Bearings – Rotary bearing – Fluid bearing
Reexamination Certificate
2001-11-29
2003-06-10
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Fluid bearing
C384S112000
Reexamination Certificate
active
06575633
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic bearing motor, and particularly to a hydraulic bearing motor which, even though it is formed thin, can still satisfy features of exhibiting small NRRO, and vibration and shock resistance.
2. Description of the Related Art
In general, a bearing of a mass produced motor has a structure of supporting a motor shaft by using ball bearings. In such a bearing, however, steel balls as ball bearings, being in a state of rotating on a shaft or a support in principle, tend to generate noise. In particular, in an information home appliance mounted with an HDD (hard disk drive) recently becoming denser, a motor for driving the HDD at a higher speed generates larger noise from the bearing to cause a noise problem. Moreover, a bearing using the ball bearing tends to cause a large NRRO (non-resonant rotary oscillation) This causes read/write error in an HDD becoming denser.
Therefore, in recent years, development work is increasing about a bearing known as a hydraulic bearing (or a dynamic pressure bearing) in which oil is used as a lubricant. In the hydraulic bearing, a lubricating oil filling a space between a shaft and a sleeve (a supporter of the shaft) provides a rotation without causing the both to contact with each other. This hardly produces noise in principle with a trace of the rotating shaft being almost round to cause a considerably smaller NRRO compared with that of the bearing with the ball bearings.
FIG.
1
and
FIG. 2
are cross sectional views each showing a principal part of a related hydraulic bearing motor. In
FIG. 1
, there is shown a bearing known as an inverted T type and in
FIG. 2
, there is shown a bearing known as a T type.
The hydraulic bearing motor
300
shown in
FIG. 1
is provided with a hydraulic bearing assembled with the following being taken as prime components, a sleeve (a support)
31
formed with a cylindrical shaft body inserting hole, a frame
32
securing the lower side of the sleeve
31
, a cylindrical shaft body
33
having a cross sectional form of an inverted T and being inserted into a space formed by the shaft body inserting holes the sleeve
31
and the frame
32
, with a clearance being created between the shaft body
33
and inner walls of the sleeve
31
and the frame
32
, a hub
34
securely mounted on an upper portion of the shaft body
33
, and oil
35
filling the above clearance. In addition, the hydraulic bearing motor
300
comprises a core
36
laminated with steel plates disposed on the periphery of the sleeve
31
, a coil
37
wound onto the core
36
, and a magnet
38
mounted on the hub
34
and positioned so as to face the core
36
and the coil
37
the hydraulic bearing motor
300
functions so that a varying magnetic field generated by the core
36
and the coil
37
acts on the magnet
38
to rotate the hub
34
with resulting rotation of the shaft body
33
.
In the hydraulic bearing, when the shaft body
33
is in rotation, a pressure is generated in the oil
35
. The generated pressure keeps the shaft body
33
away from the sleeve
31
side for rotation. The pressure is generated by dynamic pressure generating grooves formed on the surface of the shaft body
33
. The groove is generally known as a herringbone, by which fluid flows therein for being gathered to increase a pressure of the fluid. The fluid with an increased pressure is then made to flow out from the groove to generate a dynamic pressure. The rotated shaft body
33
itself makes the fluid flow in the dynamic pressure generating groove from an entrance side thereof.
The dynamic pressure generating grooves maybe classified into grooves provided on a surface of a radial shaft for gathering the fluid to generate a pressure in the radial direction, and grooves provided on an end face of a thrust shaft for gathering the fluid to generate a pressure in the axial direction of the radial shaft perpendicular to the radial direction. A section of the shaft body inserting hole by which the radial shaft is supported is called as a radial bearing section, and a section of the shaft body inserting hole by which the thrust shaft is supported is called as a thrust bearing section. Here, the thrust bearing section is shown as a region surrounded by the sleeve
31
and the frame
32
. Namely, the radial shaft and the thrust shaft are separately provided on the shaft body
33
with dynamic pressure generating grooves for generating dynamic pressures formed on the respective shafts.
On the radial bearing section side, there is provided a function of supporting the shaft body
33
against whirling and a moment thereof being generated. While, on the thrust bearing section side, there is provided a function of supporting a load (disks) stacked on the hub
34
with the centers of the load and the hub
34
on the same axis.
The hydraulic bearing motor
400
shown in
FIG. 2
is provided with a hydraulic bearing assembled with the following being taken as prime components, a doughnut-like upper plate
40
, a sleeve (a support)
41
formed with a cylindrical shaft body inserting hole having a cross sectional form of inverted T for fitting the upper plate
40
, a frame
42
securing the lower side of the sleeve
41
, a cylindrical shaft body
43
having a cross sectional form of a cruciform shape and being inserted into a space formed by the upper plate
40
, the shaft body inserting hole of the sleeve
41
and the frame
42
with a clearance being created between the shaft body
43
and inner walls of the upper plate
40
, the sleeve
41
and the frame
42
, a hub
44
securely mounted on an upper portion of the shaft body
43
, and oil
45
filling the above clearance. In addition, the hydraulic bearing motor
400
comprises a core
46
laminated with steel plates disposed on the periphery of the sleeve
41
, a coil
47
wound onto the core
46
, and a magnet
48
mounted on the hub
44
and positioned so as to face the core
46
and the coil
47
. The hydraulic bearing motor
400
functions so that a varying magnetic field generated by the core
46
and the coil
47
acts on the magnet
48
to rotate the hub
44
with resulting rotation of the shaft body
43
. Also in the hydraulic bearing motor
400
, a radial shaft and a thrust shaft are separately provided on the shaft body
43
with dynamic pressure generating grooves for generating dynamic pressures formed on the respective shafts.
In recent years, development is being carried out for mounting the HDD not only on a personal computer but also on a portable information device so that the device is to become multimedia equipment. The portable information device as a target of the development, in order to be provided as being lightweight and compact, requires the HDD to be also provided as being lightweight and compact. In particular, for improving portability, it is also required that the hydraulic bearing motor itself is to be made thin.
In the related hydraulic bearing motors, however, the radial shaft and the thrust shaft were designed and manufactured on condition that they are separately provided. This required a radial shaft to have a certain specified length, so that the radial shaft had a limitation in being made thin. Namely, shortened radial shaft becomes incapable of providing a stiffness for suppressing whirling of the radial shaft. Therefore, in the related hydraulic bearing motor, there was a problem in that it is impossible to satisfy features of exhibiting small NRRO, and vibration and shock resistance while satisfying requirement of making the motor thin.
Accordingly, the present invention was made in view of the foregoing with an object of providing a hydraulic bearing motor that can satisfy features of exhibiting small NRRO, and vibration and shock resistance even when being provided as a thin hydraulic bearing motor.
SUMMARY OF THE INVENTION
In order to achieve the above object, the hydraulic bearing motor according to the present invention is characterized by a constitution wherein, in a hydraulic bearing moto
Goto Hiromitsu
Iwamoto Mitsuharu
Kinoshita Shinji
Kumagai Toru
Nakayama Yukihiro
Adams & Wilks
Hannon Thomas R.
Seiko Instruments Inc.
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