1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
COOLING DEVICE
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
5 Technical Field
[0001] The present disclosure relates to a cooling device including heat pipes.
Background Art
[0002] In order to avoid damage caused by heat emission of electronic components
during energization, the electronic components are thermally coupled to a cooling
10 member. The cooling member discharges the heat transferred from the electronic
components to the air around the cooling member. The electronic components are
accordingly cooled. A typical example of the cooling member is a heat sink including
heat pipes. This type of heat sink is disclosed in Patent Literature 1, for example. The
heat sink disclosed in Patent Literature 1 includes a base plate to receive heat transferred
15 from electronic components, and heat pipes. The heat pipes include a plate heat pipe
fixed at the base plate and cylindrical heat pipes communicating with the plate heat pipe.
Citation List
Patent Literature
[0003] Patent Literature 1: Unexamined Japanese Patent Application Publication
20 No. 2003-336976
Summary of Invention
Technical Problem
[0004] The heat pipes included in the heat sink disclosed in Patent Literature 1
accommodate a refrigerant in the gas-liquid two-phase state. The refrigerant evaporated
25 by the heat transferred from the electronic components flows from the plate heat pipe into
the cylindrical heat pipes. While traveling inside the cylindrical heat pipes, the
evaporated refrigerant transfers the heat via the cylindrical heat pipes to the air around the
3
cylindrical heat pipes. The heat transfer from the refrigerant to the air lowers the
temperature of the refrigerant and condenses the refrigerant into liquid. The refrigerant
in the liquid state flows through the cylindrical heat pipes into the plate heat pipe. The
refrigerant thus repeats evaporation and condensation and thereby circulates inside the
heat pipes, resulting in cooling of the electronic 5 components.
[0005] This refrigerant may freeze when the heat sink is installed in a place in
contact with the air at a temperature equal to or lower than the melting point of the
refrigerant. In an exemplary case where the heat pipes accommodate pure water as the
refrigerant and the heat sink is installed in a place in contact with the air at a temperature
10 of 0°C or less, the pure water enclosed in the heat pipes may freeze. The frozen
refrigerant does not circulate inside the heat pipes and therefore impairs the cooling
capacity of the heat sink. The electronic components, which have not been sufficiently
cooled, may reach an excessively high temperature to break down.
[0006] In response to the above issue, an objective of the present disclosure is to
15 provide a cooling device capable of cooling electronic components even in a
low-temperature environment.
Solution to Problem
[0007] In order to achieve the above objective, a cooling device according to an
aspect of the present disclosure includes: a heat-receiving block, a first heat pipe, a
20 second heat pipe, a first refrigerant in the gas-liquid two-phase state, and a second
refrigerant in the gas-liquid two-phase state. The heat-receiving block includes a first
main surface to which a heat emitter is fixed. The first heat pipe is fixed at the
heat-receiving block. The second heat pipe is fixed at the heat-receiving block and
located adjacent to the first heat pipe. The first refrigerant is enclosed in the first heat
25 pipe. The second refrigerant is enclosed in the second heat pipe. At normal
temperature, the ratio of the amount of the second refrigerant in the liquid state to the
volume of the second heat pipe is higher than the ratio of the amount of the first
4
refrigerant in the liquid state to the volume of the first heat pipe.
Advantageous Effects of Invention
[0008] The cooling device according to an aspect of the present disclosure includes
the second heat pipe located adjacent to the first heat pipe. At normal temperature, the
ratio of the amount of the second refrigerant in the liquid state to 5 the volume of the
second heat pipe is higher than the ratio of the amount of the first refrigerant in the liquid
state to the volume of the first heat pipe. The second heat pipe that less readily freeze
than the first heat pipe is located adjacent to the first heat pipe, and therefore can rapidly
melt the frozen first refrigerant inside the first heat pipe. The cooling device is therefore
10 capable of cooling the heat emitter even in a low-temperature environment.
Brief Description of Drawings
[0009] FIG. 1 is a perspective view of a cooling device according to Embodiment 1
of the present disclosure;
FIG. 2 is a sectional view of the cooling device according to Embodiment 1 taken
15 along the line A-A of FIG. 1;
FIG. 3 illustrates a second heat pipe according to Embodiment 1;
FIG. 4 is a sectional view of a power conversion apparatus according to
Embodiment 1;
FIG. 5 is a sectional view of the power conversion apparatus according to
20 Embodiment 1 taken along the line B-B of FIG. 4;
FIG. 6 is a perspective view of a cooling device according to Embodiment 2 of the
present disclosure;
FIG. 7 is a sectional view of the cooling device according to Embodiment 2 taken
along the line C-C of FIG. 6;
25 FIG. 8 is a top view of a plate member constituting a second heat pipe according to
Embodiment 2;
FIG. 9 is a sectional view of a cooling device according to Embodiment 3 of the
5
present disclosure;
FIG. 10 is a top view of a plate member constituting a second heat pipe according
to Embodiment 3;
FIG. 11 is a sectional view of a cooling device according to Embodiment 4 of the
present 5 disclosure;
FIG. 12 is a top view of a plate member constituting a second heat pipe according
to Embodiment 4;
FIG. 13 is a perspective view of a cooling device according to a modified
embodiment; and
10 FIG. 14 is a schematic diagram of a loop heat pipe according to another
embodiment.
Description of Embodiments
[0010] A cooling device according to embodiments of the present disclosure is
described in detail with reference to the accompanying drawings. The identical or
15 corresponding components are provided with the same reference symbol.
[0011] (Embodiment 1)
In order to avoid failure of electronic components due to heat emission from the
electronic components during energization, the electronic components are thermally
coupled to a cooling device for cooling the electronic components. A cooling device 1
20 according to Embodiment 1 illustrated in FIG. 1 includes a heat-receiving block 11 to
which heat emitters are fixed, first heat pipes 12 fixed at the heat-receiving block 11 to
discharge the heat transferred from the heat emitters and thereby cool the heat emitters,
and second heat pipes 13 fixed at the heat-receiving block 11 and located adjacent to the
first heat pipes 12. Each of the first heat pipes 12 includes a primary pipe portion 12a
25 fixed at the heat-receiving block 11, and secondary pipe portions 12b that are
communicating with the primary pipe portion 12a and extend in the direction away from
the heat-receiving block 11. The meaning of fixation encompasses integral formation.
6
Specifically, the primary pipe portions 12a fixed at the heat-receiving block 11 may be
formed integrally with the heat-receiving block 11. Also, the second heat pipes 13 fixed
at the heat-receiving block 11 may be formed integrally with the heat-receiving block 11.
[0012] As illustrated in FIG. 2, which is a sectional view taken along the line A-A
of FIG. 1, the cooling device 1 further includes fins 14 fixed across 5 the secondary pipe
portions 12b. The fins 14 are not shown in FIG. 1 in order to facilitate an understanding.
The cooling device 1 also includes a first refrigerant 15 in the gas-liquid two-phase state
enclosed in the first heat pipes 12, and a second refrigerant 16 in the gas-liquid two-phase
state enclosed in the second heat pipes 13.
10 [0013] In FIGS. 1 and 2, the Z axis corresponds to the vertical direction. The X
axis is orthogonal to both of a first main surface 11a and a second main surface 11b of the
heat-receiving block 11, and the Y axis is orthogonal to both of the X and Z axes.
[0014] The components of the cooling device 1 having the above-mentioned
configuration are described, focusing on an example in which the cooling device 1
15 includes four primary pipe portions 12a, each of which is communicating with four
secondary pipe portions 12b.
As illustrated in FIG. 2, the first main surface 11a of the heat-receiving block 11 is
provided with heat emitters 31 fixed thereto. The heat emitters 31 include electronic
components that emit heat during energization. The second main surface 11b of the
20 heat-receiving block 11, opposite to the first main surface 11a, is provided with grooves
11c extending in the Y-axis direction and grooves 11d extending in the Y-axis direction.
Each of the grooves 11c receives the primary pipe portion 12a inserted thereto. The
primary pipe portions 12a are fixed at the heat-receiving block 11 by any fixing
procedure, such as bonding with an adhesive or soldering.
25 [0015] Each of the grooves 11d receives the second heat pipe 13 inserted thereto.
The second heat pipes 13 are fixed at the heat-receiving block 11 by any fixing procedure,
such as bonding with an adhesive or soldering. The grooves 11d are located adjacent to
7
the grooves 11c. Specifically, the grooves 11d are provided in the vicinity of the
grooves 11c such that the frozen first refrigerant 15 can be melted by transfer of the heat
from the second heat pipes 13 fitted in the grooves 11d to the primary pipe portions 12a
fitted in the grooves 11c, as described below. The heat-receiving block 11 is made of a
material having a high thermal conductivity, for example, a metal, 5 such as copper or
aluminum.
[0016] Each of the first heat pipes 12 includes the primary pipe portion 12a and the
secondary pipe portions 12b that are communicating with the primary pipe portion 12a.
The first heat pipes 12 accommodate the first refrigerant 15.
10 The primary pipe portions 12a are fitted in the respective grooves 11c and fixed at
the heat-receiving block 11. The primary pipe portions 12a are fixed at the
heat-receiving block 11 while being partially exposed from the heat-receiving block 11.
The primary pipe portions 12a are made of a material having a high thermal conductivity,
for example, a metal, such as copper or aluminum.
15 [0017] The secondary pipe portions 12b are fixed at the respective primary pipe
portions 12a by a procedure, such as welding or soldering, and are communicating with
the respective primary pipe portions 12a. The secondary pipe portions 12b extend in the
direction away from the second main surface 11b. The secondary pipe portions 12b are
made of a material having a high thermal conductivity, for example, a metal, such as
20 copper or aluminum.
[0018] Each of the second heat pipes 13 includes an end fitted in the groove 11d
and fixed at the heat-receiving block 11. The second heat pipe 13 defines a flow path of
which the initial point and the terminal point coincide with each other and which winds
between the edge close to the heat-receiving block 11 and the edge distant from the
25 heat-receiving block 11. In the section orthogonal to the Y axis, that is, in the XZ plane,
the second heat pipe 13 fixed at the heat-receiving block 11 extends along parts of the
outer peripheries of the primary pipe portions 12a. Specifically, as illustrated in FIG. 3,
8
the second heat pipe 13 of a self-excited oscillation type has a winding flow path of
which the initial point and the terminal point coincide with each other. The second heat
pipe 13 is bent at 90° along the bending line L1 represented in the dashed and
single-dotted line, fitted in the groove 11d, and then fixed at the heat-receiving block 11.
[0019] As illustrated in FIG. 2, the second heat pipe 13 includes 5 a surface 13a that
faces the positive Z-axis direction and a surface 13b that faces the negative X-axis
direction. The second heat pipe 13 is located adjacent to the first heat pipes 12.
Specifically, the second heat pipe 13 is located adjacent to the primary pipe portions 12a
such that the frozen first refrigerant 15 can be melted by transfer of the heat from the heat
10 emitters 31 via the individual surfaces 13a and 13b to the primary pipe portions 12a.
For example, the second heat pipe 13 is distant from the primary pipe portions 12a by
100 millimeters or less. The surfaces 13a and 13b may preferably be in contact with the
primary pipe portions 12a.
[0020] Each of the fins 14 has through holes, and is fixed across the secondary pipe
15 portions 12b while the secondary pipe portions 12b extend through the respective through
holes. The fins 14 can contribute to improve the cooling efficiency of the cooling
device 1.
[0021] The first refrigerant 15 is enclosed in the first heat pipes 12 in the gas-liquid
two-phase state. The first refrigerant 15 is made of a substance, such as water,
20 evaporated when receiving heat from the heat emitters 31 and condensed into liquid when
discharging heat to the air around the cooling device 1.
[0022] The second refrigerant 16 is enclosed in the second heat pipes 13 in the
gas-liquid two-phase state. The internal space of each second heat pipe 13 is closed by
droplets of the second refrigerant 16 due to a function of the surface tension of the second
25 refrigerant 16, so that the second refrigerant 16 in the liquid state and the second
refrigerant 16 in the gas state are distributed inside the second heat pipe 13. The second
refrigerant 16 is made of a substance, such as water, evaporated when receiving heat from
9
the heat emitters 31 and condensed into liquid when discharging heat to the air around the
cooling device 1.
[0023] At normal temperature, the ratio of the amount of the second refrigerant 16
in the liquid state to the volume of the second heat pipe 13 is higher than the ratio of the
amount of the first refrigerant 15 in the liquid state to the volume of the first 5 heat pipe 12.
The second heat pipes 13 therefore less readily freeze than the first heat pipes 12. For
example, the ratio of the amount of the second refrigerant 16 in the liquid state to the
volume of the second heat pipe 13 is preferably be 50%, while the ratio of the amount of
the first refrigerant 15 in the liquid state to the volume of the first heat pipe 12 is
10 preferably be 20%.
[0024] The cooling device 1 having the above-mentioned configuration is installed
in a power conversion apparatus 30, as illustrated in FIGS. 4 and 5. FIG. 5 is a sectional
view taken along the line B-B of FIG. 4. The power conversion apparatus 30 includes a
housing 32, the heat emitters 31 accommodated in the housing 32, and the cooling device
15 1 to cool the heat emitters 31. The housing 32 includes a partition 33 to divide the
internal space of the housing 32 into a closed compartment 32a and an open compartment
32b. The closed compartment 32a accommodates the heat emitters 31. The open
compartment 32b accommodates the cooling device 1. The partition 33 has an opening
33a. The opening 33a is closed by the first main surface 11a of the heat-receiving block
20 11 included in the cooling device 1. The heat emitters 31 are mounted on the first main
surface 11a that closes the opening 33a. The closing of the opening 33a by the first
main surface 11a can prevent the external air, water, dust, or the like from entering the
closed compartment 32a.
The housing 32 also has intake and exhaust ports 34 in the two walls that face the
25 open compartment 32b and are orthogonal to the Y-axis direction. Cooling air
introduced through one of the intake and exhaust ports 34 in one wall flows between the
secondary pipe portions 12b along the fins 14 and then exits through the other one of the
10
intake and exhaust ports 34 in the other wall. The cooling device 1 transfers the heat
from the heat emitters 31 to the cooling air, to thereby cool the heat emitters 31.
[0025] A mechanism of cooling the heat emitters 31 in the cooling device 1 having
the above-mentioned configuration is described. When the heat emitters 31 emit heat,
the heat is transferred from the heat emitters 31 via the heat-receiving 5 block 11 and the
primary pipe portions 12a to the first refrigerant 15. The transferred heat raises the
temperature of the first refrigerant 15 and evaporates a part of the first refrigerant 15.
The evaporated first refrigerant 15 flows from the primary pipe portions 12a into the
secondary pipe portions 12b, and travels inside the secondary pipe portions 12b toward
10 the upper edges in the vertical direction of the secondary pipe portions 12b. During the
travel inside the secondary pipe portions 12b toward the upper edges in the vertical
direction of the secondary pipe portions 12b, the first refrigerant 15 discharges heat to the
air around the cooling device 1 via the secondary pipe portions 12b and the fins 14. The
heat discharge from the first refrigerant 15 lowers the temperature of the first refrigerant
15 15. The first refrigerant 15 is accordingly condensed into liquid. The first refrigerant
15 in the liquid state moves along the inner walls of the secondary pipe portions 12b and
returns to the primary pipe portions 12a. When the first refrigerant 15 in the liquid state
receives the heat from the heat emitters 31 via the heat-receiving block 11, the first
refrigerant 15 is evaporated again, flows into the secondary pipe portions 12b, and then
20 travels toward the upper edges in the vertical direction of the secondary pipe portions 12b.
The first refrigerant 15 thus repeats the above-described evaporation and condensation
and thereby circulates, so that the heat generated at the heat emitters 31 is discharged to
the air around the cooling device 1, specifically, the air around the secondary pipe
portions 12b and the fins 14, resulting in cooling of the heat emitters 31.
25 [0026] If the heat emitted from the heat emitters 31 is transferred from the heat
emitters 31 via the heat-receiving block 11 and the primary pipe portions 12a to the first
refrigerant 15, then the first refrigerant 15 that has not been evaporated, that is, the first
11
refrigerant 15 in the liquid state has internal temperature differences and generates
convection. The convection allows the first refrigerant 15 to diffuse and transfer the
heat from the heat emitters 31 in the Y-axis direction, leading to efficient cooling of the
heat emitters 31.
[0027] When the heat emitters 31 emit heat, the heat is also transferred 5 from the
heat emitters 31 via the heat-receiving block 11 and the second heat pipes 13 to the
second refrigerant 16. The transferred heat evaporates a part of the second refrigerant
16 in the liquid state. The evaporated second refrigerant 16 has an increased volume
and urges the second refrigerant 16 in the liquid state and the second refrigerant 16 in the
10 gas state to travel toward the edges distant from the heat-receiving block 11, in other
words, the upper edges in the vertical direction. During the travel inside the second heat
pipes 13 toward the upper edges in the vertical direction, the evaporated second
refrigerant 16 discharges heat to the air around the cooling device 1 via the second heat
pipes 13. The heat discharge from the second refrigerant 16 lowers the temperature of
15 the second refrigerant 16. The second refrigerant 16 is accordingly condensed into
liquid. The second refrigerant 16 in the liquid state moves along the inner walls of the
second heat pipes 13 downward in the vertical direction. When the second refrigerant
16 in the liquid state receives heat from the heat emitters 31 via the heat-receiving block
11, the second refrigerant 16 is evaporated again. The second refrigerant 16 thus repeats
20 the evaporation and condensation and thereby circulates, so that the heat generated at the
heat emitters 31 is discharged to the air around the cooling device 1, specifically, the air
around the second heat pipes 13, resulting in cooling of the heat emitters 31.
[0028] The frozen first refrigerant 15, however, does not make the above-described
circulation and convection, and does not enable the cooling device 1 to cool the heat
25 emitters 31. Specifically, if the air around the cooling device 1 reaches 0°C or less
during no energization of the electronic components included in the heat emitters 31, the
first refrigerant 15 made of water may freeze. The frozen first refrigerant 15 needs to be
12
melted in order to prevent deterioration of the cooling efficiency of the cooling device 1.
[0029] A mechanism of melting the frozen first refrigerant 15 in the cooling device
1 is described. When the heat emitters 31 emit heat, the heat is transferred via the
heat-receiving block 11 and the first heat pipes 12 to the first refrigerant 15. The heat
generated at the heat emitters 31 is also transferred to the second heat 5 pipes 13, and is
then transferred from the individual surfaces 13a and 13b of the second heat pipes 13
located adjacent to the primary pipe portions 12a, via the primary pipe portions 12a to the
first refrigerant 15. As a result, the heat is transferred to the frozen first refrigerant 15 in
multiple ways, not only at the parts of the primary pipe portions 12a that face the
10 heat-receiving block 11 but also at the parts of the primary pipe portions 12a that do not
face the heat-receiving block 11 via the second heat pipes 13. The cooling device 1 can
therefore melt the frozen first refrigerant 15 more rapidly than an existing heat-pipe
cooling device without the second heat pipes 13.
[0030] As described above, the cooling device 1 according to Embodiment 1 can
15 rapidly melt the frozen first refrigerant 15 because of the second heat pipes 13. The
cooling device 1 can therefore cool the heat emitters 31 even in a low-temperature
environment.
[0031] (Embodiment 2)
The second heat pipes 13 may have any structure provided that the second heat
20 pipes 13 less readily freeze than the first heat pipes 12 and can melt the frozen first
refrigerant 15. A cooling device 2 according to Embodiment 2 illustrated in FIGS. 6
and 7 includes second heat pipes 17 in place of the second heat pipes 13. The cooling
device 2 has the structure identical to that of the cooling device 1 except for the second
heat pipes 17 and the shape of the heat-receiving block 11. The cooling device 2 can be
25 installed in the power conversion apparatus 30, like the cooling device 1.
[0032] The heat-receiving block 11 included in the cooling device 2 is provided
with grooves 11e in addition to the grooves 11d. Each of the grooves 11d receives one
13
end of the second heat pipe 17 inserted thereto.
[0033] The one end of the second heat pipe 17 is fitted in the groove 11d and fixed
at the heat-receiving block 11 by a procedure, such as bonding with an adhesive or
soldering. The second heat pipe 17 includes a plate member 19 having an internal flow
path 18. Specifically, as illustrated in FIG. 8, the plate member 19 has 5 a flat shape and
provided with the winding internal flow path 18 of which the initial point and the
terminal point coincide with each other. This plate member 19 is bent at 90° along the
bending line L2 represented in the dashed and single-dotted line, thereby yielding the
second heat pipe 17. The flow path 18 accommodates the second refrigerant 16 in the
10 gas-liquid two-phase state, as in Embodiment 1. The plate member 19 is made of a
material excellent in thermal conductivity and processability, for example, a metal, such
as copper or aluminum.
[0034] The second heat pipe 17 fabricated by bending the plate member 19 as
described above includes a surface 17a that faces the positive Z-axis direction and a
15 surface 17b that faces the negative X-axis direction, as illustrated in FIG. 7. The second
heat pipe 17 is located adjacent to the first heat pipes 12. Specifically, the second heat
pipe 17 is located adjacent to the primary pipe portions 12a such that the frozen first
refrigerant 15 can be melted by transfer of the heat from the heat emitters 31 via the
individual surfaces 17a and 17b to the primary pipe portions 12a. The surfaces 17a and
20 17b may preferably be in contact with the primary pipe portions 12a.
[0035] At normal temperature, the ratio of the amount of the second refrigerant 16
in the liquid state to the volume of the flow path 18 in the second heat pipe 17 is higher
than the ratio of the amount of the first refrigerant 15 in the liquid state to the volume of
the first heat pipe 12, as in Embodiment 1. The second heat pipes 17 therefore less
25 readily freeze than the first heat pipes 12. For example, the ratio of the amount of the
second refrigerant 16 in the liquid state to the volume of the flow path 18 in the second
heat pipe 17 is preferably be 50%, while the ratio of the amount of the first refrigerant 15
14
in the liquid state to the volume of the first heat pipe 12 is preferably be 20%.
[0036] A mechanism of cooling the heat emitters 31 in the cooling device 2 having
the above-mentioned configuration is described. The first heat pipes 12 cool the heat
emitters 31 by the mechanism identical to that in Embodiment 1. The following
description is thus directed to a mechanism of the second heat pipes 17 5 cooling the heat
emitters 31.
[0037] When the heat emitters 31 emit heat, the heat is transferred from the heat
emitters 31 via the heat-receiving block 11 and the plate members 19 to the second
refrigerant 16. The transferred heat evaporates a part of the second refrigerant 16 in the
10 liquid state. The evaporated second refrigerant 16 has an increased volume and urges
the second refrigerant 16 in the liquid state and the second refrigerant 16 in the gas state
to travel toward the edges distant from the heat-receiving block 11, in other words, the
upper edges in the vertical direction. During the travel through the flow paths 18 toward
the upper edges in the vertical direction, the evaporated second refrigerant 16 discharges
15 heat to the air around the cooling device 2 via the plate members 19. The heat discharge
from the second refrigerant 16 lowers the temperature of the second refrigerant 16. The
second refrigerant 16 is accordingly condensed into liquid. The second refrigerant 16 in
the liquid state moves along the inner walls of the flow paths 18 downward in the vertical
direction. When the second refrigerant 16 in the liquid state receives heat from the heat
20 emitters 31 via the heat-receiving block 11 and the plate members 19, the second
refrigerant 16 is evaporated again. The second refrigerant 16 thus repeats the
evaporation and condensation and thereby circulates, so that the heat generated at the heat
emitters 31 is discharged to the air around the cooling device 2, specifically, the air
around the second heat pipes 17, resulting in cooling of the heat emitters 31.
25 [0038] In addition, a part of the heat transferred from the heat emitters 31 via the
heat-receiving block 11 to the plate members 19 constituting the second heat pipes 17 is
discharged from the plate members 19 directly to the ambient air, resulting in cooling of
15
the heat emitters 31.
[0039] A mechanism of melting the frozen first refrigerant 15 in the cooling device
2 is described. When the heat emitters 31 emit heat, the heat is transferred via the
heat-receiving block 11 and the first heat pipes 12 to the first refrigerant 15, as in
5 Embodiment 1.
The heat generated at the heat emitters 31 is also transferred to the second heat
pipes 17, and is then transferred from the individual surfaces 17a and 17b of the second
heat pipes 17 located adjacent to the primary pipe portions 12a, via the primary pipe
portions 12a to the first refrigerant 15. That is, the heat is transferred to the frozen first
10 refrigerant 15 in multiple ways, not only at the parts of the primary pipe portions 12a that
face the heat-receiving block 11 but also at the parts of the primary pipe portions 12a that
do not face the heat-receiving block 11 via the second heat pipes 17. The cooling device
1 can therefore melt the frozen first refrigerant 15 more rapidly than an existing heat-pipe
cooling device without the second heat pipes 17.
15 [0040] As described above, the cooling device 2 according to Embodiment 2 can
rapidly melt the frozen first refrigerant 15 because of the second heat pipes 17. The
cooling device 2 can therefore cool the heat emitters 31 even in a low-temperature
environment.
In addition, the flow paths 18 in the second heat pipes 17 are formed inside the
20 plate members 19, and are therefore less susceptible to a variation in the temperature of
the air around the cooling device 1 and less readily freeze than the second heat pipes 13
included in the cooling device 1 according to Embodiment 1.
[0041] Furthermore, the distance between the second heat pipes 17 and the heat
emitters 31 is shorter than the distance between the primary pipe portions 12a and the
25 heat emitters 31. The heat generated at the heat emitters 31 is therefore transferred to
the second heat pipes 17 more rapidly than to the primary pipe portions 12a. This
configuration can achieve efficient heat transfer from the second heat pipes 17 via the
16
primary pipe portions 12a to the first refrigerant 15, leading to rapid melting of the frozen
first refrigerant 15.
[0042] (Embodiment 3)
The second heat pipes 13 may have any structure provided that the second heat
pipes 13 less readily freeze than the first heat pipes 12 and can melt 5 the frozen first
refrigerant 15. A cooling device 3 according to Embodiment 3 illustrated in FIG. 9
includes second heat pipes 20 in place of the second heat pipes 13. The cooling device
3 has the structure identical to that of the cooling device 1 except for the second heat
pipes 20 and the shape of the heat-receiving block 11. The cooling device 3 can be
10 installed in the power conversion apparatus 30, like the cooling devices 1 and 2.
[0043] The heat-receiving block 11 included in the cooling device 3 is provided
with the grooves 11e like those of the heat-receiving block 11 included in the cooling
device 2, and grooves 11f. Each of the grooves 11e receives one end of the second heat
pipe 20, while the groove 11f, disposed above the groove 11e in the vertical direction
15 with the two grooves 11c between the grooves 11f and 11d, receives the other end of the
second heat pipe 20.
[0044] The one end of the second heat pipe 20 is fitted in the groove 11e while the
other end is fitted in the groove 11f. The second heat pipe 20 is then fixed at the
heat-receiving block 11 by a procedure, such as bonding with an adhesive or soldering.
20 The second heat pipe 20 is fabricated by bending the plate member 19 like that in
Embodiment 2. Specifically, as illustrated in FIG. 10, the plate member 19 has a flat
shape and provided with the winding internal flow path 18 of which the initial point and
the terminal point coincide with each other. This plate member 19 is bent at 90° along
the bending lines L3 and L4 represented in the dashed and single-dotted lines, thereby
25 yielding the second heat pipe 20. The direction of bending the plate member 19 along
the bending line L3 is identical to the direction of bending the plate member 19 along the
bending line L4.
17
[0045] The second heat pipe 20 fabricated by bending the plate member 19 as
described above includes a surface 20a that faces the positive Z-axis direction, a surface
20b that faces the negative X-axis direction, and a surface 20c that faces the negative
Z-axis direction, as illustrated in FIG. 9. The second heat pipe 20 is located adjacent to
the first heat pipes 12. Specifically, the second heat pipe 20 is located 5 adjacent to the
primary pipe portions 12a such that the heat from the heat emitters 31 can be transferred
via the individual surfaces 20a, 20b, and 20c to the primary pipe portions 12a. The
surfaces 20a, 20b, and 20c of the second heat pipes 20 may preferably be in contact with
the primary pipe portions 12a.
10 [0046] At normal temperature, the ratio of the amount of the second refrigerant 16
in the liquid state to the volume of the flow path 18 in the second heat pipe 20 is higher
than the ratio of the amount of the first refrigerant 15 in the liquid state to the volume of
the first heat pipe 12, as in Embodiment 1. The second heat pipes 20 therefore less
readily freeze than the first heat pipes 12. For example, the ratio of the amount of the
15 second refrigerant 16 in the liquid state to the volume of the flow path 18 in the second
heat pipe 20 is preferably be 50%, while the ratio of the amount of the first refrigerant 15
in the liquid state to the volume of the first heat pipe 12 is preferably be 20%.
[0047] The first heat pipes 12 cool the heat emitters 31 by the mechanism identical
to that in Embodiment 1. The second heat pipes 20 cool the heat emitters 31 by the
20 mechanism identical to that in Embodiment 2. Both edges of each plate member 19
constituting the second heat pipe 20 are fixed at the heat-receiving block 11, so that both
edges of the flow path 18 are warmed by the heat transferred from the heat emitters 31
via the heat-receiving block 11. Accordingly, the evaporated second refrigerant 16 has
an increased volume and urges the second refrigerant 16 in the liquid state and the second
25 refrigerant 16 in the gas state to travel toward the middle portion of the flow path 18, in
other words, the center of the plate member 19 in the longitudinal direction.
[0048] A mechanism of melting the frozen first refrigerant 15 in the cooling device
18
3 is described. When the heat emitters 31 emit heat, the heat is transferred via the
heat-receiving block 11 and the first heat pipes 12 to the first refrigerant 15.
The heat generated at the heat emitters 31 is also transferred to the second heat
pipes 20, and is then transferred from the individual surfaces 20a, 20b, and 20c of the
second heat pipes 20 located adjacent to the primary pipe portions 12a, 5 via the primary
pipe portions 12a to the first refrigerant 15. That is, the heat is transferred to the frozen
first refrigerant 15 in multiple ways, not only at the parts of the primary pipe portions 12a
that face the heat-receiving block 11 but also at the parts of the primary pipe portions 12a
that do not face the heat-receiving block 11 via the second heat pipes 20. The cooling
10 device 3 can therefore melt the frozen first refrigerant 15 more rapidly than an existing
heat-pipe cooling device without the second heat pipes 20.
[0049] In addition, the heat generated at the heat emitters 31 is transferred via both
edges of the second heat pipes 20 to the second heat pipes 20 because the edges of the
second heat pipes 20 are fixed at the heat-receiving block 11. The heat is therefore
15 distributed to the entire second heat pipes 20 more rapidly in comparison to the cases of
the second heat pipes 13 and 17. The second heat pipes 20 can thus melt the frozen first
refrigerant 15 more rapidly than the second heat pipes 13 and 17.
[0050] As described above, the cooling device 3 according to Embodiment 3 can
rapidly melt the frozen first refrigerant 15, because of the second heat pipes 20 causing
20 the heat from the heat emitters 31 to be transferred from the surfaces 20a, 20b, and 20c
via the primary pipe portions 12a to the first refrigerant 15. The cooling device 3 can
therefore cool the heat emitters 31 even in a low-temperature environment.
[0051] (Embodiment 4)
Although the second heat pipes 13, 17, and 20 according to Embodiments 1 to 3
25 extend along parts of the outer peripheries of the primary pipe portions 12a in the XZ
plane, the second heat pipes 13, 17, and 20 may extend along parts of the outer
peripheries of the primary pipe portions 12a in the XZ plane and also extend along the
19
secondary pipe portions 12b. As illustrated in FIG. 11, a cooling device 4 according to
Embodiment 4 includes second heat pipes 21 in place of the second heat pipes 13. The
cooling device 4 has the structure identical to that of the cooling device 1 except for the
second heat pipes 21 and the shape of the heat-receiving block 11. The cooling device 4
can be installed in the power conversion apparatus 30, like the cooling 5 devices 1 to 3.
[0052] The heat-receiving block 11 included in the cooling device 4 is provided
with grooves 11g instead of the grooves 11d. Each of the grooves 11g receives the
second heat pipe 21 inserted therein. The groove 11g is located adjacent to the groove
11c at the position above the groove 11c in the vertical direction. Specifically, the
10 groove 11g is located adjacent to the groove 11c, such that the frozen first refrigerant 15
can be melted by transfer of the heat from the second heat pipe 21 fitted in the groove 11g
to the primary pipe portion 12a fitted in the groove 11c.
[0053] The second heat pipe 21 is fitted in the groove 11g and then fixed at the
heat-receiving block 11 by a procedure, such as bonding with an adhesive or soldering.
15 The second heat pipe 21 includes the internal flow path 18. Specifically, as illustrated in
FIG. 12, the plate member 19 has a flat shape and provided with the winding internal
flow path 18 of which the initial point and the terminal point coincide with each other.
This plate member 19 is bent at 90° along the bending line L5 represented in a dashed
and single-dotted line and bent along the bending line L6 represented in a dashed and
20 single-dotted line at the angle defined between the horizontal direction and the direction
of extension of the secondary pipe portion 12b, thereby yielding the second heat pipe 21.
The direction of bending the plate member 19 along the bending line L5 is opposite to the
direction of bending the plate member 19 along the bending line L6. The second heat
pipe 21 is fabricated by bending the plate member 19 at the angle defined between the
25 horizontal direction and the direction of extension of the secondary pipe portion 12b, and
thus extends along the secondary pipe portion 12b while being fixed at the heat-receiving
block 11.
20
[0054] The second heat pipe 21 fabricated by bending the plate member 19 as
described above includes a surface 21a that faces the negative Z-axis direction, a surface
21b that faces the negative X-axis direction, and a surface 21c extending along the
secondary pipe portion 12b, as illustrated in FIG. 11. The second heat pipe 21 is located
adjacent to the primary pipe portion 12a. Specifically, the second heat 5 pipe 21 is located
adjacent to the primary pipe portion 12a, such that the heat from the heat emitters 31 can
be transferred via the individual surfaces 21a and 21b to the primary pipe portion 12a.
The surfaces 21a and 21b of the second heat pipe 21 may preferably be in contact with
the primary pipe portion 12a. Also, the second heat pipe 21 is located adjacent to the
10 secondary pipe portion 12b and extends along the secondary pipe portion 12b such that
the heat from the heat emitters 31 can be transferred via the surface 21c to the secondary
pipe portion 12b. The surface 21c of the second heat pipe 21 may preferably be in
contact with the secondary pipe portion 12b.
[0055] At normal temperature, the ratio of the amount of the second refrigerant 16
15 in the liquid state to the volume of the flow path 18 in the second heat pipe 21 is higher
than the ratio of the amount of the first refrigerant 15 in the liquid state to the volume of
the first heat pipe 12, as in Embodiment 1. The second heat pipes 21 therefore less
readily freeze than the first heat pipes 12. For example, the ratio of the amount of the
second refrigerant 16 in the liquid state to the volume of the flow path 18 in the second
20 heat pipe 21 is preferably be 50%, while the ratio of the amount of the first refrigerant 15
in the liquid state to the volume of the first heat pipe 12 is preferably be 20%.
[0056] The first heat pipes 12 cool the heat emitters 31 by the mechanism identical
to that in Embodiment 1. The second heat pipes 20 cool the heat emitters 31 by the
mechanism identical to that in Embodiment 2.
25 [0057] A mechanism of melting the frozen first refrigerant 15 in the cooling device
4 is described. When the heat emitters 31 emit heat, the heat is transferred via the
heat-receiving block 11 and the first heat pipes 12 to the first refrigerant 15.
21
The heat generated at the heat emitters 31 is also transferred to the second heat
pipes 21, and is then transferred from the individual surfaces 21a and 21b of the second
heat pipes 21 located adjacent to the primary pipe portions 12a, via the primary pipe
portions 12a to the first refrigerant 15. That is, the heat is transferred to the frozen first
refrigerant 15 in multiple ways, not only at the parts of the primary pipe 5 portions 12a that
face the heat-receiving block 11 but also at the parts of the primary pipe portions 12a that
do not face the heat-receiving block 11 via the second heat pipes 20.
In addition, the heat transferred to the second heat pipes 21 is transferred from the
surfaces 21c via the secondary pipe portions 12b to the first refrigerant 15. The heat is
10 thus also transferred to the first refrigerant 15 frozen in the secondary pipe portions 12b.
The cooling device 4 can therefore melt the frozen first refrigerant 15 more rapidly than
an existing heat-pipe cooling device without the second heat pipes 21. Furthermore, the
cooling device 1 can rapidly melt the first refrigerant 15 frozen in the secondary pipe
portions 12b.
15 [0058] As described above, the cooling device 4 according to Embodiment 4 can
rapidly melt the frozen first refrigerant 15, because of the second heat pipes 21 causing
the heat from the heat emitters 31 to be transferred from the individual surfaces 21a and
21b via the primary pipe portions 12a to the first refrigerant 15 and causing the heat to be
transferred from the surfaces 21c via the secondary pipe portions 12b to the first
20 refrigerant 15. The cooling device 4 can therefore cool the heat emitters 31 even in a
low-temperature environment.
[0059] The above-described embodiments are not construed as limiting the present
disclosure. For example, some of the above-described embodiments may be arbitrarily
combined. Specifically, the second heat pipes 13 included in the cooling device 1 may
25 have the shape identical to that of the second heat pipes 20 or 21.
[0060] The heat-receiving block 11 does not necessarily have a plate shape, and
may have any shape provided that the heat emitters 31 can be fixed to the first main
22
surface 11a and the first heat pipes 12 can be fixed at the heat-receiving block 11.
[0061] The first heat pipe 12 may have any structure and shape provided that the
first heat pipe 12 can discharge the heat transferred from the heat emitters 31. For
example, the first heat pipe 12 may include the primary pipe portion 12a alone.
The section of the primary pipe portion 12a orthogonal to the longitudinal 5 direction
does not necessarily have a circular shape and may also have a flattened shape. Also,
the section of the secondary pipe portion 12b orthogonal to the longitudinal direction
does not necessarily have a circular shape and may also have a flattened shape. The
flattened shape indicates a shape formed by narrowing the width of a part of the circular
10 shape than the original width and encompasses elliptical, streamline, and elongated
circular shapes. The elongated circular shape indicates a shape defined by circles
having the same diameter and the straight lines connecting the contours of the circles with
each other. In this case, when the primary pipe portion 12a is fixed at the heat-receiving
block 11 such that the longer axis of the flattened shape is in parallel to the Z-axis
15 direction, this arrangement can improve the efficiency of heat transfer from the
heat-receiving block 11 to the primary pipe portion 12a. Furthermore, when the
secondary pipe portion 12b is fixed at the primary pipe portion 12a such that the
longitudinal direction of the secondary pipe portion 12b coincides with the direction of
flow of the cooling air, this configuration can reduce turbulence in the vicinity of the
20 secondary pipe portion 12b, leading to improvement of the cooling efficiency.
[0062] The second heat pipes 13, 17, 20, 21, and 22 may have any shape provided
that these pipes can melt the frozen first refrigerant 15. For example, the second heat
pipes 17, 20, 21, and 22 may include a member having any shape and including the
internal flow path 18.
25 As another example, FIG. 13 illustrates second heat pipes 22 each of which
includes a segment extending along parts of the outer peripheries of the primary pipe
portions 12a in the XZ plane and another segment extending along the secondary pipe
23
portion 12b. The second heat pipe 22 includes a bent segment 22a that extends along
parts of the outer peripheries of the primary pipe portions 12a in the XZ plane like the
second heat pipe 17, and a linear segment 22b that extends from the second main surface
11b of the heat-receiving block 11 along the secondary pipe portion 12b.
[0063] The flow path 18 may have any shape provided that the flow 5 path 18 allows
the second refrigerant 16 enclosed therein to circulate. For example, the flow path 18
may have a ring shape.
The second heat pipe 13, 17, 20, or 21 does not necessarily be a self-excited heat
pipe and may also be a loop heat pipe 23 illustrated in FIG. 14. The loop heat pipe 23
10 includes an evaporator 23a to transfer the heat generated at the heat emitters 31 to the
second refrigerant 16 and thereby evaporate the second refrigerant 16, a vapor pipe 23b
through which the evaporated second refrigerant 16 flows, a condenser 23c to discharge
the heat transferred from the second refrigerant 16 and thereby condense the second
refrigerant 16 into liquid, a liquid pipe 23d through which the second refrigerant 16 in the
15 liquid state flows, and a reservoir 23e to retain a part of the second refrigerant 16 flowing
through the liquid pipe 23d and thereby adjust the amount of the second refrigerant 16
flowing from the liquid pipe 23d into the evaporator 23a. In this case, the evaporator
23a is fixed at the heat-receiving block 11.
Alternatively, the loop heat pipe 23 may be formed inside a plate member, like the
20 second heat pipes 17, 20, and 21. In this case, the plate member including the internal
loop heat pipe 23 is fixed at the heat-receiving block 11 such that the evaporator 23a is
located adjacent to the heat-receiving block 11.
[0064] The heat emitters 31 fixed at the heat-receiving block 11 may be switching
elements including wide bandgap semiconductors. The wide bandgap semiconductor
25 contains, for example, a silicon carbide, gallium nitride martial, or diamond. The
switching element including a wide bandgap semiconductor has a reduced size in
comparison to a switching element including silicon, and therefore generates a larger
24
amount of heat per unit area. The heat generated in the wide bandgap semiconductors is
received at the second heat pipes 13, 17, 20, 21, or 22, which less readily freeze than the
first heat pipes 12, so that the second heat pipes 13, 17, 20, 21, or 22 can rapidly melt the
frozen first refrigerant 15.
[0065] The foregoing describes some example embodiments 5 for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,
persons skilled in the art will recognize that changes may be made in form and detail
without departing from the broader spirit and scope of the invention. Accordingly, the
specification and drawings are to be regarded in an illustrative rather than a restrictive
10 sense. This detailed description, therefore, is not to be taken in a limiting sense, and the
scope of the invention is defined only by the included claims, along with the full range of
equivalents to which such claims are entitled.
Reference Signs List
[0066] 1, 2, 3, 4 Cooling device
15 11 Heat-receiving block
11a First main surface
11b Second main surface
11c, 11d, 11e, 11f, 11g Groove
12 First heat pipe
20 12a Primary pipe portion
12b Secondary pipe portion
13, 17, 20, 21, 22 Second heat pipe
13a, 13b, 17a, 17b, 20a, 20b, 20c, 21a, 21b, 21c Surface
14 Fin
25 15 First refrigerant
16 Second refrigerant
18 Flow path
25
19 Plate member
22a Bent segment
22b Linear segment
23 Loop heat pipe
5 23a Evaporator
23b Vapor pipe
23c Condenser
23d Liquid pipe
23e Reservoir
10 30 Power conversion apparatus
31 Heat emitter
32 Housing
32a Closed compartment
32b Open compartment
15 33 Partition
33a Opening
34 Intake and exhaust port
L1, L2, L3, L4, L5, L6 Bending line
26
We Claim :
1. A cooling device comprising:
a heat-receiving block comprising a first main surface to which a heat emitter is
fixed;
a first heat pipe fixed at the heat-5 receiving block;
a second heat pipe fixed at the heat-receiving block and located adjacent to the first
heat pipe;
a first refrigerant in a gas-liquid two-phase state enclosed in the first heat pipe; and
a second refrigerant in a gas-liquid two-phase state enclosed in the second heat
10 pipe, wherein
a ratio of an amount of the second refrigerant in a liquid state to a volume of the
second heat pipe is higher than a ratio of an amount of the first refrigerant in a liquid state
to a volume of the first heat pipe, at normal temperature.
15 2. The cooling device according to claim 1, wherein the second heat pipe
comprises a member comprising an internal flow path.
3. The cooling device according to claim 1 or 2, wherein the second heat pipe
defines a flow path of which an initial point and a terminal point coincide with each other.
20
4. The cooling device according to any one of claims 1 to 3, wherein the
second heat pipe defines a flow path winding between an edge close to the heat-receiving
block and an edge distant from the heat-receiving block.
25 5. The cooling device according to any one of claims 1 to 4, wherein the first
heat pipe comprises a primary pipe portion fixed at the heat-receiving block, the primary
pipe portion extending along the first main surface.
27
6. The cooling device according to claim 5, wherein the second heat pipe
extends along a part of an outer periphery of the primary pipe portion in a section
orthogonal to a direction of extension of the primary pipe portion.
5
7. The cooling device according to claim 5 or 6, wherein the second heat pipe
is in contact with the primary pipe portion.
8. The cooling device according to any one of claims 5 to 7, wherein the first
10 heat pipe further comprises a secondary pipe portion communicating with the primary
pipe portion, the secondary pipe portion extending in a direction away from a second
main surface of the heat-receiving block, the second main surface being opposite to the
first main surface.
15 9. The cooling device according to claim 8, wherein the second heat pipe
extends along the secondary pipe portion.
10. The cooling device according to claim 8 or 9, wherein the second heat pipe
is in contact with the secondary pipe portion.