JP3774080B2 - Hydrodynamic bearing unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dynamic pressure type bearing unit. This bearing unit is particularly suitable for information equipment, for example, a spindle motor such as a magnetic disk device such as HDD or FDD, an optical disk device such as CD-ROM or DVD-ROM, a magneto-optical disk device such as MD or MO, or a laser beam printer ( It is suitable for supporting a spindle such as a polygon scanner motor of LBP).
[0002]
[Prior art]
In addition to high rotational accuracy, spindle motors of the various information devices are required to have high speed, low cost, low noise, and the like. One of the components that determine the required performance is a bearing that supports the spindle of the motor.In recent years, the use of a hydrodynamic bearing having characteristics excellent in the required performance has been studied as this type of bearing. Or it is actually used.
[0003]
FIG. 5 shows an example of this type of spindle motor. A shaft member 22 (comprised of a shaft 22a and a thrust disk 22b that becomes a flange portion when mounted on the shaft 22a) is rotatably supported by a bearing unit 21. In this structure, the motor stator 4 fixed to the bearing member 27 and the motor rotor 5 mounted on the shaft member 22 are rotationally driven by an exciting force. The bearing unit 21 is provided with a radial bearing portion 30 for supporting the shaft member 22 in the radial direction and a thrust bearing portion 31 for supporting the thrust disk 22b in the thrust direction. These bearing portions 30, 31 are both bearing surfaces. The hydrodynamic bearing has a dynamic pressure generating groove (dynamic pressure groove). The dynamic pressure grooves of the radial bearing portion 30 are formed on the inner peripheral surface of the bearing member 27, and the dynamic pressure grooves of the thrust bearing portion 31 are formed on both end surfaces of the thrust disk 22b fixed to the lower end of the shaft member 22, respectively. . The bottom of the bearing member 27 is provided with a level difference obtained by adding the thrust bearing gap width (t = 10 to 20 μm) to the thickness of the thrust disk 22b. Thrust bearing gaps Cs1 and Cs2 having the predetermined width are formed on both axial sides of the disk 22b (t = Cs1 + Cs2).
[0004]
In this bearing unit 21, after the thrust disk 22b and the back metal 33 are assembled in the bearing member 27, a shaft 22a having a smaller diameter than the inner diameter is inserted into the inner diameter portion of the bearing member 27, and the shaft 22a The tip is assembled by press-fitting the inner end of the thrust disk 22b.
[0005]
[Problems to be solved by the invention]
In the bearing unit 21, if the perpendicularity accuracy between the shaft 22a and the thrust disk 22b is poor, the thrust disk 22b may come into contact with the facing surface in the thrust bearing gaps Cs1 and Cs2, and the bearing performance may be deteriorated. Therefore, in the assembly process, it is necessary to press-fit the shaft 22a into the thrust disk 22b with high accuracy, but it is difficult to obtain the required accuracy (squareness of about 2 μm) by press-fitting. Further, even if an attempt is made to measure the squareness, since the shaft 22a and the thrust disk 22b are already incorporated in the unit, it is generally difficult to measure and confirm their accuracy, and even if possible, complicated work is required. Increase assembly costs.
[0006]
Therefore, an object of the present invention is to provide a hydrodynamic bearing unit that can improve the accuracy (perpendicularity, etc.) between the shaft and the thrust disk at low cost.
[0007]
[Means for Solving the Problems]
To achieve the above object, a hydrodynamic bearing unit according to the present invention includes a housing, a shaft member including a shaft and a flange, a bearing member fixed to the inner peripheral surface of the housing, an outer peripheral surface of the shaft, and A radial bearing gap is provided between the inner peripheral surfaces of the opposing bearing members, a radial bearing portion that supports the shaft member in the radial direction, two thrust bearing gaps on both sides of the flange portion, and a flange portion of the shaft member. A thrust bearing portion that supports in the thrust direction, and the radial bearing portion and the thrust bearing portion each support the shaft member in a non-contact manner by dynamic pressure action, and one end of the housing is opened and the other end is thrust supported. The inner peripheral surface of the housing has a cylindrical surface shape without a step, the flange portion is provided at one end of the shaft, and one end surface of the flange portion and the bearing facing this In the end surface of the wood as well as constituting one of the thrust bearing gap of the thrust bearing portion to constitute the other thrust bearing gap of the thrust bearing portion between the other end face and the thrust support portion end surface of the flange portion, and the shaft The flange portion is integrally formed. The shaft and the flange portion of the shaft member can be integrally formed by forging, or can be integrated by welding.
[0008]
If the shaft member is integrated in this way, accuracy such as the squareness between the shaft and the flange can be easily secured, and the squareness can be measured before installation in the bearing unit, so accuracy measurement And the confirmation work becomes easy.
[0011]
The dynamic pressure groove of the thrust bearing portion is preferably provided in either one of the bearing member and the thrust support portion (determined by the direction of the thrust load) or both.
[0012]
One end side of the bearing member is preferably sealed with a seal member.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0014]
FIG. 1 is a sectional view of a spindle motor for information equipment provided with a hydrodynamic bearing unit 1 according to the present invention, and shows an HDD (Hard Disk Drive) spindle motor as an example. This spindle motor is opposed to a bearing unit 1 that rotatably supports a shaft member 2 and a disk hub 3 that is attached to the shaft member 2 and holds one or more magnetic disks D via a radial gap. A motor stator 4 and a motor rotor 5. The stator 4 is attached to the cylindrical outer peripheral portion of the casing 9 that holds the bearing unit 1, and the rotor 5 is attached to the inner peripheral surface of the disk hub 3. When the stator 4 is energized, the rotor 5 is rotated by the exciting force between the stator 4 and the rotor 5, and the disk hub 3 and the shaft member 2 are rotated.
[0015]
As shown in FIGS. 1 and 2, the bearing unit 1 includes a shaft member 2, a so-called bag-shaped housing 6 having a bottomed cylindrical shape, and a thick-walled cylindrical bearing member 7 fixed to the inner peripheral surface of the housing 6. And a seal member 8 such as a seal washer that seals one end side of the bearing member 7 (referring to the opening side of the housing 6). The shaft member 2 includes a shaft 2a and a flange portion 2b provided at the lower end portion of the shaft 2a. The shaft 2a is formed on the inner peripheral portion of the bearing member 7, and the flange portion 2b is formed on the bearing member 7 and the bottom portion of the housing 6. It is accommodated and arranged between.
[0016]
The bearing member 7 is made of a soft metal such as copper or brass, for example. A radial bearing surface 10a having a dynamic pressure groove is formed on the inner peripheral surface of the bearing member 7, and from this, when the shaft member 2 and the bearing member 7 are rotated relative to each other (when the shaft member 2 is rotated in this embodiment). A dynamic pressure is generated in the radial bearing gap Cr between the radial bearing surface 10a and the outer peripheral surface of the shaft 2a, and the radial bearing portion 10 is configured to support the shaft 2a in a non-contact manner in the radial direction. Note that the width of the radial bearing gap Cr in the drawing is exaggerated (the same applies to thrust bearing gaps Cs1 and Cs2 described later).
[0017]
The bearing member 7 can be formed not only from a soft metal or the like but also from a sintered metal, for example. In this case, the dynamic pressure groove is compression-molded, that is, an uneven groove shape corresponding to the dynamic pressure groove shape of the radial bearing surface 10a (see FIG. 3A) is formed on the outer peripheral surface of the core rod, and the outer periphery of the core rod is formed. By supplying the sintered metal, pressing the sintered metal, and transferring the dynamic pressure groove corresponding to the groove shape to the inner peripheral portion of the sintered metal, it is possible to form at low cost and with high accuracy. In this case, demolding of the sintered metal can be easily performed using a spring back of the sintered metal by releasing the pressing force. Thus, when using a sintered metal as a raw material of the bearing member 7, it can be used as a hydrodynamic oil-impregnated bearing in which the bearing member 7 is impregnated with lubricating oil or lubricating grease.
[0018]
Thrust bearing gaps Cs1, Cs2, which are axial gaps, are provided on both axial sides of the flange portion 2b. The thrust bearing gap Cs1 is formed between the upper end surface 2b1 of the flange portion 2b and the end surface of the bearing member 7 facing this, and the other thrust bearing gap Cs2 is opposed to the lower end surface 2b2 of the flange portion 2b. It is formed between the upper surface of the thrust support part 13 to be performed. This embodiment illustrates a structure in which the thrust support portion 13 is formed integrally with the housing 6, and the thrust support portion 13 is a bottom portion that seals the other end opening of the housing 6. Thrust bearing surfaces 11a and 11b having dynamic pressure grooves are formed on the lower end surface of the bearing member 7 facing one thrust bearing gap Cs1 and the upper surface of the thrust support portion 13 facing the other thrust bearing gap Cs2. Further, during the rotation, dynamic pressure is generated in the thrust bearing gaps Cs1 and Cs2, and the thrust bearing portion 11 is configured to support the flange portion 2b in a non-contact manner from both sides in the thrust direction.
[0019]
The dynamic pressure groove shape of the radial bearing surface 10a and the thrust bearing surfaces 11a, 11b can be arbitrarily selected, and any one of known herringbone type, spiral type, step type, multi-arc type, etc. is selected, Or these can be used combining suitably. FIG. 3 shows a herringbone type as an example of the dynamic pressure groove shape. FIG. 3A shows a radial bearing surface 10a, and FIG. 3B shows a thrust bearing surface 11b provided on the thrust support portion 13. FIG. Indicates. As shown in the figure, the radial bearing surface 10a has a first groove region m1 in which a dynamic pressure groove 14 inclined on one side is formed, and a dynamic pressure which is axially separated from the first groove region m1 and inclined on the other side. A second groove region m2 in which the grooves 14 are arranged, and an annular smooth portion n positioned between the two groove regions m1 and m2, and a back portion 15 between the smooth portion n and the dynamic pressure groove 13; Are at the same level. The dynamic pressure groove 16 of the thrust bearing surface 11b has a substantially V shape having a bent portion at a substantially central portion in the radial direction.
[0020]
In the bearing unit 1, the shaft member 2 is inserted into the housing 6 with the flange portion 2b facing down, and the inner periphery of the housing 6 is formed so that thrust bearing gaps Cs1 and Cs2 having a predetermined width (about 10 to 20 μm) are formed. The bearing member 7 is assembled by press-fitting or bonding to a predetermined position of the part. Then, the bearing unit 1 is press-fitted or bonded to the cylindrical inner peripheral portion of the casing 9, and an assembly (motor rotor) including the rotor 5 and the disk hub 3 is press-fitted to the upper end of the shaft 2a, whereby the spindle shown in FIG. The motor is assembled.
[0021]
In the present invention, the shaft 2a and the flange portion 2b of the shaft member 2 are integrally formed by, for example, forging or machining. If the shaft member 2 has an integral structure in this way, the accuracy of the perpendicularity between the shaft 2a and the flange portion 2b can be easily increased, and the perpendicularity can be measured before assembly into the bearing unit. Accuracy measurement and confirmation can be performed easily. In addition, since the motor rotor can be mounted last, lubrication to the bearing unit 1 is facilitated, and further, handling as a spindle unit is possible, and an advantage of easy handling can be obtained. The shaft member 2 can also be manufactured by integrating the shaft 2a and the flange portion 2b by welding and then finishing to a predetermined accuracy.
[0022]
As described above, since the motor rotor is press-fitted into the shaft 2a, it is desirable that the shaft member 2 is formed of a high-hardness iron-based material. On the other hand, in the case of ferrous materials, it becomes difficult to form dynamic pressure grooves on the end face of the flange portion 2b by plastic working or machining as in the conventional case, so that the processing cost increases. This type of problem can be solved if the pressure groove is provided not on the flange portion 2b but on the end face of the bearing member 7 or the thrust support portion 13. That is, the bearing member 7 and the thrust support portion 13 can be formed of a soft metal or a sintered metal (a material that can be easily plastically processed or machined), and the processing cost can be reduced. For example, the thrust bearing surfaces 11a and 11b with the dynamic pressure grooves 16 may be formed by pressing or the like when using a soft metal, or by compression molding similar to the radial bearing surface 10a when using a sintered metal. it can. When the processing cost is not particularly problematic, the thrust bearing surfaces 11a and 11b can be formed on both end surfaces of the flange portion 2b.
[0023]
FIG. 4 shows another embodiment of the present invention. The bearing unit 1 corresponds to the configuration shown in FIG. 5, and the housing 6 and the bearing member 7 of FIG. 1 are integrated into a single bearing member 7 ′, and the bottom opening of the bearing member 7 ′ is a separate member. A structure sealed with a thrust support portion 13 (for example, a back metal 33 similar to the conventional one) is shown. Other substantial configurations are the same as those in FIGS. 1 to 3. Also in this case, the shaft member 2 has an integral structure, and the thrust bearing surfaces 11a and 11b can be provided on the end surface of the bearing member 7 ′ and the thrust support portion 13, respectively.
[0024]
【The invention's effect】
Thus, in the present invention, since the shaft member has an integral structure, the accuracy such as the perpendicularity between the shaft and the flange portion can be easily increased, and the accuracy can be easily measured and confirmed. Therefore, a highly accurate and inexpensive bearing unit suitable for a spindle motor for information equipment can be provided.
[0025]
Further, if the dynamic pressure groove of the thrust bearing portion is provided in one or both of the bearing member and the thrust support portion, even when the shaft member is formed of a hard material such as iron, the bearing member and the thrust By forming the support portion with a soft metal, a sintered metal, or the like that easily processes the dynamic pressure groove, the processing cost of the thrust bearing surface can be reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view of a spindle motor for information equipment having a hydrodynamic bearing unit according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a main part of FIG.
3A is a sectional view of a bearing member, and FIG. 3B is a plan view of a thrust bearing portion. FIG. 4 is a sectional view showing another embodiment of the present invention.
FIG. 5 is a cross-sectional view of a conventional spindle motor for information equipment.
[Explanation of symbols]
1 Hydrodynamic bearing unit 2 Shaft member
2a axis
2b Flange 7 Bearing member 7 'Bearing member 8 Seal member
10 Radial bearing
10a Radial bearing surface
11 Thrust bearing
11a Thrust bearing surface
11b Thrust bearing surface
13 Thrust support
14 Dynamic pressure groove
16 Dynamic pressure groove Cr Radial bearing clearance Cs1 Thrust bearing clearance Cs2 Thrust bearing clearance

Claims (6)

A housing, a shaft member including a shaft and a flange, a bearing member fixed to the inner peripheral surface of the housing, and a radial bearing gap between the outer peripheral surface of the shaft and the inner peripheral surface of the bearing member facing the shaft has a radial bearing portion for supporting the shaft member in a radial direction, with two thrust bearing gap on either side of the flange portion, and a thrust bearing portion for supporting the flange portion of the shaft member in the thrust direction, the radial bearing portion and In which the thrust bearing part supports the shaft member in a non-contact manner by dynamic pressure action,
One end of the housing is opened, the other end is sealed by a thrust support portion, the inner peripheral surface of the housing has a cylindrical surface shape without a step, the flange portion is provided at one end of the shaft, and one end surface of the flange portion And one end of the thrust bearing portion between the other end surface of the flange portion and the end surface of the thrust support portion. A hydrodynamic bearing unit comprising a gap and a shaft and a flange formed integrally. The dynamic pressure type bearing unit according to claim 1 , wherein the dynamic pressure groove of the thrust bearing portion is provided in the bearing member. The hydrodynamic bearing unit according to claim 1 or 2, wherein a dynamic pressure groove of the thrust bearing portion is provided in the thrust support portion. Hydrodynamic type bearing unit of claims 1 to 3, wherein any sealing the one end of the bearing member in the sealing member.   The hydrodynamic bearing unit according to claim 1, wherein the shaft and the flange portion of the shaft member are integrally formed by forging.   The hydrodynamic bearing unit according to claim 1, wherein the shaft and the flange portion of the shaft member are integrated by welding.

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