Method for processing magnetic steel, magnetic steel and electric machine

Abstract

The present disclosure relates to a processing method of a magnetic steel, the magnetic steel and a motor, the magnetic steel is an integrated annular structure, the processing method comprises the following steps: preparing superfine permanent magnetic powder; placing the superfine permanent magnetic powder in a first tool for compression molding orientation to obtain an integrated annular green body; sintering and machining the integrated annular green body to obtain an integrated magnetic ring; and magnetizing the integrated magnetic ring by using a second tool, wherein the compression molding orientation direction of the integrated annular green body and / or the magnetizing direction of the integrated magnetic ring is consistent with the actual magnetic field direction. The magnetic powder is compressed to form an integrated annular magnetic steel, and the continuous magnetic field orientation and magnetization of the annular magnetic steel are completed during the compression of the annular magnetic steel. The compression molding orientation direction and the magnetizing direction of the magnetic steel are no longer single orientation, the problem that only a small part of the magnetic field orientation meets the use requirement is solved, the overall magnetizing saturation and the anti-demagnetization capability of the magnetic steel are improved, and the assembly difficulty of the magnetic steel is reduced.

Description

Technical Field

[0001] This disclosure relates to the field of motor technology, and more particularly to a method for processing magnets, magnets, and motors. Background Technology

[0002] As a core component of high-efficiency motors such as drive motors for new energy vehicles, wind turbine generators, and industrial servo motors, the manufacturing process of magnets (permanent magnets) directly determines the power density, efficiency, and operational reliability of the motors, playing a vital supporting role in the development of industries such as new energy and high-end equipment.

[0003] In related technologies, magnets are usually made by splicing together multiple arc-shaped magnets. The arc-shaped magnets are made and magnetized separately. The performance of the spliced ​​ring magnets is affected by the splicing process and the adhesive materials. At the same time, when the Halbach magnetization method is used, the spliced ​​magnets are very prone to low magnetization saturation and demagnetization. Summary of the Invention

[0004] To overcome the problems existing in related technologies, this disclosure provides a method for processing magnets, magnets, and motors.

[0005] According to a first aspect of the present disclosure, a method for processing a magnet is provided, wherein the magnet is an integral ring structure, and the processing method includes: Preparation of ultrafine permanent magnet powder; The ultrafine permanent magnet powder is placed in the first tooling for pressing and orientation to obtain an integral annular green blank; A one-piece annular green body is sintered and machined to obtain a one-piece magnetic ring; and The integrated magnetic ring is magnetized using a second tooling. The forming orientation direction of the integral annular green blank and / or the magnetization direction of the integral magnetic ring are consistent with the actual magnetic field direction.

[0006] In the processing method of the magnets disclosed herein, magnetic powder is pressed into an integral ring-shaped magnet. During the pressing process, a specially designed pressing mold and magnetization equipment are used to complete the continuous magnetic field orientation and magnetization of the ring-shaped magnet. The pressing orientation direction and magnetization direction of the magnet are no longer a single orientation, but are consistent with the actual magnetic field direction. This solves the problem that only a very small portion of the magnetic field orientation meets the usage requirements. At the same time, the distribution is uniform, and the transition between magnetic field directions is smooth, improving the overall magnetization saturation and demagnetization resistance of the ring-shaped magnet. This avoids the problems of incomplete magnetization and easy demagnetization at the corners of segmented magnets. In addition, the integral ring-shaped structure of the magnet can reduce the assembly difficulty of the magnet and the shaft, effectively ensuring the roundness of the outer circumference of the magnet and the concentricity with the shaft. This avoids the problems of difficulty in installing the last magnet or radial unevenness of the magnet due to tolerance accumulation during the installation of segmented magnets, thus improving the performance of the motor. It also facilitates the wrapping of carbon fiber on the outer ring to increase strength.

[0007] In some possible implementations, the molding orientation step includes: A stable directional magnetic field is pre-constructed, and the ultrafine permanent magnet powder is placed in the forming cavity of the first tooling, wherein the magnetic field strength of the pre-constructed stable directional magnetic field is less than the rated orientation magnetic field strength; The magnetic field strength of the directional magnetic field is instantly increased to the rated directional magnetic field strength to press the ultrafine permanent magnet powder in the forming cavity; Maintain the combined effect of the suppressing pressure and the rated orientation magnetic field for a predetermined time; and While keeping the suppression pressure constant, the magnetic field strength of the directional magnetic field decreases gradually.

[0008] First, a measured amount of ultrafine permanent magnet powder is weighed out. The powder should be in a loose, low-agglomeration state to ensure its flowability and prevent uneven orientation due to clumping. Before filling the powder, the coil is energized to generate a magnetic field strength of 30% to 50% of the rated orientation magnetic field strength, establishing a stable directional magnetic field environment in advance. Then, the prepared ultrafine permanent magnet powder is evenly filled into the forming cavity. At this point, the magnetic moment of the powder begins to deflect under the influence of the magnetic field torque. A scraper is used to smooth the powder surface of the forming cavity, ensuring the height of the powder blank. The pressure head, driven by hydraulic equipment, slowly descends to near the powder surface but before compaction. At this point, the current flowing through the coil on the charging head is increased, causing the magnetic field generated by the charging head to instantly rise to the rated orientation magnetic field strength, performing magnetic field orientation on the one-piece green blank. The pressure head presses downwards at a set pressure and at a constant speed, maintaining a constant orientation magnetic field. After pressing to the desired position, the pressure of the pressure head and the orientation magnetic field are maintained simultaneously for 1 to 3 seconds. After the magnetization process is complete, the pressure is kept constant, and the magnetic field of the magnetizing head is slowly reduced in a gradient to perform a weak demagnetization treatment, eliminating residual magnetization inside the green body. After demagnetization is complete, the pressure head is raised, and the integral annular green body is removed for the next sintering process.

[0009] In some possible implementations, the step of preparing the ultrafine permanent magnet powder includes: The raw materials are mixed according to the composition ratio of permanent magnet alloy; The mixed raw materials are vacuum melted to obtain alloy ingots; The alloy ingot was subjected to hydrogen crushing and dehydrogenation treatment to obtain coarse powder; The coarse powder is pulverized to the target particle size using an air jet mill to obtain the ultrafine permanent magnet powder.

[0010] According to the chemical formula of neodymium iron boron magnets, appropriate other elements are added to enhance the performance of the magnets. The powder is thoroughly mixed and the raw materials are smelted in a vacuum induction melting furnace to obtain alloy ingots. The alloy ingots are then subjected to hydrogen crushing treatment. The crushed fragments are dehydrogenated in a vacuum furnace, and the hydrogen-crushed powder is processed by air jet milling. By setting the feed pressure, grinding pressure, and classifying wheel speed, magnetic powder with the required process dimensions is obtained.

[0011] In some possible implementations, the first tooling and / or the second tooling includes a base plate, a collar disposed on the base plate, a support member and an iron core, and a movable pressure head. The collar, the support member and the iron core are arranged sequentially from the inside to the outside at intervals. The iron core has a plurality of magnetizing heads and coils disposed on the corresponding magnetizing heads. The plurality of magnetizing heads are arranged around the outer surface of the support member, and a shaped cavity is formed between the collar and the support member.

[0012] During the pressing process, the collar and support components provide bidirectional constraint on the magnetic powder, ensuring the radial dimensional accuracy and uniformity of density distribution of the annular green blank during pressing, thus improving the yield rate. The magnetic field strength within the forming cavity can be controlled by manipulating the coils on multiple magnetizing heads. The pressing head moves axially, while the magnetic field generated by the surrounding magnetizing heads passes radially through the forming cavity. As the pressing head presses downwards, it does not cut or interfere with the direction of the magnetic lines of force, ensuring that the magnetic domains remain radially oriented as the powder density increases during pressing.

[0013] In some possible implementations, during the molding orientation step, The ultrafine permanent magnet powder is placed between the collar and the support to form the molding cavity; The current in the coil is controlled so that the magnetic field strength of the pre-built stable directional magnetic field is less than or equal to the rated orientation magnetic field strength; The pressure head is controlled to move downwards at a constant pressure and uniform speed to perform pressing.

[0014] Before filling with magnetic powder, the magnetic field strength of the pre-constructed directional magnetic field is controlled below the rated value. This effectively prevents the ultrafine permanent magnet powder from agglomerating or bridging due to strong magnetic attraction before entering the molding cavity, ensuring that the magnetic powder fills the molding cavity uniformly and without voids, thus guaranteeing the surface quality of the green body after molding. During the pressing stage, a constant pressure and uniform speed pressing method is adopted, which works in conjunction with the stable orientation magnetic field to ensure that the powder bears the same force at all height layers along the axial direction. This ensures the consistency of the axial density distribution of the integrated annular green body and avoids the risk of cracking during later sintering.

[0015] In some possible implementations, one end of the magnetizing head is fixed to the iron core, and the other end is provided with a pole shoe. The side of the pole shoe facing away from the iron core is a toothed surface. The toothed surface is a plane or an arc surface, and / or, the toothed surface is provided with a slot.

[0016] By designing parameters such as the number of magnetizing heads, the size and shape of pole shoes, the orientation direction of the magnets and the magnetization direction can be adjusted, thereby adjusting the magnetic field performance of the motor rotor. All of these can provide a basis for changing the orientation direction of the magnetic field and the magnetization direction.

[0017] In some possible implementations, the magnetizing head is tilted relative to the iron core in the axial direction to achieve continuous skewed poles of the magnet during molding orientation or during magnetization.

[0018] In some possible implementations, the collar may be made of a magnetic material or a non-magnetic material.

[0019] The collar is designed with a magnetically conductive material, which can produce a completely different magnetic field. Whether the collar is magnetically conductive can be designed according to needs.

[0020] In some possible implementations, the magnetic field strength of the pre-built stable directional magnetic field is 30%-50% of the rated directional magnetic field strength, and the magnetic field strength of the directional magnetic field can be adjusted by controlling the current of the control coil.

[0021] In some possible implementations, the forming orientation direction of the integral annular green blank and / or the magnetization direction of the integral magnetic ring are axially continuously inclined.

[0022] In the processing method provided in this disclosure, the magnet adopts continuous skew poles, and the continuous skew poles are implemented in the pressing orientation and magnetization process of the magnet. In the magnet manufacturing stage, the pressing orientation is continuously changed along the axial direction, so that the easy magnetization axis of the magnetic powder naturally forms a smooth torsion. The cogging torque waveforms generated at different axial positions cancel each other out in phase, and the total cogging torque amplitude is greatly reduced, minimizing the cogging torque to the greatest extent. At the same time, the harmonic loss is minimized, ensuring that the motor runs smoothly without jerking, and realizing a truly continuous skew pole.

[0023] In some possible implementations, the angles between the molding orientation direction, the magnetization direction, and the axial direction are all continuously varied along the axial direction, and the angles between the molding orientation direction and the axial direction, and the angles between the magnetization direction and the axial direction, are consistent.

[0024] During the pressing and magnetic field orientation stages, the direction of the orientation magnetic field is continuously varied along the axial direction. Similarly, during the magnetization stage, the magnetization direction is continuously varied along the axial direction to achieve continuous skewness in both the pressing and magnetization steps. Achieving continuous skewness during the pressing and orientation of the magnet, and achieving continuous skewness with the same angle during magnetization, ensures that the final product achieves truly continuous skewness.

[0025] In some possible implementations, the axial deflection angle of the forming orientation direction of the integral annular green preform and / or the magnetization direction of the integral magnetic ring is α, where 0°≤α≤ z is the number of stator teeth.

[0026] The skew angle of a continuous skewed stator is the angle at which the stator rotates through one tooth in the circumferential direction. Using this angle, the cogging torque can be minimized. Of course, the deflection angle can also be designed within this range as needed.

[0027] According to a second aspect of the present disclosure, a magnet is provided, which is an integral magnetic ring and is formed using the above-described magnet processing method.

[0028] According to a third aspect of the present disclosure, an electric motor is provided, comprising the magnet described above.

[0029] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0031] Figure 1 This is a structural schematic diagram of a magnet according to a relevant embodiment.

[0032] Figure 2 This is a schematic diagram of the structure of an electric motor according to a relevant embodiment.

[0033] Figure 3 This is a flowchart illustrating a method for processing magnetic steel according to an exemplary embodiment.

[0034] Figure 4 This is a flowchart illustrating a magnet processing method according to an exemplary embodiment, wherein the pressing and orientation step is shown.

[0035] Figure 5 This is a flowchart illustrating a magnet processing method according to an exemplary embodiment, wherein the steps of preparing ultrafine permanent magnet powder are shown.

[0036] Figure 6 This is a schematic diagram of the structure of a first tooling or a second tooling according to an exemplary embodiment.

[0037] Figure 7 This is a top view of a first or second tooling according to an exemplary embodiment.

[0038] Figure 8 This is a schematic diagram of the structure of a first or second tooling according to another exemplary embodiment.

[0039] Figure 9 This is a schematic diagram of the structure of an integral magnetic ring according to an exemplary embodiment.

[0040] Figure 10 This is a front view of an integral magnetic ring according to an exemplary embodiment.

[0041] Figure 11 and Figure 12 This is a schematic diagram of the structure of a magnetizing head according to different exemplary embodiments.

[0042] Figure 13 and Figure 14 This is a schematic diagram of the internal magnetic field lines of an integral magnetic ring according to different exemplary embodiments.

[0043] Explanation of reference numerals in the attached figures 1-First tooling; 2-Second tooling; 10-Forming cavity; 11-Base plate; 12-Shaft collar; 13-Support component; 14-Iron core; 141-Magnetic head; 142-Pole shoe; 1421-Gear surface; 1422-Slot; 15-Pressure head; 16-Shaft core; 17-Coil; 3-Stator iron core; 30-Stator slot; 4-Integrated magnetic ring; 40-Magnetic steel block; 5-Rotating shaft. Detailed Implementation

[0044] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0045] In this disclosure, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the drawing orientation of the corresponding figures; "inner" and "outer" refer to the inner and outer contours of the corresponding components; and "axial," "circumferential," and "radial" refer to the axis of rotation of the motor rotor. The terms "first," "second," etc., are used to distinguish different components and do not indicate sequence or importance. Furthermore, in the following description, when referring to the figures, unless otherwise explained, the same reference numerals in different figures denote the same or similar elements.

[0046] In related technologies, the segmented arc-shaped magnet splicing process is complex. Errors in the gaps and radial roundness between the magnet blocks 40 gradually accumulate, making it difficult to install the final magnet blocks 40 correctly. The overall outer diameter roundness of the installed ring is poor, affecting motor performance and complicating the process of winding carbon fiber around the magnet outer ring. Furthermore, the adhesive method used to fix multiple magnet blocks 40 poses a risk of breakage due to centrifugal force at high speeds. Gaps between the magnet blocks 40 can also have a cutting effect on the carbon fiber wound around the outer ring, reducing its fastening performance. Additionally, the connection strength between the magnet blocks 40 depends on the performance of the magnet adhesive, which carries a risk of disintegration under high temperature and high speed.

[0047] like Figure 1 and Figure 2 As shown, taking the Halbach arrangement structure as an example, the magnets are formed by splicing together multiple magnet blocks 40, each with a single magnetization direction. The magnetic field of the Halbach rotor structure concentrates on the side facing the air gap (the air gap between the stator and rotor, i.e., the side where the outer surface of the magnet is located) and weakens on the side away from the air gap (the side where the inner surface of the magnet is located), although it can achieve a magnetization effect on the air gap side. However, for a single magnet block 40, the magnetic field orientation of the magnet block 40 (e.g., ...) Figure 2 As shown in Figure A, the direction of the magnetic field used by the rotor is singular and does not correspond to the actual direction of the magnetic field (as shown in Figure A). Figure 2 (As shown in B) is inconsistent.

[0048] It's important to note that the magnetic field orientation of the magnet (equivalent to the molding orientation mentioned below) is determined during the magnet's manufacturing process and remains fixed; it's an inherent property of the magnet. The actual magnetic field direction during use, when the magnet is mounted on the rotor and the motor is operating, varies slightly from the initial magnetic field orientation. Only some areas have a magnetic field orientation similar to the actual operating magnetic field direction; a significant portion of the area has an inconsistent orientation, resulting in a large angle between the magnetic field orientation and the actual magnetic field direction. Thus, the actual magnetic field direction is only one component of the magnetization direction of the magnet block, and the magnetizing effect of the magnet block is not fully realized. Furthermore, during magnetization, the magnetizing magnetic field is similar to the rotor's operating magnetic field, leading to inconsistencies between the magnetizing magnetic field and the actual magnetic field orientation, resulting in incomplete magnetization. Additionally, the greater the deviation between the magnetic field orientation and magnetization direction of the magnet block and the actual magnetic field direction, the weaker the magnetic field strength at those locations. When encountering a weak magnet in the motor, these locations are more prone to demagnetization when a magnetic field is applied.

[0049] To solve the above problems, such as Figure 9 As shown, this disclosure provides an integrated ring-shaped magnet to solve various problems caused by splicing multiple magnet blocks 40. Furthermore, the magnetic field orientation and / or magnetization direction of this magnet are consistent with the actual magnetic field direction, avoiding the problem of a large angle between the magnetic field orientation and the actual magnetic field direction in traditional single magnet blocks 40. This ensures that the magnetic field strength of the magnet contributes magnetic flux entirely along the effective magnetic circuit direction, rather than merely participating as a component, thereby fully utilizing the magnet's focusing effect, significantly increasing the air gap magnetic flux density, and improving the motor's output torque and power density. Secondly, because the magnetic field orientation of the magnet is consistent with the magnetization magnetic field direction and the actual operating magnetic field direction, the magnetization magnetic field can act directly along the magnetization axis of the magnet during magnetization, achieving complete and uniform magnetization of the magnet. This eliminates the unsaturated magnetization regions present in existing technologies, ensuring that the magnetic properties of each region of the magnet reach the design value. Additionally, the magnetic field orientation of each region of the magnet in this disclosure is consistent with the actual magnetic field direction, effectively enhancing the magnet's resistance to demagnetization, avoiding motor performance degradation caused by localized demagnetization, and extending the service life of the magnet and the motor.

[0050] Accordingly, this disclosure provides a method for processing an integral ring-shaped magnet, such as... Figure 3 As shown, the processing method includes: step 301, preparing ultrafine permanent magnet powder; step 302, placing the ultrafine permanent magnet powder in the first tooling 1 for pressing and orientation to obtain an integral annular green blank; step 303, sintering and machining the integral annular green blank to obtain an integral magnetic ring 4; and step 304, using the second tooling 2 to magnetize the integral magnetic ring 4, wherein the pressing and orientation direction of the integral annular green blank and / or the magnetization direction of the integral magnetic ring 4 are consistent with the actual magnetic field direction.

[0051] It should be noted that the first tooling 1 is a molding and orientation tooling, and the second tooling 2 is a magnetizing tooling. The two can have different or the same structure. The structure of the tooling will be defined by the latter in the following text.

[0052] In the processing method of the magnets disclosed herein, magnetic powder is pressed into an integral ring-shaped magnet. During the pressing process, a special pressing mold and magnetization equipment are used to complete the continuous magnetic field orientation and magnetization of the ring-shaped magnet. The pressing orientation direction and magnetization direction of the magnet are no longer a single orientation, but are consistent with the actual magnetic field direction. This solves the problem that only a very small portion of the magnetic field orientation meets the usage requirements. At the same time, the distribution is uniform, and the transition between magnetic field directions is smooth, improving the overall magnetization saturation and demagnetization resistance of the ring-shaped magnet. This avoids the problems of incomplete magnetization and easy demagnetization at the corners of segmented magnets. In addition, the integral ring-shaped magnet structure can reduce the assembly difficulty of the magnet and the rotating shaft 5, effectively ensuring the roundness of the outer circumference of the magnet and the concentricity with the rotating shaft 5. This avoids the problems of difficulty in installing the last magnet or radial unevenness of the magnet due to tolerance accumulation during the installation of segmented magnets, thus improving the performance of the motor. It also facilitates the wrapping of carbon fiber on the outer ring to increase strength.

[0053] In exemplary embodiments of this disclosure, a processing fixture is provided. This processing fixture can be used for pressing and oriented an integral ring structure, or for magnetizing an integral magnetic ring; that is, it can be the first fixture 1 or the second fixture 2 described above. In this disclosure, as... Figure 6 and Figure 7 As shown, the first tooling 1 and / or the second tooling 2 include a base plate 11, a collar 12, a support member 13 and an iron core 14 disposed on the base plate 11, and a movable pressure head 15. The collar 12, the support member 13 and the iron core 14 are arranged sequentially from the inside to the outside. The iron core 14 has a plurality of magnetizing heads 141 and coils 17 disposed on the corresponding magnetizing heads 141. The plurality of magnetizing heads 141 are arranged around the outer surface of the support member 13. A shaped cavity 10 is formed between the collar 12 and the support member 13.

[0054] During the downward pressing process of the pressure head 15, the collar 12 and the support 13 provide bidirectional constraint on the magnetic powder, ensuring the radial dimensional accuracy and density distribution uniformity of the annular green blank during pressing, thus improving the yield of the finished product. By controlling the coils 17 on multiple magnetizing heads 141, the magnetic field strength within the forming cavity 10 can be controlled. In addition, since the pressure head 15 moves axially, and the magnetic field generated by the surrounding arrangement of the magnetizing heads 141 passes radially through the forming cavity 10, the pressure head 15 does not cut or interfere with the direction of the magnetic lines of force when pressing downwards, ensuring that the magnetic domains remain radially oriented as the powder density increases during pressing.

[0055] like Figure 4As shown, step 302 includes: step 3021, pre-constructing a stable directional magnetic field, placing ultrafine permanent magnet powder in the forming cavity 10 of the first tooling 1, wherein the magnetic field strength of the pre-constructed stable directional magnetic field is less than the rated orientation magnetic field strength. Here, "ultrafine permanent magnet powder" can be neodymium iron boron powder, with an average particle size of 0.1μm~3μm, lower than the conventional main phase alloy powder with a particle size of 2~5μm. "Rated orientation magnetic field strength" refers to the magnetic field strength value required for ultrafine permanent magnet powder to achieve sufficient orientation of its internal magnetic domains along the orientation direction under pressing pressure. It is a process parameter determined by the characteristics of the magnetic powder, not a fixed physical constant. The rated orientation magnetic field strength varies depending on the composition of the neodymium iron boron powder and the particle size distribution.

[0056] In step 3021, a fixed amount of ultrafine permanent magnet powder is weighed out. The powder is in a loose, low-agglomeration state to ensure its flowability and prevent uneven orientation due to clumping. Before filling the magnetic powder, the coil 17 (described below) is energized to generate a magnetic field strength of 30% to 50% of the rated orientation magnetic field strength (the specific strength of the pre-constructed directional magnetic field can be designed by adjusting the current of the coil 17), thus establishing a stable directional magnetic field environment in advance. Then, the prepared ultrafine permanent magnet powder is evenly filled into the forming cavity 10. At this point, the magnetic moment of the powder begins to be affected by the magnetic field torque and undergoes initial deflection. A scraper is used to smooth the magnetic powder on the surface of the forming cavity 10 to ensure the height of the powder blank.

[0057] Step 3022: Instantly increase the magnetic field strength of the directional magnetic field to the rated directional magnetic field strength to press the ultrafine permanent magnet powder in the forming cavity.

[0058] In step 3022, the pressure head 15 can be driven by a hydraulic device to slowly descend to near the powder surface but not to contact and compact it. At this time, the current of the coil 17 on the magnetic head 141 is increased, so that the magnetic field generated by the magnetic head 141 is instantly raised to the rated orientation magnetic field strength, and the integrated annular green blank is oriented by magnetic field.

[0059] Step 3023: Maintain the combined effect of the pressing pressure and the rated orientation magnetic field for a predetermined time; In step 3023, the pressure head presses downward at a set pressure at a constant speed, the orientation magnetic field remains constant, and after pressing is completed, the pressure of the pressure head and the orientation magnetic field are maintained simultaneously for 1 to 3 seconds.

[0060] Step 3024: Keep the pressure constant and make the magnetic field strength of the directional magnetic field decrease gradually.

[0061] In step 3024, after the magnetization is completed, the pressure is kept constant, and the magnetic field of the magnetizing head 141 is slowly reduced according to the gradient to perform weak demagnetization and eliminate residual magnetization inside the integrated annular green blank. After demagnetization is completed, the pressure head is raised, the integrated annular green blank is removed, and the next sintering process is carried out.

[0062] like Figure 5 As shown, step 301 includes: step 3011, mixing raw materials according to the composition ratio of permanent magnet alloy; step 3012, obtaining alloy ingots by vacuum melting of the mixed raw materials; step 3013, obtaining coarse powder by hydrogen crushing and dehydrogenation treatment of the alloy ingots; and step 3014, pulverizing the coarse powder to the target particle size by air jet milling to obtain ultrafine permanent magnet powder.

[0063] According to the chemical formula of neodymium iron boron magnets, appropriate other elements are added to enhance the performance of the magnets. The powder is thoroughly mixed and the raw materials are smelted in a vacuum induction melting furnace to obtain alloy ingots. The alloy ingots are then subjected to hydrogen crushing treatment. The crushed fragments are dehydrogenated in a vacuum furnace, and the hydrogen-crushed powder is processed by air jet milling. By setting the feed pressure, grinding pressure, and classifying wheel speed, magnetic powder with the required process dimensions is obtained.

[0064] In step 302, ultrafine permanent magnet powder is placed between the collar 12 and the support member 13 to form a molding cavity 10; the current of the coil 17 is controlled so that the magnetic field strength of the pre-constructed stable directional magnetic field is less than or equal to the rated orientation magnetic field strength; the pressure head 15 is controlled to move downward at a constant pressure and uniform speed to press.

[0065] Before filling with magnetic powder, the magnetic field strength of the pre-constructed directional magnetic field is controlled below the rated value. This effectively prevents the ultrafine permanent magnet powder from agglomerating or bridging due to strong magnetic attraction before entering the molding cavity 10, ensuring that the magnetic powder is filled uniformly and without voids within the molding cavity 10, thus guaranteeing the surface quality of the integral annular green body after molding. During the pressing stage, a constant pressure and uniform speed pressing method is adopted, which works in conjunction with the stable orientation magnetic field to ensure that the powder bears the same force at each height layer along the axial direction. This ensures the consistency of the axial density distribution of the integral annular green body and avoids the risk of cracking during later sintering.

[0066] In step 303, the integral annular green blank is sintered to ensure sintering temperature, sintering time, and sintering vacuum. The sintered body is then heat-treated, consisting of a first-stage aging treatment and a second-stage aging treatment at a temperature of 500°C and a holding time of 2 hours. The heat-treated magnet is then machined, for example, by external cylindrical grinding, internal cylindrical grinding, and end face grinding, with a machining accuracy of ±0.01mm, to obtain the integral magnetic ring 4.

[0067] In the machining tooling provided in this disclosure, such as Figure 11 and Figure 12 As shown, one end of the magnetizing head 141 is fixed to the iron core 14, and the other end is provided with a pole shoe 142. The side of the pole shoe 142 facing away from the iron core 14 is a tooth surface 1421. The tooth surface is a plane or an arc surface, and / or, the tooth surface 1421 is provided with a slot 1422.

[0068] The design can be achieved by adjusting parameters such as the number of charging heads 141, the size and shape of pole shoes 142, etc. This disclosure includes, but is not limited to, the following: Figure 7 The three pairs of magnetizing heads 141 shown can be extended to one or more pairs of magnetizing heads. In addition, the width of the pole shoe 142 can be increased, the thickness of the pole shoe 142 in the radial direction can be adjusted, the tooth tip height can be changed, the tooth surface curvature can be changed, and slots 1422 can be set. The number and shape of the slots 1422 are not limited. The forming orientation direction and magnetization direction of the magnet can be adjusted, thereby adjusting the magnetic field performance of the motor rotor. All of these can provide a basis for changing the magnetic field orientation direction and magnetization direction.

[0069] The collar 12 can be made of a magnetic or non-magnetic material. For example... Figure 13 and Figure 14 As shown, the collar 12 is designed with a magnetically conductive material, which can produce completely different magnetic fields. Whether the collar 12 is magnetically conductive can be designed as needed. To form magnets with different radial dimensions, the distance between the collar 12 and the support member 13 can be adjusted as needed. Additionally, the collar 12 can be fitted onto the shaft core 16, and the material of the collar 12 between the shaft core 16 and the integrated magnetic ring 4 can be designed as needed.

[0070] Taking a permanent magnet motor as an example, the magnets (permanent magnets) are mounted on the surface of the rotor. The cogging torque is the periodic torque generated by the interaction between the permanent magnet and the stator core when the permanent magnet motor winding is not energized. It is caused by the tangential component of the interaction force between the permanent magnet and the stator teeth. When the motor rotor rotates, the magnetic permeability of the permanent magnet changes significantly within a certain range corresponding to the stator teeth, thereby generating cogging torque, which causes the motor to vibrate, produce electromagnetic noise and run unevenly during operation.

[0071] To reduce cogging torque, the relative positions of the stator and rotor can be deflected, and torque waveforms of different phases can be superimposed to reduce it. Related technologies employ skewed pole techniques, such as segmenting and misaligning the rotor core, or using stator skew. For stator skew solutions, the stator of the drive motor typically uses flat wire windings, which prevents the stator core from using a skewed design. For skewed pole solutions with segmented and misaligned rotor cores, given a fixed axial length, such as... Figure 1 As shown in Table 1.1, the cogging torque decreases significantly with the increase of the number of segments. However, the number of segments is limited by its own size and is usually less than 8 segments, which cannot achieve the effect of continuous inclined slots in the stator core and cannot minimize the cogging torque.

[0072] Table 1.1 Cogging torque for different rotor skew pole segments

[0073] The rotor skew scheme involves dividing the rotor core or permanent magnet into several segments axially, with adjacent segments offset by a predetermined angle. Each segment uses the same skew angle, resulting in an internal relative deflection angle of 0. From the perspective of magnetic field distribution, the equivalent magnetic pole centerline is a broken line. This scheme can only achieve segmented skew (like multiple steps, each step is flat, with adjacent steps offset), and cannot achieve continuous skew, thus failing to minimize cogging torque. Furthermore, rotor skew also affects the distribution of voltage harmonics in the stator and rotor air gap magnetic fields. As shown in Table 1.2, increasing the number of segments reduces the total harmonic distortion and harmonic content. However, in the segmented skew scheme, the number of segments is limited, preventing a maximum reduction in harmonic content and consequently, a maximum reduction in harmonic losses.

[0074] Table 1.2 Total Harmonic Distortion Rate with Different Number of Rotor Skew Pole Segments

[0075] Based on the drawbacks of segmented skewed poles, this disclosure provides a continuous skewed pole technical solution. Continuous skewed poles refer to the fact that every point in the axial direction from one end of the rotor to the other is deflected relative to the axial direction. The equivalent magnetic pole centerline is smooth, continuous, and without inflection points, which can maximize the reduction of cogging torque and maximize the reduction of deceleration harmonic losses.

[0076] In related technologies, the magnetic field orientation is usually uniform and constant in the axial direction. In the continuous skew pole scheme, considering that the permanent magnet is anisotropic material, the magnetic field orientation of the permanent magnet produced by the current method is fixed at the time of manufacture. If the skew pole is only achieved through subsequent magnetization, it is impossible to achieve a truly continuous skew pole.

[0077] Based on the above, in order to achieve true continuous skew poles and minimize the cogging torque, in the above processing method, the forming orientation direction of the integral annular green blank and / or the magnetization direction of the integral magnetic ring 4 are continuously skew poles along the axial direction, thereby realizing continuous skew poles of the magnet during forming orientation or during magnetization.

[0078] "Continuous deflection" refers to the continuous axial deflection of the magnetic poles of a magnet from the first end to the second end of the axial direction. The magnetic pole at any point on the magnet is deflected relative to the axial direction. This disclosure includes embodiments in which the magnetic poles of the magnet are continuously deflected in the axial direction during molding and orientation, embodiments in which the magnetic poles of the magnet are continuously deflected in the axial direction during magnetization, and embodiments in which the magnetic poles of the magnet are continuously deflected in the axial direction during both molding and orientation and magnetization.

[0079] Unlike segmented skewed poles, the processing method provided in this disclosure uses continuous skewed poles for the magnets. This continuous skewed poles are implemented during the magnets' molding orientation and magnetization processes. During the magnet manufacturing stage, the molding orientation continuously changes along the axial direction, allowing the easily magnetized axis of the magnetic powder to naturally form a smooth twist. The cogging torque waveforms generated at different axial positions cancel each other out in phase, significantly reducing the total cogging torque amplitude. This minimizes cogging torque and harmonic losses, ensuring smooth motor operation without jerking, thus achieving truly continuous skewed poles.

[0080] "Continuous deflection" refers to the axial deflection angle of a magnet's poles changing continuously along the axial direction, rather than remaining constant. For example, Figure 10 As shown, the axial deflection angle α of the magnetic poles of the magnet refers to the angle between the equivalent magnetic pole centerline L2 and the axial axis L1 in the circumferential direction at that axial position.

[0081] Here, the axial deflection direction of the magnetic poles and the easy magnetization axis direction of the magnet are both the magnetic field orientation directions during the pressing and orientation stage. The axial deflection angle of the magnetic poles of the magnet changes continuously along the axial direction. This, unlike the step-like jump in the segmented skewed pole scheme, eliminates abrupt changes in the magnetic circuit between segments, reduces local magnetic flux concentration and eddy current losses. Because the included angle changes continuously along the axial direction, the phase difference between the cogging torque waveforms generated at various axial positions is continuously and gradually distributed, rather than a segmented abrupt change. This allows the waveforms to cancel each other out more thoroughly when superimposed, further reducing the residual fluctuation of the cogging torque, while significantly reducing harmonic losses. The motor runs more smoothly without obvious jerking or abrupt changes.

[0082] The angle between the pressing orientation direction, the magnetization direction, and the axial direction of the magnet is continuously varied along the axial direction. During the pressing and magnetic field orientation stages, the direction of the orientation magnetic field is continuously varied along the axial direction (e.g., by using an inclined magnetization head as described below). During the magnetization stage, the magnetization direction is continuously varied along the axial direction to achieve continuous tilting in the pressing orientation step and the magnetization step, respectively.

[0083] In this embodiment, the angle between the molding orientation direction and the axial direction and the magnetization direction are kept consistent. Continuous slant poles are achieved during the molding orientation of the magnet, and continuous slant poles with the same slant pole angle are achieved during magnetization, thus ensuring that the final product achieves true continuous slant poles.

[0084] The magnetic field orientation direction of the magnet, that is, the angle between the easy magnetization axis of the magnetic powder particles and the axial direction, changes continuously along the axial direction. When the easy magnetization axis of the magnet is set to continuously deflect along the axial direction during the molding orientation stage and remains fixed after sintering, the magnetization direction of the final product will also continuously deflect along the axial direction along the same skew pole angle during magnetization.

[0085] In an exemplary embodiment of this disclosure, the deflection angle α of the magnetic poles of the magnet in the axial direction can vary continuously as a linear function along the axial direction. For example... Figure 10 As shown, the deflection angle α of the magnetic poles of the magnet in the axial direction can gradually increase along the axial direction. The angle between the equivalent magnetic pole center line L2 and the axial axis L1 increases linearly. The phase difference of the cogging torque waveform generated at each position in the axial direction is constant. After superposition, the fundamental component of the cogging torque is completely canceled out, the residual fluctuation is minimized, the cogging torque can be minimized to the maximum extent, the magnetic field transition is the smoothest, and the eddy current loss inside the permanent magnet is low.

[0086] The axial deflection angle of the magnetic poles of the magnet is α, where 0° ≤ α ≤ Where z is the number of stator teeth. In this embodiment, the skew angle of the continuous skewed poles is the angle at which the stator rotates through one tooth in the circumferential direction. Using this angle, the cogging torque can be minimized. Of course, the deflection angle can also be designed within this range as needed.

[0087] Compared with segmented skewed poles, the continuous skewed pole scheme provided in this disclosure can provide more freedom in rotor design, and can be made into different skewed pole sequences and different skewed pole angles as needed.

[0088] To achieve continuous skewed poles, the machining fixtures provided in this disclosure, such as Figure 8 As shown, the magnetizing head 141 is inclined relative to the iron core 14 in the axial direction. The coil 17 is wound on the main body section of the magnetizing head 141 and stopped between the iron core 14 and the pole shoe 142. The extension direction of the main body section is inclined relative to the axial direction, causing the coil 17 wound on the main body section to also be inclined in the corresponding direction, thereby achieving the same design effect as the continuous inclined slot of the stator iron core.

[0089] According to a second aspect of this disclosure, a magnet is provided, which is an integral magnetic ring and is formed using the processing method of the magnet provided in this disclosure.

[0090] According to a third aspect of this disclosure, an electric motor is provided, comprising the magnet provided herein. This electric motor possesses all the beneficial effects of the aforementioned processing method and magnet, which will not be repeated here.

[0091] Furthermore, the term “exemplary” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as advantageous compared to other aspects or designs. Rather, the use of the term “exemplary” is intended to present the concept in a concrete manner. As used herein, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless otherwise specified or clear from the context, “X applies A or B” is intended to mean any of the natural inclusive arrangements. That is, “X applies A or B” satisfies any of the foregoing instances if X applies A; X applies B; or both X applies A and B. Additionally, unless otherwise specified or clear from the context to refer to the singular form, the articles “a” and “an” as used in this application and the appended claims are generally understood to mean “one or more.”

[0092] Similarly, although this disclosure has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. This disclosure includes all such modifications and variations and is limited only by the scope of the claims. In particular, with respect to the various functions performed by the components described above (e.g., elements, resources, etc.), unless otherwise indicated, the terminology used to describe such components is intended to correspond to any component (functionally equivalent) that performs the specific function of the described component, even if structurally not equivalent to the disclosed structure. Furthermore, although specific features of this disclosure may have been disclosed with respect to only one of several implementations, such features may be combined with one or more other features of other implementations, as may be desired and advantageous to any given or particular application. Moreover, with regard to the terms “comprising,” “owning,” “having,” “having,” or variations thereof as used in the detailed description or claims, such terms are intended to be inclusive in a manner similar to the term “including.”

[0093] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

[0094] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A method for processing magnetic steel, characterized in that, The magnet is a one-piece ring structure, and the processing method includes: Preparation of ultrafine permanent magnet powder; The ultrafine permanent magnet powder is placed in the first tooling for pressing and orientation to obtain an integral annular green blank; A one-piece annular green body is sintered and machined to obtain a one-piece magnetic ring; and The integrated magnetic ring is magnetized using a second tooling. The forming orientation direction of the integral annular green blank and / or the magnetization direction of the integral magnetic ring are consistent with the actual magnetic field direction.

2. The method for processing magnets according to claim 1, characterized in that, The molding and orientation step includes: A stable directional magnetic field is pre-constructed, and the ultrafine permanent magnet powder is placed in the forming cavity of the first tooling, wherein the magnetic field strength of the pre-constructed stable directional magnetic field is less than the rated orientation magnetic field strength; The magnetic field strength of the directional magnetic field is instantly increased to the rated directional magnetic field strength to press the ultrafine permanent magnet powder in the forming cavity; Maintain the combined effect of the suppressing pressure and the rated orientation magnetic field for a predetermined time; and While keeping the suppression pressure constant, the magnetic field strength of the directional magnetic field decreases gradually.

3. The method for processing magnets according to claim 1, characterized in that, The steps for preparing ultrafine permanent magnet powder include: The raw materials are mixed according to the composition ratio of permanent magnet alloy; The mixed raw materials are vacuum melted to obtain alloy ingots; The alloy ingot was subjected to hydrogen crushing and dehydrogenation treatment to obtain coarse powder; The coarse powder is pulverized to the target particle size using an air jet mill to obtain the ultrafine permanent magnet powder.

4. The method for processing magnets according to claim 2, characterized in that, The first and / or second tooling includes a base plate, a collar, a support member, and an iron core disposed on the base plate, and a movable pressure head. The collar, the support member, and the iron core are arranged sequentially from the inside to the outside at intervals. The iron core has multiple magnetizing heads and coils disposed on the corresponding magnetizing heads. The multiple magnetizing heads are arranged around the outer surface of the support member. A shaped cavity is formed between the collar and the support member.

5. The method for processing magnets according to claim 4, characterized in that, In the molding and orientation step, The ultrafine permanent magnet powder is placed between the collar and the support to form the molding cavity; The current in the coil is controlled so that the magnetic field strength of the pre-built stable directional magnetic field is less than or equal to the rated orientation magnetic field strength; The pressure head is controlled to move downwards at a constant pressure and uniform speed to perform pressing.

6. The method for processing magnets according to claim 4, characterized in that, One end of the magnetizing head is fixed to the iron core, and the other end is provided with a pole shoe. The side of the pole shoe facing away from the iron core is a toothed surface. The toothed surface is a plane or an arc surface, and / or, the toothed surface is provided with a groove.

7. The method for processing magnets according to claim 4, characterized in that, The magnetizing head is inclined relative to the iron core in the axial direction.

8. The method for processing magnets according to claim 2, characterized in that, The collar may be made of a magnetic material or a non-magnetic material.

9. The method for processing magnets according to claim 2, characterized in that, The magnetic field strength of the pre-constructed stable directional magnetic field is 30%-50% of the rated orientation magnetic field strength.

10. A method for processing magnets according to any one of claims 1-9, characterized in that, The forming orientation direction of the integral annular green blank and / or the magnetization direction of the integral magnetic ring are continuously inclined along the axial direction.

11. The method for processing magnets according to claim 10, characterized in that, The axial deflection angle of the forming orientation direction of the integral annular green blank and / or the magnetization direction of the integral magnetic ring changes continuously along the axial direction.

12. The method for processing magnets according to claim 10, characterized in that, The angles between the molding orientation direction, the magnetization direction, and the axial direction are all continuously varied along the axial direction, and the angles between the molding orientation direction and the axial direction, and the angles between the magnetization direction and the axial direction, are consistent.

13. The method for processing magnets according to claim 10, characterized in that, The axial deflection angle of the forming orientation direction of the integral annular green blank and / or the magnetization direction of the integral magnetic ring is α, where 0°≤α≤ z is the number of stator teeth.

14. A type of magnet, characterized in that, The magnet is an integral magnetic ring, and is formed using the processing method of the magnet as described in any one of claims 1-13.

15. An electric motor, characterized in that, Includes the magnet as described in claim 14.

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