阅读说明：本技术 空调系统以及控制方法 (Air conditioning system and control method ) 是由 中安悟 浦田和干 饭塚太树 德地干人 于 2021-03-22 设计创作，主要内容包括：本发明提供一种空调系统以及控制方法,其能够抑制间歇运转,维持舒适性。空调系统包含室内机和室外机,室内机包含热交换器、检测室内的温度的室内温度检测单元、以及用于调整在制冷循环内流动的制冷剂的流量的阀,室外机包含热交换器、压缩机、以及用于调整在制冷循环内流动的制冷剂的流量的阀,空调系统还包含控制单元,该控制单元根据由室内温度检测单元检测出的室内的温度和预定时间的该室内的温度的变化量,控制室内机的阀的开度。(The invention provides an air conditioning system and a control method, which can restrain intermittent operation and maintain comfort. The air conditioning system includes an indoor unit and an outdoor unit, wherein the indoor unit includes a heat exchanger, an indoor temperature detection unit that detects a temperature in a room, and a valve that adjusts a flow rate of a refrigerant flowing through a refrigeration cycle, and the outdoor unit includes a heat exchanger, a compressor, and a valve that adjusts a flow rate of a refrigerant flowing through a refrigeration cycle, and the air conditioning system further includes 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 detection unit and a change amount of the temperature in the room for a predetermined time.)

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

the indoor unit includes:

a heat exchanger;

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

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

the outdoor unit includes:

a heat exchanger;

a compressor; and

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

the air conditioning system includes a control unit that controls an opening degree of the valve of the indoor unit based on the indoor temperature detected by the indoor temperature detection unit and a change amount of the indoor temperature for a predetermined time.

2. The air conditioning system of claim 1,

the control unit detects a difference between an air conditioning load and an air conditioning capacity based on a difference between the indoor temperature detected by the indoor temperature detection unit and a set temperature and a change amount of the indoor temperature for the predetermined time, and performs control to reduce the opening degree of the valve of the indoor unit when the detected difference is smaller than a load threshold value.

3. The air conditioning system of claim 1,

the control means detects a difference between an air conditioning load and an air conditioning capacity based on a difference between the indoor temperature detected by the indoor temperature detection means and a set temperature and a change amount of the indoor temperature for the predetermined time, and 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.

4. An air conditioning system according to any one of claims 1 to 3,

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

5. The air conditioning system of claim 4,

the indoor unit includes 2 pipe temperature detection units, the 2 pipe temperature detection units detect the temperature 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 amount of change in the indoor temperature detected by the indoor temperature detection means and the indoor temperature for the predetermined time, and calculates an amount of change in the opening degree of the valve of the indoor unit such that the degree of superheat obtained from the difference between the 2 temperatures detected by the 2 pipe temperature detection means becomes the calculated target superheat degree.

6. An air conditioning system comprising an outdoor unit and a plurality of indoor units,

each of the indoor units includes:

a heat exchanger;

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

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

the outdoor unit includes:

a heat exchanger;

a compressor; and

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

The air conditioning system includes a control unit that controls the opening degree of each valve of each indoor unit based on the indoor temperature detected by each indoor temperature detection unit of each indoor unit and the variation amount of the indoor temperature for a predetermined time.

7. The air conditioning system of claim 6,

the control means 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 means and a set temperature and a change amount of the indoor temperature for the predetermined time for 1 or more indoor units, and performs control to reduce the opening degree of the valve of the indoor unit when the detected difference is smaller than a load threshold value.

8. The air conditioning system of claim 6,

the control means 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 means and a set temperature and a change amount of the indoor temperature for the predetermined time for 1 or more indoor units, and 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.

9. An air conditioning system according to any one of claims 6 to 8,

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

10. The air conditioning system of claim 9,

each of the indoor units includes 2 pipe temperature detection units, the 2 pipe temperature detection units detect respective temperatures of 2 pipes connecting the heat exchanger and the outdoor unit,

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

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

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

the outdoor unit includes: a heat exchanger, a compressor, and a valve for adjusting a flow rate of refrigerant flowing in the refrigeration cycle,

it is characterized in that the preparation method is characterized in that,

the control method comprises the following steps:

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 detection means; and

and controlling the opening degree of the valve of the indoor unit based on the indoor temperature detected by the indoor temperature detection means and the calculated amount of change in the indoor temperature.

Technical Field

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

Background

In a conventional air conditioning system, a method of controlling a compressor frequency of an outdoor unit according to a load of an indoor unit to adjust a room temperature is widely used. The compressor of the outdoor unit has an operable frequency range, and when the load of the indoor unit is small and the room temperature cannot be maintained even if the compressor is operated at the lowest operating frequency, the compressor is repeatedly stopped (thermally turned off) and the compressor is operated (thermally turned on), that is, so-called intermittent operation is performed, whereby the room temperature is stabilized.

However, the intermittent operation has a problem that the room temperature fluctuates and the efficiency of the equipment is lowered compared with the continuous operation without impairing the comfort.

Therefore, to avoid intermittent operation, the following techniques are known: the frequency is temporarily lowered to a range of a minimum operating frequency lower than the starting operating frequency or a lower limit operating frequency higher than the compressor use limit (see, for example, patent documents 1 and 2). In addition, a technique of reducing the opening degree of an expansion valve of an outdoor unit to reduce the amount of refrigerant circulating is also known (for example, see patent document 3)

However, the techniques described in patent documents 1 and 2 have a problem that the intermittent operation cannot be avoided when the compressor frequency required to maintain the room temperature at the set temperature is lower than the lower limit operation frequency for use of the compressor.

In the technique described in patent document 3, since the opening degree of the expansion valve of the outdoor unit is forcibly reduced to reduce the refrigerant circulation amount, thereby reducing the capacity, 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 is a problem that the room temperature cannot be maintained in a 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 laid-open publication No. 2015-102252

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

Disclosure of Invention

In view of the above problem, 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 through the refrigeration cycle, wherein the outdoor unit includes a heat exchanger, a compressor, and a valve for adjusting a flow rate of the refrigerant flowing through the refrigeration cycle, and the air conditioning system includes a control unit for controlling an opening degree of the valve of the indoor unit based on the temperature of the room detected by the indoor temperature detection unit and a change amount of the temperature of 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 provided in the air conditioning system.

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

Fig. 4 shows the 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 the 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 illustrating 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 indoors in a house, a building, or the like, and an outdoor unit 20 installed outdoors. The air conditioning system can include an operation device (remote controller) that communicates with the indoor unit 10 by wireless and operates the indoor unit, in a room where the indoor unit 10 is installed.

The indoor unit 10 and the outdoor unit 20 are connected by 2 pipes 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 by a communication cable or the like for mutual communication. The indoor unit 10 and the outdoor unit 20 are not limited to wired connection by a communication cable or the like, and may be wirelessly connected by WiFi (registered trademark) or the like.

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

The indoor unit 10 sucks in indoor air 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 indoor air so that the indoor air has a set temperature.

Therefore, the indoor unit 10 includes: a heat exchanger 11 that exchanges heat between indoor air and refrigerant; and a blower (fan) 12 that takes 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 detection unit that detects an indoor temperature in order to notify the outdoor unit 20 of an indoor temperature. The room temperature sensor 13 may be used as the indoor temperature detection unit. The indoor unit 10 further includes pipe temperature detection means for detecting the outer wall surface temperature of the 2 pipes 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 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 as a two-phase flow (liquid refrigerant) in which liquid and gas are mixed. The refrigerant exchanges heat with air taken in by the fan 12 in the heat exchanger 11, whereby a liquid component is evaporated, discharged from the heat exchanger 11 as a gas refrigerant, and sent to the outdoor unit 20. The liquid component is evaporated at a certain 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 a temperature higher than the saturation temperature. Δ t when discharged at a temperature higher than the saturation temperature by Δ t represents a temperature increase with respect to the saturation temperature, and is referred to as a degree of superheat.

The outdoor unit 20 is started upon receiving a command from the indoor unit 10, and starts operating in an operation mode set or notified from the indoor unit 10. The operation mode is a cooling mode, a heating mode, an air blowing mode, or the like. The outdoor unit 20 controls the temperature, pressure, flow rate, and the like of the refrigerant based on the set temperature, the indoor temperature, the pipe temperature, and the like set or notified from the indoor unit 10. The outdoor unit 20 stops operating in response to a command from the indoor unit 10.

The outdoor unit 20 is connected to the indoor units 10 via pipes 30 and 31, and circulates a refrigerant. Therefore, a compressor 21 for circulating the refrigerant is provided. The refrigerant gas compressed by the compressor 21 is subjected to heat exchange with air taken in by the fan 23 in the heat exchanger 22, and becomes a high-pressure liquid refrigerant. The outdoor unit 20 is also capable of performing a heating operation, and therefore includes a four-way valve 25 for reversing the direction of refrigerant flow. The outdoor expansion valve 24 is provided to change the refrigerant that has been brought into a high-pressure state during heating into a low-temperature low-pressure refrigerant 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 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 pipe temperature, and the operation mode. 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 when the compressor 21 is operated at the lowest operating frequency and the generating capacity is larger than the indoor load, the indoor temperature cannot be maintained at the set temperature by the continuous operation. Therefore, the intermittent operation of repeating the hot-on and the hot-off is performed to maintain the indoor temperature at the set temperature. However, when the intermittent operation is performed, the efficiency and reliability of the equipment are lowered and the indoor temperature also fluctuates as compared with the continuous operation, which causes a problem that the comfort is impaired.

Therefore, the outdoor unit 20 includes a frequency sensor 27 as frequency detection means for detecting the operating frequency of the compressor 21, and the control 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, the amount of change in the room temperature within a predetermined time, and the operating frequency detected by the frequency sensor 27.

When the compressor 21 is operated at a frequency near the lowest operating frequency, the controller 26 decreases the opening degree of the indoor expansion valve 16, decreases the flow rate of the refrigerant flowing into the heat exchanger 11, and decreases the resulting air conditioning capacity (cooling capacity). Accordingly, even if the compressor 21 operates at the lowest operation frequency, the cooling capacity can be further reduced, and therefore, even in an air conditioning load that conventionally requires intermittent operation of the compressor 21, the intermittent operation of the compressor 21 can be avoided. The details thereof will be described below.

Fig. 2 shows an example of the hardware configuration of control device 26 used in the air conditioning system. The control device 26 includes a CPU40, a flash memory 41, a RAM42, a communication I/F43, and a control I/F44. Components such as the CPU40 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 CPU40, various data, and the like. The RAM42 provides the CPU40 with a work area. The CPU40 realizes the above control by reading out and executing the program stored in the flash memory 41 into the RAM 42.

The communication I/F43 is connected to the indoor unit 10, and receives information such as the indoor temperature, the liquid pipe temperature, and the gas pipe temperature from the indoor unit 10. In addition, the communication I/F43 also receives information from the frequency 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.

Here, the control device 26 realizes the above control by the CPU40 reading out and executing a program from the flash memory 41, but the control may be realized by hardware such as a circuit.

Hereinafter, specific control will be described in detail as control during the cooling operation. Fig. 3 is a flowchart illustrating a first example of the opening degree control of the indoor expansion valve 16. The control starts from step 100 when the cooling operation is started. In step 101, it is determined whether or not the operating frequency F is less than the lowest operating frequency F_minLarge arbitrary frequency (frequency threshold) F_d. For the lowest operating frequency F_minWith a certain margin for determining the frequency threshold F_dSo that the intermittent operation is not started until the opening degree control of the indoor expansion valve 16 is started. The determination in step 101 is repeated until the determination is made with respect to the opening degree control of the indoor expansion valve 16Is defined as F is less than F_dUntil now.

When it is determined in step 101 that F is smaller than F_dIn the case of (3), the process proceeds to step 102, where it is determined whether or not the difference RL between the indoor air conditioning load and the cooling generation 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 within a predetermined time. The predetermined time can be set to, for example, about several minutes because the amount of change is too small in a short time such as the time (about several seconds) taken to control the indoor expansion valve 16, and the amount of change cannot be detected, and there is a possibility that the intermittent operation will be performed during this time in a long time.

After determining RL as RL_thIn the above case, since the cooling capacity is relatively small with respect to the air conditioning load and the capacity does not need to be reduced, the opening degree of the indoor expansion valve 16 is not controlled. Therefore, the control is continued by returning to step 101.

On the other hand, when it is determined that RL ratio RL is in step 102_thIf the refrigerant flow rate is small, the cooling capacity is relatively large with respect to the air conditioning load, and therefore the process proceeds to step 103, where the opening degree of the indoor expansion valve 16 is decreased in order to decrease the refrigerant flow rate. When the opening degree of the indoor expansion valve 16 is decreased, the flow rate of the refrigerant is decreased, and the two-phase refrigerant is brought into a gas phase by a smaller heat exchange amount due to a lower pressure, so that the area (effective area) of the portion of the heat transfer pipe functioning as the evaporator of the heat exchanger 11 is also decreased. Since the indoor air is cooled mainly by latent heat at the time of evaporation of the refrigerant, the effective area is reduced, and the cooling capacity can be reduced. The refrigerant can be totally evaporated by the decrease in the cooling capacity, and can be discharged from the heat exchanger 11 by imparting a superheat degree.

The control 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 that the degree of superheat is maintained within a certain range. Therefore, when the indoor load is large, the control 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 is gradually reduced and the operation of the compressor 21 reaches the lowest operation frequency, the cooling capacity is reduced by reducing the opening degree of the indoor expansion valve 16, and the room temperature can be maintained even if the compressor 21 continues to operate at the lowest operation frequency. Therefore, the continuous operation of the compressor 21 can be maintained.

After the opening degree of the indoor expansion valve 16 is decreased in step 103, the process 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 the time history of power consumption after the start of operation in the conventional control and the opening degree control of the indoor expansion valve 16 shown in fig. 3, in which the broken line relates to the conventional control and the solid line relates to the present control. The conventional control is a control in which the intermittent operation is repeated, and the time history is shown by a broken line. In the conventional control, the power consumption is zero when the hot-off is performed, but a large amount of power is consumed when the hot-on is performed. On the other hand, when the opening degree of the indoor expansion valve 16 is controlled (this control), the thermal shutdown/thermal startup does not occur, and only a certain low power is consumed, so the total power consumption (the value of the time integral of the power consumption) surrounded by the time axis and the solid line becomes smaller than the total power consumption of the conventional control similarly surrounded by the time axis and the broken line. Therefore, the present control can reduce power consumption compared to the conventional control.

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

Fig. 5 is a flowchart illustrating a second example of the opening degree control of the indoor expansion valve 16. From step 200, similarly to the control shown in fig. 3, in step 201, the operation is determinedWhether the rotation frequency F is greater than the frequency threshold value F_dIs small. When it is judged that F is smaller than F_dIn the case of (3), the process proceeds to step 202, where it is determined whether or not the difference RL between the indoor air conditioning load and the cooling generation capacity is smaller than a threshold value RL_th. And, when determined as RL ratio RL_thIf the flow rate is small, the process proceeds to step 203, where the opening degree of the indoor expansion valve 16 is decreased to decrease the flow rate of the refrigerant. After the opening degree of the indoor expansion valve 16 is decreased, the process returns to step 201 to continue the control.

When it is determined in step 201 that F is F_dIn the above case, or in step 202, it is determined that RL is RL _thIn the above case, the process proceeds to step 204, where the opening degree of the indoor expansion valve 16 is increased. In the case that F is F_dIn the above case, it is indicated that the cooling capacity needs to be improved, and in order to improve the cooling capacity, the circulation amount of the refrigerant is increased, the degree of superheat on the outlet side of the heat exchanger 11 is decreased to increase the effective area, and therefore, the opening degree of the indoor expansion valve 16 is increased. At RL is RL_thIn the above case, the air conditioning load is relatively larger than the cooling generation capacity, and when the air conditioning load is larger, the circulation amount of the refrigerant is still small and the effective area is still small, resulting in an inefficient operation, and therefore 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 process returns to step 201 to continue the control. 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 for decreasing or increasing the opening degree of the indoor expansion valve 16, but when the opening degree is once changed greatly, the room temperature fluctuates. In addition, depending on the air conditioning load, the variation in the room temperature may be small when the opening degree of the indoor expansion valve 16 is maintained without being changed. This is because the variation in the room temperature is large, and the comfort is impaired. Therefore, control for 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 determined as RL ratio RL in step 302_thIf the temperature is small, the process proceeds to step 303, where the change dT in the room temperature for a predetermined time is determined_inWhether or not the opening degree is smaller than a preset opening degree and the change amount dT starts to decrease_dec. The dT_decIs the amount of change in the room temperature that becomes the reference for starting the reduction in the opening degree of the indoor expansion valve 16. Can change the room temperature by dT_inThe amount of change in the detection value of the room temperature sensor 13 calculated as the predetermined time.

When it is determined as dT in step 303_inLess than dT_decIn the case of (2), since the room temperature is rapidly decreased and the cooling capacity needs to be decreased, the process proceeds to step 304, where dT is changed by the amount of change in room temperature_inThe 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 decreased based on the amount of change. Then, the process returns to step 301 to continue the control.

When it is determined as dT in step 303_inIs dT_decIn the above case, the process proceeds to step 305, where the room temperature T is determined_inAnd a set temperature T_setWhether or not the temperature difference is smaller than a preset opening degree and the temperature difference Δ T starts to decrease_dec。ΔT_decIs the temperature difference between the room temperature and the set temperature, which is the reference for starting the reduction of the opening degree of the indoor expansion valve 16. When it is judged that the temperature difference ratio Delta T is present _decWhen the amount of change is small, dT is the ratio of change in room temperature_decHowever, since the room temperature is low and the cooling capacity needs to be reduced, the process proceeds to step 304, where the opening degree of the indoor expansion valve 16 is decreased. Then, the process returns to step 301 to continue the control.

On the other hand, when it is determined in step 305 that the temperature difference is Δ T_decIn the above case, it can be determined that the room temperature is not decreasing, and if the opening degree of the indoor expansion valve 16 is controlled to be decreased, the generation capacity may be excessively decreased to increase the room temperature. Therefore, the process 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 to continue the control.

When it is determined in step 301 that F is F_dIn the above case, or in step 302, RL is determined to be RL_thIn the above case, the process proceeds to step307, decision dT_inWhether the opening degree is larger than the preset opening degree and the increase change amount dT is started_inc。dT_incIs the amount of change in the room temperature that becomes the reference for starting to increase the opening degree of the indoor expansion valve 16. At dT_inGreater than dT_incIn the case of (3), since the room temperature greatly changes due to an increase in the outside air temperature, it is necessary to increase the opening degree of the indoor expansion valve 16 to increase the flow rate of the refrigerant. Therefore, it is judged to be dT_inGreater than dT_incIn the case of (3), the process proceeds to step 308, where 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 it is judged as dT in step 307_inIs dT_incIn the following case, the process proceeds to step 309, where room temperature T is determined_inAnd a set temperature T_setWhether or not the temperature difference is larger than a preset opening degree and the temperature difference Δ T starts to increase_inc。ΔT_incIs the temperature difference between the room temperature and the set temperature, which is the reference for starting to increase the opening degree of the indoor expansion valve 16. At a temperature difference greater than Δ T_incIn the case of (3), the opening degree of the indoor expansion valve 16 needs to be increased to increase the flow rate of the refrigerant, and the process proceeds to step 308. On the other hand, if the temperature difference is Δ T_incIn 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 decreased. Accordingly, the process 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 to continue the control.

By controlling the opening degree of the indoor expansion valve 16 to be adjusted and maintained in this manner, the room temperature can be further stabilized. 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 opening degree of the indoor expansion valve 16, but control for setting the degree of superheat of the refrigerant on the outlet side of the indoor heat exchanger to a target value can be performed by using the detection values of the pipe temperature sensors 14 and 15. 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 illustrating a fourth example of the opening degree control of the indoor expansion valve 16. In this case, only a part different from the processing shown in fig. 5 will be described. In step 403, dT is determined_inWhether or not it is less than the degree of superheat and starts to increase by the change amount dT_inc. In the example shown in FIG. 6, dT_incThe opening degree starts increasing by the change amount, but in this example, the degree of superheat starts increasing by the change amount. Similarly, dT is used in this example_decTo start decreasing the amount of change in superheat, Δ T is set_incTo increase the temperature difference for the beginning of superheat, Δ T is set_decThe temperature difference starts to decrease for the degree of superheat.

dT_incIs the amount of change in the room temperature, dT, which is the standard for starting to increase the degree of superheat_desIs the amount of change in the room temperature that becomes the reference for starting the reduction in the degree of superheat. Delta T_incIs the temperature difference between the room temperature and the set temperature, delta T, which is the reference for starting to increase the degree of superheat_decThe temperature difference between the room temperature and the set temperature is a reference for starting the reduction of the degree of superheat.

In step 404, a target superheat on the outlet side of the refrigerant in the heat exchanger 11 is calculated based on the detection value of the room temperature sensor 13 and the amount of change in the detection value of the room temperature sensor 13 for a predetermined time. In this case, the flow rate of the refrigerant is reduced, and the superheat degree is given to reduce the effective area, thereby reducing the cooling capacity, and therefore the superheat degree is increased.

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 on the outlet side of the indoor heat exchanger becomes the target degree of superheat determined 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 decreased. Then, the control returns to step 401 to continue the control.

When it is determined as T in step 406_inAnd T_setIs less than delta T_incIn the case of (1), the flow proceeds to step 404 where it is determined as T_inAnd T_setHas a temperature difference of Δ T_incIn the above case, the process proceeds to step 407. In step 407, the target superheat degree is calculated in the same manner as in step 404, but since the cooling capacity is not reduced, the superheat degree is adjustedThe current degree of superheat is maintained, and in step 408, the opening degree of the indoor expansion valve 16 is maintained at the current opening degree. Then, the control returns to step 401 to continue the control.

When it is determined as dT in step 409_inGreater than dT_decIn the case of (3), the process proceeds to step 410, and 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, the degree of superheat is decreased, and the effective area is increased to improve the cooling capacity, so the degree of superheat is decreased.

In step 411, the amount of change in the opening degree of the indoor expansion valve 16 such that the degree of superheat of the refrigerant on the outlet side of the indoor heat exchanger becomes the target degree of superheat determined 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 control returns to step 401 to continue the control.

When it is determined as T in step 412_inAnd T_setHas a temperature difference of Δ T_decWhen the process proceeds to step 410, it is determined as T_inAnd T_setIs greater than delta T_decIn the case of (3), 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 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 control returns to step 401 to continue the control. In this case, when the operation of the air conditioning system is stopped, the control is terminated.

Although the opening degree control of the indoor expansion valve 16 is performed by the control device 26 provided in the outdoor unit 20, the opening degree control of the indoor expansion valve 16 is not limited to the control device 26. For example, the present invention may be implemented by a control device provided in the indoor unit 10, or may be implemented by a centralized control device provided separately from the indoor unit 10 and the outdoor unit 20.

The air conditioning system is not limited to being constructed by one indoor unit 10 and one outdoor unit 20. Therefore, 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 used. 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.

Each of the indoor units 10a to 10c is installed in each room, and the room temperature in each room is adjusted to a set temperature. Since each of the indoor units 10a to 10c includes the indoor expansion valves 16a to 16c, the cooling capacity can be adjusted for each room. Therefore, even when the air conditioning load differs for each room, the room temperature can be stabilized while avoiding intermittent operation.

By avoiding intermittent operation to realize continuous operation, power consumption can be reduced, the number of times of starting and stopping can be reduced, and therefore, the efficiency of the plant can be improved, and the reliability can be improved because failures and the like are reduced. In addition, since the room temperature can be stabilized, comfort can be maintained.

In the example described above, the operating frequency F of the compressor 21 is detected, and the detected operating frequency F is greater than the frequency threshold value F_dSmall air conditioner load and capacity difference RL to load threshold RL_thWhen the opening degree is small, the opening degree of the indoor expansion valve 16 is controlled. Therefore, when there are a plurality of indoor units 10, for example, in addition to 1 indoor unit 10, the difference RL between the air conditioning load and the capacity is greater than the load threshold RL_thSmall, however, the load of the 1 indoor unit 10 is large, and F exceeds F_dIn the case of (3), the opening degree of the indoor expansion valve 16 is not controlled at all. This makes it impossible to stabilize the room temperature and maintain comfort.

Therefore, in the opening degree control shown in fig. 3 and 5 to 7, as the opening degree control in which step 101, step 201, step 301, and step 401 are deleted, it is determined only by whether or not the difference RL is smaller than the load threshold value RL_thThe opening degree of the indoor expansion valve 16 can be controlled. In fig. 9 to 12, the opening degree control is 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 at step 500. In step 501, it is not determined whether or not the operating frequency F is less than the frequencyThreshold value F_dOnly 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 judged_th. Step 502 is the same as step 103 of fig. 3, and therefore, the description thereof is omitted here.

Fig. 10 is a flowchart illustrating a sixth example of the opening degree control of the indoor expansion valve 16. From step 600, in step 601, it is determined whether or not the difference RL is smaller than the load threshold RL as in the example shown in fig. 9_th. The processing of step 602 and subsequent steps is the same as the processing of step 203 and subsequent steps in 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, in step 701, it is determined whether or not the difference RL is smaller than the load threshold RL as in the example shown in fig. 9 and 10 _th. The processing of step 702 and subsequent steps is the same as the processing of step 303 and subsequent steps in 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. The processing of step 802 and subsequent steps is the same as the processing of step 403 and subsequent steps in fig. 7.

As in the examples shown in fig. 9 to 12, it is determined only whether or not the difference RL is smaller than the load threshold RL_thThis control can be operated regardless of the current operating frequency. This can avoid the situation where the opening degree of the indoor expansion valve 16 is not controlled uniformly, and RL ratio RL can be set to RL_thThe opening degree of the indoor expansion valve 16 of the small indoor unit 10 is appropriately controlled, so that the room temperature can be stabilized and the comfort can be maintained.

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, but the present invention is not limited to the above embodiments, and may be implemented in other embodiments, or may be modified within the scope of the present invention as long as the functions and effects of the present invention are achieved in any of the embodiments, such as addition, modification, and deletion.

Description of reference numerals

10. 10a-10c … indoor machine 11, 11a-11c … heat exchanger 12, 12a-12c … fan 13, 13a-13c … room temperature sensor 14, 14a-14c, 15a-15c … piping temperature sensor 16, 16a-16c … indoor expansion valve 20 … outdoor machine 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.