Shaft bearing structure of spindle motor

Details Shaft bearing structure of spindle motor Shaft bearing structure of spindle motor

2002-10-04

2004-04-06

Footland, Lenard A. (Department: 3682)

Bearings

Rotary bearing

Plain bearing

Reexamination Certificate

active

06715921

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shaft bearing structure of spindle motor capable for a laser beam printer (hereinafter referred to as LBP) or an optical disc drive.
2. Description of the Related Art
A laser beam printer (hereinafter referred to as LBP) is capable of high speed printing, so that the use of such an LBP is increasing especially in business field.
As the recent LBP complies with color printing, a spindle motor for LBP is required to stably rotate in high speed. In other words, the spindle motor for LBP is required to have a shaft bearing which provides stable rotation in high speed.
FIG. 1
is a diagram for explaining a structure and operation of a LBP. In
FIG. 1
, a LBP “A” is composed of a semiconductor laser driver
100
controlled by an external equipment (such as a computer)
101
through a controller
102
and a DC controller
103
, a scanner motor driver
104
controlled by the DC controller
103
, a cylindrical lens
105
to pass a laser beam emitted from a semiconductor laser controlled by the semiconductor laser driver
100
, a polygon mirror
106
attached to a spindle motor (not shown) of which rotation is controlled by the motor driver
104
by the controller
103
to reflect the laser beam emitted through the cylindrical lens
105
, a spherical lens
107
and a toric lens
108
for spreading the laser beam onto a photosensitive unit
109
for printing information onto a sheet of paper not shown, a horizontal synchronizing mirror
110
and a BD lens
111
for monitoring the laser beam through an optical fiber
112
for feedback control.
The polygon mirror
106
has four to six sides and is maintained at the rotational velocity of 20,000 to 30,000 rpm. As the polygon mirror
106
reflects the laser beam onto the photosensitive unit
109
, a slight inclination of the polygon mirror
106
(which may be caused by wobbling of rotational axis of the spindle shaft) may not reflect the laser beam properly on the photosensitive unit
109
for scanning.
In this sense, the spindle motor for rotating the polygon mirror
106
should rotate very fast and stable in high-degree of accuracy.
However, the spindle motor used for the LBP has a problem of leakage of lubricating oil in the rotational shaft as it rotate very fast in high revolution. The leakage of lubricating oil of the spindle motor may affect the duration of the motor. Further, the leakage of lubricating oil may damage the inside mechanism of the LBP or spoil the printing paper.
FIG. 2
is a cross sectional view of half-side of a spindle motor. The cross sectional view of the spindle motor is symmetry to the half-side view. The spindle motor is basically composed of a rotor
201
and a stator
202
. The rotor
201
has a bush
203
pressed to a spindle shaft
204
and fixed with the polygon mirror
106
. The rotor
201
is attached to the spindle shaft
204
and the spindle shaft
204
is rotationally attached to the stator
202
by a shaft bearing
205
and a bearing holder
206
.
FIG. 3
is a cross sectional enlarged view of inside portion of the surrounding of the spindle shaft
204
and the bush
203
and the bearing holder
206
and the shaft bearing
205
. In
FIG. 3
, a hydraulic pressure
31
presses lubricating oil
30
by the rotation of the spindle shaft
204
and the lubricating oil
30
moves along the surface of the spindle shaft
204
and comes out on the surface of the bush
203
. Then the lubricating oil
30
leaks out from a gap portion
32
formed between the bearing holder
206
and the bush
203
.
The height of the spindle motor may be shortened by mechanical design of an LBP, which makes the gap portion
32
narrower. In the case that the gap portion becomes narrower, the lubricating oil
30
tends to leak out even more.
SUMMARY OF THE INVENTION
Accordingly, in consideration of the above mentioned problems of the related art, an object of the present invention is to provide a shaft bearing structure of spindle motor, including, a rotor rotationally attached to a shaft bearing and a bearing holder fixed on a motor base of a stator, wherein the rotor is fixed with a spindle shaft and confronted with the stator, and the shaft bearing structure is characterized in that an oil cycle material (
40
,
41
) retains and re-flows lubricating oil circulating around the spindle shaft in the shaft bearing, wherein the oil cycle material (
40
,
41
) is placed in the gap between the inner circumference of the bearing holder and the periphery of the spindle shaft, and placed at least contiguous to one edge of the shaft bearing in axial direction of the spindle shaft.
Other object and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.


REFERENCES:
patent: 04-107313 (1992-04-01), None
patent: 10-184665 (1998-07-01), None
patent: 3029121 (2000-02-01), None

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