JP2023173282A - drive train - Google Patents

Abstract

To provide a drive train with high chain holding power.SOLUTION: A first front sprocket chain engagement axial width is smaller than an outer link space defined by between a pair of opposing outer link plates of a drive chain, and is larger than an inner link space defined between a pair of opposing inner link plates of the drive chain. A second front sprocket chain engagement axial width is smaller than the inner link space. A first rear sprocket chain engagement axial width is smaller than the outer link space and larger than the inner link space. A second rear sprocket chain engagement axial width is smaller than the inner link space. The drive train does not have another front sprocket and another rear sprocket.SELECTED DRAWING: Figure 3

Description

The present invention relates to drive train technology for human powered vehicles.

Conventionally, drive trains for human-powered vehicles are known. For example, Patent Document 1 discloses a technology for a drive train that includes a front sprocket around which a drive chain is wound.

US2013/0139642A1

Patent Document 1 discloses that the sprocket teeth of a front sprocket are smaller than the outer link space defined by a pair of mutually opposing outer link plates of a drive chain, and the sprocket teeth of a front sprocket are smaller than an outer link space defined by a pair of mutually opposing inner link plates of a drive chain. A front sprocket is disclosed that has improved chain retention by including a first group of teeth larger than the inner link space defined by the inner link space and a second group of teeth smaller than the inner link space defined by the front sprocket. However, Patent Document 1 does not describe the idea of improving the chain holding force of the entire drive train including the rear sprocket.

An object of the present disclosure is to provide a drive train with excellent chain holding power.

A drive train according to a first aspect of the present disclosure is a drive train for a human-powered vehicle, and includes a single front sprocket and a single rear sprocket, and the single front sprocket has a front sprocket body. and a plurality of front sprocket teeth extending radially outward from the front sprocket body in a front sprocket radial direction with respect to the front sprocket rotation center axis of the single front sprocket, and the plurality of front sprocket teeth are The plurality of first front sprocket teeth includes a plurality of first front sprocket teeth and a plurality of second front sprocket teeth, and the plurality of first front sprocket teeth have a first front sprocket chain engagement axial width with respect to the front sprocket rotation center axis. and the plurality of second front sprocket teeth have a second front sprocket chain engagement axial width with respect to the front sprocket rotation center axis, and the first front sprocket chain engagement axial width has a drive chain engagement width. smaller than an outer link space defined between a pair of mutually opposing outer link plates of the drive chain, and larger than an inner link space defined between a mutually opposing pair of inner link plates of the drive chain; The second front sprocket chain engagement axial width is smaller than the inner link space, and the single rear sprocket has a rear sprocket diameter with respect to the rear sprocket body and the rear sprocket rotation center axis of the single rear sprocket. a plurality of rear sprocket teeth extending radially outward from the rear sprocket body in a direction, the plurality of rear sprocket teeth including a plurality of first rear sprocket teeth and a plurality of second rear sprocket teeth. The plurality of first rear sprocket teeth have a first rear sprocket chain engagement axial width with respect to the rear sprocket rotation center axis, and the plurality of second rear sprocket teeth have a first rear sprocket chain engagement axial width with respect to the rear sprocket rotation center axis. a second rear sprocket chain engagement axial width with respect to the center, the first rear sprocket chain engagement axial width being smaller than the outer link space and larger than the inner link space; A rear sprocket chain engagement axial width is less than the inner link spacing, and the drive train does not include a separate front sprocket and a separate rear sprocket.
According to the drive train of the first aspect, the chain holding force in the front sprocket can be improved by the first front sprocket chain engagement axial width and the second front sprocket chain engagement axial width. The chain holding force of the rear sprocket can be improved by the first rear sprocket chain engagement axial width and the second rear sprocket chain engagement axial width. By improving the chain holding force at the front sprocket and the chain holding force at the rear sprocket, the entire drivetrain has excellent chain holding force. Since the entire drive train has excellent chain holding power, the drive chain does not come off easily even when a human-powered vehicle drives off-road, for example.

In the drive train of the second aspect according to the first aspect, each of the plurality of front sprocket teeth has a front sprocket tooth bottom that defines a front sprocket tooth bottom axial center plane with respect to the front sprocket rotation center axis, and Each of the plurality of rear sprocket teeth has a rear sprocket tooth bottom that defines an axial center plane of the rear sprocket tooth bottom with respect to the rotation center axis of the rear sprocket, and the rear sprocket tooth bottom axial center plane defines the rear sprocket tooth bottom axial center plane with respect to the rear sprocket rotation center axis. In the axial direction of the rear sprocket with respect to the rotation center axis, it is aligned with the axial center plane of the tooth bottom of the front sprocket.
According to the drive train of the second side, the chain line is not inclined, so that the chain holding force is further excellent.

In the drive train of the third aspect according to the first aspect, each of the plurality of front sprocket teeth has a front sprocket tooth bottom that defines a front sprocket tooth bottom axial center plane with respect to the front sprocket rotation center axis, and Each of the plurality of rear sprocket teeth has a rear sprocket tooth bottom that defines an axial center plane of the rear sprocket tooth bottom with respect to the rotation center axis of the rear sprocket, and the rear sprocket tooth bottom axial center plane defines the rear sprocket tooth bottom axial center plane with respect to the rear sprocket rotation center axis. In the axial direction of the rear sprocket with respect to the rotation center axis, it is offset from the axial center plane of the bottom of the front sprocket tooth.
According to the drive train of the third aspect, it can be applied to frames of various specifications while having a necessary and sufficient chain holding force.

In the drive train of the fourth aspect according to the third aspect, the rear sprocket root axial center plane is offset with respect to the front sprocket root axial center plane by an offset distance in a range of 1 mm to 10 mm.
According to the drive train of the fourth aspect, it can be applied to frames of various specifications while having a necessary and sufficient chain holding force.

In the drive train of the fifth aspect according to the first aspect, at least one of the plurality of front sprocket teeth has a hardened layer formed by at least one of vanadizing treatment and chromizing treatment.
According to the drive train of the fifth aspect, the wear resistance of the front sprocket teeth can be improved by the hardened layer, so that the life of the drive train can be extended.

In the drive train of the sixth aspect according to the first aspect, at least one of the plurality of rear sprocket teeth has a hardened layer formed by at least one of vanadizing treatment and chromizing treatment.
According to the drive train of the sixth aspect, the wear resistance of the rear sprocket teeth can be improved by the hardened layer, so that the life of the drive train can be extended.

The drive train of the seventh aspect according to the first aspect further includes the drive chain including a plurality of outer link plates, a plurality of inner link plates, a plurality of chain rollers, and a plurality of chain pins, At least one of the link plate, the plurality of inner link plates, the plurality of chain rollers, and the plurality of chain pins has a hardened layer formed by at least one of vanadizing treatment and chromizing treatment.
According to the drive train of the seventh aspect, the wear resistance of the drive chain can be improved by the hardened layer, so that the life of the drive train can be extended.

The drive train of the eighth aspect according to the first aspect further includes the drive chain including a plurality of outer link plates and a plurality of inner link plates, and each of the plurality of inner link plates is connected to the drive chain. to one of the plurality of first front sprocket teeth or one of the plurality of first rear sprocket teeth in the engaged state of engaging the plurality of front sprocket teeth and the plurality of rear sprocket teeth. and a sprocket tooth retaining edge configured to at least partially overlap.
According to the drive train of the eighth aspect, since the first front sprocket teeth or the first rear sprocket teeth can be held by the inner link plate, the chain holding force can be effectively improved, and the drive chain is more difficult to come off.

In the drive train of the ninth aspect according to the first aspect, a difference in the number of teeth between the total number of front teeth of the single front sprocket and the total number of rear teeth of the single rear sprocket is 3 or more.
According to the drive train of the ninth aspect, since the difference in the number of teeth is 3 or more, the human-powered vehicle can run at high speed.

In the drive train according to the tenth aspect according to the ninth aspect, the difference in the number of teeth is 35 or less.
According to the drive train of the tenth aspect, since the difference in the number of teeth is 35 or less, the human-powered vehicle can easily run even on an uphill slope.

The drive train of the eleventh aspect according to the first aspect further includes an internal transmission hub assembly.
According to the drive train of the eleventh aspect, gears can be changed without moving the chain line.

In the drive train of the twelfth aspect according to the eleventh aspect, the internal transmission hub assembly includes a planetary gear mechanism.
According to the drive train of the twelfth aspect, it is possible to change gears without moving the chain line.

The drive train according to the thirteenth aspect according to the first aspect further includes a drive unit including an electric actuator configured to assist human driving force.
According to the drive train of the thirteenth aspect, the electric actuator assists the human-powered driving force, so that the rider can comfortably drive the human-powered vehicle.

According to the drive train of the present disclosure, it is possible to provide a drive train with excellent chain holding power.

FIG. 1 is a side view showing the drive train according to the first embodiment. A side view showing a front sprocket and a drive chain. (a) is a diagram showing the front sprocket and the drive chain when viewed from the direction VD1 shown in FIG. 2, and (b) is a diagram showing the front sprocket teeth when viewed from the direction VD1 shown in FIG. 2. A plan sectional view of a front sprocket and a drive chain. (a) is an enlarged side view showing a front sprocket and a drive chain, and (b) is an enlarged side view showing front sprocket teeth. A side sectional view showing a front sprocket and a drive chain. An enlarged side view showing an inner link plate and a front sprocket. A side view showing a rear sprocket and a drive chain. (a) is a diagram showing the rear sprocket and the drive chain when viewed from the direction VD2 shown in FIG. 8, and (b) is a diagram showing the rear sprocket teeth when viewed from the direction VD2 shown in FIG. 8. A plan sectional view showing a rear sprocket and a drive chain. A side sectional view showing a rear sprocket and a drive chain. (a) is a diagram showing the positional relationship between a front sprocket and a rear sprocket, and (b) is a diagram showing a chain line. (a) is a diagram showing the positional relationship between a front sprocket and a rear sprocket according to a second embodiment, and (b) is a diagram showing a chain line. FIG. 7 is a plan view showing a front sprocket according to a third embodiment.

(First embodiment)
A drive train 1 according to a first embodiment will be explained. In the following description, terms representing front and rear and left and right directions are used with reference to the directions in which the rider is seated on the seat of the human-powered vehicle. FIGS. 1 to 12 are used to explain the drive train 1 according to the first embodiment. The drive train 1 shown in FIG. 1 is provided in a human-powered vehicle.

A human-powered vehicle is a vehicle that has at least one wheel and can be driven by at least human-powered driving force. Human powered vehicles include various types of bicycles, such as mountain bikes, road bikes, city bikes, cargo bikes, hand bikes, and recumbent bikes. The number of wheels that a human-powered vehicle has is not limited. Human powered vehicles include, for example, unicycles and vehicles having two or more wheels. A human-powered vehicle is not limited to a vehicle that can be driven solely by human-powered driving force. The human-powered vehicle includes an E-bike that uses not only human-powered driving force but also the driving force of the electric actuator 51 for propulsion. E-bikes include electrically assisted bicycles whose propulsion is assisted by electric actuators 51.

The drivetrain 1 shown in FIG. 1 is configured to transmit human driving power to the wheels. In this embodiment, the drive train 1 is for a human-powered vehicle, and includes a single front sprocket 10 and a single rear sprocket 20. Drivetrain 1 further includes an internal transmission hub assembly 40. The drive train 1 further includes a drive unit 50 including an electric actuator 51 configured to assist human driving force.

An example of a drive train 1 is shown in FIG. 1 . The drivetrain 1 shown in FIG. 1 includes a single front sprocket 10, a single rear sprocket 20, a drive chain 30, an internal transmission hub assembly 40, and a drive unit 50.

The single front sprocket 10 shown in FIGS. 1 to 3 is connected to the crankshaft of a human-powered vehicle via a drive force transmission section 52 of a drive unit 50. The front sprocket 10 has a front sprocket rotation center axis CA1. The front sprocket rotation center axis CA1 coincides with the rotation center axis of the crankshaft. The front sprocket 10 is configured to rotate relative to the frame of the human-powered vehicle around the front sprocket rotation center axis CA1. In this embodiment, the front sprocket axial direction AD1 with respect to the front sprocket rotation center axis CA1 points in the left-right direction of the human-powered vehicle.

The single front sprocket 10 includes a front sprocket body 11 and a plurality of front sprocket teeth extending radially outward from the front sprocket body 11 in the front sprocket radial direction with respect to the front sprocket rotation center axis CA1 of the single front sprocket 10. 16.

The front sprocket body 11 shown in FIG. 2 is formed into an annular shape having an outer circumferential portion 12 and an inner circumferential portion 13. The front sprocket body 11 shown in FIG. The inner peripheral portion 13 has a plurality of connecting portions 13a. The plurality of connecting portions 13a are formed to protrude toward the front sprocket rotation center axis CA1. The front sprocket body 11 is connected to a driving force transmitting section 52 of the drive unit 50 via a plurality of connecting sections 13a.

The plurality of front sprocket teeth 16 are formed to protrude radially outward from the outer peripheral portion 12 of the front sprocket body 11 in the front sprocket radial direction with respect to the front sprocket rotation center axis CA1. The plurality of front sprocket teeth 16 are provided so as to be continuous in the front sprocket circumferential direction CD1. The plurality of front sprocket teeth 16 includes a plurality of first front sprocket teeth 17 and a plurality of second front sprocket teeth 18.

The first front sprocket teeth 17 and the second front sprocket teeth 18 are arranged alternately in the front sprocket circumferential direction CD1. As shown in FIG. 3(b) and FIG. 5(b), a front tooth bottom 16a is formed between the first front sprocket tooth 17 and the second front sprocket tooth 18.

The first front sprocket tooth 17 and the second front sprocket tooth 18 of this embodiment will be explained using FIGS. 2 to 6. Each of the plurality of first front sprocket teeth 17 is formed with a first front tooth tip 17a, a first front tooth connecting portion 17b, and a first front tooth axial surface 17c.

The first front tooth tip 17a shown in FIG. 3(b) and FIG. 5(b) is a portion of the first front sprocket tooth 17 that most protrudes from the outer peripheral portion 12 of the front sprocket body 11. show.

The first front tooth connecting portion 17b is formed to connect the front tooth bottom 16a and the first front tooth tip 17a. The first front tooth connecting portions 17b are formed on one side and the other side of the first front sprocket tooth 17, respectively, in the front sprocket circumferential direction CD1.

The first front tooth axial direction surface 17c is formed to face the front sprocket axial direction AD1. In this embodiment, at least a portion of the first front tooth axial surface 17c is formed on the outermost side of the first front sprocket tooth 17 in the front sprocket axial direction AD1. In this specification, the outermost portion of the first front tooth axial surface 17c is referred to as the outer end of the first front tooth axial surface 17c. The first front tooth axial surface 17c is formed on one side and the other side of the first front sprocket tooth 17 in the front sprocket axial direction AD1, respectively.

As shown in FIG. 3, the plurality of first front sprocket teeth 17 have a first front sprocket chain engagement axial width AW1 with respect to the front sprocket rotation center axis CA1. The first front sprocket chain engagement axial width AW1 indicates the width from one end of the first front sprocket tooth 17 to the other end in the front sprocket axial direction AD1. In this embodiment, the first front sprocket chain engagement axial width AW1 is the width from the outer end of one first front tooth axial surface 17c to the outer end of the other first front tooth axial surface 17c. shows.

The plurality of second front sprocket teeth 18 shown in FIG. 2 are formed in a different shape from the first front sprocket teeth 17. The plurality of second front sprocket teeth 18 are provided in the same number as the plurality of first front sprocket teeth 17. Each of the plurality of second front sprocket teeth 18 is formed with a second front tooth tip 18a, a second front tooth connecting portion 18b, and a second front tooth axial surface 18c.

The second front tooth tip 18a shown in FIG. 3(b) and FIG. 5(b) is a portion of the second front sprocket tooth 18 that most protrudes from the outer peripheral portion 12 of the front sprocket body 11. show. The distance from the second front tooth tip 18a to the front sprocket rotation center axis CA1 is shorter than the distance from the first front tooth tip 17a to the front sprocket rotation center axis CA1.

The second front tooth connecting portion 18b is formed to connect the front tooth bottom 16a and the second front tooth tip 18a. The second front tooth connecting portions 18b are formed on one side and the other side of the second front sprocket teeth 18, respectively, in the front sprocket circumferential direction CD1.

The second front tooth axial direction surface 18c is formed to face the front sprocket axial direction AD1. In this embodiment, at least a portion of the second front tooth axial surface 18c is formed on the outermost side of the second front sprocket tooth 18 in the front sprocket axial direction AD1. In this specification, the outermost portion of the second front tooth axial surface 18c is referred to as the outer end of the second front tooth axial surface 18c. The second front tooth axial surface 18c is formed on one side and the other side of the second front sprocket tooth 18 in the front sprocket axial direction AD1, respectively.

As shown in FIG. 3, the plurality of second front sprocket teeth 18 have a width AW2 in the second front sprocket chain engagement axial direction with respect to the front sprocket rotation center axis CA1. The second front sprocket chain engagement axial width AW2 indicates the width from one end of the second front sprocket tooth 18 to the other end in the front sprocket axial direction AD1. In this embodiment, the second front sprocket chain engagement axial width AW2 is the width from the outer end of one second front tooth axial surface 18c to the outer end of the other second front tooth axial surface 18c. shows.

Each of the plurality of front sprocket teeth 16 has a front sprocket tooth bottom that defines a front sprocket tooth bottom axial center plane CP1 with respect to the front sprocket rotation center axis CA1. In this embodiment, the front sprocket tooth bottom includes a front tooth bottom 16a shown in FIG. 3(b) and FIG. 5(b). The front sprocket bottom axial center plane CP1 shown in FIGS. 3 and 4 is a hypothetical plane that passes through the center of the front sprocket bottom 16a and divides the front sprocket 10 into two in the front sprocket axial direction AD1. Formed as a surface. The front sprocket tooth bottom axial center plane CP1 faces in the front sprocket axial direction AD1. In this embodiment, the front sprocket bottom axial center plane CP1 is orthogonal to the front sprocket axial direction AD1.

At least one of the plurality of front sprocket teeth 16 has a hardened layer formed by at least one of vanadizing treatment and chromizing treatment. In this embodiment, all front sprocket teeth 16 have a hardened layer. The hardened layer includes the front tooth hardened layer 16b shown in FIGS. 4 and 6.

The front tooth hardening layer 16b is formed on the front tooth bottom 16a, the first front tooth tip 17a, the first front tooth connecting portion 17b, the second front tooth tip 18a, and the second front tooth connecting portion 18b. The portion where the front tooth hardening layer 16b is formed is not limited to this embodiment. The front tooth hardened layer 16b may be formed, for example, on the first front tooth axial surface 17c. The front sprocket teeth 16 can have improved wear resistance by having the front tooth hardening layer 16b.

The single rear sprocket 20 shown in FIGS. 1 and 8 is connected to a hub axle HS of a human-powered vehicle via an internal transmission hub assembly 40. The rear sprocket 20 has a rear sprocket rotation center axis CA2. The rear sprocket rotation center axis CA2 coincides with the rotation center axis of the hub shaft HS. The rear sprocket 20 is configured to rotate relative to the frame around the rear sprocket rotation center axis CA2. In this embodiment, the rear sprocket axial direction AD2 with respect to the rear sprocket rotation center axis CA2 points in the left-right direction of the human-powered vehicle.

The single rear sprocket 20 includes a rear sprocket body 21 and a plurality of rear sprocket teeth extending radially outward from the rear sprocket body 21 in the rear sprocket radial direction with respect to the rear sprocket rotation center axis CA2 of the single rear sprocket 20. 26. The rear sprocket body 21 shown in FIG. 8 is formed into an annular shape having an outer circumferential portion 22 and an inner circumferential portion 23. The rear sprocket body 21 shown in FIG. Inner peripheral portion 23 is connected to internal transmission hub assembly 40 .

The plurality of rear sprocket teeth 26 are formed to protrude radially outward from the outer peripheral portion 22 of the rear sprocket body 21 in the rear sprocket radial direction with respect to the rear sprocket rotation center axis CA2. The plurality of rear sprocket teeth 26 are provided so as to be continuous in the rear sprocket circumferential direction CD2. The plurality of rear sprocket teeth 26 includes a plurality of first rear sprocket teeth 27 and a plurality of second rear sprocket teeth 28 .

The first rear sprocket tooth 27 shown in FIG. 9(b) and FIG. 11 is formed similarly to the first front sprocket tooth 17. The first rear sprocket tooth 27 is formed with a first rear tooth tip 27a, a first rear tooth connecting portion 27b, and a first rear tooth axial surface 27c.

The first rear tooth tip 27a is formed similarly to the first front tooth tip 17a of the first front sprocket tooth 17 shown in FIG. The first rear tooth connection portion 27b is formed similarly to the first front tooth connection portion 17b of the first front sprocket tooth 17. The first rear tooth axial surface 27c is formed similarly to the first front tooth axial surface 17c of the first front sprocket tooth 17.

As shown in FIG. 9, the plurality of first rear sprocket teeth 27 have a width AW3 in the first rear sprocket chain engagement axial direction with respect to the rear sprocket rotation center axis CA2. The first rear sprocket chain engagement axial width AW3 indicates the width from one end of the first rear sprocket tooth 27 to the other end in the rear sprocket axial direction AD2. In this embodiment, the first rear sprocket chain engagement axial width AW3 is the width from the outer end of one first rear tooth axial surface 27c to the outer end of the other first rear tooth axial surface 27c. shows.

The second rear sprocket tooth 28 shown in FIG. 9(b) and FIG. 11 is formed similarly to the second front sprocket tooth 18. The second rear sprocket tooth 28 is formed with a second rear tooth tip 28a, a second rear tooth connecting portion 28b, and a second rear tooth axial surface 28c.

The second rear tooth tip 28a is formed similarly to the second front tooth tip 18a of the second front sprocket tooth 18 shown in FIG. The second rear tooth connection portion 28b is formed similarly to the second front tooth connection portion 18b of the second front sprocket tooth 18. The second rear tooth axial surface 28c is formed similarly to the second front tooth axial surface 18c of the second front sprocket tooth 18.

As shown in FIG. 9, the plurality of second rear sprocket teeth 28 have a width AW4 in the second rear sprocket chain engagement axial direction with respect to the rear sprocket rotation center axis CA2. The second rear sprocket chain engagement axial width AW4 indicates the width from one end of the second rear sprocket tooth 28 to the other end in the rear sprocket axial direction AD2. In this embodiment, the second rear sprocket chain engagement axial width AW4 is the width from the outer end of one second rear tooth axial surface 28c to the outer end of the other second rear tooth axial surface 28c. shows.

Each of the plurality of rear sprocket teeth 26 has a rear sprocket tooth bottom that defines a rear sprocket tooth bottom axial center plane CP2 with respect to the rear sprocket rotation center axis CA2. In this embodiment, the rear sprocket tooth bottom includes a rear tooth bottom 26a shown in FIG. 9(b) and FIG. 11. The rear sprocket tooth bottom axial direction central plane CP2 shown in FIGS. 9 and 10 is an imaginary plane that passes through the center of the rear tooth bottom 26a and divides the rear sprocket 20 into two in the rear sprocket axial direction AD2. Formed as a surface. The rear sprocket tooth bottom axial direction center plane CP2 faces in the rear sprocket axial direction AD2. In the present embodiment, the rear sprocket bottom axial center plane CP2 is orthogonal to the rear sprocket axial direction AD2.

As shown in FIG. 12, the rear sprocket tooth bottom axial center surface CP2 is aligned with the front sprocket tooth bottom axial center surface CP1 in the rear sprocket axial direction AD2 with respect to the rear sprocket rotation center axis CA2. By aligning the rear sprocket tooth bottom axial center plane CP2 with the front sprocket tooth bottom axial center plane CP1, in this embodiment, the plurality of rear sprocket teeth 26 can be connected to the drive train from the front direction or the rear direction. 1, they are arranged so as to overlap the plurality of front sprocket teeth 16 as a whole.

As shown in FIG. 12(b), a chain line L1 indicating the trajectory of the drive chain 30 is formed in a straight line extending parallel to the front-rear direction when viewed from above. The front sprocket tooth bottom axial center surface CP1 and the rear sprocket tooth bottom axial center surface CP2 shown in FIG. 12(a) extend parallel to the chain line L1.

At least one of the plurality of rear sprocket teeth 26 has a hardened layer formed by at least one of vanadizing treatment and chromizing treatment. In this embodiment, all rear sprocket teeth 26 have a hardened layer. The hardened layer includes the rear tooth hardened layer 26b shown in FIGS. 10 and 11. The rear tooth hardening layer 26b is formed in the same manner as the front tooth hardening layer 16b. The rear sprocket teeth 26 can have improved wear resistance by having the rear tooth hardened layer 26b.

As shown in FIG. 1, in this embodiment, the total number of rear sprocket teeth 26 is less than the total number of front sprocket teeth 16. In this specification, the total number of rear sprocket teeth 26 may be referred to as the total number of rear teeth. In this specification, the total number of front sprocket teeth 16 may be referred to as the total number of front teeth.

In this embodiment, the difference in the number of teeth between the total number of front teeth of the single front sprocket 10 and the total number of rear teeth of the single rear sprocket 20 is 3 or more. The difference in the number of teeth in FIG. 1 is 13. The difference in the number of teeth is not limited to 13. The difference in the number of teeth may be 14 or more or 12 or less. By having a difference in the number of teeth of 3 or more, the ratio of the total number of rear teeth to the total number of front teeth is prevented from becoming too low, and the human-powered vehicle can run at high speed.

In this embodiment, the difference in the number of teeth is 35 or less. By setting the difference in the number of teeth to 35 or less, the ratio of the total number of rear teeth to the total number of front teeth is prevented from becoming too large, and the human-powered vehicle can easily run even on an uphill slope.

The drive chain 30 shown in FIG. 1 is configured to transmit driving force from a single front sprocket 10 to a single rear sprocket 20. As shown in FIGS. 2, 3(a), and 5(a), the drive chain 30 includes a plurality of outer link plates 31, a plurality of inner link plates 32, a plurality of chain rollers 33, A plurality of chain pins 34 are included.

A pair of outer link plates 31 are provided so as to face each other. A plurality of the pair of outer link plates 31 are arranged in the chain drive direction DD. As shown in FIGS. 3 and 5, a pair of outer link plates 31 located around a single front sprocket 10 engages a first front sprocket tooth 17 of front sprocket teeth 16. As shown in FIGS. As shown in FIG. 9, a pair of outer link plates 31 located around the single rear sprocket 20 engage with the first rear sprocket tooth 27 of the rear sprocket tooth 26. As shown in FIG. Each of the plurality of outer link plates 31 is formed with a first outer surface 31a, a second outer surface 31b, and an outer link hole 31c.

As shown in FIG. 3, the first outer surface 31a faces the axial center plane CP1 of the front sprocket tooth bottom. The second outer surface 31b faces in the opposite direction to the first outer surface 31a. As shown in FIGS. 4 to 6, the outer link hole 31c is provided so as to penetrate the outer link plate 31 along the thickness direction of the outer link plate 31. Two outer link holes 31c are provided in one outer link plate 31 at intervals in the chain drive direction DD.

A pair of inner link plates 32 are provided so as to face each other. A plurality of the pair of inner link plates 32 are arranged in the chain drive direction DD. The pair of inner link plates 32 are arranged inside the pair of outer link plates 31. The pair of inner link plates 32 are offset in the chain drive direction DD with respect to the pair of outer link plates 31.

As shown in FIGS. 3 and 5, a pair of inner link plates 32 located around the single front sprocket 10 engage a second front sprocket tooth 18 of the front sprocket teeth 16. As shown in FIGS. As shown in FIG. 9, a pair of inner link plates 32 located around a single rear sprocket 20 engages a second rear sprocket tooth 28 of rear sprocket teeth 26. As shown in FIG.

In an engaged state in which the drive chain 30 engages the plurality of front sprocket teeth 16 and the plurality of rear sprocket teeth 26, each of the plurality of inner link plates 32 has one of the plurality of first front sprocket teeth 17, Alternatively, the sprocket tooth retaining edge 32e is configured to at least partially overlap one of the plurality of first rear sprocket teeth 27. An example of the inner link plate 32 is shown in FIGS. 2 to 7. The plurality of inner link plates 32 shown in FIGS. 2 to 7 have a first inner surface 32a, a second inner surface 32b, an inner link hole 32c, a cylindrical portion 32d, and a sprocket tooth retaining edge 32e.

As shown in FIG. 3, the first inner surface 32a faces the axial center plane CP1 of the front sprocket tooth bottom. The second inner surface 32b faces in the opposite direction to the first inner surface 32a. As shown in FIGS. 4 to 6, the inner link hole 32c is provided so as to penetrate the inner link plate 32 along the thickness direction of the inner link plate 32. Two inner link holes 32c are provided in one inner link plate 32 at intervals in the chain drive direction DD. The inner link hole 32c overlaps with the outer link hole 31c in a side view.

The cylindrical portion 32d is formed to surround the outer link hole 31c. The cylindrical portion 32d protrudes from the second inner surface 32b toward the left and right inner sides of the pair of inner link plates 32.

The sprocket tooth retaining edges 32e shown in FIGS. 3 and 7 are formed at the ends of the inner link plate 32 in the chain drive direction DD and in the opposite direction to the chain drive direction DD, respectively. As shown in FIG. 3, the sprocket tooth retaining edge 32e overlaps the first front sprocket tooth 17 when the single front sprocket 10 is viewed from the radial direction regarding the front sprocket rotation center axis CA1. . As shown in FIG. 7, the sprocket tooth retaining edge 32e overlaps the first front sprocket tooth 17 in a side view. By overlapping the sprocket tooth retaining edge 32e with the first front sprocket tooth 17, the sprocket tooth retaining edge 32e of the inner link plate 32 can retain the first front sprocket tooth 17.

As shown in FIG. 9, the sprocket tooth retaining edge 32e overlaps the first rear sprocket tooth 27 when the single rear sprocket 20 is viewed from the radial direction regarding the rear sprocket rotation center axis CA2. . Like the first front sprocket tooth 17, the sprocket tooth retaining edge 32e overlaps the first rear sprocket tooth 27 in a side view. By overlapping the sprocket tooth holding edge 32e with the first rear sprocket tooth 27, the sprocket tooth holding edge 32e of the inner link plate 32 can hold the first rear sprocket tooth 27. The sprocket tooth retaining edge 32e may not be formed on the inner link plate 32.

The chain roller 33 shown in FIGS. 3, 4, and 6 is rotatably supported by the cylindrical portions 32d of the pair of inner link plates 32. A large number of chain rollers 33 are provided at intervals in the chain drive direction DD. When the drive chain 30 is driven, the chain roller 33 rotates in contact with the front sprocket teeth 16 and the rear sprocket teeth 26. When the chain roller 33 rotates, it slides on the first inner surface 32a of the inner link plate 32 and the cylindrical portion 32d.

The chain pin 34 shown in FIGS. 4 to 6 is formed in a cylindrical shape. The chain pin 34 is arranged with its axial direction facing in the left-right direction. The chain pin 34 is inserted into the outer link hole 31c and the inner link hole 32c, thereby connecting the pair of outer link plates 31 and the pair of inner link plates 32 such that they can rotate relative to each other. Since the inner diameter of the outer link hole 31c is smaller than the outer diameter of the chain pin 34, the chain pin 34 is fixed to the outer link hole 31c. When the drive chain 30 is driven, the outer link plate 31 and the inner link plate 32 rotate relative to each other, and the inner diameter of the inner link hole 32c is formed larger than the outer diameter of the chain pin 34. slides on the inner peripheral surface of the inner link hole 32c.

At least one of the plurality of outer link plates 31, the plurality of inner link plates 32, the plurality of chain rollers 33, and the plurality of chain pins 34 has a hardened layer formed by at least one of vanadizing treatment and chromizing treatment. has. In this embodiment, each of the plurality of outer link plates 31, the plurality of inner link plates 32, the plurality of chain rollers 33, and the plurality of chain pins 34 has a hardened layer. The hardened layer includes an outer hardened layer 31d, an inner hardened layer 32f, a roller hardened layer 33a, and a pin hardened layer 34a.

The outer hardened layer 31d shown in FIG. 4 is formed on at least one outer link plate 31. In this embodiment, the outer hardened layer 31d is formed on all the outer link plates 31. The outer hardened layer 31d is formed at a portion where the outer link plate 31 and a member different from the outer link plate 31 slide. In this embodiment, the outer hardened layer 31d is formed on the inner peripheral surface of the outer link hole 31c. The portion where the outer hardened layer 31d is formed is not limited to this embodiment.

The inner hardened layer 32f is formed on at least one inner link plate 32. In this embodiment, the inner hardened layer 32f is formed on all inner link plates 32. The inner hardened layer 32f is formed at a portion where the inner link plate 32 and a member different from the inner link plate 32 slide. In this embodiment, the inner hardened layer 32f is formed on the inner circumferential surface of the inner link hole 32c, the outer circumferential surface of the cylindrical portion 32d, and around the cylindrical portion 32d of the first inner surface 32a. The portion where the inner hardened layer 32f is formed is not limited to this embodiment.

The roller hardening layer 33a shown in FIGS. 4 and 6 is formed on at least one chain roller 33. In this embodiment, the roller hardening layer 33a is formed on all chain rollers 33. The roller hardening layer 33a is formed over the entire area of the chain roller 33. The portion where the roller hardened layer 33a is formed is not limited to this embodiment.

A pin hardening layer 34a is formed on at least one chain pin 34. In this embodiment, the pin hardening layer 34a is formed on all chain pins 34. The pin hardening layer 34a is formed on the outer peripheral surface of the chain pin 34. The portion where the pin hardened layer 34a is formed is not limited to this embodiment.

As shown in FIG. 3(a), in this embodiment, a plurality of spaces are defined by the drive chain 30. The plurality of spaces include an outer link space S1 and an inner link space S2. The outer link space S1 is defined between a pair of outer link plates 31 facing each other. In this embodiment, the outer link space S1 is formed between the first outer surface 31a of the pair of outer link plates 31, the inner link plate 32, and the chain roller 33.

The inner link space S2 is defined between a pair of inner link plates 32 facing each other. In this embodiment, the inner link space S2 is formed between the first inner surfaces 32a of the pair of inner link plates 32 and the chain roller 33.

The first front sprocket chain engagement axial width AW1 is smaller than the outer link space S1 defined between the pair of mutually opposing outer link plates 31 of the drive chain 30, and is larger than the inner link space S2 defined by between the inner link plates 32 of. The second front sprocket chain engagement axial width AW2 is smaller than the inner link space S2.

In this embodiment, the first front sprocket tooth 17 having the first front sprocket chain engagement axial width AW1 is arranged inside the outer link space S1. A second front sprocket tooth 18 having a second front sprocket chain engagement axial width AW2 is located inside the inner link space S2. By arranging the first front sprocket teeth 17 and the second front sprocket teeth 18, the gap between the single front sprocket 10 and the outer link space S1 and the inner link space S2 can be reduced. By making the gap smaller, the chain holding power of the front sprocket 10 can be improved.

The first rear sprocket chain engagement axial width AW3 shown in FIG. 9 is smaller than the outer link space S1 and larger than the inner link space S2. The second rear sprocket chain engagement axial width AW4 is smaller than the inner link space S2.

In this embodiment, the first rear sprocket tooth 27 having the first rear sprocket chain engagement axial width AW3 is arranged inside the outer link space S1. A second rear sprocket tooth 28 having a second rear sprocket chain engagement axial width AW4 is located inside the inner link space S2. By arranging the first rear sprocket teeth 27 and the second rear sprocket teeth 28, the gap between the single rear sprocket 20 and the outer link space S1 and the inner link space S2 can be reduced. By making the gap smaller, the chain holding power of the rear sprocket 20 can be improved.

In this embodiment, the drive train 1 includes a single front sprocket 10 and a single rear sprocket 20. The drive train 1 does not include a separate front sprocket and a separate rear sprocket. The drive train 1 has excellent chain holding power because the drive chain 30 is not replaced at either the front sprocket 10 or the rear sprocket 20. Due to the drive train 1 having excellent chain holding power, the drive chain 30 is difficult to come off even when the human-powered vehicle runs off-road.

The internal transmission hub assembly 40 shown in FIG. 1 is configured to change the transmission ratio of a human-powered vehicle. In this embodiment, the internal transmission hub assembly 40 is connected to a single rear sprocket 20 and is provided at the rear hub of a human-powered vehicle. The internal transmission hub assembly 40 may be provided around the crank of a human-powered vehicle. Driving force is input to the internal transmission hub assembly 40 via the rear sprocket 20. The internal transmission hub assembly 40 changes the speed of the input driving force and transmits it to the wheels of the human-powered vehicle.

Internal transmission hub assembly 40 includes a planetary gear mechanism 41 . In this embodiment, internal transmission hub assembly 40 further includes a hub shell 42 . The planetary gear mechanism 41 includes a plurality of sun gears, a plurality of planet gears, a planet gear carrier, and a ring gear. A plurality of sun gears, a plurality of planet gears, and a ring gear form a plurality of paths for transmitting power from the rear sprocket 20 to the hub shell 42. The planetary gear mechanism 41 changes the speed ratio of the human-powered vehicle by changing the path for transmitting power.

The hub shell 42 is configured to rotate relative to the frame of the human-powered vehicle around the rotation center axis of the hub shaft HS. The hub shell 42 is connected to a wheel of a human-powered vehicle. The driving force changed in speed by the planetary gear mechanism 41 is transmitted to the hub shell 42 . By transmitting the driving force to the hub shell 42, the wheels of the human-powered vehicle rotate.

The internal transmission hub assembly 40 allows the transmission ratio of a human-powered vehicle to be changed in a drivetrain 1 with a single front sprocket 10 and a single rear sprocket 20. Internal transmission hub assembly 40 may include a different mechanism than planetary gear mechanism 41. Internally variable transmission hub assembly 40 may include, for example, a continuously variable transmission mechanism.

Drive unit 50 is configured to assist in propulsion of the human powered vehicle. The drive unit 50 is provided around the crank of the human-powered vehicle. The drive unit 50 may be provided at a rear hub or a front hub of a human-powered vehicle. The drive unit 50 may be provided on both the rear hub and the front hub of the human-powered vehicle. Drive unit 50 includes an electric actuator 51 and a driving force transmission section 52.

In this embodiment, the electric actuator 51 is provided so as to transmit rotation to a power transmission path of human-powered driving force from the pedals of the human-powered vehicle to the rear wheels. In this embodiment, the electric actuator 51 is provided to transmit rotation to a power transmission path from the crankshaft of the human-powered vehicle to the single front sprocket 10. Electric actuator 51 includes an electric motor. The electric actuator 51 operates according to, for example, human power driving force. In addition to the electric actuator 51, the drive unit 50 may include a speed reducer configured to reduce the rotational speed of the rotating shaft of the electric motor.

The driving force transmission section 52 is configured to rotate relative to the frame of the human-powered vehicle around the front sprocket rotation center axis CA1 shown in FIG. 2. The driving force transmission section 52 is connected to the front sprocket body 11 of the front sprocket 10. The human drive force and the drive force of the electric actuator 51 are transmitted to the drive force transmission section 52 . The driving force transmitting unit 52 rotates when human driving force or the like is transmitted. The front sprocket 10 rotates as the driving force transmission section 52 rotates.

(Second embodiment)
A drive train 61 of a second embodiment will be explained. FIG. 13 is used to explain the drive train 1 of the second embodiment. Components that are common to the first embodiment are given the same reference numerals as those in the first embodiment, and redundant explanations will be omitted.

As shown in FIG. 13(a), the drive train 61 includes a single front sprocket 70, a single rear sprocket 80, and a drive chain 30. The front sprocket 70 is formed in the same shape as the front sprocket 10 of the first embodiment. The front sprocket tooth bottom of the front sprocket 70 defines a front sprocket tooth bottom axial center plane CP11.

The single rear sprocket 80 is formed to have the same shape as the rear sprocket 20 of the first embodiment. The rear sprocket tooth bottom of the rear sprocket 80 defines a rear sprocket tooth bottom axial center plane CP12.

In this embodiment, the rear sprocket tooth bottom axial center surface CP12 is offset from the front sprocket tooth bottom axial center surface CP11 in the rear sprocket axial direction AD2 with respect to the rear sprocket rotation center axis CA2. The rear sprocket tooth bottom axial center surface CP12 is located inside the frame of the human-powered vehicle than the front sprocket tooth bottom axial center surface CP11. The rear sprocket tooth bottom axial center surface CP12 is offset from the front sprocket tooth bottom axial center surface CP11 by an offset distance D1 ranging from 1 mm to 10 mm.

As shown in FIG. 13(b), when the rear sprocket tooth bottom axial center plane CP12 is offset from the front sprocket tooth bottom axial center plane CP11, the chain line L11 indicating the trajectory of the drive chain 30 is a flat surface. As seen, the sprocket tilts to one side in the left-right direction as it goes from the single rear sprocket 80 to the single front sprocket 70.

In the drive train 61, the front sprocket 70 and the rear sprocket 80 are formed in the same manner as in the first embodiment, and the drive chain 30 is not replaced, so that the drive train 61 has excellent chain holding power. Since the drive train 61 has excellent chain holding power, the drive chain 30 is difficult to come off even if the chain line L11 is inclined.

The rear sprocket tooth bottom axial center plane CP12 may be offset to the outside of the frame instead of to the inside of the frame with respect to the front sprocket tooth bottom axial center surface CP11. The drive train 61 in which the rear sprocket tooth bottom axial center plane CP12 is offset from the front sprocket tooth bottom axial center plane CP11 can be applied to frames of various specifications.

(Third embodiment)
A front sprocket 91 according to a third embodiment will be explained. FIG. 3 and FIG. 14 are used to explain the front sprocket 91 of the third embodiment. Configurations common to the first embodiment and the second embodiment are given the same reference numerals as those in the first embodiment and the second embodiment, and redundant explanation will be omitted.

FIG. 14 shows a single front sprocket 91 viewed from the radial direction with respect to the front sprocket rotation center axis CA1. Single front sprocket 91 includes multiple front sprocket teeth 92. The plurality of front sprocket teeth 92 includes a first front sprocket tooth 93 and a second front sprocket tooth 18 shown in FIG. The first front sprocket tooth 93 is formed to be inclined with respect to the axial center plane CP1 of the front sprocket tooth bottom. The first front sprocket tooth 93 will be explained using FIG. 14.

The first front sprocket tooth 93 includes a first end 93a and a second end 93b. The first end 93a is formed at one end in the front sprocket circumferential direction CD1. The second end 93b is formed at the other end in the front sprocket circumferential direction CD1. The second end 93b is offset from the first end 93a in the front sprocket axial direction AD1.

In this embodiment, the first front tooth center line CL1 is defined by the center portion of the first end portion 93a in the front sprocket axial direction AD1 and the center portion of the second end portion 93b in the front sprocket axial direction AD1. The first front tooth center line CL1 is formed to pass through a central portion of the first end 93a in the front sprocket axial direction AD1 and a central portion of the second end 93b in the front sprocket axial direction AD1.

The first front tooth center line CL1 is inclined with respect to the front sprocket tooth bottom axial center plane CP1 in plan view. Since the first front tooth center line CL1 is inclined with respect to the axial center plane CP1 of the front sprocket tooth bottom, the first front sprocket tooth 93 is formed to be inclined with respect to the axial center plane CP1 of the front sprocket tooth bottom. be done.

The first front sprocket tooth 93 has a first front sprocket chain engagement axial width AW11. The first front sprocket chain engagement axial width AW11 is the width of the front sprocket shaft from the first end 93a in the front sprocket axial direction AD1 to the second end 93b in the front sprocket axial direction AD1. The width along the direction AD1 is shown. The first front sprocket chain engagement axial width AW11 is longer than the first front sprocket chain engagement axial width AW1 of the first embodiment shown in FIG. The first front sprocket chain engagement axial width AW11 allows the gap between the first front sprocket teeth 93 and the outer link space S1 to be further reduced, so that the chain holding force of the front sprocket 91 can be improved.

The single front sprocket 90 may include, instead of the second front sprocket teeth 18, second front sprocket teeth that are inclined with respect to the axial center plane CP1 of the front sprocket tooth bottom.

(Modified example)
The description regarding each embodiment is an illustration of the forms that the present invention can take, and is not intended to limit the present invention. The present invention may take the form of, for example, a modification of each embodiment shown below, or a combination of at least two modifications that are not mutually contradictory.

For example, the configuration of the drive train 1 in each embodiment is an example, and the drive train 1 may include various devices not shown in each embodiment, and may not include some of the various devices shown in each embodiment. It may also be a configuration. For example, the drive train 1 may have a configuration that does not include the drive unit 50.

The various numerical values illustrated in each embodiment are not limited and may be set arbitrarily. For example, the offset distance D1 in the second embodiment may be less than 1 mm or greater than 10 mm.

The configurations illustrated in each embodiment may be combined with each other to the extent that they do not contradict each other. The rear sprocket 20 of the first embodiment may include a first rear sprocket tooth formed similarly to the first front sprocket tooth 93 of the third embodiment.

The expression "at least one" as used herein means "one or more" of the desired options. As an example, the expression "at least one" as used herein means "only one option" or "both of the two options" if there are two options. As another example, the expression "at least one" as used herein means "only one option" when there are three or more options, or "a combination of any two or more options". ” means.

DESCRIPTION OF SYMBOLS 1... Drive train, 10... Single front sprocket, 11... Front sprocket body, 16... Front sprocket tooth, 16a... Front tooth bottom, 16b, 26a, 31d, 32e, 33a, 34a... Hardened layer, 17... First Front sprocket tooth, 18... Second front sprocket tooth, 20... Single rear sprocket, 21... Rear sprocket body, 26... Rear sprocket tooth, 26a... Rear tooth bottom, 27... First rear sprocket tooth, 28... Second Rear sprocket tooth, 30... Drive chain, 31... Outer link plate, 32... Inner link plate, 32e... Sprocket tooth retaining edge, 33... Chain roller, 34... Chain pin, 40... Internal transmission hub assembly, 41... Planetary gear mechanism , 50... Drive unit, 51... Electric actuator, AW1... First front sprocket chain engagement axial width, AW2... Second front sprocket chain engagement axial width, AW3... First rear sprocket chain engagement axial width, AW4 ...Second rear sprocket chain engagement axial width, CA1...Front sprocket rotation center axis, CA2...Rear sprocket rotation center axis, CP1...Front sprocket tooth bottom axial center surface, CP2...Rear sprocket tooth bottom axial center Surface, D1...offset distance, S1...outer link space, S2...inner link space

Claims (13)

A drive train for a human-powered vehicle,
Equipped with a single front sprocket and a single rear sprocket,
The single front sprocket includes a front sprocket body, and a plurality of front sprocket teeth extending radially outward from the front sprocket body in a front sprocket radial direction with respect to the front sprocket rotation center axis of the single front sprocket. including;
The plurality of front sprocket teeth includes a plurality of first front sprocket teeth and a plurality of second front sprocket teeth,
The plurality of first front sprocket teeth have a first front sprocket chain engagement axial width with respect to the front sprocket rotation center axis,
The plurality of second front sprocket teeth have a second front sprocket chain engagement axial width with respect to the front sprocket rotation center axis,
The first front sprocket chain engagement axial width is smaller than an outer link space defined by a pair of mutually opposing outer link plates of the drive chain, and is smaller than an outer link space defined by a pair of mutually opposing inner links of the drive chain. larger than the inner link space defined by between the plates,
the second front sprocket chain engagement axial width is smaller than the inner link space;
The single rear sprocket includes a rear sprocket body, and a plurality of rear sprocket teeth extending radially outward from the rear sprocket body in a rear sprocket radial direction with respect to the rear sprocket rotation center axis of the single rear sprocket. including;
The plurality of rear sprocket teeth include a plurality of first rear sprocket teeth and a plurality of second rear sprocket teeth,
The plurality of first rear sprocket teeth have a first rear sprocket chain engagement axial width with respect to the rear sprocket rotation center axis,
The plurality of second rear sprocket teeth have a second rear sprocket chain engagement axial width with respect to the rear sprocket rotation center axis,
The first rear sprocket chain engagement axial width is smaller than the outer link space and larger than the inner link space,
the second rear sprocket chain engagement axial width is smaller than the inner link space;
The drive train does not include a separate front sprocket and a separate rear sprocket. Each of the plurality of front sprocket teeth has a front sprocket tooth bottom that defines a front sprocket tooth bottom axial center plane with respect to the front sprocket rotation center axis,
Each of the plurality of rear sprocket teeth has a rear sprocket tooth bottom that defines an axial center plane of the rear sprocket tooth bottom with respect to the rear sprocket rotation center axis,
The drive train according to claim 1 , wherein the rear sprocket root axial center plane is aligned with the front sprocket root axial center plane in an axial direction of the rear sprocket with respect to the rear sprocket rotation center axis. Each of the plurality of front sprocket teeth has a front sprocket tooth bottom that defines a front sprocket tooth bottom axial center plane with respect to the front sprocket rotation center axis,
Each of the plurality of rear sprocket teeth has a rear sprocket tooth bottom that defines an axial center plane of the rear sprocket tooth bottom with respect to the rear sprocket rotation center axis,
The drive train according to claim 1, wherein the rear sprocket tooth bottom axial center surface is offset from the front sprocket tooth bottom axial center surface in the axial direction of the rear sprocket with respect to the rear sprocket rotation center axis. 4. The drivetrain of claim 3, wherein the rear sprocket root axial center plane is offset from the front sprocket root axial center plane by an offset distance in the range of 1 mm to 10 mm. The drivetrain of claim 1 , wherein at least one of the plurality of front sprocket teeth has a hardened layer formed by at least one of a vanadizing process and a chromizing process. The drivetrain according to claim 1, wherein at least one of the plurality of rear sprocket teeth has a hardened layer formed by at least one of a vanadizing process and a chromizing process. The drive chain further includes a plurality of outer link plates, a plurality of inner link plates, a plurality of chain rollers, and a plurality of chain pins,
At least one of the plurality of outer link plates, the plurality of inner link plates, the plurality of chain rollers, and the plurality of chain pins has a hardened layer formed by at least one of vanadizing treatment and chromizing treatment. The drive train according to claim 1, having: The drive chain further includes a plurality of outer link plates and a plurality of inner link plates,
Each of the plurality of inner link plates includes one of the plurality of first front sprocket teeth in an engaged state in which the drive chain engages the plurality of front sprocket teeth and the plurality of rear sprocket teeth; The drivetrain of claim 1 , further comprising a sprocket tooth retaining edge configured to at least partially overlap one of the plurality of first rear sprocket teeth. The drive train according to claim 1, wherein a difference in the number of teeth between the total number of front teeth of the single front sprocket and the total number of rear teeth of the single rear sprocket is 3 or more. The drive train according to claim 9, wherein the tooth number difference is 35 or less. The drivetrain of claim 1 further comprising an internal transmission hub assembly. 12. The drivetrain of claim 11, wherein the internal transmission hub assembly includes a planetary gear mechanism. The drivetrain of claim 1, further comprising a drive unit including an electric actuator configured to assist human driving force.

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