JP4369583B2 - Micro-groove machining method and fluid dynamic pressure bearing manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a minute groove machining method and a fluid dynamic pressure bearing manufacturing method.
[0002]
[Prior art]
For example, it is often required to form minute grooves on the order of several hundreds to several tens of microns on the circumferential bearing surface of a cylindrical member or the flat bearing part of a disk-like member such as a fluid dynamic pressure bearing.
[0003]
Conventionally, methods such as rolling, chemical etching, and electrolytic etching using plastic deformation of metals have been used as a general method for forming such microgrooves.
[0004]
Among these, the micro-groove processing method using electrolytic etching, in particular, enables groove formation at a high speed, enables the processing surface to be smooth and high-quality processing, and makes the etching solution safe for the human body. In recent years, it has attracted particular attention due to the fact that it can use a salt and is excellent in safety.
[0005]
For example, Japanese Patent Application Laid-Open No. 9-192932 has a workpiece in which a predetermined minute groove shape is electrolytically processed, and an electrode exposure portion having a minute groove shape corresponding to the minute groove shape to be processed in the workpiece. The electrode tool and the electrode tool are disposed in close proximity to each other, and the workpiece and the electrode tool are connected to the negative electrode and the positive electrode of the electrode machining power source, respectively, and a predetermined electrolyte is placed between the electrode tool and the workpiece. The electrode tool and the workpiece are relatively stationary with a predetermined machining gap when the workpiece is eluted corresponding to the shape of the minute groove by energizing while flowing and the minute groove is subjected to electrolytic machining. And by outputting a pulse voltage at a predetermined time interval from the electrode processing power source and controlling the total amount of electricity given from the electrolytic processing power source, It controls electrolytic processing amount, thereby, a method of performing electrolysis microgrooves machining is disclosed.
[0006]
[Problems to be solved by the invention]
However, in the conventional electrolytic etching method, the groove width to be processed is limited mainly by the distance between the processed electrode having an electrode shape corresponding to the groove pattern and the workpiece, and the dynamic pressure groove having a groove width of 200 μm or less When machining the above, the distance must be narrowed to 500 μm or less, preferably about 200 to 300 μm, which makes it difficult to manage the flow rate of the electrolyte and to manage the distance, making mass production difficult.
[0007]
That is, as shown in FIG. 4, the processing electrode 101 and the workpiece 102 are opposed to each other, the insulating material 103 is disposed around the processing electrode 101, and the electrolytic solution 105 is interposed in the processing gap 104. In the case where the minute groove 102A corresponding to the shape of the machining electrode 101 is to be formed in 102, if the width d of the machining gap 104 is large, the width W2 of the machining groove tends to be larger than the width W1 of the machining electrode 101. Have This expansion 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 machining gap 104 cannot be secured, and the machining efficiency is lowered or machining is not performed. In order to become stable, the value of the width d has to be increased to some extent, and the above-described problem occurs.
[0008]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to propose a micro-grooving method and a fluid dynamic bearing manufacturing method that can solve the above-mentioned problems in the prior art.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, according to the present invention, there is provided a processing method for forming a groove pattern on a surface of a workpiece, the step of forming and fixing a film on the surface of the workpiece, and a laser beam. Removing the portion of the coating corresponding to the groove pattern, with the machining electrode opposed to the workpiece, and interposing an electrolyte in the machining gap between the workpiece and the machining electrode. Then, there is proposed a processing method comprising a step of applying a pulse voltage to etch a processed surface of the workpiece and a step of removing the film.
[0010]
According to the present invention, there is also provided a fluid dynamic pressure bearing manufacturing method for forming a dynamic pressure groove on a bearing surface of a fluid dynamic pressure bearing member, the step of forming and fixing a film on the bearing surface, and a laser. Removing the portion of the coating corresponding to the dynamic pressure groove with light, and interposing an electrolytic solution in the 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 a pulse voltage to etch the bearing surface and a step of removing the film is proposed.
[0011]
The film may be an organic film containing a sublimable dye.
[0012]
In the etching step, the electrolytic solution may flow in the processing gap, thereby increasing the processing speed.
[0013]
According to the above-described configuration, the pulse voltage is applied so 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 processing gap width may be wide, so that it is not necessary to force the electrolyte to flow, and the configuration of the apparatus can be simplified.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 1 is a view for explaining an embodiment in the case where a minute groove is formed on a surface 1A of a workpiece 1 which is a stainless steel material by the method of the present invention.
[0016]
First, the resist layer 2 is formed by spray-coating an organic binder containing a sublimable dye on the surface 1A of the workpiece 1 to an appropriate thickness, and drying after coating. Thereafter, the resist layer 2 is patterned according to the required shape of the minute groove, and the resist layer 2 is provided with a window 2A corresponding to the minute groove.
[0017]
Thereafter, the processing electrode 3 is opposed to the workpiece 1 provided with the resist layer 2 patterned on the surface 1A so that the flat surface 3A of the processing electrode 3 and the surface 1A are parallel to each other. 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 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 in such a polarity that the workpiece 1 is positive and the machining electrode 3 is negative.
[0018]
As a result, a machining pulse current flows in the electrolytic solution 5 from the workpiece 1 to the machining electrode 3 in the machining gap 4 and is defined by the window 2A formed in the resist layer 2 by the electrolytic action thereby. A minute groove 1B according to the shape is formed on the surface 1A of the workpiece 1.
[0019]
Thus, according to this method, there is no need 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 3 is simple. Further, since the shape of the minute groove 1B formed in the workpiece 1 is substantially determined by the window 2A formed by patterning the resist layer 2, even if the width of the processing gap 4 is widened, the dimensional accuracy of the groove processing by this is increased. The minute groove 1B having a required dimension and shape can be formed with high accuracy. Therefore, since the width of the machining gap 4 can be increased, the flow rate control of the electrolytic solution 5 in the machining gap 4 becomes extremely easy.
[0020]
Further, since the width of the machining gap 4 can be increased, the pressure when the electrolytic solution 5 is forced to flow using a pump or the like in the machining gap 4 can be reduced, and the required machining can be performed smoothly. It can be carried out.
[0021]
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 can be similarly applied to the case where the surface 1A of the workpiece 1 is a curved surface. In this case, the flat surface 3A of the processing electrode 3 may be a curved surface corresponding to the surface 1A.
[0022]
FIG. 2 is a process diagram showing a part of a process for explaining an example of an embodiment of a manufacturing method of a fluid dynamic bearing using the present invention. Referring to FIG. 2A, a cylindrical stainless steel material 11 which is a workpiece for manufacturing a fluid dynamic pressure bearing is prepared, and the outer peripheral surface 11A of the stainless steel material 11 is sufficiently cleaned.
[0023]
Next, as shown in FIG. 2 (B), an organic binder containing a sublimable dye is spray-applied on the outer peripheral surface 11A of the stainless steel material 11 to a thickness of about 10 μm and dried after application. A resist layer 12 is formed.
[0024]
Then, as shown in FIG. 2C, the stainless steel material 11 on which the resist layer 12 is formed is rotated in the direction of the arrow X by an appropriate rotating device 13, and the carbon dioxide laser device 14 is synchronized with this rotation. The laser beam 14A is scanned along the rotation axis direction on the resist layer 12 to perform patterning for removing the sublimable dye in a portion corresponding to the dynamic pressure groove pattern. Here, in order to improve the dye sublimation efficiency, it is preferable to pattern the resist layer 12 in a state where the stainless steel material 11 is heated to, for example, about 80 to 100 ° C.
[0025]
As a result, a portion of the resist layer 12 corresponding to the required dynamic pressure groove is removed, and the dynamic pressure groove pattern 15 is formed in the resist layer 12 ((D) in FIG. 1).
[0026]
After completion of this patterning step, the processing electrode is made to face the stainless steel material 11 in the state shown in FIG. 2D, and a processing gap formed between the stainless steel material 11 and the processing electrode is made of NaCl or the like. A pulse voltage is applied through an electrolytic solution, and etching of the outer peripheral surface 11A of the stainless steel material 11 is performed through the dynamic pressure groove pattern 15, whereby a dynamic pressure groove having a shape corresponding to the dynamic pressure groove pattern 15 is formed. 11 on the outer peripheral surface 11A.
[0027]
FIG. 3 shows an electrolytic processing apparatus for electrolytically etching the stainless steel material 11 in the state shown in FIG. 3D obtained by the series of steps shown in FIG.
[0028]
The electrolytic processing apparatus 20 includes a processing tank 22 filled with an electrolytic solution 21, and the workpiece 1 is set in a cylindrical processing electrode 23 provided in the processing tank 22. . The processing electrode 23 has an inner peripheral surface 23 </ b> A that is a cylindrical smooth surface, and the outer peripheral surface 12 </ b> A of the resist layer 12 formed on the outer peripheral surface 11 </ b> A of the stainless steel material 11 is surrounded by the inner peripheral surface 23 </ b> A. The stainless steel material 11 is processed by the processing electrode 23 using a fixing jig (not shown) so that the gap width W of the processing gap G formed between the outer peripheral surface 11A and the inner peripheral surface 23A is uniform over the entire circumference. It is coaxially arranged inside.
[0029]
Since both the stainless steel material 11 and the processing electrode 23 are immersed in the electrolytic solution 21, the machining gap G is also filled with the electrolytic solution 21.
[0030]
In order to apply a machining pulse voltage necessary for machining to the machining gap G, a DC power source 24 is electrically connected via a switch 25 as shown in FIG. That is, the negative electrode of the DC power supply 24 is directly connected to the processing electrode 23, and the positive electrode of the DC power supply 24 is connected to the stainless steel material 11 via the switch 25.
[0031]
An on / off controller 26 is provided to periodically turn on and off the switch 25, and the switch 25 repeatedly turns on and off in response to an on / off control signal S from the on / off controller 26. Thus, the machining pulse voltage is applied to the machining gap G. Here, the switch 25 may be a semiconductor switching element such as a transistor.
[0032]
What is indicated by reference numeral 27 is an electrolytic solution reprocessing device for purifying the electrolytic solution 21 in the processing tank 22 and returning the purified electrolytic solution to the processing tank 22 again. The electrolytic solution reprocessing apparatus 27 takes in the electrolytic solution 21 in the processing tank 22 through the drain pipe 27A, and returns the reprocessed electrolytic solution to the processing tank 22 through the supply pipe 27B. Therefore, a detailed description thereof will be omitted.
[0033]
Next, a specific processing example by the electrolytic processing apparatus 20 will be described. In this embodiment, an NaCl aqueous solution is used as the electrolytic solution 21, and a groove is formed in the stainless steel material 11 by intermittently flowing a pulse current through the machining gap G for a predetermined time by applying a machining pulse voltage. .
[0034]
The voltage value and application time of the processing pulse voltage at this time 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.
[0035]
For example, when a 35% NaCl aqueous solution at 30 ° C. is used as the electrolytic solution 21 and the gap width W is 500 μm, a pulse voltage having a duty of 1/5 is applied at 2 V × 1 A, and a dynamic pressure groove having a depth of 6 μm is obtained. Was formed in about 3 seconds.
[0036]
If the dynamic pressure grooves are formed in the stainless steel material 11 in this way, 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. A fluid dynamic pressure bearing in which predetermined dynamic pressure grooves are formed can be obtained.
[0037]
As mentioned above, although an example of the manufacturing method about an axial bearing was demonstrated with reference to FIG.2 and FIG.3, a thrust bearing can also be manufactured by the method similar to this. That is, by using the method shown in FIG. 1, a minute dynamic pressure groove can be formed in the same manner on the plane of the disk-shaped member. In either case, the following advantages can be obtained.
[0038]
On the outer peripheral surface 11A of the stainless steel material 11, a dynamic pressure groove is formed with high dimensional accuracy by electrolytic etching in accordance with a dynamic pressure groove pattern 15 formed as a window of the resist layer 12. 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 a smooth surface may be left. Therefore, the formation of the processing electrode 23 is extremely simple.
[0039]
As described above, since the shape of the dynamic pressure groove formed in the stainless steel material 11 is substantially determined by patterning of the resist layer 12, even if the value of the gap width W of the processing gap G is large to some extent, the dimensional accuracy in forming the dynamic pressure groove. Will not be affected. Therefore, the gap width W can be set to a value that makes it easy to manage the flow rate of the electrolytic solution 21. In particular, since it is not necessary to forcibly create the flow of the electrolyte solution 21 in the machining 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 in the machining gap G is provided, thereby further improving the machining speed.
[0040]
【The invention's effect】
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 patterned into a dimension and shape corresponding to the required machining groove and then electrolytic etching is performed, the dimension and shape of the groove to be machined are affected by the width of the machining gap. It is difficult to receive, and minute groove processing such as a dynamic pressure groove can be realized with high dimensional accuracy. For this reason, the distance between the workpiece and the processing electrode can be made relatively large, and it is not necessary to forcibly flow the electrolytic solution in the processing gap. Various excellent effects such as easy flow rate management can be obtained.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram for explaining an embodiment in the case of performing microgrooving 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 electrolytically 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 material 11A Outer peripheral surface 12 Resist layer 14 Carbon dioxide laser device 14A Laser beam 20 Electrolysis Processing device 21 Electrolytic solution 22 Processing tank 23 Processing electrode 23A Inner peripheral surface 24 DC power supply 25 Switch 26 On / off controller 27 Electrolyte reprocessing device G Processing gap

Claims (4)

A processing method for forming a groove pattern on the surface of a workpiece,
Forming and fixing an organic film containing a sublimable dye on the surface of the workpiece;
Removing a portion of the film corresponding to the groove pattern by laser light;
A machining electrode is made to face the workpiece, a pulse electrode is applied through a machining gap between the workpiece and the machining electrode, and a machining surface of the workpiece is etched. Process,
Removing the film;
A micro-grooving method characterized by comprising: A fluid dynamic pressure bearing manufacturing method for forming a dynamic pressure groove on a bearing surface of a fluid dynamic pressure bearing member,
Forming and fixing an organic film containing a sublimable dye on the bearing surface;
Removing a portion corresponding to the dynamic pressure groove of the coating with a laser beam;
Etching the bearing surface by applying a pulse voltage by interposing an electrolyte in a machining gap between the bearing surface and the machining electrode with the machining electrode facing the bearing surface;
Removing the film;
A method of manufacturing a fluid dynamic pressure bearing, comprising: The method for manufacturing a fluid dynamic pressure bearing according to claim 2 , wherein the film is patterned in a state where the fluid dynamic pressure bearing member is heated in the removing step. The method for manufacturing a fluid dynamic bearing according to claim 3, wherein a temperature for the heating is in a range of 80 ° C. to 100 ° C. 5.

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