US20060160471A1

US20060160471A1 - Surface finishing apparatus and method, dimple die, and head suspension

Info

Publication number: US20060160471A1
Application number: US11/332,069
Authority: US
Inventors: Yasuji Takagi; Hiroshi Okamoto; Tomohiro Kawarabayashi
Original assignee: NHK Spring Co Ltd
Current assignee: NHK Spring Co Ltd
Priority date: 2005-01-14
Filing date: 2006-01-13
Publication date: 2006-07-20
Also published as: JP2006192536A

Abstract

A surface finishing apparatus mirror-finishes a three-dimensional surface of a workpiece. The surface finishing apparatus has an ejector to eject a water jet to a concave surface of a dimple die and a feeder to feed microscopic grains so that the microscopic grains are propelled by the water jet to hit and mirror-finish the concave surface. The dimple die is movably supported so that the concave surface is entirely hit with the water jet. The water jet has a speed in the range of 200 m/sec to 1000 m/sec. The microscopic grains have grain diameters in the range of 4 nm to 100 nm.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a surface finishing apparatus and method for finishing the surface of a dimple die that is used to press a dimple of a head suspension of a disk drive incorporated in an information processor such as a computer. The present invention also relates to a dimple die whose surface is finished with the surface finishing apparatus and method, and to a head suspension having a dimple pressed with the dimple die.
2. Description of Related Art
A hard disk drive (HDD) such as a magnetic disk drive employs hard disks that are rotated at high speed. On each rotating hard disk, a slider attached to a head of a head suspension is slightly floated to write and read data to and from the hard disk through a transducer incorporated in the slider. Namely, the head with the slider is supported with the head suspension so that the slider may be slightly raised from the hard disk.
The head suspension includes a flexure, a tongue formed at a front end of the flexure and supporting the slider, a load beam, and a dimple formed on the load beam. The dimple applies load to the slider and movably supports the slider. The dimple is formed by pressing the load beam and has a spherical surface. When the head suspension is raised from the hard disk, the dimple supports the slider to allow the slider to sway during the rotation of the hard disk. Namely, the dimple secures a smooth movement of the slider with respect to the hard disk.
Thus, the spherical surface of the dimple must be accurately finished.
The dimple is pressed with a dimple die having a spherical concave pressing face that is formed by electric discharge machining. The concave face formed by electric discharge machining frequently has low-melting-point compounds adhered thereto and microcracks. Due to this, the concave face of the dimple die is very rough. For example, a center line average roughness “Ra” of the concave face of the dimple die is 300 to 400 nm. There is a requirement for improving the smoothness of the concave face of the dimple die.
To achieve this, a conventional liquid or dry honing technique may be used. The liquid honing technique jets water containing an abrasive of about 8 μm in grain diameter at a speed of 30 to 60 m/s to finish the concave surface. The dry honing technique jets air containing an abrasive of about 6 μm in grain diameter to finish the concave surface.
The liquid honing technique has a limit on a usable grain diameter that is about 8 μm. An abrasive having a smaller grain diameter will make clusters in water, to thereby increase the grain diameter. The dry honing technique is unable to maintain a good working environment because the abrasive scatters in the air (refer to, for example, Japanese Unexamined Patent Application Publication No. 62-24969).

SUMMARY OF THE INVENTION

An object of the present invention is to provide a surface finishing apparatus and method for mirror-finishing a three-dimensional surface of a workpiece. Another object of the present invention is to provide a dimple die finished with such a surface finishing apparatus and method. Still another object of the present invention is to provide a head suspension having a dimple pressed with such a dimple die.
In order to accomplish the objects, an aspect of the present invention provides a surface finishing apparatus having an ejector for ejecting a water jet toward a three-dimensional surface of a workpiece and a feeder for feeding microscopic grains so that the microscopic grains are propelled by the water jet to hit and mirror-finish the three-dimensional surface.
The water jet causes the microscopic grains to hit and correctly mirror-finish the three-dimensional surface of the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view generally showing a surface finishing apparatus according to a first embodiment of the present invention;
FIG. 2 is a sectional view showing a dimple die according to the first embodiment of the present invention;
FIG. 3 is a plan view showing the dimple die of FIG. 2;
FIG. 4 is an enlarged plan view partly showing the dimple die of FIG. 3;
FIG. 5 is an enlarged sectional view partly showing the dimple die of FIG. 2;
FIG. 6 is a plan view showing a head suspension according to the first embodiment of the present invention;
FIG. 7 is an enlarged plan view partly showing the head suspension of FIG. 6;
FIG. 8 is a sectional view taken along a line VIII-VIII of FIG. 7; and
FIG. 9 is a view generally showing a surface finishing apparatus according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention capable of mirror-finishing a three-dimensional surface of a workpiece with the use of a water jet and microscopic grains dispersed in water will be explained. [First Embodiment][Surface Finishing Apparatus]
FIG. 1 is a view generally showing a surface finishing apparatus according to the first embodiment of the present invention.
In FIG. 1, the surface finishing apparatus 1 has a jet nozzle or an ejector 3, a feeder 5 for feeding microscopic grains, and a worktable 7.
The ejector 3 is connected to a pressurized water source and ejects a water jet 9 toward a three-dimensional surface of a workpiece 11. The water jet 9 has a speed in the range of, for example, 200 m/sec to 1000 m/sec.
The feeder 5 feeds microscopic grains. An end of the feeder 5 is connected to a water solution source (not shown) for supplying a water solution in which microscopic grains are dispersed. The other end of the feeder 5 is connected to the ejector 3, to feed a grain-dispersed water solution 10 into the water jet 9. The microscopic grains are, for example, ultra-dispersed diamonds (UDD) having producible minimum grain diameters in the range of, for example, 6 nm to 100 nm.
The worktable 7 is inclined by an angle of θ relative to an ejection axis J of the ejector 3. The worktable 7 is rotatable around an inclined rotation axis C and is movable in a direction parallel to the rotation axis C. The worktable 7 supports the workpiece 11. The workpiece 11 is a dimple die. The dimple die 11 is movable together with the worktable 7, so that the water jet 9 hits a three-dimensional surface, i.e., a concave surface of the dimple die 11.
[Dimple Die]
FIGS. 2 to 5 show the dimple die 11, in which FIG. 2 is a sectional view, FIG. 3 is a plan view, FIG. 4 is an enlarged partial plan view, and FIG. 5 is an enlarged partial sectional view.
In FIGS. 2 to 5, the dimple die 11 is formed in a cylindrical shape and has the central concave surface 13 to be surface-finished. The size of the concave surface 13 corresponds to the size of a dimple that is processed with the dimple die 11.
[Surface Finishing]
The concave surface 13 of the dimple die 11 is formed by electric discharge machining. The electric discharge machining produces low-melting-temperature compounds and microcracks on the concave surface 13. As a result, the concave surface 13 is very rough. For example, the concave surface 13 has a center line average roughness Ra of 300 to 400 nm.
To smooth the concave surface 13, the surface finishing apparatus 1 of FIG. 1 is used. The surface finishing apparatus 1 strikes the concave surface 13 of the dimple die 11 with the water jet 9 mixed with the microscopic grains, to thereby mirror-finish the concave surface 13.
In FIG. 1, the dimple die 11 processed by electric discharge machining is aligned on the worktable 7.
The ejector 3 ejects the water jet 9. At the same time, the worktable 7 is turned around the rotation axis C and is moved back and forth in a direction S.
The water jet 9 draws the grain-dispersed water solution 10 from the feeder 5, and with the microscopic grains, hits the concave surface 13 of the dimple die 11. The worktable 7 is turned around the rotation axis C and is moved back and forth in the direction S, so that the microscopic grains in the water jet 9 uniformly hit the concave surface 13 of the dimple die 11.
The microscopic grains have grain diameters in the range of 4 nm to 100 nm and are made so that the grains may disperse in water without forming clusters, i.e., without increasing grain diameters. According to the embodiment, the microscopic grains are ultra-dispersed diamonds that do not make clusters and evenly hit the concave surface 13 of the dimple die 11.
Hitting the concave surface 13 of the dimple die 11 with the microscopic grains mirror-finishes the concave surface 13 and provides the concave surface 13 with a surface roughness Ra of, for example, 30 nm.
[Head Suspension]
FIGS. 6 to 8 show a head suspension having a dimple pressed with the dimple die 11 having the mirror-finished concave surface 13. FIG. 6 is a plan view showing the head suspension, FIG. 7 is an enlarged plan view partly showing the same, and FIG. 8 is a sectional view taken along a line VIII-VIII of FIG. 7.
In FIGS. 6 to 8, the head suspension 15 has a load beam 17, a base 19, and a flexure 21.
The load beam 17 applies load onto a head 23 and includes a rigid part 25 and a resilient part 27. The rigid part 25 is made of, for example, stainless steel and is relatively thick, for example, about 100 μm thick.
The resilient part 27 is a separate component from the rigid part 25 and is made of, for example, a resilient thin stainless-steel rolled plate. The resilient part 27 has a precision spring constant that is lower than that of the rigid part 25. The thickness of the resilient part 27 is, for example, about 40 μm. A first end of the resilient part 27 is fixed to a rear end of the rigid part 25 by, for example, laser welding. A second end of the resilient part 27 is integral with a reinforcing plate 29.
The base 19 has a base plate 31. The base plate 31 is laid over the reinforcing plate 29 and is fixed thereto by, for example, laser welding. The reinforcing plate 29 strengthens the base plate 31, to form the base 19. The base 19 is attached to an arm of a carriage so that it can turn around an axis. The base 19 is on the arm side to resiliently support the load beam 17.
The flexure 21 has a metal base made of, for example, a thin resilient stainless-steel rolled plate, an insulating layer formed on a surface of the metal base, and conductive wiring 33 formed on the insulating layer. The flexure 21 is fixed to the rigid part 25 by, for example, laser welding. A first end of the wiring 33 is connected to write and read terminals 35 of the head 23 and a second end thereof is extended toward the base 19.
The head 23 has a cantilever tongue 37. The tongue 37 is in contact with the dimple 39 of the load beam 17. The dimple 39 has a height of, for example, about70 μm. The tongue 37 and dimple 39 are in contact with each other to maintain the swaying freedom of the head 23. In FIG. 8, the tongue 37 has a write/read slider 41. The slider 41 has terminals corresponded and electrically connected to the terminals 35.
The load beam 17 is formed by, for example, etching, and then the dimple 39 is pressed with the dimple die 11 having the mirror-finished concave surface 13.
When a hard disk on which the head suspension 15 is arranged is rotated, the head suspension 15 is raised from the hard disk. At this time, the tongue 37 and slider 41 are swayable due to the dimple 39. The dimple 39 is pressed with the dimple die 11 having the mirror-finished concave surface 13, and therefore, the spherical surface of the dimple 39 is highly accurate. Accordingly, the dimple 39 correctly swayable supports the slider 41 and applies load thereto through the tongue 37. As a result, the slider 41 can correctly write and read data to and from the hard disk. In addition, the durability of the slider 41 improves.
The microscopic grains are dispersed in the water solution 10, which is ejected with the water jet 9 to hit the dimple die 11. Accordingly, the microscopic grains never scatter in the air, to thereby maintain a good working environment.
In this way, the surface finishing apparatus according to the first embodiment of the present invention has the ejector (jet nozzle) 3 for ejecting the water jet 9 toward the concave surface (three-dimensional surface) 13 of the dimple die (workpiece) 11 and the feeder 5 for feeding ultra-dispersed diamonds (microscopic grains) so that the diamonds are propelled by the water jet to hit and mirror-finish the concave surface 13.
The feeder 5 is connected to the ejector 3, to feed the water solution 10 in which the diamonds are dispersed into the water jet 9. The water jet 9 easily draws the water solution 10 without clustering the diamonds and hits the concave surface 13 with the diamonds.
The dimple die (workpiece) 11 supported on the worktable 7 is movable, so that the concave surface 13 is entirely hit and correctly mirror-finished with the water jet 9.
The microscopic grains (diamonds) have grain diameters in the range of 4 nm to 100 nm, to correctly mirror-finish the concave surface 13.
The concave surface 13 of the dimple die 11 mirror-finished with the surface finishing apparatus 1 is used to press the dimple 39 of the head suspension 15 for a hard disk drive. Accordingly, the pressed dimple 39 has precise dimensions.
The precise dimple 39 of the head suspension 15 pressed with the dimple die 11 allows the slider 41 to correctly write and read data to and from a hard disk. The precise dimple 39 also improves the durability of the slider 41.
[Second Embodiment]
FIG. 9 shows a surface finishing apparatus according to the second embodiment of the present invention. In the second embodiment, parts that are the same as those of the first embodiment are represented with the same reference marks and parts that are different from those of the first embodiment are represented with the same numerals plus “A.”
In FIG. 9, the surface finishing apparatus 1A according to the second embodiment employs a vessel 5A serving as a feeder for feeding microscopic grains. The vessel 5A is filled with a water solution 10A in which the microscopic grains are dispersed. Within the water solution 10A, the ejector 3 ejects a water jet 9.
The water jet 9 draws the surrounding water solution 10A, so that the water solution 10A containing the microscopic grains is propelled by the water jet 9 and hits the dimple die 11 set on the worktable 7.
The second embodiment provides the same effect and operation as those of the first embodiment.
By simply filling the vessel 5A with the water solution 10A, the second embodiment simplifies the structure of the surface finishing apparatus 1A.
Each of the above-mentioned embodiments employs ultra-dispersed diamonds as microscopic grains dispersed in water. Any other microscopic grains are usable if they are dispersible in water.
The surface finishing apparatus according to any one of the embodiments is applicable not only to mirror-finishing a dimple die but also to finishing any other three-dimensional surface.

Claims

1. A surface finishing apparatus comprising:

an ejector configured to eject a water jet toward a three-dimensional surface of a workpiece; and

a feeder configured to feed microscopic grains so that the microscopic grains are propelled by the water jet to hit and mirror-finish the three-dimensional surface.

2. The apparatus of claim 1, wherein:

the feeder is connected to the ejector and is configured to feed a water solution in which the microscopic grains are dispersed into the water jet.

3. The apparatus of claim 1, wherein:

the feeder is a vessel being filled with a water solution in which the microscopic grains are dispersed and in which the water jet is ejected.

4. The apparatus of claim 1, wherein:

the workpiece is movably supported so that the three-dimensional surface is entirely hit with the water jet.

5. The apparatus of claim 1, wherein:

the microscopic grains have grain diameters in the range of 4 nm to 100 nm.

6. A dimple die comprising a concave surface that is mirror-finished with the surface finishing apparatus of claim 1 and is used to press a dimple of a head suspension for a hard disk drive.

7. A dimple die comprising a concave surface that is mirror-finished with the surface finishing apparatus of claim 2 and is used to press a dimple of a head suspension for a hard disk drive.

8. A dimple die comprising a concave surface that is mirror-finished with the surface finishing apparatus of claim 3 and is used to press a dimple of a head suspension for a hard disk drive.

9. A dimple die comprising a concave surface that is mirror-finished with the surface finishing apparatus of claim 4 and is used to press a dimple of a head suspension for a hard disk drive.

10. A dimple die comprising a concave surface that is mirror-finished with the surface finishing apparatus of claim 5 and is used to press a dimple of a head suspension for a hard disk drive.

11. Ahead suspension comprising a dimple pressed with the dimple die of claim 6.

12. A head suspension comprising a dimple pressed with the dimple die of claim 7.

13. A head suspension comprising a dimple pressed with the dimple die of claim 8.

14. A head suspension comprising a dimple pressed with the dimple die of claim 9.

15. A head suspension comprising a dimple pressed with the dimple die of claim 10.

16. A surface finishing method comprising:

hitting a three-dimensional surface of a workpiece with microscopic grains propelled by a water jet, thereby mirror-finishing the three-dimensional surface.

17. A surface finishing method comprising:

hitting a three-dimensional surface of a workpiece with microscopic grains propelled by a water jet from the surface finishing apparatus of claim 1, thereby mirror-finishing the three-dimensional surface.

18. A surface finishing method comprising:

hitting a three-dimensional surface of a workpiece with microscopic grains propelled by a water jet from the surface finishing apparatus of claim 2, thereby mirror-finishing the three-dimensional surface.

19. A surface finishing method comprising:

hitting a three-dimensional surface of a workpiece with microscopic grains propelled by a water jet from the surface finishing apparatus of claim 3, thereby mirror-finishing the three-dimensional surface.

20. A surface finishing method comprising:

hitting a three-dimensional surface of a workpiece with microscopic grains propelled by a water jet from the surface finishing apparatus of claim 4, thereby mirror-finishing the three-dimensional surface.

21. A surface finishing method comprising:

hitting a three-dimensional surface of a workpiece with microscopic grains propelled by a water jet from the surface finishing apparatus of claim 5, thereby mirror-finishing the three-dimensional surface.