WO2014199788A1 - Air-conditioning device - Google Patents

Abstract

An air-conditioning device (1) wherein the operating capacity of a compressor (21) and/or the operating capacity of an outdoor fan (36) is changed, after which the change in the amount of refrigerant circulation passing through an upstream expansion valve (24, 26) and a downstream expansion valve (26, 24) is predicted, with the prediction condition being based on the correlation relationship between a high-pressure-side pressure difference (obtained by subtracting an intermediate pressure from a high pressure) and a low-pressure-side pressure difference (obtained by subtracting a low pressure from the intermediate pressure), and the predicted change in the amount of refrigerant circulation is taken into account to perform a control for changing the degree of opening of the upstream expansion valve (24, 26) and the downstream expansion valve (26, 24).

Description

Air conditioner

The present invention relates to an air conditioner, and more particularly, an air conditioner that circulates a refrigerant while expanding a high-pressure refrigerant discharged from a compressor by an upstream expansion valve and a downstream expansion valve in two stages in the order of intermediate pressure and low pressure. About.

Conventionally, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 10-132393), high-pressure refrigerant discharged from a compressor by an upstream expansion valve and a downstream expansion valve is expanded in two stages in the order of intermediate pressure and low pressure. There is an air conditioner having a refrigerant circuit that circulates a refrigerant while allowing the refrigerant to circulate. Specifically, the refrigerant circuit of the air conditioner is configured by connecting a compressor, an outdoor heat exchanger, two expansion valves, and an indoor heat exchanger.

Further, as shown in Patent Document 2 (Japanese Patent Laid-Open No. 2003-106683), as control of the opening degree of the expansion valve, high pressure and low pressure before and after the change of the operating capacity of the compressor (pressure of the refrigerant at the inlet and outlet of the expansion valve) There is an air conditioner that performs feedforward control in which the opening degree of the expansion valve is changed based on such a predicted value.

Here, in the air conditioner having the two-stage expansion refrigerant circuit shown in Patent Document 1, it is conceivable to apply the feedforward control of the expansion valve as in Patent Document 2.

At this time, in order to perform feedforward control for each of the two expansion valves constituting the refrigerant circuit of the two-stage expansion, it is necessary to predict the refrigerant pressure at the inlet and outlet of the expansion valve before and after the change in the operation capacity of the compressor There is. In such prediction, it is necessary to know not only the high pressure and low pressure in the refrigeration cycle, but also the intermediate pressure in the refrigeration cycle, which is the pressure of the refrigerant between the two expansion valves.

However, if a sensor for detecting the intermediate pressure is provided, the cost increases. Therefore, it is possible to perform feed-forward control of the two expansion valves without providing a sensor for detecting the intermediate pressure. Is desirable.

An object of the present invention is to enable feed-forward control of two expansion valves without providing a sensor for detecting an intermediate pressure in an air conditioner having a refrigerant circuit with two-stage expansion. is there.

An air conditioner according to a first aspect is configured by connecting a compressor, an outdoor heat exchanger, an upstream expansion valve, a downstream expansion valve, and an indoor heat exchanger, and includes an upstream expansion valve and a downstream side. A refrigerant circuit that circulates the refrigerant while expanding the high-pressure refrigerant discharged from the compressor by an expansion valve in two steps in the order of intermediate pressure and low pressure, and outdoor air that serves as a cooling source or heating source is supplied to the outdoor heat exchanger It is an air conditioner having an outdoor fan. And here, the operating capacity of the compressor and / or the outdoor under the prediction condition based on the correlation between the high pressure side pressure difference obtained by subtracting the intermediate pressure from the high pressure and the low pressure side pressure difference obtained by subtracting the low pressure from the intermediate pressure. Predicting changes in the amount of refrigerant circulating through the upstream and downstream expansion valves after changing the fan operating capacity, change the operating capacity of the compressor and / or the outdoor fan. In this case, control is performed to change the opening degree of the upstream side expansion valve and the downstream side expansion valve in consideration of the predicted change in the refrigerant circulation amount.

Here, when performing feedforward control of the upstream side expansion valve and downstream side expansion valve, the operating capacity of the compressor or outdoor fan is changed under a prediction condition based on the correlation between the high pressure side pressure difference and the low pressure side pressure difference. The change of the refrigerant circulation amount passing through the upstream side expansion valve and the downstream side expansion valve after being made is predicted.

Thereby, here, without providing a sensor for detecting the intermediate pressure, a change in the refrigerant circulation amount passing through the upstream expansion valve and the downstream expansion valve is predicted, and the upstream expansion valve and the downstream expansion valve are predicted. Feedforward control can be performed. And when the operating capacity of a compressor or an outdoor fan changes, the control followability of the opening degree of an upstream side expansion valve and a downstream side expansion valve can be improved.

The air conditioner according to the second aspect is the air conditioner according to the first aspect, wherein the correlation is before and after the operating capacity of the compressor and / or the operating capacity of the outdoor fan is changed. The relationship between the pressure difference and the low pressure side pressure difference is constant.

The air conditioner according to the third aspect is the air conditioner according to the first aspect, wherein the correlation is before and after the operating capacity of the compressor and / or the operating capacity of the outdoor fan is changed. The relationship is that the pressure difference is constant.

An air conditioner according to a fourth aspect is the air conditioner according to any one of the first to third aspects, wherein the upstream side expansion valve serves as a radiator radiator of the outdoor heat exchanger and the indoor heat exchanger. The opening degree is controlled so that the degree of subcooling of the refrigerant at the outlet of the functioning heat exchanger becomes a predetermined target degree of subcooling, and the downstream expansion valve is an evaporator of the refrigerant among the outdoor heat exchanger and the indoor heat exchanger. The degree of opening is controlled so that the degree of superheat of the refrigerant at the outlet of the heat exchanger that functions as a predetermined target superheat degree.

Here, as the opening degree control of the upstream side expansion valve and the downstream side expansion valve, feedback control based on the degree of supercooling and the degree of superheat is performed together with feedforward control. Therefore, here, when the operating capacities of the compressor and the outdoor fan change, the opening degree of the upstream expansion valve and the downstream expansion valve is adjusted by feedforward control after the operating capacities of the compressor and the outdoor fan change. Can be made to coincide with the optimum opening degree by feedback control after being brought close to the optimum opening degree in advance.

Thereby, here, the time required for feedback control of the upstream side expansion valve and the downstream side expansion valve can be effectively shortened. And when the operating capacity of a compressor or an outdoor fan changes, the control followability of the opening degree of an upstream side expansion valve and a downstream side expansion valve can be improved.

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 figure which shows the detail of a control structure of a compressor, an outdoor fan, and two expansion valves. It is a flowchart of feedforward control of two expansion valves. It is a flowchart of feedforward control of two expansion valves concerning a modification.

Hereinafter, embodiments of the air-conditioning apparatus according to the present invention and modifications thereof 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 and its modification, 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 that can cool and heat 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. Various refrigerants can be used as the refrigerant sealed in the refrigerant circuit 10, but here, R32, which is a kind of HFC refrigerant, is enclosed as the refrigerant.

<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 room 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 sucking indoor air into the indoor unit 4 and exchanging heat with the refrigerant in the indoor heat exchanger 41 and supplying the indoor air as supply air. The indoor fan 42 is driven by an indoor fan motor 43.

The indoor unit 4 is provided with various sensors. Specifically, the indoor heat exchanger 41 includes an indoor heat exchange liquid side temperature sensor 57 that detects the temperature Trrl of the refrigerant on the liquid side of the indoor heat exchanger 41, and the refrigerant in the intermediate portion of the indoor heat exchanger 41. An indoor heat exchanger intermediate temperature sensor 58 for detecting the temperature Trrm is provided. The indoor unit 4 is provided with an indoor temperature sensor 59 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 44 that controls the operation of each unit constituting the indoor unit 4. The indoor side control unit 44 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 8a.

<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, a first expansion valve 24, a receiver 25, a second expansion valve 26, and a liquid side closing valve 27. And a gas side closing valve 28.

The compressor 21 is a device that compresses the low-pressure refrigerant in the refrigeration cycle until it reaches a high pressure. The compressor 21 has a hermetic structure in which a displacement type compression element (not shown) such as a rotary type or a scroll type is driven by a compressor motor 21a whose frequency is controlled by an inverter. Thereby, the compressor 21 is configured such that its operating capacity is variable. 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 suction pipe 31 is provided with an accumulator 29. 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 discharge pipe 32 is provided with a check valve 32a.

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 that 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 first expansion valve 24 functions as an upstream expansion valve for expanding the refrigerant discharged from the compressor 21 in two stages during the cooling operation, and the high-pressure refrigerant in the refrigeration cycle radiating heat in the outdoor heat exchanger 23 is It is a valve that reduces the pressure to an intermediate pressure in the refrigeration cycle. In addition, the first expansion valve 24 functions as a downstream expansion valve for expanding the refrigerant discharged from the compressor 21 in two stages during the heating operation, and is an intermediate-pressure refrigerant in the refrigeration cycle stored in the receiver 25. Is a valve for reducing the pressure to a low pressure in the refrigeration cycle. The first expansion valve 24 is provided in a portion of the liquid refrigerant pipe 35 between the outdoor heat exchanger 23 and the receiver 25.

The receiver 25 is provided between the first expansion valve 24 and the second expansion valve 26 (that is, between the upstream expansion valve and the downstream expansion valve). The receiver 25 is a container that can store an intermediate-pressure refrigerant in the refrigeration cycle during cooling operation and heating operation.

The second expansion valve 26 functions as a downstream expansion valve for expanding the refrigerant discharged from the compressor 21 in two stages during the cooling operation, and refrigerates the intermediate-pressure refrigerant in the refrigeration cycle stored in the receiver 25. A valve that reduces the pressure to a low pressure in the cycle. The second expansion valve 26 functions as an upstream expansion valve for expanding the refrigerant discharged from the compressor 21 in two stages during the heating operation, and has a high pressure in the refrigeration cycle that dissipates heat in the indoor heat exchanger 41. It is a valve that reduces the refrigerant to an intermediate pressure in the refrigeration cycle. The second expansion valve 26 is provided in a portion of the liquid refrigerant pipe 35 between the receiver 25 and the liquid side closing valve 27.

The liquid side shut-off valve 27 and the gas side shut-off valve 28 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 27 is provided at the end of the liquid refrigerant pipe 35. The gas side closing valve 28 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, exchanging heat with the refrigerant in the outdoor heat exchanger 23, and then discharging the air to the outside. The outdoor fan 36 is driven by an outdoor fan motor 37 capable of controlling the rotation speed. As a result, the outdoor fan 36 has a variable operating capacity.

The outdoor unit 2 is provided with various sensors. Specifically, the suction pipe 31 is provided with a suction temperature sensor 51 that detects the temperature Ts of the low-pressure refrigerant in the refrigeration cycle sucked into the compressor 21. The discharge pipe 32 is provided with a discharge temperature sensor 52 that detects the temperature Td of the high-pressure refrigerant in the refrigeration cycle discharged from the compressor 21. The outdoor heat exchanger 23 includes an outdoor heat exchange intermediate temperature sensor 53 that detects a refrigerant temperature Torm in an intermediate portion of the outdoor heat exchanger 23, and an outdoor that detects a refrigerant temperature Torl on the liquid side of the outdoor heat exchanger 23. A heat exchanger side temperature sensor 54 is provided. The outdoor unit 2 is provided with an outdoor temperature sensor 55 that detects the temperature Toa of the outdoor air sucked into the outdoor unit 2. The liquid refrigerant pipe 35 is provided with a liquid pipe temperature sensor 56 that detects a liquid pipe temperature Tlp of the refrigerant in a portion between the second expansion valve 26 and the liquid side closing valve 27.

The outdoor unit 2 includes an outdoor control unit 38 that controls the operation of each unit constituting the outdoor unit 2. The outdoor control unit 38 includes a microcomputer and a memory provided for controlling the outdoor unit 2, and exchanges control signals and the like with the indoor unit 4 via the transmission line 8 a. 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 refrigerant circuit 10 of the air conditioner 1 switches the four-way switching valve 22 to the cooling cycle state, so that the compressor 21, the outdoor heat exchanger 23, the first expansion valve 24 as the upstream expansion valve, and the downstream expansion valve. The second expansion valve 26 and the indoor heat exchanger 41 are connected, and the compressor 21 is connected by the first expansion valve 24 as the upstream side expansion valve and the second expansion valve 26 as the downstream side expansion valve. A cooling operation is performed in which the high-pressure refrigerant discharged from the refrigerant is circulated in two stages in the order of intermediate pressure and low pressure. Moreover, the refrigerant circuit 10 of the air conditioning apparatus 1 switches the four-way switching valve 22 to the heating cycle state, so that the compressor 21, the indoor heat exchanger 41, the second expansion valve 26 as an upstream expansion valve, and the downstream side. A first expansion valve 24 as an expansion valve and an outdoor heat exchanger 23 are connected, and compression is performed by a second expansion valve 26 as an upstream expansion valve and a first expansion valve 24 as a downstream expansion valve. Heating operation is performed in which the high-pressure refrigerant discharged from the machine 21 is expanded in two stages in the order of intermediate pressure and low pressure, and the refrigerant is circulated. The air conditioner 1 also includes an outdoor fan 36 that supplies outdoor air to the outdoor heat exchanger 23 as a cooling source or a heating source.

<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 44 and the outdoor side control unit 38. That is, the control unit 8 that performs operation control of the entire air conditioner 1 including the cooling operation and the heating operation described above is configured by the transmission line 8a that connects between the indoor side control unit 44 and the outdoor side control unit 38. Has been. As shown in FIG. 2, the control unit 8 is connected so as to receive detection signals from various sensors 51 to 59 and the like, and based on these detection signals and the like, various devices and valves 21a, 22 are connected. , 24, 26, 37, 43, etc. are connected so that they can be controlled.

(2) Basic operation | movement of an air conditioning apparatus Next, the basic operation | movement of the air conditioning apparatus 1 is demonstrated using FIG. The air conditioner 1 can perform a cooling operation and a heating operation as basic operations.

<Heating operation>
During the heating operation, the four-way switching valve 22 is switched to the heating cycle state (the state indicated by the broken line in FIG. 1).

In the refrigerant circuit 10, the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21, compressed after being compressed to a high pressure in the refrigeration cycle, and then discharged.

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 28 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 second expansion valve 26 as the upstream side expansion valve through the liquid refrigerant communication pipe 5 and the liquid side closing valve 27.

The high-pressure liquid refrigerant sent to the second expansion valve 26 is depressurized to the intermediate pressure in the refrigeration cycle by the second expansion valve 26, and becomes an intermediate-pressure gas-liquid two-phase refrigerant.

The intermediate-pressure gas-liquid two-phase refrigerant decompressed by the second expansion valve 26 is temporarily stored in the receiver 25 and then sent to the first expansion valve 24 as a downstream expansion valve.

The intermediate-pressure gas-liquid two-phase refrigerant sent to the first expansion valve 24 is depressurized by the first 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 first 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.

During such heating operation, the control unit 8 controls the operating capacity of the compressor 21 and the outdoor fan 36 according to the required heating load of the indoor unit 4, and controls the opening of the expansion valves 24 and 26. Is also going. The control of the operating capacity of the compressor 21 and the outdoor fan 36 and the opening control of the expansion valves 24 and 26 will be described later.

<Cooling operation>
During the cooling operation, the four-way switching valve 22 is switched to the cooling cycle state (state indicated by the solid line in FIG. 1).

In the refrigerant circuit 10, the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21, compressed after being compressed to a high pressure in the refrigeration cycle, and then discharged.

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 a first expansion valve 24 as an upstream expansion valve.

The high-pressure liquid refrigerant sent to the first expansion valve 24 is depressurized to the intermediate pressure in the refrigeration cycle by the first expansion valve 24, and becomes an intermediate-pressure gas-liquid two-phase refrigerant.

The intermediate-pressure gas-liquid two-phase refrigerant decompressed by the first expansion valve 24 is temporarily stored in the receiver 25 and then sent to the second expansion valve 26 as a downstream expansion valve.

The intermediate-pressure gas-liquid two-phase refrigerant sent to the second expansion valve 26 is depressurized to a low pressure in the refrigeration cycle by the second expansion valve 26 to become a low-pressure gas-liquid two-phase refrigerant.

The low-pressure gas-liquid two-phase refrigerant decompressed by the second expansion valve 26 is sent to the indoor heat exchanger 41 through the liquid side closing valve 27 and the liquid refrigerant communication pipe 5.

The low-pressure gas-liquid two-phase refrigerant sent to the indoor heat exchanger 41 evaporates in the indoor heat exchanger 41 by exchanging heat with indoor air supplied as a heating source by the indoor fan 42. 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 28 and the four-way switching valve 22.

During such cooling operation, the control unit 8 controls the operation capacity of the compressor 21 and the outdoor fan 36 according to the required heating load of the indoor unit 4, and controls the opening degree of the expansion valves 24 and 26. Is also going. The control of the operating capacity of the compressor 21 and the outdoor fan 36 and the opening control of the two expansion valves 24 and 26 will be described later.

(3) Control of Compressor, Outdoor Fan, and Two Expansion Valves Next, control of the compressor 21, the outdoor fan 36, and the two expansion valves 24, 26 will be described with reference to FIGS.

<Control of operating capacity of compressor and outdoor fan>
Control of the operating capacity of the compressor 21 and / or the outdoor fan 36 is performed by a capacity controller 82 of the controller 8 as shown in FIG. The capacity control unit 82 controls the operating capacity of the compressor 21 and / or the outdoor fan 36 so that the low pressure or high pressure in the refrigeration cycle of the refrigerant circuit 10 becomes a target value. Here, the target value of the low pressure or high pressure (or the evaporation temperature or the condensation temperature corresponding to the low pressure or high pressure) in the refrigeration cycle of the refrigerant circuit 10 is set by a target value determination unit 81 of the control unit 8 as shown in FIG. Is set. Hereinafter, the control of the operation capacity of the compressor 21 and / or the outdoor fan 36 will be described separately for the cooling operation and the heating operation.

-During heating operation-
In the heating operation, the target value determination unit 81 sets the indoor set temperature Tt input from a remote controller (not shown) or the like, and the refrigerant temperature Trrm in the indoor heat exchanger 41 detected by the indoor heat exchanger intermediate temperature sensor 58. Based on (here, corresponding to the condensation temperature Tc corresponding to the high pressure in the refrigeration cycle of the refrigerant circuit 10), the target condensation temperature Tcs that is the target value of the condensation temperature Tc is set. For example, when the temperature difference obtained by subtracting the refrigerant temperature Trrm in the indoor heat exchanger 41 from the set temperature Tt is large, the heating capacity needs to be increased, so the target condensing temperature Tcs is set to be high. In addition, when the temperature difference obtained by subtracting the refrigerant temperature Trrm in the indoor heat exchanger 41 from the set temperature Tt is small, the heating capacity needs to be reduced, so the target condensation temperature Tcs is set to be low.

The capacity control unit 82 changes the frequency of the compressor motor 21a so that the condensation temperature Tc corresponding to the high pressure in the refrigeration cycle of the refrigerant circuit 10 becomes the target condensation temperature Tcs set by the target value determination unit 81. By doing so, the operating capacity of the compressor 21 is controlled. For example, when the condensation temperature Tc is lower than the target condensation temperature Tcs, the operating capacity of the compressor 21 is changed to increase by increasing the frequency of the compressor motor 21a. In addition, when the condensation temperature Tc is higher than the target condensation temperature Tcs, the operating capacity of the compressor 21 is changed to be decreased by decreasing the frequency of the compressor motor 21a. The capacity control unit 82 controls the operating capacity of the outdoor fan 36 by changing the rotational speed of the outdoor fan motor 37 so that the condensation temperature Tc becomes the target condensation temperature Tcs. For example, when the condensation temperature Tc is lower than the target condensation temperature Tcs, the rotational speed of the outdoor fan motor 37 is increased to change the operating capacity of the outdoor fan 36. When the condensation temperature Tc is higher than the target condensation temperature Tcs, the rotational speed of the outdoor fan motor 37 is decreased to change the operating capacity of the outdoor fan 36.

Here, the capacity control unit 82 controls the operating capacities of the compressor 21 and the outdoor fan 36. However, only the operating capacities of the compressor 21 may be controlled, or the operating of the outdoor fan 36 may be controlled. Only the capacity may be controlled.

-During cooling operation-
In the cooling operation, the target value determining unit 81 sets the indoor set temperature Tt input from a remote controller (not shown) or the like, and the refrigerant temperature Trrm in the indoor heat exchanger 41 detected by the indoor heat exchanger intermediate temperature sensor 58. Based on (here, corresponding to the evaporation temperature Te corresponding to the low pressure in the refrigeration cycle of the refrigerant circuit 10), the target evaporation temperature Tes that is the target value of the evaporation temperature Te is set. For example, when the temperature difference obtained by subtracting the set temperature Tt from the refrigerant temperature Trrm in the indoor heat exchanger 41 is large, it is necessary to increase the cooling capacity, so that the target evaporation temperature Tes is set to be low. Further, when the temperature difference obtained by subtracting the set temperature Tt from the refrigerant temperature Trrm in the indoor heat exchanger 41 is small, it is necessary to reduce the cooling capacity, so that the target evaporation temperature Tes is set to be high.

Then, the capacity control unit 82 changes the frequency of the compressor motor 21a so that the evaporation temperature Te corresponding to the low pressure in the refrigeration cycle of the refrigerant circuit 10 becomes the target evaporation temperature Tes set by the target value determining unit 81. By doing so, the operating capacity of the compressor 21 is controlled. For example, when the evaporation temperature Te is higher than the target evaporation temperature Tes, the operating capacity of the compressor 21 is changed to increase by increasing the frequency of the compressor motor 21a. Further, when the evaporation temperature Te is lower than the target evaporation temperature Tes, the operating capacity of the compressor 21 is changed in a direction to decrease by decreasing the frequency of the compressor motor 21a. The capacity control unit 82 controls the operating capacity of the outdoor fan 36 by changing the rotational speed of the outdoor fan motor 37 so that the evaporation temperature Te becomes the target evaporation temperature Tes. For example, when the evaporation temperature Te is higher than the target evaporation temperature Tes, the rotational speed of the outdoor fan motor 37 is increased to change the operating capacity of the outdoor fan 36. Further, when the evaporation temperature Te is lower than the target evaporation temperature Tes, the operation speed of the outdoor fan 36 is changed by decreasing the rotational speed of the outdoor fan motor 37.

Here, the capacity control unit 82 controls the operating capacities of the compressor 21 and the outdoor fan 36. However, only the operating capacities of the compressor 21 may be controlled, or the operating of the outdoor fan 36 may be controlled. Only the capacity may be controlled.

<Feedback control of expansion valve>
Here, as the opening control of the two expansion valves 24 and 26, feedback control based on the degree of supercooling and the degree of superheat is performed along with feedforward control described later. The feedback control of the expansion valves 24 and 26 is performed by a feedback control unit 84 of the control unit 8 as shown in FIG. The feedback control unit 84 expands the refrigerant so that the degree of subcooling of the refrigerant at the outlet of the heat exchanger functioning as a refrigerant radiator of the outdoor heat exchanger 23 and the indoor heat exchanger 41 becomes a predetermined target subcooling degree. Of the valves 24 and 26, the opening degree of the expansion valve that functions as the upstream side expansion valve is controlled. Further, the feedback control unit 84 expands the refrigerant so that the superheat degree of the refrigerant at the outlet of the heat exchanger functioning as the refrigerant evaporator of the outdoor heat exchanger 23 and the indoor heat exchanger 41 becomes a predetermined target superheat degree. Of the valves 24 and 26, the opening degree of the expansion valve that functions as a downstream side expansion valve is controlled. Hereinafter, feedback control of the expansion valves 24 and 26 will be described separately for the cooling operation and the heating operation.

-During heating operation-
During the heating operation, the feedback control unit 84 functions as an upstream expansion valve located on the upstream side of the receiver 25 so that the refrigerant subcooling degree SC at the outlet of the indoor heat exchanger 41 becomes the target subcooling degree SCs. The opening degree of the second expansion valve 26 is controlled. For example, when the supercooling degree SC is larger than the target supercooling degree SCs, the opening degree of the second expansion valve 26 is changed to be increased in order to increase the flow rate of the refrigerant passing through the indoor heat exchanger 41. To do. Further, when the degree of supercooling SC is smaller than the target degree of supercooling SCs, in order to reduce the flow rate of the refrigerant passing through the indoor heat exchanger 41, the opening degree of the second expansion valve 26 is changed to be smaller. To do. Here, the supercooling degree SC of the refrigerant at the outlet of the indoor heat exchanger 41 is the temperature of the refrigerant detected by the indoor heat exchanger side temperature sensor 57 from the refrigerant temperature Trrm detected by the indoor heat exchanger intermediate temperature sensor 58. It is obtained by subtracting Trrl.

Further, during the heating operation, the feedback control 84 is a downstream expansion valve located on the downstream side of the receiver 25 so that the superheat degree SH of the refrigerant at the outlet of the outdoor heat exchanger 23 becomes a predetermined target superheat degree SHs. The opening degree of the first expansion valve 24 is controlled. For example, when the superheat degree SH is larger than the target superheat degree SHs, the opening degree of the first expansion valve 24 is changed to increase in order to increase the flow rate of the refrigerant passing through the outdoor heat exchanger 23. Further, when the superheat degree SH is smaller than the target superheat degree SHs, the opening degree of the first expansion valve 24 is changed to be smaller in order to reduce the flow rate of the refrigerant passing through the outdoor heat exchanger 23. Here, the superheat degree SH of the refrigerant at the outlet of the outdoor heat exchanger 23 is obtained by subtracting the refrigerant temperature Tor detected by the outdoor heat exchanger intermediate temperature sensor 53 from the refrigerant temperature Ts detected by the suction temperature sensor 51. can get.

The sensor for obtaining the degree of supercooling SC and the degree of superheating SH is not limited to the above, and when a pressure sensor for detecting high pressure and low pressure in the refrigeration cycle is provided and / or heat When other temperature sensors are provided in the exchanger and in the vicinity thereof, detection values of these sensors may be used.

-During cooling operation-
During the cooling operation, the feedback control unit 84 functions as an upstream expansion valve located on the upstream side of the receiver 25 so that the refrigerant subcooling degree SC at the outlet of the outdoor heat exchanger 23 becomes the target subcooling degree SCs. The opening degree of the first expansion valve 24 is controlled. For example, when the degree of supercooling SC is larger than the target degree of supercooling SCs, the opening degree of the first expansion valve 24 is changed to increase in order to increase the flow rate of the refrigerant passing through the outdoor heat exchanger 23. To do. Further, when the degree of supercooling SC is smaller than the target degree of supercooling SCs, in order to reduce the flow rate of the refrigerant passing through the outdoor heat exchanger 23, the opening degree of the first expansion valve 24 is changed to be smaller. To do. Here, the supercooling degree SC of the refrigerant at the outlet of the outdoor heat exchanger 23 is the temperature of the refrigerant detected by the outdoor heat exchanger side temperature sensor 54 from the refrigerant temperature Tor detected by the outdoor heat exchanger intermediate temperature sensor 53. It is obtained by subtracting Tor.

Further, during the cooling operation, the feedback control 84 is a downstream expansion valve located on the downstream side of the receiver 25 so that the superheat degree SH of the refrigerant at the outlet of the indoor heat exchanger 41 becomes a predetermined target superheat degree SHs. The opening degree of the second expansion valve 26 is controlled. For example, when the superheat degree SH is larger than the target superheat degree SHs, the opening degree of the second expansion valve 26 is changed to increase in order to increase the flow rate of the refrigerant passing through the indoor heat exchanger 41. When the superheat degree SH is smaller than the target superheat degree SHs, in order to reduce the flow rate of the refrigerant passing through the indoor heat exchanger 41, the opening degree of the second expansion valve 26 is changed. Here, the superheat degree SH of the refrigerant at the outlet of the indoor heat exchanger 41 is obtained by subtracting the refrigerant temperature Trrm detected by the indoor heat exchanger intermediate temperature sensor 58 from the refrigerant temperature Ts detected by the suction temperature sensor 51. can get.

The sensor for obtaining the degree of supercooling SC and the degree of superheating SH is not limited to the above, and when a pressure sensor for detecting high pressure and low pressure in the refrigeration cycle is provided and / or heat When other temperature sensors are provided in the exchanger and in the vicinity thereof, detection values of these sensors may be used.

<Feed-forward control of expansion valve>
Here, as the opening control of the two expansion valves 24, 26, the refrigerant that passes through the expansion valves 24, 26 when the operation capacity of the compressor 21 and / or the operation capacity of the outdoor fan 36 is changed. Feed-forward control is performed in which a change in the circulation amount is predicted, and the opening degree of the two expansion valves 24 and 26 as the upstream expansion valve and the downstream expansion valve is changed in consideration of the predicted change in the refrigerant circulation amount. I am doing so. The feedforward control of the expansion valves 24 and 26 is performed by a feedforward control unit 83 of the control unit 8 as shown in FIG. The feedforward control unit 83 includes a prediction unit 83a and an opening change unit 83b. The predicting unit 83a includes a compressor under a prediction condition based on a correlation between a high pressure side pressure difference obtained by subtracting the intermediate pressure in the refrigeration cycle from a high pressure in the refrigeration cycle and a low pressure side pressure difference obtained by subtracting the low pressure in the refrigeration cycle from the intermediate pressure. 21 and / or a change in the refrigerant circulation amount passing through the two expansion valves 24 and 26 as the downstream expansion valve after changing the operation capacity of the outdoor fan 36 is predicted. . The predicting unit 83a takes into account the change in the refrigerant circulation amount predicted when the operating capacity of the compressor 21 and / or the operating capacity of the outdoor fan 36 is changed. The opening degree of the two expansion valves 24 and 26 as the expansion valves is calculated. The opening changing unit 83b performs control to change the opening of the two expansion valves 24 and 26 as the upstream expansion valve and the downstream expansion valve to the opening calculated by the prediction unit 83a. Hereinafter, the feedforward control of the expansion valves 24 and 26 will be described separately for the cooling operation and the heating operation.

-During heating operation-
During the heating operation, the feedforward control unit 83 first determines whether or not the operation capacity of the compressor 21 and / or the operation capacity of the outdoor fan 36 changes as shown in FIG. 4 (step ST1). . Here, the operating capacity of the compressor 21 and / or the outdoor fan 36 is changed by controlling the operating capacity of the compressor 21 and / or the outdoor fan 36 described above. For this reason, when it determines with the operation capacity of the compressor 21 and / or the outdoor fan 36 changing in step ST1, the control of the operation capacity of the above-mentioned compressor 21 and / or the outdoor fan 36 is performed. Means. If it is determined in step ST1 that the operating capacity of the compressor 21 and / or the outdoor fan 36 changes, the process proceeds to steps ST2 to ST7.

Next, in step ST2, the prediction unit 83a of the feedforward control unit 83 performs two expansions immediately before the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, immediately before the operation capacity changes). A virtual combined opening EVFF before the change in operating capacity is calculated by adding the openings EVu and EVd of the valves 24 and 26. For example, when an expansion valve having a characteristic in which the opening degree and the Cv value are proportional to each other is adopted as the expansion valves 24 and 26, the virtual total opening degree EVFF before the operation capacity change is calculated by the following formula <1>.

1 / EVFF = 1 / EVu + 1 / EVd (1)
Here, EVu is the value of the upstream side expansion valve (here, the second expansion valve 26) immediately before the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, immediately before the operation capacity changes). The opening degree (here, the opening degree normalized so that the maximum opening degree is 1). In addition, EVd indicates that the downstream expansion valve (here, the first expansion valve 24) is opened immediately before the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, immediately before the operation capacity changes). Degree (here, the opening degree normalized so that the maximum opening degree is 1).

Next, in step ST3, the prediction unit 83a passes through the two expansion valves 24 and 26 immediately before the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, immediately before the operation capacity changes). The refrigerant circulation amount Gr before the operating capacity change is calculated. Here, the refrigerant circulation amount Gr before the operation capacity change can be expressed as a function of the virtual total opening EVFF before the operation capacity change calculated in step ST2, as in the following formula <2>.

Gr = f (EVFF) (2)
Next, in step ST4, the prediction unit 83a sets the two expansion valves 24 and 26 immediately after the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, immediately after the operation capacity is changed). The refrigerant circulation amount Grc after the change in operating capacity to pass through is calculated. Here, the refrigerant circulation amount Grc after the change in the operation capacity is the operation capacity ratio Fcc / Fc before and after the change in the operation capacity of the compressor 21 and the change in the operation capacity of the outdoor fan 36 before and after the change as shown in the following equation <3>. It can be expressed as a function of the operating capacity ratio Ffc / Ff, the condensation temperature Tc in the refrigeration cycle before the operating capacity change, the evaporation temperature Te in the refrigeration cycle before the operating capacity change, and the refrigerant circulation amount Gr before the operating capacity change.

Grc = f (Fcc / Fc, Ffc / Ff, Tc, Te) × Gr (3)
Here, Fcc is the operating capacity of the compressor 21 immediately after the operating capacity of the compressor 21 is controlled (that is, immediately after the operating capacity changes), and Fc is the control of the operating capacity of the compressor 21. Is the operating capacity of the compressor 21 immediately before the operation is performed (that is, immediately before the operating capacity is changed). Here, the frequency ratio of the compressor motor 21a before and after the change in the operation capacity of the compressor 21 is used as the operation capacity ratio Fcc / Fc before and after the change in the operation capacity of the compressor 21. Ffc is the operating capacity of the outdoor fan 36 immediately after the operating capacity of the outdoor fan 36 is controlled (that is, immediately after the operating capacity is changed), and Ff is the operating capacity of the outdoor fan 36. This is the operating capacity of the outdoor fan 36 immediately before it is performed (that is, immediately before the operating capacity changes). Here, the rotational speed ratio of the outdoor fan motor 37 before and after the change in the operating capacity of the outdoor fan 36 is used as the operating capacity ratio Ffc / Ff before and after the change in the operating capacity of the outdoor fan 36. Further, as the condensation temperature Tc in the refrigeration cycle before the operation capacity change, during the heating operation, the refrigerant temperature Trrm in the indoor heat exchanger 41 functioning as a refrigerant condenser is used, and the refrigeration cycle before the operation capacity change. As the evaporation temperature Te, the refrigerant temperature Tor in the indoor heat exchanger 23 functioning as the refrigerant evaporator is used (during cooling operation, the temperature Tor becomes the condensation temperature Tc, and the temperature Trrm is equal to the evaporation temperature Te. Become).

Next, in step ST5, the prediction unit 83a determines whether the two expansion valves 24 and 26 immediately after the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, immediately after the operation capacity is changed). A virtual combined opening EVFFc after changing the operating capacity is calculated by adding the opening (that is, the opening EVuc of the upstream expansion valve after changing the operating capacity and the opening EVdc of the downstream expansion valve after changing the operating capacity). To do. Here, the virtual combined opening EVFFc after the change in the operation capacity can be expressed as a function of the refrigerant circulation amount Grc after the change in the operation capacity calculated in step ST4 as in the following formula <4>.

EVFFc = f (Grc) (4)
Next, in step ST6, the prediction unit 83a uses the virtual total opening EVFFc after the change in operating capacity calculated in step ST5, and the openings EVuc and EVdc after the changes in operating capacity of the two expansion valves 24 and 26. Is calculated.

Here, in order to calculate the opening degree EVuc and EVdc after the operation capacity change of the two expansion valves 24 and 26, the refrigerant pressure at the inlet and outlet of the first expansion valve 24, the inlet of the second expansion valve 26 and It is necessary to predict the refrigerant pressure at the outlet. In such prediction, it is necessary to know not only the high pressure Ph and low pressure Pl in the refrigeration cycle, but also the intermediate pressure Pm in the refrigeration cycle, which is the pressure of the refrigerant between the two expansion valves 24 and 26.

However, here, the sensors 53 and 58 for detecting the condensation temperature Tc corresponding to the high pressure Ph and the evaporation temperature Te corresponding to the low pressure Pl are provided, but a sensor for detecting the intermediate pressure Pm is provided. Not.

Therefore, here, a prediction condition is set based on the correlation between the high pressure side pressure difference ΔPh obtained by subtracting the intermediate pressure Pm from the high pressure Ph and the low pressure side pressure difference ΔP1 obtained by subtracting the low pressure Pl from the intermediate pressure Pm. Specifically, as this correlation, the relationship between the high pressure side pressure difference ΔPh and the low pressure side pressure difference ΔPl is constant before and after the operating capacity of the compressor 21 and / or the outdoor fan 36 is changed. It is set.

That is, here, the following two formulas <5> and <6>, the virtual combined opening EVFFc after the operating capacity change calculated in step ST5, and the opening EVu and EVd before the known operating capacity change, Is used to calculate the opening degree EVuc and EVdc after the change of the operating capacity of the two expansion valves 24 and 26.

1 / EVFFc = 1 / EVuc + 1 / EVdc... <5>
EVu: EVd = EVuc: EVdc ... <6>
Next, in step ST7, the opening changing unit 83b of the feedforward control unit 83 performs control to change the opening of the two expansion valves 24 and 26 to the opening EVuc and EVdc calculated in step ST6.

Then, the process returns to step ST1 again, and each time the operating capacity of the compressor 21 and / or the outdoor fan 36 is changed, the process of steps ST2 to ST7 is performed. In this way, feedforward control of the two expansion valves 24 and 26 is performed.

-During cooling operation-
Even during the cooling operation, the same feedforward control as that during the heating operation described above is performed. During heating operation, the second expansion valve 26 functions as an upstream expansion valve, the first expansion valve 24 functions as a downstream expansion valve, and the indoor heat exchanger 41 functions as a refrigerant condenser. And the outdoor heat exchanger 23 functions as a refrigerant evaporator, whereas the first expansion valve 24 functions as an upstream expansion valve and the second expansion valve during cooling operation. 26 is functioning as a downstream expansion valve, the outdoor heat exchanger 23 is functioning as a refrigerant condenser, and the indoor heat exchanger 41 is functioning as a refrigerant evaporator. Since it is the same as that at the time of heating operation except for a point, detailed description is abbreviate | omitted here.

(4) Features of the air conditioner The air conditioner 1 of the present embodiment has the following features.

Here, as described above, under the prediction condition based on the correlation between the high pressure side pressure difference ΔPh obtained by subtracting the intermediate pressure Pm from the high pressure Ph and the low pressure side pressure difference ΔP1 obtained by subtracting the low pressure Pl from the intermediate pressure Pm, the compressor 21 and / or a change in the amount of refrigerant circulating through the upstream expansion valve and the downstream expansion valve (in this case, the expansion valves 24 and 26) after changing the operation capacity of the outdoor fan 36 is predicted. Then, when the operating capacity of the compressor 21 and / or the operating capacity of the outdoor fan 36 is changed, the upstream expansion valve and the downstream expansion valve are opened in consideration of the predicted change in the refrigerant circulation amount. Control is performed to change the degree.

That is, here, in performing feedforward control of the upstream side expansion valve and the downstream side expansion valve, the compressor 21 and the outdoor fan are used under the prediction condition based on the correlation between the high pressure side pressure difference ΔPh and the low pressure side pressure difference ΔPm. The change of the refrigerant circulation amount passing through the upstream side expansion valve and the downstream side expansion valve after changing the operation capacity of 36 is predicted. Here, as a correlation, the ratio between the high pressure side pressure difference ΔPh and the low pressure side pressure difference ΔPl is constant before and after the operation capacity of the compressor 21 and / or the operation capacity of the outdoor fan 36 is changed. The relationship that there is.

Thereby, here, without providing a sensor for detecting the intermediate pressure Pm, a change in the refrigerant circulation amount passing through the upstream expansion valve and the downstream expansion valve is predicted, and the upstream expansion valve and the downstream expansion valve are predicted. Valve feedforward control can be performed. And when the operating capacity of the compressor 21 and the outdoor fan 36 changes, the control followability of the opening degree of the upstream side expansion valve and the downstream side expansion valve can be improved.

Here, as described above, heat exchange in which the upstream expansion valve (here, one of the expansion valves 24 and 26) functions as a refrigerant radiator of the outdoor heat exchanger 23 and the indoor heat exchanger 41. The degree of opening of the refrigerant is controlled so that the refrigerant supercooling degree SC at the outlet of the evaporator becomes a predetermined target supercooling degree SCs, and the downstream expansion valve (here, the other of the expansion valves 24 and 26) is connected to the outdoor heat exchanger 23. In addition, the opening degree is controlled so that the superheat degree SH of the refrigerant at the outlet of the heat exchanger functioning as the refrigerant evaporator of the indoor heat exchanger 41 becomes a predetermined target superheat degree SHs.

Here, feedback control based on the degree of supercooling and the degree of superheat is performed together with the feedforward control described above as the opening degree control of the upstream side expansion valve and the downstream side expansion valve. Therefore, here, when the operating capacities of the compressor 21 and the outdoor fan 36 change, the opening degrees of the upstream side expansion valve and the downstream side expansion valve are controlled by feedforward control to operate the compressor 21 and the outdoor fan 36. After approaching the optimum opening after the change in capacity in advance, it can be made to coincide with the optimum opening by feedback control.

Thereby, here, the time required for feedback control of the upstream side expansion valve and the downstream side expansion valve can be effectively shortened. And when the operating capacity of the compressor 21 and the outdoor fan 36 changes, the control followability of the opening degree of the upstream side expansion valve and the downstream side expansion valve can be improved.

(5) Modified Example In the feed forward control (see FIG. 4) of the two expansion valves 24 and 26 described above, when performing the feed forward control of the upstream expansion valve and the downstream expansion valve, the high pressure side pressure difference ΔPh and the low pressure side As a correlation with the pressure difference ΔPm, the ratio between the high pressure side pressure difference ΔPh and the low pressure side pressure difference ΔPl is constant before and after the operation capacity of the compressor 21 and / or the operation capacity of the outdoor fan 36 is changed. Although there is a relationship that there is, it is not limited to this.

For example, as a correlation, a relationship in which the high-pressure side pressure difference ΔPh is constant before and after the operation capacity of the compressor 21 and / or the operation capacity of the outdoor fan 36 is changed may be set. Hereinafter, feedforward control of the expansion valves 24 and 26 adopting this correlation will be described. Here, as in the above-described feedforward control, only the content during the heating operation will be described, and the content during the cooling operation will be omitted.

During the heating operation, as shown in FIG. 5, the feedforward control unit 83 firstly operates the capacity of the compressor 21 and / or the outdoor, similarly to step ST1 in the above-described feedforward control (see FIG. 4). It is determined whether or not the operating capacity of the fan 36 changes (step ST11). If it is determined in step ST11 that the operating capacity of the compressor 21 and / or the outdoor fan 36 changes, the process proceeds to steps ST12 to ST20.

Next, in step ST12, the prediction unit 83a of the feedforward control unit 83 controls the operating capacity of the compressor 21 and / or the outdoor fan 36 in the same manner as in step ST2 in the above-described feedforward control (see FIG. 4). A virtual combined opening EVFF before the operation capacity change is calculated by adding the openings EVu and EVd of the two expansion valves 24 and 26 immediately before the operation capacity is changed (that is, immediately before the operation capacity is changed). For example, when an expansion valve having a characteristic in which the opening degree and the Cv value are proportional to each other is adopted as the expansion valves 24 and 26, the virtual total opening degree EVFF before the change in the operation capacity is the above feedforward control (FIG. 4). In the same manner as in step ST2 in the reference), it is calculated by the following formula <11>.

1 / EVFF = 1 / EVu + 1 / EVd ... <11>
Next, in step ST13, the prediction unit 83a immediately before the control of the operating capacity of the compressor 21 and / or the outdoor fan 36 is performed as in step ST3 in the above-described feedforward control (see FIG. 4) (that is, The refrigerant circulation amount Gr before the change of the operation capacity passing through the two expansion valves 24 and 26 immediately before the change of the operation capacity is calculated. Here, the refrigerant circulation amount Gr before the change in the operation capacity is the same as that in step ST3 in the above-described feedforward control (see FIG. 4), as shown in the following formula <12>, before the change in the operation capacity. Can be expressed as a function of the virtual combined opening EVFF.

Gr = f (EVFF) ... <12>
Next, in step ST14, unlike step ST3 in the above feedforward control (see FIG. 4), immediately after the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, the operation capacity changes). The operation capacity of the compressor 21 and / or the outdoor fan 36 of the upstream side expansion valve (the second expansion valve 26 during the heating operation or the first expansion valve 24 during the cooling operation) is controlled. The refrigerant circulation amount Gruc that passes through the upstream expansion valve after the change in the operating capacity immediately after (that is, immediately after the operating capacity changes) is calculated. Here, the refrigerant circulation amount Gruc that passes through the upstream side expansion valve after the change in the operation capacity is equal to the operation capacity ratio Fcc / Fc before and after the change in the operation capacity of the compressor 21, as shown in the following formula <13>. It can be expressed as a function of the operation capacity ratio Ffc / Ff before and after the change of the operation capacity and the refrigerant circulation amount Gr before the operation capacity change.

Gruc = f (Fcc / Fc, Ffc / Ff) × Gr (13)
Here, in the above formula <13>, unlike the formula <3> in the above feedforward control (see FIG. 4), the condensation temperature Tc in the refrigeration cycle before the change in operating capacity and the refrigeration cycle before the change in operating capacity. What is not a function of the evaporation temperature Te is that there is substantially no change in the high pressure Ph, intermediate pressure Pm and low pressure Pl in the refrigeration cycle before and after the change in operating capacity, that is, high pressure before and after the change in operating capacity. This is because the correlation that the side pressure difference ΔPh is constant is taken into consideration. That is, the refrigerant circulation amount Gruc passing through the upstream side expansion valve after the change of the operation capacity is the value after the change of the operation capacity calculated under the condition that the high pressure Ph, the intermediate pressure Pm, and the low pressure Pl are not changed before and after the change of the operation capacity. Refrigerant circulation amount.

Next, in step ST15, the prediction unit 83a determines the opening degrees of the two expansion valves 24 and 26 after the change in the operation capacity under the condition that there is no change in the high pressure Ph, the intermediate pressure Pm, and the low pressure Pl before and after the change in the operation capacity. The virtual combined opening EVFFuc after the change of the combined operation capacity is calculated. Here, the virtual total opening EVFFuc after the change in the operation capacity under the condition that there is no change in the high pressure Ph, the intermediate pressure Pm and the low pressure Pl before and after the change in the operation capacity is calculated in step ST14 as shown in the following formula <14>. It can be expressed as a function of the refrigerant circulation amount Gruc after the change in the operation capacity under the condition that there is no change in the high pressure Ph, the intermediate pressure Pm and the low pressure Pl before and after the change in the operation capacity.

EVFFuc = f (Gruc) ... <14>
Next, in step ST16, the prediction unit 83a determines the virtual total opening EVFFuc after the change in operating capacity under the condition that there is no change in the high pressure Ph, the intermediate pressure Pm, and the low pressure Pl before and after the change in operating capacity calculated in step ST15. Is used to calculate the opening degree EVuc after the operation capacity change of the upstream side expansion valve (the second expansion valve 26 during the heating operation or the first expansion valve 24 during the cooling operation).

Here, by solving the simultaneous equations <15> and <16> similar to the equations <5> and <6> in the feedforward control described above (see FIG. 4), the operating capacity of the upstream side expansion valve is changed. The opening degree EVuc of is calculated. However, in step S16, unlike step ST6 of the above-described feedforward control (see FIG. 4), the downstream side expansion valve (the first expansion valve 24 during the heating operation or the second expansion valve during the cooling operation). The opening degree EVdc after the change of the operation capacity in 26) is not calculated, but is calculated in steps ST17 to ST19.

1 / EVFFuc = 1 / EVuc + 1 / EVdc ... <15>
EVu: EVd = EVuc: EVdc ... <16>
Next, in step ST17, the prediction unit 83a immediately after the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, similarly to step ST4 in the above-described feedforward control (see FIG. 4) (that is, The refrigerant circulation amount Grc after the change of the operation capacity passing through the two expansion valves 24 and 26 immediately after the operation capacity is changed is calculated. Here, the refrigerant circulation amount Grc after the change in the operation capacity is the operation capacity ratio Fcc / Fc before and after the change in the operation capacity of the compressor 21 and the change in the operation capacity of the outdoor fan 36 before and after the change as shown in the following equation <17>. It can be expressed as a function of the operating capacity ratio Ffc / Ff, the condensation temperature Tc in the refrigeration cycle before the operating capacity change, the evaporation temperature Te in the refrigeration cycle before the operating capacity change, and the refrigerant circulation amount Gr before the operating capacity change.

Grc = f (Fcc / Fc, Ffc / Ff, Tc, Te) × Gr ... <17>
Next, in step ST18, the prediction unit 83a sets the two expansion valves 24 and 26 immediately after the operation capacity of the compressor 21 and / or the outdoor fan 36 is controlled (that is, immediately after the operation capacity is changed). A virtual combined opening EVFFc after changing the operating capacity is calculated by adding the opening (that is, the opening EVuc of the upstream expansion valve after changing the operating capacity and the opening EVdc of the downstream expansion valve after changing the operating capacity). To do. Here, the virtual combined opening EVFFc after the change in the operation capacity can be expressed as a function of the refrigerant circulation amount Grc after the change in the operation capacity calculated in step ST17, as in the following formula <18>.

EVFFc = f (Grc) ... <18>
Next, in step ST19, the prediction unit 83a determines the virtual total opening degree EVFFc after the change in operating capacity calculated in step ST18 and the opening degree EVuc of the upstream side expansion valve after the change in operating capacity calculated in step ST16. Is used to calculate the opening degree EVdc after the operation capacity change of the downstream side expansion valve (the first expansion valve 24 during the heating operation or the second expansion valve 26 during the cooling operation).

Here, the opening degree EVdc calculated in step ST16 and the opening degree EVFFc calculated in step ST18 are substituted into the expression <19> similar to the expression <5> in the above-described feedforward control (see FIG. 4). Thus, the opening degree EVdc after the operation capacity change of the downstream side expansion valve (the first expansion valve 24 during the heating operation or the second expansion valve 26 during the cooling operation) is calculated.

1 / EVFFc = 1 / EVuc + 1 / EVdc ... <19>
Next, in step ST20, the opening changing unit 83b of the feedforward control unit 83 changes the opening of the two expansion valves 24 and 26 to the opening EVuc and EVdc calculated in step ST16 and step ST19. I do.

Then, returning to the process of step ST11 again, each time the operating capacity of the compressor 21 and / or the outdoor fan 36 is changed, the process of steps ST12 to ST20 is performed. In this way, feedforward control of the two expansion valves 24 and 26 is performed.

In the feedforward control of the two expansion valves 24 and 26 according to the present modification, as in the feedforward control of the two expansion valves 24 and 26 (see FIG. 4), a sensor for detecting the intermediate pressure Pm. Without providing the above, it is possible to perform feedforward control of the upstream expansion valve and the downstream expansion valve by predicting a change in the refrigerant circulation amount passing through the upstream expansion valve and the downstream expansion valve. And when the operating capacity of the compressor 21 or the outdoor fan 36 changes, the control followability of the opening degree of the upstream side expansion valve and the downstream side expansion valve can be improved.

Further, as the opening degree control of the upstream side expansion valve and the downstream side expansion valve, the feedback control based on the degree of supercooling and the degree of superheat is performed together with the above-described feedforward control (see FIG. 5). When the operating capacity of 36 changes, the opening degree of the upstream side expansion valve and the downstream side expansion valve is brought close to the optimum opening degree after the change of the operating capacity of the compressor 21 and the outdoor fan 36 by feedforward control. After that, the optimum opening degree can be matched by feedback control.

The present invention is widely applied to an air conditioner that circulates a refrigerant while expanding a high-pressure refrigerant discharged from a compressor by an upstream expansion valve and a downstream expansion valve in two stages in the order of intermediate pressure and low pressure. Is possible.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 10 Refrigerant circuit 21 Compressor 23 Outdoor heat exchanger 24 1st expansion valve (upstream side expansion valve, downstream side expansion valve)
26 Second expansion valve (downstream expansion valve, upstream expansion valve)
36 Outdoor fan 41 Indoor heat exchanger

JP-A-10-132393 JP 2003-106683 A

Claims (4)

The compressor (21), the outdoor heat exchanger (23), the upstream side expansion valves (24, 26), the downstream side expansion valves (26, 24), and the indoor heat exchanger (41) are connected to each other. A refrigerant circuit (10) for circulating the refrigerant while expanding the high-pressure refrigerant discharged from the compressor by the upstream expansion valve and the downstream expansion valve in two stages in the order of intermediate pressure and low pressure; In an air conditioner having an outdoor fan (36) for supplying outdoor air serving as a cooling source or a heating source to a heat exchanger,
In the prediction condition based on the correlation between the high pressure side pressure difference obtained by subtracting the intermediate pressure from the high pressure and the low pressure side pressure difference obtained by subtracting the low pressure from the intermediate pressure, the operating capacity of the compressor and / or the Predicting a change in the amount of refrigerant circulating through the upstream expansion valve and the downstream expansion valve after changing the operating capacity of the outdoor fan, the operating capacity of the compressor and / or the outdoor fan When the operating capacity is changed, control is performed to change the opening degree of the upstream side expansion valve and the downstream side expansion valve in consideration of the predicted change in the refrigerant circulation amount.
Air conditioner (1). The correlation is such that the ratio between the high pressure side pressure difference and the low pressure side pressure difference before and after the operating capacity of the compressor (21) and / or the operating capacity of the outdoor fan (36) is changed. The relationship is constant,
The air conditioner (1) according to claim 1. The correlation is a relationship that the high-pressure side pressure difference is constant before and after the operating capacity of the compressor (21) and / or the operating capacity of the outdoor fan (36) is changed.
The air conditioner (1) according to claim 1. The upstream expansion valves (24, 26) have a refrigerant subcooling degree at the outlet of a heat exchanger functioning as a refrigerant radiator of the outdoor heat exchanger (23) and the indoor heat exchanger (41). The opening degree is controlled so as to achieve a predetermined target supercooling degree,
In the downstream expansion valves (26, 24), the superheat degree of the refrigerant at the outlet of the heat exchanger functioning as the refrigerant evaporator of the outdoor heat exchanger and the indoor heat exchanger becomes a predetermined target superheat degree. So that the opening is controlled,
The air conditioner (1) according to any one of claims 1 to 3.

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