A draw reducing die for improving the uniformity of the thickness of a hole wall

Abstract

The application discloses a thinning and stretching die for improving the uniformity of hole wall thickness, which comprises an upper die base and a lower die base, an upper backing plate, a top rod fixing plate and a concave die sleeve fixing plate which are fixed on the upper die base in sequence, and a thinning concave die sleeve is arranged on the concave die sleeve fixing plate; a thinning convex die is fixed on the lower die base; the thinning convex die comprises a solid cylindrical part and a variable end head on the cylindrical part, the diameter of the variable end head gradually decreases from one end which is connected with the cylindrical part to the end, a counter-cone counterbore is arranged at the end of the variable end head, and a group of separation joints which are arranged along the axis direction of the thinning convex die are uniformly distributed on the side wall of the variable end head, the separation joints separate the variable end head into a plurality of thinning and stretching pieces which are independent of each other; the top rod fixing plate is provided with a top rod which can support the variable end head, and a conical frustum which is matched with the counterbore is arranged at the end of the top rod. The application can improve the uniformity inside the fin hole and improve the height of the fin hole.

Description

Technical Field

[0001] This invention relates to the field of fin processing technology, and in particular to a thinning stretching die for improving the uniformity of hole wall thickness. Background Technology

[0002] Radiators and heat exchangers mainly consist of fins and copper tubes inserted into the fins. Multiple fins are stacked, and the spacing between fins is limited by the height of the fin holes. The copper tubes are inserted into the fin holes and tightened using a tube expander to secure them. The fin holes are formed through multiple drawing, punching, and flanging processes, followed by thinning and stretching to increase the height of the fin holes. The higher the fin holes, the larger the spacing between adjacent fins, the fewer fins are required for each radiator or heat exchanger, and the lower the cost. In the drawing and punching / flanging processes, both the drawing punch and the punching / flanging punch start drawing from the bottom of the fin hole, pressing the material upwards step by step. Therefore, the inner wall of the entire hole has a wrinkled structure of varying thickness.

[0003] The existing thinning and stretching process still uses a cylindrical solid punch and die. The stretching of the fin hole begins as soon as the solid punch enters the die, meaning the thinning still starts from the bottom of the fin hole and works upwards. This easily leads to localized excessively thin material, resulting in weakened strength or even breakage. The stretching height is affected by the thickness of the thinnest area, limiting the stretching amount. Furthermore, the uniformity of the inner wall thickness of the stretched fin hole is not improved, remaining a wrinkled structure with varying thicknesses. When this fin hole mates with the copper tube, the fit is poor, resulting in low tension force. This not only affects assembly reliability but also, due to the low fit, reduces the heat exchange efficiency between the copper tube and the fins, leading to poor heat dissipation.

[0004] Furthermore, in mold processing, the machining and assembly precision requirements for the thinning die and thinning punch are particularly high to ensure the consistency of their centers. Existing mold structures do not allow for adjustment or movement of either the thinning die or the thinning punch, meaning they cannot achieve automatic alignment during fin machining based on the other's position. When the thinning die and the thinning punch are not concentric, the force applied to the fin holes can easily cause height differences, or even breakage and material damage (damage to the fin holes). Therefore, existing molds have certain deficiencies in terms of both the stability of fin machining and the height and uniformity of the fin holes. Summary of the Invention

[0005] The purpose of this invention is to provide a thinning stretching die that improves the uniformity of hole wall thickness, and solves the problems of low fin hole height, poor inner wall uniformity, and easy breakage in existing die structures.

[0006] The technical solution adopted by this invention to solve its technical problem is: a thinning stretching die for improving the uniformity of hole wall thickness, comprising an upper die base and a lower die base, wherein an upper pad plate, an ejector pin fixing plate, and a die sleeve fixing plate are sequentially stacked and fixed on the upper die base, and a thinning die sleeve is provided on the die sleeve fixing plate; a thinning punch is fixedly provided on the lower die base; the thinning punch includes a solid cylindrical part and a variable end located on the cylindrical part, the diameter of the variable end gradually decreases from the end that abuts with the cylindrical part to the end end, an inverted conical countersunk hole is provided at the end of the variable end, and a set of thinning punches are evenly distributed on the side wall of the variable end. A partition slit is provided along the axial direction, which divides the variable end into multiple independent thinning and stretching plates; a top rod is provided on the top rod fixing plate to open the variable end, and the end of the top rod is provided with a truncated cone adapted to the countersunk hole; when the truncated cone is in place with the countersunk hole, the variable end is fully opened so that the outer diameter of the variable end is consistent with that of the cylindrical part; during the thinning and forming of the fin hole, the variable end is first opened, and during the opening process, the inner wall of the fin hole is squeezed to flatten the inner wall of the fin hole. Then, the opened variable end moves upward relative to the fin hole, and squeezes the fin hole material upward to achieve the thinning and stretching of the fin hole wall.

[0007] To facilitate adjusting the position where the thinning punch first contacts the inner wall of the fin hole, a punch fixing plate is provided on the lower die holder to fix the thinning punch; a height adjustment device for adjusting the height of the punch fixing plate is provided below the punch fixing plate.

[0008] Furthermore, the height adjustment device includes a lower inclined wedge disposed on the lower die base and an upper inclined wedge that cooperates with the lower inclined wedge, and the punch fixing plate is supported on the upper inclined wedge.

[0009] Furthermore, a push rod spring is provided above the fixed end of the push rod to apply pressure to the push rod. A pressure plate is provided on the thinning punch, and a stripper plate is floating above the pressure plate. A stripper spring is provided between the stripper plate and the lower die base, and the spring force of the push rod spring is greater than that of the stripper spring. A pressure rod is also provided on the upper die base, and a pressure rod spring is provided between the pressure rod and the upper die base. Under the action of the pressure rod spring, the front end of the pressure rod extends out of the die sleeve fixing plate; the spring force of the pressure rod spring is greater than that of the push rod spring.

[0010] The beneficial effects of this invention are as follows: This invention utilizes the cooperation between a thinning punch and an ejector pin. Under the action of the ejector pin, the thinning punch first expands and compresses the inner wall of the fin hole to level it, and then stretches and thins the fin hole. Therefore, compared to existing structures, this invention achieves a more uniform inner wall and a higher stretching height in the fin hole, thus significantly improving fin performance. When the cone-shaped ejector pin enters the countersunk hole, under the action of the countersunk hole, the ejector pin drives the thinning die sleeve to move together, enabling the ejector pin and the thinning die sleeve to automatically align with the thinning punch. This ensures concentricity with the fin hole, preventing uneven stretching on one side and uneven stretching on the other during the stretching and thinning process. This avoids height differences in the fin hole, and even problems such as hole breakage or material damage (fin hole crushing). The thinning punch can also adjust its initial height through a height adjustment device, thereby adjusting the position where the thinning punch first contacts the inner wall of the fin hole. Therefore, the height of the thinning punch can be adjusted according to the thickness of the inner wall of the fin hole before thinning and stretching, so that the thinning punch first contacts the thickest position of the inner wall of the fin hole for leveling, thereby meeting the processing requirements of fins of different heights.

[0011] The present invention will now be described in more detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the mold in the open state of the present invention.

[0013] Figure 2 This is a structural schematic diagram of the mold in working state one of the present invention.

[0014] Figure 3 for Figure 2 A magnified view of part A in the image.

[0015] Figure 4 This is a schematic diagram of the second working state of the mold of the present invention.

[0016] Figure 5 for Figure 4 A magnified view of part B in the image.

[0017] Figure 6 A schematic diagram of the working state three of the mold of the present invention.

[0018] Figure 7 for Figure 6 A magnified view of part C.

[0019] Figure 8 This is a structural schematic diagram of the mold in working state three of the present invention.

[0020] Figure 9 for Figure 8 A magnified view of part of D.

[0021] Figure 10 This is a partial three-dimensional structural diagram of the thinning punch in this invention. Detailed Implementation

[0022] Examples, such as Figures 1 to 10 As shown, a thinning and stretching die for improving the uniformity of fin wall thickness is used to thin and stretch the fin hole 100 after fin flanging, thereby improving the uniformity of the fin hole 100 wall thickness and thus increasing the stretching height of the fin hole 100. The thinning and stretching die for improving the uniformity of fin wall thickness includes an upper die assembly and a lower die assembly that cooperate with each other. The upper die assembly includes an upper die base 1, an upper pad 3, a push rod fixing plate 4, and a die sleeve fixing plate 5 that are sequentially stacked and fixed on the upper die base 1. A thinning die sleeve 51 is fixedly installed on the die sleeve fixing plate 5. During part processing, the mounting hole on the die sleeve fixing plate 5 for installing the thinning die sleeve 51 is clearance-fitted with the thinning die sleeve 51. That is, during part processing, the diameter of the mounting hole is larger than the diameter of the thinning die sleeve 51. Therefore, the thinning die sleeve 51 can have a certain amount of displacement when installed on the die sleeve fixing plate 5. The lower die assembly includes a lower die base 2, a height adjustment device 10 mounted on the lower die base 2, a punch fixing plate 9 mounted on the height adjustment device 10, a thinning punch 6 fixedly mounted on the punch fixing plate 9, and a pressure plate 12 for pressing the thinning punch 6 on the punch fixing plate 9. A stripper plate 13 is also floating above the pressure plate 12. The specific mating structure of the stripper plate 13 is as follows: a stripping spring 14 is provided between the stripper plate 13 and the lower die base 2 to push the stripper plate 13 upwards; a limiting block 15, which has a 7-shaped structure, is also fixedly mounted on the lower die base 2 to limit the upward stroke of the stripper plate 13.

[0023] The thinning punch 6 includes a solid cylindrical portion 61 and a variable end 62 located on the cylindrical portion 61. The diameter of the variable end 62 gradually decreases from the end that abuts against the cylindrical portion 61 to the end. The taper R of the variable end 62 is 0.2-0.5°. An inverted conical countersunk hole 621 is provided at the end of the variable end 62, and a set of partition slits 622 are evenly distributed on the side wall of the variable end 62 along the axial direction of the thinning punch 6. The partition slits 622 divide the variable end 62 into multiple independent thinning stretching pieces 623. The ejector pin fixing plate 4 is provided with an ejector pin 7 that opens the variable end 62. The ejector pin 7 passes through the thinning die sleeve 51 and is precisely fitted with the thinning die sleeve 51, that is, there is no offset allowance between the two. The ejector pin 7 drives the thinning die sleeve 51 to move together. The end of the ejector rod 7 is provided with a truncated cone 71 that matches the countersunk hole 621. An ejector spring 8 is provided above the fixed end of the ejector rod 7 to apply pressure to it. An upper pressure plate 11 is provided at the other end of the ejector spring 8, and the upper pressure plate 11 is fixedly mounted on the upper mold base 1. When the truncated cone 71 and the countersunk hole 621 are in place, the variable end 62 is fully opened so that its outer diameter remains consistent with that of the cylindrical portion 61. To control the order of engagement of each component, ensuring that after the thinning punch 6 enters the fin hole 100, the variable end 62 is first opened to press and straighten the inner wall of the fin hole 100, and then the thinning punch 6 moves upward to stretch the fin hole 100, the spring force of the ejector spring 8 is greater than the spring force of the unloading spring 14. The upper mold base 1 is also provided with a pressure rod 18, and a pressure rod spring 19 is provided between the pressure rod 18 and the upper mold base 1. Under the action of the pressure rod spring 19, the front end of the pressure rod 18 extends out of the concave mold sleeve fixing plate 5; the spring force of the pressure rod spring 19 is greater than the spring force of the push rod spring 8.

[0024] The height adjustment device 10 includes a lower inclined wedge 101 disposed on the lower die base 2 and an upper inclined wedge 102 that cooperates with the lower inclined wedge 102. The punch fixing plate 9 is supported on the upper inclined wedge 102. A screw 16 is also provided to push the lower inclined wedge 101 to move. A digital display device 17 is installed on the screw 16 for accurately reading the advance distance of the screw 16. The height adjustment device 10 can adjust the initial contact position between the variable end 62 of the thinning punch 6 and the inner wall of the fin hole 100, so that the thickest part of the fin hole 100 wall is contacted and pressed first, and then stretched, thereby increasing the stretching height of the fin hole 100.

[0025] The specific movement process is as follows: (e.g.) Figure 1As shown, in the initial state, the mold is open, and the ejector pin 7 is at its lowest point under the action of the ejector spring 8. The pressure pin 18 is at its lowest point under the action of the pressure pin spring 19, causing the end of the pressure pin 18 to extend out of the die sleeve fixing plate 5. The stripper plate 13 is pushed upward under the action of the stripper spring 14, and the stripper plate 13 is at its upper limit position. When the upper mold assembly moves downward, the pressure pin 18 first contacts the stripper plate 13. At this time, the cone 71 begins to enter the countersunk hole 621 but does not contact the countersunk hole 621. At the same time, the thinning punch 6 does not enter the fin hole 100. Figure 2 , Figure 3 As shown.

[0026] As the upper mold assembly continues to move downwards, the spring force of the pressure rod spring 19 is greater than that of the stripper spring 14. Under the action of the pressure rod 18, the stripper plate 13 is pressed downwards until it is tightly pressed against the pressure plate 12. At this time, the outer wall of the cone 71 is in contact with the inner wall of the countersunk hole 621 but is not under force. The thinning die sleeve 51 is fitted outside the fin hole 100, and the thinning punch 6 enters the fin hole 100. During the downward movement, the ejector rod 7, under the action of the countersunk hole 621, continuously adjusts the position of the ejector rod 7 and the thinning die sleeve 51 to achieve automatic alignment between the thinning die sleeve 51 and the thinning punch 6. At the same time, the ejector spring 8 is in a critical state. If more force is applied, it will contract and deform. Figure 4 , Figure 5 As shown.

[0027] As the upper mold assembly continues to move downwards, when the spring force on the ejector spring 8 exceeds a critical value, the ejector spring 8 contracts inwards, and the thinning punch 6 moves upwards relative to the fin hole 100. When the outer wall of the variable end 62 of the thinning punch 6 contacts the inner wall of the fin hole 100, the spring force exerted by the ejector spring 8 on the ejector rod 7 is less than the force required to open the variable end 62. The position where the variable end 62 first contacts the inner wall of the fin hole 100 is the position with the thickest wall of the fin hole 100, facilitating the initial leveling of the thickest position. To accommodate different fin processing needs where the position of the thickest part of the inner wall of the fin hole 100 varies, the initial height of the thinning punch 6 can be adjusted by the height adjustment device 10 to ensure that the variable end 62 contacts the thickest part of the fin hole 100 first. Figure 6 , Figure 7 As shown.

[0028] As the upper mold assembly continues to move downwards, the spring force of the ejector spring 8 acting on the ejector rod 7 is greater than the force required to open the variable end 62. The ejector rod 7 then pushes the variable end 62 outwards. As the required force to open it increases, the ejector spring 8 also continuously contracts upwards until the ejector rod 7 fully opens the variable end 62, at which point the ejector spring 8 is compressed to its uppermost point. Figure 5As shown, during the outward expansion process, the variable end 62 continuously compresses the inner wall of the fin hole 100, causing the material of the inner wall of the fin hole 100 to transfer upward during the compression, thus straightening the inner wall of the fin hole.

[0029] The upper die assembly continues to move downwards, overcoming the spring force of the pressure rod spring 19, causing the pressure rod 18 to move upwards, completing the closure of the upper and lower die assemblies. During this process, the thinning punch 6 stretches the wall of the fin hole upwards, completing the thinning and stretching of the fin hole. Figure 8 , Figure 9 As shown.

[0030] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A thinning stretching die for improving the uniformity of hole wall thickness, comprising an upper die base (1) and a lower die base (2), wherein an upper pad plate (3), an ejector pin fixing plate (4), and a die sleeve fixing plate (5) are sequentially stacked and fixed on the upper die base (1), characterized in that: A thinning die sleeve (51) is provided on the die sleeve fixing plate (5); a thinning punch (6) is fixedly provided on the lower die base (2); the thinning punch (6) includes a solid cylindrical part (61) and a variable end (62) located on the cylindrical part (61). The diameter of the variable end (62) gradually decreases from the end that is connected to the cylindrical part (61) to the end. An inverted conical countersunk hole (621) is provided at the end of the variable end (62), and a set of partition slits (622) are evenly distributed on the side wall of the variable end (62) along the axial direction of the thinning punch (6). The partition slits (622) divide the variable end (62) into multiple independent thinning pulls. Extension plate (623); The top rod fixing plate (4) is provided with a top rod (7) to open the variable end (62), and the end of the top rod (7) is provided with a cone (71) that matches the countersunk hole (621); When the cone (71) and the countersunk hole (621) are in place, the variable end (62) is fully opened so that the outer diameter of the variable end (62) is consistent with that of the cylindrical part (61); When the fin hole is thinned and formed, the variable end (62) is first opened, and the inner wall of the fin hole is squeezed during the opening process to flatten the inner wall of the fin hole. Then the opened variable end (62) moves upward relative to the fin hole and squeezes the fin hole material upward to achieve the thinning and stretching of the fin hole wall.

2. The thinning stretching die for improving the uniformity of hole wall thickness as described in claim 1, characterized in that: The lower die base (2) is provided with a punch fixing plate (9) for fixing the thinning punch (6); a height adjustment device (10) for adjusting the height of the punch fixing plate (9) is provided below the punch fixing plate (9).

3. The thinning stretching die for improving the uniformity of hole wall thickness as described in claim 2, characterized in that: The height adjustment device (10) includes a lower inclined wedge (101) disposed on the lower mold base (2) and an upper inclined wedge (102) that cooperates with the lower inclined wedge (102), and the punch fixing plate (9) is supported on the upper inclined wedge (102).

4. The thinning stretching die for improving the uniformity of hole wall thickness as described in claim 1, characterized in that: The mounting hole on the die fixing plate (5) for installing the thinning die sleeve (51) is clearance-fitted with the thinning die sleeve (51). After assembly, the thinning die sleeve (51) can move left, right, back and forth within the mounting hole of the die fixing plate (5).

5. The thinning stretching die for improving the uniformity of hole wall thickness as described in claim 1, characterized in that: A push rod spring (8) is provided above the fixed end of the push rod (7) to apply pressure to the push rod (7).

6. The thinning stretching die for improving the uniformity of hole wall thickness as described in claim 5, characterized in that: A pressure plate (12) is provided on the thinning punch (6), and a stripper plate (13) is floating above the pressure plate (12). A stripper spring (14) is provided between the stripper plate (13) and the lower die base (2). The spring force of the ejector spring (8) is greater than that of the stripper spring (14).

7. The thinning stretching die for improving hole wall thickness uniformity as described in claim 6, characterized in that: The upper mold base (1) is also provided with a pressure rod (18), and a pressure rod spring (19) is provided between the pressure rod (18) and the upper mold base (1). Under the action of the pressure rod spring (19), the front end of the pressure rod (18) extends out of the die sleeve fixing plate (5); the spring force of the pressure rod spring (19) is greater than the spring force of the push rod spring (8).

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