A direct-current brushless outer rotor motor with fractional slots

Abstract

The application discloses a direct-current brushless outer rotor motor with fractional slots, characterized by comprising a stator, a rotor and a rotating shaft, the rotor is coaxially arranged inside the stator, the stator is composed of a stator tooth, a stator slot and a winding arranged on the stator tooth, a plurality of neodymium-iron-boron permanent magnetic steels are attached to the outer circumferential surface of the rotor core, and the plurality of neodymium-iron-boron permanent magnetic steels are arranged in a Halbach array. The neodymium-iron-boron permanent magnetic steels are attached to the surface of the rotor core, and the neodymium-iron-boron permanent magnetic steels are arranged in a Halbach array, so that the motor power density and the permanent magnet utilization rate are effectively improved. The number of neodymium-iron-boron permanent magnetic steels per pole slot is an irreducible true fraction, the number of virtual unit motors is reduced, and the motor pulsation is reduced. The outer surface of the neodymium-iron-boron permanent magnetic steel is provided with a carbon fiber magnetic steel fixing layer, the carbon fiber magnetic steel fixing layer offsets the centrifugal force of the magnetic steel in high-speed operation, and the motor stability and service life are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of motor magnetic circuit, and particularly relates to a direct current brushless internal rotor motor with a Halbach array. BACKGROUND

[0002] The existing motor used by small household appliances such as washing machines is generally a DD motor and a BLDC motor. The DD motor and the BLDC motor are both direct current brushless motors, and the driving principle of the BLDC motor is to connect the motor and the load device by a belt, that is, a small wheel drives a large wheel. However, the belt transmission will cause the motor rotation to have a reverse gap, inertia, friction and insufficient rigidity, resulting in large energy loss and low motor efficiency. The DD motor is the development direction of the industry, and the DD motor directly adopts rigid connection between the DD motor and the passive workpiece, without the need for a lead screw, a gear, a speed reducer and other intermediate links, thereby avoiding the problems of reverse gap, inertia, friction and insufficient rigidity in the transmission system to the greatest extent. However, the DD motor needs to change the traditional production mode of washing machines due to the change in structure, and the cost is high. In addition, the DD motor does not have the speed ratio of the belt, and has the problems of low acceleration, difficulty in high speed, low power density of the motor and large torque ripple.

[0003] For example, a "direct drive motor convenient to adjust speed" disclosed in Chinese patent document, with the publication number "CN212323852U", includes a direct drive motor body, a fixed rod is arranged at the top and the bottom right side of the direct drive motor body, a machine cover is arranged at the right side of the direct drive motor body, a clamping box is arranged at the top and the bottom of the machine cover, the fixed rod is located in the inner box of the clamping box, a moving plate is arranged in the inner cavity of the clamping box, sliding grooves matched with the moving plate are formed in the two sides of the inner cavity of the clamping box, springs are arranged at the two sides of the connection between the top of the moving plate and the clamping box, a pull rod is arranged at the top of the moving plate, the pull rod penetrates through and extends to the top of the clamping box, and a pull ring is arranged at the top of the pull rod. However, the above scheme installs a structure convenient to disassemble on the top and the bottom of the motor to facilitate the maintenance of the motor by the staff, and does not essentially improve the power performance of the motor. The direct drive motor still has the problems of low acceleration, difficulty in high speed, difficult to break through the power density of the motor, and large torque ripple causing vibration and noise of the motor. SUMMARY

[0004] The present application is to overcome the problems of difficult to break through the power density of the direct drive brushless motor, low acceleration of the motor, difficulty in high speed, and difficult to reduce the vibration and noise of the motor in the prior art, and provides a direct current brushless external rotor motor with a fractional slot.

[0005] In order to achieve the above object, the application adopts the following technical scheme: a direct-current brushless outer rotor motor with fractional slots, comprising a motor stator and a motor rotor coaxially arranged outside the motor stator, the stator is composed of stator teeth, stator slots and windings wound on the stator teeth, the inner circumferential surface of the outer rotor is uniformly distributed with a plurality of magnetic steel slots, the outer rotor magnetic poles are composed of a plurality of neodymium iron boron permanent magnetic steels respectively embedded in the plurality of magnetic steel slots, and the plurality of neodymium iron boron permanent magnetic steels are arranged in a Halbach array. The output waveform tends to be a perfect sine wave, greatly weakening the influence of harmonic magnetic potential, effectively improving the power density of the permanent magnet synchronous wind power generator and the utilization rate of the permanent magnet.

[0006] Preferably, the plurality of neodymium iron boron permanent magnetic steels are arranged at equal angles, the magnetization included angles between every two adjacent neodymium iron boron permanent magnets are equal, and the magnetization included angle between every two adjacent neodymium iron boron permanent magnetic steels is not greater than 45°. The Halbach magnetic steel array further improves the excitation magnetic field to increase the motor torque density and improve the motor performance.

[0007] Preferably, the number of slots per pole of the neodymium iron boron permanent magnetic steel satisfies q=z / 2pm, q is an irrational fraction,

[0008] Wherein, m is the number of phases, 2p is the number of magnetic poles, and z is the total number of stator slots. The fractional slot effectively weakens the high-order harmonic potential generated by the non-sine distribution of the magnetic pole magnetic field, improves the electromotive force waveform, reduces the pulse amplitude of the magnetic flux per pole caused by the change of air gap permeance, and reduces the pulse loss on the surface of the magnetic pole.

[0009] Preferably, the cross section of the magnetic steel slot is a fan ring, the outer side of the fan ring is a curved surface, the inner side of the fan ring is a plane, and symmetric chamfers are arranged at both ends of the inner side of the magnetic steel slot, Y-shaped magnetic separation slots are arranged between the two adjacent magnetic steel slots, and the opening end of the magnetic separation slot faces the outer circumferential surface of the stator. The magnetic separation slot reduces the magnetic flux path through the pole separation magnetic position of the two adjacent permanent magnets during magnetization, and improves the magnetic flux waveform.

[0010] Preferably, the radial width of the neodymium iron boron permanent magnetic steel is greater than the circumferential width, and the cross section of the neodymium iron boron permanent magnetic steel is the same as the cross section of the magnetic steel slot. The cross section of the neodymium iron boron permanent magnetic steel is a fan ring, the outer side of the fan ring is a curved surface, the inner side of the fan ring is a plane, and symmetric chamfers are arranged at both ends of the inner side of the magnetic steel slot, so that the inner side of the neodymium iron boron permanent magnetic steel and the inner side of the magnetic steel slot form a salient pole structure, effectively improving the motor torque.

[0011] Preferably, the end face of the inner ring of the magnetic steel slot is provided with a first hollow window, and the opposite end faces of the two adjacent magnetic steel slots are provided with a second hollow window. While enhancing the mechanical reliability of the magnetic steel, the magnetic circuit loss is reduced, and the motor efficiency is further improved.

[0012] Therefore, the present application has the following advantages: (1) the present application applies Halbach array to the outer rotor motor, effectively improving motor power density and permanent magnet utilization rate; (2) the number of Nd-Fe-B permanent magnet magnetic steel per pole slot is an irreducible true fraction, reducing the number of virtual unit motors, thereby achieving the effect of reducing motor pulsation; (3) the magnetic steel is fixed by embedding the magnetic steel slot, and a hollow window is arranged on the magnetic steel slot, which enhances the mechanical reliability of the magnetic steel while reducing the magnetic circuit loss, further improving the motor efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0013] Fig. 1 is a structural schematic diagram of an embodiment of the present application.

[0014] Fig. 2 is a cross-sectional structural schematic diagram of an embodiment of the present application.

[0015] In the figure: 1, rotor; 2, magnetic steel slot; 3, stator; 4, stator slot; 5, Nd-Fe-B permanent magnet magnetic steel; 6, stator tooth; 7, chamfer; 8, magnetic separation slot; 9, first hollow window; 10, second hollow window. DETAILED DESCRIPTION

[0016] The present application will be further described below in combination with the drawings and specific embodiments.

[0017] Embodiment:

[0018] As shown in one kind has fractional slot's direct current brushless outer rotor motor, Figs. 1-2

[0019] including motor stator and coaxial setting in motor stator outside motor rotor 1, the stator is by stator tooth 6, stator slot 4 and winding on stator tooth 6 Winding is composed, the outer rotor 1 inner circumferential surface evenly distributed with several magnetic steel slots 2, the cross section of magnetic steel slot 2 is fan ring, the outer side of fan ring is arc surface, the inner side of fan ring is plane, the inner side of magnetic steel slot 2 is provided with symmetrical chamfer 7 at both ends angle, Y-shaped magnetic separation slot 8 is arranged between adjacent two magnetic steel slots 2, and the opening end of the magnetic separation slot 8 faces the outer circumferential surface of the stator. The magnetic separation slot 8 reduces the magnetic flux path formed by the magnetic separation position between the poles of two adjacent permanent magnets when magnetizing, and improves the magnetic density waveform.

[0020] ​The outer rotor 1 magnetic pole is composed of a plurality of neodymium iron boron permanent magnet 5 embedded in a plurality of magnetic steel slot 2, the plurality of neodymium iron boron permanent magnet 5 is in a Halbach array distribution. A plurality of neodymium iron boron permanent magnet 5 is arranged at equal angle interval, the magnetization angle between adjacent two neodymium iron boron permanent magnet is equal, and the magnetization angle between adjacent two neodymium iron boron permanent magnet 5 is not greater than 45°. The radial width of neodymium iron boron permanent magnet 5 is greater than the circumferential width, the cross section of the neodymium iron boron permanent magnet 5 is the same as the cross section shape of the magnetic steel slot 2. The cross section of the neodymium iron boron permanent magnet 5 is a fan ring, the outer side of the fan ring is an arc surface, the inner side of the fan ring is a plane, the inner side of the neodymium iron boron permanent magnet 5 and the inner side of the magnetic steel slot 2 form a salient pole structure at the two end angles of the inner side of the magnetic steel slot 2, effectively improving the motor torque.

[0021] The end face of the inner ring of the magnetic steel slot 2 is provided with a first hollow window 9, and the opposite end faces of the two adjacent magnetic steel slots 2 are provided with a second hollow window 10. While enhancing the mechanical reliability of the magnetic steel, the magnetic circuit loss is reduced, and the motor efficiency is further improved.

[0022] The specific embodiments described herein merely exemplify the spirit of the present application. Those skilled in the art of the present application can make various modifications or supplements to the described specific embodiments or use similar ways to replace, but will not deviate from the spirit of the present application or exceed the scope defined by the appended claims.

[0023] Although the terms rotor, stator, magnetic steel slot, Halbach array, and magnetic separation slot are used more frequently herein, the possibility of using other terms is not excluded. The use of these terms is only to facilitate the description and explanation of the essence of the present application; any interpretation as an additional limitation is contrary to the spirit of the present application.

Claims

1. A fractional-slot direct-current brushless outer rotor motor, characterized by, The motor stator and the motor rotor coaxially arranged outside the motor stator, the stator is composed of stator teeth, stator slots and windings wound on the stator teeth, the outer rotor inner circumferential surface is uniformly distributed with a plurality of magnetic steel grooves, the magnetic steel groove inner side surface two end angles are provided with symmetrical chamfers, the outer rotor magnetic pole is composed of a plurality of neodymium iron boron permanent magnetic steel respectively embedded in a plurality of magnetic steel grooves, and the plurality of neodymium iron boron permanent magnetic steel is distributed in a Halbach array; the end surface of the magnetic steel groove inner ring is provided with a first hollow window, and the opposite end surfaces of the adjacent two magnetic steel grooves are provided with second hollow windows.

2. A fractional-slot direct-drive brushless external rotor electric motor according to claim 1, characterized in that, The plurality of neodymium iron boron permanent magnetic steels are arranged at equal angles, the magnetization included angles between every two adjacent neodymium iron boron permanent magnets are equal, and the magnetization included angles between every two adjacent neodymium iron boron permanent magnetic steels are not greater than 45°.

3. A fractional-slot direct-drive brushless external rotor electric motor according to claim 2, characterized in that, The number of neodymium iron boron permanent magnetic steels per pole slot satisfies q=z / 2pm, q is an irrational fraction, Wherein, m is the phase number, 2p is the number of magnetic poles, and z is the total number of stator slots.

4. A fractional-slot direct-drive brushless external rotor electric motor according to claim 3, characterized in that, The cross section of the magnetic steel groove is a fan ring, the outer side surface of the fan ring is an arc surface, the inner side surface of the fan ring is a plane, Y-shaped magnetic separation grooves are arranged between the adjacent two magnetic steel grooves, and the opening ends of the magnetic separation grooves face the outer circumferential surface of the stator.

5. A fractional-slot direct-drive brushless external rotor electric motor according to claim 4, characterized in that, The radial width of the neodymium iron boron permanent magnetic steel is greater than the circumferential width.

6. A fractional-slot direct-drive brushless external rotor electric motor according to claim 5, characterized in that, The cross section of the neodymium iron boron permanent magnetic steel is the same as the cross section shape of the magnetic steel groove.

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