A coaxiality control structure of a bicycle transmission shaft

Abstract

The utility model discloses a coaxality control structure of bicycle transmission axle center, including two locating rings, two locating rings equal inside diameter, and the outside diameter of locating ring and the inside diameter of bicycle five through bearing are adapted, two locating rings are respectively set in two bearing cooperation department outer periphery of transmission axle center, and two locating rings are along transmission axle center axial parallel interval arrangement, the outer periphery of locating ring is equipped with the locating portion, and the locating portion is used for with external fixture cooperation, to limit the axial spacing of two locating rings on transmission axle center through external fixture, and makes the axis of two locating rings coincide, when heat processing, the inside diameter of locating ring is used for limiting the thermal expansion deformation of corresponding bearing cooperation department, makes the coaxality of two bearing cooperation department consistent, the technical scheme of the utility model, simple structure, easy realization and low in cost, solve the technical problem that two bearing cooperation department of present bicycle transmission axle center appears coaxality deviation, and further leads to the technical problem of crank deflection.

Description

Technical Field

[0001] This utility model relates to the field of bicycle technology, specifically to a coaxiality control structure for a bicycle drive shaft. Background Technology

[0002] The bicycle driveshaft is the core component that connects the left and right cranks and transmits power. It needs to be inserted into the bottom bracket of the bicycle and work with the two bearings inside the bottom bracket to achieve rotational support. The coaxiality accuracy of the bearing mating parts on the left and right sides of the driveshaft, which are directly in contact with the inner ring of the bearings, directly determines the assembly accuracy of the bearings. If there is a coaxiality deviation, it will affect the smoothness of the rotation of the left and right cranks and the riding experience.

[0003] Currently, carbon fiber bicycle driveshafts have become the mainstream choice due to their light weight and high strength. However, they face significant technical challenges in manufacturing: after forming, carbon fiber driveshafts require heat treatment to improve their mechanical properties and structural strength. During heat treatment, on the one hand, the driveshaft expands as a whole, and since the bearing mating parts have no additional constraints, they are prone to asymmetrical deformation due to uneven thermal expansion, leading to a misalignment of the two mating parts. This misalignment will then be transmitted to the bottom bracket bearing, causing inconsistent bearing coaxiality, which in turn causes the left and right cranks to wobble. This not only results in jerking and abnormal noises during riding but also accelerates the wear of the bearings and bottom bracket, shortening the service life of the drivetrain. On the other hand, the thermal expansion of the driveshaft also increases its outer diameter. Subsequently, it is necessary to grind the outer diameter with sandpaper to match the inner diameter of the bottom bracket bearing. This process is cumbersome and the precision is difficult to guarantee, further affecting assembly efficiency and reliability. Utility Model Content

[0004] This utility model provides a coaxiality control structure for a bicycle drive shaft. Its structure is simple, easy to implement, and low in cost. It solves the technical problem of coaxiality deviation in the mating parts of the two bearings in existing bicycle drive shafts, which leads to crankshaft wobble. The main technical solution adopted is as follows:

[0005] A coaxiality control structure for a bicycle drive shaft includes two positioning rings. The inner diameters of the two positioning rings are equal, and the outer diameter of the positioning rings is adapted to the inner diameter of the bicycle bottom bracket bearing. The two positioning rings are respectively sleeved on the outer periphery of two bearing mating parts of the drive shaft, and the two positioning rings are arranged parallel to each other along the axial direction of the drive shaft. The outer periphery of each positioning ring is provided with a positioning part, which is used to cooperate with an external clamp to limit the axial distance between the two positioning rings on the drive shaft and to make the axes of the two positioning rings coincide. During hot working of the drive shaft, the inner diameter of the positioning rings is used to limit the thermal expansion deformation of the corresponding bearing mating parts, so that the coaxiality of the two bearing mating parts is consistent.

[0006] Preferably, the positioning part is a ring platform arranged around the outer circumference of the positioning ring, and the ring platform extends radially toward the positioning ring.

[0007] Preferably, the ring platform is located at the axial middle part of the positioning ring, and the cross-section of the ring platform is parallel to the cross-section of the positioning ring; the axial length of the ring platform is less than the axial length of the positioning ring.

[0008] Preferably, the positioning portions of the two positioning rings are equidistant from their respective ends near the center of the transmission shaft.

[0009] Preferably, the radial height of the ring platform is uniform along the circumference of the positioning ring.

[0010] Preferably, both end faces of the ring platform are planar, and the end faces are perpendicular to the axis of the positioning ring.

[0011] Preferably, the axial length of the positioning ring is equal to the axial length of the bearing mating part of the transmission shaft.

[0012] As can be seen from the above description of this utility model, compared with the prior art, this utility model has the following beneficial effects:

[0013] This invention provides a coaxiality control structure for a bicycle driveshaft. The structure is simple and low-cost, solving the technical problem of coaxiality deviation in the mating parts of the two bearings in existing bicycle driveshafts, which leads to crank wobbling. The technical solution of this invention uses two positioning rings with equal inner diameters directly fitted onto the outer circumference of the two bearing mating parts of the driveshaft. Combined with the cooperation of the positioning rings' outer circumference positioning parts and external clamps, this establishes a unified coaxial reference for the two positioning rings. Furthermore, during the hot working of the driveshaft, the inner diameter of the positioning rings constrains the thermal expansion deformation of the bearing mating parts, effectively controlling the coaxiality of the two bearing mating parts. This avoids asymmetrical deformation of the carbon driveshaft due to uneven thermal expansion, solving the coaxiality deviation of the two bearing mating parts and the subsequent crank wobbling problems. Simultaneously, the outer diameter of the driveshaft can quickly adapt to the inner diameter of the bicycle bottom bracket bearing through the positioning rings, eliminating the need for sanding to adjust the outer diameter of the driveshaft as in existing technologies. This effectively avoids the tedious operation and insufficient precision of manual grinding, improving assembly efficiency and reliability. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1This is a schematic diagram of the assembly of the bicycle drive shaft with the left and right cranks according to an embodiment of the present invention;

[0016] Figure 2 This is an exploded view of the bicycle drive shaft and positioning ring according to an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of the positioning ring in an embodiment of the present invention;

[0018] Figure 4 This is a schematic diagram of the structure of the positioning ring when it is assembled on the bicycle drive shaft according to an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of the structure of the positioning ring after it has been machined according to an embodiment of the present invention.

[0020] The annotations in the attached figures are explained as follows:

[0021] 1. Drive shaft; 1a. Bearing mating part; 2. Locating ring; 21. Locating part; 2a. End face. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are preferred embodiments of the present utility model and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0023] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims, description, and drawings of this utility model is for distinguishing different objects and not for describing a specific order.

[0024] Unless otherwise expressly defined, in the claims, description, and accompanying drawings of this utility model, the use of directional terms such as "center," "lateral," "longitudinal," "horizontal," "vertical," "top," "bottom," "inner," "outer," "upper," "lower," "front," "rear," "left," "right," "clockwise," and "counterclockwise" to indicate orientation or positional relationships is based on the orientation and positional relationships shown in the accompanying drawings and is only for the convenience of describing this utility model and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the specific protection scope of this utility model.

[0025] Unless otherwise expressly defined, the terms "fixed connection" or "fixed connection" used in the claims, description and drawings of this utility model shall be interpreted broadly to refer to any connection in which there is no displacement or relative rotation relationship between the two parties, including non-removable fixed connection, detachable fixed connection, integral connection and fixed connection through other devices or components.

[0026] In the claims, description and accompanying drawings of this utility model, the terms "comprising", "having", and variations thereof are used to mean "including but not limited to".

[0027] Please see Figures 1 to 5 .

[0028] This embodiment provides a coaxiality control structure for a bicycle driveshaft 1. Its structure is simple, easy to implement, and low in cost, solving the technical problem of coaxiality deviation in the two bearing mating parts 1a of existing bicycle driveshaft 1, which leads to crank wobbling. Existing bicycle driveshafts 1 all have two bearing mating parts 1a corresponding to the two bearings inside the bottom bracket. When the driveshaft 1 is inserted into the bottom bracket of the bicycle, the two bearing mating parts 1a need to be aligned with the two bearings inside the bottom bracket. If the coaxiality of the two bearing mating parts 1a is deviated, it will directly lead to a deviation in the coaxiality of the two bearings. To solve the above problems, this utility model mainly sets up a structure of two positioning rings 2; wherein,

[0029] The outer diameters of the two locating rings 2 are matched with the inner diameters of the two bearings inside the bicycle's bottom bracket; that is, the outer diameter of the locating rings 2 is the same as the inner diameter of the bearings. (See also...) Figures 2 to 4 The two positioning rings 2 have the same inner diameter and are respectively fitted around the outer periphery of the two bearing mating parts 1a of the transmission shaft 1. The two positioning rings 2 are made of high temperature resistant material and are arranged parallel to each other along the axial direction of the transmission shaft 1. In this way, the two positioning rings 2 can just cover the outer periphery of the bearing mating parts 1a to form a fit.

[0030] In this embodiment, to ensure a more precise correspondence between the positioning ring 2 on the shaft center and the bearing mating part 1a, a positioning part 21 is provided on the outer periphery of the positioning ring 2. This positioning part 21 is used to cooperate with an external clamp to limit the axial distance between the two positioning rings 2 on the transmission shaft center 1 and to make the axes of the two positioning rings 2 coincide. Specifically, the clamp itself serves as a reference. After the positioning parts 21 of the two positioning rings 2 are clamped with the clamp, the distance and height between the two positioning parts 21 are limited and fixed, ensuring that the two positioning rings 2 maintain consistent coaxiality. Thus, during hot working, the transmission shaft center 1 will begin to expand and deform due to heat. The inner diameter of the positioning ring 2 can limit the thermal expansion and deformation of the corresponding bearing mating part 1a, ensuring that the coaxiality of the two bearing mating parts 1a is consistent, that is, the coaxiality of the two bearing mating parts 1a is equivalent to the coaxiality of the two positioning rings 2.

[0031] In this embodiment, see Figure 3 To increase the contact area between the external clamp and the positioning part 21 and improve the clamping force, the positioning part 21 is designed as a ring platform arranged around the outer circumference of the positioning ring 2, extending radially towards the positioning ring 2. This ring platform structure ensures that the mating surfaces of the ring platform and the external clamp are distributed in a ring shape for a tight fit. The clamping force of the clamp on the ring platform is more uniform, preventing localized stress that could cause the positioning ring 2 to wobble. Furthermore, it further ensures the accuracy of the alignment of the axes of the two positioning rings 2 and improves the stability of coaxiality control.

[0032] In this embodiment, see Figure 3 The ring platform is located at the axial center of the positioning ring 2, and its cross-section is parallel to that of the positioning ring 2. The axial length of the ring platform is less than that of the positioning ring 2. This location of the ring platform at the axial center of the positioning ring 2 ensures that the end faces 2a on both sides of the positioning ring 2 remain balanced under stress, preventing the positioning ring 2 from tilting due to the offset of the positioning part 21. Furthermore, the smaller axial length of the ring platform reduces the impact of the positioning part 21 on the overall structural strength of the positioning ring 2 and reduces material costs.

[0033] In this embodiment, the distances from the positioning parts 21 of the two positioning rings 2 to their respective ends near the transmission shaft 1 are equal, further ensuring the uniformity of the positioning reference. In other embodiments, if it is necessary to adapt to a transmission shaft 1 of a special specification, the shapes of the two positioning rings 2 may differ, but it is necessary to ensure that the inner diameters are equal, the outer diameters are adapted to the bearings, and the spacing between the positioning parts 21 is symmetrical, so as to avoid introducing new deviations.

[0034] In this embodiment, see Figure 3 The radial height of the ring platform is uniform along the circumference of the positioning ring 2. That is, the ring body is set in a circular ring and the radial height of the ring platform is uniform. This ensures that the contact gap between the external clamp and the ring platform is equal everywhere, without any local gap that is too large or too small, thus avoiding circumferential stress concentration in the positioning ring 2 when the clamp is held.

[0035] In this embodiment, see Figure 3 Both end faces 2a of the ring platform are flat, and the end faces 2a are perpendicular to the axis of the positioning ring 2. Since both end faces 2a of the ring platform are flat, the end faces 2a will be perpendicular to the axis of the transmission shaft 1, and the clamping surface of the external fixture can achieve planar contact, avoiding point contact or line contact clamping force, and preventing the positioning ring 2 from shifting in the axial direction.

[0036] In this embodiment, the axial length of the positioning ring 2 is equal to the axial length of the bearing mating part 1a of the transmission shaft 1. After the fixture clamps and positions the positioning ring 2, the axial length of the positioning ring 2 is completely matched with the bearing mating part 1a, which can achieve full-length wrapping of the bearing mating part 1a, avoid thermal expansion runaway caused by partial exposure of the bearing mating part 1a, and prevent the problem of local coaxiality failure.

[0037] The working principle and usage process of this utility model:

[0038] When machining bicycle drive shaft 1,

[0039] First, prepare the transmission shaft 1 to complete the basic product molding;

[0040] Second, see Figure 4 Two positioning rings 2 are respectively fitted onto the outer circumference of the two bearing mating parts 1a of the transmission shaft 1. At this time, the axial position of the positioning rings 2 is not fixed, and the positioning rings 2 cannot completely and accurately cover the bearing mating parts 1a. Further adjustments are required.

[0041] Third, an external clamp (not shown) is used to clamp and fix the transmission shaft 1 and the two positioning rings 2 on the transmission shaft 1 (through the ring platform). The clamp uses itself as a reference to adjust and limit the axial distance between the two positioning rings 2 and make the axes of the two positioning rings 2 coincide. At this time, the positioning rings 2 completely and accurately cover the bearing mating part 1a of the transmission shaft 1.

[0042] Fourth, the transmission shaft 1 is subjected to heat treatment. During the heat treatment process, the transmission shaft 1 expands as a whole due to thermal expansion. The two bearing mating parts 1a are constrained by the inner diameter of the positioning ring 2 and can only expand within the inner diameter range of the positioning ring 2 until the outer wall surface of the bearing mating part 1a is tightly attached to the inner wall surface of the positioning ring 2, so that the coaxiality of the two bearing mating parts 1a is consistent with that of the positioning ring 2. During this process, the positioning ring 2 is made of high temperature resistant material, so it is not affected by thermal deformation and the overall structure is stable. The outer diameter of the positioning ring 2 will not expand or shrink and will always maintain a matching state with the inner diameter of the bearing.

[0043] Fifth, after the transmission shaft 1 has cooled to room temperature, loosen the external clamp and remove the transmission shaft 1 (leaving the locating ring 2 on the transmission shaft 1); fix the transmission shaft 1 on the lathe and begin machining again, see [link to relevant documentation]. Figure 5The outer ring of the positioning ring 2 is removed by turning on a lathe without touching the main body of the transmission shaft 1. This protects the structural strength of the carbon transmission shaft 1 and keeps the outer wall of the positioning ring 2 smooth without damaging its outer diameter.

[0044] Sixth, insert the drive shaft 1 with the positioning ring 2 into the bottom bracket. The outer wall of the positioning ring 2 mates with the inner wall of the bottom bracket bearing. Because the coaxiality meets the standard and the dimensions are suitable, the drive shaft 1 rotates smoothly without any wobble. See also Figure 1 This refers to the assembly state of the drive shaft 1 with the left and right cranks of the bicycle. Therefore, this utility model has a simple structure and low cost, solving the technical problem of coaxiality deviation in the two bearing mating parts 1a of the existing bicycle drive shaft 1, which leads to crank wobble. The technical solution of this utility model is to directly fit two positioning rings 2 with equal inner diameters onto the outer circumference of the two bearing mating parts 1a of the drive shaft 1. Combined with the cooperation of the positioning part 21 on the outer circumference of the positioning ring 2 and the external clamp, it not only establishes a unified coaxial reference for the two positioning rings 2, but also constrains the thermal expansion deformation of the bearing mating parts 1a by the inner diameter of the positioning rings 2 during the hot working of the drive shaft 1, effectively controlling the coaxiality of the two bearing mating parts 1a, avoiding asymmetrical deformation of the carbon drive shaft 1 due to uneven thermal expansion, and solving the coaxiality deviation of the two bearing mating parts 1a and the subsequent crank wobble problems. At the same time, the outer diameter of the drive shaft 1 can be quickly adapted to the inner diameter of the bicycle bottom bracket bearing by the positioning rings 2, without the need to adjust the outer diameter of the drive shaft 1 by sanding as in the prior art, effectively avoiding the tedious operation and insufficient precision of manual grinding, improving assembly efficiency and reliability.

[0045] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this utility model, but does not constitute a limitation on the scope of protection of this utility model. Modifications, equivalent substitutions, or other improvements to the embodiments of this utility model or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this utility model or the foregoing embodiments, should all be included within the scope of protection of this utility model.

Claims

1. A coaxiality control structure for a bicycle drive shaft, characterized in that: Includes two positioning rings; The two positioning rings have the same inner diameter, and the outer diameter of the positioning rings is adapted to the inner diameter of the bicycle bottom bracket bearing; the two positioning rings are respectively sleeved on the outer circumference of the two bearing mating parts of the transmission shaft, and the two positioning rings are arranged parallel and spaced apart along the axial direction of the transmission shaft. The outer periphery of the positioning ring is provided with a positioning part, which is used to cooperate with an external clamp to limit the axial distance between the two positioning rings on the transmission shaft and make the axes of the two positioning rings coincide. During hot working, the inner diameter of the positioning ring is used to limit the thermal expansion deformation of the corresponding bearing mating parts, so that the coaxiality of the two bearing mating parts is consistent.

2. The coaxiality control structure for a bicycle drive shaft as described in claim 1, characterized in that: The positioning part is a ring platform arranged around the outer circumference of the positioning ring, and the ring platform extends radially toward the positioning ring.

3. The coaxiality control structure for a bicycle drive shaft as described in claim 2, characterized in that: The ring platform is located at the axial middle part of the positioning ring, and the cross-section of the ring platform is parallel to the cross-section of the positioning ring; the axial length of the ring platform is less than the axial length of the positioning ring.

4. The coaxiality control structure for a bicycle drive shaft as described in claim 1, characterized in that: The positioning portions of the two positioning rings are equidistant from their respective ends near the center of the transmission shaft.

5. The coaxiality control structure for a bicycle drive shaft as described in claim 2, characterized in that: The radial height of the ring platform is uniform along the circumference of the positioning ring.

6. The coaxiality control structure for a bicycle drive shaft as described in claim 5, characterized in that: Both end faces of the ring platform are flat, and these end faces are perpendicular to the axis of the positioning ring.

7. A coaxiality control structure for a bicycle drive shaft as described in any one of claims 1 to 6, characterized in that: The axial length of the positioning ring is equal to the axial length of the bearing mating part of the transmission shaft.

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