JP2005095998A - Method of manufacturing parts for dynamic bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture parts for a dynamic bearing with remarkable durability at a low cost while ensuring miniaturization and high performance. <P>SOLUTION: This method of manufacturing the parts for the dynamic bearing has a machining process for machining a dynamic bearing part material into predetermined shape, and a surface treating process for forming the surface of the dynamic bearing part material machined into the predetermined shape in the machining process, into a predetermined surface state. The surface treating process has magnetic barrel polishing treatment wherein a fluid 300, magnetic media 400 serving as polishing media, and the dynamic bearing parts 33 which are polished bodies, are put in a container 100, and the magnetic media 400 are moved by the external moving magnetic field with magnets 201 fixed to a turntable 200, to polish the polished bodies. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a dynamic pressure bearing component in which a concave / convex pattern for generating dynamic pressure is formed on a surface portion, for example, a hard disk drive (HDD), a digital versatile tile, In addition to disk rotating storage devices such as disk (DVD) drive devices, it is used for the manufacture of dynamic pressure bearing components that make up the dynamic pressure generating part of dynamic pressure bearing devices used as bearings for rotating parts such as polygon mirrors. it can.

  In general, a hydrodynamic bearing device applies dynamic pressure to hydraulic oil filled in a gap between a rotating portion including a rotating shaft and a fixed portion using the rotational force of the rotating shaft, and the rotating portion is fixed by the dynamic pressure. The rotating shaft is supported rotatably by setting it in a state of floating with respect to the part. The dynamic pressure bearing device includes a dynamic pressure generating bearing member having a concavo-convex pattern formed on a surface portion to generate a dynamic pressure by causing a predetermined physical force to act on the hydraulic oil as it rotates, and the dynamic pressure A dynamic pressure shaft receiving component having a dynamic pressure bearing member as a counterpart component that is disposed to face the generating bearing member to form a bearing gap is used.

  By the way, for example, in a hydrodynamic bearing device in a small motor such as a spindle motor for HDD, the rotating portion is fixed to the rotating portion when the rotating portion is levitated and supported with respect to the fixed portion by the dynamic pressure generated with the rotation of the rotating shaft. The width dimension of the gap formed with the part is set to a very small gap of about 2 to 3 μm ± 0.5 μm in consideration of the facing area, load capacity, fluid viscosity, etc. It is common. Further, the height of the uneven pattern formed on the surface portion of the dynamic pressure generating bearing member used in the dynamic pressure bearing device used in this case is also set to about 5 to 20 μm.

  Therefore, a very high machining accuracy is required for the production of a dynamic pressure bearing part having a dynamic pressure generating bearing member and a dynamic pressure bearing member as a counterpart part. For this reason, for example, the manufacture of a dynamic pressure generating bearing member is performed by applying a so-called photolithography method or the like to a predetermined surface portion of a dynamic pressure bearing component material processed into a predetermined shape by a lathe or the like. A pattern is formed, and then the surface portion on which the uneven pattern is formed is subjected to precision polishing using abrasive grains to finish the flatness and surface roughness of the surface portion extremely precisely. . In addition, the dynamic pressure bearing member, which is a counterpart member of this dynamic pressure bearing component, is processed into a shape that forms a predetermined bearing gap when it is disposed opposite to the dynamic pressure generating bearing member, and then is similarly formed on the surface portion. Precision polishing using abrasive grains is performed to finish the flatness and surface roughness of the surface portion extremely precisely.

  By the way, as HDDs are improved and newly developed, various stricter demands have been made for spindle motor bearing devices for HDDs. That is, for example, there is a request for downsizing due to downsizing of a hard disk, a request for further durability improvement, a request for cost reduction and productivity improvement, and the like. The hydrodynamic bearing device is considered to be very advantageous in principle compared with other types of bearing devices such as a conventional ball bearing type in response to these requests. It has been found that there are cases where it is not always sufficient.

  That is, the HDD reads and writes information by flying the magnetic head over the hard disk, and the operation is mainly performed by a so-called CSS (contact start / stop) system. Since this CSS system always repeats the rotation / stop operation of the hard disk, the spindle motor bearing device is also required to have sufficient durability against the repeated rotation / stop operation.

  Although the conventional hydrodynamic bearing device using the conventional hydrodynamic bearing component has a certain durability (repeated durability of about 400,000 times), it may be difficult to obtain a higher durability. It turns out. In addition, it has been found that, after a considerable endurance test, the shaft may come into close contact with the bearing and fail to start after a considerable durability test.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a dynamic pressure bearing part that makes it possible to manufacture a dynamic pressure bearing part having remarkable durability while ensuring small size and high performance at low cost.

As means for solving the above-mentioned problem, the first means is:
A method for producing a hydrodynamic bearing part for producing a hydrodynamic bearing part, comprising:
A processing step of processing a fluid pressure bearing component material into a predetermined shape;
A surface treatment step of bringing the surface of the dynamic pressure bearing component material processed into a predetermined shape in the processing step into a predetermined surface state,
In the surface treatment step, a magnetic barrel polishing process is performed in which a fluid, a magnetic medium as a polishing medium, and an object to be polished are placed in a container, and the object to be polished is polished by moving the magnetic medium by an external kinetic magnetic field. It is a manufacturing method of the components for dynamic pressure bearings characterized by having.
The second means is
In the method of manufacturing a hydrodynamic bearing component according to the first means, the polishing step is performed by performing the magnetic barrel polishing process after performing precise polishing using abrasive grains. This is a manufacturing method for parts.
The third means is
In the method of manufacturing a hydrodynamic bearing component according to the first or second means, the magnetic medium used for the magnetic barrel polishing is a magnetic stainless steel wire having a predetermined length. This is a method for manufacturing a bearing component.

  In the above-mentioned means, the magnetic barrel polishing process is performed in the polishing process, so that it has a remarkable durability, the shaft does not come into close contact with the bearing at the time of CSS, and the manufacturing is extremely easy. It turned out that the effect of being is obtained. It is the first time that the inventor of the present application has tried to perform various surface treatments by trial and error to obtain the above-mentioned effects by performing magnetic barrel polishing.

  The mechanism by which such effects are obtained has not been clarified theoretically, but is presumed to be due to the following reason. In other words, the conventional method of precision polishing using abrasive grains and the like to precisely finish the flatness and surface roughness of the surface part numerically makes the flatness and surface roughness very high. Can do. Therefore, it is considered that durability should be excellent as long as it is. However, as described above, in practice, good results are not always obtained.

  This is because when polishing with abrasive grains, etc., the metal surface tends to be easily peeled (fluffy), fluffed (fluffed), or burred (flickered), causing these to peel and become foreign matter, which can damage the bearing. It is thought to become. Moreover, since there are many sharp unevenness | corrugations, it is thought that wear tends to occur during operation. Furthermore, if the surface roughness is improved in order to prevent these problems, it is considered that the problem of close contact during CSS occurs.

  On the other hand, by applying a magnetic barrel, the metal surface is easily peeled away (fluffy), fuzz (fluff) or burr (fuzzy), the metal surface is smoothed, and it is gentle and moderate. Concavities and convexities having a large roughness are formed, and further, the metal surface is trained to work harden and eliminate the risk of peeling and the like. As a result, it is considered that effects such as remarkable improvement in durability and prevention of adhesion phenomenon are obtained.

  FIG. 1 is an explanatory view of a magnetic barrel polishing process in a method of manufacturing a dynamic pressure bearing part according to an embodiment of the present invention, and FIG. 2 is a cross section of a second annular member 33 which is a dynamic pressure bearing part according to an embodiment of the present invention. 3 is a plain view of the second annular member 33, FIG. 4 is a side view of the rotating member 31 as a fluid dynamic bearing component according to an embodiment of the present invention, and FIG. 5 is formed on the surface portion of the rotating member 31. FIG. 6 is a developed view of the concavo-convex pattern 31B, FIG. 6 is a graph showing the result of measuring the surface roughness of the concavo-convex pattern surface after precision polishing using abrasive grains, and FIG. 7 is the surface of the concavo-convex pattern after magnetic barrel polishing treatment. FIG. 8 is a cross-sectional view showing an example in which a component for a hydrodynamic bearing according to an embodiment of the present invention is incorporated in an HDD rotation drive unit 10, and FIG. 9 is a hydrodynamic bearing. 3 is an enlarged cross-sectional view of the device 20. FIG. Hereinafter, a method for manufacturing a fluid dynamic bearing component according to the embodiment will be described with reference to these drawings.

  First, a dynamic pressure bearing component is processed into a predetermined shape by a predetermined means, and when a dynamic pressure generating bearing member is manufactured, an uneven pattern for generating dynamic pressure is formed on the surface portion. Next, the surface is subjected to a surface treatment such as a predetermined polishing process to finish a surface state having a predetermined flatness and surface roughness. When manufacturing a dynamic pressure bearing member that is a counterpart member of the dynamic pressure generating bearing member, the same process as the manufacturing of the dynamic pressure generating bearing member is performed except that the uneven pattern is not formed. Therefore, in the following description, a dynamic pressure generating bearing member will be described as an example, and description regarding the dynamic pressure bearing member which is the counterpart member will be omitted. The second annular member 33 shown in FIGS. 2 and 3 is a kind of dynamic pressure generating bearing member, and is a kind of thrust bearing. 4 and FIG. 5 is also a kind of dynamic pressure generating bearing member and a kind of journal bearing.

  When the second annular member 33 is manufactured, an annular member having a predetermined size is obtained by cutting or the like, and then the convex portion 33Bp and the concave shape are formed on one surface 33B by using a well-known photolithography method, electrolytic processing method, or the like. A concave / convex pattern for generating dynamic pressure composed of the portion 33Bn is formed. When the rotating member 31 is manufactured, a cylindrical member having a predetermined size is obtained by cutting or the like, and then similarly, the convex portion 31Bp and the concave shape are formed on the surface 31A by using a well-known photolithography method, electrolytic processing method, or the like. A concave / convex pattern for generating dynamic pressure composed of the portion 31Bn is formed.

  Next, the surface portion of the dynamic pressure bearing component material on which the dynamic pressure generating uneven pattern is formed in the uneven pattern forming step is subjected to a precision polishing process. Specifically, this polishing step is performed by polishing with a flat polishing machine (lap polishing machine or polishing polishing machine) or cylindrical grinding, and the average roughness Ra is about 0.04 μm. FIG. 6 is a graph showing the results of measuring the surface roughness of the surface of the concavo-convex pattern after precision polishing using polishing abrasive grains. The surface roughness was measured using a stylus type surface roughness meter manufactured by Taylor Hobson.

  Next, a magnetic barrel polishing process is further performed on the polished surface. As shown in FIG. 1, in this magnetic barrel polishing process, a fluid 300, a magnetic medium 400 that is a polishing medium, and a hydrodynamic bearing component 33 that is an object to be polished are placed in a container 100 placed on a fixed base 110. The object to be polished is polished by moving the magnetic medium 400 by an external kinetic magnetic field with the lid 101 and the magnet 201 fixed to the turntable 200.

  In this case, as the fluid 300, for example, about 5cc (1 to 2% of the total) of compound and about 0.1g of citric acid are added to 350 to 400cc of water. In addition, as the magnetic medium 400, for example, a magnetic stainless steel pin having a diameter of 0.5 mm and a length of 5 mm is used by putting 150 to 180 g with respect to the fluid. Then, the turntable 200 is rotated at about 600 rpm and polished for about 30 minutes. FIG. 7 is a graph showing the results of measuring the surface roughness of the surface of the concavo-convex pattern after the magnetic barrel polishing treatment. The surface roughness was measured using a stylus type surface roughness meter manufactured by Taylor Hobson.

  As shown in FIG. 6, the surface roughness of the surface of the concavo-convex pattern after precision polishing using polishing abrasive grains is an average roughness Ra = 0.04 μm, and is finished with extremely high accuracy. On the other hand, as shown in FIG. 7, the surface after the magnetic barrel polishing seems to be numerically rather degraded. However, when the surface state shown in FIG. 6 is analyzed, it is estimated that there are many sharp irregularities, and there are many wrinkles, fluff or burr that are easily peeled off the metal surface. . For this reason, it is considered that wear may easily occur during operation, and stuffiness, fluff, or burr may peel off and become foreign matter, which may cause damage to the bearing.

  On the other hand, the surface after magnetic barrel polishing seems numerically rather less accurate, but the metal surface is prone to peeling, fluff, fluff or burr. It is considered that the metal surface is smoothed, and unevenness having a moderately large roughness is formed, and further, the metal surface is forged and work hardened and there is no possibility of peeling. It is done. As a result, it is considered that effects such as remarkable improvement in durability and prevention of adhesion phenomenon are obtained.

  Hereinafter, an example in which the above-described dynamic pressure bearing component is used in the HDD rotation drive unit will be described. In FIG. 8, a hydrodynamic bearing device 20 is disposed at the center of the HDD rotation drive unit 10. A hub 11 on which a storage disk (not shown) is mounted is fitted and fixed to the upper portion of the rotary shaft member 31 disposed at the rotation center of the dynamic pressure bearing device 20, and rotates together with the rotary shaft member 31. . A motor driving magnet member 12 is fitted and fixed to the inner peripheral surface of the hub 11, and a motor stator portion 13 fixed to the stator support member 14 is provided inside the motor driving magnet member 12. ing. The motor driving magnet member 12 is rotationally driven by an alternating magnetic field generated by an alternating current applied to the motor stator portion 13, whereby the storage disk rotates together with the hub 11.

  The size of the HDD rotation drive unit 10 depends on, for example, the outer diameter (diameter) of the hub 11 of about 20 mm, and the overall thickness (height dimension) of the hydrodynamic bearing device 20 depends on the structure of the motor stator unit 13. Is about 1.5 to 5.8 mm, and the shaft diameter (diameter) of the rotary shaft member 31 is about 2 mm. In FIG. 9, the hydrodynamic bearing device 20 includes a rotating part 30 and a fixed part 40. In addition, a dynamic pressure bearing portion 50 is formed between the rotating portion 30 and the fixed portion 40, and the rotating portion 30 is rotatably supported by the fixed portion 40 through the dynamic pressure bearing portion 50.

  The rotating unit 30 includes a cylindrical rotating shaft member 31, and an annular first annular member 32 and a second annular member 33 that are fitted and fixed to the outer peripheral surface of the rotating shaft member 31. . The first annular member 32 and the second annular member 33 are coated with an adhesive only on the inner peripheral surfaces 32A and 33A, which are fitting surfaces with the outer peripheral surface 31A of the rotary shaft member 31, and on the upper and lower end surfaces. The adhesive is not applied.

  The fixed portion 40 is a saucer-like lower support member 41 disposed on the lower end side of the rotary shaft member 31, and is fitted and fixed to the upper portion of the lower support member 41, so that the first annular member 32 and the second annular member 33 An annular intermediate member 42 disposed between the annular member 42, an annular magnet member 43 disposed on the outer peripheral side of the intermediate member 42, and an outer peripheral surface of the intermediate member 42 disposed on the upper side of the magnet member 43. A substantially flange-like upper yoke 44 fitted and fixed is provided. Note that the bottom plate of the lower support member 41 does not apply any load and needs only to be able to enclose a liquid. For example, it may have a thickness of about 0.05 mm and takes up little space in the height direction.

  The hydrodynamic bearing portion 50 includes a thrust bearing portion 51 that receives a thrust load acting on the rotating portion 30 and a journal bearing portion 52 that receives a radial load acting on the rotating portion 30. The thrust bearing portion 51 is formed of two layers of an upper thrust bearing portion 51A and a lower thrust bearing portion 51B. The upper thrust bearing portion 51A includes a lower end surface 32B of the first annular member 32, an upper end surface 42A of the intermediate member 42 facing the lower end surface 32B, and a first gap formed between the opposing surfaces 32B and 42A. And hydraulic oil 53 for generating dynamic pressure filled in 54.

  The lower thrust bearing portion 51B includes an upper end surface 33B of the second annular member 33, a lower end surface 42B of the intermediate member 42 opposed to the upper end surface 33B, and a second portion formed between the opposed surfaces 33B and 42B. It is comprised with the hydraulic oil 53 for dynamic pressure generation with which the clearance gap 55 was filled. The journal bearing portion 52 includes an outer peripheral surface 31A of the rotary shaft member 31, an inner peripheral surface 42C of the intermediate member 42 facing the outer peripheral surface 31A, and a third gap 56 formed between the opposing surfaces 31A and 42C. And hydraulic oil 53 for generating a dynamic pressure filled in.

  On one surface of each of the opposing surfaces 32B and 42A constituting the upper thrust bearing portion 51A and on one surface of each of the opposing surfaces 33B and 42B constituting the lower thrust bearing portion 51B, a dynamic pressure (not shown) is provided. An uneven pattern for generation is formed. The shape and depth of these concavo-convex patterns are arbitrary, and may be a general one suitable for generating dynamic pressure. In addition, a concavo-convex pattern 31B for generating dynamic pressure is also formed on the outer peripheral surface 31A of the rotary shaft member 31 constituting the journal bearing portion 52 in a belt-like region that goes around the outer peripheral surface 31A. However, the shape and depth of the concavo-convex pattern 31B are arbitrary, and may be a general one suitable for generating dynamic pressure, and are not limited to the illustrated shape. Further, the first gap 54, the second gap 55, the third gap 56, and the gap 57 formed between the lower end surface of the rotary shaft member 31 and the second annular member 33 and the bottom surface of the lower support member 41. Are all in communication.

  Of the surfaces of the first annular member 32 and the upper yoke 44, which are constituent members disposed in the vicinity of the boundary surface 53A between the hydraulic oil 53 and the external space 60, at least the portion indicated by the alternate long and short dash line in FIG. An oil repellent for preventing the oil 53 from bleeding is applied. The oil repellent may be applied to a portion other than the portion indicated by the alternate long and short dash line in the figure. For example, as will be described later, when the oil repellent is used instead of the cutting agent when machining the first annular member 32 and the upper yoke 44, the whole of the members 32 and 44 are covered with the oil repellent. However, it is not a problem because the film thickness is very small. Moreover, the part shown with the dashed-dotted line in the figure among the surfaces of the 1st annular member 32 is the taper surface 32C.

  A magnetic fluid is used for the hydraulic oil 53. Among these, the first magnetic fluid 53B is disposed in the vicinity of the boundary surface 53A, and the portions other than the vicinity of the boundary surface 53A, that is, the gaps 54 to 57, A second magnetic fluid 53C having a concentration lower than that of the first magnetic fluid 53B is disposed. Here, as the first magnetic fluid 53B, for example, a magnetic fluid of about 100 to 200 gauss sufficient to be held in a strong magnetic field can be suitably used. As the second magnetic fluid 53C, for example, there is no limit. A magnetic fluid having a low concentration of about 10 to 30 gauss, which is close to that of a general lubricating oil (the content of metal fine particles is about ¼ compared with a magnetic fluid having a saturation magnetization of 200 gauss) can be suitably used. .

  The magnet member 43 is magnetized in a direction (vertical direction in the drawing) along the axis of the rotary shaft member 31, thereby causing the magnet member 43 -the upper yoke 44 -the first annular member 32 -the rotary shaft member 31 -the second annular shape. A magnetic closed circuit is formed by a path of member 33-lower support member 41-magnet member 43. Accordingly, a strong magnetic field is formed in the vicinity of the boundary surface 53A, that is, between the outer peripheral surface of the first annular member 32 and the inner peripheral surface of the upper yoke 44 opposed thereto, whereby the first magnetic fluid 53B is Is retained. As the magnet member 43, for example, a magnet member (Sm—Fe—N magnet) formed by blending samarium, iron, and nitrogen can be suitably used. This is a bonded magnet having a particle diameter of, for example, about 5 μm.

  When the durability of the HDD rotational drive unit having the above-described configuration was tested, it was found that it could withstand a CSS test of 1.3 million times or more.

  The present invention relates to a hydrodynamic bearing device used as a bearing of a rotating part of a polygon mirror or the like in addition to a disk rotating storage device such as a hard disk drive (HDD) or digital versatile disk (DVD) drive device. It can utilize for manufacture of the components for dynamic-pressure bearings which comprise this dynamic pressure generation part.

It is explanatory drawing of the magnetic barrel grinding | polishing process in the manufacturing method of the components for dynamic pressure bearings concerning the Example of this invention. It is sectional drawing of the 2nd annular member 33 which is the components for dynamic pressure bearings concerning the Example of this invention. 4 is a plan view of a second annular member 33. FIG. It is a side view of the rotation member 31 which is the components for dynamic pressure bearings concerning the Example of this invention. 4 is a development view of a concavo-convex pattern 31B formed on the surface portion of the rotating member 31. FIG. It is a graph which shows the result of having measured the surface roughness of the surface of the uneven | corrugated pattern after the precision polishing process using an abrasive grain. It is a graph which shows the result of having measured the surface roughness of the surface of the uneven | corrugated pattern after a magnetic barrel grinding | polishing process. 1 is a cross-sectional view showing an example in which a component for a hydrodynamic bearing according to an embodiment of the present invention is incorporated in an HDD rotation drive unit 10. 3 is an enlarged cross-sectional view of a fluid dynamic bearing device 20. FIG.

Explanation of symbols

33 Hydrodynamic bearing component 200 Turntable 201 Magnet 300 Abrasive fluid 400 Magnetic media

Claims (3)

A method for producing a hydrodynamic bearing part for producing a hydrodynamic bearing part, comprising:
A processing step of processing a fluid pressure bearing component material into a predetermined shape;
A surface treatment step of bringing the surface of the dynamic pressure bearing component material processed into a predetermined shape in the processing step into a predetermined surface state,
In the surface treatment step, a magnetic barrel polishing process is performed in which a fluid, a magnetic medium as a polishing medium, and an object to be polished are placed in a container, and the object to be polished is polished by moving the magnetic medium by an external kinetic magnetic field. A method for producing a component for a hydrodynamic bearing, comprising:   2. The method of manufacturing a hydrodynamic bearing part according to claim 1, wherein the surface treatment step is performed by performing the magnetic barrel polishing after the fine polishing using polishing abrasive grains. Manufacturing method of bearing parts.   3. The method of manufacturing a fluid dynamic bearing part according to claim 1, wherein the magnetic medium used for the magnetic barrel polishing is a magnetic stainless steel wire having a predetermined length. Method of manufacturing parts.

Images