JPH0694960B2 - Multi-room air conditioner - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multi-room air conditioner, and more particularly to a multi-room air conditioner in which a plurality of indoor units are connected to one outdoor unit. Is.

[Conventional technology]

As a conventional multi-room air conditioner of this type, for example, the configuration of a multi-room air conditioner disclosed in Japanese Utility Model Publication No. 55-28993 is shown in FIG. That is, in FIG. 14, reference numeral 1 is a compressor, 2 is a four-way valve which is connected to the upstream side of the compressor 1 and which is a switching valve for performing cycle switching between cooling and heating,
3 is an outdoor heat exchanger in which one is connected to the four-way switching valve 2 and the other is connected to the expansion valve 22 and the receiver 28 in series.
Is an accumulator connected between the compressor 1 and the four-way valve 2, 23 is a check valve connected in parallel with the expansion valve 22, and constitutes a main circuit portion of the air conditioner. There is. Also, 5a, 5b are parallel branched from the main circuit section,
A plurality of indoor heat exchangers connected between the four-way valve 2 and the receiver 28 via gas-side solenoid valves 6a, 6b and liquid-side solenoid valves 24a, 24b, respectively. Bowl 5
Also for a and 5b, parallel circuits of expansion valves 26a and 26b and check valves 25a and 25b are connected in series between the liquid side solenoid valves 24a and 24b. In the case of the multi-room air conditioner according to this conventional example, the refrigerant is circulated by the switching operation of the four-way valve 2 as shown by the solid arrow in FIG. 14 for the cooling operation and as shown by the dotted arrow in the heating operation. is there.

And, in the case of the configuration of this conventional example, each indoor heat exchanger 5a, 5
b, that is, the plurality of indoor units are provided with expansion valves 26a, 26b for cooling, and these are unbalanced in load of the plurality of indoor units during cooling, or the installed positional relationship of each indoor unit is relatively large. Its main purpose is to supply a proper amount of refrigerant to each indoor unit even when it is not equal, but there is a means to distribute an appropriate amount of refrigerant to multiple indoor units during heating. However, the circuit configuration is not always sufficient as an air conditioner for multiple rooms. In addition, in a so-called one-to-one correspondence general air conditioner in which one outdoor unit corresponds to one indoor unit, the same reference numerals are used in FIG. 15 for the portions corresponding to FIG. As described above, the indoor unit is not provided with the expansion valve for controlling the refrigerant, and the capillary tube 27 provided in the outdoor unit controls both cooling and heating, which is a very simple and inexpensive circuit configuration. Is normal.

[Problems to be solved by the invention]

However, as an indoor unit for a multi-room air conditioner, it is difficult to apply the one-to-one correspondence indoor unit that is relatively inexpensive and has a large number of productions, and it is difficult to use it during heating and cooling. Control requires a receiver that stores excess refrigerant due to changes in operating conditions, and requires two refrigerant absorption containers together with an accumulator to prevent liquid return to the compressor in an excessive state. there were.

Furthermore, in the conventional multi-room air conditioner, when the junction of the liquid side branch circuit during heating operation is a high-pressure liquid refrigerant, and even if one of the indoor units is stopped, In order to collect the refrigerant, the refrigerant recovery circuit connected to the low-pressure circuit of the compressor via the check valve and the capillary tube is required, which causes a problem that the refrigerant circuit becomes complicated.

The present invention has been made to solve the above-mentioned problems, and while being a simple refrigerant circuit, it can be directly connected to a standard indoor unit used for a one-to-one air conditioner, An object of the present invention is to obtain a multi-room air conditioner that appropriately distributes refrigerant during heating and cooling operation to a plurality of indoor units, and that does not require a refrigerant recovery circuit and can adjust the amount of refrigerant only by an accumulator. .

[Means for solving problems]

The multi-room air conditioner according to the present invention, each gas side branch pipe connected to a plurality of indoor units is provided with an electromagnetic valve, and each liquid side branch pipe is provided with an expansion valve driven by an electric signal. A heat exchanger for exchanging heat with the refrigerant in the accumulator is provided between the confluence of the outdoor unit heat exchanger and the liquid side branch pipe, and the pressure or temperature obtained by the means for detecting the high pressure or the saturation temperature, and the accumulator. The control device for controlling the expansion valve is provided by the liquid level height of the above and the temperature obtained by the temperature detector of the gas side branch pipe or the input signal of the switch for setting the capacity of each indoor unit.

[Work]

The multi-room air conditioner according to the present invention, at the time of cooling and heating,
The expansion valve controls the degree of supercooling while balancing the supply of refrigerant to multiple indoor units, and can properly distribute the refrigerant to multiple indoor units, as well as supercooling by the amount of excess refrigerant accumulated in the accumulator. The target value of the temperature can be changed, and the standard indoor unit can be connected as it is with a simple refrigerant circuit.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, 1 is a compressor, 2 is a four-way valve which is a switching valve, 3
Is an outdoor heat exchanger, 4 is an accumulator, and these constitute the main part of the air conditioner. Reference numeral 8 is a heat exchanger in the accumulator, and the piping between the liquid side branch circuit and the outdoor heat exchanger 3 exchanges heat with the refrigerant in the accumulator. 6a to 6c are gas side electromagnetic valves provided in the gas side branch pipes 14a to 14c, and 7a to 7c are reversible expansion valves driven by electronic or electric signals provided in the liquid side branch pipes 15a to 15c. Further, the indoor heat exchanger 5a in a plurality of indoor units (not shown) via the connecting pipes 16a to 16c and 17a to 17c between the gas side branch pipes 14a to 14c and the liquid side branch pipes 15a to 15c. ,Five
b and 5c are connected. Reference numeral 10 is a pressure sensor which is a pressure detecting means for detecting the discharge pressure of the compressor 1, 12a to 12c are temperature sensors which are temperature detectors for detecting the temperature of the gas side branch pipe,
13a to 13c are temperature sensors that are temperature detectors that detect the temperature of the liquid side branch pipe, 11 is a temperature sensor that detects the outlet temperature of the outdoor heat exchanger during cooling, and 80 is the liquid level height of the refrigerant in the accumulator 4. Detecting means 9 is a control device for taking in the temperature signal of the temperature sensor and the pressure signal of the pressure sensor and the refrigerant liquid level signal of the height detecting means to control the reversible expansion valves 7a to 7c.

FIG. 2 is a partial refrigerant circuit diagram showing an example of the liquid level height detecting means 80 of the accumulator 4. In FIG. 2, 31a and 31b are liquid level detection bypass circuits from a predetermined height position on the side surface of the accumulator 4 to the suction pipe 35 of the compressor 1 via the capillaries 32a and 32b, and 33a and 33b are the bypass circuits. A temperature sensor for detecting the temperature of 31a, 31b, 34 is a pressure sensor for detecting the pressure of the inlet pipe 36 of the accumulator 4, so that the signals of the temperature sensors 33a, 33b and the pressure sensor 34 are input to the control device 9. It is configured.

FIG. 3 is a block diagram of the control device, which includes an analog-digital converter (A / D converter) 51, an input circuit 52, a central processing unit (CPU) 53, a memory 54, an output circuit 55, and an output buffer 56. It is configured. It should be noted that the input / output unit is shown as an example only.

Next, the operation of this embodiment will be described. In FIG. 1, during cooling, the high-pressure gas refrigerant discharged from the compressor 1 passes through the four-way valve 2, is liquefied by the outdoor heat exchanger 3, and is further cooled by the heat exchanger 8 in the accumulator 4 to obtain the degree of supercooling. Is taken to a branch circuit. Further, the pressure is reduced by expansion valves 7a to 7c provided in the respective branch pipes, enters the indoor heat exchangers 5a to 5c through the connecting pipes 17a to 17c, and evaporates there. The evaporated refrigerant is connected to the gas side communication pipes 16a to 16c.
Through the solenoid valves 6a to 6c provided in the gas side branch pipes 14a to 114c, and then returns to the compressor 1 via the four-way valve 2 and the accumulator 4. At this time, the pressure sensor 10 and the temperature sensor 11 at the outlet of the outdoor heat exchanger 3 bring the subcooling degree at the outlet of the outdoor heat exchanger 3 (hereinafter referred to as subcool) to the target subcool, and at the same time, to the gas side branch pipes 14a to 14c. The control devices 9 control the expansion valves 7a to 7c so that the temperature of each branch circuit is made uniform by the temperature sensors 12a to 12c provided.

Further, the target subcool is determined by the amount of refrigerant in the accumulator 4 obtained by the liquid level height detection means 80.

Next, the operation of the liquid level detection means 80 will be described. A part of the refrigerant in the accumulator 4 always passes through the liquid level detection bypass circuits 31a and 31b, and a very small amount flows toward the suction pipe 35 of the compressor 1. The capillaries 32a and 32b are for limiting the flow rate of the refrigerant. The refrigerant in the accumulator 4 is separated into a liquid portion and a gas portion. On the Mollier diagram of FIG. 4, the liquid portion corresponds to point A on the saturated liquid line and the gas portion corresponds to point B on the saturated air line. . Here, if the amount of refrigerant in the accumulator 4 is small and the inlet portions of the liquid level detection bypass circuits 31a and 31b are gas refrigerant, gas refrigerant flows in the liquid level detection bypass circuit, and there is a large amount of refrigerant. If the liquid refrigerant is accumulated and the inlet portion of the liquid level detecting bypass circuit is the liquid refrigerant, the liquid refrigerant flows in the liquid level detecting bypass circuit. Since the refrigerant in the accumulator 4 is lower than the ambient temperature,
In the liquid level detection bypass circuit, heat is exchanged between the refrigerant flowing inside and the surrounding air.At this time, if the refrigerant flowing inside is liquid, the temperature rise in the liquid level detection bypass circuit does not occur. There is almost no, and the pipe temperature is almost equal to the saturation temperature. Further, when the refrigerant flowing inside is a gas, a degree of superheat is accompanied and the pipe temperature rises. That is, if there is a heat exchange of Δi between the refrigerant and the ambient air, the state of the refrigerant in the middle of the liquid level detection bypass circuit is as shown in the Mollier diagram of FIG. It corresponds to point A ', and in the case of a gas refrigerant, it corresponds to point B', and the respective temperatures are t ₁ and t ₂
And the temperature rises by Δt = t ₂ −t ₁ . Therefore, the saturation temperature of the pressure detected by the pressure sensor 34 and the pipe temperature in the middle of the liquid level detection bypass circuit are detected and compared by the temperature sensors 33a and 33b, so that the liquid refrigerant flows through the liquid level detection bypass circuit. It is possible to determine whether the refrigerant is flowing or the gas refrigerant is flowing, and it is possible to determine whether the refrigerant is accumulated up to a certain height to which the liquid level detection bypass circuit of the accumulator is attached.

FIG. 5 and FIG. 6 are flowcharts for explaining an example of controlling the expansion valves 7a to 7c by the control device 9 during cooling.

FIG. 5 is a flow chart for determining the target subcool, in which the low pressure is detected by the pressure sensor 34 in step 41, converted into the saturation temperature ts and input. In step 42, the liquid level detection bypass circuit 31a. , 31 temperature sensor
33a, 33b, upper pipe temperature ta, lower pipe temperature respectively
tb is detected and input. In steps 43 and 44, the difference between the low pressure saturation temperature ts and the upper pipe temperature ta and the lower pipe temperature tb is determined.For example, when the pipe temperature ta, tb is higher than the low pressure saturation temperature ts by 3 deg or more, the gab part If it is 3 deg or less, it is determined to be a liquid part. Therefore, if the liquid has accumulated up to the upper bypass circuit (upper limit level),
Proceed to step 47. If the liquid level is below the lower bypass circuit (lower limit level), proceed to step 46. Otherwise, proceed to step 45. In steps 45 to 47, the target subcool is set according to the liquid level of the accumulator. Where the liquid level is
When it is between the lower limit bypass circuit and the upper limit bypass circuit, it is at the standard target subcool (eg 6deg), and when the liquid level is higher than the upper limit bypass circuit, it is higher than the standard target subcool (eg 8deg) and the liquid level is at the lower limit. If it is lower than the bypass circuit, it is lower than the standard target subcool (for example,
4deg), the target subcool is set.

Further, in FIG. 6, when the flow starts, the high pressure saturation temperature is detected by the pressure sensor 10 in step 61, this saturation temperature t ₁ is arithmetically processed, and in step 62, it is provided on the outlet side of the outdoor heat exchanger 3. The outlet temperature t ₂ of the outdoor heat exchanger 3 is detected by the temperature sensor 11 and the outlet temperature t ₂
Is entered and in step 63, SC as these temperature differences
Is calculated. Deviation from the target subcool SCo calculated as the set value of subcool in step 64 | SC−SCo |
Is compared with a certain value, for example, 3 deg or less, and if it is determined that the deviation exceeds 3 deg, in step 65, the sum of the expansion valve openings is calculated. Is the formula Is calculated using.

Where Nj is the opening of each expansion valve Nj ^* : The opening of each expansion valve before the change A: A constant determined by experiments The total opening ΣNj of each expansion valve is calculated and when the subcool is large, the expansion valve The overall opening is adjusted in the opening direction, and when the opening is small, it is adjusted in the closing direction, and the process proceeds to step 66. When it is determined that the deviation is 3 ° C. or less, the total opening is not changed in step 65, and the process proceeds to step 66. In step 66, the detected values T _{1 to} T ₃ of the gas pipe temperature by the temperature sensors 12a to 12c including thermistors are input, and in step 67, the detected values T ₁ to T ₃ are input.
The average value T _{AV of} T ₃ is calculated, and in step 68, the variation | T
It is determined whether _j −T _AV | is 2 deg or less. Steps 68 and onward belong to a conventional technique and therefore will not be described in detail. The temperature of each branch circuit is adjusted by increasing the valve opening degree for a branch tube with a higher temperature and decreasing the valve opening degree for a branch tube with a lower temperature. B in the formula for calculating the new opening degree of each expansion valve 7a to 7c in step 70 is a positive constant determined by an experiment, and in the case of the pressure sensor in step 61, it is converted to the saturation temperature. According to this flowchart, the subcool is adjusted and the temperature of the branch circuit is controlled to be the same.

FIG. 7 shows the state of the refrigerant at the outlet of the evaporator and the change in the average heat transfer coefficient. As can be seen from the figure, when the outlet enters the superheat region, the performance deteriorates sharply. It can be seen that using the outlet in a wet state (dryness x = around 0.9) is important for improving performance. The above-mentioned control uses this, positively increasing the subcool to keep the evaporator outlet wet, and even if the dryness of the outlet changes slightly in each circuit,
It is designed to have a stable capacity, and it has multiple branch pipes 14
In distributing the refrigerant to a to 14c and 15a to 15c, the controllability is very good, and at the same time, in the outdoor heat exchanger 3,
Since the subcool is properly taken, the outdoor heat exchanger 3 can be effectively used. As a matter of course, the amount of the refrigerant is filled so that the evaporator outlet is in a wet state even when all the indoor units are operated. Furthermore, when the number of operating indoor units decreases, the refrigerant supply is stopped by fully closing the expansion valves 7a, 7b, 7c of the liquid side branch pipes corresponding to the stopped indoor units, while the excess refrigerant is It also has a function of being able to be stored in the accumulator 4.

At this time, since the target subcool is set while detecting the liquid level in the accumulator 4 by the height detection means 80, the subcool is set large when the amount of refrigerant is large, and more liquid refrigerant is accumulated in the condenser, By lowering the liquid level in the accumulator, the liquid refrigerant is prevented from overflowing. Further, when the amount of refrigerant is small, the liquid level in the accumulator becomes low, and the function of the heat exchanger 8 in the accumulator 4 deteriorates. Therefore, the subcool is set to a small value, and the liquid refrigerant in the condenser is returned to the accumulator to some extent, The control device 9 controls so that 8 works properly. Therefore, stable operation can always be performed even when the refrigerant changes.

During heating, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 has a four-way valve 2 whose passage is switched as shown by the broken line in FIG.
Through the solenoid valves 6a to 6c provided on the gas side branch pipes 14a to 14c, and are led to the indoor heat exchangers 5a to 5c via the connecting pipes 16a to 16c. The liquefied refrigerant here is the indoor / outdoor communication pipe 17a.
Through 17c, returns to the outdoor unit, is decompressed by the expansion valves 7a to 7c provided in the liquid side branch pipes 15a to 15c, evaporates in the outdoor heat exchanger 3, and passes through the four-way valve 2 and the accumulator 4 to the compressor. Configure a cycle that returns to 1. At this time, with the pressure sensor 10,
By the temperature sensors 13a to 13c provided on the liquid side branch pipes 15a to 15c, the subcool at the outlets of the indoor heat exchangers 5a to 5c is set to a target value, and at the same time, the controller 9 expands the expansion valves by the controller 9 so that the temperatures of the respective branch pipes are equalized. Control 7a-7c. Further, when the number of operating indoor units decreases, the refrigerant supply is stopped by closing the solenoid valve of the gas side branch circuit corresponding to the stopped indoor unit. The surplus refrigerant can be stored in the accumulator 4 at the same time as cooling.

In addition, when both the cold side and the heating side have a junction at the downstream side of the branch circuit that is on the low pressure side and there is a stopped indoor unit, the refrigerant can be recovered by closing the branch circuit inlet and opening the outlet. Becomes

According to the embodiment of the present invention, since the control device is controlled by the electric signal, the subcool at the outlet of the indoor heat exchanger can be set to the target value by the pressure sensor and the temperature sensor provided in the liquid side branch pipe during heating. The temperature of each branch pipe can be equalized,
During cooling, the subcool can be adjusted to the target value by the pressure sensor and the temperature sensor provided at the outlet of the outdoor heat exchanger, and the refrigerant is properly distributed by the temperature sensor provided at the gas side branch pipe, so there is no need to provide a receiver. The advantages are that it can be easily combined with a standard indoor unit, has good distribution performance, has good stability against variations in the amount of refrigerant, and does not require a refrigerant recovery circuit. Further, in the multi-room air conditioner of one embodiment of the present invention, the expansion valve is controlled by the microcomputer, which is convenient when the frequency of the compressor is to be controlled by an inverter.

FIG. 8 is a refrigerant circuit diagram showing a modified example of this embodiment. In this modified example, a saturation temperature detection circuit 18 is used instead of the pressure sensor 10, and a temperature sensor 19 which is saturation temperature detection means for directly detecting the saturation temperature instead of the pressure is used for detection. The detection circuit 18 includes a heat exchanger 21 and a capillary tube.
The refrigerant at the outlet of the compressor 1 is cooled by the heat exchanger 21 to become a two-phase refrigerant, which is decompressed to the suction pressure of the compressor 1 by the capillary tube 20 and becomes a low-temperature two-phase refrigerant.
By exchanging heat at 21, the low-pressure refrigerant has an enthalpy almost the same as the enthalpy of the refrigerant at the compressor outlet, completing the cycle. FIG. 9 shows the behavior of this refrigerant on the Mollier diagram, where the solid line shows the state of the refrigerant in the detection circuit 18, and the broken line ABCD shows the state of the refrigerant in the normal refrigeration cycle. In FIG. 9, E indicates the inlet state of the capillary tube 20, and by mounting the temperature sensor 19 at this location, it becomes possible to detect the high pressure saturation temperature without using the pressure sensor.

Although not shown, it goes without saying that the high pressure saturation temperature during cooling and heating can also be detected by detecting the temperature of the pipe near the center of the indoor and outdoor heat exchangers.

10 to 12 show another embodiment of the present invention. 10th
In FIG. 11 and FIG. 11, the same reference numerals as those in FIGS. 1 and 3 indicate the same or corresponding parts, and 81a to 81c are switches for setting the capacity of the indoor unit. Here, the capacity of the indoor unit is the cooling capacity and the heating capacity, and can be the capacity of the indoor unit, that is, the size of the indoor heat exchanger. In this embodiment, the switches 81a to 81c are provided in place of the temperature sensor which is the temperature detector for detecting the temperature of the gas side branch pipe shown in FIGS. 1 and 3, and the input of the switch is provided to the controller 9. The point that the reversible expansion valves 7a to 7c are taken in and controlled by the control device 9 is different from the embodiment described in detail with reference to FIGS. Then, the capacity setting switches 81a-8
Each 1c is composed of a 3-bit switch. For example, if the connected indoor unit has a cooling capacity of 2000 kcal / h, the switch setting is "000", and if it is 2500 kcal / h, it is "001".
Each of the eight settings is possible.

Further, in another embodiment shown in FIG. 10 and FIG. 11, the controller 9 expands by the capacity setting switches 81a to 81c so as to distribute the entire opening depending on the size of each registered indoor unit. Control valves 7a-7c. That is, in the flowchart of FIG. 12 in which the same reference numerals as those in FIG. 6 indicate the same or corresponding portions, steps 61 to 65 perform the same operation as in the case of FIG. 6, but the deviation from the target subcool is 3 deg or less. If it is determined that the total opening degree of the expansion valve is not changed, the process proceeds to step 67. In step 67, the capacity code Qj proportional to the capacity of each indoor unit in operation set by the capacity setting switch, for example, the cooling capacity is 20
Qj = 4 at 00kcal / h, Qj = 5, 4000 at 2500kcal / h
When kcal / h, read Qj = 8 from the controller. And
In step 70, the total opening is distributed by the capacity code Qj, and in step 71, the new opening Nj is output. According to the flowchart shown in FIG. 12, the adjustment of the subcool and the distribution of the refrigerant to each indoor unit can be properly performed, and the same effect as that of the embodiment shown in FIGS. 1 to 7 can be obtained.

Further, FIG. 13 is a refrigerant circuit diagram corresponding to FIG. 8 showing a modification of the embodiment shown in FIGS. 10 to 12, in which a saturation temperature detecting circuit is used instead of the pressure sensor, The pressure saturation temperature can be detected. In FIG. 13, the same symbols as those in FIG. 8 indicate the same or corresponding portions.

〔The invention's effect〕

As described above, according to the present invention, the expansion valve driven by an electric signal is controlled by the control device while the subcool is set to a constant target value, the temperatures of the plurality of branch circuits before the merging are equalized, and the surplus accumulated in the accumulator is accumulated. Since it can be controlled to change the target value of the subcool depending on the refrigerant, it can be combined with a standard indoor unit, does not require a receiver, has good distribution performance, and has good stability against fluctuations in the refrigerant amount. This has the effect of providing a multi-room air conditioner that does not require a recovery circuit.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram of a multi-room air conditioner according to an embodiment of the present invention, FIG. 2 is a partial refrigerant circuit diagram showing an example of liquid level height detecting means of the accumulator, and FIG. 3 is the same control. Block diagram of the apparatus, FIG. 4 is a Mollier diagram for explaining the operation of the liquid level detecting means, FIGS. 5 and 6 are flowcharts for explaining the control operation, and FIG. 7 is a refrigerant state at the outlet of the evaporator. And FIG. 8 is a diagram showing the relationship between the average heat transfer coefficient, FIG. 8 is a refrigerant circuit diagram of a multi-room air conditioner according to a modification of the embodiment of the present invention, and FIG. 9 is a state of refrigerant in the saturation temperature detection circuit. Fig. 10 is a Mollier diagram showing Fig. 10, Fig. 10 is a refrigerant circuit diagram of a multi-room air conditioner according to another embodiment of the present invention, Fig. 11 is a block diagram of the same control device, and Fig. 12 is a description of the same control operation. Flow chart, No.
FIG. 13 is a refrigerant circuit diagram of a multi-room air conditioner according to a modified example of another embodiment, and FIGS. 14 and 15 are refrigerant circuit diagrams of different conventional air conditioners. 1 ... Compressor, 2 ... four-way valve (switching valve), 3 ... outdoor heat exchanger, 4 ... accumulator, 5a-5c ... indoor heat exchanger, 6a-6c ... solenoid valve, 7a-7c ...... Expansion valve, 8 ...... Heat exchanger in accumulator, 9 ...... Control device, 10 ...... Pressure sensor, 11, 12a to 12c, 13a to 13c ...... Temperature sensor, 14a to 1
4c …… Gas side branch pipe, 15a ～ 15c …… Liquid side branch pipe, 16a ～ 1
6c, 17a to 17c …… Communication piping, 18 …… Saturation temperature detection circuit, 8
0 …… Liquid level detection means, 81a to 81c …… Capacity setting switch. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (3)

[Claims] 1. An outdoor unit capable of switching between cooling and heating, which comprises a compressor, a switching valve, an accumulator, and an outdoor heat exchanger as main members, and has a branch in parallel with a liquid pipe and a gas pipe of the outdoor unit. In a multi-room air conditioner in which pipes are provided and a plurality of indoor units are connected to these branch pipes through communication pipes, each gas side branch pipe is equipped with a solenoid valve, and each liquid side branch pipe is electrically connected. An expansion valve driven by a signal is provided, a heat exchanger capable of exchanging heat with the refrigerant in the accumulator is provided in the pipe between the confluence point of the outdoor heat exchanger and the liquid side branch pipe, and further, the liquid side branch pipe and A temperature detector is provided in each cooling outlet pipe of the outdoor heat exchanger, and a detecting means for detecting high pressure or saturation temperature, a liquid level height detecting means for the accumulator, and a cooling outlet pipe of the gas side branch pipe. Temperature detector provided or connection A switch for setting the capacity of the indoor unit, the temperature obtained by the temperature detector of the liquid side branch pipe and the outdoor heat exchanger, the pressure or saturation temperature obtained by the detection means, the liquid level height of the accumulator, and the above. A multi-room air conditioner comprising: a controller for controlling the expansion valve according to a temperature obtained by a temperature detector of a gas side branch pipe or an input signal of the switch. 2. The control device controls the degree of supercooling to a constant target value and changes the target value of the degree of supercooling according to the liquid level height obtained by the liquid level height detecting means. The multi-room air conditioner according to claim 1. 3. A liquid level height detecting means detects a liquid level height of two levels or more, and when the liquid level is between an upper limit level and a lower limit level, the degree of supercooling becomes a standard target value. The expansion valve is controlled to set the supercooling degree to a value lower than the standard target value when the liquid level is lower than the lower limit level, and the supercooling degree is higher than the standard target value when the liquid level is higher than the upper limit level. Claim 1 which controls the said expansion valve to each value.
The multi-room air conditioner according to item 2 or item 2.