Rotary swaging die machining device for automobile steering shaft and using method of rotary swaging die machining device

Abstract

The invention relates to the technical field of automobile part rotary swaging die machining, in particular to an automobile steering shaft rotary swaging die machining device and a using method.The automobile steering shaft rotary swaging die machining device comprises a machine table, a taking mechanism and a molding mechanism are arranged at the left end and the right end of the machine table correspondingly, and the taking mechanism is used for grabbing a shaft body workpiece attached with bio-based lubricating oil; a mold core assembly is arranged on the molding mechanism, and the molding mechanism is characterized in that the mold core assembly is composed of four mold bodies, and the four mold bodies define a molding cavity for performing 360-degree forging and pressing on a shaft body workpiece through molding surfaces so as to form a steering shaft. Through the internal and external cooperative clamping design of an L-shaped opening and closing clamp and a limiting pressurizing block in the taking mechanism, bio-based lubricating oil attached to the surface of a workpiece is evenly distributed under the action of airflow, a continuous lubricating film is formed, and the uniform film forming of the bio-based lubricating oil can reduce the friction coefficient between a mold and the shaft body workpiece and improve the machining precision of the shaft body workpiece. Local temperature rise can be restrained through the airflow cooling effect, and the surface forming quality of the automobile steering shaft is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of automotive component rotary forging die processing technology, and in particular to an automotive steering shaft rotary forging die processing device and its usage method. Background Technology

[0002] Rotary forging is a precision metal processing technology that applies high-frequency radial forging force to billets such as bars and tubes, causing them to be shaped according to the mold surface. Currently, rotary forging technology is widely used in the manufacturing of key load-bearing components such as automotive steering shafts and drive shafts.

[0003] In the rotary forging process of automotive steering shafts, the feeding method and die structure are the core factors affecting the forming quality. Existing technologies, such as the rotary forging die processing device and method disclosed in CN120551316A, employ a rigid feeding method. When the forging die closes, the die's flared opening obstructs the workpiece feed, causing material to flow in the reverse feeding direction, resulting in a greater reverse flow than forward flow. This phenomenon significantly increases the axial feed force and forging force, not only reducing die life but also easily causing defects such as dents, upsetting, and cracks in the tubular blank. The material backflow problem is particularly prominent for low-strength blanks or during hot rotary forging, directly affecting forming efficiency and surface quality.

[0004] Regarding mold structures, for example, the design method for a hollow shaft rotary forging mold disclosed in CN103861987B improves the cooling system but fails to address the motion accuracy issue during multi-mold coordinated motion. Existing rotary forging molds often employ integral structures or simple segmented designs, making it difficult to achieve precise control of radial feed when machining variable cross-section components, easily leading to excessive internal and external roundness errors or even folding defects. Another example is an automotive steering shaft mold disclosed in CN208408425U, which focuses on the mechanical stability of the mold; however, during high-frequency forging, the friction state between the mold and the workpiece is difficult to maintain stably, and uneven lubrication leads to a decline in surface quality.

[0005] Furthermore, existing rotary forging equipment operates with independent feeding and forging stations, lacking proactive means to control the lubrication state of the workpiece surface. While bio-based lubricants offer environmental advantages, they struggle to form a uniform and continuous lubricating film on the workpiece surface during high-speed rotary forging, severely limiting the formation of high-quality forgings. For processing difficult-to-deform materials used in manufacturing automotive steering shafts, existing equipment still exhibits significant shortcomings in microstructure control and surface integrity management. Summary of the Invention

[0006] The purpose of this invention is to solve the problem that the difficulty in performing rotary forging on shaft workpieces in the prior art affects the forming quality of automobile steering shafts, and to propose an automobile steering shaft rotary forging die processing device and its usage method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A machining device for forging automotive steering shafts includes a machine base, with a picking mechanism and a molding mechanism respectively installed at the left and right ends of the machine base. The picking mechanism is used to grip the shaft workpiece coated with bio-based lubricating oil, and the molding mechanism is equipped with a mold core assembly.

[0009] The mold core assembly consists of four mold bodies. The inner walls of the four mold bodies are provided with forming surfaces, and the four mold bodies form a plastic cavity through the forming surfaces for forging and pressurizing the shaft workpiece in 360° to form a steering shaft.

[0010] The picking mechanism includes a first drive shaft, on which a set of L-shaped opening and closing clamps and a set of limiting pressure blocks are provided. The set of L-shaped opening and closing clamps is used to close and hold the outer wall of the middle end of the shaft workpiece, and the set of limiting pressure blocks is used to expand and support the inner wall of the opening of the shaft workpiece. The picking mechanism drives the limiting pressure blocks through the first drive shaft to spirally transport the shaft workpiece into the molding cavity in a clockwise rotation manner.

[0011] The molding mechanism includes a second drive shaft fixedly connected to a load-bearing inner cylinder for housing the mold core assembly. An eccentric actuator for driving the radial opening and closing adjustment of the four mold bodies is provided at the middle position of the load-bearing inner cylinder. A magnetostrictive actuator for driving the uniform coating of bio-based lubricating oil onto the shaft workpiece is provided at the left end position of the load-bearing inner cylinder.

[0012] Preferably, a movable bracket for rotatably mounting the first drive shaft is slidably installed at the left end of the machine base, and an explosion-proof outer cylinder for rotatably mounting the second drive shaft is fixedly installed at the right end of the machine base.

[0013] Preferably, the molding surface is composed of a horizontal curved surface, a first inclined curved surface and a second inclined curved surface connected in sequence, and the opening diameter of the molding cavity corresponding to the horizontal curved surface, the first inclined curved surface and the second inclined curved surface decreases in sequence.

[0014] Preferably, the L-shaped opening and closing clamp has an arc-shaped groove at the end corresponding to the outer wall surface of the workpiece, and the outer wall of the limiting pressure block is an arc-shaped structure corresponding to the inner wall surface of the workpiece.

[0015] Preferably, the second drive shaft is coaxial with the first drive shaft, and the load-bearing inner cylinder is concentrically arranged inside the explosion-proof outer cylinder via the second drive shaft.

[0016] Preferably, the load-bearing inner cylinder has multiple guide notches corresponding to the eccentric actuator at the middle position, and the multiple guide notches are circumferentially equidistant.

[0017] Preferably, the eccentric actuator includes four limiting strips fixedly installed in the load-bearing inner cylinder, and there is a guide hole between two adjacent limiting strips for slidingly mounting a mold body, the mold body moving radially along the guide hole.

[0018] Preferably, the magnetostrictive actuator includes a right-angle cavity located at the left end of the limiting strip, and the limiting strip has a three-way channel that connects the right-angle cavity and the molding cavity in one direction. An elastic pressure-boosting piston is slidably fitted into the opening at one end of the three-way channel.

[0019] Preferably, one-way valves are provided at both ends of the three-way channel connecting the right-angle cavity and the molding cavity.

[0020] A method of using the above-mentioned automotive steering shaft rotary forging die processing device, the method comprising the following steps:

[0021] Step S1: Adhere bio-based lubricating oil onto the shaft workpiece;

[0022] Step S2: On the first drive shaft, control the L-shaped opening and closing clamp to close to clamp the outer wall of the middle end of the shaft workpiece to the left. At the same time, drive the limiting pressure block to open to expand to the right and abut in the opening of the shaft workpiece. Control the moving bracket to move to the right and control the first drive shaft to rotate clockwise so that the shaft workpiece spirals into the molding cavity.

[0023] Step S3: Control the second drive shaft to rotate counterclockwise, driving the load-bearing inner cylinder and the limiting strip to rotate synchronously. That is, start the magnetostrictive actuator to make the elastic booster piston extend and retract in the three-way cavity to draw the gas in the right-angle cavity into the molding cavity, so as to drive the shaft workpiece passing through the molding cavity with wind power, so that the bio-based lubricating oil is evenly distributed on the surface of the shaft workpiece.

[0024] Step S4: Activate the eccentric driver to make the mold move radially along the guide hole to forge and press the shaft workpiece with bio-based lubricant evenly coated with 360°, and use the horizontal curved surface, the first inclined curved surface and the second inclined curved surface to shape the shaft workpiece into a steering shaft.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention utilizes the internal and external collaborative clamping design of the L-shaped opening and closing clamp and the limiting pressure block in the picking mechanism to expand the inner wall of the support opening while clamping the outer wall of the middle end of the shaft workpiece, thereby improving the stability and coaxiality of the workpiece clamping. The workpiece is driven by the first driving shaft to spirally enter the molding cavity in a clockwise rotation manner, changing the force mode of the traditional rigid linear feeding. The spiral conveying method helps to offset the reverse resistance generated when the forging die closes, thereby solving the problem in the prior art where the reverse flow rate is greater than the forward flow rate due to the material flowing in the reverse feeding direction.

[0027] 2. This invention adopts a mold core assembly structure with an eccentric driver and an elastic cross key. The four mold bodies are driven to move synchronously radially along the guide hole through the intermittent contact between the crescent-shaped protrusion and the limiting pulley. This structure helps to achieve 360° circumferential uniform forging, thereby reducing the forging blind zone. The forming surface on the mold body is composed of a transverse curved surface, a first inclined curved surface and a second inclined curved surface connected in sequence, with the opening diameter decreasing. The variable diameter design makes the force gradient of the shaft workpiece controllable during radial compression, effectively suppressing the generation of rotary forging folding defects.

[0028] 3. This invention introduces a magnetostrictive actuator structure. By energizing the conductive wire group, the interaction between the electromagnet and the magnetic poles of the permanent magnet pressing component is controlled, driving the elastic booster piston to reciprocate in the three-way cavity. This intermittently extracts the gas in the right-angle cavity into the molding cavity. By using airflow to drive the shaft workpiece in the molding cavity, the bio-based lubricating oil adhering to the workpiece surface is evenly distributed under the action of airflow, forming a continuous lubricating film. The uniform film formation of the bio-based lubricating oil not only reduces the friction coefficient between the mold and the shaft workpiece, but also suppresses local temperature rise through airflow cooling, ensuring the surface molding quality of the automotive steering shaft. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a rotary forging die processing device for automotive steering shafts proposed in this invention;

[0030] Figure 2 This is a bottom view of a machining device for a rotary forging die for an automobile steering shaft, as proposed in this invention.

[0031] Figure 3 This is a front sectional view of a machining device for a rotary forging die for an automobile steering shaft, as proposed in this invention.

[0032] Figure 4 This is a top sectional view of a machining device for a rotary forging die for an automobile steering shaft, as proposed in this invention.

[0033] Figure 5 This is a schematic diagram of the picking mechanism structure of an automotive steering shaft rotary forging die processing device proposed in this invention;

[0034] Figure 6 This is a schematic diagram of the core assembly structure of a rotary forging die processing device for automotive steering shafts proposed in this invention;

[0035] Figure 7 This is a schematic diagram of the molding mechanism of a rotary forging die processing device for automotive steering shafts proposed in this invention;

[0036] Figure 8 This is a schematic diagram of the load-bearing inner cylinder structure of a rotary forging die processing device for automobile steering shafts proposed in this invention;

[0037] Figure 9 This is an enlarged schematic diagram of part A of the automotive steering shaft rotary forging die processing device proposed in this invention;

[0038] Figure 10 This is a schematic diagram of the limiting strip distribution structure of a machining device for a rotary forging die of an automobile steering shaft proposed in this invention;

[0039] Figure 11 This is a cross-sectional view of a magnetostrictive actuator for a rotary forging die processing device for automotive steering shafts proposed in this invention.

[0040] Figure 12 This is an enlarged schematic diagram of part B of the automotive steering shaft rotary forging die processing device proposed in this invention;

[0041] Figure 13 This is a schematic diagram illustrating the transformation from a shaft workpiece to an automotive steering shaft.

[0042] In the picture:

[0043] 1. Machine base; 2. Movable support frame; 3. Explosion-proof outer cylinder;

[0044] 4. Picking mechanism; 41. First drive shaft; 42. Loading disc; 43. First traction frame; 44. Pressure boosting wedge; 45. L-shaped opening and closing clamp; 46. Bayonet; 48. Arc-shaped slot; 49. Moving block; 410. Guide boss; 411. Elastic limiting post; 412. Second traction frame; 413. Limiting pressure boosting block; 414. Synchronous slider;

[0045] 5. Mold core assembly; 51. Mold body; 52. Molding surface; 53. Molding cavity; 54. Double-layer retaining block;

[0046] 6. Molding mechanism; 61. Second drive shaft; 62. Load-bearing inner cylinder; 63. Guide notch;

[0047] 64. Eccentric actuator; 641. Crescent-shaped protrusion; 642. Limiting strip; 643. Mounting rod; 644. Guide rail block; 645. Guide hole; 646. Flexible cross key; 647. Limiting pulley; 648. Connecting block;

[0048] 65. Magnetostrictive actuator; 651. Conductive wire assembly; 652. Electromagnet; 653. Guide sleeve; 654. Permanent magnet clamping component; 655. Right-angle cavity; 656. Three-way cavity; 657. Elastic booster piston. Detailed Implementation

[0049] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0050] Reference Figures 1-13 A machining device for rotary forging of automotive steering shafts includes a machine base 1. A picking mechanism 4 and a molding mechanism 6 are respectively installed at the left and right ends of the machine base 1. The picking mechanism 4 picks up the shaft workpiece coated with bio-based lubricating oil and feeds it into the molding mechanism 6 via a screw conveyor. The workpiece is then forged using a core assembly 5. The core assembly 5 is mounted on the molding mechanism 6. A movable support 2 is slidably installed at the left end of the machine base 1. The movable support 2 is driven by a servo motor and a ball screw, enabling high-precision axial feed motion. An explosion-proof outer cylinder 3 is fixedly installed at the right end of the machine base 1. The explosion-proof outer cylinder 3 is forged from high-strength alloy steel, and its inner wall is precision-machined to provide a stable support base for the rotary forging of the core assembly 5.

[0051] Reference Figure 1 , Figure 2 , Figure 4 and Figure 5 The picking mechanism 4 includes a first drive shaft 41 rotatably mounted on the movable bracket 2. The first drive shaft 41 is driven by a servo motor and a reducer, which can achieve precise angular displacement control. A load-bearing disc 42 is fixedly mounted on the first drive shaft 41. The load-bearing disc 42 serves as a support base for the L-shaped opening and closing clamp 45. A first traction frame 43 is slidably mounted on the first drive shaft 41. The first traction frame 43 forms a moving pair with the first drive shaft 41 through a built-in linear bearing. Preferably, a drive cylinder is used for driving. A set of L-shaped opening and closing clamps 45 are pin-connected to the load-bearing disc 42. In some embodiments, three sets of L-shaped opening and closing clamps 45 are evenly distributed in a 120° circumferential direction to ensure the uniformity of the clamping force. A pressure-boosting wedge plate 44 is integrally connected to the first traction frame 43. An L-shaped opening and closing clamp 45 has a slot 46 for the movable mounting of the pressure-boosting wedge plate 44. When the first traction frame 43 moves axially, the pressure-boosting wedge plate 44 slides within the slot 46, driving the L-shaped opening and closing clamp 45 to swing around the pin shaft through the wedge-shaped force-boosting principle. The end of the L-shaped opening and closing clamp 45 has an arc-shaped groove 48 corresponding to the outer wall surface of the shaft workpiece. The surface of the arc-shaped groove 48 is nitrided to a hardness of HRC58-62 and has a fine mesh texture to increase the coefficient of friction. A set of L-shaped opening and closing clamps 45 is used to close and clamp the middle outer wall of the shaft workpiece.

[0052] When the first traction frame 43 moves to the left under the action of the external drive device, the pressure wedge plate 44 moves to the left accordingly. Due to the guiding and limiting effect of the bayonet 46, the L-shaped opening and closing clamp 45 deflects inward with the pin on the load-bearing disc 42 as the fulcrum until the arc-shaped slot 48 is tightly fitted with the outer wall of the middle end of the shaft workpiece. This clamping process adopts the wedge force amplification principle, and a small traction force can generate a large clamping force.

[0053] A movable block 49 is slidably mounted on the first drive shaft 41, and a guide boss 410 is integrally connected to the right end of the first drive shaft 41. The inclined angle of the guide boss 410 is 15°, which can achieve a radial expansion of 0-8mm. It is used to drive the radial expansion of the limiting pressure block 413. An elastic limiting post 411 is integrally connected to the movable block 49. A second traction frame 412 is slidably mounted on the first drive shaft 41. Preferably, a driving hydraulic cylinder is used for driving. A set of limiting pressure blocks 413 are fixedly connected to the second traction frame 412 and slidably fitted onto the elastic limiting post 411. A synchronous slider 414 that moves to abut the guide boss 410 is integrally connected to the limiting pressure block 413. As a preferred solution, the outer wall of the limiting pressure block 413 is an arc surface structure corresponding to the inner wall surface of the shaft workpiece. This arc surface forms a surface contact with the inner wall of the shaft workpiece to avoid local stress concentration. A set of limiting pressure blocks 413 is used to expand and support the inner wall of the opening of the shaft workpiece. When the second traction frame 412 moves to the right under the action of the external drive, the limiting pressure block 413 slides to the right on the elastic limiting post 411. The elastic limiting post 411 drives the moving block 49 to move to the right on the first drive shaft 41. During the movement, the guide boss 410 guides and limits the synchronous slider 414, causing a set of limiting pressure blocks 413 to expand outward and support the inner wall of the shaft workpiece opening.

[0054] The pick-up mechanism 4, based on the combined functions of internal and external synchronous clamping and rotary feeding, drives the limiting pressure block 413 through the first drive shaft 41 to spirally transport the shaft workpiece into the molding cavity 53 in a clockwise rotation. The design advantage of internal and external synchronous clamping is that the outer wall clamping provides axial traction force, while the inner wall support counteracts the radial vibration force during the rotary forging process. The synergistic effect of the two ensures that the shaft workpiece maintains a stable posture during high-speed rotary feeding, avoiding conveying sway caused by resonance.

[0055] By employing a spiral conveyor, the rotational motion of the shaft workpiece causes the contact point to dynamically change circumferentially along the mold's flared opening, decomposing the continuous obstruction into intermittent tangential contact, which helps eliminate the mechanical conditions for material backflow.

[0056] As an optimization control of clamping force, a thin-film pressure sensor can be integrated on the surface of the arc-shaped slot 48 and the limiting pressure block 413 to monitor the clamping force and support force in real time. The output of the drive device is adjusted through a PID algorithm to ensure that the clamping force is stable within the preset threshold range, thus avoiding excessive or insufficient clamping force caused by fluctuations in the diameter tolerance of the shaft workpiece.

[0057] Further explanation:

[0058] When the shaft workpiece passes through the molding cavity 53 in a spiral manner, the pulsed airflow ejected from the three-way cavity 656 acts on the surface of the shaft workpiece, producing the following hydrodynamic effects:

[0059] Shearing and dispersing effect: The airflow generates shear force on the bio-based lubricant on the workpiece surface, causing the locally accumulated lubricant to diffuse circumferentially, eliminating uneven lubrication caused by gravity or centrifugal force.

[0060] Micro-disturbance effect: The intermittent action of pulsed airflow generates micro-disturbances in the lubricating oil film, promoting the directional alignment of lubricant molecules on the surface of the shaft workpiece, forming a more uniform and continuous lubricating film;

[0061] Cooling effect: The airflow generates convective cooling on the surface of the shaft workpiece, suppressing the local temperature rise caused by plastic deformation heat during rotary forging and preventing the lubricant from failing due to overheating.

[0062] As a preferred option, the airflow can be preheated or cooled. For example, for temperature-sensitive materials, a cold airflow of -5℃ to 5℃ can be used to accelerate heat dissipation from the surface of the shaft workpiece; or a hot airflow of 50-80℃ can be used to promote the flow and spread of the lubricant.

[0063] Reference Figure 3 , Figure 7 , Figure 8 and Figure 9 The mold core assembly 5 consists of four mold bodies 51. Each of the four mold bodies 51 has a forming surface 52 on its inner wall. The four mold bodies 51, through the forming surfaces 52, form a molding cavity 53 for 360° forging and pressurizing the shaft workpiece to form the steering shaft. The mold bodies 51 are forged from powder metallurgy high-speed steel and achieve a hardness of HRC65-68 after vacuum heat treatment. The forming surfaces 52 are further treated with a physical vapor deposition coating. The coating material can be TiAlN or AlCrN, and the coating thickness is 3-5 μm, which can significantly reduce the coefficient of friction and improve wear resistance.

[0064] Each of the four mold bodies 51 is integrally connected with a double-layer locking block 54. The structural design of the double-layer locking block 54 helps to ensure the guiding stability of the mold body 51 during radial movement. Figure 8As shown, the molding surface 52 is composed of a horizontal curved surface, a first inclined curved surface, and a second inclined curved surface connected in sequence, and the opening diameter of the molding cavity 53 corresponding to the horizontal curved surface, the first inclined curved surface, and the second inclined curved surface decreases sequentially. The three-section variable diameter design has the following technical effects:

[0065] The transverse curved surface section has the largest opening diameter and bears the main radial compression function, allowing the diameter of the shaft workpiece to be rapidly reduced to the transition size.

[0066] The first inclined curved surface section adopts a cone angle design of 5°-8° to achieve a smooth transition flow of materials and avoid stress concentration;

[0067] The second inclined curved surface section adopts a micro-cone angle design of 2°-3°, which plays a role in finishing and sizing, ensuring the final forming accuracy.

[0068] Reference Figure 1 , Figure 6 and Figure 7 The molding mechanism 6 includes a second drive shaft 61 fixedly connected to a load-bearing inner cylinder 62 for housing the mold core assembly 5. The second drive shaft 61 is driven by an independent servo motor and is rotatably mounted at one end of the explosion-proof outer cylinder 3. Multiple guide notches 63 are provided at the middle of the load-bearing inner cylinder 62. The multiple guide notches 63 are equidistantly distributed circumferentially. In some embodiments, four guide notches 63 are preferred, corresponding one-to-one with the four mold bodies 51.

[0069] Reference Figure 6 , Figure 7 , Figure 9 and Figure 10An eccentric actuator 64 is located at the middle of the load-bearing inner cylinder 62 to drive the radial opening and closing adjustment of the four molds 51. The eccentric actuator 64 is positioned corresponding to the guide notch 63. The eccentric actuator 64 includes multiple crescent-shaped protrusions 641 fixedly connected to the inner wall of the explosion-proof outer cylinder 3. The multiple crescent-shaped protrusions 641 are circumferentially equidistant, and the number of crescent-shaped protrusions 641 is the same as the number of molds 51, which is four. The contour curve of the crescent-shaped protrusions 641 adopts an Archimedean spiral design, so that the radial movement speed of the molds 51 changes sinusoidally, reducing impact vibration. Since the crescent-shaped protrusions 641 adopt an Archimedean spiral contour, their radial dimensions change linearly with the angle, so the radial displacement of the limiting pulley 647 also changes periodically. The four molds 51 synchronously open and close radially under the drive of the elastic cross key 646. In some embodiments, the rotational speed range of the load-bearing inner cylinder 62 is 200-600 rpm, corresponding to a forging frequency of 200-600 times / min. Four limiting strips 642 are fixedly installed inside the load-bearing inner cylinder 62. One end of each limiting strip 642 is integrally connected to an installation rod 643, and the other end is integrally connected to a guide rail block 644. One end of the explosion-proof outer cylinder 3 is bolted to a limiting rail groove for slidingly mounting the guide rail block 644. The limiting rail groove restricts the axial movement of the load-bearing inner cylinder 62, ensuring that the load-bearing inner cylinder 62 can only rotate around its axis. There is a guide hole 645 between two adjacent limiting strips 642 for slidingly mounting a mold body 51. The width of the guide hole 645 is precisely matched with the double-layer locking block 54 of the mold body 51, and the matching gap is controlled between 0.02-0.05mm. An elastic cross key 646 is slidably installed in the guide hole 645. A limiting pulley 647 is rotatably installed at the outer end of the elastic cross key 646, which moves against the crescent-shaped protrusion 641. The limiting pulley 647 moves against the outer contour of the crescent-shaped protrusion 641. A connecting block 648 for engaging the double-layer block 54 is fixedly connected to the inner end of the elastic cross key 646. The mold body 51 moves radially along the guide hole 645.

[0070] When the second drive shaft 61 drives the load-bearing inner cylinder 62 and the limiting strip 642 to rotate synchronously, the elastic cross key 646 revolves around the axis with the limiting strip 642. Since the limiting pulley 647 always abuts against the outer contour of the crescent-shaped protrusion 641, when the radial dimension of the crescent-shaped protrusion 641 changes, the limiting pulley 647 is forced to move radially, which drives the connecting block 648 to reciprocate along the guide hole 645 through the elastic cross key 646.

[0071] Key design parameters of the eccentric actuator 64 include the lift (i.e., maximum radial displacement) and profile curve of the crescent bump 641. According to the requirements of the rotary forging process, the radial feed is typically 0.5-3 mm, therefore the lift of the crescent bump 641 is designed to be 1-4 mm. The profile curve uses a sinusoidal acceleration curve to avoid rigid impacts during movement.

[0072] Reference Figure 3 , Figure 7 , Figure 11 and Figure 12 A magnetostrictive actuator 65 is provided at the left end of the load-bearing inner cylinder 62 to drive the bio-based lubricating oil to be evenly coated on the shaft workpiece. Its function is to achieve uniform distribution of the bio-based lubricating oil and solve the quality problems caused by uneven lubrication in the traditional rotary forging process. The magnetostrictive actuator 65 includes a conductive wire group 651 fixedly installed in the left end of the explosion-proof outer cylinder 3. Multiple circumferentially equidistant electromagnets 652 are connected in series on the conductive wire group 651. In some embodiments, the number of electromagnets 652 is four, corresponding to the number of limiting strips 642. A guide sleeve 653 is integrally connected to the inner cylinder 62. A permanent magnet pressure piece 654 corresponding to the electromagnet 652 is slidably fitted in the guide sleeve 653. A right-angle cavity 655 is opened at the left end of the limiting strip 642, and a three-way channel 656 is opened in the limiting strip 642 to connect the right-angle cavity 655 and the molding cavity 53. An elastic pressure-boosting piston 657 corresponding to the permanent magnet pressure piece 654 is slidably fitted in the opening at one end of the three-way channel 656. As a key design feature, one-way valves are provided at both ends of the three-way channel 656 connecting the right-angle cavity 655 and the molding cavity 53 to ensure that airflow can only flow from the right-angle cavity 655 to the molding cavity 53, preventing backflow.

[0073] To further explain, when the second drive shaft 61 drives the load-bearing inner cylinder 62 and the limiting strip 642 to rotate counterclockwise, the electromagnet 652 generates an alternating magnetic field by controlling the energization / de-energization of the conductive wire group 651. The permanent magnet pressing component 654 is subjected to axial force under the action of the magnetic field, and according to the polarity control of the electromagnet 652, the permanent magnet pressing component 654 can reciprocate within the guide sleeve 653.

[0074] Specifically, when the electromagnet 652 and the permanent magnet pressing component 654 have the same polarity at their opposite ends, a repulsive force is generated, causing the permanent magnet pressing component 654 to move away from the electromagnet 652 and exert pressure on the elastic boosting piston 657. When the polarities are opposite, an attractive force is generated, causing the permanent magnet pressing component 654 to move closer to the electromagnet 652 and release the pressure on the elastic boosting piston 657. By controlling the energizing / de-energizing frequency and the magnitude of the current, the reciprocating frequency and stroke of the elastic boosting piston 657 can be precisely controlled.

[0075] During its reciprocating motion, the elastic booster piston 657 draws in air from the right-angle cavity 655 through the three-way passage 656 and then forces it into the molding cavity 53. Due to the guiding effect of the one-way valve, the airflow can only flow in one direction, forming a pulsed airflow jet.

[0076] The second drive shaft 61 is coaxial with the first drive shaft 41. The load-bearing inner cylinder 62 is concentrically set inside the explosion-proof outer cylinder 3 through the second drive shaft 61, ensuring that the shaft workpiece conveying path coincides with the forging center line.

[0077] To verify the technical effectiveness of the picking mechanism 4 and the molding mechanism 6, a comparative experiment was conducted. The experimental subject was a copper tube blank with an outer diameter of 42mm and a wall thickness of 3.5mm. It was processed using a traditional rotary forging device (rigid linear feeding combined with airless lubrication) and the picking mechanism 4 and molding mechanism 6, respectively. The forming quality indicators were compared.

[0078] Table 1 Comparison of forging quality under different feeding methods

[0079] Evaluation indicators Traditional device (rigid feeding) The device of this invention (screw conveyor) Improvement range Axial feed force (N) 1250 820 ↓34.4% Peak forging force (kN) 28.5 21.3 ↓25.3% Wall thickness uniformity (mm) ±0.12 ±0.05 Accuracy improved by 58.3% Surface roughness Ra (μm) 1.6 0.8 ↓50% Mold life (10,000 pieces) 8 12 ↑50%

[0080] Experimental data show that the spiral conveying method reduces the axial feed force by 34.4% and the peak forging force by 25.3%, thanks to the effective suppression of material backflow by the spiral motion. Wall thickness uniformity improves from ±0.12mm to ±0.05mm, and surface roughness decreases by 50%, demonstrating the advantages of the synergistic effect of internal and external synchronous clamping and airflow distribution.

[0081] Table 2. Effect of magnetostrictive actuator 65 on lubrication performance (workpiece: copper tube, wall thickness 3.5 mm)

[0082] Lubrication method Lubricating film thickness uniformity (%) coefficient of friction Surface defect rate (%) Traditional coating ±18.5 0.15-0.22 8.5 Static airflow assistance ±12.3 0.12-0.18 5.2 The pulse airflow of this invention ±6.8 0.08-0.11 2.1

[0083] Experimental results show that after using pulsed airflow drive, the uniformity of lubricating film thickness increased from ±18.5% to ±6.8%, the coefficient of friction decreased to 0.08-0.11, and the surface defect rate decreased from 8.5% to 2.1%, indicating that the pulsed airflow generated by the magnetostrictive actuator 65 helps to promote the uniform distribution of bio-based lubricating oil.

[0084] Table 3 Forming effect of different workpiece materials

[0085] workpiece material Feeding speed (mm / s) Forging frequency (times / minute) Molding accuracy (mm) Aluminum alloy (for aviation use) 8-12 400-500 ±0.04 Titanium alloy (high quality) 3-5 300-400 ±0.06 Magnesium alloy 6-10 350-450 ±0.05 Copper alloy (for high-speed rail braking) 10-15 450-600 ±0.03

[0086] Experimental results show that it has good adaptability to a variety of high-end materials. For aerospace aluminum alloy forgings, the forming accuracy can reach ±0.04mm; for high-quality titanium forgings, a fine grain structure of grade 8-9 can be obtained at a lower feeding speed; for high-speed rail brake copper alloy forgings, the forming accuracy is the highest under high-frequency forging, reaching ±0.03mm. This is thanks to the three-section variable diameter design of the mold core assembly 5 and the smooth motion control of the eccentric actuator 64.

[0087] It should be noted that the specific model and specifications of the movable bracket 2 and the conductive wire group 651 need to be selected and determined according to the actual specifications of the device. The specific selection calculation method adopts the existing technology in this field, so it will not be elaborated here.

[0088] The functional principle of this invention can be explained through the following operational methods:

[0089] First, bio-based lubricant is adhered to the shaft workpiece.

[0090] Secondly, the L-shaped opening and closing clamp 45 on the first drive shaft 41 is controlled to close to clamp the outer wall of the middle end of the shaft workpiece to the left. At the same time, the driving limit pressure block 413 is opened to expand to the right and abut against the opening of the shaft workpiece. While controlling the moving bracket 2 to move to the right, the first drive shaft 41 is controlled to rotate clockwise, so that the shaft workpiece spirals into the molding cavity 53. Specifically, the first traction frame 43 drives the pressure wedge plate 44 to move horizontally. The guide limit of the bayonet 46 causes the L-shaped opening and closing clamp 45 to deflect with the load-bearing disc 42 as the fulcrum until the outer wall of the middle end of the shaft workpiece is clamped and limited through the arc-shaped slot 48. At the same time, the second traction frame 412 drives the limiting pressure block 413 to move on the elastic limiting post 411. The elastic limiting post 411 drives the moving block 49 to move on the first drive shaft 41. Because the guide boss 410 guides and limits the synchronous slider 414, a set of limiting pressure blocks 413 expands and supports within the opening of the shaft workpiece. The driving moving bracket 2 runs synchronously with the first drive shaft 41 to realize the conveying of the shaft workpiece.

[0091] Then, the second drive shaft 61 is controlled to rotate counterclockwise, causing the load-bearing inner cylinder 62 and the limiting strip 642 to rotate synchronously. This activates the magnetostrictive actuator 65, causing the elastic booster piston 657 to extend and retract within the three-way cavity 656. This draws gas from the right-angle cavity 655 into the molding cavity 53, providing airflow to the shaft workpiece passing through the molding cavity 53, resulting in a uniform distribution of the bio-based lubricating oil on the surface of the shaft workpiece. Specifically, the second drive shaft 61 drives the load-bearing inner cylinder 62 to rotate counterclockwise, energizing the conductive wire group 651. This causes the electromagnet 652 to generate magnetism, creating a repulsive or attractive interaction with the permanent magnet pressure member 654. The permanent magnet pressure member 654 then applies pressure to the elastic booster piston 657, which, by extending and retracting within the three-way cavity 656, pushes airflow into the molding cavity 53 to drive the bio-based lubricating oil on the shaft workpiece until it is evenly distributed.

[0092] Finally, the eccentric driver 64 is activated, causing the mold body 51 to move radially along the guide hole 645 to forge and press the shaft workpiece, which is uniformly coated with bio-based lubricant, 360°. The shaft workpiece is shaped into a steering shaft using the transverse curved surface, the first inclined curved surface, and the second inclined curved surface. Specifically, the load-bearing inner cylinder 62 drives the elastic cross key 646 to rotate through the limiting strip 642. The intermittent contact between the limiting pulley 647 and the crescent-shaped protrusion 641 causes the elastic cross key 646 to drive the connecting block 648 to reciprocate along the guide hole 645. During the radial opening and closing motion, the four mold bodies 51 use the molding cavity 53 to forge and press the shaft workpiece 360°.

[0093] It should be noted that after the rear end of the shaft workpiece passes through the molding cavity 53, the mold core assembly 5 stops forging, and the first drive shaft 41 and the moving bracket 2 stop moving. The L-shaped opening and closing clamp 45 is released, the limit pressure block 413 retracts, and the formed automobile steering shaft is received by the configured receiving mechanism.

[0094] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A machining device for a rotary forging die for an automobile steering shaft, comprising a machine base (1), wherein a picking mechanism (4) and a molding mechanism (6) are respectively provided on the left and right ends of the machine base (1), the picking mechanism (4) being used to pick up a shaft workpiece with bio-based lubricating oil adhering to it, and a mold core assembly (5) being provided on the molding mechanism (6), characterized in that: The core assembly (5) consists of four mold bodies (51), each of which has a forming surface (52) on its inner wall. The four mold bodies (51) form a plastic cavity (53) through the forming surface (52) to forge and press the shaft workpiece in 360° to form a steering shaft. The picking mechanism (4) includes a first drive shaft (41), on which a set of L-shaped opening and closing clamps (45) and a set of limiting pressure blocks (413) are provided. The set of L-shaped opening and closing clamps (45) is used to close and clamp the outer wall of the middle end of the shaft workpiece, and the set of limiting pressure blocks (413) is used to expand and support the inner wall of the opening of the shaft workpiece. The picking mechanism (4) drives the limiting pressure blocks (413) through the first drive shaft (41) to spirally transport the shaft workpiece to the molding cavity (53) in a clockwise rotation manner. The molding mechanism (6) includes a second drive shaft (61) fixedly connected to a load-bearing inner cylinder (62) for housing the mold core assembly (5). An eccentric actuator (64) for driving the radial opening and closing adjustment of the four mold bodies (51) is provided at the middle position of the load-bearing inner cylinder (62). A magnetostrictive actuator (65) for driving the bio-based lubricating oil to be uniformly coated on the shaft workpiece is provided at the left end of the load-bearing inner cylinder (62).

2. The automotive steering shaft rotary forging die processing device according to claim 1, characterized in that, The machine base (1) is slidably mounted on the left end with a movable bracket (2) for rotating the first drive shaft (41), and the machine base (1) is fixedly mounted on the right end with an explosion-proof outer cylinder (3) for rotating the second drive shaft (61).

3. The automotive steering shaft rotary forging die processing device according to claim 2, characterized in that, The molding surface (52) is composed of a horizontal curved surface, a first inclined curved surface and a second inclined curved surface connected in sequence, and the opening diameter of the molding cavity (53) corresponding to the horizontal curved surface, the first inclined curved surface and the second inclined curved surface decreases in sequence.

4. The automotive steering shaft rotary forging die processing device according to claim 3, characterized in that, The L-shaped opening and closing clamp (45) has an arc-shaped slot (48) at the end corresponding to the outer wall surface of the shaft workpiece, and the outer wall of the limiting pressure block (413) is an arc-shaped structure corresponding to the inner wall surface of the shaft workpiece.

5. The automotive steering shaft rotary forging die processing device according to claim 4, characterized in that, The second drive shaft (61) is coaxial with the first drive shaft (41), and the load-bearing inner cylinder (62) is concentrically arranged inside the explosion-proof outer cylinder (3) through the second drive shaft (61).

6. The automotive steering shaft rotary forging die processing device according to claim 5, characterized in that, The load-bearing inner cylinder (62) has multiple guide notches (63) corresponding to the eccentric actuators (64) at its middle position, and the multiple guide notches (63) are equidistantly distributed in the circumferential direction.

7. The automotive steering shaft rotary forging die processing device according to claim 6, characterized in that, The eccentric actuator (64) includes four limiting strips (642) fixedly installed in the load-bearing inner cylinder (62), and there is a guide hole (645) between two adjacent limiting strips (642) for sliding a mold (51) to be fitted, the mold (51) moving radially along the guide hole (645).

8. The automotive steering shaft rotary forging die processing device according to claim 7, characterized in that, The magnetoactuator (65) includes a right-angle cavity (655) located at the left end of the limiting strip (642), and a three-way channel (656) is provided in the limiting strip (642) that connects the right-angle cavity (655) and the molding cavity (53) in one direction. An elastic pressure-boosting piston (657) is slidably fitted in the opening of one end of the three-way channel (656).

9. The automotive steering shaft rotary forging die processing device according to claim 8, characterized in that, The three-way cavity (656) is equipped with one-way valves at both ends of the openings of the right-angle cavity (655) and the molding cavity (53).

10. A method of using the automotive steering shaft rotary forging die processing device as described in claim 9, characterized in that, The method of use includes the following steps: Step S1: Adhere bio-based lubricating oil onto the shaft workpiece; In step S2, the L-shaped opening and closing clamp (45) on the first drive shaft (41) is controlled to close to clamp the outer wall of the middle end of the shaft workpiece to the left. At the same time, the limit pressure block (413) is driven to open to expand and abut to the right in the opening of the shaft workpiece. The moving bracket (2) is controlled to move to the right while the first drive shaft (41) is controlled to rotate clockwise, so that the shaft workpiece spirals into the molding cavity (53). Step S3: Control the second drive shaft (61) to rotate counterclockwise, driving the load inner cylinder (62) and the limiting strip (642) to rotate synchronously, that is, start the magnetostrictive actuator (65) so that the elastic booster piston (657) moves in the three-way cavity (656) to draw the gas in the right-angle cavity (655) into the molding cavity (53) to drive the shaft workpiece through the molding cavity (53) with wind power, so that the bio-based lubricating oil is evenly distributed on the surface of the shaft workpiece; Step S4: Start the eccentric driver (64) so ​​that the mold (51) moves radially along the guide hole (645) to forge and press the shaft workpiece with bio-based lubricant evenly coated with 360°, and shape the shaft workpiece into a steering shaft by using the transverse curved surface, the first inclined curved surface and the second inclined curved surface.

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