TWM513838U - Chain disengagement prevention structure - Google Patents

Description

Chain shedding prevention structure

The present invention relates to a chain fall prevention structure, and more particularly to a bicycle chain fall prevention structure for preventing a chain from coming off a bicycle sprocket.

In the bicycle sprocket, when stepping on, the chain that is engaged with the sprocket may fall off from the sprocket. Especially in the front sprocket, when the chain is detached from the sprocket, the chain tends to get caught between the crank arm and the sprocket and is difficult to disengage. In order to prevent the chain from coming off the front sprocket, a chain detachment prevention protrusion that protrudes from the front sprocket toward the crank arm has been conventionally provided (for example, US Pat. No. 7,738,815, B2).

In the case of the rear sprocket, in order to prevent the chain from falling off from the rear sprocket, a chain detachment prevention pin that protrudes toward the wheel is provided in the rear sprocket close to the wheel (for example, US Pat. No. 7,931,553 B2).

In the prior art, if the gap between the front sprocket and the crank arm, Or if the gap between the rear sprocket and the spoke wire is constant, the chain can be prevented from falling off. However, the gap between the front sprocket and the crank arm, or the gap between the rear sprocket and the spoke wire, tends to vary due to specifications. When the gap is increased, the conventional chain fall prevention projection and the chain fall prevention pin may prevent the chain from coming off the sprocket.

The problem of the present invention is to provide a chain fall prevention structure that prevents the chain from coming off the sprocket even if the gap between the front sprocket and the crank arm or the gap between the rear sprocket becomes large.

The chain fall prevention structure of the present invention is provided on at least one of a crank arm having a rotation center axis and a front sprocket or a rear sprocket having a rotation center axis. The chain fall prevention structure includes a chain fall prevention member and an axial length extension member attached to the chain fall prevention member.

In the chain fall prevention structure, when the axial length extension member is attached to the chain fall prevention member, the axial length of the entire structure can be lengthened. Therefore, it is possible to provide a chain fall prevention structure that prevents the chain from coming off the sprocket even if the gap between the front sprocket and the crank arm or the gap between the rear sprocket and the rear wheel becomes large.

The axial length extension member may be detachably attached to the chain fall prevention member. In this case, since the axial length extension member can be attached and detached, the gap between the front sprocket of the bicycle and the crank arm or the gap between the rear sprocket and the rear wheel can be matched, and the axial direction can be selectively installed. Extend the component.

The axial length extension member may be screwed to the chain fall prevention member. In this case, the axial length extension member can be easily attached and detached.

The axial length extension member may have one of a male screw portion and a female screw portion. The chain fall prevention member may have the other of the male screw portion and the female screw portion.

The chain fall prevention member may have a first engagement portion. The axial length extension member may have a second engagement portion that is engaged with the first engagement portion to prevent the first engagement portion from coming off. In this case, the axial length extension member can be attached to the chain fall prevention member by an appropriate engagement structure such as elastic engagement.

The first engaging portion and the second engaging portion may be elastically engaged with one of the other. In this case, by the elastic engagement, the axial length extension member can be detachably attached to the chain fall prevention member without using a tool.

One of the first engagement portion and the second engagement portion may have one of an enlargeable portion and a narrowable portion. In this case, one of the first engagement portion and the second engagement portion can be elastically enlarged or reduced with respect to the other to be attached.

The first engaging portion may have an amplifying portion. In this case, the chain fall prevention member is elastically enlarged and attached to the axial length extension member.

The first engaging portion may have a narrowable portion. In this case, The chain fall prevention member is elastically reduced and attached to the axial length extension member.

The second engaging portion may have an amplifying portion. In this case, the axial length extension member is elastically enlarged and attached to the axial length extension member.

The second engaging portion may have a narrowable portion. In this case, the axial length extension member is elastically reduced and attached to the axial length extension member.

The enlargeable portion and the narrowable portion may have at least one slit extending in the axial direction. In this case, the expandable portion and the narrowable portion are flexibly flexed by the slit, so that the enlargeable portion and the narrowable portion can be easily enlarged and reduced.

The slits may be provided in plural at intervals in the circumferential direction. In this case, the enlargeable portion and the narrowable portion are more easily enlarged and reduced.

The axial length extension member may be attached to the chain fall prevention member by press fitting. In this case, the axial length extension member can be attached to the chain fall prevention member with a simple structure.

The axial direction length extension member may also have a vent hole. In this case, since the compressed air at the time of press-fitting can escape to the outside, the press-in operation can be smoothly performed.

The axial length extension member may be attached to the chain fall prevention member by means of adhesive bonding. In this case, the axial length extension member can be easily fixed to the chain fall prevention member.

Axial direction length extension member, mounted on chain fall prevention The outer peripheral portion of the member. In this case, the rigidity of the chain fall prevention structure can be improved.

The axial length extension member may be attached to the inner peripheral portion of the chain fall prevention member. In this case, the chain fall prevention structure can be made lighter.

The chain fall prevention member may also be provided to the front sprocket. The axial length extension member may be attached to the chain fall prevention member so that a gap extending in the axial direction between the axial length extension member and the crank arm is formed. In this case, even if the gap between the front sprocket and the crank arm becomes large, the chain can be prevented from coming off.

The chain fall prevention member may also be provided to the rear sprocket. The axial length extension member may be attached to the chain fall prevention member so that a gap extending in the axial direction is formed between the axial length extension member and the rear wheel of the bicycle. In this case, even if the gap between the rear sprocket and the bicycle rear wheel becomes large, the chain can be prevented from coming off.

The chain fall prevention member may also be provided to the crank arm. The axial length extension member may be attached to the chain fall prevention member so that a gap extending in the axial direction is formed between the axial length extension member and the front sprocket. In this case, even if the gap between the front sprocket and the crank arm becomes large, the chain can be prevented from coming off.

The chain fall prevention member may also be integrally formed on the front sprocket or the rear sprocket. In this case, the fixing work of the chain fall prevention member can be saved.

The chain fall prevention member can also be installed separately in front of the individual Sprocket or rear sprocket. In this case, the chain fall prevention members of various axial lengths can be selectively attached to the gap.

The chain fall prevention member may also be integrally formed on the crank arm. In this case, the fixing work of the chain fall prevention member can be saved.

The chain fall prevention member may also be attached to the crank arm differently. In this case, the chain fall prevention members of various axial lengths can be selectively attached to the gap.

The chain fall prevention member may also be made of metal. In this case, the strength of the chain fall prevention member can be highly maintained.

The chain fall prevention member may also be made of a non-metal. In this case, the weight reduction of the chain fall prevention member can be achieved.

The axial length extension member may also be made of a non-metal. In this case, the weight reduction of the axial length extension member can be achieved.

The axial length extension member may also be composed of a material containing a resin. In this case, the axial length extension member having a complicated structure such as an elastic engagement structure can be easily manufactured by molding the mold.

The axial length extension member may also be made of metal. In this case, the strength of the axial length extension member can be highly maintained.

The chain fall prevention member may also be provided to the front sprocket. The length in the axial direction of the axial length extension member and the crank arm that faces the chain fall prevention member in the axial direction is 2 mm or more and 3 mm or less. In this case, even if the chain fall prevention member is provided to the front sprocket, such as the shifting chain, it is possible to prevent the chain of the inner link width from falling off due to the inner link width (for example, 3.30 mm) of the standard chain. Lead chain The case where the bar is snapped into the crank arm.

The chain fall prevention member may also be provided to the crank arm. The length in the axial direction of the axial length extension member and the front sprocket facing the axial direction and the chain fall prevention member is 2 mm or more and 3 mm or less. In this case, even if the chain fall prevention member is provided to the crank arm, such as the shifting chain, it can be prevented that the chain of the inner link width is smaller than the inner link width (for example, 3.30 mm) of the standard chain. The case where the chain is snapped into the crank arm.

The chain fall prevention member may also be provided to the rear sprocket. The length in the axial direction of the axial length extension member and the rear wheel of the bicycle facing the axial direction and the chain fall prevention member is 2 mm or more and 3 mm or less. In this case, even if the chain fall prevention member is provided to the rear sprocket, such as the shifting chain, it is possible to prevent the chain of the inner link width from falling off due to the inner link width (for example, 3.30 mm) of the standard chain. Causes damage to the rear wheel of the bicycle.

According to the present invention, it is possible to provide a chain fall prevention structure which prevents the chain from coming off the sprocket even if the gap between the front sprocket and the crank arm or the gap between the rear sprocket and the rear wheel of the bicycle becomes large.

8‧‧‧Chain

12‧‧‧1st front sprocket

16b‧‧‧ crank arm

20, 120, 220, 320, 420, 520, 620, 720, 820, 920, 1020‧‧‧ chain fall prevention structure

22, 122, 222, 322, 422, 522, 622, 722, 822, 922, 1022‧‧‧ chain fall prevention members

24, 224, 324, 424, 524, 624, 724, 824, 924, 1024‧‧‧ axial length extension members

222c, 324a‧‧‧ male thread

224a, 322c‧‧‧ female thread

422b, 522b, 622b‧‧‧1st engagement

424a, 524a, 624a‧ ‧ 2nd engagement

424d, 524d, 622e‧‧ slit

424b, 524b‧‧‧ can be reduced

622c‧‧‧Amplify

A‧‧‧ gap

B‧‧‧ gap

C1, C2‧‧‧ rotating central axis

Fig. 1 is a chain fall prevention method according to the first embodiment of the present invention Front view of the constructed crank assembly for bicycles.

Fig. 2 is a side view of the bicycle crank assembly.

Fig. 3 is an enlarged cross-sectional view showing the chain fall prevention structure of the first embodiment.

Fig. 4 is a view corresponding to Fig. 3 of the first modification of the first embodiment.

Fig. 5 is a view corresponding to Fig. 3 in a second modification of the first embodiment.

Fig. 6 is a view corresponding to Fig. 3 in a third modification of the first embodiment.

Fig. 7 is a view corresponding to Fig. 3 in a fourth modification of the first embodiment.

Fig. 8 is a cross-sectional view of the fourth modification taken along the cutting line VIII of Fig. 7.

Fig. 9 is a view corresponding to Fig. 3 in a fifth modification of the first embodiment.

Fig. 10 is a view corresponding to Fig. 3 in a sixth modification of the first embodiment.

Fig. 11 is a view corresponding to Fig. 3 of the second embodiment of the present invention.

Fig. 12 is a view corresponding to the third figure in the first modification of the second embodiment.

Fig. 13 is a side view of the bicycle rear sprocket assembly using the chain fall prevention structure of the third embodiment of the present invention.

Figure 14 is a rear view of the rear sprocket with the largest number of teeth.

Fig. 15 is an enlarged cross-sectional view showing the chain fall prevention structure of the third embodiment.

Fig. 16 is a view corresponding to Fig. 15 in a first modification of the third embodiment.

<First Embodiment>

In the bicycle crank assembly 10 of the chain fall prevention structure 20 according to the first embodiment of the present invention, the first front sprocket 12, the second front sprocket 14, and the crank 16 are provided in the first and second figures. The chain fall prevention structure 20. The first front sprocket 12 has more teeth than the second front sprocket 14, and is disposed on the crank 16 side. The first front sprocket 12 and the second front sprocket 14 are made of, for example, metal.

The crank 16 has a sprocket attachment portion 16a and a crank arm 16b extending in the radial direction from the sprocket attachment portion 16a. In the present embodiment, the first front sprocket 12 and the second front sprocket 14 are attached to the sprocket attachment portion 16a. The crank arm 16b extends in the radial direction from the center of the sprocket mounting portion 16a. The crank arm 16b is disposed at a distance from the first front sprocket 12 than the conventional crank arm. A hollow crankshaft 18 is fixed to the crank arm 16b. The crank 16 is made of a metal, a synthetic resin (for example, a fiber-reinforced resin), or a combination of a metal and a synthetic resin. The first front sprocket 12 and the crank arm 16b have the same rotation center axis C1.

In the first embodiment and the second embodiment, the chain fall prevention structure is provided to prevent the chain 8 from falling between the first front sprocket 12 and the crank arm 16b from the first front sprocket 12. The chain fall prevention structure is provided on at least one of the crank arm 16b having the rotation center axis C1 and the first front sprocket 12. In the first embodiment, as shown in FIGS. 1 and 2, the chain fall prevention structure 20 is provided on the surface of the first front sprocket 12 on the side of the crank arm 16b so as to face the crank arm 16b.

In the first embodiment, as shown in FIG. 3, the chain fall prevention structure 20 includes the chain fall prevention member 22 provided in the first front sprocket 12 and the axial length extension attached to the chain fall prevention member 22. Member 24. The chain fall prevention member 22 is a metal cylindrical member that is fixed radially inward with respect to the rotation center axis C1 with respect to the rotation center axis C1 with respect to the sprocket 12a of the first front sprocket 12. The chain fall prevention member 22 has a first shaft portion 22a, a positioning portion 22b, and a second shaft portion 22c. The first shaft portion 22a is attached to the attachment hole 12b by press fitting, and the attachment hole 12b is provided in the first front sprocket 12, and the end portion of the first shaft portion 22a is expanded to prevent falling off. The positioning portion 22b is disposed between the first shaft portion 22a and the second shaft portion 22c, and positions the chain fall prevention member 22 in the axial direction with respect to the first front sprocket 12, and positions the axial length extension member 24 at Axis direction. The positioning portion 22b has a larger diameter than the first shaft portion 22a and the second shaft portion 22c. The axial length extension member 24 is attached to the second shaft portion 22c by press fitting.

The axial direction length extension member 24 is a cylindrical member made of metal. In the present embodiment, the axial length extension member 24 is attached to the chain. The outer peripheral portion of the fall prevention member 22 is removed. The axial length extension member 24 is attached to the chain fall prevention member 22 so that the gap A extending in the axial direction is formed between the axial length extension member 24 and the first front sprocket 12 . By projecting the front end of the tool into the gap A, the axial length extension member 24 can be easily detached from the chain fall prevention member 22. The axial length extension member 24 has a press-fitting hole 24a that is press-fitted into the outer peripheral surface of the second shaft portion 22c, and a small-diameter vent hole 24b that is arranged in alignment with the press-fitting hole 24a. The axial length of the press-fitting hole 24a is slightly longer than the axial length of the second shaft portion 22c. The inner diameter of the press-fitting hole 24a is slightly larger than the outer diameter of the second shaft portion 22c. The press-fitting may be performed by slightly pressing the axial length extending member 24 to the extent that it can be attached or detached by hand, or may be strongly pressed in such a manner that it cannot be easily attached or detached.

Preferably, the axial length extension member 24 is attached to the first front sprocket 12 before the first front sprocket 12 is fixed to the sprocket attachment portion 16a. When the axial length extension member 24 is attached to the chain fall prevention member 22, the gap B between the axial length extension member 24 and the inner side surface 16c of the crank arm 16b facing the first front sprocket 12 is 2 mm to 3 mm. The scope. The gap B is the distance between the distal end of the axial length extension member 24 and the inner side surface 16c of the crank arm 16b facing the distal end of the axial length extension member 24 along the center line CL of the chain fall prevention member 22. Defined.

Thereby, the gap B is made smaller than the outer width of the shift chain 8, and the chain 8 is prevented from falling off from the first front sprocket 12. Even if the gap between the first front sprocket 12 and the crank arm 16b becomes larger, by selectively mounting the axial direction The length extension member 24 can provide the chain fall prevention structure 20 which prevents the chain 8 from falling off from the 1st front sprocket 12.

<First Modification>

In the chain fall prevention structure 120 according to the first modification of the first embodiment shown in FIG. 4, the structure of the first front sprocket 112 and the chain fall prevention member 122 is different from that of the first embodiment. In the following description, the same structures as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted. For the member corresponding to the configuration of the first embodiment, the same three-digit or four-digit symbol is used for the last two-digit symbol. In the modification and the second embodiment of the first embodiment, the gap between the distal end of the chain fall prevention member and the inner side surface 16c of the crank arm 16b, or the front end of the chain fall prevention member and the first front sprocket are also included. The gap C of 12 is the same as that of the first embodiment. The gap B between the chain fall prevention structure and the crank arm 16b, or the gap B between the chain fall prevention structure and the first front sprocket 12 is the same as that of the first embodiment, and is 2 mm or more and 3 mm or less.

The chain fall prevention member 122 of the first modification is integrally formed on the first front sprocket 112. Then, the first shaft portion is not provided in the chain fall prevention member 122. Other structures, operations, and effects of the chain fall prevention structure 120 are the same as those of the first embodiment, and thus the description thereof is omitted.

<Second Modification and Third Modification>

In the second modification shown in Fig. 5, the axial length extension member 224 of the chain fall prevention structure 220 is detachably provided to the chain. The member 222 is prevented. In the third modification shown in FIG. 6, the axial length extension member 324 of the chain fall prevention structure 320 is detachably provided in the chain fall prevention member 322.

As shown in Fig. 5, the chain fall prevention member 222 has a first shaft portion 22a, a positioning portion 222b, and a male screw portion 222c. The positioning portion 222b has a longer axial length than the first embodiment. The male screw portion 222c is screwed to the axial length extension member 224. The axial direction length extension member 224 has a female screw portion 224a that is screwed to the male screw portion 222c. The axial length extension member 224 has a non-circular cross section (for example, a hexagonal shape) and can be used to lock a tool such as a wrench or a wrench.

As shown in Fig. 6, the chain fall prevention member 322 has a first shaft portion 22a, a positioning portion 322b, and a female screw portion 322c. The positioning portion 322b has a length in the axial direction that is longer than that of the first embodiment, and is a length in which the positioning portion 22b and the second shaft portion 22c of the first embodiment are added. The female screw portion 322c is screwed to the axial length extension member 324. The axial direction length extension member 324 has a male screw portion 324a that is screwed to the female screw portion 322c. The axial length extension member 324 has a non-circular cross section (for example, a hexagonal shape) and can be used to lock a tool such as a wrench or a wrench. Instead of making the cross section of the outer circumferential surface of the axial direction length extension member 224 and the axial direction length extension member 324 non-circular, a non-circular shape (for example, a hexagonal shape) that can be engaged with the shank wrench is provided on the front end surface. ) tool card hole.

Other structures, operations, and effects of the chain fall prevention structures 220 and 320 are the same as those of the first embodiment, and thus the description thereof is omitted.

<Fourth Modification, Fifth Modification, and Sixth Modification>

In the fourth to sixth modifications, the axial length extension member is detachably attached to the chain fall prevention member by elastic engagement.

In the fourth modification shown in Fig. 7, the chain fall prevention member 422 of the chain fall prevention structure 420 is made of, for example, metal. The chain fall prevention member 422 has a first shaft portion 22a, a first engagement portion 422b, and a second shaft portion 422c. The first engagement portion 422b is formed between the first shaft portion 22a and the second shaft portion 422c.

The axial length extension member 424 is made of a non-metal, and is made of, for example, a synthetic resin having elasticity. The axial length extension member 424 has a second engagement portion 424a that is engaged with the first engagement portion 422b to prevent it from coming off. The second engagement portion 424a is disposed to be fitted to the outer circumferential surface of the second shaft portion 422c. One of the first engaging portion 422b and the second engaging portion 424a is elastically engaged with the other. In the fourth modification, the second engagement portion 424a is elastically engaged with the first engagement portion 422b. One of the first engaging portion 422b and the second engaging portion 424a has one of an elastically expandable expandable portion and an elastically constrainable narrowable portion. In the fourth modification, the second engaging portion 424a has an amplifying portion 424b. The amplifying portion 424b has a projection portion 424c that is engaged with the first engagement portion 422b to prevent falling off on the inner circumferential surface of the distal end portion. The amplifying portion 424b has at least one slit 424d. In the fourth modification, as shown in FIG. 8, the slit 424d is provided in plural in the circumferential direction (for example, two to six: four in the eighth drawing).

In the chain fall prevention structure 420 of the fourth modification, the axial length extension member 424 is from the front end of the chain fall prevention member 422 When the portion is mounted and pressed toward the first front sprocket 12, the protruding portion 424c slides up to the outer peripheral surface of the second shaft portion 422c of the chain drop preventing member 422, and the second engaging portion 424a is elastically enlarged in the radial direction. When the protruding portion 424c is engaged with the first engaging portion 422b, the second engaging portion 424a is elastically restored to its original shape, and the second engaging portion 424a is fixed to the first engaging portion 422b to prevent falling off.

In the fifth modification shown in FIG. 9, the chain fall prevention member 522 of the chain fall prevention structure 520 is made of, for example, metal. The chain fall prevention member 522 has a first shaft portion 22a, a first engagement portion 522b, and a second shaft portion 522c. The first engagement portion 522b and the end portion on the first shaft portion 22a side of the second shaft portion 522c are formed in plural (for example, four) intervals in the axial direction. The first engaging portion 522b is an annular groove.

The axial direction length extension member 524 is made of, for example, a synthetic resin having elasticity. The axial length extension member 524 has a second engagement portion 524a that is engaged with any one of the plurality of first engagement portions 522b to prevent it from coming off. The second engagement portion 524a is disposed to be fitted to the outer circumferential surface of the second shaft portion 522c. One of the first engaging portion 522b and the second engaging portion 524a is elastically engaged with the other. In the fifth modification, the second engagement portion 524a is elastically engaged with the first engagement portion 522b. One of the first engagement portion 522b and the second engagement portion 524a has one of an elastically expandable expandable portion and an elastically constrainable narrowable portion. In the fifth modification, the second engaging portion 524a has an amplifying portion 524b. The amplifying portion 524b has a projection portion 524c that is engaged with any one of the plurality of first engagement portions 522b on the inner circumferential surface of the distal end portion to prevent separation. The amplifying portion 524b can be enlarged as shown in FIG. As shown in section X-X, there is at least one slit 524d. In the fifth modification, as in the fourth modification, the slits 524d are provided in plural (for example, four) intervals in the circumferential direction. In the fifth modification, the length of the gap B can be adjusted by selectively engaging the axial length extension member 524 to any of the plurality of first engagement portions 522b.

In the chain fall prevention structure 520 of the fifth modification, when the axial length extension member 524 is attached from the front end portion of the chain fall prevention member 522 and pressed toward the first front sprocket 12, the projection 524c slides up to the chain drop-off. The outer peripheral surface of the second shaft portion 522c of the member 522 is prevented, and the second engaging portion 524a is elastically enlarged in the radial direction. When the protruding portion 524c is engaged with the first engaging portion 522b on the side of the crank arm 16b, the second engaging portion 524a is elastically restored to its original shape, and the second engaging portion 524a is positioned at the first engaging portion. 522b prevents falling off. In this state, when the axial length extension member 524 is further pressed toward the first front sprocket 12, the second engagement portion 524a is engaged with the next first engagement portion 522b located on the first front sprocket 12 side. The axial length extension members are positioned to different lengths in the axial direction. In the fifth modification, the axial length extension members 524 are positioned at four positions having different lengths in the axial direction by the four first engagement portions 522b, and are prevented from coming off. In the fifth modification, the chain-elongation prevention member 520 that can selectively change the length in the axial direction is obtained by the one axial length extension member 524.

In the sixth modification shown in FIG. 10, the chain fall prevention structure 620 includes a chain fall prevention member 622 and an axial length extension member 624. The chain fall prevention member 622 is, for example, elastic. Made of resin. The chain fall prevention member 622 has a first shaft portion 22a and a first engagement portion 622b. The axial direction length extension member 624 is made of, for example, metal. The axial length extension member 624 has a second engagement portion 624a that is engaged with the first engagement portion 622b to prevent it from coming off. The second engagement portion 624a is an annular groove into which the first engagement portion 622b is fitted. The first engagement portion 622b is disposed to be fitted to the inner circumferential surface of the axial length extension member 624. One of the first engaging portion 622b and the second engaging portion 624a is elastically engaged with the other. In the sixth modification, the first engaging portion 622b is elastically engaged with the second engaging portion 624a. One of the first engaging portion 622b and the second engaging portion 624a has one of an elastically expandable expandable portion and an elastically constrainable narrowable portion. In the sixth modification, the second engagement portion 624a has a narrowable portion 622c that is elastically contractible to the first engagement portion 622b. The narrowable portion 622c has a projection portion 622d that is engaged with the second engagement portion 624a on the inner circumferential surface of the distal end portion to prevent separation. The narrowable portion 622c has at least one slit 622e as shown in the cross section Y-Y of Fig. 10. In the sixth modification, as in the fourth modification, the slits 622e are provided in plural (for example, four) intervals in the circumferential direction.

In the chain fall prevention structure 620 of the sixth modification, when the axial length extension member 624 is attached from the front end portion of the chain fall prevention member 622 and pressed toward the first front sprocket 12, the projection portion 622d is elongated by the axial length. The inner peripheral surface of the fitting recessed portion 624b of the member 624 is pressed, and the first engaging portion 622b is elastically reduced inward in the radial direction. When the protruding portion 622d is engaged with the second engaging portion 624a, the first engaging portion 622b is elastically restored to its original shape, and the second engaging portion 624a is fixed to the first engaging portion. The portion 622b prevents falling off.

Other structures, operations, and effects of the chain fall prevention structures 420, 520, and 620 are the same as those of the first embodiment, and thus the description thereof is omitted.

<Second Embodiment>

In the second embodiment, as shown in Fig. 11, the chain fall prevention structure 720 is provided to the crank arm 16b. The chain fall prevention structure 720 has a chain fall prevention member 722 and an axial length extension member 724. The chain fall prevention member 722 has substantially the same structure as that of the first embodiment, and includes a first shaft portion 22a, a positioning portion 22b, and a second shaft portion 22c. In the chain fall prevention member 22, the first shaft portion 22a is fixed to the crank arm 16b by an appropriate fixing method such as adhesion or press fitting. The axial direction length extension member 724 has substantially the same structure as that of the first embodiment, and is attached to the outer peripheral portion of the chain fall prevention member 22 . The axial length extension member 724 is attached to the chain fall prevention member 722 so that the gap A extending in the axial direction is formed between the axial length extension member 724 and the crank arm 16b. By projecting the front end of the tool into the gap A, the user can easily detach the axial length extension member 724 from the chain fall prevention member 722. The axial length extension member 724 has a press-fitting hole 24a that is press-fitted into the outer peripheral surface of the second shaft portion 22c, and a small-diameter vent hole 24b that is disposed adjacent to the press-fitting hole 24a.

Thereby, the gap B is made smaller than the outer width of the shift chain 8, and the chain 8 is prevented from falling off from the first front sprocket 12. Even if the gap between the first front sprocket 12 and the crank arm 16b becomes larger, by selectively mounting the axial direction The length extension member 724 can provide the chain fall prevention structure 20 that prevents the chain 8 from coming off the first front sprocket 12.

<First Modification of Second Embodiment>

In the chain fall prevention structure of the first modification of the second embodiment, as shown in Fig. 12, unlike the second embodiment, the chain fall prevention member 822 and the crank arm 16b are integrally formed. The axial direction length extension member 824 is made of synthetic resin. The axial direction length extension member 824 is not fixed by press fitting, but is fixed to the chain fall prevention member by adhesion. The other structure is the same as that of the second embodiment, and thus the description thereof is omitted. In the first modification of the second embodiment and the second embodiment, the structure of each modification disclosed in the first embodiment can be employed.

<Third embodiment>

In the third embodiment, as shown in Figs. 13 and 14, the chain detachment preventing structure 920 is attached to the first rear sprocket 40a instead of the first front sprocket 12. The first rear sprocket 40a and the plurality of (for example, ten) first to fourth rear sprockets 40a to 40j are disposed at positions closest to the spokes 42 of the wheel. The first rear sprocket 40a to the tenth rear sprocket 40j each have a rotation center axis C2. The first rear sprocket 40a to the tenth rear sprocket 40j are attached to the rear hub 44 that constitutes the wheel of the bicycle.

The chain fall prevention structure 920 has the same structure as that of the first embodiment as shown in Fig. 15 . However, since the gap between the first rear sprocket 40a and the spoke of the rear wheel is different from that of the first front sprocket 12 and the crank arm 16b Since the gap is formed, the axial direction length of the chain fall prevention structure 920 is different from that of the first embodiment.

The chain fall prevention structure 920 has a chain fall prevention member 922 and an axial length extension member 924. The chain drop prevention member 922 has substantially the same structure as that of the first embodiment, and has a first shaft portion 22a that is press-fitted into the first rear sprocket 40a, a positioning portion 22b, and a second shaft portion 22c. The axial direction length extension member 924 has substantially the same structure as that of the first embodiment, and is attached to the outer peripheral portion of the chain fall prevention member 922. The axial length extension member 924 is attached to the chain fall prevention member 922 so that the gap A extending in the axial direction is formed between the axial length extension member 924 and the first rear sprocket 40a. By projecting the front end of the tool into the gap A, the user can easily detach the axial length extension member 924 from the chain fall prevention member 922. The axial length extension member 924 has a press-fitting hole 24a that is press-fitted into the outer peripheral surface of the second shaft portion 22c, and a small-diameter vent hole 24b that is disposed adjacent to the press-fitting hole 24a. The gap B of the third embodiment is defined by the distance between the tip end of the axial length extension member 924 and the filament 42 facing the axial length extension member 924 along the center line CL of the chain fall prevention member 22. . The gap B is 2 mm or more and 3 mm or less, similarly to the first embodiment and the second embodiment.

Thereby, the gap B is made smaller than the outer width of the shift chain 8, and the chain 8 is prevented from falling off from the first rear sprocket 40a.

Even if the gap between the first rear sprocket 40a and the spoke wire 42 becomes large, by selectively mounting the axial direction length extending member 924, it is possible to provide protection The chain fall prevention structure 920 that the chain stop 8 is detached from the first rear sprocket 40a.

<First Modification of Third Embodiment>

In the chain fall prevention structure 1020 according to the first modification of the third embodiment, as shown in Fig. 16, unlike the third embodiment, the chain fall prevention member 1022 and the first rear sprocket 40a are integrally formed. The other structure is the same as that of the third embodiment, and thus the description thereof is omitted. In the first modification of the third embodiment and the third embodiment, the structure of each modification disclosed in the first embodiment can be employed. The gap B of the third embodiment and its modification is the tip end of the axial length extension member 924 (or 1024) along the center line CL of the chain fall prevention member 22, and the axial length extension member 924 (or 1024). The distance between the opposing filaments 42 is defined. The gap B is 2 mm or more and 3 mm or less, similarly to the first embodiment and the second embodiment. The gap C between the tip end of the chain fall prevention member 922 (or 1022) and the spoke 42 is the same as that of the first embodiment and the second embodiment.

<Other Embodiments>

The three embodiments of the present invention have been described above, and the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the invention. In particular, the plural embodiments and modifications described in the present specification can be arbitrarily combined as needed.

(a) In the above embodiment, although the chain is detached The stopper member is integrally formed or press-fitted, and the present invention is not limited thereto. It is also possible to detachably fix the chain detachment prevention member or to fix it in the axial direction.

(b) In the second and third embodiments of the first embodiment shown in FIGS. 5 and 6 , the chain fall prevention member and the axial length extension member are fixed by screwing, and the present invention does not Limited to this. It is also possible to extend the length of the male screw portion screwed to the female screw portion and attach the lock nut to the male screw portion. By fastening the lock nut to the member having the female screw portion, the axial direction position of the axial length extension member can be arbitrarily adjusted.

(c) In the first embodiment and the second embodiment, the chain fall prevention structure is provided on one of the crank arm and the front sprocket, and the present invention is not limited thereto. The chain fall prevention structure may also be provided on both the crank arm and the front sprocket. For example, the chain fall prevention member is provided on both the crank arm and the front sprocket, and the axial length extension member is attached to the chain fall prevention member provided on one of the crank arm and the front sprocket. Further, the chain fall prevention member is provided on both the crank arm and the front sprocket, and the axial length extension members are respectively attached to the chain fall prevention members provided on both the crank arm and the front sprocket.

12‧‧‧1st front sprocket

12a‧‧‧Sprocket teeth

12b‧‧‧ mounting hole

16b‧‧‧ crank arm

16c‧‧‧ inside

20‧‧‧Chain fall prevention structure

22‧‧‧Chain drop prevention member

22a‧‧‧1st shaft

22b‧‧‧ Positioning Department

22c‧‧‧2nd shaft

24‧‧‧Axis length extension member

24a‧‧‧Indented hole

24b‧‧‧ venting holes

A‧‧‧ gap

B‧‧‧ gap

C‧‧‧ gap

CL‧‧‧ center line

Claims (33)

A chain fall prevention structure provided on at least one of a crank arm and a front sprocket having a rotation center axis or a rear sprocket having a rotation center axis; the chain fall prevention structure includes: a chain fall prevention member, and mounting The axial length extension member of the chain fall prevention member. The chain fall prevention structure according to the first aspect of the invention, wherein the axial length extension member is detachably attached to the chain fall prevention member. The chain fall prevention structure according to the second aspect of the invention, wherein the axial length extension member is screwed to the chain fall prevention member. The chain fall prevention structure according to claim 3, wherein the axial length extension member has one of a male screw portion and a female screw portion, and the chain fall prevention member has the other of the male screw portion and the female screw portion. . The chain fall prevention structure according to the second aspect of the invention, wherein the chain fall prevention member has a first engagement portion, and the axial length extension member has a first engagement portion that is engaged with the first engagement portion to prevent the separation. 2 card joints. A chain fall prevention structure according to item 5 of the patent application scope, The first engagement portion and the second engagement portion are elastically engaged with one of the first engagement portions. The chain fall prevention structure of the sixth aspect of the invention, wherein one of the first engagement portion and the second engagement portion has one of an enlargeable portion and a narrowable portion. The chain fall prevention structure according to claim 7, wherein the first engaging portion has the above-described expandable portion. The chain fall prevention structure according to claim 7, wherein the first engaging portion has the narrowable portion. The chain fall prevention structure according to claim 7, wherein the second engagement portion has the above-described expandable portion. The chain fall prevention structure according to claim 7, wherein the second engagement portion has the above-described narrowable portion. The chain fall prevention structure according to claim 7, wherein the expandable portion and the narrowable portion have at least one slit extending in the axial direction. The chain fall prevention structure of claim 12, wherein the slits are provided in plural at intervals in the circumferential direction. The chain fall prevention structure according to the first aspect of the invention, wherein the axial length extension member is attached to the chain fall prevention member by press fitting. The chain fall prevention structure of claim 14, wherein the axial length extension member has a vent hole. A chain fall prevention structure according to item 1 of the patent application scope, The center-axis direction length extension member is attached to the chain fall prevention member by a bonding method. The chain fall prevention structure according to the first aspect of the invention, wherein the axial length extension member is attached to an outer peripheral portion of the chain fall prevention member. The chain fall prevention structure of the first aspect of the invention, wherein the axial length extension member is attached to an inner peripheral portion of the chain fall prevention member. The chain fall prevention structure according to the first aspect of the invention, wherein the chain fall prevention member is provided in the front sprocket; and a gap extending in the axial direction is formed between the axial length extension member and the front sprocket The axial length extension member is attached to the chain fall prevention member. The chain fall prevention structure according to the first aspect of the invention, wherein the chain fall prevention member is provided in the rear sprocket; and a gap extending in the axial direction is formed between the axial length extension member and the rear sprocket The axial length extension member is attached to the chain fall prevention member. The chain fall prevention structure according to the first aspect of the invention, wherein the chain fall prevention member is provided in the crank arm; and a gap extending in the axial direction is formed between the axial length extension member and the crank arm; The axial length extension member is attached to the chain fall prevention member. Chain fall prevention structure as claimed in claim 19 or 20 In the above, the chain fall prevention member is integrally formed on the front sprocket or the rear sprocket. The chain fall prevention structure according to claim 19 or 20, wherein the chain fall prevention member is attached to the front sprocket or the rear sprocket differently. The chain fall prevention structure according to claim 21, wherein the chain fall prevention member is integrally formed on the crank arm. The chain fall prevention structure according to claim 21, wherein the chain fall prevention member is attached to the crank arm differently. A chain fall prevention structure according to the first aspect of the invention, wherein the chain fall prevention member is made of metal. The chain fall prevention structure according to claim 1, wherein the chain fall prevention member is made of a non-metal. The chain fall prevention structure according to claim 1, wherein the axial length extension member is made of a non-metal. The chain fall prevention structure of claim 28, wherein the axial length extension member is made of a material containing a resin. The chain fall prevention structure according to claim 1, wherein the axial length extension member is made of metal. The chain fall prevention structure according to the first aspect of the invention, wherein the chain fall prevention member is provided on the front sprocket; the axial length extension member and the crank arm facing the chain fall prevention member in an axial direction Axial length of the gap It is 2 mm or more and 3 mm or less. The chain fall prevention structure according to the first aspect of the invention, wherein the chain fall prevention member is provided on the crank arm; the axial length extension member and the front sprocket facing the chain fall prevention member in an axial direction The axial gap between the gaps is 2 mm or more and 3 mm or less. The chain fall prevention structure according to the first aspect of the invention, wherein the chain fall prevention member is provided in the rear sprocket; the axial length extension member and a rear wheel of the bicycle facing the chain fall prevention member in the axial direction The axial direction between the gaps is 2 mm or more and 3 mm or less.