JP7378660B2 - Air conditioner and expansion valve control method - Google Patents

Description

The present disclosure relates to an air conditioner and an expansion valve control method.

Conventionally, in an air conditioner equipped with a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a ring through refrigerant piping, the opening degree of the expansion valve is determined by the amount of air discharged from the compressor. Generally, it is controlled based on the discharge temperature, which is the refrigerant temperature (for example, Patent Document 1).

By controlling based on the discharge temperature as described above, it is possible to suppress an excessive rise in the discharge temperature and prevent failure of peripheral components including the compressor, thereby ensuring reliability of the refrigerant circuit.

Japanese Patent Application Publication No. 2018-146208

By the way, when the heat load of the air-conditioned space is low, that is, when the air conditioning load is low, the compressor is in a state where it repeats operation and stop (so-called start-stop operation). If the opening degree of the expansion valve is controlled based on the discharge temperature in such a state, it will take time for the evaporation temperature to reach an appropriate temperature, and it will take time for the air conditioning capability to be achieved.

As a result, there is a problem that the room temperature continues to vibrate up and down, and user comfort cannot be immediately ensured.

The present disclosure has been made to solve the above problems, and provides an air conditioner and an expansion valve control method that can quickly ensure user comfort even under low load. With the goal.

In order to achieve the above object, the air conditioner according to the present disclosure includes:
a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a ring through refrigerant piping;
a plurality of temperature sensors each measuring the temperature of the refrigerant circulating in the refrigerant pipe;
A control means for controlling the opening degree of the expansion valve,
When the control mode is a low load mode, the control means controls a reference change value of the opening determined according to a difference between the temperature of the refrigerant at the outlet of the evaporator and a target evaporation temperature, a degree of subcooling, and a degree of superheat. The opening degree of the expansion valve is controlled based on the temperature of the refrigerant discharged from the compressor when the control mode is the normal mode.

According to the present disclosure, it is possible to quickly ensure user comfort even when the load is low.

A diagram showing the hardware configuration of an air conditioner in Embodiment 1 A block diagram showing the hardware configuration of a control circuit included in the outdoor unit in Embodiment 1. A block diagram showing the hardware configuration of a control circuit included in the indoor unit in Embodiment 1. A diagram showing the functional configuration of a control circuit included in the outdoor unit in Embodiment 1. A diagram for explaining control of the expansion valve during low load control in Embodiment 1 A diagram for explaining control of the expansion valve during low load control in Embodiment 1 Flowchart showing the procedure of expansion valve control processing in Embodiment 1 A diagram showing the functional configuration of a control circuit included in the outdoor unit in Embodiment 2 Diagram for explaining expansion valve control during low load control in Embodiment 2 Diagram for explaining expansion valve control during low load control in Embodiment 2

Embodiments of the present disclosure will be described in detail below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing a hardware configuration of an air conditioner 1 according to Embodiment 1 of the present disclosure. The air conditioner 1 is an example of an air conditioner according to the present disclosure. The air conditioner 1 is a heat pump type air conditioner that uses an HFC (hydrofluorocarbon) such as R32 or a natural refrigerant such as CO ₂ as a refrigerant, and is a so-called room air conditioner.

As shown in FIG. 1, the air conditioner 1 includes an outdoor unit 2 installed outdoors, an indoor unit 3 installed indoors, and a remote control 4. The outdoor unit 2 and the indoor unit 3 are connected via a refrigerant pipe 5 for circulating refrigerant and a communication line 6. The refrigerant pipe 5 is an example of a refrigerant pipe according to the present disclosure.

The outdoor unit 2 includes a control circuit 20, a compressor 21, a four-way valve 22, a heat exchanger 23, a fan 24, an expansion valve 25, refrigerant temperature sensors 26a to 26d, an air temperature sensor 27, and a humidity sensor. A sensor 28 is provided. A compressor 21, a four-way valve 22, a heat exchanger 23, and an expansion valve 25 in the outdoor unit 2, and a heat exchanger 31 (described later) in the indoor unit 3 are connected to a refrigerant circuit (in this disclosure) connected in an annular manner by a refrigerant pipe 5. An example of such a refrigerant circuit) is configured.

The control circuit 20 is an example of a control means according to the present disclosure, and is a microcontroller that controls the air conditioner 1 in an integrated manner. As shown in FIG. 2, the control circuit 20 has a hardware configuration including a CPU (Central Processing Unit) 200, a ROM (Read Only Memory) 201, a RAM (Random Access Memory) 202, and an auxiliary storage device 203. and an input/output interface 204. These components are interconnected via bus 205.

CPU 200 centrally controls control circuit 20 . Details of the functions of the control circuit 20 realized by the CPU 200 will be described later. The ROM 201 stores a startup program and data used when executing the startup program. RAM 202 is used as a work area for CPU 200.

The auxiliary storage device 203 is composed of a readable/writable nonvolatile semiconductor memory or the like. Examples of the readable and writable nonvolatile semiconductor memory include EEPROM (Electrically Erasable Programmable Read-Only Memory) and flash memory. The auxiliary storage device 203 stores a program for air conditioning operation in the air conditioner 1 (hereinafter referred to as an air conditioning program) and data used when executing the air conditioning program.

The above air conditioning program can be downloaded to the outdoor unit 2 from another device. In addition, air conditioning programs can be stored in computers such as CD-ROMs (Compact Disc Read Only Memory), DVDs (Digital Versatile Discs), magneto-optical disks, USB (Universal Serial Bus) memories, HDDs, SSDs (Solid State Drives), and memory cards. It is also possible to store it in a readable recording medium and distribute it. By connecting such a recording medium to the outdoor unit 2, the outdoor unit 2 can also import the air conditioning program from the recording medium.

The input/output interface 204 is connected to other components of the outdoor unit 2 (namely, the compressor 21, the four-way valve 22, the fan 24, the expansion valve 25, the refrigerant temperature sensors 26a to 26d, the air temperature sensor 27, and the humidity sensor 28). It is configured to include an interface for communicating and an interface for communicating with the indoor unit 3 via the communication line 6.

Returning to FIG. 1, the compressor 21 is an example of a compressor according to the present disclosure, and compresses refrigerant. Specifically, the compressor 21 compresses a low-temperature, low-pressure refrigerant, and discharges the high-pressure, high-temperature refrigerant to the four-way valve 22 . The compressor 21 includes an inverter circuit that can change the operating capacity according to the drive frequency. The operating capacity is the amount of refrigerant that the compressor 21 pumps out per unit. The compressor 21 changes its operating capacity in accordance with a signal from the control circuit 20 that indicates a driving frequency change value.

The four-way valve 22 is a valve for switching the refrigerant circulation direction. The four-way valve 22 is switched as shown by the solid line in FIG. 1 during cooling operation. Thereby, the refrigerant circulates in the order of the compressor 21, the four-way valve 22, the heat exchanger 23, the expansion valve 25, and the heat exchanger 31. On the other hand, the four-way valve 22 is switched as shown by the broken line in FIG. 1 during heating operation. Thereby, the refrigerant circulates in the order of the compressor 21, the four-way valve 22, the heat exchanger 31, the expansion valve 25, and the heat exchanger 23.

The heat exchanger 23 exchanges heat between the outdoor air (ie, outside air) drawn in by the fan 24 and the refrigerant. The heat exchanger 23 functions as a condenser (an example of a condenser according to the present disclosure) during cooling operation, and functions as an evaporator (an example of an evaporator according to the present disclosure) during heating operation. The fan 24 is, for example, a propeller fan, which sucks in outside air and sends out the air that has been heat-exchanged by the heat exchanger 23 to the outdoors. The rotation speed of the fan 24 is adjusted according to a signal from the control circuit 20 indicating a change in the rotation speed.

The expansion valve 25 is an example of an expansion valve according to the present disclosure. The expansion valve 25 is installed between the heat exchanger 23 and the heat exchanger 31, and reduces the pressure of the refrigerant flowing through the refrigerant pipe 5 to expand it. The expansion valve 25 is, for example, an electronic expansion valve whose aperture opening can be adjusted by a stepping motor (not shown). The expansion valve 25 adjusts the pressure of the refrigerant by changing the opening degree in accordance with a signal indicating the change value of the opening degree from the control circuit 20.

The refrigerant temperature sensors 26a to 26d are examples of temperature sensors according to the present disclosure, and measure the temperature of the refrigerant. The refrigerant temperature sensor 26a is provided on the discharge side of the compressor 21 and measures the temperature of the refrigerant discharged from the compressor 21 (hereinafter referred to as discharge temperature). The refrigerant temperature sensor 26a outputs a signal indicating the measured discharge temperature to the control circuit 20.

The refrigerant temperature sensor 26b is provided near the heat exchanger 23 between the compressor 21 and the heat exchanger 23, and measures the temperature of the refrigerant at the outlet of the evaporator during heating operation (hereinafter referred to as evaporator outlet temperature). measure. Refrigerant temperature sensor 26b outputs a signal indicating the measured evaporator outlet temperature to control circuit 20.

The refrigerant temperature sensor 26c is provided near the center of the heat exchanger 23 and measures the condensation temperature during cooling operation. Refrigerant temperature sensor 26c outputs a signal indicating the measured condensation temperature to control circuit 20. Moreover, the refrigerant temperature sensor 26c measures the evaporation temperature during heating operation. Refrigerant temperature sensor 26c outputs a signal indicating the measured evaporation temperature to control circuit 20.

The refrigerant temperature sensor 26d is provided near the heat exchanger 23 between the heat exchanger 23 and the expansion valve 25, and measures the temperature of the refrigerant at the outlet of the condenser during cooling operation (hereinafter referred to as condenser outlet temperature). measure. The refrigerant temperature sensor 26d outputs a signal indicating the measured condenser outlet temperature to the control circuit 20. Furthermore, the refrigerant temperature sensor 26d measures the temperature of the refrigerant at the inlet of the evaporator during heating operation (hereinafter referred to as evaporator inlet temperature). The refrigerant temperature sensor 26d outputs a signal indicating the measured evaporator inlet temperature to the control circuit 20.

The air temperature sensor 27 measures the temperature of the outside air sucked in by the fan 24 and outputs a signal indicating the measured outside air temperature to the control circuit 20. The humidity sensor 28 measures the humidity of the outside air sucked in by the fan 24 and outputs a signal indicating the measured humidity of the outside air to the control circuit 20.

The indoor unit 3 includes a control circuit 30, a heat exchanger 31, a fan 32, refrigerant temperature sensors 33a to 33c, an air temperature sensor 34, and a humidity sensor 35.

The control circuit 30 is a microcontroller that controls the indoor unit 3 in an integrated manner. As shown in FIG. 3, the control circuit 30 includes a CPU 300, a ROM 301, a RAM 302, an auxiliary storage device 303, and an input/output interface 304 as a hardware configuration. These components are interconnected via a bus 305.

CPU 300 centrally controls control circuit 30 . The ROM 301 stores a startup program and data used when executing the startup program. RAM 302 is used as a work area for CPU 300.

The auxiliary storage device 303 is composed of a readable/writable nonvolatile semiconductor memory or the like. Examples of the readable and writable nonvolatile semiconductor memory include EEPROM and flash memory. The auxiliary storage device 303 stores programs for operation in the indoor unit 3 and data used when executing the programs.

The input/output interface 304 is an interface for communicating with other components included in the indoor unit 3 (i.e., fan 32, refrigerant temperature sensors 33a to 33c, air temperature sensor 34, and humidity sensor 35), and an interface for communicating with the outdoor unit 2. It is configured to include an interface for communicating via the line 6 and an interface for communicating with the remote controller 4 by wire or wirelessly.

The heat exchanger 31 exchanges heat between the indoor air sucked in by the fan 32 and the refrigerant from the outdoor unit 2 . The heat exchanger 31 functions as an evaporator (an example of an evaporator according to the present disclosure) during cooling operation, and functions as a condenser (an example of a condenser according to the present disclosure) during heating operation.

The fan 32 is, for example, a propeller fan, and sucks indoor air from an inlet (not shown), and sends out air that has been heat exchanged by the heat exchanger 31 into the room from an outlet (not shown). The rotation speed of the fan 32 is adjusted according to a signal from the control circuit 30 indicating a change in the rotation speed.

The refrigerant temperature sensors 33a to 33c are examples of temperature sensors according to the present disclosure, and measure the temperature of the refrigerant. The refrigerant temperature sensor 33a is provided near the heat exchanger 31 between the expansion valve 25 and the heat exchanger 31, and measures the evaporator inlet temperature during cooling operation. The refrigerant temperature sensor 33a outputs a signal indicating the measured evaporator inlet temperature to the control circuit 30. Moreover, the refrigerant temperature sensor 33a measures the condenser outlet temperature during heating operation. Refrigerant temperature sensor 33a outputs a signal indicating the measured condenser outlet temperature to control circuit 30.

The refrigerant temperature sensor 33b is provided near the center of the heat exchanger 31 and measures the condensation temperature during heating operation. The refrigerant temperature sensor 33b outputs a signal indicating the measured condensation temperature to the control circuit 30. Further, the refrigerant temperature sensor 33b measures the evaporation temperature during cooling operation. Refrigerant temperature sensor 33b outputs a signal indicating the measured evaporation temperature to control circuit 30.

The refrigerant temperature sensor 33c is provided near the heat exchanger 31 between the heat exchanger 31 and the compressor 21, and measures the evaporator outlet temperature during cooling operation. The refrigerant temperature sensor 33c outputs a signal indicating the measured evaporator outlet temperature to the control circuit 30.

The air temperature sensor 34 measures the temperature of the air sucked in by the fan 32 (ie, room temperature), and outputs a signal indicating the measured room temperature to the control circuit 30. The humidity sensor 35 measures the humidity of the air sucked in by the fan 32 (ie, indoor humidity), and outputs a signal indicating the measured indoor humidity to the control circuit 30.

The control circuit 30 periodically transmits indoor unit data including the rotation speed of the fan 32, the evaporator inlet temperature and evaporator outlet temperature during cooling operation, and the condensation temperature and condenser outlet temperature during heating operation. /Or transmitted to the control circuit 20 in response to a request from the control circuit 20 of the outdoor unit 2.

The remote controller 4 is installed embedded in the wall of a room that is an air-conditioned space, or is installed in a manner that is hung on the wall, and is used to receive air-conditioning-related operations from a user in the room. The remote control 4 is communicatively connected to the control circuit 30 of the indoor unit 3 by wire or wirelessly. By operating the remote controller 4, the user can instruct the air conditioner 1 to start and stop various operations such as cooling operation, heating operation, ventilation operation, dehumidification operation, etc. That is, it is possible to instruct changes in the air conditioning target temperature, wind speed, wind direction, etc.

When the user performs an operation related to air conditioning via the remote controller 4, the control circuit 30 of the indoor unit 3 transmits operation data indicating the content of the operation to the control circuit 20 of the outdoor unit 2.

Next, the functions of the control circuit 20 included in the outdoor unit 2 will be explained in detail. FIG. 4 is a diagram showing the functional configuration of the control circuit 20. As shown in FIG. As shown in FIG. 4, the control circuit 20 includes a temperature control start/stop condition determining section 210, a timer 211, a control mode setting section 212, and a control mode switching section 213 as characteristic functional configurations according to the present disclosure. , a target evaporation temperature estimation section 214 , a valve opening control section 215 , and a fan rotation speed control section 216 . These functional units are realized by the CPU 200 executing the above-mentioned air conditioning program stored in the auxiliary storage device 203.

The temperature regulation start/stop condition determination unit 210 determines whether or not the temperature regulation start condition is satisfied, and determines whether or not the temperature regulation stop condition is satisfied. The temperature control start condition means a condition for starting temperature control, and starting temperature control means starting the compressor 21, that is, starting the operation. Further, the temperature control stop condition means a condition for stopping temperature control, and stopping temperature control means stopping the operation of the compressor 21.

In this embodiment, the temperature control start condition is when the difference between the room temperature and the set temperature (room temperature - set temperature) becomes larger than a predetermined value during the cooling operation in the non-temperature control mode; During operation, this is the case when the difference between the set temperature and the room temperature (set temperature - room temperature) becomes larger than a predetermined value.

In addition, the temperature control stop condition is when the difference between the room temperature and the set temperature (room temperature - set temperature) becomes smaller than a predetermined value during temperature control, during cooling operation, and when the difference between the room temperature and the set temperature becomes smaller than a predetermined value during heating operation. This is a case where the difference between the temperature and the room temperature (set temperature - room temperature) becomes smaller than a predetermined value.

The timer 211 measures the time from when temperature control is stopped to when temperature control is started. Further, the timer 211 measures the elapsed time after starting low load control, which will be described later.

The control mode setting unit 212 sets the control mode for the operation of the air conditioner 1 to either normal mode or low load mode. The control mode setting unit 212 sets the control mode to the low load mode if the low load condition is satisfied at the start of temperature control, and sets the control mode to the normal mode if the low load condition is not satisfied.

In this embodiment, the low load condition is defined as a case where the time from stopping the temperature control to starting the current temperature control is within a predetermined time (minutes), or the difference between the room temperature and the set temperature (room temperature - This is a case where the absolute value of the set temperature) is less than or equal to a predetermined value.

Hereinafter, as needed, the control of the control circuit 20 when the control mode is the low load mode will be referred to as low load control, and the control of the control circuit 20 when the control mode is the normal mode will be referred to as normal control.

The control mode switching unit 213 switches the control mode from the low load mode to the normal mode when the normal mode switching conditions are satisfied. In this embodiment, the normal mode switching condition is when the elapsed time from the start of low load control reaches a predetermined time (minutes), or when the discharge temperature reaches a predetermined temperature (for example, 50 ° C. 60°C) or higher.

The target evaporation temperature estimation unit 214 periodically estimates a target evaporation temperature, which is a target value of the evaporation temperature, during low load control. In the present embodiment, the target evaporation temperature estimating unit 214 calculates the temperature of the air that exchanges heat with the refrigerant passing through the evaporator (hereinafter referred to as heat exchange air temperature), and the temperature of the air that exchanges heat with the refrigerant passing through the evaporator. The humidity of the air to be exchanged (hereinafter referred to as heat exchange air humidity), the volume of air that exchanges heat with the refrigerant passing through the evaporator (hereinafter referred to as heat exchange air volume), and the exchange required for the evaporator. The target evaporation temperature is estimated based on at least one of the following:

As the above-mentioned heat exchange air temperature, the air temperature (i.e., room temperature) measured by the air temperature sensor 34 is used during cooling operation, and the air temperature (i.e., room temperature) measured by air temperature sensor 27 is used during heating operation. That is, the outside temperature) is used.

Furthermore, as the heat exchange air humidity, during cooling operation, the air humidity (i.e., indoor humidity) measured by the humidity sensor 35 is used, and during heating operation, the air humidity measured by the humidity sensor 28 is used. (i.e., outside air humidity) is used.

Further, as the heat exchange air volume, the rotation speed of the fan 32 is used during the cooling operation, and the rotation speed of the fan 24 is used during the heating operation.

In addition, the above exchanged heat amount is the measured evaporation temperature (that is, the evaporation temperature measured by the refrigerant temperature sensor 33b during cooling operation or the evaporation temperature measured by the refrigerant temperature sensor 26c during heating operation), the compressor 21 It is derived from the driving frequency etc.

The valve opening degree control section 215 controls the opening degree of the expansion valve 25 during temperature regulation. During normal control, the valve opening degree control section 215 controls the opening degree of the expansion valve 25 based on the discharge temperature, as in the conventional case. On the other hand, during low load control, the valve opening degree control unit 215 controls the opening degree of the expansion valve 25 that is predetermined according to the difference between the evaporator outlet temperature and the target evaporation temperature estimated by the target evaporation temperature estimation unit 214. The opening degree of the expansion valve 25 is controlled based on the reference change value, the degree of subcooling, and the degree of superheating.

The degree of supercooling is the difference between the condenser outlet temperature and the condensing temperature (condenser outlet temperature - condensing temperature), and is also referred to as the subcool degree. The degree of superheat is the difference between the evaporator outlet temperature and the evaporator inlet temperature (evaporator outlet temperature - evaporator inlet temperature), and is also called the superheat degree.

In order to develop the air conditioning ability more quickly, it is desirable to bring the degree of superheat closer to the appropriate value (approximately 3° C.) sooner, but the inventors have confirmed the following phenomenon based on experiments.
(1) When the degree of superheating is greater than 0℃ (i.e., the refrigerant is a superheated gas at the outlet of the evaporator) and the degree of supercooling is 0℃ (i.e., the refrigerant is a gas liquid at the outlet of the condenser) (in a two-phase state), reducing the opening of the expansion valve will reduce the degree of superheating.
(2) If the degree of superheating is greater than 0℃ and the degree of supercooling is greater than 0℃ (the refrigerant is a supercooled liquid at the outlet of the condenser), reducing the opening of the expansion valve will reduce the degree of superheating. To increase.

The valve opening degree control unit 215 controls the opening degree of the expansion valve 25 during low load control using a new method obtained from the above knowledge.

In this embodiment, the valve opening degree control unit 215 determines the change value of the opening degree of the expansion valve by multiplying the above reference change value by a correction coefficient determined based on the degree of subcooling and the degree of superheating. . The reference change value is a value indicating the amount of change that becomes a reference. FIG. 5 shows the correspondence between the difference between the evaporator outlet temperature and the target evaporation temperature and the correction coefficient when the degree of supercooling (denoted as SC in the figure) is greater than 0° C. (case 1). Further, FIG. 6 shows the correspondence between the difference between the evaporator outlet temperature and the target evaporation temperature and the correction coefficient when the degree of supercooling is 0° C. (case 2).

The reference change value for the opening degree of the expansion valve 25 is predetermined in accordance with the difference between the evaporator outlet temperature and the target evaporation temperature, regardless of the value of the degree of supercooling. Hereinafter, the difference between the evaporator outlet temperature and the target evaporation temperature will be referred to as evaporation temperature difference. In this embodiment, the reference change value when the evaporation temperature difference is 10°C is 10 (pulse), and the reference change value when the evaporation temperature difference is 5°C is 5 (pulse). The reference change value when the difference is 0°C is 0 (pulse), and the reference change value when the evaporation temperature difference is -5°C is -5 (pulse). Note that the positive or negative of the pulse value indicates the direction in which the opening degree of the expansion valve 25 is changed. That is, when the pulse value is positive, the opening degree of the expansion valve 25 is changed to a more open direction, while when it is negative, it means that the opening degree of the expansion valve 25 is changed to a more narrowed direction.

First, case 1 (ie, the case where the degree of supercooling is greater than 0° C.) shown in FIG. 5 will be described. When the superheat degree (denoted as SH in the figure) is 0°C, the correction coefficient is set to "-1" (excluding when the evaporation temperature difference is 0°C; the same applies hereinafter). This is because it is necessary to reduce the opening degree of the expansion valve 25 by a large amount in order to lower the evaporation temperature and increase the degree of superheating. Further, when the degree of superheat is greater than 0° C. and smaller than 5° C., the correction coefficient is set to “−1/2”. This is because, while it is necessary to reduce the degree of opening in order to lower the evaporation temperature, it is also necessary to reduce the amount of change in order to prevent the degree of superheating from becoming too large.

Further, when the degree of superheat is 5° C. or higher, the correction coefficient is set to “1/2”. This is because if the degree of superheat is too large, the evaporator cannot be used efficiently, so the degree of opening must be increased to reduce the degree of superheat, and the degree of superheat is determined by the degree of opening of the expansion valve 25. This is because the amount of change needs to be smaller than that required when changing the evaporation temperature, since the evaporation temperature reacts sensitively to changes in the evaporation temperature.

Regarding case 2 in FIG. 6 (that is, when the degree of supercooling is 0° C.), the sign of the correction coefficient is opposite to the sign of the correction coefficient in case 1 of FIG. The rest is the same as case 1. Data corresponding to the contents of FIGS. 5 and 6 are stored in advance in the auxiliary storage device 203 of the control circuit 20.

Note that Case 1 requires that the degree of supercooling be greater than 0°C, and Case 2 requires that the degree of supercooling be 0°C, but this "0°C" is shown conceptually. , is actually set to a value larger than "0° C." in consideration of measurement errors of the refrigerant temperature sensors 26a to 26d, 33a to 33c and instability of the refrigerant state. Similarly, "0°C" in the condition that the degree of superheating is 0°C and the condition that the degree of superheating is greater than 0°C and less than 5°C is actually set to a value larger than "0°C". .

During low load control, the valve opening control unit 215 first obtains the evaporation temperature difference, the degree of supercooling, and the degree of superheat. Then, the valve opening degree control unit 215 obtains a reference change value from the evaporation temperature difference, and obtains a correction coefficient from the degree of supercooling and the degree of superheating. Then, the valve opening degree control unit 215 calculates a changed value of the opening degree of the expansion valve 25 by multiplying the acquired reference changed value and the acquired correction coefficient. The valve opening controller 215 outputs a signal indicating the calculated change value (pulse) to the expansion valve 25.

During normal control, the valve opening control section 215 performs conventional so-called discharge temperature control. Description of the discharge temperature control will be omitted.

Returning to FIG. 4, the fan rotation speed control unit 216 controls the rotation speed of the evaporator side fan and the rotation speed of the condenser side fan during low load control. Hereinafter, the fan on the evaporator side (that is, the fan that sends air to the evaporator) will be referred to as the evaporator fan, and the fan on the condenser side (that is, the fan that will send air to the condenser) will be referred to as the condenser fan.

In other words, during low-load control during cooling operation, the fan rotation speed control unit 216 controls the rotation speed of the fan 32 of the indoor unit 3, which is an evaporator fan, and controls the rotation speed of the fan 24 of the outdoor unit 2, which is a condenser fan. Control the rotation speed. Furthermore, during low load control during heating operation, the fan rotation speed control unit 216 controls the rotation speed of the fan 24 of the outdoor unit 2, which is an evaporator fan, and controls the rotation speed of the fan 32 of the indoor unit 3, which is a condenser fan. Control the rotation speed.

The fan rotation speed control unit 216 sets the rotation speed of the evaporator fan during low load control to a value smaller than the rotation speed of the evaporator fan during normal control. For example, the fan rotation speed control unit 216 sets the rotation speed of the evaporator fan during low load control to the rotation speed of the evaporator fan at the time of the previous temperature control stop. Thereby, the degree of superheating can be brought closer to an appropriate value (for example, 3° C.) more quickly.

Further, the fan rotation speed control unit 216 sets the rotation speed of the condenser fan to a value larger than the rotation speed of the condenser fan during normal control. For example, the rotation speed is set to the maximum rotation speed of the air conditioner 1 that is determined to be operable in terms of motor performance, vibration, noise, etc. Thereby, the degree of supercooling can be made higher than 0° C. more quickly.

However, during heating operation, the fan rotation speed control section 216 does not increase the rotation speed of the condenser fan. This is because during heating operation, the temperature of the condenser (i.e., the heat exchanger 31 of the indoor unit 3) is not sufficiently warmed up immediately after operation, so increasing the rotation speed of the fan 32 causes the user to experience low temperature. This is because comfort is impaired by the wind, and even if the user is not immediately after driving, the dry air from the heater hits the user, impairing comfort. In this case, the fan rotation speed control unit 216 sets the rotation speed of the condenser fan during low load control to the rotation speed of the condenser fan at the time of the previous temperature control stop.

The fan rotation speed control unit 216 stores the rotation speed of the evaporator fan and the rotation speed of the condenser fan in the auxiliary storage device 203 when temperature control is stopped.

FIG. 7 is a flowchart showing the procedure of the expansion valve control process executed by the control circuit 20 of the outdoor unit 2. The control circuit 20 starts the expansion valve control process when the user performs an operation to start air conditioning operation (cooling operation or heating operation) via the remote controller 4. Alternatively, when the air conditioning operation on-timer time set by the user via the remote controller 4 has elapsed, the control circuit 20 starts the expansion valve control process.

Then, when the user performs an operation to stop the air conditioning operation via the remote control 4, or when the off timer time of the air conditioning operation has elapsed, the control circuit 20 stops the expansion valve control process.

(Step S101)
The control circuit 20 determines whether the temperature control start conditions are satisfied. As mentioned above, the temperature control start condition is when the difference between the room temperature and the set temperature (room temperature - set temperature) becomes larger than a predetermined value during cooling operation, and when the difference between the set temperature and the set temperature during heating operation This is a case where the difference from room temperature (set temperature - room temperature) becomes larger than a predetermined value.

If the temperature adjustment start conditions are satisfied (step S101; YES), the process of the control circuit 20 transitions to step S102. On the other hand, if the temperature adjustment start condition is not satisfied (step S101; NO), the control circuit 20 continues to perform the process of step S101.

(Step S102)
The control circuit 20 determines whether a low load condition is satisfied. As mentioned above, the low load condition is defined as when the time from stopping temperature control to starting the current temperature control is within a predetermined time (minutes), or when the difference between the room temperature and the set temperature (room temperature - set temperature) This is a case where the absolute value of temperature) is less than or equal to a predetermined value.

If the low load condition is satisfied (step S102; YES), the process of the control circuit 20 transitions to step S103. On the other hand, if the low load condition is not satisfied (step S102; NO), the process of the control circuit 20 transitions to step S104.

(Step S103)
The control circuit 20 sets the control mode for the operation of the air conditioner 1 to a low load mode. After that, the process of the control circuit 20 transitions to step S105.

(Step S104)
The control circuit 20 sets the control mode for the operation of the air conditioner 1 to the normal mode. After that, the process of the control circuit 20 transitions to step S110.

(Step S105)
The control circuit 20 starts low load control. That is, the control circuit 20 controls the opening degree of the expansion valve 25 based on the reference change value of the opening degree determined according to the evaporation temperature difference, the degree of subcooling, and the degree of superheating. The control circuit 20 also controls the rotation speed of the evaporator fan and the rotation speed of the condenser fan. After that, the process of the control circuit 20 transitions to step S106.

(Step S106)
The control circuit 20 determines whether the temperature control stop conditions are satisfied. As mentioned above, the temperature control stop condition is when the difference between the room temperature and the set temperature (room temperature - set temperature) becomes smaller than a predetermined value during cooling operation, and when the difference between the set temperature and the set temperature during heating operation becomes smaller. This is a case where the difference from room temperature (set temperature - room temperature) becomes smaller than a predetermined value.

If the temperature control stop condition is satisfied (step S106; YES), the process of the control circuit 20 transitions to step S107. On the other hand, if the temperature control stop condition is not satisfied (step S106; NO), the process of the control circuit 20 transitions to step S108.

(Step S107)
The control circuit 20 stops temperature control. Specifically, the operation of the compressor 21 is stopped. After that, the process of the control circuit 20 returns to step S101.

(Step S108)
The control circuit 20 determines whether the normal mode switching conditions are satisfied. As mentioned above, the normal mode switching condition is when the elapsed time from the start of low load control reaches a predetermined time (minutes), or when the discharge temperature reaches a predetermined temperature (for example, 50°C to This is the case when the temperature exceeds 60°C.

If the normal mode switching conditions are satisfied (step S108; YES), the process of the control circuit 20 transitions to step S109. On the other hand, if the normal mode switching condition is not satisfied (step S108; NO), the process of the control circuit 20 returns to step S106.

(Step S109)
The control circuit 20 switches the control mode for the operation of the air conditioner 1 from the low load mode to the normal mode. After that, the process of the control circuit 20 transitions to step S110.

(Step S110)
The control circuit 20 starts normal control. That is, the control circuit 20 controls the opening degree of the expansion valve 25 based on the discharge temperature. After that, the process of the control circuit 20 transitions to step S111.

(Step S111)
The control circuit 20 determines whether the temperature control stop conditions are satisfied. As mentioned above, the temperature control stop condition is when the difference between the room temperature and the set temperature (room temperature - set temperature) becomes smaller than a predetermined value during cooling operation, and when the difference between the set temperature and the set temperature during heating operation becomes smaller. This is a case where the difference from room temperature (set temperature - room temperature) becomes smaller than a predetermined value.

If the temperature control stop condition is satisfied (step S111; YES), the process of the control circuit 20 transitions to step S112. On the other hand, if the temperature adjustment stop condition is not satisfied (step S111; NO), the control circuit 20 continues to perform the process of step S111.

(Step S112)
The control circuit 20 stops temperature control. After that, the process of the control circuit 20 returns to step S101.

As explained above, the air conditioner 1 of the present embodiment adjusts the opening degree of the expansion valve 25 to a predetermined value according to the difference between the evaporator outlet temperature and the estimated target evaporation temperature during low load control. The opening degree of the expansion valve 25 is controlled based on the reference change value, the degree of subcooling, and the degree of superheating.

Specifically, the air conditioner 1 determines the change value of the opening degree of the expansion valve by multiplying the above reference change value by a correction coefficient determined based on the degree of subcooling and the degree of superheat. Since the magnitude of the absolute value of this correction coefficient is determined according to the magnitude of the degree of superheating, the degree of superheating is appropriately adjusted and the required air conditioning capacity is developed earlier than before. As a result, the temperature change in the room is reduced, and user comfort can be quickly ensured.

Further, since the opening/closing direction of the expansion valve 25 is determined depending on whether the degree of supercooling is greater than 0° C., the opening degree of the expansion valve 25 can be controlled more appropriately.

Furthermore, in the air conditioner 1 of the present embodiment, the opening degree of the expansion valve 25 is controlled to match the target evaporation temperature during low load control, so the time required to develop the necessary air conditioning capacity is further shortened. can do.

(Embodiment 2)
Next, a second embodiment of the present disclosure will be described. Note that in the following description, the same components and the like as those in Embodiment 1 are given the same reference numerals, and the description thereof will be omitted.

The hardware configuration of the air conditioner 1 of the second embodiment is the same as that of the first embodiment (see FIG. 1), and the hardware configuration of the control circuit 20 and the control circuit 30 is also the same as that of the first embodiment (see FIG. 1). (See Figures 2 and 3). However, in the second embodiment, the functional configuration of the control circuit 20 is different from that in the first embodiment.

FIG. 8 is a diagram showing the functional configuration of the control circuit 20 of this embodiment. As shown in FIG. 8, the control circuit 20 of the present embodiment includes a temperature control start/stop condition determining section 210, a timer 211, a control mode setting section 212, as characteristic functional configurations according to the present disclosure. It includes a control mode switching section 213, a valve opening control section 215A, and a fan rotation speed control section 216. These functional units are realized by the CPU 200 executing an air conditioning program stored in the auxiliary storage device 203, which is a program for air conditioning operation in the air conditioner 1 of this embodiment.

In the control circuit 20 of this embodiment, the temperature control start/stop condition determination section 210, timer 211, control mode setting section 212, control mode switching section 213, and fan rotation speed control section 216 are the same as in the first embodiment. Therefore, the explanation is omitted.

Like the valve opening degree control unit 215 of Embodiment 1, the valve opening degree control unit 215A controls the opening degree of the expansion valve 25 based on the discharge temperature during normal control. On the other hand, during low load control, the valve opening degree control section 215A controls the opening degree of the expansion valve 25 using another new method obtained from the above-mentioned knowledge. Specifically, the valve opening degree control unit 215A controls the opening degree of the expansion valve 25 based on a predetermined change value of the opening degree of the expansion valve 25 according to the degree of subcooling and the degree of superheating.

FIG. 9 shows the relationship between the degree of superheating (denoted as SH in the diagram) and the change value of the opening degree when the degree of supercooling (denoted as SC in the diagram) is greater than 0° C. (case 1). Further, FIG. 10 shows the relationship between the degree of superheating and the change value of the opening degree when the degree of supercooling is 0° C. (case 2). In addition, in FIGS. 9 and 10, the positive or negative sign of the change value indicates the direction in which the opening degree of the expansion valve 25 is changed. That is, when the change value is positive, the opening degree of the expansion valve 25 is changed to a more open direction, while when it is negative, it means that the opening degree of the expansion valve 25 is changed to a more narrowed direction.

In both case 1 shown in FIG. 9 and case 2 shown in FIG. There is. This is to achieve an appropriate degree of superheating more quickly.

Specifically, in case 1 (that is, when the degree of supercooling is greater than 0° C.), when the degree of superheating is 0° C., the change value is set to “−10”. This is because in order to increase the degree of superheating, it is necessary to reduce the opening degree of the expansion valve 25 by a large amount of change. Further, when the degree of superheat is greater than 0° C. and smaller than 3° C., the change value is set to “−2”. This is because while it is necessary to increase the degree of superheating, it is also necessary to reduce the amount of change in order to prevent the degree of superheating from becoming too large.

Furthermore, when the degree of superheat is greater than 3°C and less than 5°C, the change value is set to "2". This is because if the degree of superheat is too large, the evaporator cannot be used efficiently, so it is necessary to reduce the degree of superheat, but it is also necessary to reduce the amount of change in order to prevent the degree of superheat from becoming too small. For some reason.

Further, when the degree of superheat is higher than 5° C., the change value is set to “10”. This is because in order to reduce the superheat degree more quickly, the opening degree of the expansion valve 25 needs to be increased by a large amount of change.

Regarding case 2 in FIG. 10 (that is, when the degree of supercooling is 0° C.), the sign of the change value is opposite to the sign of the change value in case 1 of FIG. The rest is the same as case 1. Data corresponding to the contents of FIGS. 9 and 10 are stored in advance in the auxiliary storage device 203 of the control circuit 20.

Note that Case 1 requires that the degree of supercooling be greater than 0°C, and Case 2 requires that the degree of supercooling be 0°C, but this "0°C" is shown conceptually. , is actually set to a value larger than "0° C." in consideration of measurement errors of the refrigerant temperature sensors 26a to 26d, 33a to 33c and instability of the refrigerant state. Similarly, "0°C" in the condition that the degree of superheating is 0°C and the condition that the degree of superheating is greater than 0°C and less than 3°C is actually set to a value larger than "0°C". .

During low load control, the valve opening control section 215A first obtains the degree of supercooling and the degree of superheat. Then, the valve opening degree control unit 215A obtains a change value of the opening degree of the expansion valve 25 from the degree of subcooling and the degree of superheating. The valve opening controller 215A outputs a signal indicating the acquired change value (pulse) to the expansion valve 25.

As explained above, the air conditioner 1 of the present embodiment expands during low load control based on the change value of the opening degree of the expansion valve 25 that is predetermined according to the degree of subcooling and the degree of superheating. The opening degree of the valve 25 is controlled. Since the magnitude of the absolute value of this change value is determined according to the magnitude of the degree of superheating, the degree of superheating is appropriately adjusted and the required air conditioning capacity is developed earlier than before. As a result, the temperature change in the room is reduced, and user comfort can be quickly ensured.

Further, since the opening/closing direction of the expansion valve 25 is determined depending on whether the degree of supercooling is greater than 0° C., the opening degree of the expansion valve 25 can be controlled more appropriately.

Moreover, since the air conditioner 1 of this embodiment does not need to estimate the target evaporation temperature, it can be realized at low cost.

The present disclosure is not limited to each of the embodiments described above, and various changes can of course be made without departing from the gist of the present disclosure.

For example, the normal mode switching condition, which is a condition for switching the control mode from the low load mode to the normal mode, may be when the degree of supercooling becomes greater than 0°C.

Further, all or part of the functional units (see FIGS. 4 and 8) of the control circuit 20 included in the air conditioner 1 may be realized by dedicated hardware. The dedicated hardware is, for example, a single circuit, a composite circuit, a programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

The technical ideas related to each of the above-mentioned modifications may be realized individually, or may be realized in combination as appropriate.

This disclosure is capable of various embodiments and modifications without departing from its broad spirit and scope. Further, the embodiments described above are for explaining the present disclosure, and do not limit the scope of the present disclosure. In other words, the scope of the present disclosure is indicated by the claims rather than the embodiments. Various modifications made within the scope of the claims and the meaning of the disclosure equivalent thereto are considered to be within the scope of the present disclosure.

The present disclosure can be suitably employed in an air conditioner that air-conditions a building.

1 air conditioner, 2 outdoor unit, 3 indoor unit, 4 remote control, 5 refrigerant piping, 6 communication line, 20, 30 control circuit, 21 compressor, 22 four-way valve, 23, 31 heat exchanger, 24, 32 fan, 25 expansion valve, 26a to 26d, 33a to 33c refrigerant temperature sensor, 27, 34 air temperature sensor, 28, 35 humidity sensor, 200, 300 CPU, 201, 301 ROM, 202, 302 RAM, 203, 303 auxiliary storage device, 204, 304 input/output interface, 205, 305 bus, 210 temperature control start/stop condition determination unit, 211 timer, 212 control mode setting unit, 213 control mode switching unit, 214 target evaporation temperature estimation unit, 215, 215A valve opening degree Control unit, 216 Fan rotation speed control unit

Claims (11)

a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a ring through refrigerant piping;
a plurality of temperature sensors each measuring the temperature of the refrigerant circulating in the refrigerant pipe;
A control means for controlling the opening degree of the expansion valve,
When the control mode is a low load mode, the control means controls a reference change value of the opening determined according to a difference between the temperature of the refrigerant at the outlet of the evaporator and a target evaporation temperature, a degree of subcooling, and a degree of superheat. The air conditioner controls the opening degree of the expansion valve based on the temperature of the refrigerant discharged from the compressor when the control mode is the normal mode. a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a ring through refrigerant piping;
a plurality of temperature sensors each measuring the temperature of the refrigerant circulating in the refrigerant pipe;
A control means for controlling the opening degree of the expansion valve,
The control means controls the opening degree of the expansion valve based on the degree of subcooling and a change value of the degree of opening determined according to the value of the degree of superheating when the control mode is the low load mode; An air conditioner that controls the opening degree of the expansion valve based on the temperature of refrigerant discharged from the compressor when in normal mode. The air conditioner according to claim 1 or 2, wherein the control means sets the control mode to the low load mode when the compressor is started within a predetermined time after the compressor stops operating. Any one of claims 1 to 3, wherein the control means sets the control mode to the low load mode when the absolute value of the difference between the room temperature and the set temperature at the time of starting the compressor is less than or equal to a predetermined value. The air conditioner according to item 1. Any one of claims 1 to 4, wherein the control means switches the control mode from the low load mode to the normal mode when a predetermined time has elapsed after starting control in the low load mode. Air conditioners listed in section. Any one of claims 1 to 5, wherein the control means switches the control mode from the low load mode to the normal mode when the temperature of the refrigerant discharged from the compressor exceeds a predetermined temperature. Air conditioners listed in section. The air conditioner according to any one of claims 1 to 6, wherein the control means switches the control mode from the low load mode to the normal mode when the degree of supercooling becomes greater than 0°C. In the case of the low load mode, the control means sets the rotation speed of an evaporator fan, which is a fan that sends air to the evaporator, to a value smaller than the rotation speed of the evaporator fan in the normal mode. The air conditioner according to any one of claims 1 to 7. In the case of the low load mode, the control means sets the rotation speed of a condenser fan, which is a fan that sends air to the condenser, to a value larger than the rotation speed of the condenser fan in the normal mode. The air conditioner according to any one of claims 1 to 8. An air conditioner includes a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a ring through refrigerant piping,
When the control mode is the low load mode, the expansion is performed based on the reference change value of the opening determined according to the difference between the temperature of the refrigerant at the outlet of the evaporator and the target evaporation temperature, the degree of subcooling, and the degree of superheat. An expansion valve control method, comprising controlling the opening degree of the expansion valve, and controlling the opening degree of the expansion valve based on the temperature of refrigerant discharged from the compressor when the control mode is a normal mode. An air conditioner includes a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a ring through refrigerant piping,
When the control mode is a low load mode, the opening degree of the expansion valve is controlled based on the degree of subcooling and a change value of the opening degree determined according to the value of the degree of superheating, and when the control mode is the normal mode, An expansion valve control method, comprising controlling the opening degree of the expansion valve based on the temperature of refrigerant discharged from the compressor.

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