Tilting wheel spoke center hole process and male die

Abstract

The invention relates to a tilting wheel spoke center hole process which comprises a forming procedure: in the spoke forming process, a boss with the height of h is stretched at the preset center hole position of a spoke, so that a spoke body with the boss is obtained; the periphery of the spoke body is subjected to trimming treatment, a center hole d0 is pre-punched in the boss, the boss and the pre-punched center hole d0 are coaxial, and the punching direction is opposite to the subsequent flanging direction; a flanging process: flanging the boss; the method has the beneficial effects that the boss is stretched at the position of the preset center hole in the forming process, and the center hole d0 is pre-punched in the boss in the trimming process, so that the hole flanging coefficient is improved, and the stability and the reliability of the spoke center hole are improved in the subsequent flanging process.

Description

Technical Field

[0001] The invention relates to the technical field of manufacturing passenger cars, in particular to a process for turning a spoke center hole of a steel wheel and a punch. Background Art

[0002] Based on the development trend of automobile energy conservation and emission reduction, lightweighting is an effective means of energy conservation and emission reduction. In the automobile industry, there is a saying that one kilogram under the sprung weight is equal to ten kilograms on the sprung weight. The effect of reducing the weight of the unsprung mass (wheels, tires, brakes, etc.) is far greater than that of reducing the weight of the sprung mass. When the sprung mass remains unchanged, the reduction of the unsprung mass can effectively improve the acceleration, stability and handling of the car. Therefore, wheel weight reduction is a key component optimized by major OEMs. The advancement of lightweight steel wheels has promoted the continuous improvement of the strength grade of high-strength wheel-specific steel. However, the higher the grade of high-strength steel, the lower the formability, which increases the difficulty of the steel wheel manufacturing process. The wheel is a load-bearing rotating part between the tire and the axle. It carries the vehicle's vertical load, lateral load, driving (braking) torque, and various forces during driving. Its safety is self-evident. Limited by its formability, the appearance of steel wheels is not as beautiful as that of aluminum alloy or magnesium alloy wheels. In order to improve the aesthetics, a bearing cover is installed in the center. In order to ensure that the bearing cover is not easy to fall off, the center hole height is generally relatively high in design and manufacturing control. Originally, the flanging coefficient of the center hole of the spoke was relatively low, but increasing the center hole height further reduced the flanging coefficient. Therefore, it is necessary to optimize and improve the stability and reliability of the wheel manufacturing process to reduce the scrap rate and outflow risk.

[0003] The spoke center hole flanging belongs to the elongation type flanging. The deformation zone of the blank is in a bidirectional tensile stress state, and the tensile stress acting in the tangential direction is the maximum principal stress. Elongation deformation occurs in this direction, and its forming limit is mainly limited by the cracking of the edge of the blank in the deformation zone. In the mass production process, the center hole is prone to cross-sectional microcracks and cracking quality problems.

[0004] Therefore, how to prepare the spoke center hole to solve the above defects is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The invention aims at the technical problems existing in the prior art and provides a process and a punch for turning the center hole of a steel wheel spoke.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: The first aspect protects a process for turning the center hole of a steel wheel spoke, including: Forming process: During the spoke forming process, a boss with a height of h is stretched at a preset center hole position of the spoke to obtain a spoke body with a boss; Trimming process: trimming the outer periphery of the spoke body, and pre-punching a center hole d0 at the boss, the boss is coaxial with the pre-punched center hole d0, and the punching direction is opposite to the flanging direction; Flanging process: flanging the boss.

[0007] As a further technical solution, the height h of the boss is 5-6 mm.

[0008] As a further technical solution, in the forming process, the outer diameter D2 of the punch used for the stretching boss is smaller than the outer diameter D3 of the punch used for the flanging process, and D2 is 0.5-1 mm smaller than D3.

[0009] As a further technical solution, in the forming process, the radius R1 of the die used for the stretching boss is consistent with the R value of the center hole.

[0010] As a further technical solution, in the flanging process, the punch used includes a guide section, an inner concave arc section, and an outer concave arc section connected in sequence from bottom to top, and the contact point between the inner concave arc section and the outer concave arc section is the circumscribed point of the circle where the inner concave arc section is located and the circle where the outer concave arc section is located.

[0011] As a further technical solution, the punch structure is designed so that in the flanging process, the guide section of the punch has a guiding function, so that after guiding and as the flanging process proceeds, the inner concave arc section extrude the cross-section of the pre-punched hole d0, and then the outer concave arc section is used to transition to the working diameter D3, and the size of D3 is the inner diameter of the center hole of the spoke.

[0012] As a further technical solution, the male and female dies used in the trimming process are both treated with TD or VPD coating.

[0013] As a further technical solution, in the trimming process, the center hole D3 is turned after the center hole d0 is pre-punched, and 13-15% of the material thickness is used as the single-side clearance for punching d0.

[0014] The second aspect of the present invention protects a punch for the center hole of a steel wheel spoke, comprising a guide section, an inner concave arc section, and an outer concave arc section connected in sequence from bottom to top, wherein the contact point between the inner concave arc section and the outer concave arc section is the circumscribed point of the circle where the inner concave arc section is located and the circle where the outer concave arc section is located, so that the inner wall of the center hole is expanded during the flanging process.

[0015] The beneficial effects of the present invention are: 1. By stretching a boss at the preset center hole position in the forming process, pre-punching the center hole d0 in the boss in the trimming process to increase the hole-turning coefficient, so as to improve the stability and reliability of the spoke center hole in the subsequent stamping process; In addition, a special punch structure is used during flanging to bulge the pre-punched center hole d0 at the stretched boss, and the punching direction is opposite to the flanging direction, so that the quality defect of cracking in the prepared spoke center hole is eliminated, the scrap rate is reduced, and the efficiency and cost are effectively improved; 2. In the present application, the inner wall of the spoke center hole is shaped by thinning the flange with negative gap, thereby improving the quality defect of residual bending deformation at the flange edge when flanging the circular hole in the prior art; 3. The process of the present invention solves the problem of cracking of the center hole of the spoke, thereby reducing the production failure rate and quality risk, making the product quality stable and reliable, and then preventing the outflow of such waste products, thereby improving the safety of the wheel; 4. The structural design of the punch in the present invention improves the brightness of the cross section during the flanging process, and avoids the defect of residual bending deformation at the flanging edge of the circular hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a process schematic diagram of a process for turning the center hole of a steel wheel spoke according to the present invention; Figure 2 It is a schematic diagram of the structure of the male mold used in the flanging process of the present invention; Figure 3 It is a schematic diagram of the structure of the boss stretched in the forming process; Figure 4 It is a partially enlarged structural schematic diagram of the working process of the punch and die in the forming process; Figure 5 It is a schematic diagram of the use of the punch and die in the trimming process, which is used to illustrate the stamping direction and the structure of the punch and die used; Figure 6 This is a flanging process diagram in Example 1, used to show the punch and the flanging direction.

[0017] In the accompanying drawings, the components represented by the reference numerals are listed as follows: Boss 1, punch 2, guide section 21, inner concave arc section 22, outer concave arc section 23. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0019] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0020] In the description of the present application, the term "for example" is used to mean "used as an example, illustration or description". Any embodiment described as "for example" in the present application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any technician in the field to implement and use the present invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid unnecessary details to obscure the description of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the present application.

[0021] Example 1 During the wheel manufacturing process, a bearing cap is usually installed at the center of the wheel. To ensure that the bearing cap is not easy to fall off, the accuracy of the center hole of the spoke is also an important indicator affecting its effect. The main factors affecting the maximum flanging coefficient of the round hole are (1) the state of the hole edge; (2) the shape of the punch; (3) the plate thickness; and (4) the mechanical properties of the material. Material properties not only include deep drawing strength, but are also related to factors such as material surface quality, stress, and hardening. However, material properties mainly depend on the quality control of the steel plant. After the product design is completed, the material properties and thickness are selected, which cannot be changed in the manufacturing process.

[0022] If the punch shape is flat-bottomed, spherical-bottomed, or conical-bottomed, the hole expansion coefficient of the material will increase in sequence, which is mainly due to the increase in the number of neckings at the hole edge. There is a certain improvement in the optimization of the taper angle, and the general optimization range is between 10︒ and 15︒. After the punch shape is designed, the surface is hardened. When center cracking occurs in production during application, it is mainly controlled by controlling the quality of the punching process before the center hole; if the punching section is good and the microcracks or cracks in the center hole cannot be improved, the center hole can be polished and burrs can be removed to improve the deformation capacity of the material; high-frequency heating can also be used to heat the blank at the center hole to eliminate hardening, improve the toughness of the material, and improve the flanging performance. However, these measures affect production efficiency and increase manufacturing costs; and this embodiment introduces a process for flanging the center hole of a steel wheel spoke, that is, optimizing the process to solve the above-mentioned manufacturing problems. The process specifically includes the following steps (see Figure 1 ): Step S1, forming process: during the spoke forming process, a boss 1 with a height of h is stretched at the preset center hole position of the spoke to obtain a spoke body having the boss 1; (see Figure 3 ) Step S2, trimming process: trimming the outer periphery of the spoke body and pre-punching a center hole d0 at the boss 1 (see Figure 4 ), the boss 1 is coaxial with the pre-punched center hole d0, and the punching direction is opposite to the flanging direction (such as the blanking direction in the trimming process: see Figure 5 ); Step S3, flanging process: flanging the boss 1 (see Figure 6 ).

[0023] It can be seen that the spoke center hole is the center hole D3 after flanging on the boss, and the size of D3 is the inner diameter of the spoke center hole, and d1 is the outer diameter of the spoke center hole. It should be noted that in this embodiment, there are at least blanking, drawing, and reverse drawing processes before the forming process, and there are at least bolt hole punching and heat dissipation hole punching processes after the flanging process, and the specific implementation method can be implemented in a conventional manner; In this embodiment, the flanging coefficient is increased during process design to reduce the occurrence of center hole cracking from the perspective of process performance. In the forming process, a boss 1 is first stretched at a preset center hole position, and in the trimming process, a center hole d0 is pre-punched at the boss 1 to solve the defect that the center hole of the prepared spoke is prone to cracking. In order to further improve the flanging deformation ability of the punched edge, in the punching process of this embodiment, the punching direction is opposite to the flanging direction.

[0024] For example, if the flanging die adopts an inverted die structure (i.e., the flanging concave die and die core are in the lower die, and the punch is in the upper die), it is convenient for manual feeding, and the flanging material can also be fed with an automated material receiving mechanism. The inverted die structure flips the trimming process parts when flanging and leaving them for the next flanging process, so that the burr belt faces upward and is flanging toward the center hole punch. When the production line adopts an automatic robot arm picker, the flanging die is designed as a normal flanging die structure to facilitate the displacement of process parts.

[0025] In the specific implementation process, if the height h of the boss 1 stretched in the forming process is too large, the inner diameter of the center hole d0 punched subsequently becomes larger, the wall of the die is thin during trimming, the strength is weakened and the edge is easily broken. At the same time, the bearing cover is installed in the middle or slightly above the center hole, and this installation position also needs to be avoided; if it is too small, the hole turning coefficient is still small during hole turning, and the cracking of the center hole cannot be eliminated. Therefore, the height h of the boss 1 is 5-6mm.

[0026] In the specific implementation process, since this process adopts a forming process, a boss 1 with a height of h is first stretched at the position where the center hole of the spoke is set, so when the center hole of the spoke is flanging at a later stage, the hole wall of the center hole of the spoke is not easy to be straightened; and in the forming process, the outer diameter D2 of the punch used for stretching the boss 1 is smaller than the outer diameter D3 of the punch for flanging in the flanging process (see Figure 4 ), and D2 is 0.5-1mm smaller than D3, so that the punch used for flanging the hole during flanging can expand the inner wall of the boss 1, improve the bending mark, and avoid the risk of the bearing cover falling off during installation.

[0027] In addition, in the forming process, the die radius R1 (see Figure 4 ) is consistent with the R value of the center hole. No two fillet marks will appear on the center hole of the spoke of the prepared spoke product, and the product has a good appearance.

[0028] In order to improve the state of the hole edge, the round hole flanging is most sensitive to the state of the hole edge. Due to the hardened layer produced by the punching edge, the uneven surface and even the existence of tiny cracks, its elongation deformation ability is greatly reduced relative to the parent material. Improving the blank punching processing conditions can effectively improve its subsequent flanging deformation ability. Therefore, the punching gap affects the flanging cracking situation. In this embodiment, in the trimming process, the center hole D3 is punched after the pre-punching center hole d0, and the punching d0 hole uses 13-15% of the material thickness as the single-side gap. The gap can be slightly adjusted according to the material thickness and material grade. When the punching die edge becomes blunt, the deformation ability of the obtained pre-punched hole in the flanging is reduced. Therefore, in this embodiment, the punch and die used in the trimming process are treated with TD or VPD coating to improve the wear resistance and roughness of the punch and die, improve the quality of the punching section, and can also effectively improve the flanging center cracking situation. It can be explained that this method improves the section of the wheel flanging center hole.

[0029] In the specific implementation process of this embodiment, during the flanging process, the punch 2 used includes a guide section 21, an inner concave arc section 22, and an outer concave arc section 23, which are sequentially connected from bottom to top. The contact point between the inner concave arc section 22 and the outer concave arc section 23 is the circumscribed point between the circle where the inner concave arc section 22 and the circle where the outer concave arc section 23 are located. The structural design of the punch 2 is such that during the flanging process, the guide section 21 of the punch 2 has a guiding function, so that after guiding and as the flanging process proceeds, the inner concave arc section 22 extrude the cross section of the pre-punched hole d0, thereby improving the brightness of the cross section during the flanging process, and then the outer concave arc section 23 is used to transition to the working diameter D3, the size of D3 being the inner diameter of the center hole of the spoke. The structure and process are simple, and to a certain extent, it also avoids the reverse belting of the inner plane of the flanging center hole when the material is withdrawn. (See Figure 2 ) At the end of the flanging deformation, insufficient radial tensile stress can easily cause quality defects such as residual bending deformation on the edge of the flanging. Therefore, in this embodiment, the gap between the punch and die for the center hole is negative, and the negative value is about 5%. Combined with the boss 1 stretched in the forming process of this embodiment, the bending mark is further shaped during flanging, that is, the negative gap thins the flanging and effectively shapes the wall of the flanging center hole.

[0030] The process of this embodiment eliminates microcracks and cracking defects in the center hole of the flanging through the forming process, the trimming process, and the flanging process combined with the punch structure used in the flanging process, improves the stability and reliability of the material in the stamping process, and reduces the scrap rate and quality risk; By thinning the flange with negative clearance and shaping the inner wall of the spoke center hole, the quality defect of residual bending deformation on the flange edge during the process is improved.

[0031] Example 2 The present embodiment provides a punch for the center hole of a steel wheel spoke, characterized in that it includes a guide section 21, an inner concave arc section 22, and an outer concave arc section 23 connected in sequence from bottom to top, and the contact point between the inner concave arc section 22 and the outer concave arc section 23 is the circumscribed point of the circle where the inner concave arc section 22 and the circle where the outer concave arc section 23 are located, so that during the flanging process, the punch for flanging the hole compresses the shearing zone from the burr side on the cross section of the center hole, and expands the inner wall of the center hole at the same time.

[0032] The structure is not limited to use in the flanging process of the center hole of the spoke, and the structure punch can be used for any center hole that needs to achieve a similar effect.

[0033] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0034] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0035] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A process for turning the center hole of a steel wheel spoke, characterized in that: include Forming process: During the spoke forming process, a boss with a height of h is stretched at a preset center hole position of the spoke to obtain a spoke body with a boss; Trimming process: trimming the outer periphery of the spoke body, and pre-punching a center hole d0 at the boss, the boss is coaxial with the pre-punched center hole d0, and the punching direction is opposite to the subsequent flanging direction; Flanging process: flanging the boss.

2. The process for turning the center hole of a steel wheel spoke according to claim 1 is characterized in that: The height h of the boss is 5-6 mm.

3. The process for turning the center hole of a steel wheel spoke according to claim 1 is characterized in that: In the forming process, the outer diameter D2 of the punch used for the stretching boss is smaller than the outer diameter D3 of the punch used for the flanging process, and D2 is 0.5-1 mm smaller than D3.

4. The process for turning the center hole of a steel wheel spoke according to claim 1 is characterized in that: In the forming process, the radius R1 of the die used for the stretching boss is consistent with the R value of the center hole.

5. The process for turning the center hole of a steel wheel spoke according to claim 1 is characterized in that: In the flanging process, the punch used includes a guide section, an inner concave arc section, and an outer concave arc section connected in sequence from bottom to top, and the contact point between the inner concave arc section and the outer concave arc section is the circumscribed point of the circle where the inner concave arc section is located and the circle where the outer concave arc section is located.

6. The process for turning the center hole of a steel wheel spoke according to claim 5 is characterized in that: The punch structure is designed so that in the flanging process, the guide section of the punch has a guiding function, so that after guiding and as the flanging process proceeds, the inner concave arc section extrude the cross-section of the pre-punched hole d0, and then the outer concave arc section is used to transition to the working diameter D3, and the size of D3 is the inner diameter of the center hole of the spoke.

7. The process for turning the center hole of a steel wheel spoke according to claim 1 is characterized in that: The male and female dies used in the trimming process are both treated with TD or VPD coating.

8. The process for turning the center hole of a steel wheel spoke according to claim 1 is characterized in that: In the trimming process, the center hole D3 is turned after the center hole d0 is pre-punched, and 13-15% of the material thickness is used as the single-side clearance for punching the d0 hole.

9. A punch for the center hole of a wheel spoke, characterized in that: It includes a guide section, an inner concave arc section, and an outer concave arc section connected in sequence from bottom to top, wherein the contact point between the inner concave arc section and the outer concave arc section is the circumscribed point of the circle where the inner concave arc section is located and the circle where the outer concave arc section is located, so that the inner wall of the center hole is expanded during the flanging process.

Images