JPH09131040A - Longitudinally arranged vr-type stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a longitudinally arranged VR-type stepping motor, which can reinforce torque without increasing detent torque. SOLUTION: In a longitudinally arranged VR-type stepping motor, a permanent magnet 5 is provided so as to face the side surface of the circumferential direction of a pole tooth 163 of a stator core 16, and a permanent magnet 6 is provided so as to face the side surface of the circumferential direction of a pole tooth 323. Then, the magnetic pole surfaces of the permanent magnets 5 and 6 are provided so as to face the side surfaces of the circumferential direction of the pole teeth 163 and 323. The magnetic pole surfaces are magnetized in the same polarity as the pole tooth 163 and 323. In this way, the magnetic fluxes, which are outputted from and inputted into the side surfaces of the circumferential direction of the pole teeth 163 and 323 can be decreased. Therefore, the torque is improved, and the magnetic pole surfaces of the permanent magnets 5 and 6 are not exposed to the facing pole teeth. Thus, the increase in detent torque can be disregarded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a column-arranged VR stepping motor, and more particularly to increasing the output thereof.

[0002]

2. Description of the Related Art Since VR type stepping motors can ignore detent torque, they are often used in applications where the presence of detent torque is not desirable, such as actuators that return to the origin by a spring or the like. However,
VR type stepping motors are PM type or H type with the same physical structure.
It has a slightly lower output than the B type stepping motor,
The improvement is desired.

Japanese Unexamined Patent Publication (Kokai) No. 3-15259 discloses an HB stepping motor in which a magnet is embedded around the pole teeth of a stator core or a rotor core to reduce the leakage flux (ineffective flux) of the pole teeth and increase the output. It is proposed that Further, JP-A-62-185552 and JP-A-2-111252 disclose a leakage magnetic flux (ineffective magnetic flux) of a pole tooth by embedding a magnet around the pole tooth of a stator core or a rotor core in an HB type stepping motor. ) Is reduced to increase the output.

[0004]

However, the permanent magnets disposed on the side of the pole teeth of the stator (or rotor) in order to reduce the above-mentioned leakage flux are the rotor (or stator).
Since the surface facing the magnetic pole is magnetized so as to become a magnetic pole surface, the magnetic force generated by the permanent magnet for reducing the leakage magnetic flux acts on the pole teeth of the rotor to cause detent torque, which may increase or increase the problem. there were.

The present invention has been made in view of the above problems, and an object thereof is to provide a cascade-arranged VR stepping motor capable of improving torque while suppressing detent torque.

[0006]

According to a first aspect of the present invention, a column arrangement V is formed by arranging a plurality of phase units having a so-called claw pole structure stator core in series in the axial direction.
In the R-type stepping motor, permanent magnets are arranged so as to face (including the case of being adhered to) the circumferential side surfaces of the pole teeth of the stator core. Then, the surface of the permanent magnet facing the circumferential side surface of the pole tooth is magnetized to have the same polarity as the pole tooth.

By doing so, the magnetic flux flowing in and out of the circumferential side surfaces of the pole teeth can be reduced, so that the magnetic field strength at the main magnetic pole surface of the pole teeth of the stator core (the main surface that can face the main magnetic pole surface of the rotor core). And the magnetic field strength between the two adjacent pole teeth of the stator core increases, the amount of change in magnetic flux penetrating the pole teeth of the rotor core per unit rotation angle increases, and the magnetic flux change per unit rotation angle increases. The torque increases in proportion to the quantity.

Further, the advantage of the above-mentioned permanent magnet magnetization method is that since the magnetic pole surface of the permanent magnet is formed so as to face or contact the circumferential side surface of the pole teeth of the stator core, the magnetic pole surface of this permanent magnet is the magnetic pole surface of the rotor core. Permanent magnets to the rotor teeth of the rotor core, either because they are away from the teeth or because the area of the rotor core facing the pole teeth is very small, or because the magnetic flux of the permanent magnet is shorted by the stator core without penetrating the pole teeth of the rotor core. The influence of the magnetic pole surface of is extremely small or becomes a negligible level, so that the detent torque can be greatly reduced to zero.

According to a second aspect of the present invention, in a VR type stepping motor having a cascade arrangement in which a plurality of phase units each having a rotor core having a so-called claw pole structure are continuously arranged in an axial direction, a circumferential side surface of pole teeth of the rotor core is provided. The permanent magnets are arranged facing each other (including the case where they are adhered). Then, the surface of the permanent magnet facing the circumferential side surface of the pole tooth is magnetized to a polarity equal to the polarity induced in the pole tooth.

With this configuration, the magnetic flux flowing in and out of the circumferential side surfaces of the pole teeth of the rotor core can be reduced, so that the main magnetic pole surface of the pole teeth of the rotor core (the main surface that can face the main magnetic pole surface of the stator core) can be reduced. The amount of change in magnetic flux per unit rotational angle that goes in and out increases, and the torque proportional to the amount of change in magnetic flux per unit rotational angle increases. Further, the advantage of the permanent magnet magnetizing method described above is that since the magnetic pole surface of the permanent magnet is formed so as to face or contact the circumferential side surface of the pole teeth of the rotor core, the magnetic pole surface of this permanent magnet is separated from the pole teeth of the stator core. Because of the extremely small area facing the pole teeth of the stator core, or because the magnetic flux of the permanent magnet is short-circuited by the rotor core without penetrating the pole teeth of the stator core, the pole surface of the permanent magnet with respect to the pole teeth of the stator core. Is extremely small or can be ignored, so that the detent torque can be greatly reduced to zero.

According to a third aspect of the invention, in the means of the first and second aspects, the magnetic shield portion is disposed close to the circumferential side surfaces of the pole teeth of both the stator core and the rotor core. Therefore, it is possible to further improve the torque. According to a fourth aspect of the present invention, in addition to the first aspect, the magnetic shield portion and the second magnetic shield portion adjacent to the first pole tooth are further provided.
Since it has an axial support portion made of a permanent magnet that connects the magnetic shield portions close to the pole teeth of the above and strengthens the residual magnetic field of these magnetic shield portions, another magnetic pole surface that causes detent torque may occur. In addition, since the magnetic field of the permanent magnet can be magnetically short-circuited by the stator core, the detent torque can be set to 0 and the torque can be improved.

According to the means of claim 5, in the means of claim 1, the magnetic shield part adjacent to the third pole tooth and the magnetic shield part adjacent to the fourth pole tooth are connected to each other. Since there is an axial support portion made of a permanent magnet that strengthens the residual magnetic field of these magnetic shield portions, there is no other magnetic pole surface that causes detent torque, and the magnetic field of this permanent magnet is magnetically generated by the rotor core. Therefore, the detent torque can be reduced to 0 and the torque can be improved.

According to the means of claim 6, claim 4 or 5
Furthermore, in the described means, the magnetic shield portion and the axial support portion are connected by the circumferential support portion extending in the circumferential direction, so that the magnetic shield portion and the axial support portion can be formed in a cylindrical shape as a whole, and the structure and the assembly can be simplified. it can. According to the means of claim 7, in the means of claim 6, the torque is increased because the circumferential support portion is magnetized in a direction to reduce the leakage flux coming in and out from the axial side surface of the pole tooth. You can

According to the eighth aspect of the present invention, in a vertical arrangement VR type stepping motor in which a plurality of phase units are continuously arranged in the axial direction, interphases provided in an axial gap between a pair of adjacent phase units. Since the magnetic shield part moves in and out from the axial end faces of the pole teeth, the torque increases. Further, since this interphase magnetic shield has a magnetic pole surface that faces the axial end faces of the pole teeth and suppresses the magnetic flux entering and exiting from the end faces, this magnetic pole face almost eliminates the detent torque as in the first and second embodiments. It can be zero.

According to the means of claim 9, in the means of claim 8, the interphase magnetic shield portion is formed in the shape of a wheel plate, so that the ring-shaped interphase magnetic shield portion is magnetized over the entire circumference. The detent torque can be made zero.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below based on Examples. (Embodiment 1) FIG. 1 shows an axial sectional view of a VR type stepping motor having a four-phase tandem arrangement, and FIG.

This stepping motor has a housing 2 in which a stator 1 is fixed to the inner peripheral surface. The housing 2 includes a resin-molded case 21 having a bottomed cylindrical shape with a flange, and a cover plate 22 that is fixed to a flange portion of the case 21 by a fastening screw (not shown) and closes the opening of the case 21. The bottom of 21 and the cover plate 22 rotatably support the rotating shaft 4 to which the rotor 3 is fixed.

The stator 1 is composed of four phase stators 11 to 14 arranged axially in a row on the inner circumference of the case 21, and a non-magnetic spacer 15 made of a resin wheel plate is provided between the phase stators 11 to 14. Is installed. Phase stator 11
14 are claw pole type stator cores 16 respectively.
Has a shape surrounding the stator coil 17. A resin 18 is filled between the stator core 16 and the stator coil 17 when molding the case 21 with the stator core 16 inserted.

The stator core 16 is composed of a left core portion 16a and a right core portion 16b which are mirror images of each other, and both core portions 16a and 16b are wheel-shaped main portions 161.
And an outer protrusion 162 axially extending in a ring shape so as to wrap the stator coil 17 from the outer peripheral portion of the main portion 161.
The main portion 161 is composed of a plurality of pole teeth 163 which are provided so as to project radially inward from the inner periphery at regular intervals in the circumferential direction. The pole tooth 163 of the left core portion 16a constitutes the first pole tooth in the present invention, and the pole tooth 163 of the right core portion 16b constitutes the second pole tooth in the present invention.

Each of the phase stators 11 to 14 has a cylindrical permanent magnet 5 which will be described later and is located between a pair of adjacent pole teeth 163. The rotor 3 includes a cylindrical resin cylindrical body 31 fixed to the rotating shaft 4 and the resin cylindrical body 3
1. Four rotor cores 3 that are axially cascaded on the outer periphery of 1
2, a non-magnetic spacer 33 made of a resin wheel plate is interposed between the rotor cores 32.

The rotor core 32 has a claw pole shape, and the rotor core 32, the non-magnetic spacer 33 and a permanent magnet 6 which will be described later are inserted into a mold, and resin is injected to form the resin cylindrical body 31. By molding, the rotor core 32 and the like are fixed to the resin cylindrical body 31. The rotor core 32 is composed of a left core portion 32a and a right core portion 32b which have a mirror image relationship with each other.
The reference numeral 32b includes a cylindrical main portion 321 and a plurality of pole teeth 323 projecting from the inner circumference on the outer side in the axial direction of the main portion 321 radially inward at regular intervals in the circumferential direction. Pole teeth 3 of the left core portion 32a
Reference numeral 23 denotes the third pole tooth in the present invention, and the right core portion 32
The pole tooth 323 of b constitutes the fourth pole tooth in the present invention.

Each rotor core 32 has a cylindrical permanent magnet 6 which will be described later and is located between a pair of adjacent pole teeth 323. Pole teeth 323 of the rotor core 32
Of the pole teeth 163 of the stator core 16 on the radially outer side.
5 can be faced with a small radial gap.

Next, the permanent magnets 5 and 6 will be described with reference to the partial plan view of FIG. 3 and the perspective view of FIG. Since the permanent magnet 6 has a similar shape except that it has a smaller diameter than the permanent magnet 5 and has the same arrangement, only the permanent magnet 5 is shown in FIGS. 3 and 4 in order to avoid redundant description. And explain. The pole teeth 163 of the left core portion 16a are
They are arranged at equal angular positions in the circumferential direction with the pole teeth 163 of b, that is, are arranged side by side in the axial direction, and are magnetized as N poles or S poles during the period in which the stator coil 17 is energized. In FIG. 3, the upper pole tooth 163 is the pole tooth of the left core portion 16a magnetized to the N pole, and the lower pole tooth 163 is the pole tooth of the right core portion 16b magnetized to the S pole. . The pole tooth 163 has a magnetic pole surface 165 oriented in the radial inward direction, that is, a direction facing the pole tooth 323, a pair of circumferential side surfaces 166, an axial inner surface 167, and an axial outer surface 168. ing.

The permanent magnet 5 has a magnetic pole surface 50 facing the circumferential side surfaces 166 of the bipolar teeth 163 in FIG. 3, and a pair of upper and lower magnetic shield portions 51 and an axial direction connecting the magnetic shield portions 51 in the axial direction. The support portion 52 and the circumferential support portion 53 that connects the axial support portions 52 in the circumferential direction are formed into a cylindrical shape as a whole (see FIG. 4). The magnetic pole surface 50 facing the circumferential side surface 166 of the pole tooth 163 which becomes the N pole when the stator coil 17 is energized is magnetized to the N pole,
Pole teeth 16 that become S poles by energizing the stator coil 17
The magnetic pole surface 50 facing the circumferential side surface 166 of No. 3 is magnetized to the S pole. Further, the magnetic pole surface 54 facing the axially inner side surface 167 of the pole tooth 163 that becomes the N pole when the stator coil 17 is energized is magnetized to the N pole, and the pole tooth that becomes the S pole when the stator coil 17 is energized. The magnetic pole surface 54 facing the axially inner side surface 167 of 163 is magnetized to the S pole. Such magnetization (magnetization) is performed by applying a DC magnetic field to the permanent magnet 5 in its axial direction. Such magnetization can be performed by the permanent magnet 5 alone, or by applying a DC magnetic field in the axial direction to the entire motor after the permanent magnet 5 or the permanent magnet 6 described later is assembled. Further, with the rotor 3 removed or with the rotor 3 provided, a large current is instantaneously applied to each stator coil 17 in the direction opposite to the driving direction to form a magnetic field.
Can also be performed by magnetizing in the opposite direction.

The pole teeth 16 of each phase stator 11-14
3 or the pole teeth 323 of the rotor 3 are
The rotor 3 is displaced by 4 pole tooth pitches in the circumferential direction, and if the four stator coils 17 are sequentially energized, the rotor 3 rotates by 1/4 pole tooth pitch each time the energization is switched. Next, the torque increasing action of the permanent magnets 5 and 6 which characterizes the present embodiment will be described.

(Explanation 1) FIG. 5 does not include the permanent magnets 5 and 6,
Therefore, the pole face 165 of the pole tooth 163 of the stator core 16 is
Of the magnetic flux Φ2 between the magnetic pole surface 325 of the pole tooth 323 of the rotor core 32 and the magnetic flux Φ from the circumferential side surface 166 of the stator core 16 and the pole tooth 323 of the rotor core 32.
1, Φ3 in and out.

FIG. 5A shows the pole teeth 16 of the stator core 16.
3 shows a state in which the pole teeth 323 of the rotor core 32 are separated from each other. FIG. 5B shows the pole teeth 163 of the stator core 16.
In contrast, the pole teeth 323 of the rotor core 32 are shown close to each other. The torque is proportional to the magnetic flux change rate dΦ / dt between the bipolar teeth 163 and 323, and the magnetic flux change rate dΦ / dt is d
Since Φ2 / dt + d (Φ1 + Φ3) / dt, it can be seen that the torque is the sum of the change rate dΦ2 / dt of the magnetic flux between the magnetic pole faces Φ2 / dt and the change ratio d (Φ1 + Φ3) / dt of the side face magnetic flux Φ1 + Φ3. As can be seen from FIG. 5, the polar teeth 323
In the process of approaching the pole tooth 163, the magnetic flux Φ2 between the magnetic pole faces increases to generate a positive torque, but the side face magnetic flux Φ1 + Φ3.
Is reduced to produce negative torque. Therefore, the pole teeth 163 and the circumferential side surfaces 166, 32 of the pole teeth 323 are arranged.
It can be seen that the torque is increased by arranging the magnetic shield 51 of the permanent magnets 5 and 6 having the magnetic pole surfaces having the same polarity as those facing the magnet 6.

(Description 2) Next, the torque increasing effect of the permanent magnets 5 and 6 will be described with reference to FIG. 6 using the vector of the magnetostatic force F. However, in FIG.
Is the pole tooth 163 located behind the pole tooth 323,
It is assumed that 31 is a pole tooth 163 located in front of the pole tooth 323. FIG. 6A schematically shows magnetic force lines 200 and 201 without the permanent magnets 5 and 6, and FIG. 6B schematically shows magnetic force lines 200 and 201 with the permanent magnets 5 and 6. . It is assumed that 200 is a line of magnetic force between the rear pole tooth 1630 and 201 is a line of magnetic force between the front pole tooth 1631.

The magnetostatic force F acting on one pole tooth 323 is a circumferential vector component Fa1 of a negative force Fa between the pole tooth 1630 on the rear side and a positive force Fb between the pole tooth 1631 on the front side. With the vector component Fb1 in the circumferential direction of (-Fa1 + Fb1)
Becomes When the permanent magnets 5 and 6 are not provided (see FIG. 6A), the side surfaces 166 of the pole teeth 3230 and 3231 and the pole teeth 3 are provided.
Since the magnetic flux comes in and goes out from the side surface 326 of 23, the magnetic force line F
a and Fb stand in the axial direction. That is, each pole tooth 1
Assuming that 63, 3230, and 3231 are point magnetic poles, the point magnetic poles that represent the respective pole teeth 163, 3230, and 3231 are:
Since the magnetic flux comes in and goes out from the side surface, it can be considered that the magnetic flux exists at a position where the magnetic flux on the other side recedes in the axial direction.

This fact means that the angle θ becomes large as shown in FIG. 6 (a) and the sum of the circumferential vector component forces (-Fa1).
+ Fb1) becomes smaller. On the other hand, if it is assumed that the magnetic flux does not flow in and out from the circumferential side surfaces 166 and 326 of the pole teeth 163 and 323 due to the mounting of the permanent magnets 5 and 6, as shown in FIG. 16
The point magnetic poles representing 3, 3230 and 3231 are the magnetic pole surface 1
65, 325 can be assumed to exist at the center in the circumferential direction, and as a result, the angle θ becomes smaller and the torque (-
It can be seen that Fa1 + Fb1) × r increases significantly.
Note that r is the radius of the magnetic pole surface 325.

Further, in the present embodiment, as shown in FIG. 3, the axial end surface of the circumferential support portion 53 of the permanent magnet 5 (or 6) has the same polarity as the axial side surface of the facing pole tooth 163 (or 323). Since it is magnetized to the rotor core 3
It is possible to reduce the leakage magnetic flux that leaks without passing through the second pole tooth 323, increase the effective magnetic flux by that amount, and increase the torque.

The magnetic poles of these permanent magnets 5 and 6 (N
As described above, the pole and the S pole are the pole teeth 163 (or the pole teeth 3).
23) only on the circumferential side surface 166 or the axial side surface 167, the magnetic field of the permanent magnet 5 is almost short-circuited through the stator core 16, and the magnetic field of the permanent magnet 6 is substantially short-circuited through the rotor core 32. Torque can be prevented from occurring.

(Embodiment 2) Another embodiment will be described with reference to FIG. This embodiment is different from the first embodiment in that the ring-shaped space formed by increasing the inner diameter of the non-magnetic spacer 15 made of a resin wheel plate and the ring-shaped space formed by increasing the outer diameter of the spacer 33. In the space of the pole teeth 163 and 323 and the axially protruding portions 59 of the permanent magnets 5 and 6, the cylindrical permanent magnets 7 and 8 (inter-phase magnetic shield portions) are provided adjacently in the axial direction. is there.

FIG. 8 shows the stator core 16, the permanent magnets 5,
7 and an exploded view of the spacer 15 are shown in FIG.
2, an exploded view of the permanent magnets 6, 8 and the spacer 33 is shown. Each member is divided into two. By doing so, it is possible to reduce the magnetic flux flowing in and out between the axially outer side surface 168 of the pole tooth 163 of the stator core 16 and the axially outer side surface 328 of the pole tooth 323 of the rotor core 32, and thus the magnetic flux of the first embodiment is reduced. Polar tooth 1
The torque can be enhanced by the same action as the torque enhancing action by reducing the magnetic flux flowing in and out from the circumferential side surfaces 166 of 63 and 323.

Since the magnetic poles of the permanent magnets 7 and 8 are not exposed to the pole teeth 323 of the rotor 3 as in the first embodiment, no detent torque is generated. (Embodiment 3) Another embodiment will be described with reference to FIG.
In this embodiment, a permanent magnet 500 having a shape in which the axial protrusion 59 of the permanent magnet 5 in Embodiment 2 is omitted on only one side is used instead of the permanent magnet 5, and the omitted axial protrusion 59 is adjacent. The permanent magnet for the stator is attached to the permanent magnet 700.

In this way, the permanent magnets 500, 70
0 can have the same shape. (Embodiment 4) Another embodiment will be described with reference to FIG.
In this embodiment, a permanent magnet 600 having a shape in which the axial protrusion 69 of the permanent magnet 6 in Embodiment 2 is omitted on only one side is used instead of the permanent magnet 6, and the omitted axial protrusion 69 is adjacent. The permanent magnet for a rotor is attached to the permanent magnet 800.

In this way, the permanent magnets 600, 80
0 can have the same shape. (Fifth Embodiment) Another embodiment will be described with reference to FIG.
This embodiment is a permanent magnet for a stator using permanent magnets 501 and 701 instead of the permanent magnets 5 and 7 in the second embodiment.

The assembly shape of the permanent magnets 501 and 701 is the same as that of the permanent magnets 5 and 7, but in this embodiment, the side surfaces of each pole tooth 163 are formed by a pair of permanent magnets 501 and 701 from both axial sides. Is covered. Permanent magnets 501, 7
01 is formed in the same shape, which can reduce the number of parts. (Sixth Embodiment) Another embodiment will be described with reference to FIG.

This embodiment is a permanent magnet for a rotor using permanent magnets 601 and 801 instead of the permanent magnets 6 and 8 in the second embodiment. The assembly shape of the permanent magnets 601 and 801 is the same as the assembly shape of the permanent magnets 6 and 8, but in this embodiment, the side surface of each pole tooth 323 is covered with a pair of permanent magnets 601 and 801 from both axial sides. There is. Permanent magnet 6
01 and 801 are formed in the same shape, which can reduce the number of parts.

[Brief description of the drawings]

FIG. 1 is an axial cross-sectional view of a vertically arranged VR stepping motor according to a first embodiment.

FIG. 2 is an axially enlarged partial sectional view of a main part of FIG.

FIG. 3 is a partial plan view of the permanent magnet 5 of FIG.

FIG. 4 is a perspective view of a permanent magnet 5 shown in FIG.

5 (a) and 5 (b) are explanatory views showing the torque increasing action of the first embodiment, and FIG. 5 (a) shows a state where the pole teeth 163 and the pole teeth 323 are separated when the permanent magnets 5 and 6 are not provided, and FIG.
Shows a state in which the pole teeth 163 and the pole teeth 323 are close to each other.

6 (a) and 6 (b) are explanatory views showing the torque increasing action of the embodiment 1, in which (a) shows the state of the magnetostatic force between the pole teeth 163 and the pole teeth 323 when the permanent magnets 5 and 6 are not provided,
(B) shows pole teeth 16 when the permanent magnets 5 and 6 are provided
3 shows the state of the magnetostatic force between the pole teeth 323.

FIG. 7 is an axially enlarged partial cross-sectional view of a main part of a vertically arranged VR stepping motor according to a second embodiment.

8 is a partially exploded perspective view of the stator shown in FIG.

9 is a partial exploded perspective view of the rotor of FIG. 7. FIG.

FIG. 10 is a partial exploded perspective view of a stator according to a third embodiment.

FIG. 11 is a partial exploded perspective view of a rotor of the fourth embodiment.

FIG. 12 is a partial exploded perspective view of a stator according to a fifth embodiment.

FIG. 13 is a partially exploded perspective view of a rotor according to a sixth embodiment.

[Explanation of symbols]

Reference numeral 16 is a stator core, 163 is a pole tooth (first pole tooth, second pole tooth) of the stator core 16, 17 is a stator coil,
32 is a rotor core, 323 is a pole tooth (3rd pole tooth, 4th pole tooth), 5 and 6 are permanent magnets, 51 is a magnetic shield part, 52 is an axial direction support part, 53 is a circumferential direction support part, 7 , 8 are permanent magnets (interphase magnetic shield).

Claims (9)

[Claims] 1. A plurality of first pole teeth arranged at a predetermined pitch in the circumferential direction, and a plurality of first pole teeth arranged at the pitch in the circumferential direction at a predetermined interval in the axial direction with respect to the first pole teeth. A plurality of second pole teeth, and a stator core having a yoke portion that magnetically connects the first and second pole teeth, and the stator core is wound around the stator core to magnetize the both pole teeth to polarities different from each other. And stator poles having pole faces having pole faces facing the pole faces of the first pole teeth and the second pole teeth, and arranged so as to be rotatable relative to the stator core in the circumferential direction. A cascade-arranged VR stepping motor in which a plurality of phase units each having a rotor core and a rotor core are connected in an axial direction, the stepping motor having a magnetic pole surface facing a circumferential side surface of the first pole tooth or the second pole tooth. The same polarity as the pole teeth that the pole faces face A VR type stepping motor arranged in tandem, comprising: 2. A plurality of first pole teeth arranged at a predetermined pitch in the circumferential direction, and a plurality of first pole teeth arranged at the pitch in the circumferential direction at a predetermined interval in the axial direction with respect to the first pole teeth. A plurality of second pole teeth, and a stator core having a yoke portion that magnetically connects the first and second pole teeth, and the stator core is wound around the stator core to magnetize the both pole teeth to polarities different from each other. Stator coil, a plurality of third pole teeth arranged in the circumferential direction at the pitch, and having magnetic pole surfaces that can face the magnetic pole surface of the first pole tooth with a small gap. A plurality of fourth pole teeth arranged at the above-mentioned pitch in the circumferential direction having a pole surface capable of facing each other with a small gap on the pole surface of one pole tooth; and the third and fourth pole teeth. And a yoke portion for magnetically connecting to each other, and is disposed so as to be rotatable relative to the stator core in the circumferential direction. And a rotor core and a plurality of phase units including the rotor core, which are arranged in series in the axial direction, in a vertical arrangement VR type stepping motor having a magnetic pole surface facing the circumferential side surface of the third pole tooth or the fourth pole tooth. Also, a cascade-arranged VR stepping motor is provided with a magnetic shield portion having a polarity equal to the polarity induced by the pole teeth facing the magnetic pole surface. 3. The cascade-arranged VR stepping motor according to claim 1, wherein the magnetic shield portion is arranged in proximity to the circumferential side surfaces of the pole teeth of both the stator core and the rotor core. 4. The magnetic shield part extending in the axial direction and adjacent to the first pole tooth and the magnetic shield part adjacent to the second pole tooth are connected to each other, and the both magnetic shield parts are connected. 2. The VR motor according to claim 1, further comprising an axial support portion magnetized in a direction for strengthening the residual magnetic field. 5. The magnetic shield part extending in the axial direction and adjacent to the third pole tooth and the magnetic shield part adjacent to the fourth pole tooth are connected to each other, and the both magnetic shield parts are connected. 2. The VR motor according to claim 1, further comprising an axial support portion magnetized in a direction for strengthening the residual magnetic field. 6. The magnetic shielding part and the axial support part are formed in a cylindrical shape together with a circumferential support part extending in the circumferential direction and connecting the axial support parts. Vertically arranged VR type stepping motor. 7. The cascade-arranged VR type stepping motor according to claim 6, wherein the circumferential support portion is magnetized in a direction that reduces a leakage magnetic flux coming in and out from an axial side surface of the pole tooth. 8. A plurality of first pole teeth arranged at a predetermined pitch in the circumferential direction, and a plurality of first pole teeth arranged at the pitch in the circumferential direction at a predetermined interval in the axial direction with respect to the first pole teeth. A plurality of second pole teeth, and a stator core having a yoke portion that magnetically connects the first and second pole teeth, and the stator core is wound around the stator core to magnetize the both pole teeth to polarities different from each other. Stator coil, a plurality of third pole teeth arranged in the circumferential direction at the pitch, and having magnetic pole surfaces that can face the magnetic pole surface of the first pole tooth with a small gap. A plurality of fourth pole teeth arranged at the above-mentioned pitch in the circumferential direction having a pole surface capable of facing each other with a small gap on the pole surface of one pole tooth; and the third and fourth pole teeth. And a yoke portion for magnetically connecting to each other, and is disposed so as to be rotatable relative to the stator core in the circumferential direction. In a vertical arrangement VR type stepping motor in which a plurality of phase units having a rotor core and a rotor core are connected in an axial direction, a VR core stepping motor is provided in an axial gap between a pair of adjacent phase units, and A vertical arrangement VR type stepping motor characterized in that a magnetic pole surface composed of end faces facing each other in the axial direction has an interphase magnetic shield portion having the same polarity as the facing pole teeth. 9. The cascade-arranged VR type stepping motor according to claim 8, wherein the interphase magnetic shield is formed in a wheel shape.