JP2001079749A - Deburring method of yoke part of voice coil motor for hard disc drive and voice coil motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deburr all crest lines including parts finely worked and to manufacture a clean voice coil motor from which burrs harmful for a hard disc drive are removed under a manufacturing method of a yoke part applied with deburring to constitute a magnetic circuit of the voice coil motor for the hard disc drive. SOLUTION: This method removes burrs existing on a yoke part surface made of low carbon steel of a voice coil motor for a hard disc drive, and a barrel polishing process and a heat deburring process are sequentially carried out against a yoke part. After this heat deburring process, a chemical polishing process is carried out. In this case, burr thickness or size is specified as not more than 0.5 mm.

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.

On the other hand, in the removal of burrs by thermal deburring, burrs having thin roots generated by cutting or the like can be removed, but burrs generated by shearing have a shape in which the root is wider with respect to the tip. There is a disadvantage that the heat generated in the burrs is easily transmitted to the yoke main body and cannot be removed by oxidation, and is not generally used for deburring yoke components constituting a magnetic circuit of a voice coil motor for a hard disk drive. .

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. By applying barrel polishing to the carbon steel yoke part first and then performing thermal deburring, the finely worked part of the entire yoke part, that is, the abrasive material of barrel polishing cannot sufficiently collide Through holes, screw holes, dents and radii of 5 m or less, which are difficult to remove burrs
The present inventors have found that burrs existing on all ridge lines, including portions with a bending process of m or less, can be reliably removed, and have accomplished the present invention.

Accordingly, the present invention is a method of 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 a thermal deburring step for the yoke part. And a voice coil motor for a hard disk drive using a 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 sequentially performs a barrel polishing step and a thermal deburring step on a yoke component having the above-mentioned burrs. Hereinafter, various steps performed in the present invention will be described. .

[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 thermal 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 base is thinner than before the barrel polishing, so that it can be formed into a shape that can be easily removed by thermal 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.

[Thermal deburring step] Thermal deburring is present in the yoke part of the yoke part which constitutes the magnetic circuit of the voice coil motor for the hard disk drive, such as a through-hole, a bend, a screw hole and the like where fine work is performed. The purpose is to remove burrs that cannot be removed by barrel polishing with a thickness or thickness of 0.5 mm or less.

In the heat deburring, a yoke component is put in a sealable combustion chamber to be sealed, and a combustion gas is injected from a combustible gas supply port. The filling pressure is set at about 3 to 10 atm according to the number of yoke parts and the situation of burrs, but it is preferable to select a pressure as low as possible to avoid deformation of the yoke parts.
The combustion gas generally has a composition represented by CH ₄ : O ₂ = 1: 2.5, and contains an excess of oxygen more than required for methane combustion. The excess oxygen is consumed for burr combustion. Therefore, it is desirable to set an optimum mixing ratio in accordance with the state of burr generation, and it is necessary to avoid remaining of the burr due to insufficient combustion due to lack of oxygen and remarkable oxidation of the yoke component body due to excess oxygen.

Next, the combustion gas is ignited by an ignition plug. Then, the combustion gas instantaneously burns and 30
A heat wave of about 00 ° C. oxidizes and removes burrs. Since the surface of the yoke component body is slightly oxidized by the thermal deburring step, it is desirable to remove the oxide film by pickling or the like after the thermal deburring step. 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 made thin by forcibly 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 conventional thermal deburring alone.

The burrs generated by cutting finely worked portions such as screw holes and dents due to cutting are finely polished and completely removed by heat deburring because the roots are thin.

The thermal deburring device is described in "Instant Deburring by Thermal Shock" (Mechanical Technology, Vol. 29, N.
o. 8, pp. 135-137 (1981)).

Here, when thermal deburring is performed without performing barrel polishing in the previous step, the burr generated by shearing has a shape with a wide base at the tip, and the heat generated by the burr Easily propagates to the yoke body,
As described above, it is not possible to remove by oxidation.If thermal deburring was performed without performing barrel polishing in the previous process, it occurred due to shearing of all ridge lines including finely worked parts No burrs are removed.

In rare cases, the thickness or thickness existing in the yoke component is 0.1 mm or less in the finely worked portion of the yoke component in which the barrel polishing step and the thermal deburring step are sequentially performed. Since the micro burrs generated by the shearing fall down and adhere to the yoke component main body and release heat to the yoke component main body, the burrs are not oxidized and may still not be removed to some extent. If such a material exists, it is effective to dissolve it by performing chemical polishing for finishing. In chemical polishing, the yoke component is placed in an aqueous solution containing 1 to 40% of hydrogen peroxide, ammonium hydrogen difluoride or phosphoric acid as a main component for 10 seconds to
Immerse for 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 thermal deburring step can be continuously performed by using a common jig for fixing or suspending the yoke component.

FIG. 3 schematically shows a process in which shear burrs generated in the through holes are removed in each step of barrel polishing, thermal deburring, and chemical polishing as an auxiliary finishing process.
(A) before barrel polishing, (B) after barrel polishing, (C)
Shows the state after thermal deburring, and (D) shows the state after chemical polishing. In the drawing, reference numeral 1 denotes a yoke component main body, and 2 denotes a through hole formed in the yoke component body. Before barrel polishing (A), a small shearing 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, and these burrs 11 and 12 are formed.
Project outward in 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 thermal deburring. When barrel polishing is performed on the yoke component 1 in such a burr state (B), the abrasive material 3 hits the burr 11 and 12,
These burrs 11 and 12 are pushed 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 thermal deburring is performed (C), since the bases of the burrs 11 and 12 are thinned by the barrel polishing as described above, the burrs 11 and 12 are removed by thermal deburring. 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 of the yoke component that was not removed by using only one of the thermal deburring alone was not applied to the finely-worked portion generated by shearing of 0.5 mm or less. All burrs, including burrs, are removed. 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 thermal 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

[Thermal deburring step] Combustion gas composition CH ₄ : O ₂ = 1: 2.5 Mixed gas filling pressure 7.0 kg / cm ² Yoke parts input 150

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) One in which only the [thermal deburring step] of the above step was performed.

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 [thermal deburring step] and then performing the [chemical polishing step], it is possible to completely remove shear burrs of 0.1 mm or less shown in Table 1. did it.

[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 thermal deburring, and (D). FIG. 3 is an explanatory view of a 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 Continuing on the front page (72) Inventor Nobutaka Kobayashi 2-1-5 Kitafu, Takefu-shi, Fukui Shin-Etsu Chemical Co., Ltd. Takefu Plant F-term (reference) 3C058 AA01 AA09 AB08 BA02 CB03 CB05 DA12 5H615 AA01 BB01 PP01 PP07 SS03 SS08 SS38 TT05 TT13

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 a thermal 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 thermal 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: