JP2010183655A - Rotating electrical machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce torque ripple of a rotating electrical machine. <P>SOLUTION: The rotating electrical machine has: a rotor 13 which includes a magnetic flux generating member that adds up and generates the magnetic flux of permanent magnets equivalent to the number of a plurality of different magnetic poles on its surface; and a stator 12 which adds up a plurality of current fields corresponding to the number of plural magnetic poles and gives a current for rotating the rotor 13. In the machine, permanent magnets 131N and 131S are arranged so that the widths of magnetic poles for the gap magnetic flux density of an N pole and an S pole that constitute one pole pair of a rotor 13 may be different from each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rotating electrical machine that generates a magnetic flux corresponding to a plurality of different numbers of magnetic poles.

  Conventionally, as this type of technology, for example, those described in the following documents are known (see Patent Document 1). In this document, the torque per unit magnet is improved by arranging N pole and S pole magnets at equal intervals, that is, by arranging N pole and S pole magnets at unequal intervals. An invention is described in which torque is maximized by appropriately setting the arrangement interval.

JP 2007-151236 A

  However, by adopting a configuration in which the N-pole and S-pole magnets are not arranged at equal intervals, the magnet arrangement interval becomes non-uniform and the torque ripple of the motor increases.

  Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide a rotating electrical machine with reduced torque ripple.

  In order to achieve the above object, a means for solving the problems of the present invention is a pole pair of a rotor provided with a magnetic flux generating member that generates a magnetic flux corresponding to a plurality of different magnetic poles on the surface. The magnets of the rotating electrical machine are arranged so that the magnetic pole widths of the gap magnetic flux density between the N pole and the S pole constituting the same are different.

  According to the present invention, since the magnetic pole width of the gap magnetic flux density between the N pole and the S pole constituting one pole pair of the rotor is different, torque ripple can be reduced.

It is a figure which shows the structure of the rotary electric machine which concerns on Example 1 of this invention. It is a figure which shows the other structure of a permanent magnet. It is a figure which shows the other structure of a permanent magnet. It is a figure which shows the gap magnetic flux density waveform for one electrical angle period. It is a figure which shows the structure of the conventional rotary electric machine. It is a figure which shows the linear model for 1 period of fundamental waves. It is a figure which shows the relationship between the deviation | shift amount of a pole center and a magnet center, and a torque. It is a figure which shows the relationship between the deviation | shift amount of a pole center and a magnet center, and a torque ripple rate. It is a figure which shows the gap magnetic flux density pattern model for 1 period of fundamental waves. It is a figure which shows the relationship between magnetic pole center distance / pole node length, and a torque ripple rate. It is a figure which shows the relationship between magnetic pole center distance / pole node length, and a torque ratio.

  Embodiments for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a configuration of a rotating electrical machine according to Embodiment 1 of the present invention. The rotating electrical machine of the first embodiment shown in FIG. 1 functions as a synchronous motor having an embedded magnet type rotor (rotor), and a stator (stator) 12 and a rotor 13 are coaxially centered around a shaft 11. Has been placed.

  The stator 12 is composed of 24 stator teeth 121, and coils 122 are wound around these stator teeth 121 in a concentrated manner. This winding is a set of eight windings arranged every three windings, connected in series or in parallel, one of which is connected to one of the other phases as a neutral point, the other not shown Inside the inverter, it is connected to the P side and the N side of the power supply line via a switching element. This inverter is configured to control a three-phase electric motor. The coil is applicable not only to concentrated winding but also distributed winding.

  In this embodiment, the rotor 13 has two types of pole pairs, an 8-pole pair and a 16-pole pair. The N-pole permanent magnet 131N has a flat plate shape, and the S-pole permanent magnet 131S is arranged in a V shape. In FIG. 1, the S-pole permanent magnet 131 </ b> S has a V shape, but is not limited to this shape.

  For example, as shown in FIG. 2 (showing a 1/8 model), the permanent magnet may be composed of permanent magnets having different magnet thicknesses. For example, the magnet width ratio between the N pole and the S pole is 1: 2. When the thickness ratio is 2: 1, the minimum unit of magnets can be aligned by dividing the width and thickness by the magnitude of the greatest common divisor of both, and the magnet cost can be reduced.

  Further, as shown in FIG. 3 (showing a 1/8 model), the permanent magnet may be composed of permanent magnets having different electrical characteristics. For example, the N pole is composed of an alnico magnet and the S pole is composed of a neodymium magnet. May be.

  In addition, from the balance of required magnet characteristics and cost, combinations of magnets having various characteristics other than the above can be considered.

  Next, the operation of the rotating electrical machine having the configuration shown in FIG. 1 will be described with reference to FIG.

  FIG. 4 is a diagram showing a gap magnetic flux density waveform in a section from A to A ′ corresponding to one period of the electrical angle of the magnet magnetic flux constituting the 8-pole pair in FIG. 1. In FIG. 4, the N pole side has a wider magnetic pole width than the S pole side, but the magnetic flux density is small. This is because the magnet on the S pole side is composed of a V-shaped magnet. In this embodiment, since the amount of N pole and S pole magnets is the same, the area (S (N)) on the N pole side surrounded by 0 [T] on the horizontal axis and the magnetic flux density in FIG. Are equal in area S (S).

  When such a magnetic flux density waveform is Fourier transformed, it can be seen that magnet magnetic fluxes corresponding to the 8-pole pair and the 16-pole pair appear as the spectrum of the fundamental wave and the second harmonic. Therefore, by applying a composite current corresponding to the magnetic flux to the coil 122 of the stator 12, a torque obtained by adding the torques of the magnets of the 8-pole pair and the 16-pole pair can be obtained. Further, as will be described later, by changing the magnetic pole width and magnetic flux density of the N pole and S pole, it is possible to change the magnetic flux ratio between the fundamental wave and the second harmonic of the magnet magnetic flux.

  Next, the advantageous effects of the present embodiment over the prior art will be described by comparing the conventional technique mentioned in the background section with the present embodiment.

  First, FIG. 5 shows a cross-sectional configuration of a rotating electrical machine that employs a conventional technique as compared with the present embodiment. In the rotating electrical machine as shown in FIG. 5, the torque ratio changes depending on the amount of deviation between the pole (node) center and the magnet center, and there is an optimum amount of deviation according to the magnet width. FIGS. 6A and 6B show a linear model for one period of the fundamental wave of the rotating electrical machine, and FIG. 7 shows the relationship between the deviation amount between the pole center and the magnet center and the torque ratio. Here, when the distance to the pole center of the fundamental wave is K and the distance to the magnet width center is Km, the deviation amount (%) is expressed by (K−Km) / K.

  The torque ratio shown in FIG. 7 is obtained by performing Fourier transform on the gap magnetic flux density waveform, extracting the amplitude of the fundamental wave and the second harmonic magnetic flux, calculating the magnet torque using the following equation (1), and then regarding each magnet width. Normalized with a torque value of zero deviation. Note that each current component of the fundamental wave and the second harmonic is calculated based on the ratio of the magnetic flux component using the following equations (2) and (3) in order to fix the effective current value.

ここで、Ｔ：トルク［Ｎｍ］、ｐ１：基本波極対数、ｐ２：二次高調波極対数、Ψ１：基本波無負荷磁束［Ｗｂ］、Ψ２：二次高調波無負荷磁束［Ｗｂ］、Ｉ１：基本波電流［Ａ］、Ｉ２：二次高調波電流［Ａ］、ｋ：比例定数とする。

Here, T: torque [Nm], p1: number of fundamental wave pole pairs, p2: number of second harmonic pole pairs, Ψ1: fundamental wave no-load magnetic flux [Wb], Ψ2: second harmonic no-load magnetic flux [Wb], I1: Fundamental wave current [A], I2: Second harmonic current [A], k: Proportional constant.

  Next, FIG. 8 shows the relationship between the deviation amount and the ripple rate when the relationship shown in FIG. 7 is provided. In FIG. 8, the ripple rate is the ratio of the amplitude value of the vibration component of the torque to the average torque. The vibration component of the torque is obtained from the sum of the product of the magnetic flux component of the fundamental wave and the current component of the second harmonic, and the product of the magnetic flux component of the second harmonic and the current component of the fundamental wave. As can be seen from FIG. 8, torque improvement and torque ripple are in a trade-off relationship. This is considered to be because the term of the vibration component becomes large because the magnetic flux of the fundamental wave and the second harmonic becomes the same ratio in a region where the torque ratio is large.

  Next, the effect of the present embodiment in the case where the magnet amount is approximately equal to that of the model A which is one of the optimum magnet arrangements in the conventional rotating electric machine mentioned above will be described.

  FIG. 9 shows a pattern model of the gap magnetic flux density for one period of the fundamental wave magnetic flux. W1 and W2, and P1 and P2 indicate the magnetic pole width and magnetic pole deviation amount of the N pole and the S pole. Here, in order to facilitate understanding, the magnetic pole strength is “1” and “−W2 / W1”, and the areas on the N pole side and the S pole side surrounded by 0 [T] on the horizontal axis are the same. explain. In addition, the distance between magnetic pole centers when magnets are arranged at equal intervals is the pole node length.

  FIGS. 10 and 11 show the torque ripple ratio and the torque ratio when W1: W2 = 3: 2. The torque ratio is normalized by the torque of model A shown in FIG. Referring to FIG. 10 and FIG. 11, it can be seen that the torque ripple rate is reduced by arranging the magnet as employed in the present embodiment, while the torque is almost the same as the conventional one. Further, since there is a trade-off relationship between the torque ripple rate and the torque ratio, which one is prioritized can be determined by appropriately selecting the distance between the magnetic pole centers according to the required specifications.

  The examples shown in FIGS. 9 to 11 are examples, and the same can be said even when W1 and W2 are other than 3: 2. In addition, among permanent magnets of N pole and S pole, the permanent magnet having a thin magnet thickness and having a strong magnetic field applied from the outside of the permanent magnet is made of a permanent magnet having a high holding power or a small thermal demagnetization. By doing so, it is possible to suppress demagnetization.

  As described above, in the above embodiment, the permanent magnets are not arranged at equal intervals on the rotor, that is, non-uniformly arranged, so that magnetic fluxes corresponding to different numbers of magnetic poles are added to the surface and generated. A magnetic flux generating member is provided on the rotor, a plurality of current magnetic fields corresponding to the number of magnetic poles are added together, and a coil to which current can be applied so that the rotor can be rotated is provided on the stator. Since the magnetic pole widths of the gap magnetic flux density of the N pole and S pole constituting the pole pair are made different, the effect of reducing the magnet amount with respect to a general permanent magnet motor having permanent magnets arranged at equal intervals is impaired. Torque ripple can be reduced.

  When the magnetic pole width of the gap magnetic flux density between the N pole and the S pole is W1 and W2, and the magnitude of the magnetic flux density is B1 and B2, the torque per magnet amount is increased by setting W1> W2 and B1 <B2. It becomes possible. Further, since there is no large difference in the total magnetic flux amount between the N pole and S pole constituting one pole pair, a magnetic circuit can be easily configured.

  With the gap magnetic flux density of 0 [T] as a reference, the area surrounded by the magnetic pole width and the magnetic flux density is made equal between the N pole and the S pole (W1 × B1 = W2 × B2), so that the N pole and the S pole The amount of magnets can be made equal. On the other hand, with the gap magnetic flux density of 0 [T] as a reference, by setting the area surrounded by the magnetic pole width and the magnetic flux density to be different between the N pole and the S pole (W1 × B1 ≠ W2 × B2), The balance of the magnetic flux amount between the pole and the S pole is different, and an apparent magnetic pole is generated in a pole with a small amount of magnetic flux, and the amount of magnet can be reduced.

  By making the distance between the magnetic pole centers of the N pole and S pole equal to the pole node distance of the rotor, the torque ripple can be minimized. On the other hand, the average torque can be increased by setting the distance between the magnetic pole centers of the N pole and the S pole to be different from the pole nodal distance of the rotor.

  When selecting the ratio of the magnetic pole widths W1 and W2 of the N pole and S pole and the distance between the magnetic pole centers, the torque ripple is set between the minimum value and the maximum value, and the change in torque is between the minimum value and the maximum value. By setting at, it is possible to widen the selection range of the magnet arrangement according to the torque ripple reduction rate and the required torque value.

  By setting the N-pole and S-pole permanent magnets to different thicknesses, the magnet's smallest unit can be reduced by dividing the N-pole and S-pole magnet thicknesses and magnet widths by the greatest common divisor. It becomes possible to make it equal, and the cost of the magnet can be reduced.

  By disposing one or both of the N poles and the S poles in a V shape, a gap magnetic flux density waveform having a high magnetic flux density with a narrow magnetic pole width can be obtained.

  By configuring the N-pole and S-pole permanent magnets with magnets having different characteristics, options for controlling the gap magnetic flux density waveform can be expanded. Further, for example, by using an alnico or ferrite magnet, the cost of the magnet can be reduced as compared with the case of using a neodymium magnet.

  Of the N and S permanent magnets, the permanent magnet whose operating point is closer to the knick point is a permanent magnet having a higher holding force than the other permanent magnet, so that it is always strong with a material having a high holding force, for example. A permanent magnet to which a magnetic field is applied can be configured to suppress demagnetization.

  Of the N-pole and S-pole permanent magnets, the permanent magnet having the higher magnetic flux density at the operating point is a permanent magnet having a smaller thermal demagnetization than the other permanent magnet. Even when heat is generated by current, thermal demagnetization can be reduced.

DESCRIPTION OF SYMBOLS 11 ... Shaft 12 ... Stator 13 ... Rotor 121 ... Stator teeth 122 ... Coil 131N, 131S ... Permanent magnet

Claims (12)

A rotor provided with a magnetic flux generating member for generating a magnetic flux corresponding to a plurality of different magnetic poles on the surface thereof; a plurality of current magnetic fields corresponding to the plurality of magnetic poles; and the rotor In a rotating electrical machine having a stator for supplying a current for rotating
A rotating electrical machine characterized in that the magnets are arranged such that the magnetic pole widths of the gap magnetic flux density of the N pole and S pole constituting one pole pair of the rotor are different. 2. The W 1> W 2 and B 1 <B 2, wherein the magnetic pole widths of the gap magnetic flux density of the N pole and the S pole are W 1 and W 2 and the magnitudes of the magnetic flux densities are B 1 and B 2, respectively. Rotating electric machine. 3. The rotating electrical machine according to claim 1, wherein an area surrounded by a magnetic pole width and a magnetic flux density is made equal on the N pole side and the S pole side with a gap magnetic flux density of 0 [T] as a reference. . The rotating electrical machine according to any one of claims 1 to 3, wherein a distance between the magnetic pole centers of the N pole and the S pole is equal to a pole node distance of the rotor. The rotating electrical machine according to any one of claims 1 to 3, wherein a distance between the magnetic pole centers of the N pole and the S pole is different from a pole node distance of the rotor. When setting the ratio of the magnetic pole width of the N pole and the S pole and the distance between the magnetic pole centers, the change width of the torque ripple is between the minimum value and the maximum value, and the change width of the torque is between the minimum value and the maximum value. The rotating electrical machine according to claim 1, wherein the rotating electrical machine is a rotating electrical machine. 3. The rotating electrical machine according to claim 1, wherein the area surrounded by the magnetic pole width and the magnetic flux density is different between the N pole side and the S pole side with a gap magnetic flux density of 0 [T] as a reference. The rotating electric machine according to any one of claims 1 to 7, wherein the N-pole and S-pole magnets are composed of permanent magnets having different thicknesses. The rotating electric machine according to any one of claims 1 to 7, wherein the magnet of one or both of the N pole and the S pole is configured by a permanent magnet arranged in a V shape. . The rotating electric machine according to any one of claims 1 to 7, wherein the N-pole and S-pole magnets are composed of permanent magnets having different characteristics. 11. The magnet according to claim 1, wherein the magnet having an operating point closer to the knick point among the N-pole and S-pole magnets is a permanent magnet having a higher holding force than the other magnet. The rotating electrical machine according to claim 1. 11. The magnet having a higher magnetic flux density at the operating point among the N-pole and S-pole magnets is composed of a permanent magnet having a smaller thermal demagnetization than the other magnet. The rotating electrical machine according to any one of claims.

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