JP3636286B2 - Deburring method for yoke part of voice coil motor for hard disk drive and voice coil motor - Google Patents

Description

◎：観察したすべてのヨーク部品において、バリは完全に除去されている。
○：バリはほぼ完全に除去されているが、わずかに残っているヨーク部品もある。
△：バリ除去に若干の効果はあったが、バリはまだ大半のヨーク部品で残っている。
×：観察したすべてのヨーク部品において、バリは全く除去されていない。
−：バリ除去処理前より該当するバリが存在しない。
【００４０】
なお、実施例において、［超音波によるバリ取り工程］を施した後、［化学研磨工程］を続いて行ったところ、表１に示す０．１ｍｍ以下のせん断バリを完全に除去することができた。
【００４１】
【発明の効果】
本発明によるハードディスクドライブ用ボイスコイルモーターの磁気回路を構成するバリ取りを施したヨーク部品の製造方法は、細かい細工をしている部分を含むすべての稜線に対するバリ除去に有効であり、ハードディスクドライブに有害なバリを除去した清浄なボイスコイルモーターの製造に極めて有効である。
【図面の簡単な説明】
【図１】ボイスコイルモーターの概略斜視図である。
【図２】ヨーク部品に存在するバリの態様を模式的に示すもので、（Ａ）はプレスしたヨークのせん断バリ、（Ｂ）は切削したヨークのヒゲ状バリの説明図である。
【図３】ヨーク部品の貫通穴に生じたバリの除去過程を模式的に示し、（Ａ）はバレル研磨前、（Ｂ）はバレル研磨後、（Ｃ）は超音波によるバリ取り後、（Ｄ）は化学研磨後の状態の説明図である。
【符号の説明】
１ ヨーク部品本体
２ 貫通穴
３ 研磨材
１１，１２ バリ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a deburring method for a surface of a yoke part that constitutes a magnetic circuit of a voice coil motor for a hard disk drive, and in particular, a yoke part that can remove burrs on all ridge lines including a finely crafted portion. It relates to the deburring method. The present invention also relates to a voice coil motor for a hard disk drive using a yoke part from which such burrs are removed.
[0002]
[Prior art and problems to be solved by the invention]
As shown in FIG. 1, the hard disk drive voice coil motor is mainly composed of a rare earth magnet a having high magnetic properties and a yoke part b constituting a magnetic circuit (in the figure, c is a coil), and in recent years, there has been an increasing demand for cleaning the magnetic head so that the head does not crash due to a decrease in the flying height of the magnetic head accompanying an increase in the storage capacity of the hard disk.
[0003]
Among these, especially yoke parts manufactured by press sheet metal, cutting, etc. mainly use low carbon steel to obtain excellent motor performance, but low carbon steel has a tendency to stick, There is a drawback that shear burrs and cutting burrs are likely to occur.
[0004]
In addition, as hard disk drives have become smaller year by year, the yoke parts that make up the magnetic circuit of the voice coil motor used for these hard disks have become smaller and more complex in shape, such as through holes, bending, screw holes, etc. There is an increasing number of finely crafted yoke parts, and the frequency of burrs tends to increase. For example, shear burrs or cutting burrs having a thickness or thickness of 0.5 mm or less often occur in through holes or screw holes having an outer diameter of about 3 mm. This burr is not only attached to the surface of the yoke part, but can easily fall off due to physical and chemical factors.
[0005]
Further, since the surface of the yoke part 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.
[0006]
The loss of burrs causes deterioration of the cleanliness of the voice coil motor for the hard disk drive. If the burrs that have fallen off during the operation of the hard disk drive collide with the magnetic head, problems such as head crashes occur. Particularly in recent years, the flying height of the head has become 0.1 μm or less, and burrs falling off of 0.5 mm or less can cause a head crash.
[0007]
Further, if the burr that has dropped off adheres to the hard disk, the burr exhibits ferromagnetism, which causes problems such as damage to recorded data. Particularly in recent years, the recording density of hard disks has become 1 gigabyte / cm ² or more, and omission of burrs of about 0.5 mm can also cause serious damage to recorded data.
[0008]
Various deburring methods have been proposed in order to remove burrs from yoke parts constituting the magnetic circuit of the voice coil motor for hard disk drive, but none of these methods are perfect as deburring methods. For example, removal of burrs by barrel polishing is effective for removing large burrs that occur on ridges on the outer periphery of yoke parts, but yokes that are subjected to fine work such as through holes, bending, and screw holes. The burr having a thickness or thickness of 0.5 mm or less present in the part has a disadvantage that it cannot be removed because the abrasive does not sufficiently collide.
[0009]
In addition, deburring by chemical polishing is effective for removing microburrs with a thickness or thickness of 0.1 mm or less that are present in the yoke component at any location of the entire yoke component. However, since the yoke component main body is melted by itself, there is a disadvantage that the burr having a thickness or thickness of 0.5 mm or less existing in the yoke component cannot be melted and removed. Normally, in chemical polishing, the thickness or thickness existing in the yoke part of a part that has been finely crafted such as a through-hole, bending process, screw hole or the like that is smaller than the diameter of the abrasive that cannot be removed by barrel polishing is 0. Although it is used for the purpose of supplementarily reducing burrs of 5 mm or less, as described above, it does not have an effect of completely removing these burrs.
[0010]
On the other hand, the burr removal by ultrasonic waves removes the thin whisker-like burr at the root of cutting, but the burr generated by shearing has a shape with a wide root at the tip, and vibration by ultrasonic waves However, it is not used for deburring of yoke parts constituting a magnetic circuit of a voice coil motor for a hard disk drive.
[0011]
In conventional technology, barrel polishing alone or chemical polishing after barrel polishing is the mainstream of deburring of yoke parts that make up the magnetic circuit of voice coil motors for hard disk drives. A burr having a thickness or thickness of 0.5 mm or less present in a yoke part in a finely crafted portion such as a hole cannot be removed and may be removed with a brush or the like.
[0012]
However, the parts that have been finely crafted to cause burrs are difficult to automate brushing because the shape of the yoke parts differs from product to product, and it is necessary to do it manually. There was a problem that it took too much.
[0013]
The present invention has been made in order to improve the above situation, and a hard disk capable of reliably and efficiently removing burrs present on all ridge lines including finely crafted portions of yoke parts. It is an object of the present invention to provide a deburring method for a yoke part constituting a magnetic circuit of a voice coil motor for a drive, and a hard disk drive voice coil motor using the deburred yoke part.
[0014]
Means for Solving the Problem and Embodiment of the Invention
As a result of earnest studies to achieve the above object, the present inventor first barrel-polished the low-carbon steel yoke part that has been subjected to shearing, cutting, etc. to produce burrs, and then By deburring with ultrasonic waves in water, the outer part of the yoke part that has been finely crafted, that is, the barrel polishing abrasive cannot collide sufficiently and burrs are difficult to remove. It has been found that burrs existing on all ridge lines including parts such as through holes, screw holes, indentations of 10 mm or less, and bending processes of radius 5 mm or less can be surely removed, and the present invention has been made. is there.
[0015]
Accordingly, the present invention is a method of removing burrs present on the surface of a yoke part made of low carbon steel of a voice coil motor for a hard disk drive, wherein the yoke part is subjected to a barrel polishing step and then subjected to ultrasonic waves in water. A deburring method for a yoke part characterized by performing a deburring process according to the above, and a voice coil motor for a hard disk drive using a yoke part from which a deburr is removed by this deburring method.
[0016]
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 part constituting a magnetic circuit of a voice coil motor for a hard disk drive using low carbon steel, and particularly the thickness or thickness is 0.5 mm or less. This refers to burrs that occur on all ridges including the finely crafted parts. FIG. 2 schematically shows a burr embodiment, (A) shows the shear burr of the pressed yoke, (B) shows the mustard burr of the cut yoke, and shows the definition of the thickness and thickness of the burr. However, the present invention is not limited to this.
[0017]
The deburring method of the present invention sequentially performs a barrel polishing process and an ultrasonic deburring process on the yoke part in which the above-mentioned burrs are generated. Hereinafter, various processes performed in the present invention will be described.
[0018]
[Barrel polishing process]
Barrel polishing is a ridgeline where abrasives can sufficiently collide with the barrel, except for finely crafted parts such as through-holes, bending, and screw holes in the yoke parts that make up the magnetic circuit of a voice coil motor for hard disk drives. The purpose is to remove the generated burrs. At the same time, the thickness or thickness of the yoke parts in the finely crafted parts such as through-holes and bending are not enough to remove burrs caused by shearing with a thickness of 0.5 mm or less, At the same time, it has the purpose of making the shape easy to remove in the deburring process by the next ultrasonic wave by forcibly rolling and narrowing the root by colliding the abrasive.
[0019]
Barrel polishing uses an abrasive whose main component is alumina, silica, magnesia, etc., and simultaneously seals the yoke parts and water added with rust prevention liquid in a rotating barrel, vibration barrel, centrifugal barrel, etc. And the yoke part can be made to collide with each other by rotation, vibration or the like. In this case, the size of the abrasive is not less than 3 mm, particularly not less than 5 mm, not more than 20 mm, particularly not more than 15 mm, and usually has a spherical or triangular shape of about 10 mm, and it is not desirable to add too fine abrasive grains. This is because abrasive grains remain in screw holes and indentations. Through this process, the thickness or thickness generated on the ridgeline where the abrasive material can sufficiently collide with the burr from various angles other than the finely crafted parts such as the through hole, bending process and screw hole of the yoke part. Burrs of 1.0 mm or less are removed. However, burrs with a thickness or thickness of 0.5 mm or less generated by shearing of finely crafted parts such as through holes and bending work can only be impacted from a limited direction of the abrasive and rolled. It has a shape like that and remains without being removed. However, the root is thinner than before barrel polishing, and can be made into a shape that can be easily removed by deburring by ultrasonic waves in the next step.
[0020]
In the conventional technology, the thickness or thickness existing in the yoke parts generated by shearing of the fine holes such as through holes and bending that are not removed in these barrel polishing processes is 0.5 mm or less. As described above, the film was left to stand or was dissolved and supplemented by chemical polishing to make it small, but not completely removed.
[0021]
[Ultrasonic deburring process]
Ultrasonic deburring is performed on the yoke parts that are finely crafted such as through holes, bends, screw holes, etc. of the yoke parts that make up the magnetic circuit of the voice coil motor for hard disk drives. The purpose is to remove burrs that cannot be removed by barrel polishing with a thickness of 0.5 mm or less.
[0022]
Deburring with ultrasonic waves is achieved by irradiating strong ultrasonic waves into water and applying strong vibrations to the burrs using cavitation (flickering of minute bubbles) generated in the resonance region. Fatigue and remove. 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 in that region.
[0023]
When there are a plurality of locations where deburring is desired, the yoke component may be suspended in water with a jig or the like and swung. Regarding the frequency of the ultrasonic wave, it is desirable to use an ultrasonic wave with a low frequency of about 25 kHz. When an ultrasonic wave with a high frequency exceeding 30 kHz is used, the resonance region in water increases, but the cavitation is small. As a result, burrs are not removed. If an ultrasonic wave having a frequency lower than 20 kHz, which is close to the sound range, is used, there is a risk that intense noise is generated, and therefore an ultrasonic wave of 20 to 30 kHz is preferable. Regarding the output of the ultrasonic oscillator, a high output of about 1200 W is used, and the burr removing ability can be enhanced by arranging the ultrasonic oscillators at high density. 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, the effect increases. Similarly, since oil and air in water also inhibit the occurrence of cavitation, if it is difficult to remove burrs, it is more effective to use pure water and degas before deburring as necessary. The processing time for deburring with ultrasonic waves is about 30 seconds to 10 minutes depending on the shape of the burr. After deburring with ultrasonic waves, the yoke parts are wet and easily rusted, so it is desirable to immediately dry them with an oven, air blower, or the like. As a result, the burr generated by shearing with a thickness or thickness of 0.5 mm or less present in the yoke parts of the finely crafted parts created in the punching press process such as through holes and bending, in particular, By forcibly rolling by the barrel polishing in the previous step and having a narrow base, it is possible to remove shear burrs generated by pressing that cannot be removed by conventional ultrasonic deburring alone.
[0024]
In addition, since the roots of the whisker-like burrs generated by cutting finely crafted parts such as screw holes and indentations are thin, they are completely removed by ultrasonic vibration.
[0025]
Such a device is described in Precision Surface Finishing and Burr Technology Ultra Fine Deburring and Surface Finishing [b (2)] JA F145A Mechanical Technology (JPN) 44 [(2)].
[0026]
Here, when deburring with ultrasonic waves is performed without barrel polishing in the previous process, the burr generated by shearing has a shape that has a wide root at the tip, and uses ultrasonic vibration. Even so, the removal from the root cannot be performed as described above, and the burrs generated by the shearing of all the ridgelines including the finely crafted portion are not removed at all.
[0027]
In rare cases, the thickness or thickness present in the yoke part is 0.1 mm or less in the finely crafted part of the yoke part that has been sequentially subjected to the barrel polishing process and the ultrasonic deburring process. In some cases, the minute burrs generated by the shearing fall down and adhere to the yoke component main body, and are still not removed slightly without receiving vibration due to ultrasonic waves. If such a material is present, it is effective to remove it by dissolving it by chemical polishing for finishing. In chemical polishing, the yoke parts are immersed for 10 seconds to 10 minutes in an aqueous solution containing 1 to 40% of hydrogen peroxide, ammonium hydrogen fluoride or phosphoric acid as the main component, and the burrs are chemically dissolved and removed. To do.
[0028]
When performing chemical polishing, since the surface of the yoke part is activated, it is desirable to perform plating (nickel, copper, etc.) immediately after completion of chemical polishing by washing with water and pickling. It should be noted that the chemical polishing and plating steps after the ultrasonic deburring step can be continuously performed by using a common jig or the like for fixing or hanging the yoke component.
[0029]
FIG. 3 schematically shows the process of removing the shear burr generated in the through hole in each step of barrel polishing, deburring by ultrasonic waves, and chemical polishing as an auxiliary finishing process, and (A) is barrel polishing. Before, (B) shows the state after barrel polishing, (C) shows the state after deburring by ultrasonic waves, and (D) shows the state after chemical polishing. In the figure, 1 is a yoke part body, 2 is a through hole formed in the yoke part body, and before barrel polishing (A), a minute shear burr 11 is formed on the outer peripheral edge of the through hole 2 and the thickness is 0.5 mm or less. Shear burrs 12 are formed, and these burrs 11 and 12 protrude outward along the penetration direction of the through hole 2. These burrs 11 and 12 are both thick at the tip and cannot be removed only by deburring with ultrasonic waves. When barrel polishing is performed on the yoke component 1 in such a burr state (B), the abrasive 3 hits the burrs 11 and 12 and pushes the burrs 11 and 12 inwardly (through hole 2 direction). As a result, these burrs 11 and 12 are not removed by this barrel polishing, but are rolled to narrow the roots. In addition, as shown in the figure, the small shear burr 11 may fall on the inner peripheral wall of the through hole 2 and fall asleep (the tip side abuts against the inner peripheral wall). Next, when the ultrasonic treatment is performed (C), as described above, the bases of the burrs 11 and 12 are thinned by barrel polishing, so that the burrs 11 and 12 are removed by the ultrasonic treatment. However, the minute shear burr 11 that has fallen into the inner peripheral wall of the through hole 2 may not be removed. Even if such a small amount of the shear burr 11 remains, it is completely removed by performing chemical polishing (D). In the present invention, the deburring mode is not limited to FIG.
[0030]
Based on the above conditions, the yoke parts that make up the magnetic circuit of a voice coil motor for hard disk drives are conventionally barrel-polished, from large burrs to burrs with fine work such as through holes, bending, and screw holes. Of parts that have been finely crafted by shearing with a thickness or thickness of 0.5 mm or less existing in the yoke parts, which could not be removed by using only one of the deburring by All burrs are removed, including burrs. By plating this, it is commercialized as a yoke component of a voice coil motor that does not need to worry about burrs falling off harmful to the hard disk drive.
[0031]
By using this yoke component and bonding and magnetizing the magnet, it can be commercialized as a voice coil motor that does not need to worry about burrs falling off harmful to the hard disk drive. The other components and configuration of the voice coil motor incorporating the yoke component can be known.
[0032]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
[0033]
〔Example〕
Using a SPCC cold-rolled steel plate having a thickness of 3.2 mm, a yoke part having a weight of 30 g constituting a magnetic circuit of a voice coil motor for a hard disk drive was produced by press punching. The yoke has a flat plate shape with a diagonal of about 5 cm, but has two through holes with an outer diameter of 3 mm and one rolling tap with an outer diameter of 2.5 mm in the thickness direction. These are used for positioning when incorporating a voice coil motor into a hard disk drive. In the punched state, shear burrs are generated on all the press die side ridge lines including the ridge line of the through hole having an outer diameter of 3 mm. In addition, whisker-like burrs due to screwing are generated in the thread in the rolled tap hole having an outer diameter of 2.5 mm. The test piece was sequentially subjected to rotating barrel polishing and deburring with ultrasonic waves under the following conditions.
[0034]
[Rotating barrel polishing process]
Yoke parts input 50 pieces x 30g
Outer 15mm spherical abrasive input 5kg
(Abrasive: Alumina and silica as main components)
Rotational speed 46r. p. m
Polishing time 1 hour [0035]
[Ultrasonic deburring process]
Ultrasonic frequency: 25 kHz
Ultrasonic output: 1,200W
Water temperature: 10 ° C
Water quality: pure water The yoke part was hung with a wire under the above conditions, and deburred for 1 minute while swinging up and down.
[0036]
The yoke subjected to the above treatment was plated with nickel. In this case, normal burrs at the ridge line portion, shear burrs at the ridge line portion of the 3 mm outer diameter through hole, and whisker-like burrs of the 2.5 mm outer diameter rolled tap were observed. The results are shown in Table 1.
[0037]
[Comparative example]
For comparison, the following yokes were prepared at the same time, and the burr removal state was similarly evaluated.
(Comparative Example 1)
Only the [barrel polishing process] of the above process was performed.
(Comparative Example 2)
What carried out the [barrel polishing process] and the [chemical polishing process] of the above process.
(Comparative Example 3)
Performed only the [Deburring process by ultrasonic wave] of the above process.
[0038]
In the [chemical polishing step], a chemical polishing liquid (CPL-100 manufactured by Mitsubishi Gas Chemical Co., Ltd.) mainly composed of hydrogen peroxide solution and ammonium hydrogen difluoride is diluted three times, and then at 20 ° C. for 1 minute. Processed.
These results are also shown in Table 1.
[0039]
[Table 1]

(Double-circle): The burr | flash is completely removed in all the yoke parts observed.
○: The burr is almost completely removed, but there are some yoke parts that remain slightly.
Δ: There was a slight effect in removing burrs, but burrs still remain in most yoke parts.
X: Burr is not removed at all in all observed yoke parts.
-: No corresponding burr exists before the burr removal treatment.
[0040]
In the examples, after performing the [deburring step by ultrasonic wave] and subsequently performing the [chemical polishing step], the shear burrs of 0.1 mm or less shown in Table 1 can be completely removed. It was.
[0041]
【The invention's effect】
The method of manufacturing a deburred yoke part 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 finely crafted parts. It is extremely effective in manufacturing a clean voice coil motor that removes harmful burrs.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a voice coil motor.
FIGS. 2A and 2B are diagrams schematically showing burrs present in a yoke part, where FIG. 2A is an explanatory view of shear burrs of a pressed yoke, and FIG.
FIGS. 3A and 3B schematically show a process of removing burrs generated in a through hole of a yoke part, (A) before barrel polishing, (B) after barrel polishing, (C) after deburring by ultrasonic waves, ( D) is an explanatory diagram of a state after chemical polishing.
[Explanation of symbols]
1 Yoke part body 2 Through hole 3 Abrasive material 11, 12 Burr

Claims (6)

  A method of removing burrs present on the surface of a yoke part made of low carbon steel of a voice coil motor for a hard disk drive, wherein a barrel polishing process is performed on the yoke part, followed by a deburring process using ultrasonic waves in water. A deburring method for a yoke part, characterized in that:   The deburring method according to claim 1, wherein a chemical polishing step is performed after the ultrasonic deburring step.   The deburring method according to claim 1 or 2, wherein the ultrasonic deburring step is performed at 10 ° C or lower.   4. The deburring method according to claim 1, wherein the burr has a thickness or thickness of 0.5 mm or less.   The deburring method according to any one of claims 1 to 4, wherein the burr is a burr generated by a shearing process in manufacturing a yoke part.   A voice coil motor for a hard disk drive using a yoke part from which burrs are removed by the deburring method according to claim 1.

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