JP2014147151A - Permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet motor employing a permanent magnet having a high magnetic density and a high coersive force.SOLUTION: In a rotor core 160 forming a rotor of a permanent magnet motor, main magnetic pole parts and auxiliary magnetic pole parts are alternately disposed along a circumferential direction. In the main magnetic pole part, a magnet insertion hole 161 is formed into which a permanent magnet 170 is inserted. The permanent magnet 170 includes at least one communication hole 175. The permanent magnet 170 is formed by dispersing at least one of dysprosium and terbium to a rare earth magnet body containing neodymium after forming the communication hole 175 in the rare earth magnet body. The communication hole 175 is formed at a position where a region formed from a line drawn in a distance of 1.5 mm from an outer peripheral surface of the permanent magnet 170 to the inside of the permanent magnet 170 in a cross-sectional view crossing an extending direction of the communication hole 175 is covered with a region within a range of 1.5 mm from an inner peripheral surface of the communication hole 175 to an outer peripheral surface side of the permanent magnet 170.

Description

  The present invention relates to a permanent magnet motor.

  As a permanent magnet for a permanent magnet motor, a high-performance rare earth magnet having a high magnetic flux density is used. As the rare earth magnet, a neodymium magnet containing neodymium (Nd), for example, a [neodymium-iron-boron (Ne—Fe—B) magnet] is typically known. Such neodymium magnets are required to have an improved holding force because the holding force decreases as the ambient temperature increases. Conventionally, the technique currently disclosed by patent documents 1-4 is known as a technique which raises the retention strength of such a neodymium magnet. In the techniques disclosed in Patent Documents 1 to 4, dysprosium (Dy) and terbium (Tb) are diffused from the outer peripheral surface of the Ne—Fe—B magnet along the crystal-crystal interface (grain boundary). ing. Thereby, the holding power of a neodymium magnet can be improved with a small amount of dysprosium (Dy) or terbium (Tb).

JP 2008-263179 A JP 2009-289994 A International Publication No. WO2008 / 075710 International Publication WO 2007/088718

In the technique of diffusing Dy and Tb from the outer peripheral surface of the Ne—Fe—B magnet disclosed in Patent Documents 1 to 4, the diffusion effect is sharp when the distance from the outer peripheral surface (diffusion surface) of the magnet is 1.5 mm or more. To drop. For example, in the case of the rare earth magnet body 870 having a height H1 mm, a width W1 mm, and a thickness T1 mm shown in FIG. 15, when the thickness T1 exceeds 3 mm, the outer surface of the rare earth magnet body 870 is 1.5 mm or more. In the distant region, Dy and Tb are hardly diffused. For this reason, in the prior art, there is a limit to the size of a permanent magnet that can be manufactured.
Note that Patent Document 4 discloses a technique capable of diffusing Dy and Tb inside a rare earth magnet body even when it has a thickness of 3 mm or more. However, the technique disclosed in Patent Document 4 requires a process of diffusing metal from the outer peripheral surface of the rare earth magnet body.
The present invention has been made in view of such a point, and an object thereof is to provide a permanent magnet motor using a permanent magnet that has a high magnetic flux density and a high holding force and can be easily manufactured.

The present invention includes a stator and a rotor, and the rotor has a main magnetic pole portion and an auxiliary magnetic pole portion alternately arranged along the circumferential direction when viewed in a cross section perpendicular to the axial direction. The present invention relates to a permanent magnet motor in which a magnet insertion hole extending along a direction intersecting the d axis is formed, and a permanent magnet is inserted into the magnet insertion hole. As the permanent magnet, a permanent magnet formed by diffusing at least one of dysprosium (Dy) and terbium (Tb) in a rare earth magnet body containing neodymium (Nd) is used. As the rare earth magnet body containing neodymium, a neodymium magnet containing at least neodymium, typically a Ne—Fe—B magnet is used.
According to one aspect of the present invention, the permanent magnet has at least one communication hole that extends in a direction intersecting with the direction in which the magnet insertion hole extends and is open at both ends when viewed in a cross section perpendicular to the axial direction. doing.
The communication hole is formed at a position where the length between the outer peripheral surfaces of the permanent magnets is 3 mm or more along a line passing through the center of the communication hole when viewed in a cross section perpendicular to the direction in which the communication hole extends. ing. The “center of the communication hole” corresponds to, for example, the center point of the cross-sectional shape perpendicular to the direction in which the communication hole extends.
In the present invention, it is possible to configure a permanent magnet motor using a permanent magnet that can increase the diffusion region of Dy or Tb only by forming a communication hole in the rare earth magnet body.

The outer peripheral surface of the permanent magnet is formed by a plurality of partial outer peripheral surfaces when viewed in a cross section perpendicular to the direction in which the communication hole extends. The outer peripheral surface formed by the plurality of partial outer peripheral surfaces is typically a polygonal outer peripheral surface formed by a linear partial outer peripheral surface.
In this case, the following forms can be taken.
In one embodiment, the at least one communication hole has an area within a range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet when viewed in a cross section perpendicular to the direction in which the communication hole extends. (Referred to as “inner peripheral surface diffusion region of communication hole”) is a region within the range of 1.5 mm from the outer peripheral surface of at least one of the partial outer peripheral surfaces to the inner side of the permanent magnet (the outer periphery of the partial outer peripheral surface A communication hole formed at a position at least partially overlapping with the “surface diffusion region”) is included.
In this embodiment, it is possible to configure a permanent magnet motor using a permanent magnet in which an outer peripheral surface diffusion region of at least one partial outer peripheral surface is made continuous with an inner peripheral surface diffusion region of at least one communication hole.
In a different form, the at least one communication hole includes a plurality of communication holes formed at positions where the inner peripheral surface diffusion region of the communication hole overlaps at least partially with the outer peripheral surface diffusion region of the at least one partial outer peripheral surface. It is.
In this embodiment, it is possible to configure a permanent magnet motor using a permanent magnet in which the outer peripheral surface diffusion region of at least one partial outer peripheral surface is made continuous with the inner peripheral surface diffusion region of each of the plurality of communication holes.
In another different form, at least one of the plurality of communication holes formed at a position where the inner peripheral surface diffusion region of the communication hole overlaps at least partially with the outer peripheral surface diffusion region of at least one partial outer peripheral surface is The inner peripheral surface diffusion region of the at least one communication hole is formed at a position at least partially overlapping with the outer peripheral surface diffusion region of another partial outer peripheral surface adjacent to at least one partial outer peripheral surface.
In this embodiment, the outer peripheral surface diffusion region of at least one partial outer peripheral surface is continued to the inner peripheral surface diffusion region of at least one communication hole, and the outer peripheral surface of another partial inner peripheral surface adjacent to at least one partial outer peripheral surface A permanent magnet motor using a permanent magnet in which the diffusion region is made continuous with the inner peripheral surface diffusion region of at least one other communication hole can be configured.
In another different form, the plurality of communication holes formed at positions where the inner peripheral surface diffusion region of the communication hole overlaps at least partially with the outer peripheral surface diffusion region of at least one partial outer peripheral surface, The shortest distance among the distances between the peripheral surface and at least one partial outer peripheral surface is the same.
In this embodiment, a permanent magnet motor using a permanent magnet that can efficiently arrange a plurality of communication holes having an inner peripheral surface diffusion region continuous with an outer peripheral surface diffusion region of at least one partial outer peripheral surface is configured. be able to.
In another different form, the plurality of communication holes formed at positions where the inner peripheral surface diffusion region of the communication hole overlaps with the outer peripheral surface diffusion region of at least one partial outer peripheral surface is at least one partial outer periphery The inner peripheral surface diffusion region of each of the communication holes adjacent in the direction in which the surface extends is formed at a position where at least a part thereof overlaps.
In this embodiment, the outer peripheral surface diffusion region of at least one partial outer peripheral surface is continued to the inner peripheral surface diffusion region of the plurality of communication holes, and the inner peripheral surface is adjacent along the direction in which at least one partial outer peripheral surface extends. A permanent magnet motor using a permanent magnet with continuous diffusion regions can be configured.

In another invention, the permanent magnet has at least one communication hole that extends along the axial direction and is open at both ends.
The communication hole is formed at a position where the length between the outer peripheral surfaces of the permanent magnets is 3 mm or more along a line passing through the center of the communication hole when viewed in a cross section perpendicular to the direction in which the communication hole extends. ing. The “center of the communication hole” corresponds to, for example, the center point of the cross-sectional shape perpendicular to the direction in which the communication hole extends.
The outer peripheral surface of the permanent magnet may be formed by a plurality of partial outer peripheral surfaces as viewed in a cross section perpendicular to the direction in which the communication hole extends, or may be formed in a curved shape such as a circle.
In the present invention, it is possible to configure a permanent magnet motor using a permanent magnet that can increase the diffusion region of Dy or Tb only by forming a communication hole in the rare earth magnet body.
The present invention can take the following forms.
In one embodiment, the at least one communication hole has an area within a range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet when viewed in a cross section perpendicular to the direction in which the communication hole extends. ("Inner peripheral surface diffusion region of the communication hole") is at least a part of a region within a range of 1.5 mm from the outer peripheral surface of the permanent magnet to the inside of the permanent magnet (referred to as "permanent magnet outer surface diffusion region"). The communication hole formed in the overlapping position is included.
In this embodiment, a permanent magnet motor using a permanent magnet in which the outer peripheral surface diffusion region of the permanent magnet is made continuous with the inner peripheral surface diffusion region of at least one communication hole can be configured.
In a different form, the at least one communication hole includes a plurality of communication holes formed so that the inner peripheral surface diffusion region of the communication hole overlaps with the outer peripheral surface diffusion region of the permanent magnet at least partially.
In this embodiment, it is possible to configure a permanent magnet motor using a permanent magnet in which the outer peripheral surface diffusion region of the permanent magnet is made continuous with the inner peripheral surface diffusion region of each of the plurality of communication holes.
In another different form, the plurality of communication holes formed at positions where the inner peripheral surface diffusion region of the communication hole overlaps at least partly with the outer peripheral surface diffusion region of the permanent magnet are formed on the inner peripheral surface of each communication hole. It is formed at a position where the shortest distance among the distances from the outer peripheral surface of the magnet becomes equal.
In this embodiment, it is possible to configure a permanent magnet motor using a permanent magnet that can efficiently arrange a plurality of communication holes having an inner peripheral surface diffusion region continuous with an outer peripheral surface diffusion region of the permanent magnet.
In another different form, the outer peripheral surface of the permanent magnet extends in the plurality of communication holes formed at positions where the inner peripheral surface diffusion region of the communication hole overlaps at least partially with the outer peripheral surface diffusion region of the permanent magnet. The inner peripheral surface diffusion region of each communication hole adjacent in the direction is formed at a position where at least a part thereof overlaps.
In this embodiment, the outer peripheral surface diffusion region of the permanent magnet is made continuous with the inner peripheral surface diffusion region of the plurality of communication holes, and the adjacent inner peripheral surface diffusion region is made continuous along the direction in which the outer peripheral surface of the permanent magnet extends. A permanent magnet motor using a permanent magnet can be configured.

In still another different form, each communication hole has the same outer peripheral surface and the same cross-sectional area as viewed in a cross section perpendicular to the direction in which the communication hole extends.
In this embodiment, it is possible to form a permanent magnet motor using a permanent magnet that can easily form the communication hole and that can easily set the formation position of the communication hole.
In still another different form, each communication hole is located at a position where the first line extending along the first direction and the second line extending along the second direction orthogonal to the first direction intersect. Is formed. Alternatively, each communication hole is a position where the first line extending along the first direction and the second line extending along the second direction orthogonal to the first direction intersect each other. And alternate positions along the second direction and the second direction.
The second direction is preferably set to a direction orthogonal to the first direction. The interval between the first lines and the interval between the second lines is set according to the cross-sectional shape and cross-sectional area of the permanent magnet, the cross-sectional shape and cross-sectional area of the inner peripheral surface of the communication hole, and the like. Preferably, the interval between the first lines and the interval between the second lines are set equal.
In this embodiment, it is possible to configure a permanent magnet motor using a permanent magnet that can easily set the formation position of the communication hole.
In still another different embodiment, each communication hole has a region formed by a line drawn at a distance of 1.5 mm inward from the outer peripheral surface of the permanent magnet (referred to as “outer peripheral surface diffusion region boundary line”). It is formed at a position covered by the inner peripheral surface diffusion region of the inner peripheral surface of the communication hole.
In this embodiment, it is possible to configure a permanent magnet motor using a permanent magnet in which at least one of Dy and Tb is diffused in the entire area of the permanent magnet when viewed in a cross section perpendicular to the direction in which the communication hole extends.

  According to the present invention, it is possible to provide a permanent magnet motor using a permanent magnet that can easily increase the diffusion region of dysprosium or terbium into a rare earth magnet body only by forming a communication hole in the rare earth magnet body.

It is a figure which shows schematic structure of the permanent magnet electric motor of 1st Embodiment. It is sectional drawing of the rotor of the permanent magnet electric motor of 1st Embodiment. It is a figure explaining one embodiment of a permanent magnet manufacturing method. It is a figure explaining one embodiment of a permanent magnet manufacturing method. It is a figure explaining one embodiment of a permanent magnet manufacturing method. It is a perspective view of the permanent magnet of a 1st embodiment. It is the figure seen from the arrow VII direction of FIG. It is a figure which shows the permanent magnet of 2nd Embodiment. It is a figure which shows the example by which the communicating hole is formed in the position where the inner peripheral surface spreading | diffusion area | region of a communicating hole overlaps with the area | region enclosed by the outer peripheral surface spreading | diffusion area | region boundary line of a permanent magnet at least partially. It is sectional drawing of the rotor of the permanent magnet electric motor of 2nd Embodiment. It is sectional drawing of the rotor of the permanent magnet electric motor of 3rd Embodiment. It is a figure which shows the permanent magnet of 3rd Embodiment. It is a figure which shows the permanent magnet of 4th Embodiment. It is a figure which shows the relationship between the depth from a diffusion surface, and a diffusion effect. It is a figure which shows the conventional permanent magnet.

Embodiments of the present invention will be described below with reference to the drawings.
In this specification, the “axial direction” refers to the direction of the rotation center line passing through the center point (rotation center point) O of the rotor in a state where the rotor is rotatably supported with respect to the stator. Show. The “circumferential direction” refers to the center point O of the rotor as viewed in a cross section perpendicular to the axial direction (direction of the rotation center line) in a state where the rotor is rotatably supported with respect to the stator. Indicates the circumferential direction. The “radial direction” refers to a center point O of the rotor as viewed in a cross section perpendicular to the axial direction (direction of the rotation center line) in a state where the rotor is rotatably supported with respect to the stator. Indicates direction.
In addition, the “d-axis” is the center along the circumferential direction of the main magnetic pole portion (for example, along the circumferential direction of the portion corresponding to the main magnetic pole portion of the outer peripheral surface of the rotor) when viewed in a cross section perpendicular to the axial direction. Center line) and the center point O of the rotor, and the “q-axis” is the center along the circumferential direction of the auxiliary magnetic pole part between the main magnetic pole parts (for example, of the outer peripheral surface of the rotor) The center point along the circumferential direction of the portion corresponding to the outer peripheral surface of the auxiliary magnetic pole portion) and the center point O of the rotor are represented by a line.

A first embodiment 100 of a permanent magnet motor using the permanent magnet of the present invention is shown in FIGS.
The permanent magnet electric motor 100 according to the first embodiment includes a stator 110 and a rotor 150 that is rotatably supported with respect to the stator 110.
The stator 110 includes a stator core 120 formed by laminating electromagnetic steel plates and a stator winding 130. The stator core 120 includes a yoke extending along the circumferential direction when viewed in a cross section perpendicular to the axial direction, and a plurality of teeth extending from the yoke along the radial direction toward the center point of the rotor 150; It has a slot formed by teeth adjacent in the circumferential direction. The stator winding 130 is inserted into the slot.

The rotor 150 includes a rotor core 160 formed by laminating electromagnetic steel plates, a permanent magnet 170, and a rotating shaft 180.
In the rotor core 160, the main magnetic pole portions and the auxiliary magnetic pole portions are alternately arranged along the circumferential direction when viewed in a cross section perpendicular to the axial direction. A magnet insertion hole 161 extending in the axial direction is formed in the main magnetic pole portion, and the permanent magnet 170 is inserted into the magnet insertion hole 161.
In the present embodiment, when viewed in a cross section perpendicular to the axial direction, the magnet insertion hole 161 is formed in a straight line along a direction intersecting (orthogonal to) the d axis of the main magnetic pole portion. A plate-like permanent magnet 170 having a quadrangular cross section perpendicular to the axial direction is inserted into the magnet insertion hole 161. The permanent magnet 170 is magnetized so that adjacent main magnetic pole portions have different polarities. For example, as shown in FIG. 2, a permanent magnet 170 magnetized with an N pole on the outer peripheral side and an S pole on the center side and a permanent magnet 170 magnetized with an S pole on the outer peripheral side and an N pole on the center side are adjacent to each other. The magnetic pole portions are alternately inserted into the magnet insertion holes.
The permanent magnet 170 is formed with a communication hole 175 that is open at both ends. In the present embodiment, as shown in FIG. 2, the communication hole 175 is orthogonal to the direction in which the permanent magnet 170 extends (the direction in which the magnet insertion hole 161 extends) when viewed in a cross section perpendicular to the axial direction. It is formed along a direction (including a “substantially orthogonal direction”). The communication hole 175 will be described later.
A rotation shaft 180 is inserted into a rotation shaft insertion hole 162 formed on the center side of the rotor core 160.

In the present embodiment, as the permanent magnet 170, [neodymium-iron-boron (Nd-Fe-B) magnet body], which is a rare earth magnet body containing high-performance neodymium (Nd) with high magnetic flux density, has a holding power. A permanent magnet formed by diffusing at least one of dysprosium (Dy) and terbium (Tb) for preventing the decrease is used.
Here, FIG. 14 shows the relationship between the depth from the diffusion surface and the diffusion effect when Dy or Tb is diffused from the outer peripheral surface of the [Ne—Fe—B magnet body]. In FIG. 14, the horizontal axis indicates the distance from the outer peripheral surface (diffusion surface) of [Ne-Fe-B magnet body], and the vertical axis indicates the diffusion effect of Dy and Tb.
From FIG. 14, it can be understood that the diffusion effect is high up to a distance of 1.5 mm from the diffusion surface, but the diffusion effect sharply decreases when the distance from the diffusion surface exceeds 1.5 mm.
From this, for example, when Nd and Tb are diffused from the outer peripheral surface of the [Ne-Fe-B magnet body] 870 having the shape shown in FIG. 15, the magnet body 870 starts from the outer peripheral surface of the magnet body 870. It can be seen that Dy and Tb are not sufficiently diffused in a region formed by a line drawn at a distance of 1.5 mm on the inside. That is, in order to increase the holding power of the [Ne-Fe-B magnet body], Nd and Tb in a region formed by a line drawn at a distance of 1.5 mm from the outer peripheral surface of the magnet body to the inside of the magnet body. It is necessary to increase the diffusion effect.
The present inventors are a method for solving the problem of enhancing the diffusion effect of Nd and Tb in a region formed by a line drawn at a distance of 1.5 mm from the outer peripheral surface of the magnet body to the inside of the magnet body. Various studies were made. As a result, it has been found that this problem can be easily solved by forming a communication hole in the magnet body and using not only the outer peripheral surface of the magnet body but also the inner peripheral surface of the communication hole as the diffusion surface.

Below, the manufacturing method of the permanent magnet 170 used with the permanent magnet electric motor 100 of this Embodiment is demonstrated with reference to FIGS. In the following, for convenience, the x direction is set as the height direction, the y direction as the width direction, and the z direction as the thickness direction. Further, since the method of diffusing Dy or Tb is the same, the case of diffusing Dy will be described.
First, a rectangular parallelepiped [Ne-Fe-B magnet body] 10 having a height H1, a width W1, and a thickness T shown in FIG. 3 is manufactured. As a method for producing [Ne—Fe—B magnet body] (hereinafter simply referred to as “magnet body”), various known methods disclosed in Patent Documents 1 to 4 and the like can be used. For example, it is possible to use a method in which powdery raw materials are mixed, compression-molded into a predetermined shape, and then sintered. In FIG. 3, the magnet body 10 is magnetized so that both end faces along the thickness direction (z direction) are N poles or S poles.
The shape and magnetization direction of the magnet body 10 are appropriately set according to the shape of the permanent magnet 170 to be manufactured.
This step corresponds to the “first step (magnet body manufacturing step)” of the permanent magnet manufacturing method of the present invention.

Next, as shown in FIG. 4, a communication hole 20 having both ends opened is formed in the magnet body 10. In FIG. 4, a plurality of linear communication holes 20 parallel to the width direction (z direction) are formed. Further, when viewed in a cross section (xy plane) perpendicular to the width direction (z direction), the communication hole 20 has a circular cross section. In addition, the formation location, the number, the cross-sectional shape, and the like of the communication hole 20 are appropriately selected according to the outer peripheral shape of the permanent magnet 170 to be manufactured.
This step corresponds to the “second step (communication hole forming step)” of the permanent magnet manufacturing method of the present invention.

Next, Dy is diffused in the magnet body 10 in which the communication holes 20 are formed. As a method of diffusing Dy in the magnet body 10, various known methods disclosed in Patent Documents 1 to 4 and the like can be used. For example, a method of diffusing Dy along the crystal grain boundary of the raw material by attaching Dy to the outer peripheral surface of the magnet body 10 and the inner peripheral surface of the communication hole can be used.
This step corresponds to the “third step (diffusion step)” of the method for manufacturing a permanent magnet of the present invention.

Next, as shown in FIG. 5, the magnet body 10 is cut to obtain a permanent magnet 170. In FIG. 5, it is cut along a cutting line 30 extending in a direction (a direction along the xy plane) orthogonal to the direction (z direction) in which the communication hole 20 extends. Thus, a rectangular parallelepiped plate-like permanent magnet 170 having a height H1, a width W1, and a thickness T1 is manufactured. In addition, the cutting line 30 should just be a direction which cross | intersects the direction (z direction) where the communicating hole 20 is extended.
This step corresponds to the “fourth step (cutting step)” of the method for manufacturing a permanent magnet of the present invention.
Depending on the application of the permanent magnet, the magnet body 10 in which Dy is diffused can be used without cutting. In this case, the fourth step is omitted.
In addition, the permanent magnet 170 after the fifth step (polishing step) for polishing the outer shape of the magnet body 10 to a predetermined shape before the second step for forming the communication hole 20 or after the fourth step for cutting the magnet body 10 is performed. The 6th process (polishing process) which grind | polishes the external shape of this to a predetermined shape can also be provided.

A permanent magnet 170 of the present embodiment is shown in FIGS. FIG. 6 is a perspective view of the permanent magnet 170, and FIG. 7 is a view as seen from the direction of arrow VII (z direction) in FIG. 6 and 7, the direction in the x to z direction is different from the direction in the x to z direction in FIGS. 3 to 5.
The permanent magnet 170 of the present embodiment is formed in a plate-shaped rectangular parallelepiped having a height H, a width W, and a thickness T. Also, the outer peripheral surfaces on both sides in the thickness direction (z direction) shown in FIG. 7 have a quadrangle formed by partial outer peripheral surfaces 171a, 171b, 171c, and 171d. The communication hole 175 is formed along the thickness direction (z direction). Note that the rectangular parallelepiped (rectangle) does not have to be strictly a rectangular parallelepiped (rectangle), and chamfering or the like may be formed at the corners.
The partial outer peripheral surfaces 171a to 171d correspond to “partial outer peripheral surfaces” of the permanent magnet of the present invention. Further, the “peripheral surfaces perpendicular to the direction in which the communication holes extend” of the permanent magnet of the present invention are formed by the partial outer peripheral surfaces 171a to 171d.
In a state where the permanent magnet 170 is inserted into the magnet insertion hole 161, the height direction (x direction) is arranged along the axial direction (vertical direction in FIG. 1, front and rear direction in FIG. 2), and the width direction (y direction). ) Is arranged along the direction in which the magnet insertion hole 161 extends (direction perpendicular to the d-axis), and the thickness direction (z-direction) is arranged along the d-axis.

When Dy is diffused in the magnet body, as described above, the region having a high Dy diffusion effect is within a range of 1.5 mm from the diffusion surface (hereinafter, simply referred to as “diffusion region”). Therefore, in the permanent magnet 170 formed by diffusing Dy in the magnet body 10 in which the communication hole 175 is formed, the permanent magnet 170 is within a range of 1.5 mm from the partial outer peripheral surfaces 171a to 171d to the inside of the permanent magnet 170. 173 (hereinafter referred to as “permanent magnet outer peripheral surface diffusion region”) 173 and a region within a range of 1.5 mm from the inner peripheral surface of each of the communication holes 175a to 175f to the outer peripheral surface side of the permanent magnet 170 (hereinafter, 177a to 177f (referred to as “inner peripheral surface diffusion regions of communication holes”) are regions having high Dy diffusion effects (“diffusion regions”). The outer peripheral surface diffusion region 173 of the permanent magnet 170 includes partial outer peripheral surfaces 171a to 171d of the permanent magnet 170, and lines drawn from the partial outer peripheral surfaces 171a to 171d to a position 1.5 mm away from the inner surface of the permanent magnet 170 (hereinafter referred to as the permanent magnet 170). , Referred to as “peripheral surface diffusion region boundary line”) 172a to 172d. Further, the inner peripheral surface diffusion regions of the communication holes 175a to 175f are 1.5 mm away from the inner peripheral surface of the communication holes 175a to 175f and the inner peripheral surface of the communication holes 175a to 175f to the outer peripheral surface side of the permanent magnet 170, respectively. It is a region surrounded by lines 176a to 176f (hereinafter referred to as “inner peripheral surface diffusion region boundary lines”) drawn at positions.
In the present embodiment, the region where the Dy diffusion effect from the partial outer peripheral surfaces 171a to 171d of the permanent magnet 170 is low, that is, the region surrounded by the outer peripheral surface diffusion region boundary lines 172a to 172d is the respective communication holes 175a to 175f. Communication holes 175a to 175f are formed at positions covered by the inner peripheral surface diffusion regions 177a to 177f. Accordingly, since Dy is diffused over the entire surface of the permanent magnet 170 when viewed in a cross section perpendicular to the direction in which the communication holes 175a to 175f extend, the holding force can be effectively increased.

Further, in the permanent magnet 170 of the first embodiment shown in FIG. 7, the communication holes 175a to 175f have lines 181 and 182 extending in parallel along the height direction (x direction), and a height Lines 191 to 193 extending in parallel along the width direction (y direction) orthogonal to the vertical direction (x direction) are formed at positions where they intersect. One of the lines 181 and 182 extending along the height direction (x direction) and the lines 191 to 193 extending along the width direction (y direction) is the “first” of the permanent magnet of the present invention. The other corresponds to the “first line extending along the direction”, and the other corresponds to the “second line extending along the second direction orthogonal to the first direction”.
The interval between the lines 181 and 182 extending along the height direction (x direction) and the interval between the lines 191 to 193 extending along the width direction (y direction) are the sectional shape and sectional area of the permanent magnet 170, It is set according to the cross-sectional shape and cross-sectional area of the inner peripheral surface of the communication holes 175a to 175f. Preferably, the distance between the lines 181 and 182 and the distance between the lines 191 to 193 are set equal.
As described above, the communication holes 175a to 175f are extended along the first line extending along the first direction and the direction orthogonal to the first direction (including "substantially orthogonal"). By forming at the position where the two lines intersect, the formation position of the communication hole can be set easily and efficiently.
The number of communication holes and the number of first lines and second lines are appropriately set according to the cross-sectional shape of the permanent magnet 170 and the like.

A permanent magnet 270 according to the second embodiment will be described with reference to FIG. FIG. 8 is a view of the permanent magnet 270 of the second embodiment viewed from a direction orthogonal to the direction in which the communication hole extends.
The permanent magnet 270 of the present embodiment can be manufactured by the same method as the permanent magnet 170 of the first embodiment.
In the permanent magnet 270 of the present embodiment, communication holes 275a to 275m are formed in parallel along the width direction (z direction). The communication holes 275a to 275m are regions in which the diffusion effect of Dy from the partial outer peripheral surfaces 271a to 271d of the permanent magnet 270 is low, that is, regions surrounded by the outer peripheral surface diffusion region boundary lines 272a to 272d, respectively. Are formed at positions covered by the inner peripheral surface diffusion regions 277a to 277m. Thereby, since Dy is diffused on the entire surface of the permanent magnet 270 when viewed in a cross section perpendicular to the direction in which the communication holes 275a to 275m extend, the holding force can be effectively increased.

Further, in the permanent magnet 270 of the second embodiment shown in FIG. 8, the communication holes 275 a to 275 m have a line 281 to 283 extending in parallel along the height direction (x direction), and a height It is a position where lines 291 to 299 extending in parallel along the width direction (y direction) orthogonal to the vertical direction (x direction) intersect, and in the height direction (x direction) and the width direction (y direction) It is formed at every other position along. One of the lines 281 to 283 extending along the height direction (x direction) and the lines 291 to 299 extending along the width direction (y direction) is the “first” of the permanent magnet of the present invention. The other corresponds to the “first line extending along the direction”, and the other corresponds to the “second line extending along the second direction orthogonal to the first direction”.
The interval between the lines 281 to 283 extending along the height direction (x direction) and the interval between the lines 291 to 299 extending along the width direction (y direction) are the sectional shape and sectional area of the permanent magnet 270, It is set according to the cross-sectional shape and cross-sectional area of the inner peripheral surface of the communication holes 275a to 275m. Preferably, the interval between the lines 281 to 283 and the interval between the lines 291 to 299 are set equal.
As described above, the communication holes 275a to 275m are extended along the first line extending along the first direction and the direction orthogonal to the first direction (including "substantially orthogonal"). By forming the two lines at alternate positions along the first direction and the second direction, the formation position of the communication hole can be set easily and efficiently. .
The number of communication holes and the number of first lines and second lines are appropriately set according to the cross-sectional shape of the permanent magnet 270 and the like.

In the permanent magnets of the first and second embodiments, the communication hole is formed at a position where the region surrounded by the outer peripheral surface diffusion region boundary line of the permanent magnet is covered by the inner peripheral surface diffusion region of each communication hole. The communication hole only needs to be formed at a position where the inner peripheral surface diffusion region of the communication hole overlaps at least partially with the region surrounded by the outer peripheral surface diffusion region boundary line of the permanent magnet. By forming the communication hole at such a position, the diffusion region of Dy can be increased and the holding force can be increased as compared with the conventional permanent magnet in which the communication hole is not formed.
This will be described with reference to FIG.
The communication hole 375a shown in FIG. 9 is located at a position where the inner peripheral surface of the communication hole 375a and the outer peripheral surface diffusion region boundary line 372b drawn at a position 1.5 mm away from the partial outer peripheral surface 371b of the permanent magnet 370 overlap. Is formed.
The communication hole 375b shown in FIG. 9 includes an inner peripheral surface diffusion region boundary line 376b drawn at a position 1.5 mm away from the inner peripheral surface of the communication hole 375b to the outer peripheral surface side of the permanent magnet 370, and the permanent magnet 370. The outer peripheral surface diffusion region boundary line 372b drawn at a position 1.5 mm away from the partial outer peripheral surface 371b is formed at a position where it overlaps.
The communication hole 375c shown in FIG. 9 has an outer peripheral surface diffusion region boundary line in which the inner peripheral surface diffusion region 377c of the communication hole 375c is drawn at a position 1.5 mm away from the partial outer peripheral surfaces 371a to 371d of the permanent magnet 370. It is formed at a position included in a region surrounded by 372a to 372d.
In any of the communication holes 375a to 375c, the inner peripheral surface diffusion regions 377a to 377c of the communication holes 375a to 375c overlap at least partially with the region surrounded by the outer peripheral surface diffusion region boundary lines 372a to 372d. Thereby, the diffusion effect of Dy in this overlapping region is enhanced.
The communication holes 375a to 375c are the lengths between the outer peripheral surfaces of the permanent magnets 370 along a line passing through the centers of the communication holes 375a to 375c when viewed in a cross section perpendicular to the direction in which the communication holes 375a to 375c extend. Is formed at a position of 3 mm or more. The “center of the communication hole” corresponds to the center point of a polygon or a circle when the cross section of the communication hole is a polygon or a circle. In FIG. 9, the length (for example, the length along the partial outer peripheral surface 371a) along the line passing through the center point P of the cross section of the communication holes 375a to 375c is 3 mm or more.

A second embodiment of a permanent magnet motor using the permanent magnet of the present invention will be described with reference to FIG. FIG. 10 is a cross-sectional view perpendicular to the axial direction of the rotor of the permanent magnet motor according to the second embodiment.
In the permanent magnet motor of the second embodiment, a magnet insertion hole is formed in a V shape in the main magnetic pole portion of the rotor core 460 of the rotor. In other words, the first magnet insertion hole 461a and the second magnet insertion hole 461b are linearly formed on both sides along the circumferential direction with the bridge portion 463 interposed therebetween in a state inclined with respect to the d-axis. Then, plate-like permanent magnets 470a and 470b having a quadrangular cross section perpendicular to the axial direction are inserted into the first magnet insertion hole 461a and the second magnet insertion hole 461b, respectively. The permanent magnets 470a and 470b are magnetized so that adjacent main magnetic pole portions have different polarities.
The permanent magnets 470a and 470b are formed with communication holes 475 that are open at both ends. In the present embodiment, as shown in FIG. 10, the communication hole 475 has a direction in which the permanent magnets 470 a and 470 b extend (the magnet insertion holes 461 a and 461 b extend) when viewed in a cross section perpendicular to the axial direction. Are formed along a direction (including a “substantially orthogonal direction”) orthogonal to the direction.

A third embodiment of a permanent magnet motor using the permanent magnet of the present invention will be described with reference to FIG. FIG. 11 is a cross-sectional view perpendicular to the axial direction of the rotor of the permanent magnet motor according to the third embodiment.
In the permanent magnet motor of the third embodiment, a magnet insertion hole is formed in a trapezoidal shape in the main magnetic pole portion of the rotor core 560 of the rotor. That is, a central portion extending linearly in a direction perpendicular to the d-axis, and an end extending linearly in a state inclined from the both ends of the central portion in opposite directions along the circumferential direction with respect to the d-axis A magnet insertion hole 561 having a portion is formed. Then, plate-like permanent magnets 570b, 570a, and 570c having a quadrangular cross section perpendicular to the axial direction are inserted into the center and both ends of the magnet insertion hole 561, respectively. Permanent magnets 570b, 570a and 570c are magnetized such that adjacent main magnetic pole portions have different polarities.
The permanent magnets 570b, 570a and 570c are formed with communication holes 575 that are open at both ends. In the present embodiment, as shown in FIG. 11, the communication hole 575 has a direction in which the permanent magnets 570b, 570a and 570c extend (the center of the magnet insertion hole 561) as viewed in a cross section perpendicular to the axial direction. Formed in a direction (including a “substantially orthogonal direction”) perpendicular to the direction in which the portion and both ends extend.

Next, the permanent magnet 670 of 3rd Embodiment is demonstrated with reference to FIG. The permanent magnet 670 of the third embodiment is formed in a long shape (for example, a rod shape or a vertically long plate shape), and a communication hole is formed along the longitudinal direction. For example, in the permanent magnet 170 shown in FIG. 6, communication holes are formed along the height direction (x direction) or the width direction (y direction).
The permanent magnet 670 of the present embodiment can be manufactured by the same method as the permanent magnet 170 of the first embodiment.
FIG. 12 is a view of the permanent magnet 670 of the third embodiment viewed from a direction perpendicular to the longitudinal direction.
Permanent magnet 670 of this embodiment has a trapezoidal outer peripheral surface having a partial outer peripheral surface 671b as an upper base, a partial outer peripheral surface 671d as a lower bottom, and partial outer peripheral surfaces 671a and 671c as legs, as viewed in a cross section perpendicular to the longitudinal direction. have.
The communication holes 675a to 675f extending along the longitudinal direction are outer peripheral surface diffusion region boundary lines 672a to 672d drawn from the partial outer peripheral surfaces 671a to 671d of the permanent magnet 670 to a position 1.5 mm away from the inner side of the permanent magnet 670. Are formed at positions covered by the inner peripheral surface diffusion regions 677a to 677f of the communication holes 675a to 675f, respectively. In FIG. 12, the center P of the communication holes 675a to 675f is parallel to the partial outer peripheral surfaces 671a to 671d, and is at a position along the line N that is separated from the partial outer peripheral surfaces 671a to 671d by an equal distance inside the permanent magnet 670. Is formed.
The number of communication holes, the cross-sectional shape, the formation position, and the like can be appropriately set.

Next, the permanent magnet 770 of 4th Embodiment is demonstrated with reference to FIG. Similar to the permanent magnet 670 of the third embodiment, the permanent magnet 770 of the fourth embodiment is formed in a long shape, and a communication hole is formed along the longitudinal direction.
The permanent magnet 770 of the present embodiment can be manufactured by the same method as the permanent magnet 170 of the first embodiment.
FIG. 13 is a view of the permanent magnet 770 according to the fourth embodiment viewed from a direction perpendicular to the longitudinal direction.
The permanent magnet 770 of the present embodiment has a circular outer peripheral surface 771 when viewed in a cross section perpendicular to the longitudinal direction.
The communication holes 775 a to 775 e extending along the longitudinal direction are defined by an outer peripheral surface diffusion region boundary line 772 (line M) drawn at a position 1.5 mm away from the outer peripheral surface 771 of the permanent magnet 770 inside the permanent magnet 770. The area | region enclosed is formed in the position covered with the internal peripheral surface spreading | diffusion area | region 777a-777e of each communicating hole 775a-775e. In FIG. 13, the center P of the communication holes 775 a to 775 e is formed at a position along a line N that is parallel to the outer peripheral surface 771 and is separated from the outer peripheral surface 771 by an equal distance to the inside of the permanent magnet 770.
The number of communication holes, the cross-sectional shape, the formation position, and the like can be appropriately set.

If a high-performance permanent magnet with a high magnetic flux density is used as a permanent magnet to be inserted into the magnet insertion hole of the rotor of the permanent magnet motor, the magnetic flux density of the electromagnetic steel sheet forming the rotor core increases and the iron Loss increases. Here, when the permanent magnets of the first and second embodiments are inserted into the magnet insertion holes of the rotor, when viewed in a cross section perpendicular to the axial direction, in a direction orthogonal to the direction in which the magnet insertion holes extend. A communication hole is arranged. Thereby, even if the 1st and 2nd permanent magnet is high performance, the surface area of the 1st and 2nd permanent magnet becomes small by the communicating hole formed in the 1st and 2nd permanent magnet, The amount of magnetic flux coming out of the first and second permanent magnets decreases. Therefore, it can suppress that the magnetic flux density of the electromagnetic steel plate which forms the rotor core becomes high, and can suppress that the iron loss of an electromagnetic steel plate increases.
When the permanent magnets of the third and fourth embodiments are inserted into the magnet insertion holes of the rotor core, the communication holes of the third and fourth permanent magnets are arranged along the axial direction. Thereby, the communication hole formed in the 3rd and 4th permanent magnet can be used as a passage for cooling of a rotor core, and a permanent magnet can be cooled. A neodymium magnet is likely to be demagnetized at a high temperature, but can be cooled by the cooling effect of the communication hole by being configured as in the third and fourth embodiments. Therefore, demagnetization of the neodymium magnet can be suppressed even when the permanent magnet motor in which the neodymium magnet is inserted into the magnet insertion hole of the rotor is operated at a high temperature. Further, similarly to the permanent magnets of the first and second embodiments, the amount of magnetic flux coming out of the third and fourth permanent magnets is reduced. Therefore, it can suppress that the magnetic flux density of the electromagnetic steel plate which forms the rotor core becomes high, and can suppress that the iron loss of an electromagnetic steel plate increases.
The long permanent magnets of the third and fourth embodiments may be cylindrical (for example, donut-shaped) with a hole formed in the center. In such a permanent magnet, when the distance between the outer peripheral surface of the permanent magnet and the inner peripheral surface on the center side is 3 mm or more, the holding force can be increased by forming the communication hole described above.

The present invention is not limited to the configuration described in the embodiment, and various changes, additions, and deletions are possible.
Each configuration described in the embodiment can be used alone, or can be used in combination with appropriately selected configurations.
The outer shape of the permanent magnet can be appropriately changed according to the usage pattern of the permanent magnet.
The number of communication holes formed in the permanent magnet, the cross-sectional shape, the cross-sectional area, the arrangement position, and the like can be appropriately changed according to the cross-sectional shape, cross-sectional area, and the like of the permanent magnet.
In the embodiments, the case where the permanent magnet of the present invention is used in a permanent magnet motor has been described. However, the permanent magnet of the present invention can be used in various devices other than the permanent magnet motor.
The present invention can be configured as a permanent magnet motor or a permanent magnet.

DESCRIPTION OF SYMBOLS 10 Magnet body 20 Communication hole 30 Cutting line 100 Permanent magnet motor 110 Stator 120 Stator core 130 Stator winding 150 Rotor 160, 460a, 461b, 561 Magnet insertion holes 170, 270, 370, 470a, 470b, 570a, 570b, 570c, 670, 770, 870 Permanent magnets 171a-171d, 271a-271d, 371a-371d, 671a-671d Partial outer peripheral surfaces 172a-172d, 272a-272d, 372a-372d, 672a 672d, 772 Peripheral surface diffusion region boundary lines 173, 273, 373. 673, 773 Peripheral surface diffusion regions 175, 175a-175f of permanent magnets, 275a-275m, 375a, 375b, 475, 575, 675a-675f, 775a- 75e Communicating holes 176a to 176f, 276a to 276m, 376a, 376b, 676a to 676f, 776a to 776e Inner peripheral surface diffusion region boundary lines 177a to 177f, 277a to 277m, 377a, 377b, 677a to 677f, 777a to 777e Inner peripheral surface diffusion region 180 of rotating shaft 771 outer peripheral surface

Claims (15)

The rotor includes a stator and a rotor, and the rotor has main magnetic pole portions and auxiliary magnetic pole portions alternately arranged along a circumferential direction when viewed in a cross section perpendicular to the axial direction. A magnet insertion hole extending along the direction intersecting the d axis is formed, and the magnet insertion hole is a permanent magnet electric motor in which a permanent magnet is inserted,
The permanent magnet is formed by diffusing at least one of dysprosium (Dy) and terbium (Tb) in a rare earth magnet body containing neodymium (Nd),
Further, the permanent magnet has at least one communication hole that extends in a direction intersecting with the direction in which the magnet insertion hole extends and has both ends open,
The communication hole is formed at a position where the length between the outer peripheral surfaces of the permanent magnets is 3 mm or more along a line passing through the center of the communication hole when viewed in a cross section perpendicular to the direction in which the communication hole extends. A permanent magnet motor characterized by being made. The permanent magnet motor according to claim 1,
The outer peripheral surface of the permanent magnet is formed by a plurality of partial outer peripheral surfaces when viewed in a cross section perpendicular to the direction in which the communication hole extends,
The at least one communication hole has an area within a range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet when viewed in a cross section perpendicular to the direction in which the communication hole extends. The communication hole formed in the position which overlaps at least partially with the area | region in the range of 1.5 mm inside the permanent magnet from the at least one partial outer peripheral surface of several partial outer peripheral surfaces is included. Characteristic permanent magnet motor. The permanent magnet motor according to claim 2,
The at least one communication hole has an area within a range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet, and 1.5 mm from the at least one partial outer peripheral surface to the inner side of the permanent magnet. A permanent magnet electric motor comprising a plurality of communication holes formed at a position at least partially overlapping a region within the range. The permanent magnet motor according to claim 3,
A region in the range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet is at least partly in a region of 1.5 mm from the at least one partial outer peripheral surface to the inside of the permanent magnet. At least one of the plurality of communication holes formed in the overlapping position has an area within a range of 1.5 mm from the inner peripheral surface of the at least one communication hole to the outer peripheral surface side of the permanent magnet. A permanent magnet motor, wherein the permanent magnet motor is formed at least partially overlapping with a region within a range of 1.5 mm from the outer peripheral surface of another portion adjacent to one outer peripheral surface to the inside of the permanent magnet. The permanent magnet motor according to claim 3 or 4,
A region in the range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet is at least partly in a region of 1.5 mm from the at least one partial outer peripheral surface to the inside of the permanent magnet. The plurality of communication holes formed at overlapping positions are formed at positions where the shortest distances among the distances between the inner peripheral surface of each communication hole and the at least one partial outer peripheral surface are equal. Permanent magnet motor characterized by The permanent magnet motor according to any one of claims 3 to 5,
A region in the range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet is at least partly in a region of 1.5 mm from the at least one partial outer peripheral surface to the inside of the permanent magnet. The plurality of communication holes formed at overlapping positions are within a range of 1.5 mm from the inner peripheral surface of each of the adjacent communication holes in the direction in which the at least one partial outer peripheral surface extends to the outer peripheral surface side of the permanent magnet. The permanent magnet motor is characterized by being formed at a position where at least a part of the region overlaps. The rotor includes a stator and a rotor, and the rotor has main magnetic pole portions and auxiliary magnetic pole portions alternately arranged along a circumferential direction when viewed in a cross section perpendicular to the axial direction. A magnet insertion hole extending along the direction intersecting the d axis is formed, and the magnet insertion hole is a permanent magnet electric motor in which a permanent magnet is inserted,
The permanent magnet is formed by diffusing at least one of dysprosium (Dy) and terbium (Tb) in a rare earth magnet body containing neodymium (Nd),
The permanent magnet extends along the axial direction and has at least one communication hole that is open at both ends.
The communication hole is formed at a position where the length between the outer peripheral surfaces of the permanent magnets is 3 mm or more along a line passing through the center of the communication hole when viewed in a cross section perpendicular to the direction in which the communication hole extends. A permanent magnet motor characterized by being made. The permanent magnet motor according to claim 7,
The at least one communication hole has a region within a range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet when viewed in a cross section perpendicular to the direction in which the communication hole extends. A permanent magnet electric motor comprising a communication hole formed at a position overlapping at least partially with a region within a range of 1.5 mm from the outer peripheral surface of the magnet to the inside of the permanent magnet. The permanent magnet motor according to claim 8,
The at least one communication hole includes a region within a range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet, and a range of 1.5 mm from the outer peripheral surface of the permanent magnet to the inner side of the permanent magnet. A permanent magnet electric motor comprising a plurality of communication holes formed at a position at least partially overlapping with the region. The permanent magnet motor according to claim 9,
Position where a region in the range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet overlaps at least partly with a region in the range of 1.5 mm from the outer peripheral surface of the permanent magnet to the inner side of the permanent magnet The plurality of communication holes formed in the permanent hole are formed at positions where the shortest distances among the distances between the inner peripheral surface of each communication hole and the outer peripheral surface of the permanent magnet are equal. Magnet motor. The permanent magnet motor according to claim 9 or 10,
Position where a region in the range of 1.5 mm from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet overlaps at least partly with a region in the range of 1.5 mm from the outer peripheral surface of the permanent magnet to the inner side of the permanent magnet The plurality of communication holes formed in the at least one region within a range of 1.5 mm from the inner peripheral surface of each of the communication holes adjacent in the direction in which the outer peripheral surface of the permanent magnet extends to the outer peripheral surface side of the permanent magnet. The permanent magnet motor is characterized in that it is formed at a position overlapping with each other. The permanent magnet motor according to any one of claims 1 to 11,
Each of the communication holes has an outer peripheral surface having the same shape as viewed in a cross section perpendicular to the direction in which the communication holes extend, and has the same cross-sectional area. . The permanent magnet motor according to any one of claims 1 to 12,
Each of the communication holes is formed at a position where a first line extending along a first direction and a second line extending along a second direction orthogonal to the first direction intersect. Permanent magnet motor characterized by The permanent magnet motor according to any one of claims 1 to 12,
Each of the communication holes is a position where a first line extending along a first direction and a second line extending along a second direction orthogonal to the first direction intersect, The permanent magnet motor is formed at every other position along the first direction and the second direction. The permanent magnet motor according to any one of claims 1 to 14,
Each of the communication holes has a region formed by a line drawn at a distance of 1.5 mm inward from the outer peripheral surface of the permanent magnet at a distance of 1. from the inner peripheral surface of the communication hole to the outer peripheral surface side of the permanent magnet. The permanent magnet motor is formed at a position covered by an area within a range of 5 mm.

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