AIR CONDITIONING DEVICE

Abstract

An air conditioning device according to one embodiment includes an outdoor unit, a plurality of indoor units, a plurality of switching units, and a control unit. If an outdoor heat exchanger functions as an evaporator and, among the plurality of indoor units, some are in cooling operation and some are in heating operation, the control unit adjusts the opening degree of an indoor expansion valve of an indoor unit during a cooling operation, such adjustment being in accordance with the outdoor temperature and the indoor temperature that was detected by an indoor temperature detection unit of an indoor unit during a heating operation.

Claims

1. An air conditioning device comprising: an outdoor unit including a compressor sucking, compressing, and discharging a refrigerant, an outdoor heat exchanger functioning as an evaporator or a condenser which performs heat exchange between outdoor air and the refrigerant, an outdoor blower sucking the outdoor air and blowing the air subjected to heat exchange by the outdoor heat exchanger to the outside, an outdoor expansion valve adjusting a flow rate of the refrigerant flowing through the outdoor heat exchanger in accordance with an opening, and an outdoor temperature detection unit detecting an outdoor temperature which is a temperature of the outdoor air; a plurality of indoor units including an indoor heat exchanger functioning as an evaporator or a condenser which performs heat exchange between indoor air and the refrigerant, an indoor blower sucking the indoor air and blowing the air subjected to heat exchange by the indoor heat exchanger into the room, an indoor expansion valve adjusting a flow rate of the refrigerant flowing through the indoor heat exchanger in accordance with an opening, and an indoor temperature detection unit detecting an indoor temperature which is a temperature of the indoor air; a plurality of switching units switching the flow of the refrigerant between the outdoor unit and each of the indoor units to one of two flow paths for cooling and heating; and a control unit controlling operations of the outdoor unit, the plurality of indoor units, and the plurality of switching units, and switching each of the plurality of indoor units between cooling and heating, wherein when the outdoor heat exchanger functions as an evaporator and when the indoor units which are in cooling operation and the indoor units which are in heating operation, among the plurality of indoor units, exist, the control unit adjusts the opening of the indoor expansion valve of the indoor unit in cooling operation in accordance with the outdoor temperature and the indoor temperature detected by the indoor temperature detection unit of the indoor unit in heating operation.

2. The air conditioning device of claim 1, wherein the control unit adjusts the opening of the indoor expansion valve of the indoor unit which is in cooling operation, in accordance with a target value of a degree of superheat of the refrigerant, and corrects the target value in accordance with the outdoor temperature and the indoor temperature detected by the indoor temperature detection unit of the indoor unit which is in heating operation.

3. The air conditioning device of claim 2, wherein the control unit corrects the target value by adding a correction value to the target value to be corrected, maintains the target value if a temperature difference between the indoor temperature detected by the indoor temperature detection unit of the indoor unit which is in heating operation and the outdoor temperature is smaller than or equal to a predetermined threshold value, and corrected the target value with the correction value which is larger as the temperature difference becomes larger if the temperature difference exceeds the threshold value.

4. The air conditioning device of claim 1, wherein the control unit adjusts the opening of the indoor expansion valve of the indoor unit which is in cooling operation such that the opening becomes smaller as the temperature difference between the indoor temperature detected by the indoor temperature detection unit of the indoor unit which is in heating operation and the outdoor temperature is larger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a circuit diagram schematically showing an air conditioning device according to an embodiment.

[0009] FIG. 2 is a control flowchart of an opening adjustment process in the air conditioning device according to the embodiment.

[0010] FIG. 3 is a graph showing an example of a relationship between an indoor/outdoor temperature difference (the difference between the indoor temperature and the outdoor temperature) and a correction value for a target degree of superheat in the air conditioning device according to the embodiment.

DETAILED DESCRIPTION

[0011] In general, according to one embodiment, an air conditioning device comprises an outdoor unit, a plurality of indoor units, a plurality of switching units, and a control unit.

[0012] The outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor blower, an outdoor expansion valve, and an outdoor temperature detection unit. The compressor sucks, compresses, and discharges a refrigerant. The outdoor heat exchanger functions as an evaporator or a condenser which exchanges heat between the outdoor air and the refrigerant. The outdoor blower sucks the outdoor air and blows the air which is subjected to heat exchange in the outdoor heat exchanger to the outside. The outdoor expansion valve adjusts the flow rate of the refrigerant flowing through the outdoor heat exchanger in accordance with its opening. The outdoor temperature detection unit detects the outdoor temperature, which is the temperature of the outdoor air.

[0013] The indoor unit includes an indoor heat exchanger, an indoor blower, an indoor expansion valve, and an indoor temperature detection unit. The indoor heat exchanger functions as a condenser or evaporator which exchanges heat between indoor air and the refrigerant. The indoor blower sucks the indoor air and blows out the air which is subjected to heat exchange in the indoor heat exchanger into the room. The indoor expansion valve adjusts the flow rate of the refrigerant flowing through the indoor heat exchanger in accordance with its opening. The indoor temperature detection unit detects the indoor temperature, which is the temperature of the indoor air.

[0014] The switching unit switches the flow of the refrigerant between the outdoor unit and each of the indoor units to one of two flow paths for cooling and heating.

[0015] The control unit controls the operations of the outdoor unit, the plurality of indoor units, and the plurality of switching units, and switches each of the plurality of indoor units between cooling and heating. When the outdoor heat exchanger functions as an evaporator and when the indoor units which are in cooling operation and the indoor units which are in heating operation, among the plurality of indoor units, exist, the control unit adjusts the opening of the indoor expansion valve of the indoor unit in cooling operation in accordance with the outdoor temperature and the indoor temperature detected by the indoor temperature detection unit of the indoor unit in heating operation.

[0016] An embodiment of the present will be described hereinafter with reference to the accompanying drawings.

[0017] FIG. 1 is a circuit diagram schematically showing the air conditioning device according to the embodiment. As shown in FIG. 1, the air conditioning device 1 comprises an outdoor unit 2 and a plurality of indoor units 4 connected by flow paths through which a refrigerant flows. FIG. 1 shows a configuration example in which three indoor units 4 (4a, 4b, and 4c) are connected to one outdoor unit 2, but the number of indoor units 4 is not limited to this. The flow path is configured to be connected to a plurality of pipes. These pipes include a pipe (hereinafter referred to as an outdoor side pipe) 201 that constitutes the flow path on the outdoor unit 2 side, and a pipe (hereinafter referred to as an indoor side pipe) 401 that constitutes the flow path of the indoor unit 4.

[0018] In addition, the air conditioning device 1 also includes multiple switching units 6 that switch the flow of refrigerant between the outdoor unit 2 and each of the multiple indoor units 4 to one of two flow paths, cooling or heating. Each of the plurality of switching units 6 is provided for each of the plurality of indoor units 4. In the example shown in FIG. 1, a configuration example in which three switching units 6 (6a, 6b, and 6c) are provided one for each of the three indoor units 4. The number of switching units 6 needs only to match the number of indoor units 4. Thus, a predetermined switching unit 6 is linked to each of the plurality of indoor units 4.

[0019] By comprising these switching units 6, the air conditioning device 1 can perform simultaneous cooling and heating operation (mixed cooling and heating operation). The simultaneous cooling and heating operation is an operating mode of the air conditioning device 1 in which each of the plurality of indoor units 4 can optionally select the cooling operation or the heating operation and perform the operation. During the simultaneous cooling and heating operation, the air conditioning device 1 is in the operation mode of either a main cooling operation in which the outdoor unit 2 performs the cooling operation or a main heating operation in which the outdoor unit 2 performs the heating operation.

[0020] In the following descriptions, it is assumed that the air conditioning device 1 is in the operation mode of the main heating operation, that the outdoor unit 2 performs the heating operation, and that the indoor unit 4 which is in cooling operation and the indoor unit 4 which is in heating operation exist (exist together), unless otherwise specified in relation to the simultaneous cooling and heating operation. When the indoor unit 4 is in cooling operation, this means that the indoor unit 4 is in a state of actually performing the cooling operation at that time (hereinafter referred to as a cooling operation thermo-on state). When the indoor unit 4 is in heating operation, this means that the indoor unit 4 is in a state of actually performing the heating operation at that time (hereinafter referred to as a heating operation thermo-on state).

[0021] States other than the two states of cooling operation and heating operation include a state in which the indoor unit 4 is stopped (operation is ended), a thermo-off state in the cooling operation (hereinafter referred to as a cooling operation thermo-off state), and a thermo-off state in the heating operation (hereinafter referred to as a heating operation thermo-off state). The thermo-off state is, for example, a state in which the indoor temperature has reached the cooling set temperature and the cooling operation is temporarily stopped, or a state in which the indoor temperature has reached the heating set temperature and the heating operation is temporarily stopped.

[0022] In addition, the air conditioning device 1 comprises a control unit 8 that controls the operations of the outdoor unit 2, the plurality of indoor units 4, and the plurality of switching units 6, and that switches each of the plurality of indoor units 4 to either the cooling operation or the heating operation.

[0023] The outdoor unit 2 includes as its main components a compressor 202, an outdoor heat exchanger 203, an outdoor blower 204, an outdoor expansion valve 205, an outdoor temperature detection unit 206, and the like.

[0024] The compressor 202 sucks refrigerant from a suction pipe 201a, compresses the refrigerant, and discharges the compressed refrigerant to a discharge pipe 201b. Each of the suction pipe 201a and the discharge pipe 201b constitutes a part of the outdoor side pipe 201. For example, the compressor 202 is configured with a sealed container, a rotation shaft, a compression mechanism, an electric mechanism, and the like, and discharges a high-temperature and high-pressure gas-phase refrigerant to the discharge pipe 201b.

[0025] The outdoor heat exchanger 203 exchanges heat between the outdoor air and the refrigerant. As described above, it is assumed in the present embodiment that the air conditioning device 1 is simultaneously operated for cooling and heating during mainly performing the heating operation. For this reason, the outdoor heat exchanger 203 functions as an evaporator, and evaporates the liquid phase refrigerant, the gas-liquid two-phase refrigerant, or the like, which is heat exchanged in the indoor heat exchanger 402 (indoor unit 4a in the example shown in FIG. 1) of the indoor unit 4 in the heating operation thermo-on state by heat exchange with the air, and changes the refrigerant into a low-temperature and low-pressure gas phase refrigerant or a gas-liquid two-phase refrigerant. However, when the air conditioning device 1 is simultaneously operated for cooling and heating during mainly performing the cooling operation, the outdoor heat exchanger 203 functions as a condenser. In this case, the outdoor heat exchanger 203 condenses the high-temperature and high-pressure gas-phase refrigerant discharged from the compressor 202 by heat exchange, and changes the refrigerant into a high-pressure liquid-phase refrigerant.

[0026] The outdoor blower 204 sucks outdoor air (hereinafter referred to as outside air) and blows the air which is subjected to the heat exchange in the outdoor heat exchanger 203 to the outside. The outdoor air sucked by the outdoor blower 204 is blown onto the outdoor heat exchanger 203. Accordingly, heat exchange between the outdoor air and the refrigerant flowing through the outdoor heat exchanger 203 is performed. The outdoor blower 204 is provided near the outdoor heat exchanger 203.

[0027] The outdoor expansion valve 205 adjusts the flow rate of the refrigerant flowing through the outdoor heat exchanger 203 in accordance with its opening. The outdoor expansion valve 205 has, for example, a valve structure in which the amount of throttled refrigerant is adjusted by controlling the opening of the valve between a minimum opening and a maximum opening, and is configured as a pulse motor valve (PMV) whose opening changes continuously in accordance with the number of drive pulses supplied. The outdoor expansion valve 205 has its opening adjusted by the control unit 8, and supplies a value of the current opening (actual opening) to the control unit 8 by a wired or wireless manner.

[0028] In the example shown in FIG. 1, the outdoor expansion valve 205 is provided in a flow path (hereinafter referred to as a liquid pipe) 90 through which the liquid-phase refrigerant or the gas-liquid two-phase refrigerant flows. The liquid pipe 90 is configured by, for example, connecting a plurality of pipes with a joint (for example, a packed valve) PV0, with one end connected to the outdoor expansion valve 205 and the other end connected to an indoor expansion valve 404 of each indoor unit 4 to be described later. The liquid pipe 90 constitutes a part of the outdoor side pipe 201 and the indoor side pipe 401. As described above, in the present embodiment, the air conditioning device 1 is simultaneously operated for cooling and heating during mainly performing the heating operation, i.e., the outdoor unit 2 is operated for heating. For this reason, the liquid-phase refrigerant, the gas-liquid two-phase refrigerant or the like returned from the indoor unit 4 (indoor unit 4a in the example shown in FIG. 1) in heating operation (heating operation thermo-on state) flows through the liquid pipe 90.

[0029] Incidentally, when the air conditioning device 1 is simultaneously operated for cooling and heating during mainly performing the cooling operation, i.e., when the outdoor unit 2 is operated for cooling, the liquid phase refrigerant, the gas-liquid two-phase refrigerant, or the like, which is subjected to heat exchange in the outdoor heat exchanger 203 flows through the liquid pipe 90. In this case, high-temperature and high-pressure gas phase refrigerant discharged from the compressor 202 is guided by a second four-way valve 208 to be described below to flow into the outdoor heat exchanger 203. At that time, the second four-way valve 208 has ports connected as represented by dashed lines in FIG. 1.

[0030] The outdoor temperature detection unit 206 detects the outdoor temperature, which is the temperature of the outside air, i.e., the outside air temperature. In this case, the outdoor area is an outdoor area opposed to an indoor area which is the space to be air-conditioned, for example, an outdoor space in which the outdoor heat exchanger 203 and the outdoor blower 204 are provided, or the like. The outdoor temperature detection unit 206 is, for example, a temperature sensor (thermistor) having a temperature sensor provided near the outdoor heat exchanger 203 to detect the outdoor temperature. The outdoor temperature detection unit 206 supplies the detected outdoor temperature value to the control unit 8 by a wired or wireless manner.

[0031] As described above, in the present embodiment, the air conditioning device 1 is simultaneously operated for cooling and heating during mainly performing the heating operation, and, among the plurality of indoor units 4, indoor units which are in cooling operation and indoor units which are in heating operation exist (exist together). In the example shown in FIG. 1, among the three indoor units 4a, 4b, and 4c, the indoor unit 4a is in heating operation, i.e., in the heating operation thermo-on state, the indoor unit 4b is in the heating operation thermo-off state, and the indoor unit 4c is in cooling operation, i.e., in the cooling operation thermo-on state.

[0032] Each of the plurality of indoor units 4 includes as its main components an indoor heat exchanger 402, an indoor blower 403, an indoor expansion valve 404, an indoor temperature detection unit 405, and the like.

[0033] The indoor heat exchangers 402 exchange heat between the indoor air and the refrigerant. In the present embodiment, indoor units which are in cooling operation and indoor units which are in heating operation exist (exist together), among the plurality of indoor units 4, and the indoor heat exchangers 402 of the indoor units 4 in cooling operation function as evaporators, and the indoor heat exchangers 402 of the indoor units 4 in heating operation function as condensers. In the example shown in FIG. 1, an indoor heat exchanger 402a of the indoor unit 4a in the heating operation thermo-on state and an indoor heat exchanger 402b of the indoor unit 4b in the heating operation thermo-off state function as condensers. In contrast, an indoor heat exchanger 402c of the indoor unit 4c in the cooling operation thermo-on state functions as an evaporator.

[0034] The indoor blowers 403 (403a, 403b, and 403c) suck indoor air (hereinafter referred to as indoor air) and blow the air which is subjected to heat exchange in the indoor heat exchangers 402 into the room. The outside air sucked by the indoor blowers 403 is blown against the indoor heat exchangers 402. Accordingly, heat exchange between the indoor air and the refrigerant flowing through the indoor heat exchangers 402 is performed. The indoor blowers 403 are provided near the indoor heat exchangers 402.

[0035] The indoor expansion valve 404 adjusts the flow rate of the refrigerant flowing through the indoor heat exchangers 402 in accordance with the opening. The indoor expansion valve 404 has, for example, a valve structure in which the amount of refrigerant throttling is adjusted by controlling the opening of the valve between the minimum opening and the maximum opening, and is configured as a pulse motor valve (PMV) whose opening changes continuously in accordance with the number of drive pulses supplied. The indoor expansion valve 404 has the opening adjusted by the control unit 8, and supplies the current opening (actual opening) value to the control unit 8 by a wired or wireless manner.

[0036] The indoor expansion valve 404 is provided in the liquid pipe 90. In the example shown in FIG. 1, an indoor expansion valve 404a is provided in a first branch pipe 90a that branches off from the liquid pipe 90. An indoor expansion valve 404b is provided in a second branch pipe 90b that branches off from the liquid pipe 90. An indoor expansion valve 404c is provided in a third branch pipe 90c that branches off from the liquid pipe 90. The third branch pipe 90c corresponds to the other end of the liquid pipe.

[0037] When the indoor unit 4 is in the cooling thermo-on state and the heating thermo-on state, the indoor expansion valve 404 is opened. In contrast, when the indoor unit 4 is in the cooling thermo-off state and the heating thermo-off state, the indoor expansion valve 404 is closed. In addition, when the indoor unit 4 is stopped, the indoor expansion valve 404 is closed. In the example shown in FIG. 1, the indoor expansion valve 404a of the indoor unit 4a in the heating operation thermo-on state and the indoor expansion valve 404c of the indoor unit 4c in the cooling operation thermo-on state are opened. In contrast, the indoor expansion valve 404b of the indoor unit 4b in the heating operation thermo-off state is closed.

[0038] The indoor temperature detection unit 405 detects the indoor temperature, which is the temperature of the air in the room to be conditioned by the indoor unit 4, i.e., the inside air temperature. The indoor temperature detection unit 405 is, for example, a temperature sensor (thermistor) that detects the indoor temperature by a temperature sensor provided in the housing of the indoor unit 4 or the like. The indoor temperature detection unit 405 supplies the detected indoor temperature value to the control unit 8 by a wired or wireless manner. In the example shown in FIG. 1, indoor temperature detection unit 405a, 405b, and 405c are provided for three indoor units 4a, 4b, and 4c, respectively.

[0039] Each of the plurality of switching units 6 switches the flow of refrigerant to either of two flow paths for cooling and heating between the outdoor unit 2 and each of the plurality of indoor units 4. The switching units 6 are provided for the plurality of indoor units 4, respectively. In the example shown in FIG. 1, three switching units 6a, 6b, and 6c are provided to correspond to three indoor units 4a, 4b, and 4c, respectively. In the following descriptions, an element common to these three switching units 6a, 6b, and 6c will be referred to as a switching unit 6, and components of each of the switching units 6a, 6b, and 6c will be given corresponding suffixes.

[0040] In order to switch the flow of the refrigerant in this manner, each of the switching units 6 has two switching valves 61 and 62.

[0041] One of the two switching valves (hereinafter referred to as a first switching valve 61) switches between flowing in and blocking the refrigerant to the indoor heat exchanger 402. The first switching valve 61 opens when the corresponding indoor unit 4 is in the heating operation thermo-on state and the heating operation thermo-off state. On the other hand, the first switching valve 61 closes when the corresponding indoor unit 4 is in the cooling operation thermo-on state and the cooling operation thermo-off state.

[0042] In contrast, the other of the two switching valves (hereinafter referred to as a second switching valve 62) switches between flowing in and blocking the refrigerant from the indoor heat exchanger 402. The second switching valve 62 opens when the corresponding indoor unit 4 is in the cooling operation thermo-on state and the cooling operation thermo-off state. On the other hand, the second switching valve 62 closes when the corresponding indoor unit 4 is in the heating operation thermo-on state and the heating operation thermo-off state.

[0043] Incidentally, for example, at least one of the first switching valve 61 and the second switching valve 62 closes when the corresponding indoor unit 4 is stopped.

[0044] In the example shown in FIG. 1, the first switching valve 61a of the switching unit 6a corresponding to the indoor unit 4a in the heating operation thermo-on state and the first switching valve 61b of the switching unit 6b corresponding to the indoor unit 4b in the heating operation thermo-off state are open. On the other hand, the second switching valves 62a and 62b of the switching units 6a and 6b corresponding to these indoor units 4a and 4b are closed.

[0045] In contrast, the second switching valve 62c of the switching unit 6c corresponding to the indoor unit 4c in the cooling operation thermo-on state is open. On the other hand, the first switching valve 61c of the switching unit 6c corresponding to this indoor unit 4c is closed.

[0046] The first switching valve 61 and the second switching valve 62 have, for example, a valve structure in which the flow of the refrigerant can be blocked by controlling the opening of the valves, and are configured as pulse motor valves (PMV) whose opening changes continuously in accordance with the number of drive pulses supplied. The first switching valve 61 and the second switching valve 62 have operations controlled, for example, openings adjusted by a control unit 8 to be described below, and supply values of the openings to the control unit 8 by a wire or wireless manner.

[0047] In the example shown in FIG. 1, the first switching valve 61 is provided in a flow path (hereinafter referred to as a first gas pipe) 91 through which the high-temperature and high-pressure gas-phase refrigerant discharged from the compressor 202 flows. The first gas pipe 91 is configured to have, for example, a plurality of pipes connected with a joint (for example, a packed valve) PV1, and one end is connected to the discharge pipe 201b via a four-way valve (first four-way valve) 207, and the other end is connected to the indoor heat exchanger 402 of each indoor unit 4. The first gas pipe 91 constitutes a part of the outdoor side pipe 201 and the indoor side pipe 401. In the example shown in FIG. 1, the first four-way valve 207 has one of its four ports blocked, and essentially functions as a three-way valve.

[0048] Incidentally, when the outdoor unit 2 performs the simultaneous cooling and heating operation during mainly performing the cooling operation for performing the cooling operation, the high-temperature and high-pressure gas-phase refrigerant discharged from the compressor 202 is guided by the four-way valve (second four-way valve) 208 and flows into the outdoor heat exchanger 203, and a part of the high-temperature and high-pressure gas-phase refrigerant discharged from the compressor 202 is guided by the first four-way valve 207 and flows through the first gas pipe 91.

[0049] The first switching valve 61a is provided in a first branch pipe 91a that branches off from the first gas pipe 91. The first switching valve 61b is provided in a second branch pipe 91b that branches off from the first gas pipe 91. The first switching valve 61c is provided in a third branch pipe 91c that branches off from the first gas pipe 91. The third branch pipe 91c corresponds to the other end of the first gas pipe 91.

[0050] In the example shown in FIG. 1, the second switching valve 62 is provided in a flow path (hereinafter referred to as a second gas pipe) 92 through which the refrigerant flowing out of the indoor heat exchanger 402 of the indoor unit 4 in cooling operation (cooling thermo-on state), for example, the gas-phase refrigerant evaporated in the indoor heat exchanger 402 or the gas-liquid two-phase refrigerant, flows. The second gas pipe 92 is configured to have, for example, a plurality of pipes connected with a joint (for example, packed valve) PV2, and one end is connected to the indoor heat exchanger 402 of each indoor unit 4, and the other end is connected to an accumulator (first accumulator) 209. The second gas pipe 92 merges with the first gas pipe 91 between the indoor heat exchanger 402 and the switching unit 6 (the first switching valve 61 and the second switching valve 62). The second gas pipe 92 constitutes a part of the outdoor side pipe 201 and the indoor side pipe 401.

[0051] The accumulator 209 separates the refrigerant flowing out from the indoor heat exchanger 402 of the indoor unit 4 during the cooling operation into gas and liquid, and supplies only the gas-phase refrigerant to the compressor 202. The refrigerant separated into gas and liquid in the accumulator 209 is guided to a gas-liquid separator (second accumulator) 210. The gas-liquid separator 210 further separates the refrigerant into gas and liquid such that the compressor 202 does not compress the liquid-phase refrigerant.

[0052] The second switching valve 62a is provided in a first branch pipe 92a that branches off from the second gas pipe 92. The second switching valve 62b is provided in a second branch pipe 92b that branches off from the second gas pipe 92. The second switching valve 62c is provided in a third branch pipe 92c that branches off from the second gas pipe 92. The third branch pipe 92c corresponds to one end of the second gas pipe 92.

[0053] In the air conditioning device 1 configured as described above, the refrigerant flows as indicated by white arrows in FIG. 1. The gas phase refrigerant discharged from the compressor 202 to the discharge pipe 201b is guided to the first gas pipe 91 by the first four-way valve 207. The refrigerant flowing through the first gas pipe 91 flows into the indoor heat exchanger 402a through the first switching valve 61a of the switching unit 6a corresponding to the indoor unit 4a in heating operation (heating operation thermo-on state). The refrigerant which flows into the indoor heat exchanger 402a and changes to the liquid phase or gas-liquid phases flows into the liquid pipe 90 through the indoor expansion valve 404a.

[0054] The refrigerant flowing through the liquid pipe 90 passes through the outdoor expansion valve 205 and flows into the outdoor heat exchanger 203. The refrigerant which flows into the outdoor heat exchanger 203 and changes to the gas phase or gas-liquid phases is guided to the accumulator 209 by the second four-way valve 208. In addition, a part of the refrigerant flowing through the liquid pipe 90 flows into the indoor heat exchanger 402c through the indoor expansion valve 404c of the indoor unit 4c in cooling operation (cooling operation thermo-on state). The refrigerant which flows into the indoor heat exchanger 402c and changes to the gas phase or gas-liquid phases flows into the second gas pipe 92 through the second switching valve 62c of the switching unit 6c corresponding to the indoor unit 4c. The refrigerant flowing through the second gas pipe 92 is guided to the accumulator 209 by the first four-way valve 207.

[0055] The refrigerant guided to the accumulator 209 is separated into gas and liquid through the gas-liquid separator 210. Then, the separated gas-phase refrigerant is returned to the compressor 202.

[0056] The control unit 8 controls the operations of the outdoor unit 2, the plurality of indoor units 4, and the plurality of switching units 6. Then, the control unit 8 switches the flow of the refrigerant and switches each of the plurality of indoor units 4 to either of the cooling operation and the heating operation.

[0057] The control unit 8 includes a CPU, a memory, a storage device (nonvolatile memory), an input/output circuit, a timer, and the like, and executes predetermined arithmetic processing. For example, the control unit 8 reads various data via the input/output circuit, performs calculation processing using a program read from the storage device to the memory in the CPU, and controls the operations of the compressor 202, the outdoor blower 204, the outdoor expansion valve 205, the outdoor temperature detection unit 206, the indoor blower 403, the indoor expansion valve 404, the first switching valve 61, the second switching valve 62, and the like, based on the processing results.

[0058] The control unit 8 includes an operation control unit 81 that performs such operation control. The operation control unit 81 is configured as a program (operation control program) that causes the CPU to execute predetermined calculation processes for controlling the operations of each of the above-mentioned components (operation control targets), for example, startup (start of operation) and shutdown. The operation control unit 81 is stored in, for example, a storage device (nonvolatile memory) of the control unit 8 and is read to the memory during the execution. The operation control unit 81 transmits and receives control signals and data signals to and from the operation control targets by a wire or wireless manner. In other words, the operation control unit 81 and the operation control targets are electrically connected by a wire or wireless manner.

[0059] As described above, in the present embodiment, the air conditioning device 1 is simultaneously operated for heating and cooling during mainly performing the heating operation. In other words, the outdoor heat exchanger 203 of the outdoor unit 2 functions as an evaporator and, among the plurality of indoor units 4, indoor units which are in cooling operation and indoor units which are in heating operation, exist. During the simultaneous heating and cooling operation according to the present embodiment, the control unit 8 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation (cooling operation thermo-on state). To perform such adjustment (hereinafter referred to as an opening adjustment process), the control unit 8 includes an opening adjustment unit 82. The opening adjustment unit 82 is configured as, for example, a program (opening adjustment program) that causes the CPU to execute a predetermined calculation process for adjusting the opening of the indoor expansion valve 404 of the indoor unit 4 during the cooling operation. The opening adjustment unit 82 is stored in, for example, a storage device (nonvolatile memory) of the control unit 8 and is read to the memory when executed.

[0060] In the example shown in FIG. 1, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404c of the indoor unit 4c in cooling operation (cooling operation thermo-on state). On the other hand, the opening adjustment unit 82 does not adjust the opening of the indoor expansion valve 404a of the indoor unit 4a in heating operation (heating operation thermo-on state) and the indoor expansion valve 404b of the indoor unit 4b in the heating operation thermo-off state, but maintains the openings at the current openings.

[0061] In the opening adjustment process, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 during the cooling operation in accordance with the outdoor temperature and the indoor temperature. For example, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation (cooling operation thermo-on state) in accordance with a difference between the indoor temperature and the outdoor temperature (hereinafter referred to as an indoor/outdoor temperature difference). At that time, the opening adjustment unit 82 corrects the target degree of superheat of the refrigerant. The target degree of superheat is a target value when controlling the degree of superheat of the refrigerant. The degree of superheat is calculated as a difference (TS-TE) between a temperature (TS) of the refrigerant sucked into the compressor 202 and a temperature (TE) of the refrigerant flowing into the outdoor heat exchanger 203, which is an evaporator.

[0062] The opening adjustment process in the air conditioning device 1 will be described below in accordance with the control flow of the control unit 8. FIG. 2 shows a control flow of the control unit 8 in the opening investigation process. When performing the opening adjustment process, the control unit 8 reads, for example, an operation control program which is the operation control unit 81 and an opening adjustment program which is the opening adjustment unit 82 from the storage device (nonvolatile memory) to the memory, and executes the programs with the CPU.

[0063] When performing the opening adjustment process, the air conditioning device 1 starts operation (S101). More specifically, the operation control unit 81 starts the compressor 202 and opens the outdoor expansion valve 205 and the like, to circulate the refrigerant through the flow path constituted by the outdoor side pipe 201 and the indoor side pipe 401. In this case, the air conditioning device 1 becomes in an operation mode of main heating operation that performs the heating operation, and the outdoor heat exchanger 203 functions as an evaporator.

[0064] When the air conditioning device 1 starts the operation in this manner, the opening adjustment unit 82 determines the operation conditions of the air conditioning device 1. The operation conditions are conditions for determining whether or not the air conditioning device 1 is simultaneously operated for cooling and heating. In this case, the opening adjustment unit 82 determines whether the air conditioning device 1 is simultaneously operated for cooling and heating, i.e., whether the indoor units which are in cooling operation and the indoor units which are in heating operation, among the plurality of indoor units 4, exist (exist together) (S102).

[0065] The operation of the indoor unit 4 is started by, for example, a user setting either the cooling operation or the heating operation using a remote controller. At that time, if the indoor unit 4 is in the cooling operation thermo-on state and the cooling operation thermo-off state, the control unit 8 closes the first switching valve 61 of the switching unit 6 corresponding to the indoor unit 4 and opens the second switching valve 62. In contrast, if the indoor unit 4 is in the heating operation thermo-on state and the heating operation thermo-off state, the control unit 8 opens the first switching valve 61 of the switching unit 6 corresponding to the indoor unit 4 and closes the second switching valve 62. Therefore, except a case where all the first switching valves 61 are closed and all the second switching valves 62 are open or vice versa, the opening adjustment unit 82 determines that the air conditioning device 1 is simultaneously operated for cooling and heating operation, i.e., the operation conditions are met. On the other hand, if all the first switching valves 61 are closed and all of the second switching valves 62 are open or vice versa, the opening adjustment unit 82 determines that the air conditioning device 1 is not simultaneously operated for cooling and heating, i.e., the operation conditions are not met.

[0066] In the example shown in FIG. 1, the first switching valves 61a and 61b are open and the first switching valve 61a is closed, and the second switching valves 62a and 62b are closed and the second switching valve 62c is open. Therefore, in the illustrated example, the opening adjustment unit 82 determines that the air conditioning device 1 is simultaneously operated for cooling and heating, i.e., the operation conditions are met.

[0067] When determining that the air conditioning device 1 is simultaneously operated for heating and cooling (Yes in S102), the opening adjustment unit 82 determines the temperature condition. The opening adjustment unit 82 determines whether the difference between an indoor temperature (TA) and an outdoor temperature (TO) (indoor/outdoor temperature difference) exceeds a predetermined threshold value (hereinafter referred to as a reference threshold value) (X) (S103). The indoor temperature (TA) is the temperature of the air in the room to be air-conditioned, which is air-conditioned by the indoor unit 4 in heating operation (heating operation thermo-on state), i.e., the temperature detected by the indoor temperature detection unit 405 of the indoor unit 4 during the heating operation. The outdoor temperature (TO) is the temperature detected by the outdoor temperature detection unit 206 of the outdoor unit 2. In other words, the indoor/outdoor temperature difference is the difference between the indoor temperature of the air-conditioned object, which is air-conditioned by the indoor unit 4 in a heating operation (heating operation thermo-on state) and the outdoor temperature.

[0068] Incidentally, if a plurality of indoor units 4 in heating operation (heating operation thermo-on state) exist, for example, the higher of the temperatures detected by the indoor temperature detection units 405 of each of these indoor units 4 may be set as the indoor temperature under the temperature conditions.

[0069] The state in which the indoor/outdoor temperature difference is large during the simultaneous heating and cooling operation corresponds to a state in which the pressure of the refrigerant flowing through the liquid pipe 90 (liquid pipe pressure) is decreasing. In other words, the temperature condition also serves as a condition for determining whether or not the liquid pipe pressure is decreasing. If the condition is met, it can be determined that the liquid pipe pressure is decreasing.

[0070] The reference threshold value (X) is the lower limit of the indoor/outdoor temperature difference that requires correction of the target degree of superheat of the refrigerant, and is set to, for example, approximately 0 C. to 10 C. In addition, the reference threshold value also serves as a determination threshold value for whether or not the liquid pipe pressure is decreasing. The set value of the reference threshold value is stored in, for example, a storage device (nonvolatile memory) of the control unit 8. The stored reference threshold value is read when determining the temperature conditions in S103 and is used as a parameter. When determining the temperature conditions, the opening adjustment unit 82 obtains the outdoor temperature from the outdoor temperature detection unit 206 and obtains the indoor temperature from the indoor temperature detection unit 405 of the indoor unit 4 in heating operation (heating operation thermo-on state). In the example shown in FIG. 1, the opening adjustment unit 82 obtains the indoor temperature from the indoor temperature detection unit 405a of the indoor unit 4a.

[0071] When determining that the indoor/outdoor temperature difference exceeds the reference threshold value (TATO>X) (Yes in S103), the opening adjustment unit 82 corrects the target degree of superheat of the refrigerant (S104). The opening adjustment unit 82 adds a predetermined correction value to the value of the target degree of superheat. The correction value is set to be larger as the indoor/outdoor temperature difference becomes larger beyond the reference threshold value. FIG. 3 is a graph showing an example of a relationship between the indoor/outdoor temperature difference and the correction value of the target degree of superheat. In the example shown in FIG. 3, the correction value is 0 when the indoor/outdoor temperature difference is equal to or smaller than the reference threshold value, and the correction value increases in proportion to the indoor/outdoor temperature difference as represented by a trajectory indicated by L3 when the indoor/outdoor temperature difference exceeds the reference threshold value. Incidentally, the relationship shown in FIG. 3 is merely an example, and the relationship between the indoor/outdoor temperature difference exceeding the reference threshold value and the correction value of the target degree of superheat may be, for example, a relationship indicated by the trajectory of a quadratic function or a relationship in which the correction value increases stepwise. The corrected value of the target degree of superheat is stored in, for example, the memory of the control unit 8.

[0072] When correcting the target degree of superheat, the opening adjustment unit 82 controls the degree of superheat of the refrigerant such that the degree of superheat becomes the target degree of superheat (S105). In other words, the degree of superheat of the refrigerant is controlled at the target degree of superheat. If the target degree of superheat in S105 is corrected in S104, the target degree of superheat is the corrected value.

[0073] When correcting the target degree of superheat in S104, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 during the cooling operation such that the degree of superheat of the refrigerant becomes the corrected target degree of superheat. In other words, the opening adjustment unit 82 reduces the opening of the indoor expansion valve 404 of the indoor unit 4 during the cooling operation in accordance with the corrected target degree of superheat. As described above, the corrected value of the target degree of superheat becomes larger as the indoor/outdoor temperature difference exceeds the reference threshold value. Therefore, the opening of the indoor expansion valve 404 of the indoor unit 4 during the cooling operation becomes smaller (throttled) as the target degree of superheat increases. In other words, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 during the cooling operation such that the opening becomes smaller as the indoor/outdoor temperature difference is larger.

[0074] In the example shown in FIG. 1, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404c of the indoor unit 4c such that the opening becomes smaller as the indoor/outdoor temperature difference becomes larger. On the other hand, the opening adjustment unit 82 does not adjust the opening of the indoor expansion valves 404a and 404b of the indoor units 4a and 4b, but maintains the opening at their current opening (the opening at the time of executing the opening adjustment process).

[0075] Incidentally, if a plurality of indoor units 4 in cooling operation (cooling operation thermo-on state), the opening adjustment unit 82 adjusts the opening of the indoor expansion valves 404 of all the indoor units 4 in cooling operation.

[0076] In contrast, if the air conditioning device 1 is not simultaneously operated for cooling and heating (No in S102) and the indoor/outdoor temperature difference is smaller than or equal to the reference threshold value (TATOX) (No in S103), the target degree of superheat is not corrected. In these cases, the target degree of superheat is a predetermined value which is set in accordance with, for example, the rotation speed of the compressor 202, or the like, and is the value to be corrected as mentioned in S104 (for example, an initial value). In other words, the target degree of superheat corresponds to the target degree of superheat to be corrected relative to the corrected target degree of superheat.

[0077] Therefore, if the air conditioning device 1 is not simultaneously operated for cooling and heating (No in S102) or if the indoor/outdoor temperature difference is smaller than or equal to the reference threshold value (No in S103), the opening adjustment unit 82 controls the degree of superheat of the refrigerant to the target degree of superheat (the target degree of superheat to be corrected).

[0078] When controlling the degree of superheat of the refrigerant in this manner, the control unit 8 determines operation stop conditions of the air conditioning device 1 (S106). The operation atop conditions are conditions for determining whether or not to stop the operation of the air conditioning device 1. The operation stop conditions are determined, for example, based on whether or not the control unit 8 has received a signal indicating the stop of the operation of the air conditioning device 1. The signal indicating the operation stop is transmitted, for example, when a user or the like selects the operation stop from an operation panel of the outdoor unit 2 or a remote controller of the indoor unit 4.

[0079] If the operation stop conditions are met (Yes in S106), the operation control unit 81 stops the operation of the air conditioning device 1 (S107). If the stopped air conditioning device 1 subsequently starts the cooling operation again, a new opening adjustment process is executed.

[0080] In contrast, if the operation stop conditions are not met (No in S106), the opening adjustment unit 82 determines whether the air conditioning device 1 is simultaneously operated for cooling and heating as the operation condition of the air conditioning device 1 (S102). Then, the control unit 8 (the operation control unit 81 and the opening adjustment unit 82) selectively executes subsequent processes (S103 to S107) depending on the determination result of the operation condition.

[0081] In other words, a series of opening adjustment processes is repeated while the air conditioning device 1 is being operated. Then, when the operation of the air conditioning device 1 is stopped, the series of opening adjustment processes also ends.

[0082] As described above, according to the present embodiment, if the air conditioning device 1 is in an operation mode of mainly performing the heating operation, if the outdoor unit 2 is operated for heating, and if the indoor units 4 which are in cooling operation and the indoor units 4 which are in heating operation exist (exist together), the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation can be appropriately adjusted. More specifically, the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation can be appropriately adjusted in accordance with the difference between the indoor temperature and the outdoor temperature (indoor/outdoor temperature difference) of the air-conditioned object (hereinafter referred to as a heated room) air-conditioned by the indoor unit 4 in heating operation.

[0083] For example, if the outdoor temperature is particularly low compared to the indoor temperature inside the heated room, i.e., if the indoor/outdoor temperature difference is relatively large, the degree of superheat increases, and the indoor expansion valve 404 of the indoor unit 4 in cooling operation is fully opened, and the liquid pipe pressure is likely to be reduced. In the present embodiment, the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation can be reduced as the indoor/outdoor temperature difference becomes larger beyond the reference threshold value. Accordingly, the reduction in liquid pipe pressure can be suppressed.

[0084] In addition, when the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation is reduced in this manner, the target degree of superheat of the refrigerant can be corrected in the present embodiment. More specifically, by adding a predetermined correction value to the value of the target degree of superheat, the correction value can be increased as the indoor/outdoor temperature difference becomes larger beyond the reference threshold value. Accordingly, the value of the corrected target degree of superheat can be made larger than the value before correction. In contrast, if the indoor/outdoor temperature difference is smaller than or equal to the reference threshold value, the value of the target degree of superheat can be maintained with the correction value set to 0.

[0085] Therefore, according to the present embodiment, the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation can be reduced and the reduction in liquid pipe pressure can be appropriately suppressed under the conditions that the indoor/outdoor temperature difference under which the liquid pipe pressure is likely to be reduced is large as described above. In contrast, the degree of superheat of the refrigerant can be controlled at the target degree of superheat (the value to be corrected; for example, the initial value) without making a correction to increase the target degree of superheat, under the conditions that the indoor/outdoor temperature difference under which the reduction in liquid pipe pressure is unlikely to occur is small. Accordingly, the air conditioning device 1 can be operated while improving the energy efficiency.

[0086] Thus, according to the present embodiment, an air conditioning device 1 capable of improving the energy efficiency while appropriately suppressing the reduction in liquid pipe pressure even during the simultaneous cooling and heating operation, can be implemented.

[0087] While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.