A servo motor rotating shaft, a rotating shaft processing method and a servo system

Abstract

The application discloses a servo motor rotating shaft, a rotating shaft machining method and a servo system, the rotating shaft comprises an outer shaft cylinder and a coaxial closed inner flow guide pipe, and an annular cavity is formed between the outer shaft cylinder and the inner flow guide pipe; the outer wall of the inner flow guide pipe is provided with variable pitch distance core flow guide spiral blades, the axial both ends of the variable pitch distance core flow guide spiral blades are wide in pitch distance and the middle section is narrow in pitch distance, centrifugal force and coriolis force are coupled to realize targeted forced heat exchange of a high heat area of a rotor; the inner wall of the outer shaft cylinder is subjected to ultrasonic vibration finishing and cryogenic phase change treatment, fatigue microcrack sources are eliminated and machining residual stress is released, and the thermal state size stability is ensured; meanwhile, the rotating shaft is combined with a heteromorphic metal roll seam welding packaging, an inner and outer double circulation liquid cooling system with intelligent control of a three-way valve and a dynamic labyrinth seal water retaining structure for preventing the cooling medium from penetrating into a machine shell. The application solves the technical problems of the rotor heat island effect, thermal state irreversible deformation and insulation failure caused by fluid leakage which are faced by a high power density servo motor.

Description

Technical Field

[0001] This invention relates to the field of servo motor technology, specifically to a servo motor shaft, a shaft machining method, and a servo system. Background Technology

[0002] With the rapid development of modern industrial automation, robotics, and electric drive systems for new energy vehicles, servo motors, as core power actuators, are evolving towards higher torque density, higher power density, and compactness. During motor operation, electromagnetic interactions generate energy loss and are converted into heat, leading to temperature gradients and heat accumulation within the motor. Traditional motor thermal management technologies often employ open-type air-cooling structures or completely enclosed heat conduction structures. Open-type motors rely on ambient air entering the motor, but their protection level is low, and dust and moisture can easily penetrate, affecting their lifespan. While enclosed structures combined with stator water jackets can cool the stator, the rotor's cooling effect is limited due to the air gap insulation layer between the stator and rotor, easily forming a "heat island." Against this backdrop, hollow shaft motor technology has emerged, extracting heat by introducing a cooling medium inside the shaft.

[0003] A search of existing patent literature reveals, for example, patent application CN108475968A, which discloses a hollow rotor for distributing cooling medium by centrifugal force. The cooling medium is discharged onto the inner surface of the hollow rotor shaft via a funnel-shaped component for heat dissipation. Additionally, utility model patent CN221520973U discloses a cooling spiral hollow shaft, which incorporates an inner tube within the hollow cavity of the spiral shaft and spiral blades on the shaft for cooling.

[0004] However, the existing technology has the following technical problems:

[0005] First, existing hollow cooling structures (such as direct-through or simple spiral flow channels) are difficult to achieve targeted, localized enhanced heat dissipation when faced with uneven thermal loads from servo motors. When the fluid encounters enclosed walls or reversing channels, heat is easily reversed, and the centrifugal force during axial flow causes the boundary layer to thicken, weakening the convective heat transfer capacity.

[0006] Secondly, when using machining processes such as deep hole drilling, traditional thin-walled hollow shafts are prone to leaving pits and surface scratches on the inner wall on the order of tens of micrometers (e.g., about 45 micrometers deep). The pits (dents) indicate plastic deformation at the bottom of the pits. Under the alternating torque load and thermal shock of the motor, these tiny defects can cause stress concentration, becoming the initiation source of fatigue cracks and easily leading to shaft breakage.

[0007] Third, the high integration of servo motor shafts means that the cutting heat generated during machining can be converted into deep residual stress. In traditional processes, this residual stress is released when the motor operates at high temperatures, leading to irreversible thermal deformation of the shaft and thus compromising the vector control accuracy and thermal stability of the control system. Summary of the Invention

[0008] In order to overcome the shortcomings and deficiencies of the existing technology, the present invention aims to provide a servo motor shaft, a shaft processing method and a servo system. This solution combines fluid dynamics reconstruction design with specific anti-fatigue and anti-deformation processing technology, thereby improving heat dissipation efficiency and spindle structural stability under high power density.

[0009] This invention is achieved through the following technical solution: In a first aspect, the present invention discloses a servo motor shaft, comprising: Outer shaft cylinder; An inner guide tube is coaxially fixed inside the outer shaft cylinder. The two ends of the inner guide tube are physically sealed by sealing plates, and an annular cavity is reserved between the outer wall of the inner guide tube and the inner wall of the outer shaft cylinder. The head shaft and tail shaft are respectively connected to both ends of the outer shaft cylinder; And variable pitch core guide spiral blades disposed on the outer wall of the inner guide tube; The variable pitch guide spiral blades have a wider pitch at both ends of the rotor axial direction and a narrower pitch in the middle section of the rotor axial direction. This is used to drive the cooling medium to perform radial mixing and enhance heat transfer in the annular cavity through the coupling of centrifugal force and Coriolis force when the motor is rotating at high speed. The inner wall of the outer shaft cylinder has a surface that has been smoothed by ultrasonic vibration.

[0010] In conjunction with the first aspect, furthermore, the outer shaft cylinder, the inner guide tube, the head shaft, and the tail shaft are made of different metal materials to form a heterogeneous metal combination. The different materials of the heterogeneous metal combination are sealed by roll seam welding through resistance heat generated by electric current, thereby achieving fluid sealing of the annular cavity.

[0011] In conjunction with the first aspect, furthermore, the two ends of the rotating shaft are respectively provided with a cooling medium inlet and a cooling medium outlet. The cooling medium pumped in by the cooling medium inlet first travels axially in the inner cavity of the inner guide tube, and after encountering the closed pipe opening, it changes direction and flows back into the annular cavity.

[0012] In conjunction with the first aspect, the outer shaft cylinder undergoes cryogenic treatment, resulting in a residual compressive stress state on its surface.

[0013] Secondly, the present invention discloses a method for manufacturing a servo motor shaft, which is used to manufacture the servo motor shaft as described above, and includes the following steps: Deep hole boring is performed on the inner hole of the outer shaft cylinder; Ultrasonic vibration honing technology is introduced to perform a finishing process on the inner surface of the outer shaft cylinder. The outer shaft cylinder, after finishing, is sent into a liquid nitrogen cryogenic chamber for programmed cryogenic treatment and slow tempering. The inner guide tube and the variable pitch guide spiral blade are assembled inside the outer shaft cylinder after cryogenic treatment, and the connection joint area between the outer shaft cylinder and the head shaft and the tail shaft is instantaneously softened and pressure welded using roll weld technology.

[0014] In conjunction with the second aspect, furthermore, the finishing process of the ultrasonic vibration honing technology has a cutting depth greater than 45 mm. It is used to eliminate the structural deformation at the bottom of the pit left by the deep hole boring and to remove the fatigue crack initiation source that causes radial fracture under alternating torque.

[0015] Furthermore, in conjunction with the second aspect, the outer shaft cylinder is made of titanium alloy, and the programmed cryogenic treatment temperature ranges from -196℃ to -150℃, which is used to promote metastability within the titanium alloy material. small towards each other Martensite transformation and release of residual cutting stress.

[0016] In conjunction with the second aspect, both the head shaft and the tail shaft are made of high-strength structural steel, and the roll seam welding technology is used to achieve concentrated and rapid joining of the two dissimilar metal structures of titanium and steel.

[0017] Thirdly, the present invention discloses a servo system, which includes a servo motor and a dual-circulation liquid cooling heat dissipation device. The servo motor includes a stator housing, a stator winding, a rotor containing a permanent magnet, a temperature sensor, and a servo motor shaft as described above. The dual-circulation liquid cooling heat dissipation device includes a spiral cooling circuit wound around the outside of the stator housing, an internal forced liquid cooling circuit connected to the servo motor shaft, a three-way valve, and a circulating cooling component. The spiral cooling circuit and the internal forced liquid cooling circuit are connected to the circulating cooling component alternately or synchronously through the three-way valve.

[0018] In conjunction with the third aspect, the servo motor further includes a cooling medium rotary joint and a shaft end cover. The cooling medium rotary joint is respectively disposed at both ends of the servo motor shaft. A water baffle ring is coaxially mounted on the shaft end cover located behind the cooling medium rotary joint. A water baffle platform is provided on the water baffle ring, and the end face of the water baffle platform is higher than the end face of the shaft end cover in the axial direction. The water baffle platform and the shaft end cover are staggered to form a dynamic labyrinth sealing structure. Leaking cooling medium is thrown into the water baffle ring by centrifugal force and guided to the outside of the stator housing through a preset water passage hole for discharge.

[0019] The beneficial effects of this invention are: For servo motor shafts, this invention reduces the amount of cooling medium retained, lowers operating weight, and reduces rotational inertia through a pre-reserved annular cavity between the inner guide tube and the outer shaft cylinder. The variable pitch guide spiral blades are designed with a narrow pitch in the middle section where electromagnetic losses are high, forcing a reduction in fluid cross-sectional area and an increase in flow velocity. This utilizes the Coriolis force to disrupt the stable boundary layer of the fluid, achieving targeted and enhanced heat dissipation for the rotor's heat island. Simultaneously, the inner wall of the outer shaft cylinder undergoes ultrasonic vibration finishing, eliminating microscopic pit defects inherent in traditional machining. This removes the source of fatigue crack initiation under alternating torque and reduces fluid boundary layer frictional resistance.

[0020] Regarding the machining methods for rotating shafts, the present invention combines machining with programmed cryogenic treatment. Liquid nitrogen cryogenic treatment promotes metastability within the titanium alloy material. small towards each other The martensitic transformation completely releases the internal stress accumulated during the previous machining process, ensuring that the shaft maintains good thermal geometric stability when subjected to operating temperature rises and preventing thermal deformation. Combined with roll-welding technology to encapsulate dissimilar metals, the concentrated heat input and short action time not only achieve the sealing of the cooling medium chamber but also ensure that the stress-free state is not damaged by a large heat-affected zone.

[0021] For servo motors, the servo motor of this invention is equipped with a dual-circuit liquid cooling heat dissipation device, which can intelligently adjust the three-way valve based on the data monitored by the temperature sensor. Under low load conditions, it can operate in a single loop, and under extremely high load conditions, it can simultaneously activate forced cooling of the stator housing and the inside of the shaft, achieving continuous heat dissipation throughout the entire area. This ensures that the operating temperature of the permanent magnet is within a safe threshold, avoiding irreversible demagnetization due to high temperature. Attached Figure Description

[0022] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0023] Figure 1 This is a cross-sectional schematic diagram of the internal structure of the servo motor shaft in an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the overall dual-cycle cooling system for the servo motor in an embodiment of the present invention.

[0025] Figure Labels Outer shaft cylinder -- 1, Inner guide tube -- 2, Sealing plate -- 3, Annular cavity -- 4, Head shaft -- 5, Tail shaft -- 6, Variable pitch guide spiral blade -- 7, Cooling medium inlet -- 8, Cooling medium outlet -- 9. Stator housing--10, stator winding--11, rotor--12, temperature sensor--13, spiral cooling circuit--14, internal forced liquid cooling circuit--15, three-way valve--16, circulating cooling assembly--17, cooling medium rotary joint--18, shaft end cover--19, water baffle ring--20, water baffle platform--21, dynamic labyrinth seal structure--22, water passage hole--23. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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.

[0028] Furthermore, 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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0029] Example 1 like Figure 1 and Figure 2 As shown, this embodiment provides a servo motor shaft, the main body of which is composed of a high-strength outer shaft cylinder 1 and an inner guide tube 2 coaxially sleeved inside the outer shaft cylinder 1.

[0030] In terms of structural design, the two ends of the inner guide tube 2 are physically sealed by the front end sealing plate 3 and the rear end sealing plate 3 respectively, forming a closed central blind cavity inside; between the outer wall of the inner guide tube 2 and the inner wall of the outer shaft cylinder 1, an annular cavity 4 with a radial width of 2 to 5 mm is coaxially reserved; the head shaft 5 of the rotating shaft has a cooling medium inlet 8 at its center, and the tail shaft 6 has a cooling medium outlet 9 at its center.

[0031] On the outer wall of the inner guide tube 2, a variable pitch core guide spiral blade 7 is integrally formed. The pitch of the variable pitch core guide spiral blade 7 is asymmetrically and gradually distributed along the axial direction. That is, at both ends of the rotor 12 axial direction (i.e., the winding end area where the heat generation of the motor stator is relatively low), the pitch of the variable pitch core guide spiral blade 7 is wider, set to 20 to 30 mm; in the middle section of the rotor 12 axial direction (i.e., the core high-heat area corresponding to the iron core of the rotor 12), the pitch is continuously narrowed to 8 to 12 mm.

[0032] Furthermore, the heat exchange flow path of the cooling medium in this embodiment will be described in detail.

[0033] After being pumped into the head shaft 5 through the cooling medium inlet 8, the cooling medium first enters the central blind cavity of the inner guide tube 2 and travels at high speed along the axial direction. When the fluid touches the closed port at the rear end, it is obstructed, and the flow direction is reversed by 180 degrees. It overflows through the radial through hole reserved at the end of the inner guide tube 2 and enters the outer annular cavity 4. In the annular cavity 4, the cooling medium flows back towards the head shaft 5 along the variable pitch guide spiral blades 7 and is finally discharged from the cooling medium outlet 9.

[0034] When the motor rotates at high speed, the wide-pitch section effectively reduces the overall friction loss of the fluid. When the fluid enters the narrow-pitch region in the middle section, the flow cross-sectional area contracts, forcing a sharp increase in local velocity. At this time, because the system is in a high-speed rotating system, the fluid is not only tightly pressed against the inner wall of the outer shaft cylinder 1 due to centrifugal force, but also experiences strong Coriolis forces due to the abrupt changes in radial and axial velocity. The intervention of the Coriolis force causes the fluid within the boundary layer to become unstable, inducing strong secondary eddies, thereby achieving targeted forced convection heat transfer in the core high-heat region.

[0035] To reduce the overall rotational inertia of rotor 12 and ensure the torque rigidity of the main shaft, the outer shaft cylinder 1 in this embodiment is made of low-density titanium alloy (such as TC4), while the head shaft 5, tail shaft 6 and inner guide tube 2 are made of high-strength structural steel (such as 42CrMo).

[0036] The encapsulation between different materials employs a roll-welding process. Specifically, the end of the titanium alloy outer shaft cylinder 1 is overlapped with the assembly surfaces of the structural steel head shaft 5 and tail shaft 6, and placed between the upper and lower roller electrodes. While applying continuous mechanical pressure, a pulsed current is passed through, utilizing the localized resistance heat generated at the contact surface of the two metal layers to microscopically melt the materials. As the rollers roll continuously, a series of overlapping and dense molten nuclei are formed at the joint, thereby completely sealing the annular cavity 4, achieving absolute fluid sealing, and preventing the cooling medium from seeping into the air gap between the stator winding 11 and the rotor 12.

[0037] For the aforementioned heterogeneous metal bonding structure, scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS) was used to conduct microscopic examination of the welded section. SEM morphology images showed that a continuous metallurgical transition layer with a uniform width between 10 and 20 micrometers was formed at the physical interface between the titanium alloy and the structural steel, without macroscopic cracks or porosity defects. EDS line scan data showed that titanium and iron elements exhibited a clear concentration gradient diffusion distribution within the transition layer. Further phase qualitative analysis of the transition layer using X-ray diffraction (XRD) revealed... and The presence of diffraction peaks of the two intermetallic compounds, the detection of the micron-scale continuous transition layer and the specific intermetallic compounds, definitively prove that a stable metallurgical bond has been formed between the dissimilar metals, ensuring the structural integrity of the 18 rotary joints of the cooling medium under high pressure.

[0038] Furthermore, in order to eliminate fatigue crack sources left over from machining and prevent thermal deformation, the outer shaft cylinder 1 must undergo ultrasonic vibration finishing and deep cryogenic phase transformation coupling treatment of the inner hole before assembly.

[0039] After conventional deep hole boring, the inner wall is finished using an ultrasonic honing head (applying ultrasonic vibration at a frequency of approximately 20 kHz and an amplitude of approximately 30 micrometers). Subsequently, the entire outer shaft cylinder 1 is placed in a liquid nitrogen cryogenic chamber and cooled to -196°C at a set rate. After heat preservation treatment, it is slowly tempered to room temperature.

[0040] For qualitative and quantitative surface morphology testing, a white light interferometric surface profilometer or atomic force microscope (AFM) was used to measure the roughness of the inner wall of the outer shaft cylinder 1. The tests showed that after ultrasonic finishing, the inner surface roughness was reduced from approximately 3 mm / s by the roughness left over from conventional boring. It decreased significantly to 0.16. Approximately 100 mm. High-magnification SEM observation confirmed that the surface pits and tear layers with a depth of 45 micrometers left by the original boring process were completely removed, and the microstructure showed a fine and uniform state, thus eliminating the fatigue crack source under alternating torque from the source.

[0041] Regarding the characterization of phase transformation structure and residual stress, the effect of cryogenic treatment on the microstructure of materials was analyzed using XRD. After conventional machining, the TC4 titanium alloy outer shaft cylinder 1, in addition to the stable phase transformation structure and residual stress, exhibits the following characteristics: phase and In addition, it also contains metastable residues left over from cutting heat and plastic deformation. Phase. After cryogenic treatment, the XRD pattern shows... The intensity of the phase characteristic diffraction peaks decreased significantly, and the following appeared The diffraction characteristics of the martensitic phase prove metastableness. small towards each other Martensitic transformation; simultaneously, X-ray residual stress measurement (based on Bragg equation and The surface stress of the outer shaft cylinder 1 was tested using a method (e.g., ultrasonic finishing and cryogenic treatment). The test results showed that, through the combined effect of ultrasonic finishing and cryogenic treatment, the stress state of the material surface changed from the original residual tensile stress of approximately +320 MPa to the residual compressive stress of approximately -40 MPa. This microstructural transformation and the full release of internal stress demonstrate that the outer shaft cylinder 1 of this invention can maintain high thermal geometric stability when facing extreme internal temperature rises in the motor (e.g., above 150°C), and will not undergo irreversible thermal expansion and deformation.

[0042] Example 2 Based on the shaft structure of Embodiment 1, in order to ensure the fatigue resistance and thermal dimensional stability of the servo motor shaft under extreme working conditions, this embodiment provides a processing route that integrates dynamic mechanical cutting, microscopic phase transformation control and precision connection of dissimilar metals. This process route is preferably run on a CNC honing machine and relies heavily on the online real-time feedback control of the CNC system and the offline pre-calculation model based on material phase transformation dynamics during operation.

[0043] After traditional deep hole boring, the inner hole of the outer shaft sleeve 1 inevitably retains a tear layer and micro-pits with a depth of about 40 to 50 micrometers. These defects are prone to evolving into fatigue crack initiation under alternating torque. Therefore, this embodiment introduces a honing finishing process based on high-frequency ultrasonic vibration after deep hole boring to eliminate the aforementioned defect layer.

[0044] To precisely control the material removal amount during finishing and ensure a cutting depth strictly greater than 45 micrometers without damaging the macroscopic dimensional accuracy of the tube wall, the CNC honing equipment in this embodiment incorporates an online real-time material removal depth measurement and control algorithm. This algorithm runs in the programmable logic controller (PLC) at the bottom of the equipment. The system obtains the normal grinding force in real time at a millisecond-level sampling rate through a piezoelectric triaxial force gauge integrated at the spindle end, and calculates the cumulative removal depth in real time based on the following dynamic differential equation with nonlinear correction. :

[0045] in, This represents the instantaneous effective contact area between the honing stone and the inner wall of the outer shaft cylinder 1, and its initial value is preset by the CAD / CAM system; The normal contact force is collected in real time by the piezoelectric sensor, and its value usually fluctuates between 50 and 300 N. Set the axial feed speed for the honing head; The amplitude of the ultrasonic tool head is set to a range of 10 to 30. ; Let be the angular frequency of the ultrasonic vibration, satisfying The ultrasonic frequency is set at 20 to interval; The abrasive wear coefficient is typically found in... Within the range; To target the nonlinear strain rate strengthening index of titanium alloy materials, a value of approximately 1.15 was determined through previous high strain rate dynamic compression experiments using Hopkinson bar (SHPB).

[0046] The derivation of this formula is based on the classic Preston wear equation, and incorporates the transient excitation velocity caused by high-frequency ultrasonic oscillation. With macro feed rate Vector superposition was performed. The CNC system uses... For periodic numerical integration calculations, online monitoring of cumulative removal volume. When the score results are displayed Cross When the critical threshold is reached, the control system immediately issues a command to stop the ultrasonic generator and cause the spindle to retract. Through this closed-loop control process, the surface roughness of the inner bore of the outer shaft cylinder can be reduced from the initial approximately... Stable down to This process, by adjusting the left and right sides, eliminates the microscopic geometric defects that induce radial fractures at the source, while ensuring processing efficiency.

[0047] After mechanical finishing, residual tensile stress caused by the cutting thermal gradient still remains inside the material. In order to release these stresses and give the shaft extremely high thermal stability, the machining process enters the liquid nitrogen programmed deep cryogenic stage.

[0048] Unlike traditional empirical isothermal cryogenic treatment, this embodiment employs an offline pre-calculated phase transformation kinetics algorithm to guide the design of the cryogenic chamber's temperature control curve. The core metallurgical objective of this process is to induce metastable stability within the unstable titanium alloy. The phase transforms into finer particles to the greatest extent possible. Martensite. To accurately predict the degree of phase transformation at different cryogenic temperatures, the process development team adopted an improved Koistinen-Marburger (KM) equation for offline solution:

[0049] Represents cooling to the target cryogenic temperature Transformation variables of martensite; For metastable phase The martensitic phase transformation initiation temperature is affected by the metastable material remaining after processing. The phase is enriched with vanadium, and its phase transformation initiation temperature is much lower than that of the TC4 titanium alloy bulk. The phase transition temperature is typically between 180°C and 260°C. This parameter is determined by measuring the volume change curve during the cooling process using a thermal expansion meter. The target cryogenic temperature can be set, and the range is strictly limited to... to between; The phase transformation rate constant reflects the combined influence of carbon atoms and alloying elements on the lattice shear resistance. Based on previous quantitative calibration of X-ray diffraction phases under different temperature gradients, its value is taken as 0.011 to... .

[0050] By executing this offline algorithm, process engineers can clearly deduce: when Set to liquid nitrogen vaporization temperature At that time, the exponential term decays to a minimum value, theoretically the martensite conversion rate... Greater than Based on this rigorous theoretical calculation, the system will... The target parameters and corresponding cooling slope are written into the PID temperature controller of the cryogenic treatment equipment. This step ensures the metastability of the titanium alloy. The phase is almost exhausted, and the microscopic volume expansion caused by the phase transformation completely offsets the residual tensile stress generated by the previous cutting.

[0051] The titanium alloy outer shaft cylinder 1, after cryogenic treatment and in a stress-free state, then enters the final assembly stage, where it is nested and assembled with the head shaft 5 and tail shaft 6, made of high-strength structural steel, as well as the internal inner guide tube 2 and the variable pitch guide spiral blades 7. The core challenge at this stage is how to achieve absolute sealing of the closed annular flow channel while avoiding the significant heat input from conventional welding that could disrupt the lattice stability established by the cryogenic treatment.

[0052] This embodiment utilizes roll-seam welding technology to achieve rapid bonding of two dissimilar metals, titanium and steel. During processing, the assembled shaft end is placed between a pair of copper roller electrodes carrying high-frequency pulsed current. By precisely controlling the pulse width ratio and peak current, a large amount of Joule heat is concentrated on the micron-level physical contact interface between the titanium and steel. With the continuous rolling and pressing of the rollers, the contact surface undergoes instantaneous local melting and interatomic diffusion, followed by solidification within milliseconds. This processing method strictly compresses the heat-affected zone to within millimeter levels, ensuring the sealing strength of the cooling medium chamber between the different material tube walls and preventing secondary thermal deformation and warping of the spindle body.

[0053] Example 3 like Figure 2 As shown, this embodiment discloses a servo system, which includes a servo motor, corresponding parts for overall thermal management and fault-tolerant sealing mechanisms. Because in a three-dimensional assembly state, the external stator and housing completely enclose and shield the internal rotating shaft, therefore... Figure 2 The circulating cooling component 17 and the three-way valve 16 on the right serve as the control hub of the entire cooling system. To clearly illustrate the parallel logic of the fluid, the motor is drawn in two parts.

[0054] The motor view on the left focuses on showing how the cooling medium, after being diverted from the three-way valve 16, enters and flows through the external stator spiral cooling circuit 14. The motor view on the right focuses on showing how another cooling medium enters the motor spindle through the cooling medium rotary joint 18 and flows through the internal forced liquid cooling circuit 15.

[0055] Since the overall heat dissipation of a servo motor relies not only on localized heat exchange within the shaft but also on coordinated thermal management at the stator and rotor system level, this embodiment provides a servo motor architecture with dual-cycle liquid cooling for coordinated heat dissipation, based on the aforementioned variable-pitch shaft.

[0056] In terms of structural layout, a spiral cooling circuit 14 with a high thermal conductivity is laid on the outside of the stator housing 10. This circuit is closely attached to the outer wall of the stator housing 10 to directly absorb and remove the copper and iron loss heat generated by the stator windings 11 and the stator core. Parallel to this is an internal forced liquid cooling circuit 15 connected to the end of the servo motor shaft. The two circulation pipes are alternately or synchronously connected to the main circulation cooling assembly 17 through a three-way valve located outside the housing. The three-way valve consists of a valve body and an actuator, which can automatically realize the connection, disconnection, reversal, and proportional adjustment of each cooling pipe according to the command of the electrical signal.

[0057] To achieve dynamic and precise temperature control logic, high-sensitivity temperature sensors 13 are embedded at the ends of the stator winding 11 and near the air gap of the rotor 12 magnets. When the motor is under rated load or low-frequency operation, the overall temperature rise curve monitored by the sensors is flat. At this time, the control system sends a command to the three-way valve to mainly connect the spiral cooling circuit 14, while the internal circulation of the shaft maintains only a very low flow rate to reduce the power consumption of the fluid circulation pump. However, when the servo motor enters the high-frequency start-stop or continuous maximum speed operation stage, the temperature slope of the rotor 12 magnet area increases sharply. Once the temperature in this area approaches the set warning threshold, the system immediately drives the three-way valve to fully open, so that the stator spiral circuit and the internal forced liquid cooling circuit 15 of the shaft operate synchronously at full load. This internal and external coordinated flow path switching mechanism directly driven by the heat source temperature field can ensure that the permanent magnet is locked within a safe temperature window when facing extreme transient thermal shock, eliminating the risk of high-temperature demagnetization at the system level.

[0058] Furthermore, in a high-pressure liquid cooling system, if the cooling medium leaks into the air gap between the stator winding 11 and the rotor 12 inside the motor, it will lead to catastrophic insulation breakdown. Although the rotary joint 18 for the cooling medium can ideally isolate the internal and external environments, after long-term exposure to alternating pressure pulsations and high-speed mechanical friction, a small amount of liquid leakage will inevitably occur in its internal mechanical seals. Based on this, in the system integration stage, this invention constructs a purely physical, non-contact dynamic labyrinth seal and leakage tolerance mechanism at the end of the shaft.

[0059] In terms of spatial arrangement, the liquid supply system and the cooling medium rotary joint 18 are connected to the end of the rotating shaft. Immediately behind the cooling medium rotary joint 18, a water-blocking ring 20 is coaxially fixed to the surface of the servo motor's shaft end cover 19. The water-blocking ring 20 extends a stepped water-blocking platform 21 towards the stator cavity, with the end face of the water-blocking platform 21 axially higher than the end face of the shaft end cover 19. Simultaneously, an annular groove matching the size of the water-blocking platform 21 is machined on the smooth surface of the shaft end cover 19. The water-blocking platform 21 of the water-blocking ring 20 is non-contactly nested into this groove, with a sub-millimeter gap between them, thus forming a dynamic labyrinth seal structure 22 in a two-dimensional cross-section, alternating between radial and axial directions.

[0060] In actual operation, if a high-pressure micro-leak occurs at the outermost rotating joint 18 for the cooling medium, the escaping droplets will first adhere to the surface of the component rotating at high speed with the spindle. In this state, the strong centrifugal force of rotation will force the droplets to fly away radially outwards quickly, and then be effectively intercepted by the inner wall of the outer water-blocking ring 20. Due to the drastic changes in the cross-section of the dynamic labyrinth seal structure 22, if the droplets attempt to penetrate into the motor, they will face enormous frictional resistance and throttling pressure reduction effects. In addition, the physical barrier of the water-blocking platform 21 prevents the fluid from actually overcoming this tortuous barrier. Conversely, the intercepted cooling medium will flow down the inclined surface at the bottom of the water-blocking ring 20 under the combined action of gravity and residual centripetal force, eventually converging into the water passage hole 23 pre-set below the end cover, and being safely discharged through the guide groove outside the housing. This non-contact fault-tolerant mechanism not only avoids the additional frictional power consumption caused by using contact oil seals, but also cuts off the path for water to enter the core electromagnetic region at the fluid dynamics level.

[0061] To further ensure the long-term structural stability of the aforementioned water-retaining ring 20 under high-temperature cooling medium splashing and high-frequency alternating stress environments, the water-retaining ring 20 in this embodiment is made of a special polyether ether ketone (PEEK) polymer composite material through precision injection molding. The chemical structure and thermal stability of this polymer material were rigorously characterized using Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA).

[0062] In FTIR spectroscopy testing, 1650 The strong absorption peak of the carbonyl group of benzophenone that appeared nearby is similar to that at 1220. The characteristic peaks of aromatic ether bonds at the [location] qualitatively confirmed the stable aromatic heterocyclic molecular skeleton within it. More importantly, quantitative TGA thermal analysis results showed that the water-retaining ring 20 material maintained a mass retention rate of over 99% during heating from room temperature to 400°C in air, without any observable thermo-oxidative degradation. This data conclusively proves that even with extreme temperature rises of 150°C to 180°C inside the servo motor housing, and prolonged immersion of the water-retaining ring 20 in a hot cooling medium, its polymer chain segments do not undergo conformational relaxation or volume expansion. This superior thermodynamic stability of the material ensures the permanent precision of the sub-millimeter physical gap within the dynamic labyrinth seal structure 22, thereby endowing the motor with high-tolerance, long-term maintenance-free sealing performance.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A servo motor shaft, characterized in that, include: Outer shaft cylinder; An inner guide tube is coaxially fixed inside the outer shaft cylinder. The two ends of the inner guide tube are physically sealed by sealing plates, and an annular cavity is reserved between the outer wall of the inner guide tube and the inner wall of the outer shaft cylinder. The head shaft and tail shaft are respectively connected to both ends of the outer shaft cylinder; And variable pitch core guide spiral blades disposed on the outer wall of the inner guide tube; The variable pitch guide spiral blades have a wider pitch at both ends of the axial direction of the rotating shaft and a narrower pitch in the middle section of the axial direction of the rotating shaft. This is used to drive the cooling medium to perform radial mixing and enhance heat exchange in the annular cavity through the coupling of centrifugal force and Coriolis force when the motor is rotating at high speed. The inner wall of the outer shaft cylinder has a surface that has been smoothed by ultrasonic vibration.

2. The servo motor shaft according to claim 1, characterized in that, The outer shaft, the inner guide tube, the head shaft, and the tail shaft are made of different metals to form a heterogeneous metal combination. The different materials of the heterogeneous metal combination are sealed by roll welding through resistance heat generated by electric current to achieve fluid sealing of the annular cavity.

3. The servo motor shaft according to claim 1, characterized in that, The two ends of the rotating shaft are respectively provided with a cooling medium inlet and a cooling medium outlet. The cooling medium pumped in by the cooling medium inlet first travels axially in the inner cavity of the inner guide tube, and after encountering the closed pipe opening, it changes direction and flows back into the annular cavity.

4. The servo motor shaft according to claim 1, characterized in that, The outer shaft cylinder undergoes cryogenic treatment, and its surface layer exhibits residual compressive stress.

5. A method for machining a servo motor shaft, characterized in that, The method for manufacturing a servo motor shaft as described in any one of claims 1 to 4 includes the following steps: Deep hole boring is performed on the inner hole of the outer shaft cylinder; Ultrasonic vibration honing technology is introduced to perform a finishing process on the inner surface of the outer shaft cylinder. The outer shaft cylinder, after finishing, is sent into a liquid nitrogen cryogenic chamber for programmed cryogenic treatment and slow tempering. The inner guide tube and the variable pitch guide spiral blade are assembled inside the outer shaft cylinder after cryogenic treatment, and the connection joint area between the outer shaft cylinder and the head shaft and the tail shaft is instantaneously softened and pressure welded using roll weld technology.

6. The machining method for a servo motor shaft according to claim 5, characterized in that, The ultrasonic vibration honing technology achieves a finishing cutting depth greater than 45 mm. It is used to eliminate the structural deformation at the bottom of the pit left by the deep hole boring and to remove the fatigue crack initiation source that causes radial fracture under alternating torque.

7. The machining method for a servo motor shaft according to claim 5, characterized in that, The outer shaft cylinder is made of titanium alloy, and the programmed cryogenic treatment is conducted at a temperature range of -196°C to -150°C to promote metastability within the titanium alloy material. small towards each other Martensite transformation and release of residual cutting stress.

8. The machining method for a servo motor shaft according to claim 7, characterized in that, Both the head shaft and the tail shaft are made of high-strength structural steel, and the roll seam welding technology is used to achieve concentrated and rapid joining of the two dissimilar metal structures of titanium and steel.

9. A servo system, characterized in that, It includes a servo motor and a dual-circulation liquid cooling heat dissipation device. The servo motor includes a stator housing, stator windings, a rotor containing permanent magnets, a temperature sensor, and a servo motor shaft as described in any one of claims 1 to 4. The dual-circulation liquid cooling heat dissipation device includes a spiral cooling circuit wound around the outside of the stator housing, an internal forced liquid cooling circuit connected to the servo motor shaft, a three-way valve, and a circulating cooling component. The spiral cooling circuit and the internal forced liquid cooling circuit are connected to the circulating cooling component alternately or synchronously through the three-way valve.

10. The servo system according to claim 9, characterized in that, The servo motor also includes a cooling medium rotary joint and a shaft end cover. The cooling medium rotary joint is respectively disposed at both ends of the servo motor shaft. A water baffle ring is coaxially mounted on the shaft end cover located behind the cooling medium rotary joint. A water baffle platform is disposed on the water baffle ring. The end face of the water baffle platform is higher than the end face of the shaft end cover in the axial direction. The water baffle and the shaft core end cover intersect to form a dynamic labyrinth sealing structure. The leaked cooling medium is thrown into the water baffle ring by centrifugal force and guided to the outside of the stator housing through the preset water passage hole for discharge.

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