Air conditioning device

Abstract

According to one embodiment, an air conditioning device is provided with an outdoor unit, a plurality of indoor units, a plurality of switching units, and a control unit. The switching unit switches the flow of the refrigerant between the outdoor unit and each of the plurality of indoor units to any one of the flow paths of both cooling and heating systems. When the outdoor heat exchanger functions as an evaporator and there are an indoor unit in a cooling operation and an indoor unit in a heating operation among the plurality of indoor units, the control unit controls the outdoor heat exchanger according to the outdoor temperature and the indoor temperature detected by the indoor temperature detection part of the indoor unit in the heating operation. The opening degree of an indoor expansion valve of an indoor unit during cooling operation is adjusted.

Description

Technical Field

[0001] An embodiment of the present invention relates to an air conditioning apparatus. Background Art

[0002] In conventional air conditioning systems utilizing a refrigeration cycle (heat pump cycle), an outdoor unit comprising a compressor, a four-way valve, an outdoor heat exchanger, flow control devices such as an expansion valve, and an indoor unit comprising an indoor heat exchanger are connected by refrigerant piping to form a refrigerant circuit that circulates the refrigerant. In air conditioning systems, the indoor heat exchanger absorbs heat from the air as the refrigerant evaporates, generating cooling, and dissipates heat to the air as the refrigerant condenses, generating heating.

[0003] For example, when an air-conditioning device has multiple indoor units, there is an air-conditioning device that can perform simultaneous cooling and heating operations (mixed cooling and heating operations). It determines which cooling or heating is appropriate based on the set temperature of the remote control of each indoor unit and the temperature around the indoor unit, and can perform cooling or heating for different indoor units.

[0004] Furthermore, simultaneous cooling and heating operation utilizes heat recovery between multiple indoor units. Therefore, when the cooling and heating air conditioning loads are roughly equal, the amount of heat exchanged by the outdoor unit is reduced, improving both comfort and energy efficiency. Furthermore, by adjusting the refrigerant flow rate to the outdoor heat exchanger based on the respective capacities of cooling and heating operations, the amount of heat exchanged by the outdoor unit is controlled, achieving enhanced comfort and energy efficiency.

[0005] However, when the outdoor unit is operating as a heating unit during simultaneous cooling and heating operations at a relatively low outdoor temperature, the outdoor heat exchanger becomes an evaporator under low outside air, and the indoor heat exchanger of the indoor unit in cooling operation becomes an evaporator under normal temperature. Therefore, the evaporation temperature becomes a temperature close to the outdoor temperature, and the difference between the evaporation temperature and the indoor temperature in the indoor unit becomes larger, and the superheat becomes larger. Generally, the lower the superheat, the higher the energy efficiency of the air-conditioning device, so the target superheat is set to a smaller value. On the other hand, if the target superheat is small, there is a case where the opening of the expansion valve becomes too large, for example. Therefore, due to insufficient pressure reduction on the low-pressure side, the outdoor temperature (outside air temperature) is lower than the evaporation temperature, and the refrigerant accumulates in the outdoor heat exchanger, the low-pressure accumulator, etc., so that the hydraulic pressure (liquid pipe pressure) of the refrigerant flowing in the liquid pipe is sometimes reduced. When the outdoor unit is operating as a cooling unit and the outdoor heat exchanger becomes a condenser, there is a case where the same hydraulic pressure reduction occurs.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 2522361

[0009] Patent Document 2: International Publication No. 2016 / 009488 Pamphlet Summary of the Invention

[0010] Technical problem to be solved by the invention

[0011] The present invention has been made in view of the above situation, and an object of the present invention is to provide an air conditioning apparatus capable of appropriately suppressing a decrease in liquid pipe pressure during simultaneous cooling and heating operation.

[0012] Solutions for solving the above technical problems

[0013] An air conditioning apparatus according to one embodiment includes an outdoor unit, a plurality of indoor units, a plurality of switching units, and a control unit.

[0014] The outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor blower, an outdoor expansion valve, and an outdoor temperature detector. The compressor draws in, compresses, and discharges a refrigerant. The outdoor heat exchanger functions as an evaporator or condenser that performs heat exchange between outdoor air and the refrigerant. The outdoor blower draws in outdoor air and blows the air, which has undergone heat exchange in the outdoor heat exchanger, to the outside of the room. The outdoor expansion valve adjusts the flow rate of the refrigerant flowing through the outdoor heat exchanger according to its opening degree. The outdoor temperature detector detects the temperature of the outdoor air, i.e., the outdoor temperature.

[0015] The indoor unit includes an indoor heat exchanger, an indoor blower, an indoor expansion valve, and an indoor temperature detector. The indoor heat exchanger functions as a condenser or evaporator that exchanges heat between the indoor air and the refrigerant. The indoor blower draws in indoor air and blows the air, which has undergone 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 according to its opening. The indoor temperature detector detects the temperature of the indoor air, i.e., the indoor temperature.

[0016] The switching unit switches the flow of the refrigerant between the outdoor unit and each of the plurality of indoor units to either a cooling system or a heating system.

[0017] The control unit controls the operation of the outdoor unit, the plurality of indoor units, and the plurality of switching units to switch each of the plurality of indoor units to either cooling or heating operation. When the outdoor heat exchanger functions as an evaporator and the plurality of indoor units include indoor units in cooling operation and indoor units in heating operation, the control unit adjusts the opening of the indoor expansion valve of the indoor unit in cooling operation based on the outdoor temperature and the indoor temperature detected by the indoor temperature detection unit of the indoor unit in heating operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a circuit diagram schematically showing the air conditioning apparatus according to the embodiment.

[0019] Figure 2 This is a control flow chart during the opening adjustment process in the air-conditioning apparatus according to the embodiment.

[0020] Figure 3 This is a diagram showing an example of the relationship between the indoor and outdoor temperature difference (the difference between the indoor temperature and the outdoor temperature) and the correction value of the target superheat degree in the air-conditioning apparatus according to the embodiment. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0022] Figure 1 1 is a circuit diagram schematically showing the air conditioning device 1 of this embodiment. Figure 1 As shown, the air conditioning apparatus 1 includes an outdoor unit 2 and a plurality of indoor units 4 connected by a flow path through which a refrigerant flows. Figure 1 , a configuration example is shown in which three indoor units 4 (4a, 4b, 4c) are connected to one outdoor unit 2. However, the number of indoor units 4 is not limited to this. The flow path is formed by connecting multiple pipes. These pipes include pipes 201 forming the flow path on the outdoor unit 2 side (hereinafter referred to as outdoor-side pipes) and pipes 401 forming the flow path on the indoor unit 4 side (hereinafter referred to as indoor-side pipes).

[0023] Furthermore, the air conditioning device 1 includes a plurality of switching units 6 for switching the flow of the refrigerant between the outdoor unit 2 and each of the plurality of indoor units 4 to either the cooling or heating system. The plurality of switching units 6 are provided one for each of the plurality of indoor units 4. Figure 1 The example shown shows a configuration example in which three switching units 6 (6a, 6b, 6c) are provided, one for each of the three indoor units 4. The number of switching units 6 can be the same as the number of indoor units 4. Thus, a specific switching unit 6 is associated with each of the multiple indoor units 4.

[0024] By including these switching units 6, the air conditioner 1 can perform simultaneous cooling and heating operation (mixed cooling and heating operation). Simultaneous cooling and heating operation is an operating mode of the air conditioner 1 in which each of the multiple indoor units 4 can arbitrarily select either cooling operation or heating operation. During simultaneous cooling and heating operation, the air conditioner 1 can operate in either a cooling mode, with the outdoor unit 2 performing the cooling operation, or a heating mode, with the outdoor unit 2 performing the heating operation.

[0025] In the following description, unless simultaneous cooling and heating operation is specifically described, the air conditioner 1 is primarily operating in heating mode, with the outdoor unit 2 performing heating operation, and the indoor units 4 operating in cooling and heating modes (a mixture of these). The indoor unit 4 being in cooling operation refers to the state in which the indoor unit 4 is actually performing cooling operation at that point in time (hereinafter referred to as the cooling operation temperature control on state). The indoor unit 4 being in heating operation refers to the state in which the indoor unit 4 is actually performing heating operation at that point in time (hereinafter referred to as the heating operation temperature control on state).

[0026] States other than the two states of cooling operation and heating operation include a state in which the indoor unit 4 is stopped (operation terminated), a temperature control OFF state in cooling operation (hereinafter referred to as the cooling operation temperature control OFF state), and a temperature control OFF state in heating operation (hereinafter referred to as the heating operation temperature control OFF state). The temperature control OFF state is, for example, a state in which the cooling operation is temporarily stopped when the indoor temperature reaches the cooling set temperature, or a state in which the heating operation is temporarily stopped when the indoor temperature reaches the heating set temperature.

[0027] Furthermore, the air conditioning apparatus 1 includes 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 switches each of the plurality of indoor units 4 to either cooling or heating operation.

[0028] The outdoor unit 2 includes a compressor 202 , an outdoor heat exchanger 203 , an outdoor fan 204 , an outdoor expansion valve 205 , an outdoor temperature detection unit 206 and the like as main elements.

[0029] Compressor 202 draws in refrigerant from suction pipe 201a, compresses it, and discharges the compressed refrigerant into discharge pipe 201b. Suction pipe 201a and discharge pipe 201b each constitute a portion of outdoor piping 201. For example, compressor 202 includes a sealed container, a rotating shaft, a compression mechanism, and a motor mechanism, and discharges high-temperature, high-pressure gas-phase refrigerant into discharge pipe 201b.

[0030] The outdoor heat exchanger 203 performs heat exchange between the outdoor air and the refrigerant. As described above, in this embodiment, it is assumed that the air conditioner 1 performs simultaneous cooling and heating operations with the heating operation as the main body. Therefore, the outdoor heat exchanger 203 functions as an evaporator, so that the indoor heat exchanger 402 (in the case of the indoor unit 4 in the heating operation temperature control on state) of the indoor unit 4 is Figure 1 In the example shown, the liquid-phase refrigerant or gas-liquid two-phase refrigerant that has undergone heat exchange in the indoor unit 4a evaporates through heat exchange with the air, transforming into a low-temperature, low-pressure gas-phase refrigerant or gas-liquid two-phase refrigerant. However, when the air conditioner 1 is primarily operating in cooling mode and performing simultaneous cooling and heating, the outdoor heat exchanger 203 functions as a condenser. In this case, the outdoor heat exchanger 203 condenses the high-temperature, high-pressure gas-phase refrigerant discharged from the compressor 202 through heat exchange with the air, transforming it into a high-pressure liquid-phase refrigerant.

[0031] The outdoor blower 204 draws in outdoor air (hereinafter referred to as outside air) and blows the air, which has undergone heat exchange in the outdoor heat exchanger 203, out to the outside. The outside air drawn in by the outdoor blower 204 is blown into the outdoor heat exchanger 203. Thus, heat exchange occurs between the outside air and the refrigerant flowing through the outdoor heat exchanger 203. The outdoor blower 204 is positioned near the outdoor heat exchanger 203.

[0032] The outdoor expansion valve 205 adjusts the flow rate of refrigerant flowing through the outdoor heat exchanger 203 based on its opening. For example, the outdoor expansion valve 205 has a valve structure that adjusts the throttling amount of the refrigerant by controlling the valve opening between a minimum opening and a maximum opening. It is configured as a PMV (Pulse Motor Valve) whose opening continuously changes based on the number of supplied drive pulses. The opening of the outdoor expansion valve 205 is adjusted by the control unit 8, and the current opening (actual opening) value is transmitted to the control unit 8 via wired or wireless communication.

[0033] exist Figure 1 In the example shown, the outdoor expansion valve 205 is arranged in the flow path (hereinafter referred to as liquid pipe) 90 for the flow of liquid-phase refrigerant and gas-liquid two-phase refrigerant. The liquid pipe 90 is composed of a plurality of pipes connected by a joint (for example, a filling valve) PV0, one end of which is connected to the outdoor expansion valve 205, and the other end of which is connected to the indoor expansion valve 404 of each indoor unit 4 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 this embodiment, the air-conditioning device 1 performs simultaneous cooling and heating operation with the heating operation as the main body, that is, the outdoor unit 2 performs heating operation. Therefore, from the indoor unit 4 (in the heating operation (heating operation temperature control is turned on) Figure 1In the illustrated example, liquid-phase refrigerant, gas-liquid two-phase refrigerant, etc. returned from the indoor unit 4 a) flows in the liquid pipe 90 .

[0034] In addition, when the air conditioner 1 is in cooling operation and performing simultaneous cooling and heating operation, that is, when the outdoor unit 2 is in cooling operation, liquid phase refrigerant, gas-liquid two-phase refrigerant, etc., which have undergone heat exchange in the outdoor heat exchanger 203, flows in the liquid pipe 90. In this case, the high-temperature and high-pressure gas phase refrigerant discharged from the compressor 202 is guided by the second four-way valve 208 described later and flows into the outdoor heat exchanger 203. At this time, the second four-way valve 208 is as shown in FIG. Figure 1 Connect the ports as shown by the dotted lines.

[0035] Outdoor temperature detection unit 206 detects the outdoor air temperature, or the outside air temperature. The "outdoors" here refers to the area outside the room, which is the air-conditioned space, and may include, for example, the outdoor space where outdoor heat exchanger 203 and outdoor blower 204 are located. Outdoor temperature detection unit 206 is, for example, a temperature sensor (thermistor) that detects the outdoor temperature by placing a temperature sensing element near outdoor heat exchanger 203. Outdoor temperature detection unit 206 transmits the detected outdoor temperature value to control unit 8 via wired or wireless communication.

[0036] As described above, in this embodiment, the air conditioner 1 performs simultaneous cooling and heating operations with heating as the main operation, and the plurality of indoor units 4 include (mixed with) indoor units in cooling operation and indoor units in heating operation. Figure 1 In the example shown, the indoor unit 4a among the three indoor units 4a, 4b, and 4c is in heating operation, that is, the heating operation temperature control is on, the indoor unit 4b is in heating operation temperature control is off, and the indoor unit 4c is in cooling operation, that is, the cooling operation temperature control is on.

[0037] Each of the plurality of indoor units 4 includes an indoor heat exchanger 402 , an indoor fan 403 , an indoor expansion valve 404 , an indoor temperature detection unit 405 and the like as main elements.

[0038] The indoor heat exchanger 402 performs heat exchange between the indoor air and the refrigerant. In this embodiment, there are (are mixed with) indoor units in cooling operation and indoor units in heating operation in the plurality of indoor units 4. The indoor heat exchanger 402 of the indoor unit 4 in cooling operation functions as an evaporator, and the indoor heat exchanger 402 of the indoor unit 4 in heating operation functions as a condenser. Figure 1In the example shown, the indoor heat exchanger 402a of the indoor unit 4a with the heating operation temperature control on and the indoor heat exchanger 402b of the indoor unit 4b with the heating operation temperature control off function as condensers. Meanwhile, the indoor heat exchanger 402c of the indoor unit 4c with the cooling operation temperature control on functions as an evaporator.

[0039] Indoor air blowers 403 (403a, 403b, 403c) draw in indoor air (hereinafter referred to as inside air) and blow the air, which has undergone heat exchange in indoor heat exchanger 402, out into the room. The outside air drawn in by indoor air blowers 403 is blown into indoor heat exchanger 402. Heat is thereby exchanged between the inside air and the refrigerant flowing through indoor heat exchanger 402. Indoor air blowers 403 are positioned near indoor heat exchanger 402.

[0040] The indoor expansion valve 404 adjusts the flow rate of the refrigerant flowing through the indoor heat exchanger 402 based on its opening. For example, the indoor expansion valve 404 has a valve structure that adjusts the throttling amount of the refrigerant by controlling the valve opening between a minimum opening and a maximum opening. It is configured as a PMV (Pulse Motor Valve) whose opening continuously changes based on the number of supplied drive pulses. The opening of the indoor expansion valve 404 is adjusted by the control unit 8, and the current opening (actual opening) value is transmitted to the control unit 8 via wired or wireless communication.

[0041] The indoor expansion valve 404 is arranged on the liquid pipe 90. Figure 1 In the example shown, the indoor expansion valve 404a is disposed in a first branch pipe 90a branching from the liquid pipe 90. The indoor expansion valve 404b is disposed in a second branch pipe 90b branching from the liquid pipe 90. The indoor expansion valve 404c is disposed in a third branch pipe 90c branching from the liquid pipe 90. The third branch pipe 90c corresponds to the other end of the liquid pipe.

[0042] When the indoor unit 4 is in the cooling operation temperature control on state or the heating operation temperature control on state, the indoor expansion valve 404 is open. On the other hand, when the indoor unit 4 is in the cooling operation temperature control off state or the heating operation temperature control 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. Figure 1 In the example shown, the indoor expansion valve 404a of the indoor unit 4a in the heating operation temperature control on state and the indoor expansion valve 404c of the indoor unit 4c in the cooling operation temperature control on state are open. On the other hand, the indoor expansion valve 404b of the indoor unit 4b in the heating operation temperature control off state is closed.

[0043] The indoor temperature detection unit 405 detects the temperature of the air in the room being conditioned by the indoor unit 4, that is, the indoor temperature, that is, the internal air temperature. The indoor temperature detection unit 405 is, for example, a temperature sensor (thermistor) that detects the indoor temperature by arranging a temperature sensing element in the housing of the indoor unit 4. The indoor temperature detection unit 405 transmits the detected indoor temperature value to the control unit 8 via wired or wireless communication. Figure 1 In the illustrated example, the indoor temperature detection units 405a, 405b, and 405c are provided by providing one indoor temperature detection unit for each of the three indoor units 4a, 4b, and 4c.

[0044] Each of the plurality of switching units 6 switches the flow of the refrigerant between the outdoor unit 2 and each of the plurality of indoor units 4 to either the cooling or heating system. Each switching unit 6 is provided one for each of the plurality of indoor units 4. Figure 1 In the example shown, three switching units 6a, 6b, and 6c are provided, one each corresponding to the three indoor units 4a, 4b, and 4c. In the following description, common features of the three switching units 6a, 6b, and 6c are referred to as switching units 6, and corresponding reference numerals are assigned to the components of the switching units 6a, 6b, and 6c.

[0045] In order to switch the flow of the refrigerant in this manner, each switching unit 6 includes two switching valves 61 and 62 .

[0046] One of the two switching valves (hereinafter referred to as the first switching valve 61) switches between allowing and blocking the flow of refrigerant into the indoor heat exchanger 402. The first switching valve 61 is open when the corresponding indoor unit 4 is in the heating operation temperature control on state or the heating operation temperature control off state. On the other hand, the first switching valve 61 is closed when the corresponding indoor unit 4 is in the cooling operation temperature control on state or the cooling operation temperature control off state.

[0047] In contrast, the other of the two switching valves (hereinafter referred to as the second switching valve 62) switches between allowing and blocking the flow of refrigerant from the indoor heat exchanger 402. The second switching valve 62 is open when the corresponding indoor unit 4 is in the cooling operation temperature control on state or the cooling operation temperature control off state. On the other hand, the second switching valve 62 is closed when the corresponding indoor unit 4 is in the heating operation temperature control on state or the heating operation temperature control off state.

[0048] When the corresponding indoor unit 4 is stopped, at least one of the first switching valve 61 and the second switching valve 62 is closed, for example.

[0049] exist Figure 1In the example shown, the first switching valve 61a of the switching unit 6a corresponding to the indoor unit 4a in the heating operation temperature control on state and the first switching valve 61b of the switching unit 6b corresponding to the indoor unit 4b in the heating operation temperature control 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.

[0050] On the other hand, the second switching valve 62c of the switching unit 6c corresponding to the indoor unit 4c in the cooling operation temperature control on state is opened, while the first switching valve 61c of the switching unit 6c corresponding to the indoor unit 4c is closed.

[0051] The first switching valve 61 and the second switching valve 62 have, for example, a valve structure capable of blocking the flow of refrigerant by controlling the valve opening, and are configured as PMVs (Pulse Motor Valves) whose opening continuously changes according to the number of supplied drive pulses. The first switching valve 61 and the second switching valve 62 are controlled by a control unit 8 (described later), for example, to adjust their opening, and the opening value is transmitted to the control unit 8 via wired or wireless communication.

[0052] exist Figure 1 In the example shown, the first switching valve 61 is arranged in the flow path (hereinafter referred to as the first gas pipe) 91 for the flow of the high-temperature and high-pressure gas-phase refrigerant discharged from the compressor 202. The first gas pipe 91 is composed of a plurality of pipes connected by a joint (for example, a filling valve) PV1, one end of which is connected to the discharge pipe 201b via a four-way valve (the 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 pipe 201 and the indoor pipe 401. Figure 1 In the illustrated example, one of the four ports of the first four-way valve 207 is closed, and the first four-way valve 207 substantially functions as a three-way valve.

[0053] In addition, when the outdoor unit 2 performs cooling and heating operations of the cooling operation body, the high-temperature and high-pressure gas-phase refrigerant discharged from the compressor 202 is guided by the four-way valve (the second four-way valve) 208 to flow 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 to flow in the first gas pipe 91.

[0054] The first switching valve 61a is disposed in a first branch pipe 91a branching from the first gas pipe 91. The first switching valve 61b is disposed in a second branch pipe 91b branching from the first gas pipe 91. The first switching valve 61c is disposed in a third branch pipe 91c branching from the first gas pipe 91. The third branch pipe 91c corresponds to the other end of the first gas pipe 91.

[0055] exist Figure 1 In the illustrated example, the second switching valve 62 is disposed in a flow path (hereinafter referred to as a second gas pipe) 92 through which refrigerant flowing out of the indoor heat exchanger 402 of the indoor unit 4 in cooling operation (cooling operation temperature control on state), for example, gas-phase refrigerant or gas-liquid two-phase refrigerant evaporated in the indoor heat exchanger 402, flows. The second gas pipe 92 is formed by connecting a plurality of pipes via a joint (e.g., a filling valve) PV2. One end of the second gas pipe is connected to the indoor heat exchanger 402 of each indoor unit 4, and the other end is connected to the 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 portion of the outdoor pipe 201 and the indoor pipe 401.

[0056] The accumulator 209 separates the refrigerant flowing out of the indoor heat exchanger 402 of the indoor unit 4 in cooling operation into gas-liquid phase, and supplies only the gas-phase refrigerant to the compressor 202. The refrigerant separated from the gas and liquid phase by the accumulator 209 is guided to the gas-liquid separator (second accumulator) 210. The gas-liquid separator 210 further separates the refrigerant from the gas and liquid phase so that the compressor 202 does not compress the liquid-phase refrigerant.

[0057] The second switching valve 62a is disposed in a first branch pipe 92a branching from the second gas pipe 92. The second switching valve 62b is disposed in a second branch pipe 92b branching from the second gas pipe 92. The second switching valve 62c is disposed in a third branch pipe 92c branching from the second gas pipe 92. The third branch pipe 92c corresponds to one end portion of the second gas pipe 92.

[0058] In the air conditioning device 1 having the above configuration, the refrigerant is Figure 1 The refrigerant flows as indicated by the hollow arrows. 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 in the first gas pipe 91 passes through the first switching valve 61a of the switching unit 6a corresponding to the indoor unit 4a in heating operation (heating operation temperature control on state) and flows into the indoor heat exchanger 402a. The refrigerant, having entered the indoor heat exchanger 402a and converted to a liquid phase or a two-phase gas-liquid phase, passes through the indoor expansion valve 404a and flows into the liquid pipe 90.

[0059] The refrigerant flowing through the liquid pipe 90 flows into the outdoor heat exchanger 203 through the outdoor expansion valve 205. The refrigerant that has entered the outdoor heat exchanger 203 and has changed into a gas phase or a gas-liquid two-phase state is guided to the accumulator 209 by the second four-way valve 208. Furthermore, a portion 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 temperature control on state). The refrigerant that has entered the indoor heat exchanger 402c and changed into a gas phase or a gas-liquid two-phase state passes through the second switching valve 62c of the switching unit 6c corresponding to the indoor unit 4c and flows into the second gas pipe 92. The refrigerant flowing through the second gas pipe 92 is guided to the accumulator 209 by the first four-way valve 207.

[0060] The refrigerant guided to the accumulator 209 is separated into gas and liquid by passing through the gas-liquid separator 210. Then, the gas-phase refrigerant after the gas-liquid separation returns to the compressor 202.

[0061] 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. The control unit 8 switches the flow of the refrigerant to switch each of the plurality of indoor units 4 to either cooling or heating operation.

[0062] The control unit 8 includes a CPU, memory, a storage device (non-volatile memory), input / output circuits, a timer, and other components, and performs predetermined computations. For example, the control unit 8 reads various data via the input / output circuits, performs computations in the CPU using a program read from the storage device into the memory, and then controls the operation of the compressor 202, the outdoor fan 204, the outdoor expansion valve 205, the outdoor temperature detector 206, the indoor fan 403, the indoor expansion valve 404, the first switching valve 61, and the second switching valve 62 based on the processing results.

[0063] The control unit 8 includes an action control unit 81 for performing such action control. The action control unit 81 is configured to cause the CPU to execute a program (action control program) for controlling the actions of each of the aforementioned components (action control targets), such as startup (operation start) and shutdown, and other predetermined computational processing. The action control unit 81 is stored in, for example, a storage device (non-volatile memory) of the control unit 8 and read out to the memory during execution. The action control unit 81 transmits and receives control signals and data signals to and from the action control target via wired or wireless communication. In other words, the action control unit 81 is electrically connected to the action control target via wired or wireless communication.

[0064] As described above, in this embodiment, the air-conditioning device 1 performs simultaneous cooling and heating operations with the heating operation as the main body. That is, the outdoor heat exchanger 203 of the outdoor unit 2 functions as an evaporator, and among the multiple indoor units 4, there are indoor units in cooling operation and indoor units in heating operation. During such simultaneous cooling and heating operations of this embodiment, the control unit 8 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation (cooling operation temperature control open state). In order to perform this adjustment (hereinafter referred to as opening adjustment processing), the control unit 8 has an opening adjustment unit 82. The opening adjustment unit 82 is configured to, for example, cause the CPU to execute a program (opening adjustment program) for a prescribed calculation process for adjusting the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling. The opening adjustment unit 82 is, for example, stored in a storage device (non-volatile memory) of the control unit 8 and is read out to the memory when executed.

[0065] exist Figure 1 In the example shown, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404c of the indoor unit 4c in cooling operation (cooling operation temperature control 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 temperature control on state) or the indoor expansion valve 404b of the indoor unit 4b in the heating operation temperature control off state, but maintains their openings.

[0066] During the opening adjustment process, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 during cooling operation based on 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 during cooling operation (cooling operation thermostat on state) based on the difference between the indoor temperature and the outdoor temperature (hereinafter referred to as the indoor-outdoor temperature difference). At this time, the opening adjustment unit 82 corrects the target superheat of the refrigerant. The target superheat is the target value for controlling the superheat of the refrigerant. The superheat is calculated as the difference (TS - TE) between the temperature (TS) of the refrigerant drawn into the compressor 202 and the temperature (TE) of the refrigerant flowing into the outdoor heat exchanger 203, which serves as the evaporator.

[0067] Hereinafter, the opening degree adjustment process in the air-conditioning apparatus 1 will be described according to the control flow of the control unit 8 . Figure 2 The following figure shows the control flow of the control unit 8 during the opening adjustment process. When performing the opening adjustment process, the control unit 8 reads, for example, an operation control program of the operation control unit 81 and an opening adjustment program of the opening adjustment unit 82 from a storage device (non-volatile memory) into a memory and executes them with the CPU.

[0068] During the opening adjustment process, the air conditioner 1 begins operation (S101). Specifically, the operation control unit 81 activates the compressor 202 and opens the outdoor expansion valve 205, thereby circulating the refrigerant through the flow path formed by the outdoor pipe 201 and the indoor pipe 401. Here, the air conditioner 1 enters the heating operation mode, with the outdoor unit 2 performing the heating operation, and the outdoor heat exchanger 203 functions as an evaporator.

[0069] Thus, when the air conditioner 1 starts operating, the opening adjustment unit 82 determines the operating conditions of the air conditioner 1. The operating conditions are conditions for determining whether the air conditioner 1 is performing simultaneous cooling and heating operation. Here, the opening adjustment unit 82 determines whether the air conditioner 1 is performing simultaneous cooling and heating operation, that is, whether there are (a mixture of) indoor units 4 in cooling operation and indoor units in heating operation (S102).

[0070] The indoor unit 4 starts operation by, for example, setting either cooling or heating operation to a user's remote control. If the indoor unit 4 is in the cooling operation temperature control on state or the cooling operation temperature control off state, the control unit 8 closes the first switching valve 61 and opens the second switching valve 62 of the switching unit 6 corresponding to the indoor unit 4. Conversely, if the indoor unit 4 is in the heating operation temperature control on state or the heating operation temperature control off state, the control unit 8 opens the first switching valve 61 and closes the second switching valve 62 of the switching unit 6 corresponding to the indoor unit 4. Therefore, unless all first switching valves 61 are closed and all second switching valves 62 are open, or vice versa, the opening adjustment unit 82 determines that the air conditioner 1 is performing simultaneous cooling and heating operation, i.e., the operating conditions are met. On the other hand, if all first switching valves 61 are closed and all second switching valves 62 are open, or vice versa, the opening adjustment unit 82 determines that the air conditioner 1 is not performing simultaneous cooling and heating operation, i.e., the operating conditions are not met.

[0071] exist Figure 1 In the example shown, the first switching valves 61a and 61b are open, the first switching valve 61c is closed, and the second switching valves 62a and 62b are closed, while the second switching valve 62c is open. Therefore, in the illustrated example, the opening adjustment unit 82 determines that the air conditioner 1 is performing simultaneous cooling and heating operation, that is, the operating conditions are met.

[0072] If it is determined that the air conditioner 1 is performing simultaneous cooling and heating operation (YES in S102), the opening adjustment unit 82 determines the temperature conditions. Here, the opening adjustment unit 82 determines whether the difference between the indoor temperature (TA) and the 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 indoor air of the air-conditioned object being air-conditioned by the indoor unit 4 in heating operation (heating operation temperature control is on), that is, the temperature detected by the indoor temperature detection unit 405 of the indoor unit 4 in 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 and the outdoor temperature of the air-conditioned object being air-conditioned by the indoor unit 4 in heating operation (heating operation temperature control is on).

[0073] When there are multiple indoor units 4 in heating operation (heating operation temperature control on state), for example, the higher temperature among the temperatures detected by the indoor temperature detection units 405 of the indoor units 4 may be used as the indoor temperature in the temperature condition.

[0074] During simultaneous cooling and heating operation, a large difference in indoor and outdoor temperature corresponds to a reduced pressure (liquid line pressure) of the refrigerant flowing in liquid pipe 90. In other words, the temperature condition also serves as a criterion for determining whether the liquid line pressure has decreased, and if satisfied, it can be determined that the liquid line pressure has decreased.

[0075] The reference threshold (X) is the lower limit of the indoor and outdoor temperature difference that requires correction of the target superheat of the refrigerant, and is set to, for example, about 0°C to 10°C. In addition, the reference threshold also serves as a threshold for determining whether the liquid pipe pressure is reduced. The setting value of the reference threshold is stored in, for example, a storage device (non-volatile memory) of the control unit 8. The stored reference threshold is read out and used as a parameter when determining the temperature condition in S103. When determining the temperature condition, 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 temperature control is on). In Figure 1 In the illustrated example, the opening degree adjustment unit 82 acquires the indoor temperature from the indoor temperature detection unit 405a of the indoor unit 4a.

[0076] If it is determined that the indoor-outdoor temperature difference exceeds the reference threshold (TA-TO > X) (YES in S103), the opening adjustment unit 82 corrects the target superheat of the refrigerant (S104). Here, the opening adjustment unit 82 adds a predetermined correction value to the target superheat. The correction value is set such that the larger the indoor-outdoor temperature difference exceeds the reference threshold, the larger the correction value. Figure 3 : is a diagram showing an example of the relationship between the indoor and outdoor temperature difference and the correction value of the target superheat degree. Figure 3 In the example shown, when the indoor and outdoor temperature difference is below the reference threshold, the correction value is 0. When the indoor and outdoor temperature difference exceeds the reference threshold, the correction value increases in proportion to the indoor and outdoor temperature difference, as shown by the trajectory L3. Figure 3 The relationship shown is merely an example. The relationship between the indoor / outdoor temperature difference exceeding the reference threshold and the target superheat correction value may be represented by, for example, a quadratic function trajectory, or may be such that the correction value gradually increases. The corrected target superheat value is stored in, for example, the memory of the control unit 8.

[0077] If the target superheat is corrected, the opening adjustment unit 82 controls the refrigerant superheat to the target superheat (S105). In other words, the refrigerant superheat is controlled to the target superheat. If the target superheat is corrected in S104, the target superheat in S105 is the corrected value.

[0078] When the target superheat is corrected in S104, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation so that the superheat of the refrigerant reaches the corrected target superheat. In other words, the opening adjustment unit 82 reduces the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation based on the corrected target superheat. As described above, the larger the indoor and outdoor temperature difference exceeds the reference threshold, the larger the correction value of the target superheat. Therefore, the larger the target superheat, the smaller the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation becomes (throttling). In other words, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation so that the opening becomes smaller as the indoor and outdoor temperature difference increases.

[0079] exist Figure 1 In the example shown, the opening adjustment unit 82 adjusts the opening of the indoor expansion valve 404c of the indoor unit 4c so that the opening decreases as the difference between the indoor and outdoor temperatures increases. On the other hand, the opening adjustment unit 82 does not adjust the openings of the indoor expansion valves 404a and 404b of the indoor units 4a and 4b, but maintains their original openings (the openings at the time the opening adjustment process is executed).

[0080] Furthermore, when there are a plurality of indoor units 4 in cooling operation (cooling operation thermostat on state), the opening degree adjustment unit 82 adjusts the opening degrees of the indoor expansion valves 404 of all the indoor units 4 in cooling operation.

[0081] In contrast, if the air conditioner 1 is not performing simultaneous cooling and heating operation (No in S102) or if the indoor and outdoor temperature difference is below the reference threshold (TA - TO ≤ X) (No in S103), the target superheat is not corrected. In these cases, the target superheat is a predetermined value set based on, for example, the rotational speed of the compressor 202, and is the value before correction (for example, the initial value) as in S104. Specifically, the target superheat here corresponds to the target superheat before correction relative to the target superheat after correction.

[0082] Therefore, when the air-conditioning device 1 is not performing simultaneous cooling and heating operation (No in S102), or when the indoor and outdoor temperature difference is below the reference threshold (No in S103), the opening adjustment unit 82 controls the superheat of the refrigerant to achieve the target superheat (target superheat before correction).

[0083] After the refrigerant superheat is controlled in this manner, the control unit 8 determines the operation stop condition for the air conditioner 1 (S106). The operation stop condition refers to the condition that determines whether the air conditioner 1 should be stopped. The operation stop condition is determined, for example, based on whether the control unit 8 receives a signal indicating the operation stop of the air conditioner 1. The operation stop signal is transmitted, for example, by a user selecting the operation stop from the operation panel of the outdoor unit 2 or the remote control of the indoor unit 4.

[0084] If the operation stop condition is satisfied (Yes in S106), the operation control unit 81 stops the operation of the air conditioner 1 (S107). If the air conditioner 1 restarts the cooling operation after the stop, the opening adjustment process is executed again.

[0085] In contrast, if the operation stop condition is not met (No in S106), the opening adjustment unit 82 determines whether the air conditioner 1 is performing simultaneous cooling and heating operation as the operating condition of the air conditioner 1 (S102). Then, the control unit 8 (operation control unit 81 and opening adjustment unit 82) selectively executes the subsequent processing (S103 to S107) based on the determination result of the operating condition.

[0086] That is, a series of opening adjustment processes are repeated while the air-conditioning apparatus 1 is operating. Then, when the operation of the air-conditioning apparatus 1 is stopped, the series of opening adjustment processes are also completed.

[0087] As described above, according to this embodiment, when the air conditioner 1 is primarily operating in the heating mode, with the outdoor unit 2 performing the heating mode, and both indoor units 4 operating in the cooling mode and indoor units 4 operating in the heating mode exist (or are mixed), the opening of the indoor expansion valve 404 of the indoor unit 4 operating in the cooling mode can be appropriately adjusted. Specifically, the opening of the indoor expansion valve 404 of the indoor unit 4 operating in the cooling mode can be appropriately adjusted based on the difference between the indoor temperature and the outdoor temperature (indoor-outdoor temperature difference) of the air-conditioned target (hereinafter referred to as the heating room) being air-conditioned by the indoor unit 4 operating in the heating mode.

[0088] For example, when the outdoor temperature is significantly lower than the indoor temperature in the heating room, that is, when 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 becomes fully open, which tends to reduce the liquid line pressure. In this embodiment, as the indoor-outdoor temperature difference exceeds the reference threshold and increases, the opening of the indoor expansion valve 404 of the indoor unit 4 in cooling operation is reduced. This can suppress the reduction in liquid line pressure.

[0089] Furthermore, when the opening of the indoor expansion valve 404 of the indoor unit 4 during cooling operation is reduced in this manner, the target superheat of the refrigerant can be corrected in this embodiment. Specifically, a predetermined correction value can be added to the target superheat value. The correction value increases as the indoor / outdoor temperature difference exceeds a reference threshold. This allows the target superheat value to be higher after correction than before correction. Conversely, when the indoor / outdoor temperature difference is below the reference threshold, the correction value can be set to zero to maintain the target superheat value.

[0090] Therefore, according to this embodiment, as described above, under conditions of a large indoor / outdoor temperature difference, which easily causes a drop in liquid line pressure, the opening degree of the indoor expansion valve 404 of the indoor unit 4 during cooling operation can be reduced, thereby appropriately suppressing a drop in liquid line pressure. In contrast, under conditions of a small indoor / outdoor temperature difference, which is less likely to cause a drop in liquid line pressure, the refrigerant superheat is controlled at the target superheat (the value before correction, or, as an example, the initial value) without making a correction to increase the target superheat. This allows the air conditioner 1 to operate with improved energy efficiency.

[0091] As described above, according to the present embodiment, it is possible to realize the air-conditioning apparatus 1 that can appropriately suppress a drop in liquid pipe pressure and achieve improved energy saving even during simultaneous cooling and heating operation.

[0092] While the embodiments of the present invention have been described above, these embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their variations are included within the scope and gist of the invention, and are included within the invention set forth in the claims and their equivalents.

[0093] Description of Reference Numerals

[0094] 1 Air conditioning unit

[0095] 2 outdoor units

[0096] 4, 4a, 4b, 4c indoor units

[0097] 6, 6a, 6b, 6c switching unit

[0098] 8Control unit

[0099] 61, 61a, 61b, 61c 1st switching valve

[0100] 62, 62a, 62b, 62c Second switching valve

[0101] 81 Motion Control Unit

[0102] 82 opening adjustment unit

[0103] 90 liquid tube

[0104] 90a 1st branch pipe

[0105] 90b second branch pipe

[0106] 90c third branch pipe

[0107] 91 No. 1 Gas Pipe

[0108] 91a 1st branch pipe

[0109] 91b Second branch pipe

[0110] 91c third branch pipe

[0111] 92 Second Gas Pipe

[0112] 92a 1st branch pipe

[0113] 92b Second branch pipe

[0114] 92c third branch pipe

[0115] 201 outdoor side pipe

[0116] 201a No. 1 pipe (suction pipe)

[0117] 201b Second pipe (discharge pipe)

[0118] 202 compressor

[0119] 203 outdoor heat exchanger

[0120] 204 outdoor fan

[0121] 205 outdoor expansion valve

[0122] 206 Outdoor Temperature Detection Department

[0123] 207 four-way valve (first four-way valve)

[0124] 208 four-way valve (second four-way valve)

[0125] 209 liquid reservoir (first liquid reservoir)

[0126] 210 gas-liquid separator (second liquid reservoir)

[0127] 401 indoor side pipe

[0128] 402, 402a, 402b, 402c indoor heat exchangers

[0129] 403, 403a, 403b, 403c indoor fans

[0130] 404, 404a, 404b, 404c indoor expansion valves

[0131] 405, 405a, 405b, 405c indoor temperature detection unit

[0132] PV0, PV1, PV2 connectors.

Claims

1. An air conditioning device, characterized in that: It has an outdoor unit, multiple indoor units, multiple switching units and a control unit. The outdoor unit comprises: a compressor for sucking in, compressing and discharging refrigerant; The outdoor heat exchanger functions as an evaporator or a condenser for performing heat exchange between outdoor air and the refrigerant; the outdoor blower draws in the outdoor air and blows the air, which has undergone heat exchange in the outdoor heat exchanger, to the outside of the room; an outdoor expansion valve, adjusting the flow rate of the refrigerant flowing in the outdoor heat exchanger according to an opening degree; and an outdoor temperature detection unit for detecting the outdoor air temperature, i.e., the outdoor temperature. The indoor unit includes an indoor heat exchanger that functions as a condenser or an evaporator for performing heat exchange between indoor air and the refrigerant; an indoor blower that draws in indoor air and blows the air, which has undergone heat exchange in the indoor heat exchanger, into the room; an indoor expansion valve, adjusting the flow rate of the refrigerant flowing in the indoor heat exchanger according to an opening degree; and an indoor temperature detection unit for detecting the temperature of the indoor air, i.e., the indoor temperature. The switching unit switches the flow of the refrigerant between the outdoor unit and each of the plurality of indoor units to either a cooling system or a heating system. The control unit controls the operation of the outdoor unit, the plurality of indoor units, and the plurality of switching units, and switches each of the plurality of indoor units to either cooling or heating operation. When the outdoor heat exchanger functions as an evaporator and there are indoor units in cooling operation and indoor units in heating operation among the multiple indoor units, the control unit adjusts the opening of the indoor expansion valve of the indoor unit in cooling operation according to 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 according to claim 1, wherein The control unit adjusts the opening of the indoor expansion valve of the indoor unit in cooling operation according to a target value of the superheat of the refrigerant, and corrects the target value according to the outdoor temperature and the indoor temperature detected by the indoor temperature detection unit of the indoor unit in heating operation.

3. The air conditioning device according to claim 2, wherein: The control unit corrects the target value by adding a correction value to the target value before correction. When the temperature difference between the indoor temperature and the outdoor temperature detected by the indoor temperature detection unit of the indoor unit in heating operation is below a specified threshold value, the target value is maintained. When the temperature difference exceeds the threshold value, the larger the temperature difference, the larger the correction value is used to correct the target value.

4. The air conditioning device according to claim 1, wherein The control unit adjusts the opening degree of the indoor expansion valve of the indoor unit in cooling operation so that the opening degree becomes smaller as the temperature difference between the indoor temperature detected by the indoor temperature detection unit of the indoor unit in heating operation and the outdoor temperature increases.

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