JPH03256555A - Pm stepping motor of flat rotor type - Google Patents

Abstract

PURPOSE:To heighten the precision of the geometrical position of pole pieces by arranging an internal yoke ring section and an external yoke ring section on the same plane, and by bonding them integrally with bonding sections. CONSTITUTION:Yoke plates 8, 12 are formed with an internal yoke ring section 15 and an external yoke ring section 16. The internal yoke ring section 15 is provided with 6 pole pieces 17 according to every other position in 12 magnetic-sections arranged along the peripheral direction of a disc type magnet 5. Besides, the external yoke ring section 16 is provided with 6 other pole pieces 18 aligned to be pectinated along the peripheral direction of the 6 pole pieces 17. Then, the internal yoke ring section 15 and the external yoke ring section 16 are arranged along the same plane, and are integrally bonded to be positioned, with bonding sections 19. By using the yoke plates formed in this manner, the precision of a geometrical position in the circumferential direction of the yoke pole pieces is heightened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flat rotor type PM step motor, and particularly to its yoke structure.

[Conventional technology]

Conventionally, small PM step motors have been used to drive the heads of OA equipment such as hard disk drives and floppy disk drives, or to drive the objective lens focusing of still cameras and video cameras.

PM step motors used for such applications include:
For example, as shown in FIG. 4, a cylindrical rotor type is used. As shown in the figure, this type of step motor is composed of a rotor 41 made of a cylindrical magnet magnetized with multiple poles in the radial direction, and a pair of stators 42 and 43 surrounding the rotor from above and below. For example, the upper stator 42 includes a coil 44 and a yoke case 45 that accommodates the coil.
It consists of a yoke plate 46 that engages with a yoke case 45. Yoke case 45 and yoke brake) 4
Each pole piece B has a plurality of deep-drawn magnetic pole pieces, which are arranged around the rotor 41 so as to fit into each other in a comb-tooth shape. However, in a PM step motor having this shape, since the cylindrical magnet is magnetized in the radial direction, there is a problem that the magnetic flux generation ability of the magnet cannot be fully utilized when the size of the cylindrical magnet is reduced. In addition, since the magnetic pole pieces in the stator are formed by deep drawing, there is a limit to the accuracy of the shape, size, and position, and there are drawbacks such as difficulty in processing when miniaturizing the stator.

In order to eliminate the drawbacks of the above-mentioned cylindrical rotor type PM step motor, flat rotor type PM step motors have been proposed. As shown in FIG. 5, this type of step motor includes a rotor 51 consisting of a disc-shaped magnet with multipolar rocks arranged in the direction of the rotation axis, and a pair of fixed fixed magnets arranged opposite to the rotor 51 from above and below. It is composed of children 52 and 53. For example, the upper stator 52 includes a coil 54 and a coil 54.
It consists of a yoke case 55 that houses the yoke, and a pair of inner yoke ring 56 and outer yoke ring 57. The inner and outer yoke rings are arranged to face each other on one surface of the disc-shaped magnet, with their respective magnetic pole pieces arranged in a comb-tooth shape along the circumferential direction. A flat rotor type PM having such a structure
Step motors have the advantage of being able to make full use of the magnetic flux generation ability of the magnets because they are used as rotors by magnetizing disc-shaped magnets along the direction of the rotation axis, and the magnetic pole pieces of the yoke ring are arranged in a plane. It has the advantage that it can be processed easily.

(rjjJ m point to be solved by the invention) However, in the conventional flat rotor type PM step motor, the pair of inner and outer yoke rings are constructed as independent parts separated from each other.When assembling the step motor, the inner The magnetic pole pieces of the yoke ring and the magnetic pole pieces of the outer yoke ring are arranged and fixed so that they align with each other in a comb shape along the circumferential direction.At this time, accurate positioning of both requires work time and is difficult to assemble. In addition, the pair of inner yoke ring and outer yoke ring are used for the upper stator and lower stator, respectively, and the yoke ring is used along the circumferential direction between both stators. It is necessary to accurately position the four yoke rings, but it takes a lot of effort to align the four yoke rings.If the relative positional accuracy of the four yoke rings is not accurately determined, There was a problem in that an error occurred in the stop position of the step motor.

Means for Solving the Problems] In view of the problems of the conventional flat rotor type PM step motor described above, the present invention provides an improved step motor having a structure that allows easy alignment of the yoke ring. The purpose is to

The step motor according to the present invention has, as its basic components, a pair of stators that are arranged opposite to each other with a predetermined gap in the direction of the rotating shaft, and a rotor that is attached to the gap. The rotor is composed of disk magnets. This disk-shaped magnet has a plurality of magnetic domains magnetized in the direction of the rotation axis, and the polarity of each magnetic domain is set alternately in the circumferential direction.

In order to achieve the above object, each stator is composed of a coil, a yoke case for housing the coil, and a yoke plate that engages with the yoke case and is disposed opposite to one surface of a disc-shaped magnet. .

The yoke plate includes an inner yoke ring part having magnetic pole pieces corresponding to every other magnetic domain, and an outer yoke ring part having magnetic pole pieces arranged circumferentially in a comb-tooth shape on the magnetic pole pieces. Contains. Further, the inner yoke ring part and the outer yoke ring part are arranged along the same plane and are integrally positioned and connected by the connecting part.

[For production]

In the present invention, a yoke plate is used in which an inner yoke ring portion and an outer yoke ring portion are integrally positioned and connected. Therefore, when assembling the step motor, it is only necessary to relatively align the yoke plate of the upper stator and the yoke plate of the lower stator.
Assembling workability is improved, and the relative positional accuracy of a total of four yoke rings is also improved.

〔Example〕

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of a flat rotor type PM step motor according to the present invention taken along the rotational axis direction. As shown in the figure, the step motor is composed of a pair of upper stator 1 and lower stator 2 that are arranged opposite to each other with a predetermined gap in the direction of the rotation axis, and a rotor 3 that is installed in the gap. There is.

The rotor 3 is composed of a rotating shaft 4 and a disc-shaped magnet 5, and the center of the disc-shaped magnet 5 is fixed to the rotating shaft 4.

Further, the disk-shaped magnet 5 has a plurality of magnetic domains, for example, 12, which are magnetized in the direction of the rotation axis. The polarity of each magnetic domain is set to be alternately reversed along the circumferential direction.

The upper stator 1 includes a coil 6, a yoke case 7 housing the coil 6, and a disk-shaped magnet 5 that engages with the yoke case 7.
The yoke plate 8 is arranged opposite to the upper surface of the yoke plate 8. The yoke case 7 and the yoke plate 8 are assembled to surround the annular coil 6 and form a magnetic circuit that guides the magnetic flux generated from the coil 6. A bearing 9 is attached to the central upper opening of the yoke case 7 and supports one end of the rotating shaft 4 .

The first stator 2 also has a similar configuration to the upper stator 1.

That is, it is composed of a coil IO, a yoke case 11 that houses the coil 10, and a yoke plate 12 that engages with the yoke case 11. A bearing 13 is attached to the central lower end opening of the lower stator 2, and supports the other end of the rotating shaft 4.

To assemble a step motor having such a configuration, the upper stator 1 is attached to one end of the rotating shaft 4 via the bearing 9,
The lower stator 2 is attached to the other end of the rotating shaft 4 via a bearing I3. In this state, the upper stator 1 and the lower stator 2 are coaxially aligned using the guide ring 14 and fixed to each other by welding. At this time, the upper yoke plate 8 and the lower yoke plate 12 are arranged at a predetermined interval from each other along the rotation axis direction by the guide ring 14. A disk magnet 5 is rotatably mounted within this interval. A magnetic gap is formed between the upper and lower surfaces of the disc-shaped magnet 5 and the corresponding yoke plate, and by energizing the pair of coils 6 and 1O in a predetermined phase relationship, the upper and lower yoke plates and the disc-shaped A magnetic attraction and repulsion force is generated between the rotor 3 and the magnet, and the rotor 3 rotates in steps.

In the step motor according to the present invention, since the disk-shaped magnet is magnetized in the direction of the rotation axis to form magnetic domains, it is possible to use anisotropic ferrite magnets, and the cylindrical rotor type using isotropic magnets is possible. It is possible to obtain a high-performance rotor with approximately 2.5 times the energy product compared to a PM step motor.

FIG. 2 shows a yoke plate 8 or 12 which is the main part of the present invention.
FIG. 2 is a plan view showing one embodiment of the invention. As shown in the figure, the yoke plate is composed of an inner yoke ring part 15 and an outer yoke ring part 16. Inner yoke ring part 15
is equipped with six magnetic pole pieces 17 corresponding to every other one of the twelve magnetic domains arranged along the circumferential direction of the disc-shaped magnet 5. Further, the outer yoke ring portion 16 is connected to the six magnetic pole pieces 17 and the other six magnetic pole pieces 1 arranged in a comb shape along the circumferential direction.
It has 8. The inner yoke ring part 15 and the outer yoke ring part 16 are arranged along the same plane and are integrally positioned and connected by a connecting part 19.

In the embodiment shown in FIG. 2, there are a total of 12 pole pieces 17.
and 18 for connecting the inner and outer yoke ring parts. A yoke plate having such a structure can be easily obtained by processing a thin plate of magnetic material, for example, by press punching. Further, since the relative positional accuracy of each magnetic pole piece is uniformly determined by the dimensional accuracy of the press die, it is possible to obtain a yoke plate component having an extremely highly accurate dimensional shape.

The press punched parts obtained in this way can be used in common for the yoke plates 8 and 12.

When assembling the step motor, the upper yoke plate 8 is engaged with the yoke case 7, and the lower yoke plate 12 is connected to the lower yoke case 1 with a predetermined phase difference with respect to the upper yoke plate 8. All you have to do is engage. Therefore, relative positioning of yoke plates 8 and 12 is extremely easy.

FIG. 3 is a plan view showing another embodiment of the yoke plate. In this embodiment, the inner yoke ring part 15 and the outer yoke ring part 16 are connected to each other by two narrow connections 19. Since the role of the connecting portion 19 is to integrally position the inner yoke ring portion 15 and the outer yoke ring portion 16, mechanical strength is not necessarily required. Therefore, the size and shape of the connecting portion 19 or the number of connected portions can be appropriately set ηf according to the required characteristics of the step motor and the workability of the parts of the yoke plate. In the embodiment shown in FIG. 3, the connecting portion 19 is easily magnetically saturated and the inner yoke ring portion 15 and the outer yoke ring portion 16 can be magnetically separated.

〔Effect of the invention〕

As described above, according to the present invention, by using a yoke plate in which the inner yoke ring and the outer yoke ring are integrally molded, the geometric positional accuracy of the yoke magnetic pole pieces in the circumferential direction can be improved compared to the conventional method. As a result, the step angle accuracy is significantly improved. In addition,
There is also the effect that the processing of yoke parts is easier than in the past, and the manufacturing cost of the step motor is reduced.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a flat rotor type PM step motor according to the present invention in the rotational axis direction, FIG. 2 is a plan view showing an example of a yoke plate used in the step motor shown in FIG. 1, and FIG. FIG. 4 is a plan view showing another embodiment of the yoke plate, FIG. 4 is an exploded view showing a conventional cylindrical rotor type PM step motor, and FIG. 5 is a conventional flat rotor type PM step motor.
FIG. 3 is an exploded view showing the structure of a step motor. 1... Upper stator 2... Lower stator 3.
...Rotor 4...Rotating shaft 5...Disk magnet 6...Coil 7...Yoke case 8...Yoke plate 10...Coil 12...Yoke plate 9... Bearing 11...Yoke case 13...Bearing 15...Inner yoke ring part 16...Outer yoke ring part 17...Magnetic pole piece 18
...Magnetic pole piece 19...Connection part 14...
guide ring

Claims (1)

[Claims] 1. A pair of stators that are arranged opposite to each other with a predetermined gap in the direction of the rotation axis, and a plurality of magnetic domains that are magnetized in the direction of the rotation axis and whose polarities alternate in the circumferential direction. In a step motor including a rotor mounted in the gap and a disk-shaped magnet set to The yoke plate is composed of an inner yoke ring portion having a magnetic pole piece corresponding to every other magnetic domain in the plurality of magnetic domains, and an inner yoke ring portion having a comb-tooth shape on the magnetic pole piece. It has an outer yoke ring part having magnetic pole pieces aligned with each other, and the inner yoke ring part and the outer yoke ring part are arranged along the same plane and are integrally positioned and connected by a connecting part. step motor. 2. The step motor according to claim 1, wherein the connecting portion is formed to generate magnetic saturation so that the inner yoke ring portion and the outer yoke ring portion can be substantially magnetically separated.