JP2003191133A - Electrochemical machining electrode for dynamic pressure groove and method for machining dynamic pressure groove using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical machining electrode for a dynamic pressure groove capable of stably maintaining a predetermined machining accuracy for a long period of time; and a method for machining the dynamic pressure groove using it. <P>SOLUTION: In order to form a machining pattern (electric conductive part 10a) corresponding to a shape of the dynamic pressure groove 11b on a surface of an electrode tool 1, a recessed part 10b having a depth D of 0.1 mm or higher is formed at an area other than the machining pattern. By this structure, a workpiece 11 surface (land part 11a) opposed to the recessed part 10b does not almost receive an elution action by an electrochemical machining and it is not required that a film by an insulator is formed thereon. Accordingly, a failure of the machined shape caused by a peeling off of the insulator, an electric short circuit or the like does not occur and a predetermined machining accuracy can be stably maintained for a long period of time. Since a slight current also flows in the land part 11a of the workpiece 11 opposed to the recessed part 10b and a fine projection or the like is selectively removed, an effect of improving a surface roughness of the surface of the workpiece 11 can be also exhibited. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for electrolytically machining a dynamic pressure groove capable of maintaining a predetermined machining accuracy for a long period of time, and a method for machining a dynamic pressure groove using the electrode.

[0002]

2. Description of the Related Art In recent years, a dynamic pressure bearing device has been widely used as a bearing device used in a mechanism such as a hard disk device that requires high-speed and high-precision rotation. In a dynamic pressure bearing, in general, a working fluid is injected between the shaft and the bearing, and a dynamic pressure groove is formed in either one of the shaft and the bearing. The pressure is increased, and the dynamic pressure supports the shaft so that the shaft can rotate relative to the bearing.

The dynamic pressure groove formed in the dynamic pressure bearing adopts, for example, a spiral pattern, a V pattern, or a herringbone pattern, and the groove depth is ± 0.5.
In order to achieve high precision of about μm, the electrolytic processing method has been mainly used conventionally.

FIG. 4 is a diagram schematically showing the overall structure of an electrolytic processing apparatus used to form a dynamic pressure groove. The workpiece 11 on which the dynamic pressure groove is to be formed is arranged in the processing tank 21 with the electrode (hereinafter, referred to as an electrode tool) 2 facing a predetermined surface to be processed at a predetermined distance. To be done. The processing tank 21 has a liquid inflow pipe 2 communicating with the electrolytic solution tank 22.
2a and a liquid discharge pipe 22b are arranged so that the electrolytic solution flows between the workpiece 11 and the electrode tool 2 (machining gap 30) by driving the pump 23. A positive electrode of a machining power source 24 is connected to the workpiece 11, while a negative electrode of the machining power source 24 is similarly connected to the electrode tool 2, and an electrolytic solution is provided between the workpiece 11 and the electrode tool 2. In the flowing state, for example, a pulsed current is passed. Electrode tool 2
A predetermined processing pattern (conductive portion 10a) is formed on the surface of the workpiece 11 facing the workpiece 11, and the current from the processing power supply 24 causes the conductive portion 10a to flow with the electrolytic solution interposed.
Flowing between the workpiece 11 and the workpiece 11 elutes the workpiece 11 at a portion facing the conductive portion 10a by an electrochemical reaction, and a pattern equivalent to the conductive pattern of the electrode tool 2 on the surface of the workpiece 11 Thus, the dynamic pressure groove of is transferred and formed.

As an electrode tool used for the electrolytic machining of such a dynamic pressure groove, generally, the surface of a metal base is concealed in a region other than the pattern so that the metal part is exposed in the pattern. A structure coated with a non-conductive material (insulator) is used.

FIG. 5 schematically shows a structural example of a conventional electrode tool used for electrolytic machining of dynamic pressure grooves. The structure of the electrode tool includes a metal base 10 as shown in FIG.
After a uniform resist film made of a non-conductive material is formed on the surface of the substrate, the processed pattern portion is removed by using a photolithography technique to form the insulator 12, and the exposed surface of the substrate 10 is used as the conductive portion 10a. The electrode tool 2 having the structure to be used, or a region of the surface of the substrate 10 excluding the processing pattern as shown in FIG. 5B is scraped off by etching or the like, and a non-conductive material is embedded in the formed recess 10b for insulation. The body 13 is formed, and the exposed surface of the base 10 is connected to the conductive portion 10a.
The electrode tool 3 having a structure used as is mainly used.

[0007]

By the way, in the electrode (electrode tool) used for the electrolytic machining of the dynamic pressure groove as described above, the non-conductive material (insulator) used for covering the region other than the machining pattern is used. Has a weak adhesion to the substrate, and due to the influence of the electrolyte flowing in the machining gap during electrolytic machining,
There was a problem that this insulator would peel off.

The electrolytic machining used for forming the dynamic pressure groove is performed by setting a narrow machining gap between the electrode tool and the workpiece because the shape to be machined is minute. Therefore, the flow velocity of the electrolytic solution that flows in the processing gap also increases, and the fluid resistance that the insulator receives from the electrolytic solution increases. In the case of an electrode tool of a type in which the insulator 12 protrudes from the surface like the electrode tool 2 shown in the conventional example, the finer the processing pattern, the weaker the adhesive force between the base body 10 and the insulator 12, and The rate of occurrence of peeling is increased. Further, like the electrode tool 3, in the case of an electrode tool of a type in which the insulator 13 is embedded in the recessed portion 10b that has been scraped off and the surface is substantially flat, it is less affected by the electrolytic solution than the electrode tool 2. Though
The problem that the insulator 13 eventually peels off is unavoidable.

When such peeling of the insulator occurs, an accurate machining pattern cannot be transferred to the workpiece, and the peeling piece of the insulator clogs the machining gap between the electrode tool and the workpiece. There is also the problem of being lost. The clogging of the peeling piece partially obstructs the flow of the electrolytic solution,
Not only does it cause defects in the processed shape of that part,
In the worst case, it can cause some form of electrical short circuit, causing damage to both the electrode tool and the work piece.

The present invention has been made in order to address such a problem, and it is intended to provide an electrolytic machining electrode having a dynamic pressure groove capable of stably maintaining a predetermined machining accuracy for a long period of time, and a dynamic electrode using the same. It is an object of the present invention to provide a method for processing a pressure groove.

[0011]

In order to achieve the above object, the invention according to claim 1 is to form a dynamic pressure groove on the surface of a workpiece and a conductive portion of a predetermined pattern on the surface. The electrode thus formed is immersed in an electrolytic solution so as to face it, and while the electrolytic solution is caused to flow between the workpiece and the electrode, the workpiece and the electrode are positive and negative electrodes of a power source for processing. In each of the electrodes for electrolytic processing in which a dynamic pressure groove having a shape corresponding to the pattern of the conductive portion of the electrode is formed on the surface of the workpiece by connecting and flowing an electric current, the electrode is composed only of a conductive material, In addition, a recess having a depth of 0.1 mm or more is formed on the surface in a region other than the predetermined pattern.

Here, in the method for machining a dynamic pressure groove of the present invention, the gap between the conductive portion of the electrode and the surface of the workpiece is 0.0
Electrolytic machining is performed by a method in which a current of 150 A / cm ² or less is passed between these electrodes and the workpiece in a state of being set to 5 mm or more and 0.2 mm or less (claim 2).

According to the present invention, instead of covering a region other than the machining pattern on the surface of the electrode tool with a non-conductive material (insulator), a recess having a predetermined depth is formed in the region, and this electrode tool is used. By carrying out electrolytic processing, the intended purpose is achieved. That is, in the present invention, since a machining pattern corresponding to the dynamic pressure groove shape is formed on the surface of the electrode tool, a recess having a depth of 0.1 mm or more is formed in a region other than the machining pattern. Generally, the amount of processing per time in electrolytic processing is proportional to the current density on the surface of the workpiece (anode) when the other conditions are constant. Further, the current density on the surface of the workpiece has a correlation with the distance (machining gap) between the portion involved in the machining of the electrode tool surface and the surface of the workpiece when other conditions are constant,
It is known that it gradually decreases with the distance and gradually approaches zero. As a result of diligent research based on such an electrochemical law, the present inventors have found that when electrolytically machining a dynamic pressure groove having a groove depth of several μm to several tens of μm, the depth of the electrode tool surface is zero. It has been found that when a recess of 1 mm or more is formed, the surface of the workpiece facing the recess is hardly subjected to the elution action (engraving) by electrolytic processing.

By forming this recess in the electrode tool, the region other than the machining pattern is moved to a distance that is hardly involved in the engraving of the dynamic pressure groove, and the non-conductive material on the surface of the electrode tool that has been conventionally required. The covering with (insulator) can be eliminated. As a result, it is possible to completely eliminate defective machining shapes, electrical short circuits and the like due to the peeling of the insulator, and thus it is possible to obtain an electrode tool that can maintain a predetermined machining accuracy stably for a long period of time.

Further, since the recess is not covered with an insulator, a weak current that does not participate in the formation of the dynamic pressure groove flows on the surface of the workpiece facing the recess. As a result, minute projections and the like on the surface of the workpiece other than the dynamic pressure grooves are removed, so that the electrode tool of the present invention can also achieve the effect of improving the surface roughness of the surface of the workpiece. it can.

On the other hand, according to the method of machining a dynamic pressure groove of the present invention, when the dynamic pressure groove formed in the member of the dynamic pressure bearing is formed by electrolytic machining, the conductive portion of the electrode tool and the surface of the workpiece are processed. With the clearance (machining gap) set to 0.05 mm or more and 0.2 mm or less, 1 is set between the electrode tool and the workpiece.
A current of 50 A / cm ² or less is passed.

Considering that the optimum machining gap for machining the hydrodynamic groove is in the above range, in order to maintain high machining accuracy of the hydrodynamic groove and reproducibility of the hydrodynamic groove shape, 150 A / c.
It is preferable to use a method in which a pulsed current is applied in a plurality of times at a low current density of m ² or less and the processing is performed.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of an electrode tool according to an embodiment of the present invention.
Is an enlarged view of the P portion. Further, FIG. 3 is a diagram schematically showing the overall configuration of the electrolytic processing apparatus of the present invention used to form the dynamic pressure grooves. Note that constituent members having the same functions as those of the conventional example shown in FIGS. 4 and 5 are denoted by the same reference numerals.

As shown in FIG. 1, the structure of the electrode tool 1 used in the present embodiment has a depth D of 0.1 in the region of the surface of the metal base 10 excluding the processing pattern.
It is characterized in that a recess 10b having a size of not less than mm is formed. As a method of forming the recess 10b, it is possible to use a method such as electrolytic processing, etching, or mechanical processing. Since a relatively deep groove shape can be accurately carved, laser processing or electric discharge processing is preferably adopted. . Further, by forming the recess 10b, the conductive portion 10a involved in the processing of the workpiece 11 can be patterned into a predetermined shape.

Next, a method of processing the dynamic pressure groove using the electrode tool 1 will be described. The electrolytic processing apparatus of the present invention shown in FIG. 3 also has the same basic configuration as the conventional example. The workpiece 11 on which the dynamic pressure groove is to be formed is
The electrode tool 1 is placed in the processing tank 21 in a state of being opposed to each other with a gap of 0.05 mm or more and 0.2 mm or less.
A liquid inflow pipe 22a and a liquid discharge pipe 22b communicating with the electrolytic solution tank 22 are arranged in the processing tank 21, and by driving the pump 23, a space between the workpiece 11 and the electrode tool 1 (processing gap 3
Electrolyte is allowed to flow in 0). The type of electrolytic solution used is not particularly limited, but in general, an aqueous solution containing 30% by weight or less of sodium nitrate (NaNO ₃ ) is preferably used.

A positive electrode of a machining power source 24 is connected to the work piece 11, while a machining power source 2 is similarly connected to the electrode tool 1.
The negative electrode 4 is connected, and an electric current is passed between the workpiece 11 and the electrode tool 1 while the electrolytic solution is flowing. A pulse power source is preferably adopted as the processing power source 24,
By applying a pulsed current having a current density of cm ² or less a plurality of times, processing is performed while controlling the total amount of applied electricity.

Here, as shown in FIG. 1, the machining gap L between the electrode tool 1 and the workpiece 11 is separated by a predetermined distance (for example, 0.
1mm), when the current is passed in the state, this current becomes
The conductive portion 10a mainly on the surface of the electrode tool 1 and the conductive portion 10a
It will flow only between the surface of the workpiece 11 facing a. Then, only the workpiece 11 in the portion facing the conductive portion 10a is eluted by the electrochemical reaction due to the electric current, and the dynamic pressure groove 11b having the same pattern as the conductive portion 10a is formed on the surface thereof.
Is formed. At the same time, the surface of the workpiece 11 facing the recess 10b of the electrode tool 1 remains as a hill 11a without being electrolytically machined.

As described in detail above, the electrode tool 1 according to the present embodiment is provided with the concave portion 10b having the depth D of 0.1 mm or more in the area other than the processing pattern on the surface thereof. The recess 10b has almost no involvement in the engraving process of the dynamic pressure groove 11b, and therefore it is not necessary to form a coating of a non-conductive material as used in the conventional electrode tool.

Further, since the hill portion 11a of the workpiece 11 has not been electrolytically machined, there is a possibility that minute projections 11d as shown in FIG. 2 remain on the surface thereof. However, since the electrode tool 1 of the present invention does not cover with the non-conductive material, the hill portion 11a facing the recess 10b is
A weak current that does not contribute to the formation of the dynamic pressure groove 11b flows, and only the minute protrusion 11d on the surface of the hill portion 11a is selectively removed. As a result, the electrode tool 1 of the present invention can smooth the surface of the hill 11a and improve the surface roughness of the surface of the workpiece 11. Furthermore, this hill 11a
The weak current that flows through the conductive layer 10a also has the effect of smoothing the corner portions 11c on both sides of the upper edge of the hill portion 11a, which has a relatively large R shape due to the current from the conductive portion 10a.

Then, in the method for machining the dynamic pressure groove according to the present embodiment, the machining gap L between the conductive portion 10a of the electrode tool 1 and the surface of the workpiece 11 is set to 0.05 mm or more and 0.2 mm or less. Then, by applying a current of 150 A / cm ² or less between the electrode tool 1 and the workpiece 11 to perform machining, the dynamic pressure groove 11b having a fine shape can be formed with high accuracy and reproducibility. You can

In order to process a dynamic pressure groove having a groove depth of several μm to several tens of μm with high accuracy of about ± 0.5 μm, the distance between the electrode tool 1 and the workpiece 11 (processing gap L) is set. It is desirable that the processing is performed within a fixed range while flowing a current at a low current density. That is, in such dynamic pressure groove machining,
If the processing gap L is less than 0.05 mm, the surface of the workpiece 11 other than the required dynamic pressure groove shape will also be engraved, and an accurate dynamic pressure groove shape cannot be reproduced. If the processing gap L exceeds 0.2 mm, a high current density is required for processing, and the processed dynamic pressure groove shape becomes wide, which is not suitable for precision engraving processing. Therefore, the processing gap L is 0.05m
The optimum range is to form the dynamic pressure groove in the range of m or more and 0.2 mm or less.

Further, since this electrolytic processing is carried out by using the electrode tool 1 which does not have a coating made of a non-conductive material on its surface, there are few troubles caused by the electrode tool 1. As a result, the number of spare electrode tools 1 to be prepared can be reduced, and the number of exchanges of the electrode tool 1 in operation can be reduced, so that the efficiency of electrolytic processing can be increased in addition to the above effects.

In the above embodiment, the electrolytic machining is performed by applying the pulsed current a plurality of times, but the type of the machining power source 24 and the method of controlling the total applied electricity amount are not particularly limited. Any type of power source or control method may be used.

Further, the configuration of the electrodynamic machining apparatus for the dynamic pressure groove according to the present invention is not limited to the present embodiment, and the present invention can be applied to other arbitrary configurations in the same manner. Of course.

[0030]

As described above, according to the present invention, the depth of 0.
By forming a recess of 1 mm or more, the surface of the workpiece facing the recess is not engraved.
As a result, it is not necessary to form an insulator for patterning the conductive portion on the surface of the electrode tool, and there is no possibility of a defective machining shape or an electrical short circuit due to peeling of the insulator. Therefore, the electrode tool of the present invention can stably maintain a predetermined machining accuracy for a long period of time.

By not covering the area other than the machining pattern on the surface of the electrode tool with the insulator, a weak current that does not contribute to the formation of the dynamic pressure groove also flows on the surface of the workpiece facing the area. This weak current has the effect of selectively removing minute projections and the like on the surface of the workpiece, so the electrode tool of the present invention also has the effect of smoothing the surface of the workpiece and improving the surface roughness. Can be played.

Using the electrode tool of the present invention, the gap between the conductive portion of the electrode tool and the surface of the workpiece is 0.05 mm.
By setting an electric current of 150 A / cm ² or less between the electrode tool and the workpiece to perform machining in the state of being set to 0.2 mm or less, the dynamic pressure groove with a fine shape can be highly accurately formed. In addition, it can be formed with good reproducibility. Further, since the number of times of exchanging the electrode tool due to a decrease in processing accuracy or a trouble is reduced, the efficiency of electrolytic processing of the dynamic pressure groove can be increased in addition to the above effect.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of an electrode tool for electrolytically machining a dynamic pressure groove according to an embodiment of the present invention.

FIG. 2 is an enlarged schematic view of a P portion of FIG.

FIG. 3 is a schematic diagram showing an overall configuration of an electrolytic processing apparatus for a dynamic pressure groove according to an embodiment of the present invention.

FIG. 4 is a schematic diagram showing an overall configuration of a conventional electrolytic processing apparatus used for electrolytic processing of dynamic pressure grooves.

FIG. 5 is a schematic cross-sectional view showing a configuration example of a conventional electrode tool used for electrolytic machining of dynamic pressure grooves.

[Explanation of symbols]

1,2,3 electrode tool 10 Base 10a conductive part 10b recess 11 Workpiece 11a hill 11b Dynamic pressure groove 11c corner 11d Small protrusion 12,13 insulator 21 Processing tank 22 Electrolyte tank 22a Liquid inflow pipe 22b Distribution pipe 23 pumps 24 Processing power supply 30 Processing gap D depth L processing gap

Claims (2)

[Claims] 1. A workpiece on which a dynamic pressure groove is to be formed,
An electrode having a conductive portion of a predetermined pattern formed on its surface is immersed in an electrolytic solution so as to face the electrolytic solution, and while the electrolytic solution is caused to flow between the workpiece and the electrode, the workpiece and the electrode are processed. In the electrode for electrolytic processing in which a dynamic pressure groove having a shape corresponding to the pattern of the conductive portion of the electrode is formed on the surface of the workpiece by connecting and to the positive electrode and the negative electrode of the processing power source, respectively, and applying a current, the electrode Is an electrode for electrolytic processing, characterized in that it is composed only of a conductive material, and a recess having a depth of 0.1 mm or more is formed in a region other than the predetermined pattern on the surface thereof. 2. A gap between the conductive portion of the electrode and the surface of the workpiece is set to 0.05 mm or more and 0.2 mm or less, and 150 A / cm between the electrode and the workpiece.
^A method for processing a dynamic pressure groove, characterized in that electrolytic processing is performed by applying an electric current of ² or less.