CN117559692B - Rotor structure of high-torque-density multidirectional magnetism-gathering axial flux permanent magnet motor - Google Patents

Abstract

The present invention relates to a rotor structure of a high torque density multi-directional magnetic axial flux permanent magnet motor, comprising a coaxially arranged rotor outer layer, a rotor middle layer and a rotor inner layer, wherein the rotor inner layer is a rotor core block and a tangentially arranged permanent magnet, wherein the rotor core block and the tangentially arranged permanent magnet are alternately and evenly arranged in the circumferential direction; the rotor middle layer is a radial Halbach array permanent magnet, wherein the radial Halbach array permanent magnet comprises a main magnetic pole and an auxiliary magnetic pole, wherein the main magnetic pole and the auxiliary magnetic pole are alternately and evenly arranged in the circumferential direction, wherein the main magnetic pole corresponds to the radial outer side of the rotor core block, and the auxiliary magnetic pole corresponds to the radial outer side of the tangentially arranged permanent magnet, wherein the center line of the main magnetic pole has an angle α with the center line of the rotor core block, and the center line of the auxiliary magnetic pole also has an angle α with the center line of the tangentially arranged permanent magnet; the rotor outer layer is a rotor yoke. The rotor structure of the present invention has good magnetic concentration effect, high air gap magnetic density, low torque pulsation, high torque density and high torque quality.

Description

A rotor structure of a high torque density multi-directional magnetic axial flux permanent magnet motor

Technical Field

The invention belongs to the technical field of axial flux permanent magnet motors, and in particular relates to a rotor structure of a high torque density multi-directional magnetic concentration axial flux permanent magnet motor.

Background Art

Axial flux permanent magnet motors have the advantages of small aspect ratio, compact structure, high efficiency, high power density and torque density. They are often used in places with strict space restrictions and high torque output requirements, such as electric vehicle drives. The rotor structures of axial flux permanent magnet motors mainly include surface-mounted and built-in types. Due to its simple structure and low cost, the surface-mount type is the most commonly used rotor structure for axial flux permanent magnet motors. However, the traditional axial magnetized surface-mounted rotor structure has the disadvantages of low air gap flux density and low torque density. The surface-mounted axial Halbach array permanent magnet plays a magnetic gathering role by adding auxiliary poles perpendicular to the magnetizing direction of the main poles. This simultaneously strengthens the air gap side flux density, improves the air gap flux density waveform distortion rate, and weakens the back iron side flux density, reduces the rotor back iron thickness, and improves the output torque.

With the increase of the number of Halbach array blocks and the optimization of the magnetization angle, the effect of improving the air gap magnetic flux density is better, but the difficulty of processing and installation will also increase greatly. Surface-mounted axial Halbach array permanent magnets will also increase the amount of permanent magnets. However, the surface-mounted rotor structure has the same problem, that is, due to the symmetry of the alternating and direct axis magnetic circuits, the reluctance torque cannot be utilized, which limits the further improvement of the torque density of the axial flux permanent magnet motor. In addition, the surface-mounted rotor structure also has problems such as large eddy current loss of permanent magnets, small inductance, and small weak magnetic speed range. The built-in rotor structure uses tangentially magnetized permanent magnets. The reluctance torque generated by the asymmetric magnetic circuit can be fully utilized through the rotor core block, thereby improving the torque density of the axial flux permanent magnet motor and expanding the speed regulation range. However, this structure has more air gap magnetic flux harmonics and larger torque fluctuations, which will affect the torque output characteristics.

In summary, the magnetic concentrated rotor structure can achieve the effect of improving the torque density of the axial flux permanent magnet motor. However, it is a design difficulty to overcome the shortcomings of the surface mounted rotor structure that cannot utilize the magnetic resistance torque, the large eddy current loss of the permanent magnet and the large torque fluctuation of the built-in rotor structure, so as to maximize the output torque quality of the axial flux permanent magnet motor.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a rotor structure of a high torque density multi-directional magnetic concentration axial flux permanent magnet motor, which has the advantages of good magnetic concentration effect, high air gap magnetic density, large reluctance torque, large inductance, wide speed range, small amount of permanent magnets, low torque pulsation and high torque density.

The present invention solves the technical problem by the following technical solutions:

A rotor structure of a high torque density multi-directional magnetic axial flux permanent magnet motor, characterized in that it includes a coaxially arranged rotor outer layer, a rotor middle layer and a rotor inner layer, the rotor inner layer is a rotor core block and a tangentially arranged permanent magnet, the rotor core block and the tangentially arranged permanent magnet are alternately and evenly arranged in the circumferential direction; the rotor middle layer is a radial Halbach array permanent magnet, the radial Halbach array permanent magnet includes a main pole and an auxiliary pole, the main pole and the auxiliary pole are alternately and evenly arranged in the circumferential direction, the main pole corresponds to the radial outer side of the rotor core block, the auxiliary pole corresponds to the radial outer side of the tangentially arranged permanent magnet, the center line of the main pole has an angle α with the center line of the rotor core block, and the center line of the auxiliary pole has an angle α with the center line of the tangentially arranged permanent magnet; the rotor outer layer is a rotor yoke.

Moreover, the magnetizing direction of the tangentially arranged permanent magnets is tangential, the magnetizing direction of the main magnetic poles is radial, and the magnetizing direction of the auxiliary magnetic poles is tangential; the magnetizing directions of the tangentially arranged permanent magnets on both sides of the rotor core block are opposite; the magnetizing directions of the auxiliary magnetic poles on both sides of the main magnetic poles are opposite; the magnetizing directions of the main magnetic poles on both sides of the auxiliary magnetic poles are opposite; the magnetizing directions of the auxiliary magnetic poles and the adjacent tangentially arranged permanent magnets are consistent; the magnetizing directions of the main magnetic poles and the tangentially arranged permanent magnets on both sides of the adjacent rotor core blocks point to or away from the rotor core block together.

Moreover, the inner layer of the rotor is a rotor yoke, the middle layer of the rotor is a radial Halbach array permanent magnet, and the outer layer of the rotor is a rotor core block and a tangentially arranged permanent magnet.

Moreover, the rotor core block, the tangentially arranged permanent magnets, the main magnetic poles and the auxiliary magnetic poles are in the shape of isosceles trapezoids, and the upper base and the lower base are both in the shape of arcs.

Moreover, the corresponding circular diameters of the inner and outer arc edges of the rotor core block are respectively the same as the corresponding circular diameters of the inner and outer arc edges of the tangentially arranged permanent magnets; the corresponding circular diameters of the inner and outer arc edges of the main magnetic poles and the auxiliary magnetic poles are the same; the corresponding circular diameter of the outer arc edge of the tangentially arranged permanent magnet is the same as the corresponding circular diameter of the inner arc edge of the main magnetic pole and the auxiliary magnetic pole; the corresponding circular diameter of the outer arc edge of the main magnetic pole and the auxiliary magnetic pole is the same as the inner diameter of the rotor yoke.

Moreover, the invention comprises a first rotor and a second rotor, wherein the second rotor has the same structure as the first rotor, the first rotor and the second rotor are axially symmetrically arranged in a manner corresponding to opposite polarities of the permanent magnets, the first rotor comprises a coaxially arranged rotor outer layer, a rotor middle layer and a rotor inner layer, the rotor inner layer comprises a rotor core block and a tangentially arranged permanent magnet, the rotor core block and the tangentially arranged permanent magnet are alternately and evenly arranged in the circumferential direction; the rotor middle layer comprises a radial Halbach array permanent magnet, the radial Halbach array permanent magnet comprises a main magnetic pole and an auxiliary magnetic pole, the main magnetic pole and the auxiliary magnetic pole are alternately and evenly arranged in the circumferential direction, the main magnetic pole corresponds to the radial outer side of the rotor core block, the auxiliary magnetic pole corresponds to the radial outer side of the tangentially arranged permanent magnet, the center line of the main magnetic pole has an angle α with the center line of the rotor core block, and the center line of the auxiliary magnetic pole also has an angle α with the center line of the tangentially arranged permanent magnet; the rotor outer layer is a rotor yoke.

The advantages and beneficial effects of the present invention are:

1. The rotor structure of the high torque density multi-directional magnetic concentration axial flux permanent magnet motor of the present invention adopts a tangentially arranged permanent magnetic radial Halbach array permanent magnet to form an axial main magnetic circuit through the rotor core block, thereby achieving a multi-directional magnetic concentration effect, strengthening the magnetic field on the air gap side, and improving the sinusoidal nature of the air gap magnetic flux waveform. The arrangement of permanent magnets in different magnetizing directions can also reduce leakage magnetic flux.

2. The rotor structure of the high torque density multi-directional magnetic concentration axial flux permanent magnet motor of the present invention fully utilizes the inner and outer diameter spaces, increases the output, and has a greater output torque under the same motor size.

3. The rotor structure of the high torque density multi-directional magnetic concentration axial flux permanent magnet motor of the present invention has radial Halbach array permanent magnets and tangentially arranged permanent magnets with staggered poles, which effectively weakens the magnetic field harmonics and reduces torque pulsation.

4. The rotor structure of the high torque density multi-directional magnetic concentration axial flux permanent magnet motor of the present invention increases the ferromagnetic material of the direct axis magnetic circuit, improves the direct axis inductance, strengthens the weak magnetic capability and expands the speed regulation range. At the same time, due to the asymmetric magnetic circuit, the magnetic resistance torque can be fully utilized to improve the torque density.

5. The rotor structure of the high torque density multi-directional magnetic concentration axial flux permanent magnet motor of the present invention reduces the eddy current loss of the permanent magnet due to the shielding effect of the ferromagnetic material and the permanent magnet segmentation.

6. The rotor structure of the high torque density multi-directional magnetic concentration axial flux permanent magnet motor of the present invention uses less permanent magnets and reduces costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a rotor structure of the present invention;

FIG2 is another schematic diagram of the rotor structure of the present invention;

FIG3 is a schematic diagram of the magnetization direction of the permanent magnet of the rotor structure of the present invention;

FIG4 is a schematic diagram of the magnetic circuit of the rotor structure of the present invention;

FIG5 is a schematic structural diagram of a dual-rotor structure of the present invention;

FIG. 6 is a torque comparison diagram of the rotor structure of the present invention at different angles and that of the rotor structure with only one permanent magnet arrangement.

Description of Reference Numerals

1. Rotor core block, 2. Tangentially arranged permanent magnets, 3. Radial Halbach array permanent magnets, 3a. Main magnetic poles, 3b. Auxiliary magnetic poles, 4. Rotor yoke, α. The angle between the center line of the tangentially arranged permanent magnets and the center line of the auxiliary magnetic poles, and the angle between the center line of the rotor core block and the center line of the main magnetic poles, 5. The first rotor, 6. The second rotor.

DETAILED DESCRIPTION

The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

As shown in FIGS. 1 and 2 , a rotor structure of a high torque density multi-directional magnetic concentrated axial flux permanent magnet motor comprises a rotor core block (1), tangentially arranged permanent magnets (2), radial Halbach array permanent magnets (3) and a rotor yoke (4), wherein the radial Halbach array permanent magnets (3) comprise main magnetic poles (3a) and auxiliary magnetic poles (3b).

The rotor core blocks (1) and the tangentially arranged permanent magnets (2) are alternately and evenly arranged in the inner layer of the rotor in the circumferential direction; the main magnetic poles (3a) and the auxiliary magnetic poles (3b) of the radial Halbach array permanent magnets (3) are alternately and evenly arranged in the middle layer of the rotor; and the rotor yoke (4) is arranged in the outer layer of the rotor.

The rotor core block (1), the tangentially arranged permanent magnet (2), the radial Halbach array permanent magnet (3) and the rotor yoke (4) are arranged concentrically; the rotor core block (1), the tangentially arranged permanent magnet (2), the main magnetic pole (3a) and the auxiliary magnetic pole (3b) are in an isosceles trapezoidal shape, and the upper base and the lower base are both in an arc shape; the inner and outer arc edges of the rotor core block (1) have the same corresponding circular diameters as the inner and outer arc edges of the tangentially arranged permanent magnet (2); the inner and outer arc edges of the main magnetic pole (3a) and the auxiliary magnetic pole (3b) have the same corresponding circular diameters; the outer arc edges of the tangentially arranged permanent magnet (2) have the same corresponding circular diameters as the inner arc edges of the main magnetic pole (3a) and the auxiliary magnetic pole (3b); the outer arc edges of the main magnetic pole (3a) and the auxiliary magnetic pole (3b) have the same corresponding circular diameters as the inner diameter of the rotor yoke (4).

The center angle of the tangentially arranged permanent magnet (2) is equal to the center angle of the corresponding outer auxiliary magnetic pole (3b); the center angle of the rotor core block (1) is equal to the center angle of the corresponding outer main magnetic pole (3a).

The main magnetic pole (3a) is arranged radially outside the rotor core block (1), and the auxiliary magnetic pole (3b) is arranged radially outside the tangentially arranged permanent magnet (2); the center line of the main magnetic pole (3a) and the center line of the rotor core block (1) have a certain angle α, and the center line of the auxiliary magnetic pole (3b) and the center line of the tangentially arranged permanent magnet (2) also have the same angle α.

The axial lengths of the rotor core block (1), the tangentially arranged permanent magnets (2), the radial Halbach array permanent magnets (3) and the rotor yoke (4) are equal.

As shown in FIG3 , the magnetizing direction of the tangentially arranged permanent magnet (2) is tangential; the magnetizing direction of the main magnetic pole (3a) is radial; and the magnetizing direction of the auxiliary magnetic pole (3b) is tangential.

The magnetization directions of the tangentially arranged permanent magnets (2) on both sides of the rotor core block (1) are opposite; the magnetization directions of the secondary magnetic poles (3b) on both sides of the main magnetic pole (3a) are opposite; the magnetization directions of the main magnetic poles (3a) on both sides of the secondary magnetic poles (3b) are opposite; the magnetization directions of the secondary magnetic poles (3b) and the adjacent tangentially arranged permanent magnets (2) are consistent; the magnetization directions of the main magnetic poles (3a) and the tangentially arranged permanent magnets (2) on both sides of the adjacent rotor core block (1) are both directed toward or away from the rotor core block (1).

FIG4 is a schematic diagram of the magnetic circuit of the motor, in which the main magnetic circuit is jointly generated by the tangentially arranged permanent magnets (2) and the radial Halbach array permanent magnets (3), as shown by the solid line in FIG4. The tangential magnetic circuit generated by the tangentially arranged permanent magnets (2) is converted into an axial main magnetic circuit through the rotor core block (1); the radial magnetic circuit generated by the radial Halbach array permanent magnets (3) is converted into an axial main magnetic circuit through the rotor core block (1).

The main magnetic pole (3a) is the main part of the radial Halbach array permanent magnet (3) to generate the main magnetic circuit, and together with the rotor yoke (4) forms a closed magnetic circuit; the auxiliary magnetic pole (3b) plays an auxiliary role, and the leakage magnetic circuit generated passes through the rotor yoke (4), as shown in the dotted magnetic circuit in Figure 4. Since the leakage magnetic circuit in the rotor yoke (4) is opposite to the main magnetic circuit, the saturation degree of the rotor yoke (4) can be reduced, the thickness of the rotor yoke (4) can be reduced, and the air gap magnetic density of the main magnetic circuit can be strengthened. The radial Halbach array permanent magnet (3) can also reduce the air gap harmonic distortion rate and improve the torque output quality.

Due to the arrangement and combination of permanent magnets with different magnetizing directions, the main magnetic path gathers magnetism in multiple directions, thereby improving the air gap magnetic flux density and enhancing the torque output capacity of the motor. In addition, the auxiliary magnetic pole (3b) is on the inter-pole leakage magnetic path of the tangentially arranged permanent magnet (2), and the tangentially arranged permanent magnet (2) is on the inter-pole leakage magnetic path of the main magnetic pole (3a). The magnetizing direction of the permanent magnet of the present invention is opposite to the above leakage magnetic field, which can effectively reduce the leakage magnetic field. At the same time, the radial Halbach array permanent magnet (3) and the tangentially arranged permanent magnet (2) are staggered, and by adjusting the angle (α), the magnetic field phases generated by the two can be reversed to produce the effect of suppressing magnetic field harmonics and reducing torque pulsation.

As shown in FIG5 , in the dual-rotor three-dimensional structure, the composition of the second rotor (6) is the same as that of the first rotor (5), and the first rotor (5) and the second rotor (6) are axially symmetrically placed in a manner that the corresponding permanent magnets have opposite polarities, and a dual-rotor structure can also be formed.

Generally, the outer diameter of the stator coil end of the axial flux permanent magnet motor is larger than the outer diameter of the permanent magnet, which leaves a certain margin in the outer diameter space of the rotor. The rotor structure of the multi-directional magnetic axial flux permanent magnet motor utilizes the outer diameter space margin of the rotor, increases the rotor middle layer and outer layer, enhances the outer diameter main magnetic field, maximizes space utilization, and has a higher output torque of the motor under the same installation size.

Based on the dual rotor structure of FIG5 , the torque of the rotor structure of the present invention at different angles as shown in FIG6 is compared with that of a rotor structure with only one permanent magnet arrangement. The comparison results are shown in Table 1.

Table 1

Under the same current, the average torque of the rotor structure of the present invention is almost equal when the angle α≠0 is 0 or 0, but the torque pulsation when the angle α≠0 is 29% less than the torque pulsation when α=0. Compared with the rotor structure with only one permanent magnet arrangement for excitation (only tangentially arranged permanent magnets (2) or only radial Halbach array permanent magnets (3)), the average torque of the rotor structure of the present invention is larger, almost equal to the sum of the average torques of the two permanent magnet arrangements, and the torque pulsation of the rotor structure of the present invention is significantly improved. The average torque of the rotor structure of the present invention is 24% greater than the average torque of the rotor with only tangentially arranged permanent magnets (2) for excitation, but the added mass of the radial Halbach array permanent magnets (3) and the rotor yoke (4) in the rotor of the present invention only accounts for 4.2% of the effective weight of the motor, so the rotor structure of the present invention can effectively improve the torque density of the motor.

Due to the presence of the rotor core block (1), the direct axis inductance is increased, the magnetic circuit is asymmetric, and the salient pole effect is obvious, which strengthens the weak magnetic performance of the motor, expands the speed regulation range, and can fully utilize the magnetic resistance torque, thereby improving the power density and torque density. Due to the shielding effect of the ferromagnetic material and the permanent magnet block, the eddy current loss of the permanent magnet is reduced, and the risk of permanent magnet overheating or even demagnetization is reduced. Compared with the traditional surface-mounted rotor structure, the amount of permanent magnets is saved and the manufacturing cost of the motor is reduced.

Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims (2)

1. A rotor structure of a high torque density multidirectional magnetism gathering axial flux permanent magnet motor is characterized in that: the rotor comprises a rotor outer layer, a rotor middle layer and a rotor inner layer which are coaxially arranged, wherein the rotor inner layer comprises rotor core blocks (1) and tangentially arranged permanent magnets (2), and the rotor core blocks (1) and the tangentially arranged permanent magnets (2) are alternately and uniformly arranged in the circumferential direction; the rotor middle layer is a radial Halbach array permanent magnet (3), the radial Halbach array permanent magnet (3) comprises a main magnetic pole (3 a) and an auxiliary magnetic pole (3 b), the main magnetic pole (3 a) and the auxiliary magnetic pole (3 b) are alternately and uniformly arranged in the circumferential direction, the main magnetic pole (3 a) corresponds to the radial outer side of the rotor core block (1), the auxiliary magnetic pole (3 b) corresponds to the radial outer side of the tangential arrangement permanent magnet (2), an included angle alpha is formed between the central line of the main magnetic pole (3 a) and the central line of the rotor core block (1), and an included angle alpha is formed between the central line of the auxiliary magnetic pole (3 b) and the central line of the tangential arrangement permanent magnet (2); the outer layer of the rotor is a rotor yoke (4);

The magnetizing direction of the tangentially arranged permanent magnets (2) is tangential, the magnetizing direction of the main magnetic pole (3 a) is radial, and the magnetizing direction of the auxiliary magnetic pole (3 b) is tangential; the magnetizing directions of the tangentially arranged permanent magnets (2) on two sides of the rotor core block (1) are opposite; the magnetizing directions of the auxiliary magnetic poles (3 b) at two sides of the main magnetic pole (3 a) are opposite; the magnetizing directions of the main magnetic poles (3 a) at two sides of the auxiliary magnetic pole (3 b) are opposite; the auxiliary magnetic pole (3 b) is consistent with the magnetizing direction of the adjacent tangentially arranged permanent magnets (2); the main magnetic pole (3 a) and the magnetizing directions of the tangentially arranged permanent magnets (2) on two sides of the adjacent rotor core blocks (1) are jointly pointed to or away from the rotor core blocks (1);

The rotor inner layer is a rotor yoke (4), the rotor middle layer is a radial Halbach array permanent magnet (3), and the rotor outer layer is a rotor core block (1) and a tangential permanent magnet (2);

the rotor core block (1), the tangentially arranged permanent magnets (2), the main magnetic pole (3 a) and the auxiliary magnetic pole (3 b) are isosceles trapezoid, and the upper bottom edge and the lower bottom edge are arc-shaped;

The diameters of circles corresponding to the inner arc edge and the outer arc edge of the rotor core block (1) are respectively the same as those of circles corresponding to the inner arc edge and the outer arc edge of the tangentially arranged permanent magnets (2); the diameters of the corresponding circles of the inner arc edges and the outer arc edges of the main magnetic pole (3 a) and the auxiliary magnetic pole (3 b) are the same; the diameter of the circle corresponding to the outer arc edge of the tangentially arranged permanent magnet (2) is the same as the diameter of the circle corresponding to the inner arc edge of the main magnetic pole (3 a) and the auxiliary magnetic pole (3 b); the diameters of the corresponding circles of the outer arc edges of the main magnetic pole (3 a) and the auxiliary magnetic pole (3 b) are the same as the inner diameter of the rotor yoke (4).

2. The rotor structure of a high torque density multidirectional-flux concentrated axial flux permanent magnet machine of claim 1, wherein: the rotor comprises a first rotor (5) and a second rotor (6), wherein the second rotor (6) has the same structure as the first rotor (5), the first rotor (5) and the second rotor (6) are axially and symmetrically arranged in a mode of opposite polarities of corresponding permanent magnets, the first rotor (5) comprises a rotor outer layer, a rotor middle layer and a rotor inner layer which are coaxially arranged, the rotor inner layer comprises rotor core blocks (1) and tangentially arranged permanent magnets (2), and the rotor core blocks (1) and the tangentially arranged permanent magnets (2) are alternately and uniformly arranged in the circumferential direction; the rotor middle layer is a radial Halbach array permanent magnet (3), the radial Halbach array permanent magnet (3) comprises a main magnetic pole (3 a) and auxiliary magnetic poles (3 b), the main magnetic pole (3 a) and the auxiliary magnetic poles (3 b) are alternately and uniformly arranged in the circumferential direction, the main magnetic pole (3 a) corresponds to the radial outer side of the rotor iron core block (1), the auxiliary magnetic pole (3 b) corresponds to the radial outer side of the tangential arrangement permanent magnet (2), an included angle (alpha) is formed between the center line of the main magnetic pole (3 a) and the center line of the rotor iron core block (1), and an included angle (alpha) is formed between the center line of the auxiliary magnetic pole (3 b) and the center line of the tangential arrangement permanent magnet (2); the outer layer of the rotor is a rotor yoke (4).