Bicycle sprocket and bicycle sprocket assembly

Abstract

Bicycle sprocket (14) with a rotational center axis (X), the a first tooth (332a) having a first axial chain engagement width (W1) which is smaller than a first axial distance (L1) of an outer plate (2a) and greater than a second axial distance (L2) of an inner plate (2b) coupled to the outer plate (2a), and a second tooth (332b) having a second axial chain engagement width (W2) which is smaller than the second axial distance (L2), wherein the first tooth (332a) has an inclined portion (353) to avoid excessive interference with the inner plate (2b) and the first tooth (332a) further comprises a first surface (352a), a second surface (352b) and a third surface (352c) extending in the circumferential direction between the first surface (352a) and the second surface (352b) in the axial direction, and the inclined portion (353) has a first tapered surface (353a) formed to extend from the first surface (352a) to the third surface (352c) on the drive side, a second tapered surface (353b) formed to extend from the second surface (352b) to the third surface (352c) on the drive side, a third tapered surface (353c) formed to extend from the first surface (352a) to the third surface (352c) on the non-drive side, and a fourth tapered surface (353d) formed to extend from the second surface (352b) to the third surface (352c) on the non-drive side.

Description

The present invention relates to a bicycle sprocket and a bicycle sprocket assembly.A conventional bicycle sprocket is provided on each crank link and rear wheel. A chain engages and bridges the sprocket of the crank linkage and the sprocket of the rear wheel. Accordingly, the rotation of the crank linkage is transmitted to the rear wheel via the chain.In a chain, inner link plates and outer link plates are alternately coupled. Further, the space between two inner link plates facing each other is formed to be smaller than the space between two outer link plates facing each other. Accordingly, when the sprocket teeth are formed such that the thickness (engagement width) of all the sprocket teeth is the same, in the thickness direction of the sprocket, the gap between the outer link plates and the sprocket teeth will be larger than the gap between the inner link plates and the sprocket teeth.In this conventional structure, due to the gap between the outer link plates and the sprocket teeth in the thickness direction of the sprocket, the engagement between the chain and the sprocket usually loosens with time. Thus, a sprocket formed such that the thickness of the teeth engaging the outer link plates is greater than the thickness of the teeth engaging the inner link plates is proposed, as disclosed in US 2013 / 0 139 642 A1, for example.In a conventional sprocket, the thickness of the teeth engaging the outer link plates is increased from the thickness of the teeth engaging the inner link plates by cutting the teeth engaging the inner link plates, as disclosed in US 2013 / 0 139 642 A1.Such a conventional sprocket wheel with different tooth thicknesses can also be produced by cold forging, as disclosed, for example, in US 2007 / 0 265 122 A1.US 2015 / 0 226 306 A1 discloses a conventional sprocket with alternating thicknesses of the teeth, which are moreover cut in such a way that they have a phase in the drive direction in order to improve the chain engagement.Such a tooth geometry, which is not symmetrical, aimed at improving the chain engagement in the drive rotational direction is also evident from US 2007 / 0 060 428 A1, in which the tip of the tooth tip is made narrower in the drive rotational direction than on the side of the non-drive rotational direction.US 2015 / 0 285 364 A1 provides inserts made of a material different from the sprocket material for changing the tooth thickness of the teeth which engage with the outer link plates, which inserts are fastened to the teeth, for example, by means of a plug connection.In this case, there is a problem that the processing time for forming a sprocket increases at the time of cutting. That is, in manufacturing the above sprocket, it has been difficult to improve performance of the sprocket.The present invention has been made in the light of the above-described problem, and an object of the present invention is to provide a bicycle sprocket having high chain holding force and excellent performance. Further, an object of the present invention is to provide a bicycle sprocket assembly having a high chain holding force and excellent performance.According to the present invention, a bicycle sprocket further has a rotational center axis. The present bicycle sprocket includes a first tooth and a second tooth. The first tooth has a first axial chain engagement width. The first axial chain engagement width is less than a first axial distance in an outer link plate of the bicycle chain. Further, the first axial chain engagement width is greater than a second axial distance in an inner link plate coupled to the outer link plate. The second tooth has a second axial chain engagement width. The second axial chain engagement width is smaller than the second axial distance. The first tooth has an inclined portion to avoid excessive interference with the inner link.In the present sprocket, the first chain engagement axial width of the first tooth is smaller than the first axial distance in the outer link plate and larger than the second axial distance in the inner link plate. Further, the second axial chain engagement width of the second tooth is smaller than the second axial distance. Accordingly, the chain can be securely held by the sprocket.Further, since the first tooth has an inclined portion, even if the first teeth are disposed between the outer link plates, excessive interference with the inner link plate can be avoided, and a tooth shape for securely holding the outer link plates can be easily formed by press working such as forging.Preferably, the bicycle sprocket may also be configured as follows. The first tooth further includes a first surface, a second surface, and a third surface. The third surface extends in the circumferential direction between the axis directions of the first surface and the second surface. The inclined portion includes a first tapered surface, a second tapered surface, a third tapered surface, and a fourth tapered surface. The first tapered surface is formed to extend from the first surface to the third surface on the driving side. The second tapered surface is formed to extend from the second surface to the third surface on the driving side. The third tapered surface is formed to extend from the first surface to the third surface on the non-driving side. The fourth tapered surface is formed to extend from the second surface to the third surface on the non-driving side. In this case, excessive interference between the first tooth and the inner link plates by the first to fourth tapered surfaces can be avoided, and a tooth shape for securely holding the outer link plates can be easily formed by press working such as forging.Preferably, the bicycle sprocket may also be configured as follows. A first axis direction contact width at which the driving surface of the first tooth contacts the chain roller is formed to have substantially the same length as a second axis direction contact width at which the driving surface of the second tooth contacts the chain roller. In this case, since the first axis direction contact width and the second axis direction contact width have the same length, the driving force can be stably transmitted from the sprocket to the chain.According to the present invention, a bicycle sprocket further has a rotational center axis. The present bicycle sprocket includes a first tooth and a second tooth. The first tooth has a first axial chain engagement width. The first axial chain engagement width is less than a first axial distance in the outer link plate of the bicycle chain. Further, the first axial chain engagement width is greater than a second axial distance in the inner link plate coupled to the outer link plate. The second tooth has a second axial chain engagement width. The second axial chain engagement width is smaller than the second axial distance. At least one of the first tooth or the second tooth has a plated layer.In the present sprocket, the first chain engagement axial width of the first tooth is smaller than the first axial distance in the outer link plate and larger than the second axial distance in the inner link plate. Further, the second axial chain engagement width of the second tooth is smaller than the second axial distance. Accordingly, the chain can be securely held by the sprocket.Further, since at least one of the first tooth or the second tooth has a plated layer, the abrasion resistance and rust resistance of at least one of the first tooth or the second tooth can be improved.Preferably, the bicycle sprocket may also be configured as follows. The first tooth and the second tooth are made of aluminum. The plated layer is a nickel plated layer. In this case, the abrasion resistance of the first tooth and the second tooth can be improved.Preferably, the bicycle sprocket may also be configured as follows. The first tooth and the second tooth are made of iron. The plated layer is a nickel and chromium plated layer. In this case, the rust resistance of the first tooth and the second tooth can be improved.According to the present invention, a bicycle sprocket assembly further includes one of the sprockets described above.Preferably, with the present sprocket assembly, the same effects as the above-described effects can be obtained.Preferably, the bicycle sprocket assembly can also be configured as follows. In the present sprocket assembly, the sprocket is a single front sprocket.Even with the sprocket assembly formed in this manner, the same effects as the above-described effects can be obtained.Preferably, the bicycle sprocket assembly can also be configured as follows. In the present sprocket assembly, the sprocket is a plurality of front sprockets.Even with the sprocket assembly formed in this manner, the same effects as the above-described effects can be obtained.Preferably, the bicycle sprocket assembly can also be configured as follows. In the present sprocket assembly, the sprocket can be moved along the rotational center axis.Even with the sprocket assembly formed in this manner, the same effects as the above-described effects can be obtained.Preferably, the bicycle sprocket assembly can also be configured as follows. In the present sprocket assembly, the sprocket is a rear sprocket.Even with the sprocket assembly formed in this manner, the same effects as the above-described effects can be obtained.According to the present invention, a bicycle sprocket having high chain holding force and excellent performance can be provided. Further, a bicycle sprocket assembly having high chain holding force and excellent performance can be provided.Selected embodiments of the present invention will now be explained with reference to the drawings, wherein FIG. 1 is a front view of the bicycle crank linkage according to the first and second embodiments of the present invention. FIG. 2 is an oblique front view of the first sprocket according to the first embodiment. FIG. 3 is a rear view of the first sprocket according to the first embodiment. FIG. 4 is a partial oblique rear view of the first and second sprockets according to the first embodiment. FIG. 5 is a partial side view of the first sprocket and the second sprocket according to the first embodiment as viewed from the radially outer side. FIG. 6 is an oblique front view of the second sprocket according to the first embodiment. FIG. 7 is a cross-sectional view of the first tooth of the first sprocket and the third tooth of the second sprocket according to the second embodiment of the present invention. FIG. 8 is a front view of the first tooth of the first sprocket and the third tooth of the second sprocket according to another embodiment of the present invention. FIG. 9 is a partial front view of the tooth portion of the first and second sprockets according to another embodiment of the present invention. FIG. 10 is a partial side view of the tooth portion of the first and second sprockets according to another embodiment of the present invention as viewed from the radially outer side. FIG. 11 is a front view of the first sprocket according to another embodiment of the present invention. FIG. 12A is a front view of the first sprocket according to another embodiment of the present invention. FIG. 12B is a partial cross-sectional view of the first sprocket according to another embodiment of the present invention. FIG. 13 is a schematic diagram illustrating the formation state of the second tooth and the fourth tooth according to another embodiment of the present invention.Like reference numerals designate corresponding or identical elements throughout the several drawings.As shown in FIG. 1, a bicycle crank linkage 10 (hereinafter referred to as a crank linkage) according to the first embodiment includes a crank arm 12, a first sprocket 14 (an example of a bicycle sprocket), and a second sprocket 16 (an example of a bicycle sprocket). Further, the first sprocket 14 and the second sprocket 16 are examples of a bicycle sprocket assembly.In the crank linkage 10, the first sprocket 14 and the second sprocket 16 may engage with a chain 2. The second sprocket 16 has fewer teeth than the first sprocket 14. the chain 2 includes two outer link plates 2 a, two inner link plates 2 b, and a sprocket 2 ccoupling the two outer link plates 2 aand the two inner link plates 2 b.The crank arm 12 is integrally and rotatably coupled to a crankshaft 19. The crank arm 12 includes a sprocket attachment portion 20 and an arm portion 22 provided integrally with or separately from the sprocket attachment portion 20.The sprocket attachment portion 20 includes a plurality (e.g., four) of sprocket attachment arms 24. The plurality of sprocket attachment arms 24 are arranged in the circumferential direction with intervals therebetween. The intervals of the sprocket attachment arms 24 in the circumferential direction are regular intervals. Here, an example of a case is shown in which the intervals of the sprocket attachment arms 24 in the circumferential direction are regular intervals, but the intervals of the sprocket attachment arms 24 in the circumferential direction may be irregular intervals.The sprocket attachment arm 24 includes a first attachment portion 24 aand a second attachment portion 24 b. The first attachment portion 24 ais for attaching the first sprocket 14, and the first attachment portion 24 ais formed at a distal end portion of the sprocket attachment arm 24. The first fixing portion 24 ais, for example, a through hole. The first sprocket 14 is fixed to the first attachment portion 24 a.The second attachment portion 24 bis for attaching the second sprocket 16, and the second attachment portion 24 bis formed at a proximal end portion of the sprocket attachment arm 24 radially inward from the first attachment portion 24 a. The second fixing portion 24 bis, for example, a lower screw hole. The second sprocket 16 is fixed to the second attachment portion 24 b.The arm portion 22 is provided integrally with or separately from the sprocket attachment portion 20. Here, the arm portion 22 is integrally formed with the sprocket attachment portion 20. A pedal attachment portion 22 ais provided at the distal end portion of the arm portion 22. A pedal (not shown) may be mounted to the pedal attachment portion 22 a. A coupling hole 22 bis provided at the proximal end portion of the arm portion 22. The crankshaft 19 is integrally and rotatably coupled to the coupling hole 22 b.As shown in FIGS. 2 to 5, the first sprocket 14 has a rotational center axis X. The first sprocket 14 includes a first sprocket body 30 (an example of a main body portion), a first annular portion 31 (an example of an annular portion), a plurality of teeth 32 (an example of a first tooth portion and a second tooth portion), and a first shifting region 34 (see FIGS. 3 and 4 ; an example of a shifting region).The first sprocket body 30 is non-metallic and made of synthetic resin such as carbon fiber reinforced resin. The first sprocket body 30 is integrally formed with the first annular portion 31. As shown in FIGS. 2 to 4, the first sprocket body 30 includes a plurality (for example, four) of first fixing portions 30 a. The plurality of first fixing portions 30 aare arranged in the circumferential direction with intervals therebetween.Each first fixing portion 30 ais, for example, a through hole. Each first fixing portion 30a is disposed at an opposite position with respect to each first fixing portion 24a. In this state, the first fastening bolt 26 (see FIG. 1 ) is inserted into each first fixing portion 30 aand each first fastening portion 24 aand screwed onto a nut member (not shown). Thus, the first sprocket body 30 is fixed to the sprocket attachment arm 24.The first annular portion 31 is fixed to the first sprocket body 30. Specifically, the first annular portion 31 is fixed to the outer periphery of the first sprocket body 30. The first annular portion 31 is made of metal such as aluminum, titanium, or iron / stainless steel. A plurality of teeth 32 are formed on the outer periphery of the first annular portion 31.A plurality of teeth 32 (including a first tooth 32 aand a second tooth 32 bdescribed below) are provided on the outer periphery of the first annular portion 31. Specifically, the plurality of teeth 32 (for example, 30 to 60) are arranged side by side in the circumferential direction on the outer periphery of the first annular portion 31, and are integrally formed with the outer peripheral portion of the first annular portion 31. The plurality of teeth 32 are made of metal such as aluminum, titanium, or iron / stainless steel.The plurality of teeth 32 includes a plurality of first teeth 32 a(an example of a first tooth) and a plurality of second teeth 32 b(an example of a second tooth). The first tooth 32 aand the second tooth 32 bare alternately arranged in the circumferential direction, that is, side by side in the circumferential direction.The first tooth 32a is formed so as to be engageable with the outer link plates 2a. Specifically, the first tooth 32 ais formed so as to be engageable between two of the outer link plates 2 ain the axial direction. The first tooth 32 ais formed in a divergent cone shape so that the width in the axis direction gradually becomes smaller toward the radially outer side. The axis direction includes the direction in which the rotation center axis X extends and the directions parallel to the rotation center axis X. The axis direction used here corresponds to the directions parallel to the rotational center axis X.As shown in FIG. 4, the first tooth 32 apreferably has a first recess 32 e(an example of a recess). The first recess 32 eis provided at an edge portion of the first tooth 32 a. The surface of the first recess 32 eon the first side surface 14 aside is preferably formed flush with the surface of the second tooth 32 bon the first side surface 14 aside. The surface of the first recess 32 eon the second side surface 14 bside is preferably formed flush with the surface of the second tooth 32 bon the second side surface 14 bside.Here, the first side surface 14 a(see FIG. 1 ) is the front surface of the crank link 10 when mounted on the bicycle, disposed axially outward and spaced apart from the bicycle frame. Further, the second side surface 14 b(see FIGS. 3 and 4 ) is the rear surface, disposed axially inward and close to the bicycle frame.The first recess 32 eis formed by press working such as forging. Here, an example of a case where the first recess 32 eis formed by press working is shown, but the first recess 32 emay be formed by cutting.As shown in FIG. 5, the first recess 32 eis formed to face the end portion of the inner link plate 2 b. Excessive interference between the first tooth 32 aand the inner link plates 2 bcan be prevented by the first recess 32 e. Further, as shown in FIGS. 2, 4, and 5, by providing the first recess 32 eon the first tooth 32 a, the first tooth 32 a(excluding the first tooth 32 a 1 and the first gear shift tooth 32 a 2) is formed in a substantially +-shape (plus sign shape) as viewed from the radially outer side.Here, as shown in FIGS. 2 to 3, the plurality of first teeth 32 aincludes a plurality (for example, two) of first teeth 32 a 1 for shifting gears and a plurality (for example, two) of first teeth 32 a 2 for shifting gears. The first gear shift tooth 32 a 1 serves to shift down in which the chain 2 moves from the first sprocket 14 to the second sprocket 16. The first gear speed change tooth 32 a 2 serves to upshift in which the chain 2 moves from the second sprocket 16 to the first sprocket 14. The first gear shifting tooth 32 a 1 and the first gear shifting tooth 32 a 2 are preferably formed in a substantially T-shape as viewed from the radially outer side by being provided with a first recess 32 eas described above.As shown in FIG. 5, the first tooth 32 ahas a first maximum axis width W 1 (an example of a first axial chain engagement width). The first maximum axis width W 1 is the axis width of the portion where the length of the first tooth 32 ais longest in the axis direction. The first maximum axis width W 1 is smaller than a first axis distance L 1 in two of the outer link plates 2 a. Further, the first maximum axis width W 1 is larger than a second axis distance L 2 in two of the inner link plates 2 b.The first axis distance L 1 is the distance in the axis direction between the facing surfaces of a pair of the outer link plates 2 a. The second axis distance L 2 is the distance in the axis direction between the facing surfaces of a pair of the inner link plates 2 b.As shown in FIGS. 2 to 4, the second tooth 32 bis formed to be engageable with the inner link plates 2 b. Specifically, the second tooth 32 bis formed so as to be engageable between two of the inner link plates 2 bin the axial direction.The second tooth 32 bis preferably formed in a substantially -shape (minus sign shape) as viewed from the radially outer side. The second tooth 32 bis formed in a divergent cone shape so that the width in the axis direction gradually becomes smaller toward the radially outer side.As shown in FIG. 5, the second tooth 32 bhas a second maximum axis width W 2 (an example of a second axial chain engagement width). The second maximum axis width W 2 is the axis width of the portion where the length of the second tooth 32 bin the axis direction is longest. The second maximum axis width W 2 is smaller than the above-described second axis distance L 2. The second maximum axis width W 2 is smaller than the first maximum axis width W 1.The second tooth 32b is formed by machining the second tooth 32b in the following manner, thereby obtaining the above configuration. The second tooth 32 bis formed by deforming the material. Specifically, the second tooth 32 bis formed by press working. More specifically, the second tooth 32 bis formed by forging. Specifically, the second tooth 32 bis formed together with the first recesses 32 eby forging. The second maximum axis width W 2 of the second tooth 32 bis set by press working, for example, by forging the second tooth 32 bcorrespondingly.The first shifting region 34 is provided for shifting the chain 2. The first shifting region 34 is the region where the chain engages the teeth 32 of the first sprocket 14 during an upshift from the second sprocket 16 to the first sprocket 14. Further, the first shifting region 34 is the region where the chain engages the teeth 32 of the first sprocket 14 during a downshifting operation from the first sprocket 14 to the second sprocket 16.As shown in FIGS. 2 to 4, the first shift region 34 includes a plurality of first shift teeth 32 c. Here, the plurality of (for example, two) first gear shift teeth 32 a 1 correspond to the first shift teeth 32 c. Further, the two second teeth 32 badjacent to each of the first speed change gear teeth 32 a 1 correspond to the first speed change gear teeth 32 c.As shown in FIGS. 2 and 3, the first shift teeth 32 chave a first guide surface 32 d. The first guide surface 32 dis used for guiding the chain 2. the first guide surface 32 dis provided on the first ratchet teeth 32 c, on the first surface side 14 a(see FIG. 2 ) or the second surface side 14 b(see FIGS. 3 and 4 ) of the first sprocket 14. The first guide surface 32 dis concaved so that its thickness gradually becomes thinner toward the side portion of the first shift teeth 32 c.Further, the first switching region 34 preferably includes a first protrusion 36 aand a second protrusion 36 b.The first protrusion 36 aand the second protrusion 36 bare provided on the first sprocket body 30, and can hold the chain 2. Here, a pair of the first protrusion 36 aand the second protrusion 36 bare arranged side by side in the circumferential direction.The first protrusion 36 ais provided on the second side surface 14 bof the first sprocket body 30 for guiding the chain 2 to the teeth 32 of the first sprocket 14 in a protruding manner. For example, the first protrusion 36 aguides the chain 2 to the second tooth 32 bshown by the hatching in FIG. 3. the second protrusion 36 bis provided on the second side surface 14 bof the first sprocket body 30 for guiding the chain 2 to the first protrusion 36 ain a protruding manner.Further, as shown in FIGS. 3 and 4, the first switching region 34 includes a stepped portion 38. The stepped portion 38 is for easier engagement of the chain 2 supported on the first protrusion 36 awith the teeth 32 of the first sprocket 14. Further, the stepped portion 38 is provided on the downstream side in the forward rotational direction R from the first protrusion 36 a. The stepped portion 38 is concaved in a substantially triangular shape.As shown in FIGS. 4 and 6, the second sprocket 16 has a rotational center axis Y. The rotational center axis Y and the rotational center axis X are concentric. The second sprocket 16 includes a second sprocket body 40 (an example of a main body portion), a second annular portion 41 (an example of an annular portion), a plurality of teeth 42 (an example of a first tooth portion and a second tooth portion), and a second shifting region 44 (an example of a shifting region).The second sprocket body 40 is made of metal such as aluminum, titanium, or iron / stainless steel. The second sprocket body 40 includes a plurality (for example, four) of second fixing portions 40 a. The plurality of second fixing portions 40 aare arranged in the circumferential direction with intervals therebetween.Each second fixing portion 40 ais, for example, a through hole. Each second fixing portion 40a is disposed at an opposite position with respect to each second fixing portion 24b. In this state, a second fastening bolt 28 is inserted into each second fixing portion 40 aand each second fixing portion 24 b, and the second fastening bolt 28 is screwed onto a nut member (not shown). Thus, the second sprocket body 40 is fixed to the sprocket attachment arm 24.The second annular portion 41 is provided on the outer periphery of the second sprocket body 40. The second annular portion 41 is made of metal such as aluminum, titanium, or iron / stainless steel. A plurality of teeth 42 are formed on the outer periphery of the second annular portion 41.A plurality of teeth 42 (including a third tooth 42 aand a fourth tooth 42 bdescribed below) are provided on the outer periphery of the second annular portion 41. Specifically, the plurality of teeth 42 (for example, 20 to 40) are arranged side by side in the circumferential direction on the outer periphery of the second annular portion 41 and are integrally formed with the outer peripheral portion of the second annular portion 41. The plurality of teeth 42 are made of metal such as aluminum, titanium, or iron / stainless steel.The plurality of teeth 42 includes a plurality of third teeth 42 a(an example of a first tooth) and a plurality of fourth teeth 42 b(an example of a second tooth). The third tooth 42 aand the fourth tooth 42 bare arranged alternately in the circumferential direction, that is, side by side in the circumferential direction.The third tooth 42 ais formed to be engageable with the outer link plates 2 a. Specifically, the third tooth 42 ais formed so as to be engageable between two of the outer link plates 2 ain the axial direction. The third tooth 42 ais formed in a divergent cone shape so that the width in the axis direction gradually becomes smaller toward the radially outer side.As shown in FIG. 6, the third tooth 42 apreferably has a second recess 42 e(an example of a recess). The second recess 42 eis provided at an edge portion of the third tooth 42 a. The surface of the second recess 42 eon the first side surface 14 aside is formed flush with the surface of the fourth tooth 42 bon the first side surface 14 aside. The surface of the second recess 42 eon the second side surface 14 bside is formed flush with the surface of the fourth tooth 42 bon the second side surface 14 bside.The second recess 42 eis formed by press working such as forging. Here, an example of a case where the second recess 42 eis formed by press working is shown, but the second recess 42 emay be formed by cutting.The second recess 42 eis formed to face the end portion of the inner link plate 2 bin the same manner as the above-described first recess 32 e. Excessive interference between the third tooth 42 aand the inner link plates 2 bcan be prevented by the second recess 42 e. Further, as shown in FIGS. 4 and 6, by providing the second recess 42 eon the third tooth 42 a, the third tooth 42 ais formed in a substantially + shape (plus sign shape) as viewed from the radially outer side.As shown in FIG. 5, the third tooth 42 ahas a third maximum axis width W 3 (an example of a first axial chain engagement width). The third maximum axis width W 3 is the width in the axis direction of the portion where the length of the third tooth 42 ais longest. The third maximum axis width W 3 is smaller than the first axis distance L 1. Further, the third maximum axis width W 3 is larger than the second axis distance L 2 in two of the inner link plates 2 b.As shown in FIGS. 4 to 6, the fourth tooth 42 bis formed to be engageable with the inner link plates 2 b. Specifically, the fourth tooth 42 bis formed so as to be engageable between two of the inner link plates 2 bin the axial direction.The fourth tooth 42 bis formed in a substantially -shape (minus sign shape) as viewed from the radially outer side. The fourth tooth 42 bis formed in a divergent cone shape so that the width in the axis direction gradually becomes smaller toward the radially outer side.As shown in FIG. 5, the fourth tooth 42 bhas a fourth maximum axis width W 4 (an example of a second axial chain engagement width). The fourth maximum axis width W 4 is the width in the axis direction of the portion where the length of the fourth tooth 42 bis longest. The fourth maximum axis width W 4 is smaller than the second axis distance L 2. Further, the fourth maximum axis width W 4 is smaller than the third maximum axis width W 3.The fourth tooth 42 bis formed by machining the fourth tooth 42 bin the following manner, thereby obtaining the above configuration. The fourth tooth 42 bis formed by deforming the material. Specifically, the fourth tooth 42 bis formed by press working. More specifically, the fourth tooth 42 bis formed by forging. The fourth maximum axis width W 4 of the fourth tooth 42 bis set by press working, for example, by forging the fourth tooth 42 bcorrespondingly.The second shifting region 44 is provided for shifting the chain 2. The second shifting region 44 is the region where the chain engages the teeth 42 of the first sprocket 14 during an upshift from the second sprocket 16 to the first sprocket 14, or the region where the chain disengages from the teeth 42 of the first sprocket 14 during a downshift from the first sprocket 14 to the second sprocket 16.The second shift region 44 includes a plurality (e.g., two) of second shift teeth 42 c. The second shift teeth 42 care provided in the circumferential direction with intervals therebetween. The second shift teeth 42 chave a second guide surface 42 d. The second guide surface 42 dis provided on the fourth side surface 16 bside (see FIG. 6 ) located on the opposite side of the third side surface 16 a(see FIG. 1 ), and guides the chain 2. the second guide surface 42 dis formed concave so that its thickness gradually becomes thinner toward the side portion of the second shift teeth 42 c.Here, the third side surface 16 aof the second sprocket 16 is the front surface of the crank link 10 when mounted on the bicycle, disposed axially outward and spaced apart from the bicycle frame. The fourth side surface 16 bis the rear surface, disposed axially inward and close to the bicycle frame.Here, an example of a case where the second switching region 44 does not include the protrusion or the recess that the first switching region 34 includes is shown, but the second switching region 44 may include at least one of the protrusions or the recess.In a crank linkage 10 configured in this manner, the crank linkage 10 rotates in a forward rotational direction R when an upshift 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 opposite to the second sprocket 16 to a position opposite to the first sprocket 14, the chain 2 disengages from the teeth of the second sprocket 16. Then, the chain 2 supported on the first protrusion 36 aby the stepped portion 38 of the first shifting region 34 is guided to and engaged with the teeth 32 of the first sprocket 14.On the other hand, the crank linkage 10 rotates in a forward rotational direction R when a downshift operation from the first sprocket 14 to the second sprocket 16 is performed by the front derailleur. In this state, when the front derailleur moves from a position opposite to the first sprocket 14 to a position opposite to the second sprocket 16, the chain 2 disengages from the teeth of the first sprocket 14, and then the chain 2 is guided to the teeth 42 of the second sprocket 16 and engages with the teeth 42.As shown in FIG. 1, a bicycle crank linkage 110 according to the second embodiment includes a crank arm 12, a first sprocket 114 (an example of a bicycle sprocket), and a second sprocket 116 (an example of a bicycle sprocket). Further, the first sprocket 114 and the second sprocket 116 are an example of a bicycle sprocket assembly.The configuration of the second embodiment is substantially the same as that of the first embodiment except for the configurations of the first sprocket 114 and the second sprocket 116. Accordingly, only the descriptions for the configurations of the first sprocket 114 and the second sprocket 116 are given here, and the descriptions for the configurations that are substantially the same as the first embodiment have been omitted. Nevertheless, configurations omitted here are intended to correspond to the configurations of the first embodiment. Further, configurations that are the same as the first embodiment have been denoted by the same reference numerals.The first sprocket 114 includes a first sprocket body 30 (an example of a main body portion), a first annular portion 31 (an example of an annular portion), a plurality of teeth 132 (an example of a first tooth portion and a second tooth portion), and a first shifting region 34 (an example of a shifting region).Here, the configuration of the first sprocket body 30, the configuration of the first annular portion 31, and the configuration of the first shifting region 34 are substantially the same as the configurations of the first embodiment, and thus descriptions thereof have been omitted. Further, regarding the configuration of the plurality of teeth 132, only configurations different from the configurations of the first embodiment will be described below.As shown in FIG. 7, each of the plurality of first teeth 132 a(an example of a first tooth) included in the plurality of teeth 132 includes a first main body portion 132 ab, a first recess 32 e, and a first additional portion 132 c. The first recess 32 eis formed in the same manner as in the first embodiment, and thus the description thereof is omitted.The first main body portion 132 abis provided on the first annular portion 31. Specifically, the first main body portion 132 abis integrally formed with the first annular portion 31 so as to protrude radially outward from the first annular portion 31. The first main body portion 132 abincludes a front surface 20 aof the first side surface 14 aside and a rear surface 20 bof the second side surface 14 aside. The back surface 20 bis a surface on the opposite side of the front surface 20 ain the axis direction of the rotation center axis X.The first additional portion 132 cis fixed to the first main body portion 132 abto increase the width of the first main body portion 132 ab. Specifically, the first additional portion 132 cis fixed to both the front surface 20 aand the rear surface 20 bof the first main body portion 132 b. A first maximum axis width W 1 is set to a prescribed width by fixing the first additional portion 132 cin this manner to both the front surface 20 aand the rear surface 20 bof the first main body portion 132 ab. The first additional portion 132 cis made of metal such as aluminum, titanium, or iron / stainless steel. This first additional portion 132 cis fixed to the first tooth 132 aby joining, diffusion joining, cold forging, or casting.Here, an example is shown in which the first additional portion 132 cis fixed to both the front surface 20 aand the rear surface 20 bof the first main body portion 132 ab. Instead, the first maximum axis width W 1 may be set by attaching the first additional portion 132 cto only the front surface 20 aor only the rear surface 20 bof the first main body portion 132 ab.The second sprocket 116 includes a second sprocket body 40 (an example of a main body portion), a second annular portion 41 (an example of an annular portion), a plurality of teeth 142 (an example of a first tooth portion and a second tooth portion), and a second shifting region 44 (an example of a shifting region).Here, the configuration of the second sprocket body 40, the configuration of the second annular portion 41, and the configuration of the second shifting region 44 are substantially the same as the configurations of the first embodiment, and thus descriptions thereof have been omitted. Further, regarding the configuration of the plurality of teeth 142, only the configurations different from the configurations of the first embodiment will be described below.Further, each of the plurality of third teeth 142 a(an example of a first tooth) included in the plurality of teeth 142 includes a second main body portion 142 band a second additional portion 142 c. The configurations of the second main body portion 142 band the second additional portion 142 care substantially the same as the configurations of the above-described first main body portion 132 aband the first additional portion 132 c. That is, a third maximum axis width W 3 is set to a predetermined width by fixing the second additional portion 142 cto both the front surface 20 aand the rear surface 20 bof the second main body portion 142 b.In the first and second embodiments, two front sprockets 14 and 16 ( 114, 116) have been shown as an example of a bicycle sprocket assembly, but the present invention is not limited thereto. The present invention can be applied to a bicycle sprocket assembly provided with a single front sprocket having no shifting region.In the first and second embodiments, a case where the second sprocket body 40 and the plurality of teeth 42, 142 are integrally formed has been shown as an example, but the present invention is not limited thereto. The second sprocket body 40 may be a separate body from the plurality of teeth 42, 142. For example, the plurality of teeth 42, 142 may be metal, while the second sprocket body 40 may be non-metal. In this case, by using aluminum, titanium, or iron / stainless steel for the metal and synthetic resins such as carbon fiber reinforced resin for the non-metal, the weight can be reduced.The portion where the first tooth 32 a, 132 aand the second tooth 32 bengage with the sprocket 2 cand the portion where the third tooth 42 a, 142 aand the fourth tooth 42 bengage with the sprocket 2 cmay be formed as shown in FIG. 8 in the first and second embodiments.This configuration is substantially the same as the first sprocket 14, 114 and the second sprocket 16, 116. Thus, the configuration using the first tooth 232 aand the second tooth 232 bof the first sprockets 14 and 114 will be described here.A chain roller 2 cmay be engaged between the first tooth 232 aand the second tooth 232 b(see FIGS. 1 and 5 ). As shown in FIG. 8, each of the first tooth 232 aand the second tooth 232 bhas a driving surface 233 and a non-driving surface 234.Since this configuration is substantially the same in the first tooth 232 aand the second tooth 232 b, description will be given here using the first tooth 232 a.Each of the first tooth 232 aand the second tooth 232 bhas a front surface 20 aof the first side surface 14 a, a rear surface of the second side surface 14 b(not shown), a driving surface 233, and a non-driving surface 234. The back surface 20 bis a surface on the opposite side of the front surface 20 ain the axis direction of the rotation center axis X (the direction perpendicular to the paper surface in FIG. 8 ).The driving surface 233 is a surface connecting the front surface 20 aand the rear surface on a downstream side in the forward rotation direction R in the axis direction. The driving surface 233 has a contact point CP and a first extension portion 233 a(an example of a driving surface extension portion). The contact point CP is where the chain roller 2c makes contact. Specifically, the contact point CP is where the sprocket 2 cis in contact with the driving surface 233 during traveling.The first extension portion 233 ais integrally formed with the driving surface 233. The first extension portion 233 aextends radially outward in the circumferential direction from the contact point CP. Specifically, the first extension portion 233 aprotrudes radially outward toward the downstream side in the forward rotation direction R from the contact point CP.The non-driving surface 234 is a surface connecting the front surface 20 aand the rear surface on an upstream side in the forward rotation direction R in the axis direction. For example, the non-driving surface 234 is formed line-symmetrically with the driving surface 233 with respect to a straight line CL connecting the rotational center axis X and the center position of the first tooth 232 a(second tooth 232 b) in the circumferential direction. The non-driving surface 234 may be formed asymmetrically with respect to the driving surface 233 with respect to the straight line CL connecting the rotational center axis X and the center position of the first tooth 232 a(second tooth 232 b) in the circumferential direction.The non-driving surface 234 includes a second extension portion 234 a(an example of a non-driving surface extension portion). The radially outward movement of the chain roller 2 cis suppressed by the second extension portion 234 a. The second extension portion 234 ais integrally formed with the non-driving surface 234. Here, since the non-driving surface 234 is formed in line symmetry with the driving surface 233, the second extension portion 234 aextends to the opposite side of the first extension portion 233 ain the circumferential direction. That is, the second extension portion 234 aextends in a circumferential direction toward the upstream side in the forward rotation direction R, for example.Accordingly, the driving force of the first sprocket 14 can be reliably transmitted to the chain roller 2 c, that is, the chain 2 through the driving surface 233. Further, the radially outward movement of the chain roller 2 cmay be reliably suppressed by the driving surface 233 and the non-driving surface 234.Here, as an example, a case has been shown in which each of the first tooth 232 aand the second tooth 232 bhas a driving surface 233 and a non-driving surface 234. Instead, the configuration may be such that only the first tooth 232 aor only the second tooth 232 bhas a driving surface 233 and a non-driving surface 234. Further, the first tooth 232 aand / or the second tooth 232 bmay be formed to have only one driving surface 233 or only one non-driving surface 234.In the first and second embodiments, an example has been shown in which the front sprockets 14 and 16 are immovably mounted on the crankshaft 19 by means of a crank arm 12. Instead, the front sprockets 14 and 16 may move along the crankshaft 19 (rotational center axis X). Further, only a single front sprocket 14 may be used, with the front sprocket 14 moving along the crankshaft 19 (rotational center axis X).A contour of the front sprockets 14 and 16 shown in the above first and second embodiments can be formed with a 3D printer, after which the second tooth 32 band the fourth tooth 42 bare formed by press working such as forging.In the first and second embodiments described above, an example in which the first tooth 32 a, 132 aand the third tooth 42 a, 142 aare formed in a substantially + shape has been shown, but the present invention is not limited thereto. For example, at least a portion of the first tooth 32 aand third tooth 42 amay have a different shape, such as a diamond shape, a trapezoidal shape, a triangular shape, a hexagonal shape, or an octagonal shape.As shown in FIG. 10, the first tooth 332 aand / or the third tooth 342 apreferably have an octagonal shape when viewed from the radial direction of the bicycle sprocket. In this case, excessive interference between the first tooth 332 aand / or the third tooth 342 aand the inner link plates 2 bcan be avoided, and a tooth shape for securely holding the outer link plates 2 acan be easily formed by press working such as forging.Here, an octagonal shape is not limited to a regular octagon shape, and may be any shape having eight sides. Further, the eighth sides constituting the octagon are not limited to straight lines and may be curved lines having a slight curvature.Specifically, as shown in FIGS. 9 and 10, when the first tooth 332 aand the third tooth 342 ahave the octagonal shape described above, the first tooth 332 aand the third tooth 342 ahave a first surface 352 a, a second surface 352 b, a third surface 352 c, and an inclined portion 353.The first surface 352 ais a surface of the first tooth 332 aon the first side surface 14 aside of the first sprocket 14 and a surface of the third tooth 342 aon the third side surface 16 aside of the second sprocket 16.The second surface 352 bis a surface of the first tooth 332 aon the second side surface 14 bside of the first sprocket 14 and a surface of the third tooth 342 aon the fourth side surface 16 bside of the second sprocket 16.The third surface 352 cextends in the circumferential direction between the axis directions of the first surface 352 aand the second surface 352 b. The third surface 352 cincludes a driving surface 352 d, a non-driving surface 352 e, and a distal end surface 352 fconnecting the driving surface 352 dand the non-driving surface 352 ein the circumferential direction. The inclined portion 353 is provided to prevent the inner link plates 2 bfrom being excessively affected. The inclined portion 353 includes a first inclined surface 353 a, a second inclined surface 353 b, a third inclined surface 353 c, and a fourth inclined surface 353 d.The first chamfered surface 353 ais formed to extend from the first surface 352 ato the third surface 352 con the driving side. The second tapered surface 353 bis formed to extend from the second surface 352 bto the third surface 352 con the driving side. The third tapered surface 353 cis formed to extend from the first surface 352 ato the third surface 352 con the non-driving side. The fourth tapered surface 353 dis formed to extend from the second surface 352 bto the third surface 352 con the non-driving side.In other words, the first chamfered surface 353 ais formed in an edge portion formed by the first surface 352 aand the third surface 352 con the driving side. The second chamfered surface 353 bis formed in an edge portion formed by the second surface 352 band the third surface 352 con the driving side. The third chamfered surface 353 cis formed in an edge portion formed by the first surface 352 aand the third surface 352 con the non-driving side. The fourth chamfered surface 353 dis formed in an edge portion formed by the second surface 352 band the third surface 352 con the non-driving side.Here, the first tooth 332 aand the third tooth 342 aon the driving side appear to interfere excessively with the inner link plates 2 bin comparison with the non-driving side; therefore, the first chamfered surface 353 aand the second chamfered surface 353 bformed on the driving side preferably have a larger area in comparison with the third chamfered surface 353 cand the fourth chamfered surface 353 dformed on the non-driving side.Excessive interference of the first tooth 332 aand the third tooth 342 awith the inner link plates 2 bcan be prevented by the first to fourth tapered surfaces 353 a, 353 b, 353 c, and 353 d. Further, the first to fourth tapered surfaces 353 a, 353 b, 353 c, and 353 dhave a shape different from the recess in the above first and second embodiments, are inclined surfaces formed of straight or slightly curved lines, and are thus easily formed by press working such as forging.Further, when the first tooth 332 aand the third tooth 342 ahave an octagonal shape, a first axis direction contact width L 3 at which the driving surface of the first tooth 332 aand the third tooth 342 acontact the sprocket 2 cis preferably formed to have substantially the same length as a second axis direction contact width L 4 at which the driving surface of the second tooth 332 band the fourth tooth 342 bcontact the sprocket 2 c.In the first and second embodiments described above, an example in which the first tooth 32 a / 132 ais formed in a substantially T-shape has been shown, but the present invention is not limited thereto. For example, a portion of the first tooth 32 amay have another shape, such as a diamond shape, a trapezoidal shape, a triangular shape, a hexagonal shape, or an octagonal shape.In the first and second embodiments described above, a first switching region 34 has a second protrusion 36 b, but a second protrusion 36 bmay not be provided.In the first and second embodiments described above, the number of the plurality of sprocket attachment arms 24 is four, but the number of the sprocket attachment arms is not limited to four.In the first and second embodiments described above, the first sprocket 14 may have a -shaped (minus sign-shaped) second tooth 32 bin a first shifting region 34, and the second sprocket 16 may have a -shaped (minus sign-shaped) fourth tooth 42 bin a second shifting region 44.In the second embodiment described above, an example has been shown in which the additional portion of the first tooth 32 ais made of metal, but the additional portion may be non-metallic. For example, if the additional portion is non-metallic, this additional portion is attached to the first tooth by bonding or an integral molding process. In this case, the noise caused during pedaling by contact between the chain and the sprocket teeth can be reduced.At least one of the first tooth 32 a / 132 aor the second tooth 32 b / 132 bof the bicycle sprocket of the present invention may preferably include a plated layer.For example, when the first tooth 32 a / 132 aand the second tooth 32 b / 132 bare made of aluminum, the plated layer is preferably a nickel plated layer for the purpose of abrasion resistance. Further, when the first tooth 32 a / 132 aand the second tooth 32 b / 132 bare made of iron, the plated layer is preferably a nickel and chromium plated layer for rust resistance.However, when the first tooth 32 a / 132 aand the second tooth 32 b / 132 bare made of iron, the first tooth 32 a / 132 aand the second tooth 32 b / 132 bmay preferably have an electrodeposited coating layer for the purpose of rust resistance and coloring.In the first and second embodiments described above, an example has been shown in which the first sprocket 14 is formed to form a synthetic resin first sprocket body 30, a first annular portion 31, and a metal first tooth portion 32 b.Alternatively, the first sprocket 14 may be formed of metal, and the first sprocket body 30, the first annular portion 31, and the first tooth portion 32 bmay be integrally formed. In this case, the first sprocket body 30, the first annular portion 31, and the first tooth portion 32 bare formed of metal such as aluminum, titanium, or iron / stainless steel.An example of a first sprocket 314 thus formed is shown in FIG. 11. The configuration in FIG. 11 is substantially the same as the above-described first and second embodiments, and the corresponding configurations are given the same reference numerals as in the first embodiment.Instead of the first sprocket 14 / 114 of the above-described first and second embodiments, a first sprocket 214 may be formed as shown in FIGS. 12A and 12B. However, in FIGS. 12A and 12B, the configurations that are substantially the same as the above-described first and second embodiments are denoted by the same reference numerals as the first embodiment.In the first sprocket 214, a first through hole 130 ais provided on a first sprocket body 30. Further, a second through hole 130 bis provided at a first annular portion 31. An annular member 130 csuch as an underlay disk is disposed in the first through hole 130 a. Specifically, the first sprocket body 30 is integrally formed with the first annular portion 31 and the ring member 130 csuch that the inner circumferential surface of the ring member 130 cis substantially flush with the inner circumferential surface of the second through hole 130 b.When the first sprocket 214 is formed in this manner, a first fastening bolt 26 is inserted into each ring member 130 c, each second through hole 130 b, and each first fastening portion 24 aand screwed onto a nut member (not shown). Thus, the first sprocket body 30 is fixed to the sprocket attachment arm 24.In the first and second embodiments described above, an example has been shown in which the second tooth 32 bof the first sprocket 14 is formed together with the first recess 32 eby press working such as forging. Instead, as shown in FIGS. 13A-13D, the second tooth 32 bmay be formed by press working (such as forging) and a cutting process. In FIGS. 13A-13D, each step is schematically illustrated for ease of description.In this case, the second tooth 32 bis formed by a first pressing step (see FIG. 13B ), a cutting step (see FIG. 13C ) after the first pressing step, and a second pressing step (see FIG. 13D ) after the cutting step.As shown in FIG. 13D, the second tooth 32 bhas a fifth surface 52 a(an example of a first surface) and a sixth surface 52 b(an example of a first surface). For example, the fifth surface 52 ais formed on the second tooth 32 aon the first side surface 14 aside (see FIG. 2 ) of the first sprocket 14. The sixth surface 52 bis a surface located on the opposite side of the fifth surface 52 ain an axis direction parallel to the rotational center axis X. For example, the sixth surface 52 bis formed on the second tooth 32 bon the second side surface 14 bside (see FIG. 4 ) of the first sprocket 14.Specifically, as shown in FIG. 13A, at the initial stage, the surface on which the fifth surface 52 aof the second tooth 32 bis formed (first pressing portion 152 adescribed below) and the surface on which the sixth surface 52 bis formed (second pressing portion 152 cdescribed below) are formed on substantially the same surface as the outer surface of the first annular portion 31 of the first sprocket 14.A first pressing step is a step of pressing the fifth surface side 52 aof the second tooth 32 b. As shown in FIG. 13B, in the first pressing step with the first annular portion 31 in a fixed state, the fifth surface 52 aof the second tooth 32 bis pressed by a pressing member A of a pressing device (not shown).Here, the first pressing portion 152 awhere the pressing member A applies pressure is the portion where the second tooth 32 band the first recess 32 eare formed. In this way, when the pressing member A presses the first pressing portion 152 a, the fifth surface 52 aof the second tooth portion 32 bis formed, and a portion on the sixth surface side 52 bsubstantially located on the opposite side of the first pressing portion 152 aprotrudes. Hereinafter, this portion is referred to as the protrusion 152 b.The cutting step is a step of cutting the protrusion 152 bprotruding in the axis direction due to the first pressing step on the sixth surface 52 bside of the second tooth 32 b. As shown in FIG. 13C, in the cutting step, the protrusion 152 bformed on the sixth surface 52 bis cut with a cutter B. Specifically, the protrusion 152 bis cut with the cutting device B such that the area remaining after the cutting is substantially the same as the outer surface of the first annular portion 31.A second pressing step is a step of pressing the sixth surface side 52 bof the second tooth 32 b. As shown in FIG. 13D, in the second pressing step, in a state where a mold D for forming the outer shape of the second tooth 32 bis adjacent to the first pressing portion 152 a, the sixth surface side 52 bof the second tooth 32 bis pressed by a pressing member C of the pressing device.Here, the second pressing portion 152 cwhere the pressing member C applies pressure is the portion where the second tooth 32 band the first recess 32 eare formed. In this way, when the pressing member C presses the second pressing portion 152 c, the sixth surface 52 bof the second tooth portion 32 bis formed. Further, the tooth edge 52 cof the second tooth portion 32 bas well as the fifth surface 52 aand the sixth surface 52 bare formed.As described above, the second tooth 32 bmay be formed using the first pressing step, the cutting step, and the second pressing step. However, after the second tooth 32 bis formed in the above manner, a polishing step for adjusting the shape of the second tooth 32 band a plating step (preferably, a nickel plating method) for improving the abrasion resistance of the second tooth 32 bmay be optionally added.Here, an example has been shown in which the second tooth 32 bis formed by press working and a cutting process, but the fourth tooth 42 bof the second sprocket 16 may also be formed in the same manner.In the first and second embodiments and the other embodiments described above, front sprockets 14 and 16 have been shown as examples of a bicycle sprocket, but the present invention is not limited thereto. The present invention can also be applied to a rear sprocket.The present invention can be applied to bicycle sprockets and bicycle sprocket assemblies over a wide range.REFERENCE NUMERALS2 Chain 2 aout link plate 2 binner link plate 2 crail 10, 110 bicycle crank linkage 12, 112 crank arm 14, 114, 214, 314 first sprocket 14 afirst side surface 14 bsecond side surface 16, 116 second sprocket 16 athird side surface 16 b fourth side surface 19 crankshaft 20 sprocket attachment portion 20 afront surface 20 bback surface 22 arm portion 22 a pedal attachment portion 22 bcoupling hole 24 attachment arm 24 afirst attachment portion 24 bsecond attachment portion 26 first attachment screw 28 second attachment screw 30 first sprocket body 30 afirst fixing portion 31 first annular portion 32 a plurality of teeth 32 a, 132 a, 232 a, 332 afirst tooth 32 a 1, 32 a 2first gear shift tooth 32 b, 132 b, 232 b, 332 bsecond tooth 32 cfirst ratchet tooth 32 dfirst guide surface 32 efirst recess 34 first ratchet region 36 afirst protrusion 36 bsecond protrusion 38 stepped portion 40 second sprocket body 40 asecond fixing portion 41 second annular portion 42 multiple teeth 42 a, 142 a, 342 athird tooth 42 b, 342 b, fourth tooth 42 c, second ratchet tooth 42 e, second recess 44 second ratchet region 52 a, first surface 52 b, second surface 52 c, tooth edge 130 a, first through hole 130 b, second through hole 130 c, ring member 132 ab, first main body portion 132 c, first additional portion 142 b, second main body portion 142 c, second additional portion 152 a, first pressing portion 152 b, protrusion 152 c, second pressing portion 233, driving surface 233 a, driving surface extension portion 234 non-driving surface 234 a, non-driving surface extension portion 352 a, first surface 352 b, second surface 352 c, third surface 352 d, driving surface 352 e, non-driving surface 352 f, distal end surface 353 inclined portion 353 a, first inclined surface 353 b, second inclined surface 353 c, third inclined surface 353 d, fourth inclined surface A, c Pressing member B Cutting device D Die CL Straight line CP Contact point L 1 First axis distance L 2 Second axis distance L 3 First axial contact width L 4 Second axial contact width R Forward rotation direction W 1 First maximum axis width W 2 Second maximum axis width W 3 Third maximum axis width W 4 Fourth maximum axis width X, Y Rotation center axis

Claims

A bicycle sprocket (14) having a rotational center axis (X) and comprising a first tooth (332a) having a first axial chain engagement width (W1) less than a first axis distance (L1) of an outer link plate (2a) and greater than a second axis distance (L2) of an inner link plate (2b) coupled to the outer link plate (2a), and a second tooth (332b) having a second axial chain engagement width (W2) less than the second axis distance (L2), wherein the first tooth (332a) comprises an inclined portion (353) for preventing excessive interference with the inner link plate (2b), and the first tooth (332a) further comprises a first surface (352a), a second surface (352b) and a third surface (352c), which extends in the circumferential direction between the first surface (352a) and the second surface (352b) in the axis direction, and the inclined portion (353) includes a first chamfered surface (353a) formed to extend from the first surface (352a) to the third surface (352c) on the driving side, a second chamfered surface (353b) formed to extend from the second surface (352b) to the third surface (352c) on the driving side, a third chamfered surface (353c) formed to extend from the first surface (352a) to the third surface (352c) on the non-driving side, and a fourth chamfered surface (353d) formed so as to extend in the direction of the axis direction, having it extending from the second surface (352b) to the third surface (352c) on the non-driving side.The bicycle sprocket (14) according to claim 1, wherein a first axial contact width (L3) at which a driving surface of the first tooth (332a) comes into contact with a chain roller (2c) is formed to have substantially the same length as the second axial contact width (L4) at which a driving surface of the second tooth (332b) comes into contact with a chain roller (2c).The bicycle sprocket (14) according to claim 1 or 2, wherein at least one of the first tooth (32a) or the second tooth (32b) comprises a plated layer.The bicycle sprocket (14) according to claim 3, wherein the first tooth (32a) and the second tooth (32b) are made of aluminum, and the plated layer is a nickel plated layer.The bicycle sprocket (14) according to claim 3, wherein the first tooth (32a) and the second tooth (32b) are made of iron, and the plated layer is a nickel and chromium plated layer.A bicycle sprocket assembly comprising the bicycle sprocket (14) according to any preceding claim.The bicycle sprocket assembly according to claim 6, wherein the sprocket (14) is a single front sprocket.The bicycle sprocket assembly according to claim 7, wherein the sprocket (14) is movable along the rotational center axis (X).The bicycle sprocket assembly according to any one of claims 6 to 8, wherein the sprocket (14) includes a plurality of front sprockets.The bicycle sprocket assembly according to claim 6, wherein the sprocket (14) is a rear sprocket.

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