JPH06303756A - Step motor - Google Patents

Abstract

PURPOSE:To reduce the dimensions in axial direction by laying out a field part at the inner and outer peripheries of a ring-shaped magnet. CONSTITUTION:Outside yokes 21 and 22 are provided with a number of comb- shaped outside magnetic pole pieces 211 and 221 protruding in axial direction on inner-periphery side surfaces, these magnetic pole pieces are laid out so that they engage one another via a specific spacing, thus forming a plurality of a pair of outside magnetic pole pieces. An annular part 312 is laid out inside an annular space which is formed between an inside stator 10 and art outside stator 20 and the inner periphery opposes the magnetic pole pieces 111 and 121 of the inside stator 10 and the outer periphery opposes the magnetic pole pieces 211 and 221 of the outside stator 20. The inner periphery of the annular part 312 is magnetized at a constant pitch intermittently in the periphery direction and the outer periphery is magnetized to N pole corresponding to it. Then, the number of the magnetic poles pieces 111 and 121 is equal to that of the S pole of the inner periphery of the annular part 312 and then the number of the magnetic pole pieces 111 and 121 is equal to that of the N pole of the outer periphery of the annular part 312.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor having stators arranged on both the outer peripheral side and the inner peripheral side of a rotor.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the thickness, a step motor has been proposed in which stators are arranged on both the inner circumference and the outer circumference of an annular magnet, for example, as disclosed in Japanese Patent Application Laid-Open No. 58-207856. .

This conventional step motor will be described with reference to FIG. As shown in the figure, the magnetic pole pitch is 96, N pole, S
An annular magnet 90, whose poles are magnetized alternately in the circumferential direction, is arranged between an inner yoke 91 and an outer yoke 92. These yokes 91 and 92 have magnetic pole pieces 911, 912 and 921, 922 which are meshed with each other alternately.
have. The number of magnetic pole pieces of each of the yokes 91 and 92 is the same as the number of poles of the magnet 90 facing each other. In each yoke 91, 92, the pole pieces 911 and 91
2, and the pole pieces 921 and 922 are excited to different poles as shown in the figure, and have N poles with a pole pitch 93.
A magnetic field is formed in which the south poles alternate in the circumferential direction.

With the above structure, when the excitation of each magnetic pole piece is switched and the magnetic flux acting on the magnet 90 is changed, the rotor (not shown) having the magnet 90 rotates. For example, the excitation state of the magnetic pole pieces 921 and 922 of the outer yoke 92 is the state shown in FIG. 1A (921: N pole, 922: S).
1) to the state (921: S pole, 92) shown in FIG.
2: N pole), the magnet 90 moves in the direction of arrow 95 by the step angle 94. The step angle 94 is 1/2 of the magnetic pole pitch 93.

[0005]

In recent years, there has been a demand for higher resolution, smaller size and higher accuracy of step motors. Higher resolution and smaller size can be achieved by shortening the magnetizing pitch. Higher precision is achieved by giving the magnet a sufficient magnetic force.

However, the above-mentioned conventional devices cannot sufficiently achieve these. That is, as shown in FIG. 6, the magnet applied to the conventional stepping motor is generally a magnetic member in which a plurality of magnetizing coils 97 are arranged on the outer peripheral side of the magnet material 90 'and a magnetic path is formed on the inner peripheral side. 9
8 are arranged, and the magnetizing coils 97 are magnetized by exciting the magnetizing coils 97 so that the magnetic flux is opposite between the adjacent magnetizing coils. The reduction of the magnetic pole pitch is achieved by reducing the distance between the magnetizing coils 97. However, it is necessary to reduce the size of the magnetizing coil 97 in order to shorten the interval between the magnetizing coils 97, and the number of turns of the coil must be reduced in order to reduce the size. Therefore, the exciting force of the magnetizing coil 97 decreases as the magnetizing pitch is shortened, and as a result, the magnetic force of the magnetized magnet becomes insufficient and the accuracy deteriorates.

On the contrary, in order to give the magnetized magnet a sufficient magnetic force, it is necessary to increase the number of windings of the magnetized coil, and the interval between the magnetized coils becomes large, and the magnet becomes large. .

Therefore, an object of the present invention is to apply a magnet capable of favorably shortening the magnetizing pitch, thereby achieving high resolution, miniaturization and high accuracy.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has the disadvantage of the above-mentioned conventional technique that the N pole and the S pole are alternately arranged in the circumferential direction at a predetermined pitch on each of the inner circumference and the outer circumference. Focusing on the fact that a magnetized magnet is applied, the following technical means is provided.

That is, according to the present invention, a rotor having a ring shape and having magnets magnetized on its inner and outer circumferences, an inner coil wound on an inner bobbin, and provided on the outer circumference of this inner coil, An inner field portion having an inner yoke having a plurality of pairs of inner magnetic pole pieces which are meshed with each other in the circumferential direction and face the inner circumferential magnetized portion of the magnet, and the inner field portion is wound around the outer bobbin. An outer coil, and an outer yoke that is provided on the inner circumference of the outer coil and that meshes alternately in the circumferential direction and that has a plurality of pairs of outer magnetic pole pieces facing the outer peripheral magnetized portion of the magnet. An outer magnetic field portion, and one pole of an N pole and an S pole is intermittently magnetized in the circumferential direction in the inner peripheral magnetized portion of the magnet. The magnetized part has the other pole It is intermittently magnetized in the circumferential direction,
Provided is a step motor in which the number of poles in the inner magnetized portion of the magnet is equal to the number of the pair of inner magnetic pole pieces, and the number of poles in the outer magnetized portion of the magnet is equal to the number of the pair of outer magnetic pole pieces. To do.

[0011]

According to the above construction, since the field magnet portion is arranged on the inner and outer circumferences of the ring-shaped magnet, the axial dimension can be reduced.

Further, since the number of pairs of magnetic pole pieces alternately meshing with each yoke is the same as the number of poles magnetized on the inner and outer circumferences of the magnet, the number of magnetic pole pieces is twice the number of poles. Since the step angle corresponds to the number of magnetic pole pieces of the yoke, the present invention has the following effects when the number of magnetic pole pieces and the number of poles are the same as in the above-described conventional technique.

First, when the step angles of both are the same, the number of poles of the magnet can be halved and the magnetizing pitch can be doubled. Therefore, the space for magnetizing the magnet is doubled, and a magnetizing coil having a large number of turns of the magnetizing coil and a large physique can be applied, and the magnetic force of the magnetized magnet can be increased to increase the magnetism. An accurate stepping motor can be obtained.

Next, when the two magnetizing pitches are the same, the step angle of the present invention can be halved.
A step motor having double the resolution can be obtained. When the step angle and the magnetization pitch are the same, the magnet can be downsized and the step motor can be downsized.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the step motor of the present invention is shown in FIG.
From now on, it will be explained based on FIG. FIG. 1 is a sectional view of the above embodiment, and FIG. 2 is an exploded perspective view.

The inner stator 10 corresponding to the inner field portion has first and second inner yokes 11 and 12, and an inner coil 13.
Have and. Each of the first and second inner yokes 11 and 12 has a large number of comb tooth-shaped inner magnetic pole pieces 111 and 121 protruding in the axial direction on the outer peripheral side surface.
1, 121 are arranged so as to be alternately meshed with each other at a predetermined interval, and form a plurality of pairs of inner magnetic pole pieces. A tubular portion 112 is formed on the inner circumference of the first inner yoke. Four protrusions 113 are formed at the end of the cylindrical portion 112.

The coil 13 is wound around a resin inner bobbin 131. Two protrusions 132 are formed at one end of the bobbin 131 in the axial direction, and a terminal 133 is integrally formed at the tip of the protrusion 132. The terminal 133 and the terminal of the coil 13 are electrically connected, and an external wiring (not shown) and the coil 13 are electrically connected via the terminal 133.

Further, two notches 1 corresponding to the protruding portion 132 of the bobbin 131 are formed on the inner peripheral portion of the second inner yoke 12.
22 is provided. The outer stator 20 corresponding to the outer field portion has first and second outer yokes 21 and 22, and an outer coil 23.

The first and second outer yokes 21 and 22 respectively have a large number of comb tooth-shaped outer magnetic pole pieces 211 and 221 axially protruding from their inner peripheral side surfaces.
1, 221 are arranged so as to mesh with each other at predetermined intervals, and form a plurality of pairs of outer magnetic pole pieces. A cylindrical portion 212 is formed on the outer circumference of the first outer yoke. Four protrusions 2 are provided on each end of the tubular portion 212.
13 and 214 are formed.

The coil 23 is wound around an outer bobbin 231 made of resin. Two protruding portions 232 are formed at one end of the bobbin 231 in the axial direction, and a terminal 233 is integrally formed at the tip of the protruding portion 232. The terminal 233 and the terminal of the coil 23 are electrically connected, and an external wiring (not shown) and the annular coil 23 are electrically connected via the terminal 233.

Further, two notches 2 corresponding to the protrusion 232 of the bobbin 231 are formed on the outer peripheral portion of the second outer yoke 12.
22 is provided. The rotor 30 is an annular magnet 3
1 and a rotating shaft 32. The annular magnet 31 has a disc portion 311 and a ring portion 312 that extends from the outer periphery of the disc portion 311 in the axial direction. The rotary shaft 32 is press-fitted in the center of the disc portion 311. The ring portion 312 is arranged in an annular space formed between the inner stator 10 and the outer stator 20, the inner circumference of which faces the magnetic pole pieces 111 and 121 of the inner stator 10, and the outer circumference of which is the outer stator 20.
Of the magnetic pole pieces 211 and 221. Also, the ring part 3
The inner circumference of 12 has a constant pitch in the circumferential direction (for example, 1
2 °) is magnetized to the S pole, and the outer circumference is magnetized to the N pole corresponding to the S pole on the inner circumference. Then, the number of the pair of magnetic pole pieces 111 and 121 of the inner stator 10 and the ring portion 312.
The number of S poles on the inner circumference is the same, and the number of the pair of magnetic pole pieces 211 and 221 of the outer stator 20 is the same as the number of N poles on the inner circumference of the ring portion 312.

As shown in FIG. 3, the ring portion 312 has a ring portion 3
Magnetic flux generated by exciting the magnetizing coil 81 flows through a yoke 80 that forms a closed magnetic path that includes a magnetic path that penetrates the radial direction 12 and is magnetized.

At the center of the disk-shaped upper case 40, the rotary shaft 3 is provided.
2 penetrates through, and a through hole 41 that rotatably supports the rotating shaft 32 is formed, and the first outer yoke 2 is provided on the outer periphery.
Four step portions 42 are formed corresponding to one protruding portion 214.

A cylindrical protrusion 51 is formed at the center of the disk-shaped lower case 50, and a rotary shaft 32 is inserted in the center of the protrusion 51 so that the rotary shaft 32 can rotate. The insertion hole 51 for supporting is opened. In the disc part,
4 through-holes 53 and 2 through-holes 5 along the protrusion 51
4 is opened, and four notches 55 and two notches 56 are formed on the outer circumference. The through holes 53 and 54 are
Each corresponds to the protruding portion 113 of the first inner yoke 11 and the protruding portion 132 of the bobbin 131. Notch 55,
56 are the protrusions 21 of the first outer yoke 21, respectively.
3, corresponding to the protruding portion 232 of the bobbin 231.

The washers 60 and 70 are provided to prevent rattling in the axial direction of the rotor and to improve slidability, and the upper surface of the disk portion 311 of the rotor 30 and the upper case 40, respectively.
Of the disk portion 311 of the rotor 30 and the upper surface of the protruding portion 51 of the lower case 50.

The stepping motor having the above-mentioned structure is laminated and assembled on the lower case 50 in order from the second inner yoke 12. At this time, the protrusion 132 of the bobbin 131 is inserted into the through hole 5 of the lower case 50 via the cutout 122 of the inner yoke 12.
4, the bobbin 131 and the inner yoke 12 are positioned with respect to the lower case 50. The protruding portion 113 of the first inner yoke 11 is connected to the through hole 53 of the lower case 50.
After passing through, the protruding portion 113 is bent to the outer diameter side to fix the first inner yoke 11 to the lower case. Therefore, the second inner yoke 12 and the bobbin 131
Are sandwiched and fixed by the first inner yoke 11 and the lower case 50.

The outer stator 20 is also the inner stator 1 described above.
Assembled like 0. In addition, the upper case 40 is the first
The protruding portion 214 of the outer yoke 21 is bent and engaged with the step portion 41, so that the outer yoke 21 is fixed to the first outer yoke 21.

Next, the operation of the step motor having the above construction will be described with reference to FIG. FIG. 4A shows the outer stator 2
The magnetic flux from the magnetic pole pieces 211 and 221 of 0 and the magnetic pole pieces 111 and 121 of the inner stator 10 and the magnetic flux from the magnet form a stable magnetic flux, and the rotor 30 is stable at a predetermined position. The magnetizing pitch in this embodiment is twice the magnetic pole pitch. Further, as shown in FIG. 4, the magnetic pole pieces 111 and 121 of the inner stator 10 and the magnetic pole pieces 211 and 221 of the outer stator 20 have a magnetic pole pitch of 9
They are arranged so that they are offset by 1/2 of 3 '.

From the state shown in FIG. 4 (a), the outer stator 2
When the energization direction of the 0 annular coil is reversed and the poles of the magnetic pole pieces 211 and 221 of the outer stator 20 are reversed as shown in FIG. 4B, the rotor 30 is attached to the right side of the drawing as shown in the figure. An urging magnetic flux is generated, and this urging force causes the magnet to move to the position shown in FIG. 4 (c) and stabilize.

Subsequently, from this state, the inner stator 10
Similarly, when the poles of the magnetic pole pieces are reversed, a magnetic flux for urging the rotor 30 to the right in the drawing is generated as shown in FIG.
This urging force moves the magnet to the position shown in FIG. 4 (e) and stabilizes it.

As described above, the rotor is rotated by repeating the above steps as one cycle. The step angle 94 'is 1/2 of the magnetic pole pitch 93', and the magnetic pole pitch 93 'is 1/2 of the magnetizing pitch 96'.

Compared to the prior art shown in FIG. 5, in the above-mentioned embodiment, when the step angles of both are the same, the magnetizing pitch of the magnet of this embodiment is twice the magnetizing pitch of the prior art. Become. Therefore, first, the gap between the magnetizing coils for magnetizing the magnet can be widened, and the number of turns of the magnetizing coil can be increased. Therefore, it is possible to obtain a highly accurate step motor in which the magnet has a large magnetic force after being magnetized.

Next, when the magnetization pitches of the two are made the same, the step angle of this embodiment is half that of the prior art,
It is possible to obtain a step motor having twice the resolution of the conventional one.

When the step angle and the magnetization pitch are the same, the magnet can be downsized and the step motor can be downsized.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a step motor of the present invention.

FIG. 2 is an exploded perspective view showing the above embodiment.

FIG. 3 is a plan view for explaining a magnetizing method of the magnet according to the embodiment.

FIG. 4 is a plan view for explaining the operation of the above embodiment.

FIG. 5 is a plan view for explaining a conventional step motor.

FIG. 6 is a plan view for explaining a conventional magnetizing method for the magnet.

[Explanation of symbols]

 10 inner field part 11,12 inner yoke 111,121 inner pole piece 13 inner coil 131 inner bobbin 20 outer field part 21,22 outer yoke 211,221 outer pole piece 23 outer coil 231 outer bobbin 30 rotor 312 ring part ( magnet)

Claims (1)

[Claims] 1. A ring-shaped rotor having magnets magnetized on its inner and outer circumferences, an inner coil wound on an inner bobbin, and provided on the outer circumference of this inner coil, alternating in the circumferential direction. An inner field magnet having an inner yoke formed with a plurality of pairs of inner magnetic pole pieces opposed to the inner circumferential magnetized portion of the magnet, and an outer coil wound on an outer bobbin, An outer field magnet portion provided on the inner circumference of the outer coil and alternately meshed in the circumferential direction and having an outer yoke formed with a plurality of pairs of outer magnetic pole pieces facing the outer magnetized portion of the magnet. The inner peripheral magnetized portion of the magnet has one of N pole and S pole intermittently magnetized in the circumferential direction, and the inner peripheral magnetized portion of the magnet has an outer peripheral magnetized portion. Is the other pole intermittently in the circumferential direction It is magnetized, the number of poles of the inner peripheral magnetized portion of the magnet is equal to the number of the pair of inner magnetic pole pieces, and the number of poles of the outer peripheral magnetized portion of the magnet and the number of the pair of outer magnetic pole pieces. Equal step motor.