Method of manufacturing a rotor assembly and brushless electric machine

Abstract

The application discloses a preparation method of a rotor assembly and a brushless motor, and relates to the technical field of motors. The rotor assembly comprises a rotor shell, a rotor magnetic steel and a code disc. The preparation method of the rotor assembly comprises the following steps: installing a first magnetic isolation support on the rotor shell and cooperating with the rotor shell to form a first filling groove; filling a magnetic steel raw material into the first filling groove and then wet-pressing to obtain a first magnetic steel part; installing a second magnetic isolation support on the rotor shell and the first magnetic steel part to form a second filling groove; filling a magnetic steel raw material into the second filling groove and then wet-pressing to obtain a second magnetic steel part, and the second magnetic steel part is combined with the first magnetic steel part to form an integrated structure; sintering the integrated structure, and cooling the sintered integrated structure to room temperature; and magnetizing the first magnetic steel part and the second magnetic steel part in the cooled integrated structure respectively to obtain the rotor magnetic steel and the code disc. The application solves the problem that miniaturization is difficult to realize in the prior art.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to a method for manufacturing a rotor assembly and a brushless motor. Background Technology

[0002] Currently, with the rapid development of fields such as robotics, drones, and medical equipment, the requirements for miniaturization and integration of rotor assembly manufacturing methods are increasing. Existing technologies require separate axial installation spaces for the rotor magnets and encoder disks during motor assembly, resulting in a large axial dimension of the rotor assembly, which is difficult to meet the needs of miniaturized applications. Summary of the Invention

[0003] The main objective of this invention is to propose a method for manufacturing a rotor assembly and a brushless motor, which addresses the problem of miniaturization that is difficult to achieve in existing technologies.

[0004] To achieve the above objectives, this invention proposes a method for manufacturing a rotor assembly, the rotor assembly comprising a rotor housing, rotor magnets, and an encoder disk, the method comprising: The first magnetic shielding bracket is installed on the rotor housing, and the first magnetic shielding bracket and the rotor housing cooperate to form a first filling groove. The first filling groove is arranged in a ring around the circumference of the rotor housing. Fill the first filling groove with magnet raw material, and wet press the rotor housing filled with the magnet raw material to obtain the first magnet part; The second magnetic shielding bracket is installed on the rotor housing and the first magnet part. The second magnetic shielding bracket cooperates with the rotor housing and the first magnet part to form a second filling groove. The second filling groove is arranged in a ring around the circumference of the rotor housing. The second magnetic shielding bracket is located on one side of the first magnetic shielding bracket along the axial direction of the rotor housing. The second filling groove is filled with magnetic steel raw material, and a pressing force is applied to the magnetic steel raw material in the second filling groove for wet pressing molding. The pressing force is transmitted to the first magnetic steel part through the magnetic steel raw material in the second filling groove, so that the first magnetic steel part is pressurized a second time. The magnetic steel raw material in the second filling groove forms the second magnetic steel part, and the second magnetic steel part and the first magnetic steel part are combined into an integral structural component. The integral structural component is sintered, and the sintered integral structural component is cooled to room temperature. The first and second magnet parts in the cooled integrated structural component are magnetized separately to obtain the rotor magnet and the encoder disk, respectively.

[0005] In one embodiment, the code disk includes a first code disk portion and a second code disk portion arranged radially spaced along the rotor housing, and the code disk forming step includes: The second magnetic shielding bracket is installed on the rotor housing. The second magnetic shielding bracket, the rotor housing and the first magnet part cooperate to form the first code disk filling groove. The first code disk filling groove is filled with magnet raw material, and the rotor housing filled with the magnet raw material is wet-pressed to obtain the first code disk part. The third magnetic shielding bracket is installed on the rotor housing. The third magnetic shielding bracket and the second magnetic shielding bracket are arranged at a radial distance along the rotor housing. The third magnetic shielding bracket, the second magnetic shielding bracket and the first magnet part cooperate to form the second code disk filling groove. The second code disk filling groove is filled with magnet raw material, and the rotor housing filled with the magnet raw material is wet-pressed to obtain the second code disk part.

[0006] In one embodiment, when installing the third magnetic shielding bracket, the third magnetic shielding bracket is positioned relative to the second magnetic shielding bracket by a preset angle in the circumferential direction, so that the sensing magnetic poles of the formed second code disk part and the sensing magnetic poles of the first code disk part are offset from each other by the preset angle in the circumferential direction of the rotor housing.

[0007] In one embodiment, the first magnetic shielding support is provided with a plurality of first magnetic shielding teeth along the circumference of the rotor housing, and the magnetic steel raw material filled in the space between two adjacent first magnetic shielding teeth forms a driving magnetic pole with alternating N / S arrangement after being magnetized; the second magnetic shielding support is provided with a plurality of second magnetic shielding teeth along the circumference of the rotor housing, and the magnetic steel raw material filled in the space between two adjacent second magnetic shielding teeth forms a sensing magnetic pole after being magnetized, and the number of pairs of sensing magnetic poles is greater than the number of pairs of driving magnetic poles.

[0008] In one embodiment, after magnetizing the first magnet section and the second magnet section respectively, the method further includes point-by-point detection of each sensing magnetic pole of the code disk, wherein the point-by-point detection step includes: The integrated structural component is rotated relative to the single-point detection head. For each preset angle of rotation, the magnetization of a sensing magnetic pole corresponding to that angle is detected by the single-point detection head. If the test is successful, continue testing the next angle; if the test fails, remagnetize the failed sensing pole. The detection of all sensing magnetic poles of the code disk is completed sequentially.

[0009] In one embodiment, the magnetic steel raw material comprises the following components in weight percentage: R: 28wt%~33wt%, B: 0.85wt%~0.94wt%, Co: 0.02wt%~0.2wt%, Cu: 0.5wt%~1.5wt%, M1: 0.05wt%~1.1wt%, M2: 0.1wt%~0.5wt%, balance Fe; Wherein, R is a rare earth element, containing at least PrNd and Ce, and Ce accounts for 50% to 70% of the total mass of R; M1 is Al and / or Sn; and M2 is Zr, Ti and / or Nb.

[0010] In one embodiment, the filling is performed using a variable pressure injection method. The process of injecting the magnetic steel raw material into the first filling groove and / or the second filling groove includes: In the first stage, the material is injected at a first injection pressure P1, which is 0.1MPa~0.3MPa, so that the magnetic steel raw material slowly fills the filling groove under low pressure. In the second stage, after the magnetic steel raw material fills the filling groove, it is pressurized and replenished with a second injection pressure P2. The second injection pressure P2 is 0.5MPa~1.0MPa, satisfying: P2>P1; In the first and second stages, the gas in the filling tank is discharged simultaneously.

[0011] In one embodiment, the wet pressing is performed in an orientation magnetic field to apply a magnetic field to the magnetic steel raw material and simultaneously extrude the magnetic steel raw material in the corresponding filling groove, so that the magnetic steel powder particles in the magnetic steel raw material are oriented and arranged along the direction of the magnetic field; wherein, the magnetic field strength of the orientation magnetic field is 2.2T~3.5T, the pressing pressure of the wet pressing is 18MPa~30MPa, and the holding time is 12s~25s.

[0012] In one embodiment, the sintering employs a multi-stage heating method, which includes: First stage: Increase the temperature from room temperature to 450℃~550℃ at a first heating rate of 5℃ / min~8℃ / min, and hold for 0.5h~2h; Second stage: Increase the temperature to 800℃~900℃ at a second heating rate of 3℃ / min~5℃ / min, and hold for 1h~3h; The third stage: heating at a third heating rate of 1℃ / min~3℃ / min to 1000℃~1060℃, and holding at that temperature for 1h~6h to carry out densification sintering.

[0013] The present invention also proposes a brushless motor, including a motor body and a rotor assembly disposed within the motor body. The rotor assembly includes an integrally formed magnet and a code disk, which are prepared by the above-described method for preparing the rotor assembly.

[0014] This invention integrates the rotor magnets and the encoder disk into a single structural component within the same axial region by placing the second magnetic shielding bracket along the axial direction of the rotor housing on one side of the first magnetic shielding bracket. This eliminates the need for separate installation spaces in the axial direction, effectively shortening the axial dimension of the rotor assembly and facilitating motor miniaturization. Furthermore, by directly forming and sintering the first and second magnet parts onto the rotor housing using the magnetic shielding bracket, they are positioned in the same process, avoiding accumulated tolerances caused by separate manufacturing and subsequent assembly. This ensures the relative positional accuracy between the rotor magnets and the encoder disk, thereby improving the accuracy of the encoder disk detection signal. Finally, by directly forming the rotor magnets and encoder disk on the same rotor housing through sequential filling, wet pressing, sintering, and magnetization steps, the invention eliminates the need for separate manufacturing and assembly of two independent components, reducing multiple intermediate processes and assembly steps in separate manufacturing, thus simplifying the process flow and improving production efficiency. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 A schematic flowchart illustrating the method for preparing the rotor assembly provided by the present invention; Figure 2 This is a schematic diagram of the structure of the brushless motor provided by the present invention; Figure 3 for Figure 2 A schematic diagram of one embodiment; Figure 4 This is a schematic diagram of the rotor assembly provided by the present invention.

[0017] Explanation of icon numbers: 110. Rotor housing; 120. Rotor magnet; 121. Encoder disk.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] Please see Figure 1 and Figure 2 In one embodiment of the present invention, a method for manufacturing a rotor assembly is provided. The rotor assembly includes a rotor housing 110, rotor magnets 120, and an encoder disk 121. The method for manufacturing the rotor assembly includes: S100: The first magnetic shielding bracket is installed on the rotor housing 110. The first magnetic shielding bracket and the rotor housing 110 cooperate to form a first filling groove. The first filling groove is arranged in a ring around the circumference of the rotor housing 110. S200: Fill the first filling groove with magnet raw material, and wet press the rotor housing 110 filled with the magnet raw material to obtain the first magnet part. S300: The second magnetic shielding bracket is installed on the rotor housing 110 and the first magnet part. The second magnetic shielding bracket cooperates with the rotor housing 110 and the first magnet part to form a second filling groove. The second filling groove is arranged in a ring around the circumference of the rotor housing 110. The second magnetic shielding bracket is located on one side of the first magnetic shielding bracket along the axial direction of the rotor housing 110. S400: Fill the second filling groove with magnetic steel raw material and apply pressure to the magnetic steel raw material in the second filling groove for wet pressing molding. The pressure is transmitted to the first magnetic steel part through the magnetic steel raw material in the second filling groove, so that the first magnetic steel part is pressurized a second time. The magnetic steel raw material in the second filling groove forms the second magnetic steel part, and the second magnetic steel part and the first magnetic steel part are combined into an integral structural component. S500: Sinter the integral structural component and cool the sintered integral structural component to room temperature; S600: The first magnet part and the second magnet part in the cooled integrated structural component are magnetized respectively to obtain rotor magnet 120 and encoder disk 121 respectively.

[0023] Understandably, the raw material for the magnet is a mixed slurry containing permanent magnet powder and binder, which has good fluidity and can fill all corners of the first filling groove. During the wet pressing process, pressure is applied to the rotor housing 110 filled with the raw material for the magnet by a pressing mold, so that the raw material for the magnet is pressed into shape in the first filling groove.

[0024] Optionally, the magnetic steel raw material can be pre-prepared into a slurry with a predetermined moisture content before being filled into the first filling tank, so as to facilitate orientation and densification in the subsequent wet pressing process.

[0025] In this embodiment, the second magnetic shielding support is located on one side of the first magnetic shielding support along the axial direction of the rotor housing 110. Exemplarily, the second magnetic shielding support can be stacked on the upper surface of the first magnet part, or it can be at least partially embedded in the first magnet part, as long as the second magnetic shielding support, the rotor housing 110 and the first magnet part together form the second filling groove, and no specific limitation is made here.

[0026] It is understandable that the second filling groove is located on the axial outside of the first magnet part, so that the second magnet part formed in the second filling groove and the first magnet part are arranged adjacent to each other in the axial direction. The two do not need to reserve additional independent installation space in the axial direction, which is beneficial to shorten the axial dimension of the rotor assembly.

[0027] In this embodiment, when the magnetic steel raw material in the second filling groove is wet-pressed, the pressing force is transmitted to the first magnetic steel part below through the magnetic steel raw material in the second filling groove, so that the first magnetic steel part is pressed again on the basis of the initial molding; after pressing is completed, the blank of the second magnetic steel part and the blank of the first magnetic steel part are combined into one piece at the interface through the interlocking of magnetic steel raw material particles and the bridging effect of adhesive, forming an integral structural part with an integral structure.

[0028] In this embodiment, sintering is carried out at high temperature, causing the magnetic powder particles in the first and second magnetic steel parts to diffuse and recrystallize, thereby achieving densification sintering. After sintering, the first and second magnetic steel parts form a stronger integrated structure through grain bonding at the interface, and the integrated structure is cooled to room temperature after sintering is completed.

[0029] Understandably, during the sintering process, the first and second magnetic shielding supports retain the partitioned structure of the raw magnetic steel material during molding, allowing the first and second magnetic steel sections to maintain their respective shapes and partitions after sintering. Optionally, the magnetic shielding supports are made of high-temperature resistant non-magnetic materials to maintain dimensional stability during sintering.

[0030] It should be noted that the first and second magnet parts are not magnetized after sintering and do not possess magnetism. By applying charging magnetic fields to the first and second magnet parts respectively, the first magnet part is magnetized to form the rotor magnet 120, and the second magnet part is magnetized to form the code disk 121.

[0031] It should be noted that separate magnetization refers to magnetizing the first magnet section and the second magnet section separately. For example, the first magnet section and the second magnet section can be magnetized with different magnetization directions or different magnetization intensities to meet the different requirements of the rotor magnet 120 and the code disk 121 for magnetic pole direction and magnetic properties. It should be noted that the rotor magnet 120 needs to form alternating N / S magnetic poles along the circumference, while the code disk 121 needs to form uniformly distributed sensing magnetic poles along the circumference. Since their magnetic pole distribution and magnetization requirements are different, separate magnetization is necessary.

[0032] This embodiment involves sequentially installing a first magnetic shielding bracket and a second magnetic shielding bracket on the rotor housing 110, forming a first filling groove and a second filling groove respectively. The two filling grooves are then filled with raw magnetic steel material and wet-pressed, allowing the first and second magnetic steel parts to be integrated into a single structural component on the rotor housing 110. After sintering and separate magnetization, an integrated rotor magnet 120 and encoder disk 121 are obtained. Since the first and second magnetic steel parts are arranged adjacent to each other axially, there is no need to reserve separate installation spaces in the axial direction, effectively shortening the axial dimension of the rotor assembly and meeting the needs of miniaturized applications. Simultaneously, because the two are directly formed and sintered into one piece in the same process, the accumulated tolerances caused by separate manufacturing and subsequent assembly are avoided, improving the relative positional accuracy between the rotor magnet 120 and the encoder disk 121, thereby enhancing the accuracy of the encoder disk 121's detection signal.

[0033] In one implementation, see Figure 3 and Figure 4 The code disk 121 includes a first code disk portion and a second code disk portion arranged radially at intervals along the rotor housing 110. The forming steps of the code disk 121 include: A second magnetic shielding bracket is installed on the rotor housing 110. The second magnetic shielding bracket, the rotor housing 110, and the first magnet part cooperate to form a first code disk filling groove. Magnetic steel raw material is filled into the first code disk filling groove, and the rotor housing 110 filled with the magnetic steel raw material is wet-pressed to obtain the first code disk part. A third magnetic shielding bracket is installed on the rotor housing 110. The third magnetic shielding bracket and the second magnetic shielding bracket are arranged radially apart along the rotor housing 110. The third magnetic shielding bracket, the second magnetic shielding bracket, and the first magnet part cooperate to form a second code disk filling groove. Magnetic steel raw material is filled into the second code disk filling groove, and the rotor housing 110 filled with the magnetic steel raw material is wet-pressed to obtain the second code disk part.

[0034] For example, the second magnetic shielding bracket is an annular bracket with a radial dimension larger than that of the subsequently installed third magnetic shielding bracket; the third magnetic shielding bracket is an annular bracket with a radial dimension smaller than that of the second magnetic shielding bracket; the third magnetic shielding bracket can be installed on the rotor housing 110 and located radially inside the second magnetic shielding bracket, with a predetermined interval maintained between the two.

[0035] The third magnetic shielding bracket, together with the second magnetic shielding bracket and the first magnet portion, forms a second code disk filling groove. Magnet raw material is filled into the second code disk filling groove, and the rotor housing 110 filled with the magnet raw material is wet-pressed to obtain the second code disk portion. Exemplarily, magnet raw material is filled into the second code disk filling groove, and pressure is applied using a pressing mold to densify and form the second code disk portion.

[0036] It is understandable that the first code disk is located on the outer radial side and the second code disk is located on the inner radial side. The two are arranged radially at intervals along the rotor housing 110, so that the code disk 121 forms an inner and outer ring structure in the radial direction, which can provide more detection signals, thereby improving the detection accuracy and resolution of the encoder.

[0037] In an optional embodiment, the rotor magnets 120 are configured as two layers spaced apart along the axial direction of the rotor housing 110, namely a first layer of rotor magnets 120 and a second layer of rotor magnets 120. It is understood that the first encoder portion is radially arranged inside and outside the first layer of rotor magnets 120 and corresponds axially, and the second encoder portion is radially arranged inside and outside the second layer of rotor magnets 120 and corresponds axially; the first layer of rotor magnets 120 and the second layer of rotor magnets 120 are axially separated by different magnetic shielding supports, and each layer of rotor magnets 120 is used to provide a driving magnetic field during motor operation.

[0038] The first encoder disk is correspondingly arranged with the first layer of rotor magnets 120 and is used to detect the rotational position of the first layer of rotor magnets 120; the second encoder disk is correspondingly arranged with the second layer of rotor magnets 120 and is used to detect the rotational position of the second layer of rotor magnets 120. With this arrangement, each layer of rotor magnets 120 corresponds to one encoder disk, and the rotational position signal of their respective layers can be detected independently. This is suitable for application scenarios that require the detection of the rotational position of different magnet layers separately. When the motor needs to obtain the speed or position information of different magnet layers under different operating conditions, the signals can be collected separately by their respective encoder disks to meet diverse control requirements. At the same time, the two encoder disks and the two layers of rotor magnets 120 are formed into an integral structure in the same sintering process, and the relative positional accuracy between the components is high.

[0039] In one embodiment, when installing the third magnetic shielding bracket, the third magnetic shielding bracket is positioned relative to the second magnetic shielding bracket by a preset angle in the circumferential direction, so that each sensing magnetic pole of the formed second code disk part is offset from each sensing magnetic pole of the first code disk part by the preset angle in the circumferential direction of the rotor housing 110.

[0040] It should be noted that since the first code disk and the second code disk are arranged radially at intervals, if they are completely aligned in the circumferential direction, when the code disk 121 detection head is detecting, the first code disk and the second code disk will generate detection signals at the same angular position. The signals of the two will completely overlap in time, making it impossible for the encoder to distinguish which ring of code disk 121 the signal comes from. It is also difficult to use two rings of code disk 121 to achieve higher precision position detection, thus limiting the detection resolution and signal recognition accuracy of the encoder.

[0041] In this embodiment, when installing the third magnetic shielding bracket, the third magnetic shielding bracket is positioned by deflecting it circumferentially by a preset angle relative to the second magnetic shielding bracket. For example, after the second magnetic shielding bracket is installed on the rotor housing 110, its circumferential position is fixed. When the third magnetic shielding bracket is installed on the rotor housing 110, it is rotated around the axis of the rotor housing 110, causing it to deflect circumferentially by a preset angle relative to the fixed second magnetic shielding bracket. After the position is adjusted to the correct position, the third magnetic shielding bracket is fixed to the rotor housing 110.

[0042] For example, the preset angle can be set according to the required detection accuracy and resolution of the code disk. During installation, the third magnetic shielding bracket can be placed in the installation position first, and then rotated relative to the second magnetic shielding bracket by a predetermined angle. After adjustment, it can be fixed.

[0043] Because the third magnetic shielding bracket is deflected at a preset angle relative to the second magnetic shielding bracket in the circumferential direction, the second code disk part located on the radial inner side is offset from the first code disk part located on the radial outer side in the circumferential direction. When the rotor assembly rotates, the first code disk part and the second code disk part generate detection signals at different positions in the circumferential direction. The encoder detection head can clearly distinguish the signals generated by the two code disk parts, avoiding the problem of mutual interference or difficulty in distinguishing signals caused by the complete overlap of the two code disks 121 in the circumferential direction, and further improving the detection resolution and signal accuracy of the encoder.

[0044] In one embodiment, the first magnetic shielding support is provided with a plurality of first magnetic shielding teeth along the circumference of the rotor housing 110, and the magnetic steel raw material filled in the space between two adjacent first magnetic shielding teeth forms a driving magnetic pole with alternating N / S arrangement after being magnetized; the second magnetic shielding support is provided with a plurality of second magnetic shielding teeth along the circumference of the rotor housing 110, and the magnetic steel raw material filled in the space between two adjacent second magnetic shielding teeth forms a sensing magnetic pole after being magnetized, and the number of pairs of sensing magnetic poles is greater than the number of pairs of driving magnetic poles.

[0045] It is understood that the first magnetic isolation bracket is provided with multiple first magnetic isolation teeth along the circumference. The multiple first magnetic isolation teeth divide the rotor magnet 120 into multiple magnetic pole regions in the circumference. The space between two adjacent first magnetic isolation teeth constitutes a filling unit. The raw material of the magnet is formed in the filling unit and forms a magnetic pole after subsequent magnetization. Since the magnetic poles are distributed in the circumference in an alternating manner of N poles and S poles, the N poles and S poles appear in pairs to form driving magnetic poles. The driving magnetic poles are used to provide a driving magnetic field after the motor is powered on to drive the rotor assembly to rotate.

[0046] Similarly, the second magnetic shielding bracket is provided with multiple second magnetic shielding teeth along the circumference. The magnetic steel raw material filled in the space between two adjacent second magnetic shielding teeth is magnetized to form a sensing magnetic pole. The sensing magnetic pole is used to cooperate with the external encoder detection head. When the rotor assembly rotates, the magnetic field change of the sensing magnetic pole is captured by the detection head and converted into a position signal, thereby realizing the detection of the rotation position of the rotor assembly.

[0047] Understandably, since the number of driving pole pairs determines the number of pole pairs in the motor, and the sensing poles are used for position detection, the more sensing poles there are, the more detection points the encoder head can capture during one rotation of the rotor assembly, resulting in higher position detection resolution and more refined signal feedback. Therefore, by setting the number of sensing pole pairs to be greater than the number of driving pole pairs, the accuracy and resolution of position detection are effectively improved while ensuring the normal driving function of the motor.

[0048] In one embodiment, after magnetizing the first magnet section and the second magnet section respectively, the method further includes point-by-point detection of each sensing magnetic pole of the code disk 121, wherein the point-by-point detection step includes: The integrated structural component is rotated relative to the single-point detection head. For each preset rotation angle, the magnetization of a sensing magnetic pole corresponding to that angle is detected by the single-point detection head. If the detection is qualified, the detection continues to the next angle. If the detection is unqualified, the unqualified sensing magnetic pole is remagnetized. The detection of all sensing magnetic poles of the code disk 121 is completed in sequence.

[0049] It should be noted that after magnetization, the actual magnetization amount of each sensing pole of the code disk 121 may vary due to factors such as material uniformity, positioning accuracy of the magnetization head, or distribution of the magnetization magnetic field. If the magnetization amount of a certain sensing pole is insufficient, the detection signal strength at that position will be weak, thus affecting the uniformity and accuracy of the overall detection signal of the encoder. If the magnetization amount of a certain sensing pole is too large, it may cause signal distortion or interference with the signals of adjacent poles. Therefore, after magnetization, each sensing pole of the code disk 121 needs to be tested point by point to verify whether the magnetization amount of each sensing pole meets the requirements.

[0050] In this embodiment, the integrated structural component is rotated relative to the single-point detection head. For example, the integrated structural component can be mounted on a rotating platform, which drives the integrated structural component to rotate around its axis, causing each sensing magnetic pole of the code disk 121 to sequentially pass the detection position of the single-point detection head. After rotating by a preset angle, so that one sensing magnetic pole is directly facing the single-point detection head, rotation is paused, and the single-point detection head detects the magnetization level of the sensing magnetic pole corresponding to that angle.

[0051] In this embodiment, the preset angle can be set according to the number of sensing magnetic poles. For example, if the number of sensing magnetic poles is N, the preset angle is 360° / N, that is, every time the preset angle is rotated, the single-point detection head faces the next sensing magnetic pole, ensuring that each sensing magnetic pole can be detected one by one.

[0052] If the test result is qualified, the magnetization of the sensing pole meets the requirements, and the rotation continues to the next angle to test the next sensing pole. If the test result is unqualified, the magnetization of the sensing pole does not meet the requirements. In this case, the unqualified sensing pole is remagnetized, that is, a magnetizing field is applied to the sensing pole again to supplement its magnetization to meet the qualified standard. By combining point-by-point testing with remagnetization, it is possible to ensure that the magnetization of each sensing pole of the code disk 121 is uniform and consistent, avoiding the problem of encoder detection signal deviation or abnormality caused by the unqualified magnetization of individual sensing poles, further improving the uniformity of the detection signal of the code disk 121 and the detection accuracy of the encoder. After the detection of all sensing poles of the code disk 121 is completed in sequence, an integrated structural component with the magnetization of each sensing pole meeting the requirements can be obtained, ensuring the overall detection performance of the encoder.

[0053] In one embodiment, the magnetic steel raw material comprises the following components in weight percentage: R: 28wt%~33wt%, B: 0.85wt%~0.94wt%, Co: 0.02wt%~0.2wt%, Cu: 0.5wt%~1.5wt%, M1: 0.05wt%~1.1wt%, M2: 0.1wt%~0.5wt%, with the balance being Fe; wherein R is a rare earth element, containing at least PrNd and Ce, and Ce accounts for 50%~70% of the total mass of R; M1 is Al and / or Sn; and M2 is Zr, Ti and / or Nb.

[0054] It should be noted that R represents rare earth elements, of which PrNd is a praseodymium-neodymium alloy, the main rare earth component of neodymium iron boron magnets, used to provide remanence and coercivity of the magnets; Ce is a highly abundant rare earth element with a relatively low price. By setting the proportion of Ce in the total mass of R to 50%~70%, that is, replacing some of the more expensive PrNd with the lower-cost Ce, the cost of raw materials is effectively reduced while ensuring the basic magnetic properties of the magnets.

[0055] Boron (B) is a non-metallic element in neodymium iron boron magnets, used to form the main phase Nd₂Fe. 14 B, with a content of 0.85wt%~0.94wt%, can ensure the stability of the main phase structure and magnetic properties.

[0056] In this embodiment, the Co content is set to a low level, which helps to increase the Curie temperature of the magnet and improve the temperature stability of the magnet. Furthermore, since Co itself is expensive, setting the Co content to 0.02wt%~0.2wt% further reduces the cost of raw materials.

[0057] The content of Cu is 0.5wt%~1.5wt%. In NdFeB magnets, Cu is mainly distributed in the grain boundary phase, which helps to improve the wettability of the grain boundary phase and the squareness of the magnet. At the same time, the addition of Cu also helps to improve the corrosion resistance of the magnet.

[0058] M1 is Al (aluminum) and / or Sn (tin). Al is used to improve the anisotropic field of the magnet; Sn is used to improve the grain boundary structure and enhance the coercivity of the magnet.

[0059] M2 is Zr (zirconium), Ti (titanium), and / or Nb (niobium). Zr, Ti, and Nb are all grain-refining elements that can suppress abnormal grain growth during magnet manufacturing, making the grain size smaller and more uniform, thereby improving the coercivity and magnetic performance consistency of the magnet.

[0060] Understandably, by replacing part of PrNd with a high Ce content and combining it with a low Co content, the cost of raw materials is effectively reduced while ensuring the magnetic properties of the magnet. Simultaneously, the addition of Cu and the combined use of M1 and M2 further optimize the grain boundary structure and microstructure of the magnet, improving its overall magnetic properties. The magnet raw materials prepared using the above-mentioned proportions, when used in the rotor assembly preparation method of this embodiment, exhibit good formability during filling and wet pressing, and achieve good densification during subsequent sintering.

[0061] Optionally, the aforementioned magnetic steel raw materials can be prepared using conventional neodymium iron boron (NdFeB) manufacturing processes. For example, magnetic powder with a predetermined particle size is produced through processes such as batching, smelting, hydrogen crushing, and air jet milling. The magnetic powder is then prepared into a slurry form for filling, facilitating wet pressing into various filling slots.

[0062] In one embodiment, the filling is performed using a variable pressure injection method. The process of injecting the magnetic steel raw material into the first filling groove and / or the second filling groove includes: In the first stage, material is injected at a first injection pressure P1, which is 0.1 MPa to 0.3 MPa, so that the magnetic steel raw material slowly fills the filling groove under low pressure. In the second stage, after the magnetic steel raw material fills the filling groove, it is pressurized and replenished at a second injection pressure P2, which is 0.5 MPa to 1.0 MPa, satisfying that P2 > P1. In both the first and second stages, the gas in the filling groove is discharged simultaneously.

[0063] It should be noted that, since the filling groove is formed by the cooperation of the magnetic shielding support and the rotor housing 110, its internal space is relatively narrow. Especially when the magnetic shielding support is provided with multiple magnetic shielding teeth, the groove structure between adjacent magnetic shielding teeth is more refined. If constant high pressure injection is used, the slurry of the magnet raw material rushes into the filling groove at high speed under high pressure, which can easily form eddies in the corners or narrow gaps of the filling groove. This causes the gas to be unable to be discharged in time and is trapped inside the slurry. Ultimately, bubbles or pore defects are formed in the formed magnet part, affecting the density and magnetic properties of the magnet part.

[0064] In the first stage of filling the magnetic steel raw material in this embodiment, the material is injected at a relatively low first injection pressure P1, allowing the magnetic steel raw material slurry to flow slowly under low pressure and fill various areas of the filling tank. During the low-pressure injection process, the slurry flows slowly, giving the gas in the filling tank sufficient time to escape from the injection port or exhaust channel, thus avoiding the problem of gas being quickly trapped inside the slurry during high-pressure injection. After the magnetic steel raw material fills the filling tank, the second stage begins, where the material is pressurized and replenished at a second injection pressure P2. Since the second injection pressure P2 is greater than the first injection pressure P1, the pressurized replenishment can further compact the slurry, making it denser in the filling tank. At the same time, the small amount of residual gas in the filling tank is further discharged under pressure.

[0065] For example, the first injection pressure P1 can be 0.2 MPa, and the second injection pressure P2 can be 0.8 MPa. By first injecting with low pressure to uniformly fill all corners of the filling groove with slurry, and then supplementing with high pressure to further densify the slurry, it is ensured that the slurry is fully filled in the fine structure, and that the formed magnet part has a high density, thus avoiding the generation of defects such as bubbles and holes.

[0066] It is understandable that the filling of the filling groove by the raw material of the magnet in the first stage can be determined by the change in the injection pressure. For example, when the injection pressure rises continuously from the first injection pressure P1 and approaches the second injection pressure P2, it indicates that the filling groove is full of slurry. At this time, the process can be switched to the second stage for pressurized feeding. In this embodiment, the variable pressure injection method of low-pressure slow injection in the first stage and high-pressure feeding in the second stage, combined with the operation of simultaneous venting during the injection process, allows the raw material of the magnet to be uniformly and densely filled into all areas of the filling groove. This ensures the consistency of the internal quality and magnetic properties of the magnet after molding, while avoiding the problem of reduced yield caused by insufficient filling or residual air bubbles.

[0067] In one embodiment, the wet pressing is performed in an orientation magnetic field to apply a magnetic field to the magnetic steel raw material and simultaneously extrude the magnetic steel raw material in the corresponding filling groove, so that the magnetic steel powder particles in the magnetic steel raw material are oriented and arranged along the direction of the magnetic field; wherein, the magnetic field strength of the orientation magnetic field is 2.2T to 3.5T, the pressing pressure of the wet pressing is 18MPa to 30MPa, and the holding time is 12s to 25s.

[0068] It should be noted that the magnetic steel powder particles in the raw material of the magnetic steel are anisotropic particles, and their crystal easy magnetization axis has a specific direction. If no orientation magnetic field is applied during wet pressing, the magnetic steel powder particles will exhibit random orientation in the filling groove, resulting in the magnetic steel part after molding failing to obtain ideal magnetic properties after magnetization.

[0069] In this embodiment, an orientation magnetic field is applied during the wet pressing process, causing the magnetic steel powder particles to rotate along the direction of the magnetic field, aligning their easy magnetization axis with the direction of the magnetic field. For example, a rotor housing 110 filled with magnetic steel raw material is placed in the orientation magnetic field. While applying pressure to the magnetic steel raw material, the orientation magnetic field continuously acts on the magnetic steel powder particles within the raw material, causing the powder particles to rearrange under pressure, ultimately forming a particle arrangement structure with a consistent orientation direction.

[0070] It is understandable that synchronization refers to the simultaneous application of an orientation magnetic field and a pressing force to the magnetic steel raw material. During the pressing process, the magnetic steel raw material gradually densifies under the pressing force, reducing the porosity between powder particles and increasing the friction between particles. It should be noted that if orientation is applied before pressing, some oriented particles may deviate from their orientation direction due to relative sliding and rotation between particles during the pressing process. This embodiment, through simultaneous orientation and pressing, ensures that the magnetic steel powder particles maintain their orientation under the influence of the orientation magnetic field, while the pressing force gradually compacts and fixes the particles, thus avoiding the reduction in orientation degree caused by prior orientation followed by pressing.

[0071] For example, the magnetic field strength of the orientation magnetic field can be 2.2T to 3.5T. When the magnetic field strength is too low, the orientation torque on the magnetic steel powder particles is insufficient, making it difficult to overcome the frictional resistance between particles and achieve sufficient orientation; when the magnetic field strength is too high, it will significantly increase equipment cost and energy consumption; setting the magnetic field strength range to 2.2T to 3.5T can enable the magnetic steel powder particles to be fully oriented, while taking into account the controllability of equipment cost and energy consumption.

[0072] In this embodiment, the pressing pressure of the wet pressing is 18MPa to 30MPa, and the holding time is 12s to 25s. If the pressing pressure is too low, the magnetic steel raw material is difficult to densify sufficiently, resulting in insufficient green density and affecting the magnetic properties and mechanical strength of the magnet after sintering. Since the first and second magnetic steel parts need to be combined into a single structural component in this embodiment, the bonding strength at the interface is quite sensitive to the pressing pressure. If the pressing pressure is higher than 30MPa, it may cause deformation or damage to the magnetic shielding support, while also increasing equipment wear and energy consumption. If the holding time is less than 12s, the internal stress of the magnetic steel raw material will not be fully released, and the pressure distribution between the filling slots will be uneven, which may easily lead to inconsistent elastic recovery of the green blank after demolding. If the holding time is higher than 25s, it will affect production efficiency and increase the production cycle and energy consumption per unit product. The range of 12s to 25s can fully release internal stress, ensure the consistency of molding quality of each filling slot, and take into account production efficiency.

[0073] In one embodiment, the sintering employs a multi-stage heating method, which includes: a first stage: heating from room temperature to 450℃ to 550℃ at a first heating rate of 5℃ / min to 8℃ / min, and holding at that temperature for 0.5h to 2h; a second stage: heating to 800℃ to 900℃ at a second heating rate of 3℃ / min to 5℃ / min, and holding at that temperature for 1h to 3h; and a third stage: heating to 1000℃ to 1060℃ at a third heating rate of 1℃ / min to 3℃ / min, and holding at that temperature for 1h to 6h for densification sintering.

[0074] It should be noted that the integral structural component contains organic binder and adsorbed water. If the temperature rises too quickly in the early stage of sintering, the organic binder will decompose rapidly and generate a large amount of gas, causing the internal gas pressure of the blank to rise sharply, thereby causing cracking or delamination defects.

[0075] The first stage is used to remove organic binders and adsorbed water from the raw materials of the magnetic steel; the temperature range of 450℃ to 550℃ can ensure that the organic binders are fully decomposed and volatilized, while avoiding excessive temperature that would cause the binders to decompose too quickly and generate a large amount of gas, resulting in cracking of the billet; holding the temperature for 0.5h to 2h can allow the binders to decompose fully, while also taking into account production efficiency; the heating rate of 5℃ / min to 8℃ / min can ensure that the temperature rises uniformly, and can also avoid excessive temperature difference between the inside and outside of the billet due to excessive heating, which would generate thermal stress.

[0076] The second stage is used for pre-sintering and degassing. Within the temperature range of 800℃ to 900℃, the magnetic steel powder particles begin to undergo preliminary diffusion and sintering neck formation. At the same time, the residual gas inside the billet has a high diffusion rate at this temperature and can be fully discharged. Holding for 1h to 3h allows the pre-sintering to proceed fully, laying the foundation for subsequent high-temperature densification sintering. The heating rate of 3℃ / min to 5℃ / min is reduced compared to the first stage to adapt to the shrinkage characteristics of the billet in this temperature range and avoid cracking caused by excessive shrinkage.

[0077] The third stage is the densification sintering stage. The temperature range of 1000℃ to 1060℃ allows the magnetic steel powder particles to fully diffuse and recrystallize, achieving complete densification. The heating rate of 1℃ / min to 3℃ / min is lower than that of the previous two stages to ensure that the temperature of the billet rises uniformly when entering the final densification stage and to avoid thermal stress concentration. The holding time of 1h to 6h is adjusted according to the billet size and furnace loading to ensure sufficient densification.

[0078] Understandably, the first, second, and third heating rates decrease sequentially. By employing gradually decreasing heating rates, the integrated structural component passes through the low-temperature zone more quickly in the initial stage of sintering, improving production efficiency. The heating rate is moderately reduced during the pre-sintering stage to prevent excessive shrinkage of the blank. The heating rate is further reduced during the high-temperature densification stage to ensure temperature uniformity and sufficient densification. This setup guarantees sintering efficiency while preventing cracking of the integrated structural component due to excessive thermal stress during sintering, ensuring the quality of the interface bonding between the rotor magnet section and the encoder disk section, and the overall reliability of the integrated structural component.

[0079] For example, for magnetic steel raw materials containing a high Ce formulation, due to Ce2Fe 14 B has a melting point slightly lower than Nd2Fe. 14 B. Setting the upper limit of the temperature for the third stage to 1060℃ can prevent abnormal grain growth of high Ce magnets at excessively high temperatures, thereby ensuring the coercivity and magnetic properties of the magnets; after sintering, the integrated structural component can be cooled to room temperature with the furnace.

[0080] This invention also proposes a brushless motor, see reference. Figures 2 to 4 The brushless motor includes a motor body and a rotor assembly. The rotor assembly includes a rotor housing 110, a rotor magnet 120, and an encoder 121. The rotor magnet 120 and the encoder 121 are integral structures made by the rotor assembly preparation method described in any of the above claims.

[0081] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing a rotor assembly, characterized in that, The rotor assembly includes a rotor housing, rotor magnets, and an encoder disk. The method for manufacturing the rotor assembly includes: The first magnetic shielding bracket is installed on the rotor housing, and the first magnetic shielding bracket and the rotor housing cooperate to form a first filling groove. The first filling groove is arranged in a ring around the circumference of the rotor housing. Fill the first filling groove with magnet raw material, and wet press the rotor housing filled with the magnet raw material to obtain the first magnet part; The second magnetic shielding bracket is installed on the rotor housing and the first magnet part. The second magnetic shielding bracket cooperates with the rotor housing and the first magnet part to form a second filling groove. The second filling groove is arranged in a ring around the circumference of the rotor housing. The second magnetic shielding bracket is located on one side of the first magnetic shielding bracket along the axial direction of the rotor housing. The second filling groove is filled with magnetic steel raw material, and a pressing force is applied to the magnetic steel raw material in the second filling groove for wet pressing molding. The pressing force is transmitted to the first magnetic steel part through the magnetic steel raw material in the second filling groove, so that the first magnetic steel part is pressurized a second time. The magnetic steel raw material in the second filling groove forms the second magnetic steel part, and the second magnetic steel part and the first magnetic steel part are combined into an integral structural component. The integral structural component is sintered, and the sintered integral structural component is cooled to room temperature. The first and second magnet parts in the cooled integrated structural component are magnetized separately to obtain the rotor magnet and the encoder disk, respectively.

2. The method for preparing the rotor assembly as described in claim 1, characterized in that, The code disk includes a first code disk portion and a second code disk portion arranged radially at intervals along the rotor housing. The code disk forming step includes: The second magnetic shielding bracket is installed on the rotor housing. The second magnetic shielding bracket, the rotor housing and the first magnet part cooperate to form the first code disk filling groove. The first code disk filling groove is filled with magnet raw material, and the rotor housing filled with the magnet raw material is wet-pressed to obtain the first code disk part. The third magnetic shielding bracket is installed on the rotor housing. The third magnetic shielding bracket and the second magnetic shielding bracket are arranged at a radial distance along the rotor housing. The third magnetic shielding bracket, the second magnetic shielding bracket and the first magnet part cooperate to form the second code disk filling groove. The second code disk filling groove is filled with magnet raw material, and the rotor housing filled with the magnet raw material is wet-pressed to obtain the second code disk part.

3. The method for preparing the rotor assembly as described in claim 2, characterized in that, When installing the third magnetic shielding bracket, the third magnetic shielding bracket is positioned relative to the second magnetic shielding bracket by a preset angle in the circumferential direction, so that the sensing magnetic poles of the formed second code disk part and the sensing magnetic poles of the first code disk part are offset from each other by the preset angle in the circumferential direction of the rotor housing.

4. The method for preparing the rotor assembly as described in claim 1, characterized in that, The first magnetic shielding support is provided with a plurality of first magnetic shielding teeth along the circumference of the rotor housing. The magnetic steel raw material filled in the space between two adjacent first magnetic shielding teeth forms a driving magnetic pole with alternating N / S arrangement after being magnetized. The second magnetic shielding support is provided with a plurality of second magnetic shielding teeth along the circumference of the rotor housing. The magnetic steel raw material filled in the space between two adjacent second magnetic shielding teeth forms a sensing magnetic pole after being magnetized. The number of pairs of sensing magnetic poles is greater than the number of pairs of driving magnetic poles.

5. The method for preparing the rotor assembly as described in claim 1, characterized in that, After magnetizing the first and second magnet sections respectively, the method further includes point-by-point detection of each sensing magnetic pole of the code disk. The point-by-point detection step includes: The integrated structural component is rotated relative to the single-point detection head. For each preset angle of rotation, the magnetization of a sensing magnetic pole corresponding to that angle is detected by the single-point detection head. If the test is successful, continue testing the next angle; if the test fails, remagnetize the failed sensing pole. The detection of all sensing magnetic poles of the code disk is completed sequentially.

6. The method for preparing the rotor assembly as described in any one of claims 1 to 5, characterized in that, The raw materials for the magnetic steel include the following components in weight percentage: R: 28wt%~33wt%, B: 0.85wt%~0.94wt%, Co: 0.02wt%~0.2wt%, Cu: 0.5wt%~1.5wt%, M1: 0.05wt%~1.1wt%, M2: 0.1wt%~0.5wt%, balance Fe; Wherein, R is a rare earth element, containing at least PrNd and Ce, and Ce accounts for 50% to 70% of the total mass of R; M1 is Al and / or Sn; and M2 is Zr, Ti and / or Nb.

7. The method for preparing the rotor assembly according to any one of claims 1 to 5, characterized in that, The filling process, which employs a variable pressure injection method, involves injecting the magnetic steel raw material into the first filling groove and / or the second filling groove, including: In the first stage, the material is injected at a first injection pressure P1, which is 0.1MPa~0.3MPa, so that the magnetic steel raw material slowly fills the filling groove under low pressure. In the second stage, after the magnetic steel raw material fills the filling groove, it is pressurized and replenished with a second injection pressure P2. The second injection pressure P2 is 0.5MPa~1.0MPa, satisfying: P2>P1; In the first and second stages, the gas in the filling tank is discharged simultaneously.

8. The method for preparing the rotor assembly as described in any one of claims 1 to 5, characterized in that, The wet pressing is carried out in an orientation magnetic field to apply a magnetic field to the magnetic steel raw material and simultaneously extrude the magnetic steel raw material in the corresponding filling groove, so that the magnetic steel powder particles in the magnetic steel raw material are oriented and arranged along the direction of the magnetic field; wherein, the magnetic field strength of the orientation magnetic field is 2.2T~3.5T, the pressing pressure of the wet pressing is 18MPa~30MPa, and the holding time is 12s~25s.

9. The method for preparing the rotor assembly as described in any one of claims 1 to 5, characterized in that, The sintering process employs a multi-stage heating method, which includes: First stage: Increase the temperature from room temperature to 450℃~550℃ at a first heating rate of 5℃ / min~8℃ / min, and hold for 0.5h~2h; Second stage: Increase the temperature to 800℃~900℃ at a second heating rate of 3℃ / min~5℃ / min, and hold for 1h~3h; The third stage: heating at a third heating rate of 1℃ / min~3℃ / min to 1000℃~1060℃, and holding at that temperature for 1h~6h to carry out densification sintering.

10. A brushless motor, characterized in that, The device includes a motor body and a rotor assembly disposed within the motor body. The rotor assembly includes an integrally formed magnet and a code disk, which are prepared by the method for preparing the rotor assembly according to any one of claims 1 to 9.

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