Lightweight crank assembly and forming method thereof

Abstract

The invention discloses a light-weight crank assembly and a forming method thereof.The crank assembly comprises a first connecting structure and a second connecting structure, the first connecting structure comprises a middle shaft and a first crank, the periphery of the middle shaft is sleeved with two mounting rings, one end of the middle shaft is connected with the first crank, and the inner wall of the other end of the middle shaft is provided with a first connecting piece; the middle shaft, the first crank, the mounting ring and the first connecting piece are integrally formed; the second connecting structure comprises a second crank and a second connecting piece, and the second connecting piece and the second crank are integrally formed; and the fastener is arranged on the second crank in a penetrating manner and is respectively connected with the first connecting piece and the second connecting piece. According to the crank assembly and the forming method thereof, the crank and the middle shaft are all made of the carbon fiber materials, the overall weight is reduced by 15%-20%, the crank assembly does not need to be glued repeatedly during installation, the installation efficiency of the whole crank assembly is improved, the time cost is reduced, and a product can be more stable in the subsequent use process.

Description

Technical Field

[0001] This invention relates to the field of bicycle crank structure technology, and more specifically, to a lightweight crank assembly and its molding method. Background Technology

[0002] Bicycle crank assemblies typically include a metal bottom bracket, two carbon fiber crank arms connected to both ends of the bottom bracket, one end of each crank arm connected to the bottom bracket via a metal connector, and the other end attached to a pedal. Existing crank assemblies have many metal components, making the entire assembly heavy and requiring significant load during riding, contradicting the need for lightweight design. Furthermore, in existing crank assemblies, the bottom bracket, crank arms, and connectors are machined or molded separately, and then the two crank arms are glued to the connectors. The bottom bracket is then fixed to the crank arms via the glued connectors to prevent detachment. However, this method requires cleaning and surface treatment of all surfaces to be glued, and localized surface treatment is needed for other non-glued parts, which is time-consuming and labor-intensive. It also requires additional adhesive, increasing material costs; the long curing process further increases time costs.

[0003] In view of this, the inventors of this application have invented a lightweight crank assembly and its molding method. Summary of the Invention

[0004] The purpose of this invention is to provide a lightweight crank assembly and its molding method, solving the problems of excessive weight and complex manufacturing process of existing crank assemblies.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a lightweight crank assembly, comprising: The first connecting structure includes a central shaft and a first crank. Two mounting rings for mounting bearings are sleeved on the outer periphery of the central shaft. One end of the central shaft is connected to the first crank. A first connecting member is provided on the inner wall of the other end of the central shaft. The central shaft and the first crank are made of carbon fiber material. The mounting rings and the first connecting member are both made of metal. The central shaft, the first crank, the mounting rings and the first connecting member are integrally formed. The second connection structure includes a second crank and a second connector. The second crank is made of carbon fiber material, and the second connector is made of metal. The second connector is integrally formed with the second crank. The fastener has a first connector at the end of the central shaft that mates with the second connector. The fastener passes through the second crank on the side of the second crank away from the central shaft and is connected to the first connector and the second connector respectively, so that the first connecting structure and the second connecting structure are connected and fixed.

[0006] As an alternative implementation, an end cap is included, which is inserted into a second connector along the side of the second crank away from the central axis, and is threadedly connected to the second connector, and abuts against the inner wall of the second crank and against the end of a fastener.

[0007] As an optional implementation, the outer periphery of the central shaft is provided with two annular grooves, and the two mounting rings are respectively embedded in the annular grooves.

[0008] As an optional implementation, the wall thickness of the mounting ring is 0.5-2.5 mm.

[0009] As an optional implementation, the first crank has a first pedal connector, the second crank has a second pedal connector, both the first pedal connector and the second pedal connector are made of metal, and the first pedal connector is integrally formed with the first connecting structure, and the second pedal connector is integrally formed with the second connecting structure.

[0010] The present invention also provides a method for molding a lightweight crank assembly, comprising: A first mold and a first carbon fiber preform are provided, wherein the first carbon fiber preform includes a first connector, a mounting ring and a first foot pedal connector. The first carbon fiber preform is placed into the first mold to prepare an integral first connecting structure. A second mold and a second carbon fiber preform are provided, wherein the second carbon fiber preform includes a second connector and a second foot pedal connector. The second carbon fiber preform is placed into the second mold to prepare an integral second connection structure. The end of the central shaft with the first connecting member is assembled with the second connecting member, and then fasteners are used to connect and fix the first connecting member and the second connecting member, so that the first connecting structure and the second connecting structure are connected as one.

[0011] As an optional implementation, the mounting ring has a circumferentially arranged positioning protrusion, and the first mold has a positioning groove. When the first carbon fiber preform is placed into the first mold, the positioning protrusion is correspondingly embedded in the positioning groove.

[0012] As an optional implementation, after the first connecting structure is prepared from the first mold, the method for forming the crank assembly further includes: The mounting ring undergoes surface treatment to remove the positioning protrusion and ensure that the surface accuracy of the mounting ring meets the requirements for mounting the bearing.

[0013] As an optional implementation, prior to providing the first carbon fiber preform and the second carbon fiber preform, the method for forming the crank assembly further includes: The first foot pedal connector and the second foot pedal connector are surface treated.

[0014] As an optional implementation, the first mold includes a first body, a first protective structure, and a second protective structure. The first body has a first cavity, and the first and second protective structures are disposed within the first cavity. The step of placing the first carbon fiber preform into the first mold includes: The first protective structure is inserted into the end of the first carbon fiber preform where the first connector is located, so that the first connector is covered by the first protective structure. The second protective structure is inserted into the first pedal connector and adhered to the first carbon fiber preform, so that the first pedal connector is covered by the second protective structure. The first carbon fiber preform, the first protective structure, and the second protective structure are placed into the corresponding positions within the first cavity. The second mold includes a second body, a third protective structure, and a fourth protective structure. The second body has a second cavity, and the third and fourth protective structures are disposed within the second cavity. The step of placing the second carbon fiber preform into the second mold includes: The third protective structure is inserted into the second connector and attached to the second carbon fiber preform, so that the second connector is covered by the third protective structure. The fourth protective structure is inserted into the second pedal connector and adhered to the second carbon fiber preform, so that the second pedal connector is covered by the fourth protective structure. The second carbon fiber preform, the third protective structure, and the fourth protective structure are placed in their corresponding positions within the second cavity.

[0015] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: This invention relates to a crank assembly and its molding method. Both the crank and bottom bracket are made of carbon fiber, reducing the overall weight by 15%-20%, achieving lightweighting of the crank assembly. A metal mounting ring is added to the bottom bracket, reducing weight while meeting the precision requirements of subsequent component assembly. Both the first crank and bottom bracket are integrally molded from carbon fiber, eliminating issues of rotation and loosening, and eliminating the need for adhesives or other bonding methods. This improves product quality, simplifies the production process, and enhances enterprise efficiency. The bottom bracket, first crank, and first connector are integrally molded, as are the second crank and second connector. Finally, the bottom bracket and second crank are connected. Compared to existing crank assemblies, this method eliminates the need for multiple adhesive bonding steps during installation, improving the overall installation efficiency of the crank assembly, reducing time costs, and ensuring greater product stability during subsequent use. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the crank assembly of the present invention; Figure 2 This is an exploded view of the crank assembly of the present invention; Figure 3 This is a cross-sectional schematic diagram of the crank assembly of the present invention; Figure 4 yes Figure 3 Enlarged view of point I in the middle; Figure 5 yes Figure 3 Enlarged schematic diagram at point II; Figure 6 This is a schematic diagram of the structure of the first mold of the present invention; Figure 7 This is a cross-sectional schematic diagram of the first mold of the present invention; Figure 8 yes Figure 7 Enlarged schematic diagram at point III; Figure 9 yes Figure 7 Enlarged schematic diagram at point IV; Figure 10 This is a schematic diagram of the structure of the second mold of the present invention; Figure 11 This is a top view of the second mold of the present invention; Figure 12 for Figure 11 A cross-sectional view along the AA direction; Figure 13 yes Figure 12 Enlarged view of point V in the middle; Figure 14 yes Figure 12 Enlarged diagram of point VI in the middle.

[0017] Explanation of reference numerals in the attached figures: 100-crank assembly, 110 - First connection structure, 111 - Central axis, 1111 - Annular groove 112 - First crank, 113-Mounting ring, 1131-Positioning protrusion ring, 114 - First connector, 115 - First pedal connector, 120 - Second connection structure, 121-Second crank, 1211-Anti-slip step, 122-Second connector, 1221-Anti-detachment groove, 123 - Second foot pedal connector, 130 - Fastener, 131 - Limiting flange 140 - End cap, 150 - Snap ring, 160 - Hoop sleeve 200 - First mold 210-First entity, 220 - First protective structure, 221 - First insert, 222 - First sealing ring 230 - Second protective structure, 231 - Second insert, 232 - Second sealing ring 240 - First cavity, 241 - Positioning groove 300 - Second mold, 310 - Second Body, 320 - Third protective structure, 321 - Third insert, 322 - Third sealing ring, 323 - Third kit. 330 - Fourth protective structure, 331 - Fourth insert, 332 - Fourth sealing ring 340 - Second cavity. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] It should be noted that in this invention, the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element of this invention must have a specific orientation, and therefore should not be construed as a limitation of this invention.

[0020] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0021] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0022] The technical solution of the present invention will be further described below with reference to the embodiments and accompanying drawings. Example

[0023] Cooperate Figures 1 to 5 As shown, the present invention discloses a lightweight crank assembly 100, including a first connecting structure 110, a second connecting structure 120 and a fastener 130.

[0024] The first connecting structure 110 includes a central shaft 111 and a first crank 112. Two mounting rings 113 for mounting bearings are sleeved on the outer periphery of the central shaft 111. One end of the central shaft 111 is connected to the first crank 112, and the inner wall of the other end of the central shaft 111 is provided with a first connecting member 114. The central shaft 111 and the first crank 112 are made of carbon fiber material, and the mounting rings 113 and the first connecting member 114 are made of metal. The central shaft 111, the first crank 112, the mounting rings 113 and the first connecting member 114 are integrally formed. The second connection structure 120 includes a second crank 121 and a second connector 122. The second crank 121 is made of carbon fiber material, and the second connector 122 is made of metal. The second connector 122 is integrally formed with the second crank 121. Fastener 130, the end of the central shaft 111 with the first connector 114 is assembled with the second connector 122, the fastener 130 passes through the second crank 121 on the side of the second crank 121 away from the central shaft 111, and is connected to the first connector 114 and the second connector 122 respectively, so that the first connecting structure 110 and the second connecting structure 120 are connected and fixed.

[0025] Cooperate Figures 1 to 5As shown, the central shaft 111 is made of carbon fiber and is integrally formed with the first crank 112. Compared with the metal central shaft 111 in the prior art, its weight is significantly reduced. At the same time, the central shaft 111 and the first crank 112 no longer need to be connected by other connecting structures, simplifying the overall structure. The problem of loosening and rotation between the central shaft 111 and the first crank 112 will no longer occur. Furthermore, the corresponding gluing and assembly processes can be omitted, effectively improving product quality and increasing production efficiency.

[0026] The mounting ring 113, made of metal, is used for subsequent bearing installation. The mounting ring 113 is also positioned on the central shaft 111 where the bearing will be installed. The bearing installation requires high precision, which the machining precision of carbon fiber cannot meet. Therefore, a metal mounting ring 113 is added to the outer circumference of the carbon fiber central shaft 111 to achieve the required bearing installation precision. Similarly, the first connecting member 114 is used to connect with the second connecting structure 120. The inner wall of the first connecting member 114 is threaded to facilitate connection with the second connecting structure 120. The first connecting member 114 is made of metal to meet the structural connection requirements.

[0027] Cooperate Figures 1 to 3 , Figure 5 As shown, the second connecting member 122 is a spline sleeve made of metal. The outer periphery of the spline sleeve engages with the second crank 121 via a keyway and key teeth arranged circumferentially. The engagement of the keyway and key teeth further prevents rotation between the second connecting member 122 and the second crank 121. Furthermore, the second connecting member 122 is provided with a circumferentially extending anti-detachment groove 1221, and the second crank 121 is provided with an anti-detachment step 1211 correspondingly embedded in the anti-detachment groove 1221. The engagement of the anti-detachment groove 1221 and the anti-detachment step 1211 further prevents the second crank 121 from axially disengaging from the second connecting member 122 along the central shaft 111.

[0028] Fastener 130 is made of metal and is used to connect and fix the first connecting structure 110 and the second connecting structure 120. The end of the central shaft 111 with the first connecting member 114 is assembled with the second connecting member 122. Specifically, the outer periphery of the end of the central shaft 111 and the inner wall of the second connecting member 122 are engaged by a keyway and key teeth arranged circumferentially. The keyway and key teeth engagement can further prevent rotation between the second connecting member 122 and the central shaft 111. One end of the fastener 130 is provided with an external thread, which extends into the second connecting member 122 and the first connecting member 114 and is threadedly engaged with the first connecting member 114. The other end of the fastener 130 is provided with a limiting flange 131. When the fastener 130 and the first connecting member 114 are threadedly engaged, the limiting flange 131 is also pressed against the second connecting member 122.

[0029] The first crank 112 has a first pedal connector 115, and the second crank 121 has a second pedal connector 123. Both the first pedal connector 115 and the second pedal connector 123 are made of metal, and the first pedal connector 115 is integrally formed with the first connecting structure 110, and the second pedal connector 123 is integrally formed with the second connecting structure 120. One end of the first crank 112 / second crank 121 is connected to the central shaft 111, and the other end is connected to the pedal through the pedal connector. Both the first pedal connector 115 and the second pedal connector 123 are made of metal and are integrally formed with the first connecting structure 110 and the second connecting structure 120, respectively.

[0030] It should be noted that in this embodiment, the first connecting member 114, the second connecting member 122, the first pedal connecting member 115, and the second pedal connecting member 123 are integrally formed with the first connecting structure 110 / second connecting structure 120, and various assembly structures are already formed. Their spline structure, thread structure, etc., have all been fully processed and surface treated for protection after the shape is processed, such as anodizing (black or natural color), to avoid oxidation, corrosion, etc. during use. Therefore, in this embodiment, the crank assembly 100 does not need to process the specific structure of the above-mentioned metal parts after the first connecting structure 110 and the second connecting structure 120 are connected and formed, which reduces the processing procedures, reduces the processing difficulty and cost. At the same time, compared with integral forming with the first connecting structure 110 / second connecting structure 120 and then surface processing, the above-mentioned metal parts are processed first and then formed, which has higher precision.

[0031] Cooperate Figure 2 , Figure 5 As shown, the crank assembly 100 of this embodiment also includes an end cap 140, a retaining ring 150, and a clamp 160. The end cap 140 is inserted into the second connector 122 along the side of the second crank 121 away from the central shaft 111, and is threadedly connected to the second connector 122. It abuts against the inner wall of the second crank 121 and against the end of the fastener 130, thus further preventing the second connector 122 from disengaging from the second crank 121. The retaining ring 150 is sleeved on the central shaft 111. Specifically, the retaining ring 150 is embedded in the side of the second connector 122 away from the second crank 121. The clamp 160 is sleeved on the end of the central shaft 111 that connects to the first crank 112, and is located inside the first crank 112.

[0032] Furthermore, the outer periphery of the central shaft 111 is provided with two annular grooves 1111, and the two mounting rings 113 are respectively embedded in the annular grooves 1111. The mounting rings 113 are embedded in the annular grooves 1111 to prevent the mounting rings 113 from moving on the central shaft 111. Preferably, the surface of the mounting rings 113 protrudes slightly from the outer surface of the central shaft 111, that is, the wall thickness of the mounting rings 113 is slightly greater than the groove depth of the annular grooves 1111. Specifically, the wall thickness of the mounting rings 113 is 0.5-2.5mm, wherein the wall thickness of the mounting rings 113 is preferably 1.5mm.

[0033] Cooperate Figures 6 to 14 As shown, the present invention also discloses a method for molding a lightweight crank assembly 100, comprising: S1: Provide a first mold 200 and a first carbon fiber preform, wherein the first carbon fiber preform includes a first connector 114, a mounting ring 113 and a first foot pedal connector 115. Place the first carbon fiber preform into the first mold 200 to prepare an integral first connecting structure 110.

[0034] Cooperate Figures 6 to 9 As shown, the first carbon fiber preform is a carbon fiber preform prepared by impregnating carbon fiber body in epoxy resin matrix, and has been pre-formed into a semi-finished product. The first connector 114 and the first foot pedal connector 115 are both in a state of surface processing and forming. The mounting ring 113 has not yet undergone surface finishing treatment. It will undergo subsequent surface processing after the first connecting structure 110 is formed. The first connector 114, the mounting ring 113 and the first foot pedal connector 115 are all pre-embedded in the corresponding positions during the pre-forming process of the first carbon fiber preform.

[0035] After the first carbon fiber preform is placed into the first mold 200, the first connecting structure 110 is formed by heating and pressurizing. Pressurization is achieved by placing air bags inside the central shaft 111 and the first crank 112 respectively, and blowing air into the air bags to form a certain wind pressure. The first mold 200 is provided with air bag channels to accommodate the air bags. Using air bags to form carbon fiber products is a conventional method in this field and will not be elaborated here.

[0036] S2: Provide a second mold 300 and a second carbon fiber preform, wherein the second carbon fiber preform includes a second connector 122 and a second foot pedal connector 123. Place the second carbon fiber preform into the second mold 300 to prepare an integral second connecting structure 120.

[0037] Cooperate Figures 10 to 14As shown, the second connector 122 and the second foot pedal connector 123 are both surface-processed and pre-embedded in their respective positions during the pre-forming process of the second carbon fiber preform. The forming method of the second carbon fiber preform is the same as that of the first carbon fiber preform.

[0038] S3: Assemble the end of the central shaft 111 with the first connector 114 and the second connector 122, and then use fasteners 130 to connect and fix the first connector 114 and the second connector 122, so that the first connecting structure 110 and the second connecting structure 120 are connected as one.

[0039] The first connecting structure 110 and the second connecting structure 120 are connected together by fasteners 130 to form the corresponding crank assembly 100. Specifically, before the fasteners 130 connect and fix the first connecting structure 110 and the second connecting structure 120, the retaining ring 150 and the clamp 160 are installed first.

[0040] Furthermore, in coordination Figures 6 to 9 As shown, the mounting ring 113 has a circumferentially positioned convex ring 1131, and the first mold 200 has a positioning groove 241. When the first carbon fiber preform is placed into the first mold 200, the positioning convex ring 1131 is correspondingly embedded in the positioning groove 241. The positioning convex ring 1131 and the positioning groove 241 enable the first carbon fiber preform to be quickly and accurately positioned in the first mold 200. After the first connecting structure 110 is prepared from the first mold 200, i.e., after step S2 and before step S3, the forming method of the crank assembly 100 further includes: The mounting ring 113 undergoes surface treatment to remove the positioning protrusion 1131 and ensure that the surface precision of the mounting ring 113 meets the requirements for mounting bearings. The mounting ring 113 is used to mount bearings and requires high surface precision. Performing surface processing after product molding avoids resin overflow from the carbon fiber preform during molding from contaminating the surface of the mounting ring 113. Furthermore, since the surface of the mounting ring 113 is completely exposed, surface processing is convenient. Using a pre-molding followed by processing approach is convenient and ensures processing accuracy.

[0041] Furthermore, prior to providing the first carbon fiber preform and the second carbon fiber preform, the forming method of the crank assembly 100 further includes: surface treatment of the first pedal connector 115 and the second pedal connector 123. That is, before being embedded into the first carbon fiber preform and the second carbon fiber preform, the first pedal connector 115 and the second pedal connector 123 have undergone surface processing. Their surface structures, such as threaded structures, have been processed and protected by surface treatments, such as anodizing, to avoid surface processing of the first pedal connector 115 and the second pedal connector 123 after the crank assembly is formed, thus ensuring the precision of the first pedal connector 115 and the second pedal connector 123.

[0042] Furthermore, the first connector 114, the second connector 122, the first foot pedal connector 115, and the second foot pedal connector 123 have all undergone surface processing before entering the first mold 200 / second mold 300. To prevent resin overflow from the first carbon fiber preform / second carbon fiber preform during the molding process from contaminating the surface of the aforementioned metal parts, protective structures are provided in both the first mold 200 and the second mold 300 to protect the surface of the aforementioned metal parts. Specifically: Cooperate Figures 6 to 9 As shown, the first mold 200 includes a first body 210, a first protective structure 220, and a second protective structure 230. The first body 210 has a first cavity 240, and the first protective structure 220 and the second protective structure 230 are disposed within the first cavity 240. The step of placing the first carbon fiber preform into the first mold 200 includes: The first protective structure 220 is inserted into the end of the first carbon fiber preform where the first connector 114 is located, so that the first connector 114 is covered by the first protective structure 220. The second protective structure 230 is inserted into the first pedal connector 115 and adhered to the first carbon fiber preform, so that the first pedal connector 115 is covered by the second protective structure 230. The first carbon fiber preform, the first protective structure 220, and the second protective structure 230 are placed into the corresponding positions within the first cavity 240.

[0043] The first protective structure 220 covers and protects the surface of the first connector 114, and the second protective structure 230 covers and protects the surface of the first pedal connector 115, thus effectively preventing resin from overflowing onto the surfaces of the first connector 114 and the first pedal connector 115.

[0044] Specifically, the first protective structure 220 includes a first insert 221 and a first sealing ring 222. One end of the first insert 221 is inserted into the first connector 114. There are two first sealing rings 222, which are located between the first insert 221 and the first connector 114. The second protective structure 230 includes a second insert 231 and a second sealing ring 232. The second insert 231 includes two inserts with matching ends. The two inserts are inserted from both sides of the first pedal connector 115 and are respectively in close contact with both sides of the first crank 112. There are two second sealing rings 232, which are respectively located between the two inserts and the first crank 112.

[0045] Cooperate Figures 10 to 14 As shown, the second mold 300 includes a second body 310, a third protective structure 320, and a fourth protective structure 330. The second body 310 has a second cavity 340, and the third protective structure 320 and the fourth protective structure 330 are disposed within the second cavity 340. The step of placing the second carbon fiber preform into the second mold 300 includes: The third protective structure 320 is inserted into the second connector 122 and attached to the second carbon fiber preform, so that the second connector 122 is covered by the third protective structure 320. The fourth protective structure 330 is inserted into the second pedal connector 123 and adhered to the second carbon fiber preform, so that the second pedal connector 123 is covered by the fourth protective structure 330. The second carbon fiber preform, the third protective structure 320, and the fourth protective structure 330 are placed in the corresponding positions within the second cavity 340.

[0046] The third protective structure 320 covers and protects the surface of the second connector 122, and the fourth protective structure 330 covers and protects the surface of the second pedal connector 123, thus effectively preventing resin from overflowing onto the surfaces of the second connector 122 and the second pedal connector 123.

[0047] Specifically, the third protective structure 320 includes a third insert 321, a third sealing ring 322, and a third fitting 323. The third insert 321 is inserted into the second connector 122 from the side opposite to the central shaft 111 and fits against the second crank 121. The third fitting 323 is fitted onto the other side of the second connector 122 and fits against the second crank 121. There are two third sealing rings 322, which are respectively located between the third insert 321 and the fixture of the second crank 121, and between the third fitting 323 and the second crank 121. The fourth protective structure 330 includes a fourth insert 331 and a fourth sealing ring 332. The specific structure of the fourth protective structure 330 is the same as that of the second protective structure 230, and will not be repeated here.

[0048] The above-mentioned crank assembly 100 is formed by integrally molding the first crank 112 and the bottom bracket 111 from carbon fiber, integrally molding the second crank 121 and the second connecting piece 122, and then connecting the bottom bracket 111 and the second crank 121. The entire crank assembly 100 is simple and easy to implement, and does not require bonding between the various parts, thus improving assembly efficiency. At the same time, the integral structural design during the molding process is more robust than the method of bonding parts multiple times, resulting in greater stability during subsequent use. The dimensions of the crank assembly 100 can be more precisely controlled.

[0049] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lightweight crank assembly, characterized in that: include: The first connecting structure includes a central shaft and a first crank. Two mounting rings for mounting bearings are sleeved on the outer periphery of the central shaft. One end of the central shaft is connected to the first crank. A first connecting member is provided on the inner wall of the other end of the central shaft. The central shaft and the first crank are made of carbon fiber material. The mounting rings and the first connecting member are both made of metal. The central shaft, the first crank, the mounting rings and the first connecting member are integrally formed. The second connection structure includes a second crank and a second connector. The second crank is made of carbon fiber material, and the second connector is made of metal. The second connector is integrally formed with the second crank. The fastener has a first connector at the end of the central shaft that mates with the second connector. The fastener passes through the second crank on the side of the second crank away from the central shaft and is connected to the first connector and the second connector respectively, so that the first connecting structure and the second connecting structure are connected and fixed.

2. The lightweight crank assembly as described in claim 1, characterized in that: Includes an end cap, which is inserted into the second connector along the side of the second crank away from the central axis, and is threadedly connected to the second connector, and abuts against the inner wall of the second crank and against the end of the fastener.

3. The lightweight crank assembly as described in claim 1, characterized in that: The outer circumference of the central shaft is provided with two annular grooves, and the two mounting rings are respectively embedded in the annular grooves.

4. A lightweight crank assembly as described in claim 1, characterized in that: The wall thickness of the mounting ring is 0.5-2.5 mm.

5. A lightweight crank assembly as described in claim 1, characterized in that: The first crank has a first pedal connector, and the second crank has a second pedal connector. Both the first pedal connector and the second pedal connector are made of metal, and the first pedal connector is integrally formed with the first connecting structure, and the second pedal connector is integrally formed with the second connecting structure.

6. A method for molding a lightweight crank assembly, characterized in that, include: A first mold and a first carbon fiber preform are provided, wherein the first carbon fiber preform includes a first connector, a mounting ring and a first foot pedal connector. The first carbon fiber preform is placed into the first mold to prepare an integral first connecting structure. A second mold and a second carbon fiber preform are provided, wherein the second carbon fiber preform includes a second connector and a second foot pedal connector. The second carbon fiber preform is placed into the second mold to prepare an integral second connection structure. The end of the central shaft with the first connecting member is assembled with the second connecting member, and then fasteners are used to connect and fix the first connecting member and the second connecting member, so that the first connecting structure and the second connecting structure are connected as one.

7. The molding method of a lightweight crank assembly as described in claim 6, characterized in that: The mounting ring has a circumferentially positioned protrusion, and the first mold has a positioning groove. When the first carbon fiber preform is placed into the first mold, the positioning protrusion is correspondingly embedded in the positioning groove.

8. The molding method of a lightweight crank assembly as described in claim 7, characterized in that: After the first connecting structure is prepared from the first mold, the method for forming the crank assembly further includes: The mounting ring undergoes surface treatment to remove the positioning protrusion and ensure that the surface accuracy of the mounting ring meets the requirements for mounting the bearing.

9. The molding method of a lightweight crank assembly as described in claim 6, characterized in that: Prior to the steps of providing the first carbon fiber preform and the second carbon fiber preform, the method for forming the crank assembly further includes: The first foot pedal connector and the second foot pedal connector are surface treated.

10. The molding method of a lightweight crank assembly as described in claim 6, characterized in that: The first mold includes a first body, a first protective structure, and a second protective structure. The first body has a first cavity, and the first and second protective structures are disposed within the first cavity. The step of placing the first carbon fiber preform into the first mold includes: The first protective structure is inserted into the end of the first carbon fiber preform where the first connector is located, so that the first connector is covered by the first protective structure. The second protective structure is inserted into the first pedal connector and adhered to the first carbon fiber preform, so that the first pedal connector is covered by the second protective structure. The first carbon fiber preform, the first protective structure, and the second protective structure are placed into the corresponding positions within the first cavity. The second mold includes a second body, a third protective structure, and a fourth protective structure. The second body has a second cavity, and the third and fourth protective structures are disposed within the second cavity. The step of placing the second carbon fiber preform into the second mold includes: The third protective structure is inserted into the second connector and attached to the second carbon fiber preform, so that the second connector is covered by the third protective structure. The fourth protective structure is inserted into the second pedal connector and adhered to the second carbon fiber preform, so that the second pedal connector is covered by the fourth protective structure. The second carbon fiber preform, the third protective structure, and the fourth protective structure are placed in their corresponding positions within the second cavity.

Images