U.S. patent application number 12/910107 was filed with the patent office on 2011-07-28 for cooling apparatus.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. Invention is credited to Tatsuro Hirose, Shigetoshi Ipposhi, Kazuo Kadowaki, Takumi Kijima, Takayuki Nakao.
Application Number | 20110179806 12/910107 |
Document ID | / |
Family ID | 44307906 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110179806 |
Kind Code |
A1 |
Ipposhi; Shigetoshi ; et
al. |
July 28, 2011 |
COOLING APPARATUS
Abstract
Disclosed is a cooling apparatus including: a heat receiving
plate to which a plurality of heating elements are attached; a
radiator plate to which a plurality of Peltier devices are
attached; a thermal transport heat pipe that couples the heat
receiving plate with the radiator plate; and a heat dissipating
device being provided on an exothermic side of the Peltier devices;
wherein the plurality of heating elements are arranged along a
longitudinal direction of the thermal transport heat pipe, and the
plurality of Peltier devices are arranged along the longitudinal
direction of the thermal transport heat pipe, whereby, when using a
plurality of Peltier devices, reducing power consumption thereof by
equalizing each operation of the respective Peltier devices.
Inventors: |
Ipposhi; Shigetoshi; (Tokyo,
JP) ; Hirose; Tatsuro; (Tokyo, JP) ; Kadowaki;
Kazuo; (Tokyo, JP) ; Kijima; Takumi; (Tokyo,
JP) ; Nakao; Takayuki; (Tokyo, JP) |
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Chiyoda-ku
JP
|
Family ID: |
44307906 |
Appl. No.: |
12/910107 |
Filed: |
October 22, 2010 |
Current U.S.
Class: |
62/3.3 ;
165/104.26; 165/64; 62/3.7 |
Current CPC
Class: |
F28D 15/0266 20130101;
H01L 23/38 20130101; F25B 25/00 20130101; F25B 2700/2107 20130101;
H01L 2924/0002 20130101; F25B 21/02 20130101; H01L 2924/0002
20130101; F25B 23/006 20130101; H01L 23/427 20130101; H01S 5/02415
20130101; H01L 2924/00 20130101; F25B 2321/021 20130101; H01S
5/4093 20130101 |
Class at
Publication: |
62/3.3 ; 62/3.7;
165/104.26; 165/64 |
International
Class: |
F25B 21/04 20060101
F25B021/04; F25B 21/02 20060101 F25B021/02; F28D 15/04 20060101
F28D015/04; F25B 29/00 20060101 F25B029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2010 |
JP |
2010-016409 |
Claims
1. A cooling apparatus, comprising: a heat receiving plate to which
a plurality of heating elements are attached; a radiator plate to
which a plurality of Peltier devices are attached; a thermal
transport heat pipe that couples the heat receiving plate with the
radiator plate; and a heat dissipating device being provided on an
exothermic side of the Peltier devices; wherein the plurality of
heating elements are arranged along a longitudinal direction of the
thermal transport heat pipe, and the plurality of Peltier devices
are arranged along the longitudinal direction of the thermal
transport heat pipe.
2. The cooling apparatus according to claim 1, wherein the heat
dissipating device includes: a second heat receiving plate in
contact with the exothermic sides of the Peltier devices; a
radiating heat pipe coupled to the second heat receiving plate; and
a radiating fin coupled to the radiating heat pipe.
3. The cooling apparatus according to claim 2, wherein a plurality
of radiating heat pipes are arranged at the same interval along a
direction perpendicular to the longitudinal direction of the
thermal transport heat pipe.
4. The cooling apparatus according to claim 1, further comprising:
a temperature sensor located near a coupling portion between the
heat dissipating device and the thermal transport heat pipe; a
plurality of drive circuits for individually driving the respective
Peltier devices; and a control circuit for individually controlling
the respective drive circuit based on an output from the
temperature sensor.
5. The cooling apparatus according to claim 1, wherein a tip end of
the thermal transport heat pipe is protruded from the end face of
the heat dissipating device.
6. The cooling apparatus according to claim 1, wherein the heat
receiving plate and the radiator plate are coupled by a plurality
of thermal transport heat pipes, and a smaller amount of liquid is
sealed in the heat pipe which is located at a larger distance from
the heating element attachment portion.
7. The cooling apparatus according to claim 1, wherein a wick that
generates a capillary force is fixed to an inner surface of the
thermal transport heat pipe.
8. The cooling apparatus according to claim 1, wherein the thermal
transport heat pipe is bent in a U-shape, and both ends of the
thermal transport heat pipe are thermally coupled by another heat
pipe.
9. The cooling apparatus according to claim 1, wherein the thermal
transport heat pipe is bent in a U-shape, and the heat receiving
plate and the radiator plate are integrated into a single piece and
disposed perpendicularly to each other.
10. The cooling apparatus according to claim 1, wherein the heating
element which is located at a portion closer to the end of the
thermal transport heat pipe generates a smaller amount of heat.
11. The cooling apparatus according to claim 1, wherein an
electronic or optical device is located at a position other than
under a endothermic surface of the Peltier device in a vertical
direction.
12. The cooling apparatus according to claim 1, wherein the heat
receiving plate is provided with a heater.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a cooling apparatus for
cooling heating elements.
[0003] 2. Description of the Related Art
[0004] A cooling system, such as natural air cooling, forced air
cooling, water cooling, and ebullient cooling, is well known. In
recent years, heating elements that require temperature regulation,
such as light emitting devices, are widely used. For example, the
following Patent Document 1 proposes a semiconductor laser
apparatus which is provided with a cooling mechanism by combining a
Peltier device with a heat pipe.
[0005] In such a cooling mechanism as described in Patent Document
1, power consumption tends to increase because the Peltier device
has a relatively small thermoelectric conversion efficiency.
Further, if an endothermic amount of the Peltier device is
increased, it may fall into a supercooled state, thereby resulting
in dew condensation.
[0006] The related prior arts are listed as follows: Japanese
Patent Unexamined Publications (kokai) JP-5-167143A (1993),
JP-2001-332806A, JP-11-121816A (1999), JP-5-312455A (1993), and
International Patent Publication WO2004/029532, and Japanese
Utility Model Unexamined Publication JP-61-194170U (1986).
SUMMARY OF THE INVENTION
[0007] An object of the present invention is to provide a cooling
apparatus capable of, when using a plurality of Peltier devices,
reducing power consumption thereof by equalizing each operation of
the respective Peltier devices.
[0008] In order to achieve the above object, the cooling apparatus
according to an embodiment of the present invention includes:
[0009] a heat receiving plate to which a plurality of heating
elements are attached;
[0010] a radiator plate to which a plurality of Peltier devices are
attached;
[0011] a thermal transport heat pipe that couples the heat
receiving plate with the radiator plate; and
[0012] a heat dissipating device being provided on an exothermic
side of the Peltier devices;
[0013] wherein the plurality of heating elements are arranged along
a longitudinal direction of the thermal transport heat pipe,
and
[0014] the plurality of Peltier devices are arranged along the
longitudinal direction of the thermal transport heat pipe.
[0015] It is preferable that the heat dissipating device includes:
a second heat receiving plate in contact with the exothermic sides
of the Peltier devices; a radiating heat pipe coupled to the second
heat receiving plate; and a radiating fin coupled to the radiating
heat pipe.
[0016] It is preferable that a plurality of radiating heat pipes
are arranged at the same interval along a direction perpendicular
to the longitudinal direction of the thermal transport heat
pipe.
[0017] It is preferable that the cooling apparatus further
comprising: a temperature sensor located near a coupling portion
between the heat dissipating device and the thermal transport heat
pipe; a plurality of drive circuits for individually driving the
respective Peltier devices; and a control circuit for individually
controlling the respective drive circuit based on an output from
the temperature sensor.
[0018] It is preferable that a tip end of the thermal transport
heat pipe is protruded from the end face of the heat dissipating
device.
[0019] It is preferable that the heat receiving plate and the
radiator plate are coupled by a plurality of thermal transport heat
pipes, and a smaller amount of liquid is sealed in the heat pipe
which is located at a larger distance from the heating element
attachment portion.
[0020] It is preferable that a wick that generates a capillary
force is fixed to an inner surface of the thermal transport heat
pipe.
[0021] It is preferable that the thermal transport heat pipe is
bent in a U-shape, and both ends of the thermal transport heat pipe
are thermally coupled by another heat pipe.
[0022] It is preferable that the thermal transport heat pipe is
bent in a U-shape, and the heat receiving plate and the radiator
plate are integrated into a single piece and disposed
perpendicularly to each other.
[0023] It is preferable that the heating element which is located
at a portion closer to the end of the thermal transport heat pipe
generates a smaller amount of heat.
[0024] It is preferable that an electronic or optical device is
located at a position other than under a endothermic surface of the
Peltier device in a vertical direction.
[0025] It is preferable that the heat receiving plate is provided
with a heater.
[0026] According to an embodiment of the present invention, heat
generated by the plurality of heating elements is dissipated
through the heat receiving plate and the thermal transport heat
pipes by the plurality of Peltier devices. Therefore, operations of
the Peltier devices can be equalized to collectively control the
temperature. Further, a difference in temperature between an
endothermic side and an exothermic side of each Peltier device can
be decreased, thereby reducing power consumption of the Peltier
devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIGS. 1A and 1B are a plan view and a front view, showing a
cooling apparatus according to Embodiment 1 of the present
invention;
[0028] FIGS. 2A and 2B are a front view and a side view, showing a
cooling apparatus according to Embodiment 2 of the present
invention;
[0029] FIGS. 3A and 3B are a plan view and a front view, showing a
cooling apparatus according to Embodiment 3 of the present
invention;
[0030] FIGS. 4A, 4B and 4C are a left side view, a front view and a
right side view, showing a cooling apparatus according to
Embodiment 4 of the present invention;
[0031] FIGS. 5A and 5B are a plan view and a front view, showing a
cooling apparatus according to Embodiment 5 of the present
invention; and
[0032] FIG. 6 is a plan view showing a cooling apparatus according
to Embodiment 6 of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] This application is based on an application No. 2010-16409
filed on Jan. 28, 2010 in Japan, the disclosure of which is
incorporated herein by reference.
[0034] Hereinafter, preferred embodiments will be described with
reference to drawings.
Embodiment 1
[0035] FIGS. 1A and 1B are a plan view and a front view, showing a
cooling apparatus according to Embodiment 1 of the present
invention. This cooling apparatus includes a heat receiving plate
2, a radiator plate 4, thermal transport heat pipes 5, a plurality
of Peltier devices 3 and a heat sink 6.
[0036] The heat receiving plate 2 is made of a material having
favorable thermal conductivity, like a metallic material such as
copper or aluminum. An upper surface of the heat receiving plate 2
has a flat shape, on which a plurality of heating elements 1 such
as semiconductor lasers are mounted. FIG. 1 shows one example in
which three heating elements 1 are mounted, but the number of the
heating elements 1 may be two or four or more. A lower surface of
the heat receiving plate 2 has a shape substantially conforming to
a shape of each of the thermal transport heat pipes 5, thereby
ensuring favorable thermal coupling.
[0037] The thermal transport heat pipes 5 are constituted such that
working fluid is sealed within a metallic pipe, and provide a
function of effectively transporting heat by means of evaporation
of the working fluid, traveling of vapor, condensation of the
vapor, and reflux of liquid due to a capillary force within the
heat pipe. One end of each of the thermal transport heat pipes 5 is
joined with the heat receiving plate 2, and the other end is
coupled with the radiator plate 4, thus the heat receiving plate 2
is thermally coupled with the radiator plate 4, thereby efficiently
transporting heat from the heat receiving plate 2 to the radiator
plate 4. FIG. 1 shows one example in which two thermal transport
heat pipes 5 are provided, but the number of the thermal transport
heat pipes 5 may be one or three or more.
[0038] The radiator plate 4 is made of a material having favorable
thermal conductivity, like a metallic material such as copper or
aluminum. A lower surface of the radiator plate 4 has a shape
substantially conforming to a shape of each of the thermal
transport heat pipes 5, thereby ensuring favorable thermal
coupling. An upper surface of the radiator plate 4 has a flat
shape, on which a plurality of Peltier devices 3 are mounted. FIG.
1 shows one example in which three Peltier devices are mounted, but
the number of the Peltier devices 3 may be two or four or more.
[0039] The Peltier devices 3 utilize the Peltier effect in which an
endothermic or exothermic phenomenon can occur at a junction
between a p-type and an n-type semiconductors according to the
direction of a current flowing through the junction. The
endothermic surfaces of the Peltier devices 3 are in contact with
the upper surface of the radiator plate 4. The exothermic surface
of the Peltier devices 3 are attached with the heat sink 6.
[0040] The heat sink 6 is made of a material having favorable
thermal conductivity, like a metallic material such as copper or
aluminum, and has such a configuration that a number of radiating
fins are provided upright on a base plate.
[0041] As to a temperature control circuit, the cooling apparatus
further includes a temperature sensor 7, a plurality of drive
circuits 52 for individually driving the respective Peltier devices
3, and a control circuit 51 for individually controlling the
respective drive circuits 52 based on an output from the
temperature sensor 7.
[0042] Next, an operation of this cooling apparatus is described by
way of example based on a laser television, i.e., a television that
generates video images using light from R/G/B (Red/Green/Blue)
light emitting elements, as one application of the present
invention. The three heating elements 1 including an R element, a G
element and a B element generate heat during emission of desired
light as each element is energized. The heat generated by each of
the heating elements 1 is transferred to the heat receiving plate
2, and then transferred to one end of the thermal transport heat
pipes 5. The thermal transport heat pipes 5 can efficiently
transport heat by circulation of working fluid sealed therein. At
this time, when the working fluid receives heat from the plurality
of heating elements 1, there is the same pressure within the heat
pipe at portions at which each of the heating elements 1 is
attached, and the working fluid can receive heat and evaporate at
the same temperature and the vapor thus generated can move in a
collective manner. Accordingly, each of attachment surfaces of the
R element, the G element and the B element has a substantially even
temperature.
[0043] On the other hand, since at a portion where each of the
Peltier devices 3 is attached the vapor is uniformly dispersed and
condensed such that each of inner wall surfaces within the heat
pipes has the same temperature through the intermediary of the
radiator plate 4, each of the endothermic surfaces of the plurality
of Peltier devices 3 can receive a uniform amount of heat at an
even temperature through the intermediary of the radiator plate 4.
In this manner, each of the Peltier devices 3 can receive an
averaged heat quantity, and can transfer the thermal energy
received from the endothermic surface to the heat sink 6 using the
Peltier effect. At this time, the Peltier device 3 has a lower
temperature on the side of the radiator plate and a higher
temperature on the side of heat sink. Therefore, the heat sink 6
has a temperature higher than that of the thermal transport heat
pipes 5, resulting in more efficient heat dissipation due to larger
difference of temperature with respect to the ambient temperature.
Further, the temperature of each of the thermal transport heat
pipes, thus the temperature at the portion where the heating
element is attached can be controlled by varying power supply to
the Peltier devices 3.
[0044] Further, the Peltier device 3 may have a higher temperature
on the side of the radiator plate and a lower temperature on the
side of heat sink by inverting the flowing direction of a current
supplied to the Peltier devices 3. In other words, when heating the
radiator plate 4, the heat is transferred through the radiator
plate 4 and the thermal transport heat pipes 5 to the attachment
surfaces, temperature of each is thus increased. Accordingly, each
of the attachment surfaces of the R/G/B elements can be maintained
at any constant temperature regardless of the ambient temperature.
For example, even when the ambient temperature rises from
-5.degree. C. up to 45.degree. C., each of the endothermic surfaces
of the Peltier devices 3 can be maintained at a constant
temperature of 30.degree. C. In the case of laser televisions, in
view of the longer life of the R/G/B elements and the reduction of
Peltier power consumption, it is preferable to maintain the
temperature at each of the endothermic surfaces of the Peltier
devices 3 in a range of 20 to 35.degree. C., more preferably in a
range of 25.degree. C. to 30.degree. C.
[0045] Thus, the heating elements 1 can be cooled by temperature
regulation, and it is possible to obtain desired properties (e.g.,
optical output) of the heating elements 1 by controlling the
heating elements 1 at a desired temperature. The temperature used
for temperature regulation can be measured using the temperature
sensor 7 such as thermocouple, thermistor, or diode. A measuring
position of the temperature sensor 7 may be at any point from the
heat receiving plate 2 to the heat sink 6, but preferably at the
radiator plate 4, in particular, as shown in FIG. 1, more
preferably near a coupling portion between the radiator plate 4 and
the thermal transport heat pipe 5. Moreover, when coupling with the
plurality of thermal transport heat pipes 5, it is preferable to
locate the sensor 7 near the intermediate of the adjacent heat
pipes on the radiator plate 4.
[0046] In the cooling apparatus according to this embodiment, the
thermal transport heat pipes 5 are used for heat uniformizing
elements, and the plurality of heating elements 1 are arranged
linearly along the longitudinal direction of the thermal transport
heat pipes 5, and the plurality of Peltier devices 3 are arranged
linearly along the longitudinal direction of the thermal transport
heat pipes 5. Accordingly, the heat transferred from the plurality
of heating elements 1 is transported in a collective manner, and
uniformly exhausted to the plurality of Peltier devices 3. As a
result, the heat receiving plate 2 and the radiator plate 4 can be
maintained at a uniform temperature within the respective
planes.
[0047] Further, even when the heat generated by each of the heating
elements 1 is not uniform, the heat can be uniformly transferred to
each of the Peltier devices 3. Accordingly, the thermal transport
efficiency of each of the Peltier devices 3 can be maintained at a
maximal state, in other words, the difference in temperature
between the endothermic surface and the exothermic surface of each
Peltier device 3 can be maintained at a uniform condition. As a
result, it is possible to reduce the power consumption of the
Peltier devices 3. Moreover, since the heat is uniformly
transferred to each of the Peltier devices 3, local supercooling
can be prevented, thereby improving dew condensation
resistance.
[0048] Further, in a case where each of the plurality of heating
elements 1 generates heat in a different mode (for example, one
condition in which R element: large, G element: small, B element:
medium changes rapidly to another condition in which R element:
medium, G element: medium, B element: small), compared to the case
in which the Peltier device 3 is provided for every heating element
1, each Peltier device can receive heat of an average heat quantity
out of the plurality of heating elements 1. Accordingly, the
variation of the generated heat quantity becomes moderate, thereby
facilitating the control of the temperature. In particular, when
forming a video image of ocean (blue), for example, even when the R
element: 0 (no load), the G element: 0 (no load), and the B
element: large, the R/G/B elements are provided for the same heat
pipe, thereby preventing abnormally low temperature (0.degree. C.
when the ambient temperature is 0.degree. C.). Further, even when a
particular heating element generates a larger mount of heat among
the plurality of heating elements 1, as long as the other heating
elements generate a smaller mount of heat, a total amount of heat
exhausted is kept relatively small, thereby maintaining the
particular heating element 1 at a lower temperature.
[0049] Each of the R/G/B elements may change its coloring
(wavelength) and light intensity depending on the temperature of a
luminescent body (LD) inside the element, and therefore it is
preferable that the temperature of the LD does not change too much
in order to obtain desired light. However, each of the R/G/B
elements has its unique thermal resistance, and the temperature of
the LD element (junction temperature) may change by the temperature
difference obtained by integration of the generated heat quantity
that corresponds to the ever-changing light output for forming
various video images (motion pictures). According to the present
invention, since the attachment surface can be maintained at a
constant temperature as described above, the temperature of each of
the LD elements can be more easily predicted and/or controlled only
based on each thermal resistance value that is a fixed value and
generated heat quantity (supplied power) that represents transient
change, without being affected by environment changes such as
ambient temperature and surrounding wind speed, which means high
robustness. Further, abnormally lower temperature can be avoided
even when any of the elements is under no load, and the temperature
of the LD element varies only in a smaller range, which defines a
minimum temperature. Therefore it is possible to resume the
temperature with favorable light emitting efficiency in the next
light output.
[0050] Incidentally, in the case of performing temperature
regulation individually for each of the R/G/B elements using the
Peltier devices, 1.5 or more Peltier devices are required in order
to cool the R element with the adequately efficient number of the
Peltier devices. In other words, in the individual cooling, the
number of the Peltier devices required for the R element is 1.5,
the number of the Peltier devices required for the G element is
2.3, and the number of the Peltier devices required for the B
element is 1.2. Consequently, the total number of the required
Peltier devices is seven, which is a physically possible total
number of 2, 3, and 2. However, by collectively cooling according
to the present invention, all the elements can be satisfactory
cooled with five Peltier devices at a maximum output, and
practically with four Peltier devices due to interference of heat
generation modes of individual elements, thereby decreasing the
number of the Peltier devices and reducing the size, power
consumption, and cost.
Embodiment 2
[0051] FIGS. 2A and 2B are a front view and a side view, showing a
cooling apparatus according to Embodiment 2 of the present
invention. This cooling apparatus has a configuration similar to
that shown in FIG. 1, but is different in that each thermal
transport heat pipe 5 is bent in a U-shape, and a heat receiving
and radiating plate 8 is used in which the heat receiving plate 2
and the radiator plate 4 shown in FIG. 1 are integrated into a
single piece and disposed perpendicularly to each other. With such
a configuration, it is possible to realize downsizing of the entire
apparatus. The temperature control circuit of the cooling apparatus
has the same configuration as that shown in FIG. 1, and therefore
not shown in the drawing.
[0052] The thermal transport heat pipe 5 according to this
embodiment can be a common heat pipe including a circular pipe, a
grooved pipe, a wire-lined pipe, or a particle sintered pipe.
However, when bending the heat pipe more than one time, a problem
may occur that a wick (such as thin wire or particle) that
generates an inner capillary force is peeled off from an inner
surface of the pipe. Further, when operating at a ultralow
temperature (40.degree. C. or lower in the case of water), another
problem may occur that a maximum amount of heat transport is
reduced as viscosity coefficient of liquid increases. In such
cases, it is preferable to use a heat pipe manufactured by lining a
number of thin wires along an inner wall of a grooved pipe,
followed by providing a ribbon for holding the thin wires from the
inner side thereof, and then sintering it to fix the thin wires. By
using a heat pipe of this type, the inner wick is hardly peeled off
even in deformation due to post processing such as bending more
than once, and the maximum amount of heat transport can be improved
by ensuring a large flow path configured of grooves that facilitate
reflux of high viscosity liquid.
[0053] Further, in the case of using the plurality of thermal
transport heat pipes 5, a problem may occur that a difference in
temperature between a wall of the heat pipe and a liquid becomes
smaller as a distance between a heat pipe and the heating element
attachment portion increases, resulting in an operational failure
(for example, vapor does not easily travel) and deterioration in
the thermal transport property. In such a case, it is preferable to
seal a smaller amount of liquid in the heat pipe which is located
at a larger distance from the heating element attachment portion.
Thus, thickness of a liquid film formed on the inner wall of the
heat pipe can be made smaller, and evaporation phenomenon can
easily occur even with a smaller difference in temperature. As a
result, it is possible to ensure thermal transport under normal
vapor, thereby improving the maximum amount of heat transport and
realizing thermal transport even with a smaller difference in
temperature.
[0054] Moreover, a portion closer to the end of the thermal
transport heat pipe 5 that is in contact with the heat receiving
plate 2 has a longer liquid reflux distance, with reflux properties
of the liquid being lowered. Therefore, providing the heating
element 1 that generates a larger amount of heat at the end of the
heat pipe may cause occurrence of "dryout", that is, no liquid is
resupplied and the temperature at the attachment portion may rise
up. In order to address this problem, among the plurality of
heating elements 1 attached to the heat receiving plate 2, a
heating element that generates a smaller amount of heat is
preferably located at a portion closer to the end of the thermal
transport heat pipe. Consequently, an allowable limit value of a
total amount of exhaust heat quantity to be dissipated from the
plurality of heating elements 1, that is, the maximum amount of
heat transport of the heat pipe is further increased.
[0055] In the case of the laser television, the G element is likely
to generate the largest amount of heat, therefore, the G element is
preferably located at a position closest to the heat sink along the
heat pipe.
Embodiment 3
[0056] FIGS. 3A and 3B are a plan view and a front view, showing a
cooling apparatus according to Embodiment 3 of the present
invention. This cooling apparatus includes the heat receiving plate
2, the radiator plate 4, the thermal transport heat pipes 5, the
plurality of Peltier devices 3, and a heat dissipating unit 20. The
cooling apparatus has a configuration similar to that shown in FIG.
1, but is different in that the heat dissipating unit 20 including
radiating heat pipes 10 is used in place of the heat sink 6 shown
in FIG. 1. The temperature control circuit of the cooling apparatus
has the same configuration as that shown in FIG. 1, and therefore
not shown in the drawing.
[0057] The heat dissipating unit 20 includes a second heat
receiving plate 9 in contact with the exothermic side of each
Peltier device 3, the plurality of radiating heat pipes 10 coupled
to the second heat receiving plate 9, and radiating fins 11 coupled
to the respective radiating heat pipes 10.
[0058] The second heat receiving plate 9 is made of a material
having favorable thermal conductivity, like a metallic material
such as copper or aluminum. A lower surface of the second heat
receiving plate 9 has a flat shape which is in contact with the
exothermic side of the plurality of Peltier devices 3. An upper
surface of the second heat receiving plate 9 has a shape
substantially conforming to a shape of each of the radiating heat
pipes 10, thereby ensuring favorable thermal coupling.
[0059] The radiating heat pipe 10 is constituted similarly to the
thermal transport heat pipe 5, such that working fluid is sealed
within a metallic pipe, and provides a function of effectively
transporting heat by means of evaporation of the working fluid,
traveling of vapor, condensation of the vapor, and reflux of liquid
due to a capillary force within the heat pipe. One end of each
radiating heat pipe 10 is joined with the second heat receiving
plate 9, and the other end is joined with the radiating fins 11,
thereby efficiently transporting heat from the second heat
receiving plate 9 to the radiating fins 11. FIG. 3 shows one
example in which six radiating heat pipes 10 are provided, but the
number of the radiating heat pipes 10 may be one to five or seven
or more.
[0060] The radiating fin 11 is configured of a plurality of plates
made of a material having favorable thermal conductivity, like a
metallic material such as copper or aluminum. The plates are
arranged at substantially the same interval along the longitudinal
direction of the radiating heat pipe 10.
[0061] According to this embodiment, a heat dissipating capability
is dramatically improved by using the heat dissipating unit 20 as
described above. Further, it is preferable that the plurality of
radiating heat pipes 10 are arranged at the same interval along a
direction perpendicular to the longitudinal direction of the
thermal transport heat pipe 5. Thus, in the case where the
plurality of Peltier devices 3 are provided, a larger number of
heat dissipating heat pipes 5 can be located as compared to the
case where the thermal transport heat pipes 5 and the radiating
heat pipes 10 are parallelly located, thereby further improving
heat dissipating properties. Moreover, in the case of using the
above-mentioned U-shaped heat pipe, it is preferable to place the
heat pipe in a horizontal plane because the operation may be
deteriorated if the liquid sealed within the heat pipe accumulates
around a U-shaped portion or both ends by gravity. In this case,
the entire apparatus can be downsized by providing the heat
dissipating unit including the perpendicular heat pipes.
[0062] The heat dissipating 20 is required to exhaust the total
amount of heat including the heat quantity generated from the
heating elements 1 and the driving power of the Peltier devices 3,
thus desired to exhaust a greater amount of heat and to have a
larger value of maximum heat transport capability. Moreover, the
further the heat dissipating properties of the heat dissipating
unit 20 improves, the lower the temperature of the exothermic
surface of the Peltier device 3 becomes, and the smaller the
difference in temperature between the endothermic surface and the
exothermic surface of the Peltier device 3 becomes. Accordingly,
the power consumption of the Peltier devices 3 can be reduced to
save energy.
Embodiment 4
[0063] FIGS. 4A, 4B and 4C are a left side view, a front view and a
right side view, showing a cooling apparatus according to
Embodiment 4 of the present invention. This cooling apparatus has a
configuration similar to that shown in FIG. 2, but is different in
that each thermal transport heat pipe 5 is bent in a U-shape, and
the heat receiving and radiating plate 8 is used in which the heat
receiving plate 2 and the radiator plate 4 shown in FIG. 1 are
integrated into a single piece and disposed perpendicularly to each
other. With such a configuration, it is possible to realize
downsizing of the entire apparatus. The temperature control circuit
of the cooling apparatus has the same configuration as that shown
in FIG. 1, and therefore not shown in the drawing.
[0064] In this embodiment, a tip end 12 of the thermal transport
heat pipes 5 is protruded from the end face of the radiator plate
4. If there is an initial residual non-condensable gas (e.g.,
nitrogen) or a non-condensable gas generated from residual metals
(e.g., hydrogen) present within the heat pipe, the gas can be moved
to remain at a condensation side end portion of the heat pipe
during operation. Further, an excess of the liquid sealed within
the heat pipe can be also moved to remain at the condensation side
end portion. Accordingly, the vapor cannot enter the condensation
side end portion of the heat pipe, at which the heat cannot be
exchanged. If the Peltier devices are attached to this portion,
which is then forcibly cooled, this condensation side end portion
may have an abnormally lower temperature with respect to other
condensation portions. Once dew condensation occurs at the
abnormally lower temperature portion, the condensed water droplets
are possibly attached to electronic and optical components.
[0065] In contrast, when a tip end 12 of the thermal transport heat
pipes 5 is protruded from the end face of the radiator plate 4, a
non-cooling portion can be formed at the tip end 12 of the thermal
transport heat pipes 5, thereby ensuring a space that can
accommodate the non-condensable gas and the excessive liquid. As a
result, the above-mentioned problems, such as abnormally lower
temperature and dew condensation, can be solved.
[0066] Further, according to this embodiment, a bypass heat pipe 13
is provided in addition to the thermal transport heat pipes 5. One
end of the heat pipe 13 is coupled to the vicinity of a coupling
portion between the heat receiving plate 2 and one end of the
thermal transport heat pipe 5. The other end of the heat pipe 13 is
coupled to the vicinity of another coupling portion between the
radiator plate 4 and the other end of the thermal transport heat
pipe 5.
[0067] As described above, the condensation side end portion of the
thermal transport heat pipe 5 is likely to be supercooled by the
Peltier devices 3, causing dew condensation. As a countermeasure to
this problem, providing the additional heat pipe 13 can make direct
supply of heat to a portion to which heat is not easily transferred
through vapor movement in the thermal transport heat pipe 5. As a
result, dew condensation caused by supercooling can be
prevented.
[0068] Further, since an end portion on the heat receiving side of
the thermal transport heat pipe 5 has the longest distance for
reflux of the condensation liquid, and thus lower reflux capability
of the liquid. If too large a mount of heat is supplied to this end
portion, the liquid inside the pipe is dried, thus causing
"dryout". Also in this case, providing the additional heat pipe 13
allows a part of the heat quantity supplied from the heating
elements 1 to be transferred in a bypass manner via the heat pipe
13 to the radiator plate 4, thereby preventing the dryout.
[0069] Moreover, according to this embodiment, in the case where
the heating elements 1, the heat receiving plate 2, and a control
board 14 are to be located from the above under gravity
environment, as shown in FIG. 4A, it is preferable that the control
board 14 is not positioned under the Peltier devices 3. Further, it
is more preferable that the control board 14 is positioned above
the Peltier devices 3. In this arrangement, even if any one of the
Peltier devices 3 is supercooled to a lowest temperature, causing
dew condensation and fallen water droplets, then the water droplets
can be prevented from attaching to the control board 14, thereby
surely preventing electrical and optical problems, such as short
circuit, contamination, etc.
Embodiment 5
[0070] FIGS. 5A and 5B are a plan view and a front view, showing a
cooling apparatus according to Embodiment 5 of the present
invention. This cooling apparatus has a configuration similar to
that shown in FIG. 3, but is different in that the heat receiving
plate 2 is provided with a heater 30. In this configuration, it is
possible to perform temperature regulation by energizing the heater
30 to heat the heat receiving plate 2, even when the ambient
temperature falls and the temperature of the entire apparatus also
falls so that the heating elements 1 cannot have a desired
temperature during heat generation. Incidentally, the temperature
of the attachment surface can be raised up by inverting the
direction of a current flowing through the Peltier devices 3 to
raise up the temperature of the radiator plate 4, but inverting the
direction of a current flowing through the Peltier devices 3 shifts
the lower temperature surface into the higher temperature surface,
and vice versa, thereby causing large variation in temperature.
Consequently, the material constituting the Peltier device 3 is
likely to thermally expand and contract at a higher degree,
resulting in fatigue breakdown. Therefore, providing such a heater
as described above can achieve longer duration of life. In
addition, directly heating the heat receiving plate 2 can rapidly
increase the temperature of the attachment surface of the R/G/B
elements, thereby improving response of the temperature
regulation.
[0071] In the case of the laser television, at too low a
temperature the R/G/B elements cannot generate adequate optical
outputs due to their properties, but the R/G/B elements can
generate adequate optical outputs according to this embodiment.
Further, when turning on the television which has been kept at a
lower temperature in a turning-off condition, the R/G/B elements
having a lower temperature cannot generate optical outputs, thereby
extending a latency time to wait for image formation. According to
this embodiment, when the television is turned off, energizing the
heater 30 can keep the R/G/B elements at a desired temperature,
thereby reducing the latency time.
[0072] Further, when the heater 30 is provided, a power source for
the Peltier devices 3 or a power source for the heater 30 can
alternately operate, hence, the power source can be shared to
downsize the apparatus.
Embodiment 6
[0073] FIG. 6 is a plan view showing a cooling apparatus according
to Embodiment 6 of the present invention. This embodiment has a
configuration similar to that shown in FIG. 3, but is different in
that the plurality of heating elements 1 are arranged non-linearly
along the longitudinal direction of the thermal transport heat
pipes 5, and the plurality of Peltier devices 3 are arranged
non-linearly along the longitudinal direction of the thermal
transport heat pipes 5. Also with such a configuration, the heat
transferred from the plurality of heating elements 1 is transported
in a collective manner, and uniformly exhausted to the plurality of
Peltier devices 3. As a result, the heat receiving plate 2 and the
radiator plate 4 can be maintained at a uniform temperature within
the respective planes.
[0074] Although the present invention has been fully described in
connection with the preferred embodiments thereof and the
accompanying drawings, it is to be noted that various changes and
modifications are apparent to those skilled in the art. Such
changes and modifications are to be understood as included within
the scope of the present invention as defined by the appended
claims unless they depart therefrom.
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