A cold stamping process for the front lower arm of an automobile

Abstract

The invention relates to the technical field of swing arm processing, and discloses a cold stamping process for a front lower swing arm of an automobile, comprising blanking, punching; stretching; bottom forming, shaping; trimming, punching; flanging forming, burr pressing; side shaping, side trimming; flanging, punching; side cutting semicircle, side punching, and side cutting semicircle, burr pressing and other processes. By first forming a corner bulge and then forming a middle bulge, the flanging height can be increased and the formed C-shaped corner area will not crack or wrinkle. By pressing the burr, the phenomenon of micro cracks in the flanging area can be avoided. The process adopts thick steel plates and can successfully form a front lower swing arm of an automobile with higher flanging and flanging, avoids product defects such as wrinkling and cracking, and improves the strength and rigidity of the product.

Description

Technical Field

[0001] The invention relates to the technical field of swing arm processing, in particular to a cold stamping process for a front lower arm of an automobile. Background Art

[0002] The front lower arm is used as a suspension guide component to connect the subframe and the steering knuckle to transfer the force between the wheel and the body, ensuring that the wheel jumps along the set trajectory for the whole vehicle. During use, the strength and rigidity of the front lower arm are required to be high. To meet the use requirements, the front lower arm is mostly made of high-strength thick steel plate and pressed by cold stamping dies. In order to further increase the strength and rigidity of the front lower arm, there will be a raised shape on the bottom surface of the front lower arm when designing the product, which will greatly increase the difficulty of forming during the cold stamping process.

[0003] A Chinese patent with announcement number CN111842635A discloses a forming process for a front lower control arm of an automobile, in which a sheet is subjected to three stretching forming and subsequent staged shaping, wherein during the first stretching, a convex rib in the middle of the workpiece and a bulge in the middle located on one side of the product are formed simultaneously, and a corner bulge bulges upward at the flange of the corner, the connection between the corner bulge and the sheet is an arc-shaped transition, the middle bulge is arc-shaped and the connection with the convex rib is an arc-shaped transition.

[0004] The corner area of ​​the front lower arm of the car has always been a difficult problem to overcome in the industry. The higher the flange height at the corner, the greater the strength. Figure 1 When the workpiece shown in the figure is formed, the following process defects will occur due to the obvious increase in the height of the flanging and the hole: 1. The angle between the flanging and the sheet at the corner bulge of the automobile front lower control arm of the above-mentioned patent is greater than 90°, and the flanging height is relatively low. Once the flanging height is further increased, it will interfere with other parts of the automobile chassis; 2. Simultaneous formation of the middle bulge and the corner bulge and further increase of the flanging height will cause product defects such as wrinkling and cracking in the corner area; 3. The front lower control arm is elastically connected to the subframe through a bushing. In order to ensure the driving safety of the automobile, there must be sufficient pulling force between the bushing and the front lower control arm. Therefore, there will be certain requirements for the height of the hole. Using the above process to directly perform the hole flanging and ensure a sufficiently high hole flanging height will cause micro cracks to easily occur after the hole flanging. Summary of the invention

[0005] The present invention aims at the disadvantages in the prior art that when thick steel plates are used for production, once the height of the flange or the hole is increased, the corner area is prone to wrinkling and cracking, and cracks are prone to appear at the hole. The present invention provides a cold stamping process that can avoid wrinkling and cracking at the corners and cracking at the hole when using thick steel plates to produce the front lower arm of an automobile.

[0006] In order to solve the above technical problems, the present invention is solved by the following technical solutions:

[0007] A cold stamping process for a front lower arm of an automobile comprises the following steps:

[0008] 1) Blanking and punching: Put the flat steel plate into the mold for punching to obtain the blank and punch out two process positioning holes;

[0009] 2) Stretching: The horizontally extended part of the bottom surface is used as the blank holder, and the side wall surface of the C-shaped corner is used as the shape of the stretching punch, and the corner bulge is formed by stretching;

[0010] 3) Bottom forming and shaping: a bulge is formed in the middle of the bottom, and the stretched fillet formed by the corner bulge and the sheet in step 2 is shaped and pressed into a "J"-shaped fillet;

[0011] 4) Trimming and punching: Punch out the process holes required for the holes on both sides, and punch out two process positioning holes on the middle bulge;

[0012] 5) Flanging and burr pressing: Flanging the back side and the side walls of the product, and at the same time press the fracture zone of the process hole to form a rounded corner;

[0013] 6) Side shaping and side trimming: Use the inclined wedge mechanism to shape the side flange in step 5 and cut off the C-shaped corner waste area at the same time;

[0014] 7) Hole punching: punching the process hole formed in step 4) to form a hole punching part;

[0015] 8) Side cutting semicircle and side punching: Use the inclined wedge mechanism to cut off the semicircular waste on one side of the C-shaped corner area, and punch out three mounting holes at the end of the workpiece away from the process hole;

[0016] 9) Side cutting of semicircle: Use the inclined wedge mechanism to cut off the semicircular waste on the other side of the C-shaped corner area.

[0017] By adopting the above scheme, the existing technology of simultaneously forming the corner bulge and the middle bulge in the same step is changed to first forming a C-shaped corner bulge in step 2), and then forming the middle bulge in step 3) and shaping the C-shaped corner bulge formed in step 2. The advantage is that the C-shaped corner bulge is formed first. At this time, the surface of the pressure ring is smooth, which can ensure that during the stretching process, when the required height of the flange is pulled out, the C-shaped corner area will not wrinkle or crack. If the existing process in the background technology is used, wrinkles and cracks will appear once the flange height is increased; then, in step 3), the middle bulge is stretched and shaped Corner bulge: Since the main body of the corner bulge has been formed, shaping on the main body is less likely to cause cracking or wrinkling than one-piece molding; and in step 5, the fracture zone of the process hole is pressed to burr. The existence of burrs is the cause of micro cracks in the hole turning. Once the burrs are flattened, it can avoid the occurrence of micro cracks in the hole turning part during the subsequent hole turning operation. The above process steps can produce automobile front lower control arms with significantly increased flange height and hole turning height. It is also suitable for the production of conventional front lower control arms, which can improve the applicability of the mold and significantly increase the strength and rigidity of the product after production.

[0018] Preferably, in step 4), the waste area formed with the process positioning hole and the C-shaped corner area in step 1) is cut off, and in step 6), the remaining waste area of ​​the C-shaped corner is cut off.

[0019] By adopting the above scheme, the waste material removal step is arranged to be implemented in two steps. The advantage is that the punching edge and the punching force when the waste material is removed sequentially can be reduced, thereby protecting the product and the mold.

[0020] Preferably, in step 9), the three mounting holes formed in step 8) are simultaneously deburred.

[0021] With the above solution, the function of the mounting hole is to use a bolt to pass through it and then fix it with the ball pin. The presence of burrs will cause the bolt to fail to be tightened, affecting the travel safety of the car. In this process, after pressing the burr, it can be ensured that the bolt can be tightened.

[0022] Preferably, in step 1), one steel plate can simultaneously punch two offset spliced ​​sheets.

[0023] By adopting the above scheme and the above arrangement, the punching efficiency can be effectively improved.

[0024] Preferably, in step 2), the height of the corner bulge is 30-40 mm higher than the highest point of the product side wall.

[0025] By adopting the above solution, the above height can ensure that there is sufficient margin for trimming the side edges at the subsequent corner positions.

[0026] Preferably, in step 2), the stretching fillet radius of the C-shaped corner area is greater than 20 mm.

[0027] By adopting the above scheme, the above stretching radius can ensure that the molding thinning rate at this position is within 15%.

[0028] Preferably, in step 5), two circular convex hull-shaped reference surfaces are simultaneously formed on the bottom of the workpiece.

[0029] By adopting the above scheme, when the reference surface is formed in this step, in order to avoid multiple molding resulting in multiple imprints on the reference surface, affecting the inspection and testing results of the product.

[0030] Preferably, in step 7), two reference holes are punched out simultaneously, wherein one of the reference holes is located on the reference surface.

[0031] With the above solution, the reference hole is punched out in this step in order to be used for positioning in the subsequent process.

[0032] Preferably, steps 2-3 adopt a positioning method that mainly uses process positioning holes and supplements edge positioning; step 4 adopts a positioning method that combines edge positioning and surface positioning; steps 5-7 adopt a process hole positioning method; and steps 8-9 adopt a reference hole positioning method.

[0033] By adopting the above scheme, the punched holes of waste materials or the process holes or reference holes in the previous process are used as positioning holes, which does not occupy the actual workpiece area and is cleverly applied.

[0034] The present invention has a significant technical effect due to the adoption of the above technical scheme: the prior art method of simultaneously forming the corner bulge and the middle bulge in the same step is changed to first forming a C-shaped corner bulge in step 2), and then forming the middle bulge in step 3) and shaping the C-shaped corner bulge formed in step 2. The advantage is that when the C-shaped corner bulge is formed first, the profile of the pressure ring is smooth, which can ensure that during the stretching process, when the required height of the flange is pulled out, the C-shaped corner area will not wrinkle or crack. If the existing process in the background technology is used, wrinkles and cracks will appear once the flange height is increased; then, in step 3), the C-shaped corner bulge is stretched. The bulge in the middle is formed and the corner bulge is shaped. Since the main body of the corner bulge has been formed, shaping it on the main body is less likely to cause cracking or wrinkling than one-piece molding. In step 5, the fracture zone of the process hole is pressed to deburr. The presence of burrs is the cause of micro cracks in the hole turning. Once the burrs are flattened, micro cracks in the hole turning part can be avoided during the subsequent hole turning operation. The above process steps can produce automobile front lower control arms with significantly increased flange height and hole turning height. It is also suitable for the production of conventional front lower control arms, which can improve the applicability of the mold and significantly increase the strength and rigidity of the product after production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the automobile front lower swing arm product of this embodiment;

[0036] Figure 2 It is a structural schematic diagram of the state change of the semi-finished product in step 1 of this embodiment;

[0037] Figure 3 It is a structural schematic diagram of the state change of the semi-finished product in step 2 of this embodiment;

[0038] Figure 4 It is a structural schematic diagram of the state change of the semi-finished product in step 3 of this embodiment;

[0039] Figure 5 It is a structural schematic diagram of the state change of the semi-finished product in step 4 of this embodiment;

[0040] Figure 6 It is a structural schematic diagram of the state change of the semi-finished product in step 5 of this embodiment;

[0041] Figure 7 It is a structural schematic diagram of the state change of the semi-finished product in step 6 of this embodiment;

[0042] Figure 8 It is a structural schematic diagram of the state change of the semi-finished product in step 7 of this embodiment;

[0043] Fig. 9 It is a structural schematic diagram of the state change of the semi-finished product in step 8 of this embodiment;

[0044] Fig.10 It is a structural schematic diagram of the state change of the semi-finished product in step 9 of this embodiment. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Example

[0046] Combination Figure 1-Figure 10 As shown in the product forming process structure diagram of the forming process of the front lower arm of the present invention, the forming process of the front lower arm of the automobile includes the following steps:

[0047] Blanking, punching: see Figure 2 As shown, a steel plate with a size of 620mm*455mm*4mm is placed in the mold, and two left-right symmetrical sheets 1-1 each having two process positioning holes 2 can be punched out at one time;

[0048] Stretch: See Figure 3As shown, the stretching positioning is mainly based on the process positioning hole 2, supplemented by the edge positioning. One of the process positioning holes 2 is located at the center of the end hole circle, with a hole diameter of φ30mm, and the other process positioning hole 2 is located in the product waste area (an ear-shaped protrusion with an area of ​​about 35mm*40mm), with a waist-shaped hole with a diameter of φ20mm as positioning. After the sheet 1-1 is placed in the mold, the first positioning column 4 is inserted into the above two process positioning holes 2 in turn to form the main positioning, and the sheet 1-1 is fitted with the second positioning column 5 around to form an auxiliary positioning. The above positioning method can effectively ensure the stability of the stretching forming.

[0049] During stretching, the bottom surface is horizontally extended as a pressure ring, and the side wall surface of the C-shaped corner is the shape of the stretching punch. The corner bulge 3 at the stretching position has a height that is 30~40mm higher than the highest point of the side wall surface of the C-shaped corner of the product to ensure that there is enough trimming allowance for subsequent side trimming at the corner position. The stretching radius 3-1 at the corner position is greater than R20mm to ensure that the forming thinning rate at this position is within 15%.

[0050] The above steps form a sheet 1-2, and the sheet 1-2 only forms a corner convex hull 3. By using a flat pressure ring, the corner convex hull can be stretched to a sufficient height without wrinkling or cracking at the corner position;

[0051] Bottom forming and shaping: refer to Figure 4 As shown, the sheet 1-3 is placed in the mold, and the positioning method is the same as step 2, with the process positioning hole 2 being used as the main positioning and the edge positioning as the auxiliary positioning. During the molding, the middle convex hull 6 is molded, and the stretched fillet 3-1 of the C-shaped corner 3 area is shaped and reduced to be consistent with the product digital model, and pressed into a "J"-shaped fillet 3-2, which is convenient for trimming in the subsequent steps. After the above steps, the sheet 1-3 is formed;

[0052] Trimming, punching: refer to Figure 5 As shown, the positioning of this process adopts the method of edge positioning and profile positioning. In this process, two process holes 7 required for subsequent punching are punched out, and two process positioning holes 9 are punched out at the position of the middle bulge 6 for positioning in subsequent processes. The waste areas 8 such as the ear-shaped protrusions and the C-shaped corner areas are cut off. The removal of these waste areas 8 can reduce the blanking edge length and blanking force during the subsequent side trimming. The upper step forms the blanks 1-4;

[0053] Flanging and burring: refer to Figure 6As shown, this process uses the process positioning hole 9 generated in the previous process as the positioning hole. In this process, the rear side and the side walls of the workpiece are formed with flanges 10-1; at the same time, the corner area formed in the above process is reshaped so that the subsequent side trimming process is more in line with the tool to improve the stability of the side trimming; at the same time, two circular reference convex hulls 12 are formed, which can avoid multiple stamping conditions on the reference surface caused by multiple moldings, and avoid affecting the inspection and testing results of the product; at the same time, the process hole 7 is pressed to remove burrs. The reason for pressing burrs is that the punching process will produce bright bands and fracture bands, and there will be burrs on one side of the fracture band. These burrs will cause microcracks in the product after the hole is flipped. In this process, one side of the fracture band is pressed to form a fillet of about R1mm, which can avoid the occurrence of microcracks during subsequent hole flipping.

[0054] Side shaping, side trimming: refer to Figure 7 As shown, the positioning method of this process is consistent with the previous process. In this process, an inclined wedge mechanism is used to shape the flange 10-1 in the previous process. The direction of the arrow in the figure is the direction of the inclined wedge. Through the inclined wedge shaping, the surface contour of the side wall of the workpiece can be guaranteed to meet the requirements of the product drawing; the surface of the C-shaped corner area has been formed multiple times in the previous multiple processes, and the surface contour of this area has also met the requirements of the product drawing; in this process, the inclined wedge mechanism is also used to cut off the remaining waste area 10-2. Since the previous stretching process has formed the height of this area to be higher than the product, the forming thinning area is mainly concentrated in the extra waste area 10-2. Once the waste area is cut off, the product forming thinning rate can be controlled at about 10%, meeting the requirements of the drawing;

[0055] Punching and drilling: refer to Figure 8 As shown, the positioning method of this process is consistent with the previous process. In this process, the two process holes 7 on the product are punched and the punched hole portion 7-1 is formed. After the punched hole portion 7-1 is deburred in the previous process, it meets the requirements of the product drawing. At the same time, the reference hole 13 on the reference surface is also punched out in this process.

[0056] Side cutting semicircle, side punching: refer to Fig. 9 As shown, the positioning of this process uses the previous reference hole 13 as the positioning hole. In this process, the semicircular waste 14 in the C-shaped corner area is cut off by the inclined wedge mechanism; at the same time, the three mounting holes 15 at the end are positioned by the reference hole by the inclined wedge mechanism, which can better ensure that the contour of the semicircular waste 14 meets the requirements of the drawing;

[0057] Side cutting semicircle, pressing burr: refer to Fig.10 As shown, the positioning method of this process is consistent with that of the previous process. In this process, the semicircular waste 16 in the C-shaped corner area is cut off by an inclined wedge mechanism, and the three mounting holes 15 of the previous process are deburred 17. This deburring process can avoid the situation where the bolts cannot be tightened due to the burrs.

[0058] After the above steps, the production Figure 1 The automobile lower arm workpiece shown in the figure has the following process difficulties: A: wrinkling and cracking at C-type corners and B: micro cracks at the hole-turning part. The above steps can avoid the above two product defects A and B.

Claims

1. A cold stamping process for a front lower arm of an automobile, characterized in that: The following steps are involved: Blanking and punching: a flat steel plate is placed in a die for punching, and two offset spliced ​​sheets (1-1) can be punched at the same time, and each sheet can punch out two process positioning holes (2); Stretching: The horizontally extended portion of the bottom surface is used as the blank holder, and the side wall surface of the C-shaped corner is used as the shape of the stretching punch, and the corner bulge is formed by stretching (3). The stretching fillet radius of the C-shaped corner area is greater than 20 mm, and the height of the corner bulge is 30-40 mm higher than the highest point of the product side wall; Bottom forming and shaping: forming a middle bulge (6) in the middle of the bottom, shaping and pressing the stretched rounded corner (3-1) formed by the corner bulge (3) and the material sheet (1-1) in step 2 into a "J"-shaped rounded corner (3-2); Trimming and punching: punch out the process holes (7) required for the two side holes, and punch out two process positioning holes (9) on the middle bulge (6); Flanging and burr pressing: forming side flanges (10-1) on the rear side and the two side walls of the product, and at the same time pressing the fracture zone of the process hole (7) to form a rounded corner; Side shaping and side trimming: Use an inclined wedge mechanism to shape the side flange (10-1) in step 5, and cut off the C-shaped corner waste area at the same time; Hole punching: punching the process hole (7) formed in step 4) to form a hole punching portion (7-1); Side cutting and side punching: Use an inclined wedge mechanism to cut off the semicircular waste material (14) on one side of the C-shaped corner area, and punch out three mounting holes (15) at the end of the workpiece away from the process hole (7); Side cutting of semicircle: using an inclined wedge mechanism to cut off the semicircular waste on the other side of the C-shaped corner area (16); Step 2) ~ Step 3) adopts the positioning method of process positioning hole as the main method and edge positioning as the auxiliary method; Step 4) adopts the positioning method combining edge positioning and surface positioning; Step 5) ~ Step 7) adopts the process hole positioning method; Step 8) ~ Step 9) adopts the reference hole positioning method.

2. The cold stamping process of the front lower arm of an automobile according to claim 1, characterized in that: In step 4), the waste area (8) formed with the process positioning hole and the C-shaped corner area in step 1) is cut off, and in step 6), the remaining waste area (10-2) of the C-shaped corner is cut off.

3. The cold stamping process of the front lower arm of an automobile according to claim 1, characterized in that: In step 9), the three mounting holes (15) formed in step 8) are simultaneously deburred (17).

4. The cold stamping process of the front lower arm of an automobile according to claim 1, characterized in that: In step 5), two circular convex hull-shaped reference surfaces (12) are simultaneously formed at the bottom of the workpiece.

5. The cold stamping process of the front lower arm of an automobile according to claim 4, characterized in that: In step 7), two reference holes (13) are punched out simultaneously, one of which is located on the reference surface.

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