JP2009178000A - Surface magnet type motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface magnet type motor which effectively uses a reluctance torque, increases an output torque without enlarging the size, and allows miniaturization in the case of the same output torque. <P>SOLUTION: An even number of first permanent magnets 17 are provided on an outer peripheral face of a rotor core 15 at predetermined intervals in such a state as N poles and S poles of the adjacent permanent magnets become reverse. Second permanent magnets 18 of which magnetic force is stronger than that of the first permanent magnets 17 are provided in the rotor core 15, respectively, while a magnetic pole at a central side of the rotor core 15 is identical to a magnetic pole at a central side of the first permanent magnets 17 corresponding to each first permanent magnet 17, so that q-axis magnetic flux Fq may pass between the first permanent magnets 17 and the second permanent magnets 18. The second permanent magnets 18 are rare-earth magnets, and formed to be flat, and the first permanent magnets 17 are constituted by ferrite magnets. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface magnet type electric motor, and more particularly to a surface magnet type electric motor that can use reluctance torque in addition to magnet torque.

  As a permanent magnet type synchronous motor, as shown in FIG. 5, a stator (stator) 52 having a cylindrical shape and a plurality of slots 51 provided inside, and a plurality of (for example, 4) There is a surface magnet type electric motor provided with a rotor (rotor) 54 provided with a plurality of permanent magnets 53. Adjacent permanent magnets 53 are arranged such that the north and south poles are alternately on the rotor center side. In the permanent magnet type synchronous motor, a magnetic path from the stator 52 through the permanent magnet 53 with the rotor 54 to the stator 52 through the adjacent permanent magnet 53 is called a d-axis magnetic path. Further, a magnetic path from the stator 52 between adjacent permanent magnets 53 with the rotor 54 and via the rotor 54 to between the adjacent permanent magnets 53 and reaching the stator 52 is referred to as a q-axis magnetic path.

When the winding resistance is ignored, the torque T is expressed by the following equation in the d-axis-q-axis coordinate system.
T = Pn · {ψ · Iq + (Ld−Lq) · Id · Iq} (1)
However, Pn: Number of pole pairs, Id: d-axis current, Iq: q-axis current, Ld: d-axis inductance, Lq: q-axis inductance, ψ: Armature flux linkage of permanent magnet Reluctance torque. Since the d-axis current Id is negative, if the salient pole ratio: Lq / Ld can be increased, the utilization factor of the reluctance torque increases from the equation (1). However, reluctance torque is hardly utilized (utilized) in a general surface magnet type electric motor.

  In view of this, a surface magnet type synchronous motor has been proposed in which a reluctance torque can be utilized to eliminate the need for a magnetic pole position detection sensor, thereby improving maintainability and reducing costs (see Patent Document 1). ). As shown in FIG. 6A, the surface magnet type electric motor of Patent Document 1 has an N pole and an S pole on the surface of the rotor 62 disposed inside the stator 61 at an angular interval with respect to the center of the rotor 62. One or more pairs of first permanent magnets 63 as a pair are provided. Inside the rotor 62, a slit 64 is formed between each first permanent magnet 63 and the center of the rotor 62 so as to extend in the axial direction and intersect the radial direction. The permanent magnet 65 is inserted and arranged in the same direction as the magnetic pole of the first permanent magnet 63. Further, as shown in FIG. 6B, a plurality of slits 64 that are convex toward the center of the rotor 62 and straight slits 64 that intersect perpendicularly in the radial direction are formed. A configuration is also disclosed in which a second permanent magnet 65 is inserted into 64.

In these configurations, the slit 64 is formed between the first permanent magnet 63 that is a part of the d-axis magnetic path and the center of the rotor 62, and the second permanent magnet 65 is inserted into the slit 64. As a result, the magnetic resistance of the d-axis magnetic path is increased because an area having a low magnetic permeability exists in the magnetic path as compared with the case where the slit 64 and the second permanent magnet 65 are not provided. On the other hand, the magnetoresistance of the q-axis magnetic path is the same as before the second permanent magnet 65 is provided, and there is no change. As a result, the d-axis inductance Ld becomes smaller than the q-axis inductance Lq.
JP 2003-284273 A

In a surface magnet type motor, it is required to increase the output torque without increasing the size or to reduce the size with the same output torque.
In the surface magnet type electric motor, as in Patent Document 1, by adopting a configuration in which the second permanent magnet 65 is embedded in the rotor 62 corresponding to the first permanent magnet 63, the d-axis inductance Ld is changed to the q-axis inductance. It is possible to make it smaller than Lq. However, in the case of Patent Document 1, no consideration is given to the amount of the second permanent magnet 65 provided in the rotor 62 and the types of the first permanent magnet 63 and the second permanent magnet 65. In addition, no consideration is given to increasing the torque without increasing the size of the electric motor or reducing the size of the electric motor when the output torque is the same.

  The present invention has been made in view of the above-described conventional problems, and the object thereof is to effectively use the reluctance torque, increase the output torque without increasing the size, or reduce the size in the case of the same output torque. It is an object of the present invention to provide a surface magnet type electric motor that can be used.

  In order to achieve the above object, according to the first aspect of the present invention, an even number of first permanent magnets are arranged on the outer circumferential surface of the rotor core at predetermined intervals, and the N poles and S of the permanent magnets adjacent in the circumferential direction. Provided with the poles reversed, a second permanent magnet having a stronger magnetic force than the first permanent magnet is provided inside the rotor core, and a q-axis magnetic flux between the first permanent magnet and the second permanent magnet. The magnetic poles on the center side of the rotor core are provided so as to be the same as the magnetic poles on the center side of the first permanent magnet, corresponding to each first permanent magnet.

  In this invention, when a current flows through the coil of the stator (stator), the q-axis magnetic flux enters the rotor core from between the adjacent first permanent magnets provided on the rotor core from the stator, and the first permanent magnet and It will be in the state which passes along the path | route which leads to a stator through another adjacent 1st permanent magnet via the corresponding 2nd permanent magnet. In order to increase the output torque of the electric motor, it is necessary to make it easy for the q-axis magnetic flux to pass between the first permanent magnet and the second permanent magnet. If the distance between the first permanent magnet and the second permanent magnet increases, the q-axis magnetic flux easily passes between the first permanent magnet and the second permanent magnet. Further, when the distance is the same, the magnetic force of the second permanent magnet that is strong makes it easier for the magnetic flux from the stator toward the rotor core to enter the rotor core as a q-axis magnetic flux between adjacent first permanent magnets. If the second permanent magnet is composed of a ferrite magnet generally used for a surface magnet type electric motor, the second permanent magnet must be thicker than the radial thickness of the first permanent magnet. The magnetic force of the permanent magnet cannot be greater than the magnetic force of the first permanent magnet. However, when the thickness of the second permanent magnet in the radial direction is increased, the space between the second permanent magnet and the first permanent magnet is narrowed, and as a result, the effect that the q-axis magnetic flux easily passes is canceled out. However, in the present invention, since the second permanent magnet is composed of a magnet whose magnetic force is stronger than that of the first permanent magnet, the q-axis magnetic flux easily passes between the first permanent magnet and the second permanent magnet. Become. Therefore, the reluctance torque can be used effectively, and the output torque can be increased without increasing the size, or the size can be reduced when the output torque is the same.

  According to a second aspect of the present invention, in the first aspect of the present invention, the first permanent magnet and the second permanent magnet are arranged such that an opening angle of the second permanent magnet is larger than an opening angle of the first permanent magnet. The length of the second permanent magnet in the direction orthogonal to the rotor core radial direction is set. Therefore, in the present invention, the magnetic flux directed from the stator to the rotor core is guided into the rotor core as a q-axis magnetic flux from between the adjacent first permanent magnets, and is passed between the first permanent magnet and the second permanent magnet. It becomes easy to make it go to a stator from between the adjacent 1st permanent magnets.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the first permanent magnet is provided in a state of being accommodated in a groove provided in the rotor core. Therefore, in the present invention, the distance between the outer peripheral surface of the rotor core and the opposing surface of the stator between the adjacent permanent magnets is shorter than the configuration in which the entire permanent magnet is provided in a state of protruding from the outer peripheral surface of the rotor core. Become. As a result, when the size and arrangement of the first and second permanent magnets are the same, the magnetic flux from the stator toward the rotor core side enters the rotor core as a q-axis magnetic flux between adjacent first permanent magnets. It becomes easy.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the second permanent magnet is formed in a flat plate shape. In the present invention, the processing becomes easier as compared to forming the second permanent magnet into a curved shape or a bent shape. For example, a rare earth magnet used as a permanent magnet having a stronger magnetic force than a ferrite magnet has poor formability compared to a ferrite magnet, but there is no problem in processing if it is a flat plate.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the first permanent magnet is composed of a ferrite magnet. Since it is necessary to form at least one surface of the first permanent magnet into an arc surface, a magnet with good moldability is preferable. In this invention, since the 1st permanent magnet is comprised with the ferrite magnet, the conditions are satisfy | filled. In addition, since ferrite magnets are less expensive than rare earth magnets and other permanent magnets with strong magnetic force, the manufacturing cost of the rotor and thus the manufacturing cost of the electric motor can be reduced.

  According to the present invention, it is possible to provide a surface magnet type electric motor that can effectively use reluctance torque and can increase output torque without increasing the size or reduce the size in the case of the same output torque. .

  Hereinafter, an embodiment in which the present invention is embodied in a surface magnet type motor having four poles, that is, two pole pairs, will be described with reference to FIGS. FIG. 1 is a schematic diagram corresponding to a half of the entire rotor and stator.

  As shown to Fig.1 (a), the stator (stator) 11 of the electric motor 10 is cylindrical, and the some teeth 12 are provided in the inner side at equal intervals. A coil (winding) 13 is wound around the tooth 12. The winding method of the coil 13 may be distributed winding or concentrated winding.

  A rotor (rotor) 14 is disposed inside the stator 11. The rotor 14 includes a rotor core 15 in which a plurality of (for example, several tens) disk-shaped electromagnetic steel plates made of a high permeability material such as an electromagnetic steel plate are stacked, and a rotor shaft (rotary shaft) that is inserted through the center of the rotor core 15. 16. The electromagnetic steel plates are integrally fixed with an adhesive or the like as necessary. The rotor 14 is rotatably supported by a bearing of a housing (not shown) via a rotor shaft 16 with the outer peripheral surface of the rotor core 15 spaced apart from the teeth 12.

  On the outer peripheral surface of the rotor core 15, an even number (four in this embodiment) of arc-shaped first permanent magnets 17 whose cross-sectional shape is centered on the rotation center of the rotor core 15, a predetermined interval in the circumferential direction (this embodiment) Are provided at regular intervals. The first permanent magnet 17 is fixed to the surface of the rotor core 15 with an adhesive. The first permanent magnets 17 are provided in a state where the N poles and S poles of adjacent permanent magnets are alternately on the center side of the rotor core 15.

  Inside the rotor core 15, a second permanent magnet 18 having a stronger magnetic force than the first permanent magnet 17 is arranged so that the q-axis magnetic flux passes between the first permanent magnet 17 and the second permanent magnet 18. Corresponding to each of the first permanent magnets 17, the magnetic pole on the center side of the rotor core 15 is provided in the same state as the first permanent magnet 17. That is, the first permanent magnet 17 and the second permanent magnet 18 corresponding to each other in the radial direction of the rotor core 15 are arranged so that the opposite magnetic poles are different magnetic poles. The accommodating portion of the second permanent magnet 18 is constituted by a hole portion punched out when the electromagnetic steel sheet constituting the rotor core 15 is pressed into a predetermined shape.

  The second permanent magnet 18 is composed of a permanent magnet having a stronger magnetic force than the first permanent magnet. In this embodiment, the 1st permanent magnet 17 is comprised with the ferrite magnet, and the 2nd permanent magnet 18 is comprised with the rare earth magnet. As the rare earth magnet, for example, a neodymium-iron-boron magnet (Nd—Fe—B magnet) is used.

  The length of the first permanent magnet 17 and the second permanent magnet 18 in the direction perpendicular to the rotor core radial direction so that the opening angle θ2 of the second permanent magnet 18 is larger than the opening angle θ1 of the first permanent magnet 17. Is set. The opening angle means an angle formed by two straight lines connecting a position far from the center of the rotor core 15 and the center of the rotor core 15 at both ends of the permanent magnet in a direction orthogonal to the radial direction of the rotor core 15. In this embodiment, the 2nd permanent magnet 18 is formed in flat form, and is arrange | positioned in the state orthogonal to the radial direction of the rotor core 15 in the center of a flat plate.

Next, the operation of the electric motor 10 configured as described above will be described.
When the electric motor is driven in a loaded state, the coil 13 of the stator 11 is energized and a rotating magnetic field acts on the rotor 14. Then, the rotor 14 rotates by the action of the rotating magnetic field and the magnetic fluxes of the first and second permanent magnets 17 and 18. In the case of a normal surface magnet type motor in which the second permanent magnet 18 is not present, the reluctance torque is hardly utilized, and the output torque of the motor 10 is proportional to the product of the q-axis current and the armature linkage flux of the permanent magnet. To do. However, in the electric motor 10 of this embodiment, in addition to the first permanent magnet 17 provided on the surface of the rotor core 15, the second permanent magnet 18 is provided inside each first permanent magnet 17 in the rotor core 15. Therefore, the magnetic flux from the stator 11 toward the rotor core 15 side easily enters the rotor core 15 as a q-axis magnetic flux Fq from between the adjacent first permanent magnets 17. Then, as shown in FIG. 1B, the q-axis magnetic flux Fq that has entered the rotor core 15 is further adjacent to the first permanent magnet 17 via the corresponding second permanent magnet 18. It will be in the state which passes along the path | route which leads to the stator 11 through between the other 1st permanent magnets 17. FIG.

  One way to increase the reluctance torque is to make it easier for the q-axis magnetic flux Fq to pass between the first permanent magnet 17 and the second permanent magnet 18. For this purpose, the distance Lm between the surface of the first permanent magnet 17 facing the rotor core 15 and the surface of the second permanent magnet 18 on the surface side of the rotor core 15 may be increased. As a method of increasing the distance Lm, when the thickness of the second permanent magnet 18 is simply reduced, the magnetic force of the second permanent magnet 18 becomes weaker as much as the second permanent magnet 18 becomes thinner. In order for the magnetic flux from the stator 11 toward the rotor core 15 to enter the rotor core 15 from between the adjacent first permanent magnets 17, the magnetic force of the second permanent magnet 18 needs to be larger than the magnetic force of the first permanent magnet 17. There is.

  When the second permanent magnet 18 and the first permanent magnet 17 are made of the same magnet, the thickness of the second permanent magnet 18 needs to be thicker than that of the first permanent magnet 17. For example, when the first and second permanent magnets 17 and 18 are made of ferrite magnets, the distance Lm is reduced as shown in FIG. 2, and the q-axis magnetic flux Fq is difficult to pass. If the first and second permanent magnets 17 and 18 are made of rare earth magnets, the rare earth magnet has a maximum energy product representing the strength of the magnet about 10 times that of the ferrite magnet, so that as shown in FIG. The distance Lm can be increased by reducing the thickness of the first and second permanent magnets 17 and 18. If the output torque is the same, the entire motor 10 can be downsized. However, rare earth magnets have poor moldability, and yield tends to be poor when trying to produce arcuate surfaces. In contrast, if the first permanent magnet 17 is made of a ferrite magnet and the second permanent magnet 18 is made of a rare earth magnet, the distance Lm can be increased, and the yield of the second permanent magnet 18 is also increased. It does not decline.

  In order to increase the utilization rate of the reluctance torque, as shown in FIG. 3B, the opening angle θ1 is set so that the q-axis magnetic flux Fq can easily pass between the first permanent magnet 17 and the second permanent magnet 18. If the distance Lm is simply increased in a state larger than the opening angle θ2, the torque ripple, that is, the value of the fluctuation of the output torque of the electric motor 10 as a percentage with respect to the average torque increases. In order to suppress an increase in torque ripple, the distance Lm is set within a range in which the opening angle θ2 of the second permanent magnet 18 is set to be larger than the opening angle θ1 of the first permanent magnet 17 and no magnetic saturation occurs. It is preferable to make it smaller. For example, the opening angle θ1 of the first permanent magnet 17 is preferably an electrical angle of 110 ° to 130 °, and particularly preferably 120 °. The opening angle θ2 of the second permanent magnet 18 is preferably an electrical angle of 120 ° to 150 °, and particularly preferably 130 ° to 140 °.

According to this embodiment, the following effects can be obtained.
(1) The electric motor 10 is provided on the outer peripheral surface of the rotor core 15 with an even number of first permanent magnets 17 at predetermined intervals in a state where the N poles and S poles of adjacent permanent magnets are reversed in the circumferential direction. It has been. Inside the rotor core 15, a second permanent magnet 18 having a stronger magnetic force than the first permanent magnet 17 is arranged so that the q-axis magnetic flux Fq passes between the first permanent magnet 17 and the second permanent magnet 18. Corresponding to the first permanent magnets 17, the magnetic poles on the center side of the rotor core 15 are provided in the same state as the magnetic poles on the center side of the first permanent magnets 17. Therefore, the reluctance torque can be used effectively, and the output torque can be increased without increasing the size of the rotor core 15 and the stator 11, or the size can be reduced when the output torque is the same.

  (2) The first permanent magnet 17 and the second permanent magnet 18 are orthogonal to the rotor core radial direction so that the opening angle θ2 of the second permanent magnet 18 is larger than the opening angle θ1 of the first permanent magnet 17. The direction length is set. Therefore, the magnetic flux from the stator 11 toward the rotor core 15 is guided into the rotor core 15 as a q-axis magnetic flux Fq from between the adjacent first permanent magnets 17 and passes between the first permanent magnet 17 and the second permanent magnet 18. Thus, it becomes easy to move from the space between the other adjacent first permanent magnets 17 toward the stator 11.

  (3) The surface of the first permanent magnet 17 facing the rotor core 15 and the rotor core of the second permanent magnet 18 within a range in which the opening angle θ2 is set to be larger than the opening angle θ1 and not magnetically saturated. The distance Lm with the surface on the surface side of 15 is set as small as possible. Therefore, the reluctance torque can be used effectively, and an increase in torque ripple can be suppressed.

  (4) Since the second permanent magnet 18 is formed in a flat plate shape, the processing becomes easier as compared to forming the permanent magnet into a curved shape or a bent shape. In this embodiment, the second permanent magnet 18 is composed of a rare earth magnet having poor formability as compared with a ferrite magnet. However, since the shape of the second permanent magnet 18 is a flat plate, there is no problem in processing.

  (5) The first permanent magnet 17 is composed of a ferrite magnet. The first permanent magnet 17 is preferably a magnet with good formability because at least one side needs to be formed into an arc surface. However, a ferrite magnet has better formability than a rare earth magnet and can be formed without any problem in the arc shape or the like. be able to. Further, since the ferrite magnet is less expensive than rare earth magnets or other strong permanent magnets, the manufacturing cost of the rotor 14 and thus the manufacturing cost of the electric motor 10 can be reduced.

  (6) Since the second permanent magnet 18 is composed of a rare earth magnet, the thickness is as long as the magnetic force is the same as compared with the case where the second permanent magnet 18 is composed of an alnico magnet or a ferrite magnet. The (thickness in the radial direction of the rotor core 15) can be reduced, and Lm can be easily adjusted.

The embodiment is not limited to the above, and may be embodied as follows, for example.
The first permanent magnet 17 is not limited to a configuration that is provided so as to protrude entirely from the surface of the rotor core 15. For example, as shown in FIG. 4, the groove portion 19 is formed on the outer peripheral surface of the rotor core 15 in a state orthogonal to the circumferential direction, and the first permanent magnet 17 is accommodated in the groove portion 19 with only the surface exposed. Also good. In this case, the surface of the rotor core 15 between the adjacent first permanent magnets 17 can be compared with the configuration in which the entire first permanent magnet 17 is provided so as to protrude from the outer peripheral surface of the rotor core 15 as in the above embodiment. The distance from the opposing surface of the stator 11 is shortened. As a result, when the first and second permanent magnets 17 and 18 are compared in the same size and arrangement, the magnetic flux directed from the stator 11 toward the rotor core 15 side is between the adjacent first permanent magnets 17 and the q-axis magnetic flux. It becomes easier to enter into the rotor core 15.

The depth of the groove 19 is not limited to the depth at which only the surface of the first permanent magnet 17 is exposed, but may be the depth at which a part of the side surface of the first permanent magnet 17 is exposed.
○ As a configuration in which the first permanent magnet 17 is accommodated in the groove portion 19 provided on the outer periphery of the rotor core 15, a bar formed of a ferromagnetic material is provided on the surface of the rotor core 15 between the adjacent first permanent magnets 17. It may be fixed by welding or the like. Even in this configuration, as a result, the first permanent magnet 17 is accommodated in the groove portion 19 formed on the outer peripheral surface of the rotor core 15.

  The electric motor 10 has four first permanent magnets 17 and the number of teeth 12 is not limited to twelve. The number of first permanent magnets 17 may be an even number. For example, the number of the first permanent magnets 17 is 6 (6 poles) and the number of teeth 12 is 12, the number of the first permanent magnets 17 is 4 (4 poles) and the number of the teeth 12 is 6, The number of the permanent magnets 17 may be six and the number of the teeth 12 may be 18. The number of teeth 12 is not limited to an even number and may be an odd number.

○ The teeth 12 may not be equally spaced. Depending on how the coil 13 is wound and the control method, the rotor 14 rotates smoothly even if the teeth 12 are not equally spaced.
The second permanent magnet 18 has only to be provided so that the magnetic force is stronger than the first permanent magnet 17 and the q-axis magnetic flux passes between the first permanent magnet 17 and the second permanent magnet 18. . For example, the first permanent magnet 17 is not limited to a combination of a ferrite magnet and the second permanent magnet 18 is a combination of rare earth magnets, but the first permanent magnet 17 is a ferrite magnet and the second permanent magnet 18 is an alnico magnet. The one permanent magnet 17 may be an alnico magnet and the second permanent magnet 18 may be a rare earth magnet.

  The second permanent magnet 18 is not limited to a flat plate shape, and may have a V-shaped cross section or a circular arc shape. Further, the first permanent magnet 17 is not limited to an arc shape in cross section, and the surface facing the stator 11 may be an arc surface, and the opposite surface is not limited to an arc surface. For example, the second permanent magnet 18 If the surface of the rotor core 15 to be fixed is a plane, it is formed in a plane.

  The opening angle θ2 of the second permanent magnet 18 may not be larger than the opening angle θ1 of the first permanent magnet 17. Even if the opening angle θ2 is not larger than the opening angle θ1, it is possible to suppress an increase in torque ripple by adjusting the distance Lm and appropriately setting the magnitude of the magnetic force of the first and second permanent magnets 17 and 18. Is possible.

The stator 11 may be annular and the inner side may be substantially circular, and the outer shape does not need to be circular. The outer shape may be a polygonal shape such as a quadrangle in accordance with the cross-sectional shape of the housing.
The following technical idea (invention) can be understood from the embodiment.

  (1) In the invention according to claim 2, the distance between the surface of the first permanent magnet facing the rotor core and the surface of the second permanent magnet on the surface side of the rotor core is within a range where magnetic saturation does not occur. It is set as small as possible.

  (2) In the invention described in claims 1 to 5 and the technical idea (1), the second permanent magnet is formed of a rare earth magnet.

(A) is a schematic diagram which shows the half of the electric motor in one Embodiment, (b) is a schematic diagram which shows the state of q-axis magnetic flux. The schematic diagram at the time of producing the 1st and 2nd permanent magnet with a ferrite magnet. (A) is the schematic diagram at the time of producing similarly with a rare earth magnet, (b) is the schematic diagram at the time of shortening a 2nd permanent magnet. The schematic diagram which shows the half of the electric motor in another embodiment. The schematic diagram which shows a prior art. (A), (b) is a schematic diagram which shows another prior art.

Explanation of symbols

  θ1, θ2 ... opening angle, Fq ... q-axis magnetic flux, 15 ... rotor core, 17 ... first permanent magnet, 18 ... second permanent magnet, 19 ... groove.

Claims (5)

  An even number of first permanent magnets are provided on the outer peripheral surface of the rotor core at predetermined intervals in a state where the N poles and S poles of the permanent magnets adjacent in the circumferential direction are alternately located on the center side of the rotor core. In each of the first permanent magnets, a second permanent magnet having a stronger magnetic force than the first permanent magnet is provided so that the q-axis magnetic flux passes between the first permanent magnet and the second permanent magnet. A surface magnet type electric motor characterized in that the magnetic pole on the center side of the rotor core is provided in the same state as the first permanent magnet corresponding to the magnet.   The length of the first permanent magnet and the second permanent magnet in a direction perpendicular to the rotor core radial direction is such that the opening angle of the second permanent magnet is larger than the opening angle of the first permanent magnet. The surface magnet type electric motor according to claim 1 which is set.   The surface magnet type electric motor according to claim 1, wherein the first permanent magnet is provided in a state of being accommodated in a groove provided in the rotor core.   The surface magnet type electric motor according to any one of claims 1 to 3, wherein the second permanent magnet is formed in a flat plate shape.   The surface magnet type electric motor according to any one of claims 1 to 4, wherein the first permanent magnet is composed of a ferrite magnet.

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