KR102558826B1 - Air conditioner system and control method - Google Patents

Abstract

A system or method capable of suppressing intermittent driving and maintaining comfort is provided.
An air conditioning system includes an indoor unit, an outdoor unit, and the indoor unit includes a heat exchanger, an indoor temperature detecting means for detecting the indoor temperature, and a valve for adjusting the flow rate of a refrigerant flowing in a refrigerating cycle, and includes an outdoor unit, a heat exchanger, a compressor, and a valve for adjusting the flow rate of a refrigerant flowing in the refrigerating cycle, and further includes control means for controlling the opening degree of a valve of the indoor unit according to the indoor temperature detected by the indoor temperature detecting means and the amount of change in the indoor temperature in a predetermined time. .

Description

Air conditioning system and control method {AIR CONDITIONER SYSTEM AND CONTROL METHOD}

The present invention relates to an air conditioning system and a method for controlling the operation of the air conditioning system.

In a conventional air conditioning system, a method of adjusting the room temperature by controlling the frequency of a compressor of an outdoor unit according to the load of the indoor unit is widely adopted. The compressor of the outdoor unit has a frequency range in which it can be operated, and when the load of the indoor unit is small and the room temperature cannot be maintained even when the compressor operates at the lowest operating frequency, an operation in which the compressor is stopped (thermo-off) and the compressor is operated (thermo-on) is repeated, so-called intermittent operation is performed to stabilize the room temperature.

However, intermittent operation has a problem in that room temperature fluctuates up and down, impairs comfort, and lowers the efficiency of equipment compared to continuous operation.

Therefore, for the purpose of avoiding intermittent operation, a technique for temporarily lowering the frequency to a minimum operating frequency lower than the operating frequency for start-up or in a range equal to or higher than the lower limit operating frequency for use of the compressor is known (for example, see Patent Documents 1 and 2). In addition, a technique for reducing the amount of circulation of the refrigerant by reducing the opening of the expansion valve of the outdoor unit is also known (for example, see Patent Document 3).

Japanese Unexamined Patent Publication No. 2011-202885 Japanese Unexamined Patent Publication No. 2015-102252 Japanese Unexamined Patent Publication No. Hei 10-141740

However, in the techniques described in Patent Literatures 1 and 2, when the compressor frequency required to maintain the room temperature at the set temperature is lower than the lower limit operating frequency of the compressor, intermittent operation becomes unavoidable. There was a problem.

In the technology disclosed in Patent Literature 3, the opening of the expansion valve of the outdoor unit is forcibly reduced to reduce the refrigerant circulation amount to lower the capacity. Therefore, when a plurality of indoor units are connected, the cooling capacity of all the indoor units is reduced. Therefore, when the indoor unit is located in a room with a different load, there has been a problem that the room temperature cannot be maintained in the room with a large load, and comfort cannot be maintained.

In view of the above problems, the present invention is an air conditioning system including an indoor unit and an outdoor unit,

indoor unit,

a heat exchanger,

indoor temperature detecting means for detecting indoor temperature;

Including a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle,

outdoor unit,

a heat exchanger,

compressor,

Including a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle,

An air conditioning system includes control means for controlling the opening degree of a valve of an indoor unit in accordance with the indoor temperature detected by the indoor temperature detecting means and the amount of change in the indoor temperature in a predetermined period of time.

According to the present invention, it is also possible to suppress intermittent driving and maintain comfort.

1 is a diagram showing a first configuration example of an air conditioning system;
2 is a diagram illustrating a hardware configuration of a control device provided in an air conditioning system;
3 is a flowchart showing a first example of controlling the opening degree of an indoor expansion valve;
Fig. 4 is a diagram showing time histories of power consumption after the start of operation in the conventional control and in the present control.
5 is a flowchart showing a second example of controlling the opening degree of an indoor expansion valve;
Fig. 6 is a flowchart showing a third example of controlling the opening degree of an indoor expansion valve;
Fig. 7 is a flowchart showing a fourth example of controlling the opening degree of an indoor expansion valve;
Fig. 8 is a diagram showing a second configuration example of an air conditioning system;
Fig. 9 is a flowchart showing a fifth example of controlling the opening degree of an indoor expansion valve;
Fig. 10 is a flowchart showing a sixth example of controlling the opening degree of an indoor expansion valve;
Fig. 11 is a flowchart showing a seventh example of controlling the opening of an indoor expansion valve;
Fig. 12 is a flowchart showing an eighth example of controlling the opening degree of an indoor expansion valve;

1 is a diagram showing a first configuration example of an air conditioning system. An air conditioning system includes an indoor unit 10 installed indoors, such as a house or a building, and an outdoor unit 20 installed outdoors. The air conditioning system may include an operating device (remote controller) for operating the indoor unit by communicating with the indoor unit 10 by radio in a room where the indoor unit 10 is installed.

The indoor unit 10 and the outdoor unit 20 are connected by two pipes 30 and 31 through which refrigerant as a heating medium circulates. As a refrigerant, hydrofluorocarbons, such as R410a and R32, are used, for example. In addition, the indoor unit 10 and the outdoor unit 20 are connected by a communication cable or the like to communicate with each other. In addition, the indoor unit 10 and the outdoor unit 20 are not limited to being wired connected by a communication cable or the like, and may be wirelessly connected using WiFi (registered trademark) or the like.

The indoor unit 10 is activated or stopped in response to a user's operation. When the indoor unit 10 starts up, it commands the outdoor unit 20 to start up, and notifies the set temperature set in the indoor unit 10, the measured room temperature, and the like. The indoor unit 10 also notifies the outdoor unit 20 of the changed operating conditions when a change in operating conditions such as an operating mode or set temperature is received from the user. When the indoor unit 10 stops, it commands the outdoor unit 20 to stop operation.

During operation, the indoor unit 10 introduces air inside the room, exchanges heat between the introduced air and the refrigerant supplied from the outdoor unit 20, blows out cooled air or warmed air, and cools or warms the room to a set temperature.

For this reason, the indoor unit 10 includes a heat exchanger 11 that exchanges heat between indoor air and a refrigerant, and a blower (fan) 12 that introduces indoor air into the heat exchanger 11 and blows out the air heat-exchanged by the heat exchanger 11.

The indoor unit 10 includes an indoor temperature detecting means for detecting the indoor temperature in order to notify the outdoor unit 20 of the indoor temperature. As the room temperature detecting means, a room temperature sensor 13 can be used. Further, the indoor unit (10) is provided with pipe temperature detection means for detecting the outer wall temperature of the two pipes (30, 31) connected to the heat exchanger (11). As the pipe temperature detecting means, the pipe temperature sensors 14 and 15 can be used. In addition, the indoor unit 10 includes an indoor expansion valve 16 for adjusting the flow rate of the refrigerant flowing through the heat exchanger 11 by expanding the refrigerant.

When the indoor unit 10 is used for cooling, the heat exchanger 11 functions as an evaporator, and the refrigerant flows into the heat exchanger 11 in a two-phase state in which liquid and gas are mixed (liquid refrigerant). The refrigerant exchanges heat with the air introduced by the fan 12 in the heat exchanger 11 to evaporate liquid components, and is discharged from the heat exchanger 11 as a gaseous refrigerant and sent to the outdoor unit 20. The liquid component evaporates at a constant temperature (saturation temperature) corresponding to the pressure in the heat exchanger 11, and is discharged from the heat exchanger 11 at or at a temperature higher than the saturation temperature. Δt in the case of discharge at a temperature about Δt higher than the saturation temperature indicates a temperature rise from the saturation temperature and is called superheat.

The outdoor unit 20 is activated upon receiving a designation from the indoor unit 10, and starts operating in the operation mode set or notified from the indoor unit 10. The operation mode is a cooling mode, a heating mode, a ventilation mode, or the like. The outdoor unit 20 controls the temperature, pressure, flow rate, and the like of the refrigerant according to the set temperature, room temperature, pipe temperature, and the like that have been set or notified from the indoor unit 10 . In addition, the outdoor unit 20 stops operating upon receiving a command from the indoor unit 10 .

The outdoor unit 20 is connected to the indoor unit 10 through pipes 30 and 31 and circulates the refrigerant. For this reason, a compressor 21 for circulating the refrigerant is provided. The refrigerant gas compressed by the compressor 21 exchanges heat with the air introduced by the fan 23 in the heat exchanger 22 to become a high-pressure liquid refrigerant. In addition, the outdoor unit 20 is provided with a four-way valve 25 for reversing the direction in which the refrigerant flows in order to enable heating operation. The outdoor expansion valve 24 is provided to adjust the flow rate of the refrigerant while converting the refrigerant, which has become high-pressure during heating, into a low-temperature, low-pressure refrigerant.

The compressor 21 changes the flow rate of the refrigerant by changing the operating frequency.

The outdoor unit 20 includes a control device 26 . The controller 26 controls the operating frequency of the compressor 21 and the opening degree of the outdoor expansion valve 24 based on the indoor temperature detected by the room temperature sensor 13, the set temperature, the piping temperature, and the operation mode. In addition, the four-way valve 25 is switched according to the set operation mode.

The operating frequency of the compressor 21 has a lower limit, and even if the compressor 21 operates at the lowest operating frequency, if the generation capacity is greater than the indoor load, the indoor temperature cannot be maintained at the set temperature by continuous operation. Therefore, intermittent operation is performed in which thermo-on and thermo-off are repeated to maintain the room temperature at the set temperature. However, when intermittent operation is performed, compared to continuous operation, there is a problem that the efficiency and reliability of the equipment are lowered, and comfort is impaired because the room temperature fluctuates.

Therefore, the outdoor unit 20 is configured to include a frequency sensor 27 as a frequency detection means for detecting the operating frequency of the compressor 21, and the controller 26 controls the opening degree of the indoor expansion valve 16 according to the room temperature detected by the room temperature sensor 13 and the amount of change in the room temperature in a predetermined time and the operating frequency detected by the frequency sensor 27.

When the compressor 21 is operating at around the lowest operating frequency, the controller 26 reduces the opening of the indoor expansion valve 16 to reduce the flow rate of the refrigerant flowing into the heat exchanger 11, thereby reducing the generated air conditioning capacity (cooling capacity). As a result, even if the compressor 21 is operating at the lowest operating frequency, the cooling capacity can be further reduced, so that intermittent operation of the compressor 21 can be avoided even for air conditioning loads that conventionally require intermittent operation of the compressor 21. This detail is explained below.

Fig. 2 is a diagram showing an example of the hardware configuration of the control device 26 used in the air conditioning system. The control device 26 includes a CPU 40, a flash memory 41, a RAM 42, a communication I/F 43, and a control I/F 44. Components such as the CPU 40 are connected to the bus 45 and exchange information and the like via the bus 45 .

The flash memory 41 stores programs executed by the CPU 40, various data, and the like. RAM 42 provides a work area for CPU 40 . The CPU 40 realizes the above control by reading the program stored in the flash memory 41 into the RAM 42 and executing it.

The communication I/F 43 is connected to the indoor unit 10 and receives information such as room temperature, liquid pipe temperature, and gas pipe temperature from the indoor unit 10 . In addition, the communication I/F 43 also receives information from the frequency sensor 27 . The control I/F 44 is connected to the compressor 21, the fan 23, the outdoor expansion valve 24, the four-way valve 25, and the indoor expansion valve 16, and controls each device.

Here, the control device 26 realizes the above control by having the CPU 40 read and execute a program from the flash memory 41, but the above control may be realized using hardware such as a circuit.

Specific control will be described in detail below as control during cooling operation. FIG. 3 is a flowchart showing a first example of controlling the opening degree of the indoor expansion valve 16. As shown in FIG. This control starts from step 100 at the stage where cooling operation is started. In step 101, it is determined whether the operating frequency F is smaller than an arbitrary frequency (frequency threshold value) F _d larger than the lowest operating frequency F _min . The frequency threshold value _Fd is determined with a certain margin to the lowest operating frequency _Fmin so as not to enter intermittent operation before starting control of the degree of opening of the indoor expansion valve 16 . In the control of the opening degree of the indoor expansion valve 16, the determination in step 101 is repeated until it is determined that F is smaller than _Fd .

When it is determined in step 101 that F is smaller than _Fd , the process proceeds to step 102, and it is determined whether the difference RL between the indoor air conditioning load and the generated cooling capacity is smaller than the load threshold value RL _th .

The difference RL between the indoor air-conditioning load and the generated capacity can be detected using a set temperature, a detected value (room temperature) detected by the room temperature sensor 13, and a change in room temperature within a predetermined period of time. The predetermined time can be set to, for example, several minutes, since in a short time, such as the time taken to control the indoor expansion valve 16 (about several seconds), the amount of change is too small and the amount of change cannot be detected, and in a long time, intermittent operation may occur during that time.

When it is determined that RL is greater than or equal to RL _th , since the cooling capacity is relatively small with respect to the air conditioning load and there is no need to reduce the capacity, the opening degree control of the indoor expansion valve 16 is not performed. For this reason, it returns to step 101 and continues control.

On the other hand, when it is determined in step 102 that RL is smaller than RL _th , since the cooling capacity is relatively large with respect to the air conditioning load, the flow proceeds to step 103, and the opening of the indoor expansion valve 16 is made small to reduce the flow rate of the refrigerant. When the opening of the indoor expansion valve 16 is reduced, the flow rate of the refrigerant is reduced, and the pressure is low, so the two-phase refrigerant becomes a gas phase with a smaller heat exchange amount, so the partial area (effective area) of the heat exchanger pipe serving as the evaporator of the heat exchanger 11 is also reduced. Since indoor air is cooled mainly by latent heat when the refrigerant evaporates, the cooling capacity can be reduced by reducing the effective area. By lowering the cooling capacity, all of the refrigerant can be evaporated and, furthermore, a degree of superheating can be given and discharged from the heat exchanger (11).

The controller 26 controls the rotational speed of the compressor 21 based on the set temperature and the detected value of the room temperature sensor 13, and controls the opening of the outdoor expansion valve 24 to maintain the superheat within a certain range. Accordingly, when the indoor load is large, the controller 26 increases the rotational speed of the compressor 21 to increase the amount of circulation of the refrigerant, and when the indoor load decreases, the rotational speed of the compressor 21 is decreased to decrease the circulation amount of the refrigerant.

Even when the indoor load gradually decreases and the compressor 21 operates at the lowest operating frequency, by reducing the opening of the indoor expansion valve 16 to reduce the cooling capacity, the room temperature can be maintained even if the compressor 21 continues to operate at the lowest operating frequency. For this reason, it becomes possible to maintain the continuous operation of the compressor 21.

After reducing the opening degree of the indoor expansion valve 16 in step 103, it returns to step 101 and continues control. In addition, when the operation of the air conditioning system is stopped, this control also ends.

FIG. 4 shows time histories of power consumption after start of operation in the conventional control and the control of the opening of the indoor expansion valve 16 shown in FIG. 3 . Conventional control is control that repeats intermittent operation, and time histories are indicated by broken lines. Conventional control consumes zero power when the thermostat is turned off, but consumes a lot of power when the thermostat is turned on. On the other hand, when the opening degree control (main control) of the indoor expansion valve 16 is performed, thermo-off/thermo-on does not occur, and constant low power is consumed. Therefore, the total power consumption (time integral value of power consumption) enclosed by the time axis and solid line is smaller than the total power consumption of the conventional control, which is similarly surrounded by the time axis and the broken line. Therefore, this control can reduce power consumption compared to conventional control.

The control shown in FIG. 3 is control only for reducing the opening degree of the indoor expansion valve 16. However, when the room temperature rises due to a rise in outside air temperature and the air conditioning load increases, there is a case where it is desired to improve the reduced cooling capacity. In addition, if the circulating amount of the refrigerant is small and the effective area of the evaporator remains small when the air conditioning load is large, the operation becomes inefficient. Therefore, control capable of improving the cooling capacity will be described with reference to FIG. 5 .

5 is a flowchart showing a second example of controlling the opening degree of the indoor expansion valve 16. As shown in FIG. Starting from step 200, similarly to the control shown in FIG. 3, in step 201, it is determined whether or not the driving frequency F is smaller than the frequency threshold value _Fd . If it is determined that F is smaller than _Fd , the process proceeds to step 202 to determine whether the difference RL between the indoor air conditioning load and the generated cooling capacity is smaller than a threshold value RL _th . Then, when it is determined that RL is smaller than RL _th , the process proceeds to step 203 to reduce the opening of the indoor expansion valve 16 in order to reduce the flow rate of the refrigerant. After reducing the opening degree of the indoor expansion valve 16, the flow returns to step 201 and the control continues.

When it is determined in step 201 that F is equal to or greater than _Fd , or when it is determined in step 202 that RL is greater than or equal to RL _th , the process proceeds to step 204 and the degree of opening of the indoor expansion valve 16 is increased. When F is greater than or equal to _Fd , it indicates that the cooling capacity needs to be improved. To improve the cooling capacity, the circulating amount of the refrigerant is increased, and the degree of superheat on the outlet side of the heat exchanger 11 is reduced. In order to increase the effective area, the opening degree of the indoor expansion valve 16 is increased. When RL is equal to or greater than RL _th , it indicates that the air conditioning load is relatively large compared to the generated cooling capacity. If the refrigerant circulation amount is small and the effective area remains small even though the air conditioning load is increased, the operation becomes inefficient. Therefore, the opening degree of the indoor expansion valve 16 is increased to increase the refrigerant circulation amount.

After increasing the degree of opening of the indoor expansion valve 16, the flow returns to step 201 and the control continues. Also in this case, when the operation of the air conditioning system is stopped, the control is terminated.

The control shown in Fig. 5 is a control in which the degree of opening of the indoor expansion valve 16 is reduced or increased. In addition, depending on the air conditioning load, there is a case where the variation in room temperature is smaller when the degree of opening of the indoor expansion valve 16 is maintained without being changed. This is because room temperature fluctuates, and when the fluctuation is large, comfort is impaired. Therefore, control that can adjust and maintain the opening degree of the indoor expansion valve 16 will be described with reference to FIG. 6 .

6 is a flowchart showing a third example of controlling the opening degree of the indoor expansion valve 16. As shown in FIG. Since steps 301 and 302 shown in Fig. 6 are the same as steps 201 and 202 shown in Fig. 5, the description thereof is omitted.

When it is determined in step 302 that RL is smaller than RL _th , the process proceeds to step 303 to determine whether or not the change amount dT _in of the room temperature in the predetermined time is smaller than the preset change amount dT _dec of the opening reduction start. dT _dec is a change in room temperature serving as a standard for starting a decrease in the degree of opening of the indoor expansion valve 16 . In addition, the amount of change in room temperature dT _in can be calculated as the amount of change in the detected value of the room temperature sensor 13 in a predetermined period of time.

If it is determined in step 303 that dT _in is smaller than dT _dec , since the room temperature has rapidly decreased and the cooling capacity needs to be reduced, the process proceeds to step 304 to calculate the amount of change in the opening degree of the indoor expansion valve 16 according to the amount of change in room temperature dT _in , and reduce the degree of opening of the indoor expansion valve 16 according to the amount of change. And it returns to step 301, and control continues.

When it is determined in step 303 that dT _in is greater than or equal to dT _dec , the process proceeds to step 305 to determine whether or not the temperature difference between the room temperature T _in and the set temperature T _set is smaller than the preset temperature difference ΔT _dec for the opening reduction start. ΔT _dec is a temperature difference between room temperature and a set temperature serving as a reference for starting a decrease in the degree of opening of the indoor expansion valve 16 . If it is determined that the temperature difference is less than ΔT _dec , the change in room temperature is greater than dT _dec , but since the room temperature is low, the cooling capacity needs to be reduced. And it returns to step 301, and control continues.

On the other hand, when it is determined in step 305 that the temperature difference is greater than or equal to ΔT _dec , it can be determined that the room temperature has not decreased, and if control is performed to reduce the opening of the indoor expansion valve 16, the room temperature may rise due to too small a generating capacity. For this reason, it proceeds to step 306, and the opening degree of the indoor expansion valve 16 is maintained at the current opening degree. And it returns to step 301, and control continues.

When F is determined to be greater than or equal to F _d in step 301, or when RL is determined to be greater than or equal to RL _th in step 302, the process proceeds to step 307 to determine whether dT _in is larger than a preset change amount dT _inc of opening degree increase. dT _inc is an amount of change in room temperature serving as a reference for starting an increase in the degree of opening of the indoor expansion valve 16 . When dT _in is greater than dT _inc , it indicates that the room temperature has changed greatly due to a rise in outside air temperature, and thus it is necessary to increase the flow rate of the refrigerant by increasing the opening of the indoor expansion valve 16. For this reason, when it is determined that dT _in is greater than dT _inc , the process proceeds to step 308, the amount of change in the opening degree of the indoor expansion valve 16 is calculated according to the amount of change in the detected value of the room temperature sensor 13, and the degree of opening of the indoor expansion valve 16 is increased.

When it is determined in step 307 that dT _in is less than or equal to dT _inc , the process proceeds to step 309 to determine whether or not the temperature difference between the room temperature T _in and the set temperature T _set is larger than a preset temperature difference at which the opening degree is increased ΔT _inc . ΔT _inc is a temperature difference between room temperature and a set temperature serving as a reference for starting an increase in the degree of opening of the indoor expansion valve 16. If the temperature difference is larger than ΔT _inc , the flow rate of the refrigerant needs to be increased by increasing the opening of the indoor expansion valve 16, so the process proceeds to step 308. On the other hand, if control is performed to increase the opening of the indoor expansion valve 16 when the temperature difference is ΔT _inc or less, the cooling capacity may be increased and the room temperature may be lowered even if the room temperature does not rise. For this reason, it proceeds to step 310, and the opening degree of the indoor expansion valve 16 is maintained at the current opening degree. And it returns to step 301, and control continues.

In this way, the room temperature can be further stabilized by performing control to adjust and maintain the opening of the indoor expansion valve 16 . Also in this case, when the operation of the air conditioning system is stopped, the control is terminated.

The control shown in FIG. 6 is control for adjusting and maintaining the degree of opening of the indoor expansion valve 16, but by using the detected values of the pipe temperature sensors 14 and 15, it is possible to control the degree of superheat of the refrigerant on the outlet side of the indoor heat exchanger as a target value. Then, control using the detected values of the pipe temperature sensors 14 and 15 will be described with reference to FIG. 7 .

7 is a flowchart showing a fourth example of controlling the opening degree of the indoor expansion valve 16. As shown in FIG. In this case as well, only parts different from the processing shown in FIG. 5 will be described. In step 403, it is determined whether dT _in is smaller than the superheat increase start change amount dT _inc . In the example shown in Fig. 6, dT _inc is the opening degree increase start change amount, but in this example, the superheat degree increase start change amount. Similarly, in this example, _dTdec is the superheat reduction start change amount, ΔT _inc is the superheat increase start temperature difference, and ΔT _dec is the superheat degree decrease start temperature difference.

dT _inc is the amount of change in room temperature that serves as a reference for starting an increase in degree of superheat, and dT _des is the amount of change in room temperature that serves as a reference for initiating a decrease in degree of superheat. ΔT _inc is a temperature difference between room temperature and a set temperature as a reference for starting an increase in superheat, and ΔT _dec is a temperature difference between room temperature and a set temperature as a reference for starting a decrease in superheat.

In step 404, the target superheat on the refrigerant outlet side of the heat exchanger 11 is calculated based on the detected value of the room temperature sensor 13 and the amount of change in the detected value of the room temperature sensor 13 over a predetermined period of time. In this case, since the cooling capacity is lowered by reducing the flow rate of the refrigerant and imparting a degree of superheat to reduce the effective area, the degree of superheat is increased.

In step 405, the degree of opening of the indoor expansion valve 16 is controlled by calculating the amount of change in the opening degree of the indoor expansion valve 16 at which the superheat degree of the refrigerant at the outlet side of the indoor heat exchanger becomes the target superheat degree obtained in step 404. Here, the degree of opening of the indoor expansion valve 16 is reduced. And it returns to step 401, and control continues.

When it is determined in step 406 that the temperature difference between T _in and T _set is less than ΔT _inc , the process proceeds to step 404, and when it is determined that the temperature difference between T _in and T _set is greater than or equal to ΔT _inc , the process proceeds to step 407. In step 407, the target superheat degree is calculated in the same way as in step 404, but since the cooling capacity is not reduced, the superheat degree is maintained at the current superheat degree, and in step 408, the opening degree of the indoor expansion valve 16 is maintained at the current opening degree. And it returns to step 401, and control continues.

If it is determined in step 409 that dT _in is greater than dT _dec , the process proceeds to step 410, and similarly to step 404, the target superheat degree is calculated. In this case, since the cooling capacity is improved by increasing the effective area by increasing the flow rate of the refrigerant and reducing the degree of superheat, the degree of superheat is reduced.

In step 411, in the same manner as in step 405, the amount of change in the opening degree of the indoor expansion valve 16 at which the superheat degree of the refrigerant at the outlet side of the indoor heat exchanger becomes the target superheat degree obtained in step 410 is calculated, and the degree of opening of the indoor expansion valve 16 is controlled. In this case, the degree of opening of the indoor expansion valve 16 is increased. And it returns to step 401, and control continues.

When it is determined in step 412 that the temperature difference between T _in and T _set is ΔT _dec or less, the process proceeds to step 410, and when it is determined that the temperature difference between T _in and T _set is greater than ΔT _dec , the process proceeds to step 413. In step 413, the target superheat is calculated in the same way as in step 404, but since the cooling capacity is not increased, the superheat is maintained at the current superheat, and in step 414, the opening of the indoor expansion valve 16 is maintained at the current opening. And it returns to step 401, and control continues. Also in this case, when the operation of the air conditioning system is stopped, the control is terminated.

So far, it has been described that the control of the opening of the indoor expansion valve 16 is performed by the control device 26 included in the outdoor unit 20, but the control of the opening of the indoor expansion valve 16 is not limited to being controlled by the control device 26. For example, it may be implemented by a control device provided in the indoor unit 10, or by a centralized control device or the like provided separately from the indoor unit 10 or the outdoor unit 20.

The air conditioning system is not limited to a single indoor unit 10 and one outdoor unit 20. Therefore, a system in which a plurality of indoor units 10 are connected to one outdoor unit 20 or a system in which a plurality of outdoor units 20 and a plurality of indoor units 10 are connected may be used. FIG. 8 shows an example of a system in which a plurality of indoor units 10 are connected to one outdoor unit 20 . In the example shown in Fig. 8, the three indoor units 10a to 10c and the outdoor unit 20 are connected.

Each indoor unit 10a to 10c is installed in each room and adjusts the room temperature of each room to a set temperature. Since each of the indoor units 10a to 10c includes indoor expansion valves 16a to 16c, respectively, the cooling capacity can be adjusted for each room. For this reason, even if the air conditioning load is different for each room, it is possible to stabilize the room temperature in each room while avoiding intermittent operation.

By avoiding intermittent operation and realizing continuous operation, power consumption can be reduced, and the number of starts and stops can be reduced, so the efficiency of the device can be improved, and failures and the like are reduced, so reliability can be improved. Moreover, since room temperature can be stabilized, comfort can be maintained.

Further, in the example described so far, the operating frequency F of the compressor 21 is detected, and the opening of the indoor expansion valve 16 is controlled when the detected operating frequency F is smaller than the frequency threshold value _Fd and the difference RL between the air conditioning load and the capacity is smaller than the load threshold value RL _th . Accordingly, even if a plurality of indoor units 10 are present and, for example, except for one indoor unit 10, the difference RL between the air conditioning load and the capacity is smaller than the load threshold value RL _th , when the load of the single indoor unit 10 is large and F exceeds _Fd , control of the opening degree of the indoor expansion valve 16 is not uniformly performed. With this, room temperature cannot be stabilized and comfort cannot be maintained.

Therefore, in the opening degree control shown in FIGS. 3 and 5 to 7, step 101, step 201, step 301 and step 401 are omitted, and the opening degree of the indoor expansion valve 16 can be controlled only by determining whether the difference RL is smaller than the load threshold RL _th . 9 to 12, each opening degree control is shown as fifth to eighth examples.

9 is a flowchart showing a fifth example of controlling the opening degree of the indoor expansion valve 16. As shown in FIG. This control starts from step 500 at the stage where cooling operation is started. In step 501, it is not determined whether the operating frequency F is smaller than the frequency threshold value _Fd , but only whether the difference RL between the indoor air conditioning load and the generated cooling capacity is smaller than the load threshold value RL _th is determined. Since step 502 is the same as step 103 in Fig. 3, description thereof is omitted here.

FIG. 10 is a flowchart showing a sixth example of controlling the opening degree of the indoor expansion valve 16. As shown in FIG. Starting from step 600, in step 601, similarly to the example shown in FIG. 9, it is determined whether or not the difference RL is smaller than the load threshold value RL _th . The processing after step 602 is the same as the processing after step 203 in FIG. 5 .

11 is a flowchart showing a seventh example of controlling the opening degree of the indoor expansion valve 16. Starting from step 700, in step 701, similarly to the examples shown in Figs. 9 and 10, it is determined whether or not the difference RL is smaller than the load threshold value RL _th . The processing after step 702 is the same as the processing after step 303 in FIG. 6 .

12 is a flowchart showing an eighth example of controlling the opening of the indoor expansion valve 16. Starting from step 800, in step 801, similarly to the examples shown in Figs. 9 to 11, it is determined whether or not the difference RL is smaller than the load threshold value RL _th . The processing after step 802 is the same as the processing after step 403 in FIG.

As in the examples shown in Figs. 9 to 12, this control can be operated regardless of the current operating frequency only by determining whether the difference RL is smaller than the load threshold value RL _th . In this way, it is possible to avoid not uniformly controlling the opening degree of the indoor expansion valve 16, and to appropriately control the opening degree of the indoor expansion valve 16 of the indoor unit 10 in which RL is smaller than RL _th , thereby stabilizing the room temperature and maintaining comfort.

Although the indoor unit, air conditioning system, and control method of the present invention have been described in detail with the above-described embodiments, the present invention is not limited to the above-described embodiments, and other embodiments, additions, changes, deletions, etc., can be modified within the scope conceived by those skilled in the art, and in any embodiment, as long as the action and effect of the present invention are exhibited, they are included within the scope of the present invention.

10, 10a to 10c: indoor unit
11, 11a to 11c: heat exchanger
12, 12a to 12c: fan
13, 13a to 13c: room temperature sensor
14, 14a to 14c, 15, 15a to 15c: pipe temperature sensor
16, 16a to 16c: indoor expansion valve
20: outdoor unit
21: Compressor
22: heat exchanger
23: fan
24: outdoor expansion valve
25: four-way valve
26: control device
27: frequency sensor
30, 31: piping
40: CPU
41: flash memory
42 RAM
43: communication I/F
44: Control I/F
45: bus

Claims (11)

An air conditioning system having an indoor unit and an outdoor unit,
the indoor unit,
a heat exchanger,
indoor temperature detecting means for detecting indoor temperature;
Including a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle,
the outdoor unit,
a heat exchanger,
compressor,
Including a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle,
and control means for controlling the opening degree of the valve of the indoor unit in accordance with the temperature of the room detected by the room temperature detecting means and a change in the temperature of the room in a predetermined period of time;
The air conditioning system in which the control means detects a difference between the air conditioning load and the air conditioning capacity from the difference between the indoor temperature and the set temperature detected by the indoor temperature detecting means and the amount of change in the indoor temperature for the predetermined time period, and when the detected difference is smaller than a load threshold, controls to reduce the opening degree of the valve of the indoor unit. delete According to claim 1,
wherein the control means performs control to increase the opening degree of the valve of the indoor unit when the detected difference is equal to or greater than a load threshold. According to claim 1 or 3,
wherein the control means calculates the amount of change in the opening degree of the valve of the indoor unit based on the indoor temperature detected by the room temperature detecting means and the amount of change in the indoor temperature for the predetermined time period. According to claim 4,
the indoor unit,
two pipe temperature detecting means for detecting respective temperatures of two pipes connecting the heat exchanger and the outdoor unit;
The control means calculates a target superheat of the refrigerant discharged from the heat exchanger based on the indoor temperature detected by the room temperature detecting means and the amount of change in the indoor temperature in the predetermined time period, and calculates a change in the valve opening of the indoor unit where the superheat obtained from the difference between the two temperatures detected by the two pipe temperature detecting means is the calculated target superheat. An air conditioning system having a plurality of indoor and outdoor units,
Each indoor unit,
a heat exchanger,
indoor temperature detecting means for detecting indoor temperature;
Including a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle,
the outdoor unit,
a heat exchanger,
compressor,
Including a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle,
and control means for controlling the opening degree of each valve of each indoor unit in accordance with the temperature of each room detected by the room temperature detecting means of each indoor unit and the amount of change in the temperature of each room in a predetermined time period;
The air conditioning system in which the control unit detects a difference between an air conditioning load and an air conditioning capacity of the at least one indoor unit from a difference between the indoor temperature and a set temperature detected by the indoor temperature detecting unit and a variation in the indoor temperature for the predetermined time period, and when the detected difference is smaller than a load threshold value, controls to reduce the opening degree of the valve of the indoor unit. delete According to claim 6,
wherein the control means performs control to increase the opening degree of the valve of the one or more indoor units when the detected difference is equal to or greater than a load threshold value. According to claim 6 or 8,
The air conditioning system in which the control means calculates the amount of change in the opening degree of the valve of the indoor unit based on the indoor temperature detected by the indoor temperature detecting means of the indoor unit and the amount of change in the indoor temperature for the predetermined time. According to claim 9,
Each of the indoor units,
two pipe temperature detecting means for detecting respective temperatures of two pipes connecting the heat exchanger and the outdoor unit;
wherein, for at least one of the indoor units, the control unit calculates a target superheat of the refrigerant discharged from the heat exchanger of the indoor unit based on the indoor temperature detected by the indoor temperature detecting unit of the indoor unit and the amount of change in the indoor temperature in the predetermined time period, and calculates a variation in the valve opening of the indoor unit in which a superheat obtained from a difference between two temperatures detected by the two pipe temperature detecting units of the indoor unit is the calculated target superheat. air conditioning system. an indoor unit including a heat exchanger, an indoor temperature detecting means for detecting the indoor temperature, and a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle;
An outdoor unit including a heat exchanger, a compressor, and a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle;
A control method executed by said control means of an air conditioning system, comprising a control means;
calculating a change amount of the indoor temperature in a predetermined time from the indoor temperature detected by the indoor temperature detecting means;
controlling the opening degree of the valve of the indoor unit according to the indoor temperature detected by the indoor temperature detecting means and the calculated amount of change in the indoor temperature;
wherein the control unit detects a difference between the air conditioning load and the air conditioning capacity from the difference between the room temperature detected by the room temperature detecting unit and a set temperature and a change in room temperature for the predetermined time period, and when the detected difference is smaller than a load threshold value, controls to reduce the opening degree of the valve of the indoor unit.