U.S. patent application number 14/000311 was filed with the patent office on 2013-12-05 for vehicle cooling system.
This patent application is currently assigned to NIPPON SOKEN, INC.. The applicant listed for this patent is Yuki Jojima, Yoshiaki Kawakami, Yasuhiro Kawase, Yuichi Ohno, Kousuke Sato, Eizo Takahashi, Kazuhide Uchida. Invention is credited to Yuki Jojima, Yoshiaki Kawakami, Yasuhiro Kawase, Yuichi Ohno, Kousuke Sato, Eizo Takahashi, Kazuhide Uchida.
Application Number | 20130319038 14/000311 |
Document ID | / |
Family ID | 45876810 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130319038 |
Kind Code |
A1 |
Kawase; Yasuhiro ; et
al. |
December 5, 2013 |
VEHICLE COOLING SYSTEM
Abstract
A cooling system includes a compressor that circulates
refrigerant; a condenser that condenses the refrigerant; an
expansion valve that reduces a pressure of the refrigerant that has
been condensed by the condenser; an evaporator that vaporizes the
refrigerant that has been reduced in pressure by the expansion
valve; a refrigerant passage through which the refrigerant flows
from an outlet of the condenser toward an inlet of the expansion
valve, and that includes a passage forming portion that forms part
of the refrigerant passage; a second passage that is connected in
parallel with the passage forming portion; a cooling portion that
is provided in the second passage and cools a heat source using the
refrigerant; and an expansion valve that is arranged upstream of
the cooling portion in the second passage.
Inventors: |
Kawase; Yasuhiro;
(Nishio-shi, JP) ; Ohno; Yuichi; (Nishio-shi,
JP) ; Uchida; Kazuhide; (Hamamatsu-shi, JP) ;
Kawakami; Yoshiaki; (Nagoya-shi, JP) ; Jojima;
Yuki; (Nagoya-shi, JP) ; Takahashi; Eizo;
(Chiryu-shi, JP) ; Sato; Kousuke; (Toyota-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kawase; Yasuhiro
Ohno; Yuichi
Uchida; Kazuhide
Kawakami; Yoshiaki
Jojima; Yuki
Takahashi; Eizo
Sato; Kousuke |
Nishio-shi
Nishio-shi
Hamamatsu-shi
Nagoya-shi
Nagoya-shi
Chiryu-shi
Toyota-shi |
|
JP
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
NIPPON SOKEN, INC.
Nishio, Aichi
JP
TOYOTA JIDOSHA KABUSHIKI KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
45876810 |
Appl. No.: |
14/000311 |
Filed: |
February 21, 2012 |
PCT Filed: |
February 21, 2012 |
PCT NO: |
PCT/IB2012/000301 |
371 Date: |
August 19, 2013 |
Current U.S.
Class: |
62/498 |
Current CPC
Class: |
B60H 2001/3298 20130101;
F25B 2341/0012 20130101; B60H 2001/00307 20130101; F25B 31/006
20130101; F25B 5/04 20130101; B60H 1/323 20130101; B60H 2001/00949
20130101; F25B 1/00 20130101; F25B 2600/2511 20130101; B60H 1/00278
20130101 |
Class at
Publication: |
62/498 |
International
Class: |
F25B 1/00 20060101
F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2011 |
JP |
2011-035754 |
Claims
1. A cooling system that cools a heat source, comprising: a
compressor that circulates refrigerant; a condenser that condenses
the refrigerant; a first pressure reducer that reduces a pressure
of the refrigerant that has been condensed by the condenser; an
evaporator that vaporizes the refrigerant that has been reduced in
pressure by the first pressure reducer; a first passage through
which the refrigerant flows from an outlet of the condenser toward
an inlet of the first pressure reducer, and that includes a passage
forming portion that forms part of the first passage; a second
passage that is connected in parallel with the passage forming
portion; a cooling portion that is provided in the second passage
and cools the heat source using the refrigerant from the condenser;
a second pressure reducer that is arranged upstream of the cooling
portion in the second passage; and another condenser arranged in
the first passage, wherein the passage forming portion is provided
between the condenser and the other condenser.
2. The cooling system according to claim 1, further comprising a
flow control valve that is arranged in the passage forming portion
and regulates a flowrate of the refrigerant that flows through the
passage forming portion and a flowrate of the refrigerant that
flows through the second passage.
3. (canceled)
4. The cooling system according to claim 1, wherein the condenser
has a greater heat releasing capability to release heat from the
refrigerant than the other condenser does.
5. The cooling system according to claim 1, further comprising a
pressure increasing device that increases a pressure of the
refrigerant that flows from the cooling portion toward the other
condenser.
6. The cooling system according to claim 5, further comprising
another cooling portion that is provided in a path for the
refrigerant that flows from the pressure increasing device toward
the other condenser, and that cools another heat source that is
different from the heat source, using the refrigerant.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a cooling system. More
particularly, the invention relates to a cooling system that cools
a heat source using a vapor compression refrigeration cycle.
[0003] 2. Description of Related Art
[0004] In recent years, hybrid vehicles, fuel cell vehicles, and
electric vehicles and the like that run using the driving force of
an electric motor have become attractive as a way to address
environmental concerns. In these types of vehicles, electrical
equipment such as a motor, generator, inverter, converter, and
battery generate heat by the sending and receiving electric power.
Therefore, this electrical equipment must be cooled.
[0005] Thus, technology has been proposed to cool a heat generating
body using a vapor compression refrigeration cycle that is used for
a vehicle air conditioner. For example, Japanese Patent Application
Publication No. 11-23081 (JP-A-11-23081) describes a system that
cools heat generating equipment with intermediate pressure
refrigerant, and is provided with a cooler configured such that
intermediate pressure refrigerant of a refrigeration cycle cools
heat generating equipment, and electrical expansion valves, the
valve opening amounts of which are able to be controlled by
external signals, that are arranged one on each of the upstream
side and the downstream side of the cooler. Japanese Patent
Application Publication No. 2005-90862 (JP-A-2005-90862) describes
a cooling system provided with heat generating body cooling means
for cooling the heat generating body, that is provided in a bypass
passage that bypasses a compressor, an evaporator, and a pressure
reducer of an air conditioning refrigeration cycle.
[0006] Japanese Patent Application Publication No. 2007-69733
(JP-A-2007-69733) describes a cooling system that cools a heat
generating body using refrigerant for an air conditioning system,
and in which a heat exchanger that performs heat exchange with air
for air conditioning, and a heat exchanger that performs heat
exchange with the heat generating body, are arranged in parallel in
a refrigerant passage that leads from an expansion valve to a
compressor. Japanese Patent Application Publication No. 2001-309506
(JP-A-2001-309506) describes a cooling system that circulates
refrigerant of a vehicle air conditioning refrigeration cycle
system to a cooling member of an inverter circuit portion that
drive-controls an electric motor for running a vehicle, and
suppresses cooling of air conditioning airflow by an evaporator of
the vehicle air conditioning refrigeration cycle system when
cooling of the air conditioning airflow is unnecessary.
[0007] With the cooling systems described in JP-A-11-23081,
JP-A-2005-90862, and JP-A-2007-69733, a cooling path for cooling a
heat source such as electrical equipment is incorporated into a
vapor compression refrigeration cycle, and when cooling the heat
source, all of the refrigerant of the refrigeration cycle is
introduced into the cooling path for cooling the heat source. As a
result, supercooling of the heat source, pressure loss related to
the flow of refrigerant, and power consumption of the compressor
and the like, increase.
SUMMARY OF THE INVENTION
[0008] This invention therefore provides a cooling system capable
of inhibiting supercooling of a heat source, reducing pressure
loss, and reducing power consumption of a compressor.
[0009] A first aspect of the invention relates to a cooling system
that cools a heat source. This cooling system includes a compressor
that circulates refrigerant; a condenser that condenses the
refrigerant; a first pressure reducer that reduces a pressure of
the refrigerant that has been condensed by the condenser; an
evaporator that vaporizes the refrigerant that has been reduced in
pressure by the first pressure reducer; a first passage through
which the refrigerant flows from an outlet of the condenser toward
an inlet of the first pressure reducer, and that includes a passage
forming portion that forms part of the first passage; a second
passage that is connected in parallel with the passage forming
portion; a cooling portion that is provided in the second passage
and cools the heat source using the refrigerant from the condenser;
and a second pressure reducer that is arranged upstream of the
cooling portion in the second passage.
[0010] The cooling system according to this aspect may also include
a flow control valve that is arranged in the passage forming
portion and regulates a flowrate of the refrigerant that flows
through the passage forming portion and a flowrate of the
refrigerant that flows through the second passage.
[0011] The cooling system described above may also include another
condenser arranged in the first passage, and the passage forming
portion may be provided between the condenser and the other
condenser.
[0012] In the cooling system described above, the condenser may
have a greater heat releasing capability to release heat from the
refrigerant than the other condenser does.
[0013] The cooling system described above may also include a
pressure increasing device that increases a pressure of the
refrigerant that flows from the cooling portion toward the other
condenser.
[0014] The cooling system described above may also include another
cooling portion that is provided in a path for the refrigerant that
flows from the pressure increasing device toward the other
condenser, and that cools another heat source that is different
from the heat source, using the refrigerant.
[0015] With the cooling system of the invention described above,
supercooling of a heat source is able to be inhibited, and pressure
loss as well as power consumption of a compressor are able to be
reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] 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:
[0017] FIG. 1 is a view showing a frame format of the structure of
a cooling system according to a first example embodiment of the
invention;
[0018] FIG. 2 is a Mollier diagram showing the state of refrigerant
of a vapor compression refrigeration cycle according to the first
example embodiment;
[0019] FIGS. 3A to 3D are views schematically showing opening
amount control of a flow control valve according to the first
example embodiment;
[0020] FIG. 4 is a view showing a frame format of the structure of
a cooling system according to a second example embodiment of the
invention;
[0021] FIG. 5 is a Mollier diagram showing the state of refrigerant
of a vapor compression refrigeration cycle according to the second
example embodiment;
[0022] FIG. 6 is a view showing a frame format of the structure of
a cooling system according to a third example embodiment of the
invention;
[0023] FIG. 7 is a Mollier diagram showing the state of refrigerant
of a vapor compression refrigeration cycle according to the third
example embodiment;
[0024] FIG. 8 is a view showing a frame format of the structure of
a cooling system according to a fourth example embodiment of the
invention; and
[0025] FIG. 9 is a Mollier diagram showing the state of refrigerant
of a vapor compression refrigeration cycle according to the fourth
example embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
[0026] Example embodiments of the invention will be described below
with reference to the accompanying drawings. In the following
description, like or corresponding parts will be denoted by like
reference characters, and detailed descriptions of those parts will
not be repeated.
[0027] FIG. 1 is a view of a frame format showing the structure of
a cooling system 1 according to a first example embodiment of the
invention. As shown in FIG. 1, the cooling system 1 includes a
vapor compression refrigeration cycle 10. This vapor compression
refrigeration cycle 10 is provided in a vehicle in order to cool
the interior of the vehicle, for example. Cooling using the vapor
compression refrigeration cycle 10 is performed when, for example,
a switch for performing cooling is turned on, or when an automatic
control mode that automatically adjusts the temperature in the
cabin of the vehicle so that it comes to match a set temperature is
selected and the temperature in the vehicle cabin is higher than
the set temperature.
[0028] The vapor compression refrigeration cycle 10 includes a
compressor 12, a condenser 14, an expansion valve 16 that serves as
an example of a pressure reducer, and an evaporator 18. The vapor
compression refrigeration cycle 10 also includes a refrigerant
passage 21 that communicates the compressor 12 with the condenser
14, a refrigerant passage 22 that serves as a first passage that
communicates the condenser 14 with The expansion valve 16, a
refrigerant passage 23 that communicates the expansion valve 16
with the evaporator 18, and a refrigerant passage 24 that
communicates the evaporator 18 with the compressor 12. The vapor
compression refrigeration cycle 10 is formed by the compressor 12,
the condenser 14, the expansion valve 16, and the evaporator 18
being connected together by the refrigerant passages 21 to 24.
[0029] The compressor 12 operates with an electric motor or an
engine mounted in the vehicle as the power source, and
adiabatically compresses refrigerant gas to create superheated
refrigerant gas. When operating, the compressor 12 draws in and
compresses gas-phase refrigerant that flows through the refrigerant
passage 24 from the evaporator 18, and discharges it into the
refrigerant passage 21. The compressor 12 circulates the
refrigerant in the vapor compression refrigeration cycle 10 by
discharging the refrigerant into the refrigerant passage 21.
[0030] The condenser 14 isobarically releases heat from the
superheated refrigerant gas that has been compressed in the
compressor 12 to an external medium, thus creating refrigerant
liquid. The gas-phase refrigerant discharged from the compressor 12
is condensed (i.e., liquefied) by being cooled through releasing
its heat to the surroundings in the condenser 14. The condenser 14
includes a tube through which refrigerant flows, and fins for
performing heat exchange between the refrigerant that flows through
the tube and the surrounding air in the condense 14. The condenser
14 performs heat exchange between the refrigerant and cool air
supplied by the natural flow of air produced as the vehicle runs.
The temperature of the refrigerant drops from the heat exchange in
the condenser 14, and as a result, the refrigerant becomes
liquefied.
[0031] The expansion valve 16 injects the high-pressure
liquid-phase refrigerant that flows through the refrigerant passage
22 from a small hole so that it expands and changes to
low-temperature, low-pressure atomized refrigerant. The expansion
valve 16 reduces the pressure of the refrigerant liquid that has
been condensed by the condenser 14, thereby creating wet vapor of a
gas-liquid mixture. Unlike an expansion valve 33 that will be
described later, the expansion valve 16 functions as a first
pressure reducer for reducing the pressure of the refrigerant
liquid that flows through the refrigerant passage 22. The pressure
reducers are not limited to being the expansion valves 16 and 33
that throttle and expand. That is, they may be capillaries
instead.
[0032] The evaporator 18 absorbs the heat in the surrounding air
that has been introduced so as to contact the evaporator 18, by the
atomized refrigerant that flows through the evaporator 18 being
vaporized. The evaporator 18 cools the inside of vehicle cabin by
absorbing the vaporization heat when the wet vapor of the
refrigerant vaporizes and becomes refrigerant gas from the air in
the vehicle cabin that is a portion to be cooled, using the
refrigerant that has been reduced in pressure by the expansion
valve 16. The inside of the vehicle cabin is cooled led by the air,
whose temperature has been reduced by the heat being absorbed by
the evaporator 18, being returned again into the vehicle cabin. The
refrigerant is heated by absorbing heat from the surroundings in
the evaporator 18.
[0033] The evaporator 18 includes the tube through which
refrigerant flows, and the fins for performing heat exchange
between the refrigerant that flows through the tube and the
surrounding air in the evaporator 18. Refrigerant in a wet vapor
state flows through the tube. When the refrigerant flows through
the tube, it vaporizes by absorbing the heat of the air inside the
vehicle cabin as latent heat of vaporization via the fins, and then
becomes superheated vapor by sensible heat. The vaporized
refrigerant flows into the compressor 12 through the refrigerant
passage 24, and the compressor 12 compresses the refrigerant that
flows in from the evaporator 18.
[0034] The refrigerant passage 21 is a passage for leading
refrigerant from the compressor 12 to the condenser 14. The
refrigerant flows from the outlet of the compressor 12 toward the
inlet of the condenser 14 via the refrigerant passage 21. The
refrigerant passage 22 is a passage for leading refrigerant from
the condenser 14 to the expansion valve 16. The refrigerant flows
from the outlet of the condenser 14 toward the inlet of the
expansion valve 16 via the refrigerant passage 22. The refrigerant
passage 23 is a passage for leading refrigerant from the expansion
valve 16 to the evaporator 18. The refrigerant flows from the
outlet of the expansion valve 16 toward the inlet of the evaporator
18 via the refrigerant passage 23. The refrigerant passage 24 is a
passage for leading refrigerant from the evaporator 18 to the
compressor 12. The refrigerant flows from the outlet of the
evaporator 18 toward the inlet of the compressor 12 via the
refrigerant passage 24.
[0035] Refrigerant flows through points A, B, C, E, and F, in that
order, shown in FIG. 1, inside the vapor compression refrigeration
cycle 10, such that refrigerant circulates to the compressor 12,
the condenser 14, the expansion valve 16, and the evaporator 18.
The refrigerant circulates through the vapor compression
refrigeration cycle 10 by passing through a refrigerant circulation
flow path in which the compressor 12, the condenser 14, the
expansion valve 16, and the evaporator 18 are connected in that
order by the refrigerant passages 21 to 24.
[0036] Carbon dioxide, a hydrogen oxide such as propane or
isobutane, ammonia, or water, for example, may be used as the
refrigerant of the vapor compression refrigeration cycle 10.
[0037] The refrigerant passage 22 through which refrigerant flows
from the condenser 14 toward the expansion valve 16 includes a
passage forming portion 26. The passage forming portion 26 forms
part of the refrigerant passage 22. Point C shown in FIG. 1
represents an upstream end portion of the passage forming portion
26, i.e., an end portion of the passage forming portion 26 that is
on the side near the condenser 14. Point E in FIG. 1 represents a
downstream end portion of the passage forming portion 26, i.e., an
end portion of the passage forming portion that is on the side near
the expansion valve 16.
[0038] The cooling system 1 includes a second passage that is
connected in parallel with the passage forming portion 26. A
cooling portion 30 is provided in this second passage. The cooling
portion 30 is provided in a path for the refrigerant that flows
from the condenser 14 toward the expansion valve 16. The cooling
portion 30 includes an HV equipment heat source 31 that is
electrical equipment mounted in the vehicle, and a cooling passage
32 that is a conduit through which refrigerant flows. The HV
equipment heat source 31 is one example of a heat source. The
second passage described above includes the cooling passage 32. The
second passage also includes refrigerant passages 34, 35, and 36
that are conduits through which refrigerant flows. The expansion
valve 33 that serves as a second pressure reducer that is different
from the first pressure reducer (i.e., the expansion valve 16) is
arranged upstream of the cooling portion 30 in the second passage.
The expansion valve 33 expands the high-pressure liquid-phase
refrigerant discharged from the condenser 14, thereby reducing the
temperature and the pressure of the refrigerant, just like the
expansion valve 16.
[0039] The second passage through which refrigerant flows parallel
with the passage forming portion 26 from point C toward point E in
FIG. 1 is divided into a refrigerant passage 34 that is upstream
(i.e., on the side near the condenser 14) of the expansion valve
33, a refrigerant passage 35 that is between the expansion valve 33
and the cooling portion 30, the cooling passage 32 that is included
in the cooling portion 30, and the refrigerant passage 36 that is
downstream (i.e., on the side near the expansion valve 16) of the
cooling portion 30. The refrigerant passages 34 and 35 are passages
for leading refrigerant from point C to the cooling portion 30. The
refrigerant passage 36 is a passage for leading refrigerant from
the cooling portion 30 to point E. Point C is a branch point
between the refrigerant passage 22 and the refrigerant passage 34,
and point E is a branch point between the refrigerant passage 22
and the refrigerant passage 36.
[0040] Refrigerant that is discharged from the condenser 14 and
branches off at point C to flow through the second passage flows
toward the cooling portion 30 via the refrigerant passage 34, the
expansion valve 33, and the refrigerant passage 35. The refrigerant
that has flowed to the cooling portion 30 and through the cooling
passage 32 removes heat from the HV equipment heat source 31 that
is the heat source, thereby cooling the HV equipment heat source
31. The cooling portion 30 cools the HV equipment heat source 31
using the low-temperature, low-pressure refrigerant that has been
discharged from the condenser 14 and reduced in pressure by the
expansion valve 33. The refrigerant then flows from the cooling
portion 30 toward point E via the refrigerant passage 36, and
reaches the expansion valve 16 via the refrigerant passage 22. The
upstream end portion of the cooling passage 32 is connected to the
refrigerant passage 35, and the downstream end portion of the
cooling passage 32 is connected to the refrigerant passage 36.
[0041] The cooling portion 30 is provided with a structure that
enables heat exchange between the refrigerant and the HV equipment
heat source 31 at the cooling passage 32. In this example
embodiment, the cooling portion 30 has the cooling passage 32 that
is formed such that an outer peripheral surface of the cooling
passage 32 directly contacts the case of the HV equipment heat
source 31. The cooling passage 32 has a portion that is adjacent to
the case of the HV equipment heat source 31. Heat exchange between
the refrigerant that flows through the cooling passage 32 and the
HV equipment heat source 31 is possible at this portion.
[0042] The HV equipment heat source 31 is directly connected to the
outer peripheral surface of the cooling passage 32 that forms part
of the refrigerant path from the condenser 14 to the expansion
valve 16 of the vapor compression refrigeration cycle 10, and is
thus cooled. The HV equipment heat source 31 is arranged on an
outer portion of the cooling passage 32, so the HV equipment heat
source 31 will not interfere with the flow of refrigerant that
flows through the cooling passage 32. Therefore, pressure loss in
the vapor compression refrigeration cycle 10 will not increase, so
the HV equipment heat source 31 is able to be cooled without
increasing the power of the compressor 12.
[0043] Alternatively, the cooling portion 30 may be provided with a
suitable well-known heat pipe interposed between the HV equipment
heat source 31 and the cooling passage 32. In this case, the HV
equipment heat source 31 is connected to an outer peripheral
surface of the cooling passage 32 via the heat pipe, and is cooled
by heat being transferred from the HV equipment heat source 31 to
the cooling passage 32 via the heat pipe. By making the HV
equipment heat source 31 the heating portion of the heat pipe, and
the cooling passage 32 the cooling portion of the heat pipe,
heat-transfer efficiency between the cooling passage 32 and the HV
equipment heat source 31 is able to be increased, so cooling
efficiency of the HV equipment heat source 31 can be improved. For
example, a wick type heat pipe may be used.
[0044] The heat pipe enables heat to be reliably transferred from
the HV equipment heat source 31 to the cooling passage 32, so there
may be distance between the HV equipment heat source 31 and the
cooling passage 32, and there is no need for a complex arrangement
of the cooling passage 32 in order to connect the cooling passage
32 to the HV equipment heat source 31. As a result, the degree of
freedom in the arrangement of the HV equipment heat source 31 is
able to be improved.
[0045] The HV equipment heat source 31 includes electrical
equipment that generates heat as a result of sending and receiving
electric power. The electrical equipment includes at least one of,
for example, an inverter for converting direct current (DC)
electric power into alternating current (AC) electric power, a
motor-generator that is a rotary electric machine, a battery that
is a power storage device, a converter for stepping up the voltage
of the battery, and a DC/DC converter for stepping down the voltage
of the battery. The battery is a secondary battery such as a
lithium-ion battery or a nickel-metal hydride battery. A capacitor
may also be used instead of a battery.
[0046] FIG. 2 is a Mollier diagram showing the state of refrigerant
of the vapor compression refrigeration cycle 10 according to the
first example embodiment. The horizontal axis in FIG. 2 represents
the specific enthalpy (unit: kJ/kg) of the refrigerant, and the
vertical axis in FIG. 2 represents the absolute pressure (unit:
MPa) of the refrigerant. The curve in the drawing is a saturated
vapor line and a saturated liquid line of the refrigerant. FIG. 2
shows the thermodynamic equation of state of the refrigerant at
each point (i.e., points A, B, C, D, E, and F in FIG. 1) in the
vapor compression refrigeration cycle 10, in which refrigerant
flows from the refrigerant passage 22 at the outlet of the
condenser 14 to the refrigerant passage 34 via point C and is
expanded at the expansion valve 33, after which it flows through
the refrigerant passage 35, cools the HV equipment heat source 31,
and then returns from the refrigerant passage 36 to the refrigerant
passage 22 at the inlet of the expansion valve 16 via point E.
[0047] As shown in FIG. 2, refrigerant in a superheated vapor state
that is drawn into the compressor 12 (point A) is adiabatically
compressed along a geometric entropy line in the compressor 12. As
this refrigerant is compressed, the pressure and temperature of the
refrigerant rises, and it becomes high-temperature, high-pressure
superheated vapor with a large degree of superheat (point B). The
refrigerant then flows to the condenser 14. The high-pressure
refrigerant vapor that has entered the condenser 14 is cooled in
the condenser 14, and changes from the superheated vapor to dry
saturated vapor while remaining at constant pressure, such that the
refrigerant vapor then releases latent heat of condensation and is
gradually liquidized, becoming wet vapor of a gas-liquid mixture.
When all of the refrigerant condenses, it becomes saturated liquid.
Moreover, the refrigerant releases sensible heat and becomes
supercooled liquid (point C).
[0048] The liquefied refrigerant flows into the expansion valve 33
via the refrigerant passage 34. In the expansion valve 33, the
supercooled liquid-state refrigerant is throttled and expanded, so
the temperature and pressure of the refrigerant decrease without
the specific enthalpy of the refrigerant changing (point D). The
refrigerant that has been reduced in temperature in the expansion
valve 33 flows via the refrigerant passage 35 to the cooling
passage 32 of the cooling portion 30, where it cools the HV
equipment heat source 31. By performing heat exchange with the HV
equipment heat source 31, the degree to which the refrigerant is
supercooled lessens, and the temperature of the refrigerant in the
supercooled liquid state rises and approaches a saturation
temperature of liquid refrigerant (point E).
[0049] Then the refrigerant flows into the expansion valve 16. In
the expansion valve 16, the refrigerant in the supercooled liquid
state is throttled and expanded, so the temperature and pressure
decrease without the specific enthalpy changing, thus creating
low-temperature, low-pressure wet vapor of a gas-liquid mixture
(point F). The heat of the refrigerant in the wet vapor state that
is discharged from the expansion valve 16 is absorbed from the
outside, so the refrigerant vaporizes while remaining at constant
pressure from the latent heat of vaporization in the evaporator 18.
When all of the refrigerant becomes dry saturated vapor, the
refrigerant vapor further rises in temperature from the sensible
heat and becomes superheated vapor (point A), which is then drawn
into the compressor 12. The refrigerant continuously changes states
repeatedly from compressed, to condensed, to throttled and
expanded, to vaporized, according to this kind of cycle.
[0050] In the description of the vapor compression refrigeration
cycle above, a theoretical refrigeration cycle is described.
However, in the actual vapor compression refrigeration cycle 10, it
is of course necessary to take into account loss in the compressor
12, pressure loss of the refrigerant, and heat loss.
[0051] While the vapor compression refrigeration cycle 10 is
operating, refrigerant cools the inside of the vehicle cabin by
absorbing, in the evaporator 18, vaporization heat from the air
inside the vehicle cabin. In addition, high-pressure liquid
refrigerant discharged from the condenser 14 branches off at point
C, such that some of the refrigerant flows to the HV equipment heat
source 31 and performs heat exchange with the HV equipment heat
source 31, thereby cooling the HV equipment heat source 31. The
cooling system 1 cools the HV equipment heat source 31 that is the
heat source mounted in the vehicle, using the vapor compression
refrigeration cycle 10 for air-conditioning the inside of the
vehicle cabin.
[0052] The HV equipment heat source 31 is cooled using the vapor
compression refrigeration cycle 10 provided to cool the portion to
be cooled at the evaporator 18. Therefore, there is no need to
provide equipment such as a special water circulating pump or
cooling fan in order to cool the HV equipment heat source 31.
Accordingly, the structure necessary for the cooling system 1 of
the HV equipment heat source 31 can be reduced so the structure of
the apparatus can be simple, and as a result, the manufacturing
cost of the cooling system 1 is able to be reduced. In addition,
there is no need to operate a power supply such as a pump or a
cooling fan in order to cool the HV equipment heat source 31, so
power does not need to be consumed to operate the power supply.
Therefore, the power consumption for cooling the HV equipment heat
source 31 is able to be reduced.
[0053] The HV equipment heat source 31 can be cooled using
refrigerant with a temperature that has been lowered by the
refrigerant being expanded by the expansion valve 33, so the HV
equipment heat source 31 is able to be cooled more efficiently. The
temperature of the refrigerant that cools the HV equipment heat
source 31 with the cooling portion 30 can be appropriately
regulated by optimally selecting the specifications of the
expansion valve 33. Therefore, the HV equipment heat source 31 can
be cooled by supplying the cooling portion 30 with refrigerant of a
lower temperature suitable for cooling the HV equipment heat source
31.
[0054] The passage forming portion 26 that is a path that does not
pass through the cooling portion 30, and the second passage that is
a path for refrigerant that cools the HV equipment heat source 31
via the cooling portion 30, are provided in parallel as paths
through which refrigerant flows from the outlet of the condenser 14
toward the inlet of the expansion valve 16. Therefore, only some of
the refrigerant that is discharged from the condenser 14 flows to
the cooling portion 30. Refrigerant of an amount necessary to cool
the HV equipment heat source 31 is made to flow to the cooling
portion 30, such that the HV equipment heat source 31 is able to be
appropriately cooled. Accordingly, the HV equipment heat source 31
is able to be inhibited from being supercooled. Not all of the
refrigerant flows to the cooling portion 30, so pressure loss
related to the flow of refrigerant through the cooling portion 30
can be reduced, and in turn, the power consumption necessary to
operate the compressor 12 in order to circulate the refrigerant can
be reduced.
[0055] The refrigerant is cooled in the condenser 14 until it
becomes supercooled liquid, and is then heated to a temperature
slightly below the saturation temperature by receiving sensible
heat from the HV equipment heat source 31. Then the refrigerant
passes through the expansion valve 16, and as a result, the
refrigerant becomes low-temperature, low-pressure wet vapor. At the
outlet of the expansion valve 16, the refrigerant has the
temperature and pressure originally required to cool the inside of
the vehicle cabin. The heat releasing capability of the condenser
14 is set such that the condenser 14 is able to sufficiently cool
the refrigerant.
[0056] When the low-temperature, low-pressure refrigerant that has
passed through the expansion valve 16 is used to cool the HV
equipment heat source 31, the cooling capability of the evaporator
18 with respect to the air inside of the vehicle cabin decreases,
so the vehicle cabin cooling capability decreases. Therefore, with
the cooling system 1 in this example embodiment, the refrigerant is
cooled to a sufficiently supercooled state in the condenser 14, and
high-pressure refrigerant from the outlet of the condenser 14 is
used to cool the HV equipment heat source 31. Thus, the HV
equipment heat source 31 is able to be cooled without adversely
affecting the cooling capability to cool the air inside the vehicle
cabin. The temperature required to cool the HV equipment heat
source 31 is preferably lower than at least an upper limit value of
a target temperature range as the temperature range of the HV
equipment heat source 31.
[0057] The specifications of the condenser 14 (i.e., the size or
heat releasing performance of the condenser 14) are set such that
the temperature of the liquid-phase refrigerant after passing
through the condenser 14 is lower than the temperature required to
cool the inside of the vehicle cabin. The specifications of the
condenser 14 are set such that the refrigerant has a heat discharge
that is greater than the condenser of the vapor compression
refrigeration cycle when not cooling the HV equipment heat source
31, by the amount of heat that it is estimated that the refrigerant
will receive from the HV equipment heat source 31. The cooling
system 1 provided with the condenser 14 having such specifications
is able to appropriately cool the HV equipment heat source 31
without increasing the power of the compressor 12, while
maintaining cooling performance for the inside of the vehicle
cabin.
[0058] Returning now to FIG. 1, the cooling system 1 includes a
flow control valve 28. The flow control valve 28 is provided in the
refrigerant passage 22 that leads from the condenser 14 toward the
expansion valve 16. The flow control valve 28 is arranged in the
passage forming portion 26 that forms part of the refrigerant
passage 22. The flow control valve 28 appropriately regulates the
flowrate of the refrigerant that flows through the passage forming
portion 26 and the flowrate of the refrigerant that flows through
the second passage that includes the cooling passage 32, by
changing its opening amount (i.e., the opening amount of the flow
control valve 28) to increase or decrease pressure loss of the
refrigerant that flows through the passage forming portion 26.
[0059] For example, if the flow control valve 28 is fully closed
such that the valve opening amount is 0%, the entire amount of the
refrigerant that is discharged from the condenser 14 will flow from
point C into the refrigerant passage 34. If the opening amount of
the flow control valve 28 is increased, the flowrate of refrigerant
that directly flows to the expansion valve 16 via the passage
forming portion 26, of the refrigerant that flows from the
condenser 14 to the refrigerant passage 22, will increase, and
consequently, the flowrate of the refrigerant that flows via the
refrigerant passages 34 and 35 to the cooling passage 32 where it
cools the HV equipment heat source 31 will decrease. Conversely, if
the opening amount of the flow control valve 28 is decreased, the
flowrate of refrigerant that directly flows to the expansion valve
16 via the passage forming portion 26, of the refrigerant that
flows from the condenser 14 to the refrigerant passage 22, will
decrease, and consequently, the flowrate of the refrigerant that
flows through the cooling passage 32 where it cools the HV
equipment heat source 31 will increase.
[0060] If the opening amount of the flow control valve 28 is
increased, the flowrate of the refrigerant that cools the HV
equipment heat source 31 will decrease, so the cooling capability
for the HV equipment heat source 31 will be reduced. If the opening
amount of the flow control valve 28 is decreased, the flowrate of
the refrigerant that cools the HV equipment heat source 31 will
increase, so the cooling capability for the HV equipment heat
source 31 will be improved. In this way, the amount of refrigerant
that flows to the HV equipment heat source 31 can be optimally
regulated using the flow control valve 28, so supercooling of the
HV equipment heat source 31 can be inhibited, and in addition, both
pressure loss related to the flow of refrigerant through the second
passage, and the power consumption of the compressor 12 for
circulating the refrigerant are able to be reduced.
[0061] Next, an example of control related to the adjustment of the
opening amount of the flow control valve 28 will be described.
FIGS. 3A to 3D are views schematically showing opening amount
control of the flow control valve 28. The horizontal axis shown in
the graphs in FIGS. 3A to 3D represents time. The vertical axis of
the graph in FIG. 3A represents the valve opening amount when the
flow control valve 28 is an electrical expansion valve with a
stepping motor. The vertical axis of the graph in FIG. 3B
represents the opening amount when the flow control valve 28 is a
temperature-type expansion valve that opens and closes according to
a change in temperature. The vertical axis of the graph in FIG. 3C
represents the temperature of the HV equipment heat source 31. The
vertical axis of the graph in FIG. 3D represents a temperature
difference between the inlet and the outlet (i.e., an inlet/outlet
temperature difference) of the HV equipment heat Source 31.
[0062] The HV equipment heat source 31 is cooled by refrigerant
flowing through the cooling portion 30. The adjustment of the
opening amount of the flow control valve 28 is performed by, for
example, monitoring the temperature of the HV equipment heat source
31, or the temperature difference between the outlet temperature
and the inlet temperature of the HV equipment heat source 31. For
example, referring to the graph in FIG. 3C, a temperature sensor
that intermittently measures the temperature of the HV equipment
heat source 31 is provided, and the temperature of the HV equipment
heat source 31 is monitored. Also, for example, referring to the
graph in FIG. 3D, a temperature sensor that measures the inlet
temperature and the outlet temperature of the HV equipment heat
source 31 is provided, and the temperature difference between the
inlet and outlet of the HV equipment heat source 31 is
monitored.
[0063] If the temperature of the HV equipment heat source 31
exceeds a target temperature, or if the inlet/outlet temperature
difference of the HV equipment heat source 31 exceeds a target
temperature difference (such as 3 to 5.degree. C.), the opening
amount of the flow control valve 28 will decrease, as shown in the
graphs in FIGS. 3A and 3B. Throttling the opening amount of the
flow control valve 28 increases the flowrate of the refrigerant
that flows to the cooling portion 30 through the refrigerant
passages 34 and 35, as described above, so the HV equipment heat
source 31 can be cooled even more effectively. As a result, the
temperature of the HV equipment heat source 31 can be reduced to
equal than or less the target temperature, as shown in the graph in
FIG 3C, or the inlet/outlet temperature difference of the HV
equipment heat source 31 can be reduced to equal to or less than
the target temperature difference, as shown in the graph in FIG.
3D.
[0064] In this way, by optimally adjusting the opening amount of
the flow control valve 28, it is possible to ensure refrigerant of
an amount that enables the heat releasing capability required to
keep the HV equipment heat source 31 within an appropriate
temperature range to be obtained, such that the HV equipment heat
source 31 can be appropriately cooled. Therefore, the problem of
the HV equipment heat source 31 overheating and becoming damaged is
able to be inhibited from occurring.
[0065] FIG. 4 is a view showing a frame format of the structure of
the cooling system 1 according to a second example embodiment of
the invention. The cooling system 1 of the second example
embodiment differs from that of the first example embodiment in
that a condenser 15 that is another condenser that is different
from the condenser 14 is arranged in the refrigerant passage 22
that joins the condenser 14 and the expansion valve 16
together.
[0066] The cooling system 1 of the second example embodiment
includes the condenser 14 that serves as a first condenser, and the
condenser 15 that serves as a second condenser. The condenser 15 is
provided, so the refrigerant passage 22 branches into two, i.e.,
into a refrigerant passage 22a that is upstream (i.e., on the side
near the condenser 14) of the condenser 15, and a refrigerant
passage 22b that is downstream (i.e., on the side near the
expansion valve 16) of the condenser 15. In the vapor compression
refrigeration cycle 10, high-pressure refrigerant that has been
discharged from the compressor 12 is condensed by both the
condenser 14 and the condenser 15.
[0067] The passage forming portion 26 that forms part of the
refrigerant passage 22 is provided in the refrigerant passage 22a
between the condenser 14 and the condenser 15. A second passage
that is a cooling system of the HV equipment heat source 31 that
includes the cooling passage 32 is arranged parallel with the
passage forming portion 26. A path for refrigerant that flows from
the condenser 14 to the condenser 15, and a path for refrigerant
that flows from the condenser 14 to the condenser 15 via the
cooling portion 30 are provided in parallel, and pressure loss when
refrigerant flows to the cooling system of the HV equipment heat
source 31 is able to be reduced by having only some of the
refrigerant flow to the cooling portion 30.
[0068] FIG. 5 is a Mollier diagram showing the state of refrigerant
of the vapor compression refrigeration cycle 10 according to the
second example embodiment. The horizontal axis in FIG. 5 represents
the specific enthalpy (unit: kJ/kg) of the refrigerant, and the
vertical axis in FIG. 5 represents the absolute pressure (unit:
MPa) of the refrigerant. The curve in the drawing is a saturated
vapor line and a saturated liquid line of the refrigerant. FIG. 5
shows the thermodynamic equation of state of the refrigerant at
each point (i.e., Points A, B, C, D, E, G, and F) in the vapor
compression refrigeration cycle 10, in which refrigerant flows from
the refrigerant passage 22a at the outlet of the condenser 14 to
the refrigerant passage 34 via point C and is expanded at the
expansion valve 33, after which it flows through the refrigerant
passage 35, cools the HV equipment heat source 31, and then returns
from the refrigerant passage 36 to the refrigerant passage 22a at
the inlet of the condenser 15 via point E.
[0069] The vapor compression refrigeration cycle 10 in the second
example embodiment is the same as that in the first example
embodiment except for the system from the condenser 14 to the
expansion valve 16. That is, the states of the refrigerant from
point G to point B via points F and A in the Mollier diagram in
FIG. 5 are the same as the states of the refrigerant from point E
to point B via points F and A in the Mollier diagram in FIG. 2.
Therefore, the particular states of the refrigerant from point B to
point G in the vapor compression refrigeration cycle 10 of the
second example embodiment will be described below.
[0070] High-temperature, high-pressure refrigerant in a superheated
vapor state (point B) that has been adiabatically compressed by the
compressor 12 is cooled in the condenser 14. This refrigerant
releases sensible heat and thus changes from superheated vapor to
dry saturated vapor while remaining at constant pressure, such that
the refrigerant releases the latent heat of condensation and is
gradually liquidized, becoming wet vapor of a gas-liquid mixture.
All of the refrigerant condenses and becomes saturated liquid
(point C).
[0071] The refrigerant in a saturated liquid state that flows out
from the condenser 14 flows from point C into the expansion valve
33 via the refrigerant passage 34. In the expansion valve 33, the
refrigerant in a supercooled liquid state is throttled and
expanded, so the temperature and pressure of the refrigerant
decrease without the specific enthalpy of the refrigerant changing,
and the refrigerant becomes wet vapor that is a mixture of the
saturated liquid and the saturated vapor (point D). The refrigerant
that has been reduced in temperature in the expansion valve 33
flows via the refrigerant passage 35 to the cooling passage 32 of
the cooling portion 30, where it cools the HV equipment heat source
31. Heat exchange with the HV equipment heat source 31 heats the
refrigerant and thus increases the degree of dryness of the
refrigerant. The refrigerant receives latent heat from the HV
equipment heat source 31 and some of this refrigerant consequently
vaporizes, such that the ratio of saturated vapor in the
refrigerant that is in the wet vapor state increases (point E).
[0072] Then the refrigerant flows into the condenser 15. The wet
vapor of the refrigerant is again condensed in the condenser 15,
and when all of the refrigerant condenses, it becomes saturated
liquid. Moreover, the refrigerant releases sensible heat and
becomes supercooled liquid that is supercooled (point G). Then the
refrigerant becomes low-temperature, low-pressure wet vapor (point
F) by passing through the expansion valve 16.
[0073] By sufficiently cooling the refrigerant in the condenser 15,
at the outlet of the expansion valve 16, the refrigerant has the
temperature and pressure originally required to cool the inside of
the vehicle cabin. Therefore, the amount of heat that can be
received from the outside when the refrigerant vaporizes in the
evaporator 18 can be made sufficiently large. Setting the heat
releasing capability of the condenser 15 that is able to
sufficiently cool the refrigerant in this way enables the HV
equipment heat source 31 to be cooled without adversely affecting
the cooling capability to cool the air inside the vehicle cabin.
Therefore, both the cooling capability for the HV equipment heat
source 31 and the vehicle cabin cooling capability are able to be
ensured.
[0074] With the vapor compression refrigeration cycle 10 according
to the first example embodiment;the condenser 14 is arranged
between the compressor 12 and the expansion valve 16, so it is
necessary to further cool the refrigerant from a saturated liquid
state in the condenser 14 so that the refrigerant has a
predetermined degree of supercooling. If the refrigerant in a
supercooled liquid state is cooled, the temperature of the
refrigerant will approach atmospheric temperature, and the cooling
efficiency of the refrigerant will decrease, so the capacity of the
condenser 14 must be increased. As a result, the size of the
condenser 14 will increase, which is a drawback for the cooling
system 1 that is to be mounted in a vehicle. On the other hand, if
the condenser 14 is made small in order to mount it in a vehicle,
the heat releasing capability of the condenser 14 will also be
less, and as a result, the temperature of the refrigerant at the
outlet of the expansion valve 16 may not be sufficiently low, so
the vehicle cabin cooling capability may be insufficient.
[0075] In contrast, with the vapor compression refrigeration cycle
10 according to the second example embodiment, two condensers 14
and 15 are arranged between the compressor 12 and the expansion
valve 16, and the cooling system of the HV equipment heat source 31
is provided between the condenser 14 and the condenser 15. With the
condenser 14, the refrigerant simply needs to be cooled to a
saturated liquid state, as shown in FIG. 5. Refrigerant that is in
a wet vapor state as a result of having received the latent heat of
vaporization from the HV equipment heat source 31 such that some of
the refrigerant has vaporized is again cooled by the condenser 15.
Until the refrigerant that is in a wet vapor state is condensed and
completely turns into saturated liquid, the refrigerant changes
states at a constant temperature. The condenser 15 further cools
the refrigerant to a degree of supercooling necessary for cooling
the inside of the vehicle cabin. Therefore, compared with the first
example embodiment, there is no need to increase the degree of
supercooling of the refrigerant, so the capacity of the condensers
14 and 15 can be decreased. Accordingly, the vehicle cabin cooling
capability can be ensured, and the size of the condensers 14 and 15
can be reduced, so the cooling system 1 that is small and
advantageous for being mounted in a vehicle is able to be
obtained.
[0076] The refrigerant that flows from the condenser 14 to the HV
equipment heat source 31 is heated as a result of receiving heat
from the HV equipment heat source 31 when it cools the HV equipment
heat source 31. When the refrigerant is heated to equal to or
greater than a saturated vapor temperature in the HV equipment heat
source 31 and all of the refrigerant vaporizes, the amount of heat
exchange between the refrigerant and the HV equipment heat source
31 decreases, so the HV equipment heat source 31 is no longer able
to be cooled efficiently, and the pressure loss when the
refrigerant flows through the conduit increases. Therefore, it is
preferable to sufficiently cool the refrigerant in the condenser 14
to the point where not all of the refrigerant will vaporize after
cooling the HV equipment heat source 31.
[0077] More specifically, the state of the refrigerant at the
outlet of the condenser 14 is made to be a state that is close to
saturated liquid, typically, a state in which the refrigerant is on
the saturated liquid line at the outlet of the condenser 14. When
the condenser 14 has the capability to sufficiently cool the
refrigerant in this way, the heat releasing capability to release
heat from the refrigerant of the condenser 14 consequently becomes
higher than the heat releasing capability of the condenser 15.
Sufficiently cooling the refrigerant in the condenser 14 that has
relatively greater heat releasing capability enables refrigerant
that has received heat from the HV equipment heat source 31 to be
held in a wet vapor state, so a decrease in the amount of heat
exchange between the refrigerant and the HV equipment heat source
31 can be avoided, thus enabling the HV equipment heat source 31 to
be sufficiently cooled efficiently. The refrigerant in a wet vapor
state after cooling the HV equipment heat source 31 is again
efficiently cooled in the condenser 15, and is cooled until it
comes to be in a supercooled liquid state below the saturation
temperature. Therefore, the cooling system 1 that enables both the
vehicle cabin cooling capability and the cooling capability for the
HV equipment heat source 31 to be ensured can be provided.
[0078] FIG. 6 is a view showing a frame format of the structure of
the cooling system 1 according to a third example embodiment of the
invention. The cooling system 1 in the third example embodiment
differs from that in the second example embodiment in that it
includes an ejector 38. The ejector 38 serves as a pressure
increasing device that makes the high-pressure refrigerant before
passing through the expansion valve 33 into a driven flow and makes
the refrigerant after passing through the expansion valve 33 and
cooling the HV equipment heat source 31 in the cooling portion 30
into a secondary flow, and mixes the driven flow and the secondary
flow to increase the pressure of the low-pressure refrigerant that
flows from the cooling portion 30 toward the condenser 15.
[0079] More specifically, as shown in FIG. 6, a refrigerant passage
37 that branches off from the refrigerant passage 34 on the inlet
side of the expansion valve 33 is connected to the ejector 38. The
refrigerant passage 36 that is a flow path of refrigerant that
flows through the cooling portion 30 toward the condenser 15 is
also connected to the ejector 38. High-pressure refrigerant that
has flowed from the refrigerant passage 37 into the ejector 38 is
injected as the driven flow from a nozzle. Refrigerant from the
refrigerant passage 36 is drawn into the ejector 38 by negative
pressure generated inside of the ejector 38 by the injection of the
driven flow, and the viscosity of the driven flow. Inside the
ejector 38, the refrigerant that has flowed in from the refrigerant
passage 37 completely mixes with the refrigerant that has flowed in
from the refrigerant passage 36. Then this mixture is passed
through a diffuser so that its pressure increases, and after which
it is discharged to a refrigerant passage 39. The refrigerant that
has been reduced in pressure by passing through the expansion valve
33 is increased in pressure by the ejector 38, and flows to the
condenser 15.
[0080] FIG. 7 is a Mollier diagram showing the state of refrigerant
of the vapor compression refrigeration cycle 10 according to the
third example embodiment. The horizontal axis in FIG. 7 represents
the specific enthalpy (unit: kJ/kg) of the refrigerant, and the
vertical axis in FIG. 7 represents the absolute pressure (unit:
MPa) of the refrigerant. The curve in the drawing is a saturated
vapor line and a saturated liquid line of the refrigerant. FIG. 7
shows the thermodynamic equation of state of the refrigerant at
each point (i.e., points A, B, C, D, H, E, G, and F) in the vapor
compression refrigeration cycle 10, in which refrigerant flows from
the refrigerant passage 22a at the outlet of the condenser 14 to
the refrigerant passage 34 via point C and is expanded at the
expansion valve 33, after which it flows through the refrigerant
passage 35, cools the HV equipment heat source 31, is then
increased in pressure by the ejector 38, and is returned from the
refrigerant passage 39 to the refrigerant passage 22a at the inlet
of the condenser 15 via point E.
[0081] The vapor compression refrigeration cycle 10 in the third
example embodiment is the same as that in the second example
embodiment except for the system from the condenser 14 to the
expansion valve 16. That is, the states of the refrigerant from
point F to point C via points A and B in the Mollier diagram in
FIG. 7 are the same as the states of the refrigerant from point F
to point C via points A and B in the Mollier diagram in FIG. 5.
Therefore, the particular states of the refrigerant from point C to
point F in the vapor compression refrigeration cycle 10 of the
third example embodiment will be described below.
[0082] The refrigerant in a saturated liquid state that flows out
from the condenser 14 flows from point C into the expansion valve
33 via the refrigerant passage 34. In the expansion valve 33, the
refrigerant in a supercooled liquid state is throttled and
expanded, so the temperature and pressure of the refrigerant
decrease without the specific enthalpy of the refrigerant changing,
and the refrigerant becomes wet vapor that is a mixture of the
saturated liquid and the saturated vapor (point D). The refrigerant
that has been reduced in temperature in the expansion valve 33
flows via the refrigerant passage 35 to the cooling passage 32 of
the cooling portion 30, where it cools the HV equipment heat source
31. Heat exchange with the HV equipment heat source 31 heats the
refrigerant such that the degree of dryness of the refrigerant
increases. The refrigerant receives latent heat from the HV
equipment heat source 31 and some of this refrigerant consequently
vaporizes, such that the ratio of saturated vapor in the
refrigerant that is in the wet vapor state increases (point H).
[0083] The refrigerant that has been warmed in the cooling portion
30 is increased in pressure by the ejector 38. The high-pressure
refrigerant from the outlet of the condenser 14 is supplied from
the refrigerant passage 37 to the ejector 38, and low-pressure
refrigerant that has been reduced in pressure by passing through
the expansion valve 33 is supplied from the refrigerant passage 36
to the ejector 38. As a result, the pressure of the low-pressure
refrigerant increases, and the temperature of the low-pressure
refrigerant rises. With the high-pressure refrigerant being driven
gas and the low-pressure gas being suction gas, the ejector 38
introduces the low-pressure refrigerant into the ejector 38 using
the differential pressure between the high-pressure refrigerant and
the low-pressure refrigerant, and raises the pressure of the
low-pressure refrigerant and discharges the resultant
medium-pressure refrigerant that has a higher pressure (point
E).
[0084] The ejector 38 is used as a pressure increasing device for
increasing the pressure of the low-pressure refrigerant, so there
is no need to increase the pressure of the refrigerant by driving a
compressor that consumes power. Therefore, an increase in power
consumption can be avoided. The ejector 38 has a simple structure
in which a nozzle is combined with a diffuser, and has no working
parts, so an extremely durable and reliable pressure increasing
device is able to be provided.
[0085] Then the refrigerant flows into the condenser 15. The wet
vapor of the refrigerant that has been increased in pressure by
passing through the ejector 38 is again condensed-in the condenser
15, and when all of the refrigerant condenses, it becomes saturated
liquid. Moreover, the refrigerant releases sensible heat and
becomes supercooled liquid that is supercooled (point G). Then the
refrigerant becomes low-temperature, low-pressure wet vapor (point
F) by passing through the expansion valve 16.
[0086] In the condenser 15, the refrigerant is cooled by heat
exchange between the outside air and the refrigerant by the
refrigerant releasing heat to the outside air. If the refrigerant
pressure is low at this time, the temperature difference with the
outside air will be small and the heat releasing capability of the
condenser 15 with respect to the outside air will decrease. Unless
the refrigerant is able to be sufficiently cooled by the condenser
15, the amount of heat that the refrigerant is able to receive from
the outside air in the evaporator 18 may not be sufficiently large,
so the cooling capability to cool the air inside the vehicle cabin
may decrease. Therefore, the refrigerant that flows into the
condenser 15 is able to be increased in temperature by raising the
pressure of the low-pressure refrigerant that has cooled the HV
equipment heat source 31 at the cooling portion 30, using the
ejector 38. As a result, a decrease in the heat releasing
capability of the condenser 15 can be avoided, so the efficiency of
the condenser 15 can be improved. Accordingly, refrigerant is able
to be sufficiently cooled in the condenser 15, so a decrease in
cooling capability can be avoided.
[0087] FIG. 8 is a view showing a frame format of the structure of
the cooling system 1 according to a fourth example embodiment of
the invention. The cooling system 1 in the fourth example
embodiment differs from that in the third example embodiment in
that a cooling portion 40 that is another cooling portion that is
different from the cooling portion 30 described above is provided
in the refrigerant passage 39 that is a path for refrigerant that
has been increased in pressure by the ejector 38. The cooling
portion 40 is provided in the path for refrigerant that flows from
the ejector 38 toward the condenser 15, between the ejector 38 and
the condenser 15.
[0088] The cooling portion 40 includes an HV equipment heat source
41 that is that is electrical equipment mounted in the vehicle, and
a cooling passage 42 that is a conduit through which refrigerant
flows. The HV equipment heat source 41 is one example of another
heat source that is different from the HV equipment heat source 31.
A passage for refrigerant from the ejector 38 toward point E in
FIG. 8 is divided into a refrigerant passage 39a that is upstream
(i.e., on the side near the ejector 38) of the cooling portion 40,
the cooling passage 42 that is included in the cooling portion 40,
and a refrigerant passage 39b that is downstream (i.e., on the side
near point E) of the cooling portion 40.
[0089] Refrigerant that is discharged from the ejector 38, flows to
the cooling portion 40 via the refrigerant passage 39a, and flows
through the cooling passage 42 removes heat from the HV equipment
heat source 41 that is a heat source, thereby cooling the HV
equipment heat source 41. The cooling portion 40 cools the HV
equipment heat source 41 using the medium-pressure refrigerant
discharged from the ejector 38. Refrigerant also flows from the
cooling portion 40 toward point E via the refrigerant passage 39b,
and then to the condenser 15 via the refrigerant passage 22a. An
upstream end portion of the cooling passage 42 is connected to the
refrigerant passage 39a, and a downstream end portion of the
cooling passage 42 is connected to the refrigerant passage 39b.
[0090] Like the cooling portion 30, the cooling portion 40 is
provided with a structure that enables heat exchange between the
refrigerant and the HV equipment heat source 41 at the cooling
passage 42. An outer peripheral surface of the cooling passage 42
may directly contact a case of the HV equipment heat source 41, or
a heat pipe may be interposed between the HV equipment heat source
41 and the outer peripheral surface of the cooling passage 42. The
HV equipment heat source 41 is arranged on an outer portion of the
cooling passage 42, so the HV equipment heat source 41 will not
interfere with the flow of refrigerant that flows through the
cooling passage 42. Therefore, pressure loss in the vapor
compression refrigeration cycle 10 will not increase, so the HV
equipment heat source 41 is able to be cooled without increasing
the power of the compressor 12.
[0091] FIG. 9 is a Mollier diagram showing the state of refrigerant
of the vapor compression refrigeration cycle 10 according to the
fourth example embodiment. The horizontal axis in FIG. 9 represents
the specific enthalpy (unit: kJ/kg) of the refrigerant, and the
vertical axis in FIG. 9 represents the absolute pressure (unit:
MPa) of the refrigerant. The curve in the drawing is a saturated
vapor line and a saturated liquid line of the refrigerant. FIG. 9
shows the thermodynamic equation of state of the refrigerant at
each point (i.e., points A, B, C, D, H, I, E, G, and F) in the
vapor compression refrigeration cycle 10, in which refrigerant
flows from the refrigerant passage 22a at the outlet of the
condenser 14 to the refrigerant passage 34 via point C and is
expanded at the expansion valve 33, after which it flows through
the refrigerant passage 35, cools the HV equipment heat source 31,
and then is increased in pressure by the ejector 38, and goes on to
cool the HV equipment heat source 41, after which it is returned
from the refrigerant passage 39 to the refrigerant passage 22a at
the inlet of the condenser 15 via point E.
[0092] The vapor compression refrigeration cycle 10 in the fourth
example embodiment is the same as that in the third example
embodiment except far the system from the ejector 38 to the
condenser 15. That is, the states of the refrigerant from point G
to point H via points F, A, B, C, and D in the Mollier diagram in
FIG. 9 are the same as the states of the refrigerant from point G
to point H via points F, A, B, C, and D in the Mollier diagram in
FIG. 7. Therefore, the particular states of the refrigerant from
point H to point G in the vapor compression refrigeration cycle 10
of the fourth example embodiment will be described below.
[0093] High-pressure refrigerant discharged from the outlet of the
condenser 14 is supplied from the refrigerant passage 37, and
low-pressure refrigerant (point H) that has been reduced in
pressure by passing through the expansion valve 33 is supplied from
the refrigerant passage 36. The low-pressure refrigerant is
increased in pressure and the resultant medium-pressure refrigerant
that has a higher pressure is discharged from the ejector 38 (point
I). The refrigerant that has been increased in pressure by the
ejector 38 flows via the refrigerant passage 39a to the cooling
passage 42 of the cooling portion 40, where it cools the HV
equipment heat source 41. Heat exchange with the HV equipment heat
source 41 heats the refrigerant such that the degree of dryness of
the refrigerant increases. The refrigerant receives latent heat
from the HV equipment heat source 41 and some of this refrigerant
consequently vaporizes, such that the saturated liquid in the
refrigerant that is in the wet vapor state decreases and the
saturated vapor increases (point E).
[0094] Then the refrigerant flows into the condenser 15. The wet
vapor of the refrigerant that has cooled the HV equipment heat
source 41 is again condensed in the condenser 15, and when all of
the refrigerant condenses, it becomes saturated liquid. Moreover,
the refrigerant releases sensible heat and becomes supercooled
liquid that is supercooled (point G).
[0095] Both the HV equipment heat source 31 and the HV equipment
heat source 41 are cooled using the vapor compression refrigeration
cycle 10, so special equipment for cooling the HV equipment heat
sources 31 and 41 is not necessary. Therefore, the structure
required to cool the HV equipment heat sources 31 and 41 can be
reduced, which in turn enables the manufacturing cost of the
cooling system 1 to be reduced. In addition, there is no need to
operate a power supply such as a pump or a cooling fan in order to
cool the HV equipment heat sources 31 and 41, so power consumption
for cooling the HV equipment heat sources 31 and 41 can be
reduced.
[0096] The temperature suitable for cooling the HV equipment heat
source 41 is higher than the temperature suitable for cooling the
HV equipment heat source 31. This kind of HV equipment heat source
41 may also be a transaxle, for example. If a transaxle is cooled
too much, the viscosity of ATF (Automatic Transaxle Fluid) inside
the transaxle increases, which leads to a decrease in fuel
efficiency. Therefore, it is preferable to cool the transaxle by
the necessary heat amount in a higher temperature range than the
motor-generator and the PCU (Power Control Unit). By using the
cooling system 1 of the fourth example embodiment, the HV equipment
heat source 31 is cooled by the low-temperature refrigerant that
has been expanded by the expansion valve 33, and the HV equipment
heat source 41 is cooled by the refrigerant that has been
discharged from the ejector 38 and increased in temperature.
[0097] By optimally selecting the specifications of the expansion
valve 33 and the ejector 38, the temperature of the refrigerant
that cools the HV equipment heat source 31 at the cooling portion
30, and the temperature of the refrigerant that cools the HV
equipment heat source 41 at the cooling portion 40 can be
appropriately regulated. Therefore, the HV equipment heat sources
31 and 41 that have different temperatures suitable for cooling are
able to be simultaneously cooled at their respective optimal
temperatures.
[0098] In the first to the fourth example embodiments, the cooling
system 1 that cools electrical equipment mounted in a vehicle, of
which the HV equipment heat sources 31 and 41 are given as
examples, is described. The electrical equipment is not limited to
the electrical equipment described, e.g., an inverter, a
motor-generator, a transaxle, and the like. That is, the electrical
equipment may be any appropriate electrical equipment as long as it
at least generates heat by operating. If a plurality of electrical
equipment is to be cooled, the plurality of electrical equipment
preferably has a common target temperature range for cooling. The
target temperature range for cooling is a temperature range that is
suitable as a temperature environment for operating the electrical
equipment.
[0099] Moreover, the heat source that is cooled by the cooling
system 1 of the invention is not limited to electrical equipment
mounted in a vehicle, but may be any equipment that generates heat,
or any heat-generating portion of equipment.
[0100] While example embodiments of the invention are described
above, the structures of the example embodiments may also be
combined as appropriate. Also, the example embodiments disclosed
herein are in all respects merely examples and should in no way be
construed as limiting. The scope of the invention is indicated not
by the foregoing description but by the scope of the claims for
patent, and is intended to include all modifications that are
within the scope and meanings equivalent to the scope of the claims
for patent.
[0101] The cooling system of the invention may be applied, with
particular advantage, to cooling electrical equipment that uses a
vapor compression refrigeration cycle for cooling the inside of a
vehicle, in a vehicle such as a hybrid vehicle, a fuel cell
vehicle, or an electric vehicle or the like, that is provided with
electric equipment such as a motor-generator and an inverter and
the like.
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