Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-09-01
2001-05-22
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C384S107000
Reexamination Certificate
active
06236129
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a motor having a hydrodynamic bearing, and further relates to a heat sink device using this motor for efficiently cooling, e.g. semiconductor devices.
BACKGROUND OF THE INVENTION
FIG. 4
is a cross section depicting a structure of a conventional heat sink device employing a motor having a hydrodynamic bearing.
FIG. 5
is a cross section of a motor-bearing employed in the heat sink device of FIG.
4
.
A structure of the prior art is described hereinafter with reference to FIG.
4
and FIG.
5
.
Housing
151
having one open side and being cup shaped is protrusively formed on a recess of frame
101
. Housing
151
secures stator
103
on its outer wall, and stator
103
is wound with coil
102
. Driving circuit substrate
104
is disposed around housing
151
. Substrate
104
holds stator
103
and connects electrically a terminal of coil
102
to printed wiring formed on substrate
104
by soldering. Substrate
104
is equipped with electronic components constituting the driving circuit and Hall elements. Insulating sheet
107
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. Thruster
105
made of resin is disposed on a bottom face of housing
151
. Sleeve
106
, is fit into housing
151
. Stator unit
115
comprises these elements discussed above, i.e. frame
101
, housing
151
, sleeve
106
, coil
102
and stator
103
.
Rotary shaft
109
extends through sleeve
106
, and is axially supported by thruster
105
as well as journaled by sleeve
106
. Fan
108
is mounted to shaft
109
. 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.
5
.
In
FIG. 5
, sleeve
106
is equipped with oil reservoir
155
near the center of its inner wall. Oil reservoir
155
has a greater inner diameter than other parts of the inner wall of sleeve
106
. Sleeve
106
has dynamic-pressure-generating-grooves
113
on both sides of oil reservoir
155
. Grooves
113
are formed by a ball-rolling-process, which eventually accompanies burrs on inner wall of sleeve
106
. Thus sizing is further provided to remove the burrs so that an error of the inner diameter of the sleeve is kept to as little as not more than ±2 &mgr;m. Oil
114
is provided as lubricant to grooves
113
for sleeve
106
and shaft
109
. Radial bearing
117
is thus formed as discussed above.
The tip of shaft
109
facing thruster
105
is machined into a spherical face that contacts thruster
105
so that thruster
105
supports shaft
109
axially. Thrust bearing
118
is thus structured as discussed above.
The conventional motor employing this hydrodynamic bearing, however, has the following problems.
Electronic apparatuses including personal computers and electric home appliances have been downsized in recent years, which entails requiring the cooling fan—one of the components of the apparatuses and appliances—to be smaller and slimmer. In order to meet this requirement, the bearing space is narrowed, which forces the outer diameter of rotary shaft
109
and inner diameter of sleeve
106
to be narrowed.
In the prior art, since a bite shank having ca. 2 mm diameter has been used in machining the bearing, oil reservoir
155
can be machined with regard to sleeve
106
having not less than 3 mm inner diameter. However, when sleeve
106
is downsized to have not more than 2 mm inner diameter, the bite shank must have a diameter not more than 1 mm in order to form the oil reservoir. The shank having a diameter not more than 1 mm encounters abnormal vibrations due to the narrowed body when machining the sleeve, and is broken frequently. If the machining speed is slowed down to avoid this breakage, the machining time increases, which boosts the manufacturing cost. Narrowing of the inner diameter of the sleeve has thus been at a standstill from the machining view of point.
If oil reservoir
155
is traded off against narrowing the diameter of sleeve
106
to be not more than 2 mm, the quantity of oil
114
retained within the bearing decreases so that the lubricating quantity should be as little as not more than 0.0005 ml. Constant lubrication by such a small amount is hardly possible, and surplus oil would travel on shaft
109
as well as fan
108
and flow out. The flow-out oil would be scattered around the motor. Not only surplus oil, but also necessary oil, would follow the flow-out oil little by little, which lowers the reliability of the bearing.
Further, apparatuses and appliances which are equipped with more functions and have undergone the downsizing process are obliged to liberate a greater heating value. The cooling-fan-motor mounted in these apparatuses and appliances experiences significant temperature changes, and is forced to drive at a high rotational speed in order to promote cooling efficiency. When the motor works frequently in an environment where significant temperature changes occur, oil
114
within the bearing or air entrapped in the oil repeatedly expand and contracts. In the conventional bearing, oil
114
flows out from the opening end of sleeve
106
during expansion, and the bearing is short of oil
114
during contraction. As a result, the reliability of bearing is lowered.
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 during operation as well as having less oil-shortage for a smooth operation, and also provides a heat sink device using the same motor for achieving efficient cooling.
The motor of the present invention comprises the following elements:
(a) a frame having an opening;
(b) a 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 housing and having an inner wall machined straight in its axial direction;
(e) a rotary shaft extending through the sleeve and being journaled by the sleeve;
(f) a ventilating path formed on at least one of inner wall of the housing or outer wall of the sleeve, and extending from an opening to a bottom of the housing;
(g) an annular recess for pooling oil formed on the outer wall of the sleeve and communicating with the ventilating path;
(h) a rotor having a magnet opposite to the stator; and
(i) oil provided in the space between the shaft and sleeve, in the annular recess, and in a space between the bottom of housing and the sleeve.
The foregoing construction allows the oil to pool in the annular recess formed on the outer wall of sleeve. The inner wall of the sleeve can thus be machined straight in the axial direction. In other words, the grooves can be formed after the inner wall of sleeve is machined in straight direction. The narrowed bearing can be thus machined with ease.
Since the oil is pooled in the grooves of the sleeve and the annular recess, the oil can be supplied anytime to the space between the inner wall of sleeve and the outer wall of shaft even if the oil splashes or flows out from the grooves by centrifugal force. The oil supplied to this space has a surface tension greater than that of the oil pooled in the grooves of sleeve and in the annular recess, whereby the oil is prevented from spilling out from the bearing.
The heat sink device of the present invention comprises the following elements:
(a) a frame having an opening on a first face and being mounted with a heating element on a second face;
(b) a housing formed on a face with an opening of the frame and having an open end;
(c) a stator secured on an outer wall of the housing;
(d) a sleeve fit into the housing and having an inner wall thereof machined straight in its axial direction;
(e) a rotary shaft extending through the sleeve and being journaled by the sleeve;
(f) grooves pr
Matsushita Electric - Industrial Co., Ltd.
Tamai Karl
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Motor with hydrodynamic bearing and heat sink device... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motor with hydrodynamic bearing and heat sink device..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor with hydrodynamic bearing and heat sink device... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2455908