WO2019017516A1

WO2019017516A1 - Bicycle crank structure

Info

Publication number: WO2019017516A1
Application number: PCT/KR2017/008185
Authority: WO
Inventors: 박경래; 박동원; 최웅재; 오세현; 신승우; 최승호
Original assignee: 윈엔윈(주)
Priority date: 2017-07-18
Filing date: 2017-07-28
Publication date: 2019-01-24
Also published as: KR101785704B1

Abstract

The present invention relates to a bicycle crank structure which has a firm support structure comprising a crankshaft coupled in a frame hub of a bicycle, and crank arms coupled to both ends of the crankshaft, and which has an assembly structure that is easily reparable and replaceable. A bicycle crank structure is provided wherein, the crankshaft has provided thereto: a main shaft provided in the frame hub; coupling shafts each integrally formed on both ends of the main shaft and protruding towards the outer side of the hub; and binding holes each penetrating in a predetermined length direction inside the respective coupling shafts. The binding holes are formed so that the inner diameters thereof gradually decrease towards the inside, and first fastening holes, communicating with the binding holes and having inner diameters that are smaller than the minimum values of the inner diameters of the binding holds, extend in a predetermined length direction towards the inside of the main shaft via the insides of the coupling shafts so as to be formed as plugged holes. Recess parts and protrusion parts are repeatedly arranged on the outer circumferential surfaces of the coupling shafts in the length directions of the coupling shafts, and cut holes, communicating with the binding holes and the first fastening holes, are each formed on a recess part on one side, and a recess part on the other side facing the recess part on the one side.

Description

Crank structure of bicycle

The present invention relates to a crank structure of a bicycle, and more particularly, to a crane structure having a crank shaft coupled to a frame hub of a bicycle and a crank arm coupled to both ends of the crank shaft, &Lt; / RTI > relates to a crank structure of a bicycle.

Generally, bicycles are mainly used for transportation, transportation, and the like. Recently, bicycles are increasingly used for leisure activities such as mountain driving, cycling, and long-distance bicycle travel.

Conventionally, when a pedal coupled to a crank arm is stepped on and a crankshaft to which the crank arm is coupled is rotated, a rear wheel connected to the crankshaft is interlocked and rotated through a chain transmission. In the middle part, a saddle is installed so that a person can sit on the pedal and a handle is installed on the front side to control the direction of advance of the front wheel.

In such a conventional bicycle, the crankshaft is one of the most important parts for performing a function of converting rotational motion using human force into kinetic energy for imparting a propulsion force to the bike, and is supported rotatably in the engagement hole of the bicycle frame Respectively.

In the related art, a cylindrical first housing and a second housing are screwedly coupled to both ends of a coupling hole of a bicycle frame to which the crankshaft is coupled, and a first housing and a second housing are coupled to each other. A pair of bearings are provided, and the outer ring of the bearing is seated on the step formed on the inner surface of the first housing and the inner surface of the second housing, respectively.

In this case, the conventional crankshaft is assembled so as to be coupled to a coupling hole of a frame, and its shape is formed into a cylindrical shape. The crankshaft is combined with a crank arm coupled to both ends of the crankshaft by a fastening means such as a bolt, The crankshaft and the connecting portion between the crankshaft and the crank arm may be loosened or broken.

SUMMARY OF THE INVENTION The present invention has been devised to solve the problems as described above, and it is an object of the present invention to provide a crankshaft which can be firmly fixed regardless of driving of a crankshaft of a bicycle, And a crank structure of the bicycle.

The present invention relates to a crank structure of a bicycle comprising a crankshaft which is immersed in a frame hub of a bicycle and a crank arm which is coupled to both ends of the crankshaft,

Wherein the crankshaft is formed integrally with a main shaft extending to the frame hub and a coupling shaft projecting to the outside of the hub integrally with both ends of the main shaft and a coupling hole penetrating the coupling shaft in a predetermined longitudinal direction is formed, The first fastening hole communicating with the fastening hole and having an inner diameter smaller than the inner diameter minimum value of the fastening hole extends in the predetermined longitudinal direction into the main shaft through the inside of the fastening hole so as to form the shape of the clogging hole Wherein a concave portion and a convex portion are repeatedly arranged in the longitudinal direction of the coupling shaft on the outer circumferential surface of the coupling shaft and a cutout hole communicating with the coupling hole and the first coupling hole is formed in the other concave portion and the other concave portion facing the one concave portion,

The crank arm is provided with a shaft hole at one end thereof so as to be coupled to the coupling shaft of the crank shaft. A recess and a convex portion are repeatedly arranged in the shaft hole in the shaft hole so as to correspond to repetitive recesses and protrusions formed on the outer circumferential surface of the crankshaft- .

A first intermittent tab protruding from both sides of the outer circumferential surface of the coupling shaft so as to be coupled to the cutout hole of the coupling shaft while forming an outer circumferential surface corresponding to the inner circumferential surface shape of the coupling hole so as to be inserted into the coupling hole of the coupling shaft when the crank arm is coupled to the coupling shaft of the crank shaft And a first guiding portion formed with first insertion holes passing through opposite ends of the first guiding portion,

And a second insertion hole formed in the outer end of the crank arm so as to be inserted and interposed between the opposite ends of the crank arm,

The first insertion hole of the expansion guide portion through the second insertion hole of the cap portion and being screwed to the coupling shaft first coupling hole of the crankshaft and the second insertion hole being located in the second insertion hole, There is provided a crank structure for a bicycle including a fastening bolt having a head portion forming an outer circumferential surface.

On the other hand, a coupling hole formed on both sides of the crankshaft and a receiving hole passing through both ends of the crankshaft without the first coupling hole are formed,

And a second intermittent tab which is provided on both sides of the outer circumferential surface so as to be coupled to the cutout hole of the coupling shaft, the second intermittent tab being formed on the outer circumferential surface of the outer end, A pair of auxiliary shafts having a second hole formed in the shape of a blind hole are formed in the outer end of the second shaft and the second shaft is formed in a symmetrical structure so that a recessed portion and an iron portion of the inner peripheral shaft correspond to each other,

And the fastening bolt is screwed to the second fastening hole of the auxiliary shaft provided in the receiving hole of the crankshaft through the first insertion hole of the expansion guide portion through the second insertion hole of the cap portion.

A crank structure of the bicycle is provided with threads on the inner circumferential surface of the first insertion hole of the expansion guide portion.

On the other hand, a circumferential stepped engagement groove is formed on the outer peripheral surface between the outer peripheral edge of the auxiliary shaft and the second intermittent tab, and three guide holes spaced apart from each other by the second engagement hole are formed on the outer circumference of the engagement groove ,

A crank structure of a bicycle is provided in which three ridges that are seated on one surface of the latch groove and protruding from an inner rim of the rim and are threaded on an end portion of the rim that is extended into the guide hole are arranged in the latch groove in the circumferential direction .

According to the above-described crank structure for a bicycle according to the present invention, the crank shaft coupling shaft and the shaft hole of the crank arm coupled to the coupling shaft are firmly fixed regardless of the drive due to the corresponding coupling between the concave portion and the convex portion, Tight coupling structure is formed between the crankshaft and the crank arm so as to maximize the tight and firm coupling relationship between the crankshaft and the crank arm, The crank arm can be firmly fixed between the axle holes of the crank arm by exhibiting a further improved expansion and tightening structure, and the crank structure can be easily and easily assembled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a structural view of a bicycle crank structure according to an embodiment of the present invention mounted on a hub of a bicycle frame; FIG.

2 is a perspective view of a crank structure of a bicycle according to an embodiment of the present invention;

3 is a sectional view of a crank structure of a bicycle according to an embodiment of the present invention.

4 is an exploded view of a crank structure of a bicycle according to an embodiment of the present invention.

5 is a perspective view (a) and a cross-sectional view (b) of a crankshaft in a crank structure of a bicycle according to an embodiment of the present invention.

6 is a structural view of a crank structure of a bicycle according to an embodiment of the present invention in which an expansion guide portion is assembled to a coupling shaft of a crankshaft.

7 is a perspective view of a crank arm in a crank structure of a bicycle according to an embodiment of the present invention.

8 is a cross-sectional view of a crank structure of a bicycle according to an embodiment of the present invention, in which the auxiliary shaft is provided in the crankshaft.

FIG. 9 is a cross-sectional view of a crankshaft in which a sub-shaft is provided in the crank structure of the bicycle according to the embodiment of the present invention shown in FIG. 8;

10 is a perspective view (a) and a sectional view (b) of the auxiliary shaft in the crank structure of the bicycle according to the embodiment of the present invention.

11 is an assembly exploded view of a crankshaft and a subsidiary shaft in a crank structure of a bicycle according to an embodiment of the present invention.

FIG. 12 is an exploded view of a crank structure of a bicycle according to an embodiment of the present invention in which a supplementary shaft-crank arm-expanded guide portion-cap portion-fastening bolt is assembled to the crank shaft.

13 is an exploded view of a crank structure of a bicycle according to an embodiment of the present invention, in which a bracing member is assembled to a sub-shaft.

FIG. 14 is a view (a) and a perspective view (b) showing the mounting portion of the crankshaft in the crank structure of the bicycle according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements throughout. The same reference numerals in the drawings denote like elements throughout the drawings.

First, a crank structure of a bicycle according to the present invention will be described. Hereinafter, the direction of the inside of the crankshaft 100 is referred to as 'inside' and the direction outside of the crankshaft 100 is defined as 'outside' with reference to the crankshaft 100 for convenience.

A crank structure 10 according to the present invention has a housing (not shown) coupled to both sides of a hub 21 formed on a frame 20 of a bicycle and has a bearing portion (not shown) A crankshaft 100 whose both ends are extended to the hub 21 of the frame 20 and both ends of which are projected to the outside of the hub 21 in a structure in which the hub 21 is mounted, The crankshaft 100 is connected to the hub 21 of the frame 20 by a crank arm (or rod) 200 that is coupled to an end of the shaft 100 to mount a pedal (not shown) And the crank arm 200 coupled to the crankshaft 100 is constituted by a crank structure 10. One crank arm 200 of the two crank arms 200 is provided with a coupling mechanism for coupling gears (not shown) connecting the chains.

The crankshaft 100 is installed on the hub 21 of the frame 20 of the bicycle and the crank arm 200 is coupled to the crank arm 200. The crankshaft 100 and the crank arm 200 are coupled to each other, (10) and the coupling relationship thereof will be described as follows.

1 to 7, a crankshaft 100 which is engaged with a hub 21 of a frame 20 of a bicycle and a crankshaft 100 which is coupled to both ends of the crankshaft 100, The crankshaft 100 is integrally formed with both the main shaft 110 which extends to the hub 21 of the frame 20 and both ends of the main shaft 110, A coupling shaft 120 protruding outward from the hub 21 is formed and a coupling hole 121 passing through the coupling shaft 120 in a predetermined longitudinal direction is formed and the inner diameter gradually decreases toward the inside And the first fastening hole 111 having an inner diameter smaller than the minimum inner diameter of the fastening hole 121 is communicated with the fastening hole 121 through the inside of the fastening hole 120, And is formed in the shape of a blind hole extending in a predetermined longitudinal direction, The concave portion 122 and the convex portion 123 are repeatedly arranged on the outer circumferential surface of the coupling shaft 120 in the longitudinal direction and the concave portion 122 and the

concave portion

122, 121 and the first fastening hole 111,

The crank arm 200 has a shaft hole 210 formed at one end thereof so as to be coupled to the coupling shaft 120 of the crank shaft 100. The crank shaft 200 has a repetitive recessed portion 210 formed on the outer circumferential surface of the coupling shaft 120, The concave portion 211 and the convex portion 212 are repeatedly arranged in the longitudinal direction of the shaft hole 210 in the shaft hole 210 so as to correspond to the shaft portion 122 and the shaft portion 123,

An outer circumferential surface corresponding to the inner circumferential surface shape of the binding hole 121 is formed so as to be brought into engagement with the binding hole 121 of the coupling shaft 120 when the crank arm 200 is coupled to the coupling shaft 120 of the crank shaft 100 A first intermittent tab 301 protruded on both sides of the outer circumferential surface so as to be coupled to the cutout hole 124 of the coupling shaft 120 is formed and a first insertion hole 302 passing through both side ends is formed An enlarging guide portion 300 is provided,

A cap portion 400 is formed which is inserted into the outer end of the shaft hole 210 of the crank arm 200 to form a second insertion hole 401 which passes through both ends of the shaft hole 210 and becomes smaller in diameter toward the inner end,

Is passed through the first insertion hole 302 of the expansion guide portion 300 through the second insertion hole 401 of the cap portion 400 and is inserted into the first fastening hole 111 of the coupling shaft 120 of the crankshaft 100 And a fastening bolt (500) having a head portion (501) formed in the second insertion hole (401) and forming an outer circumferential surface corresponding to the inner circumferential surface shape of the second insertion hole (401) Thereby providing a crank structure 10.

3 to 5, the crankshaft 100 is coupled to the hub 21 of the frame 20 and has a longitudinal direction identical to the longitudinal direction of the hub 21 And a coupling shaft 120 integrally connected to both ends of the cylindrical main shaft 110 and the main shaft 110.

A binding hole 121 penetrating through the coupling shaft 120 from the outside to the inside with a predetermined length is formed and the inner diameter gradually decreases toward the inside and is connected to the binding hole 121, The first fastening hole 111 having an inner diameter smaller than the minimum inner diameter of the coupling shaft 120 is formed in the form of a blind hole extending in the longitudinal direction of the main shaft 110 through the inside of the coupling shaft 120, A screw thread is formed on the inner circumferential surface of the fastening hole (111).

That is, a coupling hole 121 is formed at one side of the coupling shaft 120, and a part of the first coupling hole 111 communicating with the coupling hole 121 is formed at the other side of the coupling shaft 120, The remaining length of the first fastening hole 111 of the main shaft 120 is formed to extend into the main shaft 110.

The concave portion 122 and the convex portion 123 are repeatedly arranged on the outer circumferential surface of the coupling shaft 120 in the horizontal length direction of the coupling shaft 120 so that the one concave portion 122 and the other concave portion 122 facing the one concave portion 122 A cutting hole 124 communicating with the fastening hole 121 and the first fastening hole 111 is formed in the first fastening hole 122.

4 and 7, the crank arm 200 is coupled to a coupling shaft 120 formed at both ends of the crank shaft 100, and is connected to the coupling shaft 120 of the crank shaft 100 And a pedal (not shown) is mounted on the other end of the shaft hole 210 so that the shaft hole 210 is coupled to the crank shaft 100 The concave portion 211 and the convex portion 212 are repeatedly inserted into the shaft hole 210 in the horizontal length direction of the shaft hole 210 in such a manner that the shaft hole 210 and the convex concave portion 122 formed on the outer circumferential surface of the shaft hole 210, And when the shaft hole 210 is coupled to the coupling shaft 120, the convex portion 212 of the shaft hole 210 is coupled to the concave portion 122 of the coupling shaft 120, .

4 and 6, after the crank arm 200 is coupled to the coupling shaft 120 of the crank shaft 100, the expansion guide hole 300 of the coupling shaft 120, The inner diameter of the bellows hole 121 is formed to be larger than the inner diameter of the bellows hole 121 and the inner diameter of the bellows hole 121 is greater than the inner diameter of the binding hole 121, The outer circumferential surface of the divergent guide portion 300 moves toward the inner circumferential surface of the binding hole 121 as the divergent guide portion 300 moves toward the inside of the binding hole 121 when the diverging guide portion 300 moves into the binding hole 121 of the coupling shaft 120 So that the coupling shaft 120 separated from the two side incision holes 124 is opened to the outside so that the outer peripheral surface of the coupling shaft 120 strongly presses the inner peripheral surface of the shaft hole 210.

The first intermittent tabs 301 protruded from both sides of the outer circumferential surface of the expanded guiding portion 300 so that the expanded guiding portion 300 is linearly moved without rotating when moved to the binding hole 121 of the coupling shaft 120 And is coupled to the cutting hole 124 of the coupling shaft 120 and is guided to move inside the binding hole 121.

A first insertion hole 302 is formed in the inside of the expansion guide 300 so as to pass through both side ends of the expansion guide 300 so that a fastening bolt 500 to be described later is passed therethrough.

3 and 4, the cap part 400 is installed after a part of the expansion guide part 300 is inserted into the coupling hole 121 of the coupling shaft 120, and the crank arm 200, And a second insertion hole 401 which is interposed between the outer ends of the shaft holes 210 to be mutually engaged with each other at both ends thereof and whose inner diameter decreases toward the inner end.

3 and 4, the fastening bolt 500 is installed after the cap portion 400 is coupled to the shaft hole 210 of the crank arm 200, Is inserted into the first coupling hole 111 of the coupling shaft 120 of the crankshaft 100 through the first insertion hole 302 of the expansion guide portion 300 through the insertion hole 401, The head portion 510 is formed in the second insertion hole 401 of the first insertion hole 401 and forms an outer peripheral surface corresponding to the inner peripheral surface shape of the second insertion hole 401. [

The end of the tightening bolt 500 is screwed to the first fastening hole 111 of the fastening shaft 120 and enters the first fastening hole 111 of the main shaft 110. At this time, The inner surface of the cap portion 400 interrupting the portion 510 is pressed against the outer surface of the expanded guide portion 300 and the expanded guide portion 300 is inserted into the binding hole 121 of the coupled shaft 120 The outer circumferential surface of the expansion inducing portion 300 is pressed on the inner circumferential surface of the binding hole 121 so that the coupling shaft 120 expands outward and the outer circumferential surface of the coupling shaft 120 contacts the inner circumferential surface of the shaft hole 210 of the crank arm 200 So that the crank shaft 100 and the crank arm 200 have a rigid assembling structure.

8 to 12, the coupling holes 121 of the two coupling shafts 120 are connected to the inside of the main shaft 110 so as to communicate with each other without the first coupling holes 111 formed in the crankshaft 100. [ A through-receiving hole 112 is formed,

A concave portion 601 and a convex portion 602 are repeatedly arranged on the inner circumference and the stepped outer circumference of the inner side while the end is provided in the receiving hole 112 and the end is protruded into the binding hole 121, A second intermittent tab 604 protruded on both sides of the outer circumferential surface so as to be coupled to the cutout hole 124 of the coupling shaft 120 is formed on the outer circumferential surface of the end portion, A pair of auxiliary shafts 600 in which the fastening holes 605 are formed are provided in a symmetrical structure so that the recessed portions 601 of the inner peripheral end and the convex portions 602 are coupled to each other in an engaging manner,

The fastening bolt 500 passes through the first insertion hole 302 of the expansion guide portion 300 through the second insertion hole 401 of the cap portion 400 and is inserted into the receiving hole 112 of the crankshaft 100 And the second fastening hole (605) of the auxiliary shaft (600).

The receiving hole 112 and the first fastening hole 111 of the crankshaft 100 described in the above embodiment are not formed and the receiving hole 112 penetrating the inside of the crankshaft 100 while opening both sides of the crankshaft 100 .

8 and 11, a pair of the auxiliary shafts 600 are coupled to each other in the receiving hole 112, and a pair of the auxiliary shafts 600 are coupled to each other in the form of a bilaterally symmetrical structure, 112 of the crankshaft 100 so that the end of the crankshaft 100 is protruded into the binding hole 121.

10 (a) and 10 (b), the concave portion 601 and the convex portion 602 are repeatedly arranged in the circumferential direction on the inner circumferential end of the auxiliary shaft 600, And a pair of auxiliary shafts 600 are formed in the inside of the receiving hole 112 symmetrically with respect to the receiving hole 112. The concave portion 601 and the convex portion 601 602 are mutually mated in an intermeshed manner.

10A, a second intermittent tab 604 protruding from both sides of the outer peripheral surface of the auxiliary shaft 600 is formed so as to be inserted into the receiving hole 112 of the crankshaft 100, The second intermittent tab 604 is coupled to the cutout hole 124 of the coupling shaft 120 and inserted into the receiving hole 112. At this time, The second intermittent tab 604 of the shaft 600 and the first intermittent tab 301 of the expanded guide portion 300 are located on the other side of the cutout hole 124.

As shown in FIG. 10 (b), a second fastening hole 605 is formed through the outer end of the auxiliary shaft 600 to have a predetermined length and has a blind hole shape, A screw thread is formed on the inner circumferential surface of the expanding portion 605 and the fastening bolt 500 passes through the first insertion hole 302 of the expanding guide portion 300 through the second insertion hole 401 of the cap portion 400, The inner surface of the cap portion 400 presses the outer surface of the expanded guide portion 300 while the screw portion 400 is screwed into the second fixing hole 605 of the shaft 600, The outer circumferential surface of the coupling shaft 120 presses the outer peripheral surface of the shaft hole 210 of the crank arm 200.

In this case, the outer diameter of the auxiliary shaft 600 is set to be equal to the minimum outer diameter of the diameter guide guide 300, so that the diameter guide guide 300 is inserted into the diameter guide hole 300 of the coupling shaft 120, So that the inner surface of the auxiliary shaft 600 is brought into close contact with the outer surface of the auxiliary shaft 600.

Although not shown in the drawing, a thread is formed on the inner circumferential surface of the first insertion hole 302 of the expanded guiding portion 300, and the fastening bolt 500 is screwed to the first insertion hole 302 when fastened The fastening bolt 500 is moved and screwed to the second fastening hole 605 of the auxiliary shaft 600. At this time, by the rotation of the fastening bolt 500, the fastening guide portion 300 is inserted into the fastening hole 121, respectively.

As shown in FIGS. 13 and 14, a circumferential stepped engagement groove 606 is formed on the outer peripheral surface between the outer peripheral end of the auxiliary shaft 600 and the second intermittent tab 604, and the engagement groove 606 Three guide holes 607 are formed at equal intervals, which are communicated with the second fastening holes 605,

And a projecting piece 720 protruding from the center of the inner side of the frame 710 and being engaged with the guide hole 607 and having a screw thread formed at an end portion thereof, The crank structure 10 of the bicycle is provided with three stopper portions 700 arranged and arranged in the circumferential direction in the engaging groove 606.

14 (b), the enlargement / contraction support portion 700 is formed integrally with a rim 710 and a protruding piece 720 protruding from the center of the inside of the rim 710, and as shown in Fig. 14 (a) The frame 710 has a curved shape and the three extending portions 700 are engaged with the engaging groove 606 of the auxiliary shaft 600 so that the ends of the three extending portions 700 Are mutually interviewed to form a ring.

The outer circumferential surface of the auxiliary shaft 600 on which the engagement groove 606 is formed is positioned inside the coupling shaft 120 of the crank shaft 100 by the engagement groove 606 When the fastening bolt 500 is screwed into the second fastening hole 605 of the auxiliary shaft 600, the fastening bolt 500 is fastened to the second fastening hole 607 through the guide hole 607 of the fastening groove 606 The threaded portion of the fastening bolt 500 is engaged with the thread of the end of the protruding piece 720 while the protruded piece 720 of the enlarged projection 700 protruded from the protruded piece 720 is in close contact with the guide hole 607, The rim 700 is widened to the outside of the auxiliary shaft 600. That is, the rim 710 of the rim 700, which is seated in the latching groove 606, is moved in an excited state, The engaging shaft 120 of the crank arm 700 is strongly pressed by the rim 710 of the crank arm 700 and the engaging shaft 120 is expanded so that the engaging shaft 120 is strongly pressed against the shaft hole 210 of the crank arm 200, (100) Crank arm 200 is coupled to have a solid structure.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

[Description of Symbols]

Crank structure 10 crank shaft 100 main shaft 110

The first fastening hole 111, the receiving hole 112, the engaging shaft 120

Coupling hole 121 concave portion 122 convex portion 123

Cut-off ball 124 crank arm 200 shaft hole 210

The lumbar part 211 the convex part 212 the expansion guide part 300

First intermittent tab 301 first insert hole 302 cap portion 400

Second insertion hole 402 Fastening bolt 500 Secondary shaft 600

Recessed portion 601 convex portion 602 second intermittent tab 604

Second fastening hole 605 fastening groove 606 guide hole 607

Expanded branch 700 Border 710 Overhang 720

Claims

A crank structure (10) of a bicycle comprising a crankshaft (100) that is engaged with a hub (21) of a bicycle frame (20) and a crank arm (200) coupled to both ends of the crankshaft (100)

The crankshaft 100 is formed with a main shaft 110 extending to the hub 21 of the frame 20 and a coupling shaft 120 integrally formed at both ends of the main shaft 110 and projecting outwardly of the hub 21 The coupling shaft 120 is formed with a coupling hole 121 passing through a predetermined length in the coupling shaft 120. The inner diameter of the coupling shaft 120 gradually decreases toward the inside of the coupling shaft 120. The coupling hole 120 is in communication with the coupling hole 121, A first fastening hole 111 having an inner diameter smaller than a minimum inner diameter of the coupling shaft 121 is formed in the shape of a blind hole by extending in the longitudinal direction of the main shaft 110 through the inside of the coupling shaft 120, The concave portion 122 and the convex portion 123 are repeatedly arranged in the longitudinal direction of the coupling shaft 120 on the outer circumferential surface of the coupling shaft 120 and the other concave portion 122 and the other concave portion 122 facing the one concave portion 122 And the first fastening hole 111 and the second fastening hole 111, respectively,

The crank arm 200 has a shaft hole 210 formed at one end thereof so as to be coupled to the coupling shaft 120 of the crank shaft 100. The crank shaft 200 has a repetitive recessed portion 210 formed on the outer circumferential surface of the coupling shaft 120, The concave portion 211 and the convex portion 212 are repeatedly arranged in the longitudinal direction of the shaft hole 210 in the shaft hole 210 so as to correspond to the shaft portion 122 and the shaft portion 123,

An outer circumferential surface corresponding to the inner circumferential surface shape of the binding hole 121 is formed so as to be brought into engagement with the binding hole 121 of the coupling shaft 120 when the crank arm 200 is coupled to the coupling shaft 120 of the crank shaft 100 A first intermittent tab 301 protruded on both sides of the outer circumferential surface so as to be coupled to the cutout hole 124 of the coupling shaft 120 is formed and a first insertion hole 302 passing through both side ends is formed An enlarging guide portion 300 is provided,

A cap portion 400 is formed which is inserted into the outer end of the shaft hole 210 of the crank arm 200 to form a second insertion hole 401 which passes through both ends of the shaft hole 210 and becomes smaller in diameter toward the inner end,

Is passed through the first insertion hole 302 of the expansion guide portion 300 through the second insertion hole 401 of the cap portion 400 and is inserted into the first fastening hole 111 of the coupling shaft 120 of the crankshaft 100 A fastening bolt 500 is provided which is threaded and formed with a head 501 which is positioned at the second insertion hole 401 and forms an outer circumferential surface corresponding to the inner circumferential surface shape of the second insertion hole 401 A crank structure of a bicycle.
The crankshaft according to claim 1, wherein the crankshaft includes a receiving hole penetrating into the main shaft to communicate with the coupling holes of the coupling shafts without the first coupling holes formed in the crankshaft, 112)

A concave portion 601 and a convex portion 602 are repeatedly arranged on the inner circumference and the stepped outer circumference of the inner side while the end is provided in the receiving hole 112 and the end is protruded into the binding hole 121, A second intermittent tab 604 protruded on both sides of the outer circumferential surface so as to be coupled to the cutout hole 124 of the coupling shaft 120 is formed on the outer circumferential surface of the end portion, A pair of auxiliary shafts 600 in which the fastening holes 605 are formed are provided in a symmetrical structure so that the recessed portions 601 of the inner peripheral end and the convex portions 602 are coupled to each other in an engaging manner,

The fastening bolt 500 passes through the first insertion hole 302 of the expansion guide portion 300 through the second insertion hole 401 of the cap portion 400 and is inserted into the receiving hole 112 of the crankshaft 100 Is screwed into the second fastening hole (605) of the auxiliary shaft (600).
The method according to claim 2, wherein a circumferential stepped engagement groove (606) is formed on the outer peripheral surface between the outer peripheral end of the auxiliary shaft (600) and the second intermittent tab (604) Three guide holes 607 spaced apart at equal intervals and communicating with the two fastening holes 605 are formed,

And a projecting piece 720 protruding from the center of the inner side of the frame 710 and being engaged with the guide hole 607 and having a screw thread formed at an end portion thereof, And three stopper portions (700) are arranged in the engagement groove (606) in the circumferential direction and are seated.