JP2024106666A - Rear sprocket for human-powered vehicles - Google Patents

Abstract

[Problem] To provide a rear sprocket for a human-powered vehicle that can prevent dirt such as mud from adhering to an area that facilitates gear shifting. [Solution] A rear sprocket for a human-powered vehicle includes a sprocket body and a plurality of sprocket teeth extending radially outward from an outer periphery of the sprocket body, the plurality of sprocket teeth including a plurality of upshift promotion teeth, the plurality of upshift promotion teeth including an upshift initiation tooth and an upshift recess tooth, the upshift initiation tooth having a first upshift recess, the upshift recess tooth having a second upshift recess, a first upshift tooth root defined circumferentially between the upshift initiation tooth and the upshift recess tooth, and a first upshift chamfer provided on at least the first upshift tooth root. [Selected Figure] Figure 3

Description

This disclosure relates to a rear sprocket for a human-powered vehicle.

The rear sprocket disclosed in Patent Document 1 has a shift promotion area to promote shifting by the derailleur.

U.S. Pat. No. 6,340,338

One of the objectives of this disclosure is to provide a rear sprocket for a human-powered vehicle that can prevent dirt, such as mud, from adhering to the area that facilitates gear shifting.

A rear sprocket according to a first aspect of the present disclosure is a rear sprocket for a human-powered vehicle, the rear sprocket having a central axis of rotation defining axial, radial, and circumferential directions, an axially outer side surface, and an axially inner side surface provided on the opposite side of the axially outer side surface in the axial direction and configured to face a central axis surface of the human-powered vehicle when the rear sprocket is mounted on the human-powered vehicle in an installed state. The rear sprocket according to a first aspect of the present disclosure is a rear sprocket for a human-powered vehicle, the rear sprocket having a axially outer side surface and an axially inner side surface configured to face a central axis surface of the human-powered vehicle when the rear sprocket is mounted on the human-powered vehicle. The rear sprocket has a sprocket body and a plurality of sprocket teeth extending radially outward from an outer periphery of the sprocket body in the radial direction, the plurality of sprocket teeth including a plurality of upshift promoting teeth configured to promote an upshift operation in which a drive chain moves from the rear sprocket towards the adjacent small sprocket adjacent to the rear sprocket such that there is no other sprocket between the rear sprocket and the adjacent small sprocket, and the plurality of upshift promoting teeth are configured to promote an upshift operation in which a drive chain moves from the rear sprocket towards the adjacent small sprocket adjacent to the rear sprocket such that there is no other sprocket between the rear sprocket and the adjacent small sprocket, the upshift start tooth includes an upshift initiation tooth configured to be first to disengage from a drive chain, and an upshift recess tooth, the upshift initiation tooth having a first upshift recess provided on the axially outer surface of the upshift initiation tooth to be recessed in the axial direction from the axially outer surface toward the axially inner surface, the upshift recess tooth having a second upshift recess provided on the axially outer surface of the upshift initiation tooth to be recessed in the axial direction from the axially outer surface toward the axially inner surface, adjacent the upshift start tooth upstream of the upshift start tooth in a direction of driving rotation of the rear sprocket such that there are no other teeth between the upshift start tooth and the upshift recess tooth in the circumferential direction, a first upshift tooth root is defined between the upshift start tooth and the upshift recess tooth in the circumferential direction, and a first upshift chamfer is provided on at least the first upshift tooth root.
According to the rear sprocket on the first side, the first upshift chamfer portion can remove mud and other contaminants from the first upshift tooth bottom, thereby preventing the adhesion of mud and other contaminants to the shift promotion area that promotes upshift operations.

In a second aspect of the rear sprocket according to the first aspect of the present disclosure, the first up-shift chamfer has a first maximum circumferential length of 6 mm or greater.
According to the rear sprocket with the second side, the first upshift chamfer has a first maximum circumferential length of 6 mm or more, thereby preventing mud and the like from adhering to the area of the rear sprocket that promotes upshift operation.

In a rear sprocket of a third aspect according to the second aspect of the present disclosure, the first maximum circumferential length is 9 mm or less.
According to the rear sprocket of the third aspect, the first maximum circumferential length is equal to or greater than 6 mm and equal to or less than 9 mm, thereby ensuring the strength of the area of the rear sprocket that facilitates upshifting operations.

In a rear sprocket of a fourth aspect according to any one of the first to third aspects of the present disclosure, the first upshift chamfer has a first maximum axial length of 0.2 mm or greater.
According to the rear sprocket of the fourth aspect, the first upshift chamfer has a first maximum axial length of 0.2 mm or more, thereby preventing mud and the like from adhering to an area of the rear sprocket that promotes upshift operation.

In a rear sprocket according to a fifth aspect of the present disclosure, the first maximum axial length is 0.4 mm or less.
According to the rear sprocket of the fifth aspect, the first maximum axial length is not less than 0.2 mm and not more than 0.4 mm, thereby ensuring the strength of the area of the rear sprocket that facilitates upshifting operations.

In a rear sprocket of a sixth aspect according to any one of the first to fifth aspects of the present disclosure, the plurality of sprocket teeth further include an adjacent tooth adjacent to the upshift recess tooth upstream of the upshift recess tooth in the driving rotation direction such that there are no other teeth between the upshift recess tooth and the adjacent tooth in the circumferential direction, a second upshift tooth root is defined between the upshift recess tooth and the adjacent tooth in the circumferential direction, and a second upshift chamfer is provided on at least the second upshift tooth root.
According to the rear sprocket with the sixth side face, the second upshift chamfer portion can remove mud and other contaminants from the second upshift tooth bottom, thereby preventing the adhesion of mud and other contaminants to areas of the rear sprocket that promote upshift operations.

In a rear sprocket of a seventh aspect in accordance with the sixth aspect of the present disclosure, the second up shift chamfer has a second maximum circumferential length of 6 mm or greater.
According to the rear sprocket of the seventh side, the second upshift chamfer has a second maximum circumferential length of 6 mm or more, thereby preventing dirt such as mud from adhering to the area of the rear sprocket that promotes upshift operation.

In the rear sprocket of an eighth aspect according to the seventh aspect of the present disclosure, the second maximum circumferential length is 9 mm or less.
According to the rear sprocket of the eighth aspect, the second maximum circumferential length is equal to or greater than 6 mm and equal to or less than 9 mm, thereby ensuring the strength of the area of the rear sprocket that facilitates upshifting operations.

In a rear sprocket of a ninth aspect according to any one of the sixth to eighth aspects of the present disclosure, the second up shift chamfer has a second maximum axial length of 0.2 mm or greater.
According to the rear sprocket of the ninth aspect, the second upshift chamfer has a second maximum axial length of 0.2 mm or more, thereby preventing dirt such as mud from adhering to the area of the rear sprocket that promotes upshift operation.

In a rear sprocket of a tenth aspect in accordance with the ninth aspect of the present disclosure, the second maximum axial length is equal to or less than 0.4 mm.
According to the rear sprocket of the tenth aspect, the second maximum axial length is not less than 0.2 mm and not more than 0.4 mm, thereby ensuring the strength of the area that promotes upshifting operation in the rear sprocket.

In a rear sprocket of an eleventh aspect according to any one of the first to tenth aspects of the present disclosure, the sprocket body has a first minimum axial thickness of 0.7 mm or more at a portion corresponding to the upshift-initiating tooth.
According to the rear sprocket of the eleventh aspect, the portion of the sprocket body corresponding to the upshift initiation tooth has a first minimum axial thickness of 0.7 mm or more, thereby ensuring the strength of the area that promotes upshift operation in the rear sprocket.

In a rear sprocket of a twelfth aspect in accordance with an eleventh aspect of the present disclosure, the first minimum axial thickness is 1.3 mm or less.
According to the rear sprocket of the twelfth side surface, the first minimum axial thickness is equal to or greater than 0.7 mm and is equal to or less than 1.3 mm, thereby enabling the rear sprocket to be made lighter.

In a rear sprocket of a thirteenth aspect according to any one of the sixth to twelfth aspects of the present disclosure, the sprocket body has a second minimum axial thickness of 0.8 mm or greater at a portion corresponding to the up shift recess teeth.
According to the rear sprocket of the thirteenth side, the portion of the sprocket body corresponding to the upshift recessed tooth has a second minimum axial thickness of 0.8 mm or more, thereby ensuring the strength of the area that promotes upshift operation in the rear sprocket.

In a rear sprocket of a fourteenth aspect in accordance with the thirteenth aspect of the present disclosure, the second minimum axial thickness is 1.6 mm or less.
According to the rear sprocket of the fourteenth side surface, the second minimum axial thickness is not less than 0.8 mm and not more than 1.6 mm, thereby enabling the rear sprocket to be made lighter.

In a rear sprocket of a fifteenth side according to any one of the first to fourteenth sides of the present disclosure, the first upshift chamfer extends from the first upshift root toward the axially outer side.
According to the rear sprocket with the fifteenth side, the first upshift chamfer extends from the first upshift tooth bottom toward the axially outer side, thereby suppressing the adhesion of dirt such as mud to the area of the rear sprocket that promotes upshift operation and reducing shock during upshift operation.

In a rear sprocket of a sixteenth side according to any one of the sixth to tenth, thirteenth, and fourteenth sides of the present disclosure, the second upshift chamfer extends from the second upshift root toward the axially outer side.
According to the rear sprocket with the 16th side, the second upshift chamfer extends from the second upshift tooth bottom toward the axially outer side, thereby suppressing the adhesion of dirt such as mud to the area of the rear sprocket that promotes upshift operation and reducing shock during upshift operation.

In a rear sprocket having a 17th side according to any one of the first to sixteenth sides of the present disclosure, the first upshift chamfer portion is asymmetric with respect to a first reference radial line passing through the rotational center axis and a first circumferential root center point of the first upshift root.
According to the rear sprocket of the 17th side, the first upshift chamfer portion is asymmetric with respect to the first reference radial line, thereby preventing dirt such as mud from adhering to the area of the rear sprocket that promotes upshift operation and ensuring the strength of the area that promotes upshift operation.

In a rear sprocket having an 18th side according to any one of the 6th to 10th, 13th, 14th, and 16th sides of the present disclosure, the second upshift chamfer portion is asymmetric with respect to a second reference radial line passing through the rotational center axis and a second circumferential root center point of the second upshift root.
According to the rear sprocket of the 18th side, the second upshift chamfer portion is asymmetric with respect to the second reference radial line, thereby preventing dirt such as mud from adhering to the area of the rear sprocket that promotes upshift operation and ensuring the strength of the area that promotes upshift operation.

A rear sprocket according to a nineteenth aspect of the present disclosure is a rear sprocket for a human-powered vehicle, the rear sprocket having a central axis of rotation defining an axial direction, a radial direction, and a circumferential direction, an axially outer side surface, and an axially inner side surface provided on the opposite side of the axially outer side surface in the axial direction and configured to face a central axis surface of the human-powered vehicle when the rear sprocket is mounted on the human-powered vehicle in an installed state, the rear sprocket comprising a sprocket body and a plurality of sprocket teeth extending radially outward from an outer periphery of the sprocket body in the radial direction, the plurality of sprocket teeth including a plurality of downshift promoting teeth configured to promote a downshift operation in which a drive chain moves from an adjacent small sprocket towards the rear sprocket, the adjacent small sprocket being configured to have ... and a downshift recess tooth adjacent the rear sprocket configured to first engage the drive chain during a downshift operation, the downshift recess tooth being adjacent to the downshift start tooth downstream of the downshift start tooth relative to a direction of driving rotation of the rear sprocket such that there are no other teeth between the downshift start tooth and the downshift recess tooth in the circumferential direction, the downshift recess tooth having a downshift recess provided on the axially outer surface of the downshift recess tooth such that it is recessed from the axially outer surface to the axially inner surface in the axial direction, a downshift tooth root is defined between the downshift start tooth and the downshift recess tooth in the circumferential direction, and a downshift chamfer is provided on at least the downshift tooth root.
According to the rear sprocket of the nineteenth aspect, the downshift chamfered portion allows mud and other contaminants to be removed from the downshift tooth bottom, thereby preventing the adhesion of mud and other contaminants to areas of the rear sprocket that facilitate downshift operations.

The rear sprocket for a human-powered vehicle disclosed herein can prevent dirt such as mud from adhering to areas that facilitate gear shifting.

1 is a schematic diagram showing a human-powered vehicle having a rear sprocket assembly including a rear sprocket for a human-powered vehicle according to an embodiment. FIG. FIG. 2 is a side view of the rear sprocket assembly of FIG. FIG. 3 is a side view of a rear sprocket for the human-powered vehicle of FIG. FIG. 4 is a side view showing an upshift facilitating region of the rear sprocket for the human-powered vehicle of FIG. 3 . FIG. 4 is a top view of a plurality of upshift facilitation teeth and a drive chain of FIG. FIG. 4 is a top view of the plurality of downshift facilitator teeth and drive chain of FIG. FIG. 5 is a perspective view illustrating a plurality of upshift facilitating teeth, a first shift chamfer, and a second shift chamfer of the rear sprocket for the human-powered vehicle of FIG. FIG. 4 is a side view showing various dimensions of a first shift chamfer and a second shift chamfer of the rear sprocket for the human-powered vehicle of FIG. 3 . FIG. 9 is a plan view showing the axial dimensions of a portion of the sprocket body corresponding to the upshift start tooth, a portion of the sprocket body corresponding to the upshift recess tooth, a first shift chamfer portion, and a second shift chamfer portion of the rear sprocket for a human-powered vehicle in FIG. 8 . 10 is a schematic diagram illustrating a state in which an outer link of the drive chain is in a position corresponding to an upshift displacement tooth and the drive chain disengages from an upshift initiation tooth in an upshift operation of the embodiment; FIG. FIG. 11 is a side view showing a downshift chamfered portion of a modified rear sprocket for a human-powered vehicle.

<Embodiment>
A rear sprocket 30 for a human-powered vehicle according to an embodiment will be described with reference to Figs. 1 to 10. The human-powered vehicle 10 shown in Fig. 1 is, for example, a vehicle that has at least one wheel and can be driven at least by human-powered driving force. The human-powered vehicle 10 includes various types of bicycles, such as mountain bikes, road bikes, city bikes, cargo bikes, hand bikes, and recumbents. The number of wheels that the human-powered vehicle 10 has is not limited. The human-powered vehicle 10 also includes, for example, one-wheeled vehicles and vehicles with two or more wheels. The human-powered vehicle 10 is not limited to vehicles that can be driven only by human-powered driving force. The human-powered vehicle 10 includes, for example, an E-bike that uses not only human-powered driving force but also the driving force of an electric motor for propulsion. The E-bike includes, for example, an electrically assisted bicycle whose propulsion is supported by an electric motor. In the following embodiment, the human-powered vehicle 10 will be described as a bicycle.

In this specification, the following directional terms "front," "rear," "forward," "backward," "left," "right," "sideways," "upward," and "downward," as well as any other similar directional terms, refer to those directions determined with respect to the rider facing the handlebars in a reference position on the human-powered vehicle 10 (e.g., on the saddle or seat).

As shown in FIG. 1, for example, a human-powered vehicle 10 includes a crank 12, a front sprocket 14, a hub assembly 16, a drive chain 18, and a rear sprocket assembly 20. The front sprocket 14 is attached to the crank 12, for example.

The crank 12 includes, for example, a crankshaft 22, a first crank arm 24A, and a second crank arm 24B. The first crank arm 24A and the second crank arm 24B are attached, for example, to both ends of the crankshaft 22. For example, a first pedal 26A is rotatably connected to the first crank arm 24A. For example, a second pedal 26B is rotatably connected to the second crank arm 24B.

The hub assembly 16 includes, for example, a hub axle 28. The hub axle 28 is attached to the frame 10A, for example, so as not to rotate relative to the frame 10A. The rear sprocket assembly 20 is attached to the hub assembly 16, for example, so as to be rotatable relative to the frame 10A of the human-powered vehicle 10. The hub assembly 16 includes, for example, a sprocket support 16A. The rear sprocket assembly 20 is connected to the hub axle 28 via, for example, the sprocket support 16A.

The rear sprocket assembly 20 includes, for example, a plurality of sprockets. The dimensions of the plurality of sprockets are, for example, different from one another. The number of the plurality of sprockets can be selected, for example, as desired. As shown in FIG. 2, the rear sprocket assembly 20 includes, for example, nine sprockets. The rear sprocket assembly 20 may include two or more sprockets but less than nine sprockets, or may include ten or more sprockets.

The human-powered vehicle 10 further includes, for example, a rear derailleur. The rear derailleur is configured to perform a gear shifting operation. The gear shifting operation is, for example, an operation of moving the drive chain 18, which is engaged with one of the multiple sprockets, from one of the multiple sprockets to another of the multiple sprockets.

The drive chain 18 is wound around, for example, the front sprocket 14 and one of a number of sprockets included in the rear sprocket assembly 20. The front sprocket 14 may include a single sprocket or multiple sprockets. The drive chain 18 transmits torque applied to, for example, the first pedal 26A and the second pedal 26B from the front sprocket 14 to the rear sprocket assembly 20. The rear sprocket assembly 20 transmits the torque to the rear wheel of the human-powered vehicle 10 via, for example, the hub assembly 16.

1 and 5, the drive chain 18 includes, for example, a plurality of rollers 18A, a plurality of outer links 18B, and a plurality of inner links 18C. The outer link 18B is configured, for example, so that a pair of outer plates are aligned in the axial direction AD. The inner link 18C is configured, for example, so that a pair of inner plates are aligned in the axial direction AD. The teeth of the front sprocket 14 are configured to be positionable in the space between the pair of outer plates of the outer link 18B and the space between the pair of inner plates of the inner link 18C. The teeth of each of the multiple sprockets included in the rear sprocket assembly 20 are configured to be positionable in the space between the pair of outer plates of the outer link 18B and the space between the pair of inner plates of the inner link 18C.

As shown in Figures 1 and 2, in this embodiment, the sprocket with the second largest diameter among the multiple sprockets included in the rear sprocket assembly 20 is described as the rear sprocket 30. In this embodiment, the sprocket with the third largest diameter among the multiple sprockets included in the rear sprocket assembly 20 is described as the adjacent small sprocket 20A. The adjacent small sprocket 20A is, for example, a sprocket adjacent to the rear sprocket 30 and has a smaller diameter than the rear sprocket 30. The adjacent small sprocket 20A is adjacent to the rear sprocket 30 such that there is no other sprocket between the rear sprocket 30 and the adjacent small sprocket 20A.

The rear sprocket 30 for a human-powered vehicle has a central axis of rotation C, an axially outer surface 30X, and an axially inner surface 30Y. The central axis of rotation C of the rear sprocket 30 coincides with the central axis of rotation of the rear sprocket assembly 20, for example. The central axis of rotation C defines the axial direction AD, the radial direction RD, and the circumferential direction CD. The axially inner surface 30Y is provided on the opposite side of the axially outer surface 30X in the axial direction AD. The axially inner surface 30Y is configured to face the central axis plane CS of the human-powered vehicle 10 in the mounted state in which the rear sprocket 30 is mounted on the human-powered vehicle 10. The central axis plane CS passes through, for example, the center of the human-powered vehicle 10 in the left-right direction. The mounted state is, for example, a state in which the rear sprocket assembly 20 is attached to the human-powered vehicle 10. In the mounted state, the rear sprocket assembly 20 is attached to the hub axle 28.

2 and 3, the sprocket body 32 includes a plurality of sprocket teeth 34. The sprocket body 32 includes, for example, an outer annular portion 36, an inner annular portion 38, and a plurality of connecting arms 40. The outer annular portion 36 has, for example, an outer peripheral portion 36A on which the plurality of sprocket teeth 34 are provided, and an inner peripheral portion 36B opposite the outer peripheral portion 36A in the radial direction RD. The inner annular portion 38 has a plurality of spline teeth 38A that engage with the sprocket support 16A of the hub assembly 16. The plurality of connecting arms 40 are located between the outer annular portion 36 and the inner annular portion 38 in the radial direction RD. One sprocket tooth 34 is defined, for example, as a portion between two adjacent tooth roots in the circumferential direction CD.

The plurality of sprocket teeth 34 extend radially outward from the outer periphery of the sprocket body 32 in the radial direction RD. The plurality of sprocket teeth 34 extend radially outward from the outer periphery 36A of the outer annular portion 36 in the radial direction RD, for example. Each sprocket tooth 34 has, for example, a drive surface 34A and a non-drive surface 34B provided on the opposite side of the drive surface 34A in the circumferential direction CD. As shown in Figures 1, 3, and 5, each sprocket tooth 34 engages, for example, with the roller 18A of the drive chain 18 at the drive surface 34A. The manual drive force applied to the first pedal 26A and the second pedal 26B is transmitted to the rear sprocket assembly 20 via the drive chain 18 by the roller 18A engaging with the drive surface 34A.

1, 3, and 4, the plurality of sprocket teeth 34 includes a plurality of upshift promoting teeth 42 configured to promote an upshift operation. In an upshift operation, the drive chain 18 moves from the rear sprocket 30 toward the adjacent small sprocket 20A. In an upshift operation, the drive chain 18 is moved from the rear sprocket 30 to the adjacent small sprocket 20A by, for example, the rear derailleur. The plurality of upshift promoting teeth 42 includes an upshift initiation tooth 44 and an upshift recess tooth 46. The plurality of upshift promoting teeth 42 may further include, for example, an upshift displacement tooth 48.

The rear sprocket 30 includes, for example, at least one upshift promoting area. The at least one upshift promoting area is, for example, an area that promotes an upshift operation in the rear sprocket 30. The at least one upshift promoting area includes, for example, a plurality of upshift promoting teeth 42. The at least one upshift promoting area includes, for example, an upshift initiation tooth 44, an upshift recess tooth 46, and an upshift displacement tooth 48. The rear sprocket 30 of this embodiment includes four upshift promoting areas. The number of upshift promoting areas is determined, for example, according to the dimensions of the rear sprocket 30, etc.

1 to 5, the upshift tooth 48 is configured to facilitate the displacement of the drive chain 18 from the rear sprocket 30 toward the adjacent small sprocket 20A during an upshift operation. The axial inner surface 48Y of the upshift tooth 48 is provided with, for example, a first axial recess 50. The first axial recess 50 is provided on the axial inner surface 48Y of the upshift tooth 48 so as to be recessed from the axial inner surface 30Y toward the axial outer surface 30X in the axial direction AD. The first axial recess 50 is configured, for example, so that the axial inner surface 48Y of the upshift tooth 48 is inclined from the outer periphery 36A of the outer annular portion 36 of the sprocket body 32 toward the tip 48C of the upshift tooth 48. The first axial recess 50 may be provided on the axial inner surface 48Y of the upshift tooth 48 by step-pressing.

The first axial recess 50 is disposed, for example, at least at the tip 48C of the upshift tooth 48. The first axial recess 50 extends, for example, in the radial direction RD from the tip 48C of the upshift tooth 48 radially inward. The first axial recess 50 extends, for example, in the radial direction RD from the tip 48C of the upshift tooth 48 to the outer periphery 36A of the outer annular portion 36 of the sprocket body 32 radially inward. The first axial recess 50 extends, for example, in the circumferential direction CD from the drive surface 48A of the upshift tooth 48 to the non-drive surface 48B of the upshift tooth 48.

The upshift initiation tooth 44 is adjacent to the upshift displacement tooth 48, for example, upstream of the upshift displacement tooth 48 in the drive rotation direction D, such that there are no other teeth between the upshift initiation tooth 44 and the upshift displacement tooth 48 in the circumferential direction CD. The upshift initiation tooth 44 is configured to be the first to disengage from the drive chain 18 in an upshift operation. The upshift initiation tooth 44 has a first upshift recess 52.

The first upshift recess 52 is provided on the axially outer surface 44X of the upshift-initiating tooth 44 so as to recess from the axially outer surface 30X toward the axially inner surface 30Y in the axial direction AD. The first upshift recess 52 reaches, for example, at least the drive surface 44A of the upshift-initiating tooth 44. The first upshift recess 52 extends, for example, from the drive surface 44A of the upshift-initiating tooth 44 to the non-drive surface 44B of the upshift-initiating tooth 44 in the circumferential direction CD. The first upshift recess 52 extends, in the axial direction AD, from the axially outer surface 44X of the upshift-initiating tooth 44 to the axially outer surface 30X of the rear sprocket 30. The first upshift recess 52 extends, for example, to the sprocket body 32.

1-5, the upshift recess tooth 46 is adjacent to the upshift initiation tooth 44 upstream of the upshift initiation tooth 44 with respect to the driving rotation direction D of the rear sprocket 30 such that there are no other teeth between the upshift initiation tooth 44 and the upshift recess tooth 46 in the circumferential direction CD. The upshift recess tooth 46 is configured not to engage the drive chain 18 disengaged from the upshift initiation tooth 44, for example, during an upshift operation. The upshift recess tooth 46 has a second upshift recess 54.

The second upshift recess 54 is provided on the axial outer side surface 46X of the upshift recess tooth 46 so as to recess from the axial outer side surface 30X toward the axial inner side surface 30Y in the axial direction AD. The second upshift recess 54 reaches at least the drive surface 46A of the upshift recess tooth 46. The second upshift recess 54 extends, for example, from the drive surface 46A of the upshift recess tooth 46 to the non-drive surface 46B of the upshift recess tooth 46. The second upshift recess 54 is configured such that the recess bottom surface is inclined from the drive surface 46A of the upshift recess tooth 46 toward the non-drive surface 46B of the upshift recess tooth 46 in the circumferential direction CD. The recess bottom surface is included, for example, in the axial outer side surface 30X of the upshift recess tooth 46. The second upshift recess 54 extends, for example, in the axial direction AD from the axial outer side surface 46X of the upshift recess tooth 46 to the axial outer side surface 30X of the rear sprocket 30. The second upshift recess 54 extends, for example, to the sprocket body 32. The second upshift recess 54 is adjacent to the first upshift recess 52 upstream of the first upshift recess 52 in the driving rotation direction D such that there are no other recesses between the second upshift recess 54 and the first upshift recess 52 in the circumferential direction CD.

7 and 8, the first upshift tooth root 56 is defined between the upshift initiation tooth 44 and the upshift recess tooth 46 in the circumferential direction CD. The first upshift tooth root 56 is defined, for example, between the drive surface 44A of the upshift initiation tooth 44 and the non-drive surface 46B of the upshift recess tooth 46. The first upshift tooth root 56 includes, for example, a first circumferential tooth root center point P1 in the circumferential direction CD. The first circumferential tooth root center point P1 is, for example, the center point in the circumferential direction CD between the upshift initiation tooth 44 and the upshift recess tooth 46. The first circumferential tooth root center point P1 is, for example, provided on the axially outer surface 30X of the rear sprocket 30.

7 and 8, the first upshift chamfer 58 is provided at least on the first upshift tooth root 56. The first upshift chamfer 58 is provided, for example, on the axially outer surface 30X of the rear sprocket 30. The first upshift chamfer 58 is provided, for example, on the axially outer surface 30X of the rear sprocket 30 so as to pass through at least the first circumferential tooth root center point P1. The first upshift chamfer 58 extends, for example, from the first upshift tooth root 56 toward the axially outer surface 30X. The first upshift chamfer 58 may extend toward the axially inner surface 30Y, or toward both the axially outer surface 30X and the axially inner surface 30Y.

The first upshift chamfer 58 is formed, for example, by C chamfering. The first upshift chamfer 58 may be formed by R chamfering. The first upshift chamfer 58 includes, for example, a first end 58A on the drive surface 44A side of the upshift start tooth 44 in the circumferential direction CD, and a second end 58B opposite the first end 58A. The second end 58B is, for example, the end of the first upshift chamfer 58 on the non-drive surface 46B side of the upshift recess tooth 46 in the circumferential direction CD.

The first upshift chamfered portion 58 is asymmetric with respect to a first reference radial line L1 passing through, for example, the rotation center axis C and the first circumferential bottom center point P1 of the first upshift bottom 56. The length in the circumferential direction CD of the first end side portion 58C on the first end 58A side of the first upshift chamfered portion 58 with respect to the first reference radial line L1 is shorter than, for example, the length in the circumferential direction CD of the second end side portion 58D on the second end 58B side of the first upshift chamfered portion 58 with respect to the first reference radial line L1. In this embodiment, the length in the circumferential direction CD of the first end side portion 58C is shorter than the length in the circumferential direction CD of the second end side portion 58D, so that the first upshift chamfered portion 58 is asymmetric with respect to the first reference radial line L1.

As shown in FIG. 8, the first upshift chamfered portion 58 has a first maximum circumferential length CL1 of, for example, 6 mm or more. The first maximum circumferential length CL1 is, for example, the length in the circumferential direction CD from the first end 58A of the first upshift chamfered portion 58 to the second end 58B of the first upshift chamfered portion 58. The first maximum circumferential length CL1 is, for example, 9 mm or less. The first maximum circumferential length CL1 is, for example, 6 mm or more and 9 mm or less. The first maximum circumferential length CL1 is, for example, 7.7 mm.

As shown in FIG. 9, the sprocket body 32 has a first minimum axial thickness AT1 of, for example, 0.7 mm or more at a portion corresponding to the upshift start tooth 44. The portion of the sprocket body 32 corresponding to the upshift start tooth 44 is, for example, a portion where the first upshift recess 52 is provided. The first minimum axial thickness AT1 is, for example, 1.3 mm or less. The first minimum axial thickness AT1 is, for example, 0.7 mm or more and 1.3 mm or less. The first minimum axial thickness AT1 is, for example, 1 mm.

The sprocket body 32 has a second minimum axial thickness AT2 of, for example, 0.8 mm or more at a portion corresponding to the upshift recess tooth 46. The portion of the sprocket body 32 corresponding to the upshift recess tooth 46 is, for example, a portion where the second upshift recess 54 is provided. The second minimum axial thickness AT2 is, for example, 1.6 mm or less. The second minimum axial thickness AT2 is, for example, 0.8 mm or more and 1.6 mm or less. The second minimum axial thickness AT2 is, for example, 1.2 mm.

The first upshift chamfered portion 58 has a first maximum axial length AL1 of, for example, 0.2 mm or more. The first maximum axial length AL1 is, for example, the maximum length of the first upshift chamfered portion 58 in the axial direction AD when the first upshift chamfered portion 58 is viewed from the radial direction RD. The first maximum axial length AL1 is, for example, 0.4 mm or less. The first maximum axial length AL1 is, for example, 0.2 mm or more and 0.4 mm or less. The first maximum axial length AL1 is, for example, 0.35 mm.

The first maximum axial length AL1 of the first upshift chamfer 58 is, for example, less than or equal to the first minimum axial thickness AT1 of the portion of the sprocket body 32 corresponding to the upshift start tooth 44. The first maximum axial length AL1 is, for example, less than the first minimum axial thickness AT1. The first maximum axial length AL1 is, for example, greater than or equal to one-quarter and less than or equal to two-thirds of the first minimum axial thickness AT1. The first maximum axial length AL1 is, for example, greater than or equal to one-third and less than or equal to one-half of the first minimum axial thickness AT1.

The first maximum axial length AL1 of the first upshift chamfer 58 is, for example, equal to or less than the second minimum axial thickness AT2 of the portion corresponding to the upshift recess tooth 46 in the sprocket body 32. The first maximum axial length AL1 is, for example, smaller than the second minimum axial thickness AT2. The first maximum axial length AL1 is, for example, equal to or more than one-sixth and equal to or less than two-thirds of the second minimum axial thickness AT2. The first maximum axial length AL1 is, for example, equal to or more than one-fifth and equal to or less than one-half of the second minimum axial thickness AT2. The first maximum axial length AL1 is, for example, equal to or more than one-quarter and equal to or less than one-third of the second minimum axial thickness AT2.

The first maximum axial length AL1 of the first upshift chamfer 58 is, for example, less than half the thickness in the axial direction AD of the portion of the sprocket body 32 that corresponds to the first upshift chamfer 58. The portion of the sprocket body 32 that corresponds to the first upshift chamfer 58 includes, for example, the end of the first upshift chamfer 58 on the side of the central axis C of rotation.

3 and 4, the plurality of sprocket teeth 34 further includes, for example, an adjacent tooth 60. The adjacent tooth 60 is adjacent to the upshift recess tooth 46, for example, upstream of the upshift recess tooth 46 in the driving rotation direction D such that there are no other teeth between the upshift recess tooth 46 and the adjacent tooth 60 in the circumferential direction CD. The adjacent tooth 60 includes, for example, a driving surface 60A and a non-driving surface 60B opposite the driving surface 60A in the circumferential direction CD.

4, 7, and 8, the second upshift tooth root 62 is defined between the upshift recess tooth 46 and the adjacent tooth 60 in the circumferential direction CD. The second upshift tooth root 62 is defined, for example, between the drive surface 46A of the upshift recess tooth 46 and the non-drive surface 60B of the adjacent tooth 60. The second upshift tooth root 62 includes, for example, a second circumferential tooth root center point P2 in the circumferential direction CD. The second circumferential tooth root center point P2 is, for example, the center point in the circumferential direction CD between the upshift recess tooth 46 and the adjacent tooth 60. The second circumferential tooth root center point P2 is, for example, provided on the axially outer surface 30X of the rear sprocket 30.

7 and 8, for example, the second upshift chamfer 64 is provided at least on the second upshift tooth root 62. The second upshift chamfer 64 is provided, for example, on the axially outer side surface 30X of the rear sprocket 30. The second upshift chamfer 64 is provided, for example, on the axially outer side surface 30X of the rear sprocket 30 so as to pass through at least the second circumferential tooth root center point P2. The second upshift chamfer 64 extends, for example, from the second upshift tooth root 62 toward the axially outer side surface 30X. The second upshift chamfer 64 may extend toward the axially inner side surface 30Y, or may extend toward both the axially outer side surface 30X and the axially inner side surface 30Y.

The second upshift chamfer 64 is formed, for example, by C chamfering. The second upshift chamfer 64 may be formed by R chamfering. The second upshift chamfer 64 includes, for example, a first end 64A on the drive surface 46A side of the upshift recess tooth 46 in the circumferential direction CD, and a second end 64B opposite the first end 64A. The second end 64B is, for example, the end of the second upshift chamfer 64 on the non-drive surface 60B side of the adjacent tooth 60 in the circumferential direction CD.

8, the second upshift chamfered portion 64 is asymmetric with respect to the second reference radial line L2 passing through, for example, the rotation center axis C and the second circumferential bottom center point P2 of the second upshift bottom 62. The length in the circumferential direction CD of the first end side portion 64C on the first end 64A side of the second upshift chamfered portion 64 with respect to the second reference radial line L2 is shorter than, for example, the length in the circumferential direction CD of the second end side portion 64D on the second end 64B side of the second upshift chamfered portion 64 with respect to the second reference radial line L2. In this embodiment, the length in the circumferential direction CD of the first end side portion 64C with respect to the second reference radial line L2 is shorter than the length in the circumferential direction CD of the second end side portion 64D, so that the second upshift chamfered portion 64 is asymmetric with respect to the second reference radial line L2.

As shown in FIG. 8, the second upshift chamfered portion 64 has a second maximum circumferential length CL2 of, for example, 6 mm or more. The second maximum circumferential length CL2 is, for example, the length in the circumferential direction CD from the first end 64A of the second upshift chamfered portion 64 to the second end 64B of the second upshift chamfered portion 64. The second maximum circumferential length CL2 is, for example, 9 mm or less. The second maximum circumferential length CL2 is, for example, 6 mm or more and 9 mm or less. The first maximum circumferential length CL1 is, for example, 7.7 mm.

As shown in FIG. 9, the second upshift chamfer 64 has a second maximum axial length AL2 of, for example, 0.2 mm or more. The second maximum axial length AL2 is, for example, the maximum length of the second upshift chamfer 64 in the axial direction AD when the second upshift chamfer 64 is viewed from the radial direction RD. The second maximum axial length AL2 is, for example, 0.4 mm or less. The second maximum axial length AL2 is, for example, 0.2 mm or more and 0.4 mm or less. The second maximum axial length AL2 is, for example, 0.35 mm. The second maximum axial length AL2 is, for example, equal to the first maximum axial length AL1.

The second maximum axial length AL2 is, for example, less than half the thickness in the axial direction AD of the portion of the sprocket body 32 that corresponds to the second upshift chamfered portion 64. The portion of the sprocket body 32 that corresponds to the second upshift chamfered portion 64 includes, for example, the end portion of the second upshift chamfered portion 64 on the side of the central axis C of rotation.

As shown in FIG. 8, in the circumferential direction CD, the first radial height H1 from the tooth root circle BR passing through the first circumferential tooth root center point P1 to the first pitch circle PR1 passing through the first end 58A of the first upshift chamfer 58 and the first end 64A of the second upshift chamfer 64 is, for example, 0.9 mm or more and 1.4 mm or less. The first radial height H1 is, for example, 1.15 mm. The second radial height H2 from the tooth root circle BR to the second pitch circle PR2 passing through the second end 58B of the first upshift chamfer 58 and the second end 64B of the second upshift chamfer 64 is, for example, 1.8 mm or more and 2.2 mm or less. The second radial height H2 is, for example, 2 mm.

3 to 5, the plurality of upshift facilitating teeth 42 may further include an additional upshift displacement tooth 66. The additional upshift displacement tooth 66 is adjacent to the upshift displacement tooth 48 downstream of the upshift displacement tooth 48 in the driving rotation direction D so that there are no other teeth between the additional upshift displacement tooth 66 and the upshift displacement tooth 48 in the circumferential direction CD. The additional upshift displacement tooth 66 has, for example, a driving surface 66A and a non-driving surface 66B provided opposite the driving surface 66A in the circumferential direction CD. For example, a second axial recess 68 is provided on the axial inner surface 66Y of the additional upshift displacement tooth 66 so as to be recessed from the axial inner surface 30Y toward the axial outer surface 30X in the axial direction AD.

The second axial recess 68 is disposed, for example, at least at the additional displacement tooth tip 66C of the additional upshift displacement tooth 66. The second axial recess 68 extends, for example, in the radial direction RD from the additional displacement tooth tip 66C radially inward. The second axial recess 68 extends, for example, in the radial direction RD from the additional displacement tooth tip 66C to the outer periphery 36A of the outer annular portion 36 of the sprocket body 32 radially inward. The second axial recess 68 reaches, for example, from the drive surface 66A of the additional upshift displacement tooth 66 to the non-drive surface 66B of the additional upshift displacement tooth 66. The second axial recess 68 is adjacent to the first axial recess 50 downstream of the first axial recess 50 in the drive rotation direction D such that there is no other recess between the second axial recess 68 and the first axial recess 50, for example, in the circumferential direction CD.

As shown in Figures 1, 3, and 6, the plurality of sprocket teeth 34 includes, for example, a plurality of downshift promoting teeth 70. The plurality of downshift promoting teeth 70 is configured to promote a downshift operation. In a downshift operation, the drive chain 18 moves from the adjacent small sprocket 20A toward the rear sprocket 30. In a downshift operation, the drive chain 18 is moved from the adjacent small sprocket 20A to the rear sprocket 30 by, for example, the rear derailleur of the human-powered vehicle 10.

The rear sprocket 30 includes, for example, at least one downshift area. One downshift area is formed by a plurality of downshift promoting teeth 70. In this embodiment, the rear sprocket 30 includes three downshift areas. The number of downshift areas is determined according to the dimensions of the rear sprocket 30, etc.

The plurality of downshift facilitating teeth 70 include, for example, a downshift initiating tooth 72 and a downshift recess tooth 74. The downshift initiating tooth 72 is configured to be the first to engage the drive chain 18 in a downshift operation, for example. The initiating tooth tip 72C of the downshift initiating tooth 72 is inclined in the axial direction AD from the driving surface 72A of the downshift initiating tooth 72 toward the non-driving surface 72B of the downshift initiating tooth 72 so as to approach the axially outer surface 30X.

For example, a third axial recess 76 is provided on the axial inner surface 72Y of the downshift start tooth 72 so as to be recessed from the axial inner surface 30Y toward the axial outer surface 30X in the axial direction AD. In this embodiment, the third axial recess 76 is provided so that the axial inner surface 72Y of the downshift start tooth 72 is inclined from the outer periphery 36A of the outer annular portion 36 of the sprocket body 32 toward the start tooth tip 72C of the downshift start tooth 72. The third axial recess 76 may be provided on the axial inner surface 72Y of the downshift start tooth 72 by stepped pressing.

The third axial recess 76 is disposed, for example, at least at the start tooth tip 72C of the downshift start tooth 72. The third axial recess 76 extends, for example, in the radial direction RD from the start tooth tip 72C of the downshift start tooth 72 radially inward. The third axial recess 76 extends, for example, in the radial direction RD from the start tooth tip 72C of the downshift start tooth 72 to the outer periphery 36A of the outer annular portion 36 of the sprocket body 32 radially inward. The third axial recess 76 extends, for example, in the circumferential direction CD from the drive surface 72A of the downshift start tooth 72 to the non-drive surface 72B of the downshift start tooth 72.

The downshift recess tooth 74 is adjacent to the downshift start tooth 72 downstream of the downshift start tooth 72 with respect to the driving rotation direction D of the rear sprocket 30, such that there are no other teeth between the downshift start tooth 72 and the downshift recess tooth 74, for example, in the circumferential direction CD. The downshift recess tooth 74 is configured to promote movement of the drive chain 18 in the axial direction AD from the axially outer side 30X toward the axially inner side 30Y, for example, in a downshift operation. The downshift recess tooth 74 has, for example, a driving surface 74A and a non-driving surface 74B provided on the opposite side of the driving surface 74A, for example, in the circumferential direction CD. The downshift recess tooth 74 has, for example, a recess tooth tip 74C. The recess tooth tip 74C is inclined from the driving surface 74A toward the non-driving surface 74B in the axial direction AD so as to approach the axially inner side 30Y.

The downshift recess tooth 74 has, for example, a downshift recess 78. The downshift recess 78 is provided on the axially outer surface 74X of the downshift recess tooth 74 so as to be recessed from the axially outer surface 30X to the axially inner surface 30Y in the axial direction AD, for example.

The downshift recess 78, for example, does not reach the drive surface 74A of the downshift recess tooth 74. The downshift recess 78 may reach the drive surface 74A of the downshift recess tooth 74. The downshift recess 78, for example, reaches the non-drive surface 74B of the downshift recess tooth 74. The downshift recess 78 extends, for example, from the outer periphery 36A to the inner periphery 36B of the outer annular portion 36 of the sprocket body 32.

The plurality of downshift facilitating teeth 70 includes, for example, an additional downshift recess tooth 80. The additional downshift recess tooth 80 is adjacent to the downshift recess tooth 74 downstream of the downshift recess tooth 74 in the driving rotation direction D of the rear sprocket 30 such that there are no other teeth between the additional downshift recess tooth 80 and the downshift recess tooth 74 in the circumferential direction CD. The additional downshift recess tooth 80 is configured to, for example, promote movement of the drive chain 18 in the axial direction AD from the axially outer surface 30X toward the axially inner surface 30Y in a downshift operation.

The additional downshift recess tooth 80 has, for example, an additional downshift recess 82. The additional downshift recess 82 is provided on the axially outer side surface 80X of the additional downshift recess tooth 80 so as to be recessed from the axially outer side surface 30X toward the axially inner side surface 30Y in the axial direction AD. The additional downshift recess 82 is adjacent to the downshift recess 78 downstream of the downshift recess 78 in the driving rotation direction D of the rear sprocket 30 so that there is no other recess between the downshift recess 78 and the additional downshift recess 82 in the circumferential direction CD.

As shown in FIG. 3, the rear sprocket 30 includes, for example, at least one common shift area. The common shift area is, for example, an area where a downshift area overlaps with an upshift area adjacent to the upstream side of the downshift area in the driving rotation direction D. The rear sprocket 30 of this embodiment includes three common shift areas. The number of common shift areas is determined according to the dimensions of the rear sprocket 30, etc.

3, 5, and 6, the common shift area includes the upshift displacement tooth 48 and the additional upshift displacement tooth 66. The additional upshift displacement tooth 66 in the common shift area is adjacent to the downshift initiation tooth 72 upstream of the downshift initiation tooth 72 in the drive rotation direction D such that there are no other teeth between the additional upshift displacement tooth 66 and the downshift initiation tooth 72 in the circumferential direction CD.

The upshift displacement tooth 48 and the additional upshift displacement tooth 66 also serve as downshift engagement promoting teeth that promote downshift operations, for example. The upshift displacement tooth 48 and the additional upshift displacement tooth 66 are configured to promote movement of the drive chain 18 in the axial direction AD from the axial outer surface 30X toward the axial inner surface 30Y, for example, during downshift operations. The upshift displacement tooth 48 is configured to promote downshift operations, for example, by the first axial recess 50. The additional upshift displacement tooth 66 is configured to promote downshift operations, for example, by the second axial recess 68.

1-5 and 10, the operation of the drive chain 18 during an upshift operation will now be described.
When the rear derailleur applies a force to the drive chain 18 to move it toward the adjacent small sprocket 20A and the outer link 18B moves to a position where it engages with the upshift tooth 48, the first axial recess 50 moves the tip 48C of the upshift tooth 48 axially outward, so that the drive chain 18 is moved toward the adjacent small sprocket 20A. The first upshift recess 52 moves the start tooth tip 44C of the upshift start tooth 44 axially inward, so that the drive chain 18, which is moved toward the adjacent small sprocket 20A, tends to disengage from the upshift start tooth 44. Specifically, the first upshift recess 52 moves the start tooth tip 44C of the upshift start tooth 44 axially inward, so that the inner link 18C corresponding to the upshift start tooth 44 tends to disengage from the upshift start tooth 44. Furthermore, since the first upshift chamfer 58 is provided at least on the first upshift tooth root 56, the inner link 18C can easily move along the first upshift chamfer 58 toward the adjacent small sprocket 20A. This allows the drive chain 18 to move smoothly from the rear sprocket 30 to the adjacent small sprocket 20A.

The second upshift recess 54 moves the recess tooth tip 46C of the upshift recess tooth 46 axially inward, so that the drive chain 18 that has come off the upshift start tooth 44 is less likely to re-engage with the upshift recess tooth 46. Specifically, the second upshift recess 54 moves the recess tooth tip 46C of the upshift recess tooth 46 axially inward, so that the outer link 18B corresponding to the upshift recess tooth 46 is prevented from engaging with the upshift recess tooth 46. In addition, since the second upshift chamfer 64 is provided at least on the second upshift tooth bottom 62, even if the drive chain 18 does not move sufficiently to the adjacent small sprocket 20A and the outer link 18B comes into contact with the second upshift tooth bottom 62, the outer link 18B is more likely to move along the second upshift chamfer 64 toward the adjacent small sprocket 20A. Therefore, the drive chain 18 can move smoothly from the rear sprocket 30 to the adjacent small sprocket 20A. Then, as the rear sprocket 30 rotates in the driving rotation direction D, the drive chain 18 disengages from the rear sprocket 30 and engages with the adjacent small sprocket 20A, completing the upshift operation.

The greater the tooth thickness of the upshift facilitating teeth 42, the greater the rigidity of the rear sprocket 30. If the tooth thickness of the upshift facilitating teeth 42 is large, contact between the drive chain 18 and the rear sprocket 30 is more likely to occur during gear shifting, which can increase the risk of gear shift shock. With the rear sprocket 30 of this embodiment, the first upshift chamfer 58 allows the drive chain 18 to move smoothly from the rear sprocket 30 to the adjacent small sprocket 20A. Therefore, the tooth thickness of the upshift facilitating teeth 42 can be ensured while reducing the shock that occurs when the human-powered vehicle 10 changes gears.

1-3 and 6, the operation of the drive chain 18 during a downshift operation will now be described.
In a downshift operation, the drive chain 18 engaged with the adjacent small sprocket 20A is moved toward the downshift recess tooth 74 of the rear sprocket 30 by the rear derailleur. For example, the drive chain 18 is moved toward the rear sprocket 30 by the rear derailleur and guided radially outward of the adjacent small sprocket 20A along the downshift recess 78. The start tooth tip 72C of the downshift start tooth 72 is inclined from the drive surface 72A of the downshift start tooth 72 toward the non-drive surface 72B of the downshift start tooth 72 so as to approach the axially outer side surface 30X, so that the drive chain 18 is easily fitted into the downshift start tooth 72. The tooth tip of the downshift start tooth 72 fits into the drive chain 18 guided radially outward, so that the downshift start tooth 72 engages with the drive chain 18. Thereafter, as the rear sprocket 30 rotates in the drive rotation direction D, the drive chain 18 disengages from the adjacent small sprocket 20A. The downshift operation is completed when the drive chain 18 disengages from the adjacent small sprocket 20A and engages the rear sprocket 30.

<Example of change>
The description of the embodiment is an example of a possible form of a rear sprocket for a human-powered vehicle according to the present disclosure, and is not intended to limit the form. A rear sprocket for a human-powered vehicle according to the present disclosure may take the form of, for example, the modified example of the embodiment shown below, or a combination of at least two modified examples that are not mutually contradictory. In the modified examples below, parts that are common to the embodiment are given the same reference numerals as the embodiment, and their description is omitted.

6 and 11, the downshift tooth bottom 84 may be defined between the downshift start tooth 72 and the downshift recess tooth 74 in the circumferential direction CD, and the downshift chamfer 86 may be provided at least on the downshift tooth bottom 84. The downshift chamfer 86 may be provided, for example, on the axially outer surface 30X of the rear sprocket 30. The downshift chamfer 86 may extend, for example, in the axial direction AD from the downshift tooth bottom 84 toward the axially outer surface 30X. The downshift chamfer 86 may extend, in the axial direction AD, toward the axially inner surface 30Y, or toward both the axially outer surface 30X and the axially inner surface 30Y. The downshift chamfer 86 may extend, for example, in the circumferential direction CD from the non-drive surface 72B of the downshift start tooth 72 to the drive surface 74A of the downshift recess tooth 74. The downshift chamfer 86 may be formed, for example, by C chamfering. The downshift chamfered portion 86 may be formed by R chamfering.

The term "at least one" as used herein means "one or more" of the desired options. As an example, the term "at least one" as used herein means "only one option" or "both of two options" if the number of options is two. As another example, the term "at least one" as used herein means "only one option" or "any combination of two or more options" if the number of options is three or more.

10...Manually-driven vehicle, 18...Drive chain, 20A...Adjacent small sprocket, 30...Rear sprocket, 30X...Axial outer surface, 30Y...Axial inner surface, 32...Sprocket body, 34...Sprocket teeth, 42...Upshift facilitating teeth, 44...Upshift initiating teeth, 46...Upshift recess teeth, 52...First upshift recess, 54...Second upshift recess, 56...First upshift tooth root, 58...First upshift chamfer, 60...Adjacent teeth, 62...Second upshift tooth root, 64...Second upshift chamfer, 70...Downshift facilitating teeth, 72...Downshift initiating teeth, 74...Downshift recess teeth, 78...Downshift recess, 84...Downshift tooth root, 86...Downshift chamfer.

Claims (19)

A rear sprocket for a human-powered vehicle, the rear sprocket having a central axis of rotation that defines an axial direction, a radial direction, and a circumferential direction, an axially outer surface, and an axially inner surface that is provided on the opposite side of the axially outer surface in the axial direction and that is configured to face a central axis surface of the human-powered vehicle when the rear sprocket is mounted on the human-powered vehicle,
A sprocket body;
a plurality of sprocket teeth extending radially outward from an outer periphery of the sprocket body in the radial direction,
the plurality of sprocket teeth include a plurality of upshift promoting teeth configured to promote an upshift operation of a drive chain moving from the rear sprocket toward the small adjacent sprocket adjacent the rear sprocket such that there are no other sprockets between the rear sprocket and the small adjacent sprocket;
the plurality of upshift facilitation teeth include an upshift initiation tooth configured to disengage from the drive chain first during the upshift operation and an upshift recess tooth;
the up shift start tooth has a first up shift recess provided on the axially outer surface of the up shift start tooth so as to be recessed in the axial direction from the axially outer surface to the axially inner surface,
The upshift recess teeth include
a second up shift recess provided on the axially outer surface of the up shift recess tooth so as to be recessed from the axially outer surface toward the axially inner surface in the axial direction,
adjacent to the upshift start tooth upstream of the upshift start tooth in a driving rotational direction of the rear sprocket such that there are no other teeth between the upshift start tooth and the upshift recess tooth in the circumferential direction;
a first up shift tooth root is defined in the circumferential direction between the up shift initiation tooth and the up shift recess tooth;
A rear sprocket, wherein a first up shift chamfer is provided on at least the first up shift root. The rear sprocket according to claim 1, wherein the first upshift chamfer has a first maximum circumferential length of 6 mm or more. The rear sprocket according to claim 2, wherein the first maximum circumferential length is 9 mm or less. The rear sprocket according to claim 1, wherein the first upshift chamfer has a first maximum axial length of 0.2 mm or more. The rear sprocket according to claim 4, wherein the first maximum axial length is 0.4 mm or less. the plurality of sprocket teeth further includes an adjacent tooth adjacent to the up shift recess tooth upstream of the up shift recess tooth in the driving rotation direction such that there is no other tooth between the up shift recess tooth and the adjacent tooth in the circumferential direction;
a second up shift tooth root is defined between the up shift recess tooth and the adjacent tooth in the circumferential direction;
2. The rear sprocket according to claim 1, wherein a second upshift chamfer is provided on at least said second upshift root. The rear sprocket according to claim 6, wherein the second upshift chamfer has a second maximum circumferential length of 6 mm or more. The rear sprocket according to claim 7, wherein the second maximum circumferential length is 9 mm or less. The rear sprocket according to claim 6, wherein the second upshift chamfer has a second maximum axial length of 0.2 mm or more. The rear sprocket according to claim 9, wherein the second maximum axial length is 0.4 mm or less. The rear sprocket according to claim 1, wherein the sprocket body has a first minimum axial thickness of 0.7 mm or more at a portion corresponding to the upshift start tooth. The rear sprocket according to claim 11, wherein the first minimum axial thickness is 1.3 mm or less. The rear sprocket according to claim 6, wherein the sprocket body has a second minimum axial thickness of 0.8 mm or more at a portion corresponding to the upshift recess teeth. The rear sprocket according to claim 13, wherein the second minimum axial thickness is 1.6 mm or less. The rear sprocket according to claim 1, wherein the first upshift chamfer portion extends from the first upshift tooth root toward the axially outer side surface. The rear sprocket according to claim 6, wherein the second upshift chamfer portion extends from the second upshift tooth root toward the axially outer side surface. The rear sprocket according to claim 1, wherein the first upshift chamfer is asymmetric with respect to a first reference radial line passing through the central axis of rotation and a first circumferential root center point of the first upshift tooth root. The rear sprocket according to claim 6, wherein the second upshift chamfer is asymmetric with respect to a second reference radial line passing through the central axis of rotation and a second circumferential bottom center point of the second upshift tooth bottom. A rear sprocket for a human-powered vehicle, the rear sprocket having a central axis of rotation that defines an axial direction, a radial direction, and a circumferential direction, an axially outer surface, and an axially inner surface that is provided on the opposite side of the axially outer surface in the axial direction and that is configured to face a central axis surface of the human-powered vehicle when the rear sprocket is mounted on the human-powered vehicle,
A sprocket body;
a plurality of sprocket teeth extending radially outward from an outer periphery of the sprocket body in the radial direction,
the plurality of sprocket teeth including a plurality of downshift facilitating teeth configured to facilitate a downshift operation of a drive chain moving from an adjacent small sprocket toward the rear sprocket;
the adjacent small sprocket is adjacent to the rear sprocket such that there are no other sprockets between the rear sprocket and the adjacent small sprocket;
the plurality of downshift facilitating teeth includes a downshift initiation tooth configured to first engage the drive chain during the downshift operation, and a downshift recess tooth adjacent to the downshift initiation tooth downstream of the downshift initiation tooth relative to a driving rotational direction of the rear sprocket such that there are no other teeth between the downshift initiation tooth and the downshift recess tooth in the circumferential direction;
The downshift recess tooth has a downshift recess provided on the axially outer surface of the downshift recess tooth so as to be recessed in the axial direction from the axially outer surface to the axially inner surface,
a downshift tooth root is defined in the circumferential direction between the downshift initiation tooth and the downshift recess tooth;
A downshift chamfer is provided on at least the downshift root of the rear sprocket.

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