KR101336720B1 - Air conditioning system - Google Patents

Abstract

In the air conditioning system according to the present invention, since the first expansion valve is gradually opened by controlling the opening degree change amount according to the opening time of the first expansion valve, the stability of the system can be improved.

Air conditioning system, phase separator, injection, refrigerant, valve, opening

Description

[0001] Air conditioning system [0002]

The present invention relates to an air conditioning system, and more particularly, to an air conditioning system in which the performance and stability of the system can be improved.

In general, an air conditioning system is a device for cooling or heating an indoor space by performing a process of compressing, condensing, expanding, and evaporating a refrigerant.

The air conditioning system is divided into a general air conditioning system in which one indoor unit is connected to an outdoor unit, and a multi air conditioning system in which a plurality of indoor units are connected to the outdoor unit. In addition, the air conditioning system is divided into a cooling system that only operates the refrigerant cycle in one direction to supply only cool air to the room, and a cooling and heating system that can operate the refrigerant cycle in both directions to supply cold or warm air to the room.

The air conditioning system includes a compressor, a condenser, an expansion valve, and an evaporator. The refrigerant discharged from the compressor is condensed in the condenser, and then expanded in the expansion valve. The expanded refrigerant is evaporated in the evaporator, and then sucked into the compressor. During the cooling operation or the heating operation, the refrigerant is injected into the compressor to improve the performance.

However, in the air conditioning system according to the related art, when the superheat and the intermediate pressure of the refrigerant are not smoothly controlled, the system becomes unstable and the compressor may be damaged.

An object of the present invention is to provide an air conditioning system in which stability and performance of a system can be improved.

The present invention passes through a condenser for condensation of a refrigerant, a first expansion device for condensing the refrigerant passing through the condenser, a second expansion device for condensing the refrigerant passing through the first expansion device, and the second expansion device. Detecting an evaporator in which a refrigerant is evaporated, a refrigerant passing through the evaporator, a refrigerant branched and injected between the first expansion device and the second expansion device, and compressed, and at least one operating variable The target opening degree of the first expansion device is determined based on a pre-stored set value corresponding to the sensed operating variable value, and the first expansion device is opened until the opening degree of the first expansion device reaches the target opening degree. Provided is an air conditioning system including a control unit for controlling an opening degree change amount according to the opening time of a single expansion device.

The present invention also provides a condenser for condensing refrigerant, a first expansion device for condensing the refrigerant passing through the condenser, a second expansion device for condensing the refrigerant passing through the first expansion device, and the second expansion device. An evaporator through which the refrigerant passing through the evaporator evaporates, a refrigerant passing through the evaporator, a refrigerant branched and injected between the first expansion device and the second expansion device, and compressed therein, and at least one operating variable. And determine a target opening degree of the first expansion device based on a pre-stored set value corresponding to the detected operating variable value, and until the opening degree of the first expansion device reaches the target opening degree. And a changing process of changing the opening degree of the first expansion device and a holding process of maintaining the opening degree, and at least part of the changing process is performed at the opening time of the first expansion device. La opening can be provided an air conditioning system comprising a control unit for controlling to change the service.

The present invention also provides a condenser for condensing refrigerant, a first expansion device for condensing the refrigerant passing through the condenser, a second expansion device for condensing the refrigerant passing through the first expansion device, and the second expansion device. An evaporator through which the refrigerant passing through the evaporator evaporates, a refrigerant passing through the evaporator, a refrigerant branched and injected between the first expansion device and the second expansion device, and compressed therein, and at least one operating variable. And determine a target opening degree of the first expansion device based on a pre-stored set value corresponding to the detected operating variable value, and until the opening degree of the first expansion device reaches the target opening degree. And a changing step of changing the opening degree of the first expansion device and a holding step of maintaining the opening degree, in at least some of the holding steps depending on the opening time of the first expansion device. D. It may provide an air conditioning system including a control unit for controlling the opening degree maintenance time is changed.

The present invention also provides a condenser for condensing refrigerant, a first expansion device for condensing the refrigerant passing through the condenser, a second expansion device for condensing the refrigerant passing through the first expansion device, and the second expansion device. An evaporator through which the refrigerant passing through the evaporator evaporates, a refrigerant passing through the evaporator, a refrigerant branched between the first expansion device and the second expansion device, and injected and compressed, and at least one operating variable. And determine a target opening degree of the first expansion device based on a pre-stored set value corresponding to the detected operating variable value, and until the opening degree of the first expansion device reaches the target opening degree. And a changing process of changing the opening degree of the first expansion device and a holding process of maintaining the opening degree, wherein at least a part of the changing process changes the opening degree change amount with time. In the lock control, and the maintenance process may provide an air conditioning system comprising a control unit for controlling to change the holding time also opened in accordance with the opening degree change amount.

In the present invention, the compressor includes: a first compression section in which a refrigerant that has passed through the evaporator flows and is compressed; a refrigerant that has passed through the first compression section and branched from the first expansion device and the second expansion device, And a second compression unit in which the refrigerant is introduced and compressed.

In the present invention, the opening degree change amount is preset according to the difference between the target opening degree and the current opening degree, and the opening degree of the first expansion device is controlled based on a combination of the opening degree change amount with the current opening degree. do.

In the present invention, the opening degree change amount is preset to be proportional to the difference between the target opening degree and the current opening degree.

In the present invention, the at least one operating variable may be a plurality of operating variables, and the plurality of operating variables may independently change a target opening degree of the first expansion device.

In the present invention, the target opening degree of the first expansion device may be determined based on the product of the set values of the operation variables.

In the air conditioning system according to the present invention, by controlling the opening degree change amount according to the opening time of the first expansion device, since the first expansion device is gradually opened, the stability of the system can be improved.

The air conditioning system includes a general air conditioning air conditioner for performing only cooling operation, a heating air conditioner for performing only heating operation, a heat pump type air conditioner for performing both cooling and heating operation, a plurality of indoor spaces for cooling / It includes all multi-type air conditioners. Hereinafter, a heat pump type air conditioner (hereinafter referred to as an " air conditioner ") will be described in detail as an embodiment of an air conditioning system.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of an air conditioner 100 according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a control flow of the air conditioner 100. Referring to FIG.

1 and 2, the air conditioner 100 includes a compressor 110, an indoor heat exchanger 120, an outdoor heat exchanger 130, a first expansion valve 141, and a second expansion valve 142. ), The phase separator 150 and the four-way valve 160. The indoor heat exchanger 120 serves as an evaporator during cooling operation and as a condenser during heating operation. The outdoor heat exchanger 130 acts as a condenser during cooling operation and as an evaporator during heating operation. The compressor (110) compresses the introduced low-temperature low-pressure refrigerant into high-temperature high-pressure refrigerant. The compressor 110 includes a first compression unit 111 and a second compression unit 112. The first compression unit 111 compresses the refrigerant introduced from the evaporator and the second compression unit 112 compresses the refrigerant discharged from the first compression unit 111 and the refrigerant branched from the evaporator and the condenser, The refrigerant is mixed and compressed. However, the present invention is not limited to this, and the compressor 110 may have a multi-stage structure having three or more stages.

The four-way valve 160 guides the refrigerant compressed by the compressor 110 to the outdoor heat exchanger 130 when it is cooled, and the indoor heat exchanger (120). The four-way valve 160 and the compressor 110 are connected to a first connection pipe 171. A discharge temperature sensor 181 and a discharge pressure sensor 182 are disposed in the first connection pipe 171 to measure discharge temperature and pressure of the refrigerant discharged from the compressor 110. The indoor heat exchanger 120 is disposed in the room and connected to the four-way valve 160 through a second connection pipe 172.

The phase separator 150 separates the refrigerant flowing into the gas-phase refrigerant and the liquid-phase refrigerant, sends the liquid-phase refrigerant to the evaporator, and sends the gaseous refrigerant to the second compression unit 112. The first connection part 151 of the phase separator 150 and the indoor heat exchanger 120 are connected to the third connection pipe 173. The first connection part 151 is a liquid refrigerant discharge pipe during a cooling operation and is a refrigerant inflow pipe for heating operation.

The first expansion valve 141 is disposed on the third connection pipe 173 and is a second expansion device for exchanging the liquid refrigerant introduced from the phase separator 150 during cooling operation. And is a first expansion device for exchanging the liquid refrigerant introduced from the indoor heat exchanger (120).

The outdoor heat exchanger 130 is disposed outdoors and connected to the second connection unit 152 and the fourth connection pipe 174 of the phase separator 150. The second connection portion 152 is a refrigerant inlet pipe during the cooling operation and a liquid refrigerant discharge pipe during the heating operation.

The second expansion valve 142 is disposed on the fourth connection pipe 174 and is a first expansion device for exchanging the liquid refrigerant introduced from the outdoor heat exchanger 130 during cooling operation. Is a second expansion device for exchanging the liquid refrigerant introduced from the phase separator (150).

The outdoor heat exchanger 130 is connected to the four-way valve 160 through a fifth connection pipe 175. In addition, the four-way valve 160 and the inflow pipe of the compressor 110 are connected to the sixth connection pipe 176. A compressor inlet temperature sensor 184 for measuring the temperature of the inlet side of the compressor 110 is disposed on the sixth connection pipe 176.

The second compression unit 112 is connected to the third connection unit 153 of the phase separator 150 through an injection pipe 180. The third connection part 153 is used as a gaseous refrigerant discharge pipe in the cooling and heating operation. An injection valve 143 is disposed on the injection pipe 180. The injection valve 143 controls the amount of refrigerant and the refrigerant pressure injected from the phase separator 150 to the second compression unit 112. When the injection valve 143 is opened, the gaseous refrigerant in the phase separator 150 flows into the second compression unit 112 through the injection pipe 180. An injection temperature sensor 183 for measuring the temperature of the injected refrigerant is disposed on the injection pipe 180.

The amount of opening of the first and second expansion valves 141 and 142 and the injection valve 143 is controlled by a control unit 200 that controls the operation of the air conditioner.

3 shows the flow of the refrigerant during the heating operation of the air conditioner.

3, the high-temperature, high-pressure gaseous refrigerant discharged from the compressor 110 flows into the indoor heat exchanger 120 via the four-way valve 160. [ The gaseous refrigerant in the indoor heat exchanger (120) undergoes heat exchange with the room air and is condensed. The condensed refrigerant is throttled in the first expansion valve 141, and then flows into the phase separator 160. The liquid refrigerant separated in the phase separator 160 is again throttled by the second expansion valve 142, and then flows into the outdoor heat exchanger 130. In the outdoor heat exchanger (130), the refrigerant evaporates due to heat exchange with the outside air, and the evaporated refrigerant flows into the first compression section (111).

When the operation of gas injection is requested during the heating operation, the control unit 200 opens the injection valve 143. The injection valve 143 is opened and the gaseous refrigerant separated by the phase separator 160 is injected into the second compression unit 112 through the injection pipe 180. [ In the second compression unit 112, the injected refrigerant and the refrigerant from the first compression unit 111 are mixed and then compressed. The refrigerant compressed by the second compression unit 112 circulates back to the four-way valve 160.

4 shows the flow of the refrigerant during the cooling operation of the air conditioner.

4, the high-temperature, high-pressure gaseous refrigerant discharged from the compressor 110 flows into the outdoor heat exchanger 130 through the four-way valve 160. In the outdoor heat exchanger (130), the gaseous refrigerant undergoes heat exchange with indoor air and is condensed. The condensed refrigerant is throttled in the second expansion valve 142, and then flows into the phase separator 150. The liquid refrigerant separated in the phase separator 150 is again throttled in the first expansion valve 141 and then flows into the indoor heat exchanger 120. [ In the indoor heat exchanger (120), the refrigerant evaporates due to heat exchange with the outside air, and the evaporated refrigerant flows into the first compression section (111). The control unit 200 shuts the injection valve 143 so that the gaseous refrigerant from the phase separator 150 is not injected into the second compression unit 112. However, the present invention is not limited to this, and the gaseous refrigerant from the phase separator 150 may be injected into the second compression unit 112 even during the cooling operation.

A control method of an air conditioner according to an embodiment of the present invention will now be described.

When the user drives the air conditioner 100 in order to heat and cool the indoor space, the controller 200 senses a driving command. The control unit 200 initializes the first and second expansion valves 141 and 142 and the injection valve 143. That is, the controller 200 completely opens the first and second expansion valves 141 and 142, and shields the injection valve 143. By blocking the injection valve 143, liquid refrigerant can be prevented from flowing into the compressor 110 at the beginning of the operation.

When initialization of the first and second expansion valves 141 and 142 and the injection valve 143 is completed, the controller 200 overheats the refrigerant of the air conditioner 100 to reach a predetermined target superheat degree. After adjusting the degree, the refrigerant is allowed to reach a predetermined intermediate pressure.

Here, the superheat degree refers to the temperature difference of the refrigerant between the outlet side of the evaporator and the inlet side of the compressor 110. Generally, the refrigerant does not include the liquid refrigerant after passing through the evaporator, but in the case of a sudden load change, it may include the liquid refrigerant. In this case, when liquid refrigerant flows into the compressor 110, the compressor 110 is damaged. Therefore, in order to prevent this, the temperature of the refrigerant passing through the evaporator is transferred to the compressor 110 to remove the liquid phase refrigerant, and between the outlet of the evaporator and the inlet of the compressor 110. The temperature difference between the refrigerants is called superheat degree. When the amount of the refrigerant flowing into the evaporator is reduced, evaporation of the refrigerant is completed before completely passing through the evaporator, and the gas refrigerant is continuously heated, thereby increasing the degree of superheat. On the other hand, if the amount of refrigerant is increased, the degree of superheat can be reduced. The superheat degree may be measured by a sensor 185 installed in the indoor heat exchanger, a sensor 186 installed in the outdoor heat exchanger, and a compressor inlet temperature sensor 184 installed at the inlet side of the compressor 110.

The intermediate pressure is the pressure in the phase separator 160. By setting the intermediate pressure to a predetermined intermediate pressure, it is possible to reduce the work required in the compressor 110 and to increase the efficiency. By adjusting the amount of refrigerant supplied to the phase separator 160 from the condenser, the intermediate pressure can be adjusted. The intermediate pressure can be measured by the injection temperature sensor 183 provided in the injection pipe 180.

In order to control the degree of superheat, the amount of opening of the valve disposed between the phase separator 160 and the evaporator is controlled, and the pressure of the valve disposed between the condenser and the phase separator 160 Adjust the opening amount.

When the air conditioner is a heating operation, the first expansion valve 141 serves as a first expansion device for adjusting the intermediate pressure, the second expansion valve 142 is a second expansion device for adjusting the degree of superheat It will play a role.

The controller 200 controls the first expansion valve 141 in a first control mode, and controls the second expansion valve 142 in a second control mode different from the first control mode.

When the initialization of the second expansion valve 142 is completed, the controller 200 adjusts the opening amount of the second expansion valve 142 to the second control mode in order to adjust the degree of superheat. In the second control mode, the superheat degree of the refrigerant is measured in real time, and the opening degree of the second expansion valve 142 is changed accordingly. The control unit 200 is provided with a control unit 200 for controlling the outdoor heat exchanger 130 based on the sensor 186 installed in the outdoor heat exchanger 130 and the overheat measured by the compressor temperature sensor 184, The purge table is stored, and the opening amount of the second expansion valve 142 is determined from the purge table.

In the second control mode, the superheat degree of the coolant is measured in real time until the superheat degree of the coolant reaches the target superheat degree, and the opening degree of the second expansion valve 142 is determined based on the measured superheat degree. Keep changing Therefore, the degree of superheat of the refrigerant can be adjusted more accurately.

5 is a flowchart showing a control method of the first expansion valve when the air conditioner shown in Fig. 1 performs heating operation.

Referring to FIG. 5, when the initialization of the first expansion valve 141 is completed (S1), the controller 200 controls the opening amount of the first expansion valve 141 to control the intermediate pressure. Adjust to the mode.

In the first control mode, the operating variable value of at least one operating variable is sensed. (S2) The operating variables include a gas injection operation in which a refrigerant is injected into the second compression unit 112 and the compressor 110. The frequency of the air conditioner, the indoor temperature of the air conditioner 100, the outdoor temperature, the indoor and outdoor temperature difference, the discharge pressure of the compressor 110, the discharge temperature of the compressor 110 may be included. The set values for the operating parameter values of the operating parameters are predetermined and stored in the form of a table in the controller 200. [ The set value for the frequency of the compressor 110 may be set differently depending on whether the gas injection is operated or not.

The control unit 200 obtains setting values for the operation variable values from the table (S3).

The target opening degree of the first expansion valve 141 is determined based on the set value. (S4) The setting values for the operation variable values independently change the target opening degree.

A method for obtaining the target opening degree according to the result is as follows.

Target opening degree = F (A1, A2, A3, A4, A5 .....)

Here, A1 to A5 are the operating variable values. The above F (A1, A2, A3, A4, A5 .....) can be expressed by the following equation.

As an example, the target degree of opening may be obtained by multiplying the set values corresponding to the operating variable values, and the following equation can be used.

(A1) * f (A2) * f (A3) * f (A4) * f (A5) *

Here, C is a proportional constant, and f (A1), f (A2), .. are the setting values for A1, A2, ..

Since the operating parameters independently vary the target opening degree of the first expansion valve 141, the set values for the respective operating parameters can be easily obtained and the control is easy. However, the present invention is not limited to this, and the target degree of opening may be obtained by adding the set values to each other or by other combinations.

The controller 200 detects and stores the current opening degree of the first expansion valve 141 in real time. (S5) Then, the current opening degree and the size of the target opening degree of the stored first expansion valve 141 are stored. (S6) When the current opening degree and the target opening degree are different, an opening degree change amount is determined according to a difference between the current opening degree and the target opening degree. (S7) The opening degree change amount is the current opening degree and the target. Predetermined according to the difference in the opening degree is stored in the form of a table in the control unit 200. The opening change amount is obtained from the table.

When the opening degree change amount is determined, the opening degree of the first expansion valve 141 is changed by the opening degree change amount. (S8)

Thereafter, the current degree of opening of the first expansion valve 141 is re-sensed, and the current degree of opening of the first expansion valve 141 is compared with the target degree of opening again. If the current opening and the target opening degree are different, the difference is calculated and the opening change amount is re-determined accordingly. When the opening change amount is re-determined, the opening degree of the first expansion valve 141 is changed by the recrystallized opening change amount.

Thereafter, the above process is repeated until the current degree of opening of the first expansion valve 141 is equal to or less than the target opening degree.

6 is a graph showing the amount of change in the opening degree of the first expansion valve 141 according to the opening time when the air conditioner shown in FIG. 1 is heated.

Referring to FIG. 6, the opening degree change amounts B1, B2, and B3 may be set to be proportional to the difference between the current opening degree and the target opening degree. That is, since the difference between the current opening degree and the target opening degree is large at the beginning of the opening degree control of the first expansion valve 141, the opening degree change amount according to the opening time is increased, so that the control is made more quickly. Thereafter, as the opening degree of the first expansion valve 141 reaches the target opening degree, the amount of change in the opening degree according to the opening time is reduced, so that the control can be made more accurately.

Therefore, in the first control mode, the opening degree change amounts B1, B2, and B3 are determined in consideration of the current opening degree of the first expansion valve 141, and the current opening degree of the first expansion valve 141 is determined. The opening degree of the first expansion valve 141 is determined by re-determining the opening degree change amount until the target opening degree is reached, and controlling the opening amount of the first expansion valve 141 a plurality of times by the opening degree change amount. It may increase or decrease gradually. That is, the cycle may be more stable since the amount of the refrigerant is gradually increased or decreased.

On the other hand, the control unit 200 determines whether the operating parameters such as the discharge temperature of the refrigerant discharged from the compressor 110 and the temperature of the refrigerant passing through the indoor heat exchanger 120 is out of a predetermined normal operating range. (S9) When operating variables such as the discharge temperature of the refrigerant discharged from the compressor 110 and the temperature of the refrigerant passing through the indoor heat exchanger 120 are out of a predetermined normal operating range, the controller ( The control unit 200 controls the first expansion valve 141 by switching from the first control mode to the third control mode.

In the third control mode, the correction opening degree is determined based on the operating variable values (S10), and the correction opening degree is combined with the opening degree stored in the first control mode (S11). The opening degree of the valve is controlled (S12). After the third control mode is executed, the current opening degree of the first expansion valve is stored in real time (S13) and the current opening degree stored while the third control mode is performed. The combination is controlled by combining the correction opening degree.

Therefore, when the operating variable value of the air conditioner is out of the normal operating range, the stability of the system can be improved by switching the control mode of the first expansion valve.

In addition, in the first control mode, the current opening degree of the first expansion valve is sensed and stored, and the opening degree of the first expansion valve is gradually increased or decreased. Switching to other control modes can also be facilitated.

On the other hand, in the cooling operation, since the first expansion valve 141 serves as a second expansion device for adjusting the degree of superheat, the first expansion valve 141 can be controlled in the second control mode. In addition, when there is no gas injection operation request, the second expansion valve 142 and the injection valve 143 may be completely opened.

FIG. 7 is a flowchart illustrating a control method of the first expansion valve when the air conditioner according to another embodiment of the present invention is heated. FIG. 8 is a view illustrating a change in opening degree according to the opening time in the control method of FIG. 7. It is a graph. Hereinafter, differences from the above-described embodiment will be mainly described. The same reference numerals as in the above-described embodiment indicate the same members.

The difference from the above embodiment is that the control unit 200 changes the opening degree of the first expansion valve 141 until the opening degree of the first expansion valve 141 reaches a target opening degree. (S20) and the maintenance process for maintaining the opening degree (S21). That is, when the opening degree change amount is determined according to the difference between the target opening degree and the current opening degree, the opening degree is changed by the opening degree change amount (S20). After that, the control of the first expansion valve 141 is stopped, and a predetermined time is The opening degree of the first expansion valve 141 is maintained for a while. (S21) By changing the opening degree and having the time to maintain the opening degree, the cycle at the time of controlling the first expansion valve 141 is maintained. More stable.

The change process and the maintenance process may be performed a plurality of times until the current opening degree of the first expansion valve 141 reaches the target opening degree. As an example, referring to FIG. 8, the changing process and the maintaining process are performed three times each. The opening degree change amounts C1, C2, and C3 in a plurality of changes are controlled in proportion to the opening time. That is, since the difference between the current opening degree and the target opening degree is large in the initial opening degree control of the first expansion valve 141, the opening degree change amount is increased, so that the control is made more quickly. Thereafter, as the opening time increases and the opening degree of the first expansion valve 141 reaches the target opening degree, the amount of change in the opening degree is made smaller, so that the control can be made more accurately. In addition, the opening degree holding time (T1, T2, T3) in a plurality of said holding process is also controlled to be proportional to the opening time. That is, in the initial opening degree control of the first expansion valve 141, the opening degree holding time is long. Thereafter, as the opening time gradually increases, the opening degree holding time (T1, T2, T3) becomes smaller. In addition, the opening degree holding time (T1, T2, T3) may be set to be proportional to the opening degree change amount (C1, C2, C3) in the change process. Therefore, the larger the opening degree change amount C1, C2, C3 of the first expansion valve 141, the longer the opening degree holding time (T1, T2, T3), so that the cycle at the time of controlling the first expansion valve 141 is increased. More stable.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

1 is a configuration diagram of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the control flow of the air conditioner shown in FIG. 1. FIG.

3 is a configuration diagram showing the flow of the refrigerant during the heating operation of the air conditioner shown in Fig.

FIG. 4 is a configuration diagram showing the flow of the refrigerant during the cooling operation of the air conditioner shown in FIG.

5 is a flowchart showing a control method of the first expansion valve when the air conditioner shown in Fig. 1 performs heating operation.

6 is a graph showing the amount of change in the opening degree of the first expansion valve 141 according to the opening time when the air conditioner shown in FIG. 1 is heated.

7 is a flowchart illustrating a control method of the first expansion valve when the air conditioner according to another embodiment of the present invention is heated.

8 is a graph showing the amount of change in the opening degree according to the opening time in the control method shown in FIG.

BRIEF DESCRIPTION OF THE DRAWINGS Fig.

100: air conditioner 110: compressor

120: indoor heat exchanger 130: outdoor heat exchanger

141: first expansion valve 142: second expansion valve

143: Injection valve 150: Phase separator

160: Four-way valve 180: Injection piping

200:

Claims (9)

A condenser for condensing the refrigerant; A first expansion device through which the refrigerant passing through the condenser is throttled; A second expansion device in which the refrigerant having passed through the first expansion device is throttled; An evaporator through which the refrigerant having passed through the second expansion device is evaporated; A refrigerant passing through the evaporator and a compressor into which a refrigerant branched and injected between the first expansion device and the second expansion device flows and is compressed; Detect at least one or more operating variables, determine a target opening degree of the first expansion device based on a pre-stored set value corresponding to the sensed driving variable value, and openness of the first expansion device; And a change process for changing the opening degree of the first expansion device and a holding process for maintaining the opening degree until reaching a degree.  The control unit, When the detected operating variable value is out of a predetermined normal operating range, the correction opening degree is determined based on the operating variable values, and the correction opening degree is combined with the target opening degree to open the first expansion valve. To control the quantity At least part of the change process is controlled to change the amount of change in opening degree according to the opening time, The air conditioning system for controlling the opening degree maintenance time is changed in accordance with the opening degree change amount. delete delete delete The method according to claim 1, Wherein the compressor includes a first compression section in which a refrigerant passing through the evaporator flows and is compressed, and a refrigerant that is branched and injected between the first expansion device and the second expansion device, And a second compression unit that compresses the compressed air. The method according to claim 1, The opening degree change amount is preset according to the difference between the target opening degree and the current opening degree, And an opening amount of the first expansion device based on a value obtained by combining the opening degree change amount with the current opening degree. The method of claim 6, And the opening degree change amount is proportional to a difference between the target opening degree and the current opening degree. The method according to claim 1, Wherein the at least one operating parameter is a plurality of operating parameters, Wherein the plurality of operating variables independently vary the target opening degree of the first expansion device. The method of claim 8, And determine a target opening degree of the first expansion device based on a value multiplied by the set values for the operation variables.

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