JPH10174417A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stepping motor having high assembly precision, high manufacturing efficiency, cost reduction, and high performance. SOLUTION: A stator 21 is constituted by integrally forming bobbins 26, 30 and yokes 27, 28, 31, and 32 with a synthetic resin which forms the bobbins. A magnetic circuit is ensured by the yokes and a cylindrical frame 22 to form the yokes into a disc shape, and the whole stator is formed into a bobbin shape, so as to wind a coil around the bobbins after they have been integrated with the yokes. A bearing 35a which supports a shaft 20a of a rotor 20 is firmly fitted directly into the stator, and other bearing 35b is fixed on a fitting plate 23. Positioning of the fitting plate and the stator is conducted by fitting protrusions 33a, 33b, formed at the opening edge of the stator with the fitting holes 23a, 23b which are open at the fitting plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor used for various types of equipment requiring stepping drive.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional stepping motor of this type.
On the inner peripheral surfaces of the outer yoke 1a and the inner yoke 2a, pole teeth are erected at equal intervals in the circumferential direction, and are alternately arranged at equal intervals in the circumferential direction so that the pole teeth face each other. A ring-shaped coil 4a wound around the bobbin 3a is incorporated in the outer periphery of the pole teeth. A mounting plate 5 for mounting the motor main body to another device is fixed to an end surface of the outer yoke 1a by welding or the like. The first stator portion 10a is formed by fixing one bearing 7a that supports the shaft 6a to the rotor 6 to the mounting plate 5.

On the other hand, on the inner peripheral surfaces of the outer yokes 1b and 2b, similarly, pole teeth are erected at equal intervals in the circumferential direction, and alternately and equally in the circumferential direction so that the pole teeth face each other. A ring-shaped coil 4b wound around the bobbin 3b is incorporated around the pole teeth at intervals. A side plate 8 is fixed to an end surface of the outer yoke 1b by welding or the like. A second stator portion 10b is formed by fixing the other bearing 7b that supports the shaft 6a of the rotor 6 to the center of the side plate 8.

[0004] The first stator portion 10a and the second stator portion 10b are fixed to each other with their phases shifted from each other by a step angle of the motor with respect to the axis, thereby forming the stator 10. Further, on the outer peripheral surface of the rotor 6, a permanent magnet 6b in which different magnetic poles are alternately magnetized in the circumferential direction is fixed. In the stepping motor having the above configuration, the pair of yokes 1a, 2a
The rotor 6 is driven in a stepping manner by sequentially and intermittently changing the magnetic poles of the plurality of pole teeth a, 1b, and 2b.

[0005]

The above-described conventional stepping motor has the following problems to be solved, and improvement thereof is desired. That is, in the above-mentioned conventional stepping motor, when assembling the stator 10 first, the bobbins 3a and 3b around which the coils 4a and 4b are wound are respectively connected to the pair of yokes 1a,
Secure by wrapping in 2a and 1b, 2b. At this time, a pair of yokes 1a, 2a and 1b, 2b are used to form
Therefore, the coil needs to be wound on the bobbin in advance. As described above, the pair of yokes 1a, 2a and 1b, 2b each have a plurality of pole teeth formed on the inner peripheral surface, so that the pair of yokes 1a, 2a and 1b, 2b In between,
The polar teeth must be opposed to each other and arranged alternately and at equal intervals in the circumferential direction.

For this reason, each yoke is connected to a jig or yoke 2a,
The entire positioning is performed while fixing by the unevenness of 2b,
The yokes are fixed to each other by welding. Since the coil is wound around the bobbin in advance and the bobbin is further surrounded and fixed by the yoke, the number of steps is increased. In addition, since the coil is wound around the bobbin and the yoke is further inserted into the bobbin, the coil, bobbin, and yoke are separately mounted. Was easy to occur. Further, the work of positioning and fixing the yokes is a process in which a positioning error is likely to occur, and the work requires skill.

A pair of bearings 7a and 7b for supporting the shaft 6a of the rotor 6 are fitted and fixed to the center portions of the mounting plate 5 and the side plate 8, respectively. Positioning and fixing with the center plate 10 are performed by positioning welding using a center jig having the same diameter as the inner diameter of the pole teeth of the outer yokes 1a and 1b, or
In addition, a positioning hole is formed at a corresponding position of the side plate 8 and welding is performed. Therefore, the stator 1
An error is likely to occur in the positioning (centering) of the bearings 0a and the bearings 7a and 7b, which is likely to be an obstacle to improving the performance of the motor. That is, if an error occurs in the positioning between the stator 10 and the bearings 7a, 7b, the clearance between the rotor 6 whose rotational position is determined by the bearings 7a, 7b and the pole teeth becomes non-uniform. Is inaccurate or the driving efficiency is reduced. Further, as described above, since the assembling process is performed manually, the accuracy is likely to vary, and the manufacturing efficiency is low.

The present invention has been made to effectively solve such problems of the conventional stepping motor, and provides an inexpensive and high-performance stepping motor having high assembling accuracy, high manufacturing efficiency, and high efficiency. It is intended for.

[0009]

According to a first aspect of the present invention, there is provided a stepping motor comprising a rotor and a stator accommodating the rotor rotatably with a gap therein. A bottomed cylindrical frame that houses the stator that houses the rotor, and a mounting plate that closes the opening of the bottomed cylindrical frame that houses the stator, wherein the stator has at least The stator portion is composed of a bobbin around which a coil is wound in a ring shape, and a pair of yokes arranged on both sides of the bobbin. A plurality of pole teeth formed on the inner peripheral surface of the yoke are alternately arranged at equal intervals, and each bobbin is made of synthetic resin, and is integrally formed so as to integrally fix each pair of yokes. Cage, the outer diameter of each of the yoke,
The outer peripheral surface of the yoke and the inner peripheral surface of the frame are set to be in close contact with each other, a bottom is formed at one end of the stator, and one bearing that supports the shaft of the rotor is fixed to the bottom. The other end of the stator is opened, and at least two positioning fitting projections are formed on the peripheral surface of the opening edge, and the other bearing that supports the shaft of the rotor at the center of the mounting plate. And a positioning fitting hole for fitting with a positioning fitting projection formed on an opening edge of the stator is formed in a peripheral surface of the mounting plate.

[0010] The invention described in claim 2 is the same as the claim 1.
Wherein the stator is formed of two stator portions and is integrally formed of a synthetic resin forming the bobbin. Further, the stepping motor according to claim 3 is the stepping motor according to claim 1 or 2, wherein at least one of the outer peripheral surfaces of each of the yokes does not contact the inner peripheral surface of the frame at all. A play section is provided.

In the stepping motor according to the first aspect of the present invention, the bobbin and the yoke are integrally formed with high dimensional accuracy because the stator is formed by integrally molding the bobbin and the yoke with the synthetic resin forming the bobbin. Can be In addition, since the magnetic circuit is secured by the yoke and the cylindrical frame, the yoke can be formed into a disk shape, and the entire stator can be formed into a bobbin shape. The coil can be wound, so that the winding accuracy of the coil can be easily secured. Further, one bearing for supporting the shaft of the rotor is directly fitted and fixed to the stator, and the other bearing is fixed to the mounting plate. The positioning between the mounting plate and the stator is determined by the opening edge of the stator. Projections formed on the
Since the fitting is performed by fitting the fitting hole formed in the mounting plate, the center axis of the stator and the rotating shaft of the rotor can be accurately and easily aligned, and the number of assembling steps is reduced. There is no need for skill.

According to the second aspect of the present invention, the number of coils and the number of pole teeth can be reduced, the number of control steps can be easily increased, and more precise control can be performed. Even in this case, since the stator portion can be integrally formed by injection molding at one time, the manufacturing efficiency is excellent. Further, according to the stepping motor of the third aspect, the notch play portion is provided at at least one position on the outer peripheral surface of the yoke, so that the outer peripheral surface of the yoke and the inner peripheral surface of the frame can be in contact with each other. Non-uniformity is introduced along the direction, and the bias increases the contact pressure between the remaining outer peripheral surface of the yoke and the inner peripheral surface of the frame, so that the yoke and the cylindrical frame are used. The density of the magnetic circuit can be increased, and the driving efficiency of the motor can be improved.

[0013]

FIG. 2 to FIG. 6 show an embodiment of the present invention. This stepping motor rotatably accommodates the rotor 20 with a small gap therein. , A bottomed cylindrical frame 22 that houses the stator 21 that houses the rotor 20, and a mounting plate 23 that closes the opening of the bottomed cylindrical frame 22 that houses the stator 21. This is schematically configured from the above. Here, the rotor 20 is a column-shaped rotationally symmetric body about the shaft 20a,
On the outer peripheral surface, a permanent magnet 2 alternately magnetized in a different direction in the circumferential direction
b is fixed.

As shown in FIGS. 2 to 5, the stator 21 includes two stator portions, that is, a first stator portion 23 and a second stator portion 24.
Here, the first stator portion 23 is a ring-shaped coil 2.
5 comprises a bobbin 26 around which the bobbin 5 is wound, and a pair of yokes 27 and 28 arranged on both sides of the bobbin 26. The inner peripheral surface is formed on the inner peripheral surface of each of the yokes 27 and 28. A plurality of pole teeth 27a and 28a are alternately arranged at equal intervals.

Similarly, the second stator portion 24 includes a bobbin 30 around which a ring-shaped coil 29 is wound, and a pair of yokes 31 and 32 disposed on both sides of the bobbin 30. On the peripheral surface, a plurality of pole teeth 31a, 32a formed on the inner peripheral surface of each of the yokes 31, 32 are alternately arranged at equal intervals. The bobbins 26 and 30 are made of synthetic resin, and are integrally formed by injection molding so as to integrally fix the pair of yokes 27, 28 and 31, 32, as described later. The stator 21 is an integrally formed body. The coil 25,
29 is wound around the bobbins 26 and 30 after the stator 21 is integrally formed. Bobbin 26
And 30 have almost the same shape and the same size, but the bobbin 26 has an exposed end thereof, that is, a positioning fitting at a position on the peripheral surface of the opening edge 21a of the stator 21 at a position facing the diameter. The protrusions 33a and 33b are formed, and the plug terminal portion 34 in which a terminal row connected to the ends of the wires constituting the coils 25 and 29 is fixed to a part of the outer peripheral edge of the opening edge 21a is outside. It is different that it is projected. On the other hand, in the bobbin 30, a central portion of the exposed end is formed with a bottom that slightly protrudes outward, and a central portion of the central bottom portion 30 a has one bearing 35 a that axially supports the shaft 20 a of the rotor 20. The difference is that a fitting concave portion 36 for fixing is formed. A through hole 36a is formed at the center of the fitting recess 36 to allow the shaft 20a to pass therethrough.

The outer diameter of each of the yokes 27, 28, 31, 32 is set such that the outer peripheral surface of the yoke and the inner peripheral surface of the frame 22 are in close contact with each other. The shapes of these yokes will be described using the yokes 27 and 28 as representatives. FIG.
Shows a pair of yokes 27 and 28 constituting the stator 21 having the above configuration. Each of the yokes 27 and 28 is a disk-shaped member made of metal and has a through hole formed at the center thereof, and a plurality of yokes 27 and 28 arranged at equal intervals along the inner circumference at the edges of the through holes. Pole teeth 27
a and 28a are erected. Also, yoke 2
A pair of recesses 27b and 28b are formed on the outer peripheral edges of each of 7 and 28 at opposing positions along the diameter. Further, the outer peripheral edge of each of the yokes 27 and 28 is provided with a notched flat edge 27 at an intermediate portion between each of the pair of concave portions 27b, 27b and 28b, 28b.
c and 28c are formed. Although the yokes 27 and 28 are formed in the same shape and the same size, the positions of the pole teeth 27a... And 28a. That is, when the recesses 27b and 28b of the yokes 27 and 28 and the notched flat edges 27c and 28c are accurately aligned, and the yokes 27 and 28 face each other, the respective pole teeth 27a. Are formed so as to face each other and alternately at equal intervals.

Furthermore, notch play portions 27d and 28d are formed at portions of the outer peripheral surfaces of the yokes 27 and 28 located on the facing circumference of the notch flat portions 27c and 28c, and the recesses 27b, 27b and 28b, 28
Notch play portions 27e, 27e and 28e, 28e are also formed at two places in FIG. These notch play portions 27d, 27e, 27e and 28d, 28e, 28
Due to e, an intermittent play portion occurs on the continuous arc-shaped outer peripheral surfaces of the yokes 27 and 28. This play part,
That is, the notch play portions 27d, 27e, 27e and 2
8d, 28e, and 28e are portions that do not contact the inner peripheral surface of the frame 22 at all when the yokes 27, 28 are fitted to the frame 22. Therefore, non-uniformity occurs along the outer peripheral surfaces of the yokes 27 and 28 from the viewpoint of contactability. As a result, the contact pressure between the outer peripheral surface of the yokes 27 and 28 and the inner peripheral surface of the frame 22 and the inner peripheral surface of the frame 22 increases, and surface contact is realized at that portion, and as a result, Resulting in an increased contact area. Therefore, the magnetic circuit realized between the yokes 27 and 28 and the frame 22 can be made sufficient, and the performance of the stepping motor can be improved.

The shapes of the yokes 27 and 28 and the relationship between the yokes 27 and 28 and the frame 22 are similarly realized in the yokes 31 and 32. The four yokes 27, 28, 3
In the stator 21 composed of 1, 32, the pole teeth on the inner peripheral surface are alternately arranged at equal intervals in the circumferential direction. For example, they are arranged alternately and at equal intervals in the circumferential direction as pole teeth 27a-32a-28a-31a.

The frame 22 is made of metal and is formed in a cylindrical shape with a bottom as shown in FIG. At the center of the bottom of the frame 22, a fixing hole 22a for fitting the center bottom 30a of the stator 21 is formed. Also, a part of the outer peripheral wall of the frame 22 includes:
A cutout window 22b that opens to the upper opening is formed. The notch window 22b and the notch flat edges 27c and 28c of the yokes 27 and 28 secure a space for locating the plug terminal portion 34 for supplying a current from an external power supply to the stator 21 housed in the frame 22. It is for doing. The inner peripheral dimension of the frame 22 formed in such a shape is determined by the inner peripheral surface thereof and the respective yokes 27,
The yokes 27, 28, 31, 32 are set to have substantially the same outer dimensions as the yokes 27, 28, 31, 32 so that the outer peripheral surfaces of the yokes 27, 31, 32 are in close contact with the outer peripheral surfaces. Thus, each yoke 27, 28, 3
The purpose of bringing the frames 1 and 32 into close contact with the frame 22 is that the yokes 27, 28, 31, and 32 and the frame 22 need to form a magnetic circuit of the stepping motor, as described above.

At the center of the mounting plate 23, the rotor 20
The other bearing 35b that supports the shaft 20a is fixed, and the positioning fitting projection 33 formed on the opening edge 21a of the stator 21 is formed on the peripheral surface of the mounting plate 23.
Positioning fitting holes 23a and 23b are formed to fit with the holes 33a and 33b. Further, a part of the outer periphery of the mounting plate 23 is cut off to form a flat edge 23c located in the cutout window 22b of the frame 22. Further, the mounting plate 23
A plurality of concave steps 23d are formed at substantially equal intervals on the outer peripheral edge so as to protrude downward. These concave steps 2
3d is provided corresponding to a step formed between the upper end surfaces of the bobbin 26 and the yoke 27, and serves to stably mount the mounting plate 23 on the upper portion of the stator 21.

Further, a part of the opposing outer peripheral edges along the diameter of the mounting plate 23 protrudes outward to form a pair of mounting pieces 23E, 23E.
An attachment hole 23e for attaching the stepping motor to another device is formed. This mounting piece 23E,
23E, locking recesses 22E and 22E are formed on the opening edge of the frame 22, and the mounting plate 23
The mounting pieces 23E, 23E are fitted into the locking recesses 22E, 22E of the frame 22, and the outer peripheral surface thereof is brought into close contact with the inner peripheral surface of the frame to be positioned on the frame 22. At this time, the positioning fitting holes 23a of the mounting plate 23,
23b is fitted with positioning fitting projections 33a, 33b formed on the opening edge 21a of the stator 21. As a result, the positioning of the stator 21, the frame 22, and the mounting plate 23 can be accurately and simultaneously achieved. As a result, the centering of one bearing 35a fixed to the stator 21 and the other bearing 35 fixed to the mounting plate 23 is performed.
Accurate and easy to achieve.

Next, an example of a method for integrally forming the stator 21 having the above-described structure will be described with reference to FIG. In the figure, reference numeral 40 denotes a fixed mold, and 41, 42a, 42b, 43a, 43
Reference numeral b denotes a movable mold, and the fixed mold 40 and the movable molds 41, 42a, 42b, 43a, 43b form a cavity 44 having the same shape and the same dimensions as the stator 21.
Here, the movable mold 41 defines the bottom surface of the stator 21,
The movable dies 42a and 42b define the outer peripheral shape of the first stator portion 23 of the stator 21, and the movable dies 43a and 43b
Defines the outer peripheral shape of the second stator portion 24 of the stator 21, and the fixed mold 40 defines the inner peripheral shape with the upper surface portion of the stator 21. When molding, first
The yokes 27, 28, 31, 32 are set at predetermined positions of the cavity 44. The positioning at this time is performed by fitting the concave portion 27b, the notch flat edge 27c, and the notch play portions 27d and 27e into corresponding positions in the cavity 44, for example, based on the above-described yoke 27.
After the installation of the yoke is completed, each mold is closed, a molten synthetic resin is injected into the formed cavity 44, and after the resin is cooled and cured, the mold is opened to take out a molded product. 21 is obtained.

In the description of the above embodiment, the notch play portion has a flat cutout shape, but the cutout shape is not particularly limited.

[0024]

As described above, in the stepping motor according to the present invention, the stator is formed by integrally molding the bobbin and the yoke with the synthetic resin constituting the bobbin, so that the bobbin and the yoke are combined. It can be integrated with high dimensional accuracy. In addition, since the magnetic circuit is secured by the yoke and the cylindrical frame, the yoke can be formed into a disk shape, and the entire stator can be formed into a bobbin shape. The coil can be wound, and as a result, the winding accuracy of the coil can be easily ensured. Further, one bearing for supporting the shaft of the rotor is directly fitted and fixed to the stator, and the other bearing is fixed to the mounting plate. The positioning between the mounting plate and the stator is determined by the opening edge of the stator. Is formed by fitting the projection formed on the mounting plate with the fitting hole formed in the mounting plate, so that the center axis of the stator and the rotating shaft of the rotor can be accurately and easily aligned, and the number of assembling steps can be reduced. And the need for skill in assembly is eliminated.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a conventional stepping motor.

FIG. 2 is an exploded perspective view showing one embodiment of the stepping motor of the present invention.

FIG. 3 is a top view illustrating a configuration of a stator included in the stepping motor illustrated in FIG. 2;

FIG. 4 is a bottom view of the stator.

FIG. 5 is a sectional view taken along the line V-V 'of FIG.

FIG. 6 is a perspective view of a pair of yokes constituting the stator.

FIG. 7 is a sectional view of an injection mold for explaining an integral molding method of the stator by injection molding.

[Explanation of symbols]

 Reference Signs List 20 rotor 20a shaft 21 stator 21a opening edge 22 frame 23 mounting plate 23a, 23b positioning fitting hole 23, 24 stator portion 25, 29 coil 26, 30 bobbin 27, 28, 31, 32 yoke 27a, 28a, 31a, 32a pole Tooth 27a, 27e, 28a, 28e Notch play 30b Central bottom (bottom of stator) 33a, 33b Positioning fitting protrusion 35a, 35b Bearing

Claims (3)

[Claims] 1. A rotor, a stator accommodating the rotor rotatably with a gap therein, a bottomed cylindrical frame accommodating the stator accommodating the rotor therein, and an accommodating the stator inside And a mounting plate for closing an opening of the bottomed cylindrical frame, wherein the stator is constituted by at least one stator portion, and the stator portion is a bobbin around which a coil is wound in a ring shape, A plurality of pole teeth formed on an inner peripheral surface of each of the yokes are alternately arranged at equal intervals on an inner peripheral surface of the stator portion; Each bobbin is made of a synthetic resin, and is integrally formed so as to integrally fix the pair of yokes. The outer diameter of each of the yokes is defined by the outer peripheral surface of the yoke and the inner periphery of the frame. surface There is set to a dimension in close contact, at one end of the stator bottom part is formed, the bottom portion,
One bearing that supports the shaft of the rotor is fixed, the other end of the stator is opened, and at least two positioning fitting protrusions are formed on the peripheral surface of the opening edge,
At the center of the mounting plate, the other bearing that supports the shaft of the rotor is fixed, and on the peripheral surface of the mounting plate, a positioning fitting protrusion formed on an opening edge of the stator is fitted. A stepping motor having a fitting hole. 2. The stepping motor according to claim 1, wherein the stator comprises two stator portions, and is integrally formed of a synthetic resin forming the bobbin. 3. The frame according to claim 1, wherein at least one of the outer peripheral surfaces of each of the yokes is provided with a notch play portion that does not contact the inner peripheral surface of the frame at all.
Or the stepping motor according to 2.