Cold heading production method of universal joint external spline sliding fork

Abstract

The invention relates to a cold heading production method of a universal joint external spline sliding fork, which comprises the following steps of: cutting a raw material into a cylindrical blank, and performing cold extrusion diameter reduction to form a rod part, a transition circular truncated cone and a cylinder for manufacturing a spline; the fork-shaped part of the universal joint fork is upset through the working procedures of pre-forming, first-time forming of the fork part, second-time forming of the fork part, third-time forming of the fork part and the like, and spline forming of the spline shaft part and shaping and trimming of the fork-shaped part are completed through the cold upsetting finishing working procedure; and finally, the universal joint sliding yoke is machined to form a bearing hole and a check ring groove, and extrusion flashes and burrs generated in the extrusion production process are removed and polished. Compared with traditional hot forging machining, the machining method of the universal joint external spline sliding yoke saves energy consumption of heating forging through a cold forming mode, the needed external spline structure can be synchronously machined, the workload of machining is greatly reduced, raw materials are saved, and the mechanical strength and the surface quality of parts are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing transmission parts, and particularly to a cold heading production method for a universal joint outer spline sliding fork. Background Art

[0002] During the mechanical transmission process, when the angle between transmission shafts changes due to the change in the position between transmission parts, the cross-axis universal joint transmission is widely used, especially in the transmission system and steering system of automobiles.

[0003] In the field of mechanical manufacturing, at present, the structure of the universal joint sliding fork generally adopts the hot forging production process, and its process basically includes: blanking - intermediate frequency heating - hot die forging pre-forging - final forging - trimming to manufacture the blank of the universal joint sliding fork, and then the spline at the lower end of the sliding fork is processed by metal cutting; the bearing hole of the fork part and the groove for axial positioning of the bearing or the fixing end cover screw hole axially positioned by the end cover.

[0004] The manufacture of the hot forging blank is carried out through multiple processes such as heating, pre-forging, final forging, and trimming, which consumes a large amount of energy, has a long processing time, high energy costs and labor costs, and low productivity; the spline part is completed by machining methods, which also requires consuming equipment and machining labor hours, is time-consuming and laborious, increases the manufacturing cost, and wastes raw materials.

[0005] With the development of the cold heading forming process and the realization of the large (heavy) and precision of cold heading forming equipment. Some parts originally processed by hot forging can be completely processed by cold heading. Cold heading processing is a kind of less or non-cutting processing technology, which can obtain a complete metal streamline and improve the mechanical properties of products. Summary of the Invention

[0006] The purpose of the present invention is to provide a cold heading production method for a universal joint outer spline sliding fork. The key manufacturing process of the present invention is manufactured by a multi-station cold heading equipment. For the universal joint sliding fork with an outer spline, the lower spline shaft part of the universal joint sliding fork is strengthened by necking through cold forming, and the spline part is directly upset and formed at one time in the last process, eliminating the machining work of the spline; the shape of the fork part at the head is relatively complex and needs to be formed through multiple extensions and extrusions to ensure the shape and dimensional accuracy requirements of the fork part structure, so that most of the production content of the universal joint sliding fork parts is achieved through cold heading forming, and only the two mounting holes of the cross shaft bearing are completed by machining methods. This processing method saves the energy consumption of heating and forging compared with the traditional hot forging processing, and can simultaneously process the required outer spline structure, greatly reducing the workload of machining, saving raw materials, and improving the mechanical strength and surface quality of the parts.

[0007] To solve the above technical problems, the present invention is achieved by the following technical measures: A cold heading production method for a universal joint outer spline sliding fork, characterized by comprising the following processes.

[0008] 1. Blanking: Cut the raw material into a blank, and the blank is a cylindrical blank;

[0009] 2. Shaping and reducing the diameter: Cold extrude the cylindrical blank, and the shape after cold extrusion includes a rod part, a transition frustum, and a cylinder, and the diameter of the cylinder is larger than the diameter of the rod part;

[0010] 3. Pre-forming: Further perform cold extrusion, and the shape after cold extrusion includes a frustum formed by chamfering at the bottom, a cylindrical rod part, an arc transition frustum formed by arc transition, a chamfer transition frustum formed by chamfer transition, a cylindrical part, and a fork part initial blank formed by upsetting the head, which is composed of a lower semi-free upsetting part, a constrained upsetting part, an upper semi-free upsetting part, and a pre-formed top;

[0011] 4. First forming of the fork part: Continue to perform extrusion on the pre-formed shape to make it into a basic fork shape separated left and right. The extrusion forms two left-right symmetric structures including the left top after the first forming of the fork part and the left side face after the first forming of the fork part, and the fork-shaped bottom after the first forming of the fork part;

[0012] 5. Second forming of the fork part: Broaden the inner intervals of the fork-shaped part, and the material thickness of the fork-shaped part is extruded to become thinner and the height is stretched; The shape after cold extrusion includes the shape of the left top after the second forming of the fork part, the right top after the second forming of the fork part, and the fork-shaped bottom after the second forming of the fork part;

[0013] 6. Third forming of the fork part: Cold extrude the left top after the second forming of the fork part and the right top after the second forming of the fork part into an arc top, and perform a fillet treatment on the bottom edge of the fork-shaped bottom after the second forming of the fork part, and finally become a structure with the shapes of the left top after the third forming of the fork part, the right top after the third forming of the fork part, and the fork-shaped bottom after the third forming in three regions;

[0014] 7. Forming of the spline shaft part and shaping and trimming of the fork part: Perform a cold extrusion forming on the structure of the lower rod part once to form a spline shaft part, which is composed of several external spline grooves, and a spline shaft chamfer is provided at its end; Perform shaping and trimming on the surface quality of the fork part. The fork part is shaped to the left arc top and the right arc top of the fork shape that reach the external shape accuracy of the part, and the fork-shaped bottom and its connecting cylinder, transition chamfer, and transition arc shape of the fork part that transitions with the spline.

[0015] 8. Machining process: Machining the bearing holes and snap ring grooves: Machine two symmetrically arranged bearing holes on the fork-shaped part, and set snap ring grooves for fixing the bearings beside the bearing holes; Remove and polish the extrusion flash and burrs generated during the extrusion production process.

[0016] The cold heading production process of the universal joint outer spline sliding fork of the present invention adopts large-scale, heavy-duty, multi-station cold heading forming equipment, applies advanced cold heading forming production technology and design methods, and determines the deformation rate, the number of cold heading processes and the required upsetting force for cold heading forming. The advantages of the cold heading production process of the universal joint outer spline sliding fork provided by the present invention are as follows:

[0017] 1. Using large-diameter bar stock for necking down to improve the mechanical properties of the shaft: Using bar stock with a slightly larger diameter for necking down extrusion to cause plastic deformation to strengthen the material and improve its mechanical strength, and finally forming the basic dimensions for machining the spline shaft part. When higher strength requirements for the shaft are needed, secondary necking down extrusion can be carried out to further improve the mechanical strength of the spline shaft part.

[0018] 2. Spline extrusion forming to improve the spline strength and surface quality, while saving the workload of machining and reducing material waste: The external spline of the universal joint sliding fork is cold heading extruded in one step at the last station (process), and is also extruded and strengthened again after the spline necking down strengthening, further improving the mechanical strength of the spline part and the spline shaft structure. The deformation streamline of the material is consistent with the direction of spline sliding, the surface is smooth, and the surface strengthening during the extrusion process improves the hardness and wear resistance. Since the spline is extruded and formed instead of being produced by mechanical cutting, there is no workload of using machine tools for machining, and no cutting waste is generated, saving production man-hours and material waste.

[0019] 3. Multiple composite extrusion forming of the universal joint fork-shaped part, with small extrusion force, high mechanical strength, complete structure and few defects: The extrusion forming of the fork-shaped part is a composite extrusion mainly based on free upsetting and flattening, supplemented by constrained deformation, with coexistence of forward extrusion and backward extrusion. The formed metal streamline is natural, the material flow and filling are uniform, the external shape and internal structure of the formed fork-shaped part are complete, the probability of generating defects is low, the finished product rate is high, and the mechanical strength is high; The molds used in the extrusion are all of open structure form, the extrusion force used during production is small, and the expansion force on the mold is also small, which is beneficial to improving the service life of the mold and reducing the equipment load.

[0020] 4. Low energy consumption, low processing cost, and high productivity: Compared with the hot forging manufacturing of traditional universal joint sliding fork blanks, the cold heading production process does not require heating the original blank, saving the thermal energy required for heating. The hot forging manufacturing of blanks requires primary forging, final forging, and trimming processes, and the spline part also needs to be obtained by machining. The cold heading production process adopted in the present invention continuously processes and forms the blank and the spline. The cold heading production rhythm is usually about 60 r / min, that is, one piece can be produced per second, realizing high-volume and high-efficiency production, and at the same time saving the labor cost and machine tool cost for spline processing.

[0021] 5. High raw material utilization rate: Compared with the hot forging manufacturing of universal joint sliding forks, the cold heading production process only consumes the material of the bearing hole part, saving the material of the spline milling part, and significantly improving the material utilization rate.

[0022] 6. High dimensional accuracy and good surface quality: Usually, the accuracy of cold heading dies is relatively high. The quality of cold heading products mainly depends on the accuracy of cold heading machines and dies, and the stability and consistency of the products are good. Generally, the processing accuracy of the cold heading production process is within 0.05 mm, which can meet the quality requirements of most parts. The main working surface is formed in one step under the action of extrusion pressure. The geometric features such as surface roughness and surface texture, as well as the mechanical and physical properties of the surface, are significantly improved compared with machining.

[0023] As an improvement of the present invention, except for the bearing hole 2 and the bearing axial positioning structure being machined, other structures are all realized by the cold heading production process. When the axial positioning structure of the bearing adopts the end cover form, the retaining ring groove for fixing the bearing is replaced by a threaded hole on the outer side of the bearing hole. The purpose of selecting this design: Another connection method for fixedly connecting the outer spline sliding fork bearing of the universal joint. When limited by the end cover, a threaded hole is required for cooperation.

[0024] The outer spline groove can be formed by one-step extrusion. The technical effect brought by one-step extrusion is that the surface streamline and extrusion trajectory are consistent with the movement direction, and extrusion strengthens the surface, having high mechanical strength and surface quality.

[0025] As an improvement of the present invention, the cross-sectional reduction rate of the rod part is 50%. The purpose of selecting this design: When the cross-sectional reduction rate is 50% during cold extrusion, the extrusion stress required on the punch is small, and an ideal extrusion effect can be obtained.

[0026] The die used for extrusion adopts an open structure. The extrusion force used during production is small, and the expansion force received by the die is also small, which is beneficial to improving the die life and reducing the equipment load. Description of the Drawings

[0027] The accompanying drawings, which form a part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0028] In the drawings:

[0029] Figure 1a is a schematic structural view of the sliding yoke part of the universal joint external spline;

[0030] Figure 1b is a schematic structural view of the sliding yoke of the universal joint external spline provided with a threaded hole;

[0031] Figure 2 is a structural view of the cylindrical blank for cold heading processing of the sliding yoke of the universal joint external spline;

[0032] Figure 3 is a schematic structural view after the first forming process of the present invention;

[0033] Figure 4 is a schematic structural view after the second forming process of the present invention;

[0034] Figure 5 is a schematic structural view after the third forming process of the present invention;

[0035] Figure 6 is a schematic structural view after the fourth forming process of the present invention;

[0036] Figure 7 is a schematic structural view after the fifth forming process of the present invention;

[0037] Figure 8 is a schematic structural view of the workpiece after the sixth forming process of the present invention.

[0038] Description of reference numerals: 1, cylindrical blank; 2, bearing hole; 3, snap ring groove; 4, spline groove; 5, chamfer of spline shaft; 6, fillet; 7, threaded hole; 11, rod portion; 12, transition frustum; 13, cylinder; 21, frustum; 22, cylindrical rod portion; 23, arc transition frustum; 24, chamfer transition frustum; 25, cylindrical portion; 26, lower part of semi-free upsetting; 27, constrained upsetting portion; 28, upper part of semi-free upsetting; 29, top after preforming; 31, left top after the first forming of the fork portion; 32, left side face after the first forming of the fork portion; 33, fork-shaped bottom after the first forming of the fork portion; 41, left top after the second forming of the fork portion; 42, right top after the second forming of the fork portion; 43, fork-shaped bottom after the second forming of the fork portion; 51, left top after the third forming of the fork portion; 52, right top after the third forming of the fork portion; 53, fork-shaped bottom after the third forming; 61, left arc top of the fork shape; 62, right arc top of the fork shape; 63, fork-shaped bottom; 64, connecting cylinder of the fork portion; 65, transition chamfer; 66, transition arc; 67, spline shaft portion. Detailed implementation manners

[0039] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0040] Embodiment 1

[0041] Please refer to FIGS. 1-8.

[0042] The core object of the present invention is to provide a multi-station cold heading production process for manufacturing a universal joint external spline sliding fork and its similar structures, so as to obtain good upsetting quality and die life.

[0043] The present invention will be further described in detail below with reference to the accompanying drawings. As shown in FIG. 1, it is a schematic structural diagram of the part of the universal joint external spline sliding fork formed by the present invention; Figures 2 to 8 It is a schematic structural diagram of each station after forming in the cold heading production method of this kind of universal joint external spline sliding fork. Its cold heading production process is implemented on a six-station cold heading machine, and successively includes a shearing operation for shearing the blank and six forming processes ( Figures 3 - 8 ); A machining process is also required for the entire production of the universal joint sliding fork:

[0044] 1. Blanking: Cut the raw material into blanks of a predetermined size. The blank is a cylindrical blank 1, as shown in Figure 2 . Its volume is designed according to the principle of volume invariance to determine the volume size; its cylindrical diameter is comprehensively determined according to the deformation characteristics of the selected material, the necking requirement of the strength of the part rod portion, the upsetting force, and the die life;

[0045] 2. Shaping and necking: ForFigure 2 The shown blank is cold-extruded to form Figure 3 the intermediate transition form shown. This form includes a rod portion 11, a transition frustum 12, and a cylinder 13. The diameter of the rod portion 11 is designed according to the requirements of the necking process. During the first necking, the diameter of the rod portion 11 is upset to leave a gap of 0.05 - 0.1 mm between the blank for subsequent processes and the die, that is, upset to a diameter slightly smaller than the product size; the length of the rod portion 11 is designed considering subsequent extrusion deformation and is usually shorter than the finished product length; the transition frustum 12 connects the requirements of necking of the rod portion 11 and upsetting of the head. The small circular surface at the lower end has the same diameter as the rod portion 11, and the large circular surface at the upper part has the same diameter as the upper cylinder 13;

[0046] 3. Preforming: For Figure 3 the intermediate transition form shown, further cold extrusion is carried out, with the focus on extruding the head to form Figure 4 the preformed form shown. The form after cold extrusion includes a frustum 21 formed by chamfering at the bottom, a cylindrical rod portion 22, an arc transition frustum 23 formed by arc transition, a chamfer transition frustum 24 formed by chamfer transition, a cylindrical portion 25, and a fork-shaped blank formed by upsetting the head, which consists of a lower part 26 of semi-free upsetting, a constrained upsetting portion 27, an upper part 28 of semi-free upsetting, and a top 29 after preforming;

[0047] Features such as the frustum 21 formed by chamfering below, the cylindrical rod portion 22, the arc transition frustum 23 formed by arc transition, the chamfer transition frustum 24 formed by chamfer transition, and the cylindrical portion 25 are processed and completed during this upset forging. The lengths of the cylindrical portion 22 and the cylindrical portion 25 meet the requirements of spline cold extrusion in the final process, and the diameter size is preferably reserved with a gap of 0.05 mm for fitting with the die in each process.

[0048] Above is the fork-shaped part of the universal joint slip fork, which is the preforming content of this process. The purpose is to upset the material of the cylindrical part into a shape similar to a cuboid, then split it from the middle, and form the fork-shaped structures on both sides of the universal joint through compound extrusion. The main feature of the extrusion of the fork-shaped part is to restrict the deformation in the width direction and guide the material to deform along the length direction. During the deformation process, the middle part area is restricted by the die, and most of the upper and lower areas are in a free thickening (elongation) state.

[0049] The lower part 26 of semi-free upsetting is restricted more in the width direction than in the length direction. When being upset forged, it guides the material to flow along the length direction, forming a state where the lower part of this section is free to flow in both the length and width directions. The front and rear surfaces above generate a circular arc cylindrical surface due to the restraint in the width direction. The intersection line of this circular arc cylindrical surface and the surface of semi-free upsetting gradually widens from bottom to top; the constrained upsetting part 27 is under the restraint in the width direction during the overall preforming process of the head. After the material flows along the length direction and reaches the limit of preforming requirements, it is completely constrained by the die on all four sides of the length and width, generating a complete columnar structure required for forming; the deformation process of the upper part 28 of semi-free upsetting is similar to that of the lower part 26 of semi-free upsetting, but the deformation gradually decreases from bottom to top. Restricted by the width direction, the restricted areas on both sides in the width direction also gradually narrow until they are unrestricted and become free deformation; the preformed top 29 is to determine the central symmetry position for the upset forging of the fork-shaped structure of the universal joint head and prepare the stamping structure for the backward extrusion forming on both sides of the fork. The backward extrusion punch at the central position is designed as a truncated cone frustum shape.

[0050] 4. First forming of the fork part: The first forming of the fork part is to continue the extrusion on the preformed shape shown in Figure 4 to make it into a basic fork shape separated left and right, Figure 4 and extrude each part with the reference numerals 26 - 29 in Figure 5 to form two left and right symmetric structures, namely the left top 31 after the first forming of the fork part and the left side face part 32 after the first forming of the fork part as shown in

[0051] The so-called extrusion is a compound extrusion. The material is further extruded and elongated along the length direction. The fork is restricted in most areas in the height direction at both ends of the length position; the extrusion in the width direction is restricted, and the width requirements can be guaranteed basically in the whole area; from the deformation distribution in the height direction, there is a free extrusion deformation state on the outer sides near the length in the upper and lower parts. The extrusion force is mainly applied to the fork bottom 33 area after the first forming of the fork part, forming an outward and upward extrusion deformation.

[0051] 5. Second forming of the fork part: The second forming of the fork part is to widen the inner interval of the fork part on the basis of the first forming. The material thickness of the fork part is extruded and thinned, and the height is stretched and raised; it is formed under restraint within the range of length and width, and is not constrained in the height direction for free deformation; the shapes of the left top 31 after the first forming of the fork part, the left side face part 32 after the first forming of the fork part, and the fork bottom 33 after the first forming of the fork part are like those of the left top 41 after the second forming of the fork part, the right top 42 after the second forming of the fork part, and the fork bottom 43 after the second forming of the fork part as shown in Figure 6

[0052] 6. Third forming of the fork part: After the initial pre-forming, the first forming, and the second forming of the fork part from a cylinder, its basic structure has been formed. In this forming process, by restricting and constraining the peripheral shape of the fork, the left top 41 after the second forming of the fork part and the right top 42 after the second forming of the fork part are cold-extruded into arc tops, and the bottom edge of the fork bottom 43 after the second forming of the fork part is rounded, so as to basically meet the required external shape and dimensional requirements, and become as Figure 7 shown. The final fork part becomes a structure with three regional shapes: the left top 51 after the third forming of the fork part, the right top 52 after the third forming of the fork part, and the fork bottom 53 after the third forming.

[0053] 7. Spline forming, fork part shaping and trimming: This is the last step of cold heading forming. In this process, on the basis of the Figure 7 structure, the fork is shaped and trimmed; the spline structure of the lower rod part 11 is cold-extruded once to form a spline shaft part 67. The spline shaft part is composed of several spline grooves 4, and a spline shaft chamfer 5 is provided at its end. The structure after cold heading is as Figure 8 .

[0054] The spline shaft part 67 is formed by one-time extrusion upset forging. Compared with the milling process of the spline, the spline part is strengthened, the material texture and flow direction of the key and the key side are retained intact, the contact strength, torsional strength and fatigue resistance are improved, thereby enhancing the bearing capacity of the transmission part; the surface layer structure is smooth. Compared with the processed structure with the same surface roughness value, there are no tiny pits caused by cutting marks affecting the axial movement, and a higher surface roughness can be achieved, making the axial telescopic sliding of the universal joint sliding fork smooth; the spline centering accuracy of the spline shaft part 67 is guaranteed by the accuracy of the die, the consistency of the processing quality is good, and the processing cost is low.

[0055] The shape change of the fork part is complex, the surface quality requirement is high, and the processing difficulty is large. In this process, the surface quality of the fork is shaped and trimmed, so that the left arc top 61 and the right arc top 62 of the fork on both sides of the fork part structure, the fork bottom 63 reach the specified shape and dimensional requirements, and the fork part connecting cylinder 64 connected to the fork part, the transition chamfer 65 and the transition arc 66 to the spline also meet the accuracy requirements of the parts. The overall productivity is high and the economy is good.

[0056] The above processes are the cold heading processes for the processing of the universal joint sliding fork. The production of the universal joint sliding fork also requires a machining process. After cold heading and before or after the machining of the bearing hole 2, it is necessary to remove and polish the extrusion flash and burrs generated during the extrusion production process of the universal joint sliding fork, and special processes can be arranged for treatment.

[0057] 8. Machining process: Machining the bearing hole 2 and the axial positioning structure of the bearing. In a complete universal joint slip yoke part, there is a set of bearing holes 2 for the installation of the cross shaft and its axial positioning structure (such as the retaining ring groove 3 for the hole retaining ring or the end cover fixing screw holes when the bearing is positioned by the end cover) at the fork-shaped part. The accuracy and surface quality requirements of this part of the structure are high, and it can only be completed by machining methods. It can be machining two symmetric bearing holes 2 on the fork-shaped part, and setting the retaining ring groove 3 for fixing the bearing beside the bearing hole 2; removing and grinding the extrusion flash and burrs generated on the fork part during the extrusion production process.

[0058] Except for machining the bearing hole 2 and the axial positioning structure of the bearing in this embodiment, other structures can all be realized by the cold heading production process; when the axial positioning structure of the bearing adopts the end cover form, the retaining ring groove 3 for fixing the bearing (such as Figure 1a ) can be replaced by the threaded hole 7 (such as Figure 1b ) on the outer side of the bearing hole 2; the external spline groove 4 can be formed by one-time extrusion; the cross-sectional reduction rate of the rod part 11 can be controlled to 50%; the die used for extrusion can adopt an open structure.

[0059] The beneficial effects of the present invention: This processing method saves the energy consumption of heating and forging compared with the traditional hot forging processing, and can simultaneously machine the required external spline structure, greatly reducing the workload of machining, saving raw materials, and improving the mechanical strength and surface quality of the parts.

[0060] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "vertical", "upper", "lower", "horizontal", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0061] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0062] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A cold heading production method for the sliding fork of a universal joint external spline, characterized by including the following processes: 1.1 Blanking: Cut the raw material into a blank, and the blank is a cylindrical blank (1). 1.2 Shaping and reducing diameter: Cold extrude the cylindrical blank (1), and the shape after cold extrusion includes a rod part (11), a transition frustum (12), and a cylinder (13), and the diameter of the cylinder (13) is greater than the diameter of the rod part (11). 1.3 Pre - forming: Further cold extrude, and the shape after cold extrusion includes a frustum (21) formed by chamfering at the bottom, a cylindrical rod part (22), an arc - transition frustum (23) formed by arc transition, a chamfer - transition frustum (24) formed by chamfer transition, a cylindrical part (25), and a fork - part initial blank formed by upsetting the head, which consists of a semi - free upsetting lower part (26), a constrained upsetting part (27), a semi - free upsetting upper part (28), and a pre - formed top (29). 1.4 First forming of the fork part: Continue to extrude on the shape after pre - forming to make it into a basic fork shape separated left and right. The extrusion forms two left - right symmetric structures including the left top (31) after the first forming of the fork part and the left side face part (32) after the first forming of the fork part, and the fork - shaped bottom (33) after the first forming of the fork part. 1.5 Second forming of the fork part: Broaden the inner intervals of the fork - shaped part, and the material thickness of the fork - shaped part is extruded to become thinner and the height is stretched. The shape after cold extrusion includes the left top (41) after the second forming of the fork part, the right top (42) after the second forming of the fork part, and the shape of the fork - shaped bottom (43) after the second forming of the fork part. 1.6 Third forming of the fork part: Cold extrude the left top (41) and the right top (42) after the second forming of the fork part into arc tops, and perform a fillet (6) treatment on the bottom edge of the fork - shaped bottom (43) after the second forming of the fork part, and finally become a structure with the shapes of the left top (51) after the third forming of the fork part, the right top (52) after the third forming of the fork part, and the fork - shaped bottom (53) after the third forming. 1.7 Spline shaft part forming, fork part shaping and trimming: Cold extrude the structure of the following rod part (11) once to form the spline shaft part (67), which consists of several external spline grooves (4), and a spline shaft chamfer (5) is provided at its end; Shape and trim the surface quality of the fork, and the fork shaping reaches the left arc top (61) and the right arc top (62) of the fork with the external shape accuracy of the part, and the fork bottom (63) and its cylindrical connection (64), transition chamfer (65), transition arc (66) of the fork part connecting with the spline; 1.8 Machining process: Machine the bearing holes (2) and snap ring grooves (3). Machine two symmetrically left and right bearing holes (2) in the fork part, and a snap ring groove (3) for fixing the bearing is provided beside the bearing hole (2); Remove and polish the extrusion flash and burrs generated in the fork part during the extrusion production process.

2. The cold heading production method of the universal joint external spline sliding fork according to claim 1, characterized in that: Except for machining the bearing holes (2) and the bearing axial positioning structure, other structures are all realized by the cold heading production process; When the axial positioning structure of the bearing adopts the end cover form, the snap ring groove (3) for fixing the bearing is replaced by a threaded hole on the outer side of the bearing hole (2).

3. The cold heading production method of the universal joint external spline sliding fork according to claim 1, characterized in that: The external spline groove (4) is formed by one-time extrusion.

4. The cold heading production method of the universal joint external spline sliding fork according to claim 1, characterized in that: The cross-sectional reduction rate of the rod part (11) is 50%.

5. The cold heading production method of the universal joint external spline sliding fork according to claim 1, characterized in that: The die used for extrusion adopts an open structure.

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