JP2001231240A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stepping motor which can realize a high torque while its diameter is reduced. SOLUTION: This stepping motor has rotor magnets 2, which are subjected to multiple magnetization and supported rotatably by a shaft in a casing 14, and a plurality of stators 13, which are composed respectively of exciting coils 8 and 10 of a plurality of phases and provided around the rotor magnets 2. The plurality of independent stators 13 are linked with each other to form a multiple-structured stator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor, and more particularly, to a small stepping motor with high torque.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional small stepping motor. The stepping motor of FIG. 3 includes a rotor magnet 2 that is multipolarly magnetized in a circumferential direction,
A phase which is provided so as to surround the rotor magnet 2,
This is a PM-type two-phase stepping motor that is roughly configured by a stator 13 including a pair of B-phase stator portions 13A and 13B.

Here, the A-phase side stator portion 13A
A stator yoke 11 having a large number of pole teeth 11a erected at equal intervals in a circumferential direction on an inner peripheral surface as shown in FIG.
and a ring-shaped exciting coil 8 wound around a bobbin 7 mounted on the outer periphery of the B. The B-phase-side stator portion 13B has a large number of pole teeth on its inner peripheral surface in the same manner as described above. 1
Stator yoke 12 in which 2a are erected at equal intervals in the circumferential direction
And an exciting coil 10 wound around a bobbin 9 mounted on the outer periphery of the pole teeth 12a.

The A-phase side stator portion 13A and the B-phase side stator portion 13B are made of magnetic material with a constant phase (deviation) corresponding to the step angle of the motor with respect to the shaft 1 supporting the rotor magnet 2. The stator 13 is configured by being positioned and fixed in a cylindrical casing 14. At this time, each stator 13
A and 13B individually form a magnetic circuit by each stator yoke and casing. The rotor magnet 2 is rotatably supported by side plates 5 and 6 of a casing 14 via bearings 3 and 4 so as to be surrounded by the stator portions 13A and 13B.

In the above-described stepping motor, A / A
By energizing the exciting coils 8 and 10 of each phase B and sequentially changing the magnetic poles of the plurality of pole teeth 11a and 12a of the stator yokes 11 and 12 intermittently with respect to the magnetic poles of the rotor magnet 2, The rotor magnet 2 can be step-driven at a predetermined rotation angle determined by the number of pole teeth of the pair of stator yokes 11 and 12.

[0006]

However, such a small stepping motor is used for a portable device which does not require a large rotating torque, such as driving a hand of a timepiece, driving a diaphragm of a camera, or driving a reading head of a CD. It is used as a drive, but when used as a drive source that is mounted on a small device and requires a relatively high rotational torque, for example, for feeding out roll paper of a portable thermal printer, the torque is slightly insufficient. Was.

In driving such roll paper, it is important to keep the outer diameter of the motor within the winding diameter of the roll paper from the viewpoint of making the equipment thinner, and the size in the motor radial direction increases due to the increase in torque. Is not preferred.

As a method of increasing the torque, the pole teeth 11a, 12a of the stator yokes 11, 12 are used.
A structure is conceivable in which a is elongated in the axial direction and the number of windings of the exciting coils 8 and 10 of each phase is extended in the direction of the shaft 1. However, when such an elongated stator yoke is manufactured by punching a sheet metal, Since the size of the pole teeth is determined by the inner diameter of the yoke, the outer diameter of the yoke increases accordingly, and consequently the motor diameter increases. As another method, in the case of manufacturing by drawing of a press, that is, a disk is drawn to form a flanged cylindrical body, and this cylindrical portion is cut off to form a plurality of pieces as shown in FIG. In the method of forming the pole teeth described above, although a small diameter can be obtained, there is a problem in strength because the thickness of the pole teeth portion is reduced by drawing. Thus, in any case, the strength is excellent,
It was difficult to produce a stator yoke with a small diameter and long pole teeth.

For these reasons, there is a demand for a small stepping motor having a small diameter and a high rotational torque in the recent trend of miniaturization, thinning and weight reduction of equipment.

The present invention has been made in view of the above problems, and has as its object to provide a small-diameter, high-torque stepping motor.

[0011]

That is, according to the first aspect of the present invention, a stator in which a plurality of phases of excitation coils (8, 10) are mounted outside a multi-pole magnetized rotor magnet (2). (13) and a stepping motor in which the rotor magnet (2) is rotatably supported in a casing (14). It is characterized by forming a multiple structure. In this way, a high rotational torque can be obtained by forming the stator in a multiple structure. In addition, since the stator can have a small diameter as in the related art, the radial dimension of the motor does not increase.

Further, according to the present invention, the non-magnetic material (15) is interposed between the adjacent stators (13). As a result, magnetic independence between the stators is ensured, and individual magnetic circuits that are not magnetically influenced by each other can be formed. Therefore, the excitation effect on the pole teeth of each stator yoke is stabilized, and stepping due to magnetic interference is performed. It is possible to prevent the rotation torque and the angle accuracy of the motor from decreasing. According to a third aspect of the present invention, the rotor magnet (2) is individually divided corresponding to the plurality of stators (13). As a result, the magnetic influence between the adjacent stators can be reduced, the inertia of the rotor magnet can be reduced, and the self-starting frequency can be improved.

According to a fourth aspect of the present invention, the casing (14) is a cylindrical body formed by bending a plate-shaped magnetic material. Sheet metal bending is less expensive than drawing.
In addition, since an elongated casing can be manufactured without reducing the thickness, sufficient strength can be ensured.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view showing the internal structure of a PM type two-phase stepping motor to which the present invention is applied. To simplify the description, the same reference numerals are used in the following description for portions common to the related art.

In this embodiment, three rotor magnets 2 each of which is multipolar magnetized in the circumferential direction are independently fixed to the shaft 1 and three stators 13 corresponding to these rotor magnets 2 are circumferentially fixed. And constitute a stepping motor having a triple structure.

Each of the stators 13 has the same configuration as the conventional stator 13 shown in FIG. 3, and includes a stator yoke 11 and an A-phase side stator portion 13A having an exciting coil 8 incorporated therein. 12 and a B-phase side stator portion 13B provided with the excitation coil 10. The pair of stators 13 are arranged at equal intervals in the direction of the shaft 1 with a non-magnetic material 15 interposed therebetween. .

In the stepping motor of the present configuration, similarly to the conventional stepping motor shown in FIG. 11
By sequentially and intermittently changing the magnetic poles a and 12a, the rotor magnet 2 can be step-driven. However, in this configuration, since the stator 13 has a triple structure, it is possible to obtain a comprehensively high rotational torque by a synergistic effect of the magnetizing force exhibited by the pole teeth of each stator 13. Moreover, since the structure and dimensions of each stator are the same as those of the conventional type, there is no increase in the diameter of the stator yoke (that is, the diameter of the motor itself) due to the increase in torque, and it is possible to maintain the conventional small diameter.

The non-magnetic members 15 interposed between the adjacent stators 13 ensure the magnetic independence of each of the stators 13, and cause mutual magnetic influence (interference of lines of magnetic force between exciting coils of each stator). Independent magnetic circuits can be formed. As a result, the excitation effect on each pole tooth is stabilized, and it is possible to avoid a decrease in rotational torque and angular accuracy when the stepping motor is driven.

In this embodiment, the rotor magnet 2 is divided corresponding to each of the stators 13. However, the rotor magnet 2 may be integrated without using such a divided structure. However, the split structure as in the present embodiment allows the magnetization on the rotor magnet corresponding to each stator 13 to be magnetically separated, thereby reducing the magnetic influence between adjacent stators. There is an advantage that the inertia can be reduced and the self-starting frequency can be improved.

As a modified example of the stator 13,
A configuration as shown in FIG. 2 is also possible. That is, while the above embodiment has a configuration in which three A-phase side stator portions 13A and three B-phase side stators 13B are connected in series, in the modification of FIG. 2, the A-phase side stator portion 13A and the B-phase side Stator 13
B are grouped three by one and connected in series. In this case, all the in-phase pole teeth are positioned in phase with each other, and are positioned so as to have a constant phase corresponding to the step angle of the motor with respect to the shaft 1 with respect to the out-of-phase stator portion. I have. The non-magnetic material 15 may be interposed between the different-phase stators.

Next, the casing 14 will be described. The casing 14 is a cylindrical body made of a magnetic material. Side plates 5 and 6 made of a magnetic material are attached to both ends of the opening of the cylindrical body, and the rotor magnet 2 is supported by bearings 3 and 4 fixed to the side plates. Structure.

Here, the casing 14 is formed by bending a plate-shaped magnetic material into a cylindrical shape, and although not shown, a mating portion of the cylinder is formed to have both convex and concave portions so that each convex portion and concave portion are engaged with each other. The both ends of the mating portion are crimped or joined by welding or the like to form a cylindrical body.

[0023] In such a production by sheet metal bending, it can be manufactured at a lower cost than a method of forming a cylinder by drawing.
Cost reduction can be achieved. In particular, in the case of the elongated casing 14 as in the present invention, the sheet thickness is not reduced unlike drawing, which is advantageous in terms of strength.

As described above, in the present embodiment, the stepping motor having a triple structure has been described as the structure of the stator 13. However, the present invention is not limited to this, and the structure can be appropriately adjusted according to the rotational torque and the motor size. Also,
It is not limited to a two-phase stepping motor.

[0025]

As described above, according to the first aspect of the invention, since the stator has a multiple structure, a high rotational torque can be obtained without increasing the radial dimension of the motor. .

According to the present invention as set forth in claim 2,
Since the non-magnetic material is interposed between the adjacent stators, the interference of the lines of magnetic force between the exciting coils of each stator can be suppressed, and a decrease in rotational torque and angular accuracy can be prevented.

According to the third aspect of the present invention,
Since the rotor magnet is divided for each stator, the magnetization on the rotor magnet corresponding to each stator can be magnetically separated, the magnetic effect between adjacent stators can be reduced, and the inertia of the rotor magnet can be reduced. It can contribute to improvement of the starting frequency.

According to the present invention described in claim 4,
Since the casing is manufactured by bending the plate-shaped magnetic material into a cylindrical shape, the cost can be reduced and the cost can be reduced as compared with the case of drawing. In addition, since an elongated casing can be manufactured without reducing the sheet thickness, it is advantageous in terms of strength.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a stepping motor according to the present invention.

FIG. 2 is a sectional view showing a structure of a stator of the stepping motor.

FIG. 3 is a longitudinal sectional view of a conventional stepping motor.

FIG. 4 is a perspective view of a stator yoke of the stepping motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaft 2 Rotor magnet 8, 10 Excitation coil 13 Stator 14 Casing 15 Non-magnetic material

Claims (4)

[Claims] 1. A multi-pole magnetized rotor magnet (2)
A stepping motor in which a stator (13) on which a plurality of phases of excitation coils (8, 10) are mounted is provided on the outer side of the rotor and the rotor magnet (2) is rotatably supported in a casing (14). 3. The stepping motor according to claim 1, wherein a plurality of the stators (13) are independently connected to each other to form a multiple structure. 2. A non-magnetic material (15) interposed between adjacent stators (13).
4. The stepping motor according to claim 1. 3. The stepping motor according to claim 1, wherein the rotor magnet is divided into a plurality of parts corresponding to the plurality of stators. . 4. The stepping motor according to claim 1, wherein the casing (14) is a cylindrical body formed by bending a plate-shaped magnetic material.