JPH11164528A - Apparatus and method for magnetization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform magnetization into a magnetized waveform of a samarium cobalt magnet even through it is a neodymium magnet. SOLUTION: A magnetizing yoke 1, into which an annular member 2 to be magnetized is inserted, is provided. The magnetizing yoke 1 is a column, whose cross section is approximately square and the magnitude of each gap formed between the magnetizing yoke 1 and an internal peripheral surface 7 of the member 2 to be magnetized is made larger at the center part of a magnetic pole of the member 2 to be magnetized than at the boundary parts 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetizing device and a magnetizing method for magnetizing a drive magnet used in a disk drive motor.

[0002]

2. Description of the Related Art In a disk drive motor, various magnets are applied to a drive magnet in accordance with the application (rotation speed, storage capacity, etc.). The disk drive motor is required to have a high torque and a small torque fluctuation. This is because if the torque fluctuation is large, smooth rotation cannot be realized.

As a method of magnetizing a driving magnet used in the motor, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-223872, a coil portion is integrally molded with a non-magnetic material, a magnetic flux is generated by an electromagnet, and a cross section is formed. , A non-magnetized magnet is externally fitted to a circular magnetized coil body, and further, a member composed of a non-magnetic portion and a ferromagnetic portion is externally fitted. The magnet is magnetized by generating a magnetic flux by energizing the magnetizing coil body.

However, as a material of the driving magnet, a samarium-cobalt (Sm-Co) -based magnet (hereinafter, referred to as a samakoba magnet), which is one of rare earth magnets, has been generally used. However, with the cost reduction of disk drives, there has been a demand for lower cost motors.
In some cases, a relatively expensive samakoba magnet is one of the same rare earth magnets and is an inexpensive neodymium-iron-boron (Nd-Fe-B) -based magnet (hereinafter referred to as a neodymium magnet).

[0005]

However, neodymium magnets could not have the same magnetic properties as samakoba magnets. That is, the starting torque waveform of the motor incorporating the samakoba magnet is shown in FIG. 6, but the starting torque waveform of the motor incorporating the neodymium magnet is shown in FIG. 7, and the torque ripple of the starting torque waveform of the neodymium magnet increases. This has led to a decrease in characteristics. This is because, as shown in FIG. 7, the minimum value a of the starting torque waveform is located at the energization switching point b of the excitation current, the deviation of the energization switching timing during motor operation determines the minimum value as it is, and the torque ripple increases. Was causing it. In addition, in order not to increase the torque ripple, it is necessary to accurately switch the energization so as not to cause the displacement, so that the magnet is difficult to use. Note that a starting torque waveform is usually used as a characteristic of the driving magnet. The starting torque waveform is a waveform representing the fluctuation of torque serving as a driving source of rotation. For example, in the case of a three-phase motor, a torque generated when current is sequentially supplied to each winding is synthesized into a waveform. It is.

On the other hand, in the case of the samba cover magnet, as shown in FIG. 6, the magnetic center point lower than the energization switching point b has the minimum value a as shown in FIG. From the switching point b to the center point of the magnetic pole, deviation of the energization switching is allowed, and the torque ripple does not increase. Therefore, the samakoba magnet has better characteristics than the neodymium magnet and can be said to be an easy-to-use driving magnet.

As described above, it is understood that it is preferable to make the magnetization characteristics of the neodymium magnet close to those of the samakoba magnet.

Therefore, according to the present invention, a magnet can be obtained which can obtain the same magnetization characteristics as a samakoba magnet with an inexpensive neodymium magnet and, when incorporated in a motor, is a highly accurate motor with little torque fluctuation. It is an object of the present invention to provide a magnetizing device and a magnetizing method that can perform the magnetizing.

[0009]

In order to achieve the above object, a magnetizing device according to the present invention is a magnetizing device having a magnetizing yoke into which a ring-shaped magnetized member is inserted. In the magnetized yoke, the size of the gap formed between the magnetized yoke and the inner peripheral surface of the magnetized member is larger at the center of the magnetic pole of the magnetized member than at the boundary.

Further, the magnetized yoke may be a column having a substantially square cross section or a column having a star cross section.

Further, the magnetizing method according to the present invention provides a ring-shaped neodymium-iron-boron magnet before magnetizing a cylindrical magnetized yoke having cutouts formed at predetermined intervals along the circumferential direction on the outer peripheral surface. Is externally fitted to magnetize the magnet.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a main part of a magnetizing device according to the present invention. The magnetizing device includes a magnetizing yoke 1, and a ring-shaped magnetized member 2 is inserted into the magnetizing yoke 1. The magnetized member 2 is magnetized. The magnetized yoke 1 is formed of a columnar body having a notch 5 formed on the outer peripheral surface thereof and having a substantially square cross section. The magnetized member 2 is formed of neodymium-iron-boron (one of rare earth magnets). It consists of Nd-Fe-B) based magnets.

On the outer peripheral surface of the magnetized yoke 1,
A groove 3 is provided at one of the corners, and a coil 4 is fitted into the groove 3. That is, when a current flows through the coil 4, a magnetic flux is generated from the magnetized yoke 1, and the magnetized member 2 is magnetized. The outer periphery of the magnetized member 2 is surrounded by a magnetic yoke member (not shown). That is, this magnetic yoke member has, for example, a short cylindrical non-magnetic portion provided on the inner peripheral side, and a short cylindrical ferromagnetic portion made of electromagnetic steel provided on the outer peripheral side, and flows to the magnetized member 2. This increases the magnetic flux.

As described above, on the outer peripheral surface of the magnetized yoke 1,
Since the notch 5 is formed, a gap 6 having a substantially arc-shaped cross section is formed between the notch surface of the notch 5 and the inner peripheral surface 7 of the magnetized member 2 facing the notch. That is, when the notch 5 is not formed (when the cross section is circular like a conventional magnetized yoke), the gap S between the outer peripheral surface of the magnetized yoke 1 and the inner peripheral surface 7 of the magnetized member 2 is formed. Is constant over the entire circumference, but by providing the notch 5, the size of the gap 6 formed between the center of the magnetic pole of the magnetized member 2 and the inner peripheral surface 7 of the magnetized member 2 is increased. The length is made larger than the magnetic pole boundary portion 10.

As a result, the magnitude of the magnetic flux at the time of magnetization gradually decreases as the distance from the magnetic pole boundary portion 10 to the intermediate portion of the gap 6 decreases, and the magnitude of the magnetic flux of the magnet decreases slightly, as shown in FIG. In addition, the magnetization waveform representing the magnetization characteristics of the magnet is formed such that the concave portion 9 is emphasized in the peak portion 8 as compared with the conventional case. In other words, samarium cobalt (Sm−
It becomes a waveform like the magnetization waveform of the Co) system magnet.

Accordingly, the starting torque waveform when this magnet is incorporated in the motor is substantially the same as in FIG. 6, even if the energization switching is deviated because the magnetic pole center point lower than the energization switching point has the minimum value. Since a shift in the energization switching is allowed from the energization switching point to the center point of the magnetic pole, the waveform is similar to that of the Samakoba magnet with small torque ripple.
That is, the starting torque waveform in the neodymium magnet in this case is as shown in FIG. 3A, and the waveform as shown in FIG. 6 representing that of the above-mentioned samakoba magnet is continuous. The starting torque waveform of the neodymium magnet according to the conventional magnetizing method is as shown in FIG. 3A, which is a continuation of the waveform of FIG. Comparing FIG. 3A and FIG. 3A, it can be determined that the larger the width between the maximum value and the minimum value of the waveform, the larger the torque ripple, and as shown in FIG. When this happens, the minimum value changes each time due to a shift in switching timing, resulting in unstable rotation. (The torque ripple is large.)

FIG. 4 shows another magnetized yoke 1. In this case, the cutout 5 is cut further than that of FIG. 1 so that the cross section has a so-called star shape. Therefore,
In the magnetized yoke 1 of FIG. 4 as well, the size of the gap 6 formed between the magnetic pole center of the magnetized member 2 and the inner peripheral surface 7 of the magnetized member 2 is determined by the magnetic pole boundary 10. Is also bigger.

Therefore, as shown in FIG. 5, the magnetized waveform is a waveform similar to the magnetized waveform of the samakoba magnet in which the concave portion 9 is formed in the crest 8 more emphasized than that in FIG.

The magnetized yoke 1 shown in FIGS. 1 and 4 has a square or star-shaped cross section, because the magnet is for four poles and is for six poles. If so, six notches 5 may be formed. That is, the gap corresponding to the center of the magnetic pole of the magnet may be set slightly larger at the time of magnetization, and is not limited to four poles or six poles.

[0021]

According to the present invention, the following significant effects can be obtained by the above-described structure.

According to the first or fourth aspect, it is possible to form a magnet such as a magnetized waveform of a samakoba magnet by using a neodymium magnet, and to form a magnet which is inexpensive and has excellent magnetic characteristics. If incorporated into a motor, a high-precision motor with little torque fluctuation is obtained.

According to the second or third aspect, the magnet for four poles can be formed easily and reliably.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a magnetizing device according to the present invention.

FIG. 2 is a magnetization waveform diagram.

FIG. 3 is a starting torque waveform diagram.

FIG. 4 is a sectional view of a main part of another magnetizing device.

FIG. 5 is a magnetization waveform diagram.

FIG. 6 is a waveform diagram of a starting torque of a samako magnet.

FIG. 7 is a starting torque waveform diagram of the neodymium magnet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetization yoke 2 Magnetized member 5 Notch 6 Gap 7 Inner peripheral surface 10 Boundary part

Claims (4)

[Claims] 1. A magnetizing device comprising a magnetized yoke 1 into which a ring-shaped magnetized member 2 is inserted, wherein the magnetized yoke 1 is in contact with an inner peripheral surface 7 of the magnetized member 2. A magnetizing device characterized in that the size of the gap (6) formed therebetween is larger at the center of the magnetic pole of the magnetized member (2) than at the boundary (10). 2. The magnetizing device according to claim 1, wherein the magnetizing yoke 1 is a column having a substantially square cross section. 3. The magnetizing device according to claim 1, wherein the magnetizing yoke 1 is a column having a star-shaped cross section. 4. A ring-shaped neodymium-iron-boron-based magnet before magnetizing is externally fitted to a cylindrical magnetized yoke 1 having notches 5 formed at a predetermined pitch along the circumferential direction on the outer peripheral surface. A magnetizing method characterized by magnetizing a magnet.