JPH10180545A - Electrochemical machining method and device for dynamic pressure groove in dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform electrochemical machining high accurately in an arbitrary groove depth in accordance with a groove position, while attaining reduction of a cost and improvement of productivity, even in a dynamic pressure groove of complicated and fine shape. SOLUTION: Based on a characteristic in which a machining speed in the groove depth direction in a workpiece 142 by electrochemical machining is in inverse proportion to a machining clearance 150 between an electrode exposed part 143a and the workpiece 142, the machining clearance 150, corresponding to a groove depth of a worked dynamic pressure groove 142a, is narrowed relating to a location deepening the groove depth, and widened relating to a location shallowing the groove depth, electrochemical machining is performed, so as to deepen the groove depth in a location of the narrow machining clearance 150 and shallow the groove depth in a location of the wide machining clearance 150, in accordance with a groove position, so that electrochemical machining of arbitrary groove depth can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrolytic machining in which a dynamic pressure groove formed on a dynamic pressure surface of a dynamic pressure bearing is formed into a predetermined groove shape having a different groove depth depending on a portion by electrolytic machining. The present invention relates to a method and an electrolytic processing apparatus.

[0002]

2. Description of the Related Art In recent years, dynamic pressure bearings having excellent high-speed bearing characteristics have been attracting attention as bearing devices used in polygon mirror scanner motors, hard disk drive (HDD) spindle motors, and the like. This dynamic pressure bearing
A predetermined bearing fluid is injected between a bearing and a shaft which are relatively rotatably arranged, and the bearing fluid is moved by the pumping action of a dynamic pressure groove provided on at least one of the bearing and the shaft. Pressure is generated, and the bearing and the shaft are supported so as to be relatively rotatable by the dynamic pressure.

A dynamic pressure groove provided in such a dynamic pressure bearing has a herringbone shape with respect to a dynamic pressure surface of a bearing or a shaft.
It is processed into a predetermined groove shape such as a spiral shape. As the processing means, various forming methods such as cutting, rolling, coining (coining), etching, and electrolytic processing have been conventionally used.

[0004]

In order to improve the dynamic pressure action in the dynamic pressure bearing, the shape of the dynamic pressure groove formed in the dynamic pressure surface is not merely a rectangular shape but a shape according to design needs, for example, It is necessary to change the depth of the dynamic pressure groove. However, in the above-mentioned etching method and electrolytic processing method, since the groove depth is formed uniformly, the groove depth cannot be varied depending on the portion.

In the above cutting method, the tool is multi-axis (3
Dimension) It is necessary to control, and small motors such as polygon mirror scanner motors and HDD spindle motors require positioning accuracy in the order of μm, which makes the equipment expensive and expensive.
Since the grooves must be formed one by one, there is a problem that productivity is reduced.

[0006] In addition, the coining or the rolling method has a problem that the tool for transferring the groove shape is severely worn and the tool life is shortened, so that the cost is increased. In particular, in the dynamic pressure groove of the small motor as described above, since a complicated and fine shape is required, wear of the tool becomes remarkable. Also, it is necessary to remove burrs generated during rolling and to improve flatness for thrust bearings and improve cylindricity for radial bearings. There is a problem that variation occurs.

Therefore, the present invention enables high-precision machining to an arbitrary groove depth according to the groove position while reducing the cost and improving the productivity, even for a dynamic pressure groove having a complicated and fine shape. An object of the present invention is to provide an electrolytic machining method and an electrolytic machining apparatus for a dynamic pressure groove in a dynamic pressure bearing configured as described above.

[0008]

In order to achieve the above object, an electrolytic machining method according to the present invention provides a hydrodynamic groove for generating a hydrodynamic pressure for bearing support in a bearing fluid with respect to a hydrodynamic surface of a hydrodynamic bearing. In the method of electrolytically machining a dynamic pressure groove in a dynamic pressure bearing for machining into a predetermined groove shape by electrolytic machining, the dynamic pressure groove includes a workpiece to be electrolytically machined, and a dynamic pressure groove to be machined in the workpiece. An electrode tool having a corresponding groove-shaped electrode exposed portion is fixedly opposed to each other while being fixed to each other with a predetermined gap therebetween, and machining the electrode exposed portion and the workpiece. The gap is made narrower in the portion where the groove depth is formed deeper in accordance with the groove depth of the dynamic pressure groove to be machined, and these workpieces and electrode tools are connected to the positive electrode and the negative electrode of the power source for electrolytic machining, respectively. And flowing a predetermined electrolyte between the electrode tool and the workpiece. Want the workpiece has been made to the structure of electrochemical machining dynamic pressure grooves eluted corresponding to the groove shape by energizing.

Further, in the electrolytic processing apparatus according to the present invention, a dynamic pressure groove for generating a dynamic pressure for supporting a bearing fluid is formed into a predetermined groove shape by electrolytic processing on a dynamic pressure surface of a dynamic pressure bearing. In a hydrodynamic groove electrolytic machining apparatus in a dynamic pressure bearing configured as described above, a power supply for electrolytic machining, a workpiece on which the dynamic pressure groove is electrolytically machined, and a groove-shaped electrode exposed portion corresponding to the dynamic pressure groove. Having an electrode tool fixed in a relatively immobile state so as to oppose the workpiece with a predetermined machining gap,
An electrolytic solution supply means for flowing a predetermined electrolytic solution between the electrode tool and the workpiece; and connecting the workpiece and the electrode tool to a positive electrode and a negative electrode of the electrolytic machining power source, respectively. The workpiece is eluted in accordance with the groove shape by applying an electric current while flowing an electrolytic solution between the tool and the workpiece, and the dynamic pressure groove is formed by electrolytic processing, and the electrode The exposed portion is configured such that the processing gap with respect to the workpiece becomes narrower at a portion where the groove depth is formed to be deeper in accordance with the groove depth of the dynamic pressure groove to be processed.

In the method and the apparatus for electrodynamic machining of a hydrodynamic groove in a hydrodynamic bearing having such a configuration, the machining speed in the groove depth direction of the workpiece by electrolytic machining is such that the electrode-exposed portion and the workpiece Based on the characteristic that the working gap is inversely proportional to the working gap, the working gap is narrowed for the part where the groove depth is increased corresponding to the groove depth of the dynamic pressure groove to be machined, and the groove depth is reduced. Since the part to be processed is widened, when electrolytic processing is performed, the groove depth of the part with a narrow processing gap becomes deep, and the groove depth of the part with a wide processing gap becomes shallow. Accordingly, electrolytic processing with an arbitrary groove depth is performed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. First, as a device provided with a dynamic pressure bearing formed according to the present invention, for example, a structure of a shaft rotation type HDD spindle motor as shown in FIG. 12 will be described.
FIG. 12 shows the right half of the motor in cross section, and shows the groove formed on the bearing side so that the middle of the shaft is broken. This motor is composed of a stator set mounted on a frame 1 side and a rotor set mounted axially on the stator set, and a cylindrical bearing holder 2 is vertically mounted on the frame 1. It is provided so as to be erected. A stator core 4 around which the winding 3 is wound is mounted on an outer peripheral portion of the cylindrical bearing holder 2. Further, a cylindrical radial bearing 5 is mounted on the inner side of the bearing holder 2, and a rotating shaft 6 is inserted through the radial bearing 5.
Is rotatably supported.

That is, the rotating shaft 6 and the radial bearing 5
A bearing portion is formed at a portion opposed to the above, and the bearing portion is filled with a lubricating fluid Q made of a magnetic fluid or the like.
In addition, on the inner peripheral surface of the radial bearing 5 in the bearing portion,
A pair of radial grooves 5a for generating dynamic pressure are formed in the axial direction, and the rotating shaft 6 is rotatably supported by the dynamic pressure of the lubricating fluid Q generated by the pumping action of the radial grooves 5a, 5a. Has become.

The upper end of the rotary shaft 6 in the figure is fixed to the center of the hub 8 so as to rotate integrally.
The hub 8 has a body 8a for mounting a medium such as a magnetic disk on the outer periphery, and a mounting portion 8b provided on the lower edge side of the body 8a so as to project radially outward. Drive magnet 10 via back yoke 9
Are mounted in an annular shape. The drive magnet 10 is
The stator core 4 is disposed so as to annularly face the outer peripheral surface.

A magnetic fluid seal 11 is provided at the upper end opening of the bearing holder 2 in the figure. The magnetic fluid seal 11 is disposed to prevent the leakage of the lubricating fluid Q to the outside.
Are sandwiched in the axial direction by a pair of pole pieces 11b, 11b, and a seal is formed at a position facing the inner peripheral edge of the pole pieces 11b, 11b and the outer peripheral surface of the rotary shaft 6. Magnetic fluids 11c, 11c are held in the unit so as to shut off from the outside. The lubricating fluid Q in the bearing portion is sealed in the cylindrical space defined in the inner space of the bearing holder 2 by the external blocking action of the magnetic fluid seal 11, whereby the lubricating fluid Q Is prevented from leaking outside, and the inflow of dust and the like from the outside is prevented.

Next, a description will be given of an electrolytic processing apparatus according to an embodiment of the present invention for forming a radial groove 5a for generating a dynamic pressure by processing an inner surface of the radial bearing 5 described above. As shown in FIG. 1, a hollow housing 21 made of a non-conductive material is provided with a cavity for electrolytic processing, and an axial direction (vertical direction in the drawing) in the cavity is substantially provided. A bearing material 22 as a hollow cylindrical workpiece made of a metal material is fixed to the central portion.

As described above, the bearing material 22 as a workpiece in the present embodiment is used to process the radial bearing 5 of a small dynamic pressure bearing device used for a polygon mirror scanner motor, a hard disk drive (HDD) spindle motor, and the like. Bearing material before the
As the material of No. 2, stainless steel (SUS) 304 or copper is used.

A cylindrical electrode tool 23 is fixed to the housing 21 so as to penetrate the bearing material 22 in the axial direction. Both ends of the electrode tool 23 in the axial direction (vertical direction in the drawing) are fixed to closing walls 21a and 21b at both ends in the axial direction of the housing 21, respectively.
A pair of electrode exposed portions 23a, 23a formed at a substantially central portion in the axial direction of the electrode tool 23 are arranged so as to face the inner peripheral wall surface 22a of the bearing material 22. Each of the electrode exposed portions 23a has a number of herringbone-shaped grooves arranged in parallel in the circumferential direction.

That is, the outer surface of the electrode tool 23 is
The electrode tool 2 is entirely covered with a non-conductive material 23b except for the above-mentioned predetermined groove-shaped electrode exposed portion 23a.
The electrode tool 23 and the bearing material 22 are coaxial so that the groove-shaped bottom wall surface of the third electrode exposed portion 23a has a predetermined machining gap over the entire circumference with respect to the inner peripheral wall surface 22a of the bearing material 22. Has been adjusted. The electrode-exposed portion 23a of the electrode tool 23 and the inner peripheral wall surface 22a of the bearing material 22 are opposed to each other via a predetermined machining gap, thereby forming the electrolytically-machined portion A.

Further, a contact piece 24a extending from the positive electrode (+ pole) of the electrolytic machining pulse power source 24 is provided on the bearing material 22.
Is connected, and an ammeter 25 for detecting a value of an energizing current between the electrode tool 23 and the bearing material 22 is provided at a portion on the way of extension. On the other hand, to the electrode tool 23, a contact piece 24b extending from the negative electrode (-) of the electrolytic machining pulse power supply 24 is connected. An energizing switch 26 for turning on and off is provided. The output voltage of the electrolytic machining pulse power supply 24 in this embodiment is such that the current density between the electrode tool 23 and the bearing material 22 is 20 A /
The voltage is set to be cm ² .

The value of the current flowing between the electrode tool 23 and the bearing material 22 detected by the ammeter 25 is input to the electric quantity calculating means 27 constituting the machining control means.
The electric quantity calculating means 27 calculates the current density from the value of the current flowing between the electrode tool 23 and the bearing material 22 detected by the ammeter 25 and the area of the electrode tool 23 facing the electrode surface. It has a function of calculating the total amount of electricity for obtaining the target amount of electrolytic processing, that is, the total energization time, from the current density. The calculation method in the electric quantity measuring means 27 will be described later.

The electric quantity calculating means 27 outputs a command signal for setting the total amount of electricity for obtaining the target amount of electrolytic machining, that is, the total energizing time. Energization control means 2 constituting means
8 received. The processing control means 28 is provided with a timer 28a, and the ON / OFF operation of the energizing switch 26 described above is performed according to a command from the timer 28a. Specifically, the turning-off operation of the energizing switch 26 by the timer 28a is performed when the total energizing time set by the electric quantity calculating means 27 has elapsed.

On the other hand, the electrolyte storage tank 30 contains Na
A predetermined amount of electrolyte 31 containing 30% by weight of NO ₃ (sodium nitrate) is stored, and a liquid supply pipe 32 as an electrolyte supply means and a liquid supply pipe 32 are provided between the electrolyte storage tank 30 and the housing 21. The discharge pipe 33 is connected. The liquid supply pipe 32 is connected to the electrolyte storage tank 30 via a pump 34 so as to open into the cavity above the housing 21, that is, into the cavity above the bearing material 22. Tube 33 is
The electrolyte solution 31 that extends from the lower side of the housing 21 in the drawing, that is, the cavity on the lower side of the bearing material 22 toward the electrolyte solution storage tank 30, and is supplied from the solution supply pipe 32 into the housing 21, From the upper side of the bearing material 22, the bearing material 22 and the electrode exposed portion 2 of the electrode tool 23
It is configured to pass through the electrolytic processing portion A between the base material 3a and the lower side of the bearing material 22 and to be recovered from there through the liquid discharge pipe 33 into the electrolytic solution storage tank 30.

As shown in FIG. 2, in the electrolytic solution supply means in this embodiment, a relief valve 3 for adjusting pressure is provided on the inlet side and the outlet side of the electrolytic processing section A.
5 and 36, respectively, and a pressure gauge 37,
38 is attached. And these pressure gauges 37,
Pressure relief valves 35, 36 while monitoring 38
Is appropriately operated, whereby the flow rate of the electrolytic solution 31 in the electrolytic processing part A is set to a predetermined value. In the present embodiment, the flow rate of the electrolytic solution 31 in the electrolytic processing section A is set to be 10 m / sec.

The electrolyte supply means is provided with a flow switching means (not shown) for reversing the flow direction of the electrolyte 31. As the flow switching means, a means capable of reversing the pump 34, a pipe switching means for switching the flow direction between the liquid supply pipe 32 and the liquid discharge pipe 33, and the like are employed. Thus, the electrolytic solution passing through the electrolytic processing section A is reversely flown, and the electrolytic solution passing through the electrolytic processing section A is alternately reversed at an arbitrary time interval.

At this time, the calculation by the electric quantity calculating means 27 is executed based on the relationship data between the current density and the groove machining amount, which are obtained in advance, as shown in FIGS. 3 and 4, for example. It has become. That is, in each figure, the current density (horizontal axis; A / cm ² ) obtained from the value of the energizing current between the electrode tool 23 and the bearing material 22 detected by the ammeter 25 under the device conditions described above, Processing amount per unit time corresponding to the current density (vertical axis: μm / sec)
c) is shown. The processing amount per unit time on the vertical axis is obtained as an average value when 10 μm electrolytic processing is performed for each processing material, and FIG.
FIG. 4 shows the case of copper. That is, as the machining gap gradually increases with the progress of the electrolytic machining, the machining speed changes accordingly. In each of the above-described drawings, a small amount (0.1 mm) is set with respect to the initial machining gap (0.1 mm). 10 μm) is obtained by averaging the processing speed when processing is performed only by 10 μm).

As is clear from these figures, the amount of electrolytic processing changes substantially linearly with respect to a certain range of current density. Therefore, the processing time is fixed within the range having the linear relationship. If the current density is changed by changing the current density, or the current density is fixed and the processing time is changed as in the present embodiment, the processing amount, that is, the processing depth changes in proportion to the current density. In other words, if the current density is managed based on the above data, the desired shape accuracy can be obtained. If the current density is kept constant and the energization time is changed, the processing depth changes. The processing depth) can be controlled in the order of μm or sub-μm by strictly controlling the total amount of electricity required for the groove processing, so that high-precision electrolytic processing can be easily realized.

Next, an embodiment of the electrolytic processing method according to the present invention using the above-described electrolytic processing apparatus will be described. First, the electrode tool 23 is placed in the housing 21 of the above-described electrolytic processing apparatus.
And the bearing material 22 are coaxially fixed to form an electrolytically processed portion A having a predetermined processing gap (about 0.1 mm). Then, the energizing switch 26 is turned on to apply a predetermined pulse voltage to the electrolytic machining section A from the electrolytic machining pulse power supply 24. When such a pulse voltage is used, the accumulation of Joule heat and hydrogen gas generated in the electrolytic processing can be eliminated, and the processing accuracy can be improved.

At this time, the value of the current supplied from the electrolytic machining pulse power supply 24 is constantly detected by the ammeter 25,
The electrode tool 23 and the bearing material 2 detected by the ammeter 25
2 is input to the electric quantity calculating means 27 constituting the machining control means. This electric quantity calculation means 27
Then, the current density is calculated from the value of the energizing current between the electrode tool 23 and the bearing material 22 detected by the ammeter 25, and the relationship between the current density and the amount of groove machining determined in advance from the current density is calculated. Based on the data (see FIGS. 3 and 4), the total amount of electricity required for groove processing, that is, the total energizing time is calculated.

The total energization time is set in a timer 28a provided in the energization control means 28 by the total energization time setting signal output from the electric quantity calculation means 27. After the energization switch 26 is turned on, the energization switch 26 is turned on. It is turned off by a switching signal issued from the timer 28a when the total energization time has elapsed.

In the electrolytic processing method and the electrolytic processing apparatus having such a configuration, since the processing is performed while the electrode tool 23 is fixed without moving, the electrode tool 23 is fixed.
In addition to preventing the decrease in groove machining accuracy due to the feeding error, the relationship between the amount of electrolytic machining of the dynamic pressure groove shape and the total amount of electricity required for the electrolytic machining is substantially linear and proportional, and The amount of groove processing on the object 23 is accurately controlled by controlling the total amount of electricity, and high-precision electrolytic processing of the groove shape is easily performed.

The basic electrolytic machining method and apparatus according to the present invention have been described above. Next, a radial groove for generating dynamic pressure will be described using the electrolytic machining apparatus for radial bearing grooves configured as described above. The gist of the present invention in which the depth of the groove is changed according to the groove position will be described with reference to FIG. In the embodiment shown in FIG. 5, the electrode exposed portions 12 correspond to the groove depth of the radial groove to be processed.
An electrode tool 123 having a different working gap 112 with respect to the bearing material 122 of 3a is used. Electrode exposed portion 123a of electrode tool 123 not covered by non-conductive material 123b
As shown in FIG. 5, a linear portion 123aa along the axial direction, and an inclined portion 123ab connected to the upper and lower ends of the linear portion 123aa at an obtuse angle,
The outer diameter of the linear portion 123aa is larger than the outer diameter of the inclined portion 123ab, and the outer diameter of the inclined portion 123ab gradually decreases from the portion connected to the linear portion 123aa toward the end.

That is, the machining gap 112a between the linear portion 123aa and the bearing material 122 is equal to the inclined portion 123ab.
Narrower than the machining gap 112b between the bearing material 122 and
Working gap 11 between inclined portion 123ab and bearing material 122
2b gradually widens from the continuous portion to the end.

Here, the machining speed in the groove depth direction in the workpiece by electrolytic machining is v, the current efficiency is η, the specific machining volume is Vs, the current density is i, the specific conductivity of the electrolytic solution is κ, and the voltage drop. Is E, and the machining gap between the electrode exposed portion and the workpiece is y, the following relationship exists. v = η · Vs · i = η · Vs · κ · E / y

From the above equation, the processing speed v in the groove depth direction is inversely proportional to the processing gap y between the electrode exposed portion and the workpiece. In other words, if the processing time is constant, the processing amount increases and the groove depth increases as the processing gap y decreases, and the processing amount decreases and the groove depth decreases as the processing gap y increases.

Therefore, when the above-mentioned electrolytic machining is performed by applying the electrode tool 123 to the apparatus shown in FIG. 1, the radial grooves formed on the inner peripheral surface of the bearing material 122 correspond to the linear portions 123aa. The groove depth of the radial groove becomes deeper than the groove depth of the radial groove corresponding to the inclined portion 123ab, and the groove depth of the radial groove corresponding to the inclined portion 123ab goes from the continuous portion to the end. The shape becomes gradually shallower.

That is, the groove depth of the radial groove for generating dynamic pressure can be varied according to the groove position.

In the present embodiment, as shown in FIG. 7, the electrode width W1 of the electrode exposed portion 123a is slightly smaller than the width W2 of the dynamic pressure groove (radial groove) 122a to be processed. (W1 <W2). The reason why such a difference is provided is that in the ideal electrolytic processing, the current density immediately becomes 0 outside the surface to be processed, but actually decreases gradually outward. Because it approaches zero. Therefore, the above-described difference is reduced by reducing the processing gap. Since FIG. 7 shows a thrust bearing, the electrode tool 123 and the bearing material 1
Although 22 is drawn flat, in the radial bearing as in the present embodiment, the electrode tool 123 and the bearing material 122 are actually curved surfaces.

Next, in the electrolytic processing apparatus of the embodiment shown in FIG. 6, a flat thrust bearing material is used as the workpiece 42. That is, as shown in FIG. 6, in a cavity provided in a hollow housing 41 formed of a non-conductive material, a thrust bearing material 42 as a flat workpiece in a substantially horizontal state is provided. Is fixed, and the flat electrode tool 43 is fixed substantially horizontally so as to face the upper side of the thrust bearing material 42, and the electrolytically processed portion B extends in the substantially horizontal direction therebetween. Is formed. In addition, the electrolytic processing part B
The electrolytic solution supplied from the liquid supply pipe 52 opening to the upper right side in the drawing is discharged through the electrolytic processing section B to the outside from the liquid discharge pipe 53.

As shown in FIG. 7, the opposed portion of the flat electrode tool 43 is covered with a non-conductive material 43b except for an electrode exposed portion 43a having a predetermined groove shape, as shown in FIG.
The parallelism between the electrode tool 43 and the thrust bearing material 42 is adjusted so that the groove-shaped bottom wall surface of the electrode exposed portion 43a and the thrust bearing material 42 have a predetermined machining interval over the entire surface. The non-conductive material 43b is formed by coating a predetermined resin material by printing or the like.

The electrode exposed portion 43a is a herringbone type,
It is formed in a shape corresponding to each shape of the spiral type dynamic pressure groove, and the electrode width W1 has the electrode width W1 to be machined as in the case of the radial bearing.
(W1 <W2). Other configurations are the same as those of the embodiment described with reference to FIGS. 1 to 4, and therefore, the corresponding components are denoted by the same reference numerals, and description thereof will be omitted. The same electrolytic processing method as the embodiment described with reference to FIGS. 1 to 4 can be performed, and the same operation and effect can be obtained.

Next, in the electrolytic machining apparatus for machining a thrust bearing groove configured as described above, the point that the groove depth of the thrust groove for generating the dynamic pressure is made different according to the groove position will be described with reference to FIGS. This will be described with reference to FIG. In such a case, the processed thrust groove 142
An electrode tool 143 having a different working gap 150 with respect to the thrust bearing material 142 of the electrode exposed portion 143a is used in accordance with the groove depth a. As shown in FIG. 9, the surface of the electrode tool 143 facing the thrust bearing material 142 is inclined so that the thickness of the electrode tool 143 increases in the circumferential direction from the center of the electrode tool 143. , Except for the electrode exposed portion 143a corresponding to the thrust groove 142a, and is covered with a non-conductive material 143b.

That is, the electrode exposed portion 1 of the electrode tool 143
Working gap 150 between 43a and thrust bearing material 142
Is gradually narrowed in the circumferential direction from the center of the electrode tool 143.

In this embodiment, the electrolytic solution is not flown in one direction in the diameter direction as shown in FIG. The liquid is caused to flow radially (see FIG. 9).

Therefore, when electrolytic processing is performed using the electrolytic processing apparatus for processing a thrust bearing groove configured as described above,
As described above, since the processing speed in the groove depth direction of the workpiece by the electrolytic processing is inversely proportional to the processing gap y between the electrode exposed portion and the workpiece, the processing speed is formed on the opposing surface of the thrust bearing material 142. The thrust groove 142a has a shape in which the groove depth gradually increases from the center of the thrust bearing material 142 toward the outer periphery along the shape of the electrode exposed portion 143a, and gradually increases in the groove in the circumferential direction. Become.

That is, the groove depth of the thrust groove for generating dynamic pressure can be made different depending on the groove position.

FIG. 10 is an enlarged plan view showing another embodiment of the electrode tool used in the apparatus of FIG. 6 in forming the thrust groove of the thrust bearing to an arbitrary groove depth according to the groove position, and FIG. FIG. 11 is a cross-sectional explanatory view showing an enlarged electrode tool and a workpiece when the electrode tool of FIG. 10 is applied to the apparatus of FIG. 6.

Thrust bearing material 1 of this electrode tool 153
The surface opposite to the non-conductive material 153b except for the electrode exposed portion 153a corresponding to the thrust groove 152a
As shown in FIG. 11, the electrode exposed portion 153a is gradually inclined along the shape from the center of the electrode tool 153 toward the outer periphery so that the thickness of the electrode tool 153 increases. Configuration.

That is, the electrode exposed portion 1 of the electrode tool 153
Working gap 160 between 53a and thrust bearing material 152
The electrode tool 153 follows the shape of the electrode exposed portion 153a.
From the center to the outer periphery.

Also in this embodiment, similarly to FIG. 9, the electrolytic solution is poured from the center of the electrode tool 153 into the electrolytic processing portion B to radially flow the electrolytic solution. (See FIG. 11).

Therefore, when the electrolytic machining is performed using the electrolytic machining apparatus for machining the thrust bearing groove configured as described above,
The thrust groove 152a formed on the opposing surface of the thrust bearing material 152 has a groove depth of the electrode exposed portion 153a.
The shape gradually becomes deeper from the center of the thrust bearing material 152 to the outer periphery along the shape of the thrust bearing material 152.

That is, even with this configuration, the groove depth of the thrust groove for generating dynamic pressure can be made different depending on the groove position.

8 to 11, the electrode width W1 of the electrode exposed portion is naturally formed to be slightly smaller than the width W2 of the dynamic pressure groove to be processed in the same manner as described above. It is.

In the above-described electrolytic processing method and apparatus, the processing gap is set to about 0.1 mm. However, when the processing gap is narrowed, the shape transfer accuracy of the electrode exposed portion is improved, and the current density is also reduced. The processing speed tends to increase, and the processing efficiency tends to improve. However, on the other hand, the flow rate of the electrolytic solution is reduced due to the gap resistance, and as a result, there arise problems such as an increase in the temperature of the electrolytic solution and a failure to remove hydrogen bubbles generated from the electrode surface satisfactorily. . That is, the processing gap described above may be determined in consideration of the pump performance, the required roughness of the processing surface, the shape transfer accuracy, the processing speed, and the like.

When the bearing length is increased, there may be a difference in the processing amount, that is, the groove depth, between the bearing processing portion on the upstream side and the bearing processing portion on the downstream side of the flow of the electrolyte. .
This is because the conductivity of the electrolyte increases as the temperature of the electrolyte goes downstream, and the thickness of the layer in which the hydrogen bubbles are mixed increases as the downstream side, and the volume of the bubbles increases with the liquid temperature, This is because the conductivity is thereby reduced. Therefore, in order to obtain a uniform groove depth on the upstream side and the downstream side of the electrolytic solution, it is necessary to process the two conductivity changes under conditions that cancel each other out.

In order to offset the above two changes in conductivity, the groove depth can be made uniform by alternately flowing the electrolytic solution through the electrolytic processing portion by the flow switching means. For example, if the processing time is 1.4 seconds, flowing the electrolytic solution from one side for the first 0.7 seconds, and flowing the opposite side for the remaining 0.7 seconds, the processing conditions in the flow direction of the electrolytic solution are reduced. As a result, a good processing state can be obtained.

It is also possible to count the number of output pulses from the pulse power source for electrolytic machining, and to turn on / off the energizing switch based on the total number of pulses. Further, the present invention can be similarly applied to the electrolytic processing for the above-described stainless steel (SUS) material and metal materials other than copper.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and may be variously modified without departing from the gist thereof. Needless to say. For example,
In the above-described embodiment, a pulse power supply is used to vary the groove depth of the dynamic pressure groove according to the groove position. However, a DC power supply may be used. Further, the bearing material is not limited to a normal bearing that supports the rotating shaft, and may be a fixed shaft that rotatably supports the rotating body.

For example, a groove having a substantially hemispherical shape as described in Japanese Patent Publication No. 56-53661 or an opposite surface may be formed by using an electrode tool having an electrode exposed portion having a different machining gap. Dynamic pressure grooves (having radial and thrust functions) having different depths can be formed, and the present invention can be similarly applied to all kinds of shape processing.

Furthermore, in the above embodiment, the processing gap between the electrode exposed portion and the workpiece is continuously changed, but may be changed in steps.

[0060]

As described above, in the electrolytic processing method and the electrolytic processing apparatus according to the present invention, the processing speed in the groove depth direction of the workpiece by the electrolytic processing is such that the processing between the electrode exposed portion and the workpiece is performed. Based on the characteristic that it is inversely proportional to the gap, the machining gap is made narrower for the part where the groove depth is made deeper corresponding to the groove depth of the dynamic pressure groove to be machined, and for the part where the groove depth is made shallower The width of the groove should be wide, electrolytic processing should be performed, and the depth of the groove should be deep at the narrow part of the processing gap and shallow at the part of the wide processing gap. Since it is configured so that electrolytic processing of
Compared with the cutting method that requires dimensional control, it is not necessary to make the equipment expensive, so it is possible to reduce the cost, improve the productivity by simultaneously forming many grooves and improve the productivity, and compared to the coining and rolling method. Even if the shape of the dynamic pressure groove is complex or fine, there is no tool wear and the tool life can be made semi-permanent, cost reduction can be achieved, and there is no need to remove burrs or follow-up process. A dynamic pressure groove having an arbitrary groove depth can be obtained with high precision according to the groove position without occurrence.

[Brief description of the drawings]

FIG. 1 is a principle explanatory view showing an electrolytic processing apparatus according to an embodiment of the present invention.

FIG. 2 is a system explanatory diagram showing a circulation system of an electrolytic solution used in the apparatus of FIG.

FIG. 3 is a diagram illustrating a case of SUS304 of relation data between a current density and a processing amount obtained in advance.

FIG. 4 is a diagram showing the relationship data between the current density and the processing amount obtained in advance for copper.

FIG. 5 shows an electrode tool used for forming a dynamic pressure groove of a radial bearing to an arbitrary groove depth according to the groove position.
It is an enlarged side explanatory view of an electrode tool and a workpiece when applied to the apparatus of FIG.

FIG. 6 is a principle explanatory view showing an electrolytic processing apparatus according to another embodiment of the present invention.

FIG. 7 is an explanatory side view showing a relationship between a width of an electrode exposed portion and a width of a dynamic pressure groove.

8 is an enlarged plan explanatory view showing an embodiment of an electrode tool used in the apparatus of FIG. 6 in forming a dynamic pressure groove of a thrust bearing to an arbitrary groove depth according to a groove position.

9 is an explanatory cross-sectional view showing an enlarged electrode tool and a workpiece when the electrode tool of FIG. 8 is applied to the apparatus of FIG. 6;

10 is an enlarged plan view showing another embodiment of the electrode tool used in the apparatus of FIG. 6 in forming the dynamic pressure groove of the thrust bearing to an arbitrary groove depth according to the groove position.

11 is an explanatory cross-sectional view showing an enlarged electrode tool and a workpiece when the electrode tool of FIG. 10 is applied to the apparatus of FIG. 6;

FIG. 12 shows an HD with a bearing formed according to the invention.
FIG. 3 is a half sectional explanatory view showing an example of a D motor.

[Explanation of symbols]

112 (112a, 112b), 150, 160 Working gap 122, 142, 152 Workpiece 122a, 142a, 152a Dynamic pressure groove 123, 143, 153 Electrode tool 123a (123aa, 123ab), 143a, 15
3a Electrode exposed part

Claims (5)

[Claims] An electrolytic machining of a dynamic pressure groove in a dynamic pressure bearing in which a dynamic pressure groove for generating a dynamic pressure for bearing support in a bearing fluid is formed into a predetermined groove shape by electrolytic machining on a dynamic pressure surface of the dynamic pressure bearing. In the method, a workpiece on which the dynamic pressure groove is electrolytically machined, and an electrode tool having a groove-shaped electrode exposed portion corresponding to the dynamic pressure groove to be machined on the workpiece are brought close to each other, and The gap between the electrode exposed portion and the workpiece is set so that the groove depth is set to correspond to the groove depth of the dynamic pressure groove to be machined. The deeply formed portion is narrowed, these workpieces and the electrode tool are connected to the positive electrode and the negative electrode of the power source for electrolytic machining, respectively, and a current is supplied while flowing a predetermined electrolyte between the electrode tool and the workpiece. The workpiece is eluted according to the groove shape An electrolytic machining method for a dynamic pressure groove in a dynamic bearing in which the pressure groove is electrolytically processed. 2. The method according to claim 1, wherein one of the electrode tool and the workpiece is formed of a hollow cylindrical body, and the other is formed of a cylindrical body coaxially insertable into the hollow of the hollow cylindrical body. A method for electrolytically machining a dynamic pressure groove in a dynamic pressure bearing, wherein a dynamic pressure groove for a radial bearing is formed on an inner peripheral surface of a hollow cylindrical body or an outer peripheral surface of a cylindrical body constituting a workpiece. . 3. An electrode tool and a workpiece according to claim 1, wherein the electrode tool and the workpiece have opposing surfaces, and a dynamic pressure groove for a thrust bearing is formed on the opposing surface of the workpiece. A method for electrolytically machining a dynamic pressure groove in a dynamic pressure bearing. 4. The electrode tool and the workpiece according to claim 1 have curved surfaces facing each other, and a dynamic pressure groove for a radial bearing and a thrust bearing is formed on the curved surface of the workpiece. An electrolytic machining method for a dynamic pressure groove in a dynamic pressure bearing. 5. A hydrodynamic bearing in which a hydrodynamic groove for generating a hydrodynamic pressure for bearing in a bearing fluid is formed into a predetermined groove shape by electrolytic machining on a hydrodynamic surface of the hydrodynamic bearing. A groove electrolytic processing apparatus, comprising: a power supply for electrolytic processing; a workpiece on which the dynamic pressure groove is electrolytically processed; and a groove-shaped electrode exposed portion corresponding to the dynamic pressure groove. An electrode tool fixed in a relatively immovable state so as to be opposed to each other with a processing gap, and an electrolyte supply means for flowing a predetermined electrolyte between the electrode tool and the workpiece. The workpiece and the electrode tool are connected to the positive electrode and the negative electrode of the power supply for electrolytic machining, respectively, and the workpiece is made to correspond to the groove shape by applying an electric current while flowing the electrolyte between the electrode tool and the workpiece. And elute to form the dynamic pressure groove by electrolytic processing A shall, said electrode exposed portion, the machining gap with respect to the workpiece,
An electrolytic machining apparatus for a dynamic pressure groove in a dynamic pressure bearing, wherein a portion in which the groove depth is formed to be deeper corresponding to the groove depth of the dynamic pressure groove to be processed is configured to be narrower.