CN113551437B - Air conditioning system and control method - Google Patents

Abstract

The invention provides an air conditioning system and a control method, which can inhibit intermittent operation and maintain comfort. The air conditioning system includes an indoor unit including a heat exchanger, an indoor temperature detecting unit that detects a temperature in the indoor space, and a valve for adjusting a flow rate of a refrigerant flowing in a refrigeration cycle, and an outdoor unit including a heat exchanger, a compressor, and a valve for adjusting a flow rate of a refrigerant flowing in a refrigeration cycle, and further includes a control unit that controls an opening degree of the valve of the indoor unit based on the temperature in the indoor space detected by the indoor temperature detecting unit and a change amount of the temperature in the indoor space for a predetermined time.

Description

Air conditioning system and control method

Technical Field

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

Background

In the conventional air conditioning system, a method of controlling the frequency of a compressor of an outdoor unit according to the load of an indoor unit to adjust the room temperature is widely used. The compressor of the outdoor unit has a frequency range in which the compressor can be operated, and when the load on the indoor unit is small and the indoor unit cannot be maintained at room temperature even when the compressor is operated at the lowest operating frequency, the operation of repeatedly stopping (thermally closing) the compressor and operating (thermally opening) the compressor, that is, so-called intermittent operation, is performed to stabilize the room temperature.

However, intermittent operation has a problem that the efficiency of the apparatus is lowered as compared with continuous operation in which comfort is not impaired, because the room temperature varies up and down.

Therefore, in order to avoid intermittent operation, the following techniques are known: the frequency is temporarily reduced to a range equal to or higher than the lowest operating frequency lower than the operating frequency for starting or the lower operating frequency at which the compressor is used (for example, refer to patent documents 1 and 2). In addition, a technique of reducing the opening degree of an expansion valve of an outdoor unit and reducing the refrigerant circulation amount is also known (for example, refer to patent document 3

However, in the techniques described inpatent documents 1 and 2, if the compressor frequency required to maintain the room temperature at the set temperature is lowered below the lower limit operation frequency for the use of the compressor, intermittent operation is unavoidable.

In the technique described in patent document 3, since the opening degree of the expansion valve of the outdoor unit is forcibly reduced and the refrigerant circulation amount is reduced to reduce the capacity, when a plurality of indoor units are connected, the refrigerating capacity of all the indoor units is reduced. Therefore, when the indoor unit is located in a room with a different load, the room temperature cannot be maintained in the room with a large load, and the comfort cannot be maintained.

Patent document 1: japanese patent laid-open publication No. 2011-202885

Patent document 2: japanese patent application laid-open No. 2015-102252

Patent document 3: japanese patent laid-open No. 10-141740

Disclosure of Invention

In view of the above problems, the present invention provides an air conditioning system including an indoor unit and an outdoor unit, the indoor unit including: a heat exchanger; an indoor temperature detection unit that detects an indoor temperature; and a valve for adjusting a flow rate of the refrigerant flowing in the refrigeration cycle, the outdoor unit including a heat exchanger, a compressor, and a valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle, the air conditioning system including a control unit that controls an opening degree of the valve of the indoor unit based on the temperature in the room detected by the indoor temperature detecting unit and a variation amount of the temperature in the room for a predetermined time.

According to the present invention, intermittent operation can be suppressed, and comfort can be maintained.

Drawings

Fig. 1 shows a first configuration example of an air conditioning system.

Fig. 2 illustrates a hardware configuration of a control device included in the air conditioning system.

Fig. 3 is a flowchart showing a first example of the opening degree control of the indoor expansion valve.

Fig. 4 shows a time history of power consumption after the start of operation in the conventional control and the present control.

Fig. 5 is a flowchart showing a second example of the opening degree control of the indoor expansion valve.

Fig. 6 is a flowchart showing a third example of the opening degree control of the indoor expansion valve.

Fig. 7 is a flowchart showing a fourth example of the opening degree control of the indoor expansion valve.

Fig. 8 shows a second configuration example of an air conditioning system.

Fig. 9 is a flowchart showing a fifth example of the opening degree control of the indoor expansion valve.

Fig. 10 is a flowchart showing a sixth example of the opening degree control of the indoor expansion valve.

Fig. 11 is a flowchart showing a seventh example of the opening degree control of the indoor expansion valve.

Fig. 12 is a flowchart showing an eighth example of the opening degree control of the indoor expansion valve.

Detailed Description

Fig. 1 shows a first configuration example of an air conditioning system. The air conditioning system includes an indoor unit 10 installed in a house, a building, or the like, and an outdoor unit 20 installed outdoors. The air conditioning system may include an operation device (remote control) for wirelessly communicating with the indoor unit 10 and operating the indoor unit 10 in the room where the indoor unit 10 is provided.

The indoor unit 10 and the outdoor unit 20 are connected by 2pipes 30 and 31 through which a refrigerant as a heat medium circulates. As the refrigerant, for example, hydrofluorocarbons such as R410a and R32 are used. The indoor unit 10 and the outdoor unit 20 are connected to each other by a communication cable or the like for communication. The indoor unit 10 and the outdoor unit 20 are not limited to wired connection via a communication cable or the like, and may be connected wirelessly using WiFi (registered trademark) or the like.

The indoor unit 10 is started or stopped by receiving a user operation. The indoor unit 10 instructs the outdoor unit 20 to start up at the time of starting up, and notifies the set temperature set in the indoor unit 10, the measured room temperature, and the like. When the indoor unit 10 receives a change in the operation conditions such as the operation mode and the set temperature from the user, the outdoor unit 20 is notified of the changed operation conditions. When the indoor unit 10 is stopped, the outdoor unit 20 is instructed to stop operation.

The indoor unit 10 sucks in air in the room during operation, exchanges heat between the sucked air and the refrigerant supplied from the outdoor unit 20, and blows out cooled air or heated air to cool or heat the room so that the room becomes a set temperature.

Accordingly, the indoor unit 10 includes: a heat exchanger 11 that exchanges heat between indoor air and a refrigerant; and a blower (fan) 12 that takes in indoor air into the heat exchanger 11 and blows out air heat-exchanged by the heat exchanger 11.

The indoor unit 10 includes indoor temperature detecting means for detecting an indoor temperature in order to notify the indoor temperature to the outdoor unit 20. As the indoor temperature detecting unit, the room temperature sensor 13 may be used. The indoor unit 10 further includes piping temperature detecting means for detecting the temperatures of the outer wall surfaces of the 2pipes 30 and 31 connected to the heat exchanger 11. The pipe temperature sensors 14 and 15 can be used as the pipe temperature detection means. The indoor unit 10 further includes an indoor expansion valve 16 for expanding the refrigerant to adjust the flow rate of the refrigerant flowing through the heat exchanger 11.

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 flow state (liquid refrigerant) in which the refrigerant is mixed with the gas. The refrigerant exchanges heat with the air taken in by the fan 12 in the heat exchanger 11, whereby the liquid component evaporates, 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 the saturation temperature or at a temperature higher than the saturation temperature. The temperature rise with respect to the saturation temperature is indicated by Δt when the temperature is discharged at a temperature higher than the saturation temperature by Δt, and is referred to as the superheat degree.

The outdoor unit 20 is started in response to a command from the indoor unit 10, and starts operating in the set operation mode or the operation mode notified from the indoor unit 10. The operation modes include a cooling mode, a heating mode, and a blowing mode. The outdoor unit 20 controls the temperature, pressure, flow rate, and the like of the refrigerant based on the set temperature, indoor temperature, piping temperature, and the like, which are set or notified from the indoor unit 10. The outdoor unit 20 receives a command from the indoor unit 10 and stops operating.

The outdoor unit 20 is connected to the indoor unit 10 viapipes 30 and 31, and circulates the refrigerant. Therefore, the compressor 21 for circulating the refrigerant is provided. The refrigerant gas compressed by the compressor 21 exchanges heat with air taken in by the fan 23 in the heat exchanger 22, and becomes a high-pressure liquid refrigerant. Further, the outdoor unit 20 is also capable of performing a heating operation, and therefore, is provided with a four-way valve 25 for reversing the direction of the refrigerant flow. The outdoor expansion valve 24 is provided to change the refrigerant in a high-pressure state to a low-temperature low-pressure refrigerant during heating and to adjust the flow rate of the refrigerant.

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

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

There is a lower limit on the operating frequency of the compressor 21, and when the capacity of the compressor 21 for generating an operation at the lowest operating frequency is larger than the indoor load, the indoor temperature cannot be maintained at the set temperature by the continuous operation. Thus, intermittent operation is performed in which the thermal opening and the thermal closing are repeated, and the indoor temperature is maintained at the set temperature. However, if intermittent operation is performed, efficiency and reliability of the equipment are reduced as compared with continuous operation, and the indoor temperature also fluctuates, so that there is a problem that comfort is impaired.

Accordingly, the outdoor unit 20 includes afrequency sensor 27 as frequency detecting means for detecting the operating frequency of the compressor 21, and thecontrol device 26 is configured to control the opening degree of the indoor expansion valve 16 based on the room temperature detected by the room temperature sensor 13 and the amount of change in the room temperature during a predetermined time, and the operating frequency detected by thefrequency sensor 27.

When the compressor 21 is operated near the lowest operating frequency, thecontrol device 26 reduces the opening degree of the indoor expansion valve 16, reduces the flow rate of the refrigerant flowing into the heat exchanger 11, and reduces the generated air conditioning capacity (cooling capacity). Accordingly, the cooling capacity can be further reduced even when the compressor 21 is operated at the lowest operating frequency, and thus, even in the air conditioning load that conventionally required intermittent operation of the compressor 21, intermittent operation of the compressor 21 can be avoided. Details thereof are described below.

Fig. 2 shows an example of a hardware configuration of thecontrol device 26 used in the air conditioning system. Thecontrol device 26 includes a CPU40, aflash memory 41, a RAM42, a communication I/F43, and a control I/F44. The CPU40 and other components are connected to thebus 45, and exchange information and the like via thebus 45.

Theflash memory 41 stores programs executed by the CPU40, various data, and the like. The RAM42 provides a work area for theCPU 40. The CPU40 realizes the above control by reading out and executing the program stored in theflash memory 41 into theRAM 42.

The communication I/F43 is connected to the indoor unit 10, and receives information such as an indoor temperature, a liquid piping temperature, and a gas piping temperature from the indoor unit 10. In addition, the communication I/F43 also receives information from thefrequency sensor 27. The control I/F44 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 the respective devices.

Thecontrol device 26 reads out and executes a program from theflash memory 41 by the CPU40 to realize the control described above, but the control may be realized by hardware such as a circuit.

Specific control is described in detail below as control during cooling operation. Fig. 3 is a flowchart showing a first example of the opening degree control of the indoor expansion valve 16. The control starts in step 100 at the stage when the cooling operation is started. In step 101, it is determined whether or not the operation frequency F is smaller than the lowest operation frequency F_min Large arbitrary frequency (frequency threshold) F_d . For the lowest operating frequency F_min With a certain margin for determining the frequency threshold F_d So that the intermittent operation is not entered until the opening degree control of the indoor expansion valve 16 is started. Regarding the opening degree control of the indoor expansion valve 16, the determination of step 101 is repeated until it is determined that F is smaller than F_d Until that point.

When it is determined in step 101 that F is smaller than F_d If so, the routine proceeds to step 102, where it is determined whether or not the difference RL between the indoor air conditioning load and the cooling capacity is smaller than the load threshold RL_th 。

The difference RL between the indoor air conditioning load and the generation capacity can be detected using the set temperature, the detection value (room temperature) detected by the room temperature sensor 13, and the amount of change in the room temperature over a predetermined time. The predetermined time is, for example, about several minutes because the amount of change is too small to detect the amount of change in a short time (about several seconds) as it takes for the control of the indoor expansion valve 16, and the intermittent operation may be performed during this time.

Upon determining that RL is RL_th In the above case, the refrigerating capacity is relatively small with respect to the air conditioning load, and the capacity reduction is not required, so that the opening degree control of the indoor expansion valve 16 is not performed. Thus, the process returns to step 101, and control is continued.

On the other hand, when it is determined in step 102 that the RL is larger than the RL_th If the flow rate is small, the flow rate of the refrigerant is reduced in step 103 because the cooling capacity is relatively large with respect to the air conditioning load, and the opening degree of the indoor expansion valve 16 is reduced. When the opening degree of the indoor expansion valve 16 is reduced, the flow rate of the refrigerant is reduced, and the pressure is low, so that the two-phase refrigerant becomes a gas phase with a smaller heat exchange amount, and therefore the area (effective area) of the portion of the heat transfer pipe of the heat exchanger 11 functioning as an evaporator is also reduced. The air in the room is cooled mainly by latent heat generated when the refrigerant evaporates, and therefore the effective area is reduced, and the refrigerating capacity can be reduced. By decreasing the cooling capacity, the refrigerant can be entirely evaporated, and the refrigerant can be discharged from the heat exchanger 11 while giving a degree of superheat.

Thecontrol device 26 controls the rotation speed of the compressor 21 based on the set temperature and the detection value of the room temperature sensor 13, and controls the opening degree of the outdoor expansion valve 24 so as to keep the degree of superheat within a certain range. Therefore, when the indoor load is large, thecontrol device 26 increases the rotation speed of the compressor 21 to increase the circulation amount of the refrigerant, and when the indoor load is small, decreases the rotation speed of the compressor 21 to decrease the circulation amount of the refrigerant.

Even when the indoor load gradually decreases and the operation of the compressor 21 becomes the lowest operation frequency, the opening degree of the indoor expansion valve 16 is reduced to reduce the cooling capacity, and even if the compressor 21 is continuously operated at the lowest operation frequency, the room temperature can be maintained. Therefore, the continuous operation of the compressor 21 can be maintained.

After the opening degree of the indoor expansion valve 16 is reduced in step 103, the routine returns to step 101 to continue the control. When the operation of the air conditioning system is stopped, the control is also ended.

Fig. 4 shows a time history of power consumption after the start of operation in the conventional control and the opening control of the indoor expansion valve 16 shown in fig. 3, wherein a broken line relates to the conventional control and a solid line relates to the present control. The conventional control is to repeat intermittent operation, and the time history is shown by a dotted line. In the conventional control, when the heat is turned off, the power consumption is zero, but a large amount of power is consumed when the heat is turned on. On the other hand, when the opening degree control (this control) of the indoor expansion valve 16 is performed, since only a certain low power is consumed without generating thermal closing/thermal opening, the total power consumption (the time-integrated value of the power consumption) surrounded by the time axis and the solid line becomes smaller than the total power consumption of the conventional control also surrounded by the time axis and the broken line. Therefore, the present control can reduce power consumption as compared with the conventional control.

The control shown in fig. 3 is a control to reduce only the opening degree of the indoor expansion valve 16, but when the room temperature increases due to an increase in the outside air temperature or the like, and the air conditioning load increases, it is sometimes desirable to increase the reduced cooling capacity. When the air conditioning load increases, the circulation amount of the refrigerant is still small, and the effective area of the evaporator is still small, so that the operation becomes inefficient. Therefore, control capable of improving the cooling capacity will be described with reference to fig. 5.

Fig. 5 is a flowchart showing a second example of the opening degree control of the indoor expansion valve 16. From step 200, in the same manner as in the control shown in fig. 3, in step 201, it is determined whether or not the operating frequency F is greater than the frequency threshold F_d Is small. Upon determining that F is less than F_d If so, the routine proceeds to step 202, where it is determined whether or not the difference RL between the indoor air conditioning load and the cooling capacity is smaller than the threshold RL_th . And, when it is determined that the RL ratio is RL_th If it is small, the flow proceeds to step 203, where the opening degree of the indoor expansion valve 16 is reduced in order to reduce the flow rate of the refrigerant. After decreasing the opening degree of the indoor expansion valve 16, the flow returns to step 201, and control is continued.

When it is determined in step 201 that F is F_d In the above case, or in step 202, it is determined that RL is RL_th In the above case, the routine proceeds to step 204 to increase the opening degree of the indoor expansion valve 16. At F is F_d In the above case, it is indicated that the refrigerating capacity needs to be increased, the circulation amount of the refrigerant is increased to increase the refrigerating capacity, the degree of superheat on the outlet side of the heat exchanger 11 is decreased to increase the effective area, and the opening degree of the indoor expansion valve 16 is increased. At RL is RL_th In the above case, the air conditioning load is relatively large compared to the cooling generation capacity, and when the air conditioning load is large, the circulation amount of the refrigerant is still small, and the effective area is smallAlso, since the operation is inefficient in a small period, the opening degree of the indoor expansion valve 16 is increased, and the circulation amount of the refrigerant is increased.

After increasing the opening degree of the indoor expansion valve 16, the routine returns to step 201 to continue the control. In this case, when the operation of the air conditioning system is stopped, the control is ended.

The control shown in fig. 5 is a control to decrease or increase the opening degree of the indoor expansion valve 16, but when the opening degree is changed greatly once, the room temperature fluctuates. In addition, there is a case where the variation in room temperature is small in the case where the opening degree of the indoor expansion valve 16 is maintained without changing depending on the air conditioning load. This is because, when the room temperature fluctuates, the comfort is impaired when the fluctuation is large. Therefore, control capable of adjusting and maintaining the opening degree of the indoor expansion valve 16 will be described with reference to fig. 6.

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

When it is determined in step 302 that the RL is larger than the RL_th If it is small, the routine proceeds to step 303, where it is determined that the amount of change dT in room temperature is a predetermined time_in Whether or not the opening degree is smaller than a preset opening degree starts to decrease the variation dT_dec . The dT is_dec Is the amount of change in room temperature that becomes the reference for starting to reduce the opening of the indoor expansion valve 16. The change dT of the room temperature can be reduced_in The amount of change in the detected value of the room temperature sensor 13 is calculated as a predetermined time.

When dT is determined in step 303_in Less than dT_dec In the case of (2), since the room temperature is rapidly decreased, the cooling capacity is required to be decreased, and the process proceeds to step 304, and the amount of change dT in the room temperature is calculated based on the amount of change dT in the room temperature_in The amount of change in the opening degree of the indoor expansion valve 16 is calculated, and the opening degree of the indoor expansion valve 16 is reduced based on the amount of change. Then, the process returns to step 301, and control is continued.

When dT is determined in step 303_in Is dT_dec In the above case, the routine proceeds to step 305, where it is determined that the room temperature T is_in And a set temperature T_set Whether or not the temperature difference is smaller than a preset opening degreeTemperature difference DeltaT_dec 。ΔT_dec The temperature difference between the room temperature and the set temperature is a reference for starting to reduce the opening of the indoor expansion valve 16. At the time of determining the temperature difference ratio DeltaT_dec When the variation ratio dT is small, the variation ratio dT is set as the room temperature_dec Since the cooling capacity is required to be reduced because the room temperature is low, the flow proceeds to step 304, where the opening degree of the indoor expansion valve 16 is reduced. Then, the process returns to step 301, and control is continued.

On the other hand, when it is determined in step 305 that the temperature difference is Δt_dec In the above case, it can be determined that the room temperature is not lowered, and if the opening degree of the indoor expansion valve 16 is controlled to be reduced, the generation capacity may be excessively reduced, and the room temperature may be raised. Accordingly, the flow proceeds to step 306, where the opening degree of the indoor expansion valve 16 is maintained at the current opening degree. Then, the process returns to step 301, and control is continued.

When it is determined in step 301 that F is F_d In the above case, or in step 302, it is determined that RL is RL_th In the above case, the routine proceeds to step 307, where dT is determined_in Whether or not the opening degree is larger than a preset opening degree starts to increase the variation dT_inc 。dT_inc Is the amount of change in room temperature that becomes the reference for starting to increase the opening of the indoor expansion valve 16. At dT_in Greater than dT_inc In this case, since the room temperature greatly changes due to an increase in the outside air temperature, the opening degree of the indoor expansion valve 16 needs to be increased to increase the flow rate of the refrigerant. Therefore, when dT is determined_in Greater than dT_inc If the flow proceeds to step 308, the amount of change in the opening degree of the indoor expansion valve 16 is calculated based on the amount of change in the detection value of the room temperature sensor 13, and the opening degree of the indoor expansion valve 16 is increased.

When dT is determined in step 307_in Is dT_inc In the following case, the routine proceeds to step 309, where it is determined that the room temperature T is_in And a set temperature T_set Whether or not the temperature difference is larger than a preset opening degree starts to increase the temperature difference deltat_inc 。ΔT_inc The temperature difference between the room temperature and the set temperature is a reference for starting to increase the opening of the indoor expansion valve 16. At a temperature difference greater than DeltaT_inc In the case of (a), it is necessary to enlarge the roomThe opening degree of the expansion valve 16 increases the flow rate of the refrigerant, and thus, the process proceeds to step 308. On the other hand, if the temperature difference is DeltaT_inc In the following case, if the opening degree of the indoor expansion valve 16 is controlled to be increased, the cooling capacity may be improved without increasing the room temperature, and the room temperature may be lowered. Accordingly, the flow proceeds to step 310, where the opening degree of the indoor expansion valve 16 is maintained at the current opening degree. Then, the process returns to step 301, and control is continued.

In this way, by controlling the opening degree of the indoor expansion valve 16 to be adjusted and maintained, the room temperature can be stabilized. In this case, when the operation of the air conditioning system is stopped, the control is ended.

The control shown in fig. 6 is a control to adjust and maintain the opening degree of the indoor expansion valve 16, but by using the detection values of the pipe temperature sensors 14 and 15, it is possible to perform control to set the degree of superheat of the refrigerant at the outlet side of the indoor heat exchanger to a target value. Therefore, control using the detection values of the pipe temperature sensors 14 and 15 will be described with reference to fig. 7.

Fig. 7 is a flowchart showing a fourth example of the opening degree control of the indoor expansion valve 16. In this case, only a portion different from the process shown in fig. 5 will be described. In step 403, dT is determined_in Whether or not the degree of superheat is smaller than the degree of superheat and the change dT is increased_inc . In the example shown in FIG. 6, dT_inc The opening degree start increasing the change amount, but in this example, the superheat degree start increasing the change amount is set. Similarly, dT is used in this example_dec To start reducing variation for superheat, delta T is set_inc To start to increase the temperature difference for the superheat degree, make DeltaT_dec The temperature difference starts to decrease for the degree of superheat.

dT_inc Is the amount of change of room temperature dT which becomes a reference for starting to increase the degree of superheat_des Is the amount of change in room temperature that becomes a reference for starting to reduce the degree of superheat. Delta T_inc Is the temperature difference between the room temperature and the set temperature, deltaT, which becomes the reference for starting to increase the superheat degree_dec The difference between the room temperature and the set temperature is a reference for starting the reduction of the superheat degree.

In step 404, a target superheat degree of the refrigerant on the 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 for a predetermined time. In this case, the flow rate of the refrigerant is reduced, and the effective area is reduced by giving the degree of superheat, so that the refrigerating capacity is reduced, and the degree of superheat increases.

In step 405, the amount of change in the opening degree of the indoor expansion valve 16, such that the degree of superheat of the refrigerant at the outlet side of the indoor heat exchanger becomes the target degree of superheat obtained in step 404, is calculated, and the opening degree of the indoor expansion valve 16 is controlled. Here, the opening degree of the indoor expansion valve 16 is reduced. Then, the process returns to step 401, and control is continued.

When it is determined in step 406 that T_in And T is_set Is less than delta T_inc If it is determined that the number is T, the routine proceeds to step 404_in And T is_set Is delta T_inc In the above case, the process proceeds to step 407. In step 407, the target degree of superheat is calculated in the same manner as in step 404, but the cooling capacity is not lowered, so that the degree of superheat is maintained at the current degree of superheat, and in step 408, the opening degree of the indoor expansion valve 16 is maintained at the current opening degree. Then, the process returns to step 401, and control is continued.

When dT is determined in step 409_in Greater than dT_dec If the routine proceeds to step 410, the target superheat degree is calculated in the same manner as in step 404. In this case, the flow rate of the refrigerant is increased, and the superheat degree is decreased to increase the effective area, thereby improving the refrigerating capacity, and the superheat degree is decreased.

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

When it is determined in step 412 that T_in And T is_set Is delta T_dec In the following case, the routine proceeds to step 410, and when it is determined that T_in And T is_set Is greater than delta T_dec If so, the process proceeds to step 413. In step 413, the target degree of superheat is calculated in the same manner as in step 404, but the cooling capacity is not increased, so that the degree of superheat is maintained at the current degree of superheat, and in step 414, the opening degree of the indoor expansion valve 16 is maintained at the current opening degree. Then, the process returns to step 401, and control is continued. In this case, when the operation of the air conditioning system is stopped, the control is ended.

Although thecontrol device 26 provided in the outdoor unit 20 has been described as executing the opening degree control of the indoor expansion valve 16, the opening degree control of the indoor expansion valve 16 is not limited to thecontrol device 26. For example, the control device provided in the indoor unit 10 may be executed, or the centralized control device provided separately from the indoor unit 10 and the outdoor unit 20 may be executed.

The air conditioning system is not limited to the configuration of one indoor unit 10 and one outdoor unit 20. Accordingly, a system in which a plurality of indoor units 10 are connected to 1 outdoor unit 20 or a system in which a plurality of outdoor units 20 are connected to a plurality of indoor units 10 may be employed. Fig. 8 shows an example of a system in which a plurality of indoor units 10 are connected to 1 outdoor unit 20. In the example shown in fig. 8, 3 indoor units 10a to 10c are connected to the outdoor unit 20.

The indoor units 10a to 10c are provided in the respective chambers, and the room temperature in the respective chambers is adjusted to a set temperature. The indoor units 10a to 10c each have an indoor expansion valve 16a to 16c, and therefore can adjust the cooling capacity for each indoor unit. Therefore, even when the air conditioning load is different for each room, intermittent operation can be avoided, and the room temperature in each room can be stabilized.

By avoiding intermittent operation to realize continuous operation, power consumption can be reduced, and the number of times of starting and stopping can be reduced, so that efficiency of the apparatus can be improved, faults and the like can be reduced, and reliability can be improved. In addition, since the room temperature can be stabilized, the comfort can be maintained.

In the example described above, the operation frequency F of the compressor 21 is detected, and the detected operation frequency F is compared with the frequency threshold F_d Small and air conditioning load to capacity difference RL is less than load threshold RL_th When the opening degree of the indoor expansion valve 16 is small, the opening degree control is performed. Therefore, in the case where there are a plurality of indoor units 10, for example, except for 1 indoor unit 10, the difference RL in air conditioning load and capacity is smaller than the load threshold RL_th Small, however, the 1 indoor unit 10 has a large load, and F exceeds F_d In this case, the opening degree control of the indoor expansion valve 16 is not performed at all. Thus, the room temperature cannot be stabilized, and the comfort cannot be maintained.

Therefore, in the opening degree control shown in fig. 3, 5 to 7, as the opening degree control in which step 101, step 201, step 301, and step 401 are deleted, only by determining whether or not the difference RL is smaller than the load threshold RL_th The opening degree of the indoor expansion valve 16 can be controlled. In fig. 9 to 12, the respective opening degree controls are shown as fifth to eighth examples.

Fig. 9 is a flowchart showing a fifth example of the opening degree control of the indoor expansion valve 16. In this control, the cooling operation is started in step 500. In step 501, it is not determined whether the operating frequency F is less than the frequency threshold F_d Only whether or not the difference RL between the indoor air conditioning load and the cooling generation capacity is smaller than the load threshold RL is determined_th . Step 502 is the same as step 103 of fig. 3, and therefore, a description thereof is omitted here.

Fig. 10 is a flowchart showing a sixth example of the opening degree control of the indoor expansion valve 16. Beginning at step 600, in step 601, it is determined whether the difference RL is less than the load threshold RL, as in the example shown in FIG. 9_th . The processing at step 602 and thereafter is the same as the processing at step 203 and thereafter of fig. 5.

Fig. 11 is a flowchart showing a seventh example of the opening degree control of the indoor expansion valve 16. From step 700, instep 701, it is determined whether or not the difference RL is smaller than the load threshold RL, as in the examples shown in fig. 9 and 10_th . The processing of step 702 and thereafter is the same as the processing of step 303 and thereafter of fig. 6.

Fig. 12 is a flowchart showing an eighth example of the opening degree control of the indoor expansion valve 16. From step 800, in step 801, it is determined whether or not the difference RL is smaller than the load threshold RL as in the examples shown in fig. 9 to 11_th . Step 802 and subsequent processingThe same as in step 403 and subsequent processes of fig. 7.

As in the examples shown in fig. 9 to 12, only by determining whether the difference RL is smaller than the load threshold RL_th The present control can be operated regardless of the current operating frequency. This can avoid the situation where the opening degree control of the indoor expansion valve 16 is not performed at all, and the RL ratio RL can be controlled_th The indoor expansion valve 16 of the small indoor unit 10 is appropriately controlled in opening degree, and can stabilize the room temperature and maintain the comfort.

Although the indoor unit, the air conditioning system, and the control method according to the present invention have been described in detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may be implemented in other embodiments, and may be modified within the scope of the present invention as long as the operations and effects of the present invention are achieved in any of the embodiments, such as addition, modification, and deletion, as will occur to those skilled in the art.

Description of the reference numerals

10. 10a-10c … indoor units 11, 11a-11c … heat exchanger 12, 12a-12c … fans 13, 13a-13c … room temperature sensors 14, 14a-14c, 15a-15c 4639 piping temperature sensors 16, 16a-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/F44 … control I/F45 … bus.

Claims (9)

1. An air conditioning system comprising an indoor unit and an outdoor unit, characterized in that,

the indoor unit includes:

a heat exchanger;

an indoor temperature detection unit that detects an indoor temperature; and

an indoor expansion valve for adjusting a flow rate of a refrigerant flowing in the refrigeration cycle,

the outdoor unit includes:

a heat exchanger;

a compressor;

an outdoor expansion valve for adjusting a flow rate of refrigerant flowing in the refrigeration cycle; and

a frequency sensor which detects an operating frequency of the compressor,

the air conditioning system includes a control unit that controls an opening degree of the indoor expansion valve of the indoor unit based on the indoor temperature detected by the indoor temperature detecting unit, an amount of change in the indoor temperature for a predetermined time, and an operation frequency detected by the frequency sensor,

the control unit determines whether or not the operation frequency is smaller than a frequency threshold, detects a difference between an air conditioning load and an air conditioning capacity from a difference between the indoor temperature detected by the indoor temperature detection unit and a set temperature and an amount of change in the indoor temperature for the predetermined time when the operation frequency is smaller than the frequency threshold, and performs control to reduce the opening degree of the indoor expansion valve of the indoor unit when the detected difference is smaller than a load threshold.

2. An air conditioning system according to claim 1, wherein,

the control means detects a difference between an air conditioning load and an air conditioning capacity from a difference between the indoor temperature and a set temperature detected by the indoor temperature detection means and an amount of change in the indoor temperature for the predetermined time, and when the detected difference is equal to or greater than a load threshold, performs control to increase the opening degree of the indoor expansion valve of the indoor unit.

3. An air conditioning system according to claim 1 or 2, characterized in that,

the control unit calculates a variation in the opening degree of the indoor expansion valve of the indoor unit based on the indoor temperature detected by the indoor temperature detection unit and a variation in the indoor temperature for the predetermined time.

4. An air conditioning system according to claim 3, wherein,

the indoor unit includes 2 pipe temperature detecting means for detecting temperatures of 2 pipes connecting the heat exchanger and the outdoor unit,

the control means calculates a target superheat degree of the refrigerant discharged from the heat exchanger based on the temperature in the room detected by the room temperature detecting means and the amount of change in the temperature in the room for the predetermined time, and calculates a change in the opening degree of the indoor expansion valve of the indoor unit such that the superheat degree obtained from the difference between the 2 temperatures detected by the 2 pipe temperature detecting means becomes the calculated target superheat degree.

5. An air conditioning system comprising an outdoor unit and a plurality of indoor units, characterized in that,

each indoor unit includes:

a heat exchanger;

an indoor temperature detection unit that detects an indoor temperature; and

an indoor expansion valve for adjusting a flow rate of a refrigerant flowing in the refrigeration cycle,

the outdoor unit includes:

a heat exchanger;

a compressor;

an outdoor expansion valve for adjusting a flow rate of refrigerant flowing in the refrigeration cycle; and

a frequency sensor which detects an operating frequency of the compressor,

the air conditioning system includes a control unit that controls the opening degree of each indoor expansion valve of each indoor unit based on the temperature of each indoor unit detected by each indoor temperature detection unit of each indoor unit, the amount of change in the temperature of each indoor unit for a predetermined time, and the operating frequency detected by the frequency sensor,

the control means determines whether or not the operation frequency is smaller than a frequency threshold, detects a difference between an air conditioning load and an air conditioning capacity of the indoor units based on a difference between the indoor temperature detected by the indoor temperature detection means and a set temperature and an amount of change in the indoor temperature for a predetermined time, and controls the opening degree of the indoor expansion valve of the indoor unit to be reduced when the detected difference is smaller than a load threshold.

6. An air conditioning system according to claim 5, wherein,

the control means detects a difference between an air conditioning load and an air conditioning capacity of 1 or more of the indoor units based on a difference between the indoor temperature detected by the indoor temperature detecting means and a set temperature and an amount of change in the indoor temperature for the predetermined time, and when the detected difference is equal to or greater than a load threshold, performs control to increase an opening degree of the indoor expansion valve of the indoor unit.

7. An air conditioning system according to claim 5 or 6, characterized in that,

the control means calculates, for at least 1 of the indoor units, a change amount of the opening degree of the indoor expansion valve of the indoor unit based on the indoor temperature detected by the indoor temperature detection means of the indoor unit and a change amount of the indoor temperature for the predetermined time.

8. An air conditioning system according to claim 7, wherein,

each of the indoor units includes 2 pipe temperature detecting means for detecting temperatures of 2 pipes connecting the heat exchanger and the outdoor unit,

the control means calculates a target superheat degree of the refrigerant discharged from the heat exchanger of the indoor unit for 1 or more indoor units based on the indoor temperature detected by the indoor temperature detecting means of the indoor unit and the amount of change in indoor temperature for the predetermined time, and calculates an amount of change in the opening degree of the indoor expansion valve of the indoor unit such that the degree of superheat obtained from a difference in 2 temperatures detected by the 2 pipe temperature detecting means of the indoor unit becomes the calculated target degree of superheat.

9. A control method performed by a control unit of an air conditioning system, the air conditioning system comprising: indoor unit, outdoor unit, and the control unit,

the indoor unit includes: a heat exchanger, an indoor temperature detecting unit for detecting the temperature in the indoor, and an indoor expansion valve for adjusting the flow rate of the refrigerant flowing in the refrigeration cycle,

the outdoor unit includes: a heat exchanger, a compressor, an outdoor expansion valve for adjusting the flow rate of refrigerant flowing in a refrigeration cycle, and a frequency sensor for detecting the operating frequency of the compressor,

it is characterized in that the method comprises the steps of,

the control method comprises the following steps:

a step of calculating a change amount of the temperature in the room for a predetermined time based on the temperature in the room detected by the room temperature detecting means;

a step of controlling the opening degree of the indoor expansion valve of the indoor unit based on the indoor temperature detected by the indoor temperature detecting means, the calculated amount of change in the indoor temperature, and the operating frequency detected by the frequency sensor; and

determining whether or not the operation frequency is smaller than a frequency threshold, detecting a difference between an air conditioning load and an air conditioning capacity from a difference between the indoor temperature and a set temperature detected by the indoor temperature detecting means and an amount of change in the indoor temperature for the predetermined time when the operation frequency is smaller than the frequency threshold, and performing control to reduce an opening degree of the indoor expansion valve of the indoor unit when the detected difference is smaller than a load threshold.

Images