CN215399160U

CN215399160U - Crank assembling and disassembling structure for bicycle

Info

Publication number: CN215399160U
Application number: CN202021081751.8U
Authority: CN
Inventors: 中井範光
Original assignee: Aides Co ltd
Current assignee: Aides Co ltd; Ides KK
Priority date: 2019-07-09
Filing date: 2020-06-12
Publication date: 2022-01-04
Anticipated expiration: 2030-06-12
Also published as: JP7411222B2; KR20210131245A; JP2021011253A

Abstract

The utility model discloses a structure for easily assembling and disassembling a crank arm and the like. The bicycle crank attachment/detachment structure includes: a rotatable crankshaft supported by a body frame of a bicycle; a fluted disc capable of rotating integrally with the crankshaft; two crank arms respectively arranged on two sides of the crankshaft and capable of rotating together with the crankshaft; the assembling and disassembling component can assemble and disassemble and fix one side crank arm on the crankshaft. The loading and unloading assembly is provided with a main body part and an operating part. The main body part can be inserted into the one side crank arm from the outside of the shaft direction and fixed on the crankshaft; the operating member is movable by an external operation, and the fixed state is released by the movement to remove the crankshaft.

Description

Crank assembling and disassembling structure for bicycle

Technical Field

The present invention relates to a crank attachment/detachment structure for a bicycle, which enables easy attachment/detachment of a crank shaft, pedals, and the like of the bicycle, and a bicycle provided with the attachment/detachment structure.

Background

A conventional general bicycle includes the following: a crank shaft and a chain (also referred to as a sprocket) which are supported by the frame so as to be rotatable as a whole; crank arms which are assembled on the side edge of the end part of the crank shaft and extend along the cross direction of the crank shaft; a pedal supported by the end of the crank arm in the extending direction; and a fixing bolt inserted into the central part of the crank arm from the outer side of the shaft direction and screwed into the crankshaft.

However, in such a conventional bicycle structure, it is sometimes necessary to remove the crank arms, the pedals, and the like.

For example, when a bicycle beginner such as an infant or a child exercises a bicycle, it is necessary to perform balance exercise so as not to fall down while advancing on the ground with the pedals rather than pedaling the bicycle. In the case of performing such exercises, the crank arms and the pedals may catch on the feet to cause hindrance, and it is desirable to remove them.

In addition, when the bicycle is transported, it is sometimes desired to remove the crank arm, the footboard, and the like that protrude outward so as to prevent them from obstructing the transportation.

When the crank arm of a bicycle of a conventional structure is removed, the fixing bolt is loosened by a tool such as a hexagonal wrench, and the crank arm is removed from the crank shaft by a tool such as a pulling tool dedicated to the bicycle.

As described above, when the crank arm is removed, it is necessary to use various tools such as general and special tools, and it is also necessary to have special technical knowledge and take a long time.

Moreover, even if the crank arm is removed, the crank shaft still has a residual outward projection, and still collides with the foot to block the forward movement during practice. Further, the remaining crankshafts collide with surrounding articles during conveyance to cause obstacles, and the package size width is also increased by the remaining crankshafts during boxing.

SUMMERY OF THE UTILITY MODEL

To solve at least some of the problems described above, the present invention includes:

the bicycle crank attachment/detachment structure includes: a crankshaft supporting the bicycle body frame for rotation; a fluted disc capable of rotating integrally with the crankshaft; two crank arms respectively provided on both sides of the crankshaft and rotatable integrally with the crankshaft; a detachable assembly for fixing one side crank arm on the crankshaft.

The crank attaching and detaching structure for a bicycle is provided with a main body member capable of inserting the attaching and detaching unit into the crank arm on one side from the outside in the axial direction and fixing the attaching and detaching unit to the crank shaft, and an operating member movable by an external operation, and is provided with the crank attaching and detaching structure for a bicycle having the above feature in which the crank shaft is detached from the main body member after the fixed state is released by the operation.

The present invention is configured as described above, and the crank arm can be easily attached and detached.

Drawings

Fig. 1 is an exploded schematic view illustrating an example of a mounting and dismounting structure of a bicycle crank according to the present invention. The chain gears and the like are schematically shown in the drawings.

Fig. 2a shows the crankshaft before it is connected to the crank arm.

Fig. 2b shows the crankshaft and crank arm connected together.

Fig. 3a is a crankshaft removal sequence diagram.

FIG. 3b is a crankshaft removal sequence.

Figure 4a shows the crankshaft in a disengaged condition,

fig. 4b shows the crank arm including the dismounting assembly in a disengaged state.

Fig. 5 is a sectional view of the crank arm and the crankshaft assembled after replacing the attachment/detachment unit with a bolt.

FIG. 6 is a cross-sectional view of a crank arm bolted to a crankshaft.

FIG. 7 is an exploded perspective view of another embodiment of the bicycle crank attachment structure of the present invention. The chain gears and the like are schematically shown in the drawings.

FIG. 8a is a crank attachment and detachment structure for the bicycle of FIG. 7 prior to attachment of the crank arm to the crankshaft,

fig. 8b shows the crank arm after it has been connected to the crankshaft.

Wherein the content of the first and second substances,

10: vehicle body frame

20, 20': crankshaft

20 a: engaging and disengaging tubular part

21: clamping part

22: fastening and releasing part

23: fitting tube part

24: screw thread part

30, 30': toothed disc

32, 32': clamping cylinder part

33: clamping hole

40, 40',50, 50': crank arm

41, 41',51, 51': barrel part

41 a: connecting hole

41 a': is stopped the hole

41 b: clamped hole

43: clamping convex column

51a, 51 a': clamped hole

60, 60': loading and unloading assembly

61: main body part

62: operating member

62 a: shaft-like part

62 b: press-in button part

62: concave part

621: top touch part

622: containing part

63: force application member

64: ball body

70: fixing bolt

A, B: attachment/detachment structure for crank of bicycle

Detailed Description

The following features are disclosed with respect to the present embodiment.

The 1 st feature: the bicycle crank attachment/detachment structure includes: a crankshaft supporting the bicycle body frame for rotation; a fluted disc capable of rotating integrally with the crankshaft; two crank arms respectively provided on both sides of the crankshaft and rotatable integrally with the crankshaft; a detachable assembly for fixing one side crank arm on the crankshaft.

The detachable unit includes a main body member that is inserted into the crank arm on the one side from an outer side in the axial direction and is fixed to the crank shaft, and an operating member that is movable by an external operation. And the crankshaft can be removed from the main body member after the fixed state is released by the operation (see fig. 1 to 5).

The 2 nd feature: the main body member is formed in a substantially cylindrical shape along the axial direction of the crank shaft, the operating member has a shaft-like portion into which the main body member is inserted at a front side, and a push button portion capable of being operated externally is provided at a rear side of the shaft-like portion, and a pressed surface of the push button portion is disposed so as to be recessed inside an axially outer side surface of the crank arm (see fig. 3a, 3b, 4a, and 4 b).

Feature 3: the main body member is formed in a substantially cylindrical shape along an axial direction of the crankshaft, the operating member has a shaft-like portion into which the main body member is inserted at a front side, and a push button portion which is capable of being operated externally is provided at a rear side of the shaft-like portion, and the attachment/detachment unit includes an urging member which urges the operating member toward the rear side, and a spherical body which is supported by a peripheral wall of the main body member in a penetrating manner and protrudes from an outer peripheral surface portion of the main body member. The shaft-shaped portion is provided with a concave portion capable of embracing the ball in a radial direction of the shaft-shaped portion. A contact portion that is provided inside the recessed portion and comes into contact with the spherical body from a radially inner side so that the spherical body protrudes from an outer peripheral surface of the main body member; and a receiving portion is provided so that the ball on the rear side does not protrude from the outer peripheral surface of the main body member. The crank shaft is provided with a fitting cylinder portion including the ball and fittable to an outer periphery of the main body member. The peripheral wall of the fitting cylinder portion is provided with a locking/releasing portion into which the ball is fitted. The ball is separated from the engaging and disengaging portion and is accommodated in the accommodating portion by pushing the operating member forward, and the locked state is released. (refer to FIGS. 3a, 3b, 4a, and 4b)

The term "clasping" is used herein to mean supporting like clasping.

The "substantially cylindrical" includes cylindrical and angular cylindrical shapes

The 4 th feature: an engagement cylinder portion is provided on a center side of the chain sprocket and projects outward in an axial direction in a state where the crankshaft is inserted. The crank arm has a connecting hole formed in a base end side of the chain sprocket side surface and adapted to allow the crankshaft to be inserted therein and to be connected to rotate integrally therewith, and an engaged hole formed in an axially inner side of the connecting hole and adapted to be engaged with the engaging cylinder portion to rotate integrally therewith. (see FIGS. 1 to 2).

The 5 th feature: an engagement hole that opens toward the crank arm is provided in the chain toothed disc side surface on a radially outer side of the inserted crankshaft. The crank arm is provided with an engagement boss (see fig. 7, 8a and 8b) which is inserted into an engagement hole in the side surface of the chain toothed disc and is fitted thereto.

The 6 th feature: has a fixing bolt which can be replaced by the above-mentioned assembling and disassembling component. The fixing bolt is inserted into the crank arm on the one side from the outside in the axial direction and is screwed with the crankshaft. (refer to FIGS. 1, 5 and 6)

The 7 th feature: the bicycle is provided with the assembling and disassembling structure of the crank for the bicycle.

Specific embodiments having the above-described features will be described in detail below with reference to the drawings.

In the present description, the term "axially outward" refers to a direction away from the center along the axial direction of the crankshaft 20. "axially inward" refers to a direction toward the center along the axial direction of the crankshaft 20.

"radially outward" refers to a direction away from the center along the radial direction of the crankshaft 20. "radially inward" refers to a direction toward the center along the radial direction of the crankshaft 20.

< first embodiment >

The bicycle crank attaching/detaching structure A is attached to a crankshaft 20 supported by a bicycle body frame 10 of a bicycle so as to be rotatable integrally with the crankshaft 20, a chainring 30 attached to both ends of the crankshaft 20 and having two crank

arms

40, 50 attached to both ends of the crankshaft 20 so as to be rotatable integrally with the crankshaft 20, and an attaching/detaching unit 60 detachably fixed to the crankshaft 20 and a fixing bolt 70 capable of replacing the attaching/detaching unit 60 are attached to one crank arm 50.

The vehicle body frame 10 is configured as a small-sized bicycle for children.

The vehicle body frame 10 is integrally supported by a cylindrical member located at an intersection of: a lower main tube 11 extending obliquely downward and rearward from a head tube (not shown) on the handlebar side, a seat tube 12 extending obliquely downward and forward from a seat cushion (not shown), and left and right rear fork tubes 13 extending forward from both sides of a rear wheel axle (not shown).

The through pipe 14 is a cylindrical member whose axis direction is directed to the vehicle width, and the crankshaft 20 is rotatably supported therein via a bearing member (not shown) such as a bearing.

The crankshaft 20 is a long cylindrical member inserted into the pipe 14 so that one end thereof penetrates the pipe 14 to the other end thereof and projects outward in the axial direction.

In the drawings, the crankshaft 20 is attached to and detached from the through pipe 14 only, but as a preferable example not shown, the crankshaft 20 and its surrounding bearings, bearing supports, and the like constitute an integrally combined bottom bracket, and the bottom bracket may be attached to and detached from the through pipe 14 in the axial direction.

Further, the crank arm 40 is connected to one end of the crankshaft 20 at the base end side thereof, and is not rotatable relative to the crankshaft and also not movable relative to the crankshaft in the axial direction. The other end of the crankshaft 20 is detachably connected to the base end side of the crank arm 50, and is not rotatable relative to the crank shaft and also not movable relative to the crank shaft in the axial direction. (refer to FIG. 1)

The crankshaft 20 is provided with an insertion/removal cylindrical portion 20a at one end thereof, and the removable unit 60 including the spherical body 64 is fitted to the outer periphery of the main body member 61 of the removable unit 60.

As shown in fig. 5, the insertion and extraction cylindrical portion 20a has the following portions: the crank arm 50 is provided with a locking portion 21 which can lock the crank arm to be non-rotatable, a locking portion 22 which can be locked to and unlocked from the ball 64 of the detachable unit 60, an engaging cylinder portion 23 which is engaged with the outer periphery of the main body member 61 of the detachable unit 60, and a screw portion 24 which can be fastened to the back side of the fixing bolt 70.

The engaging portion 21 is formed in a zigzag shape by connecting a plurality of projections and recesses linearly in the axial direction and provided on the outer periphery of the engaging and disengaging cylindrical portion 20 a.

The engaging and disengaging portion 22 is a circular through hole that is located between the engaging portion 21 and the fitting cylinder portion 23 and penetrates the peripheral wall of the fitting and disengaging cylinder portion 20 a.

In addition, according to the preferred embodiment, two engaging and disengaging portions 22 are provided on both sides of the engaging and disengaging cylindrical portion 20a in the radial direction, but in other embodiments, one engaging and disengaging portion may be deleted. When the engagement and disengagement portion 22 is disengaged from the ball 64, a recess provided on the inner peripheral surface of the engagement and disengagement cylindrical portion 20a may be replaced.

The fitting cylinder portion 23 is cylindrical without irregularities except for the engaging and disengaging portion 22. Is removably fitted to the small diameter portion 61b of the removable module 60.

The threaded portion 24 is provided with a female thread on the back side (axially inner side) of the fitting cylinder portion 23. So as to be able to screw the fastening bolt.

The toothed plate 30 is a disk-shaped member and includes engaging teeth 30a engageable with a peripheral chain (not shown). The fluted disc center is provided with the following parts: a through hole 31 into which the entire crankshaft can be inserted; an engaging cylinder portion 32 projecting outward in the axial direction from the periphery of the through hole 31 and adapted to engage the crank arm 40.

The through hole 31 is cylindrical and can pass through the crankshaft 20 and a bearing or a bottom bracket (not shown) for supporting the crankshaft 20.

The engaging cylinder portion 32 is formed with a lot of alternating concave-convex saw-like shapes over its entire circumference so that the outer circumference thereof is engaged with the engaged hole 41b in the crank arm 40.

As shown in fig. 1 and 2, the crank arm 40 located near the toothed plate 30 has a cylinder 41 attached to an end of the crankshaft 20, and a wrist portion 42 extending radially outward from the cylinder 41. A foot pedal, not shown in the figures, is mounted at the end of wrist 42. The cylindrical portion 41 of the crank arm 40 is engaged with the engagement cylindrical portion 32 of the toothed disc 30, and rotates the toothed disc 30 by the driving force.

The cylindrical portion 41 is cylindrical and slightly larger than the diameter of the engagement cylindrical portion 32 of the toothed disc 30. The interior of the utility model has the following two parts: a connecting hole 41a which is fitted to the crankshaft 20 and is integrally rotatable; and a receiving hole 41b connected to the axially inner side of the connecting hole 41a and provided to be rotatable integrally with the engagement cylinder 32 of the toothed disc 30.

As a method for connecting the connecting hole 41a to the crankshaft 20, the following can be cited: welding, press fitting, screw assembling, meshing by a rack, and the like. The crankshaft 20 is fixedly connected to the connecting hole 41a so that the crankshaft 20 cannot move in the axial direction and cannot idle.

When the cylinder 41 is connected to the crankshaft 20, an annular space s (see fig. 2b) is required between the engaged hole 41b in the cylinder 41 and the outer periphery of the crankshaft 20. The engagement cylinder 32 of the gear plate 30 can be inserted into the gap s and engaged with the engaged hole 41 b.

The engaged hole 41b (see fig. 2a and 2b) is configured to be able to be pulled out in the axial direction without relative rotation after being fitted to the engagement cylinder 32. As shown in the drawings, the engaged hole 41b has a saw-toothed shape and can be engaged with the saw-toothed shape of the outer periphery of the engaging cylinder 32.

As shown in fig. 1, the crank arm 50 on the other side of the chainring 30 has the following two parts: a cylinder 51 assembled to an end of the crankshaft 20; an elongated arm 52 extends radially outward from the tube 51. A foot pedal, not shown, is mounted to the end of wrist 52. The angle between the wrist portion 52 of the crank arm 50 and the wrist portion 42 of the crank arm 40 on the other side is 180 °.

The cylindrical portion 51 is cylindrical and has an outer diameter slightly larger than the crankshaft 20. As shown in fig. 5, the cylinder 51 and the crankshaft are arranged as follows: an engaged hole 51a for inserting and extracting the insertion and extraction cylindrical portion 20a of the crankshaft 20; a hole-shrinking portion 51b is provided on the outside of the axial direction of the hole-to-be-clamped 51 a; next, the outer side of the axial direction of the shrinkage hole part 51b is provided with a hole-expanding part 51.

The retainer hole 51a is formed in a cylindrical-like inner peripheral surface so as to be capable of integrally rotating with the crankshaft 20.

In detail: in order to allow the engaging portion of the outer circumferential serration located in the engaging and disengaging cylindrical portion 20a of the crankshaft 20 to be inserted and removed in the axial direction and to prevent idling, the inner circumferential surface of the engaging hole 51a is provided with serration engageable therewith.

The shrinkage cavity portion 51b is a cylindrical cavity and is fitted to the

small diameter portions

61b and 72 of the removable block 60 and the fixing bolt 70. And a step is formed between the constricted portion 51b and the engaged hole 51 a. The stepped portion is press-fitted to an end surface in the axial direction of the crankshaft 20.

The enlarged hole portion 51 is formed with a stepped portion with respect to the reduced hole portion 51b, and is configured to receive cylindrical members of the large diameter portions 61a and 71 (head portions) of the attachment/detachment unit 60 and the fixing bolt 70. The stepped portion is pressed in the axial direction by the removable unit 60 and the

large diameter portions

61a and 71 of the fixing bolt 70.

The loading and unloading unit 60 includes the following parts: a main body member 61 that is inserted into the crank arm 50 from the outside in the axial direction along the outside in the reverse direction of the toothed disc and then engaged with the fitting cylinder portion 23 of the crankshaft 20; an operation member 62 movable in the axial direction by an external operation; a biasing member 63 for biasing the operating member 62 outward in the axial direction; and a ball 64 supported by the peripheral wall of the body member 61 in a penetrating manner and partially protruding from the outer peripheral surface of the body member 61.

The detachable unit 60 is capable of releasing the locked state with the crankshaft 20 by moving the operating member 62 inward in the axial direction, and after the released state, the crankshaft 20 is detached from the body member 61.

The body member 61 is formed in a cylindrical shape along the axial direction of the crankshaft 20. In detail: the main body member 61 includes: a large diameter portion 61a on the outer side (rear side) in the axial direction; and a small diameter portion 61b that is radially inwardly (forward) of the large diameter portion 61a in the axial direction.

When the large diameter portion 61a is housed in the counterbore portion 51 of the crank arm 50, the rear end thereof is formed into a cylindrical shape having a length shorter than the axial length of the counterbore portion 51 so as not to project rearward of the counterbore portion 51. (refer to FIGS. 3a, 3b, 4a, and 4b)

The small diameter portion 61b is provided with a cylindrical portion that can be fitted to the fitting cylinder portion 23 of the crankshaft 20, and a through hole 61b1 that penetrates the support ball 64 is provided in the peripheral wall thereof.

The diameter of the through hole 61b1 is set to be slightly smaller than the outer diameter of the ball 64 so that the ball 64 does not fall off or fall off from the outside in the radial direction of the attaching and detaching unit 60.

The thickness of the peripheral wall of the small diameter portion 61b is set to an appropriate thickness so that a part of the spherical body 64 can slightly protrude outward in the radial direction of the peripheral wall.

The operation member 62 includes the following two portions: a shaft-like portion 62a having a small diameter portion 61b inserted into the body member 61 on the axially inner side (front side); the push button portion 62b is provided on the axially outer side (rear side) and is operable from the outside.

The pressed surface of the press button portion 62b is recessed inside the cylindrical portion 51 of the crank arm 50 in the axial direction, and has a stepped portion. Such as the X dimension in fig. 3a, 3 b.

With this configuration, it is possible to prevent an erroneous operation in which the pressed surface of the push button portion 62b is inadvertently touched by a hand or a foot or other objects.

Further, if necessary, a removable cap having a cylindrical shape or the like may be attached to the X-size recessed portion, and the opening of the recessed portion may be closed by the cap.

The shaft-like portion 62a has a cylindrical shape similar to a long bar, and a concave portion 62 is provided to receive the ball 64 when the ball 64 is inserted or withdrawn in the radial direction of the shaft-like portion 62 a.

The concave portion 62 is provided with the following two portions: a contact portion 621 which contacts the inner side in the radial direction of the spherical body 64 and pushes the spherical body 64 out of the outer peripheral surface of the small-diameter portion 61b of the main body member 61; a receiving portion 622 is provided on the outer side in the axial direction of the top contact portion 621, in which the ball 64 does not protrude from the outer peripheral surface of the small diameter portion 61 b.

The abutting portion 621 is located on the inner side in the axial direction and forms an inclined surface in contact with the ball 64.

The receiving portion 622 is a bottom surface that is located on the axially outer side (left side in the drawing) of the top contact portion 621, and this bottom surface ensures a recessed space for receiving the half ball 64. (refer to FIGS. 4a and 4b)

The fixing bolt 70 is provided with a cylindrical large diameter portion 71 (head) located on the outer side (rear side) in the axial direction, and a cylindrical small diameter portion 72 located on the inner side (front end) in the axial direction of the large diameter portion 71 and having a reduced diameter.

The end face of the large diameter portion 71 is provided with a jig insertion hole 71a into which a fastening jig such as a hexagonal wrench can be inserted and fitted.

The small diameter portion 72 has a screw 72a on the outer peripheral surface at the distal end thereof, and this portion is screwed with the screw portion 24 of the crankshaft 20.

The reference numeral 80 in the drawings denotes a ring-shaped spring member which is annularly attached to the outer periphery of the crankshaft 20 between the crank arm 50 and the end surface of the through pipe 14. The annular spring body 80 may be a wave washer, a spring washer, a compression coil spring, or the like.

Next, the step of removing the crank arm 50 will be described in detail with respect to the attaching and detaching structure a of the bicycle crank configured as described above.

In the initial state, as shown in fig. 3a, the main body member 61 of the detachable unit 60 is fitted into the fitting cylinder portion 23 of the crankshaft 20, and a part of the ball 64 is fitted into the engaging and disengaging portion 22, so that the crankshaft 20 is caught in the crank arm 50 and cannot be pulled out. The engaged hole 51a in the side surface of the crank arm 50 and the engaging portion 21 in the side surface of the crank shaft 20 are engaged with each other, and the crank shaft 20 engages with the crank arm 50 so that the fixed body cannot slip freely.

As shown in fig. 3b, when the operating member 62 of the attaching and detaching unit 60 is pressed from the outside and the operating member 62 is moved inward in the axial direction, the ball 64 is separated from the engaging portion 22 and falls into the receiving portion 622.

Thus, as best seen in FIGS. 4a and 4b, the crankshaft 20 can be pulled axially away from the crank arms 50 and the assembly 60. At this time, the cylinder portion 41 of the crank arm 40 at the other end of the crankshaft 20 can be pulled out from the engagement cylinder portion 32 of the chainring 30 (see fig. 1, 2a and 2 b).

Thereafter, as shown in fig. 4b, the crank arm 50 and the attachment/detachment unit 60 can be pulled away from the through-pipe 14 to the outside in the axial direction.

In addition, when the end of the crankshaft 20 is pressed into the engaged hole 51a of the crank arm 50 in a state where the crankshaft 20 penetrating the through pipe 14 is connected to the crank arm 50, the ball 64 is pressed against the end of the crank arm 50, and the operating member 62 advances in the axial direction inward while sliding along the abutting portion 621 and into the receiving portion 622. When the axial positions of the spherical body 64 and the engaging and disengaging portion 22 on the crankshaft 20 side substantially match, the spherical body 64 is fitted into the engaging and disengaging portion 22, and returns to the initial state (see fig. 3 a).

As described above, when the crank arm 50 and the attachment/detachment assembly 60 are detached from the crankshaft 20, the attachment/detachment assembly 60 is replaced with the fixing bolt 70, and the crank arm 50 is connected to the crankshaft 20 by the fixing bolt 70 (see fig. 4a, 4 b-6).

At this time, when the attachment/detachment unit 60 is removed, the fixing bolt 70 is inserted into the cylindrical portion 51 of the crank arm 50 from the outside in the axial direction, the small diameter portion 72 of the fixing bolt 70 is inserted into one end of the crankshaft 20, and the threaded portion 72a of the small diameter portion 72 and the threaded portion 24 in the crankshaft 20 are screwed together.

Therefore, if the bicycle crank attachment/detachment structure a (not shown) is provided, the two crank

arms

40 and 50 on the body frame 10 can be easily attached and detached.

For example, when a bicycle beginner such as a child or a child exercises the bicycle, the two crank

arms

40 and 50 are detached from the body frame 10 by the attaching and detaching unit 60, so that the user can exercise how to balance the bicycle while moving forward with the ground.

When the trainee can balance, the two crank

arms

40, 50 can be easily attached to the vehicle body frame 10 by operating the attachment/detachment assembly 60.

In the above-described embodiment, the locking structure of the locking portion 21 and the locked hole 51a and the locking structure of the locking cylinder 32 and the locked hole 41b are formed by engaging the male rack and the female rack with each other. However, in other examples, a single or plural number of the convex portions may be fitted to the concave portions, or a key may be fitted to the key groove.

< second embodiment >

Next, another embodiment of the present invention will be described.

In the embodiments described below, since the above-described attachment/detachment structure a of the bicycle crank is partially modified, the modified portions will be mainly described in detail, and the same portions will be denoted by the same reference numerals to avoid redundancy.

The bicycle crank attachment and detachment structure B shown in fig. 7, 8a, and 8B is the bicycle crank attachment and detachment structure a described above, in which the crankshaft 20 is replaced with the crankshaft 20 ', the chainring 30 is replaced with the chainring 30 ', the

chainrings

40, 50 are replaced with the chainrings 40 ', 50 ', and the attachment and detachment assembly 60 is replaced with the attachment and detachment assembly 60 ', and the annular spring body 80 is omitted.

The crankshaft 20' is formed by omitting the retainer 21 and providing flat portions 25 on the outer peripheral surfaces of one end side and the other end side of the crankshaft 20 (see fig. 7, 8a, and 8 b).

The flat surface portion 25 is positioned on the outer peripheral surface of the end portion side of the cylindrical crankshaft 20 'and has a flat cut parallel to the central axis of the crankshaft 20'. A plurality of flat portions 25 are provided on the outer peripheral portion of the crankshaft 20', and the flat portions 25 are arranged at specific angular intervals (four flat portions 25 are arranged at 90-degree intervals in the figure). That is, the outer peripheral surfaces of the crankshaft 20' on the one end side and the other end side are each in a quadrangular prism shape.

The through-hole engaging and disengaging portion 22 is provided on one flat surface portion 25 on the axially inner side (left side in the drawing) of the crankshaft 20' (see fig. 7).

In other examples than those shown in the drawings, the two parallel flat surface portions 25 may be provided only at positions on both sides in the radial direction.

An inner peripheral surface of a top end side (a left end as shown in fig. 7) of the crankshaft 20 'is provided with a fitting cylinder portion (not shown) into which a detachable unit 60' described below can be fitted, and a screw portion 24 (see fig. 5) is further provided on a rear side of the fitting cylinder portion.

The fitting cylinder portion of the crankshaft 20' is formed in a square hole shape having a substantially square cross section by the fitting cylinder portion 23 (see fig. 5).

The toothed disc 30 'is formed by replacing the engagement cylinder portion 32 with an engagement cylinder portion 32' having no irregularities on the outer peripheral portion, and providing an engagement hole 33 opening toward the crank arm 40 'on the radially outer side of the engagement cylinder portion 32'.

The engaging cylinder 32 'is located at the center of the gear plate 30'. When the crankshaft 20 'is inserted into the engagement cylindrical portion 32', the cylindrical portion 41 'of the crank arm 40' abuts against the end surface thereof.

The engaging hole 33 is a through hole located radially outward of the engaging cylinder 32 'and radially inward of the meshing teeth 30a and substantially parallel to the central axis of the toothed disc 30'. The opening of the engagement hole 33 faces the engagement boss 43 of the crank arm 40' (see fig. 7).

In the crank arm 40 ', the cylinder portion 41 is replaced with a cylinder portion 41' and an engagement boss 43 (see fig. 7 and 8) which can be inserted into and fitted into the engagement hole 33 is provided in the extending direction of the arm portion 42 in the crank arm 40.

The cylindrical portion 41' is formed by changing the shape of the inside of the cylindrical portion 41 (see fig. 8 a). The detailed description is as follows: the cylinder portion 41 'is provided therein with a corner cylindrical stopped hole 41 a' into which the plurality of flat portions 25 of the crankshaft 20 'are fitted, and an enlarged diameter hole portion (not shown) having an enlarged diameter cylindrical shape is provided on the outer side in the axial direction of the stopped hole 41 a'.

The fixing bolt 70 is insertable into the cylindrical portion 41' from the outside in the axial direction. When the screw portion 72a of the fixing bolt 70 and a screw portion (not shown) at the end of the crankshaft 20' are screwed to each other, the large diameter portion 71 is also fitted into the enlarged diameter hole portion.

The crankshaft 20 ', the crank arm 40', and the fixing bolt 70 integrated as described above are not supposed to be disassembled in a normal use state.

The engagement boss 43 is a shaft-like projection portion located inside the wrist portion 42 and projecting from the inside surface. The radial position is set so as to correspond to the engagement hole 33 of the toothed plate 30'.

When the crankshaft 20' is inserted into the through hole 31, the engagement boss 43 is fitted into the engagement hole 33 (see fig. 7).

The other crank arm 50 'is obtained by replacing the cylindrical portion 51 of the crank arm 50 with a cylindrical portion 51'.

The cylindrical portion 51 ' is symmetrical to the cylindrical portion 41 ' of the crank arm 40 ', and includes the following in the inside: a cylindrical receiving hole 51 a' fitted in the plurality of flat surface portions 25 on the end portion side of the crankshaft 20; a cylindrical enlarged hole portion 51 (see fig. 5) on the axially outer side of the engaged hole 51 a'.

The detachable unit 60 'can be inserted into the cylindrical portion 51' from the outside in the axial direction.

The removable module 60 'is configured such that the cylindrical small-diameter portion 61b is replaced with a small-diameter portion 61 b' having a quadrangular prism shape in appearance with respect to the removable module 60.

The internal structure of the small diameter portion 61 b' is the same as that of the small diameter portion 61 b.

One of the four flat surfaces of the small diameter portion 61 b' is provided with a through hole 61b1, which may be a penetrating support ball 64 (see fig. 4a, 4b, and 5) as in the case of the above attaching and detaching unit 60.

The removable unit 60 ' is inserted into the cylindrical portion 51 ' from the outside in the axial direction, and the small diameter portion 61b ' is fitted into a fitting cylindrical portion (not shown) inside the crankshaft 20 ', and the large diameter portion 61a is fitted into the enlarged hole portion 51 inside the cylindrical portion 51 ' (see fig. 5). The shape of the fitting cylinder portion (not shown) inside the crankshaft 20' is changed from the shape of the fitting cylinder portion 23 (see fig. 5) to a corner cylinder shape.

Therefore, according to the bicycle crank attachment/detachment structure B shown in fig. 7 and 8, the crank arm 40 'can be stopped from rotating relative to the chainring 30' by fitting the engagement hole 33 of the chainring 30 'and the engagement projection 43 of the crank arm 40' to each other.

Further, since both ends of the crank shaft 20 'having a quadrangular prism-like shape are fitted into the crank arm 40' and the crank arm 50 ', the crank shaft 20' and the crank arms 40 'and 50' can be rotated integrally with a simple structure.

The attaching and detaching structure B of the bicycle crank has the same function as the attaching and detaching structure a of the bicycle crank described above, and the two crank arms 40 ', 50' can be easily attached to and detached from the body frame 10.

In the illustrated bicycle crank attachment and detachment structure B, only the small diameter portion 61B ', the ball 64, and the concave portion 62 are provided on one side in the radial direction, but in another example, the attachment and detachment unit 60 ' may be configured symmetrically about the center line thereof, and the small diameter portion 61B ', the ball 64, and the concave portion 62 may be provided on both sides in the radial direction.

< other modification example >

In the above-described embodiment, the operation member 62 is pressed inward in the axial direction, but when the operation member is replaced with another operation member, a method of pulling outward in the axial direction, a method of pressing in a direction intersecting the axial direction, a method of pulling, or the like may be employed.

The present invention is not limited to the above-described embodiments, and can be modified as appropriate without changing the gist of the present invention.

Claims

1. A crank mounting/dismounting structure for a bicycle includes a crankshaft for supporting a bicycle body frame to rotate; a fluted disc capable of rotating integrally with the crankshaft; two crank arms respectively arranged at two sides of the crankshaft and capable of rotating integrally with the crankshaft; a detachable assembly for fixing one side crank arm on the crankshaft; the method is characterized in that: the detachable unit is inserted into the crank arm on one side from the outside in the axial direction, and has a main body component capable of being fixed on the crank shaft and an operating component capable of being moved by external operation.

2. The bicycle crank attachment/detachment structure according to claim 1, wherein: the main body member is cylindrical along the axial direction of the crankshaft; the front end of the operating component is provided with a shaft-shaped part which can be inserted into the main component, and the rear side of the shaft-shaped part is provided with a press button which can be operated externally; the pressed surface of the press button portion is disposed recessed inward of the axially outer side surface of the crank arm.

3. The bicycle crank attachment/detachment structure according to claim 1, wherein: the main body member is cylindrical along the axial direction of the crankshaft; the front end of the operating component is provided with a shaft-shaped part which can be inserted into the main component, and the rear side of the shaft-shaped part is provided with a press button which can be operated externally; the detachable assembly is provided with a force applying member for applying force to the operating member to the rear side and supported by the main body member in a penetrating manner, and a ball body partially protruding from the outer peripheral surface of the main body member; a concave portion is provided at the shaft-shaped portion, and the concave portion can accommodate the ball when the ball is retracted and extended in the radial direction; the following components are arranged at the inner side of the concave part: a push-contact portion which is in contact with the inner side in the radial direction of the ball body and is pushed out of the outer peripheral surface of the main body member; the back side of the top contact part is provided with a containing part which can contain the ball body without protruding; a fitting cylinder portion including the spherical body and fittable to an outer periphery of the main body member is provided on the crankshaft; the peripheral wall of the embedding cylinder part is provided with a clamping and releasing part embedded with the ball body; the ball is dropped into the receiving portion and separated from the engaging portion by an operation of pressing the operating member toward the tip end, and the fixed state is released.

4. The bicycle crank attachment/detachment structure according to claim 1, wherein: the center of the fluted disc is provided with a clamping cylinder part; the crankshaft can be inserted into the clamping cylinder part in a penetrating way, and the clamping cylinder part is protruded towards the outer side of the axial direction; the following are provided at the end of the above-mentioned crank arm on the side of the toothed disc: a connecting hole for connecting the crankshaft after being inserted and rotating integrally; and a clamped hole which is communicated with the inner side of the connecting hole in the axial direction and can be fixed relatively to the clamping cylinder part for integral rotation.

5. The bicycle crank attachment/detachment structure according to claim 1, wherein: an engagement hole that opens toward the crank arm on the side of the toothed disc is provided on the toothed disc at a position radially outward of the crankshaft after the crankshaft is inserted; the crank arm at the side of the gear plate is provided with a clamping convex column which can be inserted into the clamping hole to be embedded with the clamping convex column.

6. The bicycle crank attachment/detachment structure according to claim 1, wherein: a fixing bolt which can be replaced by the assembling and disassembling component is arranged; the fixing bolt is inserted into the one crank arm from the outside in the axial direction and is screwed with the crankshaft.