Bicycle crank connecting structure
By adopting a double-ended screw connection method with pitch difference, the problems of difficult disassembly of bicycle cranks and loosening during riding are solved, achieving labor-saving disassembly and improving connection stability, enhancing safety, and making it easier to distinguish and install.
Patent Information
- Application Number
- CN202520493324.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-20
- Publication Date
- 2026-01-06
- Estimated Expiration
- 2035-03-20
AI Technical Summary
The existing connection method of bicycle crank has high friction during disassembly and is not easy to disassemble. It is easy to loosen during riding. The traditional screw connection has large changes in locking force when riding and vibrating, which is not safe enough.
The system uses a double-ended screw connection with a pitch difference. The screws are gradually tightened and loosened by the pitch difference, which avoids extra effort in disassembly and improves connection stability. The end with the larger pitch is designed to be easy to distinguish and install.
It makes disassembly easier and less prone to loosening, improves the safety and stability of the connection, reduces the risk of stress concentration, and facilitates installation and disassembly.
Smart Images
Figure CN223764650U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of bicycle technology, and in particular to a bicycle crank connection structure. Background Technology
[0002] The crank is an important component of a bicycle drivetrain. It connects the pedals and the chainring and is responsible for transmitting the rider's power from the pedals to the chainring, which in turn drives the chain and ultimately the rear wheel.
[0003] Currently, a crankshaft typically includes a first crankshaft and a second crankshaft with a bottom bracket, with the first crankshaft mounted on the end of the bottom bracket furthest from the second crankshaft. The end of the bottom bracket furthest from the second crankshaft has a tapered spline, and correspondingly, the end of the first crankshaft facing the bottom bracket has a tapered keyway. A threaded hole is formed in the center of the tapered spline. The first crankshaft is connected to this threaded hole by a screw, and during tightening, the spline is pulled to gradually insert into the keyway for final tightening, thus completing the connection between the two crankshafts.
[0004] However, this connection method has two drawbacks. First, to ensure the stability of the connection between the spline and the key, they need to be pressed together as tightly as possible during installation. Therefore, during disassembly, even after removing the screw, the spline and key remain locked, resulting in significant friction and making disassembly very difficult. Second, this traditional single-screw connection is prone to loosening under vibrations and bumps during riding. Therefore, further improvements are needed. Utility Model Content
[0005] To ensure that the crank does not easily loosen during riding and to facilitate disassembly during disassembly, this application provides a bicycle crank connection structure.
[0006] The technical solution for a bicycle crank connection structure provided in this application is as follows:
[0007] A bicycle crank connection structure includes a first crank and a second crank with a bottom bracket. The first crank is mounted on the end of the bottom bracket away from the second crank and connected by a stud. The end of the bottom bracket for connecting to the first crank is formed with a tapered spline, and the end of the first crank for connecting to the bottom bracket is formed with a tapered key, which is adapted to the spline. A first threaded hole extending through the other side of the first crank is formed in the key, and a second threaded hole is formed in the spline. The two ends of the stud are respectively connected to the first threaded hole and the second threaded hole, and the pitch of the stud at the end connected to the first threaded hole is smaller than the pitch of the end connected to the second threaded hole.
[0008] By adopting the above technical solution, during installation, the double-ended screw is screwed into the first threaded hole from the keyway side of the first crank, and tightened as much as possible. Then, the first crank is installed on the bottom bracket of the second crank, so that the spline is inserted into the keyway. Next, the double-ended screw is screwed in from the outside of the first crank towards the bottom bracket, so that the other end of the double-ended screw is continuously screwed into the second threaded hole. In this process, due to the pitch difference between the two ends of the double-ended screw, the spline is engaged with a pitch difference in the keyway with each turn of the double-ended screw, thus gradually tightening and fixing it. This application uses a double-ended screw with a pitch difference for connection. On the one hand, during disassembly, when the double-ended screw is unscrewed outward, the spline and the keyway gradually separate until they detach due to the pitch difference, without the need for extra force to pull it out, which is convenient and labor-saving. On the other hand, this double-ended screw connection method has greater friction generated by the threads at both ends, making it less prone to loosening under vibration or bumps during riding. Furthermore, in traditional screw tightening methods, the tightening force changes primarily during the last half-turn; once loosened by half a turn, the screw essentially loses its connection. This application, however, utilizes the pitch difference between the two ends of a double-ended screw for gradual tightening. Even if loosening occurs, the change in tightening force is relatively gradual, preventing sudden loosening and ensuring higher safety in use.
[0009] Optionally, the pitch difference between the two ends of the double-ended screw is 0.6mm-1mm.
[0010] Optionally, the end of the double-ended screw with a larger pitch is larger than the end with a smaller pitch.
[0011] By adopting the above technical solution, since the screw difference is small, it is sometimes not easy for the human eye to quickly distinguish them. However, by designing the end with the larger pitch of the double-ended screw to be larger than the end with the smaller pitch, it is easier for users to quickly distinguish them and facilitates actual installation work.
[0012] Optionally, the two ends of the double-ended screw are transitioned by rounded corners.
[0013] By adopting the above technical solution and rounding the corners between the two ends of the double-ended screw, stress concentration at this location can be avoided, thereby improving the overall connection strength of the double-ended screw.
[0014] Optionally, the screw holes at both ends of the double-ended screw are the same.
[0015] By adopting the above technical solution, the screw holes at both ends of the double-ended screw are designed to be identical, so that the two ends of the double-ended screw can be operated with the same tool, which facilitates the actual installation and disassembly work.
[0016] Optionally, the screw holes at both ends of the double-ended screw are connected.
[0017] By adopting the above technical solution, the screw holes at both ends of the double-ended screw are designed to be connected, which facilitates one-time processing during actual processing and reduces processing difficulty.
[0018] Optionally, the larger end of the double-ended screw has a weight-reducing opening formed inside the screw hole.
[0019] By adopting the above technical solution, a weight-reducing opening is formed inside the screw hole at the larger end of the double-ended screw, which can further reduce weight while ensuring its structural strength.
[0020] In summary, this application includes at least one of the following beneficial technical effects:
[0021] 1. This application uses a double-ended screw with a pitch difference for connection. On the one hand, during disassembly, when the double-ended screw is unscrewed outwards, the spline and key gradually separate until they detach due to the pitch difference, without requiring extra force to pull it out, making it convenient and labor-saving. On the other hand, this double-ended screw connection method generates greater friction between the threads at both ends, making it less prone to loosening even during vibrations or bumps while riding. Furthermore, the traditional screw tightening method relies primarily on the last half-turn of the tightening force; when it loosens by half a turn, it essentially loses its connection function. This application, however, utilizes the pitch difference between the two ends of the double-ended screw for gradual tightening. Even if loosening occurs, the change in tightening force is relatively gradual, preventing sudden loosening and ensuring higher safety in use.
[0022] 2. Because the difference in screw pitch is small, it is sometimes difficult for the human eye to quickly distinguish them. By designing the end of the double-ended screw with the larger pitch to be larger than the end with the smaller pitch, it is easier for users to quickly distinguish them and facilitates actual installation work.
[0023] 3. By rounding the corners between the two ends of the double-ended screw, stress concentration at that location can be avoided, thereby improving the overall connection strength of the double-ended screw. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the assembled state of a bicycle crank connection structure according to this application.
[0025] Figure 2 This is a first-view diagram of a bicycle crank connection structure of this application under an explosive state.
[0026] Figure 3 This is a second-view diagram of a bicycle crank connection structure of this application under an explosive state.
[0027] Figure 4This is a first-view view of the double-ended screw in this application.
[0028] Figure 5 This is a second-view view of the double-ended screw in this application.
[0029] Explanation of reference numerals in the attached figures:
[0030] 1. First crank; 2. Second crank; 3. Bottom shaft; 4. Spline; 5. Keyway; 6. First threaded hole; 7. Second threaded hole; 8. Double-ended screw; 9. Screw hole; 10. Weight reduction port. Detailed Implementation
[0031] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail.
[0032] This application discloses a bicycle crank connection structure.
[0033] Reference Figure 1 A bicycle crank connection structure includes a first crank 1 and a second crank 2 with a bottom bracket 3, wherein the first crank 1 is mounted on the end of the bottom bracket 3 away from the second crank 2.
[0034] Reference Figure 2 and Figure 3 The central shaft 3 has a tapered spline 4 at one end for connecting to the first crank 1, and the spline is tapered. Correspondingly, the first crank 1 has a tapered keyway 5 at one end for connecting to the central shaft 3, and the keyway 5 is adapted to the spline 4. A first threaded hole 6 extending through the keyway 5 to the other side of the first crank 1 is provided, and a second threaded hole 7 is provided in the spline 4. The second threaded holes 7 of the first threaded holes 6 are connected by a double-ended screw 8, and the pitch of the end of the double-ended screw 8 connected to the first threaded hole 6 is smaller than the pitch of the end connected to the second threaded hole 7.
[0035] During installation, screw the double-ended screw 8 into the first threaded hole 6 from the keyway 5 side of the first crank 1, tightening it as much as possible. Then, install the first crank 1 onto the bottom bracket 3 of the second crank 2, inserting the spline 4 into the keyway 5. Next, screw the double-ended screw 8 from the outside of the first crank 1 towards the bottom bracket 3, continuously screwing the other end of the double-ended screw 8 into the second threaded hole 7. During this process, due to the pitch difference between the two ends of the double-ended screw 8, with each rotation of the double-ended screw 8, the spline 4 is engaged by a pitch difference within the keyway 5, gradually tightening and securing it.
[0036] In this embodiment, the pitch difference between the two ends of the double-ended screw 8 is 0.6mm-1mm. Preferably, in this embodiment, the pitch difference between the two ends of the double-ended screw 8 is 0.8mm, and the pitches at both ends are 1.8mm and 1.0mm respectively, both being positive threads. When screwed in one turn in the forward direction, the end with the larger pitch takes in 1.8mm, and the end with the smaller pitch takes in 1.0mm. That is, in the double-ended screw 8, the larger end takes in 0.8mm of the pitch relative to the smaller end. In other embodiments, the pitch difference between the two ends can be 0.7mm, 0.9mm, etc.
[0037] Reference Figure 4 In this embodiment, the end of the double-ended screw 8 with a larger pitch is larger than the end with a smaller pitch, forming a stepped shaft shape with one end larger than the other. The two ends of the double-ended screw 8 are transitioned by rounded corners. On one hand, because the difference in screw pitch is small, it is sometimes difficult for the human eye to quickly distinguish between them. By designing the end of the double-ended screw 8 with a larger pitch than the end with a smaller pitch, it is easier for users to quickly distinguish between them, facilitating actual installation. On the other hand, by rounding the two ends of the double-ended screw 8, stress concentration at that location can be avoided, thereby improving the overall connection strength of the double-ended screw 8. This allows users to quickly distinguish between the two ends and facilitates actual installation.
[0038] In reference Figure 4 and Figure 5 In this embodiment, the screw holes 9 at both ends of the double-ended screw 8 are identical and interconnected. On one hand, designing the screw holes 9 at both ends of the double-ended screw 8 to be identical allows for operation of both ends of the double-ended screw 8 using the same tool, facilitating actual installation and disassembly. On the other hand, designing the screw holes 9 at both ends of the double-ended screw 8 to be interconnected facilitates one-time machining during actual processing, reducing machining difficulty.
[0039] Reference Figure 5 The larger end of the double-ended screw 8 has a weight-reducing opening 10 formed inside the screw hole 9, which can further reduce weight while ensuring its structural strength.
[0040] The principle of implementation is as follows: During installation, the double-ended screw 8 is screwed into the first threaded hole 6 from the keyway 5 side of the first crank 1, and tightened as much as possible. Then, the first crank 1 is installed on the bottom bracket 3 of the second crank 2, so that the spline 4 is inserted into the keyway 5. Next, the double-ended screw 8 is screwed in from the outside of the first crank 1 towards the bottom bracket 3, so that the other end of the double-ended screw 8 is continuously screwed into the second threaded hole 7. During this process, due to the pitch difference between the two ends of the double-ended screw 8, each turn of the double-ended screw 8 causes the spline 4 to engage with the keyway 5 by a pitch difference, gradually tightening and securing it. Similarly, during disassembly, when the double-ended screw 8 is unscrewed outwards, due to the pitch difference, the spline 4 gradually separates from the keyway 5 until it detaches, without requiring extra effort to pull it out, making it convenient and labor-saving.
[0041] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A bicycle crank connection structure, characterized by: The utility model provides a crankshaft, including first crank (1) and with the second crank (2) of axle (3), first crank (1) is installed to the one end of axle (3) away from the second crank (2), and is connected through stud bolt (8), the one end of axle (3) for being connected with first crank (1) is shaped with the taper spline (4) of having, the one end of first crank (1) for being connected with axle (3) is shaped with the keyway (5) of having taper, and the keyway (5) is adapted with spline (4), the first threaded hole (6) of extending through the other side of first crank (1) is set up in the keyway (5), the second threaded hole (7) is set up in the spline (4), both ends of stud bolt (8) are connected with first threaded hole (6) and second threaded hole (7) respectively, and the pitch of the one end of stud bolt (8) connected with first threaded hole (6) is less than the pitch of the one end connected with second threaded hole (7).
2. A bicycle crank connection structure according to claim 1, characterized in that: The pitch difference of both ends of the stud bolt (8) is 0.6mm-1mm.
3. A bicycle crank connection structure according to claim 1, characterized in that: The larger end of the stud bolt (8) is larger than the smaller end.
4. A bicycle crank connection structure according to claim 3, characterized in that: The size of both ends of the stud bolt (8) is connected through a round corner.
5. A bicycle crank connection structure according to claim 1, characterized in that: The screw holes (9) of both ends of the stud bolt (8) are the same.
6. A bicycle crank connection structure according to claim 5, characterized in that: The screw holes (9) of both ends of the stud bolt (8) are connected.
7. A bicycle crank connection structure according to claim 6, characterized in that: The larger end of the stud bolt (8) is formed with a weight-reducing port (10) at the screw hole (9).