Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-02-26
2004-07-20
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C384S112000, C384S115000
Reexamination Certificate
active
06765326
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a motor having a hydrodynamic bearing, and more particularly to a cooling device using the motor for efficiently cooling e.g. semiconductor devices.
BACKGROUND OF THE INVENTION
FIG. 7
is a cross section depicting a structure of a conventional cooling device employing a motor having a hydrodynamic bearing.
FIG. 8
is a cross section of a motor-bearing employed in the cooling device of FIG.
7
.
A structure of the prior art is described hereinafter with reference to FIG.
7
and FIG.
8
.
Housing
141
having one open side and a cup-shape is protrusively formed on a recess of frame
101
. Housing
141
secures stator
103
on its outer wall, and stator
103
is wound with coil
102
. Driving circuit substrate
104
is disposed around housing
141
. Substrate
104
holds stator
103
and connects electrically a terminal of coil
102
to a wiring formed on substrate
104
by soldering. Substrate
104
is equipped with electronic components constituting the driving circuit and Hall elements. Insulating sheet
120
is disposed between substrate
104
and frame
101
.
Frame
101
is surrounded by a side wall and has an upward opening. Bell-mouth
119
is disposed around the opening to promote airflow. Housing
141
fixedly secures thrust plate
106
and thrust sheet
107
on its bottom face. Sleeve
105
is fit into housing
141
. Stator unit
115
comprises these elements discussed above, i.e. frame
101
, housing
141
, sleeve
105
, coil
102
and stator
103
.
Rotary shaft
109
extends through sleeve
105
and is axially supported by thrust plate
106
as well as rotatably supported by sleeve
105
. Fan
108
is mounted to shaft
109
. Washer
110
fixed on shaft
109
prevents fan
108
from coming off from sleeve
105
. Magnet
111
is bonded to fan
108
via magnet yoke
112
so that magnet
111
faces stator
103
. Rotor
116
comprises the elements discussed above, i.e. magnet
111
, yoke
112
and fan
108
.
The bearing of the motor is detailed hereinafter with reference to FIG.
8
.
In
FIG. 8
, sleeve
105
is equipped with oil reservoir
147
in the center portion of its inner wall. Oil reservoir
147
has a greater inner diameter than other parts of the inner wall of sleeve
105
. Sleeve
105
has dynamic-pressure-generating grooves
113
. Grooves
113
are formed by a ball-rolling-process. Oil
114
is provided to grooves
113
as lubricant for sleeve
105
and shaft
109
. Radial bearing
117
is thus formed as discussed above.
The tip of shaft
109
facing thrust plate
106
is finished into a spherical face that contacts thrust sheet
107
so that thrust plate
106
and thrust sheet
107
support shaft
109
axially. Thrust bearing
118
is thus structured as discussed above.
The conventional motor employing this hydrodynamic bearing, however, has the following problems.
In recent years, electronics apparatuses have been obliged to generate a greater amount of heat in order to satisfy market demands such as higher performance as well as down sizing. This situation forces the cooling devices and the cooling-fan-motors of those apparatuses to encounter greater changes in temperatures, and requires them to increase their cooling performance.
In the conventional motor, first, stopper washer
110
is mounted to shaft
109
in order to prevent fan
108
from coming off from the bearing, then thrust sheet
107
and thrust plate
106
are fixedly press-fitted into frame
101
. Therefore, temperature change cycles produce a gap between thrust plate
106
and frame
101
, and thus oil
114
spills from the gap.
Since thrust plate
106
is independent of frame
101
, the flatness of the bottom face of frame
101
is difficult to improve, which reduces adherence between this cooling device and a heating element
300
. Further, the center portion, which produces a greater amount of heat than other portions of the heating element, or a device attached to this heating device, can not be substantially cooled down.
The cooling device requires a higher rotational speed in order to increase the cooling performance, which also increases centrifugal forces produced by shaft
109
and fan
108
. Oil
114
in the bearing thus flows out along shaft
109
and fan
108
, which entails the outflow of oil
114
from dynamic-pressure-generating groove
113
. This out-flow causes an oil shortage, which lowers the number of rotations and produces locking of rotor
116
.
Further, the downsizing of motors narrows the space for the bearing, miniaturizes the components, and increases the number of components of motors. Thus fabrication of the motor requires more complicated work.
SUMMARY OF THE INVENTION
The present invention addresses the problems discussed above, and aims to provide a motor free from oil-spill from its bearing due to temperature change cycles or motor rotation, and also provides a cooling device using the motor for achieving efficient cooling.
The motor of the present invention comprises the following elements:
(a) a frame having an opening;
(b) a frame-housing provided on the unitary frame and having one side thereof open;
(c) a stator secured on an outer wall of the frame-housing;
(d) a sleeve fit into the frame-housing;
(e) a thrust supporter provided on a unitary bottom face of the frame housing;
(f) a shaft supported by the thrust supporter at the end thereof, inserted into the sleeve, and rotatably supported by the sleeve;
(g) a rotor securing the shaft;
(h) a magnet disposed on the rotor and opposite to the stator; and
(i) oil provided in the space between the shaft and sleeve.
The construction discussed above saves the fitted section of the frame and thrust supporter, because the thrust supporter is unitarily formed with the bottom face of the frame housing. The oil-spill due to the temperature change cycles can thus be avoided, and as a result, the reliability and life-span of the motor can be increased.
The unitary forming of the thrust supporter with the bottom face of the frame-housing can improve the flatness of the bottom face, whereby the adherence between the bottom face and the heating element is improved. The heat conductivity from the heating element to the frame can thus be improved. As a result, the cooling performance of the cooling device can be boosted.
In another motor of the present invention, a rib is formed on the rotor rim within which the shaft is mounted, thereby blocking the oil splashed from the space between the shaft and sleeve. As a result, the oil can be prevented from flowing out from the bearing when the motor is in operation.
The cooling device of the present invention comprises the following elements:
(a) a frame having a first opening on a first face surrounded by a side wall and being mountable with a heating element on a second face;
(b) a frame-housing formed on the frame and having one side thereof open;
(c) a stator secured on an outer wall of the housing;
(d) a sleeve fit into the frame-housing;
(e) a thrust supporter unitarily formed with a bottom face of the frame-housing;
(f) a shaft supported by the thrust supporter at the end of the shaft, inserted into the sleeve, and rotatably supported by the sleeve;
(g) a rotor securing the shaft;
(h) a magnet disposed on the rotor and opposite to the stator;
(i) oil provided in the space between the shaft and sleeve;
(j) second openings provided on the side wall of the frame; and
(k) a fan provided on the rotor.
The construction discussed above saves the fitted section of the frame and thrust supporter, because the thrust supporter is unitarily formed with the bottom face of the frame housing. The oil-spill due to the temperature change cycles can thus be avoided, and as a result, the reliability and life-span of the motor can be increased.
The unitary formation of thrust supporter with the bottom face of frame-housing can improve the flatness of the bottom face, whereby the adherence between the bottom face and the heating element is improved. The heat conductivity from the heating element to the frame can thus be improve
Nakazono Eiichiro
Yamashita Akitomo
Tamai Karl
Wenderoth , Lind & Ponack, L.L.P.
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