JP2018011466A - Permanent-magnet embedded synchronous machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in a permanent-magnet embedded synchronous machine, a technology for achieving both a torque improvement and an improvement in resistance to decrease in magnetism.SOLUTION: A rotor (4) of a permanent-magnet embedded synchronous machine (100) in the present disclosure comprises a rotor core (7), a plurality of permanent magnets (5), and a plurality of flux barriers (13). The rotor core (7) has: a slit (19) provided between a magnetic pole (4a) and another magnetic pole (4a) adjacent to each other in a circumferential direction of the rotor (4) and having a recessed shape toward the center of the shaft (3) from an outer peripheral face (4p) of the rotor (4); and a projection (16) provided next to the slit (19) in each flux barrier (13) and projecting toward an end of the corresponding permanent magnet (5).SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a permanent magnet embedded synchronous machine.

  Permanent magnet embedded motors are widely used in home appliances, hybrid cars, trains, and the like, and the demand is increasing year by year. As is well known, the rotor of a permanent magnet embedded motor has a rotor core and a plurality of permanent magnets embedded in the rotor core. Since the reluctance torque resulting from the asymmetry of the magnetic resistance as well as the magnet torque by the permanent magnet can be used, the permanent magnet embedded motor has high efficiency and high output. The structure of the rotor is very important because it directly relates to the efficiency and reliability of the permanent magnet embedded motor.

  FIG. 9 partially shows the rotor of the permanent magnet embedded motor described in Patent Document 1. The rotor 105 of the permanent magnet embedded motor has a slit 125 and a flux barrier 123. The hole defining portion of the magnet insertion hole 121 includes an extending portion 111b. The extending portion 111 b extends toward the inter-electrode core portion 111 c in the rotor core 111 at a portion located further outward in the circumferential direction than the end surface in the width direction of the permanent magnet 113. The distance between the slit 125 and the core outer peripheral surface 111a is La, the distance between the slit 125 and the outer peripheral side surface 113a of the permanent magnet 113 is Lb, the shortest distance between the extension portion 111b and the inter-core core portion 111c is Lc, and the permanent magnet 113 When the thickness is Ld, the distance Lb is larger than the distance La, and the shortest distance Lc is smaller than the thickness Ld.

International Publication No. 2014/069438

  In the prior art shown in FIG. 9, when an excessive reverse magnetic field acts on the rotor 105, demagnetization at the end of the permanent magnet 113 is suppressed by the action of the extending portion 111 b. However, since the extension portion 111b is a part of the rotor core 111 that is in close contact with the permanent magnet 113, the adjacent magnetic poles are passed through the extension portion 111b even when a current of a level that generates a rated torque flows through the winding. Magnetic flux leaks considerably. Therefore, the structure shown in FIG. 9 has a problem that the effective magnetic flux decreases and the torque decreases.

  An object of the present disclosure is to provide a technique for achieving both improvement in torque and improvement in resistance to demagnetization in a permanent magnet embedded synchronous machine.

That is, this disclosure
A shaft,
A rotor supported by the shaft;
With
The rotor includes a rotor core, a plurality of permanent magnets embedded in the rotor core, and a plurality of flux barriers formed of space or a nonmagnetic material,
A plurality of magnet embedding holes are formed in the rotor core along the circumferential direction of the rotor, and the permanent magnet is disposed in each of the plurality of magnet embedding holes to form a plurality of magnetic poles on the rotor. And
Each of the plurality of flux barriers is located at each end of the plurality of magnet embedding holes,
In the flux barrier, the rotor core is provided between the magnetic poles adjacent to each other in the circumferential direction of the rotor and the magnetic poles, and has a concave shape from the outer peripheral surface of the rotor toward the center of the shaft. There is provided a permanent magnet embedded synchronous machine having a protrusion provided adjacent to the slit and protruding toward an end of the permanent magnet.

  According to the technique of the present disclosure, in the permanent magnet embedded synchronous machine, it is possible to achieve both improvement in torque and improvement in resistance to demagnetization.

FIG. 1 is a cross-sectional view of a permanent magnet embedded synchronous machine according to a first embodiment of the present disclosure. FIG. 2 is a partially enlarged sectional view of the rotor of the permanent magnet embedded synchronous machine shown in FIG. FIG. 3 is a magnetic flux diagram in the vicinity of the flux barrier when torque is generated in the rotor of the permanent magnet embedded synchronous machine according to the first embodiment. FIG. 4 is a magnetic flux diagram in the vicinity of the flux barrier when a reverse magnetic field acts on the rotor of the permanent magnet embedded synchronous machine according to the first embodiment. FIG. 5 is a graph showing the relationship between torque and current. FIG. 6A is a partially enlarged cross-sectional view of a rotor of a permanent magnet embedded synchronous machine according to a second embodiment of the present disclosure. FIG. 6B is a diagram in which dimension lines are added to FIG. 6A. FIG. 7 is a magnetic flux diagram in the vicinity of the flux barrier when torque is generated in the rotor of the permanent magnet embedded synchronous machine according to the second embodiment. FIG. 8 is a magnetic flux diagram in the vicinity of the flux barrier when a reverse magnetic field is applied to the rotor of the permanent magnet embedded synchronous machine according to the second embodiment. FIG. 9 is a partially enlarged sectional view of a rotor of a conventional permanent magnet embedded electric motor. FIG. 10 is a partial enlarged cross-sectional view of the rotor of the reference example.

The permanent magnet embedded synchronous machine according to the first aspect of the present disclosure is:
A shaft,
A rotor supported by the shaft;
With
The rotor includes a rotor core, a plurality of permanent magnets embedded in the rotor core, and a plurality of flux barriers formed of space or a nonmagnetic material,
A plurality of magnet embedding holes are formed in the rotor core along the circumferential direction of the rotor, and the permanent magnet is disposed in each of the plurality of magnet embedding holes to form a plurality of magnetic poles on the rotor. And
Each of the plurality of flux barriers is located at each end of the plurality of magnet embedding holes,
In the flux barrier, the rotor core is provided between the magnetic poles adjacent to each other in the circumferential direction of the rotor and the magnetic poles, and has a concave shape from the outer peripheral surface of the rotor toward the center of the shaft. A protrusion provided adjacent to the slit and protruding toward an end of the permanent magnet.

  According to the first aspect, the nonmagnetic portion having a sufficient volume is provided in the vicinity of the q axis and in the vicinity of the outer peripheral surface of the rotor. The nonmagnetic portion includes a flux barrier and a slit. By the action of these non-magnetic portions, leakage magnetic flux from a certain magnetic pole to an adjacent magnetic pole can be reduced. That is, the synchronous machine of the first aspect can achieve high torque. When an excessive reverse magnetic field acts on the rotor, the strong magnetic flux that has penetrated deeply into the rotor core is released from the magnetic pole to the adjacent magnetic pole through the protrusion. Thereby, it can avoid that a strong reverse magnetic field acts on a permanent magnet. That is, the synchronous machine of the first aspect is also excellent in resistance to demagnetization.

  In the second aspect of the present disclosure, for example, the rotor core of the permanent magnet embedded synchronous machine of the first aspect is a plurality of bridges that are located radially outside the flux barrier when viewed from the center of the shaft. And in the cross section of the rotor perpendicular to the shaft, the side close to the bridge is the root side of the projection, the side close to the center of the shaft is the tip side of the projection, and the circumferential direction of the rotor When the direction perpendicular to the q axis that forms the boundary line between the adjacent magnetic poles is defined as the width direction, the width of the protrusion on the tip side is larger than the width of the protrusion on the root side. According to the second aspect, a sufficiently large magnetic resistance can be secured near the outer peripheral surface of the rotor, and the leakage magnetic flux from a certain magnetic pole to an adjacent magnetic pole can be effectively reduced.

  In the third aspect of the present disclosure, for example, the width of the flux barrier on the root side of the protrusion of the permanent magnet embedded synchronous machine of the second aspect is the inner peripheral surface of the flux barrier on the tip side of the protrusion. It is larger than the shortest distance from the protrusion. Such a structure is advantageous for improving torque. That is, a sufficiently large magnetic resistance can be secured near the outer peripheral surface of the rotor, and the leakage magnetic flux from a certain magnetic pole to an adjacent magnetic pole can be effectively reduced.

  In the fourth aspect of the present disclosure, for example, the plurality of flux barriers of the permanent magnet embedded synchronous machine according to the second or third aspect include a boundary line between the magnetic pole and the magnetic pole adjacent to each other in the circumferential direction of the rotor. A pair of the flux barriers adjacent to each of the q axes formed, the protrusions being provided on each of the pair of flux barriers, and an inner circumference of one of the flux barriers selected from the pair of flux barriers The sum of the shortest distance between the surface and the protrusion, the shortest distance between the inner peripheral surface of the other flux barrier selected from the pair of the flux barriers and the protrusion, and the width of the slit is related to the magnetization direction. Less than twice the thickness of the permanent magnet. According to the fourth aspect, when an excessive reverse magnetic field magnetic flux acts on the rotor, the reverse magnetic field magnetic flux easily leaks to the adjacent magnetic pole through the tip portion of the protrusion before reaching the permanent magnet. That is, the reverse magnetic field acting on the permanent magnet can be effectively reduced.

  In the fifth aspect of the present disclosure, for example, the plurality of flux barriers of the permanent magnet embedded synchronous machine according to any one of the first to fourth aspects include the magnetic pole and the magnetic pole adjacent to each other in the circumferential direction of the rotor. Including the pair of flux barriers adjacent to the q-axis forming the boundary line, and the protrusion is provided only on one selected from the pair of flux barriers. Such a configuration is suitable for applications in which torque is generated only in one direction (clockwise direction or counterclockwise direction).

  In the sixth aspect of the present disclosure, for example, the protrusion of the permanent magnet embedded synchronous machine according to any one of the first to fifth aspects includes a root portion having a certain width adjacent to the slit. According to such a protrusion, a sufficiently large magnetic resistance can be ensured near the outer peripheral surface of the rotor, and leakage flux from a certain magnetic pole to an adjacent magnetic pole can be effectively reduced. This is advantageous for improving the torque.

  In the seventh aspect of the present disclosure, for example, in the cross section of the rotor perpendicular to the shaft of the permanent magnet embedded synchronous machine according to any one of the first to sixth aspects, an outline of the slit is a circumferential direction of the rotor In FIG. 1, the magnetic poles adjacent to each other include a pair of sides parallel to the q-axis that form a boundary line between the magnetic poles. According to the seventh aspect, a sufficiently large magnetic resistance can be ensured near the outer peripheral surface of the rotor.

  In the eighth aspect of the present disclosure, for example, the slit of the permanent magnet embedded synchronous machine according to any one of the first to seventh aspects is filled with a nonmagnetic material. According to the eighth aspect, the strength of the rotor can be increased.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

  In the present specification, the “cross section” means a cross section perpendicular to the rotation axis O common to the shaft and the rotor. "Permanent magnet embedded synchronous machine" is a general term for electric machines including a rotor having permanent magnets and a stator having coils. In the present specification, the term “synchronous machine” is used as a term including all of an electric motor, a generator, and an electric machine in which the electric motor and the generator are combined. Therefore, the term “permanent magnet embedded synchronous machine” is not limited to one of “motor” and “generator”.

(Embodiment 1)
As shown in FIG. 1, a permanent magnet embedded synchronous machine 100 (hereinafter also simply referred to as “synchronous machine 100”) includes a stator 2, a shaft 3, and a rotor 4. The stator 2 includes an annular yoke 10 and a plurality of teeth 11. A winding (not shown) is wound around each tooth 11. The rotor 4 includes a rotor core 7 and a plurality of permanent magnets 5. The rotor 4 faces the stator 2 through a cylindrical air gap 9. In other words, the rotor 4 is surrounded by the stator 2. The air gap 9 may be a so-called unequal gap. The rotor 4 is rotatably supported by the shaft 3. In the present embodiment, the synchronous machine 100 is a 6 pole 9 teeth inner rotor type. However, the number of poles and the number of teeth are not particularly limited. The winding method is not particularly limited, and a winding may be wound around each tooth 11 (concentrated winding), or a winding may be wound across a plurality of teeth 11 (distributed winding).

  In the rotor 4, the rotor core 7 is typically formed by stacking a plurality of circular electromagnetic steel plates. Therefore, the rotor core 7 has a cylindrical shape. The shape of the rotor core 7 may be determined so that the air gap 9 becomes an unequal gap. A plurality of permanent magnets 5 are embedded in the rotor core 7. Specifically, the rotor core 7 is formed with a plurality of magnet embedding holes 6 along the circumferential direction of the rotor 4 (circumferential direction of the shaft 3). The magnet embedding hole 6 extends in a direction parallel to the rotation axis O of the shaft 3 and the rotor 4. A permanent magnet 5 is disposed in each of the plurality of magnet embedding holes 6. Thereby, a plurality of magnetic poles 4 a are formed on the rotor 4. In the cross section of the rotor 4 perpendicular to the shaft 3, the magnetic pole 4a has a fan shape. The permanent magnet 5 is a ferrite magnet, an alnico magnet, a cobalt magnet or a neodymium magnet, and is typically a neodymium magnet. The permanent magnet 5 has a rectangular and plate shape in plan view. In other words, the permanent magnet 5 is a plate-like permanent magnet having a rectangular parallelepiped shape. The faces of the permanent magnet 5 facing each other are parallel. The surfaces facing each other in the thickness direction of the permanent magnet 5 are the widest surfaces and are the main surfaces of the permanent magnet 5. The corners of the permanent magnet 5 may be chamfered in a range of 0.2R to 0.5R (unit: mm), for example.

  In the present embodiment, the magnetization direction of the permanent magnet 5 is parallel to the thickness direction. In other words, the d-axis direction (magnetic flux direction) formed by the permanent magnet 5 is parallel to the thickness direction. The central axis of the magnetic pole 4a by the permanent magnet 5 can be defined as the d axis. In the present embodiment, the directions of the N poles (and S poles) of the pair of permanent magnets 5 adjacent to each other in the circumferential direction of the rotor 4 are opposite to each other. The N pole of one permanent magnet 5 is far from the rotation axis O and the S pole is close to the rotation axis O. The N pole of the other permanent magnet 5 is close to the rotation axis O and the S pole is far from the rotation axis O. Since the axis that is electrically and magnetically orthogonal to the d-axis is the q-axis, it passes between a pair of permanent magnets 5 adjacent to each other in the circumferential direction of the rotor 4 and travels outward from the rotational axis O in the radial direction. Is the q-axis direction. Further, the q axis forms a boundary line between the magnetic pole 4 a and the magnetic pole 4 a that are adjacent to each other in the circumferential direction of the rotor 4.

  As shown in FIG. 2, the rotor 4 further includes a plurality of flux barriers 13 (magnetic flux barriers). The flux barrier 13 is a portion that does not allow magnetic flux to pass therethrough, and prevents the magnetic flux from wrapping around the rotor 4 and increases the magnetic flux interlinking with the stator 2 through the air gap 9. In the present embodiment, the flux barrier 13 is formed by a space. Each of the plurality of flux barriers 13 is located at each end of the plurality of magnet embedding holes 6. That is, the magnet embedding hole 6 and the flux barrier 13 are formed by one continuous hole. More specifically, the magnet embedding hole 6 and the two flux barriers 13 are formed by one continuous hole (through hole). However, the flux barrier 13 may be formed of a nonmagnetic material such as resin, ceramic, or nonmagnetic metal.

  As shown in FIGS. 1 and 2, the rotor core 7 includes a plurality of slits 19, a plurality of bridges 15, and a plurality of protrusions 16. Each slit 19 is provided between the magnetic pole 4 a and the magnetic pole 4 a that are adjacent to each other in the circumferential direction of the rotor 4, and has a concave shape from the outer peripheral surface 4 p of the rotor 4 toward the center of the shaft 3. The slit 19 has a groove structure extending in a direction parallel to the rotation axis O. In the present embodiment, the number of slits 19 matches the number of poles of the rotor 4. Each bridge 15 is a portion located on the outer side in the radial direction from the flux barrier 13 when viewed from the center (rotation axis O) of the shaft 3. Specifically, the bridge 15 is a portion provided between the flux barrier 13 and the outer peripheral surface 4 p of the rotor 4. A pair of bridges 15 adjacent to each other in the circumferential direction of the rotor 4 are separated by a slit 19. The width of the bridge 15 in the radial direction of the rotor 4 is sufficiently narrow. In the present embodiment, the dimensions of the bridge 15 in the radial direction of the rotor 4 are constant over the circumferential direction of the rotor 4. The protrusion 16 is a portion protruding toward the end of the permanent magnet 5, and is provided adjacent to the slit 19 in the flux barrier 13. Specifically, the protrusion 16 protrudes from the bridge 15 toward the end of the permanent magnet 5. In the present embodiment, one protrusion 16 is provided for one flux barrier 13.

  The rotor core 7 further has a plurality of connecting portions 22. Each connecting portion 22 extends in a direction parallel to the q axis. The connecting portion 22 separates a pair of flux barriers 13 adjacent to each other in the circumferential direction of the rotor 4, and connects the pair of bridges 15 and the inner portion of the rotor core 7. Specifically, the connecting portion 22 is located between the protrusion 16 and the protrusion 16, and connects the pair of bridges 15 and the inner portion of the rotor core 7 via the protrusion 16. In other words, the protrusion 16 is a portion that connects the connecting portion 22 and the bridge 15. In the present embodiment, the width L7 of the connecting portion 22 is constant.

  In the present specification, a direction perpendicular to the q axis in the cross section of the rotor 4 is defined as a width direction WD. Unless otherwise specified, the dimension of each part in the width direction WD is defined as “width”.

  According to the structure of this embodiment, a nonmagnetic portion having a sufficient volume (area in the cross section of FIG. 2) is provided in the vicinity of the q axis and in the vicinity of the outer peripheral surface 4p of the rotor 4. The nonmagnetic portion includes a flux barrier 13 and a slit 19. By the action of these non-magnetic portions, leakage magnetic flux from a certain magnetic pole 4a to the adjacent magnetic pole 4a can be reduced. That is, the synchronous machine 100 of this embodiment can achieve high torque. When an excessive reverse magnetic field acts on the rotor 4, the strong magnetic flux that has penetrated deeply into the rotor core 7 is released from the magnetic pole 4 a to the adjacent magnetic pole 4 a through the protrusion 16. Thereby, it can avoid that a strong reverse magnetic field acts on the permanent magnet 5. That is, the synchronous machine 100 of this embodiment is also excellent in resistance to demagnetization.

  The structure of the rotor 4 will be described in more detail.

  As shown in FIG. 2, in the cross section of the rotor 4, the outline of the slit 19 includes a pair of sides 19 a parallel to the q axis. There is a q-axis between the pair of sides 19a. The dimension of the slit 19 in the direction parallel to the q axis is represented by, for example, the length of the side 19a in the direction parallel to the q axis. In the present embodiment, the dimension of the slit 19 in the direction parallel to the q axis is larger than the dimension of the bridge 15 in the radial direction of the rotor 4. According to such a structure, a sufficiently large magnetic resistance can be secured near the outer peripheral surface 4 p of the rotor 4.

  In this specification, the phrase “parallel” does not necessarily mean that they are completely parallel. For example, when the inclination angle of the side 19a with respect to the q axis is 3 degrees or less, the side 19a can be regarded as being parallel to the q axis. This also applies to elements other than the slit 19.

  As shown in FIG. 2, in the cross section of the rotor 4, the outline of the protrusion 16 includes a side 20 that extends toward the permanent magnet 5. Specifically, the side 20 extends toward the corner of the permanent magnet 5 on the side close to the outer peripheral surface 4 p of the rotor 4. In the present embodiment, the side 20 is a line segment inclined with respect to the q axis, but may be a curved line. The side close to the bridge 15 is defined as the root side of the protrusion 16, and the side close to the center of the shaft 3 is defined as the tip side of the protrusion 16. The width L2 of the protrusion 16 on the distal end side is larger than the width L1 of the protrusion 16 on the root side. Specifically, the width of the protrusion 16 continuously increases from the bridge 15 toward the center of the shaft 3. In other words, the width of the protrusion 16 continuously increases in the direction parallel to the q axis. According to such a structure, a sufficiently large magnetic resistance can be secured near the outer peripheral surface 4p of the rotor 4, and leakage flux from a certain magnetic pole 4a to the adjacent magnetic pole 4a can be effectively reduced. The width of the protrusion 16 may be increased stepwise in a direction parallel to the q axis. The width of the protrusion 16 corresponds to the distance between the side 20 and the side 19 a of the slit 19. The ratio of the width L2 to the width L1 (L2 / L1) is in the range of 1.2 to 3, for example.

  In the cross section of the rotor 4, the slit 19 has, for example, a rectangular shape. However, the shape of the slit 19 is not limited to a rectangle. The slit 19 may be U-shaped or V-shaped. That is, the width L4 of the slit 19 may be constant with respect to the direction parallel to the q axis or may be changed. Further, the width L4 of the slit 19 may coincide with the width L7 of the connecting portion 22, may be larger than the width L7 of the connecting portion 22, or may be smaller than the width L7 of the connecting portion 22. . If the slit 19 has a sufficient width L4, stress concentration due to centrifugal force can be avoided in the vicinity of the slit 19, so that sufficient strength can be imparted to the rotor core 7. When the connecting portion 22 has a sufficient width L7, the strength of the outer peripheral portion of the rotor core 7 can be sufficiently secured. It is appropriate that the width L4 of the slit 19 is close to the width L7 of the connecting portion 22.

  The width L3 (gap length L3) of the flux barrier 13 on the base side of the protrusion 16 is larger than the width L5 (gap length L5) of the narrowest portion of the flux barrier 13 on the tip side of the protrusion 16. The width L5 of the narrowest part of the flux barrier 13 is represented by the distance (shortest distance) between the protrusion 16 and the inner peripheral surface 23 of the flux barrier 13. In the present embodiment, the width of the flux barrier 13 decreases as the distance from the bridge 15 increases. Such a structure is advantageous for improving torque. That is, a sufficiently large magnetic resistance can be secured near the outer peripheral surface 4p of the rotor 4, and leakage flux from a certain magnetic pole 4a to the adjacent magnetic pole 4a can be effectively reduced. The ratio of the width L3 to the width L5 (L3 / L5) is, for example, in the range of 4-6.

  The pair of flux barriers 13 in the pair of magnetic poles 4a adjacent to each other in the circumferential direction of the rotor 4 has a symmetrical shape with respect to the q axis. The pair of protrusions 16 also have a symmetrical shape with respect to the q axis. When attention is paid to a structure including a pair of flux barriers 13 adjacent to one connecting portion 22, at a position adjacent to two bridges 15 (inner peripheral surface of the bridge 15), a portion made of a magnetic material is 2 There are two protrusions 16. Therefore, the width of the portion made of the magnetic material is represented by the sum of the width L1 of the one protrusion 16 and the width L1 of the other protrusion 16. In the position adjacent to the bridge 15 (the base side of the protrusion 16), the nonmagnetic portions are the two flux barriers 13 and the slit 19. The width of the nonmagnetic portion is represented by the sum of the width L3 of one flux barrier 13, the width L3 of the other flux barrier 13, and the width L4 of the slit 19. In this embodiment, the width of the non-magnetic part (total width: L3 + L3 + L4) is larger than the width of the part made of a magnetic material (total width: L1 + L1). On the base side of the protrusion 16, the ratio of the width of the nonmagnetic portion to the width of the portion made of the magnetic material is, for example, in the range of 2-3.

  On the other hand, on the tip side of the protrusion 16 (near the end of the permanent magnet 5), the portions made of a magnetic material are the two protrusions 16 and the connecting portion 22. Accordingly, the width of the portion made of the magnetic material is represented by the sum of the width L2 of the one protrusion 16, the width L2 of the other protrusion 16, and the width L7 of the connecting portion 22. On the tip side of the protrusion 16, the nonmagnetic part is two flux barriers 13. The width of the non-magnetic portion is represented by the sum of the width L5 of the narrowest portion of one flux barrier 13 and the width L5 of the narrowest portion of the other flux barrier 13. In this embodiment, the width (total width: L5 + L5) of the non-magnetic portion is smaller than the width (total width: L2 + L2 + L7) of the portion made of the magnetic material. That is, the magnitude relationship between the width of the nonmagnetic portion and the width of the portion made of the magnetic material is opposite between the root side of the protrusion 16 and the tip side of the protrusion 16. On the tip side of the protrusion 16, the ratio of the width of the portion made of the magnetic material to the width of the nonmagnetic portion is in the range of 5 to 6, for example.

  In the present embodiment, the plurality of flux barriers 13 include a pair of flux barriers 13 adjacent to the q axis. A protrusion 16 is provided on each of the pair of flux barriers 13. The shortest distance (width L5) between the inner peripheral surface 23 of one flux barrier 13 selected from the pair of flux barriers 13 and the protrusion 16 and the inner peripheral surface of the other flux barrier 13 selected from the pair of flux barriers 13. The sum of the shortest distance (width L5) between the protrusion 23 and the width L4 of the slit 19 is smaller than twice the thickness L6 of the permanent magnet 5 with respect to the magnetization direction. According to such a configuration, when an excessive reverse magnetic field magnetic flux acts on the rotor 4, the reverse magnetic field magnetic flux easily leaks to the adjacent magnetic pole 4 a through the tip portion of the protrusion 16 before reaching the permanent magnet 5. Since the reverse magnetic field acting on the permanent magnet 5 can be effectively reduced, the synchronous machine 100 of this embodiment is excellent in resistance to demagnetization. The ratio of the sum of the width L4, the width L5, and the width L5 ((L4 + L5 + L5) / (L6 + L6)) to twice the thickness L6 is, for example, in the range of 0.3 to 0.5.

  Next, the action of the flux barrier 13, the slit 19 and the protrusion 16 will be described in detail based on the result of computer simulation.

  FIG. 3 is a magnetic flux diagram created by magnetic field analysis, and shows a state when torque is generated in the counterclockwise direction. In the present embodiment, the width L 3 of the flux barrier 13 at a position adjacent to the bridge 15 is sufficiently larger than the width L 5 of the flux barrier 13 on the tip side of the protrusion 16. Therefore, the magnetic resistance of the flux barrier 13 is sufficiently high in the vicinity of the outer peripheral surface 4 p of the rotor 4. As a result, the leakage magnetic flux (broken arrow) from a certain magnetic pole 4a to the adjacent magnetic pole 4a is sufficiently reduced. Even at the tip end side of the protrusion 16, a part of the connecting portion 22 is magnetically saturated, and an appropriate amount of magnetic resistance is secured by the flux barrier 13. Therefore, it is possible to prevent magnetic flux from leaking from the magnetic pole 4a passing through the two protrusions 16 to the adjacent magnetic pole 4a. As shown in FIG. 3, the leakage magnetic flux at the time of torque generation is small, and the magnetic flux effectively generates torque.

  Further, the magnetic flux between the magnetic pole 4a and the magnetic pole 4a is increased by the leakage magnetic flux passing through the bridge 15 bypassing the slit 19. Thereby, leakage magnetic flux can be reduced.

  FIG. 4 is a magnetic flux diagram when a reverse magnetic field is applied to the rotor. In general, a state in which an excessive demagnetizing field acts on the permanent magnet of the rotor means that a magnetic field due to energization of the stator winding that becomes N pole acts on the N pole of the rotor, and S on the rotor S pole. It means a state in which a magnetic field is applied by energizing the windings of the stator that is the pole. In this case, a large magnetic flux flows from the teeth serving as the N pole to the adjacent teeth serving as the S pole through the rotor due to energization of the stator windings. At this time, an excessive reverse magnetic field acts near the boundary between the north and south poles of the rotor, and local demagnetization tends to occur at the end of the permanent magnet. An excessive reverse magnetic field penetrates not only in the vicinity of the rotor surface but also deeply into the rotor.

  FIG. 4 shows a state where an excessive reverse magnetic field is applied to the rotor of the present embodiment. The bridge 15 is magnetically saturated due to an excessive reverse magnetic field, and the magnetic flux penetrates into the rotor core 7. However, the width of the protrusion 16 is wide at the tip side, and the magnetic resistance is relatively low at the tip side of the protrusion 16. The width L5 of the narrowest portion of the flux barrier 13 on the tip side of the protrusion 16 is smaller than the thickness L6 of the permanent magnet 5 with respect to the magnetization direction. Therefore, before the excessive reverse magnetic field magnetic flux acting on the rotor 4 reaches the permanent magnet 5, it leaks from a certain magnetic pole 4 a to the adjacent magnetic pole 4 a through the tip portion of the protrusion 16 and the connecting portion 22 (broken arrow). As a result, the reverse magnetic field acting on the permanent magnet 5 is reduced, and demagnetization of the permanent magnet 5 is prevented.

  FIG. 5 is a graph showing the relationship between the rated current and the rated torque calculated from the result of the magnetic field analysis. First, a reverse magnetic field is applied to the synchronous machine of the reference example using the rotor 107 (FIG. 10) obtained by removing the protrusions 16 and the slits 19 from the rotor 4 of the present embodiment by computer simulation. The current value that does not occur (demagnetization limit current) was specified. A predetermined ratio (for example, 1/3) of the demagnetization limit current was set as the rated current, and the torque generated when the rated current was passed through the winding was calculated as the rated torque. The rated current and rated torque of the synchronous machine of the reference example were defined as 100% current and torque, respectively. Point P in FIG. 5 is data of the synchronous machine of the reference example.

  Next, the same simulation was performed for the synchronous machine using the rotor of the prior art shown in FIG. 9, the rated current and the rated torque were calculated, and the ratio to the data (point P) of the synchronous machine of the reference example was calculated. . Point Q in FIG. 5 is data of a conventional synchronous machine. The demagnetization resistance of the conventional synchronous machine was superior to the synchronous machine of the reference example. In the conventional synchronous machine, it was possible to flow a current of 118% of the rated current of the synchronous machine of the reference example while avoiding demagnetization. Torque also improved to 115%.

  Next, for the synchronous machine 100 of the present embodiment, the rated current and the rated torque were calculated, and the ratio to the data (point P) of the synchronous machine of the reference example was calculated. Point X in FIG. 5 is data of the synchronous machine of the present embodiment. The demagnetization resistance of the synchronous machine of this embodiment was superior to that of the reference example and the conventional synchronous machine. In the synchronous machine 100 of the present embodiment, it was possible to flow a current of 128% of the rated current of the synchronous machine of the reference example while avoiding demagnetization. Torque also improved to 127%.

(Embodiment 2)
As shown in FIGS. 6A and 6B, the rotor 14 (specifically, the rotor core 17) according to the second embodiment has an asymmetric structure with respect to the q axis. Specifically, a plurality of flux barriers 43 and 44 are formed on the rotor core 17. The plurality of flux barriers 43 and 44 include a pair of flux barriers 43 and 44 adjacent to one q-axis. The protrusion 26 is provided only on one flux barrier 43 selected from the pair of flux barriers 43 and 44. The synchronous machine including such a rotor 14 is suitable for an application that generates torque only in one direction (counterclockwise direction in FIG. 6A). The flux barrier 43 is located on the clockwise side with respect to the q axis. The flux barrier 44 is located on the counterclockwise side with respect to the q axis. In other words, the flux barrier 43 is located at the end of the magnet embedding hole 6 on the counterclockwise direction with reference to the d-axis of the permanent magnet 5. The flux barrier 44 is located at the end of the magnet embedding hole 6 on the clockwise side with respect to the d-axis of the permanent magnet 5. The rotor core 17 has a crank-shaped connecting portion 42. The connecting portion 42 is a portion that connects the pair of bridges 15 and the inner portion of the rotor core 17. Other configurations of the rotor 14 are the same as those of the rotor 4 of the first embodiment, and the description thereof may be omitted. The values of Embodiment 1 can also be used for examples such as ratio. FIG. 6B is a diagram in which dimension lines are added to FIG. 6A.

  In the present embodiment, a flux barrier 43 (first flux barrier) provided with a protrusion 26 is located at one end (counterclockwise end) of the magnet embedding hole 6, and the other end of the magnet embedding hole 6. The flux barrier 44 (second flux barrier) where the protrusion 26 is not provided is located at the end (clockwise end). The flux barrier 43 faces the flux barrier 44 via the q axis. The protrusion 26 protrudes from the bridge 15 toward the center of the shaft 3. Since the rotor 14 according to the present embodiment has a structure in which magnetic flux can easily flow in one direction, it can exhibit higher torque than a rotor having no directionality. Further, the shape of the flux barrier 44 without the protrusions 26 is relatively simple. Therefore, compared with the case where each flux barrier is provided with a protrusion, the rotor 14 of this embodiment is easy to produce with high accuracy.

  In the present embodiment, the protrusion 26 has a root portion 26a and a tip portion 26b. The root portion 26 a has a constant width L 11 and is adjacent to the bridge 15. The distal end portion 26b has a width L2 wider than the root portion 26a, and is located on the distal end side of the root portion 26a. The width L2 is the width at the widest position of the tip end portion 26b. In the cross section of the rotor 14, the outline of the protrusion 26 includes a side 32 parallel to the q axis and another side 33 extending toward the permanent magnet 5. A root portion 26 a is formed by one side 32 parallel to the q-axis and a side 19 a constituting the outline of the slit 19. That is, the root portion 26 a is adjacent to the slit 19. The other side 33 forms a tip portion 26b. The width of the tip portion 26b may change in a direction parallel to the q axis, or may be constant. According to such a protrusion 26, a sufficiently large magnetic resistance can be secured near the outer peripheral surface 4p of the rotor 14, and the leakage magnetic flux from a certain magnetic pole 4a to the adjacent magnetic pole 4a can be effectively reduced. This is advantageous for improving the torque.

  The connecting portion 42 includes two first portions 42 a that extend in a direction parallel to the q axis, and a second portion 42 b that extends in the width direction WD or the circumferential direction of the rotor 14. The second portion 42b is located between the two first portions 42a. The connecting portion 42 separates the flux barrier 43 and the flux barrier 44 and connects the pair of bridges 15 and the inner portion of the rotor core 17. Specifically, the connecting portion 42 connects the inner portion of the rotor core 17 and the bridge 15 facing the flux barrier 44 where the protrusions 26 are not provided. The protrusion 26 is connected to the second portion 42 b of the connecting portion 42, so that the bridge 15 facing the flux barrier 43 provided with the protrusion 26 is connected to the rotor core 17 via the protrusion 26 and the connecting portion 42. Connected to the inner part.

  The two first portions 42a of the connecting portion 42 have a width L12 and a width L7, respectively. The widths of the two first portions 42a may coincide with each other or may be different. For example, the width of the second portion 42 b of the connecting portion 42 matches the width L 41 of the slit 19.

  In the position adjacent to the bridge 15 (the base side of the protrusion 26), the portions made of the magnetic material are the protrusion 26 and the connecting portion 42. Therefore, the width of the portion made of the magnetic material is represented by the sum of the width L11 of the base portion 26a of the protrusion 26 and the width L12 of the first portion 42a of the connecting portion 42. In the position adjacent to the bridge 15, the nonmagnetic portions are the flux barrier 43, the flux barrier 44, and the slit 19. The width of the nonmagnetic portion is represented by the sum of the width L31 of the flux barrier 43, the width L32 of the flux barrier 44, and the width L41 of the slit 19. Similarly to the first embodiment, also in this embodiment, the width of the nonmagnetic part (total width: L31 + L32 + L41) is larger than the width of the part made of a magnetic material (total width: L11 + L12).

  On the other hand, on the tip end side of the protrusion 26, the portions made of the magnetic material are the protrusion 26 and the connecting portion 42. Therefore, the width of the portion made of the magnetic material is represented by the sum of the width L2 of the protrusion 26, the width L12 of the first portion 42a of the connecting portion 42, and the width L41 of the second portion 42b of the connecting portion 42. The On the tip side of the protrusion 26, the nonmagnetic portions are two flux barriers 43 and 44. Specifically, the nonmagnetic portion is represented by the sum of the width L51 (gap length L51) of the flux barrier 43 and the width L52 (gap length L52) of the flux barrier 44. The width L51 is equal to the distance between the protrusion 26 and the inner peripheral surface 52 of the flux barrier 43. The width L52 is equal to the distance between the inner peripheral surface 53 of the flux barrier 44 and the second portion 42b of the connecting portion 42. Also in this embodiment, the width of the non-magnetic portion (total width: L51 + L52) is smaller than the width of the portion made of a magnetic material (total width: L2 + L41 + L12). That is, the magnitude relationship between the width of the nonmagnetic portion and the width of the portion made of the magnetic material is opposite between the root side of the protrusion 26 and the tip side of the protrusion 26.

  Further, the flux barrier 43 has an inner peripheral surface 52 that faces the protrusion 26. The flux barrier 44 has an inner peripheral surface 53 that faces the connecting portion 42. The maximum distance D1 from the q axis to the inner peripheral surface 52 of the flux barrier 43 is smaller than the maximum distance D2 from the q axis to the inner peripheral surface 53 of the flux barrier 44.

  FIG. 7 is a magnetic flux diagram created by magnetic field analysis, and shows a state when torque is generated in the counterclockwise direction. The width (total width) of the nonmagnetic portion (gap) at a position adjacent to the bridge 15 is sufficiently larger than the width (total width) of the nonmagnetic portion (gap) on the tip side of the protrusion 26. Therefore, the magnetic resistance of the flux barriers 43 and 44 is sufficiently high in the vicinity of the outer peripheral surface 4p of the rotor 14. As a result, the leakage magnetic flux (broken arrow) from a certain magnetic pole 4a to the adjacent magnetic pole 4a is sufficiently reduced. Also on the tip side of the protrusion 26, a moderately large magnetic resistance is secured by the non-magnetic portion (gap). Therefore, it is possible to prevent magnetic flux from leaking from the magnetic pole 4a passing through the protrusion 26 to the adjacent magnetic pole 4a. As shown in FIG. 7, the leakage magnetic flux at the time of torque generation is small, and the magnetic flux effectively generates torque.

  Further, the magnetic flux between the magnetic pole 4a and the magnetic pole 4a is increased by the leakage magnetic flux passing through the bridge 15 bypassing the slit 19. Thereby, leakage magnetic flux can be reduced.

  FIG. 8 is a magnetic flux diagram when a reverse magnetic field is applied to the rotor. Due to the excessive reverse magnetic field, the bridge 15 is magnetically saturated, and the magnetic flux penetrates into the rotor core 17. However, the width of the protrusion 26 is wide on the tip side, and the magnetic resistance is relatively low on the tip side of the protrusion 26. On the tip side of the protrusion 26, the width L51 of the flux barrier 43 is smaller than the thickness L6 of the permanent magnet 5 with respect to the magnetization direction. The width L52 of the flux barrier 44 is also smaller than the thickness L6 of the permanent magnet 5. Therefore, the excessive reverse magnetic field magnetic flux acting on the rotor 14 leaks from a certain magnetic pole 4a to the adjacent magnetic pole 4a through the tip portion 26b and the connecting portion 42 of the protrusion 26 before reaching the permanent magnet 5 (broken arrow). As a result, the reverse magnetic field acting on the permanent magnet 5 is reduced, and demagnetization of the permanent magnet 5 is prevented.

  As shown in FIG. 5, for the synchronous machine using the rotor 14 of the present embodiment, the rated current and the rated torque are respectively calculated by the simulation described in the first embodiment, and the data (point P) of the synchronous machine of the reference example is calculated. The percentage was calculated. Point Y in FIG. 5 is data of the synchronous machine of this embodiment. The demagnetization resistance of the synchronous machine of this embodiment was superior to that of the reference example, the prior art, and the synchronous machine of the first embodiment. In the synchronous machine of this embodiment, it was possible to flow a current of 137% of the rated current of the synchronous machine of the reference example while avoiding demagnetization. Torque also improved to 134%.

(Modification)
In the first and second embodiments, the slit 19 is formed in a space. However, when the slit 19 is filled with a nonmagnetic material, the same effect as that obtained when the slit 19 is a space can be obtained. Furthermore, when the slit 19 is filled with a nonmagnetic material, the strength of the rotor 4 or 14 can be increased. Nonmagnetic materials include resins, ceramics, and nonmagnetic metals. When all of the slits 19 having a concave shape are filled with a nonmagnetic material, the rotor 4 or 14 has a circular cross section (contour). Further, only a part (for example, half) of the slit 19 may be filled with a nonmagnetic material.

  The permanent magnet embedded synchronous machine according to the present disclosure is excellent in resistance to demagnetization and can generate high torque. The permanent magnet embedded synchronous machine according to the present disclosure is useful for electric machines such as an electric motor and a generator.

3 Shaft 4, 14 Rotor 4 p Rotor outer peripheral surface 4 a Magnetic pole 5 Permanent magnet 6 Magnet embedding hole 7, 17 Rotor core 13, 43, 44 Flux barrier 15 Bridge 16, 26 Protrusion 19 Slit 19 a Slit contour side 26 a Root portion 26 b Tip Part 100 Permanent magnet embedded synchronous machine WD Width direction

Claims (8)

A shaft,
A rotor supported by the shaft;
With
The rotor includes a rotor core, a plurality of permanent magnets embedded in the rotor core, and a plurality of flux barriers formed of space or a nonmagnetic material,
A plurality of magnet embedding holes are formed in the rotor core along the circumferential direction of the rotor, and the permanent magnet is disposed in each of the plurality of magnet embedding holes to form a plurality of magnetic poles on the rotor. And
Each of the plurality of flux barriers is located at each end of the plurality of magnet embedding holes,
In the flux barrier, the rotor core is provided between the magnetic poles adjacent to each other in the circumferential direction of the rotor and the magnetic poles, and has a concave shape from the outer peripheral surface of the rotor toward the center of the shaft. A permanent magnet embedded synchronous machine having a protrusion provided adjacent to the slit and protruding toward an end of the permanent magnet. The rotor core further includes a plurality of bridges located radially outside the flux barrier when viewed from the center of the shaft;
In the cross section of the rotor perpendicular to the shaft, the side close to the bridge is the root side of the protrusion, the side close to the center of the shaft is the tip side of the protrusion, and the magnetic poles adjacent to each other in the circumferential direction of the rotor When the direction perpendicular to the q axis that forms the boundary line with the magnetic pole is defined as the width direction,
2. The permanent magnet embedded synchronous machine according to claim 1, wherein a width of the protrusion on the tip side is larger than a width of the protrusion on the root side.   3. The permanent magnet embedded synchronization according to claim 2, wherein a width of the flux barrier on the base side of the protrusion is larger than a shortest distance between an inner peripheral surface of the flux barrier on the tip side of the protrusion and the protrusion. Machine. The plurality of flux barriers include a pair of flux barriers adjacent to each other in the q axis that forms a boundary line between the magnetic poles adjacent to each other in the circumferential direction of the rotor,
The protrusions are provided on each of the pair of flux barriers;
The shortest distance between the inner peripheral surface of one flux barrier selected from a pair of the flux barriers and the protrusion, and the inner peripheral surface of the other flux barrier selected from a pair of the flux barriers and the protrusion. The permanent magnet embedded synchronous machine according to claim 2 or 3, wherein the sum of the shortest distance and the width of the slit is smaller than twice the thickness of the permanent magnet with respect to the magnetization direction. The plurality of flux barriers include a pair of flux barriers adjacent to each other in the q axis that forms a boundary line between the magnetic poles adjacent to each other in the circumferential direction of the rotor,
The permanent magnet embedded synchronous machine according to any one of claims 1 to 4, wherein the protrusion is provided only on one selected from the pair of flux barriers.   The permanent magnet embedded synchronous machine according to any one of claims 1 to 5, wherein the protrusion has a root portion having a constant width adjacent to the slit.   In the cross section of the rotor perpendicular to the shaft, the outline of the slit includes a pair of sides parallel to the q axis that form a boundary line between the magnetic pole and the magnetic pole adjacent to each other in the circumferential direction of the rotor. Item 7. The permanent magnet embedded synchronous machine according to any one of Items 1 to 6.   The permanent magnet embedded synchronous machine according to claim 1, wherein the slit is filled with a nonmagnetic material.

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