motor

Abstract

A motor (100) includes a stator (10) and a rotor (20). The stator includes a plurality of first teeth (11b) arranged at an interval in a circumferential direction, and an armature winding (12) wound around each of the plurality of first teeth. The armature winding is a ring connection (13). A DC power supply (50) is connected to one end and another end of the ring connection. Magnetic poles of the same polarity are formed at each of the plurality of first teeth by DC current flowing through the armature winding. The rotor includes a rotor core (21) and a plurality of permanent magnets (22). The rotor core includes an outer diameter surface (21a) facing outward in a radial direction, and an inner diameter surface (21b) that is a surface opposite the outer diameter surface in the radial direction. The rotor core includes, on the outer diameter surface, a plurality of salient poles (21e) that create a first magnetic pole. The plurality of salient poles are arranged at an interval along the circumferential direction.

Description

motor

[0001] The present disclosure relates to a motor.

[0002] For example, Japanese Patent Application Laid-Open Publication No. 2012-110213 (Patent Document 1) describes a motor. The motor described in Patent Document 1 is a consequent pole motor. A consequent pole motor has a rotor in which first magnetic poles formed by permanent magnets and second magnetic poles formed by part of the rotor core are alternately arranged along the circumferential direction. The motor described in Patent Document 1 is advantageous from the perspectives of cost reduction and resource risk avoidance because it can halve the number of permanent magnets. However, the motor described in Patent Document 1 is disadvantageous when operating at a constant output because the field magnetic flux is kept almost constant due to the characteristics of the permanent magnets.

[0003] For example, Japanese Patent Laid-Open Publication No. 2007-252071 (Patent Document 2) describes a motor. The motor described in Patent Document 2 is also a consequent pole motor. In the motor described in Patent Document 2, the rotor has a field winding. As a result, unlike the motor described in Patent Document 1, the motor described in Patent Document 2 is able to appropriately adjust the amount of field magnetization depending on the operating point at which it is operated.

[0004] JP 2012-110213 A JP 2007-252071 A

[0005] However, the motor described in Patent Document 2 requires a field winding, which complicates the structure and reduces productivity. This disclosure has been made in consideration of the problems of the prior art described above. More specifically, this disclosure provides a motor that can expand its operable range by adjusting the field flux without using a field winding.

[0006] The motor disclosed herein includes a stator and a rotor. The stator has a plurality of first teeth spaced apart in the circumferential direction and an armature winding wound around each of the first teeth. The armature winding is connected in a ring-shaped configuration. A DC power supply is connected to one end and the other end of the ring-shaped configuration. A magnetic pole of the same polarity is formed on each of the first teeth by a DC current flowing through the armature winding. The rotor has a rotor core and a plurality of permanent magnets. The rotor core has an outer diameter surface facing outward in the radial direction and an inner diameter surface that is the opposite surface of the outer diameter surface in the radial direction. The rotor core has a plurality of salient poles on the outer diameter surface that form first magnetic poles. The salient poles are arranged at intervals along the circumferential direction. Each of the plurality of permanent magnets is attached to the outer diameter surface so as to be located between two adjacent salient poles in the circumferential direction, and forms a second magnetic pole. The plurality of salient poles and the plurality of permanent magnets face the stator in the radial direction with a gap therebetween.

[0007] According to the motor of the present disclosure, it is possible to expand the operable range by adjusting the field magnetic flux without using a field winding.

[0008] 1. A cross-sectional view of the motor 100. A cross-sectional view taken along line II-II in FIG. 1. A schematic circuit diagram of the motor 100. A cross-sectional view of the motor 100A. A schematic circuit diagram of the motor 100B. A cross-sectional view showing an example of the rotor 20 in the motor 100C. A cross-sectional view showing another example of the rotor 20 in the motor 100C. A cross-sectional view of the rotor 20 in the motor 100D. A perspective view of the rotor 20 in the motor 200.

[0009] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant descriptions will not be repeated.

[0010] First Embodiment A motor according to the first embodiment will be described. The motor according to the first embodiment is designated as motor 100.

[0011] (Configuration of Motor 100) The configuration of the motor 100 will be described below.

[0012] FIG. 1 is a cross-sectional view of a motor 100. FIG. 1 shows a cross-section of the motor 100 perpendicular to the axial direction. The case 40 is not shown in FIG. 1. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. As shown in FIGS. 1 and 2, the motor 100 has a stator 10, a rotor 20, a shaft 30, and a case 40. The axial direction is the direction of the central axis of the shaft 30, and the radial direction is a direction that passes through the central axis of the shaft 30 and is perpendicular to the axial direction. The circumferential direction is the direction of a circle centered on the central axis of the shaft 30.

[0013] The stator 10 has a stator core 11 and an armature winding 12. The stator core 11 is formed of a magnetic material. The stator core 11 has a core back 11a and a plurality of teeth 11b. The core back 11a is annular and extends circumferentially. The teeth 11b protrude radially inward from the inner diameter surface of the core back 11a. The plurality of teeth 11b are arranged at intervals in the circumferential direction. The teeth 11b forming the U-pole are referred to as teeth 11ba. The teeth 11b forming the V-pole are referred to as teeth 11bb. The teeth 11b forming the W-pole are referred to as teeth 11bc. In the example shown in FIGS. 1 and 2, the number of teeth 11b is six.

[0014] The number of teeth 11ba, the number of teeth 11bb, and the number of teeth 11bc are all equal. In the example shown in Figures 1 and 2, the number of teeth 11ba, the number of teeth 11bb, and the number of teeth 11bc are each 2. The teeth 11ba, the teeth 11bb, and the teeth 11bc are arranged in this order, for example, in a counterclockwise direction.

[0015] The armature winding 12 is made of a conductive material. The armature winding 12 is made of, for example, copper or a copper alloy. The armature winding 12 is wound around each of the multiple teeth 11b. The portion of the armature winding 12 wound around the tooth 11ba is referred to as winding portion 12a. The portion of the armature winding 12 wound around the tooth 11bb is referred to as winding portion 12b. The portion of the armature winding 12 wound around the tooth 11bc is referred to as winding portion 12c. The winding directions of the winding portions 12a, 12b, and 12c are all the same.

[0016] FIG. 3 is a schematic circuit diagram of the motor 100. As shown in FIG. 3, the winding portions 12a, 12b, and 12c form the ring connection 13. A DC power supply 50 is connected to one end and the other end of the ring connection 13. The DC power supply 50 causes a DC current to flow through the ring connection 13. The DC current flowing through the ring connection 13 can be adjusted by the DC power supply 50. As described above, the winding direction of the winding portion 12a, the winding direction of the winding portion 12b, and the winding direction of the winding portion 12c are all the same. Therefore, this DC current causes the teeth 11ba, 11bb, and 11bc to have magnetic poles of the same polarity.

[0017] A connection wire 14a is connected between the winding portion 12a and the winding portion 12b. A connection wire 14b is connected between the winding portion 12a and the winding portion 12c. A connection wire 14c is connected between the winding portion 12b and the DC power supply 50. A three-phase AC power supply (not shown) is electrically connected to the ring connection 13 by the connection wires 14a, 14b, and 14c.

[0018] As shown in FIGS. 1 and 2 , the rotor 20 has a rotor core 21 and a plurality of permanent magnets 22. The rotor core 21 is formed of a magnetic material. The rotor core 21 has an outer diameter surface 21a and an inner diameter surface 21b. The outer diameter surface 21a and the inner diameter surface 21b extend along the circumferential direction. The outer diameter surface 21a faces radially outward. The outer diameter surface 21a faces the stator 10 (teeth 11b) across a gap in the radial direction. The inner diameter surface 21b is the surface opposite the outer diameter surface 21a in the radial direction. In other words, the inner diameter surface 21b faces radially inward. A plurality of grooves 21c are formed in the outer diameter surface 21a. The plurality of grooves 21c are arranged at intervals along the circumferential direction. The outer diameter surface 21a is recessed radially inward at the grooves 21c.

[0019] The rotor core 21 has a plurality of salient poles 21d on its outer diameter surface 21a. The portions of the rotor core 21 between two adjacent grooves 21c form the salient poles 21d. Therefore, the plurality of salient poles 21d are arranged at intervals along the circumferential direction. In the example shown in FIGS. 1 and 2, there are two grooves 21c, and therefore there are two salient poles 21d. Permanent magnets 22 are attached to the outer diameter surface 21a. More specifically, the permanent magnets 22 are attached to the grooves 21c. Therefore, the permanent magnets 22 are located between two adjacent salient poles 21d in the circumferential direction. The permanent magnets 22 form a first magnetic pole. The permanent magnets 22 form a second magnetic pole. The first and second magnetic poles are alternately arranged in the circumferential direction. The first and second magnetic poles are, for example, south and north poles, respectively. The salient poles 21d and the permanent magnets 22 face the stator 10 (teeth 11b) across a gap in the radial direction.

[0020] The shaft 30 is made of a magnetic material. The shaft 30 extends along the axial direction. The shaft 30 is attached to the inner diameter surface 21b. The case 40 is made of a magnetic material. The case 40 covers the stator 10 and the rotor 20. The shaft 30 is supported by a rolling bearing 60 attached to the case 40 so as to be rotatable around the central axis of the shaft 30.

[0021] In Figure 3, magnetic flux is indicated by solid arrows. In the example of Figure 3, magnetic flux is generated from the teeth 11b toward the inside in the radial direction. The magnetic flux generated in the teeth 11b passes through the gap between the teeth 11b and the outer diameter surface 21a, interlinks with the rotor 20, and flows toward the shaft 30. This magnetic flux is divided into magnetic flux that flows toward one side in the axial direction of the shaft 30 and magnetic flux that flows toward the other side in the axial direction. The magnetic flux that has been divided into one side and the other side in the axial direction passes through the case 40 and the core back 11a and returns to the teeth 11b. Note that if the direction of the DC current flowing through the armature winding 12 is reversed, the magnetic flux will pass through the above-mentioned path in the opposite direction.

[0022] (Effects of the Motor 100) The effects of the motor 100 will be described below.

[0023] When magnetic flux directed radially outward is generated in the teeth 11b, the magnetic flux is directed in a direction that forms an S pole in the salient pole 21d. This strengthens the magnetic flux of the S pole of the salient pole 21d formed by the permanent magnet 22, and as a result, the magnetic flux density of the rotating magnetic field in the gap between the stator 10 and the outer diameter surface 21a increases. When the magnetic flux density of the rotating magnetic field in the gap between the stator 10 and the outer diameter surface 21a increases, the torque of the motor 100 increases.

[0024] On the other hand, when magnetic flux directed radially inward is generated in the teeth 11b, the magnetic flux is oriented in a direction that forms an N pole in the salient pole 21d. This weakens the magnetic flux of the S pole of the salient pole 21d formed by the permanent magnet 22, thereby reducing the magnetic flux density of the rotating magnetic field in the gap between the stator 10 and the outer diameter surface 21a. Increasing the magnetic flux density of the rotating magnetic field in the gap between the stator 10 and the outer diameter surface 21a can suppress voltage saturation during high-speed rotation, thereby expanding the constant-power operating range of the motor 100. Furthermore, increasing the magnetic flux density of the rotating magnetic field in the gap between the stator 10 and the outer diameter surface 21a can reduce iron loss during high-speed rotation and copper loss due to field-weakening current.

[0025] As described above, with motor 100, the magnetic flux density of the rotating magnetic field can be varied by controlling the DC current flowing through armature winding 12, making it possible to expand the operable range without using a field winding. Furthermore, since motor 100 does not require a field winding, the space factor of armature winding 12 can be improved and winding resistance can be reduced. Furthermore, with motor 100, the winding process can be simplified, making it possible to improve manufacturability.

[0026] Embodiment 2 A motor according to embodiment 2 will be described. The motor according to embodiment 2 is designated as motor 100A. Here, differences from motor 100 will be mainly described, and overlapping descriptions will not be repeated.

[0027] (Configuration of Motor 100A) The configuration of the motor 100A will be described below.

[0028] Fig. 4 is a cross-sectional view of the motor 100A. Fig. 4 shows a cross section of the motor 100A perpendicular to the axial direction. As shown in Fig. 4, the motor 100A has a stator 10, a rotor 20, a shaft 30, and a case 40 (not shown). In this respect, the configuration of the motor 100A is common to the configuration of the motor 100.

[0029] In the motor 100A, the stator core 11 has a plurality of teeth 11c. The teeth 11c protrude circumferentially inward from the inner diameter surface of the core back 11a. They are arranged between two adjacent teeth 11b. The armature windings 12 are not wound around the teeth 11c. From another perspective, the teeth on which the armature windings 12 are wound and the teeth on which the armature windings 12 are not wound are arranged alternately in the circumferential direction. In these respects, the configuration of the motor 100A differs from the configuration of the motor 100.

[0030] (Effects of Motor 100A) The effects of the motor 100A will be described below.

[0031] In the motor 100A, when a DC current flows through the armature winding 12, magnetic flux is generated in the teeth 11b. This magnetic flux passes through the gap between the stator 10 and the outer diameter surface 21a and interlinks with the rotor 20. This magnetic flux also passes through the gap between the stator 10 and the outer diameter surface 21a, interlinks with the teeth 11c, and returns to the teeth 11b through the core back 11a. In the example shown in FIG. 4, there are six teeth 11b and six teeth 11b. Therefore, in the motor 100A, a fixed magnetic field of 12 poles (six pole pairs) exists in the gap between the stator 10 and the outer diameter surface 21a.

[0032] Furthermore, the motor 100A has eight salient poles 21d and eight permanent magnets 22. Therefore, in the motor 100A, as the rotor 20 rotates, the six-pole pair fixed magnetic field formed by DC magnetic flux is flux-modulated by the eight salient poles 21d, and a four-pole (two-pole pair) rotating magnetic field is generated in the gap between the stator 10 and the outer diameter surface 21a. In the motor 100A, the rotating magnetic field in the gap between the stator 10 and the outer diameter surface 21a is synchronized with the rotating magnetic field caused by the three-phase AC current flowing through the armature winding 12, thereby generating torque.

[0033] In motor 100A, when a magnetic flux directed radially inward is generated in teeth 11 b due to a direct current flowing through armature winding 12, it is possible to increase torque resulting from the direct current magnetic flux in addition to torque due to permanent magnets 22. Furthermore, in motor 100A, when a magnetic flux directed radially outward is generated in teeth 11 b due to a direct current flowing through armature winding 12, it is possible to mitigate voltage saturation during high-speed rotation by suppressing back electromotive force.

[0034] In motor 100A, the armature magnetic flux of DC current circulates in a plane perpendicular to the axial direction without passing through shaft 30 or case 40. Therefore, motor 100A does not need to use shaft 30 or case 40 as a magnetic path, making it possible to reduce the weight and size of the motor.

[0035] Embodiment 3 A motor according to embodiment 3 will be described. The motor according to embodiment 3 is designated as motor 100B. Here, differences from motor 100 will be mainly described, and overlapping descriptions will not be repeated.

[0036] (Configuration of Motor 100B) The configuration of the motor 100B will be described below.

[0037] The motor 100B has a stator 10, a rotor 20, a shaft 30, and a case 40. In this respect, the configuration of the motor 100B is common to the configuration of the motor 100.

[0038] FIG. 5 is a schematic circuit diagram of the motor 100B. As shown in FIG. 5, the motor 100B further includes an inverter 70 and a DC bus 71. The inverter 70 is driven by the DC bus 71 and outputs three-phase AC current to the armature winding 12 (annular connection 13) via connection lines 14a, 14b, and 14c. The voltage of the DC bus 71 is defined as a first voltage. The voltage of the DC power supply 50 is defined as a second voltage. The first voltage is set to be larger than the second voltage. In these respects, the configuration of the motor 100B differs from the configuration of the motor 100.

[0039] (Effects of Motor 100B) The effects of motor 100B will be described below.

[0040] If the first voltage is equal to or lower than the second voltage, the inverter 70 is energized by the DC power supply 50 via a diode included in the inverter 70. As a result, in this case, it becomes impossible to supply three-phase AC current from the inverter 70 to the armature winding 12 (annular connection 13) via the connection lines 14a, 14b, and 14c. On the other hand, in the motor 100B, because the first voltage is greater than the second voltage, it is possible to prevent the inverter 70 from being energized by the DC power supply 50, and it is possible to supply three-phase AC current from the inverter 70 to the armature winding 12 (annular connection 13) via the connection lines 14a, 14b, and 14c.

[0041] Embodiment 4 A motor according to embodiment 4 will be described. The motor according to embodiment 4 is designated as motor 100C. Here, differences from motor 100 will be mainly described, and overlapping descriptions will not be repeated.

[0042] (Configuration of Motor 100C) The configuration of the motor 100C will be described below.

[0043] The motor 100C has a stator 10, a rotor 20, a shaft 30, and a case 40. In this respect, the configuration of the motor 100C is common to the configuration of the motor 100.

[0044] Fig. 6 is a cross-sectional view showing an example of the rotor 20 in the motor 100C. As shown in Fig. 6, a virtual line passing through one circumferential end of the salient pole 21d and the center of the rotor core 21 is designated as line L1, and a virtual line passing through the other circumferential end of the salient pole 21d and the center of the rotor core 21 is designated as line L2. A virtual line passing through one circumferential end of the permanent magnet 22 and the center of the rotor core 21 is designated as line L3, and a virtual line passing through the other circumferential end of the permanent magnet 22 and the center of the rotor core 21 is designated as line L4.

[0045] The angle between the lines L1 and L2 is defined as angle θ1, and the angle between the lines L3 and L4 is defined as angle θ2. In the motor 100C, the angle θ1 is equal to the angle θ2. FIG. 7 is a cross-sectional view showing another example of the rotor 20 in the motor 100C. As shown in FIG. 7, in the motor 100C, the angle θ1 may be different from the angle θ2. In the motor 100C, the angle θ1 may be greater than the angle θ2, or the angle θ1 may be smaller than the angle θ2. In these respects, the configuration of the motor 100C differs from the configuration of the motor 100.

[0046] (Effects of Motor 100C) The effects of the motor 100C will be described below.

[0047] In the motor 100C, the operating range can be adjusted by changing the ratio between the angles θ1 and θ2. For example, by making the angle θ1 larger than the angle θ2, the magnetic flux generated by the permanent magnet 22 can be suppressed, and by making the angle θ1 smaller than the angle θ2, the magnetic flux generated by the permanent magnet 22 can be increased. Furthermore, by changing the magnitude relationship between the angles θ1 and θ2, the magnitude of the modulated wave also changes. In this way, by changing the ratio between the angles θ1 and θ2, the magnetic flux generated by the permanent magnet 22 and the magnitude of the modulated wave change, and the operating range of the motor 100C is adjusted.

[0048] Fifth Embodiment A motor according to a fifth embodiment will be described. The motor according to the fifth embodiment is designated as motor 100D. Here, differences from motor 100 will be mainly described, and overlapping descriptions will not be repeated.

[0049] (Configuration of Motor 100D) The configuration of the motor 100D will be described below.

[0050] The motor 100D has a stator 10, a rotor 20, a shaft 30, and a case 40. In this respect, the configuration of the motor 100D is common to the configuration of the motor 100.

[0051] FIG. 8 is a cross-sectional view of the rotor 20 in the motor 100D. In FIG. 8, the tip positions of the teeth 11b in the radial direction are indicated by dotted lines. The minimum distance between the salient poles 21d and the stator 10 in the radial direction is defined as distance DIS1. The minimum distance between the permanent magnets 22 and the stator 10 in the radial direction is defined as distance DIS2. In the motor 100D, the distances DIS1 and DIS2 are different from each other. More specifically, in the motor 100D, the distance DIS1 may be greater than the distance DIS2, or the distance DIS1 may be smaller than the distance DIS2. Note that FIG. 8 shows an example in which the distance DIS1 is smaller than the distance DIS2. In these respects, the configuration of the motor 100D differs from the configuration of the motor 100.

[0052] (Effects of Motor 100D) The effects of the motor 100D will be described below.

[0053] In the motor 100D, for example, by making the distance DIS1 shorter than the distance DIS2, it is possible to reduce the amount of magnetic flux generated in the teeth 11b that interlinks with the permanent magnet 22, thereby reducing eddy current loss generated in the permanent magnet 22. In this case, it is also possible to improve the demagnetization resistance of the permanent magnet 22. Furthermore, in this case, it is possible to prevent damage to the permanent magnet 22 due to contact between the stator 10 and the permanent magnet 22 during assembly or operation. Note that if the second distance is approximately the same, there is almost no reduction in the magnetic flux due to the permanent magnet 22 and the field magnetic flux due to the field current.

[0054] Sixth Embodiment A motor according to a sixth embodiment will be described. The motor according to the fifth embodiment will be referred to as motor 200. Here, differences from motor 100A will be mainly described, and overlapping descriptions will not be repeated.

[0055] (Configuration of Motor 200) The configuration of the motor 200 will be described below.

[0056] Motor 200 has a stator 10, a rotor 20, a shaft 30, and a case 40. In motor 200, stator 10 has a stator core 11 including a core back 11a, a plurality of teeth 11b and a plurality of teeth 11c, and an armature winding 12 wound around each of the plurality of teeth 11b. In these respects, the configuration of motor 200 is common to the configuration of motor 100A.

[0057] FIG. 9 is a perspective view of the rotor 20 in the motor 200. As shown in FIG. 9, the rotor 20 in the motor 200 includes a first rotor unit 23 and a second rotor unit 24. The first rotor unit 23 and the second rotor unit 24 are aligned along the axial direction. The first rotor unit 23 is configured with a rotor core 23a. A plurality of salient poles 23b are formed on the outer diameter surface of the rotor core 23a at intervals along the circumferential direction. The second rotor unit 24 includes a rotor core 24a and a plurality of permanent magnets 24b. The plurality of permanent magnets 24b are attached to the outer peripheral surface of the rotor core 24a in a line along the circumferential direction. In these respects, the configuration of the motor 200 is common to the configuration of the motor 100A. Note that in this example, the rotor 20 is configured with two rotor units, but the rotor 20 may include three or more rotor units.

[0058] (Effects of Motor 200) The effects of motor 200 will be described below.

[0059] In motor 200, stator 10 has stator core 11 including core back 11a, multiple teeth 11b and multiple teeth 11c, and armature winding 12 wound around each of multiple teeth 11b, similar to motor 100A, and therefore torque can be generated in second rotor unit 24. In motor 200, torque generated in first rotor unit 23 can be adjusted by controlling the DC current flowing through armature winding 12 with DC power supply 50.

[0060] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The basic scope of the present disclosure is defined by the claims, not by the above-described embodiments, and it is intended to include all modifications within the meaning and scope of the claims.

[0061] 100, 100A, 100B, 100C, 100D, 200 motor, 10 stator, 11 stator core, 11a core back, 11b, 11ba, 11bb, 11bc, 11c teeth, 12 armature winding, 12a, 12b, 12c winding portion, 13 ring connection, 14a, 14b, 14c connecting wire, 20 rotor, 21 rotor core, 21a outer diameter surface, 21b inner diameter surface, 21c groove, 21d salient pole, 22 permanent magnet, 23 first rotor unit, 23a rotor core, 23b salient pole, 24 second rotor unit, 24a rotor core, 24b permanent magnet, 30 shaft, 40 case, 50 DC power supply, 60 rolling bearing, 70 Inverter, 71 DC bus, DIS1, DIS2 distance, L1, L2, L3, L4 straight line.

Claims

1. A magnetic stator comprising: a stator; and a rotor, wherein the stator has a plurality of first teeth arranged at intervals in the circumferential direction, and an armature winding wound around each of the plurality of first teeth, the armature winding being connected in an annular connection, and a DC power supply being connected to one end and the other end of the annular connection, and a magnetic pole of the same polarity is formed on each of the plurality of first teeth by a DC current flowing through the armature winding, the rotor has a rotor core and a plurality of permanent magnets, the rotor core has an outer diameter surface facing outward in the radial direction, and an inner diameter surface that is the opposite surface of the outer diameter surface in the radial direction, the rotor core has a plurality of salient poles on the outer diameter surface that form first magnetic poles, the plurality of salient poles are arranged at intervals along the circumferential direction, and each of the plurality of permanent magnets is attached to the outer diameter surface so as to be located between two adjacent ones of the plurality of salient poles in the circumferential direction, and forms a second magnetic pole, The motor, wherein the plurality of salient poles and the plurality of permanent magnets face the stator in the radial direction with a gap therebetween.

2. The motor according to claim 1, wherein the winding direction of the armature winding is the same for each of the plurality of first teeth.

3. The motor of claim 1, further comprising a shaft and a case, wherein the shaft and the case are formed of a magnetic material, the shaft is attached to the inner diameter surface, the case covers the stator and the rotor, and magnetic flux generated in each of the plurality of first teeth by a direct current flowing through the armature winding passes through the air gap, each of the plurality of salient poles, the shaft and the case, and returns to each of the plurality of first teeth.

4. The motor according to claim 1, wherein the stator further has a plurality of second teeth arranged at intervals in the circumferential direction, and each of the second teeth is arranged between two adjacent ones of the first teeth.

5. A motor according to any one of claims 1 to 4, wherein the minimum value of the distance between each of the plurality of permanent magnets and the stator is different from the minimum value of the distance between each of the plurality of salient poles and the stator.

6. The motor according to any one of claims 1 to 4, wherein each of the plurality of permanent magnets has a first end and a second end in the circumferential direction, each of the plurality of salient poles has a third end and a fourth end in the circumferential direction, and a first angle formed by a first imaginary line passing through the first end and the center of the rotor core and a second imaginary line passing through the second end and the center is different from a second angle formed by a third imaginary line passing through the third end and the center and a fourth imaginary line passing through the fourth end and the center.

7. The motor according to any one of claims 1 to 4, further comprising a power converter electrically connected to the armature winding, the power converter being driven by a DC bus, and the voltage of the DC bus being greater than the voltage of the DC power supply.

8. A motor comprising: a stator; and a rotor arranged radially with a gap between it and the stator, wherein the stator has a plurality of teeth arranged at intervals in the circumferential direction and an armature winding wound around each of the plurality of teeth, wherein the armature winding is connected in an annular manner, and a DC power source is connected to one end and the other end of the annular manner, and wherein magnetic poles of the same polarity are formed on each of the plurality of teeth by the DC current flowing through the armature winding, and the rotor has a first rotor unit and a second rotor unit, wherein the first rotor unit and the second rotor unit are aligned axially, and the field poles of the first rotor unit are composed only of salient poles, and the field poles of the second rotor unit are composed only of permanent magnets.