Front sprocket assembly for human-powered vehicle

Abstract

This invention discloses a front sprocket assembly including a first sprocket and a second sprocket. The second sprocket includes a second sprocket body and a plurality of second sprocket teeth. At least one of the plurality of second sprocket teeth includes a low chain interference groove disposed on a second axially inward surface. The low chain interference groove is configured to reduce interference between the at least one tooth of the plurality of second sprocket teeth and the chain during an upshift operation in which one of the chains shifts from the first sprocket to the second sprocket. The low chain interference groove has a radially innermost end located radially inward from the root circle of one of the plurality of second sprocket teeth. The radial distance from the root circle to the radially innermost end relative to a rotation center axis is equal to or greater than 1.0 mm.

Description

Technical Field

[0001] This invention relates to a front sprocket assembly for a human-powered vehicle. Prior Technology

[0002] A human-powered vehicle includes a sprocket assembly configured to engage with a chain. The sprocket assembly includes a plurality of sprockets with different outer diameters. The chain may interfere with one of the sprockets during a shifting operation, whereby the chain shifts from one sprocket to another. One object of the present invention is to smooth a shifting operation in a front sprocket assembly. Summary of the Invention

[0003] According to a first aspect of the present invention, a front sprocket assembly for a human-powered vehicle includes a first sprocket and a second sprocket. The first sprocket has a first axially outward surface and a first axially inward surface. The first axially inward surface is disposed on the opposite side of the first axially outward surface in an axial direction relative to a rotational center axis of the front sprocket assembly. The first sprocket includes a first sprocket body and a plurality of first sprocket teeth. The plurality of first sprocket teeth extend radially outward from a first outer periphery of the first sprocket body relative to the rotational center axis. The first sprocket has a first pitch circle diameter. The second sprocket has a second axially outward surface and a second axially inward surface. The second axially inward surface is disposed on the opposite side of the second axially outward surface in the axial direction. The second axially inward surface is configured to face the first axially outward surface of the first sprocket in the axial direction in an assembled state of the front sprocket assembly. The second sprocket includes a second sprocket body and a plurality of second sprocket teeth. The plurality of second sprocket teeth extend radially outward from a second outer periphery of one of the second sprocket bodies relative to the rotation center axis. The second sprocket has a second pitch circle diameter larger than the first pitch circle diameter. The second sprocket is adjacent to the first sprocket, and there is no other sprocket between the first sprocket and the second sprocket in the axial direction. At least one tooth of the plurality of second sprocket teeth includes a low chain interference groove disposed on a second axially inward surface. The low chain interference groove is configured to reduce interference between the at least one tooth of the plurality of second sprocket teeth and the chain during an upshift operation in which one of the chains shifts from the first sprocket to the second sprocket. The at least one tooth of the plurality of second sprocket teeth has a drive surface and a non-drive surface disposed on the opposite side of the drive surface in a circumferential direction relative to one of the rotation center axes. The low chain interference groove extends radially inward relative to the rotation center axis in an elongation direction inclined from the drive surface toward an upstream side relative to one of the drive rotation directions of the front sprocket assembly. The low-chain interference groove has a radially innermost end located radially inward from the root circle of one of the plurality of second sprocket teeth. The radial distance from the root circle to the radially innermost end relative to the axis of rotation is equal to or greater than 1.0 mm.

[0004] Regarding the sprocket assembly prior to the first configuration, the low chain interference groove reduces interference between at least one tooth of the plurality of second sprocket teeth and the chain during the upshift operation. Therefore, the low chain interference groove makes the upshift operation smooth.

[0005] According to a second configuration of the present invention, the sprocket assembly prior to the first configuration is configured such that the radial distance is equal to or greater than 1.3 mm.

[0006] Regarding the sprocket assembly prior to the second state sample, the low chain interference groove reliably smooths the upshift operation.

[0007] According to one of the third states of the present invention, the sprocket assembly is configured such that the radial distance is equal to or less than 2.0 mm prior to the first or second state.

[0008] Based on the sprocket assembly prior to the third state, sufficient strength of the second sprocket body can be ensured.

[0009] According to a fourth embodiment of the present invention, the sprocket assembly is configured such that the first sprocket has a first total number of teeth, based on any one of the first to third embodiments. The second sprocket has a second total number of teeth, which is greater than the first total number of teeth.

[0010] Regarding the sprocket assembly prior to the fourth state sample, the low chain interference groove reliably smooths the upshift operation.

[0011] According to a fifth configuration of the present invention, the sprocket assembly prior to the fourth configuration is configured such that a tooth difference between the first total number of teeth and the second total number of teeth is equal to or greater than 9.

[0012] Regarding the sprocket assembly prior to the fifth state sample, the tooth difference provides a wider gear ratio range for the front sprocket assembly, while the low chain interference groove makes the upshifting operation smooth.

[0013] According to a sixth configuration of the present invention, the sprocket assembly prior to the fifth configuration is configured such that the difference in the number of teeth between the first total number of teeth and the second total number of teeth is equal to or less than 20.

[0014] Regarding the sprocket assembly prior to the sixth state sample, the tooth difference reliably provides a wider gear ratio range for one of the front sprocket assemblies, while the low chain interference groove makes the upshifting operation smooth.

[0015] According to a seventh configuration of the present invention, the sprocket assembly is configured such that the second total number of teeth is equal to or greater than 50, according to any one of the fourth to sixth configurations.

[0016] Regarding the sprocket assembly prior to the seventh configuration, this second total number of teeth achieves a wider gear ratio range on its high-speed gear side. Therefore, a transmission system with a larger gear ratio can be provided.

[0017] According to an eighth embodiment of the present invention, the sprocket assembly further includes a shift assist protrusion prior to any one of the first to seventh embodiments, at least a portion of which is arranged radially inward relative to the rotation center axis from the non-drive surface of at least one of the plurality of second sprocket teeth.

[0018] Regarding the sprocket assembly prior to the eighth state, the shift assist protrusion can smooth the shifting operation in the sprocket assembly with a large tooth number difference.

[0019] According to a ninth embodiment of the present invention, the sprocket assembly prior to the eighth embodiment is configured such that the innermost radial end of the low chain interference groove is positioned downstream of one of the shift assist protrusions relative to the transmission rotation direction of the front sprocket assembly.

[0020] Based on the previous sprocket assembly in the ninth state, this upshift operation can be made smoother.

[0021] According to one of the tenth states of the present invention, the sprocket assembly is configured such that the shift assist protrusion is arranged radially inward from the low chain interference groove relative to the rotation center axis, according to the eighth or ninth state.

[0022] Based on the sprocket assembly prior to the tenth state, this upshift operation can be reliably made smoother.

[0023] According to one of the eleventh states of the present invention, the sprocket assembly is configured such that the low chain interference groove has a maximum lateral length and a maximum radial length, according to any one of the first to tenth states. The maximum radial length is greater than the maximum lateral length.

[0024] Regarding the sprocket assembly prior to the eleventh configuration, the low chain interference groove effectively reduces interference between at least one tooth of the plurality of second sprocket teeth and the chain during the upshift operation. Therefore, the low chain interference groove effectively smooths the upshift operation.

[0025] According to one of the twelfth states of the present invention, the sprocket assembly is configured such that the low chain interference groove extends radially inward from the drive surface relative to the rotation center axis to have a curvature, according to any one of the first to eleventh states.

[0026] Regarding the sprocket assembly prior to the twelfth state, the low chain interference groove can more effectively smooth the upshift operation.

[0027] According to one of the thirteenth states of the present invention, the sprocket assembly prior to the twelfth state is configured such that the curvature of the low chain interference groove is configured to correspond to one of the rotational trajectories of the chain.

[0028] Regarding the sprocket assembly prior to the thirteenth state sample, the low chain interference groove can more effectively smooth the upshift operation.

[0029] According to one of the fourteenth versions of the invention, the sprocket assembly is configured such that the low chain interference groove is configured to reduce interference between at least one tooth of the plurality of second sprocket teeth and one of the outer chain plates of the chain during the upshift operation.

[0030] Regarding the sprocket assembly prior to the fourteenth configuration, the low chain interference groove reduces interference between at least one tooth of the plurality of second sprocket teeth and the outer chain plate during the upshift operation. Therefore, the low chain interference groove effectively smooths the upshift operation.

[0031] According to a fifteenth embodiment of the present invention, the sprocket assembly is configured such that at least two teeth of the plurality of second sprocket teeth each include the low chain interference groove disposed on the second axially inward surface.

[0032] Regarding the sprocket assembly prior to the fifteenth state, the low chain interference grooves of at least two of the plurality of second sprocket teeth can effectively smooth the upshift operation.

[0033] According to a sixteenth embodiment of the present invention, the sprocket assembly prior to the fifteenth embodiment is configured such that at least four of the plurality of second sprocket teeth each include the low chain interference groove disposed on the second axially inward surface.

[0034] Regarding the sprocket assembly prior to the sixteenth state, the low chain interference grooves of at least four of the plurality of second sprocket teeth can more effectively smooth the upshift operation. Simple Explanation of the Diagram

[0035] A more complete understanding and better appreciation of the invention and its many accompanying advantages will be readily obtained by referring to the following detailed description in conjunction with the accompanying drawings.

[0036] Figure 1 is a schematic diagram of a transmission system of a human-powered vehicle including a front sprocket assembly according to a first embodiment.

[0037] Figure 2 is a perspective view of one of the crank assemblies of the transmission system shown in Figure 1.

[0038] Figure 3 is a side view of the sprocket assembly in front of the crank assembly shown in Figure 2.

[0039] Figure 4 is a cross-sectional view of the sprocket assembly taken along line IV-IV of Figure 3.

[0040] Figure 5 is a side view of the sprocket assembly in front of the crank assembly shown in Figure 3, which has a chain (upshifting operation).

[0041] Figure 6 is a partial side view of the sprocket assembly in front of the crank assembly shown in Figure 3.

[0042] Figure 7 is a perspective view of the sprocket assembly in front of the crank assembly shown in Figure 3.

[0043] Figure 8 is an enlarged side view of one of the sprocket assemblies in front of the crank assembly shown in Figure 3.

[0044] Figure 9 is a cross-sectional view of the sprocket assembly taken along line IX-IX of Figure 8.

[0045] Figure 10 is a cross-sectional view of one of the sprocket assemblies obtained along line XX in Figure 8.

[0046] Figure 11 is a cross-sectional view of the sprocket assembly taken along line XI-XI of Figure 8.

[0047] Figure 12 is a cross-sectional view of the sprocket assembly taken along line XII-XII in Figure 8.

[0048] Figure 13 is a cross-sectional view of one of the sprocket assemblies taken along line XIII-XIII in Figure 8.

[0049] Figure 14 is a cross-sectional view of a front sprocket assembly according to one of the comparative examples, wherein a low chain interference groove is omitted.

[0050] Figure 15 is a side view of a sprocket assembly based on a comparative example, which has a chain (upshifting operation).

[0051] Figure 16 is a side view of the sprocket assembly in front of the crank assembly shown in Figure 3, which has a chain (upshifting operation).

[0052] Figure 17 is a perspective view of a crank assembly including a front sprocket assembly according to a second embodiment.

[0053] Figure 18 is a side view of the sprocket assembly in front of the crank assembly shown in Figure 17, which has a chain (upshifting operation).

[0054] Figure 19 is an enlarged side view of one of the sprocket assemblies in front of the crank assembly shown in Figure 17.

[0055] Figure 20 is a cross-sectional view of one of the sprocket assemblies taken along line XX-XX in Figure 19.

[0056] Figure 21 is a cross-sectional view of the sprocket assembly taken along line XXI-XXI in Figure 19.

[0057] Figure 22 is a cross-sectional view of one of the sprocket assemblies obtained along line XXII-XXII in Figure 19. Implementation

[0058] Several embodiments will now be described with reference to the accompanying drawings, wherein the same element symbols in all the various figures indicate corresponding or identical elements. First Embodiment

[0059] As shown in Figure 1, a transmission system 10 for a human-powered vehicle 2 includes a crank assembly 12, a rear sprocket assembly 14, and a chain C. The crank assembly 12 is configured to be rotatably coupled to the vehicle body 2A of the human-powered vehicle 2 about a central axis of rotation A1. The rear sprocket assembly 14 is configured to be rotatably coupled to the vehicle body 2A of the human-powered vehicle 2 about a central axis of rotation A2. The crank assembly 12 includes a front sprocket assembly 16. The front sprocket assembly 16 is configured to engage with the chain C. The rear sprocket assembly 14 is configured to engage with the chain C.

[0060] The vehicle body 2A has a transverse center plane TP perpendicular to the rotation center axis A1. The transverse center plane TP is defined to bisect the transverse length of the vehicle body 2A in an axial direction D1 relative to the rotation center axis A1.

[0061] As shown in Figure 2, the crank assembly 12 includes a crankshaft 18, a first crank arm 20, and a second crank arm 22. The crankshaft 18 extends along the rotation center axis A1. The first crank arm 20 and the second crank arm 22 are fixed to the crankshaft 18. During pedaling, the crank assembly 12 rotates about the rotation center axis A1 in a transmission rotation direction D21 relative to the vehicle body 2A of the human-powered vehicle 2.

[0062] The front sprocket assembly 16 is rotatable about a rotational center axis A1, together with the crankshaft 18, the first crank arm 20, and the second crank arm 22, relative to the vehicle body 2A of the human-powered vehicle 2. The front sprocket assembly 16 is configured to couple to at least one of the crankshaft 18 and the first crank arm 20. In this embodiment, the front sprocket assembly 16 is configured to couple to the first crank arm 20. However, the front sprocket assembly 16 may be configured to couple to the crankshaft 18 or both the crankshaft 18 and the first crank arm 20 as needed and / or desired.

[0063] In this application, a human-powered vehicle is a vehicle propelled by a prime mover, the prime mover being at least one human power source from the user (i.e., the rider) of the human-powered vehicle. Human-powered vehicles include various types of bicycles, such as mountain bikes, road bikes, city bikes, cargo bikes, hand-cranked bicycles, and recumbent bicycles. Furthermore, human-powered vehicles include electric bicycles (E-bikes). Electric bicycles include electric-assisted bicycles configured to use an electric motor to assist in the propulsion of a vehicle. However, the total number of wheels on a human-powered vehicle is not limited to two. For example, a human-powered vehicle includes a vehicle having one wheel or three or more wheels. Human-powered vehicles, in particular, do not include vehicles that use only an internal combustion engine as a prime mover. Generally, a light road vehicle (which includes vehicles that do not require a public road driving license) is considered a human-powered vehicle.

[0064] In this application, the following directional terms "forward," "rearward," "forward," "backward," "left," "right," "lateral," "upward," and "downward," and any other similar directional terms, refer to the direction determined based on a user (e.g., a rider) facing a handlebar or steering mechanism in a standard position of the user in the human-powered vehicle 2 (e.g., on a saddle or seat). Therefore, when used to describe the crank assembly 12, the front sprocket assembly 16, or other components, these terms should be interpreted relative to the human-powered vehicle 2 equipped with the crank assembly 12, the front sprocket assembly 16, or other components, such as in an upright riding position on a horizontal surface.

[0065] As shown in Figure 3, the sprocket assembly 16 for the human-powered vehicle 2 includes a first sprocket 24 and a second sprocket 26. The first sprocket 24 includes a first sprocket body 28 and a plurality of first sprocket teeth 30. The plurality of first sprocket teeth 30 extend radially outward from a first outer periphery of the first sprocket body 28 relative to a rotational axis A1. In other words, the plurality of first sprocket teeth 30 extend radially outward from a first outer periphery of the first sprocket body 28 relative to a rotational axis A1. The first sprocket 24 has a first pitch circle diameter DM1. The first pitch circle diameter DM1 is defined as the diameter of a first pitch circle PC1 of the first sprocket 24.

[0066] The second sprocket 26 includes a second sprocket body 34 and a plurality of second sprocket teeth 36. The plurality of second sprocket teeth 36 extend radially outward from a second outer periphery of the second sprocket body 34 relative to a rotational central axis A1. In other words, the plurality of second sprocket teeth 36 extend radially outward from a second outer periphery of the second sprocket body 34 relative to a rotational central axis A1. The second sprocket 26 has a second pitch circle diameter DM2. The second pitch circle diameter DM2 is larger than the first pitch circle diameter DM1. The second pitch circle diameter DM2 is defined as the diameter of a second pitch circle PC2 of the second sprocket 26.

[0067] The first sprocket 24 corresponds to one of the low-speed gears in the front sprocket assembly 16. The second sprocket 26 corresponds to one of the high-speed gears in the front sprocket assembly 16. However, the front sprocket assembly 16 may include an additional sprocket assembly as needed and / or desired.

[0068] The first sprocket 24 has a first total number of teeth. The first total number of teeth is the total number of the first sprocket teeth 30. The second sprocket 26 has a second total number of teeth. The second total number of teeth is the total number of the second sprocket teeth 36. The second total number of teeth is greater than the first total number of teeth. The second total number of teeth is equal to or greater than 50. The difference in the number of teeth between the first total number of teeth and the second total number of teeth is equal to or greater than 9. The difference in the number of teeth between the first total number of teeth and the second total number of teeth is equal to or less than 20.

[0069] In this embodiment, the first tooth count is 36. The second tooth count is 52. The tooth count difference is 16. However, the first total tooth count is not limited to 36. The second total tooth count is not limited to 52. The tooth count difference may be equal to or less than 9 as needed and / or desired. The tooth count difference may be equal to or greater than 20.

[0070] As shown in Figure 4, the first sprocket 24 has a first axially outward surface 24A and a first axially inward surface 24B. The first axially inward surface 24B is disposed on the opposite side of the first axially outward surface 24A in the axial direction D1 relative to the rotation center axis A1 of the front sprocket assembly 16. The first axially inward surface 24B is configured to face the transverse center plane TP of the vehicle body 2A in the installation state in which the front sprocket assembly 16 is mounted to the vehicle body 2A of the human-powered vehicle 2.

[0071] The second sprocket 26 has a second axially outward surface 26A and a second axially inward surface 26B. The second axially inward surface 26B is disposed on the opposite side of the second axially outward surface 26A in the axial direction D1. The second axially inward surface 26B is configured to face the transverse center plane TP of the vehicle body 2A in the installation state in which the front sprocket assembly 16 is mounted to the vehicle body 2A of the human-powered vehicle 2.

[0072] The second axially inward surface 26B is configured to face the first axially outward surface 24A of the first sprocket 24 in the axial direction D1 when one of the front sprocket assemblies 16 is assembled. The second sprocket 26 is adjacent to the first sprocket 24, and there is no other sprocket between the first sprocket 24 and the second sprocket 26 in the axial direction D1.

[0073] For example, an upshift occurs when chain C shifts from one sprocket to an adjacent larger sprocket in an upshift direction D41. A downshift occurs when chain C shifts from one sprocket to an adjacent smaller sprocket in a downshift direction D42.

[0074] In this embodiment, the second sprocket body 34 includes a first annular body 34A, a second annular body 34B, a first cover 34C, and a second cover 34D. The first annular body 34A is disposed radially outward of the second annular body 34B. The first annular body 34A and a plurality of second sprocket teeth 36 are integrally formed as a single-piece component. The first cover 34C and the second cover 34D are attached to the first annular body 34A and the second annular body 34B to define an internal space 34E between the first cover 34C and the second cover 34D. The second annular body 34B is disposed between the first cover 34C and the second cover 34D. The first annular body 34A is at least partially disposed in the internal space 34E. The second annular body 34B is at least partially disposed in the internal space 34E.

[0075] In this embodiment, the first annular body 34A is partially disposed within the internal space 34E. The second annular body 34B is completely disposed within the internal space 34E. However, the first annular body 34A may be completely disposed within the internal space 34E as needed and / or desired. The second annular body 34B may be partially disposed within the internal space 34E as needed and / or desired.

[0076] As shown in Figure 3, at least one tooth 36A of the plurality of second sprocket teeth 36 includes a low chain interference groove 40. The low chain interference groove 40 is disposed on the second axially inward surface 26B. At least two teeth 36A of the plurality of second sprocket teeth 36 each include a low chain interference groove 40 disposed on the second axially inward surface 26B. At least four teeth 36A of the plurality of second sprocket teeth 36 each include a low chain interference groove 40 disposed on the second axially inward surface 26B.

[0077] In this embodiment, each of the eight teeth 36A of the plurality of second sprocket teeth 36 includes a low chain interference groove 40 disposed on the second axially inward surface 26B. However, at least one tooth of the plurality of second sprocket teeth 36 may include a low chain interference groove 40 as needed and / or desired.

[0078] The low-chain interference grooves 40 have the same structure as each other. However, at least one of the low-chain interference grooves 40 may have a structure different from that of the other low-chain interference groove 40 as needed and / or desired.

[0079] As shown in Figure 5, the low chain interference groove 40 is configured to reduce interference between at least one tooth 36A of the plurality of second sprocket teeth 36 and the chain C during an upshifting operation where the chain C shifts from the first sprocket 24 to the second sprocket 26. The low chain interference groove 40 is also configured to reduce interference between at least one tooth 36A of the plurality of second sprocket teeth 36 and one of the outer chain plates C2 (e.g., C2A) of the chain C during the upshifting operation.

[0080] As shown in Figure 6, at least one tooth 36A of the plurality of second sprocket teeth 36 has a driving surface 42 and a non-driving surface 44. The non-driving surface 44 is disposed on the opposite side of the driving surface 42 in a circumferential direction D3 relative to the rotation center axis A1. In this embodiment, each tooth of the plurality of second sprocket teeth 36 includes a driving surface 42 and a non-driving surface 44. The driving surface 42 is configured to face the transmission rotation direction D21 to transmit a rotational force to the chain C. The non-driving surface 44 is configured to face a reverse rotation direction D22, which is the opposite direction to the transmission rotation direction D21.

[0081] Each of the second sprocket teeth 36 includes a tooth tip 45. The tooth tip 45 of the second sprocket tooth 36 is located at the outermost radial end of one of the second sprocket teeth 36.

[0082] Each of the second sprocket teeth 36 includes a first tooth root 46 and a second tooth root 47. The second sprocket tooth 36 is disposed between the first tooth root 46 and the second tooth root 47. The first tooth root 46 of the second sprocket tooth 36A is disposed on the downstream side of one of the second tooth roots 47 of the second sprocket tooth 36A in the transmission rotation direction D21. The tooth root circle TC is defined as the circle connecting the first tooth root 46 and the second tooth root 47 of the second sprocket tooth 36.

[0083] The transmission surface 42 extends from the tooth tip 45 to the first tooth root 46 of the second sprocket tooth 36A. The non-transmission surface 44 extends from the tooth tip 45 to the second tooth root 47 of the second sprocket tooth 36A.

[0084] The low chain interference groove 40 has a radially innermost end 40A. The radially innermost end 40A is radially positioned inward from the tooth root circle TC of a plurality of second sprocket teeth 36.

[0085] The front sprocket assembly 16 further includes a shift assist protrusion 50, at least a portion of which is radially inwardly disposed relative to the rotation center axis A1 from the non-drive surface 44 of at least one tooth 36A of a plurality of second sprocket teeth 36. The shift assist protrusion 50 is coupled to the second sprocket 26. The shift assist protrusion 50 is configured to engage with the chain C to assist upshifting operations.

[0086] The innermost radial end 40A of the low chain interference groove 40 (e.g., 40X) is positioned downstream of one of the shift assist protrusions 50 relative to the drive rotation direction D21 of the front sprocket assembly 16. The shift assist protrusion 50 is positioned radially inward from the low chain interference groove 40 (e.g., 40X) relative to the rotation center axis A1. The low chain interference groove 40 is at least partially located downstream of one of the shift assist protrusions 50 in the drive rotation direction D21, and there are no sprocket teeth between the low chain interference groove 40 and the shift assist protrusion 50 in the drive rotation direction D21. The low chain interference groove 40 is at least partially located radially outward of the shift assist protrusion 50.

[0087] In this embodiment, the low chain interference groove 40 is completely disposed downstream of the shift assist protrusion 50 in the transmission rotation direction D21, and there are no sprocket teeth between the low chain interference groove 40 and the shift assist protrusion 50 in the transmission rotation direction D21. The low chain interference groove 40 is partially disposed radially outward of the shift assist protrusion 50. However, the low chain interference groove 40 may be disposed completely radially outward of the shift assist protrusion 50 as needed and / or desired.

[0088] The transmission surface 42 includes a curved surface with a concave shape. The non-transmission surface 44 includes a curved surface with a concave shape. The transmission surface 42 and the non-transmission surface 44 define a reference circle RC with a reference center RC1. The second segment circle PC2 is defined on the reference center RC1 of the reference circle RC. When viewed in the axial direction D1, the low chain interference groove 40 is partially disposed between the tooth root circle TC and the second segment circle PC2.

[0089] As shown in Figure 7, the second sprocket tooth 36A includes an inclined surface 51. The inclined surface 51 is disposed along the transmission surface 42 of the second sprocket tooth 36A. The inclined surface 51 includes a first chamfered end 51A and a second chamfered end 51B. The inclined surface 51 of the second sprocket tooth 36A extends from the first chamfered end 51A to the second chamfered end 51B along the transmission surface 42 of the second sprocket tooth 36A. The first chamfered end 51A is closer to the tooth tip 45 than the second chamfered end 51B. The second chamfered end 51B is closer to the first tooth root 46 than the first chamfered end 51A.

[0090] The low chain interference groove 40 extends radially inward from the inclined surface 51. The low chain interference groove 40 protrudes radially inward from the inclined surface 51. The low chain interference groove 40 extends radially inward from the middle portion of one of the inclined surfaces 51 located between the first chamfered end 51A and the second chamfered end 51B. The inclined surface 51 may be omitted from the second sprocket tooth 36A.

[0091] The second sprocket 26 includes an attachment groove 52. The attachment groove 52 is disposed on the second axially inward surface 26B. The shift assist protrusion 50 is disposed in the attachment groove 52.

[0092] The second sprocket 26 includes a first additional groove 54. The first additional groove 54 is disposed on the second axially inward surface 26B. The first additional groove 54 is configured to reduce interference between the second sprocket body 34 and the chain C during upshifting operations.

[0093] As shown in Figure 6, the low chain interference groove 40 is at least partially disposed radially outside the first additional groove 54. In this embodiment, the low chain interference groove 40 is completely disposed radially outside the first additional groove 54. However, the low chain interference groove 40 may be partially disposed radially outside the first additional groove 54.

[0094] The second sprocket 26 includes a second additional groove 56. The second additional groove 56 is disposed on the second axially inward surface 26B. The second additional groove 56 is configured to reduce interference between the second sprocket body 34 and the chain C during upshifting operations.

[0095] A first additional groove 54 is at least partially disposed on the downstream side of the shift assist protrusion 50 in the transmission rotation direction D21. A second additional groove 56 is at least partially disposed on the downstream side of the shift assist protrusion 50 in the transmission rotation direction D21. In this embodiment, the first additional groove 54 is completely disposed on the downstream side of the shift assist protrusion 50 in the transmission rotation direction D21. The second additional groove 56 is completely disposed on the downstream side of the shift assist protrusion 50 in the transmission rotation direction D21. However, the first additional groove 54 may be partially disposed on the downstream side of the shift assist protrusion 50 in the transmission rotation direction D21. The second additional groove 56 may be partially disposed on the downstream side of the shift assist protrusion 50 in the transmission rotation direction D21. The second additional groove 56 is at least partially disposed on the downstream side of the first additional groove 54 in the transmission rotation direction D21. The second additional groove 56 is completely disposed on the downstream side of the first additional groove 54 in the transmission rotation direction D21. However, the second additional groove 56 may be provided on the downstream side of the first additional groove 54 in the transmission rotation direction D21.

[0096] As seen in Figures 2 and 3, in this embodiment, the front sprocket assembly 16 includes a plurality of shift assist protrusions 50. The second sprocket 26 includes a plurality of first additional recesses 54 and a plurality of second additional recesses 56. The total number of shift assist protrusions 50 is 4. The total number of first additional recesses 54 is 4. The total number of second additional recesses 56 is 4. However, the total number of shift assist protrusions 50 is not limited to 4. The total number of first additional recesses 54 is not limited to 4. The total number of second additional recesses 56 is not limited to 4.

[0097] The second sprocket tooth 36A includes second sprocket teeth 36X and second sprocket teeth 36Y. The low chain interference groove 40 includes low chain interference groove 40X and low chain interference groove 40Y. The total number of one of the second sprocket teeth 36X is 4. The total number of one of the second sprocket teeth 36Y is 4. The total number of one of the low chain interference grooves 40X is 4. The total number of one of the low chain interference grooves 40Y is 4. However, the total number of second sprocket teeth 36X is not limited to 4. The total number of second sprocket teeth 36Y is not limited to 4. The total number of low chain interference grooves 40X is not limited to 4. The total number of low chain interference grooves 40Y is not limited to 4. The second sprocket tooth 36X includes low chain interference groove 40X. The second sprocket tooth 36Y includes low chain interference groove 40Y.

[0098] The second sprocket tooth 36X is adjacent to the shift assist protrusion 50 in the circumferential direction D3, and there is no other sprocket tooth between the second sprocket tooth 36X and the shift assist protrusion 50 in the circumferential direction D3. The low chain interference groove 40X is adjacent to the shift assist protrusion 50 in the circumferential direction D3, and there is no sprocket tooth between the low chain interference groove 40X and the shift assist protrusion 50 in the circumferential direction D3. The second sprocket tooth 36Y is located in a position not corresponding to one of the shift assist protrusions 50. The low chain interference groove 40Y is located in a position not corresponding to one of the shift assist protrusions 50. However, as needed and / or desired, the second sprocket tooth 36Y may be located in a position corresponding to one of the shift assist protrusions 50, just like the second sprocket tooth 36X. As needed and / or desired, the low chain interference groove 40Y may be located in a position corresponding to one of the shift assist protrusions 50, just like the low chain interference groove 40X.

[0099] As shown in Figure 8, the low chain interference groove 40 extends radially inward relative to the rotation center axis A1 on an elongation direction D5 that is inclined upstream of the transmission rotation direction D21 relative to the front sprocket assembly 16 from the self-drive surface 42. A boundary 60 is provided between the low chain interference groove 40 and the inclined surface 51.

[0100] The radial distance DS1, relative to the rotation center axis A1, from the tooth root circle TC to the innermost radial end 40A, is equal to or greater than 1.0 mm. The radial distance DS1 is equal to or greater than 1.3 mm. The radial distance DS1 is equal to or less than 2.0 mm. In this embodiment, the innermost radial end 40A of the low chain interference groove 40 includes a radial innermost point 40D. The radial innermost point 40D is located in one of the other portions of the radial innermost end 40A closest to the rotation center axis A1. The radial distance DS1 is radially defined relative to the rotation center axis A1 from the tooth root circle TC to the innermost radial point 40D. In other words, the radial distance DS1 is defined along the radial direction relative to the rotation center axis A1 from the tooth root circle TC to the innermost radial point 40D. The radial distance DS1 is equal to 1.5 mm. However, the radial distance DS1 is not limited to the above distances and ranges. The radial distance DS1 may also refer to a first radial distance DS1.

[0101] The low chain interference groove 40 has a maximum lateral length L1 and a maximum radial length L2. The maximum radial length L2 is greater than the maximum lateral length L1. The maximum radial length L2 is defined in the elongation direction D5. When viewed in the axial direction D1, the maximum lateral length L1 is defined in a width direction D6 perpendicular to the elongation direction D5. The elongation direction D5 and the width direction D6 are perpendicular to the axial direction D1. The low chain interference groove 40 includes a protrusion 40B. The protrusion 40B protrudes radially inward from the inclined surface 51. The protrusion 40B includes a radially innermost end 40A. The protrusion 40B has the maximum lateral length L1.

[0102] When viewed in the axial direction D1, the low chain interference groove 40 has a longitudinal axis A5. When viewed in the axial direction D1, the low chain interference groove 40 extends along the longitudinal axis A5. The elongation direction D5 is parallel to the longitudinal axis A5 of the low chain interference groove 40. When viewed in the axial direction D1, the width direction D6 is perpendicular to the longitudinal axis A5. However, the maximum radial length L2 may, as needed and / or desired, be less than or equal to the maximum lateral length L1.

[0103] As seen in Figures 9 and 10, the low chain interference groove 40 includes a bottom surface 40C. The bottom surface 40C is configured to face the transverse center plane TP of the vehicle body 2A in an installation state in which the front sprocket assembly 16 is mounted to one of the vehicle bodies 2A of the human-powered vehicle 2 (see, for example, Figure 1).

[0104] The second sprocket tooth 36A has a central plane CP perpendicular to the rotation center axis A1. The central plane CP of the second sprocket tooth 36A is defined to divide the axial width 36W of the second sprocket tooth 36A in the axial direction D1.

[0105] The low chain interference groove 40 is recessed in the axial direction D1 from the second axial direction inwards from the inner surface 26B toward the central plane CP. The bottom surface 40C is closest to the central plane CP in the axial direction D1 within the low chain interference groove 40.

[0106] As shown in Figure 9, the shift assist protrusion 50 protrudes from the second sprocket tooth 36A in the axial direction D1 to engage with the chain C. The shift assist protrusion 50 is configured to engage with one of the inner chain plates C1 or one of the outer chain plates C2 of the chain C during upshifting operations.

[0107] As shown in Figure 8, the bottom surface 40C extends along the longitudinal axis A5. The bottom surface 40C extends along the longitudinal axis A5 between the boundary 60 and the radially innermost end 40A. The bottom surface 40C has a radially innermost bottom end 40E. A second radial distance DS2 is radially defined relative to the rotation center axis A1 from the tooth root circle TC to the radially innermost bottom end 40E. In other words, the second radial distance DS2 is defined radially relative to the rotation center axis A1 from the tooth root circle TC to the radially innermost bottom end 40E.

[0108] A reference point RT is the intersection point of a first reference line RL1 and a second reference line RL2 when viewed in the axial direction D1. The first reference line RL1 is perpendicular to the longitudinal axis A5 and connects to the reference center RC1 of a reference circle RC located on the upstream side of one of the second sprocket teeth 36A in the transmission rotation direction D21. The second reference line RL2 extends radially outward from the rotation center axis A1, passing through the innermost point 40D of the innermost radial end 40A.

[0109] In this embodiment, when viewed in the axial direction D1, the innermost radial end 40E is positioned at the reference point RT. However, when viewed in the axial direction D1, the innermost radial end 40E may be offset from the reference point RT as needed and / or desired.

[0110] A third reference line RL3 is defined to extend between the reference centers RC1 of adjacent reference circles RC, and there is no other reference circle between the reference circles RC in the circumferential direction D3. When viewed in the axial direction D1, a first reference angle AG1 is defined between the first reference line RL1 and the third reference line RL3. When viewed in the axial direction D1, a second reference angle AG2 is defined between the third reference line RL3 and the longitudinal axis A5 of the low-chain interference groove 40. In this embodiment, the first reference angle AG1 is equal to 30 degrees. The second reference angle AG2 is equal to 60 degrees. However, the first reference angle AG1 is not limited to the above angle. The second reference angle AG2 is not limited to the above angle.

[0111] The second radial distance DS2 is equal to or greater than 0.5 mm. The second radial distance DS2 is equal to or less than 2.0 mm. In this embodiment, the second radial distance DS2 is in the range of 0.5 mm to 0.6 mm. However, the second radial distance DS2 is not limited to the above distances and ranges.

[0112] The innermost radial end 40A of the low chain interference groove 40 is at least partially located radially within the first reference line RL1. The innermost radial end 40A of the low chain interference groove 40 is at least partially located radially within the reference point RT. In this embodiment, the innermost radial end 40A of the low chain interference groove 40 is completely located radially within the first reference line RL1. The innermost radial end 40A of the low chain interference groove 40 is partially located radially within the reference point RT. However, the innermost radial end 40A of the low chain interference groove 40 may be partially located radially within the first reference line RL1 as needed and / or desired. The innermost radial end 40A of the low chain interference groove 40 may be completely located radially within the reference point RT as needed and / or desired.

[0113] As seen in Figures 11 to 13, the boundary 60 protrudes in the axial direction D1 to form a low chain interference groove 40 and an inclined surface 51. The boundary 60 smoothly connects the low chain interference groove 40 and the inclined surface 51.

[0114] As shown in Figures 5 and 9, during upshifting, chain C shifts gears from the first sprocket 24 to the second sprocket 26 via a gear changer, such as a derailleur, while pedaling.

[0115] As shown in Figure 5, when the current sprocket assembly 16 rotates in the transmission rotation direction D21, the shift assist protrusion 50 lifts the chain C radially outward from the first sprocket tooth 30 to the second sprocket tooth 36 relative to the rotation center axis A1. In one chain phase shown in Figure 5, the shift assist protrusion 50 lifts the inner chain plate C1A of the chain C radially outward from the first sprocket tooth 30 to the second sprocket tooth 36 relative to the rotation center axis A1. In another chain phase, the shift assist protrusion 50 lifts the outer chain plate C2A of the chain C radially outward from the first sprocket tooth 30 to the second sprocket tooth 36 relative to the rotation center axis A1. When the shift assist protrusion 50 raises the inner chain plate C1A radially outward relative to the rotation center axis A1 in the chain phase shown in FIG5, the low chain interference groove 40 (e.g., 40X) is positioned closer to the outer chain plate C2A of the chain C than to the inner chain plate C1A. When the inner chain plate C1A raises the chain C radially outward from the first sprocket tooth 30 to the uppermost position shown in FIG13, the second sprocket tooth 36B is inserted between the opposite pair of outer chain plates C2B.

[0116] As seen in Figures 14 and 15, the second sprocket tooth 36 may interfere with the outer chain plate C2A of chain C in cases where the second sprocket tooth 36 does not include one of the low chain interference grooves 40 (e.g., 40X). The interference between the second sprocket tooth 36 and the outer chain plate C2A of chain C may restrict the smooth completion of the upshift operation. For example, the interference between the second sprocket tooth 36 and the outer chain plate C2A of chain C may restrict the movement of the inner chain plate C1A and / or the outer chain plate C2A relative to the rotation center axis A1 and the second sprocket 26 before the upshift operation is completed.

[0117] However, as seen in Figures 9 and 16, the low chain interference groove 40 (e.g., 40X) is configured to reduce interference between the second sprocket teeth 36 and the chain C during upshifting. The low chain interference groove 40 (e.g., 40X) is configured to reduce interference between at least one tooth 36A of the plurality of second sprocket teeth 36 and the outer chain plate C2A of the chain C during upshifting. The low chain interference groove 40 (e.g., 40X) is configured to facilitate radial outward movement of the inner chain plate C1A and / or the outer chain plate C2A relative to the rotation center axis A1 and relative to the second sprocket 26 before the upshifting operation is completed. The low chain interference groove 40 (e.g., 40X) is particularly configured to facilitate radial outward movement of the inner chain plate C1A and / or the outer chain plate C2A relative to the rotation center axis A1 and relative to the second sprocket 26 in one of the chain phases in which the inner chain plate C1A engages with the shift assist protrusion 50. Therefore, the low chain interference groove 40 (e.g., 40X) allows for smooth upshifting operations. Second Embodiment

[0118] The following description, with reference to Figures 17 to 22, describes a front sprocket assembly 216 according to a second embodiment. Except for the low chain interference groove 40, the front sprocket assembly 216 has the same structure and / or configuration as the front sprocket assembly 16. Therefore, elements having substantially the same function as those in the first embodiment will be numbered the same here, and for the sake of brevity, will not be described in detail or illustrated further.

[0119] As shown in Figure 17, the sprocket assembly 216 for the human-powered vehicle 2 includes a first sprocket 24 and a second sprocket 226. The second sprocket 226 includes a second sprocket body 34 and a plurality of second sprocket teeth 36. In this embodiment, the first number of teeth is 40. The second number of teeth is 54. The difference in the number of teeth is 14. However, the first total number of teeth is not limited to 40. The second total number of teeth is not limited to 54. The difference in the number of teeth is not limited to 14.

[0120] At least one tooth 36A of the plurality of second sprocket teeth 36 includes a low chain interference groove 240. The low chain interference groove 240 is disposed on the second axially inward surface 26B. At least two teeth 36A of the plurality of second sprocket teeth 36 each include a low chain interference groove 240 disposed on the second axially inward surface 26B. At least four teeth 36A of the plurality of second sprocket teeth 36 each include a low chain interference groove 240 disposed on the second axially inward surface 26B.

[0121] In this embodiment, each of the four teeth 36A of the plurality of second sprocket teeth 36 includes a low chain interference groove 240 disposed on the second axially inward surface 26B. However, at least one tooth of the plurality of second sprocket teeth 36 may include a low chain interference groove 240 as needed and / or desired.

[0122] The low chain interference grooves 240 have the same structure as each other. However, at least one of the low chain interference grooves 240 may have a structure different from that of the other low chain interference groove 240 as needed and / or desired.

[0123] As shown in Figure 18, the low chain interference groove 240 is configured to reduce interference between at least one tooth 36A of the plurality of second sprocket teeth 36 and the chain C during an upshift operation in which the chain C shifts from the first sprocket 24 to the second sprocket 226. The low chain interference groove 240 is also configured to reduce interference between at least one tooth 36A of the plurality of second sprocket teeth 36 and the outer chain plate C2 (e.g., C2A) of the chain C during the upshift operation.

[0124] As shown in Figure 19, the low chain interference groove 240 has a radially innermost end 240A. The radially innermost end 240A is positioned radially inward from the tooth root circle TC of a plurality of second sprocket teeth 36.

[0125] The innermost radial end 240A of the low chain interference groove 240 is positioned downstream of one of the shift assist protrusions 50 relative to the transmission rotation direction D21 of the front sprocket assembly 216. The shift assist protrusion 50 is positioned radially inward from the low chain interference groove 240 relative to the rotation center axis A1. The low chain interference groove 240 extends from the transmission surface 42 of the second sprocket tooth 36A toward the shift assist protrusion 50. The low chain interference groove 240 is at least partially located downstream of one of the shift assist protrusions 50 in the transmission rotation direction D21, and there are no sprocket teeth between the low chain interference groove 240 and the shift assist protrusion 50 in the transmission rotation direction D21. The low chain interference groove 240 is at least partially located radially outward of the shift assist protrusion 50.

[0126] In this embodiment, the low chain interference groove 240 is completely disposed downstream of the shift assist protrusion 50 in the transmission rotation direction D21, and there are no sprocket teeth between the low chain interference groove 240 and the shift assist protrusion 50 in the transmission rotation direction D21. The low chain interference groove 240 is partially disposed radially outward of the shift assist protrusion 50. However, the low chain interference groove 240 may be disposed completely radially outward of the shift assist protrusion 50 as needed and / or desired.

[0127] The low chain interference groove 240 extends radially inward from the drive surface 42. The low chain interference groove 240 protrudes radially inward from the inclined surface 51. The inclined surface 51 may be omitted from the second sprocket tooth 36A.

[0128] The low chain interference groove 240 extends radially inward relative to the rotation center axis A1 on an elongation direction D52 that is inclined upstream of the transmission rotation direction D21 relative to the front sprocket assembly 216 from the self-drive surface 42. A boundary 260 is provided between the low chain interference groove 240 and the inclined surface 51.

[0129] The radial distance DS12, defined radially from the tooth root circle TC to the innermost radial end 240A relative to the rotation center axis A1, is equal to or greater than 1.0 mm. The radial distance DS12 is equal to or greater than 1.3 mm. The radial distance DS12 is equal to or less than 2.0 mm. In this embodiment, the innermost radial end 240A of the low chain interference groove 240 includes a radial innermost point 240D. The radial innermost point 240D is located in one of the other portions of the radial innermost end 240A closest to the rotation center axis A1. The radial distance DS12 is defined radially from the tooth root circle TC to the innermost radial point 240D relative to the rotation center axis A1. In other words, the radial distance DS12 is defined radially from the tooth root circle TC to the innermost radial point 240D relative to the rotation center axis A1. The radial distance DS12 is equal to 1.4 mm. However, the radial distance DS12 is not limited to the above distances and ranges. The radial distance DS12 may also refer to a first radial distance DS12.

[0130] The low chain interference groove 240 has a maximum lateral length L12 and a maximum radial length L22. The maximum radial length L22 is greater than the maximum lateral length L12. The maximum radial length L22 is defined in the elongation direction D52. When viewed in the axial direction D1, the maximum lateral length L12 is defined in a width direction D62 perpendicular to the elongation direction D52. The elongation direction D52 and the width direction D62 are perpendicular to the axial direction D1. The low chain interference groove 240 includes a protrusion 240B. The protrusion 240B protrudes radially inward from the inclined surface 51. The protrusion 240B includes a radially innermost end 240A. The protrusion 240B has a maximum lateral length L12. The radially innermost end 240A has a maximum lateral length L12.

[0131] When viewed in the axial direction D1, the low chain interference groove 240 has a longitudinal axis A52. When viewed in the axial direction D1, the innermost radial end 240A of the low chain interference groove 240 extends along the longitudinal axis A52. The elongation direction D52 is parallel to the longitudinal axis A52 of the low chain interference groove 240. When viewed in the axial direction D1, the width direction D62 is perpendicular to the longitudinal axis A52. The maximum radial length L22 may be less than or equal to the maximum lateral length L12 as needed and / or desired.

[0132] The low-chain interference groove 240 extends radially inward from the drive surface 42 relative to the rotation center axis A1, having a curvature. The curvature of the low-chain interference groove 240 is configured to correspond to a rotation trajectory 240L of the chain C. The curvature of the low-chain interference groove 240 is configured to correspond to the rotation trajectory 240L of the inner chain plate C1. The rotation trajectory 240L has a rotation center disposed on a reference center RC1 of a reference circle RC, which is disposed on an upstream side of the low-chain interference groove 240. The low-chain interference groove 240 extends radially inward from the drive surface 42 along the rotation trajectory 240L to its innermost radial end 240A.

[0133] As seen in Figures 20 and 21, the low chain interference groove 240 includes a bottom surface 240C. The bottom surface 240C is configured to face the transverse center plane TP of the vehicle body 2A in an installation state in which the front sprocket assembly 216 is mounted to one of the vehicle bodies 2A of the human-powered vehicle 2 (see, for example, Figure 1).

[0134] The low chain interference groove 240 is recessed in the axial direction D1 from the second axial direction inwards from the inner surface 26B toward the central plane CP. The bottom surface 240C is closest to the central plane CP in the axial direction within the low chain interference groove 240.

[0135] As shown in Figure 19, the bottom surface 240C extends along the longitudinal axis A52. The bottom surface 240C has a radially innermost bottom end 240E. A second radial distance DS22 is radially defined relative to the rotation center axis A1 from the tooth root circle TC to the radially innermost bottom end 240E. In other words, the second radial distance DS22 is defined radially relative to the rotation center axis A1 from the tooth root circle TC to the radially innermost bottom end 240E.

[0136] A reference point RT2 is the intersection point of a first reference line RL12 and a second reference line RL22 when viewed in the axial direction D1. The first reference line RL12 is perpendicular to the longitudinal axis A52 and is connected to the reference center RC1 of a reference circle RC located on the upstream side of one of the second sprocket teeth 36A in the transmission rotation direction D21. The second reference line RL22 extends radially outward from the rotation center axis A1, passing through the innermost point 240D of the innermost radial end 240A.

[0137] In this embodiment, when viewed in the axial direction D1, the innermost radial end 240E is positioned at the reference point RT2. However, when viewed in the axial direction D1, the innermost radial end 240E may be offset from the reference point RT2 as needed and / or desired.

[0138] When viewed in the axial direction D1, a first reference angle AG12 is defined between the first reference line RL12 and the third reference line RL3. When viewed in the axial direction D1, a second reference angle AG22 is defined between the third reference line RL3 and the longitudinal axis A52 of the low-chain interference groove 240. In this embodiment, the first reference angle AG12 is equal to 30 degrees. The second reference angle AG22 is equal to 60 degrees. However, the first reference angle AG12 is not limited to the above angles. The second reference angle AG22 is not limited to the above angles.

[0139] The second radial distance DS22 is equal to or greater than 0.5 mm. The second radial distance DS22 is equal to or less than 2.0 mm. In this embodiment, the second radial distance DS22 is in the range of 0.7 mm to 0.9 mm. However, the second radial distance DS22 is not limited to the above distances and ranges.

[0140] The innermost radial end 240A of the low chain interference groove 240 is at least partially located radially within the first reference line RL12. The innermost radial end 240A of the low chain interference groove 240 is located radially within the reference point RT2.

[0141] The innermost radial end 240A of the low chain interference groove 240 is at least partially located radially within the reference point RT2. In this embodiment, the innermost radial end 240A of the low chain interference groove 240 is partially located radially within the first reference line RL12. However, the innermost radial end 240A of the low chain interference groove 240 may, as needed and / or desired, be completely located radially within the first reference line RL12. The innermost radial end 240A of the low chain interference groove 240 may, as needed and / or desired, be completely located radially within the reference point RT2.

[0142] As shown in Figure 22, boundary 260 protrudes in the axial direction D1 to form a low-chain interference groove 240 and an inclined surface 51. Boundary 260 connects the low-chain interference groove 240 and the inclined surface 51. Boundary 260 is pointed. However, boundary 260 may have other shapes.

[0143] The low chain interference groove 240 has the same advantageous effects as the low chain interference groove 40, as discussed in the first embodiment with reference to Figures 9 and 14 to 16. Therefore, the description of the advantageous effects of the low chain interference groove 40 in the first embodiment can be applied to the advantageous effects of the low chain interference groove 240 in the second embodiment. For the sake of brevity, the advantageous effects of the low chain interference groove 240 will not be described in detail here. Revise

[0144] In the first embodiment, as seen in FIG8, an inclined surface 51 is disposed between the transmission surface 42 and the low chain interference groove 40. The low chain interference groove 40 extends radially inward from the inclined surface 51 relative to the rotation center axis A1. However, like the low chain interference groove 240 of the second embodiment, the low chain interference groove 40 may be configured to extend radially inward from the transmission surface 42 relative to the rotation center axis A1 as needed and / or desired. Furthermore, as seen in FIG8, the low chain interference groove 40 extends linearly in the elongation direction D5. However, like the low chain interference groove 240 of the second embodiment, the low chain interference groove 40 may be configured to extend radially inward relative to the rotation center axis A1 to have a curvature as needed and / or desired.

[0145] In the second embodiment, as seen in FIG19, the low chain interference groove 240 extends radially inward from the drive surface 42 relative to the rotation center axis A1. However, as with the low chain interference groove 40 of the first embodiment, the inclined surface 51 may be disposed between the drive surface 42 and the low chain interference groove 240, and the low chain interference groove 240 may be configured to extend radially inward from the inclined surface 51 relative to the rotation center axis A1 as needed and / or desired. Furthermore, as seen in FIG19, the low chain interference groove 240 extends radially inward relative to the rotation center axis A1 with a curvature. However, as with the low chain interference groove 40 of the first embodiment, the low chain interference groove 240 may be configured to extend linearly in the elongation direction D52 as needed and / or desired.

[0146] In this application, as used herein, the term "comprising" and its derivatives are intended to be open-ended terms, specifically referring to the presence of the stated features, elements, components, groups, integers, and / or steps, but not excluding the presence of other unstated features, elements, components, groups, integers, and / or steps. This concept also applies to terms with similar meanings, such as the terms "having," "comprising," and their derivatives.

[0147] The terms “component,” “section,” “part,” “part,” “element,” “body,” and “structure” used in the singular can have a dual meaning of a single component or a plurality of components.

[0148] The ordinal numbers such as "first" and "second" used in this application are merely identifiers and do not have any other meaning, such as a specific order or the like. Furthermore, for example, the term "first element" does not imply the existence of "second element," and the term "second element" does not imply the existence of "first element."

[0149] As used herein, the term "pair" may refer to configurations in which the elements have the same shape or structure as each other, or configurations in which the elements have different shapes or structures from each other.

[0150] The terms "a", "one or more" and "at least one" are used interchangeably in this document.

[0151] As used in this invention, the phrase "at least one of..." means "one or more" of a selection. For example, as used in this invention, if the number of selections is two, the phrase "at least one of..." means "only one single selection" or "all two selections". For another example, as used in this invention, if the number of selections is equal to or greater than three, the phrase "at least one of..." means "only one single selection" or "any combination of equal to or greater than two selections". For example, the phrase "at least one of A and B" covers (1) only A, (2) only B, and (3) both A and B. The phrase "at least one of A, B, and C" covers (1) only A, (2) only B, (3) only C, (4) both A and B, (5) both B and C, (6) both A and C, and (7) all A, B, and C. In other words, in this invention, the phrase "at least one of A and B" does not mean "at least one of A and at least one of B".

[0152] Finally, as used herein, degree terms such as “substantially,” “about,” and “approximately” refer to a reasonable deviation from the modified term that does not significantly alter the final result. All numerical values ​​described in this application may be interpreted as including terms such as “substantially,” “about,” and “approximately.”

[0153] Obviously, many modifications and variations of the present invention can be made in light of the foregoing teachings. Therefore, it should be understood that the present invention can be practiced in ways other than those specifically described herein, within the scope of the appended claims.

[0154] 2: Human-powered transportation 2A: Vehicle Body 10: Transmission System 12: Crank assembly 14: Rear sprocket assembly 16: Front sprocket assembly 18: Crankshaft 20: First crank arm 22: Second crank arm 24: First sprocket 24A: First axial outward surface 24B: First axial inward surface 26: Second sprocket 26A: Second axial outward surface 26B: Second axial inward surface 28: First sprocket body 30: First sprocket tooth 34: Second sprocket body 34A: First annular body 34B: Second Ring Body 34C: First Cover 34D: Second cover 34E: Interior space 36: Second sprocket tooth 36A: Second sprocket tooth 36B: Second sprocket tooth 36W: Axial width 36X: Second sprocket tooth 36Y: Second sprocket tooth 40: Low chain interference groove 40A: Innermost radial end 40B: Prominent Part 40C: Bottom 40D: Innermost radial point 40E: Innermost radial end 40X: Low chain interference groove 40Y: Low chain interference groove 42: Transmission surface 44: Non-transmission surface 45: Tooth cusp 46: First tooth root 47: Second tooth bottom 50: Shift assist pops up 51: Inclined surface 51A: First chamfer end 51B: Second chamfer end 52: Attachment Groove 54: First Additional Groove 56: Second additional groove 60: Boundary 216: Front sprocket assembly 226: Second sprocket 240: Low chain interference groove 240A: Innermost radial end 240B: Protruding part 240C: Bottom 240D: Innermost radial point 240E: Innermost radial bottom end 240L: Rotational trajectory 260: Boundary A1: Rotation center axis A2: Rotation center axis A5: Vertical axis A52: Longitudinal axis AG1: First reference angle AG2: Second reference angle AG12: First reference angle AG22: Second Reference Angle C: Chain C1: Inner Link Plate C1A: Inner Link Plate C2: External Link Plate C2A: External Link Plate C2B: External Link Board CP: Central Plane D1: Axial direction D3: Circumferential direction D5: Direction of elongation D6: Width direction D21: Direction of transmission rotation D22: Reverse rotation direction D41: Upshift Direction D42: Downshift direction D52: Direction of elongation D62: Width direction DM1: Diameter of the first section circle DM2: Diameter of the second section circle DS1: First radial distance DS2: Second radial distance DS12: First radial distance DS22: Second radial distance L1: Maximum horizontal length L2: Maximum radial length L12: Maximum lateral length L22: Maximum radial length PC1: First section of the circle PC2: Second Circle RC: Reference Circle RC1: Reference Center RL1: First Reference Line RL2: Second Reference Line RL3: Third Reference Line RL12: First Reference Line RL22: Second Reference Line RT: Reference point RT2: Reference point TC: Tooth root circle TP: Lateral center plane

Claims

1. A front sprocket assembly for a human-powered vehicle, the front sprocket assembly comprising: A first sprocket has a first axially outward surface and a first axially inward surface disposed on the opposite side of the first axially outward surface in an axial direction relative to a rotational center axis of the front sprocket assembly. The first sprocket includes: a first sprocket body; and a plurality of first sprocket teeth, which extend radially outward from a first outer periphery of the first sprocket body relative to the rotational center axis. The first sprocket has a first pitch circle diameter. A second sprocket has a second axially outward surface and a second axially inward surface disposed on the opposite side of the second axially outward surface in the axial direction. The second axially inward surface is configured to face the first axially outward surface of the first sprocket in the axial direction in an assembled state of the front sprocket assembly. The second sprocket includes: A second sprocket body; and a plurality of second sprocket teeth, which extend radially outward from a second outer periphery of the second sprocket body relative to the rotation center axis, the second sprocket having a second pitch circle diameter larger than the first pitch circle diameter, the second sprocket being adjacent to the first sprocket and there being no other sprocket between the first sprocket and the second sprocket in the axial direction; at least one tooth of the plurality of second sprocket teeth includes a low chain interference groove disposed on the second axially inward surface, the low chain interference groove being configured to reduce interference between the at least one tooth of the plurality of second sprocket teeth and the chain during an upshift operation in which one chain shifts from the first sprocket to the second sprocket; the at least one tooth of the plurality of second sprocket teeth has a drive surface and a non-drive surface disposed on the opposite surface of the drive surface in a circumferential direction relative to the rotation center axis; the low chain interference groove extends radially inward relative to the rotation center axis in an elongation direction inclined from the drive surface toward an upstream side of a drive rotation direction relative to a front sprocket assembly; The low chain interference groove has a radially innermost end located radially inward from the tooth root circle of one of the plurality of second sprocket teeth; the low chain interference groove has a maximum lateral length and a maximum radial length; the maximum radial length is greater than the maximum lateral length; and the maximum radial length is in the elongation direction.

2. The sprocket assembly prior to request item 1, wherein the first sprocket has a first total number of teeth and the second sprocket has a second total number of teeth greater than the first total number of teeth.

3. As in request item 2, the sprocket assembly wherein the difference in the number of teeth between the first total number of teeth and the second total number of teeth is equal to or greater than 9.

4. As in request item 3, the sprocket assembly wherein the difference in the number of teeth between the first total number of teeth and the second total number of teeth is equal to or less than 20.

5. As in request item 2, the sprocket assembly in which the second total number of teeth is equal to or greater than 50.

6. As per request item 1, the sprocket assembly further includes: A shift assist protrusion, at least a portion of which is arranged radially inward relative to the rotation center axis from the non-drive surface of at least one of the plurality of second sprocket teeth.

7. The sprocket assembly prior to claim 6, wherein the innermost radial end of the low chain interference groove is positioned downstream of one of the shift assist protrusions relative to the drive rotation direction of the front sprocket assembly.

8. As requested in item 6, the sprocket assembly wherein the shift assist protrusion is positioned radially inward from the low chain interference groove relative to the rotation center axis.

9. The sprocket assembly prior to claim 1, wherein the low chain interference groove extends radially inward from the drive surface with a curvature relative to the axis of rotation.

10. The sprocket assembly prior to claim 9, wherein the curvature of the low chain interference groove is configured to correspond to one of the rotational trajectories of the chain.

11. The sprocket assembly prior to claim 1, wherein the low chain interference groove is configured to reduce interference between at least one tooth of the plurality of second sprocket teeth and one of the outer chain plates of the chain during the upshift operation.

12. The sprocket assembly prior to claim 1, wherein at least two of the plurality of second sprocket teeth each include the low chain interference groove disposed on the second axially inward surface.

13. The sprocket assembly prior to claim 12, wherein at least four of the plurality of second sprocket teeth each include the low chain interference groove disposed on the second axially inward surface.

14. As requested in item 1, the sprocket assembly wherein the radial distance from the tooth root circle to one of the innermost radial ends relative to the axis of rotation is equal to or greater than 1.0 mm.

15. The sprocket assembly prior to request item 14, wherein the radial distance is equal to or greater than 1.3 mm.

16. The sprocket assembly prior to request item 14, wherein the radial distance is equal to or less than 2.0 mm.

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