CN103688445A - Stator for electric motors and permanent magnet rotating machines - Google Patents

Abstract

The present invention provides a stator and a permanent magnet type rotating electrical machine that can secure a creepage distance and can be applied to a small-sized electrical machine. In a stator (1) of a motor comprising a yoke core (11) and a plurality of tooth cores (12) extending in the radial direction of the yoke core (11), a A plurality of bobbins (13) made of insulating materials, the bobbins (13) include a main body (131) for winding the field winding of the stator (1) and two ends formed on the main body (131) Flange parts (132, 133), the stator (1) of the motor is provided with adjacent coils on the circumferential end faces of the flange parts (132, 133) on the inner diameter side of the above-mentioned flange parts (132, 133). A fitting portion that connects the plurality of coil bobbins (13) to each other in the circumferential direction by concavo-convex fitting of flange portions (132, 133) of the bobbins (13).

Description

Stator for electric motors and permanent magnet rotating machines

technical field

The present invention relates to a stator of an electric motor and a permanent magnet rotating electrical machine equipped with the stator.

Background technique

As a motor, such as a motor installed in a machine or electronic equipment like a servo motor, there is an endless demand for its miniaturization.

As a method of reducing the size of the motor, it is generally effective to increase the number of coils wound and increase the density of the coil wires (winding wires).

As one of the means to implement this method, such a stator structure can be used. That is, a stator core constituting a stator (stator) is divided into a plurality of split cores. Next, a coil (winding) is wound a predetermined number of times for each of the split cores. Then, according to the number of slots required, the divided iron cores wound with coils are assembled into a ring-shaped stator.

However, in such a stator structure, the surface of the coil winding insulator formed on the tooth core of each split iron core becomes a creepage surface (creepage surface) from the viewpoint of insulation performance. There is a creepage distance (creeping distance) on the creepage surface, that is, the shortest distance between two conductive parts along the surface of the insulator.

In general, when operating a control device or device that controls a motor, insulation space distance, creepage distance, temperature rise, etc. are specified from the viewpoint of safety and operating performance.

The creepage distance is required to be, for example, 2 to 3 mm for a 200V class motor.

Thus, in the motor, this creepage surface causes a problem of reduction of the insulation distance (insulation space distance, creepage distance, etc.). Especially in the case of miniaturization of the motor, there is a high demand for high density inside the motor, and the insulation distance between the two conductive parts is also reduced. From the perspective of safety and operating performance, the necessary insulation performance Difficult to obtain protection, which has become a bigger problem.

Conventionally, the following motor stator structures have been proposed.

That is, one is a stator winding structure of a rotating electric machine in which coils (field windings) are wound on a stator (stator) via an insulating bobbin, and integrally formed elastic tongues are provided at both ends of the sides of the insulating bobbin. By positioning the tongue pieces between the respective coil windings, electrical conduction between the coil windings and the stator can be prevented and the insulation of the coil windings can be improved (Patent Document 1).

In addition, the second relates to an insulator (insulation member) of a motor, wherein two insulators having a coil housing portion and an inner wall portion are attached to each tooth portion of the stator core inside a core body including a tooth portion, and the inner wall portion A staggered step-shaped connecting portion is provided on the end surface in the circumferential direction, and a plurality of insulators are combined through the connecting portion to form an annular stator structure (Patent Document 2).

In addition, in the prior art, an axial gap motor (axial gap motor) provided with an insulator has also been proposed. The insulator is configured to be embedded from both sides of the H-shaped stator core to cover the stator core. and cover the outer circumference of the stator core, but leave the side of the tooth surface of the coil winding part of the stator core (refer to Patent Documents 3, 4, 5, and 6). Here, the insulator is provided with two coupling members at the end of the flange portion in the circumferential direction for coupling the core elements including the yoke and the teeth to each other in the circumferential direction, that is, for coupling each The iron core element includes a hook portion annularly connected to each other around the rotor output shaft, and a locking shaft locked to the hook portion. In addition, the insulator is formed in a bobbin shape having a pair of parallel flanges along the tooth surface and the yoke piece, and the flange on the tooth surface side is formed axially lower than the tooth surface side. Therefore, the tooth surface becomes the highest position. Thereby, the gap with the rotor can be reduced, and the width direction dimension can be reduced.

In addition, there has been proposed a slender stator including a bobbin surrounding the split core along the outer peripheral portion of the I-shaped split core of the split stator core, and a flange inside the bobbin Combining grooves and coupling protrusions are formed on the top, and a circumferential molding surface is formed on the outer flange, and the assembly between the split iron core and the coil bobbin is performed by insert molding using a thermosetting resin to form them into one body (refer to the patent document 7, 8).

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2000-175393

Patent Document 2: Japanese Patent Laid-Open No. 2007-252031

Patent Document 3: Japanese Patent Laid-Open No. 2008-118833

Patent Document 4: Japanese Patent Laid-Open No. 2008-125278

Patent Document 5: Japanese Patent Laid-Open No. 2010-88166

Patent Document 6: Japanese Patent Laid-Open No. 2011-114993

Patent Document 7: Japanese Patent Laid-Open No. 2010-154740

Patent Document 8: Japanese Patent Laid-Open No. 2010-154741

Contents of the invention

The problem to be solved by the invention

The invention described in Patent Document 1 improves the shape of the insulator and uses a shape that covers the entire coil winding, that is, uses an insulating bobbin as the insulator.

However, since the insulating bobbin is provided with integral elastic tongues at both ends of its side, and the tongues are located between the windings, the density of the coil windings is correspondingly restricted, and there is a problem that the performance of the motor cannot be improved. question.

In addition, in the invention described in Patent Document 2, the coil housing portion is surrounded by two insulators, an outer insulator and an inner insulator assembled in the circumferential direction, and the coil windings housed in the coil housing portion of the insulator are spray-coated with Dispense agent, so as to apply coating agent on the entire coil winding.

Therefore, when spraying the coating agent, care must be taken not to leak the coating agent to the outside of the insulator. Therefore, on the end surface in the circumferential direction of the inner wall portion of the insulator, staggered step-shaped connection portions are provided. However, this complicates its structure.

In other words, the staggered step-like connecting portions formed at the ends of two types of insulators with different shapes are formed to prevent the coating agent from flowing out of the coil housing portion before the coating agent is cured. At first glance, the connection of the insulator seems to be a shape that increases the creepage distance, but in fact, there must be an interface at the connection of the insulator.

Therefore, as a result, the creepage distance cannot be improved much, and the above-mentioned problem caused by the creepage distance still exists as in the prior art, and it cannot be a technology to solve the problem.

In addition, since the coil winding is surrounded by inner insulators and outer insulators, their assembly is difficult, and it is difficult to say that they are suitable for downsizing motors.

Furthermore, when spraying the coating agent for insulation of the coil winding, not to mention the coating agent, its spraying mechanism, labor and time for performing the spraying operation are also indispensable, and it is not preferable from the viewpoint of cost.

In addition, the inventions described in Patent Documents 3 to 6 are aimed at preventing the occurrence of magnetic loss due to the gap between the tooth surface of the stator and the magnetic pole surface of the rotor.

The inventions described in Patent Documents 7 to 8 are aimed at reducing the vibration caused by the air gap error between the rotor and the stator.

However, none of them considered increasing the creepage distance between the split tooth core and the coil, and the insulators are also embedded from both sides of the H-shaped stator core to cover the inner peripheral surface of the stator core and cover the The outer circumference of the stator core, but the structure of the tooth surface side of the coil winding part of the stator core is left.

Therefore, in the inventions described in these patent documents, when the connecting mechanism is a hook and a locking shaft, or a flange shape consisting of protrusions and grooves, it is impossible to increase the creepage distance and further reduce the size of the motor.

Means used to solve technical problems

The present invention has been made to solve the above problems. Its purpose is to provide an electric motor and a permanent magnet type rotating electric machine that can cope with the miniaturization of electric motors (motors, electric motors), have the necessary creepage distance from the viewpoint of safety and operating performance, and can be applied to small motors the stator structure.

In order to achieve the above objects, the present invention has, for example, the following technical features.

A stator of an electric motor, comprising: a plurality of divided tooth cores; a yoke core having a plurality of recesses formed along the axial direction on the inner peripheral surface into which the front ends of the tooth cores are inserted; Multiple bobbins made of material. The above-mentioned bobbin includes: a bobbin main body part on which the above-mentioned coil is wound and having a through-hole for installing the above-mentioned tooth core; a flange part formed on the outer diameter side end of the bobbin main part; The flange portion of the end portion on the inner diameter side of the bobbin body portion. The flange portion of the inner diameter side end portion has an inner surface formed with a concavo-convex portion, the concavo-convex portion fits when the bobbin is mounted on the yoke core and adjacent bobbins are assembled, and the radially inner end portion A plate-shaped protruding piece extending in the circumferential direction and extending in the axial direction is also formed on the flange portion of the body. The stator of the electric motor has a structure capable of securing a long creepage distance between the coil and the tooth core by the protruding piece.

In addition, the stator of this electric motor is characterized in that, for example, the flange portion of the radially inner end portion extends beyond an angular range obtained by dividing the entire circumference of 360 degrees by the number of the bobbins.

In addition, for example, the stator of this electric motor is characterized in that the flange portion of the radially outer end portion extends over an angle range obtained by dividing the entire circumference of 360 degrees by the number of the bobbins.

In addition, the stator of this electric motor has, for example, a feature that the flange portions of the radially inner end and the radially outer end have shapes that do not decrease in thickness even at their front ends.

In addition, the present invention also provides, for example, a permanent magnet type rotating electric machine equipped with the stator of the electric motor described above.

The effect of the invention

According to the present invention, the conventional technical problems can be solved, and the stator of the motor can be obtained to ensure the necessary creepage distance from the viewpoint of safety and operating performance without reducing the creepage distance of the coil bobbin, which is the insulating material of the coil winding portion. structure. Therefore, it can be applied to a small motor without changing the voltage specification.

In addition, according to the present invention, even if the inner diameter of the stator (of the tooth core) and the number of slots of the stator are fixed, it is impossible to increase the inner diameter, increase the number of slots, or change the circumferential length assigned to each tooth core , It is also possible to ensure the necessary creepage distance from the viewpoint of safety and operational performance, and to obtain a motor stator that is also applicable to a motor that wants to be further miniaturized.

Thereby, a compact and high-performance rotating electric machine can be provided.

Description of drawings

FIG. 1 is a configuration diagram showing a schematic configuration of a stator of a motor according to the present invention.

Fig. 2 is an enlarged structural view showing the structure of the bobbin which is an insulating member attached to the tooth core of the stator according to the present invention.

Fig. 3 is an enlarged view when a plurality of bobbins in Fig. 2 are combined.

Fig. 4 is an exploded perspective view showing main parts of a yoke core, a tooth core, and a bobbin of the stator according to the present invention.

Fig. 5 is an exploded perspective view illustrating assembly of a yoke core, a tooth core, and a bobbin of the stator of the present invention.

FIG. 6 is a diagram schematically showing creepage distances in the prior art.

Detailed ways

Embodiments of the present invention will be described below with reference to the drawings.

Example

Fig. 1 is a structural diagram showing the stator structure of the main components included in the stator of the motor according to the present invention. Fig. 2 is a structural diagram showing the structure of the bobbin by enlarging a part (single body) of the bobbin of Fig. 1 , and Fig. 3 It is a structural diagram illustrating the combination of adjacent bobbins by combining a plurality of bobbins. FIG. 4 and FIG. 5 show the main parts and assembly structures of the yoke core, tooth core, and bobbin of the stator of the present invention. Exploded stereogram.

In these figures, 1 denotes a stator (stator) that interacts with the rotor (not shown) of the motor to generate rotational momentum. The stator includes a cylindrical yoke core (yoke core) 11 and a yoke core provided on the yoke core. Parts described later inside the cylinder. The stator also includes a plurality of T-shaped tooth cores 12 made of split iron cores, a plurality of bobbins 13 made of insulating members with through holes for the insertion of the plurality of tooth cores, and respectively wound and mounted on the plurality of teeth cores. Coil winding (field winding) 14 on the bobbin.

By employing the divided tooth core 12 in the stator 1, the copper wire can be wound more neatly than in the case of employing an integrated iron core in the stator.

That is, since the coil is wound at a high density, it is possible to suppress "copper loss" that causes a decrease in energy conversion efficiency, and to improve the performance of the motor.

In this embodiment, the tooth core 11 and the coil 14 have 12 slots. However, it is not necessarily limited to this number. In addition, a rotor mounted on a rotating shaft via a bearing is disposed inside the bobbin 13 , but it is omitted in this embodiment and is not shown here.

The bobbin 13 is individually attached to the plurality of tooth cores 12 so as to cover the tooth cores 12 as shown in FIG. 2 . The bobbin 131 includes a cylindrical bobbin main body 131 on which the coil 14 is wound and installed, and an integrally formed plate-shaped bobbin extending in the axial direction at one end of the bobbin main body 131 on the yoke core side (outer diameter side). The flange portion 132 (see FIG. 4 ) and the integrally formed plate-shaped flange portion 133 (see FIG. 4 ) extending in the axial direction on the rotor side (inner diameter side) of the bobbin body portion 131 .

The bobbin main body 131 of the bobbin 13 extends in the axial direction as shown in FIG. 4 , and a through hole 1311 into which a part 121 of the tooth core 12 is inserted is provided inside. In addition, in order to wind the coil 14 around the bobbin main body 13, a coil winding space 6 surrounded by the bobbin main body 131 and flanges 132 and 133 on both sides of the bobbin main body is provided.

The flange portions 132, 133 of the bobbin 13 are formed to ensure insulation between the end portion of the coil winding on the end portion of the bobbin body 131 of the adjacent bobbin 13 and the end portion 122 on the inner diameter side of the tooth core 12 ( Creepage distance L) and strength after assembly.

That is, each of the flange portions 132 and 133 has a plate shape (protruding piece) extending in the axial direction and extending in the circumferential direction. The flange portion is made larger than the bobbin body portion 131 in the axial direction and the circumferential direction so that the above-mentioned coil winding space portion 6 is formed by the protruding piece and the bobbin body portion.

Thus, the shape of the flange parts 132 and 133 integrally formed at both ends of the bobbin main body part 131 is extended and protruded in the axial direction and the circumferential direction. Thus, the creepage distance L between the coil winding 14 wound on the bobbin main body 131 and the inner diameter side end 122 of the tooth core 12 mounted in the through hole 1311 of the bobbin main body can be ensured (see Figure 3) is longer. The combination of bobbins will be described later.

In addition, the clockwise and counterclockwise end surfaces 1321, 1322 of the flange portion 132 on the outer diameter side of the bobbin 13 are formed as inclined surfaces inclined sideways to each other, so that when a plurality of bobbins are assembled to each other, for example, As shown in FIG. 3 , both end surfaces of the flange portions of adjacent bobbins face each other and are in close contact with each other.

The flange portion 133 on the inner diameter side of the bobbin 13 is formed in a plate shape extending in the circumferential direction with different thicknesses so as to be slightly R-curved with respect to the bonding surface with the bobbin body portion 131 . That is, as shown in the drawing, the plate shape on the counterclockwise side is formed to have a step difference from the plate shape on the clockwise side.

The purpose of this is to achieve a good combination of the flange portion 133 and ensure a creepage distance due to the joint surface when the bobbins are combined.

In addition, concavo-convex portions that can be fitted with each other are formed on the inner peripheral surface side, so that when the adjacent bobbins are combined, the two bobbins are closely contacted to each other as shown in FIG. 3 , for example. However, as shown in FIG. 4 , the concavo-convex portion is formed to extend over the entire inner peripheral surface of the flange portion 133 in the axial direction.

That is, at one end portion of the plate shape including the curved surface R of the flange portion 133, there are formed concavo-convex portions 1331, 1332, 1333 facing the end portion of the flange portion of the adjacent bobbin, and one of the convex portions ( The convex part 1334) of the bobbin arrange|positioned in the circumferential direction on the right side in a drawing fits in the other concave part 1331.

Specifically, the convex portions 1332 and 1333 of the flange portion 133 extend in the circumferential direction so as to surround the concave portion 1331 . This concave portion 1331 is fitted with a convex portion 1334 formed at one end of the flange portion of the adjacent bobbin when it is combined with the adjacent bobbin, as shown in FIG. 3 .

In the drawing, when the convex portion 1332 is combined with the adjacent right bobbin, as shown in FIG. 3 , it overlaps with the upper surface of the convex portion 1334 of the flange portion 133 of the adjacent bobbin 13 . In addition, the front end thereof has a length capable of contacting the side surface of the bobbin main body 131 of the adjacent bobbin.

By forming the protrusions and recesses in this way, the creepage distance can be further increased, and more importantly, as shown in FIG. 4 , the protrusions and protrusions are extended over the entire surface of the flange portion 133 in the axial direction. In other words, the flange portion 133 is formed larger, and the entire bobbin body portion—that is, not only the end portion of the bobbin body portion 131 but also the central portion—is integrally formed from both sides of the bobbin body portion 133 . surrounded.

In this way, the protruding pieces 1332 and 1334 of the flange portion 133 are extended in the axial direction not only at the ends of the bobbin main body 1331 but also at the central portion. Thus, compared with the creepage distance L' at the junction between the bobbins when using the bobbin shown in FIG. 6 in which the flange portion is formed only at the end of the bobbin main body, the protruding piece can be ensured. amount of creepage distance. Here, the creepage distance L' in FIG. 6 is a value in the case of the bobbin shape shown in Patent Document 2, for example, in which only the ends of the bobbin main body have concave-convex joints. As a result, the performance specifications are also compared based on the creepage distance, and the stator can be reduced in size and weight in accordance with the distance.

The convex portion 1333 is configured to overlap with the convex portion 1334 of the flange portion of the adjacent bobbin at the lower side thereof. In addition, it has a length shorter than the convex portion 1332 in contact with the side surface of the flange portion of the adjacent bobbin.

On the other end portion of the flange portion 133 , the above-mentioned convex portion 1334 is formed so as to extend in the circumferential direction at a position lowered by one step from the position of the end surface of the bobbin main body portion 131 .

That is, at one end portion (the right side in FIG. 2 ) of the flange portion 133 of the bobbin 13, a concave portion 1331 for fitting the convex portion 1334 of the flange portion of the adjacent bobbin is formed, and from the top and bottom Two protrusions 1332 and 1333 having different lengths are interposed between the fitted protrusion 1334 .

In addition, at the other end portion (left side in FIG. 2 ) of the flange portion 133 of the bobbin 13, a convex portion 1334 and a step are formed for fitting into the concave portion 1331 of the flange portion of the adjacent bobbin. Differential parts 1335, 1336.

That is, both ends of the flange portion 133 are formed so that when adjacent bobbins are combined, they can overlap in the vertical direction as shown in FIG. Concave-convex shapes combined in different ways. The respective thicknesses of the protrusions and recesses of the flange portion 133 are approximately 0.3 mm. The length of the protruding piece extending in the circumferential direction of the flange portion 133 is about 1 to 2 mm.

Next, assembly of the bobbin and the like will be described with reference to FIGS. 4 and 5 . First, a necessary number of coils is wound around the bobbin main body portion 131 of the bobbin 13 .

Then, a part 121 of the T-shaped tooth core 12 is inserted into the through-hole 1311 of the bobbin main body 131 . Its state is shown in FIG. 5 .

Thereafter, the front end portion of a part 121 of the tooth core 12 protruding from the outer diameter side surface of the bobbin 13 is inserted from the position shown in FIG. In the recessed part 111 extended in the axial direction, it mounts sequentially in this way.

At this time, the bobbins are slid so that one of the convex portions 1335 of the flange portions 133 of adjacent bobbins slides from one end surface of the other concave portion 1334 to the other end surface side, and as a result, the flange portions 133 The concavo-convex portions 1331 to 1333 on the one end face side of the torso are fitted with the concavo-convex portions 1334 to 1336 on the other end face side, and are combined in the state shown in FIG. 3 .

Here, each part of the tooth core 12 and the coil winding (field winding) 14 is insulated from each other by the bobbin 13 attached to the tooth core 12 . At this time, among the distances from the coil winding portion 14 formed by winding the coil 14 along the coil winding space 6 and the coil surface to the tooth core 12 , the shortest distance L as the minimum creepage distance determines the insulation performance.

In the above-described embodiments, the surface path along the surface of the coil winding has a fitting portion of the concavo-convex portion provided on the end portion of the flange portion 133 of the bobbin 13 . By fitting the concavo-convex parts and using two convex parts of one bobbin to overlap the other convex part of the adjacent bobbin in such a way as to sandwich it, the surface path is enlarged, so it is possible to crawl The electrical distance is ensured to be long, and as a result, the specified value of the creepage distance required from the viewpoint of safety and operating performance can be satisfied, and at the same time, miniaturization can be achieved.

In other words, in this embodiment, using the above-mentioned shape of the flange portion 133, from the bobbin main body 131 of one of the bobbins adjacent to each other and the root end portion of the convex portion 1332 of the flange portion 133, through the surface of the convex portion, and the other The distance between the flange portion 133 of the bobbin body 131 of one bobbin, the convex portion 1334 of the flange portion of the other bobbin, and the convex portion 1333 of the flange portion 133 of the other bobbin is as follows: Creepage distance L. By adopting such a structure, the creepage distance can be ensured to be long, and the amount of the creepage distance ensured is larger than that of the conventional technology under the same conditions, and it is also possible to cope with the miniaturization of the motor.

In the above-mentioned present embodiment, an example in which fitting is performed by using the concavo-convex portions provided on the facing flange portions has been described, but the fitting itself is not essential. The range of the angle allocated to each bobbin obtained by dividing the angle by the number of bobbins only needs to be such that the flange portions of the opposing bobbins overlap in the radial direction. As a result, the creepage distance can be ensured to be large, so that the same effects as those of the above-described embodiment can be obtained.

In addition, regarding the thickness of the insulator forming the overlapped portion, if there is a taper (wedge), the portion smaller than the minimum necessary thickness specified by the material properties will not be judged as the presence of the insulator. Therefore, the present invention must be shaped such that there is no taper at the end of the insulator.

industrial availability

The present invention can be applied to a permanent magnet type rotating electric machine having the above stator structure.

Explanation of reference signs

1 stator of the electric motor

11 Yoke core (yoke core)

12 tooth core

13 insulated bobbin

131 Coil Skeleton Main Body

132, 133 flange part

14 coils (coil winding part)

Claims (5)

1. A stator of an electric motor, characterized in that, comprising: Divided multiple tooth cores; a yoke core in which a plurality of recesses into which a front end portion of the tooth core is inserted is formed on an inner peripheral surface along the axial direction; and A plurality of bobbins made of insulating material for coil winding, The bobbin includes: a bobbin body portion around which the coil is wound and having a through hole for mounting the tooth core; a flange portion formed at an end portion on an outer diameter side of the bobbin body portion; and The flange portion formed at the end portion on the inner diameter side of the bobbin body portion, The flange portion of the inner diameter side end portion has an inner surface forming a concavo-convex portion which fits when the bobbin is mounted on the yoke core and adjacent bobbins are assembled to each other, and the A plate-shaped protruding piece extending in the circumferential direction and extending in the axial direction is formed on the flange portion of the inner diameter side end, and the creepage distance between the coil and the tooth core can be ensured by the protruding piece. longer. 2. A permanent magnet rotating electrical machine, characterized in that: A stator equipped with the electric motor according to claim 1 . 3. A stator of an electric motor, characterized in that it comprises: Divided multiple tooth cores; a yoke core in which a plurality of recesses into which a front end portion of the tooth core is inserted is formed on an inner peripheral surface along the axial direction; and A plurality of bobbins made of insulating material for coil winding, The bobbin includes: a bobbin body portion around which the coil is wound and having a through hole for mounting the tooth core; a flange portion formed at an end portion on an outer diameter side of the bobbin body portion; and The flange portion formed at the end portion on the inner diameter side of the bobbin body portion, The flange portion of the radially inner end portion extends beyond an angular range obtained by dividing the entire circumference of 360 degrees by the number of the bobbins. 4. A stator of an electric motor, characterized in that it comprises: Divided multiple tooth cores; a yoke core in which a plurality of recesses into which a front end portion of the tooth core is inserted is formed on an inner peripheral surface along the axial direction; and A plurality of bobbins made of insulating material for coil winding, The bobbin includes: a bobbin body portion around which the coil is wound and having a through hole for mounting the tooth core; a flange portion formed at an end portion on an outer diameter side of the bobbin body portion; and The flange portion formed at the end portion on the inner diameter side of the bobbin body portion, The flange portion of the radially outer end portion extends beyond an angular range obtained by dividing the entire circumference of 360 degrees by the number of the bobbins. 5. A stator of an electric motor, characterized in that it comprises: Divided multiple tooth cores; a yoke core in which a plurality of recesses into which a front end portion of the tooth core is inserted is formed on an inner peripheral surface along the axial direction; and A plurality of bobbins made of insulating material for coil winding, The bobbin includes: a bobbin body portion around which the coil is wound and having a through hole for mounting the tooth core; a flange portion formed at an end portion on an outer diameter side of the bobbin body portion; and The flange portion formed at the end portion on the inner diameter side of the bobbin body portion, The flange portion at the end portion on the inner diameter side and the flange portion at the end portion on the outer diameter side have shapes that do not decrease in thickness dimension even at their front ends.

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