JP2001078397A - Method for removing weld flash of yoke part of voice coil motor for hard disk drive and voice coil motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a clean voice coil motor that is effective for eliminating weld flashes for all ridges including a part with fine work and eliminated the flashes which are harmful to hard disk drive. SOLUTION: In this method for eliminating weld flashes 11 and 12, that are generated by shear machining on a surface 1 of yoke parts, made of low carbon steel of a voice coil motor for a hard disk drive, and has a thickness of 0.5 mm or smaller, to the yoke parts are subjected to a barrel polishing process B and a flash removal process C successively. After the flashes have been removed, chemical polishing is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing burrs on a surface of a yoke component constituting a magnetic circuit of a voice coil motor for a hard disk drive, and more particularly to removing burrs on all ridge lines including finely worked portions. The present invention relates to a method for deburring a yoke component. Also,
The present invention relates to a voice coil motor for a hard disk drive using a yoke component from which such burrs have been removed.

[0002]

2. Description of the Related Art As shown in FIG. 1, a voice coil motor for a hard disk drive is mainly composed of a rare-earth magnet a having high magnetic properties and a yoke constituting a magnetic circuit. It is composed of component b (c in the figure is a coil), and in recent years, it has been increasingly desired to purify the magnetic head in order to prevent a head crash due to a decrease in the flying height of the magnetic head accompanying an increase in the storage capacity of the hard disk. Have been.

[0003] Among them, yoke parts manufactured by press sheet metal, cutting, and the like mainly use low carbon steel in order to obtain excellent motor performance, but low carbon steel has a sticky property. Therefore, there is a disadvantage that shear burrs and cutting burrs are easily generated.

Further, as hard disk drives have been miniaturized year by year, yoke components constituting a magnetic circuit of a voice coil motor used therein have been miniaturized and complicated in shape, and through holes, bending, and screws have been required. The number of yoke parts with fine work such as holes is increasing, and the frequency of occurrence of burrs tends to increase. For example, in a through hole or a screw hole having an outer diameter of about 3 mm, shear burrs or cutting burrs having a thickness or a thickness of 0.5 mm or less often occur. This burr is not only attached to the yoke component surface, but also due to physical factors,
It can easily fall off due to chemical factors.

Further, since the surface of the yoke component is plated with nickel, even if the burr does not fall off, the nickel powder on the surface may fall off when the burr receives an impact.

Dropping of burrs causes deterioration of cleanliness of a voice coil motor for a hard disk drive, and if the burrs fall off during operation of the hard disk drive and collide with a magnetic head, a problem such as a head crash occurs. In particular, in recent years, the flying height of the head has been reduced to 0.1 μm or less, and burrs of 0.5 mm or less may cause head crash.

If burrs fall off onto the hard disk, the burrs show ferromagnetism, which causes a problem such as breakage of recorded data. Particularly, in recent years, the recording density of a hard disk has been increased to 1 gigabyte / cm ² or more, and burrs of about 0.5 mm may cause serious damage to recorded data.

Various deburring methods have been proposed for removing burrs on yoke components constituting the magnetic circuit of such a voice coil motor for a hard disk drive, but all of these methods are completely deburring methods. is not. For example, the removal of burrs by barrel polishing is effective for removing large burrs generated on the ridge line and the like on the outer periphery of the yoke component. However, the yoke in the portion where fine work is performed, such as through holes, bending, screw holes, etc. There is a disadvantage that burrs having a thickness or a thickness of 0.5 mm or less existing on the part cannot be removed because the abrasive does not sufficiently collide.

The removal of burrs by chemical polishing is effective for removing the thin burrs having a thickness of 0.1 mm or less existing on the yoke parts at any place on the whole yoke parts, but is effective for a long time. The chemical polishing treatment alone also melts the yoke component body, so that there is a disadvantage that the burr existing in the yoke component or having a thickness of 0.5 mm or less cannot be melted and removed. . Normal,
In chemical polishing, the thickness or thickness existing in the yoke part of the finely worked part such as a through hole, bending work, screw hole, etc. that is smaller than the diameter of the abrasive material that can not be removed by barrel polishing is 0.5 mm or less As described above, it is used for the purpose of reducing the size of burrs, but has no effect of completely removing these burrs.

[0010] On the other hand, in the removal of burrs by ultrasonic waves, a thin bald burr generated by cutting or the like can be removed.
The burr generated by shearing has a shape with a wide root at its tip, and it has the disadvantage that it cannot be removed from the root by using ultrasonic vibration. Generally, the magnetic circuit of a voice coil motor for hard disk drives It is not used for deburring the yoke parts constituting the above.

In the prior art, the mainstream of deburring a yoke component constituting a magnetic circuit of a voice coil motor for a hard disk drive is to perform only barrel polishing or chemical polishing after barrel polishing. A burr having a thickness or a thickness of 0.5 mm or less existing in the yoke component in a part where fine work such as machining and screw holes is performed cannot be removed, and may be removed with a brush or the like.

However, since the shape of the yoke part differs for each product in the part where the burr remains and the fine work is performed, it is difficult to automate the brushing. However, there was a problem that the cost was too high.

SUMMARY OF THE INVENTION The present invention has been made in order to improve the situation described above, and it is an object of the present invention to reliably and efficiently remove burrs existing on all ridge lines including finely worked portions of a yoke component. It is an object of the present invention to provide a method for deburring a yoke component constituting a magnetic circuit of a voice coil motor for a hard disk drive, and a voice coil motor for a hard disk drive using the yoke component subjected to the deburring.

[0014]

Means for Solving the Problems and Embodiments of the Invention The present inventor has conducted intensive studies in order to achieve the above-mentioned object, and as a result, it has been found that a low burr generated by shearing, cutting and the like is generated. The carbon steel yoke part is first subjected to barrel polishing, and then deburring by ultrasonic waves, so that the finely worked portion of the entire yoke part, that is, the abrasive material for barrel polishing sufficiently collides. It is difficult to remove burrs and it is difficult to remove burrs existing on all ridge lines, including through-holes with a diameter of 10 mm or less, screw holes, dents, and parts with a bending radius of 5 mm or less. It has been found that the present invention has been accomplished.

Accordingly, the present invention is a method for removing burrs present on the surface of a yoke component made of low carbon steel of a voice coil motor for a hard disk drive, comprising a barrel polishing step and ultrasonic deburring for the yoke component. And a decoupling method for a yoke component, and a voice coil motor for a hard disk drive using the yoke component from which burrs have been removed by the deburring method.

Hereinafter, the present invention will be described in more detail.
In the deburring to which the method of the present invention is applied, the burr is present in a yoke component constituting a magnetic circuit of a voice coil motor for a hard disk drive using a low carbon steel, and particularly has a thickness or thickness of 0.5 mm or less. Refers to burrs that have occurred on all ridgelines, including those with fine workmanship. FIGS. 2A and 2B schematically show aspects of burrs. FIG. 2A shows shear burrs of a pressed yoke, FIG. 2B shows whisker-like burrs of a cut yoke, and shows definitions of thickness and thickness of burrs. However, the present invention is not limited to this.

The deburring method of the present invention comprises sequentially performing a barrel polishing step and an ultrasonic deburring step on a yoke component having the above-mentioned burrs. explain.

[Barrel Polishing Step] Barrel polishing is a process in which the abrasive is a barrel other than a finely worked portion such as a through-hole, a bending process, a screw hole, etc. of a yoke component constituting a magnetic circuit of a voice coil motor for a hard disk drive. The purpose of the present invention is to remove burrs generated on ridge lines that can sufficiently collide with the ridge line. At the same time, the thickness or thickness existing in the yoke component in the part where fine work such as through-holes or bending is performed is 0.5
The burrs generated by shearing less than mm are not sufficient to remove burrs, but by colliding abrasives,
It also has the purpose of forcibly rolling and narrowing the root to form a shape that can be easily removed in the subsequent ultrasonic deburring step.

The barrel polishing uses an abrasive mainly composed of alumina, silica, magnesia, etc., and simultaneously encloses a yoke component and water to which a rust preventive liquid is added in a rotary barrel, a vibration barrel, a centrifugal barrel, or the like. This can be performed by causing the abrasive and the yoke component to collide with each other by rotation, vibration, or the like. In this case, the size of the abrasive is 3 mm or more, especially 5 mm.
mm or more, 20 mm or less, particularly 15 mm or less, usually about 10 mm spherical or triangular,
It is not desirable to add very fine abrasive grains. This is because abrasive grains remain in the screw holes and depressions. Due to this process, the thickness or thickness of the ridgeline where the abrasive material can sufficiently collide with the burr from various angles except for the finely worked parts such as through holes, bending, screw holes, etc. Burrs less than 1.0 mm are removed. However, through holes,
Burrs with a thickness or thickness of 0.5 mm or less caused by shearing of parts that have been subjected to fine work such as bending work can only collide with abrasives from a limited direction, and have a rolled shape It remains without being removed. However, the root is thinner than before the barrel polishing, and can be formed into a shape that can be easily removed by ultrasonic deburring in the next step.

In the prior art, the thickness or thickness existing in a yoke component generated by shearing of a portion that has been subjected to fine work such as a through hole or a bending process that is not removed in the barrel polishing step is 0.5 mm. The following burrs were left to stand or were supplementarily melted by chemical polishing to reduce the size, but as described above, they were not completely removed.

[Deburring Step by Ultrasonic Wave] Deburring by ultrasonic wave is performed on a finely worked portion such as a through-hole, a bending process, and a screw hole of a yoke component constituting a magnetic circuit of a voice coil motor for a hard disk drive. An object of the present invention is to remove burrs existing in a yoke component and having a thickness or a thickness of 0.5 mm or less, which cannot be removed by barrel polishing.

Deburring by ultrasonic waves is performed by irradiating strong ultrasonic waves into water and applying strong vibration to the burrs by utilizing cavitation (blinking of minute bubbles) generated in the resonance region. Burrs cause metal fatigue and are removed.
Since the resonance region where cavitation occurs can only occur in a limited region calculated from the frequency of the ultrasonic wave, it is desirable to fix the portion where deburring is desired to be performed in that region.

If there are a plurality of locations where deburring is desired, the yoke component may be hung underwater with a jig or the like and rocked. Regarding the frequency of the ultrasonic wave, it is desirable to use an ultrasonic wave having a low frequency of about 25 kHz.
When high-frequency ultrasonic waves having a frequency exceeding kHz are used, the resonance area in water increases, but cavitation decreases and burrs cannot be removed. If an ultrasonic wave having a frequency lower than 20 kHz which is close to the sound range is used, intense noise may be generated.
30 kHz ultrasound is preferred. With respect to the output of the ultrasonic oscillator, a high output power of about 1200 W is used, and by arranging the ultrasonic oscillators at a high density, it is possible to enhance the burr removing capability. The water used for deburring by ultrasonic waves has a higher cavitation effect as the temperature is lower. Therefore, if the temperature is controlled at a low temperature of 10 ° C. or lower as needed, the effect increases. Similarly, oil and air in the water also inhibit the generation of cavitation. Therefore, when it is difficult to remove burrs, it is more effective to use pure water and to perform deaeration before removing burrs as necessary. The processing time of deburring by ultrasonic waves is performed for about 30 seconds to 10 minutes depending on the shape of the burr. After deburring by ultrasonic waves, the yoke components are easily wetted and rusted, so it is desirable to immediately dry them with an oven, an air blower or the like. As a result, the thickness or thickness of the burr generated by shearing with a thickness or a thickness of 0.5 mm or less existing in the yoke component in the finely machined portion created by the punching press process such as a through hole and a bending process is particularly large. Since the base is thinned by forcible rolling in the barrel polishing in the previous step, it is possible to remove shear burrs generated by press working which could not be obtained by the conventional ultrasonic deburring alone.

The burrs generated by cutting finely worked portions such as screw holes and dents are completely removed by ultrasonic vibration because the roots are thin.

Such an apparatus is described in Precision Surface Finishing and Burr Technology, Microburr Removal and Surface Finishing by Ultrasonic Cleaning [b] JA F145A Mechanical Technology (JPN) 44 [].

Here, in the case where deburring by ultrasonic waves is performed without performing barrel polishing in the previous step, the burrs generated by shearing have a shape with a wide base at the tip thereof, and As described above, it is not possible to remove from the root even by using vibration, and burrs generated by shearing of all ridge lines including a part with fine work are not removed at all.

Although rare, the thickness or thickness existing in the yoke component is small in the finely worked portion of the yoke component in which the barrel polishing step and the ultrasonic deburring step are sequentially performed. Fine burrs generated by shearing of 1 mm or less fall down and adhere to the yoke component body,
In some cases, it has not been removed to some extent without receiving vibrations caused by ultrasonic waves. If such a material exists, it is effective to dissolve it by performing chemical polishing for finishing. In chemical polishing, the main component is hydrogen peroxide water, ammonium hydrogen difluoride, phosphoric acid, etc.
% Is immersed in an aqueous solution containing 10% for 10 seconds to 10 minutes to chemically dissolve and remove burrs.

In the case of performing chemical polishing, since the surface of the yoke component is activated, it is preferable to immediately perform water washing and pickling after completion of the chemical polishing and to perform plating (nickel, copper, etc.). The chemical polishing and plating steps after the ultrasonic deburring step can be continuously performed by using a common jig for fixing or suspending the yoke components.

FIG. 3 schematically shows a process in which shear burrs generated in through holes are removed in each step of barrel polishing, deburring by ultrasonic waves, and chemical polishing as an auxiliary finishing treatment. Shows a state before barrel polishing, (B) shows a state after barrel polishing, (C) shows a state after deburring by ultrasonic waves, and (D) shows a state after chemical polishing. In the figure, reference numeral 1 denotes a yoke component main body, and 2 denotes a through hole formed in the yoke component body. Before the barrel polishing (A), a small shear burr 11 is formed on the outer peripheral edge of the through hole 2 and has a thickness of 0.5 mm or less. Shear burrs 12 are formed,
These burrs 11 and 12 protrude outward along the direction of penetration of the through hole 2. Each of these burrs 11 and 12 has a thick root with respect to the tip, and cannot be removed only by ultrasonic deburring. When barrel polishing is performed on the yoke component 1 in such a burr state (B), the burr 1
The abrasive 3 hits the burrs 1 and 12 and pushes the burrs 11 and 12 inward (in the direction of the through holes 2). As a result, the burrs 11 and 12 are not removed by the barrel polishing, but are rolled to have a thinner root. In addition, as shown in the figure, the minute shear burr 11 may fall down on the inner peripheral wall of the through-hole 2 and fall down (the tip side contacts the inner peripheral wall). Next, when ultrasonic treatment is performed (C),
As described above, since the bases of the burrs 11 and 12 are thinned by the barrel polishing, the burrs 11 and 12 are removed by ultrasonic treatment. However, the minute shear burrs 11 that have fallen into the inner peripheral wall of the through hole 2 may not be removed yet. Even if the minute shear burrs 11 slightly remain, they are completely removed by performing the chemical polishing (D). In the present invention, the mode of deburring is not limited to FIG.

Under the above conditions, the yoke components constituting the magnetic circuit of the voice coil motor for a hard disk drive are conventionally barrel-polished from large burrs to burrs of finely machined portions such as through holes, bending, screw holes and the like. ,
The thickness or thickness existing in the yoke component has been subjected to fine work generated by shearing of 0.5 mm or less, which could not be removed by using only one of the ultrasonic deburring alone. All burrs are removed, including some burrs. By plating this, it will be commercialized as a yoke part for a voice coil motor without having to worry about burrs coming off the hard disk drive.

By using this yoke component and bonding and magnetizing a magnet to produce a voice coil motor, there is no need to worry about burrs falling off the hard disk drive. The other components and configuration of the voice coil motor incorporating the yoke component can be known.

[0032]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

EXAMPLE A 30 g yoke component constituting a magnetic circuit of a voice coil motor for a hard disk drive was prepared by stamping out a 3.2 mm-thick SPCC cold-rolled steel plate. Yoke is 5cm diagonal
Although it is a flat plate of the order, two through holes having an outer diameter of 3 mm and one rolling tap having an outer diameter of 2.5 mm are formed in the thickness direction. These are used for positioning when incorporating the voice coil motor into the hard disk drive. In the punched state, shear burrs are generated on all the ridges on the press die side including the ridges of the through holes having an outer diameter of 3 mm. In addition, a whisker-like burr due to threading is generated in a screw thread in a rolled tap hole having an outer diameter of 2.5 mm. This test piece was sequentially subjected to rotary barrel polishing and ultrasonic deburring under the following conditions.

[Rotary barrel polishing process] Yoke parts input: 50 pieces × 30 g External diameter: 15 mm Spherical abrasive input: 5 kg (polishing material: mainly composed of alumina and silica) Number of revolutions: 46 r. p. m Polishing time 1 hour

[Deburring Step by Ultrasonic Wave] Ultrasonic frequency: 25 kHz Ultrasonic output: 1,200 W Water temperature: 10 ° C. Water quality: pure water Under the above conditions, the yoke component is hung with a wire, and is burred up and down for 1 minute. I took it.

The yoke subjected to the above processing was plated with nickel. In this case, the normal burrs at the ridge,
Shear burr on ridge of 3mm through hole, 2.5m outside diameter
The burrs on the m-rolled tap were observed. Table 1 shows the results.
Shown in

Comparative Example For comparison, the following yokes were prepared at the same time, and the burrs were similarly evaluated. (Comparative Example 1) Only the above-mentioned [barrel polishing step] was performed. (Comparative Example 2) One in which the above-mentioned [barrel polishing step] and [chemical polishing step] were performed. (Comparative Example 3) [Deburring step by ultrasonic wave] in the above step
Those that only implemented.

In the [chemical polishing step], a chemical polishing liquid (CPL-100 manufactured by Mitsubishi Gas Chemical Co., Ltd.) containing hydrogen peroxide solution and ammonium hydrogen difluoride as main components is diluted three-fold and heated to 20 ° C. For 1 minute. Table 1 shows these results.
It is described together.

[0039]

[Table 1] A: In all the yoke components observed, the burrs were completely removed. ：: The burr was almost completely removed, but some yoke parts remained slightly. Δ: Although there was some effect in removing burrs, burrs still remain in most yoke parts. X: In all the observed yoke parts, burrs were not removed at all. -: There is no applicable burr since before the burr removal processing.

In the examples, after performing the [ultrasonic deburring step] and then performing the [chemical polishing step], the shear burrs of 0.1 mm or less shown in Table 1 are completely removed. I was able to.

[0041]

The method of manufacturing a deburred yoke component constituting a magnetic circuit of a voice coil motor for a hard disk drive according to the present invention is effective for removing burrs on all ridge lines including a finely worked portion. Yes, it is extremely effective in manufacturing a clean voice coil motor that removes burrs harmful to hard disk drives.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a voice coil motor.

FIGS. 2A and 2B schematically show burrs present in a yoke component. FIG. 2A shows shear burrs of a pressed yoke,
(B) is an explanatory view of a mustache-like burr of a cut yoke.

FIG. 3 schematically shows a process of removing burrs generated in a through hole of a yoke component, (A) before barrel polishing, (B) after barrel polishing, (C) after ultrasonic deburring, ( (D) is an explanatory view of the state after chemical polishing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Yoke component main body 2 Through hole 3 Abrasive material 11, 12 Burr

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B24B 31/00 B24B 31/00 Z (72) Inventor Nobutaka Kobayashi 2-1 Kitafu, Takefu-shi, Fukui 5 Shin-Etsu Chemical Co., Ltd. Takefu Plant F-term (reference) 3C058 AA01 AA09 CA01 CB01 CB03 CB10 DA02 5D068 AA01 BB01 CC12 GG25 5H002 AA07 5H615 AA01 BB01 PP07 PP17 SS03 SS08 TT04 TT13 5H633 HH05 HH16H

Claims (5)

[Claims] 1. A method for removing burrs present on a surface of a yoke component made of low carbon steel of a voice coil motor for a hard disk drive, comprising: sequentially performing a barrel polishing process and an ultrasonic deburring process on the yoke component. A deburring method for a yoke component. 2. The deburring method according to claim 1, wherein a chemical polishing step is performed after the ultrasonic deburring step. 3. The method according to claim 1, wherein the burr has a thickness or a thickness of 0.5 mm or less. 4. The deburring method according to claim 1, wherein the burr is a burr generated by a shearing process at the time of manufacturing the yoke component. 5. A voice coil motor for a hard disk drive using a yoke component from which burrs have been removed by the deburring method according to claim 1. Description: