JP5201175B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner that controls the opening of an expansion valve so that the degree of superheat of a refrigerant at the outlet of an evaporator becomes a target degree of superheat.

  Conventionally, there exists an air conditioning apparatus as shown by patent document 1 (patent 2976905). This air conditioner has a refrigerant circuit mainly configured by connecting a compressor, a four-way switching valve, an outdoor heat exchanger, an outdoor electric expansion valve, an indoor electric expansion valve, and an indoor heat exchanger. ing. In the air conditioning apparatus, during the cooling operation, the indoor electric expansion is performed so that the superheat degree of the refrigerant at the outlet of the indoor heat exchanger functioning as the refrigerant evaporator becomes a predetermined temperature (hereinafter, referred to as a target superheat degree). Superheat control is performed to control the opening of the valve.

  In the conventional air conditioner, the opening degree of the indoor electric expansion valve may be small. When the opening degree of the indoor electric expansion valve becomes small, the ratio of the flow rate change to the opening change becomes larger than in the state where the opening degree of the indoor electric expansion valve is large. For this reason, there is a problem that the behavior of the refrigerant circulating in the refrigerant circuit becomes unstable and hunting occurs. When such hunting becomes large, high pressure and low pressure in the refrigeration cycle operation are disturbed, and there is a possibility that a desired air conditioning operation cannot be performed.

  Thus, in the air conditioner that controls the opening degree of the expansion valve so that the superheat degree of the refrigerant at the outlet of the evaporator becomes the target superheat degree, the superheat degree control can be performed stably while suppressing the occurrence of hunting. It is desired.

  An object of the present invention is to suppress the occurrence of hunting and to perform stable superheat degree control in an air conditioner that controls the opening degree of an expansion valve so that the superheat degree of the refrigerant at the outlet of the evaporator becomes a target superheat degree. Is to be able to do.

  The air conditioning apparatus concerning a 1st viewpoint has a refrigerant circuit and a control part. The refrigerant circuit is configured by sequentially connecting a compressor, a radiator, a first expansion valve, a second expansion valve, and an evaporator. The compressor compresses the refrigerant. The radiator radiates heat of the refrigerant compressed in the compressor. The first expansion valve depressurizes the refrigerant that has radiated heat in the radiator. The second expansion valve depressurizes the refrigerant depressurized in the first expansion valve. The evaporator evaporates the refrigerant decompressed in the second expansion valve. A control part performs superheat degree control which controls the opening degree of a 2nd expansion valve so that the superheat degree of the refrigerant | coolant in the exit of an evaporator may turn into target superheat degree. And a control part performs 1st control which makes the opening degree of a 1st expansion valve small, when the opening degree of a 2nd expansion valve becomes small to the improvement start opening degree in superheat degree control.

  In this air conditioner, since the pressure reduction range of the refrigerant in the first expansion valve can be increased by the first control, the pressure of the refrigerant sent from the first expansion valve to the second expansion valve becomes low. In addition, when the refrigerant is in a gas-liquid two-phase state due to the decompression of the refrigerant in the first expansion valve, the refrigerant flowing between the first expansion valve and the second expansion valve is more than in the liquid state. Since the pressure loss is increased, the pressure of the refrigerant sent from the first expansion valve to the second expansion valve is further reduced. Then, when the opening degree of the second expansion valve is the same before and after the first control, the pressure of the refrigerant at the outlet of the evaporator decreases, and the degree of superheat of the refrigerant at the outlet of the evaporator tends to increase. . For this reason, the opening degree of the second expansion valve performing the superheat degree control increases to maintain the superheat degree of the refrigerant at the outlet of the evaporator at the target superheat degree, and decreases to the improvement start opening degree. The opening degree of the expansion valve can be made larger than the improvement start opening degree.

  Thereby, in this air conditioner, by performing the first control in the superheat degree control, the state in which the ratio of the flow rate change with respect to the change in the opening degree of the second expansion valve is improved, the occurrence of hunting is suppressed, Stable superheat control can be performed.

  An air conditioner according to a second aspect is the air conditioner according to the first aspect, wherein the control unit is configured such that when the high pressure in the refrigeration cycle operation of the refrigerant circuit is lower than the first improvement prohibition pressure in the superheat control. The first control is performed.

  When the first control is performed, the opening degree of the first expansion valve becomes small, so that the high pressure may be increased at least temporarily. And it is not preferable to perform the first control under operating conditions with high pressure because it may cause the high pressure to be excessively high.

  Therefore, in this air conditioner, the first control is performed only when the high pressure is lower than the first improvement prohibiting pressure.

  Thereby, in this air conditioner, the first control is not performed under an operating condition where the high pressure is high, and the first control can be performed while the high pressure is stable.

  An air conditioner according to a third aspect is the air conditioner according to the first or second aspect, wherein the opening of the second expansion valve is increased to the improvement end opening after the control unit performs the first control. If this happens, the second control is performed to increase the opening of the first expansion valve.

  If the pressure loss of the refrigerant when flowing between the first expansion valve and the second expansion valve is increased by the first control, there is a possibility that the power consumption of the compressor increases and the operation efficiency decreases. For this reason, performing the first control in spite of the state in which the stable superheat control can be performed without performing the first control after performing the first control This is not preferable because it maintains the state in which the power consumption increases and the operating efficiency decreases.

  Therefore, in this air conditioner, the second control is performed when the opening of the second expansion valve increases to the improvement end opening after the first control. For this reason, the opening degree of the first expansion valve, which has been reduced by the first control, is increased again, and the pressure loss of the refrigerant when flowing between the first expansion valve and the second expansion valve can be reduced.

  Thereby, in this air conditioner, when the opening degree of the second expansion valve increases to the improvement end opening degree after the first control, the second control is performed, and the compressor of the first control is performed. An increase in power consumption and a decrease in operating efficiency can be suppressed.

  An air conditioner according to a fourth aspect is the air conditioner according to the third aspect, wherein the improvement end opening is larger than the improvement start opening.

  In this air conditioner, since the improvement end opening is made larger than the improvement start opening, the opening of the second expansion valve becomes sufficiently larger than the improvement start opening, and the first control is unnecessary. The second control can be performed if

  Thereby, in this air conditioning apparatus, it is possible to perform stable superheat control while suppressing the need for the first control again immediately after performing the second control.

  An air conditioner according to a fifth aspect is the air conditioner according to the third or fourth aspect, wherein the high pressure in the refrigeration cycle operation of the refrigerant circuit is the second improvement prohibition pressure after the control unit performs the first control. The second control is also performed when the value becomes higher.

  When the first control is performed, the opening degree of the first expansion valve becomes small, so that the high pressure in the refrigeration cycle operation of the refrigerant circuit may be increased at least temporarily. For this reason, it cannot be said that maintaining the state in which the first control is performed when the high pressure becomes excessively high by performing the first control is not preferable.

  Therefore, in this air conditioner, the second control is performed even when the high pressure increases to the second improvement prohibition pressure after the first control. For this reason, it can suppress that the opening degree of the 1st expansion valve which became small by 1st control becomes large again, and high pressure becomes high too much.

  Thereby, in this air conditioner, not only when the opening degree of the second expansion valve increases to the improvement end opening degree after performing the first control, but also after the first control is performed, the high pressure is prohibited from the second improvement. Even when the pressure increases, the second control is performed, and the high pressure can be prevented from becoming excessively high.

  An air conditioner according to a sixth aspect is the air conditioner according to any one of the first to fifth aspects, wherein the high pressure in the refrigeration cycle operation of the refrigerant circuit after the controller performs the first control is the restoration pressure. The first control is released when it becomes higher.

  When the first control is performed, the opening degree of the first expansion valve becomes small, so that the high pressure in the refrigeration cycle operation of the refrigerant circuit may be increased at least temporarily. For this reason, it cannot be said that maintaining the state in which the first control is performed when the high pressure becomes excessively high by performing the first control is not preferable.

  Therefore, in this air conditioner, the first control is canceled when the high pressure reaches the restoration pressure after the first control. For this reason, it can suppress that the opening degree of the 1st expansion valve which became small by 1st control becomes large again, and high pressure becomes high too much.

  Thereby, in this air conditioning apparatus, when the high pressure increases to the recovery pressure after performing the first control, the first control is not performed, and the high pressure can be suppressed from becoming excessively high.

  In the air conditioner according to the seventh aspect, in the air conditioner according to any one of the first to sixth aspects, the control unit causes the supercooling degree of the refrigerant at the outlet of the radiator to be a target supercooling degree. In addition, supercooling degree control for controlling the opening degree of the first expansion valve is performed. Then, the control unit performs the first control by increasing the target supercooling degree.

  In this air conditioner, when the supercooling degree of the refrigerant at the outlet of the radiator is smaller than the target supercooling degree, in order to maintain the supercooling degree of the refrigerant at the outlet of the radiator at the target supercooling degree, The opening degree of the first expansion valve performing the cooling degree control is reduced.

  Therefore, in this air conditioner, when the first control is required, the opening degree of the first expansion valve is reduced by increasing the target supercooling degree in the supercooling degree control.

  Thereby, in this air conditioning apparatus, the first control can be performed while performing the supercooling degree control using the first expansion valve.

  An air conditioner according to an eighth aspect is the air conditioner according to any of the third to fifth aspects, wherein the first expansion is performed such that the degree of supercooling of the refrigerant at the outlet of the radiator becomes a target degree of subcooling. Supercooling control is performed to control the opening of the valve. And a control part performs 2nd control by making target supercooling degree small.

  In this air conditioner, when the degree of supercooling of the refrigerant at the outlet of the radiator is larger than the target degree of supercooling, the supercooling degree of the refrigerant at the outlet of the radiator is maintained at the target degree of supercooling. The opening degree of the first expansion valve performing the cooling degree control is increased.

  Therefore, in this air conditioner, when the second control is required, the opening degree of the first expansion valve is increased by reducing the target supercooling degree in the supercooling degree control.

  Thereby, in this air conditioning apparatus, the second control can be performed while performing the supercooling degree control using the first expansion valve.

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

  In the air conditioner according to the first aspect, by performing the first control in the superheat degree control, the state in which the flow rate change ratio with respect to the opening change of the second expansion valve is large is improved, so that the occurrence of hunting is suppressed. Thus, stable superheat control can be performed.

  In the air conditioner according to the second aspect, the first control is not performed under an operating condition where the high pressure is high, and the first control can be performed while the high pressure is stable.

  In the air conditioner according to the third aspect, the second control is performed when the opening of the second expansion valve increases to the improvement end opening after the first control, and the compression by the first control is performed. It is possible to suppress an increase in power consumption of the machine and a decrease in operating efficiency.

  In the air conditioner according to the fourth aspect, it is possible to perform stable superheat control by suppressing the need for the first control again immediately after performing the second control.

  In the air conditioner according to the fifth aspect, not only when the opening degree of the second expansion valve increases to the improvement end opening degree after the first control is performed, but the second pressure is increased after the first control is performed. Even when the improvement prohibition pressure is increased, the second control is performed, and the high pressure can be prevented from becoming excessively high.

  In the air conditioner according to the sixth aspect, the first control is not performed when the high pressure rises to the recovery pressure after the first control, and the high pressure can be prevented from becoming excessively high.

  In the air conditioning apparatus according to the seventh aspect, the first control can be performed while performing the supercooling degree control using the first expansion valve.

  In the air conditioner according to the eighth aspect, the second control can be performed while performing the supercooling degree control using the first expansion valve.

It is a schematic block diagram of the air conditioning apparatus concerning one Embodiment of this invention. It is a control block diagram of the air conditioning apparatus concerning one Embodiment of this invention. It is a flowchart which shows control of the outdoor expansion valve of the air conditioning apparatus concerning one Embodiment of this invention. It is a flowchart which shows control of the indoor expansion valve of the air conditioning apparatus concerning the modification of this invention. It is a schematic block diagram of the air conditioning apparatus concerning other embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an air conditioner according to the present invention will be described based on the drawings.

(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 an apparatus used for indoor cooling by performing a vapor compression refrigeration cycle. The air conditioner 1 mainly includes an outdoor unit 2, an indoor unit 3, and a liquid refrigerant communication tube 5 and a gas refrigerant communication tube 6 that connect the outdoor unit 2 and the indoor unit 3. That is, the vapor compression refrigerant circuit 10 of the air conditioning apparatus 1 of the present embodiment is configured by connecting the outdoor unit 2, the indoor unit 3, and the refrigerant communication pipes 5 and 6.

<Indoor unit>
The indoor unit 3 is installed indoors. The indoor unit 3 is connected to the outdoor unit 2 via the liquid refrigerant communication tube 5 and the gas refrigerant communication tube 6 and constitutes a part of the refrigerant circuit 10.

  Next, the configuration of the indoor unit 3 will be described. The indoor unit 3 mainly has an indoor refrigerant circuit 10 a that constitutes a part of the refrigerant circuit 10. The indoor refrigerant circuit 10a mainly includes a compressor 31, an indoor expansion valve 34 as a second expansion valve, an indoor heat exchanger 33, and an accumulator 35.

  The compressor 31 is a compressor that compresses the refrigerant. The compressor 31 is a positive displacement compressor driven by a compressor motor 31a.

  The indoor heat exchanger 33 is a heat exchanger that functions as a refrigerant evaporator and cools indoor air. The gas side of the indoor heat exchanger 33 is connected to the accumulator 35, and the liquid side of the indoor heat exchanger 33 is connected to the indoor expansion valve 34.

  The indoor expansion valve 34 is an electric expansion valve that decompresses the refrigerant flowing into the indoor heat exchanger 33. The indoor expansion valve 34 is connected between the liquid side of the indoor heat exchanger 33 and the liquid refrigerant communication pipe 5.

  The accumulator 35 is a container for temporarily storing the refrigerant circulating in the refrigerant circuit 10 before being sucked into the compressor 31. The accumulator 35 is connected between the gas side of the indoor heat exchanger 33 and the suction side of the compressor 31.

  The indoor unit 3 has an indoor fan 36 for supplying indoor air as supply air after sucking indoor air into the unit and exchanging heat with the refrigerant in the indoor heat exchanger 33. In this embodiment, the indoor fan 36 is a centrifugal fan or a multiblade fan driven by the indoor fan motor 36a.

  The indoor unit 3 is provided with various sensors. Specifically, the indoor unit 3 includes a suction pressure sensor 38, a discharge pressure sensor 39, a suction temperature sensor 40, a discharge temperature sensor 41, an indoor heat exchange liquid side temperature sensor 42, and an indoor heat exchange gas side. A temperature sensor 43 is provided. The suction pressure sensor 38 is a pressure sensor that detects the suction pressure Ps of the compressor 31. The discharge pressure sensor 39 is a pressure sensor that detects the discharge pressure Pd of the compressor 31. The suction temperature sensor 40 is a temperature sensor that detects the suction temperature Ts of the compressor 31. The discharge temperature sensor 41 is a temperature sensor that detects the discharge temperature Td of the compressor 31. The indoor heat exchange liquid side temperature sensor 42 is a temperature sensor that detects the refrigerant temperature Til on the liquid side of the indoor heat exchanger 33 (that is, the inlet when functioning as an evaporator of the refrigerant). The indoor heat exchange gas temperature sensor 43 is a temperature sensor that detects the temperature Tig of the refrigerant on the gas side of the indoor heat exchanger 33 (that is, the outlet when functioning as an evaporator of the refrigerant).

  Furthermore, the indoor unit 3 includes an indoor side control unit 37 that controls the operation of each unit constituting the indoor unit 3. And the indoor side control part 37 has the inverter circuit etc. which control the microcomputer provided for performing control of the indoor unit 3, memory, and the motor 31a for compressors. The indoor control unit 37 can exchange control signals and the like with the outdoor unit 2 via the transmission line 7a.

<Outdoor unit>
The outdoor unit 2 is installed outdoors. The outdoor unit 2 is connected to the indoor unit 3 via the liquid refrigerant communication tube 5 and the gas refrigerant communication tube 6, and constitutes a refrigerant circuit 10 with the indoor unit 3.

  Next, the configuration of the outdoor unit 2 will be described. The outdoor unit 2 mainly has an outdoor refrigerant circuit 10 b that constitutes a part of the refrigerant circuit 10. The outdoor refrigerant circuit 10b mainly includes an outdoor heat exchanger 21, an outdoor expansion valve 22 as a first expansion valve, and a receiver 23.

  The outdoor heat exchanger 21 is a heat exchanger that functions as a refrigerant radiator. The gas side of the outdoor heat exchanger 21 is connected to the gas refrigerant communication pipe 6, and the liquid side of the outdoor heat exchanger 21 is connected to the outdoor expansion valve 22.

  The outdoor expansion valve 22 is an electric expansion valve that decompresses the refrigerant flowing out of the outdoor heat exchanger 21. The outdoor expansion valve 22 is connected between the liquid side of the outdoor heat exchanger 21 and the receiver 23.

  The receiver 23 is a container that can store a refrigerant flowing between the indoor expansion valve 34 and the outdoor expansion valve 22. The receiver 23 is connected between the outdoor expansion valve 22 and the liquid refrigerant communication tube 5.

  The outdoor unit 2 has an outdoor fan 24 for sucking outdoor air into the unit and exchanging heat with the refrigerant in the outdoor heat exchanger 21 and then discharging the air to the outside. In the present embodiment, the outdoor fan 24 is a propeller fan or the like driven by the outdoor fan motor 24a.

  The outdoor unit 2 is provided with various sensors. Specifically, the outdoor unit 2 is provided with an outdoor heat exchange liquid side temperature sensor 26. The outdoor heat exchange liquid side temperature sensor 26 is a temperature sensor that detects the refrigerant temperature Tol on the liquid side of the outdoor heat exchanger 21 (that is, the outlet when functioning as a refrigerant radiator).

  Further, the outdoor unit 2 has an outdoor side control unit 25 that controls the operation of each unit constituting the outdoor unit 2. The outdoor control unit 25 includes a microcomputer, a memory, and the like provided for controlling the outdoor unit 2, and is connected to the indoor control unit 37 of the indoor unit 3 via the transmission line 7 a. The control signals can be exchanged. That is, the control part 7 which performs operation control of the whole air conditioning apparatus 1 is comprised by the transmission line 7a which connects between the indoor side control part 37 and the outdoor side control part 25. FIG.

  As shown in FIG. 2, the control unit 7 is connected so that it can receive detection signals of various sensors 38 to 43, 26, and based on these detection signals, various devices and valves 24a, 22, It is connected so that 31a, 36a, 34 can be controlled. Here, FIG. 2 is a control block diagram of the air conditioner 1.

<Refrigerant communication pipe>
Refrigerant communication pipes 5 and 6 are refrigerant pipes constructed on site when the air conditioner 1 is installed in a building or the like, such as a combination of the installation location or the outdoor unit 2 and the indoor unit 3. Depending on the installation conditions, those having various lengths and pipe diameters are used.

  As described above, by connecting the indoor refrigerant circuit 10a having the compressor 31, the indoor heat exchanger 32, the indoor expansion valve 34, and the like, and the outdoor refrigerant circuit 10b having the outdoor heat exchanger 21, etc., A refrigerant circuit 10 of the air conditioner 1 is configured. And the air conditioning apparatus 1 comes to be able to control each apparatus of the outdoor unit 2 and the indoor unit 3 by the control part 7 comprised from the indoor side control part 37 and the outdoor side control part 25. Yes.

(2) Basic operation | movement of an air conditioning apparatus Next, the basic operation | movement (here cooling operation) of the air conditioning apparatus 1 is demonstrated using FIG.

  The refrigerant in the refrigerant circuit 10 is sucked into the compressor 31 of the indoor unit 3 and compressed to become a high-pressure gas refrigerant. The high-pressure gas refrigerant is sent from the indoor unit 3 to the outdoor unit 2 via the gas refrigerant communication pipe 6. The high-pressure gas refrigerant sent to the outdoor unit 2 is sent to an outdoor heat exchanger 21 as a refrigerant radiator. This high-pressure gas refrigerant is condensed in the outdoor heat exchanger 21 by exchanging heat with the outdoor air supplied by the outdoor fan 24 to dissipate heat, and becomes high-pressure liquid refrigerant. This high-pressure liquid refrigerant is sent to the outdoor expansion valve 22 serving as the first expansion valve, and the pressure is reduced in the outdoor expansion valve 22. The refrigerant decompressed in the outdoor expansion valve 22 is temporarily stored in the receiver 23 and then sent from the outdoor unit 2 to the indoor unit 3 via the liquid refrigerant communication tube 5. The refrigerant sent to the indoor unit 3 is decompressed by the indoor expansion valve 34 as the second expansion valve, and becomes a low-pressure gas-liquid two-phase refrigerant. This low-pressure gas-liquid two-phase refrigerant is sent to an indoor heat exchanger 33 as a refrigerant evaporator, and heat is exchanged with indoor air supplied by the indoor fan 36 in the indoor heat exchanger 33. As a result, it evaporates and becomes a low-pressure gas refrigerant. At this time, the indoor air is cooled by heat exchange with the refrigerant in the indoor heat exchanger 33 and supplied indoors. Then, the low-pressure gas refrigerant evaporated in the indoor heat exchanger 33 is sent to the accumulator 35 and again sucked into the compressor 31. In this way, the cooling operation is performed.

(3) Control of indoor expansion valve and outdoor expansion valve During the above basic operation, the control unit 7 sets the superheat degree SH of the refrigerant at the outlet of the indoor heat exchanger 33 as the refrigerant evaporator to the target superheat degree SHs. Thus, the superheat degree control which controls the opening degree of the indoor expansion valve 34 as a 2nd expansion valve is performed. Here, the superheat degree SH of the refrigerant at the outlet of the indoor heat exchanger 33 is calculated based on the temperature Tig of the refrigerant on the gas side of the indoor heat exchanger 33 detected by the indoor heat exchanger gas temperature sensor 43, and the temperature of the indoor heat exchanger liquid side. It is obtained by subtracting the refrigerant temperature Til on the liquid side of the indoor heat exchanger 33 detected by the sensor 42. Note that the method of calculating the superheat degree SH is not limited to this. For example, the suction pressure Ps detected by the suction pressure sensor 38 is converted into the refrigerant saturation temperature Te and detected by the temperature Tig or the suction temperature sensor 40. Alternatively, the saturation temperature Te may be subtracted from the suction temperature Ts.

  However, the degree of opening of the indoor expansion valve 34 may be small only by performing the superheat control. When the opening of the indoor expansion valve 34 is in a small state, the rate of change in flow rate with respect to the change in opening is greater than in the state where the opening of the indoor expansion valve 34 is large. For this reason, the behavior of the refrigerant circulating in the refrigerant circuit 10 becomes unstable, and hunting may occur. When such hunting increases, the high pressure HP (here, the discharge pressure Pd of the compressor 31) and the low pressure LP (here, the suction pressure of the compressor 31) in the refrigeration cycle operation (here, cooling operation) of the refrigerant circuit 10 are increased. Ps) is disturbed, and the desired cooling operation may not be performed.

  Therefore, in the present embodiment, in order to suppress the occurrence of hunting and to perform stable superheat control, the outdoor expansion valve 22 as the first expansion valve as described below is controlled. I am doing so. Here, FIG. 3 is a flowchart showing the control of the outdoor expansion valve 22 of the air-conditioning apparatus 1 according to the present embodiment.

  First, in step S1, it is determined whether or not a predetermined time t1 has elapsed since the start of the refrigeration cycle operation (here, the cooling operation) of the refrigerant circuit 10 accompanied by the superheat control. Here, “the start of the operation of the refrigeration cycle” is not only the case where the operation is started from the state where the operation of the air conditioner 1 is stopped, but also the compressor 31 when the room temperature reaches a predetermined target temperature. This includes a state in which the operation is temporarily stopped (so-called thermo-off state). And after time t1 passes in step S1, it transfers to step S2.

  Next, in step S2, the opening of the outdoor expansion valve 22 (“outdoor EV opening” in FIG. 3) is set to a predetermined opening Q. Here, the opening degree Q is a fully open state or an opening degree close thereto. For example, when the fully closed state of the outdoor expansion valve 22 is represented as 0% and the fully opened state is represented as 100%, the opening degree Q is set to 100% or an opening degree close thereto.

  Next, in step S <b> 3, it is determined whether or not the opening of the indoor expansion valve 34 (“indoor EV opening” in FIG. 3) has decreased to a predetermined improvement start opening X. More specifically, whether or not the state in which the opening of the indoor expansion valve 34 is smaller than the improvement start opening X and the high pressure HP is lower than the predetermined first improvement prohibiting pressure α continues for a predetermined time t2. Determine. Here, the improvement start opening degree X means an opening degree at which the ratio of the flow rate change to the opening degree change is likely to cause hunting, and is set to an opening degree of about 5% to 20%. In addition, in order to prevent the indoor expansion valve 34 from being fully closed in the superheat degree control, a lower limit opening may be set, but the improvement start opening X is set to an opening larger than such a lower limit opening. Is set. The first improvement prohibition pressure α is set to determine whether or not the high pressure HP is in a stable state. The time t2 is set to determine whether or not the opening of the indoor expansion valve 34 is smaller than the improvement start opening X and the high pressure HP is lower than the first improvement prohibiting pressure α. Has been. For example, the time t2 is set to about several tens of seconds to several minutes. In step S3, until it is determined that the state in which the opening degree of the indoor expansion valve 34 is smaller than the improvement start opening degree X and the high pressure HP is lower than the first improvement prohibiting pressure α continues for the time t2. The process of step S3 is repeated (that is, superheat degree control is performed in a state where the opening degree of the outdoor expansion valve 22 is set to the opening degree Q). In Step S3, when it is determined that the state in which the opening degree of the indoor expansion valve 34 is smaller than the improvement start opening degree X and the high pressure HP is lower than the first improvement prohibiting pressure α continues for the time t2. Shifts to the process of step S4.

  Next, in step S4, the opening of the outdoor expansion valve 22 (“outdoor EV opening” in FIG. 3) is obtained by multiplying the current opening (here, opening Q) by a predetermined closing rate V. The first control is changed every time. Here, the closing rate V is set to a value less than 1 of about 0.9 to 0.99. That is, the first control is control for reducing the opening degree of the outdoor expansion valve 22. The method of reducing the opening of the outdoor expansion valve 22 is not limited to the above, and may be obtained by subtracting a predetermined opening from the current opening, for example. And since the decompression width of the refrigerant in the outdoor expansion valve 22 can be increased by this first control, the pressure of the refrigerant sent from the outdoor expansion valve 22 to the indoor expansion valve 34 becomes low. Moreover, when the refrigerant is in a gas-liquid two-phase state due to the decompression of the refrigerant in the outdoor expansion valve 22, the refrigerant flowing when flowing between the outdoor expansion valve 22 and the indoor expansion valve 34 is more than when the refrigerant is in the liquid state. Since the pressure loss increases, the pressure of the refrigerant sent from the outdoor expansion valve 22 to the indoor expansion valve 34 is further reduced. Then, when the opening degree of the indoor expansion valve 34 before and after the first control is the same, the pressure of the refrigerant at the outlet of the indoor heat exchanger 33 that functions as the refrigerant evaporator becomes low, and the indoor heat exchanger 33. The degree of superheating SH of the refrigerant at the outlet of the refrigerant tends to increase. For this reason, the opening degree of the indoor expansion valve 34 that performs superheat degree control increases to maintain the superheat degree SH at the target superheat degree SHs, and the opening of the indoor expansion valve 34 that has decreased to the improvement start opening degree X is opened. The degree can be made larger than the improvement start opening X. As described above, by performing the first control in the superheat degree control, the state in which the rate of change in the flow rate with respect to the change in the opening degree of the indoor expansion valve 34 is large is improved. Control can be performed. In step S3, it is determined whether or not the high pressure HP is lower than the first improvement prohibiting pressure α. However, when the first control is performed, the opening degree of the outdoor expansion valve 22 decreases. This is because at least temporarily, the high-pressure HP may become high. That is, in order to suppress the high pressure HP from becoming excessively high by performing the first control, it is determined whether or not the high pressure HP is lower than the first improvement prohibiting pressure α, and this determination condition is satisfied. In addition, the first control is performed.

  Next, in step S5, it is determined whether or not the high pressure HP has reached the recovery pressure α + β + γ after performing the first control. Here, the restoration pressure α + β + γ is set to determine whether the high pressure HP is excessively high by performing the first control. The restoration pressure α + β + γ is set to a pressure obtained by adding the pressure β + γ to the first improvement prohibition pressure α. In step S5, when it is determined that the high pressure HP is higher than the restoration pressure α + β + γ, it is considered that the high pressure HP is excessively high by performing the first control. It is not preferable to maintain the state in which the first control is performed. Therefore, in this case, the process returns to the process of step S2, the first control is canceled, and the opening degree of the outdoor expansion valve 22 is returned to the original opening degree Q. Thereby, the opening degree of the outdoor expansion valve 22 that is reduced by the first control is increased again, and the high pressure HP can be suppressed from becoming excessively high. In Step S5, when it is determined that the high pressure HP is not higher than the restoration pressure α + β + γ, the state in which the first control is performed may be maintained. For this reason, in this case, the process proceeds to step S6.

  Next, in step S6, the same determination process as in step S3 is performed again in a state where the first control in step S4 is performed. That is, it is determined whether or not the first control is necessary in the state where the first control is performed in step S4. In addition, since the determination process itself of step S6 is the same as that of step S3, description is abbreviate | omitted here. In step S6, when it is determined that the state in which the opening degree of the indoor expansion valve 34 is smaller than the improvement start opening degree X and the high pressure HP is lower than the first improvement prohibiting pressure α continues for the time t2. Shifts to the process of step S7 and performs the same first control as that of step S4 again. That is, the first control is performed to reduce the opening degree of the outdoor expansion valve 22 to the opening degree obtained by multiplying the current opening degree (here, the opening degree Q × V) by the closing rate V, and the process proceeds to step S5. To do. Thus, the first control (that is, the processing of steps S5, S6, and S7) is repeatedly performed until the opening of the indoor expansion valve 34 that has been reduced to the improvement start opening X becomes larger than the improvement start opening X. become. And when it determines with not satisfy | filling said determination conditions in step S6, it transfers to the process of step S8.

  Next, in step S8, it is determined whether or not the opening of the indoor expansion valve 34 has increased to a predetermined improvement end opening X + Y after performing the first control (that is, the processing of steps S4 and S7). More specifically, it is determined whether or not the state in which the opening of the indoor expansion valve 34 is larger than the improvement end opening X + Y has continued for a predetermined time t3. Here, the improvement completion opening X + Y means an opening at which the state in which the ratio of the flow rate change with respect to the opening change is large is eliminated and hunting is less likely to occur, and the opening is about 15% to 30%. Is set. Further, the improvement end opening X + Y is set to an opening larger than the improvement start opening X. For example, the improvement end opening X + Y can be set to an opening larger by about 10% than the improvement start opening X by setting the opening Y to an opening of about 10%. In step S8, it is determined whether or not the high pressure HP has increased to a predetermined second improvement prohibition pressure α + β after performing the first control (that is, the processing in steps S4 and S7). More specifically, it is determined whether or not the state in which the high pressure HP is higher than the second improvement prohibition pressure α + β continues for the time t3. Here, the second improvement prohibition pressure α + β is set to determine whether or not the high pressure HP is in a stable state even after the first control is performed. The second improvement prohibition pressure α + β is set to a pressure obtained by adding the pressure β to the first improvement prohibition pressure α. The second improvement prohibition pressure α + β is set to a pressure that is smaller than the restoration pressure α + β + γ by the pressure γ. That is, here, the second improvement prohibition pressure α + β is set to a pressure that is larger than the first improvement prohibition pressure α and smaller than the recovery pressure α + β + γ. Further, at time t3, in order to determine whether the opening of the indoor expansion valve 34 is larger than the improvement end opening X + Y or whether the high pressure HP is lower than the second improvement prohibiting pressure α + β. Is set. For example, the time t3 is set to about several tens of seconds to several minutes. In step S8, until it is determined that the state in which the opening degree of the indoor expansion valve 34 is larger than the improvement end opening degree X + Y or the state in which the high pressure HP is higher than the second improvement prohibiting pressure α + β has continued for time t3. The processes in steps S5 to S8 are repeated (that is, superheat control with the first control is performed). In step S8, when it is determined that the state in which the opening degree of the indoor expansion valve 34 is larger than the improvement end opening degree X + Y or the state in which the high pressure HP is higher than the second improvement prohibiting pressure α + β has continued for time t3. In step S9, the process proceeds to step S9.

  Next, in step S9, the second control is performed to change the opening of the outdoor expansion valve 22 to an opening obtained by multiplying the current opening (here, opening Q × V, etc.) by a predetermined opening ratio W. Do. Here, the opening ratio W is set to a value larger than 1 in the range of about 1.01 to 1.1. That is, the second control is control for increasing the opening degree of the outdoor expansion valve 22. The method for increasing the opening of the outdoor expansion valve 22 is not limited to the above, and for example, a predetermined opening may be added to the current opening. And by this 2nd control, the opening degree of the outdoor expansion valve 22 which became small by 1st control becomes large again, and the pressure loss of the refrigerant | coolant at the time of flowing between the outdoor expansion valve 22 and the indoor expansion valve 34 is made small. Moreover, it can suppress that high pressure HP becomes high too much. By the way, if the pressure loss of the refrigerant when flowing between the outdoor expansion valve 22 and the indoor expansion valve 34 is increased by the first control, the power consumption of the compressor 31 may increase or the operation efficiency may decrease. For this reason, performing the first control in spite of being in a state in which stable superheat control can be performed without performing the first control after performing the first control, the compressor 31 This is not preferable because it maintains the state in which the power consumption increases and the operating efficiency decreases. Moreover, when the opening degree of the outdoor expansion valve 22 is decreased by the first control, the high pressure HP may be increased at least temporarily. For this reason, it cannot be said that maintaining the state which performed 1st control when high voltage | pressure HP becomes high too much by performing 1st control is not preferable. That is, after the first control is performed, the second control is performed when the opening of the indoor expansion valve 34 is larger than the improvement end opening X + Y, thereby reducing the power consumption of the compressor 31 by the first control. Increase and decrease in operating efficiency can be suppressed. In addition, when the high pressure HP becomes higher than the second improvement prohibition pressure α + β after performing the first control, it is possible to suppress the high pressure HP from becoming excessively high by performing the second control. Here, since the improvement end opening X + Y is set to be larger than the improvement start opening X, the opening of the indoor expansion valve 34 is sufficiently larger than the improvement start opening X, and the first The second control can be performed when the control is unnecessary. And thereby, the state where the first control is necessary again immediately after performing the second control (that is, the processing of steps S6 and S7 is performed immediately after performing the second control) is suppressed, Stable superheat control can be performed.

  Next, in step S10, it is determined whether the opening degree of the outdoor expansion valve 22 is larger than the opening degree Q by the second control (that is, the process of step S9). In Step S10, when it is determined that the opening degree of the outdoor expansion valve 22 is not larger than the opening degree Q, the process returns to Step S5. And when it determines with the opening degree of the outdoor expansion valve 22 being larger than the opening degree Q in step S10, the opening degree of the outdoor expansion valve 22 is changed into the opening degree Q in step S11, The process returns to step S5. Here, the processing of steps S10 and S11 is performed in order to suppress an excessive decrease in the high-pressure HP or the like when the opening degree of the outdoor expansion valve 22 is larger than the opening degree Q. is there.

(4) Modified Example In this modified example, during the above basic operation, the control unit 7 causes the supercooling degree SC of the refrigerant at the outlet of the outdoor heat exchanger 21 as the refrigerant radiator to become the target supercooling degree SCs. Thus, the degree of supercooling is controlled to control the opening degree of the outdoor expansion valve 22 as the first expansion valve. Here, the degree of supercooling SC of the refrigerant at the outlet of the outdoor heat exchanger 21 is calculated by converting the discharge pressure Pd detected by the discharge pressure sensor 39 into the saturation temperature Tc of the refrigerant, and the outdoor heat exchange liquid from the saturation temperature Tc. It is obtained by subtracting the refrigerant temperature Tol on the liquid side of the outdoor heat exchanger 21 detected by the side temperature sensor 26.

  When such supercooling degree control is performed, unlike the first control and the second control (that is, the processes of steps S4, S7, and S9 in FIG. 3), the outdoor expansion valve 22 is opened. The degree cannot be changed or set directly.

  Therefore, in this modified example, as shown in FIG. 4, instead of the processing of steps S2, S4, S7, S9, S10, and S11 in which the opening degree of the outdoor expansion valve 22 is directly changed or set, the target overshoot is performed. Steps S12, S14, S17, S19, S20, and S21 for changing or setting the degree of cooling SCs are employed.

  Specifically, in step S12 employed instead of step S2, the target supercooling degree SCs (“target SC” in FIG. 4) in the supercooling degree control (“SC control” in FIG. 4) is set to a predetermined supercooling degree. Set the cooling degree A.

  Further, in steps S14 and S17 employed in place of steps S4 and S7, a predetermined supercooling degree B is added to the current target supercooling degree SCs (here, supercooling degree A, supercooling degree A + B, etc.). The first control is performed by changing to the degree of supercooling obtained. That is, the first control is control for increasing the target supercooling degree SCs. Here, when the refrigerant subcooling degree SC at the outlet of the outdoor heat exchanger 21 is smaller than the target supercooling degree SCs, the refrigerant subcooling degree SC at the outlet of the outdoor heat exchanger 21 is set as the target subcooling degree SCs. Therefore, the opening degree of the outdoor expansion valve 22 performing the supercooling degree control is reduced. For this reason, by increasing the target supercooling degree SCs as described above, the opening degree of the outdoor expansion valve 22 can be reduced as in step S7. Thereby, in this modification, 1st control can be performed, performing supercooling degree control using the outdoor expansion valve 22. FIG.

  Further, in step S19 employed instead of step S9, the supercooling degree is obtained by subtracting a predetermined supercooling degree C from the current target supercooling degree SCs (here, supercooling degree A + B, etc.). Thus, the second control is performed. That is, this second control is control for reducing the target supercooling degree SCs. Here, when the refrigerant subcooling degree SC at the outlet of the outdoor heat exchanger 21 is larger than the target supercooling degree SCs, the refrigerant subcooling degree SC at the outlet of the outdoor heat exchanger 21 is set as the target subcooling degree SCs. Therefore, the degree of opening of the outdoor expansion valve 22 that performs supercooling control is increased. For this reason, by reducing the target supercooling degree SCs as described above, the opening degree of the outdoor expansion valve 22 can be increased as in step S9. Thereby, in this modification, 2nd control can be performed, performing supercooling degree control using the outdoor expansion valve 22. FIG.

  Further, in steps S20 and S21 employed instead of steps S10 and S11, it is determined whether or not the target supercooling degree SCs is smaller than the supercooling degree A by the second control (that is, the process of step S19). . In step S20, when it is determined that the target supercooling degree SCs is not smaller than the supercooling degree A, the process returns to step S5. If it is determined in step S20 that the target supercooling degree SCs is smaller than the supercooling degree A, the target supercooling degree SCs is changed to the supercooling degree A in step S21, and step S5 is performed. Return to the process. Here, the processing of steps S20 and S21 is performed in order to suppress an excessive decrease in the high-pressure HP when the supercooling degree SC is larger than the supercooling degree A.

  As described above, in the present modification, the first control and the second control can be performed while performing the supercooling degree control using the outdoor expansion valve 22 as the first expansion valve. The same effect can be obtained.

(5) Other Embodiments Although the embodiments of the present invention and the modifications thereof have been described with reference to the drawings, the specific configuration is not limited to these embodiments and the modifications thereof, and Changes can be made without departing from the scope of the invention.

  <A> In the above-described embodiment and its modification, importance is placed on maintaining a stable state of the high-pressure HP when performing the first control and the second control. For this reason, in said embodiment and its modification, the outdoor expansion valve as a restriction | limiting of high pressure HP like step S3, S5, S6, S8, or a 1st expansion valve like step S10, S11, S20, S21. The opening degree of 22 and the restriction of the target supercooling degree are added. However, when the fluctuation of the high pressure HP is allowed to some extent, these restrictions may be omitted depending on the required degree of stability of the high pressure HP.

<B>
In the above-described embodiment and its modification, the example in which the present invention is applied to the remote condenser type air conditioner 1 in which the compressor 31 is provided in the indoor unit 3 has been described. The present invention may be applied to an air conditioner having another unit configuration such as a separate air conditioner provided with a compressor 31.

<C>
In the above-described embodiment and its modification, the example in which the present invention is applied to the air conditioner 1 including the cooling-only refrigerant circuit 10 has been described. However, the present invention is not limited thereto, and switching between the cooling operation and the heating operation is possible. You may apply this invention to the air conditioning apparatus provided with the refrigerant circuit comprised in this.

  For example, you may apply this invention to the air conditioning apparatus 101 provided with the refrigerant circuit 110 as shown in FIG. Here, the air conditioner 101 mainly includes the outdoor unit 2, the indoor unit 103, and the liquid refrigerant communication tube 5 and the gas refrigerant communication tube 6 that connect the outdoor unit 2 and the indoor unit 103. That is, the vapor compression refrigerant circuit 110 of the air conditioner 101 is configured by connecting the outdoor unit 2, the indoor unit 103, and the refrigerant communication tubes 5 and 6.

  And the indoor unit 103 has the indoor side refrigerant circuit 110a which comprises a part of refrigerant circuit 110 mainly. The indoor refrigerant circuit 110a mainly includes a compressor 31, a switching mechanism 32, an indoor expansion valve 34 as a second expansion valve, an indoor heat exchanger 33, and an accumulator 35. That is, the air conditioner 101 is different from the air conditioner 1 of the above-described embodiment and its modified example in that the indoor unit 103 has the switching mechanism 32. Here, the switching mechanism 32 is a four-way switching valve capable of switching between a cooling operation state in which the indoor heat exchanger 33 functions as a refrigerant evaporator and a heating operation state in which the indoor heat exchanger 33 functions as a refrigerant radiator. It is. Here, the solid line in the switching mechanism 32 in FIG. 5 indicates the cooling operation state, and the broken line in the switching mechanism 32 in FIG. 5 indicates the heating operation state. The switching mechanism 32 is connected to the discharge side of the compressor 31, the suction side of the compressor 31, the gas refrigerant communication pipe 6, and the gas side of the indoor heat exchanger 33. The switching mechanism 32 is not limited to a four-way switching valve, and is configured to have a function of switching the flow direction of the refrigerant as described above, for example, by combining a plurality of electromagnetic valves. There may be. The indoor heat exchanger 33 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 gas side of the indoor heat exchanger 33 is connected to the switching mechanism 32, and the liquid side of the indoor heat exchanger 33 is connected to the indoor expansion valve 34. The indoor expansion valve 34 decompresses the refrigerant flowing into the indoor heat exchanger 33 during the cooling operation, and decompresses the refrigerant flowing out from the indoor heat exchanger 33 during the heating operation. The indoor expansion valve 34 is connected between the liquid side of the indoor heat exchanger 33 and the liquid refrigerant communication pipe 5. The accumulator 35 is connected between the switching mechanism 32 and the suction side of the compressor 31. Moreover, it connects to the control part 7 so that the switching mechanism 32 can be controlled with other apparatuses and valves.

  In addition, the structure of the air conditioning apparatus 101 is the same as that of the air conditioning apparatus 1 of said embodiment and its modification except said point. For this reason, in the air conditioning apparatus 101, there is a difference in that the switching mechanism 32 that is switched to the cooling operation state is interposed during the cooling operation, but the cooling operation similar to the air conditioning apparatus 1 of the above-described embodiment and the modified example thereof. The basic operation at the time, the indoor expansion valve 34 and the outdoor expansion valve 22 can be controlled. Further, during the heating operation, the switching mechanism 32 is switched to the heating operation state, so that the refrigerant in the refrigerant circuit 110 is supplied to the compressor 31, the switching mechanism 32, the indoor heat exchanger 33 as a refrigerant radiator, and the first expansion valve. As the indoor expansion valve 34, the receiver 23, the outdoor expansion valve 22 as the second expansion valve, the outdoor heat exchanger 21 as the refrigerant evaporator, the switching mechanism 32, and the accumulator 35 can be circulated in this order. . In such a heating operation, when performing the superheat degree control for controlling the opening degree of the outdoor expansion valve 22 so that the superheat degree SH at the outlet of the outdoor heat exchanger 21 becomes the target superheat degree SHs, the indoor expansion is performed. The first control and the second control in the above embodiment can be applied to the valve 34. Further, in the case of further performing supercooling degree control for controlling the opening degree of the indoor expansion valve 34 so that the supercooling degree SC at the outlet of the indoor heat exchanger 33 becomes the target supercooling degree SCs, The first control or the second control can be applied.

  The present invention is widely applicable to an air conditioner that controls the opening degree of an expansion valve so that the degree of superheat of the refrigerant at the outlet of the evaporator becomes a target degree of superheat.

DESCRIPTION OF SYMBOLS 1,101 Air conditioning apparatus 7 Control part 10,110 Refrigerant circuit 21 Outdoor heat exchanger (radiator, evaporator)
22 Outdoor expansion valves (first expansion valve, second expansion valve)
31 Compressor 33 Indoor heat exchanger (evaporator, radiator)
34 Indoor expansion valves (second expansion valve, first expansion valve)

Japanese Patent No. 2976905

Claims (8)

A compressor (31) that compresses the refrigerant, a radiator (21, 33) that radiates the refrigerant compressed in the compressor, and a first expansion valve (22) that depressurizes the refrigerant radiated in the radiator 34), a second expansion valve (34, 22) for depressurizing the refrigerant decompressed by the first expansion valve, and an evaporator (33, 21) for evaporating the refrigerant decompressed by the second expansion valve. And a refrigerant circuit (10, 110) configured by sequentially connecting,
A control unit (7) for performing superheat control for controlling the opening degree of the second expansion valve so that the superheat degree (SH) of the refrigerant at the outlet of the evaporator becomes a target superheat degree (SHs);
With
The controller performs a first control to reduce the opening of the first expansion valve when the opening of the second expansion valve is reduced to the improvement start opening in the superheat control.
Air conditioner (1, 101). The controller (7) performs the first control when a high pressure (HP) in the refrigeration cycle operation of the refrigerant circuit (10) is lower than a first improvement prohibiting pressure in the superheat control.
The air conditioner (1, 101) according to claim 1. The controller (7) performs the first expansion valve (22, 34) when the opening of the second expansion valve (34, 22) increases to the improvement end opening after the first control. ) To increase the opening of the second control,
The air conditioner (1, 101) according to claim 1 or 2. The improvement end opening is larger than the improvement start opening,
The air conditioner (1, 101) according to claim 3. The control unit (7) performs the second control even when the high pressure (HP) in the refrigeration cycle operation of the refrigerant circuit (10) is increased to the second improvement prohibition pressure after performing the first control. ,
The air conditioner (1, 101) according to claim 3 or 4. The controller (7) cancels the first control when the high pressure (HP) in the refrigeration cycle operation of the refrigerant circuit (10) has increased to the restoration pressure after performing the first control.
The air conditioner (1, 101) according to any one of claims 1 to 5. The control unit (7) controls the first expansion valve (22, 34) so that the supercooling degree (SC) of the refrigerant at the outlet of the radiator (21, 33) becomes a target supercooling degree (SCs). Supercooling degree control is performed to control the opening,
The control unit performs the first control by increasing the target supercooling degree.
The air conditioning apparatus (1, 101) according to any one of claims 1 to 6. Supercooling degree control is performed to control the opening degree of the first expansion valve (22, 34) so that the supercooling degree (SC) of the refrigerant at the outlet of the radiator becomes the target supercooling degree (SCs). ,
The control unit performs the second control by reducing the target supercooling degree.
The air conditioner (1, 101) according to any one of claims 3 to 5.

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