A coreless brushless DC motor

Abstract

The invention discloses a coreless brushless DC motor, comprising a bearing, a stator, a rotor, and a rotor position sensor assembly. The stator coreless winding is a concentric multilayer winding. The winding lead is welded by an adapter plate assembly. The multi-pole annular magnetic pole is P, and the HALBACH structure is used for overall multi-pole magnetization to ensure that the air gap magnetic density waveform of the winding coupling part is sinusoidal. The motor end cover, housing, stator, rotor, bearing, and Hall positioning circle center are all on the coaxial center line. The invention provides a coreless brushless motor with the advantages of simple product structure, convenient assembly, compact structure, small size, small volume, light weight, small loss, high efficiency, large power and torque density, high back electromotive force sinusoidal, low waveform distortion rate, low operating noise and vibration, small torque fluctuation, high dynamic response speed, stable control operation, high control accuracy, high reliability, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of brushless DC motors, and more specifically, to a motion actuator. Background Art

[0002] Coreless brushless motors are DC permanent magnet servo micro motors. The main difference from ordinary brushless DC motors is that there is no tooth slot on the armature core, and the motor winding is made into a cup-shaped motor according to a special winding process. Compared with traditional slot motors, it has the following advantages: 1. High efficiency: The efficiency of coreless motors is mostly above 70%, and some products are even close to 90%, while the efficiency of traditional slot motors is below 70% under the same volume and weight; 2. Small size, light weight, high power and torque density: Due to the improved work efficiency and reduced loss, the power density of coreless motors has been greatly improved. Compared with traditional slot motors, the volume and weight can be reduced by about 30%; 3. Good control performance: There is no torque fluctuation caused by the slot effect, and the motor runs smoothly; the electromechanical time constant is low, the dynamic response is good, the inductance of the motor is very low, the conventional electrical time constant is within 0.1ms, and the electromechanical time constant is about 2ms. The motor responds quickly and the control is precise. It is suitable for application in high-precision drive systems, such as communications, robots, security, aerospace, rudder control systems and other fields.

[0003] With the expansion of the application scope of aircraft models, drones, robots, gimbals and other products, the driving power motors are required to be light weight, miniaturized, high power density, high torque density, high efficiency, high dynamic response, high reliability and safety. At present, due to the limitation of process, the hollow cup brushless motor mostly adopts one pole pair, hexagonal winding structure and triangle wiring method. The speed of the motor with this structure is high, and the back electromotive force and motor torque coefficient are low, which makes it impossible to develop hollow cup brushless DC motors with high torque density and power density. Summary of the invention

[0004] The invention overcomes the shortcomings of the prior art and provides a coreless brushless DC motor that is integrated, miniaturized, light in weight, highly dynamic in response and highly reliable.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A coreless brushless DC motor comprises a bearing, a stator, a rotor and a rotor position sensor assembly, wherein the stator comprises a front end cover, a housing, an annular stator core, a stator coreless winding, a support ring and an adapter plate assembly; the stator coreless winding is a concentric multilayer winding, and the lead of the stator coreless winding is connected to the adapter plate assembly by welding leads; the rotor comprises a rotor shaft, a multi-pole annular magnetic ring, a detection magnetic steel sheath and a detection magnetic steel, the magnetic pole of the multi-pole annular magnetic ring is P, and the HALBACH structure is used for overall multi-pole magnetization to achieve a sinusoidal air gap magnetic density waveform of the stator coreless winding coupling part; the rotor position sensor assembly comprises a rear end cover, a Hall plate assembly, screws, an O-ring and a wave spring.

[0007] Furthermore, the positioning centers of the bearing, stator, rotor, and Hall plate assembly are on the same axis; the number of Halls in the Hall plate assembly is 3;

[0008] The adapter plate assembly is radially positioned and axially positioned by the housing and the support ring, respectively, and a 0.5mm to 1mm installation gap is reserved between the adapter plate assembly and the stator hollow cup winding;

[0009] The tail lead of the stator hollow cup winding is welded on the adapter plate assembly, and a three-phase power line is led out from the adapter plate assembly.

[0010] Furthermore, the rear cover and / or the front cover are provided with a bearing chamber, and a mounting groove for placing an O-type rubber ring is provided in the bearing chamber; the O-type rubber ring elastically supports the bearing, effectively absorbs the vibration generated during the operation of the motor, and reduces the vibration and noise of the motor operation;

[0011] A wave spring is arranged between the bearing and the corresponding end cover to provide the bearing preload force of the motor and eliminate the axial assembly error of the motor.

[0012] Furthermore, the casing is cylindrical as a whole; the annular stator core is bonded to the inner side of the casing by interference fit and applying glue to the outer wall; the coreless stator winding is fixed to the inner side of the annular stator core, and insulating paper is provided between the coreless stator winding and the annular stator core; the coreless stator winding is wound by self-adhesive enameled wire and rolled into a cylindrical structure;

[0013] The stator armature is manufactured by the casing, the annular stator core and the hollow cup stator winding. After the stator armature is assembled in place, the front end cover is pressed into the annular casing, and then the stator is potted as a whole, and the resin is filled in the installation gaps between the hollow cup stator windings and between the hollow cup stator windings and the annular stator core; wherein the casing is made of non-magnetic stainless steel, and the annular punching sheets formed by the annular stator core in the casing are formed by laminating at least two silicon steel sheets with a thickness of 0.1mm to 0.5mm.

[0014] Furthermore, the rotor shaft and the multi-pole annular magnetic ring are bonded and fixed by high-temperature resistant and high-strength glue; the number of poles of the multi-pole annular magnetic ring is P, and the value of P is between 4 and 12 and is a common multiple of 2; the material of the multi-pole annular magnetic ring is high-temperature resistant and high-performance neodymium iron boron or samarium cobalt; the surface magnetic curve of the multi-pole annular magnetic ring is approximately sinusoidal distribution, and the peak value of the surface magnetic is greater than or equal to 3000 Gauss;

[0015] The rotor shaft is made of high-strength magnetic stainless steel;

[0016] The number of poles of the multi-pole annular magnetic ring is equal to the number of poles of the detection magnetic steel, and the polarities correspond one to one; the detection magnetic steel adopts multiple pieces of sector-shaped magnetic steel spliced ​​into a circular ring structure, and the sector angle α satisfies α=360 / P, and the magnetic steel orientation of the detection magnetic steel is magnetized along the axial direction of the sector;

[0017] After the rotor is assembled, dynamic balancing is performed, and the balancing grade is ≤G6.3, which satisfies the requirement for stable operation when the rotor speed is greater than or equal to 10,000 rpm.

[0018] Furthermore, the rotor position sensor assembly is sequentially loaded with an O-type rubber ring, a wave spring, and a bearing based on the rear end cover, and then the Hall plate assembly is fastened with screws. The Hall plate assembly is composed of three Hall sensors flat on the PCB board, and the mechanical angle between adjacent Halls is θ, θ=240N / P, N is a positive integer, P is the number of poles of the magnetic ring, and θ limits the angle to be less than or equal to 120°;

[0019] The bottom surface of the Hall plate assembly of the rotor position sensor assembly should satisfy the HD value between the distance H from the bearing chamber step and the bearing width D being between 1.5 mm and 3 mm.

[0020] Furthermore, the rear end cover, the front end cover and the housing are transitionally matched, and welding is performed after the motor performance debugging is completed;

[0021] The stator hollow cup winding is coupled with the main magnetic circuit and obtains a waveform with a sinusoidal degree higher than the back electromotive force as the rotor multi-pole annular magnetic ring rotates.

[0022] Furthermore, in terms of the radial space of the motor, the inner diameter of the annular core is enlarged, and in terms of the axial space, the size of the magnetic steel is enlarged. Through the magnetic field structure, the air gap flux of the motor is increased, the effective number of turns per unit back electromotive force is reduced, and the motor resistance and loss are further reduced.

[0023] Furthermore, after the motor is assembled, the closest distance between the Hall sensing surface on the rotor position sensor assembly and the detection magnetic steel plane on the rotor is t, and t is between 0.5 mm and 2 mm.

[0024] A coreless brushless DC motor, wherein the motor is a coreless brushless DC motor of any of the above-mentioned components.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention realizes a compact product structure, small size, small volume, light weight, high efficiency, low loss, high power and torque density, high back EMF sinusoidal, low waveform distortion rate, stable control operation and high precision;

[0027] 2. By optimizing the magnetic field distribution, the core yoke thickness, air gap length, magnetic steel thickness, and rotor yoke thickness are selected, which effectively increases the magnetic flux per unit volume, thereby increasing the back electromotive force and torque coefficient per unit turns of the motor, further reducing the resistance under unit torque coefficient, reducing the copper loss of the motor, and effectively improving the motor efficiency, torque density, and power density.

[0028] 3. By optimizing the air gap magnetic field, the motor back EMF has high sinusoidality and low waveform distortion rate, the motor runs smoothly, the noise and vibration are low, the torque fluctuation is small, and the control operation is smooth and high in precision.

[0029] 4. The concentric winding and layout are adopted, the winding has no overlapping part, the air gap is short under the effective number of turns, and the multi-layer winding layout can be realized under the limited annular air gap, thereby improving the winding space utilization rate, the resistance under the unit back electromotive force is low, the motor copper loss is small, the motor copper loss is reduced, and the motor efficiency, torque density and power density are effectively improved;

[0030] 5. By optimizing the air gap magnetic field, adopting the HALBACH structure integral multi-pole magnetized magnetic ring, and rationally arranging the key parameters such as the number of magnetic ring poles, air gap length, and stator yoke thickness, the motor air gap magnetic density waveform has good sinusoidality, good back electromotive force sinusoidality, and low waveform distortion rate. The motor back electromotive force has high sinusoidality and low waveform distortion rate. The motor runs smoothly, with low noise and vibration, small torque fluctuation, and stable control operation with high precision.

[0031] 6. The overall multi-pole annular magnetic steel design simplifies the rotor transfer process and reduces the difficulty of production and manufacturing. The tracking magnetic steel is directly connected to the end tracking magnetic steel to effectively shorten the axial size of the motor, making the motor more compact and the rotor stiffness good. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural cross-sectional diagram of the present invention;

[0033] Figure 2 is a cross-sectional view of the stator structure of the present invention;

[0034] Figure 3 A cross-sectional view of the rotor structure of the present invention;

[0035] Figure 4 It is a surface magnetic curve diagram of the multi-pole annular magnetic ring of the present invention;

[0036] Figure 5 is a structural cross-sectional view of a rotor position sensor assembly of the present invention;

[0037] Figure 6 Schematic diagram of the Hall plate assembly of the present invention.

[0038] Numbers in the figure:

[0039] Bearing 1, stator 2, rotor 3, rotor position sensor assembly 4;

[0040] Front end cover 21, housing 22, annular stator core 23, stator hollow cup winding 24, support ring 25, adapter plate assembly 26; rotor shaft 31, multi-pole annular magnetic ring 32, detection magnetic steel sleeve 33, detection magnetic steel 34; rear end cover 41, Hall plate assembly 42, screw 43, O-ring 44, wave spring 45; t Hall sensing distance, D bearing thickness, H the distance from the end cover bearing chamber step to the bottom surface of the PCB board of the Hall plate assembly. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments are only specific descriptions of the present invention, and their purpose is to allow those skilled in the art to better understand the technical solution of the present invention, and should not be regarded as limiting the present invention. The structures not described in detail are all processed and connected using traditional structures.

[0042] It should also be noted that, in the absence of conflict, the embodiments and features of the embodiments in this solution can be combined with each other. In the description of this solution, the directions or positional relationships indicated by "center", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation to the present invention.

[0043] At present, due to the limitation of technology, coreless brushless motors mostly adopt one pole pair, hexagonal winding structure and triangle wiring method. From the analysis of magnetic circuit structure, the yoke of such motor is generally thicker and the outer diameter of the rotor is smaller. Based on the following formula of brushless DC motor:

[0044]

[0045] According to the formula, the motor length L a , speed n, pole arc coefficient α i , winding coefficient k ω, magnetic field strength A, air gap average motor B δ Under the same heat dissipation conditions, the motor output power P' is proportional to the armature or rotor outer diameter D a 2 . At present, for one pair of poles with the same motor outer dimensions, the overall magnetic flux of the motor is low due to the large stator yoke and small effective motor size Da, which further affects the torque and power output of the hollow cup brushless DC motor, as well as the motor efficiency. If the same torque density output is to be achieved, the motor volume must be increased. Therefore, as power density, torque density, miniaturization and other indicators gradually increase, under specific motor outer diameter and thickness conditions, it is necessary to fully utilize the magnetic circuit characteristics, take into account the air gap magnetic density and effective rotor diameter, and improve the effective working magnetic flux of the motor. The specific implementation method of this scheme is as follows:

[0046] like Figure 1 As shown, a coreless brushless DC motor includes components such as a bearing 1, a stator 2, a rotor 3, and a rotor position sensor assembly 4. The positioning centers of the bearing 1, the stator 2, the rotor 3, and the Hall plate assembly 42 are on the coaxial centerline.

[0047] like Figure 2 As shown, the stator 2 includes a front cover 21, a housing 22, an annular stator core 23, a stator hollow cup winding 24, a support ring 25, and an adapter plate assembly 26. The stator hollow cup winding 24 is a concentric multi-layer winding, and the lead wire of the stator hollow cup winding 24 is connected to the adapter plate assembly 26 by welding the lead wire.

[0048] The rear end cover 41 of the rotor position sensor assembly 4 and / or the front end cover 21 of the stator 2 are provided with a bearing chamber, and a mounting groove for placing an O-type rubber ring 44 is provided in the bearing chamber; the O-type rubber ring 44 elastically supports the bearing 1, effectively absorbs the vibration generated during the operation of the motor, and reduces the vibration and noise of the motor operation. A wave spring 45 is also provided between the bearing 1 and the corresponding end cover, and the wave spring 45 provides a preload force for the bearing 1 of the motor and eliminates the axial assembly error of the motor.

[0049] The housing 22 is cylindrical in shape as a whole; the annular stator core 23 is bonded to the inner side of the housing 22 by interference fit and glue applied to the outer wall; the coreless stator winding 24 is fixed to the inner side of the annular stator core 23, and insulating paper is provided between the coreless stator winding 24 and the annular stator core 23; the coreless stator winding 24 is wound by self-adhesive enameled wire and rolled into a cylindrical structure. The adapter plate assembly 26 is radially positioned and axially positioned by the housing 22 and the support ring 25, respectively, and a 0.5mm to 1mm installation gap is reserved between the adapter plate assembly 26 and the stator coreless winding 24. The tail lead of the stator coreless winding 24 is welded to the adapter plate assembly 26, and the three-phase power line is led out from the adapter plate assembly 26.

[0050] After the stator armature is manufactured by the casing 22, the annular stator core 23, and the hollow cup stator winding 24, and the stator armature is assembled in place, the front end cover 21 is pressed into the annular casing 22, and then the stator 2 is potted as a whole, and the resin is filled between the hollow cup stator winding 24 and the installation gap between the hollow cup stator winding 24 and the annular stator core 23 to improve the strength and heat dissipation effect of the entire stator 2. Among them, the casing 22 is made of non-magnetic stainless steel, and the annular punching sheet formed by the annular stator core 23 in the casing 22 is formed by laminating at least two silicon steel sheets with a thickness of 0.1mm to 0.5mm.

[0051] like Figure 3 As shown, the rotor includes a rotor shaft 31, a multi-pole annular magnetic ring 32, a detection magnetic steel sheath 33, and a detection magnetic steel 34. Figure 4 As shown, the magnetic pole of the multi-pole annular magnetic ring 32 is P, and the HALBACH structure is used for overall multi-pole magnetization, so that the air gap magnetic density waveform of the coupled part of the stator hollow cup winding 24 is sinusoidal, and the stator hollow cup winding 24 can be coupled with the main magnetic circuit to obtain an effect in which the sinusoidality is higher than the back electromotive force waveform as the rotor multi-pole annular magnetic ring 32 rotates.

[0052] The rotor shaft 31 is made of high-strength magnetic stainless steel. The rotor shaft 31 and the multi-pole annular magnetic ring 32 are bonded and fixed by high-temperature resistant and high-strength glue. The number of poles of the multi-pole annular magnetic ring 32 is P, and the P value is between 4 and 12, and is a common multiple of 2. The material of the multi-pole annular magnetic ring 32 is high-temperature resistant and high-performance neodymium iron boron or samarium cobalt; the surface magnetic curve of the multi-pole annular magnetic ring 32 is approximately sinusoidal distribution, and the peak value of the surface magnetic is greater than or equal to 3000 Gauss. The number of poles of the multi-pole annular magnetic ring 32 is equal to the number of poles of the detection magnetic steel 34, and the polarity corresponds one to one; the detection magnetic steel 34 uses multiple pieces of fan-shaped magnetic steel spliced ​​into a circular ring structure, and the fan-shaped angle α satisfies α=360 / P. The magnetic steel orientation of the detection magnetic steel 34 is magnetized along the fan-shaped axial direction. After the rotor is assembled, dynamic balancing is performed, and the balance level is ≤G6.3, which satisfies the condition that the rotor speed is greater than or equal to 10000rpm and runs smoothly.

[0053] like Figure 5 , 6 As shown, the rotor position sensor assembly 4 includes a rear end cover 41, a Hall plate assembly 42, screws 43, an O-ring 44, and a wave spring 45. The number of Halls in the Hall plate assembly 42 is 3.

[0054] The rotor position sensor assembly 4 is installed with the O-type rubber ring 44, the wave spring 45, and the bearing 1 in sequence with the rear end cover 41 as the reference, and then the Hall plate assembly 42 is fastened with screws 43. The Hall plate assembly 42 is three Hall sensors flat on the PCB board, and the mechanical angle between adjacent Halls is θ, θ = 240N / P, N is a positive integer, P is the number of poles of the magnetic ring, and θ limits the angle to be less than or equal to 120°. The bottom surface of the Hall plate assembly 42 of the rotor position sensor assembly 4 should satisfy the HD value between 1.5mm and 3mm from the step distance H of the bearing chamber and the bearing width D.

[0055] As a preferred embodiment, the rear end cover 41, the front end cover 21 and the housing 22 are transitionally matched, and the motor is fully tested for performance according to the functions and performance requirements of the hollow cup brushless DC motor. After all indicators meet the design requirements, the motor end cover and the housing are welded to complete the production of a hollow cup brushless DC motor. Among them, after the motor is assembled, the closest distance between the Hall sensing surface on the rotor position sensor assembly 4 and the plane of the detection magnetic steel 34 on the rotor 3 is t, and t is between 0.5mm and 2mm. In terms of the radial space of the motor, the inner diameter of the annular stator core 23 can be fully enlarged while ensuring the strength. In terms of the layout of the axial space, considering the structural characteristics of the parts, the size within the range of the spacing between the two bearings is fully utilized, and the size of the magnetic steel is as large as possible. Through the above layout, the magnetic field structure is optimized, the air gap flux of the motor is increased, the effective number of turns per unit back electromotive force is reduced, and the motor resistance and loss are further reduced, which is conducive to improving the efficiency, torque and power density of the motor.

[0056] In summary, this scheme optimizes the motor magnetic field, increases the air gap flux per unit volume as much as possible, and adopts the HALBACH structure for the orientation and magnetization of the magnetic ring, so that the motor air gap magnetic field approaches sinusoidal, the motor operation harmonic content is low, and the winding back electromotive force is sinusoidal. It can effectively reduce motor loss, improve motor efficiency, torque density, power density, etc., improve the stability of motor control and operation, reduce torque pulsation, and reduce motor vibration and noise. The weak part of the winding is encapsulated with epoxy resin, which improves the structural strength, waterproof properties, insulation strength and heat dissipation properties of the winding, improves the working life and reliability of the motor, and improves the power density of the motor at the same volume. The hollow cup brushless DC motor has the advantages of simplified structure, convenient assembly, compact structure, small size, small volume, light weight, low loss, high efficiency, large power and torque density, high back electromotive force sine, low waveform distortion rate, low operating noise and vibration, small torque fluctuation, high dynamic response speed, stable control operation, high control accuracy, and high reliability.

[0057] The preferred implementation of the present solution is described in detail above in conjunction with the accompanying drawings, but the present solution is not limited thereto. Within the technical concept of the present solution, the technical solution of the present solution can be subjected to a variety of simple variations, including the combination of various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present solution will not further describe various possible combinations. However, these simple variations and combinations should also be regarded as the contents disclosed by the present solution and belong to the protection scope of the present solution.

Claims

1. A coreless brushless DC motor, comprising a bearing (1), a stator (2), a rotor (3) and a rotor position sensor assembly (4), characterized in that: The stator (2) comprises a front end cover (21), a housing (22), an annular stator core (23), a stator hollow cup winding (24), a support ring (25) and an adapter plate assembly (26); the stator hollow cup winding (24) is a concentric multi-layer winding, and the lead wire of the stator hollow cup winding (24) is connected to the adapter plate assembly (26) by welding the lead wire; the rotor comprises a rotor shaft (31), a multi-pole annular magnetic ring (32), a detection magnetic steel sheath (33) and a detection magnetic steel (34); the magnetic pole of the multi-pole annular magnetic ring (32) is P, and the HALBACH structure is used for overall multi-pole magnetization, so that the air gap magnetic density waveform of the coupling part of the stator hollow cup winding (24) is sinusoidal; the rotor position sensor assembly (4) comprises a rear end cover (41), a Hall plate assembly (42), a screw (43), an O-type rubber ring (44), and a wave spring (45); The positioning centers of the bearing (1), the stator (2), the rotor (3), and the Hall plate assembly (42) are on a coaxial centerline; the number of Halls in the Hall plate assembly (42) is three; The adapter plate assembly (26) is radially positioned and axially positioned by the housing (22) and the support ring (25), respectively, and a mounting gap of 0.5 mm to 1 mm is reserved between the adapter plate assembly (26) and the stator hollow cup winding (24); The tail lead of the stator hollow cup winding (24) is welded to the adapter plate assembly (26), and a three-phase power line is led out from the adapter plate assembly (26); The rear end cover (41) and / or the front end cover (21) are provided with a bearing chamber, and a mounting groove for placing an O-type rubber ring (44) is provided in the bearing chamber; the O-type rubber ring (44) elastically supports the bearing (1), effectively absorbs vibration generated during the operation of the motor, and reduces vibration and noise during the operation of the motor; A wave spring is arranged between the bearing (1) and the corresponding end cover to provide a preload force for the bearing (1) of the motor and eliminate an axial assembly error of the motor; The rotor position sensor assembly (4) is sequentially installed with an O-type rubber ring (44), a wave spring (45), and a bearing (1) based on the rear end cover (41), and then the Hall plate assembly (42) is fastened with screws (43). The Hall plate assembly (42) is composed of three Hall sensors flatly attached to the PCB board. The mechanical angle between adjacent Halls is θ, θ=240N / P, N is a positive integer, P is the number of poles of the magnetic ring, and θ limits the angle to be less than or equal to 120°; The bottom surface of the Hall plate assembly (42) of the rotor position sensor assembly (4) should satisfy a HD value between a distance H from the bearing chamber step and a bearing width D of 1.5 mm to 3 mm.

2. The coreless brushless DC motor according to claim 1, characterized in that: The casing (22) is cylindrical in shape as a whole; the annular stator core (23) is bonded to the inner side of the casing (22) by means of interference fit and glue applied to the outer wall; the stator hollow cup winding (24) is fixed to the inner side of the annular stator core (23), and insulating paper is provided between the stator hollow cup winding (24) and the annular stator core (23); the stator hollow cup winding (24) is wound with self-adhesive enameled wire and rolled into a cylindrical structure; The stator armature is manufactured by a casing (22), an annular stator core (23), and a stator hollow cup winding (24). After the stator armature is assembled in place, the front end cover (21) is pressed into the annular casing (22), and then the stator (2) is potted as a whole, and the installation gaps between the stator hollow cup windings (24) and between the stator hollow cup windings (24) and the annular stator core (23) are filled with resin; wherein the casing (22) is made of non-magnetic stainless steel material, and the annular punching sheet formed by the annular stator core (23) in the casing (22) is formed by laminating at least two silicon steel sheets with a thickness of 0.1 mm to 0.5 mm.

3. The coreless brushless DC motor according to claim 1, characterized in that: The rotor shaft (31) and the multi-pole annular magnetic ring (32) are bonded and fixed by high-temperature resistant and high-strength glue; the number of poles of the multi-pole annular magnetic ring (32) is P, and the value of P is between 4 and 12 and is a common multiple of 2; the material of the multi-pole annular magnetic ring (32) is high-temperature resistant and high-performance neodymium iron boron or samarium cobalt; the surface magnetic curve of the multi-pole annular magnetic ring (32) is approximately a sine wave distribution, and the peak value of the surface magnetic is greater than or equal to 3000 Gauss; The rotor shaft (31) is made of high-strength magnetically conductive stainless steel; The number of poles of the multi-pole annular magnetic ring (32) is equal to the number of poles of the detection magnetic steel (34), and the polarities correspond one to one; the detection magnetic steel (34) is a circular ring structure formed by splicing a plurality of fan-shaped magnetic steels, the fan-shaped angle α satisfies α=360 / P, and the magnetic steel orientation of the detection magnetic steel (34) is magnetized along the fan-shaped axial direction; After the rotor is assembled, dynamic balancing is performed, and the balancing grade is ≤G6.3, which satisfies the requirement for stable operation when the rotor speed is greater than or equal to 10,000 rpm.

4. The coreless brushless DC motor according to claim 1, characterized in that: In terms of the radial space of the motor, the inner diameter of the annular core is enlarged, and in terms of the axial space, the size of the magnetic steel is enlarged. Through the magnetic field structure, the air gap flux of the motor is increased, the effective number of turns per unit back electromotive force is reduced, and the motor resistance and loss are further reduced.

5. The coreless brushless DC motor according to claim 1, characterized in that: After the motor is assembled, the closest distance between the Hall sensing surface on the rotor position sensor assembly (4) and the plane of the detection magnetic steel (34) on the rotor (3) is t, and t is between 0.5 mm and 2 mm.

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