Rotating electric machine having rotor embedded-permanent-magnets with inner-end magnetic gaps and outer-end magnetic gaps, and electric car using the same electric machine

CLAIM OF PRIORITY

0001The present application claims priority from Japanese application serial no. 2004-66465, filed on Mar. 10, 2004, the content of which is hereby incorporated by reference into this application.

FIELD OF THE INVENTION

0002The present invention relates to a permanent magnet rotating electric machine suitable for use for an electric car and the electric car using it.

BACKGROUND OF THE INVENTION

0003A motor used to drive an electric car, particularly an electric vehicle and a hybrid electric vehicle, is desired to be small, light, and highly efficient. In recent years, by development of a highly efficient magnet material, as a drive motor for an electric car (particularly an electric vehicle and a hybrid electric vehicle), in consideration of the respect that it can be made smaller, lighter, and more highly efficient than an induction motor and a reluctance motor, a permanent magnet motor has been used predominantly. The reason is that the permanent magnet motor can generate a large amount of magnetic flux without supplying a large current. Particularly, in a region of high torque at a low speed, the characteristic can be realized. On the other hand, at a high speed, an occurrence of iron loss and an occurrence of high voltage due to the magnetic flux amount often come into a problem.

0004As a rotor structure of a motor used for an electric car, particular an electric vehicle and a hybrid electric vehicle, in consideration of countermeasures for an occurrence of iron loss and an occurrence of high voltage and retention of permanent magnets, an embedding type permanent magnet rotating electric machine for embedding permanent magnets in a laminated silicone steel plate is known. Furthermore, as described in Japanese Patent Laid-Open No. Hei09(1997)-261901, as a structure of reducing the rate of torque by magnets and reducing the magnetic flux amount of permanent magnets, a structure of arranging auxiliary salient poles between permanent magnets is known. In this structure, since the magnetic flux of the permanent magnets is little, the iron loss at a comparatively high speed is little, while in a region requiring low speed torque, reluctant torque is produced by the auxiliary salient poles and little magnetic torque can be compensated for.

SUMMARY OF THE INVENTION

0005However, even in the structure described in Japanese Patent Laid-Open No. Hei09(1997)-261901, particularly in a case of a drive motor used in a hybrid electric vehicle, the iron loss due to the magnetic flux of the permanent magnets becomes braking force and increases fuel expenses of the car, so that the iron loss in a high-speed region comes into a problem.

0006Further, as a motor used to drive an electric car, particularly an electric vehicle and a hybrid electric vehicle, the reduction in the torque ripple is important from the viewpoint of comfortableness to ride in and noise reduction, though this respect is not taken into account in conventional motors.

0007The first object of the present invention is to provide a highly efficient permanent magnet rotating electric machine capable of more reducing effects of iron loss and an electric car using it.

0008Further, the second object of the present invention is to provide a permanent magnet rotating electric machine of a low torque ripple capable of reducing the torque ripple and an electric car using it.

0009(1) To accomplish the above first object, the present invention is a permanent magnet rotating electric machine comprising a stator having stator windings wound round a stator iron core and a permanent magnet rotor having a plurality of inserted permanent magnets in which the polarity is alternately arranged in the peripheral direction in the rotor iron core, wherein the iron core of the permanent magnet rotor is composed of magnetic pole pieces positioned on the air gap face of the permanent magnets for forming the magnetic path of the permanent magnets, auxiliary magnetic poles projected up to the air gap face of the permanent magnets for producing reluctant torque, and a stator yoke positioned on the reversed air gap face of the permanent magnets for forming the magnetic path of the auxiliary salient poles and permanent magnets, and the iron core has concavities formed on the air gap face of the magnetic pole pieces of the rotor iron core of the permanent magnets, gently tilting from the central part of the magnetic poles to the end thereof.

0010By use of such a constitution, the effect of iron loss can be reduced more and high efficiency can be realized.

0011(2) In (1) mentioned above, the change in the air gap length at the central part of the magnetic poles at the position of the concavities is preferably smaller than the change in the air gap length at the end of the magnetic poles.

0012(3) In (1) mentioned above, the air gap length of the auxiliary salient pole portion is preferably smaller than the air gap length of the magnetic pole piece portion.

0013(4) To accomplish the above second object, the present invention is a permanent magnet rotating electric machine comprising a stator having stator windings wound round a stator iron core and a permanent magnet rotor having a plurality of inserted permanent magnets in which the polarity is alternately arranged in the peripheral direction in the rotor iron core, wherein the iron core of the permanent magnet rotor is composed of magnetic pole pieces positioned on the air gap face of the permanent magnets for forming the magnetic path of the permanent magnets, auxiliary magnetic poles projected up to the air gap face of the permanent magnets for producing reluctant torque, and a stator yoke positioned on the reversed air gap face of the permanent magnets for forming the magnetic path of the auxiliary salient poles and permanent magnets, and the iron core has concavities formed on the air gap face of the magnetic pole pieces of the rotor iron core of the permanent magnets on both sides of the magnetic pole center at a position within the range from an electrical angle of 20° to 30° from the magnetic pole center when the number of slots of the stator iron core per pole and per phase is 2 or at a position within the range from an electrical angle of 15° to 45° from the magnetic pole center when the number of slots of the stator iron core per pole and per phase is 1.

0014By use of such a constitution, the torque ripple can be reduced.

0015(5) To accomplish the above first object, the present invention is an electric car comprising a permanent magnet rotating electric machine, wheels driven by the permanent magnet rotating electric machine, and a control means for controlling drive torque outputted by the permanent magnet rotating electric machine, wherein the permanent magnet rotating electric machine is composed of a stator having stator windings wound round a stator iron core and a permanent magnet rotor having a plurality of inserted permanent magnets in which the polarity is alternately arranged in the peripheral direction in the rotor iron core, and the iron core of the permanent magnet rotor is composed of magnetic pole pieces positioned on the air gap face of the permanent magnets for forming the magnetic path of the permanent. magnets, auxiliary magnetic poles projected up to the air gap face of the permanent magnets for producing reluctant torque, and a stator yoke positioned on the reversed air gap face of the permanent magnets for forming the magnetic path of the auxiliary salient poles and permanent magnets, and the iron core has concavities formed on the air gap face of the magnetic pole pieces of the rotor iron core of the permanent magnets, gently tilting from the magnetic pole central part to the end.

0016By use of such a constitution, an electric car of low vibration and low noise can be obtained.

0017(6) To accomplish the above second object, the present invention is an electric car comprising a permanent magnet rotating electric machine, wheels driven by the permanent magnet rotating electric machine, and a control means for controlling drive torque outputted by the permanent magnet rotating electric machine, wherein the permanent magnet rotating electric machine is composed of a stator having stator windings wound round a stator iron core and a permanent magnet rotor having a plurality of inserted permanent magnets in which the polarity is alternately arranged in the peripheral direction in the rotor iron core, and the iron core of the permanent magnet rotor is composed of magnetic pole pieces positioned on the air gap face of the permanent magnets for forming the magnetic path of the permanent magnets, auxiliary magnetic poles projected up to the air gap face of the permanent magnets for producing reluctant torque, and a stator yoke positioned on the reversed air gap face of the permanent magnets for forming the magnetic path of the auxiliary salient poles and permanent magnets, and the iron core has concavities formed on the air gap face of the magnetic pole pieces of the rotor iron core of the permanent magnets on both sides of the magnetic pole center at a position within the range from an electrical angle of 20° to 30° from the magnetic pole center when the number of slots of the stator iron core per pole and per phase is 2 or at a position within the range from an electrical angle of 15° to 45° from the magnetic pole center when the number of slots of the stator iron core per pole and per phase is 1.

0018By use of such a constitution, an electric car of low vibration and low noise can be obtained.

0019According to the present invention, an electric car in which the effect of iron loss can be reduced more, and a highly efficient permanent magnet rotating electric machine can be obtained, and fuel expenses can be reduced, and low vibration and noise can be realized can be obtained.

0020According to the present invention, a permanent magnet rotating electric machine of a low torque ripple can be obtained and an electric car of low vibration and noise can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

0021<figref idref="DRAWINGS">FIG. 1</figref> is a cross sectional view showing the constitution of the permanent magnet rotating electric machine of the first embodiment of the present invention.

0022<figref idref="DRAWINGS">FIG. 2</figref> is a cross sectional view showing the constitution of the permanent magnet rotating electric machine of the first embodiment of the present invention.

0023<figref idref="DRAWINGS">FIG. 3</figref> is an enlarged cross sectional view showing the detailed constitution of the rotor of the permanent magnet rotating electric machine of the first embodiment of the present invention.

0024<figref idref="DRAWINGS">FIG. 4</figref> is an illustration for the air gap length of the magnetic pole pieces of the rotor of the permanent magnet rotating electric machine of the first embodiment of the present invention.

0025<figref idref="DRAWINGS">FIG. 5</figref> is an illustration for iron loss of the rotor of the permanent magnet rotating electric machine of the first embodiment of the present invention.

0026<figref idref="DRAWINGS">FIG. 6</figref> is an illustration for iron loss of the rotor of the permanent magnet rotating electric machine of the first embodiment of the present invention.

0027<figref idref="DRAWINGS">FIG. 7</figref> is a cross sectional view showing the constitution of the permanent magnet rotating electric machine of the second embodiment of the present invention.

0028<figref idref="DRAWINGS">FIG. 8</figref> is a cross sectional view showing the constitution of the permanent magnet rotating electric machine of the third embodiment of the present invention.

0029<figref idref="DRAWINGS">FIG. 9</figref> is an illustration for the relationship between the concavities <b>77</b> and the torque ripple formed on the outer periphery of the magnetic pole pieces of the rotor of the permanent magnet rotating electric machine of the third embodiment of the present invention.

0030<figref idref="DRAWINGS">FIG. 10</figref> is an illustration for the relationship between the concavities <b>77</b> and the torque ripple formed on the outer periphery of the magnetic pole pieces of the rotor of the permanent magnet rotating electric machine of the third embodiment of the present invention.

0031<figref idref="DRAWINGS">FIG. 11</figref> is a block diagram showing the constitution of the machine driving system of the electric car loading the permanent magnet rotating electric machine of each embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

0032Hereinafter, the constitution of the permanent magnet rotating electric machine Of the first embodiments of the present invention will be explained with reference to <figref idref="DRAWINGS">FIGS. 1 to 6</figref>. Here, as an example, an example of a permanent magnet motor in which a rotating electric machine has a winding structure of distribution winding as a stator and a rotor has <b>8</b> poles will be explained.

0033Firstly, by referring to <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, the whole constitution of the permanent magnet rotating electric machine of this embodiment will be explained.

0034<figref idref="DRAWINGS">FIGS. 1 and 2</figref> are cross sectional views showing the constitution of the permanent magnet rotating electric machine of the first embodiment of the present invention. <figref idref="DRAWINGS">FIG. 1</figref> is a cross sectional view in the parallel direction with the rotation axis and <figref idref="DRAWINGS">FIG. 2</figref> is a cross sectional view in the perpendicular direction to the rotation axis and a view in the A-A direction shown in <figref idref="DRAWINGS">FIG. 1</figref>. Further, in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, the same numerals indicate the same parts.

0035As shown in <figref idref="DRAWINGS">FIG. 1</figref>, a permanent magnet rotating electric machine <b>1</b> includes a stator <b>2</b>, a rotor <b>3</b>, and end brackets <b>9</b>A and <b>9</b>B. The stator <b>2</b> has a stator iron core <b>4</b> and stator windings <b>5</b>. The rotor <b>3</b> has a rotor iron core <b>7</b> composed of a magnetic substance and a shaft <b>8</b>. Further, the rotor <b>3</b>, via the shaft <b>8</b> fit into the rotor iron core <b>7</b>, is rotatably held by bearings <b>10</b>A and <b>10</b>B fit into the end brackets <b>9</b>A and <b>9</b>B. Further, the constitution shown in the drawing has no frame on the outer periphery of the stator iron core <b>4</b>. However, a frame may be used if necessary.

0036On the shaft <b>8</b> of the rotor <b>3</b>, a magnetic pole position sensor PS for detecting the position of the rotor <b>3</b> and a position sensor E are installed. According to the position of the rotor detected by the magnetic pole position sensor PS for detecting the position of the rotor <b>3</b> and the position sensor E, a 3-phase current is supplied to the stator windings <b>5</b>, thus a rotating magnetic field is generated. Magnetic attraction and repulsion force are generated between the rotating magnetic field and the permanent magnets of the rotor <b>3</b>, thus continuous rotary power is generated. Here, when the current phase is properly selected, in the low speed and large torque region, the composite torque of the torque by permanent magnet torque <b>6</b> and the torque by auxiliary salient poles <b>71</b> is controlled so as to be maximized.

0037On the other hand, in the high speed region where the induced voltage of the permanent magnets is higher than the terminal voltage of the motor, the current vector is moved forward, thus the rotating magnetic field by the stator winding current is controlled by weak field control so as to be applied to the center of the permanent magnets <b>6</b> as demagnetizing force. By doing this, the magnetic flux of the permanent magnets <b>6</b> is effectively reduced, thus the iron loss of the rotating electric machine can be reduced and a highly efficient operation can be performed.

0038Next, as shown in <figref idref="DRAWINGS">FIG. 2</figref>, the stator iron core <b>4</b> is composed of a circular ring shaped stator yoke <b>41</b> and iron core teeth <b>42</b>. Between the neighboring stator teeth <b>42</b>, slots <b>43</b> for storing the stator windings <b>5</b> are installed. Here, round the stator windings <b>5</b>, general 3-phase (phase U, phase V, phase W) distribution windings are wound. The number of stator teeth <b>42</b> is 48 and the number of slots <b>43</b> is also 48. The number of stator teeth (salient poles) <b>42</b> per phase is 16.

0039The rotor iron core <b>7</b> has insertion holes <b>70</b> for the permanent magnets <b>6</b> arranged at even intervals in the peripheral direction. The permanent magnets <b>6</b> are inserted into the insertion holes <b>70</b>. The number of poles of the rotor <b>3</b> is 8 and the number of insertion holes <b>70</b> is 16. For example, permanent magnets <b>6</b>A<b>1</b> and <b>6</b>A<b>2</b> inserted into two insertion holes <b>70</b>A<b>1</b> and <b>70</b>A<b>2</b> constitute the same pole, thus one pole is formed. For example, assuming the polarity of the permanent poles <b>6</b>A<b>1</b> and <b>6</b>A<b>2</b> as pole S, the polarity of the neighboring permanent magnets <b>6</b>B<b>1</b> and <b>6</b>B<b>2</b> in the peripheral direction becomes pole N and mutual polarity is obtained in the peripheral direction. The insertion holes <b>70</b>A<b>1</b> and <b>70</b>A<b>2</b> are arranged symmetrically with respect to line in the radial direction of the rotor iron core <b>7</b> and in a V shape. Therefore, two permanent magnets <b>6</b>B<b>1</b> and <b>6</b>B<b>2</b> are arranged per magnetic pole, so that the flux density per magnetic pole is increased.

0040The rotor iron core <b>7</b> has magnetic pole pieces <b>72</b> installed on the outer periphery of the permanent magnets <b>6</b>. The magnetic pole pieces <b>72</b> form a magnetic circuit through which the magnetic flux generated by the permanent magnets <b>6</b> flows toward the stator <b>2</b> via the air gap formed between the rotor <b>3</b> and the stator <b>2</b>.

0041The permanent magnets <b>6</b> forming the respective magnetic poles adjoin each other via the auxiliary salient poles <b>71</b> which are a part of the rotor iron core <b>7</b>. The auxiliary magnetic poles <b>71</b> bypass the magnetic circuit of the magnets and directly generate the magnetic flux on the stator side by the electromotive force of the stator. The magnetic pole pieces <b>72</b> and the auxiliary salient poles <b>71</b> are connected by bridges <b>73</b> to increase the mechanical strength thereof.

0042Between the magnets <b>6</b>A<b>1</b> and <b>6</b>A<b>2</b> and the bridges <b>73</b>, triangular air gaps <b>75</b>A<b>1</b> and <b>75</b>A<b>2</b> are respectively formed and between the magnets <b>6</b>A<b>1</b> and <b>6</b>A<b>2</b> forming the same pole, a triangular air gap <b>75</b>A<b>3</b> is formed. Air exists inside the air gaps <b>75</b>A<b>1</b>, <b>75</b>A<b>2</b>, and <b>75</b>A<b>3</b> and the leakage flux is reduced.

0043The inner peripheral side of the insertion holes <b>70</b>, the auxiliary salient poles <b>71</b>, and the air gaps <b>75</b>A<b>1</b>, <b>75</b>A<b>2</b>, and <b>75</b>A<b>3</b> is a rotor yoke <b>74</b> constituting the magnetic path of the permanent magnets <b>6</b>. By the above constitution, the so-called embedding type permanent magnet rotating electric machine is formed.

0044The aforementioned control by weak field current, by increasing the current, can reduce the basic wave part of the iron loss, though the high frequency component of the iron loss is increased inversely and after all, the iron loss may not be reduced.

0045On the other hand, when the air gap length is increased, the iron loss by high frequency waves is decreased. However, in correspondence to an increase in the air gap length, the torque is reduced. Therefore, it is important to suppress an increase in the iron loss at a high speed while suppressing the reduction in an occurrence of torque.

0046Therefore, in this embodiment, on the peripheral part of the rotor iron core <b>7</b>, that is, on the air gap face of the magnetic pole pieces <b>72</b>, concavities <b>76</b> gently tilting from the central part of the magnetic poles to the end thereof are formed. Particularly, since the concavities <b>76</b> gently tilting from the central part of the magnetic poles to the end thereof are formed on the air gap face of the magnetic pole pieces of the rotor iron core, when the air gap length at the central part of the auxiliary salient poles <b>71</b> and the magnetic pole pieces <b>72</b> which greatly contribute to an occurrence of torque and do not affect an occurrence of iron loss is reduced and the air gap portion of the magnetic pole pieces from the center of the magnetic poles to the end thereof causing high frequency iron loss rather than an occurrence of torque is increased as shown in <figref idref="DRAWINGS">FIG. 2</figref>, consistency of a reduction in the iron loss with insurance of an occurrence of torque can be realized. This respect will be explained by referring to <figref idref="DRAWINGS">FIG. 3</figref> and the subsequent drawings.

0047Next, by referring to <figref idref="DRAWINGS">FIG. 3</figref>, the detailed constitution of the rotor of the permanent magnet rotating electric machine of this embodiment.

0048<figref idref="DRAWINGS">FIG. 3</figref> is an enlarged cross sectional view showing the detailed constitution of the rotor of the permanent magnet rotating electric machine of the first embodiment of the present invention. <figref idref="DRAWINGS">FIG. 3</figref> shows the essential section shown in <figref idref="DRAWINGS">FIG. 2</figref> which is enlarged. Further, the same numerals as those shown in <figref idref="DRAWINGS">FIG. 2</figref> indicate the same parts.

0049The line connecting the center of the permanent magnets <b>6</b>A<b>1</b> and <b>6</b>A<b>2</b> constituting the same pole, that is, the center of the air gap <b>75</b>A<b>3</b> and the center of the rotor <b>3</b>, that is, the center of the shaft <b>8</b> is assumed as L<b>1</b>. The insertion holes <b>70</b>A and <b>70</b>A<b>2</b> are arranged so as to be symmetrical with respect to the line L<b>1</b>. Therefore, the permanent magnets <b>6</b>A<b>1</b> and <b>6</b>A<b>2</b> are also arranged so as to be symmetrical with respect to the line L<b>1</b>. The line L<b>1</b> is a line indicating the central part of one magnetic pole.

0050Further, the lines connecting the centers of bridges <b>73</b>A<b>1</b> and <b>73</b>A<b>2</b> and the center of the rotor <b>3</b>, that is, the center of the shaft <b>8</b> are assumed respectively as L<b>2</b> and L<b>3</b>. The range between the lines L<b>2</b> and L<b>3</b> forms one magnetic pole. The angle ζ<b>1</b> of one magnetic pole is an electric angle of 180° and is composed of 8 poles, so that it is a mechanical angle of 45°. Further, the angle θ2 in the drawn example is an electric angle of 130°.

0051Lines L<b>4</b> and L<b>5</b> are lines connecting the right corner of the permanent magnet <b>6</b>A<b>1</b> and the left corner of the permanent magnet <b>6</b>A<b>2</b> and the center of the rotor <b>3</b>, that is, the center of the shaft <b>8</b>.

0052Here, at the position of the central part of the magnetic poles, the air gap length between the outer peripheral part of the rotor <b>3</b> and the inner peripheral part of the stator <b>2</b> is assumed as G<b>1</b>, and the air gap length at the positions on the outer periphery of the rotor <b>3</b> where concavities <b>76</b>A<b>1</b> and <b>76</b>A<b>2</b> are formed are assumed as G<b>2</b>, and the air gap length at the end of the magnetic poles is assumed as G<b>3</b>. The air gap lengths G<b>1</b> and G<b>2</b> are longer than the air gap length G<b>3</b> and in the rotor <b>3</b>, in the neighborhood of the center of the magnetic pole portion thereof, the concavities <b>76</b> are formed on the outer periphery. Moreover, the air gap length G<b>1</b> is shorter than the air gap length G<b>2</b> and on the air gap face of the magnetic pole pieces <b>72</b>, the concavities <b>76</b> gently tilting from the center of the magnetic poles to the end thereof are formed. An example of it is that the air gap length G<b>1</b> is 0.5 mm, and the air gap length G<b>2</b> is 1.5 mm, and the air gap length G<b>3</b> is 0.3 mm.

0053Here, by referring to <figref idref="DRAWINGS">FIG. 4</figref>, the air gap length of the magnetic pole pieces of the rotor of the permanent magnet rotating electric machine of this embodiment will be explained concretely.

0054<figref idref="DRAWINGS">FIG. 4</figref> is an illustration for the air gap length of the magnetic pole pieces of the rotor of the permanent magnet rotating electric machine of the first embodiment of the present invention.

0055The air gap length G<b>1</b> is assumed as 0.5 mm, and the air gap length G<b>2</b> is assumed as 1.5 mm, and between them, the change in the air gap length, as shown by a solid line of X<b>1</b> in <figref idref="DRAWINGS">FIG. 4</figref>, is in a shape convex downward. Namely, the change in the air gap length at the central part of the magnetic poles is smaller than the change in the air gap length at the end of the magnetic poles. Further, in the drawing, the dashed line X<b>2</b> is a straight line and the alternate long and short dashed line X<b>3</b> is a curve convex upward.

0056Here, by referring to <figref idref="DRAWINGS">FIGS. 5 and 6</figref>, the iron loss of the rotor of the permanent magnet rotating electric machine of this embodiment will be explained. Further, the values shown in <figref idref="DRAWINGS">FIGS. 5 and 6</figref> are values obtained by theoretical calculation and are different from the values indicated in the explanation shown in <figref idref="DRAWINGS">FIG. 4</figref>.

0057<figref idref="DRAWINGS">FIGS. 5 and 6</figref> are illustrations for iron loss of the rotor of the permanent magnet rotating electric machine of the first embodiment of the present invention.

0058<figref idref="DRAWINGS">FIG. 5</figref> shows, in the high speed rotating region, the whole iron loss Wfe for the weak field current when the air gap length is fixed and the breakdown of the basic wave part and harmonic part. The drawing shows that, as mentioned above, when the weak field current is increased, the basic wave part of the iron loss is reduced, while the harmonic part is increased, and the whole iron loss is not reduced.

0059<figref idref="DRAWINGS">FIG. 6</figref> shows the torque T when the air gap length is changed at a fixed weak field current and changes in the iron loss Wfe. The iron loss Wfe<b>1</b> indicates an iron loss when the air gap length G is kept at 0.5 mm. The iron loss Wfe<b>2</b> indicates an iron loss when the air gap length G is changed evenly and the drawing shows that when the air gap length is increased, the iron loss mainly due to a reduction in the harmonic part is suddenly reduced and the occurred torque T is reduced due to a reduction in the basic wave part of the magnetic flux density.

0060Further, the iron loss WfeInv shown in the drawing is the calculation result of the permanent magnet rotating electric machine having the structure of this embodiment shown in <figref idref="DRAWINGS">FIGS. 1 to 4</figref>. In the reduction comparison of the iron loss at the point where the torque becomes the same, an iron loss reduction effect of 35% or higher than the conventional one is shown and in the iron loss comparison, the iron loss reduction is 30% or more. Therefore, according to this embodiment, rather than just an increase in the air gap length, the ratio of (reduction in iron loss)/(reduction in torque) can be increased.

0061As a shape of the concavities <b>76</b>, in any of the lines X<b>1</b>, X<b>2</b>, and X<b>3</b> shown in <figref idref="DRAWINGS">FIG. 4</figref>, the reduction in the torque can be suppressed while reducing the iron loss. Among them, particularly as shown by the solid line X<b>1</b> in <figref idref="DRAWINGS">FIG. 4</figref>, as a shape of the concavities <b>76</b>, when the change in the air gap length at the central part of the magnetic poles is made smaller than the change in the air gap length at the end of the magnetic poles, the air gap distribution of the magnetic pole pieces <b>72</b> can be made larger at the center of the magnetic poles and smaller at the end thereof and can be made in a sine wave shape as a whole and the iron loss can be reduced.

0062Further, in this embodiment, the air gap length G<b>3</b> of the auxiliary salient poles <b>71</b> is made smaller than the air gap lengths G<b>1</b> and G<b>2</b> of the magnetic pole pieces <b>72</b>, thus the torque producing ratio of the auxiliary salient poles <b>71</b> not affecting greatly the iron loss of the permanent magnets <b>6</b> is increased and while keeping the torque reduction little, the iron loss can be reduced.

0063As explained above, according to this embodiment, the effect of iron loss can be reduced more and a highly efficient permanent magnet rotating electric machine can be obtained.

0064Next, by referring to <figref idref="DRAWINGS">FIG. 7</figref>, the constitution of the permanent magnet rotating electric machine of the second embodiment of the present invention will be explained. Here, the whole constitution of the permanent magnet rotating electric machine of this embodiment is the same as that shown in <figref idref="DRAWINGS">FIG. 1</figref>.

0065<figref idref="DRAWINGS">FIG. 7</figref> is a cross sectional view showing the constitution of the permanent magnet rotating electric machine of the second embodiment of the present invention. <figref idref="DRAWINGS">FIG. 7</figref>, similarly to <figref idref="DRAWINGS">FIG. 2</figref>, is a cross sectional view in the direction perpendicular to the rotation axis and a view in the direction of A-A. Further, the same numerals as those shown in <figref idref="DRAWINGS">FIGS. 1 and 2</figref> indicate the same parts.

0066In the constitution shown in <figref idref="DRAWINGS">FIG. 2</figref>, 2 permanent magnets constitute one magnetic pole of the rotor and are arranged in a V shape, while in this embodiment, as shown in <figref idref="DRAWINGS">FIG. 7</figref>, one permanent magnet <b>6</b>J constitutes one magnetic pole of the rotor and is inserted into an insertion hole <b>70</b>J in which the long sides of the section in a rectangular block shape are arranged so as to be directed in the peripheral direction of the rotor <b>3</b>.

0067Although the arrangement of the permanent magnets, that is, the constitution of the magnetic poles is different from that shown in <figref idref="DRAWINGS">FIG. 2</figref>, the shape of the concavities <b>76</b> of the outer peripheral part of the rotor <b>3</b> formed on the magnetic pole pieces <b>72</b>, similarly to that described in detail in <figref idref="DRAWINGS">FIG. 3</figref>, is a shape of concavities gently tilting from the central part of the magnetic poles to the end thereof on the air gap face of the magnetic pole pieces of the rotor iron core. Therefore, the air gap lengths G<b>1</b> and G<b>2</b> are the same as those shown in <figref idref="DRAWINGS">FIG. 4</figref>.

0068Since the permanent magnets are arranged in such a block shape, compared with the arrangement in the V shape shown in <figref idref="DRAWINGS">FIG. 2</figref>, the number of magnets per magnetic pole is reduced, so that the material expenses and the assembly man-hour are reduced, thus the rotating electric machine can be reduced in cost.

0069On the other hand, when the permanent magnets are arranged in the block shape, compared with the arrangement in the V shape, the magnetic flux density of the magnets on the air gap face side is reduced, so that in this respect, the torque is slightly reduced.

0070As described above, also by this embodiment, the effect of the iron loss can be reduced more and a highly efficient permanent magnet rotating electric machine can be obtained.

0071Next, by referring to <figref idref="DRAWINGS">FIGS. 8 to 10</figref>, the constitution of the permanent magnet rotating electric machine of the third embodiment of the present invention will be explained. Here, the whole constitution of the permanent magnet rotating electric machine of this embodiment is the same as that shown in <figref idref="DRAWINGS">FIG. 1</figref>.

0072<figref idref="DRAWINGS">FIG. 8</figref> is a cross sectional view showing the constitution of the permanent magnet rotating electric machine of the third embodiment of the present invention. <figref idref="DRAWINGS">FIG. 8</figref>, similarly to <figref idref="DRAWINGS">FIG. 2</figref>, is a cross sectional view in the direction perpendicular to the rotation axis and a view in the direction of A-A. Further, the same numerals as those shown in <figref idref="DRAWINGS">FIGS. 1 and 2</figref> indicate the same parts.

0073In this embodiment, on the outer peripheral part of the magnetic pole pieces <b>72</b> of the rotor <b>3</b> of the permanent magnet rotating electric machine <b>1</b>, at the position of θ<b>4</b> from the center of the magnetic poles, concavities <b>77</b> are installed. The other constitution is the same as that shown in <figref idref="DRAWINGS">FIG. 2</figref>. However, the concavities <b>76</b> shown in <figref idref="DRAWINGS">FIG. 2</figref> are not installed.

0074Next, by referring to <figref idref="DRAWINGS">FIGS. 9 and 10</figref>, the concavities <b>77</b> formed on the outer periphery of the magnetic pole pieces of the rotor of the permanent magnet rotating electric machine of this embodiment will be explained.

0075<figref idref="DRAWINGS">FIGS. 9 and 10</figref> are illustrations for the relationship between the concavities <b>77</b> and the torque ripple formed on the outer periphery of the magnetic pole pieces of the rotor of the permanent magnet rotating electric machine of the third embodiment of the present invention.

0076<figref idref="DRAWINGS">FIG. 9</figref> shows the torque ripple value Y<b>2</b> under the maximum torque occurrence condition when the angle θ<b>4</b> formed between the center of the magnetic poles and the central position of the concavities <b>77</b> is assumed as a variable. In the example shown in <figref idref="DRAWINGS">FIG. 8</figref>, when the number of slots per pole and per phase is 2 (48 slots, 3 phases, 8 poles), nspp=2.

0077Further, the torque ripple value Y<b>1</b> shown in <figref idref="DRAWINGS">FIG. 9</figref> indicates the characteristic of nspp=2 when the number of slots per pole and per phase is 1. In this case, the slot width and tooth width are set at double values of those when the number of slots per pole and per phase is 2. In the drawing, the positive side of the symbol θ indicates the region applied with the magnetizing force of the electromotive force by the stator windings in the rotational direction.

0078The torque ripple Y<b>2</b> when the slots (the concavities <b>77</b>) are not arranged, is 20 Nm when the number of slots per pole and per phase is 2. On the other hand, when the position of the concavities <b>77</b> is within the range from an electrical angle θa<b>1</b> of 15° to 45° from the central position of the magnetic poles, the torque ripple can be reduced compared with a case of no concavities formed.

0079Further, the torque ripple Y<b>1</b> when the slots (the concavities <b>77</b>) are not arranged is 54 Nm when the number of slots per pole and per phase is 1. On the other hand, when the position of the concavities <b>77</b> is within the range from an electrical angle θa<b>2</b> of 20° to 30° from the central position of the magnetic poles, the torque ripple can be reduced compared with a case of no concavities formed.

0080<figref idref="DRAWINGS">FIG. 10</figref> compares the torque ripple (the solid line Z<b>2</b>) when an electrical angle θ is 24° and the hole size is optimized under the condition that the number of slots per pole and per phase is 2 with the torque ripple (the solid line Z<b>0</b>) when no hole is formed. As clearly shown in <figref idref="DRAWINGS">FIG. 10</figref>, when the concavities <b>77</b> are formed at a proper position of the magnetic pole pieces, the torque ripple can be reduced to about ⅓.

0081As described above, according to this embodiment, the torque ripple of the permanent magnet rotating electric machine can be reduced.

0082Further, for example, in Japanese Patent Application 8-251846 and Japanese Patent Application 2002-171730, an embedding type magnet rotor in which slots are arranged on both sides of magnetic pole pieces are disclosed. However, in the embedding type magnet rotor described in Japanese Patent Application 8-251846, the slots arranged on the rotor surface are different in the slot shape and slot position from those of this embodiment and are formed for magnetic flux leakage prevention between the magnetic pole pieces and the auxiliary salient poles but not for iron loss prevention and torque ripple reduction. Further, in the embedding type magnet rotor described in Japanese Patent Application 2002-171730, the slots are different in the slot shape and slot position from those of this embodiment and are intended to interrupt the magnetic flux by the reaction of the armature but are not intended to reduce the iron loss and torque ripple.

0083Next, by referring to <figref idref="DRAWINGS">FIG. 11</figref>, the constitution of the machine driving system of an electric car loading the permanent magnet rotating electric machine of each embodiment of the present invention will be explained.

0084<figref idref="DRAWINGS">FIG. 11</figref> is a block diagram showing the constitution of the machine driving system of the electric car loading the permanent magnet rotating electric machine of each embodiment of the present invention.

0085In the drawing, the permanent magnet rotating electric machine <b>1</b> is a one described in any of the aforementioned embodiments. A frame <b>100</b> of the electric car is supported by 4 wheels <b>110</b>., <b>112</b>, <b>114</b>, and <b>116</b>. The electric car is driven by the front wheels, so that the permanent magnet rotating electric machine <b>1</b> is directly attached to a front axle <b>154</b>. The control torque of the permanent magnet rotating electric machine <b>120</b> is controlled by a controller <b>130</b>. As a power source of the controller <b>130</b>, a battery <b>140</b> is installed, and power is supplied to the permanent magnet rotating electric machine <b>1</b> from the battery <b>140</b> via the controller <b>130</b>, and the permanent magnet rotating electric machine <b>1</b> is driven, and the wheels <b>110</b> and <b>114</b> are rotated. The rotation of a handle <b>150</b> is transferred to the two wheels <b>110</b> and <b>114</b> via a transfer mechanism composed of a steering gear <b>152</b>, a tie rod, and a knuckle arm and the angle of the wheels is changed.

0086Further, in this embodiment, a case that the front wheels <b>110</b> and <b>114</b> are driven to rotate by the permanent magnet rotating electric machine <b>1</b> is described. However, the rear wheels <b>112</b> and <b>116</b> may be driven to rotate.

0087When power-running an electric vehicle (at the time of starting, traveling, acceleration, etc.), the front wheels <b>110</b> and <b>114</b> are driven by the motor of the permanent magnet rotating electric machine <b>1</b>. The voltage of the battery <b>140</b> is supplied to the permanent magnet rotating electric machine <b>1</b> via the controller <b>130</b> and the permanent magnet rotating electric machine <b>1</b> is driven and generates rotation output. By doing this, the front wheels <b>110</b> and <b>114</b> are driven to rotate.

0088When regenerating the electric vehicle (at the time of stepping on the brake, easing up on the accelerator, or stopping on the accelerator), the rotation output of the front wheels <b>110</b> and <b>114</b> is transferred to the permanent magnet rotating electric machine <b>1</b> via the front axle <b>154</b> and the permanent magnet rotating electric machine <b>1</b> is driven to rotate. By doing this, the permanent magnet rotating electric machine <b>1</b> operates as a generator. By this operation, in the stator windings of the permanent magnet rotating electric machine <b>1</b>, 3-phase AC power is generated. The generated 3-phase AC power is converted to predetermined DC power by an inverter and is charged in the battery <b>140</b>.

0089Further, in the above description, it is explained that the permanent magnet rotating electric machine is used to drive the wheels of an electric car. However, even if the machine is applied to a hybrid electric car having a hybrid drive mechanism by an engine and a motor or the so-called engine start device arranged between an engine and a drive mechanism for starting the engine and generating power, high efficiency and low noise of the drive portion of the hybrid electric car can be realized by the same effect.

0090As explained above, according to this embodiment, when the permanent magnet rotating electric machine of low iron loss and low torque ripple of the present invention is loaded in an electric car, an electric car characterized by little iron loss at a high speed, low fuel expenses, low vibration, and low noise can be obtained by a simple constitution.