JP2006073085A - Method for removing burr of yoke part of voice coil motor for hard disk drive and yoke part of voice coil motor for hard disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for effectively and efficiently removing/reducing burrs which can be minute metallic chips causing a problem in operating a hard disk drive, and which can not be removed completely with a regular barrel polishing, especially burrs which are produced in a microfabricated part causing the problem in yoke parts of a voice coil motor for large capacity hard disk drive, and to provide the yoke parts of the voice coil motor for hard disk drive in which such burrs are reduced as far as possible. <P>SOLUTION: In this method for removing the burrs present on surfaces of the yoke parts of the voice coil motor for hard disk drive, after part or the whole of edge portions present near the boundary of open space where barrel polishing particles reach in the barrel polishing and dead space where the barrel polishing particles do not reach are worked into the shape of a curved face or a tapered face among edge portions of the yoke parts, they are subjected to the barrel polishing. Consequently, according to this method, the burrs which can be the minute metallic chips causing the problem in operating the hard disk drive, and which can not be removed completely with the regular barrel polishing, especially the burrs which are produced in the microfabricated part causing the problem in the yoke parts of the voice coil motor for large capacity hard disk drive can be effectively and efficiently removed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  INDUSTRIAL APPLICABILITY The present invention is suitable for manufacturing a yoke part constituting a magnetic circuit of a voice coil motor for a hard disk drive, particularly a yoke part of a voice coil motor for a large capacity hard disk drive in which the generation of metal chips is reduced as much as possible. The present invention relates to a burr removal method for a yoke part and a yoke part of a voice coil motor for a hard disk drive.

  As shown in FIG. 1, a hard disk drive voice coil motor is generally composed of a rare earth magnet m mainly having high magnetic properties and a plurality of (four in the case of FIG. 1) pieces constituting a magnetic circuit. The yoke parts 11, 12, 13, and 13 are configured as follows (note that c in FIG. 1 is a coil). Since the risk of head crashes increases due to a decrease in the flying height of the magnetic head accompanying an increase in the storage capacity of the hard disk, in recent years, there has been a strong demand for yoke parts that are less likely to cause metal chip contamination that causes head crashes. Yes.

  The yoke parts are manufactured by using low carbon steel as a material mainly for obtaining excellent motor performance, and processing the low carbon steel by press sheet metal, cutting or the like. However, since the low carbon steel has a tendency to be sticky, it has a defect that shear burrs and cutting burrs are likely to occur in the processing process of the yoke part.

  In addition, since hard disk drives are becoming smaller year by year, the yoke parts that make up the magnetic circuit of the voice coil motor used for them are becoming smaller and more complex. Finer machining increases in machining, screw hole machining, half punch machining, stepping machining, etc., and these parts of the yoke part to be manufactured (for example, the through hole 111, the half punch part 112, the stepping shown in FIG. 1) The frequency of occurrence of burrs in the processing part 113, the notch part 114, etc.) tends to increase.

  The burr generated in the yoke part during processing is a problem even if it is only attached to the surface of the yoke part, but it may easily fall off when subjected to impacts, etc. The chip becomes a cause of contamination of the voice coil motor for the hard disk drive, and when the burr (metal chip) dropped off during the operation of the hard disk drive collides with the magnetic head, the head crashes. Head crash is a fatal problem in hard disks.

Particularly in recent years, the flying height of the head has become 0.1 μm or less, and dropout of a metal chip of 0.1 mm or less can cause a head crash. In addition, if the dropped metal chip adheres to the hard disk, the metal chip exhibits ferromagnetism, resulting in damage of recorded data and the like, which is also a problem. Particularly in recent years, the recording density of the hard disk has become 1 gigabyte / cm ² or more, and dropping of a metal chip of about 0.1 mm can cause damage to recorded data, which is a serious problem.

  Such burrs generated during press molding and cutting are generally removed by barrel polishing, but it is difficult to completely remove burrs by this alone. Most yoke parts have a through hole of about φ1 to 10 mm and a half punch of about φ1 to 3 mm, and it is necessary to select a barrel abrasive having a size that does not clog these holes. Therefore, as shown in FIG. 2 (A), the burr generated at the normal edge portion without the dead space where the abrasive does not reach is shown in FIG. 2 (B) because the abrasive collides from all directions. The burrs generated at the edge portion can be effectively removed by barrel polishing (FIG. 2C), but as shown in FIG. 3A, the burrs are smaller in diameter than the diameter of the barrel abrasive. There is a dead space where the abrasive does not reach the through hole, and the burr generated at the edge of the micro-machined portion as shown in FIG. 3B has an open space, that is, the space side where the abrasive reaches. Since the abrasive material collides only from the dead space side and does not collide from the dead space side, the burr is simply pushed down and pushed into the dead space side of the micro-machined part. Furthermore, the abrasive material collides only from a specific side in this way. Accordingly, there is also originally fear that by generating a new burr (secondary burr) to part had no burr (Fig. 3 (C)). Also, the half punch portion shown in FIG. 4A, the stepped portion shown in FIG. 4B, and the diameter of the barrel abrasive formed on the outer peripheral edge of the yoke part shown in FIG. The same applies to burrs in micromachined parts such as notches. 2 to 4, 11 is a yoke part, 111 is a through hole, 112 is a half punch part, 113 is a stepped part, 114 is a notch part, 2 is an abrasive, b is a burr, and d is a dead space. , O indicates an open space.

  As a method for removing burrs from yoke parts constituting a magnetic circuit of a voice coil motor for a hard disk drive, the present inventor sequentially performs a barrel polishing process and a water jet deburring process on a yoke member (Patent Literature). 1: JP 2001-78398 A), a method of sequentially performing a barrel polishing step and a magnetic polishing step on a yoke member (Patent Document 2: JP 2001-79750 A), a barrel polishing step on a yoke member And a method of sequentially performing a deburring process using ultrasonic waves (Patent Document 3: Japanese Patent Application Laid-Open No. 2001-78397), and a method of sequentially performing a barrel polishing process and an abrasive fluidizing process on the yoke member (Patent Document 4: Japanese Patent Laid-Open No. 2001-78418 has been reported. However, with these methods, the flying height of the magnetic head as described above is small. Since the burrs generated in the micro-machined part of the hard disk yoke parts cannot be removed effectively, barrel polishing is performed after press forming or cutting the yoke parts, and once the normal edge part without dead space is applied. After deburring, it is necessary to apply additional deburring.

  As an additional deburring step, it is also effective to perform chemical polishing after barrel polishing. However, in general, deburring with a size of about 1 mm is necessary for chemical deburring of fine deburring of 0.5 mm or less. In order to obtain a sufficient deburring effect, chemical polishing is required for a long time, and as a result, the yoke part body is also melted, making it difficult to control the thickness and dimensions of the finely processed parts. It is.

  Furthermore, after deburring using an electropolishing technique, electroplating is performed in order to ensure the size of the edge portion that has been preferentially melted (Patent Document 5: JP-A-2002-262523). A yoke part without burrs can be produced, but electropolishing itself is a factor in increasing costs, and dimensional control is difficult. Therefore, a simpler and less expensive method is desired.

JP 2001-78398 A JP 2001-79750 A JP 2001-78397 A JP 2001-78418 A JP 2002-262523 A

  The present invention has been made to remedy the above-mentioned problems, and burrs that cannot be removed by ordinary barrel polishing, which may cause a problem in the operation of a hard disk drive, such as a minute metal chip, particularly large capacity. A method for effectively and efficiently removing and reducing burrs generated in micro-machined parts that are problematic in yoke parts of voice coil motors for hard disk drives, and for hard disk drives in which such burrs are reduced as much as possible. The object is to provide a yoke component of a voice coil motor.

  As a result of diligent study to solve the above-mentioned problems, the present inventor, when removing burrs existing on the surface of the yoke part of the voice coil motor for hard disk drive by barrel polishing, out of the edge part of the yoke part, the barrel polishing material Yoke parts by processing a part or all of the edge portion in the vicinity of the boundary between the open space where the particles reach and the dead space where the barrel abrasive particles do not reach into a curved or tapered shape and then barrel polishing Edge parts of micro-machined parts such as through-holes, half-punch parts, stepped parts, notched parts, etc. formed by press molding or cutting of steel, for example, both peripheral edges of through-holes smaller in diameter than the diameter of barrel abrasive Burr formed on the outer peripheral edge of the yoke part, the peripheral edge of the tip of the half punch part, the edge of the shoulder of the stepped part, It is possible to reduce the frequency of occurrence of burrs at one or more parts selected from both peripheral edges of the notch having a width smaller than the diameter of the abrasive, and to reduce burrs generated in the above processing, particularly a voice coil for a hard disk drive. Burrs that have occurred in the micro-machined part, which is a problem in the yoke part of the motor, can be removed by barrel polishing in the same manner as in the past, and further, the barrel abrasive particles are removed from the micro-machined part during barrel polishing. The present inventors have found that secondary burrs are less likely to occur even when colliding with an edge portion, and thus completed the present invention.

That is, the present invention provides the following deburring method for a yoke part of a voice coil motor for a hard disk drive and a yoke part for a voice coil motor for a hard disk drive.
Claim 1: A method of removing burrs present on the surface of a yoke part of a voice coil motor for hard disk drive by barrel polishing, wherein an open portion in which barrel abrasive particles reach in barrel polishing among edge parts of the yoke part. A voice coil motor for a hard disk drive characterized in that a part or all of an edge portion existing in the vicinity of a boundary between a space and a dead space where a barrel abrasive particle does not reach is subjected to barrel polishing after processing a curved surface or a tapered surface. Deburring method for yoke parts.
Claim 2: The edge portion existing in the vicinity of the boundary includes both peripheral edge portions of the through-hole having a diameter smaller than the diameter of the barrel abrasive, the tip peripheral edge portion of the half punch portion, the edge portion of the shoulder portion of the stepped portion, and the above 2. The burr removing method according to claim 1, wherein the burr removing method is one or two or more parts selected from both peripheral parts of the notch part having a width smaller than the diameter of the barrel abrasive formed on the outer peripheral part of the yoke part.
Claim 3: A hard disk drive voice coil motor yoke part obtained by removing burrs present on the surface of a yoke part of a hard disk drive voice coil motor by barrel polishing, and among the edge parts of the yoke part, A hard disk drive characterized in that a part or all of an edge portion in the vicinity of a boundary between an open space where barrel abrasive particles reach and barrel space where barrel abrasive particles do not reach in barrel polishing is a curved surface or a tapered surface. Yoke parts for voice coil motors.
Claim 4: The edge portion existing in the vicinity of the boundary includes both peripheral edge portions of the through-hole having a diameter smaller than the diameter of the barrel abrasive, the front peripheral edge portion of the half punch portion, the peripheral edge portion of the shoulder portion of the stepped portion, and the above 4. The yoke part according to claim 3, wherein the yoke part is one or two or more parts selected from both peripheral parts of the notch part having a width smaller than the diameter of the barrel abrasive formed on the outer peripheral part of the yoke part.

  According to the present invention, there is a problem with a burr that cannot be removed by normal barrel polishing, which may result in a minute metal chip that becomes a problem during operation of a hard disk drive, particularly in a yoke component of a voice coil motor for a large capacity hard disk drive. The burrs generated in the micro-machined parts can be effectively and efficiently removed, and a fine metal chip is a particular problem for the hard disk drive voice coil motor yoke parts from which such burrs are removed. It is suitable as a yoke part of a voice coil motor for a large capacity hard disk drive.

BEST MODE FOR CARRYING OUT THE INVENTION

  The present invention is a method of removing burrs present on the surface of a yoke part of a voice coil motor for hard disk drive by barrel polishing, and an open space where barrel abrasive particles reach in barrel polishing among edge parts of the yoke part, Barrel polishing is performed after the edge portion existing in the vicinity of the boundary with the dead space where the barrel abrasive particles do not reach is subjected to curved surface (R surface) processing or tapered surface processing.

  In order to obtain excellent motor performance, yoke parts of voice coil motors for hard disk drives are generally made of low carbon steel, for example, Mn is 1% or less and carbon content is 0.05 to 0.25%. The low carbon steel such as SPCC, S15C, etc. is used, and the yoke part is produced by press sheet metal punching using the low carbon steel. As shown in FIG. 1, the yoke parts 11 and 12 are formed with micro-machined parts such as a through hole 111, a half punch part 112, a stepped part 113, and a notch part 114.

  Such yoke parts are subjected to barrel polishing in order to remove the burrs generated on the above-described micro-processed parts, etc., but in barrel polishing for the yoke parts, the yoke parts are formed on the yoke parts. Since the barrel abrasive particles larger than the diameter of the formed through-hole are used so that the barrel abrasive particles are not clogged with the formed through-holes, etc., the barrel abrasive adjacent to the yoke part surface where the barrel abrasive particles reach A dead space is created where particles cannot reach. As shown in FIGS. 2 to 4, the dead space is formed in the outer peripheral edge of a through hole, a half punch portion, a stepped portion, and a yoke component having a diameter smaller than the diameter of the barrel abrasive, for example, φ1 to 10 mm. The inner diameter of the barrel abrasive is smaller than the diameter of the barrel abrasive, for example, 1 to 10 mm. A large number of burrs are generated at the edge portion in the vicinity of the boundary between the open space where the barrel abrasive particles reach and the dead space where the barrel abrasive particles do not reach. The burr generated at the edge of the processed part collides only from the open space side, that is, the space side where the abrasive reaches, and does not collide from the dead space side. Just push it to the side. Even if there is no burr, a new burr (secondary burr) may occur due to the abrasive material colliding only from a specific side.

  In the present invention, the barrel part is barrel-polished after the edge portion existing in the vicinity of the boundary between the open space where the barrel abrasive particles reach and the dead space where the barrel abrasive particles do not reach in the barrel polishing. To do. By barrel-polishing after processing the edge part into a tapered shape, burrs in the micro-machined part can be reduced and the generated burrs can be easily removed. Furthermore, secondary burrs are generated by barrel polishing. Can be suppressed.

  In barrel polishing, as a method of processing a curved surface or a tapered surface of an edge portion existing near the boundary between an open space where barrel abrasive particles reach and a dead space where barrel abrasive particles do not reach, during press sheet metal punching, There are a method of performing a curved surface process or a tapered surface process using a mold in which a predetermined edge part is a curved surface or a tapered surface, a method of cutting an edge part of a yoke part into a curved surface or a tapered surface after press sheet metal punching, etc. Can be mentioned.

  In the through hole, a curved surface or a tapered surface is formed at the edge portions (both peripheral edge portions) existing at both ends of the peripheral surface forming the through hole. For example, a predetermined edge portion is a curved surface during press sheet metal punching. Alternatively, with respect to a method of performing curved surface processing or taper surface processing using a die that becomes a tapered surface, a case where a tapered surface is formed at the edge portion of the through hole will be described in detail as shown in FIG. 5A. First, a hole slightly smaller than the diameter of the through hole to be finally formed is formed by press punching in the yoke component 11, and then, as shown in FIG. Using a die formed on the tapered surface, the tapered surface t is formed at the edge of the through hole by press punching so that the diameter of both ends of the through hole is slightly larger than the diameter of the finally formed through hole. To do. Finally, as shown in FIG. 5C, the through hole 111 is formed by shearing once again by press punching so that the through hole has a predetermined diameter. This method is preferable in that the edge portion can be processed only by the press punching process without using a physical or chemical method in the additional process. Alternatively, it is possible to form a tapered surface. In addition, as an angle of a taper surface, it is preferable to set it as 95-175 degree | times with respect to the surrounding surface of a through-hole, especially 130-150 degree | times. If the angle of the taper surface is too shallow or conversely too deep, secondary burrs may increase in barrel polishing in the next step.

  On the other hand, when the curved surface (R surface) is formed in the edge portion, the above-described mold in which the portion that punches out the edge portion is formed in the curved surface (R surface) may be used. In this case, the curved surface (R surface) is preferably, for example, C (R) of 0.05 mm or more, particularly 0.2 mm or more. By doing so, secondary in barrel polishing in the next step is performed. Generation of burrs can be suppressed. The upper limit of the height of the taper surface and the C (R) of the curved surface (R surface) is preferably ½ or less, particularly ３ or less of the length of the through-hole, and has a penetration of about φ1 to 10 mm. In the case of a hole, it is desirable that it is 0.5 mm or less.

  The half punch part is generally used for positioning when the voice coil motor is incorporated in a hard disk drive, or for positioning when attaching a magnet to a yoke part. In the half punch part, the tip of the half punch part is used. A curved surface or a tapered surface is formed at the edge portion (tip peripheral portion). In this case, using the mold in which the edge part is punched from the beginning at the time of punching formation of the half punch, the curved surface processing or taper surface processing of the edge part is performed at the same time as the punching formation of the half punch part. The punching of the half punch portion and the formation of the curved surface or the tapered surface may be performed separately, for example, by a method of forming a curved surface or a tapered surface by cutting or the like after the punching of the half punch portion. Good.

  In addition, it is preferable that the angle of a taper surface is the same as that of the case of the through-hole mentioned above about the angle with respect to the surrounding surface of a half punch part. The curved surface (R surface) can also be the same as in the case of the above-described through hole. In this case, the upper limit of the height of the tapered surface and the C (R) of the curved surface (R surface) is that of the half punch portion. It is preferable that the height is 1/2 or less, particularly 1/3 or less. For example, in the case of a half punch part having a height of 0.5 to 2.0 mm and a diameter of 0.5 to 3.0 mm, 0.5 mm or less. It is desirable that

  In the stepped portion, a curved surface or a tapered surface is formed at the edge portion (the edge portion of the shoulder portion) on the step. In this case, using a mold in which the edge portion is punched from the beginning when the stepped portion is punched, the edge portion is curved or tapered at the same time as the stepped portion is punched. The process may be performed at once, or the stepped portion is punched separately and the curved surface or tapered surface is formed separately. For example, after the stepped portion is punched, a curved surface or tapered surface is formed by cutting or the like. May be implemented.

  In addition, it is preferable that the angle of the taper surface is the same as the case of the through hole described above with respect to the step surface of the stepped portion. The curved surface (R surface) can also be the same as in the case of the above-described through-hole. In this case, in particular, when a curved surface or a tapered surface is formed by cutting or the like after punching of the stepped portion. The upper limit of the height of the tapered surface and the C (R) of the curved surface (R surface) is preferably 1/2 or less, particularly 1/3 or less of the step of the stepped portion. In the case of a stepped portion of about ~ 3.0 mm, it is desirable that it is 0.5 mm or less.

  Further, in the stepped processed portion, the entire stepped surface of the stepped processed portion can be a curved surface or a tapered surface as shown in FIG. In this case, for example, in the case of press sheet metal punching, if a curved surface or a tapered surface is processed using a mold having a stepped surface that is a curved surface or a tapered surface, the physical or chemical process in the additional process is performed only in the press punching process. However, it is also possible to form a curved surface or a tapered surface by cutting or the like after punching the through hole. In FIG. 5D, 11 is a yoke part, 113 is a stepped portion, and t is a tapered surface. In addition, as the taper surface angle when the entire stepped surface of the stepped portion is a taper surface, the inclination of the taper surface is 40 to 85 degrees, particularly 40 to 60 degrees (the taper surface angle with respect to the step upper surface is 95 degrees). -140 degrees, particularly 120-140 degrees).

  The yoke part that forms the boundary between the part along the outer periphery of the yoke part (both peripheral parts) and the notch part of the outer peripheral surface of the yoke part as an edge part in the notch part formed on the outer peripheral part of the yoke part There are portions along the thickness direction, and any portion can form a curved surface or a tapered surface, but in particular, an edge portion formed in a direction perpendicular to the shear direction of press punching, that is, a yoke part It is preferable to form a curved surface or a tapered surface at the edge portion (both peripheral edge portions) along the outer periphery of the substrate.

  In this case, as a method of forming a curved surface or a tapered surface, as in the case of the above-described through-hole, first, by press punching, shear formation is performed slightly smaller than the size of the final formation of the notch, and then Using a mold in which the edge portion is punched into a curved surface or a tapered surface, the curved surface or tapered surface is formed in the edge portion by press punching so that the upper end is larger than the notch portion finally formed. Form. Finally, a method of shearing the cutout portion by press punching once again so that the cutout portion has a predetermined size is suitable, but after punching the edge portion, a curved surface or a tapered surface is obtained by cutting or the like. It is also possible to form

  In addition, it is preferable that the angle of a taper surface is the same as that of the through-hole mentioned above about the angle with respect to the surface (circumferential surface) which comprises a notch part. Also, the curved surface (R surface) can be the same as that of the above-described through-hole, but in this case, the upper limit of the height of the tapered surface and C (R) of the curved surface (R surface) is that of the notch. It is preferable to set it to 1/2 or less, particularly 1/3 or less, of the size (thickness of the yoke part), for example, a notch having a thickness of about 1.0 to 3.0 mm and a width of about 1.0 to 10.0 mm. In the case of a part, it is desirable that it is 0.5 mm or less.

  The formation of such a curved surface or tapered surface on the edge portion was formed at the outer peripheral edge of a through hole, a half punch portion, a stepped portion, or a yoke part in which a so-called “sag surface” is formed in press punching. Although it is suitable in a notch part etc., for example, it is also possible to form at a normal edge part where there is no dead space where the abrasive on the outer peripheral surface of the yoke part does not reach, so-called `` burr surface '', in this case, Before completely shearing the yoke part, hit the edge of the burr surface that has already been sheared from the opposite direction, and perform so-called "counter punch" to form the same curved surface or tapered surface to the burr surface. You can go. On this burr surface, the burr generated at the time of shearing is buried in the edge of the yoke part, and it may not be removed in the next step of chamfering the barrel, and may fall off afterwards. In many cases, the surface has a fracture surface, and although it is slightly, as a result, it often has a shape close to a curved surface or a tapered surface, and the occurrence of secondary burrs in barrel polishing is rather than a sagging surface. Since there are few, it is preferable to determine the necessity of forming the curved surface or the tapered surface on the burr surface while actually observing the burr state on the yoke part.

  In the case of the method of cutting the edge part of a yoke part into a curved surface or a tapered surface after punching a stamped sheet metal, a through hole, a half punch part, a stepped part, a notch formed by a conventional stamped sheet metal stamping process The edge portion of a micro-machined part such as a part is formed by cutting, for example, to form a curved surface or a tapered surface. This cutting process is performed by, for example, grinding with sandpaper, a file, a grindstone, etc. It is possible by machining, electric discharge machining, etc.

  In the present invention, the yoke part is barrel-polished after the above-described edge portion of the yoke part is subjected to curved surface processing or tapered surface processing.

  Barrel polishing uses an abrasive whose main component is alumina, silica, magnesia, etc., and simultaneously seals the yoke member and water added with rust prevention liquid into a rotating barrel, vibration barrel, centrifugal barrel, etc. And the yoke member can be made to collide with each other by rotation, vibration or the like.

  In this case, a spherical or regular tetrahedron having a diameter of 3 mm or more, particularly 5 mm or more, 20 mm or less, particularly 15 mm or less, especially around 10 mm is preferably used. In particular, it is better to avoid using an abrasive having a diameter smaller than the diameter of the through-hole or the width of the notch, because the abrasive may remain on them.

  This barrel polishing removes burrs present on the surface of the yoke part and also polishes the surface of the yoke part. In the present invention, the open space and the barrel abrasive that the barrel abrasive particles reach in barrel polishing. Barrel polishing formed in the edge part existing near the boundary with the dead space where particles do not reach, especially in the through hole, half punch part, stepped part, and outer peripheral part of the yoke part smaller than the diameter of the barrel abrasive Since the edge part such as a notch part with a width smaller than the diameter of the material is subjected to curved surface processing or taper surface processing, the amount of burrs generated at these edge parts is small and burrs are generated. However, since the barrel abrasive particles are more likely to enter the edge portion than before, it is easy to remove burrs, and the edge portion is curved or tapered. Because it is, even less occurrence of secondary burrs.

  It is also possible to perform chemical polishing on the yoke part after barrel polishing. The time for chemical polishing is preferably a short time, usually about 1 to 3 minutes. When the treatment is performed for a long time, it is effective for removing the micro burrs remaining on the yoke component, but the dimensional accuracy of the micro-machined portion of the yoke component may be impaired.

  For yoke parts after barrel polishing, a coating such as nickel plating is generally formed on the surface of the yoke parts by a method such as electroless plating, and ultrasonic cleaning is performed to reduce metal chips harmful to hard disk drives. Commercialized as a yoke component for voice coil motors.

  Then, by using this yoke part and magnetizing and assembling by bonding a magnet, it can be commercialized as a voice coil motor for a hard disk drive.

  Examples Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[Example 1]
Using a 2 mm thick SPCC cold-rolled steel plate, press punching to form a magnetic circuit of a voice coil motor for a hard disk drive, a weight of 26 g as shown in FIG. 1, a length of about 6.5 cm and a width of about 2.5 cm 100 plate-shaped yoke parts were produced.

  This yoke part has an edge portion that is neither a curved surface nor a tapered surface, and has a through hole with a diameter of 4.0 mm (two locations), a convex half with a diameter of 2.0 mm and a height of 1.5 mm. A punched portion (three locations), a stepped portion with a step of 1.0 mm (two locations), and a semi-cylindrical cutout portion (two locations) with a diameter of 2.0 mm are formed. FIG. 6A shows the shape of the through hole, FIG. 6B shows the half punched portion, FIG. 6C shows the stepped portion, and FIG. 6D shows the shape of the notched portion. In FIG. 6, 11 is a yoke part, 111 is a through hole, 112 is a half punch portion, 113 is a stepped portion, and 114 is a notch (the same applies to the following drawings).

  Next, the upper edge part (tip peripheral part) of the half punch part (three places) is cut by grinding with a grindstone, and the edge part of the half punch part has a tapered surface as shown in FIG. Processing (the angle with respect to the peripheral surface of the half punch portion was 135 degrees) was performed. In FIG. 7A, t indicates a tapered surface (the same applies to the following drawings).

  Next, with respect to 100 yoke parts in which the half punched portion is tapered by the above method, through holes (2 locations), half punched portions (3 locations), stepped portions (2 locations), and notches The occurrence of burrs of 0.5 mm or less was observed with a microscope (20 times) at (three places), and the number of burrs was counted. The results are shown in Table 1.

Next, this barrel part was subjected to rotating barrel polishing and chemical polishing under the following conditions.
[Rotating barrel polishing]
Yoke parts 100 Abrasives 7mm outer diameter spherical abrasive (alumina, silica main component) 5 liters Rotation speed 20rpm
Polishing time 2 hours [Chemical polishing process]
A chemical polishing liquid (CPL-100, manufactured by Mitsubishi Gas Chemical Co., Ltd.) containing hydrogen peroxide water and ammonium hydrogen difluoride as main components was diluted 3 times with water, and immersed for 1 minute at 20 ° C.

  Furthermore, an electroless plating solution was used, and an electroless nickel plating process was performed under the conditions commonly used for plating of yoke parts to form a 7 μm thick nickel plating film on the surface of the yoke parts. With respect to 100 yoke parts on which this plating film is formed, through holes (2 places), half punch parts (3 places), stepped parts (2 places) and notches (3 places) are made into a microscope (20 times). The occurrence of burrs of 0.5 mm or less was observed, and the number of burrs was counted. The results are shown in Table 1.

  Next, the plated yoke parts were cleaned with ultrapure water at 60 ° C. for 2 minutes in an ultrasonic cleaner (manufactured by Shimada Rika Kogyo Co., Ltd.) at 40 kHz and an output of 600 W for a class 100 clean room. And assembled as a voice coil motor for a hard disk drive together with a magnet.

  With respect to 100 obtained hard disk drive voice coil motors, the surface of the magnet was observed with a microscope (20 times) for a metal chip of 0.5 mm or less, and the number of metal chips adhered was counted. The results are shown in Table 1.

[Example 2]
The half punch portion is subjected to taper surface processing in the same manner as in Example 1, and further, the edge portion (the edge portion of the shoulder portion) on the step of the stepped portion (two locations) is cut with a grindstone, A yoke having a yoke part and a nickel plating film formed in the same manner as in Example 1 except that the taper surface processing (the angle with respect to the peripheral surface of the stepped portion is 135 degrees) as shown in FIG. Parts and a voice coil motor for hard disk were obtained, and the state of burrs and metal chips was observed in the same manner as in Example 1 and the number thereof was counted. The results are shown in Table 1.

[Example 3]
Using a 2 mm thick SPCC cold-rolled steel plate, press punching to form a magnetic circuit of a voice coil motor for a hard disk drive, a weight of 26 g as shown in FIG. 1, a length of about 6.5 cm and a width of about 2.5 cm 100 plate-shaped yoke parts were produced.

  This yoke part has a through hole (2 locations) having a diameter of 4.0 mm, a convex half punch portion (3 locations) having a diameter of 2.0 mm and a height of 1.5 mm, and a stepped processed portion (2 ) And semi-cylindrical cutouts (2 places) with a diameter of 2.0 mm are formed, but the edge of the through hole, the stepped portion and the cutout portion are subjected to curved surface processing and tapered surface processing. Neither is given. On the other hand, in the half punch portion, a die having a curved surface (R surface R = 0.5 mm) is formed by punching the upper edge portion of the half punch portion at the time of press punching. A curved surface (R surface R = 0.5 mm) is formed in the upper edge portion (tip peripheral portion). The shape of this half punch portion is shown in FIG. In FIG. 8A, r indicates a curved surface (R surface).

  Next, the edge portion (the edge of the shoulder portion) on the step of the stepped portion (two locations) is cut with a grindstone, and tapered surface processing (stepping processing) as shown in FIG. The angle with respect to the peripheral surface of the part was 135 degrees). In this yoke part, the shape of the through hole and the notch is the same as in Example 1, and is as shown in FIGS. 6 (A) and 6 (D).

  Next, with respect to 100 yoke parts subjected to curved surface (R surface) processing and tapered surface processing by the above method, through holes (2 locations), half punch portions (3 locations), stepped processing portions (2 locations), and The notch portions (3 locations) were observed for occurrence of burrs of 0.5 mm or less with a microscope (20 times), and the number of burrs was counted. The results are shown in Table 1.

  Next, this yoke part was subjected to rotating barrel polishing, chemical polishing, and electroless nickel plating under the same conditions as in Example 1 to obtain a yoke part on which a nickel plating film was formed. Were observed and counted, and a voice coil motor for a hard disk was obtained in the same manner as in Example 1, and the state of the metal chip was observed and counted. The results are shown in Table 1.

[Example 4]
Tapering surface processing is performed on the half punch portion and the stepped portion by the same method as in Example 2, and the edge portions (both peripheral edge portions) at both ends of the peripheral surface forming the through holes of the through holes (two places) are further formed. The yoke parts and nickel plating were made in the same manner as in Example 2 except that a taper surface machining (the angle with respect to the peripheral surface of the through hole was 135 degrees) as shown in FIG. A yoke component and a hard disk voice coil motor on which a film was formed were obtained, and the states of burrs and metal chips were observed in the same manner as in Example 1 and the numbers thereof were counted. The results are shown in Table 1.

[Example 5]
In the same manner as in Example 4, taper surface processing is performed on the half punch portion, the stepped portion, and the through hole, and further, on the outer periphery of the yoke part orthogonal to the shear direction of the press punching processing of the notch portions (two places). The taper surface is cut with a grindstone at the edge portions (both peripheral edge portions) along, and the angle with respect to the taper surface processing (the peripheral surface of the notch portion (the outer peripheral surface of the yoke part)) as shown in FIG. The yoke part, the yoke part on which the nickel plating film was formed, and the voice coil motor for the hard disk were obtained in the same manner as in Example 4 except that 135 ° was applied, and the state of burrs and metal chips was observed as in Example 1. And their number was counted. The results are shown in Table 1.

[Comparative Example 1]
Using the yoke part in which the edge part produced in Example 1 is neither a curved surface nor a tapered surface as it is without performing either curved surface processing or tapered surface processing, a nickel plating film is formed in the same manner as in Example 1. The yoke parts and the voice coil motor for hard disk were obtained, and the states of burrs and metal chips were observed in the same manner as in Example 1 and the number thereof was counted. The results are shown in Table 1.

  The burrs before barrel polishing are shear burrs generated at the edge part by press punching, and in this example, no shear burrs were generated by press punching in the half punch part and the stepped part. Further, in the yoke part after plating, many secondary burrs caused by barrel polishing were observed in a portion not subjected to curved surface processing or taper surface processing.

It is a schematic exploded perspective view of the voice coil motor for hard disk drives. It is sectional drawing for demonstrating the state of the burr | flash which exists in the normal edge part which does not have the dead space which the abrasive | polishing material of a yoke component does not reach, and this burr removed by the abrasive. It is sectional drawing for demonstrating the state of the burr | flash which exists in the edge part of the through-hole of yoke components, the state by which this burr | flash was pushed into the through-hole inside by the abrasive, and the state which the secondary burr | flash generate | occur | produced. (A) is sectional drawing which shows the state of the burr | flash existing in the edge part of the half punch part of a yoke component, (B) is sectional drawing which shows the state of the burr | flash existing in the edge part of the stepped process part of a yoke part, C) is a cross-sectional view showing a state of burrs existing at the edge portion of the cutout portion having a width smaller than the diameter of the barrel abrasive formed on the outer peripheral edge portion of the yoke part. (A)-(C) is explanatory drawing of the method of forming a taper surface by the press punching process in the edge part of the through-hole of a yoke component, (A) forms a hole slightly smaller diameter than the diameter of a through-hole. (B) is a sectional view showing a state in which a tapered surface is formed at an edge portion, and (C) is a sectional view showing a state in which a through hole having a predetermined diameter is formed. Further, (D) is a cross-sectional view showing a stepped portion of a yoke part in which the entire stepped surface of the stepped portion is formed into a tapered surface. It is a figure which shows the micro process part of the yoke component in which neither a curved surface nor a taper surface is formed in the edge part, (A) is a through-hole, (B) is a half punch part, (C) is a stepped process part, (D) is sectional drawing which shows the shape of a notch part. It is a figure which shows the shape and dimension of the microfabrication part of the yoke component in each Example, (A) is the half punch part which formed the taper surface in the edge part, (B) is the step which formed the taper surface in the edge part It is sectional drawing which shows a process part. It is a figure which shows the shape and dimension of the micro process part of a yoke component in each Example, (A) is a half punch part which formed the curved surface (R surface) in the edge part, (B) forms a taper surface in the edge part. (C) is a cross-sectional view showing a notch portion in which a tapered surface is formed at an edge portion.

Explanation of symbols

11, 12, 13 Yoke part 111 Through hole 112 Half punch part 113 Stepped part 114 Notch part 2 Abrasive material b Burr c Coil d Dead space m Rare earth magnet o Open space r Curved surface (R surface)
t Tapered surface

Claims (4)

  A method of removing burrs present on the surface of a yoke part of a voice coil motor for hard disk drive by barrel polishing, and among the edge parts of the yoke part, open space where barrel abrasive particles reach in barrel polishing and barrel polishing A part of or a whole edge portion in the vicinity of a boundary with a dead space to which material particles do not reach is subjected to curved surface processing or taper surface processing, followed by barrel polishing. Removal method.   Edge portions existing in the vicinity of the boundary are both peripheral portions of the through holes having a diameter smaller than that of the barrel abrasive, the peripheral edge portion of the tip end portion of the half punch portion, the peripheral portion of the shoulder portion of the stepped portion, and the outside of the yoke component. 2. The deburring method according to claim 1, wherein the deburring method is one or two or more portions selected from both peripheral portions of the cutout portion having a width smaller than the diameter of the barrel abrasive formed on the peripheral portion.   A yoke part of a voice coil motor for a hard disk drive obtained by removing burrs existing on the surface of a yoke part of a voice coil motor for a hard disk drive by barrel polishing. A voice coil motor for a hard disk drive, wherein a part or all of an edge portion existing near a boundary between an open space where abrasive particles reach and a dead space where barrel abrasive particles do not reach is a curved surface or a tapered surface Yoke parts. Edge portions existing in the vicinity of the boundary are both peripheral portions of the through holes having a diameter smaller than that of the barrel abrasive, the peripheral edge portion of the tip end portion of the half punch portion, the peripheral portion of the shoulder portion of the stepped portion, and the outside of the yoke component. 4. The yoke component according to claim 3, wherein the yoke component is one or two or more portions selected from both peripheral portions of the cutout portion having a width smaller than the diameter of the barrel abrasive formed on the peripheral portion.

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