KR20210153921A - Motor and a coil winding apparatus for preparing it - Google Patents

Abstract

The present invention provides a motor comprising: a shaft; a rotor coupled to the shaft; and a stator disposed outside the rotor. The stator includes a stator core and a coil wound to the stator core. The stator core includes a yoke and a plurality of teeth protruding from the yoke in a radial direction. The teeth include first teeth and second teeth disposed adjacent to the first teeth. The first teeth include a first side disposed to face the second teeth. The second teeth include a second side facing the first side. The shortest distance between a coil disposed on the first side and a coil disposed on the second side is 0.5 to 1.5 mm.

Description

A motor and a coil winding apparatus for manufacturing the same

The embodiment relates to a motor and a coil winding device for manufacturing the same.

A motor is a device that converts electrical energy into mechanical energy to obtain rotational force, and is widely used in vehicles, home electronic products, industrial devices, and the like.

In particular, the electronic power steering system (Electronic Power Steering System, hereafter referred to as EPS) in which a motor is used drives the motor in an electronic control unit according to driving conditions to ensure turning stability and provide quick recovery. , to enable the driver to drive safely.

The motor may include a housing, a shaft, a stator disposed on an inner circumferential surface of the housing, and a rotor disposed on an outer circumferential surface of the shaft. Here, the stator of the motor induces electrical interaction with the rotor to induce rotation of the rotor.

The stator may include a stator core and a coil wound around the stator core. And, the stator core includes a plurality of teeth on which the coil is wound. At this time, while the coil is wound on the plurality of teeth, the nozzle passes between the plurality of teeth.

Accordingly, a space for passing the nozzle must be secured between the plurality of teeth, and there is a limitation in that the number of windings of the coil must be reduced by the thickness of the nozzle. For this reason, as the number of windings of the coil decreases, there is a problem in that the torque density of the motor decreases.

Accordingly, the embodiment is intended to solve the above problems, and it is a problem to provide a motor having an increased number of windings of the coil and a coil winding device for manufacturing the same.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned here will be clearly understood by those skilled in the art from the following description.

The embodiment includes a support member including a space in which the coil is disposed; a guide member including a first guide member and a second guide member spaced apart in a first direction with the support member interposed therebetween; and a coil winding device coupled to the support member and including a driving member for reciprocating between the first guide member and the second guide member.

Preferably, the support member includes a first support member and a second support member spaced apart from the first support member in the first direction, and between the first support member and the second support member, the A space portion may be disposed.

Preferably, it may further include a sensor for generating a detection signal by sensing the position of the support member.

Preferably, when the sensing signal is received from the sensor unit, the driving member may move at least one of the first support member and the second support member to adjust the size of the space portion.

Preferably, when the sensing signal is received from the sensor unit, the driving member may remove at least one of the first supporting member and the second supporting member so that the length in the first direction of the space corresponds to the diameter of the coil. It can be moved in one direction.

Preferably, the first support member includes a first curved surface disposed to face the space portion, and the second support member includes a second curved surface disposed to face the space portion, and the first curvature A curvature of the surface and the second curved surface may correspond to a curvature of the stator coil.

Preferably, the first support member may include a first jaw disposed on an edge of the first curved surface, and the second support member may include a second jaw disposed on an edge of the second curved surface. .

Preferably, based on the second direction perpendicular to the first direction, a ratio of the width of the support member to the width of the coil may be 0.9 to 1.1.

Preferably, the first guide member and the second guide member may have guide grooves formed on the surfaces facing each other.

Preferably, the guide groove of the first guide member and the guide groove of the second guide member may be arranged on the same line with respect to the first direction.

Preferably, based on a second direction perpendicular to the first direction, a width of the guide groove may be greater than a width of the support member.

Preferably, the first guide member and the second guide member include a first member and a second member that are spaced apart from each other with the guide groove, and the first member and the second member are formed on surfaces facing each other. The edges may be tapered.

Embodiments include a shaft; a rotor coupled to the shaft; and a stator disposed outside the rotor, wherein the stator includes a stator core and a coil wound around the stator core, wherein the stator core includes a yoke and a plurality of teeth protruding in a radial direction from the yoke, , The tooth includes a first tooth and a second tooth disposed adjacent to the first tooth, the first tooth comprising a first side disposed toward the second tooth, the second tooth comprising the It provides a motor including a second side facing the first side, the shortest distance between the coil disposed on the first side and the coil disposed on the second side is 0.5 to 1.5 mm.

Preferably, the first tooth comprises a first protrusion extending from the end toward the second tooth, the second tooth comprises a second protrusion extending from the end toward the first protrusion, and the first protrusion and The distance between the second protrusions may be greater than the shortest distance between the coil disposed on the first side surface and the coil disposed on the second side surface.

Preferably, a ratio of the shortest distance between the coil disposed on the first side surface and the coil disposed on the second side surface to the distance between the first projection and the second projection may be 0.16 to 0.5.

According to the motor according to the embodiment, it is possible to obtain the effect of increasing the torque density of the motor by increasing the number of windings of the coil.

According to the coil winding apparatus according to the embodiment, it is possible to smoothly implement the operation of the support member for drawing out the coil, thereby preventing defective winding of the coil of the stator due to a malfunction of the coil winding apparatus.

1 is a cross-sectional view of a motor according to an embodiment.
2 is a plan view of a stator according to an embodiment.
3 is a partial plan view of a stator according to an embodiment;
4 is a state diagram of a coil winding device according to an embodiment of the present invention.
5 is a cross-sectional view of the support member and the driving member shown in FIG.
6 is a front view of the support member on which the coil shown in FIG. 4 is disposed.
7 is a plan view illustrating the first support member, the coil, and the stator core shown in FIG. 4 .
8 is a front view illustrating the first support member, the first guide member, and the coil shown in FIG. 4 .
9 and 10 are diagrams schematically illustrating a method of operating a coil winding device according to an embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings and preferred embodiments. And in describing the present invention, detailed descriptions of related known technologies that may unnecessarily obscure the gist of the present invention will be omitted.

Terms including an ordinal number such as second, first, etc. may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

1 is a side cross-sectional view of a motor according to an embodiment.

Referring to FIG. 1 , the motor according to the embodiment may include a shaft 100 , a rotor 200 , a stator 300 , a housing 400 , and a bus bar 500 .

The shaft 100 may be coupled to the rotor 200 . When electromagnetic interaction occurs between the rotor 200 and the stator 300 through the supply of current, the rotor 200 rotates and the shaft 100 rotates in conjunction therewith. The shaft 100 may be connected to the steering shaft of the vehicle to transmit power to the steering shaft.

The rotor 200 rotates through electrical interaction with the stator 300 .

The rotor 200 may include a rotor core and a magnet. The rotor core may be implemented in a shape in which a plurality of plates in the form of a circular thin steel plate are stacked or in the form of a single cylinder. A hole to which the shaft 100 is coupled may be disposed at the center of the rotor core. A protrusion for guiding the magnet may protrude from the outer circumferential surface of the rotor core. The magnet may be attached to the outer peripheral surface of the rotor core. The plurality of magnets may be arranged along the circumference of the rotor core at regular intervals. The rotor 200 may include a can member that surrounds the magnet to fix the magnet not to be separated from the rotor core and prevents the magnet from being exposed.

The stator 300 may include a stator core 310 , an insulator 320 , and a coil 330 . The insulator 320 is mounted on the stator core 310 . The coil 330 is wound around the insulator 320 . The coil 330 generates an induced current when power is applied. The coil 330 causes electrical interaction with the rotor 200 .

The housing 400 may accommodate the rotor 200 and the stator 300 therein. The housing is formed in a cylindrical shape.

The bus bar 500 may be disposed on the stator 300 . The bus bar 500 may include a terminal and a bus bar body that insulates the terminal.

2 is a plan view of the stator according to the embodiment, and FIG. 3 is a partial plan view of the stator according to the embodiment.

2 and 3 , the stator 300 includes a stator core 310 and a coil 330 . In addition, the stator core 310 includes a yoke 311 and a plurality of teeth 312 . The yoke 311 may be formed in a cylindrical shape. In addition, the yoke 311 may connect a plurality of teeth 312 . In this case, the plurality of teeth 312 may extend radially from the inner circumferential surface of the yoke 311 .

The plurality of teeth 312 may be spaced apart from each other in the circumferential direction. In this case, the teeth 312 may include a first tooth 3121 and a second tooth 3122 . The first tooth 3121 and the second tooth 3122 may be disposed adjacent to each other.

The first tooth 3121 may include a first protrusion 3121S extending to an end thereof. The first protrusion 3121S may extend in the circumferential direction toward the second tooth 3122 . And, the second tooth 3122 may include a second protrusion 3122S extending to the end. The second protrusion 3122S may extend in the circumferential direction toward the first protrusion 3121S. In this case, the end of the first protrusion 3121S and the end of the second protrusion 3122S may face each other in the circumferential direction. In addition, an end of the first protrusion 3121S facing each other and an end of the second protrusion 3122S may be spaced apart from each other in the circumferential direction. In this case, the distance between the end of the first protrusion 3121S and the end of the second protrusion 3122S may be 2 to 5 mm, preferably 2.5 to 3.5 mm, more preferably 3 mm. However, the present invention is not limited thereto.

A coil 330 is wound around the teeth 312 . At this time, the coil 330 is disposed on the plurality of surfaces of the first tooth 3121 . The first tooth 3121 may include a first side surface 3121A on which the coil 330 is disposed. The first side 3121A may be disposed to face the second tooth 3122 . Also, the coil 330 is disposed on a plurality of surfaces of the second tooth 3122 . In this case, the second tooth 3122 may include a second side surface 3122A on which the coil 330 is disposed. The second side surface 3122A is disposed to face the first side surface 3121A. In addition, the coil 330 disposed on the first side surface 3121A and the coil 330 disposed on the second side surface 3122A may be spaced apart from each other in the circumferential direction. At this time, the shortest distance between the coil 330 disposed on the first side surface 3121A and the coil 330 disposed on the second side surface 3122A is 0.5 to 2 mm, preferably 0.5 to 1.5 mm, more preferably 1 mm. can

According to this, the spaced distance between the end of the first protrusion 3121S and the end of the second protrusion 3122S is the coil 330 disposed on the first side surface 3121A and the coil 330 disposed on the second side surface 3122A. ) can be greater than the shortest distance. At this time, the coil 330 disposed on the first side surface 3121A and the coil 330 disposed on the second side surface 3122A with respect to the spaced distance between the end of the first protrusion 3121S and the end of the second protrusion 3122S. ) the ratio of the shortest distance between them may be 0.16 to 0.5.

Hereinafter, a coil winding device for manufacturing a motor according to an embodiment of the present invention will be described with reference to FIGS. 4 to 10 .

4 is a view showing a state of use of the coil winding device according to the embodiment, FIG. 5 is a cross-sectional view of the supporting member and the driving member shown in FIG. 4 , FIG. 6 is a front view of the supporting member on which the coil shown in FIG. 4 is disposed, and FIG. 7 FIG. 4 is a plan view illustrating the first support member, the coil, and the stator core.

4 to 6, the coil winding device is a device for winding a coil on the stator core. This coil winding device passes between the teeth and winds the coil on the stator core.

To this end, the coil winding device may include a support member 10 , a guide member 20 , and a driving member 30 .

The support member 10 reciprocates in the first direction while supporting the coil 330 . At this time, the coil 330 supported by the support member 10 may be drawn out from the support member 10 when a pulling force is applied thereto. The support member 10 may include a space portion 13 in which the coil 330 is disposed.

The support member 10 may include a first support member 11 and a second support member 12 .

The first support member 11 and the second support member 12 may be disposed in the first direction. In addition, the first support member 11 and the second support member 12 may be spaced apart from each other with a space 13 . In this case, the first direction may be the same direction as the axial direction of the shaft 100 shown in FIG. 1 .

The first support member 11 may be disposed on one side of the coil 330 . In this case, the first support member 11 may have a first curvature surface 11A disposed on the surface facing the coil 330 . The curvature of the first curvature surface 11A may correspond to the curvature of the coil 330 . In this case, the first curved surface 11A may be spaced apart from one side of the coil 330 . Meanwhile, as the first support member 11 is moved by the driving member 30 to be described later, the first curved surface 11A and the coil 330 may come into contact with each other.

The second support member 12 may be disposed on the opposite side of the coil 330 . In this case, the second support member 12 may have a second curvature surface 12A disposed on the surface facing the coil 330 . The curvature of the second curvature surface 12A may correspond to the curvature of the coil 330 . In this case, the second curved surface 12A may be spaced apart from the opposite side of the coil 330 . Meanwhile, as the second support member 12 is moved by the driving member 30 to be described later, the second curved surface 12A and the coil 330 may come into contact with each other.

)는 코일의 지름(

) 보다 클 수 있다.The first curved surface 11A and the second curved surface 12A may face each other. In addition, the first curved surface 11A and the second curved surface 12A may be spaced apart from each other in the first direction. At this time. The spaced distance between the first curved surface 11A and the second curved surface 12A (

) is the diameter of the coil (

) can be greater than

)는 제1 곡률면(11A)과 제2 곡률면(12A)의 이격된 거리(

)보다 작을 수 있다. The first support member 11 may include a first jaw 11S disposed on the edge of the first curved surface 11A. And, the second support member 12 may include a second jaw (12S) disposed on the edge of the second curved surface (12A). At this time, the separation distance between the first jaw (11S) and the second jaw (12S) (

) is the spaced distance between the first curved surface 11A and the second curved surface 12A (

) can be smaller than

Referring to FIG. 7 , the width in the second direction of the first support member 11 may be the same as the diameter of the coil 330 . Alternatively, the width of the first support member 11 in the second direction may be smaller than the diameter of the coil 330 . Also, the width in the second direction of the second support member 12 may be equal to the diameter of the coil 330 . In addition, the width of the first support member 12 in the second direction may be smaller than the diameter of the coil 330 . In this case, the width in the second direction of the first support member 11 may be the same as the width of the second support member 12 . The first support member 11 and the second support member 12 minimize the space occupied while passing between the teeth, thereby increasing the number of windings of the coil.

The guide member 20 guides the movement of the support member 10 . To this end, the guide member 20 may include a first guide member 21 and a second guide member 22 .

The first guide member 21 and the second guide member 22 are spaced apart from each other in the first direction. A support member 10 is disposed between the first guide member 21 and the second guide member 22 . At this time, the support member 10 reciprocates between the first guide member 21 and the second guide member 22 . Meanwhile, a stator core 310 may be disposed between the first guide member 21 and the second guide member 22 . At this time, the stator core 310 may rotate in the second direction between the first guide member 21 and the second guide member 22 .

The first guide member 21 and the second guide member 22 are each formed with guide grooves 20G on opposite surfaces. In addition, the guide grooves 20G of the first guide member 21 and the second guide member 22 may be disposed on the same line in the first direction. At this time, the support member 10 that reciprocates in the first direction may be inserted into the guide groove 20G.

The first guide member 21 and the second guide member 22 may have the same shape as each other. For convenience of explanation, only the first guide member 21 is described as an example in FIG. 8, but the same structure may be applied to the second guide member.

Referring to FIG. 8 , a guide groove 20G may be formed in the first guide member 21 . The guide groove 20G may be disposed to face the stator core. In addition, the guide groove 20G may extend in the first direction. In this case, the width in the second direction of the guide groove 20G may be smaller than the length in the first direction. In addition, the width G2 in the second direction of the guide groove 20G may be greater than the width G1 in the second direction of the first support member 11 and the second support member 12 . At this time, the first support member 11 and the second support member 12 that reciprocate in the first direction may be inserted into the guide groove 20G.

In addition, the first guide member 21 may include a first member 20a and a second member 20b. The first member 20a and the second member 20b may be spaced apart from each other in the second direction. In this case, a guide groove 20G may be disposed between the first member 20a and the second member 20b. The first member 20a and the second member 20b may include a tapered portion 20c formed at corners of surfaces facing each other. In this case, the tapered portion 20c may be formed at all corners of the first member 20a and the second member 20b. The tapered portion 20c may have a predetermined curvature. According to this, while the support member 10 is inserted into the guide groove 20G or slides in the guide groove 20G, it is possible to prevent a phenomenon from being caught at the corners of the first member 20a and the second member 20b. can

The coil winding apparatus according to the embodiment smoothly implements the operation of the support member 10 for drawing out the coil, thereby preventing defective winding of the stator coil due to a malfunction of the coil winding apparatus.

The driving member 30 drives the support member 10 . The driving member 30 reciprocates the support member 10 in the first direction. At this time, the support member 10 may reciprocate in the first direction and withdraw the stator coil 330 . In addition, the drawn coil 330 may be wound around the rotating stator core 310 .

The driving member 30 may drive the first supporting member 11 and the second supporting member 12 , respectively. To this end, the coil winding device may further include a sensor (not shown). The sensor (not shown) may be an infrared sensor. A sensor (not shown) may detect a position of the support member 10 in the first direction. The driving member 30 may separately drive the first supporting member 11 and the second supporting member 12 according to the detected position of the supporting member 10 in the first direction.

Hereinafter, a method of operating a coil winding device according to an embodiment will be described with reference to FIGS. 9 and 10 .

9 and 10 are diagrams schematically illustrating a method of operating a coil winding device according to an embodiment.

According to the embodiment, the coil winding device moves the first support member 11 and the second support member 12 from the first guide member 21 toward the second guide member 22 .

For convenience of explanation, the process of moving from the first guide member 21 to the second guide member 22 will be first described, and the process of moving from the second guide member 22 to the first guide member 21 will be It may take precedence.

Referring to FIG. 9A , the first support member 11 and the second support member 12 move from the first guide member 21 toward the second guide member 22 in a state in which the coil is accommodated. do. At this time, the coil 330 is drawn out from the support member 10 , and the coil 330 is disposed on the side surface of the stator core 310 .

Referring to FIG. 9B , the first support member 11 and the second support member 12 are inserted into the guide groove of the second guide member 22 .

Referring to FIG. 9C , the stator core 310 disposed between the first guide member 21 and the second guide member 22 rotates in the second direction. At this time, the coil 330 is drawn out from the support member 10 , and the coil 330 is disposed on the lower surface of the stator core 310 .

Referring to (d) of FIG. 9 , a sensor (not shown) detects a signal when the first support member 11 and the second support member 12 reach a predetermined position within the guide groove of the second guide member 22 . to create At this time, the driving member (not shown) presses the coil 330 by moving the first supporting member 11 toward the second supporting member 12 according to the sensing signal. At this time, the coil 330 is fixed by the first support member 11 and the second support member 12 and is not drawn out even if a pulling force is applied thereto. And tension is applied to the coil 330 .

Referring to FIG. 9E , the first support member 11 and the second support member 12 move toward the first guide member 21 again. At this time, the coil 330 is fixed by the first support member 11 and the second support member 12 .

Next, referring to FIG. 10 , in the coil winding apparatus according to the embodiment, the first support member 11 and the second support member 12 are moved from the second guide member 22 to the first guide member 21 again. move

Referring to (a) of FIG. 10 , the first support member 11 and the second support member 12 support the first guide member 211 from the second guide member 22 in a state in which the coil 330 is fixed. can move toward At this time, the coil 330 is maintained in a fixed state by the first support member 12 and the second support member 12 .

Referring to (b) of FIG. 10 , a sensor (not shown) generates a detection signal when the first support member 11 and the second support member 12 are adjacent to the side surface of the stator core 310 . A driving member (not shown) moves the first supporting member 11 to the opposite side of the second supporting member 12 according to the sensing signal. In addition, the first support member 11 is spaced apart from the coil 330 . At this time. The coil 330 may be withdrawn from the support member when a pulling force is applied. In addition, the first support member 11 and the second support member 12 continuously move from the second guide member 22 toward the first guide member 211 . Accordingly, the coil 330 is drawn out and the coil 330 is disposed on the side surface of the stator core 310 .

Referring to FIG. 10C , the first support member 11 and the second support member 12 are inserted into the guide groove of the first guide member 21 . At this time, the stator core 310 rotates in the second direction between the first guide member 21 and the second guide member 22 . Accordingly, the coil 330 is drawn out from the support member 10 , and the coil 330 is disposed on the upper surface of the stator core 310 .

And, when the first support member 11 and the second support member 12 reach a predetermined position in the guide groove of the first guide member 21, a detection signal is generated by a sensor (not shown). At this time, the driving member (not shown) presses the coil 330 by moving the first supporting member 11 toward the second supporting member 12 according to the sensing signal. At this time, the coil 330 is fixed by the first support member 11 and the second support member 12 and is not drawn out even if a pulling force is applied thereto. And tension is applied to the coil 330 .

The coil winding apparatus according to the embodiment may wind the coil without sagging by applying tension to the coil while the coil is disposed on the guide member.

Such a coil winding device can obtain the effect of increasing the torque density of the motor by increasing the number of windings of the coil. In addition, by smoothly implementing the operation of the support member for drawing out the coil, it is possible to prevent defective winding of the coil of the stator due to a malfunction of the coil winding device.

As described above, the motor according to a preferred embodiment of the present invention has been described in detail with reference to the accompanying drawings.

It is to be understood that one embodiment of the present invention described above is illustrative in all respects and not restrictive, and the scope of the present invention will be indicated by the appended claims rather than the foregoing detailed description. And it should be construed that all changes or modifications derived from the meaning and scope of the claims as well as equivalent concepts are included in the scope of the present invention.

10: support member
11: first support member
12: second support member
13: space part
20: guide member
21: first guide member
22: second guide member
30: driving member
100: shaft
200: rotor
300: stator
310: stator core
320: insulator
311: Tooth
312: York

Claims (15)

a support member including a space in which the coil is disposed;
a guide member including a first guide member and a second guide member spaced apart from each other in a first direction with the support member interposed therebetween; and
and a driving member coupled to the support member to reciprocally move the support member between the first guide member and the second guide member. According to claim 1,
The support member includes a first support member and a second support member spaced apart from the first support member in the first direction,
A coil winding device in which the space portion is disposed between the first support member and the second support member. 3. The method of claim 2,
Coil winding device further comprising a sensor for generating a detection signal by sensing the position of the support member. 4. The method of claim 3,
When the sensing signal is received from the sensor, the driving member moves at least one of the first support member and the second support member to adjust the size of the space portion. 5. The method of claim 4,
When the sensing signal is received from the sensor unit, the driving member moves at least one of the first support member and the second support member in a first direction so that the length of the space portion in the first direction corresponds to the diameter of the coil. Letting coil winding device. 6. The method of claim 5,
The first support member includes a first curvature surface disposed to face the space,
The second support member includes a second curved surface disposed to face the space,
The curvature of the first curved surface and the second curved surface corresponds to the curvature of the coil winding apparatus. 7. The method of claim 6,
The first support member includes a first jaw disposed on the edge of the first curvature,
The second support member is a coil winding device including a second jaw disposed on the edge of the second curved surface. According to claim 1,
A ratio of a width of the support member to a width of the coil with respect to a second direction perpendicular to the first direction is 0.9 to 1.1. According to claim 1,
The first guide member and the second guide member are
A coil winding device in which guide grooves are formed on surfaces facing each other. 10. The method of claim 9,
The guide groove is a coil winding device disposed on the same line with respect to the first direction. 11. The method of claim 10,
Based on a second direction perpendicular to the first direction, a width of the guide groove is greater than a width of the support member. 12. The method of claim 11,
The first guide member and the second guide member are
It includes a first member and a second member spaced apart from the guide groove,
A coil winding device in which the first member and the second member have tapered edges of the surfaces facing each other. shaft;
a rotor coupled to the shaft; and
It includes a stator disposed on the outside of the rotor,
The stator includes a stator core and a coil wound around the stator core,
The stator core includes a yoke and a plurality of teeth projecting radially from the yoke,
The tooth includes a first tooth and a second tooth disposed adjacent to the first tooth,
The first tooth includes a first side disposed toward the second tooth, the second tooth includes a second side facing the first side,
The shortest distance between the coil disposed on the first side and the coil disposed on the second side is 0.5 to 1.5 mm. 14. The method of claim 13,
The first tooth includes a first protrusion extending from the end toward the second tooth,
The second tooth includes a second protrusion extending from the end toward the first protrusion,
A distance between the first protrusion and the second protrusion is greater than a shortest distance between the coil disposed on the first side surface and the coil disposed on the second side surface. 14. The method of claim 13,
A ratio of the shortest distance between the coil disposed on the first side surface and the coil disposed on the second side surface to the distance between the first projection and the second projection is 0.16 to 0.5.

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