JP2021069148A - Rotor and variable field motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress irreversible demagnetization of a magnet. SOLUTION: A rotor core 15, a plurality of magnets 16 arranged at intervals in the circumferential direction of the rotor core 15 and magnetized in one direction in the radial direction of the rotor core 15 to become magnetic poles, and each magnet 16 formed on the rotor core 15 In a rotor for a variable field motor, which includes a salient pole 40 formed between them and serves as a magnetic pole, is surrounded by a stator so as to face each other in the radial direction, and receives a field magnetic flux from the stator, the rotor core 15 is a magnet 16. The rotor core axial end surface and the core extension portion 60 projecting outward in the axial direction from the axial end surface of the stator core of the stator when the rotor is assembled as a motor are included, and the core extension portion 60 is outside the rotor core radial direction of the magnet 16. It is provided on the side. [Selection diagram] Fig. 6

Description

The present invention relates to a rotor for a variable field motor in which magnets and salient poles are alternately arranged in the circumferential direction, and a variable field motor including the rotor.

As an example of a half magnet type motor in which the number of magnets attached to the rotor is reduced to half, a concave pole type motor is known, and the rotor is called a concave pole type rotor. In this sequential pole type rotor, salient poles formed integrally with the rotor core and magnets magnetized in one direction are alternately arranged in the circumferential direction. Further, a variable field motor including a concave pole type rotor is also known. In the variable field motor, the magnetic flux from the field yoke to the rotor can be controlled by using a field coil to perform field weakening control, field strengthening control, and the like (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2008-43099

In a variable field motor provided with a sequential pole type rotor, the field current magnetic flux (also referred to as field magnetic flux) generated by energizing the field coil with a current acts in the direction opposite to the magnetizing direction of the magnet. FIG. 16 is a diagram showing a three-phase current magnetic flux and a field current magnetic flux acting on the rotor in a variable field motor including a sequential pole type rotor. As shown in FIG. 16, the magnet 116 arranged on the rotor core 115 of the rotor 114 is magnetized outward in the radial direction of the rotor core 115 (direction of arrow AR11), and the three-phase current magnetic flux and the field current magnetic flux AR12 Flows from the stator core 121 of the stator 120 into the rotor core 115 in the direction opposite to the magnetizing direction AR11 of the magnet 116.

As shown in FIG. 16, the field current magnetic flux and the three-phase current magnetic flux are concentrated at the axial end of the rotor core 115 in the radial direction of the magnet 116, and increase the reverse magnetic field AR13 at the axial end of the magnet 116. Let me. When the reverse magnetic field acting on the magnet 116 increases above a certain threshold value, the magnet 116 undergoes irreversible demagnetization, and the magnetic force of the magnet 116 weakens.

An object of the present invention is to suppress irreversible demagnetization of a magnet of a rotor in a variable field motor including a sequential pole type rotor.

The present invention comprises a rotor core, a plurality of magnets arranged at intervals in the circumferential direction of the rotor core and magnetized in one direction in the radial direction of the rotor core to form magnetic poles, and between the rotor cores formed on the rotor core. A rotor for a variable field motor that includes salient poles formed to serve as magnetic poles, is surrounded by a stator so as to face each other in the radial direction, and receives a field magnetic flux from the stator. The rotor core is a rotor of the magnet. The rotor core axial end surface and the core extension portion protruding axially outward from the axial end surface of the stator core of the stator when the rotor is assembled as a motor are included, and the core extension portion is outward in the rotor core radial direction of the magnet. It is provided in.

According to this configuration, the axial end face of the magnet and the core extension portion protruding axially outward from the axial end face of the stator core are provided on the radial outer side of the magnet (rotor core radial outer side), so that the magnetic flux The axial end of the rotor core (the axial end of the core extension) where the magnetic flux is concentrated can be separated from the magnet. Therefore, the reverse magnetic field acting on the magnet can be reduced, and the irreversible demagnetization of the magnet can be suppressed.

Further, in the present invention, the core extension portion may be provided over the entire axial end portion of the rotor core.

Further, in the present invention, the core extension portion provided on the outer side in the rotor core radial direction of the magnet is a magnet outer core extension portion, and the plurality of magnet outer core extension portions are connected to each other. The outer peripheral core extension portion, which is the core extension portion provided at the outer peripheral end of the rotor core, may be included.

According to this configuration, the mechanical strength of the core extension portion can be increased.

Further, in the present invention, the inner peripheral core extension portion which is the core extension portion provided in an annular shape around the shaft hole of the rotor core is connected to the outer peripheral core extension portion and the inner peripheral core extension portion. It may include a connection core extension portion which is the core extension portion provided at the salient pole of the rotor core.

According to this configuration, the mechanical strength of the core extension portion can be further increased.

Further, in the present invention, the core extension portion may be smaller in the rotor core radial direction of the magnet than in the rotor core radial direction outer direction of the magnet.

According to this configuration, the magnetic resistance on the magnet side remains high due to the small number of core extension portions inward in the rotor core radial direction of the magnet, and an increase in field current torque can be expected.

Further, in the present invention, there are fewer core extension portions in the rotor core radial direction inner direction of the magnet than in the rotor core radial direction outer direction of the magnet, and the protrusions that are the core extension portions provided at the salient poles of the rotor core. The polar core extension portion and the inner peripheral core extension portion which is the core extension portion provided in an annular shape around the shaft hole of the rotor core are included, and the outer peripheral core extension portion and the inner peripheral core extension portion include the outer peripheral core extension portion and the inner peripheral core extension portion. It may be connected by the salient pole core extension portion.

According to this configuration, the magnetic resistance on the magnet side remains high due to the small number of core extension portions in the rotor core radial direction of the magnet, and the magnetic resistance of the salient pole is reduced by providing the salient pole core extension portion. , The reluctance difference between the magnet pole and the salient pole can be expanded to increase the field current torque. In addition, the mechanical strength of the core extension portion can be increased.

Further, the variable field motor according to the present invention includes the rotor as described above.

According to the present invention, in a variable field motor including a sequential pole type rotor, irreversible demagnetization of the rotor magnet can be suppressed.

It is a figure which shows the whole structure of the variable field motor of Embodiment 1. It is a radial cross-sectional view of a part of a variable field motor. It is a perspective view which shows the structure of the rotor of Embodiment 1. FIG. It is a figure which shows the three-phase current magnetic flux and the field current magnetic flux acting on the rotor of Embodiment 1. FIG. It is a figure which shows the comparison result of the reverse magnetic field acting on the magnet of the prior art and the magnet of Embodiment 1. It is a perspective view which shows the structure of the rotor of Embodiment 2. It is a figure which shows the comparison result of the reverse magnetic field acting on the magnet of the prior art and the magnet of Embodiment 2. It is a figure which shows the comparison result of the torque of the motor of Embodiment 1 and the motor of Embodiment 2. It is a perspective view which shows the structure of the rotor of Embodiment 3. It is a figure which shows the comparison result of the reverse magnetic field acting on the magnet of the prior art and the magnet of Embodiment 3. It is a perspective view which shows the structure of the rotor of Embodiment 4. It is a figure which shows the comparison result of the reverse magnetic field acting on the magnet of the prior art and the magnet of Embodiment 4. It is a perspective view which shows the structure of the rotor of Embodiment 5. It is a figure which shows the comparison result of the reverse magnetic field acting on the magnet of the prior art and the magnet of Embodiment 5. It is a figure which shows the comparison result of the torque of each motor of Embodiments 1, 4 and 5. It is a figure which shows the three-phase current magnetic flux and the field current magnetic flux acting on the rotor of the prior art.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Similar elements are designated by the same or similar reference numerals in all drawings, and duplicate description will be omitted. The present invention is not limited to the embodiments described herein.

FIG. 1 is a diagram showing an overall configuration of the variable field motor 10a of the first embodiment. The motor case is not shown.

The shaft 12 is a round bar-shaped output shaft, and a rotor 14a is fixed around the shaft 12. The rotor 14a includes a rotor core 15 and a plurality of magnets 16 arranged on the rotor core 15. The rotor core 15 is made of a magnetic material such as an electromagnetic steel plate or a powder magnetic powder, and has a cylindrical shape as a whole. In this example, each of the plurality of magnets 16 is arranged at a position close to the outer circumference of the rotor core 15. The magnet 16 is a permanent magnet, and is inserted and fixed in a plate-shaped magnet hole 18 extending in the axial direction. The rotor 14a is a sequential pole type, and the magnetic poles are composed of magnets 16 and salient poles formed on the rotor core 15 alternately located in the circumferential direction. All the magnets 16 are magnetized in the same direction, and in this example, they are magnetized outward in the radial direction.

An annular stator 20 is arranged around the rotor 14a so as to surround the rotor 14a through a predetermined gap. The stator 20 includes a stator core 21 and a stator coil 26 (also referred to as a three-phase coil). The stator core 21 includes an annular stator yoke 22 located on the outer peripheral side and a plurality of teeth 24 extending inward in the radial direction from the stator yoke 22. As shown in FIG. 2, the teeth 24 are formed at regular intervals in the circumferential direction, and a slot is formed between two adjacent teeth 24. Then, using this slot, the stator coil 26 is wound around the teeth 24. In FIG. 1, a coil end portion protruding in the axial direction of the stator coil 26 is shown. In this example, the stator coil 26 is a three-phase coil, and a rotating magnetic field is formed by passing a three-phase alternating current through the stator coil 26. The magnetic flux generated by passing a three-phase alternating current through the stator coil 26 is called a three-phase current magnetic flux.

A field yoke 30 is connected to the stator yoke 22. The field yoke 30 has an annular outer wall portion 32 extending from the stator yoke 22 on both sides in the axial direction, a donut plate-shaped side wall portion 34 extending inward in the radial direction, and the side wall portion 34 toward the axial end surface of the rotor 14a. Includes an annular inner wall portion 36 that extends. Further, the tip end portion of the inner wall portion 36 faces the axial end surface of the rotor 14a. By providing such a field yoke 30, a magnetic circuit is formed between the rotor 14a and the stator 20 via the field yoke 30. Then, the field coil 38 is arranged inside the intersection of the inner wall portion 36 and the side wall portion 34, and by passing a current through the field coil 38, the field yoke 30 is magnetized, and the field weakening magnet and the field strengthening magnetic field are strengthened. Etc. can be controlled. As described above, in the variable field motor 10a, the field can be controlled not only by the field by the magnet 16 but also by the field current to the field coil 38. The magnetic flux generated by passing a field current through the field coil 38 is called a field current magnetic flux or a field magnetic flux. The central side of the inner wall portion 36 of the field yoke 30 is rotatably supported by the shaft 12 via a bearing 50.

In FIG. 1, the field yoke 30 is configured to extend in the axial direction from both sides in the axial direction of the stator yoke 22, but is configured to surround the stator yoke 22 from the outer peripheral side of the stator yoke 22. May be good.

FIG. 2 is a radial cross-sectional view of a part of the variable field motor 10a. A salient pole 40 is formed at a position adjacent to the magnet 16 in the circumferential direction. In this example, the magnetizing direction of the magnet 16 is outward in the radial direction. Therefore, the magnetic poles of the magnet 16 are directed outward in the radial direction, and the magnetic poles of the salient pole 40 are directed inward in the radial direction. Holes 42 extending in the axial direction are provided on both sides of the magnet hole 18 in the circumferential direction. A bridge 46a is formed between the hole 42 and the magnet hole 18, and a bridge 46b is formed between the hole 42 and the outer peripheral end of the rotor core 15.

FIG. 3 is a perspective view showing the configuration of the rotor 14a of the first embodiment. In this example, four magnets 16 are arranged on the rotor 14a. Therefore, the rotor 14a has eight magnetic poles, including the magnetic poles of the magnet 16 and the salient poles 40.

Here, as shown in FIG. 1, the rotor core 15 of the rotor 14a includes a core extension portion 60 projecting outward in the axial direction from the axial end surface of the magnet 16 and the axial end surface of the stator core 21. The core extension portion 60 is integrally formed with other parts of the rotor core 15 (referred to as a rotor core main body), and is made of a magnetic material such as an electromagnetic steel plate or a powder magnetic powder. However, the core extension portion 60 may have a magnetic material different from the rotor core main body attached to the rotor core main body. As shown in FIG. 3, in the rotor 14a of the first embodiment, the core extension portion 60 is provided over the entire axial end portion of the rotor core 15. Of the core extension portions 60, the core extension portion provided on the outer side in the radial direction of the magnet 16 is referred to as a magnet outer core extension portion 60a.

FIG. 4 is a diagram showing a three-phase current magnetic flux and a field current magnetic flux acting on the rotor 14a when the variable field motor 10a of the first embodiment is operated. In FIG. 4, AR1 represents the magnetizing direction of the magnet 16, AR2 represents the three-phase current magnetic flux and the field current magnetic flux, and AR3 represents the reverse magnetic field at the axial end of the magnet 16. As shown in FIG. 4, according to the variable field motor 10a of the first embodiment, the core extension portion 60 projecting outward in the axial direction from the axial end surface of the magnet 16 and the axial end surface of the stator core 21 is the magnet 16. (See reference numeral 60a). Therefore, the axial end portion of the rotor core 15 (the axial end portion of the core extension portion 60a) where the three-phase current magnetic flux and the field current magnetic flux AR2 are concentrated can be separated from the magnet 16. Therefore, the reverse magnetic field AR3 acting on the axial end of the magnet 16 can be reduced. FIG. 5 is a diagram showing the magnitude of the reverse magnetic field acting on the magnet of the prior art (motor 100 shown in FIG. 16) and the magnet of the first embodiment calculated by simulation. As shown in this figure, the reverse magnetic field acting on the magnet of the first embodiment is smaller than that of the prior art. According to the first embodiment, since the reverse magnetic field acting on the magnet 16 can be reduced in this way, the irreversible demagnetization of the magnet 16 can be suppressed. Therefore, it is possible to suppress a decrease in motor torque due to irreversible demagnetization of the magnet 16.

Next, the variable field motors 10b to 10e of the second to fifth embodiments will be described. The variable field motors 10b to 10e of the second to fifth embodiments are different from the variable field motors 10a of the first embodiment in that the core extension portion 60 is partially provided at the axial end portion of the rotor core 15. Since the other motor configurations are the same as those of the variable field motor 10a of the first embodiment, the description thereof will be omitted as appropriate.

FIG. 6 is a perspective view showing the configuration of the rotor 14b of the variable field motor 10b of the second embodiment. In the rotor 14b of the second embodiment, the core extension portion 60 is provided only on the radial outer side of the magnet 16. That is, only the magnet outer core extension portion 60a is provided. Also in this configuration, the reverse magnetic field acting on the axial end of the magnet 16 can be reduced. FIG. 7 is a diagram showing the magnitude of the reverse magnetic field acting on the magnet of the conventional technique (motor 100 shown in FIG. 16) and the magnet 16 of the second embodiment calculated by simulation. As shown in this figure, the reverse magnetic field acting on the magnet of the second embodiment is smaller than that of the prior art.

Further, as shown in FIG. 6, in the rotor 14b of the second embodiment, the thickness of the magnetic material in the axial direction of the bridges 46a and 46b near the magnet 16 is thinner than that of the rotor 14a of the first embodiment. , The magnetic resistance of the bridges 46a and 46b is high. With this structure, it is possible to suppress a state in which the magnetic flux flows through the bridges 46a and 46b and the magnetic flux is short-circuited between the N and S poles of the magnet 16 (see the one-dot chain line in FIG. 6, the generation of the short-circuit magnetic flux). Therefore, the motor torque (also referred to as magnet torque) caused by the magnetic flux from the magnet 16 can be increased.

Further, in the rotor 14b of the second embodiment, the axial thickness of the magnetic material in the radial direction of the magnet 16 is thinner than that of the rotor 14a of the first embodiment, and the magnetic resistance of the magnet pole is high. .. With this structure, an increase in motor torque (also called field current torque) due to field current magnetic flux can be expected. The field current torque will be described in detail later. FIG. 8 is a diagram showing a comparison result of torques of the motor 10a of the first embodiment and the motor 10b of the second embodiment calculated by simulation. FIG. 8 shows the ratio of the torque of the motor 10b of the second embodiment when the torque of the motor 10a of the first embodiment is 100%. As shown in this figure, the torque of the motor 10b of the second embodiment is larger than the torque of the motor 10a of the first embodiment.

Next, the variable field motor 10c of the third embodiment will be described. FIG. 9 is a perspective view showing the configuration of the rotor 14c of the variable field motor 10c according to the third embodiment. The rotor 14c of the third embodiment has a core extension portion provided at the outer peripheral end of the rotor core 15 so as to connect each of the plurality of magnet outer core extension portions 60a to each other in addition to the plurality of magnet outer core extension portions 60a. The outer peripheral core extension portion 60b is included. According to this configuration, the mechanical strength of the core extension portion can be increased by connecting the plurality of magnet outer core extension portions 60a in a ring shape. Further, also in the motor 10c of the third embodiment, the reverse magnetic field acting on the axial end portion of the magnet 16 can be reduced. FIG. 10 is a diagram showing the magnitude of the reverse magnetic field acting on the magnet of the conventional technique (motor 100 shown in FIG. 16) and the magnet 16 of the third embodiment calculated by simulation.

Next, the variable field motor 10d of the fourth embodiment will be described. FIG. 11 is a perspective view showing the configuration of the rotor 14d of the variable field motor 10d of the fourth embodiment. In the rotor 14d of the fourth embodiment, in addition to the plurality of magnet outer core extension portions 60a and the outer peripheral core extension portion 60b, the inner peripheral core which is a core extension portion provided in an annular shape around the shaft hole 52 of the rotor core 15 The extension portion 60c includes a connection core extension portion 60d which is a core extension portion provided at the salient pole 40 of the rotor core 15 so as to connect the outer peripheral core extension portion 60b and the inner peripheral core extension portion 60c. The connecting core extension portion 60d can also be said to be a beam connecting the outer peripheral core extension portion 60b and the inner peripheral core extension portion 60c. According to this structure, the mechanical strength of the core extension portion can be further increased as compared with the rotor 14c of the third embodiment. Further, also in the motor 10d of the fourth embodiment, the reverse magnetic field acting on the axial end portion of the magnet 16 can be reduced. FIG. 12 is a diagram showing the magnitude of the reverse magnetic field acting on the magnet of the conventional technique (motor 100 shown in FIG. 16) and the magnet 16 of the fourth embodiment calculated by simulation.

Next, the variable field motor 10e of the fifth embodiment will be described. FIG. 13 is a perspective view showing the configuration of the rotor 14e of the variable field motor 10e of the fifth embodiment. The rotor 14e of the fifth embodiment has a structure in which the connecting core extension portion 60d of the rotor 14d of the fourth embodiment is expanded over the entire salient pole. The core extension portion expanded over the entire salient pole is referred to as a salient pole core extension portion 60e. Here, the core extension portion is not provided inward in the radial direction of the magnet 16. In the rotor 14e of the fifth embodiment, the magnetic material in the axial direction of the salient pole is thickened by the salient pole core extension portion 60e, and the magnetic resistance of the salient pole is low. Further, since the core extension portion is not provided in the radial direction of the magnet 16, the magnetic material in the radial direction of the magnet 16 is thinned, and the magnetic resistance on the magnet side (magnet electrode) is high. .. Although it is stated here that the core extension portion is not provided in the radial direction of the magnet 16, the core extension portion may be slightly provided in the radial direction of the magnet 16, that is, the rotor core radial direction of the magnet 16. It suffices that the number of core extension portions is smaller in the rotor core radial direction of the magnet 16 than in the outer direction.

FIG. 13 shows a part of the field current magnetic flux AR4. For example, when trying to increase the motor torque, the field current magnetic flux AR4 is flowed inward in the radial direction as shown in FIG. At this time, the field current magnetic flux toward the magnet side (magnet pole), which is the direction of the magnetic pole opposite to the flow direction of the field current magnetic flux, is suppressed, and the salient pole is in the same magnetic pole direction as the flow direction of the field current magnetic flux. By increasing the field current magnetic flux toward, the motor torque (field current torque) caused by the field current magnetic flux can be increased. That is, the field current torque can be increased by increasing the magnetic resistance of the magnet pole and lowering the magnetic resistance of the salient pole (increasing the magnetic resistance difference between the magnet pole and the salient pole). Since the rotor 14e of the fifth embodiment has such a magnetic resistance difference as described above, the field current torque can be increased. FIG. 15 is a diagram showing a comparison result of torques of the motors of the first, fourth, and fifth embodiments calculated by simulation. FIG. 15 shows the ratio of the torques of the motors 10d and 10e of the fourth and fifth embodiments when the torque of the motor 10a of the first embodiment is 100%. As shown in this figure, the torque of the motor 10e of the fifth embodiment is larger than the torque of the motors 10a and 10d of the first and fourth embodiments.

Further, also in the motor 10e of the fifth embodiment, the reverse magnetic field acting on the axial end portion of the magnet 16 can be reduced. FIG. 14 is a diagram showing the magnitude of the reverse magnetic field acting on the magnet of the prior art (motor 100 shown in FIG. 16) and the magnet 16 of the fifth embodiment calculated by simulation. As shown in this figure, the reverse magnetic field acting on the magnet of the fifth embodiment is smaller than that of the prior art.

10a, 10b, 10c, 10d, 10e, 100 motors, 12 shafts, 14a, 14b, 14c, 14d, 14e, 114 rotors, 15,115 rotor cores, 16,116 magnets, 18 magnet holes, 20,120 stators, 21,1 121 stator core, 22 stator yoke, 24 teeth, 26 stator coil (3-phase coil), 30 field yoke, 32 outer wall part, 34 side wall part, 36 inner wall part, 38 field coil, 40 salient poles, 42 holes, 46a, 46b bridge, 50 bearing, 52 shaft hole, 60 core extension, 60a magnet outer core extension, 60b outer core extension, 60c inner core extension, 60d connection core extension, 60e salient core extension, AR1 , AR11 magnetizing direction, AR2, AR12 3-phase current magnetic flux and field current magnetic flux, AR3, AR13 reverse magnetic field, AR4 field current magnetic flux.

Claims (7)

A rotor core, a plurality of magnets arranged at intervals in the circumferential direction of the rotor core and magnetized in one direction in the radial direction of the rotor core to become magnetic poles, and magnetic fluxes formed on the rotor core and formed between the magnets. A rotor for a variable field motor that includes salient poles, is surrounded by a stator so as to face each other in the radial direction, and receives field magnetic flux from the stator.
The rotor core includes a rotor core axial end surface of the magnet and a core extension portion that projects axially outward from the axial end surface of the stator core of the stator when the rotor is assembled as a motor.
The core extension portion is provided outside the rotor core radial direction of the magnet.
Rotor. The rotor according to claim 1.
The core extension is provided over the entire axial end of the rotor core.
Rotor. The rotor according to claim 1.
The core extension portion provided outside the rotor core radial direction of the magnet is a magnet outer core extension portion.
The outer peripheral core extension portion which is the core extension portion provided at the outer peripheral end of the rotor core so as to connect each of the plurality of magnet outer core extension portions to each other is included.
Rotor. The rotor according to claim 3.
An inner peripheral core extension portion, which is the core extension portion provided in an annular shape around the shaft hole of the rotor core,
The outer peripheral core extension portion and the connection core extension portion, which is the core extension portion provided at the salient pole of the rotor core so as to connect the inner peripheral core extension portion, are included.
Rotor. The rotor according to claim 1.
The core extension portion is smaller in the rotor core radial direction of the magnet than in the rotor core radial direction outer direction of the magnet.
Rotor. The rotor according to claim 3.
The rotor core radial inner side of the magnet has fewer core extension portions than the rotor core radial outer side of the magnet, and the salient pole core extension portion which is the core extension portion provided at the salient pole of the rotor core and the salient pole core extension portion. The inner peripheral core extension portion, which is the core extension portion provided in an annular shape around the shaft hole of the rotor core, is included.
The outer peripheral core extension portion and the inner peripheral core extension portion are connected by the salient pole core extension portion.
Rotor. A variable field motor including the rotor according to any one of claims 1 to 6.

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