U.S. patent application number 09/731409 was filed with the patent office on 2001-11-08 for air conditioner.
This patent application is currently assigned to SANYO ELECTRIC CO., LTD.. Invention is credited to Ito, Shinichi, Kaeriyama, Haruyuki, Kobayashi, Kenji, Nishino, Shigetaka, Ogawa, Takeshi, Tsuzurano, Naoki.
Application Number | 20010037654 09/731409 |
Document ID | / |
Family ID | 26578442 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010037654 |
Kind Code |
A1 |
Kobayashi, Kenji ; et
al. |
November 8, 2001 |
Air conditioner
Abstract
In an air conditioner including a compressor, a four-way valve,
an outdoor heat exchanger, a pressure-reducing mechanism, an indoor
heat exchanger and an accumulator which are successively connected
to one another to construct a loop-like refrigerant circuit,
non-azeotropic mixture refrigerant composed of first refrigerant
having a high boiling point and second refrigerant having a low
boiling point being filled in the refrigerant circuit and the flow
of the non-azeotropic mixture refrigerant being inverted between
cooling operation and heating operation by operating the four-way
valve, when one of the outdoor heat exchanger and the indoor heat
exchanger serves as an evaporator, the first refrigerant of the
non-azeotropic mixture refrigerant is stocked in the accumulator
while the second refrigerant of the non-azeotropic mixture
refrigerant is circulated in the refrigerant circuit, thereby
increasing the refrigerant pressure in the evaporator.
Inventors: |
Kobayashi, Kenji;
(Nitta-gun, JP) ; Kaeriyama, Haruyuki; (Ota-shi,
JP) ; Tsuzurano, Naoki; (Nitta-gun, JP) ;
Nishino, Shigetaka; (Oura-gun, JP) ; Ito,
Shinichi; (Oura-gun, JP) ; Ogawa, Takeshi;
(Ashikaga-shi, JP) |
Correspondence
Address: |
PAUL FIELDS, ESQ.
DARBY & DARBY P.C.
805 Third Avenue
New York
NY
10022
US
|
Assignee: |
SANYO ELECTRIC CO., LTD.
|
Family ID: |
26578442 |
Appl. No.: |
09/731409 |
Filed: |
December 6, 2000 |
Current U.S.
Class: |
62/222 ;
62/223 |
Current CPC
Class: |
F25B 45/00 20130101;
F25B 2400/03 20130101; F25B 13/00 20130101; F25B 2400/16 20130101;
F25B 9/006 20130101; F25B 49/02 20130101 |
Class at
Publication: |
62/222 ;
62/223 |
International
Class: |
F25B 041/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 1999 |
JP |
P11-347166 |
Dec 7, 1999 |
JP |
P11-347167 |
Claims
What is claimed is:
1. An air conditioner including a compressor, a four-way valve, an
outdoor heat exchanger, a pressure-reducing mechanism, an indoor
heat exchanger and an accumulator which are successively connected
to one another to construct a loop-like refrigerant circuit,
non-azeotropic mixture refrigerant composed of first refrigerant
having a high boiling point and second refrigerant having a low
boiling point being filled in the refrigerant circuit and the flow
of the non-azeotropic mixture refrigerant being inverted between
cooling operation and heating operation by operating the four-way
valve, characterized in that when one of said outdoor heat
exchanger and said indoor heat exchanger serves as an evaporator,
the first refrigerant of the non-azeotropic mixture refrigerant is
stocked in said accumulator while the second refrigerant of the
non-azeotropic mixture refrigerant is circulated in said
refrigerant circuit, thereby increasing the refrigerant pressure in
said evaporator.
2. The air conditioner as claimed in claim 1, wherein when the
outside temperature is low in cooling operation, the first
refrigerant of the non-azeotropic mixture refrigerant is stocked in
said accumulator while the second refrigerant of the non-azeotropic
mixture refrigerant is circulated in said refrigerant circuit,
thereby increasing the refrigerant pressure in the evaporator.
3. The air conditioner as claimed in claim 2, wherein said
pressure-reducing mechanism comprises an expansion valve, and the
stock of the first refrigerant into said accumulator is performed
by increasing the valve opening degree of said expansion valve when
the temperature of the refrigerant flowing in said indoor heat
exchanger is equal to a first predetermined temperature or
less.
4. The air conditioner as claimed in claim 3, wherein when the
temperature of the refrigerant flow in said indoor heat exchanger
is equal to a second predetermined temperature or less, the second
predetermined temperature being lower than the first predetermined
temperature, the number of revolution of an indoor fan for blowing
air to said indoor heat exchanger is increased.
5. The air conditioner as claimed in claim 2, wherein the number of
revolution of an outdoor fan for blowing air to said outdoor heat
exchanger is set to any one of plural levels in accordance with the
outside temperature.
6. The air conditioner as claimed in claim 1, wherein in heating
operation, the first refrigerant of the non-azeotropic mixture
refrigerant is stocked in said accumulator while the second
refrigerant of the non-azeotropic mixture refrigerant is circulated
in said refrigerant circuit, thereby increasing the refrigerant
pressure in said evaporator.
7. The air conditioner as claimed in claim 6, wherein said
pressure-reducing mechanism comprises an expansion valve, and the
stock of the first refrigerant into said accumulator is performed
by setting the valve opening degree of said expansion valve on the
basis of the room temperature when the heating operation is started
and on the basis of a target discharged refrigerant temperature
after a predetermined time elapses from the start of the heating
operation.
8. The air conditioner as claimed in claim 7, wherein the stock of
the first refrigerant into the accumulator on the basis of the room
temperature is performed by setting the valve opening degree of
said expansion valve to a predetermined fixed opening degree.
9. The air conditioner as claimed in claim 7, wherein the stock of
the first refrigerant into the accumulator is performed by setting
the valve opening degree of said expansion valve on the basis of
the temperature difference between the actual discharged
refrigerant temperature of the refrigerant discharged from said
compressor and a predetermined target discharged refrigerant
temperature so that the temperature difference is equal to
zero.
10. An air conditioner including a compressor, a four-way valve, an
outdoor heat exchanger, a pressure-reducing mechanism, an indoor
heat exchanger and an accumulator which are successively connected
to one another to construct a loop-like refrigerant circuit,
non-azeotropic mixture refrigerant composed of at least one first
refrigerant having a high boiling point and at least one second
refrigerant having a low boiling point being filled in the
refrigerant circuit and the flow of the non-azeotropic mixture
refrigerant being inverted between cooling operation and heating
operation by operating the four-way valve, characterized by further
including: a controller for controlling the pressure-reducing
degree of said pressure-reducing mechanism so that when the heating
operation is carried out or the cooling operation under a low
outside temperature is carried out, the first refrigerant of the
non-azeotropic mixture refrigerant is stocked in said accumulator
and the second refrigerant of the non-azeotropic mixture
refrigerant is circulated in said refrigerant circuit, thereby
increasing the refrigerant pressure in said evaporator.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an air conditioner using
non-azeotropic mixture refrigerant composed of refrigerant having a
high boiling point and refrigerant having a low boiling point.
[0003] 2. Description of the Related Art
[0004] In a heat pump type air conditioner, a compressor, a
four-way valve, an outdoor heat exchanger, a pressure-reducing
mechanism, an indoor heat exchanger and an accumulator are arranged
so as to be successively connected to one another in this order,
thereby constructing a loop-like refrigerant circuit. According to
this type air conditioner, the refrigerant is circulated through
the above parts in the above order under cooling operation by
operating the four-way valve, whereby the indoor heat exchanger
serves as an evaporator while the outdoor heat exchanger serves as
a condenser). On the other hand, the refrigerant is circulated
through the above parts in the opposite order to the above order,
whereby the indoor heat exchanger serves as a condenser (the
outdoor heat exchanger serves as an evaporator).
[0005] Recently, from the viewpoint of preventing the destruction
of the ozone layer, there has been such a tendency that
non-azeotropic mixture refrigerant composed of the mixture of
refrigerant having a high boiling point and refrigerant having low
boiling point, such as R407C or the like is used as refrigerant for
air conditioners. Further, particularly in North America, cooling
operation is carried out even in the winter season under which
outdoor temperature is low because an air conditioner is put in a
computer room or both of a heat source machine and an air
conditioner are put side by side in most cases.
[0006] When non-azeotropic mixture refrigerant as described above
is used, the refrigerant in the evaporator is harder to evaporate
as compared with the case where single refrigerant such as R22 or
the like is used, and thus the refrigerant pressure in the
evaporator is reduced. Therefore, for example when cooling
operation is carried out in such an air conditioner under a state
where the outside temperature is low, freezing is liable to occur
in the indoor heat exchanger. If the freezing is grown, the indoor
heat exchanger would be broken, or the evaporation of the
refrigerant in the indoor heat exchanger would be insufficient, so
that liquid-back to the compressor occurs and thus the compressor
is broken. Therefore, in order to avoid the above disadvantage, in
the cooling operation under the state that the outdoor temperature
is low, the compressor is stopped at the time when occurrence of
the freezing in the indoor heat exchanger starts. However, such a
control operation to the air conditioner makes it impossible to
carry out the cooling operation continuously, so that a stable
cooling effect cannot be achieved.
[0007] Further, when heating operation is carried out in such an
air conditioner as described above, frost is also liable to occur
in the outdoor heat exchanger serving as an evaporator even under
the cooling operation standard condition of JIS. When frost is
liable to occur in the outdoor heat exchanger in the heating
operation, the heating operation must be stopped for a long time to
carry out a defrost operation, resulting in reduction in the
heating power.
SUMMARY OF THE INVENTION
[0008] The present invention has been implemented in view of the
foregoing situation, and has an object to provide an air
conditioner which can suppress occurrence of freezing in an indoor
heat exchanger and thus show a stable cooling effect in cooling
operation under a state where the outside temperature is low even
when non-azeotropic mixture refrigerant is used.
[0009] Another object of the present invention is to provide an air
conditioner which can suppress occurrence of frost in an outdoor
heat exchanger in heating operation and thus enhance the heating
power.
[0010] In order to attain the above objects, according to a first
aspect of the present invention, an air conditioner including a
compressor, a four-way valve, an outdoor heat exchanger, a
pressure-reducing mechanism, an indoor heat exchanger and an
accumulator which are successively connected to one another to
construct a loop-like refrigerant circuit, non-azeotropic mixture
refrigerant composed of first refrigerant having a high boiling
point and second refrigerant having a low boiling point being
filled in the refrigerant circuit and the flow of the
non-azeotropic mixture refrigerant being inverted between cooling
operation and heating operation by operating the four-way valve, is
characterized in that when one of the outdoor heat exchanger and
the indoor heat exchanger serves as an evaporator, the first
refrigerant of the non-azeotropic mixture refrigerant is stocked in
the accumulator while the second refrigerant of the non-azeotropic
mixture refrigerant is circulated in the refrigerant circuit,
thereby increasing the refrigerant pressure in the evaporator.
[0011] According to a second aspect of the present invention, an
air conditioner including a compressor, a four-way valve, an
outdoor heat exchanger, a pressure-reducing mechanism, an indoor
heat exchanger and an accumulator which are successively connected
to one another to construct a loop-like refrigerant circuit,
non-azeotropic mixture refrigerant composed of first refrigerant
having a high boiling point and second refrigerant having a low
boiling point being filled in the refrigerant circuit and the flow
of the non-azeotropic mixture refrigerant being inverted between
cooling operation and heating operation by operating the four-way
valve, is characterized in that in cooling operation under a state
where the outside temperature is low, the first refrigerant of the
non-azeotropic mixture refrigerant is stocked in the accumulator
while the second refrigerant of the non-azeotropic mixture
refrigerant is circulated in the refrigerant circuit, thereby
increasing the refrigerant pressure in the evaporator.
[0012] In the air conditioner of the second aspect of the present
invention, the stock of the first refrigerant into the accumulator
is performed by increasing the valve opening degree of the
pressure-reducing mechanism (expansion valve) when the temperature
of the refrigerant flowing in the indoor heat exchanger is equal to
a first predetermined temperature or less.
[0013] In the air conditioner of the second aspect of the present
invention, when the temperature of the refrigerant flow in the
indoor heat exchanger is equal to a second predetermined
temperature or less, the second predetermined temperature being
lower than the first predetermined temperature, the number of
revolution of an indoor fan for blowing air to the indoor heat
exchanger is increased.
[0014] In the air conditioner of the second aspect of the present
invention, the number of revolution of an outdoor fan for blowing
air to the outdoor heat exchanger is set to any one of plural
levels in accordance with the outside temperature.
[0015] According to the second aspect of the present invention, in
the cooling operation under the state where the outside temperature
is low, the first refrigerant (the refrigerant having the high
boiling point) of the non-azeotropic mixture refrigerant is stocked
in the accumulator, and the second refrigerant (the refrigerant
having the low boiling point) of the non-azeotropic mixture
refrigerant is circulated in the refrigerant circuit. Therefore,
the refrigerant in the indoor heat exchanger serving as the
evaporator in the cooling operation is more liable to evaporate,
and thus the refrigerant pressure in the indoor heat exchanger is
increased. Therefore, occurrence of freezing in the indoor heat
exchanger can be suppressed in the cooling operation under the
state where the outside temperature is low.
[0016] Accordingly, the frequency at which the compressor must be
stopped in order to prevent the indoor heat exchanger or the
compressor from being broken due to occurrence of the freezing can
be remarkably reduced. Therefore, even when the non-azeotropic
mixture refrigerant is used, the cooling operation can be
continuously carried out under the state where the outdoor
temperature is low. As a result, the stable cooling effect can be
realized, and an excellent comfortable environment can be
achieved.
[0017] Further, since the refrigerant having the high boiling point
is positively stocked in the accumulator in the cooling operation
under the state where the outside temperature is low, there is not
required any receiver tank which has been hitherto disposed to
avoid the refrigerant from being stocked in the accumulator, and
this also enables omission of a pressure-reducing mechanism which
has been hitherto required to be disposed in the neighborhood of
the outdoor heat exchanger due to the disposition of the receiver
tank. As a result the refrigerant circuit can be simplified in
construction and the cost thereof can be lowered.
[0018] Still further, when the number of revolution of the indoor
fan for blowing air to the indoor heat exchanger is increased, the
refrigerant flowing in the indoor heat exchanger is more liable to
evaporate, so that the refrigerant pressure in the indoor heat
exchanger is increased and the refrigerant temperature is
increased. As a result, the refrigerant pressure in the indoor heat
exchanger serving as the evaporator is increased by circulating the
refrigerant having the low boiling point of the non-azeotropic
mixture refrigerant, whereby the effect of suppressing occurrence
of the freezing in the indoor heat exchanger can be enhanced and
thus the occurrence of the freezing in the indoor heat exchanger
can be more surely suppressed.
[0019] In addition, by stepwise adjusting the number of revolution
of the outdoor fan for blowing air to the outdoor heat exchanger in
accordance with the outside temperature, the refrigerant in the
outdoor heat exchanger serving as the condenser is harder to be
condensed, so that the refrigerant pressure in the outdoor heat
exchanger is increased and the refrigerant temperature is also
increased. This increases the refrigerant pressure in the indoor
heat exchanger serving as the evaporator and also increases the
refrigerant temperature, so that the occurrence of the freezing in
the indoor heat exchanger can be more surely suppressed.
[0020] According to a third aspect of the present invention, an air
conditioner including a compressor, a four-way valve, an outdoor
heat exchanger, a pressure-reducing mechanism, an indoor heat
exchanger and an accumulator which are successively connected to
one another to construct a loop-like refrigerant circuit,
non-azeotropic mixture refrigerant composed of first refrigerant
having a high boiling point and second refrigerant having a low
boiling point being filled in the refrigerant circuit and the flow
of the non-azeotropic mixture refrigerant being inverted between
cooling operation and heating operation by operating the four-way
valve, is characterized in that in heating operation, the first
refrigerant of the non-azeotropic mixture refrigerant is stocked in
the accumulator while the second refrigerant of the non-azeotropic
mixture refrigerant is circulated in the refrigerant circuit,
thereby increasing the refrigerant pressure in the evaporator.
[0021] In the third aspect of the present invention, the stock of
the first refrigerant into the accumulator is performed by setting
the valve opening degree of an expansion valve serving as the
pressure-reducing mechanism on the basis of the room temperature
when the heating operation is started and on the basis of a target
discharged refrigerant temperature after a predetermined time
elapses from the start of the heating operation.
[0022] In the third aspect of the present invention, the stock of
the first refrigerant into the accumulator on the basis of the room
temperature is performed by setting the valve opening degree of the
expansion valve to a predetermined fixed opening degree.
[0023] In the third aspect of the present invention, the stock of
the first refrigerant into the accumulator is performed by setting
the valve opening degree of the expansion valve on the basis of the
temperature difference between the actual discharged refrigerant
temperature of the refrigerant discharged from the compressor and a
predetermined target discharged refrigerant temperature so that the
temperature difference is equal to zero.
[0024] According to the air conditioner of the third aspect of the
present invention, under the heating operation, the refrigerant
having the high boiling point of the non-azeotropic mixture
refrigerant is stocked in the accumulator and the refrigerant
having the low boiling point is circulated in the refrigerant
circuit, so that the refrigerant in the outdoor heat exchanger
serving as the evaporator in the heating operation is more liable
to evaporate and thus the refrigerant pressure in the outdoor heat
exchanger is increased, thereby suppressing the frost in the
outdoor heat exchanger. Therefore, the ratio of the defrost
operating time to the heating operation is reduced. Further, since
the refrigerant having the low boiling point is circuited in the
refrigerant circuit under the heating operation, the refrigerant
pressure in the indoor heat exchanger serving as the condenser is
increased and thus the heating power of the indoor heat exchanger
can be enhanced. As a result, the heating power under the heating
operation as the whole air conditioner can be enhanced.
[0025] Further, since the refrigerant having the high boiling point
is stocked in the accumulator under the heating operation, there is
not required any receiver tank which has been hitherto disposed to
avoid the refrigerant from being stocked in the accumulator in the
refrigerant circuit, and this also enables omission of a
pressure-reducing mechanism which has been disposed in the
neighborhood of the outdoor heat exchanger because of the
disposition of the receiver tank. As a result, the refrigerant
circuit can be simplified in construction and the cost thereof can
be lowered.
[0026] According to a fourth aspect of the present invention, an
air conditioner including a compressor, a four-way valve, an
outdoor heat exchanger, a pressure-reducing mechanism, an indoor
heat exchanger and an accumulator which are successively connected
to one another to construct a loop-like refrigerant circuit,
non-azeotropic mixture refrigerant composed of at least one first
refrigerant having a high boiling point and at least one second
refrigerant having a low boiling point being filled in the
refrigerant circuit and the flow of the non-azeotropic mixture
refrigerant being inverted between cooling operation and heating
operation by operating the four-way valve, is characterized by
further including: a controller for controlling the
pressure-reducing degree of said pressure-reducing mechanism so
that when the heating operation is carried out or the cooling
operation under a low outside temperature is carried out, the first
refrigerant of the non-azeotropic mixture refrigerant is stocked in
said accumulator and the second refrigerant of the non-azeotropic
mixture refrigerant is circulated in said refrigerant circuit,
thereby increasing the refrigerant pressure in said evaporator.
[0027] According to the air conditioner of the fourth aspect of the
present invention, the pressure-reducing degree of said
pressure-reducing mechanism is controlled by the controller so that
when the heating operation is carried out or the cooling operation
under a low outside temperature is carried out, the first
refrigerant of the non-azeotropic mixture refrigerant is stocked in
said accumulator and the second refrigerant of the non-azeotropic
mixture refrigerant is circulated in said refrigerant circuit,
thereby increasing the refrigerant pressure in said evaporator.
Therefore, the refrigerant in each of the outdoor heat exchanger
and the indoor heat exchanger when they serves as the evaporator in
the heating operation or in the cooling operation under the low
outside temperature state is more liable to evaporate and thus the
refrigerant pressure in the evaporator is increased, thereby
suppressing the freezing or frost in the evaporator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a diagram showing a refrigerant circuit according
to a first embodiment of an air conditioner of the present
invention;
[0029] FIG. 2 is a flowchart showing cooling control under low
outside temperature in cooling operation of the air conditioner
shown in FIG. 1;
[0030] FIG. 3 is a diagram showing a refrigerant circuit according
to a second embodiment of the air conditioner of the present
invention; and
[0031] FIG. 4 is a flowchart showing discharged refrigerant
temperature control in heating operation of the air conditioner
shown in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Preferred embodiments according to the present invention
will be described hereunder with reference to the accompanying
drawings.
[0033] FIG. 1 is a diagram showing a refrigerant circuit according
to a first embodiment of an air conditioner (heat pump type air
conditioner) of the present invention.
[0034] As show in FIG. 1, a heat pump type air conditioner 10 of
this embodiment includes an outdoor unit 11, an indoor unit 12 and
a controller 13, and an outdoor refrigerant pipe 14 of the outdoor
unit 11 and an indoor refrigerant pipe 15 of the indoor unit 12 are
linked to each other.
[0035] The outdoor unit 11 is disposed outdoors, and it includes a
compressor 16, an accumulator 17 disposed at the suction side of
the compressor 16, a four-way valve 18 disposed at the discharge
side of the compressors 16 and an outdoor heat exchanger 19 at the
four-way valve (18) side, these parts being disposed so as to be
connected to one another through the outdoor refrigerant pipe 14.
In addition, an outdoor fan 20 for blowing air to the outdoor heat
exchanger 19 is disposed adjacently to the outdoor heat exchanger
19.
[0036] The indoor unit 12 is disposed in a room, and it includes an
indoor heat exchanger 21 and an expansion valve 22 serving as a
pressure-reducing mechanism disposed in the neighborhood of the
indoor heat ex(hanger 21, these parts being disposed so as to be
connected to each other through the indoor refrigerant pipe 15. An
indoor fan 23 for blowing air to the indoor heat exchanger 21 is
disposed so as to be adjacent to the indoor heat exchanger 21.
[0037] By linking the indoor refrigerant pipe 14 and the indoor
refrigerant pipe 15 to each other, the accumulator 17, the
compressor 16, the four-way valve 18, the outdoor heat exchanger
19, the expansion valve 22 and the indoor heat exchanger 21 are
successively linked to one another in this order, and the
accumulator 17 is linked through the four-way valve 18 to the
indoor heat exchanger 21, whereby the air conditioner 10 constructs
a loop-like refrigerant circuit 9.
[0038] The controller 13 controls the operation of the outdoor unit
11 and the indoor unit 12, and specifically it controls the
compressor 16, the four-way valve 18 and the outdoor fan 20 of the
outdoor unit 11, and the expansion valve 22 and the indoor fan 23
of the indoor unit 12.
[0039] The controller 13 switches the four-way valve 18 to set the
air conditioner 10 to one of the cooling operation and the heating
operation. That is, when the controller 13 switches the four-way
valve 18 to the cooling side, the refrigerant flows in a direction
indicated by a solid-line arrow. In this case, the outdoor heat
exchanger 19 serves as a condenser, and the indoor heat exchanger
21 serves as an evaporator to keep the air conditioner under the
cooling operation. That is, the indoor heat exchanger 21 cools the
interior of the room. On the other hand, when the controller 13
switches the four-way valve to the heating side, the refrigerant
flows in a direction indicated by a broken-line arrow. In this
case, the indoor heat exchanger 21 series as the condenser, and the
outdoor heat exchanger 19 serves as the evaporator to keep the air
conditioner under the heating operation. That is, the indoor heat
exchanger 21 heats the interior of the room.
[0040] Further, under the cooling operation and the heating
operation, the controller 13 controls the valve opening degree of
the expansion valve 22 serving as the pressure-reducing mechanism
and the number of revolution of each of the outdoor fan 20 and the
indoor fan 23 in accordance with the air conditioning load.
[0041] According to the first embodiment of the present invention,
the controller 13 adjusts the opening degree of the expansion valve
22 and the number of revolution of the outdoor fan 20 and the
indoor fan 23 as described later under the cooling operation to
perform a cooling control operation under a low outside
temperature. Here, the cooling control operation under the low
outside temperature means the control of the cooling operation when
the outside temperature is low, for example under the winter
season.
[0042] Here, the refrigerant used in the air conditioner of the
present invention is non-azeotropic mixture refrigerant formed by
mixing plural refrigerant materials which are different in boiling
point. For example, R407C may be used as the non-azeotropic mixture
refrigerant. R407C is three-components refrigerant in which 52 Wt %
of R134a, 25 Wt % of R125 and 23 wt % of R32 are mixed. The boiling
points of the respective refrigerant materials are as follows:
R134a (-26.degree. C.), R125 (-48.degree. C.) and R32 (-52.degree.
C.). Accordingly, R125 and R32 are more liable to evaporate because
the boiling points thereof are relatively low, and R134a is harder
to evaporate because the boiling point thereof is relatively
high.
[0043] In this embodiment, the controller 13 executed the following
cooling control operation under the low outside temperature in the
cooling operation so that the refrigerant having the higher boiling
point (R134a) of the non-azeotropic mixture refrigerant is stocked
in the accumulator 17 while the refrigerant having the lower
boiling point (R125 and R32) of the non-azeotropic mixture
refrigerant are circulated in the refrigerant circuit 9, thereby
varying the composition of the refrigerant circulated in the
refrigerant circuit 9.
[0044] In order to perform the cooling control operation under the
low outside temperature, an outside temperature sensor 24 is
provided to detect the temperature of the outside air sucked to the
outdoor heat exchanger 19 (that is, the outside temperature), and
the sucked air temperature thus detected is input to the controller
13. Further, an indoor heat exchanger temperature sensor 27 is
provided to detect the temperature of the refrigerant flowing at
the middle position between the inlet and outlet ports of the
indoor heat exchanger 21 (that is, the indoor heat exchanger
refrigerant temperature), and the indoor heat exchanger refrigerant
temperature thus detected is also input to the controller 13.
[0045] Under the cooling operation, the controller 13 carries out
the cooling control operation under the low outside temperature as
shown in the flowchart of FIG. 2. In the cooling control operation
under the low outside temperature, the controller 13 first controls
the outside temperature sensor 24 to detect the outside temperature
when the cooling operation is started (S1), and sets the number of
revolution of the outdoor fan 20 to one of plural levels (for
example, three levels) in conformity with the outside temperature
thus detected (S2).
[0046] The number of revolution of the outdoor fan 20 is stepwise
set to "strong blow", "middle blow" and "weak blow" in the
decreasing order of blowing intensity. For example, the controller
13 sets the number of revolution of the outdoor fan 20 to "strong
blow" when the outside temperature is above 25.degree. C., "middle
blow" when the outside temperature is in the range from 7.degree.
C. to 25.degree. C., and "weak blow" when the outside temperature
is below 7.degree. C.
[0047] By reducing the number of revolution of the outdoor fan 20
when the outside temperature is lower, the refrigerant in the
outdoor heat exchanger 19 serving as the condenser is harder to
evaporate, and the refrigerant pressure in the outdoor heat
exchanger 19 is increased and also the refrigerant temperature
rises up. As a result, the refrigerant pressure in the indoor heat
exchanger 21 serving as the evaporator is increased and also the
refrigerant temperature rises up, thereby suppressing occurrence of
freezing in the indoor heat exchanger 21.
[0048] Subsequently, the controller 13 judges whether the indoor
heat exchanger refrigerant temperature detected by the indoor heat
exchanger temperature sensor 27 is reduced to a first predetermined
temperature (for example, 1.degree. C.) or less (S3). If so, the
controller 13 increases the valve opening degree of the expansion
valve 22 to a value higher than a normal value (S4). For example,
the controller 13 sets the valve opening degree of the expansion
valve 22 to 60 steps per 30 seconds.
[0049] By increasing the valve opening degree of the expansion
valve 22 as described above, the amount of the refrigerant
circulating in the refrigerant circuit 9 is increased and thus the
refrigerant material (R134a) having a high boiling point which is
harder to evaporate in the non-azeotropic mixture refrigerant
(R407C) is stocked in the accumulator 17 while the refrigerant
materials (R125 and R32) having low boiling points which are more
liable to evaporate are circulated in the refrigerant circuit 9.
Accordingly, the composition of the refrigerant circulated in the
refrigerant circuit 9 is varied. As a result, the evaporation of
the refrigerant in the indoor heat exchanger 21 is promoted and the
refrigerant pressure in the indoor heat exchanger is increased,
thereby suppressing occurrence of freezing in the indoor heat
exchanger 21.
[0050] Further, the increase of the valve opening degree of the
expansion valve 22 lowers the pressure-reducing level of the
refrigerant by the expansion valve 22, so that the refrigerant
pressure in the indoor heat exchanger 21 is increased and thus the
refrigerant temperature is increased, whereby the occurrence of
freezing in the indoor heat exchanger 21 can be further
suppressed.
[0051] Subsequently, the controller 13 judges whether the in door
heat exchanger refrigerant temperature detected by the indoor heat
exchanger temperature sensor 27 is further reduced to a second
predetermined temperature (lower than the first predetermined
temperature) or less (for example, 0.degree. C. or less) (S5). If
the indoor heat exchanger refrigerant temperature is below
0.degree. C., the controller 13 controls to increase the number of
revolution of the indoor fan 23 (S6). When the number of revolution
of the indoor fan 23 is set to three stepwise levels of "strong
blow", "middle blow" and "weak blow" in the blow-intensity
decreasing order, the controller 13 sets the number of revolution
of the indoor fan 23 from "weak blow" to "middle blow".
[0052] When the number of revolution of the indoor fan 23 is
increased, the refrigerant in the indoor heat exchanger 21 is more
liable to evaporate, so that the refrigerant pressure in the indoor
heat exchanger 21 is increased and the refrigerant temperature is
increased, thereby suppressing the occurrence of freezing in the
indoor heat exchanger 21. This; freezing suppressing effect further
promotes the freezing suppressing effect achieved due to the
composition variation effect that the main refrigerant flowing in
the indoor heat exchanger 21 is the refrigerant materials having
the low boiling points (R125 and R35).
[0053] Therefore, according to this embodiment, the following
effects can be achieved.
[0054] (1) In the cooling operation under the low outside
temperature state, the refrigerant having the high boiling point in
the non-azeotropic mixture refrigerant is stocked in the
accumulator 17, and the refrigerant having the low boiling point in
the non-azeotropic mixture refrigerant is circulated in the
refrigerant circuit. Therefore, the refrigerant in the indoor heat
exchanger serving as the evaporator in the cooling operation is
more liable to evaporate, and thus the refrigerant pressure in the
indoor heat exchanger 21 is increased, so that the occurrence of
freezing in the indoor heat exchanger 21 can be suppressed in the
cooling operation under the low outside temperature state.
Accordingly, the frequency at which the compressor 16 is stopped
because the breaking of the indoor heat exchanger 21 and the
breaking of the compressor due to liquid-back are prevented when
freezing occurs can be reduced. Therefore, even when any
non-azeotropic mixture refrigerant is used, the cooling operation
can be continuously performed even when the outside temperature is
low. As a result, a stable cooling effect can be achieved and an
excellent comfortable environment can be achieved.
[0055] (2) When the cooling operation is carried out under the
state that the outside temperature is low, the refrigerant having
the high boiling point is stocked in the accumulator 17. Therefore,
any receiver which has been hitherto disposed to avoid the
refrigerant from being stocked in the accumulator 17 is not
required, and this enables omission of a pressure-reducing
mechanism such as an expansion valve or the like which has been
hitherto disposed in the neighborhood of the outdoor heat exchanger
19 because the receiver tank is disposed. As a result, the
refrigerant circuit 9 can be simplified in construction and the
cost of the air conditioner 10 can be lowered.
[0056] (3) When the number of revolution of the indoor fan 23 for
blowing air to the indoor heat exchanger 21 is increased, the
refrigerant flowing in the indoor heat exchanger 21 is more liable
to evaporate, so that the refrigerant pressure in the indoor heat
exchanger 21 is increased and the refrigerant temperature is also
increased. As a result, by circulating the refrigerant having the
low boiling point in the non-azeotropic mixture refrigerant, the
refrigerant pressure in the indoor heat exchanger 21 is increased,
whereby the occurrence of the freezing in the indoor heat exchanger
21 can be more surely suppressed in cooperation with the effect (1)
of suppressing the occurrence of the freezing in the indoor heat
exchanger 21.
[0057] As described above, according to this embodiment, in the air
conditioner in which the non-azeotropic mixture refrigerant is
circulated in the refrigerant circuit, in the cooling operation
under the low outside temperature state, the refrigerant having the
high boiling point in the non-azeotropic mixture refrigerant is
stocked in the accumulator while the refrigerant having the low
boiling point is circulated in the refrigerant circuit, so that the
occurrence of the freezing in the indoor heat exchanger can be
suppressed in the cooling operation under the low outside
temperature state and thus the stable cooling effect can be
achieved even when non-azeotropic mixture refrigerant is used.
[0058] FIG. 3 is a diagram showing a refrigerant circuit according
to a second embodiment of the air conditioner of the present
invention. The refrigerant circuit of FIG. 3 is substantially the
same construction as the first embodiment, and only the different
points will be described. The same parts are represented by the
same reference numerals, and the description thereof is
omitted.
[0059] In this embodiment, under heating operation, the controller
13 adjusts the valve opening degree of the expansion valve 22 as
described later to perform a discharged refrigerant temperature
control operation.
[0060] That is, under the heating operation, the controller 13
carries out the following discharged refrigerant temperature
control operation to stock the refrigerant (R134a) having the high
boiling point in the non-azeotropic mixture refrigerant into the
accumulator and circulating the refrigerant having the low boiling
point (R125 and R32) in the refrigerant circuit 9, thereby varying
the composition of the refrigerant circulated in the refrigerant
circuit 9.
[0061] In order to perform the discharged refrigerant temperature
control operation, the temperature of sucked air to the indoor heat
exchanger 21 (that is, the room temperature) is detected by a room
temperature sensor 28, and the sucked air temperature thus detected
is input to the controller 13. Further, the temperature of the
discharged refrigerant from the compressor 16 (that is, the actual
discharged refrigerant temperature) is detected by a discharged
refrigerant temperature sensor 25, and the actual discharged
refrigerant temperature thus detected is input to the controller
13. Still further, the temperature of the refrigerant flowing at
the middle position between the inlet and outlet ports of the
outdoor heat exchanger 19 (that is, the outdoor heat exchanger
refrigerant temperature) is detected by an outdoor heat exchanger
temperature sensor 26, and the outdoor heat exchanger refrigerant
temperature thus detected is input to the controller 13. In
addition, the temperature of the refrigerant flowing at the middle
position between the inlet and output ports of the indoor heat
exchanger 21 (that is, the indoor heat exchanger refrigerant
temperature) is detected by an indoor heat exchanger temperature
sensor 27, and the indoor heat exchanger refrigerant temperature
thus detected is input to the controller 13.
[0062] The controller 13 carries out the following discharged
refrigerant temperature control operation under the heating
operation. As show in the flowchart of FIG. 4, the controller 13
first detects the room temperature by using the room temperature
sensor for a predetermined time (for example, several minutes)
after the heating operation is started (S11), and sets the valve
opening degree of the expansion valve 22 to a fixed opening degree
which is determined on the basis of the room temperature detected
by the room temperature sensor 28 (S12).
[0063] The fixed opening degree is determined so that the
refrigerant having the high boiling point (R134a) in the
non-azeotropic mixture refrigerant is stocked in the accumulator
17. Therefore, when the expansion valve 22 is set to the fixed
opening degree, the refrigerant having the high boiling point
(R134a) which is harder to evaporate is stocked in the accumulator
17, and the refrigerant having the low boiling point (R125 and R32)
which is more liable to evaporate is circulated in the refrigerant
circuit 9, so that the composition of the refrigerant circulating
in the refrigerant circuit 9 is varied.
[0064] At this time, when a built-in operating timer (not shown) of
the controller 13 detects the lapse of the above predetermined lime
(several minutes) after the start of the heating operation (S 13),
the controller 13 subsequently detects the temperature of the
refrigerant discharged from the compressor 16 by the discharged
refrigerant temperature sensor 25, and compares the actual
discharged refrigerant temperature thus detected with a target
discharged refrigerant temperature (S14).
[0065] The target discharged refrigerant temperature is determined
on the basis of a calculation equation using as parameters the
outdoor heat exchanger refrigerant temperature detected by the
outdoor heat exchanger temperature sensor 26 and the indoor heat
exchanger refrigerant temperature detected by the indoor heat
exchanger temperature sensor 27. The target discharged refrigerant
temperature is set so that R134a is continuously stocked in the
accumulator 17, for example, the degree of superheat SH of the
suction of the compressor 16 is set to -1.degree. C.
[0066] Subsequently, if it is judged in step S14 that the actual
discharged refrigerant temperature is lower than the target
discharged refrigerant temperature (the judgment in step S14: YES),
the controller 13 reduces the valve opening degree of the expansion
valve 22 to lower the amount of the refrigerant circulating in the
refrigerant circuit 9 (S15). On the other hand, if it is judged in
step S14 that the actual discharged refrigerant temperature is not
lower than the target discharged refrigerant temperature (the
judgment in step S14:NO), the controller 13 increases the valve
opening degree of the expansion valve 22 to increase the amount of
the refrigerant circulating in the refrigerant circuit 9 (step
S16). Through this operation, R134a is stocked in the accumulator
while R125 and R32 are circulated in the refrigerant circuit 9.
[0067] Through the above discharged refrigerant temperature control
operation, the refrigerant circulated in the refrigerant circuit 9
varies in composition (i.e., the refrigerant containing R134a, R125
and R32 is varied to the refrigerant containing R125 and R32), and
thus the refrigerant in the outdoor heat exchanger 19 serving as
the evaporator in the heating operation is more liable to evaporate
as compared with R407C containing R134a, R125 and R32, that is,
before the composition of the refrigerant is varied). Therefore,
the refrigerant pressure in the outdoor heat exchanger 19 is
increased, and thus occurrence of frost in the outdoor heat
exchanger 19 can be suppressed. At the same time, with the
refrigerant after the composition is varied, the refrigerant
pressure in the indoor heat exchanger 21 serving as the condenser
is increased to a value higher than that before the composition is
varied, so that the heating power of the indoor heat exchanger 21
is enhanced.
[0068] Accordingly, according to this embodiment, the following
effects (1) and (2) are achieved.
[0069] (1) Under the heating operation, the refrigerant having the
high boiling point (R134a) in the non-azeotropic mixture
refrigerant (R407C) is stocked in the accumulator 17, and the
refrigerant having the low boiling point (R125 and R32) is
circulated in the refrigerant circuit 9. Therefore, the refrigerant
is more liable to evaporate in the outdoor heat exchanger 19
serving as the evaporator under the heating operation, and thus the
refrigerant pressure in the outdoor heat exchanger 19 is increased,
thereby preventing occurrence of frost in the outdoor heat
exchanger 19. Therefore, the ratio of the defrosting time to the
overall heating operation can be reduced. Further, since the
refrigerant having the low boiling refrigerant is circulated in the
refrigerant circuit 9 under the heating operation, the refrigerant
pressure in the indoor heat exchanger 21 serving as the condenser
is increased and thus the heating power of the indoor heat
exchanger 21 is enhanced. As a result, the overall heating power of
the air conditioner 10 under the heating operation can be
enhanced.
[0070] (2) Under the heating operation, the refrigerant having the
high boiling point (R134a) is stocked in the accumulator 17, and
thus any receiver tank which has been hitherto disposed to avoid
the refrigerant from being stocked in the accumulator 17 is not
required. In addition, any pressure-reducing mechanism (for
example, expansion valve) which has been hitherto disposed in the
neighborhood of the outdoor heat exchanger 19 due to the mount of
the receiver tank is not required. Therefore, the refrigerant
circuit 9 can be simplified in construction and the cost of the air
conditioner 10 can be lowered.
[0071] As described above, according to the second embodiment of
the present invention, in the air conditioner in which the
non-azeotropic mixture refrigerant is circulated in the refrigerant
circuit, under the heating operation, the refrigerant having the
boiling point in the non-azeotropic mixture refrigerant is stocked
in the accumulator while the refrigerant having the low boiling
point is circulated in the refrigerant circuit. Therefore, even
when the non-azeotropic mixture refrigerant is used, the outdoor
heat exchanger can be prevented from being frosted in the heating
operation, and thus the heating power can be enhanced.
[0072] The present invention is not limited to the above
embodiments, and various modifications may be made without
departing from the subject matter of the present invention. For
example, in the above embodiments, R407C is used as the
non-azeotropic mixture refrigerant, however, other kinds of
materials such as R410A, etc. may be used as the non-azeotropic
mixture refrigerant.
* * * * *