Double-click forming die and forming process of U-shaped fork head of intermediate shaft of automobile steering system

Abstract

The invention relates to a double-click forming mold and a forming process for a U-shaped fork head of an intermediate shaft of an automobile steering system. The double-click forming mold comprises an upper mold assembly and a lower mold assembly. The lower mold assembly is provided with a lower concave mold for placing a workpiece, and a fork head forming cavity for forming the U-shaped fork head is provided in the upper concave mold; the upper mold assembly is connected to an upper mold plate of a hydraulic press and moves up and down with the upper mold plate of the press; the upper mold assembly comprises a first upper punch and a second upper punch respectively used in conjunction with the fork head forming cavity, the first upper punch and the second upper punch are connected side by side on a horizontal sliding member, the horizontal sliding member is suspended on a guide rail in the upper mold assembly, and slides horizontally along the guide rail under the drive of a horizontal driving mechanism; the automobile steering system intermediate shaft forming process combines the two processes of upsetting and back extrusion of the U-shaped fork head into one process, thereby eliminating the influence of cold work hardening between the two processes, saving the annealing process, improving the mold life and production efficiency, and reducing the production cost.

Description

Technical Field

[0001] The invention belongs to the field of automobile parts processing, and in particular relates to a U-shaped fork double-click forming die and a forming process for an intermediate shaft of an automobile steering system. Background Art

[0002] The intermediate shaft of the automobile steering system is one of the core components of the automobile transmission system. It includes a male shaft and a female shaft, which are connected by spline sliding. One end of the male shaft of the intermediate shaft is a U-shaped fork head, and the rest is a connecting rod, which is processed with a slideway, that is, an external spline.

[0003] At present, there are two main solutions for processing the intermediate shaft male shaft:

[0004] Option 1: The intermediate shaft uses an annealed billet with a diameter similar to that of its connecting rod. The head is first upset, then annealed, and then reversely extruded to form a U-shaped fork head. Alternatively, the U-shaped fork head is reversely extruded without annealing and heated to 900°C.

[0005] Solution 2: The intermediate shaft uses an annealed billet with a diameter similar to that of the connecting rod, and cold extrude one end of the bar stock to make the material flow radially to form a T-shaped head to obtain a T-shaped billet, and then bend the two wings of the T-shaped head towards each other to form an arc to obtain a U-shaped fork and a U-shaped fork inner groove at the end of the male shaft. For details of this solution, please refer to the patent previously applied by the inventor: CN201911345824.1.

[0006] The above two solutions have the following disadvantages:

[0007] For Option 1, during the forming process, the head needs to be annealed after upsetting and then reversely extruded to form a U-shaped fork head, or the head needs to be heated instead of annealed after upsetting and then reversely extruded to form a U-shaped fork head; for the former, the processing cost is relatively high, and for the latter, not only the processing cost is high, but also the mold life is relatively low.

[0008] For Option 2, when the material flows radially, the mold is subjected to greater force at the rounded corners of the two wings of the T-head, resulting in a shorter mold life. In addition, the residual burrs in the cylindrical area of ​​the extrusion end of the T-head need to be cleaned, increasing production costs. In the subsequent bending process, there is a risk of cracking in the outer arc part of the fork head. Summary of the invention

[0009] The purpose of the present invention is to provide a double-click forming die and forming process for a U-shaped fork head of an intermediate shaft of an automobile steering system. The die combines the two processes of upsetting and back-extrusion of the U-shaped fork head into one process, thereby eliminating the influence of cold working hardening between the two processes, saving the annealing process, improving the die life and production efficiency, and reducing the production cost.

[0010] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a double-click forming mold for a U-shaped fork head of an intermediate shaft of an automobile steering system, comprising an upper mold assembly and a lower mold assembly, the lower mold assembly is provided with a lower concave mold for placing a workpiece, and the upper concave mold is provided with a fork head forming cavity for forming the U-shaped fork head; the upper mold assembly is connected to the upper mold plate of the hydraulic press, and moves up and down with the upper mold plate of the press, the upper mold assembly includes a first upper punch and a second upper punch respectively used in conjunction with the fork head forming cavity, the first upper punch and the second upper punch are connected side by side on a horizontal sliding member, the horizontal sliding member is suspended on a guide bar in the upper mold group, and slides horizontally along the guide bar driven by a horizontal driving mechanism.

[0011] The punch fixing seat of the first upper punch is connected to the connecting dovetail sub-seat of the upper mold assembly, the punch fixing seat of the second upper punch is connected to the station fixing seat plate of the upper mold assembly, and the connecting dovetail sub-seat and the station fixing seat plate are fixedly connected to the horizontal sliding member.

[0012] Two retreat guide bars are symmetrically arranged outside the mold core of the second upper punch. The retreat guide bars are slidably arranged along the outer surface of the mold core, and each retreat guide bar is connected to a lever.

[0013] A spring slide bracket is arranged on the side of the punch fixing seat of the second upper punch, a slide is arranged in the spring slide bracket, and a spring is installed in the slide, one end of the lever is rotatably connected to the spring slide bracket as a fulcrum, the other end of the lever is rotatably connected to the retreat guide strip, and the upper part of the lever near the fulcrum presses on the spring.

[0014] A lubricant groove is provided in the lower die assembly, and the lubricant groove is located directly below the initial position of the second upper punch. When the first upper punch is pressed downward toward the fork head forming cavity, the core of the second upper punch enters the lubricant groove to dip in the lubricant.

[0015] A forming process for an intermediate shaft of an automobile steering system comprises the following steps: pre-treating an annealed cold-drawn bar stock to obtain a shaft part with a thin rod portion, wherein one end of the shaft part is a thick-diameter end for forming a U-shaped fork head, and the rest of the shaft part is a thin rod portion with a diameter smaller than the thick-diameter end; then, the thick-diameter end of the shaft part is cold-extruded twice by using the double-click forming die to form a U-shaped fork head; and then, the part with the formed U-shaped fork head is post-treated to obtain a finished intermediate shaft of an automobile steering system.

[0016] In the above process, when the double-click forming mold successively cold-extrudes the thick-diameter end of the shaft part, the core of the first upper punch is first used to upset the thick-diameter end of the part downward, and at the same time, the second upper punch moves downward synchronously, and the core of the second upper punch dips the lubricant in the lubricant groove; then, the upper mold plate of the press drives the first upper punch and the second upper punch to return, and then the horizontal driving mechanism pushes the first upper punch and the second upper punch to move horizontally, so that the second upper punch is located directly above the fork head forming cavity, and then the upper mold plate of the press descends, and the core of the second upper punch reversely extrudes the upset thick-diameter end of the part downward to obtain a U-shaped fork head.

[0017] When the second upper punch reverses and extrude the part, as the length of the U-shaped fork increases, the upper end of the fork contacts the retreat guide strip and pushes the retreat guide strip upward to retreat along the core of the second upper punch, and drives the end of the lever connected to the retreat guide strip to lift up, compressing the spring abutting the lever.

[0018] The pre-treatment includes blanking, shot blasting, film treatment and positive rod extrusion treatment.

[0019] The post-processing includes deburring the U-shaped fork head, coating the parts and performing slideway processing on the thin rod part of the parts.

[0020] The beneficial effect of the present invention is that in the conventional method, the intermediate shaft parts processed by the present invention will produce a cold work hardening effect during the head upsetting and reverse extrusion processes, so it is necessary to add an annealing process between the two processes to eliminate the influence of the head hardening effect on the mold life of the reverse extrusion process. After adopting the double-click forming mold described in the present invention, the two processes of head upsetting and reverse extrusion are combined into one process for continuous processing, which can avoid the influence of cold work hardening (the influence is mainly the reduction of mold life), and also eliminate the intermediate annealing process, reducing production costs. Moreover, this process is carried out on a single-station hydraulic press, which effectively improves the disadvantage that a single-station equipment can only process one process at a time, thereby improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural cross-sectional view of the front side of the double-click forming die of the present invention;

[0022] Figure 2 It is a structural cross-sectional view of the front side of the lower mold assembly in the double-click molding mold of the present invention;

[0023] Figure 3 It is a structural cross-sectional view of the front side of the upper mold component in the double-click molding mold of the present invention;

[0024] Figure 4 It is a structural cross-sectional view of the side surface of the second upper punch in the double-click forming die of the present invention;

[0025] Figure 5 This is a schematic diagram of the mold structure after the first upper punch of the present invention extrude the workpiece;

[0026] Figure 6 It is a schematic diagram of the die structure before the second upper punch of the present invention extrude the workpiece;

[0027] Figure 7 This is a schematic diagram of the mold structure after the second upper punch of the present invention extrude the workpiece;

[0028] Figure 8 It is a schematic diagram of the state change of a workpiece during the forming process of the intermediate shaft of the automobile steering system according to the present invention;

[0029] Markings in the figure: 1. Lock nut for top cylinder suspension rod, 2. Top cylinder frame plate of press, 3. Replacement of gaskets at four corners, 4. Block on the back of press, 5. Universal push rod of press, 6. Pressing and quenching insert, 7. Inverted T-type ejector, 8. Thickening and height adjustment pad, 9. Main bearing pad, 10. Tail reduction core, 11. Correction cavity inner core, 12. Correction cavity outer sleeve, 13. Forming cavity core, 1301, fork head forming cavity, 14. Forming cavity middle sleeve, 15. Forming cavity outer sleeve, 16. Stepped cylinder seat, 17. Lower large cover nut, 18. First upper punch, 1801, first upper core, 1802, first Upper die center ring, 1803, first punch fixing seat, 1804, pad, 19, second upper punch, 1901, second upper die core, 1902, second upper die center ring, 1903, second punch fixing seat, 1904, main bearing dividing pad, 1905, slide, 20, station fixing seat plate, 21, cylinder connecting groove, 22, T-type guide rail pad, 23, connecting dovetail sub-seat, 24, lubricant groove, 25, retreat guide strip, 26, variable range lever, 27, spring slide bracket, 28, spring, 29, slide, 30, press upper template, 31, press guide strip.

[0030] 100. Bar stock, 200. Shaft parts with thin rods, 300. Upset parts, 400. U-shaped fork parts, 500. Parts with slideways, 600. Finished intermediate shafts. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the invention in any way.

[0032] Example 1: A double-click forming mold for a U-shaped fork of an intermediate shaft of an automobile steering system, comprising an upper mold assembly and a lower mold assembly, wherein the upper mold assembly is mounted on an upper mold plate of a hydraulic press and moves up and down with the upper mold plate of the press, and the lower mold assembly is connected to the bottom plate of a lower beam of the press.

[0033] The lower die assembly includes a top cylinder hanger lock nut 1, a press top cylinder frame plate 2, four corner replacement gaskets 3, a press back block 4, a press universal push rod 5, a clamping quenching insert 6, an inverted T-shaped ejector 7, a thickening height adjustment pad 8, a main bearing pad 9, a tail reduction core 10, a correction cavity inner core 11, a correction cavity outer sleeve 12, a molding cavity core 13, a molding cavity middle sleeve 14, a molding cavity outer sleeve 15, a step mold cylinder seat 16 and a lower large cover nut 17.

[0034] The press back block 4 and the press top cylinder frame plate 2 are connected to the lower surface of the press lower beam bottom plate through bolts and top cylinder hanger lock nuts 1. Four bolts are provided, which are distributed at the four corners of the press back block 4, and four-corner replacement gaskets 3 are provided between the press back block 4 and the press lower beam bottom plate and between the press back block 4 and the press top cylinder frame plate 2. A through hole that passes through from top to bottom is provided in the middle of the press back block 4, a sink is provided at the upper end of the through hole, and a clamping quenching insert 6 is installed in the sink. The clamping quenching insert 6 and the press back block 4 are transitionally matched. The clamping quenching insert 6 is used to receive the inverted T-shaped top piece 7 above. The universal push rod 5 of the press passes through the through hole of the press back block 4 and the clamping quenching insert 6 from bottom to top, supporting the lower end of the inverted T-shaped top piece 7. The inverted T-shaped top piece 7 is movably arranged in the through hole of the bottom plate of the lower beam of the press, and the inverted T-shaped top piece 7 passes through the bottom plate of the lower beam of the press upward. A thickening and height-adjusting pad 8 is placed on the upper surface of the bottom plate of the lower beam of the press and connected with bolts. A cylindrical step die cylinder seat 16 is bolted to the upper surface of the thickening and height-adjusting pad 8. A main bearing pad 9 and a lower concave die are arranged in the step die cylinder seat 16. The main bearing pad and the thickening and height-adjusting pad 8 are connected with bolts and pressed against the thickening and height-adjusting pad 8 by the step surface of the inner wall of the step die cylinder seat 16.

[0035] The lower concave mold includes a tail diameter reduction mold core 10, a correction cavity inner core 11, a correction cavity outer sleeve 12, a molding cavity mold core 13, a molding cavity middle sleeve 14 and a molding cavity outer sleeve 15. The inner hole of the tail diameter reduction mold core 10 is used to form the diameter reduction structure of the tail end of the intermediate shaft, the tail diameter reduction mold core 10 and the correction cavity inner core 11 are installed in the inner hole of the correction cavity outer sleeve 12, and the tail diameter reduction mold core 10 is located below the correction cavity inner core 11, and the tail diameter reduction mold core 10 and the correction cavity inner core 11 are both interference fit with the correction cavity outer sleeve 12. The molding cavity mold core 13, the molding cavity middle sleeve 14 and the molding cavity outer sleeve 15 are arranged in sequence from the inside to the outside in the radial direction, and are located above the correction cavity outer sleeve 12, and the molding cavity mold core 13 and the molding cavity middle sleeve 14, and the molding cavity middle sleeve 14 and the molding cavity outer sleeve 15 are in an interference fit relationship. The forming cavity core 13, the correction cavity inner core 11 and the tail diameter reduction core 10 form a cavity for placing the workpiece, and the upper end of the cavity is a fork head forming cavity 1301 located in the forming cavity core 13 for forming the U-shaped fork head of the intermediate shaft. The forming cavity jacket 15 and the correction cavity jacket 12 are connected by bolts, and the outer circumferential surface of the forming cavity jacket 15 is provided with a positioning step, and the lower large cover nut 17 is pressed against the positioning step of the forming cavity jacket 15, and the lower large cover nut 17 is bolted to the step mold cylinder seat 16.

[0036] A lubricant groove 24 is provided on the outer side of the step die cylinder seat 16 to contain lubricant.

[0037] The upper die assembly includes a first upper punch 18 , a second upper punch 19 , a connecting dovetail sub-seat 23 and a station fixed seat plate 20 .

[0038] The first upper punch 18 is used to perform upsetting on the workpiece head. The first upper punch 18 includes a first upper die core 1801, a first upper die middle ring 1802 and a first punch fixing seat 1803 arranged from the inside to the outside. The first upper die core 1801 and the first upper die middle ring 1802 are fitted by cylindrical interference, the first upper die middle ring 1802 and the first punch fixing seat 1803 are fitted by conical interference, and a cushion block 1804 is also assembled in the first punch fixing seat 1803 by interference fit. The upper end surfaces of the first upper die core 1801 and the first upper die middle ring 1802 are pressed against the cushion block 1804. The first punch fixing seat 1803 is arranged in the C-shaped dovetail sub-seat 23, and the upper part of the first punch fixing seat 1803 is hung on the dovetail sub-seat 23.

[0039] The second upper punch 19 is used for reverse-extrusion of the workpiece head after upsetting to form a U-shaped fork head of the part. The second upper punch 19 includes a second upper die core 1901, a second upper die middle circle 1902 and a second punch fixing seat 1903 which are arranged from the inside to the outside. The second upper die core 1901 and the second upper die middle circle 1902 are fitted with a cylindrical interference fit, and the second upper die middle circle 1902 and the second punch fixing seat 1903 are fitted with a conical interference fit. A main bearing splitting pad 1904 is also assembled in the second punch fixing seat 1903 by a clearance fit, and the upper end faces of the first upper die core 1901 and the first upper die middle circle 1902 are pressed against the main bearing splitting pad 1904. The second punch fixing seat 1903 is connected to the station fixing seat plate 20, the station fixing seat plate 20 is fixedly connected to the connecting dovetail sub-seat 23, and the station fixing seat plate 20 and the connecting dovetail sub-seat 23 are both connected to the T-type guide rail pad 22, the T-type guide rail pad 22 is slidably arranged on the press guide rail bar 31, the press guide rail bar 31 is fixedly connected to the press upper template 30, and a cylinder connecting groove 21 is arranged on one side of the T-type guide rail pad 22, and a horizontal cylinder for pushing the T-type guide rail pad 22 to slide horizontally is threadedly connected to the cylinder connecting groove 21. The first upper punch 18 and the second upper punch 19 are pushed to move horizontally by the extension and contraction of the cylinder piston rod to switch the upper punch that cooperates with the lower die assembly.

[0040] In the second upper punch 19, two retreat guide strips 25 are respectively arranged on opposite sides of the second upper mold core 1901, and the retreat guide strips 25 are slidably arranged in the slide grooves 1905 of the second upper mold center ring 1902 and the main bearing splitting pad 1904, and the retreat guide strips 25 are fitted with the second upper mold core 1901. A notch is arranged on the side of the retreat guide strip 25 to connect the range-changing lever 26. A spring slide bracket 27 is arranged on the outside of the second punch fixing seat 1903 of the second upper punch 19, and the spring slide bracket 27 is fixedly connected to the second punch fixing seat 1903 or the upper mold plate 30 of the press, and a slide 29 for installing a spring 28 is arranged in the spring slide bracket 27, and the lower part of the spring slide bracket 27 is rotatably connected to one end of the range-changing lever 26, and a movable space for the range-changing lever 26 to move up and down is arranged in the spring slide bracket 27, and the movable space is connected to the slide 29 so that the spring 28 can abut against the boss on the upper part of the range-changing lever 26; the second punch fixing seat 1903 is provided with a movable groove for the range-changing lever 26 to pass through and move up and down, and the range-changing lever 26 extends into the slide groove 1905 of the second upper mold middle circle 1902 through the movable groove, and is rotatably connected through the pin shaft and the notch on the side of the retreat guide strip 25.

[0041] When the fork portion of the workpiece is counter-extruded by the second upper punch 19, the fork extends upward to push up the retreat guide strip 25, so that the retreat guide strip 25 moves up along the second upper die core 1901, and lifts the range-changing lever 26 to compress the spring 28. During the return stroke of the press upper die plate 30, the elastic force of the spring 28 is released, and the retreat guide strip 25 is driven to move downward through the range-changing lever 26 to return to the initial position. The setting of the retreat guide strip 25 can guide the second upper punch 19 on the one hand, and reasonably distribute the gap on both sides of the second upper die core 1901 on the other hand, to ensure that the thickness of the fork portion of the part is uniform.

[0042] Embodiment 2: A molding process of an intermediate shaft of an automobile steering system, wherein the material thereof is SCM415H, comprises the following steps:

[0043] Step 1: Use annealed cold drawn bar stock for cutting to obtain Figure 8 The bar 100 shown in the figure has the following requirements for the annealed cold drawn bar: the outer diameter is ∅24.9±0.05, the outer circle has no cracks, slag inclusions and other defects, the roughness is within Ra3.2, and the annealing hardness is ≤120HB;

[0044] Step 2: Shot blasting, using stainless steel shot with a diameter of 0.6 mm, for 10 to 15 minutes;

[0045] Step 3: film treatment, using phosphorus saponification treatment or graphene lubrication + saponification treatment;

[0046] Step 4: Squeeze the rod to form a Figure 8 The shaft part 200 with a thin rod portion shown in the figure has one end as a thick-diameter end for forming a U-shaped fork head, and the rest of the shaft part is a thin rod portion with a diameter smaller than the thick-diameter end, which is used for subsequent processing of a slideway;

[0047] Step 5, double-click molding. This process uses the double-click molding mold described in Example 1, which is mainly used to mold the fork head part of the part on the hydraulic press. The mold is a one-die and two-punch structure. The fork head molding steps are as follows: the first upper punch is used to upset the large end of the rod to fill the fork head molding cavity 1301 of the mold; the second upper punch is used to mold the large end after upsetting into a fork head. The extrusion of the two punches is performed in the same concave mold cavity. The fork head is formed by one process, which avoids the annealing process caused by cold work hardening caused by the upsetting process, and also avoids the short mold life caused by cold work hardening caused by upsetting without annealing, and saves processes, improves production efficiency, and reduces manufacturing costs.

[0048] Step 6, deburring: Use polishing to remove the burrs on the edges of the fork head;

[0049] Step 7: Film treatment: phosphorus saponification treatment or graphene lubrication + saponification treatment;

[0050] Step 8: Slideway processing: Process the slideway on the thin rod part of the part in the positive extrusion process as the connecting part of the intermediate shaft of the automobile steering system, that is, Figure 8 The slideway part 500 is shown;

[0051] Step nine, turning the cylindrical end face to form the tail end of the slideway portion of the intermediate shaft of the automobile steering system, thus completing the processing of the finished product 600 of the intermediate shaft of the automobile steering system.

[0052] In the above steps, the specific steps of double-click molding are:

[0053] (1) The workpiece after positive extrusion is placed in the forming cavity core 13 and the correction cavity inner core 11. The upper die plate 30 of the press moves downward, driving the upper die assembly to press down together. At this time, the first upper die core 1801 of the first upper punch 18 contacts the workpiece, so that the head of the workpiece is upset and fills the cavity, and the following is obtained: Figure 8 In the upsetting part 300 shown, while the first upper punch 18 extrude the workpiece, the second upper punch 19 moves downward synchronously, and the second upper die core 1901 of the second upper punch 19 enters the lubricant groove 24 to dip in lubricant.

[0054] (2) The upper mold plate 30 of the press drives the upper punch assembly to return.

[0055] (3) The horizontal oil cylinder pushes the T-shaped guide rail pad 22 to move horizontally along the press guide rail 31, driving the first upper punch 18 and the second upper punch 19 to move horizontally, so that the second upper punch 19 finally stops above the molding cavity core 13.

[0056] (4) The upper die plate 30 of the press moves downward again, and the second upper die core 1901 of the second upper punch 19 contacts and extrude the head of the upsetting part 300 obtained in the above process to form a U-shaped fork head, that is, Figure 8 The U-shaped fork head part 400 is shown; during the U-shaped fork head forming process, as the length of the fork increases, the top end of the fork contacts the retreat guide strip 25 and pushes the retreat guide strip 25 upward and retreats along the second upper mold core 1901. At the same time, the variable range lever 26 connected to the retreat guide strip 25 is lifted, compressing the spring 28.

[0057] (5) The upper template 30 of the press machine returns, and at the same time, the compressed spring 28 releases its elastic force, pushing the variable range lever 26 to drive the retreat guide bar 25 to slide downward to its original position.

[0058] (6) The return stroke of the horizontal oil cylinder piston generates a pulling force, which pulls the T-shaped guide rail pad 22 to drive the first upper punch 18 and the second upper punch 19 to move horizontally, so that the first upper punch 18 returns to the top of the molding cavity core 13.

[0059] (7) Use the universal ejector rod 5 of the press to lift the inverted T-shaped ejector 7 upward to eject the formed workpiece out of the lower die assembly.

[0060] (8) The above process is a cycle of the double-click forming mold action. By repeating the above process, the double-click forming mold can be used for continuous action to complete the double-click forming of multiple workpiece heads.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art should understand that the specific implementation modes of the present invention may be modified or replaced by equivalents with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the pending claims.

Claims

1. A double-click forming mold for a U-shaped fork of an intermediate shaft of an automobile steering system, comprising an upper mold assembly and a lower mold assembly, wherein the lower mold assembly is provided with a lower concave mold for placing a workpiece, and a fork forming cavity for forming the U-shaped fork is provided in the lower concave mold; Features: The upper die assembly is connected to the upper die plate of the hydraulic press and moves up and down with the upper die plate of the hydraulic press. The upper die assembly includes a first upper punch and a second upper punch respectively used in conjunction with the fork head forming cavity. The first upper punch and the second upper punch are connected side by side to a horizontal sliding member. The horizontal sliding member is suspended on a guide rail in the upper die assembly and slides horizontally along the guide rail driven by a horizontal driving mechanism. Two retreat guide bars are symmetrically arranged outside the mold core of the second upper punch, and the retreat guide bars are slidably arranged along the outer surface of the mold core, and each retreat guide bar is connected to a lever; A spring slide bracket is arranged on the side of the punch fixing seat of the second upper punch, a slide is arranged in the spring slide bracket, and a spring is installed in the slide, one end of the lever is rotatably connected to the spring slide bracket as a fulcrum, the other end of the lever is rotatably connected to the retreat guide strip, and the upper part of the lever near the fulcrum presses on the spring.

2. A double-click forming die for a U-shaped fork of an intermediate shaft of an automobile steering system according to claim 1, Features: The punch fixing seat of the first upper punch is connected to the connecting dovetail sub-seat of the upper mold assembly, the punch fixing seat of the second upper punch is connected to the station fixing seat plate of the upper mold assembly, and the connecting dovetail sub-seat and the station fixing seat plate are fixedly connected to the horizontal sliding member.

3. The double-click forming mold for the U-shaped fork of the intermediate shaft of the automobile steering system according to claim 1, Features: A lubricant groove is provided in the lower die assembly, and the lubricant groove is located directly below the initial position of the second upper punch. When the first upper punch is pressed downward toward the fork head forming cavity, the core of the second upper punch enters the lubricant groove to dip in the lubricant.

4. A molding process for the intermediate shaft of an automobile steering system, Features: The annealed cold-drawn bar is pre-treated to obtain a shaft part with a thin rod portion, one end of which is a thick-diameter end for forming a U-shaped fork head, and the rest of the shaft part is a thin rod portion with a diameter smaller than the thick-diameter end. The thick-diameter end of the shaft part is then cold-extruded twice using the double-click forming mold as described in any one of claims 1 to 3 to form a U-shaped fork head, and then the part with the formed U-shaped fork head is post-treated to obtain a finished intermediate shaft of an automobile steering system.

5. The molding process of the intermediate shaft of the automobile steering system according to claim 4, Features: When the double-click forming mold successively cold-extrudes the thick-diameter end of the shaft part, the core of the first upper punch is first used to upset the thick-diameter end of the part downward, and at the same time, the second upper punch moves downward synchronously, and the core of the second upper punch dips the lubricant in the lubricant groove; then, the upper mold plate of the press drives the first upper punch and the second upper punch to return, and then the horizontal driving mechanism pushes the first upper punch and the second upper punch to move horizontally, so that the second upper punch is located directly above the fork head forming cavity, and then the upper mold plate of the press moves downward, and the core of the second upper punch reversely extrude the upset thick-diameter end of the part downward to obtain a U-shaped fork head.

6. The molding process of the intermediate shaft of the automobile steering system according to claim 5, Features: When the second upper punch reverses and extrude the part, as the length of the U-shaped fork increases, the upper end of the fork contacts the retreat guide strip and pushes the retreat guide strip upward to retreat along the core of the second upper punch, and drives the end of the lever connected to the retreat guide strip to lift up, compressing the spring abutting the lever.

7. The molding process of the intermediate shaft of the automobile steering system according to claim 4, Features: The pre-treatment includes blanking, shot blasting, film treatment and positive rod extrusion treatment.

8. The molding process of the intermediate shaft of the automobile steering system according to claim 4, Features: The post-processing includes deburring the U-shaped fork head, coating the parts and performing slideway processing on the thin rod part of the parts.

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