• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to an electrode for the electrochemical machining of a metallic workpiece with an electrode body (48) consisting of an electrode core (50) of an electrically conductive material, the surface of the electrode core (50) having a plurality of elevations (50a, 50a ') and countersinks (50b ), wherein the counterbores (50b) are filled to the upper edge of the elevations with an electrically insulating material (52), so that the electrode body has a smooth surface (54) with electrically conductive regions of the electrically conductive material and electrically insulating regions of the comprising electrically insulating material, characterized in that at least two of the plurality of projections (50a, 50a ') of the electrode core (50) have a different cross-sectional area and / or a different height measured from the bottom surface of the adjacent counterbores (50b).
    公开号:AT518722A1
    申请号:T50477/2016
    申请日:2016-05-25
    公开日:2017-12-15
    发明作者:Martin Bauer Dr
    申请人:Minebea Co Ltd；
    IPC主号:
    专利说明:

    Electrode for the electrochemical machining of a metallic workpiece
    Field of the invention:
    The invention relates to an electrode for the electrochemical machining of a metallic workpiece, for example an electrode for the electrochemical machining of bearing components of a fluid dynamic bearing. In particular, the invention relates to an electrode according to the features of the preamble of claim 1.
    Description of the Related Art
    Electrochemical machining (ECM) electrodes of metallic workpieces are used in manufacturing technology, inter alia for introducing bearing structures in surfaces of fluid dynamic bearings. Fluid dynamic bearings are used for example for the rotational mounting of spindle motors. To build up a hydrodynamic pressure in the bearing gap, the bearing surfaces are provided with groove structures. As a result of a rotational relative movement of the two bearing components, these groove structures generate a pumping action on the bearing fluid and thus a pressure in the bearing gap.
    In the case of the electrochemical removal method, material is removed from the workpiece by anodic dissolution of the electrically conductive material of the workpiece. For this purpose, a circuit between the anode (workpiece) and the cathode (electrode) via an electrolyte solution, for example, a saline solution or sodium nitrate solution (NaNO3), closed. In the electrochemical removal method, a DC voltage between about 10 to 60 volts or preferably a pulse voltage between about 5 to 20 volts is used, the intensity of material removal via the current density and the time during which the closed circuit acts on the site to be processed, is controlled.
    The geometry of the electrodes used is adapted to the geometry of the workpieces to be machined and to the processing task to be solved and the desired final contour of the tool. For introducing bearing groove structures in the surface of a bearing bore of a fluid dynamic bearing, for example, a rod-shaped cylindrical electrode can be used, which is inserted into the bearing bore. The diameter of the electrode is slightly smaller than the diameter of the bearing bore, leaving an annular gap between the electrode and the surface of the bore into which the electrolyte is filled. The smaller the width of the gap, i. the distance between the electrode and the surface of the bore is, the greater the effective current density and consequently the material removal.
    Such an electrode for electrochemical machining of a metallic workpiece comprises an electrode body of an electrically conductive material, wherein the surface of the electrode core has a plurality of elevations and depressions, and the reductions are filled up to the upper edge of the elevations with an electrically insulating material, so that the electrode body a smooth surface having both electrically conductive regions of the electrically conductive material and electrically insulating regions of the electrically insulating material. The material removal in the electrochemical removal process takes place on the workpiece only in the areas which are opposite to the electrically conductive regions of the electrode. In the fabrication of fluid dynamic bearing groove structures, it is sometimes desirable to provide different width groove structures. This can be achieved by adapting the width of the conductive regions on the electrode to the desired width of the groove structures in the workpiece.
    The depth of the groove structures can be controlled by the distance between the electrode and the workpiece as well as the time of the applied current and its voltage. It is preferred to achieve an optimum current density in order to achieve a constant cross section of the groove structures.
    Particular difficulties in the preparation prepares the simultaneous production of several Lagerrillenstrukturen, each having a different individual depth or of individual Lagerrillenstrukturen whose depth varies over the length of the groove. Such structures are very difficult to produce.
    AT 5150351 A1 discloses an electrode for the electrochemical machining of a metallic workpiece with an electrode body comprising electrically-suffering regions and electrically insulating regions, wherein the electrode is shaped such that the width of the working gap varies between the electrode and the workpiece. Thus, it is possible to produce different deep groove structures on the surface of the workpiece in a single operation, as varied by the variable distance between the electrode and the workpiece current density. If the working gap becomes too large, unclean groove contours and undesired connections of closely spaced groove structures can occur.
    Disclosure of the invention
    It is the object of the invention to specify an electrode for the electrochemical machining of metallic workpieces, with which structures of different depths can be produced in one machining pass. In this case, a constant accuracy of the contours is to be maintained at the different depth structures.
    This object is achieved by an electrode having the features specified in claim 1.
    Advantageous embodiments of the invention and further preferred features are disclosed in the dependent claims.
    The electrode according to the invention is characterized in that at least two of the plurality of elevations of the electrode core have a different cross-sectional area and / or a different height, measured from the bottom surface of the adjacent depressions.
    Alternatively or additionally, it may be provided that the cross-sectional area and / or the height of a survey varies in the course of the survey.
    According to the invention, the depth of the groove structures produced by this electrode is controlled by the current density which determines the rate of material removal at the workpiece. By shaping the cross-sectional area of the elevations of the electrode core and / or by the height of the elevations measured from the bottom surface of the adjacent depressions, the electrical resistance of the individual elevations can be determined or adjusted and thus also the relative current density of the electrically conductive regions formed by the elevations the electrode.
    The electrode itself has a smooth surface, and it is particularly provided that the distance between the electrode and the surfaces of the workpiece to be machined, i. the working gap, preferably the same everywhere. The material removal rate on the workpiece is determined according to the invention only by the cross-sectional areas of the elevations and / or their height, which in turn determine the electrical conductivity of the electrically conductive regions of the electrode formed by the elevations.
    According to the invention, the cross-sectional areas of the elevations are in particular of different sizes. It is also possible for the height and / or width of the cross-sectional areas of the elevations to be of different sizes. The cross-sectional areas of the elevations may be the same or different
    Have shape and, for example, in cross-section rectangular, trapezoidal or stepped or terraced.
    For locally increasing the achievable current density at the surface of the elevations, it may be provided that the width of the cross-sectional area of the elevations in the region of the bottom surface of the adjacent depressions is greater than the width in the region of the surface of the electrode. As a result, the electrical resistance of the surveys is kept as low as possible.
    On the other hand, a reduction in the local current density at the surface of the elevations can be achieved in that the width of the cross-sectional area of the elevations in the area of the bottom surface of the adjacent depressions is smaller than the width in the area of the surface of the electrode. This increases the relative electrical resistance of the elevations.
    Preferably, the elevations are in the form of elongated ribs and the counterbores are in the form of grooves. However, the invention is not limited to this shape. Other shapes such as circular structures, polygonal structures, rectangular structures, or undulating structures may also be provided.
    In particular, the invention also relates to a tool for machining bearing surfaces of a fluid-dynamic bearing, which is characterized by an electrode having the features described above.
    The invention further relates to a method for applying different deep groove structures on the bearing surface of a fluid dynamic bearing, wherein an electrode is used with the features described above.
    Brief description of the drawings
    Fig. 1 shows a section through a spindle motor with fluid dynamic bearing system and Lagerrillenstrukturen.
    Fig. 2 shows a section through the surface of an ECM electrode according to a first embodiment of the invention.
    Fig. 3 shows a section through the surface of an ECM electrode according to a second embodiment of the invention.
    Fig. 4 shows a section through the surface of an ECM electrode according to a third embodiment of the invention.
    Fig. 5 shows a section through the surface of an ECM electrode according to a fourth embodiment of the invention.
    Fig. 6 shows a section through the surface of an ECM electrode according to a fifth embodiment of the invention.
    DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
    Fig. 1 shows a section through a spindle motor with a fluid dynamic bearing system. The spindle motor comprises a fixed base plate 10 with a cylindrical opening in which a bearing bushing 12 is mounted. The bearing bush 12 has an axial, cylindrical bearing bore, in which a shaft 14 is rotatably received. Between the inner diameter of the bearing bore and the slightly smaller outer diameter of the shaft 14, an axially extending portion 18a of a bearing gap 18 is formed, which is filled with a bearing fluid, such as a lubricating oil. Corresponding bearing surfaces on the wall of the bearing bore of the bearing bush 12 together with associated bearing surfaces of the shaft 12, two fluid dynamic radial bearings 24, 26 which are characterized by corresponding radial bearing grooves 24a, 26a. The radial bearing grooves 24 a, 26 a are arranged on the surface of the bearing bore and / or the surface of the shaft 14. The radial bearing grooves 24a, 26a are preferably introduced into the surface of the bearing bush 12 or the surface of the shaft 14 by an electrochemical removal process.
    When the shaft 14 is rotated in the bearing sleeve 12, the radial bearing grooves 24a, 26a exert a pumping action on the bearing fluid located in the axially extending portion 18a of the bearing gap 18. In this way arises in the bearing gap 18, a hydrodynamic pressure, which makes the radial bearings 24, 26 sustainable. As long as the shaft 14 rotates in the bearing bore, this is stabilized by the fluid dynamic pressure generated by the radial bearing grooves 24a, 26a and runs without contact in the bearing bore, separated by the bearing gap 18. The two radial bearings 24, 26 are through an area with increased bearing gap width , the so-called Separatorspalt 28, axially separated from each other.
    The radial bearing groove structures 24a of the upper radial bearing 24 are preferably sinusoidal and asymmetrical with respect to an apex line extending in the circumferential direction of the shaft 14 and the bearing bore. As a result, the radial bearing grooves 24a do not generate a uniform pumping action in both directions of the axial portion 18a of the bearing gap 18, but a directional pumping action directed predominantly downward toward the second radial bearing 26. The second radial bearing 26 includes radial bearing groove structures 26 a that are symmetrical to the apex line, for example, so that the second radial bearing 26 generates a uniform pumping action on the bearing fluid in both directions of the axial portion 18 a of the bearing gap 18.
    Due to the downward pumping action of the upper radial bearing 24, a flow direction of the bearing fluid in the bearing gap 18 is given downward in the direction of the pressure plate 20.
    The pressure plate 20 is arranged at one end of the shaft 14 and pressed onto the shaft 14 or alternatively formed in one piece with the shaft 14. Opposite the pressure plate 20, the bearing bush 12 is closed by a cover plate 22. Both the pressure plate 20 and the cover plate 22 are received in corresponding recesses of the bearing bush 12 concentric with the bearing bore. The upper end face of the pressure plate 20 forms, together with an opposite surface of the bearing bush 12, a first thrust bearing 30. The lower end face of the pressure plate 20 forms, together with an opposite surface of the cover plate 22, a second thrust bearing 32. The thrust bearings 30, 32 comprise axial bearing grooves 30a, 32a (not shown), which are arranged on the bearing surfaces of the pressure plate 20 and / or the bearing bush 12 or the pressure plate 20 and / or the cover plate 22. The Axiallagerrillen 30a, 32a are formed, for example, spiral-shaped or herringbone.
    When the pressure plate 20 is rotated together with the shaft 14, the thrust bearing grooves 30 a of the first thrust bearing 30 exert a pumping action on the bearing fluid located in a first radial portion 18 b of the bearing gap 18. In the radial section 18b of the bearing gap 18, a hydrodynamic pressure builds up, so that the axial bearing 30 becomes load-bearing. At the same time, the thrust bearing grooves 32a of the second thrust bearing 32 exert a pumping action on the bearing fluid located in a second radial portion 18c of the bearing gap 18. In the radial section 18c of the bearing gap 18, a hydrodynamic pressure builds up, so that the axial bearing 32 becomes load-bearing. The two thrust bearings 30, 32 act against each other insofar as that the bearing forces generated by the thrust bearings 30, 32 are axially directed against each other, so that the pressure plate 20 is positioned substantially axially in the center of the recess provided in the bearing bush 12 and the bearing fluid to the pressure plate 20 can flow around.
    The thrust bearing grooves 30a, 32a of the first and second thrust bearings 30, 32 are preferably likewise introduced into the bearing surfaces of the thrust bearings 30, 32 by means of an electrochemical removal method.
    Above the first radial bearing 24, the open end of the bearing gap 18 is sealed by a seal, for example a capillary sealing gap 34. The seal gap 34 is formed by an outer peripheral surface of the shaft 14 and an inner peripheral surface of the bearing bush 12. The inner peripheral surface of the bearing bush 12 is preferably bevelled so that the seal gap 34 has a substantially conical cross section. The sealing gap 34 is directly connected to the bearing gap 18 and proportionately filled with bearing fluid.
    The free end of the shaft 14 is connected to a hub 16. The hub 16 is formed according to the purpose of the spindle motor and in the present
    Example made of aluminum. If the spindle motor is intended to drive a hard disk drive, one or more storage disks (not shown) of the hard disk drive are placed and secured on the hub 16.
    At an inner, lower edge of the hub 16, an annular rotor magnet 40 is arranged with a plurality of permanent magnetic pole pairs. The rotor magnet 40 abuts against a return ring 38. This return ring can be optionally omitted if the hub is made of ferromagnetic steel. Radially opposite the rotor magnet 40, a stator assembly 36 is fixed to the base plate 10 which is separated from the rotor magnet 40 by a radial air gap. The stator assembly 36 has corresponding stator windings which, when energized, generate an electromagnetic alternating field such that the rotor, consisting of the hub 16, shaft 14 and rotor magnet 40, is rotated.
    2 shows a section through a part of the electrode body 48 of an electrode for the electrochemical machining of a workpiece, wherein the electrode body 48 comprises an electrode core 50, which consists of electrically good conductive material. For example, the electrode body 48 is cylindrical, as is known in the art. For the production of axial bearing structures, electrodes with a circular or annular electrode body are also used, which are likewise encompassed by the invention.
    In the electrode core 50, a series of protrusions 50a and recesses 50b are incorporated, wherein the recesses 50b are filled with an electrically insulating material 52. The electrically insulating material 52 extends to the surface of the elevations 50a, so that a smooth surface 54 of the electrode body 48 results. The surface 54 of the electrode body 48 has electrically conductive regions of the electrically conductive material of the elevations 50a and electrically insulating regions of the electrically insulating material 52.
    In the embodiment according to FIG. 2, the elevations 50a, 50a 'have different heights or the depressions 50b have different depths, while the width b of the upper surface of the elevations 50a, 50a' on the surface 54 of the electrode is the same. Due to the different fleas of the elevations 50a, 50a ', these have a different electrical resistance. The higher the bumps 50a, 50a 'are, the greater the electrical resistance between the foot and the top of the bumps 50a. If an electric current is applied to the electrode, then different current densities result on the upper side of the elevations 50a, 50a 'due to the different resistance of the elevations 50a, 50a', so that groove depths of different depths are produced in the workpiece to be machined.
    Fig. 3 shows another embodiment of an electrode according to the invention with an electrode core 50 having corresponding projections 50a and intermediate depressions 50b. These reductions 50b are filled with an electrically insulating material 52. While a part of the elevations 50a is approximately rectangular in cross-section, another part of the elevations 50a 'is configured in cross-section such that, starting from the electrode core 50, initially a narrow section extends upwards, which then extends in the direction of the surface 54 of the electrode widened in cross section.
    Thus, the cross section of the elevations 50a 'changes and, starting from the electrode core 50, increases up to the surface 54 of the electrode body 48. The width b of the elevations on the electrode surface 54 is the same. Due to the initially narrowing and then widening cross-section, the elevations 50a 'have a greater electrical resistance than the elevations 50a, so that on the surface of the electrode 54, the current density in the region of the elevations 50a' is smaller than in the region of the elevations 50a.
    FIG. 4 shows a further embodiment of an electrode according to the invention in which protrusions 50a are formed, which are rectangular in cross-section, while further protrusions 50a 'are formed which are trapezoidal in cross-section, wherein the bottom surface of the Trapezes smaller than the area at the top 54 of the electrode body 48. Thus, different widths bi, b2 of the electrically conductive regions on the surface 54 of the electrode body 48, wherein the rectangular cross-section projections 50a have a smaller width bi, while the Cross-section trapezoidal elevations 50a 'have a greater width b2. During the electrochemical removal process, such an electrode results in a lower current density than in the region of rectangular elevations 50a due to the trapezoidal cross section of the elevations 50a 'and their greater width b2 on the surface of the electrode 54.
    5 shows an embodiment of an electrode according to the invention, in which the elevations 50a are approximately rectangular in cross section, while the elevations 50a 'have a step, so that their cross section decreases in the direction of the surface 54 of the electrode body 48. The elevations 50a have a width bi on the surface 54 of the electrode body 48, while the elevations 50a 'on the surface 54 of the electrode have a smaller width b3. If a circuit is closed via the electrode, a lower current density results on the surface 54 of the electrode body 48 in the region of the elevations 50a having a width bi which are rectangular in cross-section than in the region of the elevations 50a 'which are stepped in cross-section and which only surface on the surface 54 have a width b3.
    Finally, FIG. 6 shows an embodiment of an electrode according to the invention with elevations 50a having a width b in cross-section and drop-shaped or stepped pyramidal elevations 50a 'in cross-section. The elevations 50a and 50a 'are designed, for example, such that they have the same width b on the surface 54 of the electrode body 48. Due to the increased cross-section of the elevations 50a 'starting from the electrode core 50, a larger current density occurs in the region of the elevations 50a' during operation of the electrode than in the area of the elevations 50a.
    By varying the length and / or the cross section of the elevations 50a, 50a according to the invention, which form the electrically conductive regions on the surface 54 of the electrode body 48, the relative current density can be arbitrarily adjusted on the surface 54 of the electrode body 48, and it is possible to Create a single operation groove structures of different depths on the workpiece to be machined. The width of the working gap filled with the electrolyte between the surface 54 of the electrode body 48 and the workpiece does not have to be changed for this purpose. According to the invention, it is possible, for example, to produce a plurality of groove structures with different depths in one operation. But it is also possible, the elevations 50a, 50a 'form such that the depth varies within a single groove structure.
    List of Reference Numerals 10 Base plate 12 Bearing bushing 14 Shaft 16 Hub 18 Bearing gap 18a Axial bearing 32a Axial bearing grooves 18a Axial bearing grooves 32A Axial bearing grooves 18A Axial bearing grooves 32A Axial bearing grooves 34 sealing gap 36 stator arrangement 38 return ring 40 rotor magnet 42 rotation axis 48 electrode body 50 electrode core 50a elevations 50b counterbores 52 electrically insulating material 54 surface of the electrode body
    权利要求:
    Claims (9)
    [1]
    claims
    1. Electrode for electrochemical machining of a metallic workpiece with an electrode body (48) consisting of an electrode core (50) of an electrically conductive material, the surface of the electrode core (50) having a plurality of elevations (50a, 50a ') and countersinks (50b) wherein the depressions (50b) are filled to the upper edge of the elevations with an electrically insulating material (52), so that the electrode body has a smooth surface (54) with electrically conductive regions of the electrically conductive material and electrically insulating regions of the electrically characterized in that at least two of the plurality of projections (50a, 50a ') of the electrode core (50) have a different cross-sectional area and / or a different height measured from the bottom surface of the adjacent countersinks (50b), and / or Cross-sectional area and / or height of a survey (50, 50a ') in the course d he survey varies.
    [2]
    2. An electrode according to claim 1, characterized in that the cross-sectional areas of the elevations (50a, 50a ') are different in size.
    [3]
    3. Electrode according to one of claims 1 or 2, characterized in that the height and / or width of the cross-sectional areas of the elevations (50a, 50a ') is different in size.
    [4]
    4. Electrode according to one of claims 1 to 3, characterized in that the cross-sectional areas of the elevations (50a, 50a ') have the same or a different shape and are optionally rectangular, trapezoidal or stepped.
    [5]
    5. Electrode according to one of claims 1 to 4, characterized in that the width of the cross-sectional area of the elevations (50a, 50a ') in the region of the bottom surface of the adjacent depressions (50b) is greater than the width in the region of the surface (54) of Electrode body (48).
    [6]
    6. Electrode according to one of claims 1 to 4, characterized in that the width of the cross-sectional area of the elevations (50a, 50a ') in the region of the bottom surface of the adjacent depressions (50b) is smaller than the width in the region of the surface (54) of Electrode body (48).
    [7]
    7. Electrode according to one of claims 1 to 6, characterized in that the elevations (50a, 50a ') in the form of elongated ribs and the counterbores (50b) are in the form of grooves.
    [8]
    8. Tool for machining bearing surfaces of a fluid dynamic bearing, characterized by an electrode according to one of claims 1 to 7.
    [9]
    9. A method for applying different deep groove structures on the bearing surfaces of a fluid dynamic bearing, characterized by the use of an electrode according to one of claims 1 to 7.
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    同族专利:
    公开号 | 公开日
    AT518722B1|2020-10-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    JPH10180545A|1996-12-24|1998-07-07|Sankyo Seiki Mfg Co Ltd|Electrochemical machining method and device for dynamic pressure groove in dynamic pressure bearing|
    JPH10220460A|1997-02-04|1998-08-21|Sankyo Seiki Mfg Co Ltd|Method and device for electro-chemical machining of dynamic pressure groove in dynamic pressure bearing|
    US6693036B1|1999-09-07|2004-02-17|Sony Corporation|Method for producing semiconductor device polishing apparatus, and polishing method|
    US20050121328A1|2002-01-31|2005-06-09|Mitsuhiko Shirakashi|Electrolytic processing apparatus and method|
    US20090134036A1|2005-09-02|2009-05-28|Ebara Corporation|Electrolytic Processing Method and Electrolytic Processing Apparatus|CN111136352A|2019-12-31|2020-05-12|安徽工业大学|Flexible plate strip type electrochemical machining tool cathode and machining method thereof|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    ATA50477/2016A|AT518722B1|2016-05-25|2016-05-25|Electrode for the electrochemical processing of a metallic workpiece|ATA50477/2016A| AT518722B1|2016-05-25|2016-05-25|Electrode for the electrochemical processing of a metallic workpiece|
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