JP2011083114A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress pulsation of a magnetic resistor to an electric angle and to reduce cogging torque, torque ripples and iron loss much more. <P>SOLUTION: A motor includes a rotor having a plurality of permanent magnet groups, teeth arranged at equal intervals and slots formed between the teeth. The respective permanent magnet groups are arranged at the equal intervals and are constituted of two permanent magnets. The two permanent magnets are disposed in a V-shape opened outward from a rotor center. A shape of a part positioned between the permanent magnet groups which are arranged at equal intervals in an outer circumference of the rotor and have the V-shape has a recessed shape. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric motor, and more particularly to an electric motor that suppresses pulsation of magnetic resistance with respect to an electrical angle and also reduces cogging torque, torque ripple, and iron loss.

As drive motors mounted on vehicles such as EVs, HEVs, PHEVs, FCVs, etc., electric motors in which a permanent magnet is embedded in a rotor (permanent magnet embedded motor: IPM motor) are employed.
In this motor, the reluctance torque, which is the rotational force generated by the change in magnetic energy due to the position of the self-inductance, can be effectively utilized by devising the shape, arrangement, and path of the magnetic flux. By utilizing this, the total torque (motor torque) can be enhanced by combining the magnet torque generated by the product of the interlinkage magnetic flux formed by the magnetic field of the permanent magnet and the armature current.

Japanese Patent Laid-Open No. 2004-328956 JP-A-2005-102461

By the way, in a conventional electric motor, an electric motor used for a driving motor such as HEV and EV is required to have a wide variable speed characteristic in addition to a large torque and a low rotation reduction.
In order to realize this, it is effective to effectively use the reluctance torque as described above, and as a shape of the rotor, a method of arranging permanent magnets in a V shape is widely adopted.

An example of the electric motor 101 including the rotor 102 in which the permanent magnets 106 and 107 are arranged in a V shape is shown in FIG.
In FIG. 5, the electric motor 101 includes the rotor 102 and a stator 103 disposed on the outer peripheral side of the rotor 102.
The rotor 102 has a plurality of permanent magnet groups 105 arranged at equal intervals in the circumferential direction.
The permanent magnet group 105 includes two permanent magnets 106 and 107, and is arranged in a V shape that opens outward from the center of the rotor 102.
The stator 103 has a plurality of teeth 112 arranged at equal intervals on the inner peripheral side, and slots 113 formed between the teeth 112.
A U-phase coil 114, a V-phase coil 115, and a W-phase coil 116 as winding phases are wound around the tooth 112 through a slot 113.
Further, the electric motor 101 employs a V-shaped arrangement in which the permanent magnets 106 and 107 are arranged in a V shape, so that the permeance is adjusted by adjusting the opening degree of the permanent magnets 106 and 107 compared to the flat plate arrangement. Can be fine-tuned, the induced voltage harmonic content can be lowered, and there is an effect of reducing iron loss due to the harmonic component.

However, an electric motor in which the permanent magnets are arranged in a V shape to form a V shape has a large difference in magnetic resistance with respect to the electrical angle when the ratio of reluctance torque increases, that is, when the salient pole ratio increases. There is an inconvenience that the torque ripple of the motor torque is increased.
And the V-shaped arrangement that secures the q-axis magnetic path and can effectively use the reluctance torque has a larger salient pole ratio than the case where the permanent magnet is arranged in a flat plate near the rotor outer diameter. There is a disadvantage that the torque ripple of the motor torque increases.
The increase in the torque ripple of the motor torque affects the ride comfort when the electric motor is used as a driving motor for the vehicle.
Further, the torque ripple of the motor torque, that is, the harmonic torque, leads to an increase in electromagnetic noise, resulting in an unpleasant sound for the driver and should be reduced as much as possible.

By providing a groove at a location as described in Patent Document 1 described above, a measure for reducing the torque ripple of the motor torque and reducing the iron loss has the disadvantage that the groove shape is complex and product variations tend to occur.
Further, there is a concern that the centrifugal force is concentrated and there is a risk of cracking, or that the BH characteristics deteriorate due to residual stress due to press punching, and the resistance of the q-axis magnetic path increases.

  An object of the present invention is to suppress the pulsation of the magnetic resistance with respect to the electrical angle, and to further reduce the cogging torque, torque ripple, and iron loss.

  Accordingly, in order to eliminate the above-described disadvantages, the present invention provides an electric motor including a rotor having a plurality of permanent magnet groups, teeth arranged at equal intervals, and slots formed between the teeth. The permanent magnet group is arranged at equal intervals and is composed of two permanent magnets, and the two permanent magnets are arranged in a V shape that opens outward from the rotor center, and are arranged on the inner periphery of the rotor. The shape of the part which is arrange | positioned at equal intervals and is located between permanent magnet groups provided with V shape has a recessed part shape, It is characterized by the above-mentioned.

As described in detail above, according to the present invention, in an electric motor including a rotor having a plurality of permanent magnet groups, teeth arranged at equal intervals, and slots formed between the teeth, each permanent magnet group is provided. Are arranged at equal intervals and composed of two permanent magnets, and the two permanent magnets are arranged in a V shape that opens outward from the rotor center, and are arranged at equal intervals in the outer periphery of the rotor. And the shape of the part located between permanent magnet groups provided with V shape has a recessed part shape.
Therefore, it is possible to suppress the pulsation of the magnetic resistance with respect to the electrical angle.
Further, cogging torque, torque ripple, and iron loss can be further reduced.

FIG. 1 is a partial cross-sectional view of an electric motor. (Example) FIG. 2 is a partial cross-sectional view of an electric motor showing a modification. (Example) FIG. 3 is a diagram showing a comparison of no-load induced voltage waveforms. (Example) FIG. 4 is a diagram showing a comparison between the cutting depth and the torque ripple. (Example) FIG. 5 is a partial cross-sectional view of an electric motor showing the prior art of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

1 to 4 show an embodiment of the present invention.
In FIG. 1, 1 is an electric motor, 2 is a rotor (also referred to as “rotor” or “rotor core”), and 3 is a stator (“stator” or “stator core”) disposed on the outer peripheral side of the rotor 2. .)
The rotor 2 is formed in a cylindrical shape by a magnetic material fixed to the rotating shaft 4, and a plurality of permanent magnet groups 5 are arranged on the rotor 2 at equal intervals in the circumferential direction.
Further, the permanent magnet groups 5 adjacent to each other in the circumferential direction of the rotor 2 are arranged so that the magnetic poles are alternately different in the circumferential direction.
Each permanent magnet group 5 is arranged at equal intervals and is composed of two first and second permanent magnets 6 and 7.
Two first and second magnet insertion holes 8 and 9 for inserting and fixing two first and second permanent magnets 6 and 7 constituting each permanent magnet group 5 in the rotor 2 respectively. Are formed in the axial direction.
At this time, the pair of first and second magnet insertion holes 8 and 9 are formed in a rectangular shape in cross section, and are arranged in a V shape whose longitudinal direction is opened outward from the center of the rotor 2.
As shown in FIG. 1, flux barriers 10 and 11 for preventing the passage of magnetic flux are formed at both longitudinal ends of the first and second magnet insertion holes 8 and 9, respectively.
The first and second permanent magnets 6 and 7 are respectively formed in the same rectangular shape as the first and second magnet insertion holes 8 and 9, and are inserted into the first and second magnet insertion holes 8 and 9, respectively. To be fixed.
The flux barrier 10 is disposed at both longitudinal ends of the first magnet insertion hole 8 to which the first permanent magnet 6 is fixed, and the second magnet insertion hole to which the second permanent magnet 7 is fixed. The flux barriers 11 are disposed at both longitudinal ends of 9.

Further, as shown in FIG. 1, the stator 3 of the electric motor 1 is formed in a cylindrical shape by a magnetic material, and is formed between teeth 12 disposed at equal intervals on the inner peripheral side of the stator 3. Slot 13.
A U-phase coil 14, a V-phase coil 15, and a W-phase coil 16 serving as winding phases are wound around the teeth 12 through, for example, five teeth 12 and through slots 13.
At this time, the U-phase coil 14 is located on the inner peripheral side of the tooth 12 and is disposed with one tooth 12 sandwiched in the circumferential direction.
The V-phase coil 15 is located on the outer peripheral side of the U-phase coil 14, is disposed with one tooth 12 sandwiched in the circumferential direction, and is shifted in the circumferential direction so as to overlap the U-phase coil 14. It is arranged.
Further, the W-phase coil 16 is located on the outer peripheral side of the V-phase coil 15, is arranged with one tooth 12 sandwiched in the circumferential direction, and overlaps the V-phase coil 15 while being shifted in the circumferential direction. It is arranged.
The electric motor 1 has permanent magnet groups 5 arranged at equal intervals in the circumferential direction of the rotor 2, and a rotating magnetic field is generated by the U-phase coil 14, the V-phase coil 15 and the W-phase coil 16 of the stator 3. The rotor 2 is rotated by the interaction with the magnetic field 5.

And in the said motor 1, the shape of the part located in the outer periphery of the said rotor 2 at equal intervals, and located between the permanent magnet groups 5 provided with V-shape has the shape of a recessed part 17. Yes.
More specifically, when a plurality of permanent magnet groups 5 are provided on the outer periphery of the rotor 2, as shown in FIGS. 1 and 2, each permanent magnet group 5 is disposed between adjacent permanent magnet groups 5. Out of the two first and second permanent magnets 6, 7 constituting the outer end corner 6 t of the first permanent magnet 6 of one permanent magnet group 5 and the second permanent magnet 7 of the other permanent magnet group 5. Between the end corner 7t or between the outer end corner 7t of the second permanent magnet 7 of one permanent magnet group 5 and the outer end corner 6t of the first permanent magnet 6 of the other permanent magnet group 5. The concave portion 17 is formed by shaving.
Further, the electric motor 1 has a rotor 2 outer diameter shape as shown in FIG. 1 and FIG. 2 in contrast to the perfect circular rotor structure in which the conventional electric motor (FIG. 5) has a permanent magnet arranged on the rotor 2 in a V shape. A recess 17 is formed to form a non-round rotor structure.
The electric motor 1 is a general three-phase IPM motor in which a rotor 2 is a three-pole pair, and the stator 3 is wound around 36 slots 13 and teeth 12 at 5 pitches.
The motor torque of the electric motor 1 that is an IPM motor has a magnitude obtained by adding the magnet torque and the reluctance torque.
Therefore, the torque ripple of the motor torque is naturally a magnitude obtained by adding the ripples of both the magnet torque and the reluctance torque.
In the shape of the rotor 2 of the motor 1, the magnetic resistance of the electrical angle with respect to the electrical angle can be increased by increasing the magnetic resistance of the q-axis magnetic flux by increasing the air gap length of the q-axis magnetic path by the recessed portion 17 of the outer diameter shape of the rotor 2. The difference can be reduced.

Further, the motor 1 has a low salient pole ratio due to the difficulty of passing the q-axis armature reaction magnetic flux, and as a result, the reluctance torque ripple can be reduced.
Since the torque ripple is the sum of the magnet torque and the reluctance torque ripple, the torque ripple is naturally reduced.
Therefore, the electric motor 1 can further reduce the cogging torque and the torque ripple as compared with the conventional electric motor.
As is apparent from the solid line and other line segments a, b, and c in FIG. 4, the torque ripple is reduced by the cutting depth (a: 0.2 mm, b: 0) of the recessed portion 17 having the outer shape of the rotor 2 added. .3 mm, c: 0.4 mm).
Therefore, even if the rotor 2 of the electric motor 1 is formed with a recess 27 having an extremely large cutting depth as shown in FIG. 2, torque ripple can be reduced. However, since the reluctance torque is reduced, the motor torque is reduced. For this reason, it is necessary to determine the appropriate cutting depth of the recess 17 having the outer diameter shape of the rotor 2 based on the required torque and the amount of torque ripple reduction.
Further, by adjusting the cutting depth and the cutting width of the concave portion 17 of the outer diameter of the rotor 2 to be added, the induced voltage harmonic content can be reduced, and there is an effect of reducing the iron loss due to the harmonic component. Can be further reduced.

  In FIG. 3, the no-load induced voltage waveform by the conventional V-shaped arrangement (corresponding to the “base model” in FIG. 3) and the outer diameter shape of the rotor 2 of the present invention are provided with a recess 17 (cutting depth 0 .3 mm) is substantially the same as the no-load induced voltage waveform obtained by the V-shaped arrangement (corresponding to the “shaving depth of 0.3 mm” in FIG. 3).

Thus, in the electric motor 1, the shape of the portion located between the permanent magnet groups 5 that are arranged at equal intervals on the outer periphery of the rotor 2 and have a V-shape has the shape of the recess 17. .
Thereby, the electric motor 1 can reduce the torque ripple of the motor torque, and when the electric motor 1 is used as a driving motor for a vehicle, it can contribute to an improvement in comfort.

In addition, the slots 13 in which the outer end corners 6t and 7t of the two first and second permanent magnets 6 and 7 constituting one permanent magnet group 5 are arranged in the left and right directions on both sides of one tooth 12 are counted. The second slot 13 is positioned on a straight line connecting the center in the width direction and the center of the rotor 2.
That is, when the two first and second permanent magnets 6 and 7 are line-symmetrically divided and formed as a straight line L1 passing through the center R0 (Earth Zero) of the rotor 2, as shown in FIG. One tooth 12 positioned at the center in the width direction is defined as a reference tooth 12a.
Further, the slots 13 arranged in the left and right directions on both sides of the reference tooth 12a are referred to as a left first slot 13a and a right first slot 13x.
The second slot 13 counted from the left first slot 13a is defined as the left third slot 13c, and the second slot 13 counted from the right first slot 13x is defined as the right third slot 13z.
At this time, a straight line passing through the center in the width direction of the left third slot 13c and the center R0 of the rotor 2 is defined as L2.
A straight line passing through the center in the width direction of the right third slot 13z and the center R0 of the rotor 2 is defined as L3.
Then, as shown in FIG. 1, the outer end corner 6t of the first permanent magnet 6 is positioned on the straight line L2, while the outer end corner 7t of the second permanent magnet 7 is positioned on the straight line L3. It will be. Therefore, cogging torque and torque ripple can be further reduced.

Further, the permanent magnet group 2 is arranged at a position where the magnetic flux lines with which the electric current is linked when the rotor 2 is an iron core are not hindered.
In other words, the magnetic flux line displays a magnetic flux (also referred to as “magnetic induction flux”) obtained by adding the vertical components of the magnetic field lines passing through a certain area in the magnetic field as a virtual line segment. Must be arranged so as not to be obstructed by the permanent magnet group 2.
For example, as disclosed in the embodiment of the present invention, the plurality of permanent magnet groups 2 are arranged at equal intervals and in a V-shape.
Therefore, it becomes possible to arrange the permanent magnet group 2 at a position where it does not hinder the magnetic flux lines interlinked with the electric current, which can contribute to the improvement of the driving efficiency of the electric motor 1.

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Rotor (it can also be called "rotor" or "rotor core")
3 Stator (also referred to as “stator” or “stator core”)
4 Rotating shaft 5 Permanent magnet group 6 First permanent magnet 6t Outer end corner 7 Second permanent magnet 7t Outer end corner 8 First magnet insertion hole 9 Second magnet insertion hole 10, 11 Flux barrier 12 Teeth 13 Slot 14 U Phase coil 15 V phase coil 16 W phase coil 17, 27 Recess

Claims (3)

  In an electric motor including a rotor having a plurality of permanent magnet groups, teeth arranged at equal intervals, and slots formed between the teeth, each permanent magnet group is arranged at equal intervals, and two It is composed of permanent magnets, and the two permanent magnets are arranged in a V-shape that opens outward from the rotor center, are arranged at equal intervals in the outer periphery of the rotor, and have a V-shape. The electric motor characterized in that the shape of the portion located between the permanent magnet groups has a concave shape.   The outer end corners of the two permanent magnets constituting one permanent magnet group count the slots arranged in the left and right directions on both sides of the one tooth, respectively, the width direction center of the second slot, the rotor center, The electric motor according to claim 1, wherein the electric motor is located on a straight line connecting the two.   The electric motor according to claim 2, wherein the permanent magnet group is disposed at a position where the magnetic flux lines interlinked with the electric current are not obstructed when the rotor is an iron core.

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