JP5618801B2 - Air conditioner - Google Patents

Description

The present invention relates to an air conditioner that uses R32 (chemical formula CH ₂ F ₂ , HFC32 (difluoromethane)) alone or a mixed refrigerant containing at least 70 percent by weight of R32 as the refrigerant.

Challenges to the global environment in air conditioners that operate refrigeration cycles using refrigerants include protection of the ozone layer, global warming response (reducing CO ₂ emissions, etc.), energy saving, and resource reuse (recycling). is there.

Among these global environmental issues, for the protection of the ozone layer, the refrigerant used is R22 (HFC22), which has a high ozone destruction coefficient, and R410A (HFC32: HFC125 = 50: 50 (weight ratio)) where the ozone destruction coefficient is zero. The air conditioner switched to) has already been commercialized. Incidentally, HFC125 is a chemical formula _CHF 2 -CF ₃ (chemical name pentafluoroethane).

On the other hand, the demand for global warming prevention measures is increasing. In an air conditioner, evaluation is performed using a global warming index called a total equivalent warming impact (TEWI). This TEWI is the CO ₂ that is emitted to produce the energy consumed when producing the materials that make up the air conditioner, as well as the effects (direct effects) due to the atmospheric release of the refrigerant and the energy consumption (indirect effects) of the device. It is expressed as the sum of

  For the calculation of TEWI, the global warming potential GWP (Global Warming Potential) of refrigerant, the amount of refrigerant, and the annual energy consumption efficiency APF (Annual Performance Factor) representing the efficiency of the air conditioner are used. In order to prevent global warming, it is necessary to select a refrigerant having a small GWP value and a large APF value in order to reduce the TEWI value.

  Currently used R410A has a GWP of 2090, which is larger than the conventionally used R22 of 1810. Therefore, in order to prevent global warming, hydrocarbon-based R290 has been developed as a refrigerant with a GWP value of zero, and HFO1234yf has been developed as a low GWP refrigerant with a GWP of 50 or less. Therefore, R32 (HFC32) is cited as a candidate as a refrigerant having a relatively low GWP.

  The GWP value of R32 is 675, which is about 1/3 compared to the GWP values of R22 and R410A, and can reduce the impact on global warming. However, compared to R290 and HFO1234yf, Therefore, when using R32, it is necessary to reduce the amount of refrigerant.

As for energy saving, CO ₂ is indirectly discharged by power consumption when the air conditioner is operated. Therefore, the performance of the air conditioner is enhanced to save energy, thereby contributing to the prevention of global warming.

In home air conditioners, the proportion of indirect CO ₂ emissions due to power consumption during use accounts for a large proportion. Therefore, by promoting energy saving, it is possible to reduce CO ₂ emissions. When R32 is used as the refrigerant, it is not a low GWP refrigerant as described above. Therefore, in order to reduce the influence on global warming, it is necessary to reduce the amount of refrigerant while simultaneously realizing energy saving.

JP 2001-194016 A

  As a conservation measure for the global environment, the refrigerant used as the working fluid of a household refrigeration cycle apparatus was changed from HCFC, which is a fluorocarbon gas that destroys the ozone layer, to R410A, which is an HFC that does not destroy the ozone layer. In recent years, in addition to protecting the ozone layer, the importance of preventing global warming has increased, and as a working fluid for refrigeration cycle devices, refrigerants that not only destroy the ozone layer but also have a low global warming potential are sought. It is getting to be. For this reason, it is effective as a countermeasure against global warming to use R32 which is about 1/3 of R410A GWP. However, since R32 has slight flammability, it is required to reduce the amount of refrigerant sealed in the device as much as possible from the viewpoints of global warming countermeasures and ensuring safety.

R32 is characterized in that the liquid density is smaller than that of R410A as a physical property of the refrigerant. Saturated liquid density at 20 ° C. for R410A is ^{1083.1 [kg / m 3],} R32 is 981.4kg / ^{m 3]} at R32 for R410A, is a liquid density of about 90.6% . For this reason, the mass of the refrigerant with the same internal volume is smaller in R32.

  Further, R32 has a feature that the pressure loss when passing through the pipe is smaller than that of R410A and is about 70%.

  Considering the characteristics of the refrigerant physical properties of R32, it is effective to reduce the pipe diameter of the heat exchanger in order to reduce the refrigerant amount. However, when the pipe cross-sectional area is reduced to 70% or less, the pressure loss per pipe increases, so it is a good idea to reduce the pressure loss by increasing the number of passes.

  In the calculation of APF, the ratio of energy consumption efficiency (COP) during heating operation is high, so in order to achieve a high APF value, it is effective to increase the efficiency in heating operation and to obtain high energy efficiency. It is important to maximize the heat transfer performance of heat exchangers.

  The heat transfer performance of the heat exchanger is mainly determined by heat transfer between the fin and air (external heat transfer) and heat transfer between the pipe inner surface of the pipe and the refrigerant (internal heat transfer). The heat transfer in the tube is high when the state of the refrigerant is in the gas-liquid two-phase state, and the heat transfer coefficient decreases when the liquid single-phase state is reached. In the gas-liquid two-phase state, the refrigerant changes in latent heat, so the temperature hardly changes, but in the liquid single-phase state, the sensible heat changes, so by exchanging heat with air, the temperature of the refrigerant moves toward the outlet. Decreases, the temperature difference between the air and the refrigerant decreases, and heat transfer outside the tube also decreases. In particular, when the temperature of the refrigerant becomes the same as the temperature of the air passing through the fins, heat exchange is not performed, and the heat exchanger does not function.

  In order to obtain high performance as a heat exchanger, subcooling should be used to increase the area of the heat exchanger where the refrigerant is in a gas-liquid two-phase state and to increase the enthalpy difference from the inlet to the outlet of the heat exchanger. It must be large.

  As this means, a configuration in which an auxiliary heat exchanger is mounted in addition to the main heat exchanger and a subcooling is secured by the auxiliary heat exchanger is used.

  It is desirable that the subcool region, which is in the liquid phase, is stored in the auxiliary heat exchanger, and the main heat exchanger is operated so as to be in a gas-liquid two-phase state.

  However, when the diameter of the heat exchanger tube is reduced using R32 as the refrigerant, a wide range can be made into a subcooling region with a small amount of refrigerant compared to the conventional case. The sensitivity of the change in the subcool region to the change in the amount becomes high, and the phenomenon that the subcool region expands in the main heat exchanger is likely to occur.

  If the subcooling region where the heat transfer coefficient in the tube and the heat transfer rate outside the tube are low spreads to the main heat exchanger, the heat transfer performance of the main heat exchanger decreases, and at the same time, the refrigerant temperature near the outlet of the auxiliary heat exchanger Since the temperature difference becomes small asymptotically approaching the temperature of the passing air, the heat transfer performance of the auxiliary heat exchanger is also lowered. As a result, COP decreases.

  The present invention has been made to solve the above-described problems. By using R32 having a low global warming potential GWP as a refrigerant, the amount of refrigerant is reduced as compared with the conventional technique, and high energy consumption efficiency (COP) is achieved. To provide energy-saving air conditioners that respond to global warming.

The air conditioner according to the present invention uses HFC32 (difluoromethane) as a working fluid, compresses the working fluid, a four-way valve that switches the flow direction of the working fluid, an indoor heat exchanger, a pressure reducing device, an outdoor A refrigeration cycle in which heat exchangers are sequentially connected;
A control unit for controlling the refrigeration cycle;
In an air conditioner that switches the flow direction of the refrigeration cycle by a four-way valve between cooling operation and heating operation,
The indoor heat exchanger
A main heat exchanger;
An auxiliary heat exchanger,
In the flow direction of the refrigerant in the heating operation, a condensation temperature thermistor that is provided near the middle point of the refrigerant flow path length of the main heat exchanger and detects the condensation temperature;
An auxiliary heat exchanger thermistor that detects an auxiliary heat exchanger pipe temperature near the inlet of the auxiliary heat exchanger in the flow direction of the refrigerant in the heating operation,
Based on the detection results of the condensing temperature thermistor and the auxiliary heat exchanger thermistor, the control unit stores the subcool region, which is the liquid phase of the refrigeration cycle, in the auxiliary heat exchanger, and the main heat exchanger The decompression device is controlled so as to be in a two-phase state.

  In the air conditioner according to the present invention, the control unit stores the subcool region, which is the liquid phase of the refrigeration cycle, in the auxiliary heat exchanger based on the detection results of the condensation temperature thermistor and the auxiliary heat exchanger thermistor. At the same time, by controlling the pressure reducing device so that the main heat exchanger is in a gas-liquid two-phase state, the range of the subcool region is stabilized, and the COP during the heating operation of the air conditioner can be stably kept high. I can do it. Thereby, R32 is used for a refrigerant | coolant, a heat exchanger can be reduced in diameter, a refrigerant | coolant amount can be reduced, and an air conditioner with a high energy-saving property and a small influence on global warming can be implement | achieved.

FIG. 3 shows the first embodiment, and is a refrigerant circuit diagram of the air conditioner 100. FIG. FIG. 5 shows the first embodiment and is an exploded perspective view of the indoor unit 100b. FIG. 5 shows the first embodiment and is a longitudinal sectional view of the indoor unit 100b. FIG. 3 shows the first embodiment and is a configuration diagram of the indoor heat exchanger 5. Fig. 5 shows the first embodiment, and is a conceptual diagram showing a refrigerant flow in the indoor heat exchanger 5 during heating operation. The figure which shows Embodiment 1 and is a block diagram of the indoor heat exchanger 105 of the modification which used the flat tube 18 for a part. FIG. 5 shows the first embodiment, and shows the change in refrigerant temperature from the inlet to the outlet of the indoor heat exchanger 5. FIG. The figure which shows Embodiment 1 and the figure which shows the state in which the range of the sub-crule area | region in the indoor heat exchanger 5 is appropriate. The figure which shows Embodiment 1 and the figure which shows the state in which the range of the sub-crule area | region in the indoor heat exchanger 5 is too wide. FIG. 6 is a diagram illustrating the second embodiment, and is a longitudinal sectional view of the compressor 1.

Embodiment 1 FIG.
FIG. 1 is a diagram showing the first embodiment, and is a refrigerant circuit diagram of the air conditioner 100. First, an example of a refrigerant circuit of an air conditioner will be described with reference to FIG.

  The air conditioner 100 includes an outdoor unit 100a and an indoor unit 100b. The outdoor unit 100a and the indoor unit 100b are connected by a gas pipe extension pipe 4 and a liquid pipe extension pipe 6 which are extension pipes (connection pipes).

  The outdoor unit 100a includes a charge valve closed valve 3 connected to the gas pipe extension pipe 4 and a liquid pipe stop valve 7 connected to the liquid pipe extension pipe 6 at the end on the extension pipe side.

  Copper pipes having a predetermined diameter and length are used for the gas pipe extension pipe 4 and the liquid pipe extension pipe 6. When the air conditioner 100 is installed, the gas pipe extension pipe 4 and the liquid pipe extension pipe 6 are made in accordance with the local situation.

  The outdoor unit 100a includes a compressor 1 that compresses a refrigerant (working fluid), a four-way valve 2 that switches a refrigerant flow direction between a cooling operation and a heating operation, an outdoor heat exchanger 9 that is a heat source side heat exchanger, and a decompression device 8 Is provided.

  As the compressor 1 that compresses the refrigerant, for example, a rotary compressor, a scroll compressor, or the like is used. Although not shown, the compressor 1 houses a compression mechanism (also referred to as a compression element) and an electric motor (also referred to as an electric element) for driving the compression mechanism in a hermetically sealed container, and includes a sliding portion of the compression mechanism. The refrigerating machine oil to be lubricated is enclosed in an airtight container. As the electric motor, a brushless DC motor capable of torque control with high efficiency is often used. The brushless DC motor is driven by an inverter and the rotation speed is controlled.

  In FIG. 1, the four-way valve 2 that switches the refrigerant flow direction between the cooling operation and the heating operation is indicated by a solid line in FIG. Moreover, the flow path of the refrigerant | coolant at the time of heating operation is shown with the broken line.

  The outdoor heat exchanger 9 which is a heat source side heat exchanger operates as a condenser during the cooling operation, and operates as an evaporator during the heating operation. Moreover, ventilation is performed to the outdoor heat exchanger 9 by an outdoor blower (not shown), and heat exchange between the refrigerant and the air is promoted.

  For the decompression device 8, for example, an electronic expansion valve is used.

  In addition, a discharge temperature thermistor 10 that measures the temperature of the discharge gas discharged from the compressor 1 is attached to the compressor 1 at a predetermined position (for example, a discharge pipe (not shown)).

  The indoor unit 100b includes an indoor heat exchanger 5 that is a use side heat exchanger. The indoor heat exchanger 5 operates as an evaporator during the cooling operation. Moreover, it operates as a condenser during heating operation. In addition, air is sent to the indoor heat exchanger 5 by an indoor blower (not shown) to promote heat exchange between the refrigerant and the air, and conditioned air is sent to the conditioned space.

  As will be described later, a dehumidifying valve 35 that is normally open and closed during reheat dehumidifying operation is provided at a predetermined position inside the indoor heat exchanger 5. Description of the dehumidifying valve 35 is omitted.

  In the refrigerant circuit of the air conditioner 100, R32 (HFC32) is used as a working fluid as a refrigerant having a relatively low GWP.

  FIG. 2 shows the first embodiment, and is an exploded perspective view of the indoor unit 100b. The present embodiment is characterized by the indoor heat exchanger 5 of the indoor unit 100b or parts (described later) attached to the indoor heat exchanger 5. First, the overall configuration of the indoor unit 100b will be described.

As shown in FIG. 2, the indoor unit 100b includes the following elements.
(1) Front opening / closing panel 41: The front opening / closing panel 41 is attached to the front of the indoor unit 100b so as to be freely opened and closed.
(2) Front frame body 42: The front frame body 42 constitutes the front surface of the outer wall of the indoor unit 100b and supports the front opening / closing panel 41.
(3) Drain pan 43: The drain pan 43 receives defrost water generated from the indoor heat exchanger 5. Moreover, the back surface of the drain pan 43 serves as a conditioned air flow guide portion that constitutes the upper surface of the air path from the indoor blower 46 to the outlet (described later).
(4) Automatic filter cleaning mechanism 44: The automatic filter cleaning mechanism 44 is a mechanism for automatically cleaning a filter (not shown) that removes dust contained in indoor air.
(5) Indoor heat exchanger 5: Details of the indoor heat exchanger 5 will be described later.
(6) Electrical component box 45: The electrical component box 45 stores, for example, a board on which a microcomputer or the like constituting a control unit that performs indoor control is mounted.
(7) Indoor blower 46: The indoor blower 46 blows conditioned air generated by the indoor heat exchanger 5 into the room. Normally, a cross flow fan is used for the indoor blower 46. The drive unit that drives the crossflow fan of the indoor blower 46 includes a mold stator that includes a substrate on which the inverter unit is mounted, and a rotor (including a shaft and a bearing) that uses a permanent magnet (usually a resin magnet). An electric motor provided with a bracket is used.
(8) Support frame 47: It constitutes the back of the outer wall of the indoor unit 100b and supports the indoor heat exchanger 5, the indoor blower 46, and the like.

  FIG. 3 shows the first embodiment and is a longitudinal sectional view of the indoor unit 100b. As shown in FIG. 3, a suction port 48 for sucking room air is formed on the upper surface of the indoor unit 100b. In the vicinity of the suction port 48, a filter (not shown) of the automatic filter cleaning mechanism 44 is arranged to remove dust from indoor air.

  A substantially inverted V-shaped indoor heat exchanger 5 is disposed so as to face the suction port 48. Details of the indoor heat exchanger 5 will be described later.

  An indoor blower 46 is disposed inside the substantially inverted V-shaped indoor heat exchanger 5 (on the side opposite to the suction port 48).

  An air outlet 49 that opens into the room is formed in the lower part of the indoor unit 100b. The air outlet 49 is provided with a wind direction control unit 50 that controls the air direction of the conditioned air. The wind direction control unit 50 illustrated in FIG. 3 controls the wind direction in the vertical direction. Although not shown, a device that controls the wind direction in the left-right direction is also used.

  A drain pan 43 is provided below the indoor heat exchanger 5. The drain pan 43 receives the defrost water generated in the indoor heat exchanger 5, and the defrost water temporarily stored in the drain pan 43 is discharged from the drain hose connected to the drain pan 43 to the outside. In addition, although the drain pan is provided also in the back surface, description is abbreviate | omitted.

  4 and 5 are diagrams showing Embodiment 1, FIG. 4 is a configuration diagram of the indoor heat exchanger 5, and FIG. 5 is a conceptual diagram showing a refrigerant flow in the indoor heat exchanger 5 during heating operation. As shown in FIG. 4, the substantially inverted V-shaped indoor heat exchanger 5 includes a main heat exchanger 14 and an auxiliary heat exchanger 15.

  The main heat exchanger 14 is formed in a substantially inverted V shape, and includes a front upper main heat exchanger 14a, a front lower main heat exchanger 14b, and a rear main heat exchanger 14c.

  In the refrigerant circuit of the main heat exchanger 14, the front lower main heat exchanger 14b and the rear main heat exchanger 14c are connected in parallel, and the front upper main heat exchanger 14a is connected to these via a dehumidification valve 35 therebetween. Is done.

  The condensation temperature thermistor 12 is provided between the dehumidification valve 35 and the front upper main heat exchanger 14a.

  The auxiliary heat exchanger 15 includes a front upper auxiliary heat exchanger 15a and a front lower auxiliary heat exchanger 15b. The refrigerant circuits of the front upper auxiliary heat exchanger 15a and the front lower auxiliary heat exchanger 15b are connected in series.

  An auxiliary heat exchanger thermistor 13 that detects the temperature of the auxiliary heat exchanger pipe 17 is provided in the front lower auxiliary heat exchanger 15b.

  For example, during the heating operation of the air conditioner 100, as shown in FIGS. 4 and 5, the gas refrigerant that has passed through the four-way valve 2 is converted into the front lower main heat exchanger 14b (two passes) and the rear main heat exchanger 14c. (2 passes). Thereafter, the refrigerant that flows into the dehumidifying valve 35 and exits the dehumidifying valve 35 flows into the front upper main heat exchanger 14a (two passes). Further, after flowing in the order of the front lower auxiliary heat exchanger 15b (1 pass) and the front upper auxiliary heat exchanger 15a (1 pass), the flow proceeds to the decompression device 8.

  To reduce the amount of refrigerant enclosed in the refrigerant circuit, the main heat exchanger pipe 16 of the main heat exchanger 14 is not a circular pipe having an outer diameter of 7 mm widely used in R410A, but an outer diameter of 5 mm or 4 mm. Or a flat tube 18 in which the inside of the tube is divided into a plurality of spaces by partition walls as shown in FIG.

  FIG. 6 is a diagram showing the first embodiment, and is a configuration diagram of a modified indoor heat exchanger 105 in which the flat tube 18 is partially used. The indoor heat exchanger 105 of the modified example has substantially the same configuration as the indoor heat exchanger 5 shown in FIG. 4 and has a main heat exchanger 114 (front upper main heat exchanger 114a, front lower main heat exchanger 114b, rear main heat exchanger 114). Heat exchanger 114c) and auxiliary heat exchanger 115 (front upper auxiliary heat exchanger 115a, front lower auxiliary heat exchanger 115b).

  A feature of the indoor heat exchanger 105 of the modification is that a flat tube 18 is used for the piping of the main heat exchanger 114. The flat tube 18 is divided into a plurality of spaces by a partition wall, and contributes to a reduction in the amount of refrigerant enclosed in the refrigerant circuit.

  On the other hand, in order to secure the heat transfer area with the air and not to increase the ventilation resistance in the main heat exchanger 14, the area of the fin 19 is made equal to the case of R410A. The cross-sectional area of the main heat exchanger pipe 16 is about half of the outer diameter of 5 mm and about one third of the outer diameter of 4 mm compared to the outer diameter of 7 mm.

In order to detect the temperature of the indoor heat exchanger 5, an auxiliary for detecting the temperature of the refrigerant in a pipe near the inlet of the auxiliary heat exchanger 15 (pipe of the lower front auxiliary heat exchanger 15b) in the refrigerant flow during the heating operation. A heat exchanger thermistor 13 is provided. The detected temperature of the auxiliary heat exchanger thermistor 13 is _TSCin .

Further, a condensation temperature thermistor 12 for detecting the condensation temperature is installed near the intermediate point of the refrigerant flow path length of the main heat exchanger 14 (a pipe between the dehumidification valve 35 and the front upper main heat exchanger 14a). . The detected temperature of the condensation temperature thermistor 12, and _{T C.}

  FIG. 7 is a diagram showing the first embodiment, and is a diagram showing a change in refrigerant temperature from the inlet to the outlet of the indoor heat exchanger 5, and FIG. 8 is an appropriate range of the sub-crule area in the indoor heat exchanger 5. FIG. 9 is a diagram showing a state where the range of the sub-clur region in the indoor heat exchanger 5 is too wide.

  The horizontal axis of FIG. 7 is the pipe length [m] from the inlet of the indoor heat exchanger 5, and the vertical axis is the refrigerant temperature [° C.]. FIG. 7 shows the positions of the condensation temperature thermistor 12 and the auxiliary heat exchanger thermistor 13.

A detected temperature _{T C} of the condensation temperature thermistor 12, the difference between the detected temperature _{T SCIN} of the auxiliary heat exchanger thermistor 13, and [Delta] T.
_{ΔT = T C - T SCin (} 1)

  The energy consumption efficiency (COP) at the time of heating operation is the best when the refrigerant is not in the liquid phase (gas-liquid two-phase state) in the main heat exchanger 14 and the subcool is the largest. . That is, it is desirable to control the auxiliary heat exchanger 15 so that the refrigerant is in a liquid phase and the main heat exchanger 14 is in a gas-liquid two-phase state (see, for example, FIG. 8).

  In order to keep this state stable, the control unit (not shown) sets the target value range of ΔT from Ta to Tb (Ta <Tb), and from the relationship between ΔT and the values of Ta and Tb, Control the aperture.

  As shown in FIG. 7, the auxiliary heat exchanger thermistor 13 attached to the auxiliary heat exchanger 15 is attached to a position where the temperature is lower than the condensing temperature even when the subcool is in an appropriate state. Set the value.

  When ΔT <Ta, since the subcool region is small, the control unit performs control to narrow down the decompression device 8.

  When Ta <ΔT <Tb, since the subcool is appropriate, the control unit does not perform control.

  When Tb <ΔT, since the subcool is large, the subcool region extends to a part of the main heat exchanger 14 (see, for example, FIG. 9), and the energy consumption efficiency (COP) during heating operation is appropriate for the subcool. Compared to Therefore, the control unit performs control to open the decompression device 8.

  By performing the above control, the control unit can stably keep the subcool region within the predetermined range of the indoor heat exchanger 5, and stably adjust the air conditioning in a state where the efficiency of the indoor heat exchanger 5 is high. The machine 100 can be operated.

Embodiment 2. FIG.
FIG. 10 shows the second embodiment and is a longitudinal sectional view of the compressor 1. The compressor 1 which comprises the refrigerant circuit of the air conditioner 100 of FIG. 1 is a 2-cylinder rotary compressor as shown in FIG. 10, for example. Since the two-cylinder rotary compressor is a known one, a detailed description is omitted.

  The compressor 1 stores a two-cylinder rotary compression mechanism 1a that compresses refrigerant, an electric motor 1b (for example, a brushless DC motor) that drives the compression mechanism 1a, and the like in a sealed container 1d. When the compression mechanism 1a is driven by the electric motor 1b, the refrigerant (R32) is compressed, and high-temperature and high-pressure refrigerant gas is discharged into the sealed container 1d. The discharged gas passes through the electric motor 1b and travels from the discharge pipe 1c to the four-way valve 2 of the refrigerant circuit.

  A discharge temperature thermistor 10 that detects the temperature of the discharge gas discharged from the compressor 1 is attached to the discharge pipe 1c.

  A sealed container temperature thermistor 11 that detects the temperature of the sealed container 1d is attached to the upper surface of the sealed container 1d near the discharge pipe 1c.

  However, either the discharge temperature thermistor 10 or the closed container temperature thermistor 11 is attached.

  In the configuration of the refrigerant circuit and the heat exchanger of the first embodiment, the temperature (discharge temperature) detected by the discharge temperature thermistor 10 attached to the discharge pipe 1c of the compressor 1 is used to control the throttle of the decompression device 8. .

  Further, instead of the discharge temperature thermistor 10, the closed container temperature detected by the closed container temperature thermistor 11 attached to the upper surface of the closed container 1d near the discharge pipe 1c may be used.

  The target discharge temperature is set for each rotation speed of the compressor 1, and the control unit controls the throttle of the decompression device 8 so that the target set temperature is reached. The controller throttles the opening of the decompression device 8 when the detected discharge temperature is lower than the target value, and opens the opening of the decompression device 8 when the detected discharge temperature is higher than the target value.

  In order to stabilize the subcool region in the above discharge temperature control, correction is made to the target temperature of the discharge temperature.

  When ΔT <Ta, the target temperature of the discharge temperature is corrected to be higher by α ° C.

  When Ta <ΔT <Tb, the target discharge temperature is not corrected.

  When Tb <ΔT, the target temperature of the discharge temperature is corrected to be lower by β ° C.

  The target temperature correction values α and β are set according to the specifications of the indoor heat exchanger 5.

  As described above, by correcting the target value of the basic control for controlling the opening degree of the decompression device 8, it is possible to realize the control that stabilizes the subcool region without greatly changing the basic control.

  DESCRIPTION OF SYMBOLS 1 Compressor, 1a Compression mechanism part, 1b Electric motor, 1c Discharge pipe, 1d Sealed container, 2 Four-way valve, 3 Close valve with charge port, 4 Gas pipe extension pipe, 5 Indoor heat exchanger, 6 Liquid pipe extension pipe, 7 Liquid pipe closing valve, 8 Pressure reducing device, 9 Outdoor heat exchanger, 10 Discharge temperature thermistor, 11 Sealed container temperature thermistor, 12 Condensation temperature thermistor, 13 Auxiliary heat exchanger thermistor, 14 Main heat exchanger, 14a Front upper main heat exchange 14b Front lower main heat exchanger, 14c Rear main heat exchanger, 15 Auxiliary heat exchanger, 15a Front upper auxiliary heat exchanger, 15b Front lower auxiliary heat exchanger, 16 Main heat exchanger piping, 17 Auxiliary heat exchange Equipment piping, 18 flat tube, 35 dehumidification valve, 41 front open / close panel, 42 front frame, 43 drain pan, 44 filter automatic cleaning mechanism, 45 electrical box, 46 Indoor blower, 47 support frame, 48 suction port, 49 air outlet, 50 air direction control unit, 100 air conditioner, 100a outdoor unit, 100b indoor unit.

Claims (8)

A refrigeration cycle in which HFC32 (difluoromethane) is used as a refrigerant, and at least a compressor, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger are connected in order,
A control unit for controlling the refrigeration cycle,
The indoor heat exchanger is
The refrigerant which is arranged inside the outer wall of the indoor unit and divided into a front side, an upper side, a front side, a lower side and a back side of the indoor unit, and compressed into the gas state by the compressor during heating operation A main heat exchanger that exchanges heat with air;
Auxiliary heat for exchanging heat between the refrigerant and the air that is arranged inside the outer wall of the indoor unit and overlaps with the main heat exchanger in the front-rear direction of the indoor unit and has exchanged heat with the main heat exchanger An exchange,
A condensation temperature thermistor for detecting the temperature of the main heat exchanger;
An auxiliary heat exchanger thermistor for detecting the temperature near the inlet of the auxiliary heat exchanger;
The controller is
Based on the detection results of the condensing temperature thermistor and the auxiliary heat exchanger thermistor, the refrigerant that has undergone heat exchange in the main heat exchanger and is in a gas-liquid two-phase state flows out of the main heat exchanger. Until the gas-liquid two-phase state is maintained, and it is determined whether or not it is in a liquid phase state near the inlet of the auxiliary heat exchanger, and according to the determination result, by controlling the opening of the expansion valve, An air conditioner that is controlled so that a subcooling region is accommodated in the auxiliary heat exchanger. The auxiliary heat exchanger is divided into a front side, an upper part, a front side, and a lower part of the indoor unit inside the outer wall of the indoor unit, and the main heat exchanger and the front part on the front side and the upper part of the indoor unit, respectively. The air conditioner according to claim 1, wherein the air conditioner is disposed so as to overlap with the main heat exchanger on the side and the lower part. Before SL condensation temperature thermistor, connected in series and a front side and a lower portion of the main heat exchanger and the front side of the rear side of the main heat exchanger and the indoor unit and the upper portion of the main heat exchanger of the indoor unit It is provided in piping, The air conditioner of Claim 1 or 2 characterized by the above-mentioned. The controller is
If the difference ΔT between the detected temperature of the condensation temperature thermistor and the detected temperature of the auxiliary heat exchanger thermistor is smaller than the lower limit Ta, the heat exchange is performed in the main heat exchanger and the gas-liquid two-phase state is obtained. If it is determined that the refrigerant is not in a liquid phase near the inlet of the auxiliary heat exchanger, the opening of the expansion valve is lowered, and if the difference ΔT is larger than the upper limit value Tb, heat exchange is performed in the main heat exchanger. It is determined that the gas-liquid two-phase state is not maintained until the refrigerant that has been put into a gas-liquid two-phase state flows out of the main heat exchanger, and the opening degree of the expansion valve is increased. Item 4. The air conditioner according to any one of Items 1 to 3 . A discharge temperature thermistor for detecting the temperature of the refrigerant when the refrigerant compressed in the compressor and in a gas state is discharged from the compressor;
The controller is
The opening of the expansion valve is controlled so that the detected temperature of the discharge temperature thermistor becomes a target set temperature, and if the difference ΔT is smaller than the lower limit value Ta, the target set temperature is set higher. The air conditioner according to claim 4 , wherein if the ΔT is larger than the upper limit value Tb, the target set temperature is set lower. A closed vessel temperature thermistor for detecting the temperature of the closed vessel of the compressor;
The controller is
The opening of the expansion valve is controlled so that the detected temperature of the hermetic container temperature thermistor becomes a target set temperature, and if the difference ΔT is smaller than the lower limit value Ta, the target set temperature is set higher, The air conditioner according to claim 4 , wherein if the difference ΔT is larger than the upper limit value Tb, the target set temperature is set lower. The air conditioner according to any one of claims 1 to 6 , wherein a circular pipe having an outer diameter of 4 to 5 mm is used for a heat exchange pipe of the main heat exchanger. The air conditioner according to any one of claims 1 to 6 , wherein a flat tube in which the inside of the tube is divided into a plurality of spaces by partition walls is used for the heat exchange pipe of the main heat exchanger.

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