U.S. patent application number 11/507833 was filed with the patent office on 2008-12-25 for supercritical refrigeration cycle system.
This patent application is currently assigned to DENSO Corporation. Invention is credited to Yoshinori Murase, Hiromi Ohta.
Application Number | 20080314071 11/507833 |
Document ID | / |
Family ID | 37459435 |
Filed Date | 2008-12-25 |
United States Patent
Application |
20080314071 |
Kind Code |
A1 |
Ohta; Hiromi ; et
al. |
December 25, 2008 |
SUPERCRITICAL REFRIGERATION CYCLE SYSTEM
Abstract
A supercritical refrigeration cycle system (10) having a
simplified flow path configuration comprises a compressor (1) for
sucking in and compressing a refrigerant, a radiator (2) for
radiating the heat of the high-pressure refrigerant discharged from
the compressor (1), a high-pressure control valve (5) and a
superheat control valve (12) into which the high-pressure
refrigerant flowing out of the radiator (2) flows after being
distributed, a first evaporator (6) for evaporating the influent
refrigerant decompressed by the high-pressure control valve (5),
and a second evaporator (9) for evaporating the influent
refrigerant decompressed by the superheat control valve (12). The
outlet of the second evaporator (9) and the inlet of the first
evaporator (6) are connected to each other by the refrigerant path
(13) in such a manner that the refrigerant flowing out of the
second evaporator (9) flows into the first evaporator (6). An
increase in the blowout air temperature can be reduced by
controlling the refrigerant flowing in each of the plurality of the
evaporators.
Inventors: |
Ohta; Hiromi; (Okazaki-city,
JP) ; Murase; Yoshinori; (Nagoya-city, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO Corporation
Kariya-city
JP
|
Family ID: |
37459435 |
Appl. No.: |
11/507833 |
Filed: |
August 22, 2006 |
Current U.S.
Class: |
62/498 |
Current CPC
Class: |
F25B 40/00 20130101;
F25B 9/008 20130101; F25B 2700/21175 20130101; F25B 5/04 20130101;
F25B 2700/21174 20130101; F25B 2700/2117 20130101; F25B 41/39
20210101; F25B 2309/061 20130101; F25B 2341/063 20130101; F25B
2600/2501 20130101; F25B 5/02 20130101 |
Class at
Publication: |
62/498 |
International
Class: |
F25B 6/02 20060101
F25B006/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 23, 2005 |
JP |
2005-241654 |
Claims
1. A supercritical refrigeration cycle system of vapor compression
type with pressure in the refrigeration cycle reaching and
exceeding a critical pressure of a refrigerant, the supercritical
refrigeration cycle system comprising: a compressor for sucking in
and compressing the refrigerant; a radiator for radiating heat of
the refrigerant discharged from the compressor; a plurality of
decompressors into which the refrigerant discharged from the
radiator flows; a first evaporator for evaporating refrigerant
decompressed by the first decompressor; and a second evaporator for
evaporating refrigerant decompressed by the second decompressor;
wherein the refrigerant flowing out of one of the first evaporator
and the second evaporator flows into the other of the first
evaporator and the second evaporator.
2. A supercritical refrigeration cycle system according to claim 1,
wherein one of the plurality of the decompressors comprises a
high-pressure control valve for maintaining a high pressure to
maximize a coefficient of performance of the refrigeration
cycle.
3. A supercritical refrigeration cycle system according to claim 1,
wherein the refrigerant flowing out of the second evaporator flows
into the first evaporator, and the second decompressor comprises a
mechanical superheat control valve for controlling a superheat
amount of the refrigerant at an outlet of the second
evaporator.
4. A supercritical refrigeration cycle system according to claim 1,
wherein the refrigerant flowing out of the second evaporator flows
into the first evaporator, and the second decompressor comprises
one of a fixed diaphragm unit and a differential pressure valve
with an opening area thereof changeable by pressure before and
after a diaphragm mechanism.
5. A supercritical refrigeration cycle system according to claim 1,
wherein the refrigerant flowing out of the second evaporator flows
into the first evaporator and the second decompressor comprises an
electrical expansion valve.
6. A supercritical refrigeration cycle system according to claim 5,
wherein an opening degree of the electrical expansion valve is
controlled based on temperature information of the refrigerant
before and after the second evaporator.
7. A supercritical refrigeration cycle system of vapor compression
type with pressure in the refrigeration cycle reaching and
exceeding a critical pressure of a refrigerant, the supercritical
refrigeration cycle system comprising: a compressor for sucking in
and compressing the refrigerant; a radiator for radiating heat of
the refrigerant discharged from the compressor; a plurality of
refrigerant paths for distributing refrigerant flowing out of the
radiator; a first evaporator and a second evaporator for
evaporating the refrigerant distributed from the plurality of
refrigerant paths; and an accumulator for separating inflowing
refrigerant into a gas-phase refrigerant and a liquid-phase
refrigerant and supplying the gas-phase refrigerant to come
compressor, wherein the plurality of the refrigerant paths include
a bypass allowing decompressed refrigerant to flow into the
accumulator and a first distribution path and a second distribution
path for distributing the refrigerant to the first evaporator and
the second evaporator, respectively, the system further comprising
a superheat control valve for controlling a superheat amount of at
least one of the refrigerant at an outlet of the first evaporator
and the refrigerant at an outlet of the second evaporator.
8. A supercritical refrigeration cycle system according to claim 7,
wherein the bypass includes a high-pressure control valve for
maintaining a high pressure to maximize a coefficient of
performance of the refrigeration cycle.
9. A supercritical refrigeration cycle system according to claim 7,
wherein the bypass includes one of a fixed diaphragm unit and a
differential pressure valve having an opening area variable by a
pressure before and after a fixed diaphragm mechanism.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a supercritical refrigeration
cycle system of a vapor-compression-type comprising a plurality of
evaporators in which the refrigeration pressure on high pressure
side increases to at least the critical pressure.
[0003] 2. Description of the Related Art
[0004] A conventional refrigeration cycle system of this type is
known to include a compressor for compressing a refrigerant, a
radiator for cooling the refrigerant discharged from the
compressor, a first decompressor and a second decompressor for
reducing the pressure of the refrigerant flowing out of the
radiator, a first evaporator for evaporating the refrigerant
flowing out of the first decompressor, a second evaporator for
evaporating the refrigerant flowing out of the second decompressor,
and a solenoid valve for controlling the refrigerant flow from the
radiator into the second decompressor, wherein the air blown into
the front part of the compartment is cooled by the first evaporator
and the air blown into the rear part of the compartments is cooled
by the second evaporator (Japanese Unexamined Patent Publication
No. 2000-35250 (Patent Document 1)).
[0005] As a measure for suppressing the production cost, on the
other hand, a system in which the number of expansion valves for
decompressing the refrigerant is reduced and the decompressed
refrigerant is distributed to each evaporator has been proposed
(Japanese Unexamined Patent Publication No. 2005-106318 (Patent
Document 2)).
[0006] In the refrigeration cycle system described in Patent
Document 1, however, if the low pressure of the refrigerant is
reduced during the transient period of starting or increasing the
rotational speed of the compressor, and because a temperature-type
expansion valve is used as a second decompressor, the drop in the
low pressure immediately acts to open the second decompressor as
shown in the example of the behavior of starting the system using a
mechanical expansion valve (see FIGS. 11A, 11B). Further, the
temperature drop at the evaporator outlet is accompanied by the
delay due to heat transmission and, therefore, the valve opening
degree of the second decompressor is excessively increased
temporarily, with the result that the refrigerant flow rate is not
properly distributed to each evaporator, thereby posing the problem
that the blowout air temperature, of the evaporator short in the
refrigerant flow rate, increases.
[0007] In the case where an electrical expansion valve is used as a
second decompressor, on the other hand, the low pressure has no
effect. Even in the case where the low pressure drops during the
transient period, therefore, the valve opening degree is not
excessively increased. Although the detection of a superheat amount
requires the detection of the refrigerant temperature at the outlet
of the evaporator, an excessively fast response destabilizes the
operation of the electrical expansion valve and leads to the
problem of hunting, etc. To secure stability, the response to
temperature detection is required to be somewhat slow. In the case
where the thermal load or the rotational speed of the compressor
undergo an abrupt change, therefore, the refrigerant flows
excessively, temporarily, and the resultant increased superheat
amount of the first evaporator may increase the blowout air
temperature.
[0008] In the refrigeration cycle system described in Patent
Document 2, on the other hand, the high-pressure refrigerant, after
being decompressed in the expansion valve, is required to be sent
to each evaporator by piping. In the automotive air conditioning
system, for example, the refrigerant is sent to the front
evaporator in the dashboard for the front seats on the one hand and
must send the low-pressure low-temperature refrigerant to the rear
evaporator for the rear seats through a long pipe. To suppress the
heat loss in the long pipe and the frosting of the pipe, the pipe
is required to be covered by a heat insulating material.
SUMMARY OF THE INVENTION
[0009] This invention has been developed to solve the problems
described above and the object thereof is to provide a
supercritical refrigeration cycle system having a simple flow path
structure in which the refrigerants flowing in a plurality of
evaporators are appropriately controlled to suppress the increase
in the blowout air temperature.
[0010] In order to achieve the object described above, this
invention employs the technical means described below.
Specifically, the supercritical refrigeration cycle system of vapor
compression type according to the invention, in which the high
pressure in the refrigeration cycle reaches a value not lower than
the critical pressure of the refrigerant, comprises a compressor
(1) for sucking in and compressing the refrigerant, a radiator (2)
for radiating the heat of the high-pressure refrigerant discharged
from the compressor (1), a plurality of decompressors (5, 12) into
which the high-pressure refrigerant flowing out from the radiator
(2) is distribute and flows, a first evaporator (6) for evaporating
the refrigerant decompressed by the first decompressor (5), and a
second evaporator (9) for evaporating the refrigerant decompressed
by the second decompressor (12), wherein the refrigerant flowing
out of one of the first evaporator (6) and the second evaporator
(9) flows into the other evaporator.
[0011] According to a first aspect of the invention, there is
provided a supercritical refrigeration cycle system, wherein the
high-pressure refrigerant is distributed and then decompressed, and
the refrigerant flowing out of one of the first evaporator (6) and
the second evaporator (9) is rendered to flow into the other
evaporator, so that the refrigerant flowing through each evaporator
can be properly controlled with a simple refrigerant path
configuration. Especially, a stable air-conditioning air can be
supplied by reducing the difference of the blowout air temperatures
between the evaporators.
[0012] According to a second aspect of the invention, there is
provided a supercritical refrigeration cycle system, wherein one of
the plurality of the decompressors constitutes a high-pressure
control valve (5) for maintaining a high pressure maximizing the
coefficient of performance of the refrigeration cycle.
[0013] In the second aspect of the invention, one of the plurality
of the decompressors constitutes the high-pressure control valve
(5) and the operation efficiency of the refrigeration cycle is
improved.
[0014] According to a third aspect of the invention, there is
provided a supercritical refrigeration cycle system, wherein the
refrigerant flowing out of the second evaporator (9) flows into the
first evaporator (6), and the second decompressor constitutes a
mechanical superheat control valve (12) for controlling the
superheat amount of the refrigerant at the outlet of the second
evaporator (9).
[0015] In the third aspect of the invention, the control circuit
for controlling the superheat amount is eliminated and the cycle
configuration is simplified.
[0016] According to a fourth aspect of the invention, there is
provided a supercritical refrigeration cycle system, wherein the
refrigerant flowing out of the second evaporator (9) flows into the
first evaporator (6), and the second decompressor constitutes a
fixed diaphragm unit (14) or a differential pressure valve with the
opening area thereof variable by the pressure before and after the
diaphragm mechanism.
[0017] In the fourth aspect of the invention, the trouble of
hunting is not caused in the high pressure control which otherwise
might be caused by the superheat control of the refrigerant at the
outlet of the evaporator, thereby improving the operation
efficiency of the refrigeration cycle.
[0018] According to a fifth aspect of the invention, there is
provided a supercritical refrigeration cycle system, wherein the
refrigerant flowing out of the second evaporator (9) flows into the
first evaporator (6) and the second decompressor makes up an
electrical expansion valve (19).
[0019] In the fifth aspect of the invention, the fact that the
second decompressor constitutes the electrical expansion valve (19)
makes it possible to switch on/off the refrigerant flowing into the
second evaporator (9) with the electrical expansion valve alone
without using any on/off solenoid valve.
[0020] According to a sixth aspect of the invention, there is
provided a supercritical refrigeration cycle system, wherein the
opening degree of the electrical expansion valve (19) is controlled
based on the temperature information of the refrigerant before and
after the second evaporator (9).
[0021] In the sixth aspect of the invention, the refrigerant flow
can be controlled with a fast response.
[0022] According to a seventh aspect of the invention, there is
provided a supercritical refrigeration cycle system of vapor
compression type wherein the high pressure in the refrigeration
cycle reaches a level not lower than the critical pressure of the
refrigerant, comprising a compressor (1) for sucking in and
compressing a refrigerant, a radiator (2) for radiating the heat of
the high-pressure refrigerant discharged from the compressor (1), a
plurality of refrigerant paths for distributing the high-pressure
refrigerant flowing out of the radiator (2), a first evaporator (6)
and a second evaporator (9) for evaporating the distributed
high-pressure refrigerants, respectively, and an accumulator (34)
for separating the inflowing refrigerant into a gas-phase
refrigerant and a liquid-phase refrigerant and supplying the
gas-phase refrigerant to the compressor (1), wherein the plurality
of the refrigerant paths include at least a bypass (28) through
which the distributed high-pressure refrigerant is decompressed and
flows into the accumulator (34), a first distribution path (29) and
a second distribution path (31) for distributing the high-pressure
refrigerant to the first evaporator (6) and the second evaporator
(9), respectively, the system further comprising a superheat
control valve (25, 27) for controlling the superheat amount of at
least one of the refrigerant at the outlet of the first evaporator
(6) and the refrigerant at the outlet of the second evaporator
(9).
[0023] In the seventh aspect of the invention, the system comprises
the bypass (28) for decompressing the high-pressure refrigerant in
addition to the first distribution path (29) and the second
distribution path (31) for distributing the high-pressure
refrigerant into the first evaporator (6) and the second evaporator
(9), and, therefore, the refrigerant flowing in each evaporator can
be appropriately controlled and an increase in the blowout air
temperature can be suppressed with a simple configuration of the
refrigerant paths.
[0024] According to an eighth aspect of the invention, there is
provided a supercritical refrigeration cycle system, wherein the
bypass (28) includes a high-pressure control valve (23, 33) for
maintaining a high pressure maximizing the coefficient of
performance of the refrigeration cycle.
[0025] In the eighth aspect of the invention, the operation
efficiency of the refrigeration cycle can be improved.
[0026] According to a ninth aspect of the invention, there is
provided a supercritical refrigeration cycle system, wherein the
bypass (28) includes a fixed diaphragm mechanism (32) or a
differential pressure valve having an opening area changeable by
the pressure before and after the diaphragm mechanism.
[0027] In the ninth aspect of the invention, the trouble of hunting
is not caused in the high-pressure control which otherwise might be
caused by the superheat control of the refrigerant at the outlet of
the evaporator thereby improving the operation efficiency of the
refrigeration cycle.
[0028] The reference numerals in the parentheses attached to the
respective means indicate the correspondence with the specific
means of the embodiments described later.
[0029] The present invention may be more fully understood from the
description of preferred embodiments of the invention, as set forth
below, together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a schematic diagram showing a configuration of a
refrigeration cycle system according to a first embodiment of the
invention.
[0031] FIG. 2 is a schematic diagram showing a configuration of a
refrigeration cycle system according to a second embodiment of the
invention.
[0032] FIG. 3 is a schematic diagram showing a configuration of a
refrigeration cycle system according to a third embodiment of the
invention.
[0033] FIG. 4 is a block diagram showing the relation between the
component parts and the control means of the refrigeration cycle
system according to the first, second, third, fourth, fifth, sixth
and seventh embodiments.
[0034] FIG. 5 is a flowchart showing the operation of the
refrigeration cycle according to the third embodiment to make the
determination using the difference in refrigerant temperature
between the first evaporator and the second evaporator.
[0035] FIG. 6 is a flowchart showing the operation of the
refrigeration cycle system according to the third embodiment to
make the determination using the difference between the
temperatures of the blowout air passing through the first
evaporator and the second evaporator.
[0036] FIG. 7 is a schematic diagram showing a configuration of a
refrigeration cycle system according to a fourth embodiment of the
invention.
[0037] FIG. 8 is a schematic diagram showing a configuration of a
refrigeration cycle system according to a fifth embodiment of the
invention.
[0038] FIG. 9 is a schematic diagram showing a configuration of a
refrigeration cycle system according to a sixth embodiment of the
invention.
[0039] FIG. 10 is a schematic diagram showing a configuration of a
refrigeration cycle system according to a seventh embodiment of the
invention.
[0040] FIG. 11A is a graph showing the temperature behavior at the
time of starting the system with the superheat control valve set to
SH of 5.degree. C. in the conventional refrigeration cycle
system.
[0041] FIG. 11B is a graph showing the pressure behavior at the
time of starting the system in the conventional refrigeration cycle
system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0042] A first embodiment of the invention is explained below with
reference to FIG. 1. The supercritical refrigeration cycle system
according to this embodiment is of vapor compression type and
includes a plurality of evaporators. A dual-type air conditioning
system used for automobiles or the like is described as an example.
Also, carbon dioxide is used as a refrigerant for the supercritical
refrigeration cycle system.
[0043] A refrigeration cycle system 10 according to this embodiment
includes a compressor 1 for sucking in and supplying a refrigerant
under pressure, a radiator 2 corresponding to a high-pressure heat
exchanger for radiating the heat of the high-pressure refrigerant
discharged from the compressor 1, a first decompressor and a second
decompressor into which the high-pressure refrigerant flowing out
of the radiator 2 is distributed and flows, a first evaporator 6
for evaporating the influent refrigerant decompressed by a
high-pressure control valve 5 corresponding to the first
decompressor, and a second evaporator 9 for evaporating the
inflowing refrigerant decompressed by a mechanical superheat
control valve 12 corresponding to the second decompressor. The
refrigeration cycle system 10 further comprises an internal heat
exchanger 4 for exchanging heat between a high-pressure refrigerant
and a low-pressure refrigerant and a solenoid valve 8 connected in
series to the superheat control valve 12 upstream of the second
evaporator 9 for controlling the refrigerant flowing into the
second evaporator 9.
[0044] The outlet of the second evaporator 9 and the inlet of the
first evaporator 6 are connected to each other by a refrigerant
path 13 arranged so that the refrigerant flowing out of the second
evaporator 9 flows into the first evaporator 6. The refrigerant
flowing out of the first evaporator 6 is separated into a
liquid-phase refrigerant and a gas-phase refrigerant by an
accumulator 34 for storing the extraneous refrigerant in the
refrigeration cycle. The gas-phase refrigerant constituting a
low-pressure refrigerant exchanges heat with the high-pressure
refrigerant in the internal heat exchanger 4 and flows to the inlet
of the compressor 1.
[0045] The compressor 1 is a variable replacement refrigerant
compressor so configured that the discharge capacity thereof is
electrically controlled by an ECU 80 to control the cooling
capacity. The information on the rotational speed of the compressor
1 is sent to the ECU 80. The compressor 1 may alternatively be
configured of a clutch controlled by a clutch control output signal
from the ECU 80.
[0046] In the radiator 2, heat is exchanged between the
high-pressure, high-temperature refrigerant discharged from the
compressor 1 and the air blown by a fan or the air flow generated
by the running vehicle, so that the refrigerant pressure in the
radiator 2 exceeds the critical pressure. The radiator 2 is cooled
by an electrically-operated cooling fan 3. The cooling fan 3 may be
directly connected to an engine as a coupling fan or driven by a
hydraulic motor. Also, the cooling fan 3 may double as a radiator
cooling fan or may be used only for the radiator 2. Further, the
cooling fan 3 may be mounted integrally with the radiator 2 or
fixed on a vehicle parts.
[0047] The first evaporator 6 is a heat exchanger for absorbing
heat from the atmospheric air and evaporating the liquid
refrigerant reduced in pressure by the high-pressure control valve
5. The air passed through the heat transmission of the first
evaporator 6 by the air blown from the blower 7 controlled by the
ECU 80 shown in FIG. 4 is deprived of heat, and after being cooled
while at the same time being dehumidified, sent from the front of
the compartments toward the occupants in the front seats as a cool
air.
[0048] The temperature sensing cylinder portion of the
high-pressure control valve 5 detects the temperature of the
refrigerant at the outlet of the radiator 2, and maintains a high
pressure maximizing the COP (coefficient of performance) of the
refrigeration cycle. Also, the high-pressure control valve 5 may be
an electrical expansion valve electrically controlled by the ECU 80
instead of the mechanical one described above.
[0049] The superheat control valve 12 is an expansion valve for
detecting the refrigerant temperature at the outlet of the second
evaporator 9 and the refrigerant pressure in the second evaporator
9 to thereby control the superheat amount at the outlet of the
second evaporator 9. The superheat control valve 12 is arranged in
parallel to the high-pressure control valve 5 in the refrigeration
cycle, and is located at a position exposed to the air blown by the
blower 1 upstream of the second evaporator 9 in the air flow. This
arrangement makes it possible to detect the temperature of the
temperature detecting tube, which detects superheat at an outlet of
evaporator and to be responsive accurately, since the decompressed
low-temperature refrigerant is less influential in changing
pressure of the gas sealed in the diaphragm. The superheat control
valve 12 may be of either a built-in type for sensing the
temperature through a built-in working rod or a temperature sensing
cylinder type in which the temperature is sensed through a
temperature sensing cylinder by capillary communication of the
refrigerant sealed on the diaphragm.
[0050] The second evaporator 9 is a heat exchanger for absorbing
heat from the atmospheric air and evaporating the liquid
refrigerant reduced in pressure by the superheat control valve 12.
The air passed through the heat transmission of the second
evaporator 9 by the air blown from the blower 11 under the control
of the ECU 80 shown in FIG. 4, after being deprived of heat cooled
while at the same time being dehumidified, is sent from the rear
part of the compartments toward the occupants in the rear seats as
cool air.
[0051] The solenoid valve 8, under the control of the ECU 80, can
be switched either to stop the inflow of the refrigerant from the
radiator 2 into the second evaporator 9 or to allow the refrigerant
to flow into the second evaporator 9. The solenoid valve 8 has the
function of switching on/off a cooling operation of the second
evaporator 9 such as the operation of cooling the rear part of the
compartments. By the switching operation of the air-conditioning
operation unit 21 by the user, the solenoid valve 8 opens and the
refrigerant flows into the second evaporator 9 when the rear
air-conditioning mode is on, while the solenoid valve 8 is closed
and the refrigerant flow to the second evaporator 9 is blocked when
the rear air-conditioning mode is off.
[0052] Instead of the two evaporators employed in this embodiment,
the refrigeration cycle system 10 according to the invention may
employ three or more evaporators. The system having three
evaporators, for example, may be configured of a high-pressure
control valve for controlling the flow rate of the refrigerant
flowing in one of the evaporators and a superheat control valve for
controlling the flow rate of the refrigerant flowing in the
remaining two evaporators.
[0053] Next, the refrigerant state in the refrigeration cycle due
to the operation of the refrigeration cycle system 10 is explained.
First, in steady system operation, the proportion of flow rate of
the refrigerant in the first evaporator 6 and the second evaporator
9 is adjusted in the manner described below. The superheat control
valve 12 controls the flow rate of the refrigerant in the second
evaporator 9 in such a manner that the superheat amount at the
outlet of the second evaporator 9 assumes a set value, and the
refrigerant with the superheat amount thus controlled is mixed with
the liquid refrigerant reduced in pressure by the high-pressure
control valve 5 and flows into the first evaporator 6 through the
refrigerant path 13. The saturated gas refrigerant produced by
evaporation of the liquid refrigerant by heat exchange with the air
blown into the compartments and the saturated gas refrigerant
produced by mixing and heat exchange between the superheat gas
refrigerant flowing in from the second evaporator 9 and the liquid
refrigerant are sent to the accumulator 34 from the first
evaporator 9. In the accumulator 34, only the saturated gas is
sucked into the compressor 1 through the internal heat exchanger 4
from the accumulator 34. As a result, the enthalpy of evaporation
of the influent liquid refrigerant is balanced to an amount equal
to the sum of the enthalpy for cooling the superheat gas from the
second evaporator 9 by the saturated gas and the enthalpy of the
heat exchanged by the first evaporator with the air blown into the
compartments. Thus, a predetermined low-pressure state is
maintained.
[0054] In the refrigeration cycle system 10, the refrigerant
flowing out of the second evaporator 9 flows into the first
evaporator 6 again. Even in the case where the provisional drop in
pressure excessively increases the opening degree of the superheat
control valve 12 and the refrigerant flowing in the second
evaporator 9 becomes excessive in amount at the time of starting or
accelerating the vehicle, therefore, the refrigerant flow rate in
the first evaporator 6 does not run short, so that the temperature
of the blown air passing through the evaporator is not
inconveniently increased.
[0055] Also, the superheat control valve 12 functions as an
expansion valve for decompressing the high-pressure refrigerant. By
arranging the superheat control valve 12 in the vicinity of the
second evaporator 9, therefore, the low-pressure pipe upstream of
the second evaporator 9 can be shortened, thereby making it
possible to reduce the heat loss midway through the pipe. At the
same time, the long high-pressure pipe and the short
low-temperature low-pressure pipe of the refrigeration cycle can
reduce the heat loss and the consumption of the heat insulating
material for preventing the frosting of the pipes. In the case
where the evaporator is arranged in the rear seat of the vehicle,
for example, the heat insulating material or the like would be
required to be attached on the long pipe leading to the evaporator.
Such a heat insulating material is eliminated in the refrigeration
cycle system 10 according to this embodiment.
[0056] The high-pressure pipe is also arranged on the upstream side
of the solenoid valve 8, and therefore the high-pressure
refrigerant exists in the pipe also in the off state of the second
evaporator 9. Thus, the variation of the refrigerant amount caused
by the on/off operation of the second evaporator 9 is also reduced.
In the configuration of the conventional refrigeration cycle system
described in Patent Document 2, no liquid refrigerant exists in the
pipe leading to the second evaporator as long as the refrigerant to
the second evaporator 9 is cut off by a solenoid valve or the like.
As long as the solenoid valve is open, on the other hand, both the
gas-phase refrigerant and the liquid-phase refrigerant flow in the
pipe. Thus, a great difference in the flow rate in the pipe
develops according to whether the solenoid valve is open or closed,
resulting in a need for a bulky accumulator for storing the
extraneous refrigerant while the valve is closed. In the
refrigeration cycle system 10 according to this embodiment,
however, such a large accumulator is not required.
[0057] Also, both the first evaporator 6 and the second evaporator
9 are connected to an expansion valve for decompressing the
high-pressure refrigerant. In spite of the pressure-loss of one of
the paths, therefore, the refrigerant can be supplied at an
arbitrary proportion of flow rate by adjusting the opening degree
of the expansion valve, and the pressure loss of the first
evaporator 6 and the second evaporator 9 can be adjusted. Thus, the
addition of extraneous parts or a complicated valve for adjusting
the flow rate distribution is not required.
[0058] In a configuration of refrigeration cycle with the first and
second evaporators connected in series to each other and the
refrigerant distributed to each evaporator after decompression, the
opening area of the path leading to each evaporator is required to
be adjusted. Thus, a switching valve complicated in structure is
required or in order to supply any of the evaporators at a greater
flow rate, a flow resistance must be added. In the refrigeration
cycle system 10 according to this embodiment, however, the flow
rate of the refrigerant can be controlled appropriately without
such a complicated configuration.
[0059] As described above, the refrigeration cycle system according
to this embodiment includes a compressor 1, a radiator 2 for
radiating the heat of a high-pressure refrigerant discharged from
the compressor 1, a plurality of decompressors into which the
high-pressure refrigerant flows from the radiator 2 after
distribution, a first evaporator 6 for evaporating the refrigerant
decompressed by one of the decompressors constituting the
high-pressure control valve 5 and a second evaporator 9 for
evaporating the refrigerant decompressed by the superheat control
valve 12, wherein the refrigerant flowing out of the second
evaporator 9 flows into the first evaporator 6. This configuration
makes it possible to control appropriately the refrigerant flowing
in each evaporator with a simple refrigerant path configuration.
Especially, a refrigeration cycle system is obtained in which the
difference in blowout air temperature between the evaporators is
reduced and a stable air-conditioning air can be supplied. Also,
the use of one of the plurality of the decompressors as the
high-pressure control valve 5 can improve the operation efficiency
of the refrigeration cycle.
[0060] Also, the refrigerant flowing out of the second evaporator 9
flows into the first evaporator 6, and the superheat amount of the
refrigerant at the outlet of the second evaporator 9 is controlled
by a mechanical superheat control valve 12. By employing this
configuration, the control circuit for controlling the superheat
amount is eliminated and the cycle configuration simplified.
Second Embodiment
[0061] A second embodiment of the invention is explained with
reference to FIG. 2. A refrigeration cycle system 20 according to
this embodiment is different from the refrigeration cycle system 10
according to the first embodiment in that the second embodiment
employs a fixed diaphragm unit 14, such as an orifice, as a second
decompressor constituting a diaphragm means. The diaphragm means
may be configured of a differential pressure valve with the opening
area thereof variable by the pressure before and after the
diaphragm mechanism.
[0062] In the case where the adjustment range of the refrigerant
flow rate is narrow for the superheat control valve according to
the first embodiment and the second evaporator 9 is smaller in size
than the first evaporator 6, the second evaporator 9 requires a
lower refrigerant flow rate, and therefore, a less expensive
diaphragm means can be used. Especially, in the case where a
solenoid valve is used for on/off operation of the second
evaporator 9, the diaphragm means can be integrated with the
solenoid valve and therefore the number of joins can also be
reduced.
[0063] Even in the case where the thermal load of the second
evaporator 9 is so small that the liquid refrigerant flows out of
the outlet thereof, the evaporation of the liquid refrigerant
through the first evaporator 6 prevents the blowout air temperature
of the first evaporator 6 from being inconveniently increased.
[0064] In the configuration and the refrigerant flow shown in FIG.
2, the component elements identical or similar to those in FIG. 1
are designated by the same reference numerals, respectively, as
those in FIG. 1 and will not be explained.
[0065] As described above, with the refrigeration cycle system
according to this embodiment, the refrigerant flowing out of the
second evaporator 9 flows into the first evaporator 6, and the
second decompressor is configured as a a fixed diaphragm unit 14 or
a differential pressure valve with the opening area thereof
variable under the pressure before and after the diaphragm
mechanism. With this configuration, such a trouble as hunting in
the high-pressure control operation with the superheat control
operation of the refrigerant at the outlet of the evaporator is
prevented, thereby improving the operation efficiency of the
refrigeration cycle.
Third Embodiment
[0066] A third embodiment is explained with reference to FIGS. 3
and 4. A refrigeration cycle system 30 according to this embodiment
is different from the refrigeration cycle system 10 according to
the first embodiment in that an electrical expansion valve 19 is
employed as a second decompressor. The refrigeration cycle system
30 includes a refrigerant temperature sensor 17 for detecting the
temperature of the refrigerant upstream of the inlet of the second
evaporator 9, a refrigerant temperature sensor 18 for detecting the
refrigerant temperature downstream of the outlet of the second
evaporator 9, and blowout air temperature sensors 15, 16 for
detecting the temperature of the blowout air passed through the
first evaporator 6 and the second evaporator 9, respectively. The
blowout air temperature sensors 15, 16 are arranged in an
air-conditioning unit case (not shown) nearer to the compartments
than the evaporator to detect the temperature of the
air-conditioning air cooled by the first evaporator 6 and the
second evaporator 9 and flowing into the compartments. The
resultant detection information, together with the detection
information from the refrigerant temperature sensors 17, 18, is
sent to the ECU 80 constituting a control means.
[0067] The opening degree of the electrical expansion valve 19 can
be controlled to an arbitrary value including the closed-up state
based on the information detected by the refrigerant temperature
sensors 17, 18 and the blowout air temperature sensors 15, 16.
Therefore, the refrigerant flow rate can be controlled over a wide
range and the flow path can be closed. Also, the provision of the
electrical expansion valve 19 can eliminate the need of the
solenoid valve 12 of the first embodiment.
[0068] In the configuration of FIG. 3, the same reference numerals
as those in FIG. 1 designate the same component elements,
respectively, as in the first embodiment and will not be
explained.
[0069] Next, the control operation of the electrical expansion
valve 19 of the refrigeration cycle system 30 according to this
embodiment is explained with reference to FIGS. 5, 6. The control
methods shown in FIGS. 5, 6 are implemented by the ECU 80
constituting a control means.
[0070] The flowchart of FIG. 5 shows the process including the
steps of detecting the refrigerant temperature before and after the
second evaporator 9, controlling the opening degree including the
closed-up state of the electrical expansion valve 19 based on the
detection information on the refrigerant temperature and
controlling the superheat amount at the outlet of the second
evaporator 9.
[0071] First, this control method starts with the on state of the
air-conditioning switch. Next, the state of the operating switch of
the second evaporator 9, i.e. the state of the operating switch of
the rear air-conditioner is detected (step S100). Upon this
detection, the state of the operating switch of the second
evaporator 9 (rear air-conditioner) is determined (step S110). In
the case where the state of this operating switch is on, the
refrigerant temperature T17 upstream of the second evaporator 9 and
the refrigerant temperature T18 downstream of the second evaporator
9 are detected by the refrigerant temperature sensors 17 and 18,
respectively (step S120). In the case where the operating switch of
the rear air-conditioner is off, on the other hand, the process
jumps to step S160 and the electrical expansion valve 19 is closed.
This process is repeated until the operating switch of the rear
air-conditioner turns on.
[0072] The difference (T18-T17)-T0 between the temperatures T17 and
T18 detected in step S120 is calculated using a predetermined value
T0 (step S130). The difference value this calculated is compared
with a table, prepared in advance, and, in accordance with the
comparison result, the target opening degree of the electrical
expansion valve 19 is calculated (step S140). The opening degree of
the electrical expansion valve 19 is controlled to achieve the
calculated target opening degree (step S150) thereby to control the
amount of the refrigerant flowing into the second evaporator 9. The
process is then returned again to step S100, and the flow rate of
the refrigerant flowing in the second evaporator 9 continues to be
controlled.
[0073] The flowchart of FIG. 6 described below shows the process
including the steps of detecting the temperature T15 of the blowout
air passing through the first evaporator 6 and the temperature T16
of the blowout air passing through the second evaporator 9 and
controlling the opening degree including the closed-up state of the
electrical expansion valve 19 based on the temperature detection
information.
[0074] This control method also starts with the on state of the
air-conditioning switch. Then, the state of the operating switch of
the second evaporator 9, i.e. the state of the operating switch of
the rear air-conditioner is detected (step S200). With this
detection, the state of the operating switch of the second
evaporator 9 (rear air-conditioner) is determined (step S210), and
in the case where the state of the particular switch is on, the
temperature T15 of the blowout air passing through the first
evaporator 6 and the temperature T16 of the blowout air passing
through the second evaporator 9 are detected by the blowout air
temperature sensors 15, 16, respectively (step S220). In the case
where the state of the operating switch of the rear air-conditioner
is off, on the other hand, the process jumps to step S260, in which
the electrical expansion valve 19 is closed and the process is
repeated until the operating switch of the rear air-conditioner
turns on.
[0075] The difference (T16-T15)-TA between the temperatures T15 and
T16 detected in step S220 is calculated using a predetermined value
TA (step S230).
[0076] The difference value thus calculated is compared with a
table prepared in advance, and in accordance with the comparison
result, the target opening degree of the electrical expansion valve
19 is calculated (step S240). The opening degree of the electrical
expansion valve 19 is controlled to achieve the calculated target
opening degree (step S250) thereby to control the amount of the
refrigerant flowing into the second evaporator 9. The process is
then returned again to step S200, and the flow rate of the
refrigerant flowing to the second evaporator 9 continues to be
controlled.
[0077] The control methods shown in FIGS. 5, 6 can be implemented
also in the refrigeration cycle systems 10, according to the first
and second embodiments and the refrigeration cycle systems 40, 50,
60, 70 according to the fourth to seventh embodiments described
later by the provision of the refrigerant temperature sensors 17,
18 or the blowout air temperature sensors 15, 16.
[0078] As described above, the refrigeration cycle system according
to this embodiment is so configured that the refrigerant flowing
out of the second evaporator 9 flows into the first evaporator 6
and the electrical expansion valve 19 is employed as a second
decompressor. This configuration makes it possible to turn on/off
the refrigerant flowing into the second evaporator 9 using the
electrical expansion valve alone without any on/off solenoid valve,
while at the same time making it possible to control the
refrigerant flow rate over a wide range.
[0079] The opening degree of the electrical expansion valve 19 is
controlled based on the information on the refrigerant temperature
before and after the second evaporator 9. The use of this control
method can control the refrigerant flow rate with a high
response.
Fourth Embodiment
[0080] A fourth embodiment is explained with reference to FIG. 7.
The refrigeration cycle system 40 according to this embodiment
described below is different from the refrigeration cycle system 10
of the first embodiment in that a diaphragm means such as an
orifice or the like fixed diaphragm unit 22 or a differential
pressure valve with the opening area thereof variable under the
pressure before and after the diaphragm mechanism is employed as a
first decompressor. Although the refrigeration cycle system 40
employs the superheat control valve 12 as a second decompressor, a
fixed diaphragm unit or an electrical expansion valve may
alternatively be employed. With regard to the configuration and the
refrigerant flow shown in FIG. 7, the same reference numerals
designate the same component elements, respectively, as those of
the first embodiment and not explained below any further.
[0081] As described above, the refrigeration cycle system 40
according to this embodiment includes, as a first decompressor, a
fixed diaphragm unit 22 constituting a diaphragm means or a
differential pressure valve with the opening area thereof variable
by the pressure before and after the diaphragm mechanism.
Especially in the case where the compressor 1 is an external
variable replacement refrigerant compressor, the high pressure can
be controlled by changing the capacity of the compressor, and
therefore, the system can be configured even with a fixed diaphragm
unit having a narrow flow rate control range, in a more simplified
structure and at a lower cost, than the high-pressure control
valve.
Fifth Embodiment
[0082] A fifth embodiment is explained with reference to FIG. 8. A
refrigeration cycle system 50 according to this embodiment
comprises a compressor 1 for sucking in and compressing the
refrigerant, a radiator 2 for radiating the heat of the
high-pressure refrigerant discharged from the compressor 1, a
plurality of refrigerant paths for distributing the high-pressure
refrigerant flowing out of the radiator 2, a first evaporator 6 and
a second evaporator 9 for evaporating the distributed high-pressure
refrigerants, respectively, and an accumulator 34 for separating
the inflowing refrigerant into a gas-phase refrigerant and a
liquid-phase refrigerant and supplying the gas-phase refrigerant to
the compressor 1. The plurality of the refrigerant paths include at
least a bypass 28 through which the distributed high-pressure
refrigerant is decompressed by the high-pressure control valve 23
and flows into the accumulator 34, a first distribution path 29 and
a second distribution path 31 for distributing the high-pressure
refrigerant into the first evaporator 6 and the second evaporator
9. Further, the system includes superheat control valves 25, 27 for
controlling the superheat amount of at least one of the refrigerant
at the outlet of the first evaporator 6 and the refrigerant at the
outlet of the second evaporator 9. Furthermore, a solenoid valve 24
is arranged upstream of the first evaporator 6 in the first
distribution path 29, and a solenoid valve 26 upstream of the
second evaporator 9 in the second distribution path 31.
[0083] The solenoid valve 24, under the control of the ECU 80, can
be switched between the state in which the refrigerant distributed
to the first distribution path 29 from the radiator 2 is prevented
from flowing into the second evaporator 9 and the state in which it
is allowed to flow into the first evaporator 6. The solenoid valve
24 has the function of turning on/off the operation of the first
evaporator 6 for cooling the rear part of the compartments. By the
switching operation of the air-conditioning operation unit 21 by
the user, the solenoid valve 24 is opened and the refrigerant is
supplied to the first evaporator 6 in the case where the front
air-conditioner is on, while the refrigerant flow to the first
evaporator 6 is blocked by closing the solenoid valve 24 in the
case where the front air-conditioner is off.
[0084] Similarly, the solenoid valve 26, under the control of the
ECU 80, is switched between the state in which the refrigerant
distributed to the first distribution path 31 from the radiator 2
is prevented from flowing into the second evaporator 9 and the
state in which it is allowed to flow into the second evaporator 9.
The solenoid valve 26 has the function of turning on/off the
operation of cooling the rear part of the compartment. By the
switching operation of the air-conditioning operation unit 21 by
the user, the solenoid valve 26 is opened and the refrigerant is
supplied to the second evaporator 9 in the case where the rear
air-conditioner is on, while the refrigerant flow to the second
evaporator 9 is blocked by the solenoid valve 26 closed in the case
where the rear air-conditioner is off.
[0085] The solenoid valves 24, 26 are assumed to behave similarly.
Specifically, the on/off timing of the respective solenoid valves
24, 26, i.e. the presence or absence of the refrigerant flow occur
at the same timing, and can be controlled in such a manner as to
eliminate the refrigerant flow rate difference between the first
evaporator 6 and the second evaporator 9.
[0086] The component elements shown in FIG. 8 are similar to those
of the first embodiment of FIG. 1 are designated by the same
reference numerals, respectively, and will not be described.
[0087] A refrigeration cycle system 50 according to this embodiment
comprises a compressor 1, a radiator 2 for radiating the heat of
the high-pressure refrigerant discharged from the compressor 1, a
plurality of refrigerant paths for distributing the high-pressure
refrigerant flowing out of the radiator 2, a first evaporator 6 and
a second evaporator 9 for evaporating the distributed high-pressure
refrigerants, respectively, and an accumulator 34 for separating
the influent refrigerant into a gas-phase refrigerant and a
liquid-phase refrigerant and supplying the gas-phase refrigerant to
the compressor 1. The plurality of the refrigerant paths include at
least a bypass 28 through which the distributed high-pressure
refrigerant is decompressed and flows into the accumulator 34, a
first distribution path 29 and a second distribution path 31 for
distributing the high-pressure refrigerant into the first
evaporator 6 and the second evaporator 9, respectively. Further,
the system includes superheat control valves 25, 27 for controlling
the superheat amount of at least one of the refrigerant at the
outlet of the first evaporator 6 and the refrigerant at the outlet
of the second evaporator 9. With this configuration, the
configuration of the refrigerant paths is simplified and the
refrigerant flowing in each evaporator can be appropriately
controlled.
[0088] Also, the bypass 28 includes a high-pressure control valve
23 for maintaining a high pressure to maximize the coefficient of
performance of the refrigeration cycle. This configuration can
improve the operation efficiency of the refrigeration cycle.
[0089] Also, the refrigeration cycle system 50 includes the
superheat control valve to control the superheat amount at the
outlet of each evaporator. Even in the case where the opening
degree of the superheat control valve temporarily increases to an
excessive level due to the change in low pressure, therefore, the
refrigerant flow rate increases in all the evaporators similarly,
and therefore the trouble is prevented in which only the blowout
air temperature of the first evaporator 6 increases.
[0090] Also, the distribution of the high-pressure refrigerant
leads to the advantage that, like in the refrigeration cycle
systems 10, 20, 30, 40, the heat loss is small, the pipe requiring
the heat insulation is short and the refrigerant variation by the
on/off operation of the evaporator is small.
[0091] Further, in the refrigeration cycle system 50, the
high-pressure control valve 23 is connected to the bypass 28 and,
therefore, the flow of the refrigeration cycle is never closed. As
a result, the evaporators can be advantageously switched on/off in
an arbitrary combination.
Sixth Embodiment
[0092] A sixth embodiment is explained with reference to FIG. 9.
The refrigeration cycle system 60 according to this embodiment
explained below is different from the refrigeration cycle system 50
according to the fifth embodiment in that a fixed diaphragm unit 32
constituting a diaphragm means such as an orifice or a differential
pressure valve with the opening area thereof variable by the
pressure before and after the diaphragm mechanism is employed as a
high-pressure control valve of the bypass 28. In the configuration
and the refrigerant flow shown in FIG. 9, the same or similar
component elements as or to those in FIG. 1 or 8 are designated by
the same reference numerals, respectively, as in the first
embodiment and will not be described.
[0093] As described above, the refrigeration cycle system 60
according to this embodiment is so configured that the bypass 28
includes a fixed diaphragm unit 32 or a differential pressure valve
with the opening area thereof variable by the pressure before and
after the diaphragm mechanism. This configuration prevents a
trouble such as hunting in the high-pressure control operation
otherwise caused by the superheat control of the refrigerant at the
outlet of the evaporator, thereby improving the operation
efficiency of the refrigeration cycle.
Seventh Embodiment
[0094] A seventh embodiment of the invention is explained with
reference to FIG. 10. The refrigeration cycle system 70 according
to this embodiment is different from the refrigeration cycle system
50 according to the fifth embodiment in that a high-pressure
control valve 33 having a temperature sensor built therein is
arranged in the bypass 28. In the configuration and the refrigerant
flow shown in FIG. 10, the component elements similar or identical
to those in FIG. 1 or 8 are designated by the same reference
numerals, respectively, as in the fifth and first embodiments and
will not be described.
[0095] The temperature sensor of the high-pressure control valve 33
detects the temperature at the outlet of the radiator 2 to perform
the high pressure control operation. In view of some correlation
between the outlet temperature of the radiator 2 and the outlet
temperature of the internal heat exchanger 4, however, the
high-pressure refrigerant can be controlled using the outlet
temperature of the internal heat exchanger 4.
[0096] The refrigerant at the outlet of the internal heat exchanger
4 directly flows into the high-pressure control valve 33. In the
case where the temperature of the refrigerant at the outlet of the
internal heat exchanger is used for the control operation,
therefore, the temperature sensor can be arranged in the
high-pressure control valve 33 and therefore the step of mounting
the temperature sensor can be eliminated.
[0097] As described above, in the refrigeration cycle system 70
according to this embodiment, the bypass 28 includes the
high-pressure control valve 33 having a temperature sensor built
therein which maintains a high pressure to maximize the coefficient
of performance of the refrigeration cycle. This configuration
improves the operation efficiency of the refrigeration cycle.
Other Embodiments
[0098] The embodiments described above refer to a refrigeration
cycle using carbon dioxide as a refrigerant. Nevertheless,
ethylene, ethane, nitrogen oxide or the like refrigerant, usable in
a supercritical area, can be used in place of carbon dioxide.
[0099] Also, the embodiments described above are so configured that
the air blown to the front part of the compartments is cooled by
the first evaporator 6 and the air blown to the rear part of the
compartments by the second evaporator 9. Conversely, however, the
air blown to the front part of the compartments may be cooled by
the second evaporator 9 and the air blown to the rear part of the
compartments by the first evaporator 6.
[0100] Further, the high-pressure control operation of the
high-pressure control valve 33 having the temperature sensor built
therein according to the seventh embodiment may be implemented in
combination with any other embodiments described above.
[0101] While the invention has been described by reference to
specific embodiments chosen for purposes of illustration, it should
be apparent that numerous modifications could be made thereto by
those skilled in the art without departing from the basic concept
and scope of the invention.
* * * * *