A rear sprocket and a rear sprocket assembly

Abstract

This invention discloses a sprocket (S1) comprising a sprocket body (41) and a plurality of sprocket teeth (43). The plurality of sprocket teeth (43) includes at least one downshift actuating tooth (51). The at least one downshift actuating tooth (51) has a driving surface (45a) and a non-driving surface (47a). The non-driving surface (47a) has a chain lifting area (47a2). The minimum chain lifting distance (D1) is equal to or greater than half the pitch circle diameter (r2) minus 4.1 mm and equal to or less than half the pitch circle diameter minus 2.1 mm.

Description

Technical Field

[0001] This invention relates to a rear sprocket and a rear sprocket assembly. Prior Technology

[0002] Human-powered vehicles, especially bicycles, are becoming an increasingly popular form of recreation and a means of transportation. Furthermore, cycling has become a highly popular competitive sport for both amateurs and professional athletes.

[0003] Whether these rickshaws are used for recreation, transportation, or racing, the rickshaw industry continuously improves various systems of rickshaws. One widely redesigned rickshaw system is a rear sprocket and a rear sprocket assembly. This rear sprocket and assembly is used to mount to a frame of a rickshaw. The rear sprocket assembly typically includes multiple rear sprockets, allowing a drive chain to be shifted from one sprocket to another via a rear derailleur. During a downshift operation where the drive chain shifts from a small sprocket to an adjacent large sprocket, a tooth on the small sprocket can interfere with the drive chain before it engages with the tooth on the adjacent large sprocket. This interference between the drive chain and the sprocket tooth on the small sprocket often occurs when the difference in the number of teeth between the small sprocket and the adjacent large sprocket is relatively small (e.g., less than three). If the teeth of one of the smaller sprockets interfere with the drive chain before the drive chain engages with the teeth of one of the adjacent larger sprockets, the downshifting operation will no longer be smooth. Therefore, there is a need for a sprocket that can still achieve a smooth downshifting operation even when the tooth count difference between one of the adjacent rear sprockets is small. Summary of the Invention

[0004] According to a first aspect of the present invention, a rear sprocket can be mounted to a rear wheel hub assembly of a human-powered vehicle. The rear sprocket has a pitch circle relative to a pitch circle diameter. The rear sprocket includes a sprocket body and a plurality of sprocket teeth. The plurality of sprocket teeth extend radially outward from the outer periphery of a sprocket body in a radial direction relative to a rotational central axis of the rear sprocket.

[0005] The plurality of sprocket teeth includes at least one downshift actuating tooth. The at least one downshift actuating tooth is configured to facilitate a downshift operation in which a drive chain is displaced in an axial direction relative to the rotation center axis from the rear sprocket toward one of the adjacent large sprockets adjacent to the rear sprocket, and there is no other sprocket between the rear sprocket and the adjacent large sprocket.

[0006] The at least one downshifting actuating tooth has a driving surface and a non-driving surface disposed on the opposite side of the driving surface in a circumferential direction relative to the rotation center axis. The non-driving surface has a chain lifting area.

[0007] A minimum chain lifting distance is defined along the radial direction from the rotation center axis to the chain lifting area of ​​the non-driving surface. This minimum chain lifting distance is equal to or greater than half the pitch circle diameter minus 4.1 mm and equal to or less than half the pitch circle diameter minus 2.1 mm.

[0008] In the case of the sprocket following the first configuration, the plurality of sprocket teeth includes at least one downshifting actuating tooth. The at least one downshifting actuating tooth has a driving surface and a non-driving surface. The non-driving surface has a chain lifting area.

[0009] The minimum chain lifting distance is equal to or greater than half the diameter of the link circle minus 4.1 mm and equal to or less than half the diameter of the link circle minus 2.1 mm.

[0010] In this way, the rear sprocket can smoothly perform downshifting operations because, as mentioned above, the non-drive surface has a chain lifting area, and the minimum chain lifting distance is defined.

[0011] Specifically, even if the sprocket following the adjacent large sprocket is a small-diameter sprocket and / or even if the difference between the total number of teeth of one of the rear sprockets and the total number of teeth of one of the adjacent large sprockets is one or two, the rear sprocket can still effectively perform downshifting operations.

[0012] In this situation, the curvature of the drive chain is small when it meshes with the small-diameter sprocket. If the minimum chain lift distance is less than half the pitch circle diameter minus 4.1 mm, it is difficult to smoothly lift the drive chain for performing downshifting operations in which the drive chain shifts from the rear sprocket toward the adjacent large sprocket.

[0013] If the minimum chain lift distance is greater than half the pitch circle diameter minus 2.1 mm, the non-driving surface of the downshift facilitator tooth can interfere with the drive chain before the drive chain engages with the sprocket teeth of one of the adjacent large sprockets. This defect can be overcome by using the above configuration for the rear sprocket.

[0014] According to a second embodiment of the present invention, after the first embodiment, the sprocket is configured such that a maximum chain lifting distance is defined along the radial direction from the rotation center axis to the non-driving surface of the chain lifting area. This maximum chain lifting distance is equal to or greater than half the pitch circle diameter minus 1.3 mm and equal to or less than half the pitch circle diameter plus 0.5 mm.

[0015] In the case of the sprocket following the second state, the sprocket can smoothly perform downshifting operation because, as described above, the non-drive surface has a chain lifting area and the maximum chain lifting distance is defined.

[0016] Specifically, even if the rear sprocket and the adjacent large sprocket are small-diameter sprockets as described above, and / or even if the total number of teeth of one of the rear sprockets and the total number of teeth of one of the adjacent large sprockets are one or two as described above, the rear sprocket can still effectively perform downshifting operations.

[0017] According to a third configuration of the present invention, the sprocket is configured such that the total number of teeth of the sprocket is equal to or less than twelve, according to the first or second configuration.

[0018] In the case of the sprocket following the third state, even if the rear sprocket and the adjacent large sprocket are small-diameter sprockets as described above, the rear sprocket can still effectively perform downshifting operations.

[0019] According to a fourth state of the present invention, the sprocket is configured such that the total number of teeth of the sprocket is equal to or less than ten after the third state.

[0020] In the case of the sprocket following the fourth state, even if the rear sprocket and the adjacent large sprocket are small-diameter sprockets as described above, the rear sprocket can still effectively perform downshifting operations.

[0021] According to a fifth embodiment of the present invention, after any one of the first to fourth embodiments, the sprocket is configured such that the at least one downshifting actuating tooth has an axial tooth root thickness measured at the tooth root circle of the rear sprocket in the axial direction relative to the rotation center axis. The axial tooth root thickness is equal to or greater than 1.3 mm.

[0022] In the case of the sprocket after the fifth state sample, the sprocket can sufficiently ensure the strength of the downshifting promotion tooth because the axial tooth root thickness is equal to or greater than 1.3 mm.

[0023] According to one of the sixth states of the present invention, the sprocket is configured such that the axial tooth root thickness is equal to or less than 2.1 mm after the fifth state.

[0024] In the case of the sprocket according to the sixth state, the sprocket can be firmly engaged with the drive chain, and the noise generated by the downshifting of the sprocket to promote the contact between the teeth and the drive chain of the adjacent sprocket of the sprocket is reduced, because the axial tooth root thickness is equal to or less than 2.1 mm.

[0025] According to a seventh embodiment of the present invention, the sprocket is configured such that the at least one downshifting facilitator tooth has a maximum tooth tip diameter that is smaller than one of the pitch circle diameters of the rear sprocket.

[0026] In the case of the sprocket following the seventh state, the sprocket can securely hold the drive chain on at least one downshifting actuating tooth.

[0027] According to an eighth embodiment of the present invention, after any one of the first to seventh embodiments, the sprocket is configured such that the pitch circle is defined by a plurality of imaginary chain rollers, each of the plurality of imaginary chain rollers having one of a plurality of roller central axes such that each of the imaginary chain rollers contacts one of a plurality of drive surfaces of the plurality of sprocket teeth, and the pitch circle passes through all of the plurality of roller central axes.

[0028] A pitch polygon is defined by linearly connecting the central axes of the plurality of rollers. The at least one downshift actuating tooth has a radially outermost tooth tip, which is positioned radially outward from the pitch polygon relative to the rotational central axis.

[0029] In the case of the sprocket following the eighth state, the sprocket can securely hold the drive chain on the at least one downshifting actuating tooth and fully transmit the driving force from the drive chain to the at least one downshifting actuating tooth.

[0030] According to a ninth embodiment of the present invention, a rear sprocket assembly includes a rear sprocket and an adjacent large sprocket according to any one of the first to eighth embodiments.

[0031] The adjacent large sprocket includes at least one downshift initiating tooth. This at least one downshift initiating tooth is configured to engage with the drive chain first during downshifting.

[0032] When viewed from the axial direction, in the circumferential direction, at least one downshift actuating tooth of the rear sprocket is adjacent to at least one downshift initiating tooth of the adjacent large sprocket at the downstream side of at least one downshift initiating tooth of the adjacent large sprocket relative to the driving rotation direction of one of the rear sprocket assemblies, and there is no other tooth between at least one downshift initiating tooth of the adjacent large sprocket and at least one downshift actuating tooth of the rear sprocket.

[0033] In the case of the sprocket assembly according to the ninth state, the adjacent large sprocket includes at least one downshift initiating tooth. When viewed from the axial direction, in the circumferential direction, the at least one downshift promoting tooth is adjacent to the at least one downshift initiating tooth on the downstream side of the at least one downshift initiating tooth relative to the drive rotation direction.

[0034] In this way, the rear sprocket assembly can smoothly perform the downshift operation. Specifically, even if the rear sprocket and the adjacent large sprocket are small-diameter sprockets and / or even if the difference between the total number of teeth of one of the rear sprockets and the total number of teeth of one of the adjacent large sprockets is one or two, the rear sprocket assembly can still effectively perform the downshift operation. Simple Explanation of the Diagram

[0035] Now refer to the accompanying diagrams, which are part of this original disclosure:

[0036] Figure 1 is a side view of a bicycle according to an embodiment of the present invention;

[0037] Figure 2 is an exploded perspective view of a drive chain according to one embodiment of the present invention;

[0038] Figure 3 is a front view of a rear sprocket assembly according to one embodiment of the present invention;

[0039] Figure 4 is a front view of a first rear sprocket and a second rear sprocket according to one embodiment of the present invention;

[0040] Figure 5 is a front view of one of the first rear sprockets according to an embodiment of the present invention;

[0041] Figure 6 is a front view of one of the first rear sprockets according to an embodiment of the present invention;

[0042] Figure 7 is a front view of one of the second rear sprockets according to an embodiment of the present invention;

[0043] Figure 8A is a partially enlarged front view of a first rear sprocket and a second rear sprocket according to an embodiment of the present invention; and

[0044] Figure 8B is a partially enlarged front view of a first rear sprocket and a second rear sprocket according to an embodiment of the present invention. Implementation

[0045] The selected embodiments of the present invention will now be explained with reference to the accompanying drawings. Those skilled in the art will understand from this invention that the following description of embodiments of the present invention is for illustrative purposes only and not for limiting the scope of the invention, which is defined by the appended claims and their equivalents.

[0046] In the following embodiments, where a plurality of components and portions correspond to each other, the corresponding components and portions are indicated by the same symbol. [Example] [ ]

[0047] <The General Configuration of a Bicycle>

[0048] As shown in Figure 1, a bicycle 1 includes a drive chain 9, a frame 11, a handlebar 13, front and rear wheels 17 and 19, a gear shifting device 24, a drive system 25, and a front fork 20. The bicycle 1 is an example of a human-powered vehicle described in the claims.

[0049] The front fork 20 is rotatably attached to the frame 11. The handlebar 13 is fixed to the front fork 20. The front wheel 17 is rotatably attached to the front fork 20. The rear wheel 19 is rotatably attached to a rear portion of the frame 11 via a rear wheel hub assembly 29. A front tire 17a is attached to the front wheel 17. A rear tire 19a is attached to the rear wheel 19.

[0050] The shifting mechanism 24 is attached to the handlebars 13. The shifting mechanism 24 operates a bicycle rear derailleur 26 via a control cable. For example, the bicycle rear derailleur 26 is attached to a rear portion of the frame 11.

[0051] The bicycle rear derailleur 26 moves the drive chain 9 from one bicycle rear sprocket of a rear sprocket assembly 28 to another bicycle rear sprocket of the rear sprocket assembly 28 via the shifting device 24. The bicycle rear sprocket is illustrated by a simplified depiction in Figure 1.

[0052] The drive system 25 mainly includes a crank assembly 27, a rear sprocket assembly 28, and a rear wheel hub assembly 29. The drive chain 9 can also be considered part of the drive system 25.

[0053] As shown in Figure 2, the drive chain 9 comprises a plurality of chain units 31. The drive chain 9 is configured by connecting the plurality of chain units 31 to each other. Each of the plurality of chain units 31 includes an outer link plate 33a, 33b, a pair of inner link plates 35a, 35b, a pair of chain rollers 37a, 37b, and a pair of chain pins 39a, 39b.

[0054] The outer link plates 33a and 33b are positioned at a predetermined interval in the axial direction relative to the pivot axes P1 and P2 of the chain pins 39a and 39b. The inner link plates 35a and 35b are positioned between the outer link plates 33a and 33b at a predetermined interval in the axial direction relative to the pivot axes P1 and P2 of the chain pins 39a and 39b.

[0055] Chain rollers 37a and 37b are axially positioned between the inner link plates 35a and 35b relative to the pivot axes P1 and P2 of chain pins 39a and 39b. Each of the chain rollers 37a and 37b includes a roller pivot P3. The roller pivot P3 is coaxial with each of the pivot axes P1 and P2. The chain pins 39a and 39b connect the outer link plates 33a and 33b to the inner link plates 35a and 35b via the chain rollers 37a and 37b.

[0056] The crank assembly 27 is rotatably supported on a lower portion of the frame 11. The crank assembly 27 includes at least one bicycle front sprocket 35. In this embodiment, the crank assembly 27 includes a bicycle front sprocket 35 that meshes with the drive chain 9. The rear wheel hub assembly 29 is mounted on the rear portion of the frame 11. The rear wheel hub assembly 29 rotatably supports the rear sprocket assembly 28.

[0057] Rear sprocket assembly

[0058] As shown in Figure 3, the rear sprocket assembly 28 has a rotational central shaft C1. The rear sprocket assembly 28 is mounted to the rear wheel hub assembly 29 to rotate relative to the rotational central shaft C1. The rotational central shaft C1 is coaxial with one of the hub shafts of the rear wheel hub assembly 29.

[0059] The rear sprocket assembly 28 includes a plurality of rear sprockets S1 to S12. For example, the rear sprocket assembly 28 includes a first rear sprocket S1 and a second rear sprocket S2. The rear sprocket assembly 28 further includes third to twelfth rear sprockets S3 to S12. The third to twelfth rear sprockets S3 to S12 are respectively indicated by the double imaginary chainlines in Figure 3. However, the total number of one of the plurality of rear sprockets in the rear sprocket assembly 28 is not limited to twelve. The total number of the plurality of rear sprockets in the rear sprocket assembly 28 may be less than or greater than twelve.

[0060] In this embodiment, the features of the invention are illustrated by using a first rear sprocket S1 and a second rear sprocket S2. The first rear sprocket S1 is an example of a rear sprocket described in the claims. The second rear sprocket S2 is an example of a large adjacent sprocket described in the claims.

[0061] (First rear sprocket)

[0062] As shown in Figure 3, the first rear sprocket S1 can be mounted to the rear wheel hub assembly 29 of the bicycle 1. One of the rotational axes of the first rear sprocket S1 is coaxial with the rotational axis C1 of the rear sprocket assembly 28. In the following description, the rotational axis of the first rear sprocket S1 may be indicated by the symbol "C1".

[0063] As shown in Figures 4 and 5, the total number of teeth on the first rear sprocket S1 is equal to or less than twelve. The total number of teeth on the first rear sprocket S1 may be equal to or less than ten. In this embodiment, the total number of teeth on the first rear sprocket S1 is nine. However, the total number of teeth on the first rear sprocket S1 is not limited to nine. The total number of teeth on the first rear sprocket S1 may be less than or greater than nine.

[0064] The first rear sprocket S1 includes a sprocket body 41 and a plurality of sprocket teeth 43. The sprocket body 41 is formed in a ring shape. The plurality of sprocket teeth 43 extend radially outward from the outer periphery of one of the sprocket bodies 41 relative to the rotation center axis C1 of one of the first rear sprockets S1.

[0065] As shown in Figure 5, a plurality of sprocket teeth 43 each have a plurality of driving surfaces 45 and a plurality of non-driving surfaces 47. Each of the plurality of driving surfaces 45 is disposed on the upstream side of one of the plurality of sprocket teeth 43 relative to a driving rotation direction R1. Chain rollers 37a and 37b contact the driving surfaces 45 and transmit driving force to the plurality of sprocket teeth 43.

[0066] Each of the plurality of non-driving surfaces 47 is disposed on the downstream side of one of the plurality of sprocket teeth 43 relative to the driving rotation direction R1. In other words, each of the plurality of non-driving surfaces 47 is disposed on the opposite side of one of the plurality of driving surfaces 45 in a circumferential direction relative to the rotation center axis C1.

[0067] As shown in Figure 5, the plurality of sprocket teeth 43 includes at least one downshifting actuating tooth 51. In this embodiment, an example is illustrated where the total number of at least one downshifting actuating tooth 51 on the first rear sprocket S1 is one. However, depending on the total number of teeth on the first rear sprocket S1, the total number of at least one downshifting actuating tooth 51 on the first rear sprocket S1 may be greater than one. At least one downshifting actuating tooth 51 is included in the plurality of sprocket teeth 43.

[0068] At least one downshift actuating tooth 51 is configured to facilitate a downshift operation, wherein the drive chain 9 is displaced in an axial direction relative to the rotation center axis C1 from the first rear sprocket S1 toward the second rear sprocket S2 adjacent to the first rear sprocket S1, and there is no other sprocket between the first rear sprocket S1 and the second rear sprocket S2. The configuration of the second rear sprocket S2 is described below.

[0069] The second sprocket S2 includes at least one downshift initiating tooth 57. As shown in FIG4, when viewed from the axial direction, in the circumferential direction, at least one downshift promoting tooth 51 of the first rear sprocket S1 is adjacent to at least one downshift initiating tooth 57 of the second rear sprocket S2 downstream of one of the downshift initiating teeth 57 of the second rear sprocket S2 relative to the drive rotation direction R1 of the rear sprocket assembly 28, and there is no other tooth between the at least one downshift initiating tooth 57 of the second rear sprocket S2 and the at least one downshift promoting tooth 51 of the first rear sprocket S1.

[0070] At least one downshift initiation tooth 57 will be explained later in the explanation of the second rear sprocket S2.

[0071] As shown in Figure 5, at least one downshift facilitator tooth 51 has a driving surface 45a and a non-driving surface 47a disposed on the opposite side of the driving surface 45a in the circumferential direction relative to the rotation center axis C1.

[0072] The drive surface 45a is disposed on at least one downshift actuating tooth 51 on the upstream side relative to the drive rotation direction R1. Chain rollers 37a and 37b contact the drive surface 45a and transmit driving force to at least one downshift actuating tooth 51.

[0073] At least one downshift facilitator tooth 51 has a drive surface 45a contained in a plurality of drive surfaces 45 of a plurality of sprocket teeth 43.

[0074] A non-driving surface 47a is disposed on at least one downshift actuating tooth 51 on the downstream side relative to the driving rotation direction R1. The non-driving surface 47a of at least one downshift actuating tooth 51 is included in a plurality of non-driving surfaces 47 of a plurality of sprocket teeth 43.

[0075] The non-drive surface 47a has a chain lifting area 47a2. For example, the non-drive surface 47a has a base end area 47a1 and a chain lifting area 47a2. The base end area 47a1 is disposed on the sprocket body 41 side of the non-drive surface 47a of at least one downshift promoting tooth 51.

[0076] The chain lifting area 47a2 is disposed on the tooth tip side of one of the non-driving surfaces 47a of at least one downshift facilitator tooth 51. The chain lifting area 47a2 extends radially from the base end area 47a1 toward the tooth tip relative to the rotation center axis C1 of the first rear sprocket S1 and is disposed outside the base end area 47a1.

[0077] As shown in Figures 8A and 8B, during the downshifting operation, the inner link plate 35a rises radially relative to the rotation center axis C1 in the chain lifting area 47a2. This inner link plate 35a is positioned radially relative to the rotation center axis C1 outside the chain lifting area 47a2 and contacts the chain lifting area 47a2.

[0078] As shown in Figure 6, the first rear sprocket S1 has a tooth root circle BC relative to a tooth root diameter r1. The tooth root diameter r1 is one of the diameters of the tooth root circle BC. The tooth root circle BC is defined by a circle passing through the tooth root of one of the teeth of the first rear sprocket S1 in the circumferential direction relative to the rotation center axis C1.

[0079] At least one downshift facilitator tooth 51 has an axial tooth root thickness measured in the axial direction relative to the rotation center axis C1 at one of the tooth root circles BC of the first rear sprocket S1.

[0080] For example, the axial tooth root thickness is at least one downshift at a radial position of the tooth root circle BC relative to the rotation center axis C1 to promote the maximum axial thickness of one of the teeth 51.

[0081] The axial tooth root thickness is equal to or greater than 1.3 mm. The axial tooth root thickness is equal to or less than 2.1 mm.

[0082] As shown in Figure 6, the first rear sprocket S1 has a pitch circle PC relative to a pitch circle diameter r2. The pitch circle diameter r2 is one of the diameters of the pitch circle PC.

[0083] The pitch circle PC is defined by a plurality of imaginary chain rollers 37c, each of which has one of a plurality of roller central shafts P3 such that each imaginary chain roller 37c contacts one of a plurality of drive surfaces 45 of a plurality of sprocket teeth 43 and the pitch circle PC passes through all of the plurality of roller central shafts.

[0084] For example, in a hypothetical state where chain roller 37c contacts one of the plurality of drive surfaces 45 of a plurality of sprocket teeth 43, the pitch circle PC is defined by one of the circles passing through the central axis P3 of all the plurality of rollers.

[0085] As shown in Figure 6, at least one downshift facilitator tooth 51 has a radially outermost tooth tip 51a. In the radial direction relative to the rotation center axis C1, the radially outermost tooth tip 51a is located at the outermost position in the distance from the rotation center axis C1 to one of the tooth tips of at least one downshift facilitator tooth 51.

[0086] The first rear sprocket S1 has a tooth tip circle TC passing through one of the radially outermost tooth tips 51a. The tooth tip circle TC has a maximum tooth tip diameter r3.

[0087] For example, at least one downshift actuating tooth 51 has a maximum tooth tip diameter r3 that is smaller than the pitch circle diameter r2 of the first rear sprocket S1. At least one downshift actuating tooth 51 may also have a maximum tooth tip diameter r3 that is equal to or greater than the pitch circle diameter r2 of the first rear sprocket S1.

[0088] Specifically, a pitch polygon PG is defined by linearly connecting a plurality of roller center axes. In this embodiment, the pitch polygon PG is a nonagon. However, depending on the total number of teeth of one of the first rear sprockets S1, the pitch polygon is not limited to a nonagon. The radially outermost tooth tip 51a of at least one downshift actuating tooth 51 is positioned radially outward from the pitch polygon PG relative to the rotation center axis C1.

[0089] (Second rear sprocket)

[0090] As shown in Figure 3, the second rear sprocket S2 can be mounted to the rear wheel hub assembly 29 of the bicycle 1. One of the rotational centers of the second rear sprocket S2 is coaxial with the rotational center axis C1. In the following description, the rotational center axis of the second rear sprocket S2 may be indicated by the symbol "C1".

[0091] As shown in Figures 4 and 7, the second rear sprocket S2 includes a sprocket body 53 and a plurality of sprocket teeth 55. The sprocket body 53 is formed in a ring shape. The plurality of sprocket teeth 55 extend radially outward from the outer periphery of one of the sprocket bodies 53 in a radial direction relative to the rotation center axis C1 of one of the second rear sprockets S2.

[0092] Chain rollers 37a and 37b respectively mesh with a plurality of sprocket teeth 55 and transmit driving force to the plurality of sprocket teeth 55 respectively.

[0093] As shown in Figures 4 and 7, the second rear sprocket S2 includes at least one downshift initiation tooth 57. The at least one downshift initiation tooth 57 is contained within a plurality of sprocket teeth 55.

[0094] As shown in Figures 8A and 8B, at least one downshift initiation tooth 57 is configured to engage with the drive chain 9 first during downshifting operation.

[0095] For example, at least one downshift initiating tooth 57 is configured to engage with the chain roller 37a of the drive chain 9 first during downshifting operation. In this embodiment, the total number of at least one downshift initiating tooth 57 of the second rear sprocket S2 is one. However, depending on the total number of teeth of the second rear sprocket S2, the total number of at least one downshift initiating tooth 57 of the second rear sprocket S2 may be greater than one.

[0096] As shown in Figure 8A, a minimum chain lifting distance D1 is defined along the radial direction from the rotation center axis C1 to the chain lifting area 47a2 of the non-driving surface 47a.

[0097] For example, the minimum chain lifting distance D1 is defined by a distance in the radial direction from the rotation center axis C1 to the innermost point RP1 of the chain lifting area 47a2 of the non-driving surface 47a in the radial direction.

[0098] In this embodiment, the inner link plate 35a first contacts the innermost radial point RP1 during downshifting. However, the inner link plate 35a may not first contact the innermost radial point RP1 during downshifting.

[0099] The minimum chain lifting distance D1 is equal to or greater than half the pitch circle diameter r2 minus 4.1 mm and equal to or less than half the pitch circle diameter r2 minus 2.1 mm.

[0100] As shown in Figure 8B, a maximum chain lifting distance D2 is defined along the radial direction from the rotation center axis C1 to the chain lifting area 47a2 of the non-driving surface 47a.

[0101] For example, the maximum chain lifting distance D2 is defined by a distance in the radial direction from the rotation center axis C1 to the outermost point RP2 of the chain lifting area 47a2 of the non-driving surface 47a.

[0102] In this embodiment, the inner link plate 35a contacts the radial outermost point RP2 after contacting the radial innermost point RP1 during the downshift operation. However, the inner link plate 35a may contact the radial outermost point RP2 before contacting the radial innermost point RP1 during the downshift operation.

[0103] The maximum chain lifting distance D2 is equal to or greater than half the pitch circle diameter r2 minus 1.3 mm and equal to or less than half the pitch circle diameter r2 plus 0.5 mm.

[0104] 1: Bicycle 9: Drive chain 11: Chassis 13: Handle 17: Front wheel 17a: Front tire 19: Rear wheel 19a: Rear tire 20: Front fork 24: Gear shifting device / gear shifting mechanism 25: Drive System 26: Bicycle rear derailleur 27: Crank assembly 28: Rear sprocket assembly 29: Rear wheel hub assembly 31: Chain Unit 33a: External link plate 33b: External Link Plate 35: Front sprocket 35a: Inner Link Plate 35b: Inner Link Plate 37a: Chain roller 37b: Chain roller 37c: Imaginary chain roller 39a: Chain pin 39b: Chain pin 41: Sprocket body 43: Sprocket teeth 45: Driving surface 45a: Driving surface 47: Non-driving surface 47a1: Basement terminal region 47a2: Chain lifting area 51: Downshifting promotes gear development 51a: Outer radial tooth tip 53: Sprocket body 55: Sprocket teeth 57: Downshift starting gear BC: Tooth root circle C1: Rotation center axis D1: Minimum chain lifting distance D2: Maximum chain lift distance P1: Pivot Center Axis P2: Pivot Center Axis P3: Roller center shaft PC: Jieyuan PG: Pitch Polygon r1: Tooth root diameter r2: Pitch circle diameter r3: Maximum tooth tip diameter R1: Direction of rotation RP1: Innermost radial point RP2: Outermost radial point S1: First rear sprocket / rear sprocket S2: Second rear sprocket / rear sprocket S3: Third rear sprocket S4: Fourth rear sprocket S5: Fifth rear sprocket S6: Sixth rear sprocket S7: Seventh rear sprocket S8: Eighth rear sprocket S9: Ninth rear sprocket S10: Tenth rear sprocket S11: Eleventh rear sprocket S12: Twelfth rear sprocket TC: Tooth tip round

Claims

1. A rear sprocket for mounting to a rear wheel hub assembly of one of a human-powered vehicles, the rear sprocket having a pitch circle relative to a pitch circle diameter, the rear sprocket comprising: A sprocket body; and a plurality of sprocket teeth extending radially outward from the outer periphery of one of the sprocket bodies in a radial direction relative to a rotational central axis of one of the rear sprockets, the plurality of sprocket teeth including at least one downshifting actuating tooth configured to facilitate a downshifting operation in which a drive chain shifts axially from the rear sprocket toward a neighboring large sprocket adjacent to the rear sprocket, with no other sprocket between the rear sprocket and the neighboring large sprocket, the at least one downshifting actuating tooth having a driving surface and a non-driving surface disposed on the opposite side of one of the driving surfaces in a circumferential direction relative to the rotational central axis, the non-driving surface having a chain lifting area; a minimum chain lifting distance is defined along the radial direction from the rotational central axis to the chain lifting area of ​​the non-driving surface; and the minimum chain lifting distance is equal to or greater than half the pitch circle diameter minus 4.1 mm and equal to or less than half the pitch circle diameter minus 2.1 mm.

2. As requested in item 1, the sprocket, wherein a maximum chain lifting distance is defined along the radial direction from the rotation center axis to the chain lifting area of ​​the non-driving surface; the maximum chain lifting distance is equal to or greater than half the pitch circle diameter minus 1.3 mm and equal to or less than half the pitch circle diameter plus 0.5 mm.

3. The sprocket following request item 1 or 2, wherein the total number of teeth on one of the following sprockets is equal to or less than twelve.

4. The sprocket following request item 3, wherein the total number of teeth on the following sprocket is equal to or less than ten.

5. The sprocket following claim 1 or 2, wherein the at least one downshifting actuating tooth has an axial tooth root thickness measured in the axial direction relative to the rotation center axis at one tooth root circle of the rear sprocket; and the axial tooth root thickness is equal to or greater than 1.3 mm.

6. As requested in item 5, the sprocket has an axial tooth root thickness equal to or less than 2.1 mm.

7. The sprocket following claim 1 or 2, wherein the at least one downshift facilitator tooth has a maximum tooth tip diameter smaller than one of the pitch circle diameters of the following sprocket.

8. A sprocket as requested in item 1 or 2, wherein the pitch circle is defined by a plurality of imaginary chain rollers, each of the plurality of imaginary chain rollers having one of a plurality of roller central axes such that each of the imaginary chain rollers contacts one of a plurality of drive surfaces of the plurality of sprocket teeth, and the pitch circle passes through all of the plurality of roller central axes; a pitch polygon is defined by linearly connecting the plurality of roller central axes; the at least one downshift actuating tooth has a radially outermost tooth tip; and the radially outermost tooth tip of the at least one downshift actuating tooth is arranged radially outward from the pitch polygon relative to the rotational central axis.

9. A rear sprocket assembly, comprising: The sprocket is after any of the requests from 1 to 8; The adjacent sprocket includes at least one downshift initiating tooth configured to engage with the drive chain first during the downshift operation; and when viewed from the axial direction, in the circumferential direction, the at least one downshift amplifying tooth of the rear sprocket is adjacent to the at least one downshift initiating tooth of the adjacent sprocket on the downstream side of one of the at least one downshift initiating teeth of the adjacent sprocket relative to one of the drive rotation directions of the rear sprocket assembly, and there is no other tooth between the at least one downshift initiating tooth of the adjacent sprocket and the at least one downshift amplifying tooth of the rear sprocket.

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