BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
[0001] The present invention relates to a multi-unit air-conditioning apparatus having an
oil-recovery function for recovering a lubricant that is circulated through a refrigerant
circuit together with a refrigerant discharged from a compressor and that accumulates
in the refrigerant circuit.
2. DESCRIPTION OF RELATED ART
[0002] With air-conditioning apparatuses using a refrigerant-compression refrigeration cycle,
cooling and heating are carried out by compressing a refrigerant with a compressor
and circulating the refrigerant inside a refrigerant circuit. The compressor contains
a lubricant for lubricating a slidable section. Some of the lubricant is discharged
from the compressor together with the compressed refrigerant. The lubricant circulates
through the refrigerant circuit together with the refrigerant and then is returned
to the compressor. However, some of the lubricant may accumulate in the refrigerant
circuit. The amount of accumulated lubricant varies depending on the length of the
refrigerant pipes in each indoor unit or the operation state of each indoor unit.
However, in general, it is presumed that the amount of accumulated lubricant increases
in proportion to the operating time of the air-conditioning apparatus.
[0003] As described above, as the amount of accumulated lubricant in the refrigerant circuit
increases, the amount of lubricant retained in the compressor decreases. This affects
the lubricating action of the compressor, and may cause, in some cases, failure or
damage to the compressor due to lack of lubricant. Accordingly, at predetermined intervals
of operating time (e.g., every eight hours) of the air-conditioning apparatus, an
oil-recovery operation for forcefully recovering the lubricant accumulated inside
the refrigerant circuit from the compressor is carried out for a predetermined amount
of time (e.g., three minutes). A known oil-recovery operation is a method for recovering
a lubricant accumulated together with a liquid refrigerant from a refrigerant circuit
to a compressor by carrying out a liquid return operation in which the compressor
is operated at a set rotational speed and indoor and outdoor expansion valves are
set at predetermined degrees of opening.
[0004] With multi-unit air-conditioning apparatuses that include a plurality of indoor units
connected in parallel, and, in particular, apparatuses that are installed for air-conditioning
of a building, the length of refrigerant pipes is extremely large, and, in most cases,
the lengths of the refrigerant pipes differ for each indoor unit. As described above,
with a multi-unit air-conditioning apparatus, even when an oil-recovery operation
is carried out constantly for a predetermined amount of time, the expected amount
of lubricant may not be returned to the compressor, causing defective lubrication.
[0005] To prevent such an incident, there is a proposed method for determining whether or
not a lubricant has returned to a compressor during an oil-recovery operation, on
the basis of suction superheating of a refrigerant sucked by the compressor, and changing
the oil-recovery operation time when required (for example, refer to
Japanese Unexamined Patent Application, Publication No. HEI-10-288410).
[0006] With the above-described multi-unit air-conditioning apparatus, after the air-conditioning
apparatus is installed on site, an appropriate amount of refrigerant corresponding
to the length of the refrigerant pipe of each indoor unit must be added. The amount
of refrigerant to be added directly affects whether or not the rated air-conditioning
performance can be achieved can be achieved. Therefore, the length of the refrigerant
pipe must be determined as accurately as possible, and an appropriate amount of refrigerant
corresponding to the length of the refrigerant pipe must be added. A system and method
for detecting the length of the refrigerant pipe has been proposed (for example, refer
to
Japanese Unexamined Patent Application, Publication No. 2006-183979).
[0007] However, according to
Japanese Unexamined Patent Application, Publication No. HEI-10-288410, it is determined whether or not a lubricant has returned to a compressor on the
basis of suction superheating of a refrigerant sucked by the compressor, and the oil-recovery
operation is completed when the suction superheating is constantly equal to or less
than a predetermined value for a predetermined amount of time or when a predetermined
maximum amount of time elapses after the oil-recovery operation is started. Therefore,
regardless of the difference in the lengths of the refrigerant pipes for a plurality
of indoor units, suction superheating of the compressor decreases due to a liquid
refrigerant that returns after circulating in an indoor unit having a relatively short
refrigerant pipe. As a result, the oil recovery operation time is determined. Thus,
with this configuration, there is a problem in that the lubricant accumulated in indoor
units having relatively long refrigerant pipes and the refrigerant circuit cannot
be sufficiently recovered.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention has been conceived in light of the problems described above.
Accordingly, it is an object of the present invention to provide an air-conditioning
apparatus capable of reliably recovering lubricant accumulated in indoor units and
their refrigerant circuit, regardless of the different lengths of refrigerant pipe
of the indoor units which are connected to each other.
[0010] To achieve the above-described object, the air-conditioning apparatus according to
the present invention provides the following solutions.
[0011] An air-conditioning apparatus according to a first aspect of the present invention
includes an outdoor unit including a compressor and an outdoor heat-exchanger; a plurality
of indoor units connected in parallel with each other, each of the indoor units including
an indoor heat-exchanger and an indoor expansion valve; a refrigerant circuit formed
by connecting, in order, the compressor, the outdoor heat-exchangers, the plurality
of an indoor heat-exchangers, and the indoor expansion valves using refrigerant pipes;
and an oil-recovery operating unit configured to carry out a liquid return operation
at each indoor unit at a predetermined timing, to carry out a oil-recovery operation
for recovering lubricant accumulated in the refrigerant circuit, and to terminate
the oil-recovery operation when liquid return is detected at the outdoor unit. The
oil-recovery operating unit includes a refrigerant-pipe-length detecting unit configured
to detect the refrigerant pipe length of each of the indoor units; a refrigerant-pipe-length
storing unit configured to store the refrigerant pipe lengths detected by the refrigerant-pipe-length
detecting unit; and an oil-recovery control unit configured to change the operation
time during the oil-recovery operation on the basis of the refrigerant pipe length
of each of the indoor units stored in the refrigerant-pipe-length storing unit.
[0012] "Liquid return operation", as herein used, means an operation in which the degree
of superheating of a refrigerant returning from an indoor unit to an outdoor unit
via a gas pipe during a cooling cycle is lowered so as to return the refrigerant from
the indoor unit to the outdoor unit in a state in which at least part of the refrigerant
has been actively brought in a liquid state.
[0013] With the first aspect according to the present invention, since the oil-recovery
operating unit includes a refrigerant-pipe-length detecting unit configured to detect
the refrigerant pipe length of each indoor unit, a refrigerant-pipe-length storing
unit configured to store the refrigerant pipe lengths detected by the refrigerant-pipe-length
detecting unit, and an oil-recovery control unit configured to change the operation
time during the oil-recovery operation on the basis of the refrigerant pipe length
of each of the indoor units stored in the refrigerant-pipe-length storing unit, the
lubricant accumulated in the indoor units and the refrigerant circuit can be recovered,
even when the refrigerant pipe length of each indoor unit differs, by changing the
operation time during the oil-recovery operation on the basis of the refrigerant pipe
length of each indoor unit so as to set an appropriate oil-recovery operation time.
Therefore, the lubricant accumulated in the indoor units having long refrigerant pipes
and the refrigerant circuit can be reliably recovered to the compressor. Thus, a predetermined
amount of lubricant can be constantly retained in the compressor, reliably preventing
defective lubrication caused by lack of lubricant in the compressor due to a large
amount of lubricant being discharged to the refrigerant circuit.
[0014] With the air-conditioning apparatus according to the first aspect, the oil-recovery
control unit may determine the refrigerant-pipe length differences among each of the
indoor units and may change the operation completion time during the oil-recovery
operation on the basis of the refrigerant-pipe length differences.
[0015] According to this configuration, since the refrigerant-pipe length differences among
each of the indoor units are determined and the operation completion time is changed
during the oil-recovery operation on the basis of the refrigerant-pipe length differences,
when it is determined that the refrigerant pipe long, the completion time of the oil-recovery
operation can be delayed by an amount of time corresponding to the refrigerant-pipe
length differences, and the operation time can be extended. In this way, the lubricant
accumulated in the indoor unit having a long refrigerant pipe and the refrigerant
circuit can be reliably recovered. Thus, defective lubrication caused by lack of lubricant
in the compressor can be reliably prevented.
[0016] With the air-conditioning apparatus according to the first aspect having the above-described
structure, the oil-recovery control unit may determine a distribution of the refrigerant-pipe
lengths of the indoor units and may change the operation completion time during the
oil-recovery operation on the basis of the distribution of the refrigerant-pipe lengths.
[0017] According to this configuration, since a distribution of the refrigerant-pipe lengths
of the indoor units is determined and the operation completion time is changed during
the oil-recovery operation on the basis of the distribution of the refrigerant-pipe
lengths, when it is determined that the number of indoor units having a refrigerant
pipe length larger than the average refrigerant pipe length is provided, the completion
time of the oil-recovery operation can be delayed by an amount of time corresponding
to the refrigerant-pipe length difference, and the operation time can be extended.
In this way, the lubricant accumulated in the indoor units having long refrigerant
pipes and the refrigerant circuit can be reliably recovered. Thus, defective lubrication
caused by lack of lubricant in the compressor can be reliably prevented.
[0018] With the air-conditioning apparatus according to the first aspect having the above-described
structure, the oil-recovery control unit may add the refrigerant-pipe lengths of the
indoor units and may change the operation completion time during the oil-recovery
operation on the basis of the total refrigerant-pipe length.
[0019] According to this configuration, since the refrigerant-pipe lengths of the indoor
units are added and the operation completion time is changed during the oil-recovery
operation on the basis of the total refrigerant-pipe length, when it is determined
that the refrigerant pipe is long, the completion time of the oil-recovery operation
can be delayed by an amount of time corresponding to the refrigerant-pipe length difference,
and the operation time can be extended. In this way, the lubricant accumulated in
the indoor units having long refrigerant pipes and the refrigerant circuit can be
reliably recovered. Thus, defective lubrication caused by lack of lubricant in the
compressor can be reliably prevented.
[0020] With the air-conditioning apparatus according to the first aspect having the above-described
structure, the oil-recovery control unit may determine the refrigerant-pipe length
differences among each of the indoor units and may change the operation start time
during the oil-recovery operation on the basis of the refrigerant-pipe length differences.
[0021] According to this configuration, since the refrigerant-pipe length differences among
each of the indoor units are determined and the operation start time is changed during
the oil-recovery operation on the basis of the refrigerant-pipe length difference,
the oil-recovery operation is started from the indoor unit having the longest refrigerant
pipe so that the longer the refrigerant pipe of the indoor unit is, the greater the
degree of opening is. In this way, the lubricant accumulated in the indoor units having
long refrigerant pipes and the refrigerant circuit can be reliably recovered. Thus,
defective lubrication caused by lack of lubricant in the compressor can be reliably
prevented.
[0022] An air-conditioning apparatus according to a second aspect of the present invention
includes an outdoor unit including a compressor and an outdoor heat-exchanger; a plurality
of indoor units connected in parallel with each other, each of the indoor units including
an indoor heat-exchanger and an indoor expansion valve; a refrigerant circuit formed
by connecting, in order, the compressor, the outdoor heat-exchangers, the plurality
of indoor heat-exchangers, and the indoor expansion valves using refrigerant pipes;
and an oil-recovery operating unit configured to carry out a liquid return operation
at each indoor unit at a predetermined timing, to carry out an oil-recovery operation
for recovering lubricant accumulated in the refrigerant circuit, and to complete the
oil-recovery operation when liquid return is detected at the outdoor unit. The oil-recovery
operating unit includes a refrigerant-pipe-length detecting unit configured to detect
the refrigerant pipe length of each of the indoor units; a refrigerant-pipe-length
storing unit configured to store the refrigerant pipe lengths detected by the refrigerant-pipe-length
detecting unit; and an oil-recovery control unit configured to change the degree of
opening of each indoor expansion valve during the oil-recovery operation on the basis
of the refrigerant pipe length of each of the indoor units stored in the refrigerant-pipe-length
storing unit.
[0023] With the second aspect according to the present invention, since the oil-recovery
operating unit includes a refrigerant-pipe-length detecting unit configured to detect
the refrigerant pipe length of each indoor unit, a refrigerant-pipe-length storing
unit configured to store the refrigerant pipe lengths detected by the refrigerant-pipe-length
detecting unit, and an oil-recovery control unit configured to change the degree of
opening of each indoor expansion valve during the oil-recovery operation on the basis
of the refrigerant pipe length of each of the indoor units stored in the refrigerant-pipe-length
storing unit, the lubricant accumulated in the indoor units and the refrigerant circuit
can be recovered, even when the refrigerant pipe length of each indoor unit differs,
by changing the degree of opening of each indoor expansion valve during the oil-recovery
operation on the basis of the refrigerant pipe length of each indoor unit so as to
make an appropriate amount of refrigerant flow through each indoor unit. Therefore,
the lubricant accumulated in the indoor units having long refrigerant pipes and the
refrigerant circuit can be reliably recovered to the compressor. Thus, a predetermined
amount of lubricant can be constantly retained in the compressor, reliably preventing
defective lubrication caused by lack of lubricant in the compressor due to a large
amount of lubricant being discharged to the refrigerant circuit.
[0024] With the air-conditioning apparatus according to the second aspect having the above-described
structure, the oil-recovery control unit may determine the refrigerant-pipe length
differences among each of the indoor units and may set the degree of opening of the
indoor expansion valve so that the longer the refrigerant pipe of the indoor unit
is, the greater the degree of opening is.
[0025] According to this configuration, since the refrigerant-pipe length differences among
each of the indoor units are determined and the degrees of opening of the indoor expansion
valves are set so that the longer the refrigerant pipe of the indoor unit is, the
greater the degree of opening is, and the longer the refrigerant pipe of the indoor
unit, the greater the amount of refrigerant to be discharged. Thus, liquid return
can be actively carried out so as to recover the lubricant. In this way, the lubricant
accumulated in the indoor units having long refrigerant pipes and the refrigerant
circuit can be reliably recovered. Thus, defective lubrication caused by lack of lubricant
in the compressor can be reliably prevented.
[0026] According to the present invention, since the operation time (completion time or
start time) of the oil-recovery operation or the degree of opening of the indoor expansion
valve is changed on the basis of the refrigerant pipe length of each indoor unit,
even when the refrigerant pipe length differs for each indoor unit, the lubricant
accumulated in the indoor units having long refrigerant pipes and the refrigerant
circuit can be reliably recovered, reliably preventing defective lubrication caused
by lack of lubricant in the compressor.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0027] Fig. 1 illustrates a refrigerant circuit of an air-conditioning apparatus according
to a first embodiment of the present invention.
[0028] Fig. 2 is a control flowchart of an oil-recovery control unit of the air-conditioning
apparatus according to the first embodiment of the present invention.
[0029] Figs. 3A and 3B are control flowcharts of an oil-recovery control unit of an air-conditioning
apparatus according to a second embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Embodiments of the present invention will be described with reference to the drawings.
First Embodiment
[0031] A first embodiment of the present invention will be described with reference to Figs.
1 and 2.
[0032] Fig. 1 illustrates a refrigerant circuit of a multi-unit air-conditioning apparatus
1 according to the first embodiment of the present invention. The air-conditioning
apparatus 1 includes one outdoor unit 2 and a plurality of indoor units 3A, 3B, and
3C that are connected in parallel to the outdoor unit 2. In this embodiment, the three
indoor units 3A, 3B, and 3C are connected. However, the number of indoor units 3A,
3B, and 3C to be connected is not limited thereto.
[0033] The outdoor unit 2 includes an inverter-driven compressor 4 configured to compress
a refrigerant, a four-way diverter valve 5 configured to switch the circulation direction
of the refrigerant, an outdoor heat-exchanger 6 configured to carry out heat exchange
between the refrigerant and outdoor air, an outdoor electronic expansion valve 7 for
heating, a receiver 8 configured to retain a liquid refrigerant, a supercooling heat-exchanger
9 configured to supercool the liquid refrigerant, and an accumulator 10 configured
to supply the compressor 4 only with a gas refrigerant by separating the liquid component
in the refrigerant gas. These components are connected by a known refrigerant pipe
11 to configure a refrigerant circuit 12 for the outdoor unit 2. The supercooling
heat-exchanger 9 is a double-pipe heat-exchanger. The refrigerant from the refrigerant
pipe 11 is guided in the inner pipe of the supercooling heat-exchanger 9 via an electronic
expansion valve 13 so as to cool the liquid refrigerant circulating in the outer pipe
of the supercooling heat-exchanger 9. The refrigerant guided in the inner pipe is
guided to the inlet of the accumulator 10 as a gas refrigerant.
[0034] A gas-side control valve 14 and a liquid-side control valve 15 are provided in the
outdoor unit 2. A gas pipe 16 and a liquid pipe 17 that extend to the indoor units
3A, 3B, and 3C are connected via the gas-side control valve 14 and the liquid-side
control valve 15. The plurality of indoor units 3A, 3B, and 3C are connected in series
to the gas pipe 16 and the liquid pipe 17 via a branching unit and indoor refrigerant
pipes 18A, 18B, and 18C, which are not shown in the drawing.
[0035] The indoor units 3A, 3B, and 3C each include an indoor heat-exchanger 19 configured
to carry out heat exchange with indoor air and an indoor electronic expansion valve
(EEV) 20 for cooling. The indoor units 3A, 3B, and 3C are provided for each air-conditioning
zone or each room. The length of each indoor refrigerant pipe 18A, 18B, or 18C connected
to the indoor units 3A, 3B, and 3C depends on the position of each indoor unit 3A,
3B, or 3C. Here, the relationship of the lengths of the indoor refrigerant pipes 18A,
18B, and 18C is 18A > 18B > 18C. By connecting the indoor refrigerant pipes 18A, 18B,
and 18C with the refrigerant circuit 12 on the side of the outdoor unit 2 via the
gas pipe 16 and the liquid pipe 17, a completely closed single-system refrigerant
circuit 21 is configured.
[0036] The air-conditioning apparatus 1 includes an oil-recovery operating unit 22 configured
to carry out liquid return operation of the indoor units 3A, 3B, and 3C at a predetermined
timing, for example, after the elapse of predetermined operation times so as to carry
out an oil-recovery operation for recovering the lubricant accumulated in the gas
side of the refrigerant circuit 21 and to complete the oil-recovery operation when
a return of liquid refrigerant is detected at the outdoor unit 2. The timing for carrying
out the oil-recovery operation is not limited thereto and may be carried out at other
timings, such as when the cumulative flow amount of the lubricant, calculated on the
basis of a predetermined formula, reaches a predetermined limit flow amount. In the
liquid return operation, the indoor electronic expansion valves 20 of the indoor units
3A, 3B, and 3C can be set at predetermined degrees of opening for the oil-recovery
operation. Whether or not liquid refrigerant is returning to the outdoor unit 2 during
oil-recovery operation can be detected by determining the degree of superheating of
the suction refrigerant from values detected by a low-pressure sensor 23 and an intake-refrigerant
temperature sensor 24 that are provided on the refrigerant pipe 11 on the inlet side
of the accumulator 10.
[0037] A refrigerant-pipe-length detecting unit 26 that detects the pipe length of each
indoor refrigerant pipe 18A, 18B, or 18C connected to each indoor unit 3A, 3B, or
3C, respectively, and a refrigerant-pipe-length storage unit 27 that stores the detected
pipe length are provided in the oil-recovery operating unit 22. For detecting the
refrigerant pipe length, the above-mentioned invention in
Japanese Unexamined Patent Application, Publication No. 2006-183979, filed by the present assignee, may be employed. According to this refrigerant-pipe-length
detection method, the pressure loss of a low-pressure gas pipe (i.e., indoor refrigerant
pipe 18A, 18B, and 18C and the gas pipe 16) is calculated from the suction pressure
of the compressor 4 (detected by the low-pressure sensor 23) and the saturation pressure
of the indoor refrigerant pipe 18A, 18B, or 18C (calculated from the refrigerant temperature
detected by heat-exchanger temperature sensors 25 provided on the indoor refrigerant
pipes 18A, 18B, and 18C) during cooling operation. On the basis of the pressure loss,
the length of the low-pressure gas pipe is determined by employing Darcy's formula,
as follows:

where λ represents Darcy's coefficient of pipe friction, Δx represents the length
of the low-pressure gas pipe, D represents the inner diameter of the pipe, ρ represents
the relative density of the refrigerant, and u represents the average flow speed.
Darcy's coefficient of pipe friction λ, the inner diameter D of the pipe, relative
density ρ of the refrigerant, and the average flow speed u are determined in advance.
The average flow speed u can be determined by calculating the average flow volume
of the refrigerant flowing inside the refrigerant circuit 21 on the basis of the discharge
amount of the compressor 4 and dividing the derived value by the cross-sectional area
of the refrigerant pipe (πD
2/4).
[0038] Detection of the refrigerant pipe length is not limited to the above-described method;
other known methods may be employed. For example, the refrigerant pipe length may
be calculated on the basis of the amount of time required for the temperature of the
gas discharged from the compressor to reach a predetermined temperature after the
degree of opening of the expansion valve is forcefully changed after the cooling operation
is stabilized.
[0039] The detection of the refrigerant pipe length by the refrigerant-pipe-length detecting
unit 26 is carried out so as to add an appropriate amount of refrigerant corresponding
to the refrigerant pipe length after the air-conditioning apparatus 1 is installed.
This detection result may be stored in the refrigerant-pipe-length storage unit 27
and may be used when the oil-recovery operation is carried out.
[0040] An oil-recovery control unit 28 that changes the amount of time for carrying out
the oil-recovery operation on the basis of the length of each indoor refrigerant pipe
18A, 18B, or 18C (actually the length of the low-pressure gas pipe including the length
of the gas pipe 16) of each indoor unit 3A, 3B, or 3C stored in the refrigerant-pipe-length
storage unit 27 when the oil-recovery operation is carried out at the above-described
timing is provided in the oil-recovery operating unit 22.
[0041] The oil-recovery control unit 28 controls the oil-recovery operation time in accordance
with the control flow illustrated in Fig. 2.
[0042] At the oil-recovery control unit 28, first, it is determined, on the basis of the
detection result of the refrigerant pipe length, whether the difference between the
refrigerant pipe length (Lmax) of the indoor refrigerant pipe 18A connected to the
furthest indoor unit 3A and the refrigerant pipe length (Lmin) of the indoor refrigerant
pipe 18C connected to the closest indoor unit 3C is greater than a set pipe length
difference Llim (for example, 40 m) (S1). If the refrigerant-pipe length difference
is smaller than the set pipe length difference Llim, the process proceeds to normal
control, and the above-described oil-recovery operation is carried out. When liquid
return is detected in the outdoor unit 2, the oil-recovery operation is completed
after the elapse of an oil-recovery operation time Tk (for example, after 30 seconds)
set on the basis of the refrigerant pipe length. When the refrigerant-pipe length
difference is greater than the set pipe length difference Llim, the completion condition
of the oil-recovery operation is changed (S2).
[0043] To change the completion condition of the oil-recovery operation, it is determined
by how much time the oil-recovery operation completion time is to be delayed on the
basis of the refrigerant-pipe length difference (Lmax - Lmin) (S3). If the refrigerant-pipe
length difference (Lmax - Lmin) is within a set range (for example, 40 m < Lmax -
Lmin ≤ 60 m), the operation completion time is delayed from the set completion time
by, for example, 30 seconds, and the oil-recovery operation time is extended by 30
seconds (S4). When the refrigerant-pipe length difference (Lmax - Lmin) exceeds a
set value (for example, 60 m), the operation completion time is delayed from the set
completion time by, for example, 60 seconds, and the oil-recovery operation time is
extended by 60 seconds (S5). The operation completion condition changed in the above-described
manner is stored in the oil-recovery operating unit 22, which controls the outdoor
unit 2 (S6). Then, the control is switched to normal control so as to carry out the
above-described oil-recovery operation.
[0044] The following advantages are achieved according to this embodiment having the above-described
structure.
[0045] While normal air-conditioning operation is being carried out, some of the lubricant
discharged from the compressor 4 together with the refrigerant gas circulates in the
refrigerant circuit 21 together with the refrigerant gas and returns to the compressor
4. However, some of the lubricant is accumulated in the indoor units 3A, 3B, and 3C
and the indoor refrigerant pipes 18A, 18B, and 18C, i.e., mainly in the gas side refrigerant
pipes. At a predetermined timing, for example, when a predetermined amount of operation
time elapses, or when the flow amount of the lubricant reaches a limit flow amount,
the oil-recovery operation is started.
[0046] During the oil-recovery operation, a liquid return operation is carried out in a
cooling cycle while the indoor electronic expansion valves 20 of the indoor units
3A, 3B, and 3C are set at a predetermined degree of opening for the oil-recovery operation
so as to return the liquid refrigerant to the outdoor unit 2. In this way, the lubricant
accumulated in the indoor units 3A, 3B, and 3C and the indoor refrigerant pipes 18A,
18B, and 18C is flushed with the refrigerant flow and is recovered to the compressor
4.
[0047] When the liquid refrigerant returns to the outdoor unit 2, the liquid return is detected
and the oil-recovery operation is completed. Whether or not the liquid refrigerant
has returned to the outdoor unit 2 can be determined by calculating the degree of
superheating of the suction refrigerant from values detected by the low-pressure sensor
23 and the intake-refrigerant temperature sensor 24 provided on the refrigerant pipe
11 on the inlet side of the accumulator 10. The oil-recovery operation is completed
a predetermined amount of time (30 seconds according to this embodiment) after the
liquid return to the outdoor unit 2 is detected.
[0048] In general, when the refrigerant pipe is long, pressure loss is large. Therefore,
the pressure difference on both sides of an expansion valve is reduced, causing the
flow amount of refrigerant to be reduced. Accordingly, the oil recovery is unsatisfactory.
When the refrigerant pipe is long, heat loss from the pipe is large. Therefore, even
during liquid return, the refrigerant becomes nearly overheated while it flows through
the pipes. It is easier to recover the oil during liquid return; however, oil recovery
is unsatisfactory when the oil is overheated.
[0049] According to this embodiment, the refrigerant-pipe length difference (Lmax - Lmin)
of the indoor units 3A, 3B, and 3C detected in advance by the refrigerant-pipe-length
detecting unit 26 and stored in the refrigerant-pipe-length storage unit 27 is compared
with the set pipe length difference Llim (for example, 40 m) (S1 in Fig. 2). If the
refrigerant-pipe length difference (Lmax - Lmin) is less than 40 m, as described above,
the oil-recovery operation is completed 30 seconds after liquid return is detected.
If the refrigerant-pipe length difference (Lmax - Lmin) is equal to or greater than
40 m, the completion condition of the oil-recovery operation is changed.
[0050] When it is determined whether or not the refrigerant-pipe length difference of the
indoor unit 3A and the indoor unit 3C is within the range of 40 m < Lmax - Lmin ≤
60 m (S3 in Fig. 2), the completion condition of the oil-recovery operation is set
such that, when the refrigerant-pipe length difference is between 40 and 60 m, the
oil-recovery operation time is extended by 30 seconds (S4 in Fig. 2), and the oil-recovery
operation is completed 60 seconds after liquid return is detected at the outdoor unit
2. When the refrigerant-pipe length difference exceeds 60 m, the oil-recovery operation
time is extended by 60 seconds (S5 in Fig. 2), and the oil-recovery operation is completed
90 seconds after liquid return is detected at the outdoor unit 2. In this way, even
when the refrigerant pipe length differs for each indoor unit 3A, 3B, or 3C, the oil-recovery
operation time can be changed on the basis of the refrigerant pipe length of each
indoor unit 3A, 3B, or 3C so as to set an appropriate oil-recovery operation time
corresponding to the indoor unit 3A that has the largest refrigerant pipe length.
Therefore, the lubricant accumulated in the indoor units 3A, 3B, and 3C and their
refrigerant circuits can be reliably collected.
[0051] In particular, according to this embodiment, the refrigerant-pipe length difference
of the indoor units 3A, 3B, and 3C is determined, and the completion time of the oil-recovery
operation can be changed on the basis of the determined refrigerant-pipe length difference.
Therefore, when it is determined that the refrigerant-pipe length difference is large,
the completion time of the oil-recovery operation can be delayed by an amount of time
corresponding to the refrigerant-pipe length difference, and the oil-recovery operation
time can be extended. In this way, the lubricant accumulated in the indoor unit 3A
having the largest refrigerant pipe length and the indoor refrigerant pipe 18A can
be reliably recovered to the compressor 4. Accordingly, a predetermined amount of
lubricant can be constantly retained in the compressor 4, reliably preventing defective
lubrication caused by lack of lubricant in the compressor 4 due to a large amount
of lubricant being discharged to the refrigerant circuit 21.
[0052] According to this embodiment, when the refrigerant-pipe length difference is equal
to or greater than the set pipe difference, the oil-recovery operation time is changed
in two steps. However, it may be changed in three steps or may be changed continuously.
[0053] The oil-recovery operation time is changed on the basis of the refrigerant-pipe length
difference of the indoor units 3A, 3B, and 3C. However, the process of changing the
oil-recovery operation time is not limited thereto, and various modifications, as
described below, may be employed.
[0054] First, the distribution of the refrigerant pipe length is determined on the basis
of the detection result of the refrigerant pipe lengths of the indoor units 3A, 3B,
and 3C. When many of the indoor units have refrigerant pipes longer than the average
refrigerant pipe length, the completion time of the oil-recovery operation is delayed
by an amount of time corresponding to the indoor units having long refrigerant pipes
so as to extend the oil-recovery operation time. In this way, similar to the above-described
embodiment, the lubricant accumulated in the indoor units having long refrigerant
pipes and their refrigerant pipes can be reliably recovered to the compressor 4. Thus,
a sufficient amount of lubricant can be constantly retained in the compressor 4, and
defective lubrication caused by lack of lubricant can be reliably prevented.
[0055] Second, the total length of the refrigerant pipes of the indoor units 3A, 3B, and
3C is calculated on the basis of the detection result of the length of the indoor
units 3A, 3B, and 3C. When it is determined that the total refrigerant pipe length
is larger than a reference pipe length on the basis of the total refrigerant pipe
length, the completion time of the oil-recovery operation is delayed by an amount
of time corresponding to the length, and the oil-recovery operation time is extended.
In this way, also, the same advantages according to the above-described embodiment
may be achieved.
[0056] Third, according to the above-described embodiment and modifications, the completion
time of the oil-recovery operation is delayed in accordance with the indoor unit having
the longest refrigerant pipe on the basis of the refrigerant pipe lengths of the indoor
units 3A, 3B, and 3C so as to extend the oil-recovery operation time. Instead, however,
a reference oil-recovery operation time may be set in accordance with the indoor unit
3A having the longest refrigerant pipe, and the start time of the oil-recovery operation
may be changed for the indoor unit 3C having the shortest refrigerant pipe. In other
words, the oil-recovery operation is started in order from the indoor unit 3A having
the longest refrigerant pipe, and the oil-recovery operation time of the indoor unit
3A having the longest refrigerant pipe is extended and the oil-recovery operation
time of the indoor unit having a small refrigerant pipe length is shortened by delaying
the start time of the oil-recovery operation of the indoor unit 3C having a small
refrigerant pipe length. In this way, also, the same advantages according to the above-described
embodiment may be achieved.
[0057] According to this embodiment, the operation time changed during the oil-recovery
operation is not limited to that described above, and may be set appropriately. However,
since the oil-recovery operation is a liquid return operation, it is desirable to
limit the maximum operation time by taking into consideration the volume of the accumulator
10.
Second Embodiment
[0058] Next, a second embodiment of the present invention will be described with reference
to Figs. 1, 3A and 3B.
[0059] The structure of an oil-recovery control unit 38 according to this embodiment differs
from that according to the above-described first embodiment. Since other structures
according to this embodiment are the same as those according to the first embodiment,
descriptions thereof are not repeated here.
[0060] The oil-recovery control unit 38 according to this embodiment changes the degrees
of opening of the indoor electronic expansion valves 20 on the basis of the refrigerant
pipe lengths of the indoor units 3A, 3B, and 3C, instead of changing the oil-recovery
operation time.
[0061] The oil-recovery control unit 38 controls the degrees of opening of the indoor electronic
expansion valves 20 during the oil recovery operation in accordance with the flowchart
shown in Figs. 3A and 3B.
[0062] As shown in Figs. 3A and 3B, on the basis of the refrigerant pipe lengths detected
by the refrigerant-pipe-length detecting unit 26 and stored in the refrigerant-pipe-length
storage unit 27, the oil-recovery control unit 38 determines whether or not the difference
between the refrigerant pipe length (Lmax) of the farthest indoor unit 3A having the
longest indoor refrigerant pipe 18A and the refrigerant pipe length (Lmin) of the
closest indoor unit 3C having the shortest indoor refrigerant pipe 18C is greater
than a set pipe-length difference Llim (for example, 40 m) (S11). If the refrigerant
pipe-length difference is smaller than the set pipe-length difference Llim, the process
proceeds to normal control, and the above-described oil recovery operation is carried
out. The oil recovery operation is completed 30 seconds after liquid return is detected
at the outdoor unit 2. When the refrigerant pipe-length difference is greater than
the set pipe-length difference Llim, the oil-recovery operation conditions, i.e.,
the degree of opening of the indoor electronic expansion valve 20 of each indoor unit
3A, 3B, and 3C, is changed as described below.
[0063] First, the average length Lave of each indoor refrigerant pipe 18A, 18B, and 18C
of each indoor unit 3A, 3B, and 3C, respectively, is calculated by the formula Lave
= (Lmax - Lmin)/2 (actually the average length of the low-pressure gas pipe includes
the length of the gas pipe 16) (S12). Next, the total refrigerant pipe length Li (where
i equals the number of unit(s) connected) and the average length Lave are compared
(S13), and it is determined whether Li > Lave (S14). As a result, when Li is greater
("Yes"), it is determined whether Li > Lave + 20 (S15). When Li is smaller ("No"),
it is determined whether Li > Lave - 20 (S16).
[0064] Here, "+20" and "-20" correspond to "X = +20 pulses" and "X = -20 pulses", respectively,
when the pulse number corresponding to the newly set degree of opening is defined
as "X pulses" with respect to the originally set degree of opening of the indoor electronic
expansion valve 20 during the oil-recovery operation.
[0065] Next, based on the comparison result of Li > Lave + 20, when Li is greater ("Yes"),
the corresponding indoor electronic expansion valve 20 of the indoor unit is determined
to be, for example, +40 pulses with respect to the set degree of opening, i.e., is
determined to have a degree of opening 40 pulses greater than the set degree of opening
(S17). When Li is small ("No"), the indoor electronic expansion valve 20 of the corresponding
indoor unit is determined to be, for example, +20 pulses with respect to the set degree
of opening, i.e., is determined to have a degree of opening 20 pulses greater than
the set degree of opening (S18). Based on the comparison result of Li > Lave - 20,
when Li is greater ("Yes"), the corresponding indoor electronic expansion valve 20
of the indoor unit is determined to be, for example, -20 pulses with respect to the
set degree of opening, i.e., is determined to have a degree of opening 20 pulses smaller
than the set degree of opening (S19). When Li is small ("No"), the indoor electronic
expansion valve 20 of the corresponding indoor unit is determined to be, for example,
-40 pulses with respect to the set degree of opening, i.e., is determined to have
a degree of opening 40 pulses smaller than the set degree of opening (S20).
[0066] As described above, the degree of opening of each indoor electronic expansion valve
20 is determined, and a degree-of-opening changing instruction is sent to each indoor
electronic expansion valve 20 (S21). Each indoor electronic expansion valve 20 is
set to the determined degree of opening, and the oil-recovery operation is carried
out. When liquid return is detected at the outdoor unit 2, as described above, while
the oil-recovery operation is being carried out, the oil-recovery operation is completed
30 seconds thereafter. As a method of changing the degree-of-opening changing instruction
of each indoor electronic expansion valve 20, either of the following two methods
may be employed (S22).
- 1) The new degree of opening of each indoor electronic expansion valve 20 is sent
to each of the indoor units 3A, 3B, and 3C; the indoor units 3A, 3B, and 3C store
the information; and during the oil-recovery operation, the degree of opening of each
indoor electronic expansion valve 20 is corrected on the basis of the information.
- 2) During oil-recovery, the degree of opening of each indoor electronic expansion
valve 20 forcefully corrected by the outdoor unit 2 is reported to each of the indoor
units 3A, 3B, and 3C.
[0067] As described above, even when the refrigerant pipe length differs for each of the
indoor units 3A, 3B, and 3C, by changing the degree of opening of each indoor electronic
expansion valve 20 during the oil-recovery operation on the basis of the refrigerant
pipe length of each of the indoor units 3A, 3B, and 3C, the liquid return operation
can be carried out by discharging an appropriate amount of refrigerant corresponding
to the refrigerant pipe length of each of the indoor units 3A, 3B, and 3C, and the
lubricant accumulated in the indoor units 3A, 3B, and 3C and the indoor refrigerant
pipes 18A, 18B, and 18C can be recovered. Therefore, the lubricant retained in the
indoor unit 3A having a great refrigerant pipe length and its indoor refrigerant pipe
18A can be reliably recovered to the compressor 4.
[0068] Since the refrigerant-pipe length difference of each of the indoor units 3A, 3B,
and 3C is determined and the degree of opening of the indoor electronic expansion
valve 20 of the indoor unit 3A having the longest refrigerant pipe is set to the largest
value, the lubricant accumulated in the indoor unit 3A having the longest refrigerant
pipe can be actively recovered by discharging a large amount of refrigerant.
[0069] Accordingly, also with this embodiment, similar to the above-described first embodiment,
a predetermined amount of lubricant can be constantly retained in the compressor 4.
Therefore, defective lubrication caused by lack of lubricant in the compressor 4 is
reliably prevented.
[0070] According to the above-described embodiments, as the various sensors, including the
low-pressure sensor 23, the intake-refrigerant temperature sensor 24, and the heat-exchanger
temperature sensor 25, known sensors already installed in the air-conditioning apparatus
1 may be employed, and, thus, new sensors do not have to be installed. Furthermore,
a refrigerant-pipe length detection system installed for adding refrigerant may also
be used as the refrigerant-pipe-length detecting unit 26.
1. An air-conditioning apparatus (1) comprising:
an outdoor unit (2) including a compressor (4) and an outdoor heat-exchanger (6);
a plurality of indoor units (3A-3C) connected in parallel with each other, each of
the indoor units (3A-3C) including an indoor heat-exchanger (19) and an indoor expansion
valve (20);
a refrigerant circuit (21) formed by connecting, in order, the compressor (4), the
outdoor heat-exchanger (6), the plurality of indoor heat-exchangers (19), and the
indoor expansion valves (20) using refrigerant pipes (11, 16, 17, 18A-18C); and
an oil-recovery operating unit (22) configured to carry out a liquid return operation
at each indoor unit (3A-3C) at a predetermined timing, to carry out an oil-recovery
operation for recovering lubricant accumulated in the refrigerant circuit (21), and
to complete the oil-recovery operation when liquid return is detested at the outdoor
unit (2),
characterized in that the oil-recovery operating unit (22) include
a refrigerant-pipe-length detecting unit (26) configured to detect the refrigerant
pipe length of each of the indoor units (3A-3C),
a refrigerant-pipe-length storing unit (27) configured to store the refrigerant pipe
lengths detected by the refrigerant-pipe-length detecting unit (26), and
an oil-recovery control unit (28) configured to change the operation time during oil-recovery
operation on the basis of the refrigerant pipe length of each of the indoor units
(3A-3C) stored in the refrigerant-pipe-length storing unit (27).
2. The air-conditioning apparatus (1) according to Claim 1, wherein the oil-recovery
control unit (28) determines refrigerant-pipe length differences among each of the
indoor units (3A-3C) and changes the operation completion time during the oil-recovery
operation on the basis of the refrigerant-pipe length differences.
3. The air-conditioning apparatus (1) according to Claim 1, wherein the oil-recovery
control unit (28) determines a distribution of the refrigerant-pipe lengths of the
indoor units (3A-3C) and changes the operation completion time during the oil-recovery
operation on the basis of the distribution of the refrigerant-pipe lengths.
4. The air-conditioning apparatus (1) according to Claim 1, wherein the oil-recovery
control unit (28) adds the refrigerant-pipe lengths of the indoor units (3A-3C) and
changes the operation completion time during the oil-recovery operation on the basis
of the total refrigerant-pipe length.
5. The air-conditioning apparatus (1) according to Claim 1, wherein the oil-recovery
control unit (29) determines the refrigerant-pipe length differences among each of
the indoor units (3A-3C) and changes the operation start time during the oil-recovery
operation on the basis of the refrigerant-pipe length differences.
6. An air-conditioning apparatus (1) comprising:
an outdoor unit (2) including a compressor (4) and an outdoor heat-exchanger (6);
a plurality of indoor units (3A-3C) connected in parallel with each other, each of
the indoor units (3A-3C) including an indoor heat-exchanger (19) and an indoor expansion
valve (20);
a refrigerant circuit (21) formed by connecting, in order, the compressor (4), the
outdoor heat-exchanger (6), the plurality of indoor heat-exchangers (19), and the
indoor expansion valves (20) using refrigerant pipes (11, 16, 17, 18A-18C); and
an oil-recovery operating unit (22) configured to carry out a liquid return operation
at each indoor unit (3A-3C) at a predetermined timing, to carry out an oil-recovery
operation for recovering lubricant accumulated in the refrigerant circuit (21), and
to complete the oil-recovery operation when liquid return is detected at the outdoor
unit (2),
characterized in that the oil-recovery operating unit (22) incudes
a refrigerant-pipe-length detecting unit (26) configured to detect the refrigerant
pipe length of each of the indoor units (3A-3C),
a refrigeraht-pipe-lehgth storing unit (27) configured to store the refrigerant pipe
lengths detected by the refrigerant-pipe-length detecting unit (26), and
an oil-recovery control unit (28) configured to change the degree of opening of each
indoor expansion valve (20) during the oil-recovery operation on the basis of the
refrigerant pipe length of each of the indoor units (3A-3C) stored in the refrigerant-pipe-length
storing unit (27).
7. The air-conditioning apparatus (1) according to Claim 6, wherein the oil-recovery
control unit (28) determines the refrigerant-pipe length differences among each of
the indoor units (3A-3C) and sets the degree of opening of the indoor expansion valve
(20) so that the longer the refrigerant pipe (18A-18C) of the indoor unit (3A-3C)
is, the greater the degree of opening is.
1. Klimaanlage (1), umfassend:
- eine Außeneinheit (2), einschließlich eines Kompressors (4) und eines Außen-Wärmetauschers
(6);
eine Vielzahl von parallel miteinander verbundenen Inneneinheiten (3A-3C), wobei jede
Inneneinheit (3A-3C) einen Innen-Wärmetauscher (19) und ein Innen-Expansionsventil
(20) einschließt;
- einen Kühlmittelkreislauf (21), der dadurch ausgebildet wird, dass der Kompressor (4), der Außen-Wärmetauscher (6), die Vielzahl
der Innen-Wärmetauscher (19) und die Innen-Expansionsventile (29) unter Verwendung
von Kühlrohren (11, 16, 17, 18A-18C) hintereinander verbunden werden; und
- eine Ölrückgewinnungs-Betriebseinheit (22), die zum Ausführen eines Liquidrückführungs-Vorgangs
bei jeder Inneneinheit (3A-3C) zu einem vorgegebenen Zeitpunkt ausgestaltet ist, um
einen Ölrückgewinnungs-Vorgang zum Rückgewinnen von Schmiermitteln, die sich in dem
Kühlkreislauf (21) angesammelt haben, auszuführen und um den Ölrückgewinnungs-Vorgang
abzuschließen, wenn eine Liquidrückführung von der Außeneinheit (2) detektiert wird,
dadurch gekennzeichnet, dass die Ölrückgewinnungs-Betriebseinheit (22) einschließt:
- eine Kühlleitungslängen-Detektiereinheit (26), die zum Detektieren der Länge der
Kühlleitung bei jeder Inneneinheit (3A-3C) ausgelegt ist,
- eine Kühlleitungslängen-Abspeichereinheit (27), die zum Abspeichern der von der
Kühlleitungslängen-Detektiereinheit (26) detektierten Kühlleitungslängen ausgelegt
ist,
- eine Ölrückgewinnungs-Steuerungseinheit (28), welche zum Ändern der Betriebsdauer
während des Ölrückgewinnungs-Vorgangs aufgrund der Kühlmittelrohrlänge bei jeder Inneneinheit
(3A-3C) ausgelegt ist, welche in der Kühlleitungslängen-Abspeichereinheit (27) abgespeichert
ist.
2. Klimaanlage (1) nach Anspruch 1, bei der die Ölrückgewinnungs-Steuerungseinheit (28)
die Unterschiede der Kühlrohrlänge bei jeder Inneneinheit (3A-3C) bestimmt und den
Zeitpunkt zum Beendigen des Vorgangs während des Ölrückgewinnungs-Vorgangs aufgrund
der Unterschiede in der Kühlleitungslänge ändert.
3. Klimaanlage (1) nach Anspruch 1, bei der die Ölrückgewinnungs-Steuerungseinheit (28)
eine Verteilung der Kühlrohrlängen bei den Inneneinheiten (3A-3C) bestimmt und den
Zeitpunkt zum Beendigen des Vorgangs während des Ölrückgewinnungs-Vorgangs aufgrund
der Verteilung der Kühlrohrlängen ändert.
4. Klimaanlage (1) nach Anspruch 1, bei der die Ölrückgewinnungs-Steuerungseinheit (28)
die Kühlrohrlängen bei den Inneneinheiten (3A-3C) hinzuaddiert und den Zeitpunkt zum
Beendigen des Vorgangs während des Ölrückgewinnungs-Vorgangs aufgrund der Gesamtlänge
der Kühlrohre ändert.
5. Klimaanlage (1) nach Anspruch 1, bei der die Ölrückgewinnungs-Steuerungseinheit (28)
die Unterschiede in der Kühlrohrlänge bei jeder Inneneinheit (3A-3C) bestimmt und
den Zeitpunkt des Beginns des Vorgangs während des Ölrückgewinnungs-Vorgangs aufgrund
der Unterschiede in der Kühlleitungslänge ändert.
6. Klimaanlage (1), umfassend:
- eine Außeneinheit (2), einschließlich eines Kompressors (4) und eines Außen-Wärmetauschers
(6);
eine Vielzahl von parallel miteinander verbundenen Inneneinheiten (3A-3C), wobei jede
Inneneinheit (3A-3C) einen Innen-Wärmetauscher (19) und ein Innen-Expansionsventil
(20) einschließt;
- einen Kühlmittelkreislauf (21), der dadurch ausgebildet wird, dass der Kompressor (4), der Außen-Wärmetauscher (6), die Vielzahl
der Innen-Wärmetauscher (19) und die Innen-Expansionsventile (29) unter Verwendung
von Kühlrohren (11, 16, 17, 18A-18C) hintereinander verbunden werden; und
- eine Ölrückgewinnungs-Betriebseinheit (22), die zum Ausführen eines Liquidrückführungs-Vorgangs
bei jeder Inneneinheit (3A-3C) zu einem vorgegebenen Zeitpunkt ausgestaltet ist, um
einen Ölrückgewinnungs-Vorgang zum Rückgewinnen von Schmiermitteln, die sich in dem
Kühlkreislauf (21) angesammelt haben, auszuführen und um den Ölrückgewinnungs-Vorgang
abzuschließen, wenn eine Liquidrückführung von der Außeneinheit (2) detektiert wird,
dadurch gekennzeichnet, dass die Ölrückgewinnungs-Betriebseinheit (22) einschließt:
- eine Kühlleitungslängen-Detektiereinheit (26), die zum Detektieren der Länge der
Kühlleitung bei jeder Inneneinheit (3A-3C) ausgelegt ist,
- eine Kühlleitungslängen-Abspeichereinheit (27), die zum Abspeichern der von der
Kühlleitungslängen-Detektiereinheit (26) detektierten Kühlleitungslängen ausgelegt
ist,
- eine Ölrückgewinnungs-Steuerungseinheit (28), welche zum Ändern des Öffnungsgrades
bei jedem Innen-Expansionsventil (20) während des Ölrückgewinnungs-Vorgangs aufgrund
der Kühlmittelrohrlänge bei jeder Inneneinheit (3A-3C) ausgelegt ist, welche in der
Kühlleitungslängen-Abspeichereinheit (27) abgespeichert ist.
7. Klimaanlage (1) nach Anspruch 6, bei der die Ölrückgewinnungs-Steuerungseinheit (28)
die Unterschiede in der Kühlrohrlänge bei jeder Inneneinheit (3A-3C) bestimmt und
den Öffnungsgrad des Innen-Expansionsventils (20) so einstellt, dass der Öffnungsgrad
um so größer ist, je länger das Kühlrohr (18A-18C) bei der Inneneinheit (3A-3C) ist.
1. Appareil de climatisation d'air (1) comprenant :
une unité extérieure (2) comprenant un compresseur (4) et un échangeur de chaleur
externe (6) ;
une pluralité d'unités intérieures (3A-3C) raccordées en parallèle entre elles, chacune
des unités intérieures (3A-3C) comprenant un échangeur de chaleur interne (19) et
une soupape d'expansion interne (20) ;
un circuit de réfrigérant (21) formé en raccordant, dans l'ordre, le compresseur (4),
l'échangeur de chaleur externe (6), la pluralité d'échangeurs de chaleur internes
(19) et les soupapes d'expansion internes (20) en utilisant des tuyaux de réfrigérant
(11, 16, 17, 18A-18C) ; et
une unité d'actionnement de récupération d'huile (22) configurée pour réaliser une
opération de retour de liquide au niveau de chaque unité interne (3A-3C) à un moment
prédéterminé, pour réaliser une opération de récupération d'huile afin de récupérer
le lubrifiant accumulé dans le circuit de réfrigérant (21), et pour terminer l'opération
de récupération d'huile lorsque le retour de liquide est détecté au niveau de l'unité
externe (2),
caractérisé en ce que l'unité d'actionnement de récupération d'huile (22) comprend :
une unité de détection de longueur de tuyau de réfrigérant (26) configurée pour détecter
la longueur de tuyau de réfrigérant de chacune des unités internes (3A-3C),
une unité de stockage de longueur de tuyau de réfrigérant (27) configurée pour stocker
les longueurs de tuyau de réfrigérant détectées par l'unité de détection de longueur
de tuyau de réfrigérant (26), et
une unité de commande de récupération d'huile (28) configurée pour changer le temps
d'opération pendant l'opération de récupération d'huile en fonction de la longueur
de tuyau de réfrigérant de chacune des unités internes (3A-3C) stockées dans l'unité
de stockage de longueur de tuyau de réfrigérant (27).
2. Appareil de climatisation d'air (1) selon la revendication 1, dans lequel l'unité
de commande de récupération d'huile (28) détermine les différences de longueur de
tuyau de réfrigérant parmi chacune des unités internes (3A-3C) et change le temps
d'achèvement d'opération pendant l'opération de récupération d'huile en fonction des
différences de longueur de tuyau de réfrigérant.
3. Appareil de climatisation d'air (1) selon la revendication 1, dans lequel l'unité
de commande de récupération d'huile (28) détermine une distribution des longueurs
de tuyau de réfrigérant des unités internes (3A-3C) et change le temps d'achèvement
d'opération pendant l'opération de récupération d'huile en fonction de la distribution
des longueurs de tuyau de réfrigérant.
4. Appareil de climatisation d'air (1) selon la revendication 1, dans lequel l'unité
de commande de récupération d'huile (28) ajoute les longueurs de tuyau de réfrigérant
des unités internes (3A-3C) et change le temps d'achèvement d'opération pendant l'opération
de récupération d'huile en fonction de la longueur de tuyau de réfrigérant totale.
5. Appareil de climatisation d'air (1) selon la revendication 1, dans lequel l'unité
de commande de récupération d'huile (28) détermine les différences de longueur de
tuyau de réfrigérant parmi chacune des unités internes (3A-3C) et change le temps
de début d'opération pendant l'opération de récupération d'huile en fonction des différences
de longueur de tuyau de réfrigérant.
6. Appareil de climatisation d'air (1) comprenant :
une unité externe (2) comprenant un compresseur (4) et un échangeur de chaleur externe
(6) ;
une pluralité d'unités internes (3A-3C) raccordées en parallèle entre elles, chacune
des unités internes (3A-3C) comprenant un échangeur de chaleur interne (19) et une
soupape d'expansion interne (20) ;
un circuit de réfrigérant (21) formé en raccordant, dans l'ordre, le compresseur (4),
l'échangeur de chaleur externe (6), la pluralité d'échangeurs de chaleur internes
(19) et les soupapes d'expansion internes (20) en utilisant les tuyaux de réfrigérant
(11, 16, 17, 18A-18C) ; et
une unité d'actionnement de récupération d'huile (22) configurée pour réaliser une
opération de retour de liquide au niveau de chaque unité interne (3A-3C) à un moment
prédéterminé, pour réaliser une opération de récupération d'huile afin de récupérer
le lubrifiant accumulé dans le circuit de réfrigérant (21), et pour achever l'opération
de récupération d'huile lorsque le retour de liquide est détecté au niveau de l'unité
externe (2),
caractérisé en ce que l'unité d'actionnement de récupération d'huile (22) comprend :
une unité de détection de longueur de tuyau de réfrigérant (26) configurée pour détecter
la longueur de tuyau de réfrigérant de chacune des unités internes (3A-3C),
une unité de stockage de longueur de tuyau de réfrigérant (27) configurée pour stocker
les longueurs de tuyau de réfrigérant détectées par l'unité de détection de longueur
de tuyau de réfrigérant (26), et
une unité de commande de récupération d'huile (28) configurée pour changer le degré
d'ouverture de chaque soupape d'expansion interne (20) pendant l'opération de récupération
d'huile en fonction de la longueur de tuyau de réfrigérant de chacune des unités internes
(3A-3C) stockée dans l'unité de stockage de longueur de tuyau de réfrigérant (27).
7. Appareil de climatisation d'air (1) selon la revendication 6, dans lequel l'unité
de commande de récupération d'huile (28) détermine les différences de longueur de
tuyau de réfrigérant parmi chacune des unités internes (3A-3C) et détermine le degré
d'ouverture de la soupape d'expansion interne (20) de sorte que plus le tuyau de réfrigérant
(18A-18C) de l'unité interne (3A-3C) est long, plus le degré d'ouverture est important.