JP2024042366A - motor - Google Patents

Abstract

[Problem] To provide a motor capable of reducing cogging torque. [Solution] The motor includes a rotor having a magnet, and a stator. The stator includes a yoke, a first coil fixed to the yoke and forming a first phase, and a second coil fixed to the first coil and forming a second phase. The second coil is adjacent to the first coil in the radial direction. The first coil and the second coil form a magnetic circuit together with the rotor. [Selected Figure] Figure 5

Description

The present invention relates to a motor.

In the field of motors, there has been a demand for higher torque, and for example, by increasing the effective magnetic flux density of a magnet, the torque of a motor can be improved (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2003-318012

However, when a motor with high magnetic flux density is used, cogging torque may increase and motor efficiency may decrease.

In view of the above problems, the present invention provides a motor that can reduce cogging torque.

In order to solve the above-mentioned problems and achieve the objects, a motor according to the present invention includes a rotor having a magnet and a stator, the stator is fixed to a yoke, and a first phase is fixed to the yoke. and a second coil fixed to the first coil and forming a second phase, the second coil is adjacent to the first coil in the radial direction, and the second coil is adjacent to the first coil, and The first coil and the second coil form a magnetic circuit with the rotor.

According to one aspect, the motor according to the present invention can reduce cogging torque.

FIG. 1 is a plan view of a motor according to a first embodiment. FIG. 2 is a perspective view of the motor shown in FIG. 1. FIG. 3 is an exploded perspective view of the motor shown in FIG. 2. FIG. 4 is a perspective view showing a multi-phase coil included in the motor shown in FIG. 2. FIG. FIG. 5 is a perspective view showing one phase coil of the plural phase coils shown in FIG. 4. FIG. FIG. 6 is a cross-sectional view taken along arrow AA in FIG. 7 is a perspective view showing the rotor shown in FIG. 1 and the coil shown in FIG. FIG. 8 is a perspective view showing a coil of a first modification in the motor according to the first embodiment. FIG. 9 is a perspective view showing a coil of a second modification in the motor according to the first embodiment. FIG. 10 is a perspective view showing the coil of the second embodiment. FIG. 11 is a perspective view showing one phase coil of the plural phase coils shown in FIG. 10.

Below, a motor according to an embodiment will be described in detail based on the drawings. Note that the dimensional relationship of each element, the ratio of each element, etc. in the drawings may differ from reality. Drawings may also include portions that differ in dimensional relationships and ratios.

[First embodiment]
FIG. 1 is a plan view of a motor 1 according to the first embodiment. FIG. 2 is a perspective view of the motor 1 shown in FIG. FIG. 3 is an exploded perspective view of the motor 1 shown in FIG. 2. FIG. 4 is a perspective view showing a multi-phase coil 33 included in the motor 1 shown in FIG. FIG. 5 is a perspective view showing one phase coil 33 of the plural phase coils 33 shown in FIG. 4. FIG. FIG. 6 is a cross-sectional view taken along arrow AA in FIG. FIG. 7 is a perspective view showing the rotor 2 shown in FIG. 1 and the first coil 33U shown in FIG. 5. In addition, in FIG. 6, the coil 33 is shown with a plurality of protrusions described later omitted.

In each drawing, for ease of explanation, the direction in which a shaft 21 (described later) extends is referred to as an axial direction A, and the direction in which a rotor 2 (described later) rotates is referred to as a circumferential direction C. The direction that is included, passes through the axis 21o of the shaft 21, and is perpendicular to the circumferential direction C is called the radial direction R.

The motor 1 according to the embodiment is an electric motor that converts electrical energy from, for example, a three-phase AC power source into a driving force that rotates the shaft 21 in the circumferential direction C. Further, the motor 1 according to the present embodiment is, for example, an inner rotor type brushless motor in which the rotor 2 is located inside the stator 3 in the radial direction R.

The motor 1 shown in FIG. 1 includes, for example, a rotor 2 and a stator 3. As shown in FIG. 2, the rotor 2 includes a shaft 21, a rotor core 22, a magnet 23, and a rotor case 24.

The shaft 21 is a rotating shaft and is disposed at the innermost position in the radial direction R of the rotor 2 . The rotor core 22 is located outside the shaft 21 in the radial direction R, and is made of a magnetic material such as stainless steel or a magnetic steel plate. The magnet 23 is, for example, a permanent magnet, and is located outside the rotor core 22 in the radial direction R. The rotor case 24 is located outside the magnet 23 in the radial direction R, and is made of a magnetic material such as stainless steel or a magnetic steel plate. The rotor case 24 is located at the outermost side of the rotor 2 in the radial direction R, and forms the outer circumferential surface of the rotor 2 .

The rotor 2 is rotatably provided in the motor 1 around a shaft 21 that is a rotating shaft. The rotor 2 according to this embodiment includes, for example, ten magnets 23. The plurality of magnets 23 are arranged at intervals in the circumferential direction C. The magnet 23 according to this embodiment is of a segment type and can form a parallel magnetic field. Each of the magnets 23 is fixed to the outer circumferential surface of the rotor core 22 on the outer side in the radial direction R, and is fixed to the inner circumferential surface of the rotor case 24 on the inner side in the radial direction R.

The stator 3 is a portion that generates a force for rotating the rotor 2 in the circumferential direction C. As shown in FIG. 3, the stator 3 includes a case 31, a yoke 32, and multiple-phase coils 33.

The case 31 is disposed at the outermost side of the stator 3 in the radial direction R, and is made of, for example, a rigid material and has a cylindrical shape with a bottom. The yoke 32 is formed into a cylindrical shape of a magnetic material such as stainless steel or a magnetic steel plate, and has magnetism. The yoke 32 according to this embodiment is formed by laminating a plurality of silicon steel plates. Further, the yoke 32 is formed in a cylindrical shape and does not have a magnetic pole portion that protrudes in the radial direction R from the outer circumferential surface and the inner circumferential surface of the yoke 32 in the radial direction R. That is, the motor 1 according to this embodiment is a so-called coreless motor. Therefore, when the motor 1 is assembled, the magnetic pole portions are not inserted into the first space 331s1 and the second space 331s2, which will be described later. As a result, the distribution of the magnetic field does not differ between when the motor 1 is stationary and when it is driven. Therefore, the motor 1 according to this embodiment can reduce cogging torque.

The coils 33 are formed, for example, by punching out a flat plate of conductive metal such as copper. Each of the coils 33 is covered with an insulating coating layer (insulating portion) made of a heat-resistant resin such as polyimide.

As shown in FIG. 4, the multi-phase coil 33 includes a first coil 33U, a second coil 33V, and a third coil 33W. The first coil 33U constitutes the U phase of the motor 1. Further, the second coil 33V constitutes the V phase of the motor 1. Furthermore, the third coil 33W forms the W phase of the motor 1.

The first coil 33U is arranged outside the second coil 33V and the third coil 33W in the radial direction R. The first coil 33U is arranged in an annular shape when viewed from the axial direction A. The first coil 33U is fixed to the inner circumferential surface of the yoke 32, for example, with an adhesive. The first coil 33U is covered with an insulating coating layer (insulating portion), and therefore is adjacent to the yoke 32 in the radial direction R via the insulating portion.

The second coil 33V is arranged inside the first coil 33U in the radial direction R and outside the third coil 33W in the radial direction R. The second coil 33V is arranged in an annular shape when viewed from the axial direction A. Such a second coil 33V is fixed to the inner circumferential surface of the first coil 33U, for example, via an adhesive. The second coil 33V is covered with an insulating coating layer (insulating portion), and thus is adjacent to the first coil 33U in the radial direction R via the insulating portion.

The third coil 33W is arranged inside the first coil 33U and the second coil 33V in the radial direction R. The third coil 33W is arranged in an annular shape when viewed from the axial direction A. Such a third coil 33W is fixed to the inner circumferential surface of the second coil 33V, for example, via an adhesive. The third coil 33W is covered with an insulating coating layer (insulating portion), and thus is adjacent to the second coil 33V in the radial direction R via the insulating portion.

That is, the motor 1 according to the present embodiment has a plurality of phases, and in the radial direction R, a second coil 33V of the V phase, which is different from the U phase, a second coil 33V of the W phase, and a second coil 33V of the V phase different from the U phase. A third coil 33W is arranged.

The first coil 33U, the second coil 33V, and the third coil 33W are formed similarly except for the size of the radius. Therefore, the first coil 33U will be described below, and the description of the second coil 33V and third coil 33W will be omitted.

The first coil 33U is formed by punching out a plate made of, for example, a conductive metal, and the surface of the punched metal material is electrodeposited to ensure insulation. Thereafter, the punched metal material is deformed along the circumferential direction C, and when viewed from the axial direction A, an annular first coil 33U is formed. That is, the first coil 33U is, for example, a press coil type formed by punching out a single sheet of metal material, and is integrally formed.

The first coil 33U according to the present embodiment is formed so as to go around the axis 21o of the shaft 21 once. The first coil 33U has five portions 331 having the same shape, and the five portions 331 are arranged along the circumferential direction C, as shown in FIG. Therefore, in order to avoid redundant explanation, one portion 331 will be explained below, and explanations of the remaining four portions 331 will be omitted.

The portion 331 is formed of, for example, an electrically conductive member (for example, a metal material), and faces the rotor 2 in the radial direction R (see FIG. 7). Further, the portion 331 includes a first portion 331a and a second portion 331b.

The first portion 331a extends obliquely with respect to the axial direction A. The second portion 331b extends obliquely with respect to the axial direction A. The length of the first portion 331a and the length of the second portion 331b are the same. Furthermore, the length of the first portion 331a in the axial direction A and the length of the second portion 331b in the axial direction A are the same. Furthermore, the length of the first portion 331a in the circumferential direction C and the length of the second portion 331b in the circumferential direction C are the same.

The first portion 331a and the second portion 331b are connected on one side in the axial direction A. Further, the first portion 331a and the second portion 331b are separated from each other on the other side in the axial direction A. More specifically, the first portion 331a and the second portion 331b are connected in a V-shape. In other words, in the axial direction A, the first portion 331a and the second portion 331b are connected, and in the circumferential direction C, the first portion 331a and the second portion 331b are separated. In the circumferential direction C, a first space 331s1 is formed between the first portion 331a and the second portion 331b. Further, in the circumferential direction C, a second space 331s2 is formed between the mutually adjacent portions 331.

In the axial direction A of the coil 33 shown in FIG. 6, the size 33L of the coil 33 excluding the first protrusion 331Uc is smaller than the size 32L of the yoke 32. Further, in the axial direction A, the size 33L of the coil 33 excluding the first protrusion 331Uc is larger than the size 2L of the rotor 2 excluding the shaft 21.

Among the five portions 331 shown in FIG. 4, one portion 331 has a first protrusion 331Uc that protrudes from the yoke 32 in the axial direction A. Furthermore, among the five portions 331, a portion 331 having a winding end portion 331Ud is arranged on the opposite side of the portion 331 having the first protrusion portion 331Uc.

The first protruding portion 331Uc is connected to a power source (not shown), and the winding end portion 331Ud is connected to a power source (not shown). In a state where the first protruding portion 331Uc and the winding end portion 331Ud are respectively connected to a power source (not shown), it is possible to apply voltage from the power source to the first coil 33U.

As shown in FIG. 4, the second coil 33V has a second protrusion 331Vc and a second winding end portion 331Vd. The second protrusion 331Vc of the second coil 33V corresponds to the first protrusion 331Uc of the first coil 33U. That is, the second coil 33V has a second protrusion 331Vc that protrudes from the yoke 32 in the axial direction A. Furthermore, the second winding end 331Vd of the second coil 33V corresponds to the winding end 331Ud of the first coil 33U.

The third coil 33W has a third protruding portion 331Wc and a third winding end portion 331Wd. The third protrusion 331Wc of the third coil 33W corresponds to the first protrusion 331Uc of the first coil 33U. That is, the third coil 33W has a third protrusion 331Wc that protrudes from the yoke 32 in the axial direction A. Furthermore, the third winding end 331Wd of the third coil 33W corresponds to the winding end 331Ud of the first coil 33U.

Next, the function of the coil 33 will be explained using the first coil 33U as an example. For example, in the first coil 33U, when a voltage is applied from a power supply (not shown) between the first protrusion 331Uc and the winding end 331Ud, a current flows from the first protrusion 331Uc to the winding end 331Ud.

Then, as described above, when the current flows through the first coil 33U, a magnetic field is formed in the space between the first portion 331a and the second portion 331b from one side to the other in the radial direction R. As a result, the first coil 33U and the magnet 23 of the rotor 2 form a magnetic circuit 33M (see FIG. 7).

After that, the direction in which the current flows is changed at an appropriate timing. That is, when a current flows from the winding end portion 331Ud to the first protruding portion 331Uc, a magnetic field is formed in the space between the first portion 331a and the second portion 331b from the other side to the one side in the radial direction R. As a result, the first coil 33U and the magnet 23 of the rotor 2 form a magnetic circuit 33M.

By changing the direction of the magnetic field formed by the first coil 33U at an appropriate timing, the magnetic force of the magnetic field formed in the first coil 33U and the magnetic field of the magnet 23 of the rotor 2 causes the rotor 2 to rotate around the rotor 2. Rotate in one direction C. Note that although the first coil 33U has been described above, the same applies to the second coil 33V. In other words, the second coil 33V and the magnet 23 of the rotor 2 form a magnetic circuit (not shown). Furthermore, the third coil 33W is also similar to the first coil 33U. In other words, the third coil 33W and the magnet 23 of the rotor 2 form a magnetic circuit (not shown).

As described above, the yoke 32 according to this embodiment is formed in a cylindrical shape and does not have magnetic pole portions that protrude in the radial direction R from the outer peripheral surface and inner peripheral surface of the yoke 32 in the radial direction R. Therefore, when the motor 1 is assembled, no magnetic pole portions are inserted into the first space portion 331s1 and the second space portion 331s2. As a result, the distribution of the magnetic field due to the magnetic pole portions does not differ between when the motor 1 is stationary and when it is driven. This allows the motor 1 according to this embodiment to reduce cogging torque.

In the coil 33 according to this embodiment, coils forming the same phase are integrally formed. Therefore, it is not necessary to separately join the first part 331a and the second part 331b, and it is not necessary to separately join the parts 331 to each other, so that the manufacturing work of the coil 33 is facilitated. Can be done.

The first coil 33U according to this embodiment has a first protrusion 331Uc that protrudes from the yoke 32 in the axial direction A. Therefore, in the motor 1 according to the present embodiment, the first protruding portion 331Uc protruding from the yoke 32 can facilitate the connection work between the power source (not shown) and the first coil 33U.

The second coil 33V according to this embodiment has a second protrusion 331Vc that protrudes from the yoke 32 in the axial direction A. Therefore, in the motor 1 according to the present embodiment, the second protruding portion 331Vc protruding from the yoke 32 can facilitate the connection work between the power source (not shown) and the second coil 33V.

In the motor 1 according to the present embodiment, the direction of the first protrusion 331Uc protruding from the first coil 33U, the direction of the second protrusion 331Vc protruding from the second coil 33V, and the direction of the third protrusion 331Vc protruding from the third coil 33W. The direction of the protrusion 331Wc extends toward one of the axial directions A. Therefore, compared to the case where protrusions are provided from the coil 33 in both directions A, the motor 1 according to this embodiment can be made smaller in size in the axial direction A.

In the stator 3 according to the first embodiment described above, each of the first coil 33U constituting the U phase, the second coil 33V constituting the V phase, and the third coil 33W constituting the W phase is five in number. What is constituted by the portion 331 has been explained. However, the number of portions 331 constituting each coil 33 of the stator 3 according to this embodiment is not limited thereto, and can be set arbitrarily.

[First modification of the first embodiment]
Next, the first coil 133U of the first modification of the motor 1 according to the first embodiment will be described using FIG. 8. FIG. 8 is a perspective view showing a first coil 133U of a first modification in the motor 1 of the first embodiment.

The first coil 133U according to this modification is formed in an annular shape when viewed from the axial direction A. Further, the first coil 133U according to the present modification is formed in a spiral shape so as to make two rotations around the axis 21o (not shown). The first coil 133U according to the present embodiment includes a first protrusion 331Uc that protrudes from the yoke 32 (not shown) and a winding end portion 331Ud. The first coil 133U includes a first coil portion 331U1 having a first protrusion 331Uc and a second coil portion 331U2 having a winding end portion 331Ud. The first coil portion 331U1 having the first protrusion 331Uc and the second coil portion 331U2 having the winding end portion 331Ud are arranged side by side in the axial direction A. That is, in the first coil 133U, two coils forming the same phase are arranged side by side in the axial direction A.

In the first coil 133U according to the present modification, coils constituting the same phase are formed side by side in the axial direction A. Therefore, the length of the portion in which current flows in the first coil 133U is longer than the length of the portion in which current flows in the first coil 33U according to the first embodiment. As a result, the magnetic force formed by passing a current through the first coil 133U is stronger than the magnetic force formed by passing a current through the first coil 33U according to the first embodiment. Therefore, the output of the motor 1 having the first coil 133U according to this modification can be made larger than the output of the motor 1 having the first coil 33U according to the first embodiment.

[Second modification of the first embodiment]
Next, the first coil 233U of the second modified example of the motor 1 according to the first embodiment will be described using FIG. 9. FIG. 9 is a perspective view showing a first coil 233U of a second modification in the motor 1 of the first embodiment.

The first coil 233U according to this modification is formed in an annular shape when viewed from the axial direction A. Further, the first coil 233U according to this modification is formed in a spiral shape so as to make four revolutions around the axis 21o (not shown). The first coil 133U according to the present embodiment includes a first protrusion 331Uc that protrudes from the yoke 32 (not shown) and a winding end portion 331Ud. The first coil 233U includes a first coil portion 331U1 having a first protrusion 331Uc, a second coil portion 331U2 having a winding end portion 331Ud, and a first coil portion 331U1 and a second coil portion in the axial direction A. 331U2 and a fourth coil portion 331U4. The first coil portion 331U1, the second coil portion 331U2, the third coil portion 331U3, and the fourth coil portion 331U4 are arranged side by side in the axial direction A. That is, in the first coil 233U, four coils forming the same phase are arranged side by side in the axial direction A.

In the first coil 233U according to this modification, coils constituting the same phase are formed side by side in the axial direction A. Therefore, the length of the portion in which current flows in the first coil 233U is longer than the length of the portion in which current flows in the first coil 33U according to the first embodiment. As a result, the magnetic force formed by passing a current through the first coil 233U is stronger than the magnetic force formed by passing a current through the first coil 33U according to the first embodiment. Therefore, the output of the motor 1 having the first coil 233U according to this modification can be made larger than the output of the motor 1 having the first coil 33U according to the first embodiment.

Note that the first coil 33U according to the first embodiment is formed so as to go around the axial center once, and the first coil 133U according to the first modification is formed so as to go around the axial center twice, and the first coil 133U according to the first modification is formed so as to go around the axial center twice. The first coil 233U has been described as being formed so as to go around the axis four times. However, the first coils 33U, 133U, and 233U according to the present embodiment and modified examples are not limited to this. For example, the first coils 33U, 133U, and 233U may be formed so as to revolve around the axis three times, or may be formed so as to go around the axis five times or more.

[Second embodiment]
Next, the coil of the second embodiment in the motor 1 according to the second embodiment will be described using FIGS. 10 and 11. FIG. 10 is a perspective view showing the coil 33 of the second embodiment. FIG. 11 is a perspective view showing the first coil 33U of the second embodiment. Regarding the configuration of the coil 333 according to the second embodiment, parts that are different from the configuration of the coil 33 according to the first embodiment will be described below, and descriptions of parts having the same configuration will be omitted.

In the coil 333 according to the second embodiment, the first coil 33U, the second coil 33V, and the third coil 33W are formed similarly except for the size of the radius. Therefore, the first coil 33U will be described below, and the description of the second coil 33V and third coil 33W will be omitted.

The first coil 33U includes a plurality of portions 3331 that face the rotor 2 (not shown) in the radial direction R, and a power supply connection portion 3332 that extends in the axial direction A. The first coil 33U according to this embodiment has nine parts 3331. The portion 3331 is formed in an L shape and includes a first portion 3331a and a second portion 3331b. The first portion 3331a extends along the circumferential direction C. The second portion 3331b extends along the axial direction A.

In the first coil 33U according to this embodiment, the length of the first portion 3331a along the circumferential direction C is different from the length of the second portion 3331b along the axial direction A. More specifically, the length of the second portion 3331b along the axial direction A is longer than the length of the first portion 3331a along the circumferential direction C.

One end of the first portion 3331a in the circumferential direction C is connected to one end of the second portion 3331b in the axial direction A. More specifically, one end of the first portion 3331a in the circumferential direction C is connected to one end of the second portion 3331b in the axial direction A in an L-shape. The other end of the first portion 3331a in the circumferential direction C is separated from the other end of the second portion 3331b in the axial direction A. A space 3331s1 is formed between the second portions 3331b of adjacent portions 3331 in the circumferential direction C.

The power supply connection portion 3332 is provided in a portion 3331 located at one end in the circumferential direction C. A first protrusion 331Uc that protrudes from the yoke 32 (not shown) is formed at one end of the power supply connection portion 3332 in the axial direction A. The portion 3331 located at the other end in the circumferential direction C is provided with a winding end portion 331Ud.

As described above, the yoke 32 according to the present embodiment is also formed in a cylindrical shape, and does not have a magnetic pole portion protruding in the radial direction R from the outer circumferential surface and the inner circumferential surface of the yoke 32 in the radial direction R. Therefore, in the assembled state of the motor 1, the magnetic pole portion is not inserted into the space portion 3331s1. As a result, the distribution of the magnetic field due to the magnetic pole portions does not differ between when the motor 1 is stationary and when it is driven. Thereby, the motor 1 according to this embodiment can reduce cogging torque.

In addition, the first coil 33U of the second embodiment described above has been described as being formed so as to make one revolution around the axial center. However, the first coil 33U according to the present embodiment is not limited thereto. For example, the first coil 33U may be formed to rotate around the axis a plurality of times. In this case, like the first coil 33U according to the first embodiment, it is preferable that the coil portions that go around the axis once are arranged side by side in the axial direction A.

Furthermore, in the stator 3 according to the second embodiment described above, each of the first coil 33U constituting the U phase, the second coil 33V constituting the V phase, and the third coil 33W constituting the W phase has nine pieces. What is constituted by the portion 3331 has been explained. However, the number of portions 3331 constituting each coil 33 of the stator 3 according to this embodiment is not limited thereto, and can be set arbitrarily.

Moreover, although the motor 1 according to the first embodiment and the second embodiment described above is applied to, for example, an inner rotor type brushless motor, the present invention is not limited thereto. The motor 1 according to these embodiments can be applied, for example, to an outer rotor type motor in which the rotor 2 is located outside the stator 3 in the radial direction R.

Further, the rotor 2 according to the first embodiment and the second embodiment described above includes ten magnets 23. However, the number of magnets 23 in the rotor 2 according to these embodiments is not limited thereto, and can be set to any number.

The above is an explanation based on an embodiment of the motor 1 according to the present invention, but the present invention is not limited to the embodiment, and it goes without saying that various modifications are possible without departing from the scope of the present invention. Such modifications without departing from the scope of the present invention are also included in the technical scope of the present invention, and this will be clear to those skilled in the art from the description of the claims.

1 Motor, 2 Rotor, 23 Magnet, 2L Size of rotor 2, 3 Stator, 32 Yoke, 32L Size of yoke 32, 33 Coil, 33L Size of coil 33, 33M Magnetic circuit, 33U 1st coil (coil) , 133U first coil (coil), 233U first coil (coil), 33V second coil, 331 part, 331a first part, 331b second part, 3331a first part, 3331b second part, 331Uc first protrusion part (protrusion), 331Vc second protrusion (protrusion), A axial direction, C circumferential direction, R radial direction

Claims (9)

Comprising a rotor having a magnet and a stator,
The stator is
York and
a first coil fixed to the yoke and forming a first phase;
a second coil fixed to the first coil and forming a second phase;
Equipped with
radially, the second coil is adjacent to the first coil,
The first coil and the second coil form a magnetic circuit with the rotor.
motor. the first coil and the second coil are arranged side by side in the radial direction;
The motor according to claim 1. The first coil and the second coil are each formed of a single conductive member.
The motor according to claim 1 or 2. The first coil has a portion facing the rotor in the radial direction,
The portion has a first portion and a second portion,
In the axial direction, the first portion and the second portion are connected,
separated from the first portion and the second portion in the circumferential direction;
The motor according to claim 1 or claim 2. The first coil has a protrusion that protrudes from the yoke in the axial direction.
The motor according to claim 1 or claim 2. The second coil has a protrusion that protrudes from the yoke in the axial direction.
The motor according to claim 1 or claim 2. The second coil is fixed to the first coil via an insulating part.
The motor according to claim 1 or claim 2. In the axial direction, the size of the first coil is smaller than the size of the yoke.
The motor according to claim 1 or claim 2. In the axial direction, the size of the first coil is larger than the size of the rotor.
The motor according to claim 8.

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