Motor shaft for reducing noise of internal spline and process method

Abstract

The invention relates to a motor shaft for reducing noise of an internal spline and a process method, the motor shaft is of an integrated structure and comprises a bearing retaining shoulder and a blind hole, a bottom hole is formed in the bottom of the blind hole, and a first groove and a second groove are sequentially formed in the outer circle of the bearing retaining shoulder at equal included angles; the first groove and the second groove are symmetrically distributed on the two sides of the bearing retaining shoulder, a pin hole is formed in the groove bottom of the first groove, the two ends of the pin hole penetrate through the groove bottom of the second groove, the pin hole penetrates through the bottom hole, hole pins are arranged at the two ends of the pin hole, and the hole pins are in interference fit with the pin hole. Compared with the prior art, the method has the advantages that the inner wall and the outer wall of the spline are uniformly heated during heat treatment, the spline precision is good, low-order howling generated by the spline is improved, beat frequency noise is modulated, and the manufacturing process and machining are simple.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle drive motor components technology, and in particular to a motor shaft and manufacturing process for reducing internal spline noise. Background Technology

[0002] The core component of the electromechanical energy conversion that drives new energy vehicles is the electric drive system. As a crucial part of the powertrain, the motor shaft outputs electromagnetic torque. The connection between the motor and the reducer typically uses internal and external splines to transmit the electromagnetic torque to the reducer's input shaft. Because the input speed of new energy vehicles can reach as high as 20,000 r / min, the precision requirements for the internal spline connection are extremely stringent.

[0003] According to the calculation method for the load-bearing capacity of internal splines in GB / T17855-2017, for error-free internal spline connections, such as... Figure 1 As shown, under the action of transmitted torque T, the tooth surfaces on one side contact each other under the action of torque, with equal backlash. All meshing teeth transmit torque and bear the same load. For internal spline connections with errors, such as... Figure 2 As shown, under the action of transmitted torque T, the load distribution of the involute internal spline pair with 46 teeth is uneven. When the internal spline motor shaft adopts an integral structure and the reducer shaft adopts an integral structure of external and internal splines, the internal spline is generally machined using a gear shaping process when a blind hole is opened on one side of the motor shaft. After gear shaping and heat treatment, the tooth skew, cumulative tooth pitch deviation, and radial runout will increase significantly, resulting in poor internal spline accuracy. After verifying and analyzing by exchanging motor shafts with good and poor internal spline accuracy, NVH testing was conducted using a QCT1132-2020 one-meter five-point microphone arrangement. The test results are as follows. Figure 3 As shown, it is evident that the high-speed amplitude of the sound pressure levels of the 3rd, 4th, and 5th orders of the internal spline motor shaft with poor precision is relatively large.

[0004] Currently, improving the accuracy of internal splines mainly focuses on two aspects. The first aspect involves improving the gear shaping process, such as the design of gear shaping tooling, the indexing mechanism of the gear shaping machine's worm gear, the clamping mechanism of the motor shaft's outer cylindrical surface, and the surface roughness of the clamped motor shaft's outer cylindrical surface. The second aspect involves improving the heat treatment process, such as heat treatment carburizing and quenching to effectively harden the layer. However, the difficulty lies in the heat treatment of the integrated motor shaft. During this process, a vortex-induced circulating vacuum zone forms on the inner side of the internal spline at the bottom position of the blind hole near one end of the motor shaft. The pressure on the outer side of the motor shaft at this corresponding position is greater than the pressure on the inner side of the internal spline near the bottom hole. Near the reducer shaft's mating sealing stop, the pressure on the inner and outer sides of the internal spline is equal. Therefore, the tooth skew and cumulative tooth pitch errors along the tooth width direction of the internal spline teeth of the motor shaft are relatively large, resulting in poor internal spline accuracy.

[0005] For example, the invention disclosed in CN108247304A presents a process method for improving the control of internal spline tooth direction accuracy. This method uses a mandrel with a smaller shrinkage rate than the shaft material to tighten the minor diameter of the internal spline, thereby controlling the stability of the deformation trend of the internal spline tooth direction. The linear reciprocating motion of the grinding rod repairs the internal spline tooth direction error, improving the internal spline accuracy. However, when applied to the internal splines of new energy vehicle motor shafts, the actual effect of grinding with a grinding rod is not ideal, and it damages the thickness of the carburized layer, leading to differences in tooth surface contact strength. After heat treatment, the motor shaft becomes harder, requiring high hardness of the grinding rod, which is prone to wear and requires a long grinding time. The accuracy requirement for the internal splines of new energy vehicle motor shafts is above grade 6, and the total tooth direction deviation is required to be between 1-2 microns; using a grinding rod does not achieve the required accuracy.

[0006] Furthermore, the invention with publication number CN108265170A discloses a method for improving the tooth profile accuracy of internal splines after carburizing heat treatment. By measuring the tooth profile slope of the internal splines after heat treatment, the change law of the tooth profile slope of the internal splines after heat treatment is analyzed and summarized. The accuracy of the internal splines is guaranteed by the reverse compensation processing principle. However, the compensation of the tooth profile slope of the internal splines is difficult in practical engineering applications. Theoretically, the statistical parameters of the internal spline accuracy follow a normal distribution. According to the actual accuracy detection and statistics of 200 motor shaft internal splines, the tooth profile slope and tooth direction slope of each internal spline have obvious nonlinearity. The reverse compensation using linear slope is difficult to implement in engineering, and when the sample size is small, it does not follow a normal distribution. After reverse compensation processing, the accuracy error of the internal splines of each motor shaft is large.

[0007] In summary, existing integrated structures of the internal spline shaft segment and motor shaft segment suffer from several drawbacks. During machining, a vortex-induced vacuum zone forms at the bottom hole of the internal spline on the motor shaft, leading to decreased precision of the internal spline. Furthermore, grinding with a grinding rod results in poor precision, long grinding time, and the internal spline tooth profile slope exhibits significant nonlinearity, making linear slope reverse compensation techniques difficult to implement. Therefore, there is a need for an integrated motor shaft with high-precision internal splines and reduced low-order noise, along with a corresponding manufacturing process. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art in processing one-piece structure motor shafts, which suffers from poor grinding precision when using grinding rods.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] This solution provides a motor shaft for reducing internal spline noise. The motor shaft is an integral structure, including a bearing shoulder and a blind hole. The bottom of the blind hole is provided with a bottom hole, and the outer circle of the bearing shoulder is provided with a first groove and a second groove at equal included angles.

[0011] The first groove and the second groove are symmetrically distributed on both sides of the bearing shoulder. The bottom of the first groove is provided with a pin hole. Both ends of the pin hole penetrate the bottom of the second groove. The pin hole passes through the bottom hole. Both ends of the pin hole are provided with pins. The pins are interference-fitted with the pin hole.

[0012] Preferably, both ends of the pin are rounded, and the two ends of the pin hole near the bottom of the first and second grooves are respectively chamfered.

[0013] Preferably, the interference fit between the pin and the pin hole is 2-4 mils.

[0014] Preferably, a sealing stop is provided at the opening of the blind hole, the sealing stop is coaxially arranged with the bottom hole, the blind hole is connected to the reducer shaft, and the sealing stop cooperates with the reducer shaft.

[0015] Preferably, the length of the pin is less than the depth of the pin hole.

[0016] Preferably, the blind hole is further provided with an internal spline and a relief groove that are configured with the bottom hole. One end of the relief groove is connected to the internal spline, and the other end is connected to the bottom hole. The distance from the end of the internal spline near the relief groove to the blind hole port is less than the distance from the bearing shoulder to the blind hole port.

[0017] Preferably, the motor shaft includes a stator core mounting section, and a keyway is provided on the outer side of the stator core mounting section along the axial direction of the motor shaft for connecting the motor shaft to the rotor core; the motor shaft is also provided with an external thread, which is located at the end of the keyway away from the blind hole for connecting a lock nut.

[0018] Preferably, the outer circle of the bearing shoulder is further provided with a first process groove and a second process groove, the first groove, the second groove and the second process groove being distributed at equal included angles on the outer circle of the bearing shoulder; the first process groove and the second process groove are symmetrically distributed on both sides of the bearing shoulder for clamping and positioning the motor shaft.

[0019] This solution also provides a motor shaft manufacturing method for reducing internal spline noise, including the following steps:

[0020] A first groove and a second groove are machined on the bearing shoulder of the motor shaft. Pin holes are machined at the bottom of the first groove and the second groove respectively. An internal spline is machined in the blind hole of the motor shaft by a gear shaping process.

[0021] After processing, the motor shaft is placed on the material rack and sent to the heat treatment furnace for heat treatment.

[0022] After heat treatment, the motor shaft is subjected to shot blasting and ultrasonic cleaning in sequence.

[0023] The pin is then installed into the pin hole, and the motor shaft is automatically straightened and precision ground.

[0024] Preferably, when machining the spline inside the motor shaft using a gear-shaping process, the motor shaft is held by a fixture, and the outer circle of the bearing shoulder is provided with a first process groove and a second process groove. The fixture is held in the first process groove and the second process groove, and the surface roughness of the contact position between the fixture and the first process groove or the second process groove is R0.7-R0.9.

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

[0026] (1) In this scheme, the bearing shoulder is provided with a first groove and a second groove that are symmetrically distributed, and a through pin hole is provided at the bottom of the first groove and the second groove. The blind hole of the motor shaft is connected to the outside through the pin hole and the bottom hole, so that the air pressure on the inside and outside of the blind hole is balanced, and the pressure at each position of the internal spline teeth in the blind hole is basically the same. During heat treatment, the internal spline is subjected to uniform force and has small deformation. After heat treatment, the pin is interference fitted into the pin hole, and the lubricating oil at the spline in the blind hole enters the motor.

[0027] By setting symmetrically distributed first and second grooves on the bearing shoulder, and opening pin holes that penetrate the bottom of the first and second grooves and pass through the bottom hole, the air pressure at both ends of the blind hole is made basically equal. This balances the pressure at various points on the spline teeth within the blind hole. During heat treatment of the motor shaft, the stress on the internal spline is uniform and relatively small, effectively improving the accuracy of the internal spline and preventing internal spline noise. Furthermore, the removable pin within the pin hole allows for interference fitting of the pin into the pin hole after heat treatment, ensuring the blind hole's airtightness and preventing lubricating oil from entering the motor interior, thus avoiding interference with motor operation and ensuring the reliability of the motor shaft.

[0028] (2) In this solution, when the motor shaft is clamped by the fixture and the internal spline is machined by the gear shaping process, the length of the gear shaping tool corresponds to the length of the internal spline. This avoids the problem of tool rigidity deterioration due to the gear shaping tool being too long, which would cause the tool to deflect during the gear shaping process and result in the cumulative error of the internal spline tooth pitch exceeding the tolerance. This ensures the accuracy of the internal spline and improves the product qualification rate. On the other hand, when the motor shaft is clamped by the fixture, the surface roughness of the fixture tooling and the process groove of the motor shaft reaches about R0.8. This avoids the situation where the motor is skewed due to the low accuracy of the clamping contact surface, which would cause the total tooth deviation of the internal spline to be too large after gear shaping. This improves the clamping stability and reliability of the motor shaft. Attached Figure Description

[0029] Figure 1 A schematic diagram of the theoretical position of an involute internal spline connection with no error, under load, and with clearance;

[0030] Figure 2 A schematic diagram of load distribution for a 46-tooth involute internal spline pair with errors, loads, and clearances;

[0031] Figure 3 A color map diagram illustrating the test of interchangeable motor shafts with poor and good internal spline precision in electric drive assemblies.

[0032] Figure 4 This is a schematic diagram of the integrated structure of the internal spline motor shaft according to an embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of the shoulder groove configuration according to an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of the internal spline under pressure during the heat treatment of the motor shaft according to an embodiment of the present invention;

[0035] Figure 7 This is a schematic diagram of the pin hole according to an embodiment of the present invention;

[0036] Figure 8 A schematic diagram showing the interference analysis results of the pin and hole after the hole is drilled in the groove of the motor shaft shoulder;

[0037] Figure 9 A schematic diagram showing the change in motor shaft strength between bearing shoulder grooves without holes and with holes and press-in pins;

[0038] Figure 10 This is a schematic diagram showing the analysis results of the vibration response of the motor shaft shoulder groove with or without openings under motor torque pulsation and first-order unbalanced excitation.

[0039] Figure 11 This is a schematic diagram of alternative scheme 1 for the integrated internal spline motor shaft structure according to an embodiment of the present invention;

[0040] Figure 12 This is a schematic diagram of alternative scheme 2 for the integrated internal spline motor shaft structure of the present invention;

[0041] In the diagram: 1. Sealing stop; 2. Internal spline; 3. Front bearing seat retaining ring groove; 4. Front bearing seat; 5. Bearing shoulder; 6. Hole pin; 7. Pin hole; 8. Relief groove; 9. Keyway; 10. Bottom hole; 11. Rotor core mounting section; 12. External thread; 13. Rear bearing seat; 14. Rear bearing seat retaining ring groove; 15. Resolver rotor mounting position; 16. Ejector pin hole; 17. Rear bearing shoulder; 31. First groove; 32. Second groove; 41. First process groove; 42. Second process groove; 81. Thread break groove; 5 5. Air area at the sealing stop; 66. Outer outer circle pressure surface; 67. Inner outer circle pressure surface; 77. Outer inner circle pressure surface of the internal spline teeth; 78. Inner inner circle pressure surface of the internal spline teeth; 88. Air area of ​​the shoulder groove pin hole; 71. Keyway pin hole; 72. Mounting section pin hole; 111. Internal spline teeth; 112. Outer and inner spline teeth; 555. Shoulder groove without hole motor shaft; 666. Shoulder groove with hole and pin motor shaft; 888. One side hole pin and hole interference fit position; 999. The other side hole pin and hole interference fit position. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0044] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0045] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0046] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0047] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0048] Example 1

[0049] like Figure 4 and Figure 5 As shown, this embodiment provides a motor shaft for reducing internal spline noise. The motor shaft is an integral structure, including a bearing shoulder 5 and a blind hole. The bottom of the blind hole is provided with a bottom hole 10. The outer circle of the bearing shoulder 5 is provided with a first groove 31 and a second groove 32 at equal included angles.

[0050] The first groove 31 and the second groove 32 are symmetrically distributed on both sides of the bearing shoulder 5. The bottom of the first groove 31 is provided with a pin hole 7. The two ends of the pin hole 7 penetrate the bottom of the second groove 32. The pin hole 7 passes through the bottom hole 10. The two ends of the pin hole 7 are provided with pins 6, and the pins 6 and the pin hole 7 are interference fit.

[0051] Working principle: such as Figure 6 As shown, the bearing shoulder 5 is provided with symmetrically distributed first grooves 31 and second grooves 32, and through pin holes 7 are provided at the bottom of the first grooves 31 and second grooves 32. The blind hole of the motor shaft is connected to the outside through the pin hole 7 and the bottom hole 10, so as to balance the air pressure on both sides of the blind hole and make the pressure at each position of the internal spline teeth in the blind hole basically the same. During heat treatment, the internal spline is subjected to uniform stress and has small deformation. After heat treatment, the pin 6 is interference-fitted into the pin hole 7, so that the lubricating oil at the spline in the blind hole enters the motor.

[0052] By setting symmetrically distributed first grooves 31 and second grooves 32 on the bearing shoulder 5, and opening pin holes 7 that penetrate the bottom of the first grooves 31 and second grooves 32 and pass through the bottom hole 10, the air pressure at both ends of the blind hole is made basically equal. This balances the pressure at various points on the spline teeth within the blind hole, resulting in uniform and relatively small stress on the internal spline during heat treatment of the motor shaft. This effectively improves the accuracy of the internal spline and avoids internal spline noise. Furthermore, the removable pin 6 within the pin hole 7 allows for interference fitting of the pin 6 into the pin hole 7 after heat treatment of the motor shaft, ensuring the blind hole's airtightness and preventing lubricating oil from entering the motor interior, thus avoiding interference with motor operation and ensuring the reliability of the motor shaft.

[0053] Preferably, such as Figure 7 As shown, both ends of the pin 6 are rounded, and the two ends of the pin hole 7 near the bottom of the first groove 31 and the second groove 32 are also chamfered. The interference fit between the pin 6 and the pin hole 7 is 2-4 microns. The length of the pin 6 is less than the depth of the pin hole 7. The chamfering at both ends of the pin 6, in conjunction with the chamfering at the outer end of the pin hole 7, prevents damage to the pin 6 or pin hole 7 during assembly.

[0054] Furthermore, a sealing stop 1 is provided at the opening of the blind hole. The sealing stop 1 is coaxially arranged with the bottom hole 10. The blind hole connects to the reducer shaft, and the sealing stop 1 mates with the reducer shaft. This ensures the airtightness of the internal spline and the reducer shaft, prevents lubricating oil from splashing from the reducer into the motor rotor, improves the spline connection contact area, and extends the service life of the spline.

[0055] The blind hole also includes an internal spline 2 and a relief groove 8, which are aligned with the bottom hole 10. One end of the relief groove 8 connects to the internal spline 2, and the other end connects to the bottom hole 10. The distance from the end of the internal spline 2 closest to the relief groove 8 to the blind hole port is less than the distance from the bearing shoulder 5 to the blind hole port. This avoids the bearing shoulder being positioned at the spline tooth location, which would affect the spline tooth root strength and the fit with the spline of the reducer input shaft.

[0056] Specifically, the motor shaft includes a stator core mounting section 11, and a keyway 9 is provided on the outer side of the stator core mounting section 11 along the axial direction of the motor shaft for connecting the motor shaft to the rotor core; the motor shaft is also provided with an external thread 12, which is located at the end of the keyway 9 away from the blind hole and is used to connect a lock nut.

[0057] The bearing shoulder 5 is provided with a first process groove 41 and a second process groove 42 on its outer circle. The first groove 31, the first process groove 41, the second groove 32 and the second process groove 42 are distributed at equal included angles on the outer circle of the bearing shoulder 5. The first process groove 41 and the second process groove 42 are symmetrically distributed on both sides of the bearing shoulder 5 for clamping and positioning the motor shaft.

[0058] This embodiment also provides a process method for machining the motor shaft described above for reducing internal spline noise, including the following steps:

[0059] A first groove 31 and a second groove 32 are machined on the bearing shoulder 5 of the motor shaft, and pin holes 7 are machined at the bottom of the grooves of the first groove 31 and the second groove 32 respectively. An internal spline is machined in the blind hole of the motor shaft by a gear shaping process.

[0060] After processing, the motor shaft is placed on the material rack and sent to the heat treatment furnace for heat treatment.

[0061] After heat treatment, the motor shaft is subjected to shot blasting and ultrasonic cleaning in sequence.

[0062] Install pin 6 into pin hole 7, and then perform automatic straightening and fine grinding on the motor shaft.

[0063] In a preferred embodiment, when machining the internal spline in the blind hole of the motor shaft, the machining is carried out by a gear shaping process, and the length of the gear shaping tool matches the length of the internal spline.

[0064] When the motor shaft is clamped in a fixture and the internal spline is machined using a gear shaping process, the length of the gear shaping tool should correspond to the length of the internal spline. This avoids the problem of the tool becoming less rigid due to the gear shaping tool being too long, causing tool deflection during the gear shaping process, which would result in the cumulative error of the internal spline tooth pitch exceeding the tolerance. This ensures the accuracy of the internal spline and improves the product qualification rate.

[0065] When machining the internal spline of the motor shaft using a gear shaping process, the motor shaft is held in a fixture. The fixture is held in a first process groove 41 and a second process groove 42. The surface roughness of the contact position between the fixture and the first process groove 41 or the second process groove 42 is R0.7-R0.9. Preferably, the surface roughness of the contact position between the fixture and the first process groove 41 or the second process groove 42 is R0.8.

[0066] When the fixture holds the motor shaft, the surface roughness of the fixture tooling and the motor shaft process groove reaches about R0.8. This avoids the situation where the motor is misaligned due to low precision of the clamping contact surface, resulting in a large total deviation of the tooth direction of the internal spline after gear cutting. This improves the clamping stability and reliability of the motor shaft. The manufacturing process and processing are simple, easy to implement, and have good cost control.

[0067] In conjunction with the preferred embodiments described above, this embodiment also provides a more specific implementation method:

[0068] like Figure 4As shown, a one-piece motor shaft with internal splines has a blind hole at the end of the shaft. The blind hole contains a bottom hole 10, a relief groove 8, an internal spline 2, and a sealing stop 1 that mates with the reducer shaft. The front bearing seat 4 and the rear bearing seat 13 support the motor shaft for rotation. The front bearing seat 4 is positioned by a retaining ring installed via a bearing shoulder 5 and a retaining ring groove 3. The rear bearing seat 13 is positioned by a retaining ring installed via a rear bearing shoulder 17 and a retaining ring groove 14. A keyway 9 is formed in the rotor core mounting section 11 of the motor shaft, mainly for mates with the rotor core. An external thread 12 is machined between the rear bearing shoulder and the rotor core mounting section 11, and the external thread 12 is used to secure the rotor core with a lock nut. On the other side of the motor shaft, a ejector rotor mounting position 15 has a ejector pin hole 16 drilled, which, along with the bearing shoulder process groove 41, is used to fix the motor shaft.

[0069] The front bearing shoulder has an axial length of 20mm. A 6mm groove with a depth of 2mm is cut along the axial direction of the front bearing shoulder. The groove is mainly used for process clamping and opening holes. Shoulder groove 31 and process shoulder groove 41 are shown below. Figure 5 As shown, there are two shoulder grooves and two process shoulder grooves, symmetrically distributed at 90° intervals to prevent dynamic imbalance response caused by stress release of the rotor shaft at high speeds, thus avoiding first-order noise. A 3mm shoulder pin hole 7 is drilled at the center of the shoulder grooves 31 on both sides. The outer side of the shoulder groove hole is chamfered to prevent the pin 6 from being pressed in and damaging the hole. After drilling the shoulder pin hole 7 and the internal spline 2 of the gear in the shoulder groove 31, other machining processes are completed, followed by heat treatment of the motor shaft. The design of the pin and hole can be a combination of triangular, quadrilateral, or other polygonal structures; the pin design can also adopt a snap-fit ​​design to ensure that it does not fall out at high speeds.

[0070] The internal spline machining is achieved through a gear shaping process. To improve spline accuracy during gear shaping, the following measures are taken during the machining process: The length of the gear shaping tool must be adapted to the length of the internal spline. If the tool is too long, its rigidity will decrease, and tool deflection may occur during the shaping process, resulting in excessive cumulative error in the spline tooth pitch. The accuracy of the indexing mechanism of the gear shaping machine must be improved. The servo motor of the gear shaping machine is connected to the worm gear, which drives the worm wheel for indexing. Prolonged operation may cause excessive clearance in the indexing mechanism, leading to a larger cumulative error in the tooth pitch when measuring the spline accuracy after gear shaping. When clamping the motor shaft during gear shaping, the surface roughness of the fixture and the motor shaft clamping position must reach approximately R0.8 to avoid misalignment of the clamping motor due to low precision of the clamping mating surfaces, which would result in a larger total deviation in the spline tooth direction after gear shaping.

[0071] Before heat treatment, the motor shaft is placed vertically on a material rack along its axial direction and then sent to the heat treatment furnace. Figure 6 As shown, the spline inside the motor shaft is under pressure during heat treatment.

[0072] If the shoulder groove is not opened, the bottom hole 10, the relief groove 8 and the inner circle pressure surface 78 of the spline tooth form a vortex circulation vacuum zone. The air pressure on the inner outer circle pressure surface 67 is greater than that on the inner circle pressure surface 78 of the spline tooth, causing large deformation of the inner circle spline tooth. The pressure on the outer outer circle pressure surface 66 is basically equal to the pressure on the outer inner circle pressure surface 77, and the spline tooth deforms less. Therefore, the entire spline tooth deforms greatly along the tooth width direction on the inner inner circle pressure surface 78, which makes the spline accuracy worse and increases the total tooth direction deviation and the cumulative tooth pitch error.

[0073] After the first groove 31 and the second groove are made into pin holes 7, air flows into the pin holes 7 during heat treatment, forming an air zone 88. The pressure is basically equal to that of the air zone 55 at the sealing stop. Therefore, the pressure at each position of the inner circle pressure surface 78, the inner outer circle pressure surface 67, the outer outer circle pressure surface 66, and the outer inner circle pressure surface 77 of the spline teeth is basically equal. During heat treatment, the spline is subjected to uniform pressure, with small deformation, high spline precision, and avoidance of spline noise.

[0074] After heat treatment, the motor shaft undergoes shot blasting and ultrasonic cleaning. After cleaning, the pin 6 is pressed into the pin hole 7.

[0075] The pin 6 has small chamfers on both sides to prevent damage during pressing. The mating surface between the pin hole 7 and the pin 6 uses an interference fit with an interference of 2-4 microns. To ensure that the pin and pin 6 do not fall off under high-speed rotation, simulation analysis was conducted. The simulation analysis boundary conditions were set with a 2-micron interference fit between the pin 6 and the shoulder pin hole 7, and peak torque and peak speed were added. Figure 8 As shown, based on the contact results of the pin 6 and the shoulder pin hole 7, one side of the pin and hole interference fit position 888 and the other side of the pin and hole interference fit position 999, the pin 6 and the pin hole 7 are tightly connected, and the average contact pressure between the pin 6 and the pin hole 7 is 285 MPa, which meets the surface pressure requirement for the pin to not fall off under high-speed rotation.

[0076] The purpose of mounting pin 6 is to prevent lubricating grease from being thrown into the motor from the spline. Therefore, the length of pin 6 is not greater than the length of the hole. The bearing shoulder 5 is positioned at the bottom hole 10 and the relief groove 8 on the inner surface of the corresponding inner diameter. This is to prevent the bearing shoulder 5 from being positioned at the spline tooth position, which would affect the strength of the spline tooth root and the fit with the spline of the reducer input shaft.

[0077] like Figure 9As shown, to verify whether drilling affects the strength performance of the motor shaft, simulation analysis was conducted on the strength changes of the motor shaft with and without a hole in the shoulder groove and with a hole in the bearing shoulder groove and a press-in pin 6. The simulation boundary conditions were that the rotor core mounting section 11 was fixed and constrained, and only the rotational degrees of freedom were released for the front bearing position 4 and the rear bearing position 13. The simulation load was added to spline 2, where the peak torque was borne. The maximum stress of the motor shaft 555 without a hole in the shoulder groove was 49 MPa, and the maximum stress of the motor shaft 666 with a hole in the shoulder groove and a pin was 47 MPa. The hole in the shoulder groove 31 had little impact on the strength. The simulation results for both were much lower than the yield strength of 835 MPa, which met the strength design requirements.

[0078] like Figure 10 As shown, to verify whether the pin hole affects the vibration response of the motor bearing, simulation analysis was performed on the vibration response before and after the bearing shoulder groove without a pin hole and before the pin hole was pressed into the shoulder groove. At high speeds, the motor shaft may experience dynamic imbalance due to stress release. This dynamic imbalance response may cause first-order problems. Therefore, the first-order vibration response caused by the unbalanced mass factor at the rear bearing position was analyzed. The analysis revealed that the vibration response amplitude at approximately 21000 rpm and 25000 rpm was 1-2 m / s². 2 Aside from the differences, the vibration response at other speed ranges was essentially unaffected. According to electromagnetic design principles, the 5th and 7th harmonics, resulting in the 6th torque pulsation, and the 11th and 13th harmonics, resulting in the 12th torque pulsation, coupled with the high-order harmonic force generated by the rotor torsional mode, pass through the motor shaft, front bearing position 4, and rear bearing position 13, causing dynamic forces in the motor bearings. Therefore, a vibration response analysis of the rear bearing position 4 under 48th-order torque pulsation excitation was conducted. Comparative analysis revealed a slight difference of 0.2 m / s in the vibration response amplitude around 13000 rpm. 2 Apart from the differences, the vibration response was unaffected in other speed ranges.

[0079] In summary, under both excitation forces, the vibration response of the bearing shoulder is similar between the bearing shoulder groove without a pin hole and the bearing shoulder groove with a pin hole and a pressed-in pin. This proves that the impact of pressing in a pin hole after the bearing shoulder is perforated has little effect on the NVH of the motor shaft.

[0080] Example 2

[0081] like Figure 11 As shown, this embodiment provides an integrated motor shaft with an internal spline. Unlike embodiment 1, the length of the bottom hole 10 is extended to one end of the keyway 9. A keyway pin hole 71 is made at an appropriate position on the keyway 9 near the internal spline 2 side. The keyway pin hole 71 connects to the bottom hole 10 and is mainly used for air circulation during heat treatment. After heat treatment, the pin 6 is pressed into the keyway pin hole 71, with an interference fit of 2-4 microns, ensuring that the pin 6 does not fall out of the keyway pin hole.

[0082] Example 3

[0083] like Figure 12 As shown, this embodiment provides an integrated motor shaft with internal splines. Unlike embodiment 2, the bottom hole 10 is extended by a certain length, and mounting pin holes 72 are drilled in the rotor core mounting section 11. The mounting pin holes 72 in the rotor core mounting position are mainly used for air circulation during heat treatment. After heat treatment, the pin 6 is pressed into the mounting pin hole 72 at a certain position, with a small interference fit of 0.5-1 micrometers. Laser welding is performed on the unfitted areas of the mounting pin hole 72 and the outer side of the pin 6 in the rotor core mounting position. The weld marks are then removed by turning and milling the shaft. After finishing, the shaft has a smooth surface, ensuring that no grease seeps out from the splines after the rotor core is installed, and that the fit between the rotor core and the shaft is not affected.

[0084] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A motor shaft for reducing internal spline noise, the motor shaft being of one-piece construction comprising a bearing shoulder (5) and a blind hole, the bottom of the blind hole being provided with a bottom hole (10), characterized in that, The first groove (31) and the second groove (32) are symmetrically arranged on the outer circle of the bearing shoulder (5). The first groove (31) and the second groove (32) are symmetrically arranged on the two sides of the bearing shoulder (5), the bottom of the first groove (31) is provided with a pin hole (7), the two ends of the pin hole (7) penetrate the bottom of the second groove (32), the pin hole (7) penetrates the bottom hole (10), and the two ends of the pin hole (7) are provided with a hole pin (6), and the hole pin (6) is in interference fit with the pin hole (7).

2. The motor shaft for reducing internal spline noise according to claim 1, characterized by, The two ends of the hole pin (6) are provided with a fillet, and the two ends of the pin hole (7) close to the bottom of the first groove (31) and the second groove (32) are respectively provided with a chamfer.

3. The motor shaft for reducing internal spline noise according to claim 1, wherein The interference amount of the hole pin (6) and the pin hole (7) is 2-4 wires.

4. The motor shaft for reducing internal spline noise according to claim 1, wherein The hole of the blind hole is provided with a sealing stop (1), the sealing stop (1) is coaxially arranged with the bottom hole (10), the blind hole is connected with the reducer shaft, and the sealing stop (1) is matched with the reducer shaft.

5. The motor shaft for reducing internal spline noise according to claim 1, wherein The length of the hole pin (6) is less than the depth of the pin hole (7).

6. The motor shaft for reducing internal spline noise according to claim 1, wherein The blind hole is also provided with an internal spline (2) and a tool withdrawal groove (8) arranged with the bottom hole (10), one end of the tool withdrawal groove (8) is connected with the internal spline (2), the other end is connected with the bottom hole (10), and the distance from the end of the internal spline (2) close to the tool withdrawal groove (8) to the blind hole port is less than the distance from the bearing shoulder (5) to the blind hole port.

7. The motor shaft for reducing internal spline noise according to claim 1, wherein The motor shaft comprises a stator core mounting section (11), and a key groove (9) is arranged on the outer side of the stator core mounting section (11) in the axial direction of the motor shaft, which is used for matching and connecting the rotor core with the motor shaft; the motor shaft is also provided with an external thread (12), and the external thread (12) is located at one end of the key groove (9) away from the blind hole, which is used for connecting a locking nut.

8. The motor shaft for reducing internal spline noise according to claim 1, wherein The outer circle of the bearing shoulder (5) is also provided with a first process groove (41) and a second process groove (42), the first groove (31), the first process groove (41), the second groove (32) and the second process groove (42) are arranged at equal angles on the outer circle of the bearing shoulder (5) in sequence; the first process groove (41) and the second process groove (42) are symmetrically arranged on the two sides of the bearing shoulder (5), which are used for clamping and positioning the motor shaft.

9. A process for reducing the noise of an internal spline of an electric machine shaft according to any one of claims 1 to 8, characterized in that, The steps include: The first groove (31) and the second groove (32) are machined on the bearing shoulder (5) of the motor shaft, the pin hole (7) is machined on the bottom of the first groove (31) and the second groove (32) respectively, and the internal spline is machined in the blind hole of the motor shaft through the gear shaping process; After the motor shaft is machined, it is placed on the material rack and sent to the heat treatment furnace for heat treatment; After the heat treatment of the motor shaft is completed, the motor shaft is sequentially subjected to shot blasting treatment and ultrasonic cleaning; The hole pin (6) is assembled into the pin hole (7), and the motor shaft is subjected to automatic straightening and fine grinding treatment.

10. The process of claim 9, wherein, The length of the gear shaping cutter is matched with the length of the internal spline when the internal spline of the motor shaft is processed by the gear shaping process; the motor shaft is clamped by a clamp, a first process groove (41) and a second process groove (42) are arranged on the outer circle of the bearing shoulder (5), the clamp is clamped on the first process groove (41) and the second process groove (42), and the surface roughness of the contact position of the clamp and the first process groove (41) or the second process groove (42) is R0.7-R0.9.

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