U.S. patent application number 13/054823 was filed with the patent office on 2011-06-09 for air conditioning apparatus.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. Invention is credited to Akiharu Kojima.
Application Number | 20110132011 13/054823 |
Document ID | / |
Family ID | 41610131 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110132011 |
Kind Code |
A1 |
Kojima; Akiharu |
June 9, 2011 |
AIR CONDITIONING APPARATUS
Abstract
An air conditioning includes a refrigerant circuit and a blower
fan. The refrigerant circuit has a compressor, a condenser, a first
expansion valve, a second expansion valve, and an evaporator
sequentially connected. The blower fan is arranged and configured
to supply air as a heat source to the condenser. An air flow rate
of the blower fan and an opening degree of the first expansion
valve are controlled such that high pressure in a refrigeration
cycle operation of the refrigerant circuit becomes a target high
pressure.
Inventors: |
Kojima; Akiharu; (Osaka,
JP) |
Assignee: |
DAIKIN INDUSTRIES, LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
41610131 |
Appl. No.: |
13/054823 |
Filed: |
July 23, 2009 |
PCT Filed: |
July 23, 2009 |
PCT NO: |
PCT/JP2009/003468 |
371 Date: |
January 19, 2011 |
Current U.S.
Class: |
62/180 |
Current CPC
Class: |
F25B 2600/21 20130101;
F25B 2600/2513 20130101; F24F 2140/12 20180101; F25B 2700/1931
20130101; F25B 41/39 20210101; F25B 2600/111 20130101; F25B
2700/21151 20130101; F25B 2600/021 20130101; Y02B 30/70 20130101;
F24F 2140/20 20180101; F25B 2400/16 20130101; F25B 2700/1933
20130101; F25B 2700/21152 20130101; F24F 11/77 20180101; F25B
2313/005 20130101; F25B 49/027 20130101 |
Class at
Publication: |
62/180 |
International
Class: |
F25D 17/06 20060101
F25D017/06; F25D 17/02 20060101 F25D017/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2008 |
JP |
2008-194955 |
Claims
1. An air conditioning apparatus comprising: a refrigerant circuit
having a compressor, a condenser, a first expansion valve, a second
expansion valve, and an evaporator sequentially connected; and a
blower fan arranged and configured to supply air as a heat source
to the condenser, an air flow rate of the blower fan and an opening
degree of the first expansion valve being controlled such that high
pressure in a refrigeration cycle operation of the refrigerant
circuit becomes a target high pressure.
2. The air conditioning apparatus according to claim 1, wherein the
opening degree of the first expansion valve is controlled such that
the high pressure becomes the target high pressure in a state where
air flow rate control of the blower fan has been performed such
that the air flow rate of the blower fan becomes a prescribed air
flow rate, and the prescribed air flow rate is changed by air flow
rate control of the blower fan when the high pressure does not
become the target high pressure by controlling the opening degree
of the first expansion valve.
3. The air conditioning apparatus according to claim 2, wherein a
receiver is connected between the first expansion valve and the
second expansion valve to accumulate refrigerant.
4. The air conditioning apparatus according to claim 3, wherein an
opening degree of the second expansion valve is controlled such
that a degree of superheat of refrigerant in an outlet of the
evaporator becomes a target degree of superheat or a state quantity
equivalent to the degree of superheat becomes a target state
quantity equivalent to the target degree of superheat.
Description
TECHNICAL FIELD
[0001] The present invention relates to an air conditioning
apparatus and particularly to an air conditioning apparatus that is
equipped with a blower fan that supplies air as a heat source to a
condenser that configures a refrigerant circuit and which air
conditioning apparatus can control the air flow rate of the blower
fan such that high pressure in a refrigeration cycle operation
becomes a target high pressure.
BACKGROUND ART
[0002] Conventionally, there has been an air conditioning apparatus
that is equipped with a blower fan that supplies air as a heat
source to a condenser that configures a refrigerant circuit and
which air conditioning apparatus controls the air flow rate of the
blower fan such that high pressure in a refrigeration cycle
operation becomes a target high pressure (see JP-A No. 1-225852 as
patent literature 1).
SUMMARY OF THE INVENTION
[0003] However, in the aforementioned air conditioning apparatus,
ensuring that the high pressure can be controlled more finely is
desired. Particularly when the outside air temperature is high, the
heat exchange efficiency in the condenser drops because the
temperature difference between the saturation temperature of the
refrigerant in the condenser and the temperature of the air becomes
smaller, and therefore there is the fear that the operating
efficiency of the apparatus overall cannot be optimized. To counter
this, it is conceivable to lower the air flow rate of the blower
fan in order to raise the high pressure in the refrigeration cycle;
however, although this can raise the saturation temperature of the
refrigerant in the condenser and increase the temperature
difference with the air, this decreases the flow rate of the air
that undergoes heat exchange with the refrigerant, so it is
difficult to increase the heat exchange duty itself in the
condenser. Further, when the outside air temperature is low, it is
conceivable to decrease the heat exchange duty in the condenser by
lowering the air flow rate of the blower fan in order to maintain
the high pressure in the refrigeration cycle operation; however,
the apparatus ends up structurally resonating when the air flow
rate is linearly changed, and control is complex, so it is
necessary to control the air flow rate stepwise in plural stages.
However, when the air flow rate is controlled stepwise in plural
stages, the high pressure that is to be in balance between each
step differs, so this results in hunting between steps and it
becomes difficult for control stability to be obtained.
[0004] It is a problem of the present invention to ensure that, in
an air conditioning apparatus that is equipped with a blower fan
that supplies air as a heat source to a condenser that configures a
refrigerant circuit and which air conditioning apparatus can
control the air flow rate of the blower fan such that high pressure
in a refrigeration cycle operation becomes a target high pressure,
the high pressure can be finely controlled.
[0005] An air conditioning apparatus pertaining to a first aspect
of the invention comprises: a refrigerant circuit that is
configured as a result of a compressor, a condenser, a first
expansion valve, a second expansion valve, and an evaporator being
sequentially connected; and a blower fan that supplies air as a
heat source to the condenser, wherein the air flow rate of the
blower fan and the opening degree of the first expansion valve are
controlled such that high pressure in a refrigeration cycle
operation of the refrigerant circuit becomes a target high
pressure. Here, "high pressure in a refrigeration cycle operation"
means the pressure of the refrigerant flowing from the discharge
side of the compressor, through the condenser, and into the first
expansion valve. Further, "target high pressure" is not something
that means just a single pressure value but is something that also
means, for example, a pressure range between a lower limit value of
the high pressure and an upper limit value of the high
pressure.
[0006] In this air conditioning apparatus, the quantity of the
refrigerant accumulating in the condenser is adjusted by
controlling the opening degree of the first expansion valve, and
therefore control of the high pressure can be performed, so even in
an operating condition where the temperature difference between the
saturation temperature of the refrigerant in the condenser and the
temperature of the air is small and where it is easy for the heat
exchange efficiency in the condenser to drop, like, for example,
when the outside air temperature is high, the high pressure can be
raised and a situation where the heat exchange efficiency in the
condenser drops can be suppressed. Further, also with respect to
hunting between steps of the air flow rate of the blower fan when
the outside air temperature is low, in a situation where the high
pressure falls too much in a step where the air flow rate is large,
the high pressure can be maintained by accumulating the refrigerant
in the condenser, and in a situation where the high pressure rises
too much in a step where the air flow rate is small, the high
pressure can be maintained by decreasing the refrigerant
accumulating in the condenser.
[0007] In this manner, in this air conditioning apparatus, not just
air flow rate control of the blower fan but opening degree control
of the first expansion valve is jointly used, so the high pressure
can be controlled finely.
[0008] An air conditioning apparatus pertaining to a second aspect
of the invention is the air conditioning apparatus pertaining to
the first aspect of the invention, wherein the opening degree of
the first expansion valve is controlled such that the high pressure
becomes the target high pressure in a state where air flow rate
control of the blower fan has been performed such that the air flow
rate of the blower fan becomes a prescribed air flow rate, and when
the high pressure does not become the target high pressure by
opening degree control of the first expansion valve, the prescribed
air flow rate is changed by air flow rate control of the blower
fan.
[0009] In this air conditioning apparatus, control is performed
such that the high pressure becomes the target high pressure by
opening degree control of the first expansion valve, and basically
opening degree control of the first expansion valve becomes
performed preferentially over air flow rate control of the blower
fan because the prescribed air flow rate of the blower fan is
changed when the high pressure does not become the target high
pressure by just opening degree control of the first expansion
valve, so the high pressure can be controlled even more finely.
[0010] An air conditioning apparatus pertaining to a third aspect
of the invention is the air conditioning apparatus pertaining to
the second aspect of the invention, wherein a receiver that can
accumulate refrigerant is connected between the first expansion
valve and the second expansion valve.
[0011] In this air conditioning apparatus, the quantity of the
refrigerant accumulating in the condenser fluctuates because of
opening degree control of the first expansion valve, but because
this fluctuation in the quantity of the refrigerant is absorbed as
a result of the quantity of the refrigerant accumulating in the
receiver fluctuating and the state of the refrigerant sent to the
evaporator is stable, a situation where the quantity of the
refrigerant in the evaporator fluctuates or where the state of the
refrigerant sucked into the compressor fluctuates, for example, can
be suppressed.
[0012] In this manner, in this air conditioning apparatus, even
though control is performed such that the high pressure becomes the
target high pressure by jointly using opening degree control of the
first expansion valve together with air flow rate control of the
blower fan, it becomes difficult for the quantity of the
refrigerant in the portion of the refrigerant circuit from the
second expansion valve via the evaporator to the compressor to
fluctuate because the receiver that can accumulate the refrigerant
is connected between the first expansion valve and the second
expansion valve, and therefore it can be made difficult for the
control to affect the operating state of the evaporator or the
compressor.
[0013] An air conditioning apparatus pertaining to a fourth aspect
of the invention is the air conditioning apparatus pertaining to
the third aspect of the invention, wherein the opening degree of
the second expansion valve is controlled such that a degree of
superheat of refrigerant in an outlet of the evaporator or a state
quantity equivalent to the degree of superheat becomes a target
degree of superheat or a target state quantity equivalent to the
target degree of superheat. Here, "state quantity equivalent to the
degree of superheat" and "target state quantity equivalent to the
target degree of superheat" mean not only the degree of superheat
of the refrigerant in the outlet of the evaporator but include also
a state quantity equivalent to the degree of superheat of the
refrigerant in the outlet of the evaporator, such as the degree of
superheat of the refrigerant in the discharge of the
compressor.
[0014] In this air conditioning apparatus, it can be made difficult
for the quantity of the refrigerant in the portion of the
refrigerant circuit from the second expansion valve via the
evaporator to the compressor to fluctuate because of the receiver,
and the quantity of the refrigerant in the evaporator and the state
of the refrigerant in the outlet of the evaporator can be
stabilized by opening degree control of the second expansion valve,
so the operating efficiency of the apparatus overall can be
optimized and the reliability of the compressor can be improved
(e.g., out-of-gas operation and wet compression can be
prevented).
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a general configuration diagram of an air
conditioning apparatus pertaining to an embodiment of the present
invention.
[0016] FIG. 2 is a control block diagram of the air conditioning
apparatus.
[0017] FIG. 3 is a flowchart mainly showing control of an outdoor
expansion valve of the air conditioning apparatus pertaining to the
embodiment of the present invention.
[0018] FIG. 4 is a flowchart mainly showing control of an outdoor
fan of the air conditioning apparatus pertaining to the embodiment
of the present invention.
[0019] FIG. 5 is a diagram showing the distribution (excluding the
insides of pipes) of liquid refrigerant when the high pressure in
the air conditioning apparatus pertaining to the embodiment of the
present invention is stable at a standard pressure.
[0020] FIG. 6 is a diagram showing the distribution (excluding the
insides of pipes) of liquid refrigerant when the high pressure in
the air conditioning apparatus pertaining to the embodiment of the
present invention is stable at a high pressure.
[0021] FIG. 7 is a diagram showing the distribution (excluding the
insides of pipes) of liquid refrigerant when the high pressure in
the air conditioning apparatus pertaining to the embodiment of the
present invention is stable at a low pressure.
DESCRIPTION OF THE EMBODIMENT
[0022] An embodiment of an air conditioning apparatus pertaining to
the present invention will be described below on the basis of the
drawings.
(1) Configuration of Air Conditioning Apparatus
[0023] FIG. 1 is a general configuration diagram of an air
conditioning apparatus 1 pertaining to the embodiment of the
present invention. The air conditioning apparatus 1 is an apparatus
used to cool the inside of a room in a building or the like by
performing a vapor compression refrigeration cycle operation. The
air conditioning apparatus 1 is mainly equipped with an outdoor
unit 2, an indoor unit 4, and a liquid refrigerant connection pipe
5 and a gas refrigerant connection pipe 6 that interconnect the
outdoor unit 2 and the indoor unit 4. That is, a vapor compression
refrigerant circuit 10 of the air conditioning apparatus 1 of the
present embodiment is configured as a result of the outdoor unit 2,
the indoor unit 4, and the liquid refrigerant connection pipe 5 and
the gas refrigerant connection pipe 6 being connected.
<Indoor Unit>
[0024] The indoor unit 4 is installed by being embedded in or hung
from a ceiling inside a room in a building or the like or by being
mounted on a wall surface inside a room or the like. The indoor
unit 4 is connected to the outdoor unit 2 via the liquid
refrigerant connection pipe 5 and the gas refrigerant connection
pipe 6 and configures part of the refrigerant circuit 10.
[0025] Next, the configuration of the indoor unit 4 will be
described. The indoor unit 4 mainly has an indoor-side refrigerant
circuit 10a that configures part of the refrigerant circuit 10.
This indoor-side refrigerant circuit 10a mainly has an indoor
expansion valve EV2 serving as a second expansion valve and an
indoor heat exchanger 41.
[0026] In the present embodiment, the indoor expansion valve EV2 is
an electrically driven expansion valve that is connected to the
liquid side of the indoor heat exchanger 41 in order to adjust, for
example, the flow rate of the refrigerant flowing through the
inside of the indoor-side refrigerant circuit 10a.
[0027] In the present embodiment, the indoor heat exchanger 41 is a
cross-fin type fin-and-tube heat exchanger configured by heat
transfer tubes and numerous fins and is a heat exchanger that
functions as an evaporator of the refrigerant to cool the room
air.
[0028] In the present embodiment, the indoor unit 4 has an indoor
fan 42 for sucking the room air into the inside of the unit,
allowing heat to be exchanged with the refrigerant in the indoor
heat exchanger 41, and thereafter supplying the air to the inside
of the room as supply air. The indoor fan 42 is, in the present
embodiment, a centrifugal fan or a multiblade fan or the like
driven by an indoor fan motor 42a.
[0029] Further, the indoor unit 4 has an indoor-side controller 43
that controls the operation of each part configuring the indoor
unit 4. Additionally, the indoor-side controller 43 has a
microcomputer and a memory and the like disposed in order to
control the indoor unit 4 and is configured such that it can
exchange control signals and the like with a remote controller (not
shown) for individually operating the indoor unit 4 and such that
it can exchange control signals and the like with the outdoor unit
2 via a transmission line 7a.
<Outdoor Unit>
[0030] The outdoor unit 2 is installed outdoors of a building or
the like, is connected to the indoor unit 4 via the liquid
refrigerant connection pipe 5 and the gas refrigerant connection
pipe 6, and configures the refrigerant circuit 10 together with the
indoor unit 4.
[0031] Next, the configuration of the outdoor unit 2 will be
described. The outdoor unit 2 mainly has an outdoor-side
refrigerant circuit 10b that configures part of the refrigerant
circuit 10. This outdoor-side refrigerant circuit 10b mainly has a
compressor 21, an outdoor heat exchanger 22, an outdoor expansion
valve EV1 serving as a first expansion valve, a receiver 23, a
liquid-side stop valve 24, and a gas-side stop valve 25.
[0032] The compressor 21 is, in the present embodiment, a positive
displacement compressor driven by a compressor motor 21a. The
compressor motor 21a is configured such that it is driven as a
result of being supplied with electrical power via an inverter
device (not shown) and such that it can vary its operating capacity
by varying its frequency (that is, its speed).
[0033] In the present embodiment, the outdoor heat exchanger 22 is
a cross-fin type fin-and-tube heat exchanger configured by heat
transfer tubes and numerous fins and is a heat exchanger that
functions as a condenser of the refrigerant. The gas side of the
outdoor heat exchanger 22 is connected to the compressor 21, and
the liquid side of the outdoor heat exchanger 22 is connected to
the outdoor expansion valve EV1.
[0034] In the present embodiment, the outdoor unit 2 has an outdoor
fan 26 serving as a blower fan for sucking outdoor air into the
inside of the unit, allowing heat to be exchanged with the
refrigerant in the outdoor heat exchanger 22, and thereafter
expelling the air to the outdoors. This outdoor fan 26 is a fan
that can vary the air flow rate of the outdoor air as a heat source
supplied to the outdoor heat exchanger 22 and, in the present
embodiment, is a propeller fan or the like driven by an outdoor fan
motor 26a comprising a DC fan motor. The outdoor fan motor 26a is
configured such that it is driven as a result of being supplied
with electrical power via an inverter device (not shown) and such
that it can vary the air flow rate of the outdoor fan 26 by
stepwise varying its frequency (that is, its speed).
[0035] The receiver 23 is a container that can accumulate
refrigerant and is connected between the outdoor expansion valve
EV1 and the liquid-side stop valve 24; the receiver 23 can absorb
fluctuations in the distribution of the quantity of the refrigerant
in the refrigerant circuit 10.
[0036] The liquid-side stop valve 24 and the gas-side stop valve 25
are valves disposed in openings to which external devices and pipes
(specifically, the liquid refrigerant connection pipe 5 and the gas
refrigerant connection pipe 6) connect. The liquid-side stop valve
24 is connected to the receiver 23. The gas-side stop valve 25 is
connected to the compressor 21.
[0037] Further, various sensors are disposed in the outdoor unit 2.
Specifically, a suction pressure sensor 27 that detects the suction
pressure of the compressor 21, a discharge pressure sensor 28 that
detects the discharge pressure of the compressor 21, a suction
temperature sensor 29 that detects the suction temperature of the
compressor 21, and a discharge temperature sensor 30 that detects
the discharge temperature of the compressor 21 are disposed in the
outdoor unit 2. In the present embodiment, the suction temperature
sensor 29 and the discharge temperature sensor 30 comprise
thermistors. Further, the outdoor unit 2 has an outdoor-side
controller 31 that controls the operation of each part configuring
the outdoor unit 2. Additionally, the outdoor-side controller 31
has a microcomputer and a memory disposed in order to control the
outdoor unit 2 and an inverter circuit and the like that controls
the compressor motor 21a, and the outdoor-side controller 31 is
configured such that it can exchange control signals and the like
with the indoor-side controller 43 of the indoor unit 4 via the
transmission line 7a. That is, a controller 7 that performs
operation control of the entire air conditioning apparatus 1 is
configured by the indoor-side controller 43, the outdoor-side
controller 31, and the transmission line 7a that interconnects the
indoor-side controller 43 and the outdoor-side controller 31.
[0038] The controller 7 is, as shown in FIG. 2, connected such that
it can receive detection signals of the various sensors 27 to 30
and is connected such that it can control the various devices and
valves 21 a, 26a, 42a, EV1, and EV2 on the basis of these detection
signals and the like. Here, FIG. 2 is a control block diagram of
the air conditioning apparatus 1.
<Refrigerant Connection Pipes>
[0039] The refrigerant connection pipes 5 and 6 are refrigerant
pipes constructed on site when installing the air conditioning
apparatus 1 in an installation location such as a building, and
pipes having various lengths and pipe diameters are used depending
on installation conditions such as the installation location and
the combination of the outdoor unit and the indoor unit.
[0040] As described above, the refrigerant circuit 10 of the air
conditioning apparatus 1 is configured as a result of the
indoor-side refrigerant circuit 10a, the outdoor-side refrigerant
circuit 10b, and the refrigerant connection pipes 5 and 6 being
connected, that is, as a result of the compressor 21, the outdoor
heat exchanger 22 serving as the condenser, the outdoor expansion
valve EV1 serving as the first expansion valve, the receiver 23,
the refrigerant pipes 5 and 6, the indoor expansion valve EV2
serving as the second expansion valve, and the indoor heat
exchanger 41 serving as the evaporator being sequentially
connected. Additionally, the air conditioning apparatus 1 of the
present embodiment is configured such that it can use the
controller 7 configured from the indoor-side controller 43 and the
outdoor-side controller 31 to perform control of each device of the
outdoor unit 2 and the indoor unit 4.
(2) Basic Operation of Air Conditioning Apparatus
[0041] Next, the basic operation (operation excluding high pressure
control described later) of the air conditioning apparatus 1 will
be described.
[0042] When the compressor 21, the outdoor fan 26 serving as the
blower fan, and the indoor fan 42 are started, low-pressure gas
refrigerant is sucked into the compressor 21, is compressed, and
becomes high-pressure gas refrigerant. Thereafter, the
high-pressure gas refrigerant is sent to the outdoor heat exchanger
22 serving as the condenser, condenses in the outdoor heat
exchanger 22 as a result of undergoing heat exchange with the
outside air supplied by the outdoor fan 26 serving as the blower
fan and being cooled, and becomes high-pressure liquid refrigerant.
Then, the high-pressure liquid refrigerant that has condensed in
the outdoor heat exchanger 22 is sent to the indoor unit 4 via the
outdoor expansion valve EV1 (here, in a completely open state)
serving as the first expansion valve, the receiver 23, the
liquid-side stop valve 24, and the liquid refrigerant connection
pipe 5. This high-pressure liquid refrigerant that has been sent to
the indoor unit 4 has its pressure reduced by the indoor expansion
valve EV2 serving as the second expansion valve, becomes
low-pressure refrigerant in a gas-liquid two-phase state, is sent
to the indoor heat exchanger 41, evaporates in the indoor heat
exchanger 41 as a result of undergoing heat exchange with the room
air supplied by the indoor fan 42 and being heated, and becomes
low-pressure gas refrigerant. This low-pressure gas refrigerant
that has evaporated in the indoor heat exchanger 41 is sent to the
outdoor unit 2 via the gas refrigerant connection pipe 6 and the
gas-side stop valve 25 and is again sucked into the compressor 21.
In this manner, in the refrigerant circuit 10 of the air
conditioning apparatus 1 of the present embodiment, a refrigeration
cycle operation that cools the inside of the room is performed.
[0043] However, within this basic operation, the heat exchange
efficiency in the outdoor heat exchanger 22 comes to fluctuate
because the temperature difference between the saturation
temperature of the refrigerant in the outdoor heat exchanger 22 and
the air temperature fluctuates depending on fluctuations in the
outside air temperature. To counter this, conventionally, sometimes
control is performed with respect to the air flow rate of the
outdoor fan 26 such that high pressure in the refrigeration cycle
operation (in the present embodiment, the pressure of the
refrigerant flowing from the discharge side of the compressor 21,
through the outdoor heat exchanger 22, and into the outdoor
expansion valve EV1) becomes a target high pressure, but with just
air flow rate control of the outdoor fan 26, the heat exchange
efficiency in the outdoor heat exchanger 22 drops and therefore
there is the fear that the operating efficiency of the air
conditioning apparatus 1 overall cannot be optimized because
sometimes the air flow rate can only be changed stepwise, it is
difficult to control the high pressure finely, and the temperature
difference between the saturation temperature of the refrigerant in
the outdoor heat exchanger 22 and the temperature of the air
becomes smaller particularly when the outside air temperature is
high.
[0044] Thus, in the present embodiment, the air conditioning
apparatus 1 is configured such that the high pressure can be
controlled finely mainly not just by air flow rate control of the
outdoor fan 26 but by jointly using opening degree control of the
outdoor expansion valve EV1.
(3) Regarding Control of Outdoor Expansion Valve, Outdoor Fan, and
Indoor Expansion Valve
[0045] Next, control of the outdoor expansion valve EV1 serving as
the first expansion valve, the outdoor fan 26 serving as the blower
fan, and the indoor expansion valve EV2 serving as the second
expansion valve in the present embodiment will be described using
FIGS. 1 to 7. Here, FIG. 3 is a flowchart mainly showing control of
the outdoor expansion valve EV1 of the air conditioning apparatus 1
pertaining to the present embodiment, FIG. 4 is a flowchart mainly
showing control of the outdoor fan 26 of the air conditioning
apparatus 1 pertaining to the present embodiment, FIG. 5 is a
diagram showing the distribution (excluding the insides of the
pipes) of liquid refrigerant when the high pressure in the air
conditioning apparatus 1 pertaining to the present embodiment is
stable at a standard pressure, FIG. 6 is a diagram showing the
distribution (excluding the insides of the pipes) of liquid
refrigerant when the high pressure in the air conditioning
apparatus 1 pertaining to the present embodiment is stable at a
high pressure, and FIG. 7 is a diagram showing the distribution
(excluding the insides of the pipes) of liquid refrigerant when the
high pressure in the air conditioning apparatus 1 pertaining to the
present embodiment is stable at a low pressure.
<Regarding Operation of Outdoor Expansion Valve>
[0046] First, regarding the control in the present embodiment, the
operation of the outdoor expansion valve EV1 will be centrally
described using FIG. 3.
[0047] In step S1, the outdoor expansion valve EV1 is placed in a
completely open state, and in step S2, it is determined whether or
not the outdoor fan 26 serving as the blower fan has reached a
prescribed air flow rate. Here, the step of changing the air flow
rate of the outdoor fan 26 is divided into plural stages, and
"prescribed air flow rate" means any of these plural steps of
changing the air flow rate. Additionally, when the flow moves from
step S1 to step S2, the prescribed air flow rate of the outdoor fan
26 is set to a predetermined initial air flow rate. In this manner,
until the air flow rate of the outdoor fan 26 reaches the
prescribed air flow rate of the outdoor fan 26 by the processing of
steps S2 and S3, changing of the air flow rate of the outdoor fan
26 in step S3 is performed, and then the flow moves to the
processing of step S4.
[0048] Next, in step S4, it is determined whether or not the
opening degree of the outdoor expansion valve EV1 is smaller than a
minimum opening degree+.alpha.. Here, a means a fluctuation in the
opening degree of the outdoor expansion valve EV1 that is needed
until the inside of the refrigerant circuit 10 becomes stable by
changing the prescribed air flow rate of the outdoor fan 26.
Additionally, when the flow first moves from step S2 to step S4,
the outdoor expansion valve EV1 is in the completely open state and
its opening degree is not smaller than the minimum opening
degree+.alpha., so the flow moves to the processing of step S5.
[0049] Next, in step S5, it is determined whether or not the high
pressure in the refrigeration cycle operation is larger than a
lower limit value of a target high pressure. Here, the discharge
pressure detected by the discharge pressure sensor 28 is used for
the high pressure.
[0050] Further, the target high pressure is defined as a pressure
range between a lower limit value and an upper limit value, and
these are set on the basis of conditions such as the operating
capacity of the compressor 21 and the outside air temperature in
step S13 described later. Then, when it has been determined in step
S5 that the high pressure in the refrigeration cycle operation is
not larger than the lower limit value of the target high pressure,
the flow moves to the processing of step S6 where a closing
operation that decreases the opening degree of the outdoor
expansion valve EV1 is performed, the flow returns to the
processing of step S4, and the closing operation of the outdoor
expansion valve EV1 in step S6 is repeated until it is determined
in step S4 that the opening degree of the outdoor expansion valve
EV1 is smaller than the minimum opening degree+.alpha. or until it
is determined in step S5 that the high pressure in the
refrigeration cycle operation is larger than the lower limit value
of the target high pressure. Then, when it has been determined in
step S5 that the high pressure in the refrigeration cycle operation
is larger than the lower limit value of the target high pressure,
the flow moves to the processing of step S7.
[0051] Next, in step S7, it is determined whether or not the high
pressure in the refrigeration cycle operation is larger than the
upper limit value of the target high pressure. Then, when it has
been determined in step S7 that the high pressure in the
refrigeration cycle operation is not larger than the upper limit
value of the target high pressure, the flow moves to the processing
of step S8 where the opening degree of the outdoor expansion valve
EV1 is maintained at the current opening degree. Further, when it
has been determined in step S7 that the high pressure in the
refrigeration cycle operation is larger than the upper limit value
of the target high pressure, the flow moves to the processing of
step S9 where an opening operation that increases the opening
degree of the outdoor expansion valve EV1 is performed, and then
the flow moves to the processing of step S10.
[0052] Next, in step S10, it is determined whether or not the
opening degree of the outdoor expansion valve EV1 is greater than
completely open-.beta.. Here, .beta. means a fluctuation in the
opening degree of the outdoor expansion valve EV1 that is needed
until the inside of the refrigerant circuit 10 becomes stable by
changing the prescribed air flow rate of the outdoor fan 26. Then,
when it has been determined in step S10 that the opening degree of
the outdoor expansion valve EV1 is not larger than completely
open-.beta., the flow returns to the processing of step S4 and goes
through the processing of steps S4 and S5, and the opening
operation of the outdoor expansion valve EV1 in step S9 is repeated
until it is determined in step S7 that the high pressure in the
refrigeration cycle operation is larger than the upper limit value
of the target high pressure or until it is determined in step S10
that the opening degree of the outdoor expansion valve EV1 is
larger than completely open-.beta..
[0053] In this manner, in the present embodiment, control of the
opening degree of the outdoor expansion valve EV1 is performed such
that the high pressure in the refrigeration cycle operation falls
inside the pressure range between the lower limit value and the
upper limit value of the target high pressure in a state where the
outdoor fan 26 has been set to a certain prescribed air flow
rate.
[0054] However, when it has not been determined in step S5 that the
high pressure in the refrigeration cycle operation is larger than
the lower limit value of the target high pressure and it has been
determined in step S4 that the opening degree of the outdoor
expansion valve EV1 is smaller than the minimum opening
degree+.alpha., or when it has not been determined in step S7 that
the high pressure in the refrigeration cycle operation is not
larger than the upper limit value of the target high pressure and
it has been determined in step S10 that the opening degree of the
outdoor expansion valve EV1 is larger than completely open-.beta.,
the high pressure in the refrigeration cycle operation cannot fall
inside the pressure range between the lower limit value and the
upper limit value of the target high pressure by just opening
degree control of the outdoor expansion valve EV1, and so the flow
moves to the processing of step S11 where the prescribed air flow
rate is changed by air flow rate control of the outdoor fan 26,
thereafter the flow returns to the processing of steps S2 and S3,
and then opening degree control of the outdoor expansion valve EV1
comprising steps S4 to S10 is again performed.
<Regarding Operation of Outdoor Fan>
[0055] Next, regarding the control in the present embodiment, the
operation of the outdoor fan 26 will be centrally described using
FIG. 4.
[0056] First, in step S12, the operating capacity of the compressor
21 is decided on the basis of conditions such as the evaporation
temperature, and the operating capacity of the compressor 21 is set
by frequency control of the compressor motor 21a. Here, a value
obtained by converting the suction pressure detected by the suction
pressure sensor 27 into the saturation temperature is used for the
evaporation temperature. Then, in step S13, a target high pressure
(here, a lower limit value and an upper limit value) is set on the
basis of conditions such as the operating capacity of the
compressor 21 decided that was in step S12 and the outside air
temperature.
[0057] Next, in step S14, like in step S7 described above, it is
determined whether or not the high pressure in the refrigeration
cycle operation is larger than the upper limit value of the target
high pressure. Then, when it has been determined in step S14 that
the high pressure in the refrigeration cycle operation is larger
than the upper limit value of the target high pressure, the flow
moves to the processing of step S15 where, like in step S10
described above, it is determined whether or not the opening degree
of the outdoor expansion valve EV1 is larger than completely
open-.beta.. Then, when it has been determined in step S15 that the
opening degree of the outdoor expansion valve EV1 is not larger
than completely open-.beta., the flow moves to step S16 where it
waits for the opening degree control of the outdoor expansion valve
EV1 described above to be reflected, and then the flow returns to
the processing of step S12. Further, when it has been determined in
step S15 that the opening degree of the outdoor expansion valve EV1
is larger than completely open-.beta., the flow moves to step S17,
which corresponds to step S11 described above, where the prescribed
air flow rate of the outdoor fan 26 is changed in a direction in
which it is increased, and then the flow returns to the processing
of step S12. Further, when it has been determined in step S14 that
the high pressure in the refrigeration cycle operation is not
larger than the upper limit value of the target high pressure, the
flow moves to the processing of step S18.
[0058] Next, in step S18, which corresponds to step S5 described
above, it is determined whether or not the high pressure in the
refrigeration cycle operation is smaller than the lower limit value
of the target high pressure. Then, when it has been determined in
step S18 that the high pressure in the refrigeration cycle
operation is smaller than the lower limit value of the target high
pressure, the flow moves to the processing of step S19 where, like
in step S10 described above, it is determined whether or not the
opening degree of the outdoor expansion valve EV1 is smaller than
the minimum opening degree+.alpha.. Then, when it has been
determined in step S19 that the opening degree of the outdoor
expansion valve EV1 is not smaller than the minimum opening
degree+.alpha., the flow moves to step S20 where it waits for the
opening degree control of the outdoor expansion valve EV1 described
above to be reflected, and then the flow returns to the processing
of step S12. Further, when it has been determined in step S19 that
the opening degree of the outdoor expansion valve EV1 is smaller
than the minimum opening degree+.alpha., the flow moves to step
S21, which corresponds to step S11 described above, where the
prescribed air flow rate of the outdoor fan 26 is changed in a
direction in which it is decreased, and then the flow returns to
step S12. Further, also when it has been determined in step S18
that the high pressure in the refrigeration cycle operation is not
smaller than the lower limit value of the target high pressure, the
flow returns to the processing of step S12.
[0059] In this manner, in the present embodiment, control of the
opening degree of the outdoor expansion valve EV1 is performed such
that the high pressure becomes the target high pressure in a state
where air flow rate control of the outdoor fan 26 has been
performed such that the air flow rate of the outdoor fan 26 becomes
the prescribed air flow rate, and when the high pressure does not
become the target high pressure by opening degree control of the
outdoor expansion valve EV1, control by which the prescribed air
flow rate is changed by air flow rate control of the outdoor fan 26
is performed.
<Regarding Operation of Indoor Expansion Valve>
[0060] In the present embodiment, together with the opening degree
control of the outdoor expansion valve EV1 and the air flow rate
control of the outdoor fan 26 described above, the opening degree
of the indoor expansion valve EV2 is controlled such that the
degree of superheat of the refrigerant in the outlet of the indoor
heat exchanger 41 serving as the evaporator becomes a target degree
of superheat. Here, the degree of superheat of the refrigerant in
the outlet of the indoor heat exchanger 41 is obtained by
converting the suction pressure detected by the suction pressure
sensor 27 into the saturation temperature and subtracting this
saturation temperature from the suction temperature detected by the
suction temperature sensor 29.
<Regarding Specific Examples of Control in Present
Embodiment>
[0061] Next, specific examples of the opening degree control of the
outdoor expansion valve EV1, the air flow rate control of the
outdoor fan 26, and the opening degree control of the indoor
expansion valve EV2 described above will be described using FIG. 3
to FIG. 7.
[0062] First, when the high pressure in the refrigeration cycle
operation is stable at a standard pressure as a result of the
opening degree control of the outdoor expansion valve EV1, the air
flow rate control of the outdoor fan 26, and the opening degree
control of the indoor expansion valve EV2 described above being
performed, the distribution (excluding the insides of the pipes) of
the liquid refrigerant in the refrigerant circuit 10 becomes the
state shown in FIG. 5 (the hatchings shown in the outdoor heat
exchanger 22, the receiver 23, and the indoor heat exchanger 41
represent the liquid refrigerant).
[0063] In contrast, when the high pressure in the refrigeration
cycle operation is stable at a high pressure as a result of the
opening degree control of the outdoor expansion valve EV1, the air
flow rate control of the outdoor fan 26, and the opening degree
control of the indoor expansion valve EV2 described above being
performed, the quantity of the liquid refrigerant accumulating in
the outdoor heat exchanger 22 increases as shown in FIG. 6 because
the opening degree of the outdoor expansion valve EV1 becomes
smaller because of the closing operation of the outdoor expansion
valve EV1 in step S6, and so the interior capacity of the outdoor
heat exchanger 22 decreases. In other words, when the opening
degree of the outdoor expansion valve EV1 becomes smaller because
of the closing operation of the outdoor expansion valve EV1, the
quantity of the liquid refrigerant accumulating in the outdoor heat
exchanger 22 increases and the interior capacity of the outdoor
heat exchanger 22 decreases, so the high pressure in the
refrigeration cycle operation can be made into a high pressure.
Moreover, in the present embodiment, the receiver 23 is connected
between the outdoor expansion valve EV1 and the indoor expansion
valve EV2, so as shown in FIG. 6, the increase in the quantity of
the liquid refrigerant accumulating in the outdoor heat exchanger
22 that arises because of the closing operation of the outdoor
expansion valve EV1 is absorbed as a result of the quantity of the
liquid refrigerant accumulating in the receiver 23 decreasing.
Therefore, the state of the refrigerant sent from the receiver 23
to the indoor heat exchanger 41 is stable, and it becomes difficult
for the quantity of the refrigerant in the portion of the
refrigerant circuit 10 from the indoor expansion valve EV2 via the
indoor heat exchanger 41 to the compressor 21 to fluctuate.
Moreover, in the present embodiment, opening degree control of the
indoor expansion valve EV2 is performed such that the degree of
superheat of the refrigerant in the outlet of the indoor heat
exchanger 41 becomes the target degree of superheat, so as shown in
FIG. 6, there become fewer increases and decreases in the quantity
of the liquid refrigerant in the indoor heat exchanger 41, and the
quantity of the refrigerant in the indoor heat exchanger 41 and the
state of the refrigerant in the outlet of the indoor heat exchanger
41 can be stabilized.
[0064] Further, when the high pressure in the refrigeration cycle
operation is stable at a low pressure as a result of the opening
degree control of the outdoor expansion valve EV1, the air flow
rate control of the outdoor fan 26, and the opening degree control
of the indoor expansion valve EV2 described above being performed,
the quantity of the liquid refrigerant accumulating in the outdoor
heat exchanger 22 decreases as shown in FIG. 7 because the opening
degree of the outdoor expansion valve EV1 becomes larger because of
the opening operation of the outdoor expansion valve EV1 in step
S8, and so the interior capacity of the outdoor heat exchanger 22
increases. In other words, when the opening degree of the outdoor
expansion valve EV1 becomes larger because of the opening operation
of the outdoor expansion valve EV1, the quantity of the liquid
refrigerant accumulating in the outdoor heat exchanger 22 decreases
and the interior capacity of the outdoor heat exchanger 22
increases, so the high pressure in the refrigeration cycle
operation can be made into a low pressure. Moreover, in the present
embodiment, the receiver 23 is connected between the outdoor
expansion valve EV1 and the indoor expansion valve EV2, so as shown
in FIG. 7, the decrease in the quantity of the liquid refrigerant
accumulating in the outdoor heat exchanger 22 that arises because
of the opening operation of the outdoor expansion valve EV1 is
absorbed as a result of the quantity of the liquid refrigerant
accumulating in the receiver 23 increasing. Therefore, the state of
the refrigerant sent from the receiver 23 to the indoor heat
exchanger 41 is stable, and it becomes difficult for the quantity
of the refrigerant in the portion of the refrigerant circuit 10
from the indoor expansion valve EV2 via the indoor heat exchanger
41 to the compressor 21 to fluctuate. Moreover, in the present
embodiment, opening degree control of the indoor expansion valve
EV2 is performed such that the degree of superheat of the
refrigerant in the outlet of the indoor heat exchanger 41 becomes
the target degree of superheat, so as shown in FIG. 7, there become
fewer increases and decreases in the quantity of the liquid
refrigerant in the indoor heat exchanger 41, and the quantity of
the refrigerant in the indoor heat exchanger 41 and the state of
the refrigerant in the outlet of the indoor heat exchanger 41 can
be stabilized.
(4) Characteristics of Present Embodiment
[0065] The air conditioning apparatus 1 of the present embodiment
has the following characteristics.
<A>
[0066] In the air conditioning apparatus 1 of the present
embodiment, the quantity of the refrigerant accumulating in the
outdoor heat exchanger 22 serving as the condenser is adjusted by
controlling the opening degree of the outdoor expansion valve EV1
serving as the first expansion valve, and therefore control of the
high pressure can be performed, so even in an operating condition
where the temperature difference between the saturation temperature
of the refrigerant in the outdoor heat exchanger 22 and the
temperature of the air is small and where it is easy for the heat
exchange efficiency in the outdoor heat exchanger 22 to drop, like,
for example, when the outside air temperature is high, the high
pressure can be raised and a situation where the heat exchange
efficiency in the outdoor heat exchanger 22 drops can be
suppressed. Further, also with respect to hunting between steps of
the air flow rate of the outdoor fan 26 when the outside air
temperature is low, in a situation where the high pressure falls
too much in a step where the air flow rate is large, the high
pressure can be maintained by accumulating the refrigerant in the
outdoor heat exchanger 22, and in a situation where the high
pressure rises too much in a step where the air flow rate is small,
the high pressure can be maintained by decreasing the refrigerant
accumulating in the outdoor heat exchanger 22.
[0067] In this manner, in the air conditioning apparatus 1 of the
present embodiment, not just air flow rate control of the outdoor
fan 26 serving as the blower fan but opening degree control of the
outdoor expansion valve EV1 is jointly used, so the high pressure
can be controlled finely. This is particularly effective when using
an outdoor fan whose air flow rate can only be changed stepwise
like the outdoor fan 26 of the present embodiment.
<B>
[0068] In the air conditioning apparatus 1 of the present
embodiment, control is performed such that the high pressure
becomes the target high pressure by opening degree control of the
outdoor expansion valve EV1, and basically opening degree control
of the outdoor expansion valve EV1 becomes performed preferentially
over air flow rate control of the outdoor fan 26 because the
prescribed air flow rate of the outdoor fan 26 is changed when the
high pressure does not become the target high pressure by just
opening degree control of the outdoor expansion valve EV1, so the
high pressure can be controlled even more finely.
<C>
[0069] In the air conditioning apparatus 1 of the present
embodiment, the quantity of the refrigerant accumulating in the
outdoor heat exchanger 22 fluctuates because of opening degree
control of the outdoor expansion valve EV1, but because this
fluctuation in the quantity of the refrigerant is absorbed as a
result of the quantity of the refrigerant accumulating in the
receiver 23 fluctuating and the state of the refrigerant sent to
the indoor heat exchanger 41 serving as the evaporator is stable, a
situation where the quantity of the refrigerant in the indoor heat
exchanger 41 fluctuates or where the state of the refrigerant
sucked into the compressor 21 fluctuates, for example, can be
suppressed.
[0070] In this manner, in the air conditioning apparatus 1 of the
present embodiment, even though control is performed such that the
high pressure becomes the target high pressure by jointly using
opening degree control of the outdoor expansion valve EV1 together
with air flow rate control of the outdoor fan 26, it becomes
difficult for the quantity of the refrigerant in the portion of the
refrigerant circuit 10 from the indoor expansion valve EV2 via the
indoor heat exchanger 41 to the compressor 21 to fluctuate because
the receiver 23 that can accumulate the refrigerant is connected
between the outdoor expansion valve EV1 and the indoor expansion
valve EV2 serving as the second expansion valve, and therefore it
can be made difficult for the control to affect the operating state
of the indoor heat exchanger 41 or the compressor 21.
<D>
[0071] In the air conditioning apparatus 1 of the present
embodiment, it can be made difficult for the quantity of the
refrigerant in the portion of the refrigerant circuit 10 from the
indoor expansion valve EV2 via the indoor heat exchanger 41 to the
compressor 21 to fluctuate because of the receiver 23, and the
quantity of the refrigerant in the indoor heat exchanger 41 and the
state of the refrigerant in the outlet of the indoor heat exchanger
41 can be stabilized by opening degree control of the indoor
expansion valve EV2, so the operating efficiency of the air
conditioning apparatus 1 overall can be optimized and the
reliability of the compressor 21 can be improved (e.g., out-of-gas
operation and wet compression can be prevented).
(5) Other Embodiments
[0072] An embodiment of the present invention has been described
above on the basis of the drawings, but the specific configurations
thereof are not limited to this embodiment and can be changed in a
range not departing from the gist of the invention.
<A>
[0073] In the embodiment described above, an example has been
described where the present invention was applied to the separate
type air conditioning apparatus 1 where the compressor 21 and the
outdoor heat exchanger 22 are disposed in the outdoor unit 2, but
the present invention is not limited to this and may also be
applied to air conditioning apparatus of other unit configurations,
such as a remote condenser type air conditioning apparatus where
the compressor 21 is disposed in the indoor unit 4.
[0074] Further, in the embodiment described above, an example has
been described where the present invention was applied to the
dedicated cooling type air conditioning apparatus 1 that performs
only cooling, but the present invention is not limited to this and
may also be applied to air conditioning apparatus of other types,
such as a cooling-and-heating switchable type air conditioning
apparatus that can switch between cooling and heating and a
simultaneous cooling-and-heating type air conditioning apparatus
that can simultaneously perform cooling and heating.
<B>
[0075] In the embodiment described above, the discharge pressure
detected by the discharge pressure sensor 28 was used as the high
pressure, but the present invention is not limited to this, and
temperatures or pressures detected by other types of sensors may
also be used; for example, when a temperature sensor is disposed in
the outdoor heat exchanger 22, the refrigerant temperature detected
by this temperature sensor may be converted to the saturation
pressure and used as the high pressure.
[0076] Further, in the embodiment described above, the target high
pressure was defined as a pressure range between the lower limit
value of the high pressure and the upper limit value of the high
pressure, but the target high pressure is not limited to this and
may also, for example, be a single pressure value.
<C>
[0077] In the embodiment described above, the opening degree of the
indoor expansion valve EV2 serving as the second expansion valve is
controlled such that the degree of superheat of the refrigerant in
the outlet of the indoor heat exchanger 41 serving as the
evaporator becomes the target degree of superheat, but the present
invention is not limited to this; the opening degree of the indoor
expansion valve EV2 may also be controlled such that a state
quantity equivalent to the degree of superheat of the refrigerant
in the outlet of the indoor heat exchanger 41, such as the degree
of superheat of the refrigerant in the discharge of the compressor
21, becomes a target state quantity equivalent to the target degree
of superheat. Here, the degree of superheat of the refrigerant in
the discharge of the compressor 21 is obtained by subtracting, from
the discharge temperature of the compressor 21 (the discharge
temperature detected by the discharge temperature sensor 30), a
value obtained by converting the discharge pressure of the
compressor 21 (the discharge pressure detected by the discharge
pressure sensor 28) into the saturation temperature.
<D>
[0078] In the embodiment described above, opening and closing the
outdoor expansion valve EV1 depending on whether the high pressure
is high or low with respect to the target high pressure has been
described, but the speed at which the outdoor expansion valve EV1
is opened and closed may also be varied depending on the difference
between the high pressure and the target high pressure, and PI
control or the like may also be applied in relation to deciding the
speed at which the outdoor expansion valve EV1 is opened and
closed.
<E>
[0079] In the embodiment described above, controlling the outdoor
expansion valve EV1 before or during changing the air flow rate of
the outdoor fan 26 has not been described, but changes in the high
pressure resulting from changing the air flow rate of the outdoor
fan 26 may be predicted beforehand, and feed-forward control that
performs control to open and close the outdoor expansion valve EV1
by a predetermined opening degree beforehand or performs control to
open and close the outdoor expansion valve EV1 at a predetermined
speed within a predetermined amount of time beforehand may also be
performed.
INDUSTRIAL APPLICABILITY
[0080] The present invention is widely applicable to air
conditioning apparatus that are equipped with a blower fan that
supplies air as a heat source to a condenser that configures a
refrigerant circuit and which air conditioning apparatus can
control the air flow rate of the blower fan such that high pressure
in a refrigeration cycle operation becomes a target high
pressure.
Reference Signs List
[0081] 1 Air Conditioning Apparatus
[0082] 10 Refrigerant Circuit
[0083] 21 Compressor
[0084] 22 Outdoor Heat Exchanger (Condenser)
[0085] 23 Receiver
[0086] 26 Outdoor Fan (Blower Fan)
[0087] 41 Indoor Heat Exchanger (Evaporator)
[0088] EV1 Outdoor Expansion Valve (First Expansion Valve)
[0089] EV2 Indoor Expansion Valve (Second Expansion Valve)
Citation List
Patent Literature
[0090] Patent Literature 1: JP-A No. 1-225852
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