JPS6152143A - Manufacture of permanent magnet rotor of stepping motor - Google Patents

Abstract

PURPOSE:To enhance the drive efficiency of a stepping motor by inserting a rotational shaft to a center, opposing the outer periphery to a magnetizer, and molding integrally with plastic containing magnetic anisotropic magnetic powder in a magnetic field while magnetizing the outer periphery. CONSTITUTION:A rotational shaft 20 is disposed at the center of a molding member 26b, and a mixture of approx. 40% of plastic of binder and anisotropic ferromagnetic powder such as ferrite series is filled and molded. When filling, a DC current is flowed through a magnetizing coil 27. Then, a crystal of magnetic anisotropic powder containing plastic as a binder is oriented along a magnetic path 34, shown, by the operation of a magnetizer 29, and desired N- and S-poles are arranged on the outer periphery of the plastic magnet 21 to be multipolarized. Thus, the crystal axis of the magnetic powder improves in the orientation by the formation of the magnetic field, thereby increasing the magnetic force to enhance the drive efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a permanent magnetic rotor used in a stepping motor, particularly when the rotor is made of plastic magnet.

[Conventional technology]

In recent years, small and lightweight PM (permanent magnet) type stepping motors, which are widely used as digital actuators in office automation equipment such as personal computers, word processors, electronic typewriters, and facsimile machines, are known for their high output, high response, and high precision positioning. At the same time, there is a demand for lower prices.

It has been conventionally used for these purposes. A longitudinal section of the stepping motor is shown in FIG. FIG. 6 is a sectional view taken along the line AA in FIG. 5. In these figures, 1 is the rotation axis, 2
Reference numerals a and 2b designate first stator ball members, each of which is press-molded from a soft mesh plate and has n pole teeth protruding in the axial direction of the rotating shaft 1.

3a and 3b are second stator ball members also made of mild steel plate, and the stake ball member 2a is arranged in the axial direction of the rotating shaft l.
n pole teeth protrude alternately with the pole teeth 2b and 2b. The pole teeth of the stator pole member 2a and the pole teeth of the stator ball member 3a are respectively at intermediate positions l! i! They are arranged as one unit, forming a total of 2n pole teeth with a pitch P. The 8i teeth of stator pole members 2b and 3b are also similar l! i! It is fixed as one unit at each location. Furthermore, the unit consisting of the stator pole members 2a and 3a) and the unit consisting of the stator pole members 2b and 3b are fixed in a rotational manner with the arrangement shifted by half the pitch P of the pole teeth, and constitute the stator of the motor. are doing. 4a is a side plate fixed to the stator pole member 2a;
Reference numeral 4b denotes a steel plate fixed to the stator pole member 2b, each having a through hole in its center, for example, an oil-impregnated bearing 5.
Axis l is supported by a and 5b. In addition, the side plate 4a
A plurality of mounting holes 5 are bored in the. 6a and 6b are bobbins, 7a and 7b are two-phase excitation coils, and are bifilar! ! It constitutes a 54-phase coil, and the lead wire 8
& and 8b to the outside and connected to a pulse oscillation source (not shown).

10 is a cylindrical permanent magnet made of, for example, sintered ferrite, which has 2n magnetic poles on its outer periphery, and the magnetic pole surface on the outer periphery is 0.2 mm inside the pole teeth of stator pole members 2a, 3a and 2b, 3b.
They are arranged concentrically with a gap of ~0.4 mm.

Reference numeral 11 denotes a cylindrical intermediate member, the outer diameter part of which is fitted into the permanent magnet 10, the inner diameter part of which is fitted with the rotating @1 eye, and each of which is bonded with 0 or more permanent magnets 10 and the rotating shaft 1. The intermediate member 11 constitutes a rotor of the motor. Both end surfaces 11a and llb of the intermediate member 11 serve as bearing surfaces for thrust bearings. Reference numeral 12 denotes a plurality of spacers fitted to the rotating shaft 1 to position the rotor relative to the stator in the axial direction, and the rotor-side thrust bearing surfaces 11a and llb are in direct contact with the pair of stator-side bearings 5a and 5b. This reduces friction during rotation. Reference numeral 13 denotes, for example, a wavy plate spring disposed between the plurality of spacers 12 to absorb play in the axial direction of the rotor.

The permanent magnet 10 is generally press-molded and fired from a material such as barium ferrite or strontium ferrite. In this case, the accuracy of both the outer diameter and length is poor, and post-processing is required. On the other hand, since the sintered ferrite magnet is a hard material, the molded product cannot be cut and must be ground, resulting in high processing costs. It also has the disadvantage of being chipped or cracked during processing, resulting in a poor processing yield. In order to increase the strength during processing, molded parts are made thicker than necessary and ground, but this results in an increase in the weight of the rotor and increases the inertial rotation. It is difficult to reduce the inertia of a rotor using ferrite FF1 stone.

This had the drawback of hindering improvements in the high response and high speed of stepping motors.

The intermediate member 11 is made of aluminum alloy, etc.
In consideration of the difference in coefficient of thermal expansion from the sintered ferrite permanent magnet 10, the gap at the fitting portion is made slightly larger. The permanent magnet 10 and the intermediate member 11 are held using a jig so that the eccentricity of the outer diameter portion of the permanent magnet 10 with respect to the rotating shaft l is minimized, and the fitting of the rotating shaft l, the intermediate member 11, and the permanent magnet IO is The joint is filled with adhesive. As a result, processing time is increased and costs are further increased.

[Problem that the invention seeks to solve]

The present invention aims to eliminate rotors such as ferrite magnets that have been conventionally used and have the above-mentioned inconveniences, and to provide an efficient manufacturing method for plastic magnets.

[Means for solving problems]

A rotating shaft is inserted in the center, and while the outer circumference is magnetized with the outer circumferential surface facing a magnetizer, it is integrally molded with plastic containing magnetically anisotropic magnetic powder in a magnetic field.

[Effect]

In this way, the crystal axis of the magnetically anisotropic magnetic powder is oriented along the magnetic field generated by the magnetizer, and a magnetic pole is formed with a strong force, thereby producing a permanent magnet φ rotor.

〔Example〕

Figure 2 is a diagram for explaining an embodiment of the manufacturing method to which the present invention is applied, and shows the state when integral magnetic field molding of the rotor is performed, as viewed from the axial direction of the rotor shaft.

FIG. 2 is a sectional view taken along line BB in FIG. 1.

The molds shown in these figures include a non-magnetic mold member 26a made of a non-magnetic material such as beryllium copper, and a non-magnetic mold member 26a made of, for example, beryllium copper.
On the outer periphery of the cylindrical mold member 26a consisting of b,
A cylindrical magnetizer 29 in which a magnetizing coil 27 is wound around a yoke pole 28 is arranged concentrically. The rotary shaft 20 is placed in the center of the mold member 26b, and a mixture of, for example, ferrite-based magnetic anisotropic ferromagnetic powder and about 40% (volume ratio) of the binder Blastiff is injected and molded (injection rotor). (not shown), during injection (plastic is in a molten state)
A direct current is passed through the magnetizing coil 27. Then, due to the action of the magnetizer 29, the crystals of the magnetically anisotropic magnetic powder using plastic as a binder are oriented along the illustrated magnetic path 34, and the desired NS poles are arranged on the outer periphery of the plastic magnet 21. It is multi-pole magnetized. Note that a part of the outer circumference of the rotating shaft 20 is provided with, for example, a knurling 20a, and a rising connecting portion 24 is provided on the inner circumference of the inner cylinder 22 of the plastic magnet 21.
There is a relatively thin outer cylinder 23 formed therein. Further, reinforcing walls are provided every 174 pitches around the circumference.

The permanent magnet rotor manufactured in this manner is assembled into a stepping motor as shown in FIG.

Permanent magnets manufactured as described above
The outer periphery of the rotor 21 is magnetized to a desired NS pole, but the rotor 21 may be further subjected to the following steps. Alternatively, the magnetizing coil 31 may be placed concentrically on a cylindrical magnetizing jig 33 wound around the yoke pole 32, and the outer periphery may be magnetized again.

The pitch of the yoke poles 32 is the same as the crystal orientation pitch of the magnetically anisotropic material of the plastic magnet, and the NS poles magnetized on the outer periphery again become as desired.

In the short chipping motor shown in FIG. 4, the end of the inner cylinder 22 is a thrust bearing. Other configurations are No. 9
Since it is the same as the conventional motor shown in FIG. 6, the explanation will be omitted.

In such a stepping motor, the drive circuit distributes a series pulse signal sent from the oscillation power supply to each phase of the motor's excitation coils 7a and 7b to flow current. , are simultaneously excited by a combination of one layer of excitation coil 7a and one layer of excitation coil 7b. As a result, the two layers of pole teeth of the stator ball member 2a@3b or 2b and 3b are excited, and the plastic magnet 2
1 attracts two layers of magnetic poles. The step angle at this time is - for the pitch P portion. Excitation coils 7a and 7b
When the coils of each layer are excited one after another in a certain combination, the plastic magnet 21 moves in steps and the rotor rotates.

〔effect〕

The permanent magnetic rotor of the stepping motor manufactured by the method of the present invention can have a strong magnetic force and high driving efficiency because the crystalline Al+ of the magnetically anisotropic magnetic powder can be improved in orientation by magnetic field molding. Become something.

Furthermore, since it is integrally molded with the rotating shaft, the number of processing steps is extremely small, making it possible to significantly reduce costs.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams explaining an embodiment of the manufacturing method to which the present invention is applied, Figure m3 is a diagram explaining another embodiment, and Figure 4 is a stepping machine using the rotor manufactured according to the present invention. FIG. 5 is a longitudinal cross-sectional view of a conventional motor, and FIG. 6 is a cross-sectional view taken along line A-A of the motor. 20 is a rotating shaft, 21 is a plastic magnet rotor,
22 is an inner cylinder, 23 is an outer cylinder, 26a and 26b are non-magnetic molds, and 29 is a magnetizer. Figure 1 Figure 3 Figure 2 Figure 4

Claims (1)

[Claims] 1. A rotary shaft is inserted in the center, and the outer circumference is magnetized with the outer circumferential surface facing a magnetizer, and the plastic containing magnetically anisotropic magnetic powder is integrally molded in a magnetic field. A method of manufacturing a permanent magnetic rotor for a stepping motor. 2. A method for manufacturing a permanent magnet rotor for a stepping motor according to claim 1, wherein the molding in a magnetic field is performed, then demagnetized once, and then the outer periphery is magnetized again.