JPH0480569A - Air-conditioning machine - Google Patents

Abstract

PURPOSE:To permit the securing of the necessary and sufficient capacity of a room cooling side indoor unit and a room heating side indoor unit even when an outdoor unit is positioned at a higher position than the indoor unit by a method wherein the amount of refrigerant, which flows through a liquid pipe, is controlled so that the detecting result of the superheating degree of refrigerant of the room cooling side indoor unit is within a given range. CONSTITUTION:When a given time (t1) has elapsed after starting operation, a difference between the detecting values of a temperature sensor 101 and a temperature sensor 105 is detected as the superheating degree SH of refrigerant in an indoor unit C1 while a difference between the detecting values of a temperature sensor 102 and a temperature sensor 106 is detected as the superheating degree SH of another indoor unit C2. Then, the opening degree of the PMV 16 of an outdoor unit A is increased by a predetermined value (a value corresponding to several pulses) until the superheating degree SH of the refrigerant becomes a value within a given range. According to this method, the pressure of the refrigerant in a liquid pipe W is controlled so as to be substantially equal to the pressure of the refrigerant in a high-pressure side gas tube G even when the outdoor unit A is positioned at a position higher than the indoor units C1-C4 whereby the refrigerant can be distributed with a good balance to supply it to the room cooling side indoor units C1, C2 and the room heating side indoor unit C3. Accordingly, the necessary and sufficient capacities of respective units C1, C2, C3 can be ensured respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a multi-system air conditioner capable of air conditioning multiple rooms.

(Prior Art) Generally, a multi-system air conditioner includes one outdoor unit and a plurality of indoor units, and the indoor unit and the outdoor unit are connected by piping via a branch unit.

The branch unit communicates with the outdoor unit via a liquid pipe, a high-pressure side gas pipe, and a low-pressure side gas pipe, and switches the flow direction of refrigerant to each indoor unit.

That is, by selecting the flow direction of the refrigerant to each indoor unit using the branch unit, it is possible to perform simultaneous cooling and heating operations in each indoor unit.

An example of this air conditioner is shown in FIG.

In the figure, A is an outdoor unit, and a branch unit B is communicated with this outdoor unit A via a liquid pipe W, a high pressure side gas pipe G, and a low pressure side gas pipe S, and the branch unit B is connected to a plurality of indoor units C1, C2, C3°C4 are connected.

The outdoor unit A is equipped with two variable capacity compressors 1.2.

A common discharge pipe 4 is connected to the discharge port of this compressor 1.2 via check valves 3,3. A common suction pipe 5 is connected to the suction port of the compressor 1.2, and a liquid tank 6 is provided in the suction pipe 5.

The discharge pipe 4 is branched into two discharge pipes 4a and 4b.

The suction pipe 5 is branched into two suction pipes 5a and 5b on the upstream side of the liquid tank 6.

An oil separator 7 is provided at the discharge port of the compressor 1, and an oil bypass 8 is provided from the oil separator 7 to the suction port of the compressor 1.

Similarly, an oil separator 7 is provided at the discharge port of the compressor 2, and an oil bypass 8 is provided from the oil separator 7 to the suction port of the compressor 2.

An outdoor heat exchanger 10 is connected to the discharge pipe 4a via a two-way valve 9.
is connected. A liquid tank 13 is connected to the outdoor heat exchanger 10 via a parallel circuit of a heating expansion valve 11 and a check valve 12, and a liquid pipe W is connected to the liquid tank 13.

The suction pipe 5b is connected to the pipe between the two-way valve 9 and the outdoor heat exchanger 10 via a two-way valve 14 and a check valve 15.

The liquid pipe W includes electronic flow control valves (pulse motor valves; hereinafter abbreviated as PMV) 21, 31 of the branch unit) B.
,41. - 51 for cooling expansion valves 22, 32, 42
．． 52 are connected. This expansion valve 22, 32.42
．． Check valves 23.33 and 43.53 are connected in parallel to 52.

The expansion valves 22, 32, 42.52 are connected to the indoor unit C1.
+C2+C3+C4 indoor heat exchanger 24°34.44.54 is connected.

A low pressure side gas pipe S is connected to the indoor heat exchangers 24, 34, 44.54 via two-way valves 25, 35, 45.45 of branch unit B, and also a two-way valve of branch unit B. 26. High pressure side gas pipe G via 36, 46°56
is connected.

The low pressure gas pipe S is an extension of the suction pipe 5a.

The high-pressure gas pipe G is an extension of the discharge pipe 4b.

Explain the action.

Indoor unit C, is in cooling operation mode, indoor unit C2
It is assumed that the indoor unit C3 is in the cooling operation mode, the indoor unit C3 is in the heating operation mode, and the indoor unit C4 is stopped. and,
Assume that the total required cooling capacity is greater than the total required heating capacity.

In this case, the cooling main operation mode is determined, the two-way valve 9 of the outdoor unit A is opened (displayed in white), the two-way valve 14 is closed (displayed in black), and the outdoor heat exchanger 10 is connected to the discharge pipe 4a. Ru.

In branch unit B, PMV21, 31.41 opens, PMV51 closes (white display), and two-way valve 25
．． 35.46 is open (white display), and two-way valve 45,5
5, 26, 36, and 56 are closed (displayed in black), the gas pipes communicating with the indoor unit CII C2 in the cooling operation mode are connected to the low pressure side gas pipe S (intake pipe 5a), and the indoor unit C3 in the heating operation mode is connected to the low pressure side gas pipe S (suction pipe 5a). A gas pipe communicating with is connected to the high pressure side gas pipe G (discharge pipe 4b).

Therefore, the refrigerant discharged from the compressors 1 and 2 passes through the two-way valve 9 and enters the outdoor heat exchanger 10.

In this outdoor heat exchanger 10, the refrigerant condenses. The refrigerant that has passed through the outdoor heat exchanger 10 passes through the check valve 12 and liquid tank 13, and then passes through the PMV 21° 31 and the expansion valve 22.
．． 32 and enters the indoor unit C□, C2. In this indoor unit ClC2, the refrigerant is vaporized. Indoor unit) C.

The refrigerant that has passed through C2 passes through the two-way valve 25, 35 and the low-pressure side gas pipe S, and is sucked into the compressors 1 and 2.

At the same time, a part of the refrigerant discharged from the compressor 1.2 passes through the high pressure side gas pipe G and the two-way valve 46 to the indoor unit C.
Enter 3. In this indoor unit C3, the refrigerant condenses. The refrigerant that has passed through the indoor unit C3 passes through the check valve 43 and P
Passing through MV41, indoor units C1 and C2 (PMv21
, 31).

That is, the outdoor heat exchanger 10 is a condenser, and the indoor heat exchanger 2 is a condenser.
4.34 works as an evaporator, and indoor heat exchanger 44 works as a condenser.

In this case, the cooling side indoor unit c1. A part of the heat absorbed by c2 is used as heat radiation from the heating indoor unit C3.

Next, the indoor unit C1 requests the heating operation mode, the indoor unit C2 requests the heating operation mode, and the indoor unit C
Assume that the request No. 3 is for the cooling operation mode and the indoor unit C4 is to stop operating. It is also assumed that the total required heating capacity is greater than the total required cooling capacity.

In this case, the heating main operation mode is determined, and as shown in Fig. 5, PMV9 of outdoor unit A is closed (displayed in black).
, the two-way valve 14 opens (displayed in white), and the outdoor heat exchanger 10 is connected to the suction pipe 5b.

In branch unit B, PMV21, 31.41 opens and PMV51 closes (displayed in white). Three-way valve 45
, 26.36 are open (displayed in white), and the two-way valves 25, 3
5, 55, 46, and 56 are closed (displayed in black), the gas pipes communicating with the indoor unit C1+ 02 in the heating operation mode are connected to the high pressure side gas pipe G (discharge pipe 4b), and the indoor unit C3 in the cooling operation mode is connected. A gas pipe communicating with is connected to the low pressure side gas pipe S (suction pipe 5a).

Therefore, the refrigerant discharged from the compressor 1.2 enters the indoor units C1, C2 through the high-pressure side gas pipe G and the two-way valve 26.36. In the indoor units C1 and C2, the refrigerant condenses. The refrigerant that has passed through the indoor units C1+C2 passes through the check valve 2333 and the PMVs 21 and 31, then the liquid tank 13 and the expansion valve 11, and enters the outdoor heat exchanger 10. In this outdoor heat exchanger 10, the refrigerant is vaporized. The refrigerant that has passed through the outdoor heat exchanger 10 is passed through the two-way valve 14. Check valve 15. and through the suction pipe 5b, the compressor 1
．． Sucked into 2.

At the same time, a portion of the refrigerant that has passed through the indoor units C1 and C2, the check valve 2333, and the PMVs 21 and 31 is transferred to the PMV 41.
and enters the indoor unit C3 through the expansion valve 42. In this indoor unit C3, the refrigerant is vaporized. The refrigerant that has passed through the indoor unit C3 is passed through the two-way valve 45 and the low pressure side gas pipe S.
through which it is sucked into compressor 1.2.

That is, the heating-side indoor heat exchangers 24 and 34 function as condensers, and the cooling-side indoor unit 44 and outdoor heat exchanger 10 function as evaporators.

In this case, the heat absorbed by the cooling-side indoor unit 44 and the outdoor heat exchanger 10 is the heating-side indoor unit)'C+.

It will be used as heat radiation for C2.

(Problems to be Solved by the Invention) In such a multi-system air conditioner, for example, as shown in FIG. 6, an outdoor unit A is installed on the roof of a building, etc., and a branch unit B and an indoor unit C1, C2°C3+ C4 may be installed on the floor or room below.

In this way, outdoor unit A becomes indoor unit)C1°C2,
When the position is higher than C3 and C4, when the refrigerant pressure in the liquid pipe W and the refrigerant pressure in the high pressure side gas pipe G are compared during simultaneous cooling and heating operation in the cooling main operation mode, it is found that they are the same at the position exiting the outdoor unit A. It's pressure. However, indoor unit C1
, C2, C31 and C4, the refrigerant pressure in the liquid pipe W is higher than the pressure of the refrigerant passing through the high-pressure side gas pipe G by the head difference.

In this case, the required amount of refrigerant flows into the cooling indoor unit, but it becomes difficult for the refrigerant to flow into the heating indoor unit.

Therefore, although sufficient cooling capacity can be ensured, the heating capacity is only about 115 times the cooling capacity.

This invention was developed in consideration of the above circumstances, and its purpose is to ensure necessary and sufficient capacity in each of the cooling-side indoor unit and the heating-side indoor unit, even if the outdoor unit is located higher than the indoor unit. Our goal is to provide air conditioners that can

[Structure of the Invention] (Means for Solving the Problems) The air conditioner of the present invention includes one outdoor unit having a compressor and an outdoor heat exchanger, and a plurality of indoor units each having an indoor heat exchanger. unit, and a branching unit that communicates with the outdoor unit via a liquid pipe, a high-pressure side gas pipe, and a low-pressure side gas pipe, and switches the flow direction of refrigerant to each of the indoor units, and controls the flow of refrigerant to each indoor unit. In a multi-system air conditioner that enables simultaneous operation of cooling and heating in each indoor unit by selecting the direction, there is a method for detecting the degree of refrigerant superheating in the indoor unit on the cooling side, and a method that keeps this detection result constant. and means for controlling the amount of refrigerant flowing into the liquid pipe so that the amount of refrigerant flows within the range.

(Function) The degree of superheating of the refrigerant in the indoor unit on the cooling side is detected, and the amount of refrigerant flowing into the liquid pipes is controlled so that the detection result is within a certain range.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. In the drawings, the same parts as in FIGS. 4 to 6 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

As shown in FIG. 1, in the outdoor unit A, PMVl 6 is connected to the pipe leading from the outdoor heat exchanger 10 to the check valve 12.
will be established.

Furthermore, in branch unit B, the following configuration is applied.

A temperature sensor 101 is attached to a liquid pipe leading from the expansion valve 22 to the indoor unit C1.

A temperature sensor 102 is attached to a liquid pipe leading from the expansion valve 32 to the indoor unit C2.

A temperature sensor 103 is attached to a liquid pipe leading from the expansion valve 42 to the indoor unit C3.

A temperature sensor 104 is attached to a liquid pipe leading from the expansion valve 52 to the indoor unit C4.

A temperature sensor 105 is attached to the gas pipe leading from the connection of the two-way valves 25 and 26 to the indoor unit C.

A temperature sensor 106 is attached to the gas pipe leading from the connection of the two-way valve 35, 36 to the indoor unit C2.

A temperature sensor 107 is attached to the gas pipe leading from the connection part of the three-way valve 45, 46 to the indoor unit C3.

A temperature sensor 108 is attached to the gas pipe leading from the connection of the two-way valve 55, 56 to the indoor unit C4.

The control circuit is shown in FIG.

The outdoor unit A includes an outdoor control section 70 consisting of a microcomputer and its peripheral circuits.

This outdoor control unit 70 includes inverter circuits 71, 72, P
MVl6 and two-way valves 9 and 14 are connected.

The inverter circuits 71 and 72 rectify the voltage of the AC power supply 73, convert it into an AC voltage of a predetermined frequency (and level) according to a command from the outdoor control unit 70, and
This is to supply driving power to M and 2M, respectively.

The branch unit B includes a multi-control unit 80 consisting of a microcomputer and its peripheral circuits. 46, 56, and temperature sensors 101, 102, 103, 104, 10
5゜Connect 106.107.108.

Indoor unit C,,C2+ c3. c4 each includes an indoor control section 90 consisting of a microcomputer and its peripheral circuits. A remote control operation unit (hereinafter referred to as a remote control) 91 and an indoor temperature sensor 92 are connected to the indoor control unit 90 .

The indoor control unit 90 includes the following functional means.

(2) Means for sending a request for a cooling operation mode or a request for a heating operation mode to the multi-control unit 80 based on the operation of the remote control 91.

(2) Means for sending the difference between the indoor temperature set by the remote controller 91 and the temperature detected by the indoor temperature sensor 92 to the multi-control unit 80 as the required cooling capacity (in the cooling operation mode) or the required heating capacity (in the heating operation mode).

In addition, the multi-control unit 80, the outdoor control unit 70, each PMV,
The two-way valves constitute the following functional means:

(2) Means for determining the cooling main operation mode when the sum of the cooling capacities requested from any of the indoor units CI, C2, C3, and C4 is greater than the sum of the heating capacities also requested.

■When the cooling main operation mode is determined, the refrigerant discharged from the compressors 1 and 2 is passed through the outdoor heat exchanger 10, and then passed through the indoor unit that is requesting the cooling operation mode.
means to return to.

■When the cooling main operation mode is determined, a part of the refrigerant discharged from the compressor 1゜2 is passed through the indoor unit that is requesting the heating operation mode, and then to the indoor unit that is requesting the cooling operation mode. means to join the refrigerant flow.

■When the cooling main operation mode is determined, the number of operating compressors 1 and 2 and the operating frequency (
means for controlling the output frequency of the inverter circuits 71 and 72;

■Means for detecting the degree of refrigerant superheat in the cooling indoor unit when the cooling main operation mode is determined.

(2) Means for controlling the amount of refrigerant passing through the liquid pipe W so that the detected degree of refrigerant superheating falls within a certain range.

(2) Means for determining the heating main operation mode when the sum of the heating capacities requested from any of the indoor units c, , C2, C3, and C4 is greater than the sum of the cooling capacities also requested.

■When the heating main operation mode is determined, the refrigerant discharged from the compressors 1 and 2 is passed through the indoor unit that is requesting the heating operation mode, and then passed through the outdoor heat exchanger 10 to the compressors 1 and 2.
means to return to.

■When the heating main operation mode is determined, part of the refrigerant that has passed through the indoor unit that is requesting the heating operation mode is passed through the indoor unit that is requesting the cooling operation mode, and then passed to the compressors 1 and 2. means of returning.

[Phase] When the heating main operation mode is determined, when the heating main operation mode is determined, the number of operating compressors 1.2 and operating frequency (output frequency of the inverter circuits 71 and 72) according to the total required heating capacity. means to control.

Next, the operation of the above configuration will be explained with reference to the flowchart of FIG. 3.

Indoor unit C1 is in cooling operation mode, indoor unit C2
It is assumed that the indoor unit C3 is in the cooling operation mode, the indoor unit C3 is in the heating operation mode, and the indoor unit C4 is stopped. and,
Assume that the total required cooling capacity is greater than the total required heating capacity.

In this case, the main cooling operation mode is determined and the outdoor unit
Open the three-way valve 9 (displayed in white) and close the two-way valve 14 (displayed in black), thereby connecting the outdoor heat exchanger 10 to the discharge pipe 4.
Connect to a.

In branch unit B, PMV21, 31.41 is opened and PMV51 is closed (white display), and two-way valve 25 is opened.
, 35, 46 open (white display), and two-way valve 45, 5
5, 26, 36, and 56 (displayed in black), connect the gas pipes of the indoor units C1 and C2 in the cooling operation mode to the low-pressure side gas pipe S (intake pipe 5a), and connect the gas pipes of the indoor unit C3 in the heating operation mode. Connect the pipe to the high pressure side gas pipe G (discharge pipe 4b).

Therefore, the refrigerant discharged from the compressors 1 and 2 passes through the two-way valve 9 and enters the outdoor heat exchanger 10.

In this outdoor heat exchanger 10, the refrigerant condenses. The refrigerant that has passed through the outdoor heat exchanger 10 passes through the check valve 12 and liquid tank 13, and then passes through the PMV 21° 31 and the expansion valve 22.
．． 32 and enters the indoor units C1 and C2. In this indoor unit C1°C2, the refrigerant is vaporized. The refrigerant that has passed through the indoor units) C1 and C2 passes through the two-way valves 25 and 35 and the low-pressure side gas pipe S, and is sucked into the compressors 1 and 2.

At the same time, a portion of the refrigerant discharged from the compressors 1 and 2 passes through the high pressure side gas pipe G and the two-way valve 46 to the indoor unit C.
Enter 3. In this indoor unit C3, the refrigerant condenses. The refrigerant that has passed through the indoor unit C3 passes through the check valve 43 and P
Passing through MV41, indoor units C1 and C2 (PMv21
, 31).

That is, the outdoor heat exchanger 10 is a condenser, and the indoor heat exchanger 2 is a condenser.
4.34 works as an evaporator, and indoor heat exchanger 44 works as a condenser.

In this case, part of the heat absorbed by the cooling-side indoor units C1 and C2 is used as heat radiation from the heating-side indoor unit C3.

The number of operating compressors 1.2 and the operating frequency (output frequency of inverter circuits 71, 72) are determined according to the total required cooling capacity.

The opening degree of the PMV 21 is controlled according to the required cooling capacity of the indoor unit C1 in the cooling operation mode, and the amount of refrigerant flowing into the indoor heat exchanger 24 is adjusted.

The opening degree of the PMV 31 is controlled according to the required cooling capacity of the indoor unit C2 in the cooling operation mode, and the amount of refrigerant flowing into the indoor heat exchanger 34 is adjusted.

Regarding the indoor unit C3 in the heating operation mode, the corresponding PMV 41 is set to full open.

Here, outdoor unit A is indoor unit C1°C2,C
3. If the position is higher than C4, the refrigerant pressure in the liquid pipe W and the high pressure side gas pipe G in the cooling main operation mode described above.
Although the refrigerant pressure is the same at the position where it exits the outdoor unit A, the refrigerant pressure in the indoor units CI, C2+ C3104
Looking at the position, the refrigerant pressure in the liquid pipe W is higher than that in the high pressure side gas pipe G.
The pressure of the refrigerant passing through the head is higher than the pressure of the refrigerant passing through the head.

In this case, although the necessary amount of refrigerant flows into the cooling-side indoor units C1 and C2, it becomes difficult for the refrigerant to flow into the heating-side indoor unit C3. Therefore, although sufficient cooling capacity can be ensured, a situation arises in which heating capacity is only about 115 of the cooling capacity.

Therefore, the control shown in FIG. 3 is executed.

At the start of cooling main operation mode, PMV1 of outdoor unit A
6 is first set to a predetermined initial opening degree.

This initial opening degree is between outdoor unit A and indoor unit CI.
+ C21 This is predetermined based on the head difference between C3 and C4, and is a little narrowed.

If the PMV 16 is a little throttled, the amount of refrigerant flowing through the liquid pipe W will be small, and the refrigerant pressure in the liquid pipe W will be set to be low first.

After the start of operation, a certain period of time t1 during which the degree of superheating of the refrigerant becomes stable
has passed, the temperature of the refrigerant entering the indoor unit C1 on the cooling side is detected by the temperature sensor 101, and the temperature of the refrigerant entering the indoor unit C1 on the cooling side is detected.
The temperature of the refrigerant flowing out from the indoor unit C1 is detected by the temperature sensor 105, and the difference between the two detected temperatures is determined as the refrigerant superheat degree S in the indoor unit C1.
Detected as H. At the same time, the indoor unit C2 on the cooling side
The temperature of the refrigerant entering the indoor unit C2 is detected by the temperature sensor 102, and the temperature of the refrigerant flowing out from the indoor unit C2 is detected by the temperature sensor 1.
06, and the difference between the two detected temperatures is detected as the refrigerant superheat degree SH in the indoor unit C2.

If at least one of the detected refrigerant superheat degrees SH is not within a certain value SHs, in other words, if at least one of the refrigerant superheat degrees SH is not within a certain range, the opening degree of PMV 16 of outdoor unit A is changed. Increase by a predetermined value (several pulses).

When the opening degree of the PMV 16 increases, the amount of refrigerant flowing through the liquid pipe W increases, and therefore the amount of refrigerant flowing into the indoor units C1 and C2 increases, and the degree of refrigerant superheat changes in a decreasing direction.

After a predetermined time t2, the refrigerant superheat degree is detected again, and PMV16 is increased by a predetermined value until the refrigerant superheat degree SH falls within the above-mentioned fixed range.

In this way, even if the outdoor unit A is located higher than the indoor unit C1+C2+C3+C4 as shown in FIG. 6, the refrigerant pressure in the liquid pipe W is adjusted to approximately the same value as the refrigerant pressure in the high-pressure side gas pipe G, and the air conditioning is maintained. Side indoor unit C,,C
The refrigerant can be distributed and supplied to the heating-side indoor unit C3 and the heating-side indoor unit C3 in a well-balanced manner.

Therefore, necessary and sufficient capacity can be ensured in each of the cooling-side indoor units C1+C2 and the heating-side indoor unit C3.

In the above embodiment, the case where there are four indoor units has been described as an example, but there is no limitation to the number of indoor units.

Moreover, although the case where the number of compressors is two is described as an example, the number is not limited and can be set as appropriate depending on the number of indoor units and the like.

[Effects of the Invention] As described above, according to the present invention, one outdoor unit having a compressor and an outdoor heat exchanger, a plurality of indoor units each having an indoor heat exchanger, and the outdoor unit and a branching unit that communicates with each other via a liquid pipe, a high-pressure side gas pipe, and a low-pressure side gas pipe, and switches the flow direction of the refrigerant to each of the indoor units. In a multi-system air conditioner that enables simultaneous operation of cooling and heating in each indoor unit, there is a means for detecting the degree of refrigerant superheating in the indoor unit on the cooling side, and a means for detecting the degree of superheating of the refrigerant in the indoor unit on the cooling side, and Since the system is equipped with a means for controlling the amount of refrigerant flowing into the liquid pipe, even if the outdoor unit is located higher than the indoor unit, necessary and sufficient capacity can be ensured in each of the cooling-side indoor unit and the heating-side indoor unit. We can provide air conditioners that can

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a refrigeration cycle according to an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a control circuit according to the embodiment, and FIG. 3 is a flowchart for explaining the operation of the embodiment. , FIG. 4 and FIG. 5 are diagrams showing the configuration of a refrigeration cycle of a conventional air conditioner, respectively, and FIG. 6 is an outdoor unit and a branch unit. and the installation of each indoor unit are diagrams showing examples. 1.2...Variable capacity compressor, 10...Outdoor heat exchanger, 16-PMV, 24,34.44.54-...Indoor heat exchanger, 101-108...Temperature sensor, A. ... Outdoor unit, B... Branch unit, C, C2, C3
゜C4... Indoor unit.

Claims (1)

[Claims] One outdoor unit having a compressor and an outdoor heat exchanger, a plurality of indoor units each having an indoor heat exchanger, and a liquid pipe, a high pressure side gas pipe, and a low pressure side gas pipe connected to the outdoor unit This multi-system consists of a branch unit that communicates with the indoor units to switch the flow direction of the refrigerant to each indoor unit, and enables simultaneous cooling and heating operation in each indoor unit by selecting the flow direction of the refrigerant to each indoor unit. type of air conditioner, comprising means for detecting the degree of superheating of refrigerant in an indoor unit on the cooling side, and means for controlling the amount of refrigerant flowing into the liquid pipe so that the detection result falls within a certain range. An air conditioner featuring: