JP2007288838A - Embedded magnet type motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an embedded magnet type motor in which the amount of magnets is reduced, reluctance torque is increased, and a maximum output identical to that when all magnets exist can be attained without causing an undue induction voltage in the high speed rotary zone. <P>SOLUTION: A stator 11 is tubular and a plurality of tees 12 are provided on the inside while spaced apart equally. A coil (winding not shown) is wound around the tees 12 by distributed winding. A rotor 13 has a rotor core 14 formed by laminating a plurality of core sheets, and a rotor shaft 15 penetrating the center of the rotor core 14. A plurality of permanent magnets 16 are embedded in the rotor core 14. The rotor core 14 has a portion where the permanent magnets 16 are arranged in V-shape every 360° of electrical angle, and a flux barrier 17 formed in V-shape. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an interior magnet type electric motor.

  It is known that an embedded magnet type electric motor can use a reluctance torque in addition to a magnet torque, so that the total torque can be increased as compared with a surface magnet type electric motor. In addition, by using field-weakening control, the induced voltage constant is equivalently reduced by applying a demagnetizing field to the magnet and the operating range is extended to a high rotation range. This is used in electric vehicles, hybrid vehicles, washing machines, etc. ing.

  FIG. 6 is a characteristic comparison between SPM (surface magnet type motor) and IPM (embedded magnet type motor). Maximum torque control is performed in the range indicated by I until the rotation speed reaches a predetermined rotation speed, and control is performed so that the torque is maximized at the maximum current of the inverter. Field weakening control is performed while lowering the inverter current so that the induced voltage does not become higher than the inverter input voltage in the range indicated by II where the rotational speed exceeds the predetermined rotational speed.

  Although an embedded magnet type electric motor has a small magnet torque, a reluctance torque can also be used, and as a result, the maximum torque can often be made equal to SPM. In addition, since there is a salient pole ratio unlike a surface magnet type motor, a flow of magnetic flux that can increase the reluctance torque while lowering the induced voltage is created by passing a field weakening current (negative d-axis current). .

Conventionally, there has been proposed an embedded magnet type electric motor that can increase the ratio of reluctance torque with a simple rotor structure (see, for example, Patent Document 1). In Patent Document 1, as shown in FIG. 7, the permanent magnet 52 in the rotor core 51 is arranged in the most efficient V-shape for utilizing the reluctance torque. It is pulled out and used as a flux barrier 53.
JP 2000-287393 A

  However, when one of the two permanent magnets 52 to be arranged in a V-shape as shown in FIG. 7 is pulled out and used as the flux barrier 53, compared to the case where all the permanent magnets 52 are present. There is a problem that the maximum output is lowered.

  Further, the portion A surrounded by the chain line in FIG. 7 is characterized in that the magnetic flux density of the iron core is low and the q-axis inductance can be increased. However, since the d-axis inductance is also increased, the induced voltage is also increased. As a result, the maximum output is decreased by the amount that the magnet torque is reduced as compared with the case where the permanent magnet 52 is not removed. In addition, the operating range in which field weakening control is performed is the same as when all permanent magnets 52 are present.

When the winding resistance is ignored, the voltage and the like in the dq coordinate system are as follows.
Vd = −ωe · Lq · Iq + Ld · dId / dt (1)
Vq = ωe · (ψ + Ld · Id) + Lq · dIq / dt (2)
V = ωe · {(ψ + Ld · Id) ² + (Lq · Iq) ² } ^0.5 (3)
T = Pn · {ψ · Iq + (Ld−Lq) · Id · Iq} (4)
Vd: d-axis voltage, ωe: electrical angular frequency, Lq: q-axis inductance, Iq: q-axis current Vq: q-axis voltage, ψ: magnet flux winding interlinkage, Ld: d-axis inductance, Id: d-axis Current V: Induced voltage, T: Torque, Pn: Number of pole pairs Since Id is negative, if the salient pole ratio: Lq / Ld can be increased, the utilization factor of the reluctance torque increases from equation (4). However, an electric motor with a particularly large current has a problem that an induced voltage becomes excessive during high-speed rotation because an increase in induced voltage due to (Lq · Iq) ² in equation (3) becomes so large that it cannot be ignored.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an embedded magnet type electric motor with a reduced amount of magnets so that an induced voltage does not become excessive in a high-speed rotation region and all magnets are present. It is an object of the present invention to provide an embedded magnet type electric motor that can obtain the same maximum output as in the case of.

  In order to achieve the above object, an invention according to claim 1 is an embedded magnet type electric motor including a rotor in which a plurality of permanent magnets are embedded in a rotor core, and the number of poles is 4 (n + 1). (Where n is an integer equal to or greater than 1), and the rotor includes a portion in which permanent magnets are arranged in a V shape or an arc shape every 360 ° of electrical angle, and a V-shaped or arc-shaped flux barrier. Have.

  Therefore, in the rotor structure of the present invention, it is possible to realize a flat torque characteristic up to the high-speed rotation range as compared with the conventional technique. This is because in the part where there is no permanent magnet and there is a flux barrier, only the magnetic flux due to the stator winding exists, so even at the maximum current, the magnetic saturation of the iron core does not occur, the salient pole ratio can be increased and the reluctance torque The use efficiency of becomes higher. In addition, in the portion where the permanent magnet exists, the induced voltage does not increase because the inductance is small although the salient pole ratio is small as compared with the prior art. As a result, in the embedded magnet type electric motor with a reduced amount of magnets, the reluctance torque is increased and the induced voltage is not excessive in the high-speed rotation range, and the same maximum output as when all the magnets are present can be obtained.

  According to a second aspect of the present invention, in the first aspect of the present invention, a coil is wound around the teeth with distributed winding. In the present invention, since the flow of magnetic flux in the gap portion is close to a sine wave as in theory, it is easy to control the rotation of the rotor with a sine wave current drive.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the permanent magnet is formed in a flat plate shape. In this invention, compared with the case where an arc-shaped permanent magnet is used, the manufacture of the permanent magnet is simplified, and as a result, the manufacturing cost of the embedded magnet type electric motor can be reduced.

  According to the present invention, in an embedded magnet type motor with a reduced amount of magnets, there is provided an embedded magnet type motor capable of obtaining the same maximum output as when there are all magnets without causing an excessive induced voltage in a high speed rotation range. can do.

  Hereinafter, an embodiment in which the present invention is embodied in an embedded magnet type motor having 8 poles, that is, 4 (n + 1) where n is 1 will be described with reference to FIGS. FIG. 1 is a schematic diagram corresponding to a half of the entire rotor and stator.

  The stator 11 is cylindrical and has a plurality of teeth 12 inside thereof, and in this embodiment, 48 (in the drawing, 24) teeth 12 are provided at equal intervals. A coil (winding) (not shown) is wound around the tooth 12 by distributed winding.

  The rotor 13 includes a rotor core 14 in which a plurality of (for example, several tens) disk-shaped core sheets made of a high permeability material such as an electromagnetic steel plate are stacked, and a rotor shaft 15 that is inserted through the center of the rotor core 14. ing. The core sheets are integrally fixed with an adhesive or the like as necessary.

  A plurality of permanent magnets 16 are embedded in the rotor core 14. The rotor core 14 has a portion where the permanent magnets 16 are arranged in a V shape every electrical angle of 360 °, and a flux barrier 17 formed in a V shape. That is, in the portion illustrated in FIG. 1, two sets of four permanent magnets 16 are arranged in the range of the central angle 90 ° of the rotor core 14, and two sets of four flux barriers 17 are arranged in the next range of the central angle 90 °. Is arranged.

  The permanent magnets 16 are formed in a flat plate shape, and four sets and eight pieces (two sets and four pieces in the drawing) are provided so as to form a V shape. The four permanent magnets 16 arranged adjacent to each other are arranged near the outer periphery of a quarter range of the rotor core 14, and one set of permanent magnets 16 is arranged so that the south pole is on the teeth 12 side, and the other The permanent magnets 16 are arranged so that the N pole is on the tooth 12 side.

  The flux barrier 17 is arranged symmetrically with the permanent magnet 16 with respect to a plane including the center of the rotor core 14, and the flux barrier 17 arranged with two pairs of permanent magnets 16 is point-symmetrically arranged. The flux barrier 17 is also provided in four groups and eight pieces (two sets and four pieces in the figure) so that holes having the same shape as the permanent magnet 16 form a V shape. That is, the flux barrier 17 is formed in a state in which the permanent magnet 16 to be arranged so as to form a V shape is removed.

Next, the operation of the interior magnet type motor configured as described above will be described.
Usually, in order to increase the reluctance torque, it is better to use a high-speed rotating electric motor. However, since the induced voltage increases due to the increase in speed, the induced voltage at the time of energization must be lowered particularly in an embedded magnet type electric motor.

In general, there are the following methods for reducing the induced voltage constant.
(1) Decreasing the lamination thickness of the rotor core 14.
(2) Lower the magnetic flux density of the magnet.
(3) Widen the gap.
(4) Reduce the number of turns of the winding.

For example, when only the magnet torque is considered, the output P is expressed by the following equation. Therefore, if Iq is constant, the magnet torque decreases. However, _KE is a constant and proportional to the torque.
P = Pn · K _E · Iq · ωe
In many cases, Iq cannot be increased because the maximum current is determined by the restrictions of the inverter rating.

  Therefore, a rotor structure that can reduce the induced voltage during energization and that can always use the peak point of reluctance torque in the high-speed rotation range can compensate for the decrease in magnet torque, so the maximum output will not be reduced. Can be.

  In the case of the rotor structure of this embodiment, since there is no permanent magnet 16 in the region 19 where the flux barrier 17 exists, only the magnetic flux due to the stator windings exists, and magnetic saturation of the iron core does not occur even at the maximum current. The salient pole ratio can be increased. In the region 18 where the permanent magnets 16 are present, the salient pole ratio is small as compared with the configuration of the prior art in which the permanent magnet is present only on one of the V-shapes, but the induced voltage does not increase because the inductance is small.

The generated torque of the rotor structure of the embodiment is expressed by the following equation (5).
T = Pn / 2 · [{ψ · Iq + (Ld ₁ −Lq ₁ ) · Id · Iq} + {(Ld ₂ −Lq ₂ ) · Id · Iq}] (5)
Where Ld ₁ : d-axis inductance of the region 18 where the permanent magnet is present, Lq ₁ : q-axis inductance of the region 18 where the permanent magnet is present, Ld ₂ : d-axis inductance of the region 19 where the flux barrier 17 exists, Lq ₂ : flux Q-axis inductance Ld ₁ <Ld ₂ , Lq ₁ <Lq ₂ in the region 19 where the barrier 17 exists
Here, since Lq ₂ >Lq> Lq ₁ (Lq is the q-axis inductance in FIG. 7), the inductance component contributing to torque generation can be increased while the inductance component contributing to the increase in induced voltage is reduced.

  Magnetic field analysis was performed by the finite element method for the case where the permanent magnet 16 was a rare earth magnet and the motor was rotated at a maximum rotational speed of 10,000 rpm and sine wave current drive. FIG. 2 shows the magnetic field analysis result of the no-load induced voltage at the base speed, and FIG. 3 shows the magnetic field analysis result of the induced voltage when the maximum current is passed at the base speed. 2 and 3, the minimum value and the maximum value of the scale of the graph are matched.

  In the analysis, what is expressed as having all the magnets means a configuration in which the permanent magnets 16 are all placed in the flux barrier 17 of the configuration of the embodiment and arranged in a V-shape, which is expressed as conventional technology. Means a configuration in which all eight sets are arranged in a V-shape with one permanent magnet 16 and one flux barrier 17 as in FIG.

  As shown in FIG. 2, the no-load induced voltage is compared with the case of the embodiment indicated by the thin line and the conventional technique indicated by the thick line (the magnet is only on one side of the V shape) as compared with the case where all the magnets indicated by the alternate long and short dash line are present Lower. However, as shown in FIG. 3, the induced voltage when the maximum current flows is almost the same in the case of the conventional technique when all the magnets are present, whereas in the case of the embodiment, the peak value of the induced voltage is halved. It is as follows. This confirms that the salient pole ratio can be increased while the induced voltage is kept small in the rotor 13 of the embodiment because magnetic saturation does not occur in the region 19 as compared with the prior art.

Further, FIG. 4 shows the result of obtaining the relationship between the rotational speed, the output, and the torque by simulation.
Regarding the output, in the case of the embodiment, the conventional technique, and all of the magnets, the output increases with an increase in the number of rotations and then decreases. When the rotational speed at which the maximum output is obtained is the same with the conventional technique and all the magnets, the values are lower than those in the embodiment, and are approximately the same, and the maximum output of the conventional technique is about 60% of the case with all the magnets. On the other hand, in the case of the embodiment, the maximum output is equal to or greater than that in the case where all the magnets are present, and a high output can be obtained even at a high rotational speed. The output in this embodiment is a value larger than the maximum output of the prior art.

  Further, regarding the torque, the output of the embodiment is lower than that of the prior art in the low speed rotation region. However, as in the case where all the magnets are provided, the output of the prior art is narrow in the low-speed rotation region of constant torque, and the range in which maximum torque current control can be performed is narrow. On the other hand, in the case of the embodiment, since the increase of the induced voltage is small, it can be seen that the rotation region where the torque is constant is wide, the range in which the maximum torque current control can be performed is wide, and the base speed can be increased. In the high-speed rotation region, the torque is higher than in the case of the conventional technology and all the magnets.

According to this embodiment, the following effects can be obtained.
(1) An embedded magnet type electric motor including a rotor 13 in which a plurality of permanent magnets 16 are embedded in a rotor core 14, wherein the number of poles is 8 and the rotor 13 has a permanent magnet every 360 °. 16 has a V-shaped portion and a V-shaped flux barrier. Therefore, in the portion (region 19) where the permanent magnet 16 is not present and the flux barrier 17 is present, only the magnetic flux due to the stator winding is present, so that the magnetic saturation of the iron core does not occur even at the maximum current, and the salient pole ratio is The reluctance torque can be used more efficiently. In addition, in the portion where the permanent magnet 16 exists (region 18), although the salient pole ratio is smaller than that in the prior art, the induced voltage does not increase because the inductance is small. As a result, in the embedded magnet type electric motor with a reduced amount of magnets, the reluctance torque is increased and the induced voltage is not excessive in the high-speed rotation range, and the same maximum output as when all the magnets are present can be obtained. In addition, compared with the prior art, a flat torque characteristic can be realized up to a high-speed rotation range, so that the range in which maximum torque current control can be performed is widened, and the base speed can be increased. As a result, it is possible to cope with the maximum torque control even in a region where field weakening control is conventionally required. Further, by setting the advance angle at the time of field weakening control to an angle at which the reluctance torque can be most efficiently used, it is not necessary to flow an extra d-axis current for reducing the magnet magnetic flux, and the efficiency is increased.

  (2) Since the amount of the permanent magnet 16 can be halved as compared with an embedded magnet type motor having all magnets, a high output embedded magnet type motor can be manufactured at a low cost in a high-speed rotation region. it can.

  (3) Coils (windings) are wound around the teeth 12 in distributed winding. Accordingly, since the flow of magnetic flux in the gap portion is close to a sine wave as theoretically, it is easy to control the rotation of the rotor 13 by sine wave current drive.

  (4) The permanent magnet 16 is formed in a flat plate shape. Therefore, as compared with the case where an arc-shaped permanent magnet is used, the manufacture of the permanent magnet 16 is simplified, and as a result, the manufacturing cost of the embedded magnet type electric motor can be reduced.

  (5) The flux barrier 17 is arranged in a V shape like the permanent magnet 16 and symmetrically with the permanent magnet 16. Accordingly, when the core sheets constituting the rotor core 14 are laminated, the holes into which the permanent magnets 16 are inserted and the flux barrier 17 may be laminated without being distinguished from each other, so that the manufacture of the rotor core 14 is simplified. .

The embodiment is not limited to the above, and may be embodied as follows, for example.
The arrangement of the permanent magnet 16 and the flux barrier 17 is not limited to a V shape. For example, as shown in FIG. 5A, the shape of the flux barrier 17 is changed to one arc shape instead of the two flux barriers 17 arranged in a V shape, and two sets of four flux barriers 17 are replaced with 2 pieces. A set of two flux barriers 17 may be used, or a total of four sets of four flux barriers 17. Moreover, the permanent magnet 16 may arrange | position one circular-arc-shaped permanent magnet 16 instead of arrange | positioning the flat permanent magnet 16 in V shape. From the viewpoint of magnetic flux flow, an arc shape is preferred. However, since the arc-shaped permanent magnet 16 is difficult to manufacture and easily broken, the manufacturing cost increases.

O It is good also as a structure which made winding 20 the concentrated winding as shown in FIG.5 (b) instead of distributed winding with respect to the teeth 12. As shown in FIG.
○ The teeth 12 may not be equally spaced. You may change according to the winding method and control of a coil | winding.

  ○ The number of poles of the embedded magnet type motor is not limited to 8 but may be 4 (n + 1) (where n is an integer of 1 or more), for example, 4 (2 + 1) = 12 poles where n is 2. There may be. In the case of 12 poles, if the permanent magnets 16 are arranged in a V shape, a total of 6 sets and 12 sets are provided in 3 locations each with 2 sets and 4 sets in the range of the central angle of the rotor core 14. A total of 6 sets and 6 sets are provided in 3 places each of 2 sets and 2 sets.

The following technical idea (invention) can be understood from the embodiment.
(1) In the invention according to any one of claims 1 to 3, the permanent magnet and the flux barrier are formed to have the same shape as viewed from the axial direction of the rotor core, and include a plane including the center of the rotor core. Are formed symmetrically.

The typical fragmentary top view which shows the relationship between the rotor of one Embodiment, and a stator. The graph which shows the no-load induced voltage in a base speed. The graph which shows the induced voltage at the time of flowing the maximum current in base speed. The graph which shows the relationship between output-rotation speed and torque-rotation speed. (A), (b) is a schematic fragmentary top view which shows the relationship between the rotor and stator in another embodiment. Comparison of characteristics between SPM (surface magnet type motor) and IPM (embedded magnet type motor). The schematic plan view of the interior magnet type electric motor in a prior art.

Explanation of symbols

  12 ... Teeth, 13 ... Rotor, 14 ... Rotor core, 16 ... Permanent magnet, 17 ... Flux barrier.

Claims (3)

An embedded magnet type electric motor having a rotor in which a plurality of permanent magnets are embedded in a rotor core,
The number of poles is 4 (n + 1) (where n is an integer equal to or greater than 1), and the rotor includes a portion in which permanent magnets are arranged in a V shape or an arc shape every electrical angle of 360 °, and a V shape or An embedded magnet type electric motor having an arc-shaped flux barrier.   The interior magnet type electric motor according to claim 1, wherein a coil is wound around the teeth by distributed winding.   The interior permanent magnet motor according to claim 1, wherein the permanent magnet is formed in a flat plate shape.

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