U.S. patent application number 14/118764 was filed with the patent office on 2014-04-24 for cooling system.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Yuki Jojima, Yoshiaki Kawakami, Yuichi Ohno, Kousuke Sato, Eizo Takahashi, Kazuhide Uchida. Invention is credited to Yuki Jojima, Yoshiaki Kawakami, Yuichi Ohno, Kousuke Sato, Eizo Takahashi, Kazuhide Uchida.
Application Number | 20140109613 14/118764 |
Document ID | / |
Family ID | 46208626 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140109613 |
Kind Code |
A1 |
Ohno; Yuichi ; et
al. |
April 24, 2014 |
COOLING SYSTEM
Abstract
A cooling system (1) includes: a compressor (12) that circulates
refrigerant; a heat exchanger (14) and a heat exchanger (15) that
carry out heat exchange between refrigerant and outside air; a
decompressor (16) that decompresses refrigerant; a heat exchanger
(18) that carries out heat exchange between refrigerant and
air-conditioning air; a cooling portion (30) that is provided in a
path of refrigerant flowing between the heat exchanger (14) and the
heat exchanger (15) and that uses refrigerant to cool a heat
generating source (31); a first line (24) through which refrigerant
circulates between the cooling portion (30) and the heat exchanger
(15); a second line (27) through which refrigerant circulates
between the heat exchanger (18) and the compressor (12); and an
internal heat exchanger (40) in which refrigerant that circulates
through the first line (24) and refrigerant that circulates through
the second line (27) exchange heat with each other.
Inventors: |
Ohno; Yuichi; (Nishio-shi,
JP) ; Uchida; Kazuhide; (Hamamatsu-shi, JP) ;
Jojima; Yuki; (Nagoya-shi, JP) ; Kawakami;
Yoshiaki; (Nagoya-shi, JP) ; Takahashi; Eizo;
(Chiryu-shi, JP) ; Sato; Kousuke; (Toyota-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ohno; Yuichi
Uchida; Kazuhide
Jojima; Yuki
Kawakami; Yoshiaki
Takahashi; Eizo
Sato; Kousuke |
Nishio-shi
Hamamatsu-shi
Nagoya-shi
Nagoya-shi
Chiryu-shi
Toyota-shi |
|
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
46208626 |
Appl. No.: |
14/118764 |
Filed: |
May 14, 2012 |
PCT Filed: |
May 14, 2012 |
PCT NO: |
PCT/IB2012/000937 |
371 Date: |
November 19, 2013 |
Current U.S.
Class: |
62/498 |
Current CPC
Class: |
B60H 2001/00949
20130101; F25B 41/04 20130101; F25B 13/00 20130101; B60H 2001/00307
20130101; F25B 2313/025 20130101; F25B 40/00 20130101; F25B 1/005
20130101; B60H 1/00278 20130101; B60H 2001/00935 20130101; F25B
30/02 20130101; B60H 2001/00957 20130101; F25B 2313/02741 20130101;
B60H 1/00907 20130101 |
Class at
Publication: |
62/498 |
International
Class: |
F25B 1/00 20060101
F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2011 |
JP |
2011-113372 |
Claims
1. A cooling system for cooling a heat generating source,
comprising: a compressor configured to circulate refrigerant; a
first heat exchanger and a second heat exchanger configured to
carry out heat exchange between the refrigerant and outside air; a
decompressor configured to decompress the refrigerant; a third heat
exchanger configured to carry out heat exchange between the
refrigerant and air-conditioning air; a cooling portion provided in
a path of the refrigerant flowing between the first heat exchanger
and the second heat exchanger, the cooling portion configured to
use the refrigerant to cool the heat generating source; a first
line through which the refrigerant flows between the cooling
portion and the second heat exchanger; a second line through which
the refrigerant flows between the third heat exchanger and the
compressor; and an internal heat exchanger in which the refrigerant
that flows through the first line and the refrigerant that flows
through the second line exchange heat with each other.
2. The cooling system according to claim 1, wherein the internal
heat exchanger is arranged between the cooling portion and the
second heat exchanger.
3. The cooling system according to claim 1, further comprising: a
third line through which the refrigerant flows between the
compressor and the first heat exchanger; and a fourth line
configured to provide fluid communication between the first line
and the third line.
4. The cooling system according to claim 3, further comprising: a
selector valve configured to switch a state of fluid communication
between the fourth line, and the first line and the third line.
5. The cooling system according to claim 4, wherein the selector
valve is configured so as to switch the state of fluid
communication into a state where the refrigerant flows through the
fourth line during a stop of the compressor.
6. The cooling system according to claim 3, wherein the cooling
portion is arranged below the first heat exchanger.
7. The cooling system according to claim 1, further comprising: a
four-way valve configured to switch between flow of the refrigerant
from the compressor toward the first heat exchanger and flow of the
refrigerant from the compressor toward the third heat
exchanger.
8. The cooling system according to claim 1, wherein the first heat
exchanger and the second heat exchanger are integrally arranged.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a cooling system and, more
particularly, to a cooling system that utilizes a vapor compression
refrigeration cycle to cool a heat generating source.
[0003] 2. Description of Related Art
[0004] In recent years, hybrid vehicles, fuel cell vehicles,
electric vehicles, and the like, that run using driving force of a
motor become a focus of attention as one of measures against
environmental issues. In such vehicles, electrical devices, such as
a motor, a generator, an inverter, a converter and a battery,
exchange electric power to generate heat. Therefore, these
electrical devices need to be cooled. Then, there has been
suggested a technique that utilizes a vapor compression
refrigeration cycle, which is used as a vehicle air conditioner, to
cool a heat generating element.
[0005] For example, Japanese Patent Application Publication No.
2006-290254 (JP 2006-290254 A) describes a cooling system for a
hybrid vehicle. The cooling system includes: a compressor that is
able to introduce and compress gaseous refrigerant; a main
condenser that is able to cool high-pressure gaseous refrigerant
using ambient air to condense the high-pressure gaseous
refrigerant; an evaporator that is able to evaporate
low-temperature liquid refrigerant to cool an refrigerating object;
and a decompressing unit, and a heat exchanger, which is able to
absorb heat from a motor, and a second decompressing unit are
connected in parallel with the decompressing unit and the
evaporator. Japanese Patent Application Publication No. 2007-69733
(JP 2007-69733 A) describes a system in which a heat exchanger that
exchanges heat with air-conditioning air and a heat exchanger that
exchanges heat with a heat generating element are arranged in
parallel with each other in a refrigerant line routed from an
expansion valve to a compressor and refrigerant for an air
conditioner is utilized to cool the heat generating element.
[0006] Japanese Patent Application Publication No. 2005-90862 (JP
2005-90862 A) describes a cooling system in which a heat generating
element cooling unit for cooling a heat generating element is
provided in a bypass line that bypasses the decompressor,
evaporator and compressor of an air-conditioning refrigeration
cycle. Japanese Patent Application Publication No. 2001-309506 (JP
2001-309506 A) describes a cooling system that circulates
refrigerant of a vehicle air-conditioning refrigeration cycle
through a cooling member of an inverter circuit portion that
executes drive control over a vehicle drive motor and, when cooling
air-conditioning air stream is not required, cooling of
air-conditioning air stream by an evaporator of the vehicle
air-conditioning refrigeration cycle is suppressed.
[0007] In the cooling system described in JP 2006-290254 A, in
order to cool a heat generating source, such as electrical devices
that are typically a motor, a DC/DC converter and an inverter, it
is necessary to constantly operate the compressor. Therefore, there
is a problem that the power consumption of the compressor increases
and the fuel economy of the vehicle deteriorates. In addition, the
heat exchanger that exchanges heat with the heat generating source
is connected in parallel with the evaporator, so refrigerant for
cooling the heat generating source is not used for cooling, and
there is a problem that cooling performance is traded off.
SUMMARY OF THE INVENTION
[0008] The invention provides a cooling system that is able to
reliably cool a heat generating source while ensuring cooling
performance, and that is able to reduce the power consumption of a
compressor.
[0009] An aspect of the invention relates to a cooling system that
cools a heat generating source. The cooling system includes: a
compressor that circulates refrigerant; a first heat exchanger and
a second heat exchanger that carry out heat exchange between the
refrigerant and outside air; a decompressor that decompresses the
refrigerant; a third heat exchanger that carries out heat exchange
between the refrigerant and air-conditioning air; a cooling portion
that is provided in a path of the refrigerant flowing between the
first heat exchanger and the second heat exchanger and that uses
the refrigerant to cool the heat generating source; a first line
through which the refrigerant flows between the cooling portion and
the second heat exchanger; a second line through which the
refrigerant flows between the third heat exchanger and the
compressor; and an internal heat exchanger in which the refrigerant
that flows through the first line and the refrigerant that flows
through the second line exchange heat with each other.
[0010] In the cooling system, the internal heat exchanger may be
arranged between the cooling portion and the second heat
exchanger.
[0011] The cooling system may further include: a third line through
which the refrigerant flows between the compressor and the first
heat exchanger; and a fourth line that provides fluid communication
between the first line and the third line. The cooling system may
further include a selector valve that switches a state of fluid
communication between the fourth line and the first line and third
line. In the cooling system, the selector valve may be configured
so as to switch the state of fluid communication into a state where
the refrigerant flows through the fourth line during a stop of the
compressor. In the cooling system, the cooling portion may be
arranged below the first heat exchanger.
[0012] The cooling system may further include a four-way valve that
switches between flow of the refrigerant from the compressor toward
the first heat exchanger and flow of the refrigerant from the
compressor toward the third heat exchanger.
[0013] In the cooling system, the first heat exchanger and the
second heat exchanger may be integrally arranged.
[0014] With the cooling system according to the aspect of the
invention, it is possible to reliably cool a heat generating source
while ensuring cooling performance, and it is possible to reduce
the power consumption of a compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Features, advantages, and technical and industrial
significance of exemplary embodiments of the invention will be
described below with reference to the accompanying drawings, in
which like numerals denote like elements, and wherein:
[0016] FIG 1 is a schematic view that shows the configuration of a
cooling system according to a first embodiment of the
invention;
[0017] FIG. 2 is a Mollier chart that shows the state of
refrigerant during cooling operation of a vapor compression
refrigeration cycle according to the first embodiment of the
invention;
[0018] FIG. 3A to FIG. 3D are graphs that schematically show
opening degree control over a flow regulating valve;
[0019] FIG. 4 is a schematic view that shows the cooling system in
a state where a four-way valve is switched;
[0020] FIG. 5 is a Mollier chart that shows the state of
refrigerant during heating operation of a vapor compression
refrigeration cycle according to the first embodiment of the
invention;
[0021] FIG. 6 is a schematic view that shows the flow of
refrigerant that cools an HV device during operation of the vapor
compression refrigeration cycle;
[0022] FIG. 7 is a schematic view that shows the flow of
refrigerant that cools the HV device during a stop of the vapor
compression refrigeration cycle;
[0023] FIG. 8 is a schematic view that shows the configuration of a
cooling system according to a second embodiment of the invention;
and
[0024] FIG. 9 is a schematic view that shows an example of the
internal structure of a heat exchanger according to the second
embodiment Of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0025] Hereinafter, embodiments of the invention will be described
with reference to the accompanying drawings. Note that, in the
following drawings, like reference numerals denote the same or
corresponding portions and the description thereof is not
repeated.
First Embodiment
[0026] FIG. 1 is a schematic view that shows the configuration of a
cooling system 1 according to a first embodiment. As shown in FIG.
1, the cooling system 1 includes a vapor compression refrigeration
cycle 10. The vapor compression refrigeration cycle 10 is, for
example, mounted on a vehicle in order to cool or heat the cabin of
the vehicle. Cooling using the vapor compression refrigeration
cycle 10 is performed, for example, when a switch for cooling is
turned on or when an automatic control mode in which the
temperature in the cabin of the vehicle is automatically adjusted
to a set temperature is selected and the temperature in the cabin
is higher than the set temperature. Heating using the vapor
compression refrigeration cycle 10 is performed, for example, when
a switch for heating is turned on or when the automatic control
mode is selected and the temperature in the cabin is lower than the
set temperature.
[0027] The vapor compression refrigeration cycle 10 includes a
compressor 12, a heat exchanger 14 that serves as a first heat
exchanger, a heat exchanger 15 that serves as a second heat
exchanger, an expansion valve 16 that is an example of a
decompressor, and a heat exchanger 18 that serves as a third heat
exchanger. The vapor compression refrigeration cycle 10 further
includes a four-way valve 13. The four-way valve 13 is arranged so
as to be able to switch between flow of refrigerant from the
compressor 12 toward the heat exchanger 14 and flow of refrigerant
from the compressor 12 toward the heat exchanger 18.
[0028] The compressor 12 is actuated by a motor or engine equipped
for the vehicle as a power source, and adiabatically compresses
refrigerant gas to obtain superheated refrigerant gas. The
compressor 12 introduces and compresses gaseous refrigerant flowing
during operation of the vapor compression refrigeration cycle 10,
and discharges high-temperature and high-pressure gaseous
refrigerant. The compressor 12 discharges refrigerant to circulate
the refrigerant in the vapor compression refrigeration cycle
10.
[0029] Each of the heat exchangers 14, 15 and 18 includes tubes and
fins. The tubes flow refrigerant. The fins are used to exchange
heat between refrigerant flowing through the tubes and air around
the heat exchanger 14, 15 or 18. Each of the heat exchangers 14, 15
and 18 exchanges heat between refrigerant and air stream supplied
by natural draft generated as the vehicle runs or air stream
supplied by a fan.
[0030] The expansion valve 16 causes high-pressure liquid
refrigerant to be sprayed through a small hole to expand into
low-temperature and low-pressure atomized refrigerant. The
expansion valve 16 decompresses condensed refrigerant liquid into
wet steam in a gas-liquid mixing state. Note that a decompressor
for decompressing refrigerant liquid is not limited to the
expansion valve 16 that carries out throttle expansion; instead,
the decompressor may be a capillary tube.
[0031] The vapor compression refrigeration cycle 10 further
includes refrigerant lines 21 to 28. The refrigerant line 21
provides fluid communication between the compressor 12 and the
four-way valve 13. Refrigerant flows from the compressor 12 toward
the four-way valve 13 via the refrigerant line 21. The refrigerant
line 22 provides fluid communication between the four-way valve 13
and the heat exchanger 14. Refrigerant flows from one of the
four-way valve 13 and the heat exchanger 14 toward the other via
the refrigerant line 22. The refrigerant line 23 provides fluid
communication between the heat exchanger 14 and a cooling portion
30 (described later). Refrigerant flows from one of the heat
exchanger 14 and the cooling portion 30 toward the other via the
refrigerant line 23. The refrigerant line 24 provides fluid
communication between the cooling portion 30 and the heat exchanger
15. Refrigerant flows from one of the cooling portion 30 and the
heat exchanger 15 toward the other via the refrigerant line 24.
[0032] The refrigerant line 25 provides fluid communication between
the heat exchanger 15 and the expansion valve 16. Refrigerant flows
from one of the heat exchanger 15 and the expansion valve 16 toward
the other via the refrigerant line 25. The refrigerant line 26
provides fluid communication between the expansion valve 16 and the
heat exchanger 18. Refrigerant flows from one of the expansion
valve 16 and the heat exchanger 18 toward the other via the
refrigerant line 26. The refrigerant line 27 provides fluid
communication between the heat exchanger 18 and the four-way valve
13. Refrigerant flows from one of the heat exchanger 18 and the
four-way valve 13 toward the other via the refrigerant line 27. The
refrigerant line 28 provides fluid communication between the
four-way valve 13 and the compressor 12. Refrigerant flows from the
four-way valve 13 toward the compressor 12 via the refrigerant line
28.
[0033] The vapor compression refrigeration cycle 10 is formed such
that the compressor 12, the heat exchangers 14 and 15, the
expansion valve 16 and the heat exchanger 18 are coupled by the
refrigerant lines 21 to 28. Note that refrigerant used in the vapor
compression refrigeration cycle 10 may be, for example, carbon
dioxide, hydrocarbon, such as propane and isobutane, ammonia,
water, or the like.
[0034] The cooling portion 30 is provided in the path of
refrigerant flowing between the heat exchanger 14 and the heat
exchanger 15. Because the cooling portion 30 is provided, the path
of refrigerant between the heat exchanger 14 and the heat exchanger
15 is divided into the refrigerant line 23 closer to the heat
exchanger 14 than the cooling portion 30 and the refrigerant line
24 closer to the expansion valve 16 than the cooling portion 30.
The cooling portion 30 includes a hybrid vehicle (HV) device 31 and
a cooling line 32. The HV device 31 is an electrical device mounted
on the vehicle. The cooling line 32 is a line through which
refrigerant flows. The HV device 31 is an example of a heat
generating source. One end portion of the cooling line 32 is
connected to the refrigerant line 23. The other end portion of the
cooling line 32 is connected to the refrigerant line 24.
[0035] Refrigerant flowing between the heat exchanger 14 and the
expansion valve 16 flows via the cooling line 32. When refrigerant
flows through the cooling line 32, the refrigerant takes heat from
the HV device 31 to cool the HV device 31. The cooling portion 30
is configured to be able to exchange heat between the HV device 31
and refrigerant because of the cooling line 32. In the present
embodiment, the cooling portion 30, for example, has the cooling
line 32 that is formed such that the outer peripheral surface of
the cooling line 32 is in direct contact with the casing of the HV
device 31. The cooling line 32 has a portion adjacent to the casing
of the HV device 31. At that portion, heat is exchangeable between
refrigerant, flowing through the cooling line 32, and the HV device
31.
[0036] The HV device 31 is directly connected to the outer
peripheral surface of the cooling line 32 that forms part of the
path of refrigerant, routed from the heat exchanger 14 to the heat
exchanger 15 in the vapor compression refrigeration cycle 10, and
is cooled. The HV device 31 is arranged on the outside of the
cooling line 32, so the HV device 31 does not interfere with flow
of refrigerant flowing inside the cooling line 32. Therefore, the
pressure loss of the vapor compression refrigeration cycle 10 does
not increase, so the HV device 31 may be cooled without increasing
the power of the compressor 12.
[0037] Alternatively, the cooling portion 30 may include a selected
known heat pipe that is interposed between the HV device 31 and the
cooling line 32. In this case, the HV device 31 is connected to the
outer peripheral surface of the cooling line 32 via the heat pipe,
and heat is transferred from the HV device 31 to the cooling line
32 via the heat pipe to thereby cool the HV device 31. The HV
device 31 serves as a heating portion for heating the heat pipe,
and the cooling line 32 serves as a cooling portion for cooling the
heat pipe to thereby increase the heat-transfer efficiency between
the cooling line 32 and the HV device 31, so the cooling efficiency
of the HV device 31 may be improved. For example, a Wick heat pipe
may be used.
[0038] Heat may be reliably transferred from the HV device 31 to
the cooling line 32 by the heat pipe, so there may be a distance
between the HV device 31 and the cooling line 32, and complex
arrangement of the cooling line 32 is not required to bring the
cooling line 32 into contact with the HV device 31. As a result, it
is possible to improve the flexibility of arrangement of the HV
device 31.
[0039] The HV device 31 includes an electrical device that
exchanges electric power to generate heat. The electrical device
includes at least any one of, for example, an inverter used to
convert direct-current power to alternating-current power, a motor
generator that is a rotating electrical machine, a battery that is
an electrical storage device, a converter that is used to step up
the voltage of the battery and a DC/DC converter that is used to
step down the voltage of the battery. The battery is a secondary
battery, such as a lithium ion battery and a nickel metal hydride
battery. A capacitor may be used instead of the battery.
[0040] The heat exchanger 18 is arranged inside a duct 90 through
which air flows. The heat exchanger 18 exchanges heat between
refrigerant and air-conditioning air flowing through the duct 90 to
adjust the temperature of air-conditioning air. The duct 90 has a
duct inlet 91 and a duct outlet 92. The duct inlet 91 is an inlet
through which air-conditioning air flows into the duct 90. The duct
outlet 92 is an outlet through which air-conditioning air flows out
from the duct 90. A fan 93 is arranged near the duct inlet 91
inside the duct 90.
[0041] As the fan 93 is driven, air flows through the duct 90. As
the fan 93 operates, air-conditioning air flows into the duct 90
via the duct inlet 91. Air flowing into the duct 90 may be outside
air or may be air in the cabin of the vehicle. The arrow 95 in FIG.
1 and FIG. 4 indicates flow of air-conditioning air that flows via
the heat exchanger 18 and exchanges heat with refrigerant in the
vapor compression refrigeration cycle 10. During cooling operation,
air-conditioning air is cooled in the heat exchanger 18, and
refrigerant receives heat transferred from air-conditioning air to
be heated. During heating operation, air-conditioning air is heated
in the heat exchanger 18, and refrigerant transfers heat to
air-conditioning air to be cooled. The arrow 96 indicates flow of
air-conditioning air that is adjusted in temperature by the heat
exchanger 18 and that flows out from the duct 90 via the duct
outlet 92.
[0042] Refrigerant that flows through the refrigerant line 24 as a
first line between the cooling portion 30 and the heat exchanger 15
and refrigerant that flows through the refrigerant line 27 as a
second line between the heat exchanger 18 and the four-way valve 13
exchange heat with each other in an internal heat exchanger 40. The
cooling system 1 includes the internal heat exchanger 40 in which
refrigerant that flows through the refrigerant line 24 and
refrigerant that flows through the refrigerant line 27 exchange
heat with each other. Because the internal heat exchanger 40 is
provided, the refrigerant line 24 is divided into a refrigerant
line 24a closer to the cooling portion 30 than the internal heat
exchanger 40 and a refrigerant line 24b closer to the heat
exchanger 15 than the Internal heat exchanger 40. The refrigerant
line 27 is divided into a refrigerant line 27a closer to the heat
exchanger 18 than the internal heat exchanger 40 and a refrigerant
line 27b closer to the four-way valve 13 than the internal heat
exchanger 40.
[0043] The internal heat exchanger 40 has a heat exchanging line 41
that is in fluid communication with the refrigerant line 24 and a
heat exchanging line 42 that is in fluid communication with the
refrigerant line 27. One end portion of the heat exchanging line 41
is connected to the refrigerant line 24a, and the other end portion
is connected to the refrigerant line 24b. During cooling operation
shown in FIG. 1, refrigerant flows from the cooling portion 30 to
the internal heat exchanger 40 via the refrigerant line 24a, flows
in the heat exchanging line 41, and reaches the heat exchanger 15
via the refrigerant line 24b. One end portion of the heat
exchanging line 42 is connected to the refrigerant line 27a, and
the other end portion is connected to the refrigerant line 27b.
During cooling operation shown in FIG. 1, refrigerant flows from
the heat exchanger 18 to the internal heat exchanger 40 via the
refrigerant line 27a, flows in the heat exchanging line 42, reaches
the four-way valve 13 via the refrigerant line 27b, and further
flows into the compressor 12 via the refrigerant line 28.
[0044] The internal heat exchanger 40 has a selected structure such
that heat is exchangeable between refrigerant that flows through
the heat exchanging line 41 and refrigerant that flows through the
heat exchanging line 42. For example, a pipe that forms the heat
exchanging line 41 and a pipe that forms the heat exchanging line
42 may be arranged such that the respective outer peripheral
surfaces directly contact with each other or may be arranged via a
high thermal conductive member or a heat pipe. In addition, for
example, it is applicable that two through holes are formed in a
metal block member having a high thermal conductivity, one of the
through holes serves as the heat exchanging line 41 and the other
one of the through holes serves as the heat exchanging line 42.
[0045] During cooling operation, refrigerant flows in the vapor
compression refrigeration cycle 10 so as to sequentially pass
through points A, B, C, D, E, F, G and H shown in FIG. 1, and
refrigerant circulates among the compressor 12, the heat exchangers
14 and 15, the expansion valve 16 and the heat exchanger 18.
Refrigerant passes through a refrigerant circulation path that is
formed by sequentially connecting the , compressor 12, the heat
exchangers 14 and 15, the expansion valve 16 and the heat exchanger
18 by the refrigerant lines 21 to 28 to circulate in the vapor
compression refrigeration cycle 10.
[0046] FIG. 2 is a Mollier chart that shows the state of
refrigerant during cooling operation of the vapor compression
refrigeration cycle 10 according to the first embodiment. In FIG.
2, the abscissa axis represents the specific enthalpy (unit: kJ/kg)
of refrigerant, and the ordinate axis represents the absolute
pressure (unit: MPa) of refrigerant. The curve in the chart is the
saturation vapor line and saturation liquid line of refrigerant.
FIG. 2 shows the thermodynamic state of refrigerant at points (that
is, points A, B, C, D, E, F, G and H) in the vapor compression
refrigeration cycle 10 when refrigerant flows from the compressor
12 into the refrigerant line 23 via the heat exchanger 14, cools
the HV device 31 and returns from the refrigerant line 24 to the
compressor 12 via the heat exchanger 15, the expansion valve 16 and
the heat exchanger 18.
[0047] As shown in FIG. 2, refrigerant (point A) in a superheated
steam state, introduced into the compressor 12, is adiabatically
compressed in the compressor 12 along a constant specific entropy
line. As refrigerant is compressed, the refrigerant increases in
pressure and temperature into high-temperature and high-pressure
superheated steam having a high degree of superheat (point B), and
then the refrigerant flows to the heat exchanger 14.
[0048] High-pressure refrigerant steam flowing into the heat
exchanger 14 exchanges heat with outside air in the heat exchanger
14 to be cooled. Refrigerant becomes dry saturated steam from
superheated steam with a constant pressure, releases latent heat of
condensation to gradually liquefy into wet steam in a gas-liquid
mixing state, and becomes saturated liquid as the entire
refrigerant condenses (point C). The heat exchanger 14 causes
superheated refrigerant gas, compressed in the compressor 12, to
release heat to an external medium with a constant pressure and to
become refrigerant liquid. Gaseous refrigerant discharged from the
compressor 12 releases heat to the surroundings to be cooled in the
heat exchanger 14 to thereby condense (liquefy). Owing to heat
exchange in the heat exchanger 14, the temperature of refrigerant
decreases, and refrigerant liquefies.
[0049] High-pressure liquid refrigerant liquefied in the heat
exchanger 14 flows to the cooling portion 30 via the refrigerant
line 23, and cools the HV device 31. In the cooling portion 30,
heat is released to liquid refrigerant that is condensed as it
passes through the heat exchanger 14 to thereby cool the HV device
31. Refrigerant is heated by exchanging heat with the HV device 31,
and the dryness of the refrigerant increases. Refrigerant receives
latent heat from the HV device 31 to partially vaporize into wet
steam that mixedly contains saturated liquid and saturated steam
(point D).
[0050] Refrigerant flowing out from the cooling portion 30 flows to
the internal heat exchanger 40 via the refrigerant line 24a. As
heat is transferred from refrigerant that flows through the heat
exchanging line 41 to refrigerant that flows through the heat
exchanging line 42 inside the internal heat exchanger 40,
refrigerant that flows through the heat exchanging line 41 is
cooled, and refrigerant that flows through the heat exchanging line
42 is heated. The percentage of saturated liquid increases and the
percentage of saturated steam reduces within refrigerant that flows
through the heat exchanging line 41 by heat exchange in the
internal heat exchanger 40, so the dryness of the refrigerant in a
wet steam state, flowing through the heat exchanging line 41,
reduces (the wetness increases) (point E).
[0051] After that, refrigerant flows into the heat exchanger 15.
Wet steam of refrigerant exchanges heat with outside air in the
heat exchanger 15 to be cooled to thereby condense again, becomes
saturated liquid as the entire refrigerant condenses, and further
releases sensible heat to become supercooled liquid (point F).
After that, refrigerant flows into the expansion valve 16 via the
refrigerant line 25. In the expansion valve 16, refrigerant in a
supercooled liquid state is throttle-expanded, and the refrigerant
decreases in temperature and pressure with the specific enthalpy of
the refrigerant unchanged to become low-temperature and
low-pressure wet steam in a gas-liquid mixing state (point G).
[0052] Refrigerant in a wet steam state from the expansion valve 16
flows into the heat exchanger 18 via the refrigerant line 26.
Refrigerant in a wet steam state flows into the tubes of the heat
exchanger 18. When refrigerant flows through the tubes of the heat
exchanger 18, the refrigerant absorbs heat of air in the cabin of
the vehicle as latent heat of vaporization via the fins to
evaporate with a constant pressure. As the entire refrigerant
becomes dry saturated steam, the temperature of refrigerant steam
further increases by sensible heat to become superheated steam
(point H). Refrigerant absorbs heat from the surroundings in the
heat exchanger 18 to be heated.
[0053] Refrigerant flowing out from the heat exchanger 18 flows to
the internal heat exchanger 40 via the refrigerant line 27a and
flows through the heat exchanging line 42. By the above described
heat exchange in the internal heat exchanger 40, refrigerant that
flows through the heat exchanging line 42 is heated, and a degree
of superheat of the refrigerant in a superheated steam state,
flowing through the heat exchanging line 42, increases (point A).
After that, refrigerant is introduced into the compressor 12 via
the refrigerant line 27b, the four-way valve 13 and the refrigerant
line 28. The compressor 12 compresses refrigerant that flows from
the internal heat exchanger 40. Refrigerant continuously repeats
changes among the compressed state, the condensed state, the
throttle-expanded state and the evaporated state in accordance with
the above described cycle.
[0054] Note that, in the above description of the vapor compression
refrigeration cycle, a theoretical refrigeration cycle is
described; however, in the actual vapor compression refrigeration
cycle 10, it is, of course, necessary to consider a loss in the
compressor 12, a pressure loss of refrigerant and a heat loss.
[0055] During cooling operation, atomized refrigerant flowing
inside the heat exchanger 18 vaporizes to absorb heat of ambient
air introduced so as to contact with the heat exchanger 18. The
heat exchanger 18 uses low-temperature and low-pressure refrigerant
decompressed by the expansion valve 16 to absorb heat of
vaporization, required at the time when wet steam of refrigerant
evaporates into refrigerant gas, from air-conditioning air flowing
to the cabin of the vehicle to thereby cool the cabin of the
vehicle. Air-conditioning air of which heat is absorbed by the heat
exchanger 18 to decrease its temperature flows into the cabin of
the vehicle to cool the cabin of the vehicle.
[0056] During operation of the vapor compression refrigeration
cycle 10, refrigerant absorbs heat of vaporization from air in the
cabin of the vehicle in the heat exchanger 18 to thereby cool the
cabin. In addition, high-pressure liquid refrigerant from the heat
exchanger 14 flows to the cooling portion 30 and exchanges heat
with the HV device 31 to thereby cool the HV device 31. The cooling
system 1 cools the HV device 31, which is the heat generating
source mounted on the vehicle, by utilizing the vapor compression
refrigeration cycle 10 for air-conditioning the cabin of the
vehicle. Note that the temperature required to cool the HV device
31 is desirably at least lower than the upper limit of a target
temperature range of the HV device 31.
[0057] During cooling operation, refrigerant is cooled into a
saturated liquid state in the heat exchanger 14, and refrigerant in
a wet steam state, which receives latent heat of vaporization from
the HV device 31 to be partially vaporized, is cooled again in the
heat exchanger 15. Refrigerant changes in state at a constant
temperature until the refrigerant in a wet steam state completely
condenses into saturated liquid. The heat exchanger 15 further
supercools liquid refrigerant to a degree of supercooling required
to cool the cabin of the vehicle. A degree of supercooling of
refrigerant does not need to be excessively increased, so the
capacity of each of the heat exchangers 14 and 15 may be reduced.
Thus, the cooling performance for cooling the cabin may be ensured,
and the size of each of the heat exchangers 14 and 15 may be
reduced, so it is possible to obtain the cooling system 1 that is
reduced in size and that is advantageous in installation on the
vehicle.
[0058] When low-temperature and low-pressure refrigerant after
passing through the expansion valve 16 is used to cool the HV
device 31, the cooling performance of air in the cabin in the heat
exchanger 18 reduces and the cooling performance for cooling the
cabin decreases. In contrast to this, in the cooling system 1
according to the present embodiment, in the vapor compression
refrigeration cycle 10, high-pressure refrigerant discharged from
the compressor 12 is condensed by both the heat exchanger 14 that
serves as a first condenser and the heat exchanger 15 that serves
as a second condenser. The two-stage heat exchangers 14 and 15 are
arranged between the compressor 12 and the expansion valve 16, and
the cooling portion 30 for cooling the HV device 31 is provided
between the heat exchanger 14 and the heat exchanger 15. The heat
exchanger 15 is provided in the path of refrigerant flowing from
the cooling portion 30 toward the expansion valve 16.
[0059] By sufficiently cooling refrigerant, which receives latent
heat of vaporization from the HV device 31 to be heated, in the
heat exchanger 15, the refrigerant has a temperature and a pressure
that are originally required to cool the cabin of the vehicle at
the outlet of the expansion valve 16. Therefore, it is possible to
sufficiently increase the amount of heat externally received when
refrigerant evaporates in the heat exchanger 18. Thus, by setting
the heat radiation performance for the heat exchanger 15 so as to
be able to sufficiently cool refrigerant, the HV device 31 may be
cooled without any influence on the cooling performance for cooling
air in the cabin. Thus, both the cooling performance for cooling
the HV device 31 and the cooling performance for cooling the cabin
may be reliably ensured.
[0060] When refrigerant flowing from the heat exchanger 14 to the
cooling portion 30 cools the HV device 31, the refrigerant receives
heat from the HV device 31 to be heated. As refrigerant is heated
to a saturated steam temperature or above and the entire amount of
the refrigerant vaporizes in the cooling portion 30, the amount of
heat exchanged between the refrigerant and the HV device 31
reduces, and the HV device 31 cannot be efficiently cooled, and, in
addition, pressure loss at the time when the refrigerant flows in
the pipe increases. Therefore, it is desirable to sufficiently cool
refrigerant in the heat exchanger 14 such that the entire amount of
refrigerant does not vaporize after cooling the HV device 31.
[0061] Specifically, the state of refrigerant at the outlet of the
heat exchanger 14 - is brought close to saturated liquid, and,
typically, refrigerant is placed in a state on the saturated liquid
line at the outlet of the heat exchanger 14. Because the heat
exchanger 14 is capable of sufficiently cooling refrigerant in this
way, the heat radiation performance of the heat exchanger 14 for
causing refrigerant to release heat is higher than the heat
radiation performance of the heat exchanger 15. By sufficiently
cooling refrigerant in the heat exchanger 14 having relatively high
heat radiation performance, refrigerant that has received heat from
the HV device 31 may be maintained in a wet steam state, and a
reduction in the amount of heat exchanged between refrigerant and
the HV device 31 may be avoided, so it is possible to sufficiently
cool the HV device 31. Refrigerant in a wet steam state after
cooling the HV device 31 is efficiently cooled again in the heat
exchanger 15, and is cooled into a supercooled liquid state below a
saturated temperature. Thus, it is possible to provide the cooling
system 1 that ensures both the cooling performance for cooling the
cabin and the cooling performance for cooing the HV device 31.
[0062] Referring back to FIG. 1, the refrigerant lines 23 and 24
and a refrigerant line 29 are connected in parallel in the path of
refrigerant flowing between the heat exchanger 14 and the heat
exchanger 15. The refrigerant line 29 provides direct fluid
communication between the refrigerant line 23 and the refrigerant
line 24. The refrigerant line 29 forms part of the path of
refrigerant flowing between the heat exchanger 14 and the heat
exchanger 15. The cooling system 1 includes the refrigerant line 29
that forms the path that does not pass through the cooling portion
30, and the refrigerant lines 23 and 24 and the cooling line 32
that form the path that passes through the cooling portion 30. The
path of refrigerant between the heat exchanger 14 and the heat
exchanger 15 branches off, and part of refrigerant flows to the
cooling portion 30.
[0063] The refrigerant lines 23 and 24 and the cooling line 32 that
form the path passing through the cooling portion 30 and the
refrigerant line 29 that forms the path not passing through the
cooling portion 30 are provided in parallel with each other as the
path through which refrigerant flows between the heat exchanger 14
and the heat exchanger 15. The cooling system for cooling the HV
device 31, including the refrigerant lines 23 and 24, is connected
in parallel with the refrigerant line 29. The path of refrigerant
flowing between the heat exchanger 14 and the heat exchanger 15
without passing though the cooling portion 30 and the path of
refrigerant flowing via the cooling portion 30 are provided in
parallel with each other, and only part of refrigerant is caused to
flow to the refrigerant lines 23 and 24. By so doing, only part of
refrigerant flowing between the heat exchanger 14 and the heat
exchanger 15 flows to the cooling portion 30.
[0064] Refrigerant in an amount required to cool the HV device 31
in the cooling portion 30 is caused to flow to the refrigerant
lines 23 and 24, and not the entire refrigerant flows to the
cooling portion 30. Thus, the HV device 31 is appropriately cooled,
and it is possible to prevent excessive cooling of the HV device
31. In addition, it is possible to reduce the pressure loss
associated with flow of refrigerant to the cooling system for
cooling the HV device 31, including the refrigerant lines 23 and 24
and the cooling line 32. Accordingly, it is possible to reduce
power consumption required to operate the compressor 12 for
circulating refrigerant.
[0065] A flow regulating valve 39 is provided in the refrigerant
line 29. The flow regulating valve 39 is arranged in the
refrigerant line 29 that forms part of the path of refrigerant
flowing between the heat exchanger 14 and the heat exchanger 15.
The flow regulating valve 39 changes its valve opening degree to
increase or reduce a pressure loss of refrigerant flowing in the
refrigerant line 29 to thereby selectively adjust the flow rate of
refrigerant flowing in the refrigerant line 29 and the flow rate of
refrigerant flowing in the cooling system for cooing the HV device
31, including the cooling line 32.
[0066] For example, as the flow regulating valve 39 is fully closed
to set the valve opening degree at 0%, the entire amount of
refrigerant from the heat exchanger 14 flows into the cooling
portion 30. When the valve opening degree of the flow regulating
valve 39 is increased, the flow rate of refrigerant that flows
directly to the heat exchanger 15 via the refrigerant line 29
increases and the flow rate of refrigerant that flows to the
cooling portion 30 to cool the HV device 31 reduces within
refrigerant that flows from the heat exchanger 14 to the
refrigerant line 23. When the valve opening degree of the flow
regulating valve 39 is reduced, the flow rate of refrigerant that
directly flows to the heat exchanger 15 via the refrigerant line 29
reduces and the flow rate of refrigerant that flows to the cooling
portion 30 to cool the HV device 31 increases within refrigerant
that flows from the heat exchanger 14 to the refrigerant line
23.
[0067] As the valve opening degree of the flow regulating valve 39
is increased, the flow rate of refrigerant that cools the HV device
31 reduces, so cooling performance for cooling the HV device 31
decreases. As the valve opening degree of the flow regulating valve
39 reduces, the flow rate of refrigerant that cools the HV device
31 increases, so cooling performance for cooling the HV device 31
improves. The flow regulating valve 39 is used to make it possible
to optimally adjust the amount of refrigerant flowing to the HV
device 31, so it is possible to reliably prevent excessive cooling
of the HV device 31, and, in addition, it is possible to reliably
reduce pressure loss associated with flow of refrigerant in the
cooling system for cooling the HV device 31 and the power
consumption of the compressor 12 for circulating refrigerant.
[0068] An example of control associated with adjustment of the
valve opening degree of the flow regulating valve 39 will be
described below. FIG. 3A to FIG. 3D are graphs that schematically
show opening degree control over the flow regulating valve 39. The
abscissa axis shown in each of the graphs of FIG. 3A to FIG. 3D
represents time.
[0069] The ordinate axis of the graph of FIG. 3A represents a valve
opening degree in the case where the flow regulating valve 39 is an
electric expansion valve that uses a stepping motor. The ordinate
axis of the graph of FIG. 3B represents a valve opening degree in
the case where the flow regulating valve 39 is a thermostatic
expansion valve that opens or closes with a fluctuation in
temperature. The ordinate axis of the graph of FIG. 3C represents
the temperature of the HV device 31. The ordinate axis of the graph
of FIG. 3D represents a difference in temperature between the inlet
and outlet of the HV device 31.
[0070] As refrigerant flows via the cooling portion 30, the HV
device 31 is cooled. The valve opening degree of the flow
regulating valve 39 is, for example, adjusted by monitoring the
temperature of the HV device 31 or the difference between the
outlet temperature and inlet temperature of the HV device 31. For
example, with reference to the graph of FIG. 3C, a temperature
sensor that continuously measures the temperature of the HV device
31 is provided to monitor the temperature of the HV device 31. In
addition, for example, with reference to the graph of FIG. 3D, a
temperature sensor that measures the inlet temperature and outlet
temperature of the HV device 31 is provided to monitor the
difference in temperature between the outlet and inlet of the HV
device 31.
[0071] As the temperature of the HV device 31 is higher than a
target temperature or the difference in temperature between the
outlet and inlet of the HV device 31 is larger than a target
temperature difference (for example, 3 to 5.degree. C.), the
opening degree of the flow regulating valve 39 is reduced as shown
in the graph of FIG. 3A and the graph of FIG. 3B. By throttling the
opening degree of the flow regulating valve 39, the flow rate of
refrigerant flowing to the cooling portion 30 increases as
described above, so it is possible to further effectively cool the
HV device 31. As a result, the temperature of the HV device 31 may
be decreased to the target temperature or below as shown in the
graph of FIG. 3C or the different in temperature between the outlet
and inlet of the HV device 31 may be reduced to the target
temperature difference or below as shown in the graph of FIG.
3D.
[0072] In this way, by optimally adjusting the valve opening degree
of the flow regulating valve 39, refrigerant in an amount by which
heat radiation performance required to keep the HV device 31 within
an appropriate temperature range is ensured is ensured to thereby
make it possible to appropriately cool the HV device 31. Thus, it
is possible to reliably suppress occurrence of inconvenience that
the HV device 31 is excessively heated to be damaged.
[0073] FIG. 4 is a schematic view that shows the cooling system 1
in a state where the four-way valve 13 is switched. By comparing
FIG. 4 with FIG. 1, the four-way valve 13 is rotated by 90.degree.
to switch the path along which refrigerant flowing from the outlet
of the compressor 12 into the four-way valve 13 flows out from the
four-way valve 13. During cooling operation shown in FIG. 1,
refrigerant compressed in the compressor 12 flows from the
compressor 12 toward the heat exchanger 14. On the other hand,
during heating operation shown in FIG. 4, refrigerant compressed in
the compressor 12 flows from the compressor 12 toward the heat
exchanger 18.
[0074] During heating operation, refrigerant flows in the vapor
compression refrigeration cycle 10 so as to sequentially pass
through points A, B, H, G, F, E, D and C shown in FIG. 4 to
circulate through the compressor 12, the heat exchanger 18, the
expansion valve 16 and the heat exchangers 15 and 14. Refrigerant
passes through a refrigerant circulation path that is formed by
sequentially connecting the compressor 12, the heat exchanger 18,
the expansion valve 16 and the heat exchangers 15 and 14 by the
refrigerant lines 21 to 28 to circulate in the vapor compression
refrigeration cycle 10.
[0075] FIG. 5 is a Mollier chart that shows the state of
refrigerant during heating operation of the vapor compression
refrigeration cycle 10 according to the first embodiment. In FIG.
5, the abscissa axis represents the specific enthalpy (unit: kJ/kg)
of refrigerant, and the ordinate axis, represents the absolute
pressure (unit: MPa) of refrigerant. The curve in the chart is the
saturation vapor line and saturation liquid line of refrigerant.
FIG. 5 shows the thermodynamic state of refrigerant at points (that
is, points A, B, H, G, F, E, D and C) in the vapor compression
refrigeration cycle 10 when refrigerant flows from the compressor
12 into the refrigerant line 24 via the heat exchanger 18, the
expansion valve 16 and the heat exchanger 15, cools the HV device
31, and returns from the refrigerant line 23 to the compressor 12
via the heat exchanger 14.
[0076] As shown in FIG. 5, refrigerant in a superheated steam state
(point A), introduced into the compressor 12, is adiabatically
compressed in the compressor 12 along a constant specific entropy
line. As refrigerant is compressed, the refrigerant increases in
pressure and temperature into high-temperature and high-pressure
superheated steam having a high degree of superheat (point B).
Refrigerant flowing out from the compressor 12 flows to the
internal heat exchanger 40. As heat is transferred from refrigerant
that flows through the heat exchanging line 42 to refrigerant that
flows through the heat exchanging line 41 inside the internal heat
exchanger 40, refrigerant that flows through the heat exchanging
line 42 is cooled, and refrigerant that flows through the heat
exchanging line 41 is heated. By heat exchange in the internal heat
exchanger 40, a degree of superheat of refrigerant that flows
through the heat exchanging line 42 reduces. That is, the
temperature of refrigerant in a superheated steam state decreases,
and approaches a saturated temperature of refrigerant steam (point
H).
[0077] After that, refrigerant flows to the heat exchanger 18.
High-pressure refrigerant steam in the heat exchanger 18 is cooled
in the heat exchanger 18, becomes dry saturated steam from
superheated steam with a constant pressure, releases latent heat of
condensation to gradually liquefy into wet steam in a gas-liquid
mixing state, becomes saturated liquid as the entire refrigerant
condenses, and further releases sensible heat to become supercooled
liquid (point G). The heat exchanger 18 causes superheated
refrigerant gas, compressed in the compressor 12, to release heat
to an external medium with a constant pressure and to become
refrigerant liquid. Gaseous refrigerant discharged from the
compressor 12 releases heat to the surroundings to be cooled in the
heat exchanger 18 to thereby condense (liquefy). Owing to heat
exchange in the heat exchanger 18, the temperature of refrigerant
decreases, and refrigerant liquefies. Refrigerant releases heat to
the surroundings in the heat exchanger 18 to be cooled.
[0078] High-pressure liquid refrigerant liquefied in the heat
exchanger 18 flows into the expansion valve 16 via the refrigerant
line 26. In the expansion valve 16, refrigerant in a supercooled
liquid state is throttle-expanded, and the refrigerant decreases in
temperature and pressure with the specific enthalpy of the
refrigerant unchanged to become low-temperature and low-pressure
wet steam in a gas-liquid mixing state (point F). Refrigerant of
which the temperature is decreased in the expansion valve 16 flows
into the heat exchanger 15 via the refrigerant line 25. Refrigerant
in a wet steam state flows into the tubes of the heat exchanger 15.
When refrigerant flows through the tubes, the refrigerant absorbs
heat of outside air via the fins as latent heat of vaporization to
evaporate with a constant pressure. Refrigerant exchanges heat with
outside air in the heat exchanger 15 to be heated, and the dryness
of the refrigerant increases. Part of refrigerant receives latent
heat in the heat exchanger 15 to vaporize, so the percentage of
saturated steam contained in the refrigerant in a wet steam state
increases (point E).
[0079] Refrigerant in a wet steam state, flowing out from the heat
exchanger 15, flows to the internal heat exchanger 40 via the
refrigerant line 24b and flows through the heat exchanging line 41.
By the above described heat exchange in the internal heat exchanger
40, refrigerant that flows through the heat exchanging line 41 is
heated, and the dryness of the refrigerant in a wet steam state,
flowing through the heat exchanging line 41, increases (point D).
Next, refrigerant flows to the cooling line 32 of the cooling
portion 30 to cool the HV device 31. Refrigerant is heated by
exchanging heat with the HV device 31, and the dryness of the
refrigerant increases. Part of refrigerant receives latent heat
from the HV device 31 to vaporize, so the percentage of saturated
steam contained in the refrigerant in a wet steam state increases
(point C).
[0080] Refrigerant in a wet steam state, flowing out from the
cooling portion 30, flows into the heat exchanger 14 via the
refrigerant line 23. Refrigerant in a wet steam state flows into
the tubes of the heat exchanger 14. When refrigerant flows through
the tubes, the refrigerant absorbs heat of outside air via the fins
as latent heat of vaporization to evaporate with a constant
pressure. As the entire refrigerant becomes dry saturated steam,
the refrigerant steam further increases in temperature by sensible
heat to become superheated steam (point A). Vaporized refrigerant
is introduced into the compressor 12 via the refrigerant line 22.
The compressor 12 compresses refrigerant flowing from the heat
exchanger 14. Refrigerant continuously repeats changes among the
compressed state, the condensed state, the throttle-expanded state
and the evaporated state in accordance with the above described
cycle.
[0081] During heating operation, refrigerant steam flowing inside
the heat exchanger 18 condenses to release heat to ambient air
introduced so as to contact with the heat exchanger 18. The heat
exchanger 18 uses high-temperature and high-pressure refrigerant
adiabatically compressed in the compressor 12 to release heat of
condensation, required at the time when refrigerant gas condenses
into wet steam of refrigerant, to air-conditioning air flowing to
the cabin of the vehicle to thereby heat the cabin of the vehicle.
Air-conditioning air that receives heat from the heat exchanger 18
to increase its temperature flows into the cabin of the vehicle to
thereby heat the cabin of the vehicle.
[0082] During operation of the vapor compression refrigeration
cycle 10, refrigerant releases heat of condensation to air in the
cabin of the vehicle in the heat exchanger 18 to thereby heat the
cabin. In addition, refrigerant in a wet steam state, flowing out
from the heat exchanger 15, flows to the cooling portion 30 and
exchanges heat with the HV device 31 to thereby cool the HV device
31. During heating as well, as in the case during cooling, the
cooling system 1 utilizes the vapor compression refrigeration cycle
10 for air-conditioning the cabin of the vehicle to thereby cool
the HV device 31.
[0083] The four-way valve 13 is used to switch the direction in
which refrigerant flows in the vapor compression refrigeration
cycle 10 between cooling operation and heating operation. During
cooling operation, in the heat exchanger 18, low-temperature and
low-pressure refrigerant throttle-expanded in the expansion valve
16 absorbs heat from air-conditioning air to cool the cabin. During
heating operation, in the heat exchanger 18, high-temperature and
high-pressure refrigerant adiabatically compressed in the
compressor 12 releases heat to air-conditioning air to heat the
cabin. The cooling system 1 uses the single heat exchanger 18 to be
able to appropriately adjust the temperature of air-conditioning
air flowing into the cabin of the vehicle during both cooling
operation and heating operation. Thus, it is not required to
arrange two heat exchangers that exchange heat with
air-conditioning air, so the cost of the cooling system 1 may be
reduced, and the size of the cooling system 1 may be reduced.
[0084] During both cooling operation and heating operation,
refrigerant flows to the cooling portion 30 to exchange heat with
the HV device 31 to thereby cool the HV device 31. The cooling
system 1 cools the HV device 31, which is the heat generating
source mounted on the vehicle, by utilizing the vapor compression
refrigeration cycle 10 for air-conditioning the cabin of the
vehicle. The vapor compression refrigeration cycle 10 that is
provided in order to exchange heat with air-conditioning air in the
heat exchanger 18 to air-condition the cabin of the vehicle is
utilized to cool the HV device 31.
[0085] It is not necessary to provide a device, such as an
exclusive water circulation pump and a cooling fan, in order to
cool the HV device 31. Therefore, components required for the
cooling system 1 to cool the HV device 31 may be reduced to make it
possible to simplify the system configuration, so the manufacturing
cost of the cooling system 1 may be reduced. In addition, it is not
necessary to operate a power source, such as a pump and a cooling
fan, in order to cool the HV device 31, and power consumption for
operating the power source is not required. Thus, it is possible to
reduce power consumption for cooling the HV device 31.
[0086] As shown in FIG. 1 and FIG. 4, the cooling system 1
according to the present embodiment further includes a
communication line 51 that serves as a fourth line. The
communication line 51 provides fluid communication between the
refrigerant line 22 that serves as a third line, through which
refrigerant flows between the compressor 12 and the heat exchanger
14, and the refrigerant line 24 (24b) that serves as the first
line. A selector valve 52 is provided in the refrigerant line 24
and the communication line 51. The selector valve 52 switches the
state of fluid communication between the communication line 51 and
the refrigerant lines 24 and 22. The selector valve 52 switches
between the open state and the closed state to thereby allow or
interrupt flow of refrigerant via the communication line 51. By
switching the path of refrigerant using the selector valve 52,
refrigerant after cooling the HV device 31 may be caused to flow to
any selected one of the paths, that is, to the heat exchanger 15
via the refrigerant line 24 or to the heat exchanger 14 via the
communication line 51 and the refrigerant line 22.
[0087] More specifically, two valves 57 and 58 are provided as the
selector valve 52. During cooling operation of the vapor
compression refrigeration cycle 10, the valve 57 is fully open
(valve opening degree 100%) and the valve 58 is fully closed (valve
opening degree 0%), and the valve opening degree of the flow
regulating valve 39 is adjusted such that a sufficient amount of
refrigerant flows through the cooling portion 30. By so doing,
refrigerant after cooling the HV device 31 may be reliably caused
to flow to the heat exchanger 15 via the refrigerant line 24. On
the other hand, during a stop of the vapor compression
refrigeration cycle 10, the valve 58 is fully open and the valve 57
is fully closed, and, furthermore, the flow regulating valve 39 is
fully closed. By so doing, it is possible to form an annular path
that causes refrigerant to circulate between the cooling portion 30
and the heat exchanger 14.
[0088] FIG. 6 is a schematic view that shows flow of refrigerant
that cools the HV device 31 during cooling operation of the vapor
compression refrigeration cycle 10. When the compressor 12 is
driven and the vapor compression refrigeration cycle 10 is
operated, the flow regulating valve 39 is adjusted in valve opening
degree such that a sufficient amount of refrigerant flows through
the cooling portion 30. The selector valve 52 is operated so as to
flow refrigerant from the cooling portion 30 to the expansion valve
16 via the heat exchanger 15. That is, as the valve 57 is fully
open and the valve 58 is fully closed, the path of refrigerant that
causes refrigerant to flow the whole of the cooling system 1 is
selected. Therefore, the cooling performance of the vapor
compression refrigeration cycle 10 may be ensured, and the HV
device 31 may be efficiently cooled.
[0089] FIG. 7 is a schematic view that shows flow of refrigerant
that cools the HV device 31 during a stop of the vapor compression
refrigeration cycle 10. As shown in FIG. 7, when the compressor 12
is stopped and the vapor compression refrigeration cycle 10 is
stopped, the selector valve 52 is operated so as to circulate
refrigerant from the cooling portion 30 to the heat exchanger 14.
That is, as the valve 57 is fully closed, the valve 58 is fully
open and the flow regulating valve 39 is fully closed, refrigerant
flows via the communication line 51. By so doing, a closed annular
path that is routed from the heat exchanger 14 to the cooling
portion 30 via the refrigerant line 23, further passes through the
refrigerant line 24, the communication line 51 and the refrigerant
line 22 sequentially and returns to the heat exchanger 14 is
formed.
[0090] Refrigerant may be circulated between the heat exchanger 14
and the cooling portion 30 via the annular path without operating
the compressor 12. When refrigerant cools the HV device 31, the
refrigerant receives latent heat of vaporization from the HV device
31 to evaporate. Refrigerant steam vaporized by exchanging heat
with the HV device 31 flows to the heat exchanger 14 via the
refrigerant line 24, the communication line 51 and the refrigerant
line 22 sequentially. In the heat exchanger 14, refrigerant steam
is cooled to condense by running wind of the vehicle or draft from
a radiator fan for cooling an engine. Refrigerant liquid liquefied
in the heat exchanger 14 returns to the cooling portion 30 via the
refrigerant line 23.
[0091] In this way, a heat pipe in which the HV device 31 serves as
a heating portion and the heat exchanger 14 serves as a cooling
portion is formed by the annular path that passes through the
cooling portion 30 and the heat exchanger 14. Thus, when the vapor
compression refrigeration cycle 10 is stopped, that is, when a
cooler for the vehicle is stopped as well, the HV device 31 may be
reliably cooled without the necessity of start-up of the compressor
12. Because the compressor 12 is not required to constantly operate
in order to cool the HV device 31, the power consumption of the
compressor 12 is reduced to thereby make it possible to improve the
fuel economy of the vehicle and, in addition, to extend the life of
the compressor 12, so it is possible to improve the reliability of
the compressor 12.
[0092] FIG. 6 and FIG. 7 show a ground 60. The cooling portion 30
is arranged below the heat exchanger 14 in the vertical direction
perpendicular to the ground 60. In the annular path that circulates
refrigerant between the heat exchanger 14 and the cooling portion
30, the cooling portion 30 is arranged below, and the heat
exchanger 14 is arranged above. The heat exchanger 14 is arranged
at the level higher than the cooling portion 30.
[0093] In this case, refrigerant steam heated and vaporized in the
cooling portion 30 goes up in the annular path, reaches the heat
exchanger 14, is cooled in the heat exchanger 14, condenses into
liquid refrigerant, goes down in the annular path by the action of
gravity and returns to the cooling portion 30. That is, a
thermo-siphon heat pipe is formed of the cooling portion 30, the
heat exchanger 14 and the paths of refrigerant that connect them.
Because the heat transfer efficiency from the HV device 31 to the
heat exchanger 14 may be improved by forming the heat pipe, when
the vapor compression refrigeration cycle 10 is stopped as well,
the HV device 31 may be further efficiently cooled without
additional power.
[0094] The selector valve 52 that switches the state of fluid
communication between the communication line 51 and the refrigerant
lines 24 and 22 may be the above described pair of valves 57 and 58
or may be a three-way valve that is arranged at the branching
portion between the refrigerant line 24 and the communication line
51. In any cases, during both operation and stop of the vapor
compression refrigeration cycle 10, the HV device 31 may be
efficiently cooled. The valves 57 and 58 just need to have a simple
structure so as to be able to open or close the refrigerant line,
so the valves 57 and 58 are not expensive, and the two valves 57
and 58 are used to make it possible to provide the further low-cost
cooling system 1. On the other hand, it is presumable that a space
required to arrange the three-way valve is smaller than a space
required to arrange the two valves 57 and 58, and the three-way
valve is used to make it possible to provide the cooling system 1
having a further reduced size and excellent vehicle
mountability.
[0095] As described above, in the cooling system 1 according to the
present embodiment, refrigerant after cooling the HV device 31 in
the cooling portion 30 and refrigerant after exchanging heat with
air, used for the cabin, in the heat exchanger 18 exchange heat
with each other in the internal heat exchanger 40. By so doing,
during cooling operation, refrigerant heated by exchanging heat
with the HV device 31 is cooled in the internal heat exchanger 40.
Therefore, refrigerant after passing through the heat exchanger 15
may be cooled into a supercooled liquid state without increasing
the capacity of the heat exchanger 15, so the size of the heat
exchanger 15 may be reduced. When the amount of heat generated by
the HV device 31 is small, a degree of supercooling of refrigerant
increases, so the cooling performance may be improved. In this
case, additionally, the power of the compressor 12 may be reduced,
so power saving of the cooling system 1 may be achieved. When the
amount of heat generated by the HV device 31 is large as well, the
cooling system 1 is controlled such that refrigerant is reliably
cooled into a supercooled liquid state, so controllability of
cooling operation may be improved.
[0096] During heating operation, refrigerant absorbs heat from
outside air to be heated in the heat exchangers 15 and 14.
Refrigerant is additionally heated in the internal heat exchanger
40 as well, and absorbs heat from the HV device 31 to be further
heated in the cooling portion 30. Because refrigerant is heated not
only in the heat exchangers 15 and 14 but also in the internal heat
exchanger 40 and the cooling portion 30, the refrigerant may be
heated into a sufficient superheated steam state at the outlet of
the heat exchanger 14, so the HV device 31 may be appropriately
cooled while maintaining excellent heating performance in the cabin
of the vehicle.
[0097] Therefore, refrigerant after passing through the heat
exchanger 14 may be heated into a superheated steam state without
increasing the capacities of the heat exchangers 15 and 14, so the
size of each of the heat exchangers 14 and 15 may be reduced.
Refrigerant is heated in the cooling portion 30 and heat waste from
the HV device 31 may be effectively utilized to heat the cabin, so
the coefficient of performance improves, and the power consumption
for adiabatically compressing refrigerant in the compressor 12
during heating operation may be reduced.
Second Embodiment
[0098] FIG. 8 is a schematic view that shows the configuration of a
cooling system 1 according to a second embodiment. The cooling
system 1 according to the second embodiment differs from the
cooling system 1 according to the first embodiment in that the heat
exchanger 14 and the heat exchanger 15 are manufactured as an
integrated heat exchanger.
[0099] FIG. 9 is a schematic view that shows an example of the
internal structure of the heat exchangers 14 and 15 according to
the second embodiment. As shown in FIG. 9, the heat exchanger 14
and the heat exchanger 15 are integrally arranged. The integrally
arranged heat exchanger 14 and heat exchanger 15 are, for example,
provided next to an engine cooling radiator mounted on the vehicle,
and carries out heat exchange between running wind of the vehicle
or cooling air supplied by a cooling fan and refrigerant.
[0100] The heat exchanger 14 includes a plurality of tubes 146
through which refrigerant flows and a plurality of fins 148 that
are used to exchange heat between refrigerant in the plurality of
tubes 146 and air around the heat exchanger 14. The plurality of
tubes 146 are arranged in parallel with one another between an
inlet portion 142 and an outlet portion 144. The inlet portion 142
is connected to the refrigerant line 22, and introduces refrigerant
from the compressor 12. The outlet portion 144 is connected to the
refrigerant line 23 routed to the cooling portion 30. Refrigerant
introduced via the inlet portion 142 flows through the plurality of
tubes 146 in a distributed manner.
[0101] Each of the plurality of fins 148 are arranged next to the
gap between any adjacent two of the plurality of tubes 146 between
the inlet portion 142 and the outlet portion 144. Refrigerant
exchanges heat with air around the heat exchanger 14 via the fin
148 to be condensed in each of the plurality of tubes 146.
Refrigerant after being condensed in the heat exchanger 14 flows
from the outlet portion 144 to the cooling portion 30.
[0102] The heat exchanger 15 includes a plurality of tubes 156 and
fins 158. The plurality of tubes 156 flow refrigerant. The fins 158
are used to exchange heat between refrigerant in the plurality of
tubes 156 and air around the heat exchanger 15. The plurality of
tubes 156 are arranged in parallel with one another between an
inlet portion 152 and an outlet portion 154. The inlet portion 152
is connected to the refrigerant line 24, and introduces refrigerant
from the cooling portion 30. The outlet portion 154 is connected to
the refrigerant line 25 routed to the expansion valve 16.
Refrigerant introduced via the inlet portion 152 flows through the
plurality of tubes 156 in a distributed manner.
[0103] Each of the plurality of fins 158 is arranged next to the
gap between any adjacent two of the plurality of tubes 156 between
the inlet portion 152 and the outlet portion 154. Refrigerant is
cooled by exchanging heat with air around the heat exchanger 15 via
the fin 158 in each of the plurality of tubes 156. Refrigerant
after being cooled in the heat exchanger 15 flows from the outlet
portion 154 to the heat exchanger 18 via the expansion valve
16.
[0104] As shown in FIG. 9, a partition and individual outlets and
inlets are provided for the integrated heat exchanger to thereby
make it possible to cause the integrated heat exchanger to
separately serve as the two heat exchangers 14 and 15, so
manufacturing cost of the heat exchangers 14 and 15 may be
reduced.
[0105] The cooling system 1 according to the second embodiment
further includes a check valve 54. The check valve 54 is arranged
in the refrigerant line 22 between the compressor 12 and the heat
exchanger 14 on the side closer to the compressor 12 than the
connection portion between the refrigerant line 22 and the
communication line 51. The check valve 54 allows flow of
refrigerant from the compressor 12 toward the heat exchanger 14 and
prohibits flow of refrigerant in the opposite direction.
[0106] By so doing, when the flow regulating valve 39 is fully
closed (valve opening degree 0%) and the selector valve 52 is
adjusted such that refrigerant flows from the refrigerant line 24
to the communication line 51 and does not flow to the heat
exchanger 15, a closed loop path of refrigerant for circulating
refrigerant between the heat exchanger 14 and the cooling portion
30 may be reliably formed.
[0107] When no check valve 54 is provided, refrigerant may flow
from the communication line 51 to the refrigerant line 22 adjacent
to the compressor 12. By providing the check valve 54, it is
possible to reliably prohibit flow of refrigerant from the
communication line 51 toward the side adjacent to the compressor
12, so it is possible to prevent a decrease in the cooling
performance for cooling the HV device 31 during a stop of the vapor
compression refrigeration cycle 10, using the heat pipe that forms
the annular refrigerant path. Thus, when the cooler for the cabin
of the vehicle is, stopped as well, it is possible to efficiently
cool the HV device 31.
[0108] In addition, when the amount of refrigerant in the closed
loop path of refrigerant is insufficient during a stop of the vapor
compression refrigeration cycle 10, the compressor 12 is operated
only in a short period of time to thereby make it possible to
supply refrigerant to the closed loop path via the check valve 54.
By so doing, the amount of refrigerant in the closed loop may be
increased to thereby increase the amount of heat exchanged in the
heat pipe. Thus, the amount of refrigerant in the heat pipe may be
ensured, so it is possible to avoid insufficient cooling of the HV
device 31 because of an insufficient amount of refrigerant.
[0109] The cooling system 1 according to the second embodiment
further includes a gas-liquid separator 70. Refrigerant flowing out
from the heat exchanger 14 is separated into gas and liquid in the
gas-liquid separator 70. Liquid refrigerant separated in the
gas-liquid separator 70 flows via the refrigerant line 23 and is
supplied to the cooling portion 30 to cool the HV device 31. The
liquid refrigerant is refrigerant in a just saturated liquid state.
By taking only liquid refrigerant from the gas-liquid separator 70
and flowing the liquid refrigerant to the cooling portion 30, the
performance of the heat exchanger 14 may be fully utilized to cool
the HV device 31, so it is possible to provide the cooling system 1
having improved cooling performance for cooling the HV device
31.
[0110] Refrigerant in a saturated liquid state at the outlet of the
gas-liquid separator 70 is introduced into the cooling line 32 that
cools the HV device 31 to thereby make it possible to minimize
gaseous refrigerant within refrigerant that flows in the cooling
system for cooling the HV device 31, including the refrigerant
lines 23 and 24 and the cooling line 32. Therefore, it is possible
to suppress an increase in pressure loss due to an increase in flow
rate of refrigerant steam flowing in the cooling system of the HV
device 31, and the power consumption of the compressor 12 for
flowing refrigerant may be reduced, so it is possible to avoid
deterioration of the performance of the vapor compression
refrigeration cycle 10.
[0111] Refrigerant liquid in a saturated liquid state is stored
inside the gas-liquid separator 70 as shown in FIG. 8. The
gas-liquid separator 70 functions as a reservoir that temporarily
stores refrigerant liquid inside. When refrigerant liquid in a
predetermined amount is stored in the gas-liquid separator 70, the
flow rate of refrigerant flowing from the gas-liquid separator 70
to the cooling portion 30 may be maintained at the time of
fluctuations in load. Because the gas-liquid separator 70 has the
function of storing liquid, serves as a buffer against load
fluctuations and is able to absorb load fluctuations, the cooling
performance for cooling the HV device 31 may be stabilized.
[0112] Note that, in the above described embodiments, the cooling
system 1 that cools an electrical device mounted on the vehicle is
described using the HV device 31 as an example. The electrical
device is not limited to the illustrated electrical devices, such
as an inverter and a motor generator. The electrical device may be
any electrical device as long as it generates heat when it is
operated. In the case where there are a plurality of electrical
devices to be cooled, the plurality of electrical devices desirably
have a common cooling target temperature range. The target
temperature range for cooling is an appropriate temperature range
as a temperature environment in which the electrical devices are
operated.
[0113] Furthermore, the heat generating source cooled by the
cooling system 1 according to the embodiments of the invention is
not limited to the electrical device mounted on the vehicle;
instead, it may be any device that generates heat or may be a heat
generating portion of any device.
[0114] The embodiments of the invention are described above;
however, the configurations of the embodiments may be combined
where appropriate. In addition, the embodiments described above
should be regarded as only illustrative in every respect and not
restrictive. The scope of the invention is indicated not by the
above description but by the appended claims, and is intended to
include all modifications within the meaning and scope equivalent
to the scope of the appended claims.
[0115] The cooling system according to the aspect of the invention
may be particularly advantageously applied to cooling of an
electrical device, such as a motor generator and an inverter, using
a vapor compression refrigeration cycle for cooling and heating a
cabin, in a vehicle, such as a hybrid vehicle, a fuel-cell vehicle
and an electric vehicle, equipped with the electrical device.
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