Manufacturing and assembling method of motor shell installation type conical permanent magnet

Abstract

The invention discloses a method for manufacturing and assembling a motor shell mounting type conical permanent magnet, which comprises the following steps of: S1, preparing an unmagnetized conical permanent magnet blank of which the initial uniform radial thickness is greater than the final design thickness; s2, the unmagnetized conical permanent magnet blank is subjected to precise conical machining, a variable radial thickness profile is formed, and the conical permanent magnet is kept in an unmagnetized state in the whole machining process; s3, after all machining is completed, concentrated magnetization is carried out on the completely-machined conical permanent magnet; s4, performing surface treatment on the outer diameter surface of the conical permanent magnet and the inner wall of the motor shell 1, and preparing a structural adhesive for controllable bonding; s5, coating at least one part of the surface of the conical permanent magnet or the inner wall of the motor shell with an adhesive, and fixing the radial, circumferential and axial positions of the conical permanent magnet under the action of the self-positioning structural characteristics; s6, performing a one-step composite thermocuring process to permanently lock the conical permanent magnet; and S7, verifying the magnetic performance and the bonding strength of the cured assembly.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet motor manufacturing, and in particular to a method for manufacturing and assembling a conical permanent magnet mounted on a motor housing, covering magnet processing, magnetization, bonding and integrated curing. Background Technology

[0002] In the field of new energy vehicle motors, rare earth permanent magnet motors, with their advantages of high power density and high efficiency, have become the mainstream choice for core drive components such as electronic parking brake (EPB) motors, permanent magnet DC (PMDC) motors, and automotive actuators. Among them, the motors used in automotive actuators include, but are not limited to: EPB—electronic parking brake actuator, ABS modulator pump, ESC / ESP hydraulic control unit motor, HVAC blower / cabin fan, wiper motor (brushed DC motor), seat adjustment / seat rail motor, window lift motor, sunroof motor / trunk opening motor, HVAC damper actuator motor, permanent magnet DC (PMDC) micro motor, rear differential unit (RDU) motor, other permanent magnet DC (PMDC) and brushed DC motors, electric tailgate / trunk opening motor, radiator cooling fan (older models), headlight leveling motor, throttle body actuator, vacuum pump actuator motor (electric / hybrid vehicles), electric bicycle hub motor, remote control model motor (large brushed), permanent magnet DC (PMDC) or other brushed DC motors. As the core carrier of the motor's magnetic circuit, the manufacturing precision, magnetic performance consistency, and assembly reliability of the permanent magnet directly determine the motor's output efficiency, operational stability, and service life. Currently, the mainstream traditional manufacturing process in the industry is as follows: preparing a uniformly thick conical permanent magnet blank using powder metallurgy → pre-magnetizing the blank → correcting the dimensions through secondary machining → manually or mechanically applying adhesive and bonding it to the inner wall of the motor housing → staged curing and molding.

[0003] However, this traditional process has revealed many intractable technical defects in practical applications, specifically in the following aspects: 1. High material costs and significant waste: Rare earth permanent magnet materials (such as neodymium iron boron) are expensive, and traditional processes require an excess processing allowance of 10% to 30% to avoid the impact of post-magnetization processing on magnetic properties, resulting in a high material loss rate; at the same time, the equal thickness design does not match the actual magnetic field distribution requirements of the motor, and the material in the non-core working areas at both ends of the magnet is not fully utilized, resulting in redundant waste. 2. Poor consistency of magnetic properties: After the magnetization process is carried out, the magnet needs to undergo secondary machining to meet the dimensional requirements. However, sintered permanent magnets are brittle, and the mechanical stress generated during processing will destroy the internal magnetic domain structure of the magnet. In addition, the heat generated during processing may cause irreversible demagnetization, ultimately resulting in a magnetic property deviation of more than 8% in the same batch of products, which seriously affects the stability of motor operation. Furthermore, the magnetized magnet will attract iron filings during processing, which will interfere with the processing accuracy and further affect the uniformity of magnetic properties. 3. Processing risks and low product qualification rate: Magnetized magnets face the risk of demagnetization during grinding, cutting and other processing. They are also prone to internal micro-cracks, chipping and other structural damage due to mechanical stress. At the same time, the interaction of magnetic fields can cause processing positioning deviations, which significantly reduce the product qualification rate. Furthermore, secondary processing will damage the protective coating on the magnet surface, accelerate oxidation and corrosion, and shorten the magnet's service life. 4. Insufficient bonding reliability: Traditional processes often use manual or simple mechanical gluing methods, making it difficult to precisely control the adhesive thickness. Mutually attracting magnets are prone to resulting in an excessively thin adhesive layer due to adsorption, while mutually repulsive magnets are difficult to position due to repulsive forces, leading to an uneven adhesive layer. At the same time, the lack of effective positioning constraints during the curing process makes the magnets susceptible to displacement and delamination due to factors such as vibration and differences in thermal expansion. Furthermore, the adhesive is prone to aging under the heat generated by the motor operation, further increasing the risk of magnet detachment and affecting the service life of the motor. 5. Low production efficiency: The core processes such as processing, magnetization, bonding, and curing are independent and carried out in separate steps. The transfer and positioning adjustments between processes are time-consuming and highly dependent on manual labor. The efficiency of sorting and testing is low, making it difficult to meet the needs of large-scale mass production of automotive motors. At the same time, the long cycle of traditional curing processes further restricts the overall production efficiency.

[0004] More importantly, the industry currently lacks an integrated manufacturing process that can simultaneously achieve precise control of magnet geometry, stable and uniform magnetization performance, high-yield bonding results, and one-step integrated curing of the magnet mounted on the housing. Existing processes often only optimize one aspect and cannot fundamentally solve the problem of ensuring multi-dimensional performance synergy, thus hindering the development of automotive motors towards lower cost, higher reliability, and higher efficiency. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a method for manufacturing and assembling a conical permanent magnet mounted on a motor housing, which can solve the following technical problems: high material cost and serious waste, poor magnetic performance consistency caused by secondary processing after magnetization, low processing risk and low product qualification rate, insufficient bonding reliability, and low production efficiency.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for manufacturing and assembling a conical permanent magnet mounted on a motor housing, comprising the following steps: S1, preparing an unmagnetized conical permanent magnet blank, the initial uniform radial thickness of which is greater than the final designed thickness; S2, performing precision conical machining on the unmagnetized conical permanent magnet blank to form a variable radial thickness profile, and maintaining the conical permanent magnet in an unmagnetized state throughout the machining process; S3, after all machining is completed, concentrating magnetization on the fully machined conical permanent magnet to generate a target magnetic field; S4, performing surface treatment on the outer diameter surface of the conical permanent magnet and the inner wall of the motor housing 1, and preparing... S5, applying the adhesive to at least one location on the surface of the conical permanent magnet or the inner wall of the motor housing, inserting the conical permanent magnet into the housing under the action of the self-positioning structural features to fix the radial, circumferential and axial positions of the conical permanent magnet; S6, performing a one-step composite thermosetting process to completely cross-link the adhesive and permanently lock the position of the conical permanent magnet relative to the housing; S7, verifying the magnetic properties and bonding strength of the cured component; wherein, the processing in S2 is completely completed before the magnetization in S3, and the curing in step S6 is performed in a single thermal cycle, thereby forming a closed-loop manufacturing control process that simultaneously stabilizes magnetic properties and assembly positioning.

[0007] As a preferred technical solution of the present invention, the processing of S2 is carried out by CNC grinding under continuous coolant circulation conditions, and the surface temperature is kept below 80°C. The magnetization of S3 is carried out by a pulsed magnetic field with a peak intensity of not less than 2.8T.

[0008] As a preferred technical solution of the present invention, the surface activation of the bonding in S4 includes at least one of plasma treatment, chemical activation, and sandblasting treatment, so that the surface roughness Ra reaches 2.0-3.2μm. The structural adhesive prepared in S4 is a high-temperature resistant epoxy adhesive with a working temperature of not less than 180℃.

[0009] As a preferred embodiment of the present invention, the thickness of the adhesive coated by S5 is controlled at 0.08-0.20 mm, and the self-positioning structural features include at least one of radial gasket, circumferential limiting block, axial stop block, and fastener.

[0010] As a preferred embodiment of the present invention, the curing of S6 is carried out at a temperature of 130-170°C for a duration of 20-40 minutes. The magnetic property verification of S7 includes testing the uniformity of air gap magnetic flux density using a Hall sensor. The bonding strength verification includes testing the shear strength, with a minimum pass value of 15 MPa.

[0011] An electric motor includes a housing, a rotor disposed within the housing, and at least one conical permanent magnet fixed to the inner wall of the housing. The radial thickness of the conical permanent magnet is non-uniformly distributed circumferentially, such that the conical permanent magnet has the maximum thickness in the center region of the magnetic pole and the minimum thickness in the edge region of at least one magnetic pole. The thickness of the conical permanent magnet decreases gradually or stepwise from the center region of the magnetic pole to the edge region of the magnetic pole. This reduces the amount of permanent magnet material used in the circumferential region where the magnetic flux utilization efficiency is low, while maintaining sufficient magnetomotive force in the main working magnetic flux region. Thus, the amount of permanent magnet material consumed is reduced while maintaining the effective working air gap magnetic flux required for the operation of the electric motor.

[0012] As a preferred embodiment of the present invention, the maximum thickness of the conical permanent magnet in the central region of the magnetic pole is 2.8-3.2 mm, and the minimum thickness in the edge region of the magnetic pole is 1.8-2.2 mm.

[0013] As a preferred embodiment of the present invention, the maximum thickness of the conical permanent magnet in the central region of the magnetic pole is 3.0 mm, and the minimum thickness in the edge region of the magnetic pole is 2.0 mm.

[0014] The tapered permanent magnet has a maximum thickness of 3.0 mm in the central region of the magnetic pole and a minimum thickness of 1.8 mm in the edge region of the magnetic pole.

[0015] As a preferred embodiment of the present invention, the circumferential thickness of the conical permanent magnet varies linearly, curvilinearly, or in a multi-step manner, and the thickness variation is designed to reduce local magnetic saturation and circumferential leakage in the magnetic pole edge region. The conical permanent magnet is an arc-shaped magnetic tile with an arc angle of 120 to 160 degrees, and its axial length is basically consistent with the axial length of the rotor.

[0016] Compared with the prior art, the beneficial effects that this invention can achieve are: 1. Significantly reduce material costs and waste: This invention adopts the "process first, then magnetize" mode, which eliminates the need to reserve excessive margin to avoid magnetic performance damage during processing after magnetization. Combined with the conical processing design, the central pole area (core working area) of the magnet retains a reasonable thickness, while the non-core areas at both ends are thinned, which accurately matches the magnetic field distribution requirements of the motor, effectively reducing the consumption of rare earth permanent magnet materials and significantly controlling raw material costs. 2. Improve processing quality and product qualification rate: The processing adopts CNC precision grinding (or double-sided grinding), and with continuous coolant circulation to control the surface temperature below 80℃, stress-free conical processing is achieved, avoiding structural damage such as micro-cracks and edge chipping caused by traditional secondary processing; at the same time, processing in the unmagnetized state eliminates magnetic field interference and has higher positioning accuracy. 3. High bonding reliability and extended service life: By performing plasma treatment and sandblasting activation treatment on the bonding surface of the magnet and the inner wall of the shell, and using a high-temperature resistant epoxy structural adhesive with a temperature resistance of ≥180℃, the mechanical interlocking ability and aging resistance of the bonding interface are greatly improved; at the same time, the use of precision dispensing, gasket thickness control and self-positioning structure ensures that the adhesive layer is uniform and controllable, and there is no risk of magnet displacement or delamination during the curing process; 4. Simplify processes and improve production efficiency: The process integrates the scattered processes of processing, magnetization, bonding, and curing into a closed-loop integrated process. In particular, the "one-step composite thermosetting" replaces the traditional multi-stage curing, eliminating time-consuming steps such as transfer and secondary positioning between processes. At the same time, the surface activation, precision dispensing, and self-positioning assembly processes can be automated, reducing reliance on manual labor. 5. Wide range of applications and strong versatility: The manufacturing process of this invention is not only applicable to electronic parking brake (EPB) motors, but can also be widely used in the production of housing-mounted conical permanent magnets for various automotive motors such as brushed DC motors, permanent magnet DC motors (PMDC motors), and automotive actuator motors (such as seat motors, brake motors, and pump motors). It does not require significant process adjustments for different motor types, has strong versatility, and is applicable to a wide range of scenarios. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the manufacturing and assembly process of the present invention. Figure 2 This is a schematic diagram of the standard magnetic tile's three-dimensional structure; Figure 3 This is a schematic diagram of the three-dimensional structure of the magnetic tile of the present invention; Figure 4 This is a three-dimensional schematic diagram of the motor housing of the present invention; Figure 5 This is a three-dimensional schematic diagram of half of the motor housing of the present invention; Figure 6 This is a full sectional view of the assembled motor housing and magnet of the present invention; The components include: 1. Housing; 2. Circumferential limiting block; 3. Radial gasket; 4. Adhesive guide channel; 5. Axial stop block; 6. Fastener; 7. Conical permanent magnet. Detailed Implementation

[0018] To make the technical means, creative features, objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of this invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention.

[0019] Example 1 - Permanent Magnet Manufacturing and Assembly Process Please refer to Figure 1 As shown, this invention provides a method for manufacturing and assembling a housing-mounted conical permanent magnet 7. This conical permanent magnet 7 is applied to housing-mounted or stator-side permanent magnet configuration motors such as electronic parking brake (EPB) motors, brushed DC motors and permanent magnet DC motors, automotive actuator motors, seat motors, brake motors, and pump motors. Among these, motors used in automotive actuators include, but are not limited to: EPB—electronic parking brake actuator, ABS modulator pump, ESC / ESP hydraulic control unit motor, HVAC blower / cabin fan, wiper motor (brushed DC motor), and seat... Adjustment / seat rail motor, window lift motor, sunroof motor / trunk opening motor, HVAC damper actuator motor, permanent magnet DC (PMDC) micro motor, rear differential unit (RDU) motor, other permanent magnet DC (PMDC) and brushed DC motors, electric tailgate / trunk opening motor, radiator cooling fan (older models), headlight leveling motor, throttle body actuator, vacuum pump actuator motor (electric / hybrid vehicles), electric bicycle hub motor, remote control model motor (large brushed), permanent magnet DC (PMDC) or other brushed DC motors; First, in step S1, a sintered NdFeB permanent magnet blank of grade MGC36B-III is prepared. This magnet blank has a central angle of 140°, an axial length of 30 mm, an initial uniform radial thickness of 3.2 mm, and an inner radius of 27.5 mm. During this stage, the magnet blank is intentionally kept completely unmagnetized to avoid introducing thermal or mechanical stress, and machining allowances are reserved to ensure sufficient material for subsequent precision grinding. The purpose of this step is to obtain a stress-free permanent magnet blank, suitable for high-precision forming without magnetic performance degradation.

[0020] like Figure 1As shown, in S2, the unmagnetized magnet blank obtained in S1 undergoes stress-free conical precision machining. A CNC double-sided grinding machine is used for machining, forming a gradually varying thickness structure along the arc direction of the inner diameter surface. After machining, the final thickness t1 of the magnet's central pole region is 3.0 mm, and the thickness t2 of the two end regions after thinning is 2.0 mm. The thickness gradually varies circumferentially between the center and edge of the magnetic pole. This structure reduces the amount of permanent magnet material used in areas with low magnetic flux utilization efficiency, while retaining sufficient magnetomotive force in the main working magnetic flux region, thereby maintaining effective air gap magnetic flux and starting torque. During grinding, the spindle speed is controlled to be no higher than 1500 r / min, continuous coolant circulation is used, and the grinding surface temperature is strictly controlled to be below 80℃. By completing all machining before magnetization, demagnetization, internal microcracks, and stress concentration within magnetic domains caused by machining are fundamentally avoided, ensuring that geometric accuracy and intrinsic magnetomotive force are preserved. The setting of processing step S2 is not contrary to the goal of saving materials. As a precision forming process, it is used to transform standardized permanent magnet blanks into functionally optimized magnetic components, thereby avoiding the use of high-grade or excessively thick permanent magnets in the final motor assembly. In steps S1 and S2, it's important to clarify that S1 produces a magnet blank of uniform thickness, while S2 processes this uniformly thick blank into a conical magnet blank. The manufacturing process isn't merely about reducing raw material usage at the blank stage, but about achieving a controlled magnetic field distribution and optimizing the effective utilization of the permanent magnet. In traditional motors, permanent magnets are designed with a uniform thickness based on the most severe magnetic requirements, leading to localized magnetic saturation and ineffective utilization of magnetic material in some circumferential areas. This over-designed thickness directly increases the cost of the permanent magnet and generates unnecessary magnetic losses. In contrast, this invention specifically sets a functionalized thickness distribution for the permanent magnet along the circumference, reducing the thickness in low-contribution areas and maintaining or increasing the thickness only in torque-critical regions. The precision machining process after sintering serves only to achieve this functionalized thickness profile, ensuring high precision and repeatability, rather than being an independent material-saving process. Although some material is removed during processing, the overall specifications of the permanent magnets required for the motor can be downgraded. Compared to traditional uniform thickness designs, lower grade magnetic materials can be used, the average thickness can be reduced, or the initial blank size can be decreased. Therefore, from a system-level perspective, this invention effectively reduces the cost of magnetic materials while improving torque stability and vibration performance. Accordingly, the processing steps do not aim for zero-waste manufacturing, but rather achieve a functional thickness distribution of the permanent magnets, thereby reducing the over-design of permanent magnets and allowing the use of lower grade or thinner permanent magnets at the motor system level.

[0021] S3, after machining, is centrally magnetized. After the conical machining is completed, the fully machined magnet is transferred to a high-field pulse magnetizer for radial magnetization. The peak magnetization field strength is not less than 2.8T, and the pulse width is controlled within the range of 2-4ms. After magnetization, the remanence Br of the magnet is not less than 440mT, the intrinsic coercivity Hc is not less than 330kA / m, and the batch magnetic performance deviation is controlled within ±2.5%. Since all machining has been completed before magnetization, the magnet does not bear structural stress during and after magnetization, ensuring that the magnetic performance remains highly stable and consistent in mass production.

[0022] S4. Surface activation and adhesive preparation are performed. First, the inner wall of the steel motor housing is ultrasonically degreased with ethanol. Then, the interior of the motor housing 1 and the outer diameter surface of the conical permanent magnet 7 are surface-treated. Surface treatment includes at least one of plasma treatment, chemical activation, and sandblasting, achieving a surface roughness Ra of 2.0-3.2 μm to improve the mechanical bonding ability of the adhesive. Simultaneously, the bonding surfaces of the magnets are plasma-activated and then air-dried under low pressure to avoid contamination. A high-temperature resistant epoxy structural adhesive with a temperature resistance of not less than 180℃ is prepared, degassed, and stored for later use to achieve controllable dispensing. Through the above treatments, a stable and high-strength bonding interface is ensured.

[0023] S5, implements positioning-controlled adhesive assembly. Executing step S5 achieves positioning-controlled adhesive assembly. For example... Figure 4-6As shown, an automatic volumetric dispensing system is used to apply the prepared adhesive to the inner surface of the motor housing 1. The conical permanent magnet 7 is separated from the housing 1 by the radial gasket 3, so that the thickness of the target adhesive can be more accurately controlled at 0.12±0.02mm. The inner wall of the housing 1 is pre-designed with self-positioning structural features, including radial gaskets 3 for controlling adhesive thickness, circumferential limiting blocks 2 to prevent circumferential rotation of the magnet, axial stop blocks 5 to prevent axial sliding, and fasteners 6 to suppress micro-movements before curing. Four circumferential limiting blocks 2 are provided, all fixed to the inner wall of the housing 1. Two circumferential limiting blocks 2 are provided on both sides of each conical permanent magnet 7. The circumferential limiting blocks 2 on both sides can circumferentially block the conical permanent magnet 7, preventing circumferential sliding. Multiple adhesive flow channels 4 are formed on the inner wall of the housing 1, evenly distributed in the middle of the two sets of circumferential limiting blocks 2, guiding the flow of adhesive when the conical permanent magnet 7 is pressed onto the radial gaskets 3. To eliminate air bubbles, promote uniform spread of the adhesive, and prevent the magnets from "floating," four axial stop blocks 5 are equidistantly arranged on the innermost circumference of the inner wall of the housing. Each conical permanent magnet 7 corresponds to two axial stop blocks 5, which are symmetrically arranged. During the drying process, the motor housing 1 is placed vertically with the opening facing upwards. At this time, the axial stop blocks 5 can support the conical permanent magnet 7 and prevent it from moving axially. At the same time, in order to prevent the conical permanent magnet 7 from shifting due to vibration during processing, a fastener 6 is fixedly installed at the end of the axial stop block 5 to hold the conical permanent magnet 7 in place. The surface of the fastener 6 that contacts the conical permanent magnet 7 is an arc-shaped surface, so that the fastener 6 can fit stably with the conical permanent magnet 7. Subsequently, the magnetized conical permanent magnet 7 is pressed into the housing 1 through a guide mechanical insertion. Under the combined action of the adhesive layer and the self-positioning structure, the conical permanent magnet 7 automatically achieves precise radial alignment, accurate angular positioning, and firm axial fixation without any external clamps, jigs, or manual adjustments.

[0024] S6, further composite thermosetting. After assembly, the housing-magnet assembly is placed in a curing oven and heated to 150°C for 30 minutes, then allowed to cool naturally to room temperature. During a single thermal cycle, the adhesive completes full cross-linking, the magnet position is permanently locked, and the thermal stress between the housing 1, the adhesive, and the conical permanent magnet 7 is uniformly released, ultimately forming an integrated composite adhesive structure. This one-step curing method replaces the traditional multi-stage curing and secondary positioning process, significantly improving production efficiency and dimensional consistency.

[0025] S7, Verification of Magnetic Properties and Adhesion. Using a Hall effect probe, air gap magnetic flux was measured at multiple circumferential positions. The results showed that the uniformity of air gap magnetic flux density was improved by at least 20% compared to traditional processes. The shear strength of the adhesive between the magnet and the housing was tested to be no less than 15 MPa. Furthermore, after the assembly underwent 100 thermal cycles from -40℃ to 120℃, no magnet displacement, delamination, or cracking was observed. Dimensional inspection further confirmed that the radial positioning tolerance of the magnet was within ±0.05 mm, and the angular deviation was within ±0.3°. These results demonstrate that this closed-loop manufacturing process ensures excellent magnetic stability, adhesive reliability, and thermal durability.

[0026] Example 2 - Application of Small Permanent Magnet DC (PMDC) Motor In another embodiment, this closed-loop manufacturing process is applied to a small permanent magnet direct current (PMDC) motor. The magnet has a central angle of 120°, an axial length of 25 mm, and an initial uniform thickness of 2.5 mm. After tapering, the final thickness of the central region is 2.3 mm, and the thickness at both ends is reduced to 1.7 mm. All subsequent steps (including post-processing magnetization, surface activation, controlled dispensing, self-positioning assembly, and one-step thermosetting) are consistent with those in Example 1. This embodiment demonstrates that the present invention is applicable not only to EPB motors but also to small and medium power DC motors.

[0027] Example 3 - Cost Optimization Balance The permanent magnet has a maximum radial thickness of approximately 3.0 mm at the center of the magnetic pole and a minimum radial thickness of approximately 1.8 mm at the edge of the magnetic pole. Compared to the first embodiment, this structure optimizes the magnetic flux distribution and reduces local magnetic saturation, thereby further reducing the amount of permanent magnet material used while maintaining effective working magnetic flux. This embodiment is suitable for applications requiring additional cost reduction and allowing for small deviations in starting torque.

[0028] In this embodiment, the present invention can be applied to a housing-mounted permanent magnet DC motor for automotive actuators. The motor includes a cylindrical steel housing 1, a rotor disposed within the housing 1, and two conical permanent magnets 7 bonded to the inner wall of the housing by adhesive. Each conical permanent magnet 7 constitutes a magnetic pole, covering a circumferential pole arc of approximately 140 degrees. The inner diameter of the housing 1 is 55 mm, the axial length of the conical permanent magnet 7 is 30 mm, and the nominal radial thickness of the magnet in conventional designs is 3.0 mm. This motor has a two-pole structure, with the two magnets arranged opposite each other and a non-magnetic gap between them.

[0029] Example 4 - Comparative Example (Traditional Process) For comparison, similar magnets were assembled using a traditional manufacturing process. In this traditional process, the magnets are first magnetized, then edge-grinding, manual adhesive application, and two-stage thermosetting. This traditional process results in processing-induced demagnetization, with magnetic performance deviations reaching ±8%. Occasionally, magnet displacement occurs during curing, leading to a total scrap rate between 6% and 8%. Compared to this invention, the traditional process exhibits poorer magnetic performance consistency, lower bonding reliability, and lower production efficiency. The comparative results clearly demonstrate that the closed-loop manufacturing process disclosed in this invention has significant technical advantages.

[0030] Formula verification In this invention, each conventional uniform-thickness magnetic tile is replaced with a tapered magnetic tile whose thickness varies circumferentially. The tapered design ensures the magnet is thickest in the central region of the magnetic pole, where magnetic flux utilization efficiency is highest, and gradually thins towards the pole edges where magnetic flux can easily saturate the casing or cause circumferential leakage. This tapered thickness distribution reduces unnecessary permanent magnet material usage while maintaining effective working air gap magnetic flux. The thickness distribution function is defined along a circumferential angle θ from the pole center (θ=0) to the pole edge (θ=±70°). In this embodiment, the magnet has the maximum thickness t in the central region. max And linearly decrease to the minimum thickness t of the edge region. min The thickness distribution expression is as follows:

[0031] Among them, t max and t min The magnet is selected based on its grade, demagnetization margin, and manufacturing capability. In typical applications, t max =3.0mm, t min =1.8mm. The tapered structure can be approximated using a continuous linear slope or a multi-segment stepped design. The magnet's radius of curvature matches the inner diameter of the housing to ensure assembly compatibility.

[0032] The manufacturing process of conical magnets includes blank preparation, precision machining, magnetization, and controlled bonding assembly. Prepare sintered arc-shaped magnetic blanks to ensure the required curvature and length (e.g., ferrite magnetic blanks with an initial thickness of 3.0 mm or slightly thicker to allow for machining allowance). The magnetic blank is machined by CNC grinding or double-sided grinding to form a tapered thickness profile. The grinding process uses a special fixture based on the curvature to ensure that the dimensional tolerances of the inner surface on the air gap side meet the standards, and that the outer surface on the shell side is tapered. After machining, a special magnetizing fixture is used to magnetize the magnet to obtain the specified magnetization direction and magnetic pole orientation. In one embodiment, the magnetization process is performed after machining to avoid chipping of the magnet edges and to ensure the magnetization uniformity of the tapered profile.

[0033] Calculation of material savings (volume reduction) in permanent magnets To quantify the cost reduction effect, the volume of a magnet in a traditional constant thickness design is first calculated: For a single arc-shaped magnetic tile, the arc length along the inner diameter of the shell is calculated as follows:

[0034] Where θ = 140°, D = 55 mm. Substituting these values ​​into the calculation, we get:

[0035] The approximate formula for the volume of a uniformly thick arc-shaped magnet is:

[0036] Where L = 30 mm, t0 = 3.0 mm. Therefore:

[0037] Calculation of the volume of a conical magnet (linear thickness distribution, t) max =3.0mm, t min =1.8mm) Average thickness:

[0038] Volume of the conical magnet:

[0039] Volume reduction of a single magnet:

[0040] Percentage reduction in volume:

[0041] Calculations show that using a typical tapered design of 3.0mm to 1.8mm reduces the amount of permanent magnet material per magnet tile by approximately 20%. For dual-magnet motors, since both magnets use the same tapered design, the total permanent magnet material reduction is still approximately 20%. If a more aggressive tapered design (e.g., t...) is adopted... min =1.5mm), then t avg =2.25mm, the material reduction ratio can reach about 25%, which shows that the material saving effect can be flexibly controlled by adjusting the minimum thickness.

[0042] Calculation of the effects of magnetic flux and torque (torque sustaining principle) In traditional designs, the effective air gap magnetic flux is not strictly proportional to the magnet volume. This is because some areas of the magnetic circuit may become saturated, and the edge regions contribute less to the effective working magnetic flux due to magnetic leakage. A conical magnet redistributes the magnetomotive force along the pole arc: the center of the pole retains sufficient thickness to maintain a stable magnetomotive force, while the pole edges are thinned to suppress saturation and magnetic leakage. The simplified engineering model assumes that the total magnetic reluctance of the magnetic circuit is mainly determined by the air gap and the ferromagnetic path, and that the magnetomotive force provided by the magnet in local regions is approximately proportional to its thickness. Under the lumped parameter approximation, the air gap magnetic flux is:

[0043] The torque formula within the linear region is:

[0044] When the tapered design reduces the magnetomotive force in the edge region, the flux loss is significantly suppressed because this region typically exhibits leakage flux in shell-mounted magnet motors. To quantify this effect, the magnetic poles are divided into a "high-utilization central region" and a "low-utilization edge region": Typical division ratio: the central 60% arc is a high-utilization area, and the edge 40% arc is a low-utilization area; In this embodiment, the central region retains almost the full thickness (approximately 3.0 mm), while the thickness of the edge region is reduced (approximately 1.8 mm). Assume that the effective magnetic flux contribution coefficient in the central region is high (e.g., 1.0), while the contribution coefficient in the peripheral region is low (e.g., 0.4) due to leakage flux and saturation tendency.

[0045] Based on the above practical assumptions, the "effective thickness index" is defined as follows:

[0046] For a uniform magnet, the effective thickness index is:

[0047] The effective magnetomotive force index decreased by a certain percentage:

[0048] That is, with a 20% reduction in magnet volume, the simplified effective magnetic flux driving capability only decreases by about 8.4%. Furthermore, the tapered design simultaneously reduces saturation and leakage flux in the edge region, improving magnetic flux utilization and partially compensating for the aforementioned reduction. If the tapered design reduces leakage flux, increasing the edge region utilization coefficient from 0.4 to 0.55 (since the magnetic flux is no longer excessively "driven" into saturation, this improvement is practically feasible), then:

[0049]

[0050] This means that the effective magnetic flux driving capability decreases by only about 3.7%, while the amount of magnet material used is reduced by 20%. In practical applications, because the conical design makes the magnetic flux distribution closer to a sine wave and reduces leakage flux, the torque reduction is usually less than the original reduction in thickness. Therefore, this conical design can achieve significant savings in permanent magnet material while keeping the starting torque deviation within a small range (e.g., a few percentage points). The specific deviation range depends on the degree of conical radicalization and the saturation level of the housing.

[0051] Calculation of starting torque variation (direct correlation) With the current and winding design remaining constant, the torque ratio can be approximated as:

[0052] If the optimized conical design maintains the magnetic flux at 97%-100% of the baseline value, then the torque can also be maintained at 97%-100% of the baseline value. In the example above, the effective magnetic flux index ratio is approximately 0.963, indicating that while reducing the magnet volume by 20%, the reduction in starting torque can be controlled to approximately 4%. This can be achieved by slightly increasing t... min (For example, adjusting from 1.8mm to 2.0mm), or adopting a stepped tapered design that retains more thickness in the transition area, can further limit torque reduction while still achieving significant material savings.

[0053] Applicability and Validation Methods The above embodiments demonstrate that the present invention achieves cost reduction by reducing the amount of permanent magnet material used in low-utilization areas and maintaining effective air gap magnetic flux by optimizing the magnetic flux distribution. Verification can be performed by comparing the performance parameters of a traditional constant-thickness magnet motor and a conical magnet motor under the same winding and current conditions. Key measurable indicators include: starting torque, stall current, no-load current; and air gap magnetic flux density distribution measured by a Hall sensor.

[0054] In addition, the conical magnet reduces excessive magnetic flux concentration and decreases sensitivity to local saturation, thereby relaxing the magnet performance tolerance requirements and improving manufacturing consistency without sacrificing the required torque margin.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method of manufacturing and assembling a motor housing mounted conical permanent magnet, characterized by: Includes the following steps: S1, prepare an unmagnetized conical permanent magnet blank (7) with an initial uniform radial thickness greater than the final design thickness; S2, the unmagnetized conical permanent magnet (7) blank is precisely conical to form a variable radial thickness profile, and the conical permanent magnet (7) remains unmagnetized throughout the entire processing; S3, After all machining is completed, the fully machined conical permanent magnet (7) is magnetized in a concentrated manner to generate the target magnetic field; S4, the outer diameter surface of the conical permanent magnet (7) and the inner wall of the motor housing 1 are surface treated, and a structural adhesive for controllable bonding is prepared. S5, apply adhesive to at least one part of the surface of the conical permanent magnet (7) or the inner wall of the motor housing (1), and insert the conical permanent magnet (7) into the housing (1) under the action of the self-positioning structural feature to fix the radial, circumferential and axial positions of the conical permanent magnet (7); S6, a one-step composite thermosetting process is carried out to make the adhesive completely cross-linked and the position of the conical permanent magnet (7) relative to the shell (1) is permanently locked. S7, verify the magnetic properties and bonding strength of the cured components; In this process, the processing of S2 is completed before the magnetization of S3, and the curing of step S6 is performed in a single thermal cycle, thereby forming a closed-loop manufacturing control process that simultaneously stabilizes magnetic properties and assembles and positions the components.

2. A method of manufacturing and assembling a motor housing mounted conical permanent magnet according to claim 1, characterized in that: The processing of S2 is carried out by CNC grinding under continuous coolant circulation, and the surface temperature is kept below 80°C. The magnetization of S3 is carried out by a pulsed magnetic field with a peak intensity of not less than 2.8T.

3. A method of manufacturing and assembling a motor housing mounted conical permanent magnet according to claim 1, characterized in that: The surface activation of the bonding in S4 includes at least one of plasma treatment, chemical activation, and sandblasting, so that the surface roughness Ra reaches 2.0-3.2μm. The structural adhesive prepared by S4 is a high-temperature resistant epoxy adhesive with a working temperature of not less than 180℃.

4. A method of manufacturing and assembling a motor housing mounted conical permanent magnet according to claim 1, characterized in that: The thickness of the adhesive coated on S5 is controlled between 0.08 and 0.20 mm, and the self-positioning structural features include at least one of the following: radial gasket (3), circumferential limiting block (2), axial stop block (5), and fastener (6).

5. A method of manufacturing and assembling a motor housing mounted conical permanent magnet according to claim 1, characterized in that: The curing of S6 is carried out at a temperature of 130-170℃ for 20-40 minutes. The magnetic property verification of S7 includes testing the uniformity of air gap magnetic flux density using a Hall sensor. The bond strength verification includes shear strength testing, with a minimum pass value of 15MPa.

6. An electric motor manufactured by the manufacturing and assembly method according to any one of claims 1-8, characterized in that: The device includes a housing (1), a rotor arranged inside the housing (1), and at least one conical permanent magnet (7) fixed to the inner wall of the housing (1). The radial thickness of the conical permanent magnet (7) is non-uniformly distributed along the circumference, such that the conical permanent magnet (7) has the maximum thickness in the center region of the magnetic pole and the minimum thickness in at least one edge region of the magnetic pole. The thickness of the conical permanent magnet (7) decreases gradually or stepwise from the center region of the magnetic pole to the edge region of the magnetic pole. This reduces the amount of permanent magnet material used in the circumferential region where the magnetic flux utilization efficiency is low, while maintaining sufficient magnetomotive force in the main working magnetic flux region. Thus, the consumption of permanent magnet material is reduced while maintaining the effective working air gap magnetic flux required for the operation of the motor.

7. The electric motor according to claim 6, characterized in that: The maximum thickness of the conical permanent magnet (7) in the central region of the magnetic pole is 2.8-3.2 mm, and the minimum thickness in the edge region of the magnetic pole is 1.8-2.2 mm.

8. The electric motor according to claim 7, characterized in that: The maximum thickness of the conical permanent magnet (7) in the central region of the magnetic pole is 3.0 mm, and the minimum thickness in the edge region of the magnetic pole is 2.0 mm.

9. The electric motor according to claim 7, characterized in that: The maximum thickness of the conical permanent magnet (7) in the central region of the magnetic pole is 3.0 mm, and the minimum thickness in the edge region of the magnetic pole is 1.8 mm.

10. An electric motor according to claim 6, characterized in that: The circumferential thickness of the conical permanent magnet (7) varies linearly, curvilinearly, or in a multi-step manner, and the thickness variation is designed to reduce local magnetic saturation and circumferential leakage in the magnetic pole edge region. The conical permanent magnet (7) is an arc-shaped magnetic tile with an arc angle of 120 to 160 degrees, and its axial length is basically consistent with the axial length of the rotor.

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