Modulation magnetic field motor

Abstract

A modulation magnetic field motor is characterized in that A, a plurality of tooth grooves are arranged in a 360-degree mechanical space of the circumference of a stator, the number of the tooth grooves is Z, B, a stator winding is divided into m phases in the 360-degree mechanical space of the circumference of the stator, Z = m * n, n = 1, 2, 3,..., c, in a 360-degree mechanical space of the circumference of the stator, the number of pole pairs of a fundamental wave magnetomotive force magnetic field formed by a stator winding is Pm; d, the rotor magnets are sequentially arranged in the circumferential direction according to the N-pole and S-pole sequence, and the number of pole pairs of the rotor magnets formed in the 360-degree mechanical space along the circumference of the rotor is Pr; the number Pr of pole pairs of the rotor magnet of the modulated magnetic field motor must meet the following conditions: Pr = Z + / -Pm, Z / (2 * Pr) is not equal to 1, 1.5 * Pm < = Z, and [Z / (m * Pm))] is not equal to an integer.

Description

Technical Field

[0001] The present invention relates to an electric motor, and particularly to a modulated magnetic field motor. Background Art

[0002] The volume of an electric motor is related to the material usage cost and the required installation space. Especially for permanent magnet motors, since rare earth permanent magnet materials are non-renewable resources, it is urgent to design an electric motor with a smaller volume. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a modulated magnetic field motor in view of the deficiencies of the existing electric motors above, so as to reduce the volume and improve the power density.

[0004] The technical solution adopted by the present invention to solve the above problems is as follows: A modulated magnetic field motor, comprising: A. On the 360° mechanical space of the stator circumference, a number of tooth grooves are provided, and the number of grooves is Z. B. On the 360° mechanical space of the stator circumference, the stator winding is divided into m phases, Z = m×n, n = 1, 2, 3, …. C. On the 360° mechanical space of the stator circumference, the fundamental wave magnetomotive force magnetic field formed by the stator winding has a pole pair number of Pm. D. The rotor magnets are arranged in sequence according to the N pole and S pole in the circumferential direction. Along the 360° mechanical space of the rotor circumference, the pole pair number of the formed rotor magnets is Pr. It is characterized in that: the pole pair number Pr of the rotor magnets of the modulated magnetic field motor must satisfy: Pr = Z ± Pm, and Z / (2×Pr) ≠ 1, 1.5×Pm ≤ Z, and [Z / (m×Pm)] ≠ integer.

[0005] The following is a further description of the modulated magnetic field motor of the present invention: Principle of the modulated magnetic field motor: A. Whether it is BLDC control or PMSM control, the necessary condition for the rotation of the motor rotor is that the pole pair number of the magnetic field generated by the stator winding in the motor air gap is equal to the pole pair number of the rotor magnets; B. After the stator winding is energized, a fundamental wave magnetomotive force is generated in the motor air gap. Under the action of the stator tooth groove permeance, a series of modulated magnetic fields are distributed along the air gap space; C. When the pole pair number of a specific air gap harmonic magnetic field is equal to the pole pair number Pr of the rotor magnets, a stable electromagnetic torque will be output.

[0006] To meet the principle of the modulated magnetic field motor, the following conditions must be met: A. The pole pair number Pr of the rotor magnets of the modulated magnetic field motor must satisfy: Z ± Pm = Pr. And 1.5×Pm≤Z, and Z / m×Pm≠ integer, and Z / (2×Pr)≠1, and the reasons are as follows: ① According to Ampere's circuital law: ∑H×L = W×I = F, where, H - magnetic field strength, L - magnetic path length, W - number of turns of the coil, I - coil current, F - magnetomotive force; coil turns, I - coil current, F - magnetomotive force; ② In the closed magnetic circuit of the motor, it mainly forms a closed loop through ferromagnetic materials and the motor air gap. Therefore, the motor Ampere's circuital law is expressed as: H(δ)×L(δ)+H(ferromagnetic)×L(ferromagnetic)=W×I = F. Since in ferromagnetic materials, H(ferromagnetic) is very small and can be approximately zero, so H(δ)×L(δ)=W×I = F; ③ The relationship between magnetic induction intensity B and magnetic field strength H is: B = μ×H, where, μ - permeability; ④ Therefore, F = WI = B(δ)×L(δ) / μ0, where, μ0 - air permeability; ⑤ The magnetic induction intensity of the motor air gap can be expressed as: B(δ)=F×μ0 / L(δ)=F×ʌ(δ), where, ʌ(δ) - magnetic conductance of the motor air gap. The smaller the air gap, the greater the magnetic conductance; ⑥ The spatial distribution of the magnetomotive force F in the motor air gap is a rectangular wave and can be expressed according to Fourier series as: F(α)=(2 / π)×F×[sin(Pm×α)+(1 / 3)×sin(3×Pm×α)+ … +(1 / n)×sin(n×Pm×α)], where, n = 1, 2, 3..., α - represents the mechanical spatial angle along the circumferential direction of the air gap. It can be seen that the fundamental wave amplitude of the magnetomotive force is the largest, and the expression of the fundamental wave magnetomotive force is: F1(α)=(2 / π)×F×sin(Pm×α)=(2×WI / π)×sin(Pm×α) ⑦ The magnetic conductance ʌδ of the teeth in the motor air gap is approximately a rectangular wave in spatial distribution and can be expressed according to Fourier series as: ʌδ(α)=ʌ0+ʌ1×cos(Z×α)+ʌ2×cos(2×Z×α)+…+ʌn×cos(n×Z×α), where, n = 1, 2, 3..., the fundamental wave magnetic conductance amplitude is the largest, and its expression is: ʌδ1(α)=ʌ0+ʌ1×cos(Z×α); ⑧ The expression of the magnetic induction intensity generated by the fundamental wave magnetomotive force of the stator winding along the spatial distribution in the motor air gap under the modulation of the stator tooth magnetic conductance: B(α)=F×ʌ(δ)=(2×WI / π)×sin(Pm×α)×[ʌ0+ʌ1×cos(Z×α)] = Bm0×sin(Ps×α) + Bm1×sin(Pm×α)×cos(Z×α), where Bm0 = 2×WI×ʌ0 / π, Bm1 = 2×WI×ʌ1 / π. Using the trigonometric formula theorem: sin(a)×cos(b) = [sin(a + b) + sin(a - b)] / 2, transform the above formula to obtain: B(α) = Bm0×sin(Pm×α) + (Bm1 / 2)×sin[(Z + Pm)×α] + (Bm1 / 2)×sin[(Z - Pm)×α] As can be seen from the above formula, the fundamental magnetomotive force generated by the stator phase winding energization can generate the following three magnetic fields in the motor air gap: a. The fundamental magnetomotive force magnetic field with pole pair number Pm, and the nature of this magnetic field is equivalent to the magnetic field formed when the stator has no slots. b. The tooth harmonic permeance magnetic field with pole pair number (Z + Pm), and the nature of this magnetic field is equivalent to the magnetic field formed after the fundamental magnetomotive force is modulated by the stator teeth and slots. c. The tooth harmonic permeance magnetic field with pole pair number (Z - Pm), and the nature of this magnetic field is equivalent to the magnetic field formed after the fundamental magnetomotive force is modulated by the stator teeth and slots.

[0007] ⑨ Selection of the rotor magnet pole pair number Pr of the modulation magnetic field motor: a. According to the basic principle of motor operation, only when the pole pair number of the rotor magnetic field is equal to the pole pair number of the magnetic field formed by the stator winding, the motor will output a stable electromagnetic torque. b. According to the above principle, the rotor magnet pole pair number Pr of the modulation magnetic field motor must satisfy: Z + Pm = Pr or Z - Pm = Pr.

[0008] ⑩ Regarding Z / (2×Pr) ≠ 1 In addition to meeting the performance, the motor also requires the cogging torque to be as small as possible. The larger the number of cogging torque fluctuation cycles (the number of cycles of cogging torque fluctuation when the rotor rotates one week), the smaller the cogging torque. The number of cogging torque fluctuation cycles is the least common multiple of the number of rotor magnet poles and the number of stator teeth and slots of the motor.

[0009] When Z = 2×Pr, at this time the number of cogging torque fluctuation cycles = Z, and the motor cogging torque is the largest, so this condition is excluded.

[0010] B. Selection of the stator slot number Z of the modulation magnetic field motor: Z = m×n, where n = 1, 2, 3…, and the number of phases m of the motor is an integer; since Z / m = integer, the motor will work normally; since Z / m = n, so n takes integer values, where n = 1, 2, 3….

[0011] C. The stator winding of the modulated magnetic field motor is wound according to the designed number of pole pairs Pm of the stator magnetic field (magnetomotive force), and it must satisfy 1.5×Pm≤Z, and [Z / (m×Pm)]≠ integer. The reasons are as follows: To obtain a higher back electromotive force BEMF of the winding, a winding coefficient ≥0.866 is selected. According to the basic principle of the motor: winding coefficient = SIN{90°×number of slots spanned / [Z / (2×Pm)]}, and the selected number of slots spanned = |Z / (2×Pm)| rounded to the nearest integer (1, 2, 3...). If the winding coefficient ≥0.866, according to the properties of the sine function: 60°≤90°×number of slots spanned / [Z / (2×Pm)]≤120°. After rearrangement, 2 / 3≤number of slots spanned / [Z / (2×Pm)]≤4 / 3; When Z / (2×Pm)≥1, 2 / 3≤number of slots spanned / [Z / (2×Pm)]≤4 / 3 holds naturally; When Z / (2×Pm)<1, the number of slots spanned can only be 1, and it is inevitable that 2 / 3≤number of slots spanned / [Z / (2×Pm)]; If the condition of number of slots spanned (taking 1) / [Z / (2×Pm)]≤4 / 3 is to be satisfied, it must satisfy 2×Pm≤(4 / 3)×Z. After rearrangement, it is obtained that: 1.5×Pm≤Z.

[0012] The control method of the modulated magnetic field motor described above can be applied to the BLDC control method or the PMSM control method. Among them, BLDC is a square wave voltage (current) drive method, and PMSM is a sine wave voltage (current) drive method. These two are both common motor control methods and will not be described in detail.

[0013] Since the present invention adopts the modulated magnetic field motor with the above requirements, the reasons for its ability to improve the power density are as follows: A. Basic evaluation index of the permanent magnet motor: As a rotating mechanical device, the motor will inevitably generate vibration and noise, and the cogging torque ripple of the motor is an important source of the motor's vibration and noise. Therefore, while the motor pursues the power density (watts per liter) to the extreme, it must also reduce the cogging torque ripple at the same time to ensure that the motor's vibration and noise are within a reasonable range. Only in this way does it make practical sense to improve the power density.

[0014] B. The main means to improve the power density of the permanent magnet motor are as follows: a. Optimizing the magnetic circuit of the motor has limited improvement effect; b. Selecting a permanent magnet material with a higher energy product or a larger electromagnetic body will cause a significant increase in manufacturing cost; c. Reduce the air gap value between the motor stator and rotor: Basically, the amplitude of the air gap magnetic field is inversely proportional to the air gap value, so the improvement effect is obvious. However, since the amplitude of the cogging torque is proportional to the square of the amplitude of the air gap magnetic field, reducing the air gap value of the motor will significantly increase the cogging torque ripple of the motor, resulting in a significant increase in the vibration and noise of the motor.

[0015] C. Effective methods to reduce the amplitude of the motor cogging torque ripple.

[0016] a. Under the condition of maintaining a fixed air gap value of the motor, theoretical research shows that an effective method to reduce the motor cogging torque ripple is to increase the number of cogging torque fluctuation cycles of the motor. Among them, the number of fluctuation cycles is equal to the least common multiple of the number of stator slots and the number of rotor magnet poles; b. From the comparison results in the following table, it can be seen that for the modulated magnetic field motor of the present invention with the same number of stator slots, compared with the traditional permanent magnet motor, the number of cogging torque fluctuation cycles of the modulated magnetic field motor shows an obvious increasing trend. Therefore, it can greatly reduce the amplitude of the motor cogging torque ripple, thereby improving the power density of the permanent magnet motor.

[0017] Table 1 Comparison table of the number of fluctuation cycles between the modulated magnetic field motor and the traditional motor under the condition of the same number of stator slots

[0018] More specifically, the rotor magnet can be a permanent magnet or an electromagnet.

[0019] Preferably, the inner arc surface, the left inclined surface of the dovetail groove, and the right inclined surface of the dovetail groove of the rotor lamination are respectively matched with the outer arc surface, the left inclined surface, and the right inclined surface of the permanent magnet for radial and circumferential positioning of the permanent magnet, improving the positioning accuracy of the permanent magnet to ensure the smooth operation of the modulated magnetic field motor.

[0020] Preferably, radial holes and axial holes are provided on the motor shaft of the stator assembly to facilitate the wire harness to pass through the radial holes and pass through the axial holes.

[0021] Preferably, elastic fixing clips and positioning posts are provided on the stator assembly, which can improve the positioning accuracy of the control module and make its fixation more firm and reliable.

[0022] Alternatively, the permanent magnet of the rotor assembly and the housing are designed to be connected in a surface-mounted manner, without using the rotor lamination and dovetail groove structure for positioning, and an auxiliary tooling is used for positioning during the bonding process of the permanent magnet.

[0023] Alternatively, considering the convenience of the processing process, a permanent magnet is divided into multiple segments, which can achieve equivalent performance.

[0024] Alternatively, the modulated magnetic field motor is designed as an outer stator and inner rotor according to different uses, which can achieve equivalent performance.

[0025] Alternatively, the modulation magnetic field motor is designed as an outer stator and inner rotor, and the permanent magnets of the rotor assembly can be bonded in a surface-mounted manner or an embedded manner, achieving equivalent performance.

[0026] Alternatively, the modulation magnetic field motor is designed as an outer stator and inner rotor structure, adopting a PMSM control method. The permanent magnets of the rotor assembly can be embedded, achieving equivalent performance.

[0027] Compared with the prior art, the advantages of the present invention are as follows: Through the combination of the set number of stator slots and the number of rotor magnet poles, the modulation magnetic field motor of the present invention greatly increases the number of cogging torque fluctuation cycles, so that a smaller motor air gap can be adopted, greatly increasing the air gap magnetic field strength, enabling the output power of the modulation magnetic field motor to increase proportionally, and the power volume density of the modulation magnetic field motor also increasing proportionally. Compared with traditional motors, under the condition of the same output power, the volume of the modulation magnetic field motor is reduced by more than half, that is, the weight of the modulation magnetic field motor is also reduced by more than half. Therefore, the cost of motor materials can be significantly saved, especially the cost of rare earth permanent magnet materials, greatly enhancing the competitive advantage of the product.

[0028] The modulation magnetic field motor of the present invention can be matched with traditional BLDC and PMSM motor control modules, and has strong versatility in control. Therefore, it is also convenient for the iterative update of existing motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a perspective view of the modulation magnetic field motor according to an embodiment of the present invention.

[0030] Figure 2 is an exploded schematic view of the modulation magnetic field motor according to an embodiment of the present invention.

[0031] Figure 3 is a structural schematic view of the modulation magnetic field motor according to an embodiment of the present invention.

[0032] Figure 4a is Figure 3 a partial view of the sectional view taken along line A-A in

[0033] Figure 4b is Figure 3 a partial view of the sectional view taken along line B-B in

[0034] Figure 5a is Figure 4a a partial enlarged view of F in

[0035] Figure 5b is Figure 4b a partial enlarged view of P in

[0036] Figure 6It is an exploded view of the rotor assembly according to an embodiment of the present invention.

[0037] Figure 7 is Figure 6 a partially enlarged view of the local rotation of W in

[0038] Figure 8 It is a three-dimensional view of the permanent magnet according to an embodiment of the present invention.

[0039] Figure 9 It is an exploded view of the stator assembly according to an embodiment of the present invention.

[0040] Figure 10 It is a cross-sectional view of the motor shaft according to an embodiment of the present invention.

[0041] Figure 11 It is a structural diagram of the outer rotor of the modulation magnetic field motor according to another embodiment of the present invention.

[0042] Figure 12 It is a structural diagram of the inner rotor of the modulation magnetic field motor according to another embodiment of the present invention.

[0043] Figure 13 It is a structural diagram of the inner rotor of the modulation magnetic field motor according to still another embodiment of the present invention.

[0044] Figure 14 It is a structural diagram of the inner rotor of the modulation magnetic field motor according to still another embodiment of the present invention.

[0045] Figure 15 It is a structural diagram of the rotor magnetic pole as an electromagnet according to another embodiment of the present invention, which is obtained by Figure 5b replacing the permanent magnet in Detailed implementation manners

[0046] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0047] As Figure 1 , 2 shown, a modulation magnetic field motor includes a rotor assembly 1, a stator assembly 2, a control module 3, and a wire harness 4, and the wire harness 4 and the control module 3 are placed inside the modulation magnetic field motor body.

[0048] When the modulation magnetic field motor is powered on and operates, torque is output through the rotation of the rotor assembly 1 to realize the conversion of electrical energy into mechanical energy.

[0049] As Figures 3 to 10 shown, the rotor assembly 1 includes a housing 11, a rotor lamination 12, and a permanent magnet 13.

[0050] The rotor lamination 12 is bonded to the inner circular surface of the housing 11 by an adhesive.

[0051] The rotor lamination 12 is evenly provided with 34 permanent magnets on the inner circle, that is, 17 pairs of poles.

[0052] The inner arc surface 1201, the left inclined surface 1202 of the dovetail groove, and the right inclined surface 1203 of the dovetail groove of the rotor lamination 12 are respectively matched with the outer arc surface 1301, the left inclined surface 1302, and the right inclined surface 1303 of the permanent magnet 13 to position the permanent magnet 13 in the radial and circumferential directions, and are adhesively bonded in the dovetail groove of the rotor lamination 12 in an alternating arrangement of N poles and S poles to improve the running stability of the modulated magnetic field motor.

[0053] The lamination of the stator assembly 2 is evenly provided with 12 tooth grooves 121 on the outer circle. The fundamental pole pair number of the fundamental magnetomotive force of each phase winding is 5, and the number of turns of each phase winding is 4.

[0054] Each phase winding has 2 element sides. Each stator slot is designed with a double-layer winding, and 2 element sides are placed on the upper and lower layers or on the left and right sides. The number of stator slots is equal to the total number of phase windings.

[0055] The outer circle of the lamination of the stator assembly 2 and the permanent magnet 13 of the rotor assembly 1 form the air gap L of the modulated magnetic field motor.

[0056] The wire harness 4 and the control module 3 are connected by welding.

[0057] The stator assembly 2 is provided with elastic fixing clips 212 and positioning posts 213 to position and fix the control module 3, making the fixing of the control module 3 more firm and reliable.

[0058] Radial holes 2111 and axial holes 2112 are provided on the motor shaft 211 of the stator assembly 2 to facilitate the wire harness 4 to pass through the radial holes 2111 and pass through the axial holes 2112 to realize the extraction of the wire harness 4.

[0059] The cylindrical bearings 23 and 28 provided by the stator assembly 2 are fixed in the housing 11 of the rotor assembly 1 and play a role in supporting and positioning the rotor assembly 1. The rotor assembly can rotate in the circumferential direction when the modulated magnetic field motor is powered on.

[0060] The stator assembly 2 is provided with stop rings 25 and 26 to fix the cylindrical bearings 23 and 28 respectively to axially limit the rotor assembly 1, and the wear-resistant gaskets 24 and 27 provided play a role in reducing friction.

[0061] In this embodiment, the motor is designed with the number of stator slots Z = 12, the rotor magnetic field uses permanent magnets, the pole pair number Pr = 17, the fundamental pole pair number Pm of the fundamental magnetomotive force magnetic field of the stator winding is 5, and the number of phases m = 3.

[0062] As can be seen from Table 1, since the motor parameters that meet the requirements of the present invention are adopted: Pr = Z ± Pm, and Z / (2×Pr) ≠ 1, 1.5×Pm ≤ Z, and [Z / (m×Pm)] ≠ integer, therefore, it has a higher cogging torque fluctuation period number than the existing permanent magnet motors, thus being able to improve the power density. Under the condition of the same output power, the volume of the modulated magnetic field motor is reduced by more than half, that is, the weight of the modulated magnetic field motor is also reduced by more than half.

[0063] As Figure 11 shown, the permanent magnets N and S of the rotor assembly are designed to be connected to the housing 111 in a surface-mounted manner. Without using the dovetail groove positioning of the rotor lamination, it can also achieve the same positioning effect on the permanent magnets.

[0064] As Figure 12 and Figure 13 shown, the modulated magnetic field motor is designed with an outer stator and an inner rotor structure. The permanent magnets N and S of the rotor assembly are connected to the rotor lamination 222 in a surface-mounted or surface-embedded manner, and the same performance can be achieved.

[0065] As Figure 14 shown, the modulated magnetic field motor is designed with an outer stator and an inner rotor structure and adopts a PMSM control method. The permanent magnets N and S of the rotor assembly can be embedded, and the same performance can also be achieved.

[0066] As Figure 15 shown, the N and S poles of the permanent magnet 13 of the rotor assembly (see Figure 5b ) can be changed to electromagnets. The electromagnet includes an exciting winding 15 and a pole shoe 16, and the exciting winding 15 is wound around the pole shoe 16 to form an electromagnet.

Claims

1. A modulated magnetic field motor, comprising: A. On the 360° mechanical space of the stator circumference, a number of tooth grooves are provided, and the number of grooves is Z. B. On the 360° mechanical space of the stator circumference, the stator winding is divided into m phases, Z = m×n, where n = 1, 2, 3, …. C. On the 360° mechanical space of the stator circumference, the fundamental magnetomotive force magnetic field formed by the stator winding has a pole pair number of Pm. D. The rotor magnets are arranged in sequence according to the N pole and S pole in the circumferential direction. Along the 360° mechanical space of the rotor circumference, the pole pair number of the formed rotor magnets is Pr. It is characterized in that the pole pair number Pr of the rotor magnets of the modulated magnetic field motor must satisfy: Pr = Z ± Pm, and Z / (2×Pr) ≠ 1, 1.5×Pm ≤ Z, and [Z / (m×Pm)] ≠ integer.

2. The modulated magnetic field motor according to claim 1, wherein: The number of tooth grooves Z = 12, the pole pair number Pr of the rotor magnetic field = 17, the pole pair number Pm of the fundamental magnetomotive force magnetic field = 5, and the number of phases m = 3.

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