Bicycle crank assembly

Abstract

The bicycle crank assembly comprises a transmission middle shaft, a left crank module and a right crank module are formed at the left end and the right end of the transmission middle shaft respectively, and a bearing set is arranged at the middle end of the transmission middle shaft; the transmission middle shaft is sleeved with a pre-pressing ring close to the left crank module. Wherein the pre-pressing ring is attached to the left crank module to form an initial position; the pre-pressing ring abuts against the bearing set to form a locking position. And the jacking mechanism comprises a jacking piece and at least one guide hole formed in the left crank module, and the guide hole axially extends towards the transmission middle shaft. According to the technical scheme, the axial constraining force is applied to the pre-pressing ring, so that the pre-pressing ring is always kept at the locking position, the phenomenon that the pre-pressing ring is reversed and loosened is prevented, unnecessary cost expenditure caused by collision damage of the bicycle bottom bracket and accessories is effectively avoided, certain potential safety hazards are solved, and the safety of the bicycle is improved.

Description

Technical Field

[0001] The invention relates to the technical field of bicycles, and in particular to a bicycle crank assembly. Background Art

[0002] Most bicycle cranks on the market are equipped with thickness adjustment shims to help operators adjust the gaps on both sides of the cranks to adapt to the different widths of the bottom bracket so that the cranks will not shake left and right on the bottom bracket. However, since the thickness of the shims is usually 0.5mm, 1mm, etc., which is greater than 0.5mm or an integer multiple of 0.5mm, when the required adjustment gap is less than 0.5mm or not an integer multiple of 0.5mm, that is, simply adding shims can no longer solve such gap problems, refer to Figure 1 , an adjustment thread is machined on the bicycle transmission middle shaft, and a threaded pre-load ring structure is mounted on the adjustment thread. By slightly twisting the pre-load ring, the axial left and right displacement of the pre-load ring on the middle shaft is controlled to change the position of the pre-load ring on the middle shaft. Then, a fastening bolt is inserted through the pre-load ring and counteracted with the adjustment thread to achieve the positioning of the pre-load ring, so that the pre-load ring can adapt to fill the gap, thereby achieving the purpose of adjusting the unconventional gap of the crank.

[0003] However, this gap adjustment method of threading the preload ring on the middle shaft has many defects: first, because the preload ring is directly threaded on the middle shaft, when the preload ring is subjected to the torsional force of pedaling, the preload ring will always rotate coaxially with the pedaling. Over time, the preload ring will inevitably reverse, and the preload ring will automatically shift along the axial friction of the external thread of the middle shaft on the middle shaft, and the gap will gradually expand, and the crank will begin to loosen. As a result, the entire crank will shift during riding, and the crank will shake left and right, which will not only cause collision damage to the frame's five-way bracket and bearing group, but also reduce the overall stiffness, making the riding process more dangerous. Second, although the positioning function can be achieved by locking the preload ring on the middle shaft by tightening the bolts, However, since the fastening bolt is in contact with the adjustment thread of the middle shaft, its contact area is small, and the pre-stressing ring also drives the fastening bolt to rotate for a long time, the fastening bolt is more likely to fall off under the rotation friction, which accelerates the automatic reversal of the pre-stressing ring; thirdly, the size of the adjustment gap of the pre-stressing ring relative to the middle shaft depends on the length of the adjustment thread machined by the middle shaft, that is, if the length of the adjustment thread is not enough to adapt to the gap on both sides of the crank, the gap adjustment cannot be completed, which is extremely inconvenient for the user, and the middle shaft can only be replaced, causing unnecessary waste; fourthly, since the pre-stressing ring is on the inside of the crank, the space for the user to adjust is extremely small. When the user finds that the crank is loose and adjusts the gap by himself, it is extremely inconvenient, time-consuming and laborious for the user to do so. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects or problems existing in the background technology and to provide a bicycle crank assembly which can effectively solve the problem that the preload ring of the existing bicycle is reversed after long-term riding, resulting in the crank being often loose.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A bicycle crank assembly, a bicycle crank assembly, characterized in that it includes a transmission middle shaft, the left and right ends of the transmission middle shaft are respectively formed with a left crank module and a right crank module, and the middle end is provided with a bearing group; the transmission middle shaft sleeve is provided with a pre-stressing ring close to the left crank module; wherein the pre-stressing ring is fitted on the left crank module to form an initial position; the pre-stressing ring abuts against the bearing group to form a locking position; a supporting mechanism includes a supporting member and a guide hole provided on the left crank module, the guide hole has at least one, which extends axially toward the transmission middle shaft; the supporting member is installed in the guide hole and can be axially displaced in the guide hole; the supporting member is axially displaced toward the transmission middle shaft, passes through the guide hole and abuts on the pre-stressing ring, and axially constrains the pre-stressing ring from the initial position to the locking position.

[0007] Preferably, the left crank module includes a left crank arm, and a connector located on the transmission center axis, the left crank arm is sleeved on the connector, and the pre-stressing ring has the initial position relative to the left crank arm; the connector is penetrated by a guide hole.

[0008] Preferably, three guide holes are arranged in a circle on the connecting head, and the three guide holes are distributed in a circle at equal angles corresponding to the end face of the pre-compression ring, and the end face is parallel to the radial section of the transmission center axis.

[0009] Preferably, the pre-compression ring is respectively provided with a plurality of limiting grooves corresponding to the guide holes, and when the supporting member is connected to the pre-compression ring, the supporting member is clamped on the limiting grooves so that the pre-compression ring can rotate synchronously with the transmission center shaft.

[0010] Preferably, the left crank module also includes a crank limiting ring, which is sleeved on the transmission center shaft and located between the left crank arm and the pre-stressing ring, and is bonded and fixed to the left crank arm and the connecting head, so that when the left crank arm is sleeved on the connecting head, the left crank arm is constrained and restricted to the connecting head by the crank limiting ring to prevent the left crank arm from displacement.

[0011] Preferably, the crank limiting ring has a clearance hole for the lifting member to pass through, and the lifting member passes through the clearance hole to be connected to the pre-compression ring.

[0012] Preferably, the crank limiting ring has at least one protruding portion, and the connecting head is provided with a slot matched with the protruding portion. When the crank limiting ring is bonded and fixed to the left crank arm and the connecting head, the protruding portion is clamped on the slot, so that the crank limiting ring and the left crank arm rotate synchronously.

[0013] Preferably, the protruding portion and the supporting member are coaxially distributed.

[0014] Preferably, the supporting member is a "connecting bolt", a thread matching the supporting member is formed in the guide hole, and the supporting member is screwed to the guide hole.

[0015] Preferably, it also includes a detachable anti-loosening mechanism. When the supporting member is axially displaced toward the transmission center shaft, passes through the guide hole and abuts against the pre-load ring, the anti-loosening mechanism is blocked in the guide hole to axially constrain the supporting member in the guide hole.

[0016] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) When the bicycle crank adjusts the clearance, the preload ring moves axially relative to the transmission center axis to form a locking position against the bearing group, and the preload ring only needs to be kept in the locking position to keep the clearance from expanding; however, if the preload ring is only held in the locking position by radial constraint force similar to the existing method, the preload ring will inevitably reverse and loosen axially on the transmission center axis during long-term rotation. Therefore, the technical solution of the present invention abandons the existing radial constraint force structure, and maintains the preload ring in the locking position by adding a supporting mechanism, specifically controlling the supporting member to move axially through the guide hole until the supporting member passes through the guide hole and is connected to the preload ring, applying axial constraint force to the preload ring, so that the preload ring is always kept in the locking position to prevent the preload ring from reverse and loosening, which not only effectively avoids the bicycle five-way and accessories from being damaged by collision and causing unnecessary cost expenditure, but also solves certain safety hazards and increases the safety of the bicycle.

[0018] (2) The guide hole is set on the connecting head of the transmission middle shaft. The transmission middle shaft is mainly used as a new type of accessory, while the left crank arm can also use traditional structural accessories. The two can be adapted to each other. Therefore, only by replacing a different transmission middle shaft and some of its accessories, the adaptation and installation with the existing left crank arm can be completed to achieve the anti-reversal of the pre-load ring. It is highly practical and can be replaced and applied simply by replacement.

[0019] (3) The number of top supports corresponds to the number of guide holes. When there are only one or two guide holes, the top supports can also realize the axial constraint of the preload ring. However, after a long period of rotation, the axial force applied to the preload ring is not evenly distributed, and the preload ring is very likely to tilt or deflect on the transmission shaft. It is also possible that it will rub against the bearing group or the transmission shaft during rotation, which will not only cause a certain amount of noise, but also wear the bearing group or the transmission shaft. Therefore, in order to solve this problem, the connector ring in this solution is provided with three guide holes, and the three guide holes are distributed at equal angles around the ring to evenly apply constraint force to the preload ring to prevent the preload ring from tilting or deflecting.

[0020] (4) The supporting member is clamped on the limiting groove so that the preload ring and the transmission center shaft can rotate synchronously, thereby preventing the preload ring and the bearing from rubbing against each other after the preload ring and the bearing assembly come into contact with each other.

[0021] (5) The left crank arm is constrained and restricted to the position of the connector by a crank limit ring to prevent the left crank arm from being displaced and causing safety hazards.

[0022] (6) The extension portion is inserted into the slot of the connector, which not only makes it easier to position and install the crank limit ring, but also expands the bonding area when the crank limit ring, the left crank arm and the connector are bonded and fixed, making the three of them more secure.

[0023] (7) The extension portion and the supporting member are coaxially distributed. The extension portion is provided to reduce and disperse the rotational torsional force on the supporting member, thereby preventing the supporting member from loosening and reversing, and improving the service life of the supporting member.

[0024] (8) The supporting member may be a positioning pin or a connecting bolt, but the present invention adopts a connecting bolt mainly because the thread of the bolt itself can provide a certain axial constraint to prevent the supporting member from loosening and shifting on its own.

[0025] (9) In order to better ensure that the jacking member always contacts the pre-stressing ring and prevent the crank from having a gap due to loosening and displacement of the jacking member, an anti-loosening mechanism is installed on the guide hole so that the jacking member will always constrain the pre-stressing ring in the locked position. At the same time, the anti-loosening mechanism is detachable, which is convenient for the installation and adjustment of the jacking member.

[0026] (10) In this solution, the top support, that is, the connecting bolt, is a replaceable part. By replacing the connecting bolts of different lengths, it can be adapted to various types of bicycle bottom brackets, without having to replace only the entire middle axis as in the existing method. It has low cost and is easy to disassemble and assemble.

[0027] (11) In order to solve the problem that the existing preload rings are all on the inside of the crank, resulting in very little space for users to adjust, and it is inconvenient to adjust the gap by themselves. Therefore, in this solution, an external screwdriver on the outside of the crank assembly can control the displacement of the jacking member in the guide hole of the connector to adjust the gap. It does not need to be operated in a small space, and is convenient for disassembly and assembly, saving time and effort, and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0029] Figure 1 It is a structural schematic diagram of a bicycle crank assembly in the prior art;

[0030] Figure 2 The overall explosion of the embodiment of the present invention Figure 1 ;

[0031] Figure 3 The overall explosion of the embodiment of the present invention Figure 2 ;

[0032] Figure 4 for Figure 3 A partial enlarged view of part A shown;

[0033] Figure 5 This is a schematic structural diagram of a crank limit ring according to an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of the structure of a pre-compression ring according to an embodiment of the present invention;

[0035] Figure 7 This is a structural schematic diagram of an embodiment of the present invention in which a pre-compression ring is attached to a left crank module and is located in an initial position;

[0036] Figure 8 This is a schematic diagram of the structure in which the pre-compression ring of an embodiment of the present invention abuts against the bearing assembly and is located in a locked position;

[0037] Fig. 9 It is a schematic structural diagram of the anti-loosening mechanism in other embodiments of the present invention.

[0038] The description of the accompanying drawings is as follows: 11. Transmission center shaft; 12. Left crank module; 121. Left crank arm; 122. Connector; 122a. Slot; 123. Crank limiting ring; 123a. Clearance hole; 123b. Extension portion; 13. Right crank module; 14. Bearing group; 15. Pre-load ring; 16. Fastening bolt; 151. Limiting groove; 21. Support member; 22. Guide hole; 3. Anti-loosening mechanism; 31. Blocking portion. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are preferred embodiments of the present invention and should not be regarded as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] In the claims, description and the above-mentioned drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" etc. are for distinguishing different objects rather than for describing a specific order.

[0041] In the claims, specification and the above-mentioned drawings of the present invention, unless otherwise explicitly defined, directional words, such as the terms "center", "lateral", "longitudinal", "horizontal", "vertical", "top", "bottom", "inside", "outside", "up", "down", "front", "back", "left", "right", "clockwise", "counterclockwise", etc., indicating directions or positional relationships are based on the directions and positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the specific protection scope of the present invention.

[0042] In the claims, specification and the above drawings of the present invention, unless otherwise clearly defined, if the term "fixed connection" or "fixed connection" is used, it should be understood in a broad sense, that is, any connection method without a displacement relationship and relative rotation relationship between the two, that is to say, including non-detachable fixed connection, detachable fixed connection, integrated connection and fixed connection through other devices or elements.

[0043] In the claims, description and drawings of the present invention, if the terms "include", "have" and their variations are used, they are intended to mean "including but not limited to".

[0044] See also Figures 1 to 8 .

[0045] The present invention provides a bicycle crank assembly to solve the following problems: Figure 1The conventional bicycle crank assembly shown in the figure adopts a fastening bolt 16 that penetrates through the preload ring 15 and abuts against the adjusting thread to realize the radial constraint of the preload ring 15. As a result, the preload ring 15 is prone to reverse rotation, which often causes the crank to become loose.

[0046] See also Figure 2 and Figure 3 In this embodiment, it mainly includes a transmission center shaft 11 and a supporting mechanism. The left and right ends of the transmission center shaft 11 are respectively formed with a left crank module 12 and a right crank module 13, and the middle end is provided with a bearing group 14 ( Figure 2 and Figure 3 The bearing assembly 14 is fixed on the bicycle bottom bracket (not shown). The left crank module 12 includes a left crank arm 121 and a connector 122 located on the transmission center shaft 11. The left crank arm 121 and the connector 122 are connected by a spline sleeve to complete the installation of the left crank module 12 and the transmission center shaft 11. A pre-stressing ring 15 is sleeved on the transmission center shaft 11, which is close to the left crank module 12, that is, close to the left crank arm 121. The pre-stressing ring 15 is attached to the left crank arm 121 to form an initial position (see Figure 7 ), and abuts against the bearing assembly 14 to form a locked position (see Figure 8 ). As long as the preload ring 15 is axially against the bearing assembly 14, it will have a locked position. Since the clearance between the bearing assembly 14 and the left crank arm 121 of each bicycle is different, the locking position of each bicycle is not necessarily the same, that is, the locking position is not unique; but the initial position is the same, and it will be formed as long as the preload ring 15 and the left crank arm 121 are in contact.

[0047] See also Figure 2 and Figure 3 In this embodiment, the lifting mechanism includes a lifting member 21 and a guide hole 22 provided on the connector 122. In this solution, there is at least one guide hole 22, or a plurality of guide holes 22, the number of which is equal to the number of lifting members 21. The lifting member 21 mainly functions to push the preload ring 15 from the initial position to the locked position through left and right axial displacement. As long as the length of the lifting member 21 is sufficient, it can be adapted to adjust any crank clearance.

[0048] In this embodiment, there are three supporting members 21 and three guide holes 22. Each guide hole 22 is arranged on the connector 122, and extends in the axial direction toward the transmission center shaft 11. The axial direction of the supporting members 21 passes through the entire connector 122. The three supporting members 21 are respectively installed in the three guide holes 22, and can perform axial displacement movement in each guide hole 22. The supporting members 21 are axially displaced in the guide holes 22 toward the transmission center shaft 11, pass through the guide holes 22 and contact the preload ring 15, so that the preload ring 15 can be moved from the initial position (see Figure 7) axially constrained in the locked position (see Figure 8 ), that is, the supporting member 21 pushes the pre-stressing ring 15 axially so that the pre-stressing ring 15 abuts against the bearing assembly 14, so that the pre-stressing ring 15 is in a locked position for fixing.

[0049] See also Figure 2 and Figure 3 In this embodiment, the three guide holes 22 are distributed in a circle at equal angles corresponding to the end surface of the pre-load ring 15, and the end surface is parallel to the radial section of the transmission center shaft 11, so as to ensure that after the three supporting members 21 are respectively installed in the guide holes 22, the three supporting members 21 can maintain axial movement and evenly apply restraining force to the pre-load ring 15 to prevent the pre-load ring 15 from tilting or deflecting and causing influence.

[0050] In order to prevent the supporting member 21 from abutting against the pre-pressing ring 15, which would cause the supporting member 21 to rub against the surface of the pre-pressing ring 15 and cause noise when rotating, the pre-pressing ring 15 is provided with a plurality of limiting grooves 151 (see Figure 6 ), when the supporting member 21 is connected to the pre-stressing ring 15, the supporting member 21 is clamped on the limiting groove 151, so that the pre-stressing ring 15 can rotate synchronously with the transmission center shaft 11, which can not only prevent the pre-stressing ring 15 and the supporting member 21 from making noise, but also prevent the pre-stressing ring 15 and the bearing group 14 from making friction with each other and causing noise after they abut against each other.

[0051] In this embodiment, the left crank module 12 also includes a crank limit ring 123, which is sleeved on the transmission center shaft 11 and located between the left crank arm 121 and the pre-load ring 15, and is bonded and fixed to the left crank arm 121 and the connecting head 122, so that when the left crank arm 121 is sleeved on the connecting head 122, the left crank arm 121 is constrained and restricted on the connecting head 122 by the crank limit ring 123 to prevent the left crank arm 121 from displacement.

[0052] In this embodiment, the crank stop ring 123 has a clearance hole 123a for the support member 21 to pass through, and the support member 21 passes through the clearance hole 123a to be connected to the pre-compression ring 15. Therefore, the setting of the crank stop ring 123 can not only ensure that the left crank arm 121 will not be displaced left and right, but also ensure that the displacement effect of the support member 21 is not affected by the setting of the clearance hole 123a, thereby improving the overall strength and stability of the crank assembly.

[0053] In this embodiment, the crank limit ring 123 has at least one protruding portion 123b. In this scheme, three protruding portions 123b are provided. The protruding portion 123b and the top supporting member 21 are coaxially distributed. The protruding portion 123b is provided to reduce and disperse the rotational torsional force on the top supporting member 21, thereby preventing the top supporting member 21 from loosening and reversing. That is, the more the protruding portions 123b, the less torsional force the top supporting member 21 can bear, thereby increasing the service life of the top supporting member 21.

[0054] In this embodiment, the connecting head 122 is provided with a slot 122a adapted to the protruding portion 123b. When the crank limiting ring 123 is bonded and fixed to the left crank arm 121 and the connecting head 122, the protruding portion 123b is clamped on the slot 122a, so that the crank limiting ring 123 can rotate synchronously with the left crank arm 121.

[0055] In this embodiment, the supporting member 21 may be a positioning pin or a connecting bolt. The connecting bolt is used in this solution mainly because the thread of the bolt itself can provide a certain axial constraint to prevent the supporting member 21 from loosening and self-displacement.

[0056] In this embodiment, if it is found that the length of the connecting bolt is not enough to push the pre-compression ring 15 from the initial position to the locked position, it can be done by simply replacing a different connecting bolt.

[0057] The working principle and use process of the present invention:

[0058] During installation, see Figure 3 First, the left crank arm 121 is mounted on the connecting head 122 of the transmission center shaft 11 by means of spline adaptation; then, the crank limiting ring 123 is mounted on the transmission center shaft 11 until it is located on the right side of the left crank arm 121; thereafter, the three protruding portions 123b of the crank limiting ring 123 are inserted into the three slots 122a of the connecting head 122 for positioning, and the crank limiting ring 123, the left crank arm 121 and the connecting head 122 are bonded and fixed; then, the three connecting bolts are inserted into the guide holes 22 for threaded connection, and the pre-stressing ring 15 is mounted on the left side of the transmission center shaft 11, close to the left crank arm 121, so that the pre-stressing ring 15 is located in the initial position. At this point, the transmission center shaft 11 can be installed on the bicycle five-way bracket, and adapted to be installed with the bearing group 14 on the bicycle five-way bracket, as shown in FIG. Figure 7As shown; then, the three bolts can be screwed separately by an external screwdriver to make the bolts move axially in the guide hole 22 respectively, until they pass through the connector 122, and then the preload ring 15 is pushed from the initial position to the side of the bearing group 14, that is, the locked position; finally, the right crank module 13 is fixed to the right side of the transmission center shaft 11 to complete the installation. The technical solution of the present invention abandons the existing radial constraint force structure, and the preload ring 15 is always kept in the locked position by adding a top support mechanism, specifically, the top support member 21 is controlled to move axially through the guide hole 22, until the top support member 21 passes through the guide hole 22 and is connected to the preload ring 15, and an axial constraint force is applied to the preload ring 15, so that the preload ring 15 is always kept in the locked position to prevent the preload ring 15 from being reversed and loosened, which not only effectively avoids the collision damage of the bicycle five-way and accessories, thereby causing unnecessary cost expenditure, but also solves certain safety hazards and increases the safety of the bicycle.

[0059] Other embodiments

[0060] See also Fig. 9 In order to better allow the supporting member 21 to always support the pre-stressing ring 15 and prevent the crank from having a gap due to the loose displacement of the supporting member 21; the present invention provides an anti-loosening mechanism 3 on the leftmost side of the left crank arm 121, and the anti-loosening mechanism 3 is blocked on the guide hole 22, so that the supporting member 21 will always constrain the pre-stressing ring 15 in the locked position; at the same time, the anti-loosening mechanism 3 is detachable, which is convenient for the installation and adjustment of the supporting member 21.

[0061] In this embodiment, the anti-loosening mechanism 3 includes an outer cover having a plurality of blocking portions 31. The blocking portions 31 are arranged correspondingly according to the number and orientation of the guide holes 22. The blocking portions 31 are blocked in the guide holes 22 and abut against the connecting bolts to constrain the connecting bolts in the guide holes 22 so that the connecting bolts cannot move in the axial direction at all times.

[0062] In this embodiment, the blocking portion 31 has an external thread, and the blocking portion 31 is screwed into the guide hole 22 to realize the detachable outer cover. Therefore, the setting of the anti-loosening mechanism 3 can not only play a certain decorative role, but also prevent dust and water from splashing into the guide hole 22, thereby improving the service life of the supporting member 21.

[0063] The description of the above specification and embodiments is used to explain the protection scope of the present invention, but does not constitute a limitation on the protection scope of the present invention. Through the enlightenment of the present invention or the above embodiments, ordinary technicians in this field can obtain modifications, equivalent substitutions or other improvements to the embodiments of the present invention or part of the technical features thereof through logical analysis, reasoning or limited experiments, which should be included in the protection scope of the present invention.

Claims

1. A bicycle crank assembly, characterized in that: include A transmission center shaft, wherein the left and right ends of the transmission center shaft are respectively formed with a left crank module and a right crank module, and the middle end is provided with a bearing group; the transmission center shaft sleeve is provided with a pre-stressing ring close to the left crank module; wherein the pre-stressing ring is fitted to the left crank module to form an initial position; the pre-stressing ring is against the bearing group to form a locking position; The lifting mechanism comprises a lifting member and a guide hole provided on the left crank module, wherein the guide hole has at least one and extends axially toward the transmission center shaft; the lifting member is installed in the guide hole and can be axially displaced in the guide hole; The supporting member is axially displaced toward the transmission center axis, passes through the guide hole and is abutted against the pre-compression ring, so as to axially constrain the pre-compression ring from the initial position to the locking position.

2. A bicycle crank assembly according to claim 1, characterized in that: The left crank module includes a left crank arm and a connector located on the transmission center axis, the left crank arm is sleeved on the connector, and the pre-stressing ring has the initial position relative to the left crank arm; the connector is penetrated by a guide hole.

3. A bicycle crank assembly as claimed in claim 2, characterized in that: The guide holes are arranged in three on the connector, and the three guide holes are arranged in a circle at equal angles corresponding to the end face of the pre-pressing ring, and the end face is parallel to the radial section of the transmission center axis.

4. A bicycle crank assembly as claimed in claim 3, characterized in that: The pre-compression ring is respectively provided with a plurality of limiting grooves corresponding to the guide holes. When the supporting member is connected to the pre-compression ring, the supporting member is clamped on the limiting grooves so that the pre-compression ring can rotate synchronously with the transmission center shaft.

5. A bicycle crank assembly as claimed in claim 4, characterized in that: The left crank module also includes a crank limiting ring, which is sleeved on the transmission center shaft and located between the left crank arm and the pre-stressing ring, and is bonded and fixed to the left crank arm and the connecting head, so that when the left crank arm is sleeved on the connecting head, the left crank arm is constrained and restricted on the connecting head by the crank limiting ring to prevent the left crank arm from displacement.

6. A bicycle crank assembly as claimed in claim 5, characterized in that: The crank limiting ring has a clearance hole for the jacking member to pass through, and the jacking member passes through the clearance hole to be connected to the pre-pressing ring.

7. A bicycle crank assembly as claimed in claim 6, characterized in that: The crank limiting ring has at least one protruding portion, and the connecting head is provided with a slot matched with the protruding portion. When the crank limiting ring is bonded and fixed to the left crank arm and the connecting head, the protruding portion is clamped on the slot, so that the crank limiting ring and the left crank arm rotate synchronously.

8. A bicycle crank assembly as claimed in claim 7, characterized in that: The protruding portion and the supporting member are coaxially distributed.

9. A bicycle crank assembly as claimed in any one of claims 1 to 8, characterized in that: The supporting member is a "connecting bolt", a thread matching the supporting member is formed in the guide hole, and the supporting member is screwed to the guide hole.

10. A bicycle crank assembly as claimed in claim 9, characterized in that: It also includes a detachable anti-loosening mechanism. When the supporting member is axially displaced toward the transmission center shaft, passes through the guide hole and abuts against the pre-load ring, the anti-loosening mechanism is blocked in the guide hole to axially constrain the supporting member in the guide hole.

Images