A modulated magnetic field motor

Abstract

This utility model discloses a modulated magnetic field motor, comprising: A. a plurality of slots, Z, arranged in a 360° mechanical space around the stator circumference; B. the stator windings are divided into m phases, Z = m × n, n = 1, 2, 3, ..., in the 360° mechanical space around the stator circumference; C. the number of pole pairs of the fundamental magnetomotive force magnetic field formed by the stator windings in the 360° mechanical space around the stator circumference is Pm; D. the rotor magnets are arranged sequentially in the circumferential direction according to the N pole and S pole order, and the number of rotor magnet pole pairs formed along the 360° mechanical space around the rotor circumference is Pr; the number of rotor magnet pole pairs Pr 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.

Description

Technical Field

[0001] This utility model relates to an electric motor, and more particularly to a modulated magnetic field motor. Background Technology

[0002] The size of an electric motor is related to the cost of materials used and the required installation space, especially for permanent magnet motors. Since rare earth permanent magnet materials are non-renewable resources, there is an urgent need to design a smaller motor. Summary of the Invention

[0003] The technical problem to be solved by this utility model is to provide a modulated magnetic field motor that can reduce the size and increase the power density, thereby addressing the shortcomings of the existing motors.

[0004] The technical solution adopted by this utility model to solve the above-mentioned problems is as follows:

[0005] A modulated magnetic field motor, comprising:

[0006] A. A number of toothed slots, Z in number, are set on the 360° mechanical space around the stator circumference.

[0007] B. In the 360° mechanical space of the stator circumference, the stator winding is divided into m phases, Z=m×n, n=1,2,3, …;

[0008] C. The number of pole pairs of the fundamental magnetomotive force magnetic field formed by the stator winding in the 360° mechanical space of the stator circumference is Pm;

[0009] D. The rotor magnets are arranged in the order of N pole and S pole in the circumferential direction. The number of rotor magnet pole pairs formed along the 360° mechanical space of the rotor circumference is Pr.

[0010] The characteristic is that the number of pole pairs Pr of the rotor magnet 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.

[0011] The modulated magnetic field motor of this utility model is further described below:

[0012] The principle of a modulated magnetic field motor: A. Regardless of whether it is controlled by BLDC or PMSM, the necessary condition for the motor rotor to rotate is that the number of pole pairs of the magnetic field generated by the stator winding in the motor air gap is equal to the number of pole pairs of the rotor magnet; B. After the stator winding is energized, a fundamental magnetomotive force is generated in the motor air gap. Under the action of the stator tooth cogging magnetic permeability, a series of modulated magnetic fields are distributed along the air gap space; C. When the number of pole pairs of a specific air gap harmonic magnetic field is equal to the number of pole pairs Pr of the rotor magnet, a stable electromagnetic torque will be output.

[0013] To satisfy the principle of a modulated magnetic field motor, the following conditions must be met:

[0014] A. The number of rotor magnet pole pairs Pr of a modulated magnetic field motor must satisfy: Z ± Pm = Pr.

[0015] Furthermore, 1.5 × Pm ≤ Z, and Z / m × Pm ≠ integer, and Z / (2 × Pr) ≠ 1, for the following reasons:

[0016] ①According to Ampere's circuital law: ∑H×L=W×I=F, where H—magnetic field strength, L—magnetic circuit length, W—linear magnetic field strength.

[0017] Number of turns; I—coil current; F—magnetic motive force;

[0018] ② In the closed loop of the motor magnetic field, the loop is mainly formed by ferromagnetic material and the air gap of the motor. Therefore, Ampere's circuital law for the motor is expressed as: H(δ)×L(δ)+H(ferromagnetic)×L(ferromagnetic)=W×I=F. Since H(ferromagnetic) is very small in ferromagnetic material and can be approximately equal to zero, H(δ)×L(δ)=W×I=F.

[0019] ③ The relationship between magnetic induction intensity B and magnetic field intensity H is: B = μ × H, where μ is the permeability;

[0020] ④ Therefore, F=WI=B(δ)×L(δ) / μ0, where μ0—air permeability;

[0021] ⑤ The magnetic induction intensity of the air gap of the motor can be expressed as: B(δ)=F×μ0 / L(δ)=F×ʌ(δ), where ʌ(δ) — the magnetic permeability of the air gap of the motor. The smaller the air gap, the greater the magnetic permeability.

[0022] ⑥ The magnetomotive force F is spatially distributed as a rectangular wave in the air gap of the motor, which can be expressed as a Fourier series:

[0023] F(α)=(2 / π)×F×[sin(Pm×α)+(1 / 3)×sin(3×Pm×α)+ … +(1 / n)×sin(n×Pm×α)],

[0024] Where n = 1, 2, 3 ..., α — represents the mechanical spatial angle along the circumference of the air gap. It can be seen that the magnetomotive force...

[0025] The fundamental wave has the largest amplitude, and the expression for the fundamental wave magnetomotive force is:

[0026] F1(α)=(2 / π)×F×sin(Pm×α)=(2×WI / π)×sin(Pm×α)

[0027] ⑦ The air gap tooth permeability ʌδ of the motor is spatially distributed as an approximate rectangular wave, which can be expressed as follows according to the Fourier series:

[0028] ʌδ(α)=ʌ0+ʌ1×cos(Z×α)+ʌ2×cos(2×Z×α)+…+ʌn×cos(n×Z×α), where,

[0029] For n=1, 2, 3 ..., the fundamental magnetic permeability amplitude is the largest, and its expression is: ʌδ1(α)=ʌ0+ʌ1×cos(Z×α);

[0030] ⑧ The expression for the magnetic induction intensity generated by the fundamental magnetomotive force of the stator winding in the air gap of the motor under the modulation of the stator tooth permeability is as follows:

[0031] B(α)=F×ʌ(δ)=(2×WI / π)×sin(Pm×α)×[ʌ0+ʌ1×cos(Z×α)]

[0032] =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(ab)] / 2, we can transform the above formula to obtain:

[0033] B(α)=Bm0×sin(Pm×α)+(Bm1 / 2)×sin[(Z+Pm)×α]+(Bm1 / 2)×sin[(Z-Pm)×α]

[0034] As can be seen from the above equation, the fundamental magnetomotive force generated by the energization of the stator phase windings can produce the following three magnetic fields in the air gap of the motor:

[0035] a. A fundamental magnetomotive force magnetic field with a pole pair number of Pm, the properties of which are equivalent to the magnetic field formed when the stator has no slots;

[0036] b. A tooth harmonic magnetic field with a pole pair number of (Z+Pm), the nature of which is equivalent to the magnetic field formed after the fundamental magnetomotive force is modulated by the stator slots;

[0037] c. A tooth harmonic magnetic field with a pole pair number of (Z-Pm) is a magnetic field whose properties are equivalent to the magnetic field formed after the fundamental magnetomotive force is modulated by the stator slots.

[0038] ⑨ Selection of the number of rotor magnet pairs Pr for a modulated magnetic field motor:

[0039] a. According to the basic operating principle of motors, the motor will only output a stable electromagnetic torque when the number of rotor magnetic field pole pairs is equal to the number of magnetic field pole pairs formed by the stator windings.

[0040] b. Based on the above principle, the number of rotor magnet pole pairs Pr of the modulated magnetic field motor must satisfy: Z + Pm = Pr or Z - Pm = Pr.

[0041] ⑩ Regarding Z / (2×Pr)≠1

[0042] In addition to meeting performance requirements, motors also need to minimize cogging torque. The larger the number of cogging torque fluctuation cycles (the number of cycles of cogging torque fluctuation in one revolution of the rotor), 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 slots.

[0043] When Z = 2 × Pr, the number of cycles of cogging torque fluctuation is Z, and the motor cogging torque is at its maximum, so this condition is excluded.

[0044] B. Selection of the number of stator slots Z of the modulated magnetic field motor: Z = m×n, where n=1, 2, 3…, and the number of phases m of the motor is an integer; the motor will work normally only if Z / m=an integer; since Z / m=n, n takes the value of an integer, where n=1, 2, 3….

[0045] C. The stator winding of the modulated field motor, wound according to the designed number of stator magnetic field (magnetomotive force) pole pairs Pm, must satisfy 1.5×Pm≤Z, and [Z / (m×Pm)]≠integer, for the following reasons:

[0046] To obtain a high back electromotive force (BEMF) of the winding, a winding factor ≥ 0.866 is selected. According to the basic principle of motors, the winding factor = SIN{ 90° × number of slots / [Z / (2 × Pm)]}. The selected number of slots = |Z / (2 × Pm)| is taken as the closest integer (1, 2, 3, ...). If the winding factor is to be ≥ 0.866, according to the properties of the sine function: 60° ≤ 90° × number of slots / [Z / (2 × Pm)] ≤ 120°, we can deduce that 2 / 3 ≤ number of slots / [Z / (2 × Pm)] ≤ 4 / 3.

[0047] When Z / (2×Pm)≥1, the following holds true: 2 / 3≤number of slots / [Z / (2×Pm)]≤4 / 3.

[0048] When Z / (2×Pm)<1, the span distance can only be 1, which necessarily leads to 2 / 3≤span number of spans / [Z / (2×Pm)];

[0049] To satisfy the condition that the number of slots spanned (take 1) / [Z / (2 × Pm)] ≤ 4 / 3, it is necessary to satisfy 2 × Pm ≤ (4 / 3) × Z. After simplification, we get: 1.5 × Pm ≤ Z.

[0050] The control method of the modulated magnetic field motor can be applied to either BLDC control or PMSM control. BLDC is a square wave voltage (current) drive method, and PMSM is a sine wave voltage (current) drive method. Both of these are common motor control methods and will not be described in detail.

[0051] The reason why this utility model can improve the power volume density is as follows, because it adopts the modulated magnetic field motor as described above:

[0052] A. Basic evaluation indicators of permanent magnet motors: As a rotating mechanical device, motors inevitably generate vibration and noise. The cogging torque pulsation of motors is an important source of motor vibration and noise. Therefore, while pursuing the ultimate power volume density (watts per liter), motors must also reduce cogging torque pulsation to ensure that motor vibration and noise are within a reasonable range. Only in this way can improving power volume density have practical significance.

[0053] B. The main methods to increase the power volume density of permanent magnet motors are as follows:

[0054] a. Optimizing the motor's magnetic circuit has limited effect;

[0055] b. Using permanent magnet materials with higher magnetic energy products or larger electromagnets will significantly increase manufacturing costs;

[0056] c. Reduce the air gap between the stator and rotor of the motor: 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 pulsation of the motor, which will also significantly increase the vibration and noise of the motor.

[0057] C. Effective methods to reduce the amplitude of motor cogging torque pulsation.

[0058] a. Under the condition of maintaining a fixed air gap value of the motor, theoretical research shows that an effective way to reduce the cogging torque pulsation of the motor is to increase the number of cogging torque pulsation cycles, where the number of pulsation cycles is equal to the least common multiple of the number of stator slots and the number of rotor magnet poles;

[0059] b. As can be seen from the comparison results in the table below, when the number of stator slots is the same, the modulated magnetic field motor of this utility model shows a significant increase in the number of cogging torque fluctuation cycles compared to the traditional permanent magnet motor. Therefore, it can greatly reduce the amplitude of motor cogging torque pulsation, thereby improving the power volume density of the permanent magnet motor.

[0060] Table 1. Comparison of the number of oscillation cycles between modulated magnetic field motors and conventional motors under the same stator slot number condition.

[0061]

[0062] More specifically, the rotor magnet can be a permanent magnet or an electromagnet.

[0063] Better still, the inner arc surface, left inclined surface and right inclined surface of the dovetail groove of the rotor lamination are respectively matched with the outer arc surface, left inclined surface and right inclined surface of the permanent magnet to position the permanent magnet in the radial and circumferential directions, thereby improving the positioning accuracy of the permanent magnet and ensuring the smooth operation of the modulated magnetic field motor.

[0064] Better still, the stator assembly has radial and axial holes on the motor shaft to facilitate the wire harness passing through the radial holes and through the axial holes.

[0065] Even better, the stator assembly is provided with elastic fixing clips and positioning posts, which can improve the positioning accuracy of the control module and make it more secure and reliable.

[0066] Alternatively, the permanent magnets of the rotor assembly are connected to the housing via surface mounting, without using rotor laminations or dovetail groove structures for positioning. The permanent magnet bonding process uses auxiliary tooling for positioning.

[0067] Alternatively, considering the ease of processing, the permanent magnet can be divided into multiple segments to achieve the same performance.

[0068] Alternatively, the modulated magnetic field motor can be designed with an outer stator and an inner rotor, depending on the application, to achieve equivalent performance.

[0069] Alternatively, the modulated magnetic field motor is designed with an outer stator and an inner rotor. The permanent magnets of the rotor assembly can be bonded using either surface mounting or surface embedding methods, achieving equivalent performance.

[0070] Alternatively, the modulated magnetic field motor is designed with an external stator and internal rotor structure and adopts PMSM control. The permanent magnets of the rotor assembly can be embedded to achieve equivalent performance.

[0071] Compared with existing technologies, the advantages of this invention are as follows: The modulated magnetic field motor of this invention, through a set combination of stator slot number and rotor magnet pole number, significantly increases the number of cogging torque fluctuation cycles, thereby allowing for a smaller motor air gap and a substantial increase in air gap magnetic field strength. This results in a proportional increase in the output power of the modulated magnetic field motor, and its power volume density also increases proportionally. Compared with traditional motors, under the same output power conditions, the volume of the modulated magnetic field motor is reduced by more than half, meaning its weight is also reduced by more than half. Therefore, it significantly saves on motor material costs, especially the cost of rare-earth permanent magnet materials, greatly enhancing the product's competitive advantage.

[0072] The modulated magnetic field motor of this invention can be matched with traditional BLDC and PMSM motor control modules, and its control has strong versatility. Therefore, it is also convenient for iterative updates of existing motors. Attached Figure Description

[0073] Figure 1 This is a perspective view of the modulated magnetic field motor according to an embodiment of the present invention.

[0074] Figure 2 This is an exploded view of the modulated magnetic field motor according to an embodiment of the present invention.

[0075] Figure 3 This is a schematic diagram of the structure of the modulated magnetic field motor according to an embodiment of the present invention.

[0076] Figure 4a yes Figure 3 A partial view of the AA section.

[0077] Figure 4b yes Figure 3 A partial view of the BB section.

[0078] Figure 5a yes Figure 4a A magnified view of part F.

[0079] Figure 5b yes Figure 4b A magnified view of part P.

[0080] Figure 6 This is an exploded view of the rotor assembly according to an embodiment of the present invention.

[0081] Figure 7 yes Figure 6 A magnified view of the local rotation of W.

[0082] Figure 8 This is a perspective view of the magnet in an embodiment of this utility model.

[0083] Figure 9 This is an exploded view of the stator assembly according to an embodiment of the present invention.

[0084] Figure 10 This is a cross-sectional view of the motor shaft in an embodiment of this utility model.

[0085] Figure 11 This is a schematic diagram of the external structure of a modulated magnetic field motor according to another embodiment of the present invention.

[0086] Figure 12 This is a schematic diagram of the structure of a modulated magnetic field motor rotor, which is another embodiment of this utility model.

[0087] Figure 13 This is a schematic diagram of the structure of a modulated magnetic field motor rotor, which is another embodiment of this utility model.

[0088] Figure 14 This is a schematic diagram of the structure of a modulated magnetic field motor rotor, which is another embodiment of this utility model.

[0089] Figure 15 This is a schematic diagram of the structure of the rotor magnet and the electromagnet of another embodiment of the present invention, which consists of... Figure 5b The permanent magnet was replaced with an electromagnet. Detailed Implementation

[0090] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0091] like Figure 1 , 2 As shown, a modulated magnetic field motor includes a rotor assembly 1, a stator assembly 2, a control module 3, and a wiring harness 4, wherein the wiring harness 4 and the control module 3 are placed inside the modulated magnetic field motor body.

[0092] When the modulated magnetic field motor is powered on, it outputs torque through the rotation of rotor assembly 1, thereby converting electrical energy into mechanical energy.

[0093] like Figures 3 to 10 As shown, the rotor assembly 1 includes a housing 11, rotor laminations 12, and permanent magnets 13.

[0094] The rotor laminations 12 are bonded to the inner circular surface of the housing 11 with an adhesive.

[0095] The rotor lamination 12 has 34 permanent magnets evenly arranged on its inner circle, i.e., 17 pairs of poles.

[0096] The rotor laminations 12 are provided with an inner arc surface 1201, a left inclined surface 1202 and a right inclined surface 1203 of the dovetail groove, which respectively cooperate 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. They are also bonded to the dovetail grooves of the rotor laminations 12 with an adhesive in an alternating N pole and S pole arrangement to improve the smooth operation of the modulated magnetic field motor.

[0097] The stator assembly 2 has 12 slots 121 evenly arranged on its outer circumference, and the number of fundamental magnetomotive force pole pairs per phase coil is 5, and the number of coils per phase is 4.

[0098] Each coil has two element sides, and each stator slot is designed with a double-layer winding, with two element sides placed on the top and bottom layers or on the left and right sides. The number of stator slots is equal to the total number of coils.

[0099] The outer circle of the laminations of the stator assembly 2 and the permanent magnet 13 of the rotor assembly 1 form a modulated magnetic field motor air gap L.

[0100] The wiring harness 4 is connected to the control module 3 by welding.

[0101] The stator assembly 2 is equipped with an elastic fixing clip 212 and a positioning post 213 to position and fix the control module 3, making the fixation of the control module 3 more secure and reliable.

[0102] The stator assembly 2 has a radial hole 2111 and an axial hole 2112 on its motor shaft 211 to facilitate the wire harness 4 to pass through the radial hole 2111 and through the axial hole 2112, thereby enabling the wire harness 4 to be led out.

[0103] The cylindrical bearings 23 and 28 of the stator assembly 2 are fixed inside the housing 11 of the rotor assembly 1 and provide support and positioning for the rotor assembly 1. When the modulated magnetic field motor is powered on, the rotor assembly can rotate in a circumferential direction.

[0104] The stator assembly 2 is provided with stop rings 25 and 26 to fix the cylindrical bearings 23 and 28 respectively, so as to achieve axial positioning of the rotor assembly 1. The wear-resistant shims 24 and 27 are provided to reduce friction.

[0105] In this embodiment, the motor is designed with 12 stator slots, a permanent magnet rotor magnetic field with 17 pole pairs (Pr), a fundamental magnetomotive force magnetic field with 5 pole pairs (Pm), and 3 phases (m).

[0106] As shown in Table 1, due to the adoption of motor parameters that meet the requirements of this utility model: Pr=Z±Pm, and Z / (2×Pr)≠1, 1.5×Pm≤Z, and [Z / (m×Pm))]≠integer, it has a higher number of cogging torque fluctuation cycles than existing permanent magnet motors, thereby improving the power volume density. Under the same output power conditions, 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.

[0107] like Figure 11 As shown, the permanent magnets N and S of the rotor assembly are connected to the housing 111 by surface mounting. The positioning effect of the permanent magnets can be achieved without using the dovetail groove positioning of the rotor laminations.

[0108] like Figure 12 and Figure 13 As 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 bonded to the rotor laminations 222 by surface mounting or surface embedding, which can achieve equivalent performance.

[0109] like Figure 14 As shown, the modulated magnetic field motor is designed with an outer stator and an inner rotor structure and adopts PMSM control. The permanent magnets N and S of the rotor assembly can be embedded to achieve the same performance.

[0110] like Figure 15As shown, the N and S poles of the permanent magnet 13 of the rotor assembly (see...) Figure 5b It can be replaced with an electromagnet, which includes an excitation winding 15 and a pole shoe 16. The excitation winding 15 is wound around the pole shoe 16 to form an electromagnet.

Claims

1. A modulated magnetic field motor, comprising: A. A number of toothed slots, Z in number, are set on the 360° mechanical space around the stator circumference. B. In the 360° mechanical space of the stator circumference, the stator winding is divided into m phases, Z=m×n, n=1,2,3, …; C. The number of pole pairs of the fundamental magnetomotive force magnetic field formed by the stator winding in the 360° mechanical space of the stator circumference is Pm; D. The rotor magnets are arranged in the order of N pole and S pole in the circumferential direction. The number of rotor magnet pole pairs formed along the 360° mechanical space of the rotor circumference is Pr. The characteristic is that the number of pole pairs Pr of the rotor magnet 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 as described in claim 1, characterized in that: The number of tooth slots Z=12, the number of rotor magnetic field pole pairs Pr=17, the number of fundamental magnetomotive force magnetic field pole pairs Pm=5, and the number of phases m=3.

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