Electromagnetic-thermal decoupling isolated permanent magnet synchronous brushless motor

Abstract

The application provides an electromagnetic-thermal decoupling isolation type permanent magnet synchronous brushless motor, which comprises a shell, an outer rotor assembly, a stator assembly, a rotor position sensor and a motor control board. The outer rotor assembly comprises a rotor yoke, a permanent magnet and an output shaft, the stator assembly comprises a stator core and a stator winding, and the motor control board is provided with a motor driving circuit, a communication circuit and a protection circuit. A heterogeneous material welding stress release bushing is arranged between the output shaft and the rotor yoke. An electromagnetic-thermal decoupling isolation disc is arranged between the stator assembly and the motor control board, and the electromagnetic-thermal decoupling isolation disc is closely attached to the stator core in the axial direction. The electromagnetic-thermal decoupling isolation disc is added, electromagnetic-thermal decoupling and isolation between the stator assembly and the motor control board are realized, and the adverse effects of the heat generated by the stator assembly and the high-frequency electromagnetic radiation emitted by the stator assembly on the motor control board are reduced to a certain extent. The heterogeneous material welding stress release bushing is arranged, and the probability of slippage of the output shaft and the rotor yoke in the outer rotor assembly is reduced.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, and more specifically, relates to an electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor. Background Technology

[0002] With the rapid development of vehicle electrification and intelligence, passenger vehicle comfort actuators are increasingly adopting brushless DC motors or permanent magnet synchronous motors. However, due to the extremely limited space in vehicles, distributed actuators typically require motors with extremely high torque density and highly integrated control boards.

[0003] In existing integrated external rotor motors, to maximize space efficiency, the motor control board is typically placed close to the stator windings. However, this structural layout design is prone to technical problems: First, the stator windings experience a dramatic temperature rise under high-frequency, high-load conditions, with heat directly radiating to the motor control board. This causes automotive-grade electronic components (especially active chips and capacitors) to operate at excessively high temperatures for extended periods, severely shortening their lifespan. Second, the strong electromagnetic high-frequency radiation from the stator windings directly couples to the sensitive control circuits of the motor control board, leading to deterioration in electromagnetic compatibility and easily exceeding stringent automotive EMC standards.

[0004] In addition, the vehicle environment is accompanied by long-term severe vibration and wide temperature alternation. If laser welding is directly performed between the outer rotor yoke and the output shaft of the motor, micro-stress cracks often occur in the weld area due to the difference in the linear expansion coefficients of the dissimilar materials and the hardening tendency of high carbon steel welding. This can lead to the outer rotor yoke and the output shaft slipping off under long-term high-frequency reciprocating high-torque conditions. Summary of the Invention

[0005] In view of this, the present invention provides an electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor.

[0006] The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor of the present invention includes a housing, an outer rotor assembly, a stator assembly, a rotor position sensor, and a motor control board; The outer rotor assembly includes a rotor yoke, a permanent magnet, and an output shaft; the stator assembly includes a stator core and stator windings; and the motor control board is equipped with a motor drive circuit, a communication circuit, and a protection circuit. A stress-relieving bushing made of dissimilar materials is provided between the output shaft and the rotor yoke. An electromagnetic-thermal decoupling isolation disk is provided between the stator assembly and the motor control board, and the electromagnetic-thermal decoupling isolation disk is tightly fitted with the stator core in the axial direction.

[0007] Optionally, the heterogeneous material welded stress relief bushing is press-fitted onto the outer periphery of the output shaft, and the outer wall of the heterogeneous material welded stress relief bushing is fixedly connected to the central hole of the rotor yoke by laser circumferential welding. At least two axially parallel circumferential stress adaptive relief grooves are formed on the outer peripheral surface of the heterogeneous material welding stress relief bushing.

[0008] Alternatively, the center of the weld in the laser circumferential welding is located at the interface between the heterogeneous material welding stress relief bushing and the rotor yoke.

[0009] Optionally, the electromagnetic-thermal decoupling isolation disk includes a substrate core layer; A ceramic thermal barrier coating is formed on the side of the substrate core layer facing the stator assembly, and a grounded conductive oxide layer is formed on the side of the substrate core layer facing the motor control board.

[0010] Alternatively, the substrate core layer is made of aluminum-based silicon carbide; Inside the core layer of the matrix, there are staggered microcavities, which are filled with paraffin-based phase change heat storage microcapsules.

[0011] Optionally, the electromagnetic-thermal decoupling isolation disk is provided with an insulated wire-passing hole for the stator winding lead wire to pass through, and the outer periphery of the electromagnetic-thermal decoupling isolation disk is thermally connected to the inner wall of the outer shell through thermally conductive silicone.

[0012] Optionally, an electromagnetic shielding cavity is provided at the bottom of the outer casing, and a common-mode filter module and a surge protection module are provided inside the electromagnetic shielding cavity; The communication interface harness extending from the motor control board extends into the electromagnetic shielding cavity and is functionally coupled with the common-mode filter module and the surge protection module before exiting the outer casing.

[0013] Optionally, the rotor position sensor includes a circular magnet coaxially mounted to the end of the output shaft and a differential magnetic encoder chip disposed on the motor control board. An axial spring damping pad is provided between the circular magnet and the end of the output shaft.

[0014] Optionally, the inner wall of the housing is provided with a conductive oxide shielding layer, which is electrically connected to the grounded conductive oxide layer of the electromagnetic-thermal decoupling isolation disk and the shielding ground of the motor control board through a ring-shaped elastic metal braid.

[0015] Optionally, the stator winding leads and the motor control board are connected by laser brazing through U-shaped flexible interconnecting elastic contacts; The U-shaped flexible interconnect elastic contact is configured to absorb the thermal expansion shear stress between the stator winding and the motor control board through its own mechanical elastic deformation under a predetermined temperature alternation environment.

[0016] The beneficial effects of this invention are as follows: The electromagnetic-thermal decoupling isolated permanent magnet synchronous brushless motor of the present invention, on the one hand, achieves electromagnetic-thermal decoupling and isolation between the stator assembly and the motor control board by setting an electromagnetic-thermal decoupling isolation disk between the stator assembly and the motor control board. This reduces the adverse effects of heat generated by the stator assembly and the high-frequency electromagnetic radiation emitted by it on the motor control board to a certain extent, thereby ensuring the service life and electromagnetic compatibility of the motor control board. On the other hand, the outer rotor assembly of the present invention has a dissimilar material welded stress relief bushing between the output shaft and the rotor yoke. This dissimilar material welded stress relief bushing can absorb the difference in thermal expansion and contraction stress between the output shaft and the rotor yoke under wide temperature conditions in the vehicle, thereby reducing the probability of slippage between the output shaft and the rotor yoke in the outer rotor assembly.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The present invention can be better understood by referring to the following description taken in conjunction with the accompanying drawings, in which the same or similar reference numerals are used throughout the drawings to denote the same or similar parts.

[0019] Figure 1 An exploded structural diagram of an electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to an embodiment of the present invention is shown.

[0020] Figure 2 A schematic diagram showing the fit between a heterogeneous material welded stress relief bushing, an output shaft, and a rotor yoke according to an embodiment of the present invention is provided.

[0021] Figure 3 A cross-sectional schematic diagram of the electromagnetic-thermal decoupling isolation disk according to an embodiment of the present invention is shown. Detailed Implementation

[0022] To enable those skilled in the art to more fully understand the technical solutions of the present invention, exemplary embodiments of the present invention will be described more comprehensively and in detail below with reference to the accompanying drawings. Obviously, the one or more embodiments of the present invention described below are merely one or more specific ways to implement the technical solutions of the present invention, and are not exhaustive. It should be understood that other ways belonging to a general inventive concept can be used to implement the technical solutions of the present invention, and should not be limited to the embodiments described exemplary. Based on one or more embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] Example: Figure 1 An exploded structural diagram of an electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to an embodiment of the present invention is shown. Figure 2 This diagram illustrates the fit between the dissimilar material welding stress relief bushing, the output shaft, and the rotor yoke according to an embodiment of the present invention. Figure 3 A cross-sectional structural schematic diagram of the electromagnetic-thermal decoupling isolation disk according to an embodiment of the present invention is shown (insulating wire holes are not shown).

[0024] Reference Figures 1-3 The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor of this invention includes a housing 1, an outer rotor assembly 2, a stator assembly 3, a rotor position sensor 4, and a motor control board 5; The outer rotor assembly 2 includes a rotor yoke 21, a permanent magnet 22 and an output shaft 23; the stator assembly 3 includes a stator core 31 and a stator winding 32; and the motor control board 5 is equipped with a motor drive circuit, a communication circuit and a protection circuit. A stress-relieving bushing 6 made of dissimilar materials is provided between the output shaft 23 and the rotor yoke 21; An electromagnetic-thermal decoupling isolation disk 7 is provided between the stator assembly 3 and the motor control board 5, and the electromagnetic-thermal decoupling isolation disk 7 is tightly fitted with the stator core 31 in the axial direction.

[0025] Specifically, in this embodiment of the invention, the outer shell 1 is a cylindrical structure made of cast aluminum and is formed by integrated die casting process; the stator core 31 adopts a 12-slot structure, which forms a 12N14P slot-pole fit with the 14-pole outer rotor assembly 2; the output shaft 23 is made of GCr15 bearing steel, and the surface of the output shaft 23 is quenched and tempered at low temperature, with a hardness of HRC60~64.

[0026] Furthermore, in this embodiment of the invention, the heterogeneous material welded stress relief bushing 6 is press-fitted onto the outer periphery of the output shaft 23, and the outer wall of the heterogeneous material welded stress relief bushing 6 is fixedly connected to the central hole of the rotor yoke 21 by laser circumferential welding. At least two axially parallel circumferential stress adaptive relief grooves 61 are provided on the outer peripheral surface of the heterogeneous material welding stress relief bushing 6.

[0027] Specifically, in this embodiment of the invention, the stress relief bushing 6 for welding heterogeneous materials is made of low-carbon stainless steel or nickel-based alloy.

[0028] Furthermore, in this embodiment of the invention, the center of the weld seam in the laser circumferential welding is located at the interface between the dissimilar material welding stress relief bushing 6 and the rotor yoke 21.

[0029] Specifically, in this embodiment of the invention, the welding depth of laser circumferential welding is 1.2mm~1.5mm, and a microstructure gradient transition zone is formed, with a slip torque between the output shaft 23 and the rotor yoke 21 greater than 16Nm.

[0030] Furthermore, in this embodiment of the invention, the electromagnetic-thermal decoupling isolation disk 7 includes a substrate core layer 71; A ceramic thermal barrier coating 72 is formed on the side of the substrate core layer 71 facing the stator assembly 3, and a grounded conductive oxide layer 73 is formed on the side of the substrate core layer 71 facing the motor control board 5.

[0031] Furthermore, in this embodiment of the invention, the substrate core layer 71 is made of aluminum-based silicon carbide, and the ceramic thermal barrier coating 72 is a zirconium dioxide layer. Inside the matrix core layer 71, there are staggered micro-cavities filled with paraffin-based phase change heat storage microcapsules 74.

[0032] Furthermore, in this embodiment of the invention, the electromagnetic-thermal decoupling isolation disk 7 is provided with an insulated wire hole 75 through which the lead wire of the stator winding 32 passes. The outer periphery of the electromagnetic-thermal decoupling isolation disk 7 is thermally connected to the inner wall of the outer shell 1 through thermally conductive silicone to form a radial thermally conductive channel from the stator assembly 3 to the outer shell 1.

[0033] Furthermore, in this embodiment of the invention, an electromagnetic shielding cavity 11 is provided at the bottom of the outer shell 1, and a common-mode filter module and a surge protection module are provided inside the electromagnetic shielding cavity 11. The communication interface harness 8 extending from the motor control board 5 extends into the electromagnetic shielding cavity 11 and is functionally coupled with the common mode filter module and the surge protection module before exiting the outer casing 1.

[0034] Specifically, in this embodiment of the invention, the bottom of the outer shell 1 is integrally die-cast with an internally separated front-cabin type independent electromagnetic shielding cavity, the common-mode filtering module is implemented using a common-mode choke array, and the surge protection module is implemented using a TVS transient suppression diode group.

[0035] Furthermore, in this embodiment of the invention, the rotor position sensor 4 includes a circular magnet 41 coaxially mounted on the end of the output shaft 23 and a differential magnetic encoding chip 42 disposed on the motor control board 5. An axial spring damping pad 9 is provided between the end of the circular magnet 41 and the output shaft 23.

[0036] Specifically, in this embodiment of the invention, the differential magnetic encoding chip 42 adopts a dual-path matrix Hall induction array, which eliminates the leakage magnetic field measurement error caused by the axial movement of the output shaft 23 in real time through differential operation.

[0037] Furthermore, in this embodiment of the invention, the inner wall of the outer shell 1 is provided with a conductive oxide shielding layer. The conductive oxide shielding layer is electrically connected to the grounded conductive oxide layer 73 of the electromagnetic-thermal decoupling isolation disk 7 and the shielding ground of the motor control board 5 through a ring-shaped elastic metal braid. With this configuration, the strong electromagnetic interference area where the stator winding 32 is located and the weak electrical control area where the motor control board 5 is located can be physically and completely isolated in the cavity inside the motor.

[0038] Furthermore, in this embodiment of the invention, the lead wires of the stator winding 32 are laser brazed to the motor control board 5 via U-shaped flexible interconnecting elastic contacts. The U-shaped flexible interconnect elastic contact is configured to absorb the thermal expansion shear stress between the stator winding 32 and the motor control board 5 through its own mechanical elastic deformation under a predetermined temperature alternation environment.

[0039] Furthermore, the outer contour dimensions of the electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor in this embodiment of the invention are 42mm×42mm×52.86mm, the rated speed is 2500rpm, the rated torque is 0.2Nm, and the maximum torque is 0.5Nm. The outer casing 1 is equipped with a standardized mechanical mounting interface for direct adaptation to vehicle seat slide rail adjustment mechanism, vehicle electric armrest movement adjustment mechanism, vehicle foot pedal unfolding and folding adjustment mechanism, electric window adjustment mechanism or electric sunroof adjustment mechanism.

[0040] The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor of the present invention will be described in more detail below.

[0041] like Figure 1 and Figure 2As shown, the electromagnetic-thermal decoupling isolated permanent magnet synchronous brushless motor of this embodiment of the invention exhibits an ultra-compact overall profile of 42mm × 42mm × 52.86mm. The output shaft 23 is made of high-hardness GCr15 bearing steel, and its surface is quenched and tempered at low temperature to a hardness of HRC60~64. To prevent cracking during direct welding, a dissimilar material welding stress relief bushing 6 made of low-carbon nickel-based alloy is inserted into the welding section of the output shaft 23 by interference cold pressing. The outer wall of the dissimilar material welding stress relief bushing 6 has two circumferential stress adaptive relief grooves 61 with a depth of 0.3mm. During assembly, the output shaft 23 with the dissimilar material welding stress relief bushing 6 is pressed into the central hole of the rotor yoke 21 made of low-carbon steel, and circumferential oscillating laser welding is performed using a fiber laser welding machine, with a welding depth of 1.2mm. During the welding thermal cycle, the circumferential stress adaptive relief groove 61 on the heterogeneous material welding stress relief bushing 6 undergoes slight elastic yielding, perfectly releasing the welding residual stress and ensuring that there are no microcracks inside the weld. The actual measured slip torque after welding reaches 16.2 Nm, demonstrating extremely high connection reliability.

[0042] like Figure 1 and Figure 3 As shown, in this embodiment of the invention, the stator core 31 adopts a 12-slot design, and the stator winding 32 adopts a concentrated winding structure, forming a high-power-density 12N14P slot-pole combination with the 14-pole surface-mount neodymium iron boron permanent magnet 22 on the outer rotor. To prevent the heat from the stator winding 32 during operation from being transferred to the motor control board 5, a 2.0mm thick electromagnetic-thermal decoupling isolation disk 7 is tightly installed between them. The core layer of the electromagnetic-thermal decoupling isolation disk 7 is a substrate core layer 71, composed of 35% by volume of silicon carbide particle-reinforced aluminum matrix composite material (AlSiC), which has excellent thermal conductivity and can quickly conduct lateral heat into the cast aluminum outer shell 1 and dissipate it. A ceramic thermal barrier coating 72 is formed on the side of the substrate core layer 71 facing the stator assembly 3, which has extremely low axial thermal conductivity and effectively blocks heat radiation. Simultaneously, a micro-cavity is sintered inside the core layer 71, which is densely packed with paraffin-based phase change heat storage microcapsules 74 with an average particle size of 15µm. When the motor enters a momentary overload or heavy-load condition and the stator temperature surges, the paraffin inside the microcapsules undergoes a phase change and absorbs latent heat, locking the axial heating rate of the isolation disk. A grounded conductive oxide layer 73 is formed on the side of the core layer 71 facing the motor control board 5. It is connected to the grounding busbar of the motor control board and the conductive oxide shielding layer of the outer shell 1 through a ring-shaped elastic metal braided mesh, thereby creating an electrostatic and electromagnetic shielding mesh between the high-voltage area of ​​the stator and the low-voltage area of ​​the motor control.

[0043] like Figure 1As shown, the circular magnet 41 of the rotor position sensor 4 is mounted at the end of the output shaft 23. A 0.5mm thick axial spring damping pad 9 is added between the contact surfaces of the circular magnet 41 and the output shaft 23. When the vehicle travels under extremely rough road conditions, causing high-frequency axial movement of the output shaft 23, the axial spring damping pad 9, through its high elastic deformation, greatly suppresses the displacement fluctuation of the circular magnet 41 relative to the differential magnetic encoder chip 42 on the motor control board 5. Simultaneously, the dual-channel induction array configured inside the differential magnetic encoder chip 42 performs real-time differential Taylor series calculations on the spatial magnetic field, eliminating the leakage magnetic field measurement temperature drift caused by the axial movement of the common mold, ensuring that the rotor position detection error is stable within ≤0.5°. This results in extremely precise and smooth motor commutation, with measured operating noise at 1m between 28dB and 32dB, significantly improving the quietness and comfort of the cabin.

[0044] The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor of the present invention has the following beneficial effects: I. Achieving electromagnetic and thermal decoupling: This invention, through the addition of an electromagnetic-thermal decoupling isolation disk, utilizes the high thermal conductivity hard shielding properties of aluminum-based silicon carbide and the peak-shaving and temperature-controlling effect of paraffin-based phase-change heat storage microcapsules to dynamically block the heat flow from the stator assembly to the motor control board. Experiments show that the electromagnetic-thermal decoupling isolation disk can reduce the operating ambient temperature of the motor control board by more than 15°C. Simultaneously, the grounded conductive oxide layer provides a spatial electromagnetic shielding impedance of up to 120dB, ensuring that the overall electromagnetic compatibility easily meets the stringent Level 5 automotive electromagnetic compatibility standard of GB / T18655-2018.

[0045] Second, it solved the problem of cracking in laser welding of heterogeneous materials: By using a low-carbon nickel-based or stainless steel dissimilar material welding stress relief bushing as an intermediate medium, the cracking tendency of direct welding of high-carbon GCr15 bearing steel is avoided. Combined with the circumferential stress adaptive relief groove, it can absorb welding residual stress and vehicle-mounted wide-temperature alternating stress, effectively reducing the risk of slippage between the output shaft and rotor yoke under frequent start-stop and high vibration.

[0046] While one or more embodiments of the present invention have been described above, those skilled in the art will recognize that the present invention can be implemented in any other form without departing from its spirit and scope. Therefore, the embodiments described above are illustrative and not restrictive, and many modifications and substitutions will be apparent to those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor, characterized in that, Includes housing, outer rotor assembly, stator assembly, rotor position sensor, and motor control board; The outer rotor assembly includes a rotor yoke, a permanent magnet, and an output shaft; the stator assembly includes a stator core and stator windings; and the motor control board is equipped with a motor drive circuit, a communication circuit, and a protection circuit. A stress-relieving bushing made of dissimilar materials is provided between the output shaft and the rotor yoke. An electromagnetic-thermal decoupling isolation disk is provided between the stator assembly and the motor control board, and the electromagnetic-thermal decoupling isolation disk is tightly fitted with the stator core in the axial direction.

2. The electromagnetic-thermal decoupling isolated permanent magnet synchronous brushless motor according to claim 1, characterized in that, The heterogeneous material welded stress relief bushing is press-fitted onto the outer periphery of the output shaft, and the outer wall of the heterogeneous material welded stress relief bushing is fixedly connected to the center hole of the rotor yoke by laser circumferential welding. At least two axially parallel circumferential stress adaptive relief grooves are formed on the outer peripheral surface of the heterogeneous material welding stress relief bushing.

3. The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to claim 2, characterized in that, The center of the weld in the laser circumferential welding is located at the interface between the stress-relieving bushing of the heterogeneous material and the rotor yoke.

4. The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to claim 1, characterized in that, The electromagnetic-thermal decoupling isolation disk includes a substrate core layer; A ceramic thermal barrier coating is formed on the side of the substrate core layer facing the stator assembly, and a grounded conductive oxide layer is formed on the side of the substrate core layer facing the motor control board.

5. The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to claim 4, characterized in that, The core layer of the substrate is made of aluminum-based silicon carbide. Inside the core layer of the matrix, there are staggered microcavities, which are filled with paraffin-based phase change heat storage microcapsules.

6. The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to claim 5, characterized in that, The electromagnetic-thermal decoupling isolation disk has insulated wire holes for the stator winding leads to pass through, and the outer periphery of the electromagnetic-thermal decoupling isolation disk is thermally connected to the inner wall of the outer shell through thermally conductive silicone.

7. The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to claim 1, characterized in that, An electromagnetic shielding cavity is provided at the bottom of the outer shell, and a common-mode filter module and a surge protection module are provided inside the electromagnetic shielding cavity; The communication interface harness extending from the motor control board extends into the electromagnetic shielding cavity and is functionally coupled with the common-mode filter module and the surge protection module before exiting the outer casing.

8. The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to claim 1, characterized in that, The rotor position sensor includes a circular magnet coaxially mounted on the end of the output shaft and a differential magnetic encoding chip disposed on the motor control board. An axial spring damping pad is provided between the circular magnet and the end of the output shaft.

9. The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to claim 4, characterized in that, The inner wall of the outer casing is provided with a conductive oxide shielding layer, which is electrically connected to the grounded conductive oxide layer of the electromagnetic-thermal decoupling isolation disk and the shielding ground of the motor control board through a ring-shaped elastic metal braid.

10. The electromagnetic-thermal decoupled isolated permanent magnet synchronous brushless motor according to claim 1, characterized in that, The stator winding leads are connected to the motor control board by laser brazing through U-shaped flexible interconnecting elastic contacts. The U-shaped flexible interconnect elastic contact is configured to absorb the thermal expansion shear stress between the stator winding and the motor control board through its own mechanical elastic deformation under a predetermined temperature alternation environment.

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