Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-04-01
2001-08-14
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C384S132000
Reexamination Certificate
active
06274958
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spindle motor which is used to rotate an optical disc such as a compact disc (CD), a CD-ROM or the like.
2. Description of the Prior Art
FIG. 1
is a side view showing a conventional type of spindle motor as described above. In
FIG. 1
, a spindle motor
1
comprises a stator portion
2
which is fixedly disposed, and a rotor portion
3
which is supported so as to be rotatable relatively to the stator portion
2
.
The stator portion
2
includes a stator board
2
a
, a bearing holder
2
b
secured to the stator board
2
a
, a wound coil
2
c
which is fixedly disposed so as to surround the bearing holder
2
b
in the peripheral direction, and a bearing
2
d
which is held in the bearing holder
2
b
by press-fitting or the like. The bearing
2
d
is formed as an oil-impregnation plain (sliding) bearing by metal sintering, for example, and lubricating oil is impregnated in pores
2
e
(
FIG. 2
) which occur in the sintering process.
Further, the rotor portion
3
includes a rotating shaft
3
a
which is rotatably supported by a bearing
2
d,
a cylindrical rotor yoke
3
b
which is opened at the lower end thereof and fixed to the rotating shaft
3
a
so as to surround the wound coil
2
c
from the outside, a rotor magnet
3
c
disposed on the inner surface of the rotor yoke
3
b
, a substantially disc-shaped turn table
3
d
which is fixed in the neighborhood of the upper end of the rotating shaft
2
. In this case, the lower portion of the rotating shaft
3
a
is supported by a thrust pad
4
in the bearing
2
d,
whereby the rotating shaft
3
a
is prevented from falling down.
According to the spindle motor
1
thus constructed, an optical disc (not shown) is disposed on the turn table
3
d
, and the magnetic field which is generated in the wound coil
2
c
by suitably supplying current to the wound coil
2
c
interacts with the magnetic field due to the rotor magnet
3
c
and the rotor yoke
3
b
of the rotor portion
3
, whereby the rotor portion
3
is rotated. At this time, when following the rotation of the rotor portion
3
, the rotating shaft
3
a
is rotated in the bearing
2
d
, the lubricating oil impregnated in the bearing
2
d
seeps into a slight gap between the rotating shaft
3
a
and the bearing
2
d
to form oil membrane between the rotating shaft
3
a
and the bearing
2
d
, so that the rotating shaft
3
a
is smoothly rotatable in the bearing
2
d.
However, in the spindle motor
1
thus constructed, upon following the rotation of the rotating shaft
3
a,
the lubricating oil
2
f
seeping into the gap between the rotating shaft
3
a
and the bearing
2
d
may be moved along the rotor yoke
3
b
by a centrifugal force occurring due to the rotation of the rotating shaft
3
a
as indicated by an arrow A of
FIG. 2
, so that the lubricating oil is finally scattered to the outside. Therefore, the amount of the lubricating oil in the gap between the rotating shaft
3
a
and the bearing
2
d
is reduced, and thus an oil membrane which enables the smooth rotational motion of the rotating shaft
3
a
cannot be formed. In this case, there occurs a problem that the rotating shaft
3
a
is baked and bonded to the bearing
2
d
, so that the rotor portion
3
is not normally rotated and thus the lifetime of the spindle motor
1
is reduced.
SUMMARY OF THE INVENTION
In view of the foregoing problem, an object of the present invention is to provide a spindle motor which can prevent scattering of lubricating oil with a simple construction to greatly lengthen the lifetime of the spindle motor.
In order to attain the above object, according to a first aspect of the present invention, a spindle motor according to the present invention includes a stator portion having a plain bearing, a rotor portion which has a rotating shaft and is rotatably supported by said plain bearing, and a plate which is provided on at least one end face of the plain bearing and adapted to prevent leakage of lubricating oil to the outside due to rotation of the rotor portion.
In on order to attain the above object, according to a second aspect of the present invention, a spindle motor comprises: a stator portion including a stator board which is fixedly disposed, a plain bearing which is secured onto the stator board, and a wound coil disposed around the plain bearing; a rotor portion including a rotating shaft which is rotatably supported by the plain bearing, a rotor yoke which is integrally fixed to the rotating shaft, and a rotor magnet provided to the rotor yoke; and a plate which is provided on at least one end face of the plain bearing and adapted to prevent leakage of lubricating oil to the outside due to rotation of the rotor portion.
According to the spindle motor thus constructed, since at least one end face of the plain bearing is closed by the plate, the lubricating oil which seeps from the inside of the plain bearing into the gap between the rotating shaft and the plain bearing can be prevented from being scattered to the outside due to the rotation of the rotating shaft. Accordingly, the oil membrane can be surely formed between the plain bearing and the rotating shaft, so that the smooth rotational motion of the rotating shaft can be ensured. Therefore, the rotating shaft can be surely prevented from being baked and bonded to the plain bearing, so that the lifetime of the spindle motor can be remarkably lengthened.
Further, since the plain bearing is held in the hollow cylindrical bearing holder which is fixed to the stator board and also the scattering of the lubricating oil from both the end faces of the plain bearing is prevented when the plate for preventing the scattering of the lubricating oil is resigned so as to close the end face of the plain bearing in an area between the bearing holder and the rotating shaft, the lifetime of the spindle motor can be further lengthened.
REFERENCES:
patent: 4737673 (1988-04-01), Wrobel
patent: 5325006 (1994-06-01), Uno et al.
patent: 5396134 (1995-03-01), Mochizuki
patent: 5403098 (1995-04-01), Yasui et al.
patent: 5469008 (1995-11-01), Nakajima et al.
patent: 5528092 (1996-06-01), Ohta
patent: 5540504 (1996-07-01), Cordova et al.
patent: 5610462 (1997-03-01), Takahashi
patent: 5715116 (1998-02-01), Moritan et al.
patent: 5791784 (1998-08-01), Ichiyama
patent: 5822846 (1998-10-01), Moritan et al.
patent: 5883455 (1999-03-01), Fukasawa et al.
Kobayashi Yukihiro
Watanabe Toshiaki
Bell Boyd & Lloyd LLC
Dinh Le Dang
Ramirez Nestor
Sony Corporation
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