Spindle motor

Details Spindle motor Spindle motor

1999-12-23

2001-08-07

Ponomarenko, Nicholas (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C384S107000, C384S113000

Reexamination Certificate

active

06271612

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spindle motor for information equipment and audio and visual equipment, and more particularly to a spindle motor which excels in durability and reliability and is optimally suited to a laser printer, a scanner motor for a digital copying machine, a magnetic hard disk drive (hereafter abbreviated as the HDD), an optical disk drive, and the like.
2. Description of the Related Art
As a conventional spindle motor of this type, a spindle motor for a HDD, such as the one shown in
FIG. 11
, is known. In this spindle motor, a sleeve
2
is secured to a base
1
, a shaft
3
is rotatably inserted in the sleeve
2
, and a hub
4
is integrally attached to this shaft
3
.
A lower end face of the shaft
3
is formed as a thrust receiving surface
3
s
, a thrust plate
6
having a thrust bearing surface
6
s
opposing this thrust receiving surface
3
s
is secured to the base
1
, and a dynamic-pressure generating groove
7
of, for example, a spiral shape is provided in at least one of the thrust receiving surface
3
s
and the thrust bearing surface
6
s
, thereby forming a thrust fluid bearing S.
Meanwhile, a pair of radial receiving surfaces
3
r
are formed on an outer peripheral surface of the shaft
3
at upper and lower positions with an axial interval therebetween, while a pair of radial bearing surfaces
2
r
opposing the radial receiving surfaces
3
r
are formed on an inner peripheral surface of the sleeve
2
, and a pair of dynamic-pressure generating grooves
8
of, for example, a herringbone-shape are provided in at least one of the radial receiving surfaces
3
r
and the radial bearing surfaces
2
r
, thereby forming a radial fluid bearing R.
The shaft
3
and the hub
4
are integrally driven rotatively by a motor M comprised of a stator
9
fixed to an outer periphery of the base
1
and a rotor magnet
10
fixed to an inside-diameter surface of the hub
4
.
When the shaft
3
rotates, dynamic pressure is generated in a lubricant in each bearing clearance by means of the pumping action of the respective dynamic-pressure generating grooves
7
and
8
of the thrust fluid bearing S and the radial fluid bearing R, so that the shaft
3
is supported in a state of noncontact with the sleeve
2
and the thrust plate
6
.
However, with the spindle motor in which the thrust fluid bearing S and the radial fluid bearing R are thus adopted as its bearings, if the spindle motor is used over extended periods of time, the lubricant held in the bearing clearances gradually decreases due to its evaporation and scattering during rotation. As a result, lubrication becomes faulty, so that if an attempt is made to use the spindle motor beyond the service life of the bearings, there has been the risk that the bearings become seized.
In addition, at the time of assembling by inserting the shaft
3
into the sleeve
2
, the shaft
3
is inserted after a predetermined amount of lubricant is poured in advance onto a closed cylindrical surface in the space surrounded by the inner peripheral surface of the sleeve
2
and the thrust plate
6
. For this reason, there has been a problem in that air is liable to become contained, and slight bubbles are liable to remain in the bearing clearances. The remaining bubbles can possibly cause the lubricant in the bearing clearances to be extruded to the outside as the bubbles expand due to a change in the atmospheric pressure which can occur when the assembled spindle motor product is transported by such as an airplane or due to a temperature rise during the rotation of the spindle motor in use.
SUMMARY OF THE INVENTION
The present invention has been devised by taking note of the above-described unresolved problems of the conventional art, and its object is to provide a spindle motor excelling in durability and reliability by providing a lubricant reservoir having the function whereby the bearing clearances are reliably replenished with the lubricant to compensate for the decrease of the lubricant and the remaining bubbles in the lubricant can be easily discharged.
To attain the above object, in accordance with the present invention, there is provided a spindle motor in which a shaft and a sleeve are opposed to each other via a bearing clearance of a radial fluid bearing and are relatively driven rotatively, so that a lubricant reservoir having one end communicating with the bearing clearance and another end communicating with the outside is provided on an outer peripheral side of the sleeve whose inner periphery opposes the shaft, and that a clearance of the lubricant reservoir on a side which communicates with the bearing clearance is set to a size exhibiting capillarity.
Here, the lubricant reservoir may be provided with a tapered surface formed on at least one of the mutually opposing inner wall surfaces in such a manner as to allow its clearance to become gradually narrower toward the bearing clearance.
In addition, that side of the lubricant reservoir which communicates with the bearing clearance may be open between the radial fluid bearing and a thrust bearing.


REFERENCES:
patent: 4795275 (1989-01-01), Titcomb et al.
patent: 5524728 (1996-06-01), Williams et al.
patent: 5533811 (1996-07-01), Polch et al.
patent: 5658080 (1997-08-01), Ichiyama
patent: 5707154 (1998-01-01), Ichiyama
patent: 5791784 (1998-08-01), Ichiyama
patent: 5941644 (1999-08-01), Takahashi
patent: 2509752 (1996-04-01), None
patent: 8-277835 (1996-10-01), None
patent: 8-340657 (1996-12-01), None
patent: 10-213127 (1998-08-01), None
patent: 11-2235 (1999-01-01), None

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