AIR CONDITIONER

Abstract

An air conditioning unit comprises a flow circuit in which a compressor, a flow switch, an indoor heat exchanger, a pressure reducer, and a first and second outdoor heat exchanger connected in parallel are linked by pipes through which refrigerant flows; a bypass circuit with a bypass line connecting an outlet side of the compressor to a point between the flow switch and the first outdoor heat exchanger and to a point between the flow switch and the second outdoor heat exchanger, allowing a portion of the refrigerant discharged by the compressor to be diverted into and flow through the bypass line; a flow control arrangement provided on the bypass line and configured to adjust the flow rate of the refrigerant flowing through the bypass line; and a controller configured tothat it controls the flow switching arrangement, the pressure reducer, and the flow control arrangement. The air conditioning unit is configured to operate in a normal heating mode, in which the first and second outdoor heat exchangers act as evaporators, and in a heating-defrosting mode, in which either the first or the second outdoor heat exchanger is the target to be defrosted, and the other outdoor heat exchanger acts as an evaporator. The controller is configured to compare, during the heating-defrosting mode, a first condensing temperature obtained when the target to be defrosted is switched from one to the other with a second condensing temperature obtained when the operating mode is switched from the normal heating mode to the heating-defrosting mode, and then,If the first condensing temperature is lower than the second condensing temperature, the opening degree of the flow control arrangement is reduced; if the first condensing temperature is lower than the second condensing temperature, the opening degree of the flow control arrangement is lower than the initial opening degree set when switching from normal heating mode to heating / defrosting mode; and if the first condensing temperature is higher than the second condensing temperature, the opening degree of the flow control arrangement is increased by more than the initial opening degree.

Description

TECHNICAL FIELD

[0001] The present invention relates to an air conditioning apparatus having a function for removing frost deposited on an outdoor heat exchanger. STATE OF THE ART

[0002] In recent years, from the perspective of global environmental protection, more and more cases have emerged of heat pump air conditioning units, which use air as a heat source, being used in cold climates instead of boilers that heat by burning fossil fuels. Such a heat pump air conditioning unit is configured to heat more efficiently because heat is supplied from the air in addition to the electrical power supplied to a compressor.

[0003] However, with heat pump air conditioners, the lower the outdoor temperature, the more likely frost / ice is to form on an outdoor heat exchanger, which acts as an evaporator and exchanges heat between the outside air and the refrigerant. Therefore, defrosting is necessary to melt the frost that has accumulated on the outdoor heat exchanger. Examples of defrosting methods include reversing the refrigerant flow direction during a heating cycle to direct the refrigerant from the compressor to the outdoor heat exchanger. However, this method poses the problem that heating to a room may be interrupted during defrosting, reducing indoor comfort.

[0004] To solve this problem, Patent Document 1 describes an air conditioning device in which the outdoor heat exchanger is divided into multiple outdoor heat exchangers and configured to operate in a heating / defrosting mode. The heating / defrosting mode is an operation mode in which, while one of the outdoor heat exchangers is defrosted by flowing a portion of the refrigerant discharged from the compressor into the outdoor heat exchanger, the other outdoor heat exchangers operate as evaporators. The outdoor heat exchangers are alternately defrosted in the heating / defrosting mode, thereby achieving continuous heating without using the same refrigerant cycle flow as in the cooling mode.

[0005] Furthermore, in the air conditioning device according to Patent Document 1, when one of the outdoor heat exchangers is defrosted, a flow control device provided on a bypass line is adjusted based on the evaporation pressures of the other outdoor heat exchangers operating as evaporators and the drive frequency of the compressor. When switching the operation mode to the heating / defrosting operation mode, the opening degree of the flow control device is adjusted so that refrigerant flows into the outdoor heat exchanger to be defrosted in accordance with an increase in the refrigerant flow rate. In this way, the air conditioning device according to Patent Document 1 attempts to maintain the flow rate of the refrigerant supplied to the indoor heat exchanger and prevent a reduction in heating capacity.

[0006] Patent Document 1: International Publication WO 2020 / 194 435 SUMMARY OF THE INVENTION Problems to be solved by the invention

[0007] Patent Document 1 describes cases where the flow rate of the refrigerant becomes smaller than expected, thereby reducing the heating capacity, lowering the outlet temperature of the indoor unit and affecting the comfort in the room.

[0008] The present invention has been made to overcome the above-mentioned problem and has an object to provide an air conditioning apparatus capable of preventing the temperature of the air blown into a room in the heating / defrosting operation mode from changing from that in the heating operation mode performed before the operation mode is switched to the heating / defrosting operation mode, and thus capable of improving the comfort in the room. Means to solve the problems

[0009] An air conditioning device according to an embodiment of the present invention includes a flow circuit in which a compressor, a flow switching device, an indoor heat exchanger, a pressure reducer, and a first outdoor heat exchanger and a second outdoor heat exchanger, which are connected in parallel to each other, are connected by pipes through which refrigerant flows; a bypass circuit having a bypass pipe connecting an outlet side of the compressor to a point between the flow switching device and the first outdoor heat exchanger and to a point between the flow switching device and the second outdoor heat exchanger, and allowing a portion of the refrigerant discharged from the compressor to be diverted into the bypass pipe and flow through the bypass pipe; a flow control assembly provided on the bypass pipe and configured to adjust a flow rate of the refrigerant flowing through the bypass pipe;and a controller configured to control the flow switching assembly, the pressure reducer, and the flow control assembly. The air conditioning unit is configured to operate in a normal heating mode in which the first outdoor heat exchanger and the second outdoor heat exchanger operate as evaporators, and in a heating-defrost mode in which either the first outdoor heat exchanger or the second outdoor heat exchanger is defrosted as the defrosting target and the other outdoor heat exchanger operates as an evaporator. The controller is configured to compare, during the heating-defrost mode, a first condensing temperature obtained when the defrosting target is switched from one to the other with a second condensing temperature obtained when the operating mode is switched from the normal heating mode to the heating-defrost mode, and toIf the first condensing temperature is lower than the second condensing temperature, reduce the opening degree of the flow control arrangement; if the first condensing temperature is lower than the second condensing temperature, make the opening degree of the flow control arrangement smaller than an initial opening degree that is set when the normal heating operation mode is switched to the heating-defrosting operation mode; and if the first condensing temperature is higher than the second condensing temperature, increase or make the opening degree of the flow control arrangement larger than the initial opening degree. Advantageous effects of the invention

[0010] The controller of the air conditioning device according to an embodiment of the present invention is configured to, when the condensation temperature of the indoor heat exchanger becomes lower than the condensation temperature obtained when the heating operation mode is switched to the heating-defrost operation mode, make the opening degree of the flow control device smaller than the initial opening degree to increase the flow rate of the refrigerant to be supplied to the indoor heat exchanger. With this configuration, the air conditioning device according to an embodiment of the present invention is configured to prevent the temperature of the air blown into a room in the heating-defrost operation mode from changing from that in the heating operation mode performed before the operation mode is switched to the heating-defrost operation mode, thus improving the comfort in the room. SHORT DESCRIPTIONS OF THE DRAWINGS Fig. 1 is a flow circuit showing an air conditioning apparatus according to Embodiment 1; Fig. 2 is a functional block diagram illustrating the air conditioning apparatus according to Embodiment 1; Fig. 3 is a hardware configuration diagram showing an example of the configuration of a controller; Fig. 4 is a hardware configuration diagram showing another example of the controller configuration; Fig. 5 is a flow circuit illustrating the refrigerant flow in a cooling operation mode according to Embodiment 1; Fig. 6 is a pressure-enthalpy (ph) diagram in the cooling operation mode according to Embodiment 1; Fig. 7 is a flow circuit illustrating the flow of refrigerant in the heating operation mode according to Embodiment 1; Fig. 8 is a pH diagram for the heating operation mode according to Embodiment 1; Fig. 9 is a flow circuit illustrating the flow of refrigerant in a heating / defrosting operation according to Embodiment 1; Fig. 10 is a pH diagram in the heating-defrosting operation mode according to Embodiment 1; Fig. 11 is a diagram explaining a heating-defrosting operation mode according to Embodiment 1, and Fig. 12 is a flowchart illustrating the operation of a controller 90 according to Embodiment 1. PREFERRED EMBODIMENTS OF THE INVENTION Embodiment 1

[0011] An embodiment of an air conditioning apparatus 100 according to the present invention will be described below with reference to the drawings. Fig. 1 is a flow circuit illustrating the air conditioning device 100 according to Embodiment 1. The air conditioning device 100 is a device configured to condition air in an indoor space and includes an outdoor unit 1, an indoor unit 3, and a controller 90, as shown in Fig. 1 shown.

[0012] The outdoor unit 1 is a device installed, for example, outdoors and configured to supply heating energy or cooling energy to the indoor unit 3. The outdoor unit 1 includes a compressor 11, a flow switching device 12, a pressure reducer 13, a first outdoor heat exchanger 14a, a second outdoor heat exchanger 14b, a first opening and closing device 15a, a second opening and closing device 15b, a first additional pressure reducer 16a, a second additional pressure reducer 16b, and an outdoor fan 17. The outdoor unit 1 further includes a flow control assembly 21, a first bypass opening and closing device 22a, and a second bypass opening and closing device 22b. In addition, the outdoor unit 1 includes a first outdoor pressure sensor 92a, a second outdoor pressure sensor 92b, and an outdoor temperature sensor 93. Each of the devices in the outdoor unit 1 will be described later.

[0013] The outdoor unit 1 includes an outdoor unit piping 41, an outdoor unit piping 42, an outdoor unit piping 43, an outlet piping 44, a suction piping 45, parallel piping 70, and a bypass piping 81. The outdoor unit piping 41 connects the flow switching device 12 and an extension piping 51, which will be described later. The outdoor unit piping 42 connects the flow switching device 12 to the first opening and closing device 15a and the second opening and closing device 15b. The outdoor unit piping 42 is branched at its end where the first opening and closing device 15a and the second opening and closing device 15b are arranged, and branch pipings are connected to the first opening and closing device 15a and the second opening and closing device 15b, respectively.The outdoor unit line 43 connects the first additional pressure reducer 16a and the second additional pressure reducer 16b with an extension line 52 to be described later, the outdoor unit line 43 being branched at its end where the first additional pressure reducer 16a and the second additional pressure reducer 16b are arranged, and respective branch lines are connected to the first additional pressure reducer 16a and the second additional pressure reducer 16b.

[0014] The outlet line 44 connects the pressure side of the compressor 11 and the flow switching device 12. The suction line 45 connects the suction side of the compressor 11 and the flow switching device 12.

[0015] The parallel lines 70 include a first compressor-side line 71a, a second compressor-side line 71b, a first pressure reducer-side line 72a, and a second pressure reducer-side line 72b. The first compressor-side line 71a and the second compressor-side line 71b are provided closer to the compressor 11 and the flow switching device 12 than the first pressure reducer-side line 72a and the second pressure reducer-side line 72b, which are provided closer to the pressure reducer 13 than the first compressor-side line 71a and the second compressor-side line 71b. The first compressor-side line 71a connects the first opening and closing device 15a and the first outdoor heat exchanger 14a. The second compressor-side line 71b connects the second opening and closing device 15b and the second outdoor heat exchanger 14b.The first compressor-side line 72a connects the first outdoor heat exchanger 14a and the first additional pressure reducer 16a. The second pressure reducer-side line 72b connects the second outdoor heat exchanger 14b and the second additional pressure reducer 16b. That is, one set of the first compressor-side line 71a and the first pressure reducer-side line 72a and one set of the second compressor-side line 71b and the second pressure reducer-side line 72b are connected in parallel to each other and connected to the outdoor unit line 42 and the outdoor unit line 43.

[0016] The bypass line 81 branches off from a point on the discharge line 44 and connects to the first compressor-side line 71a and the second compressor-side line 71b, bypassing the flow switching device 12. The bypass line 81 branches off at its end where the first compressor-side line 71a and the second compressor-side line 71b are located, and connects to the first compressor-side line 71a and the second compressor-side line 71b, respectively. That is, the bypass line 81 connects the discharge side of the compressor 11 to a point between the flow switching device 12 and the first outdoor heat exchanger 14a, and to a point between the flow switching device 12 and the second outdoor heat exchanger 14b. Part of the refrigerant discharged from the compressor 11 is diverted to the bypass line 81 and flows through it.It should be noted that the bypass line 81 may be configured to connect the outdoor unit line 41 to the first compressor-side pipe 71a and the second compressor-side pipe 71b.

[0017] The indoor unit 3 is a device installed, for example, in a room and configured to condition the air in the room. The indoor unit 3 includes an indoor heat exchanger 31 and an indoor fan 32. The indoor unit 3 further includes an indoor pressure sensor 91 and an indoor temperature sensor 94. Each of the devices in the indoor unit 3 will be described later.

[0018] The indoor unit 3 includes an indoor unit piping 61 and an indoor unit piping 62. The indoor unit piping 61 connects the extension piping 51 and the indoor heat exchanger 31. The indoor unit piping 62 connects the indoor heat exchanger 31 and the extension piping 52.

[0019] The extension line 51 and the extension line 52 are provided outside the outdoor unit 1 and the indoor unit 3, and connect the outdoor unit 1 and the indoor unit 3. Although a case where a single outdoor unit 1 and a single indoor unit 3 are provided is described in Embodiment 1, it should be noted that two or more outdoor units 1 may be provided, and alternatively, two or more indoor units 3 may be provided.

[0020] The compressor 11 is configured to suck in refrigerant in a low-temperature and low-pressure state, compress the sucked refrigerant into a high-temperature and high-pressure state, and discharge the refrigerant. The flow switching device 12 is configured to switch the flow direction of the refrigerant in the flow circuit and is, for example, a four-way valve. The pressure reducer 13 is a pressure reducing valve or an expansion valve configured to reduce the pressure of the refrigerant and expand the refrigerant. The pressure reducer 13 is, for example, an electronic expansion valve whose opening degree is adjustable. Although a case where the pressure reducer 13 is provided in the outdoor unit 1 is described in Embodiment 1, the pressure reducer 13 may also be provided in the indoor unit 3.

[0021] The first outdoor heat exchanger 14a is provided between the first compressor-side line 71a and the first pressure-reducing line 72a. The second outdoor heat exchanger 14b is provided between the second compressor-side line 71b and the second pressure-reducing line 72b. That is, the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b are connected in parallel. The first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b exchange heat between the refrigerant and, for example, the outside air. The first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b are configured to operate as condensers in a cooling operation mode and as evaporators in a heating operation mode. Although a case where two outdoor heat exchangers are provided is described in Embodiment 1, three or more outdoor heat exchangers may be provided.

[0022] The first opening and closing device 15a is provided between the outdoor unit piping 42 and the first compressor-side piping 71a. While the first opening and closing device 15a is open, the refrigerant flows through the first outdoor heat exchanger 14a. While the first opening and closing device 15a is closed, the refrigerant does not flow between the outdoor unit piping 42 and the first compressor-side piping 71a. The second opening and closing device 15b is provided between the outdoor unit piping 42 and the second compressor-side piping 71b. The second opening and closing device 15b is provided between the outdoor unit piping 42 and the second compressor-side piping 71b. While the second opening and closing device 15b is open, the refrigerant flows through the second outdoor heat exchanger 14b.While the second opening and closing device 15b is closed, the refrigerant does not flow between the outdoor unit piping 42 and the second compressor-side piping 71b. It is only required that the first opening and closing device 15a and the second opening and closing device 15b be capable of opening and closing a flow passage. The first opening and closing device 15a and the second opening and closing device 15b are each a solenoid valve, a four-way valve, a three-way valve, a two-way valve, or a similar device.

[0023] The first additional pressure reducer 16a is provided between the first pressure reducer-side line 72a and the outdoor unit line 43. The second additional pressure reducer 16b is provided between the second pressure reducer-side line 72b and the outdoor unit line 43. The first additional pressure reducer 16a and the second additional pressure reducer 16b are, for example, electronic expansion valves whose opening degrees are adjustable or fixed resistors, such as capillary tubes.

[0024] The outdoor fan 17 is configured to supply outside air to the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b. In Embodiment 1, a case is described where a single outdoor fan 17 supplies outside air to both the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b. However, two outdoor fans 17 may be arranged to supply outside air to each of the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b.

[0025] The indoor heat exchanger 31 exchanges heat between the refrigerant and, for example, the indoor air. The indoor heat exchanger 31 is configured to operate as an evaporator in cooling mode and as a condenser in heating mode. The indoor fan 32 is configured to send indoor air to the indoor heat exchanger 31.

[0026] The compressor 11, the flow switching device 12, the pressure reducer 13, the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b, the first opening and closing device 15a and the second opening and closing device 15b, the first additional pressure reducer 16a and the second additional pressure reducer 16b, and the indoor heat exchanger 31 are connected to each other by the outdoor unit piping 41 to 43, the outlet piping 44, the suction piping 45, the extension piping 51 and 52, the indoor unit piping 61 and 62, and the parallel piping 70 to form a main flow circuit 10 through which the refrigerant is circulated. The outdoor unit pipes 41 to 43, the discharge pipe 44, the suction pipe 45, the extension pipes 51 and 52, the indoor unit pipes 61 and 62, and the parallel pipes 70 correspond to the “pipes” of the present invention.

[0027] The flow control assembly 21 is provided on the bypass line 81 and configured to adjust the flow rate of the refrigerant flowing in the bypass line 81. The first bypass opening and closing device 22a is provided on a branched line among the branched lines of the bypass line 81, to which the first compressor-side line 71a is connected. While the first opening and closing device 22a is open, the refrigerant that has passed through the bypass line 81 flows through the first outdoor heat exchanger 14a. While the first bypass opening and closing device 22a is closed, the refrigerant that has passed through the bypass line 81 does not flow through the first outdoor heat exchanger 14a. The second bypass opening and closing device 22b is provided on the other branched line among the branched lines of the bypass line 81 to which the second compressor-side line 71b is connected.While the second bypass opening and closing device 22b is open, the refrigerant that has passed through the bypass line 81 flows through the second outdoor heat exchanger 14b. While the second bypass opening and closing device 22b is closed, the refrigerant that has passed through the bypass line 81 does not flow through the second outdoor heat exchanger 14b. It is only required that the first bypass opening and closing device 22a and the second bypass opening and closing device 22b each be capable of opening and closing a flow passage. The first bypass opening and closing device 22a and the second bypass opening and closing device 22b are each a solenoid valve, a four-way valve, a three-way valve, a two-way valve, or a similar device.

[0028] The flow control assembly 21, the first bypass opening and closing device 22a and the second bypass opening and closing device 22b are connected by the bypass line 81 to form a bypass circuit 20 through which the refrigerant flows.

[0029] The first external pressure sensor 92a is provided on the first pressure-reducing-side line 72a and between the first outdoor heat exchanger 14a and the pressure-reducing valve 13, and is configured to detect the pressure of the refrigerant flowing in the first pressure-reducing-side line 72a. The second external pressure sensor 92b is provided on the second pressure-reducing-side line 72b and between the second outdoor heat exchanger 14b and the pressure-reducing valve 13, and is configured to detect the pressure of the refrigerant flowing in the second pressure-reducing-side line 72b.

[0030] When the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b operate as a condenser, the first outdoor pressure sensor 92a serves as a sensor that detects the condensing pressure of the first outdoor heat exchanger 14a, and the second outdoor pressure sensor 92b serves as a sensor that detects the condensing pressure of the second outdoor heat exchanger 14b. When the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b operate as an evaporator, the first outdoor pressure sensor 92a serves as a sensor that detects the evaporating pressure of the first outdoor heat exchanger 14a, and the second outdoor pressure sensor 92b serves as a sensor that detects the evaporating pressure of the second outdoor heat exchanger 14b.

[0031] Furthermore, in a region where the refrigerant is in a two-phase gas-liquid state, temperature sensors configured to detect the temperature of the refrigerant may be used instead of the first external pressure sensor 92a and the second external pressure sensor 92b. In this case, the values ​​detected by the temperature sensors are each converted into a pressure of the refrigerant as a saturation temperature by the controller 90. The temperature of the refrigerant may be detected directly by having the temperature sensor in contact with the refrigerant, or indirectly by detecting the temperature of an outer surface of a pipe or heat exchanger.

[0032] The outdoor temperature sensor 93 is provided near the first outdoor heat exchanger 14a and is configured to detect the outside air temperature. Specifically, the outdoor temperature sensor 93 is installed near a location from which outside air flows into the first outdoor heat exchanger 14a and a short distance from the first outdoor heat exchanger 14a. Note that the outdoor temperature sensor 93 may be provided near the second outdoor heat exchanger 14b.

[0033] The internal pressure sensor 91 is provided on the indoor heat exchanger 31 and is configured to detect the pressure of the refrigerant flowing in the indoor heat exchanger 31. When the indoor heat exchanger 31 functions as a condenser, the internal pressure sensor 91 serves as a sensor that detects the condensing pressure of the indoor heat exchanger 31. When the indoor heat exchanger 31 functions as an evaporator, the internal pressure sensor 91 serves as a sensor that detects the evaporating pressure of the indoor heat exchanger 31. The internal pressure sensor 91 may be provided on the outlet side of the compressor 11 and detect a discharge pressure. Furthermore, at a region where the refrigerant is in a two-phase gas-liquid state, a temperature sensor configured to detect the condensing temperature of the refrigerant in the indoor heat exchanger 31 may be used instead of the internal pressure sensor 91.

[0034] The indoor temperature sensor 94 is provided near the indoor heat exchanger 31 and is configured to detect the temperature of the indoor air. Specifically, the indoor temperature sensor 94 is installed at an indoor air inlet of the indoor unit 3, which is located a short distance from the indoor heat exchanger 31.

[0035] The refrigerant circulating through the refrigerant circuit can be, for example, a chlorofluorocarbon refrigerant or a hydrofluorocarbon (HFO) refrigerant. Examples of chlorofluorocarbon refrigerants include hydrofluorocarbon (HFC)-based refrigerants such as R32, R125, and R134a, and refrigerant blends of HFC-based refrigerants such as R410A, R407c, and R404A. Examples of HFO refrigerants are HFOa234yf, HFOa234ze(E), and HFOa234ze(Z). Other refrigerants that can be used include a carbon dioxide (CO2) refrigerant, a hydrocarbon (HC) refrigerant, an ammonia refrigerant, and refrigerants for vapor-compression heat pump flow circuits, including refrigerant blends of the refrigerants described above, such as a refrigerant blend of R32 and HFOa234yf. Examples of HC refrigerants are propane and isobutane.

[0036] Fig. 2 is a functional block diagram showing the air conditioning apparatus 100 according to Embodiment 1. As in Fig. 2, the controller 90 is configured to execute each operation mode of the indoor unit 3 and change a set room temperature by controlling the compressor 11, the flow switching device 12, the pressure reducer 13, the first opening and closing device 15a and the second opening and closing device 15b, the first additional pressure reducer 16a and the second additional pressure reducer 16b, the outdoor fan 17, the flow control assembly 21, the first bypass opening and closing device 22a and the second bypass opening and closing device 22b, and the indoor fan 32 based on detection results of the indoor pressure sensor 91, the first outdoor pressure sensor 92a, the second outdoor pressure sensor 92b, the outdoor temperature sensor 93, and the indoor temperature sensor 94.

[0037] An example of hardware for the controller 90 is now described. Fig. 3 is a hardware configuration diagram illustrating an example of the configuration of the controller 90. When each function of the controller 14 is achieved by hardware, the controller 90 is as shown in Fig. 3, is formed as a processing circuit 101 and each function is achieved by the processing circuit 101.

[0038] When each function is achieved by hardware, the processing circuit 101 corresponds, for example, to a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination of these circuits.

[0039] Now another example of hardware for the controller 90 will be described. Fig. 4 is a hardware configuration diagram illustrating another example of the configuration of the controller 90. When each function of the controller 14 is achieved by software, the controller 90 is configured with a processor 102, such as a central processing unit (CPU), and a memory 103, as shown in Fig. 4. Each function of the controller is achieved by a central processing unit (CPU) and a memory 103. FIG. 4 shows that the processor 102 and the memory 103 are connected via a bus 104, so that the processor 102 and the memory 103 are configured to communicate with each other.

[0040] Each function of the controller 90 is achieved through software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in memory 103. The processor 102 is configured to read and execute the program stored in memory 103 to thereby achieve each function.

[0041] A non-volatile semiconductor memory such as a read-only memory (ROM), a flash memory, an erasable programmable ROM (EPROM), and an electrically erasable programmable ROM (EEPROM) is used as the memory 103. A volatile semiconductor memory such as a random access memory (RAM) can be used as the memory 103; in addition, a removable recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disc (CD), a mini disc (MD), and a digital versatile disc (DVD) can be used as the memory 103.

[0042] The air conditioning unit 100 is configured to operate in a cooling mode, a normal heating mode, a reverse cycle defrost mode, and a heating and defrost mode. In the cooling mode, the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b each function as a condenser, and the indoor unit 3 cools the interior of the room. In the normal heating mode, the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b each function as an evaporator, and the indoor unit 3 heats the interior of the room.

[0043] In the reverse cycle defrost mode, the refrigerant flows through the main flow circuit 10 in the same direction as in the cooling mode, thus defrosting the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b. The controller 90 is configured to switch the operating mode from the normal heating mode to the reverse cycle defrost mode when a reverse cycle defrost shift condition is met. The reverse cycle defrost shift condition may be, for example, that the operating time exceeds a predetermined maximum possible time threshold for the normal heating mode during the normal heating mode. Furthermore, the reverse cycle defrost shift condition may be that the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b are frosted.It should be noted that the determination of whether an outdoor heat exchanger is frosted or not is performed by a known method, such as a method using a detection result of each sensor. The controller 90 is configured to switch the operation mode from the reverse defrost operation mode to the normal heating operation mode when a reverse defrost end condition is met. The reverse defrost end condition is, for example, that the operation is performed in the reverse defrost operation mode for a predetermined period of time.

[0044] In the heating / defrosting mode, either the first outdoor heat exchanger 14a or the second outdoor heat exchanger 14b is selected as the defrosting target, and the other of the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b functions as an evaporator, thus maintaining both the defrosting of the outdoor heat exchanger and the heating mode. In the heating / defrosting mode, the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b are defrosted alternately. For example, in the heating / defrosting mode, the first outdoor heat exchanger 14a functions as an evaporator to perform the heating mode, while the second outdoor heat exchanger 14b is defrosted. Then, in the heating / defrosting operation mode, after the defrosting of the second outdoor heat exchanger 14b is completed, the second outdoor heat exchanger 14b operates as an evaporator to perform the heating operation mode, and the first outdoor heat exchanger 14a is defrosted.The controller 90 is configured to switch the operation mode from the normal heating operation mode to the heating-defrost operation mode when a heating-defrost switching condition is met. The heating-defrost switching condition is, for example, that the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b are defrosted during the normal heating operation mode. Furthermore, the heating-defrost shift condition may be that the drive frequency of the compressor 11 drops below a frequency threshold as the indoor air temperature approaches the set room temperature, or that a continuous operation time in the normal heating operation mode reaches a predetermined maximum possible time.

[0045] The controller 90 is configured to switch one outdoor heat exchanger to be defrosted to the other upon fulfillment of a switching condition. The switching condition may be, for example, that defrosting of the outdoor heat exchanger to be defrosted is complete or a predetermined period of time has elapsed. Furthermore, the controller 90 is configured to switch the operating mode from the heating-defrost operating mode to the normal heating operating mode upon fulfillment of a heating-defrost end condition. The heating-defrost end condition may be that the temperature of the refrigerant flowing in the first outdoor heat exchanger 14a and the temperature of the refrigerant flowing in the second outdoor heat exchanger 14b reach a predetermined temperature or higher within a predetermined maximum possible period of time.In this case, the controller 90 extends a maximum possible operating time for normal heating operation after the operation mode returns from the heating-defrost operation mode. Specifically, the controller 90 is configured to extend the maximum possible operating time for the normal heating operation mode before switching the operation mode to the reverse-cycle defrost operation mode or the heating-defrost operation mode. In this case, the controller 90 may switch the operation mode to the reverse-cycle defrost operation mode after switching the operation mode from the heating-defrost operation mode to the heating operation mode. The refrigerant flow in each operation mode is described below. (Cooling operating mode)

[0046] Fig. 5 is a flow circuit illustrating the flow of refrigerant in a cooling operation mode according to Embodiment 1. Fig. 6 is a pH diagram in the cooling mode according to Embodiment 1. In Fig. 5, solid lines represent areas where the refrigerant flows, and dashed lines represent areas where the refrigerant does not flow. In the cooling operation mode, the controller 90 switches the flow switching device 12 so that the pressure side of the compressor 11 is connected to the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b, and the suction side of the compressor 11 is connected to the indoor heat exchanger 31. In addition, the controller 90 completely closes the flow control assembly 21 and completely opens the first opening and closing device 15a and the second opening and closing device 15b, as well as the first additional pressure reducer 16a and the second additional pressure reducer 16b. As shown in Fig. As shown in Figure 5, the refrigerant sucked into the compressor 11 is compressed by the compressor 11 in the cooling mode and then discharged in a high-temperature and high-pressure gas state. During the compression of the refrigerant in the compressor 11, the refrigerant is compressed to be heated by an amount corresponding to the adiabatic efficiency of the compressor 11 compared to an adiabatic compression along an isentropic line. The change in the refrigerant at this time corresponds to a line range extending from point (a) to point (b) in Fig. 6 extends.

[0047] The refrigerant discharged from the compressor 11 in a high-temperature and high-pressure gas state passes through the flow switching device 12 and is then split into two streams, which flow into the respective first compressor-side conduit 71a and second compressor-side conduit 71b. The split refrigerant streams pass through the respective first opening and closing devices 15a and second opening and closing devices 15b and then flow into the respective first outdoor heat exchanger 14a and second outdoor heat exchanger 14b, each of which functions as a condenser. In the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b, the refrigerant exchanges heat with the outside air supplied from the outdoor fan 17, condenses, and liquefies, thereby bringing the refrigerant into a liquid state of medium temperature and high pressure.Taking a pressure loss into account, the change of the refrigerant in the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b is represented by a nearly horizontal straight line with a slight inclination, as defined by the line region extending from point (b) to point (c) in . Fig. 6. The flows of the refrigerant, which has condensed in the liquid state of medium temperature and high pressure, combine and then flow into the pressure reducer 13. In the pressure reducer 13, the refrigerant is expanded and pressure-reduced, thus converting it into a two-phase gas-liquid state of low temperature and low pressure, wherein the refrigerant in the pressure reducer 13 changes with constant enthalpy, wherein the change of the refrigerant at this time corresponds to a vertical line area extending from point (c) to point (d) in Fig. 6 extends.

[0048] In the indoor heat exchanger 31, heat exchange takes place between the refrigerant and the room air supplied by the indoor fan 32, whereby the refrigerant evaporates and vaporizes. At this time, the room air is cooled and the room is cooled. When a pressure loss is taken into account, the change in the refrigerant in the indoor heat exchanger 31 is represented by a nearly horizontal straight line with a slight inclination, as shown by the line area extending from point (d) to point (a) in Fig. 6. The refrigerant, which has evaporated in a gas state of low temperature and low pressure, passes through the extension line 51 and the flow switching device 12 and is then sucked into the compressor 11. (Normal heating mode)

[0049] Fig. 7 is a flow circuit illustrating the flow of refrigerant in a heating operation mode according to Embodiment 1. Fig. 8 is a pH diagram in heating mode according to Embodiment 1. In Fig. 7, solid lines represent areas where the refrigerant flows, and dashed lines represent areas where the refrigerant does not flow. In the heating mode, the controller 90 switches the flow switching device 12 so that the pressure side of the compressor 11 is connected to the indoor heat exchanger 31 and the suction side of the compressor 11 is connected to the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b. In addition, the controller 90 completely closes the flow control assembly 21 and completely opens the first opening and closing device 15a and the second opening and closing device 15b, as well as the first additional pressure reducer 16a and the second additional pressure reducer 16b. As shown in Fig. As shown in Figure 7, the refrigerant sucked into the compressor 11 is compressed by the compressor 11 in the heating mode and then discharged in a high-temperature and high-pressure gas state. During the compression of the refrigerant in the compressor 11, the refrigerant is compressed to be heated by an amount corresponding to the adiabatic efficiency of the compressor 11 compared to an adiabatic compression along an isentropic line. The change in the refrigerant at this time corresponds to the line area extending from point (a) to point (b) in Fig. 8 extends.

[0050] The refrigerant exiting the compressor 11 in the gaseous high-temperature and high-pressure state flows through the flow switching device 12 and the extension line 51 and then flows into the internal heat exchanger 31, which functions as a condenser. In the internal heat exchanger 31, a heat exchange takes place between the refrigerant and the room air, whereby the refrigerant condenses, liquefies, and is converted into a liquid state of medium temperature and high pressure, whereby the room air is heated and thus the room is heated. Taking into account a pressure loss, the change in the refrigerant in the internal heat exchanger 31 is represented by a nearly horizontal straight line with a slight inclination, as represented by a line area from point (b) to point (c) in Fig. 8. The refrigerant condensed in the liquid state at medium temperature and high pressure flows through the extension line 52 into the pressure reducer 13. In the pressure reducer 13, the refrigerant is expanded and pressure-reduced, thus bringing it into a two-phase gas-liquid state at medium pressure, whereby the refrigerant in the pressure reducer 13 changes with constant enthalpy. The change in the refrigerant at this time corresponds to the vertical line area extending from point (c) to point (d) in Fig. 8. It should be noted that the pressure reducer 13 is controlled so that the degree of cooling of the refrigerant in the liquid state at medium temperature and high pressure is between approximately 5 °K and 20 °K.

[0051] The refrigerant in the two-phase gas-liquid state is divided into two streams, each flowing into the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b, which each function as an evaporator. The refrigerant in the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b exchanges heat with the outside air and evaporates and gasifies in the process. Taking into account a pressure loss, the change of the refrigerant in the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b is represented by a nearly horizontal straight line with a slight inclination, as shown by the line region extending from point (d) to point (a) in Fig. 8. The flows of the refrigerant evaporated in the low-temperature and low-pressure gas state flow into the first compressor-side line 71a and the second compressor-side line 71b, respectively, pass through the first opening and closing device 15a and the second opening and closing device 15b, and merge there, whereby the refrigerant flows through the flow switching device 12 and is sucked into the compressor 11. (Reverse cycle defrosting mode)

[0052] Since the refrigerant flow in the reverse-circuit defrosting mode is the same as in the cooling mode, the illustration is omitted. However, the reverse-circuit defrosting mode differs from the cooling mode in that the refrigerant pressure in the pressure reducer 13 is not reduced and the indoor fan 32 is not operated. The refrigerant discharged from the compressor 11 in the high-temperature and high-pressure gas state passes through the flow switching device 12 and is then divided into two streams, which flow into the first compressor-side line 71a and the second compressor-side line 71b, respectively.The divided refrigerant flows pass through the respective first opening and closing device 15a and the second opening and closing device 15b, and then flow from the respective first compressor-side line 71a and the second compressor-side line 71b into the respective first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b. The refrigerant in the high-temperature and high-pressure gas state exchanges heat with the frost deposited on the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b, thereby melting the frost. (Heating-Defrosting operating mode)

[0053] Fig. 9 is a flow circuit illustrating the flow of refrigerant in a heating-defrosting operation mode according to Embodiment 1. Fig. 10 is a pH diagram in the heating-defrosting operation mode according to Embodiment 1. In Fig. 9, solid lines represent areas where the refrigerant flows, and dashed lines represent areas where the refrigerant does not flow. In the heating-defrosting operation mode, the controller 90 switches the flow switching device 12 so that the discharge side of the compressor 11 is connected to the indoor heat exchanger 31 and the suction side of the compressor 11 is connected to the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b. Furthermore, the controller 90 opens the flow control assembly 21. In the heating / defrosting operation mode, one of the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b is selected as the defrosting target and defrosted, and the other of the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b operates as an evaporator, thus continuing the heating operation mode.The controller 90 alternately switches between the open and closed states of the first opening and closing device 15a and the second opening and closing device 15b, and between the open and closed states of the first bypass opening and closing device 22a and the second bypass opening and closing device 22b. Thus, the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b are alternately selected as the defrosting target. The refrigerant flow is switched depending on the switching between the outdoor heat exchanger to be defrosted and the outdoor heat exchanger operating as an evaporator.

[0054] In Fig. 9 describes a case where the second outdoor heat exchanger 14b is selected as the defrosting target, and the first outdoor heat exchanger 14a operates as an evaporator, thus continuing the heating operation mode. In this case, the controller 90 fully opens the first opening and closing device 15a and fully closes the second opening and closing device 15b. The controller 90 fully closes the first bypass opening and closing device 22a and fully opens the second bypass opening and closing device 22b. In addition, the controller 90 controls the opening degree of the second auxiliary pressure reducing valve 16b connected to the second outdoor heat exchanger 14b so that a saturation temperature converted from the pressure of the defrosting second outdoor heat exchanger 14b is in the range of approximately 0 degrees C to 10 degrees C.The controller 90 fully opens the first additional pressure reducer 16a, which is connected to the first outdoor heat exchanger 14a operating as an evaporator. First, the flow of the refrigerant in the main flow circuit 10 is described. As shown in . Fig. As shown in Figure 9, the refrigerant sucked into the compressor 11 is compressed by the compressor 11 in the defrost heating operation mode and then discharged in a high-temperature and high-pressure gas state. During the compression of the refrigerant in the compressor 11, the refrigerant is compressed so that it is heated by an amount corresponding to the adiabatic efficiency of the compressor 11 compared to an adiabatic compression along an isentropic line, the change in the refrigerant at this time corresponding to the line area extending from point (a) to point (b) in Fig. 10 extends.

[0055] A portion of the refrigerant exiting the compressor 11 in a high-temperature and high-pressure gas state passes through the flow switching device 12 and the extension line 51 and then flows into the internal heat exchanger 31, which functions as a condenser. In the internal heat exchanger 31, the refrigerant exchanges heat with the room air. In the internal heat exchanger 31, heat exchange takes place between the refrigerant and the room air, whereby the refrigerant condenses, liquefies, and is converted into a liquid state of medium temperature and high pressure, thereby heating the room air. Taking into account a pressure loss, the change in the refrigerant in the internal heat exchanger 31 is represented by an approximately horizontal straight line with a slight inclination, as shown in Fig. 10 is represented by the line area from point (b) to point (c). The refrigerant condensed in the liquid state at medium temperature and high pressure passes through the extension line 52 and then flows into the pressure reducer 13 and the first additional pressure reducer 16a. In the pressure reducer 13 and the first additional pressure reducer 16a, the refrigerant is expanded and pressure reduced, thus bringing it into a two-phase gas-liquid state of medium pressure. The refrigerant in the pressure reducer 13 changes under a constant enthalpy. The change in the refrigerant at this time corresponds to a vertical line area extending from point (c) to point (d) in Fig. 10 extends.

[0056] The refrigerant in the two-phase gas-liquid state does not flow through the second outdoor heat exchanger 14b, which is defrosted, but flows into the first outdoor heat exchanger 14a, which functions as an evaporator. In the first outdoor heat exchanger 14a, the refrigerant exchanges heat with the outside air and evaporates and gasifies in the process. When a pressure loss is taken into account, the change in the refrigerant in the first outdoor heat exchanger 14a is represented by a nearly horizontal straight line with a slight inclination, as shown by the line area extending from point (d) to point (a) in Fig. 10. The refrigerant evaporated in a low-temperature and low-pressure gas state flows into the first compressor-side line 71a, passes through the first opening and closing device 15a and then the flow switching device 12, and is then sucked into the compressor 11.

[0057] Next, the flow of refrigerant in the flow circuit 20 will be described. A portion of the refrigerant discharged from the compressor 11 in a high-temperature and high-pressure gas state flows through the bypass line 81 and flows into the flow control device 21. In the flow control device 21, the refrigerant is depressurized. The refrigerant in the flow control device 21 changes under a constant enthalpy. The refrigerant depressurized by the flow control device 21 passes through the second bypass opening and closing device 22b, flows through the second compressor-side line 71b, and then flows into the second outdoor heat exchanger 14b, which is defrosted. The refrigerant flowing in the second outdoor heat exchanger 14b exchanges heat with the frost adhering to the second outdoor heat exchanger 14b and is thereby cooled.As described above, the refrigerant discharged from the compressor 11 flows into the second outdoor heat exchanger 14b in a high-temperature and high-pressure gas state and melts the frost adhering to the second outdoor heat exchanger 14b. The refrigerant used to defrost the second outdoor heat exchanger 14b and flowing out of the second outdoor heat exchanger 14b passes through the second auxiliary pressure reducer 16b and then joins the refrigerant flowing in the main flow circuit 10. The combined refrigerant flows into the first outdoor heat exchanger 14a, which functions as an evaporator, and evaporates.

[0058] In a case where the first outdoor heat exchanger 14a is selected as the defrosting target and the second outdoor heat exchanger 14b operates as an evaporator and thus continues heating, the opening and closing states of the first opening and closing device 15a and the second opening and closing device 15b, the opening and closing states of the first bypass opening and closing device 22a and the second bypass opening and closing device 22b, and the opening and closing states of the first additional pressure reducer 16a and the second additional pressure reducer 16b are reversed from those in the above case. Therefore, a detailed description is omitted.

[0059] The following describes an operation of the controller 90 that controls the flow control device 21 in the heating-defrosting mode. First, when the normal heating mode is switched to the heating-defrosting mode, the controller 90 sets the opening degree of the flow control device 21 to an initial opening degree Pulse. ini so that the refrigerant corresponding to an increased flow rate flows through the first outdoor heat exchanger 14a or the second outdoor heat exchanger 14b selected as the defrosting target.

[0060] In particular, it is known that the higher the drive frequency of the compressor 11 and the density of the refrigerant, the higher the flow rate of the refrigerant, and that the density of the refrigerant is directly proportional to the evaporation pressure. Therefore, the more the evaporation pressure of the outdoor heat exchanger acting as an evaporator decreases and the less the drive frequency of the compressor 11 increases, the lower the flow rate of the refrigerant to be defrosted in the first outdoor heat exchanger 14a or the second outdoor heat exchanger 14b becomes when the operation mode is switched to the heating / defrosting operation mode. Therefore, the controller 90 sets the initial opening degree Pulse ini based on the evaporation pressure of the outdoor heat exchanger operating as an evaporator and the drive frequency of the compressor 11 when the normal heating operation mode is switched to the heating / defrosting operation mode. In particular, the initial opening degree Pulseini of the flow control device 21 is set to a smaller value as a decrease in the evaporation pressure of the outdoor heat exchanger functioning as an evaporator becomes greater and the increase in the drive frequency of the compressor 11 becomes smaller. Note that the first outdoor pressure sensor 92a or the second outdoor pressure sensor 92b, which detects the pressure of the refrigerant flowing in the first outdoor heat exchanger 14a or the second outdoor heat exchanger 14b functioning as an evaporator, serves as a sensor that detects the evaporation pressure.

[0061] When switching between the outdoor heat exchangers to be defrosted in the heating / defrosting operation mode, the controller 90 then refers to the condensing temperature of the indoor heat exchanger 31 and sets the opening degree of the flow control arrangement 21 to an opening degree which is determined by correcting the initial opening degree Pulse iniis obtained. The controller 90 calculates the condensing temperature of the indoor heat exchanger 31 by converting the condensing pressure of the indoor heat exchanger 31 detected by the indoor pressure sensor 91. Specifically, the controller 90 sets the opening degree of the flow control device 21 based on a high-low relationship between a first condensing temperature TC obtained when the defrosting target is switched from one to the other and a second condensing temperature TC heat which is obtained when switching from the normal heating mode to the heating-defrost mode. That is, when the first condensing temperature TC is greater than the second condensing temperature TC heat is, the controller 90 increases the opening degree of the flow control arrangement 21 above the initial opening degree Pulse ini . If the first condensing temperature TC is less than the second condensing temperature TCheat the controller 90 reduces the opening degree of the flow control arrangement 21 below the initial opening degree Pulse ini It is understood that the controller 90 adjusts the opening degree of the flow control assembly 21 to be no less than a predetermined lower opening degree limit. The lower opening degree limit represents the minimum possible opening degree at which all frost is removed and is determined by testing using an actual device. Pulse=Pulseini×(TC−TA) / (TCheat−TAheat)

[0062] Pulse is ini the newly adjusted opening degree of the flow control assembly 21. TA is the intake temperature of indoor unit 3 when the defrost target is switched to the heating / defrosting mode. TA heatis the suction temperature that results when switching from normal heating mode to heating / defrost mode. Note that the second condensing temperature TC heat and the intake temperature TA heat , which results when switching from the normal heating operation mode to the heating / defrost operation mode, are stored in the controller 90 at the time of switching.

[0063] Fig. 11 is a diagram for explaining the heating / defrosting operation mode according to Embodiment 1. In Fig. 11, the condensing temperature, the opening degree of the flow control device 21, the indoor suction temperature, and the opening degree of the pressure reducer 13 are shown in time series by four graphs each including a case of Embodiment 1 and a case of a comparative example. Fig. 11 illustrates a case where the first condensing temperature TC obtained when the defrosting target is switched from one to the other is lower than the second condensing temperature TC heat , which is obtained when the normal heating operation mode is switched to the heating-defrosting operation mode. The comparative example represents a case where the opening degree of the flow control device 21 is not corrected based on the condensing temperature of the indoor heat exchanger 31 in Embodiment 1 described above.

[0064] In the heating / defrosting mode, the refrigerant flow rate is sometimes reduced less than expected because the volumetric efficiency of the compressor 11 deteriorates due to an increase in the difference between high and low pressures in the refrigeration cycle. At this time, as the comparative example in Fig. 11 shows when the opening degree of the flow control arrangement 21 is at the initial opening degree Pulse ini is maintained, the condensing temperature must be reduced, which leads to a reduction in the heating capacity, whereby in the comparative example a reduction in the heating capacity leads to a reduction in the suction temperature in the interior in the heating / defrosting operating mode.

[0065] In contrast, in Embodiment 1, the opening degree of the flow control device 21 is corrected based on the condensing temperature of the indoor heat exchanger 31. Specifically, in Fig. 11, since the first condensing temperature TC obtained when the defrosting target is switched from one to the other becomes lower than the second condensing temperature TC heat which is obtained when the normal heating operation mode is switched to the heating-defrosting operation mode, the controller 90 the opening degree Pulse inithe flow control arrangement 21 to less than the initial opening degree Pulse ini This maintains the condensing temperature before the start of the heating / defrosting mode in Embodiment 1, thus preventing fluctuations in the heating capacity when switching from the normal heating mode. In Embodiment 1, preventing fluctuations in the heating capacity more effectively prevents a drop in the indoor suction temperature in the heating / defrosting mode compared to the comparative example.

[0066] Furthermore, in the heating / defrosting mode, when the opening degree of the flow control assembly 21 is reduced, the controller 90 increases the opening degree of the pressure reducer 13 as the outlet temperature rises. When the operating mode returns to the normal heating mode while the opening degree of the pressure reducer 13 is maintained large, the condensing temperature may be reduced because the difference between high and low pressures is not large enough. For this reason, the controller 90, as shown in Fig. 11, change the opening degree of the pressure reducer 13 to the opening degree of the pressure reducer 13 used just before switching the operation mode to the heating / defrosting operation mode when the operation mode returns to the normal heating operation mode, so that the difference between high and low pressures is secured and a reduction in the condensing pressure is prevented.

[0067] Since the flow control assembly 21 is controlled by the controller 90 in this way, fluctuation of the heating power in the heating operation mode is prevented even during the heating / defrosting operation mode or even when the flow rate of the refrigerant is reduced when the operation mode returns to the normal heating operation mode, thus maintaining the temperature of the air blown into the room.

[0068] When the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b are obtained from a single outdoor heat exchanger by dividing them into an upper outdoor heat exchanger and a lower outdoor heat exchanger, operation in the heating / defrosting mode is performed as follows. That is, the lower outdoor heat exchanger, i.e., the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b, is set as the first defrosting target, and then the upper outdoor heat exchanger is set as the defrosting target, so that all surfaces are defrosted, thereby preventing water resulting from defrosting the upper outdoor heat exchanger from combining with frost on the lower outdoor heat exchanger. Furthermore, the lower heat exchanger can be defrosted again after the upper heat exchanger is defrosted, so that the water that runs down the lower heat exchanger, which functions as an evaporator, due to defrosting the upper heat exchanger, does not freeze.A case where the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b are arranged independently of each other above and below, that is, a case where one of the first outdoor heat exchanger 14a and the second outdoor heat exchanger 14b is provided below the other outdoor heat exchanger, has the same effect as the case where the single outdoor heat exchanger is divided.

[0069] For this reason, the opening degree of the flow control assembly 21 when the lower outdoor heat exchanger is defrosted for the second time may be smaller than the opening degree of the flow control assembly 21 when the lower outdoor heat exchanger is defrosted for the first time, and may be smaller than the opening degree of the flow control assembly 21 when the upper outdoor heat exchanger is defrosted. Furthermore, the period during which the lower outdoor heat exchanger is defrosted for the second time may be shorter than the period during which the lower outdoor heat exchanger is defrosted for the first time, and may be shorter than the period during which the upper outdoor heat exchanger is defrosted.

[0070] Fig. 12 is a flowchart illustrating an operation of the controller 90 according to Embodiment 1. The operation of the controller 90 from switching the operation mode from the normal heating operation mode to the heating-defrosting operation mode to returning the operation mode to the normal heating operation mode will be described with reference to Fig.12. The control of the first bypass opening and closing device 22a and the second bypass opening and closing device 22b is not described in the following procedure. First, the controller 90 determines whether or not the condition for switching to the heating / defrosting operation mode is met during execution in the normal heating operation mode (step S1). If it is determined that the condition for switching to the heating / defrosting operation mode is not met (NO in step S1), the controller 90 maintains the normal heating operation mode until the condition for switching to the heating / defrosting operation mode is met, and periodically performs the processing of step S1 during this period. If the heating / defrosting switching condition is met (YES in step S1), the controller 90 obtains the second condensing temperature TC. heatof the indoor heat exchanger 31 (step S2) and controls each device to switch the operation mode to the heating / defrosting operation mode (step S3). At this time, the opening degree of the flow control device 21 is set to the initial opening degree Pulse ini set.

[0071] The controller 90 determines whether the heating defrost end condition is satisfied during execution in the heating defrost operation mode (step S4). If the heating defrost end condition is not satisfied (NO in step S4), the controller 90 determines whether the condition for switching the defrosting target is satisfied in the heating defrost operation mode (step S5). If the defrost target switching condition is not satisfied, the controller 90 continues operation in the heating / defrost operation mode in which one of the outdoor heat exchangers is defrosted until the defrost target switching condition is satisfied, and periodically performs the processing of step S5 during this period. If the defrost target switching condition is satisfied (YES in step S5), the first condensing temperature TC of the indoor heat exchanger 31 is obtained (step S6).

[0072] Then, the controller 90 determines whether the first condensing temperature TC of the indoor heat exchanger 31 is higher than the second condensing temperature TC heat or not (step S7). If the first condensing temperature TC of the indoor heat exchanger 31 is higher than the second condensing temperature TC heat (YES in step S7), the controller 90 increases the opening degree of the flow control arrangement 21 above the initial opening degree Pulse ini (step S8). If the first condensing temperature TC of the indoor heat exchanger 31 is lower than or equal to the second condensing temperature TC heat (NO in step S7), the controller 90 determines whether the first condensing temperature TC of the indoor heat exchanger 31 is lower than the condensing temperature TC heat or not (step S9). If the first condensing temperature TC of the indoor heat exchanger 31 is lower than the second condensing temperature TC heat(YES in step S9), the opening degree of the flow control device 21 is reduced to a smaller value than the initial opening degree Pulse ini (Step S10). Note that when the determination in Step S7 and Step S8 is NO, that is, when the first condensing temperature TC of the indoor heat exchanger 31 is equal to the second condensing temperature TC heat is, the degree of opening of the flow control arrangement 21 compared to the initial degree of opening Pulse ini is not changed. When the correction of the opening degree of the flow control device 21 is completed, the controller 90 controls each device to switch the defrosting target from one to the other (step S11), and then determines again whether the condition for terminating the heating / defrosting operation mode is met or not (step S4).

[0073] If the condition for ending the heating / defrosting operation is met (YES in step S4), the controller 90 controls each device to switch the operation mode to the normal heating operation mode (step S12). Note that the order of the processing described above is only an example. For example, the order between steps S2 and S3, the order between steps S8 and S11, and the order between steps S10 and S11 can be interchanged.

[0074] As described above, the controller 90 of Embodiment 1 is configured to reduce the opening degree of the flow control device 21 to a value smaller than the initial opening degree when, during the heating / defrosting operation mode, the condensing temperature becomes lower than the condensing temperature reached when switching from the heating operation mode to the heating / defrosting operation mode. Therefore, the air conditioning device 100 of Embodiment 1 is configured to prevent the temperature of the air blown into the room from changing in the heating / defrosting operation mode from that in the heating operation mode immediately before switching the operation mode to the heating / defrosting operation mode, and is thus configured to improve the comfort in the room.

[0075] Although the embodiment of the present invention is described above, the present invention is not limited to the configuration of the above-mentioned embodiment, and various modifications or combinations are possible within the scope of the technical spirit of the present invention. For example, the first additional pressure reducer 16a and the second additional pressure reducer 16b may be omitted from the air conditioning device 100. List of reference symbols 1 outdoor unit 3 Indoor unit 10 Main circuit 11 compressors 12 Flow switch device 13 pressure reducers 14a first outdoor heat exchanger 14b second outdoor heat exchanger 15a first opening and closing device 15b second opening and closing device 16a first additional pressure reducer 16b second additional pressure reducer 17 outdoor fans 20 Bypass circuit 21 Flow control arrangement 22a first bypass opening and closing device 22b second bypass opening and closing device 31 indoor heat exchangers 32 interior fans 41 Outdoor unit cable 42 Outdoor unit cable 43 Outdoor unit cable 44 Blow-out line 45 intake line 51 Extension cable 52 extension cable 61 Indoor unit cable 62 Indoor unit cable 70 parallel line 71a first compressor-side line 71b second compressor-side line 72a first pressure reducer-side line 72b second pressure reducer side line 81 Bypass line 90 Control 91 Internal pressure sensor 92a first external pressure sensor 92b second external pressure sensor 93 outside temperature sensor 94 indoor temperature sensors 100 air conditioning units 101 Processing circuit 102 processor 103 storage 104 buses QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2020 / 194 435

[0006]

Claims

[1] Air conditioning unit comprising: a flow circuit in which a compressor, a flow switching device, an indoor heat exchanger, a pressure reducer, and a first outdoor heat exchanger and a second outdoor heat exchanger connected in parallel are connected by pipes and through which refrigerant flows; a bypass circuit having a bypass line connecting a discharge side of the compressor to a point between the flow switching device and the first outdoor heat exchanger and to a point between the flow switching device and the second outdoor heat exchanger, and allowing a portion of the refrigerant discharged from the compressor to be diverted into the bypass line and flow through the bypass line; a flow control arrangement provided on the bypass line and configured to adjust a flow rate of the refrigerant flowing through the bypass line; and a controller configured to control the flow switching device, the pressure reducer and the flow control arrangement, wherein the air conditioning device is configured to operate in a normal heating operation mode in which the first outdoor heat exchanger and the second outdoor heat exchanger operate as evaporators, and in a heating-defrost operation mode in which one of the first outdoor heat exchanger and the second outdoor heat exchanger is defrosted as a target to be defrosted and another outdoor heat exchanger operates as an evaporator, the controller is configured to compare, during the heating-defrosting operating mode, a first condensing temperature obtained when the target to be defrosted is switched from one to the other with a second condensing temperature obtained when the operating mode is switched from the normal heating operating mode to the heating-defrosting operating mode, and when the first condensing temperature is lower than the second condensing temperature, reduce the opening degree of the flow control arrangement to a smaller value than an initial opening degree set when the normal heating operating mode is switched to the heating-defrosting operating mode and when the first condensing temperature is greater than the second condensing temperature,sets the opening degree of the flow control arrangement to a value greater than the initial opening degree., [2] The air conditioning apparatus according to claim 1, wherein the controller is configured to change, when the heating-defrosting operation mode is switched to the normal heating operation mode, the opening degree of the pressure reducers to the opening degree of the pressure reducers used immediately before the operation mode is switched to the heating-defrosting operation mode. [3] The air conditioning apparatus according to claim 1 or 2, wherein the controller is configured to adjust the opening degree of the flow control device so that the opening degree of the flow control device does not become lower than a predetermined opening degree lower limit. [4] Air conditioning device according to one of claims 1 to 3, wherein one outdoor heat exchanger, the first outdoor heat exchanger or the second outdoor heat exchanger is provided below the other outdoor heat exchanger, and wherein the controller is configured to set the defrosting target in the heating-defrosting operation mode so that the one outdoor heat exchanger provided at the bottom, the other outdoor heat exchanger provided at the top, and the one outdoor heat exchanger provided at the bottom are defrosted in that order. [5] The air conditioning apparatus according to claim 4, wherein the controller is configured to make the opening degree of the flow control means when the one outdoor heat exchanger provided below is defrosted a second time smaller than the opening degree of the flow control means when the one outdoor heat exchanger provided below is defrosted for the first time. [6] The air conditioning apparatus according to claim 4 or 5, wherein the controller is configured to set the time for defrosting the one outdoor heat exchanger provided at the bottom for the first time point shorter than the time for defrosting the one outdoor heat exchanger provided at the bottom for the second time point or shorter than the time for defrosting the other outdoor heat exchanger provided at the top. [7] An air conditioning device according to any one of claims 1 to 6, further comprising: an outside pressure sensor provided on the first outside heat exchanger or the second outside heat exchanger, the outside pressure sensor being configured to detect the evaporation pressure of the refrigerant in the first outside heat exchanger or the second outside heat exchanger during the heating operation mode, wherein the controller is configured to, when the normal heating operation mode is switched to the heating-defrosting operation mode, set the initial opening degree based on the evaporation pressure of the first outdoor heat exchanger or the second outdoor heat exchanger detected by the outdoor pressure sensor and the drive frequency of the compressor. [8] An air conditioning device according to any one of claims 1 to 7, further comprising: an internal pressure sensor provided on the internal heat exchanger, the internal pressure sensor being configured to detect the condensation pressure of the refrigerant in the internal heat exchanger during the heating operation mode, wherein the controller is configured to convert the condensing pressure detected by the internal pressure sensor and calculate the first condensing temperature and the second condensing temperature.

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