A production process of an electric power steering gear ensuring the center position of a steering wheel during loading

Abstract

The application discloses a kind of electric power steering gear production processes for guaranteeing steering wheel loading middle position, including steps: S1, the intermediate position of input shaft limiting structure and gear shaft limiting structure cooperation is determined by positioning equipment and record, torsion bar is assembled to gear shaft, then input shaft is assembled to torsion bar according to intermediate position;S2, limit component that is adapted to half stroke length of rack is used to fix rack input shaft end, limit component includes first component and second component, second component is adapted to the connecting structure of rack end;S3, the relative position of input shaft's loading end flat square structure and main casing assembly is fixed by positioning tool, after angle adjustment is carried out to main casing assembly, main casing assembly is rotated again, finally gear shaft is slid into rack casing;S4, assemble upper cover assembly and fastening component.The electric power steering gear production process of the application, process flow is simple, the process of machining input shaft flat square in sub-assembly state is saved, the relative position accuracy of input shaft flat square and spline can be improved, product quality and processing efficiency are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of vehicle steering systems. Specifically, this invention relates to a manufacturing process for an electric power steering system that ensures the steering wheel is centered in the vehicle. Background Technology

[0002] The connection structure between the electric power steering unit and the drive shaft was previously commonly achieved using a pure spline connection. However, this structure can lead to inconsistent positioning angles between the input shaft and the fork during vehicle assembly, resulting in misaligned installation. This ultimately causes the steering wheel to tilt after installation, and in severe cases, requires readjustment of the connection position between the steering unit and the drive shaft fork, making the process quite cumbersome. With the optimization of the overall vehicle assembly process, the connection between the input shaft and the drive shaft fork of the electric power steering unit has been improved by adding flat squares at the connection points of the drive shaft fork and the steering unit input shaft for positioning. This ensures consistency between the steering unit input shaft and the drive shaft fork in each installation, improving assembly efficiency.

[0003] To ensure that the position of the input shaft flat at the vehicle mounting end (hereinafter referred to as the input shaft flat) meets the assembly requirements of the entire vehicle, the steering gear housing, rack, gear shaft, torsion bar, and input shaft are assembled first. Then, the input shaft flat is machined using metalworking. This approach involves complex process flows, increases assembly costs, and scrapping the input shaft flat during machining leads to the scrapping of the entire assembly. Furthermore, the input shaft flat and spline are prone to misalignment, causing the steering wheel angle to tilt after the electric power steering system is installed. Moreover, the machined input shaft flat at the vehicle mounting end lacks rust resistance, reducing product quality and lowering customer satisfaction.

[0004] This invention provides a manufacturing process for electric power steering systems that ensures the steering wheel is centered during vehicle installation, with a particular focus on improving product quality and processing efficiency. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, with the aim of improving product quality and processing efficiency.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, comprising the following steps: S1. Determine and record the intermediate position of the input shaft limiting structure and the gear shaft limiting structure by using a positioning device, assemble the torsion bar to the gear shaft, and then assemble the input shaft to the torsion bar according to the intermediate position. S2. The rack input shaft end is fixed by a limiting component adapted to the rack half-stroke length. The limiting component includes a first part and a second part that cooperate with each other. The second part is adapted to the connection structure of the rack end. The limiting depth of the first part is equal to the rack half-stroke length. S3. Using a positioning fixture to fix the relative position of the flat square structure at the loading end of the input shaft and the main housing assembly, after adjusting the angle of the main housing assembly, rotate the main housing assembly again, and finally slide the gear shaft into the rack housing. S4. Assemble the upper cover assembly and fastening components to control the midpoint of the rack travel and the angular position of the flat square structure at the loading end of the input shaft.

[0007] In step S1, the input shaft is positioned by its outer circle, and the caliper of the positioning device clamps the spline of the input shaft; the gear shaft is positioned by its outer circle, and another caliper of the positioning device clamps the gear shaft tooth profile; the torsion bar is positioned by its spline outer circle, and the torsion bar spline is clamped by the pneumatic clamp of the positioning device; and the axes of the gear shaft and the input shaft are aligned on the same axis. The first drive mechanism of the positioning device provides power to make the gear shaft move linearly downward along the first linear guide rail, causing the groove of the gear shaft to fall into the limiting boss on the input shaft; the second drive mechanism of the positioning device provides power to make the input shaft rotate to its left and right extreme positions respectively. The angle sensor of the positioning device records the angle values ​​of the input shaft rotating to the left and right extremes respectively. The control system analyzes the recorded data to determine the intermediate angle position, makes the left and right rotation angles equal and records this position, and positions the input shaft at this position. The clamping caliper of the gear shaft moves linearly along the first linear guide rail to return to the starting point; the pneumatic clamping fixture of the torsion bar moves linearly along the second linear guide rail, causing the axis of the torsion bar to move to the point where it coincides with the axis of the gear shaft; the clamping caliper of the gear shaft moves linearly downward along the first linear guide rail, causing the torsion bar to be pressed into the set position of the gear shaft. The gear shaft with the torsion bar pressed in returns to the starting point along the first linear guide rail, and the pneumatic clamping fixture of the torsion bar returns to the starting point via the second linear guide rail; After the torsion bar and gear shaft are press-fitted, the caliper clamping the gear shaft with the torsion bar press-fitted moves downward along the first linear guide rail, pressing the other end of the torsion bar into the set position of the input shaft. The caliper clamping the spline of the input shaft is released, and the gear shaft assembly with the torsion bar and input shaft press-fitted returns to the starting point along the first linear guide rail. The gear shaft assembly is manually held, the caliper clamping the gear shaft tooth is released, and the gear shaft assembly is removed.

[0008] The first drive mechanism includes a first motor, and the second drive mechanism includes a second motor.

[0009] The positioning fixture includes a mounting plate, on which a positioning pin and a splined inner hole are provided. A limiting surface that mates with the flat rectangular structure at the loading end of the input shaft is provided in the splined inner hole. In step S3, the positioning pin is inserted into the positioning hole of the main housing assembly, and the flat rectangular structure at the loading end of the input shaft is inserted into the splined inner hole and fits against the limiting surface.

[0010] The machining process of the input shaft includes the following steps: First, the material is cut, then the end face and outer diameter are machined, then the inner hole is machined, then heat treatment is performed, then the outer diameter is precision ground and the inner hole is precision bored, then the spline teeth are rolled, then the limiting boss, spline, and flat square structure of the loading end are machined, and finally cleaning is performed.

[0011] During the machining of the input shaft, the flat square structure and the limiting structure at the loading end are machined simultaneously using the spline shape as the positioning reference to eliminate the phase angle error between the two and the spline.

[0012] The machining process of the gear shaft includes the following steps: First, the material is cut, then the end face and outer circle are machined, then the inner hole is machined, then the groove is milled, then rough hobbing is performed with the groove as the reference, then carburizing and quenching, grinding the center hole, fine grinding the outer circle, fine boring the inner hole, then fine hobbing the gear shape with the groove as the reference, and finally cleaning.

[0013] During the machining process of the gear shaft, the tooth profile is machined based on its groove structure to ensure the phase angle relationship between the tooth profile and the groove structure in the circumferential direction.

[0014] The processing technology of the rack includes the following steps: First, the material is cut, then the two ends of the outer circle are machined, then the outer circle is ground, then the end face is positioned and the teeth are hobbed with a forming cutter, then quenched, straightened, inspected for flaws, polished, and finally rust-proofed.

[0015] During the rack machining process, a forming tool is used to process the tooth shape to ensure the accuracy of the tooth shape and the axial tooth pitch, and the positional accuracy of the tooth shape relative to the end face is ensured by end face positioning and clamping.

[0016] The electric power steering system manufacturing process of the present invention, which ensures the center position of the steering wheel during vehicle installation, has a simple process flow. It eliminates the step of machining the input shaft flat section in the assembly state, which can improve the relative positional accuracy of the input shaft flat section and the spline, thereby improving product quality and processing efficiency. Attached Figure Description

[0017] This manual includes the following figures, which illustrate the following: Figure 1 This is a schematic diagram of the electric power steering system; Figure 2 This is a schematic diagram of the rack housing; Figure 3 This is a schematic diagram of the main shell structure; Figure 4 This is a schematic diagram of the rack structure; Figure 5-1 and Figure 5-2 This is a schematic diagram of the rack shaft structure; Figure 6 This is a schematic diagram of the input shaft structure; Figure 7-1 This is a sectional view of the spindle assembly; Figure 7-2 This is a cross-sectional view of the limiting structure and the limiting groove; Figure 8 This is a structural schematic diagram of the rack and pinion housing assembly; Figure 9-1 This is a structural schematic diagram of the positioning fixture; Figure 9-2 This is a sectional view of the main housing assembly; Figure 9-3 This is a schematic diagram of the positioning tooling fitting into the main housing assembly; Figure 9-4 This is a schematic diagram of the main housing assembly being installed into the rack housing assembly; Figure 10-1 This is a structural diagram of the positioning device; Figure 10-2 yes Figure 10-1 Enlarged view of point A in the middle; The markings in the diagram are as follows: 1. Top cover assembly; 2. Long bolt; 3. Rack housing assembly; 4. Mounting hole; 5. First connecting hole; 6. Rack hole; 7. Second connecting hole; 8. Bearing hole; 9. Limiting groove; 10. Tooth profile; 11. Gear shaft groove projection line; 12. Spline; 13. Flat square structure at the loading end; 14. Limiting structure; 15. Input shaft; 16. Torque bar; 17. Gear shaft; 18. Limiting groove; 19. Rack housing; 20. Bolt; 21. Sleeve; 22. Rack; 24. Mounting plate; 23. Locating pin; 25. Spline inner hole; 26. Torque angle sensor; 27. Main housing assembly; 28. Worm gear; 29. ​​Bearing; 30. Main housing positioning hole; 31. First drive mechanism; 32. Second drive mechanism; 33. First linear guide; 34. Second linear guide; 35. Cylinder. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0019] This invention provides a manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, comprising the following steps: S1. Determine and record the intermediate position of the input shaft limiting structure 14 and the gear shaft limiting structure using the positioning device. Assemble the torsion bar onto the gear shaft, and then assemble the input shaft onto the torsion bar at the intermediate position. Then assemble the torque angle sensor, worm gear, and bearing onto the gear shaft to form the main shaft assembly. S2. A limiting component adapted to the rack half-stroke length is used to fix the rack input shaft end. The limiting component includes a first part and a second part that cooperate with each other. The second part is adapted to the connection structure of the rack end. The limiting depth of the first part is equal to the rack half-stroke length. S3. Using a positioning fixture to fix the relative position of the flat square structure at the loading end of the input shaft and the main housing assembly, after adjusting the angle of the main housing assembly, rotate the main housing assembly again, and finally slide the gear shaft into the rack housing. S4. Assemble the upper cover assembly 1 and fastening components to control the midpoint of the rack travel and the angular position of the flat square structure at the loading end of the input shaft.

[0020] Specifically, in step S1 above, the positioning device automatically finds and records the intermediate position. The input shaft limiting structure 14 is a limiting boss provided on the input shaft, and the gear shaft limiting structure is a limiting groove 18 provided on the gear shaft.

[0021] In step S1 above, the positioning device used is such as Figure 10-1 and Figure 10-2 As shown, the positioning device includes an angle sensor, a first drive mechanism 31, a second drive mechanism 32, a first linear guide rail 33, a second linear guide rail 34, and multiple pneumatic calipers. In the positioning device, the input shaft is positioned by its outer diameter, with one caliper clamping the spline of the input shaft; the gear shaft is positioned by its outer diameter, with another caliper clamping the gear shaft teeth; the torsion bar is positioned by its spline outer diameter, and the pneumatic caliper clamps the torsion bar spline; and the gear shaft and input shaft axes are aligned on the same axis, ensuring they are coaxial.

[0022] The first drive mechanism 31 of the positioning device provides power, causing the clamping caliper of the gear shaft to move downwards in a straight line along the first linear guide 33, fitting the limiting groove 18 of the gear shaft onto the limiting boss on the input shaft; the limiting boss on the input shaft falls into the limiting groove 18 on the gear shaft, and the limiting boss of the input shaft and the limiting groove 18 on the gear shaft are in an initial engagement state; then the second drive mechanism 32 of the positioning device provides power, causing the clamping caliper of the input shaft to rotate the input shaft to the left until the limiting boss contacts the first sidewall of the limiting groove 18, and the input shaft rotates to the first limit position. At this time, the angle sensor of the positioning device records this first limit position as the first limit angle value; then the second... The drive mechanism 32 rotates in reverse, causing the clamping caliper to rotate the input shaft to the right until the limiting boss contacts the second sidewall of the limiting groove 18. The input shaft rotates to its second limit position, at which point the angle sensor of the positioning device records this second limit position as the second limit angle value. The control system of the positioning device analyzes the first and second limit angle values ​​and calculates the intermediate angle position (i.e., the position corresponding to the average of the first and second limit angle values). This intermediate angle position must satisfy the following condition: the angle at which the input shaft rotates to the left limit from this position is exactly equal to the angle at which it rotates to the right limit (ensuring symmetrical left and right turning angles during subsequent turns). Figure 7-1 , 7-2 .

[0023] The positioning equipment's control system records the obtained intermediate angular position as the reference position for assembling the input shaft and gear shaft; after determining the intermediate angular position of the input shaft, component assembly is performed: The first drive mechanism 31 provides power, causing the clamping caliper of the gear shaft to move linearly along the first linear guide 33 back to the starting point; the pneumatic clamping fixture of the torsion bar moves linearly along the second linear guide 34, causing the axis of the torsion bar to move to the point where it coincides with the axis of the gear shaft, and the torsion bar moves to below the gear shaft and the two are coaxial; then the clamping caliper of the gear shaft moves linearly downward along the first linear guide 33, causing the torsion bar to be pressed into the set position of the gear shaft, and the gear shaft with the torsion bar pressed in returns along the first linear guide 33. Returning to the starting point, the pneumatic clamp for positioning the torsion bar returns to the starting point via the second linear guide 34; after the torsion bar and gear shaft are pressed together, the caliper clamping the gear shaft with the torsion bar pressed together moves downward in a straight line along the first linear guide 33, pressing the other end of the torsion bar into the set position of the input shaft. The caliper clamping the spline of the input shaft is released, and the gear shaft assembly with the torsion bar and input shaft pressed together returns to the starting point along the first linear guide 33. The gear shaft assembly is manually held, the caliper clamping the gear shaft teeth is released, and the gear shaft assembly is removed.

[0024] The first drive mechanism 31 includes a first motor, and the second drive mechanism 32 includes a second motor. The first motor, the second motor, the angle sensor, and the control system of the positioning device are electrically connected, and the angle sensor transmits the detected angle data to the control system.

[0025] Step S1 ensures precise relative rotational alignment between the input shaft and the gear shaft, allowing for direct alignment with the steering wheel after vehicle installation (preventing steering wheel misalignment). This is a prerequisite for subsequent steps (such as rack alignment and main housing assembly). Any deviation in alignment during this step will lead to a chain reaction of alignment errors throughout the entire steering gear. Step S1 achieves alignment calibration between the input shaft and the gear shaft through both mechanical structural fit and angle measurement, providing a fundamental guarantee for the overall alignment accuracy of the steering gear.

[0026] In step S2 above, the rack input shaft end is fixed by a limiting component that measures the half-stroke length of the rack. The rack of the electric power steering system is installed in the rack housing. The rack is used to mesh with the gear shaft of the electric power steering system. The gear shaft drives the rack to move linearly. The worm gear is coaxial with the gear shaft and the input shaft.

[0027] In this embodiment of the invention, the rack half-stroke length refers to the linear distance the rack travels from its middle position (i.e., the rack's stationary position when the steering wheel is in the straight position) to any of its extreme positions (maximum left / right steering positions). This distance is typically equal to half of the rack's total travel, and the left and right half-stroke lengths should theoretically be equal to ensure that the steering system's left and right steering angles are symmetrical.

[0028] like Figure 8 As shown, the limiting assembly includes a first component and a second component that cooperate with each other. The first component is a sleeve 21, and the second component is a bolt. The first component has an internally hollow structure and is used to fit onto the input shaft end of the rack, which is one end along the length of the rack. The second component is used to connect threadedly to the input shaft end of the rack. The second component is tightened onto and locked onto the first component. The specifications of the second component match the specifications of the internal threads at both ends along the length of the rack. The depth of the center hole of the first component (i.e., the limiting depth of the first component) is set to be equal to the half-stroke length of the rack.

[0029] In step S2 above, the rack is installed in the rack housing, the first component is sleeved on the input shaft end of the rack, the input shaft end of the rack is inserted into the center hole of the first component, the first component is located outside the rack housing, and then the second component is tightened. The second component passes through the through hole provided at one end of the first component and is inserted into the internal thread hole at the input shaft end of the rack, so as to realize the fixed connection between the first component and the rack. At the same time, the other end face of the first component contacts the surface of the rack housing, so as to limit the rack.

[0030] In step S2 above, a limiting component is used to limit the rack. The limiting depth of sleeve 21 is equal to the half-stroke length of the rack, ensuring that the maximum movement distance of the rack in both directions is equal. This directly corresponds to the "middle position" of the input shaft in step S1, making the steering angle of the steering system symmetrical and avoiding deviations such as "steering more on one side and less on the other". Errors in the machining and assembly of the rack teeth may cause the actual stroke to be inconsistent with the design value. By physically limiting the end point of the stroke, these errors can be compensated, ensuring that the number of rotations of the steering wheel from the middle position to the left and right is the same. Moreover, before the gear shaft meshes with the rack, the rack position is fixed by the limiting component to avoid rack displacement during subsequent assembly, reducing the need for repeated adjustments. The limiting depth of sleeve 21 has been determined in the design stage. During assembly, simply put sleeve 21 on the end of the rack and tighten the bolt to automatically achieve precise limiting, without the need to use measuring tools to measure the stroke length in real time.

[0031] like Figure 9-1 and Figure 9-3 As shown, the positioning fixture includes a mounting plate 24, on which a positioning pin and a splined inner hole are provided. The splined inner hole has a limiting surface that mates with the flat rectangular structure at the mounting end of the input shaft. The splined inner hole is a through hole formed in the mounting plate 24, used to mesh with the external spline on the input shaft. The limiting surface is a plane inside the splined inner hole, parallel to the axis of the splined inner hole. The limiting surface is used to mate with an outer surface of the flat rectangular structure at the mounting end of the input shaft; this outer surface is a plane and serves as a limiting mating surface. The positioning pin is fixedly mounted at one end of the mounting plate 24 and is used to insert into the positioning hole of the main housing assembly.

[0032] like Figures 9-1 to 9-4 As shown, in step S3 above, after the spindle assembly is inserted into the main housing assembly, the correct positions of the input shaft flat and the main housing assembly are fixed by the positioning fixture. The positioning pin is inserted into a positioning hole of the main housing assembly, and the vehicle-mounted flat structure of the input shaft is inserted into the spline inner hole, with the mating surface of the vehicle-mounted flat structure of the input shaft fitting against the limiting surface.

[0033] In step S3 above, after determining the correct position of the flat rectangular structure at the loading end of the input shaft, visually inspect the alignment of the connecting holes of the main housing and the rack housing. Assemble the main housing assembly fitted with the positioning fixture onto the rack housing. When the gear shaft contacts the rack, due to the helix angle of the gear shaft, it cannot be directly inserted into the meshing position of the rack, resulting in resistance. At this point, it is necessary to rotate the main housing assembly fitted with the positioning fixture in the opposite direction to the gear shaft rotation, so that the gear shaft is offset from its current position by one tooth profile, i.e., 45° < rotation angle. If the angle is less than 90°, visually rotate the three connecting holes of the main housing to be approximately offset from the three connecting holes of the rack housing to the middle position. (For example, if the gear shaft has 8 teeth, the angle of each gear shaft tooth profile is 360° / 8=45°. If the three connecting holes of the main housing and the three connecting holes of the rack housing are offset to the middle position, the gear shaft will rotate by an angle of approximately 360° / 3 / 2=60°). Then, following the direction of the gear shaft tooth profile, screw the gear shaft into the rack tooth profile for meshing and assembly. Finally, slide the gear shaft into the rack housing.

[0034] In step S3 above, the splined inner hole of the positioning fixture meshes with the outer spline of the input shaft, and a limiting surface that fits against the flat surface of the flat structure is provided in the splined inner hole. This design ensures that the circumferential positioning relationship between the fixture and the input shaft is unique, that is, the angle of the flat structure is strictly constrained by the limiting surface of the splined inner hole. During assembly, the positioning pin on the positioning fixture is inserted into the positioning hole of the main housing assembly, establishing the positional relationship between the fixture and the main housing. Subsequent assembly indirectly associates the angle of the flat structure with the vehicle mounting reference of the entire steering gear through the positioning pin. When the positioning fixture simultaneously constrains the spline and the flat structure, the accuracy of the machining stage is directly transferred to the assembly process, avoiding the cumulative error caused by multi-process positioning. The flat structure is associated with the main housing assembly through the positioning fixture, and the main housing assembly is finally fixed to the rack housing that meshes with the gear shaft. The angle position of the flat structure at the vehicle mounting end of the input shaft is uniquely determined as the correct position required by the design, thereby ensuring that the product quality of the electric power steering gear meets the design standards.

[0035] like Figure 1 As shown, in step S4 above, after the main housing assembly is fitted to the rack housing, the positioning fixture is removed. Then, the upper cover assembly 1 is installed on the main housing assembly, and then the long bolt 2 is assembled. By tightening the long bolt 2, the upper cover assembly 1, the main housing assembly, and the rack housing are fixedly connected together. The long bolt 2 passes through the upper cover assembly 1, the main housing assembly, and the rack housing in sequence, and the upper cover assembly 1 seals the inner cavity of the main housing assembly. After assembly, the center position of the rack travel and the flat angle position of the input shaft mounting end are effectively controlled. The limiting component is then removed to form the electric power steering system.

[0036] In this embodiment of the invention, the mechanical parts that affect the flatness angle of the input shaft of the electric power steering assembly are: rack housing, main housing, rack, gear shaft, and input shaft.

[0037] Design method for the dimensional tolerances of characteristic positions of various mechanical parts that affect the flatness angle of the input shaft after the electric power steering assembly is assembled: ① Rack housing machining process control design: The rack hole 6, three connecting threaded holes, and four mounting holes 4 for vehicle assembly are machined simultaneously in one operation. The relative dimensional and positional tolerances are controlled according to the design requirements. See attached document. Figure 2 ; ② Main housing machining process control design: The bearing hole 8 and three connecting holes for assembly and positioning are machined simultaneously in one operation. The diameter and position tolerances of the three connecting holes are controlled according to design requirements (see attached). Figure 3 ; ③ Gear rack machining process control design: Control the distance from the tooth profile center to the rack end face near the tooth profile and the total length of the rack according to the design requirements, see Appendix Figure 4 ; ④ Gear shaft machining process control design: Control the positional tolerances of the limiting groove 9 and the tooth profile according to the design requirements, see Appendix 5; ⑤ Input shaft machining process control design: First, machine the external spline. Then, using the spline shape as the positioning datum, simultaneously machine the flat surface and the limiting step. Control the positional tolerances of the spline, flat surface, and limiting boss according to the design requirements. See appendix. Figure 6 .

[0038] In this embodiment of the invention, the processing technology of the input shaft includes the following steps: First, the material is cut, then the end face and outer diameter are machined, then the inner hole is machined, then heat treatment is performed, then the outer diameter is precision ground and the inner hole is precision bored, then the spline teeth are rolled, then the limiting boss, spline, and flat square structure of the loading end are machined, and finally cleaning is performed.

[0039] During the input shaft machining process, the flat square structure and the limiting structure at the loading end are machined simultaneously using the spline shape as the positioning reference to eliminate the phase angle error between the two and the spline.

[0040] In this embodiment of the invention, the processing technology of the input shaft further includes the following steps: After the flat square structure at the loading end is processed, the workpiece is placed in an electroplating solution for electroplating treatment, so that a coating can be formed on the flat square part of the input shaft loading end to improve the product's rust resistance.

[0041] During the input shaft machining process, the input shaft is positioned by splines. The flat square at the spline and the limiting boss on the other side are machined in one go, which can effectively eliminate machining errors and phase angle errors between the features on both sides and the spline, thereby greatly eliminating errors caused by machining and manufacturing.

[0042] In this embodiment of the invention, the machining process of the gear shaft includes the following steps: First, the material is cut, then the end face and outer circle are machined, then the inner hole is machined, then the groove is milled, then rough hobbing is performed with the groove as the reference, then carburizing and quenching, grinding the center hole, fine grinding the outer circle, fine boring the inner hole, then fine hobbing the gear shape with the groove as the reference, and finally cleaning.

[0043] In this embodiment of the invention, during the gear shaft machining process, the tooth profile is machined based on its groove structure to ensure the phase angle relationship between the tooth profile and the groove structure in the circumferential direction, which can greatly eliminate the errors generated by machining and manufacturing.

[0044] In this embodiment of the invention, the processing technology of the rack includes the following steps: First, the material is cut, then the two ends of the outer circle are machined, then the outer circle is ground, then the end face is positioned and the teeth are hobbed with a forming cutter, then quenched, straightened, inspected for flaws, polished, and finally rust-proofed.

[0045] In this embodiment of the invention, during the rack machining process, a forming tool is used to process the tooth shape to ensure the accuracy of the tooth shape and the axial pitch accuracy, and the positional accuracy of the tooth shape relative to the end face is ensured by end face positioning and clamping, which can greatly eliminate the errors generated by the machining and manufacturing.

[0046] The electric power steering system manufacturing process of the present invention, which ensures the steering wheel is in the center position during vehicle installation, has the following advantages: 1. It eliminates the need for assembling the final product and then machining the flat shape, simplifying the process. 2. Reduced scrap rate and costs; 3. Effectively control the flatness angle of the input shaft mounting end from the design stage; 4. The relative position of the input shaft flatness and spline is effectively guaranteed, preventing misalignment and improving product quality; 5. A plating layer can be added to the flat square part of the input shaft mounting end to improve the product's rust resistance.

[0047] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, characterized in that, Including the following steps: S1. Determine and record the intermediate position of the input shaft limiting structure and the gear shaft limiting structure by using a positioning device, assemble the torsion bar to the gear shaft, and then assemble the input shaft to the torsion bar according to the intermediate position. S2. The rack input shaft end is fixed by a limiting component adapted to the rack half-stroke length. The limiting component includes a first part and a second part that cooperate with each other. The second part is adapted to the connection structure of the rack end. The limiting depth of the first part is equal to the rack half-stroke length. S3. Using a positioning fixture to fix the relative position of the flat square structure at the loading end of the input shaft and the main housing assembly, after adjusting the angle of the main housing assembly, rotate the main housing assembly again, and finally slide the gear shaft into the rack housing. S4. Assemble the upper cover assembly and fastening components to control the midpoint of the rack travel and the angular position of the flat square structure at the loading end of the input shaft.

2. The manufacturing process for an electric power steering system that ensures the steering wheel is in the center position during vehicle installation, as described in claim 1, is characterized in that... In step S1, the input shaft is positioned by its outer circle, and the caliper of the positioning device clamps the spline of the input shaft; the gear shaft is positioned by its outer circle, and another caliper of the positioning device clamps the gear shaft tooth profile; the torsion bar is positioned by its spline outer circle, and the torsion bar spline is clamped by the pneumatic clamp of the positioning device; and the axes of the gear shaft and the input shaft are aligned on the same axis. The first drive mechanism of the positioning device provides power to make the gear shaft move linearly downward along the first linear guide rail, causing the groove of the gear shaft to fall into the limiting boss on the input shaft; the second drive mechanism of the positioning device provides power to make the input shaft rotate to its left and right extreme positions respectively. The angle sensor of the positioning device records the angle values ​​of the input shaft rotating to the left and right extremes respectively. The control system analyzes the recorded data to determine the intermediate angle position, makes the left and right rotation angles equal and records this position, and positions the input shaft at this position. The clamping caliper of the gear shaft moves linearly along the first linear guide rail to return to the starting point; the pneumatic clamping fixture of the torsion bar moves linearly along the second linear guide rail, causing the axis of the torsion bar to move to the point where it coincides with the axis of the gear shaft; the clamping caliper of the gear shaft moves linearly downward along the first linear guide rail, causing the torsion bar to be pressed into the set position of the gear shaft. The gear shaft with the torsion bar pressed in returns to the starting point along the first linear guide rail, and the pneumatic clamping fixture of the torsion bar returns to the starting point via the second linear guide rail; After the torsion bar and gear shaft are press-fitted, the caliper clamping the gear shaft with the torsion bar press-fitted moves downward along the first linear guide rail, pressing the other end of the torsion bar into the set position of the input shaft. The caliper clamping the spline of the input shaft is released, and the gear shaft assembly with the torsion bar and input shaft press-fitted returns to the starting point along the first linear guide rail. The gear shaft assembly is manually held, the caliper clamping the gear shaft tooth is released, and the gear shaft assembly is removed.

3. The manufacturing process for an electric power steering system that ensures the steering wheel is in the center position during vehicle installation, as described in claim 2, is characterized in that... The first drive mechanism includes a first motor, and the second drive mechanism includes a second motor.

4. The manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, as described in any one of claims 1 to 3, is characterized in that... The positioning fixture includes a mounting plate, on which a positioning pin and a splined inner hole are provided. A limiting surface that mates with the flat rectangular structure at the loading end of the input shaft is provided in the splined inner hole. In step S3, the positioning pin is inserted into the positioning hole of the main housing assembly, and the flat rectangular structure at the loading end of the input shaft is inserted into the splined inner hole and fits against the limiting surface.

5. The manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, as described in any one of claims 1 to 3, is characterized in that... The machining process of the input shaft includes the following steps: First, the material is cut, then the end face and outer diameter are machined, then the inner hole is machined, then heat treatment is performed, then the outer diameter is precision ground and the inner hole is precision bored, then the spline teeth are rolled, then the limiting boss, spline, and flat square structure of the loading end are machined, and finally cleaning is performed.

6. The manufacturing process for an electric power steering system that ensures the steering wheel is in the center position during vehicle installation, as described in claim 5, is characterized in that... During the machining of the input shaft, the flat square structure and the limiting structure at the loading end are machined simultaneously using the spline shape as the positioning reference to eliminate the phase angle error between the two and the spline.

7. The manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, as described in any one of claims 1 to 3, is characterized in that... The machining process of the gear shaft includes the following steps: First, the material is cut, then the end face and outer circle are machined, then the inner hole is machined, then the groove is milled, then rough hobbing is performed with the groove as the reference, then carburizing and quenching, grinding the center hole, fine grinding the outer circle, fine boring the inner hole, then fine hobbing the gear shape with the groove as the reference, and finally cleaning.

8. The manufacturing process for an electric power steering system that ensures the steering wheel is in the center position during vehicle installation, as described in claim 7, is characterized in that... During the machining process of the gear shaft, the tooth profile is machined based on its groove structure to ensure the phase angle relationship between the tooth profile and the groove structure in the circumferential direction.

9. The manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, as described in any one of claims 1 to 3, is characterized in that... The processing technology of the rack includes the following steps: First, the material is cut, then the two ends of the outer circle are machined, then the outer circle is ground, then the end face is positioned and the teeth are hobbed with a forming cutter, then quenched, straightened, inspected for flaws, polished, and finally rust-proofed.

10. The manufacturing process for an electric power steering system that ensures the steering wheel is centered during vehicle installation, as described in any one of claims 1 to 3, is characterized in that... During the rack machining process, a forming tool is used to process the tooth shape to ensure the accuracy of the tooth shape and the axial tooth pitch, and the positional accuracy of the tooth shape relative to the end face is ensured by end face positioning and clamping.

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