Processing and forming method of carbon fiber crank

Abstract

A carbon fiber crank machining and forming method comprises the steps that a metal blank is subjected to rough machining to form a first rough blank, and the first rough blank is subjected to lathe machining to form a metal ring with the stepped outer surface; an upper mold with a pouring gate and a lower mold with a stepped column body are closed, the stepped column body abuts against the upper mold after mold closing, short carbon fibers are injected into a mold cavity, a second rough blank is formed at the first temperature, and a spline hole with the stepped inner surface is formed in one end of the second rough blank; the second rough blank is machined through a milling machine to form a handle body, the surface of the handle body is cleaned, and the surface of the handle body is coated with a coating; and the metal ring is embedded into the spline hole and is bonded with the handle body resin at a second temperature to form a workpiece in one step.

Description

Technical Field

[0001] The invention relates to the field of bicycle accessories, and in particular to a carbon fiber crank processing and molding method. Background Art

[0002] With the advancement of material technology and the increasing demand for lightweight bicycles, more and more bicycle components on the market are now made of lightweight and high-strength materials such as carbon fiber, titanium alloy, and aluminum alloy.

[0003] Among all the components of a bicycle, the crank is an important component that connects the pedals and the sprockets. It is used to transfer the leg power of the rider to the drive system of the bicycle and drive the bicycle. Due to the trend of lightweight, many bicycle cranks are made of carbon fiber and metal parts. At present, in the processing and molding process of carbon fiber cranks, it is usually necessary to first rough-process the metal parts, and then put the carbon fiber handle body and the metal parts into a mold together to form a crank. Then, the crank and the rough-processed metal parts are cut (finished) as an integral component and surface treated. Finally, this integral component is assembled with bicycle parts such as the shaft rod for connecting the chainring. The processing of metal parts and the processing of carbon fiber are usually not completed in the same factory due to the limitations of dedicated equipment and fields. Therefore, when this process processes the metal parts and the carbon fiber parts of the crank in sequence, there is a problem of transferring the crank between two processing plants, which greatly reduces the efficiency of the production process. If the carbon fiber components and metal components are processed separately and then connected to form a crank, the production efficiency can be improved, but there is a problem of unstable component connection during connection.

[0004] Therefore, it is necessary to provide a carbon fiber crank processing and molding method that can avoid frequent material transfer and effectively improve the stability of component connection. Summary of the invention

[0005] The object of the present invention is to provide a carbon fiber crank processing and molding method which can avoid frequent material transfer and effectively improve the stability of component connection.

[0006] According to one aspect of the present application, a method for processing and forming a carbon fiber crank is provided, the method comprising the steps of:

[0007] Rough machining a metal blank to form a first rough blank, and lathe machining the first rough blank to form a metal ring having a stepped outer surface;

[0008] An upper mold with a runner and a lower mold with a stepped column are closed, and the stepped column abuts against the upper mold after the mold is closed, short chopped carbon fibers are injected into the mold cavity, and a second rough blank is formed at a first temperature, wherein a spline hole with a stepped inner surface is formed at one end of the second rough blank;

[0009] Milling the second rough blank to form a handle body, cleaning the surface of the handle body and applying a coating on the surface;

[0010] The metal ring is embedded in the spline hole and is resin-bonded with the handle body at a second temperature to form a workpiece.

[0011] More preferably, the spline hole comprises a first part, a second part connected to the first part, and a third part connected to the second part; after the second rough blank is formed in the mold cavity, the first part abuts against the upper mold, and the third part abuts against the lower mold; the inner surface of the second part has a spline and is located between the first part and the second part;

[0012] Among them, after the first rough milling machine processes and grinds the spline hole, a smooth inner surface is formed in the spline hole, and the inner diameter R1 of the third part and the maximum inner diameter R2 of the second part satisfy the relationship: R1>R2, and the connection between the third part and the second part is a stepped structure.

[0013] More preferably, after the first rough blank is lathe-machined to form the metal ring, a shaft body and a journal integrally formed on the shaft body and having a smooth surface are formed on the metal ring, an outer diameter R3 of the journal and an inner diameter R1 of the third portion satisfy the relationship: R3=R1, and a height H1 of the journal and a depth H2 of the third portion satisfy the relationship: H1=H2, and a connection between the journal and the shaft body is a stepped structure;

[0014] When the metal ring is inserted into the spline hole, the third portion fits tightly against the shaft neck.

[0015] More preferably, the metal blank is sequentially rough-machined and lathe-machined to form the metal ring, and the chopped carbon fiber is sequentially molded and milled to form the handle body. The processing of the metal ring and the processing of the handle body are performed independently, and after the metal ring and the handle body are formed separately, the metal ring and the handle body are bonded to form the workpiece in one step.

[0016] More preferably, the lower mold further has a tapered stepped column, which abuts against the upper mold after the mold is closed, and the other end of the second rough blank is formed with a pedal hole with a tapered stepped inner surface and splines.

[0017] More preferably, during milling processing, the second rough blank is fixed on the milling machine, and the milling cutter grinds the pedal hole and the spline hole of the second rough blank. During lathe processing, the first rough blank is fixed on the lathe, the first rough blank is rotated, and the lathe cutter grinds to form the shaft neck and the shaft body, and the first rough blank is finely processed into the metal ring.

[0018] More preferably, the first temperature and the second temperature are respectively recorded as T1 and T2, and satisfy the relationship:

[0019] 120℃≤T1≤180℃,

[0020] 150℃≤T2≤220℃.

[0021] More preferably, the continuous carbon fiber material is cut into a plurality of sections of chopped carbon fibers, and the chopped carbon fibers are combined with resin and then injected into the mold cavity through the runner.

[0022] More preferably, after forming the second rough blank at the first temperature, the upper mold is opened toward a side away from the lower mold, and the second rough blank is taken out from the lower mold.

[0023] More preferably, during the process of cleaning the surface of the handle body, the surface of the handle body is polished, and after polishing, a coating is applied to the surface of the handle body, and the coating is hardened by heating to a third temperature T3, and the relationship is satisfied: 60°C≤T3≤120°C.

[0024] The present invention has the following beneficial effects:

[0025] The metal ring and the handle body are formed by sequentially processing and then finally bonding them together to form a workpiece, which replaces the method of first connecting the first rough blank and the second rough blank into one and then processing them, thereby avoiding frequent transfer of materials during the processing. The metal ring and the handle body are bonded with resin at the second temperature, so that the metal ring and the handle body can be effectively connected. The design of the metal ring outer surface being stepped and the spline hole inner surface being stepped increases the contact surface area of ​​the metal ring after being embedded in the spline hole, thereby improving the stability of the connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 It is a schematic diagram of the three-dimensional structure of the workpiece in one embodiment of the present application;

[0028] Figure 2 This is a schematic diagram of the decomposed structure of the workpiece in one embodiment of the present application;

[0029] Figure 3 A schematic diagram of a rough machining process for forming a first rough blank in a workpiece according to an embodiment of the present application;

[0030] Figure 4 It is a schematic diagram of the state of the finishing process of forming a metal ring in the workpiece in one embodiment of the present application;

[0031] Figure 5 This is a schematic diagram of a state where the upper mold and the lower mold have just been opened in one embodiment of the present application;

[0032] Figure 6 This is a schematic diagram of a state in which the upper mold and the lower mold are closed and filled with chopped fibers in one embodiment of the present application;

[0033] Figure 7 This is a schematic diagram of the state of the upper mold after mold opening in one embodiment of the present application;

[0034] Figure 8 This is a schematic diagram of a state in which the second rough blank is processed by a milling machine to form the spline hole of the handle body in one embodiment of the present application;

[0035] Fig. 9 This is a schematic diagram of a state in which the pedal hole of the handle body is formed by machining the second rough blank by a milling machine in one embodiment of the present application;

[0036] Fig.10 This is a side view of the metal ring embedded in the handle body in one embodiment of the present application;

[0037] Fig.11 This is a cross-sectional schematic diagram of the metal ring embedded in the handle body in one embodiment of the present application;

[0038] Fig.12 This is a schematic diagram of the planar structure of the metal ring in one embodiment of the present application;

[0039] Fig.13 This is a schematic diagram of the cross-sectional structure of the handle in the workpiece in one embodiment of the present application;

[0040] Explanation of the accompanying drawings: 100, workpiece; 10, metal ring; 11, journal; 12, shaft body; 20, handle body; 21, spline hole; 21A, first part; 21B, second part; 21C, third part; 22, pedal hole; 30, upper mold; 31, runner; 40, lower mold; 41, stepped column; 42, tapered stepped column; 50, first rough blank; 60, second rough blank; 70, metal blank; 200, drill bit; 300, turning tool; 400, milling cutter. DETAILED DESCRIPTION

[0041] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0042] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0044] Please refer to Figure 1 - Fig.13 An embodiment of the present application provides a method for processing and forming a carbon fiber crank, the method comprising the steps of:

[0045] S10: rough-processing the metal blank 70 to form a first rough blank 50, and lathe-processing the first rough blank 50 to form a metal ring 10 with a stepped outer surface;

[0046] S20: close the upper mold 30 with the runner 31 and the lower mold 40 with the stepped column 41, and after the mold is closed, the stepped column 41 abuts against the upper mold 30, inject short chopped carbon fibers into the mold cavity, and form a second blank 60 at the first temperature, wherein a spline hole 21 with a stepped inner surface is formed at one end of the second blank 60;

[0047] S30: milling the second rough blank 60 to form the handle body 20, cleaning the surface of the handle body 20 and coating the surface;

[0048] S40 The metal ring 10 is embedded in the spline hole 21 and is resin-bonded with the handle body 20 at a second temperature to form a workpiece 100 .

[0049] Among them, in the previous bicycle crank forming process, the rough blank made by rough processing of the metal blank 70 is usually put into the mold together with the carbon fiber material (carbon fiber strip) to form a crank (workpiece 100) with a metal part (metal ring 10) and a carbon fiber part (handle body 20). At this time, the crank is still relatively rough, and it is still necessary to continue to process its metal part and carbon fiber part separately. However, due to the significant differences in the physical properties and processing technology requirements of the two materials, different processing equipment, processes and environmental conditions are required for the processing of the two materials. At present, for the production of each component of complex products on the market, most of them adopt the outsourcing production mode of specialized division of labor between different suppliers. Under this mode, not only can the quality of the product be guaranteed, but also the production cost can be saved. However, since the rough crank needs to be sent to the metal processing plant and the carbon fiber processing plant for rework after forming, the transfer of materials is too frequent, which increases the time cost and economic cost of transportation to a certain extent. The carbon fiber crank processing and forming method proposed in this application is to first finish the metal ring 10 and the carbon fiber handle body 20, and then connect the two by resin bonding (which also relies on the development of resin bonding technology). This method does not need to further process the metal ring 10 and the handle body 20 after bonding. Compared with the traditional method, the new processing and forming method finishes all the components in place, and finally only needs to assemble (resin bond) the processed components.

[0050] In step S10, the metal blank 70 is formed into a first rough blank 50 with a through hole by a drill bit 200, and the first blank 50 is rotated in a first direction F1 during lathe processing and the outer surface of the first blank 50 is polished by a lathe tool 300 to form a metal ring 10 with a smooth outer surface and a stepped shape. After lathe processing, the metal ring 10 can be precisely matched with the carbon fiber handle body 20. The stepped structure increases the contact area between the metal ring 10 after the metal ring 10 is embedded in the spline hole 21. Once the contact area increases, it means that the friction between the two increases, and when the metal ring 10 is subjected to the force of the external environment, the force will be distributed into smaller local stresses on a larger contact area, which makes the connection structure between the two more stable. In addition, the metal part and the carbon fiber handle body 20 are connected together by resin bonding. The larger contact area also means that the amount of resin between the two can be more, and the resin bonding area is also larger, which will greatly improve the bonding strength between the metal part and the carbon fiber material, and increase the reliability in some high-intensity use scenarios of bicycles.

[0051] In step S20, by injecting chopped carbon fiber into the mold cavity and curing and molding at the first temperature, it is ensured that the carbon fiber material can be evenly distributed to form a handle body 20 with high strength and light weight. Chopped carbon fiber can effectively fill the complex geometric structure of the mold (such as the stepped cylinder 41 and the tapered stepped cylinder 42) to reduce the gaps and defects in the mold and improve the structural stability of the molded product. The structural design of the stepped spline hole 21 can have a stronger torque resistance after connecting with other components (central shaft) with spline teeth, ensuring that the workpiece 100 can withstand a large torque force without being easy to loosen or wear. This is especially important for high-stress parts such as bicycle cranks. The design of multiple spline holes 21 also increases the surface area (wavy) between the bicycle component and the spline hole 21 to a certain extent, making the connection more stable. The first temperature is a key temperature range for softening the resin and obtaining good fluidity. At this temperature, the resin can fully infiltrate the chopped fibers, while ensuring that the mixture of fibers and resin is molded into the second rough blank 60 under the mold pressure, and providing a good foundation for subsequent further curing and processing. At this temperature, the composite material formed by the combination of chopped fibers and resin begins to solidify initially and is able to maintain its shape, completing the preforming of the carbon fiber composite material.

[0052] In step S30, after the second rough blank 60 is formed, the handle body 20 is formed by fine processing by the milling cutter 400 of the milling machine. The shape of the handle body 20 meets the design requirements, especially the surface flatness and finish are controlled. Cleaning the surface can remove impurities or excess materials generated in the handle body 20 during the forming process, laying a good foundation for subsequent coating treatment. The coating provides additional protection for the handle body 20 and the carbon fiber handle body 20 to avoid environmental influences such as moisture, oxidation, etc., and prolong the service life of the product. Curing the coating by heating can ensure that the coating and the substrate are more firmly bonded, making the surface more wear-resistant and having better corrosion resistance and aesthetics.

[0053] In step S40, the metal ring 10 is coated with resin and embedded in the spline hole 21 along the second direction F2. At the second temperature, the resin (such as epoxy resin, phenolic resin, etc.) begins to soften. This allows the resin to flow between two materials (such as carbon fiber and metal) and fill the surface micropores to form good contact. In the chemical structure of thermosetting resins, there are functional groups that are not completely reacted. After heating to a specific temperature, these functional groups will undergo a chemical cross-linking reaction to generate a three-dimensional network structure. The cross-linking reaction causes the resin to gradually solidify from a softened state and become hard and irreversible. This process also allows the resin to form a strong bonding force at the connection point, firmly bonding the carbon fiber handle 20 and the metal ring 10 together.

[0054] More preferably, the spline hole 21 includes a first part 21A, a second part 21B connected to the first part 21A, and a third part 21C connected to the second part 21B. After the second rough blank 60 is formed in the mold cavity, the first part 21A abuts the upper mold 30, and the third part 21C abuts the lower mold 40. The inner surface of the second part 21B has a spline and is located between the first part 21A and the second part 21B. After the first rough blank 50 is milled and polished by a milling machine, a smooth inner surface is formed in the spline hole 21, and the inner diameter R1 of the third part 21C and the maximum inner diameter R2 of the second part 21B satisfy the relationship: R1>R2, and the connection between the third part 21C and the second part 21B is a stepped structure.

[0055] The second part 21B and the third part 21C of the spline hole 21 are filled and shaped by chopped fibers around the stepped cylinder 41 on the lower mold 40. Due to the need to consider demoulding, the first part 21A of the spline hole 21 is shaped by a cylindrical insert on the upper mold 30. The spline hole 21 and the metal ring 10 are used to install the middle shaft of the bicycle. The installation process is that the middle shaft passes through the spline hole 21 from the first part 21A, and then the metal ring 10 is screwed into the metal ring 10 from the third part 21C through a thread, and the metal ring 10 is fixed to the middle shaft, and resin is applied to the metal ring 10 to fix it to the third part 21C. The spline hole 21 is designed as a three-section type (first part 21A, second part 21B, third part 21C), the third part 21C has a larger inner diameter R1, and the second part 21B has a spline and a smaller inner diameter R2. Through such a design, the connection between the second part 21B and the third part 21C forms a stepped structure. The inner surface of the spline hole 21 after milling and grinding is smooth, making the embedding fit between the metal ring 10 and the spline hole 21 smoother. The milling process also makes the dimensions of each part of the spline hole 21 very fine, avoiding the tolerance problem of incorrect dimensions when the spline hole 21 and the metal ring 10 are connected.

[0056] More preferably, after the first rough blank 50 is lathe-machined to form the metal ring 10, the metal ring 10 is machined with a shaft body 12 and a journal 11 integrally formed on the shaft body 12 and having a smooth surface, the outer diameter R3 of the journal 11 and the inner diameter R1 of the third part 21C satisfy the relationship: R3 = R1, and the height H1 of the journal 11 and the depth H2 of the third part 21C satisfy the relationship: H1 = H2, and the connection between the journal 11 and the shaft body 12 is a stepped structure. When the metal ring 10 is embedded in the spline hole 21, the third part 21C fits tightly with the journal 11.

[0057] Among them, the lathe process processes the first rough blank 50 into a metal ring 10 with a smooth surface and finer size, so that the metal ring 10 can be embedded in the third part 21C with the same smooth surface and the same size, and the same size allows the inner surface of the journal 11 and the third part 21C to fit seamlessly, avoiding the appearance of a gap in the connection part. If there is no third part 21C with a stepped structure to embed the metal ring 10 and the two are directly connected by resin bonding, the surface area of ​​S will be lost, and S satisfies the relationship: S = π × R1 × H2. And if the two parts cannot be partially embedded, the metal ring 10 will also lose the support force given to the side of the journal 11 by the third part 21C, making the connection between the two more fragile.

[0058] More preferably, the metal blank 70 is sequentially rough-machined and lathe-machined to form the metal ring 10, and the chopped carbon fiber is sequentially molded and milled to form the handle body 20. The processing of the metal ring 10 and the processing of the handle body 20 are performed independently, and after the metal ring 10 and the handle body 20 are formed separately, the metal ring 10 and the handle body 20 are bonded to form the workpiece 100 in one step.

[0059] Among them, the handle body 20 and the metal ring 10 after fine processing have undergone the final processing steps of the milling machine and the lathe respectively, and the surfaces of the two have reached the surface smoothness and dimensional accuracy of the finished product level. Therefore, not only can the two achieve close fitting and precise docking, but also it is not necessary to further process the details of the workpiece 100 after bonding. The traditional molding processing method usually first forms a rough crank blank by curing the rough-machined metal parts and carbon fibers in the mold through resin, and then sends them to the factory for processing the metal part and the factory for processing the carbon fiber part for final fine processing. Such frequent transfer of materials greatly increases the transportation cost. In addition, during the processing of the crank blank after resin curing, there will be stress or heat caused by the milling process on the resin bonding surface, resulting in the destruction of the bonding effect of the resin after processing. The molding processing method of the present application can be used directly as a finished product after bonding, without further processing, which not only saves the cost of outsourcing processing, but also ensures the effectiveness of resin bonding.

[0060] Preferably, the lower mold 40 further has a tapered stepped column 42, which abuts against the upper mold 30 after the mold is closed, and the other end of the second blank 60 is formed with a pedal hole 22 with a tapered stepped inner surface and splines.

[0061] Among them, similar to the design of the stepped column 41, the design of the tapered stepped column 42 (the steps are not vertical but oblique) can also effectively disperse stress when subjected to force, especially when the crank is subjected to pedaling, the tapered steps provide better force distribution, avoid concentrated stress, and thus improve overall durability. The tapered stepped column 42 on the mold ensures that the geometry of the pedal hole 22 can be accurately formed when the mold is closed, ensuring the accurate size and position matching of the tapered stepped pedal hole 22 and the spline hole 21, so that the pedal can be tightly connected to the crank. The tapered stepped structure also provides a larger surface area for the pedal hole 22 to be installed with other bicycle accessories (pedal), ensuring the stability of the connection after installation. The tapered step design can also make the assembly of the pedal hole 22 and the pedal smoother, and the inner surface of the step provides multi-layer positioning for the pedal, which helps to achieve higher precision and firmness during the assembly process.

[0062] More preferably, during milling processing, the second rough blank 60 is fixed on the milling machine, and the milling cutter 400 grinds the pedal hole 22 and the spline hole 21 of the second rough blank 60; during lathe processing, the first rough blank 50 is fixed on the lathe, the first rough blank 50 is rotated, and the turning tool 300 grinds to form the shaft neck 11 and the shaft body 12, and the first rough blank 50 is finely processed into the metal ring 10.

[0063] Among them, lathe processing is suitable for precision machining of rotating workpieces 100, so it is very efficient to process circular structures such as the journal 11 and the shaft body 12 of the metal ring 10. Milling machine processing is suitable for processing workpieces 100 with complex geometric shapes, such as the processing of the pedal hole 22 and the spline hole 21 (grinding of the spline). Arrange different parts to be processed on the most suitable machine to ensure that the processing process is more accurate and efficient. When the lathe processes the first blank, by rotating and fixing the turning tool 300, accurate cylindrical structures such as the journal 11 and the shaft body 12 can be formed. This processing method can achieve higher concentricity and surface accuracy. When the milling machine grinds the spline hole 21 and the pedal hole 22 of the handle body 20, it can accurately remove material to ensure that the geometry and size of these holes meet the design requirements, especially the accuracy of the spline directly affects the stability of the combination of the metal ring 10 and the handle body 20. Separately process parts with different process requirements to avoid processing complex geometric shapes at the same time in the same process, which helps to reduce deformation and error accumulation of the workpiece 100. After the metal ring 10 is finely machined on a lathe, its journal 11 and shaft body 12 can fit tightly with the spline hole 21 machined by a milling machine. This step-by-step processing method ensures that parts of different materials can be seamlessly combined and that the structural dimensions of each part are consistent, ultimately improving the assembly accuracy and connection strength of the entire workpiece 100.

[0064] More preferably, the first temperature and the second temperature are respectively recorded as T1 and T2, and satisfy the relationship:

[0065] 120℃≤T1≤180℃,

[0066] 150℃≤T2≤220℃.

[0067] Among them, in the first temperature range, the range of 120°C to 180°C is to ensure that the resin can flow and fully wrap the fiber without premature curing reaction. In the second temperature range, 150°C is the lower limit of thermosetting resin curing. If the temperature is too low, the cross-linking reaction may not be activated, resulting in incomplete bonding. 220°C is the safe upper limit of this type of resin, which can ensure sufficient curing time and complete cross-linking, but exceeding this temperature may cause the resin to decompose or over-cure, affecting the material properties. The reason for the different values ​​in the two intervals is that the two process flows have different focuses. In the first temperature molding process, the main focus is on the fluidity of the resin to ensure that the carbon fiber material can be molded, so the temperature does not need to be too high. In the second temperature bonding process, the resin needs to be completely cured and form a solid structure to bond the metal and carbon fiber, so a higher temperature is required to ensure a thorough cross-linking reaction.

[0068] More preferably, the continuous carbon fiber material is cut into a plurality of short-cut carbon fibers, and the short-cut carbon fibers are combined with resin and then injected into the mold cavity through the runner 31 .

[0069] Among them, the continuous carbon fiber material is difficult to be injected into the mold cavity through the runner 31 and fill the mold cavity evenly due to its long length and rigidity. The chopped fibers can be mixed with the resin and injected into the mold cavity more evenly through the runner 31 to ensure that the fibers and resin are evenly distributed in the mold, especially in some molds with steps, spline holes 21 or other complex structures. Short fibers can better fill the detailed areas of the mold cavity, thereby forming a dense composite material structure, ensuring the accuracy and consistency of the shape of the final product, and avoiding the phenomenon of gaps or fibers concentrated in a certain part. The chopped fibers also effectively increase the contact area with the resin, allowing the resin to better penetrate around the carbon fibers.

[0070] More preferably, after the second blank 60 is formed at the first temperature, the upper mold 30 is opened toward the side away from the lower mold 40 , and the second blank 60 is taken out from the lower mold 40 .

[0071] Among them, since the lower mold 40 has an embedded part of a stepped column 41 and a tapered stepped column 42, the demolding of the second rough blank 60 needs to consider the extension direction of the step. The upper mold 30 is opened toward the side away from the lower mold 40 to avoid being stuck by the second rough blank 60 during the demolding process, prevent the second rough blank 60 from being deformed or damaged during demolding, and ensure the integrity of the second rough blank 60. If the mold is opened from the bottom, it may cause the residue of resin material and carbon fiber, especially at the contact surface between the molded part and the mold, where excessive material adhesion is likely to occur. Opening the upper mold 30 can reduce this situation because it reduces the contact area between the molded part and the mold surface, thereby reducing resin residue and surface defects.

[0072] More preferably, during the process of cleaning the surface of the handle body 20, the surface of the handle body 20 is polished, and after polishing, a coating is applied to the surface of the handle body 20, and heated to a third temperature T3 to harden the coating, and the relationship is satisfied: 60°C≤T3≤120°C.

[0073] Among them, grinding the surface of the handle body 20 before applying the coating can effectively remove the oxide layer, impurities or uneven parts on the surface, thereby providing better adhesion conditions for subsequent coatings, because the polished surface will form a tiny concave-convex structure. This rough surface can make the coating adhere more tightly to the carbon fiber handle body 20, reducing the risk of coating shedding or blistering. The coating will undergo a cross-linking reaction during the heating process, that is, a more stable chemical bond is formed between the molecular chains, causing the coating to change from a liquid or semi-solid state to a hard solid structure to protect the handle body 20. Most of the coatings used on bicycle cranks are epoxy resin coatings, which are suitable for low-temperature curing, and the curing temperature is generally between 60°C and 120°C.

[0074] According to the steps S10-S40, this specific embodiment provides a specific example to simulate the material transfer during the process of forming the workpiece 100:

[0075] Example scenario:

[0076] The carbon fiber crank workpiece 100 is produced by using the new crank processing technology and the traditional crank processing technology respectively. There are three factories in the example, where Factory A is used for the production and processing of carbon fiber material parts, Factory B is used for the production and processing of metal material parts, and Factory C is used for mold molding and bonding assembly.

[0077] Example process:

[0078] Old technology:

[0079] In the B factory, the metal blank 70 is processed into a first rough blank 50;

[0080] In the C factory, the first rough blank 50 and the carbon fiber are formed together in a mold to form a rough crank;

[0081] The cranks are sent to Factory A and Factory B for finishing of the carbon fiber and metal parts respectively;

[0082] After processing, it finally returns to Factory C.

[0083] The order in which the old process is transferred among the factories is: B, C, A, B, C.

[0084] New process:

[0085] In the B factory, the metal blank 70 is roughly processed into a first rough blank 50, and the first rough blank 50 is finely processed into a metal ring 10;

[0086] In the C factory, the chopped carbon fibers are formed in a mold to form a rough second blank 60;

[0087] The second rough blank 60 is sent to the A factory to process the carbon fiber part to form the handle body 20;

[0088] In the C factory, the metal ring 10 and the handle body 20 are bonded together and the processing is completed.

[0089] The order in which the new process is transferred to each factory is: B, C, A, C.

[0090] Since the metal ring 10 is processed in one step in the new process, compared with the old process, the new process lacks the step of production in Factory B.

[0091] Hereby, the metal ring 10 and the handle body 20 are formed by sequentially processing and then finally bonded to form the workpiece 100, which replaces the method of first connecting the first rough blank 50 and the second rough blank 60 into one body and then processing, thereby avoiding the frequent transfer of materials during the processing. The metal ring 10 and the handle body 20 are bonded with resin at the second temperature, so that the metal ring 10 and the handle body 20 can be effectively connected. The design of the stepped outer surface of the metal ring 10 and the stepped inner surface of the spline hole 21 increases the contact surface area of ​​the metal ring 10 after being embedded in the spline hole 21, thereby improving the stability of the connection.

[0092] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A carbon fiber crank processing and molding method, characterized in that: The method comprises the steps of: Rough machining a metal blank to form a first rough blank, and lathe machining the first rough blank to form a metal ring having a stepped outer surface; An upper mold with a runner and a lower mold with a stepped column are closed, and the stepped column abuts against the upper mold after the mold is closed, short chopped carbon fibers are injected into the mold cavity, and a second rough blank is formed at a first temperature, wherein a spline hole with a stepped inner surface is formed at one end of the second rough blank; Milling the second rough blank to form a handle body, cleaning the surface of the handle body and applying a coating on the surface; The metal ring is embedded in the spline hole and is resin-bonded with the handle body at a second temperature to form a workpiece.

2. A carbon fiber crank processing and molding method according to claim 1, characterized in that: The spline hole comprises a first part, a second part connected to the first part, and a third part connected to the second part. After the second rough blank is formed in the mold cavity, the first part abuts against the upper mold, and the third part abuts against the lower mold. The inner surface of the second part has a spline and is located between the first part and the second part. Among them, after the first rough milling machine processes and grinds the spline hole, a smooth inner surface is formed in the spline hole, and the inner diameter R1 of the third part and the maximum inner diameter R2 of the second part satisfy the relationship: R1>R2, and the connection between the third part and the second part is a stepped structure.

3. A carbon fiber crank processing and molding method according to claim 2, characterized in that: After the metal ring is formed by lathe processing of the first rough blank, a shaft body and a journal integrally formed on the shaft body and having a smooth surface are formed on the metal ring, an outer diameter R3 of the journal and an inner diameter R1 of the third part satisfy the relationship: R3=R1, and a height H1 of the journal and a depth H2 of the third part satisfy the relationship: H1=H2, and a connection between the journal and the shaft body is a stepped structure; When the metal ring is inserted into the spline hole, the third portion fits tightly against the shaft neck.

4. The carbon fiber crank processing and molding method according to claim 1, characterized in that: The metal blank is sequentially rough-machined and lathe-machined to form the metal ring, and the chopped carbon fiber is sequentially molded and milled to form the handle body. The processing of the metal ring and the processing of the handle body are performed independently, and after the metal ring and the handle body are formed separately, the metal ring and the handle body are bonded to form the workpiece in one step.

5. The carbon fiber crank processing and molding method according to claim 1, characterized in that: The lower mold also has a tapered stepped column, which abuts against the upper mold after the mold is closed. The other end of the second rough blank is formed with a pedal hole with a tapered stepped inner surface and splines.

6. The carbon fiber crank processing and molding method according to claim 3, characterized in that: During milling processing, the second rough blank is fixed on the milling machine, and the milling cutter grinds the pedal hole and spline hole of the second rough blank. During lathe processing, the first rough blank is fixed on the lathe, the first rough blank is rotated, and the turning cutter grinds to form the shaft neck and the shaft body, and the first rough blank is finely processed into the metal ring.

7. The carbon fiber crank processing and molding method according to claim 1, characterized in that: The first temperature and the second temperature are respectively denoted as T1 and T2, and satisfy the relationship: 120℃≤T1≤180℃， 150℃≤T2≤220℃。 8. The carbon fiber crank processing and molding method according to claim 1, characterized in that: The continuous carbon fiber material is cut into a plurality of short-cut carbon fibers, and the short-cut carbon fibers are combined with resin and then injected into the mold cavity through the runner.

9. The carbon fiber crank processing and molding method according to claim 1, characterized in that: After the second blank is formed at the first temperature, the upper mold is opened toward a side away from the lower mold, and the second blank is taken out from the lower mold.

10. The carbon fiber crank processing and molding method according to claim 1, characterized in that: During the process of cleaning the surface of the handle body, the surface of the handle body is polished, and after polishing, a coating is applied to the surface of the handle body, and the coating is hardened by heating to a third temperature T3, and the relationship is satisfied: 60°C≤T3≤120°C.

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