Front sprocket assembly for a human-powered vehicle

Abstract

This invention discloses a front sprocket assembly 34, comprising a first sprocket 51 and a second sprocket 53. The second sprocket 53 includes a plurality of second sprocket teeth 71. The plurality of second sprocket teeth 71 includes at least one second reference tooth 73 and at least one chain retaining tooth 75. The at least one chain retaining tooth 75 is disposed downstream of one of the at least one second reference tooth 73. The at least one chain retaining tooth 75 has an axially outward chamfer 75b and an axially inward chamfer 75c. The inward chamfer end 75e2 of the axially inward chamfer 75c of the at least one chain retaining tooth 75 is radially outward relative to the rotation center axis X1 from the outward chamfer end 75e1 of the axially outward chamfer 75b of the at least one chain retaining tooth 75.

Description

Technical Field

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

[0002] Cycling is becoming an increasingly popular form of recreation and a mode of transportation. Furthermore, cycling has become a very popular competitive sport for both amateurs and professionals.

[0003] Whether bicycles are used for recreation, transportation, or competition, the bicycle industry is constantly improving various bicycle systems. One bicycle system that has been extensively redesigned is the front sprocket assembly for a human-powered vehicle, especially for achieving smooth shifting. The front sprocket assembly for a human-powered vehicle is used for mounting to the frame of a human-powered vehicle. Summary of the Invention

[0004] 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.

[0005] The 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 rotation center axis.

[0006] 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 one of the first sprocket bodies in a radial direction relative to one of the rotation center axes. The plurality of first sprocket teeth includes at least one first reference tooth.

[0007] The 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.

[0008] The second axially inner surface is configured to face the first axially outer surface of the first sprocket in the axial direction in one of the assembled states of the front sprocket assembly.

[0009] 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 in the radial direction. The plurality of second sprocket teeth includes at least one second reference tooth and at least one chain retaining tooth.

[0010] The first sprocket has a first pitch circle diameter. The second sprocket has a second pitch circle diameter that is 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.

[0011] The at least one first reference tooth is configured to engage with the chain first during a downshift operation in which one of the chains shifts from the second sprocket toward the first sprocket, such that a non-drive surface of the at least one first reference tooth contacts a chain roller of the chain. The at least one second reference tooth is configured to disengage first from an inner chain plate of the chain during the downshift operation.

[0012] The at least one chain retaining tooth is configured to be positioned downstream of one of the at least one second reference teeth relative to the transmission rotation direction of one of the front sprocket assemblies, such that the at least one chain retaining tooth is derived from an even number of teeth of one of the at least one second reference teeth.

[0013] The at least one chain retaining tooth has a tooth tip, an axially outward chamfer disposed on one of the second axially outward surfaces, and an axially inward chamfer disposed on one of the second axially inward surfaces.

[0014] The axial outward chamfer extends radially inward from the tooth tip relative to the rotation center axis to an outward chamfer end. The axial inward chamfer extends radially inward from the tooth tip relative to the rotation center axis to an inward chamfer end. The inward chamfer end is positioned radially outward from the outward chamfer end relative to the rotation center axis.

[0015] Regarding the sprocket assembly prior to the first configuration, the at least one first reference tooth first engages with the chain during the downshift operation, such that the non-drive surface of the at least one first reference tooth contacts the chain roller of the chain. During the downshift operation, the at least one second reference tooth first disengages from the inner chain plate of the chain.

[0016] The at least one chain retaining tooth is positioned downstream of the at least one second reference tooth relative to the drive rotation direction of the front sprocket assembly. The at least one chain retaining tooth is derived from the even-numbered tooth of the at least one second reference tooth.

[0017] The inward chamfer end of the axial inward chamfer of the at least one chain retaining tooth is arranged radially outward relative to the rotation center axis from the outward chamfer end of the axial outward chamfer of the at least one chain retaining tooth.

[0018] By configuring the front sprocket assembly as described above, when the chain moves from the second sprocket to the first sprocket, at least one chain retaining tooth of the second sprocket can securely hold the chain. In this way, the front sprocket assembly can achieve a smooth shifting operation, allowing the chain to move from the second sprocket to the first sprocket.

[0019] According to a second embodiment of the invention, the sprocket assembly prior to the first embodiment is configured such that a first radial distance is radially defined relative to the rotation center axis from the inward chamfer end to the outward chamfer end. This first radial distance is equal to or greater than 1.0 mm. With respect to the sprocket assembly prior to the second embodiment, when the chain moves from the second sprocket to the first sprocket, at least one chain retaining tooth of the second sprocket can securely retain the chain by setting the first radial distance through such a configuration.

[0020] According to a third embodiment of the invention, the sprocket assembly prior to the second embodiment is configured such that the first radial distance is equal to or less than 2.0 mm. With respect to the sprocket assembly prior to the third embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth is able to securely engage with the chain by setting the first radial distance through such a configuration when the chain moves from the second sprocket to the first sprocket.

[0021] According to a fourth embodiment of the present invention, the sprocket assembly prior to any of the first to third embodiments is configured such that the second sprocket has a tooth root circle. A second radial distance is defined radially from the tooth root circle to the inwardly chamfered end relative to the rotation center axis. The second radial distance is equal to or greater than 3.0 mm. With respect to the sprocket assembly prior to the fourth embodiment, when the chain moves from the second sprocket to the first sprocket, at least one chain retaining tooth of the second sprocket can securely retain the chain by setting the second radial distance through such a configuration.

[0022] According to a fifth embodiment of the present invention, the sprocket assembly prior to the fourth embodiment is configured such that the second radial distance is equal to or less than 5.0 mm. With respect to the sprocket assembly prior to the fifth embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth can be securely engaged with the chain by setting the second radial distance through such a configuration.

[0023] According to a sixth embodiment of the present invention, the sprocket assembly prior to any one of the first to fifth embodiments is configured such that at least one chain retaining tooth is configured to retain one inner chain plate of the chain. With respect to the sprocket assembly prior to the sixth embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth of the second sprocket can be configured in such a way to securely retain the chain.

[0024] According to a seventh embodiment of the present invention, the sprocket assembly prior to any one of the first to sixth embodiments is configured such that the at least one chain retaining tooth is derived from one of the second, fourth, and sixth teeth of the at least one second reference tooth. With respect to the sprocket assembly prior to the seventh embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth of the second sprocket can securely retain the chain by configuring the at least one chain retaining tooth in such a configuration.

[0025] According to an eighth embodiment of the present invention, the sprocket assembly prior to the seventh embodiment is configured such that the at least one chain retaining tooth is derived from the fourth tooth of one of the at least one second reference teeth. With respect to the sprocket assembly prior to the eighth embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth of the second sprocket can securely retain the chain by configuring the at least one chain retaining tooth in such a configuration.

[0026] According to a ninth embodiment of the present invention, the sprocket assembly prior to any one of the first to sixth embodiments is configured such that the at least one chain retaining tooth comprises a plurality of chain retaining teeth. The plurality of chain retaining teeth comprises at least two teeth from a second tooth, a fourth tooth, and a sixth tooth of the at least one second reference tooth. With respect to the sprocket assembly prior to the ninth embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth of the second sprocket can securely retain the chain by configuring the at least one chain retaining tooth in such a configuration.

[0027] According to a tenth embodiment of the present invention, the sprocket assembly prior to any one of the first to sixth embodiments is configured such that the at least one chain retaining tooth includes at least three chain retaining teeth. The at least three chain retaining teeth respectively include at least one second tooth, a fourth tooth, and a sixth tooth from the at least one second reference tooth. With respect to the sprocket assembly prior to the tenth embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth of the second sprocket can securely retain the chain by configuring the at least one chain retaining tooth in such a configuration.

[0028] According to an eleventh embodiment of the present invention, the sprocket assembly according to any one of the first to tenth embodiments is configured such that the first sprocket has a first total number of teeth. The second sprocket has a second total number of teeth greater than the first total number of teeth. With respect to the sprocket assembly according to the eleventh embodiment, when the chain moves from the second sprocket to the first sprocket, at least one chain retaining tooth of the second sprocket can securely retain the chain by configuring the first sprocket and the second sprocket in such a configuration. Thus, the sprocket assembly enables a smooth shifting operation of moving the chain from the second sprocket to the first sprocket.

[0029] According to a twelfth embodiment of the present invention, the sprocket assembly prior to the eleventh embodiment 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. With respect to the sprocket assembly prior to the twelfth embodiment, the sprocket assembly can achieve a gear shifting system with a wide range by configuring the tooth difference in such a configuration.

[0030] According to a thirteenth embodiment of the present invention, the sprocket assembly prior to the eleventh or twelfth embodiment 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. With respect to the sprocket assembly prior to the thirteenth embodiment, the sprocket assembly can achieve shifting of the chain from the first sprocket to one of the smooth gears of the second sprocket by configuring the difference in the number of teeth in such a configuration.

[0031] According to a fourteenth embodiment of the present invention, the front sprocket assembly according to any one of the eleventh to thirteenth embodiments is configured such that the second total number of teeth is in the range of 48 to 58. With respect to the front sprocket assembly according to the fourteenth embodiment, the front sprocket assembly can achieve a transmission system with a lightweight and wide range of teeth by configuring the second total number of teeth in such a configuration.

[0032] According to a fifteenth embodiment of the present invention, the front sprocket assembly according to any one of the eleventh to fourteenth embodiments is configured such that the first total number of teeth is in the range of 31 to 44. With respect to the front sprocket assembly according to the fifteenth embodiment, the front sprocket assembly can achieve the light weight and wide range of the transmission system by configuring the second total number of teeth through such a configuration.

[0033] According to a sixteenth embodiment of the present invention, the front sprocket assembly according to any one of the eleventh to fourteenth embodiments is configured such that at least one first reference tooth is configured to first engage with one of the inner chain plates of the chain during a downshifting operation in which the chain shifts from the second sprocket to the first sprocket. With respect to the front sprocket assembly according to the sixteenth embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth of the second sprocket can securely retain the chain by configuring the at least one first reference tooth in such a configuration. Thus, the front sprocket assembly enables a smooth shifting operation in which the chain moves from the second sprocket to the first sprocket.

[0034] According to a seventeenth aspect of the present invention, a front sprocket assembly for a human-powered vehicle includes a first sprocket and a second sprocket.

[0035] The 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 rotation center axis.

[0036] 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 one of the first sprocket bodies in a radial direction relative to one of the rotation center axes. The plurality of first sprocket teeth includes at least one first reference tooth.

[0037] The 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.

[0038] The second axially inner surface is configured to face the axially outer surface of the first sprocket in the axial direction in one of the assembled states of the front sprocket assembly.

[0039] 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 in the radial direction. The plurality of second sprocket teeth includes at least one second reference tooth and at least one chain retaining tooth.

[0040] The first sprocket has a first pitch circle diameter. The second sprocket has a second pitch circle diameter that is 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.

[0041] The at least one first reference tooth is configured to engage with the chain first during a downshift operation in which one of the chains shifts from the second sprocket toward the first sprocket, such that one of the non-drive surfaces of the at least one first reference tooth contacts one of the chain rollers of the chain.

[0042] The at least one second reference tooth is configured to first disengage from one of the inner chain plates during the downshift operation.

[0043] The at least one chain retaining tooth is configured to be positioned downstream of one of the at least one second reference teeth relative to the transmission rotation direction of one of the front sprocket assemblies, such that the at least one chain retaining tooth is derived from an even number of teeth of one of the at least one second reference teeth.

[0044] The at least one chain retaining tooth has a tooth tip, an axially outward chamfer disposed on one of the second axially outward surfaces, and an axially inward chamfer disposed on one of the second axially inward surfaces.

[0045] The axial outward chamfer extends radially inward from the tooth tip relative to the rotation center axis to an outward chamfer end. The axial inward chamfer extends radially inward from the tooth tip relative to the rotation center axis to an inward chamfer end.

[0046] The second sprocket has a tooth root circle. A radial distance relative to the rotation center axis is defined radially from the tooth root circle to the inwardly chamfered end. This radial distance is equal to or greater than 3.0 mm.

[0047] Regarding the sprocket assembly prior to the seventeenth state, the at least one first reference tooth first engages with the chain during the downshift operation, such that the non-drive surface of the at least one first reference tooth contacts the chain roller of the chain. During the downshift operation, the at least one second reference tooth first disengages from the inner chain plate of the chain.

[0048] The at least one chain retaining tooth is positioned downstream of the at least one second reference tooth relative to the drive rotation direction of the front sprocket assembly. The at least one chain retaining tooth is derived from the even-numbered tooth of the at least one second reference tooth.

[0049] The radial distance from the tooth root circle of the second sprocket to the inward chamfer end of the axial inward chamfer of the at least one chain retaining tooth relative to the axis of rotation is equal to or greater than 3.0 mm.

[0050] By configuring the front sprocket assembly as described above, when the chain moves from the second sprocket to the first sprocket, at least one chain retaining tooth of the second sprocket can securely hold the chain. In this way, the front sprocket assembly can achieve a smooth shifting operation, allowing the chain to move from the second sprocket to the first sprocket.

[0051] According to an eighteenth embodiment of the present invention, the sprocket assembly prior to the seventeenth embodiment is configured such that the second radial distance is equal to or less than 5.0 mm. With respect to the sprocket assembly prior to the eighteenth embodiment, when the chain moves from the second sprocket to the first sprocket, the at least one chain retaining tooth is able to securely engage with the chain by setting the second radial distance through such a configuration when the chain moves from the second sprocket to the first sprocket. Simple Explanation of the Diagram

[0052] Selected embodiments of the present invention will now be explained with reference to the drawings that constitute a part of this invention, wherein:

[0053] Figure 1 is a side view of a bicycle according to one embodiment of the present invention;

[0054] Figure 2 is a perspective view of a crank assembly according to an embodiment of the present invention;

[0055] Figure 3 is a front view of a crank assembly according to an embodiment of the present invention;

[0056] Figure 4 is a rear view of a crank assembly according to an embodiment of the present invention;

[0057] Figure 5 is a rear view of a crank assembly according to an embodiment of the present invention;

[0058] Figure 6 is a cross-sectional view of the second sprocket cut by cutting line VI in Figure 4; and

[0059] Figure 7 is a schematic diagram of a first sprocket, a second sprocket, and a bicycle chain viewed from above. Implementation

[0060] Those skilled in the art will understand from this invention that the following description of embodiments of this technology is for illustrative purposes only and is not intended to limit the technology as defined by the appended claims and their equivalents.

[0061] In the following embodiments, if a plurality of components and parts correspond to each other, the corresponding components and corresponding parts are indicated by the same element symbol.

[0062] As shown in Figure 1, a bicycle 1 includes a bicycle chain 3, a bicycle frame 5, a handlebar 7, a front wheel 9 and a rear wheel 11, a gear shifting device 13, a drivetrain 15, and a front fork 17. The bicycle 1 further includes a front wheel hub assembly 18, a rear wheel hub assembly 19, a front derailleur 21, and a rear derailleur 23. The bicycle 1 is an example of a human-powered vehicle.

[0063] The front fork 17 is rotatably mounted to the bicycle frame 5. The handlebar 7 is fixed to the front fork 17. The bicycle front wheel hub assembly 18 is mounted to the front fork 17. The front wheel 9 is rotatably mounted to the front fork 17 via the bicycle front wheel hub assembly 18. A front tire 9a is mounted to the front wheel 9.

[0064] The bicycle rear wheel hub assembly 19 is mounted to the rear portion of the bicycle frame 5. The rear wheel 11 is rotatably mounted to the rear portion of the bicycle frame 5 via the bicycle rear wheel hub assembly 19. A rear tire 11a is mounted to the rear wheel 11.

[0065] The shifting device 13 is mounted to the handlebar 7. The shifting device 13 operates the front derailleur 21 and the rear derailleur 23 of the bicycle via a control cable such as a Bowden cable or a power cable.

[0066] The drivetrain 15 mainly includes a crank assembly 25 and a bicycle rear sprocket assembly 27. The bicycle chain 3 may be included in the drivetrain 15.

[0067] The crank assembly 25 is rotatably supported on the lower part of the bicycle frame 5. The crank assembly 25 includes a crankshaft 31, a pair of crank arms 33 and a front sprocket assembly 34.

[0068] The crankshaft 31 is rotatably supported on the lower part of the bicycle frame 5. The crankshaft 31 is mounted to the pair of crank arms 33. The crankshaft 31 includes a rotational central axis X1.

[0069] The pair of crank arms 33 includes a left crank arm 35 and a right crank arm 37. The left crank arm 35 is mounted to one end of the crankshaft 31. The left crank arm 35 rotates integrally with the crankshaft 31. A pedal is mounted to the left crank arm 35.

[0070] As shown in Figure 2, the right crank arm 37 is mounted to the other end of the crankshaft 31. The right crank arm 37 rotates integrally with the crankshaft 31. The front sprocket assembly 34 is mounted to the right crank arm 37.

[0071] As shown in Figure 3, the right crank arm 37 includes an arm body 39 and a sprocket mounting portion 41. The arm body 39 is mounted to the other end of the crankshaft 31. In this embodiment, the arm body 39 and the sprocket mounting portion 41 are integrally formed. The arm body 39 and the sprocket mounting portion 41 rotate integrally. A pedal is mounted to the arm body 39.

[0072] As shown in Figures 2 and 3, the sprocket mounting portion 41 partially overlaps with the first sprocket 51 in the radial direction relative to the rotation center axis X1. The first sprocket 51 and the second sprocket 53 are mounted to the sprocket mounting portion 41 such that the radially outer end of the sprocket mounting portion 41 is sandwiched between the first sprocket 51 and the second sprocket 53 in one of the axial directions relative to the rotation center axis X1.

[0073] As shown in Figures 2 and 3, the front sprocket assembly 34 includes a plurality of bicycle front sprockets. For example, the front sprocket assembly 34 includes a first sprocket 51 and a second sprocket 53. The first sprocket 51 and the second sprocket 53 engage with the bicycle chain 3. A detailed explanation of the front sprocket assembly 34 will be described below.

[0074] As shown in Figure 1, the bicycle front derailleur 21 is mounted to the bicycle frame 5. For example, the bicycle front derailleur 21 is mounted to one of the seatposts 6 of the bicycle frame 5. The bicycle front derailleur 21 moves the bicycle chain 3 from one of the first sprocket 51 and the second sprocket 53 to the other of the first sprocket 51 and the second sprocket 53 in response to the operation of the shifting device 13.

[0075] The bicycle rear sprocket assembly 27 is mounted to the bicycle rear wheel hub assembly 19. The bicycle rear sprocket assembly 27 includes a plurality of bicycle rear sprockets. The plurality of bicycle rear sprockets engage with the bicycle chain 3.

[0076] The bicycle rear derailleur 23 is mounted to the bicycle frame 5. The bicycle rear derailleur 23 is mounted to one of the rear portions of the bicycle frame 5. The bicycle rear derailleur 23 moves the bicycle chain 3 from one rear sprocket of the bicycle rear sprocket assembly 27 to the other rear sprocket of the bicycle rear sprocket assembly 27 via the shifting device 13.

[0077] As shown in Figures 2 and 3, the sprocket assembly 34 of the bicycle 1 includes a first sprocket 51 and a second sprocket 53.

[0078] As shown in Figure 4, the first sprocket 51 is smaller than the second sprocket 53. For example, the diameter of one of the first sprockets 51 is smaller than the diameter of one of the second sprockets 53.

[0079] Specifically, the first sprocket 51 has a first circular diameter P1. The second sprocket 53 has a second circular diameter P2 that is larger than the first circular diameter P1. The center of the first circular diameter P1 and the center of the second circular diameter P2 are defined on the rotational axis X1.

[0080] The first sprocket 51 has a first total number of teeth. The first total number of teeth is the total number of teeth of one of the plurality of first sprocket teeth 61. The first total number of teeth is in the range of 31 to 44. In this embodiment, the first total number of teeth is 34.

[0081] As shown in Figures 3 and 4, the first sprocket 51 has a first axially outward surface 55 and a first axially inward surface 57 disposed on the opposite side of the first axially outward surface 55 in the axial direction relative to the rotation center axis X1. The first sprocket 51 includes a first sprocket body 59 and a plurality of first sprocket teeth 61.

[0082] As shown in Figure 3, in the assembled state of one of the front sprocket assemblies 34, the first axially outward surface 55 is positioned in the axial direction at a predetermined distance from the second axially inward surface 67 of one of the second sprockets 53 shown in Figure 2.

[0083] The front sprocket assembly 34 is assembled in one of the states where the front sprocket assembly 34 (e.g., the first sprocket 51 and the second sprocket 53) is installed on the right crank arm 37.

[0084] As shown in Figure 3, the first axially outward surface 55 forms one of the axially outward surfaces of the first sprocket body 59 and one of the axially outward surfaces of a plurality of first sprocket teeth 61.

[0085] As shown in Figure 4, in one of the installation states of the front sprocket assembly 34, the first axially inward surface 57 faces the bicycle frame 5 in the axial direction. The installation state of the front sprocket assembly 34 refers to the state in which the front sprocket assembly 34 is installed onto the bicycle frame 5. The first axially inward surface 57 forms one axially inward surface of the first sprocket body 59 and one axially inward surface of a plurality of first sprocket teeth 61.

[0086] As shown in Figures 2 and 3, the first sprocket body 59 is formed in an annular shape. The first sprocket body 59 is mounted to the sprocket mounting portion 41 of the right crank arm 37 by means of a fixing member 46.

[0087] As shown in Figure 4, a plurality of first sprocket teeth 61 engage with the bicycle chain 3. The plurality of first sprocket teeth 61 extend radially outward from a first outer periphery of one of the first sprocket bodies 59 in a radial direction relative to the rotation center axis X1. The plurality of first sprocket teeth 61 includes at least one first reference tooth 62.

[0088] As shown in Figure 4, at least one first reference tooth 62 is configured to first engage with one of the inner chain plates 3a of the bicycle chain 3 during a downshift operation in which the bicycle chain 3 shifts from the second sprocket 53 toward the first sprocket 51. For example, during a downshift operation in which the bicycle chain 3 shifts from the second sprocket 53 toward the first sprocket 51, at least one first reference tooth 62 is initially positioned between one pair of inner chain plates 3a of the bicycle chain 3.

[0089] Specifically, at least one first reference tooth 62 is configured to engage with the bicycle chain 3 first during a downshifting operation in which the bicycle chain 3 shifts from the second sprocket 53 toward the first sprocket 51, such that one of the non-drive surfaces 62a of the at least one first reference tooth 62 contacts the bicycle chain roller 3b of the bicycle chain 3.

[0090] In this embodiment, as shown in FIG5, at least one first reference tooth 62 includes a plurality of first reference teeth 62a to 62j.

[0091] As shown in Figure 2, the second sprocket 53 is adjacent to the first sprocket 51 and there is no other sprocket between the first sprocket 51 and the second sprocket 53 in the axial direction.

[0092] The second sprocket 53 has a second total number of teeth, which is greater than one of the first total number of teeth. The second total number of teeth is one of the total number of teeth of the plurality of second sprocket teeth 71. The second total number of teeth is in the range of 48 to 58. In this embodiment, the second total number of teeth is 50.

[0093] 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. In this embodiment, the difference in the number of teeth is 16.

[0094] As shown in Figures 3 and 4, the second sprocket 53 has a second axially outward surface 65 and a second axially inward surface 67 disposed on the opposite side of the second axially outward surface 65 in the axial direction. The second sprocket 53 includes a second sprocket body 69 and a plurality of second sprocket teeth 71.

[0095] As shown in Figure 3, the second axially outward surface 65 forms one of the axially outward surfaces of the second sprocket body 69 and one of the axially outward surfaces of a plurality of second sprocket teeth 71.

[0096] As shown in Figure 4, the second axially inward surface 67 is configured to face the first axially outward surface 55 of the first sprocket 51 in the axial direction during the assembly of the front sprocket assembly 34.

[0097] The second axially inner surface 67 forms one of the axially inner surfaces of the second sprocket body 69 and one of the axially inner surfaces of a plurality of second sprocket teeth 71.

[0098] As shown in Figures 2 and 3, the second sprocket body 69 is formed in an annular shape. The second sprocket body 69 is mounted to the sprocket mounting portion 41 of the right crank arm 37.

[0099] As shown in Figure 4, a plurality of second sprocket teeth 71 engage with the bicycle chain 3. The plurality of second sprocket teeth 71 extend radially outward from the second outer periphery of one of the second sprocket bodies 69. The plurality of second sprocket teeth 71 includes at least one second reference tooth 73 and at least one chain retaining tooth 75.

[0100] As shown in Figure 4, at least one second reference tooth 73 is configured to first disengage from the inner chain plate 3a of the bicycle chain 3 during downshifting. For example, during downshifting, at least one second reference tooth 73 first moves away from the pair of inner chain plates 3a of the bicycle chain 3.

[0101] In this embodiment, as shown in FIG5, at least one second reference tooth 73 comprises a plurality of second reference teeth 73a to 73j. The plurality of second reference teeth 73a to 73j respectively correspond to a plurality of first reference teeth 62a to 62j. At least one chain retaining tooth 75 (for example) comprises a set of a plurality of chain retaining teeth 75h1, 75h2, 75h3 shown in FIG4 and is prepared for each of the plurality of second reference teeth 73a to 73j shown in FIG5.

[0102] As shown in Figure 4, at least one chain retaining tooth 75 is configured to retain one of the inner chain plates 3a of the bicycle chain 3. For example, at least one chain retaining tooth 75 is configured to retain the pair of inner chain plates 3a of the bicycle chain 3 during downshifting operations.

[0103] At least one chain retaining tooth 75 is configured to be positioned downstream of at least one of the second reference teeth 73 relative to the drive rotation direction R1 of one of the front sprocket assemblies 34, such that at least one chain retaining tooth 75 is derived from an even number of teeth of at least one of the second reference teeth 73.

[0104] The rotation direction R1 is one of the rotation directions of the front sprocket assembly 34 to move the bicycle 1 forward. The center of the rotation direction R1 is defined on the rotation axis X1.

[0105] For example, at least one chain retaining tooth 75 is one of the second tooth 75h1, a fourth tooth 75h2 and a sixth tooth 75h3 of at least one second reference tooth 73.

[0106] Preferably, at least one chain retaining tooth 75 is a fourth tooth 75h2 derived from at least one second reference tooth 73.

[0107] Specifically, if at least one chain retaining tooth 75 is selected from the second tooth 75h1, the fourth tooth 75h2 and the sixth tooth 75h3, then at least one chain retaining tooth 75 is preferably the fourth tooth 75h2 from at least one second reference tooth 73.

[0108] Preferably, at least one chain retaining tooth 75 includes a plurality of chain retaining teeth. The plurality of chain retaining teeth includes at least two teeth from at least one second reference tooth 73, namely a second tooth 75h1, a fourth tooth 75h2, and a sixth tooth 75h3.

[0109] More preferably, at least one chain retaining tooth 75 includes at least three chain retaining teeth 75. The at least three chain retaining teeth 75 respectively include at least a second tooth 75h1, a fourth tooth 75h2 and a sixth tooth 75h3 from at least one second reference tooth 73.

[0110] As shown in Figure 6, at least one chain retaining tooth 75 has a tooth tip 75a, an axially outward chamfer 75b disposed on a second axially outward surface 65, and an axially inward chamfer 75c disposed on a second axially inward surface 67. For example, each of a plurality of chain retaining teeth 75 includes a tooth tip 75a, an axially outward chamfer 75b, and an axially inward chamfer 75c.

[0111] As shown in Figure 6, the axially outward chamfer 75b extends radially inward from the tooth tip 75a relative to the rotation center axis X1 to an outward chamfer end 75e1. The outward chamfer end 75e1 is a point or line on the second axially outward surface 65 where the axially outward chamfer 75b begins to slope towards the tooth tip 75a. The axially outward chamfer 75b is positioned radially outward from the outward chamfer end 75e1 relative to the rotation center axis X1.

[0112] As shown in Figure 6, the axially inward chamfer 75c extends radially inward from the tooth tip 75a relative to the rotation center axis X1 to an inward chamfer end 75e2. The inward chamfer end 75e2 is a point or line on the second axially inward surface 67 where the axially inward chamfer 75c begins to slope toward the tooth tip 75a.

[0113] The inward chamfered end 75e2 is positioned radially outward from the outward chamfered end 75e1 relative to the rotation center axis X1. Specifically, when the chain retaining tooth 75 is viewed in the circumferential direction relative to the rotation center axis X1, the inward chamfered end 75e2 is positioned radially outward from the outward chamfered end 75e1.

[0114] As shown in Figure 7, if at least one first reference tooth 62 first engages with one of the inner chain plates 3a1 of the bicycle chain 3 during a downshift operation where the bicycle chain 3 shifts from the second sprocket 53 toward the first sprocket 51, then the chain tension between at least one first reference tooth 62 and at least one second reference tooth 73 can be increased.

[0115] When the chain tension between at least one first reference tooth 62 and at least one second reference tooth 73 increases during downshifting, the other inner chain plates 3a2 of the bicycle chain 3 tend to come closer to the second axially inward surface 67 of the second sprocket tooth 71.

[0116] Specifically, when the chain tension between at least one first reference tooth 62 and at least one second reference tooth 73 increases during downshifting, the inner chain plate 3a2 of the bicycle chain 3 tends to press against the second axially inward surface 67 of the second tooth 75h1, the fourth tooth 75h2 and the sixth tooth 75h3 of the at least one second reference tooth 73.

[0117] Specifically, when the chain tension between at least one first reference tooth 62 and at least one second reference tooth 73 increases during downshifting, the inner chain plate 3a2 of the bicycle chain 3 firmly presses against the second axially inward surface 67 of the fourth tooth 75h2.

[0118] According to the present invention, as shown in FIG6, sufficient chain contact area is obtained on one of the second axially inward surfaces 67 of at least one chain retaining tooth 75, because at least one chain retaining tooth 75 is designed such that the inwardly chamfered end 75e2 is arranged radially outward from the outwardly chamfered end 75e1 relative to the rotation center axis X1. Therefore, at least one chain retaining tooth 75 effectively retains the inner chain plate 3a of the bicycle chain 3 until the downshift operation is completed.

[0119] A first radial distance D1 is defined radially from the inward chamfer end 75e2 to the outward chamfer end 75e1 relative to the rotation center axis X1. Specifically, the first radial distance D1 is defined as a distance between the inward chamfer end 75e2 and the outward chamfer end 75e1 in the radial direction relative to the rotation center axis X1.

[0120] The first radial distance D1 is equal to or greater than 1.0 mm. The first radial distance D1 is equal to or less than 2.0 mm. In this embodiment, for example, the first radial distance D1 is 1.5 mm.

[0121] As shown in Figure 4, the second sprocket 53 has a tooth root circle T1. As shown in Figure 5, a second radial distance D2 is defined radially from the tooth root circle T1 to the inward chamfer end 75e2 relative to the rotation center axis X1. Specifically, the second radial distance D2 is defined as the distance between the tooth root circle T1 and the inward chamfer end 75e2 in the radial direction relative to the rotation center axis X1.

[0122] The second radial distance D2 is equal to or greater than 3.0 mm. The second radial distance D2 is equal to or less than 5.0 mm. In this embodiment, for example, the second radial distance D2 is 3.9 mm.

[0123] 1: Bicycle 3: Bicycle chain 3a: Inner Link Plate 3a1: Inner Link Plate 3a2: Inner Link Plate 3b: Bicycle chain rollers 5: Bicycle frame 6: Seat tube 7: Handle 9: Front wheel 9a: Front tire 11: Rear wheel 11a: Rear tire 13: Gear shifting device 15: Transmission System 17: Front fork 18: Bicycle front wheel hub assembly 19: Bicycle rear wheel hub assembly 21: Bicycle front derailleur 23: Rear derailleur of a bicycle 25: Crank assembly 27: Bicycle rear sprocket assembly 31: Crankshaft 33: Crank arm 34: Front sprocket assembly 35: Left crank arm 37: Right crank arm 39: Arm Body 41: Sprocket Mounting Section 46: Fixed components 51: First sprocket 53: Second sprocket 55: First axial outward surface 57: First axial inward surface 59: First sprocket body 61: First sprocket tooth 62: First reference tooth 62a: Non-transmission surface 62a to 62j: First reference tooth 65: Second axial outward surface 67: Second axial inward surface 69: Second sprocket body 71: Second sprocket tooth 73: Second Reference Tooth 73a to 73j: Second reference teeth 75: Chain retaining teeth 75a: Tooth cusp 75b: Axial outward chamfer 75c: Axial inward chamfer 75e1: Outward chamfer end 75e2: Inward chamfer end 75h1: Chain retaining teeth 75h2: Chain retaining teeth 75h3: Chain retaining teeth D1: First radial distance D2: Second radial distance P1: Diameter of the first section circle P2: Diameter of the second circle R1: Direction of rotation of the transmission T1: Tooth root circle X1: Rotation center axis

Claims

1. A front sprocket assembly (34) for a human-powered vehicle, the front sprocket assembly (34) comprising: A first sprocket (51) having a first axially outward surface (55) and a first axially inward surface (57) disposed on the opposite side of the first axially outward surface (55) in an axial direction relative to a rotational central axis (X1), the first sprocket (51) comprising: A first sprocket body (59); and a plurality of first sprocket teeth (61), which extend radially outward from a first outer periphery of the first sprocket body (59) in a radial direction relative to the rotation center axis (X1) and include at least one first reference tooth (62); and a second sprocket (53) having a second axially outward surface (65) and a second axially inward surface (67) disposed on the opposite side of the second axially outward surface (65) in the axial direction, the second axially inward surface (67) being configured to face the first axially outward surface (55) of the first sprocket (51) in the axial direction in an assembled state of the front sprocket assembly (34), the second sprocket (53) comprising: A second sprocket body (69); and a plurality of second sprocket teeth (71), which extend radially outward from a second outer periphery of the second sprocket body (69) in the radial direction and include at least one second reference tooth (73) and at least one chain retaining tooth (75); the first sprocket (51) has a first pitch circle diameter (P1); the second sprocket (53) has a second pitch circle diameter (P2) larger than the first pitch circle diameter (P1), the second sprocket (53) is adjacent to the first sprocket (51) and there is no other sprocket between the first sprocket (51) and the second sprocket (53) in the axial direction; The at least one first reference tooth (62) is configured to engage with the chain (3) first during a downshift operation in which one of the chains (3) shifts from the second sprocket (53) toward the first sprocket (51), such that a non-drive surface (62a) of the at least one first reference tooth (62) contacts a chain roller of the chain (3); the at least one second reference tooth (73) is configured to disengage from an inner chain plate (3a) of the chain (3) first during the downshift operation; the at least one chain retaining tooth (75) is configured to be positioned downstream of the at least one second reference tooth (73) relative to a drive rotation direction (R1) of the front sprocket assembly (34), such that the at least one chain retaining tooth (75) is an even number of teeth of the at least one second reference tooth (73); The at least one chain retaining tooth (75) has a tooth tip (75a), an axially outward chamfer (75b) disposed on the second axially outward surface (65), and an axially inward chamfer (75c) disposed on the second axially inward surface (67); the axially outward chamfer (75b) extends radially inward from the tooth tip (75a) relative to the rotation center axis (X1) to an outward chamfer end (75e1);The axial inward chamfer (75c) extends radially inward from the tooth tip (75a) relative to the rotation center axis (X1) to an inward chamfer end (75e2); and the inward chamfer end (75e2) is positioned radially outward from the outward chamfer end (75e1) relative to the rotation center axis (X1).

2. The sprocket assembly (34) prior to claim 1, wherein a first radial distance (D1) is radially defined relative to the rotation center axis (X1) from the inward chamfer end (75e2) to the outward chamfer end (75e1); and the first radial distance (D1) is equal to or greater than 1.0 mm.

3. The sprocket assembly (34) prior to request item 2, wherein the first radial distance (D1) is equal to or less than 2.0 mm.

4. The sprocket assembly (34) prior to any of claims 1 to 3, wherein the second sprocket (53) has a tooth root circle (T1); a second radial distance (D2) is radially defined relative to the rotation center axis (X1) from the tooth root circle (T1) to the inward chamfer end (75e2); and the second radial distance (D2) is equal to or greater than 3.0 mm.

5. The sprocket assembly (34) prior to request item 4, wherein the second radial distance (D2) is equal to or less than 5.0 mm.

6. The sprocket assembly (34) prior to any of claims 1 to 3, wherein the at least one chain retaining tooth (75) is configured to retain one of the inner chain plates (3a) of the chain (3).

7. The sprocket assembly (34) prior to any of claims 1 to 3, wherein the at least one chain retaining tooth (75) is one of the second tooth (75h1), the fourth tooth (75h2) and the sixth tooth (75h3) of the at least one second reference tooth (73).

8. The sprocket assembly (34) prior to claim 7, wherein the at least one chain retaining tooth (75) is a fourth tooth (75h2) of one of the at least one second reference teeth (73).

9. The sprocket assembly (34) prior to any one of claims 1 to 3, wherein the at least one chain retaining tooth (75) comprises a plurality of chain retaining teeth (75); and the plurality of chain retaining teeth (75) comprises at least two teeth from a second tooth (75h1), a fourth tooth (75h2) and a sixth tooth (75h3) of the at least one second reference tooth (73).

10. The sprocket assembly (34) prior to any one of claims 1 to 3, wherein the at least one chain retaining tooth (75) comprises at least three chain retaining teeth (75); and the at least three chain retaining teeth (75) each comprise at least one second tooth (75h1), one fourth tooth (75h2) and one sixth tooth (75h3) from the at least one second reference tooth (73).

11. The sprocket assembly (34) preceding any of claims 1 to 3, wherein the first sprocket (51) has a first total number of teeth; and the second sprocket (53) has a second total number of teeth greater than the first total number of teeth.

12. The sprocket assembly (34) prior to request item 11, 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.

13. The sprocket assembly (34) prior to request item 11, 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.

14. The sprocket assembly (34) prior to request item 11, wherein the second total number of teeth is in the range of 48 to 58.

15. The sprocket assembly (34) prior to request item 11, wherein the first total number of teeth is in the range of 31 to 44.

16. The sprocket assembly (34) prior to claim 11, wherein the at least one first reference tooth (62) is configured to first engage with one of the inner chain plates (3a) of the chain (3) during the downshifting operation in which the chain (3) shifts from the second sprocket (53) toward the first sprocket (51).

17. A front sprocket assembly (34) for a human-powered vehicle, the front sprocket assembly (34) comprising: A first sprocket (51) having a first axially outward surface (55) and a first axially inward surface (57) disposed on the opposite side of the first axially outward surface (55) in an axial direction relative to a rotational central axis (X1), the first sprocket (51) comprising: A first sprocket body (59); and a plurality of first sprocket teeth (61), which extend radially outward from a first outer periphery of the first sprocket body (59) in a radial direction relative to the rotation center axis (X1) and include at least one first reference tooth (62); and a second sprocket (53) having a second axially outward surface (65) and a second axially inward surface (67) disposed on the opposite side of the second axially outward surface (65) in the axial direction, the second axially inward surface (67) being configured to face the first axially outward surface (55) of the first sprocket (51) in the axial direction in an assembled state of the front sprocket assembly (34), the second sprocket (53) comprising: A second sprocket body (69); and a plurality of second sprocket teeth (71), which extend radially outward from a second outer periphery of the second sprocket body (69) in the radial direction and include at least one second reference tooth (73) and at least one chain retaining tooth (75); the first sprocket (51) has a first pitch circle diameter (P1); the second sprocket (53) has a second pitch circle diameter (P2) larger than the first pitch circle diameter (P1), the second sprocket (53) is adjacent to the first sprocket (51) and there is no other sprocket between the first sprocket (51) and the second sprocket (53) in the axial direction; the at least one first reference tooth (62) is configured to first engage with the chain (3) in a downshifting operation in which one chain (3) shifts from the second sprocket (53) toward the first sprocket (51), such that a non-drive surface of the at least one first reference tooth (62) contacts a chain roller of the chain (3); The at least one second reference tooth (73) is configured to first disengage from one of the inner chain plates (3a) of the chain (3) during the downshift operation; the at least one chain retaining tooth (75) is configured to be positioned downstream of one of the at least one second reference tooth (73) relative to one of the drive rotation directions (R1) of the front sprocket assembly (34), such that the at least one chain retaining tooth (75) is an even number of teeth of one of the at least one second reference tooth (73); the at least one chain retaining tooth (75) has a tooth tip (75a), an axially outward chamfer (75b) disposed to one of the second axially outward surfaces (65) and an axially inward chamfer (75c) disposed to one of the second axially inward surfaces (67); the axially outward chamfer (75b) extends radially inward from the tooth tip (75a) relative to the rotation center axis (X1) to an outward chamfer end (75e1);The axial inward chamfer (75c) extends radially inward from the tooth tip (75a) to an inward chamfer end (75e2) relative to the rotation center axis (X1); the second sprocket (53) has a tooth root circle (T1); a second radial distance is defined radially from the tooth root circle (T1) to the inward chamfer end (75e2) relative to the rotation center axis (X1); and the second radial distance is equal to or greater than 3.0 mm.

18. The sprocket assembly (34) prior to request item 17, wherein the second radial distance (D2) is equal to or less than 5.0 mm.

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