JP2020141554A - Permanent magnet type motor - Google Patents

Abstract

To provide a permanent magnet type motor that can be made further efficient.SOLUTION: A permanent magnet type motor 1 comprises a rotor 10 rotating around a rotation axis A and a stator 20. The rotor 10 includes a first permanent magnet 13 with an N pole arranged radially outward, a second permanent magnet 14 with an S pole arranged radially outward, and a magnetic member 15 arranged on the magnetic path between the first permanent magnet 13 and the second permanent magnet 14. The stator 20 includes a plurality of drive coils 22 that generate a rotating magnetic field for rotating the rotor 10, and a permeability modulation coil that has a component in which the magnetic flux generated by the first permanent magnet 13 and the second permanent magnet 14 is orthogonal to the direction through which the magnetic member 15 passes and generates a magnetic flux passing through the magnetic member 15.SELECTED DRAWING: Figure 1

Description

The present invention relates to a permanent magnet type motor.

A permanent magnet type motor that includes a rotor provided with a permanent magnet and a stator that generates a rotating magnetic field, and the rotor rotates due to a magnetic attraction or repulsion force generated between the permanent magnet and the rotating magnetic field is known. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2018-18299

In the permanent magnet type motor as described above, it is preferable that both low-speed and high-torque operation and high-speed and low-torque operation are possible in order to improve efficiency. In order to enable both of them, for example, it is conceivable to adjust the amount of magnetic flux interlinking from the rotor to the stator by passing a negative current through the drive coil to generate a reverse magnetic field. However, in such a method, it is difficult to improve efficiency because the loss (copper loss) generated in the drive coil by passing a negative current is large.

An object of the present invention is to provide a permanent magnet type motor capable of improving efficiency.

The permanent magnet type motor of the present invention includes a rotor and a stator that rotate around a rotation axis, and the rotor includes a first permanent magnet whose north pole portion is arranged radially outside and an south pole portion in the radial direction. It has a second permanent magnet arranged on the outside and a magnetic member arranged on a magnetic path between the first permanent magnet and the second permanent magnet, and the stator provides a rotating magnetic field for rotating the rotor. It has a plurality of driving coils to be generated, and a magnetic permeability modulation coil having a component in which the magnetic flux generated by the first permanent magnet and the second permanent magnet is orthogonal to the direction through which the magnetic member passes and generating the magnetic flux passing through the magnetic member.

In this permanent magnet type motor, the rotor has a magnetic member arranged on the magnetic path between the first permanent magnet and the second permanent magnet, and the stator provides a magnetic permeability modulation coil that generates a magnetic permeability modulation magnetic flux. Have. The magnetic permeability-modulated magnetic flux has a component that is orthogonal to the direction in which the magnetic flux generated by the first permanent magnet and the second permanent magnet passes through the magnetic member, and passes through the magnetic member. Permeability When the modulated magnetic flux is passed through the magnetic member, the magnetic permeability of the magnetic member decreases. Therefore, the magnetic permeability of the magnetic member can be adjusted by adjusting the magnetic flux amount of the magnetic permeability modulation magnetic flux. When the magnetic permeability of the magnetic member decreases, the magnetic resistance of the magnetic path between the first permanent magnet and the second permanent magnet increases. As a result, the leakage flux between the first permanent magnet and the second permanent magnet is reduced, and the magnetic flux interlinking the stator from the first permanent magnet and the second permanent magnet is increased. Therefore, by adjusting the magnetic permeability modulation magnetic flux, the amount of magnetic flux interlinking from the rotor to the stator can be adjusted. Therefore, according to this permanent magnet type motor, the amount of magnetic flux interlinking from the rotor to the stator can be adjusted by a method different from the conventional method as described above, and high efficiency can be achieved.

The magnetic member may be made of a soft magnetic material. In this case, the magnetic permeability of the magnetic member can be easily adjusted.

The rotor has a rotor body, and the first permanent magnet and the second permanent magnet may be embedded in the rotor body. In this case, the reluctance torque can be used, and further high efficiency can be achieved. In addition, the size of the rotor can be reduced.

The magnetic member may be arranged in a groove formed in the rotor body so as to connect the first permanent magnet and the second permanent magnet to each other. In this case, the magnetic resistance of the magnetic path between the first permanent magnet and the second permanent magnet can be preferably changed. Further, the rotor can be further miniaturized.

The rotor has a rotor body, and the magnetic member may be embedded in the rotor body. In this case, the magnetic resistance of the magnetic path between the first permanent magnet and the second permanent magnet can be preferably changed. Further, the rotor can be further miniaturized.

The magnetic member may be arranged outside the first permanent magnet and the second permanent magnet in the radial direction. In this case, the magnetic resistance of the magnetic path between the first permanent magnet and the second permanent magnet can be changed more preferably.

The stator has a pair of magnetic permeability modulation coils, and the pair of magnetic permeability modulation coils may be arranged on one side and the other side of the magnetic member in the axial direction parallel to the rotation axis, respectively. In this case, the magnetic permeability modulation magnetic flux can be suitably passed through the magnetic member.

The magnetic member includes a first portion and a second portion facing each other in an axial direction parallel to the rotation axis, and the magnetic permeability modulation coil may be arranged between the first portion and the second portion in the axial direction. Good. In this case, the magnetic permeability modulation magnetic flux can be suitably passed through the magnetic member.

The rotor has a shaft extending along the axis of rotation, and the permeability modulation coil may surround the shaft. In this case, the magnetic permeability modulation magnetic flux can be preferably generated.

The permanent magnet type motor of the present invention further includes an inverter that supplies a multi-phase alternating current to a plurality of drive coils, and the inverter supplies electricity to the magnetic permeability modulation coil so that the zero-phase current of the inverter flows through the magnetic permeability modulation coil. May be connected. In this case, an inverter that supplies a multi-phase alternating current to the drive coil allows a current to flow through the magnetic permeability modulation coil.

According to the present invention, it is possible to provide a permanent magnet type motor capable of improving efficiency.

It is sectional drawing which shows the permanent magnet type motor (PM motor) which concerns on embodiment. It is sectional drawing along the line II-II of FIG. It is a perspective view which shows the rotor. (A) is a schematic cross-sectional view showing a rotor in a non-magnetically saturated state, and (b) is a schematic cross-sectional view showing a rotor in a magnetically saturated state. (A) and (b) are perspective views for explaining the magnetic permeability modulation method. It is a figure which shows the example of the magnetic field distribution generated in a rotor. (A) and (b) are graphs showing the induced voltage waveform when the magnetomotive force of the magnetic permeability modulation coil is changed. (A) is a graph showing the result of fast Fourier transform (FFT) analysis of the induced voltage, and (b) is a graph showing the result of FFT analysis of torque. It is a graph which shows the relationship between the current phase and torque. It is a figure which shows the circuit structure of a PM motor. It is sectional drawing of the PM motor which concerns on 1st modification. It is a graph which shows the induced voltage waveform about the PM motor which concerns on embodiment. It is a graph which shows the induced voltage waveform about the PM motor which concerns on 1st modification. (A) is a graph showing the result of FFT analysis of the induced voltage for the PM motor according to the embodiment, and (b) shows the result of FFT analysis of the induced voltage for the PM motor according to the first modification. It is a graph. (A) is a graph showing the torque waveform of the PM motor according to the embodiment, and (b) is a graph showing the torque waveform of the PM motor according to the first modification. (A) is a graph showing the result of FFT analysis of torque for the PM motor according to the embodiment, and (b) is a graph showing the result of FFT analysis of torque for the PM motor according to the first modification. is there. It is sectional drawing of the PM motor which concerns on 2nd modification. (A) is a graph showing the torque waveform of the PM motor according to the second modification, and (b) is a graph showing the result of FFT analysis of the torque of the PM motor according to the second modification. (A) is a graph showing a sixth-order torque ripple of the PM motor according to the second modification, and (b) is a graph showing an example of a zero-phase current for reducing the torque ripple. (A) is a graph showing a torque waveform when the zero-phase current of FIG. 19 (b) is used, and (b) is a graph showing the result of FFT analysis for the torque of (a).

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals will be used for the same or equivalent elements, and duplicate description will be omitted.
[PM motor configuration]

As shown in FIGS. 1 to 4, the permanent magnet type motor (hereinafter, also referred to as PM motor) 1 according to the embodiment includes a rotor 10 rotating around a rotation axis A and a stator 20. The PM motor 1 is also called a permanent magnet synchronous motor. The PM motor 1 may be mounted on a vehicle and used as a power source for the vehicle, or may be mounted on another machine such as a washing machine and used.

The rotor 10 includes a rotor body 11, a shaft 12, a plurality of (two in this example) first permanent magnets 13, a plurality of (two in this example) second permanent magnets 14, and a plurality (in this example). It has four) magnetic members 15. The rotor main body 11 is composed of, for example, a plurality of electromagnetic steel sheets laminated in the Z-axis direction (axial direction parallel to the rotation axis A), and has a substantially cylindrical outer shape. The shaft 12 is formed of, for example, a metal material into a circular rod shape. The shaft 12 extends along the rotation axis A and penetrates the rotor body 11. The rotor body 11 is fixed to the shaft 12 and rotates around the rotation shaft A together with the shaft 12.

Each of the first permanent magnet 13 and the second permanent magnet 14 is formed in a rectangular plate shape by, for example, a neodymium magnet, is arranged in the groove portion 17 formed in the rotor main body 11, and is embedded in the rotor main body 11. There is. The first permanent magnet 13 and the second permanent magnet 14 are alternately arranged in the circumferential direction. The circumferential direction means the circumferential direction of the circle centered on the rotation axis A.

Each of the first permanent magnets 13 is arranged so that the N pole portion 13n is located on the outer side in the radial direction and the S pole portion 13s is located on the inner side in the radial direction (FIG. 4). The pair of first permanent magnets 13 extend parallel to each other. The S poles 13s of the pair of first permanent magnets 13 face each other via the shaft 12 (rotation axis A). The radial direction means the radial direction of the circle centered on the rotation axis A.

Each of the second permanent magnets 14 is arranged so that the north pole portion 14n is located inside in the radial direction and the south pole portion 14s is located outside in the radial direction (FIG. 4). The pair of second permanent magnets 14 extend parallel to each other. The north pole portions 14n of the pair of second permanent magnets 14 face each other via the shaft 12 (rotation axis A). The direction in which the S poles 13s of the pair of first permanent magnets 13 face each other and the direction in which the north poles 14n of the pair of second permanent magnets 14 face each other are orthogonal to each other.

In the first permanent magnet 13 and the second permanent magnet 14, the north pole portions 13n and 14n and the south pole portions 13s and 14s are alternately arranged in the circumferential direction. Each of the first permanent magnet 13 and the second permanent magnet 14 generates a magnetic field along the radial direction.

Each magnetic member 15 is formed in a rectangular parallelepiped shape by, for example, a soft magnetic material such as soft ferrite. Each magnetic member 15 is arranged on a magnetic path between the first permanent magnet 13 and the second permanent magnet 14. Each magnetic member 15 is arranged in a groove 18 formed in the rotor main body 11 and is embedded in the rotor main body 11.

The groove portion 18 connects the first permanent magnet 13 and the second permanent magnet 14 to each other (in other words, the groove portion 17 in which the first permanent magnet 13 is arranged and the groove portion 17 in which the second permanent magnet 14 is arranged. Is formed on the rotor body 11 so as to connect the two to each other. The inside of the groove 18 is, for example, a void. The groove portion 18 is also called a flux barrier.

Each groove portion 18 has a pair of extending portions 18a extending from the groove portion 17 and an arrangement portion 18b connected to the pair of extending portions 18a and in which the magnetic member 15 is arranged. The pair of extending portions 18a extend radially outward from the groove portion 17 in parallel with each other. The arrangement portion 18b has a rectangular shape (when viewed from the Z-axis direction) in a plan view. The magnetic member 15 is arranged outside the first permanent magnet 13 and the second permanent magnet 14 in the radial direction.

The stator 20 includes a stator body 21, a plurality of (six in this example) drive coils 22, and a pair of magnetic permeability modulation coils 23. The stator body 21 is formed in a substantially cylindrical shape and surrounds the rotor 10. The stator body 21 is made of, for example, a soft magnetic composite material such as SMC (Soft Magnetic composite). In this case, the molding of the stator body 21 can be facilitated. The stator main body 21 may be composed of a plurality of electromagnetic steel plates laminated in the Z-axis direction.

The stator body 21 is provided with a plurality of (six in this example) teeth 21a protruding inward in the radial direction, and a drive coil 22 is wound around each of these teeth 21a. The drive coil 22 includes a pair of U-phase coils 22A, a pair of V-phase coils 22B, and a pair of W-phase coils 22C. The pair of U-phase coils 22A, the pair of V-phase coils 22B, and the pair of W-phase coils 22C are each wound around a pair of teeth 21a facing each other via a rotor 10. The U-phase coil 22A, the V-phase coil 22B, and the W-phase coil 22C generate a rotating magnetic field for rotating the rotor 10 by supplying a three-phase alternating current from the inverter 30, which will be described later. Although the drive coil 22 is shown in a simplified manner in FIGS. 1 and 2, each drive coil 22 is composed of a coil that is spirally wound and has a cylindrical outer shape.

Further, the stator body 21 is provided with a pair of protruding portions 21b protruding inward in the Z-axis direction, and a magnetic permeability modulation coil 23 is wound around each of these protruding portions 21b. Each protrusion 21b is formed in an annular shape, for example, and surrounds the shaft 12. Therefore, the magnetic permeability modulation coil 23 also surrounds the shaft 12. The pair of magnetic permeability modulation coils 23 are arranged on one side and the other side of the magnetic member 15 in the Z-axis direction, respectively. The pair of magnetic permeability modulation coils 23 face each other via the rotor body 11 in the Z-axis direction. Although the magnetic permeability modulation coil 23 is shown in a simplified manner in FIG. 2, each magnetic permeability modulation coil 23 is composed of a coil that is spirally wound and has a cylindrical outer shape.

Each magnetic permeability modulation coil 23 generates a magnetic permeability modulation magnetic flux (magnetic field) S1 by supplying a zero-phase current from an inverter 30 described later (FIG. 2). The magnetic permeability modulation magnetic flux S1 passes through the magnetic member 15 from the outside to the inside in the radial direction. The direction in which the magnetic permeability modulation magnetic flux S1 passes through the magnetic member 15 is orthogonal (intersects) with the direction in which the magnetic flux S2 by the first permanent magnet 13 and the second permanent magnet 14 passes through the magnetic member 15. As shown in FIG. 4A, the magnetic flux S2 passes through the magnetic member 15 along the circumferential direction. The magnetic flux S2 can also be considered to pass through the magnetic member 15 along the groove 18.
[Operation of PM motor]

FIG. 5 is a diagram for explaining the principle of magnetic permeability modulation in the PM motor 1. As shown in FIG. 5A, when the magnetic permeability modulation magnetic flux S1 does not pass through the magnetic member 15, the magnetic flux S2 easily passes through the magnetic member 15. On the other hand, as shown in FIG. 5B, when the magnetic permeability modulation magnetic flux S1 passes through the magnetic member 15, the magnetic permeability of the magnetic member 15 decreases, and it becomes difficult for the magnetic magnetic flux S2 to pass through the magnetic member 15. Therefore, by adjusting the magnetic flux amount of the magnetic permeability modulation magnetic flux S1, the magnetic permeability of the magnetic member 15 can be adjusted, and the magnetic flux amount of the magnetic flux S2 passing through the magnetic member 15 can be adjusted. For example, by passing the magnetic permeability modulation magnetic flux S1 through the magnetic member 15 so that the magnetic member 15 is magnetically saturated, the magnetic permeability of the magnetic member 15 can be reduced to the same level as the magnetic permeability of air. The present inventor has found that the amount of magnetic flux of the magnet magnetic flux passing through the magnetic member can be adjusted by passing a magnetic flux having a component orthogonal to the magnetic flux of the magnet passing through the magnetic member through the magnetic member. Is.

FIG. 4A shows the rotor 10 in a non-magnetically saturated state in which the magnetic member 15 is not magnetically saturated, and FIG. 4B shows a magnetically saturated state in which the magnetic member 15 is magnetically saturated. The rotor 10 in is shown. In the non-magnetic saturation state, no exciting current is applied to the magnetic permeability modulation coil 23, and in the magnetic saturation state, an exciting current is applied to the magnetic permeability modulation coil 23.

In the non-magnetic saturation state, the magnetic path between the first permanent magnet 13 and the second permanent magnet 14 is short-circuited (the magnetic resistance of the magnetic path is low). Therefore, the amount of leakage of the magnet magnetic flux S2 between the first permanent magnet 13 and the second permanent magnet 14 increases, and the magnet magnetic flux S2 interlinking with the stator 20 decreases. As a result, in the non-magnetically saturated state, the speed electromotive force constant of the PM motor 1 becomes small, and the PM motor 1 becomes a state suitable for high-speed and low-torque operation.

In the magnetically saturated state, the magnetic resistance of the magnetic path between the first permanent magnet 13 and the second permanent magnet 14 becomes higher than in the non-magnetically saturated state. In the magnetic saturation state, the magnet magnetic flux S2 does not leak between the first permanent magnet 13 and the second permanent magnet 14 (the amount of leakage of the magnet magnetic flux S2 decreases), so that the magnet magnetic flux S2 interlinking with the stator 20 More. As a result, in the magnetically saturated state, the speed electromotive force constant of the PM motor 1 becomes larger than in the non-magnetically saturated state, and the PM motor 1 becomes a state suitable for low-speed and high-torque operation. In the PM motor 1, the exciting current applied to the magnetic permeability modulation coil 23 during high-speed operation is smaller than the exciting current applied to the magnetic permeability modulation coil 23 during low-speed operation.

FIG. 6 is a diagram showing an example of the magnetic field distribution generated in the rotor 10. JMAG-Designer 17.0 (registered trademark) was used for the analysis. The magnetomotive force of the magnetic permeability modulation coil 23 was set to 1800 AT. The magnetic member 15 was formed of soft ferrite (MB1H manufactured by JFE). From FIG. 6, it can be seen that the magnetic field over the entire magnetic member 15 is about 5000 A / m by passing a current through the magnetic permeability modulation coil 23. The initial relative permeability of MB1H is 1600 and the saturation magnetic flux density is 0.5T. In MB1H, when the magnetic field is 5000 A / m, the magnetic flux density reaches the saturated magnetic flux density, and the relative magnetic permeability drops to about 80. From the above results, it can be seen that the magnetic permeability of the magnetic member 15 can be modulated by using the magnetomotive force of the magnetic permeability modulation coil 23.

FIG. 7 is a graph showing a no-load induced voltage waveform when the magnetomotive force of the magnetic permeability modulation coil 23 is changed. FIG. 7A shows an electromotive voltage waveform when the rotor 10 is rotated at 1800 min ^-1 and the magnetomotive force of the magnetic permeability modulation coil 23 is set to 0AT. FIG. 7A shows an electromotive voltage waveform when the rotor 10 is rotated at 1800 min ^-1 and the magnetomotive force of the magnetic permeability modulation coil 23 is 1800 AT. FIG. 8A is a graph showing the result of FFT analysis of the induced voltage, and FIG. 8B shows a case where the q-axis magnetomotive force (q-axis armature magnetomotive force) of the drive coil 22 is 600AT. It is a graph which shows the result of FFT analysis of torque. “Air” in FIG. 8 shows the result when the magnetic member 15 is replaced with air.

From FIGS. 7 (a), 7 (b) and 8 (a), when the magnetomotive force of the magnetic permeability modulation coil 23 is 1800AT, the fundamental wave component of the induced voltage is 30 as compared with the case where the magnetomotive force is 0AT. It can be seen that it is about% larger. Further, from FIG. 8B, it can be seen that when the magnetomotive force of the magnetic permeability modulation coil 23 is 1800AT, the average torque is about 17% larger than that when the magnetomotive force is 0AT. From the above results, it can be seen that the fundamental wave component in the induced voltage can be adjusted by the magnetomotive force of the magnetic permeability modulation coil 23.

FIG. 9 is a graph showing a current phase-torque characteristic measured by changing the current phase at intervals of 15 degrees under the condition that the magnetomotive force of the q-axis in the drive coil 22 is 600 AT. From FIG. 9, it can be seen that the PM motor 1 has a reverse polarity in which a maximum torque per ampere (MTPA) point exists in the field weakening region.

FIG. 10 is a diagram showing a circuit configuration of the PM motor 1. As shown in FIG. 10, the PM motor 1 further includes an inverter 30. The inverter 30 has a plurality of (two in this example) DC power supplies 31 and a plurality of (six in this example) switching elements 32 electrically connected to them. The inverter 30 is electrically connected to the drive coil 22 of the stator 20, and supplies a three-phase alternating current to the drive coil 22. The inverter 30 is provided with a current path 35 that electrically connects the neutral point 33 to which the three drive coils 22 are connected and the DC bus unit 34 that connects the DC power supplies 31 to each other. The magnetic permeability modulation coil 23 is provided on the current path 35. As a result, a zero-phase current can flow from the inverter 30 to the magnetic permeability modulation coil 23.

The inverter 30 can control the zero-phase current i ₀ in addition to the three-phase balanced current (positive-phase current) for generating a rotating magnetic field. In the PM motor 1, the zero-phase magnetomotive force generated by the zero-phase current i ₀ and the magnetic permeability modulation coil 23 (zero-phase winding) is used for magnetic permeability modulation. The voltage equations for the 0-axis, d-axis and q-axis of the circuit shown in FIG. 10 are shown below.

_{Here, v 0, v d, v} q is the voltage on each 0dq _{axis, i 0, i d, i} q is the current on each 0dq axis, in winding resistance _{R a} drive coil 22 Yes, R ₀ is the winding resistance of the magnetic permeability modulation coil 23, L ₀ , L _d , L _q is the inductance on the ₀ dq axis, and Ψ _f is the field magnet magnetic flux chain crossover on the 0 dq axis. , P is the differential operator and ω is the angular velocity. From equation (1), it can be seen that the current in each axis of the 0dq axis can be controlled independently.
[Action and effect]

In the PM motor 1, the rotor 10 has a magnetic member 15 arranged on a magnetic path between the first permanent magnet 13 and the second permanent magnet 14, and the stator 20 generates a magnetic permeability-modulated magnetic flux S1. It has a magnetic flux modulation coil 23. The magnetic permeability modulation magnetic flux S1 has a component perpendicular to the direction in which the magnetic flux S2 by the first permanent magnet 13 and the second permanent magnet 14 passes through the magnetic member 15, and passes through the magnetic member 15. When the magnetic permeability modulation magnetic flux S1 is passed through the magnetic member 15, the magnetic permeability of the magnetic member 15 decreases. Therefore, the magnetic permeability of the magnetic member 15 can be adjusted (modulated) by adjusting the magnetic flux amount of the magnetic permeability modulation magnetic flux S1. When the magnetic permeability of the magnetic member 15 decreases, the magnetic resistance of the magnetic path between the first permanent magnet 13 and the second permanent magnet 14 increases. As a result, the leakage flux between the first permanent magnet 13 and the second permanent magnet 14 is reduced, and the magnetic flux interlinking the stator 20 from the first permanent magnet 13 and the second permanent magnet 14 is increased. Therefore, by adjusting the magnetic permeability modulation magnetic flux S1, the amount of magnetic flux interlinking from the rotor 10 to the stator 20 can be adjusted. That is, a variable field can be realized. Therefore, according to this PM motor 1, the amount of magnetic flux interlinking from the rotor 10 to the stator 20 can be adjusted by a method different from the conventional method as described above, and high efficiency can be achieved. In the PM motor 1, by positively utilizing the magnetic saturation characteristic of the soft magnetic material, it is possible to realize a variable field purely electromagnetically while having a reverse polarity. Further, it is possible to realize magnetic permeability modulation using a three-dimensional magnetic path.

The variable field method in the PM motor 1 is excellent in terms of controllability, power supply voltage utilization rate, and switching loss. This point will be described below. As another method for realizing the variable field, a method capable of increasing or decreasing the gap magnetic flux by using a static magnetic field generated from the field winding is being studied. However, this method has a problem that a loss in a DC / DC converter for field winding and a loss due to field copper loss for magnetizing and demagnetizing are large. Further, since the number of switching elements such as diodes and FETs is large, there is a problem that the switching loss is large. In contrast, in the method using the zero-phase current i ₀ at the PM motor 1, since the zero-phase current i ₀ can be controlled by the common mode voltage, the switching frequency of the inverter 30 does not change, the only effect on the switching losses Is. Further, when the variable field method is used for the purpose of improving the variable speed characteristic, since the zero-phase current i ₀ is used as a direct current, the potential fluctuation at the neutral point of the motor is only the voltage drop due to the winding resistance. is there. Therefore, there is almost no effect on the power supply voltage utilization rate by superimposing the zero-phase current i ₀ , and the copper loss can be reduced as compared with the conventional method. Furthermore, when using a zero-phase current i ₀ as magnetomotive force source permeability modulation coil 23, magnetomotive force caused by flowing zero-phase current i ₀ in the three-phase winding (driving coil 22) is directly contribute to the torque generation Therefore, the zero-phase copper loss that occurs in the three-phase winding can be a wasteful loss. However, this loss is compensated by the turns of the zero-phase winding ReishoOkoshi force, it can be minimized by reducing the DC value of the zero-phase current i _0.

As another method for realizing the variable field, a method of dividing the rotor into two in the axial direction and mechanically twisting one of them with respect to the other to realize the variable field has been studied. However, this method has a problem that the structure of the rotor becomes extremely complicated and a problem that another servomotor must be incorporated for the twisting operation. On the other hand, according to the variable field control method in the PM motor 1, the structure can be simplified and such a servomotor can be omitted.

In the PM motor 1, the magnetic member 15 is made of a soft magnetic material. Thereby, the magnetic permeability of the magnetic member 15 can be easily adjusted.

In the PM motor 1, the first permanent magnet 13 and the second permanent magnet 14 are embedded in the rotor main body 11. As a result, the reluctance torque can be utilized, and further high efficiency can be achieved. Further, the size of the rotor 10 can be reduced.

In the PM motor 1, the magnetic member 15 is arranged in the groove portion 18 formed in the rotor main body 11 so as to connect the first permanent magnet 13 and the second permanent magnet 14 to each other. Thereby, the magnetic resistance of the magnetic path between the first permanent magnet 13 and the second permanent magnet 14 can be suitably changed. Further, the rotor 10 can be further miniaturized.

In the PM motor 1, the magnetic member 15 is embedded in the rotor body 11. Thereby, the magnetic resistance of the magnetic path between the first permanent magnet 13 and the second permanent magnet 14 can be suitably changed. Further, the rotor 10 can be further miniaturized.

In the PM motor 1, the magnetic member 15 is arranged outside the first permanent magnet 13 and the second permanent magnet 14 in the radial direction. Thereby, the magnetic resistance of the magnetic path between the first permanent magnet 13 and the second permanent magnet 14 can be changed more preferably.

In the PM motor 1, a pair of magnetic permeability modulation coils 23 are arranged on one side and the other side of the magnetic member 15 in the Z-axis direction, respectively. As a result, the magnetic permeability modulation magnetic flux S1 can be suitably passed through the magnetic member 15.

In the PM motor 1, the magnetic permeability modulation coil 23 surrounds the shaft 12. Thereby, the magnetic permeability modulation magnetic flux S1 can be preferably generated.

The PM motor 1 includes an inverter 30 that supplies a three-phase AC current to a plurality of drive coils 22, and the inverter 30 uses the magnetic permeability modulation coil 23 so that the zero-phase current of the inverter 30 flows through the magnetic permeability modulation coil 23. It is electrically connected. As a result, the inverter 30 that supplies the three-phase alternating current to the drive coil 22 allows the current to flow through the magnetic permeability modulation coil 23.
[Modification example]

In the PM motor 1A according to the first modification shown in FIG. 11, the magnetic member 15 has a first portion 15a and a second portion 15b facing each other in the Z-axis direction. The magnetic permeability modulation coil 23 is provided not as a pair but as one, and is arranged between the first portion 15a and the second portion 15b in the Z-axis direction. The magnetic permeability modulation coil 23 surrounds the shaft 12. The magnetic permeability modulation magnetic flux S1 generated by the magnetic permeability modulation coil 23 passes through the first portion 15a from the outside to the inside in the radial direction and passes through the second portion 15b from the inside to the outside in the radial direction. The rotor body 11, the first permanent magnet 13 and the second permanent magnet 14 are also divided into two in the Z-axis direction. The drive coil 22 is wound (co-wound) around a pair of teeth 21a protruding inward in the radial direction. The pair of teeth 21a are arranged at both ends of the stator body 21 in the Z-axis direction.

The PM motor 1A according to the first modification also makes it possible to improve efficiency as in the above embodiment. Further, in the PM motor 1A, since the magnetic permeability modulation coil 23 is arranged between the first portion 15a and the second portion 15b, it is possible to reduce the size in the Z-axis direction and simplify the configuration of the stator 20. Can be done. Since the drive coil 22 is wound around the pair of teeth 21a, the winding resistance can be reduced and the structure can be simplified.

FIG. 12 is a graph showing induced voltage waveforms when the zero-phase magnetomotive force of the PM motor 1 according to the embodiment is 0AT and 1800AT, and FIG. 13 is a graph showing zero for the PM motor 1A according to the first modification. It is a graph which shows the induced voltage waveform when the magnetomotive force is 0AT and 900AT. FIG. 14A is a graph showing the result of FFT analysis of the induced voltage for the PM motor 1, and FIG. 14B is a graph showing the result of FFT analysis of the induced voltage for the PM motor 1A. The material of each part, the number of turns of each coil, and the volume of the magnet were the same between the PM motors 1 and 1A.

From FIGS. 12 to 14, it can be seen that the fundamental wave component of the no-load induced voltage can be adjusted by about 40% depending on the presence or absence of the zero-phase magnetomotive force. Further, it can be seen that in the PM motor 1A according to the first modification, even-order harmonics are not superimposed on the no-load induced voltage. In the PM motor 1 according to the embodiment, since the zero-phase magnetic flux strengthens one of the north and south poles of the first permanent magnet 13 and the second permanent magnet 14 and weakens the other, even-order harmonics are superimposed. .. On the other hand, in the PM motor 1A according to the first modification, one of the north pole and the south pole is strengthened in the upper stage in FIG. 11, and the other of the north pole and the south pole is strengthened in the lower stage. Since the phase magnetic flux acts, there is no bias in the magnetic poles as a whole, and even-order harmonics are not superimposed. Further, from FIG. 14, it can be seen that the PM motor 1A can obtain the same variable field performance as the PM motor 1 with a zero-phase magnetomotive force half that of the PM motor 1. It is considered that this is because the magnetic paths of the two upper and lower zero-phase magnetic fluxes in the PM motor 1 can be shared by using a magnetic circuit such as the PM motor 1A.

FIG. 15A is a graph showing the torque waveform of the PM motor 1, and FIG. 15B is a graph showing the torque waveform of the PM motor 1A. FIG. 16A is a graph showing the result of FFT analysis of torque for PM motor 1, and FIG. 16B is a graph showing the result of FFT analysis of torque for PM motor 1. The rotation speed was 1800 min ^-1, and the magnetomotive force of the q-axis in the drive coil 22 was 600 AT.

From FIGS. 15 and 16, it can be seen that the average torque is almost the same between the PM motors 1 and 1A. It is considered that this is because the PM motor 1A obtained the same amount of no-load induced voltage with the zero-phase magnetomotive force half that of the PM motor 1. Further, from FIG. 16, it can be seen that the PM motor 1A can reduce the tertiary component contained in the torque ripple by about 87%. It is considered that this is because the even-order harmonics of the no-load induced voltage could be reduced by adopting the magnetic circuit of the PM motor 1A. However, although the third-order component of torque can be reduced by adopting the magnetic circuit of the PM motor 1A, the variable field principle that has the same operating characteristics as the consequential pole type motor does not change, so the magnetic member 15 is made into air. The average output torque is slightly smaller than the replaced ideal state.

The following application examples can be given as applications of the variable field method using magnetic permeability modulation.
(1) PM motor with improved variable speed characteristics According to the above-mentioned variable field method, the speed electromotive force constant can be continuously adjusted according to the operating region. With this function, the variable speed characteristic can be improved.

(2) PM motor with reduced torque ripple In a conventional PM motor, reduction of torque ripple and response to load torque fluctuation are performed by controlling the armature magnetic flux. On the other hand, in the variable field method described above, the field magnetic flux can be changed in addition to the armature magnetic flux by controlling the zero-phase current. Due to this increase in control flexibility, even if the armature magnetic flux contains harmonic components, the harmonics synchronized with the harmonics are superimposed on the field magnetic flux to increase the average torque and reduce torque ripple at the same time. can do.

(3) PM motor with expanded high-efficiency operating range Generally, the operating point where copper loss and iron loss compete with each other is the highest efficiency point of the PM motor, and this maximum efficiency can be cited as one performance index. However, since the field cannot be adjusted with a general PM motor, the high efficiency region is limited. On the other hand, since the field can be controlled by the variable field method described above, the high-efficiency operating range can be expanded by controlling the field magnetic flux so that the copper loss and the iron loss are balanced.

FIG. 17 is a cross-sectional view of the PM motor 1B according to the second modification. In the PM motor 1B, the teeth 21a is composed of a plurality of electromagnetic steel plates laminated in the Z-axis direction in order to reduce torque ripple. This is because the magnetic flux flowing through the teeth 21a is only in the two-dimensional direction. Other structures are the same as those of the PM motor 1A according to the first modification. However, since the goal is to reduce the torque ripple, the shape of the magnetic member 15 is adjusted so that the variable field width and the amplitude of the reduced torque ripple are about the same. The PM motor 1B according to the second modification also makes it possible to improve efficiency as in the above embodiment. In addition, the manufacturing process can be simplified and the eddy current loss can be reduced. Further, the back yoke is formed of both an electromagnetic steel plate and a dust core, and constitutes a three-dimensional magnetic circuit.

FIG. 18A is a graph showing the torque waveform of the PM motor 1B according to the second modification, and FIG. 18B is a graph showing the result of FFT analysis of the torque of the PM motor 1B. The rotation speed was 1800 min- ¹ , the magnetomotive force of the q-axis in the drive coil 22 was 600AT, and the zero-phase magnetomotive forces were 0AT and 900AT. From FIG. 18, by adjusting the shape of the magnetic member 15, the difference in the average torque depending on the presence or absence of the zero-phase magnetomotive force becomes smaller than that of the PM motor 1A according to the first modification, and the amplitude of the sixth component is reduced. It can be seen that it is about the same as.

FIG. 19A is a graph showing a sixth-order component (torque ripple) when the zero-phase magnetomotive force is 0AT, and FIG. 19B shows an example of a zero-phase current for reducing the torque ripple. It is a graph. The zero-phase current shown in FIG. 19 has a current waveform in which the absolute value increases when the torque is small and the absolute value decreases when the torque is large.

20 (a) is a graph showing a torque waveform when the zero-phase current of FIG. 19 (b) is used, and FIG. 20 (b) shows the result of FFT analysis for the torque of FIG. 20 (a). It is a graph which shows. The q-axis magnetomotive force of the drive coil 22 was 600 AT, and the zero-phase magnetomotive force was 900 AT. From FIG. 20, it can be seen that the sixth component can be reduced by about 75% by energizing the zero-phase current having the waveform shown in FIG. 19 (b). It can also be seen that the average torque is also increased as compared with the case where the zero-phase magnetomotive force is 900AT.

By energizing a zero-phase current as shown in FIG. 19B, a sixth-order harmonic component is generated in the field magnetomotive force in the synchronous coordinate system, and a sixth-order armature is inevitably generated by the stator structure. It can be synchronized with the magnetic force. As a result, in addition to the increase in the average torque according to the effective value of the AC zero-phase current, the reduction in the sixth component can be superimposed on the average torque, and torque ripple is suppressed with an effective value smaller than that during DC excitation. However, the average torque can be increased.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, various materials, shapes and arrangements can be adopted for the materials, shapes and arrangements of each configuration, not limited to the above-mentioned examples. The magnetic member 15 does not necessarily have to be formed of a soft magnetic material, and may be formed of a magnetic material other than the soft magnetic material. Even in this case, the magnetic permeability of the magnetic member 15 can be modulated.

In the above embodiment, the magnetic permeability modulation magnetic flux S1 passes through the magnetic member 15 along the radial direction. However, in the magnetic permeability modulation magnetic flux S1, the magnetic flux S2 formed by the first permanent magnet 13 and the second permanent magnet 14 is a magnetic member. It suffices to have a component orthogonal to the direction passing through 15. For example, the magnetic permeability modulation magnetic flux S1 may pass through the magnetic member 15 along the Z-axis direction. The magnetic permeability modulation magnetic flux S1 may intersect the direction in which the magnetic flux S2 of the first permanent magnet 13 and the second permanent magnet 14 passes through the magnetic member 15. Even in these cases, the magnetic permeability of the magnetic member 15 can be modulated.

The first permanent magnet 13 and the second permanent magnet 14 may be arranged on the surface of the rotor main body 11. That is, the rotor 10 may be configured as a surface magnet type instead of the embedded magnet type. The magnetic member 15 may be arranged on the surface of the rotor body 11.

The arrangement of the magnetic member 15 is not limited to the above-mentioned example. For example, instead of or in addition to the above-mentioned magnetic member 15, the magnetic member may be arranged inside the first permanent magnet 13 and the second permanent magnet 14 in the radial direction. A magnetic member may be arranged between the first permanent magnet 13 and the second permanent magnet 14. The inverter 30 may not be electrically connected to the magnetic permeability modulation coil 23, and a current may be supplied to the magnetic permeability modulation coil 23 by another power source.

1 ... Permanent magnet type motor (PM motor), 10 ... Rotor, 11 ... Rotor body, 12 ... Shaft, 13 ... First permanent magnet, 14 ... Second permanent magnet, 13n, 14n ... N pole, 13s, 14s ... S pole part, 15 ... magnetic member, 15a ... first part, 15b ... second part, 20 ... stator, 22 ... drive coil, 23 ... magnetic permeability modulation coil, 30 ... inverter, A ... rotating shaft, i ₀ ... zero Phase current.

Claims (10)

It is equipped with a rotor that rotates around a rotation axis and a stator.
The rotor
The first permanent magnet with the N pole located on the outer side in the radial direction,
A second permanent magnet with the S pole located on the outer side in the radial direction,
It has a magnetic member arranged on a magnetic path between the first permanent magnet and the second permanent magnet.
The stator is
A plurality of drive coils that generate a rotating magnetic field for rotating the rotor, and
A permanent magnet type motor having a component in which the magnetic flux generated by the first permanent magnet and the second permanent magnet is orthogonal to the direction through which the magnetic member passes and a magnetic permeability modulation coil that generates a magnetic flux passing through the magnetic member. .. The permanent magnet type motor according to claim 1, wherein the magnetic member is made of a soft magnetic material. The rotor has a rotor body and has a rotor body.
The permanent magnet type motor according to claim 1 or 2, wherein the first permanent magnet and the second permanent magnet are embedded in the rotor body. The permanent magnet type motor according to claim 3, wherein the magnetic member is arranged in a groove formed in the rotor body so as to connect the first permanent magnet and the second permanent magnet to each other. The rotor has a rotor body and has a rotor body.
The permanent magnet type motor according to any one of claims 1 to 4, wherein the magnetic member is embedded in the rotor body. The permanent magnet type motor according to any one of claims 1 to 5, wherein the magnetic member is arranged outside the first permanent magnet and the second permanent magnet in the radial direction. The stator has a pair of magnetic permeability modulation coils.
The permanent according to any one of claims 1 to 6, wherein each of the pair of magnetic permeability modulation coils is arranged on one side and the other side of the magnetic member in an axial direction parallel to the rotation axis. Magnet type motor. The magnetic member includes a first portion and a second portion facing each other in an axial direction parallel to the rotation axis.
The permanent magnet type motor according to any one of claims 1 to 6, wherein the magnetic permeability modulation coil is arranged between the first portion and the second portion in the axial direction. The rotor has a shaft that extends along the axis of rotation.
The permanent magnet type motor according to any one of claims 1 to 8, wherein the magnetic permeability modulation coil surrounds the shaft. Further equipped with an inverter that supplies a multi-phase alternating current to the plurality of drive coils,
The permanent magnet according to any one of claims 1 to 9, wherein the inverter is electrically connected to the magnetic permeability modulation coil so that the zero-phase current of the inverter flows through the magnetic permeability modulation coil. Type motor.