Rolling forming device and method for large-modulus standard straight spur gear

Abstract

The invention relates to a rolling forming device and method for a large-modulus standard straight spur gear. The rolling forming device comprises an extrusion device and a rolling forming device body. The blank is gradually rolled by adopting a similar ring rolling process, so that the blank is in local plastic deformation which changes at any time, forming has continuity and progressiveness, meanwhile, the loading speed can be adjusted at any time according to the deformation condition, and the situation that a mold is excessively lost due to large load in the gear forming process is avoided. The rolling core roller gradually carries out expanding rolling inside, so that stable contact between the tooth-shaped position of the die and a blank can be effectively kept, tooth top shifting caused by insufficient positioning precision in the rolling process can be effectively avoided, the forming stability is good, and the gear precision is high. The gear forming device is still suitable for large-modulus gear forming, the situation that the forming efficiency and stability are affected due to the fact that the size of the gear is large and the size of the forming device is multiplied is avoided, and the device is simple in structure and convenient to operate. The forming process is simple, flash-free, complete in metal flow line preservation, high in material utilization rate and good in mechanical property of the formed gear.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical processing, and in particular relates to a rolling forming device and method for a large-module standard spur gear. Background Art

[0002] As a basic part for transmitting power and motion, cylindrical gears are widely used in the industrial field. In industrial production, gears with a modulus greater than 10mm are generally called large modulus gears. Because they are usually large in overall size, good in mechanical properties, and high in reliability, they have significant advantages in withstanding high loads and impacts, and can work stably in complex and harsh environments. Therefore, they are widely used in large lifting machinery, ship transportation, geological exploration, military equipment and other fields.

[0003] Due to the characteristics of heavy industrial equipment, large modulus gears generally have higher requirements for dimensional accuracy, surface quality, service life and mechanical properties. Compared with ordinary gears, the biggest feature of large modulus gear forming is that the gear volume is large and the pitch circle diameter is large, so the processing deformation is large, which easily leads to excessive forming load; at the same time, the large radial size easily leads to the overall size of the forming equipment, and the forming process is difficult to control; and the forming stability is difficult to ensure and the dimensional accuracy is low. Difficulties need to be solved urgently; therefore, how to reduce the forming force as much as possible while ensuring that the forming quality meets the service requirements, and at the same time, how to improve the forming stability as much as possible while keeping the process controllable has become the main problem faced by large modulus gear forming.

[0004] At present, the production of cylindrical gears generally adopts traditional cutting methods, such as hobbing, shaving, and shaping. These methods have low material utilization, low production efficiency, and high processing costs. In particular, the mechanical properties and service life of the gears are reduced due to the cutting of metal flow lines during the processing. For the closed precision forging process widely used for processing smaller parts, considering factors such as forming equipment and forming force, large modulus gears will further increase the forming force due to their larger volume, reducing the service life of the mold.

[0005] The local plastic forming process is a special continuous local metal forming process, which is mainly used to produce components with specific geometric shapes and mechanical properties. This process uses local loading to cause the material to undergo plastic deformation in a specific area, thereby forming the desired shape and structure. The local plastic forming method is easy to control the forming process and forming force, which can make up for the above-mentioned shortcomings of large modulus gear forming and is of great significance to the development of gear forming technology. It can be specifically divided into gear local extrusion and gear rolling processes.

[0006] The local extrusion process of gears is to apply pressure locally on the gear blank and form the gear through a die with a tooth shape, but it has defects such as high forming force and streamline folding.

[0007] The Chinese patent with publication number CN202010933525.6 proposes a process for forming a gear ring by extruding a multi-directional forging hammer and a core die. The forming force is reduced by multiple extrusions, but the gear sleeve is prone to plastic deformation due to multiple contractions and expansions, which affects the quality and has low forming accuracy. The gear extrusion process proposed by the Chinese patent with publication number CN1644266A requires additional customization of corresponding toothed rollers to ensure the integrity of the gear profile for gears with a large number of teeth that cannot be divided evenly. It is difficult to install, prone to flash and folding, and is not suitable for forming larger gears.

[0008] The gear rolling forming process uses a toothed hob or roller to roll the gear blank. The gear is gradually formed by multiple local pressure deformations of the metal. Currently, the rolling process is generally suitable for the production of small and medium modulus gears and toothed parts, most of which are hot rolled.

[0009] The Chinese patents with publication numbers CN115971382A and CN107695263A are both longitudinal rolling processes. For large-module gears, due to the large pitch circle diameter, the above-mentioned rolling forming process is highly dependent on equipment accuracy, which is prone to meshing deviation and affects the forming accuracy. It is not suitable for large-module gear forming.

[0010] Chinese patents with publication numbers CN205165687, CN101927309A, CN102294419A, CN107695263A, and CN104438993B all use transverse rolling methods to achieve rolling forming or improve rolling processes with different technical means. However, insufficient positioning accuracy may occur during the rolling process, resulting in "pulling" of the tooth tips, poor stability, and poor high-precision processing effects. In addition, they are not suitable for cemented carbide forming, the mold is easily worn, and the cost of use is high. Therefore, for high-precision and high-hardness gear rolling forming, similar methods are difficult to achieve the expected results.

[0011] Chinese patents with publication numbers CN106493273B, CN113210551A, and CN206046960U and U.S. patent publication number US20070068211A1 have improved the rolling forming stability of the equipment to a certain extent through numerical control or mold design optimization. However, for large-module gears, this will cause the forming equipment to be too large, reduce the stability of the equipment, and make installation and debugging difficult and the maintenance cost high. Therefore, it is also not suitable for large-module gear forming.

[0012] A Chinese patent with publication number CN118253676A proposes a ring forging rolling forming process, which rolls out the required structure of the inner surface of the forging by designing a core roller with a special-shaped structure. The outer surface of the forging is always a cylindrical surface. However, since the forming of the external cylindrical gear occurs on the outer surface of the blank, this method cannot be applied to the forming of external gears.

[0013] The Chinese patent with publication number CN116809831A proposes a bevel gear ring rolling forming process, in which the mandrel is placed in a ring-shaped blank, the main roller rotates to drive the blank to rotate, and the mandrel moves radially to form the ring, thereby obtaining a finished bevel gear. This method uses the ring rolling process to reduce the forming force, but for large-module gears, the blank needs to mesh with the main roller multiple times, which is prone to "pulling" of the tooth tip; and most of the blank is exposed to the air during the high-temperature process, which is prone to produce severe oxide scale, reducing material utilization and affecting the forming quality. Therefore, for large-module gears, if approximate ring rolling forming is used, the process still needs to be further improved.

[0014] For the forming of large-module standard spur gears, not only a reasonable metal streamline distribution is required to ensure the mechanical properties of the gears, but also a stable low-load state must be achieved during the forming process to reduce gear stress, die wear and large-scale production costs. At the same time, high precision and high stability must be pursued during the forming process to meet specific shape, strength and reliability requirements. However, this aspect has not been involved in existing work. Summary of the invention

[0015] The purpose of the present invention is to avoid the shortcomings of the prior art and provide a rolling forming device and method for large-module standard spur gears with stable process forming, complete preservation of metal streamlines, high material utilization rate, and high gear product precision.

[0016] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a rolling forming device for a large-module standard spur gear, characterized in that it includes an extrusion device for extruding a ring column blank and a rolling forming device for rolling the ring column blank in cooperation with a ring rolling device after the extrusion is completed, and the ring column blank is installed on the extrusion device through a fixed outer die, a gear die is provided between the ring column blank and the fixed outer die, and the ring column blank, the gear die, and the fixed outer die are coaxially arranged; The extrusion device comprises an extrusion platform and an extrusion punch device, wherein the extrusion platform is provided with an extrusion base and a first positioning plate and a second positioning plate respectively arranged on both sides of the extrusion base, for positioning the extrusion base on the extrusion platform; the surface of the extrusion base away from the extrusion platform is a semi-arc surface matching the fixed outer die, for supporting the extrusion punch device when extruding both sides of the annular column blank in the axial direction; The extrusion punch device comprises a first extrusion punch and a second extrusion punch coaxially arranged on both sides of the ring column blank, and a first punch sleeve and a second punch sleeve sleeved at the tail ends of the first extrusion punch and the second extrusion punch, and the first punch sleeve and the second punch sleeve are embedded in the central hole of the ring column blank to extrude the ring column blank; The rolling forming device comprises a rolling bottom plate, on which a positioning base is arranged, on which the ring column blank, the gear mold and the fixed outer mold are coaxially mounted, and the rolling forming device is fixed to the ring rolling equipment through the rolling bottom plate; It also includes a driving wheel connected to the ring rolling equipment and a driven wheel installed on the rolling bottom plate, the driving wheel and the driven wheel are both in contact with the tangent line of the fixed outer die installed on the positioning base, at least two pillars for installing the driven wheel are evenly arranged around the outer circumference of the fixed outer die on the rolling bottom plate, the bottom of the driven wheel is mounted on the pillar through a bearing sleeve, and the driven wheel is used to ensure that the fixed outer die rotates stably without eccentricity when the fixed outer die rotates with the driving wheel; It also includes an electromagnetic induction coil and a support seat for heating the fixed outer mold. A hydraulic cylinder is provided on the support seat. A positioning plate is fixedly provided on the piston rod of the hydraulic cylinder to prevent the fixed outer mold from rising and misalignment. The bottom surface of the positioning plate is 2 to 4 mm away from the axial upper surface of the fixed outer mold. There is a gap between the inner curved surface of the electromagnetic induction coil and the fixed outer mold, and the electromagnetic induction coil is fixed to the support seat by a connecting piece.

[0017] Furthermore, the extrusion platform is provided with a pair of connecting bosses, and the bottom surfaces of the first positioning plate and the second positioning plate are respectively provided with two grooves for slidingly connecting with the bosses, so as to facilitate the clamping and positioning of the extrusion base by the first positioning plate and the second positioning plate.

[0018] Furthermore, semicircular grooves are provided at the centers of the surfaces of the first positioning plate and the second positioning plate to reserve space for the first extrusion punch and the second pressing punch to rotate.

[0019] Furthermore, the positioning base is a 3 / 4 cylinder, and a 1 / 4 gap is opened on the side close to the driving wheel to reserve space for the rotation of the driving wheel.

[0020] Furthermore, a plurality of balls are arranged on the contact surface between the positioning base and the axial bottom of the fixed outer mold to reduce the friction force on the fixed outer mold during rotation.

[0021] Furthermore, the gear mold is composed of four identical gear sub-molds, which are connected and fixed by four positioning pins at the top and bottom. The outer surface of the gear mold and the inner surface of the fixed outer mold are in an interference fit with an angle, and the fit slope is 1° to 2°.

[0022] The present invention also provides a rolling forming method for a large-module standard spur gear, the specific steps of which are as follows: Step 1: Select a blank and determine the size according to the target gear, cut and uncut the blank on a band saw to obtain a ring column blank, and use an acetylene flame to heat the ring column blank to 800-1000° C. to reduce deformation resistance; Step 2: Install the ring column blank in the gear mold, adjust the position with the positioning pin, preheat the gear mold to 300-500°C, and then install the gear mold into the fixed outer mold. The inner diameter of the fixed outer mold is tapered and matches the outer diameter of the gear mold. Step 3: Place the fixed outer die axially and horizontally on the extrusion base, and fix the extrusion base by the first positioning plate and the second positioning plate. Preheat the first extrusion punch and the second extrusion punch of the extrusion punch device to 300-500° C. with an acetylene flame, and then drive the first extrusion punch and the second extrusion punch to axially extrude the ring column blank towards each other by two hydraulic devices respectively and simultaneously, and the extrusion stroke does not exceed 1 / 4 of the height of the ring column blank. Step 4: withdraw the first extrusion punch and the second extrusion punch together with the fixed outer die from the extrusion device and place them in the rolling forming device. Specifically, the fixed outer die is axially and vertically placed on the positioning base and tangentially contacted with the driving wheel, and the positioning baffle is adjusted by the hydraulic cylinder to be pressed 2 to 4 mm above the axial upper surface of the fixed outer die; the rolling core roller is placed in the center hole of the ring column blank, connected with the ring rolling equipment for coordination and debugging, and the temperature of the electromagnetic induction coil is controlled to be 300 to 500°C; Step 5: The ring rolling equipment controls the driving wheel to rotate, driving the fixed outer die, the gear die and the ring column blank to rotate synchronously, and the driven wheel ensures that the fixed outer die rotates stably without eccentricity; the electromagnetic induction coil keeps heating; at the same time, the main shaft of the ring rolling equipment controls the rolling core roller to rotate about its own central axis and translate toward the driving wheel, so as to gradually roll the ring column blank into shape; Step six, withdraw the gear mold from the rolling forming device, remove the fixed outer mold, separate the gear mold, and obtain a standard spur gear.

[0023] Furthermore, in step one, the outer diameter of the ring column blank is 1 to 2 mm smaller than the inner diameter of the gear mold.

[0024] Furthermore, in step three, the first extrusion punch and the second extrusion punch are composed of a cylinder at the tail for clamping and a cone at the head for forming, the inclination angle of the cone is 5 to 15 degrees, and the length of the cylinder does not exceed 2 / 5 of the height of the ring column blank.

[0025] Furthermore, in step five, the outer diameter of the rolling core roller is 0.8-0.9 times the diameter of the center hole of the annular column blank; and the speed of the rolling core roller moving toward the driving wheel is 0.01-0.03 times the diameter of the rolling core roller per second.

[0026] The beneficial effects of the present invention are: 1. The process of the present invention can significantly reduce the forming load required in the forming process. The blank is gradually rolled using a similar ring rolling process, so that the blank is in a local plastic deformation that changes all the time. The forming is continuous and progressive. At the same time, the loading speed can be adjusted at all times according to the deformation situation, avoiding the situation where the gear forming process has a large load and excessive wear on the mold. Therefore, it is also applicable to high-hardness alloy materials, with little damage to the mold and a long mold life.

[0027] 2. The process of the present invention has good forming stability, and the gear products produced have high precision. The axial pressure on the blank is helpful for positioning in the initial forming stage. The gradual expansion of the rolling core roller inside can effectively maintain stable contact between the mold tooth shape and the blank, which can effectively avoid the "pulling" of the tooth tip caused by insufficient positioning accuracy during rolling. The forming stability is good and the gear precision is high.

[0028] 3. The process of the present invention is still applicable to the forming of large-module gears. The large gear size will not cause the size of the forming equipment to increase several times, affecting the forming efficiency and stability. The equipment has a simple structure and is easy to operate. The forming process is simple, there is no burr, the metal streamline is intact, the material utilization rate is high, and the mechanical properties of the formed gear are good. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of the extrusion device of the present invention; Figure 2 is a cross-sectional view of the extrusion device of the present invention; Figure 3 It is an axonometric view of the roll forming device of the present invention; Figure 4 This is a front view of the rolling forming device of the present invention; Figure 5 yes Figure 4 AA section view; Figure 6 It is a right side view of the rolling forming device of the present invention; In the figure: 1-first punch sleeve, 2-first extrusion punch, 3-second extrusion punch, 4-second punch sleeve, 5-first positioning plate, 6-extrusion base, 7-second positioning plate, 8-extrusion table, 81-boss, 9-gear mold, 10-fixed outer mold, 11-positioning pin, 12-driving wheel, 13-rolling core roller, 14-positioning base, 15-positioning pressure plate, 16-electromagnetic induction coil, 17-driven wheel, 18-pillar, 19-support seat, 20-rolling bottom plate, 21-hydraulic cylinder, 22-ring column blank. DETAILED DESCRIPTION

[0030] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0031] Example 1: Figure 1-6 As shown, a rolling forming device for a large-module standard spur gear comprises an extrusion device for extruding a ring column blank 22 and a rolling forming device for rolling the ring column blank 22 in cooperation with a ring rolling device after the extrusion is completed, and the ring column blank 22 is installed on the extrusion device through a fixed outer die 10, a gear die 9 is provided between the ring column blank 22 and the fixed outer die 10, and the ring column blank 22, the gear die 9, and the fixed outer die 10 are coaxially arranged; like Figure 1 , 2 As shown, the extrusion device includes an extrusion platform 8 and an extrusion punch device, the extrusion platform 8 is provided with an extrusion base 6 and a first positioning plate 5 and a second positioning plate 7 respectively arranged on both sides of the extrusion base 6, which are used to position the extrusion base 6 on the extrusion platform 8; the surface of the extrusion base 6 away from the extrusion platform 8 is a semi-arc surface matching the fixed outer die 10, which is used to support the ring column blank 22 when the extrusion punch device extrude the two axial sides; The extrusion punch device comprises a first extrusion punch 2 and a second extrusion punch 3 coaxially arranged on both sides of the ring column blank 22, and a first punch sleeve 1 and a second punch sleeve 4 sleeved at the tail ends of the first extrusion punch 2 and the second extrusion punch 3. The first punch sleeve 1 and the second punch sleeve 4 are embedded in the central hole of the ring column blank 22 to extrude the ring column blank 22. like Figure 3 , 4 As shown in , 5 and 6, the rolling forming device includes a rolling base plate 20, a positioning base 14 is provided on the rolling base plate 20, a ring column blank 22, a gear mold 9 and a fixed outer mold 10 are coaxially mounted on the positioning base 14, and the rolling forming device is fixed on the ring rolling equipment through the rolling base plate 20; It also includes a driving wheel 12 connected to the ring rolling equipment and a driven wheel 17 installed on a rolling base plate 20. Both the driving wheel 12 and the driven wheel 17 are in tangential contact with a fixed outer mold 10 installed on a positioning base 14. Four pillars 18 for installing the driven wheel 17 are evenly arranged around the outer circumference of the fixed outer mold 10 on the rolling base plate 20. The bottom of the driven wheel 17 is mounted on the pillar 18 through a bearing sleeve. The driven wheel 17 is used to ensure that the fixed outer mold 10 rotates stably without eccentricity when the fixed outer mold 10 rotates with the driving wheel 12. It also includes an electromagnetic induction coil 16 and a support seat 19 for heating the fixed outer mold 10. A hydraulic cylinder 21 is provided on the support seat 19. A positioning plate 15 is fixedly provided on the piston rod of the hydraulic cylinder 21 to prevent the fixed outer mold 10 from rising and misalignment. The bottom surface of the positioning plate 15 is 2 to 4 mm away from the axial upper surface of the fixed outer mold 10. There is a gap between the inner curved surface of the electromagnetic induction coil 16 and the fixed outer mold 10, and the electromagnetic induction coil 16 is fixed to the support seat 19 through a connecting piece.

[0032] A pair of connecting bosses 81 are provided on the extrusion platform 8, and two grooves for slidingly connecting with the bosses 81 are respectively formed on the bottom surfaces of the first positioning plate 5 and the second positioning plate 7, so as to facilitate the clamping and positioning of the extrusion base 6 by the first positioning plate 5 and the second positioning plate 7.

[0033] Semicircular grooves are provided at the centers of the surfaces of the first positioning plate 5 and the second positioning plate 7 to reserve space for the first extrusion punch 2 and the second pressing punch 3 to rotate.

[0034] The positioning base 14 is a 3 / 4 cylinder, and a 1 / 4 gap is opened on the side close to the driving wheel 12 to reserve space for the rotation of the driving wheel 12.

[0035] A plurality of balls are disposed on the contact surface between the positioning base 14 and the axial bottom of the fixed outer mold 10 to reduce the friction force on the fixed outer mold 10 during rotation.

[0036] The gear mold 9 is composed of four identical gear sub-molds, which are connected and fixed by four positioning pins 11 at the top and bottom. The outer surface of the gear mold 9 and the inner surface of the fixed outer mold 10 are in an interference fit with an angle of 1° to 2°.

[0037] Example 2: The present invention also provides a large-module standard spur gear rolling forming method, taking the rolling forming of a standard spur gear with a module of 22, a number of teeth of 20, and a pressure angle of 20° as an example. The material is 17CrNiMo6, the tooth width is 420mm; the gear pitch circle diameter is 440mm, and the tooth top circle diameter is 484mm.

[0038] The specific steps are as follows: Step 1: Select a blank and determine the size according to the target gear, cut and uncut the blank on a band saw to obtain a ring column blank 22 with an outer diameter of Φ388 mm, an inner diameter of Φ150 mm, and a height of 466 mm; heat the ring column blank 22 to 1000° C. with an acetylene flame; Step 2, install the ring column blank 22 in the gear mold 9, adjust the positioning with the positioning pin 11, preheat the gear mold 9 to 300℃, and then install the gear mold 9 into the fixed outer mold 10; the fixed outer mold has an outer diameter of Φ630mm, an inner diameter of Φ550~570mm, and a conical distribution, with a height of 546mm; the gear mold has an outer diameter of Φ550~570mm and a total height of 546mm; the fixed outer mold 10 and the gear mold 9 are connected by interference fit, and the positioning pin 11 has a diameter of Φ20mm and a length of 122mm; the outer surface of the fixed outer mold 10 is roughened to make the contact friction coefficient reach 0.5~0.6.

[0039] Step three, placing the fixed outer die 10 on the extrusion device, specifically placing the fixed outer die 10 axially and horizontally on the extrusion base 6, and fixing the extrusion base 6 by the first positioning plate 5 and the second positioning plate 7, inserting the tail end of the first extrusion punch 2 into the first punch sleeve 1, inserting the convex head at the front end of the first extrusion punch 2 into the center hole at one end of the ring column blank 22, inserting the tail end of the second extrusion punch 3 into the second punch sleeve 4, and inserting the convex head at the front end of the second extrusion punch 3 into the center hole at the other end of the ring column blank 22; preheating the first extrusion punch 2 and the second extrusion punch 3 to 300° C. with an acetylene flame, and simultaneously driving the first extrusion punch 2 and the second extrusion punch 3 by a hydraulic device to axially extrude the ring column blank 22 towards each other, and the extrusion stroke is set to 50 mm; Step 4: withdraw the first extrusion punch 2 and the second extrusion punch 3 together with the fixed outer die 10 from the extrusion device and place them in the rolling forming device. Specifically, the fixed outer die 10 is axially and vertically placed on the positioning base 14 and tangentially contacted with the driving wheel 12. The positioning baffle 15 is adjusted by the hydraulic cylinder 21 to press 2 to 4 mm above the upper surface of the fixed outer die 10; the rolling core roller 13 is placed in the center hole of the ring column blank 22, and connected and debugged with the ring rolling equipment. The diameter of the rolling core roller 13 is Φ135 mm and the length is 1130 mm; the temperature of the electromagnetic induction coil 16 is controlled to 300°C; Step 5: The ring rolling equipment controls the driving wheel 12 to rotate, driving the fixed outer mold 10, the gear mold 9 and the ring column blank 22 to rotate synchronously at a uniform angular velocity of 0.1 rad / s, and the electromagnetic induction coil 16 is kept heated at 300° C. At the same time, the main shaft of the ring rolling equipment controls the rolling core roller 13 to rotate about its own central axis, and at the same time, the rolling is performed in a translational manner toward the driving wheel 12, and the translational speed is uniformly reduced from 0.1 mm / s to 0.05 mm / s. Step six, withdraw the gear mold 9 from the rolling forming device, remove the fixed outer mold 10, separate the gear mold 9, and obtain a standard spur gear with a module of 22 and a number of teeth of 20.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A rolling forming device for large-module standard spur gears, characterized in that: It comprises an extrusion device for extruding a ring column blank (22) and a rolling forming device for cooperating with a ring rolling device to roll and form the ring column blank (22) after the extrusion is completed, wherein the ring column blank (22) is mounted on the extrusion device via a fixed outer die (10), a gear die (9) is provided between the ring column blank (22) and the fixed outer die (10), and the ring column blank (22), the gear die (9) and the fixed outer die (10) are coaxially arranged; The extrusion device comprises an extrusion platform (8) and an extrusion punch device, wherein the extrusion platform (8) is provided with an extrusion base (6) and a first positioning plate (5) and a second positioning plate (7) respectively arranged on both sides of the extrusion base (6) for positioning the extrusion base (6) on the extrusion platform (8); the surface of the extrusion base (6) facing away from the extrusion platform (8) is a semi-arc-shaped surface matching the fixed outer die (10), and is used for supporting the annular column blank (22) when the extrusion punch device extrude the two axial sides thereof; The extrusion punch device comprises a first extrusion punch (2) and a second extrusion punch (3) coaxially arranged on both sides of the ring column blank (22), and a first punch sleeve (1) and a second punch sleeve (4) sleeved on the tail ends of the first extrusion punch (2) and the second extrusion punch (3); the first punch sleeve (1) and the second punch sleeve (4) are embedded in the central hole of the ring column blank (22) to extrude the ring column blank (22); The rolling forming device comprises a rolling base plate (20), a positioning base (14) is provided on the rolling base plate (20), and a ring column blank (22), a gear mold (9), and a fixed outer mold (10) are coaxially mounted on the positioning base (14); the rolling forming device is fixed to the ring rolling equipment via the rolling base plate (20); It also includes a driving wheel (12) connected to the ring rolling equipment and a driven wheel (17) mounted on a rolling base plate (20), the driving wheel (12) and the driven wheel (17) both being in tangential contact with a fixed outer die (10) mounted on a positioning base (14), at least two pillars (18) for mounting the driven wheel (17) being evenly arranged around the outer circumference of the fixed outer die (10) on the rolling base plate (20), the bottom of the driven wheel (17) being mounted on the pillars (18) via a bearing sleeve, the driven wheel (17) being used to ensure that the fixed outer die (10) rotates stably without eccentricity when the fixed outer die (10) rotates with the driving wheel (12); It also includes an electromagnetic induction coil (16) for heating the fixed outer mold (10) and a support seat (19); a hydraulic cylinder (21) is provided on the support seat (19); a positioning plate (15) is fixedly provided on the piston rod of the hydraulic cylinder (21) to prevent the fixed outer mold (10) from rising and being misplaced; the bottom surface of the positioning plate (15) is 2 to 4 mm away from the axial upper surface of the fixed outer mold (10); there is a gap between the inner curved surface of the electromagnetic induction coil (16) and the fixed outer mold (10); the electromagnetic induction coil (16) is fixed to the support seat (19) via a connecting piece.

2. The rolling forming device for large-module standard spur gears according to claim 1, characterized in that: The extrusion platform (8) is provided with a pair of connecting bosses (81), and the bottom surfaces of the first positioning plate (5) and the second positioning plate (7) are respectively provided with two grooves for slidingly connecting with the bosses (81), so as to facilitate the first positioning plate (5) and the second positioning plate (7) to clamp and position the extrusion base (6).

3. The large-module standard spur gear rolling forming device according to claim 1 is characterized in that: Semicircular grooves are provided at the centre of the surfaces of the first positioning plate (5) and the second positioning plate (7), so as to reserve space for the first extrusion punch (2) and the second pressing punch (3) to rotate.

4. The rolling forming device for large-module standard spur gears according to claim 1, characterized in that: The positioning base (14) is a 3 / 4 cylinder, and a 1 / 4 notch is provided on a side close to the driving wheel (12) to reserve space for the rotation of the driving wheel (12).

5. The large-module standard spur gear rolling forming device according to claim 1 is characterized in that: A plurality of balls are arranged on the contact surface between the positioning base (14) and the axial bottom of the fixed outer mold (10) to reduce the friction force exerted on the fixed outer mold (10) during rotation.

6. The rolling forming device for large-module standard spur gears according to claim 1, characterized in that: The gear mold (9) is composed of four identical gear sub-molds spliced ​​together, and the upper and lower parts are connected and fixed by four positioning pins (11) respectively. The outer surface of the gear mold (9) and the inner surface of the fixed outer mold (10) are in an interference fit at an angle, and the fit slope is 1° to 2°.

7. A rolling forming method using the large-module standard spur gear rolling forming device as claimed in claims 1 to 6, characterized in that: The specific steps are as follows: Step 1, selecting a blank and determining the size according to the target gear, cutting and uncutting the blank on a band saw to obtain a ring column blank (22), and heating the ring column blank (22) to 800-1000° C. with an acetylene flame to reduce deformation resistance; Step 2, installing the ring column blank (22) in the gear mold (9), adjusting the positioning with the positioning pin (11), preheating the gear mold (9) to 300-500° C., and then installing the gear mold (9) into the fixed outer mold (10), wherein the inner diameter of the fixed outer mold (10) is tapered and matches the outer diameter of the gear mold (9); Step 3, placing the fixed outer die (10) axially and horizontally on the extrusion base (6), and fixing the extrusion base (6) by means of a first positioning plate (5) and a second positioning plate (7), preheating the first extrusion punch (2) and the second extrusion punch (3) of the extrusion punch device to 300-500° C. with an acetylene flame, and then simultaneously driving the first extrusion punch (2) and the second extrusion punch (3) by two hydraulic devices to axially extrude the annular column blank (22) towards each other, with the extrusion stroke not exceeding 1 / 4 of the height of the annular column blank (22); Step 4, withdrawing the first extrusion punch (2) and the second extrusion punch (3) together with the fixed outer die (10) from the extrusion device and placing them in a rolling forming device, specifically, placing the fixed outer die (10) axially vertically on the positioning base (14) and in tangential contact with the driving wheel (12), adjusting the positioning baffle (15) by the hydraulic cylinder (21) to press it 2 to 4 mm above the axial upper surface of the fixed outer die (10); placing the rolling core roller (13) in the center hole of the ring column blank (22), connecting and coordinating with the ring rolling equipment, and controlling the temperature of the electromagnetic induction coil (16) to 300 to 500° C.; Step 5: The ring rolling equipment is used to control the driving wheel (12) to rotate, thereby driving the fixed outer mold (10), the gear mold (9) and the ring column blank (22) to rotate synchronously, and the driven wheel (17) ensures that the fixed outer mold (10) rotates stably without eccentricity; the electromagnetic induction coil (16) is kept heated; at the same time, the main shaft of the ring rolling equipment is controlled to drive the rolling core roller (13) to rotate about its own central axis and translate toward the driving wheel (12), thereby gradually rolling the ring column blank (22) into shape; Step six, withdraw the gear mold (9) from the rolling forming device, remove the fixed outer mold (10), separate the gear mold (9), and obtain a standard spur gear.

8. The rolling forming method of large-module standard spur gear according to claim 7, characterized in that: In step 1, the outer diameter of the ring column blank (22) is 1 to 2 mm smaller than the inner diameter of the gear mold (9).

9. The rolling forming method of large-module standard spur gear according to claim 7, characterized in that: In step three, the first extrusion punch (2) and the second extrusion punch (3) are composed of a cylinder at the tail for clamping and a cone at the head for forming, the cone has an inclination angle of 5 to 15 degrees, and the length of the cylinder does not exceed 2 / 5 of the height of the ring column blank (22).

10. The rolling forming method of large-module standard spur gear according to claim 7, characterized in that: In step five, the outer diameter of the rolling core roller (13) is 0.8-0.9 times the diameter of the center hole of the annular column blank (22); and the speed at which the rolling core roller (13) translates toward the driving wheel (12) is 0.01-0.03 times the diameter of the rolling core roller (13) per second.

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