Crank and bicycle
By designing the width of the first arm of the crank in the axial direction of the central axis, the problem of insufficient lateral rigidity of the traditional crank is solved, and the performance of the bicycle is improved.
Patent Information
- Application Number
- CN202422291296.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2025-06-27
- Estimated Expiration
- 2034-09-19
AI Technical Summary
The lateral rigidity of traditional cranks is weak and is prone to lateral deformation during riding, affecting the performance of the bicycle.
A crank is designed where the innermost contour of the first arm extends inwardly beyond the inner end face, and the outermost contour of the first arm is arc-shaped arched outwardly, increasing the width of the first arm in the axial direction of the central axis, thereby improving the lateral rigidity of the crank.
By increasing the lateral rigidity of the crank, the possibility of lateral deformation during pedaling is reduced, and the performance of the bicycle is improved.
Smart Images
Figure CN223031191U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of bicycles, in particular to a crank and a bicycle. Background Art
[0002] A bicycle is not only an environmentally friendly means of transportation, but more and more people use bicycles as fitness equipment for cycling exercise and bicycle outings.
[0003] When riding a bicycle, the pedaling force is sequentially transmitted to the pedal, the crank, the chainring and the wheel. In order to ensure the excellent performance of the bicycle to achieve a better riding effect, the crank, as an intermediate component for transmitting the pedaling force, needs to have good rigidity. However, the structural arrangement of the traditional crank results in weak lateral rigidity of the crank, and the crank with weak lateral rigidity is prone to lateral deformation during pedaling, which affects the performance of the bicycle. Summary of the Utility Model
[0004] Based on this, in view of the problem that the traditional crank has weak lateral rigidity and is prone to lateral deformation during riding, it is necessary to provide a crank and a bicycle with better lateral rigidity and reduced lateral deformation.
[0005] A crank, the crank includes a bottom bracket mounting portion, a crank arm and a pedal mounting portion that are sequentially connected in the longitudinal direction; in the axial direction of the bottom bracket, the bottom bracket mounting portion has an inner end face;
[0006] The crank arm includes a first arm and a second arm that are connected to each other in the longitudinal direction, the first arm is connected to the bottom bracket mounting portion, and the second arm is connected to the pedal mounting portion; the first arm has an innermost contour line connecting its two ends in the longitudinal direction, and the innermost contour line extends inward beyond the inner end face;
[0007] The crank arm has an outermost contour line connecting its two ends in the longitudinal direction, and the part of the outermost contour line corresponding to the first arm is an arc-shaped line that arches outward from one end close to the bottom bracket mounting portion to the other end.
[0008] In one embodiment, in the axial direction of the bottom bracket, the pedal mounting portion has an outer end face;
[0009] The outermost contour line includes an arc segment and a straight segment that are connected to each other, at least part of the arc segment corresponds to the first arm, the straight segment corresponds to the second arm, the arc segment is located within the outer end face, and the straight segment is flush with the outer end face; or
[0010] The outermost contour line extends outward beyond the outer end face and is an arch shape with the middle part arching outward.
[0011] In one embodiment, the cross-sectional shape of the first arm is drop-shaped, and the directions of the lines connecting the large end and the small end of the drop shape, the axial direction, and the longitudinal direction intersect pairwise;
[0012] When the pedal mounting portion is in front of the bottom bracket mounting portion, the large end is below the small end.
[0013] In one embodiment, the inner side surface of the second arm is recessed outward relative to the inner end surface to form an avoidance portion for avoiding the derailleur.
[0014] In one embodiment, the crank further includes a chainring socket portion, which is located inside the bottom bracket mounting portion in the axial direction of the bottom bracket and is in contact with the inner end surface of the bottom bracket mounting portion.
[0015] In one embodiment, the crank further includes a chainring fixing portion, which is located between the chainring socket portion and the bottom bracket mounting portion in the axial direction of the bottom bracket, and the chainring socket portion is in contact with the inner end surface of the bottom bracket mounting portion through the chainring fixing portion.
[0016] In one embodiment, the crank includes a body and a carbon fiber cloth layer wrapped around the body.
[0017] In one embodiment, the carbon fiber cloth layer includes a first carbon fiber filament, a second carbon fiber filament, and a third carbon fiber filament. The first extension direction of the first carbon fiber filament is parallel to the longitudinal direction. The first included angle α1 between the second extension direction of the second carbon fiber filament and the longitudinal direction satisfies the relationship 10° ≤ α1 < 45°. The second included angle α2 between the third extension direction of the third carbon fiber filament and the longitudinal direction satisfies the relationship -45° < α2 ≤ -10°.
[0018] In one embodiment, the number of layers of the carbon fiber cloth layer wrapped around the outer side surface, inner side surface, upper side surface, and lower side surface of the body are a, b, c, and d respectively, and a, b, c, and d satisfy the relationship:
[0019] a > b > c > d;
[0020] When the pedal mounting portion is in front of the bottom bracket mounting portion, the upper side surface is above the lower side surface.
[0021] A bicycle includes a crank as described above.
[0022] In the above-mentioned crank and bicycle, since the innermost contour line of the first arm extends inward beyond the inner end face, and the outermost contour line of the first arm is an arc-shaped line that bulges outward, the width of the first arm in the axial direction of the bottom bracket is increased compared to the situation where the first arm of the crank in the prior art is located outside the inner end face or flush with the inner end face. With a larger width, the moment of inertia of the cross-section of the first arm with respect to the axis extending in the longitudinal direction of the crank is larger, thereby improving the stiffness of the crank in the axial direction of the bottom bracket, making it less likely for the crank to undergo lateral deformation during pedaling and improving the performance of the bicycle. Description of the Drawings
[0023] Figure 1 Side view of a bicycle provided by an embodiment of the present application;
[0024] Figure 2 is Figure 1 Top view of the bicycle shown in
[0025] Figure 3 Axonometric view of a crank provided by an embodiment of the present application;
[0026] Figure 4 is Figure 3 Plan view of the crank shown in
[0027] Figure 5 Plan view of a crank provided by another embodiment of the present application;
[0028] Figure 6 Comparison diagram of the cross-section of the crank with and without widening;
[0029] Figure 7 is Figure 5 Cross-sectional view of the A-A plane of the first arm of the crank shown in
[0030] Figure 8 Exploded view of the partial structure of a crank provided by an embodiment of the present application;
[0031] Figure 9 Looking from direction A towards Figure 8 Plan view formed when looking at the structure diagram in
[0032] Description of the Reference Numerals:
[0033] 100, frame; 200, crank; 10, bottom bracket mounting portion; 11, mounting hole; 12, inner end face; 20, crank arm; 21, first arm; 22, second arm; 221, avoidance portion; 30, pedal mounting portion; 31, outer end face; 40, chainring socket portion; 50, chainring fixing portion; 60, body; 70, carbon fiber cloth layer; L1, innermost contour line; L2, outermost contour line; L21, arc segment; L22, straight segment; 300, chainring; 400, derailleur. Detailed implementation manners
[0034] To make the above objects, features and advantages of the present utility model more obvious and understandable, the following detailed description of the specific implementation manners of the present utility model will be given with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present utility model. However, the present utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present utility model. Therefore, the present utility model is not limited by the specific embodiments disclosed below.
[0035] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present utility model.
[0036] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present utility model, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.
[0037] In the present utility model, unless otherwise clearly defined and limited, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.
[0038] In the present utility model, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.
[0039] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation.
[0040] An embodiment of the present application provides a bicycle, which can be a two-wheel bicycle or a three-wheel bicycle, and the bicycle can be a bicycle driven solely by human power without a power assist device or a power-assisted bicycle equipped with a power assist device to assist by the power assist device, which is not limited herein.
[0041] Refer to Figure 1 and Figure 2 , the bicycle includes a frame 100, a bottom bracket (not shown in the figure), a crank 200 and pedals (not shown in the figure). The bottom bracket is connected to the bottom bracket tube of the frame 100, one end of the crank 200 is connected to the bottom bracket, and the pedals are connected to the other end of the crank 200. In this way, the pedaling force can be sequentially transmitted between the pedals, the crank 200 and the bottom bracket, prompting the bicycle to move forward.
[0042] Refer to Figure 2 and Figure 3 , the crank 200 includes a bottom bracket mounting portion 10, a crank arm 20 and a pedal mounting portion 30. In the longitudinal direction of the crank 200, the bottom bracket mounting portion 10, the crank arm 20 and the pedal mounting portion 30 are sequentially connected. That is, in the longitudinal direction of the crank 200, it includes a bottom bracket mounting portion 10, a crank arm 20 and a pedal mounting portion 30 connected in sequence. Among them, the bottom bracket mounting portion 10 is connected to the bottom bracket. Optionally, the bottom bracket mounting portion 10 is provided with a mounting hole 11 along the axial direction of the bottom bracket, and the bottom bracket passes through the mounting hole 11 of the bottom bracket mounting portion 10. The pedal mounting portion 30 is connected to the pedals, and the crank arm 20 is located between the bottom bracket mounting portion 10 and the pedal mounting portion 30, playing a role in transmitting the pedaling force.
[0043] Refer toFigure 4 and Figure 5 on the axial direction of the central shaft (generally, the axial direction of the central shaft is perpendicular to the longitudinal direction of the crank 200), the central shaft mounting portion 10 has an inner end face 12 ( Figure 4 and Figure 5 in, the position corresponding to the inner red line is the position where the inner end face 12 is located), and this end face is arranged closer to the center line of the frame 100 relative to the other end face of the central shaft mounting portion 10. That is, taking the situation when the rider is riding on the bicycle as a reference standard, the inner end face 12 is farther from the rider's feet relative to the other end face of the central shaft mounting portion 10. Continue to refer to Figure 4 The crank arm 20 includes a first arm 21 and a second arm 22 connected to each other in the longitudinal direction. The first arm 21 is connected to the central shaft mounting portion 10, and the second arm 22 is connected to the pedal mounting portion 30. The first arm 21 has an innermost contour line L1 connecting its two ends in the longitudinal direction ( Figure 4 and Figure 5 the blue line located inside in), if the plane formed by the intersection of the axial direction of the central shaft and the longitudinal direction of the crank 200 is defined as the first plane, the crank 200 has a first orthographic projection in the first plane, and the innermost contour line L1 is the inner contour line of the first orthographic projection. Among them, the innermost contour line L1 extends inward beyond the inner end face 12.
[0044] Furthermore, continue to refer to Figure 4 and Figure 5 The crank 200 has an outermost contour line L2 connecting its two ends in the longitudinal direction ( Figure 4 and Figure 5 the blue line located outside in), the part of the outermost contour line L2 corresponding to the first arm 21 is the first arm 21 having a first contour line, and the outermost contour line L2 includes the first contour line. The first contour line is an arc-shaped arching outward from the end close to the central shaft mounting portion 10 to the other end. It should be noted here that the outermost contour line L2 is the outer contour line of the first orthographic projection, and the first contour line is the outer contour line of the first arm 21.
[0045] With the above settings, since the innermost contour line L1 of the first arm 21 extends inward beyond the inner end face 12, and the outermost contour line L2 of the first arm 21 is an arc-shaped arching outward, in this way, compared with the situation in the prior art where the first arm 21 of the crank 200 is located outside the inner end face 12 or flush with the inner end face 12, the width of the first arm 21 in the axial direction of the central shaft is increased. And with a larger width, the moment of inertia of the cross-section of the first arm 21 about the axis extending in the longitudinal direction of the crank 200 is larger, thereby improving the stiffness of the crank 200 in the axial direction of the central shaft, making the crank 200 not easily undergo lateral deformation during pedaling, and improving the performance of the bicycle.
[0046] According to the formula of mechanics of materials, it can be obtained thatFigure 6 ( Figure 6 In (where the x - direction represents the axial direction of the central axis, and the y - direction is perpendicular to the x - direction), the moments of inertia of the two cross - sections are respectively: Because L 加宽 > L 不加宽 , so It can be seen therefrom that the lateral rigidity of the widened cross - section is better.
[0047] In some specific embodiments, the innermost contour line L1 is an arc - shaped line that arches inward in the middle to facilitate the machining and manufacturing of the crank 200. Of course, in some other embodiments, the shape of the innermost contour line L1 is not limited.
[0048] Further, referring continuously to Figure 4 , the inner side surface of the second arm 22 is recessed outward relative to the inner end surface 12 to form an avoidance portion 221, and the avoidance portion 221 is used to avoid the derailleur 400. By providing the avoidance portion 221, an avoidance space for avoiding the derailleur 400 is reserved, preventing the derailleur 400 from being installed too inward and interfering with other components.
[0049] In some embodiments, referring continuously to Figure 4 and Figure 5 , in the axial direction of the central axis, the pedal mounting portion 30 has an outer end surface 31 (( Figure 4 and Figure 5 In, the position corresponding to the outer red line is the position where the outer end surface 31 is located)). Referring to Figure 4 , the outermost contour line L2 includes an arc segment L21 and a straight segment L22 that are connected to each other. At least part of the arc segment L21 corresponds to the first arm 21, and the straight segment L22 corresponds to the second arm 22. That is, the arc segment L21 includes a first contour line, the second arm 22 has a second contour line, and the second contour line includes the straight segment L22. Specifically, the arc segment L21 is located within the outer end surface 31, and the straight segment L22 is flush with the outer end surface 31. This setting ensures the width of the second arm 22 in the axial direction of the central axis and can further improve the rigidity of the crank 200.
[0050] In some other embodiments, referring to Figure 5 , the outermost contour line L2 extends outward beyond the outer end surface 31 and is in an arched shape with the middle part arched outward. Optionally, the highest point of the middle part arched outward is located at the connection between the first contour line and the second contour line. Of course, in some other embodiments, the position of the highest point of the middle part arched outward is not limited. This setting not only increases the width of the first arm 21 in the axial direction of the central axis but also increases the width of the second arm 22 in the axial direction of the central axis, making the lateral rigidity of the crank 200 better.
[0051] It can be understood that in some other embodiments, the outermost contour line L2 can also adopt other setting methods, which are not limited herein.
[0052] In some embodiments, referring to Figure 7 , the cross-sectional shape of the first arm 21 is in the shape of a water droplet. The direction of the line connecting the large head end and the small head end of the water droplet, the axial direction of the central axis, and the longitudinal direction of the crank 200 intersect pairwise. Specifically, the direction of the line, the axial direction, and the longitudinal direction are perpendicular to each other pairwise. Among them, when the pedal mounting portion 30 is in front of the central axis mounting portion 10, the large head end is below the small head end. On the one hand, setting the cross-sectional shape of the first arm 21 to be in the shape of a water droplet can increase the width of the first arm 21 in the axial direction of the central axis and improve the rigidity of the crank 200 (refer to Figure 7 ). On the other hand, when the pedal mounting portion 30 of the crank 200 is in front of the central axis mounting portion 10, the first arm 21 will be subjected to a relatively large acting force on the windward side in the rotation direction of the crank 200. At this time, the large head end of the water droplet is below the small head end, and the large head end has a relatively large rigidity and can withstand a relatively large acting force, avoiding deformation of the crank 200.
[0053] It should be noted here that the front, rear, upper, lower, inner, and outer directions described in the text are all determined with reference to the perspective of the rider when riding a bicycle. The front and rear are the front and rear of the rider, and the upper and lower are the upper and lower of the rider.
[0054] It can be conceived that in some other embodiments, the cross-sectional shape of the first arm 21 is not limited. For example, the first arm 21 can also have other irregular shapes.
[0055] In some embodiments, continuing to refer to Figure 3 , the crank 200 further includes a chainring socket portion 40. The chainring socket portion 40 is located inside the central axis mounting portion 10 in the axial direction of the central axis and is connected to the inner end face 12 of the central axis mounting portion 10. The crank 200 is provided with a chainring socket portion 40. When installing the chainring 300, the chainring 300 is sleeved outside the chainring socket portion 40 to facilitate the installation of the chainring 300.
[0056] Furthermore, the crank 200 further includes a chainring fixing portion 50. The chainring fixing portion 50 is located between the chainring socket portion 40 and the central axis mounting portion 10 in the axial direction of the central axis. The chainring socket portion 40 is connected to the inner end face 12 of the central axis mounting portion 10 through the chainring fixing portion 50. In this way, after the chainring 300 is sleeved outside the chainring socket portion 40, the chainring 300 is fixed to the chainring fixing portion 50 by locking screws. Of course, in some other embodiments, the crank 200 can also omit the chainring fixing portion 50. At this time, the chainring 300 is directly locked on the central axis mounting portion 10.
[0057] It should be noted here that, for the convenience of installing the central shaft, through holes are provided on the chainring fixing part 50 and the chainring socket part 40 so that the central shaft can pass through the mounting hole 11 of the central shaft mounting part 10.
[0058] In some embodiments, referring to Figure 8 , the crank 200 includes a body 60 and a carbon fiber cloth layer 70 wrapped around the body 60. The density of carbon fiber is much lower than that of steel and aluminum alloy, but the strength is very high. By wrapping the carbon fiber cloth layer 70, the crank 200 can be made both light and strong.
[0059] The applicant's research found that during cycling, the pedaling force is sequentially transmitted to the pedal, the crank 200, the chainring 300, and the wheel. Any cross-section on the crank 200 is mainly subjected to a longitudinal bending moment M1, a lateral bending moment M2, a torque T, and a tensile force F. The directions of the two bending moments are consistent with the direction of the line connecting the center point of the central shaft mounting part 10 and the center point of the pedal mounting part 30 (the longitudinal direction of the crank 200, that is, the 0° direction of the crank 200). Since the mechanical properties of the carbon fiber cloth layer 70 in the extending direction of the carbon fiber filaments are the best among all directions, that is, when the extending direction of the carbon fiber filaments is consistent with the 0° direction of the crank 200, the crank 200 has the strongest anti-bending and anti-tensile capabilities. Therefore, when ensuring the anti-torsion ability of the crank 200 in the 90° direction, the angles of all the carbon fiber filaments of the crank 200 can be made as close to the 0° direction as possible, which can enhance the lateral anti-bending and anti-tensile capabilities of the crank 200 and increase the lateral rigidity.
[0060] Referring to Figure 9 , the carbon fiber cloth layer 70 includes a first carbon fiber filament, a second carbon fiber filament, and a third carbon fiber filament. The first extending direction of the first carbon fiber filament is parallel to the longitudinal direction, the first included angle α1 between the second extending direction of the second carbon fiber filament and the longitudinal direction satisfies the relationship 10°≤α1<45°, and the second included angle α2 between the third extending direction of the third carbon fiber filament and the longitudinal direction satisfies the relationship -45°<α2≤-10°. Since α1 and α2 are closer to 0°, compared with the carbon cloth with laying angles of 0°, +45°, and -45° in the prior art, the contribution to the anti-bending and anti-tensile capabilities of the crank 200 is greater. Therefore, the longitudinal and lateral rigidities are stronger than those of the traditional carbon fiber crank 200.
[0061] Further, continue to refer to Figure 8, the number of layers of the carbon fiber cloth layer 70 wrapped around the outer side, inner side, upper side, and lower side of the body 60 are a, b, c, and d respectively, and a, b, c, and d satisfy the relationship: a > b > c > d. Among them, when the pedal mounting portion 30 is in front of the central axis mounting portion 10, the upper side is above the lower side. Such a setting can further enhance the lateral bending resistance and tensile strength of the crank 200 and increase the lateral rigidity. In some specific embodiments, the cross-sectional shape of the first arm 21 is a water droplet shape. At this time, the number of layers of the carbon fiber cloth layer 70 on the outer side, inner side, upper side, and lower side of the water droplet-shaped cross-section are a, b, c, and d respectively, and a > b > c > d.
[0062] It can be understood that in some other embodiments, the number of layers of the carbon fiber cloth layer 70 on each side is not limited.
[0063] Another embodiment of the present application also provides a crank 200 included in the above bicycle. Since the above bicycle has beneficial effects, correspondingly, the crank 200 belonging to the above bicycle has the same beneficial effects and will not be elaborated here in detail.
[0064] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.
[0065] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the utility model patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the utility model patent shall be subject to the appended claims.
Claims
1. A crank, characterized in that: The crank comprises a central axis mounting portion (10), a crank arm (20) and a pedal mounting portion (30) which are connected in sequence in the longitudinal direction; in the axial direction of the central axis, the central axis mounting portion (10) has an inner end surface (12); The crank arm (20) comprises a first arm (21) and a second arm (22) connected to each other in the longitudinal direction, the first arm (21) being connected to the middle shaft mounting portion (10), and the second arm (22) being connected to the pedal mounting portion (30); the first arm (21) having an innermost contour line (L1) connecting its two ends in the longitudinal direction, the innermost contour line (L1) inwardly exceeding the inner end surface (12); The crank arm (20) has an outermost contour line (L2) connecting its two ends in the longitudinal direction, and the outermost contour line (L2) corresponds to the portion of the first arm (21) and is in an outwardly arched arc shape from one end close to the middle shaft mounting portion (10) to the other end.
2. The crank according to claim 1, characterized in that In the axial direction of the central axis, the pedal mounting portion (30) has an outer end surface (31); The outermost contour line (L2) comprises an arc segment (L21) and a straight segment (L22) connected to each other, at least a portion of the arc segment (L21) corresponds to the first arm (21), the straight segment (L22) corresponds to the second arm (22), the arc segment (L21) is located within the outer end surface (31), and the straight segment (L22) is flush with the outer end surface (31); or The outermost contour line (L2) extends outward beyond the outer end surface (31) and is in an arch shape with the middle portion arching outward.
3. The crank according to claim 1, characterized in that: The cross-sectional shape of the first arm (21) is a water drop shape, and the connecting direction of the large end and the small end of the water drop shape, the axial direction and the longitudinal direction intersect each other; When the pedal mounting portion (30) is located in front of the middle shaft mounting portion (10), the large head end is located below the small head end.
4. The crank according to claim 1, characterized in that The inner side surface of the second arm (22) is recessed outward relative to the inner end surface (12) to form an escape portion (221) for escaping the derailleur (400).
5. The crank according to claim 1, characterized in that: The crank also includes a toothed disc sleeve connection portion (40), which is located on the inner side of the middle shaft mounting portion (10) in the axial direction of the middle shaft and is connected to the inner end surface (12) of the middle shaft mounting portion (10).
6. The crank according to claim 5, characterized in that The crank also includes a toothed disc fixing portion (50), the toothed disc fixing portion (50) being located between the toothed disc sleeve connection portion (40) and the middle shaft mounting portion (10) in the axial direction of the middle shaft, and the toothed disc sleeve connection portion (40) being connected to the inner end surface (12) of the middle shaft mounting portion (10) via the toothed disc fixing portion (50).
7. The crank according to claim 1, characterized in that The crank comprises a body (60) and a carbon fiber cloth layer (70) wrapped outside the body (60).
8. The crank according to claim 7, characterized in that The carbon fiber cloth layer (70) comprises a first carbon fiber filament, a second carbon fiber filament and a third carbon fiber filament, wherein a first extension direction of the first carbon fiber filament is parallel to the longitudinal direction, a first angle α1 between a second extension direction of the second carbon fiber filament and the longitudinal direction satisfies a relationship of 10°≤α1<45°, and a second angle α2 between a third extension direction of the third carbon fiber filament and the longitudinal direction satisfies a relationship of -45°<α2≤-10°.
9. The crank according to claim 7, characterized in that: The number of layers of the carbon fiber cloth layer (70) wrapped on the outer side surface, inner side surface, upper side surface and lower side surface of the body (60) are respectively a, b, c, d, and a, b, c, d satisfy the relationship: a>b>c>d; When the pedal mounting portion (30) is located in front of the middle shaft mounting portion (10), the upper side surface is located above the lower side surface.
10. A bicycle, characterized in that: Comprising a crank as described in any one of claims 1-9.