Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2002-05-16
2004-12-28
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06700R, C384S100000
Reexamination Certificate
active
06836040
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a spindle motor using a hydraulic bearing, for example, adapted to a large volume disk drive such as a removable hard disk drive, and to a disk drive on which such a spindle motor is mounted.
In disk drives such as removable-hard disk drives (hereinafter, referred to as “R-HDDs”), information has been recorded and/or reproduced by removably mounting an information recording disk such as a hard disk, which has been previously contained in a removable-hard disk cartridge (hereinafter, referred to as “R-HDC”), to a spindle motor, rotating the disk at a high speed by the spindle motor to generate an air flow on a surface of the disk, and flying a flying head slider supported on a leading end of a head actuator via a suspension over a surface of the disk, thereby seeking recording tracks on the disk.
A spindle motor
101
using a hydraulic bearing shown in
FIG. 17
is used for R-HDDs of this type.
The configuration of the spindle motor
101
will be described below. An approximately cruciform hydraulic bearing
103
is formed in an approximately central portion of a motor base
102
. A spindle
104
has a lower end
104
a
and a rotating disk portion
105
fixed to or formed integrally with an outer periphery of an approximately intermediate portion of the spindle
104
in the axial direction. The lower end
104
a
of the spindle
104
and the rotating disk portion
105
are floated in oil
106
that is a fluid previously put to fill the hydraulic bearing
103
. Upper and lower portions of the hydraulic bearing
103
are sealed with an upper plate
107
and a lower plate
108
fixed to upper and lower portions of the motor base
102
, respectively. An inner wall surface
103
a
, on the motor base
102
side, of the hydraulic bearing
103
is separated from each of an outer peripheral surface of the lower end
104
a
and an outer surface of the rotating disk portion
105
with a fine gap put therebetween. The outer peripheral surface of the lower end
104
a
of the spindle
104
has a plurality of annular grooves
109
, and also each of the upper and lower sides of the outer surface of the rotating disk portion
105
has a plurality of annular grooves
110
. Because of the action of a dynamic pressure of the oil
106
caused in these annular grooves
109
and
110
, the spindle
104
and the rotating disk portion
105
are integrally rotated in a state being floated on the oil
106
, that is, in a state being not in contact with the inner wall surface
103
a
of the hydraulic bearing
103
.
A rotor
111
is fixed to a portion, near an upper end
104
b
, of the spindle
104
. A disk table
112
, to which a hard disk or the like is to be exchangeably mounted, is formed on a central portion of the upper end of the rotor
111
. An annular magnet
113
is fixed to an inner periphery of the lower end of the rotor
111
. A stator
116
, which is composed of a stack
114
of silicon steel plates and a plurality of coils
115
wound around the stack
114
, is mounted at a portion between the outer periphery of the hydraulic bearing
103
of the motor base
102
and the inner periphery of the magnet
113
.
A rotational force is generated between the plurality of coils
115
and the magnet
113
by switching the supply of a current to the coils
115
, whereby the rotor
111
is rotated, together with the spindle
104
and the rotating disk portion
105
, with respect to the motor base
102
. The spindle motor
101
having the above configuration functions as a flat brushless motor.
The related art spindle motor
101
using the hydraulic bearing
103
, however, has a disadvantage. In this spindle motor
101
, each of a pair of upper and lower corners of the outer periphery of the rotating disk portion
105
is formed as a sharp edge
105
a
. By the way, a moment stronger than a dynamic pressure caused in the hydraulic bearing
103
is generated due to external vibration/impact and the like applied during operations of recording and/or reproducing information on and/or from a hard disk or the like. Consequently, as shown in
FIG. 18
, when an axis P
2
of the spindle
104
is tilted in the hydraulic bearing
103
with respect to a vertical reference P
1
of the motor base
102
at a specific angle &thgr;
1
, the sharp edges
105
a
of the outer periphery of the rotating disk portion
105
may be often brought into contact with the inner wall surface
103
a
, particularly, of the upper plate
107
of the hydraulic bearing
103
.
The frictional force caused by such contact acts as a braking force against rotation of the rotor
111
, to cause a variation in rotational speed of the rotor
111
, thereby failing to stably record and/or reproduce information on and/or from a hard disk or the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a spindle motor using a hydraulic bearing, which is capable of preventing a variation in rotational speed of the spindle motor as much as possible, which variation is caused by tilting of the axis of the spindle motor due to external vibration/impact and the like, and to provide a disk drive using such a spindle motor.
To achieve the above object, according to a first aspect of the present invention, there is provided a spindle motor including a spindle; a rotating disk portion rotatable integrally with the spindle; and a hydraulic bearing, formed in a motor base, for rotatably supporting the rotating disk portion; wherein an escape portion is provided for preventing the rotating disk portion from being brought into contact with an inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less.
The escape portion is preferably configured as an R-face or a C-face formed at an edge of an outer periphery of the rotating disk portion.
The escape portion is preferably configured as a recess formed in the inner wall surface of the hydraulic bearing at a position facing to an edge of an outer periphery of the rotating disk portion.
A region, to be brought into contact with the inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at an angle more than the specific angle, of the rotating disk portion is preferably formed into a mirror-finished surface having a surface roughness of 0.3 s or less in Ra.
A region, to be brought into contact with the rotating disk portion when the spindle is tilted with respect to the motor base at an angle more than the specific angle, of the inner wall surface of the hydraulic bearing is formed into a mirror-finished surface having a surface roughness of 0.3 s or less in Ra.
To achieve the above object, according to a second aspect of the present invention, there is provided a disk drive including a spindle motor including a spindle, a rotating disk portion rotatable integrally with the spindle, and a hydraulic bearing, formed in a motor base, for rotatably supporting the rotating disk portion, the disk drive being operated to rotate an information recording disk by the spindle motor, thereby recording and/or reproducing information on and/or from the disk by a flying head slider; wherein an escape portion is provided for preventing the rotating disk portion from being brought into contact with an inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less.
To achieve the above object, according to a third aspect of the present invention, there is provided a hydraulic bearing structure including a hydraulic bearing, formed in a motor base, for rotatably supporting a rotating disk portion rotatable integrally with a spindle; wherein an escape portion is provided for preventing the rotating disk portion from being brought into contact with an inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less.
With the configuration of the spindle motor using a hydraulic bearing according to the first aspect of
Mamiya Toshio
Watanabe Minoru
Yamada Takashi
Yamamoto Kazuyuki
Elkassabgi Heba Y.
Kananen Ronald P.
Mullins Burton S.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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