JP7437754B2 - air conditioner - Google Patents

Description

The present invention relates to an air conditioner.

BACKGROUND ART Conventionally, an air conditioner including a receiver tank that temporarily stores liquid refrigerant is known (for example, see Patent Document 1). In Patent Document 1, a flow rate control valve is disposed downstream of an outdoor unit that functions as a condenser, a receiver tank is disposed at a location where the refrigerant whose flow rate is regulated by the flow rate control valve can flow in, and the refrigerant flowing out from the receiver tank is disposed. An expansion valve is disposed at a location where water can flow in, and an indoor unit functioning as an evaporator is disposed downstream of the expansion valve. Patent Document 1 discloses that during cooling operation, an expansion valve is opened and closed based on the temperature of the refrigerant flowing out from the indoor unit, and a flow rate adjustment valve is controlled based on the refrigerant flow rate based on the number of operating compressors and the rotation speed. It is described that it can be adjusted and controlled. Patent Document 1 attempts to improve the condensing efficiency of the refrigerant by maintaining an optimal condensing pressure even when the air conditioning load changes.

Japanese Patent Application Publication No. 2016-173200

However, the temperature at the outlet of the evaporator, the number of operating compressors, etc. are indirect information indicating the state of the condenser, and are not direct information. For this reason, even if you control the opening and closing of the expansion valve etc. based on the temperature at the outlet of the evaporator, etc., the amount of refrigerant in the condenser and the amount of refrigerant in the receiver tank will only be adjusted as a result. The state of the condenser may not be appropriately reflected in the amount of refrigerant in the condenser.
The present invention has been made in view of the above-mentioned circumstances, and provides an air conditioner that can operate a condenser while improving the coefficient of performance based on the state of the condenser even when the operating load is different. The purpose is to

In order to solve the above problems, the present invention provides an air conditioner including a refrigerant circuit in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected via piping, and the present invention provides an expansion valve arranged to adjust the amount of refrigerant flowing out from the condenser; a receiver tank arranged between the expansion valve and the pressure reducing device and capable of storing the refrigerant flowing out from the condenser; a control unit that controls opening and closing to adjust the amount of refrigerant in the condenser; The invention is characterized in that the expansion valve is controlled to open and close so as to approach a set predetermined value.
According to this, it is possible to control the opening and closing of the expansion valve based on the state of the condenser, that is, the temperature of the refrigerant flowing out from the condenser and the temperature of the outside air of the condenser. Further, when adjusting the amount of refrigerant in the condenser, surplus refrigerant can be stored in the receiver tank.

According to the present invention, even when operating loads differ, the condenser can be made to function while maintaining a good coefficient of performance based on the state of the condenser.

A diagram showing the configuration of an air conditioner according to the first embodiment Diagram showing the relationship between the amount of refrigerant sealed in the refrigerant circuit, coefficient of performance, and year-round energy consumption efficiency Block diagram of the control unit of the air conditioner according to the first embodiment Schematic diagram showing the state of refrigerant in the condenser of the first embodiment A diagram showing the relationship between the coefficient of performance, condensation pressure, and refrigerant temperature at the outlet of the condenser for the amount of refrigerant held in the condenser of the first embodiment Flowchart showing the operation of the control unit of the first embodiment

A first aspect of the invention is an air conditioner including a refrigerant circuit in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected via piping, the air conditioner being arranged at an outlet of the condenser and inside the condenser. an expansion valve that adjusts the amount of refrigerant that flows out of the condenser; a receiver tank that is arranged between the expansion valve and the pressure reducing device and is capable of storing the refrigerant that flowed out of the condenser; and a receiver tank that controls opening and closing of the expansion valve to condense the refrigerant. a control unit that adjusts the amount of refrigerant in the container; The expansion valve is controlled to open and close so as to approach the expansion valve.
According to this, the amount of refrigerant in the condenser can be adjusted by controlling the opening and closing of the expansion valve based on the conditions of the condenser, such as the temperature of the refrigerant flowing out of the condenser and the temperature of the outside air of the condenser. In addition, if the coefficient of performance is good, the excess refrigerant can be stored in the receiver tank. Therefore, even when the operating loads are different, the condenser can be operated while maintaining a good coefficient of performance based on the state of the condenser.

In a second invention, the control unit controls the expansion valve to close when the temperature difference is larger than the predetermined value, and controls the expansion valve to open when the temperature difference is smaller than the predetermined value. .
According to this, when the temperature difference is larger than a predetermined value, it is easy to assume that the degree of supercooling of the condenser is small, so it is easy to increase the amount of refrigerant in the condenser by controlling the expansion valve to close. At the same time, if the temperature difference is smaller than a predetermined value, it is likely that the degree of supercooling of the condenser is large, so the amount of refrigerant in the condenser can be easily reduced by controlling the expansion valve to open. This makes it easy to adjust the degree of supercooling so that the coefficient of performance is the highest.

In a third aspect of the present invention, the control unit controls the expansion when the degree of supercooling of the refrigerant flowing out from the condenser is larger than a target degree of supercooling when the temperature difference is larger than the predetermined value. The valve is controlled to open instead of closed.
According to this, if the temperature difference is larger than a predetermined value, it is assumed that the coefficient of performance will improve if the expansion valve is controlled to close, but depending on the load on the condenser, the opening and closing of the expansion valve and the degree of supercooling will be Since there is no correlation, the amount of refrigerant in the condenser can be adjusted more accurately by controlling based on the target degree of supercooling so that the coefficient of performance becomes the highest.

A fourth aspect of the invention is that, when the temperature difference is smaller than the predetermined value, the degree of supercooling of the refrigerant flowing out from the condenser is larger than the previous degree of supercooling, and the degree of supercooling is When the degree of supercooling is smaller than the target degree of supercooling, the expansion valve is controlled to be closed instead of being controlled to open.
According to this, it is assumed that if the temperature difference is smaller than a predetermined value, the coefficient of performance will improve if the expansion valve is controlled to open, but depending on the load on the condenser, the opening/closing of the expansion valve and the degree of supercooling may be affected. Since there is no correlation, the amount of refrigerant in the condenser can be adjusted more accurately by controlling based on the target degree of supercooling so that the coefficient of performance becomes the highest.

In a fifth aspect of the invention, when the temperature difference is smaller than the predetermined value, the degree of supercooling of the refrigerant flowing out from the condenser is smaller than the previous degree of supercooling, and the degree of supercooling is When the degree of supercooling is smaller than the target degree of supercooling, the expansion valve is not controlled to open or close instead of being controlled to open.
According to this, if the temperature difference is smaller than a predetermined value and the degree of supercooling of the refrigerant flowing out from the condenser is smaller than the previous degree of supercooling, it is assumed that the opening degree of the expansion valve is already small. Therefore, even when the degree of supercooling is smaller than the target degree of supercooling, by not controlling the expansion valve to close, it is possible to suppress the expansion valve from being closed too much.

A sixth aspect of the present invention includes a high-pressure sensor arranged on the outlet side of the compressor to detect the pressure of the refrigerant flowing out from the compressor, and a high-pressure sensor arranged on the outlet side of the condenser to detect the temperature of the refrigerant flowing out from the condenser. a refrigerant temperature sensor for detecting, the control unit determines the saturation temperature of the refrigerant in the condenser based on the detection result of the high pressure sensor, and the control unit determines the saturation temperature of the refrigerant of the condenser based on the detection result of the refrigerant temperature sensor. Based on this, the degree of subcooling of the refrigerant flowing out from the condenser is calculated.
According to this, the degree of supercooling can be calculated based on the detection results of the high pressure sensor and the refrigerant temperature sensor.

A seventh aspect of the invention includes an outside air temperature sensor that detects the temperature of outside air in the condenser, and a refrigerant temperature sensor that is disposed at a refrigerant outlet of the condenser and detects the temperature of the refrigerant flowing out from the condenser. , the control unit calculates a temperature difference between the temperature of the refrigerant flowing out from the condenser and the outside temperature of the condenser, based on the detection results of the outside air temperature sensor and the refrigerant temperature sensor.
According to this, the temperature difference can be calculated based on the detection results of the outside air temperature sensor and the refrigerant temperature sensor.

An eighth invention is configured to be operable in a first load mode and a second load mode different from the first load mode, and the receiver tank is configured to operate in the first load mode with respect to the refrigerant accommodated in the refrigerant circuit. The capacity is configured to accommodate an amount that is greater than the difference between the amount of refrigerant that gives the highest coefficient of performance in the load mode and the amount of refrigerant that gives the highest coefficient of performance in the second load mode.
According to this, the air conditioner can be operated with the amount of refrigerant that provides the highest coefficient of performance in both the first load mode and the second load mode in which the operating loads of the air conditioner are different.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
[1. First embodiment]
FIG. 1 is a diagram showing the configuration of an air conditioner 1 according to the first embodiment.
The air conditioner 1 includes a compressor 2, a condenser 3, a pressure reducing device 4, and an evaporator 5. The air conditioner 1 also includes an expansion valve 11 , a receiver tank 12 , a subcooling heat exchanger 13 , and a liquid valve 14 .

The compressor 2, the condenser 3, the expansion valve 11, the receiver tank 12, the subcooling heat exchanger 13, the pressure reducing device 4, and the evaporator 5 are connected by a refrigerant pipe 15. Further, the subcooling heat exchanger 13 and the liquid valve 14 are connected through a branch pipe 16.
Compressor 2, condenser 3, expansion valve 11, receiver tank 12, subcooling heat exchanger 13, pressure reducing device 4, evaporator 5, liquid valve 14, refrigerant pipe 15, branch pipe 16 constitutes a refrigerant circuit 17 in this embodiment. In the refrigerant circuit 17, refrigerant circulates in the direction of arrow Y1.

The compressor 2 sucks refrigerant from the inlet side, compresses it, and discharges it from the outlet side.
The condenser 3 condenses the gas refrigerant by exchanging heat between the gas refrigerant in the condenser 3 and the outside air of the condenser 3.
The pressure reducing device 4 reduces the pressure of the high-pressure refrigerant and expands it. The pressure reducing device 4 is composed of an expansion valve, and is configured to be able to adjust and control its opening degree.
The evaporator 5 exchanges heat between the liquid refrigerant in the evaporator 5 and the outside air of the evaporator 5 to vaporize the liquid refrigerant.

An expansion valve 11 is arranged on the outlet side of the condenser 3. The expansion valve 11 is configured such that its opening degree can be adjusted and controlled. By adjusting the opening degree of the expansion valve 11, the amount of refrigerant flowing out from the condenser 3 can be adjusted.
A receiver tank 12 is arranged downstream of the expansion valve 11 . The receiver tank 12 is configured to be able to store the refrigerant flowing out from the condenser 3.

A supercooling heat exchanger 13 is arranged downstream of the receiver tank 12.
A branch pipe 16 branching from the refrigerant pipe 15 is connected to the downstream side of the receiver tank 12 and the upstream side of the subcooling heat exchanger 13 . A liquid valve 14 is connected to the branch pipe 16. The liquid valve 14 is configured such that its opening degree can be adjusted and controlled. The liquid valve 14 reduces the pressure of the refrigerant flowing out from the receiver tank 12 and expands it.

A supercooling heat exchanger 13 is arranged downstream of the liquid valve 14 . In the supercooling heat exchanger 13, the refrigerant expands in the liquid valve 14 and flows on the evaporation side of the supercooling heat exchanger 13, and the refrigerant condenses in the condenser 3 and flows on the condensation side of the supercooling heat exchanger 13. Provided for heat exchange. Thereby, the supercooling heat exchanger 13 cools the refrigerant flowing on the condensing side of the supercooling heat exchanger 13 to subcool it, or increases the degree of supercooling of the refrigerant flowing on the condensing side while it is already in a supercooled state. .
A branch pipe 16 extending from the subcooling heat exchanger 13 is connected to the refrigerant pipe 15 on the downstream side of the evaporator 5 and upstream of the compressor 2.

A low pressure sensor 21 is arranged on the refrigerant inlet side of the compressor 2 to detect the pressure of the refrigerant. The low pressure sensor 21 detects the pressure of refrigerant flowing into the compressor 2.
A high pressure sensor 22 is arranged on the refrigerant outlet side of the compressor 2 to detect the pressure of the refrigerant. The high pressure sensor 22 detects the pressure of the refrigerant compressed and flowing out from the compressor 2.

An outside air temperature sensor 23 is arranged in the condenser 3 . The outside air temperature sensor 23 detects the temperature of outside air sucked into the condenser 3.
A refrigerant temperature sensor 24 is arranged on the refrigerant outlet side of the condenser 3 . Refrigerant temperature sensor 24 detects the temperature of the refrigerant flowing out from condenser 3 .

FIG. 2 is a diagram showing the relationship between the amount of refrigerant sealed in the refrigerant circuit 17, the coefficients of performance C10, C20, C11, and C21, and the year-round energy consumption efficiencies A1 and A2. In Figure 2, the horizontal axis indicates the amount of refrigerant enclosed, but the vertical axis has units corresponding to the types of values shown, and the vertical positional relationship in the diagram does not necessarily represent the magnitude relationship of different values. do not have.
In FIG. 2, the left side shows the relationship when there is no receiver tank 12, and the right side shows the relationship in the air conditioner 1 of this embodiment equipped with the receiver tank 12.
Generally, coefficients of performance (COP) C10, C20, C11, C21 and annual performance factors (APF) A1, A2 change depending on the amount of refrigerant sealed in the refrigerant circuit 17. do.

For example, when there is no receiver tank 12, the coefficient of performance C10 of the rated cooling standard (first load mode) and the coefficient of performance C20 of the intermediate cooling medium temperature (second load mode), which has a smaller operating load than the rated cooling standard, are as follows. The coefficients of performance C10 and C20 increase and decrease in a mountain-like manner as the amount of enclosed refrigerant increases, and the coefficients of performance C10 and C20 show the highest values when the amount of enclosed refrigerant is R1 and R2, respectively. The coefficient of performance C10 of the rated cooling standard increases or decreases in a region where the amount of enclosed refrigerant is large, and the coefficient of performance C20 of intermediate cooling medium temperature increases or decreases when the amount of enclosed refrigerant is small. The amount R1 of enclosed refrigerant at which the coefficient of performance C10 becomes the highest value is larger than the amount R2 of enclosed refrigerant at which the coefficient of performance C20 becomes the highest value.

Moreover, the year-round energy consumption efficiency A1 increases and decreases as the amount of enclosed refrigerant increases, and shows the highest value when the amount of enclosed refrigerant is R2. There is a difference ΔA1 in the year-round energy consumption efficiency A1 between the case where the enclosed refrigerant amount R2 has the highest coefficient of performance C20 and the case where the enclosed refrigerant amount R1 has the highest coefficient of performance C10.

On the other hand, when the receiver tank 12 is provided, if the amount of refrigerant sealed in the refrigerant circuit 17 is larger than the amount of refrigerant R1 and R2 at which the coefficients of performance C10 and C20 have the highest values, the larger amount is It becomes possible to temporarily store the amount of surplus refrigerant in the receiver tank 12. Therefore, for example, by arranging in the refrigerant circuit 17 a receiver tank 12 having a capacity V greater than the difference between the filled refrigerant amounts R1 and R2, the receiver tank 12 temporarily stores the surplus refrigerant amount during operation. becomes possible. As a result, the coefficient of performance C10 of the rated cooling standard and the coefficient of performance C20 of the intermediate cooling medium temperature are the highest values in the entire range of adding the refrigerant amount of capacity V to the enclosed refrigerant amounts R1 and R2, as shown in the figure on the right. It can be made into a curve with a coefficient of performance C11 or C21. In the coefficients of performance C11 and C21, the amounts of enclosed refrigerant showing the highest values overlap in the range W0.

In this case, the year-round energy consumption efficiency A2 shows the highest value in the overlapping range W0, and the highest value is larger than the highest value of the year-round energy consumption efficiency A1 without the receiver tank 12 by a difference ΔA2. By providing the receiver tank 12 and filling the refrigerant circuit 17 with overlapping amounts of refrigerant, the highest coefficients of performance C11 and C21 can be achieved even when the operating loads are different.

FIG. 3 is a block diagram of the control unit 100 of the air conditioner 1 of the first embodiment.
The control unit 100 includes a processor 110 such as a CPU or an MPU that executes a program, and a storage unit 120, and controls each unit of the air conditioner 1. The control unit 100 executes various processes through cooperation of hardware and software, such that the processor 110 reads the control program 121 stored in the storage unit 120 and executes the process.

The storage unit 120 has a storage area that stores programs executed by the processor 110 and data processed by the processor 110. The storage unit 120 stores a control program executed by the processor 110, setting data related to various settings of the air conditioner 1, and other various data. The storage unit 120 has a nonvolatile storage area that stores programs and data in a nonvolatile manner. Furthermore, the storage unit 120 may include a volatile storage area and constitute a work area in which programs to be executed by the processor 110 and data to be processed are temporarily stored.

The control unit 100 is electrically connected to an input unit 101, a low pressure sensor 21, a high pressure sensor 22, an outside air temperature sensor 23, and a refrigerant temperature sensor 24 as elements for inputting signals to the control unit 100. There is.

The input unit 101 includes input means such as an operation switch, a touch panel, a mouse, and a keyboard, detects the operator's operation on the input means, and outputs the detection result to the control unit 100. The control unit 100 executes processing corresponding to the operation on the input means based on the input from the input unit 101.

A display unit 102, a compressor 2, an expansion valve 11, a pressure reducing device 4, and a liquid valve 14 are electrically connected to the control unit 100 so as to be controllable as elements to which the control unit 100 outputs control signals. has been done.

The display unit 102 includes LEDs, a display panel, and the like, and executes lighting/blinking/extinguishing of the LEDs in a predetermined manner, displaying information on the display panel, etc. under the control of the control unit 100.

The control unit 100 controls the display unit 102, the compressor 2, The expansion valve 11, the pressure reducing device 4, and the liquid valve 14 are controlled.

FIG. 4 is a schematic diagram showing the state of the refrigerant in the condenser 3 of the first embodiment.
In the condenser 3, the high temperature, high pressure gas refrigerant Rg compressed by the compressor 2 is condensed into liquid refrigerant Rl. The liquid refrigerant Rl is supercooled when it is cooled below the saturation temperature. The difference between the saturation temperature and the liquid temperature is called the degree of supercooling SC.
In FIG. 4, region W1 indicates a condensation region (hereinafter referred to as condensation region W1) where gas refrigerant Rg condenses into liquid refrigerant Rl. Further, region W2 indicates a flash gas region (hereinafter referred to as flash gas region W2) where gas refrigerant Rg is generated from liquid refrigerant Rl. Furthermore, region W3 indicates a supercooling region (hereinafter referred to as supercooling region W3) in which the liquid refrigerant Rl is supercooled.
In the condensation zone W1, there is a correlation between the area of the gas refrigerant Rg and the liquid refrigerant Rl and the condensation pressure.

FIG. 5 is a diagram showing the relationship between the coefficient of performance C, condensation pressure P, and refrigerant temperature T at the outlet of the condenser 3 with respect to the amount of refrigerant held in the condenser 3 of the first embodiment. In FIG. 5, the horizontal axis indicates the amount of refrigerant held in the condenser 3, and the vertical axis takes units according to the indicated value.
As shown in FIG. 5, the refrigerant temperature T gradually decreases toward the outside air temperature T0 as the amount of refrigerant increases. Further, the condensing pressure P increases upward to the right as the amount of refrigerant increases. Further, the coefficient of performance C increases or decreases as the amount of refrigerant increases, and shows the maximum value when the amount of refrigerant is R0.
The coefficient of performance C is good in the vicinity of the refrigerant amount R0, and when the condenser 3 is to function, it is desirable to operate the refrigerant amount in the vicinity of the refrigerant amount R0. The amount of refrigerant indicates the weight of the refrigerant, and since the density of the liquid refrigerant Rl is more than ten times that of the gas refrigerant Rg, the amount of refrigerant can be controlled by adjusting the proportion of the liquid refrigerant Rl.

Therefore, the control unit 100 of this embodiment executes an optimal control process for the amount of refrigerant. In the refrigerant amount optimization process, the expansion valve 11 is controlled to open and close so that the temperature difference ΔT (=T−T0), which is the difference between the refrigerant temperature T and the outside air temperature T0, approaches a predetermined value ΔTa, and the condenser 3 is prevented from overheating. Adjust the amount of cooled liquid refrigerant Rl. Basically, the condensation pressure P in the condenser 3 can be controlled by controlling the opening and closing of the expansion valve 11, so the amount of liquid refrigerant is also changed accordingly. In this embodiment, the temperature difference ΔT approaches the predetermined value ΔTa means that the temperature difference ΔT approaches the predetermined value ΔTa, and when the temperature difference ΔT approaches the predetermined value ΔTa within a preset temperature range ΔTa+α to ΔTa− It also means that it remains at β (see FIG. 5). The range ΔTa+α to ΔTa−β is a range in which the coefficient of performance C is acceptable with respect to the coefficient of performance C of the refrigerant amount R0. Note that the predetermined value ΔTa can be set to, for example, 2° C. or more and 5° C. or less. In this embodiment, as an example, the temperature is set at 3°C.

FIG. 6 is a flowchart showing the operation of the control unit 100 of the first embodiment.
Next, the operation of the refrigerant amount optimization control process executed by the control unit 100 of the air conditioner 1 will be described.

When the control unit 100 starts the refrigerant amount optimization control process, it acquires information on the operating load (operating mode) according to the operating setting of the compressor 2 (ST1).
The control unit 100 detects using the sensors 22 to 24 (step ST2). That is, the control unit 100 detects the outside air temperature T0 of the condenser 3 using the outside air temperature sensor 23. Further, the control unit 100 detects the refrigerant temperature T of the refrigerant flowing out from the condenser 3 using the refrigerant temperature sensor 24 . Furthermore, the control unit 100 detects the refrigerant pressure of the refrigerant flowing out from the compressor 2 using the high pressure sensor 22 .
The control unit 100 calculates a temperature difference ΔT, which is the difference between the refrigerant temperature T and the outside air temperature T0 (step ST3).

Control unit 100 determines saturation temperature T1 and target degree of supercooling SC0 based on preset lookup table information (step ST4). That is, the control unit 100 refers to preset first lookup table information and determines the saturation temperature T1 corresponding to the detected refrigerant pressure (step ST4). Further, the control unit 100 refers to the second lookup table information set in advance to determine the target degree of supercooling SC0 that corresponds to the operating load of the compressor 2 and the refrigerant temperature T ( Step ST4).
The control unit 100 calculates the degree of supercooling SC, which is the difference between the saturation temperature T1 and the refrigerant temperature T (step ST5).

The control unit 100 determines whether the temperature difference ΔT is larger than a predetermined value ΔTa (step ST6).

When the control unit 100 determines that the temperature difference ΔT is larger than the predetermined value ΔTa (step ST6: YES), it determines whether the degree of supercooling SC is smaller than the target degree of supercooling SC0 (step ST7).
When the control unit 100 determines that the degree of subcooling SC is smaller than the target degree of subcooling SC0 (step ST7: YES), the control unit 100 controls the expansion valve to close by a predetermined opening degree (step ST8).
The control unit 100 determines that the degree of subcooling SC is not smaller than the target degree of supercooling SC0, that is, the degree of subcooling SC is greater than the target degree of supercooling SC0, or the degree of subcooling SC is equal to the target degree of supercooling SC0. If so (step ST7: NO), the expansion valve is controlled to open by a predetermined opening degree (step ST9).
The control unit 100 updates and holds the storage information of the degree of subcooling SC (step ST10). Thereby, the current degree of supercooling SC can be referred to as the previous degree of supercooling SC1.

In step ST6, if the control unit 100 determines that the temperature difference ΔT is not larger than the predetermined value ΔTa, that is, the temperature difference ΔT is smaller than the predetermined value ΔTa, or the temperature difference ΔT is equal to the predetermined value ΔTa (step ST6 : NO), it is determined whether or not the degree of supercooling SC is larger than the previously stored degree of supercooling SC1 (step ST11).
When the control unit 100 determines that the degree of subcooling SC is larger than the previous degree of subcooling SC1 (step ST11: YES), it determines whether the degree of subcooling SC is smaller than the target degree of subcooling SC0 (step ST12).

When the control unit 100 determines that the degree of subcooling SC is smaller than the target degree of supercooling SC0 (step ST12: YES), the control unit 100 controls the expansion valve 11 to close by a predetermined opening degree (step ST13).
The control unit 100 determines that the degree of subcooling SC is not smaller than the target degree of supercooling SC0, that is, the degree of subcooling SC is greater than the target degree of subcooling SC0, or the degree of subcooling SC is equal to the target degree of supercooling SC0. If it is determined (step ST12: NO), the expansion valve 11 is controlled to open by a predetermined opening degree (step ST14).

The control unit 100 determines that the degree of subcooling SC is not greater than the previous degree of subcooling SC1, that is, the degree of subcooling SC is smaller than the previous degree of subcooling SC1, or the degree of subcooling SC is equal to the previous degree of supercooling SC1. If so (step ST11: NO), it is determined whether or not the degree of supercooling SC is smaller than the target degree of supercooling SC0 (step ST21).
When the control unit 100 determines that the degree of subcooling SC is smaller than the target degree of subcooling SC0 (step ST21: YES), the control unit 100 moves to step ST10 without controlling the opening degree of the expansion valve 11.
The control unit 100 determines that the degree of subcooling SC is not smaller than the target degree of supercooling SC0, that is, the degree of subcooling SC is greater than the target degree of supercooling SC0, or the degree of subcooling SC is equal to the target degree of supercooling SC0. If so (step ST21: NO), the expansion valve 11 is controlled to open by a predetermined opening degree (step ST22).

After updating and retaining the stored information on the degree of subcooling in step ST10, the control unit 100 determines whether or not the operation is finished (step ST23).
When the control unit 100 determines that the operation has ended (step ST23: YES), the control unit 100 ends the refrigerant amount optimization control process.
When the control unit 100 determines that the operation has not ended (step ST23: NO), the process proceeds to step ST1.

In the air conditioner 1, when the compressor 2 starts operating, refrigerant is circulated according to the operating load. In this embodiment, surplus refrigerant is stored in the receiver tank 12 while adjusting the opening degree of the expansion valve 11 based on the outside air temperature T0 of the condenser 3 and the refrigerant temperature T at the outlet of the condenser 3. , the weight of the liquid refrigerant in the condenser 3 is adjusted. Thereby, the degree of supercooling SC of the condenser 3 is adjusted so that the coefficient of performance C is optimal depending on the load.

Conventionally, the condensing pressure was adjusted by adjusting the valve opening based on the evaporator outlet temperature and the number of compressors in operation, and as a result, the weight of the refrigerant in the condenser was adjusted. It's just that. Therefore, the state of the condenser may not be appropriately reflected in the amount of refrigerant in the condenser or the amount of refrigerant in the receiver tank.

On the other hand, in this embodiment, the opening/closing control of the expansion valve 11 is performed based on the temperature difference ΔT between the refrigerant temperature T at the outlet of the condenser 3 and the outside air temperature T0 of the condenser 3. The degree of supercooling SC can be easily adjusted by adjusting the amount of liquid refrigerant Rl in the condenser 3 while appropriately reflecting the state of the condenser 3. Therefore, even when the operating loads are different, the condenser 3 can be made to function while keeping the coefficient of performance C in a good state based on the state of the condenser 3.

Specifically, in step ST6 of the refrigerant amount optimization control process, it is determined whether the temperature difference ΔT between the refrigerant temperature T at the outlet of the condenser 3 and the outside air temperature T0 of the condenser 3 is larger than a predetermined value ΔTa. Ru. Here, as shown in FIG. 5, when the temperature difference ΔT is larger than a preset predetermined value ΔTa, the amount of liquid refrigerant in the condenser 3 is small, the degree of supercooling is small, and the load on the condenser 3 is small. Assumed to be the state. Further, when the temperature difference ΔT is smaller than a preset predetermined value ΔTa, it is assumed that the amount of liquid refrigerant in the condenser 3 is large, the degree of supercooling is large, and the load on the condenser 3 is large. Therefore, the expansion valve 11 can be controlled by determining whether or not the temperature difference ΔT is larger than a predetermined value ΔTa. Thereby, the amount of liquid refrigerant Rl in the condenser 3 can be adjusted, and the degree of supercooling can be adjusted.

In addition, when the load on the condenser 3 fluctuates due to external factors such as the operating load on the air conditioner 1, the outside air temperature on the condenser 3, and the amount of outside air taken into the condenser 3, the expansion valve 11 may be opened or closed. , the magnitude relationship of the degree of supercooling SC may be reversed, so in the optimal control process for the amount of refrigerant of this embodiment, the degree of supercooling SC and the target degree of supercooling SC0 are further determined in steps ST7, ST12, and ST21. The opening/closing control of the expansion valve 11 is performed by determining the size of the expansion valve 11. Therefore, the coefficient of performance C can be improved more accurately than when the opening/closing control of the expansion valve 11 is performed only based on the magnitude of the temperature difference ΔT and the predetermined value ΔTa.

Furthermore, when the temperature difference ΔT is smaller than the predetermined value ΔTa, it is assumed that the degree of subcooling SC is large and the load on the condenser 3 is large. In this case, if the current degree of subcooling SC is smaller than the previous degree of subcooling SC1, the opening degree of the expansion valve 11 may be sufficiently small. Therefore, in steps ST11 and ST21 of the refrigerant amount optimization control process, if the temperature difference ΔT is smaller than the predetermined value ΔTa and the current degree of supercooling SC is smaller than the previous degree of supercooling SC1, the target supercooling Even if the current supercooling degree SC has not reached the degree SC0, the expansion valve 11 is not controlled to close. This prevents the refrigerant circuit 17 from closing and stopping the circulation of the refrigerant.

As described above, the air conditioner 1 of the present embodiment includes a refrigerant circuit 17 in which a compressor 2, a condenser 3, a pressure reducing device 4, and an evaporator 5 are connected via a refrigerant pipe 15. The device 1 includes an expansion valve 11 disposed at the outlet of the condenser 3 to adjust the amount of refrigerant flowing out from the condenser 3, and an expansion valve 11 disposed between the expansion valve 11 and the pressure reducing device 4 for refrigerant flowing out from the condenser 3. The controller 100 includes a receiver tank 12 that can store refrigerant, and a control unit 100 that controls the opening and closing of the expansion valve 11 to adjust the amount of refrigerant in the condenser 3. The expansion valve 11 is controlled to open and close so that the temperature difference ΔT between the temperature T and the outside air temperature T0 of the condenser 3 approaches a predetermined value ΔTa.
According to this, by controlling the opening and closing of the expansion valve 11 based on the state of the condenser 3, which is the temperature T of the refrigerant flowing out from the condenser 3 and the outside air temperature T0 of the condenser 3, the refrigerant in the condenser 3 is The amount of liquid can be adjusted, and the remaining refrigerant can be stored in the receiver tank 12 when the coefficient of performance C is good. Therefore, even when the operating loads are different, the condenser 3 can be made to function while improving the coefficient of performance C based on the state of the condenser 3.

In this embodiment, the control unit 100 controls the expansion valve 11 to close when the temperature difference ΔT is larger than the predetermined value ΔTa, and controls the expansion valve 11 to open when the temperature difference ΔT is smaller than the predetermined value ΔTa.
According to this, when the temperature difference ΔT is larger than the predetermined value ΔTa, it is likely that the degree of subcooling SC of the condenser 3 is small, so by controlling the expansion valve 11 to close, the refrigerant in the condenser 3 is In addition to making it easier to increase the liquid amount, when the temperature difference ΔT is smaller than the predetermined value ΔTa, it is likely that the degree of supercooling SC of the condenser 3 is large, so by controlling the expansion valve 11 to open, the condenser 3 By making it easier to reduce the amount of refrigerant in the tank, the degree of supercooling can be easily adjusted so that the coefficient of performance C becomes the highest.

Furthermore, in the present embodiment, when the temperature difference ΔT is larger than the predetermined value ΔTa, and when the degree of supercooling SC of the refrigerant flowing out from the condenser 3 is larger than the target degree of supercooling SC0, , the expansion valve 11 is controlled to open instead of closed.
According to this, it is assumed that the coefficient of performance C will improve if the expansion valve 11 is controlled to close when the temperature difference ΔT is larger than the predetermined value ΔTa, but when the load on the condenser 3 changes due to external factors, Since there is no correlation between the opening and closing of the expansion valve 11 and the magnitude of the degree of supercooling SC, the refrigerant liquid in the condenser 3 is adjusted more accurately by controlling based on the target degree of supercooling SC0 so that the coefficient of performance C becomes the highest. You can adjust the amount.

Furthermore, in the present embodiment, when the temperature difference ΔT is smaller than the predetermined value ΔTa, the control unit 100 controls whether the degree of subcooling SC of the refrigerant flowing out from the condenser 3 is larger than the previous degree of subcooling SC1 and the degree of subcooling is When the degree SC is smaller than the target degree of supercooling SC0, the expansion valve 11 is controlled to be closed instead of being controlled to open.
According to this, if the temperature difference is smaller than a predetermined value, it is assumed that the coefficient of performance will improve if the expansion valve is controlled to open, but if the load on the condenser 3 fluctuates due to external factors, the expansion valve 11 and the magnitude of the degree of supercooling SC, the amount of refrigerant in the condenser can be adjusted with higher accuracy by controlling based on the target degree of supercooling so that the coefficient of performance becomes the highest.

In the present embodiment, the control unit 100 controls the degree of supercooling SC of the refrigerant flowing out from the condenser 3 to be smaller than the previous degree of supercooling SC1 and the degree of supercooling when the temperature difference ΔT is smaller than the predetermined value ΔTa. When SC is smaller than the target degree of supercooling SC0, the expansion valve 11 is not controlled to open or close instead of being controlled to open.
According to this, when the temperature difference ΔT is smaller than the predetermined value ΔTa and the degree of subcooling SC of the refrigerant flowing out from the condenser 3 is smaller than the pre-supercooling degree SC1, the opening degree of the expansion valve 11 is Since it is assumed that the subcooling degree SC is already small, even if the subcooling degree SC is smaller than the target subcooling degree SC1, the expansion valve 11 can be prevented from being closed too much by not controlling the expansion valve 11 to close.

Further, in this embodiment, a high pressure sensor 22 is arranged at the outlet side of the compressor 2 to detect the pressure of the refrigerant flowing out from the compressor 2, and a high pressure sensor 22 is arranged at the outlet side of the condenser 3 to detect the pressure of the refrigerant flowing out from the condenser 3. A refrigerant temperature sensor 24 that detects the temperature T, and the control unit 100 determines the saturation temperature T1 of the refrigerant in the condenser 3 based on the detection result of the high pressure sensor 22, and also determines the saturation temperature T1 and the refrigerant temperature sensor 24. 24, the degree of supercooling SC of the refrigerant flowing out from the condenser 3 is calculated.
According to this, the degree of supercooling SC can be calculated based on the detection results of the high pressure sensor 22 and the refrigerant temperature sensor 24.

Further, in this embodiment, an outside air temperature sensor 23 that detects the temperature T0 of the outside air of the condenser 3, and a refrigerant temperature sensor that is arranged at the refrigerant outlet of the condenser 3 and that detects the temperature T of the refrigerant flowing out from the condenser 3 are used. 24, the control unit 100 determines the temperature difference between the temperature T of the refrigerant flowing out from the condenser 3 and the outside air temperature T0 of the condenser 3, based on the detection results of the outside air temperature sensor 23 and the refrigerant temperature sensor 24. Calculate ΔT.
According to this, the temperature difference ΔT can be calculated based on the detection results of the outside air temperature sensor 23 and the refrigerant temperature sensor 24.

Further, in this embodiment, the receiver tank 12 is configured to be operable at a rated cooling standard and an intermediate cooling medium temperature different from the rated cooling standard, and the receiver tank 12 has a coefficient of performance of the rated cooling standard for the refrigerant accommodated in the refrigerant circuit 17. The capacity V is configured to accommodate an amount that is greater than the difference between the amount of refrigerant that gives the highest C11 and the amount of refrigerant that gives the highest coefficient of performance C21 for intermediate cooling medium temperature.
According to this, the air conditioner 1 can be operated with the amount of refrigerant that gives the highest coefficient of performance C even when the operating loads of the air conditioner 1 are different, rated cooling standard and intermediate cooling medium temperature.

Each of the embodiments described above merely represents one aspect of the present invention, and can be arbitrarily modified and applied within the scope of the present invention.

In each of the embodiments described above, a configuration has been described in which one device is provided in the refrigerant circuit 17, but a plurality of some devices may be provided.

Further, in each of the embodiments described above, a configuration such as a four-way valve that switches the refrigerant circulation direction may be used. In this case, the role of a certain heat exchanger is switched between a condenser and an evaporator between cooling operation and heating operation, but the present invention is applicable to a heat exchanger that functions as a condenser.

In the embodiment described above, the rated cooling standard and intermediate cooling medium temperature configurations have been described, but a configuration that allows operations with different loads may also be possible, and the capacity V of the receiver tank 12 is such that the coefficient of performance of each operation shows the highest value. Any capacity may be sufficient as long as it can accommodate the difference between the maximum value and the minimum value regarding the amount of refrigerant enclosed.

Further, the functions of the control unit 100 may be realized by a plurality of processors or semiconductor chips.

Moreover, each part shown in FIG. 3 is an example, and the specific implementation form is not particularly limited. In the embodiments described above, some of the functions implemented by software may be implemented by hardware, or some of the functions implemented by hardware may be implemented by software.

Further, for example, the step units of the operation shown in FIG. 6 are divided according to the main processing contents in order to facilitate understanding of the operation of each part of the control unit 100. The invention is not limited by the name. Depending on the processing content, the process may be divided into more steps. Furthermore, the process may be divided so that one step unit includes more processes. Further, the order of the steps may be changed as appropriate within a range that does not interfere with the spirit of the present invention.

As described above, the air conditioner according to the present invention can be used in applications including a receiver tank.

1 Air conditioner 2 Compressor 3 Condenser 4 Pressure reducing device 5 Evaporator 11 Expansion valve 12 Receiver tank 15, 16 Piping 17 Refrigerant circuit 22 High pressure sensor 23 Outside temperature sensor 24 Refrigerant temperature sensor 100 Control unit C Coefficient of performance R0 Refrigerant amount SC Degree of supercooling SC0 Target degree of supercooling SC1 Previous degree of supercooling T Refrigerant temperature (refrigerant temperature)
T0 Outside air temperature T1 Saturation temperature ΔT Temperature difference ΔTa Predetermined value

Claims (8)

An air conditioner comprising a refrigerant circuit in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected via piping,
an expansion valve arranged at the outlet of the condenser to adjust the amount of refrigerant flowing out of the condenser; and a receiver tank arranged between the expansion valve and the pressure reducing device and capable of storing the refrigerant flowing out from the condenser. and a control unit that controls opening and closing of the expansion valve to adjust the amount of refrigerant in the condenser,
The control unit controls the opening and closing of the expansion valve so that a temperature difference between the temperature of the refrigerant flowing out of the condenser and the outside air temperature of the condenser approaches a predetermined value set in advance. harmonization device. The control unit controls the expansion valve to close when the temperature difference is larger than the predetermined value, and controls the expansion valve to open when the temperature difference is smaller than the predetermined value. Item 1. The air conditioner according to item 1. When the temperature difference is larger than the predetermined value and the degree of supercooling of the refrigerant flowing out from the condenser is larger than a target degree of supercooling, the control unit controls the expansion valve to close. The air conditioner according to claim 2, wherein the air conditioner is controlled to open by opening the air conditioner. The control unit is configured such that when the temperature difference is smaller than the predetermined value, the degree of supercooling of the refrigerant flowing out from the condenser is larger than the previous degree of supercooling, and the degree of supercooling is less than the target degree of supercooling. The air conditioner according to claim 2 or 3, wherein when the expansion valve is small, the expansion valve is controlled to close instead of being controlled to open. The control unit is configured such that, when the temperature difference is smaller than the predetermined value, the degree of supercooling of the refrigerant flowing out from the condenser is smaller than the previous degree of supercooling, and the degree of supercooling is less than the target degree of supercooling. The air conditioner according to any one of claims 2 to 4, wherein if the expansion valve is small, the expansion valve is not controlled to open or close instead of being controlled to open. a high pressure sensor arranged on the outlet side of the compressor to detect the pressure of the refrigerant flowing out from the compressor; and a refrigerant temperature sensor arranged on the outlet side of the condenser to detect the temperature of the refrigerant flowing out from the condenser. , comprising;
The control unit determines the saturation temperature of the refrigerant in the condenser based on the detection result of the high pressure sensor, and determines the saturation temperature of the refrigerant flowing out from the condenser based on the saturation temperature and the detection result of the refrigerant temperature sensor. The air conditioner according to any one of claims 3 to 5, wherein the degree of subcooling of the air conditioner is calculated. an outside air temperature sensor that detects the temperature of the outside air of the condenser; and a refrigerant temperature sensor that is disposed at the refrigerant outlet of the condenser and detects the temperature of the refrigerant flowing out from the condenser,
The control unit may calculate a temperature difference between the temperature of the refrigerant flowing out from the condenser and the outside air temperature of the condenser, based on the detection results of the outside air temperature sensor and the refrigerant temperature sensor. An air conditioner according to any one of claims 1 to 6. configured to be operable in a first load mode and a second load mode different from the first load mode,
The receiver tank is configured to control the amount of refrigerant contained in the refrigerant circuit so that the coefficient of performance in the first load mode is the highest, and the amount of refrigerant that gives the highest coefficient of performance in the second load mode. The air conditioner according to any one of claims 1 to 7, wherein the air conditioner is configured to have a capacity that can accommodate an amount equal to or more than the difference.

Images