JP2004169725A - Dynamic-pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a dynamic-pressure bearing device compact and thin while securing precision of a reel-shaped shaft body. <P>SOLUTION: A large diameter part 2b is formed at a lower end of a center pin 2 which is caulked with a base 1 at a lower part. A shaft 3 is engaged and fixed in a small diameter part 2c of the center pin 2. A top ring 4 is engaged and fixed to hold the shaft 3 with the large diameter part 2a. The reel-shaped shaft body 5 is composed of the center pin 2, the shaft 3, and the top ring 4. Thrust direction dynamic pressure generating grooves 6 are formed in both end surfaces of the shaft 3. Radial direction dynamic pressure generating grooves 7 are formed in a side surface. Thrust plates 8 are disposed on both end surfaces of the shaft 3 through a micro-gap. Sleeves 9 are disposed on the side surface of the shaft 3 through micro-gaps. A bearing member 10 is composed of both thrust plates 8 and the sleeves 9. An outer circumferential surface 10a is held by hubs 13 in the thrust direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a dynamic pressure bearing device that generates a dynamic pressure in lubricating oil by a dynamic pressure generating groove formed in a bearing member to support a rotating body.
[0002]
[Prior art]
Conventionally, various dynamic pressure bearing devices have been proposed. As an example, FIG. 9 shows a side sectional view of a bearing portion in a conventional hydrodynamic bearing device. The shaft body 72 and the thrust plate 73 are integrally joined, and are rotatably held between the bearing member 71 and the thrust receiving plate 74 via a gap. A radial dynamic pressure generating groove is formed between the shaft body 72 and the bearing member 71 on one of the shaft body 72 and the bearing member 71, and a radial dynamic pressure generating section 81 having a gap of about several μm is provided. . Further, between the thrust plate 73 and the bearing member 71, a thrust dynamic pressure generating groove is formed in one of the thrust plate 73 and the bearing member 71, and an upper thrust dynamic pressure generating portion 82 is provided. A thrust dynamic pressure generating groove is formed in one of the thrust plate 73 and the thrust receiving plate 74 between the thrust receiving plate 74 and a lower thrust dynamic pressure generating portion 83 is provided. Lubricating oil or gas is interposed between the radial dynamic pressure generating section 81 and the vertical thrust dynamic pressure generating sections 82 and 83. Although not shown in the drawing, a rotating hub or a rotor magnet is attached to the shaft body 72, and the bearing member 71 and the thrust receiving plate 74 are used as fixed parts and incorporated into a motor structure having a stator or the like, thereby being used as a spindle motor. Such a dynamic pressure bearing device realizes highly accurate asynchronous rotational runout (NRRO) by an averaging effect due to dynamic pressure generated during rotation.
[0003]
Among them, in a bearing device used for a motor for an HDD or a rotary table for a precision measuring instrument, there is provided a shaft member which is a cylindrical fixed member or a rotating shaft having a central shaft portion protruding from both end surfaces. (Hereinafter, abbreviated as a frame shaft) (for example, see Patent Documents 1 and 2).
[0004]
Above all, in recent years, HDD spindle motors used especially for portable information devices and AV devices have been required to be small and thin, and Patent Document 1 is considered to be advantageous in this respect. An example of a conventional hydrodynamic bearing device using a piece shaft will be described with reference to the drawings. FIG. 4 is a side sectional view of a conventional hydrodynamic bearing device using a top shaft. In FIG. 4, reference numeral 1 denotes a base made of a metal plate or the like to which the dynamic pressure bearing device is fixed. Numeral 62 denotes a center pin made of stainless steel or the like as a central shaft part having a lower end fixed to the base 1 and provided upright. Numeral 3 denotes a shaft as a cylindrical member, and the center pin 62 is fixed to a central hole. .
[0005]
Reference numeral 65 denotes a top shaft, which is composed of a center pin 62 and a shaft 3. Reference numeral 6 denotes a thrust direction dynamic pressure generation groove formed on both end surfaces of the shaft 3. Reference numeral 7 denotes a radial dynamic pressure generating groove formed on the side surface of the shaft 3. Reference numeral 8 denotes a thrust plate as a thrust bearing portion having a center hole 8a, which is disposed on both end surfaces of the shaft 3 via a minute gap. Reference numeral 9 denotes a sleeve as a radial bearing portion held between both thrust plates 8, and has an inner peripheral surface 9a facing a side surface of the shaft 3 via a minute gap. Numeral 10 is a bearing member composed of three bodies of the two thrust plates 8 and the sleeve 9.
[0006]
With the above configuration, the top shaft member 65 has a radial bearing portion and a thrust bearing portion within the axial length of the shaft 3. With this configuration, it is not necessary to increase the axial length of the bearing portion in order to provide the thrust bearing portion. On the other hand, in the bearing structure of the type shown in FIG. 9, the length of the bearing portion in the axial direction is h. Most of the length i of the length h is the thickness dimension of the thrust plate 73 and is a portion that is not related to the radial bearing portion 81. Therefore, the bearing structure using the top shaft 65 of FIG. 4 is a particularly advantageous structure for reducing the size and thickness of the bearing structure.
[0007]
Next, the overall structure will be described. The small gap and the dynamic pressure generating grooves 6 and 7 are filled with lubricating oil (not shown). In addition, oil repellents (not shown) for preventing oil leakage are provided on the inner peripheral surface 8a and the outer end surface 8b of the thrust plate 8 and the outer peripheral surfaces 62a and 62b of the center pin 62 facing the inner peripheral surface 8a of the thrust plate 8, respectively. Processing has been applied. 11 is a recording disk, 12 is a magnet, 13 is a hub which is a rotating member, holds the bearing member 10 on the inner peripheral surface 13b, fixes the magnet 12 on the outer peripheral surface, and mounts the recording disk 11 13a. Reference numeral 14 denotes a stator fixed to the base 1, and reference numeral 15 denotes a coil wound around the stator 14.
[0008]
Next, the operation of the hydrodynamic bearing device will be described. The hub 13 is driven to rotate together with the recording disk 11 in a state where the bearing member 10 is supported by the top shaft 65 by the driving force of the magnetic circuit portion of the stator 14 and the magnet 12 by energizing the coil 15. become. With the rotation, the supporting pressure is generated in the lubricating oil by the action of the dynamic pressure generating grooves 6 and 7 of the top shaft 65, so that the bearing member 10 is lifted off the top shaft 65 so that the bearing member 10 is positioned at the center of the top shaft 65. Support rotation. Accordingly, the hub 13 on which the recording disk 11 is mounted can rotate stably without rotation even at high speed rotation.
[0009]
[Patent Document 1]
JP 2000-50568 [Patent Document 2]
JP-A-9-222119
[Problems to be solved by the invention]
However, in the bearing structure using the top shaft 65 of FIG. 4, since the radial bearing portion is provided at the same or outer side as the radially largest portion of the thrust bearing portion, the bearing of the radial bearing portion at the time of rotation is provided. The rigidity tends to be greater than the bearing rigidity of the thrust portion, and depending on the balance between the two bearing rigidities, asynchronous rotational runout (NRRO) during rotation may be reduced. From the viewpoint of balancing the bearing stiffness, it is possible to consider means for reducing the bearing stiffness of the radial bearing and means for increasing the bearing stiffness of the thrust bearing. However, in order to reduce the size and thickness of the entire bearing structure, there are restrictions on the dimensions of each part. Therefore, when designing a high-performance bearing, the bearing stiffness should be as large as possible within the limits of the respective restrictions. Naturally, it is necessary to increase the bearing rigidity of the thrust bearing as much as possible rather than to reduce the bearing rigidity of the radial bearing. In order to increase the bearing rigidity of the thrust bearing, it is necessary to increase the area of the thrust bearing. In the case of the top shaft 65 of FIG. It is necessary to reduce the outer diameter of a portion related to fitting of the shaft 62 to the shaft 3.
[0011]
FIG. 6 is a schematic side view showing a conventional two-piece comb-shaped shaft. In FIG. 6, reference numeral 45 denotes a cylindrical portion having a center hole 45a. Reference numeral 46 denotes a central shaft portion bonded and fixed to the central hole 45a, and protrudes from both end surfaces 45a and 45b of the cylindrical portion 45, respectively. At the time of processing the top shaft, the cylindrical portion 45 and the central shaft portion 46 are respectively turned, and after finishing the respective surfaces as necessary, the two are bonded. For example, in the case of a part having an inner diameter of the center hole 45a of about 5 mm, there is a sufficient contact area on the inner surface of the center hole 45a and the adhesive strength of the center shaft can be obtained, but in order to increase the area of the thrust bearing, If the inner diameter of the central hole 45a and the outer diameter of the central shaft portion 46 are designed to be small, the contact area between the internal diameter portion of the central hole 45a and the central shaft portion 46 also decreases, and the bonding strength also decreases. Therefore, with the miniaturization of the entire structure, the bonding strength between the cylindrical portion 45 and the central shaft portion 46 cannot be obtained. Even if an attempt is made to press-fit the central shaft portion 46 in order to supplement the adhesive strength, if the outer diameter of the central shaft portion 46 becomes small, there is a problem that the shaft is easily deformed at the time of press-fitting, which is difficult.
[0012]
As a measure for the adhesive strength between the cylindrical portion 45 and the central shaft 46 of the two-piece top shaft, means for integrally forming the top shaft can be considered. The problem will be described below. FIG. 5 is a schematic side view showing a conventional integrated top shaft. In FIG. 5, reference numeral 31 denotes a cylindrical portion, and shaft portions 31a and 31b are integrally formed so as to protrude from both end surfaces of the cylindrical portion 31 along the central shaft portion.
[0013]
FIG. 7 is a sectional view of a main part showing a method of processing an integrated top shaft. In FIG. 7, reference numeral 41 denotes a material blank. Reference numeral 51 denotes a lathe chuck, and reference numeral 52 denotes a cutting tool. 42 is a cutting part. At the time of processing, the material 41 is added to the chuck 51, and the cutting portion 42 is removed by the cutting tool 52 to cut out the top shaft.
[0014]
FIG. 8 is a cross-sectional view of a main part showing another method of processing the integrated top shaft. In FIG. 8, 43 and 44 are cutting parts. At the time of processing, first, the material blank 41 is added to the chuck 51 in the same manner as shown in FIG. Next, as shown in FIG. 8A, the outer diameters of the shaft portion 31a and the cylindrical portion 31 are cut while leaving the cut portion 43. Next, as shown in FIG. 8B, the material blank 41 being processed is once removed from the chuck 51, the cylindrical portion 31 is re-attached to the chuck 51, and the cutting portion 44 is cut and removed by the cutting tool 52, and the shaft portion is removed. 31b is cut out to form a top shaft.
[0015]
However, in the case of processing the above-mentioned integral type coaxial shaft body by one chuck, in order to increase the area of the thrust bearing portion, the surface a and the surface b in FIG. 5 are enlarged to form the shaft portion 31a and the shaft portion 31b. If the outer diameter is designed to be small, sufficient machining accuracy may not be obtained. Sufficient processing accuracy means that, for example, when a dynamic bearing is used for a spindle motor of a hard disk, an asynchronous rotational runout (NRRO) at the time of rotation is several nm to several tens nm in order to realize high recording density. In order to achieve this, the outer diameter, inner diameter, thickness accuracy, gap accuracy, parallelism, squareness, and other accuracy related to the bearing are required at the level of 1 μm, and the dynamic pressure generator Is required to have a surface roughness level of about Ra = 0.05 μm.
[0016]
For example, when the outer diameter of the shaft portion 31a and the shaft portion 31b is about 2 mm, the portion A shown in FIG. In the worst case, it breaks and cannot be processed. In addition, the required accuracy of both the outer dimension accuracy and the thickness dimension accuracy is 1 μm or less, but 5 μm, which is not sufficiently obtained. In the two-chuck processing, the chuck position must be changed between the first chuck and the second chuck, so that there is no reference processing. Further, since there is a change in the work setting, the surfaces a and b shown in FIG. The required parallelism with respect to the plane and the perpendicularity between the a-plane and the c-plane are each as low as about 3 μm while the required precision is 1 μm or less. Since the surfaces a, b, and d are surfaces on which the dynamic pressure generating grooves are formed, poor surface roughness causes unnecessary turbulence in the lubricating oil and induces a reduction in the rotation characteristics. On the other hand, the overall surface roughness is deteriorated to 0.1 to 0.5 μm, while the required accuracy is Ra = 0.05 μm. This is also a major cause of the inability to finish the surfaces a and b due to the presence of the shaft portions 31a and 31b.
[0017]
Further, as a processing method of the integral-shaped shaft body, there is a processing method such as injection molding or press molding method in addition to the above-mentioned cutting processing, but it is difficult to obtain sufficient processing accuracy.
[0018]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydrodynamic bearing device capable of solving the above-mentioned problems and increasing the bearing rigidity of a thrust bearing portion of a top-shaft shaft body while achieving downsizing and thinning.
[0019]
[Means for Solving the Problems]
Means of the present invention for achieving the above-mentioned object are a top shaft having a central shaft protruding from both end surfaces of a cylindrical member, a thrust bearing portion opposed to the both end surfaces via a minute gap, and the cylindrical member. A bearing member comprising a radial bearing portion having an inner peripheral surface opposed to a side surface of the member via a minute gap, and a lubricating oil filled in the minute gap, and both end surfaces of the cylindrical member or the thrust bearing portion A thrust dynamic pressure generating groove is formed on one of the surfaces facing the both end surfaces of the cylindrical member, and a radial dynamic pressure generating groove is formed on one of the side surface of the cylindrical member or the inner peripheral surface of the radial bearing portion. In the pressure bearing device, the top shaft body includes a central shaft portion having a large diameter portion near one axial end of the central shaft portion, a cylindrical member fixed to a small diameter portion of the central shaft portion, Diameter the member Characterized in that a three-body with fitted fixed ring member to the central shaft so as to sandwiched between parts.
[0020]
Further, the thrust bearing and / or the radial bearing are made of ceramics.
[0021]
Further, the top shaft is fixed to a fixed member, an outer peripheral surface of the bearing member is fitted into an inner peripheral surface of the rotating member, and both end surfaces of the bearing member in the thrust direction are inner peripheral surfaces of the rotating member. It is characterized by being held in the thrust direction by a flange portion projecting radially inward from both ends of the surface.
[0022]
Further, the center shaft portion of the top shaft is caulked to the fixing member.
[0023]
Further, the top shaft is fixed to a rotating member, an outer peripheral surface of the bearing member is fitted into an inner peripheral surface of a bearing holding portion of the fixing member, and both end surfaces in the thrust direction of the bearing member are fixed members. Characterized in that it is held in the thrust direction by flange portions projecting inward in the thrust direction from both ends of the inner peripheral surface of the first member.
[0024]
Further, the cylindrical member and / or the ring member of the top shaft member are made of ceramics.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side sectional view of a hydrodynamic bearing device according to a first embodiment of the present invention.
[0026]
First, the configuration of the dynamic pressure bearing device will be described. In FIG. 1, reference numeral 2 denotes a center pin made of a metal such as stainless steel as a central shaft portion which is crimped by a caulking portion 2a on a base 1 which is a fixing member having a lower end portion made of, for example, an aluminum plate or a stainless steel plate. is there. A large-diameter portion 2b is formed on the lower end side of the center pin 2 near one axial end. A shaft 3 which is a cylindrical member made of ceramics is fitted and fixed to the small diameter portion 2c of the center pin 2. Reference numeral 4 denotes a top ring as a ring member made of ceramics, which is fitted and fixed to the center pin 2 so that the shaft 3 is held between the large diameter portion 2a of the center pin 2 and the top ring 4.
[0027]
Reference numeral 5 denotes a top shaft of the hydrodynamic bearing device, which is composed of a center pin 2, a shaft 3, and a top ring 4. The other configuration is the same as that described in the section of the related art, so that the same components are denoted by the same reference numerals and names, and detailed description is omitted.
[0028]
Here, the bearing member 10 includes a thrust plate 8 as a thrust bearing portion and a sleeve 9 as a radial bearing portion, and is made of ceramics. Here, the radial dynamic pressure generating groove 6 may be formed on at least one of the side surface 3c of the shaft 3 and the inner peripheral surface 9b of the sleeve 9, and the thrust dynamic pressure generating groove 7 is formed on both end surfaces 3a, 3b of the shaft 3. And at least one of the opposing surfaces of the thrust plate 8 opposing them.
[0029]
Next, an assembling procedure of the hydrodynamic bearing device according to the first embodiment of the present invention will be described. First, the top shaft 5 before caulking is assembled. Next, the thrust plate 8, the sleeve 9, the top shaft 5, and the other thrust plate 8 are inserted in this order into the inner peripheral surface 13 b, which is a bearing holding portion of the hub 13 to which the magnet 12 is fixed, to hold the bearing. The end portion is swaged to form a flange 13d. Next, the base 1 in which the stator 14 has been assembled is inserted into the shaft end of the top shaft 5 and caulked to form the caulked portion 2a. Finally, an appropriate amount of lubricating oil is injected from the gap between the center hole of the thrust plate 8 and the center pin 2.
[0030]
Next, the effects of the hydrodynamic bearing device according to the first embodiment of the present invention will be described. The top shaft 4 is fixed to the top ring 4 so that the shaft 3 fitted and fixed to the center pin 2 having the large-diameter portion 2b is clamped to the large-diameter portion 2b. The inner diameter of the shaft 3, the small diameter part 2c, the large diameter part 2b of the center pin 2, and the outer diameter of the top ring 4 are reduced to ensure sufficient rigidity and a large area of the thrust bearing. By increasing the bearing rigidity of the thrust bearing portion, a dynamic pressure bearing device with stable rotational accuracy was obtained. Incidentally, a comparison was made between the case where the outer diameter of the central axis 46 of the conventional two-piece type top shaft of FIG. 6 and the outer diameter of the large diameter portion 2b of the top shaft 5 and the outer diameter of the top ring 5 of the present invention were substantially the same. However, the joining strength of the central shaft portion of the top shaft 5 of the present invention was increased. Further, by employing a structure in which the center pin 2 is swaged to the fixing member, the fixing member can be firmly and accurately erected even if the fixing member is a thin plate.
[0031]
Since the shaft 3 and the top ring 4 are of a three-piece type, the machining accuracy of each part of the top shaft 5 of this bearing device is stable. The shaft 3 can be subjected to finishing such as polishing on the outer peripheral surface, the inner peripheral surface, the end surface 3a and the end surface 3b as necessary, and the center pin 2 can also be subjected to finishing on the large-diameter portion 2b and the small-diameter portion 2c. In addition, the top ring 3 can be finished on the inner diameter surface, the outer diameter surface, and the end surface. Therefore, dimensional accuracy and surface roughness accuracy, which could not be realized by the conventional integral-type top shaft, can be finished to a sufficient accuracy for use in the dynamic pressure bearing portion. Incidentally, the parallelism of the planes a and b shown in FIG. 5 is 0.5 μm, the squareness of the planes a and c is 1 μm, the accuracy of the outer diameter and thickness is 1 μm or less, and the surface roughness is Ra = 0 after lapping. 0.05 μm. Further, by forming the shaft 3 and the top ring 4 as a three-piece frame-shaped shaft body using ceramics, the shaft 3 and the top ring 4 are resistant to strength and thermal distortion, and the rotation accuracy is stabilized. Further, since the thrust plate 8 and the sleeve 9 are made of ceramics, the surface serving as the bearing portion can be polished with high precision, and at the same time, when the hub 13 is fixed to the bearing member 10 by caulking, the bearing member is used. 10 can be assembled without deforming while maintaining dimensional accuracy. Further, by holding the bearing member 10 between the flanges of the hub 13, the assembling becomes easy, and a minute gap in the thrust direction can be obtained with high accuracy.
[0032]
When the total thickness of the dynamic pressure bearing device is to be reduced, reducing the axial thickness of the sleeve 9 and the shaft 3 has a limit for obtaining a required dynamic pressure in the dynamic pressure generating portion. Therefore, inevitably, the thickness of the base 1 and the thrust plate 8 is reduced to a thickness close to the strength limit. However, if the three-piece top frame 5 is used, the thickness of the thrust plate 8 and the thickness of the base 1 are reduced. Even if it is thin, a desired mechanical strength can be obtained, so that a thin, highly accurate dynamic pressure bearing device can be obtained.
[0033]
In the embodiment of the present invention, the shaft 3, the top ring 4, the thrust plate 8, and the sleeve 9 are made of ceramics, so that the finishing is performed with high accuracy and the strength after assembly is most preferable. Of course, it is also possible to use a metal material such as steel. In this case, ceramics and a metal material such as stainless steel may be appropriately selected and used in consideration of necessary strength, workability of the dynamic pressure generating groove, and manufacturing cost. For example, when the thrust plate 8 and the sleeve 9 held by the flange of the hub 13 are all made of ceramics, the material is the least deformable and can be firmly fixed. However, either one of the thrust plate 8 and the sleeve 9 is made of ceramics. In the case of (1), or when one of the two thrust plates 8 is made of ceramics, it is effective in firmly fixing. Regarding the fixing strength of the top shaft 5, it is most advantageous when both the top ring 4 and the shaft 3 are made of ceramics, but it is also effective when one of them is made of ceramics. Further, when the dynamic pressure generating groove is formed on the outer diameter portion of the shaft 3 or the inner diameter portion of the sleeve 9 serving as the radial bearing portion, the dynamic pressure generating groove is formed on a flat surface. Since it is more difficult than machining and often more difficult in the case of ceramics, it is a very advantageous combination in terms of manufacturing cost to use a metal material for one of the dynamic pressure generation grooves and a ceramic for the other. It is.
[0034]
Next, a second embodiment of the present invention will be described. FIG. 2 is a side sectional view of a main part of a hydrodynamic bearing device according to a second embodiment of the present invention. In FIG. 2, reference numeral 22 denotes a shaft serving as a central shaft portion, a large-diameter portion 22b is formed at one end, and a caulking portion 22a is provided at the other end. The shaft 22 is caulked and erected on the base 1 as a fixing member. ing. The top ring 4 is sandwiched between the shaft 3 and the base 1, and is fitted into the small-diameter portion 22c together with the shaft 3 so as to sandwich the shaft 3 between the large-diameter portion 22b and the top ring 4. Reference numeral 25 denotes a top shaft, which is composed of a center pin 22, a shaft 3, and a top ring 4. The configuration other than the frame-shaped shaft body 25 is the same as that of the first embodiment. Therefore, the same components are denoted by the same reference numerals and names, and description thereof is omitted. The procedure for assembling the hydrodynamic bearing device according to the second embodiment of the present invention is the same as that of the first embodiment.
[0035]
Next, a third embodiment of the present invention will be described. FIG. 3 is a sectional side view of a main part of a hydrodynamic bearing device according to a third embodiment of the present invention. In FIG. 3, reference numeral 21 denotes a base which is a fixing member, and a cylindrical bearing holding portion 21a is provided upright at the center of the base 21. The outer peripheral surface 10a of the bearing member 10 is inserted into the inner peripheral surface 21d of the bearing holding portion 21a, and both end surfaces in the thrust direction of the bearing member 10 are a flange portion 21b and a caulked portion that protrude radially from both ends of the inner peripheral surface 21d. It is sandwiched between the flange 21c. Reference numeral 23 denotes a hub as a rotating member, and the top shaft 5 is caulked by the hub 23 to form a rotating shaft.
[0036]
Next, an assembling procedure of the hydrodynamic bearing device according to the third embodiment of the present invention will be described. First, the top shaft 5 before caulking is assembled. Next, the stator 14 is inserted into the inner peripheral surface 21d of the bearing holding portion 21a of the assembled base 21 in the order of one thrust plate 8, the sleeve 9, the top shaft 5 and the other thrust plate 8, thereby holding the bearing. A flange 21c is formed by caulking the upper end of the portion 21a. Next, the hub 23 to which the magnet 12 is fixed is inserted into the shaft end of the top shaft 5 and caulked to form the caulked portion 2a.
[0037]
The hydrodynamic bearing device according to the present invention is not necessarily limited to the above-described embodiment. The rotating shaft is not the top shaft 5 having the center pin 2 but the top shaft having the center pin 22. The form which has become the body 25 may be sufficient.
[0038]
【The invention's effect】
As described above, according to the present invention, a top shaft having a central shaft protruding from both end surfaces of a cylindrical member is provided with a central shaft having a large diameter portion near one shaft end, A cylindrical member press-fitted into the small-diameter portion, and a ring member fitted and fixed to the central shaft portion so as to clamp the cylindrical member with the large-diameter portion. Thus, a dynamic pressure bearing device having a small, thin, and high-precision comb-shaped shaft body that satisfies the required accuracy with dimensional accuracy satisfying the required fixing force is obtained. As a result, it has become possible to obtain a hydrodynamic bearing device in which the outer diameter of the central shaft portion of the top shaft member is made smaller than before, the area of the thrust bearing portion is increased, and the thrust bearing rigidity is increased.
[0039]
Further, the top shaft is fixed to a fixed member, the outer peripheral surface of the bearing member is fitted into the inner peripheral surface of the hub, and both end surfaces of the bearing member are inward from both ends of the inner peripheral surface of the hub. Since the flange portion is held in the thrust direction by the protruding flange portion, assembly of the dynamic pressure bearing device is facilitated.
[0040]
Further, since the center pin of the top shaft is caulked to a fixing member, the fixing member can be firmly erected even if the fixing member is a thin plate, and a small and thin dynamic pressure bearing device is obtained. .
[Brief description of the drawings]
FIG. 1 is a side sectional view of a dynamic bearing device according to a first embodiment of the present invention.
FIG. 2 is a sectional side view of a main part of a hydrodynamic bearing device according to a second embodiment of the present invention.
FIG. 3 is a side sectional view of a dynamic bearing device according to a third embodiment of the present invention.
FIG. 4 is a side sectional view of a conventional hydrodynamic bearing device.
FIG. 5 is a schematic side view showing a conventional integral top shaft.
FIG. 6 is a schematic side view showing a conventional two-piece comb-shaped shaft.
FIG. 7 is a partial cross-sectional view for explaining a conventional method for processing an integrated top shaft.
FIG. 8 is a partial cross-sectional view for explaining another processing method of the conventional integral top shaft.
FIG. 9 is a side sectional view of a bearing portion of a conventional hydrodynamic bearing device.
[Explanation of symbols]
1, 21 Base 2, 22 Center pin 2a, 22a Caulking portion 2b, 22b Large diameter portion 2c, 22c Small diameter portion 3 Shaft 4 Top ring 5, 25 Coma-shaped shaft body 6, 7 Dynamic pressure generating groove 8 Thrust plate 9 Sleeve 9a inner peripheral surface 10 bearing member 10a outer peripheral surface 13, 23 hub 13b, 21d inner peripheral surface 13c, 13d flange

Claims (6)

A top shaft body having a central shaft protruding from both end surfaces of the cylindrical member, a thrust bearing portion facing the both end surfaces via a minute gap, and an inner peripheral surface facing a side surface of the cylindrical member via a minute gap. A bearing member comprising a radial bearing portion having: In a dynamic pressure bearing device in which a dynamic pressure generating groove is formed, and a radial dynamic pressure generating groove is formed on one of a side surface of a cylindrical member and the inner peripheral surface of the radial bearing portion, the top shaft member may have the center shaft. A central shaft portion having a large-diameter portion near one axial end of the portion, a cylindrical member fixed to the small-diameter portion of the central shaft portion, and the cylindrical member clamped by the large-diameter portion. Fits and fixes to the central shaft Dynamic bearing apparatus characterized by a three-body ring member. The dynamic pressure bearing device according to claim 1, wherein the thrust bearing portion and / or the radial bearing portion are made of ceramic. The top shaft member is fixed to a fixed member, the outer peripheral surface of the bearing member is fitted into the inner peripheral surface of a rotating member, and both end surfaces in the thrust direction of the bearing member are opposite inner peripheral surfaces of the rotating member. The dynamic pressure bearing device according to claim 1, wherein the flange portion is held in a thrust direction by a flange portion projecting radially inward from the shaft. The dynamic pressure bearing device according to claim 3, wherein the central shaft portion of the top shaft is caulked to the fixing member. The top shaft is fixed to a rotating member, an outer peripheral surface of the bearing member is fitted into an inner peripheral surface of a bearing holding portion of the fixing member, and both end surfaces of the bearing member in the thrust direction are formed inside the fixing member. 2. The hydrodynamic bearing device according to claim 1, wherein the flange portion is held in the thrust direction by flange portions projecting inward in the thrust direction from both ends of the peripheral surface. The dynamic pressure bearing device according to any one of claims 1 to 5, wherein the cylindrical member and / or the ring member of the top shaft member is made of ceramics.

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