U.S. patent application number 12/440051 was filed with the patent office on 2010-01-07 for air conditioning apparatus.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. Invention is credited to Shinichi Kasahara, Masakazu Okamoto.
Application Number | 20100000245 12/440051 |
Document ID | / |
Family ID | 39183623 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100000245 |
Kind Code |
A1 |
Kasahara; Shinichi ; et
al. |
January 7, 2010 |
AIR CONDITIONING APPARATUS
Abstract
An air conditioning apparatus is filled with a supercritical
refrigerant, and includes a compression mechanism, a radiator, an
expansion mechanism, an evaporator, a first temperature detector, a
target refrigerant temperature derivation unit, and a control unit.
The target refrigerant temperature derivation unit uses at least a
set temperature to determine a target refrigerant temperature, the
set temperature being a temperature that is set relative to the air
in the space in which the radiator is disposed, and the target
refrigerant temperature being the target temperature of the
refrigerant flowing between the outlet side of the radiator and the
refrigerant inflow side of the expansion mechanism. The control
unit controls the expansion mechanism so that the temperature
detected by the first temperature detector corresponds to the
target refrigerant temperature.
Inventors: |
Kasahara; Shinichi; (Osaka,
JP) ; Okamoto; Masakazu; (Osaka, JP) |
Correspondence
Address: |
GLOBAL IP COUNSELORS, LLP
1233 20TH STREET, NW, SUITE 700
WASHINGTON
DC
20036-2680
US
|
Assignee: |
DAIKIN INDUSTRIES, LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
39183623 |
Appl. No.: |
12/440051 |
Filed: |
August 28, 2007 |
PCT Filed: |
August 28, 2007 |
PCT NO: |
PCT/JP2007/066618 |
371 Date: |
March 5, 2009 |
Current U.S.
Class: |
62/222 ;
62/498 |
Current CPC
Class: |
F25B 2700/1931 20130101;
F25B 5/02 20130101; F25B 2313/02741 20130101; F25B 2309/061
20130101; F25B 13/00 20130101; F25B 9/008 20130101; F25B 2700/21174
20130101; F25B 2400/16 20130101; F25B 2600/17 20130101; F25B
2700/21172 20130101; F25B 2600/2513 20130101; F25B 41/31
20210101 |
Class at
Publication: |
62/222 ;
62/498 |
International
Class: |
F25B 41/04 20060101
F25B041/04; F25B 1/00 20060101 F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2006 |
JP |
2006-246156 |
Claims
1. An air conditioning apparatus filled with a supercritical
refrigerant, the air conditioning apparatus comprising: a
compression mechanism configured to compress the refrigerant; a
radiator connected to a refrigerant intake side of the compression
mechanism; an expansion mechanism connected to an outlet side of
the radiator; an evaporator connected to refrigerant outflow side
of the expansion mechanism and connected to the refrigerant intake
side of the compression mechanism; a first temperature detector
arranged to detect a refrigerant temperature between the outlet
side of the radiator and a refrigerant inflow side of the expansion
mechanism; a target refrigerant temperature derivation unit
configured to use at least a set temperature to determine a target
refrigerant temperature, the set temperature being a temperature
that is set relative to air temperature in a space in which the
radiator is disposed, and the target refrigerant temperature being
a target temperature of the refrigerant flowing between the outlet
side of the radiator and the refrigerant inflow side of the
expansion mechanism; and a control unit configured to control the
expansion mechanism so that the refrigerant temperature detected by
the first temperature detector corresponds to the target
refrigerant temperature.
2. The air conditioning apparatus according to claim 1, wherein the
radiator includes a plurality of separate radiators with each
having a separate outlet side; the expansion mechanism includes a
plurality of separate expansion mechanisms with each separate
radiator having one of the separate expansion mechanisms connected
to the separate outlet side thereof; and the first temperature
detector includes a plurality of separate temperature detectors
with each of the separate temperature detectors being arranged to
detect a refrigerant temperature between one of the separate
radiators and the separate expansion mechanism connected to the
separate outlet side thereof.
3. The air conditioning apparatus according to claim 1, wherein the
target refrigerant temperature derivation unit is configured to
determine the target refrigerant temperature using at least the set
temperature, which is one of a plurality of parameters including
the set temperature, a refrigerant temperature detected by a second
temperature detector disposed in proximity to an air blower
configured to blow air to the radiator, a pressure of refrigerant
flowing from the refrigerant discharge side of the compression
mechanism to the refrigerant inflow side of the expansion
mechanism, a temperature of refrigerant discharged from the
compression mechanism, a pressure of refrigerant flowing into the
radiator, and a temperature of refrigerant flowing into the
radiator.
4. The air conditioning apparatus according to claim 1, further
comprising: a first gain-varying unit configured to vary gain with
respect to control of the expansion mechanism in accordance with
the refrigerant temperature detected by the first temperature
detector and at least one of a pressure of refrigerant flowing from
the refrigerant discharge side of the compression mechanism to the
refrigerant inflow side of the expansion mechanism, and a
temperature of refrigerant discharged from the compression
mechanism.
5. The air conditioning apparatus according to claim 1, further
comprising: a second gain-varying unit configured to vary gain
pertaining to the determination of the target refrigerant
temperature by the target refrigerant temperature derivation unit
in accordance with the refrigerant temperature detected by the
first temperature detector and at least one of a pressure of
refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, and a temperature of refrigerant discharged
from the compression mechanism.
6. The air conditioning apparatus according to claim 2, wherein the
target refrigerant temperature derivation unit is configured to
determine the target refrigerant temperature by using at least the
set temperature, which is one of a plurality of parameters
including the set temperature, a refrigerant temperature detected
by a second temperature detector disposed in proximity to an air
blower configured to blow air to the radiator, a pressure of
refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, a temperature of refrigerant discharged from
the compression mechanism, a pressure of refrigerant flowing into
the radiator, and a temperature of refrigerant flowing into the
radiator.
7. The air conditioning apparatus according to claim 6, further
comprising: a first gain-varying unit configured to vary gain with
respect to control of the expansion mechanism in accordance with
the refrigerant temperature detected by the first temperature
detector and at least one of a pressure of refrigerant flowing from
the refrigerant discharge side of the compression mechanism to the
refrigerant inflow side of the expansion mechanism, and a
temperature of refrigerant discharged from the compression
mechanism.
8. The air conditioning apparatus according to claim 6, further
comprising: a second gain-varying unit configured to vary gain
pertaining to the determination of the target refrigerant
temperature by the target refrigerant temperature derivation unit
in accordance with the refrigerant temperature detected by the
first temperature detector and at least one of a pressure of
refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, and a temperature of refrigerant discharged
from the compression mechanism.
9. The air conditioning apparatus according to claim 2, further
comprising: a first gain-varying unit configured to vary gain with
respect to control of the expansion mechanism in accordance with
the refrigerant temperature detected by the first temperature
detector and at least one of a pressure of refrigerant flowing from
the refrigerant discharge side of the compression mechanism to the
refrigerant inflow side of the expansion mechanism, and a
temperature of refrigerant discharged from the compression
mechanism.
10. The air conditioning apparatus according to claim 2, further
comprising: a second gain-varying unit configured to vary gain
pertaining to the determination of the target refrigerant
temperature by the target refrigerant temperature derivation unit
in accordance with the refrigerant temperature detected by the
first temperature detector and at least one of a pressure of
refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, and a temperature of refrigerant discharged
from the compression mechanism.
11. The air conditioning apparatus according to claim 3, further
comprising: a first gain-varying unit configured to vary gain with
respect to control of the expansion mechanism in accordance with
the refrigerant temperature detected by the first temperature
detector and at least one of a pressure of refrigerant flowing from
the refrigerant discharge side of the compression mechanism to the
refrigerant inflow side of the expansion mechanism, and a
temperature of refrigerant discharged from the compression
mechanism.
12. The air conditioning apparatus according to claim 3, further
comprising: a second gain-varying unit configured to vary gain
pertaining to the determination of the target refrigerant
temperature by the target refrigerant temperature derivation unit
in accordance with the refrigerant temperature detected by the
first temperature detector and at least one of a pressure of
refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, and a temperature of refrigerant discharged
from the compression mechanism.
Description
TECHNICAL FIELD
[0001] The present invention relates to an air conditioning
apparatus, and particularly to an air conditioning apparatus
wherein a refrigerant reaches a supercritical state during a
refrigeration cycle.
BACKGROUND ART
[0002] Heat-pump air conditioning apparatuses in which carbon
dioxide is used as a refrigerant have recently come to be
manufactured and sold.
[0003] In an air conditioning apparatus in which a fluorocarbon
refrigerant is used as a refrigerant, the degree of subcooling is
controlled for the refrigerant flowing out of the indoor heat
exchanger or the refrigerant flowing into the expansion mechanism
during heating, and the heating capacity is appropriately
controlled. However, in a heat-pump air conditioning apparatus such
as described above in which carbon dioxide is used as the
refrigerant, subcooling control such as is described above cannot
be performed because the refrigerant delivered to the indoor heat
exchanger during heating is in a supercritical state. In other
words, the heating capacity cannot be appropriately controlled.
[0004] As a countermeasure to such problems, a proposal in the past
has been "to control an expansion valve so that the difference
between the intake air temperature and the radiator outlet
temperature in the indoor unit remains within a predetermined
range" (for example, see Patent Document 1).
[0005] <Patent Document 1>
[0006] Japanese Laid-open Patent Application No. 2003-176957
DISCLOSURE OF THE INVENTION
Technical Problem
[0007] However, it is extremely difficult to control the
temperature of an indoor space at the set temperature by merely
controlling an expansion valve so that the difference between the
intake air temperature and the radiator outlet temperature in the
indoor unit remains within a predetermined range as described
above.
[0008] An object of the present invention is to control the
temperature of an indoor space at a set temperature during a
heating operation in an air conditioning apparatus in which the
refrigerant reaches a supercritical state during the refrigeration
cycle.
<Solution to Problem>
[0009] An air conditioning apparatus according to a first aspect of
the patent invention is an air conditioning apparatus filled with a
supercritical refrigerant, the apparatus comprising a compression
mechanism, a radiator, an expansion mechanism, an evaporator, a
first temperature detector, a target refrigerant temperature
derivation unit, and a control unit. The term "supercritical
refrigerant" used herein refers to a refrigerant that reaches a
supercritical state at the high-pressure end of the refrigeration
cycle; e.g., carbon dioxide, R410A, or the like. The compression
mechanism compresses the refrigerant. The radiator is connected to
a refrigerant intake side of the compression mechanism. The
expansion mechanism is connected to outlet side of the radiator.
The evaporator is connected to refrigerant outflow side of the
expansion mechanism and connected to the refrigerant intake side of
the compression mechanism. The first temperature detector is
provided between the outlet side of the radiator and refrigerant
inflow side of the expansion mechanism. The target refrigerant
temperature derivation unit uses at least a set temperature to
determine a target refrigerant temperature, the set temperature
being a temperature set relative to the air in the space in which
the radiator is disposed, and the target refrigerant temperature
being a target temperature of the refrigerant flowing between the
outlet side of the radiator and the refrigerant inflow side of the
expansion mechanism. The target refrigerant temperature may be
determined by a method for deriving a target refrigerant
temperature determined in advance in accordance with the conditions
on the basis of a table, a function, or the like; a method for
determining a target refrigerant temperature by incorporating the
difference between the set temperature and intake temperature, a
time derivative of the difference, or another parameter into an FB
control loop (the control method may be PID control or model-based
control); or another such method. The control unit controls the
expansion mechanism so that the temperature detected by the first
temperature detector corresponds to the target refrigerant
temperature.
[0010] In this air conditioning apparatus, the target refrigerant
temperature derivation unit uses at least a set temperature to
calculate the target refrigerant temperature, which is a target
temperature of the refrigerant flowing between the outlet side of
the radiator and the refrigerant inflow side of the expansion
mechanism, and the control unit controls the expansion mechanism so
that the temperature detected by the first temperature detector
corresponds to the target refrigerant temperature. Therefore, in
this air conditioning apparatus, an appropriate target refrigerant
temperature is set according to the set temperature during the
heating operation. Consequently, with this air conditioning
apparatus, an indoor space can be controlled at a temperature equal
to the set temperature during the heating operation.
[0011] An air conditioning apparatus according to a second aspect
of the present invention is the air conditioning apparatus
according to the first aspect of the present invention, wherein a
plurality of radiators is provided. A plurality of expansion
mechanisms is provided, one for each radiator. A plurality of
temperature detectors is provided, one for each radiator.
[0012] In this air conditioning apparatus, a plurality of the
radiators is provided; a plurality of expansion mechanisms is
provided, one for each radiator; and a plurality of temperature
detectors is provided, one for each radiator. In other words, the
air conditioning apparatus is a multi-type air conditioning
apparatus. Thus, an appropriate target refrigerant temperature is
set according to the set temperature during the heating operation,
as in the description above, even if the air conditioning apparatus
is a multi-type air conditioning apparatus. Consequently, with this
air conditioning apparatus, an indoor space can be controlled at a
temperature equal to the set temperature during the heating
operation.
[0013] An air conditioning apparatus according to a third aspect of
the present invention is the air conditioning apparatus according
to the first or second aspect of the present invention, wherein the
target refrigerant temperature derivation unit determines the
target refrigerant temperature by using at least the set
temperature from among parameters including the set temperature,
the temperature detected by a second temperature detector disposed
in proximity to an air blower for blowing air to the radiator, the
pressure of the refrigerant flowing from the refrigerant discharge
side of the compression mechanism to the refrigerant inflow side of
the expansion mechanism, the temperature of the refrigerant
discharged from the compression mechanism, the pressure of the
refrigerant flowing into the radiator, and the temperature of the
refrigerant flowing into the radiator. The pressure of the
refrigerant flowing into the radiator and the temperature of the
refrigerant flowing into the radiator are effective parameters for
reliably determining the target refrigerant temperature in an air
conditioning apparatus having temperature detector on the
high-temperature side of the radiator (indoor heat exchangers),
such as a multi-type air conditioning apparatus for a building. In
such an air conditioning apparatus, the temperature of the
refrigerant flowing in proximity to the inlet of the radiator
(indoor heat exchanger) is often lower than the temperature of the
discharged refrigerant because of heat loss in the communication
pipes and other areas, and the pressure of the refrigerant flowing
in proximity to the inlet of the radiator (indoor heat exchanger)
is often less than the pressure of the discharged refrigerant
because of pressure loss in the communication pipes and other
areas.
[0014] In this air conditioning apparatus, the target refrigerant
temperature derivation unit determines the target refrigerant
temperature by using at least the set temperature from among
parameters including the set temperature, the temperature detected
by second temperature detector disposed in proximity to an air
blower for blowing air to the radiator, the pressure of the
refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, the temperature of the refrigerant discharged
from the compression mechanism, the pressure of the refrigerant
flowing into the radiator, and the temperature of the refrigerant
flowing into the radiator. Therefore, in this air conditioning
apparatus, the optimal control for the expansion mechanism can be
implemented according to the operating conditions.
[0015] An air conditioning apparatus according to a fourth aspect
of the present invention is the air conditioning apparatus
according to any of the first through third aspects of the present
invention, further comprising a first gain-varying unit. The first
gain-varying unit varies the gain pertaining to control of the
expansion mechanism in accordance with the temperature detected by
the first temperature detector and at least one of the pressure of
the refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, and the temperature of the refrigerant
discharged from the compression mechanism.
[0016] In this air conditioning apparatus, the first gain-varying
unit varies the gain pertaining to control of the expansion
mechanism in accordance with the temperature detected by the first
temperature detector and at least one of the pressure of the
refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, and the temperature of the refrigerant
discharged from the compression mechanism. Therefore, in this air
conditioning apparatus, the heating capacity is appropriately
controlled. Consequently, in this air conditioning apparatus, there
is no insufficient or excessive heating, energy consumption is
reduced, and the room is made more comfortable.
[0017] An air conditioning apparatus according to a fifth aspect of
the present invention is the air conditioning apparatus according
to any of the first through third aspects of the present invention,
further comprising a second gain-varying unit. The second
gain-varying unit varies the gain pertaining to the determination
of the target refrigerant temperature by the target refrigerant
temperature derivation unit in accordance with the temperature
detected by the first temperature detector and at least one of the
pressure of the refrigerant flowing from the refrigerant discharge
side of the compression mechanism to the refrigerant inflow side of
the expansion mechanism, and the temperature of the refrigerant
discharged from the compression mechanism. This type of second
gain-varying unit functions effectively only in cases in which the
target refrigerant temperature is determined through a feedback
control loop or the like.
[0018] In this air conditioning apparatus, the second gain-varying
unit varies the gain pertaining to the determination of the target
refrigerant temperature by the target refrigerant temperature
derivation unit in accordance with the temperature detected by the
first temperature detector and at least one of the pressure of the
refrigerant flowing from the refrigerant discharge side of the
compression mechanism to the refrigerant inflow side of the
expansion mechanism, and the temperature of the refrigerant
discharged from the compression mechanism. Therefore, in this air
conditioning apparatus, the heating capacity is appropriately
controlled. Consequently, in this air conditioning apparatus, there
is no insufficient or excessive heating, energy consumption is
reduced, and the room is made more comfortable.
ADVANTAGEOUS EFFECTS OF INVENTION
[0019] In the air conditioning apparatus according to the first
aspect of the present invention, an appropriate target refrigerant
temperature is set according to the set temperature during the
heating operation. Consequently, with this air conditioning
apparatus, an indoor space can be controlled at a temperature equal
to the set temperature during the heating operation.
[0020] In the air conditioning apparatus according to the second
aspect of the present invention, an indoor space can be controlled
at a temperature equal to the set temperature during the heating
operation.
[0021] In the air conditioning apparatus according to the third
aspect of the present invention, the optimal control for the
expansion mechanism can be implemented according to the operating
conditions.
[0022] In the air conditioning apparatus according to the fourth
aspect of the present invention, the heating capacity is
appropriately controlled. Consequently, with this air conditioning
apparatus, there is no insufficient or excessive heating, energy
consumption is reduced, and the room is made more comfortable.
[0023] In the air conditioning apparatus according to the fifth
aspect of the present invention, the heating capacity is
appropriately controlled. Consequently, with this air conditioning
apparatus, there is no insufficient or excessive heating, energy
consumption is reduced, and the room is made more comfortable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a refrigerant circuit diagram of an air
conditioning apparatus according to an embodiment of the present
invention.
[0025] FIG. 2 is a block diagram of the control performed by the
indoor control device in an air conditioning apparatus according to
an embodiment of the present invention.
[0026] FIG. 3 is an image diagram of the control table used in the
control performed by the indoor control device in an air
conditioning apparatus according to an embodiment of the present
invention.
[0027] FIG. 4 is an image diagram of the control table used in the
control performed by the indoor control device in an air
conditioning apparatus according to Modification (F).
DESCRIPTION OF THE REFERENCE SYMBOLS
[0028] 1 Air conditioning apparatus [0029] 11 Compressor
(compression mechanism) [0030] 13 Outdoor heat exchanger [0031]
31a, 31b Indoor heat exchanger [0032] 32a, 32b Indoor fan (air
blower) [0033] 33a, 33b Indoor electrical expansion valve
(expansion mechanism) [0034] 35a, 35b First intake temperature
sensor (second temperature detector) [0035] 36a, 36b First indoor
heat exchanger low-temperature sensor (first temperature detector)
[0036] 38a Radiator outlet temperature target value derivation unit
(target refrigerant temperature derivation unit) [0037] 39a
Expansion valve control unit (control unit)
BEST MODE FOR CARRYING OUT THE INVENTION
Configuration of Air Conditioning Apparatus
[0038] FIG. 1 shows a schematic refrigerant circuit 2 of an air
conditioning apparatus 1 according to an embodiment of the present
invention.
[0039] The air conditioning apparatus 1 is a multi-type air
conditioning apparatus using carbon dioxide as a refrigerant and
being capable of cooling and heating operations, and is configured
primarily from a refrigerant circuit 2, air-blowing fans 26, 32a,
32b, an outdoor control device 23, indoor control devices 34a, 34b,
a high-pressure sensor 21, indoor heat exchanger low-temperature
sensors 36a, 36b, intake temperature sensors 35a, 35b, and other
components.
[0040] The refrigerant circuit 2 is provided primarily with a
compressor 11, a four-way switching valve 12, an outdoor heat
exchanger 13, an outdoor electrical expansion valve 15, a liquid
receiver 16, indoor electrical expansion valves 33a, 33b, and
indoor heat exchangers 31a, 31b, wherein these devices are all
connected via refrigerant pipes as shown in FIG. 1.
[0041] In the present embodiment, the air conditioning apparatus 1
is a separate-type air conditioning apparatus, and can be regarded
as being configured from a first indoor unit 30a having primarily a
first indoor heat exchanger 31a, a first indoor fan 32a, a first
indoor electrical expansion valve 33a, a first indoor control
device 34a, a first indoor heat exchanger low-temperature sensor
36a, and a first intake temperature sensor 35a; a second indoor
unit 30b having primarily a second indoor heat exchanger 31b, a
second indoor fan 32b, a second indoor electrical expansion valve
33b, a second indoor control device 34b, a second indoor heat
exchanger low-temperature sensor 36b, and a second intake
temperature sensor 35b; an outdoor unit 10 having primarily the
compressor 11, the four-way switching valve 12, the outdoor heat
exchanger 13, the outdoor electrical expansion valve 15, the liquid
receiver 16, a high-pressure sensor 21, and an outdoor control
device 23; a first communication pipe 41 for connecting the liquid
refrigerant pipes of the indoor units 30a, 30b with the liquid
refrigerant pipe of the outdoor unit 10; and a second communication
pipe 42 for connecting the refrigerant gas pipes of the indoor
units 30a, 30b with the refrigerant gas pipe of the outdoor unit
10. The liquid refrigerant pipe of the outdoor unit 10 and the
first communication pipe 41 are connected via a first close valve
18 of the outdoor unit 10, and the refrigerant gas pipe of the
outdoor unit 10 and the second communication pipe 42 are connected
via a second close valve 19 of the outdoor unit 10.
[0042] (1) Indoor Unit
[0043] Since the first indoor unit 30a and the second indoor unit
30b have the same configuration, only the first indoor unit 30a is
described here. In the following description, the words "first" can
be replaced with "second" and the letters "a" with "b" to fit a
description of the second indoor unit 30b.
[0044] The first indoor unit 30a has primarily the first indoor
heat exchanger 31a, the first indoor fan 32a, the first indoor
electrical expansion valve 33a, the first indoor control device
34a, the first indoor heat exchanger low-temperature sensor 36a,
the first intake temperature sensor 35a, and other components.
[0045] The first indoor heat exchanger 31a is a heat exchanger for
exchanging heat between the refrigerant and indoor air, which is
the air inside the air conditioned room.
[0046] The first indoor fan 32a is a fan for drawing air in the air
conditioned room into the unit 30a and blowing conditioned air back
into the air conditioned room after the air has exchanged heat with
the refrigerant via the first indoor heat exchanger 31a.
[0047] The first indoor electrical expansion valve 33a is a
component for reducing the pressure of the liquid refrigerant
flowing in through the liquid receiver 16 (during the cooling
operation) or the supercritical refrigerant flowing out from the
low-temperature side of the indoor heat exchanger 31 (during the
heating operation).
[0048] The first indoor heat exchanger low-temperature sensor 36a
is disposed in proximity to the liquid side (or low-temperature
side) of the first indoor heat exchanger 31a.
[0049] The first intake temperature sensor 35a is disposed in
proximity to the first indoor fan 32a.
[0050] The first indoor control device 34a is configured primarily
from a first target refrigerant temperature derivation unit 38a and
a first expansion valve control unit 39a, as shown in FIG. 2. The
first indoor control device 34a is communicably connected to the
first indoor heat exchanger low-temperature sensor 36a, the first
intake temperature sensor 35a, a control unit 37a, and the outdoor
control device 23, as shown in FIG. 1. During the heating
operation, the first target refrigerant temperature derivation unit
38a receives information of a set temperature Ts from the control
unit 37a every time the set temperature Ts is changed in the
control unit 37a, and periodically receives information of an
intake temperature Ta from the first intake temperature sensor 35a.
The first target refrigerant temperature derivation unit 38a
subtracts the intake temperature Ta from the set temperature Ts to
calculate a first temperature difference e1, and substitutes the
first temperature difference e1 into a predetermined function
prepared in advance to calculate a target temperature T.sub.gcs of
the refrigerant flowing in proximity of the liquid side (or
low-temperature side) of the first indoor heat exchanger 31a. The
first expansion valve control unit 39a periodically receives
information of the target temperature T.sub.gcs of the refrigerant
flowing in proximity to the liquid side (or low-temperature side)
of the first indoor heat exchanger 31a from the first target
refrigerant temperature derivation unit 38a, periodically receives
information of the actual temperature T.sub.gc from the first
indoor heat exchanger low-temperature sensor 36a, and subtracts the
temperature T.sub.gc from the target temperature T.sub.gcs to
calculate a temperature difference e2. The first expansion valve
control unit 39a determines and controls the degree of opening of
the first indoor electrical expansion valve 33a on the basis of the
second temperature difference e2. Carbon dioxide is used as the
refrigerant in the air conditioning apparatus 1 according to the
present embodiment. Temperature changes in carbon dioxide in a
supercritical state under constant pressure are not uniform (not
proportionate) with respect to changes in enthalpy. In other words,
there are cases in which the necessary amount of change in heating
capacity differs even when the second temperature difference e2 is
the same. Therefore, in the air conditioning apparatus 1 according
to the present embodiment, the gain with respect to control of the
degree of opening of the first indoor electrical expansion valve
33a is changed according to high-pressure HP information (obtained
from the high-pressure sensor 21) sent to the first indoor control
device 34a via the outdoor control device 23. Specifically, a
control table (see FIG. 3) associating the degree of opening of the
first indoor electrical expansion valve 33a with the second
temperature difference e2 and the high pressure HP is made in
advance, and the first expansion valve control unit 39a determines
the degree of opening of the first indoor electrical expansion
valve 33a by checking the periodically obtained second temperature
difference e2 and high pressure HP against the control table. In
case of a high actual temperature T.sub.gc, the gain of the change
in the degree of opening of the expansion valve must be set lower
in comparison with a low actual temperature T.sub.gc. This is
because the ratio of dh/dT (the rate of change in enthalpy when the
radiator outlet temperature (T.sub.gc) changes under a constant
high pressure) does not change much even when subcooling is
increased in subcritical regions deviated from the critical point
of carbon dioxide or R410A, but the ratio of dh/dT tends to
increase significantly as the radiator outlet temperature
(T.sub.gc) increases in the supercritical regions of R410A and in
the supercritical regions and near-supercritical subcritical
regions of carbon dioxide.
[0051] By employing such a configuration, the first indoor unit 30a
can create conditioned air (cool air) during the cooling operation
by exchanging heat between the indoor air taken in by the first
indoor fan 32a and the liquid refrigerant flowing through the first
indoor heat exchanger 31a, and can create conditioned air (warm
air) during the heating operation by exchanging heat between the
indoor air taken in by the first indoor fan 32a and the
supercritical refrigerant flowing through the first indoor heat
exchanger 31a.
[0052] (2) Outdoor Unit
[0053] The outdoor unit 10 has primarily the compressor 11, the
four-way switching valve 12, the outdoor heat exchanger 13, the
outdoor electrical expansion valve 15, the liquid receiver 16, an
outdoor fan 26, the outdoor control device 23, the high-pressure
sensor 21, and other components.
[0054] The compressor 11 is a device for sucking in the
low-pressure refrigerant gas flowing through an intake tube,
compressing the refrigerant to a supercritical state, and then
discharging the refrigerant to a discharge tube.
[0055] The four-way switching valve 12 is a valve for switching the
direction of refrigerant flow in accordance with the operations,
and is capable of connecting the discharge side of the compressor
11 with the high-temperature side of the outdoor heat exchanger 13
and connecting the intake side of the compressor 11 with the gas
side of the indoor heat exchangers 31a, 31b during the cooling
operation, and is capable of connecting the discharge side of the
compressor 11 with the second close valve 19 and connecting the
intake side of the compressor 11 with the gas side of the outdoor
heat exchanger 13 during the heating operation.
[0056] The outdoor heat exchanger 13 is capable of cooling the
high-pressure supercritical refrigerant discharged from the
compressor 11 using air outside of the air conditioned room as a
heat source during the cooling operation, and of evaporating the
liquid refrigerant returning from the indoor heat exchangers 31a,
31b during the heating operation.
[0057] The outdoor electrical expansion valve 15 is a component for
reducing the pressure of the supercritical refrigerant flowing out
from the low-temperature side of the outdoor heat exchanger 13
(during the cooling operation) or the liquid refrigerant flowing in
through the liquid receiver 16 (during the heating operation).
[0058] The liquid receiver 16 is a component for storing excess
refrigerant in accordance with the operating mode or the air
conditioning load.
[0059] The outdoor fan 26 is a fan for taking outdoor air into the
unit 10 and expelling out air after the air has exchanged heat with
the refrigerant via the outdoor heat exchanger 13.
[0060] The high-pressure sensor 21 is provided to the discharge
side of the compressor 11.
[0061] The outdoor control device 23 is communicably connected to
the high-pressure sensor 21, the indoor control devices 34a, 34b,
and other components, and the outdoor control device 23 transmits
high-pressure information sent from the high-pressure sensor 21 to
the indoor control devices 34a, 34b and other components.
[0062] <Operation of Air Conditioning Apparatus>
[0063] The operating action of the air conditioning apparatus 1 is
described using FIG. 1. The air conditioning apparatus 1 is capable
of performing a cooling operation and a heating operation, as
described above.
[0064] (1) Cooling Operation
[0065] During the cooling operation, the four-way switching valve
12 is in the state shown by the solid lines in FIG. 1; i.e., the
discharge side of the compressor 11 is connected to the
high-temperature side of the outdoor heat exchanger 13, and the
intake side of the compressor 11 is connected to the second close
valve 19. At this time the first close valve 18 and the second
close valve 19 are in an open state.
[0066] When the compressor 11 is activated in this state of the
refrigerant circuit 2, the refrigerant gas is sucked into the
compressor 11 and compressed to a supercritical state, and then is
sent to the outdoor heat exchanger 13 via the four-way switching
valve 12 and cooled in the outdoor heat exchanger 13.
[0067] The cooled supercritical refrigerant is then sent to the
outdoor electrical expansion valve 15. The supercritical
refrigerant sent to the outdoor electrical expansion valve 15 is
reduced in pressure to become saturated, and is then sent to the
indoor electrical expansion valves 33a, 33b via the liquid receiver
16. The saturated refrigerant sent to the indoor electrical
expansion valves 33a, 33b is supplied to the indoor heat exchangers
31a, 31b after being reduced in pressure to a liquid refrigerant,
the refrigerant cools the indoor air, and the refrigerant is
evaporated into a refrigerant gas.
[0068] The refrigerant gas is then sucked back into the compressor
11 via the second close valve 19 and the four-way switching valve
12. Thus, the cooling operation is performed.
[0069] (2) Heating Operation
[0070] During the heating operation, the four-way switching valve
12 is in the state shown by the dashed lines in FIG. 1; i.e., the
discharge side of the compressor 11 is connected to the second
close valve 19, and the intake side of the compressor 11 is
connected to the gas side of the outdoor heat exchanger 13. At this
time, the first close valve 18 and the second close valve 19 are in
an open state.
[0071] When the compressor 11 is activated in this state of the
refrigerant circuit 2, the refrigerant gas is sucked into the
compressor 11 and compressed to a supercritical state, and is then
supplied to the indoor heat exchangers 31a, 31b via the four-way
switching valve 12 and the second close valve 19.
[0072] The supercritical refrigerant then heats the indoor air in
the indoor heat exchangers 31a, 31b and the refrigerant is cooled.
The cooled supercritical refrigerant is sent to the indoor
electrical expansion valves 33a, 33b. The supercritical refrigerant
sent to the indoor electrical expansion valves 33a, 33b is reduced
in pressure to become saturated, and is then sent to the outdoor
electrical expansion valve 15 via the liquid receiver 16. The
saturated refrigerant sent to the outdoor electrical expansion
valve 15 is sent to the outdoor heat exchanger 13 after being
reduced in pressure to a liquid refrigerant, and is evaporated in
the outdoor heat exchanger 13 into a refrigerant gas. The
refrigerant gas is sucked back into the compressor 11 via the
four-way switching valve 12. Thus, the heating operation is
performed. The control described above is implemented during the
heating operation.
[0073] <Characteristics of Air Conditioning Apparatus>
[0074] (1)
[0075] In the air conditioning apparatus 1 according to the present
embodiment, during the heating operation in the first indoor
control device 34a, the first target refrigerant temperature
derivation unit 38a subtracts the intake temperature Ta from the
set temperature Ts to calculate the first temperature difference
e1, and substitutes the first temperature difference e1 into a
predetermined function prepared in advance to calculate the target
temperature T.sub.gcs of the refrigerant flowing in proximity to
the liquid side (or low-temperature side) of the first indoor heat
exchanger 31a. The first expansion valve control unit 39a then
determines and controls the degree of opening of the first indoor
electrical expansion valve 33a on the basis of the second
temperature difference e2. Therefore, in the air conditioning
apparatus 1, an appropriate target temperature T.sub.gcs is set
according to the set temperature during the heating operation.
Consequently, in the air conditioning apparatus 1, an indoor space
can be controlled to a temperature equal to the set temperature
during the heating operation.
[0076] (2)
[0077] In the air conditioning apparatus 1 according to the present
embodiment, the first expansion valve control unit 39a changes the
gain with respect to control of the degree of opening of the first
indoor electrical expansion valve 33a according to the information
(obtained from the high-pressure sensor 21) on the high pressure
HP. Therefore, the heating capacity is appropriately controlled in
the air conditioning apparatus 1. Consequently, with the air
conditioning apparatus 1, there is no insufficient or excessive
heating, energy consumption is reduced, and the room is made more
comfortable.
[0078] <Modifications>
[0079] (A)
[0080] In the air conditioning apparatus 1 according to the
previous embodiment, the first temperature difference e1 was used
in order for the first target refrigerant temperature derivation
unit 38a to calculate the target temperature T.sub.gcs, but the set
temperature Ts, the intake temperature Ta, or the like may be used
independently in order for the first target refrigerant temperature
derivation unit 38a to calculate the target temperature T.sub.gcs,
or a time derivative of the intake temperature Ta, the high
pressure HP, the discharge temperature, or another parameter may
also be used.
[0081] (B)
[0082] In the air conditioning apparatus 1 according to the
previous embodiment, the first target refrigerant temperature
derivation unit 38a subtracts the intake temperature Ta from the
set temperature Ts to calculate the first temperature difference
e1, and substitutes the first temperature difference e1 into a
predetermined function prepared in advance to calculate the target
temperature T.sub.gcs of the refrigerant flowing in proximity to
the liquid side (or low-temperature side) of the first indoor heat
exchanger 31a. However, the first target refrigerant temperature
derivation unit 38a may also calculate the target temperature
T.sub.gcs of the refrigerant flowing in proximity to the liquid
side (or low-temperature side) of the first indoor heat exchanger
31a by checking the first temperature difference e1 against a
control table prepared in advance.
[0083] (C)
[0084] In the air conditioning apparatus 1 according to the
previous embodiment, the first expansion valve control unit 39a
determined the degree of opening of the first indoor electrical
expansion valve 33a by checking the periodically obtained second
temperature difference e2 and the high pressure HP against the
control table. However, the first expansion valve control unit 39a
may also calculate the degree of opening of the first indoor
electrical expansion valve 33a by substituting the periodically
obtained second temperature difference e2 and high pressure HP into
a predetermined function prepared in advance.
[0085] (D)
[0086] Although not particularly mentioned in the previous
embodiment, there is a nonlinear relationship between the degree of
opening (pulse number) and the actual opening area of the expansion
valve. Therefore, it is preferable that such factors be taken into
account when the first expansion valve control unit 39a determines
the degree of opening of the first indoor electrical expansion
valve 33a by checking the second temperature difference e2 and high
pressure HP against the control table.
[0087] (E)
[0088] Although not particularly mentioned in the previous
embodiment, the gain in the range of variation of the target
temperature T.sub.gcs may be varied not only according to the
information on the high pressure HP but also according to the value
of the actual temperature T.sub.gc when the target temperature
T.sub.gcs is calculated. In such cases, the first temperature
difference e1 or another parameter may be incorporated into an FB
control loop (the control method may be PID control or model-based
control) to calculate the target refrigerant temperature.
[0089] (F)
[0090] In the air conditioning apparatus 1 according to the
previous embodiment, the first target refrigerant temperature
derivation unit 38a subtracted the intake temperature Ta from the
set temperature Ts to calculate the first temperature difference
e1, and substituted the first temperature difference e1 into a
predetermined function prepared in advance to calculate the target
temperature T.sub.gcs of the refrigerant flowing in proximity to
the liquid side (or low-temperature side) of the first indoor heat
exchanger 31a. However, the first target refrigerant temperature
derivation unit 38a may also subtract the intake temperature Ta
from the set temperature Ts to calculate the first temperature
difference e1, and determine the target temperature T.sub.gcs of
the refrigerant flowing in proximity to the liquid side (or low
temperature side) of the first indoor heat exchanger 31a by
checking the first temperature difference e1 and the time
derivative of the first temperature difference e1 against a control
table such as the one shown in FIG. 4. In such cases, the first
expansion valve control unit 39a can determine and control the
degree of opening of the first indoor electrical expansion valve
33a on the basis of the second temperature difference e2, and there
is no need to check the second temperature difference e2 and the
high pressure HP against the control table to determine the degree
of opening of the first indoor electrical expansion valve 33a.
[0091] (G)
[0092] Although not particularly mentioned in the previous
embodiment, the present invention may also be applied to a
heating/cooling free-type, multi-type air conditioning
apparatus.
[0093] (H)
[0094] Although not particularly mentioned in the previous
embodiment, the present invention may also be applied to a
pair-type air conditioning apparatus.
[0095] (I)
[0096] In the air conditioning apparatus 1 according to the
previous embodiment, the first target refrigerant temperature
derivation unit 38a subtracted the intake temperature Ta from the
set temperature Ts to calculate the first temperature difference
e1, and substituted the first temperature difference e1 into a
predetermined function prepared in advance to calculate the target
temperature T.sub.gcs of the refrigerant flowing in proximity to
the liquid side (or low-temperature side) of the first indoor heat
exchanger 31a. However, the first target refrigerant temperature
derivation unit 38a may also incorporate the first temperature
difference e1 into an FB loop (the control method may be PID
control or model-based control) to calculate the target refrigerant
temperature. In this example, in cases in which the set temperature
Ts is suddenly changed by a user input or the like, it is
preferable that FF (feed forward) control be implemented in
addition to FB control and that a preset value be used.
[0097] (J)
[0098] Although not particularly mentioned in the previous
embodiment, when the gain with respect to control of the degree of
opening of the first indoor electrical expansion valve 33a is
varied, the gain may be varied using FB control, FF control, a
combination of FB control and FF control, PID control, model-based
control, or another type of control.
INDUSTRIAL APPLICABILITY
[0099] The air conditioning apparatus according to the present
invention has the characteristic of being able to control an indoor
space at a temperature equal to a set temperature during the
heating operation, and the present invention is particularly useful
for air conditioning apparatuses that use carbon dioxide or the
like as a refrigerant.
* * * * *