Gearbox assembly, gearbox input shaft and machining method of gearbox input shaft

Abstract

The invention relates to the field of gearbox part machining, and discloses a gearbox input shaft machining method which comprises the steps that a spline inner hole is machined in an input shaft blank before heat treatment, an internal spline is machined after heat treatment, then the internal spline is adopted for positioning, and center holes in the two axial ends of the input shaft blank and a journal outer circle are machined. A spline inner hole is machined before heat treatment, and an internal spline is machined after treatment, so that the small diameter of the internal spline and the pitch circle of the internal spline are used as the consent machining reference, the internal spline is used as the machining reference for positioning and machining center holes in the two axial ends of the gearbox input shaft, and the machining reference of the pitch circle of the internal spline and the machining reference of the outer circle of a shaft neck are kept uniform; the central holes in the two axial ends of the input shaft of the gearbox are used for positioning and machining the outer circle of the journal, reference conversion is achieved, the technical precision of the pitch circle of the internal spline and the outer circle of the journal is guaranteed, and the machining precision of the input shaft of the gearbox is improved. The invention further provides the gearbox input shaft and a gearbox assembly.

Description

Technical Field

[0001] This invention relates to the field of automotive parts processing technology, and in particular to a gearbox assembly and a gearbox input shaft and a processing method thereof. Background Technology

[0002] With the rapid development of the new energy vehicle industry, its powertrain and transmission systems are continuously iterating and optimizing. Among the core components of new energy vehicles, the transmission, as a key link in power transmission, directly determines the driving experience and energy efficiency of the entire vehicle. To achieve efficient and reliable power transmission, meet the transmission's requirements for high load-bearing capacity and high transmission efficiency, ensure stability under high-speed operation, and possess excellent fatigue resistance, the internal spline connection technology of the input shaft has been widely used in the field of new energy vehicle transmissions.

[0003] In the actual assembly process of a gearbox, the internal spline relies on the tooth flank and mating parts to complete the transmission. Therefore, the assembly accuracy between the internal spline tooth flank (pitch circle) and the bearing assembly outer circle (journal outer circle) must be strictly guaranteed. Once the internal spline accuracy is out of tolerance, it will directly cause a deceleration knocking problem between the input shaft and the motor shaft, which will significantly increase the assembly failure rate of the gearbox. However, in the input shaft machining process, due to the lack of standardized benchmarks, the accuracy of testing based on the outer circle of the internal spline journal (especially the cumulative runout index) is difficult to guarantee effectively. This directly results in the current machining pass rate of internal splines being only 85%. More importantly, out-of-tolerance internal spline accuracy can cause low-order knocking faults in the transmission assembly, which not only affects the overall vehicle performance but also significantly increases the internal manufacturing costs and external after-sales losses for transmission manufacturers.

[0004] Therefore, optimizing existing machining processes and improving the machining accuracy of the splines within the input shaft has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a gearbox assembly and a gearbox input shaft and a processing method thereof, so as to solve the problems existing in the above-mentioned related technologies, improve the processing accuracy of the gearbox input shaft, ensure the finished product quality of the gearbox input shaft, and improve the assembly accuracy and operational reliability of the gearbox assembly.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for machining a gearbox input shaft, comprising the following steps: Step 1: Prepare the input shaft blank and machine the spline inner hole on the input shaft blank; Step 2: Perform gear hobbing operation at the position corresponding to the external spline of the input shaft blank; Step 3: Perform heat treatment on the input shaft blank; Step 4: Machining internal splines in the splined inner hole of the heat-treated input shaft blank; Step 5: Using the machined internal spline for positioning, machine the center holes at both ends of the input shaft blank along the axial direction; Step 6: Machin the outer diameter of the journal at both ends of the input shaft blank.

[0007] Preferably, in step one, the coaxiality tolerance between the spline inner hole and the outer diameter of the journal of the input shaft blank is 0.015mm, and the total runout tolerance of the spline inner hole based on the outer diameter of the journal of the input shaft blank is <0.025mm.

[0008] Preferably, in step four, the internal splines are machined using a hard-drawing small-diameter broach.

[0009] Preferably, in step four, the minor diameter of the internal spline is machined using the two axial ends of the input shaft blank as positioning references, and the internal spline is broached using the machined minor diameter of the internal spline as a reference.

[0010] Preferably, in step five, a center hole with a shorter axial length at one end of the input shaft blank is machined using the minor diameter of the internal spline as the positioning reference; then, a center hole with a longer axial length at one end of the input shaft blank is machined using the minor diameter of the internal spline as the positioning reference.

[0011] Preferably, in step five, the positioning method of tightening the minor diameter of the internal spline is adopted by using an internal expansion clamp.

[0012] Preferably, the center holes and axial end faces at both ends of the input shaft blank are machined using a lathe and / or a turning and grinding center.

[0013] Preferably, in step five, the center holes at both ends of the input shaft blank are machined using the internal spline tooth side as the positioning reference.

[0014] The present invention also provides a gearbox input shaft, which has a cylindrical structure, an internal spline in the central hole of the gearbox input shaft, an external spline and a shoulder on the outer peripheral surface of the gearbox input shaft, and is manufactured by the gearbox input shaft machining method described above.

[0015] The present invention also provides a gearbox assembly including the gearbox input shaft described above.

[0016] The present invention achieves the following technical effects compared to related technologies: The gearbox input shaft machining method of the present invention includes the following steps: Step 1, making an input shaft blank and machining a spline inner hole on the input shaft blank; Step 2, performing a gear hobbing operation at the corresponding position of the external spline on the input shaft blank; Step 3, heat treating the input shaft blank; Step 4, machining an internal spline in the spline inner hole of the heat-treated input shaft blank; Step 5, using the machined internal spline for positioning, machining the center holes at both axial ends of the input shaft blank; Step 6, machining the outer diameter of the journal at both axial ends of the input shaft blank.

[0017] The gearbox input shaft machining method of the present invention involves machining a splined inner hole on the input shaft blank before heat treatment, machining an internal spline after heat treatment, and then using the internal spline for positioning to machine the center holes at both axial ends of the input shaft blank and the outer diameter of the journal. In existing input shaft machining methods, the machining datum changes during heat treatment, leading to a decrease in the machining accuracy of the input shaft. However, the gearbox input shaft machining method of the present invention, by machining the splined inner hole before heat treatment and the internal spline after treatment, ensures that the minor diameter and pitch circle of the internal spline are the same machining datum. Using the internal spline as the machining datum, the center holes at both axial ends of the gearbox input shaft are machined, maintaining a unified machining datum between the internal spline pitch circle and the outer diameter of the journal. The outer diameter of the journal is machined using the center holes at both axial ends of the gearbox input shaft for positioning, achieving datum conversion and ensuring the machining accuracy of the internal spline pitch circle and the outer diameter of the journal. This improves the machining accuracy of the gearbox input shaft, while also shortening the machining time, increasing machining efficiency, and reducing machining costs.

[0018] The present invention also provides a gearbox input shaft, which is manufactured using the aforementioned gearbox input shaft machining method, thereby improving the machining quality of the gearbox input shaft. Simultaneously, the present invention also provides a gearbox assembly including the aforementioned gearbox input shaft, improving the machining quality of the gearbox input shaft, thereby ensuring the assembly accuracy of the gearbox assembly and improving the operational reliability of the gearbox assembly. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the gearbox input shaft disclosed in the embodiments of the present invention; Figure 2 This is a schematic diagram of the broach used for machining the spline inner hole in the gearbox input shaft machining method disclosed in this embodiment of the invention; Figure 3 This is a schematic diagram of the broach used for machining internal splines in the gearbox input shaft machining method disclosed in this embodiment of the invention.

[0021] In the diagram: 1. Internal spline; 2. External spline; 3. Center hole; 4. Outer diameter of journal; 5. Shoulder. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The purpose of this invention is to provide a gearbox assembly and a gearbox input shaft and a processing method thereof, so as to solve the problems existing in the above-mentioned related technologies, improve the processing accuracy of the gearbox input shaft, ensure the finished product quality of the gearbox input shaft, and improve the assembly accuracy and operational reliability of the gearbox assembly.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1 This embodiment provides a method for machining a gearbox input shaft. Please refer to [reference needed]. Figures 1-3 It includes the following steps: Step 1: Prepare the input shaft blank and machine the spline inner hole on the input shaft blank; Step 2: Perform gear hobbing operation at the position corresponding to the external spline 2 of the input shaft blank; Step 3: Heat treat the input shaft blank; Step 4: Machining internal spline 1 in the spline inner hole of the heat-treated input shaft blank; Step 5: Use the machined internal spline 1 for positioning, and machine the center holes 3 at both ends of the input shaft blank along the axial direction; Step 6: Machining the outer diameter of the journal at both ends of the input shaft blank (4 mm).

[0026] The gearbox input shaft machining method of the present invention involves machining a splined inner hole on the input shaft blank before heat treatment, machining an internal spline 1 after heat treatment, and then using the internal spline 1 for positioning to machine the center holes 3 at both axial ends of the input shaft blank and the outer diameter 4 of the journal. In existing input shaft machining methods, the machining datum changes during heat treatment, leading to a decrease in the machining accuracy of the input shaft. However, the gearbox input shaft machining method of the present invention, by machining the splined inner hole before heat treatment and machining the internal spline 1 after treatment, ensures that the minor diameter and pitch circle of the internal spline are the same machining datum. Using the internal spline 1 as the machining datum, the center holes 3 at both axial ends of the gearbox input shaft are machined, maintaining a unified machining datum between the internal spline pitch circle and the outer diameter 4 of the journal. The outer diameter 4 of the journal is machined using the center holes 3 at both axial ends of the gearbox input shaft for positioning, achieving datum conversion and ensuring the machining accuracy of the internal spline pitch circle and the outer diameter 4 of the journal. This improves the machining accuracy of the gearbox input shaft, while also shortening the machining time, increasing machining efficiency, and reducing machining costs.

[0027] In step one, the coaxiality tolerance between the spline inner hole and the outer diameter 4 of the journal of the input shaft blank is 0.015mm, and the total runout tolerance of the spline inner hole with the outer diameter 4 of the journal of the input shaft blank as the reference is <0.025mm. In the machining of the gearbox input shaft, this invention ensures the coaxiality of the spline inner hole with the two outer diameters of the journal 4 (40.015mm) through the finishing stage, laying a high-precision reference foundation for the subsequent machining of the inner spline 1. Relying on this reference, the cumulative runout of the inner spline 1 is controlled within 0.025mm, which can effectively improve the overall machining accuracy of the input shaft, thereby reducing assembly errors and ensuring the transmission stability and service life of the gearbox.

[0028] After performing a gear hobbing operation at the position corresponding to the external spline 2 of the input shaft blank, the input shaft blank is heat-treated to improve the surface hardness of the input shaft.

[0029] Specifically, in step four, a hardened small-diameter broach is used to machine internal spline 1. For details on the structure of the hardened small-diameter broach, please refer to [link to details]. Figure 3 This invention uses a hard-drawing small-diameter broach for machining, ensuring that the small diameter and pitch circle of the internal spline are based on a unified datum, thus guaranteeing the consistency of the datum of the internal spline 1 itself. It should also be noted that when broaching the spline inner hole before heat treatment, a... Figure 2 The broaches shown are used in stages, with different broaches employed at different stages to control machining accuracy in response to varying material conditions. Using broaches appropriate to each stage better adapts to changes in material properties, reducing machining defects (such as chipping and surface scratches that easily occur during hardening after heat treatment), improving the stability of the machining quality of the internal spline 1, and thus ensuring the assembly quality and operational reliability of the gearbox assembly. Furthermore, it helps extend tool life and improve machining efficiency.

[0030] In this specific embodiment, in step four, the minor diameter of the internal spline is machined using the axial ends of the input shaft blank as positioning references, and the internal spline 1 is broached using the machined minor diameter of the internal spline as a reference. This establishes the connection between the minor diameter of the internal spline and the pitch circle of the internal spline (i.e., the tooth side of the internal spline), thus establishing a reference for subsequent machining.

[0031] In this specific embodiment, in step five, the shorter axially length center hole 3 at one end of the input shaft blank is machined using the minor diameter of the internal spline as the positioning datum, ensuring the roundness of the center hole 3 at the shorter axially length end of the gearbox input shaft; then, the longer axially length center hole 3 at one end of the input shaft blank is machined using the minor diameter of the internal spline as the positioning datum, ensuring the roundness of the center hole 3 at the longer axially length end. When machining the center holes 3 at both ends of the gearbox input shaft, the minor diameter of the internal spline is used as the machining datum. A unified datum helps reduce machining errors and ensures machining accuracy.

[0032] In practical applications, in step five, the positioning method of tightening the minor diameter of the inner spline using an internal expansion clamp can be adopted during the machining process. Controlling the accuracy and tension of the internal expansion sleeve ensures the centering accuracy of the internal expansion. Simultaneously, it cooperates with the shoulder 5 of the gearbox input shaft for axial positioning, ensuring the machining accuracy of the center hole 3.

[0033] It should also be noted that, in practical applications, the center holes 3 at both axial ends of the input shaft blank and the axial end face can be machined using a lathe and / or a turning and grinding center. The machining sequence of the center holes 3 at both axial ends of the gearbox input shaft can also be adjusted according to the actual working conditions to meet different machining requirements and improve the flexibility and adaptability of the gearbox input shaft machining method of the present invention. For example, using the center hole 3 positioning method, the center hole 3 and end face of the longer axial length end of the gearbox input shaft are machined using a lathe and grinding center. Then, using the end face positioning method, the center hole 3 and end face of the shorter axial length end of the gearbox input shaft are machined using a lathe. Alternatively, using the axial end face positioning method, the center hole 3 and end face of the shorter axial length end of the gearbox input shaft are machined using a lathe. Then, using the center hole 3 positioning method, the center hole 3 and end face of the longer axial length end of the gearbox input shaft are machined using a lathe. Or, using the end face positioning method, the center hole 3 and end face of the shorter axial length end of the gearbox input shaft are machined using a lathe. Then, using the end face positioning method, the center hole 3 and end face of the longer axial length end of the gearbox input shaft are machined using a lathe. In practical applications, the machining equipment can be adjusted and selected according to the actual machining requirements to meet different specific machining conditions. These will not be listed here.

[0034] In other specific embodiments achievable by this invention, in step five, the center holes 3 at both axial ends of the input shaft blank are machined using the internal spline tooth side as the positioning reference. When machining the internal spline 1, a connection is established between the minor diameter of the internal spline and the pitch circle of the internal spline (i.e., the internal spline tooth side). In practical applications, the internal spline tooth side can also be used as the positioning reference to machine the center holes 3 at both axial ends of the input shaft blank. This ensures the machining accuracy of the gearbox input shaft while improving the flexibility and adaptability of the gearbox input shaft machining method of this invention.

[0035] The existing input shaft machining process includes drilling, grinding the outer diameter, and broaching. During drilling, a grinding center is used to remove the oxide scale from the surface of the center hole 3, serving as the machining datum for post-heat machining. During the outer diameter grinding, the center hole 3 is used for positioning, and the two outer diameters of the shaft are machined. In the broaching process, the spline itself is used as the datum for positioning during broaching. In this existing input shaft machining process, the datums for the internal spline 1 and the outer diameter 4 of the journal are not unified. Therefore, the outer diameter 4 of the journal is used as the datum to detect out-of-tolerance issues with the internal spline 1, resulting in an 85% pass rate for the internal spline 1.

[0036] The gearbox input shaft machining method of the present invention employs broaching to machine the spline inner hole before heat treatment and hard drawing to machine the internal spline 1 after heat treatment. In the machining process after heat treatment, the minor diameter or tooth flank of the internal spline is used as the machining positioning reference. The finished gearbox input shaft has its internal spline 1 inspected with the outer diameter 4 of the journal. The cumulative Fp of the internal spline 1 is ≤0.043mm; the runout Fr is ≤0.05mm. The span tolerance of the internal spline 1 is 19.703 (0 / -0.115)mm, and the measuring bar size is equal to 2mm. It satisfies the condition that the coaxiality of the internal spline 1 and the outer diameter 4 of the journal is ≤0.03mm and ensures that the tooth direction consistency of the external tooth is ≤0.01mm, Fp≤0.020mm, and runout Fr≤0.016mm. The surface roughness can reach Ra0.8μm~1.6μm. Compared with the existing input shaft machining methods, this method greatly improves the machining accuracy of the gearbox input shaft, and the pass rate of machining the internal spline 1 of the gearbox input shaft can reach 99.95%.

[0037] The gearbox input shaft machining method of this invention features short single-piece machining time, significantly reducing overall costs, especially in high-volume production. Machining dimensions are stable, and the precise design of the mold or broach ensures high accuracy (typically up to IT7 level) in tooth profile, pitch, and pitch circle.

[0038] In practical applications, the invented method for machining the gearbox input shaft may include the following steps: Step 1, Hot-drawing spline: Ensure the inner hole of the spline in the input shaft blank has a coaxiality of 0.015mm with the outer diameter of the two journals, and ensure that the spline cumulative runout is <0.025mm when using the two outer diameters as a reference to check the spline during the hot-drawing spline forming process. Step 2, gear hobbing: Hob the gears of the input shaft; Step 3, Heat Treatment: Perform heat treatment on the input shaft to increase the surface hardness of the input shaft; Step 4: Grinding the holes: Remove oxide scale and impurities from the center holes. Step 5, Hard drawing of internal spline 1 after heating: Machining the minor diameter of the internal spline of the input shaft to establish the connection between the minor diameter of the internal spline of the input shaft and the spline pitch circle (tooth flank), and to establish a datum for subsequent machining; Step 6: Machine the short end center hole: Expand the minor diameter of the internal spline of the input shaft, and machine the short end center hole by positioning the end face of the input shaft shoulder 5 to ensure the roundness of the short end center hole; Step 7: Machine the center hole at the long end: Expand the small diameter of the inner spline of the input shaft, and use the center hole at the short end as an auxiliary positioning tool to machine the center hole at the long end, ensuring the roundness of the center hole at the long end; Step 8: Grind the outer diameter of one end of the journal 4: Use two top positioning tools to machine the outer diameters of the two shaft diameters of the input shaft. During the process, a machining datum conversion occurs to ensure that the datum of the inner spline 1 of the input shaft and the outer diameter of the journal 4 are consistent. Step 9: Grind the outer diameter of the journal at the other end 4: Use two top positioning tools to machine the outer diameters of the two shafts of the input shaft. During the process, a machining datum conversion occurs to ensure that the datum of the inner spline 1 of the input shaft and the outer diameter of the journal 4 are consistent.

[0039] This invention uses the internal spline 1 as a reference to machine the center hole, and then uses the center hole to grind the outer circle. The center hole serves as a medium for unifying the reference, unifying the reference of the internal spline 1 and the outer circle 4 of the journal, thus ensuring the product qualification rate. The qualification rate of the input shaft internal spline 1 reaches 99.95%.

[0040] Example 2 This embodiment provides a gearbox input shaft. The gearbox input shaft has a cylindrical structure. The central hole 3 of the gearbox input shaft has an internal spline 1, and the outer peripheral surface of the gearbox input shaft has an external spline 2 and a shoulder 5. The gearbox input shaft is manufactured using the gearbox input shaft machining method of Embodiment 1.

[0041] The gearbox input shaft is a thin-walled through-hole component with a wall thickness ranging from 5mm to 10mm. It is prone to deformation during heat treatment. It is manufactured using the gearbox input shaft machining method described in Example 1, which can improve the machining accuracy of the gearbox input shaft and ensure the accuracy of subsequent gearbox assembly.

[0042] Example 3 This embodiment provides a gearbox assembly, including the gearbox input shaft of Embodiment 2.

[0043] The gearbox assembly of this embodiment, utilizing the gearbox input shaft of Embodiment 2, can effectively improve the assembly accuracy of the gearbox assembly, reduce the failure rate of the gearbox assembly, and improve the working reliability of the gearbox assembly.

[0044] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for machining a gearbox input shaft, characterized in that, Includes the following steps: Step 1: Prepare the input shaft blank and machine the spline inner hole on the input shaft blank; Step 2: Perform gear hobbing operation at the position corresponding to the external spline of the input shaft blank; Step 3: Perform heat treatment on the input shaft blank; Step 4: Machining internal splines in the splined inner hole of the heat-treated input shaft blank; Step 5: Using the machined internal spline for positioning, machine the center holes at both ends of the input shaft blank along the axial direction; Step 6: Machin the outer diameter of the journal at both ends of the input shaft blank.

2. The gearbox input shaft machining method according to claim 1, characterized in that: In step one, the coaxiality tolerance between the spline inner hole and the outer diameter of the journal of the input shaft blank is 0.015mm, and the total runout tolerance of the spline inner hole based on the outer diameter of the journal of the input shaft blank is <0.025mm.

3. The gearbox input shaft machining method according to claim 1, characterized in that: In step four, the internal splines are machined using a hard-broaching small-diameter broach.

4. The method for machining the gearbox input shaft according to claim 1, characterized in that: In step four, the minor diameter of the internal spline is machined using the two axial ends of the input shaft blank as positioning references, and the internal spline is broached using the machined minor diameter of the internal spline as a reference.

5. The method for machining the gearbox input shaft according to claim 1, characterized in that: In step five, the center hole with a shorter axial length at one end of the input shaft blank is machined using the minor diameter of the internal spline as the positioning reference; then, the center hole with a longer axial length at one end of the input shaft blank is machined using the minor diameter of the internal spline as the positioning reference.

6. The method for machining the gearbox input shaft according to claim 5, characterized in that: In step five, the positioning method of tightening the minor diameter of the internal spline is adopted by using an internal expansion clamp.

7. The method for machining the gearbox input shaft according to claim 1, characterized in that: The center holes and axial end faces at both ends of the input shaft blank are machined using a lathe and / or a turning and grinding center.

8. The method for machining the gearbox input shaft according to claim 1, characterized in that: In step five, the center holes at both ends of the input shaft blank are machined using the internal spline tooth side as the positioning reference.

9. A gearbox input shaft, wherein the gearbox input shaft has a cylindrical structure, an internal spline is provided in the central hole of the gearbox input shaft, and an external spline and a shoulder are provided on the outer peripheral surface of the gearbox input shaft, characterized in that: The gearbox input shaft is manufactured using the gearbox input shaft machining method described in claims 1-8.

10. A transmission assembly, characterized in that: Includes the gearbox input shaft as described in claim 9.

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