Bearings – Rotary bearing – Fluid bearing
Reexamination Certificate
2002-06-25
2004-01-06
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Fluid bearing
Reexamination Certificate
active
06672767
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a dynamic bearing device and a motor having the same. This bearing device can be appropriately applied in a spindle motor of an information-processing equipment such as a magnetic disk device (e.g., HDD or FDD), an optical disk device (e.g., CD-ROM or DVD-ROM), an optical magnetic device (e.g., MD or MO), a polygon scanner motor of a laser beam printer (LBP), or a small-sized motor of an electric equipment (e.g., an axial flow fan).
Heretofore, each of the motors described above has been in need of improvements on speeding up and noise-reduction of its rotary motion, cost-reduction in its production, and so on in addition to providing a rotary motion thereof with a high degree of precision. One of the structural factors that define these required performances is a bearing that supports a spindle of the motor. In recent years, for such a kind of the bearing, the usage of a dynamic bearing having excellent features for the above required performances has been considered or actually used in the art.
For instance, a dynamic bearing device to be incorporated in a spindle motor of a disk device such as a hard disk drive (HDD) includes a radial bearing part that makes a non-contact support of an shaft member in a rotatable manner in the radial direction and a thrust bearing part that makes a non-contact support of an shaft member in the thrust direction. The dynamic bearing device utilizes a dynamic bearing as each of these bearing parts. The dynamic bearing has grooves for generating dynamic pressure in the bearing surface. Hereinafter, such grooves will be referred to as dynamic pressure generating grooves. The dynamic pressure generating grooves of the radial bearing part are formed in the inner peripheral surface of a housing or a bearing member, or the outer peripheral surface of a shaft member. When an shaft member having a flange part is used, the dynamic pressure generating grooves of the thrust bearing part are formed in both surfaces of the flange part or the surfaces facing to the respective surfaces (e.g., the end surface of the bearing member and the bottom surface of the housing).
As the above dynamic bearing device, the present applicant has already proposed the constitution of a dynamic bearing device
1
′ shown in
FIG. 7
as disclosed in Japanese Patent Application No. 2001-114317.
In
FIG. 7
, the dynamic bearing device
1
′ mainly includes a bottomed cylindrical housing
7
′ with an opening
7
a
′ formed in its top end, an shaft member
2
′ and a bearing member
8
′ which are housed in the housing
7
′, and a sealing member
10
, arranged on the opening
7
a
′ of the housing
7
′.
More concretely, the housing
7
′ includes a cylindrical side portion
7
b
′ and a bottom part
7
c
′. Furthermore, the bottom part
7
c
′ has an inner bottom surface
7
c
1
′. In the area of the bottom surface
7
c
1
′ which serves as a thrust bearing surface, as shown in
FIG. 8B
, herringbone-shaped dynamic pressure generating grooves
7
c
2
′ are formed.
Furthermore, the bearing member
8
′ is constructed of a porous material made of sintered metal. Herringbone-shaped dynamic pressure generating grooves
8
a
1
′ and
8
a
2
′ as shown by the dotted lines in
FIG. 7
are formed in the upper and lower areas which serve as radial bearing surfaces, respectively. These upper and lower areas are separated in the axial direction such that an area
8
a
3
′ having no dynamic pressure generating groove is arranged between the upper and lower areas. Furthermore, in an area, which serves as a thrust bearing surface, of the lower end surface
8
b
′ of the bearing member
8
′, herringbone-shaped dynamic pressure generating grooves
8
b
1
′ shown in
FIG. 8A
are formed.
The shaft member
2
′ includes an axial part
2
a
′ and a flange part
2
b
′. The flange part
2
b′ is integrally or separately formed on the axial part
2
a′.
The axial part
2
a
′ of the shaft member
2
′ is inserted in the inner peripheral surface
8
a
′ of the bearing member
8
′. The flange part
2
b
′ is received in a space between the lower end surface
8
b
′ of the bearing member
8
′ and the inner bottom surface
7
c
1
′ of the housing
7
′. Predetermined Radial bearing gaps are formed between the upper and lower areas of the inner peripheral surface
8
a
′ of the bearing member
8
′ which serves as radial bearing surfaces and the outer peripheral surface
2
a
1
′ of the axial part
2
a
′, respectively. Predetermined thrust bearing gaps are formed between the area of the lower end surface
8
b
′ of the bearing member
8
′ which serves as the thrust bearing surface and the upper surface
2
b
1
′ of the flange part
2
b
′, and between the area of the inner bottom surface
7
c
1
′ of the housing
7
′ which serves as the thrust bearing surface Sand the lower surface
2
b
2
′ of the flange part
2
b
′.
The inner space of the housing
7
′ being sealed with a sealing member
10
′, including pores of the bearing member
8
′, is filled with a lubricating oil.
When the shaft member
2
′ rotates, a dynamic pressure action of the lubricating oil is generated in the radial bearing gaps, so that the axial part
2
a
′ of the shaft member
2
′ is rotatably supported in the radial direction in a non-contact manner by the oil film of the lubricating oil formed in the radial bearing gaps. Thus, the radial bearing parts R
1
′ and R
2
′ which rotatably support the axial part
2
a
′ in the radial direction in a non-contact manner are constituted. Simultaneously, a dynamic pressure action is generated in the thrust bearing gaps, so that the flange part
2
b
′ of the shaft member
2
′ is rotatably supported in the thrust directions in a non-contact manner by the oil film of the lubricating oil formed in the thrust bearing gaps. Thus, the thrust bearing parts S
1
′ and S
2
′ which rotatably support the flange part
2
b
′ in the thrust directions in a non-contact manner are constituted.
In the dynamic bearing device
1
′ constituted as above, the dynamic pressure generating grooves
8
a
′ and
8
a
2
′ of the radial bearing parts R
1
′ and R
2
′ have their respective herringbone shapes which are symmetric with respect to the axial direction. Therefore, in the radial bearing part R
1
′, the lubricating oil drawn from the both sides in the axial direction by the dynamic pressure generation grooves
8
a
′ keeps its pressure balance at a position in proximity to the axial groove center of the dynamic pressure generating grooves
8
a
1
. Likewise, in the radial bearing part R
2
′, the lubricating oil drawn from the both sides in the axial direction by the dynamic pressure generating groove
8
a
2
′ keeps its pressure balance at a position in proximity to the axial groove center of the dynamic pressure generating grooves
8
a
2
′. At this time, since the radial bearing surface of each of the radial bearing parts R
1
′ and R
2
′ has a plurality of surface openings, which are formed by the pores of the bearing member
8
′ opening to the surface, in the radial bearing gap, where the pressure of the lubricating oil increases, the lubricating oil is returned from the radial bearing gap into the inside of the bearing. In addition, since there is a drawing action of each of the dynamic pressure generating grooves
8
a
1
′ and
8
a
2
′, in the peripheral area of the radial bearing gap, the lubricating oil is supplied from the inside of the bearing into the radial bearing gap. The above pressure balance can be kept while being accompanied with such a circulation of the lubricating oil. However, there is a case that the dynamic pressure generati
Hajota Kimihiko
Itsusaki Hironori
Mori Natsuhiko
Nakazeki Tsugito
Arent Fox Kintner Plotkin & Kahn
Footland Lenard A.
Nidec Corporation
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