JP2001200400A - Very small groove etching method, and manufacturing method of fluid dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently form a very small groove with high accuracy by the electrolytic etching. SOLUTION: A resist layer 2 is formed on a surface 1A of a work 1 with the very small groove to be formed thereon, the patterning corresponding to the required very small groove is performed, an electrolyte 5 is interposed between the work 1 and a machining electrode 3, the pulse voltage is applied from a pulse voltage generator 6, and the work 1 is electrolytically etched using this resist layer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for machining micro grooves and a method for manufacturing a fluid dynamic bearing.

[0002]

2. Description of the Related Art For example, several hundreds to several hundreds are provided on a circumferential bearing surface of a columnar member or a flat bearing portion of a disk-like member such as a fluid dynamic pressure bearing.
It is often required to form minute grooves on the order of tens of microns.

[0003] As a general method of forming such microgrooves, methods such as rolling, chemical etching, and electrolytic etching utilizing plastic deformation of metal have been used.

[0004] Of these methods, particularly, a method for processing micro grooves using electrolytic etching requires that grooves can be formed at a high speed, that the processing surface is smooth and high quality processing can be performed, and that the etching solution is applied to the human body. In recent years, it has attracted particular attention because it can use a safe neutral salt and is excellent in safety.

For example, Japanese Unexamined Patent Application Publication No. 9-192933 discloses a process in which a predetermined micro-groove shape is electrolytically processed and an electrode exposure of a micro-groove shape corresponding to the micro-groove shape to be processed in the workpiece. And an electrode tool having a portion are disposed close to each other and opposed to each other, and the workpiece and the electrode tool are respectively connected to the negative electrode and the positive electrode of an electrode processing power source, and a predetermined distance is provided between the electrode tool and the workpiece. In the case where the workpiece is eluted in accordance with the shape of the microgrooves and the electrolytic processing of the microgrooves is performed by energizing while flowing the electrolytic solution, the electrode tool and the workpiece are relatively separated with a predetermined processing gap. And a pulsed voltage is output from the power source for electrode processing at predetermined time intervals to control the total amount of electricity supplied from the power source for electrolytic processing. That controls the electrolytic processing amount of the fine groove shape, thereby, a method of performing electrolysis microgrooves machining is disclosed.

[0006]

However, in the conventional electrolytic etching method, the width of a groove to be processed is limited mainly by the distance between a processing electrode having an electrode shape corresponding to the groove pattern and a workpiece. When machining a dynamic pressure groove having a groove width of 200 μm or less, the above distance must be narrowed to 500 μm or less, preferably about 200 to 300 μm, and it becomes difficult to control the flow rate of the electrolyte and the distance, and mass production is performed. It was difficult.

That is, as shown in FIG.
01 and the workpiece 102 are opposed to each other, an insulating material 103 is disposed around the processing electrode 101, and the processing electrode 101 is
When the width d of the processing gap 104 is large, the width W2 of the processing groove tends to be larger than the width W1 of the processing electrode 101 when the minute groove 102A corresponding to the shape of FIG. This spread can be suppressed by reducing the width d. However, if the width d is reduced, a smooth flow of the electrolyte solution 105 in the processing gap 104 cannot be secured, and the processing efficiency is reduced, or the processing becomes impossible. In order to be stable, the value of the width d must be increased to some extent, which causes the above-described problem.

An object of the present invention is to propose a method of machining a micro groove and a method of manufacturing a fluid dynamic bearing, which can solve the above-mentioned problems in the prior art.

[0009]

According to the present invention, there is provided a processing method for forming a groove pattern on a surface of a workpiece, wherein a film is formed on the surface of the workpiece. Forming and fixing, and removing a portion of the coating corresponding to the groove pattern by laser light,
A processing electrode is opposed to the workpiece, a pulse voltage is applied with an electrolytic solution interposed in a processing gap between the workpiece and the processing electrode, and a processing surface of the workpiece is etched. A processing method comprising a step and a step of removing the film is proposed.

According to the present invention, there is also provided a method of manufacturing a fluid dynamic bearing for forming a dynamic pressure groove in a bearing surface of a fluid dynamic bearing member, the method comprising forming a film on the bearing surface and fixing the film. Removing a portion of the coating corresponding to the dynamic pressure groove by laser light, and facing a machining electrode to the bearing surface, and applying an electrolytic solution to a machining gap between the bearing surface and the machining electrode. There is proposed a method of manufacturing a fluid dynamic bearing comprising a step of interposing a pulse voltage to etch the bearing surface and a step of removing the film.

The above film may be an organic film containing a sublimable dye.

In the etching step, the electrolytic solution may be caused to flow in the processing gap, so that the processing speed can be increased.

According to the above-described structure, the pulse voltage is applied such that only the portion where the groove is to be formed by the film patterned corresponding to the predetermined groove is in contact with the electrolytic solution. Can be formed. For this reason, the width of the working gap may be wide, so that it is not necessary to forcibly flow the electrolytic solution, and the configuration of the apparatus can be simplified.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a view for explaining an embodiment in which a fine groove is formed on the surface 1A of a workpiece 1 made of stainless steel by the method of the present invention.

First, a resist layer 2 is formed by spray-coating an organic binder containing a sublimable dye to an appropriate thickness on the surface 1A of the workpiece 1 and then drying it after application. Thereafter, patterning is performed on the resist layer 2 in accordance with the shape of the required minute groove, and a window 2A corresponding to the minute groove is provided in the resist layer 2.

Thereafter, the processing electrode 3 is made to face the workpiece 1 provided with the patterned resist layer 2 on the surface 1A so that the flat surface 3A of the processing electrode 3 and the surface 1A are in a parallel state. Thus, a working gap 4 is formed. Then, a pulse voltage is repeatedly applied from the pulse voltage generator 6 to the machining gap 4 with an appropriate electrolytic solution 5 such as a NaCl solution interposed in the machining gap 4, and a machining pulse current is intermittently supplied to the machining gap 4. In this case, a pulse voltage is applied with a polarity such that the workpiece 1 is positive and the processing electrode 3 is negative.

As a result, a processing pulse current flows through the electrolytic solution 5 from the workpiece 1 to the processing electrode 3 in the processing gap 4, and the window 2 A formed in the resist layer 2 by the electrolytic action by this. A minute groove 1B according to the shape defined by the above is formed on the surface 1A of the workpiece 1.

As described above, according to this method, it is not necessary to form a groove pattern to be processed on the processing electrode 3 side, and only the flat surface 3A needs to be formed on the processing electrode 3 side. The formation of the processing electrode 3 is simple. The shape of the minute groove 1B formed in the workpiece 1 is
Is substantially defined by the window 2A formed by the patterning, so that even if the width of the processing gap 4 is widened, the influence on the dimensional accuracy of the groove processing is small, and the minute groove 1B having a required dimensional shape can be formed with high precision. . Therefore, since the width of the processing gap 4 can be increased, the processing gap 4 can be increased.
It becomes extremely easy to control the flow rate of the electrolytic solution 5 in the above.

Further, since the width of the working gap 4 can be widened, the pressure required when the electrolytic solution 5 is forced to flow in the working gap 4 by using a pump or the like can be reduced. Can be performed smoothly.

In FIG. 1, the surface 1A and the flat surface 3A are both flat, but the method of the present invention is not limited to this, and the same applies to the case where the surface 1A of the workpiece 1 is a curved surface. Applicable. In this case, the flat surface 3A of the processing electrode 3 may be a curved surface corresponding to the surface 1A.

FIG. 2 is a process diagram showing a part of a process for explaining an example of an embodiment of a method of manufacturing a fluid dynamic bearing using the present invention. Referring to FIG. 2A, a cylindrical stainless steel material 11 which is a work material for manufacturing a fluid dynamic bearing is prepared, and the outer peripheral surface 11A of the stainless steel material 11 is sufficiently washed.

Next, as shown in FIG. 2B, an organic binder containing a sublimable dye is spray-coated on the outer peripheral surface 11A of the stainless steel material 11 to a thickness of about 10 μm.
After application, the resist layer 12 is dried to form a resist layer 12.

Then, as shown in FIG. 2 (C), the stainless steel material 11 on which the resist layer 12 is formed is rotated in the direction of arrow X by an appropriate rotating device 13, and the carbon dioxide laser device is synchronized with this rotation. Laser light 1 from 14
By scanning the resist layer 12 on the resist layer 12 along the direction of the rotation axis, patterning for removing the sublimable dye at a portion corresponding to the dynamic pressure groove pattern is performed. Here, in order to improve the dye sublimation efficiency, the stainless steel material 11 is
It is preferable that the resist layer 12 is patterned while being heated to about 100 ° C.

As a result, a portion of the resist layer 12 corresponding to a required dynamic pressure groove is removed, and a state in which the dynamic pressure groove pattern 15 is formed in the resist layer 12 (FIG. 1D).

After completion of this patterning step, the working electrode is made to face the stainless steel material 11 in the state shown in FIG. 2D, and the working gap is formed between the stainless steel material 11 and this working electrode. A pulse voltage is applied with an electrolytic solution such as NaCl interposed, and the outer peripheral surface 11A of the stainless steel material 11 is etched through the dynamic pressure groove pattern 15, whereby the dynamic pressure groove having a shape corresponding to the dynamic pressure groove pattern 15 is formed. Is formed on the outer peripheral surface 11 </ b> A of the stainless steel material 11.

FIG. 3 shows an electrolytic processing apparatus for electrolytically etching the stainless steel material 11 in the state shown in FIG. 2D obtained by the series of steps shown in FIG.

The electrolytic processing apparatus 20 has a processing tank 22 filled with an electrolytic solution 21.
The workpiece 1 is set in a cylindrical machining electrode 23 provided therein. The machining electrode 23 is an inner peripheral surface 23
A is a cylindrical smooth surface, and the outer peripheral surface 12A of the resist layer 12 formed on the outer peripheral surface 11A of the stainless steel material 11
Is fixed not shown so that the gap width W of the machining gap G formed between the outer peripheral surface 11A of the stainless steel material 11 and the inner peripheral surface 23A is surrounded by the inner peripheral surface 23A and is uniform over the entire circumference. The stainless steel material 11 is coaxially arranged in the processing electrode 23 by using a jig.

Since the stainless steel material 11 and the working electrode 23 are both immersed in the electrolyte 21, the working gap G is also filled with the electrolyte 21.

A DC power supply 24 is electrically connected via a switch 25 as shown in FIG. 3 to apply a processing pulse voltage required for processing to the processing gap G. That is,
The negative electrode of the DC power supply 24 is directly connected to the processing electrode 23,
The positive electrode of the DC power supply 24 has a switch 2 connected to the stainless steel material 11.
5 are connected.

An on / off controller 26 is provided for periodically turning on and off the switch 25, and the switch 25 is turned on / off in response to an on / off control signal S from the on / off controller 26. Is repeated, whereby the processing pulse voltage is applied to the processing gap G. Here, the switch 25 can be a semiconductor switching element such as a transistor.

Reference numeral 27 denotes the processing tank 22.
This is an electrolytic solution reprocessing device for purifying the electrolytic solution 21 therein and returning the purified electrolytic solution to the inside of the processing tank 22 again. The electrolyte reprocessing device 27 includes a drain pipe 27A.
It is a device for regenerating the electrolytic solution of a known configuration, which takes in the electrolytic solution 21 in the processing tank 22 via the supply pipe and returns the reprocessed electrolytic solution into the processing tank 22 via the supply pipe 27B. A detailed description thereof will be omitted.

Next, a specific example of processing by the electrolytic processing apparatus 20 will be described. In the present embodiment, a NaCl aqueous solution is used as the electrolytic solution 21, and a groove is formed in the stainless steel material 11 by applying a pulse current intermittently for a predetermined time to the processing gap G by applying a processing pulse voltage. .

At this time, the voltage value and the application time of the processing pulse voltage are determined depending on the gap width W, the concentration and temperature of the electrolytic solution 21, the depth of the processing groove, and the processing area.

For example, when a 35% NaCl aqueous solution is used as the electrolytic solution 21 at 30 ° C. and the gap width W is set to 500 μm, a pulse voltage of 2V × 1 A and a duty of ５ is applied. A dynamic pressure groove was formed in about 3 seconds.

After the dynamic pressure grooves are formed in the stainless steel material 11 in this manner, the stainless steel material 11 is taken out of the processing tank 22 and the resist layer 12 formed on the outer peripheral surface of the stainless steel material 11 is washed with an organic solvent. The fluid dynamic pressure bearing in which the predetermined dynamic pressure grooves are formed by washing can be obtained.

As described above, an example of a method for manufacturing an axial bearing has been described with reference to FIGS. 2 and 3, but a thrust bearing can also be manufactured by the same method. That is, by using the method shown in FIG. 1, minute dynamic pressure grooves can be similarly formed on the plane of the disk-shaped member. In any case, the following advantages can be obtained.

On the outer peripheral surface 11A of the stainless steel material 11,
Dynamic pressure groove pattern 1 formed as a window in resist layer 12
According to 5, dynamic pressure grooves are formed with high dimensional accuracy by electrolytic etching. Here, it is not necessary to form the pattern of the dynamic pressure groove to be processed on the inner peripheral surface 23A of the processing electrode 23, and the smooth surface may be left, so that the formation of the processing electrode 23 is extremely simple.

As described above, since the shape of the dynamic pressure groove formed in the stainless steel material 11 is substantially determined by the patterning of the resist layer 12, the dynamic pressure groove can be formed even if the value of the gap width W of the working gap G is relatively large. Does not affect the dimensional accuracy at Therefore, the gap width W is
It is possible to set the flow rate of 1 to a value that is easy to manage. In particular, since the flow of the electrolytic solution 21 does not have to be forcibly generated in the processing gap G, the cost can be reduced accordingly. Of course, although not shown in FIG. 3, a configuration may be adopted in which a jet device for forcibly flowing the electrolytic solution 21 into the processing gap G is provided, thereby further improving the processing speed.

[0040]

According to the present invention, as described above, since it is not necessary to form a groove pattern on the processing electrode side, the formation of the processing electrode is simplified. In addition, since the film formed on the surface of the workpiece is subjected to electrolytic etching after being patterned into a size and shape corresponding to the required processing groove, the size and shape of the groove to be processed is affected by the width of the processing gap. It is hard to receive, and it is possible to realize fine groove processing such as a dynamic pressure groove with high dimensional accuracy. For this reason, the distance between the workpiece and the processing electrode can be made relatively large, so that the electrolytic solution in the processing gap does not need to be forced to flow, which contributes to cost reduction and also helps to reduce the cost. And various other excellent effects such as easy flow control.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining an embodiment in a case where microgroove processing is performed on the surface of a workpiece by the method of the present invention.

FIG. 2 is a partial process diagram for explaining an example of an embodiment of a method of manufacturing a fluid dynamic bearing according to the present invention.

FIG. 3 is a schematic configuration diagram showing a partial cross section of an example of an electrolytic processing apparatus for electrolytic etching a shaft member obtained by the process shown in FIG. 2;

FIG. 4 is an explanatory diagram for explaining a conventional electrolytic etching method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Workpiece 1A Surface 1B Micro groove 2 Resist layer 2A Window 3 Processing electrode 3A Flat surface 4 Processing gap 5 Electrolytic solution 6 Pulse voltage generator 11 Stainless steel 11A Outer peripheral surface 12 Resist layer 14 Carbon dioxide gas laser device 14A Laser beam 20 Electrolysis Processing device 21 Electrolyte solution 22 Processing tank 23 Processing electrode 23A Inner peripheral surface 24 DC power supply 25 Switch 26 On / off controller 27 Electrolyte solution reprocessing device G Processing gap

Claims (6)

[Claims] 1. A processing method for forming a groove pattern on a surface of a work, comprising: forming a film on the surface of the work and fixing the film; Removing the corresponding part, facing the processing electrode to the workpiece, applying a pulse voltage with an electrolytic solution interposed in a processing gap between the workpiece and the processing electrode, A microgroove processing method, comprising: a step of etching a processed surface of a workpiece; and a step of removing the film. 2. The method according to claim 1, wherein the film is an organic film containing a sublimable dye. 3. A method of manufacturing a fluid dynamic pressure bearing for forming a dynamic pressure groove on a bearing surface of a fluid dynamic pressure bearing member, comprising: forming a film on the bearing surface and fixing the film; Removing a portion of the film corresponding to the dynamic pressure groove, and a pulse voltage by interposing an electrolytic solution in a machining gap between the bearing surface and the machining electrode with the machining electrode facing the bearing surface. A method for manufacturing a fluid dynamic bearing, comprising: a step of applying and etching the bearing surface; and a step of removing the film. 4. The method according to claim 3, wherein the coating is an organic coating containing a sublimable dye. 5. The method of manufacturing a fluid dynamic bearing according to claim 3, wherein in the removing step, the film is patterned while the fluid dynamic bearing member is heated. 6. The temperature for heating is 80 ° C. to 10 ° C.
The method for manufacturing a fluid dynamic bearing according to claim 5, wherein the temperature is within a range of 0 ° C.