Outdoor unit and refrigeration cycle device

Abstract

Provided is an outdoor unit of an air conditioner having a refrigerant circuit in which a refrigerant circulates through flow paths configured by connecting piping to an indoor unit, the outdoor unit comprising: a compressor that compresses and discharges the refrigerant; a plurality of outdoor heat exchangers that exchange heat with air outside a space to be air-conditioned; and a refrigerant flow path switching device that switches the flow paths between a flow path in which the refrigerant passes through the plurality of outdoor heat exchangers in parallel and a flow path in which the refrigerant passes through the plurality of outdoor heat exchangers in series, the refrigerant flow path switching device switching the flow paths during a defrosting operation to the flow path in which the refrigerant discharged by the compressor passes through the plurality of outdoor heat exchangers in parallel.

Description

Outdoor units and refrigeration cycle devices

[0001] This technology relates to an outdoor unit and a refrigeration cycle device having a plurality of outdoor heat exchangers in a refrigerant circuit, and in particular to defrosting of the plurality of outdoor heat exchangers.

[0002] Conventionally, air conditioning systems such as multi-air conditioners for buildings include a refrigerant circuit that connects an outdoor unit (outdoor unit), a heat source installed outside the building, with indoor units (indoor units) installed inside the building via piping. Refrigerant circulates in the refrigerant circuit, and the indoor units heat or cool the air in the target space by utilizing the heat dissipation or absorption of the refrigerant.

[0003] An air conditioner has been proposed that includes an outdoor unit capable of switching the refrigerant flow through multiple outdoor heat exchangers between cooling and heating operations (see, for example, Patent Document 1). In this air conditioner, when the multiple outdoor heat exchangers function as evaporators, the piping connections are switched so that the refrigerant flows in parallel through each outdoor heat exchanger in the refrigerant circuit, and when the multiple outdoor heat exchangers function as condensers, the refrigerant flows in series through each outdoor heat exchanger. Connecting multiple outdoor heat exchangers that function as evaporators in parallel in the refrigerant circuit reduces pressure loss in the evaporators, improving evaporator performance and heating performance. Connecting multiple outdoor heat exchangers that function as condensers in series increases the flow rate of refrigerant passing through the condensers, improving condenser performance and cooling performance.

[0004] Japanese Patent Application Laid-Open No. 2003-121019

[0005] In the outdoor heat exchanger, which functions as an evaporator, moisture in the air precipitates and forms condensed water during heat exchange when the refrigerant's evaporation temperature is low. Furthermore, when the temperature drops below freezing, the water freezes, resulting in frost. Therefore, between heating operations, air conditioners perform defrosting (defrosting) operations as needed. The refrigerant discharged from the compressor is directed as hot gas to the outdoor heat exchanger, which functions as an evaporator, to melt and remove frost from the heat exchanger surface. Typically, during defrosting operations, the outdoor heat exchanger functions as a condenser, resulting in the same flow path as in cooling operations. Therefore, multiple outdoor heat exchangers have a serial flow path for refrigerant. When refrigerant flows through multiple outdoor heat exchangers in series, the upstream outdoor heat exchanger from the compressor radiates a large amount of heat due to the high-temperature refrigerant passing through it. However, as the refrigerant temperature decreases downstream, the amount of heat radiated gradually decreases.

[0006] For this reason, when multiple outdoor heat exchangers are connected in series, defrosting does not progress well, especially in downstream heat exchangers, and it takes a long time for the frost to melt completely. Furthermore, frost and melted drainage water may remain in the outdoor heat exchanger. If the air conditioner resumes heating operation while moisture remains in the heat exchanger, its operating capacity will decrease. Furthermore, it takes a long time to determine whether the frost has completely melted, resulting in a decrease in efficiency.

[0007] Therefore, in order to solve the above-mentioned problems, an outdoor unit and a refrigeration cycle device that can improve the operating capacity and efficiency are disclosed.

[0008] The outdoor unit according to this disclosure is an outdoor unit of an air conditioning system having a refrigerant circuit in which a refrigerant circulates through a flow path formed by piping connection to an indoor unit, and is equipped with a compressor that compresses and discharges the refrigerant, a plurality of outdoor heat exchangers that exchange heat with air outside the space to be air-conditioned, and a refrigerant flow path switching device that switches between a flow path in which the refrigerant passes through the plurality of outdoor heat exchangers in parallel and a flow path in which the refrigerant passes through in series, and during defrosting operation, the refrigerant flow path switching device switches the flow path in which the refrigerant discharged by the compressor passes through the plurality of outdoor heat exchangers in parallel.

[0009] A refrigeration cycle device according to the present disclosure includes the outdoor unit described above and an indoor unit that receives heat from the outdoor unit and heats or cools an object.

[0010] According to the outdoor unit and refrigeration cycle device disclosed herein, it is possible to improve the operating capacity and efficiency.

[0011] Fig. 1 is a diagram showing an example of the configuration of an air conditioning apparatus according to embodiment 1. Fig. 2 is a diagram explaining the flow of refrigerant in heating operation according to embodiment 1. Fig. 3 is a diagram explaining the flow of refrigerant in cooling operation according to embodiment 1. Fig. 4 is a diagram explaining the flow of refrigerant in defrosting operation according to embodiment 1. Fig. 5 is a diagram showing an example of the configuration of an air conditioning apparatus according to embodiment 2. Fig. 6 is a diagram explaining the flow of refrigerant in defrosting operation according to embodiment 2. Fig. 7 is a diagram explaining the flow of processing in a control device according to embodiment 3.

[0012] Below, outdoor units and refrigeration cycle apparatuses according to embodiments will be described with reference to the drawings. In the following drawings, components with the same reference numerals are identical or equivalent and will be common throughout the following embodiments. The dimensional relationships between components in the drawings may differ from those in reality. The configurations of components shown throughout the specification are merely illustrative and are not limited to the configurations described in the specification. Not all of the devices described in the specification may be included. In particular, the combinations of components are not limited to the combinations in each embodiment; components described in other embodiments may be applied to other embodiments. Furthermore, the levels of pressure and temperature are not determined in relation to absolute values, but are determined relatively in terms of the state, operation, etc. of the device. When multiple similar devices, distinguished by subscripts, need not be specifically distinguished or identified, the reference numerals, subscripts, etc. may be omitted.

[0013] Embodiment 1. Figure 1 is a diagram showing an example of the configuration of an air conditioning apparatus 1 according to embodiment 1. Here, the air conditioning apparatus 1 will be described as an example of a refrigeration cycle apparatus having a heat exchanger according to embodiment 1. Here, Figure 1 functionally shows the connection relationships and layout configuration of each device in the air conditioning apparatus 1, and does not necessarily show the layout relationships in physical space (the same applies to the following figures).

[0014] The air conditioning apparatus 1 is a device that adjusts the temperature of air in an indoor space to be air-conditioned. Here, Fig. 1 shows an example of a configuration in which one indoor unit 400 and an outdoor unit 100 are connected via two main pipes 500. However, the number of indoor units 400 connected to the outdoor unit 100 is not limited to one, and multiple indoor units 400 may be connected.

[0015] As shown in Fig. 1 , the air conditioning apparatus 1 in the first embodiment is configured by connecting an outdoor unit 100 and an indoor unit 400 by a main pipe 500, and has a refrigerant circuit through which a refrigerant circulates. In the refrigerant circuit in the first embodiment, the flow path through which the refrigerant flows changes in the outdoor heat exchanger 130, as will be described later. Here, in the air conditioning apparatus 1, the refrigerant filled in the refrigerant circuit is not particularly limited.

[0016] <Outdoor unit 100> The outdoor unit 100 has, as main components of a refrigerant circuit, a compressor 110, a cooling / heating flow path switching device 120, an outdoor heat exchanger 130, an outdoor expansion valve 140, a check valve 150, an accumulator 160, and an outdoor shut-off valve 170. The compressor 110, the cooling / heating flow path switching device 120, the outdoor heat exchanger 130, the outdoor expansion valve 140, the check valve 150, the accumulator 160, and the outdoor shut-off valve 170 are connected within the outdoor unit 100 by pipes that form a refrigerant circuit, and are devices that form part of the refrigerant circuit.

[0017] The compressor 110 compresses and discharges the drawn refrigerant. The compressor 110 is, for example, a scroll compressor, a reciprocating compressor, or a vane compressor. The air conditioning apparatus 1 in the first embodiment has, for example, an inverter device (not shown) or the like, which can arbitrarily change the drive frequency of the power supplied to the compressor 110. Therefore, the compressor 110 can change the drive frequency based on instructions from the control device 600 (described later), thereby changing the rotation speed of a motor (not shown) included in the compressor 110 and changing the drive capacity.

[0018] The cooling / heating flow path switching device 120 switches the flow path of the refrigerant by performing an operation based on, for example, instructions from a control device 600 (described later). The cooling / heating flow path switching device 120 in the first embodiment has a four-way valve 120a and a four-way valve 120b. The cooling / heating flow path switching device 120, together with a heat exchange switching valve 220 and a bypass control valve 320 (described later), constitutes a refrigerant flow path switching device.

[0019] For example, during cooling operation, the four-way valve 120a switches to a flow path that allows high-temperature, high-pressure refrigerant discharged from the compressor 110 to flow into the outdoor heat exchanger 130a (described later) and allows refrigerant that has flowed from the indoor unit 400 into the outdoor unit 100 to flow into the accumulator 160. On the other hand, during heating operation, the four-way valve 120a switches to a flow path that allows high-temperature, high-pressure refrigerant discharged from the compressor 110 to flow out of the outdoor unit 100 and allows refrigerant that has flowed out from the outdoor heat exchanger 130a (described later) to flow into the accumulator 160. Furthermore, during cooling operation, the four-way valve 120b, together with the check valve 150 (described later), switches to a flow path that prevents the high-temperature, high-pressure refrigerant discharged from the compressor 110 from flowing directly into the outdoor heat exchanger 130b. On the other hand, during heating operation, the four-way valve 120 b switches the flow path to allow the refrigerant flowing out from an exterior heat exchanger 130 b (described later) to flow into the accumulator 160 .

[0020] In the first embodiment, the outdoor heat exchanger 130 is, for example, a fin-and-tube heat exchanger configured with a plurality of heat transfer tubes and a plurality of fins. The outdoor heat exchanger 130 functions as a condenser during heating operation and as an evaporator during cooling operation. Here, the outdoor heat exchanger 130 in the first embodiment includes an outdoor heat exchanger 130a and an outdoor heat exchanger 130b. Here, it is assumed that the outdoor heat exchangers 130a and 130b have the same size and the same heat exchange capacity.

[0021] The outdoor heat exchanger 130a and the outdoor heat exchanger 130b allow refrigerant to flow in parallel during heating operation and in series during cooling operation, depending on the opening and closing of a heat exchange switching valve 220 installed in a heat exchange switching pipe 210 of a heat exchange switching flow path 200 (described later). During cooling operation, in which the refrigerant flows in series, the outdoor heat exchanger 130a serves as the upstream heat exchanger and the outdoor heat exchanger 130b serves as the downstream heat exchanger with respect to the refrigerant flow in the refrigerant circuit. During cooling operation, the outdoor heat exchanger 130a exchanges heat between the refrigerant discharged from the compressor 110 and the outdoor air outside the air-conditioned space, condensing the refrigerant to liquefy or convert it to two-phase gas-liquid. During cooling operation, the outdoor heat exchanger 130b exchanges heat between the refrigerant flowing out of the outdoor heat exchanger 130a and the outdoor air outside the air-conditioned space, condensing the refrigerant to liquefy or convert it to two-phase gas-liquid. On the other hand, during heating operation, the outdoor heat exchangers 130a and 130b receive refrigerant that has passed through an outdoor expansion valve 140 (described later) in parallel, and exchange heat with the outdoor air outside the air-conditioned space, evaporating the refrigerant. The outdoor fan 190 is a blower that passes outdoor air through the outdoor heat exchanger 130 to promote heat exchange in the outdoor heat exchanger 130.

[0022] The outdoor expansion valve 140 is a valve such as an electronic expansion valve that, for example, during heating operation, reduces the pressure of the refrigerant to expand it and adjust the amount of refrigerant flowing into the outdoor heat exchanger 130. The air conditioning apparatus 1 in Embodiment 1 has outdoor expansion valves 140a and 140b corresponding to the outdoor heat exchangers 130a and 130b.

[0023] During heating operation, the check valve 150 allows the refrigerant flowing out from the outdoor heat exchanger 130b to pass through and flow into the accumulator 160 via the four-way valve 120b. On the other hand, during cooling operation, the check valve 150 stops the refrigerant from the four-way valve 120b from passing through the piping toward the outdoor heat exchanger 130b. Furthermore, the branch pipe 180 is a pipe that, during heating operation, branches the refrigerant that has flowed into the outdoor unit 100 from the indoor unit 400 via the main pipe 500, and passes it through the outdoor expansion valve 140a and the outdoor expansion valve 140b, respectively.

[0024] The accumulator 160 is installed on the suction side of the compressor 110. The accumulator 160 passes gas refrigerant through the suction side of the compressor 110 and accumulates liquid refrigerant. The outdoor shut-off valves 170 are installed at the refrigerant inlet and outlet ports connecting the outdoor unit 100 and each main pipe 500. The outdoor shut-off valves 170 include valves that perform opening and closing operations, such as ball valves, on-off valves, and operating valves. For example, when the air conditioning apparatus 1 is not operating, the outdoor shut-off valves 170 close the valve to block the inflow and outflow of refrigerant between the indoor unit 400.

[0025] In addition, the outdoor unit 100 in embodiment 1 has a heat exchange switching flow path 200 and a bypass flow path 300 in the refrigerant circuit as flow paths for passing refrigerant in parallel or directly through the outdoor heat exchanger 130 depending on the operating mode of the air conditioning device 1.

[0026] The heat exchange switching flow path 200 is a flow path through which the refrigerant passes in series between the outdoor heat exchanger 130a and the outdoor heat exchanger 130b. The heat exchange switching flow path 200 includes a heat exchange switching pipe 210 and a heat exchange switching valve 220. One end of the heat exchange switching pipe 210 is connected to a pipe that serves as the refrigerant outlet side of the outdoor heat exchanger 130a during cooling operation, and the other end is connected to a pipe that serves as the refrigerant inlet side of the outdoor heat exchanger 130b. The heat exchange switching valve 220, which is one of the refrigerant flow path switching devices, is an on-off valve such as a solenoid valve that controls whether or not refrigerant is allowed to pass through the heat exchange switching pipe 210 based on instructions from a control device 600 (described later). The heat exchange switching valve 220 is open during cooling operation and closed during heating operation.

[0027] The bypass flow path 300 is a flow path through which hot gas, which is a refrigerant discharged from the compressor 110, flows when defrosting the outdoor heat exchanger 130 during defrosting operation. The bypass flow path 300 has a bypass pipe 310 and a bypass control valve 320. One end of the bypass pipe 310 is connected to a pipe on the discharge side of the compressor 110, and the other end is connected to a pipe connecting the outdoor heat exchanger 130b and the outdoor expansion valve 140b. The bypass control valve 320, which is one of the refrigerant flow path switching devices, is an on-off valve such as a solenoid valve that controls whether to allow refrigerant to pass through the bypass pipe 310 based on an instruction from a control device 600 (described later). The bypass control valve 320 is open during defrosting operation and closed during other operations.

[0028] <Indoor unit 400> The indoor unit 400 is, for example, a unit installed indoors. The indoor unit 400 has an indoor expansion valve 410, an indoor heat exchanger 420, and an indoor fan 430. The indoor expansion valve 410 and the indoor heat exchanger 420 are connected by piping within the indoor unit 400, and are devices that form part of the refrigerant circuit.

[0029] The indoor expansion valve 410 serving as a throttling device includes, for example, an electronic expansion valve, a temperature-sensitive expansion valve, etc. The indoor expansion valve 410 is a valve that adjusts the pressure and flow rate of the refrigerant passing through the indoor heat exchanger 420.

[0030] In the first embodiment, the indoor heat exchanger 420 is, for example, a fin-and-tube heat exchanger having a plurality of heat transfer tubes and a plurality of fins. During heating operation, the indoor heat exchanger 420 functions as a condenser, exchanging heat between the refrigerant discharged from the compressor 110 in the outdoor unit 100 and the indoor air, condensing the refrigerant to a liquid or to form a two-phase gas-liquid mixture, and heating the indoor air. During cooling operation, the indoor heat exchanger 420 functions as an evaporator, exchanging heat between the refrigerant flowing in from the indoor expansion valve 410 and the indoor air, evaporating the refrigerant to cool the indoor air. The indoor fan 430 is disposed near the indoor heat exchanger 420 and sends air to the indoor heat exchanger 420, thereby delivering the conditioned air into the room.

[0031] <Control System Devices> The air conditioning apparatus 1 also has a control device 600. The control device 600 is a device that controls the air conditioning apparatus 1. Here, the outdoor unit 100 is described as having the control device 600, but this is not limited to this. Another unit may also have the control device 600. Furthermore, the control device 600 may be a device independent of the unit that has the devices that make up the air conditioning apparatus 1.

[0032] The control device 600 includes, for example, a microcomputer. The microcomputer includes a control unit 610 and a memory unit 620. The control unit 610 includes, for example, a control and arithmetic processing device such as a CPU (Central Processing Unit). The control unit 610 also includes a timer and is capable of measuring time. The control unit 610 in the first embodiment particularly includes a calculation unit 611, a determination unit 612, and an equipment control unit 613. The calculation unit 611 performs calculations necessary for making determinations, for example, based on values ​​of physical quantities detected by various sensors described below. The determination unit 612 makes determinations related to the control of the air conditioning device 1. The equipment control unit 613 controls each device of the air conditioning device 1 based on, for example, the determination result of the determination unit 612, and controls the operation of the air conditioning device 1.

[0033] The storage unit 620 also includes, for example, a volatile storage device (not shown) such as random access memory (RAM) that can temporarily store data, and a non-volatile auxiliary storage device (not shown) such as flash memory. The storage unit 620 stores program data that describes the processing procedures to be performed by the control arithmetic processing unit. The control unit 610 then executes processing based on the program data. However, this is not a limitation, and the control device 600 may also be a device (hardware) dedicated to control.

[0034] The air conditioning apparatus 1 in embodiment 1 includes, as a sensor unit, various sensors that detect physical quantities used by the control device 600 when performing processes such as determinations and send detection signals to the control device 600. Here, the air conditioning apparatus 1 includes, as a sensor unit, a high-pressure sensor 710, a refrigerant temperature sensor 720, and an outdoor air temperature sensor 730. The high-pressure sensor 710 is installed on the discharge side of the compressor 110 and detects the refrigerant pressure on the high-pressure side of the refrigerant circuit as the high-pressure pressure. The refrigerant temperature sensor 720 detects the refrigerant temperature of the refrigerant flowing out of the outdoor heat exchanger 130 when the outdoor heat exchanger 130 functions as a condenser. Here, the refrigerant temperature sensor 720 is installed downstream of the branch pipe 180 in the refrigerant flow during cooling operation and defrosting operation. The outdoor air temperature sensor 730 detects the temperature of the outdoor air.

[0035] <Operation of the Air Conditioner> FIG. 2 is a diagram illustrating the flow of refrigerant during heating operation according to the first embodiment. Here, the operation of each device in the air conditioner 1 will be described based on the flow of refrigerant. First, the operation of each device in the refrigerant circuit during heating operation will be described based on the flow of refrigerant. The solid arrows in FIG. 2 indicate the flow of refrigerant during heating operation. The high-temperature, high-pressure gaseous refrigerant (hereinafter referred to as gas refrigerant) compressed and discharged by the compressor 110 passes through the cooling / heating flow switching device 120 and flows out of the outdoor unit 100. The refrigerant flowing out of the outdoor unit 100 passes through the main pipe 500 and flows into the indoor heat exchanger 420 of the indoor unit 400. While passing through the indoor heat exchanger 420, the gas refrigerant condenses and liquefies by, for example, exchanging heat with the air in the space to be air-conditioned, thereby becoming a liquid refrigerant (hereinafter referred to as liquid refrigerant). The condensed and liquefied liquid refrigerant passes through the indoor expansion valve 410. The refrigerant is decompressed as it passes through the indoor expansion valve 410. The refrigerant, which has been decompressed by the indoor expansion valve 410 and is now in a gas-liquid two-phase state, flows out of the indoor unit 400. The refrigerant flowing out of the indoor unit 400 passes through the main pipe 500 and flows into the outdoor unit 100. The refrigerant that flows into the outdoor unit 100 branches at the branch pipe 180 and passes through the outdoor expansion valve 140a and the outdoor expansion valve 140b, respectively. As the refrigerant passes through, the outdoor expansion valves 140a and 140b decompress the refrigerant and adjust the amount of refrigerant. The refrigerant that has passed through the outdoor expansion valves 140a and 140b passes through the outdoor heat exchangers 130a and 130b, respectively. In the outdoor heat exchangers 130a and 130b, the refrigerant evaporates by exchanging heat with the outdoor air sent from the outdoor fan 190, and the gasified gas refrigerant passes through the cooling / heating flow path switching device 120 and the accumulator 160, and is again drawn into the compressor 110. In this way, the refrigerant circulates in the refrigerant circuit of the air conditioner 1, and air conditioning related to heating is performed.

[0036] FIG. 3 is a diagram illustrating the flow of refrigerant during cooling operation according to the first embodiment. Next, the cooling operation will be described. The solid arrows in FIG. 3 indicate the flow of refrigerant during cooling operation. During cooling operation, the heat exchange switching valve 220 is opened, and the outdoor expansion valve 140a is closed to prevent refrigerant from passing through. High-temperature, high-pressure gas refrigerant compressed and discharged by the compressor 110 passes through the cooling / heating flow path switching device 120 and flows into the outdoor heat exchanger 130a. The refrigerant that flows into the outdoor heat exchanger 130a passes through the outdoor heat exchanger 130a, the heat exchange switching pipe 210 of the heat exchange switching flow path 200, and the outdoor heat exchanger 130a, in that order. During this passage, the refrigerant condenses and liquefies in the outdoor heat exchangers 130a and 130b by exchanging heat with outdoor air supplied by the outdoor fan 190. The liquid refrigerant that has passed through the outdoor heat exchanger 130 flows out of the outdoor unit 100. The refrigerant that has flowed out of the outdoor unit 100 passes through the main pipe 500 and the indoor expansion valve 410 of the indoor unit 400. Here, the refrigerant is decompressed as it passes through the indoor expansion valve 410, and becomes a two-phase gas-liquid state. The refrigerant that has been decompressed and become a two-phase gas-liquid state by the indoor expansion valve 410 passes through the indoor heat exchanger 420. Then, in the indoor heat exchanger 420, for example, the refrigerant exchanges heat with indoor air, evaporating, and the gasified gas refrigerant flows out of the indoor unit 400. The refrigerant that has flowed out of the indoor unit 400 passes through the main pipe 500 and flows into the outdoor unit 100. The refrigerant that has flowed into the outdoor unit 100 passes through the cooling / heating flow switching device 120 and is again drawn into the compressor 110. In this manner, the refrigerant circulates in the refrigerant circuit of the air conditioner 1, and performs air conditioning related to cooling.

[0037] FIG. 4 is a diagram illustrating the flow of refrigerant during defrosting operation according to the first embodiment. Next, the defrosting operation will be described. The solid arrows in FIG. 4 indicate the flow of refrigerant during defrosting operation. During defrosting operation, the heat exchange switching valve 220 and the outdoor expansion valve 140a are opened, and the outdoor expansion valve 140b is closed to prevent refrigerant from passing through. Furthermore, the bypass control valve 320 is opened to allow refrigerant to pass through the bypass piping 310. During defrosting operation, the outdoor fan 190 is stopped. Furthermore, the indoor fan 430 in the indoor unit 400 is also stopped.

[0038] A portion of the high-temperature, high-pressure gas refrigerant compressed and discharged by the compressor 110 passes through the cooling / heating flow switching device 120 and flows into the outdoor heat exchanger 130a as hot gas. The remaining gas refrigerant passes through the bypass piping 310 and flows into the outdoor heat exchanger 130b as hot gas. The refrigerants that flow into the outdoor heat exchangers 130a and 130b are liquefied by exchanging heat with frost that has formed on the outdoor heat exchangers 130a and 130b. The liquid refrigerant that has passed through the outdoor heat exchanger 130b passes through the heat exchange switching piping 210, merges with the liquid refrigerant that has passed through the outdoor heat exchanger 130a, and flows out of the outdoor unit 100 via the outdoor expansion valve 140a. The refrigerant flowing out of the outdoor unit 100 passes through the main pipe 500, and passes through the indoor expansion valve 410 and indoor heat exchanger 420 of the indoor unit 400, before flowing out of the indoor unit 400. At this time, the indoor unit 400 is not operating, so no heat exchange occurs in the indoor unit 400. The refrigerant flowing out of the indoor unit 400 passes through the main pipe 500 and flows into the outdoor unit 100. The refrigerant that flows into the outdoor unit 100 passes through the cooling / heating flow switching device 120 and the accumulator 160, and is again drawn into the compressor 110. In this way, the refrigerant circulates in the refrigerant circuit of the air conditioning apparatus 1, and defrosting operation is performed.

[0039] As described above, the outdoor unit 100 of the air conditioning apparatus 1 according to the first embodiment includes a refrigerant flow path switching device that switches the flow paths in the multiple outdoor heat exchangers 130. In the air conditioning apparatus according to the first embodiment, for example, the cooling / heating flow path switching device 120 (four-way valves 120a and 120b), the heat exchanger switching valve 220, and the bypass control valve 320 function as the refrigerant flow path switching device. Therefore, it is possible to pass hot gas directly through the outdoor heat exchanger 130b and pass hot gas in parallel through the multiple outdoor heat exchangers 130. By passing hot gas in parallel through the multiple outdoor heat exchangers 130, it is possible to suppress heat dissipation bias toward the upstream outdoor heat exchanger 130, as occurs when multiple outdoor heat exchangers 130 are connected in series, and to reduce bias in the amount of heat dissipated from the refrigerant in each outdoor heat exchanger 130. Therefore, the outdoor unit 100 of the air conditioner 1 in embodiment 1 can defrost multiple outdoor heat exchangers 130, including the downstream outdoor heat exchanger 130, without leaving any moisture during defrosting operation, thereby improving heating operation performance. Furthermore, the defrosting times for the multiple outdoor heat exchangers 130 can be performed simultaneously or with minimal time lag. Therefore, the outdoor unit 100 of the air conditioner 1 in embodiment 1 can shorten the defrosting time and speed up the transition from defrosting operation to heating operation, thereby improving overall operational efficiency when heating the room. When hot gas is passed through multiple outdoor heat exchangers 130 in parallel as in embodiment 1, a time reduction of approximately 20% can be expected compared to when hot gas is passed through multiple outdoor heat exchangers 130 in series.

[0040] In particular, the outdoor unit 100 in the first embodiment includes a bypass flow path 300 having a bypass pipe 310 and a bypass control valve 320. Therefore, in the outdoor unit 100 configured with a switching device that passes refrigerant in parallel through a plurality of outdoor heat exchangers 130 during cooling operation and passes refrigerant in parallel through a plurality of outdoor heat exchangers 130 during heating operation, hot gas can be passed in parallel through a plurality of outdoor heat exchangers 130 during defrosting operation.

[0041] Embodiment 2. Figure 5 is a diagram showing an example of the configuration of an air conditioning apparatus 1 according to embodiment 2. In Figure 5, devices and the like denoted with the same reference numerals as in Figure 1 perform the same operations as those described in embodiment 1. As shown in Figure 3, the outdoor unit 100 of the air conditioning apparatus 1 according to embodiment 2 is provided with an on-off control valve 151 instead of the check valve 150. Furthermore, the outdoor unit 100 according to embodiment 2 does not have a bypass flow path 300. Therefore, in the air conditioning apparatus according to embodiment 2, for example, the cooling / heating flow path switching device 120 (four-way valves 120a and 120b), the heat exchanger switching valve 220, and the on-off control valve 151 serve as the refrigerant flow path switching device.

[0042] The on-off control valve 151 is an on-off valve such as a solenoid valve that controls the flow of refrigerant through the piping connecting the four-way valve 120b of the cooling / heating flow switching device 120 and the outdoor heat exchanger 130b. The on-off control valve 151 is open during heating operation and closed during cooling operation. As a result, like the check valve 150 described in the first embodiment, the on-off control valve 151 does not allow the refrigerant discharged from the compressor 110 to pass, but allows the refrigerant that has passed through the outdoor heat exchanger 130b to pass. Therefore, the refrigerant in the refrigerant circuit flows in the same manner as in cooling operation and heating operation. On the other hand, the on-off control valve 151 is open during defrosting operation. As a result, hot gas refrigerant, which is the refrigerant discharged from the compressor 110, flows in parallel into the outdoor heat exchangers 130a and 130b.

[0043] FIG. 6 is a diagram illustrating the flow of refrigerant during defrosting operation according to the second embodiment. As described above, in the air conditioning apparatus 1 according to the second embodiment, the flow is the same during cooling operation and heating operation depending on whether the on-off control valve 151 is open or closed, and therefore the operation of each device during cooling operation and heating operation is the same. Here, the operation of each device in the refrigerant circuit during defrosting operation will be described based on the flow of refrigerant. The solid arrows in FIG. 6 indicate the flow of refrigerant during defrosting operation. During defrosting operation, the outdoor expansion valves 140b and 140a are opened, and the heat exchange switching valve 220 is closed to prevent refrigerant from passing through. Also, as described above, the on-off control valve 151 is opened. During defrosting operation, the outdoor fan 190 and the indoor fan 430 are stopped.

[0044] The high-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 110 passes through the cooling / heating flow switching device 120. The gas refrigerant that passes through the four-way valve 120a flows into the outdoor heat exchanger 130a as a hot gas. The gas refrigerant that passes through the four-way valve 120b flows into the outdoor heat exchanger 130b as a hot gas. The refrigerants that flow into the outdoor heat exchangers 130a and 130b are liquefied by exchanging heat with frost that has formed on the outdoor heat exchangers 130a and 130b. The liquid refrigerants that have passed through the outdoor heat exchangers 130a and 130b pass through the outdoor expansion valves 140a and 140b, respectively, and merge with the liquid refrigerant in the branch pipe 180 before flowing out of the outdoor unit 100. The refrigerant flowing out of the outdoor unit 100 passes through the main pipe 500, and passes through the indoor expansion valve 410 and indoor heat exchanger 420 of the indoor unit 400, before flowing out of the indoor unit 400. At this time, the indoor unit 400 is not operating, so no heat exchange occurs in the indoor unit 400. The refrigerant flowing out of the indoor unit 400 passes through the main pipe 500 and flows into the outdoor unit 100. The refrigerant that flows into the outdoor unit 100 passes through the cooling / heating flow switching device 120 and the accumulator 160, and is again drawn into the compressor 110. In this manner, the refrigerant in the air conditioning apparatus 1 circulates, and defrosting operation is performed.

[0045] As described above, the air conditioning apparatus 1 in the second embodiment includes an on-off control valve 151 between the four-way valve 120b of the cooling / heating flow switching device 120 and the outdoor heat exchanger 130b, which can control the passage of refrigerant by opening and closing the valve. The on-off control valve 151 can allow not only the refrigerant flowing from the outdoor heat exchanger 130b to the four-way valve 120b but also the refrigerant discharged from the compressor 110 to flow into the outdoor heat exchanger 130b via the four-way valve 120b. This prevents refrigerant from passing through during cooling operation, but allows the refrigerant discharged from the compressor 110 to pass as hot gas during defrosting operation, allowing the hot gas to pass through multiple outdoor heat exchangers 130 in parallel. This shortens the defrosting time, speeds up the transition from defrosting operation to heating operation, and improves overall operating efficiency.

[0046] Embodiment 3 In embodiment 3, a description will be given of the determination of the end of defrosting operation performed by the control device 600 of the air conditioning apparatus 1. Here, the air conditioning apparatus 1 in embodiment 3 is assumed to have the same configuration as the air conditioning apparatus 1 described in embodiment 1. However, this is not limited to this, and the present invention can also be applied to the air conditioning apparatus 1 in embodiment 2.

[0047] During defrosting operation, the control device 600 basically terminates the defrosting operation and transitions to heating operation when it determines, based on the refrigerant temperature detected by the refrigerant temperature sensor 720, that the frost on the outdoor heat exchanger 130 has completely melted. For example, the refrigerant that becomes hot gas passing through the outdoor heat exchanger 130 releases heat through heat exchange with the frost on the outdoor heat exchanger 130, thereby lowering the refrigerant temperature. When the frost is completely melted, heat exchange between the refrigerant and the frost ceases, and the amount of heat exchange decreases. Therefore, the refrigerant temperature rises. Therefore, the control device 600 terminates the defrosting operation of the air conditioning apparatus 1 when the refrigerant temperature reaches or exceeds the temperature represented by the operation termination determination threshold, which serves as the criterion for determining whether to terminate the defrosting operation.

[0048] Here, the refrigerant temperature detected by the refrigerant temperature sensor 720 may be affected by the outdoor environment, such as wind and air temperature. In this case, the refrigerant temperature detected by the refrigerant temperature sensor 720 may be lower than the actual temperature of the refrigerant passing through the outdoor heat exchanger 130. Furthermore, due to pressure loss in the outdoor expansion valve 140, the refrigerant temperature detected by the refrigerant temperature sensor 720 may be lower than the temperature at which the refrigerant passes through the outdoor heat exchanger 130. This may result in a longer time until the refrigerant temperature reaches the operation end determination threshold and the control device 600 determines that the defrosting operation has ended. A longer defrosting operation may result in a delay in the start of normal operation, unnecessary heat supply, and other reductions in the efficiency of the air conditioning apparatus 1.

[0049] Therefore, in the air conditioning apparatus 1 of embodiment 3, the control device 600 calculates the saturation temperature, which is the temperature of the refrigerant passing through the outdoor heat exchanger 130, based on the high-pressure detected by the high-pressure pressure sensor 710, and determines whether to terminate the defrosting operation based on the saturation temperature. The saturation temperature is hardly affected by the outdoor environment and is a temperature obtained by calculation by the control device 600, so it is possible to more accurately determine the timing to terminate the defrosting operation.

[0050] The control device 600 may simply calculate the saturation temperature and determine the end of the defrosting operation, but here the control device 600 further sets an operation end determination threshold based on the outside air temperature detected by the outside air temperature sensor 730.

[0051] For example, when the outdoor air temperature outside the air-conditioned space is low, the absolute humidity of the outdoor air is low and the amount of moisture contained in the air is small, resulting in less frost forming on the outdoor heat exchanger 130. Therefore, the time until the frost is completely melted should be shorter, and the defrosting time should be reduced. Here, the control device 600 indirectly determines that the frost has completely melted based on the temperature of the refrigerant passing through the outdoor heat exchanger 130. When the outdoor air temperature is low, the refrigerant temperature detected by the sensor reaches the operation termination threshold set during the defrosting operation, lengthening the time until the control device 600 determines that the defrosting operation has ended, which may result in a discrepancy between the actual time until the frost is completely melted and the time required for the refrigerant temperature to melt.

[0052] Therefore, in the air conditioning apparatus 1 of embodiment 3, the control device 600 resets and changes the operation termination determination threshold based on the outside air temperature detected by the outside air temperature sensor 730. Specifically, when the outside air temperature detected by the outside air temperature sensor 730 is lower than the temperature represented by the outside air temperature threshold, the control device 600 changes the operation termination determination threshold to a value lower than the initial value so that the calculated saturation temperature reaches the operation termination determination threshold more quickly.

[0053] Fig. 7 is a diagram illustrating the flow of processing in the control device 600 according to embodiment 3. The processing of determining the end of defrosting operation performed by the control device 600 will be described based on Fig. 7. The control device 600 of the air conditioning apparatus 1 according to embodiment 3 starts the processing of determining the end of defrosting operation when it causes the air conditioning apparatus 1 to start a defrosting operation.

[0054] The determination unit 612 of the control device 600 determines whether the outside air temperature detected by the outside air temperature sensor 730 is below the outside air temperature threshold (step S1). If the determination unit 612 determines that the outside air temperature is below the outside air temperature threshold, it changes the operation end determination threshold (step S2). If the determination unit 612 determines that the outside air temperature is equal to or higher than the outside air temperature threshold, it leaves the operation end determination threshold unchanged. Here, the outside air temperature threshold is, for example, -10°C. The change value is not particularly limited. For example, it may be a value obtained by adding a predetermined value to the outside air temperature and greater than 0°C.

[0055] The calculation unit 611 of the control device 600 calculates the saturation temperature based on the high-pressure detected by the high-pressure sensor 710 (step S3). Then, the determination unit 612 of the control device 600 determines whether the saturation temperature calculated by the calculation unit 611 is equal to or greater than the operation termination threshold (step S4). Here, the operation termination threshold is set to 10°C, for example. If the determination unit 612 determines that the saturation temperature is not equal to or greater than the operation termination threshold, the process returns to step S3, and the calculation and determination of the saturation temperature are repeated.

[0056] If the determination unit 612 determines that the saturation temperature is equal to or higher than the operation termination threshold, it determines whether this state has continued for a set time or longer (step S5). Here, the set time is, for example, four minutes. If the determination unit 612 determines that the state in which the saturation temperature is equal to or higher than the operation termination threshold has not continued for the set time or longer, it returns to step S3 and repeats the determination.

[0057] On the other hand, if the determination unit 612 determines that the saturation temperature has remained above the operation termination threshold for a set time or longer, the defrosting operation is terminated (step S6).Then, the equipment control unit 613 of the control device 600 switches the refrigerant flow path switching devices (cooling / heating flow path switching device 120, heat exchanger switching valve 220, and bypass control valve 320) to the flow path related to the heating operation, and performs the heating operation (step S7).

[0058] As described above, in the air conditioning apparatus 1 of Embodiment 3, when the control device 600 determines whether to terminate the defrosting operation, it does so based on the saturation temperature of the refrigerant passing through the outdoor heat exchanger 130. This makes it possible to more accurately derive the refrigerant temperature in the outdoor heat exchanger 130 without being affected by the external environment, such as the outdoor air temperature, and the control device 600 can accurately determine the timing when the frost will melt and the defrosting operation will be terminated.

[0059] Furthermore, in the air conditioning apparatus 1 according to the third embodiment, the control device 600 changes the operation termination determination threshold, which is the criterion for determining whether to terminate the defrosting operation, based on the outdoor air temperature detected by the outdoor air temperature sensor 730. Therefore, even when the outdoor air temperature is low and the amount of frost on the outdoor heat exchanger 130 is small, the time required for the temperature of the refrigerant passing through the outdoor heat exchanger 130 to reach the operation termination determination threshold can be shortened. Therefore, the control device 600 can accurately determine the timing when the frost melts and the defrosting operation is terminated. The determination of whether to change the operation termination determination threshold based on the outdoor air temperature can be applied not only to the saturation temperature but also to defrost termination determinations based on other physical quantities such as temperature.

[0060] For example, the determination unit 612 determines whether to change the operation termination determination threshold for the saturation temperature calculated by the calculation unit 611 based on the outside air temperature, but the present invention is not limited to this. The determination unit 612 may also apply to the operation termination determination threshold when determining the end of the defrosting operation based on the refrigerant temperature detected by the refrigerant temperature sensor 720. In this case, for example, the operation termination determination threshold is changed to a lower value of 7°C, taking into account the pressure loss of the outdoor expansion valve 140, while the operation termination determination threshold at the saturation temperature is 10°C.

[0061] Embodiment 4. In the air conditioner 1 in the above-described embodiments 1 to 3, the bypass flow path 300 is a flow path for passing refrigerant in parallel or directly through the outdoor heat exchanger 130 during defrosting operation, but this is not limited to this. For example, when the outdoor temperature, indoor temperature, etc. are high and the indoor unit 400 is small, the pressure of the refrigerant on the high-pressure side of the refrigerant circuit may rise too much, resulting in excessive pressure. In such cases, the bypass flow path 300 can be used as a flow path for passing the refrigerant and releasing it to the low-pressure side, thereby reducing the pressure on the high-pressure side.

[0062] Furthermore, while the air conditioner 1 in the first to third embodiments described above performs cooling and heating operations by switching the flow path in the refrigerant circuit, this is not limited to this. The present invention can be applied to a refrigeration cycle apparatus in which the outdoor heat exchanger 130 can be switched between a condenser and an evaporator. For example, the present invention can be applied to an air conditioner 1 in which multiple indoor units 400 are connected in parallel to the outdoor unit 100 through pipes, and in which some of the operating indoor units 400 perform cooling operation while the other indoor units 400 perform heating operation, enabling simultaneous cooling and heating operation. In this case, the air conditioner 1 switches the flow path so that the refrigerant passes through the multiple outdoor heat exchangers 130 in parallel or in series, depending on whether the outdoor heat exchanger 130 functions as a condenser or an evaporator. Although the present invention has been described using two outdoor heat exchangers 130 as an example, the present invention can also be applied to an air conditioner with three or more outdoor heat exchangers 130.

[0063] Furthermore, in the air conditioning apparatus 1 in the first and second embodiments described above, the refrigerant flow path switching device, the heat exchange switching valve 220, the bypass control valve 320, and the on-off control valve 151, have been described as having on-off valves such as solenoid valves, but this is not limited to this. For example, the control device 600 may have a flow control valve or the like whose opening degree can be changed as desired.

[0064] In the above-described first to fourth embodiments, the air conditioner 1 has been described as an example of a refrigeration cycle device, but the present invention is not limited to this. For example, the present invention can be applied to other refrigeration cycle devices, such as a water supply device in which multiple heat exchangers can be switched between condensers and evaporators.

[0065] 1 Air conditioning apparatus, 100 Outdoor unit, 110 Compressor, 120 Cooling / heating flow path switching device, 120a, 120b Four-way valve, 130, 130a, 130b Outdoor heat exchanger, 140, 140a, 140b Outdoor expansion valve, 150 Check valve, 151 Opening / closing control valve, 160 Accumulator, 170 Outdoor shut-off valve, 180 Branch pipe, 190 Outdoor fan, 200 Heat exchanger switching flow path, 210 Heat exchanger switching piping, 220 Heat exchanger switching valve, 300 Bypass flow path, 310 Bypass piping, 320 Bypass control valve, 400 Indoor unit, 410 Indoor expansion valve, 420 Indoor heat exchanger, 430 Indoor fan, 500 Main pipe, 600 Control device, 610 Control unit, 611 Calculation unit, 612 Determination unit, 613 equipment control unit, 620 storage unit, 710 high-pressure sensor, 720 refrigerant temperature sensor, 730 outside air temperature sensor.

Claims

1. An outdoor unit of an air conditioner having a refrigerant circuit in which refrigerant circulates through a flow path configured by connecting to an indoor unit, the outdoor unit including a compressor that compresses and discharges the refrigerant, a plurality of outdoor heat exchangers that perform heat exchange with air outside the air conditioning target space, and a refrigerant flow path switching device that switches between a flow path through which the refrigerant passes through the plurality of outdoor heat exchangers in parallel and a flow path through which the refrigerant passes through the plurality of outdoor heat exchangers in series. During defrost operation, the refrigerant flow path switching device switches the flow path so that the refrigerant discharged from the compressor passes through the plurality of outdoor heat exchangers in parallel.

2. The outdoor unit according to claim 1, further comprising a heat exchange switching pipe that connects the outdoor heat exchangers in series, and a bypass pipe that allows the refrigerant discharged from the compressor to pass through a part of the plurality of outdoor heat exchangers. The refrigerant flow path switching device includes a four-way valve that switches between flowing the refrigerant discharged from the compressor to the outdoor heat exchanger side or to the indoor unit side, a heat exchange switching valve that controls the passage of the refrigerant in the heat exchange switching pipe, and a bypass control valve that controls the passage of the refrigerant in the bypass pipe.

3. The outdoor unit according to claim 2, wherein during defrost operation, the four-way valve is switched to flow to the outdoor heat exchanger side, and the heat exchange switching valve and the bypass control valve are opened.

4. The outdoor unit according to claim 1, further comprising a heat exchange switching pipe that connects the outdoor heat exchangers in series. The refrigerant flow path switching device includes a four-way valve that switches between flowing the refrigerant discharged from the compressor to the outdoor heat exchanger side or to the indoor unit side, a heat exchange switching valve that controls the passage of the refrigerant in the heat exchange switching pipe, and an opening / closing control valve that controls the passage of the refrigerant discharged from the compressor through a part of the plurality of outdoor heat exchangers.

5. The outdoor unit according to claim 4, wherein during defrost operation, the four-way valve is switched to flow to the outdoor heat exchanger side, the opening / closing control valve is opened, and the heat exchange switching valve is closed.

6. The outdoor unit according to any one of claims 1 to 5, wherein the refrigerant flow path switching device switches such that when the plurality of outdoor heat exchangers are evaporators, the flow path is a path through which the refrigerant passes through the plurality of outdoor heat exchangers in parallel, and when the plurality of outdoor heat exchangers are condensers, the flow path is a path through which the refrigerant passes through the plurality of outdoor heat exchangers in series.

7. A high-pressure pressure sensor for detecting the high-pressure of the refrigerant discharged by the compressor, and a control device, wherein the control device includes an arithmetic unit for calculating the saturation temperature of the refrigerant passing through the outdoor heat exchanger based on the high-pressure, and a determination unit for comparing the saturation temperature with a set operation end determination threshold value to determine the end of the defrosting operation. The outdoor unit according to any one of claims 1 to 6.

8. A refrigerant temperature sensor for detecting the refrigerant temperature of the refrigerant condensed by a plurality of the outdoor heat exchangers, and a control device, wherein the control device includes a determination unit for comparing the refrigerant temperature with a set operation end determination threshold value to determine the end of the defrosting operation. The outdoor unit according to any one of claims 1 to 6.

9. An outdoor unit according to claim 7 or claim 8, further comprising an outdoor air temperature sensor for detecting the outdoor air temperature, wherein the determination unit of the control device changes the operation end determination threshold value based on the outdoor air temperature.

10. A refrigeration cycle device comprising the outdoor unit according to any one of claims 1 to 9, and an indoor unit that receives heat supply from the outdoor unit and heats or cools an object.

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