阅读说明：本技术 自行车链轮 (Bicycle chain wheel ) 是由 山崎梓 蒲田建二 于 2019-06-27 设计创作，主要内容包括：一种自行车链轮,包括链轮主体和多个链轮齿。多个链轮齿包括相对于旋转中心轴线的至少一个第一轴向凹入的升挡促进齿。多个链轮齿包括相对于旋转中心轴线的至少一个第一轴向凹入的降挡促进齿。至少一个第一轴向凹入的降挡促进齿与至少一个第一轴向凹入的升挡促进齿在相对于旋转中心轴线的周向方向上相邻,二者之间没有另一个齿。至少一个第一轴向凹入的升挡促进齿和至少一个第一轴向凹入的降挡促进齿设置有沿周向方向延伸的第一连续凹部。(A bicycle sprocket includes a sprocket body and a plurality of sprocket teeth. The plurality of sprocket teeth include at least one first axially recessed upshift facilitating tooth relative to the central axis of rotation. The plurality of sprocket teeth include at least one first axially recessed downshift facilitating tooth with respect to the central axis of rotation. The at least one first axially recessed downshift facilitating tooth is adjacent to the at least one first axially recessed upshift facilitating tooth in a circumferential direction with respect to the rotational center axis without another tooth therebetween. The at least one first axially concave upshift promoting tooth and the at least one first axially concave downshift promoting tooth are provided with a first continuous recess extending in a circumferential direction.)

1. A bicycle sprocket comprising:

a sprocket body having a first axial facing surface and a second axial facing surface with respect to a rotational center axis of a bicycle sprocket, the second axial facing surface being opposite the first axial facing surface in an axial direction with respect to the rotational center axis, the first axial facing surface being configured to face a center plane of a bicycle in an assembled state in which the bicycle sprocket is mounted to the bicycle;

a plurality of sprocket teeth extending radially outward from the sprocket body relative to the rotational center axis;

the plurality of sprocket teeth includes at least one first axially recessed upshift promoting tooth with respect to the rotational center axis, the at least one first axially recessed upshift promoting tooth being recessed from the second axial facing surface toward the first axial facing surface;

the plurality of sprocket teeth includes at least one first axially recessed downshift facilitating tooth with respect to the rotational center axis, the at least one first axially recessed downshift facilitating tooth being recessed from the second axial facing surface toward the first axial facing surface, the at least one first axially recessed downshift facilitating tooth being adjacent to the at least one first axially recessed upshift facilitating tooth in a circumferential direction with respect to the rotational center axis without another tooth therebetween; and

the at least one first axially recessed upshift promoting tooth and the at least one first axially recessed downshift promoting tooth are provided with a first continuous recess extending in the circumferential direction.

2. The bicycle sprocket as in claim 1, wherein

The at least one first axially recessed downshift facilitating tooth is disposed on an upstream side of the at least one first axially recessed upshift facilitating tooth in a rotational driving direction of the bicycle sprocket.

3. The bicycle sprocket as in claim 1, wherein

The at least one first axially recessed upshift promoting tooth comprises:

a first upshift promoting tooth that is recessed in the axial direction; and

a first additional upshift promoting tooth that is recessed along the axial direction and adjacent to the first upshift promoting tooth in the circumferential direction without another tooth therebetween.

4. The bicycle sprocket as in claim 1, wherein

The plurality of sprocket teeth include a last chain engagement upshift promoting tooth adjacent to the at least one first axially recessed upshift promoting tooth in the circumferential direction with no other tooth therebetween, the last chain engagement upshift promoting tooth being disposed on a downstream side of the at least one first axially recessed upshift promoting tooth in the rotational driving direction.

5. The bicycle sprocket as in claim 1, wherein

The at least one first axially recessed downshift facilitating tooth comprises:

a first downshift facilitating tooth that is recessed in the axial direction; and

a first additional downshift facilitation tooth that is recessed in the axial direction and adjacent to the first downshift facilitation tooth in the circumferential direction without another tooth therebetween.

6. The bicycle sprocket as in claim 1, wherein

The plurality of sprocket teeth include an initial chain engagement downshift facilitating tooth that is adjacent to the at least one first axially recessed downshift facilitating tooth in the circumferential direction without another tooth therebetween, the initial chain engagement downshift facilitating tooth being disposed upstream of the at least one first axially recessed downshift facilitating tooth in the rotational driving direction.

7. The bicycle sprocket as in claim 1, wherein

The at least one first axially recessed upshift promoting tooth comprises:

a first upshift promoting tooth that is recessed in the axial direction; and

a first additional upshift promoting tooth that is recessed in the axial direction and adjacent to the first upshift promoting tooth in the circumferential direction without another tooth therebetween,

the at least one first axially recessed downshift facilitating tooth comprises:

a first downshift facilitating tooth that is recessed in the axial direction; and

a first additional downshift facilitation tooth that is recessed in the axial direction and adjacent to the first downshift facilitation tooth in the circumferential direction with no other tooth therebetween, and

the first upshift promoting tooth, the first additional upshift promoting tooth, the first downshift promoting tooth, and the first additional downshift promoting tooth are provided with the first continuous recess.

8. The bicycle sprocket as in claim 7, wherein

The first additional upshift promoting tooth is adjacent to the first additional downshift promoting tooth in the circumferential direction without another tooth therebetween.

9. The bicycle sprocket as in claim 8, wherein

The first additional upshift promoting teeth are disposed on a downstream side of the first additional downshift promoting teeth in a rotational driving direction.

10. The bicycle sprocket as in claim 1, wherein

The plurality of sprocket teeth include at least one second axially recessed upshift promoting tooth with respect to the central axis of rotation,

the plurality of sprocket teeth include at least one second axially recessed downshift facilitating tooth with respect to the rotational center axis, the at least one second axially recessed downshift facilitating tooth being adjacent to the at least one second axially recessed upshift facilitating tooth in the circumferential direction without another tooth therebetween, the at least one second axially recessed downshift facilitating tooth being disposed on an upstream side of the at least one second axially recessed upshift facilitating tooth in a rotational driving direction of the bicycle sprocket, and

the at least one second axially recessed upshift promoting tooth and the at least one second axially recessed downshift promoting tooth are provided with a second continuous recess extending in the circumferential direction with respect to the rotational center axis.

11. The bicycle sprocket as in claim 1, wherein

The first continuous recess has a plurality of recess depths defined in the axial direction from the second axial facing surface of the sprocket body.

12. The bicycle sprocket as in claim 11, wherein

The at least one first axially recessed upshift promoting tooth comprises:

a first upshift promoting tooth that is recessed in the axial direction; and

a first additional upshift promoting tooth recessed in said axial direction and adjacent to said first axially recessed upshift promoting tooth in said circumferential direction without another tooth therebetween,

the first additional upshift promoting teeth are disposed on an upstream side of the first upshift promoting teeth in a rotational driving direction,

the plurality of recess depths comprises:

a first up-shift pocket depth defined in the axial direction from the second axial facing surface of the sprocket body; and

a second up-shift pocket depth defined in the axial direction from the second axial facing surface of the sprocket body, the second up-shift pocket depth being different from the first up-shift pocket depth,

the first upshift promoting teeth have at least partially the first upshift recess depth, and

the first additional upshift promoting teeth have at least in part the second upshift recess depth.

13. The bicycle sprocket as in claim 12, wherein

The first lifting and stopping concave part depth is greater than the second lifting and stopping concave part depth.

14. The bicycle sprocket as in claim 11, wherein

The at least one first axially recessed downshift facilitating tooth comprises:

a first downshift facilitating tooth that is recessed in an axial direction; and

a first additional downshift facilitation tooth that is recessed in an axial direction and adjacent to the first downshift facilitation tooth in the circumferential direction without another tooth therebetween,

the first additional downshift facilitation tooth is provided on a downstream side of the first downshift facilitation tooth in the rotational driving direction,

the plurality of recess depths comprises:

a first downshift recess depth defined in the axial direction from the second axial facing surface of the sprocket body; and

a second kick down recess depth defined in the axial direction from the second axial facing surface of the sprocket body, the second kick down recess depth being different than the first kick down recess depth,

the first downshift facilitating tooth has at least partially the first downshift recess depth, and

the first additional downshift facilitating tooth has at least partly the second downshift recess depth.

15. The bicycle sprocket as in claim 14, wherein

The first kick-down recess depth is greater than the second kick-down recess depth.

16. The bicycle sprocket as in claim 12, wherein

The plurality of recess depths includes a third step-up recess depth defined in the axial direction from the second axial facing surface of the sprocket body, the third step-up recess depth being different from the first step-up recess depth, and

the first upshift promoting tooth has, in part, the third upshift recess depth.

17. The bicycle sprocket as in claim 16, wherein

The third lifting and stopping concave part depth is greater than the second lifting and stopping concave part depth.

18. The bicycle sprocket as in claim 4, wherein

The last chain engagement upshift promoting tooth includes an upshift recess disposed on the same side as the first axial facing surface.

19. The bicycle sprocket as in claim 6, wherein

The initial chain engagement downshift facilitating tooth includes a downshift recess disposed on the same side of the first axially facing surface.

20. A bicycle sprocket comprising:

a sprocket body having a first axial facing surface and a second axial facing surface with respect to a rotational center axis of the bicycle sprocket, the second axial facing surface being opposite the first axial facing surface in an axial direction with respect to the rotational center axis, the first axial facing surface being configured to face a center plane of the bicycle in an assembled state of the bicycle sprocket mounted to the bicycle;

a plurality of sprocket teeth extending radially outward from the sprocket body relative to the rotational center axis;

the plurality of sprocket teeth includes at least four axially recessed teeth relative to the central axis of rotation that are recessed from the second axial facing surface toward the first axial facing surface; and

the at least four axially recessed teeth are provided with a continuous recess extending in the circumferential direction.

Technical Field

The present invention relates to bicycle sprockets.

Background

Bicycling is becoming an increasingly popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. Bicycle sprockets are one type of bicycle component that has been extensively redesigned.

Disclosure of Invention

In accordance with a first aspect of the present invention, a bicycle sprocket comprises a sprocket body and a plurality of sprocket teeth. The sprocket body has a first axial facing surface and a second axial facing surface relative to a rotational center axis of the bicycle sprocket. The second axial facing surface is opposite to the first axial facing surface in an axial direction with respect to the rotational center axis. The first axially facing surface is configured to face a center plane of the bicycle in an assembled state of the bicycle sprocket mounted to the bicycle. A plurality of sprocket teeth extend radially outward from the sprocket body relative to the rotational center axis. The plurality of sprocket teeth include at least one first axially recessed upshift facilitating tooth relative to the central axis of rotation. At least one first axially recessed upshift promoting tooth is recessed from the second axially facing surface toward the first axially facing surface. The plurality of sprocket teeth include at least one first axially recessed downshift facilitating tooth with respect to the central axis of rotation. At least one first axially recessed downshift facilitating tooth is recessed from the second axially facing surface toward the first axially facing surface. The at least one first axially recessed downshift facilitating tooth is adjacent to the at least one first axially recessed upshift facilitating tooth in a circumferential direction with respect to the central axis of rotation without another tooth therebetween. The at least one first axially concave upshift promoting tooth and the at least one first axially concave downshift promoting tooth are provided with a first continuous recess extending in a circumferential direction.

With the bicycle sprocket according to the first aspect, the first continuous recess can reduce a circumferential extent of a shift facilitation area configured to facilitate a shift operation in which a bicycle chain is shifted between the bicycle sprocket and another sprocket. This can increase the total number of shift promoting areas in the bicycle sprocket. Therefore, the shift operation can be performed surely and quickly in the shift facilitating region.

According to a second aspect of the present invention, the bicycle sprocket according to the first aspect is configured such that the at least one first axially recessed downshift facilitating tooth is disposed upstream of the at least one first axially recessed upshift facilitating tooth in a rotational driving direction of the bicycle sprocket.

With the bicycle sprocket according to the second aspect, a shifting operation can be performed more surely in the shift promoting region.

According to a third aspect of the present invention, the bicycle sprocket according to the first or second aspect is configured such that the at least one first axially recessed upshift promoting tooth includes a first upshift promoting tooth and a first additional upshift promoting tooth. The first upshift promoting teeth are recessed in the axial direction. The first additional upshift promoting tooth is recessed in the axial direction and adjacent to the first upshift promoting tooth in the circumferential direction, with no further tooth in between.

With the bicycle sprocket according to the third aspect, the first upshift promoting teeth and the first additional upshift promoting teeth smoothly perform an upshift operation in which the bicycle chain is shifted from the bicycle sprocket to a smaller sprocket.

According to a fourth aspect of the present invention, the bicycle sprocket according to any one of the first to third aspects is configured such that the plurality of sprocket teeth includes a last chain engagement upshift promoting tooth adjacent in the circumferential direction to the at least one first axially recessed upshift promoting tooth with no other tooth therebetween, the last chain engagement upshift promoting tooth being disposed on a downstream side of the at least one first axially recessed upshift promoting tooth in the rotational driving direction.

With the bicycle sprocket according to the fourth aspect, the last chain-engaging upshift promoting teeth smoothly perform an upshift operation.

According to a fifth aspect of the present invention, the bicycle sprocket according to any one of the first to fourth aspects is configured such that the at least one first axially recessed downshift facilitating tooth comprises a first downshift facilitating tooth and a first additional downshift facilitating tooth. The first downshift facilitating tooth is recessed in the axial direction. The first additional downshift facilitation tooth is recessed in the axial direction and is circumferentially adjacent to the first downshift facilitation tooth without another tooth therebetween.

With the bicycle sprocket according to the fifth aspect, the first downshift facilitating tooth and the first additional downshift facilitating tooth smoothly perform a downshift operation in which the bicycle chain is shifted from the smaller sprocket to the bicycle sprocket.

According to a sixth aspect of the present invention, the bicycle sprocket according to any one of the first to fifth aspects is configured such that the plurality of sprocket teeth includes an initial chain engagement downshift facilitating tooth that is adjacent to the at least one first axially recessed downshift facilitating tooth in the circumferential direction without another tooth therebetween, the initial chain engagement downshift facilitating tooth being disposed on an upstream side of the at least one first axially recessed downshift facilitating tooth in the rotational driving direction.

With the bicycle sprocket according to the sixth aspect, the initial chain engagement downshift facilitating tooth smoothly performs a downshift operation.

According to a seventh aspect of the present invention, the bicycle sprocket according to the first or second aspect is configured such that the at least one first axially recessed upshift promoting tooth comprises a first upshift promoting tooth and a first additional upshift promoting tooth. The first upshift promoting teeth are recessed in the axial direction. The first additional upshift promoting tooth is recessed in the axial direction and adjacent to the first upshift promoting tooth in the circumferential direction, with no further tooth in between. The at least one first axially recessed downshift facilitating tooth comprises a first downshift facilitating tooth and a first additional downshift facilitating tooth. The first downshift facilitating tooth is recessed in the axial direction. The first additional downshift facilitating tooth is recessed in the axial direction and adjacent to the first downshift facilitating tooth in the circumferential direction without another tooth therebetween. The first upshift promoting tooth, the first additional upshift promoting tooth, the first downshift promoting tooth and the first additional downshift promoting tooth are provided with a first continuous recess.

With the bicycle sprocket according to the seventh aspect, it is possible to perform a shifting operation more surely in the shift promoting region.

According to an eighth aspect of the present invention, the bicycle sprocket according to the seventh aspect is configured such that the first additional upshift promoting teeth are adjacent to the first additional downshift promoting teeth in the circumferential direction without another tooth therebetween.

With the bicycle sprocket according to the eighth aspect, the total number of shift promoting areas in the bicycle sprocket can be increased.

According to a ninth aspect of the present invention, the bicycle sprocket according to the eighth aspect is configured such that the first additional upshift promoting teeth are disposed on a downstream side of the first additional downshift promoting teeth in the rotational driving direction.

With the bicycle sprocket according to the ninth aspect, the total number of shift promoting areas in the bicycle sprocket can be increased.

According to a tenth aspect of the present invention, the bicycle sprocket according to any one of the first to ninth aspects is configured such that the plurality of sprocket teeth includes at least one second axially recessed upshift promoting tooth with respect to the rotational center axis. The plurality of sprocket teeth include at least one second axially recessed downshift facilitating tooth with respect to the central axis of rotation. The at least one second axially recessed downshift facilitating tooth is adjacent to the at least one second axially recessed upshift facilitating tooth in the circumferential direction without another tooth therebetween. The at least one second axially recessed downshift facilitating tooth is disposed on an upstream side of the at least one second axially recessed upshift facilitating tooth in a rotational driving direction of the bicycle sprocket. The at least one second axially recessed upshift promoting tooth and the at least one second axially recessed downshift promoting tooth are provided with a second continuous recess extending in a circumferential direction with respect to the rotational center axis.

With the bicycle sprocket according to the tenth aspect, the at least one second axially recessed upshift promoting tooth and the at least one second axially recessed downshift promoting tooth can make the shifting operation faster.

According to an eleventh aspect of the present invention, the bicycle sprocket according to any one of the first to tenth aspects is configured such that the first continuous recess has a plurality of recess depths defined in an axial direction from the second axial facing surface of the sprocket body.

With the bicycle sprocket according to the eleventh aspect, it is possible to maintain the strength of the bicycle sprocket in the shift promoting area and to surely perform the shifting operation in the shift promoting area.

According to a twelfth aspect of the present invention, the bicycle sprocket according to the eleventh aspect is configured such that the at least one first axially recessed upshift promoting tooth includes a first upshift promoting tooth and a first additional upshift promoting tooth. The first upshift promoting teeth are recessed in the axial direction. The first additional upshift promoting tooth is recessed in the axial direction and adjacent to the first axially recessed upshift promoting tooth in the circumferential direction, with no further tooth therebetween. The first additional upshift promoting teeth are disposed on an upstream side of the first upshift promoting teeth in the rotational driving direction. The plurality of recess depths includes a first step-up recess depth and a second step-up recess depth. The first upshift recess depth is defined in an axial direction from the second axial facing surface of the sprocket body. The second upshift recess depth is defined in the axial direction from the second axial facing surface of the sprocket body. The second raised barrier recess depth is different from the first raised barrier recess depth. The first upshift promoting teeth have, at least in part, a first upshift recess depth. The first additional upshift promoting tooth has, at least in part, a second upshift recess depth.

With the bicycle sprocket according to the twelfth aspect, it is possible to maintain the strength of the bicycle sprocket in the shift promoting area and to surely perform the shifting operation in the shift promoting area.

In accordance with a thirteenth aspect of the present invention, the bicycle sprocket according to the twelfth aspect is configured such that the first up-shift recess depth is greater than the second up-shift recess depth.

With the bicycle sprocket according to the thirteenth aspect, a shifting operation can be performed with certainty in the shift promoting area.

According to a fourteenth aspect of the present invention, the bicycle sprocket according to any of the eleventh to thirteenth aspects is configured such that the at least one first axially concave downshift facilitating tooth includes a first downshift facilitating tooth and a first additional downshift facilitating tooth. The first downshift facilitating tooth is recessed in the axial direction. The first additional downshift facilitating tooth is recessed in the axial direction and adjacent to the first downshift facilitating tooth in the circumferential direction without another tooth therebetween. The first additional downshift facilitation tooth is disposed on a downstream side of the first downshift facilitation tooth in the rotational driving direction. The plurality of recess depths includes a first kick-down recess depth and a second kick-down recess depth. The first downshift recess depth is defined in an axial direction from the second axial facing surface of the sprocket body. The second downshift recess depth is defined in the axial direction from the second axial facing surface of the sprocket body. The second downshift recess depth is different from the first downshift recess depth. The first downshift facilitating tooth has at least partly a first downshift recess depth. The first additional downshift facilitating tooth has at least partly a second downshift recess depth.

With the bicycle sprocket according to the fourteenth aspect, it is possible to maintain the strength of the bicycle sprocket in the shift promoting area and to surely perform the shifting operation in the shift promoting area.

According to a fifteenth aspect of the present invention, the bicycle sprocket according to the fourteenth aspect is configured such that the first downshift recess depth is greater than the second downshift recess depth.

With the bicycle sprocket according to the fifteenth aspect, a shifting operation can be performed with certainty in the shift promoting area.

According to a sixteenth aspect of the present invention, the bicycle sprocket according to any one of the twelfth to fifteenth aspects is configured such that the plurality of recess depths includes a third upshift recess depth defined in an axial direction from the second axial facing surface of the sprocket body. The third raised abutment recess has a depth different from the depth of the first raised abutment recess. The first upshift promoting tooth has, in part, a third upshift recess depth.

With the bicycle sprocket according to the sixteenth aspect, it is possible to maintain the strength of the bicycle sprocket in the shift promoting area and to perform a shifting operation with certainty in the shift promoting area.

According to a seventeenth aspect of the present invention, the bicycle sprocket according to the sixteenth aspect is configured such that the third up-shift recess depth is greater than the second up-shift recess depth.

With the bicycle sprocket according to the seventeenth aspect, it is possible to maintain the strength of the bicycle sprocket in the shift promoting area and to surely perform the shifting operation in the shift promoting area.

According to an eighteenth aspect of the present invention, the bicycle sprocket according to the fourth aspect is configured such that the last chain engaging upshift promoting tooth includes an upshift recess disposed on the same side as the first axial facing surface.

With the bicycle sprocket according to the eighteenth aspect, it is possible to surely perform an upshift operation in the shift promoting region.

According to a nineteenth aspect of the present invention, the bicycle sprocket according to the sixth aspect is configured such that the initial chain engagement upshift promoting teeth comprise a downshift recess disposed on the same side as the first axial facing surface.

With the bicycle sprocket according to the nineteenth aspect, it is possible to surely perform a downshift operation in the shift facilitating region.

According to a twentieth aspect of the present invention, a bicycle sprocket comprises a sprocket body and a plurality of sprocket teeth. The sprocket body has a first axial facing surface and a second axial facing surface relative to a rotational center axis of the bicycle sprocket. The second axial facing surface is opposite to the first axial facing surface in an axial direction with respect to the rotational center axis. The first axially facing surface is configured to face a center plane of the bicycle in an assembled state of the bicycle sprocket mounted to the bicycle. A plurality of sprocket teeth extend radially outward from the sprocket body relative to the rotational center axis. The plurality of sprocket teeth includes at least four axially recessed teeth relative to the central axis of rotation. At least four axially recessed teeth are recessed from the second axial facing surface toward the first axial facing surface. At least four axially recessed teeth are provided with a continuous recess extending in the circumferential direction. The twentieth aspect may be combined with any one of the first to nineteenth aspects.

With the bicycle sprocket according to the twentieth aspect, the weight of the bicycle sprocket can be reduced.

Drawings

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

FIG. 1 is a schematic diagram of a bicycle that includes a bicycle drive train.

FIG. 2 is a side elevational view of the bicycle sprocket assembly of the bicycle drive train illustrated in FIG. 1.

FIG. 3 is a partial cross sectional view of the bicycle sprocket assembly taken along line III-III in FIG. 2.

FIG. 4 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 5 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 6 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 7 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 8 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 9 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 10 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 11 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 12 is a side elevational view of the bicycle sprocket assembly illustrated in FIG. 2.

FIG. 13 is a partial side elevational view of the bicycle sprocket illustrated in FIG. 8.

FIG. 14 is a partial top view of the bicycle sprocket illustrated in FIG. 8.

FIG. 15 is a partial cross sectional view of the bicycle sprocket assembly taken along line XV-XV in FIG. 13.

FIG. 16 is a partial perspective view of the bicycle sprocket illustrated in FIG. 8.

FIG. 17 is another partial perspective view of the bicycle sprocket illustrated in FIG. 8.

FIG. 18 is another partial perspective view of the bicycle sprocket illustrated in FIG. 8.

Detailed Description

Embodiments will now be described with reference to the drawings, wherein like reference numerals represent corresponding or identical elements in the various drawings.

Referring initially to FIG. 1, a bicycle 10 includes a bicycle frame BF and a bicycle drive train 11. The bicycle drive train 11 includes a crank assembly 2, a hub assembly 4, a bicycle sprocket assembly 12 and a bicycle chain C. The bicycle sprocket assembly 12 has a center axis of rotation a 1. The bicycle sprocket assembly 12 is rotatably supported by the hub assembly 4 relative to the bicycle frame BF about a center axis of rotation a 1. The crank assembly 2 includes a crank axle 2A, a right crank arm 2B, a left crank arm 2C, and a front sprocket 2D. The right crank arm 2B and the left crank arm 2C are fixed to the crank shaft 2A. The front sprocket 2D is fixed to at least one of the crank shaft 2A and the right crank arm 2B. The bicycle chain C engages the front sprocket 2D and the bicycle sprocket assembly 12 to transmit a pedaling force from the front sprocket 2D to the bicycle sprocket assembly 12. The crank assembly 2 includes a front sprocket 2D which in the illustrated embodiment is a single sprocket. However, the crank assembly 2 may include a plurality of front sprockets. The bicycle sprocket assembly 12 is a rear sprocket assembly. However, the structure of the bicycle sprocket assembly 12 can be applied to a front sprocket.

In this application, the following directional terms "forward", "rearward", "left", "right", "lateral", "upward" and "downward" as well as any other similar directional terms refer to those directions determined based on a user (e.g., a rider) seated on a saddle (not shown) of a bicycle and facing a handlebar (not shown). Accordingly, these terms, as utilized to describe the bicycle sprocket assembly 12 should be interpreted relative to a bicycle equipped with the bicycle sprocket assembly 12 as used in an upright riding position on a horizontal surface.

As shown in fig. 2, in the mounted state of the bicycle sprocket assembly 12 onto the hub assembly 4, the bicycle sprocket assembly 12 is fixed to the sprocket support body 4A of the hub assembly 4 by the locking member 4B. The bicycle sprocket assembly 12 is configured to engage the bicycle chain C to transmit a driving rotational force F1 between the bicycle chain C and the bicycle sprocket assembly 12 during pedaling. During pedaling, the bicycle sprocket assembly 12 rotates in the rotational drive direction D11 about the central axis of rotation a 1. The rotational drive direction D11 is defined in a circumferential direction D1 relative to the rotational center axis a1 of the bicycle sprocket assembly 12. The reverse rotational direction D12 is the opposite direction of the rotational drive direction D11 and is defined in the circumferential direction D1.

The bicycle sprocket assembly 12 includes a bicycle sprocket. In this embodiment, the bicycle sprocket assembly 12 includes a plurality of bicycle sprockets SP1 to SP 9. The bicycle sprocket SP1 corresponds to a low gear. The bicycle sprocket SP9 corresponds to a high gear. The total number of the plurality of bicycle sprockets SP1 to SP9 is not limited to this embodiment.

As shown in fig. 3, the bicycle sprockets SP1 to SP9 are arranged at respective gear pitches in an axial direction D2 relative to the rotational center axis a 1. The bicycle sprocket assembly 12 includes a plurality of spacers SC1 through SC 6. The spacer SC1 is disposed between the bicycle sprockets SP1 and SP2 in the axial direction D2. The spacer SC2 is disposed between the bicycle sprockets SP2 and SP3 in the axial direction D2. The spacer SC3 is disposed between the bicycle sprockets SP3 and SP4 in the axial direction D2. The spacer SC4 is disposed between the bicycle sprockets SP4 and SP5 in the axial direction D2. The spacer SC5 is disposed between the bicycle sprockets SP5 and SP6 in the axial direction D2. The spacer SC6 is disposed between the bicycle sprockets SP6 and SP7 in the axial direction D2.

In this embodiment, the bicycle sprockets SP1 to SP9 and the spacers SC1 to SC6 are separate members from each other. However, at least one of the bicycle sprockets SP 1-SP 9 and the spacers SC 1-SC 6 can be integrally provided as a one-piece, unitary member with another one of the bicycle sprockets SP 1-SP 9 and the spacers SC 1-SC 6.

As seen in fig. 4, the bicycle sprocket SP1 includes a sprocket body SP1A and a plurality of sprocket teeth SP 1B. A plurality of sprocket teeth SP1B extend radially outward from the sprocket body SP1A relative to the rotational center axis a 1. The sprocket body SP1A includes an internally splined opening SP1C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP1C has an internally splined major diameter DM11 and an internally splined minor diameter DM 12. In this embodiment, the major diameter DM11 of the internal spline is 64.2mm and the minor diameter DM12 of the internal spline is 60.3 mm. However, the inner spline major diameter DM11 and the inner spline minor diameter DM12 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP1C is 6. However, the total number of splines of the internally splined opening SP1C is not limited to this embodiment. The sprocket body SP1A includes a plurality of pockets SP 1D. At least one of the internally splined opening SP1C and the opening SP1D can be omitted from the sprocket body SP 1A.

As seen in fig. 5, the bicycle sprocket SP2 includes a sprocket body SP2A and a plurality of sprocket teeth SP 2B. A plurality of sprocket teeth SP2B extend radially outward from the sprocket body SP2A relative to the rotational center axis a 1. The sprocket body SP2A includes an internally splined opening SP2C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP2C has an internally splined major diameter DM21 and an internally splined minor diameter DM 22. In this embodiment, the major diameter DM21 of the internal spline is 64.2mm and the minor diameter DM22 of the internal spline is 60.3 mm. However, the inner spline major diameter DM21 and the inner spline minor diameter DM22 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP2C is 6. However, the total number of splines of the internally splined opening SP2C is not limited to this embodiment. The sprocket body SP2A includes a plurality of pockets SP 2D. At least one of the internally splined opening SP2C and the opening SP2D can be omitted from the sprocket body SP 2A.

As seen in fig. 6, the bicycle sprocket SP3 includes a sprocket body SP3A and a plurality of sprocket teeth SP 3B. A plurality of sprocket teeth SP3B extend radially outward from the sprocket body SP3A relative to the rotational center axis a 1. The sprocket body SP3A includes an internally splined opening SP3C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP3C has an internally splined major diameter DM31 and an internally splined minor diameter DM 32. In this embodiment, the major diameter DM31 of the internal spline is 64.2mm and the minor diameter DM32 of the internal spline is 60.3 mm. However, the inner spline major diameter DM31 and the inner spline minor diameter DM32 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP3C is 6. However, the total number of splines of the internally splined opening SP3C is not limited to this embodiment. The sprocket body SP3A includes a plurality of pockets SP 3D. At least one of the internally splined opening SP3C and the opening SP3D can be omitted from the sprocket body SP 3A.

As seen in fig. 7, the bicycle sprocket SP4 includes a sprocket body SP4A and a plurality of sprocket teeth SP 4B. A plurality of sprocket teeth SP4B extend radially outward from the sprocket body SP4A relative to the rotational center axis a 1. The sprocket body SP4A includes an internally splined opening SP4C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP4C has an internally splined major diameter DM41 and an internally splined minor diameter DM 42. In this embodiment, the major diameter DM41 of the internal spline is 64.2mm and the minor diameter DM42 of the internal spline is 60.3 mm. However, the inner spline major diameter DM41 and the inner spline minor diameter DM42 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP4C is 6. However, the total number of splines of the internally splined opening SP4C is not limited to this embodiment. The sprocket body SP4A includes a plurality of pockets SP 4D. At least one of the internally splined opening SP4C and the opening SP4D can be omitted from the sprocket body SP 4A.

As seen in fig. 8, the bicycle sprocket SP5 includes a sprocket body SP5A and a plurality of sprocket teeth SP 5B. A plurality of sprocket teeth SP5B extend radially outward from the sprocket body SP5A relative to the rotational center axis a 1. The sprocket body SP5A includes an internally splined opening SP5C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP5C has an internally splined major diameter DM51 and an internally splined minor diameter DM 52. In this embodiment, the major diameter DM51 of the internal spline is 41.7mm and the minor diameter DM52 of the internal spline is 38.3 mm. However, the inner spline major diameter DM51 and the inner spline minor diameter DM52 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP5C is 6. However, the total number of splines of the internally splined opening SP5C is not limited to this embodiment. The sprocket body SP5A includes a plurality of pockets SP 5D. At least one of the internally splined opening SP5C and the opening SP5D can be omitted from the sprocket body SP 5A.

As seen in fig. 9, the bicycle sprocket SP6 includes a sprocket body SP6A and a plurality of sprocket teeth SP 6B. A plurality of sprocket teeth SP6B extend radially outward from the sprocket body SP6A relative to the rotational center axis a 1. The sprocket body SP6A includes an internally splined opening SP6C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP6C has an internally splined major diameter DM61 and an internally splined minor diameter DM 62. In this embodiment, the major diameter DM61 of the internal spline is 41.7mm and the minor diameter DM62 of the internal spline is 38.3 mm. However, the inner spline major diameter DM61 and the inner spline minor diameter DM62 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP6C is 6. However, the total number of splines of the internally splined opening SP6C is not limited to this embodiment. The internally splined opening SP6C may be omitted from the sprocket body SP 6A. The sprocket body SP6A can include at least one opening.

As seen in fig. 10, the bicycle sprocket SP7 includes a sprocket body SP7A and a plurality of sprocket teeth SP 7B. A plurality of sprocket teeth SP7B extend radially outward from the sprocket body SP7A relative to the rotational center axis a 1. The sprocket body SP7A includes an internally splined opening SP7C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP7C has an internally splined major diameter DM71 and an internally splined minor diameter DM 72. In this embodiment, the major diameter DM71 of the internal spline is 41.7mm and the minor diameter DM72 of the internal spline is 38.3 mm. However, the inner spline major diameter DM71 and the inner spline minor diameter DM72 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP7C is 6. However, the total number of splines of the internally splined opening SP7C is not limited to this embodiment. The internally splined opening SP7C may be omitted from the sprocket body SP 7A. The sprocket body SP7A can include at least one opening.

As seen in fig. 11, the bicycle sprocket SP8 includes a sprocket body SP8A and a plurality of sprocket teeth SP 8B. A plurality of sprocket teeth SP8B extend radially outward from the sprocket body SP8A relative to the rotational center axis a 1. The sprocket body SP8A includes an internally splined opening SP8C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP8C has an internally splined major diameter DM81 and an internally splined minor diameter DM 82. In this embodiment, the major diameter DM81 of the internal spline is 41.7mm and the minor diameter DM82 of the internal spline is 38.3 mm. However, the inner spline major diameter DM81 and the inner spline minor diameter DM82 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP8C is 6. However, the total number of splines of the internally splined opening SP8C is not limited to this embodiment. The internally splined opening SP8C may be omitted from the sprocket body SP 8A. The sprocket body SP8A can include at least one opening.

As seen in fig. 12, the bicycle sprocket SP9 includes a sprocket body SP9A and a plurality of sprocket teeth SP 9B. A plurality of sprocket teeth SP9B extend radially outward from the sprocket body SP9A relative to the rotational center axis a 1. The sprocket body SP9A includes an internally splined opening SP9C configured to engage the hub assembly 4 (fig. 3). The internally splined opening SP9C has an internally splined major diameter DM91 and an internally splined minor diameter DM 92. In this embodiment, the major diameter DM91 of the internal spline is 41.7mm and the minor diameter DM92 of the internal spline is 38.3 mm. However, the inner spline major diameter DM91 and the inner spline minor diameter DM92 are not limited to this embodiment. In this embodiment, the total number of splines of the internally splined opening SP9C is 6. However, the total number of splines of the internally splined opening SP9C is not limited to this embodiment. The internally splined opening SP9C may be omitted from the sprocket body SP 9A. The sprocket body SP9A can include at least one opening.

In this embodiment, the internal spline major diameters DM 11-DM 41 are equal to each other. The internal spline minor diameters DM 12-DM 42 are equal to each other. The internal spline major diameters DM51 through DM91 are equal to each other. The internal spline minor diameters DM 52-DM 92 are equal to each other. However, at least one of the internal spline major diameters DM 11-DM 41 may be different from another one of the internal spline major diameters DM 11-DM 41. At least one of the internal spline minor diameters DM 12-DM 42 may be different from another of the internal spline minor diameters DM 12-DM 42. At least one of the internal spline major diameters DM 51-DM 91 may be different from another one of the internal spline major diameters DM 51-DM 91. At least one of the internal spline minor diameters DM 52-DM 92 may be different from another of the internal spline minor diameters DM 52-DM 92. Further, in this embodiment, the internal spline major diameters DM 11-DM 41 are different from the internal spline major diameters DM 51-DM 91. The internal spline minor diameters DM 12-DM 42 are different from the internal spline minor diameters DM 52-DM 92. However, the inner spline major diameters DM 11-DM 41 may be equal to the inner spline major diameters DM 51-DM 91. The inner spline minor diameters DM 12-DM 42 may be equal to the inner spline minor diameters DM 52-DM 92.

The bicycle sprockets SP1 to SP9 have substantially the same structure as each other. Thus, bicycle sprocket SP5 will be described in detail, and for the sake of brevity, bicycle sprockets SP 1-SP 4 and SP 6-SP 9 will not be described in detail herein, while what is described below with respect to bicycle sprocket SP5 is applicable to bicycle sprockets SP 1-SP 4 and SP 6-SP 9.

As shown in fig. 13, the plurality of sprocket teeth SP5B includes at least one first axially recessed upshift facilitating tooth TU51 relative to the rotational center axis a 1. The plurality of sprocket teeth SP5B includes at least one first axially recessed downshift facilitating tooth TD51 with respect to the rotational center axis a 1.

The at least one first axially recessed downshift facilitation tooth TD51 is adjacent to the at least one first axially recessed upshift facilitation tooth TU51 with no other tooth therebetween in the circumferential direction D1 relative to the rotational center axis a 1. The at least one first axially recessed downshift facilitating tooth TD51 is disposed on an upstream side of the at least one first axially recessed upshift facilitating tooth TU51 in the rotational drive direction D11 of the bicycle sprocket SP 5. However, the at least one first axially recessed downshift facilitating tooth TD51 may be disposed on a downstream side of the at least one first axially recessed upshift facilitating tooth TU51 in the rotational drive direction D11 of the bicycle sprocket SP 5.

As seen in fig. 3, the sprocket body SP5A has a first axial facing surface SP5a1 and a second axial facing surface SP5a2 with respect to the rotational center axis a1 of the bicycle sprocket SP 5. The second axial facing surface SP5a2 is opposite to the first axial facing surface SP5a1 in the axial direction D2 with respect to the rotational center axis a 1. The first axial facing surface SP5a1 is configured to face the center plane 10A of the bicycle 10 in an assembled state with the bicycle sprocket SP5 mounted to the bicycle 10. The center plane 10A is defined perpendicular to the center axis of rotation a 1. As shown in fig. 1, for example, a center plane 10A is defined at the lateral center of the bicycle frame BF.

As seen in fig. 3, the sprocket body SP6A has a first axial facing surface SP6a1 and a second axial facing surface SP6a2 with respect to the rotational center axis a1 of the bicycle sprocket SP 6. The second axial facing surface SP6a2 is opposite to the first axial facing surface SP6a1 in the axial direction D2 with respect to the rotational center axis a 1. The first axial facing surface SP6a1 is configured to face the center plane 10A of the bicycle 10 in an assembled state with the bicycle sprocket SP6 mounted to the bicycle 10. The second axial facing surface SP5a2 of the bicycle sprocket SP5 faces the first axial facing surface SP6a1 of the bicycle sprocket SP6 in the axial direction D2. The spacer SC5 is disposed between the second axial facing surface SP5a2 of the bicycle sprocket SP5 and the first axial facing surface SP6a1 of the bicycle sprocket SP6 in the axial direction D2.

The sprocket body SP5A has an axial width W5 defined in the axial direction D2 from the first axial facing surface SP5a1 to the second axial facing surface SP5a 2. The axial width W5 ranges from 1.7mm to 2 mm. In this embodiment, the axial width W5 is 1.9 mm. However, the axial width W5 is not limited to this embodiment and the above range.

The sprocket body SP6A has an axial width W6 defined in the axial direction D2 from the first axial facing surface SP6a1 to the second axial facing surface SP6a 2. The axial width W6 ranges from 1.7mm to 2 mm. In this embodiment, the axial width W6 is 1.9 mm. However, the axial width W6 is not limited to this embodiment and the above range.

The bicycle sprocket SP5 has an axial center plane CP5 defined as bisecting the axial width W5. An axial center plane CP5 is defined as being perpendicular to the central axis of rotation a 1. The bicycle sprocket SP6 has an axial center plane CP6 defined as bisecting the axial width W6. An axial center plane CP6 is defined as being perpendicular to the central axis of rotation a 1.

The gear pitch GP5 is defined between the axial center planes CP5 and CP6 in the axial direction D2. The gear pitch GP5 ranges from 3.5mm to 5 mm. In this embodiment, the gear pitch GP5 is 4.1 mm. However, the gear pitch GP5 is not limited to this embodiment and the ranges described above.

Bicycle sprockets SP 1-SP 4 and SP 7-SP 9 have substantially the same axial widths as the axial widths W5 and W6 of bicycle sprockets SP5 and SP 6. The bicycle sprockets SP1 to SP4 and SP7 to SP9 have substantially the same gear spacing GP5 as the bicycle sprockets SP5 and SP 6. Therefore, for the sake of brevity, it will not be described in detail herein.

As shown in fig. 14, the at least one first axially recessed upshift promoting tooth TU51 is recessed from the second axial facing surface SP5a2 toward the first axial facing surface SP5a 1. The at least one first axially recessed downshift facilitation tooth TD51 is recessed from the second axial facing surface SP5a2 toward the first axial facing surface SP5a 1. The at least one first axially recessed upshift promoting tooth TU51 is recessed from the second axial facing surface SP5a2 in the axial direction D2 toward the first axial facing surface SP5a 1. The at least one first axially recessed downshift facilitation tooth TD51 is recessed in the axial direction D2 from the second axial facing surface SP5a2 toward the first axial facing surface SP5a 1.

As shown in fig. 13, the at least one first axially recessed upshift promoting tooth TU51 includes a first upshift promoting tooth TU51A and a first additional upshift promoting tooth TU 51B. The first additional upshift promoting tooth TU51B is adjacent to the first upshift promoting tooth TU51A, with no other tooth therebetween in the circumferential direction D1. The first additional upshift promoting teeth TU51B are disposed on an upstream side of the first upshift promoting teeth TU51A in the rotational drive direction D11. However, the first additional upshift promoting teeth TU51B may be provided on the downstream side of the first upshift promoting teeth TU51A in the rotational drive direction D11. One of the first upshift promoting teeth TU51A and the first additional upshift promoting teeth TU51B may be omitted from the at least one first axially recessed upshift promoting tooth TU 51.

The first upshift promoting tooth TU51A is configured to facilitate an upshift operation in which the bicycle chain C is shifted from the bicycle sprocket SP5 to the smaller sprocket SP6 (fig. 2). The first additional upshift promoting teeth TU51B are configured to facilitate an upshift operation. Specifically, the first upshift promoting tooth TU51A is configured to reduce interference between the bicycle sprocket SP5 and the bicycle chain C during an upshift operation. The first upshift promoting tooth TU51A is configured to first derail the bicycle chain C from the bicycle sprocket SP5 in an upshift operation. Specifically, the first upshift promoting tooth TU51A is configured to first derail the inner link plate of the bicycle chain C from the bicycle sprocket SP5 in an upshift operation. The first additional upshift promoting tooth TU51B is configured to reduce interference between the bicycle sprocket SP5 and the bicycle chain C during an upshift operation. Specifically, the first upshift promoting tooth TU51B is configured to derail the outer link plate of the bicycle chain C from the bicycle sprocket SP5 during an upshift operation.

As shown in fig. 15, the first upshift promoting teeth TU51A are recessed in the axial direction D2. The first additional upshift promoting teeth TU51B are recessed in the axial direction D2. The first upshift promoting teeth TU51A are recessed from the second axial facing surface SP5a2 toward the first axial facing surface SP5a1 in the axial direction D2. The first additional upshift promoting teeth TU51B are recessed from the second axial facing surface SP5a2 toward the first axial facing surface SP5a1 in the axial direction D2.

As shown in fig. 13, the at least one first axially recessed downshift facilitation tooth TD51 comprises a first downshift facilitation tooth TD51A and a first additional downshift facilitation tooth TD 51B. The first additional downshift facilitation tooth TD51B is adjacent to the first downshift facilitation tooth TD51A, and there is no other tooth therebetween in the circumferential direction D1. The first additional downshift facilitating tooth TD51B is disposed on the downstream side of the first downshift facilitating tooth TD51A in the rotational driving direction D11. However, the first additional downshift facilitation tooth TD51B may be provided on the upstream side of the first downshift facilitation tooth TD51A in the rotational driving direction D11. One of the first downshift facilitation tooth TD51A and the first additional downshift facilitation tooth TD51B may be omitted from the at least one first axially recessed downshift facilitation tooth TD 51.

In this embodiment, the first additional upshift promoting tooth TU51B is adjacent to the first additional downshift promoting tooth TD51B, with no other tooth therebetween in the circumferential direction D1. The first additional upshift promoting teeth TU51B are disposed on the downstream side of the first additional downshift promoting teeth TD51B in the rotational driving direction D11. However, the positional relationship between the first additional upshift promoting teeth TU51B and the first additional downshift promoting teeth TD51B is not limited to this embodiment.

The first downshift facilitating tooth TD51A is configured to facilitate a downshift operation in which the bicycle chain C is shifted from the smaller sprocket SP6 (fig. 2) to the bicycle sprocket SP 5. The first additional downshift facilitation tooth TD51B is configured to facilitate a downshift operation. Specifically, the first downshift facilitating tooth TD51A is configured to reduce interference between the bicycle sprocket SP5 and the bicycle chain C during a downshift operation. The first additional downshift facilitating tooth TD51B is configured to reduce interference between the bicycle sprocket SP5 and the bicycle chain C during a downshift operation.

As shown in fig. 15, the first downshift accelerating tooth TD51A is recessed in the axial direction D2. The first additional downshift facilitation tooth TD51B is recessed in the axial direction D2. The first downshift facilitation tooth TD51A is recessed from the second axial facing surface SP5a2 toward the first axial facing surface SP5a1 in the axial direction D2. The first additional downshift facilitation tooth TD51B is recessed from the second axial facing surface SP5a2 toward the first axial facing surface SP5a1 in the axial direction D2.

As shown in fig. 16, the at least one first axially recessed upshift promoting tooth TU51 and the at least one first axially recessed downshift promoting tooth TD51 are provided with a first continuous recess CR51 extending in the circumferential direction D1. In this embodiment, the first continuous recess CR51 is provided on the second axial facing surface SP5a 2. The first continuous recess CR51 may also be referred to as continuous recess CR 51. The first upshift promoting tooth TU51A, the first additional upshift promoting tooth TU51B, the first downshift promoting tooth TD51A, and the first additional downshift promoting tooth TD51B are provided with a first continuous recess CR 51. In other words, the plurality of sprocket teeth SP5B includes at least four axially recessed teeth TU51A, TU51B, TD51A, and TD51B relative to the rotational center axis a 1. At least four axially recessed teeth TU51A, TU51B, TD51A, and TD51B are recessed from the second axial facing surface SP5a2 toward the first axial facing surface SP5a 1. At least four axially recessed teeth TU51A, TU51B, TD51A and TD51B are provided with a continuous recess CR51 extending in the circumferential direction D1. The first continuous recess CR51 extends in the circumferential direction D1 from the first downshift promoting tooth TD51A to the first upshift promoting tooth TU 51A. However, the structure of the first continuous recess CR51 is not limited to this embodiment. At least two axially recessed teeth may be provided with a first continuous recess CR51 extending in the circumferential direction D1.

As shown in fig. 13, the plurality of sprocket teeth SP5B includes a last chain engagement upshift promoting tooth TU 51C. Finally, the chain engaging upshift promoting tooth TU51C is adjacent to at least one first axially recessed upshift promoting tooth TU51 with no other tooth in between in the circumferential direction D1. Finally, a chain engagement upshift promoting tooth TU51C is disposed on a downstream side of the at least one first axially recessed upshift promoting tooth TU51 in the rotational drive direction D11. The last chain engaging upshift promoting tooth TU51C is configured to last disengage from the outer link plate of the bicycle chain C during an upshift operation.

In this embodiment, the last chain engagement upshift promoting tooth TU51C is adjacent to the first upshift promoting tooth TU51A, with no other tooth in between in the circumferential direction D1. Finally, the chain engagement upshift promoting teeth TU51C are disposed on the downstream side of the first upshift promoting teeth TU51A in the rotational drive direction D11. However, the positional relationship between the first upshift promoting tooth TU51A, the first additional upshift promoting tooth TU51B and the last chain engagement upshift promoting tooth TU51C is not limited to this embodiment.

The plurality of sprocket teeth SP5B includes an initial chain engagement downshift facilitating tooth TD 51C. Initially the chain engaging downshift facilitation tooth TD51C is adjacent to at least one first axially recessed downshift facilitation tooth TD51 with no further tooth in between in the circumferential direction D1. Initially the chain engaging downshift facilitating tooth TD51C is disposed on the upstream side of the at least one first axially recessed downshift facilitating tooth TD51 in the rotational drive direction D11. The initial chain engagement downshift facilitating tooth TD51C is configured to first receive the bicycle chain C in a downshift operation in which the bicycle chain C is shifted from the smaller sprocket SP6 (fig. 2) to the bicycle sprocket SP 5.

In this embodiment, the initial chain engagement downshift facilitation tooth TD51C is adjacent to the first downshift facilitation tooth TD51A with no other tooth in between in the circumferential direction D1. The initial chain engagement downshift facilitating tooth TD51C is disposed on the upstream side of the first downshift facilitating tooth TD51A in the rotational driving direction D11. However, the positional relationship among the first downshift accelerating tooth TD51A, the first additional downshift accelerating tooth TD51B and the initial chain engagement downshift accelerating tooth TD51C is not limited to this embodiment.

As shown in fig. 15, the first continuous recess CR51 has a plurality of recess depths DP51 defined in the axial direction D2 from the second axial facing surface SP5a2 of the sprocket body SP 5A. The plurality of recess depths DP51 includes a first upshift recess depth DPU51A and a second upshift recess depth DPU 51B. The first upshift recess depth DPU51A is defined in the axial direction D2 from the second axial facing surface SP5a2 of the sprocket body SP 5A. The second upshift recess depth DPU51B is defined in the axial direction D2 from the second axial facing surface SP5a2 of the sprocket body SP 5A. The second upshift recess depth DPU51B is different from the first upshift recess depth DPU 51A. In this embodiment, the first upshift recess depth DPU51A is greater than the second upshift recess depth DPU 51B. However, the first upshift recess depth DPU51A may be equal to or less than the second upshift recess depth DPU 51B.

The plurality of recess depths DP51 includes a third upshift recess depth DPU51C defined in the axial direction D2 from the second axial facing surface SP5a2 of the sprocket body SP 5A. The third upshift recess depth DPU51C is different from the first upshift recess depth DPU 51A. The third upshift recess depth DPU51C is different from the second upshift recess depth DPU 51B. In this embodiment, the third upshift recess depth DPU51C is greater than the second upshift recess depth DPU 51B. The third upshift recess depth DPU51C is less than the first upshift recess depth DPU 51A. However, the dimensional relationship between the first to third upshift recess depths DPU51A to DPU51C is not limited to this embodiment. The third upshift recess depth DPU51C may be equal to or less than the second upshift recess depth DPU 51B.

In this embodiment, the first upshift promoting teeth TU51A have, at least in part, a first upshift recess depth DPU 51A. The first additional upshift promoting teeth TU51B have, at least in part, a second upshift recess depth DPU 51B. The first upshift promoting teeth TU51A partially have a third upshift recess depth DPU 51C. The first additional upshift promoting teeth TU51B have, at least in part, a first upshift recess depth DPU 51A. However, the first upshift recess depth DPU51A may be omitted from the first additional upshift promoting teeth TU 51B. The third upshift recess depth DPU51C may be omitted from the first upshift promoting teeth TU 51A.

As shown in fig. 15, the plurality of recess depths DP51 includes a first downshift recess depth DPD51A and a second downshift recess depth DPD 51B. The first downshift recess depth DPD51A is defined in the axial direction D2 from the second axial facing surface SP5a2 of the sprocket body SP 5A. The second downshift recess depth DPD51B is defined in the axial direction D2 from the second axial facing surface SP5a2 of the sprocket body SP 5A. The second downshift recess depth DPD51B is different from the first downshift recess depth DPD 51A. The first downshift recess depth DPD51A is greater than the second downshift recess depth DPD 51B. However, the first downshift recess depth DPD51A may be equal to or less than the second downshift recess depth DPD 51B.

In this embodiment, the first downshift facilitation tooth TD51A has at least partially a first downshift recess depth DPD 51A. The first additional downshift facilitation tooth TD51B has at least partly the second downshift recess depth DPD 51B. The first additional downshift facilitation tooth TD51B has at least partly a first downshift recess depth DPD 51A. However, the first downshift recess depth DPD51A may be omitted from the first additional downshift facilitating tooth TD 51B.

The second upshift recess depth DPU51B is equal to the second downshift recess depth DPD 51B. The first upshift recess depth DPU51A is different from the first downshift recess depth DPD 51A. The first upshift recess depth DPU51A is greater than the first downshift recess depth DPD 51A. However, the second upshift recess depth DPU51B may be different from the second downshift recess depth DPD 51B. The first upshift recess depth DPU51A may be equal to or less than the first downshift recess depth DPD 51A.

The first upshift promoting teeth TU51A include a first upshift axial surface TU51a1 facing the axial direction D2. The first upshift recess depth DPU51A is defined in the axial direction D2 from the first upshift axial surface TU51a1 to the second axial facing surface SP5a 2.

The first upshift promoting teeth TU51A include a first additional upshift axial surface TU51a2 facing the axial direction D2. The third upshift recess depth DPU51C is defined from the second axial facing surface SP5a2 to the first additional upshift axial surface TU51a2 in the axial direction D2.

The first additional upshift promoting teeth TU51B include a second upshift axial surface TU51B1 facing the axial direction D2. The second upshift recess depth DPU51B is defined from the second axial facing surface SP5a2 to the second upshift axial surface TU51B1 along the axial direction D2.

The first additional upshift promoting teeth TU51B include a second additional upshift axial surface TU51B2 facing the axial direction D2. The second additional upshift axial surface TU51B2 is disposed at the same axial position in the axial direction D2 as the axial position of the first upshift axial surface TU51a 1.

The first downshift facilitation tooth TD51A includes a first downshift axial surface TD51a1 facing the axial direction D2. The first downshift recess depth DPD51A is defined from the second axial facing surface SP5a2 to the first downshift axial surface TD51a1 in the axial direction D2.

The first additional downshift facilitation tooth TD51B includes a second downshift axial surface TD51B1 facing the axial direction D2. The second downshift recess depth DPD51B is defined in the axial direction D2 from the second axial facing surface SP5a2 to the second downshift axial surface TD51B 1.

The first additional downshift facilitation tooth TD51B includes a second additional downshift axial surface TD51B2 facing the axial direction D2. The second downshift axial surface TD51B2 is provided at the same axial position in the axial direction D2 as the axial position of the first downshift axial surface TD51a 1.

As shown in fig. 15, the first continuous recess CR51 includes an upshift promoting recess CR51A, a shift promoting recess CR51B, a downshift promoting recess CR51C and an additional upshift promoting recess CR 51D. The upshift promoting recess CR51A has a first upshift recess depth DPU 51A. The shift facilitation recess CR51B has a second upshift recess depth DPU51B and a second downshift recess depth DPD 51B. The downshift facilitation recess CR51C has a first downshift recess depth DPD 51A. The additional upshift promoting recess CR51D has a third upshift recess depth DPU 51C.

As shown in fig. 16, upshift promoting recesses CR51A are provided on the first upshift promoting tooth TU51A and the first additional upshift promoting tooth TU51B to facilitate an upshift operation. The shift facilitation recess CR51B is provided on the first additional upshift facilitating tooth TU51B and the first additional downshift facilitating tooth TD51B to facilitate an upshift operation and a downshift operation. The downshift facilitation recess CR51C is provided on the first downshift facilitation tooth TD51A and the first additional downshift facilitation tooth TD51B to facilitate a downshift operation.

The shift facilitation recess CR51B is provided between the upshift facilitation recess CR51A and the downshift facilitation recess CR51C in the circumferential direction D1. The downshift facilitating recess CR51C is provided on the upstream side of the shift facilitating recess CR51B in the rotational driving direction D11. The upshift promoting recess CR51A is provided on the downstream side of the shift promoting recess CR51B in the rotational driving direction D11. The additional upshift promoting recess CR51D is provided on the downstream side of the upshift promoting recess CR51A in the rotational drive direction D11. However, the structure of the first continuous recess CR51 is not limited to this embodiment. At least one of the upshift promoting recess CR51A, the shift promoting recess CR51B, the downshift promoting recess CR51C and the additional upshift promoting recess CR51D may be omitted from the first continuous recess CR 51.

As shown in fig. 17, the last chain engagement upshift promoting tooth TU51C includes a upshift recess TU51C1 disposed on the same side as the first axial facing surface SP5a 1. The upshift recess TU51C1 is configured to guide the bicycle chain C to the smaller sprocket SP6 (fig. 2) during an upshift operation.

The initial chain engagement downshift facilitating tooth TD51C includes a downshift recess portion TD51C1 provided on the same side as the first axial facing surface SP5a 1. The downshift recess TD51C1 is configured to facilitate initial receipt of the bicycle chain C at the initial chain engagement downshift facilitating tooth TD51C during a downshift operation.

As shown in fig. 18, the initial chain engagement downshift facilitation tooth TD51C includes an additional downshift recess TD51C2 provided on the same side as the second axial facing surface SP5a 2. The additional downshift recess TD51C2 is configured to facilitate initial receipt of the bicycle chain C at the initial chain engagement downshift facilitating tooth TD51C during a downshift operation.

As shown in fig. 17, the plurality of sprocket teeth SP5B includes an additional downshift facilitating tooth TD 51D. The additional downshift facilitating tooth TD51D is adjacent to the initial chain engagement downshift facilitating tooth TD51C, with no further tooth therebetween in the circumferential direction D1. The additional downshift facilitating tooth TD51D is provided on the upstream side of the initial chain engagement downshift facilitating tooth TD51C in the rotational driving direction D11.

The additional downshift facilitation tooth TD51D includes a downshift recess portion TD51D1 provided on the same side as the first axial facing surface SP5a 1. The downshift recess TD51D1 is configured to facilitate engagement of the bicycle chain C with the additional downshift facilitating tooth TD51D during a downshift operation.

As seen in fig. 13, the bicycle sprocket SP5 includes a plurality of first tooth bottoms B51A-B51H. Finally, the chain engagement upshift promoting tooth TU51C is disposed between the tooth bottoms B51A and B51B in the circumferential direction D1. The first upshift promoting teeth TU51A are disposed between the tooth bottoms B51B and B51C in the circumferential direction D1. The first additional upshift promoting tooth TU51B is disposed between tooth bottoms B51C and B51D in the circumferential direction D1. The first additional downshift facilitation tooth TD51B is disposed between the tooth bottoms B51D and B51E in the circumferential direction D1. The first downshift facilitation tooth TD51A is disposed between the tooth bottoms B51E and B51F in the circumferential direction D1. Initially the chain engagement downshift facilitating tooth TD51C is disposed in the circumferential direction D1 between tooth bottoms B51F and B51G. The additional downshift facilitation tooth TD51D is disposed between the tooth bottoms B51G and B51H in the circumferential direction D1. The first continuous recess CR51 extends in the circumferential direction D1 from the tooth bottom B51B to the tooth bottom B51F.

A radial line L51A is defined as extending from the rotational center axis a1 to the tooth bottom B51A when viewed along the rotational center axis a 1. A radial line L51B is defined as extending from the rotational center axis a1 to the tooth bottom B51B. A radial line L51C is defined as extending from the rotational center axis a1 to the tooth bottom B51C. A radial line L51D is defined as extending from the rotational center axis a1 to the tooth bottom B51D. A radial line L51E is defined as extending from the rotational center axis a1 to the tooth bottom B51E. A radial line L51F is defined as extending from the rotational center axis a1 to the tooth bottom B51F. A radial line L51G is defined as extending from the rotational center axis a1 to the tooth bottom B51G. A radial line L51H is defined as extending from the rotational center axis a1 to the tooth bottom B51H.

The first upshift axial surface TU51a1 and the first additional upshift axial surface TU51a2 are disposed between the radial lines L51B and L51C along the circumferential direction D1. The second upshift axial surface TU51B1 and the second additional upshift axial surface TU51B2 are disposed between the radial lines L51C and L51D along the circumferential direction D1. The second downshift axial surface TD51B1 and the second additional downshift axial surface TD51B2 are disposed between the radial lines L51D and L51E in the circumferential direction D1. The first downshift axial surface TD51a1 is disposed between the radial lines L51E and L51F in the circumferential direction D1.

The radial line L51E is disposed on a boundary between the first downshift axial surface TD51a1 and the second additional downshift axial surface TD51B2 as viewed along the rotational center axis a 1. A radial line L51D is provided on a boundary between the second downshift axial surface TD51B1 and the second additional upshift axial surface TU51B1 when viewed along the rotational center axis a 1. When viewed along the rotational center axis a1, a radial line L51C is provided on a boundary between the second additional upshift axial surface TU51B2 and the first upshift axial surface TU51a 1.

As seen in fig. 13, the bicycle sprocket SP5 includes a first upshift promoting region FU51 configured to facilitate an upshift operation. The bicycle sprocket SP5 includes a first downshift facilitation zone FD51 configured to facilitate a downshift operation. At least one first axially recessed upshift promoting tooth TU51 (a first upshift promoting tooth TU51A and a first additional upshift promoting tooth TU51B) and a last chain engagement upshift promoting tooth TU51C are provided in the first upshift promoting region FU 51. At least one first axially concave downshift facilitation tooth TD51 (first downshift facilitation tooth TD51A and first additional downshift facilitation tooth TD51B), an initial chain engagement downshift facilitation tooth TD51C and an additional downshift facilitation tooth TD51D are provided in the first downshift facilitation region FD 51. A first upshift promoting region FU51 is defined between tooth bottoms B51A to B51D in the circumferential direction D1. The first downshift facilitation region FD51 is defined between the tooth bottoms B51D to B51H in the circumferential direction D1. The term "upshift promoting region" as used herein is intended to refer to a region intended to promote an upshift operation. The term "downshift facilitation zone" as used herein is intended to refer to a zone intended to facilitate a downshift operation.

As shown in fig. 8, the plurality of sprocket teeth SP5B includes at least one second axially recessed upshift promoting tooth TU52 with respect to the rotational center axis a 1. The plurality of sprocket teeth SP5B includes at least one second axially recessed downshift facilitation tooth TD52 with respect to the rotational center axis a 1.

The at least one second axially recessed downshift facilitation tooth TD52 is adjacent to the at least one second axially recessed upshift facilitation tooth TU52 with no other tooth in between in the circumferential direction D1. The at least one second axially recessed downshift facilitating tooth TD52 is disposed on an upstream side of the at least one second axially recessed upshift facilitating tooth TU52 in the rotational drive direction D11 of the bicycle sprocket SP 5. However, the at least one second axially recessed downshift facilitating tooth TD52 may be disposed on a downstream side of the at least one second axially recessed upshift facilitating tooth TU52 in the rotational drive direction D11 of the bicycle sprocket SP 5.

The at least one second axially recessed upshift promoting tooth TU52 has substantially the same structure as the structure of the at least one first axially recessed upshift promoting tooth TU 51. The at least one second axially recessed downshift facilitation tooth TD52 has substantially the same structure as the structure of the at least one first axially recessed downshift facilitation tooth TD 51. Thus, the description of the at least one first axially recessed upshift promoting tooth TU51 and the at least one first axially recessed downshift promoting tooth TD51 may be used as the description of the at least one second axially recessed upshift promoting tooth TU52 and the at least one second axially recessed downshift promoting tooth TD 52.

The at least one second axially recessed upshift promoting tooth TU52 includes a second upshift promoting tooth TU52A, a second additional upshift promoting tooth TU52B and a last chain engagement upshift promoting tooth TU 52C. The second upshift promoting tooth TU52A, the second additional upshift promoting tooth TU52B and the last chain engagement upshift promoting tooth TU52C have substantially the same structure as the structure of the first upshift promoting tooth TU51A, the first additional upshift promoting tooth TU51B and the last chain engagement upshift promoting tooth TU 51C. Thus, the description of the first upshift promoting tooth TU51A, the first additional upshift promoting tooth TU51B and the last chain engagement upshift promoting tooth TU51C may be used as the description of the second upshift promoting tooth TU52A, the second additional upshift promoting tooth TU52B and the last chain engagement upshift promoting tooth TU 52C.

The at least one second axially recessed downshift facilitation tooth TD52 includes a second downshift facilitation tooth TD52A, a second additional downshift facilitation tooth TD52B, an initial chain engagement downshift facilitation tooth TD52C and an additional downshift facilitation tooth TD 52D. The second downshift facilitation tooth TD52A, the second additional downshift facilitation tooth TD52B, the initial chain engagement downshift facilitation tooth TD52C and the additional downshift facilitation tooth TD52D have substantially the same structure as the structure of the first downshift facilitation tooth TD51A, the first additional downshift facilitation tooth TD51B, the initial chain engagement downshift facilitation tooth TD51C and the additional downshift facilitation tooth TD 51D. Thus, the description of the first downshift accelerating tooth TD51A, the first additional downshift accelerating tooth TD51B, the initial chain engagement downshift accelerating tooth TD51C and the additional downshift accelerating tooth TD51D can be used as the description of the second downshift accelerating tooth TD52A, the second additional downshift accelerating tooth TD52B, the initial chain engagement downshift accelerating tooth TD52C and the additional downshift accelerating tooth TD 52D.

The at least one second axially recessed upshift promoting tooth TU52 and the at least one second axially recessed downshift promoting tooth TD52 are provided with a second continuous recess CR52 extending in a circumferential direction D1 relative to the rotational center axis a 1. In this embodiment, the second continuous recessed portion CR52 is provided on the second axial facing surface SP5a 2. The second continuous recess CR52 has substantially the same structure as the structure of the first continuous recess CR 51. Therefore, the description of the first continuous recess CR51 can be used as the description of the second continuous recess CR 52.

In this embodiment, the second continuous recess CR52 may also be referred to as continuous recess CR 52. The second upshift promoting teeth TU52A, the second additional upshift promoting teeth TU52B, the second downshift promoting teeth TD52A and the second additional downshift promoting teeth TD52B are provided with a second continuous recess CR 52. In other words, at least four axially recessed teeth TU52A, TU52B, TD52A and TD52B are provided with a continuous recess CR52 extending in the circumferential direction D1.

The bicycle sprocket SP5 includes a second upshift promoting region FU52 and a second downshift promoting region FD 52. The second upshift promoting region FU52 and the second downshift promoting region FD52 have substantially the same structure as the first upshift promoting region FU51 and the first downshift promoting region FD 51. Thus, the description of the first upshift promoting region FU51 and the first downshift promoting region FD51 can be used as the description of the second upshift promoting region FU52 and the second downshift promoting region FD 52.

As shown in fig. 8, the plurality of sprocket teeth SP5B includes at least one third axially recessed upshift promoting tooth TU53 with respect to the rotational center axis a 1. The plurality of sprocket teeth SP5B includes at least one third axially concave downshift facilitating tooth TD53 with respect to the rotational center axis a 1.

The at least one third axially recessed downshift facilitation tooth TD53 is adjacent to the at least one third axially recessed upshift facilitation tooth TU53 with no other tooth in between in the circumferential direction D1. The at least one third axially recessed downshift facilitating tooth TD53 is disposed on an upstream side of the at least one third axially recessed upshift facilitating tooth TU53 in the rotational drive direction D11 of the bicycle sprocket SP 5. However, the at least one third axially recessed downshift facilitating tooth TD53 may be disposed on a downstream side of the at least one third axially recessed upshift facilitating tooth TU53 in the rotational drive direction D11 of the bicycle sprocket SP 5.

The at least one third axially recessed upshift promoting tooth TU53 has substantially the same structure as the structure of the at least one first axially recessed upshift promoting tooth TU 51. The at least one third axially recessed downshift facilitation tooth TD53 has substantially the same structure as the structure of the at least one first axially recessed downshift facilitation tooth TD 51. Thus, the description of the at least one first axially recessed upshift promoting tooth TU51 and the at least one first axially recessed downshift promoting tooth TD51 may be used as the description of the at least one third axially recessed upshift promoting tooth TU53 and the at least one third axially recessed downshift promoting tooth TD 53.

The at least one third axially recessed upshift promoting tooth TU53 includes a third upshift promoting tooth TU53A, a third additional upshift promoting tooth TU53B and a last chain engagement upshift promoting tooth TU 53C. The third upshift promoting tooth TU53A, the third additional upshift promoting tooth TU53B and the last chain engagement upshift promoting tooth TU53C have substantially the same structure as the first upshift promoting tooth TU51A, the first additional upshift promoting tooth TU51B and the last chain engagement upshift promoting tooth TU 51C. Thus, the description of the first upshift promoting tooth TU51A, the first additional upshift promoting tooth TU51B and the last chain engagement upshift promoting tooth TU51C may be used as the description of the third upshift promoting tooth TU53A, the third additional upshift promoting tooth TU53B and the last chain engagement upshift promoting tooth TU 53C.

The at least one third axially recessed downshift facilitation tooth TD53 comprises a third downshift facilitation tooth TD53A, an initial chain engagement downshift facilitation tooth TD53C and an additional downshift facilitation tooth TD 53D. The third additional upshift promoting tooth TU53B also functions as a downshift promoting tooth corresponding to the first additional downshift promoting tooth TD 51B. Thus, the at least one third axially recessed downshift facilitation tooth TD53 further comprises a third additional upshift facilitation tooth TU 53B. The third downshift accelerating tooth TD53A, the third additional upshift accelerating tooth TU53B as the downshift accelerating teeth, the initial chain engagement downshift accelerating tooth TD53C and the additional downshift accelerating tooth TD53D have substantially the same structures as those of the first downshift accelerating tooth TD51A, the first additional downshift accelerating tooth TD51B, the initial chain engagement downshift accelerating tooth TD51C and the additional downshift accelerating tooth TD 51D. Thus, the description of the first downshift facilitation tooth TD51A, the first additional downshift facilitation tooth TD51B, the initial chain engagement downshift facilitation tooth TD51C and the additional downshift facilitation tooth TD51D can be used as a description of the third downshift facilitation tooth TD53A, the third additional upshift facilitation tooth TU53B as a downshift facilitation tooth, the initial chain engagement downshift facilitation tooth TD53C and the additional downshift facilitation tooth TD 53D.

The at least one third axially recessed upshift promoting tooth TU53 and the at least one third axially recessed downshift promoting tooth TD53 are provided with a third continuous recess CR53 extending in a circumferential direction D1 relative to the rotational center axis a 1. In this embodiment, the third continuous recessed portion CR53 is provided on the second axial facing surface SP5a 2. The third upshift promoting teeth TU53A, the third additional upshift promoting teeth TU53B and the third downshift promoting teeth TD53A are provided with a third continuous recess CR 53. The third continuous recess CR53 has substantially the same structure as the structure of the first continuous recess CR 51. Therefore, the description of the first continuous recess CR51 can be used as the description of the third continuous recess CR 53.

The bicycle sprocket SP5 includes a third upshift promoting region FU53 and a third downshift promoting region FD 53. The third upshift promoting region FU53 and the third downshift promoting region FD53 have substantially the same structure as the first upshift promoting region FU51 and the first downshift promoting region FD 51. Thus, the description of the first upshift promoting region FU51 and the first downshift promoting region FD51 can be used as the description of the third upshift promoting region FU53 and the third downshift promoting region FD 53.

The bicycle sprockets SP2 to SP4 and SP6 to SP8 have substantially the same structure as the bicycle sprocket SP 5.

As shown in fig. 5, for example, the plurality of sprocket teeth SP2B includes at least one first axially recessed upshift facilitating tooth TU21 and at least one first axially recessed downshift facilitating tooth TD 21. The at least one first axially recessed upshift promoting tooth TU21 includes a first upshift promoting tooth TU21A, a first additional upshift promoting tooth TU21B and a last chain engagement upshift promoting tooth TU 21C. The at least one first axially recessed downshift facilitation tooth TD21 comprises a first downshift facilitation tooth TD21A, a first additional downshift facilitation tooth TD21B, an initial chain engagement downshift facilitation tooth TD21C and an additional downshift facilitation tooth TD 21D.

The at least one first axially recessed upshift promoting tooth TU21 and the at least one first axially recessed downshift promoting tooth TD21 are provided with a first continuous recess CR21 extending in a circumferential direction D1 relative to the rotational center axis a 1. The first upshift promoting teeth TU21A, the first additional upshift promoting teeth TU21B, the first downshift promoting teeth TD21A and the first additional downshift promoting teeth TD21B are provided with first continuous concave portions CR 21.

As shown in fig. 5, the plurality of sprocket teeth SP2B includes at least one second axially recessed upshift promoting tooth TU22 and at least one second axially recessed downshift promoting tooth TD 22. The at least one second axially recessed upshift promoting tooth TU22 includes a second upshift promoting tooth TU22A, a second additional upshift promoting tooth TU22B and a last chain engagement upshift promoting tooth TU 22C. The at least one second axially recessed downshift facilitation tooth TD22 comprises a second downshift facilitation tooth TD22A, a second additional downshift facilitation tooth TD22B, an initial chain engagement downshift facilitation tooth TD22C and an additional downshift facilitation tooth TD 22D.

The at least one second axially recessed upshift promoting tooth TU22 and the at least one second axially recessed downshift promoting tooth TD22 are provided with a second continuous recess CR22 extending in a circumferential direction D1 relative to the rotational center axis a 1. The second upshift promoting teeth TU22A, the second additional upshift promoting teeth TU22B, the second downshift promoting teeth TD22A and the second additional downshift promoting teeth TD22B are provided with a second continuous recess CR 22.

As shown in fig. 6, the plurality of sprocket teeth SP3B includes at least one first axially recessed upshift promoting tooth TU31 and at least one first axially recessed downshift promoting tooth TD 31. The at least one first axially recessed upshift promoting tooth TU31 comprises a first upshift promoting tooth TU31A, a first additional upshift promoting tooth TU31B and a last chain engagement upshift promoting tooth TU 31C. The at least one first axially concave downshift facilitation tooth TD31 comprises a first downshift facilitation tooth TD31A, a first additional downshift facilitation tooth TD31B, an initial chain engagement downshift facilitation tooth TD31C and an additional downshift facilitation tooth TD 31D.

The at least one first axially recessed upshift promoting tooth TU31 and the at least one first axially recessed downshift promoting tooth TD31 are provided with a first continuous recess CR31 extending in a circumferential direction D1 relative to the rotational center axis a 1. The first upshift promoting teeth TU31A, the first additional upshift promoting teeth T3131B, the first downshift promoting teeth TD31A and the first additional downshift promoting teeth TD31B are provided with first continuous recesses CR 31.

As shown in fig. 7, the plurality of sprocket teeth SP4B includes at least one first axially recessed upshift promoting tooth TU41 and at least one first axially recessed downshift promoting tooth TD 41. The at least one first axially recessed upshift promoting tooth TU41 comprises a first upshift promoting tooth TU41A, a first additional upshift promoting tooth TU41B and a last chain engagement upshift promoting tooth TU 41C. The at least one first axially concave downshift facilitation tooth TD41 comprises a first downshift facilitation tooth TD41A, a first additional downshift facilitation tooth TD41B, an initial chain engagement downshift facilitation tooth TD41C and an additional downshift facilitation tooth TD 41D.

The at least one first axially recessed upshift promoting tooth TU41 and the at least one first axially recessed downshift promoting tooth TD41 are provided with a first continuous recess CR41 extending in a circumferential direction D1 relative to the rotational center axis a 1. The first upshift promoting teeth TU41A, the first additional upshift promoting teeth T4141B, the first downshift promoting teeth TD41A and the first additional downshift promoting teeth TD41B are provided with first continuous concave portions CR 41.

As shown in fig. 9, for example, the plurality of sprocket teeth SP6B includes at least one first axially recessed upshift facilitating tooth TU61 and at least one first axially recessed downshift facilitating tooth TD 61. The at least one first axially recessed upshift promoting tooth TU61 includes a first upshift promoting tooth TU61A, a first additional upshift promoting tooth TU61B and a last chain engagement upshift promoting tooth TU 61C. The at least one first axially concave downshift facilitation tooth TD61 comprises a first downshift facilitation tooth TD61A, a first additional downshift facilitation tooth TD61B, an initial chain engagement downshift facilitation tooth TD61C and an additional downshift facilitation tooth TD 61D.

The at least one first axially recessed upshift promoting tooth TU61 and the at least one first axially recessed downshift promoting tooth TD61 are provided with a first continuous recess CR61 extending in a circumferential direction D1 relative to the rotational center axis a 1. The first upshift promoting teeth TU61A, the first additional upshift promoting teeth T61, the first downshift promoting teeth TD61A and the first additional downshift promoting teeth TD61B are provided with first continuous recessed portions CR 61.

As shown in fig. 9, the plurality of sprocket teeth SP6B includes at least one second axially recessed upshift promoting tooth TU62 and at least one second axially recessed downshift promoting tooth TD 62. The at least one second axially recessed upshift promoting tooth TU62 includes a second upshift promoting tooth TU62A, a second additional upshift promoting tooth TU62B and a last chain engagement upshift promoting tooth TU 62C. The at least one second axially recessed downshift facilitation tooth TD62 includes a second downshift facilitation tooth TD62A, a second additional downshift facilitation tooth TD62B, an initial chain engagement downshift facilitation tooth TD62C and an additional downshift facilitation tooth TD 62D.

The at least one second axially recessed upshift promoting tooth TU62 and the at least one second axially recessed downshift promoting tooth TD62 are provided with a second continuous recess CR62 extending in a circumferential direction D1 relative to the rotational center axis a 1. The second upshift promoting teeth TU62A, the second additional upshift promoting teeth TU62B, the second downshift promoting teeth TD62A and the second additional downshift promoting teeth TD62B are provided with a second continuous recess CR 62.

As shown in fig. 10, for example, the plurality of sprocket teeth SP7B includes at least one first axially recessed upshift facilitating tooth TU71 and at least one first axially recessed downshift facilitating tooth TD 71. The at least one first axially recessed upshift promoting tooth TU71 includes a first upshift promoting tooth TU71A, a first additional upshift promoting tooth TU71B and a last chain engagement upshift promoting tooth TU 71C. The at least one first axially concave downshift facilitation tooth TD71 comprises a first downshift facilitation tooth TD71A, a first additional downshift facilitation tooth TD71B, an initial chain engagement downshift facilitation tooth TD71C and an additional downshift facilitation tooth TD 71D.

The at least one first axially recessed upshift promoting tooth TU71 and the at least one first axially recessed downshift promoting tooth TD71 are provided with a first continuous recess CR71 extending in a circumferential direction D1 relative to the rotational center axis a 1. The first upshift promoting teeth TU71A, the first additional upshift promoting teeth TU71B, the first downshift promoting teeth TD71A and the first additional downshift promoting teeth TD71B are provided with a first continuous recess CR 71.

As shown in fig. 10, the plurality of sprocket teeth SP7B includes at least one second axially recessed upshift promoting tooth TU72 and at least one second axially recessed downshift promoting tooth TD 72. The at least one second axially recessed upshift promoting tooth TU72 includes a second upshift promoting tooth TU72A, a second additional upshift promoting tooth TU72B and a last chain engagement upshift promoting tooth TU 72C. The at least one second axially recessed downshift facilitation tooth TD72 includes a second downshift facilitation tooth TD72A, a second additional downshift facilitation tooth TD72B, an initial chain engagement downshift facilitation tooth TD72C and an additional downshift facilitation tooth TD 72D.

The at least one second axially recessed upshift promoting tooth TU72 and the at least one second axially recessed downshift promoting tooth TD72 are provided with a second continuous recess CR72 extending in a circumferential direction D1 relative to the rotational center axis a 1. The second upshift promoting teeth TU72A, the second additional upshift promoting teeth TU72B, the second downshift promoting teeth TD72A and the second additional downshift promoting teeth TD72B are provided with a second continuous recess CR 72.

As shown in fig. 11, for example, the plurality of sprocket teeth SP8B includes at least one first axially recessed upshift facilitating tooth TU81 and at least one first axially recessed downshift facilitating tooth TD 81. The at least one first axially recessed upshift promoting tooth TU81 comprises a first upshift promoting tooth TU81A, a first additional upshift promoting tooth TU81B and a last chain engagement upshift promoting tooth TU 81C. The at least one first axially concave downshift facilitation tooth TD81 comprises a first downshift facilitation tooth TD81A, a first additional downshift facilitation tooth TD81B, an initial chain engagement downshift facilitation tooth TD81C and an additional downshift facilitation tooth TD 81D.

The at least one first axially recessed upshift promoting tooth TU81 and the at least one first axially recessed downshift promoting tooth TD81 are provided with a first continuous recess CR81 extending in a circumferential direction D1 relative to the rotational center axis a 1. The first upshift promoting teeth TU81A, the first additional upshift promoting teeth T81B, the first downshift promoting teeth TD81A and the first additional downshift promoting teeth TD81B are provided with first continuous recessed portions CR 81.

As shown in fig. 11, the plurality of sprocket teeth SP8B includes at least one third axially recessed upshift promoting tooth TU83 and at least one third axially recessed downshift promoting tooth TD 83. The at least one third axially recessed upshift promoting tooth TU83 includes a third upshift promoting tooth TU83A, a third additional upshift promoting tooth TU83B and a last chain engagement upshift promoting tooth TU 83C. The third additional upshift promoting tooth TU83B also functions as a downshift promoting tooth corresponding to the first additional downshift promoting tooth TD 81B. Thus, the at least one third axially recessed downshift facilitation tooth TD83 comprises a third downshift facilitation tooth TD83A, a third additional upshift facilitation tooth TU83B as a downshift facilitation tooth, an initial chain engagement downshift facilitation tooth TD83C and an additional downshift facilitation tooth TD 83D.

The at least one third axially recessed upshift promoting tooth TU83 and the at least one third axially recessed downshift promoting tooth TD83 are provided with a third continuous recess CR83 extending in a circumferential direction D1 relative to the rotational center axis a 1. The third upshift promoting teeth TU83A, the third additional upshift promoting teeth TU83B and the third downshift promoting teeth TD83A are provided with a third continuous recess CR 83.

The term "comprises/comprising" and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers, and/or steps. The concept also applies to words having similar meanings such as the terms, "having", "including" and their derivatives.

The terms "member," "portion," "section," "member," "body" and "structure" when used in the singular can have the dual meaning of a single part or a plurality of parts.

Ordinals such as "first" and "second" are referred to in this application as identifiers only, but without any other meaning, e.g., a particular order, etc. Further, for example, the term "first element" does not itself imply the presence of "second element," and the term "second element" does not itself imply the presence of "first element.

The term "pair" as used herein may include a configuration in which a pair of elements have shapes or structures different from each other, except for a configuration in which the pair of elements have the same shape or structure as each other.

The terms "a" (or "an"), "one or more" and "at least one" are used interchangeably herein.

Finally, terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. All numerical values described in this application may be construed to include terms such as "substantially", "about" and "approximately".

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.