JP2014103789A - Permanent magnet embedded type motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet embedded type motor capable of significantly reducing cogging torque.SOLUTION: The permanent magnet embedded type motor comprises: a stator (100) including a stator winding wire (120) wound around a stator core (104); and a rotor (150) in which a plurality of permanent magnets (162) are embedded in a rotor core (152). The rotor (150) includes a magnetic pole piece (184) which is formed in the rotor core (152) closer to the stator than the permanent magnets (162). The permanent magnets (162) embedded in the rotor core (152) are magnetized so as to alternately change their stator side polarities for each magnetic pole along a rotating direction. Auxiliary permanent magnets (172) are further embedded in the magnetic pole piece (184), and the auxiliary permanent magnets (172) are magnetized in such a manner that a polarity on a surface at a central side of the magnetic pole piece (184) in the rotating direction becomes the same as the polarity of the magnetic pole piece (184).

Description

  The present invention relates to an embedded permanent magnet motor in which a permanent magnet for making magnetic poles is embedded in a rotor.

  The permanent magnet embedded motor is hereinafter referred to as an IPM (Interior Permanent Magnet) motor. The IPM motor includes a stator that generates a rotating magnetic field and a rotor in which a plurality of permanent magnets for generating magnetic poles are embedded. The stator is supplied with an alternating current generated according to a control command and corresponding to the magnetic pole position of the rotor, and a rotating magnetic field is generated based on the alternating current. A magnetic pole is formed by a plurality of the permanent magnets embedded in the rotor, and rotational torque based on the rotating magnetic field is generated in the rotor by the magnetic action of the rotating magnetic field and the magnetic pole, and the rotation The child rotates.

  The IPM motor is attracting attention as a high-performance motor, and its use is expected to increase in a wide range of fields such as a small motor field, an electric vehicle motor field, and a large motor field. As IPM motors are used in various fields of application, various characteristics are desired to be improved, and improvements in characteristics are also desired for reducing torque pulsation. Although the IPM motor has various advantages, it has a problem that a cogging torque that causes torque pulsation is likely to occur. For example, Japanese Unexamined Patent Application Publication No. 2012-60799 (Patent Document 1) discloses a technique related to reduction of cogging torque of an IPM motor.

JP 2012-60799 A

  In Patent Document 1, in order to reduce the cogging torque of the IPM motor, a slit 42 and a slit 43 that extend at right angles to the permanent magnet insertion hole in the rotor and are arranged symmetrically with respect to the magnetic pole are provided. It is described that the torque is reduced. However, it is desired to further reduce the cogging torque.

  An object of the present invention is to provide an IPM motor that can further improve cogging torque.

  A first IPM motor that solves the above-described problems has a plurality of stator windings wound around a stator core, and a plurality of stators for generating a rotating magnetic field and a plurality of magnetic poles for forming a plurality of magnetic poles. The main permanent magnet is embedded in the rotor core, and a rotor that rotates by generating rotational torque, and the rotor is embedded by the main permanent magnet being embedded in the rotor core. A magnetic pole piece is formed in a portion of the rotor core on the stator side from the main permanent magnet, and the polarity on the stator side of the plurality of the main permanent magnets embedded in the rotor core is The magnetic pole piece is alternately changed along the rotation direction of the rotor, and an auxiliary permanent magnet is further embedded in the magnetic pole piece, and the auxiliary permanent magnet is a surface on the center side of the magnetic pole piece in the rotation direction. So that the polarity of the magnet is the same as the polarity of the pole piece It is characterized in that.

  A second IPM motor that solves the above-described problem is the first IPM motor, wherein the auxiliary permanent magnets are arranged on both sides of the central portion of the magnetic pole piece in the rotation direction, respectively. Has a shape extending in a radial direction from the main permanent magnet.

  A third IPM motor that solves the above-described problems is the second IPM motor, wherein a bridge portion for reducing magnetic flux leakage is formed between the magnetic pole piece and the adjacent magnetic pole piece, A distance L1 between the auxiliary permanent magnets arranged on both sides across the central portion of the piece is between one auxiliary permanent magnet and the end of the main permanent magnet on the one auxiliary permanent magnet side. Or a distance L3 between the other auxiliary permanent magnet and the end of the main permanent magnet on the other auxiliary permanent magnet side.

  In a fourth IPM motor that solves the above problem, in one of the first to third IPM motors, the holding force of the auxiliary permanent magnet is the holding force of the main permanent magnet for making the magnetic pole. It is smaller.

  A fifth IPM motor that solves the above problem is that, in the fourth IPM motor, the holding force of the auxiliary permanent magnet is from 0.75 times the holding force of the main permanent magnet for forming the magnetic pole. It is characterized by being in the range of 0.85 times.

  In a sixth IPM motor that solves the above problem, in one of the first to third IPM motors, the holding force of the auxiliary permanent magnet is the holding force of the main permanent magnet for forming the magnetic pole. It is larger.

  In a seventh IPM motor that solves the above problem, in one of the first to sixth IPM motors, a reluctance torque is applied between the magnetic pole piece constituting the magnetic pole and the adjacent magnetic pole piece. An auxiliary magnetic pole for generation is formed.

  An eighth IPM motor that solves the above problem is one of the first to seventh IPM motors, wherein the stator is a stator winding for generating rotational torque in the rotor. And having a control winding for controlling the position and inclination of the rotor with respect to the stator, and magnetically supporting the rotor.

  According to the present invention, an IPM motor with improved cogging torque can be provided. Note that specific effects and the like in the modes for carrying out the invention (hereinafter referred to as examples) will be described in the description of the examples.

It is a front view of the IPM motor for demonstrating the structure of the IPM motor which is one Example of this invention. It is AA sectional drawing of the IPM motor shown in FIG. It is sectional drawing which shows a cross section perpendicular | vertical to the rotating shaft of the rotor of an IPM motor. FIG. 4A is an enlarged view of a main part for explaining the operation of the present invention, FIG. 4A is an explanatory diagram for explaining the state of magnetic flux of the pole piece of the IPM motor shown in FIG. 1, and FIG. It is explanatory drawing explaining the state of the magnetic flux of a pole piece when there is no auxiliary magnet in 4 (A). It is a graph which shows the change of the magnetic flux density of the rotation angle direction in the stator side surface of a rotor. It is a characteristic view showing the state of cogging torque when the ratio of the holding force of the auxiliary magnet to the holding force of the main permanent magnet is changed. It is a characteristic view which shows the analysis result of the rotational torque fluctuation | variation based on the conventional structure. It is a characteristic view which shows the analysis result of the rotational torque fluctuation | variation of the IPM motor which concerns on this invention. It is sectional drawing which shows a cross section perpendicular | vertical to the rotating shaft of the rotor of the IPM motor which is another Example. It is explanatory drawing explaining operation | movement of the rotor of another Example.

[About the structure of the IPM motor 1]
FIG. 1 is a front view for explaining the structure of an IPM motor 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of the IPM motor 1 shown in FIG. The structure, operation and effect of the IPM motor 1 which is one embodiment of the present invention will be described with reference to FIGS. This embodiment is an example of an internal rotation type motor, and a rotor 150 formed of a laminated steel plate similar to the stator is provided inside a stator 100 formed of a laminated steel plate. In this embodiment, the rotor 150 is not a motor having a rotating shaft and mechanically supporting the rotating shaft, but has a configuration in which the rotor 150 is rotatably supported by magnetic force.
However, even if the present invention is applied to a motor in which the rotor 150 is supported by a mechanical bearing, the same effect can be expected. That is, the basic operation and operation of the present invention are the same even for a motor having a mechanical bearing. Although the present invention can be applied to both a motor that supports the rotor 150 by a mechanical bearing and a motor that supports the rotor 150 magnetically, a motor having a structure that magnetically supports the rotor 150 is used as a representative of these. explain.

[About the structure of the stator 100]
The stator 100 has twelve teeth 110 arranged on the outer periphery of the rotor 150 at equal intervals. Each of the teeth 110 and the stator core 102 connecting the teeth 110 are made by punching laminated steel plates, and a stator winding 120 is wound around each of the teeth 110. The IPM motor of this embodiment is a three-phase 12-slot motor, and the rotor 150 has four poles. Of course, the number of slots and the number of magnetic poles of the rotor 150 are examples, and the present invention is not limited to this. Further, in this embodiment, the stator winding 120 is a concentrated winding, but the present invention can be applied to a distributed winding, and a great effect can be obtained similarly. The basic principle, operation, and effect of the present invention are the same for concentrated winding and distributed winding, and these will be described below as an example of concentrated winding.

  The stator 100 not only generates rotational torque in the rotor 150 but also the rotational axis (hereinafter referred to as Z-axis) and the radial axis (hereinafter referred to as X-axis) of the rotor 150 with respect to the stator 100 at a predetermined position or a predetermined position. Magnetic flux is generated at an angle. Therefore, the stator 100 has not only the teeth 110 that face the outer peripheral surface of the rotor 150 via an air gap, but also auxiliary teeth 112 and auxiliary that face each side surface of the rotor 150 in the Z-axis direction via the air gap. The teeth 114 are provided.

  The stator 100 includes a stator winding 120, a radial direction control winding 132, a rotation axis direction control winding 134, and a tilt control winding 136. The stator winding 120 generates a rotating magnetic field to generate rotational torque in the rotor 150, and the radial control winding 132 is controlled so that the position of the Z axis is a predetermined position in the X axis direction, which is the radial direction. To do. The rotation axis direction control winding 134 controls the rotor 150 so as to be at a predetermined position in the Z axis direction. Further, the inclination control winding 136 is arranged so that the inclination of the rotor 150 with respect to the stator 100 becomes a predetermined inclination, that is, the Z-axis that is the rotation axis of the rotor 150 is the center of the teeth 110 and the inner opening of the teeth 110. The inclination of the Z axis of the rotor 150 is controlled so as to coincide with the central axis.

  The arrangement of the rotation axis direction control winding 134 and the tilt control winding 136 may be reversed in the radial direction. Further, the magnetic flux generated by the stator winding 120, the radial direction control winding 132, the rotation axis direction control winding 134, and the tilt control winding 136 may be generated by one winding. For example, a common winding is provided at the position of the radial control winding 132, and the current supplied to the stator winding 120, the radial control winding 132, the rotation axis direction control winding 134, and the gradient control winding 136 is overlapped. The same control can be performed by supplying current to the common winding. Of course, since the winding positions of the stator winding 120, the rotation axis direction control winding 134, and the gradient control winding 136 change, it is necessary to adjust the current value by changing the winding position, but the basic control concept is The same.

By magnetically supporting the rotor 150 and eliminating the need for mechanical bearings, the volume of the motor can be further reduced. In addition, there is an effect that maintenance of the machine part becomes unnecessary. For example, a pump motor for an artificial heart that is implanted in the body is very advantageous as a medical device because it does not require maintenance such as wear of mechanical parts.
On the other hand, when the rotor 150 is held by a mechanical bearing instead of a magnetic force, the auxiliary teeth 114 are not necessary, and the radial control winding 132, the rotary axial control winding 134, and the tilt control winding 136 are further eliminated. However, the structure of the stator is simplified, but the wear of the bearings must be taken into consideration, and the mechanical life or maintenance of the machine parts must be taken into consideration.

[Structure of rotor 150 and magnetic pole structure]
3 is a cross-sectional view of the rotor 150 taken along a plane perpendicular to the Z axis shown in FIG. The rotor 150 has a four-pole structure, and each magnetic pole is indicated by a magnetic pole A, a magnetic pole B, a magnetic pole C, and a magnetic pole D. The magnetic poles are formed by four rectangular main permanent magnets 162 that are embedded through the rotor core 152. Only in FIG. 3, four main permanent magnets 162 are described as a main permanent magnet 162A, a main permanent magnet 162B, a main permanent magnet 162C, and a main permanent magnet 162D. These main permanent magnets 162 have the same basic operation. In other figures, the main permanent magnets 162A to 162D are simply referred to as main permanent magnets 162, respectively. In the magnetic pole A and the magnetic pole C, the main permanent magnet 162A and the main permanent magnet 162C for forming these magnetic poles are magnetized so that the outer peripheral side which is the stator 100 side is N pole and the center side of the rotor 150 is S. ing. Further, in the magnetic pole B and the magnetic pole D, the main permanent magnet 162B and the main permanent magnet 162D for forming the magnetic pole B and the magnetic pole D are such that the opposite side of the stator, that is, the outer peripheral side is the S pole, and the center side of the rotor 150 is the N pole. Magnetized. That is, in the rotation direction of the rotor 150, the main permanent magnet 162 is magnetized so that the magnetization direction of the main permanent magnet 162 embedded for each magnetic pole is reversed. The same applies to the case where the number of magnetic poles of the rotor 150 is greater than four. The main permanent magnet 162 is magnetized so that the magnetization direction of the main permanent magnet 162 is reversed for each magnetic pole in the rotation direction of the rotor 150. ing.

  The rotor core 152 on the outer peripheral side of each of the main permanent magnets 162 of the magnetic poles A to D acts as magnetic pole pieces 184, and magnetic flux enters and exits through these magnetic pole pieces 184. For example, the magnetic flux based on the main permanent magnet 162A exits the magnetic pole piece 184 of the magnetic pole A, is guided to the stator, passes through the stator 100, and is guided from the stator 100 to the magnetic pole piece 184 of the magnetic pole B or D. It returns to the main permanent magnet 162A via the permanent magnet 162B and the main permanent magnet 162D. A force is generated by the action of this magnetic flux and the current flowing through the stator winding 120 provided in the stator 100, and acts on the rotor 150 as a rotational torque, so that the rotor 150 rotates. The same applies to the main permanent magnet 162C, and the magnetic flux is guided from the magnetic pole piece 184 of the magnetic pole C to the stator winding 120 of the stator 100, and from the stator 100 to the magnetic pole piece 184 of the magnetic pole B or D. And the magnetic flux returns to the main permanent magnet 162C via the main permanent magnet 162B and the main permanent magnet 162D. Even if the number of magnetic poles increases, the magnetic flux flow described above is the same, and the magnetic flux guided from the magnetic pole piece 184 of the magnetic pole A to the stator passes through the stator, and the magnetic poles on both sides of the rotor 150, in the case of FIG. Return to the magnetic pole piece 184 of the magnetic pole B and the magnetic pole D. In the above description, the rotational torque of the rotor 150 is explained by the magnetic flux generated by the main permanent magnet 162 and the force generated by the current flowing through the stator winding 120. However, the current of the stator 100 produced by the current flowing through the stator winding 120 is explained. It may be considered that rotational torque is generated in the rotor 150 due to the magnetic relationship between the rotating magnetic field and the main permanent magnet 162 of the rotor 150.

[Reduction structure of leakage magnetic flux of rotor 150]
When magnetic flux leaks between adjacent magnetic pole pieces 184 and magnetic flux that is not guided to the stator (hereinafter referred to as leakage magnetic flux) is generated, the leakage magnetic flux does not contribute to generation of rotational torque. For this reason, it is desirable to suppress the leakage magnetic flux between adjacent magnetic pole pieces 184. In this embodiment, end magnets 174 are provided between adjacent pole pieces 184. The end magnet 174 is magnetized to have the same polarity as the magnetic pole facing the magnet surface of the end magnet 174 so as to reduce leakage magnetic flux. When the end magnet 174 between the magnetic pole A and the magnetic pole B is described, the surface of the end magnet 174 on the magnetic pole A side is the same N pole as the magnetic pole A, and the surface of the end magnet 174 on the magnetic pole B side is the magnetic pole B. The end magnet 174 is magnetized so as to have the same S pole. As a result, the magnetic flux leakage from the magnetic pole piece 184 of the magnetic pole A to the magnetic pole piece 184 of the magnetic pole B is greatly reduced. All the end magnets 174 are magnetized according to such a magnetization method. This embodiment shows an ideal configuration in which a permanent magnet is used as the end magnet 174 and the leakage magnetic flux is extremely reduced. Even if a non-magnetic material is disposed instead of the end magnet 174, the leakage magnetic flux can be reduced. Moreover, you may make it a space | gap instead of a nonmagnetic material. Hereinafter, the nonmagnetic material in the case of using a nonmagnetic material is generically referred to as a magnetic gap, not only in the case of air.

  On the outer peripheral side of the end magnet 174, bridge portions 186 for connecting the magnetic pole pieces are provided by punching at the time of forming the rotor core. The bridge portion 186 has a mechanical structure in which centrifugal force is generated in the main permanent magnet 162 and the magnetic pole piece 184 of each magnetic pole and other auxiliary magnets 172 described later when the rotor 150 is rotated. That is, it has a shape that can sufficiently withstand the centrifugal force generated at the maximum rotational speed. Magnetic flux leaks through the bridge portion 186. However, since the cross-sectional area of the magnetic circuit formed by the bridge portion 186 is limited, the bridge portion 186 is magnetically saturated and the amount of leakage magnetic flux is small. For this reason, even if the bridge portion 186 exists, the rotational torque does not greatly decrease. The above description is valid for all the bridge portions 186 shown in FIG. 3, and when the number of poles of the rotor 150 is further increased, the bridge portions 186 are provided between the magnetic poles. On the other hand, the above explanation is valid.

[Reduction of cogging torque of rotor 150]
Next, torque based on magnetic attraction force in a non-excited state of the stator 100 in which no current is supplied to each winding of the stator 100, that is, cogging torque will be described. Cogging torque causes torque pulsation. In the present embodiment, each magnet piece 184 is provided with an auxiliary magnet 172 in order to reduce cogging torque. The configuration for reducing the cogging torque using the auxiliary magnet 172 is not limited to the structure shown in FIG. 3, and there are various considerations regarding the position of the auxiliary magnet 172, the shape of the auxiliary magnet 172, and the number of auxiliary magnets 172. However, an example using two auxiliary magnets 172 shown in FIG. 3 will be described as a typical example. The auxiliary magnet 172 acts to bring the distribution of magnetic flux entering the stator 100 from the magnetic pole piece 184 or the distribution of magnetic flux returning from the stator 100 to the magnetic pole piece 184 closer to an ideal distribution. The desirable magnetic flux distribution is a sinusoidal state in which the magnetic flux density near the bridge portion 186 is zero, and the magnetic flux density at the center of the magnetic pole piece 184 in the rotation direction, that is, at the position of 90 degrees in electrical angle, is the highest. . Note that the position of an electrical angle of 90 degrees in the magnetic pole A and the magnetic pole C is indicated by the axis C.

  Assume that the magnetic pole piece 184, which is the prior art, has no auxiliary magnet 172. In this case, for example, the magnetic flux of the magnetic pole piece 184 of the magnetic pole A is affected by other adjacent magnetic poles as shown in FIG. Since the other adjacent magnetic poles B and D have opposite polarities, the magnetic flux at the center of the magnetic pole A decreases, and the magnetic flux density closer to the magnetic pole B and magnetic pole D tends to increase.

  FIG. 5 shows a magnetic flux density at an electrical angle or a mechanical angle along the rotation direction of the surface on the stator 100 side at each magnetic pole of the rotor 150, assuming that the salient pole structure of the stator is ignored and that the core is simply uniform. It is the graph which showed change of. Characteristic A shows a change in magnetic flux density in a conventional structure that is assumed to have no auxiliary magnet 172. In this characteristic A, the peak G and the peak F, which are the apexes of the magnetic flux density, occur in the vicinity of the electrical angle of 20 degrees or 160 degrees due to the influence of the reverse polarity of the adjacent magnetic poles. On the other hand, in the vicinity of 90 degrees of the electrical angle, as indicated by the central magnetic flux density E, the lowest magnetic flux density is shown between the two apexes. As described above, in the conventional structure, a magnetic flux density peak appears in the vicinity of an electrical angle of 20 degrees or 160 degrees, and the magnetic flux density E in the central portion of the graph is the lowest between the peak G7 and the peak F. The state of the magnetic flux density of the characteristic A is far from the ideal sine wave state, and generates a large cogging torque.

  As shown in the characteristic A of FIG. 5, the peak G7 and the peak F, which are the magnetic flux density peaks, appear in the vicinity of the electrical angle of 20 degrees and 160, while the cause of the decrease in the magnetic flux density near the electrical angle of 90 degrees is as described above. It is the influence of the adjacent reverse polarity magnetic pole. More specifically, as shown in FIG. 4A, the magnetic flux generated by the main permanent magnet 162 is not directly guided to the stator 100, but is produced by the main permanent magnet 162 as shown as the magnetic flux 208 and the magnetic flux 210. This is because the magnetic flux is attracted and leaked toward the other magnetic poles adjacent to both sides.

  The auxiliary magnets 172 provided on the magnetic pole pieces 184 have the magnetic fluxes 210 and 208 to be leaked as shown in FIG. 4 (A) in the center of the magnetic pole pieces 184 and the magnetic poles A and C in the direction of the axis C. , Acts to collect magnetic flux. FIG. 4B schematically shows this state. The auxiliary magnet 172 is arranged so as to extend from the main permanent magnet 162 to the outer peripheral side. In this embodiment, it is arranged perpendicular to the main permanent magnet 162, but is not limited to being perpendicular. Taking the magnetic pole A as an example, the auxiliary magnet 172 has two surfaces 172A and 172B, and the surface 172A facing the center of the pole piece 184 is the same as the magnetic pole on which the auxiliary magnet 172 is placed. Magnetized to polar. The surface 172B facing the other adjacent magnetic pole is magnetized to the same polarity as the other adjacent magnetic pole. Since the two auxiliary magnets 172 provided on the pole piece 184 are magnetized as described above, the magnetic flux at the center of the pole piece 184 is prevented from being biased toward the adjacent magnetic pole, and FIG. As shown by the magnetic flux 202, the magnetic flux is collected at the center of the magnetic pole piece 184. Further, as shown by the magnetic flux 204 in FIG. 4B, the magnetic flux of the adjacent magnetic poles is attracted to the center side of the magnetic pole piece 184.

  Characteristic B in FIG. 5 shows the state of magnetic flux density on the outer peripheral surface of the pole piece 184 in the embodiment of FIG. 3 in which two auxiliary magnets 172 are provided. The peaks generated at the electrical angles of 20 degrees and 160 degrees are reduced as indicated by the peak K and peak J. On the other hand, the magnetic flux density near the electrical angle of 90 degrees, which is the central portion of the pole piece 184, increases from the central magnetic flux density E to the central magnetic flux density H. The magnetic flux density state indicated by the characteristic B is greatly improved with respect to the magnetic flux density state indicated by the characteristic A, which greatly contributes to the reduction of cogging torque.

[Attachment of auxiliary magnet 172]
As shown in FIG. 3, the two auxiliary magnets 172 are arranged so as to be substantially in the target positions with respect to the center in the rotation direction of each magnetic pole piece 184, that is, an electrical angle of 90 degrees. The magnetic pole A will be specifically described as a representative. The axis C is indicated at the center of the pole piece 184 in the rotational direction, that is, at a position at an electrical angle of 90 degrees. The two auxiliary magnets 172 are provided perpendicular to the main permanent magnet 162 and at a distance L1 / 2 from the axis C and symmetrical with respect to the axis C.

  The two auxiliary magnets 172 do not have to be perpendicular to the main permanent magnet 162. If there is a component extending from the main permanent magnet 162 toward the stator, the magnetic flux density of the pole piece 184 is improved. To act. That is, there is an effect of suppressing the magnetic flux in the central portion at the rotation angle of the magnetic pole piece 184 from being attracted by another adjacent magnetic pole. Further, there is an effect of collecting magnetic fluxes at both ends of the magnetic pole piece 184, that is, at positions close to other adjacent magnetic poles in the center, that is, in the direction of the axis C. Like the magnetic flux 204 in FIG. 4B, the magnetic flux of the portion on the other magnetic pole side of the auxiliary magnet 172 is collected toward the center.

  3, the distance between the two auxiliary magnets 172 is L1, the distance between the auxiliary magnet 172 closer to the magnetic pole B and the end of the main permanent magnet 162 on the magnetic pole B side is L2, and is close to the magnetic pole D. When the distance between the auxiliary magnet 172 on one side and the end of the main permanent magnet 162 on the magnetic pole D side is L3, the distance L1 is larger than the distance L2 or the distance L3. The distance L2 and the distance L3 are substantially equal. With such an arrangement, the peak F and the peak G of the characteristic A shown in FIG. 5 can be suppressed as low as the peak J and the peak K of the characteristic B. Further, the central magnetic flux density E of the characteristic A can be increased as indicated by the central magnetic flux density H of the characteristic B. In order to keep the peak F and peak G of the characteristic A low, the two auxiliary magnets 172 are brought close to other adjacent magnetic poles, and the distance L1 is made larger than the distance L2 and the distance L3, for example, about twice as large. Is desirable. By suppressing the peak F and peak G of the characteristic A as low as the peak J and peak K of the characteristic B, the cogging torque can be greatly improved. Further, by increasing the central magnetic flux density E of the characteristic A as shown by the central magnetic flux density H of the characteristic B, the cogging torque can be greatly improved.

[Effects of using a permanent magnet as the auxiliary magnet 172]
In this embodiment, a permanent magnet is used as the auxiliary magnet 172. As a result, the cogging torque can be greatly improved as described above. 4B, the magnetomotive force of the two auxiliary magnets 172 generates a magnetic flux in a direction that helps the magnetic flux of the main permanent magnet 162, and increases the magnetic flux density in the central portion of the pole piece 184. ing. This action greatly contributes to the improvement of the cogging torque, but not only that, but this magnetic flux acts as a magnetic flux that generates the rotational torque, and thus greatly contributes to the increase of the rotational torque generated by the motor of this embodiment. . The magnetic pole A, which is an N pole, has been described in detail, but the same applies to the magnetic poles B and D shown in FIG. In addition to the effect of increasing the cogging torque, there is an effect of increasing the rotational torque generated by the motor.

[In the holding force of the auxiliary magnet 172 and the main permanent magnet 162]
The main permanent magnet 162 is a permanent magnet for applying rotational torque to the motor. On the other hand, the auxiliary magnet 172 is a permanent magnet for improving the magnetic flux distribution in the rotation direction of the outer peripheral surface of the magnetic pole of the rotor 150, that is, the surface facing the teeth 110 of the stator. From this idea, one idea is to make the holding force of the auxiliary magnet 172 smaller than the holding force of the main permanent magnet 162. The analysis result by simulation or the like shows that the cogging torque can be significantly reduced by setting the holding force of the auxiliary magnet 172 to about 0.7 to 0.9 with respect to the holding force of the main permanent magnet 162. It was.

  The state of cogging torque when the rotor having the structure shown in FIG. 3 is rotated in a state where twelve teeth 110 made of laminated stator cores are arranged at equal intervals on the outer periphery of the rotor 150. The simulation result is shown in FIG. FIG. 6 shows the state of cogging torque in one tooth 110, and the simulation results are substantially the same for each tooth 110. In the graph of FIG. 6, the horizontal axis represents the mechanical angle corresponding to each tooth 110, and the vertical axis represents the cogging torque. Graph G1 shows the cogging torque when there are no two auxiliary magnets 172 provided at each magnetic pole shown in FIG. Graphs G2 to G6 are graphs when the rotor 150 having the structure shown in FIG. 3 which is an embodiment of the present invention is rotated. In the graph G2 to the graph G6, the cogging torque is greatly improved with respect to the graph G1 when the two auxiliary magnets 172 are not provided.

  Graphs G <b> 2 to G <b> 6 are results obtained by calculating the magnitude of cogging torque when the holding force of the auxiliary magnet 172 relative to the holding force of the main permanent magnet 162 is changed. Graph G2 represents the magnitude of cogging torque when the holding force of auxiliary magnet 172 is 0.5 times that of main permanent magnet 162. Graph G3 shows the magnitude of cogging torque when the holding force of auxiliary magnet 172 is 0.75 times the holding force of main permanent magnet 162, and graph G4 shows the holding force of auxiliary magnet 172 is 0 with respect to the holding force of main permanent magnet 162. .8 times the cogging torque magnitude, graph G5 shows the cogging torque magnitude when the auxiliary magnet 172 holding force is 0.85 times the holding force of the main permanent magnet 162, and graph G6 shows the main permanent magnet 162. The magnitude of the cogging torque when the holding force of the auxiliary magnet 172 is 1.0 times that of the holding force, that is, the magnitude of the cogging torque when the holding force is the same.

  In the graph G1 when there are no two auxiliary magnets 172, there are large cogging torque peaks at mechanical angles of 5 and 25 degrees. On the other hand, in the graphs G2 to G6, the cogging torque peaks at the mechanical angles of 5 degrees and 25 degrees are greatly improved. Thus, by providing the auxiliary magnet 172 on the magnetic pole piece 184, the state of magnetic flux density of each magnetic pole of the rotor 150 is improved as shown in FIG. 3, and each salient pole of the stator, that is, as shown in FIG. The magnitude of the cogging torque for the teeth 110 is greatly improved.

  FIG. 7 shows the fluctuation state of the rotational torque when the rotor without the auxiliary magnet 172 is used in the IPM motor 1 shown in FIG. A graph G1 is the same graph as the graph G1 shown in FIG. 6 and shows torque fluctuation in a state where no current is supplied to the stator winding 120, that is, cogging torque. On the other hand, G12 indicates torque fluctuation when 2 (A) current is supplied to the stator winding 120. In order to start the IPM motor 1 smoothly, it is desirable that the rotational torque is always positive at all mechanical angles. Particularly, in the artificial heart pump motor, a torque greater than 30 [mN · m] is always applied at all mechanical angles. It is desirable to be obtained. The graph shown in the graph G12 shows the fluctuation of the rotational torque in the state where the current of 2 (A) is supplied to the stator winding 120. The rotational torque is negative in the vicinity of the mechanical angle of 5 degrees, and it is difficult to generate a rotational torque of 30 [mN · m] between the mechanical angle of 0 degrees and the mechanical angle of 10. As described above, the rotational torque is negative near the mechanical angle of 5 degrees, and no rotational torque can be obtained even if the motor is started near this angle. For this reason, it is difficult to teach. Furthermore, the range in which a rotational torque of 30 [mN · m] cannot be obtained is large, and smooth rotation is impossible.

  FIG. 8 shows torque fluctuations when using the rotor 150 to which the present invention is applied, including the auxiliary magnet 172 shown in FIG. 3, and the graph G6 shown in FIG. 8 is the same as the graph G6 in FIG. . A graph G6 shown in FIG. 8 represents torque fluctuation, that is, cogging torque when the current supplied to the stator winding 120 shown in FIG. 1 is zero (A), while graph G16 shows 2 ( This is the torque fluctuation when the current of A) is supplied. As described above, the graph G6 shown in FIG. 8 has a small cogging torque, and the graph G16 has a positive rotational torque at all mechanical angles and is 30 [mN · m] except for a mechanical angle of about 15 degrees. A large amount of rotational torque is generated. Further, a rotational torque close to 30 [mN · m] is generated even in the vicinity of a mechanical angle of 15 degrees. Therefore also the motor can be started smoothly at any mechanical angle, yet stable large rotation torque is obtained and smooth rotation can be obtained.

[Operation and effect of end magnet 174]
Although the operation of the end magnet 174 has already been briefly described, it will be described again here with reference to FIG. The surface of the end magnet 174 on the magnetic pole A side is magnetized to the same polarity as the magnetic pole A. On the other hand, the surface on the magnetic pole B side or the surface on the magnetic pole D side of the end magnet 174 is magnetized to the same polarity as the polarity of the magnetic pole B or the magnetic pole D. With this configuration, the leakage magnetic flux between adjacent magnetic poles can be greatly reduced. Further, since the bridge portion 186 is sufficiently saturated with the magnetic flux of the end magnet 174 instead of the leakage magnetic flux of the main permanent magnet 162, the magnetic flux of the main permanent magnet 162 does not pass through the bridge portion 186. For this reason, the leakage magnetic flux is greatly reduced, and the magnetic flux contributing to the generation of rotational torque is efficiently used for torque generation. Further, the magnetomotive force itself of the end magnet 174 acts in the direction of generating rotational torque.

  Further, permanent magnets are arranged as the end magnets 174 between the magnetic poles, and the magnetization direction of each end magnet 174 is the above-mentioned direction, so that the distribution state of the magnetic flux on the outer peripheral surface of each magnetic pole can be improved and the cogging torque is reduced. Is also effective. For these reasons, by providing the end magnet 174, in addition to the effect of reducing the leakage magnetic flux, the effect of further increasing the rotational torque and reducing the cogging torque can be obtained.

  Note that a gap formed of a nonmagnetic material may be provided instead of the end magnet 174. This gap can reduce the leakage of magnetic flux between adjacent magnetic poles to some extent. However, in this embodiment, since the end magnet 174 is provided instead of the gap, the leakage of magnetic flux between adjacent magnetic poles can be further reduced. Further, there are effects of reducing the cogging torque and increasing the rotational torque described above. From the above, a great effect is obtained by using the end magnet 174.

[Other Examples]
A relatively small motor can produce a sufficient rotational torque with the torque based on the permanent magnet embedded in the rotor 150 without using the reluctance torque. On the other hand, a motor for driving an automobile or a larger motor requires a large rotational torque, and thus requires many permanent magnets. For permanent magnets used in motors, various rare metals such as neodymium and other reasons for improving temperature characteristics are used. For this reason, it is preferable to suppress the usage of the permanent magnet as much as possible, and it is possible to suppress the usage of the permanent magnet by utilizing a reluctance torque in addition to the torque based on the permanent magnet. The present invention can also be applied to a motor using reluctance torque. An application example of the present invention to a motor using reluctance torque will be described with reference to FIGS. FIG. 10 is a partially enlarged view of FIG.

In the embodiment shown in FIG. 3, the end magnets 174 are disposed between the magnetic poles, and the magnetic path through which the magnetic flux generated in the stator 100 passes is not present in the above-described embodiment. In other words, the magnetoresistance of the permanent magnet is very close to the vacuum magnetoresistance. For this reason, the portion of the end magnet 174 could not pass the speed at which the stator 100 was generated. Further, since the auxiliary magnet 172 is present in the pole piece 184, there is almost no magnetic path through which the magnetic flux generated in the stator 100 passes. For this reason, the reluctance torque hardly occurred in the embodiment shown in FIG.
In the sectional views of the rotor 150 shown in FIGS. 9 and 10 as another embodiment, a magnetic path through which the magnetic flux generated by the stator winding 120 of the stator 100 passes is provided between adjacent magnetic poles. Therefore, the magnetic flux 214 shown in FIG. 10 passes between the magnetic poles, and the auxiliary magnetic pole 192 is formed between the magnetic poles. The magnetic circuit of the magnetic flux 214 generated by the stator winding 120 of the stator 100 passing through these auxiliary magnetic poles 192 is composed of a rotor core and has a very small magnetic resistance. On the other hand, a magnetic circuit having an electrical angle of 90 degrees with respect to the magnetic circuit through which the magnetic flux 214 passes, for example, a magnetic circuit through which the magnetic flux 212 passes, is a main permanent magnet 162 that creates the magnetic pole A and a main permanent magnet 162 that produces the magnetic pole B. Cross the permanent magnet. Therefore, the magnetic flux generated by the stator winding 120 of the stator 100 has a very large magnetic resistance. The difference in magnetic resistance between the magnetic circuit through which the magnetic flux 214 passes and the magnetic circuit through which the magnetic flux 212 passes is very large, and therefore reluctance torque is generated. A combination of the reluctance torque and the magnet torque generated by the main permanent magnet 162 and the auxiliary magnet 172 that form the magnetic poles of the rotor 150 generates the rotational torque of the rotor 150 shown in FIGS. The auxiliary magnet 172 shown in FIGS. 9 and 10 is the same as the operation and effect described with reference to FIGS. 3 and 4, and has a great effect of reducing the cogging torque and greatly contributes to the increase of the rotational torque. . Another embodiment shown in FIGS. 9 and 10 is an example in which the present invention is applied to a motor using reluctance torque as described above.

  In another embodiment shown in FIGS. 9 and 10, a magnetic gap 176 is provided instead of the end magnet 174. The magnetic gap 176 may be a gap in which air exists, or may have a nonmagnetic material such as a resin. Since the magnetic gap 176 is made of a non-magnetic material, the magnetic resistance is large, and the leakage magnetic flux can be reduced. Further, a bridge portion 188 is provided between the magnetic gap 176 and the outer periphery of the rotor, so that the centrifugal force generated in the main permanent magnet 162, the auxiliary magnet 172, the magnetic pole piece 184, etc. when the rotor 150 rotates at high speed is provided. It has a structure that can sufficiently withstand. On the other hand, the magnetic flux is saturated with respect to the leakage magnetic flux as in the bridge portion 186, and the leakage magnetic flux is reduced. In addition, since it will become complicated if a reference is attached to all the bridge parts, a reference numeral 186 is given only to a part of the bridge parts as a representative. 188 exists to reduce leakage flux. In addition, you may provide the permanent magnet shown in FIG. 3 and FIG. 4 in the part of all the magnetic space | gap 176, respectively. However, the difference from FIG. 3 and FIG. 4 is that permanent magnets are arranged instead of the positions of the two magnetic gaps 176 respectively arranged between adjacent magnetic poles, and a reluctance torque is generated between the two permanent magnets. The auxiliary magnetic pole 192 exists.

DESCRIPTION OF SYMBOLS 1 ... IPM motor, 100 ... Stator, 102 ... Stator core, 110 ... Teeth, 114 ... Auxiliary teeth, 120 ... Stator winding, 134 ... Rotary axis direction control winding, 136 ... Inclination control winding, 150 ... Rotor, 152 ... Rotor core, 162 ... Main permanent magnet, 172 ... Auxiliary magnet, 174 ... End magnet, 176 ... Magnetic gap, 184 ... Magnetic pole piece, 186 ... Bridge part, 188 ... Bridge part, 192 ... Auxiliary magnetic pole 202 ... Magnetic flux, 204 ... Magnetic flux, 208 ... Magnetic flux, 212 ... Magnetic flux, 214 ... Magnetic flux.

Claims (8)

A stator having a plurality of stator windings wound around a stator core and generating a rotating magnetic field;
A plurality of main permanent magnets for making a plurality of magnetic poles are embedded in the rotor core, and have a rotor that generates rotational torque and rotates.
The rotor is formed by embedding the main permanent magnet in the rotor core, thereby forming magnetic pole pieces on portions of the rotor core located on the stator side from the main permanent magnets, respectively.
The polarity of the stator side of the plurality of main permanent magnets embedded in the rotor core is alternately changed for each magnetic pole along the rotation direction of the rotor,
The magnetic pole piece is further embedded with an auxiliary permanent magnet for collecting magnetic flux in the center of the magnetic pole piece,
The auxiliary permanent magnet is magnetized so that the polarity of the center side surface of the magnetic pole piece in the rotation direction is the same as the polarity of the magnetic pole piece, .   2. The embedded permanent magnet motor according to claim 1, wherein the auxiliary permanent magnets are arranged on both sides of the central portion of the magnetic pole piece in the rotation direction, and the auxiliary permanent magnets are the main permanent magnets. A permanent magnet embedded motor characterized by having a shape extending in a radial direction.   The embedded permanent magnet motor according to claim 2, wherein a bridge portion for reducing leakage of magnetic flux is formed between the magnetic pole piece and the adjacent magnetic pole piece, and a central portion of the magnetic pole piece is sandwiched therebetween. The distance L1 between the auxiliary permanent magnets arranged on both sides is the distance L2 between one auxiliary permanent magnet and the end of the main permanent magnet on the one auxiliary permanent magnet side, or the other A permanent magnet embedded type motor characterized by being longer than a distance L3 between the auxiliary permanent magnet and the end of the main permanent magnet on the side of the other auxiliary permanent magnet.   4. The embedded permanent magnet motor according to claim 1, wherein a holding force of the auxiliary permanent magnet is smaller than a holding force of the main permanent magnet for forming the magnetic pole. A permanent magnet embedded motor.   5. The embedded permanent magnet motor according to claim 4, wherein the holding force of the auxiliary permanent magnet is in the range of 0.75 to 0.85 times the holding force of the main permanent magnet for forming the magnetic pole. A permanent magnet embedded motor characterized by that.   4. The embedded permanent magnet motor according to claim 1, wherein a holding force of the auxiliary permanent magnet is larger than a holding force of the main permanent magnet for forming the magnetic pole. A permanent magnet embedded motor. The embedded magnet type motor according to any one of claims 1 to 6,
An embedded permanent magnet motor, wherein an auxiliary magnetic pole for generating a reluctance torque is formed between the magnetic pole piece constituting the magnetic pole and the adjacent magnetic pole piece. The embedded magnet type motor according to any one of claims 1 to 7,
The stator has a control winding for controlling the position and inclination of the rotor relative to the stator, in addition to the stator winding for generating rotational torque in the rotor, and the rotation A permanent magnet embedded motor characterized by magnetically supporting a child.

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