FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
REFRIGERATION CYCLE APPARATUS, AIR CONDITIONER INCLUDING
REFRIGERATION CYCLE APPARATUS, AND METHOD OF CONTROLLING
REFRIGERATION CYCLE APPARATUS;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
- 2 -
DESCRIPTION
TITLE OF INVENTION
Refrigeration Cycle Apparatus, Air Conditioner including Refrigeration Cycle
5 Apparatus, and Method of Controlling Refrigeration Cycle Apparatus
TECHNICAL FIELD
[0001] The present disclosure relates to a refrigeration cycle apparatus, an air
conditioner including the refrigeration cycle apparatus, and a method of controlling the
refrigeration cycle apparatus.
10 BACKGROUND ART
[0002] In a refrigeration cycle apparatus used in an air conditioner and the like, in order
to ensure lubricity in a compressor that compresses refrigerant, refrigeration oil is
present inside the compressor. When liquid refrigerant is present inside the
compressor, the refrigeration oil may flow out together with the refrigerant to a
15 refrigerant circuit during the operation of the compressor. When the amount of
refrigeration oil inside the compressor decreases, there is a possibility that poor
lubricity may cause a failure in the compressor.
[0003] Normally, when the operation of the compressor is started, the amount of liquid
refrigerant inside the compressor decreases as time passes, and thus, the amount of
20 refrigeration oil flowing out to the refrigerant circuit decreases. Further, the
refrigeration oil having flowed out to the refrigerant circuit also circulates through the
refrigerant circuit and returns to the compressor. This ensures the amount of
refrigeration oil inside the compressor.
[0004] However, when the compressor is operating intermittently at a low speed, the
25 liquid refrigerant inside the compressor is less likely to be discharged, with the result
that the amount of refrigeration oil flowing out to the refrigerant circuit (the flowingout amount of refrigeration oil relative to the circulation amount of refrigerant) is
continued to be large. Further, the compressor may stop before the refrigeration oil
having flowed out to the refrigerant circuit circulates through the refrigerant circuit and
- 3 -
then returns to the compressor. Thereby, the amount of refrigeration oil inside the
compressor may decrease, so that the compressor may fail.
[0005] In order to avoid the situation as described above, Japanese Patent Laying-Open
No. 2011-242097 (PTL 1) discloses that the degree of wetness of the refrigerant inside
5 the compressor is determined and, based on the determination result, the rotation speed
(the operating frequency) of the compressor is temporarily prohibited from increasing
(see PTL 1).
CITATION LIST
PATENT LITERATURE
10 [0006] PTL 1: Japanese Patent Laying-Open No. 2011-242097
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0007] However, when the operating frequency of the compressor is uniformly
prohibited from increasing based on the degree of wetness of the refrigerant inside the
15 compressor, the operation load of the refrigeration cycle apparatus is unnecessarily
suppressed, with the result that the refrigeration performance of the refrigeration cycle
apparatus may degrade.
[0008] The present disclosure has been made to solve the above-described problems.
It is an object of the present disclosure to provide a refrigeration cycle apparatus, an air
20 conditioner including the refrigeration cycle apparatus, and a method of controlling the
refrigeration cycle apparatus, by which the refrigeration performance can be ensured
while preventing refrigeration oil inside a compressor from decreasing and thus causing
a failure in the compressor.
SOLUTION TO PROBLEM
25 [0009] A refrigeration cycle apparatus of the present disclosure includes: a compressor
configured to compress refrigerant; and a controller configured to control the
compressor. The controller is configured to: execute control for prohibiting an
operating frequency of the compressor from increasing (i) when a stop frequency of the
compressor exceeds a prescribed value and (ii) when a degree of superheat of the
- 4 -
refrigerant output from the compressor is lower than a set value after start of an
operation of the compressor, the stop frequency being a frequency at which the
compressor stops when the degree of superheat is lower than the set value; and permit
the operating frequency of the compressor to increase when the stop frequency is equal
5 to or lower than the prescribed value.
[0010] Further, a method of controlling a refrigeration cycle apparatus of the present
disclosure includes: determining whether or not a degree of superheat of refrigerant
output from a compressor configured to compress the refrigerant is lower than a set
value after start of an operation of the compressor; when it is determined that the
10 degree of superheat is lower than the set value, determining whether or not a stop
frequency of the compressor exceeds a prescribed value, the stop frequency being a
frequency at which the compressor stops when the degree of superheat is lower than the
set value; when it is determined that the stop frequency exceeds the prescribed value,
executing control for prohibiting an operating frequency of the compressor from
15 increasing; and when it is determined that the stop frequency is equal to or lower than
the prescribed value, permitting the operating frequency of the compressor to increase.
ADVANTAGEOUS EFFECTS OF INVENTION
[0011] According to the refrigeration cycle apparatus, the air conditioner including the
refrigeration cycle apparatus, and the method of controlling the refrigeration cycle
20 apparatus as described above, the refrigeration performance can be ensured while
preventing the refrigeration oil inside the compressor from decreasing and thus causing
a failure in the compressor.
BRIEF DESCRIPTION OF DRAWINGS
[0012] Fig. 1 is an overall configuration diagram of an air conditioner shown as an
25 example of a refrigeration cycle apparatus according to a first embodiment.
Fig. 2 is a diagram showing a flow of refrigerant during a cooling operation.
Fig. 3 is a diagram showing a flow of refrigerant during a heating operation.
Fig. 4 is a block diagram showing an example of a hardware configuration of a
controller.
- 5 -
Fig. 5 is a flowchart illustrating an example of each process executed by the
controller when a compressor stops.
Fig. 6 is a flowchart illustrating an example of each process executed by the
controller when an operation of the compressor starts.
5 Fig. 7 is a flowchart illustrating an example of each process executed by the
controller when the operation of the compressor starts, according to a second
embodiment.
Fig. 8 is a flowchart illustrating an example of each process executed by the
controller when the operation of the compressor starts, according to a third
10 embodiment.
DESCRIPTION OF EMBODIMENTS
[0013] Embodiments of the present disclosure will be hereinafter described in detail
with reference to the accompanying drawings. While a plurality of embodiments will
be described below, it has been originally intended at the time of filing of the present
15 application to appropriately combine the configurations described in the embodiments.
In the accompanying drawings, the same or corresponding portions will be denoted by
the same reference characters, and the description thereof will not be repeated.
[0014] First Embodiment
Fig. 1 is an overall configuration diagram of an air conditioner shown as an
20 example of a refrigeration cycle apparatus according to the first embodiment.
Referring to Fig. 1, an air conditioner 1 includes a compressor 10, a four-way valve 20,
an outdoor heat exchanger 30, a fan 32, a decompression device 40, an indoor heat
exchanger 50, a fan 52, pipes 62 to 72, a temperature sensor 80, a pressure sensor 82,
and a controller 90.
25 [0015] Indoor heat exchanger 50 and fan 52 are installed as indoor units in a target
space (indoors) in which air conditioner 1 performs air conditioning. Compressor 10,
four-way valve 20, outdoor heat exchanger 30, fan 32, decompression device 40,
temperature sensor 80, pressure sensor 82, and controller 90 are installed as outdoor
units outside the target space (for example, outdoors).
- 6 -
[0016] Pipe 62 connects a discharge port of compressor 10 and a port p1 of four-way
valve 20. Pipe 64 connects a port p2 of four-way valve 20 and outdoor heat
exchanger 30. Pipe 66 connects outdoor heat exchanger 30 and decompression device
40. Pipe 68 connects decompression device 40 and indoor heat exchanger 50. Pipe
5 70 connects indoor heat exchanger 50 and a port p3 of four-way valve 20. Pipe 72
connects a port p4 of four-way valve 20 and a suction port of compressor 10.
[0017] Compressor 10 compresses the refrigerant suctioned through pipe 72 and
outputs the compressed refrigerant to pipe 62. Compressor 10 is configured to be
capable of adjusting an operating frequency in accordance with a control signal from
10 controller 90. By adjusting the operating frequency of compressor 10, the output from
compressor 10 is adjusted. Compressor 10 is filled with refrigeration oil in order to
ensure the lubricity in compressor 10. Compressor 10 may be of various types such as
a rotary type, a reciprocating type, a scroll type, and a screw type, for example.
[0018] In accordance with the control signal from controller 90, four-way valve 20 is
15 selectively switched between a first state (in a cooling operation) and a second state (in
a heating operation). In the first state, four-way valve 20 allows communication
between ports p1 and p2, and allows communication between ports p3 and p4.
Thereby, in the first state, pipes 62 and 64 are connected, and pipes 70 and 72 are
connected. In the second state, four-way valve 20 allows communication between
20 ports p1 and p3, and allows communication between ports p2 and p4. Thereby, in the
second state, pipes 62 and 70 are connected, and pipes 64 and 72 are connected.
[0019] Outdoor heat exchanger 30 is configured such that the refrigerant flowing
through a heat transfer tube provided inside outdoor heat exchanger 30 exchanges heat
with outdoor air. In outdoor heat exchanger 30, during the cooling operation, the
25 high-temperature and high-pressure superheated vapor (refrigerant) flowing from pipe
64 into outdoor heat exchanger 30 exchanges heat with outdoor air (dissipates heat),
and thereby, is condensed and liquefied, and then, liquid refrigerant is output to pipe
66. During the heating operation, the refrigerant flowing from pipe 66 into outdoor
heat exchanger 30 exchanges heat with outdoor air in outdoor heat exchanger 30, and
- 7 -
thereby, evaporates and turns into superheated vapor, which is then output to pipe 64.
Fan 32 is provided side by side with outdoor heat exchanger 30, and blows outdoor air
into outdoor heat exchanger 30.
[0020] Decompression device 40 is formed, for example, of an electronic expansion
5 valve, and the opening degree of decompression device 40 is adjusted in accordance
with a control signal from controller 90. When the opening degree changes in a
closing direction, the refrigerant pressure on the outlet side of decompression device 40
decreases, and the degree of dryness of the refrigerant rises. When the opening degree
changes in an opening direction, the refrigerant pressure on the outlet side of
10 decompression device 40 increases, and the degree of dryness of the refrigerant lowers.
During the cooling operation, decompression device 40 decompresses the refrigerant
output from outdoor heat exchanger 30 to pipe 66 and outputs the decompressed
refrigerant to pipe 68. During the heating operation, decompression device 40
decompresses the refrigerant output from indoor heat exchanger 50 to pipe 68 and
15 outputs the decompressed refrigerant to pipe 66.
[0021] Indoor heat exchanger 50 is configured such that the refrigerant flowing through
a heat transfer tube provided inside indoor heat exchanger 50 exchanges heat with air
inside the target space. In indoor heat exchanger 50, during the cooling operation, the
refrigerant flowing from pipe 68 into indoor heat exchanger 50 exchanges heat with the
20 air inside the target space (absorbs heat), and thereby, evaporates and turns into
superheated vapor, which is then output to pipe 70. During the heating operation, the
high-temperature and high-pressure superheated vapor (refrigerant) flowing from pipe
70 into indoor heat exchanger 50 exchanges heat with the air inside the target space
(dissipates heat) in indoor heat exchanger 50, and thereby, is condensed and liquefied,
25 and then, liquid refrigerant is output to pipe 68. Fan 52 is provided side by side with
indoor heat exchanger 50 and blows air into indoor heat exchanger 50.
[0022] Temperature sensor 80 detects a temperature TH of the refrigerant on the outlet
side of compressor 10, and outputs the detection value to controller 90. Pressure
sensor 82 detects a pressure PH of the refrigerant on the outlet side of compressor 10,
- 8 -
and outputs the detection value to controller 90.
[0023] Controller 90 controls each of devices in air conditioner 1. As main control
executed by controller 90, based on the detection values of temperature sensor 80 and
pressure sensor 82, the detection values of other sensors (not shown), and the like,
5 controller 90 controls the operating frequency of compressor 10 and the opening degree
of decompression device 40 such that air conditioner 1 performs a desired air
conditioning operation. Further, controller 90 switches four-way valve 20 to the first
state when performing a cooling operation, and switches four-way valve 20 to the
second state when performing a heating operation.
10 [0024] Fig. 2 is a diagram showing a flow of refrigerant during a cooling operation.
Referring to Fig. 2, during the cooling operation, the refrigerant brought into a hightemperature and high-pressure vapor state by compressor 10 is supplied to outdoor heat
exchanger 30 via four-way valve 20. The refrigerant then exchanges heat with
outdoor air in outdoor heat exchanger 30 (dissipates heat), and thereby, is condensed
15 (liquefied) and turns into high-pressure liquid refrigerant.
[0025] The refrigerant that has passed through outdoor heat exchanger 30 is
decompressed in decompression device 40, and thereby, turns into low-temperature and
low-pressure refrigerant, which is then supplied to indoor heat exchanger 50. In
indoor heat exchanger 50, the refrigerant exchanges heat with the air inside the target
20 space (absorbs heat), and thereby, evaporates (vaporizes) and turns into low-pressure
gas refrigerant. The refrigerant is subsequently suctioned again into compressor 10
via four-way valve 20. Thereby, the (indoor) space in which indoor heat exchanger
50 is installed is cooled.
[0026] Fig. 3 is a diagram showing a flow of refrigerant during a heating operation.
25 Referring to Fig. 3, during the heating operation, the refrigerant brought into a hightemperature and high-pressure vapor state by compressor 10 is supplied to indoor heat
exchanger 50 via four-way valve 20, and exchanges heat with indoor air in indoor heat
exchanger 50 (dissipates heat), and thereby, is condensed (liquefied) and turns into
high-pressure liquid refrigerant.
- 9 -
[0027] Then, the refrigerant is decompressed in decompression device 40 and supplied
to outdoor heat exchanger 30, and exchanges heat with outdoor air in outdoor heat
exchanger 30 (absorbs heat), and thereby, is evaporated (vaporized) and turns into lowpressure gas refrigerant. The refrigerant is then suctioned again into compressor 10
5 via four-way valve 20. Thereby, the (indoor) space in which indoor heat exchanger
50 is installed is heated.
[0028] In the refrigeration cycle apparatus as described above, the compressor is filled
with refrigeration oil in order to ensure the lubricity in the compressor. The
refrigeration oil essentially should be present inside the compressor. However, if
10 liquid refrigerant is present inside the compressor, the liquid refrigerant may mix with
refrigeration oil to thereby raise the liquid level (the liquid level of the mixture of the
liquid refrigerant and the refrigeration oil) inside the compressor, with the result that
the refrigeration oil may flow out together with the refrigerant to the refrigerant circuit
when the compressor operates. When the refrigeration oil flows out to the refrigerant
15 circuit and thereby the amount of refrigeration oil inside the compressor decreases,
there is a possibility that poor lubricity may cause a failure in the compressor.
[0029] In the state of an operation that is not a low-speed and intermittent operation
(which may be hereinafter referred to as a "normal operation"), as time passes,
discharging of the liquid refrigerant from the compressor progresses and the
20 temperature inside the compressor rises, and thereby, the liquid refrigerant inside the
compressor is gasified, with the result that the amount of refrigeration oil flowing out to
the refrigerant circuit decreases. Note that the amount of refrigeration oil flowing out
to the refrigerant circuit mentioned herein means the flowing-out amount of
refrigeration oil relative to the circulation amount of refrigerant. Further, the
25 refrigeration oil having flowed out to the refrigerant circuit circulates through the
refrigerant circuit and returns to the compressor. In this way, in the normal operation,
as time passes, the amount of refrigeration oil flowing out to the refrigerant circuit
decreases, and the refrigeration oil having flowed out to the refrigerant circuit rapidly
circulates through the refrigerant circuit and then returns to the compressor.
- 10 -
Accordingly, the amount of refrigeration oil inside the compressor is ensured.
[0030] However, in the case in which the compressor is operating at a low speed and
intermittently, such as a case in which the difference between the indoor temperature
and the set temperature is relatively small, the circulation amount of refrigerant is
5 relatively small, and discharging of the liquid refrigerant from the compressor does not
progress. As a result, the amount of refrigeration oil flowing out to the refrigerant
circuit (the flowing-out amount of refrigeration oil relative to the circulation amount of
refrigerant) is continued to be large. Further, the operation may stop again before the
refrigeration oil having flowed out to the refrigerant circuit circulates through the
10 refrigerant circuit and returns to the compressor. For this reason, when the
compressor is operating at a low speed and intermittently, the amount of refrigeration
oil inside the compressor decreases, so that there is a possibility that poor lubricity may
cause a failure in the compressor.
[0031] In order to avoid the situation as described above, it is conceivable to take the
15 following measures. Specifically, the degree of wetness of the refrigerant inside the
compressor is first estimated, and if the degree of wetness of the refrigerant inside the
compressor rises to such an extent that the liquid refrigerant can be determined as being
present inside the compressor, the operating frequency (rotation speed) of the
compressor is temporarily prohibited from increasing.
20 [0032] However, when the operating frequency of the compressor is uniformly
prohibited from increasing based on the degree of wetness of the refrigerant inside the
compressor, the operation load of the refrigeration cycle apparatus is unnecessarily
suppressed, with the result that the refrigeration performance of the refrigeration cycle
apparatus (for example, comfort of air conditioning by the air conditioner, and the like)
25 may degrade.
[0033] Thus, in air conditioner 1 according to the present first embodiment, it is
determined whether or not the following situation occurs, in which compressor 10
operates at a low speed and intermittently, and thereby, the amount of liquid refrigerant
inside compressor 10 increases, so that the amount of refrigeration oil flowing out of
- 11 -
compressor 10 increases. Then, if the above-mentioned situation frequently occurs, it
is determined that the amount of refrigeration oil inside compressor 10 is highly likely
to decrease. Then, the operating frequency of compressor 10 is temporarily prohibited
from increasing.
5 [0034] Specifically, a frequency at which compressor 10 stops is counted. More
specifically, the frequency counted in this case is a frequency (the number of times in a
certain time period) at which compressor 10 stops when the degree of superheat of the
refrigerant discharged from compressor 10 (hereinafter referred to as a "discharge-side
superheat degree SH") is lower than a set value. Discharge-side superheat degree SH
10 is correlated with the degree of wetness of the refrigerant inside compressor 10, and is
used as an indicator for making a determination about occurrence of a situation in
which the amount of the liquid refrigerant inside compressor 10 increases and thereby
the amount of refrigeration oil flowing out of compressor 10 increases. The frequency
at which compressor 10 stops when discharge-side superheat degree SH is lower than
15 the set value is used as an indicator for making a determination about occurrence of a
situation in which the amount of refrigeration oil inside compressor 10 decreases due to
frequent occurrence of a situation in which a relatively large amount of refrigeration oil
flows out of compressor 10.
[0035] Then, (i) when the frequency at which compressor 10 stops when discharge-side
20 superheat degree SH is lower than the set value exceeds a prescribed value, and (ii)
when discharge-side superheat degree SH is lower than the set value after start of the
operation of compressor 10, control for prohibiting the operating frequency of
compressor 10 from increasing is executed. When the frequency at which compressor
10 stops when discharge-side superheat degree SH is lower than the set value exceeds
25 the prescribed value, the amount of refrigeration oil inside compressor 10 is highly
likely to decrease. Further, when discharge-side superheat degree SH is lower than
the set value after start of the operation of compressor 10, the amount of refrigeration
oil flowing out of compressor 10 increases. Thus, the operating frequency of
compressor 10 is prohibited from increasing, to thereby prevent a failure from
- 12 -
occurring in compressor 10 due to poor lubricity.
[0036] On the other hand, when the frequency at which compressor 10 stops when
discharge-side superheat degree SH is lower than the set value is equal to or less than
the prescribed value, the operating frequency of compressor 10 is permitted to increase.
5 When the above-mentioned frequency is equal to or less than the prescribed value, it is
assumed that the amount of refrigeration oil inside compressor 10 does not decrease to
such an extent that lubricity becomes poor in compressor 10. Thus, the operating
frequency of compressor 10 is permitted to increase.
[0037] In the present first embodiment, also when discharge-side superheat degree SH
10 is equal to or greater than the set value after start of the operation of compressor 10, the
operating frequency of compressor 10 is permitted to increase. Also when dischargeside superheat degree SH becomes equal to or greater than the set value during
execution of the control for prohibiting the operating frequency of compressor 10 from
increasing, the operating frequency of compressor 10 is permitted to increase. When
15 discharge-side superheat degree SH is equal to or greater than the set value, the amount
of refrigeration oil flowing out of compressor 10 does not increase, and thus, the
operating frequency of compressor 10 is permitted to increase.
[0038] As described above, in air conditioner 1 according to the present first
embodiment, the operating frequency of compressor 10 is not uniformly prohibited
20 from increasing based on discharge-side superheat degree SH. Instead, (i) when the
frequency at which compressor 10 stops when discharge-side superheat degree SH is
lower than the set value exceeds the prescribed value, and (ii) when discharge-side
superheat degree SH is lower than the set value after start of the operation of
compressor 10, the operating frequency of compressor 10 is prohibited from increasing.
25 Then, when the frequency is equal to or less than the prescribed value, the operating
frequency of compressor 10 is permitted to increase. This makes it possible to ensure
comfort of air conditioning while preventing the refrigeration oil inside compressor 10
from decreasing and thus causing a failure in compressor 10. Further, also when
discharge-side superheat degree SH is equal to or greater than the set value after start of
- 13 -
the operation of compressor 10, the operating frequency of compressor 10 is permitted
to increase. Thus, also in this point, comfort of air conditioning can be ensured.
[0039] Fig. 4 is a block diagram showing an example of a hardware configuration of
controller 90 that implements the control as described above. Referring to Fig. 4,
5 controller 90 includes a central processing unit (CPU) 132, a random access memory
(RAM) 134, a read only memory (ROM) 136, an input unit 138, a display unit 140, and
an I/F unit 142. RAM 134, ROM 136, input unit 138, display unit 140, and I/F unit
142 are connected to CPU 132 through a bus 144.
[0040] CPU 132 deploys a program, which is stored in ROM 136, in RAM 134 and
10 executes the program. The program stored in ROM 136 is a program describing the
processing procedure for controller 90. Air conditioner 1 controls each of devices in
air conditioner 1 in accordance with these programs. Note that these controls are not
necessarily processed by software, but can also be processed by dedicated hardware (an
electronic circuit).
15 [0041] Fig. 5 is a flowchart illustrating an example of each process executed by
controller 90 when compressor 10 stops. A series of processes shown in this
flowchart are executed in response to an instruction to stop compressor 10.
Compressor 10 may be stopped in response to a request from outside by a user or the
like, or may be stopped in response to a request from the control executed when the
20 indoor temperature becomes close to a set temperature.
[0042] Referring to Fig. 5, controller 90 determines whether or not discharge-side
superheat degree SH indicating the degree of superheat of the refrigerant output from
compressor 10 is lower than a set value Ts (step S10). As described above, dischargeside superheat degree SH is a parameter reflecting the amount of liquid refrigerant
25 inside compressor 10. Thus, as the amount of liquid refrigerant inside compressor 10
increases, discharge-side superheat degree SH decreases. In other words, in step S10,
it is determined whether the amount of liquid refrigerant inside compressor 10 is
relatively large or not. As described above, in the state in which the amount of liquid
refrigerant inside compressor 10 is relatively large, a relatively large amount of
- 14 -
refrigeration oil flows out of compressor 10 into the refrigerant circuit when
compressor 10 is operated.
[0043] Discharge-side superheat degree SH can be calculated from the detection values
of temperature sensor 80 and pressure sensor 82. Specifically, the difference between
5 temperature TH and the refrigerant saturation temperature can be calculated as
discharge-side superheat degree SH. In this case, temperature TH is detected by
temperature sensor 80 (the temperature of the refrigerant output from compressor 10),
and the refrigerant saturation temperature is converted from pressure PH detected by
pressure sensor 82 (the pressure of the refrigerant output from compressor 10).
10 [0044] Set value Ts is set, for example, at a degree of superheat that is sufficient for all
the liquid refrigerant inside compressor 10 to gasify. When discharge-side superheat
degree SH is lower than set value Ts, liquid refrigerant is present in compressor 10, and
thus, it is determined that the amount of refrigeration oil flowing out of compressor 10
is relatively large. Set value Ts is set as appropriate, for example, by preliminary
15 evaluation experiments or the like.
[0045] When it is determined in step S10 that discharge-side superheat degree SH is
lower than set value Ts (YES in step S10), controller 90 increments the value of a
counter (step S20). The counter serves to measure the frequency (the number of times
in a certain time period) at which compressor 10 stops when discharge-side superheat
20 degree SH is lower than set value Ts. When the frequency at which compressor 10
stops when discharge-side superheat degree SH is lower than set value Ts is relatively
high, the amount of refrigeration oil inside compressor 10 is highly likely to decrease.
Although not particularly shown, the counter is reset to zero when the compressor
continuously operates for a certain time period.
25 [0046] When the counter is incremented in step S20, or when it is determined in step
S10 that discharge-side superheat degree SH is equal to or greater than set value Ts
(NO in step S10), controller 90 stops compressor 10 (step S30).
[0047] Fig. 6 is a flowchart illustrating an example of each process executed by
controller 90 when the operation of compressor 10 starts. A series of processes shown
- 15 -
in the flowchart are executed in response to an instruction to operate compressor 10.
The operation of compressor 10 may be started in response to a request from outside by
a user or the like, or may be started in response to a request from the control executed
based on the temperature.
5 [0048] Referring to Fig. 6, controller 90 operates compressor 10 in response to an
instruction to operate compressor 10 (step S110). Then, controller 90 determines
whether or not discharge-side superheat degree SH is lower than set value Ts (step
S120). As described also in step S10 in Fig. 5, it is determined in step S120 whether
the amount of liquid refrigerant present inside compressor 10 is relatively large or not,
10 i.e., whether the amount of refrigeration oil flowing out of compressor 10 into the
refrigerant circuit is relatively large or not. In the present example, set value Ts used
in step S120 is the same as set value Ts used in step S10 in Fig. 5, but both the set
values do not necessarily have to be the same.
[0049] When it is determined in step S120 that discharge-side superheat degree SH is
15 lower than set value Ts (YES in step S120), controller 90 further determines whether or
not a count value of the counter exceeds a prescribed value N (step S130). This count
value indicates the frequency at which compressor 10 stops when discharge-side
superheat degree SH is lower than set value Ts. When the count value exceeds the
prescribed value, it is determined that the amount of refrigeration oil inside compressor
20 10 decreases since a certain amount or more of refrigeration oil has flowed out of
compressor 10. Prescribed value N is set at the number of times, for example, at
which no failure occurs in compressor 10 due to poor lubricity even when compressor
10 normally operates at the amount of refrigeration oil that is reduced by the
intermittent operation of compressor 10. This prescribed value N is set as appropriate
25 by preliminary evaluation experiments or the like.
[0050] When it is determined in step S130 that the count value exceeds prescribed
value N (YES in step S130), controller 90 executes control for prohibiting the operating
frequency of compressor 10 from increasing (step S140). Specifically, when the
count value exceeds prescribed value N and when discharge-side superheat degree SH
- 16 -
is lower than set value Ts, the operating frequency of compressor 10 is prohibited from
increasing. In other words, when the amount of refrigeration oil inside compressor 10
decreases after start of the operation of compressor 10 (YES in step S130), and when
the amount of refrigeration oil flowing out of compressor 10 is relatively large (YES in
5 step S120), then, the operating frequency of compressor 10 is prohibited from
increasing. This is because, if the operating frequency of compressor 10 is increased
in such a situation, the refrigeration oil inside compressor 10 runs out, and thus, poor
lubricity may cause a failure in compressor 10.
[0051] On the other hand, when it is determined in step S130 that the count value is
10 equal to or less than prescribed value N (NO in step S130), controller 90 executes
normal control for permitting the operating frequency of compressor 10 to increase
(step S160). Specifically, even when discharge-side superheat degree SH is lower
than set value Ts (YES in step S120), but when the count value is equal to or less than
prescribed value N, the operating frequency of compressor 10 is permitted to increase.
15 In other words, even when the amount of refrigeration oil flowing out of compressor 10
is relatively large, but when the amount of refrigeration oil inside compressor 10 does
not decrease, the operating frequency of compressor 10 is permitted to increase.
[0052] When it is determined in step S120 that discharge-side superheat degree SH is
equal to or greater than set value Ts (NO in step S120), controller 90 resets the counter
20 to zero (step S150). Then, controller 90 shifts the process to step S160, and executes
the normal control for permitting the operating frequency of compressor 10 to increase.
When discharge-side superheat degree SH is equal to or greater than set value Ts, it is
determined that the refrigerant inside compressor 10 is gasified. Thus, there is no
need for concern that the amount of refrigeration oil inside compressor 10 may
25 decrease due to the refrigeration oil flowing out of compressor 10, and accordingly, the
counter is reset.
[0053] As described above, in the present first embodiment, (i) when the frequency at
which compressor 10 stops when discharge-side superheat degree SH is lower than set
value Ts exceeds prescribed value N, and (ii) when discharge-side superheat degree SH
- 17 -
is lower than set value Ts after start of the operation of compressor 10, the operating
frequency of compressor 10 is prohibited from increasing. On the other hand, even
when discharge-side superheat degree SH is lower than set value Ts, but when the
frequency is equal to or lower than prescribed value N, the operating frequency of
5 compressor 10 is permitted to increase. Also when discharge-side superheat degree
SH is equal to or greater than set value Ts, the operating frequency of compressor 10 is
permitted to increase. Therefore, according to the present first embodiment, the
comfort of air conditioning can be ensured while preventing the refrigeration oil inside
compressor 10 from decreasing and thus causing a failure in compressor 10.
10 [0054] Second Embodiment
In the present second embodiment, in the case in which the counter is reset to
zero when discharge-side superheat degree SH becomes equal to or greater than set
value Ts after start of the operation of compressor 10, the counter is reset to zero after a
certain time period has elapsed. In this case, when discharge-side superheat degree
15 SH becomes equal to or greater than set value Ts, the amount of refrigeration oil
flowing out of compressor 10 into the refrigerant circuit decreases, but there is still a
possibility that the refrigeration oil having flowed out to the refrigerant circuit may not
sufficiently return to compressor 10. Thus, a time margin is given such that the
refrigeration oil having flowed out to the refrigerant circuit is sufficiently recovered
20 into compressor 10.
[0055] The overall configuration of the air conditioner according to the second
embodiment is the same as that of air conditioner 1 according to the first embodiment
shown in Figs. 1 to 4. Also in the air conditioner according to the second
embodiment, a series of processes shown in the flowchart in Fig. 5 are executed when
25 compressor 10 stops.
[0056] Fig. 7 is a flowchart illustrating an example of each process executed by
controller 90 when the operation of compressor 10 starts, according to the second
embodiment. This flowchart corresponds to the flowchart shown in Fig. 6 in the first
embodiment. The series of processes shown in this flowchart are also executed in
- 18 -
response to an instruction to operate compressor 10.
[0057] Referring to Fig. 7, the processes executed in steps S210 to S240, S250 and
S260 are the same as the respective processes executed in steps S110 to S160 in Fig. 6.
[0058] In the present second embodiment, when it is determined in step S220 that
5 discharge-side superheat degree SH is equal to or greater than set value Ts (NO in step
S220), after the set time period has elapsed (YES in step S245), controller 90 shifts the
process to step S250 and then resets the counter to zero. This set time period is set as
appropriate to a time period during which the refrigeration oil having flowed out of
compressor 10 into the refrigerant circuit is sufficiently returned to compressor 10.
10 [0059] Although not particularly shown, when the value of the counter is already zero
when it is determined in step S220 that discharge-side superheat degree SH is equal to
or greater than set value Ts, controller 90 may shift the process to step S260 without
executing the processes in steps S245 and S250.
[0060] As described above, according to the present second embodiment, the time
15 margin is given such that the refrigeration oil having flowed out to the refrigerant
circuit is sufficiently recovered into compressor 10, which makes it possible to increase
the operating frequency of compressor 10 in the state in which a sufficient amount of
refrigeration oil is present in compressor 10.
[0061] Third Embodiment
20 In the above-described first and second embodiments, (i) when discharge-side
superheat degree SH is lower than set value Ts (YES in steps S120 and S220), and
further, (ii) when the value of the counter indicating the frequency at which compressor
10 stops when discharge-side superheat degree SH is lower than set value Ts exceeds
prescribed value N (YES in steps S130 and S230), the control for prohibiting the
25 operating frequency of compressor 10 from increasing is executed (steps S140 and
S240). In place of or in addition to this control for prohibiting the operating
frequency of compressor 10 from increasing, the control for quickly increasing
discharge-side superheat degree SH may be executed.
[0062] The overall configuration of the air conditioner according to the third
- 19 -
embodiment is also the same as that of air conditioner 1 shown in each of Figs. 1 to 4.
Also in the air conditioner according to the present third embodiment, a series of
processes shown in the flowchart in Fig. 5 are executed when compressor 10 stops.
[0063] Fig. 8 is a flowchart illustrating an example of each process executed by
5 controller 90 when the operation of compressor 10 starts, according to the third
embodiment. This flowchart corresponds to the flowchart shown in Fig. 6 in the first
embodiment. A series of processes shown in this flowchart are also executed in
response to an instruction to operate compressor 10.
[0064] Referring to Fig. 8, the processes executed in steps S310 to S330, S350, and
10 S360 are the same as the respective processes executed in steps S110 to S130, S150,
and S160 in Fig. 6.
[0065] Then, in the present third embodiment, when it is determined in step S330 that
the count value exceeds prescribed value N (YES in step S330), controller 90 executes
control for increasing discharge-side superheat degree SH (step S340).
15 [0066] For example, discharge-side superheat degree SH can be increased by
decreasing the opening degree of decompression device 40. Alternatively, dischargeside superheat degree SH can be increased by increasing the rotation speed of the fan of
the heat exchanger functioning as an evaporator (fan 52 of indoor heat exchanger 50
used in the cooling operation or fan 32 of outdoor heat exchanger 30 used in the
20 heating operation) or by decreasing the rotation speed of the fan of the heat exchanger
functioning as a condenser (fan 32 used in the cooling operation or fan 52 used in the
heating operation).
[0067] In the above description, in place of the control for prohibiting the operating
frequency of compressor 10 from increasing, the control for increasing discharge-side
25 superheat degree SH is executed, but the control for increasing discharge-side
superheat degree SH may be executed together with the control for prohibiting the
operating frequency of compressor 10 from increasing, as described above.
Specifically, the control for increasing discharge-side superheat degree SH (step S340)
may be executed in the flowchart shown in Fig. 6, together with the control for
- 20 -
prohibiting the operating frequency of compressor 10 from increasing (step S140).
[0068] According to the present third embodiment, executing the control for increasing
discharge-side superheat degree SH can facilitate discharging of the liquid refrigerant
inside compressor 10, which makes it possible to early eliminate the state in which the
5 amount of refrigeration oil decreases inside compressor 10.
[0069] Also in the present third embodiment, in resetting the counter to zero in step
S350, the counter may be reset after the set time period has elapsed as described in the
second embodiment.
[0070] Although an air conditioner has been described as an example of the
10 refrigeration cycle apparatus in each of the above embodiments, the refrigeration cycle
apparatus according to the present disclosure is not limited to an air conditioner but
may be applicable also to a refrigeration cycle apparatus used in a warehouse, a
showcase, or the like.
[0071] The embodiments disclosed herein are also intended to be implemented in
15 combination as appropriate within a technically consistent scope. It should be
construed that the embodiments disclosed herein are illustrative and non-restrictive in
every respect. The technical scope indicated by the present disclosure is defined by
the terms of the claims, rather than the description of the above-described
embodiments, and is intended to include any modifications within the meaning and
20 scope equivalent to the terms of the claims.
REFERENCE SIGNS LIST
[0072] 1 air conditioner, 10 compressor, 20 four-way valve, 30 outdoor heat exchanger,
32, 52 fan, 40 decompression device, 50 indoor heat exchanger, 62 to 72 pipe, 80
temperature sensor, 82 pressure sensor, 90 controller, 132 CPU, 134 RAM, 136 ROM,
25 138 input unit, 140 display unit, 142 I/F unit, 144 bus.
- 21 -
We Claim :
1. A refrigeration cycle apparatus comprising:
a compressor configured to compress refrigerant; and
5 a controller configured to control the compressor, wherein
the controller is configured to
execute control for prohibiting an operating frequency of the compressor
from increasing (i) when a stop frequency of the compressor exceeds a prescribed value
and (ii) when a degree of superheat of the refrigerant output from the compressor is
10 lower than a set value after start of an operation of the compressor, the stop frequency
being a frequency at which the compressor stops when the degree of superheat is lower
than the set value, and
permit the operating frequency to increase when the stop frequency is
equal to or lower than the prescribed value.
15
2. The refrigeration cycle apparatus according to claim 1, wherein the
controller is configured to permit the operating frequency to increase when the degree
of superheat is equal to or greater than the set value.
20 3. The refrigeration cycle apparatus according to claim 2, wherein the
controller is configured to stop the control and permit the operating frequency to
increase when the degree of superheat becomes equal to or greater than the set value
during execution of the control.
25 4. The refrigeration cycle apparatus according to claim 3, wherein the
controller is configured to stop the control and permit the operating frequency to
increase after a preset time period has elapsed when the degree of superheat becomes
equal to or greater than the set value during execution of the control.
- 22 -
5. The refrigeration cycle apparatus according to any one of claims 1 to 4,
wherein the controller is configured to further execute control for increasing the degree
of superheat in a case in which the stop frequency exceeds the prescribed value when
the degree of superheat is lower than the set value.
5
6. An air conditioner comprising the refrigeration cycle apparatus according
to any one of claims 1 to 5.
7. A method of controlling a refrigeration cycle apparatus, the method
10 comprising:
determining whether or not a degree of superheat of refrigerant output from a
compressor configured to compress refrigerant is lower than a set value after start of an
operation of the compressor;
when it is determined that the degree of superheat is lower than the set value,
15 determining whether or not a stop frequency of the compressor exceeds a prescribed
value, the stop frequency being a frequency at which the compressor stops when the
degree of superheat is lower than the set value;
when it is determined that the stop frequency exceeds the prescribed value,
executing control for prohibiting an operating frequency of the compressor from
20 increasing; and
when it is determined that the stop frequency is equal to or lower than the
prescribed value, permitting the operating frequency to increase.
8. The method of controlling a refrigeration cycle apparatus according to
25 claim 7, further comprising permitting the operating frequency to increase when it is
determined that the degree of superheat is equal to or greater than the set value after
start of an operation of the compressor.
9. The method of controlling a refrigeration cycle apparatus according to
- 23 -
claim 8, wherein the permitting the operating frequency to increase is performed when
the degree of superheat becomes equal to or greater than the set value during execution
of the control.
5 10. The method of controlling a refrigeration cycle apparatus according to
claim 9, further comprising
determining whether a preset time period has elapsed or not when the degree of
superheat becomes equal to or greater than the set value during execution of the
control, wherein
10 the permitting the operating frequency to increase is performed when the preset
time period has elapsed.
11. The method of controlling a refrigeration cycle apparatus according to any
one of claims 7 to 10, further comprising executing control for increasing the degree of
15 superheat when it is determined that the stop frequency exceeds the prescribed value.