Refrigeration cycle device and method for controlling electrically driven valve of refrigeration cycle device

Abstract

The preset invention improves reliability of control for closing an electrically driven valve. The present invention comprises: a refrigerant circuit (90) in which a refrigerant circulates, the refrigerant circuit (90) having indoor expansion valves (36a, 36b); a controller (70) that controls the opening degree of the indoor expansion valves (36a, 36b); and refrigerant sensors (38a, 38b) that detect the refrigerant leaking from the refrigerant circuit (90). If a predetermined condition is satisfied, which includes a first leakage condition that the leakage degree determined from the detection by any of the refrigerant sensors (38a, 38b) is greater than or equal to a first leakage degree, the controller (70) performs first control for increasing the valve opening degree of the corresponding indoor expansion valve (36a, 36b). If the leakage degree determined from the detection by any of the refrigerant sensors (38a, 38b) is greater than or equal to a second leakage degree that is higher than the first leakage degree, the controller (70) fully closes the corresponding indoor expansion valve (36a, 36b).

Description

Refrigeration cycle apparatus and method for controlling electric valve of refrigeration cycle apparatus

[0001] The present disclosure relates to a refrigeration cycle apparatus and a method for controlling an electric valve of the refrigeration cycle apparatus.

[0002] Conventionally, in a refrigeration cycle apparatus including a refrigerant circuit having an electric expansion valve, the passage state of refrigerant through the electric expansion valve is adjusted by controlling the valve opening degree of the electric expansion valve.

[0003] For example, according to Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2016-035356), it is proposed to perform an operation of recovering refrigerant in the refrigerant circuit to an outdoor heat exchanger by closing an expansion mechanism and operating a compressor.

[0004] However, even if control for closing an electric valve such as the expansion mechanism described above is started, for example, foreign matter such as dust present in the refrigerant circuit may enter between the valve seat and the valve body, leaving the electric valve in a state where it cannot be completely closed.

[0005] In particular, when control for closing an electric valve is performed to suppress leakage of refrigerant from the refrigerant circuit, high reliability of the control for closing the electric valve is desired.

[0006] A refrigeration cycle apparatus according to a first aspect includes a refrigerant circuit, a control unit, and a leakage detection unit. The refrigerant circuit has an electric valve. Refrigerant circulates through the refrigerant circuit. The control unit controls the opening degree of the electric valve. The leakage detection unit detects refrigerant leaked from the refrigerant circuit. The control unit performs first control to increase the valve opening degree of the electric valve when a predetermined condition is satisfied. The predetermined condition includes a first leakage condition. The first leakage condition is a condition that a detection result by the leakage detection unit is equal to or greater than a first threshold value. The control unit performs second control to fully close the electric valve when the detection result by the leakage detection unit is equal to or greater than a second threshold value that is larger than the first threshold value.

[0007] Here, "increasing the valve opening degree of the electric valve" only requires that the valve opening degree is larger than the valve opening degree of the electric valve at the time when the first control is started.

[0008] According to this refrigeration cycle system, if the detection result from the leak detection unit exceeds the first threshold (which is lower than the second threshold), the valve opening of the electric valve is increased. This makes it possible to move any foreign objects, such as debris, that are present around the electric valve to a location away from the valve. This improves the reliability of the control that fully closes the electric valve when the detection result from the leak detection unit exceeds the second threshold.

[0009] The refrigeration cycle device relating to the second perspective is the refrigeration cycle device relating to the first perspective, and the detection result by the leak detection unit is a value indicating the degree of leakage as determined from the detection information by the leak detection unit.

[0010] Furthermore, the "degree of leakage" may be calculated by the control unit performing a predetermined calculation based on the information detected by the leakage detection unit.

[0011] This refrigeration cycle system makes it possible to control the electric valves based on the degree of refrigerant leakage.

[0012] The refrigeration cycle device relating to the third perspective is the refrigeration cycle device relating to the second perspective, and the degree of leakage is determined according to at least one of the concentration and amount of the leaked refrigerant and the values ​​related thereto, or it is determined based on information regarding the change over time between the concentration and amount of the leaked refrigerant and the values ​​related thereto.

[0013] Here, "refrigerant concentration" may refer to the concentration of the refrigerant in the space where the refrigerant leaked. "Values ​​related to these" could include, for example, the leakage rate or leakage time.

[0014] This refrigeration cycle system enhances the reliability of risk management related to refrigerant leaks.

[0015] The refrigeration cycle device relating to the fourth perspective is a refrigeration cycle device relating to either the first or third perspective, and the predetermined conditions include a pre-state condition. The pre-state condition is that the valve opening of the electric expansion valve remains below a predetermined opening for a predetermined period of time.

[0016] Here, "a state below a predetermined opening degree" may refer to, for example, a valve opening degree of half or less of the valve opening degree when the electric valve is fully open, or a valve opening degree of one-third or less, or a valve opening degree of one-fifth or less.

[0017] Furthermore, the "predetermined period condition" may be, for example, the elapsed of a predetermined amount of time, or, in the case of a refrigerant circuit having a compressor, the cumulative rotational speed of the compressor.

[0018] According to this refrigeration cycle device, if the valve opening of the electric valve remains below a predetermined opening for a period of time or longer that satisfies a predetermined condition, foreign matter such as dirt is more likely to accumulate around the electric valve. However, even in such a situation where foreign matter such as dirt is likely to accumulate around the electric valve, the electric valve can be more reliably brought to a fully closed state when the second control is performed.

[0019] The refrigeration cycle device relating to the fifth aspect is the refrigeration cycle device relating to the fourth aspect, and the electric valve is an electric expansion valve. The control unit controls the electric expansion valve so that when the heat load to be processed is in a predetermined low load state, the valve opening of the electric expansion valve is less than a predetermined opening.

[0020] This refrigeration cycle system controls the valve opening of the electric expansion valve to be less than a predetermined opening when under a predetermined low load condition, thereby making it possible to limit the amount of refrigerant circulating in the refrigerant circuit to an amount corresponding to the heat load being processed.

[0021] The refrigeration cycle device according to the sixth aspect is the refrigeration cycle device according to the fifth aspect, and the refrigerant circuit has a compressor, an outdoor heat exchanger, an indoor heat exchanger, a first flow path extending from the outdoor heat exchanger to the indoor heat exchanger and equipped with an electric expansion valve, and a second flow path extending from the outdoor heat exchanger to the indoor heat exchanger and equipped with a compressor. The refrigerant circuit is capable of performing heating operation by making the indoor heat exchanger function as a refrigerant heat radiator. The control unit controls the electric expansion valve so that when the conditions for the set temperature corresponding to the indoor heat exchanger are met, the valve opening is less than a predetermined opening and is not in a fully closed state.

[0022] This refrigeration cycle system prevents liquid refrigerant from accumulating in the indoor heat exchanger during heating operation, provided that the conditions related to the set temperature corresponding to the indoor heat exchanger are met.

[0023] The refrigeration cycle device relating to the seventh aspect is the refrigeration cycle device relating to the fifth aspect, and the refrigerant circuit includes a compressor, an outdoor heat exchanger, a first indoor heat exchanger, a second indoor heat exchanger, a first electric expansion valve which is an electric expansion valve, a second electric expansion valve which is an electric expansion valve, a first main flow path extending from the outdoor heat exchanger to a first branch section, a first branch flow path extending from the first branch section to the first indoor heat exchanger and equipped with a first electric expansion valve, a second branch flow path extending from the first branch section to the second indoor heat exchanger and equipped with a second electric expansion valve, a second main flow path extending from the outdoor heat exchanger to a second branch section and equipped with a compressor, a third branch flow path extending from the second branch section to the first indoor heat exchanger, and a fourth branch flow path extending from the second branch section to the second indoor heat exchanger.

[0024] This refrigeration cycle system makes it possible to individually control the amount of refrigerant supplied to the first indoor heat exchanger and the amount of refrigerant supplied to the second indoor heat exchanger.

[0025] The refrigeration cycle system relating to the eighth aspect is the refrigeration cycle system relating to the seventh aspect, wherein the refrigerant circuit is capable of performing heating operation by making the first indoor heat exchanger and the second indoor heat exchanger function as refrigerant radiators. The control unit controls the valve opening of the first electric expansion valve to be less than a predetermined opening and not in a fully closed state when the conditions relating to the set temperature corresponding to the first indoor heat exchanger are met. The control unit controls the valve opening of the second electric expansion valve to be less than a predetermined opening and not in a fully closed state when the conditions relating to the set temperature corresponding to the second indoor heat exchanger are met.

[0026] According to this refrigeration cycle system, during heating operation, when the conditions for the set temperature corresponding to the first indoor heat exchanger are met, the accumulation of liquid refrigerant in the first indoor heat exchanger is suppressed, and when the conditions for the set temperature corresponding to the second indoor heat exchanger are met, the accumulation of liquid refrigerant in the second indoor heat exchanger is suppressed.

[0027] The refrigeration cycle device relating to the ninth perspective is a refrigeration cycle device relating to either the fourth perspective or the eighth perspective, wherein the control unit performs the second control without performing the first control if the first leakage condition is met without satisfying the prior state conditions.

[0028] According to this refrigeration cycle device, in situations where there is a low probability of foreign matter such as dust being present around the electric expansion valve that does not meet the preconditions, the first control, which increases the valve opening of the electric expansion valve, is omitted and the second control is started, making it possible to quickly bring the electric expansion valve to a fully closed state.

[0029] The refrigeration cycle device relating to the tenth viewpoint is a refrigeration cycle device relating to either the first viewpoint or the ninth viewpoint, wherein the control unit, in the first control, increases the valve opening of the electric valve to half open or more.

[0030] This refrigeration cycle system makes it possible to more reliably move foreign objects such as debris away from the electric valve, even if they are present around the electric valve.

[0031] The refrigeration cycle device relating to the 11th viewpoint is a refrigeration cycle device relating to either the 1st viewpoint or the 10th viewpoint, and the predetermined conditions include a time period condition. The time period condition is that a predetermined period has elapsed since the last time the 1st control was performed.

[0032] According to this refrigeration cycle system, once the first control has been performed and the likelihood of no foreign matter such as debris being present around the electric valve has increased, the first control, which increases the valve opening of the electric valve, is suppressed from being performed again for a predetermined period of time. This makes it possible to minimize the risk of leakage associated with temporarily increasing the valve opening when a refrigerant leak occurs.

[0033] A refrigeration cycle device relating to the 12th aspect is a refrigeration cycle device relating to either the 1st aspect or the 11th aspect, wherein the refrigerant is a refrigerant having at least one of a predetermined toxicity and a predetermined flammability.

[0034] Examples of such refrigerants include carbon dioxide refrigerant, R32, and propane.

[0035] This refrigeration cycle system makes it possible to improve the reliability of the control that fully closes the electric valve when the detection result from the leak detection unit exceeds a second threshold, in cases where a refrigerant with a predetermined toxicity or predetermined flammability is used.

[0036] The refrigeration cycle device relating to the 13th perspective is a refrigeration cycle device relating to either the 1st perspective or the 12th perspective, and the refrigerant is carbon dioxide refrigerant.

[0037] This refrigeration cycle system makes it possible to improve the reliability of electric valve control when toxic refrigerants are used.

[0038] The control method for an electric valve of a refrigeration cycle device relating to the 14th aspect is a control method for an electric valve of a refrigeration cycle device, wherein the refrigeration cycle device comprises a refrigerant circuit, a control unit, and a leak detection unit. The refrigerant circuit has an electric valve. The refrigerant circulates through the refrigerant circuit. The control unit controls the opening degree of the electric valve. The leak detection unit detects refrigerant leaking from the refrigerant circuit. The control unit performs a first control to increase the valve opening degree of the electric valve when predetermined conditions are met. The predetermined conditions include a first leak condition in which the detection result by the leak detection unit is greater than or equal to a first threshold. The control unit performs a second control to completely close the electric valve when the detection result by the leak detection unit is greater than or equal to a second threshold, which is greater than the first threshold.

[0039] Here, "increasing the valve opening of the electric valve" simply means that the valve opening is larger than the valve opening of the electric valve at the time the first control is started.

[0040] According to this control method for the electric valve of the refrigeration cycle system, when the detection result from the leak detection unit exceeds a first threshold (which is less than the second threshold), the valve opening of the electric valve is increased. This makes it possible to move any foreign objects, such as debris, that are present around the electric valve to a location away from the valve. This improves the reliability of the control that completely closes the electric valve when the detection result from the leak detection unit exceeds the second threshold.

[0041] These are schematic configuration diagrams of a refrigeration cycle apparatus according to an embodiment; a control block diagram of the refrigeration cycle apparatus; a schematic cross-sectional configuration diagram of an indoor expansion valve; and a control flowchart of refrigerant leakage prevention processing.

[0042] An embodiment of the refrigeration cycle apparatus will be described with reference to the drawings.

[0043] (1) Overall Configuration The refrigeration cycle apparatus 100 of the present embodiment will be described with reference to the schematic configuration diagram of Fig. 1.

[0044] The refrigeration cycle apparatus 100 is an air conditioner that air-conditions a plurality of air-conditioned spaces in a building. The refrigeration cycle apparatus 100 mainly includes an outdoor unit 10, a plurality of indoor units 30, and a controller 70 (see Fig. 1). Note that the number of indoor units 30 illustrated in Fig. 1 does not limit the number of indoor units 30 included in the refrigeration cycle apparatus 100. Further, unlike the present embodiment, the refrigeration cycle apparatus 100 may be an apparatus that includes only one indoor unit 30 and air-conditions a single air-conditioned space.

[0045] As shown in Fig. 1, the outdoor unit 10 and the indoor units 30 are connected via a liquid-side connection pipe 2, a first liquid-side branch pipe 2a and a second liquid-side branch pipe 2b branched at a first branch point X that is an end portion of the liquid-side connection pipe 2 on the indoor unit side, a gas-side connection pipe 4, and a first gas-side branch pipe 4a and a second gas-side branch pipe 4b branched at a second branch point Y that is an end portion of the gas-side connection pipe 4 on the indoor unit side. By connecting the outdoor unit 10 and the plurality of indoor units 30 via these pipes, a refrigerant circuit 90 that includes, in its configuration, a compressor 12, an outdoor heat exchanger 16, an outdoor expansion valve 18, an indoor expansion valve 36, an indoor heat exchanger 32, and the like described later is formed. The liquid-side connection pipe 2 is a liquid connection pipe through which refrigerant flows from the outdoor unit 10 to the indoor units 30 during cooling operation, and flows from the indoor units 30 to the outdoor unit 10 during heating operation. The gas-side connection pipe 4 is a gas connection pipe through which refrigerant flows from the indoor units 30 to the outdoor unit 10 during cooling operation, and flows from the outdoor unit 10 to the indoor units 30 during heating operation. The controller 70 controls the operation of each part of the refrigeration cycle apparatus 100.

[0046] The refrigerant used in the refrigerant circuit 90 is not particularly limited. For example, in the present embodiment, the case where a carbon dioxide refrigerant is used will be described as an example.

[0047] (2) Detailed Configuration (2-1) Indoor Unit The indoor unit 30 is installed in an air-conditioned space that is the target of air conditioning. The indoor unit 30 is, for example, a ceiling-embedded type, ceiling-suspended type, wall-mounted type, floor-standing type unit, or the like. In the present embodiment, a case where a first indoor unit 30a and a second indoor unit 30b having the same configuration as each other are provided as the indoor unit 30 will be described as an example. The first indoor unit 30a and the second indoor unit 30b are connected in parallel to each other in the refrigerant circuit 90. Components included in the first indoor unit 30a will be described with the subscript "a" added thereto, and components included in the second indoor unit 30b will be described with the subscript "b" added thereto. Hereinafter, there may be cases where the description refers to either or both of the first indoor unit 30a, the second indoor unit 30b and their constituent elements without adding either the subscript "a" or the subscript "b".

[0048] The first indoor unit 30a mainly includes a first indoor heat exchanger 32a, a first indoor fan 34a, a first indoor expansion valve 36a, a first indoor control unit 72a, a first gas-side valve 37a, a first indoor heat exchange temperature sensor 35a, a first indoor temperature sensor 33a, a first refrigerant sensor 38a, and a first casing 31a that accommodates these components.

[0049] In the first indoor heat exchanger 32a, heat exchange is performed between the refrigerant flowing inside the first indoor heat exchanger 32a and the air in the air-conditioned space. The first indoor heat exchanger 32a is, for example, a fin-and-tube heat exchanger including a plurality of heat transfer fins and a plurality of heat transfer tubes.

[0050] The first indoor fan 34a supplies air taken in from the air-conditioned space to the first indoor heat exchanger 32a. The first indoor fan 34a is, for example, a centrifugal fan such as a turbo fan or a sirocco fan. The first indoor fan 34a is driven by a motor not shown in the drawings.

[0051] The first indoor expansion valve 36a is installed in the first liquid-side branch pipe 2a, which connects the liquid-side connecting pipe 2 to the liquid-side end of the first indoor heat exchanger 32a, and is a mechanism for adjusting the pressure and flow rate of the refrigerant. The first indoor expansion valve 36a is an electrically operated expansion valve, such as an electronic expansion valve, with adjustable opening. The first indoor expansion valve 36a comprises a valve seat, a valve body, and a stepping motor that drives the valve body. By driving the stepping motor, the valve body moves relative to the valve seat, making the minimum flow path area between the valve body and the valve seat variable. The first indoor expansion valve 36a is also used as a shut-off valve to block the flow path, and is a valve with low leakage when closed. For example, the first indoor expansion valve 36a has a leakage of 300 cm³ when closed. ３ The valve has a pressure of / min (air, ΔP = 1.0 MPa) or less. Furthermore, the material of the valve seat and valve body of the first chamber expansion valve 36a is not particularly limited, but may be selected from SUS and brass, etc., and it is preferable that both the valve seat and valve body be made of SUS from the viewpoint that they have sufficient strength to be easily crushed even if foreign matter gets stuck between them.

[0052] In this embodiment, the first chamber expansion valve 36a may, more specifically as shown in Figure 3, be a motor-driven expansion valve comprising a valve body 41, a valve seat 42, and a drive mechanism (not shown). The valve body 41 is needle-shaped with a tapered tip, and its position is controlled to move axially by the drive mechanism. The valve seat 42 has an orifice hole 43 into which the tip of the valve body 41 is inserted. By controlling the position of the valve body 41 relative to the valve seat 42 in this way, the size of the flow path area in the first chamber expansion valve 36a is controlled.

[0053] The first gas-side valve 37a is provided in the first gas-side branch pipe 4a that connects the gas-side connecting pipe 4 to the gas-side end of the first indoor heat exchanger 32a, and has a variable valve opening mechanism. The first gas-side valve 37a in this embodiment is an electrically operated expansion valve such as an electronic expansion valve with adjustable opening. The first gas-side valve 37a comprises a valve seat, a valve body, and a stepping motor that drives the valve body. By driving the stepping motor, the valve body moves relative to the valve seat, making the minimum flow path area between the valve body and the valve seat variable. The first gas-side valve 37a is also used as a shut-off valve to block the flow path, and is a valve with low leakage when closed. For example, the first gas-side valve 37a has a leakage of 300 cm³ when closed. ３ This valve has a pressure of / min (air, ΔP = 1.0 MPa) or less.

[0054] The first indoor heat exchanger temperature sensor 35a detects the temperature of the refrigerant flowing at the liquid-side outlet of the first indoor heat exchanger 32a.

[0055] The first indoor temperature sensor 33a detects the temperature of the indoor air drawn in from the room before heat exchange occurs in the first indoor heat exchanger 32a.

[0056] The first refrigerant sensor 38a is a sensor that detects refrigerant leakage. The first refrigerant sensor 38a is installed, for example, near the first indoor heat exchanger 32a. In this embodiment, the first refrigerant sensor 38a is configured to detect the concentration of refrigerant leaked from the refrigerant circuit 90 in the space surrounding the first refrigerant sensor 38a.

[0057] The first indoor control unit 72a has a control arithmetic unit and a memory device. The control arithmetic unit is a processor such as a CPU and a GPU. The memory device is a storage medium such as RAM, ROM, and flash memory. The control arithmetic unit reads a program stored in the memory device and performs predetermined arithmetic processing according to the program, and in cooperation with the outdoor control unit 74 of the outdoor unit 10, acts as a controller 70 to control the operation of various devices of the refrigeration cycle device 100. The functions of the controller 70 will be described later.

[0058] The second indoor unit 30b mainly comprises a second indoor heat exchanger 32b, a second indoor fan 34b, a second indoor expansion valve 36b, a second indoor control unit 72b, a second gas-side valve 37b, a second indoor heat exchanger temperature sensor 35b, a second indoor temperature sensor 33b, a second refrigerant sensor 38b, and a second casing 31b housing these components. Since the configuration of the second indoor unit 30b is the same as that of the first indoor unit 30a, a detailed explanation is omitted.

[0059] (2-2) Outdoor Unit The outdoor unit 10 is installed on the rooftop or in the machine room of the building where the refrigeration cycle device 100 is installed. As shown in Figure 1, the outdoor unit 10 mainly includes a compressor 12, a flow path switching valve 14, an outdoor heat exchanger 16, an outdoor expansion valve 18, an accumulator 20, an outdoor fan 22, a liquid shut-off valve 24, a gas shut-off valve 26, a discharge pressure sensor 21, an intake pressure sensor 23, an intake temperature sensor 25, an outdoor heat exchanger temperature sensor 27, and an outdoor control unit 74. The outdoor unit 10 also includes an intake pipe 28a, a discharge pipe 28b, a first gas refrigerant pipe 28c, a second gas refrigerant pipe 28e, a liquid refrigerant pipe 28d, and a casing 11 that houses these.

[0060] The suction pipe 28a connects the flow path switching valve 14 to the suction side of the compressor 12. An accumulator 20 is provided in the suction pipe 28a. The discharge pipe 28b connects the discharge side of the compressor 12 to the flow path switching valve 14. The first gas refrigerant piping 28c connects the flow path switching valve 14 to the gas side end of the outdoor heat exchanger 16. The liquid refrigerant piping 28d connects the liquid side end of the outdoor heat exchanger 16 to the liquid side connecting pipe 2. An outdoor expansion valve 18 is provided in the liquid refrigerant piping 28d. A liquid shut-off valve 24 is provided at the connection between the liquid refrigerant piping 28d and the liquid side connecting pipe 2. The second gas refrigerant piping 28e connects the flow path switching valve 14 to the gas side connecting pipe 4. A gas shut-off valve 26 is provided at the connection between the second gas refrigerant piping 28e and the gas side connecting pipe 4. The liquid shut-off valve 24 and the gas shut-off valve 26 are valves that are opened and closed manually.

[0061] The compressor 12 draws in low-pressure refrigerant from the refrigeration cycle through the suction pipe 28a, compresses the refrigerant using a compression mechanism (not shown), and discharges the compressed high-pressure refrigerant from the refrigeration cycle through the discharge pipe 28b. The compressor 12 is, for example, a positive displacement compressor such as a rotary or scroll type. The compression mechanism of the compressor 12 is driven by a motor (not shown). The rotational speed of the motor of the compressor 12 can be controlled by an inverter.

[0062] The flow path switching valve 14 is a mechanism that switches the flow path of the refrigerant between a first state and a second state. In the first state, as shown by the solid line in the flow path switching valve 14 in Figure 1, the intake pipe 28a is connected to the second gas refrigerant piping 28e and the discharge pipe 28b is connected to the first gas refrigerant piping 28c. In the second state, as shown by the dashed line in the flow path switching valve 14 in Figure 1, the intake pipe 28a is connected to the first gas refrigerant piping 28c and the discharge pipe 28b is connected to the second gas refrigerant piping 28e. The flow path switching valve 14 is, for example, a four-way switching valve or a combination of multiple three-way valves.

[0063] During cooling operation, the flow path switching valve 14 sets the refrigerant flow path to the first state. At this time, the refrigerant discharged from the compressor 12 flows through the refrigerant circuit 90 in the order of outdoor heat exchanger 16, outdoor expansion valve 18, first indoor expansion valve 36a, first indoor heat exchanger 32a, and then in the order of second indoor expansion valve 36b, second indoor heat exchanger 32b, before returning to the compressor 12. In the first state, the outdoor heat exchanger 16 functions as a radiator or condenser, and the first indoor heat exchanger 32a and second indoor heat exchanger 32b function as evaporators.

[0064] During heating operation, the flow path switching valve 14 sets the refrigerant flow path to the second state. At this time, the refrigerant discharged from the compressor 12 flows through the refrigerant circuit 90 in the following order: first indoor heat exchanger 32a, first indoor expansion valve 36a, then second indoor heat exchanger 32b, second indoor expansion valve 36b, outdoor expansion valve 18, and outdoor heat exchanger 16, before returning to the compressor 12. In the second state, the outdoor heat exchanger 16 functions as an evaporator, and the first indoor heat exchanger 32a and second indoor heat exchanger 32b function as radiators or condensers.

[0065] The outdoor heat exchanger 16 performs heat exchange between the refrigerant flowing inside the outdoor heat exchanger 16 and the air surrounding the outdoor unit 10. The outdoor heat exchanger 16 is, for example, a fin-and-tube type heat exchanger having a plurality of heat transfer fins and a plurality of heat transfer tubes.

[0066] The outdoor expansion valve 18 is a mechanism for regulating the pressure and flow rate of the refrigerant flowing through the liquid refrigerant piping 28d. As shown in Figure 1, the outdoor expansion valve 18 is installed in the liquid refrigerant piping 28d. The outdoor expansion valve 18 is an electrically operated expansion valve, such as an electronic expansion valve, with adjustable opening.

[0067] The accumulator 20 is installed in the suction pipe 28a and is a container with a gas-liquid separation function that separates the incoming refrigerant into gaseous refrigerant and liquid refrigerant. The refrigerant flowing into the accumulator 20 is separated into gaseous refrigerant and liquid refrigerant, and the gaseous refrigerant that collects in the upper space flows into the compressor 12.

[0068] The outdoor fan 22 supplies air from around the outdoor unit 10 to the outdoor heat exchanger 16. The outdoor fan 22 is, for example, an axial fan such as a propeller fan. The outdoor fan 22 is driven by a motor (not shown).

[0069] The discharge pressure sensor 21 is installed between the compressor 12 and the flow path switching valve 14 and detects the pressure of the refrigerant discharged from the compressor 12.

[0070] The suction pressure sensor 23 is installed between the accumulator 20 and the compressor 12 and detects the pressure of the refrigerant being drawn into the compressor 12.

[0071] The intake temperature sensor 25 is installed between the accumulator 20 and the compressor 12 and detects the temperature of the refrigerant being drawn into the compressor 12.

[0072] The outdoor heat exchanger temperature sensor 27 detects the temperature of the refrigerant flowing at the liquid side outlet of the outdoor heat exchanger 16.

[0073] The outdoor control unit 74 has a control calculation device and a memory device. The control calculation device is a processor such as a CPU and GPU. The memory device is a storage medium such as RAM, ROM, and flash memory. The control calculation device reads a program stored in the memory device and performs predetermined calculation processing according to the program, and in cooperation with the indoor control unit 72 of the indoor unit 30, acts as a controller 70 to control the operation of various devices of the refrigeration cycle device 100. The functions of the controller 70 will be described later.

[0074] (2-3) Controller The controller 70 consists of a first indoor control unit 72a, a second indoor control unit 72b, and an outdoor control unit 74. The controller 70 controls the operation of the entire refrigeration cycle system 100 by causing the control calculation devices of the first indoor control unit 72a, the second indoor control unit 72b, and the outdoor control unit 74 to execute programs stored in their respective storage devices.

[0075] Figure 2 is a control block diagram of the refrigeration cycle device 100 in this embodiment.

[0076] As shown in Figure 2, the controller 70 is electrically connected to the first gas side valve 37a, first indoor expansion valve 36a, first indoor fan 34a, first indoor heat exchange temperature sensor 35a, first indoor temperature sensor 33a, and first refrigerant sensor 38a of the first indoor unit 30a; to the second gas side valve 37b, second indoor expansion valve 36b, second indoor fan 34b, second indoor heat exchange temperature sensor 35b, second indoor temperature sensor 33b, and second refrigerant sensor 38b of the second indoor unit 30b; and to the compressor 12, flow path switching valve 14, outdoor expansion valve 18, discharge pressure sensor 21, suction pressure sensor 23, suction temperature sensor 25, outdoor heat exchange temperature sensor 27, and outdoor fan 22 of the outdoor unit 10. The controller 70 is also electrically connected to various sensors that measure the temperature and pressure of the refrigerant, the temperature of the air in the air-conditioned space, the outside air temperature, etc. The controller 70 controls the operation of various devices in the refrigeration cycle system 100 based on control signals received by the first indoor unit 30a and the second indoor unit 30b from an operating remote control (not shown), measurement signals from various sensors, etc.

[0077] The controller 70 primarily performs cooling and heating operations. Furthermore, the controller 70 is capable of performing the refrigerant leakage prevention treatment described later.

[0078] (2-3-1) When the cooling operation controller 70 receives an instruction to perform cooling operation, for example from the operating remote control via the indoor unit 30, it sets the flow path switching valve 14 to the first state and starts the operation of the compressor 12. In addition, based on the measurement results of sensors that measure the temperature and pressure of the refrigerant, which are provided in the refrigerant circuit 90, and the set temperature, it appropriately controls the rotation speed of the compressor 12 motor and the opening degrees of the outdoor expansion valve 18, the first indoor expansion valve 36a, and the second indoor expansion valve 36b. During cooling operation, the first gas side valve 37a and the second gas side valve 37b are controlled to be fully open.

[0079] The flow of refrigerant in the refrigerant circuit 90 will be explained.

[0080] When the compressor 12 starts operating, the low-pressure gaseous refrigerant in the refrigeration cycle (hereinafter simply referred to as low-pressure) is drawn into the compressor 12 and compressed by the compressor's compression mechanism to become the high-pressure refrigerant in the refrigeration cycle (hereinafter simply referred to as high-pressure). The high-pressure refrigerant is sent to the outdoor heat exchanger 16 via the flow path switching valve 14, where it exchanges heat with the air surrounding the outdoor unit 10 supplied by the outdoor fan 22 and dissipates heat. The refrigerant that has dissipated heat in the outdoor heat exchanger 16 flows through the liquid refrigerant piping 28d and passes through the outdoor expansion valve 18. In this embodiment, for example, during cooling operation, the valve opening of the outdoor expansion valve 18 is controlled so that the degree of subcooling of the refrigerant flowing out of the outlet of the outdoor heat exchanger 16 satisfies predetermined conditions. Specifically, the degree of subcooling, determined from the pressure-equivalent saturation temperature grasped by the discharge pressure sensor 21 and the refrigerant temperature detected by the outdoor heat exchanger temperature sensor 27, is controlled to satisfy predetermined conditions. The refrigerant that has passed through the outdoor expansion valve 18 and flowed through the liquid-side connecting pipe 2 is divided at the first branching point X into a first liquid-side branching pipe 2a and a second liquid-side branching pipe 2b, and is then sent to the first indoor unit 30a and the second indoor unit 30b.

[0081] The refrigerant sent to the first indoor unit 30a is reduced in pressure by the first indoor expansion valve 36a to near the suction pressure of the compressor 12, becoming a gas-liquid two-phase refrigerant, and is sent to the first indoor heat exchanger 32a. In this embodiment, for example, during cooling operation, the valve opening of the first indoor expansion valve 36a is controlled so that the degree of superheating of the refrigerant suctioned by the compressor 12 satisfies predetermined conditions. Specifically, the degree of superheating determined from the pressure-equivalent saturation temperature grasped by the suction pressure sensor 23 and the refrigerant temperature detected by the suction temperature sensor 25 is controlled to satisfy predetermined conditions. The gas-liquid two-phase refrigerant evaporates in the first indoor heat exchanger 32a through heat exchange with the air in the conditioned space supplied to the first indoor heat exchanger 32a by the first indoor fan 34a, becoming a low-pressure gaseous refrigerant. This low-pressure gaseous refrigerant is sent from the first indoor unit 30a to the gas-side connecting pipe 4 via the first gas-side branch pipe 4a.

[0082] Furthermore, when the temperature detected by the first indoor temperature sensor 33a satisfies the conditions for the set temperature during cooling of the first indoor unit 30a, which are received by the operating remote control or the like, the first indoor unit 30a is controlled to enter a thermo-off state during cooling. Specifically, control is performed to set the valve opening of the first indoor expansion valve 36a of the first indoor unit 30a to a fully closed state. As a result, even when the thermo-off state is entered during cooling operation, evaporation of the refrigerant in the first indoor heat exchanger 32a is suppressed, and cold air is prevented from flowing out of the first indoor heat exchanger 32a into the room. The conditions for the set temperature are not particularly limited, and may include, for example, the temperature detected by the first indoor temperature sensor 33a reaching the set temperature, reaching a predetermined temperature exceeding the set temperature, or a predetermined time elapsed while the temperature was at the set temperature (the same applies hereinafter).

[0083] The liquid refrigerant sent to the second indoor unit 30b is the same as that of the first indoor unit 30a. In the second indoor expansion valve 36b, it is reduced to near the suction pressure of the compressor 12, becoming a gas-liquid two-phase refrigerant, which is then sent to the second indoor heat exchanger 32b. In this embodiment, during cooling operation, the valve opening of the second indoor expansion valve 36b is controlled so that the degree of superheating of the refrigerant suctioned by the compressor 12 satisfies predetermined conditions. Specifically, the degree of superheating determined from the pressure-equivalent saturation temperature determined by the suction pressure sensor 23 and the refrigerant temperature detected by the suction temperature sensor 25 is controlled to satisfy predetermined conditions. In the second indoor heat exchanger 32b, the gas-liquid two-phase refrigerant exchanges heat with the air in the conditioned space supplied to the second indoor heat exchanger 32b by the second indoor fan 34b, evaporates, and becomes a low-pressure gaseous refrigerant. This low-pressure gaseous refrigerant is sent from the second indoor unit 30b to the gas-side connecting pipe 4 via the second gas-side branch pipe 4b.

[0084] Furthermore, when the temperature detected by the second indoor temperature sensor 33b satisfies the conditions for the set temperature during cooling of the second indoor unit 30b, which are received via the operating remote control, the second indoor unit 30b is controlled to enter a thermo-off state during cooling. Specifically, control is performed to fully close the valve opening of the second indoor expansion valve 36b of the second indoor unit 30b. As a result, even when the thermo-off state is entered during cooling operation, evaporation of the refrigerant in the second indoor heat exchanger 32b is suppressed, and cold air is prevented from flowing out of the second indoor heat exchanger 32b into the room.

[0085] The refrigerant flowing through the gas-side connecting pipe 4 is sent to the outdoor unit 10, and flows into the accumulator 20 via the flow path switching valve 14. The low-pressure gaseous refrigerant that flows into the accumulator 20 is then drawn back into the compressor 12.

[0086] (2-3-2) When the heating operation controller 70 receives an instruction to start heating operation, for example from the operating remote control via the indoor unit 30, it sets the flow path switching valve 14 to the second state and starts the operation of the compressor 12. In addition, based on the measurement results of sensors that measure the temperature and pressure of the refrigerant provided in the refrigerant circuit 90 and the set temperature, it appropriately controls the rotation speed of the compressor 12 motor and the opening degrees of the outdoor expansion valve 18, the first indoor expansion valve 36a, and the second indoor expansion valve 36b. During heating operation, the first gas side valve 37a and the second gas side valve 37b are controlled to be fully open.

[0087] The flow of refrigerant in the refrigerant circuit 90 will be explained.

[0088] When the compressor 12 is started, low-pressure gaseous refrigerant is drawn into the compressor 12 and compressed by the compressor 12 to become high-pressure gaseous refrigerant. The high-pressure gaseous refrigerant flows through the gas-side connecting pipe 4 via the flow path switching valve 14, and at the second branching point Y, it branches into the first gas-side branching pipe 4a and the second gas-side branching pipe 4b, thereby being sent to the first indoor unit 30a and the second indoor unit 30b.

[0089] The gaseous refrigerant sent to the first indoor unit 30a passes through the first gas-side valve 37a, which is controlled to be fully open, and is sent to the first indoor heat exchanger 32a. The refrigerant sent to the first indoor heat exchanger 32a exchanges heat with the air in the conditioned space supplied to the first indoor heat exchanger 32a by the first indoor fan 34a and dissipates heat. The temperature of the air supplied to the first indoor heat exchanger 32a rises as it exchanges heat with the refrigerant flowing through the first indoor heat exchanger 32a, and the heated air is blown out into the conditioned space. The refrigerant that has dissipated heat in the first indoor heat exchanger 32a is depressurized in the first indoor expansion valve 36a. In this embodiment, for example, during heating operation, the valve opening of the first indoor expansion valve 36a is controlled so that the degree of subcooling of the refrigerant flowing out of the outlet of the first indoor heat exchanger 32a satisfies a predetermined condition. Specifically, the degree of subcooling, determined from the pressure-equivalent saturation temperature obtained from the discharge pressure sensor 21 and the refrigerant temperature detected by the first indoor heat exchanger temperature sensor 35a, is controlled to satisfy predetermined conditions. The refrigerant, which has been depressurized by the first indoor expansion valve 36a, is sent to the liquid-side connecting pipe 2 via the first liquid-side branch pipe 2a.

[0090] Furthermore, when the temperature detected by the first indoor temperature sensor 33a satisfies the conditions for the set temperature during heating of the first indoor unit 30a received by the operating remote control, etc., the first indoor unit 30a is controlled to enter a thermo-off state during heating. Specifically, the valve opening of the first indoor expansion valve 36a of the first indoor unit 30a is controlled to be in a predetermined slightly open state, which is an opening less than a predetermined slightly open state, not a fully closed state. The predetermined slightly open state is not particularly limited, and for example, it may be a valve opening that results in a flow path area of ​​half or less of the flow path area of ​​the valve opening of the first indoor expansion valve 36a in its fully open state, or a valve opening that results in a flow path area of ​​1 / 3 or less, or a valve opening that results in a flow path area of ​​1 / 5 or less. As a result, even when the thermo-off state is entered during heating operation, the state in which refrigerant flow occurs in the first indoor heat exchanger 32a is maintained, thereby suppressing the accumulation of a large amount of liquid refrigerant in the first indoor heat exchanger 32a.

[0091] The gaseous refrigerant sent to the second indoor unit 30b is the same as the refrigerant sent to the first indoor unit 30a, and passes through the second gas-side valve 37b, which is controlled to be fully open, and is sent to the second indoor heat exchanger 32b. The refrigerant sent to the second indoor heat exchanger 32b exchanges heat with the air in the conditioned space supplied to the second indoor heat exchanger 32b by the second indoor fan 34b and dissipates heat. The temperature of the air supplied to the second indoor heat exchanger 32b rises as it exchanges heat with the refrigerant flowing through the second indoor heat exchanger 32b, and the heated air is blown out into the conditioned space. The refrigerant that has dissipated heat in the second indoor heat exchanger 32b is depressurized in the second indoor expansion valve 36b. In this embodiment, for example, during heating operation, the valve opening of the second indoor expansion valve 36b is controlled so that the degree of subcooling of the refrigerant flowing at the outlet of the second indoor heat exchanger 32b satisfies a predetermined condition. Specifically, the degree of subcooling, determined from the pressure-equivalent saturation temperature obtained from the discharge pressure sensor 21 and the refrigerant temperature detected by the second chamber heat exchanger temperature sensor 35b, is controlled to satisfy predetermined conditions. The refrigerant, which has been depressurized by the second chamber expansion valve 36b, is sent to the liquid-side connecting pipe 2 via the second liquid-side branch pipe 2b.

[0092] Furthermore, when the temperature detected by the second indoor temperature sensor 33b satisfies the conditions for the set temperature during heating of the second indoor unit 30b received by the operating remote control, etc., the second indoor unit 30b is controlled to enter a thermo-off state during heating. Specifically, the valve opening of the second indoor expansion valve 36b of the second indoor unit 30b is controlled to be in a predetermined slightly open state, which is an opening less than a predetermined slightly open state, not a fully closed state. The predetermined slightly open state is not particularly limited, and for example, it may be a valve opening that results in a flow path area of ​​half or less of the flow path area of ​​the valve opening of the second indoor expansion valve 36b in a fully open state, or a valve opening that results in a flow path area of ​​1 / 3 or less, or a valve opening that results in a flow path area of ​​1 / 5 or less. As a result, even when the thermo-off state is entered during heating operation, the flow of refrigerant in the second indoor heat exchanger 32b is maintained, thereby suppressing the accumulation of a large amount of liquid refrigerant in the second indoor heat exchanger 32b.

[0093] The refrigerant flowing through the liquid side connecting pipe 2 is sent to the outdoor unit 10. In the outdoor unit 10, the refrigerant flowing through the liquid refrigerant pipe 28d is reduced in pressure by the outdoor expansion valve 18 to near the suction pressure of the compressor 12, becoming a gas-liquid two-phase refrigerant, which then flows into the outdoor heat exchanger 16. In this embodiment, for example, during heating operation, the valve opening of the outdoor expansion valve 18 is controlled so that the degree of superheating of the refrigerant suctioned by the compressor 12 satisfies predetermined conditions. Specifically, the degree of superheating determined from the pressure-equivalent saturation temperature grasped by the suction pressure sensor 23 and the refrigerant temperature detected by the suction temperature sensor 25 is controlled to satisfy predetermined conditions. The low-pressure gas-liquid two-phase refrigerant that flows into the outdoor heat exchanger 16 exchanges heat with the air surrounding the outdoor unit 10 supplied by the outdoor fan 22 and evaporates, becoming a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant flows into the accumulator 20 via the flow path switching valve 14. The low-pressure gaseous refrigerant that flows into the accumulator 20 is then drawn back into the compressor 12.

[0094] (2-3-3) Overview of refrigerant leakage prevention treatment The controller 70 performs refrigerant leakage prevention treatment, which includes pre-control and shut-off control.

[0095] If the controller 70 detects a concentration of a first predetermined concentration (an example of a first leakage condition) in either the first refrigerant sensor 38a of the first indoor unit 30a, or the second refrigerant sensor 38b of the second indoor unit 30b, and the state of being less than a predetermined minute opening continues for a predetermined period of time (an example of a predetermined period condition) or longer (an example of a pre-state condition), then the controller 70 performs pre-control (an example of a first control) by raising the valve opening of the indoor expansion valve 36 of the indoor unit 30 having the refrigerant sensor 38 that detected the first predetermined concentration. This makes it easier to ensure that there are no foreign objects around the indoor expansion valve 36, even if there are foreign objects such as dirt around the indoor expansion valve 36 of the indoor unit 30 having the refrigerant sensor 38 that detected the first predetermined concentration, by raising the valve opening, the foreign objects that were around the indoor expansion valve 36 are moved to a position away from the indoor expansion valve 36. This first predetermined concentration is an example of a first threshold.

[0096] Then, if the controller 70 detects a second predetermined concentration, which is equal to or greater than a first predetermined concentration, in either the first refrigerant sensor 38a of the first indoor unit 30a (which is an indoor unit 30) or the second refrigerant sensor 38b of the second indoor unit 30b (which is an indoor unit 30) (an example of the conditions for performing the second control), it performs shut-off control (an example of the second control) to completely close the indoor expansion valve 36 of the indoor unit 30 having the refrigerant sensor 38 that detected the second predetermined concentration, and the gas-side valve 37 of the indoor unit 30 having the refrigerant sensor 38 that detected the second predetermined concentration. This makes it possible to shut off the inflow of refrigerant into the indoor heat exchanger 32 through the liquid-side connecting pipe 2 and the gas-side connecting pipe 4 to the indoor unit 30. This second predetermined concentration is an example of a second threshold that is greater than the first threshold.

[0097] Furthermore, even if a refrigerant leak is detected in any of the indoor units 30, the controller 70 will not stop the operation of the compressor 12 and will continue the cooling / heating operation in the indoor units 30 other than the one in which the refrigerant leak was detected. However, if a refrigerant leak is detected in any of the indoor units 30, the controller 70 may stop the operation of the compressor 12 and also stop the cooling / heating operation in the indoor units 30 other than the one in which the refrigerant leak was detected.

[0098] Furthermore, if the controller 70 detects a refrigerant leak in any of the indoor units 30 via the refrigerant sensor 38, it will, for example, notify the operating remote control of which indoor unit 30 the refrigerant leak has been detected from.

[0099] (3) Control flow of refrigerant leakage prevention treatment Figure 4 shows the control flowchart of the refrigerant leakage prevention treatment.

[0100] In step S1, the controller 70 performs normal operation. Specifically, the controller 70 performs cooling or heating operation on the refrigeration cycle device 100 so that the conditions for a predetermined set temperature are met. While performing normal control, the controller 70 stores in memory historical information of the control state of the valve openings of the first indoor expansion valve 36a and the second indoor expansion valve 36b.

[0101] In step S2, the controller 70 determines whether the concentration of leaked refrigerant in any of the multiple indoor units 30 has reached a first predetermined concentration. Specifically, the controller 70 determines whether the first refrigerant sensor 38a or the second refrigerant sensor 38b has detected that the concentration of leaked refrigerant has reached a first predetermined concentration. If it is confirmed that the concentration of leaked refrigerant has reached a first predetermined concentration, the controller 70 recognizes the indoor unit 30 equipped with the refrigerant sensor 38 that detected that the concentration had reached the first predetermined concentration as a leak backup unit and proceeds with the processing from step S3 onward. If it is not detected that the concentration of leaked refrigerant has reached a first predetermined concentration, the process returns to step S1 and continues normal operation.

[0102] In step S3, the controller 70 determines whether the indoor expansion valve 36 of the leaky backup unit, which is an indoor unit 30 equipped with a refrigerant sensor 38 that detects when the concentration of leaked refrigerant reaches a first predetermined concentration, has remained below a predetermined small opening for a predetermined period of time or longer. Specifically, the controller 70 reads the control state history information of the valve opening of the indoor expansion valve 36 of the leaky backup unit, which is either the first indoor expansion valve 36a or the second indoor expansion valve 36b, from memory and determines whether the state of being below a predetermined small opening has remained for a predetermined period of time or longer. For example, when the first indoor expansion valve 36a or the second indoor expansion valve 36b is subjected to control such as subcooling control or superheating control during cooling or heating operation, if the heat load processed by the first indoor heat exchanger 32a or the second indoor heat exchanger 32b remains small, the valve opening of the first indoor expansion valve 36a or the second indoor expansion valve 36b tends to be kept small, and the state of being below a predetermined small opening may remain for a predetermined period of time or longer. Furthermore, during heating operation, when the conditions for the set temperature during heating of the first indoor unit 30a are met, the first indoor unit 30a is controlled to enter a thermo-off state during heating, and the valve opening of the first indoor expansion valve 36a is controlled to a predetermined slightly open state, which is an opening less than a predetermined small opening, not a fully closed state. Similarly, during heating operation, when the conditions for the set temperature during heating of the second indoor unit 30b are met, the second indoor unit 30b is controlled to enter a thermo-off state during heating, and the valve opening of the second indoor expansion valve 36b is controlled to a predetermined slightly open state, which is an opening less than a predetermined small opening, not a fully closed state. Thus, if it becomes clear from the control history that the valve opening of the indoor expansion valve 36 of the indoor unit 30, which is a leak backup unit, has been continuously controlled to be slightly closed, it is considered highly likely that foreign matter such as dirt is present around the indoor expansion valve 36. Therefore, the process proceeds to step S4, and control is performed to temporarily increase the valve opening of the indoor expansion valve 36. On the other hand, if there is no control history for the indoor expansion valve 36 of the indoor unit 30 of the leak backup unit, such as the valve opening being continuously controlled to be slightly closed, the process proceeds to step S6.The predetermined period is not particularly limited and may be a predetermined length of time, or it may be the time required for the cumulative rotational speed of the compressor 12 to reach a predetermined number while the opening is less than a predetermined small opening.

[0103] In step S4, the controller 70 controls the indoor expansion valve 36 of the leak backup unit 30, which is an indoor unit equipped with a refrigerant sensor 38 that detects when the concentration of leaked refrigerant reaches a first predetermined concentration, by temporarily increasing the valve opening degree from the current valve opening degree. Specifically, the controller 70 increases the valve opening degree of the indoor expansion valve 36 until it becomes equal to or greater than a predetermined opening degree. Here, the predetermined opening degree is not particularly limited and may be, for example, half-open or greater, which is half of the fully open state. In this embodiment, the state in which the valve opening degree of the indoor expansion valve 36 of the leak backup unit is set to equal or greater than the predetermined opening degree is maintained for a predetermined time. This predetermined time may be, for example, 0.5 seconds or more and 5 seconds or less, or 1 second or less, or it may be the time required to move the valve body in order to increase the valve opening degree by the predetermined amount. As a result, even if foreign matter such as dirt is present around the indoor expansion valve 36, it is possible to move the foreign matter to a location other than the indoor expansion valve 36, and even if the indoor expansion valve 36 is closed, a situation in which the indoor expansion valve 36 cannot be completely closed due to foreign matter getting stuck between the valve seat and the valve body is avoided. After the control to temporarily increase the valve opening of the indoor expansion valve 36 of the leak backup unit is performed in step S4, the control state is returned to the state before the control to temporarily increase the valve opening was performed. In this embodiment, when the control to increase the valve opening of the indoor expansion valve 36 is performed, if the compressor 12 is running, the control to reduce its rotational speed from the current level is performed. Specifically, the rotational speed of the compressor 12 is reduced by an amount corresponding to the degree to which the valve opening of the indoor expansion valve 36 is increased from the current level.

[0104] In step S5, the controller 70 waits for a predetermined time to elapse.

[0105] In step S6, the controller 70 determines whether the concentration of leaked refrigerant in any of the multiple indoor units 30 has reached a second predetermined concentration, which is higher than the first predetermined concentration. Specifically, the controller 70 determines whether the first refrigerant sensor 38a or the second refrigerant sensor 38b has detected that the concentration of leaked refrigerant has reached the second predetermined concentration. If it is confirmed that the concentration of leaked refrigerant has reached the second predetermined concentration, the controller recognizes the indoor unit 30 equipped with the refrigerant sensor 38 that detected that the concentration had reached the second predetermined concentration as the leaking unit and proceeds with the processing from step S7 onward. If it is not detected that the concentration of leaked refrigerant has reached the second predetermined concentration, the controller returns to step S1 and continues normal operation.

[0106] In step S7, the controller 70 identifies the indoor unit 30 equipped with a refrigerant sensor 38 that has detected that the concentration of leaked refrigerant has reached a second predetermined concentration, and notifies the remote control and the controller 70 of the fact of the leak.

[0107] In step S8, the controller 70 recognizes the indoor unit 30 equipped with a refrigerant sensor 38 that has detected that the concentration of leaked refrigerant has reached a second predetermined concentration as a leaking unit, and controls the closing of the gas-side valve 37 of the leaking unit. Specifically, if the first refrigerant sensor 38a detects that the concentration has reached a second predetermined concentration, the controller 70 recognizes the first indoor unit 30a as a leaking unit and controls the closing of the first gas-side valve 37a of the first indoor unit 30a. Also, if the second refrigerant sensor 38b detects that the concentration has reached a second predetermined concentration, the controller 70 recognizes the second indoor unit 30b as a leaking unit and controls the closing of the second gas-side valve 37b of the second indoor unit 30b. Note that the first gas-side valve 37a and the second gas-side valve 37b are controlled to be fully open during both cooling and heating operations, and since the valve opening is not narrowed, a state is maintained in which there is a low possibility of foreign matter such as dust being present in the surroundings. Therefore, even if control is performed to close the first gas-side valve 37a or the second gas-side valve 37b, it is unlikely that foreign matter such as debris will get stuck between the valve seat and the valve body in the first gas-side valve 37a or the second gas-side valve 37b, and the reliability of the valve closing control is high.

[0108] In step S9, the controller 70 controls the indoor expansion valve 36 of the leaker, which is an indoor unit 30 equipped with a refrigerant sensor 38 that detects that the concentration of leaked refrigerant has reached a second predetermined concentration, to be in a fully closed state.

[0109] In step S10, the controller 70 waits for a predetermined time to elapse.

[0110] In step S11, the controller 70 determines whether the refrigerant sensor 38 of the indoor unit 30, which is the leaker, has detected again that the concentration of leaked refrigerant has reached a second predetermined concentration. Specifically, it determines whether the refrigerant leak is still continuing even after a predetermined time has elapsed since the control to fully close the indoor expansion valve 36 in step S9. This makes it possible to determine whether the refrigerant leak has been stopped more reliably. If it is detected again that the second predetermined concentration has been reached, the process proceeds to step S12. If it is not detected that the second predetermined concentration has been reached, the process returns to step S1, and normal operation of the indoor units 30 other than the leaker continues.

[0111] In step S12, the controller 70 controls the indoor expansion valve 36 of the leaker to open above its current valve opening, similar to step S4. This makes it possible to more reliably move foreign matter, such as debris, away from the indoor expansion valve 36 of the leaker, even if such foreign matter is interposed between the valve body and the valve seat, although the possibility is lower than in step S4.

[0112] In step S13, the controller 70 controls the indoor expansion valve 36 of the leaker to be in a fully closed state.

[0113] (4) Features of the Embodiment According to the refrigeration cycle device 100 of this embodiment, in the preliminary state when the concentration of leaked refrigerant is a first predetermined concentration, which is the situation before the indoor expansion valve 36 is controlled to a fully closed state when the concentration of leaked refrigerant reaches a second predetermined concentration, it is possible to temporarily increase the valve opening of the indoor expansion valve 36 provided in the backup leak unit. Therefore, even if there is a risk that foreign matter such as dirt may be present around the indoor expansion valve 36 in the backup leak unit and get stuck in the gap between the valve body and the valve seat, preventing the valve from being fully closed, it is possible to move the foreign matter to a position away from the indoor expansion valve 36 before the concentration of leaked refrigerant reaches the second predetermined concentration. As a result, when the concentration of leaked refrigerant is detected to have reached a second predetermined concentration, the controller 70 can quickly begin to control the indoor expansion valve 36 to a fully closed state, thereby rapidly suppressing refrigerant leakage. At the same time, it is possible to suppress the occurrence of a situation in which refrigerant leaks out because foreign matter is interposed between the valve seat and valve body of the indoor expansion valve 36, which is being controlled to be fully closed, preventing it from being fully closed. This improves the reliability of the control to fully close the indoor expansion valve 36.

[0114] Furthermore, since the indoor expansion valves 36a and 36b can be more reliably closed to avoid situations where foreign objects get stuck, when the refrigerant sensors 38a and 38b detect that the second predetermined concentration has been reached, the continuous supply of refrigerant passing through the indoor expansion valves 36a and 36b to the corresponding indoor heat exchangers 32a and 32b is suppressed, making it possible to keep the amount of refrigerant leakage small.

[0115] Furthermore, according to the refrigeration cycle device 100 of this embodiment, even if the concentration of leaked refrigerant reaches a first predetermined concentration, the control to fully close the indoor expansion valve 36 is not performed unless it reaches a second predetermined concentration. Therefore, even if the concentration of leaked refrigerant temporarily reaches a first predetermined concentration, if it does not reach a second predetermined concentration, the indoor expansion valve 36 is controlled to fully close, preventing a situation where refrigerant is not supplied to the corresponding indoor heat exchanger 32. As a result, even if the refrigeration cycle device 100 is temporarily detected as having reached a first predetermined concentration due to gas supplied from the surrounding environment outside the device, unintended operating conditions such as the supply of refrigerant to the corresponding indoor heat exchanger 32 are suppressed.

[0116] Furthermore, the control to temporarily increase the valve opening of the indoor expansion valves 36a and 36b is limited to cases where the indoor expansion valves 36a and 36b have remained below a predetermined minute opening for a predetermined period of time or longer. As a result, in the case of an indoor unit 30 equipped with a refrigerant sensor 38 that has detected that the second predetermined concentration has been reached, if the valve opening of the indoor expansion valves 36a and 36b was slightly above a minute opening a short time prior, or in other cases where the possibility of foreign matter being present around the indoor expansion valves 36a and 36b is low, it is possible to quickly close the valves completely when the second predetermined concentration is detected without performing the control to increase the valve opening, and moreover, a situation in which refrigerant leaks out of the valves can be avoided. As a result, in cases where the rate of increase in the concentration of leaked refrigerant is rapid and the leakage situation exceeds the second predetermined concentration soon after exceeding the first predetermined concentration, if the possibility of foreign matter being present around the indoor expansion valve 36 is low, it is possible to quickly control the indoor expansion valve 36 to a completely closed state to shut off refrigerant leakage.

[0117] Furthermore, in this embodiment, the indoor expansion valves 36a and 36b can implement two functions: a flow control valve for controlling the amount of refrigerant sent to the indoor heat exchangers 32a and 32b when circulating refrigerant in the refrigerant circuit 90 to perform a refrigeration cycle, and a shut-off valve for shutting off the flow of refrigerant when a refrigerant leak is detected. This eliminates the need to separately provide a shut-off valve for shutting off the flow of refrigerant in addition to the indoor expansion valves 36a and 36b.

[0118] Furthermore, in the refrigeration cycle device 100 of this embodiment, carbon dioxide refrigerant is used as the refrigerant. When using carbon dioxide refrigerant, even at low concentrations, the risk due to toxicity tends to be a problem compared to R32 or propane, but in this embodiment, the reliability of the control that keeps the indoor expansion valve 36 in a fully closed state is high, so it is possible to more reliably suppress the leakage of carbon dioxide refrigerant and reduce the risk due to the toxicity of the leaked refrigerant.

[0119] Furthermore, in the refrigeration cycle device 100 of this embodiment, carbon dioxide is used as the refrigerant, and when the refrigeration cycle is performed, the refrigerant pressure on the high-pressure side is used at a high level. For this reason, in the refrigeration cycle device 100 of this embodiment that uses carbon dioxide as the refrigerant, the refrigerant piping and heat transfer tubes that constitute the refrigerant circuit 90 are designed to have a high design pressure and are made of thick-walled materials. In this case, the amount of heat input required when brazing the piping tends to be large, and as a result, an oxide film is likely to form on the inner surface of the piping. For this reason, when the refrigeration cycle is performed, this oxide film is likely to peel off from the inner surface of the piping and become trapped between the valve body and valve seat of the expansion valve along with foreign matter such as dirt and refrigerant. Even in this case, by controlling the valve opening to increase the degree of opening as described above, the situation in which foreign matter such as dirt gets trapped between the valve seat and valve body is suppressed.

[0120] Furthermore, in refrigeration cycle systems that use carbon dioxide as a refrigerant, the refrigerant pressure tends to be high when the refrigeration cycle is performed, and if the refrigerant leaks, the amount of leakage may be large due to the pressure difference. In contrast, in the refrigeration cycle system 100 of this embodiment, by controlling the valve opening as described above, the situation in which foreign matter such as dirt gets stuck between the valve seat and the valve body when the indoor expansion valve 36 is controlled to a fully closed state is suppressed, and thus the leakage of carbon dioxide refrigerant can be suppressed more reliably.

[0121] (5) Other Embodiments (5-1) Other Embodiment A In the above embodiment, before the indoor expansion valve 36 is controlled to a fully closed state when it is detected that the concentration of the leaked refrigerant has reached a second predetermined concentration, the case in which control is performed in advance to increase the valve opening of the indoor expansion valve 36 when the concentration of the leaked refrigerant reaches a first predetermined concentration was described as an example.

[0122] In contrast, when controlling the indoor expansion valve 36 to increase its valve opening before controlling it to a fully closed state, this control is not limited to cases where a leaked refrigerant concentration has been detected. In addition to cases where a leaked refrigerant concentration has been detected, the control may also be made to increase the valve opening of the indoor expansion valve 36 before controlling the indoor expansion valve 36 to a fully closed state when controlling the indoor expansion valve 36 of an indoor unit 30 that has entered a thermo-off state during cooling operation. For example, a precondition may be set before the thermo-off state is reached during cooling operation, and when the precondition is met, the control may be made to temporarily increase the valve opening of the indoor expansion valve 36.

[0123] This suppresses a decrease in the temperature of the indoor heat exchanger 32 of the indoor unit 30, which is in a thermostat-off state during cooling operation, and more reliably prevents cold air from being sent from the indoor heat exchanger 32 towards the air-conditioned space.

[0124] (5-2) Other Embodiments B In addition to the above examples, the control to increase the valve opening of the indoor expansion valve 36 before controlling the indoor expansion valve 36 to a fully closed state may also be performed, for example, when starting a pump-down operation for the refrigeration cycle device 100.

[0125] Pump-down operation is an operation in which the compressor 12 is driven while controlling the indoor expansion valves 36a and 36b of each indoor unit 30a and 30b to a fully closed state, causing the outdoor heat exchanger 16 to function as a refrigerant heat radiator, thereby recovering the refrigerant from the refrigerant circuit 90 by collecting the refrigerant that has been heated from the indoor expansion valves 36a and 36b into the outdoor heat exchanger 16.

[0126] The refrigeration cycle device 100 may, for example, receive an instruction to start a pump-down operation when a predetermined button provided on the refrigeration cycle device 100 is pressed, or it may receive an instruction to start a pump-down operation via operation input from a remote control. Alternatively, the pump-down operation may be started when either the first refrigerant sensor 38a or the second refrigerant sensor 38b detects that the concentration of leaked refrigerant has reached a second predetermined concentration. In this case, the control of the pump-down operation described below may be applied instead of the control of the first chamber expansion valve 36a, the second chamber expansion valve 36b, the first gas-side valve 37a, and the second gas-side valve 37b in the above embodiment.

[0127] Upon receiving the command to start the pump-down operation, the controller 70 maintains the connection state of the flow path switching valve 14 if cooling operation was being performed, or switches the connection state of the flow path switching valve 14 to the cooling operation connection state if heating operation was being performed, and starts the pump-down operation. Here, the controller 70 maintains the first gas side valve 37a and the second gas side valve 37b in a fully open state, while controlling the indoor expansion valves 36a and 36b to a fully closed state. Here, the outdoor expansion valve 18 is maintained in a state that is not fully closed, such as a fully open state. Then, when the controller 70 has completed refrigerant recovery and met the predetermined recovery completion conditions, it controls the first gas side valve 37a and the second gas side valve 37b to a fully closed state. These recovery completion conditions are not particularly limited and may include the cumulative operating time from the start of the pump-down operation reaching a predetermined time, or the superheating degree of the refrigerant suctioned by the compressor 12 reaching a predetermined value or higher. After that, the drive of the compressor 12 is stopped, and the pump-down operation is terminated.

[0128] According to the above control, it is possible to more reliably suppress the leakage of refrigerant from the indoor expansion valves 36a and 36b towards the indoor heat exchangers 32a and 32b during pump-down operation.

[0129] (5-3) Other Embodiment C In the above embodiment, carbon dioxide refrigerant was used as an example of the refrigerant used to fill the refrigerant circuit 90.

[0130] In contrast, the refrigerant used in the refrigerant circuit 90 is not limited to this, and may be R32 or propane, for example.

[0131] Although R32 and propane are flammable, more effectively suppressing the leakage of these refrigerants can reduce the risk of combustion caused by leaked refrigerants.

[0132] (5-4) Other Embodiments D In the above embodiments, the case in which gas side valves 37a and 37b are provided in indoor units 30a and 30b was described as an example.

[0133] In contrast, the gas-side valves 37a and 37b do not necessarily have to be present in the indoor units 30a and 30b. For example, a valve unit having the gas-side valves 37a and 37b may be provided as a separate unit from the indoor units 30a and 30b.

[0134] (5-5) Other Embodiments E In the above embodiment, when performing a first control to increase the valve opening of the first indoor expansion valve 36a or the second indoor expansion valve 36b, it is determined whether or not the first refrigerant sensor 38a or the second refrigerant sensor 38b has detected that the concentration of leaked refrigerant has reached a first predetermined concentration, and when performing a second control to completely close the first indoor expansion valve 36a or the second indoor expansion valve 36b, it is determined whether or not the concentration of leaked refrigerant has reached a second predetermined concentration which is higher than the first predetermined concentration.

[0135] In contrast, the conditions used to determine the degree of refrigerant leakage from the first indoor expansion valve 36a or the second indoor expansion valve 36b are not limited to those described above. For example, the conditions may include determining a first degree of leakage and a second degree of leakage that is higher than the first degree of leakage, as the degree of refrigerant leakage from the first indoor unit 30a or the second indoor unit 30b. Such determination of the degree of refrigerant leakage may include, for example, a higher degree of leakage the greater the increase in the concentration of the leaked refrigerant per unit time, a higher degree of leakage the greater the amount of refrigerant leaked, a higher degree of leakage the longer the refrigerant leakage time, a higher degree of leakage the greater the refrigerant leakage rate, a higher degree of leakage the greater the increase in the refrigerant leakage rate per unit time, or a combination of these. This degree of refrigerant leakage may be determined, for example, as a detected value from the refrigerant sensor 38 in the above embodiment, or it may be determined by the controller 70 performing calculations based on the information detected by the refrigerant sensor 38.

[0136] In the above examples, when determining the amount of increase in the concentration of leaked refrigerant per unit time, for example, instead of using a specific concentration predetermined in advance as the first predetermined concentration in the above embodiment, the controller 70 may use a concentration calculated based on the detection concentration of the first refrigerant sensor 38a or the second refrigerant sensor 38b as the leak concentration that is expected to reach the second predetermined concentration after a predetermined time such as 50 seconds.

[0137] Specifically, the controller 70 calculates the leakage rate, which is the increase per unit time of the detected concentration of the first refrigerant sensor 38a or the second refrigerant sensor 38b during a predetermined time period from the present to the past. The controller 70 then determines that, assuming the leakage rate continues from the present, the second predetermined concentration will be reached after a predetermined time period, such as 50 seconds. In this case, the controller 70 may designate the indoor unit 30 equipped with the refrigerant sensor 38 as a backup leak unit and temporarily increase the valve opening of the indoor expansion valve 36 in the backup leak unit compared to the current valve opening. In this case as well, similar to the above embodiment, the indoor expansion valve 36 in the backup leak unit may be temporarily increased above the valve opening only if the state of being below a predetermined minute opening continues for a predetermined period of time or longer.

[0138] <Other> Although embodiments of this disclosure have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of this disclosure as described in the claims.

[0139] 2: Liquid side connecting pipe (first main flow path) 2a: First liquid side branch pipe (first branch flow path) 2b: Second liquid side branch pipe (second branch flow path) 4: Gas side connecting pipe (second main flow path) 4a: First gas side branch pipe (third branch flow path) 4b: Second gas side branch pipe (fourth branch flow path) 10: Outdoor unit 12: Compressor 14: Flow path switching valve 16: Outdoor heat exchanger 18: Outdoor expansion valve 20: Accumulator 21: Discharge pressure sensor 22: Outdoor fan 23: Intake pressure sensor 24: Liquid shut-off valve 25: Intake temperature sensor 26: Gas shut-off valve 27: Outdoor heat exchanger temperature sensor 28a: Intake pipe (second main flow path) 28b: Discharge pipe (second main flow path) 28c : First gas refrigerant piping (second main flow path) 28d: Liquid refrigerant piping 28e: Second gas refrigerant piping (second main flow path) 30: Indoor unit 30a: First indoor unit 30b: Second indoor unit 31a: First casing 31b: Second casing 32: Indoor heat exchanger 32a: First indoor heat exchanger 32b: Second indoor heat exchanger 33a: First indoor temperature sensor 33b: Second indoor temperature sensor 34a: First indoor fan 34b: Second indoor fan 35a: First indoor heat exchanger temperature sensor 35b: Second indoor heat exchanger temperature sensor 36: Indoor expansion valve (electric expansion valve) 36a: First indoor expansion valve (electric expansion valve, first electric expansion valve) 36b: Second indoor expansion valve (electric expansion valve, second electric expansion valve) 37: Gas side valve 37a: First gas side valve 37b: Second gas side valve 38: Refrigerant sensor 38a: First refrigerant sensor (leak detection unit) 38b: Second refrigerant sensor (leak detection unit) 70: Controller (control unit) 72: Indoor control unit 72a: First indoor control unit 72b: Second indoor control unit 74: Outdoor control unit 90: Refrigerant circuit 100: Refrigeration cycle device X: First branching point Y: Second branching point

[0140] Japanese Patent Publication No. 2016-035356

Claims

1. A refrigeration cycle device (100) comprising: a refrigerant circuit (90) through which refrigerant circulates, having electric valves (36a, 36b); a control unit (70) that controls the opening degree of the electric valves; and a leak detection unit (38a, 38b) that detects the refrigerant leaking from the refrigerant circuit, wherein the control unit performs a first control to increase the valve opening degree of the electric valve when predetermined conditions including a first leak condition, where the detection result by the leak detection unit is greater than or equal to a first threshold, is met, and performs a second control to completely close the electric valve when the detection result by the leak detection unit is greater than or equal to a second threshold, which is greater than the first threshold.

2. The refrigeration cycle apparatus according to claim 1, wherein the detection result by the leak detection unit is a value indicating the degree of leakage as determined from the detection information by the leak detection unit.

3. The degree of leakage is determined according to at least one of the concentration and amount of the leaked refrigerant and the values ​​relating thereto, or is determined based on information regarding the change over time between the concentration and amount of the leaked refrigerant and the values ​​relating thereto, as described in claim 2.

4. The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the predetermined conditions include a prior state condition that the valve opening of the electric valve remains below a predetermined opening for a predetermined period of time.

5. The refrigeration cycle apparatus according to claim 4, wherein the electric valve is an electric expansion valve, and the control unit controls the valve opening of the electric expansion valve to be less than the predetermined opening when the heat load to be processed is in a predetermined low load state.

6. The refrigeration cycle apparatus according to claim 5, wherein the refrigerant circuit comprises a compressor (12), an outdoor heat exchanger (16), indoor heat exchangers (32a, 32b), a first flow path (2, 2a, 2b) extending from the outdoor heat exchanger to the indoor heat exchanger and equipped with the electric expansion valve, and a second flow path (4, 4a, 4b, 28e, 28a, 28b, 28c) extending from the outdoor heat exchanger to the indoor heat exchanger and equipped with the compressor, the refrigerant circuit is capable of performing a heating operation in which the indoor heat exchanger functions as a refrigerant radiator, and the control unit controls the valve opening of the electric expansion valve to be less than the predetermined opening and not in a fully closed state when the conditions relating to the set temperature corresponding to the indoor heat exchanger are met.

7. The refrigerant circuit comprises a compressor (12), an outdoor heat exchanger (16), a first indoor heat exchanger (32a), a second indoor heat exchanger (32b), a first electric expansion valve (36a) which is the electric expansion valve, a second electric expansion valve (36b) which is the electric expansion valve, a first main flow path (2) extending from the outdoor heat exchanger to a first branch section (X), and a first branch flow path (2a) extending from the first branch section to the first indoor heat exchanger and equipped with the first electric expansion valve. The refrigeration cycle apparatus according to claim 5, comprising: a second branch passage (2b) extending from the first branch to the second indoor heat exchanger and provided with the second electric expansion valve; a second main passage (4, 28e, 28a, 28b, 28c) extending from the outdoor heat exchanger to the second branch (Y) and provided with the compressor; a third branch passage (4a) extending from the second branch to the first indoor heat exchanger; and a fourth branch passage (4b) extending from the second branch to the second indoor heat exchanger.

8. The refrigeration cycle apparatus according to claim 7, wherein the refrigerant circuit is capable of performing a heating operation in which the first indoor heat exchanger and the second indoor heat exchanger function as refrigerant radiators, and the control unit controls the valve opening of the first electric expansion valve to be less than the predetermined opening and not in a fully closed state when the conditions for the set temperature corresponding to the first indoor heat exchanger are met, and controls the valve opening of the second electric expansion valve to be less than the predetermined opening and not in a fully closed state when the conditions for the set temperature corresponding to the second indoor heat exchanger are met.

9. The refrigeration cycle apparatus according to any one of claims 4 to 8, wherein the control unit performs the second control without performing the first control if the first leakage condition is met without satisfying the prior state condition.

10. The refrigeration cycle apparatus according to any one of claims 1 to 9, wherein the control unit increases the valve opening of the electric valve to half open or more in the first control.

11. The refrigeration cycle apparatus according to any one of claims 1 to 10, wherein the predetermined conditions include a time condition that a predetermined period has elapsed since the last time the first control was performed.

12. The refrigeration cycle apparatus according to any one of claims 1 to 11, wherein the refrigerant is a refrigerant having at least one of a predetermined toxicity and a predetermined flammability.

13. The refrigeration cycle apparatus according to any one of claims 1 to 12, wherein the refrigerant is a carbon dioxide refrigerant.

14. A method for controlling an electric valve (36a, 36b) of a refrigeration cycle device (100), wherein the refrigeration cycle device comprises a refrigerant circuit (90) having the electric valve and through which refrigerant circulates, a control unit (70) for controlling the opening degree of the electric valve, and a leak detection unit (38a, 38b) for detecting refrigerant leaked from the refrigerant circuit, wherein the control unit performs a first control to increase the valve opening degree of the electric valve when predetermined conditions including a first leakage condition where the detection result by the leak detection unit is greater than or equal to a first threshold, and performs a second control to completely close the electric valve when the detection result by the leak detection unit is greater than or equal to a second threshold which is greater than the first threshold.

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