Air conditioner and control method

Abstract

This multi-type air conditioner comprises one outdoor unit, a plurality of indoor units, and an expansion valve that is provided to the outdoor unit or the indoor units and that controls the amount of refrigerant flowing to the indoor units. In each of the indoor units, when detection temperature detected by an indoor unit temperature sensor reaches a preset temperature for the indoor unit, the indoor unit stops the driving of an indoor unit fan and drives the indoor unit fan only for a predetermined time at a preset time interval, and changes the time interval on the basis of the detection temperature detected by the indoor unit temperature sensor when the indoor unit fan was driven for the predetermined time and of a detection temperature detected by an outdoor unit temperature sensor.

Description

Air conditioner and control method

[0001] The present disclosure relates to an air conditioner and a control method.

[0002] In recent years, in response to energy and environmental issues, highly airtight and insulated homes with low air conditioning loads have become increasingly popular. Generally, highly airtight and insulated homes are homes with improved insulation performance, and are designed to suppress the inflow of heat load from the outside in the summer and the outflow of heat load from inside the room to the outside in the winter. On the other hand, in order to improve air quality in indoor spaces, such as viruses and carbon dioxide concentrations, there has been an increase in the use of mechanical ventilation and window opening to periodically introduce outside air into indoor spaces.

[0003] In a multi-type air conditioner in which multiple indoor units are connected to a single outdoor unit, the outdoor unit acquires information such as operating status from each indoor unit during operation and adjusts the operating conditions of components in the refrigeration cycle, such as the compressor and electronic expansion valve. Generally, the outdoor unit continues to operate the compressor if one of the connected indoor units is operating but has not yet reached the set temperature (thermo-on). In such a case, the connected indoor unit fully closes its electronic expansion valve when operating in cooling mode and slightly opens its electronic expansion valve when operating in heating mode. In addition, the indoor unit in thermo-off mode stops its indoor unit fan, but detects the indoor temperature by driving the indoor unit fan at regular intervals to check the difference between the set temperature and the indoor temperature using a room temperature sensor installed inside the indoor unit (see, for example, Patent Documents 1 and 2).

[0004] JP 2021-156513 A JP 2005-24111 A

[0005] As mentioned above, when an indoor unit reaches the set temperature during heating operation and is turned off, its electronic expansion valve is slightly open. Therefore, if other indoor units are turned on, a small amount of refrigerant will flow into the thermo-off indoor unit, causing the indoor heat exchanger to overheat. In this case, if the thermo-off indoor unit drives its indoor unit fan at regular intervals to detect the indoor temperature, it will exert its heating capacity on the indoor space, which may cause the indoor temperature to rise above the set temperature.

[0006] For example, the above-mentioned cited documents 1 and 2 disclose a technology in which an indoor unit with its thermostat turned off uses a room temperature sensor installed inside to detect the indoor temperature while the indoor unit fan is running, and changes the time interval for running the indoor unit fan based on the detected indoor temperature (for example, lengthens the time interval), thereby suppressing a rise in the indoor temperature.

[0007] However, changing the time interval for driving the indoor unit fan based only on the indoor temperature does not address the drop in indoor temperature caused by the intake of outside air into the indoor space through periodic mechanical ventilation or window ventilation, or the difference in outside air temperature between daytime and nighttime, and there is a concern that indoor comfort may decrease. Also, if a sensor that detects the indoor ambient temperature were to be placed outside the indoor unit, separate from the room temperature sensor installed inside the indoor unit, it would be possible to eliminate the periodic operation of the indoor unit fan and suppress the rise in indoor temperature, but this would result in a problem of increased product costs.

[0008] The present disclosure has been made in consideration of the above-mentioned circumstances, and one of its objects is to provide an air conditioner and a control method that can realize air conditioning control that responds to changes in the indoor and outdoor temperature environment at low cost and prevent a decrease in indoor comfort in a multi-type air conditioner in which multiple indoor units are connected to a single outdoor unit.

[0009] The air conditioner of the present disclosure is a multi-type air conditioner comprising one outdoor unit equipped with an outdoor heat exchanger, an outdoor unit fan, a compressor, and an outdoor unit temperature sensor, multiple indoor units equipped with indoor heat exchangers, indoor unit fans, and indoor unit temperature sensors, and an expansion valve provided in the outdoor unit or the indoor unit to control the amount of refrigerant flowing to the indoor unit, wherein the indoor unit is equipped with an indoor unit control unit that, when the detected temperature detected by the indoor unit temperature sensor reaches the set temperature of the indoor unit, stops driving the indoor unit fan and drives the indoor unit fan for only a predetermined time at a preset time interval, and changes the time interval based on the detected temperature detected by the indoor unit temperature sensor when the indoor unit fan is driven for the predetermined time and the detected temperature detected by the outdoor unit temperature sensor.

[0010] In addition, a control method for an air conditioner according to the present disclosure is a control method for a multi-type air conditioner having one outdoor unit equipped with an outdoor heat exchanger, an outdoor unit fan, a compressor, and an outdoor unit temperature sensor, multiple indoor units equipped with indoor heat exchangers, indoor unit fans, and indoor unit temperature sensors, and an expansion valve provided in the outdoor unit or the indoor units to control the amount of refrigerant flowing to the indoor units, and includes the steps of: when the detected temperature detected by the indoor unit temperature sensor reaches the set temperature of the indoor unit, stopping the operation of the indoor unit fan and operating the indoor unit fan for only a predetermined time at a preset time interval; and changing the time interval based on the detected temperature detected by the indoor unit temperature sensor when the indoor unit fan is operated for the predetermined time and the detected temperature detected by the outdoor unit temperature sensor.

[0011] According to the present disclosure, in a multi-type air conditioner in which multiple indoor units are connected to one outdoor unit, air conditioning control that responds to changes in the indoor and outdoor temperature environment can be achieved at low cost, thereby preventing a decrease in indoor comfort.

[0012] A configuration diagram showing a refrigerant circuit of an air conditioner according to an embodiment. A diagram showing the flow of refrigerant during cooling operation of an air conditioner according to an embodiment. A diagram showing the flow of refrigerant during heating operation of an air conditioner according to an embodiment. A schematic diagram showing a first example of state transitions during heating operation of a conventional air conditioner. A schematic diagram showing a second example of state transitions during heating operation of a conventional air conditioner. A schematic diagram showing an example of state transitions during heating operation of an air conditioner according to an embodiment.

[0013] Hereinafter, an embodiment will be described with reference to the drawings. [Air Conditioner Configuration] Fig. 1 is a configuration diagram showing a refrigerant circuit of an air conditioner according to this embodiment. The air conditioner 1 shown in this figure shows the refrigerant circuit of a general multi-type air conditioner. The air conditioner 1 includes one outdoor unit 10 and three indoor units 20 (indoor unit 20A, indoor unit 20B, and indoor unit 20C). Here, since the indoor units 20A, indoor unit 20B, and indoor unit 20C each have the same configuration, they will be referred to as indoor units 20 unless otherwise specified. For example, each of the three indoor units 20 is installed in a different indoor space and is connected to a single outdoor unit 10 installed outdoors via refrigerant piping 30.

[0014] In this embodiment, an example configuration in which the outdoor unit 10 is connected to three indoor units 20 will be described, but the number of indoor units 20 connected to the outdoor unit 10 may be two, or four or more.

[0015] 1 , the outdoor unit 10 includes an outdoor heat exchanger 11, an outdoor unit fan 12, a compressor 13, a four-way valve 14, an electronic expansion valve 15, an outdoor air temperature sensor 16, and an outdoor unit control unit 17. The indoor unit 20 includes an indoor heat exchanger 21, an indoor unit fan 22, a room temperature sensor 26, and an indoor unit control unit 27.

[0016] The outdoor heat exchanger 11, compressor 13, four-way valve 14, and electronic expansion valve 15 of the outdoor unit 10 are connected to the indoor heat exchanger 21 of the indoor unit 20 via refrigerant piping 30, and the cooling operation and heating operation can be switched by switching the four-way valve 14 to change the refrigerant circulation direction.

[0017] The electronic expansion valve 15 has a role of reducing the pressure by the throttling process and adjusting the amount of refrigerant delivered to the indoor unit 20. The electronic expansion valve 15 may be provided in the indoor unit 20 instead of the outdoor unit 10.

[0018] The outdoor air temperature sensor 16 is provided in the outdoor unit 10 and detects the outdoor air temperature. The room temperature sensor 26 is disposed inside the indoor unit 20. The outdoor unit control unit 17 is provided to control each part of the outdoor unit 10 and to communicate with the indoor unit 20. The indoor unit control unit 27 is provided to control each part of the indoor unit 20 and to communicate with the outdoor unit 10.

[0019] 2 is a diagram showing the flow of refrigerant during cooling operation of the air conditioner according to this embodiment. During cooling operation, the refrigerant sealed in the refrigerant circuit is compressed into a high-temperature, high-pressure gas by the compressor 13, and the compressed gas refrigerant is transported to the outdoor heat exchanger 11 through the four-way valve 14. The transported gas refrigerant releases heat to the outside in the outdoor heat exchanger 11, where it is condensed and liquefied. To efficiently carry out the condensation process, the outdoor unit fan 12 blows air, thereby dissipating heat to the outside of the outdoor unit 10. The refrigerant liquefied in the outdoor heat exchanger 11 is reduced in pressure from a high-temperature, high-pressure liquid refrigerant to a low-pressure liquid refrigerant through the throttling process of the electronic expansion valve 15, and is transported to the indoor unit 20 through the refrigerant piping 30.

[0020] The transported low-pressure liquid refrigerant absorbs heat from the indoor air and evaporates into a gaseous state in the indoor heat exchanger 21. To ensure efficient evaporation, the indoor unit fan 22 blows air and absorbs heat. The refrigerant that has become a gaseous state in the indoor heat exchanger 21 is transported to the outdoor unit 10 through the refrigerant piping 30 and returns to the compressor 13 through the four-way valve 14.

[0021] In the example shown in Figure 2, of the three indoor units 20, indoor unit 20A is operating in a state where the indoor temperature has not reached the set temperature (thermo on), indoor unit 20B is operating in a state where the indoor temperature has reached the set temperature (thermo off), and indoor unit 20C is not operating.

[0022] In cooling operation, the outdoor unit 10 operates to circulate the refrigerant if there is at least one thermo-on indoor unit 20. In cooling operation, the outdoor unit 10 circulates the refrigerant through the refrigerant circuit to the thermo-on indoor unit 20A, but prevents the refrigerant from flowing into the thermo-off indoor unit 20B or the stopped indoor unit 20C by fully closing the electronic expansion valves 15 of the refrigerant circuits of each.

[0023] 3 is a diagram showing the flow of refrigerant during heating operation of the air conditioner according to this embodiment. During heating operation, the outdoor unit 10 uses the four-way valve 14 to switch the refrigerant circulation path in the refrigeration cycle from cooling operation to heating operation.

[0024] During heating operation, the refrigerant sealed in the refrigerant circuit is compressed into a high-temperature, high-pressure gas by the compressor 13, and the compressed gas refrigerant is transported to the indoor unit 20 through the refrigerant piping 30. The transported high-temperature, high-pressure gas refrigerant releases heat to the outside in the indoor heat exchanger 21, where it is condensed and liquefied. To efficiently carry out the condensation process, the indoor unit fan 22 is used to blow air, and waste heat is released to the outside of the indoor unit 20.

[0025] The liquefied refrigerant is transported to the outdoor unit 10 through the refrigerant pipe 30, where it is reduced in pressure from high-temperature, high-pressure liquid refrigerant to low-pressure liquid refrigerant through the throttling process of the electronic expansion valve 15. This low-pressure liquid refrigerant absorbs heat from the surrounding outside air in the outdoor heat exchanger 11 and evaporates, becoming gaseous. To ensure efficient evaporation, the outdoor unit fan 12 blows air and absorbs heat. The gaseous refrigerant returns to the compressor 13 through the four-way valve 14.

[0026] In the example shown in Figure 3, as in the example shown in Figure 2, of the three indoor units 20, indoor unit 20A is operating in a state where the indoor temperature has not reached the set temperature (thermo on), indoor unit 20B is operating in a state where the indoor temperature has reached the set temperature (thermo off), and indoor unit 20C is not operating.

[0027] In heating operation, the outdoor unit 10 operates to circulate the refrigerant if there is at least one indoor unit 20 with the thermostat turned on. In heating operation, the outdoor unit 10 circulates the refrigerant through the refrigerant circuit to the indoor unit 20A with the thermostat turned on, but the refrigerant also flows from the outdoor unit 10 into the indoor unit 20B with the thermostat turned off and the indoor unit 20C that is stopped.

[0028] If the refrigerant flowing into the indoor heat exchanger 21 of the indoor unit 20B with its thermostat off and the indoor unit 20C that is stopped is not returned to the compressor 13 of the outdoor unit 10, the compressor 13 that generates the high-temperature, high-pressure refrigerant will not operate normally, resulting in a lack of stable air conditioning capacity. This could also lead to a malfunction of the compressor 13. Therefore, the electronic expansion valves 15 in the refrigerant circuits of the indoor unit 20B with its thermostat off and the indoor unit 20C that is stopped are slightly opened to return the refrigerant that flowed into the indoor heat exchanger 21 to the outdoor unit 10. As a result, during heating operation, the indoor heat exchangers 21 of the indoor unit 20B with its thermostat off and the indoor unit 20C that is stopped are in a heated state. During cooling operation, the electronic expansion valves 15 are fully closed, preventing the refrigerant from being transported to the indoor unit 20, and the refrigerant remains in the outdoor unit 10 (outdoor heat exchanger).

[0029] Here, the indoor unit 20A with the thermostat on drives the indoor unit fan 22 to provide air conditioning capacity to the indoor space, but the indoor unit 20B with the thermostat off stops the indoor unit fan 22 but continues to drive the indoor unit fan 22 periodically to detect the indoor temperature. This is because the room temperature sensor 26 is located inside the indoor unit 20, and so in order to correctly detect the indoor temperature, it is necessary to drive the indoor unit fan 22 to introduce air from the indoor space into the indoor unit 20. In conventional control, the indoor unit 20B with the thermostat off stops the indoor unit fan 22 and then drives the indoor unit fan 22 at regular time intervals to detect the indoor temperature.

[0030] 4 is a schematic diagram showing a first example of state transitions during heating operation of a conventional air conditioner. In this diagram, the horizontal axis represents time t, and the state transitions of the outdoor unit 10 and three indoor units 20 are shown when the air conditioner 1 starts heating operation at time t0. Here, the state transitions of "indoor unit (thermo on)," "indoor unit (thermo off)," "indoor unit (stopped)," and "outdoor unit" are shown in order from the top to the bottom.

[0031] "Outdoor unit" shows the state transition of the outdoor unit 10 (corresponding to the outdoor unit 10 in FIG. 3) that started heating operation at time t0. The outdoor unit 10 starts heating operation at time t0 (outdoor operation ON) and starts operation of the compressor 13 (compressor ON). Furthermore, "indoor unit (stopped)" shows the state transition of the indoor unit 20 (corresponding to the indoor unit 20C in FIG. 3) that has started heating operation as the air conditioner 1 but is stopped.

[0032] "Indoor unit (thermo on)" shows the state transition of the indoor unit 20 (corresponding to indoor unit 20A in FIG. 3 ) that is operating in a state where the indoor temperature has not reached the set temperature (thermo on) since heating operation started at time t0. When the indoor unit 20 starts heating operation at time t0 (indoor operation ON), it operates in thermo on mode and drives (ON) the indoor unit fan 22. As the refrigerant circulates through the refrigerant circuit during heating operation, the temperature of the indoor heat exchanger 21 rises. The heat from the indoor heat exchanger 21 is released to the outside (indoor space) by the airflow of the indoor unit fan 22, and the indoor temperature gradually rises and approaches the set temperature. Because the indoor temperature has not reached the set temperature, thermo on operation continues.

[0033] "Indoor unit (thermo-off)" shows the state transition of the indoor unit 20 (corresponding to indoor unit 20B in FIG. 3 ) that starts heating operation at time t0, operates with thermo-on, and then operates with thermo-off after time t1 because the indoor temperature reaches the set temperature. When the indoor unit 20 starts heating operation at time t0 (indoor operation ON), it operates with thermo-on and drives (ON) the indoor unit fan 22. As the refrigerant circulates through the refrigerant circuit during heating operation, the temperature of the indoor heat exchanger 21 rises. Heat from the indoor heat exchanger 21 is released to the outside (indoor space) by the airflow of the indoor unit fan 22, and the indoor temperature gradually rises and approaches the set temperature. As the indoor temperature reaches the set temperature at time t1, the indoor unit 20 transitions to thermo-off operation.

[0034] Although the indoor unit 20 stops the indoor unit fan 22 during thermo-off operation, it periodically drives the indoor unit fan 22 at regular time intervals to continue detecting the indoor temperature. The indoor unit fan 22 requires a certain amount of time (e.g., about 3 minutes) each time it is driven to discharge air stagnating near the room temperature sensor 26 located inside the indoor unit 20 and then accurately detect air at the temperature of the indoor space by taking it in again. For example, as shown in the figure, the indoor unit fan 22 is intermittently driven at regular time intervals H to detect the indoor temperature (e.g., the indoor temperatures at points A, B, C, and D), and then the indoor unit fan 22 is stopped.

[0035] As described above, when at least one of the indoor units 20 connected to the outdoor unit 10 is operating with the thermostat on, the outdoor unit 10 operates. Therefore, during heating operation, refrigerant also flows into the indoor heat exchanger 21 of the indoor unit 20 whose thermostat is off or stopped, causing the indoor unit 10 to enter a heated state. When the indoor unit 20 is stopped, the indoor unit fan 22 is stopped and no heating capacity is exerted. However, when the indoor unit 20 is operating with the thermostat off, the heating capacity is exerted each time the indoor unit fan 22 is intermittently driven. While the indoor temperature drops due to ventilation from outside and heat radiation from the building while the indoor unit fan 22 is stopped, the indoor temperature gradually rises as the indoor unit fan 22 is periodically driven (for example, the indoor temperature at points A, B, and C in the figure gradually rises), widening the gap with the set temperature and reducing comfort.

[0036] As a countermeasure against the gradual rise in indoor temperature when the indoor unit 20 is operating with the thermostat off, a technique has been disclosed in the past in which the time interval for intermittently driving the indoor unit fan 22 is lengthened when a rise in indoor temperature is detected.

[0037] Fig. 5 is a schematic diagram showing a second example of state transitions during heating operation of a conventional air conditioner. The state transitions described with reference to Fig. 5 differ from those in Fig. 4 only in the control when the indoor unit 20 is operating with the thermostat off, and the other state transitions are the same. Therefore, only the state transitions of the "indoor unit (thermo-off)" and the "outdoor unit" related to that control are shown, and the state transitions of the "indoor unit (thermo-off)" and "indoor unit (stopped)" are not shown.

[0038] At time t1, when the indoor temperature reaches the set temperature, the indoor unit 20 transitions to thermo-off operation and intermittently drives the indoor unit fan 22. While the indoor unit 20 keeps the driving time of the indoor unit fan 22 constant in order to detect the indoor temperature, it lengthens the time interval when intermittently driving the indoor unit fan 22 (i.e., the stop time of the indoor unit fan 22) based on the difference from the set temperature, etc., thereby suppressing a rise in the indoor temperature.

[0039] In the illustrated example, for example, when the indoor unit 20 first transitions to thermo-off operation, it drives the indoor unit fan 22 intermittently at preset time intervals (H1, H2). However, since the indoor temperature at points A and B shown in the figure has risen above the set temperature, the subsequent time intervals (H3, H4) of intermittent driving are lengthened, and the stop time of the indoor unit fan 22 is extended.

[0040] However, this control does not reflect the effect on the indoor temperature of changes in the external temperature load (for example, changes in the outdoor temperature between day and night, changes in the weather, etc.). Therefore, if the indoor unit fan 22 is stopped for a long time, even if the indoor temperature drops due to the effect of changes in the external temperature load, the decrease in the indoor temperature may not be detected and the indoor temperature may fall below the set temperature (for example, point D).

[0041] Therefore, in this embodiment, the indoor unit 20 with the thermostat off changes the time interval (i.e., the stop time for which the indoor unit fan 22 is stopped) when intermittently driving the indoor unit fan 22 based not only on the indoor temperature detected by the room temperature sensor 26 but also on the outdoor air temperature detected by the outdoor air temperature sensor 16 mounted on the outdoor unit 10. Below, a detailed description is given of the control of the indoor unit 20 with the thermostat off in the multi-type air conditioner 1 according to this embodiment.

[0042] When the indoor temperature detected by the room temperature sensor 26 arranged inside the indoor unit 20 reaches the set temperature, the indoor unit control unit 27 of the indoor unit 20 transitions to thermal-off operation, stops driving the indoor unit fan 22, and performs intermittent driving. In intermittent driving, the indoor unit control unit 27 drives the indoor unit fan 22 only for a predetermined time (e.g., 3 minutes) at preset time intervals.

[0043] In addition, the indoor unit control unit 27 changes the time interval (i.e., the stop time for which the indoor unit fan 22 is stopped) when intermittently driving the indoor unit fan 22 based on the indoor temperature detected by the room temperature sensor 26 when the indoor unit fan 22 is driven for a predetermined time and the outdoor air temperature detected by the outdoor air temperature sensor 16 mounted on the outdoor unit 10.

[0044] For example, the indoor unit control unit 27 changes the time interval for intermittently driving the indoor unit fan 22 based on the change in the indoor temperature detected by the room temperature sensor 26 and the change in the outdoor air temperature detected by the outdoor air temperature sensor 16 at each predetermined time when the indoor unit fan 22 is driven.

[0045] Here, the change in indoor temperature detected by the room temperature sensor 26 at each specified time is, for example, the difference between the indoor temperature detected by the room temperature sensor 26 when the indoor unit fan 22 was driven at the specified time this time and the indoor temperature detected by the room temperature sensor 26 when the indoor unit fan 22 was driven at the specified time last time.

[0046] The indoor unit control unit 27 also acquires the outdoor air temperature detected by the outdoor air temperature sensor 16 at regular intervals from the outdoor unit 10, and calculates the change in outdoor air temperature based on the acquired outdoor air temperature at regular intervals. For example, the change in outdoor air temperature is the difference in outdoor air temperature at regular intervals.

[0047] Fig. 6 is a schematic diagram showing an example of state transitions during heating operation of the air conditioner according to this embodiment. The state transitions described with reference to Fig. 5 differ from Figs. 4 and 5 only in the control when the indoor unit 20 is operating with the thermostat off, and the other state transitions are the same. Therefore, only the state transitions of the "indoor unit (thermo-off)" and the "outdoor unit" related to that control are shown, and the state transitions of the "indoor unit (thermo-off)" and "indoor unit (stopped)" are not shown.

[0048] At time t1, when the indoor temperature reaches the set temperature, the indoor unit 20 transitions to thermo-off operation and intermittently drives the indoor unit fan 22. The indoor unit 20 keeps the indoor unit fan 22 driving time constant in order to detect the indoor temperature, but in addition to lengthening the stop time of the indoor unit fan 22 based on changes in the indoor temperature (such as the difference between the indoor temperature detected this time and the indoor temperature detected last time), it also changes the time interval when intermittently driving the indoor unit fan 22 (i.e., the stop time of the indoor unit fan 22) to reflect changes in the outdoor temperature.

[0049] Here, the intervals at which the outdoor air temperature is detected by the outdoor air temperature sensor 16 and at which information is transmitted from the outdoor unit 10 to the indoor unit 20 can be set arbitrarily. For example, the outdoor air temperature is detected by the outdoor air temperature sensor 16 at regular intervals (for example, at points G1, G2, G3, and G4) without being related to the timing of the indoor temperature in the indoor unit 20. The outdoor unit control unit 17 of the outdoor unit 10 detects the outdoor air temperature using the outdoor air temperature sensor 16 at regular intervals and transmits information on the detected outdoor air temperature to the indoor unit control unit 27 of the indoor unit 20 each time.

[0050] For example, if the outdoor air temperature detected at point G1 is the outdoor air temperature "Tout-1" and the outdoor air temperature detected at point G2 is the outdoor air temperature "Tout-2," then when the outdoor air temperature at point G2 is detected, the indoor unit control unit 27 calculates the differential temperature "Tsabun" between the currently detected outdoor air temperature "Tout-2" at point G2 and the previously detected outdoor air temperature "Tout-1" at point G1 by the formula "Tsabun" = "Tout-b" - "Tout-a." If the calculated differential temperature "Tsabun" of the outdoor air temperatures exceeds a preset threshold temperature "Toutfuka," the indoor unit control unit 27 determines that there has been a significant change in the outdoor air temperature.

[0051] For example, when the indoor unit control unit 27 first transitions to thermo-off operation, it intermittently drives the indoor unit fan 22 at preset time intervals (H1, H2) and detects the indoor temperature (indoor temperature at points A and B) using the room temperature sensor 26 at the timing when the indoor unit fan 22 is driven for the predetermined time. Here, if the indoor temperature at points A and B rises above the set temperature, the indoor unit control unit 27 attempts to suppress the temperature rise by lengthening the time interval of the subsequent intermittent drive (stop time of the indoor unit fan 22).

[0052] However, when the indoor unit control unit 27 determines that the outdoor temperature has dropped significantly, it reduces the amount (time) by which the time interval (stop time) is extended so that the indoor temperature does not fall below the set temperature. For example, when the indoor unit control unit 27 determines that the outdoor temperature has dropped significantly, it shortens the time interval (stop time) calculated based on the change (rise) in the indoor temperature by dividing it by a predetermined arbitrary value (time) to reduce the amount (time) by which it is extended.

[0053] The indoor unit control unit 27 performs control for each indoor temperature detection point to correct the time interval for intermittent operation of the indoor unit fan 22 (stop time of the indoor unit fan 22) in accordance with changes in the outdoor temperature when the time interval is changed to a longer time in accordance with an increase in the indoor temperature.

[0054] The time intervals (H1, H2) for intermittent drive of the indoor unit fan 22 shown in Fig. 6 are the same as those in the conventional example shown in Fig. 5, but the time intervals (H3, H4) are longer than the time intervals (H1, H2) but shorter than those in the conventional example shown in Fig. 5. As a result, the indoor temperatures at points C, D, and E shown in Fig. 6 are prevented from rising above the set temperature, but are not lowered below the set temperature, preventing a decrease in indoor comfort. In other words, user discomfort can be reduced.

[0055] The indoor unit control unit 27 may change the time interval when intermittently driving the indoor unit fan 22 based on the difference between the indoor temperature detected by the room temperature sensor 26 at a predetermined time and the set temperature of the indoor unit 20, and on the change in the outdoor air temperature detected by the outdoor air temperature sensor 16. The indoor unit control unit 27 may also change the time interval when intermittently driving the indoor unit fan 22 based on both the change in the indoor temperature and the difference between the indoor temperature and the set temperature.

[0056] Furthermore, for each of the three indoor units 20 with the thermostat turned off and that have reached the set temperature, the indoor unit control unit 27 controls the change of the time interval when intermittently driving the indoor unit fan 22. Therefore, the time interval when intermittently driving the indoor unit fan 22 differs for each indoor unit 20 with the thermostat turned off.

[0057] Furthermore, a maximum value is set for the time interval when intermittently driving the indoor unit fan 22. After changing the time interval when intermittently driving the indoor unit fan 22 to the maximum value, the indoor unit control unit 27 maintains the state where it has been changed to the maximum value.

[0058] Furthermore, the indoor unit control unit 27 returns the time interval to a preset time interval at any timing after changing the time interval when intermittently driving the indoor unit fan 22. For example, the indoor unit control unit 27 returns the time interval to a preset time interval when the setting of the indoor unit 20 (for example, the set temperature or set air volume) is changed after changing the time interval when intermittently driving the indoor unit fan 22.

[0059] The control for changing the time interval when the indoor unit fan 22 is intermittently driven in the indoor unit 20 with the thermostat off is performed when at least one of the indoor units 20 connected to the outdoor unit 10 is operating with the thermostat on and has not yet reached the set temperature, and the outdoor unit 10 is in operation. This control is also performed when the air conditioner 1 (outdoor unit 10 and indoor unit 20) is in heating operation.

[0060] As described above, the air conditioner 1 according to this embodiment is a multi-type air conditioner including one outdoor unit 10 equipped with an outdoor heat exchanger 11, an outdoor unit fan 12, a compressor 13, and an outdoor air temperature sensor 16 (an example of an outdoor unit temperature sensor); multiple (e.g., three) indoor units 20 equipped with an indoor heat exchanger 21, an indoor unit fan 22, and a room temperature sensor 26 (an example of an indoor unit temperature sensor); and an electronic expansion valve 15 (an example of an expansion valve) provided in the outdoor unit 10 or the indoor unit 20 to control the amount of refrigerant flowing to the indoor unit 20. When the temperature (indoor temperature) detected by the room temperature sensor 26 reaches a set temperature, the indoor unit 20 stops driving the indoor unit fan 22 and drives the indoor unit fan 22 at preset time intervals for a predetermined time (e.g., three minutes). In addition, the indoor unit 20 changes the time interval for driving the indoor unit fan 22 for only a predetermined time based on the detected temperature (room temperature) detected by the room temperature sensor 26 when the indoor unit fan 22 is driven for a predetermined time and the detected temperature (outdoor temperature) detected by the outdoor air temperature sensor 16.

[0061] As a result, in a multi-type air conditioner 1, when the indoor unit 20 reaches the set temperature and transitions to thermo-off operation, the indoor unit fan 22 is intermittently driven to monitor the indoor temperature using the room temperature sensor 26 located inside. The time interval for intermittent driving is adjusted taking into account both the indoor temperature and the outdoor temperature, preventing the indoor temperature from rising or falling below the set temperature. Therefore, the air conditioner 1 can achieve air conditioning control that responds to changes in the indoor and outdoor temperature environment at low cost without installing a separate sensor to detect the indoor temperature in the indoor space outside the indoor unit 20, preventing a decrease in indoor comfort. In other words, the air conditioner 1 can reduce user discomfort.

[0062] In addition, the indoor unit 20 changes the time interval for driving the indoor unit fan 22 for only a predetermined time based on the change in the detected temperature (room temperature) detected by the room temperature sensor 26 at each predetermined time or the difference between the detected temperature (room temperature) detected by the room temperature sensor 26 at a predetermined time and the set temperature of the indoor unit 20, and the change in the detected temperature (outdoor temperature) detected by the outdoor air temperature sensor 16.

[0063] As a result, when the indoor unit 20 with the thermostat off intermittently drives the indoor unit fan 22, the air conditioner 1 changes the time interval for intermittent driving based on changes in the outdoor temperature in addition to changes in the indoor temperature or the difference between the indoor temperature and the set temperature, thereby preventing the indoor temperature from rising or falling relative to the set temperature.

[0064] In addition, the indoor unit 20 acquires from the outdoor unit 10 the detected temperature (outdoor air temperature) detected by the outdoor air temperature sensor 16 at regular intervals in the outdoor unit 10, and calculates the change in the detected temperature (outdoor air temperature) detected by the outdoor air temperature sensor 16 based on the acquired detected temperature (outdoor air temperature) at regular intervals.

[0065] As a result, the air conditioner 1 changes the time interval when the indoor unit 20, with the thermostat off, intermittently drives the indoor unit fan 22, taking into account the outdoor air temperature by obtaining information on the outdoor air temperature from the outdoor unit 10, thereby preventing the indoor temperature from rising or falling relative to the set temperature.

[0066] In addition, for each of the indoor units 20 (thermo-off indoor units) among the plurality of indoor units 20 (for example, three indoor units) that have reached the set temperature, the time interval for driving the indoor unit fan 22 for only a predetermined time is controlled.

[0067] As a result, the air conditioner 1 controls the change in the time interval when intermittently driving each indoor unit fan 22 individually in the indoor space in which each of the multiple indoor units 20 is installed, thereby preventing a decrease in comfort in each indoor space.

[0068] Furthermore, the time interval during which the indoor unit fan 22 is driven for only a predetermined time differs for each indoor unit 20 .

[0069] This allows the air conditioner 1 to appropriately control the time intervals at which the indoor unit fans 22 are intermittently driven individually in the indoor space in which each of the multiple indoor units 20 is installed.

[0070] Furthermore, a maximum value is set for the time interval for driving the indoor unit fan 22 for only a predetermined time. After the time interval is changed to the maximum value, the indoor unit 20 maintains the state in which it has been changed to the maximum value.

[0071] This allows the air conditioner 1 to prevent the time interval at which the indoor unit 20 with the thermostat turned off monitors the indoor temperature from becoming too long.

[0072] Furthermore, after changing the time interval at which the indoor unit fan 22 is driven for a predetermined time, the indoor unit 20 returns the time interval to the preset time interval at any timing.

[0073] This allows the air conditioner 1 to initialize the time interval when intermittently driving the indoor unit fan 22 in the indoor unit 20 when the thermostat is off, and then control it.

[0074] For example, the indoor unit 20 changes the time interval for driving the indoor unit fan 22 for a predetermined period of time, and then returns the time interval to the preset time interval at the timing when the set temperature or set air volume of the indoor unit 20 is changed.

[0075] As a result, when the set temperature or set air volume of the indoor unit 20 with the thermostat off is changed, the air conditioner 1 can assume that the user does not feel that the current indoor temperature is appropriate, so it can initialize the time interval for intermittently driving the indoor unit fan 22 before performing control.

[0076] In addition, in the air conditioner 1, at least one of the multiple (e.g., three) indoor units 20 is in an operating state (operating with thermo-on) where the set temperature of the indoor unit 20 has not been reached, and the outdoor unit 10 is in operation.

[0077] As a result, when the air conditioner 1 is operating with at least one indoor unit 20 not reaching the set temperature (operating with thermo-on), the outdoor unit 10 is in operation, and the effect of refrigerant flowing into the indoor unit 20 with thermo-off that has reached the set temperature can be suppressed by performing control to change the time interval when intermittently driving the indoor unit fan 22 described above.

[0078] Furthermore, the outdoor unit 10 and a plurality of (for example, three) indoor units 20 are in heating operation.

[0079] As a result, the air conditioner 1 can suppress the impact of refrigerant flowing into the indoor unit 20 with the thermostat off when the set temperature is reached during heating operation, by controlling the time interval when the above-mentioned indoor unit fan 22 is intermittently driven.

[0080] Furthermore, the control method for the multi-type air conditioner 1 according to this embodiment includes the steps of: when the detected temperature (indoor temperature) detected by the room temperature sensor 26 in the indoor unit 20 reaches the set temperature, stopping the driving of the indoor unit fan 22 and driving the indoor unit fan 22 only for a predetermined time (for example, 3 minutes) at preset time intervals; and changing the time interval for driving the indoor unit fan 22 only for a predetermined time based on the detected temperature (indoor temperature) detected by the room temperature sensor 26 when the indoor unit fan 22 is driven for the predetermined time and the detected temperature (outdoor temperature) detected by the outdoor air temperature sensor 16.

[0081] As a result, according to the control method of the air conditioner 1, when the indoor unit 20 reaches the set temperature and transitions to thermo-off operation, it intermittently drives the indoor unit fan 22 to monitor the indoor temperature using the room temperature sensor 26 located inside, and changes the time interval for intermittent drive taking into account both the indoor temperature and the outdoor temperature, thereby preventing the indoor temperature from rising or falling below the set temperature. Therefore, the control method of the air conditioner 1 realizes air conditioning control that responds to changes in the indoor and outdoor temperature environment at low cost without installing a separate sensor to detect the indoor temperature in the indoor space outside the indoor unit 20, and prevents a decrease in indoor comfort. In other words, the control method of the air conditioner 1 can reduce user discomfort.

[0082] Each embodiment has been described above in detail with reference to the drawings, but the specific configuration is not limited to these embodiments, and it is possible to combine the embodiments, or to modify or omit the embodiments as appropriate.

[0083] It is also possible to record a program for realizing the functions of the outdoor unit control unit 17 or the indoor unit control unit 27 on a computer-readable recording medium, and have a computer system load and execute the program to perform the processing of the outdoor unit control unit 17 or the indoor unit control unit 27. Note that the term "computer system" here includes hardware such as the OS and peripheral devices.

[0084] Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording media" also includes devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs over networks like the Internet or communication lines like telephone lines, and devices that store programs for a fixed period of time, such as volatile memory within computer systems that serve as servers or clients. The programs may also be programs that implement some of the aforementioned functions, or may be programs that can achieve the aforementioned functions in combination with programs already stored in the computer system. The programs may also be stored on a designated server and distributed (e.g., downloaded) over communication lines in response to requests from other devices.

[0085] Furthermore, some or all of the functions of the outdoor unit control unit 17 or the indoor unit control unit 27 may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each function may be implemented as a separate processor, or some or all of the functions may be integrated into a processor. The integrated circuit method is not limited to LSI, and may be implemented using a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology, an integrated circuit based on that technology may be used.

[0086] REFERENCE SIGNS LIST 1 Air conditioner 10 Outdoor unit 11 Outdoor heat exchanger 12 Outdoor unit fan 13 Compressor 14 Four-way valve 15 Electronic expansion valve 16 Outdoor air temperature sensor 17 Outdoor unit control unit 20 Indoor unit 21 Indoor heat exchanger 22 Indoor unit fan 26 Room temperature sensor 27 Indoor unit control unit

Claims

1. A multi-type air conditioner comprising one outdoor unit equipped with an outdoor heat exchanger, an outdoor unit fan, a compressor, and an outdoor unit temperature sensor; multiple indoor units equipped with indoor heat exchangers, indoor unit fans, and indoor unit temperature sensors; and an expansion valve provided in the outdoor unit or the indoor units to control the amount of refrigerant flowing to the indoor units, wherein the indoor units comprise an indoor unit control unit that, when the detected temperature detected by the indoor unit temperature sensor reaches the set temperature of the indoor unit, stops driving the indoor unit fan and drives the indoor unit fan for a predetermined period of time at preset time intervals, and changes the time intervals based on the detected temperature detected by the indoor unit temperature sensor when the indoor unit fan is driven for the predetermined period of time and the detected temperature detected by the outdoor unit temperature sensor.

2. The air conditioner of claim 1, wherein the indoor unit control unit changes the time interval based on a change in the detected temperature detected by the indoor unit temperature sensor at each predetermined time or a difference between the detected temperature detected by the indoor unit temperature sensor at the predetermined time and the set temperature of the indoor unit, and a change in the detected temperature detected by the outdoor unit temperature sensor.

3. The air conditioner according to claim 2, wherein the indoor unit control unit acquires from the outdoor unit the detected temperature detected by the outdoor unit temperature sensor at regular intervals, and calculates the change in the detected temperature detected by the outdoor unit temperature sensor based on the acquired detected temperature at regular intervals.

4. The air conditioner according to claim 1, wherein the indoor unit control unit controls the change of the time interval for each of the indoor units that has reached the set temperature among the plurality of indoor units.

5. The air conditioner according to claim 1, wherein the time intervals are different for each of the indoor units.

6. The air conditioner according to claim 1, wherein a maximum value is set for the time interval when it is changed, and the indoor unit control unit maintains the state in which the time interval has been changed to the maximum value after changing it to the maximum value.

7. The air conditioner according to claim 1, wherein the indoor unit control unit changes the time interval and then returns the time interval to the preset time interval at an arbitrary timing.

8. The air conditioner according to claim 7, wherein the indoor unit control unit changes the time interval and then returns the time interval to the preset time interval at the timing when the set temperature or set air volume of the indoor unit is changed.

9. The air conditioner according to claim 1, wherein at least one of the plurality of indoor units is in an operating state where the set temperature of the indoor unit has not been reached, and the outdoor unit is in operation.

10. The air conditioner according to claim 1, wherein the outdoor unit and the plurality of indoor units are in heating operation.

11. A control method for a multi-type air conditioner having one outdoor unit equipped with an outdoor heat exchanger, an outdoor unit fan, a compressor, and an outdoor unit temperature sensor, multiple indoor units equipped with indoor heat exchangers, indoor unit fans, and indoor unit temperature sensors, and expansion valves provided in the outdoor unit or the indoor units to control the amount of refrigerant flowing to the indoor units, the control method comprising the steps of: when the detected temperature detected by the indoor unit temperature sensor reaches the set temperature of the indoor unit, stopping the operation of the indoor unit fan and driving the indoor unit fan for only a predetermined time at a preset time interval; and changing the time interval based on the detected temperature detected by the indoor unit temperature sensor when the indoor unit fan is driven for the predetermined time and the detected temperature detected by the outdoor unit temperature sensor.

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