JP6024222B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner capable of switching between a cooling operation and a heating operation by a four-way switching valve.

  Conventionally, as shown in Patent Documents 1 and 2 (Japanese Patent Laid-Open Nos. 2005-300056 and 2011-145017), air that can be switched between a cooling operation and a heating operation by a four-way switching valve. There is a harmony device.

  In the above conventional air conditioner, at the start of heating operation immediately after energization, the liquid refrigerant is likely to return to the suction side of the compressor under operating conditions in which the refrigerant stagnates in the compressor. For this reason, it becomes difficult to overheat the refrigerant discharged from the compressor, and the time during which the heating operation is performed in a state where the degree of superheat of the refrigerant discharged from the compressor is less than 0 deg (that is, in a wet state) becomes longer. There is a fear.

  On the other hand, in the air conditioning apparatus described in Patent Document 1, when the refrigeration cycle is initially energized, the compressor is started while the four-way switching valve is in the cooling cycle state, and the amount of refrigerant oil discharged from the compressor is When it is determined that there is a large amount, the compressor frequency is reduced and the expansion valve is closed to store refrigeration oil in the outdoor heat exchanger, and then the four-way selector valve is switched to the heating cycle state. Thus, the refrigerating machine oil accumulated in the outdoor heat exchanger is returned to the compressor to prevent the refrigerating machine oil from being insufficient in the compressor. However, in such control at the time of initial energization, liquid refrigerant easily returns to the compressor suction side along with the refrigeration oil when the four-way switching valve is switched to the heating cycle state under an operating condition in which the refrigerant stagnates in the compressor. Become. For this reason, the state where it is difficult for the refrigerant discharged from the compressor to be overheated is promoted, and there is a possibility that the time during which the heating operation is performed in a state where the degree of superheat of the refrigerant discharged from the compressor is less than 0 deg may be increased. .

  Moreover, in the air conditioning apparatus described in Patent Document 2, the operation frequency of the compressor is gradually increased at the start of startup when power supply is restored. However, in such control at the time of restoration of power supply, no special control is performed for actuators other than the compressor, so that liquid refrigerant is likely to return to the suction side of the compressor under operating conditions in which the refrigerant stagnates in the compressor. The situation is hardly improved. For this reason, the state where it is difficult for the refrigerant discharged from the compressor to be overheated is not quickly improved, and the time during which the heating operation is performed with the degree of superheat of the refrigerant discharged from the compressor being less than 0 deg is shortened. It is difficult to do.

  An object of the present invention is to provide an air conditioner capable of switching between a cooling operation and a heating operation by a four-way switching valve, and at the start of the heating operation immediately after energization, the superheat degree of the refrigerant discharged from the compressor is 0 deg. It is in shortening the time when heating operation is performed in a state less than.

An air conditioner according to a first aspect has a refrigerant circuit configured by connecting a compressor, a four-way switching valve, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, and performs a cooling operation. And heating operation can be performed. The cooling operation is an operation in which the refrigerant is circulated in the order of the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger by switching the four-way switching valve to the cooling cycle state. The heating operation is an operation in which the refrigerant is circulated in the order of the compressor, the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger by switching the four-way switching valve to the heating cycle state. And here, when starting the heating operation before the elapse of the predetermined stop time after power feeding, the operation speed of the compressor is changed to the predetermined four-way switching lower limit rotation while the four-way switching valve is switched to the cooling cycle state. The four-way switching valve switching control for switching the four-way switching valve from the cooling cycle state to the heating cycle state is performed. And after completion | finish of four-way switching valve switching control, while reducing the driving | running rotation speed of a compressor to refrigerant | coolant superheat degree increase rotation speed smaller than four-way switching lower limit rotation speed, completion | finish of four-way switching valve switching control There row refrigerant superheat increase control for less than the opening degree at the time, when starting the heating operation after a predetermined stopping time after the power supply is performed to the four-way switching valve switching control, the four-way switching valve switching control After the end of, the refrigerant superheat degree increase control is not performed.

  Here, when starting the heating operation before the elapse of the predetermined stop time after power feeding, that is, when starting the heating operation immediately after power feeding, the four-way switching is performed to switch the four-way switching valve from the cooling cycle state to the heating cycle state. After the valve switching control is performed, the refrigerant superheat degree increase control is performed to reduce the operating speed of the compressor and reduce the opening degree of the expansion valve. For this reason, unlike conventional control such as Patent Documents 1 and 2, it becomes difficult for the liquid refrigerant to return to the suction side of the compressor.

  Thereby, here, at the start of the heating operation immediately after energization, the refrigerant discharged from the compressor is likely to be overheated, and the heating operation is performed in a state where the degree of superheat of the refrigerant discharged from the compressor is less than 0 deg. Can be shortened.

An air conditioner according to a second aspect has a refrigerant circuit configured by connecting a compressor, a four-way switching valve, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, and performs a cooling operation. And heating operation can be performed. The cooling operation is an operation in which the refrigerant is circulated in the order of the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger by switching the four-way switching valve to the cooling cycle state. The heating operation is an operation in which the refrigerant is circulated in the order of the compressor, the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger by switching the four-way switching valve to the heating cycle state. And here, when starting the heating operation before the elapse of the predetermined stop time after power feeding, the operation speed of the compressor is changed to the predetermined four-way switching lower limit rotation while the four-way switching valve is switched to the cooling cycle state. The four-way switching valve switching control for switching the four-way switching valve from the cooling cycle state to the heating cycle state is performed. And after completion | finish of four-way switching valve switching control, while reducing the driving | running rotation speed of a compressor to refrigerant | coolant superheat degree increase rotation speed smaller than four-way switching lower limit rotation speed, completion | finish of four-way switching valve switching control The refrigerant superheat degree increasing control is performed to make it smaller than the opening degree at the time. In addition, during the four-way switching valve switching control and the refrigerant superheat degree increasing control, the opening of the expansion valve is controlled to increase as the operating speed of the compressor increases.

  Here, when starting the heating operation before the elapse of the predetermined stop time after power feeding, that is, when starting the heating operation immediately after power feeding, the four-way switching is performed to switch the four-way switching valve from the cooling cycle state to the heating cycle state. After the valve switching control is performed, the refrigerant superheat degree increase control is performed to reduce the operating speed of the compressor and reduce the opening degree of the expansion valve. For this reason, unlike conventional control such as Patent Documents 1 and 2, it becomes difficult for the liquid refrigerant to return to the suction side of the compressor.

  Thereby, here, at the start of the heating operation immediately after energization, the refrigerant discharged from the compressor is likely to be overheated, and the heating operation is performed in a state where the degree of superheat of the refrigerant discharged from the compressor is less than 0 deg. Can be shortened.

In addition, here, in the four-way switching valve switching control and the refrigerant superheat degree increasing control, the opening degree of the expansion valve is changed in conjunction with the operating rotational speed of the compressor.

Thereby, here, during the refrigerant superheat degree increase control, it is possible to easily simultaneously perform the control for reducing the operating speed of the compressor and the control for reducing the opening degree of the expansion valve.

An air conditioner according to a third aspect is the air conditioner according to the first or second aspect , wherein the refrigerant circuit further includes an accumulator that temporarily stores the refrigerant sucked into the compressor. Here, after the refrigerant superheat degree increasing control is completed, accumulator forming suppression control is performed to increase the operating speed of the compressor at a change rate smaller than the change rate during the normal control of the heating operation.

  When the operating rotational speed of the compressor is rapidly increased after the refrigerant superheat degree increasing control is finished, the refrigerant pressure on the suction side of the compressor is rapidly decreased. For this reason, when the liquid refrigerant has accumulated in the accumulator, the liquid refrigerant in the accumulator may evaporate rapidly, which may cause a phenomenon of foaming (forming).

  Therefore, here, after the refrigerant superheat degree increasing control is finished, control is performed to increase the operation speed of the compressor at a change speed smaller than the change speed at the time of normal control of the heating operation.

  Thereby, generation | occurrence | production of the forming in an accumulator can be suppressed here.

An air conditioner according to a fourth aspect is the air conditioner according to any one of the first to third aspects, wherein the refrigerant superheat increase control is configured such that the superheat degree of the refrigerant sucked into the compressor is a predetermined suction overheat. When the temperature exceeds the threshold value, the superheat degree of the refrigerant discharged from the compressor becomes equal to or higher than the predetermined discharge superheat degree threshold value, or when the predetermined control time has elapsed.

  Here, when the superheat degree of the refrigerant sucked into the compressor, the superheat degree of the refrigerant discharged from the compressor, or the control time is satisfied, the refrigerant superheat degree increase control is terminated.

  Thereby, here, after the state where the superheat degree of the refrigerant discharged from the compressor is less than 0 deg is reliably eliminated, it is possible to shift to accumulator forming suppression control and normal control of heating operation.

  An air conditioner according to a fifth aspect is the air conditioner according to any one of the first to fourth aspects, wherein the outdoor air as a cooling source or a heating source of the refrigerant flowing through the outdoor heat exchanger is used as the outdoor heat exchanger. And an outdoor fan for supplying indoor air to the indoor heat exchanger as a heating source or a cooling source for the refrigerant flowing through the indoor heat exchanger. Here, the outdoor fan and the indoor fan are operated during the refrigerant superheat increase control.

  Here, the outdoor fan and the indoor fan are also operated during the refrigerant superheat degree increase control.

  Thereby, here, the heating operation can be performed under the condition that the operation speed of the compressor is small.

  As described above, according to the present invention, the following effects can be obtained.

  In the air conditioner according to the first aspect, at the start of heating operation immediately after energization, the refrigerant discharged from the compressor is likely to be overheated, and heating is performed in a state where the superheat degree of the refrigerant discharged from the compressor is less than 0 deg. The time during which the operation is performed can be shortened.

In the air conditioner according to the second aspect , at the start of heating operation immediately after energization, the refrigerant discharged from the compressor is likely to be overheated, and heating is performed in a state where the degree of superheat of the refrigerant discharged from the compressor is less than 0 deg. The time during which the operation is performed can be shortened. In addition, at the time of control for increasing the degree of refrigerant superheat, control for reducing the operating speed of the compressor and control for reducing the opening of the expansion valve can be easily performed simultaneously.

In the air conditioner according to the third aspect , the occurrence of forming in the accumulator can be suppressed.

In the air conditioner according to the fourth aspect , after the state where the superheat degree of the refrigerant discharged from the compressor is surely eliminated, it is possible to shift to accumulator forming suppression control and normal control of heating operation.

  In the air conditioner according to the fifth aspect, the heating operation can be performed while the operation speed of the compressor is low.

It is a schematic block diagram of the air conditioning apparatus concerning one Embodiment of this invention. It is a control block diagram of an air conditioning apparatus. It is a flowchart of heating deenergization starting control. It is a time chart of the compressor at the time of heating deenergization starting control, an expansion valve, an outdoor fan, and an indoor fan. It is a figure which shows the relationship between the opening degree of an expansion valve and the driving | operation rotation speed of a compressor at the time of four-way switching valve switching control and refrigerant | coolant superheat degree increase control.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an air conditioner according to the present invention will be described with reference to the drawings. In addition, the specific structure of the air conditioning apparatus concerning this invention is not restricted to the following embodiment, It can change in the range which does not deviate from the summary of invention.

(1) Configuration of Air Conditioner FIG. 1 is a schematic configuration diagram of an air conditioner 1 according to an embodiment of the present invention.

  The air conditioner 1 is a device capable of cooling and heating a room such as a building by performing a vapor compression refrigeration cycle. The air conditioner 1 is mainly configured by connecting an outdoor unit 2 and an indoor unit 4. Here, the outdoor unit 2 and the indoor unit 4 are connected via a liquid refrigerant communication tube 5 and a gas refrigerant communication tube 6. That is, the vapor compression refrigerant circuit 10 of the air conditioner 1 is configured by connecting the outdoor unit 2 and the indoor unit 4 via the refrigerant communication pipes 5 and 6.

<Indoor unit>
The indoor unit 4 is installed indoors and constitutes a part of the refrigerant circuit 10. The indoor unit 4 mainly has an indoor heat exchanger 41.

  The indoor heat exchanger 41 is a heat exchanger that functions as a refrigerant evaporator during cooling operation to cool indoor air, and functions as a refrigerant radiator during heating operation to heat indoor air. The liquid side of the indoor heat exchanger 41 is connected to the liquid refrigerant communication tube 5, and the gas side of the indoor heat exchanger 41 is connected to the gas refrigerant communication tube 6.

  The indoor unit 4 has an indoor fan 42 for supplying indoor air as supply air after sucking indoor air into the indoor unit 4 and exchanging heat with the refrigerant in the indoor heat exchanger 41. That is, the indoor unit 4 has an indoor fan 42 as a fan that supplies indoor air as a heating source or cooling source of the refrigerant flowing through the indoor heat exchanger 41 to the indoor heat exchanger 41. Here, as the indoor fan 42, a centrifugal fan or a multiblade fan driven by an indoor fan motor 43 is used.

  Various sensors are provided in the indoor unit 4. Specifically, the indoor heat exchanger 41 is provided with an indoor heat exchange temperature sensor 44 that detects the temperature Trr of the refrigerant in the indoor heat exchanger 41. The indoor unit 4 is provided with an indoor air temperature sensor 45 that detects the temperature Tra of the indoor air sucked into the indoor unit 4.

  The indoor unit 4 has an indoor side control unit 46 that controls the operation of each part constituting the indoor unit 4. The indoor side control unit 46 includes a microcomputer, a memory, and the like provided for controlling the indoor unit 4, and exchanges control signals and the like with a remote controller (not shown). Control signals and the like can be exchanged with the outdoor unit 2 via the transmission line 7.

<Outdoor unit>
The outdoor unit 2 is installed outside and constitutes a part of the refrigerant circuit 10. The outdoor unit 2 mainly includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, an expansion valve 24, an accumulator 25, a liquid side closing valve 26, and a gas side closing valve 27. doing.

  The compressor 21 is a device that compresses the low-pressure refrigerant in the refrigeration cycle until the pressure becomes high. The compressor 21 has a hermetic structure in which a rotary type or scroll type positive displacement compression element (not shown) is rotationally driven by a compressor motor 21a controlled by an inverter. The compressor 21 has a suction pipe 31 connected to the suction side and a discharge pipe 32 connected to the discharge side. The suction pipe 31 is a refrigerant pipe that connects the suction side of the compressor 21 and the first port 22 a of the four-way switching valve 22. The discharge pipe 32 is a refrigerant pipe that connects the discharge side of the compressor 21 and the second port 22 b of the four-way switching valve 22.

  The four-way switching valve 22 is a switching valve for switching the direction of refrigerant flow in the refrigerant circuit 10. During the cooling operation, the four-way switching valve 22 causes the outdoor heat exchanger 23 to function as a radiator for the refrigerant compressed in the compressor 21 and the indoor heat exchanger 41 for the refrigerant that has radiated heat in the outdoor heat exchanger 23. Switch to the cooling cycle state to function as an evaporator. That is, during the cooling operation, the four-way switching valve 22 switches between the second port 22b and the third port 22c and the first port 22a and the fourth port 22d. Thereby, the discharge side of the compressor 21 (here, the discharge pipe 32) and the gas side of the outdoor heat exchanger 23 (here, the first gas refrigerant pipe 33) are connected (four-way switching valve in FIG. 1). (See 22 solid line). Moreover, the suction side (here, the suction pipe 31) of the compressor 21 and the gas refrigerant communication pipe 6 side (here, the second gas refrigerant pipe 34) are connected (solid line of the four-way switching valve 22 in FIG. 1). See). Further, the four-way switching valve 22 causes the outdoor heat exchanger 23 to function as an evaporator of the refrigerant that has radiated heat in the indoor heat exchanger 41 during the heating operation, and the indoor heat exchanger 41 is compressed in the compressor 21. Switching to a heating cycle state that functions as a refrigerant radiator. In other words, the four-way switching valve 22 switches between the second port 22b and the fourth port 22d and the first port 22a and the third port 22c during the heating operation. Thereby, the discharge side (here, the discharge pipe 32) of the compressor 21 and the gas refrigerant communication pipe 6 side (here, the second gas refrigerant pipe 34) are connected (of the four-way switching valve 22 in FIG. 1). (See dashed line). In addition, the suction side of the compressor 21 (here, the suction pipe 31) and the gas side of the outdoor heat exchanger 23 (here, the first gas refrigerant pipe 33) are connected (four-way switching valve 22 in FIG. 1). See the dashed line). The first gas refrigerant pipe 33 is a refrigerant pipe that connects the third port 22 c of the four-way switching valve 22 and the gas side of the outdoor heat exchanger 23. The second gas refrigerant pipe 33 is a refrigerant pipe connecting the fourth port 22d of the four-way switching valve 22 and the gas refrigerant communication pipe 6 side.

  The outdoor heat exchanger 23 is a heat exchanger that functions as a refrigerant radiator that uses outdoor air as a cooling source during cooling operation, and functions as a refrigerant evaporator that uses outdoor air as a heating source during heating operation. The outdoor heat exchanger 23 has a liquid side connected to the liquid refrigerant pipe 35 and a gas side connected to the first gas refrigerant pipe 33. The liquid refrigerant pipe 35 is a refrigerant pipe that connects the liquid side of the outdoor heat exchanger 23 and the liquid refrigerant communication pipe 5 side.

  The expansion valve 24 is a valve that depressurizes the high-pressure refrigerant in the refrigeration cycle that has radiated heat in the outdoor heat exchanger 23 to the low pressure in the refrigeration cycle during the cooling operation. The expansion valve 24 is a valve that reduces the high-pressure refrigerant in the refrigeration cycle radiated in the indoor heat exchanger 41 to the low pressure in the refrigeration cycle during heating operation. The expansion valve 24 is provided in a portion of the liquid refrigerant pipe 35 near the liquid side closing valve 26. Here, an electric expansion valve is used as the expansion valve 24. More specifically, as shown in FIG. 2, the expansion valve 24 mainly has a valve main body 240, a valve body 250, and a drive mechanism 260. The valve body 240 is a member in which a valve seat 242 that opens into the valve chamber 241 is formed. The valve main body 240 is formed with a first refrigerant port 243 that opens toward the side of the valve chamber 241 and a second refrigerant port 244 that opens toward the lower side of the valve chamber 241. The first refrigerant port 243 is connected to a portion of the liquid refrigerant tube 35 near the outdoor heat exchanger 23, and the second refrigerant port 244 is connected to a portion of the liquid refrigerant tube 35 near the liquid side shut-off valve 26. Has been. For this reason, the expansion valve 24 is provided in the refrigerant circuit 10 in an arrangement state (hereinafter, referred to as a “normal cycle arrangement state”) in which the refrigerant flows in the lateral direction and flows out in the downward direction during the cooling operation. The valve seat 242 is formed with an orifice hole 242a that is open so as to communicate the valve chamber 241 and the second refrigerant port 244 in the vertical direction. The valve body 250 is a member that moves up and down with respect to the valve seat 242 by the drive mechanism 260. The drive mechanism 260 includes a motor, a solenoid, and the like. With such a configuration, the expansion valve 24 depressurizes the high-pressure refrigerant in the refrigeration cycle flowing through the liquid refrigerant pipe 35 to a low pressure.

  The accumulator 25 is a container for temporarily storing the low-pressure refrigerant sucked into the compressor 21. The accumulator 25 is provided in the suction pipe 31.

  The liquid side shutoff valve 26 and the gas side shutoff valve 27 are valves provided at connection ports with external devices and pipes (specifically, the liquid refrigerant communication pipe 5 and the gas refrigerant communication pipe 6). The liquid side closing valve 26 is provided at the end of the liquid refrigerant pipe 35. The gas side closing valve 27 is provided at the end of the second gas refrigerant pipe 34.

  The outdoor unit 2 has an outdoor fan 36 for sucking outdoor air into the outdoor unit 2 and exchanging heat with the refrigerant in the outdoor heat exchanger 23 and then discharging the air to the outside. That is, the outdoor unit 2 includes an outdoor fan 36 as a fan that supplies outdoor air as a cooling source or a heating source of the refrigerant flowing through the outdoor heat exchanger 23 to the outdoor heat exchanger 23. Here, a propeller fan or the like driven by an outdoor fan motor 37 is used as the outdoor fan 36.

  Various types of sensors are provided in the outdoor unit 2. Specifically, the outdoor heat exchanger 23 is provided with an outdoor heat exchange temperature sensor 38 that detects the temperature Tor of the refrigerant in the outdoor heat exchanger 23. The outdoor unit 2 is provided with an outdoor air temperature sensor 39 that detects the temperature Toa of the outdoor air sucked into the outdoor unit 2. The suction pipe 31 or the compressor 21 is provided with a suction temperature sensor 47 that detects the temperature Ts of the low-pressure refrigerant in the refrigeration cycle sucked into the compressor 21. The suction pipe 31 or the compressor 21 is provided with a suction pressure sensor 50 that detects the pressure Ps of the low-pressure refrigerant in the refrigeration cycle sucked into the compressor 21. The discharge pipe 32 or the compressor 21 is provided with a discharge temperature sensor 48 that detects the temperature Td of the high-pressure refrigerant in the refrigeration cycle discharged from the compressor 21. The discharge pipe 32 or the compressor 21 is provided with a discharge pressure sensor 49 that detects the pressure Pd of the high-pressure refrigerant in the refrigeration cycle discharged from the compressor 21.

  The outdoor unit 2 includes an outdoor side control unit 40 that controls the operation of each unit constituting the outdoor unit 2. The outdoor control unit 40 includes a microcomputer, a memory, and the like provided for controlling the outdoor unit 2, and exchanges control signals and the like with the outdoor unit 2 via the transmission line 7. Can be done.

<Refrigerant communication pipe>
Refrigerant communication pipes 5 and 6 are refrigerant pipes constructed on site when the air conditioner 1 is installed at an installation location such as a building, and installation conditions such as the installation location and a combination of an outdoor unit and an indoor unit. Those having various lengths and tube diameters are used.

  As described above, the refrigerant circuit 10 of the air conditioner 1 is configured by connecting the outdoor unit 2, the indoor unit 4, and the refrigerant communication pipes 5 and 6. The air conditioner 1 switches the four-way switching valve 22 to the cooling cycle state, thereby circulating the refrigerant in the order of the compressor 21, the outdoor heat exchanger 23, the expansion valve 24, and the indoor heat exchanger 41, and the outdoor fan 36. Cooling operation is performed by driving. In addition, the air conditioner 1 switches the four-way switching valve 22 to the heating cycle state, thereby circulating the refrigerant in the order of the compressor 21, the indoor heat exchanger 41, the expansion valve 24, and the outdoor heat exchanger 23, and the outdoor fan. 36 is driven to perform the heating operation.

<Control unit>
The air conditioner 1 can control each device of the outdoor unit 2 and the indoor unit 4 by the control unit 8 including the indoor side control unit 46 and the outdoor side control unit 40. That is, the control unit 8 that performs the operation control of the entire air conditioner 1 including the cooling operation and the heating operation is configured by the transmission line 7 that connects between the indoor side control unit 46 and the outdoor side control unit 40. Has been.

  As shown in FIG. 3, the control unit 8 is connected so as to be able to receive detection signals from various sensors 38, 39, 44, 45, 47 to 50 and the like, and based on these detection signals and the like, It connects so that apparatus and valve 21,22,24,37,43 etc. can be controlled.

(2) Basic Operation of Air Conditioner Next, a basic operation of the air conditioner 1 (an operation excluding the heating non-energization activation control described later) will be described with reference to FIG. The air conditioner 1 can perform a cooling operation and a heating operation as basic operations.

<Cooling operation>
In the refrigerant circuit 10 in which the four-way switching valve 22 is switched to the cooling cycle state (state shown by the solid line in FIG. 1), the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21 and becomes high pressure in the refrigeration cycle. It is discharged after being compressed.

  The high-pressure gas refrigerant discharged from the compressor 21 is sent to the outdoor heat exchanger 23 through the four-way switching valve 22.

  The high-pressure gas refrigerant sent to the outdoor heat exchanger 23 performs heat exchange with the outdoor air supplied as a cooling source by the outdoor fan 36 in the outdoor heat exchanger 23 to dissipate heat to become a high-pressure liquid refrigerant. .

  The high-pressure liquid refrigerant that has radiated heat in the outdoor heat exchanger 23 is sent to the expansion valve 24.

  The high-pressure liquid refrigerant sent to the expansion valve 24 is decompressed by the expansion valve 24 to a low pressure in the refrigeration cycle, and becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the expansion valve 24 is sent to the indoor heat exchanger 41 through the liquid side closing valve 26 and the liquid refrigerant communication pipe 5.

  The low-pressure gas-liquid two-phase refrigerant sent to the indoor heat exchanger 41 evaporates by exchanging heat with indoor air supplied as a heating source by the indoor fan 42 in the indoor heat exchanger 41. As a result, the room air is cooled and then supplied to the room to cool the room.

  The low-pressure gas refrigerant evaporated in the indoor heat exchanger 41 is again sucked into the compressor 21 through the gas refrigerant communication pipe 6, the gas side closing valve 27, and the four-way switching valve 22.

<Heating operation>
In the refrigerant circuit 10 in which the four-way switching valve 22 is switched to the heating cycle state (state indicated by the broken line in FIG. 1), the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21 and becomes high pressure in the refrigeration cycle. It is discharged after being compressed.

  The high-pressure gas refrigerant discharged from the compressor 21 is sent to the indoor heat exchanger 41 through the four-way switching valve 22, the gas side closing valve 27 and the gas refrigerant communication pipe 6.

  The high-pressure gas refrigerant sent to the indoor heat exchanger 41 radiates heat by exchanging heat with indoor air supplied as a cooling source by the indoor fan 42 in the indoor heat exchanger 41 to become a high-pressure liquid refrigerant. . Thereby, indoor air is heated, and indoor heating is performed by being supplied indoors after that.

  The high-pressure liquid refrigerant radiated by the indoor heat exchanger 41 is sent to the expansion valve 24 through the liquid refrigerant communication pipe 5 and the liquid-side closing valve 26.

  The high-pressure liquid refrigerant sent to the expansion valve 24 is decompressed by the expansion valve 24 to a low pressure in the refrigeration cycle, and becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the expansion valve 24 is sent to the outdoor heat exchanger 23.

  The low-pressure gas-liquid two-phase refrigerant sent to the outdoor heat exchanger 23 evaporates in the outdoor heat exchanger 23 by exchanging heat with the outdoor air supplied as a heating source by the outdoor fan 36. Become a gas refrigerant.

  The low-pressure refrigerant evaporated in the outdoor heat exchanger 23 is again sucked into the compressor 21 through the four-way switching valve 22.

(3) Heating deenergization start control When the heating operation is started before a predetermined stop time has elapsed after power feeding, that is, when the heating operation is started immediately after power feeding, the refrigerant stagnates in the compressor 21. Under operating conditions, the liquid refrigerant easily returns to the suction side of the compressor 21. For this reason, the refrigerant discharged from the compressor 21 is not easily overheated, and the heating operation is performed in a state where the degree of superheat of the refrigerant discharged from the compressor 21 is less than 0 deg (that is, a wet state). May be longer.

  Therefore, here, in the heating non-energization start control performed when the heating operation is started before the elapse of the predetermined stop time after power feeding, the four-way switching valve is switched from the cooling cycle state to the heating cycle state as follows. After performing the four-way switching valve switching control, the refrigerant superheat degree increasing control is performed to reduce the operating speed of the compressor and reduce the opening degree of the expansion valve.

  Next, heating non-energization activation control will be described with reference to FIGS. Here, FIG. 3 is a flowchart of the heating non-energization activation control. FIG. 4 is a time chart of the compressor 21, the expansion valve 24, the outdoor fan 36, and the indoor fan 42 at the time of heating / de-energization activation control. FIG. 5 is a diagram showing the relationship between the opening degree of the expansion valve 24 and the operating rotational speed of the compressor 21 during the four-way switching valve switching control and the refrigerant superheat degree increasing control. In addition, the heating deenergization start control described below is performed by the control unit 8 as in the above basic operation. Further, in the following description, it is described that the control for changing the operation speed of the compressor 21 is performed, but the control for changing the operation speed by changing the operation frequency may be used.

<Steps ST1 and ST6>
When a heating operation start command is issued by a remote controller (not shown) or the like, first, the control unit 8 performs a determination process in step ST1. In step ST1, it is determined whether the heating operation start command is issued before a predetermined stop time has elapsed after power feeding, that is, whether the heating operation immediately after power feeding is started. As a result, it is possible to determine whether or not there is a risk that the refrigerant has stagnated in the compressor 21 and there is an operating condition in which the liquid refrigerant is likely to return to the suction side of the compressor 21. Here, the predetermined stop time is set to a time of about 3 to 9 hours so that it can be appropriately determined whether or not the heating operation is immediately after the power feeding.

  If it is determined in step ST1 that the heating operation start command is not issued before the stop time after power feeding, the process proceeds to step ST6 and only the four-way switching valve switching control is performed. After performing, it shifts to normal control. That is, when the heating operation is not performed immediately after power feeding, the refrigerant is not trapped in the compressor 21 and the operation condition is that the liquid refrigerant does not easily return to the suction side of the compressor 21, and therefore processing in steps ST3 to ST5 described later is performed. Without performing the above, only the process of the four-way switching valve switching control in step ST6 is performed prior to the shift to the normal control. Specifically, the compressor 21 is driven while the four-way switching valve 22 is switched to the cooling cycle state to increase the operating rotational speed of the compressor 21 to a predetermined four-cut switching lower limit rotational speed Ncm. Four-way switching valve switching control for switching the path switching valve 22 from the cooling cycle state to the heating cycle state is performed. Here, not only the operating speed of the compressor 21 but also the opening of the expansion valve 24 is increased to a predetermined four-cut switching lower limit opening Xcm. Here, in the four-way switching valve switching control in step ST6, as shown in FIG. 5, the opening degree of the expansion valve 24 increases as the operating speed of the compressor 21 increases (here, Thus, the opening degree of the expansion valve 24 is controlled so as to change in conjunction with the operating rotational speed of the compressor 21. The process of step ST6 is performed in about 0.5 to 1.5 minutes (see time t1 in FIG. 4), and thereafter, the outdoor fan 36 and the indoor fan 42 are driven, and the compressor 21, the expansion valve 24, The routine shifts to normal control of the outdoor fan 36 and the indoor fan 42.

  On the other hand, if it is determined in step ST1 that the heating operation start command is issued before the stop time has elapsed after power feeding, the process proceeds to step ST2, which is the same processing content as step ST6. After performing the processing of steps ST3 to ST5, the process shifts to normal control.

<Steps ST2, ST3, ST4>
In step ST2, the same process as in step ST6 is performed. That is, while the four-way switching valve 22 is switched to the cooling cycle state, the operating speed of the compressor 21 is increased to the four-cut switching lower limit rotational speed Ncm, and the four-way switching valve 22 is changed from the cooling cycle state to the heating cycle state. Four-way switching valve switching control is performed. Also here, as in step ST6, not only the operating rotational speed of the compressor 21, but also the opening of the expansion valve 24 is increased to a predetermined four-cut switching lower limit opening Xcm.

  Next, in step ST3, after the four-way switching valve switching control in step ST2 is completed, the operating rotational speed of the compressor 21 is reduced to the refrigerant superheat degree increasing rotational speed Nsu smaller than the four-way switching lower limit rotational speed Ncm, and Refrigerant superheat degree increase control is performed to make the expansion valve 24 smaller than the opening at the end of the four-way switching valve switching control (here, the four-way switching lower limit opening Xcm). Here, the opening degree of the expansion valve 24 is reduced to the refrigerant superheat degree increasing opening degree Nsu which is smaller than the four-cut switching lower limit opening degree Xcm. In this case as well, the opening degree of the expansion valve 24 has a relationship (here, a proportional relationship) that increases as the operating rotational speed of the compressor 21 shown in FIG. 5 increases, as in steps ST2 and ST6. Therefore, control is performed so as to change in conjunction with the operating rotational speed of the compressor 21. That is, in step ST3, after the four-way switching valve 22 is switched from the cooling cycle state to the heating cycle state, control is performed to reduce not only the operating rotational speed of the compressor 21 but also the opening degree of the expansion valve 24. Yes. Here, the outdoor fan 36 and the indoor fan 42 are also operated. Accordingly, the flow rate of the refrigerant returning to the compressor 21 through the expansion valve 24 and the outdoor heat exchanger 22 can be reduced, and the suction side pressure of the compressor 21 can be kept low. Unlike conventional control, the liquid refrigerant can be made difficult to return to the suction side of the compressor 21. For this reason, the refrigerant discharged from the compressor 21 is likely to be overheated, and the heating operation is performed in a state where the degree of superheat of the refrigerant discharged from the compressor 21 is less than 0 deg (that is, in a wet state). be able to. Further, here, at the time of the refrigerant superheat degree increase control, the control for reducing the operation rotational speed of the compressor 21 and the control for reducing the opening degree of the expansion valve 24 can be easily performed simultaneously. In addition, here, the heating operation can be performed while the operating speed of the compressor 21 is low during the refrigerant superheat increase control.

  And the refrigerant | coolant superheat degree increase control in step ST3 is performed until the refrigerant | coolant superheat degree increase control termination condition in step ST4 is satisfy | filled. Here, the refrigerant superheat degree increase control end condition is that the superheat degree SHd of the refrigerant discharged from the compressor 21 when the superheat degree SHs of the refrigerant sucked into the compressor 21 becomes equal to or higher than a predetermined suction superheat degree threshold SHss. Is set to be equal to or greater than a predetermined discharge superheat degree threshold SHds, or when a predetermined control time t2 has elapsed. The superheat degree SHs of the refrigerant sucked into the compressor 21 is obtained by converting the pressure Ps of the low-pressure refrigerant into a saturation temperature and subtracting this saturation temperature from the temperature Ts of the low-pressure refrigerant. The degree of superheat SHd of the refrigerant discharged from the compressor 21 is obtained by converting the pressure Pd of the high-pressure refrigerant into a saturation temperature and subtracting this saturation temperature from the temperature Td of the high-pressure refrigerant. Further, the suction superheat degree threshold SHss is set to a value larger than 0 deg (for example, about 2 to 8 deg), the discharge superheat degree threshold SHds is set to a value larger than 0 deg (for example, about 5 to 15 deg), and the control time is set. t2 is set to about 5 to 15 minutes. Thereby, the superheat degree SHd of the refrigerant discharged from the compressor 21 can be reliably eliminated.

  And when it determines with satisfy | filling refrigerant | coolant superheat degree increase control termination conditions in step ST4, it transfers to the accumulator forming suppression control of step ST5 and the normal control of heating operation.

<Step ST5>
In the air conditioner 1 of the present embodiment, the refrigerant circuit 10 has an accumulator 25 that temporarily stores the refrigerant sucked into the compressor. For this reason, if the operating rotational speed of the compressor 21 is rapidly increased after the refrigerant superheat degree increasing control is ended, the refrigerant pressure Ps on the suction side of the compressor 21 is rapidly decreased. For this reason, when the liquid refrigerant is accumulated in the accumulator 25, the liquid refrigerant in the accumulator 25 may rapidly evaporate, and a foaming phenomenon (forming) may occur.

  Therefore, in step ST5, after the refrigerant superheat degree increase control in step ST3 is completed, accumulator forming suppression control is performed to increase the operating speed of the compressor 21 at a change rate smaller than the change rate during the normal control of the heating operation. I have to. Here, the changing speed of the operating rotational speed of the compressor 21 is suppressed to about 0.5 times the changing speed during normal control. As a result, the operating rotational speed of the compressor 21 can be increased more gradually than during normal control, so that a rapid decrease in the refrigerant pressure Ps on the suction side of the compressor 21 can be suppressed, and the forming of the accumulator 25 can be prevented. Occurrence can be suppressed.

  And after performing the accumulator forming suppression control of step ST5 for about 15-25 minutes (refer time t3 of FIG. 4), it transfers to the normal control of heating operation.

  Here, since the refrigerant circuit 10 includes the accumulator 25, the process of step ST5 is performed. However, when the refrigerant circuit 10 does not include the accumulator 25, the process of step ST5 is not performed. May be.

  In this way, heating non-energization activation control (four-way switching valve switching control, refrigerant superheat degree increase control, and accumulator forming suppression control) of the air conditioner 1 of the present embodiment is performed. And by performing such heating non-energization start-up control (especially by performing refrigerant superheat degree increase control after four-way switching valve switching control), it is discharged from the compressor 21 at the start of heating operation immediately after energization. The time during which the heating operation is performed in a state where the superheat degree SHd of the refrigerant is less than 0 deg can be shortened.

  The present invention is widely applicable to an air conditioner that can be switched between a cooling operation and a heating operation by a four-way switching valve.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 10 Refrigerant circuit 21 Compressor 22 Four-way switching valve 23 Outdoor heat exchanger 24 Expansion valve 25 Accumulator 36 Outdoor fan 41 Indoor heat exchanger 42 Indoor fan

JP 2005-300056 A JP 2011-145017 A

Claims (5)

A refrigerant circuit (10) configured by connecting a compressor (21), a four-way switching valve (22), an outdoor heat exchanger (23), an expansion valve (24), and an indoor heat exchanger (41). And performing a cooling operation for circulating the refrigerant in the order of the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger by switching the four-way switching valve to a cooling cycle state, By switching the four-way switching valve to a heating cycle state, in an air conditioner that performs a heating operation in which refrigerant is circulated in the order of the compressor, the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger,
When the heating operation is started before the elapse of a predetermined stop time after power feeding, the operation speed of the compressor is set to a predetermined four-cut switching lower limit speed while the four-way switching valve is switched to the cooling cycle state. And the four-way switching valve switching control for switching the four-way switching valve from the cooling cycle state to the heating cycle state. After the four-way switching valve switching control is completed, the operating rotational speed of the compressor is set. the four politeness換下with as small a small refrigerant superheat degree increases rotational speed than the limit rotational speed, lines physician refrigerant superheat increase control for less than the opening degree of the expansion valve at the end of the four-way switching valve switching control ,
When starting the heating operation after elapse of a predetermined stop time after power feeding, the four-way switching valve switching control is performed, but the refrigerant superheat increase control is not performed after the four-way switching valve switching control is finished.
Air conditioner (1). A refrigerant circuit (10) configured by connecting a compressor (21), a four-way switching valve (22), an outdoor heat exchanger (23), an expansion valve (24), and an indoor heat exchanger (41). And performing a cooling operation for circulating the refrigerant in the order of the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger by switching the four-way switching valve to a cooling cycle state, By switching the four-way switching valve to a heating cycle state, in an air conditioner that performs a heating operation in which refrigerant is circulated in the order of the compressor, the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger,
When the heating operation is started before the elapse of a predetermined stop time after power feeding, the operation speed of the compressor is set to a predetermined four-cut switching lower limit speed while the four-way switching valve is switched to the cooling cycle state. And the four-way switching valve switching control for switching the four-way switching valve from the cooling cycle state to the heating cycle state. After the four-way switching valve switching control is completed, the operating rotational speed of the compressor is set. the four politeness換下with as small a small refrigerant superheat degree increases rotational speed than the limit rotational speed, lines physician refrigerant superheat increase control for less than the opening degree of the expansion valve at the end of the four-way switching valve switching control ,
During the four-way switching valve switching control and the refrigerant superheat degree increasing control, the opening degree of the expansion valve (24) is controlled to increase as the operating speed of the compressor (21) increases. The
Air conditioner (1). The refrigerant circuit (10) further includes an accumulator (25) for temporarily storing refrigerant sucked into the compressor (21),
After completion of the refrigerant superheat degree increase control, accumulator forming suppression control is performed to increase the operating speed of the compressor at a change speed smaller than the change speed during the normal control of the heating operation.
The air conditioner (1) according to claim 1 or 2 . In the refrigerant superheat degree increase control, when the superheat degree of the refrigerant sucked into the compressor (21) becomes equal to or higher than a predetermined suction superheat degree threshold value, the superheat degree of the refrigerant discharged from the compressor is set to a predetermined discharge degree. When the superheat degree threshold is exceeded, or when a predetermined control time has passed,
The air conditioning apparatus (1) according to any one of claims 1 to 3 . An outdoor fan (36) for supplying outdoor air as a cooling source or heating source of the refrigerant flowing through the outdoor heat exchanger (23) to the outdoor heat exchanger, and heating of the refrigerant flowing through the indoor heat exchanger (41) An indoor fan (42) for supplying indoor air as a source or cooling source to the indoor heat exchanger;
During the refrigerant superheat increase control, the outdoor fan and the indoor fan are operated.
The air conditioning apparatus (1) according to any one of claims 1 to 4.

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