JP2002262523A - Manufacturing method for yoke member, magnetic circuit for voice coil motor, and magnetic disc device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a yoke member, and a magnetic circuit and a magnetic disc device for a voice coil motor with high quality, capable of reducing contamination due to metal particles in an electronic appliance and inferior plating caused by the contamination, and improving the yield of the yoke member. SOLUTION: A yoke material 24 with a desired thickness is obtained by cold-rolling raw material. The yoke member 12 is obtained by punching the yoke material 24, and a through hole 14 is formed at the same time. Burrs 26 are formed at the end part of the yoke member 12 and the periphery of the through-hole 14, and the burrs 26 are removed by electrolytic grinding. Electroplating is then applied to the pickled yoke member 12, and coating 28 is formed on the yoke member 12. The obtained yoke member 12 is used for the magnetic circuit 10 and the magnetic disc device 30 for the voice coil motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a yoke member, a magnetic circuit for a voice coil motor, and a magnetic disk drive, and more particularly, to a method of manufacturing a yoke member used in electronic equipment and using the yoke member. The present invention relates to a magnetic circuit for a voice coil motor and a magnetic disk drive.

[0002]

2. Description of the Related Art Conventionally, a pair of plate-like yoke members 1 as shown in FIG. 6 have been used as components constituting a magnetic circuit for a voice coil motor. A through hole 2 is formed in the yoke member 1. The upper yoke member 1 shown in FIG. 6 will be described. During manufacturing, first, a cold-rolled plate-like yoke material (not shown) is punched out to obtain the yoke member 1 as shown in FIG. At this time, the through holes 2 are formed at the same time. Then, in order to mechanically remove the burrs 3 generated at the end of the yoke member 1 and the peripheral edge of the through hole 2, the yoke member 1 is subjected to barrel polishing such as a rotary barrel, a centrifugal barrel or a vibration barrel together with a grinding stone. Therefore, it is stored in a barrel polishing machine and processed for a certain period of time. Thereafter, in order to form a uniform Ni plating film on the entire yoke member 1 including the through holes 2, electroless Ni plating is applied to a thickness of about 3 μm to 15 μm. The same applies to the lower yoke member 1 shown in FIG. The yoke member 1 thus surface-treated is washed, and a magnetic circuit for a voice coil motor is assembled using the yoke member 1 in a clean room. 4 and 7, burrs are exaggerated for ease of explanation.

[0003]

However, even in such a magnetic circuit for a voice coil motor in which cleanliness is improved by applying high-cost electroless Ni plating, the yoke member 1 is polished by mechanical processing. , FIG.
As shown in FIG. 2B, a very small (more than 20 μm) burr 3 remains at the end of the yoke member 1 and the periphery of the through hole 2, and the burr 3 comes off after assembling the voice coil motor magnetic circuit. In some cases, metal particles cause contamination of the voice coil motor magnetic circuit.

Even when the burr 3 does not fall off, since the burr 3 is removed by a mechanical process, the burr 3 is warped or crushed as shown in FIG. I will. In this case, the plating does not adhere to the burr 3 and rust occurs, or a plating solution or the like remains in the pressure-bonded portion, causing defects such as spots or discoloration, thereby preventing the yield from being improved. Therefore, the main object of the present invention is to contaminate electronic devices with metal particles.
And to provide a method of manufacturing a yoke member that can reduce plating defects associated therewith and improve the yield of the yoke member. It is another object of the present invention to provide a high quality magnetic circuit for a voice coil motor and a magnetic disk drive.

[0005]

According to a first aspect of the present invention, there is provided a method of manufacturing a yoke member for use in an electronic device, comprising: The method includes a first step of forming a member, a second step of electrolytically grinding the yoke member, and a third step of performing a surface treatment on the electrolytically ground yoke member. Claim 2
The method of manufacturing a yoke member according to the first aspect is characterized in that, in the method of manufacturing a yoke member according to the first aspect, the first step includes a step of forming a through hole in the yoke member. The method for manufacturing a yoke member according to the third aspect is the first or second aspect.
In the method of manufacturing a yoke member according to the item (1), the first step includes a punching process.

A method of manufacturing a yoke member according to a fourth aspect is characterized in that, in the method of manufacturing a yoke member according to any one of the first to third aspects, the third step includes electroplating. A magnetic circuit for a voice coil motor according to a fifth aspect uses a yoke member manufactured by the method for manufacturing a yoke member according to any one of the first to fourth aspects. A magnetic disk drive according to a sixth aspect uses the magnetic circuit for a voice coil motor according to the fifth aspect.

In the method for manufacturing a yoke member according to the first aspect, the end portion and the corner portion of the yoke member are preferentially ground by subjecting the yoke member obtained by processing the material to electrolytic grinding. Therefore, the burr of the yoke member can be removed. Therefore, by using such a yoke member, it is possible to prevent contamination of the electronic device caused by burrs. In addition, stains, rust and the like of the yoke member can be eliminated, and the yield can be improved. When a through hole is formed in the yoke member, burrs are particularly likely to be generated in the through hole. However, as in the method for manufacturing a yoke member according to claim 2, by subjecting the yoke member to electrolytic grinding, the through hole is formed. The periphery can be reliably ground and burrs can be removed. When the yoke member is formed by punching, burrs are particularly likely to occur, but the yoke member obtained by punching by subjecting the yoke member to electrolytic grinding as in the method of manufacturing a yoke member according to claim 3. Can be effectively removed.

As described above, when the yoke member is electrolytically ground, the edges and corners of the yoke member are preferentially ground (chamfered). On the other hand, when electroplating is performed on the yoke member, a so-called dog bone occurs in which the current density is concentrated on the ends and corners of the yoke member, so that the film thickness of the ends and corners is larger than the center of the yoke member. . By utilizing these phenomena, in the method of manufacturing a yoke member according to the fourth aspect, since electro-grinding is performed in advance, it becomes possible to apply electroplating instead of electroless plating. In other words, since the grinding is performed in a direction completely opposite to the manner in which the plating film is formed, a dog bone peculiar to electroplating is eliminated as a result. Therefore, a yoke member having a small difference between the end size and the center size of the yoke member is obtained, and the accuracy of the yoke member is improved. In addition, electroplating is inexpensive compared to electroless plating, and is a major factor in cost reduction.

Since the yoke member obtained by the above-mentioned method has no burrs and is of high quality, the use of the yoke member eliminates the possibility of contamination by metal particles and provides a high-quality voice. A magnetic circuit for a coil motor is obtained. As described in claim 6, if the above-described magnetic circuit for a voice coil motor is used,
Similarly, it is possible to obtain a high-quality magnetic disk device without the risk of contamination due to metal particles.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. A case where the present invention is applied to a yoke member 12 used in a magnetic circuit 10 for a voice coil motor as shown in FIGS. 1 and 2 will be described. First, the magnetic circuit 10 for a voice coil motor will be described with reference to FIGS.

The magnetic circuit 10 for a voice coil motor includes a pair of plate-like yoke members 12.
One through hole 14 is formed. On the opposing surfaces of the pair of yoke members 12, permanent magnets 16 each made of, for example, a rare earth magnet and having an arc-shaped surface are provided. The permanent magnet 16 may be provided on only one yoke member 12. The two opposing yoke members 12 are fixed using two columnar yoke members 18. That is, the lower end of the yoke member 18 is fitted into the through hole 14 of the lower yoke member 12, and the two are integrated. Then, the yoke member 18
Is inserted into the through-hole 14 of the upper yoke member 12, the screw 20 is inserted through the through-hole 14, and the yoke member 1
The pair of yoke members 12 are fixed in a state having a gap by being screwed into the end of the pair of yoke members 8. For example, a flat movable coil 22 is arranged between the two permanent magnets 16. In the voice coil motor magnetic circuit 10, when the movable coil 22 is energized, a magnetic flux as shown by an arrow A is generated, and the movable coil 22 is moved according to Fleming's left-hand rule.
And the movable coil 22 swings in the direction of arrow B.

Next, a method of manufacturing the yoke member of the yoke member 12 used in the magnetic circuit 10 for the voice coil motor will be described with reference to FIGS. FIG.
Shows a CC cross section of the upper yoke member 12 shown in FIG. First, the material is cold-rolled to obtain a yoke material 24 having a desired thickness as shown in FIG.
1). As a material, a low-carbon steel containing Mn at a maximum of 1% is used. In particular, the carbon content is 0.05% or more and 0.1% or more.
25% or less is used. Since such a material is extensible, burrs are easily generated. Then, the yoke material 24
Are punched out in the direction of arrow D to obtain a yoke member 12 as shown in FIG. 4B (step S3). At this time, the through holes 14 are formed at the same time.

Although burrs 26 are formed at the end of the yoke member 12 and the periphery of the through hole 14, the burrs 26 are reliably removed because the grinding current is concentrated on the protruding portions by electrolytic grinding (step S5). ). As the electrolytic processing liquid, for example, “Pakna electrolytic processing DL-” manufactured by Yuken Industry Co., Ltd.
2, "Pakuna electrolytic processing DL-11", "Pakuna electrolytic processing DS-1", "Pakuna electrolytic processing DS-17", and the like. According to the electrolytic grinding, as shown in FIG.
4 is ground more. Thereafter, the pickled yoke member 12 is subjected to electroplating such as electric Ni plating (step S7), and a film 28 is formed on the yoke member 12 as shown in FIG. Film 28
The end portion, the corner portion, and the peripheral edge of the through hole 14 that are cut by the electrolytic grinding are formed thicker than the flat portion of the yoke member 12. Therefore, a dimensional error such as a thickness error between the end and the center of the yoke member 12 can be reduced. The same applies to the lower yoke member 12.

According to such a method of manufacturing the yoke member 12, the burr 26 of the yoke member 12 can be removed by subjecting the yoke member 12 after punching to electrolytic grinding. In particular, the yoke member 1 generated by the punching process
The burrs 26 at the end of the second and the peripheral edge of the through hole 14 can be removed without being deformed and attached. Therefore, generation of metal particles due to the burrs 26 and contamination of the magnetic circuit 10 for the voice coil motor can be prevented, and spots, rust, discoloration and the like after plating of the yoke member 12 can be eliminated, and the yield can be improved.

Further, even if the yoke member 12 after the electrolytic grinding is subjected to the electric Ni plating, the end portion, the corner portion, and the peripheral edge of the through hole 14 which are cut by the electrolytic grinding can be restored. Since the dimensional error can be reduced, the accuracy of the yoke member 12 is improved. Further, in place of the high-cost electroless Ni plating, electric Ni plating which is overwhelmingly inexpensive can be used, and the manufacturing cost can be reduced. In addition, the electroplating is more effective as the thickness of the yoke member 12 to be plated becomes thinner, and the coating 28 can be surely formed on the inner peripheral surface of the through hole 14. If such a yoke member 12 is used in the magnetic circuit 10 for a voice coil motor shown in FIGS. 1 and 2, contamination of the magnetic circuit 10 for a voice coil motor due to metal particles can be prevented, and the quality can be improved. Further, the magnetic circuit 10 for a voice coil motor including the yoke member 12 can be applied to a magnetic disk device 30 as shown in FIG.

Referring to FIG. 5, the main configuration of the magnetic disk drive 30 will be described. The magnetic disk drive 30 includes an enclosure 32, and a base of the enclosure 32 includes:
Disks 34 that are rotationally driven by a spindle motor (not shown) are stacked. An actuator shaft 36 is erected on the base of the enclosure 32,
An actuator body 38 is rotatably attached to the actuator shaft 36. Actuator body 38
Includes a head arm 40 extending in the recording surface direction of the disk 34, and a magnetic head 44 is provided at a tip end of the head arm 40 via a head support mechanism 42. The magnetic head 44 reads / writes data from / to the disk 34.
Write. The magnetic circuit 10 for a voice coil motor is connected to such an actuator body 38.
The magnetic disk device 30 is hermetically sealed by a case (not shown) and housed in a housing of a computer or the like. If the magnetic circuit 10 for the voice coil motor is used in the magnetic disk device 30 as described above, contamination of the magnetic disk device 30 can be prevented and the quality can be improved.

Next, an experimental example of the present invention will be described. (1) Experimental Example 1 A yoke member 24 made of soft iron having a thickness of 1 mm was punched out to produce a plate-like yoke member 12 as shown in FIG. 4B. Next, the yoke member 12 was hooked on a rack to perform anodic electrolysis in an electrolytic solution. At this time, the yoke member 12
It is more effective to make only the fracture surface side of the surface facing the cathode and make it as close to the cathode as possible. The higher the current density, the shorter the processing time. Practically, the current density is 1 A / dm2 to 6
0 A / dm2 and the electrolysis time is 10 seconds to 10 minutes. As a result, as shown in FIG. 4C, the burrs 26 at the end of the yoke member 12 and the periphery of the through hole 14 could be completely dissolved and removed. At this time, the dimension (unit: μm) of the end of the yoke member 12 was W = X− (15 to 20).

(2) Comparative Example A yoke member 24 made of soft iron having a thickness of 1 mm was punched out to produce a plate-like yoke member 12 as shown in FIG. Next, the yoke member 12 was put into a rotary barrel polishing machine together with the barrel polishing stone, the compound and the polishing powder, and subjected to barrel polishing for one hour. As a result, similarly to FIG. 7B, the burrs 26 at the end of the yoke member 12 and the peripheral edge of the through hole 14 are not completely removed, and many burrs 26 are warped and pressed against the yoke surface. Was observed. After a 7 μm film was formed on the yoke member 12 by electroless Ni plating, the appearance was inspected. As a result, rust, spots, and discoloration were observed in the crimped portion of the burr 26.

(3) Experimental Example 2 A yoke member 24 made of soft iron having a thickness of 1 mm was punched to produce a plate-like yoke member 12 as shown in FIG. Next, the yoke member 12 was hooked on a rack to perform anodic electrolysis in an electrolytic solution. At this time, the yoke member 12
It is more effective to make only the fracture surface side of the surface facing the cathode and make it as close to the cathode as possible. The higher the current density, the shorter the processing time. Practically, the current density is 1 A / dm2 to 6
0 A / dm2 and the electrolysis time is 10 seconds to 15 minutes.

As a result, as shown in FIG. 4C, the burrs 26 at the end of the yoke member 12 and the peripheral edge of the through hole 14 could be completely dissolved and removed. At the same time, only the end of the yoke member 12 was preferentially ground, and the thickness of the end of the yoke member 12 became smaller by about 15 μm to 25 μm than the thickness of the central part. Thereafter, a 7 μm thick film 2 is applied to the yoke member 12.
8 was formed, the plating thickness was 7 μm at the center and 15 μm to 20 μm at the end, and the parallelism and flatness of the yoke member 12 were both good and ±
It could be kept within 5 μm. Further, when the appearance inspection was performed, it was good without rust, spots, and discoloration. Note that the present invention can be applied to a yoke member used for any electronic device.

[0021]

According to the present invention, since the burr of the yoke member can be removed, the contamination of the electronic equipment using the yoke member can be prevented, and the yoke member can be prevented from being stained, rusted, etc., and the yield can be improved. it can.
Further, if such a yoke member is used, there is no risk of contamination, and a high quality magnetic circuit for a voice coil motor and a magnetic disk device can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a main part of a magnetic circuit for a voice coil motor to which the present invention is applied.

FIG. 2 is an illustrative view showing a magnetic circuit for the voice coil motor of FIG. 1;

FIG. 3 is a flowchart showing an example of a manufacturing process of a yoke member.

FIG. 4 is an illustrative view showing one example of a manufacturing process of a yoke member; (a) is after cold rolling; (b) is after punching;
Shows the state after electrolytic grinding, and (d) shows the state after electroplating.

FIG. 5 is a partially cutaway plan view showing an example of a magnetic disk drive to which the present invention is applied.

FIG. 6 is a perspective view showing an example of a yoke member used as a component of a magnetic circuit for a voice coil motor.

FIG. 7 is an illustrative view showing one example of a conventional method of manufacturing a yoke member, wherein (a) shows a state after punching and (b) shows a state after barrel polishing.

[Explanation of symbols]

 Reference Signs List 10 magnetic circuit for voice coil motor 12, 18 yoke member 14 through hole 24 yoke material 26 burr 28 coating 30 magnetic disk device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 21/02 632 G11B 21/02 632H H02K 1/12 H02K 1/12 A 33/18 33/18 BF Terms (reference) 3C059 AA02 AB00 GC01 5D068 AA01 BB01 CC12 GG25 5H002 AA07 AA08 AB06 AC03 5H615 AA01 BB01 BB15 PP01 PP07 PP17 QQ02 QQ08 QQ19 SS03 SS08 SS38 5H633 BB02 GG03 GG06 GG08 H11H13H09

Claims (6)

[Claims] 1. A method of manufacturing a yoke member used in an electronic device, comprising: a first step of processing a material to form a yoke member; a second step of electrolytically grinding the yoke member; and an electrolytically ground yoke member. A method of manufacturing a yoke member, comprising a third step of subjecting a yoke member to a surface treatment. 2. The method according to claim 1, wherein the first step includes a step of forming a through hole in the yoke member. 3. The method for manufacturing a yoke member according to claim 1, wherein the first step includes a punching process. 4. The method for manufacturing a yoke member according to claim 1, wherein said third step includes electroplating. 5. A magnetic circuit for a voice coil motor using a yoke member manufactured by the method of manufacturing a yoke member according to claim 1. 6. A magnetic disk drive using the voice coil motor magnetic circuit according to claim 5.