of the center line Lc2 of the second lattice bar 80 with respect to the radial direction. By making the inclination angle a of the first lattice bar 70 smaller than the inclination angle β of the second lattice bar 80, the length of the first lattice bar 70 will be smaller than the length of the second lattice bar 80, and thus the increase in the area and even the mass of the sprocket 1 becomes relatively small when the width of the first lattice bar 70 is increased for the purpose of increasing the strength.

[0031] Specifically, as the lower limit of the inclination angle a of the center line Lcl of the first lattice bar 70, 40° is preferable, and 45° is more preferable. On the other hand, as the upper limit of the inclination angle a of the center line Lcl of the first lattice bar 70, 60° is preferable, and 55° is more preferable. By setting the inclination angle a of the first lattice bar 70 within the above-described range, in a typical two-wheeled motor vehicle, the bending stress and the shear stress acting on the first lattice bar 70 can be made relatively small, and thus torque acting on the sprocket 1 can be transmitted with relatively high efficiency.

[0032] The intersection point P of the first reference line Lr1 passing through the center Ch of the mounting hole 20 and parallel to the center line Lc1 of the first lattice 70 and the second reference line Lr2 passing through the center Ch of the mounting hole 20 and parallel to the center line Lc2 of the second lattice 80 is preferably located in the vicinity of the addendum circle of the sprocket tooth 30. Note that the "vicinity of the addendum circle" refers to a portion having a radial distance from the addendum circle that is less than the tooth height, and preferably less than the addendum height. According to the above-described structure, the force transmitted from the chain can be accurately decomposed into a component that transmits torque along the first lattice 70 and a component that is orthogonal to the first lattice 70 and is absorbed by the second lattice 80, and thus torque can be efficiently transmitted.

[0033] The lower limit of the ratio (γ / θ: hereinafter referred to as the lattice angle ratio) of the angle γ from the intersection point P of the first reference line Lr1 and the second reference line Lr2 to the center Ch of the mounting hole 20 on the side of the first lattice 70 with respect to the angle θ between adjacent two mounting holes 20, as a reference based on the rotation center Cs of the sprocket 1, is preferably 0.20, more preferably 0.30. On the other hand, the upper limit of the lattice angle ratio is preferably 0.45, more preferably 0.40. By setting the lattice angle ratio to be equal to or greater than the above lower limit, the maximum stress acting on the first lattice 70 can be made relatively small. Further, by setting the lattice angle ratio to be equal to or less than the above upper limit, the total length of the first lattice 70 and the second lattice 80 can be suppressed, and thus the sprocket 1 can be made lightweight by reducing the area of the first lattice 70 and the second lattice 80.

[0034] As described above, the sprocket 1 is lightweight despite having a large strength and being capable of transmitting a large torque, by having the first lattice 70 extending obliquely from the mounting hole 20 so that the driving force and the load reaction force are opposite to each other, and the second lattice 80 extending obliquely from the mounting hole 20 so that the driving force and the load reaction force are opposite to each other, and by forming the first opening 40 and the second opening 50 that define the first lattice 70 and the second lattice 80.

[0035] The design of the sprocket 1 is not necessarily limited, and can be performed according to a method including the following steps based on a required specification: a step of arranging the central opening 10, the mounting hole 20, and the sprocket tooth 30; a step of drawing a circle that determines the outer edge of the lattice 60 (the edge connecting the two corners of the first opening 40 facing the mounting hole 20) and a circle that determines the inner edge of the outer peripheral lattice 90 (the edge connecting the two corners of the second opening 50 arranged on the outer peripheral side); a step of setting the first reference line Lr1 and the second reference line Lr2; a step of determining the two edges of the first opening 40 and the second opening 50 that are straight lines parallel to the first reference line Lr1 and the second reference line Lr2 and define the side edges of the first lattice 70 and the second lattice 80; and a step of chamfering the corners of the first opening 40 and the second opening 50.

[0036] In the process of setting the first reference line Lr1 and the second reference line Lr2, the first reference line Lr1 passing through the center Ch of the mounting hole 20 can be drawn, and an intersection point P can be set on the first reference line Lr1 near the addendum circle of the sprocket tooth 30. Then, the second reference line Lr2 connecting this intersection point P with the adjacent mounting hole 20 can be drawn. In this case, the position of the intersection point P can be set as the intersection of the first reference line Lr1 and the addendum circle, but it can also be set as the intersection with an imaginary circle with a diameter that is easy to grasp, rather than the intersection with an addendum circle whose diameter is difficult to form into a suitable size.

[0037] The above description illustrates a sprocket 1 according to one embodiment of the present invention, but the structure and effects of the sprocket involved in the present invention are not limited to the above description. As an example, the first opening and the second opening of the sprocket involved in the present invention may also be formed as approximately isosceles triangles to define a first grid and a second grid that are symmetrical along the direction of rotation. Furthermore, the shapes of the sides and chamfers of the first opening and the second opening of the sprocket involved in the present invention may vary continuously or in stages.

[0038] Example

[0039] The present invention will now be described in more detail based on embodiments. It should be noted that the present invention is not limited to these embodiments.

[0040] (Model No. 1)

[0041] As model number 1, according to the above implementation method, the following is set: Figure 3 The model of the sprocket shown is as follows. For sprocket model number 1, the radius of the central opening is set to 65mm, the diameter of the mounting hole to 8.5mm, the radius of the pitch circle of the mounting hole to 75mm, the number of mounting holes to 6, the diameter of the addendum circle to 127mm, and the radius of the dedendum circle to 119mm. The radius of the outer edge of the connecting grid 60 is set to 70mm, and the radius of the inner edge of the outer circumferential grid 90 is set to 108mm. A first reference line is drawn, inclined at 60° radially from the center of the mounting hole. A second reference line is drawn, connecting the intersection of the first reference line and an imaginary circle with a radius of 128mm (grid angle ratio γ / θ = 0.39) to the center of the adjacent mounting hole. In model number 1, the width of the first grid is set to 12mm, the width of the second grid is set to 8mm, the straight line offset from the first baseline to the rotation center side by 5.0mm is set as the side edge of the first opening side of the first grid, and the second baseline (the straight line offset from the rotation center side by 0mm) is set as the side edge of the first opening side of the second grid.

[0042] (Model numbers 2-17)

[0043] Models No. 2 to 5 are models in which the angle ratio is different from that of Model No. 1. Models No. 6 to 9 are models in which the width Wl of the first grid (the amount of offset A of the side edge of the first opening side from the center of rotation of the first reference line) is different from that of Model No. 1. Models No. 10 to 13 are models in which the width W2 of the second grid (the amount of offset B of the side edge of the second opening side from the second reference line) is different from that of Model No. 1. Models No. 14 to 17 are models in which the amount of offset B of the side edge of the second opening side of the second grid from the second reference line is different from that of Model No. 1 (the widths are equal).

[0044] For Models No. 1 to 17 described above, the maximum stress was calculated by computer simulation, and the weight (volume) of the sprocket was calculated. With Model 1 as 100%, the values of the results described above are shown in Table 1 below.

[0045] [Table 1]

[0046]

[0047] By setting the ratio of the angle with the center of rotation as a reference from the intersection of the first reference line and the second reference line to the center of the mounting hole on the first grid side to the angle between the adjacent two mounting holes within the specified range, it is possible to reduce the maximum stress while suppressing an increase in weight, thereby improving the strength related to torque transmission. In addition, in order to efficiently reduce the maximum stress without increasing the weight, the center line of the first grid preferably passes near the center of the mounting hole, and the side edge of the first opening side of the second grid preferably lies near the center of the mounting hole.

[0048] Glossary of Symbols

[0049] 1 sprocket

[0050] 10 central opening

[0051] 20 mounting hole

[0052] 30 sprocket tooth

[0053] 40 first opening

[0054] 50 second opening

[0055] 60 connecting grid

[0056] 70 first grid

[0057] 80 second grid

[0058] 90 outer peripheral grid

[0059] Ch center of mounting hole

[0060] Cs center of rotation

[0061] L71, L72, L81, L82 tangent

[0062] Lc1 centerline of the 1st grid bar

[0063] Lc2 centerline of the 2nd grid bar

[0064] Lr1 1st reference line

[0065] Lr2 2nd reference line

[0066] P intersection of the 1st reference line and the 2nd reference line.

Claims

1. A sprocket comprising: mounting holes formed at equal intervals in the circumferential direction; a plurality of sprocket teeth provided on the outer periphery; a first opening formed in a substantially triangular shape with two corners each facing the mounting holes and the remaining one corner disposed on the outer periphery side; and a second opening formed in a substantially triangular shape with one corner facing the mounting holes and the remaining two corners disposed on the outer periphery side, and with a first section bar in which a driving force and a load reaction force are opposite and a second section bar in which the driving force and the load reaction force are opposite being defined between the second opening and the first opening, an intersection point of a first reference line passing through the center of the mounting hole and parallel to a center line of a portion of the first section bar in which the width is smallest and a second reference line passing through the center of the mounting hole and parallel to a center line of a portion of the second section bar in which the width is smallest being located in the vicinity of a tooth tip circle of the sprocket teeth.

2. The sprocket according to claim 1, wherein an inclination angle of the center line of the portion of the first section bar in which the width is smallest with respect to the radial direction is smaller than an inclination angle of the center line of the portion of the second section bar in which the width is smallest with respect to the radial direction.

3. The sprocket according to claim 1 or 2, wherein a ratio of an angle from the intersection point to the mounting hole on the first section bar side with respect to an angle between two adjacent mounting holes is 0.20 or more and 0.45 or less with the center of rotation as a reference.

4. The sprocket according to claim 1 or 2, wherein the minimum width of the first section bar is larger than the minimum width of the second section bar.

5. The sprocket according to claim 1 or 2, wherein a tangent line of a side edge on the first opening side at the portion of the first section bar in which the width is smallest passes through the rotation center side of the mounting hole, a tangent line of a side edge on the second opening side at the portion of the first section bar in which the width is smallest passes through the outer periphery side of the mounting hole, a tangent line of a side edge on the first opening side at the portion of the second section bar in which the width is smallest passes through the mounting hole, and a tangent line of a side edge on the second opening side at the portion of the second section bar in which the width is smallest passes through the outer periphery side of the mounting hole.

6. A sprocket comprising: mounting holes formed at equal intervals in the circumferential direction; a plurality of sprocket teeth provided on the outer periphery; a first opening formed in a substantially triangular shape with two corners each facing the mounting holes and the remaining one corner disposed on the outer periphery side; and a second opening formed in a substantially triangular shape with one corner facing the mounting holes and the remaining two corners disposed on the outer periphery side, and with a first section bar in which a driving force and a load reaction force are opposite and a second section bar in which the driving force and the load reaction force are opposite being defined between the second opening and the first opening, a tangent line of a side edge on the first opening side at the portion of the first section bar in which the width is smallest passes through the rotation center side of the mounting hole, a tangent line of a side edge on the second opening side at the portion of the first section bar in which the width is smallest passes through the outer periphery side of the mounting hole, a tangent line of a side edge on the first opening side at the portion of the second section bar in which the width is smallest passes through the mounting hole, and a tangent line of a side edge on the second opening side at the portion of the second section bar in which the width is smallest passes through the outer periphery side of the mounting hole. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A tangent line of the side edge of the second opening side at a portion where the width of the second stile is smallest passes through the outer periphery side of the mounting hole.

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