Bicycle sprocket

Abstract

A first sprocket is capable of engaging a chain. The first sprocket has a first sprocket main body, a plurality of teeth arranged along a circumferential direction on the radially outer side of the first sprocket main body, and at least one shifting portion. The teeth include at least one first tooth having a first maximum axial width and at least one second tooth having a second maximum axial width. The first maximum axial width is greater than the second maximum axial width. The first tooth is configured to be capable of engaging an outer link plate of the chain. The second tooth is configured to be capable of engaging an inner link plate of the chain.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 61 / 824,568, filed May 17, 2013, and U.S. Non-Provisional Application No. 14 / 053,630, filed October 15, 2013. The entire disclosure of U.S. Provisional Application No. 61 / 824,568 and U.S. Non-Provisional Application No. 14 / 053,630 are hereby incorporated by reference. BackgroundField of the invention

[0002] This invention relates essentially to a bicycle sprocket. Background information

[0003] Bicycle sprockets are attached to both a crank assembly located in the center of a bicycle and a rear wheel. The rotation of the crank assembly is transmitted to the rear wheel through a chain that meshes with the sprockets. In a bicycle chain, an inner connecting plate and an outer connecting plate are alternately connected. Therefore, the clearances between the outer connecting plate and the teeth of the sprockets are larger than the clearances between the inner connecting plate and the teeth of the sprockets when the teeth of the sprockets have the same thickness.In view of this, conventional sprockets (for example, the description of US Pat. No. 4,174,642 A) are known in which the axial width of the teeth (the tooth thickness) with respect to the rotational center axis of the sprocket is designed such that the axial width of the teeth meshing with the outer connecting plate is larger than the axial width of the teeth meshing with the inner connecting plate. A conventional sprocket has teeth that taper diametrically outward. Therefore, it is unlikely that the clearances between the sprocket and the chain will decrease and that the chain will disengage from the sprocket teeth.

[0004] A bicycle crank assembly, not claimed, comprises a crank arm and a chainwheel. Among such bicycle crank assemblies, a known design is one in which a plurality of chainwheels, each having a different number of teeth, are mounted on the crank arm. The chainwheels are provided for gear shifting, and the chain is moved by a derailleur between the two chainwheels, each having a different number of teeth, to perform the gear shifting operation.

[0005] For example, German document DE 10 2012 023 819 A1 teaches a single chainring for a bicycle front crank assembly for engaging a drive chain. The single chainring comprises a plurality of teeth formed around a circumference of the chainring, wherein the plurality of teeth has an even number of teeth. The plurality of teeth comprises a first tooth group and a second tooth group arranged alternately between the first tooth group. The first tooth group and the second tooth group are equal in number. Each first and second tooth group comprises an outer side and an inner side opposite the outer side, and each tooth of the first tooth group comprises at least one projection on the outer side, and each tooth of the second tooth group is formed without a first projection on the outer side and the inner side.

[0006] The German document DE 10 2008 060 501 A1 teaches a multiple sprocket assembly for a bicycle having a larger diameter sprocket and a smaller diameter sprocket, wherein the larger diameter sprocket has at least one auxiliary guide portion for facilitating the transfer of a bicycle chain from the smaller diameter sprocket to the larger diameter sprocket.

[0007] American document US 5 085 621 A discloses a multi-stage sprocket assembly for a bicycle, the assembly comprising a larger sprocket and a smaller sprocket mounted adjacent to each other; the larger sprocket having a concave portion defined in a side surface thereof opposite to the smaller sprocket, the concave portion being arranged along a path of travel of an intermediate plate portion of a drive chain shifting from the smaller sprocket to the larger sprocket, the intermediate plate portion being positioned forward in a drive rotational direction of the sprocket assembly relative to an engagement guide plate portion of the chain which first engages a tooth of the larger sprocket.

[0008] Japanese document JP S56-42 489 U discloses a sprocket for bicycles, in particular a sprocket body and a plurality of circumferentially provided tooth bodies on the outer circumference of the sprocket body, for use in a bicycle crank or a rear wheel hub for bicycles.

[0009] The German document DE 10 2012 013 645 A1 discloses a chain guide roller for a rear derailleur of a derailleur system of a bicycle for guiding a chain, comprising an annular roller body with a central opening for rotatable mounting about a rotational axis of the chain guide roller; a toothing with a plurality of radially projecting teeth arranged on an outer circumferential surface of the roller body, wherein a tooth gap is arranged between each two circumferentially adjacent teeth, wherein individual teeth in the region of a root circle of the toothing have a predetermined tooth width matched to the chain.In order to improve the guiding properties, it is provided that the chain guide roller has at least one guiding section with a greater width than the tooth width of at least one of the adjacent teeth on at least some of the tooth gaps in the area close to a tooth gap base and / or on at least some of the teeth.

[0010] The American document US 4 174 642 A discloses a chain drive including a sprocket rotatable in a plane and having an even number of wide and narrow tapered teeth, and a flexible chain comprising successive links with alternating wide and narrow tooth engagement link openings, the tooth width and the width of the link openings being measured in a direction transverse to the plane of sprocket rotation. Summary

[0011] A sprocket having teeth with different axial widths with respect to the rotational center axis of the sprocket is designed to prevent the chain from easily disengaging or jumping from the sprocket teeth. Therefore, when a sprocket having teeth with different axial widths is used in a conventional crankset to move a chain between two sprockets, the shifting operation becomes complicated.

[0012] An object of the present invention is to make the switching operation in a chain wheel having teeth with different axial widths easier or smoother.

[0013] This object is achieved by the subject matter of independent claims 1 and 3. Preferred embodiments are defined in the dependent claims

[0014] Other objects, features, aspects and advantages of the present invention will become apparent to one skilled in the art from the following detailed description, which, taken in conjunction with the accompanying drawings, discloses a preferred embodiment of the present invention. Short description of the drawings

[0015] Referring now to the accompanying drawings which form a part of this original disclosure: Fig. 1 is a front view of a bicycle crank assembly according to the first embodiment; Fig. 2 is a front perspective view of the first sprocket; Fig. 3 is a rear view of the first sprocket; Fig. 4 is a partial rear perspective view of the first and second sprockets; Fig. 5 is a partial side view of the first sprocket, the second sprocket or the third sprocket when viewed from the radial outside; Fig. 6 is a front perspective view of the second sprocket; Fig. 7 is a front view of the unclaimed bicycle crank assembly according to the second embodiment; and Fig. 8 is a surface view of the third sprocket. Detailed description of the embodiments

[0016] Selected embodiments will now be explained with reference to the drawings.

[0017] In Fig. 1, a bicycle crank assembly (hereinafter referred to as a crank assembly) 10 according to the first embodiment of the present invention includes a crank arm 12, a first sprocket 14, and a second sprocket 16, which are bicycle sprockets according to an embodiment of the present invention. The first sprocket 14 and the second sprocket 16 are front sprockets that can mesh with a chain 2. The second sprocket 16 has smaller teeth than the first sprocket 14. The chain 2 has an outer connecting plate 2a and an inner connecting plate 2b. Crank arm

[0018] The crank arm 12 is integrally and rotatably connected to a crank shaft 19. The crank arm 12 includes a sprocket attachment portion 20 and an arm portion 22, which is provided either integrally or separately from the sprocket attachment portion 20.

[0019] The sprocket attachment part 20 includes a plurality (e.g., four) of sprocket attachment arms 24 arranged at intervals in the circumferential direction. The circumferential intervals of the sprocket attachment arms 24 may be equal intervals but may also be unequal intervals. In the first embodiment, the sprocket attachment arms 24 are arranged at equal intervals and inclined with respect to the radial direction as the rotational direction R of the crank arm 12 progresses. The sprocket attachment arms 24 include first attachment parts 24a for attaching the first sprocket 14. The first attachment parts 24a are formed at the distal ends of the sprocket attachment arms 24. The sprocket attachment arms 24 include second attachment parts 24b for attaching the second sprocket 16. The second attachment parts 24b are formed further inward in the radial direction than the first attachment parts 24a.The first attachment parts 24a and the second attachment parts 24b are formed, for example, from through holes or screw holes or the like through which nothing else passes. In the first embodiment, the first attachment parts 24a are formed from through holes, and the second attachment parts 24b are formed from screw holes through which nothing else passes. The first sprocket 14 is fixed to the first attachment parts 24a by first fixing bolts 26. The second sprocket 16 is fixed to the second attachment parts 24b by second fixing bolts 28 (see ). Fig. 4) fixed.

[0020] The arm portion 22 is formed either integrally with or separately from the sprocket attachment portion 20. In the first embodiment, the arm portion 22 is formed integrally with the sprocket attachment portion 20. The arm portion 22 includes a pedal attachment portion 22a to which a pedal (not shown) can be mounted at the distal end and a connecting hole 22b to which the crankshaft 19 is integrally and rotatably connected at the proximal end. First sprocket

[0021] The first sprocket 14 has a rotational center axis X and comprises a first sprocket main body 30, a plurality (e.g., 30 to 60) of teeth 32 arranged along the circumferential direction on the radially outer side of the first sprocket main body 20, and comprises a first shifting portion 34, as shown in the Fig. 2 to 5. The first sprocket main body 30 is an example of a sprocket main body. The first shifting range 34 is an example of a shifting range. The term "shifting range" in the present invention means either a range where the chain engages with the teeth of a large sprocket during an upshifting operation from a small sprocket to a large sprocket or a range where the chain jumps or separates from the teeth of the large sprocket during a downshifting operation from the large sprocket to the small sprocket. The first sprocket main body 30 and the teeth 32 are made of metal and are integrally formed. The first sprocket main body 30 has a plurality (e.g., four) of first fixing parts 30a that are fixed to the first fixing parts 24a of the sprocket fixing arms 24 and arranged at intervals in the circumferential direction.In the first embodiment, the first fixing parts 30a are configured as through holes and are arranged at positions facing the plurality of first attachment parts 24. The first sprocket 14 is fixed to the sprocket attachment parts 24 by first fixing bolts 26 and a nut member (not shown) threadably engaged with the first fixing bolts 26.

[0022] For example, there are thirty-six of the teeth 32 in the first embodiment. The teeth 32 include at least a first tooth 32a having a first maximum axial width W1 (see Fig. 5) and includes at least one second tooth 32b having a second maximum axial width W2. The first teeth 32a are configured to be capable of engaging with an outer link plate 2a of the chain 2. The second teeth 32b are configured to be capable of engaging with an inner link plate 2b of the chain 2. The first maximum axial width W1 is greater than the second axial width W2. The first maximum axial width W1 of the first teeth 32a is in a range of preferably 2.5 mm or greater and 5.4 mm or smaller, and more preferably in a range of 3.0 mm or greater and 4.5 mm or smaller. Once the first maximum axial width W1 of the first teeth 32a is in such a range, the teeth 32a lightly engage with the outer link plate 2a without engaging with the inner link plate 2b.The second maximum axial width W2 of the second teeth 32b is preferably in a range of 1.5 mm or greater and 2.3 mm or less. When the second maximum axial width W2 of the second teeth 32b is within such a range, the second teeth 32b have the necessary rigidity and easily engage with the inner connecting plate 2b.

[0023] The first teeth 32a are preferably formed in a + (plus) shape when viewed from the radial outside, as shown in the Fig. 2 to 5. The second teeth 32b are preferably formed in a - (minus) shape when viewed from the radial outside. The first teeth 32a and the second teeth 32b are tapered to gradually decrease in axial width toward the radial outside. The first teeth 32a and the second teeth 32b are thereby more easily engaged with the outer connecting plate 2a and the inner connecting plate 2b. Among the plurality of first teeth 32a, in the first embodiment, as shown in Fig. 2, the first teeth 32a1 and the first teeth 32a2, which are / will be described below as shift teeth 32c, are formed in a T-shape when viewed from the radially outer side. The first teeth 32a1 are shift teeth 32c for downshifting with the chain 2 moving from the first sprocket 14 to the second sprocket 16, and the first teeth 32a2 are shift teeth 32c for upshifting with the chain 2 moving from the second sprocket 16 to the first sprocket 14. In the first embodiment, the first maximum axial width of the T-shaped first teeth 32a1, 32a2 is smaller than the first maximum axial width W1 of the +-shaped first teeth 32a and larger than the second maximum axial width W2 of the --shaped second teeth 32b.

[0024] At least some of the first teeth 32a and the second teeth 32b are arranged alternately in the circumferential direction, ie adjacent to each other, and in the first embodiment, all of these teeth are arranged in this manner, as shown in Fig. 2 shown.

[0025] The first shifting portion 34 includes the first shift teeth 32c provided on at least one of the teeth 32. The first shift teeth 32c are an example of shift teeth. In this embodiment, a plurality (e.g., four) of the first shift teeth 32c are provided. The first shift teeth 32c are provided between the connected first teeth 32a1 and the second teeth 32b. The first shifting portion 34 includes a first protrusion 36a and a second protrusion 36b configured to support the chain 2. The first protrusion 36a and the second protrusion 36b are examples of protrusions. Furthermore, the first shifting portion 34 includes a concave portion 38 disposed diametrically further inward than the projections of the teeth 32.

[0026] The first switching teeth 32c have first guide surfaces 32d for guiding the chain 2 in a first surface 14a (see Fig. 2) and a second surface 14b (see Fig. 3) of the first sprocket 14 (as shown in the Fig. 2 and Fig. 3). The first guide surfaces 32d are an example of a guide surface. The first guide surface 14a of the first sprocket 14 is the front surface located on the axial outer side farther from the bicycle frame when the crank assembly 10 is mounted to the bicycle. The second surface 14b is the rear surface located on the axial inner side closer to the bicycle frame. The first guide surfaces 32d are recessed to gradually decrease in thickness toward the sides of the first shift teeth 32c.

[0027] The first projection 36a is provided protrudingly in the second surface 14b of the first sprocket main body 30 to guide the chain 2 to the teeth 32 of the first sprocket 14. The second projection 36b is provided protrudingly in the second surface 14b of the first sprocket main body 30 to guide the chain 2 to the first projection 36a. In the first embodiment, the first projection 36a and the second projection 36b are provided as a pair (a plurality) spaced at intervals in the circumferential direction. The first projection 36a guides the chain to the second teeth 32b, which are indicated by hatching in Fig. 3 and which are upstream of the first projection 36a in the progressive direction of rotation R of the pedal crank assembly 10.

[0028] The distance L1 between the first projection 36a and the second projection 36b is, according to a non-inventive aspect, greater than the longitudinal length L2 of the outer connecting plate 2a and / or the inner connecting plate 2b of the chain 2, as shown in Fig. 1. The distance L1 between the first projection 36a and the second projection 36b can also be either equal to the longitudinal length L2 of the outer connecting plate 2a and / or the inner connecting plate 2b of the chain 2, or smaller than the longitudinal length L2. The first projection 36a and the second projection 36b are securely molded onto the first sprocket 14 by plastic deformation. In the present embodiment, the first projection 36a is larger in diameter than the second projection 36b.

[0029] The concave part 38 is designed to make it easier for the chain 2 to be supported in the first projection 36a to engage with the teeth of the first sprocket 14, as shown in the Fig. 3 and Fig. 4. Therefore, the concave part 38 is arranged close to the first projection 36a and further diametrically (radially) inward than the roots of the teeth 32. In the first embodiment, the concave part is arranged downstream of the first projection 36a in the advancing rotation direction R and is formed in a substantially triangular shape, which extends downstream (clockwise in Fig. 3) is inclined from the diametrically inner side to the outer side. The chain 2 is thereby radially supported on the first projection 36a. Second sprocket

[0030] The second sprocket 16 has a rotational center axis Y and comprises a second sprocket main body 40 and a plurality (e.g., 20 to 40) of teeth 42 arranged along the circumferential direction on the radially outer side of the second sprocket main body 40, as shown in FIGS. Fig. 4 and Fig. 6. The second sprocket main body 40 is an example of a sprocket main body. The second shifting portion 44 is an example of a shifting portion. The second sprocket main body 40 and the teeth 42 are made of metal and formed integrally. The second sprocket main body 40 has a plurality (e.g., four) of second fixing parts 40a, which are fixed to the second attachment parts 24b (see Fig. 1) of the sprocket attachment arms 24 and are arranged at intervals in the circumferential direction. The second fixing parts 40a are formed of through holes and are arranged in positions facing the plurality of second attachment parts 24b. The second sprocket 16 is fixed to the sprocket attachment arms 24 by means of the second fixing bolts 28 (see Fig. 4), which are threadably engaged with the second attachment part 24b.

[0031] The teeth 42 include at least a third tooth 42a having a third maximum axial width W3 (see Fig. 5) and include at least one fourth tooth 42b having a fourth maximum axial width W4. The third teeth 42a are configured to be able to engage with the outer link plate 2a of the chain 2. The fourth teeth 42b are configured to be able to engage with the inner link plate 2b of the chain 2. The third maximum axial width W3 is greater than the fourth maximum axial width W4. The third maximum axial width W3 of the third teeth 42a is preferably in a range of 2.5 mm or greater and 5.4 mm or smaller, and more preferably in a range of 3.0 mm or greater and 4.5 mm or smaller. Once the third maximum axial width W3 of the third teeth 42a is in such a range, the third teeth 42a easily engage with the outer link plate 2a without engaging with the inner link plate 2b.The fourth maximum axial width W4 of the fourth teeth 42b is preferably in a range of 1.5 mm or more and 2.3 mm or less. When the fourth maximum axial width W4 of the fourth teeth 42b is within such a range, the fourth teeth 42b have the necessary rigidity and easily engage with the inner connecting plate 2b.

[0032] The third teeth 42a are formed in a + (plus) shape when viewed from the radial outside, as shown in the Fig. 4, Fig. 5 and Fig. 6. The fourth teeth 42b are formed in a - (minus) shape when viewed from the radially outer side. The third teeth 42a and the fourth teeth 42b are tapered to gradually decrease in axial width toward the radially outer side. Therefore, the third teeth 42a and the fourth teeth 42b mesh more easily with the outer connecting plate 2a and the inner connecting plate 2b.

[0033] At least some of the third teeth 42a and the fourth teeth 42b are arranged alternately in the circumferential direction, ie adjacent to each other, and in the first embodiment, all of these teeth are arranged in this manner, as shown in Fig. 6 shown, arranged.

[0034] The second shifting portion 44 includes the second shift teeth 42c provided on at least one of the teeth 42. The second shift teeth 42c are an example of shift teeth. In the first embodiment, a plurality (e.g., two) of second shift teeth 42c are provided. The second shift teeth 42c are provided at intervals in the circumferential direction. The second shift teeth 42c have a second guide surface 42d for guiding the chain 2 in a first surface 16a (see Fig. 6) and a second surface 16b (see Fig. 4) from the second sprocket 16, as shown in the Fig. 4 and Fig. 6. The second guide surfaces 42d are an example of a guide surface. The first surface 16a of the second sprocket 16 is the front surface located on the axial outer side farther from the bicycle frame when the crank assembly 10 is mounted on the bicycle, and the second surface 16b is the rear surface located on the axial inner side closer to the bicycle frame. The second guide surfaces 42d are recessed to gradually decrease in thickness toward the sides of the second shift teeth 42c.

[0035] In the first embodiment, the second switching portion 44 may include the protrusions or the concave portion of the first switching portion 34. However, the second switching portion may also include only the protrusions or only the concave portion. Switching action in the pedal crank arrangement

[0036] In the unclaimed bicycle crank assembly 10 having such a configuration, the unclaimed bicycle crank assembly 10 is rotated in the progressive rotation direction R when the upshifting operation from the second sprocket 16 to the first sprocket 14 is performed by a front derailleur (not shown). In this state, when the front derailleur moves from a position facing the second sprocket 16 to a position facing the first sprocket 14, the chain 2 disengages from the teeth of the second sprocket 16. Disengaged from the second sprocket, the chain 2 is supported by the second projection 36b and is moved to the radially outer side, and is also supported by the first projection 36a and guided to the teeth 32 of the first sprocket 14. At this time, the chain 2 is guided to the first projection 36a through the concave part 38 of the first shifting section 34.Therefore, the chain 2 supported on the second projection 36b is easily supported on the first projection 36a.

[0037] Once a downshift operation from the first sprocket 14 to the second sprocket 16 is performed by the front derailleur (not shown), the unclaimed bicycle crank assembly 10 is rotated in the progressive rotational direction R. In this state, when the front derailleur moves from a first position facing the first sprocket 14 to a position facing the second sprocket 16, the chain 2 disengages from the teeth of the first sprocket 14. Disengaged from the first sprocket 14, the chain 2 is guided toward the teeth 42 of the second sprocket 16 and engaged with the teeth 42. Second embodiment

[0038] In the first embodiment, the unclaimed bicycle crank assembly 10 includes a first sprocket 14 and a second sprocket 16, however, the pedal crank assembly 110 of the second embodiment includes a third sprocket 18 in addition to the first sprocket 14 and the second sprocket 16, as shown in Fig. 7. The third sprocket 18 has smaller teeth than the second sprocket 16. The first sprocket 14 and the second sprocket 16 have the same configuration as in the first embodiment and are in Fig. 7 are marked by the same symbols and are not further described. Third sprocket

[0039] The third sprocket 18 has a rotational center axis Z and comprises a third sprocket main body 50, a plurality (e.g., twenty to thirty) of teeth 52 arranged along the circumferential direction on the radially outer side of the third sprocket main body 50, and a third shifting portion 54, as shown in Fig. 8. The third sprocket main body 50 is an example of a sprocket main body. The third shifting portion 54 is an example of a shifting portion. The third sprocket main body 50 and the teeth 52 are made of metal and are integrally formed. The third sprocket main body 50 has a plurality (e.g., four) of third fixing parts 50a, which are fixed to the second attachment parts 24b (see Fig. 1) of the sprocket attachment arms 24 are fixed and are arranged at intervals in the circumferential direction. The third fixing parts 50a are formed of through holes and are arranged in positions facing the plurality of second attachment parts 24b. The third sprocket 18, together with the second sprocket 16, is fixed to the sprocket attachment arms 24 by the second fixing bolts 28 (see Fig. 4), which are threadedly engaged with the second attachment parts 24b.

[0040] The teeth 52 include at least a fifth tooth 52a having a fifth maximum axial width W5 (see Fig. 5) and include at least one sixth tooth 52b having a sixth maximum width W6. The fifth teeth 52a are configured to be able to engage with the outer connecting plate 2a of the chain 2. The sixth teeth 52b are configured to be able to engage with the inner connecting plate 2b of the chain 2. The fifth maximum axial width W5 is greater than the sixth maximum axial width W6. The fifth maximum axial width W5 of the fifth teeth 52a is preferably in a range of 2.5 mm or greater and 5.4 mm or less, and is in a range of 3.0 mm or greater and 4.5 mm or less. Once the fifth maximum axial width W5 of the fifth teeth 52a is in such a range, the fifth teeth 52a easily engage with the outer connecting plate 2a without engaging with the inner connecting plate 2b.The sixth maximum axial width W6 of the sixth teeth 52b is preferably in a range of 1.5 mm or greater and 2.3 mm or less. When the sixth maximum axial width W6 of the sixth teeth 52b is within such a range, the sixth teeth 52b have the necessary rigidity and easily mesh with the inner connecting plate 2b.

[0041] The fifth teeth 52a are formed in a + (plus) shape when viewed from the radial outside as shown in the Fig. 5 and Fig. 8. The sixth teeth 52b are formed in a - (minus) shape when viewed from the radially outer side. The fifth teeth 52a and the sixth teeth 52b are tapered to gradually decrease in axial width toward the radially outer sides. Therefore, the fifth teeth 52a and the sixth teeth 52b mesh more easily with the outer connecting plate 2a and the inner connecting plate 2b.

[0042] At least some of the fifth teeth 52a and the sixth teeth 52b are arranged alternately in the circumferential direction, ie adjacent to each other, and in the first embodiment, all of these teeth are arranged in this way, as shown in Fig. 8 shown, arranged.

[0043] The third shifting portion 54 includes third shift teeth 52c provided on at least one of the teeth 52. In the second embodiment, a plurality (e.g., two) of third shift teeth 52c are provided. The third shift teeth 52c are provided at intervals in the circumferential direction. The third shift teeth 52c have third guide surfaces 52d for guiding the chain 2 in a first surface 18a (see Fig. 8) and a second surface (not shown) of the third sprocket 18, as in Fig.8. The third guide surfaces 52d are examples of a guide surface. The first surface 18a of the third sprocket 18 is the front surface located on the axial outer side farther from the bicycle frame when the crank assembly 10 is mounted on the bicycle, and the second surface is the rear surface located on the axial inner side closer to the bicycle frame. The third guide surfaces 52d are recessed to gradually decrease in thickness toward the sides of the third shift teeth 52c.

[0044] In the third embodiment, the third switching portion 54 may include the protrusions or the concave portion of the first switching portion 34. However, the third switching portion may also include only the protrusions or only the concave portion. Further embodiments

[0045] Embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments. Various modifications may be made within a range that does not deviate from the scope of the invention. In particular, the various embodiments and modifications disclosed in the specification can be arbitrarily combined as needed. (a) The first and second embodiments provide a front sprocket as an example of a bicycle sprocket. The present invention can also be applied to a rear sprocket. (b) In the bicycle sprocket assembly of the first and second embodiments, first teeth and second teeth having different axial widths are provided on all of the sprockets. Any sprocket (e.g., the second and / or third sprocket, small in diameter) may be configured with only the second teeth. (c) In the first and second embodiments, the first teeth are formed in a + shape or T shape when viewed from the radially outer side. These teeth may also be formed in other shapes, such as a diamond shape, trapezoidal shape, triangular shape, or hexagonal shape. (d) In the first and second embodiments, the first switching portion 34 has the second projection 36b, but a second projection 36b need not be provided. (e) In the first and second embodiments, there are four sprocket attachment arms 24a, however, the number of sprocket attachment arms is not limited to 4. (f) In the first and second embodiments, the sprocket main bodies and the plurality of teeth are integrally formed. The sprocket main bodies and the plurality of teeth may also be formed separately. For example, the plurality of teeth may be made of metal, and the sprocket main bodies may be made of a synthetic resin such as carbon fiber reinforced resin or a different metal than the teeth (for example, a lightweight metal such as aluminum) to reduce weight. (g) The shifting range of the sprockets may include the - (minus) shaped second teeth 32b, fourth teeth 42b and sixth teeth 52b.

[0046] It is also understood that although the terms "first" and "second" are used herein to describe different components, they should not be limited to these terms. These terms are used herein only to distinguish one component from another: Thus, for example, a first component could be referred to as a second component, and vice versa, without departing from the teachings of the present invention.

[0047] While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to one skilled in the art from this disclosure that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims. Accordingly, the foregoing descriptions of embodiments of the present invention are provided for illustrative purposes only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

Claims

[1] Bicycle sprocket for engagement with a chain (2), having a central axis of rotation (X, Y), the bicycle sprocket comprising: a sprocket main body (30, 40, 50); a plurality of teeth (32, 42, 52) arranged along a circumferential direction on a radially outer side of the sprocket main body (30, 40, 50); and at least one switching area (34, 44, 54), wherein the plurality of teeth (32, 42, 52) comprises first and second teeth (32a, 32b), each having at least one first tooth (32a) and each having a first maximum axial width (W1) for engagement with an outer connecting plate (2a) of the chain (2) and a second maximum axial width (W2) for engagement with an inner connecting plate (2b) of the chain (2), wherein the first maximum axial width (W1) is greater than the second maximum axial width (W2), wherein at least one first tooth (32a) is a switching tooth (32c) which is included at least in the switching region (34, 44, 54) and is formed in a T-shape when viewed from the radial outside. [2] Bicycle sprocket according to claim 1, wherein the first maximum axial width (W1) of the first tooth(s) (32a, 32a1, 32a2) is equal to or greater than 2.5 mm and less than or equal to 5.4 mm. [3] Bicycle sprocket for engaging with a chain (2) and having a rotational center axis (X, Y), the bicycle sprocket comprising: a sprocket main body (30, 40, 50); a plurality of teeth (32, 42, 52) arranged along a circumferential direction on the radially outer side of the sprocket main body (30, 40, 50); and at least one shifting region (34, 44, 54) including a region where the chain (2) engages with one of the plurality of teeth (32, 42, 52) of the bicycle sprocket during a shifting operation from a small sprocket to the bicycle sprocket and a region where the chain (2) separates / disconnects from one of the plurality of teeth (32, 42, 52) of the bicycle sprocket during a shifting operation from the bicycle sprocket to a small sprocket, the plurality of teeth (32, 42, 52) comprising first and second teeth (32a, 32b), each having at least one first tooth (32a) and each having a first maximum axial width (W1) to engage with an outer connecting plate (2a) of the chain (2) or a second maximum axial width (W2) to engage with an inner connecting plate (2b) of the chain (2), wherein the first maximum axial width (W1) is greater than the second maximum axial width (W2), and wherein the at least one first tooth (32a) is a switching tooth (32c), the switching tooth (32c) is formed in a T-shape when viewed from the radial outside. [4] Bicycle sprocket according to claim 3, wherein the first maximum axial width (W1) of the first tooth(s) (32a, 32a1, 32a2) is equal to or greater than 2.5 mm and less than or equal to 5.4 mm. [5] Bicycle sprocket according to claim 4, wherein the first maximum axial width (W1) of the first tooth(s) (32a, 32a1, 32a2) is equal to or greater than 3.0 mm and less than or equal to 4.5 mm, and / or the second maximum axial width (W2) of the second tooth(s) (32b) is equal to or greater than 1.5 mm and less than or equal to 2.3 mm. [6] A bicycle sprocket according to claim 1, 2 or 3 to 5, wherein the plurality of teeth (32, 42, 52) includes a plurality of first teeth (32a) and / or a plurality of second teeth (32b). [7] A bicycle sprocket according to claim 6, wherein the first teeth (32a) are formed in a + shape or are formed in a T shape when viewed from the radially outer side. [8] A bicycle sprocket according to claim 7, wherein at least some of the first and second teeth (32a, 32b) are arranged alternately in the circumferential direction. [9] Bicycle sprocket according to one of claims 1, 2 or 3 to 8, wherein the first teeth and the second teeth (32a, 32b) are arranged adjacent to each other. [10] Bicycle sprocket according to one of claims 1, 2 or 3 to 9, wherein the switching area (34, 44, 54) includes switching teeth (32c, 42c, 52c), the switching area (34, 44, 54) is provided on at least one of the plurality of teeth (32, 42, 52), wherein the switching teeth (32c, 42c, 52c) preferably have guide surfaces (32d, 42d, 52d) for guiding the chain (2). [11] A bicycle sprocket according to any one of claims 1, 2 or 3 to 10, wherein the bicycle sprocket is a front sprocket.

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