Bicycle front sprocket, bicycle crank assembly, and bicycle drive train

A bicycle front sprocket comprises a sprocket body and at least one sprocket tooth. The sprocket body includes a crank arm mounting portion including a first mounting axial surface facing toward an axial bicycle-center plane in an axial direction in a state where the bicycle front sprocket is mounted to the bicycle frame. The at least one sprocket tooth has a first chain-engagement axial surface facing toward the axial bicycle-center plane in the axial direction in a state where the bicycle front sprocket is mounted to the bicycle frame. The first chain-engagement axial surface is offset from the first mounting axial surface toward the axial bicycle-center plane in the axial direction. An axial distance is defined from the first mounting axial surface to the first chain-engagement axial surface in the axial direction and is equal to or larger than 6 mm.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a bicycle front sprocket, a bicycle crank assembly, and a bicycle drive train.

Discussion of the Background

Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One bicycle component that has been extensively redesigned is a drive train.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a bicycle front sprocket comprises a sprocket body and at least one sprocket tooth. The sprocket body includes a crank arm mounting portion to be mounted to a bicycle crank arm. The crank arm mounting portion includes a first mounting axial surface facing toward an axial bicycle-center plane in an axial direction parallel to a rotational center axis of the bicycle front sprocket in a state where the bicycle front sprocket is mounted to the bicycle frame. The axial bicycle-center plane is defined to bisect a bicycle frame in the axial direction. The at least one sprocket tooth has a first chain-engagement axial surface facing toward the axial bicycle-center plane in the axial direction in a state where the bicycle front sprocket is mounted to the bicycle frame. The first chain-engagement axial surface is offset from the first mounting axial surface toward the axial bicycle-center plane in the axial direction. An axial distance is defined from the first mounting axial surface to the first chain-engagement axial surface in the axial direction, the axial distance being equal to or larger than 6 mm.

With the bicycle front sprocket according to the first aspect, it is possible to reduce an inclination of the bicycle chain extending between the bicycle front sprocket and a rear low-gear sprocket relative to the axial bicycle-center plane. This can improve chain-driving performance of the bicycle front sprocket.

In accordance with a second aspect of the present invention, the bicycle front sprocket according to the first aspect is configured so that the axial distance is equal to or smaller than 22.5 mm.

With the bicycle front sprocket according to the second aspect, it is possible to further reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear low-gear sprocket relative to the axial bicycle-center plane. This can further improve the chain-driving performance of the bicycle front sprocket.

In accordance with a third aspect of the present invention, the bicycle front sprocket according to the second aspect is configured so that the axial distance is equal to or smaller than 11 mm.

With the bicycle front sprocket according to the third aspect, it is possible to reduce an inclination of the bicycle chain extending between the bicycle front sprocket and a rear top-gear sprocket relative to the axial bicycle-center plane. This can further improve the chain-driving performance of the bicycle front sprocket.

In accordance with a fourth aspect of the present invention, the bicycle front sprocket according to the first aspect is configured so that the axial distance is equal to or smaller than 9.5 mm and is equal to or larger than 8 mm.

With the bicycle front sprocket according to the fourth aspect, it is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear low-gear sprocket relative to the axial bicycle-center plane. It is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear top-gear sprocket relative to the axial bicycle-center plane. Furthermore, it is possible to reduce interference between the bicycle chain and the bicycle frame.

In accordance with a fifth aspect of the present invention, the bicycle front sprocket according to any one of the first to fourth aspects is configured so that the at least one sprocket tooth includes at least one first tooth and at least one second tooth. The at least one first tooth has a first chain engaging width defined in the axial direction. The at least one second tooth has a second chain engaging width defined in the axial direction. The second chain engaging width is smaller than the first chain engaging width.

With the bicycle front sprocket according to the fifth aspect, it is possible to improve chain-holding performance of the bicycle front sprocket.

In accordance with a sixth aspect of the present invention, the bicycle front sprocket according to the fifth aspect is configured so that the at least one first tooth has the first chain-engagement axial surface.

With the bicycle front sprocket according to the sixth aspect, it is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and a rear low-gear sprocket relative to the axial bicycle-center plane. This can improve chain-driving performance of the bicycle front sprocket.

In accordance with a seventh aspect of the present invention, the bicycle front sprocket according to the fifth or sixth aspects is configured so that the axial distance is equal to or larger than three times of the second chain engaging width.

With the bicycle front sprocket according to the seventh aspect, it is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and a rear low-gear sprocket relative to the axial bicycle-center plane. This can improve chain-driving performance of the bicycle front sprocket.

In accordance with an eighth aspect of the present invention, the bicycle front sprocket according to any one of the fifth to seventh aspects is configured so that the first chain engaging width is larger than an inner link space defined between an opposed pair of inner link plates of a bicycle chain and is smaller than an outer link space defined between an opposed pair of outer link plates of the bicycle chain. The second chain engaging width is smaller than the inner link space.

With the bicycle front sprocket according to the eighth aspect, it is possible to further improve the chain-holding function of the bicycle front sprocket.

In accordance with a ninth aspect of the present invention, the bicycle front sprocket according to any one of the first to eighth aspects is configured so that the sprocket body includes a radially extending portion extending from the crank arm mounting portion toward an outer periphery of the sprocket body in a radial direction perpendicular to the rotational center axis.

With the bicycle front sprocket according to the ninth aspect, it is possible to certainly transmit a rotational force from the crank arm to the bicycle front sprocket.

In accordance with a tenth aspect of the present invention, the bicycle front sprocket according to the ninth aspect is configured so that the radially extending portion includes at least four radially extending arms. The radially extending arms are spaced apart from each other in a circumferential direction defined about the rotational center axis.

With the bicycle front sprocket according to the tenth aspect, it is possible to adjust an axial position of the at least one sprocket tooth that defines a chain line of the bicycle chain relative to the bicycle crank arm by changing shapes of the radially extending arms. Accordingly, it is possible to set chain lines of the bicycle chain in accordance with the needs of the users by selectively attaching the bicycle front sprockets having different axial positions of the at least one sprocket tooth to the bicycle crank arm.

In accordance with an eleventh aspect of the present invention, the bicycle front sprocket according to any one of the first to tenth aspects is configured so that the crank arm mounting portion includes a plurality of mounting teeth configured to engage with a mounting boss of the bicycle crank arm in a state where the bicycle front sprocket is mounted to the bicycle crank arm.

With the bicycle front sprocket according to the eleventh aspect, it is possible to certainly transmit the rotational force from the crank arm to the bicycle front sprocket. Furthermore, it is possible to save total weight of coupling members coupling the bicycle front sprocket to the crank arm.

In accordance with a twelfth aspect of the present invention, the bicycle front sprocket according to any one of the first to eleventh aspects is configured so that the bicycle front sprocket is a solitary front sprocket.

With the bicycle front sprocket according to the twelfth aspect, it is possible to contribute saving of weight of the bicycle.

In accordance with a thirteenth aspect of the present invention, a bicycle crank assembly comprises a bicycle front sprocket and a bicycle crank arm. The bicycle front sprocket comprises a sprocket body and at least one sprocket tooth having an axial tooth-center plane defined to bisect a maximum axial width of the at least one sprocket tooth. The bicycle crank arm comprises an arm body and an abutment surface facing toward a bicycle bottom bracket assembly in an axial direction parallel to a rotational center axis of the bicycle front sprocket to abut against the bicycle bottom bracket assembly. The axial tooth-center plane is positioned farther from the arm body than the abutment surface in the axial direction. An axial distance is defined from the abutment surface to the axial tooth-center plane in the axial direction, the axial distance being equal to or larger than 1 mm.

With the bicycle crank assembly according to the thirteenth aspect, it is possible to reduce an inclination of the bicycle chain extending between the bicycle front sprocket and a rear low-gear sprocket relative to the axial bicycle-center plane. This can improve chain-driving performance of the bicycle front sprocket.

In accordance with a fourteenth aspect of the present invention, the bicycle crank assembly according to the thirteenth aspect is configured so that the axial distance is smaller than 5 mm.

With the bicycle crank assembly according to the fourteenth aspect, it is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear low-gear sprocket relative to the axial bicycle-center plane. Furthermore, it is possible to reduce an inclination of the bicycle chain extending between the bicycle front sprocket and a rear top-gear sprocket relative to the axial bicycle-center plane.

In accordance with a fifteenth aspect of the present invention, the bicycle crank assembly according to the thirteenth aspect is configured so that the axial distance is equal to or larger than 3 mm and is equal to or smaller than 4 mm.

With the bicycle crank assembly according to the fifteenth aspect, it is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear low-gear sprocket relative to the axial bicycle-center plane. It is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear top-gear sprocket relative to the axial bicycle-center plane. Furthermore, it is possible to reduce interference between the bicycle chain and the bicycle frame.

In accordance with a sixteenth aspect of the present invention, the bicycle crank assembly according to any one of the thirteenth to fifteenth aspects is configured so that the bicycle front sprocket is a solitary front sprocket.

With the bicycle crank assembly according to the sixteenth aspect, it is possible to contribute saving of weight of the bicycle.

In accordance with a seventeenth aspect of the present invention, a bicycle drive train comprises the bicycle crank assembly according to any one of the thirteenth to sixteenth aspects and a multiple rear sprocket assembly including a plurality of bicycle rear sprockets.

With the bicycle drive train according to the seventeenth aspect, it is possible to provide a broad gear range.

In accordance with an eighteenth aspect of the present invention, the bicycle drive train according to the seventeenth aspect is configured so that the plurality of bicycle rear sprockets includes nine rear sprockets.

With the bicycle drive train according to the eighteenth aspect, it is possible to provide the broad gear range with saving weight of the bicycle drive train.

In accordance with a nineteenth aspect of the present invention, the bicycle drive train according to the seventeenth aspect is configured so that the plurality of bicycle rear sprockets includes eleven rear sprockets.

With the bicycle drive train according to the nineteenth aspect, it is possible to provide a broader gear range.

In accordance with a twentieth aspect of the present invention, the bicycle drive train according to the seventeenth aspect is configured so that the plurality of the bicycle rear sprockets includes twelve rear sprockets.

With the bicycle drive train according to the twentieth aspect, it is possible to provide a broader gear range.

In accordance with a twenty-first aspect of the present invention, a bicycle drive train comprises a bicycle crank arm assembly and a multiple rear sprocket assembly. The bicycle crank arm assembly comprises a bicycle front sprocket. The bicycle front sprocket comprises a sprocket body and at least one sprocket tooth having an axial tooth-center plane defined to bisect a maximum axial width of the at least one sprocket tooth. The multiple rear sprocket assembly is configured to be rotatably supported around a hub axle of a bicycle hub assembly. The multiple rear sprocket assembly has an axially-disposed center plane defined to face in an axial direction parallel to a rotational center axis of the multiple rear sprocket assembly. The axial tooth-center plane is axially outwardly spaced apart from the axially-disposed center plane by an axial distance equal to or smaller than 4 mm in the axial direction in a state where the multiple rear sprocket assembly is rotatably supported around the hub axle. The hub axle comprises a first axial frame abutment surface and a second axial frame abutment surface. The first axial frame abutment surface is configured to abut against a first part of a bicycle frame in the axial direction in a state where the bicycle hub assembly is mounted to the bicycle frame. The second axial frame abutment surface is configured to abut against a second part of the bicycle frame in the axial direction in the state where the bicycle hub assembly is mounted to the bicycle frame. A hub axial distance is defined between the first axial frame abutment surface and the second axial frame abutment surface in the axial direction, the hub axial distance being larger than or equal to 146 mm.

With the bicycle drive train according to the twenty-first aspect, it is possible to reduce an inclination of the bicycle chain extending between the bicycle front sprocket and a rear low-gear sprocket relative to the axial bicycle-center plane. This can improve chain-driving performance of the bicycle front sprocket in the bicycle frame to which the hub axle having high lateral rigidity is attachable.

In accordance with a twenty-second aspect of the present invention, the bicycle drive train according to the twenty-first aspect is configured so that the bicycle front sprocket is a solitary front sprocket.

With the bicycle drive train according to the twenty-second aspect, it is possible to contribute saving of weight of the bicycle.

In accordance with a twenty-third aspect of the present invention, a bicycle drive train comprises a bicycle crank arm assembly and a multiple rear sprocket assembly. The bicycle crank arm assembly comprises a bicycle front sprocket. The bicycle front sprocket comprises a front sprocket body and at least one front sprocket tooth having an axial front-tooth-center plane defined to bisect a maximum axial width of the at least one front sprocket tooth. The multiple rear sprocket assembly is configured to be rotatably supported around a hub axle. The multiple rear sprocket assembly comprises a largest rear sprocket. The largest rear sprocket comprises a rear sprocket body and at least one rear sprocket tooth having an axial rear-tooth-center plane defined to bisect a maximum axial width of the at least one rear sprocket tooth. The largest rear sprocket is positioned axially inwardly from the bicycle front sprocket in the axial direction. An axial tooth distance is defined between the axial front-tooth-center plane and the axial rear-tooth-center plane. The axial tooth distance is equal to or smaller than 22 mm in a state where the multiple rear sprocket assembly is rotatably supported around the hub axle. The hub axle comprises a first axial frame abutment surface and a second axial frame abutment surface. The first axial frame abutment surface is configured to abut against a first part of a bicycle frame in the axial direction in a state where the bicycle hub assembly is mounted to the bicycle frame. The second axial frame abutment surface is configured to abut against a second part of the bicycle frame in the axial direction in the state where the bicycle hub assembly is mounted to the bicycle frame. A hub axial distance is defined between the first axial frame abutment surface and the second axial frame abutment surface in the axial direction, the hub axial distance being larger than or equal to 146 mm.

With the bicycle drive train according to the twenty-third aspect, it is possible to reduce an inclination of the bicycle chain extending between the bicycle front sprocket and a rear low-gear sprocket relative to the axial bicycle-center plane. This can improve chain-driving performance of the bicycle front sprocket in the bicycle frame to which the hub axle having high lateral rigidity is attachable.

In accordance with a twenty-fourth aspect of the present invention, the bicycle drive train according to the twenty-third aspect is configured so that the bicycle front sprocket is a solitary front sprocket.

With the bicycle drive train according to the twenty-fourth aspect, it is possible to contribute saving of weight of the bicycle.

In accordance with a twenty-fifth aspect of the present invention, the bicycle drive train according to the twenty-third or twenty-fourth aspect is configured so that the axial tooth distance is equal to or larger than 17 mm.

With the bicycle drive train according to the twenty-fifth aspect, it is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear low-gear sprocket relative to the axial bicycle-center plane. Furthermore, it is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear top-gear sprocket relative to the axial bicycle-center plane.

In accordance with a twenty-sixth aspect of the present invention, the bicycle drive train according to the twenty-third or twenty-fourth aspect is configured so that the axial tooth distance is equal to or smaller than 19 mm.

With the bicycle drive train according to the twenty-sixth aspect, it is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear low-gear sprocket relative to the axial bicycle-center plane. It is possible to reduce the inclination of the bicycle chain extending between the bicycle front sprocket and the rear top-gear sprocket relative to the axial bicycle-center plane. Furthermore, it is possible to reduce interference between the bicycle chain and the bicycle frame.

In accordance with a twenty-seventh aspect of the present invention, a bicycle front sprocket comprises a sprocket body and at least one sprocket tooth. The sprocket body includes a crank arm mounting portion to be mounted to a bicycle crank arm. The at least one sprocket tooth has an axial tooth-center plane defined to bisect a maximum axial width of the at least one sprocket tooth. An axial distance is defined from the axial tooth-center plane to an axial bicycle-center plane defined to bisect a bicycle frame in the axial direction. The axial distance is equal to or smaller than 48 mm in a state where the bicycle front sprocket is mounted to the bicycle frame.

With the bicycle front sprocket according to the twenty-seventh aspect, it is possible to reduce an inclination of the bicycle chain extending between the bicycle front sprocket and a rear low-gear sprocket relative to the axial bicycle-center plane. This can improve chain-driving performance of the bicycle front sprocket.

DESCRIPTION OF THE EMBODIMENTS

Referring initially toFIG. 1, a bicycle drive train10in accordance with an embodiment comprises a bicycle crank assembly12and a multiple rear sprocket assembly14. The bicycle crank assembly12comprises a bicycle front sprocket16and a bicycle crank arm18. In this embodiment, the bicycle front sprocket16is a solitary front sprocket in the bicycle crank assembly12. The multiple rear sprocket assembly14includes a plurality of bicycle rear sprockets. The plurality of bicycle rear sprockets includes eleven rear sprockets SP1to SP11. The bicycle rear sprocket SP1can also be referred to as a largest rear sprocket SP1. The bicycle rear sprocket SP11can also be referred to as a smallest rear sprocket SP11. Namely, the multiple rear sprocket assembly14comprises the largest rear sprocket SP1and the smallest rear sprocket SP11. The largest rear sprocket SP1corresponds to a low-gear sprocket and has a largest outer diameter in the multiple rear sprocket assembly14. The smallest rear sprocket SP11corresponds to a top-gear sprocket and has a smallest outer diameter in the multiple rear sprocket assembly14.

A total number of each of the bicycle front sprocket16and the plurality of rear sprockets is not limited to this embodiment. As seen inFIG. 15, for example, the plurality of bicycle rear sprockets can include nine rear sprockets SP1to SP9. In a modification illustrated inFIG. 15, the bicycle rear sprocket SP9can also be referred to as a smallest rear sprocket SP9. Furthermore, as seen inFIG. 16, the plurality of the bicycle rear sprockets can include twelve rear sprockets SP1to SP12. In a modification illustrated inFIG. 16, the bicycle rear sprocket SP12can also be referred to as a smallest rear sprocket SP12.

The bicycle crank assembly12and the bicycle front sprocket16have a rotational center axis A1. The bicycle crank assembly12is rotatable about the rotational center axis A1relative to a bicycle frame BF. The bicycle crank assembly12is rotatably coupled to the bicycle frame BF by a bicycle bottom bracket assembly BB secured to the bicycle frame BF. The multiple rear sprocket assembly14has a rotational center axis A2. The multiple rear sprocket assembly14is rotatable about the rotational center axis A2relative to the bicycle frame BF. A bicycle chain BC extends between the bicycle front sprocket16and the multiple rear sprocket assembly14. The bicycle front sprocket16and the multiple rear sprocket assembly14are engaged with the bicycle chain BC to transmit a driving rotational force from the bicycle front sprocket16to the multiple rear sprocket assembly14via the bicycle chain BC.

In the present application, the following directional terms “front”, “rear”, “forward”, “rearward”, “left”, “right”, “transverse”, “upward” and “downward” as well as any other similar directional terms refer to those directions which are determined on the basis of a user (e.g., a rider) who sits on a saddle (not shown) of a bicycle with facing a handlebar (not shown). Accordingly, these terms, as utilized to describe the bicycle drive train10, the bicycle crank assembly12and the bicycle front sprocket16, should be interpreted relative to the bicycle equipped with the bicycle drive train10as used in an upright riding position on a horizontal surface.

As seen inFIGS. 2 and 3, the bicycle front sprocket16is rotatable about the rotational center axis A1in a driving rotational direction D11during pedaling. The driving rotational direction D11is defined along a circumferential direction D1defined about the rotational center axis A1. A reversing rotational direction D12is a reverse direction of the driving rotational direction D11and is defined along the circumferential direction D1.

The bicycle crank assembly12comprises a crank axle20and an additional bicycle crank arm22. The crank axle20includes a first axle end20A and a second axle end20B and extends between the first axle end20A and the second axle end20B along the rotational center axis A1. The bicycle crank arm18is secured to the first axle end20A. The additional bicycle crank arm22is secured to the second axle end20B. The bicycle crank arm18is closer to the bicycle front sprocket16than the additional bicycle crank arm22in an axial direction D2parallel to the rotational center axis A1. In this embodiment, the bicycle crank arm18is a right crank arm, and the additional bicycle crank arm22is a left crank arm. The bicycle crank arm18comprises an arm body24. The arm body24is secured to the first axle end20A and extends radially outwardly from the first axle end20A.

As seen inFIGS. 4 and 5, the bicycle crank arm18comprises a mounting boss26and an axle-attachment part28. The mounting boss26extends from the arm body24in the axial direction D2. The bicycle front sprocket16is mounted on the mounting boss26. The axle-attachment part28is provided in the arm body24and the mounting boss26. The first axle end20A is coupled to the axle-attachment part28. The axle-attachment part28includes an axle-attachment hole28A through which the first axle end20A extends. The axle-attachment part28includes a plurality of attachment teeth28B defining the axle-attachment hole28A. The first axle end20A includes a plurality of first receiving teeth20A1meshing with the plurality of attachment teeth28B. Each of the first receiving teeth20A1and the attachment teeth28B forms splines to engage with each other. As seen inFIG. 6, the arm body24is positioned relative to the first axle end20A with a stopper20C. As seen inFIG. 5, the second axle end20B includes a plurality of second receiving teeth20B1. The additional bicycle crank arm22(FIG. 3) is detachably secured to the second axle end20B with the plurality of second receiving teeth20B1and a fastener (not shown).

The term “detachably secured” or “detachably securing”, as used herein, encompasses configurations in which an element directly secured to another element by directly affixing the element to the other element while the element is detachable from the other element without substantial damage; and configurations in which the element is indirectly secured to the other element via intermediate member(s) while the element is detachable from the other element and the intermediate member(s) without substantial damage. This concept also applies to words of similar meaning, for example, “detachably attached”, “detachably joined”, “detachably connected”, “detachably coupled”, “detachably mounted”, “detachably bonded”, “detachably fixed” and their derivatives.

As seen inFIG. 6, the bicycle crank arm18comprises an abutment surface30. The abutment surface30faces toward the bicycle bottom bracket assembly BB in the axial direction D2parallel to the rotational center axis A1of the bicycle front sprocket16to abut against the bicycle bottom bracket assembly BB. The abutment surface30is provided at an axial end of the mounting boss26. Specifically the abutment surface30comprises axially inner surface of the mounting boss26. In this embodiment, the abutment surface30is in contact with the bicycle bottom bracket assembly BB in a state where the bicycle crank assembly12is mounted to the bicycle frame BF (FIG. 1) via the bicycle bottom bracket assembly BB. However, a clearance and/or another member can be provided between the abutment surface30and the bicycle bottom bracket assembly BB in the state where the bicycle crank assembly12is mounted to the bicycle frame BF (FIG. 1) via the bicycle bottom bracket assembly BB.

As seen inFIG. 5, the bicycle front sprocket16comprises a sprocket body32and at least one sprocket tooth34. The sprocket body32includes a crank arm mounting portion36to be mounted to the bicycle crank arm18. In this embodiment, the crank arm mounting portion36has an annular shape. The at least one sprocket tooth34includes a plurality of sprocket teeth34. The sprocket teeth34extend radially outwardly from the sprocket body32and are arranged in the circumferential direction D1to engage with the bicycle chain BC. A total number of the plurality of sprocket teeth34is not limited to this embodiment. The sprocket body32can also be referred to as a front sprocket body32. The at least one sprocket tooth34can also be referred to as at least one front sprocket tooth34.

As seen inFIG. 7, the sprocket body32includes a radially extending portion38extending from the crank arm mounting portion36toward an outer periphery of the sprocket body32in a radial direction perpendicular to the rotational center axis A1. The radially extending portion38includes at least four radially extending arms40. In this embodiment, a total number of the radially extending arms40is eight. However, the total number of the radially extending arms40is not limited to this embodiment.

The radially extending arms40are spaced apart from each other in the circumferential direction D1defined about the rotational center axis A1. In this embodiment, the sprocket body32includes an outer ring42provided radially outward of the crank arm mounting portion36. The sprocket teeth34extend radially outwardly from the outer ring42. The radially extending arms40radially extend between the outer ring42and the crank arm mounting portion36to couple the outer ring42to the crank arm mounting portion36. However, the shape of the radially extending portion38is not limited to this embodiment. The shape of the bicycle front sprocket16is not limited to this embodiment.

The at least one sprocket tooth34includes at least one first tooth44and at least one second tooth46. The plurality of sprocket teeth34includes first teeth44and second teeth46. The first teeth44and the second teeth46are alternatingly arranged in the circumferential direction D1. A total number of the first teeth44is equal to a total number of the second teeth46. However, the total number of the first teeth44is not limited to this embodiment. The total number of the second teeth46is not limited to this embodiment.

As seen inFIG. 8, the crank arm mounting portion36includes a first mounting axial surface48facing toward an axial bicycle-center plane CP1in the axial direction D2parallel to the rotational center axis A1of the bicycle front sprocket16in a state where the bicycle front sprocket16is mounted to the bicycle frame BF (FIG. 1). The axial bicycle-center plane CP1is defined to bisect the bicycle frame BF in the axial direction D2. The axial bicycle-center plane CP1is perpendicular to the rotational center axis A1.

As seen inFIGS. 8 and 9, the crank arm mounting portion36includes a plurality of mounting teeth50configured to engage with the mounting boss26of the bicycle crank arm18in the state where the bicycle front sprocket16is mounted to the bicycle crank arm18. In this embodiment, the first mounting axial surface48is provided on an axial end of the mounting tooth50. The first mounting axial surface48is inclined relative to the rotational center axis A1. The first mounting axial surface48can be perpendicular to the rotational center axis A1. The first mounting axial surface48can coincide with a first axial surface36B1(described later). The plurality of mounting teeth50defines a mounting opening51through which the mounting boss26extends. However, the structure of the crank arm mounting portion36is not limited to this embodiment. The crank arm mounting portion36can include another structure other than the plurality of mounting teeth50.

As seen inFIGS. 4, 5, and 8, the mounting boss26includes a cylindrical part26A and a plurality of receiving teeth26B. The receiving teeth26B are provided on an outer periphery of the cylindrical part26A to engage with the mounting teeth50. The receiving teeth26B are arranged in the circumferential direction D1. Each of the receiving teeth26B and the mounting teeth50forms splines to engage with each other.

As seen inFIG. 7, the crank arm mounting portion36includes an annular support36A and a flange part36B. The radially extending portion38(the radially extending arms40) extends radially outwardly from the annular support36A. The flange part36B has an annular shape and extends radially inwardly from the annular support36A.

As seen inFIG. 9, the plurality of mounting teeth50is provided on an inner periphery of the flange part36B. As seen inFIG. 8, the flange part36B includes a first axial surface36B1and a second axial surface36B2. The first axial surface36B1faces in the axial direction D2. The second axial surface36B2faces in the axial direction D2. The second axial surface36B2is provided on a reverse side of the first axial surface36B1in the axial direction D2. The first axial surface36B1is closer to the axial bicycle-center plane CP1than the second axial surface36B2in the state where the bicycle front sprocket is mounted to the bicycle frame BF.

As seen inFIGS. 5 and 6, the bicycle crank assembly12includes a spacer52and a lock member54. The spacer52has an annular shape and is provided between the arm body24and the crank arm mounting portion36in the axial direction D2. The spacer52is provided radially outward of the mounting boss26of the bicycle crank arm18. The lock member54has an annular shape. The lock member54is attached to the mounting boss26to secure the bicycle front sprocket16to the bicycle crank arm18in the axial direction D2.

As seen inFIG. 8, the crank arm mounting portion36and the spacer52are provided between the lock member54and the arm body24in the axial direction D2. The lock member54is provided radially outward of the mounting boss26. The lock member54includes a threaded hole54A. The mounting boss26includes an externally threaded portion26C threadedly engaged with the threaded hole of the lock member54. The arm body24includes a receiving surface24A. The crank arm mounting portion36and the spacer52are held between the lock member54and the receiving surface24A in the axial direction D2by tightening the lock member54. Axial positions of the spacer52and the bicycle front sprocket16can be switched in the axial direction D2. It is possible to adjust the axial position of the bicycle front sprocket16relative to the bicycle crank arm18by switching of the axial positions of the spacer52and the bicycle front sprocket16. Thus, it is possible to adjust a chain line of the bicycle chain BC defined by the sprocket teeth34of the bicycle front sprocket16. The spacer52(or other chain-line adjustment structures) can be omitted from the bicycle crank assembly12.

As seen inFIG. 4, the lock member54includes a plurality of lock teeth54B. The plurality of lock teeth54B radially extends and is arranged in the circumferential direction D1. The lock teeth54B form knurling. As seen inFIG. 9, the crank arm mounting portion36includes a plurality of lock grooves56provided on the first axial surface36B1. The plurality of lock grooves56forms knurling. The plurality of lock grooves56extend radially outwardly from the plurality of mounting teeth50and is arranged in the circumferential direction D1. The plurality of lock teeth54B meshes with the plurality of lock grooves56to increase a friction force occurring between the lock member54and the crank arm mounting portion36in the circumferential direction D1.

As seen inFIG. 6, the at least one sprocket tooth34has a first chain-engagement axial surface58facing toward the axial bicycle-center plane CP1in the axial direction D2in the state where the bicycle front sprocket16is mounted to the bicycle frame BF. In this embodiment, the at least one first tooth44has the first chain-engagement axial surface58. Specifically, each of the first teeth44has the first chain-engagement axial surface58. However, the first chain-engagement axial surface58can be provided at another position other than the at least one first tooth44.

As seen inFIG. 10, the at least one first tooth44has a first chain engaging width W1defined in the axial direction D2. In this embodiment, each of the first teeth44has the first chain engaging width W1. The first tooth44includes a first additional chain-engagement axial surface60provided on a reverse side of the first chain-engagement axial surface58in the axial direction D2. The first chain-engagement axial surface58is contactable with one of an opposed pair of outer link plates BC1of the bicycle chain BC. The first additional chain-engagement axial surface60is contactable with the other of the opposed pair of outer link plates BC1. The first chain engaging width W1is defined between the first chain-engagement axial surface58and the first additional chain-engagement axial surface60in the axial direction D2.

As seen inFIG. 11, the at least one second tooth46has a second chain engaging width W2defined in the axial direction D2. In this embodiment, each of the second teeth46has the second chain engaging width W2. The second tooth46includes a second chain-engagement axial surface62and a second additional chain-engagement axial surface64. The second additional chain-engagement axial surface64is provided on a reverse side of the second chain-engagement axial surface62in the axial direction D2. The second chain-engagement axial surface62is contactable with one of an opposed pair of inner link plates BC2of the bicycle chain BC. The second additional chain-engagement axial surface64is contactable with the other of the opposed pair of inner link plates BC2. The second chain engaging width W2is defined between the second chain-engagement axial surface62and the second additional chain-engagement axial surface64in the axial direction D2.

As seen inFIG. 11, the second chain engaging width W2is smaller than the first chain engaging width W1. However, the second chain engaging width W2can be equal to or larger than the first chain engaging width W1. The first chain engaging width W1is larger than an inner link space W3defined between the opposed pair of inner link plates BC2of the bicycle chain BC and is smaller than an outer link space W4defined between the opposed pair of outer link plates BC1of the bicycle chain BC. The second chain engaging width W2is smaller than the inner link space W3. However, the first chain engaging width W1can be equal to or smaller than the inner link space W3.

As seen inFIG. 6, the first chain-engagement axial surface58is offset from the first mounting axial surface48toward the axial bicycle-center plane CP1in the axial direction D2, in the state where the bicycle front sprocket16is mounted to the bicycle frame BF. An axial distance AD1is defined from the first mounting axial surface48to the first chain-engagement axial surface58in the axial direction D2. In this embodiment, the first mounting axial surface48is inclined relative to the rotational center axis A1. Thus, the axial distance AD1is a minimum axial distance defined from the first mounting axial surface48to the first chain-engagement axial surface58in the axial direction D2. The axial distance AD1can be defined from the first axial surface36B1of the flange part36B to the first chain-engagement axial surface58in the axial direction D2.

The axial distance AD1is equal to or larger than 6 mm. The axial distance AD1is equal to or larger than approximately 6 mm. The axial distance AD1is equal to or smaller than 22.5 mm. However, the axial distance AD1can be equal to or smaller than approximately 22.5 mm. Preferably, the axial distance AD1is equal to or smaller than 11 mm. However, the axial distance AD1can be equal to or smaller than approximately 11 mm. The axial distance AD1can be larger than 11 mm. More preferably, the axial distance AD1is equal to or smaller than 9.5 mm and is equal to or larger than 8 mm. In this embodiment, the axial distance AD1is 8.9 mm. However, the axial distance AD1can be equal to or smaller than approximately 9.5 mm and can be equal to or larger than approximately 8 mm. The axial distance AD1can be larger than 9.5 mm and can be smaller than 8 mm.

In this embodiment, the axial distance AD1is equal to or larger than three times of the second chain engaging width W2. However, the axial distance AD1can be equal to or larger than approximately three times of the second chain engaging width W2. The axial distance AD1can be smaller than three times of the second chain engaging width W2.

As seen inFIGS. 10 and 11, the at least one sprocket tooth34has an axial tooth-center plane CP2defined to bisect a maximum axial width of the at least one sprocket tooth34. In this embodiment, the plurality of sprocket teeth34has the axial tooth-center plane CP2defined to bisect the maximum axial width of the plurality of sprocket teeth34. The first chain engaging width W1is the maximum axial width. Thus, as seen inFIG. 10, the first teeth44have the axial tooth-center plane CP2defined to bisect the first chain engaging width of the first teeth44. Similarly, as seen inFIG. 11, the axial tooth-center plane CP2is defined to bisect the second chain engaging width W2of the second teeth46.

The axial tooth-center plane CP2can also be referred to as an axial front-tooth-center plane CP2. Thus, the at least one front sprocket tooth34has the axial front-tooth-center plane CP2defined to bisect a maximum axial width of the at least one front sprocket tooth34.

As seen inFIG. 6, the axial tooth-center plane CP2is positioned farther from the arm body24than the abutment surface30in the axial direction D2parallel to the rotational center axis A1of the bicycle front sprocket16. An axial distance AD2is defined from the abutment surface30to the axial tooth-center plane CP2in the axial direction D2. The axial distance AD2is equal to or larger than 1 mm. However, the axial distance is equal to or larger than approximately 1 mm. The axial distance AD2is smaller than 5 mm. However, the axial distance AD2can be smaller than approximately 5 mm. The axial distance AD2can be equal to or larger than 5 mm.

Preferably, the axial distance AD2is equal to or larger than 3 mm and is equal to or smaller than 4 mm. In this embodiment, the axial distance AD2is 3.5 mm. However, the axial distance AD2can be equal to or larger than approximately 3 mm and is equal to or smaller than approximately 4 mm. The axial distance AD2can be smaller than 3 mm and can be larger than 4 mm.

As seen inFIG. 12, the multiple rear sprocket assembly14is configured to be rotatably supported around a hub axle H1of a bicycle hub assembly H. The bicycle hub assembly H is detachably secured to the bicycle frame BF with a wheel securing device WS. The bicycle hub assembly H includes the hub axle H1, a hub shell H2, and a sprocket support body H3. The hub shell H2is rotatably mounted on the hub axle H1via bearing (not shown) and is coupled to a rim (not shown) with spokes H4. The sprocket support body H3is rotatably mounted on the hub axle H1via bearing (not shown). The sprocket support body H3is coupled to the hub shell H2via a ratchet structure (not shown). The multiple rear sprocket assembly14is mounted on the sprocket support body H3.

The hub axle H1comprises a first axial frame abutment surface H11and a second axial frame abutment surface H12. The first axial frame abutment surface H11is configured to abut against a first part BF1of the bicycle frame BF in the axial direction D2in a state where the bicycle hub assembly H is mounted to the bicycle frame BF. The second axial frame abutment surface H12is configured to abut against a second part BF2of the bicycle frame BF in the axial direction D2in the state where the bicycle hub assembly H is mounted to the bicycle frame BF. A hub axial distance HD1is defined between the first axial frame abutment surface H11and the second axial frame abutment surface H12in the axial direction D2. The hub axial distance HD1is larger than or equal to 146 mm. Preferably, the hub axial distance HD1is equal to or smaller than 150 mm. In the illustrated embodiment, the hub axial distance HD1is 148 mm. However, the hub axial distance HD1can be larger than or equal to approximately 146 mm. The hub axial distance HD1can be equal to or smaller than approximately 150 mm. The hub axial distance HD1can be smaller than 146 mm. The hub axial distance HD1can be larger than 150 mm.

As seen inFIG. 12, the multiple rear sprocket assembly14has an axially-disposed center plane CP3defined to face in the axial direction D2parallel to the rotational center axis A2of the multiple rear sprocket assembly14. The axially-disposed center plane CP3is perpendicular to the rotational center axis A2of the multiple rear sprocket assembly14. The largest rear sprocket SP1includes an axial innermost surface SP1A. The smallest rear sprocket SP11includes an axial outermost surface SP11A. The axially-disposed center plane CP3is defined at an axial center between the axial innermost surface SP1A and the axial outermost surface SP11A in the axial direction D2.

As seen inFIG. 13, the largest rear sprocket SP1comprises a rear sprocket body SP1B and at least one rear sprocket tooth SP1C. In this embodiment, the largest rear sprocket SP1comprises a plurality of rear sprocket teeth SP1C. The rear sprocket teeth SP1C extend radially outwardly from the rear sprocket body SP1B.

As seen inFIG. 14, at least one rear sprocket tooth SP1C has an axial rear-tooth-center plane CP4defined to bisect a maximum axial width W10of the at least one rear sprocket tooth SP1C. The sprocket teeth SP1C have the axial rear-tooth-center plane CP4defined to bisect the maximum axial width of the rear sprocket teeth SP1C. In this embodiment, the rear sprocket tooth SP1C includes the axial innermost surface SP1A and a chain engaging surface SP1D. The axial innermost surface SP1A faces in the axial direction D2. The additional chain engaging surface SP1D faces in the axial direction D2and is provided on a reverse side of the axial innermost surface SP1A. The maximum axial width W10is defined between the axial innermost surface SP1A and the chain engaging surface SP1D in the axial direction D2.

Similarly, as seen inFIG. 13, the smallest rear sprocket SP11comprises a rear sprocket body SP11B and at least one rear sprocket tooth SP11C. In this embodiment, the smallest rear sprocket SP11comprises a plurality of rear sprocket teeth SP11C. The rear sprocket teeth SP11C extend radially outwardly from the rear sprocket body SP11B.

As seen inFIG. 14, the rear sprocket tooth SP11C includes the axial outermost surface SP11A and a chain engaging surface SP11D. The axial outermost surface SP11A faces in the axial direction D2. The additional chain engaging surface SP11D faces in the axial direction D2and is provided on a reverse side of the axial outermost surface SP11A. A maximum axial width W11is defined between the axial outermost surface SP11A and the chain engaging surface SP11D in the axial direction D2.

As seen inFIG. 6, the axial tooth-center plane CP2is axially outwardly spaced apart from the axially-disposed center plane CP3by an axial distance AD3equal to or smaller than 4 mm in the axial direction D2in a state where the multiple rear sprocket assembly14is rotatably supported around the hub axle H1(FIG. 12). The axial tooth-center plane CP2can be axially outwardly spaced apart from the axially-disposed center plane CP3by the axial distance AD3equal to or smaller than approximately 4 mm in the axial direction D2in the state where the multiple rear sprocket assembly14is rotatably supported around the hub axle H1.

As seen inFIG. 1, the largest rear sprocket SP1is positioned axially inwardly from the bicycle front sprocket16in the axial direction D2. The largest rear sprocket SP1is positioned closer to the axial bicycle-center plane CP1than the bicycle front sprocket16in the axial direction D2.

As seen inFIG. 6, an axial tooth distance AD4is defined between the axial front-tooth-center plane CP2and the axial rear-tooth-center plane CP4. The axial tooth distance AD4is equal to or smaller than 22 mm in a state where the multiple rear sprocket assembly14is rotatably supported around the hub axle H1. However, the axial tooth distance AD4is equal to or smaller than approximately 22 mm in the state where the multiple rear sprocket assembly14is rotatably supported around the hub axle H1.

Preferably, the axial tooth distance AD4is equal to or larger than 17 mm. However, the axial tooth distance AD4can be equal to or larger than approximately 17 mm. The axial tooth distance AD4can be smaller than 17 mm. More preferably, the axial tooth distance AD4is equal to or smaller than 19 mm. However, the axial tooth distance AD4can be equal to or smaller than approximately 19 mm. The axial tooth distance AD4can be larger than 19 mm. More preferably, the axial tooth distance AD4is equal to or larger than 18 mm and is equal to or smaller than 19 mm. In this embodiment, the axial tooth distance AD4is 18.2 mm.

As seen inFIG. 6, an axial distance AD5is defined from the axial tooth-center plane CP2to the axial bicycle-center plane CP1defined to bisect the bicycle frame BF in the axial direction D2. The axial distance AD5is equal to or smaller than 48 mm in the state where the bicycle front sprocket16is mounted to the bicycle frame BF. Preferably, the axial distance AD5is equal to or larger than 43 mm in the state where the bicycle front sprocket16is mounted to the bicycle frame BF. More preferably, the axial distance AD5is equal to or larger than 45 mm and equal to or smaller than 47 mm in the state where the bicycle front sprocket16is mounted to the bicycle frame BF. However, the axial distance AD5can be equal to or smaller than approximately 48 mm in the state where the bicycle front sprocket16is mounted to the bicycle frame BF. The axial distance AD5can be equal to or larger than approximately 43 mm in the state where the bicycle front sprocket16is mounted to the bicycle frame BF. The axial distance AD5can be equal to or larger than approximately 45 mm and equal to or smaller than approximately 47 mm in the state where the bicycle front sprocket16is mounted to the bicycle frame BF. More preferably, the axial distance AD5is equal to or larger than 45 mm and is equal to or smaller than 47 mm. In this embodiment, the axial distance AD5is 46 mm.

The terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein.