JP7637036B2 - Air conditioners - Google Patents

Description

This disclosure relates to an air conditioner.

Conventionally, air conditioners that condition air using a refrigerant circulating through a refrigerant circuit are known. The refrigerant circuit includes a heat source side heat exchanger, a user side heat exchanger, and a compressor for circulating the refrigerant. There is also known technology that temporarily stops the compressor when the indoor temperature reaches a predetermined target temperature, and operates the compressor again when the indoor temperature deviates from the predetermined target temperature (see, for example, Patent Document 1).

Patent No. 6072424

In the technology described in Patent Document 1, the compressor operating frequency is increased, maintained, or decreased depending on the temperature difference between the indoor temperature and the target temperature and the gradient of that temperature difference (the amount of change in the temperature difference per unit time), and the indoor temperature is controlled to approach the target temperature. For example, in a situation where the air conditioning load is low and the temperature difference is small, the compressor operating frequency is decreased to control the downward gradient of the temperature difference to be gentler. In addition, when the temperature difference between the indoor temperature and the target temperature falls below a predetermined threshold, the compressor is temporarily stopped and air conditioning is stopped.

However, in the technology described in Patent Document 1, the operating frequency of the compressor is controlled at regular time intervals (for example, every 5 minutes), so if the air conditioning load is low and the temperature difference is steeply downward, the temperature difference may fall below the threshold for temporarily stopping the compressor by the time the operating frequency of the compressor is next controlled, and the frequency with which this temporary stop and restart is repeated (hereinafter also referred to as the "start/stop frequency") may increase. A high frequency of starting and stopping the compressor places a heavy burden on the compressor.

The purpose of this disclosure is to reduce the frequency with which the compressor starts and stops.

(1) The present disclosure provides an air conditioner that performs air conditioning operation in a room,
A compressor;
A controller that controls an operating frequency of the compressor at a predetermined update interval in response to an air conditioning load in a room,
The controller shortens the update interval when a first condition indicating that the air conditioning load is low and a second condition indicating that the capacity of the compressor is high relative to the air conditioning load are satisfied.

According to the above configuration, when the air conditioning load is low and the compressor capacity is high relative to this air conditioning load, the interval (control interval) for updating the compressor's operating frequency is shortened, so that the compressor's operating frequency can be controlled before the compressor temporarily stops, suppressing temporary stops of the compressor. This makes it possible to suppress the frequency of starting and stopping the compressor.

(2) Preferably, the first condition includes a condition that a difference between an indoor temperature and an indoor target temperature is equal to or smaller than a first threshold value.
According to this configuration, it is possible to determine that the load is low when the difference between the indoor temperature, which indicates the substantial air conditioning load, and the indoor target temperature is equal to or less than the first threshold value.

(3) Preferably, the second condition includes an amount of change per unit time of the difference between the room temperature and the room target temperature being equal to or less than a second threshold value γ (where γ<0).
The amount of change per unit time in the difference between the indoor temperature and the indoor target temperature indicates the degree of compressor capacity relative to the air conditioning load, and in low-load conditions, the greater the amount of change in the negative direction, the higher the compressor capacity relative to the air conditioning load. Therefore, with the above configuration, it is possible to determine whether the compressor capacity is high relative to the air conditioning load.

(4) Preferably, the second condition includes that a change amount per unit time of a difference between the indoor temperature and the indoor target temperature is equal to or less than a second threshold value γ (where γ<0);
The first condition includes an estimation that the difference will become equal to or smaller than a first threshold within a predetermined time based on the amount of change after the second condition is satisfied.
According to the above configuration, after the second condition is satisfied, the amount of change per unit time in the difference between the indoor temperature and the target temperature is used to estimate the future progress of the difference, thereby shortening the update interval for the compressor's operating frequency early and preventing the difference from being reached at which the compressor is temporarily stopped.

(5) Preferably, after the first condition and the second condition are established, the controller maintains the shortened update interval until the first condition is lifted.
With this configuration, it is possible to suppress frequent switching between shortening and extending the update interval for the compressor operation frequency, which would otherwise cause the control to become unstable.

(6) Preferably, the controller extends the update interval when a predetermined third condition is met after the first condition is removed.

(7) Preferably, the third condition includes the passage of a predetermined time.

(8) Preferably, the third condition includes that the difference exceeds a third threshold value that is higher than the first threshold value.

1 is a schematic refrigerant circuit diagram of an air conditioner according to a first embodiment of the present disclosure. FIG. FIG. 2 is a block diagram of the air conditioner. 1A is a graph showing a schematic change over time in the difference between the indoor temperature and its target value during cooling operation; FIG. 1B is a graph showing a schematic change over time in the evaporation temperature of the refrigerant in the indoor heat exchanger and its target value; and FIG. 1C is a graph showing a schematic change over time in the operating frequency of the compressor. 4 is a graph showing an enlarged view of a main portion of the change over time in the difference between the room temperature and its target value during cooling operation. 10 is a flowchart showing a procedure for changing an update interval of an operation frequency of a compressor. 10 is a flowchart showing a procedure for changing an update interval of an operation frequency of a compressor. 13 is a graph showing an enlarged view of a main portion of the change over time in the difference between the indoor temperature and its target value during cooling operation in the second embodiment.

Hereinafter, an embodiment of an air conditioning system will be described in detail with reference to the accompanying drawings.
[First embodiment]
Fig. 1 is a schematic refrigerant circuit diagram of an air conditioner according to a first embodiment of the present disclosure. Fig. 2 is a block diagram of the air conditioner.
The air conditioner 1 adjusts the temperature of air in a room, which is a space to be air-conditioned, to a predetermined target temperature. The air conditioner 1 of this embodiment performs cooling and heating of the room. The air conditioner 1 has an outdoor unit 2, an indoor unit 3, and a refrigerant circuit 4 that circulates a refrigerant between the outdoor unit 2 and the indoor unit 3.

The refrigerant circuit 4 includes a compressor 12, a four-way switching valve 17, an outdoor heat exchanger (heat source heat exchanger) 14, a first expansion valve 13, a receiver 25, a second expansion valve 15, a liquid stop valve 19, an indoor heat exchanger (utilization heat exchanger) 11, a gas stop valve 20, an accumulator 16, and refrigerant pipes 10L and 10G that connect these.

The indoor unit 3 is equipped with an indoor heat exchanger 11 that constitutes the refrigerant circuit 4. The indoor heat exchanger 11 is a cross-fin tube type or microchannel type heat exchanger, and is used to exchange heat with the indoor air.

The indoor unit 3 further includes an indoor fan 21, an indoor controller 22, an indoor temperature sensor 23, a refrigerant temperature sensor 27, and a remote controller 24. The indoor fan 21 is configured to take in indoor air into the indoor unit 3, perform heat exchange between the taken-in air and the refrigerant flowing through the indoor heat exchanger 11, and then blow the air out into the room. The indoor fan 21 includes a motor whose operating frequency can be adjusted by inverter control.

The indoor controller 22 controls the operation of the indoor fan 21. The indoor controller 22 is configured with a microcomputer having a calculation unit such as a CPU and a storage unit such as a RAM or ROM. The indoor controller 22 may be equipped with an integrated circuit such as an FPGA or ASIC.

The indoor temperature sensor 23 measures the temperature inside the room. Information on the indoor temperature detected by the indoor temperature sensor 23 is sent to the indoor controller 22. The indoor controller 22 sends the received indoor temperature information to the outdoor controller 33, which will be described later.

The refrigerant temperature sensor 27 detects the temperature of the refrigerant (gas-liquid two-phase refrigerant) flowing through the indoor heat exchanger 11. When the indoor heat exchanger 11 is an evaporator, the temperature detected by the refrigerant temperature sensor 27 is the evaporation temperature of the refrigerant, and when the indoor heat exchanger 11 is a condenser, the temperature detected by the refrigerant temperature sensor 27 is the condensation temperature of the refrigerant. The refrigerant temperature information detected by the refrigerant temperature sensor 27 is transmitted to the indoor controller 22. The indoor controller 22 transmits the received refrigerant temperature information to the outdoor controller 33, which will be described later.

The remote controller 24 is used to perform operations such as inputting the start and stop of air conditioning operation, inputting the cooling and heating operation modes, and inputting the target temperature (set temperature) for the room. The remote controller 24 is equipped with a display unit that displays the operation mode and the set temperature. The remote controller 24 is connected to the indoor controller 22 by wire or wirelessly. Information input to the remote controller 24 is transmitted to the indoor controller 22 and the outdoor controller 33.

The outdoor unit 2 includes a compressor 12, a four-way switching valve 17, an outdoor heat exchanger 14, a first expansion valve 13, a receiver 25, a second expansion valve 15, a liquid stop valve 19, a gas stop valve 20, and an accumulator 16, which constitute the refrigerant circuit 4.

The compressor 12 draws in low-pressure gas refrigerant and discharges high-pressure gas refrigerant. The compressor 12 is equipped with a motor whose operating frequency can be adjusted by inverter control. The compressor 12 is a variable capacity type (variable capacity type) whose capacity (capacity) can be changed by inverter controlling the motor.

The four-way switching valve 17 reverses the flow of refrigerant in the refrigerant piping, switching the refrigerant discharged from the compressor 12 to either the outdoor heat exchanger 14 or the indoor heat exchanger 11. This allows the air conditioner 1 to switch between cooling operation and heating operation.

The outdoor heat exchanger 14 is, for example, a cross-fin tube type or a microchannel type heat exchanger. The outdoor heat exchanger 14 exchanges heat with the refrigerant using air as a heat source, condensing or evaporating the refrigerant. The first and second expansion valves 13, 15 are composed of motor-operated valves that can adjust the refrigerant flow rate, etc., and reduce the pressure of the refrigerant passing through them.

The receiver 25 stores excess refrigerant to allow an appropriate amount of refrigerant to circulate within the refrigerant circuit 4. The receiver 25 also functions as a gas-liquid separator that separates the liquid and gas phases of the refrigerant. One end of a bypass pipe 31 is connected to the receiver 25, and the other end of the bypass pipe 31 is connected to the refrigerant piping between the four-way switching valve 17 and the accumulator 16. The bypass pipe 31 is provided with a solenoid valve 26 that opens and closes the flow path.

The accumulator 16 temporarily stores the low-pressure refrigerant sucked into the compressor 12 and separates the gas refrigerant from the liquid refrigerant. The liquid shutoff valve 19 is a manually operated on-off valve. The gas shutoff valve 20 is also a manually operated on-off valve. The liquid shutoff valve 19 and the gas shutoff valve 20 block the flow of refrigerant in the refrigerant pipes 10L and 10G when closed, and allow the flow of refrigerant in the refrigerant pipes 10L and 10G when opened.

The outdoor unit 2 further includes an outdoor fan 18, temperature sensors 28, 29, 30, etc. The outdoor fan 18 includes a motor whose operating frequency can be adjusted by inverter control. The outdoor fan 18 is configured to take in outdoor air into the outdoor unit 2, exchange heat between the taken-in air and the refrigerant flowing through the outdoor heat exchanger 14, and then blow the air out of the outdoor unit 2.

The temperature sensors 28, 29, and 30 include refrigerant temperature sensors 28, 29, and 30 that detect the temperature of the refrigerant. The refrigerant temperature sensor 28 detects the temperature of the refrigerant (gas-liquid two-phase refrigerant) flowing through the outdoor heat exchanger 14. When the outdoor heat exchanger 14 is an evaporator, the temperature detected by the refrigerant temperature sensor 28 is the evaporation temperature of the refrigerant, and when the outdoor heat exchanger 14 is a condenser, the temperature detected by the refrigerant temperature sensor 28 is the condensation temperature of the refrigerant. The refrigerant temperature sensor 29 detects the temperature of the refrigerant sucked into the compressor 12. The refrigerant temperature sensor 30 detects the temperature of the refrigerant discharged from the compressor 12.

The refrigerant evaporation temperature and condensation temperature, the degree of superheating and subcooling, etc. of the refrigerant in the outdoor heat exchanger 14 and the indoor heat exchanger 11 are obtained using the detection values of the refrigerant temperature sensors 27, 28, 29, 30, and the operating frequency of the compressor 12 and the opening degrees of the first and second expansion valves 13, 15 are controlled to adjust these values. In addition, instead of the above control, a pressure sensor is provided on the suction side and the discharge side of the compressor 12, and the refrigerant evaporation temperature and condensation temperature, the degree of superheating and subcooling, etc. of the refrigerant in the outdoor heat exchanger 14 and the indoor heat exchanger 11 are obtained using the values of the pressure sensor and the refrigerant temperature sensors 29, 30, and the operating frequency of the compressor 12 and the opening degrees of the first and second expansion valves 13, 15 may be controlled to adjust these values.

The outdoor unit 2 further includes an outdoor controller 33. The outdoor controller 33 is configured with a microcomputer or the like having a calculation unit such as a CPU and a storage unit such as a RAM or ROM. The outdoor controller 33 performs a predetermined function by the calculation unit executing a program stored in the storage unit. The outdoor controller 33 may include an integrated circuit such as an FPGA or ASIC. The outdoor controller 33 is communicatively connected to the indoor controller 22 via a transmission line.

The detection values of the various sensors 28-30 installed in the outdoor unit 2 are input to the outdoor controller 33. The outdoor controller 33 and the indoor controller 22 control the operation of the compressor 12, expansion valves 13, 15, outdoor fan 18, indoor fan 21, etc. based on the detection values of the various sensors 27-30, etc.

When the air conditioner 1 having the above configuration performs cooling operation, the four-way switching valve 17 is held in the state shown by the solid line in FIG. 1. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 12 flows into the outdoor heat exchanger 14 through the four-way switching valve 17, and is condensed and liquefied by heat exchange with the outdoor air due to the operation of the outdoor fan 18. The liquefied refrigerant flows into the receiver 25 through the first expansion valve 13. The opening degree of the first expansion valve 13 is adjusted so that the degree of subcooling of the refrigerant flowing out of the outdoor heat exchanger 14 becomes a target value. In the receiver 25, the refrigerant is separated into a liquid phase and a gas phase, the liquid phase flows into the second expansion valve 15, and the gas phase flows into the accumulator 16 via the bypass pipe 31. The liquid phase of the refrigerant is depressurized by the second expansion valve 15 to become a gas-liquid two-phase refrigerant, flows into the indoor heat exchanger 11, and evaporates by heat exchange with the indoor air. The indoor air cooled by the evaporation of the refrigerant is blown into the room by the indoor fan 21 to cool the room. The opening degree of the second expansion valve 15 is adjusted so that the degree of superheat of the refrigerant flowing out of the indoor heat exchanger 11 is a target value. The refrigerant flowing out of the indoor heat exchanger 11 returns to the outdoor unit 2 through the gas refrigerant pipe 10G, passes through the four-way switching valve 17 and the accumulator 16, and is sucked into the compressor 12. The outdoor controller 33 compares the indoor temperature detected by the indoor temperature sensor 23 with the target temperature, and controls the operating frequency of the compressor 12 according to the difference between the two.

When the indoor temperature falls below the target temperature, the outdoor controller 33 temporarily stops the compressor 12 to stop the cooling operation, and when the indoor temperature exceeds the target temperature again, it drives the compressor 12 to resume the cooling operation. This makes it possible to prevent the indoor temperature from being cooled excessively.

When the air conditioner 1 performs heating operation, the four-way switching valve 17 is held in the state shown by the dashed line in FIG. 1. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 12 passes through the four-way switching valve 17 and flows into the indoor heat exchanger 11 of the indoor unit 3. In the indoor heat exchanger 11, the refrigerant exchanges heat with the indoor air and condenses and liquefies. The indoor air heated by the condensation of the refrigerant is blown into the room by the indoor fan 21, heating the room. The refrigerant liquefied in the indoor heat exchanger 11 returns to the outdoor unit 2 through the liquid refrigerant piping 10L and flows into the receiver 25 through the second expansion valve 15. The opening degree of the second expansion valve 15 is adjusted so that the degree of subcooling of the refrigerant flowing out of the indoor heat exchanger 11 is a target value. In the receiver 25, the refrigerant is separated into a liquid phase and a gas phase, the liquid phase flows into the first expansion valve 13, and the gas phase flows into the accumulator 16 through the bypass pipe 31. The liquid phase of the refrigerant is decompressed by the first expansion valve 13 to become a gas-liquid two-phase refrigerant, which flows into the outdoor heat exchanger 14 and evaporates through heat exchange with the outdoor air. The opening degree of the first expansion valve 13 is adjusted so that the degree of superheat of the refrigerant flowing out of the outdoor heat exchanger 14 becomes a target value. The refrigerant that has evaporated in the outdoor heat exchanger 14 is sucked into the compressor 12 via the four-way switching valve 17 and the accumulator 16. The outdoor controller 33 compares the indoor temperature detected by the indoor temperature sensor 23 with the target temperature, and controls the operating frequency of the compressor 12 according to the difference between the two.

When the indoor temperature rises above the target temperature, the outdoor controller 33 stops the heating operation by temporarily stopping the compressor 12, and when the indoor temperature falls below the target temperature again, it drives the compressor 12 to resume the heating operation. This makes it possible to prevent the indoor temperature from becoming excessively warm.

Figure 3(a) is a graph that shows the schematic change over time of the difference between the indoor temperature and its target value during cooling operation, Figure 3(b) is a graph that shows the schematic change over time of the evaporation temperature of the refrigerant in the indoor heat exchanger and its target value, and Figure 3(c) is a graph that shows the schematic change over time of the operating frequency of the compressor.

In FIG. 3(a), ΔTrs is the difference between the indoor temperature and the target temperature (= indoor temperature - target temperature (during cooling operation)). The difference ΔTrs is not an absolute value and can be either positive or negative. As described above, the outdoor controller 33 controls the operation of the compressor 12 based on the difference ΔTrs between the indoor temperature and the target temperature. Specifically, the outdoor controller 33 calculates the difference ΔTrs between the indoor temperature and the target temperature as shown in FIG. 3(a), calculates the target value TeS of the evaporation temperature Te of the refrigerant flowing through the indoor heat exchanger 11 so that this difference ΔTrs approaches a predetermined threshold value (first threshold value) α as shown in FIG. 3(b), and controls the operating frequency of the compressor 12 so that the evaporation temperature Te becomes the target value TeS as shown in FIG. 3(c).

For example, if the difference ΔTrs is greater than a predetermined threshold α, the outdoor controller 33 sets the target value TeS to further lower the evaporation temperature Te, and controls the compressor 12 to increase the operating frequency. Conversely, if the difference ΔTrs is less than the predetermined threshold α, the outdoor controller 33 sets the target value TeS to further increase or maintain the evaporation temperature Te, and controls the compressor 12 to lower or maintain the operating frequency. The threshold α can be set within a range of 0°C to 1.0°C, for example, and is preferably set to 0.5°C.

On the other hand, when the difference ΔTrs between the indoor temperature and the target temperature reaches a threshold value β that is lower than the threshold value α, the outdoor controller 33 stops the compressor 12 and temporarily stops the cooling operation to prevent the indoor temperature from being excessively cooled. After that, when the difference ΔTrs rises to a predetermined level or higher (for example, to the threshold value α), the outdoor controller 33 drives the compressor 12 again and resumes the cooling operation.

The outdoor controller 33 updates the operating frequency of the compressor 12 at predetermined time intervals. More specifically, the outdoor controller 33 controls the operating frequency of the compressor 12 at a predetermined update interval corresponding to the difference ΔTrs between the indoor temperature and the target temperature. In the example shown in Figures 3(a) to 3(c), between times t1 and t3, the outdoor controller 33 updates the operating frequency of the compressor 12 at a predetermined update interval ta.

As described above, when the difference ΔTrs reaches a predetermined threshold value β, the outdoor controller 33 stops the compressor 12 to temporarily stop the cooling operation, and when the difference ΔTrs rises again to a predetermined temperature, the outdoor controller 33 drives the compressor 12 to resume the cooling operation. If this operation causes the compressor 12 to switch between stopping and driving (on/off frequency) to increase, the burden on the compressor 12 increases, and there is a risk of reduced operating efficiency.

In the air conditioner 1 of this embodiment, in order to reduce the frequency of starting and stopping the compressor 12 as described above, the outdoor controller 33 executes a process to shorten the update interval of the operating frequency of the compressor 12. This process is described in detail below.

As shown in FIG. 3(a), when the difference ΔTrs is higher than the threshold value α, the outdoor controller 33 updates the operating frequency of the compressor 12 at every update interval ta. However, if the operating frequency of the compressor 12 is continued to be updated at the update interval ta even after the difference ΔTrs reaches the threshold value α, the difference ΔTrs will reach the threshold value β at the time before the next update (at time t4'), as shown by the two-dot chain line in FIG. 3(a), and control will be performed to temporarily stop the compressor 12. This may increase the frequency of starting and stopping the compressor 12, which may increase the burden on the compressor 12.

When the difference ΔTrs between the indoor temperature and the target temperature satisfies a predetermined condition, the outdoor controller 33 of the present embodiment executes a process of shortening the update interval of the operation frequency of the compressor 12. Specifically, the predetermined condition is as follows.
First condition: The air conditioning load is low (low-load operation)
Second condition: The compressor capacity is high relative to the air conditioning load (operating at excess capacity)

The low-load operation in the first condition refers to an operation in which a substitute value indicating the air conditioning load during cooling operation or heating operation satisfies a predetermined condition. For example, the magnitude of the air conditioning load of the air conditioner 1 can be indicated by the difference ΔTrs between the indoor temperature and the set temperature. This difference ΔTrs is the value obtained by subtracting the set temperature from the indoor temperature during cooling operation, and the value obtained by subtracting the indoor temperature from the set temperature during heating operation. The larger this difference ΔTrs is, the larger the air conditioning load is, and it is necessary to increase the air conditioning capacity until the indoor temperature reaches the target temperature. On the other hand, the smaller the difference ΔTrs is, the smaller the air conditioning load is, and not much air conditioning capacity is required to make the indoor temperature reach the target temperature. Therefore, in this embodiment, the first condition is set to be that the difference ΔTrs indicating the air conditioning load is equal to or less than a predetermined threshold (first threshold) α.

In the second condition, the excess capacity operation refers to an operation in which a proxy value indicating the capacity of the compressor 12 relative to the air conditioning load during cooling or heating operation satisfies a predetermined condition. For example, the capacity of the compressor 12 relative to the air conditioning load can be indicated by the amount of change in the difference ΔTrs per unit time. As shown in FIG. 4, this amount of change is the ratio of a predetermined time Δt to the change Δx in the difference ΔTrs at that time Δt, and corresponds to the slope A (Δx/Δt) of the graph. The smaller this slope A is, in other words, the greater the downward slope of the slope A, the higher the air conditioning capacity (excess capacity) relative to the air conditioning load. In this embodiment, the second condition is set to be that the slope A of the graph is equal to or less than a predetermined threshold (second threshold) γ (where γ<0).

In the example shown in FIG. 4, at time t3, the difference ΔTrs reaches the threshold value α, and therefore the first condition is satisfied. At time t3, the slope A (Δx/Δt) of the difference ΔTrs immediately before that is equal to or less than a predetermined threshold value γ, and therefore the second condition is satisfied. Therefore, the outdoor controller 33 shortens the update interval of the operating frequency of the compressor 12 from ta to tb. This makes it possible to update the operating frequency of the compressor 12 at time t4, before time t4' is reached, and causes the difference ΔTrs to start increasing before it reaches the threshold value β, thereby preventing the compressor 12 from temporarily stopping.

Figures 5 and 6 are flowcharts showing the process of changing the update interval of the compressor's operating frequency. An example of the process of changing the update interval of the compressor's 12 operating frequency is described below. In the following description, the normal operating state of the air conditioner 1 in which the first and second conditions are not satisfied (the operating state up to time t3 in Figure 3) is referred to as "standard operation", and the low-load and overcapacity operating state in which the first and second conditions are satisfied is referred to as "low-load operation". Note that Figures 5 and 6 only explain the process of changing the update interval of the compressor's 12 operating frequency, and do not include control of the compressor's 12 operating frequency.

In step S1 of FIG. 5, the outdoor controller 33 determines whether the operating state of the air conditioner 1 is standard operation. If the determination in step S1 is affirmative (Yes), the outdoor controller 33 proceeds to step S2, and if the determination is negative (No), the outdoor controller 33 proceeds to step S9 (see FIG. 6).

In step S2, the outdoor controller 33 acquires the indoor temperature, which is the detection value of the temperature sensor 23. Next, in step S3, the outdoor controller 33 acquires the indoor target temperature set by the remote controller 24. In step S4, the outdoor controller 33 calculates the difference ΔTrs between the acquired indoor temperature and the target temperature.

In step S5, the outdoor controller 33 determines whether the difference ΔTrs is equal to or less than a predetermined threshold value α as a first condition. If the determination in step S5 is affirmative (Yes), the outdoor controller 33 proceeds to step S6, and if the determination is negative (No), the outdoor controller 33 returns to step S1.

In step S6, the outdoor controller 33 calculates the amount of change in the difference ΔTrs per unit time immediately before the condition in step S5 is satisfied. In other words, the outdoor controller 33 calculates the ratio of a predetermined time Δt to the change Δx in the difference ΔTrs at that time Δt (the slope A of the graph (= Δx/Δt)). In step S7, the outdoor controller 33 determines whether the slope A is equal to or smaller than a predetermined threshold value γ as a second condition. If the determination in step S7 is affirmative (Yes), the outdoor controller 33 proceeds to step S8, and if the determination is negative (No), the outdoor controller 33 returns to step S1.

In step S8, the outdoor controller 33 shortens the update interval of the operating frequency of the compressor 12. For example, if the update interval is set to 30 seconds in standard operation, the update interval is set to a shorter time interval, for example 15 seconds, in low-load operation. For example, as shown in Figures 3 and 4, if the first and second conditions are satisfied at time t3, then at time t4 when the update interval tb has elapsed, the operating frequency of the compressor 12 is controlled according to the difference ΔTrs. As a result, the difference ΔTrs increases without reaching the threshold value β, and temporary suspension of the compressor 12 is suppressed.

After transitioning to low-load operation, in step S9 of FIG. 6, the outdoor controller 33 acquires the indoor temperature. Furthermore, in step S10, the outdoor controller 33 acquires the set temperature. Furthermore, in step S11, the outdoor controller 33 calculates the difference ΔTrs between the indoor temperature and the target temperature. In step S12, the outdoor controller 33 determines whether the difference ΔTrs exceeds a predetermined threshold value α. This determination is made to determine whether the first condition has been released.

If the outdoor controller 33 determines in step S12 that the first condition has been released, the process proceeds to step S13. Conversely, if the outdoor controller 33 determines in step S12 that the first condition has not been released, the process returns to step S9.

In step S13, the outdoor controller 33 determines whether a predetermined time tc has elapsed since the first condition was released. This condition is the third condition for returning from low-load operation to standard operation after the first condition is released. After the condition in step S13 is met, the outdoor controller 33 proceeds to step S14.

In step S14, the outdoor controller 33 performs a process to extend the update interval of the operating frequency of the compressor 12. Specifically, the outdoor controller 33 performs a process to return the update interval in low-load operation (e.g., 15 seconds) to the update interval in standard operation (e.g., 30 seconds). In the example shown in FIG. 3, the update interval is extended from tb to ta at time t8 after a predetermined time tc has elapsed since the difference ΔTrs exceeded the threshold value α.

By extending the update interval as described above, frequent control of the operating frequency of the compressor 12 is suppressed, enabling stable air conditioning operation.

The above describes the cooling operation, but the update interval can be changed in the heating operation as well. Specifically, the outdoor controller 33 calculates the difference ΔTrs (= target temperature - indoor temperature) between the indoor temperature and the indoor target temperature, obtains the target value of the condensation temperature in the indoor heat exchanger 11 according to this difference ΔTrs, and controls the operating frequency of the compressor 12 at a predetermined update interval (e.g., 30 seconds) so that the condensation temperature becomes the target value. When the difference ΔTrs reaches the threshold value α as the first condition, and the change amount of the difference ΔTrs per unit time becomes equal to or less than a predetermined threshold value γ as the second condition, the outdoor controller 33 performs low-load operation with the update interval of the operating frequency of the compressor 12 shortened. During low-load operation, when the difference ΔTrs exceeds the threshold value α and a predetermined time tc has passed, the outdoor controller 33 performs standard operation with the update interval of the operating frequency of the compressor 12 extended.

In the above embodiment, the update interval of the operating frequency of the compressor 12 is shortened by satisfying the second condition after the first condition is satisfied. However, the update interval of the operating frequency of the compressor 12 may be shortened by satisfying the first condition after the second condition is satisfied.

In the above embodiment, the outdoor controller 33 sets a target value for the evaporation temperature or condensation temperature in the indoor heat exchanger 11 according to the difference ΔTrs between the indoor temperature and the target temperature, and controls the operating frequency of the compressor 12 so that the evaporation temperature and condensation temperature reach the target value. However, the operating frequency of the compressor 12 may be controlled so that the difference ΔTrs between the indoor temperature and the target temperature falls within a predetermined range including a predetermined threshold value α.

[Second embodiment]
FIG. 7 is an enlarged graph showing a main part of the change over time of the difference between the indoor temperature and its target value during cooling operation in the second embodiment.
In the first embodiment, when the difference ΔTrs between the indoor temperature and the target temperature is equal to or less than a predetermined threshold α (the first condition is satisfied) and the amount of change in the difference ΔTrs per unit time is equal to or less than a predetermined threshold γ (the second condition is satisfied), the update interval of the operation frequency of the compressor 12 is shortened. In the second embodiment, as shown in Fig. 7, when the amount of change in the difference ΔTrs per unit time is equal to or less than a predetermined threshold γ (the second condition is satisfied) and it is estimated that the difference ΔTrs will become equal to or less than a predetermined threshold α by the time a predetermined time td has elapsed (the first condition is satisfied), the outdoor controller 33 shortens the update interval of the operation frequency of the compressor 12 from ta to tb.

Furthermore, in the first embodiment, when the difference ΔTrs exceeds the predetermined threshold value α, the outdoor controller 33 controls to increase the operating frequency of the compressor 12. However, in the second embodiment, when the first and second conditions are satisfied, even if the difference ΔTrs exceeds the threshold value α, the outdoor controller 33 controls to decrease or maintain the operating frequency of the compressor 12. Therefore, when the first and second conditions are satisfied, the difference ΔTrs is adjusted to be near the predetermined threshold value α and rarely falls below the threshold value β, which makes it possible to suppress temporary stops of the compressor 12 and suppress the frequency of starting and stopping.

[Other embodiments]
In the above embodiment, the timing for switching between the update interval ta and the update interval tb may be the point in time when the first condition and the second condition are satisfied, or the point in time when the update interval ta ends after the first condition and the second condition are satisfied. In the former case, the point in time when the first condition and the second condition are satisfied becomes the start point of the update interval tb, and the operation frequency of the compressor 12 is updated at this point in time. In the latter case, the point in time when the update interval ta ends becomes the start point of the update interval tb, and the operation frequency of the compressor 12 is updated at this point in time. The former is more preferable because the operation frequency of the compressor 12 is updated more quickly.

In the first embodiment, when the first condition is satisfied that the difference ΔTrs is equal to or less than a predetermined threshold value α, the second condition may be that the amount of change in the difference ΔTrs per unit time after the first condition is satisfied is equal to or less than a predetermined threshold value γ, rather than the amount of change in the difference ΔTrs per unit time before the first condition is satisfied.

In the first embodiment, the condition (third condition) for returning from low-load operation to standard operation is that a predetermined time tc has elapsed since the difference ΔTrs exceeded the predetermined threshold α, but this is not limited to the condition. For example, the condition (third condition) may be that the difference ΔTrs exceeds another threshold higher than the predetermined threshold α (for example, the upper limit of the dead band including the threshold α). The update interval ta in standard operation may be set to several types depending on the air conditioning load.

The difference ΔTrs is the value obtained by subtracting the target temperature from the indoor temperature during cooling operation, or the value obtained by subtracting the indoor temperature from the target temperature during heating operation, but it may also be a value obtained by slightly increasing or decreasing the said value by a correction value.

[Effects of the embodiment]
(1) The air conditioner 1 of the above embodiment includes a compressor 12 and a controller 33 that controls the operating frequency of the compressor 12 at a predetermined update interval in accordance with the air conditioning load in the room. The controller 33 shortens the update interval when a first condition indicating that the air conditioning load is low and a second condition indicating that the capacity of the compressor 12 is high relative to the air conditioning load are satisfied. Therefore, when the condition that the air conditioning load is low and the capacity of the compressor 12 is high relative to the air conditioning load is satisfied, the interval (control interval) for updating the operating frequency of the compressor 12 is shortened, and the operating frequency of the compressor 12 can be controlled before the compressor 12 is temporarily stopped. This makes it possible to suppress frequent temporary stopping and resumption of operation of the compressor 12.

(2) In the first embodiment described above, the first condition includes the difference ΔTrs between the indoor temperature and the indoor target temperature being equal to or less than the first threshold value α. In this way, when the difference ΔTrs between the indoor temperature and the indoor target temperature is equal to or less than the first threshold value α, it can be determined that the load is low.

(3) In the first embodiment described above, the second condition includes that the change per unit time of the difference ΔTrs between the indoor temperature and the indoor target temperature is equal to or less than the second threshold value γ (where γ<0). In this way, the change per unit time of the difference ΔTrs between the indoor temperature and the indoor target temperature indicates the degree of the capacity of the compressor 12 relative to the air conditioning load, and under low load conditions, the greater the change in the negative direction, the higher the capacity of the compressor 12 relative to the air conditioning load. Therefore, with the above configuration, it can be determined that the capacity of the compressor 12 is high relative to the air conditioning load.

(4) In the second embodiment, the second condition includes that the amount of change per unit time of the difference ΔTrs between the indoor temperature and the indoor target temperature is equal to or less than the second threshold value γ (where γ<0), and the first condition includes that after the second condition is satisfied, it is estimated that the difference ΔTrs will be equal to or less than the first threshold value α within a predetermined time td based on the amount of change. According to this configuration, after the second condition is satisfied, the amount of change in the difference ΔTrs between the indoor temperature and the target temperature is used to estimate the future course of the difference ΔTrs, thereby shortening the update interval of the operating frequency of the compressor 12 early and preventing the difference ΔTrs from reaching the threshold value β for temporarily stopping the compressor 12.

(5) In the above embodiment, after the first condition and the second condition are met, the controller 33 maintains the shortened update interval until the first condition is released. This prevents the update interval of the operating frequency of the compressor 12 from frequently switching between shortening and extending, resulting in unstable control.

(6) In the above embodiment, the controller 33 extends the update interval when a predetermined third condition is satisfied after the first condition is released. Therefore, after the first condition is released, the update interval can be maintained in a shortened state until the third condition is satisfied, and frequent switching between shortening and extending the update interval of the operating frequency of the compressor 12 can be suppressed, which causes control instability.

(7) In the above embodiment, the third condition includes the passage of a predetermined time tc after the first condition is released. Alternatively, the third condition includes the difference ΔTrs exceeding a third threshold value that is higher than the first threshold value α. In either case, the update interval is extended after a certain amount of time has elapsed after the first condition is released, and frequent switching between shortening and extending the update interval for the operating frequency of the compressor 12 can be suppressed.

The present disclosure is not limited to the above examples, but is intended to include all modifications within the scope and meaning equivalent to the claims.

1: Air conditioner 12: Compressor 33: Outdoor controller ta: Update interval tb: Update interval α: Threshold (first threshold)
γ: Threshold (second threshold)

Claims (5)

An air conditioner that performs indoor air conditioning operation,
A compressor (12);
a controller (33) that controls an operating frequency of the compressor (12) at a predetermined update interval in response to an air conditioning load in a room;
the controller (33) shortens the update interval when a first condition indicating that the air conditioning load is low and a second condition indicating that the capacity of the compressor is high relative to the air conditioning load are satisfied;
The second condition includes that a change amount per unit time of a difference (ΔTrs) between the indoor temperature and the indoor target temperature is equal to or less than a second threshold (γ) (where γ<0);
The first condition includes a condition that a difference (ΔTrs) between an indoor temperature and an indoor target temperature is equal to or smaller than a first threshold (α). An air conditioner that performs indoor air conditioning operation,
A compressor (12);
a controller (33) that controls an operating frequency of the compressor (12) at a predetermined update interval in response to an air conditioning load in a room;
the controller (33) shortens the update interval when a first condition indicating that the air conditioning load is low and a second condition indicating that the capacity of the compressor is high relative to the air conditioning load are satisfied;
The second condition includes that a change amount per unit time of a difference (ΔTrs) between the indoor temperature and the indoor target temperature is equal to or less than a second threshold (γ) (where γ<0);
The air conditioner, wherein the first condition includes an estimation that the difference (ΔTrs) will be equal to or less than a first threshold (α) within a predetermined time (td) based on the amount of change after the second condition is satisfied. The air conditioner according to claim 1 or 2, wherein the controller (33) maintains the shortened update interval after the first condition and the second condition are met until the first condition is lifted. The controller (33) extends the update interval when a predetermined third condition is satisfied after the first condition is released,
The air conditioner according to claim 3 , wherein the third condition includes the passage of a predetermined time (tc). the controller (33) extends the update interval when, after the first condition and the second condition are satisfied, the first condition is released and a predetermined third condition is subsequently satisfied;
The air conditioner according to claim 1 or 2, wherein the third condition includes that the difference (ΔTrs) exceeds a third threshold value that is higher than the first threshold value (α).

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