JPH10341565A - 3-phase stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the reduction of the inductance of a stator pole winding, the reduction of a motor thickness and, further, the construction of a motor with 25 pairs of rotor poles. SOLUTION: A stator 1 has 9 poles P1, P2, P3,... which are radially arranged and 9 windings W1, W2, W3,... which are individually applied to the poles. A cylindrical permanent magnet 5 having rotor poles 5a, 5b,... whose number of pairs is P=9n+7 or P=9n+2 (wherein (n) denotes an integer other than 1) and which are arranged in a rotating direction (circumferential direction) is provided on the outer circumference of a rotor 2. At least one stator small teeth 4 are formed on the respective surfaces of the stator poles P1, P2,... which face the rotor 2. The respective windings W1, W2,... of the stator poles P1, P2,... are so connected to each other as to construct required 3 phases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a three-phase stepping motor having nine stator magnetic poles radially on a stator.

[0002]

2. Description of the Related Art Conventionally, as a three-phase stepping motor of this type, which uses a cylindrical permanent magnet magnetized with multiple poles (multiple poles) as a rotor magnetic pole, for example, a motor cross section shown in FIG. The one shown in the figure is known. In FIG. 11, the stator 1 of the three-phase stepping motor M has six stator magnetic poles P1, P2, which are radially arranged at an equal pitch.
P3, P4, P5, P6 and the stator magnetic poles P1, P2,
‥‥‥ P6 has six windings W1, W2, sequentially and separately.
‥‥‥ W6 is wound. The rotor 2 is rotatably arranged on the axis of the stator 1 together with the rotating shaft 3 and faces the stator magnetic poles P1, P2,... P6 via a gap. The outer circumferential surface of the rotor 2 has a rotor permanent magnet 5a formed by magnetizing and forming a rotor magnetic pole 5a of 16 pole pairs along the rotation direction (circumferential direction), ie, 32 poles of N and S poles alternately. A magnet 5 is provided. Further, stator small teeth 4 are disposed on the surfaces of the stator poles P1, P2,... P6 facing the rotor 2.

The winding W1 and the winding W4 are connected so as to have the same polarity to form the first phase, and the winding W2 and the winding W5 are similarly connected to form the second phase. And winding W
3 and the winding W6 are similarly connected to form a third phase to form a three-phase winding. Therefore, the basic step angle of the stepping motor M is 360 ° / (2 × the number of phases × the number of pole pairs), so that the basic step angle in the case of 3 phases and 16 pole pairs is 3.75 °. .

[0004]

However, the conventional three-phase stepping motor M has the following problems. (1) Since the number of windings per stator magnetic pole increases, the inductance increases. (2) Since the coil end becomes high, it is disadvantageous when the thickness is reduced.

(3) Since the number of stator teeth per stator magnetic pole is large, the width of the stator magnetic pole and the width of the back yoke need to be increased, and the effective winding space is reduced.
It is disadvantageous when considering a high torque. (4) When the number of stator poles is 6, the number of possible rotor poles is 12n ± 4 (where n is a positive integer of 1 or more), so that a pole number of 50 (pole pair number of 25) cannot be formed.

[0006] The present invention has been made in view of such a point,
An object of the present invention is to provide a three-phase stepping motor which solves the above-mentioned problems and has a lower stator pole winding inductance, a higher speed, and a lower thickness than conventional ones.

Another object of the present invention is to provide a three-phase stepping motor capable of configuring the number of rotor magnetic poles to 25.

[0008]

The configuration of the three-phase stepping motor of the present invention for achieving the above object is as follows.

(1) The stator has nine stator magnetic poles P1, P2, P3,.
8, P9, and nine windings W1, W2, W3,..., W8, W9 wound around the stator magnetic pole sequentially and individually, and the rotor is provided with a gap between the stator magnetic pole and the air gap. The number of pole pairs P = 9n + 7 or P
= 9n + 2 (where n is an integer equal to or greater than 1), and the stator pole has at least one stator tooth on a surface of the stator pole facing the rotor. W1 and the winding W3 are connected so as to have opposite polarities, and the winding W3 and the winding W8 are connected so as to have the same polarity to form a first phase. The winding W4 and the winding W6 have opposite polarities. The wire W6 and the winding W2 are connected to have the same polarity to form a second phase, and the winding W
7 and the winding W9 are connected in opposite polarities, and the winding W9 and the winding W5 are connected so as to have the same polarity to constitute a third phase.

(2) The stator has nine stator magnetic poles P1, P2, P3,.
8, P9, and nine windings W1, W2, W3,..., W8, W9 wound around the stator magnetic pole sequentially and individually, and the rotor is provided with a gap between the stator magnetic pole and the air gap. The number of pole pairs P = 9n + 7 or P
= 9n + 2 (where n is an integer equal to or greater than 1), and the stator pole has at least one stator tooth on a surface of the stator pole facing the rotor. W1, W5, and W6 are connected to have the same polarity to form a first phase, and windings W4, W8, and W9 are connected to have the same polarity to form a second phase. W2, W3
Are connected so as to have the same polarity to form a third phase.

(3) In the above (1) or (2), the rotor has a rotor magnetic pole having 16 pole pairs, and each of the stator magnetic poles has two stator small teeth. I do.

(4) In the above (1) or (2), the rotor has a rotor magnetic pole having 20 pole pairs, and each of the stator magnetic poles has two stator small teeth. I do.

(5) In the above (1) or (2), the rotor has a rotor magnetic pole having 25 pole pairs, and each of the stator magnetic poles has three stator teeth. I do.

(6) In the above (1) or (2), the rotor magnetic pole extends in the axial direction on a surface facing the stator magnetic pole, and has a cylindrical shape having 2P grooves arranged at an equal pitch. Permanent magnets, the permanent magnets are aligned such that the groove and the boundary line between the respective rotor magnetic poles coincide with each other.
It is characterized in that a plurality of poles are magnetized so that the poles are alternated.

Since the present invention is configured as described above, the number of turns per stator magnetic pole can be reduced, and the inductance of the winding can be reduced. For this reason,
The thinning of the stepping motor can be expected.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. (First Embodiment) FIGS. 1 to 5 show a first embodiment of the present invention, and show an optimum embodiment of a three-phase stepping motor M1 according to claims 1 to 3. FIG. FIG. 1 shows that a stator 1 and a rotor 2 of the stepping motor M1 are
2 and 5 are torque vector diagrams, and FIGS. 3 and 4 are connection diagrams of windings of stator magnetic poles constituting three phases.

Referring to FIG. 1, the three-phase stepping motor M1 comprises a stator 1 and a rotor 2 rotatably disposed on the axis of the stator 1 together with a rotating shaft 3. The stator 1 has nine stator magnetic poles P1, P2, P3,... P8, P8 arranged radially inward at equal pitches.
9 and the stator magnetic poles P1, P2,... P9, respectively, and in turn, nine windings W1, W2, W3,.
9 and the stator magnetic poles P1, P2,.
Two stator small teeth 4 are arranged on the surface of P9 facing the rotor 2 respectively.

The rotor 2 includes the stator magnetic poles P1, P2,
９ The number of pole pairs is 16 along the rotation direction (circumferential direction) on the outer peripheral surface opposed to P9 via a gap (that is, when n = 1 in the equation of the number of pole pairs P = 9n + 7, P = 16) In the rotor magnetic pole 5a, the N-pole and the S-pole are alternately arranged, and the 32-pole rotor magnetic pole 5a is arranged as a cylindrical permanent magnet 5 magnetized and formed in a rotating direction or a radial direction. Have been.

The angle (360 ° in electrical angle) between the N pole and the N pole or between the S pole and the S pole of the adjacent rotor magnetic poles 5a, 5a of the rotor 2 is defined by the rotor magnetic pole pitch τ _R.
Assuming that τ _R = 360 ° / P, τ _R = 22.5 °. Therefore, the adjacent stator magnetic poles P
1, P2, 角度 P9, the angle forming the center of the small group of stator teeth 4 is 360 ° / (9 × 22.5) in terms of the rotor magnetic pole pitch τ _R as a unit. , (16 /
9) Since τ _R , that is, (1 + 7/9) τ _R , each of the stator small teeth 4 and the rotor 2 provided on the inner peripheral surface of the stator magnetic poles P1, P2,. The deviation angles from the south pole are (0/9) τ _R , (7/9) τ _R ,
(5/9) τ _R , (3/9) τ _R , (1/9) τ _R ,
(8/9) τ _R , (6/9) τ _R , (4/9) τ _R ,
(2/9) is a τ _R. Here, (0/9) τ _R means a deviation angle of 0 °, meaning that the stator small teeth 4 and the south pole of the rotor 2 are just opposed, and (7/9) τ _R means 7/9 of the rotor magnetic pole pitch τ _R , that is, 360 ° × 7/9 = 280 ° in electrical angle.

Here, each of the stator windings W1, W2, W
Assuming that the torques generated when the .SIGMA.3, .SIGMA.W8, and W9 are individually excited are T1, T2, T3, .SIGMA.T8, and T9, respectively, as shown in FIG.
The torque vectors are out of phase by 40 ° in electrical angle.

Therefore, as shown in FIG.
The winding W3 and the winding W3 are connected to each other in opposite polarities, and the winding W3 and the winding W8 are connected so as to have the same polarity to each other to form a first phase. The winding W6 and the winding W2 are connected so as to have the same polarity to each other to form a phase II, and the winding W7 and the winding W9 are set to the opposite polarities, and the winding W9
And the winding W5 so as to have the same polarity with each other.
Assuming that the phase is I, the phase I (windings W8, W1, W3) and the phase II
Phase (winding W2, W4, W6) and phase III (winding W
5, W7, W9), the resultant torque vectors T (I), T (II), and T (II
I) has a phase of 120 ° in electrical angle as shown in FIG.

Further, the resultant torque vectors T '(I), T' (II), T '(II),
T ′ (III) is the resultant torque vector T (I), T (I
The vectors have a phase difference of 180 ° in electrical angle with respect to I) and T (III). For this reason, the combined torque vectors T (I), T '(III), and T (I
I), T '(I), T (III), T' (II). At this time, the rotor 2 rotates 60 degrees in electrical angle (60 degrees in mechanical angle, that is, 3.75 degrees), and a three-phase stepping motor having a basic step angle of 3.75 degrees can be configured.

Each of the windings W1, W2, W3,.
と し て As a connection method of W8 and W9, as shown in FIG.
The windings W1, W5, and W6 are connected to have the same polarity to form the first phase, and the windings W4, W8, and W9 are connected to have the same polarity to form the second phase. W3 may be connected to have the same polarity to form the third phase. The state of the torque vector in this case is shown in FIG. In this case as well, FIG.
As in the case of, the combined torque vectors T (I), T '(III), T (II),
T '(I), T (III), T' (II) can be generated,
A three-phase stepping motor having a basic step angle of 3.75 ° can be configured.

(Second Embodiment) FIGS. 6 to 8 show a second embodiment of the present invention, and show an optimum embodiment of a three-phase stepping motor M2 according to claims 1, 2 and 4. . FIG. 6 is a cross-sectional view of the stator 1 and the rotor 2 of the stepping motor M2 cut along a plane perpendicular to the rotation shaft 3. The same members as those in FIG. . However, the stator magnetic poles P1, P2, P
3, the number of pole pairs 20 (that is, the number of pole pairs P = 9n)
When n = 2 in the equation of +2, the rotor magnetic pole 5a of P = 20) is arranged as a magnetized and formed cylindrical permanent magnet 5 as in the first embodiment. ing.

In this case, the rotor magnetic pole pitch τ_RIs τ_R
= 360 ° / P, τ_R= 18 °. Accordingly
And the adjacent stator magnetic poles P1, P2,.
Angle forming the center of the group of stator small teeth 4 arranged at P9
Is the rotor pole pitch τ_RWhen the unit is 360
From ゜ / (9 × 18), (20/9) τ_RIe
(2 + 2/9) τ_RTherefore, the stator magnetic poles P1,
P2, ΔP9
The deviation angle between the stator small teeth 4 and the S pole of the rotor 2 is respectively
(0/9) τ_R, (2/9) τ_R, (4/9) τ_R,
(6/9) τ_R, (8/9) τ _R, (1/9) τ_R,
(3/9) τ_R, (5/9) τ_R, (7/9) τ_RIn
You. Where (0/9) τ_RMeans a deviation angle of 0 °,
The stator teeth 4 and the S pole of the rotor 2 must be exactly opposite.
Means (2/9) τ_RIs 36 in electrical angle
0 ° × 2/9 = 80 °
Means

Therefore, each of the stator windings W1, W
2, W3, ‥‥‥ W8, and W9 are individually excited to generate torques T1, T2, T3, ‥‥‥ T8,
Assuming that T9 is as shown in FIG. 7, the state is such that the torque vectors T1, T2, T3,... T8, T9 in FIG. 2 are reversed with the axis of the torque vector T1 as a symmetric axis.

Therefore, as shown in FIG. 3, each of the stator windings W1, W2, W3,... W8, W9 is connected, and the first phase (windings W8, W1, W3) and the II
Phase (winding W2, W4, W6) and phase III (winding W
5, W7, W9) are the combined torque vectors generated when a forward current is applied to T (I), T (II), and T (I
II), each torque vector has a phase of 120 ° in electrical angle as shown in FIG.

Also, the resultant torque vectors T '(I), T' (II),
T ′ (III) is the resultant torque vector T (I), T (I
The vectors have a phase difference of 180 ° in electrical angle with respect to I) and T (III). For this reason, the combined torque vectors T (I), T '(III), and T (I
I), T '(I), T (III), T' (II). At this time, the rotor 2 rotates by 60 ° in electrical angle (60 ° / 20 in mechanical angle, that is, 3 °), and a three-phase stepping motor having a basic step angle of 3 ° can be configured.

As in the first embodiment, the method of connecting the stator windings W1, W2, W3,... W8, W9 is as shown in FIG. , W6
Are connected to have the same polarity to form the first phase, and the windings W4 and W4
W8 and W9 are connected so that they have the same polarity to form phase II,
The windings W7, W2, W3 are connected so as to have the same polarity, and
It may be in phase III. FIG. 8 shows the state of the torque vector in this case. In this case as well, as in the case of FIG. 5, the resultant torque vectors T (I), T '(III), T (II), T' (I), T ( III),
T ′ (II) can be generated, and a three-phase stepping motor having a basic step angle of 3 ° can be configured.

(Third Embodiment) FIG. 9 shows a third embodiment of the present invention, and shows an optimum embodiment of the three-phase stepping motor M3 according to the first, second and fifth aspects. FIG.
Stator 1 and rotor 2 of the stepping motor M3
Is a cross-sectional view taken along a plane perpendicular to the rotating shaft 3, and the same members as those in FIG. 1 are denoted by the same reference numerals and description thereof will be omitted.

In FIG. 9, the stator 1 includes nine stator magnetic poles P1, P2, P3,... P8, P9, which are radially arranged inward at equal pitches. On the opposing surfaces, three stator small teeth 4 are arranged, respectively. The stator magnetic poles P1, P2,.
On the outer peripheral surface facing P9, along the rotation direction, the number of pole pairs is 25 (that is, in the equation of the number of pole pairs P = 9n + 7, n =
2, the rotor magnetic pole 5a (P = 25) is arranged as a magnetized and formed cylindrical permanent magnet 5 as in the first embodiment.

In this case, the rotor magnetic pole pitch τ _R is τ _R
= 360 ° / P, τ _R = 14.4 °. Therefore, the adjacent stator poles P1, P2,.
The angle that forms the center of the group of stator small teeth 4 arranged at ‥ P9 is 360 when the rotor magnetic pole pitch τ _R is the unit.
From DEG _{/(9×14.4), (25/9) τ R} , i.e. (2 + 7/9) because it is tau _R, the stator poles P
1, P2, the deviation angle between the S pole inside each provided on the peripheral surface of the stator teeth 4 and the rotor 2 of ‥‥‥ P9, respectively (0/9) τ _R, (7/9 ) Τ _R , (5/9)
τ _R , (3/9) τ _R , (1/9) τ _R , (8/9) τ
_R , (6/9) τ _R , (4/9) τ _R , (2/9) τ _R
This is the same as in the first embodiment.

Therefore, similarly to the first embodiment, as shown in FIG. 3, each of the stator windings W1, W2, W3,
The torque vector when W8 and W9 are connected is the same as in FIG. 2, and the torque vector when connected as shown in FIG. 4 is the same as in FIG. The resultant torque vector T rotating in a certain direction
(I), T '(III), T (II), T' (I), T (III), T '
(II) can occur. At this time, the rotor 2 has an electrical angle of 60 ° (mechanical angle of 60 ° / 25, that is, 2.4).
゜), so that a three-phase stepping motor having a basic step angle of 2.4 ° can be constructed.

FIG. 10 shows a rotor magnetic pole 5a according to claim 6.
FIG. 3 is a cross-sectional view of the cylindrical permanent magnet 5 taken along a plane perpendicular to the rotation shaft 3. Usually, when the cylindrical permanent magnet 5 is magnetized in many directions in the rotating direction, the width of each magnetic pole 5a depends on the accuracy of a magnetizer or the like, and there is a problem that high-accuracy magnetization cannot be performed. There was a demand for higher positioning accuracy of the motor.

FIG. 10 is a view for explaining one method for solving the above problem. For example, FIG. 10 is an enlarged sectional view of the cylindrical permanent magnet 5 in FIG. A rotor magnetic pole 5 having 16 pole pairs, extending in the direction of the rotation axis 3 on the outer peripheral surface facing P1, P2,.
a and 5a are magnetized and formed in the rotation direction.

At the boundary between the N pole and the S pole, there are formed 2P (P is the number of pole pairs) grooves 6 extending in the axial direction and arranged at equal pitches in the rotation direction. . The permanent magnets 5 are aligned so that the groove 6 and the boundary line between the respective rotor magnetic poles 5a coincide with each other. The poles are magnetized and formed. By doing so, the width of each of the magnetic poles 5a, 5a is determined by the accuracy of the molding die of the cylindrical permanent magnet 5, and higher accuracy is achieved.

The technique of the present invention is limited to the above embodiment.
For example, how to connect the stator pole windings
Can be connected in parallel rather than in series with three windings.
It is possible. In the connection diagram of FIG.
When W5 and W6 are connected in parallel and winding W1 is connected in series
It is also possible. 3 and FIG.
Is the point of the method of connecting the stator pole windings,
Phase I winding, Phase II winding and Phase III winding, respectively
It is shown separately, but when it is actually used,
Naturally, they are star-connected or delta-connected
It is. In addition, the stator small
Tooth arrangement pitch τ_SIs τ_S= Τ_RToshii
The vernier pitch (τ_S≠ τ _ROf course)
It is possible.

The rotor magnetic pole is not a multi-pole magnetized cylindrical permanent magnet, but a 2P rod-shaped permanent magnet formed and arranged in a cylindrical shape with its longitudinal direction being the axial direction. It is of course possible to perform multipolar magnetization. It is of course also possible for the stator to be arranged inside and the rotor to be arranged outside.

[0039]

As is apparent from the above description, according to the three-phase stepping motor of the present invention, the stator has nine stator magnetic poles radially arranged at an equal pitch and the stator magnetic poles , Having nine windings wound in order and each separately,
The rotor has a pair of poles P = 9n + 7 or P =
9n + 2 (where n is an integer of 1 or more) rotor magnetic poles are formed, and one or more stator small teeth are provided on a surface of the stator magnetic pole facing the rotor, and Since the wires are connected so as to form predetermined three phases, the number of windings per stator magnetic pole can be reduced, and the inductance can be reduced. Also, by reducing the number of windings per stator magnetic pole, the coil end is also reduced, which is advantageous for reducing the thickness of the motor and improving the speed of the motor.

Further, in the case of the specific number of pole pairs (16), the number of small teeth per stator magnetic pole can be reduced as compared with the conventional one, and the magnetic pole width can be narrowed. Similarly, the width of the back yoke can be reduced. Further, there is an effect that a three-phase stepping motor having 25 pole pairs can be configured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a three-phase stepping motor according to the present invention, showing a mutual relationship between a stator and a rotor thereof.

2 is a diagram showing torque vectors generated by the respective stator magnetic poles of FIG. 1 and three-phase torque vector diagrams based on the connection of FIG.

FIG. 3 is a connection diagram of magnetic pole windings constituting three phases.

FIG. 4 is another connection diagram of magnetic pole windings constituting three phases.

5 is a diagram illustrating torque vectors generated by the respective stator magnetic poles of FIG. 1 and three-phase torque vector diagrams based on the connection of FIG.

FIG. 6 is a sectional view showing a second embodiment of the three-phase stepping motor according to the present invention, and showing a mutual relationship between a stator and a rotor thereof.

7 is a diagram illustrating torque vectors generated by the respective stator magnetic poles of FIG. 6 and three-phase torque vector diagrams based on the connection of FIG.

8 is a diagram illustrating torque vectors generated by the respective stator magnetic poles of FIG. 6 and three-phase torque vector diagrams based on the connection of FIG. 4;

FIG. 9 is a cross-sectional view showing a third embodiment of the three-phase stepping motor according to the present invention, showing a mutual relationship between a stator and a rotor thereof.

FIG. 10 is an enlarged cross-sectional view of a rotor magnetic pole used in each embodiment of the three-phase stepping motor of the present invention, taken along a plane perpendicular to the rotation axis.

FIG. 11 is a cross-sectional view showing a mutual relationship between a stator and a rotor of a conventional three-phase stepping motor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Stator 2 Rotor 3 Rotation axis 4 Stator pole tooth 5 Permanent magnet 5a Rotor pole 6 Groove M, M1, M2, M3 Three-phase stepping motor P1, P2, P3, ‥‥‥ P8, P9 Stator pole T (I), T (II), T (III) Torque vector T '(I), T' (II), T '(III) Torque vector W1, W2, W3, ‥‥‥ W8, W9 Winding τ _R Rotor pole pitch

Claims (6)

[Claims] 1. The stator comprises nine stator poles P1, P2, P3,... P8, P8 arranged radially at equal pitches.
9, and nine windings W1, W2, W3,... W8, W9 wound around the stator magnetic pole in sequence and separately, and the rotor is interposed between the stator magnetic pole and the air gap. On the opposite surface,
Number of pole pairs along the rotation direction P = 9n + 7 or P = 9n
+2 (where n is an integer of 1 or more) rotor magnetic poles, the stator magnetic poles have one or more stator teeth on a surface facing the rotor, and the winding W1
The winding W3 and the winding W3 are connected so as to have the opposite polarity, and the winding W3 and the winding W8 are connected so as to have the same polarity to form a first phase. The winding W4 and the winding W6 have the opposite polarity. W6 and the winding W2 are connected so as to have the same polarity to form a second phase, so that the winding W7 and the winding W9 have the opposite polarity, and the winding W9 and the winding W5 have the same polarity. A three-phase stepping motor, wherein the three-phase stepping motor is connected to the third phase. 2. The stator comprises nine stator magnetic poles P1, P2, P3,... P8, P8 arranged radially at equal pitches.
9, and nine windings W1, W2, W3,... W8, W9 wound around the stator magnetic pole in sequence and separately, and the rotor is interposed between the stator magnetic pole and the air gap. On the opposite surface,
Number of pole pairs along the rotation direction P = 9n + 7 or P = 9n
+2 (where n is an integer of 1 or more) rotor magnetic poles, and the stator magnetic poles have at least one stator tooth on a surface facing the rotor, and the winding W
1, W5, and W6 are connected so as to have the same polarity to form a first phase, and the windings W4, W8, and W9 are connected so as to have the same polarity to form a second phase. A three-phase stepping motor, wherein W2 and W3 are connected to have the same polarity to form a third phase. 3. The rotor according to claim 1, wherein the rotor has a rotor magnetic pole having 16 pole pairs, and each of the stator magnetic poles has two stator teeth. Three-phase stepping motor. 4. The rotor according to claim 1, wherein the rotor has a rotor magnetic pole having 20 pole pairs, and each of the stator magnetic poles has two stator teeth. Three-phase stepping motor. 5. The method according to claim 1, wherein the rotor has a rotor magnetic pole having 25 pole pairs, and each of the stator magnetic poles has three stator small teeth. Three-phase stepping motor. 6. The rotor magnetic pole comprises a cylindrical permanent magnet extending in the axial direction on a surface facing the stator magnetic pole and having 2P grooves arranged at an equal pitch. The grooves are aligned so that the boundaries of the rotor magnetic poles coincide with each other, and a plurality of poles are magnetized so that N poles and S poles alternate with the grooves as boundaries. The three-phase stepping motor according to claim 1 or 2, wherein