JPH0732561B2 - Stepping motor with resin bracket - Google Patents

Description

TECHNICAL FIELD The present invention relates to a stepping motor having a small magnetic flux leakage suitable for driving a floppy disk, a hard disk, and the like.

(Prior Art) With the rapid spread of office automation equipment in recent years, stepping motors have come to be widely used as drive motors for floppy disks, hard disks, printers and the like.

The stepping motor uses magnetism to drive the rotor, but the floppy disk or hard disk on the driven side is also an information recording medium that uses magnetism, and problems such as loss of recorded information due to leakage magnetism occur. obtain.
The stepping motor itself is the largest source of such leakage magnetism. Therefore, when a stepping motor is used for driving a magnetic recording medium such as a floppy disk or a hard disk, it is necessary to use a material having excellent magnetic shielding properties for the front and rear brackets. In many cases, electromagnetic pure iron is used as this material,
It is formed by forging or powder sintering.

(Problems to be Solved by the Invention) At present, demands for stepping motors include miniaturization, high efficiency, and small size and light weight.
A structural step is the most effective measure for achieving minute steps and high efficiency, and a hybrid type stepping motor in which a permanent magnet magnetized in the axial direction is incorporated in the rotor is suitable. On the other hand, with respect to reduction in size and weight, the material of the bracket has a great influence, but it is considerably restricted because the magnetic shielding property is required. That is, the use of a metal material such as electromagnetic pure iron is unfavorable for weight reduction, and since a forming method such as forging or powder sintering is adopted, it is difficult to reduce the size in terms of design.

(Means for Solving Problems) The present inventors have completed the present invention as a result of intensive research to solve the problems of the conventional art.

That is, according to the present invention, the vicinity of the central shaft hole of a bracket formed by injection-molding a thermoplastic resin mixed with iron fibers is incorporated into the rotor, and the permanent magnet of the permanent magnet magnetized in the axial direction has the same polarity. It is a stepping motor characterized by being magnetized with opposite polarities.

Hereinafter, the present invention will be described in detail.

The iron fiber used in the present invention is a metal fiber containing iron, for example, pure iron, silicon steel, cobalt steel, permalloy, chrome steel, manganese steel, molybdenum steel, vanadium steel, titanium steel, stainless steel, low carbon steel. , And niobium-vanadium steel and the like, one or more kinds of metal fibers are mentioned, but pure iron, silicon steel, cobalt steel, permalloy, and stainless steel are particularly preferable. Further, it is more preferable that the iron fiber is amorphous.

Examples of the method for producing the iron fiber used in the present invention include a wire drawing method, a melt spinning method, a chatter vibration cutting method, a wire rod cutting method used for producing steel wool, and a slit processing method from a foil. To be

The shape of the iron fiber is not particularly limited, but a fiber having a fiber diameter of 5 to 100 μm and a fiber length of 0.5 to 5 mm is preferably used.

The amount of the iron fiber compounded is not particularly limited as long as it has a melt fluidity and a magnetic shielding property, but a range of 100 to 500 parts by weight is preferable based on 100 parts by weight of the thermoplastic resin.
In addition to iron fibers, non-ferrous metal fibers or flakes,
A granular or powdery conductive filler can also be used together.

The thermoplastic resin used in the present invention is not particularly limited as long as it has melt fluidity and can be injection-molded, but is not limited to polyamide, polyester, polycarbonate,
Polyolefin, polyphenylene oxide, and polyphenylene sulfide are preferable.

As a method for manufacturing the bracket according to the present invention, it is sufficient that the iron fiber and the thermoplastic resin are uniformly kneaded at an arbitrary stage until the bracket is injection-molded. For example, a predetermined ratio of iron fibers and a thermoplastic resin may be melt-kneaded using a single-screw kneader or a multi-screw kneader to produce pellets, and then injection molding may be performed. The plastic resin may be directly kneaded and injection-molded. Further, it is preferable to subject the obtained bracket to annealing treatment or humidity control treatment in order to improve dimensional stability.

There are several methods of magnetizing the bracket. For example, a magnetic field injection molding machine may be used to magnetize the bracket during injection molding, or the bracket may be molded using a normal injection molding machine and then placed in a magnetic field. May be magnetized in a predetermined direction.

The strength of the magnetization of the bracket is preferably such that the leakage flux near the longitudinal center of the output side shaft of the stepping motor is about 5 gauss or less. The magnetic flux density is about 5 to 30 gauss with the polarity opposite to that of the permanent magnet incorporated in the rotor and magnetized in the axial direction on the bracket side.

(Effects of the Invention) The stepping motor according to the present invention has a resin bracket, is easy to reduce in size and weight, has a small magnetic leakage, and is suitable for driving a floppy disk, a hard disk or the like.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 100 parts by weight of nylon 6 resin (MC112 manufactured by Kanebo Synthetic Fibers Co., Ltd.), low carbon steel fiber having a fiber diameter of 30 μm and a fiber length of 2 mm obtained by chatter vibration cutting method (S15C, 50X manufactured by Kobe Cast Iron Co., Ltd.)
3) 300 parts by weight were blended and melt-kneaded using a biaxial kneader to obtain pellets.

Then, using the obtained pellets, a bracket having the same shape as that of the electromagnetic pure iron bracket used in the hybrid type stepping motor was molded under the injection molding conditions of nylon 6 resin that is usually used.

Using a permanent magnet with a magnetic flux density of 3,000 gauss to the obtained bracket, the output shaft side is the N pole near the central shaft hole, the peripheral portion is the S pole, and the opposite side to the output shaft side is the central shaft shaft. The magnet was magnetized to a magnetic flux density of 25 gauss, with the S pole near the hole and the N pole at the periphery.

Next, the magnetized bracket was incorporated into a stepping motor, and the leakage magnetic flux on the output shaft side was measured. The results are shown in Table-1. In Table 1, the case where the electromagnetic pure iron, aluminum, and resin-made brackets are assembled without being magnetized is also shown as a comparative example.

Claims (6)

[Claims] Claim: What is claimed is: 1. A bracket formed by injection-molding a thermoplastic resin containing iron fiber is provided with a rotor having a central shaft hole and a portion opposite to the polarity of the axially magnetized permanent magnet on the bracket side. A stepping motor characterized by being magnetized in the polarity of. 2. The stepping motor according to claim 1, wherein the iron fibers are pure iron, silicon steel, cobalt steel, permalloy, stainless steel and low carbon steel. 3. The first claim in which the iron fiber is amorphous.
The stepping motor according to the item. 4. An iron fiber having a fiber diameter of 5 to 150 μm and a fiber length of
The stepping motor according to claim 1, which is 0.2 to 5 mm. 5. The stepping motor according to claim 1, wherein the content of the iron fiber is 100 to 500 parts by weight with respect to 100 parts by weight of the thermoplastic resin. 6. The stepping motor according to claim 1, wherein the thermoplastic resin is polyamide, polyester, polycarbonate, polyolefin, polyphenylene oxide, or polyphenylene sulfide.