WO2023190486A1 - Air conditioner - Google Patents

Air conditioner Download PDF

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Publication number
WO2023190486A1
WO2023190486A1 PCT/JP2023/012451 JP2023012451W WO2023190486A1 WO 2023190486 A1 WO2023190486 A1 WO 2023190486A1 JP 2023012451 W JP2023012451 W JP 2023012451W WO 2023190486 A1 WO2023190486 A1 WO 2023190486A1
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WIPO (PCT)
Prior art keywords
refrigerant
compressor
unit
air conditioner
indoor
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PCT/JP2023/012451
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French (fr)
Japanese (ja)
Inventor
亮 ▲高▼岡
佑 廣崎
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株式会社富士通ゼネラル
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Publication of WO2023190486A1 publication Critical patent/WO2023190486A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle

Definitions

  • the technology of the present disclosure relates to an air conditioner.
  • the refrigerant flow rate is adjusted by controlling the opening degree of the expansion valve so that the degree of suction superheat (suction superheat (SH)) of the refrigerant sucked into the compressor reaches the target value. , maintains the state of the refrigerant sucked into the compressor in a gaseous state, thereby preventing a decrease in the reliability of the compressor.
  • suction superheat suction superheat
  • the amount of refrigerant dissolved in the refrigerating machine oil inside the compressor increases.
  • the refrigerating machine oil is diluted and its viscosity may decrease. If the viscosity of the refrigerating machine oil is low, the oil film necessary to lubricate the sliding parts of the compressor will not be maintained, resulting in poor lubrication in which the sliding parts of the compressor are no longer properly lubricated, reducing the reliability of the compressor.
  • the disclosed technology has been made in view of this point, and aims to provide an air conditioner that can suppress a decrease in air conditioning capacity when starting heating operation.
  • An air conditioner includes a refrigerant circuit that includes a compressor, a condenser, an expansion valve, and an evaporator, and that circulates refrigerant; and a suction superheat degree acquisition unit that acquires the suction superheat degree of the compressor; A pressure acquisition unit that acquires the discharge pressure of the compressor; and a control unit that controls the opening degree of the expansion valve so that the degree of suction superheat reaches a target value, and sets the target value to a larger value as the discharge pressure is lower.
  • FIG. 1A is a refrigerant circuit diagram of an embodiment of the present disclosure.
  • FIG. 1B is a block diagram illustrating an example of a control configuration according to an embodiment of the present disclosure.
  • FIG. 2 is a diagram illustrating a basic refrigerant circuit.
  • FIG. 3 is a Mollier diagram (ph diagram) relating to the refrigerant circuit of FIG. 2.
  • FIG. 4 is an explanatory diagram illustrating the amount of refrigerant dissolved in refrigerating machine oil.
  • FIG. 5 is a flowchart illustrating an example of the operation of the control unit according to the embodiment of the present disclosure.
  • FIG. 6A is an explanatory diagram illustrating setting of a target value regarding the suction superheat degree.
  • FIG. 6B is an explanatory diagram illustrating an example of setting a target value regarding the suction superheat degree.
  • FIG. 1A is a refrigerant circuit diagram of an embodiment of the present disclosure.
  • an air conditioner 1 includes an outdoor unit 2 installed outdoors, and an indoor unit 3 installed indoors and connected to the outdoor unit 2 through a liquid pipe 4 and a gas pipe 5. It is equipped with Specifically, the liquid side closing valve 25 of the outdoor unit 2 and the liquid pipe connection portion 33 of the indoor unit 3 are connected by the liquid pipe 4. Further, the gas side shutoff valve 26 of the outdoor unit 2 and the gas pipe connecting portion 34 of the indoor unit 3 are connected by a gas pipe 5. Through the above steps, the refrigerant circuit 10 of the air conditioner 1 is formed.
  • the outdoor unit 2 includes a four-way valve 22, an outdoor heat exchanger 23, an expansion valve 24, a liquid side closing valve 25 to which the liquid pipe 4 is connected, and a gas side closing valve 26 to which the gas pipe 5 is connected. It also includes an outdoor fan 27. These devices except for the outdoor fan 27 are connected to each other through refrigerant piping, which will be described later, to form an outdoor unit refrigerant circuit 10a that forms a part of the refrigerant circuit 10. Note that an accumulator (not shown) may be provided on the refrigerant suction side of the compressor 21.
  • the compressor 21 is a variable capacity compressor whose operating capacity can be changed by having its frequency controlled by an inverter (not shown).
  • the refrigerant discharge side of the compressor 21 is connected to port a of the four-way valve 22 through a discharge pipe 61. Further, the refrigerant suction side of the compressor 21 is connected to port c of the four-way valve 22 through a suction pipe 66.
  • the refrigerant used in the refrigerant circuit 10 in the embodiment of the present disclosure is, for example, R290 (propane).
  • this refrigerant is not limited to R290, and may include, for example, R50 (methane), R170 (ethane), C318, R441A, R443A, R500, R501, R600 (butane), R601 (pentane), etc. It's okay.
  • the four-way valve 22 is a valve for switching the direction in which the refrigerant flows, and includes four ports a, b, c, and d.
  • Port a is connected to the refrigerant discharge side of the compressor 21 through the discharge pipe 61, as described above.
  • Port b is connected to one refrigerant inlet/outlet of the outdoor heat exchanger 23 through a refrigerant pipe 62 .
  • the port c is connected to the refrigerant suction side of the compressor 21 through the suction pipe 66, as described above.
  • the port d is connected to the gas side closing valve 26 through an outdoor unit gas pipe 64.
  • the outdoor heat exchanger 23 exchanges heat between the refrigerant and the outside air taken into the outdoor unit 2 by the rotation of an outdoor fan 27, which will be described later.
  • one refrigerant inlet/outlet of the outdoor heat exchanger 23 is connected to port b of the four-way valve 22 through the refrigerant pipe 62, and the other refrigerant inlet/outlet is connected to the liquid side closing valve 25 through the outdoor unit liquid pipe 63.
  • the outdoor heat exchanger 23 functions as a condenser when the air conditioner 1 performs a cooling operation, and functions as an evaporator when the air conditioner 1 performs a heating operation, by switching the four-way valve 22 described later.
  • the expansion valve 24 during heating operation is an electronic expansion valve driven by a pulse motor (not shown) under the control of the control unit 200 (see FIG. 1B). Specifically, the opening degree is adjusted by the number of pulses applied to the pulse motor. The opening degree of the expansion valve 24 is adjusted so that the degree of suction superheat determined from the temperature and pressure of the refrigerant sucked into the compressor 21 becomes a predetermined target temperature.
  • the outdoor fan 27 is made of a resin material and is placed near the outdoor heat exchanger 23.
  • the outdoor fan 27 has its center connected to a rotating shaft of a fan motor (not shown).
  • the outdoor fan 27 rotates as the fan motor rotates.
  • As the outdoor fan 27 rotates outside air is drawn into the outdoor unit 2 from an inlet (not shown) of the outdoor unit 2, and the outside air, which has undergone heat exchange with the refrigerant in the outdoor heat exchanger 23, is sent outside from an outlet (not shown) of the outdoor unit 2. Release to outside of machine 2.
  • the outdoor unit 2 is provided with various sensors.
  • the discharge pipe 61 includes a discharge pressure sensor 71 that detects the pressure (discharge pressure) of the refrigerant discharged from the compressor 21 and the temperature (discharge temperature) of the refrigerant discharged from the compressor 21.
  • a discharge temperature sensor 73 is provided to detect the temperature.
  • the suction pipe 66 includes a suction pressure sensor 72 that detects the pressure of the refrigerant sucked into the compressor 21 and a suction temperature sensor 74 that detects the temperature of the refrigerant sucked into the compressor 21.
  • an outdoor unit liquid pipe temperature sensor (not shown) that detects the temperature of the refrigerant flowing out from the expansion valve 24 during heating operation.
  • the compressor 21 is provided with a motor 21a that drives the compressor 21.
  • the control unit 200 functions as a compressor state detection unit that can read the current frequency of the compressor 21 as information from the motor 21a.
  • An outside air temperature sensor 76 is provided near a suction port (not shown) of the outdoor unit 2 to detect the temperature of outside air flowing into the interior of the outdoor unit 2, that is, the outside air temperature.
  • FIG. 1B is a block diagram illustrating an example of a control configuration according to an embodiment of the present disclosure.
  • the outdoor unit 2 is equipped with a control section 200.
  • the control unit 200 is mounted on a control board stored in an electrical equipment box (not shown) of the outdoor unit 2.
  • This control section 200 includes a CPU 210, a storage section 220, a communication section 230, and a sensor input section 240.
  • the storage unit 220 is composed of a flash memory, and stores the control program for the outdoor unit 2, detected values corresponding to detection signals from various sensors, control states of the compressor 21, outdoor fan 27, expansion valve 24, etc. are doing. Although not shown, the storage unit 220 stores in advance a frequency table in which the frequency of the compressor 21 is determined according to the required capacity received from the indoor unit 3.
  • the communication unit 230 is an interface that communicates with the indoor unit 3.
  • the sensor input unit 240 takes in detection results from various sensors of the outdoor unit 2 and outputs them to the CPU 210.
  • the CPU 210 takes in the detection results from each sensor of the outdoor unit 2 described above via the sensor input section 240. Furthermore, the refrigerant circuit 10 receives a control signal transmitted from the indoor unit 3 via the communication unit 230. The CPU 210 controls the drive of the compressor 21 and the outdoor fan 27 based on the acquired detection results, control signals, and the like. Further, the CPU 210 performs switching control of the four-way valve 22 based on the captured detection results and control signals. Furthermore, the CPU 210 adjusts the opening degree of the expansion valve 24 based on the acquired detection results and control signals.
  • the control unit 200 controls the suction (evaporation) pressure, which is the value detected by the suction pressure sensor 72, or the evaporation temperature, which is the value detected by the heat exchanger temperature sensor 75, and the suction temperature sensor 74. It functions as a suction superheat degree acquisition unit that acquires the suction superheat degree of the refrigerant sucked into the compressor 21 from the suction temperature which is the detected value of. Regarding the degree of suction superheat, tables and functions that are associated with evaporation pressure (temperature) and suction temperature are stored in the storage unit 220 in advance, and the CPU 210 acquires the degree of suction superheat from the storage unit 220 by inputting each detected value. do.
  • the opening degree of the expansion valve 24 is adjusted so that the acquired suction superheat degree becomes the target value. Further, the CPU 210 calculates the discharge pressure of the refrigerant based on the detection result of a pressure sensor installed near the outlet of the compressor 21, and sets the target value of the degree of suction superheat to a larger value as the discharge pressure is lower ( (Details will be described later).
  • the indoor unit 3 includes an indoor heat exchanger 31, an indoor fan 32, a liquid pipe connection part 33 to which the other end of the liquid pipe 4 is connected, and a gas pipe connection part 34 to which the other end of the gas pipe 5 is connected.
  • the indoor unit 3 includes an indoor heat exchanger 31, an indoor fan 32, a liquid pipe connection part 33 to which the other end of the liquid pipe 4 is connected, and a gas pipe connection part 34 to which the other end of the gas pipe 5 is connected.
  • These devices except for the indoor fan 32 are connected to each other through refrigerant piping, which will be described in detail below, to form an indoor unit refrigerant circuit 10b that forms a part of the refrigerant circuit 10.
  • the indoor heat exchanger 31 exchanges heat with indoor air taken into the indoor unit 3 from a suction port (not shown) of the indoor unit 3 using a refrigerant and the rotation of an indoor fan 32 (described later).
  • One refrigerant inlet/outlet of the indoor heat exchanger 31 is connected to the liquid pipe connection part 33 by an indoor unit liquid pipe 67.
  • the other refrigerant inlet and outlet of the indoor heat exchanger 31 is connected to the gas pipe connecting portion 34 through an indoor unit gas pipe 68.
  • the indoor heat exchanger 31 functions as an evaporator when the air conditioner 1 performs a cooling operation, and functions as a condenser when the indoor unit 3 performs a heating operation.
  • the indoor fan 32 is made of resin material and is placed near the indoor heat exchanger 31.
  • the indoor fan 32 is rotated by a fan motor (not shown), draws indoor air into the interior of the indoor unit 3 from a suction port (not shown) of the indoor unit 3, and exchanges heat with a refrigerant in the indoor heat exchanger 31 to return the indoor air to the room.
  • the air is blown into the room from the air outlet (not shown) of the machine 3.
  • the indoor unit 3 is provided with various sensors.
  • the indoor unit liquid pipe 67 is provided with a liquid-side temperature sensor 77a that detects the temperature of the refrigerant flowing into or out of the air conditioner 1.
  • the indoor unit gas pipe 68 is provided with a gas-side temperature sensor 78 that detects the temperature of the refrigerant flowing out from or flowing into the indoor heat exchanger 31 .
  • a room temperature sensor 79 is provided near a suction port (not shown) of the indoor unit 3 to detect the temperature of indoor air flowing into the interior of the indoor unit 3, that is, the room temperature.
  • the CPU 210 sets the four-way valve 22 to the state shown by the solid line as shown in FIG. Switch so that c is connected.
  • the refrigerant circulates in the direction shown by the solid arrow in the refrigerant circuit 10, resulting in a heating cycle in which the outdoor heat exchanger 23 functions as an evaporator and the indoor heat exchanger 31 functions as a condenser.
  • the high-pressure refrigerant discharged from the compressor 21 flows through the discharge pipe 61 and flows into the four-way valve 22.
  • the refrigerant that has flowed into the port a of the four-way valve 22 flows through the outdoor unit gas pipe 64 from the port d of the four-way valve 22 and flows into the gas pipe 5 via the gas-side closing valve 26.
  • the refrigerant flowing through the gas pipe 5 flows into the indoor unit 3 via the gas pipe connection part 34.
  • the refrigerant flowing into the indoor unit 3 flows through the indoor unit gas pipe 68 and flows into the indoor heat exchanger 31, where it exchanges heat with the indoor air taken into the indoor unit 3 by the rotation of the indoor fan 32, and is condensed. do.
  • the indoor heat exchanger 31 functions as a condenser, and the indoor air heated by exchanging heat with the refrigerant in the indoor heat exchanger 31 is blown indoors from the outlet (not shown), so that the indoor unit 3 is installed in the room.
  • the refrigerant flowing out of the indoor heat exchanger 31 flows through the indoor unit liquid pipe 67 and flows into the liquid pipe 4 via the liquid pipe connection part 33.
  • the refrigerant flowing through the liquid pipe 4 and flowing into the outdoor unit 2 via the liquid-side closing valve 25 is depressurized when flowing through the outdoor unit liquid pipe 63 and passing through the expansion valve 24 .
  • the suction superheat degree (suction SH) of the refrigerant sucked into the compressor 21 is adjusted to a predetermined target value.
  • the refrigerant that has passed through the expansion valve 24 and entered the outdoor heat exchanger 23 exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 27, and evaporates.
  • the refrigerant flowing out from the outdoor heat exchanger 23 into the refrigerant pipe 62 flows through ports b and c of the four-way valve 22 and the suction pipe 66, and is sucked into the compressor 21 and compressed again.
  • FIG. 2 is a diagram illustrating the basic refrigerant circuit 11.
  • FIG. 3 is a Mollier diagram (ph diagram) relating to the refrigerant circuit 11 of FIG. 2.
  • point A is between the compressor 21 and the condenser (corresponding to the indoor heat exchanger 31 during heating operation, hereinafter referred to as the condenser 31).
  • Point B is between the condenser 31 and the expansion valve 24
  • point C is between the expansion valve 24 and the evaporator (corresponding to the outdoor heat exchanger 23 during heating operation, hereinafter referred to as the evaporator 23)
  • point D is between the expansion valve 24 and the evaporator (corresponding to the outdoor heat exchanger 23 during heating operation. It refers to the space between the evaporator 23 and the compressor 21 (the same applies below).
  • the state of the refrigerant from point A to point D or between each point is as shown in FIG. 3 as follows.
  • the refrigerant (between points D and A) during the compression process in the compressor 21 is compressed, and both the pressure (vertical axis) and temperature rise to become high-temperature, high-pressure superheated steam (through heat exchange with the surrounding air) (becomes easily condensed).
  • the refrigerant discharged from the compressor 21 (point A) is a high-pressure gas phase refrigerant in a superheated state.
  • the refrigerant in the evaporation process in the evaporator 23 exchanges heat (endotherm) with the surrounding air, thereby maintaining the state of wet steam and saturated steam while keeping the pressure constant. After that, it becomes low-pressure superheated steam.
  • the refrigerant flowing out from the evaporator 23 (point D) is a superheated low-pressure gas phase refrigerant.
  • the control method for the compressor 21, indoor fan 32, expansion valve 24, and outdoor fan 27, which are controlled objects in this basic refrigerant circuit 11, is as follows.
  • the indoor fan 32 is controlled according to the difference between the room temperature and the set temperature during both heating operation (when the condenser is the indoor heat exchanger 31) and cooling operation (when the condenser is the outdoor heat exchanger 23), or is controlled by the user.
  • the air volume is set to your preference.
  • the expansion valve 24 is controlled so that the temperature at point A (discharge temperature) becomes a target value (discharge temperature control), or expands by a predetermined control amount (pulse) according to the amount of change in the frequency of the compressor 21. It is controlled by control (frequency pulse control) that adjusts the opening degree of the valve 24.
  • Discharge temperature control is feedback control that adjusts the opening after disturbances such as indoor temperature or outside temperature appear in changes in discharge temperature, whereas frequency pulse control adjusts the circulation amount based on the amount of change in frequency. This is feedforward control that predicts the amount of change and adjusts the expansion valve 24 to an appropriate opening degree in advance.
  • the outdoor fan 27 is controlled based on the frequency of the compressor 21 during both heating operation (when the evaporator is on the heat source side) and cooling operation (when the evaporator is on the user side).
  • the basic operational constraints in the refrigerant circuit 11 are as follows.
  • FIG. 4 is an explanatory diagram illustrating the solubility of refrigerant in refrigerating machine oil.
  • the horizontal axis shows the solubility (weight percent) of the refrigerant in refrigerating machine oil
  • the vertical axis shows the pressure of the refrigerant.
  • each graph shown in Figure 4 shows the relationship between the refrigerant pressure and the solubility of the refrigerant in refrigerating machine oil when the refrigerant temperature is 30°C, 40°C, 50°C, 60°C, 70°C, and 80°C. It shows.
  • the control unit 200 sets the control unit 200 such that the lower the detected discharge pressure of the refrigerant (the lower the discharge pressure, the lower the discharge temperature). Therefore, the target value of the degree of suction superheat is set to a large value, and the opening degree of the expansion valve 24 is controlled so that the degree of suction superheat reaches the target value.
  • FIG. 5 is a flowchart illustrating an example of the operation of the control unit according to the embodiment of the present disclosure.
  • the control unit 200 acquires initial settings such as set temperature (S1), and acquires detection results of various sensors via the sensor input unit 240 (S2). .
  • control unit 200 calculates the suction superheat degree of the refrigerant based on the detection value of the suction temperature sensor 74 and the detection value of the suction pressure sensor 72 acquired via the sensor input unit 240 (S3).
  • control unit 200 detects the frequency of the compressor 21 (S4).
  • control unit 200 functions as a pressure acquisition unit that acquires the refrigerant discharge pressure based on the sensor detection value acquired via the sensor input unit 240 (S5).
  • control unit 200 may calculate the refrigerant discharge pressure based on the state of the compressor 21 detected in S4. For example, the control unit 200 obtains the discharge pressure by referring to a correspondence table, a function, etc. that defines the correspondence between the rotation speed and the discharge pressure. The lower the detected rotational speed of the compressor 21, the lower the discharge pressure becomes. Similarly, the control unit 200 obtains the discharge pressure by referring to a correspondence table, a function, etc. that defines the correspondence between the required capacity and the discharge pressure. The smaller the detected capacity required of the compressor 21, the lower the discharge pressure becomes.
  • control unit 200 refers to the correspondence table recorded in the storage unit 220 based on the calculated discharge pressure, and sets a target value for the suction superheat degree (suction superheat (SH)) of the refrigerant (S6 ).
  • the target value of the suction superheat degree is determined in accordance with the calculated discharge pressure, and the lower the calculated discharge pressure, the larger the value becomes.
  • FIG. 6A is an explanatory diagram illustrating the relationship between the required capacity and the target value of the degree of suction superheat.
  • the horizontal axis shows the calculated discharge pressure (required capacity/pressure machine frequency)
  • the vertical axis shows the target value for the degree of suction superheat (suction superheat (SH)).
  • the control unit 200 changes the target value of the suction superheat degree so that the lower the discharge pressure (required capacity/pressure machine frequency) is, the higher the target value of the degree of suction superheat is.
  • the configuration in which the target value is increased in response to a decrease in the discharge pressure is not limited to a stepwise change as shown in the illustrated example, and may be, for example, a smooth linear change.
  • control unit 200 controls the opening degree of the expansion valve 24 based on the target value set in S6 (S7).
  • FIG. 6B is an explanatory diagram illustrating the relationship between the required capacity and the target value of the degree of suction superheat.
  • the upper row shows an outline of a Mollier diagram (ph diagram) when the required capacity is "small” (discharge pressure is small).
  • the lower row shows an outline of a Mollier diagram (ph diagram) when the required capacity is "large” (discharge pressure is large).
  • the CPU 210 moves to the right side of the refrigerant saturated vapor line (right curve) at the evaporator outlet.
  • the target value (the target value set in S6) is set so as to make a large displacement in the region (increase the degree of superheating).
  • the solubility of the refrigerant in the refrigerating machine oil decreases, and the amount of refrigerant dissolved decreases, so it is possible to suppress a decrease in the air conditioning capacity at the time of starting the heating operation.
  • the discharge temperature tends to be lower and the amount of refrigerant dissolved in refrigerating machine oil tends to increase compared to R32 refrigerant.
  • the air conditioner 1 of the present disclosure by setting the target value of the suction superheat degree to a large value, the amount of R290 (propane) refrigerant dissolved in the refrigerating machine oil is reduced, and when using R290 (propane) refrigerant, Also, it is possible to suppress a decrease in air conditioning capacity at the time of starting heating operation.
  • the air conditioner 1 includes the compressor 21, the condenser (indoor heat exchanger 31 during heating operation, the outdoor heat exchanger 23 during cooling operation), the expansion valve 24, and the evaporator (during heating operation: It has an outdoor heat exchanger 23, an indoor heat exchanger 31 during cooling operation, and a refrigerant circuit 10 that circulates refrigerant.
  • the air conditioner 1 also includes a suction superheat degree acquisition section that acquires the suction superheat degree of the compressor 21 and a control section 200 that functions as a pressure acquisition section that acquires the discharge pressure of the compressor 21.
  • the air conditioner 1 also includes a control unit 200 that controls the opening degree of the expansion valve 24 so that the degree of suction superheat reaches a target value, and sets the target value of the degree of suction superheat to a larger value as the discharge pressure decreases. .
  • a control unit 200 controls the opening degree of the expansion valve 24 so that the degree of suction superheat reaches a target value, and sets the target value of the degree of suction superheat to a larger value as the discharge pressure decreases.
  • Discharge pressure sensor 72 ... Suction pressure sensor 73... Discharge temperature sensor 74 ...Suction temperature sensor 75...Heat exchange temperature sensor 76...Outside air temperature sensor 77a...Liquid side temperature sensor 78...Gas side temperature sensor 79...Room temperature sensor 200...Control unit 210...CPU 220...Storage unit 230...Communication unit 240...Sensor input unit A to D...Points a to d...Ports

Abstract

An air conditioner according to an embodiment of the present invention includes: a refrigerant circuit that includes a compressor, a condenser, an expansion valve, and an evaporator and circulates a refrigerant; a temperature detection unit that detects a discharge temperature of the compressor; a pressure calculation unit that calculates a discharge pressure of the compressor; and a control unit that controls an opening degree of the expansion valve such that the discharge temperature reaches a target value and sets the target value to a larger value as the discharge pressure becomes lower.

Description

空気調和機air conditioner
　本開示の技術は、空気調和機に関する。 The technology of the present disclosure relates to an air conditioner.
　空気調和機では、圧縮機に吸入される冷媒が液相状態の冷媒を含んでいると、液相冷媒は非圧縮性であることから圧縮機が破損するおそれがある。そのため、この冷凍サイクルにおいては、圧縮機に吸入される冷媒の吸入過熱度（吸入スーパーヒート（ＳＨ））が目標値となるように膨張弁の開度を制御して冷媒流量を調節することで、圧縮機に吸入される冷媒の状態を気相状態に維持し、圧縮機の信頼性低下を防いでいる。 In an air conditioner, if the refrigerant sucked into the compressor contains refrigerant in a liquid phase, the compressor may be damaged because the liquid phase refrigerant is incompressible. Therefore, in this refrigeration cycle, the refrigerant flow rate is adjusted by controlling the opening degree of the expansion valve so that the degree of suction superheat (suction superheat (SH)) of the refrigerant sucked into the compressor reaches the target value. , maintains the state of the refrigerant sucked into the compressor in a gaseous state, thereby preventing a decrease in the reliability of the compressor.
特開２００５－１２１３６１号公報Japanese Patent Application Publication No. 2005-121361
　しかしながら、上記の従来技術では、運転状態によっては圧縮機の内部の冷凍機油に冷媒が溶解し、回路内を循環する冷媒の量が少なくなることで空調能力の低下を招く場合があるという問題がある。 However, the above-mentioned conventional technology has the problem that depending on the operating conditions, refrigerant may dissolve in the refrigerating machine oil inside the compressor, reducing the amount of refrigerant circulating in the circuit, which may lead to a decrease in air conditioning capacity. be.
　また、低外気温下における暖房運転の起動後、吐出温度の上昇に時間がかかると圧縮機内部の冷凍機油に冷媒が溶解する量が増大する。冷凍機油へ冷媒が溶解すると、冷凍機油が希釈されることで粘度が小さくなることがある。冷凍機油の粘度が小さい場合、圧縮機の摺動部の潤滑に必要な油膜が保持されず、圧縮機の摺動部が適切に潤滑されなくなるという潤滑不良を生じ、圧縮機の信頼性を低下させる。また、冷凍機油に冷媒が溶け込むことで凝縮器に供給される冷媒の量が減る状態（冷媒不足）となり、空調能力の低下を引き起こすこととなる。また、冷媒の温度が低いほど冷凍機油への溶解量が増加する。例えば、Ｒ２９０（プロパン）冷媒を冷凍サイクルの作動流体として用いる場合、定常運転における理論吐出温度はＲ３２冷媒と比較して低くなるため、冷凍機油への冷媒の溶解量が増加し、上記の信頼性低下や空調能力の低下が顕著になる。 Additionally, if it takes time for the discharge temperature to rise after starting the heating operation at low outside temperatures, the amount of refrigerant dissolved in the refrigerating machine oil inside the compressor increases. When a refrigerant is dissolved in refrigerating machine oil, the refrigerating machine oil is diluted and its viscosity may decrease. If the viscosity of the refrigerating machine oil is low, the oil film necessary to lubricate the sliding parts of the compressor will not be maintained, resulting in poor lubrication in which the sliding parts of the compressor are no longer properly lubricated, reducing the reliability of the compressor. let Furthermore, as the refrigerant dissolves in the refrigerating machine oil, the amount of refrigerant supplied to the condenser is reduced (refrigerant shortage), resulting in a decrease in air conditioning capacity. Furthermore, the lower the temperature of the refrigerant, the more the amount of refrigerant dissolved in the refrigerating machine oil increases. For example, when R290 (propane) refrigerant is used as the working fluid in a refrigeration cycle, the theoretical discharge temperature during steady operation is lower than that of R32 refrigerant, so the amount of refrigerant dissolved in the refrigerating machine oil increases, resulting in the above-mentioned reliability. The decrease in air conditioning capacity becomes noticeable.
　開示の技術は、かかる点に鑑みてなされたものであって、暖房運転起動時における空調能力の低下を抑制できる空気調和機を提供することを目的とする。 The disclosed technology has been made in view of this point, and aims to provide an air conditioner that can suppress a decrease in air conditioning capacity when starting heating operation.
　本開示の一態様による空気調和機は、圧縮機、凝縮器、膨張弁および蒸発器を有し、冷媒を循環させる冷媒回路と、圧縮機の吸入過熱度を取得する吸入過熱度取得部と、圧縮機の吐出圧力を取得する圧力取得部と、吸入過熱度が目標値となるように膨張弁の開度を制御するとともに、吐出圧力が低いほど目標値として大きい値にする制御部と、を有する。 An air conditioner according to one aspect of the present disclosure includes a refrigerant circuit that includes a compressor, a condenser, an expansion valve, and an evaporator, and that circulates refrigerant; and a suction superheat degree acquisition unit that acquires the suction superheat degree of the compressor; A pressure acquisition unit that acquires the discharge pressure of the compressor; and a control unit that controls the opening degree of the expansion valve so that the degree of suction superheat reaches a target value, and sets the target value to a larger value as the discharge pressure is lower. have
　暖房運転起動時における空調能力の低下を抑制できる。 It is possible to suppress the decrease in air conditioning capacity when starting heating operation.
図１Ａは、本開示の実施形態の冷媒回路図である。FIG. 1A is a refrigerant circuit diagram of an embodiment of the present disclosure. 図１Ｂは、本開示の実施形態の制御構成例を示すブロック図である。FIG. 1B is a block diagram illustrating an example of a control configuration according to an embodiment of the present disclosure. 図２は、基本的な冷媒回路を説明する図である。FIG. 2 is a diagram illustrating a basic refrigerant circuit. 図３は、図２の冷媒回路に係るモリエル線図（ｐｈ線図）である。FIG. 3 is a Mollier diagram (ph diagram) relating to the refrigerant circuit of FIG. 2. 図４は、冷凍機油への冷媒の溶解量を説明する説明図である。FIG. 4 is an explanatory diagram illustrating the amount of refrigerant dissolved in refrigerating machine oil. 図５は、本開示の実施形態の制御部の動作例を示すフローチャートである。FIG. 5 is a flowchart illustrating an example of the operation of the control unit according to the embodiment of the present disclosure. 図６Ａは、吸入過熱度にかかる目標値の設定を説明する説明図である。FIG. 6A is an explanatory diagram illustrating setting of a target value regarding the suction superheat degree. 図６Ｂは、吸入過熱度にかかる目標値の設定例を説明する説明図である。FIG. 6B is an explanatory diagram illustrating an example of setting a target value regarding the suction superheat degree.
　以下、図面を参照して、本開示の実施形態にかかる空気調和機を説明する。実施形態において同一の機能を有する構成には同一の符号を付し、重複する説明は省略する。なお、以下の実施形態で説明する空気調和機は、一例を示すに過ぎず、実施形態を限定するものではない。また、以下の各実施形態は、矛盾しない範囲内で適宜組みあわせてもよい。 Hereinafter, an air conditioner according to an embodiment of the present disclosure will be described with reference to the drawings. In the embodiments, components having the same functions are denoted by the same reference numerals, and redundant explanations will be omitted. Note that the air conditioner described in the following embodiments is merely an example, and does not limit the embodiments. In addition, the following embodiments may be combined as appropriate within a range that does not contradict each other.
＜冷媒回路の構成＞
　まず、図１Ａを参照して、室外機２を含む空気調和機１の冷媒回路について説明する。図１Ａは、本開示の実施形態の冷媒回路図である。 <Refrigerant circuit configuration>
First, the refrigerant circuit of the air conditioner 1 including the outdoor unit 2 will be described with reference to FIG. 1A. FIG. 1A is a refrigerant circuit diagram of an embodiment of the present disclosure.
　図１Ａに示すように、本実施形態における空気調和機１は、屋外に設置される室外機２と、室内に設置され、室外機２に液管４及びガス管５で接続された室内機３を備えている。詳細には、室外機２の液側閉鎖弁２５と室内機３の液管接続部３３が液管４で接続されている。また、室外機２のガス側閉鎖弁２６と室内機３のガス管接続部３４がガス管５で接続されている。以上により、空気調和機１の冷媒回路１０が形成される。 As shown in FIG. 1A, an air conditioner 1 according to the present embodiment includes an outdoor unit 2 installed outdoors, and an indoor unit 3 installed indoors and connected to the outdoor unit 2 through a liquid pipe 4 and a gas pipe 5. It is equipped with Specifically, the liquid side closing valve 25 of the outdoor unit 2 and the liquid pipe connection portion 33 of the indoor unit 3 are connected by the liquid pipe 4. Further, the gas side shutoff valve 26 of the outdoor unit 2 and the gas pipe connecting portion 34 of the indoor unit 3 are connected by a gas pipe 5. Through the above steps, the refrigerant circuit 10 of the air conditioner 1 is formed.
　＜＜室外機の冷媒回路＞＞
　まずは、室外機２について説明する。室外機２は、四方弁２２と、室外熱交換器２３と、膨張弁２４と、液管４が接続された液側閉鎖弁２５と、ガス管５が接続されたガス側閉鎖弁２６と、室外ファン２７とを備えている。そして、室外ファン２７を除くこれら各装置が後述する各冷媒配管で相互に接続されて、冷媒回路１０の一部をなす室外機冷媒回路１０ａを形成している。なお、圧縮機２１の冷媒吸入側には、アキュムレータ（不図示）が設けられてもよい。 <<Refrigerant circuit of outdoor unit>>
First, the outdoor unit 2 will be explained. The outdoor unit 2 includes a four-way valve 22, an outdoor heat exchanger 23, an expansion valve 24, a liquid side closing valve 25 to which the liquid pipe 4 is connected, and a gas side closing valve 26 to which the gas pipe 5 is connected. It also includes an outdoor fan 27. These devices except for the outdoor fan 27 are connected to each other through refrigerant piping, which will be described later, to form an outdoor unit refrigerant circuit 10a that forms a part of the refrigerant circuit 10. Note that an accumulator (not shown) may be provided on the refrigerant suction side of the compressor 21.
　圧縮機２１は、図示しないインバータにより周波数が制御されることで、運転容量を変えることができる容量可変型圧縮機である。圧縮機２１の冷媒吐出側は、四方弁２２のポートａと吐出管６１で接続されている。また、圧縮機２１の冷媒吸入側は、四方弁２２のポートｃと吸入管６６で接続されている。 The compressor 21 is a variable capacity compressor whose operating capacity can be changed by having its frequency controlled by an inverter (not shown). The refrigerant discharge side of the compressor 21 is connected to port a of the four-way valve 22 through a discharge pipe 61. Further, the refrigerant suction side of the compressor 21 is connected to port c of the four-way valve 22 through a suction pipe 66.
　なお、本開示の実施形態における冷媒回路１０で用いる冷媒は、例えばＲ２９０（プロパン）である。なお、この冷媒については、Ｒ２９０に限定するものではなく、例えばＲ５０（メタン）、Ｒ１７０（エタン）の他、Ｃ３１８、Ｒ４４１Ａ、Ｒ４４３Ａ、Ｒ５００、Ｒ５０１、Ｒ６００（ブタン）、Ｒ６０１（ペンタン）などであってもよい。 Note that the refrigerant used in the refrigerant circuit 10 in the embodiment of the present disclosure is, for example, R290 (propane). Note that this refrigerant is not limited to R290, and may include, for example, R50 (methane), R170 (ethane), C318, R441A, R443A, R500, R501, R600 (butane), R601 (pentane), etc. It's okay.
　四方弁２２は、冷媒の流れる方向を切り替えるための弁であり、ａ、ｂ、ｃ、ｄの４つのポートを備えている。ポートａは、上述したように圧縮機２１の冷媒吐出側と吐出管６１で接続されている。ポートｂは、室外熱交換器２３の一方の冷媒出入口と冷媒配管６２で接続されている。ポートｃは、上述したように圧縮機２１の冷媒吸入側と吸入管６６で接続されている。そして、ポートｄは、ガス側閉鎖弁２６と室外機ガス管６４で接続されている。 The four-way valve 22 is a valve for switching the direction in which the refrigerant flows, and includes four ports a, b, c, and d. Port a is connected to the refrigerant discharge side of the compressor 21 through the discharge pipe 61, as described above. Port b is connected to one refrigerant inlet/outlet of the outdoor heat exchanger 23 through a refrigerant pipe 62 . The port c is connected to the refrigerant suction side of the compressor 21 through the suction pipe 66, as described above. The port d is connected to the gas side closing valve 26 through an outdoor unit gas pipe 64.
　室外熱交換器２３は、冷媒と、後述する室外ファン２７の回転により室外機２の内部に取り込まれた外気を熱交換させるものである。室外熱交換器２３の一方の冷媒出入口は、上述したように四方弁２２のポートｂと冷媒配管６２で接続され、他方の冷媒出入口は液側閉鎖弁２５と室外機液管６３で接続されている。室外熱交換器２３は、後述する四方弁２２の切替えによって、空気調和機１が冷房運転を行う場合は凝縮器として機能し、暖房運転を行う場合は蒸発器として機能する。 The outdoor heat exchanger 23 exchanges heat between the refrigerant and the outside air taken into the outdoor unit 2 by the rotation of an outdoor fan 27, which will be described later. As described above, one refrigerant inlet/outlet of the outdoor heat exchanger 23 is connected to port b of the four-way valve 22 through the refrigerant pipe 62, and the other refrigerant inlet/outlet is connected to the liquid side closing valve 25 through the outdoor unit liquid pipe 63. There is. The outdoor heat exchanger 23 functions as a condenser when the air conditioner 1 performs a cooling operation, and functions as an evaporator when the air conditioner 1 performs a heating operation, by switching the four-way valve 22 described later.
　暖房運転時における膨張弁２４は、制御部２００の制御のもと（図１Ｂ参照）、図示しないパルスモータにより駆動される電子膨張弁である。具体的には、パルスモータに加えられるパルス数によりその開度が調整される。膨張弁２４は、圧縮機２１に吸入される冷媒の温度と圧力から求める吸入過熱度が所定の目標温度となるように、その開度が調整される。 The expansion valve 24 during heating operation is an electronic expansion valve driven by a pulse motor (not shown) under the control of the control unit 200 (see FIG. 1B). Specifically, the opening degree is adjusted by the number of pulses applied to the pulse motor. The opening degree of the expansion valve 24 is adjusted so that the degree of suction superheat determined from the temperature and pressure of the refrigerant sucked into the compressor 21 becomes a predetermined target temperature.
　室外ファン２７は樹脂材で形成されており、室外熱交換器２３の近傍に配置されている。室外ファン２７は、その中心部が図示しないファンモータの回転軸に接続されている。ファンモータが回転することで室外ファン２７が回転する。室外ファン２７の回転によって、室外機２の図示しない吸込口から室外機２の内部へ外気を取り込み、室外熱交換器２３において冷媒と熱交換した外気を、室外機２の図示しない吹出口から室外機２外部へ放出する。 The outdoor fan 27 is made of a resin material and is placed near the outdoor heat exchanger 23. The outdoor fan 27 has its center connected to a rotating shaft of a fan motor (not shown). The outdoor fan 27 rotates as the fan motor rotates. As the outdoor fan 27 rotates, outside air is drawn into the outdoor unit 2 from an inlet (not shown) of the outdoor unit 2, and the outside air, which has undergone heat exchange with the refrigerant in the outdoor heat exchanger 23, is sent outside from an outlet (not shown) of the outdoor unit 2. Release to outside of machine 2.
　以上説明した構成の他に、室外機２には各種のセンサが設けられている。図１Ａに示すように、吐出管６１には、圧縮機２１から吐出される冷媒の圧力（吐出圧力）を検出する吐出圧力センサ７１と、圧縮機２１から吐出される冷媒の温度（吐出温度）を検出する吐出温度センサ７３が設けられている。吸入管６６には、圧縮機２１に吸入される冷媒の圧力を検出する吸入圧力センサ７２と、圧縮機２１に吸入される冷媒の温度を検出する吸入温度センサ７４が、室外機液管６３には、暖房運転時に膨張弁２４から流出した冷媒の温度を検出する図示しない室外機液管温度センサが設けられている。 In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, the discharge pipe 61 includes a discharge pressure sensor 71 that detects the pressure (discharge pressure) of the refrigerant discharged from the compressor 21 and the temperature (discharge temperature) of the refrigerant discharged from the compressor 21. A discharge temperature sensor 73 is provided to detect the temperature. The suction pipe 66 includes a suction pressure sensor 72 that detects the pressure of the refrigerant sucked into the compressor 21 and a suction temperature sensor 74 that detects the temperature of the refrigerant sucked into the compressor 21. is provided with an outdoor unit liquid pipe temperature sensor (not shown) that detects the temperature of the refrigerant flowing out from the expansion valve 24 during heating operation.
　また、圧縮機２１には、圧縮機２１の駆動するモータ２１ａが設けられている。制御部２００は、このモータ２１ａから圧縮機２１の現在の周波数を情報として読み取ることができる圧縮機状態検出部として機能する。 Furthermore, the compressor 21 is provided with a motor 21a that drives the compressor 21. The control unit 200 functions as a compressor state detection unit that can read the current frequency of the compressor 21 as information from the motor 21a.
　室外熱交換器２３の図示しない冷媒パスの略中間部には、室外熱交換器２３の温度である室外熱交温度を検出する熱交温度センサ７５が設けられている。そして、室外機２の図示しない吸込口付近には、室外機２の内部に流入する外気の温度、すなわち外気温度を検出する外気温度センサ７６が備えられている。 A heat exchanger temperature sensor 75 that detects the outdoor heat exchanger temperature, which is the temperature of the outdoor heat exchanger 23, is provided approximately in the middle of a refrigerant path (not shown) of the outdoor heat exchanger 23. An outside air temperature sensor 76 is provided near a suction port (not shown) of the outdoor unit 2 to detect the temperature of outside air flowing into the interior of the outdoor unit 2, that is, the outside air temperature.
　＜＜制御構成＞＞
　図１Ｂは、本開示の実施形態の制御構成例を示すブロック図である。図１Ｂに示すように、室外機２には、制御部２００が備えられている。制御部２００は、室外機２の図示しない電装品箱に格納されている制御基板に搭載されている。この制御部２００は、ＣＰＵ２１０と、記憶部２２０と、通信部２３０と、センサ入力部２４０を備えている。 <<Control configuration>>
FIG. 1B is a block diagram illustrating an example of a control configuration according to an embodiment of the present disclosure. As shown in FIG. 1B, the outdoor unit 2 is equipped with a control section 200. The control unit 200 is mounted on a control board stored in an electrical equipment box (not shown) of the outdoor unit 2. This control section 200 includes a CPU 210, a storage section 220, a communication section 230, and a sensor input section 240.
　記憶部２２０は、フラッシュメモリで構成されており、室外機２の制御プログラムや各種センサからの検出信号に対応した検出値、圧縮機２１、室外ファン２７、膨張弁２４等の制御状態等を記憶している。また、図示は省略するが、記憶部２２０には室内機３から受信する要求能力に応じて圧縮機２１の周波数を定めた周波数テーブルが予め記憶されている。 The storage unit 220 is composed of a flash memory, and stores the control program for the outdoor unit 2, detected values corresponding to detection signals from various sensors, control states of the compressor 21, outdoor fan 27, expansion valve 24, etc. are doing. Although not shown, the storage unit 220 stores in advance a frequency table in which the frequency of the compressor 21 is determined according to the required capacity received from the indoor unit 3.
　通信部２３０は、室内機３との通信を行うインターフェイスである。センサ入力部２４０は、室外機２の各種センサでの検出結果を取り込んでＣＰＵ２１０に出力する。 The communication unit 230 is an interface that communicates with the indoor unit 3. The sensor input unit 240 takes in detection results from various sensors of the outdoor unit 2 and outputs them to the CPU 210.
　ＣＰＵ２１０は、前述した室外機２の各センサでの検出結果を、センサ入力部２４０を介して取り込む。さらには、冷媒回路１０は、室内機３から送信される制御信号を、通信部２３０を介して取り込む。ＣＰＵ２１０は、取り込んだ検出結果や制御信号等に基づいて、圧縮機２１や室外ファン２７の駆動制御を行う。また、ＣＰＵ２１０は、取り込んだ検出結果や制御信号に基づいて、四方弁２２の切替制御を行う。さらには、ＣＰＵ２１０は、取り込んだ検出結果や制御信号に基づいて、膨張弁２４の開度調整を行う。具体的には、制御部２００は、暖房運転時において、吸入圧力センサ７２の検出値である吸入（蒸発）圧力、又は、熱交温度センサ７５の検出値である蒸発温度と、吸入温度センサ７４の検出値である吸入温度とから圧縮機２１に吸入される冷媒の吸入過熱度を取得する吸入過熱度取得部として機能する。吸入過熱度は、予め蒸発圧力（温度）と吸入温度に対応付けられたテーブルや関数等が記憶部２２０に記憶されており、ＣＰＵ２１０は各検出値を入力として記憶部２２０から吸入過熱度を取得する。取得した吸入過熱度が目標値となるように膨張弁２４の開度調整を行う。また、ＣＰＵ２１０は、圧縮機２１の出口近傍に設置された圧力センサの検出結果等に基づいて冷媒の吐出圧力を算出し、その吐出圧力が低いほど吸入過熱度の目標値を大きい値にする（詳細は後述する）。 The CPU 210 takes in the detection results from each sensor of the outdoor unit 2 described above via the sensor input section 240. Furthermore, the refrigerant circuit 10 receives a control signal transmitted from the indoor unit 3 via the communication unit 230. The CPU 210 controls the drive of the compressor 21 and the outdoor fan 27 based on the acquired detection results, control signals, and the like. Further, the CPU 210 performs switching control of the four-way valve 22 based on the captured detection results and control signals. Furthermore, the CPU 210 adjusts the opening degree of the expansion valve 24 based on the acquired detection results and control signals. Specifically, during the heating operation, the control unit 200 controls the suction (evaporation) pressure, which is the value detected by the suction pressure sensor 72, or the evaporation temperature, which is the value detected by the heat exchanger temperature sensor 75, and the suction temperature sensor 74. It functions as a suction superheat degree acquisition unit that acquires the suction superheat degree of the refrigerant sucked into the compressor 21 from the suction temperature which is the detected value of. Regarding the degree of suction superheat, tables and functions that are associated with evaporation pressure (temperature) and suction temperature are stored in the storage unit 220 in advance, and the CPU 210 acquires the degree of suction superheat from the storage unit 220 by inputting each detected value. do. The opening degree of the expansion valve 24 is adjusted so that the acquired suction superheat degree becomes the target value. Further, the CPU 210 calculates the discharge pressure of the refrigerant based on the detection result of a pressure sensor installed near the outlet of the compressor 21, and sets the target value of the degree of suction superheat to a larger value as the discharge pressure is lower ( (Details will be described later).
　＜＜室内機の冷媒回路＞＞
　次に、図１Ａを用いて、室内機３について説明する。室内機３は、室内熱交換器３１と、室内ファン３２と、液管４の他端が接続された液管接続部３３と、ガス管５の他端が接続されたガス管接続部３４を備えている。そして、室内ファン３２を除くこれら各装置が以下で詳述する各冷媒配管で相互に接続されて、冷媒回路１０の一部をなす室内機冷媒回路１０ｂを形成している。 <<Refrigerant circuit of indoor unit>>
Next, the indoor unit 3 will be explained using FIG. 1A. The indoor unit 3 includes an indoor heat exchanger 31, an indoor fan 32, a liquid pipe connection part 33 to which the other end of the liquid pipe 4 is connected, and a gas pipe connection part 34 to which the other end of the gas pipe 5 is connected. We are prepared. These devices except for the indoor fan 32 are connected to each other through refrigerant piping, which will be described in detail below, to form an indoor unit refrigerant circuit 10b that forms a part of the refrigerant circuit 10.
　室内熱交換器３１は、冷媒と後述する室内ファン３２の回転により室内機３の図示しない吸込口から室内機３の内部に取り込まれた室内空気を熱交換させるものである。室内熱交換器３１の一方の冷媒出入口は、液管接続部３３と室内機液管６７で接続されている。室内熱交換器３１の他方の冷媒出入口は、ガス管接続部３４と室内機ガス管６８で接続されている。室内熱交換器３１は、空気調和機１が冷房運転を行う場合は蒸発器として機能し、室内機３が暖房運転を行う場合は凝縮器として機能する。 The indoor heat exchanger 31 exchanges heat with indoor air taken into the indoor unit 3 from a suction port (not shown) of the indoor unit 3 using a refrigerant and the rotation of an indoor fan 32 (described later). One refrigerant inlet/outlet of the indoor heat exchanger 31 is connected to the liquid pipe connection part 33 by an indoor unit liquid pipe 67. The other refrigerant inlet and outlet of the indoor heat exchanger 31 is connected to the gas pipe connecting portion 34 through an indoor unit gas pipe 68. The indoor heat exchanger 31 functions as an evaporator when the air conditioner 1 performs a cooling operation, and functions as a condenser when the indoor unit 3 performs a heating operation.
　室内ファン３２は樹脂材で形成されており、室内熱交換器３１の近傍に配置されている。室内ファン３２は、図示しないファンモータによって回転することで、室内機３の図示しない吸込口から室内機３の内部に室内空気を取り込み、室内熱交換器３１において冷媒と熱交換した室内空気を室内機３の図示しない吹出口から室内へ吹き出す。 The indoor fan 32 is made of resin material and is placed near the indoor heat exchanger 31. The indoor fan 32 is rotated by a fan motor (not shown), draws indoor air into the interior of the indoor unit 3 from a suction port (not shown) of the indoor unit 3, and exchanges heat with a refrigerant in the indoor heat exchanger 31 to return the indoor air to the room. The air is blown into the room from the air outlet (not shown) of the machine 3.
　以上説明した構成の他に、室内機３には各種のセンサが設けられている。室内機液管６７には、空気調和機１に流入あるいは空気調和機１から流出する冷媒の温度を検出する液側温度センサ７７ａが設けられている。室内機ガス管６８には、室内熱交換器３１から流出あるいは室内熱交換器３１に流入する冷媒の温度を検出するガス側温度センサ７８が設けられている。そして、室内機３の図示しない吸込口付近には、室内機３の内部に流入する室内空気の温度、すなわち室温を検出する室温センサ７９が備えられている。 In addition to the configuration described above, the indoor unit 3 is provided with various sensors. The indoor unit liquid pipe 67 is provided with a liquid-side temperature sensor 77a that detects the temperature of the refrigerant flowing into or out of the air conditioner 1. The indoor unit gas pipe 68 is provided with a gas-side temperature sensor 78 that detects the temperature of the refrigerant flowing out from or flowing into the indoor heat exchanger 31 . A room temperature sensor 79 is provided near a suction port (not shown) of the indoor unit 3 to detect the temperature of indoor air flowing into the interior of the indoor unit 3, that is, the room temperature.
　＜＜冷媒回路の動作の概要＞＞
　次に、本実施形態における空気調和機１の空調運転時の冷媒回路１０における冷媒の流れや各部の動作について、より詳しくは図２を用いて説明するが、図１Ａを用いてその概要をまず説明する。以下では、図中、実線で示した冷媒の流れに基づいて、室内機３が暖房運転を行う場合について説明する。なお、破線で示した冷媒の流れが冷房運転を示している。 <<Overview of refrigerant circuit operation>>
Next, the flow of the refrigerant and the operation of each part in the refrigerant circuit 10 during air conditioning operation of the air conditioner 1 in this embodiment will be explained in more detail using FIG. 2, but the outline will first be explained using FIG. 1A. explain. In the following, a case will be described in which the indoor unit 3 performs heating operation based on the flow of refrigerant indicated by a solid line in the figure. Note that the flow of refrigerant indicated by a broken line indicates cooling operation.
　室内機３が暖房運転を行う場合、ＣＰＵ２１０は、図１Ａに示すように四方弁２２を実線で示す状態、すなわち、室外機２のポートａとポートｄが連通するよう、また、ポートｂとポートｃが連通するよう、切り替える。これにより、冷媒回路１０において実線矢印で示す方向に冷媒が循環し、室外熱交換器２３が蒸発器として機能するとともに、室内熱交換器３１が凝縮器として機能する暖房サイクルとなる。 When the indoor unit 3 performs heating operation, the CPU 210 sets the four-way valve 22 to the state shown by the solid line as shown in FIG. Switch so that c is connected. Thereby, the refrigerant circulates in the direction shown by the solid arrow in the refrigerant circuit 10, resulting in a heating cycle in which the outdoor heat exchanger 23 functions as an evaporator and the indoor heat exchanger 31 functions as a condenser.
　圧縮機２１から吐出された高圧の冷媒は、吐出管６１を流れて四方弁２２に流入する。四方弁２２のポートａに流入した冷媒は、四方弁２２のポートｄから室外機ガス管６４を流れて、ガス側閉鎖弁２６を介してガス管５に流入する。ガス管５を流れる冷媒は、ガス管接続部３４を介して室内機３に流入する。 The high-pressure refrigerant discharged from the compressor 21 flows through the discharge pipe 61 and flows into the four-way valve 22. The refrigerant that has flowed into the port a of the four-way valve 22 flows through the outdoor unit gas pipe 64 from the port d of the four-way valve 22 and flows into the gas pipe 5 via the gas-side closing valve 26. The refrigerant flowing through the gas pipe 5 flows into the indoor unit 3 via the gas pipe connection part 34.
　室内機３に流入した冷媒は、室内機ガス管６８を流れて室内熱交換器３１に流入し、室内ファン３２の回転により室内機３の内部に取り込まれた室内空気と熱交換を行って凝縮する。このように、室内熱交換器３１が凝縮器として機能し、室内熱交換器３１で冷媒と熱交換を行って暖められた室内空気が図示しない吹出口から室内に吹き出されることによって、室内機３が設置された室内の暖房が行われる。 The refrigerant flowing into the indoor unit 3 flows through the indoor unit gas pipe 68 and flows into the indoor heat exchanger 31, where it exchanges heat with the indoor air taken into the indoor unit 3 by the rotation of the indoor fan 32, and is condensed. do. In this way, the indoor heat exchanger 31 functions as a condenser, and the indoor air heated by exchanging heat with the refrigerant in the indoor heat exchanger 31 is blown indoors from the outlet (not shown), so that the indoor unit 3 is installed in the room.
　室内熱交換器３１から流出した冷媒は、室内機液管６７を流れ、液管接続部３３を介して液管４に流入する。液管４を流れ、液側閉鎖弁２５を介して室外機２に流入した冷媒は、室外機液管６３を流れて膨張弁２４を通過する際に減圧される。暖房運転時において、圧縮機２１に吸入される冷媒の吸入過熱度（吸入ＳＨ）が所定の目標値となるように調整される。 The refrigerant flowing out of the indoor heat exchanger 31 flows through the indoor unit liquid pipe 67 and flows into the liquid pipe 4 via the liquid pipe connection part 33. The refrigerant flowing through the liquid pipe 4 and flowing into the outdoor unit 2 via the liquid-side closing valve 25 is depressurized when flowing through the outdoor unit liquid pipe 63 and passing through the expansion valve 24 . During heating operation, the suction superheat degree (suction SH) of the refrigerant sucked into the compressor 21 is adjusted to a predetermined target value.
　膨張弁２４を通過して室外熱交換器２３に流入した冷媒は、室外ファン２７の回転により室外機２の内部に取り込まれた外気と熱交換を行って蒸発する。室外熱交換器２３から冷媒配管６２に流出した冷媒は、四方弁２２のポートｂ及びポートｃ、吸入管６６を流れ、圧縮機２１に吸入されて再び圧縮される。 The refrigerant that has passed through the expansion valve 24 and entered the outdoor heat exchanger 23 exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 27, and evaporates. The refrigerant flowing out from the outdoor heat exchanger 23 into the refrigerant pipe 62 flows through ports b and c of the four-way valve 22 and the suction pipe 66, and is sucked into the compressor 21 and compressed again.
　＜＜冷媒回路の動作の詳細＞＞
　次に、本実施形態における空気調和機１の空調運転時の冷媒回路１０における冷媒の流れや各部の動作について、図２から図６Ｂを用いて詳しく説明する。 <<Details of refrigerant circuit operation>>
Next, the flow of refrigerant and the operation of each part in the refrigerant circuit 10 during air conditioning operation of the air conditioner 1 in this embodiment will be described in detail using FIGS. 2 to 6B.
　＜＜基本的な冷媒回路＞＞
　図２及び図３を用いて、基本的な冷媒回路について説明する。図２は、基本的な冷媒回路１１を説明する図である。図３は、図２の冷媒回路１１に係るモリエル線図（ｐｈ線図）である。 <<Basic refrigerant circuit>>
A basic refrigerant circuit will be explained using FIGS. 2 and 3. FIG. 2 is a diagram illustrating the basic refrigerant circuit 11. FIG. 3 is a Mollier diagram (ph diagram) relating to the refrigerant circuit 11 of FIG. 2.
　図２に示すように、空気調和機１における基準点として、点Ａは圧縮機２１と凝縮器（暖房運転時の室内熱交換器３１に対応する。以下、凝縮器３１と表記）の間、点Ｂは凝縮器３１と膨張弁２４の間、点Ｃは膨張弁２４と蒸発器（暖房運転時の室外熱交換器２３に対応する。以下、蒸発器２３と表記）の間、点Ｄは蒸発器２３と圧縮機２１の間を指す（以下同様）。 As shown in FIG. 2, as a reference point in the air conditioner 1, point A is between the compressor 21 and the condenser (corresponding to the indoor heat exchanger 31 during heating operation, hereinafter referred to as the condenser 31). Point B is between the condenser 31 and the expansion valve 24, point C is between the expansion valve 24 and the evaporator (corresponding to the outdoor heat exchanger 23 during heating operation, hereinafter referred to as the evaporator 23), and point D is between the expansion valve 24 and the evaporator (corresponding to the outdoor heat exchanger 23 during heating operation. It refers to the space between the evaporator 23 and the compressor 21 (the same applies below).
　点Ａから点Ｄ、又は各点間における冷媒の状態は、図３に示すように、以下のとおりとなる。（１）圧縮機２１での圧縮過程の冷媒（点Ｄ～Ａ間）は、圧縮され、圧力（縦軸）・温度共に上昇して高温高圧の過熱蒸気となる（周囲空気との熱交換で凝縮しやすい状態になる）。（２）圧縮機２１から吐出された冷媒（点Ａ）は、過熱状態の高圧気相冷媒である。（３）凝縮器３１での凝縮過程の冷媒（点Ａ～Ｂ間）は、周囲の空気と熱交換（放熱）することで、圧力が一定のまま、過熱蒸気、飽和蒸気、湿り蒸気、飽和液の各状態を経て高圧の過冷却液となる。（４）凝縮器３１から流出した冷媒（点Ｂ）は、過冷却状態の高圧液相冷媒である。（５）膨張弁２４での膨張過程の冷媒（点Ｂ～Ｃ間）は、膨張し、圧力（縦軸）・温度共に低下して湿り蒸気となる（周囲空気との熱交換で蒸発しやすい状態になる）。（６）膨張弁２４から流出した冷媒（点Ｃ）は、液リッチ（＝液相比率が高い）状態の低圧二相冷媒である。（７）蒸発器２３での蒸発過程の冷媒（点Ｃ～Ｄ間）は、周囲の空気と熱交換（吸熱）することで、圧力が一定のまま、湿り蒸気、飽和蒸気、の各状態を経て低圧の過熱蒸気となる。（８）蒸発器２３から流出した冷媒（点Ｄ）は、過熱状態の低圧気相冷媒である。 The state of the refrigerant from point A to point D or between each point is as shown in FIG. 3 as follows. (1) The refrigerant (between points D and A) during the compression process in the compressor 21 is compressed, and both the pressure (vertical axis) and temperature rise to become high-temperature, high-pressure superheated steam (through heat exchange with the surrounding air) (becomes easily condensed). (2) The refrigerant discharged from the compressor 21 (point A) is a high-pressure gas phase refrigerant in a superheated state. (3) The refrigerant (between points A and B) in the condensation process in the condenser 31 exchanges heat (radiates heat) with the surrounding air, so that the pressure remains constant and the refrigerant is converted into superheated steam, saturated steam, wet steam, and saturated steam. After going through various liquid states, it becomes a high-pressure supercooled liquid. (4) The refrigerant flowing out from the condenser 31 (point B) is a supercooled high-pressure liquid phase refrigerant. (5) During the expansion process in the expansion valve 24, the refrigerant (between points B and C) expands, and both the pressure (vertical axis) and temperature decrease, becoming wet steam (easily evaporated by heat exchange with the surrounding air). state). (6) The refrigerant flowing out from the expansion valve 24 (point C) is a low-pressure two-phase refrigerant in a liquid-rich (=high liquid phase ratio) state. (7) The refrigerant in the evaporation process in the evaporator 23 (between points C and D) exchanges heat (endotherm) with the surrounding air, thereby maintaining the state of wet steam and saturated steam while keeping the pressure constant. After that, it becomes low-pressure superheated steam. (8) The refrigerant flowing out from the evaporator 23 (point D) is a superheated low-pressure gas phase refrigerant.
　この基本的な冷媒回路１１における制御対象である圧縮機２１、室内ファン３２、膨張弁２４及び室外ファン２７の制御方法は、次のとおりである。圧縮機２１は、室内機３側から要求される能力に基づいて制御される（要求される能力：室内熱交換器３１（暖房運転時：凝縮器、冷房時：蒸発器）の周囲温度（＝室温）と目標温度の差に応じて算出）。室内ファン３２は、暖房運転時（凝縮器が室内熱交換器３１の場合）冷房運転時（凝縮器が室外熱交換器２３の場合）ともに室温と設定温度の差に応じて制御、若しくはユーザによって好みの風量となるように設定される。膨張弁２４は、点Ａの温度（吐出温度）が目標値となるように制御（吐出温度制御）、又は、圧縮機２１の周波数の変化量に応じて予め定めた制御量（パルス）で膨張弁２４の開度を調整する制御（周波数パルス制御）によって制御される。なお、吐出温度制御は、室内温度や外気温等の外乱が吐出温度の変化に現れてから開度調整を行うフィードバック制御であるのに対し、周波数パルス制御は、周波数の変化量から循環量の変化量を予測して予め膨張弁２４が適正な開度となるように調整を行うフィードフォワード制御である。室外ファン２７は、暖房運転時（蒸発器が熱源側の場合）冷房運転時（蒸発器が利用側の場合）ともに圧縮機２１の周波数に基づいて制御される。 The control method for the compressor 21, indoor fan 32, expansion valve 24, and outdoor fan 27, which are controlled objects in this basic refrigerant circuit 11, is as follows. The compressor 21 is controlled based on the capacity required from the indoor unit 3 side (required capacity: ambient temperature (= (calculated according to the difference between the room temperature) and the target temperature). The indoor fan 32 is controlled according to the difference between the room temperature and the set temperature during both heating operation (when the condenser is the indoor heat exchanger 31) and cooling operation (when the condenser is the outdoor heat exchanger 23), or is controlled by the user. The air volume is set to your preference. The expansion valve 24 is controlled so that the temperature at point A (discharge temperature) becomes a target value (discharge temperature control), or expands by a predetermined control amount (pulse) according to the amount of change in the frequency of the compressor 21. It is controlled by control (frequency pulse control) that adjusts the opening degree of the valve 24. Discharge temperature control is feedback control that adjusts the opening after disturbances such as indoor temperature or outside temperature appear in changes in discharge temperature, whereas frequency pulse control adjusts the circulation amount based on the amount of change in frequency. This is feedforward control that predicts the amount of change and adjusts the expansion valve 24 to an appropriate opening degree in advance. The outdoor fan 27 is controlled based on the frequency of the compressor 21 during both heating operation (when the evaporator is on the heat source side) and cooling operation (when the evaporator is on the user side).
　基本的な冷媒回路１１における運転上の制約は、次のとおりである。点Ｂでは冷媒が液相状態である（＝過冷却が取れている）ことが求められる。なぜならば、膨張弁２４に二相冷媒が流入すると、冷媒流動音の発生や、制御性の悪化などの不都合が生じるからである。点Ｄでは冷媒が気相状態である（＝過熱が取れている）ことが求められる。なぜならば、圧縮機２１に液相冷媒が流入すると液圧縮（液相冷媒は非圧縮性であるため、圧縮機２１が破損する。）が発生し、信頼性が低下するからである。 The basic operational constraints in the refrigerant circuit 11 are as follows. At point B, the refrigerant is required to be in a liquid phase (=supercooled). This is because when two-phase refrigerant flows into the expansion valve 24, problems such as generation of refrigerant flow noise and deterioration of controllability occur. At point D, the refrigerant is required to be in a gaseous state (=superheated). This is because when liquid phase refrigerant flows into the compressor 21, liquid compression occurs (liquid phase refrigerant is incompressible, so the compressor 21 is damaged), and reliability decreases.
　図４は、冷凍機油への冷媒の溶解度を説明する説明図である。図４において、横軸は冷凍機油に対する冷媒の溶解度（重量パーセント）を示し、縦軸は冷媒の圧力を示している。また、図４に示す各グラフは、冷媒の温度が３０℃、４０℃、５０℃、６０℃、７０℃、８０℃の場合における、冷媒の圧力と、冷凍機油に対する冷媒の溶解度との関係を示している。 FIG. 4 is an explanatory diagram illustrating the solubility of refrigerant in refrigerating machine oil. In FIG. 4, the horizontal axis shows the solubility (weight percent) of the refrigerant in refrigerating machine oil, and the vertical axis shows the pressure of the refrigerant. In addition, each graph shown in Figure 4 shows the relationship between the refrigerant pressure and the solubility of the refrigerant in refrigerating machine oil when the refrigerant temperature is 30°C, 40°C, 50°C, 60°C, 70°C, and 80°C. It shows.
　図４に示すように、冷媒の温度が低いと、冷媒の圧力の上昇によって冷凍機油への溶解度は急激に増加する。冷凍機油へ冷媒が溶解すると、冷凍機油が希釈されることで粘度が小さくなり、圧縮機の摺動部が適切に潤滑されなくなるという潤滑不良を生じ、圧縮機の信頼性を低下させる場合がある。また、冷凍機油に冷媒が溶け込むことで凝縮器に供給される冷媒の量が減る状態（冷媒不足）となり、空調能力の低下を引き起こすこととなる。 As shown in FIG. 4, when the temperature of the refrigerant is low, the solubility in refrigerating machine oil increases rapidly due to the increase in the pressure of the refrigerant. When refrigerant dissolves in refrigeration oil, the refrigeration oil is diluted and its viscosity decreases, resulting in poor lubrication in which the sliding parts of the compressor are no longer properly lubricated, which may reduce the reliability of the compressor. . Furthermore, as the refrigerant dissolves in the refrigerating machine oil, the amount of refrigerant supplied to the condenser is reduced (refrigerant shortage), resulting in a decrease in air conditioning capacity.
　したがって、このような冷凍機油への冷媒の溶解度の増加を抑制するため、本開示の実施形態の制御部２００では、検出した冷媒の吐出圧力が低いほど（吐出圧力が低いほど吐出温度が低くなるため）、吸入過熱度の目標値を大きな値に設定し、吸入過熱度が当該目標値になるように膨張弁２４の開度を制御する。このように、吸入過熱度の目標値を大きな値に設定することで吐出温度が上昇し、冷凍機油への冷媒の溶解量が減少するため、暖房運転起動時における空調能力の低下を抑制できる。 Therefore, in order to suppress such an increase in the solubility of the refrigerant in the refrigerating machine oil, the control unit 200 according to the embodiment of the present disclosure sets the control unit 200 such that the lower the detected discharge pressure of the refrigerant (the lower the discharge pressure, the lower the discharge temperature). Therefore, the target value of the degree of suction superheat is set to a large value, and the opening degree of the expansion valve 24 is controlled so that the degree of suction superheat reaches the target value. In this way, by setting the target value of the degree of suction superheat to a large value, the discharge temperature increases and the amount of refrigerant dissolved in the refrigerating machine oil decreases, so it is possible to suppress a decrease in the air conditioning capacity at the time of starting the heating operation.
　図５は、本開示の実施形態の制御部の動作例を示すフローチャートである。図５に示すように、処理が開始されると、制御部２００は、設定温度等の初期設定を取得し（Ｓ１）、センサ入力部２４０を介して各種センサの検出結果を取得する（Ｓ２）。 FIG. 5 is a flowchart illustrating an example of the operation of the control unit according to the embodiment of the present disclosure. As shown in FIG. 5, when the process is started, the control unit 200 acquires initial settings such as set temperature (S1), and acquires detection results of various sensors via the sensor input unit 240 (S2). .
　ついで、制御部２００は、センサ入力部２４０を介して取得した吸入温度センサ７４の検出値及び吸入圧力センサ７２の検出値をもとに、冷媒の吸入過熱度を算出する（Ｓ３）。 Next, the control unit 200 calculates the suction superheat degree of the refrigerant based on the detection value of the suction temperature sensor 74 and the detection value of the suction pressure sensor 72 acquired via the sensor input unit 240 (S3).
　ついで、制御部２００は、圧縮機２１の周波数を検出する（Ｓ４）。 Next, the control unit 200 detects the frequency of the compressor 21 (S4).
　ついで、制御部２００は、センサ入力部２４０を介して取得したセンサの検出値をもとに、冷媒の吐出圧力を取得する圧力取得部として機能する（Ｓ５）。 Next, the control unit 200 functions as a pressure acquisition unit that acquires the refrigerant discharge pressure based on the sensor detection value acquired via the sensor input unit 240 (S5).
　また、制御部２００は、Ｓ４において検出した圧縮機２１の状態をもとに、冷媒の吐出圧力を算出してもよい。例えば、制御部２００は、回転数と吐出圧力との対応関係を規定した対応テーブルや関数等を参照して吐出圧力を取得する。吐出圧力は検出された圧縮機２１の回転数が小さいほど、低い値となる。同様に、制御部２００は、要求能力と吐出圧力との対応関係を規定した対応テーブルや関数等を参照して吐出圧力を取得する。吐出圧力は検出された圧縮機２１に対する要求能力が小さいほど、低値となる。 Furthermore, the control unit 200 may calculate the refrigerant discharge pressure based on the state of the compressor 21 detected in S4. For example, the control unit 200 obtains the discharge pressure by referring to a correspondence table, a function, etc. that defines the correspondence between the rotation speed and the discharge pressure. The lower the detected rotational speed of the compressor 21, the lower the discharge pressure becomes. Similarly, the control unit 200 obtains the discharge pressure by referring to a correspondence table, a function, etc. that defines the correspondence between the required capacity and the discharge pressure. The smaller the detected capacity required of the compressor 21, the lower the discharge pressure becomes.
　ついで、制御部２００は、算出した吐出圧力にもとに、記憶部２２０に記録された対応テーブルなどを参照し、冷媒の吸入過熱度（吸入スーパーヒート（ＳＨ）の目標値を設定する（Ｓ６）。具体的には、吸入過熱度の目標値は算出した吐出圧力に対応して決定され、算出した吐出圧力が低いほど大きい値となる。 Next, the control unit 200 refers to the correspondence table recorded in the storage unit 220 based on the calculated discharge pressure, and sets a target value for the suction superheat degree (suction superheat (SH)) of the refrigerant (S6 ).Specifically, the target value of the suction superheat degree is determined in accordance with the calculated discharge pressure, and the lower the calculated discharge pressure, the larger the value becomes.
　図６Ａは、要求能力と吸入過熱度の目標値との関係を説明する説明図である。図６Ａにおいて横軸は算出した吐出圧力（要求能力／圧力機周波数）を示し、縦軸は吸入過熱度にかかる目標値（吸入スーパーヒート（ＳＨ））を示している。図６Ａに示すように、制御部２００は、吐出圧力（要求能力／圧力機周波数）が低いほど、吸入過熱度の目標値が段階的に高くなるように変化させる。なお、吐出圧力の低下に応じて目標値を高くする構成は、図示例のような段階的な変化に限定するものではなく、例えば滑らかな線形変化であってもよい。 FIG. 6A is an explanatory diagram illustrating the relationship between the required capacity and the target value of the degree of suction superheat. In FIG. 6A, the horizontal axis shows the calculated discharge pressure (required capacity/pressure machine frequency), and the vertical axis shows the target value for the degree of suction superheat (suction superheat (SH)). As shown in FIG. 6A, the control unit 200 changes the target value of the suction superheat degree so that the lower the discharge pressure (required capacity/pressure machine frequency) is, the higher the target value of the degree of suction superheat is. Note that the configuration in which the target value is increased in response to a decrease in the discharge pressure is not limited to a stepwise change as shown in the illustrated example, and may be, for example, a smooth linear change.
　ついで、制御部２００は、Ｓ６で設定した目標値をもとに、膨張弁２４の開度を制御する（Ｓ７）。 Next, the control unit 200 controls the opening degree of the expansion valve 24 based on the target value set in S6 (S7).
　図６Ｂは、要求能力と吸入過熱度の目標値との関係を説明する説明図である。図６Ｂにおいて、上段は要求能力が「小」（吐出圧力が小さい）の場合のモリエル線図（ｐｈ線図）の概要を示している。また、下段は要求能力が「大」（吐出圧力が大きい）の場合のモリエル線図（ｐｈ線図）の概要を示している。ＣＰＵ２１０は、図６Ｂに示すように、要求能力が大きい場合と比較して、要求能力が小さい（吐出圧力がより小さい）場合は、蒸発器出口の冷媒飽和蒸気線（右側曲線）よりも右側の領域に大きく変位する（過熱度を大きくする）ように目標値（Ｓ６で設定した目標値）を設定する。 FIG. 6B is an explanatory diagram illustrating the relationship between the required capacity and the target value of the degree of suction superheat. In FIG. 6B, the upper row shows an outline of a Mollier diagram (ph diagram) when the required capacity is "small" (discharge pressure is small). Moreover, the lower row shows an outline of a Mollier diagram (ph diagram) when the required capacity is "large" (discharge pressure is large). As shown in FIG. 6B, when the required capacity is small (the discharge pressure is smaller) compared to when the required capacity is large, the CPU 210 moves to the right side of the refrigerant saturated vapor line (right curve) at the evaporator outlet. The target value (the target value set in S6) is set so as to make a large displacement in the region (increase the degree of superheating).
　これにより、冷凍機油への冷媒の溶解度が低下し、冷媒の溶解量が減少するため、暖房運転起動時における空調能力の低下を抑制できる。特に、Ｒ２９０（プロパン）冷媒を用いる場合は、Ｒ３２冷媒と比較して、吐出温度が低くなり、冷凍機油への冷媒の溶解量が増加する傾向がある。これに対し、本開示の空気調和機１では、吸入過熱度の目標値を大きい値にすることで、Ｒ２９０（プロパン）冷媒の冷凍機油へ溶解量を減少させ、Ｒ２９０（プロパン）冷媒を用いる場合においても、暖房運転起動時における空調能力の低下を抑制できる。 As a result, the solubility of the refrigerant in the refrigerating machine oil decreases, and the amount of refrigerant dissolved decreases, so it is possible to suppress a decrease in the air conditioning capacity at the time of starting the heating operation. In particular, when using R290 (propane) refrigerant, the discharge temperature tends to be lower and the amount of refrigerant dissolved in refrigerating machine oil tends to increase compared to R32 refrigerant. In contrast, in the air conditioner 1 of the present disclosure, by setting the target value of the suction superheat degree to a large value, the amount of R290 (propane) refrigerant dissolved in the refrigerating machine oil is reduced, and when using R290 (propane) refrigerant, Also, it is possible to suppress a decrease in air conditioning capacity at the time of starting heating operation.
　以上のように、空気調和機１は、圧縮機２１、凝縮器（暖房運転時：室内熱交換器３１、冷房運転時：室外熱交換器２３）、膨張弁２４および蒸発器（暖房運転時：室外熱交換器２３、冷房運転時：室内熱交換器３１）を有し、冷媒を循環させる冷媒回路１０を有する。また、空気調和機１は、圧縮機２１の吸入過熱度を取得する吸入過熱度取得部と、圧縮機２１の吐出圧力を取得する圧力取得部としての機能を有する制御部２００とを有する。また、空気調和機１は、吸入過熱度が目標値となるように膨張弁２４の開度を制御するとともに、吐出圧力が低いほど吸入過熱度の目標値を大きい値にする制御部２００を有する。これにより、空気調和機１では、冷凍機油への冷媒の溶解量が減少するため、暖房運転起動時における空調能力の低下を抑制できる。 As described above, the air conditioner 1 includes the compressor 21, the condenser (indoor heat exchanger 31 during heating operation, the outdoor heat exchanger 23 during cooling operation), the expansion valve 24, and the evaporator (during heating operation: It has an outdoor heat exchanger 23, an indoor heat exchanger 31 during cooling operation, and a refrigerant circuit 10 that circulates refrigerant. The air conditioner 1 also includes a suction superheat degree acquisition section that acquires the suction superheat degree of the compressor 21 and a control section 200 that functions as a pressure acquisition section that acquires the discharge pressure of the compressor 21. The air conditioner 1 also includes a control unit 200 that controls the opening degree of the expansion valve 24 so that the degree of suction superheat reaches a target value, and sets the target value of the degree of suction superheat to a larger value as the discharge pressure decreases. . As a result, in the air conditioner 1, the amount of refrigerant dissolved in the refrigerating machine oil is reduced, so that it is possible to suppress a decrease in the air conditioning capacity when starting the heating operation.
１…空気調和機
２…室外機
３…室内機
４…液管
５…ガス管
１０、１１…冷媒回路
１０ａ…室外機冷媒回路
１０ｂ…室内機冷媒回路
２１…圧縮機
２１ａ…モータ
２２…四方弁
２３…室外熱交換器
２４…膨張弁
２５…液側閉鎖弁
２６…ガス側閉鎖弁
２７…室外ファン
３１…室内熱交換器
３２…室内ファン
３３…液管接続部
３４…ガス管接続部
６１…吐出管
６２…冷媒配管
６３…室外機液管
６４…室外機ガス管
６６…吸入管
６７…室内機液管
６８…室内機ガス管
７１…吐出圧力センサ
７２…吸入圧力センサ
７３…吐出温度センサ
７４…吸入温度センサ
７５…熱交温度センサ
７６…外気温度センサ
７７ａ…液側温度センサ
７８…ガス側温度センサ
７９…室温センサ
２００…制御部
２１０…ＣＰＵ
２２０…記憶部
２３０…通信部
２４０…センサ入力部
Ａ～Ｄ…点
ａ～ｄ…ポート 1...Air conditioner 2...Outdoor unit 3...Indoor unit 4...Liquid pipe 5...Gas pipes 10, 11...Refrigerant circuit 10a...Outdoor unit refrigerant circuit 10b...Indoor unit refrigerant circuit 21...Compressor 21a...Motor 22...Four-way valve 23...Outdoor heat exchanger 24...Expansion valve 25...Liquid side closing valve 26...Gas side closing valve 27...Outdoor fan 31...Indoor heat exchanger 32...Indoor fan 33...Liquid pipe connection part 34...Gas pipe connection part 61... Discharge pipe 62... Refrigerant pipe 63... Outdoor unit liquid pipe 64... Outdoor unit gas pipe 66... Suction pipe 67... Indoor unit liquid pipe 68... Indoor unit gas pipe 71... Discharge pressure sensor 72... Suction pressure sensor 73... Discharge temperature sensor 74 ...Suction temperature sensor 75...Heat exchange temperature sensor 76...Outside air temperature sensor 77a...Liquid side temperature sensor 78...Gas side temperature sensor 79...Room temperature sensor 200...Control unit 210...CPU
220...Storage unit 230...Communication unit 240...Sensor input unit A to D...Points a to d...Ports

Claims (4)

  1. 　圧縮機、凝縮器、膨張弁および蒸発器を有し、冷媒を循環させる冷媒回路と、
    　前記圧縮機の吸入過熱度を取得する吸入過熱度取得部と、
    　前記圧縮機の吐出圧力を取得する圧力取得部と、
    　前記吸入過熱度が目標値となるように前記膨張弁の開度を制御するとともに、前記吐出圧力が低いほど前記目標値を大きい値にする制御部と、
    　を有することを特徴とする空気調和機。     a refrigerant circuit that includes a compressor, a condenser, an expansion valve, and an evaporator and circulates refrigerant;
    a suction superheat degree acquisition unit that acquires a suction superheat degree of the compressor;
    a pressure acquisition unit that acquires the discharge pressure of the compressor;
    a control unit that controls the opening degree of the expansion valve so that the suction superheat degree becomes a target value, and sets the target value to a larger value as the discharge pressure is lower;
    An air conditioner characterized by having.
  2. 　前記圧縮機の周波数を検出する圧縮機状態検出部を有し、
    　前記検出された周波数が小さいほど、前記吐出圧力は低値とする、
    　ことを特徴とする請求項１に記載の空気調和機。     a compressor state detection unit that detects a frequency of the compressor;
    The smaller the detected frequency is, the lower the discharge pressure is.
    The air conditioner according to claim 1, characterized in that:
  3. 　前記圧縮機に対する要求能力を検出する圧縮機状態検出部を有し、
    　前記検出された圧縮機に対する要求能力が小さいほど、前記吐出圧力は低値とする、
    　ことを特徴とする請求項１に記載の空気調和機。     comprising a compressor state detection unit that detects a required capacity for the compressor;
    The smaller the detected capacity required for the compressor, the lower the discharge pressure.
    The air conditioner according to claim 1, characterized in that:
  4. 　前記冷媒は、Ｒ２９０（プロパン）である、
    　ことを特徴とする請求項１乃至３のいずれか一項に記載の空気調和機。     The refrigerant is R290 (propane),
    The air conditioner according to any one of claims 1 to 3, characterized in that:
PCT/JP2023/012451 2022-03-30 2023-03-28 Air conditioner WO2023190486A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04297759A (en) * 1991-03-27 1992-10-21 Matsushita Electric Ind Co Ltd Multichamber air conditioner
JPH10253170A (en) * 1997-03-12 1998-09-25 Daikin Ind Ltd Air conditioner
JP2001227822A (en) * 2000-02-17 2001-08-24 Mitsubishi Electric Corp Refrigerating air conditioner
KR20090081909A (en) * 2008-01-25 2009-07-29 엘지전자 주식회사 Air conditioner and method for controlling the same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04297759A (en) * 1991-03-27 1992-10-21 Matsushita Electric Ind Co Ltd Multichamber air conditioner
JPH10253170A (en) * 1997-03-12 1998-09-25 Daikin Ind Ltd Air conditioner
JP2001227822A (en) * 2000-02-17 2001-08-24 Mitsubishi Electric Corp Refrigerating air conditioner
KR20090081909A (en) * 2008-01-25 2009-07-29 엘지전자 주식회사 Air conditioner and method for controlling the same

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