JP2016032384A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor in which the eddy current of a field magnet can be reduced.SOLUTION: A rotor 10 and a stator 20 face each other via an air gap in the radial direction. Teeth 211 are provided in the circumferential direction while spaced apart from each other. A yoke 212 couples the teeth 211 magnetically on the side opposite from the rotor 10. Field magnets 22 are arranged in the every other adjoining field slots 213a, out of a plurality of slots 213 formed between each other teeth 211 in the circumferential direction, while facing the pole faces of the same polarity each other in the circumferential direction. A field winding 23 is wound around the teeth 211 in the field slots 213a. An armature winding 24 is wound around the teeth 211, in the armature slots 213b other than the field slots 213a, out of the slots 213. Inductance of the field winding 23 is larger than that of the armature winding 24.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric motor, and more particularly to an electric motor including an armature winding, a field winding, and a field magnet in a stator.

  Patent Documents 1 and 2 and Non-Patent Documents 1, 2 and 3 describe electric motors. The electric motors shown in these drawings have a stator and a rotor, and the rotor faces the stator via an air gap in the radial direction. The stator is provided with a stator core having teeth and a yoke, a field magnet, a field winding, and an armature winding. In such an electric motor, the sum of the magnetic flux of the field winding and the magnetic flux of the field magnet acts as the field magnetic flux.

  In particular, in Non-Patent Document 3, a tooth in which field slots and armature slots are alternately formed is provided. The field winding is wound around two teeth sandwiched between adjacent field slots in the circumferential direction. The armature winding is wound around two teeth sandwiched between adjacent armature slots in the circumferential direction. The field magnet is disposed in the field slot.

JP 2013-2018869 A US Patent Application Publication No. 2010/0038978

E. Hoang, M. Lecrivain, M. Gabsi, “A NEW STRUCTURE OF A SWITCHING FLUX SYNCHRONOUS POLYPHASED MACHINE WITH HYBRID EXCITATION”, Power Electronics and Applications, 2007 European Conference on, IEEE, 2007, p. 1-8 E. Hoang, S. Hlioui, M. Lecrivain, M. Gabsi, `` EXPERIMENTAL COMPARISON OF LAMINATION MATERIAL CASE OF SWITCHING FLUX SYNCHRONOUS MACHINE WITH HYBRID EXCITATION '', Power Electronics and Applications, 2009. EPE '09. 13th European Conference on, IEEE 2009, p.1-7 Matsumoto, Kosaka, Matsui, Fujiami, "Examination of high-torque design of hybrid field flux switching motor", IEEJ Study Group materials. VT, Automotive Research Society, 2012, p.31-36

  In Patent Documents 1 and 2 and Non-Patent Documents 1 to 3, an eddy current is generated in the field magnet due to the magnetic flux flowing through the field magnet. Such an eddy current is not preferable from the viewpoint of the efficiency of the electric motor.

  Then, an object of this invention is to provide the electric motor which can reduce the eddy current of a field magnet.

  A first aspect of an electric motor according to the present invention includes a rotor (10) and a stator (20) facing each other through an air gap in a radial direction centered on a rotation axis (P), and the stator Is a plurality of teeth (211) alternately defining field slots (213a) and armature slots (213b) in the circumferential direction around the rotation axis, and the plurality of teeth on the opposite side of the rotor And a plurality of armatures wound around the two teeth sandwiched in the circumferential direction by the two adjacent armature slots (213b). A plurality of field windings (23) wound around the two teeth that are sandwiched in the circumferential direction by two adjacent field slots (213a), each of the winding (24), and The field slot facing the field winding in the radial direction A plurality of field magnets (22) facing each other in the circumferential direction, the inductances of the field windings being larger than the inductances of the armature windings. .

  A second aspect of the electric motor according to the present invention is the electric motor according to the first aspect, and of the stator yoke (212), the first yoke adjacent to the field slot (213a) in the radial direction. The width of the portion (212a) along the radial direction is wider than the second yoke portion (212b) of the stator yoke adjacent to the armature slot (213b) in the radial direction.

  A third aspect of the electric motor according to the present invention is the electric motor according to the first or second aspect, wherein the number of turns of each of the field windings (23) is the number of turns of each of the armature windings (24). Greater than the number of turns.

  A fourth aspect of the electric motor according to the present invention is the electric motor according to any one of the first to third aspects, wherein the field magnet is a rare earth magnet.

  According to the first aspect of the electric motor of the present invention, the field magnet is adjacent to the field magnet in the radial direction, and is located inside the armature winding as viewed along the radial direction. In the field magnet, the magnetic flux of the field winding is more likely to flow than the magnetic flux of the armature winding. In such an electric motor, since the inductance of the field winding is larger than the inductance of the armature winding, the harmonic component of the current flowing in the field winding, in particular, the carrier frequency component by PWM control can be reduced, As a result, the harmonic component of the magnetic flux of the field winding can be reduced. Since the harmonic component of the magnetic flux causes an eddy current, the eddy current of the field magnet can be effectively reduced.

  According to the 2nd aspect of the electric motor concerning this invention, it is easy to make the inductance of a field winding larger than the inductance of an armature winding.

  According to the 3rd aspect of the electric motor concerning this invention, it is easy to make the inductance of a field winding larger than the inductance of an armature winding.

  According to the 4th aspect of the electric motor concerning this invention, an eddy current tends to flow through a rare earth magnet. Therefore, this electric motor is more effective.

It is sectional drawing which shows an example of a schematic structure of an electric motor. It is a figure for demonstrating the flow of magnetic flux. It is a figure for demonstrating the flow of magnetic flux. It is sectional drawing which shows an example of the schematic structure of a stator. It is sectional drawing which shows an example of a schematic structure of an electric motor.

<Overall configuration of armature>
FIG. 1 is a cross-sectional view showing an example of a schematic configuration of the electric motor 1, and shows the configuration of the electric motor 1 in a cross section including a virtual rotation axis P. The electric motor 1 can be applied to, for example, an automobile motor.

  Hereinafter, a direction along the rotation axis P is referred to as an axial direction, and a circumferential direction and a radial direction around the rotation axis P are simply referred to as a circumferential direction and a radial direction, respectively.

  The electric motor 1 includes a rotor 10 and a stator 20. The rotor 10 and the stator 20 face each other through an air gap in the radial direction. In the illustration of FIG. 1, the rotor 10 faces the stator 20 on the rotation axis P side (inner peripheral side). Such an electric motor 1 is a so-called inner rotor type electric motor.

  The rotor 10 has a rotor core 11. The rotor core 11 is made of a soft magnetic material and has a plurality of protrusions 111 and a rotor yoke 112. The plurality of protrusions 111 are arranged side by side along the circumferential direction, and protrude toward the stator 20 in the radial direction around the rotation axis P. The rotor yoke 112 magnetically couples the ends of the plurality of protrusions 111 opposite to the stator 20 in the circumferential direction. The rotor core 11 has a gear shape when viewed along the axial direction.

  In the illustration of FIG. 1, a through-hole 113 is formed in the rotor yoke 112 in a region including the rotation axis P. The through hole 113 passes through the rotor yoke 112 along the axial direction. A shaft (not shown) is inserted into the through hole 113, and the rotor yoke 112 is fixed to the shaft. Note that, when the shaft is attached to end plates provided on both sides of the rotor 10 in the axial direction, the through hole 113 is not necessary.

  The rotor core 11 may be formed of, for example, a plurality of laminated steel plates laminated along the axial direction, or may be a dust core including an insulator. Thereby, the eddy current generated in the rotor core 11 can be reduced.

  The stator 20 includes a stator core 21, a field magnet 22, a field winding 23, and an armature winding 24.

  The stator core 21 is made of a soft magnetic material and includes a plurality of teeth 211 and a stator yoke 212. In the example of FIG. 1, an even number of teeth 211 are provided, and these are arranged around the rotation axis P. More specifically, the teeth 211 are arranged side by side along the circumferential direction, and are arranged radially about the rotation axis P.

  The stator yoke 212 magnetically connects one end of the teeth 211 (one end opposite to the rotor 10). The stator yoke 212 has, for example, a substantially cylindrical shape with the rotation axis P as the center. In the stator core 21, a space (hereinafter referred to as a slot) 213 is formed between the teeth 211 in the circumferential direction. In the illustration of FIG. 1, since the even number of teeth 211 is provided, the even number of slots 213 are also formed.

  The stator core 21 may be formed of, for example, a plurality of laminated steel plates laminated along the axial direction, or may be a dust core that includes an insulator. Thereby, the eddy current generated in the stator core 21 can be reduced.

  The field magnet 22 is a permanent magnet, for example, a rare earth magnet. Rare earth magnets have high residual magnetic flux density and coercivity. Therefore, the efficiency of the electric motor 1 can be increased. On the other hand, eddy currents are easily generated in rare earth magnets. In particular, neodymium magnets (magnets mainly composed of neodymium, iron, and boron) contain iron as one of the main components, so that the sintered body has high conductivity and easily generates eddy currents. Therefore, as will be described below, the electric motor 1 capable of reducing the eddy current of the field magnet 22 is particularly effective.

  The plurality of field magnets 22 are disposed in the plurality of field slots 213 a among the slots 213. In the illustration of FIG. 1, the field slot 213 a is a slot adjacent to the slot 213 by skipping one in the circumferential direction. The plurality of field magnets 22 are arranged with their magnetic pole faces having the same polarity in the circumferential direction. That is, the field magnet 22 is magnetized along the substantially circumferential direction, and the opposing surfaces of the field magnets 22 adjacent in the circumferential direction are magnetic pole surfaces having the same polarity. In other words, the plurality of field magnets 22 are arranged with the magnetic pole surfaces having different polarities alternately directed toward one side in the circumferential direction.

  The field winding 23 is wound around the teeth 211 in the field slot 213a. More specifically, the field winding 23 is wound around a pair of teeth 211 (hereinafter also referred to as a pair of field teeth 211a) sandwiched between a pair of field slots 213a adjacent to each other in the circumferential direction. Is done. That is, if this pair of field teeth 211a is regarded as one tooth and the field winding 23 is ignored by the armature slot 213b, it is wound by concentrated winding. The field winding 23 is wound around the pair of field teeth 211a with the axis along the radial direction as a winding axis.

  As described above, the field magnet 22 and the field winding 23 are disposed in the field slot 213a, and the field winding 23 is adjacent to the field magnet 22 in the radial direction. In the illustration of FIG. 1, the field magnet 22 is disposed on the rotor 10 side with respect to the field winding 23.

  The field winding 23 is DC-excited and a DC current flows. The direction of the direct current flowing through the field winding 23 is determined according to the polarity of the field magnet 22 adjacent to the field winding 23. The direction of the direct current will be described in detail later.

  The armature winding 24 is wound around the tooth 211 in the armature slot 213b other than the field slot 213a among the slots 213. The armature slot 213b is a slot located between the field slots 213a among the slots 213. That is, the teeth 211 alternately form field slots 213a and armature slots 213b in the circumferential direction. The armature winding 24 is wound around a pair of teeth 211 (hereinafter also referred to as armature teeth 211b) sandwiched between a pair of armature slots 213b adjacent in the circumferential direction. That is, the pair of armature teeth 211b is regarded as one tooth, and the armature winding 24 is wound around the armature winding 24 in a concentrated manner. The armature winding 24 is also wound around the pair of armature teeth 211b with the axis along the radial direction as a winding axis.

  In such a stator 20, the field magnet 22 is positioned inside the armature winding 24 when viewed along the radial direction.

  The armature winding 24 is AC-excited and an AC current flows. By appropriately supplying an alternating current to the armature winding 24, the armature winding 24 can supply a rotating magnetic field to the rotor 10. The rotor core 11 rotates around the rotation axis P according to this rotating magnetic field.

  In addition, the armature winding 24 and the field winding 23 do not indicate each one of the conductive wires constituting the armature winding 24 and the field winding 23, but indicate an aspect in which the conductive wires are wound together. The same applies to the drawings. In addition, the drawing lines at the start and end of winding and their connection are also omitted in the drawings.

<DC excitation of field winding>
A current is passed through the field winding 23 as follows. That is, a direct current is passed through the field winding 23 so that the magnetic flux generated by the field magnet 22 (hereinafter referred to as “magnet magnetic flux”) passes through the rotor core 11. If the magnet flux passes through the stator yoke 212, much of the magnet flux does not pass through the stator yoke 212 and the rotor core 11. Therefore, a current is passed through the field winding 23 so that the magnet magnetic flux does not pass through the stator yoke 212. Therefore, a current may be passed through the field winding 23 as follows. That is, the magnetic flux of the field winding 23 (hereinafter referred to as “winding magnetic flux”) is the stator in the direction opposite to the direction in which the magnetic flux flows through the stator yoke 212 when no current flows through the field winding 23. A current may be passed through the field winding 23 so as to flow through the yoke 212. Thereby, the magnet magnetic flux and the winding magnetic flux flow through the rotor core 11.

  Thus, the magnet magnetic flux and the winding magnetic flux flow through the rotor core 11 and act as field magnetic flux. Therefore, the magnitude of the field magnetic flux can be controlled by controlling the direct current flowing through the field winding 23. For example, it is possible to perform field-intensifying control to increase the rotation speed by increasing the magnitude of the field magnetic flux during low-speed rotation and performing strong field control that outputs a large torque, and reducing the field magnetic flux magnitude during high-speed rotation. .

  The direct current flowing through the field winding 23 is controlled by, for example, a chopper circuit (for example, a step-down circuit, a step-up circuit, or a step-up / down circuit). More specifically, a DC voltage applied to the field winding 23 is generated by the chopper circuit. The chopper circuit has a switching element, and the DC voltage is controlled by appropriately switching on / off the switching element. Such switching element control can be performed by, for example, a known PWM (Pulse Width Modulation) method.

  Therefore, the direct current flowing through the field winding 23 includes a harmonic component accompanying the on / off of the switching element, and the harmonic component of the direct current generates a harmonic component of the winding magnetic flux. Such a harmonic component of the winding magnetic flux is not preferable because it causes an eddy current.

<AC excitation of armature winding>
An alternating current appropriately flows through the armature winding 24, thereby applying a rotating magnetic field to the rotor 10. For example, a three-phase armature winding is adopted as the armature winding 24, and a three-phase alternating current flows through these armature windings 24. The alternating current flowing through the armature winding 24 is controlled by, for example, an inverter. More specifically, an AC voltage (for example, a three-phase AC voltage) applied to the armature winding 24 is generated by the inverter. This inverter has a switching element, and the amplitude and frequency of the AC voltage are appropriately controlled by appropriately switching on / off the switching element. Such switching element control can also be performed by, for example, a well-known PWM (Pulse Width Modulation) method.

  Therefore, the alternating current that flows through the armature winding 24 mainly includes a fundamental wave component that generates a rotating magnetic field and a harmonic component that accompanies on / off of the switching element.

  Since the magnetic flux of the armature winding 24 is an alternating magnetic flux, an eddy current is generated due to this. Further, due to the effects of slot harmonics and the like, harmonic components are also generated in the alternating magnetic flux due to the harmonic components generated in the alternating current. The harmonic component of this alternating magnetic flux also causes eddy currents.

<Eddy current generated in field magnet>
As described above, an eddy current is generated by the magnetic flux of the field winding 23 and the armature winding 24. Since magnetic flux flows through the rotor core 11, the stator core 21, and the field magnet 22, eddy currents are generated in the rotor core 11, the stator core 21, and the field magnet 22. Consider.

  The magnetic flux generated by the armature winding 24 does not pass through the field magnet 22 much, and the magnetic flux generated by the field winding 23 is more likely to pass through the field magnet 22. The reason will be described below. For the sake of simplicity, the rotor core 11 is ignored here. That is, the path through which the magnetic flux of the armature winding 24 and the field winding 23 flows changes depending on the rotational position of the rotor core 11, but here the path is considered on average for simplicity. is there.

  As described above, the armature winding 24 is wound with the axis along the radial direction as a winding axis. Therefore, the magnetic flux flows in the radial direction inside the armature winding 24. As can be understood from FIG. 1, a pair of armature teeth 211 b, a field magnet 22, and a field winding 23 are arranged inside the armature winding 24. The field magnet 22 and the field winding 23 are adjacent to each other in the radial direction between the pair of armature teeth 211b. The magnetic permeability of the field magnet 22 is lower than the magnetic permeability of the stator core 21. The field winding 23 is insulated between the conductors, and the magnetic permeability of the insulating member is lower than the magnetic permeability of the stator core 21. Therefore, the magnetic flux generated by the armature winding 24 hardly passes through the pair of armature teeth 211b in the radial direction inside the armature winding 24 and through the field winding 23 and the field magnet 22.

  The field winding 23 is also wound around the radial direction as described above. Therefore, the magnetic flux flows in the radial direction inside the field winding 23. However, unlike the armature winding 24, the field magnet 22 is provided at a position adjacent to the field winding 23 in the radial direction. The winding magnetic flux flows in the circumferential direction in a region adjacent to the field winding 23 in the radial direction, and thus more easily flows through the field magnet 22 closer to the field winding 23.

  Therefore, from the viewpoint of reducing the eddy current of the field magnet 22, it is desirable to reduce the eddy current caused by the magnetic flux of the field winding 23.

<Inductance of field winding 23 and inductance of armature winding 24>
The impedance of the field winding 23 is represented by the product of frequency and inductance. Therefore, by increasing the inductance, it is possible to increase the impedance particularly for the harmonic component. Therefore, the harmonic component of the direct current flowing through the field winding 23 can be reduced. Therefore, by increasing the inductance of the field winding 23, the harmonic component of the magnetic flux can be reduced, and as a result, the eddy current generated in the field magnet 22 can be reduced. Moreover, as described above, the magnetic flux generated by the field winding 23 is easier to pass through the field magnet 22 than the magnetic flux generated by the armature winding 24.

  Further, since the impedance of the armature winding 24 is also expressed by the product of the frequency and the inductance, the impedance of the armature winding 24 increases as the frequency of the alternating current increases. When the frequency of the alternating current flowing through the armature winding 24 (frequency of the fundamental wave component) is increased, the rotation speed of the electric motor 1 can be increased. That is, as the electric motor 1 rotates at a higher speed, the impedance of the armature winding 24 with respect to the alternating current becomes higher. Therefore, it is desirable that the inductance of the armature winding 24 be limited to some extent in order to allow a sufficient alternating current to flow.

  Therefore, the inductance of the field winding 23 is set larger than the inductance of the armature winding 24. Here, “large” includes a simple magnitude relationship, but actually it is desirable that it be sufficiently large, for example, twice or more.

  The inductance of the field winding 23 and the armature winding 24 varies depending on the rotational position of the rotor core 11. At all rotational positions, the inductance of the field winding 23 is greater than the inductance of the armature winding 24. It is desirable to set a large value.

<Inductance setting>
The inductance of the winding is determined by the product of the square of the number of turns of the winding and the reciprocal of the magnetic resistance of the path through which the magnetic flux of the winding flows. Therefore, the number of turns of the field winding 23 is preferably set larger than the number of turns of the armature winding 24. Thereby, it is easy to make the inductance of the field winding 23 larger than the inductance of the armature winding 24 compared to the reverse case.

  Next, the path through which the magnetic flux in the field winding 23 flows and the path through which the magnetic flux in the armature winding 24 flows are considered, and the magnetic resistance is considered. First, in order to consider the uneven distribution of the rotor core 11 on average, the rotor core 11 is ignored. As shown in FIG. 2, the magnetic flux of the field winding 23 passes through the first yoke portion 212 a of the stator yoke 212 that is adjacent to the field slot 213 a in the radial direction. On the other hand, as shown in FIG. 3, the magnetic flux of the armature winding 24 passes through the second yoke portion 212b of the stator yoke 212 that is adjacent to the armature slot 213b in the radial direction.

  However, the magnetic flux of the armature winding 24 may flow through the first yoke portion 212a as is well known. This depends on the state of the AC voltage applied to the armature winding 24. When the magnetic flux of the armature winding 24 does not flow through the first yoke portion 212a, the first yoke portion 212a does not affect the inductance of the armature winding 24. Therefore, the first yoke portion 212 a has a greater influence on the inductance of the field winding 23. In short, if the magnetic resistance of the first yoke portion 212a is reduced, the inductance of the field winding 23 can be increased by an amount larger than the inductance of the armature winding 24.

  The magnetoresistance is smaller as the area of the cross section perpendicular to the magnetic flux of the core is larger. Since the magnetic flux flows in the first yoke portion 212a and the second yoke portion 212b along the circumferential direction, the width along the radial direction of the first yoke portion 212a and the second yoke portion 212b is respectively set to the first yoke portion 212a. In addition, the magnetic resistance of the second yoke portion 212b is affected. More specifically, the wider the width, the smaller the magnetoresistance.

  Therefore, as illustrated in FIG. 4, the width W1 of the first yoke portion 212a may be set wider than the width W2 of the second yoke portion 212b. This makes it easier to set the inductance of the field winding 23 to be larger than the inductance of the armature winding 24 compared to the reverse case.

<Position of field magnet and field winding>
FIG. 5 is a cross-sectional view showing another example of the schematic configuration of the electric motor 1. This electric motor 1 is different from the electric motor 1 of FIG. 1 in that the position of the field magnet 22 and the field winding 23 is different. In the illustration of FIG. 5, the field magnet 22 is provided on the side opposite to the rotor 10 with respect to the field winding 23.

  Also in the electric motor 1, a direct current is supplied to the field winding 23 so that the magnetic flux of the field magnet 22 adjacent to the field winding 23 does not flow to the corresponding first yoke portion 212 a. And the magnitude | size of a field magnetic flux is controlled by controlling this direct current.

  Also in the electric motor 1 of FIG. 5, the inductance of the field winding 23 is set larger than the inductance of the armature winding 24. Thereby, there exists an effect mentioned above. The number of turns of the field winding 23 is preferably set larger than the number of turns of the armature winding 24, and the width along the radial direction of the first yoke portion 212a is set in the radial direction of the second yoke portion 212b. It is desirable that it is wider than the width along. This is because the inductance of the field winding 23 is likely to be larger than the inductance of the armature winding 24.

  In the present invention, the above-described various embodiments can be appropriately modified and omitted within the scope of the present invention as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Electric motor 10 Rotor 20 Stator 22 Field magnet 23 Field winding 24 Armature winding 211 Teeth 212 Yoke 212a 1st yoke part 212b 2nd yoke part 213 slot 213a Field slot 213b Armature slot

Claims (4)

In the radial direction around the rotation axis (P), the rotor (10) and the stator (20) facing each other through an air gap,
The stator is
A plurality of teeth (211) that alternately define field slots (213a) and armature slots (213b) in the circumferential direction around the rotation axis;
A stator yoke (212) for magnetically connecting the plurality of teeth on the opposite side of the rotor;
A plurality of armature windings (24) each wound around two teeth sandwiched in the circumferential direction by two adjacent armature slots (213b); A plurality of field windings (23) wound around the two teeth sandwiched in the circumferential direction by the slot (213a);
A plurality of field magnets (22) each provided in the field slot facing the field winding in the radial direction and facing the pole faces of the same polarity in the circumferential direction;
The electric motor in which each inductance of the field winding is larger than each inductance of the armature winding.   Of the stator yoke (212), the width along the radial direction of the first yoke portion (212a) adjacent to the field slot (213a) in the radial direction is the same as that of the stator yoke. The electric motor according to claim 1, wherein the electric motor is wider than the second yoke portion (212b) adjacent to the child slot (213b) in the radial direction.   The electric motor according to claim 1 or 2, wherein the number of turns of each of the field windings (23) is larger than the number of turns of each of the armature windings (24).   The electric motor according to claim 1, wherein the field magnet is a rare earth magnet.

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