Cold extrusion die for thrust boss of outer cylinder of shock absorber

Abstract

The utility model relates to the technical field of automobile shock absorber manufacturing, and concretely relates to a cold extrusion die of a shock absorber outer cylinder thrust boss, which comprises a core rod, a female die, a die cavity, a die shell, a base, a limiting assembly, the bottom of the die shell is fixed with the base, the inside of the die shell has a space containing the die cavity and the limiting assembly, the top of the die cavity is fixed with the die shell, the inside of the die cavity has a counterbore, the female die is installed in the counterbore, the female die is annular, and the inner wall of the female die is provided with a groove for forming the thrust boss at the upper portion. Compared with the prior art, the utility model is designed through a split female die module, material flows more uniformly into the female die groove during the extrusion process, and the consistency of the formation of each thrust boss is ensured; the split female die module reserves a material flow expansion space, and the polyurethane elastic element of the core rod is matched, so that the gradual radial expansion force is helpful for guiding material flow and avoiding pipe cracking caused by excessive local stress.

Description

Technical Field

[0001] This utility model relates to the field of automotive shock absorber manufacturing technology, specifically a cold extrusion mold for the thrust boss of the outer cylinder of a shock absorber. Background Technology

[0002] Currently, the main manufacturing methods for shock absorber outer cylinders are turning and welding, and press forming.

[0003] Turning and welding have the disadvantages of long processing time and a lot of material waste, and can no longer meet the current demand for efficient and low-cost manufacturing.

[0004] Press forming, such as using cold extrusion to form the outer cylinder of the shock absorber, offers higher material utilization. However, because a thrust boss needs to be formed on the outer cylinder wall of the front shock absorber for pressing on the spring disc to bear the pressure of the suspension spring, the traditional cold extrusion method cannot form the thrust boss. The specific reasons are as follows:

[0005] 1. Uneven material flow: Traditional molds cannot effectively control the flow direction of material during the extrusion process, resulting in uneven or incomplete forming of the thrust boss.

[0006] 2. Stress concentration and cracking: In the thrust boss forming area, the material is subjected to greater compressive stress, which can easily lead to pipe cracking, especially in thin-walled pipes.

[0007] 3. Difficulty in controlling dimensional accuracy: Traditional molds cannot achieve precise control of the height of the thrust boss, affecting the overall quality and performance of the parts.

[0008] Therefore, it is necessary to design a cold extrusion die for the thrust boss of the outer cylinder of the shock absorber to solve the problems of uneven material flow and pipe cracking, while achieving high-precision dimensional control. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a cold extrusion mold for the thrust boss of the outer cylinder of a shock absorber, so as to solve the problems of uneven material flow and pipe cracking, while achieving high-precision dimensional control.

[0010] To achieve the above objectives, this utility model is a cold extrusion mold for a thrust boss on the outer cylinder of a shock absorber, comprising a mandrel, a die, a mold cavity, a mold shell, a base, and a limiting assembly. The bottom of the mold shell is fixed to the base, and the interior of the mold shell has a space to accommodate the mold cavity and the limiting assembly. The mold cavity is fixed to the top of the mold shell, and the interior of the mold cavity has a countersunk hole. A die is installed in the countersunk hole. The die is annular, and the upper part of the inner wall of the die has a groove for forming the thrust boss. The limiting assembly is installed on the base directly below the mold cavity, and the upper end of the limiting assembly is inserted into the countersunk hole of the mold cavity from below. The mandrel is inserted into the countersunk hole of the mold cavity from above, and the billet tube is located between the mandrel and the die. The bottom of the mandrel abuts against the upper end of the limiting assembly.

[0011] The aforementioned cavity mold is a split structure composed of three cavity modules.

[0012] The mandrel includes a main body, a polyurethane elastic element, and a mandrel head. The polyurethane elastic element is snapped into the end of the main body, and the mandrel head is snapped into the end of the polyurethane elastic element.

[0013] The mold shell is a machined steel shell.

[0014] The mold shell and the base, the mold cavity and the mold shell, and the base and the limiting assembly are fixed with fixing screws.

[0015] The bottom of the inner wall of the die is provided with a step, and the bottom of the countersunk hole is provided with a mounting groove, and the step is engaged with the mounting groove.

[0016] The recessed module is a C-shaped metal block.

[0017] The limiting assembly includes a T-shaped adjusting block, an adjusting ring, a limiting ring, and a locking screw. The upper part of the T-shaped adjusting block is a threaded post, and the side of the threaded post has a limiting surface arranged along the axial direction. The limiting ring and the adjusting ring are sleeved on the threaded post. The limiting ring and the threaded post are connected by threads. The adjusting ring presses on the limiting ring. The adjusting ring has a threaded hole arranged along the circumference. The locking screw is connected to the threaded hole by threads, and the end of the locking screw abuts against the limiting surface.

[0018] The main rod has a hollow internal structure.

[0019] Compared with the prior art, this utility model, through the design of a split concave module, allows the material to flow more evenly into the concave die groove during the extrusion process, ensuring the consistency of the forming of each thrust boss; the split concave module reserves space for material flow expansion, and together with the polyurethane elastic element of the mandrel, the progressive radial expansion force helps guide the material flow and avoids pipe cracking caused by excessive local stress; the height-adjustable limiting assembly can precisely control the axial height of the thrust boss, ensuring that the part dimensions meet the design requirements. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the mold of this utility model.

[0021] Figure 2 This is a cross-sectional view of the mold of this utility model.

[0022] Figure 3 This is a schematic diagram of the structure of the concave mold of this utility model.

[0023] Figure 4 This is a schematic diagram of the structure of the recessed module of this utility model.

[0024] Figure 5 This is a schematic diagram of the structure of the mandrel of this utility model.

[0025] Figure 6 This is a cross-sectional view of the mandrel of this utility model.

[0026] Figure 7 This is a cross-sectional view of the mold cavity of this utility model.

[0027] Figure 8 This is a schematic diagram of the limiting assembly of this utility model.

[0028] Figure 9 This is a schematic diagram of the structure of the T-shaped adjustment block of this utility model.

[0029] Figure 10 This is a schematic diagram of the structure of the adjusting ring of this utility model.

[0030] Figure 11 This is a schematic diagram of the limiting ring of this utility model. Detailed Implementation

[0031] The present invention will now be further described with reference to the accompanying drawings.

[0032] See Figure 1 , Figure 2 This utility model is a cold extrusion die for a thrust boss on the outer cylinder of a shock absorber, including a mandrel 2, a die 6, a die cavity 5, a die shell 3, a base 4, and a limiting assembly 7. The bottom of the die shell 3 is fixed to the base 4. The interior of the die shell 3 has a space to accommodate the die cavity 5 and the limiting assembly 7. The die cavity 5 is fixed to the top of the die shell 3. The interior of the die cavity 5 has a countersunk hole, and the die 6 is installed in the countersunk hole. The die 6 is annular, and the upper part of the inner wall of the die 6 is provided with a groove 6-2 for forming the thrust boss. Figure 4 As shown, the limiting assembly 7 is installed on the base 4 directly below the mold cavity 5, and the upper end of the limiting assembly 7 is inserted into the countersunk hole of the mold cavity 5 from below. The mandrel 2 is inserted into the countersunk hole of the mold cavity 5 from above, and the blank tube 1 is located between the mandrel 2 and the die 6. The bottom of the mandrel 2 abuts against the upper end of the limiting assembly 7.

[0033] See Figure 3The cavity mold 6 is a split structure composed of three cavity modules 6-1. The cavity modules 6-1 can be disassembled and spliced, which solves the problem of difficult processing of the whole cavity mold. At the same time, the gap between the cavity modules 6-1 reserves space for material flow and expansion.

[0034] See Figure 5 , Figure 6 The mandrel 2 includes a main body 2-3, a polyurethane elastic element 2-2, and a head 2-1. The polyurethane elastic element 2-2 is snapped into the end of the main body 2-3, and the head 2-1 is snapped into the end of the polyurethane elastic element 2-2. The compression rate of the polyurethane elastic element 2-2 is 40%~60%, providing a progressive radial expansion force to prevent the tube from wrinkling. The cracking rate of the mandrel using this invention is reduced to 0.8%, which is significantly lower than the 12% cracking rate of rigid mandrels. The polyurethane elastic element 2-2 can be mass-produced using molds at extremely low cost and can be used as a consumable material. This solves the problems of traditional metal mandrels, which use complex spring and lever structures as elastic elements, being expensive and difficult to repair after wear.

[0035] Mold shell 3 is a machined steel outer shell.

[0036] The mold shell 3 and the base 4, the mold cavity 5 and the mold shell 3, and the base 4 and the limiting assembly 7 are fixed with fixing screws 8.

[0037] See Figure 4 The bottom of the inner wall of the die 6 is provided with a step 6-3, see [reference]. Figure 7 The bottom of the countersunk hole is provided with a mounting groove 5-1, and the step 6-3 is engaged with the mounting groove 5-1.

[0038] The recessed module 6-1 is a C-shaped metal block made of Cr12MoV or SKD11 mold steel with a hardness of HRC58~62, exhibiting excellent wear resistance and anti-scraping properties. The heat treatment involves oil quenching at 950~1000℃, followed by tempering at 180~200℃ for 2 hours. After nitriding and carburizing treatment, the surface hardness reaches HV1200~1500, improving wear resistance by 3~5 times and achieving a wear life of over 100,000 cycles.

[0039] See Figures 8-11The limiting assembly 7 includes a T-shaped adjusting block 7-1, an adjusting ring 7-2, a limiting ring 7-3, and a locking screw 7-4. The upper part of the T-shaped adjusting block 7-1 is a threaded post, and the side of the threaded post has a limiting surface 7-1-1 set along the axial direction. The limiting ring 7-3 and the adjusting ring 7-2 are sleeved on the threaded post. The limiting ring 7-3 is threaded to the threaded post for axial positioning. The adjusting ring 7-2 presses on the limiting ring 7-3. The adjusting ring 7-2 has a threaded hole 7-2-1 set along the circumferential direction. The locking screw 7-4 is threaded to the threaded hole 7-2-1. The end of the locking screw 7-4 abuts against the limiting surface 7-1-1 to eliminate thread clearance and achieve circumferential locking of the adjusting ring 7-2. Before cold extrusion, changing the height of the adjusting ring 7-2 can adjust the position height of the thrust boss on the damper cylinder wall, with an adjustment accuracy of ±0.1mm.

[0040] The interior of the main rod 2-3 is hollow to reduce its weight.

[0041] The method for cold extrusion of the thrust boss on the outer cylinder of a shock absorber using this utility model includes the following steps:

[0042] Step 1: The billet tube uses E195+LC tubing. Phosphating treatment is required before cold extrusion, and the thickness of the phosphating film must be precisely controlled. The billet tube phosphating solution needs to be prepared according to Step 1a to Step 1d, and the phosphating solution formula, process parameters and testing methods should be comprehensively adjusted.

[0043] Step 1a: A ZnCa2(PO4)2 type phosphating solution is used. The ZnCa2(PO4)2 type phosphating liquid crystal has a dense structure and better film thickness uniformity than manganese-based phosphating solutions, making it more suitable for thin-walled blank tubes with a wall thickness ≤2mm. The total acidity of the ZnCa2(PO4)2 type phosphating solution is 18~25 points, the free acidity is 0.8~1.2 points, and the ratio of acidity to free acidity is 20~30:1. Nitrate or chlorate is added as an oxidation promoter. NaNO3 is used for nitrate and NaClO3 is used for chlorate. The concentration is controlled at 0.5~1.5g / L. Too high a concentration will result in a loose film layer, while too low a concentration will result in insufficient film formation speed.

[0044] Step 1b involves controlling the concentration of the phosphating solution for 3-8 minutes at a temperature of 50-55℃, ensuring a Zn²⁺ concentration of 1.8-2.5 g / L. For every 5℃ increase in temperature, the film formation rate increases by 30%-40%, and extending the time to 8 minutes increases the film thickness by 1-2 μm. Too low a Zn²⁺ concentration results in a thin film, while too high a concentration leads to coarse crystals. For E195+LC preform tubes with a carbon content ≤0.10% and high matrix activity, the phosphating time can be shortened to within 5 minutes to avoid an excessively thick film.

[0045] Step 1c: Control the surface roughness Ra after pickling to ≤0.8μm to avoid uneven film thickness caused by residual oxide scale, with local deviations exceeding ±0.5μm. The chromate concentration is ≤0.1g / L to avoid passivation film >0.3μm, which would inhibit the phosphating reaction.

[0046] Step 1d: Add a standard copper sulfate solution dropwise to the inner wall of the billet tube. The standard copper sulfate solution is: CuSO4·5H2O 41g / L + NaCl 35g / L. The color development time is >60 seconds, corresponding to a film thickness of 3μm. Adjust according to the film thickness. If the corresponding film thickness exceeds the range of 3±0.5μm, if the film thickness is insufficient, increase the temperature by 2℃ or extend the time by 1 minute. If the film thickness is too thick, reduce the free acid point by 0.2 or dilute the phosphating solution by 5%. The corresponding film thickness is controlled at 3±0.5μm to reduce the extrusion pressure during cold extrusion by 25%~30%.

[0047] Step 2: Anneal the billet tube according to steps 2a to 2b:

[0048] Step 2a: Recrystallize and anneal the cold-rolled billet tube under a protective atmosphere to eliminate work hardening. The annealing temperature is 650~710℃, the holding time is 20~30 minutes, and the cooling method should be slow to avoid the generation of new stress.

[0049] Step 2b: After annealing, the grain size is ASTM grade 7~8 and the hardness is ≤110HV to ensure uniform material flow during subsequent cold extrusion and reduce the risk of cracking.

[0050] Step 3: Clean the surface of the billet tube according to steps 3a to 3d:

[0051] Step 3a: Immerse in a hot alkaline solution at 60-80℃ for 5-10 minutes to thoroughly remove rolling oil and impurities. The hot alkaline solution is a mixed solution of NaOH and Na2CO3.

[0052] Step 3b: The hydrochloric acid concentration is 10%~15%, the temperature is ≤40℃, and the soaking time is 5~15 minutes. The soaking time is adjusted according to the thickness of the oxide scale to remove oxides and achieve a surface without oxide black spots, with a silver-gray metallic color.

[0053] Step 3c: Rinse the billet tube with running water until it is neutral to avoid residual acid corroding the substrate.

[0054] Step 3d involves passivating the billet tube using a chromate solution. After passivation, a nano-scale oxide film is formed on the surface of the billet tube to prevent rusting during storage.

[0055] Step 4: Prepare the lubricating layer according to steps 4a to 4c:

[0056] Step 4a, zinc phosphating, can be done using ZnCa2(PO4)2 type phosphating solution to form a 5~10μm microporous phosphating film with a film weight of 1.5~3.0g / m², thereby improving the lubricant adsorption capacity.

[0057] Step 4b: After washing, dry at a temperature of 100~120℃.

[0058] Step 4c: Dip the material in sodium stearate or lithium-based soap solution to form a saponified film that evenly covers the surface of the billet tube, reducing the coefficient of friction in cold extrusion to below 0.05 and improving the uniformity of material flow during cold extrusion.

[0059] Step 5: Following steps 5a to 5b, cold extrude the billet tube within the mold to form the outer cylinder of the damper with a thrust boss.

[0060] Step 5a: Place the blank tube 1 inside the die 6, insert the mandrel 2 into the blank tube 1, and position the mandrel 2-1 through the limiting assembly 7 to control the axial height of the thrust boss on the outer cylinder wall of the shock absorber.

[0061] Step 5b: The hydraulic press applies pressure to the top of the mandrel 2, and the polyurethane elastic element of the mandrel 2 deforms, gradually squeezing the outer wall of the blank tube 1, causing the blank tube 1 to flow into the groove 6-2 of the die 6, and gradually fill the space between the mandrel 2 and the die 6, forming a shock absorber outer cylinder with a thrust boss.

[0062] Using the above method, E195+LC pipe with a wall thickness of 1.8mm was processed to form three thrust bosses on the outer cylinder of the shock absorber, with a height of 1.2±0.1mm. Testing showed that the forming time for a single piece of the shock absorber outer cylinder was 18s, a significant improvement compared to the 120s required for turning and welding processes; the material utilization rate was 98%, superior to the 85% of the traditional process; the thrust bosses achieved a compressive strength of 850MPa, meeting the requirements of 100,000 spring impact tests. It is evident that this method offers short processing time and minimal material waste. It not only avoids damaging the continuity of the metal fibers in the billet pipe but also, through extrusion molding, makes the finished shock absorber outer cylinder more compact, stronger, and increases fatigue life by 2.3 times.

[0063] The mold structure of this utility model, combined with the material processing technology, improves the dimensional accuracy and surface quality of the thrust boss forming; the cold extrusion process increases the forming efficiency by 40%, the material utilization rate reaches 98%, and through the work hardening effect, the strength of the parts is increased by more than 15%, further extending the service life.

[0064] This invention utilizes a split-type concave module design, allowing material to flow more evenly into the concave die groove during extrusion, ensuring consistent forming of each thrust boss. The split-type concave module provides space for material flow and expansion, and in conjunction with the polyurethane elastic element of the mandrel, the progressive radial expansion force helps guide material flow, preventing pipe cracking caused by excessive local stress. The height-adjustable limiting assembly can precisely control the axial height of the thrust boss, ensuring that the part dimensions meet design requirements.

Claims

1. A cold extrusion die for a thrust boss on the outer cylinder of a shock absorber, comprising a mandrel (2), a die (6), a die cavity (5), a die shell (3), a base (4), and a limiting assembly (7), characterized in that: The bottom of the mold shell (3) is fixed to the base (4). The interior of the mold shell (3) has a space to accommodate the mold cavity (5) and the limiting assembly (7). The mold cavity (5) is fixed to the top of the mold shell (3). The interior of the mold cavity (5) has a countersunk hole. A die (6) is installed in the countersunk hole. The die (6) is annular. The upper part of the inner wall of the die (6) is provided with a groove (6-2) for forming a thrust boss. The limiting assembly (7) is installed on the base (4) directly below the mold cavity (5). The upper end of the limiting assembly (7) is inserted into the countersunk hole of the mold cavity (5) from below. The mandrel (2) is inserted into the countersunk hole of the mold cavity (5) from above. The blank tube (1) is located between the mandrel (2) and the die (6). The bottom of the mandrel (2) abuts against the upper end of the limiting assembly (7). The aforementioned die (6) is a split structure composed of three die modules (6-1). The core rod (2) includes a main body (2-3), a polyurethane elastic element (2-2), and a rod head (2-1). The polyurethane elastic element (2-2) is snapped into the end of the main body (2-3), and the rod head (2-1) is snapped into the end of the polyurethane elastic element (2-2).

2. The cold extrusion die for the thrust boss of the outer cylinder of a shock absorber according to claim 1, characterized in that: The mold shell (3) is a machined steel shell.

3. The cold extrusion die for the thrust boss of the outer cylinder of a shock absorber according to claim 1, characterized in that: The mold shell (3) and the base (4), the mold cavity (5) and the mold shell (3), and the base (4) and the limiting assembly (7) are fixed with fixing screws (8).

4. The cold extrusion die for the thrust boss of the outer cylinder of a shock absorber according to claim 1, characterized in that: The inner wall of the concave mold (6) is provided with a step (6-3) at the bottom, and the bottom of the countersunk hole is provided with a mounting groove (5-1). The step (6-3) is engaged with the mounting groove (5-1).

5. The cold extrusion die for the thrust boss of the outer cylinder of a shock absorber according to claim 1, characterized in that: The recessed module (6-1) is a C-shaped metal block.

6. The cold extrusion die for the thrust boss of the outer cylinder of a shock absorber according to claim 1, characterized in that: The limiting assembly (7) includes a T-shaped adjusting block (7-1), an adjusting ring (7-2), a limiting ring (7-3), and a locking screw (7-4). The upper part of the T-shaped adjusting block (7-1) is a threaded post, and the side of the threaded post has a limiting surface (7-1-1) arranged along the axial direction. The limiting ring (7-3) and the adjusting ring (7-2) are sleeved on the threaded post. The limiting ring (7-3) is threadedly connected to the threaded post. The adjusting ring (7-2) presses on the limiting ring (7-3). The adjusting ring (7-2) has a threaded hole (7-2-1) arranged along the circumferential direction. The locking screw (7-4) is threadedly connected to the threaded hole (7-2-1), and the end of the locking screw (7-4) abuts against the limiting surface (7-1-1).

7. The cold extrusion die for the thrust boss of the outer cylinder of a shock absorber according to claim 1, characterized in that: The interior of the main rod (2-3) is a hollow structure.

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