Shifting fork grading type double-sided flattening and fine blanking forming method

Abstract

The invention relates to the technical field of shifting fork manufacturing, in particular to a shifting fork progressive type double-sided flattening fine blanking forming method which comprises the following steps that a multi-station progressive die executes a first blanking action, and a guide hole and a flattening pre-cutting notch are formed in a metal material strip; executing a first-time flattening action to form a front-side flattening characteristic; the second-time flattening action is executed to form a back face flattening characteristic, and the working face of the upper flattening male die serves as a forming datum plane of the second-time flattening action; and the second blanking action is executed to form the shifting fork in a blanking mode. Therefore, on one hand, the shifting fork forming efficiency is greatly improved, the manufacturing cost is reduced, station migration does not need to be carried out on the metal material strip in the whole process, and in addition, the metal material strip always keeps good alignment precision relative to the multi-station progressive die after being subjected to the conversion step; and on the other hand, on the premise that the metal strip does not need to reserve the machining allowance, the shifting fork finished product has extremely high size precision, shape precision and position precision.

Description

Technical Field

[0001] The invention relates to the technical field of shift fork manufacturing, in particular to a progressive double-sided flattening and fine punching forming method for a shift fork. Background Art

[0002] The shift fork is an important component of the car's gearbox. It is connected to the speed shift handle and is located at the lower end of the handle. Its main function is to shift the intermediate speed wheel to change the input or output speed ratio, realize clutch shifting, and ensure that the car can change speed smoothly during driving.

[0003] like Figure 1 As shown in , 1mm deep flattening features (red area) are formed on both the front and back sides of the fork. As far as the current technical status is concerned, the following two forming processes are usually adopted: 1) First, using a metal strip as the base material, the fork parts are punched and formed by a composite fine blanking process, and then, a machining and milling method is used to form flattening features on the front and back sides; 2) First, using a metal strip as the base material, the fork parts are punched and formed by a continuous fine blanking process, and then, a flattening feature on one side is formed by a flattening punch, and then, a machining and milling method is used to form a flattening feature on the other side. From the above description, it can be seen that both forming processes use machining and milling methods to form at least part of the flattening features, thereby ensuring that the position accuracy and dimensional accuracy of the two opposing flattening features after forming meet the design requirements. However, the above two forming process routes are cumbersome and complicated, and the fork parts need to undergo multiple station transfers during the entire forming process, which is time-consuming and labor-intensive, and the manufacturing cost of the fork remains high. Furthermore, the fork has relatively small dimensions and a total thickness of no more than 10 mm. It is difficult to clamp it during the machining and milling stage, and after forming, the clamped surface of the fork will inevitably have indentations. Therefore, on the one hand, the metal strip needs to reserve machining trimming allowance, which will increase the thickness of the metal strip to a certain extent, resulting in an increase in the raw material procurement cost and a reduction in the utilization rate of the raw materials; on the other hand, after the flattening feature of the fork is formed, secondary milling or grinding operations will be required to trim the front and back surfaces. Therefore, it is urgent for technicians to solve the above problems. Summary of the invention

[0004] Therefore, in view of the above-mentioned existing problems and defects, the designers of the present invention collected relevant information, conducted multiple evaluations and considerations, and continued to experiment and modify after many years of R&D experience by technicians engaged in this industry, which ultimately led to the emergence of the progressive double-sided flattening fine punching forming method for the fork.

[0005] In order to solve the above technical problems, the present invention relates to a progressive double-sided flattening fine blanking forming method for a shift fork, in which the shift fork is formed by a metal strip through a multi-station progressive die, and in the forming process, each time the multi-station progressive die completes an action, the metal strip moves once at a fixed step. The progressive double-sided flattening fine blanking forming method for a shift fork comprises the following steps:

[0006] S1. After the metal strip is fed in, the multi-station progressive die performs the first punching action, and the first guide hole, the second guide hole and the flattened pre-cut notch are formed on the metal strip at the same time. The flattened pre-cut notch is formed in the center of the metal strip, and the first guide hole and the second guide hole are symmetrically arranged on both sides thereof;

[0007] S2, the metal strip moves to the next process step, and the upper flattening punch of the multi-station progressive die performs the first flattening action, forming a positive flattening feature on the metal strip adjacent to the flattening pre-cut notch area;

[0008] S3, the original working step of the metal strip remains unchanged, the lower flattening punch of the multi-position progressive die performs the second flattening action, and the working surface of the upper flattening punch is used as the forming reference surface of the second flattening action, forming a back flattening feature on the metal strip adjacent to the flattening pre-cut notch area;

[0009] S4. The metal strip continues to move to the next process step, and the multi-station progressive die performs the second blanking action, so that the shift fork can be blanked and formed as a whole.

[0010] As a further improvement of the technical solution disclosed in the present invention, in step S2, the first flattening action is decomposed into multiple first flattening sub-actions. As the upper flattening punch continues to advance, the depth value of the front flattening feature increases accordingly, and the impact intensity of the first flattening sub-action shows an exponential attenuation trend, and after the depth value of the front flattening feature reaches 2a, the upper flattening punch retreats away from the front flattening feature, and the retreat distance is a.

[0011] As a further improvement of the technical solution disclosed in the present invention, in step S3, the second flattening action is decomposed into multiple second flattening sub-actions. As the action process of the lower flattening punch continues to advance, the impact intensity of the second flattening sub-action presents an exponential decay trend, the depth value of the back flattening feature gradually increases, and the depth value of the front flattening feature gradually decreases due to the reverse impact force, until the depth values ​​of both are stable at a, at which time, the front flattening feature presents a critical contact state relative to the lower flattening punch.

[0012] As a further improvement of the technical solution disclosed in the present invention, the thickness of the metal strip is b, then a≤1 / 5b, and a<1.5mm.

[0013] As a further improvement of the technical solution disclosed in the present invention, the roughness of the front and back sides of the metal strip is controlled to be below 0.1 μm. Before the metal strip is formally fed into the multi-station progressive die, the front and back sides are lubricated.

[0014] As a further improvement of the technical solution disclosed in the present invention, in step S4, the multi-station progressive die is equipped with a fine blanking gear ring. In the second blanking process, before the blanking punch contacts the metal strip, the fine blanking gear ring is used to pre-press the metal strip against the die, so that the V-shaped teeth of the fine blanking gear ring can penetrate deeply into the metal strip.

[0015] In practical applications, the metal strip is fed into a multi-station progressive die, and sequentially undergoes a blanking process, a front flattening process, a back flattening process, and a blanking process, so that a finished fork with a flattened characteristic surface can be formed in batches. The progressive double-sided flattening fine blanking forming method for a fork disclosed in the present invention can achieve at least the following beneficial technical effects, specifically:

[0016] 1) The forming efficiency of the shift fork is greatly improved, the manufacturing cost is reduced, and there is no need to transfer the metal strip to the workstation during the whole process. The front flattening, back flattening and blanking operations can be completed by relying on a single multi-station progressive die. In addition, with the synergistic effect of the first guide hole and the second guide hole, the metal strip always maintains good alignment accuracy relative to the multi-station progressive die after the conversion step, ensuring that the shift fork has good forming accuracy and dimensional consistency;

[0017] 2) There is no need to go through machining and milling processes, and the front and back surfaces of the finished fork and the flattened feature surfaces have good flatness and parallelism, which means that there is no need to reserve machining trimming allowance for the metal strip. In this way, on the one hand, the molding process route can be shortened, effectively reducing the types of molding equipment; on the other hand, the procurement cost of the metal strip can be reduced, ensuring its material utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a three-dimensional schematic diagram of the shift fork.

[0020] Figure 2 It is a three-dimensional schematic diagram (a section thereof) from one viewing angle of the metal strip disclosed in the present invention being fed into a progressive die of a workstation.

[0021] Figure 3 It is a three-dimensional schematic diagram (a section thereof) from another perspective of the metal strip disclosed in the present invention being fed into a progressive die of a workstation.

[0022] Figure 4 yes Figure 2 Front view of .

[0023] Figure 5 yes Figure 4 A partial enlarged view of I.

[0024] Figure 6 yes Figure 4 A partial enlarged view of II.

[0025] Figure 7 This is a layout diagram of the metal strip disclosed in the present invention.

[0026] Figure 8 The invention discloses a single-line layout process diagram of a progressive double-sided flattening and fine punching forming method for a shift fork.

[0027] Fig. 9 The invention discloses a double-row layout process diagram of a progressive double-sided flattening and fine punching forming method for a shift fork.

[0028] 1-first guide hole; 2-second guide hole; 3-flattened pre-cut notch; 4-front flattened feature; 5-back flattened feature. DETAILED DESCRIPTION

[0029] In order to facilitate those skilled in the art to fully understand the technical solutions disclosed in the present invention, the present invention is further described in detail below in conjunction with specific embodiments.

[0030] In this embodiment, a metal strip is used as the base material, and the shift fork is formed by the metal strip through a multi-station progressive die. During the forming process, each time the multi-station progressive die completes an action, the metal strip moves once at a fixed step.

[0031] Figure 7 , Figure 8 , Fig. 9 The metal strip layout diagram, the single-line layout process diagram and the double-line layout process diagram of the progressive double-sided flattening and fine blanking forming method disclosed in the present invention are respectively shown. It can be seen that the progressive double-sided flattening and fine blanking forming method of the fork includes the following steps:

[0032] S1, after the metal strip is fed, the multi-station progressive die performs the first punching action, and the first guide hole 1, the second guide hole 2 and the flattened pre-cut notch 3 (such as Figure 2 , 3As shown in ). The flattened pre-cut notch 3 is formed in the center of the metal strip, and the first guide hole 1 and the second guide hole 2 are symmetrically arranged on both sides thereof;

[0033] S2, the metal strip moves to the next process step, and the upper flattening punch of the multi-station progressive die performs the first flattening action, forming a positive flattening feature 4 (such as Figure 2 , 4 , as shown in 5);

[0034] S3, the original working step of the metal strip remains unchanged, the lower flattening punch of the multi-position progressive die performs the second flattening action, and the working surface of the upper flattening punch is used as the forming reference surface of the second flattening action, forming a back flattening feature 5 (such as Figure 3 , 4 , as shown in 6);

[0035] S4. The metal strip continues to move to the next process step, and the multi-station progressive die performs the second blanking action, so that the shift fork can be blanked and formed as a whole.

[0036] In actual applications, the metal strip is fed into a multi-station progressive die, and sequentially undergoes a punching process, a front flattening process, a back flattening process, and a punching and blanking process, so that finished shift forks with flattened characteristic surfaces can be formed in batches.

[0037] According to actual test results, the progressive double-sided flattening fine punching forming method of the shift fork disclosed in the present invention has achieved at least the following two beneficial technical effects, specifically:

[0038] 1) The forming efficiency of the shift fork is greatly improved, the manufacturing cost is reduced, and there is no need to transfer the workstation of the metal strip throughout the whole process. The front flattening, back flattening and blanking operations can be completed by relying on a single multi-station progressive die. In addition, with the synergistic effect of the first guide hole 1 and the second guide hole 2, the multi-station progressive die can achieve accurate positioning of the metal strip. After the metal strip undergoes the conversion step, it always maintains good alignment accuracy relative to the multi-station progressive die, ensuring that the shift fork has good forming accuracy and dimensional consistency;

[0039] 2) There is no need to go through machining and milling processes. The front and back surfaces of the finished fork and the flattened feature surfaces have good flatness and parallelism, which means that there is no need to reserve machining trimming allowance for the metal strip. In this way, on the one hand, the molding process route can be shortened and the types of molding equipment can be effectively reduced; on the other hand, the procurement cost of the metal strip can be reduced, ensuring its material utilization rate.

[0040] In the large design framework of performing the flattening operation on the metal strip by means of a multi-station progressive die, in order to improve the dimensional accuracy and position accuracy of the front flattening feature 4 and the back flattening feature 5, as a further optimization of the above technical solution, as follows Figure 4 , 5 As shown in FIG. 6 , in step S2, as the upper flattening punch continues to move forward, the depth value of the front flattening feature 4 increases accordingly, and after the depth value of the front flattening feature 4 reaches 2a, the upper flattening punch retreats to move away from the front flattening feature 4, and the retreat distance is a. In step S3, as the lower flattening punch continues to move forward, the depth of the back flattening feature 5 gradually increases, while the depth value of the front flattening feature 4 gradually decreases due to the reverse impact force, until the depth values ​​of both are stable at a, at which time, the front flattening feature 4 is in a critical contact state relative to the lower flattening punch. In other words, before the second flattening action is formally performed, the upper flattening punch actively retreats upward until the distance value between it and the front flattening feature 4 is reduced to a, and as the subsequent second flattening action continues, the distance value between the upper flattening punch and the front flattening feature 4 gradually decreases until the two are critically contacted, and at this point, the back flattening feature 5 is formed.

[0041] Furthermore, generally speaking, the forming depth of the front flattening feature needs to be more than 1mm. In addition, during the second flattening action, the back flattening feature needs to undergo reverse recovery deformation. If the impact strength of the flattening action is not reasonably controlled, the forming surface of the metal strip is very likely to be torn or wrinkled. In view of this, as a further optimization of the above technical solution, the first flattening action is decomposed into multiple first flattening actions. The second flattening action is decomposed into multiple second flattening actions. And as the flattening process continues to advance, the impact strength of the first flattening action and the second flattening action both show an exponential attenuation trend.

[0042] Furthermore, whether it is the first flattening action or the second flattening action, it can be decomposed into multiple repeated flattening actions. As the flattening time continues, the striking intensity of the flattening actions gradually weakens and shows an exponential attenuation trend. In this way, on the one hand, at the end of the forming stage of the front flattening feature 4 and the back flattening feature 5, the striking intensity is weakened to a reasonable value, which is conducive to the precise control of the single flattening deformation amount, and is conducive to improving the dimensional accuracy and position accuracy of the front flattening feature 4 and the back flattening feature 5.

[0043] It should also be emphasized here that the exponential attenuation curve equation also needs to be adaptively adjusted according to the specific material of the metal strip.

[0044] In order to further improve the dimensional accuracy and positional accuracy of the front flattened feature 4 and the back flattened feature 5 after forming, and to avoid adverse consequences such as the tearing of the metal strip due to improper selection of process parameters, as a further optimization of the above technical solution, the forming depth of the front flattened feature 4 and the back flattened feature 5 needs to be controlled within a reasonable value range, specifically: Figure 4 , 5 As shown in 6, the thickness of the metal strip is defined as b, then a≤1 / 5b, and a<1.5mm.

[0045] It is known that during the execution of the punching and flattening actions, friction is bound to occur between the metal strip and the upper flattening punch, the lower flattening punch and the die, and this friction causes great wear on the multi-station progressive die, which is bound to affect its working accuracy and service life. In view of this, as a further optimization of the above technical solution, the roughness of the front and back sides of the metal strip is controlled below 0.1μm. Before the metal strip is formally fed into the multi-station progressive die, lubrication treatment is performed on its front and back sides. In this way, on the one hand, the friction coefficient between the metal strip and the multi-station progressive die can be effectively reduced, thereby helping to reduce the working wear of the multi-station progressive die, and incidentally reducing the wear of the punching cutting edge of the metal strip and its front flattening feature 4 and back flattening feature 5; on the other hand, during the implementation of the flattening operation, the lubricant can instantly form a protective film on the front and back sides of the metal strip, thereby effectively avoiding the generation of surface defects due to oxidation.

[0046] Finally, it should be noted that in step S4, the multi-station progressive die is equipped with a fine blanking gear ring. In the second blanking process, before the blanking punch contacts the metal strip, the metal strip is pre-pressed against the die with the help of the fine blanking gear ring, and the V-shaped teeth of the fine blanking gear ring can penetrate into the metal strip. In this way, in the process of executing the blanking action, the fine blanking gear ring can effectively prevent the metal material structure from tearing and lateral flow in the shearing zone. Moreover, because the V-shaped teeth penetrate into the metal strip, the metal strip in the shearing zone is in a three-dimensional compressive stress state, and the tensile stress in this area can be weakened or eliminated, which is conducive to improving the processing plasticity of the metal strip. The metal material is blanked into a shift fork in the form of pure shear, thereby not only preventing the metal strip from being torn during the blanking process and the bending of the finished shift fork from the source, but also ensuring that the cutting surface of the finished shift fork has good finish and flatness.

[0047] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest range of convergences with the principles and novel features disclosed herein.

Claims

1. A progressive double-sided flattening fine blanking forming method for a shift fork, wherein the shift fork is formed by a metal strip through a multi-station progressive die, and during the forming process, each time the multi-station progressive die completes an action, the metal strip moves once at a fixed step, characterized in that: The fork progressive double-sided flattening fine punching forming method comprises the following steps: S1, after the metal strip is fed, the multi-station progressive die performs the first punching action, and the first guide hole, the second guide hole and the flattened pre-cut notch are simultaneously formed on the metal strip; the flattened pre-cut notch is formed at the center of the metal strip, and the first guide hole and the second guide hole are symmetrically arranged on both sides thereof; S2, the metal strip moves to the next process step, and the upper flattening punch of the multi-station progressive die performs the first flattening action to form a front flattening feature on the metal strip adjacent to the flattening pre-cut notch area; S3, the original working step position of the metal strip remains unchanged, the lower flattening punch of the multi-position progressive die performs the second flattening action, and the working surface of the upper flattening punch is used as the forming reference surface of the second flattening action, forming a back flattening feature on the metal strip adjacent to the flattening pre-cut notch area; S4, the metal strip continues to move to the next process step, the multi-station progressive die performs a second blanking action, and the shift fork is blanked and formed as a whole.

2. The progressive double-sided flattening fine blanking forming method for a shift fork according to claim 1 is characterized in that: In step S2, the first flattening action is decomposed into multiple first flattening sub-actions; as the action process of the upper flattening punch continues to advance, the depth value of the front flattening feature increases accordingly, and the impact intensity of the first flattening sub-action shows an exponential attenuation trend, and after the depth value of the front flattening feature reaches 2a, the upper flattening punch retreats away from the front flattening feature, and the retreat distance is a.

3. The progressive double-sided flattening and fine-blanking forming method for a shift fork according to claim 2 is characterized in that: In step S3, the second flattening action is decomposed into multiple second flattening sub-actions; as the movement process of the lower flattening punch continues to advance, the impact intensity of the second flattening sub-action presents an exponential attenuation trend, the depth value of the back flattening feature gradually increases, and the depth value of the front flattening feature gradually decreases due to the reverse impact force, until the depth values ​​of both are stabilized at a, at which time, the front flattening feature is in a critical contact state relative to the lower flattening punch.

4. The progressive double-sided flattening and fine-blanking forming method for a shift fork according to claim 2 is characterized in that: The thickness of the metal strip is b, then a≤1 / 5b, and a<1.5mm.

5. The progressive double-sided flattening and fine-blanking forming method for a shift fork according to claim 1 is characterized in that: The roughness of the front and back sides of the metal strip is controlled below 0.1 μm; before the metal strip is formally fed into the multi-station progressive die, the front and back sides are lubricated.

6. The progressive double-sided flattening fine blanking forming method for a shift fork according to any one of claims 1 to 5, characterized in that: In step S4, the multi-station progressive die is equipped with a fine-blanking gear ring; in the second blanking process, before the blanking punch contacts the metal strip, the fine-blanking gear ring is used to press the metal strip against the die in advance, so that the V-shaped teeth of the fine-blanking gear ring can penetrate deep into the metal strip.

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