CN109818471B - A Double Air Gap Magnetic Field Modulation Permanent Magnet Motor - Google Patents

Abstract

The invention discloses a double-air-gap magnetic field modulation permanent magnet motor suitable for electric automobiles and electric tractors, wherein a composite rotor consists of an outer rotor, an inner rotor and an end disc which have the same axial lead, a stator is coaxially positioned between the outer rotor and the inner rotor and consists of Ns stator core modules which are uniformly distributed along the circumference, permanent magnet steel is fixedly embedded between every two adjacent stator core modules, each stator core module is formed by radially combining a U-shaped module with a radial section at the outer layer and an E-shaped module at the inner layer in a radial manner, the U-shaped module at the outer layer is provided with 2 stator outer armature teeth and 1 outer layer groove, and the E-shaped module at the inner layer is provided with 2 stator inner armature teeth, 1 middle auxiliary modulation tooth and 2 inner layer grooves; a single coil of the centralized winding is wound on the armature teeth and the permanent magnet steel of the two adjacent stator core modules; an inner-layer air gap structure and an outer-layer air gap structure are formed, and composite permanent magnetic field distribution is formed in a radial space, and the magnetic field distribution has two distribution forms of a series magnetic field and a parallel magnetic field.

Description

A Double Air Gap Magnetic Field Modulation Permanent Magnet Motor

technical field

The invention belongs to the technical field of motor manufacturing, and particularly refers to a permanent magnet drive motor suitable for electric vehicles, electric tractors and the like requiring high power density, high torque density and high efficiency.

Background technique

The magnetic field modulation permanent magnet motor with the characteristics of low speed and high torque is essentially inspired by the operation characteristics of the magnetic gear power transmission device, and skillfully extends the operation principle of the magnetic gear to the design of the motor, so that the permanent magnet magnetic field of the motor can be modulated to obtain The obvious feature of "magnetic field self-acceleration". Therefore, under the action of this magnetic field modulation effect, this type of motor usually has a relatively good low-speed and high-torque capability, and is used in electric propulsion applications such as electric vehicles and electric tractors.

The current magnetic field modulation-like permanent magnet motors have evolved into two main structural types, including: magnetic gear permanent magnet motors and vernier permanent magnet motors. The Chinese patent application No. 201610356757.3 proposes a complementary magnetic gear dual-rotor motor suitable for hybrid electric vehicle drive applications, including: an outer stator, an intermediate modulation ring rotor, and an inner spoke-type permanent magnet rotor. The magnetic inner rotor is divided into two sections along the axial direction by the magnetic barrier, and there is an offset angle between the two sections of the rotor. Through the module breaking and dislocation design of the permanent magnet rotor, the motor can obtain the pulsation compensation characteristic, so as to realize the weakening of the motor torque pulsation. However, the motor has two layers of air gaps in the radial structure space, so the utilization rate and power density of the permanent magnet magnet of the motor are affected to a certain extent. In addition, the intermediate modulation ring rotor is composed of a plurality of magnetic modulation blocks. It will inevitably lead to problems such as low mechanical strength and difficult processing technology, so that its application will be greatly limited. On the basis of retaining the operating principle of magnetic field modulation, a built-in tangential excitation vernier permanent magnet motor disclosed in the Chinese patent application No. 201710781179.2 integrates the intermediate modulation ring and the stator to form a slotted stator. Under the action of the magnetic field modulation effect, the design of multiple uniformly spaced tangentially magnetized permanent magnets on the circumference of the rotor ring not only improves the power density of the motor, but also has the driving characteristics of low speed and high torque. The more complex rotor structure design of the permanent magnet rotor affects the mechanical robustness of the motor. In addition, there are still problems such as the torque ripple of the motor and the difficulty in dissipating heat from the rotor.

Therefore, how to obtain a magnetic field modulated permanent magnet motor with high utilization rate of permanent magnet magnets, high efficiency and high operational reliability has become an urgent problem to be solved in the field of high torque density magnetic field modulation motor research.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems existing in the prior art, and to provide a double-air-gap magnetic field modulation permanent magnet for electric propulsion system with simple structure, high torque density, high efficiency, small torque ripple and high utilization rate of permanent magnet Motors to meet the performance requirements of modern electric vehicles, electric tractors and other driving occasions.

In order to achieve the above purpose, the technical scheme adopted in the present invention is: including a composite rotor and a stator, the composite rotor is composed of an outer rotor, an inner rotor and an end disc with a coaxial center line, the inner rotor is sleeved inside the outer rotor, and the outer rotor and The same end of the inner rotor is fixedly connected by the end disc; the stator is coaxially located between the outer rotor and the inner rotor, and the stator is composed of Ns stator core modules evenly distributed along the circumference, Ns=2*m, m is The number of phases of the motor; a permanent magnet steel is fixedly embedded in the middle of two adjacent stator core modules, the permanent magnet steel is tangentially magnetized along the circumference of the stator, and the magnetization directions of the two adjacent permanent magnet magnets are opposite; each The stator core module is composed of a U-shaped module in the outer layer of the radial section and an E-shaped module in the inner layer along the radial direction, the connecting part is the stator yoke, and the outer U-shaped module has 2 stator outer armature teeth and 1 outer groove, the inner E-type module has 2 stator inner armature teeth, 1 middle auxiliary modulation tooth and 2 inner grooves; three-phase concentrated windings are placed in the inner and outer grooves, and the centralized A single coil of the type winding is wound on the armature teeth of two adjacent stator core modules and the permanent magnet magnet in the middle.

The outer rotor consists of an outer rotor yoke and an outer rotor salient pole. N _r outer rotor salient poles are evenly distributed along the circumferential direction on the inner wall of the outer rotor yoke, and an outer rotor slot is formed between two adjacent outer rotor salient poles; The rotor yoke is composed of N _r inner rotor salient poles, N _r inner rotor salient poles are evenly distributed on the outer wall of the inner rotor yoke along the circumferential direction, and an inner rotor slot is formed between two adjacent inner rotor salient poles; N _r = N _s ±2.

The beneficial effect that the present invention has after adopting the above-mentioned technical scheme is:

1. The present invention adopts a composite double rotor structure and a modular stator core design, so that the motor can form the characteristics of an inner and outer two-layer air gap structure while satisfying the characteristics of a single stator fixed part and a single rotor moving part. The phenomenon of magnetic flux leakage between the poles of the traditional magnetic field modulation motor is alleviated, and the motor forms a composite permanent magnetic field distribution in the radial space, and has two distribution forms of series magnetic field and parallel magnetic field, so as to obtain the permanent magnetic field of the motor. Performance benefits of increased utilization.

2. Since the present invention adopts the composite double rotor topology structure, the total output torque of the motor is formed by the superposition of the torques on the inner and outer rotor cores. Compared with the traditional single air gap magnetic field modulation permanent magnet motor, the present invention can bring the performance advantage of effectively improving the torque density of the motor.

3. The present invention implements an inner and outer unequal arc design for the modular stator core armature teeth and the permanent magnetic steel, which is used to change the direction of the change rate of the relative position angle of the stator and rotor caused by the magnetic energy contained in the air gap, so that the The cogging torque generated by the inner and outer air gaps of the motor is phase-shifted, and after the composite double rotors are superimposed, they compensate and cancel each other, thereby achieving the purpose of reducing the total cogging torque of the motor and the effect of reducing the torque ripple of the motor.

4. The present invention implements an auxiliary modulating tooth design in the inner groove of the modular stator core, changes the harmonic characteristics of the magnetic field in the inner air gap, and reasonably adjusts the amplitude of the cogging torque generated by the air gap in the motor, so that the The beneficial effect of improving the effective compensation rate of motor cogging torque and torque ripple is achieved.

5. The present invention adopts the permanent magnet magnetic steel which is alternately tangentially magnetized on the circumference, so that the motor has the characteristics of magnetization, thereby improving the magnetic flux density of the air gap.

6. The present invention only uses one set of armature windings, which cleverly avoids the electromagnetic coupling problem caused by using two sets of armature windings in the traditional double-layer air-gap permanent magnet motor. In addition, since the auxiliary modulating tooth design is implemented in the inner groove of the modular stator iron core, it has the design effect of fault-tolerant teeth, and improves the stability and reliability of the normal operation of the motor.

Description of drawings

Fig. 1 is the radial structure schematic diagram of the present invention;

Figure 2 is a reduced axial view of the composite rotor in Figure 1;

Figure 3 is a radial cross-sectional view of the composite rotor of Figure 1;

4 is an enlarged schematic diagram of the structure and geometric dimension marking of two adjacent stator core modules and permanent magnet magnets in FIG. 1;

Fig. 5 is the distribution schematic diagram of the centralized winding in Fig. 1;

6 is a partial view and a schematic diagram of a magnetic flux path developed along the circumferential direction without adding an auxiliary modulating tooth design according to the present invention;

7 is a partial view and a schematic diagram of a magnetic flux path developed along the circumferential direction of the present invention;

Fig. 8 is the no-load magnetic field distribution diagram under the design of the present invention without adding auxiliary modulation teeth;

Fig. 9 is the no-load magnetic field distribution diagram of the present invention;

10 is a three-phase no-load back EMF waveform diagram under the design of the present invention without adding auxiliary modulation teeth;

11 is a three-phase no-load back EMF waveform diagram of the present invention;

12 is a waveform diagram of the output torque of the inner and outer rotor parts under the design of the present invention without adding auxiliary modulation teeth;

Fig. 13 is the output torque waveform diagram of the inner and outer rotor parts of the present invention;

14 is a waveform diagram of total output torque under the design of the present invention without adding auxiliary modulating teeth;

FIG. 15 is a waveform diagram of the total output torque of the present invention.

In the figure: 1. Composite rotor; 2. Stator; 3. Shaft; 4. Concentrated winding;

1.1 outer rotor; 1.2 inner rotor; 1.3 end disc;

1.1.1 Outer rotor yoke; 1.1.2 Outer rotor salient pole; 1.1.3 Outer rotor slot; 1.2.1 Inner rotor yoke; 1.2.2 Inner rotor core salient pole; 1.2.3 Inner rotor slot;

2.1 stator core module; 2.2 permanent magnet steel;

2.1.1 stator inner armature teeth; 2.1.2 stator outer armature teeth; 2.1.3 stator yoke; 2.1.4 auxiliary modulation teeth.

Detailed ways

1 and 2 , the present invention is a high permanent magnet utilization rate, low torque pulsating double air gap magnetic field modulation permanent magnet motor, including a composite rotor 1 , a stator 2 , a rotating shaft 3 and a centralized winding 4 . The outermost is the composite rotor 1, the middle is the rotating shaft 3, the stator 2 is coaxially sleeved between the composite rotors 1, the rotating shaft 3 and the composite rotor 1 rotate coaxially, and the stator 2 is wound with a centralized winding 4.

The composite rotor 1 consists of an outer rotor 1.1, an inner rotor 1.2 and an end disc 1.3. The inner rotor 1.2 is sleeved inside the outer rotor 1.1, and the three are coaxial. The same ends of the outer rotor 1.1 and the inner rotor 1.2 are fixedly connected together by the end disc 1.3, and the connection method is riveting or welding, so that the composite rotor 1 becomes a whole. The stator 2 is coaxially located between the outer rotor 1.1 and the inner rotor 1.2, and the center of the inner rotor 1.3 is used to place the shaft 3. There is a radial outer air gap between the inner wall of the outer rotor 1.1 and the outer wall of the stator 2, and there is a radial inner air gap between the inner wall of the stator 2 and the outer wall of the inner stator 1.2. The thickness of the inner and outer air gaps is related to the power level of the motor, the selected The permanent magnet material is related to the processing and assembly process of the composite rotor 1 and the stator 2. The outer rotor 1.1, the inner rotor 1.2 and the stator 2 are all laminated with silicon steel sheets with a thickness of 0.35mm, and the lamination coefficient is 0.95.

Referring to Fig. 3, the outer rotor 1.1 is a salient pole structure in structure, and the iron core of the outer rotor 1.1 has neither permanent magnets nor windings. The outer rotor 1.1 is composed of an outer rotor yoke 1.1.1 and an outer rotor salient pole 1.1.2. N _r outer rotor salient poles 1.1.2 are evenly distributed on the inner wall of the outer rotor yoke 1.1.1 along the circumferential direction. In order to avoid the influence of unilateral magnetic pulling force on motor performance, the value of N _r should be an even number. An outer rotor slot 1.1.3 is formed between two adjacent outer rotor salient poles 1.1.2. The radian occupied by the pole pitch between two adjacent outer rotor salient poles 1.1.2 is β _ro , and the radian occupied by the outer rotor pole pitch β _ro and the specific number N _r of the outer rotor salient poles 1.1.2 satisfy β _ro =2π/N _r , the arc occupied by the pole arc of the outer rotor salient pole 1.1.2 is β _rao , which satisfies β _rao =k _ro *β _ro , where k _ro is the pole arc coefficient of the outer rotor salient pole 1.1.2. The radian occupied by the outer rotor slot 1.1.3 is β _ryo , the radian occupied by the outer rotor slot 1.1.3 β ryo, β _ryo, the radian occupied by the outer rotor pole arc β _rao and the radian occupied by the pole pitch β _ro The relationship satisfies β _ryo + β _rao = _βro . The radius of the outer ring of the outer rotor 1.1 is _Roro , and the radius of the inner ring is R _ori . The values of _Roro and R _ori are related to the power of the motor.

Similar to the outer rotor 1.1, the inner rotor 1.2 is a salient pole structure in structure, and the inner rotor 1.2 has neither permanent magnets nor windings on its iron core. The inner rotor 1.2 is composed of the inner rotor yoke 1.2.1 and N _r inner rotor salient poles 1.2.2, and the N _r inner rotor salient poles 1.2.2 are evenly distributed along the outer wall of the inner rotor yoke 1.2.1, the inner rotor The number of salient poles 1.2.2 is the same as that of the outer rotor salient poles 1.1.2. An inner rotor slot 1.2.3 is formed between two adjacent inner rotor salient poles 1.2.2, and the pole pitch between two adjacent inner rotor salient poles 1.2.2 occupies an arc β _ri , and the inner rotor pole pitch occupies The radian β _ri and the specific number N _r of the rotor salient pole 1.2.2 satisfy β _ri =2π/N _r , and the radian occupied by the pole arc of the inner rotor salient pole 1.2.2 is β _rai , which satisfies β _rai =k _ri *β _r , where k _ri is the 1.2.2 pole arc coefficient of the inner rotor salient pole. The radian occupied by the inner rotor slot 1.2.3 is β _ryi , and the relationship between the radian occupied by the inner rotor slot 1.2.3 β _ryi , the radian occupied by the pole arc β _rai and the radian occupied by the pole pitch β _ri satisfies β _ryi +β _rai =β _ri . The radius of the outer ring of the inner rotor 1.2 is R _iro , the radius of the inner ring is R _iri , and the values of R _oro and R _ori are related to the power of the motor.

Referring to FIG. 4 , the stator 2 is composed of Ns stator iron core modules 2.1 evenly distributed along the circumference, and a permanent magnet magnetic steel 2.2 is fixedly embedded in the middle of two adjacent stator iron core modules 2.1. The number Ns of the stator core modules 2.1 satisfies Ns=2*m, where m is the number of motor phases. At the same time, the number of stator core modules 2.1, the number of outer rotor salient poles 1.1.2 and the number N _r of inner rotor salient poles 1.2.2 should satisfy the restriction condition: N _r =N _s ±2.

The geometric structure of each stator core module 2.1 is formed by radially combining a U-shaped module in the outer layer and an E-shaped module in the inner layer along the radial direction, and the connecting part forms the stator yoke 2.1.3. Therefore, the outer U-shaped module of each stator core module 2.1 in the radial direction has one outer layer groove, and the inner layer E-shaped module has two identical inner layer grooves, and the opening of the outer layer grooves faces radially. Outside, the openings of the inner layer grooves face radially inwards. Between the outer groove and the inner groove is the connecting part, namely the stator yoke 2.1.3. The radially outer U-shaped module of the stator yoke 2.1.3 has two identical left and right stator outer armature teeth 2.1.2, and the radially inner E-shaped module has left and right two identical stator inner armature teeth 2.1.1 and 1 auxiliary modulation tooth 2.1.4 in the middle.

The radian β _so occupied by the outer stator teeth 2.1.2 and the radian β _si occupied by the inner stator teeth 2.1.1 should satisfy: β _so =β _si . In order to maximize the ability of the armature teeth to pass through the magnetic field lines while expanding the space of the concentrated winding 4 so that the motor can obtain the maximum torque output capability, the radian _βso occupied by the outer armature teeth 2.1.2 is the same as the radian β occupied by a stator core module 2.1. _s should satisfy the constraints: 0.22< _{βso /βs<0.25} . At the same time, in order to avoid the magnetic saturation of the stator yoke part 2.1.3 and ensure the space of the concentrated winding 4, the stator yoke part 2.1.3 along the radial length h _sy of the motor and the outer armature teeth 2.1.2 along the radial length h _so And the radial length h _si of the inner armature teeth 2.1.1 should satisfy the constraints: 2.1<h _so /h _sy <2.3, 2.6<h _si /h _sy <2.8.

In order to fully improve the cogging torque and torque ripple of the inner rotor 1.2 of the motor so that the cogging torque and torque ripple of the inner rotor 1.2 and the outer rotor 1.1 are close to each other, the double rotor compensation can be more effectively achieved, and the auxiliary modulation gear 2.1.4 The tangential width w _st along the motor and the stator yoke 2.1.3 The radial length h _sy along the motor should satisfy the restriction: 0.55<w _st /h _sy <0.6.

The permanent magnet steel 2.2 is magnetized tangentially along the circumference of the stator, and the magnetization directions of two adjacent permanent magnet steels 2.2 are opposite. The permanent magnet steel 2.2 adopts a fan-shaped structure in design, that is, the radian β _pmo occupied by the inner end of the permanent magnet magnet 2.2 and the radian β _pmi occupied by the outer end of the permanent magnet magnet 2.2 satisfy: β _pmo = β _pmi . The outer diameter of the permanent magnet steel 2.2 is equal to the outer diameter of the stator core module 2.1, and the inner diameter is equal to the inner diameter of the stator core module 2.1.

Referring to Figure 5, the three-phase concentrated winding 4 is placed in the inner and outer grooves of the stator core module 2.1, and a single coil of the concentrated winding 4 is wound on the armature teeth and the adjacent two stator core modules 2.1. Above the permanent magnet 2.2 in the middle. In Figure 5, "+" is the incoming direction of the concentrated winding 4, "-" is the outgoing direction of the concentrated winding 4, and A, B, and C are the three-phase windings of the motor. In order to ensure the normal operation of the motor, the centralized winding 4-pole pair number Np, the outer rotor salient pole 1.1.2, the inner rotor salient pole 1.2.2 number Nr and the stator core module 2.1 number Ns should satisfy the basic principle of magnetic field modulation, that is, satisfy the Constraints: Np=|Ns/2-Nr|. At the same time, in order to ensure that the effective harmonic speed in the air gap of the motor is high so that the motor has a high torque output capability, the number of 4-pole pairs of the centralized winding should meet the restriction condition: Np<5. In addition, in order to reduce the length of the motor winding end and improve the efficiency of the motor, the requirements of the centralized winding 4 of the motor are:

In order to avoid the problem of electromagnetic coupling caused by using two sets of armature windings in the traditional double-layer air-gap permanent magnet motor, in the present invention, the inner armature teeth 2.1.1 of the stator 2 and the outer armature teeth 2.1.2 of the stator 2 are on the A set of centralized windings 4 are used. Therefore, during the operation of the motor, the back EMF and flux linkage generated in the inner and outer armature windings can be added algebraically; at the same time, it can be ensured that when the motor is running under load, the currents flowing into the inner and outer armature windings of the motor are the same. to ensure the best operation of the motor. At the same time, a set of centralized windings 4 are used on the inner armature teeth 2.1.1 and the outer armature teeth 2.1.2, which avoids the electromagnetic coupling problem caused by the traditional double-layer air-gap permanent magnet motor using two sets of armature windings.

During the operation of the present invention, the motor is different from the design of the present invention without adding auxiliary modulating teeth on the magnetic circuit. For details, refer to FIG. 6 and FIG. 7 . During the working process of the present invention, referring to FIG. 7 , the three magnetic circuits generated, the magnetic circuit a, the magnetic circuit b, and the magnetic circuit c, operate in parallel. Since the conventional magnetic field modulation motor does not have auxiliary modulation teeth, there is no magnetic circuit c during the operation of the motor. The operating path of the conventional magnetic circuit a is as follows: from the permanent magnetic steel 2.2, through the stator inner armature teeth 2.1.1, the inner rotor 1.2, the stator inner armature teeth 2.1.1, the permanent magnet magnetic steel 2.2, and the stator outer armature teeth 2.1. 2. The outer rotor 1.1 and the stator outer armature teeth 2.1.2, and finally return to the permanent magnet 2.2; the magnetic circuit b starts from the permanent magnet 2.2 and passes through the stator outer armature teeth 2.1.2, the outer rotor 1.1, and the stator outer electric The pivot teeth 2.1.2 and the stator yoke 2.1.3 finally return to the permanent magnet 2.2; the magnetic circuit c passes through the permanent magnet 2.2 times through the stator yoke 2.1.3, the auxiliary modulation teeth 2.1.4, and the inner rotor 1.2 , stator inner armature teeth 2.1.1, permanent magnet steel 2.2, stator outer armature teeth 2.1.2, outer rotor 1.1, stator outer armature teeth 2.1.2, and finally return to permanent magnet magnet 2.2. Among them, for the magnetic circuit c, the outer rotor 1.1 of the motor and the outer stator armature teeth 2.1.2 have exactly the same path as the magnetic circuit a, so the existence of the auxiliary modulation teeth 2.1.4 has an impact on the cogging torque and the output torque of the outer rotor 1.1 of the motor. The torque part has no effect; for the rotor 1.2 in the motor and the armature teeth 2.1.1 in the stator, part of the magnetic circuit c forms a closed magnetic circuit from the auxiliary modulation tooth 2.1.4, which can improve the cogging torque and torque ripple of the internal motor. , so that the amplitudes of the cogging torque and torque ripple of the inner rotor 1.2 of the motor and the outer rotor 1.1 of the motor are close to each other, and the mutual compensation is more effectively formed, thereby reducing the cogging torque and torque ripple of the motor.

Referring to Fig. 8 and Fig. 9, using the special structural design of the present invention, it is shown from the magnetic field distribution that the magnetic flux generated by the permanent magnet steel 2.2 forms two mutually independent magnetic fields through the outer rotor 1.1, the inner rotor 1.2 and the stator 2 at the same time. A magnetic field independent of the other two magnetic fields is also formed by the composite rotor 1 and the stator 2, and the three independent magnetic fields form the composite magnetic field of the motor. At the same time, compared with the motor without the auxiliary modulation teeth added in the present invention, due to the existence of the auxiliary modulation teeth 2.1.4, the magnetic flux leakage between the inner stator 1.2 and the inner stator armature teeth 2.1.1 is greatly reduced, so that the inner rotor 1.2 With the outer rotor 1.2 cogging torque and torque ripple tend to balance.

Referring to FIG. 10 and FIG. 11 , it is a no-load back EMF waveform diagram of the present invention and the design of the present invention without adding auxiliary modulation teeth. Compared with the motor without the auxiliary modulation tooth design of the present invention, the no-load back EMF waveform of the present invention is more sinusoidal, which means that the present invention has lower cogging torque and torque ripple, showing the auxiliary modulation tooth 2.1. 4 Good torque amplitude compensation capability.

Referring to Figures 12, 13, 14 and 15, they are respectively the internal and external output torque of the present invention without the addition of auxiliary modulation teeth, the internal and external output torque of the present invention, and the total output torque of the motor without the addition of auxiliary modulation teeth of the present invention. and the total output torque of the present invention. As can be seen from the figure, compared with the design of the present invention without the addition of auxiliary modulation teeth, the modulation effect of the auxiliary modulation teeth 2.1.4 effectively increases the torque ripple amplitude of the inner rotor 1.2 of the motor, making the inner rotor 1.2 and the outer rotor 1.2. 1.1 The amplitude of torque ripple tends to be the same, and the internal and external output torques achieve more effective compensation, thereby reducing the torque ripple of the total output torque of the motor. Therefore, the structure of the present invention significantly improves the stability and reliability of the motor.

Claims (5)

1. A double-air-gap magnetic field modulation permanent magnet motor, comprising a composite rotor (1) and a stator (2), wherein the composite rotor (1) consists of an outer rotor (1.1), an inner rotor (1.2) and an end portion of a coaxial line The inner rotor (1.2) is sleeved inside the outer rotor (1.1), and the same ends of the outer rotor (1.1) and the inner rotor (1.2) are fixedly connected by the end disc (1.3); the stator ( 2) Coaxially located between the outer rotor (1.1) and the inner rotor (1.2), the stator (2) is composed of Ns stator core modules (2.1) evenly distributed along the circumference, Ns=2*m, m is the motor phase A permanent magnet (2.2) is fixedly embedded in the middle of two adjacent stator core modules (2.1), and the permanent magnet (2.2) is tangentially magnetized along the circumference of the stator, and two adjacent permanent magnets are The magnetization directions of the steel (2.2) are opposite; each stator core module (2.1) is formed by radially combining U-shaped modules in the outer layer and E-shaped modules in the inner layer, and the connecting part is the stator yoke ( 2.1.3), the outer U-type module has 2 stator outer armature teeth (2.1.2) and 1 outer groove, the inner E-type module has 2 stator inner armature teeth (2.1.1), 1 2 middle auxiliary modulating teeth (2.1.4) and 2 inner layer grooves; three-phase concentrated windings (4) are placed in the inner and outer layer grooves, and a single coil of the concentrated winding (4) is wound on the adjacent two On the armature teeth of each stator core module (2.1) and the permanent magnet steel (2.2) in the middle, it is characterized in that: the outer stator armature teeth (2.1.2) occupy the radian _βso and the stator inner armature teeth (2.1 .1) The radian β _si occupied satisfies: β _so = β _si ; the radian β _so occupied by the outer armature teeth (2.1.2) and the radian β _s occupied by a stator core module (2.1) satisfy: 0.22<β _so /β _s <0.25; the radial length h _sy of the stator yoke (2.1.3) and the stator outer armature teeth (2.1.2) along the radial length h _so and the stator inner armature teeth (2.1.1) along the radial direction The length h _si satisfies: 2.1<h _so /h _sy <2.3, 2.6<h _si /h _sy <2.8; the auxiliary modulation teeth (2.1.4) along the tangential width w _st and the stator yoke (2.1.3) along the diameter The direction length h _sy satisfies: 0.55<w _st /h _sy <0.6. 2. A double-air-gap magnetic field modulation permanent magnet motor according to claim 1, characterized in that: the outer rotor (1.1) is composed of an outer rotor yoke (1.1.1) and an outer rotor salient pole (1.1.2), N _r outer rotor salient poles (1.1.2) are evenly distributed along the circumferential direction on the inner wall of the outer rotor yoke (1.1.1), and an outer rotor slot (1.1.2) is formed between two adjacent outer rotor salient poles (1.1.2). 3); the inner rotor (1.2) is composed of the inner rotor yoke (1.2.1) and N _r inner rotor salient poles (1.2.2), and the N _r inner rotor salient poles (1.2.2) are evenly distributed in the circumferential direction. On the outer wall of the inner rotor yoke (1.2.1), an inner rotor slot (1.2.3) is formed between two adjacent inner rotor salient poles (1.2.2); N _r =N _s ±2. 3. A kind of double-air-gap magnetic field modulation permanent magnet motor according to claim 2, characterized in that: the pole distance between two adjacent outer rotor salient poles (1.1.2) occupies a radian of β _ro , radian The relationship between β _ro and N _r satisfies β _ro =2π/N _r , the radian occupied by the pole arc of the outer rotor salient pole (1.1.2) is β _rao , which satisfies β _rao =k _ro *β _ro , k _ro is the outer rotor Salient pole (1.1.2) pole arc coefficient; the pole distance between two adjacent inner rotor salient poles (1.2.2) occupies a radian of β _ri , and the radian β _ri and N _r satisfy β _ri =2π/N _r , the arc occupied by the inner rotor salient pole (1.2.2) is β _rai , which satisfies β _rai = k _ri *β _r , where k _ri is the pole arc coefficient of the inner rotor salient pole (1.2.2). 4. The double-air-gap magnetic field modulation permanent magnet motor according to claim 1, characterized in that: the outer diameter of the permanent magnet steel (2.2) is equal to the outer diameter of the stator core module (2.1), and the inner diameter is equal to the stator iron The inner diameter of the core module (2.1). 5. A double-air-gap magnetic field modulation permanent magnet motor according to claim 1, characterized in that: the number of pole pairs Np of the concentrated winding (4) and the outer rotor salient poles (1.1.2), the inner rotor salient poles ( 1.2.2) The number Nr and the number Ns of stator core modules (2.1) satisfy: Np=|Ns/2-Nr|, Np<5,

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