JP2003324933A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a stepping motor having a stator provided with comb-tooth type outer poles facing the outer circumference of a rotor magnet and inner poles facing the inner circumference thereof in which the output is enhanced by reducing the cogging torque. <P>SOLUTION: Assuming the central angle of a sector defined by the center of the magnet and one outer pole is A, the number of magnetized poles of the magnet is n, the outside diametral dimension of the magnet is D1, and the inside diametral dimension of the magnet is D2, the central angle A is set to satisfy the following relation; (226.8/n)-54×(D1-D2)/(D1×π)≤A≤(259.2/ n)-54×(D1-D2)/(D1×π). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-phase stepping motor, and more particularly to the structure of a stepping motor for reducing cogging torque and increasing rotational output.

[0002]

2. Description of the Related Art A stepping motor having a small diameter about a rotary shaft and a high output is disclosed in Japanese Patent Laid-Open No. 9-33.
It is disclosed in Japanese Patent No. 1666.

FIG. 18 shows an exploded perspective view of a motor described in Japanese Patent Laid-Open No. 9-331666, and FIG. 19 shows a side sectional view of the motor.

Reference numeral 201 denotes a rotor composed of permanent magnets divided into four in the circumferential direction and alternately magnetized to different poles, 202 denotes a first coil arranged adjacent to each other in the axial direction of the rotor, 2
Reference numeral 03 denotes a second coil arranged adjacent to each other in the axial direction of the rotor, 204 denotes a first stator excited by the first coil and made of a soft magnetic material, and 205 denotes a soft magnetic material excited by the second coil. Is the second stator. The first stator 204 has a first outer magnetic pole 204A facing the outer peripheral surface of the rotor 201 with a gap, and a first inner magnetic pole 204B facing the inner peripheral surface of the rotor 201 with a gap.
The second stator 205 includes a second outer magnetic pole 205A that faces the outer peripheral surface of the rotor 201 with a gap, and a second inner magnetic pole 205B that faces the inner peripheral surface of the rotor 201 with a gap. There is. Reference numeral 206 denotes an output shaft to which the rotor 201 is fixed, and the bearing portion 204C of the first stator 204 and the bearing portion 20 of the second stator 205.
It is rotatably held at 5C. A connecting ring 207 is made of a non-magnetic material and holds the first stator 204 and the second stator 205 at a predetermined interval.

The first coil 202 and the second coil 203
To the first outer magnetic pole 204A, the first inner magnetic pole 204B, the second outer magnetic pole 205A, and the second outer magnetic pole 205A.
The polarity of the inner magnetic pole 205B is switched to rotate the rotor.

In this motor, the magnetic flux generated by energizing the coil flows from the outer magnetic pole to the opposing inner magnetic pole, or from the inner magnetic pole to the opposing outer magnetic pole, and the magnet is located between the outer magnetic pole and the inner magnetic pole. To work efficiently. Further, since the distance between the outer magnetic pole and the inner magnetic pole can be set to about the thickness of the cylindrical magnet, the resistance of the magnetic circuit formed by the outer magnetic pole and the inner magnetic pole can be reduced. The smaller the resistance of the magnetic circuit, the more magnetic flux can be generated with a smaller current, and the output is improved.

[0007]

20 is a sectional view taken along the line AA of FIG. 19 and FIG. 20 is a sectional view taken along the line BB of FIG.
Each is shown in (b). In the motor shown in FIGS. 20A and 20B, neither the first coil 202 nor the second coil 203 is energized.

When the magnet is moved from the state shown in FIGS. 20 (a) and 20 (b), the attraction force acting between the magnet and each magnetic pole is changed to cause cogging. If the influence of this cogging is large, there arises a problem that the motor cannot be started or the motor cannot be smoothly rotated even when each coil is energized to excite each magnetic pole.

That is, as in the motor shown in FIG. 18, even if the distance between the outer magnetic pole and the inner magnetic pole facing each other is shortened to reduce the resistance of the magnetic circuit, in order to improve the output of the motor, the influence of cogging is exerted. Needs to be kept small.

In view of this point, the present application intends to further improve the output by reducing the cogging of a stepping motor having a stator including an outer magnetic pole facing the outer side of the magnet and an inner magnetic pole facing the inner side of the magnet. This is an issue.

[0011]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present application provides a cylindrical magnet in which at least the outer peripheral surface is divided in the circumferential direction and alternately magnetized to different poles. A first coil and a second coil arranged on both sides of the magnet in an axial direction of the magnet, and a first outer side which is excited by the first coil and faces an outer peripheral surface of the magnet. A magnetic pole, a first magnet which is excited by the first coil and faces the inner peripheral surface of the magnet.
Is excited by the inner magnetic pole of the first coil and the second coil.
A second outer magnetic pole that faces the outer peripheral surface of the magnet at a portion different from the outer magnetic pole, and a second outer magnetic pole that is excited by the second coil and faces the inner peripheral surface of the magnet at a different portion than the first inner magnetic pole. A motor having two inner magnetic poles, wherein the first outer magnetic pole and the second inner magnetic pole are formed in a tooth shape divided into a plurality of circumferentially by notches, in a circumferential direction of the magnet. Assuming that the number of poles is n, the outer dimension of the magnet is D1, the inner diameter dimension of the magnet is D2, and the central angle of the fan shape formed by the center of the magnet and one outer magnetic pole is A, the central angle is (226. 8 / n) -54x (D1-D2) / (D1x)
π) ≦ A ≦ (259.2 / n) −54 × (D1-D2)
It is characterized by satisfying / (D1 × π).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS.

FIG. 1 is an exploded perspective view of a stepping motor. FIG. 2 is an axial sectional view of the stepping motor of FIG. 1 after assembly.

This stepping motor has a common configuration in most parts with the stepping motor shown in FIG. 18, but each component will be described again in detail.

Reference numeral 11 denotes a cylindrical magnet that constitutes a rotor. The magnet 11, which is the rotor, has its outer peripheral surface divided into n at equal intervals in the circumferential direction (n is an even number and in the present embodiment, 4). ) And magnetized portions 11A, 11B, 11C and 11D in which the south pole and the north pole are alternately magnetized. The magnetized portions 11A and 11C are S poles, and 11B and 11D are N poles.
It is a pole. The magnet 11 is composed of a plastic magnet formed by injection molding. Since it has a simple shape, it is easy to make it small and thin. In addition, no cracking occurs even if the assembly is performed by press fitting.

Reference numeral 17 denotes a rotor shaft which serves as an output shaft, and the rotor shaft 17 is fixed to the center of the inner diameter of the magnet 11.

12 and 13 are cylindrical coils,
The center part thereof coincides with the center part of the magnet 11,
The magnets 11 are arranged side by side in the axial direction. The outer diameters of the coils 12 and 13 are substantially equal to the outer diameter of the magnet 11.

Reference numeral 18 is a first stator, and 19 is a second stator, both of which are made of a soft magnetic material. First
The stator and the second stator have the same shape and are arranged so as to face each other such that the tips of the comb-shaped magnetic poles face each other. Further, the first stator and the second stator are arranged such that the phases of the comb-teeth-shaped magnetic poles are shifted from each other by 180 / n degrees, that is, by 45 °. The first stator and the second stator each have a structure in which the outer tubular portion and the inner tubular portion are connected at one end. The first stator 18 is excited by the first coil 12, and the second stator 19 is excited by the second coil 13. The first stator 18,
The second stator 19 is provided with comb-teeth-shaped magnetic poles that are divided into a plurality of pieces in the circumferential direction by cutting out the tips of the outer cylinder portion and the inner cylinder portion, and that are axially extended. There is. The outer tubular portion of the first stator 18 has outer magnetic poles 18A and 18B formed at its tip portion, and the inner tubular portion has inner magnetic poles 18C and 18D formed at its tip portion. Outer magnetic pole 18
A and 18B are formed to be shifted by 360 / (n / 2) degrees, that is, 180 degrees, and the inner magnetic pole 18C and the outer magnetic pole 18A,
The inner magnetic pole 18D is formed so as to face the outer magnetic pole 18D. The second stator 19 also has a similar outer magnetic pole 19A,
19B and inner magnetic poles 19C and 19D are formed.

The first coil 12 is located between the outer tubular portion and the inner tubular portion of the first stator 18 and near the connecting portion of these tubular portions.
The outer magnetic poles 18A and 18B and the inner magnetic pole 18C,
One end of the magnet 11 is sandwiched between the magnet 18 and 18D. The second coil 13 is arranged between the outer tubular portion and the inner tubular portion of the second stator 19 and near the connecting portion of these tubular portions, and between the outer magnetic poles 19A and 19B and the inner magnetic poles 19C and 19D. The other end of the magnet 11 is sandwiched between. That is, the outer magnetic pole 18A,
18B, 19A and 19B face the outer peripheral surface of the magnet 11, and the inner magnetic poles 18C, 18D, 19C and 19D face the inner peripheral surface of the magnet 11.

Reference numeral 20 is a cylindrical connecting ring. Grooves 20A and 20B are formed at one end of the inside of the connecting ring 20, and grooves 20C and 20D are formed at the other end thereof. , 20D are out of phase with the grooves 20A, 20B by 180 / n degrees, that is, by 45 degrees. The grooves 20A and 20B and the grooves 20C and 20D are formed with a predetermined distance in the axial direction.
The outer magnetic poles 18A and 18B are fitted to the grooves 20C and 20D.
The outer magnetic poles 19A and 19B are fitted to and fixed with an adhesive. By fixing the first stator 18 and the second stator 19 to the connecting ring 20, the first stator 18 and the second stator 19 can be arranged at desired positions and phases. Further, the coupling ring 20 is made of a non-magnetic material, can separate the magnetic circuit between the first stator 18 and the second stator 19, and has a configuration in which mutual magnetic poles are less likely to influence each other.

FIG. 3 is a sectional view taken along the line AA and the line BB in FIG. 2, and the rotation driving method of the motor will be described using this.

FIGS. 3A and 3E are cross-sectional views of the simultaneous points, and FIGS. 3B and 3F are cross-sectional views of the simultaneous points.
3C and 3G are cross-sectional views of the simultaneous points.
(D) And (h) is sectional drawing of a simultaneous point.

From the state shown in FIGS. 3 (a) and 3 (e), the coil 12 is
And 13 are energized to excite the outer magnetic poles 18A and 18B of the first stator 18 to the N pole and the inner magnetic poles 18C and 18D to the S pole, and the outer magnetic poles 19A and 19A of the second stator 19 are excited.
When the B pole is excited to the S pole and the inner magnetic poles 19C and 19D are excited to the N pole, the magnet 11, which is the rotor, rotates 45 degrees counterclockwise, and the states shown in FIGS. 3B and 3F are obtained.

Next, the current to the coil 12 is reversed and the first
The outer magnetic poles 18A and 18B of the stator 18 of FIG.
9 outer magnetic poles 19A, 19B are S poles, inner magnetic poles 19C,
When 19D is excited to the N pole, the magnet 1 which is the rotor
1 further rotates counterclockwise by 45 degrees and enters the state shown in FIGS. 3 (c) and 3 (g).

Next, the current to the coil 13 is reversed and the first
The outer magnetic poles 18A and 18B of the stator 18 of FIG.
9 outer magnetic poles 19A, 19B are N poles, inner magnetic poles 19C,
When 19D is excited to the S pole, the magnet 1 which is the rotor
1 further rotates counterclockwise by 45 degrees and enters the state shown in FIGS. 3 (d) and 3 (h).

Thereafter, the coil 12 and the coil 1 are processed in this manner.
By sequentially switching the energizing directions to the magnets 3, the magnet 11, which is the rotor, sequentially rotates to the position corresponding to the energizing phase.

If not only the outer peripheral surface of the magnet but also the inner peripheral surface of the magnet are circumferentially divided and magnetized, the output of the motor can be further increased.

Further, two magnetizing layers, which are formed by dividing the outer peripheral surface of the magnet in the circumferential direction, are provided in the axial direction, and one magnetizing layer facing the first first stator 118 and the second stator. The other magnetizing layer facing 19 has a phase of 180 / n.
The phases of the first stator 18 and the second stator 19 may be made to be the same by shifting the phases.

The inner magnetic poles 18C, 18D, 19C,
19D may be a simple cylindrical shape without forming a notch.

When the coils 12 and 13 are not energized, the magnet 11 is held at a position where the attraction force acting between the first stator 18, the second stator 19 and the magnet 11 is stable. It FIG. 4 shows the relationship between the suction force and the rotational position of the rotor. FIG. 4 shows the relationship between the first stator 18 and the magnet, but the second
The relationship between the stator 19 and the magnet 19 is also the same. In practice, the first stator 18 and the second stator 1
It is 180 / n degrees out of phase with 9, and the combined magnetic force acts on the magnet 11.

The horizontal axis of FIG. 4 shows the position of the magnet 11 with respect to the first stator 18, that is, the rotational phase,
The vertical axis represents the magnetic force acting between the first stator 18 and the magnet 11.

At the positions indicated by points E1 and E2, if a forward rotation is attempted, a negative force acts to return to the original position, and if a reverse rotation is attempted, a positive force acts to return to the original position. The position. That is, it is the cogging position where the magnet 11 is stably positioned at the E1 point or the E2 point by the magnetic force acting between the magnet 11 and the first stator 18.

The positions indicated by the points F1, F2, and F3 are E before and after the rotation phase of the magnet 11 is slightly deviated.
It is a position in an unstable equilibrium state in which a force that tries to rotate acts on the position of point 1 or point E2.

When the coil 12 is not energized, the magnet 11 does not stop at the points F1, F2 and F3, but stops at the points E1 and E2. The points at which the magnet is stable against cogging such as points E1 and E2 exist at a cycle of 360 / n degrees when the magnetizing number of the magnet is n, and the intermediate position is F.
Magnets such as 1 point, F2 point, and F3 point are unstable points.

As a result of the numerical simulation by the finite element method, the central angle of the fan shape (hereinafter referred to as the central angle of the magnetized portion of the magnet) composed of the center of the magnet and one magnetized portion of the magnet, and the center of the magnet In accordance with the relationship between the fan-shaped central angle (which is indicated by A in FIG. 3 and is hereinafter referred to as the central angle of the outer magnetic pole) composed of one and one outer magnetic pole, the coil is not energized. It was revealed that the attraction state between the stator and the magnet changed.

When the central angle of the outer magnetic pole is smaller than the predetermined value, the magnet is stably held at the magnetized portion of the magnet, that is, the position where the center of the pole faces the center of the outer magnetic pole. It can be said that points E1 and E2 in FIG. 4 are positions where the center of the pole of the magnet faces the center of the outer magnetic pole.

On the contrary, when the central angle of the outer magnetic pole is larger than the predetermined value, the boundary of the magnetized portion of the magnet, that is,
The magnet is stably held at the position where the boundary between the poles faces the center of the outer magnetic pole. This is point E1 in Figure 4,
It can be said that the point E2 is the position where the boundary between the poles of the magnet faces the center of the outer magnetic pole.

As a result of further simulation, by changing the relationship between the thickness of the magnet and the outer peripheral length of the magnetized portion of the magnet with respect to the central angle of the magnetized portion of the magnet and the central angle of the outer magnetic pole, cogging is performed. It was found that

Simulation results are shown in FIGS. In these figures, the horizontal axis represents the rotation angle of the magnet and the vertical axis represents the cogging torque. Simulation when the center angle of the outer magnetic pole of each stepping motor is set to about 0.5 times, about 0.6 times, about 0.7 times, and about 0.8 times the center angle of the magnetized portion of the magnet The result.

In FIG. 5, the number of magnetized poles is 10, the outer diameter of the outer magnetic pole is 6.00 mm, and the outer diameter of the magnet is 4.80.
mm, the inner diameter of the magnet is 3.80 mm, the stepping motor has a central angle of the outer magnetic pole of 18 degrees,
It is a simulation result at 22 degrees, 25 degrees, and 29 degrees.

In FIG. 6, the number of magnetized poles is 20, the outer diameter of the outer magnetic pole is 10.90 mm, and the outer diameter of the magnet is 10.
The stepping motor has a magnet inner diameter of 9.00 mm and a magnet inner diameter of 9.00 mm.
It is a simulation result when it was 11 degrees, 13 degrees, and 14 degrees.

In FIG. 7, the number of magnetized poles is 20, the outer diameter of the outer magnetic pole is 11.50 mm, and the outer diameter of the magnet is 10.
A stepping motor having a magnet inner diameter of 60 mm and a magnet inner diameter of 9.60 mm, with the outer magnetic pole having a central angle of 9 mm.
It is a simulation result when it was 11 degrees, 13 degrees, and 14 degrees.

In FIG. 8, the number of magnetized poles is 20, the outer diameter of the outer magnetic pole is 11.90 mm, and the outer diameter of the magnet is 11.
The stepping motor has a magnet inner diameter of 00 mm and a magnet inner diameter of 10.00 mm, and the center angle of the outer magnetic pole is 9 mm.
It is a simulation result when it was 11 degrees, 13 degrees, and 14 degrees.

In FIG. 9, the number of magnetized poles is 20, the outer diameter of the outer magnetic pole is 12.90 mm, and the outer diameter of the magnet is 12.
The stepping motor has a magnet inner diameter of 00 mm and a magnet inner diameter of 11.00 mm.
It is a simulation result when it was 11 degrees, 13 degrees, and 14 degrees.

In FIG. 10, the number of magnetized poles is 20, the outer diameter of the outer magnetic pole is 11.90 mm, and the outer diameter of the magnet is 1.
1.00 mm, magnet inner diameter 10.40 mm
The stepping motor is a simulation result when the center angles of the outer magnetic poles are 9 degrees, 11 degrees, 13 degrees, and 14 degrees.

In FIG. 11, the number of magnetized poles is 20, the outer diameter of the outer magnetic pole is 11.90 mm, and the outer diameter of the magnet is 1.
The simulation results are for a stepping motor having a magnet inner diameter of 1.00 mm and a magnet inner diameter of 9.80 mm, and the outer magnetic poles having central angles of 9, 11, 13, and 14 degrees.

In FIG. 12, the number of magnetized poles is 12, the outer diameter of the outer magnetic pole is 11.90 mm, and the outer diameter of the magnet is 1.
1.00mm, inner diameter of magnet is 10.00mm
The stepping motor is a simulation result when the central angles of the outer magnetic poles are 15 degrees, 18 degrees, 21 degrees, and 24 degrees.

In FIG. 13, the number of magnetized poles is 24, the outer diameter of the outer magnetic pole is 11.90 mm, and the outer diameter of the magnet is 1.
1.00mm, inner diameter of magnet is 10.00mm
The stepping motor is a simulation result when the central angles of the outer magnetic poles are 8 degrees, 9 degrees, 11 degrees, and 12 degrees.

From the simulation results shown in FIGS. 5 to 13, the thickness of the magnet, the outer peripheral length of the magnetized portion of one pole of the magnet, the center angle of the outer magnetic pole, and the cogging torque of each stepping motor are approximately the minimum. FIG. 14 shows a plot of the relationship between the central angles of the magnetized portions of the magnet. The horizontal axis of FIG. 14 is (magnet thickness) / (perimeter of magnetized portion of magnet), and the vertical axis is (center angle of outer magnetic pole) / (center angle of magnetized portion of magnet).

For example, the stepping motor shown in FIG. 5 has 10 magnetic poles and an outer diameter of 6.00 m.
m, the outer diameter of the magnet is 4.80 mm, and the inner diameter of the magnet is 3.80 mm, so the thickness of the magnet is (4.80-3.80) / 2 mm, and the outer circumference of one pole of the magnetized portion is 4.80. Since it is × π / 10 mm, the value on the horizontal axis is 0.
It becomes 332. Further, it can be read from FIG. 5 that the center angle of the outer magnetic pole when the cogging torque is approximately the minimum is about 21.0 degrees, and the center angle of the magnetized portion of the magnet at this time is 360/10 degrees. , The value on the vertical axis is 0.
58.

Further, the stepping motor shown in FIG.
The number of magnetized poles is 20, and the outer diameter of the outer pole is 10.90m
m, the outer diameter of the magnet is 10.00 mm, and the inner diameter of the magnet is 9.00 mm. Therefore, the thickness of the magnet is (10.00-9.00) / 2 mm, and the outer circumference of one pole of the magnetized portion is 10.00. Since it is × π / 20 mm, the value on the horizontal axis is 0.318. Further, the center angle of the outer magnetic pole when the cogging torque is approximately the minimum is 10.7 from FIG.
It can be read that it is about a degree, and the central angle of the magnetized portion of the magnet is 360/20, so the value on the vertical axis is 0.5.
It becomes 9.

In FIG. 14, the point at which the cogging torque is approximately minimum for each stepping motor is the straight line 1 approximated by the equation Y = -0.3X + 0.63, where X is the horizontal axis and Y is the vertical axis. = −0.3X + 0.72 exists in a region sandwiched by the line 2 approximated by the equation.

Range below straight line 1, ie, Y <-0.3X
In the area of +0.63, the magnet is stably held at the position where the center of the pole of the magnet faces the center of the outer magnetic pole, and the area above the straight line 2, that is, Y> -0.3X + 0.7.
In region 2, the magnet is stably held at the position where the boundary between the poles of the magnet faces the center of the outer magnetic pole.

The area between the straight line 1 and the straight line 2 is -0.
3X + 0.63 ≦ Y ≦ −0.3X + 0.72,
If the central angle of the outer magnetic pole is A degrees, the number of magnetic poles is n, the outer diameter of the magnet is D1, and the inner diameter of the magnet is D2, then (226.8 /) − 54 × (D1−D2) / ( D1 x
π) ≦ A ≦ (259.2 / n) −54 × (D1-D2)
It can be expressed as / (D1 × π). For example, in the case of the stepping motor shown in FIG. 5, the central angle A of the outer magnetic pole is 19.10 degrees ≦
If the condition of A ≦ 22.34 degrees is satisfied, the cogging torque can be minimized.

When the shape of the outer magnetic pole is not constant but is, for example, a tapered shape in which the central angle gradually changes,
It suffices that the average central angle of the portion of the outer magnetic pole facing the magnet satisfies the above condition. That is, of the parts of the outer magnetic pole facing the magnet, the central angle near the root is 24
When the center angle near the tip is 20 degrees, the average center angle is 22 degrees, so that the cogging torque can be suppressed to a small value.

FIGS. 15 to 17 show a comparison of the cogging torque of the stepping motor in which only the central angle A of the outer magnetic pole is different from the torque generated when a voltage of 3 V is applied between the coil terminals. Show. In these figures,
The horizontal axis represents the rotation angle of the magnet, and the vertical axis represents the torque.

The stepping motor used in FIGS. 15 to 17 has 16 magnetic poles, the outer diameter of the magnet is 10.6 mm, the inner diameter of the magnet is 9.8 mm, and the outer diameter of the outer magnetic pole is 11.6 mm. Inner diameter of magnetic pole is 11.1 m
m, the outer diameter of the inner magnetic pole is 9.3 mm, the inner diameter of the inner magnetic pole is 8.8 mm, the resistance value of the coil is 10Ω, and the number of turns is 1.
It's 12 turns.

According to the above conditional expression, the central angle A of the outer magnetic pole of this stepping motor is 12.88≤A≤14.9.
If it is set to 0, the cogging torque should be able to be kept small.

In FIG. 15, the central angle of the outer magnetic pole is 10.35.
16, the central angle of the outer magnetic pole is 13.45 degrees, and FIG.
Indicates the cogging torque of the stepping motor in which the central angle of the outer magnetic pole is set to 15.52 degrees. It can be seen that when the central angle of the outer magnetic pole is changed, there is no great difference in the generated torque when 3 V is applied, but a large difference is generated in the cogging torque. FIG. 16 shows that the cogging torque is most stable, and the central angle of the outer magnetic pole of this stepping motor satisfies the above condition.

The stepping motor satisfying the above condition is very effective as a driving source for driving a lens of an optical device such as a camera.

[0061]

As described above, the first stator including the outer magnetic pole facing the outer peripheral surface on one end side of the magnet and the inner magnetic pole facing the inner peripheral surface, and the outer side facing the outer peripheral surface on the other end side of the magnet. In a stepping motor having a magnetic pole and a second stator composed of an inner magnetic pole facing the inner peripheral surface, by setting the central angle of the outer magnetic pole with respect to the center of the magnet to a value within a predetermined condition, The cogging torque can be suppressed to the minimum and the output can be increased.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a stepping motor according to an embodiment of the present invention.

2 is an axial sectional view of the stepping motor of FIG. 1 after assembly.

FIG. 3 is a radial cross-sectional view of the stepping motor of FIG.

FIG. 4 is a diagram showing the relationship between the attraction force acting between the stator and the magnet and the rotational position of the rotor.

FIG. 5 is a diagram showing simulation results of cogging torque of a stepping motor.

FIG. 6 is a diagram showing a simulation result of cogging torque of a stepping motor.

FIG. 7 is a diagram showing a simulation result of cogging torque of a stepping motor.

FIG. 8 is a diagram showing a simulation result of cogging torque of a stepping motor.

FIG. 9 is a diagram showing a simulation result of cogging torque of a stepping motor.

FIG. 10 is a diagram showing simulation results of cogging torque of a stepping motor.

FIG. 11 is a diagram showing a simulation result of cogging torque of a stepping motor.

FIG. 12 is a diagram showing a simulation result of cogging torque of a stepping motor.

FIG. 13 is a diagram showing a simulation result of cogging torque of a stepping motor.

FIG. 14 is a diagram in which the conditions under which the cogging torque is approximately minimum are plotted from the simulation results shown in FIGS. 5 to 13.

FIG. 15 is a diagram showing cogging torque when the central angle of the outer magnetic pole does not satisfy a predetermined condition.

FIG. 16 is a diagram showing cogging torque when the central angle of the outer magnetic pole satisfies a predetermined condition.

FIG. 17 is a diagram showing cogging torque when the central angle of the outer magnetic pole does not satisfy a predetermined condition.

FIG. 18 is an exploded perspective view of a conventional stepping motor.

FIG. 19 is an axial sectional view of the stepping motor of FIG. 18 after assembly.

FIG. 20 is a radial cross-sectional view of the motor of FIG. 19 when the coil is not energized.

[Explanation of symbols]

11,201 magnet 12,202 First coil 13,203 Second coil 17,206 Output shaft 18,204 First stator 19,205 Second stator 20,207 Connection ring

Claims (2)

[Claims] 1. A cylindrical magnet having at least an outer peripheral surface divided in the circumferential direction and alternately magnetized to different poles, and a first coil arranged on both sides of the magnet in the axial direction of the magnet. And a second coil, a first outer magnetic pole that is excited by the first coil and faces the outer peripheral surface of the magnet, and a first outer magnetic pole that is excited by the first coil and faces the inner peripheral surface of the magnet. The inner magnetic pole and the second
Of the second outer magnetic pole that is excited by the first coil and is opposed to the outer peripheral surface of the magnet at a portion different from that of the first outer magnetic pole, and a portion that is excited by the second coil and is different from the first inner magnetic pole. A second member that faces the inner peripheral surface of the magnet
An inner magnetic pole, wherein the first outer magnetic pole and the second inner magnetic pole are formed in a tooth shape in which a plurality of them are circumferentially divided by a notch. If the number is n, the outer dimension of the magnet is D1, the inner diameter of the magnet is D2, and the central angle of the fan shape formed by the center of the magnet and one outer magnetic pole is A, the central angle is (226.8). / N) -54x (D1-D2) / (D1x
π) ≦ A ≦ (259.2 / n) −54 × (D1-D2)
A motor characterized by satisfying / (D1 × π). 2. An optical device using the stepping motor according to claim 1 as a driving source for driving a lens.