Note: Descriptions are shown in the official language in which they were submitted.
CA 02375129 2001-11-26
HEAT SINK-EQUIPPED FAN MOTOR AND SMALL FLAT MOTOR
FIELD OF TECHNOLOGY
[0001] This invention deals with a heat sink-equipped fan motor that can be
installed
on various devices, such as IC's, that require dissipation of heat, and
improvement of a small,
flat motor that is well-suited to the constitution of that fan motor.
BACKGROUND TECHNOLOGY
[0002] In the past, heat sink-equipped fan motors like that shown in figure 11
have
had a base plate 1 that can be fixed to various devices that require
dissipation of heat, a fan
motor 2 mounted roughly in the center of the base plate 1, multiple heat
dissipation blocks 3a,
3b . . . that rise from the inner surface of the base plate 1 directly below
the region of rotation
of impellers 2a, 2b . . . and lined up like curb stones concentric with the
rotating shaft of the
fan motor 2. A cover plate 4 is attached to the sides of the base plate 1,
with one side left
open for the expulsion of air, and the air movement generated by the fan motor
1 forces the
cooling of the heat-dissipation blocks 3a, 3b . . .
(0003] Because this heat sink-equipped fan motor has heat-dissipation blocks
3a,
3b . . . located directly below the region of rotation of impellers 2a, 2b . .
., the overall
thinness of the motor is limited by the need to maintain space for the
rotation of the impellers
2a, 2b . . and by the thickness of the rise of the heat-dissipation blocks 3a,
3b . . . Moreover,
because the heat-dissipation blocks 3a, 3b . . . are lined up like curb stones
concentric with
the rotating shaft of the fan motor 2, the stream of air is obstructed by the
heat-dissipation
blocks 3a, 3b . . ., and an adequate cooling effect cannot be obtained.
[0004] Regarding that, there have been proposals, in JP H6/141507 and JP
H8/98461
for example, to form the inside of the housing that faces the outer periphery
of the impeller as
heat-dissipation fins, to make the sides thicker, and to make exhaust grooves
with a thickness
that corresponds to that of the side walls extend from the rotor circle
upstream, so that the air
movement generated by the fan motor flows through the grooves and forcibly
cools the heat-
dissipation fins on the sides.
(0005] In this heat sink-equipped fan motor, because exhaust grooves with a
thickness
that corresponds to that of the side walls extend from the rotor circle
upstream, the heat-
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CA 02375129 2001-11-26
dissipation fins that face the outer periphery of the impeller are
structurally complex, as well
as heavy. Another undesirable feature is the high production cost.
[0006] A known procedure to make this heat sink-equipped fan motor a small,
flat
motor that is quiet and has a stable rate of revolution is to put helical
grooves in opposite
directions on the outside of the rotating shaft and the inside of the dynamic
pressure sleeve
and use a dynamic pressure hydraulic bearing that circulates the oil as the
rotor bearing.
[0007] With this dynamic pressure hydraulic bearing, the dynamic pressure
sleave is
made of brass with good workability, and so the cost of the motor as a whole
is increased.
[0008] The purpose of this invention is to provide a heat sink-equipped fan
motor
which, although small and flat, has a superior heat dissipation and air-
cooling effect, and
which on the whole has a simple constitution, is easily assembled in a thin
package, and is
inexpensive.
[0009] A side from this heat sink-equipped fan motor, this invention has the
purpose
of providing a small, flat motor that can be constituted with an inexpensive
dynamic pressure
hydraulic bearing that is quiet and has a stable rate of rotation.
SUMMARY OF THE INVENTION
[0010] In the heat sink-equipped fan motor of this invention, there is a base
plate to
be fixed to various devices that require dissipation of heat, and a fan motor
that comprises a
rotor and a stator is accommodated, such that the fan motor can rotate, in an
opening located
over roughly the center of the base plate; the heat sink is assembled to
dissipate heat from the
base plate by means of multiple thin heat-dissipation fins that are stacked in
parallel with a
specked gap maintained between them.
[0011] In the heat sink-equipped fan motor of this invention, the heat sink is
assembled with a stack of multiple thin heat-dissipation fins with openings to
accommodate
the fan motor so that it can rotate, the outermost heat-dissipation fin having
an opening with a
diameter smaller than that of the fan motor.
[0012] In the heat sink-equipped fan motor of this invention, the heat sink is
assembled from a stack of multiple thin heat-dissipation fins connected and
fixed in place at
the corners by a heat-transmitting material that maintains a specified gap
between them.
[0013] In the heat sink-equipped fan motor of this invention, there is a base
plate
formed of aluminum sheet or copper sheet, and the heat sink is assembled of
heat-dissipation
fins formed of aluminum sheet or copper sheet.
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[0014] In the heat sink-equipped fan motor of this invention, there is a fan
motor with
vertical, L-shaped impellers that are gently arced in the horizontal plane and
project outward
from the outer periphery of the rotor, with each tip rising inside the opening
in the heat-
dissipating fins.
[0015] In the heat sink-equipped fan motor of this invention, there is a fan
motor with
impellers in a flat, branched wing shapes, in multiple, parallel layers at
specified intervals
along the rotor shaft so that the tips are positioned in the gaps between the
base plate and the
heat-dissipation fins.
(0016] In the heat sink-equipped fan motor of this invention, the multiple,
thin heat-
dissipation fins stacked in parallel have circular openings that center on the
rotating shaft of
the fan motor.
[0017] The small, flat motor of this invention is assembled of a stator with a
coil
wound on a core, a rotor with a magnet, a bearing that supports a rotor such
that it is able to
rotate, a bearing housing that supports and fixes in place the stator and that
has the rotor
bearing penetrating it and fixed within it, and a base plate with the bearing
housing fixed to
and rising from roughly its center, and the rotor bearing is a dynamic
pressure hydraulic
bearing that has a dynamic pressure sleeve molded of polymer, with a
protruding guard
around the periphery, and a stop ring that fits around the outside of the
dynamic pressure
sleeve to hold down the protruding guard. This dynamic pressure hydraulic
bearing is
located within the bearing housing that rises roughly from the center of the
base plate, and the
stop ring that holds down the protruding guard-of the dynamic pressure sleeve
is fitted into
and fixed to the inside diameter of the bearing housing. The rotor is
supported such that it
can rotate by the dynamic pressure hydraulic bearing that has a polymer
dynamic pressure
sleeve.
[0018] In the small, flat motor of this invention, there is a dynamic pressure
hydraulic
bearing with at least one bore hole in the end of the dynamic pressure sleeve
aligned
vertically and parallel to the central axis, which is used as an oil reserve,
which dynamic
pressure hydraulic bearing supports the rotor such that it is able to rotate.
[0019] In the small, flat motor of this invention, there is a dynamic pressure
hydraulic
bearing with multiple bore holes in the end of the dynamic pressure sleeve
spaced at
specified intervals and concentric with the central axis, which are used as
oil reserves, which
dynamic pressure hydraulic bearing supports the rotor such that it is able to
rotate.
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BRIEF EXPLANATION OF DRAWINGS
[0020] Figure 1 is a sectional side view showing the heat sink-equipped fan
motor of
this invention.
[0021] Figure 2 is a plane view showing an example of an impeller that can be
assembled into that motor.
(0022] Figure 3 is an oblique view of the impeller in figure 2.
[0023] Figure 4 is an oblique view showing the outermost heat-dissipation fin
separated from the heat sink-equipped fan motor in figure 1.
[0024] Figure 5 is a plane view showing a different impeller for the heat sink-
equipped fan motor of this invention.
[0025] Figure 6 is a sectional side view showing a heat sink-equipped fan
motor using
the impeller in figure S.
[0026] Figure 7 is a partial sectional side view showing an example of the
dynamic
pressure fluid bearing used in the small, flat motor of this invention.
[0027] Figure 8 is a plane view showing the dynamic pressure fluid bearing in
figure
7.
[0028] Figure 9 is a partial sectional side view showing another example of
the
dynamic pressure fluid bearing used in the small, flat motor of this
invention.
[0029] Figure 10 is a bottom view showing the dynamic pressure fluid bearing
in
figure 9.
[0030] Figure 11 is an oblique view showing a conventional heat sink-equipped
fan
motor.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] This explanation is explained below with reference to figures 1 through
10.
Figures 1 through 4 show a heat sink-equipped fan motor in which the fan motor
has vertical
impellers. Figures 5 and 6 show a heat sink-equipped fan motor in which the
fan motor has
flat impellers. These heat sink-equipped fan motors have basically the same
structural
components with the exception of the impellers, and corresponding parts are
labelled with the
same numbers.
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[0032] This heat sink-equipped fan motor is constituted with a small, flat
motor. The
small, flat motor has a dynamic pressure bearing with the characteristic
structure shown in
figures 7 through 10. It is appropriate to use as a small, flat drive motor in
other applications
without the heat sink.
[0033] As a heat sink-equipped fan motor, it can be used on various devices
that
require dissipation of heat, such as IC's; as shown in figure l, it is
constituted on a base plate
that is fixed on various devices that require dissipation of heat. This base
plate 10
functions as a heat absorbing plate, and can be formed from an aluminum sheet,
copper sheet
or other material with good thermal conductivity. This base plate 10 is the
base for the fan
motor, and can be formed in a thickness that will enhance its function of heat
absorption.
[0034] The heat sink-equipped fan motor has, roughly at the center of the base
plate
10, a motor M that comprises a rotor 11 and a stator 12, and the heat sink H
is located around
the periphery of the fan motor M. Within that constitution, the fan motor M
has a bearing
housing 13 that rises from and is fixed to roughly the center of the base
plate 10, and the rotor
11 is supported, free to tum, by a dynamic pressure hydraulic bearing 14 that
is framed by the
bearing housing 13. The stator 12 is fixed to and supported by the bearing
housing 13.
[0035] The rotor 11 has a ring-shaped magnet 11a; the magnet lla is held by a
magnet yoke 11b, and is covered by a circular rotor cap 11c. The rotor 11 has
a rotating shaft
that is fitted and fixed into the center boss lld of the rotor cap 11c. The
rotating shaft
penetrates and is supported, free to tum, by the dynamic pressure hydraulic
bearing 14, and is
thus accommodated by the bearing housing 13 on the base plate 10.
[0036] The stator 12 has a coil 12a wrapped on a core 12b, and the terminals
of the
coil 12a are connected to motor rotation control elements or other circuit
components on a
circuit board 12c. This stator 12 is assembled on the bearing housing 13, with
the core 12b
on which the coil 12a is wrapped fitted and fixed to the top end of the
bearing housing 13,
and the circuit board 12c fixed in place halfway up the bearing housing 13.
[0037] The fan motor M is constituted with multiple impellers 16a, 16b . . .
around
the outer periphery of the rotor cap. These impellers 16a,16b . . . can be, as
shown in figures
2 and 3, vertical impellers that are gently arced in the horizontal plane and
project outward
from the outer periphery of the rotor cap 11c, with each tip rising in an L-
shape. The fan
motor M rotates in the direction X with the insides of the arcs of the
impellers 16a, 16b . . .
facing forward.
[0038] The impellers 16a, 16b . . ., including the central ring 16c, are die-
cast as a
whole of aluminum or another material with excellent heat-dissipation
characteristics.
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Further, the impellers 16a, 16b . . . are formed separately from the rotor cap
11c, and are
fitted and fixed to the outer periphery of the rotor cap 11c by means of the
central ring 16c.
[0039] The heat sink H is arranged around the outer edge of the fan motor M,
maintaining a space in the center that accommodates, so that it is free to
turn, the fan motor
M including the roughly L-shaped impellers 16a,16b . . . As shown in figure 4,
this heat sink
H is constituted of multiple heat-dissipation fins 17 . . . having at their
center an opening 17a
that accommodates the fan motor M and allows it to rotate. These heat-
dissipation fins 17 . . .
are thin sheets cut in rectangular shape from a material with good thermal
conductivity such
as aluminum sheet or copper sheet; the heat sink H is assembled by stacking
multiple fins in
parallel, maintaining a specified gap between them.
[0040] The heat-dissipation fins . . . are assembled using spacers 17b and
rivets 17c
made of aluminum or another material with good thermal conductivity; the
spacers 17b are
sandwiched between the base plate 10 and the corners of the individual heat-
dissipation fins
17 . . . to maintain the specified gaps between them, and the rivets 17c
penetrates the fins and
the spacers 17b so that the base plate 10 and the heat-dissipation fins 17 . .
. are connected
and fixed, and so that heat can be conducted away from the base plate 10.
[0041] In the heat sink-equipped fan motor constituted in this manner, because
the
heat sink H is assembled around the fan motor M, maintaining at its center a
space that
accommodates the fan motor M so it is free to rotate, it can be made with a
flat thickness of
the base plate 10 plus the height of the fan motor M.
[0042] The heat sink H is constituted by stacking in parallel multiple thin
heat-
dissipation fins 17 . . . formed by cutting rectangular shapes from aluminum
sheet or copper
sheet with good thermal conductivity, with central openings 17a that
accommodate the fan
motor M so that it is able to rotate, and so it is structurally simple and
easy to assemble.
[0043] The spacers 17b are sandwiched between the base plate 10 and the comers
of
the individual heat-dissipation fins 17 . . . to maintain the specified gap
between them, and
the rivets 17c penetrate the individual fins and the spacers 17b and connect
and fix the heat
dissipation fins 17 . . . to the base plate 10 so that heat can be conducted
quickly away from
the base plate 10.
[0044] Moreover, because the thin heat-dissipation fins 17 . . . are assembled
by
stacking them in parallel, it is possible to ensure a large heat-dissipation
area for the heat-
dissipation fins 17 . . . And because the air movement generated by the
impellers 16a,
16b . . . of the fan motor M is used to dissipate heat from each of the heat-
dissipation fins
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17 . . ., the heat that is conducted to the heat-dissipation fins 17 . . .
from the base plate 10 can
be dissipated efficiently.
[0045] In addition to that, the impellers 16a, 16b . . . of the fan motor M
are mounted
vertically with the tips rising to form a rough L-shape, and so they can
generate a great
volume of air movement and thus cool the heat-dissipation fins 17 . . .
efficiently.
[0046] The heat sink H can be assembled by stacking multiple heat dissipation
fins
17 . . ., each having an opening 17a that accommodates the fan motor M so that
it is free to
rotate, as stated above, and also a final heat-dissipation fin 18 that has an
opening 18a with a
diameter smaller than the diameter of the rotor cap 11a. By this means, there
is an aperture
for the intake of air into the openings 17a of the heat-dissipation fins 17 .
. ., and the air
moved by the fan motor M is prevented from escaping, so that the heat-
dissipation fins 17 . . .
can function efficiently and heat can be dissipated efficiently by the heat-
dissipation fins
17 . . .,18.
[0047] In place of the vertical impellers 16a, 16b . . . described above, it
is possible
for the fan motor M to be constituted with multiple branched, wing-shaped
impellers 160 . . .
as shown in figure 5. These impellers 160 . . . are based on a central ring
161, with multiple
wings 160a through 160d that are connected to the ring 161 by adjacent main
stems 162, and
branches 163, 164 that extend from the main stems 162 and are roughly
perpendicular to
them, all punched as a unit from flat stock.
[0048] As shown in figure 6, the central rings 161 of multiple impellers 160
are fixed
sandwiched between spacer rings 165a through 165d, and spacer rings 165a
through 165d are
fitted over the outer periphery of the rotor cap 11c and fixed in place so
that they extend
radially from the rotor 11, and are parallel, separated by a specified gap.
Further, the tips of
the wings 160a through 160d of each impeller 160 . . . are located in the
spaces between the
base plate 10 and the heat-dissipation fins 15 . . . ,18, and so are able to
rotate.
[0049] The impellers 160 . . . are formed simply by punching from thin sheets,
and
are able to ensure an adequate volume of air movement generated by the multi-
branched
shape. Particularly because the tips of the wings 160a through 160d of each
impeller 160 . . .
are located in the spaces between the base plate 10 and the heat-dissipation
fins 15 . . . , 18,
the air movement generated by the tips located in the spaces between the base
plate 10 and
the heat-dissipation fins 15 . . . , 18 can function efficiently the base
plate 10 and the heat-
dissipation fins 15 . . . , 18. Now, the mufti-branched shape is not limited
to the shape shown
in the figure; it is possible to change the design of the mufti-branched shape
as appropriate.
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[0050] In each of the multiple heat-dissipation fins 17 of the heat sink H
there is a
circular opening 17a centered on the rotating shaft of the fan motor, and
because there is no
edge portion to obstruct the air movement generated by the fan motor, the
noise created by
the edge cutting the air is prevented, resulting in a low-noise fan motor.
[0051] The fan motor M is best constituted so that the rotor 11 is supported,
such that
it is able to rotate, by the dynamic pressure hydraulic bearing 14 mounted
within the bearing
housing 13, as shown in figure 7. By supporting the rotating shaft 15 so that
the oil flow is
circulated by having helical grooves 141a,141b in the dynamic pressure
hydraulic bearing 14
to provide up and down motion between the outside of the rotating shaft 15 and
the inside of
the inside of the dynamic pressure sleeve 140, it is possible to constitute a
small, flat motor
with low noise and a stable rate of rotation.
[0052] The dynamic pressure hydraulic bearing 14 has a molded polymer
hydraulic
pressure sleeve 140 with a protruding guard 142 around the outside, and a stop
ring 143 that
is fitted around the outside of the dynamic pressure sleeve 140 and that holds
down the
protruding guard 142. The dynamic pressure sleeve 140 is located within the
bearing housing
13 that rises from roughly the center of the base plate 10, and the stop ring
143 that holds
down the protruding guard 142 of the dynamic pressure sleeve 140 is fitted and
fixed to the
inside circumference of the bearing housing 13.
[0053] The dynamic pressure hydraulic bearing 14 can be constituted
inexpensively
using the polymer dynamic pressure sleeve 140. And because the protruding
guard 142 of
the dynamic pressure sleeve 140 is held down by the stop ring 143 that is
fitted and fixed to
the inside circumference of the bearing housing 13, no pressure is applied in
the direction of
the circumference of the dynamic pressure sleeve 140 by the insertion and
fixing of the
dynamic pressure sleeve 140 inside the bearing house 13, and no impact on the
degree of
precision of the inner circumference of the bearing. And so a drive motor with
low noise and
a stable rate of rotation can be constituted using a polymer dynamic pressure
sleeve 140.
[0054] In the dynamic pressure hydraulic bearing 14, when there are rounded
slide
ribs 144a through 144d established vertically at specified intervals around
the outer edge of
the protruding guard 142, as shown in figure 8, the dynamic pressure sleeve
140 can easily be
inserted and fixed inside the bearing housing 13. And by establishing grooves
145a, 145b in
the top surface of the protruding stop ring 142, it is possible to insert the
stop ring 143 into
the bearing housing 13 and fix it firmly, unable to rotate, by meshing the
grooves 145a, 145b
with projections (not illustrated) on the stop ring 143.
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[0055] Making use of this dynamic pressure hydraulic bearing 14, the magnetic
action
of the coil 12a of the stator 12 and the magnet lla of the rotor 11 will pull
the rotor as a
whole in the direction of mounting in the stator 12, and the dynamic pressure
hydraulic
bearing 14 will support the rotor 11 so that it is able to rotate stably. In
addition, it can be
assembled with a thruster 19 that faces the end of the rotating shaft 15 of
the rotor 15, as
shown in figures 1 and 5, so that the rotor 11 can rotate smoothly.
[0056] In the dynamic pressure bearing 14, there can be at least one bore hole
146 in
the end of the dynamic pressure sleeve, aligned vertically and parallel to the
central axis,
which is used as an oil reserve, as shown in figure 9. If there is an oil
reserve in the form of
this bore hole 146, it is possible to prevent the loss of oil through
deterioration during
continued use that accompanies the bearing heat produced when operating at
about 8090, and
the life of the bearing can be extended.
[0057] This bore hole used as an oil reserve can take the form, as shown in
figure 10,
of multiple holes 146 through 146g, spaced at specified intervals in a
concentric ring on the
end of the dynamic pressure sleeve 140, and can effectively prevent the loss
of oil through
deterioration during continued use that accompanies the production of heat. By
establishing
grooves 147a,147b that connect either one bore hole 146 or opposing bore holes
146,146d to
the edge, it is possible to have a thruster 19 that faces the shaft end of the
rotating shaft 15 of
the rotor 11, and enable it to rotate smoothly
INDUSTRIAL UTILITY
[0058] As stated above, in the heat sink-equipped fan motor of this invention,
by
having a fan motor that is accommodated, such that the fan motor can rotate,
in an opening
in roughly the center of the fins of the heat sink that is assembled to
dissipate heat from the
base plate by means of multiple thin heat-dissipation fins that are stacked in
parallel with a
specified gap maintained between them, it is possible to have a thin, flat,
shape with a simple
and easily assembled structure that is no thicker than the combined thickness
of the base plate
and the fan motor, it is possible to assure a large heat-dissipation area for
each of the heat-
dissipation fins that are stacked in parallel, and it is possible to dissipate
efficiently the heat
conducted to the heat-dissipation fins from the base plate by the action of
the air movement
generated by the fan motor on each of the thin heat-dissipation fins.
[0059] In the heat sink-equipped fan motor of this invention, the heat sink is
assembled with a stack of multiple thin heat-dissipation fins with openings to
accommodate
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CA 02375129 2001-11-26
the fan motor so that it can rotate, the outermost heat-dissipation fin having
an opening with a
diameter smaller than that of the fan motor, and so there is an aperture for
the intake of air
into the openings of the heat-dissipation fins, and the air moved by the fan
motor is prevented
from escaping, so that the air pressure can work efficiently on the heat-
dissipation fins.
[0060] In the heat sink-equipped fan motor of this invention, the heat sink is
assembled from a stack of multiple thin heat-dissipation fins connected and
fixed in place at
the corners by a heat-transmitting material that maintains a specified gap
between them, and
so the heat sink can be assembled such that it can conduct heat from the base
plate quickly.
[0061] In the heat sink-equipped fan motor of this invention, there is a base
plate
formed of aluminum sheet or copper sheet, and the heat sink is assembled of
heat-dissipation
fins formed of aluminum sheet or copper sheet, and so the heat sink is able to
conduct heat
from the base plate quickly.
[0062] In the heat sink-equipped fan motor of this invention, there is a fan
motor with
vertical, L-shaped impellers that are gently arced in the horizontal plane and
project outward
from the outer periphery of the rotor, with each tip rising inside the opening
in the heat-
dissipating fins, and so the air movement generated by the impeller tips is
able to work
efficiently on the base plate and heat-dissipation fins.
[0063] In the heat sink-equipped fan motor of this invention, there is a fan
motor with
impellers in flat, branched wing shapes, in multiple, parallel layers at
specified intervals
along the rotor shaft so that the tips are positioned in the gaps between the
base plate and the
heat-dissipation fins, and so the air movement generated by the tips of the
impellers can
function efficiently on the base plate and the heat-dissipation fins.
[0064] In the heat sink-equipped fan motor of this invention, the multiple
heat-
dissipation fins 17 of the heat sink H have circular openings 17a that center
on the rotating
shaft of the fan motor and there is no edge to interrupt the air movement
generated by the fan
motor, so that it is possible to constitute a low-noise fan motor that does
not produce a sound
by cutting the air.
[0065] In the small, flat motor of this invention, the rotor bearing is a
dynamic
pressure hydraulic bearing that has a dynamic pressure sleeve molded of
polymer, with a
protruding guard around the periphery, and a stop ring that fits around the
outside of the
dynamic pressure sleeve to hold down the protruding guard. This dynamic
pressure hydraulic
bearing is located within the bearing housing that rises roughly from the
center of the base
plate, and the stop ring that holds down the protruding guard of the dynamic
pressure sleeve
is fitted into and fixed to the inside diameter of the bearing housing.
Therefore, it can be
CA 02375129 2001-11-26
constituted inexpensively with a polymer dynamic pressure sleeve, and no
pressure is applied
to the circumference of the dynamic pressure sleeve, so that it is possible to
constitute a drive
motor with stable precision of the inner circumference of the bearing, even
though it uses a
polymer dynamic pressure sleeve.
[0066] In the small, flat motor of this invention, there is a dynamic pressure
hydraulic
bearing with at least one bore hole in the end of the dynamic pressure sleeve
aligned
vertically and parallel to the central axis, which is used as an oil reserve,
which dynamic
pressure hydraulic bearing supports the rotor such that it is able to rotate,
and so it is possible
to effectively prevent the loss of oil through deterioration during continued
use that
accompanies the production of heat, and thus extend the life of the bearing.
[0067] In the small, flat motor of this invention, there is a dynamic pressure
hydraulic
bearing with multiple bore holes in the end of the dynamic pressure sleeve
spaced at
specified intervals and concentric with the central axis, which are used as
oil reserves, which
dynamic pressure hydraulic bearing supports the rotor such that it is able to
rotate, and so it is
possible to effectively prevent the loss of oil through deterioration during
continued use that
accompanies the production of heat, and thus extend the life of the bearing.
[0068] The terms and expressions used above in the description of this
invention are
used solely for the purpose of explanation, and do not limit the substance of
the invention in
any way. In the event that limiting terms or expressions have been used, there
is no intention
thereby to exclude configurations or parts equivalent to this invention as
described above. It
is clear, therefore, that it is possible to make various changes that are
within the realm of this
invention for which rights have been claimed.
11
