WO2015046230A1

WO2015046230A1 - Air conditioner

Info

Publication number: WO2015046230A1
Application number: PCT/JP2014/075249
Authority: WO
Inventors: 隼人布; 知之配川
Original assignee: ダイキン工業株式会社
Priority date: 2013-09-30
Filing date: 2014-09-24
Publication date: 2015-04-02
Also published as: JP2015068569A

Abstract

During a normal cycle defrosting operation, an air conditioner (1) causes a refrigerant to be diverted from the discharge side of a compressor (21) to the intake side of the compressor (21) through a discharge-intake bypass circuit (26) by opening an overheating valve (27) and controls the intake moisture during defrosting by regulating the degree that a main valve (24) and/or the overheating valve (27) is opened so that the refrigerant is in a wet state on the intake side of the compressor (21).

Description

Air conditioner

INDUSTRIAL APPLICABILITY The present invention is an air conditioner, in particular, a discharge used in a positive cycle defrosting operation for defrosting an outdoor heat exchanger while circulating a refrigerant in the order of a compressor, an indoor heat exchanger, a main valve, and an outdoor heat exchanger. -Relates to an air conditioner having a suction bypass circuit.

Conventionally, there is an air conditioner having a compressor, an indoor heat exchanger, a throttling device (main valve), and an outdoor heat exchanger as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 61-262560). This air conditioner is capable of heating operation in which refrigerant is circulated in the order of the compressor, the indoor heat exchanger, the main valve, and the outdoor heat exchanger, and also from the discharge side of the compressor to the suction side of the compressor during the heating operation. A discharge-suction bypass circuit that allows the refrigerant to be bypassed. In this air conditioner, the discharge-suction bypass circuit is operated during the positive cycle defrosting operation in which the outdoor heat exchanger is defrosted while circulating the refrigerant in the order of the compressor, the indoor heat exchanger, the main valve, and the outdoor heat exchanger. The refrigerant is bypassed from the discharge side of the compressor to the suction side of the compressor through the discharge-suction bypass circuit.

In the above conventional air conditioner, the refrigerant sucked into the compressor may be excessively overheated during the positive cycle defrosting operation. As a result, the compressor may be burned or damaged, and as a result, the reliability of the compressor may be impaired.

An object of the present invention is to provide a discharge-suction bypass circuit used in a positive cycle defrosting operation for defrosting an outdoor heat exchanger while circulating a refrigerant in the order of a compressor, an indoor heat exchanger, a main valve, and an outdoor heat exchanger. In the air conditioning apparatus having the above, the refrigerant sucked into the compressor is prevented from being excessively overheated, and the compressor is prevented from being burned or damaged, thereby ensuring the reliability of the compressor. It is in.

The air conditioner according to the first aspect has a main refrigerant circuit and a discharge-suction bypass circuit. The main refrigerant circuit has a compressor, an indoor heat exchanger, a main valve, and an outdoor heat exchanger, and the heating operation for circulating the refrigerant in the order of the compressor, the indoor heat exchanger, the main valve, and the outdoor heat exchanger. Can be done. The discharge-suction bypass circuit has an overheat valve, and is connected to the main refrigerant circuit so that the refrigerant can be bypassed from the discharge side of the compressor to the suction side of the compressor during heating operation. Here, during the positive cycle defrosting operation in which the outdoor heat exchanger is defrosted while circulating the refrigerant in the order of the compressor, the indoor heat exchanger, the main valve, and the outdoor heat exchanger, the overheat valve is opened and the discharge-suction is performed. A defroster that bypasses the refrigerant from the discharge side of the compressor to the suction side of the compressor through a bypass circuit, and adjusts the opening degree of the main valve and / or the superheat valve so that the refrigerant on the suction side of the compressor becomes wet. Inhalation wetness control.

Here, as described above, during the positive cycle defrosting operation, the opening degree of the main valve and / or the superheat valve is adjusted so that the refrigerant on the suction side of the compressor is in a wet state (intake dehumidification control during defrosting). I am doing so. For this reason, it is possible to appropriately manage the degree of overheating and wetness of the refrigerant sucked into the compressor during the positive cycle defrosting operation. As a result, the refrigerant sucked into the compressor can be prevented from becoming excessively overheated, and the compressor can be prevented from being burned or damaged, thereby ensuring the reliability of the compressor. it can.

The air conditioner according to the second aspect is the air conditioner according to the first aspect, wherein the dehumidification suction wetness control is performed from the temperature of the refrigerant on the discharge side of the compressor to the degree of superheat of the refrigerant on the discharge side of the compressor. Thus, the opening degree of the main valve and / or the superheat valve is adjusted so that the superheat degree of the refrigerant on the discharge side of the compressor becomes equal to or less than the target discharge superheat degree.

The degree of superheat and wetness of the refrigerant sucked into the compressor tends to appear as the degree of superheat of the refrigerant on the discharge side of the compressor. Specifically, as the degree of superheat of the refrigerant on the discharge side of the compressor increases, the degree of superheat of the refrigerant sucked into the compressor tends to increase, and conversely, the degree of wetness tends to decrease.

Therefore, as described above, as described above, as the dehumidification suction wetting control, the superheat degree of the refrigerant on the discharge side of the compressor obtained from the temperature of the refrigerant on the discharge side of the compressor becomes equal to or less than the target discharge superheat degree. The control which adjusts the opening degree of the main valve and / or the superheat valve is adopted. As a result, by setting the target discharge superheat degree to a value that takes into account the degree of superheat and wetness of the refrigerant sucked into the compressor, the refrigerant sucked into the compressor is overheated. It can be surely suppressed.

An air conditioner according to a third aspect is the air conditioner according to the second aspect, wherein the temperature of the refrigerant on the discharge side of the compressor is detected by a discharge temperature sensor provided on the discharge side of the compressor. The superheat degree of the refrigerant on the discharge side of the compressor is obtained from the temperature of the refrigerant on the discharge side of the compressor, obtained from the temperature of the refrigerant detected by the indoor heat exchanger temperature sensor provided in the indoor heat exchanger. Is obtained from the refrigerant temperature on the discharge side of the compressor detected by the discharge temperature sensor and the saturation temperature of the refrigerant on the discharge side of the compressor detected by the indoor heat exchanger temperature sensor.

Here, as described above, since the saturation temperature of the refrigerant on the discharge side of the compressor is obtained by the indoor heat exchanger temperature sensor, the pressure on the discharge side of the compressor is detected and this pressure value is set to the saturation temperature. By converting, it becomes unnecessary to obtain the saturation temperature of the refrigerant on the discharge side of the compressor. That is, in obtaining the degree of superheat of the refrigerant on the discharge side of the compressor, it is possible to dispense with providing a pressure sensor on the discharge side of the compressor.

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 operation | movement (flow of a refrigerant | coolant) at the time of air_conditionaing | cooling operation. It is a figure which shows the operation | movement (flow of a refrigerant | coolant) at the time of heating operation. It is a figure which shows the operation | movement (flow of a refrigerant | coolant) at the time of a normal cycle defrost operation. It is a time chart which shows operation | movement of the superheat valve, the main valve, the compressor, the outdoor fan, and the indoor fan at the time of the forward cycle defrosting operation and the heating operation before and after that. It is a time chart which shows operation | movement of the overheat valve, the main valve, a compressor, an outdoor fan, and an indoor fan at the time of the normal cycle defrost operation in the modification 1 of this invention, and the heating operation before and behind that. It is a time chart which shows operation | movement of the superheat valve, the main valve, a compressor, an outdoor fan, and an indoor fan at the time of the normal cycle defrost operation in the modification 2 of this invention, and the heating operation before and behind that. It is a schematic block diagram of the air conditioning apparatus concerning the modification 2 of this invention (The flow of the refrigerant | coolant at the time of a normal cycle defrost operation is also shown in figure). It is a time chart which shows operation | movement of the superheat valve, the main valve, a compressor, an outdoor fan, and an indoor fan at the time of the normal cycle defrost operation in the modification 3 of this invention, and the heating operation before and behind that. It is a time chart which shows operation | movement of the superheat valve, the main valve, the compressor, the outdoor fan, and the indoor fan at the time of the forward cycle defrost operation in the modification 4 of this invention, and the heating operation before and behind that.

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.

<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. That is, the indoor unit 4 has an indoor fan 42 as a fan that supplies indoor air as a heating source or cooling source of the refrigerant flowing through the indoor heat exchanger 41 to the indoor heat exchanger 41. Here, as the indoor fan 42, a centrifugal fan, a multiblade fan or the like driven by an indoor fan motor 42a capable of rotating speed control is used.

The indoor unit 4 is provided with various sensors. Specifically, the indoor heat exchanger 41 is provided with an indoor heat exchange temperature sensor 55 that detects the temperature Txi of the refrigerant in the indoor heat exchanger 41. The indoor unit 4 is provided with an indoor temperature sensor 56 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 43 that controls the operation of each unit constituting the indoor unit 4. And the indoor side control part 43 has the microcomputer, memory, etc. which were provided in order to control the indoor unit 4, and is with the remote control (not shown) for operating the indoor unit 4 separately. Control signals and the like can be exchanged between them, and control signals and the like can be exchanged with the outdoor unit 2 via the transmission line 7.

<Outdoor unit>
The outdoor unit 2 is installed outside and constitutes a part of the refrigerant circuit 10. The outdoor unit 2 mainly includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, a main valve 24, and a discharge-suction bypass circuit 26.

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 sealed structure in which a rotary type or scroll type positive displacement compression element (not shown) is rotationally driven by a compressor motor 21a capable of frequency control by an inverter. The compressor 21 has a suction pipe 31 connected to the suction side via an attached accumulator 21b, 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 four-way switching valve 22. The discharge pipe 32 is a refrigerant pipe that connects the discharge side of the compressor 21 and the four-way switching valve 22.

The four-way switching valve 22 is a switching valve for switching the direction of refrigerant flow in the refrigerant circuit 10. During the cooling operation, the four-way switching valve 22 causes the outdoor heat exchanger 23 to function as a radiator for the refrigerant compressed in the compressor 21 and the indoor heat exchanger 41 for the refrigerant that has radiated heat in the outdoor heat exchanger 23. Switch to the cooling cycle state to function as an evaporator. That is, in the cooling operation, the four-way switching valve 22 is connected between 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). (See the solid line of the four-way selector valve 22 in FIG. 1). 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. That is, in the heating operation, the four-way switching valve 22 is connected to 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). (Refer to the broken line of the four-way switching valve 22 in FIG. 1). 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). Here, the first gas refrigerant pipe 33 is a refrigerant pipe connecting 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 that connects 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 main valve 24 is a valve that depressurizes the high-pressure refrigerant of the refrigeration cycle radiated in the outdoor heat exchanger 23 to the low pressure of the refrigeration cycle during the cooling operation. Further, the main valve 24 is a valve that reduces the high-pressure refrigerant of the refrigeration cycle radiated in the indoor heat exchanger 41 to the low pressure of the refrigeration cycle during the heating operation. The main valve 24 is provided in the liquid refrigerant pipe 35. Here, an electric expansion valve capable of opening degree control is used as the main valve 24.

The discharge-suction bypass circuit 26 is a refrigerant pipe that allows the refrigerant to be bypassed from the discharge side of the compressor 21 to the suction side of the compressor 21 during heating operation. Here, the discharge-suction bypass circuit 26 is provided so as to branch from the discharge pipe 32 and join the suction pipe 31. The discharge-suction bypass circuit 26 has an overheat valve 27. Here, an electric expansion valve capable of opening degree control is used as the overheating valve 27.

The outdoor unit 2 has an outdoor fan 25 for sucking outdoor air into the outdoor unit 2 and exchanging heat with the refrigerant in the outdoor heat exchanger 23 and then discharging the air to the outside. That is, the outdoor unit 2 has an outdoor fan 25 as a fan that supplies outdoor air as a cooling source or a heating source of the refrigerant flowing through the outdoor heat exchanger 23 to the outdoor heat exchanger 23. Here, as the outdoor fan 25, a propeller fan or the like driven by an outdoor fan motor 25a capable of rotating speed control is used.

The outdoor unit 2 is provided with various sensors. Specifically, the outdoor heat exchanger 23 is provided with an outdoor heat exchanger temperature sensor 53 that detects the temperature Txo of the refrigerant in the outdoor heat exchanger 23. The outdoor unit 2 is provided with an outdoor air temperature sensor 54 that detects a temperature Toa of outdoor air sucked into the outdoor unit 2. The discharge pipe 32 or the compressor 21 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 unit 2 includes an outdoor control unit 28 that controls the operation of each unit constituting the outdoor unit 2. The outdoor control unit 28 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 7. Can be done.

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. Here, the refrigerant circuit 10 mainly includes a main refrigerant circuit 11 having a compressor 21, an indoor heat exchanger 41, a main valve 24, and an outdoor heat exchanger 23 (part of the refrigerant circuit 10 excluding the discharge-suction bypass circuit 26). ) Is connected to a discharge-suction bypass circuit 26 having an overheat valve 27. The main refrigerant circuit 11 of the refrigerant circuit 10 switches the four-way switching valve 22 to the heating cycle state as will be described later, so that the compressor 21, the indoor heat exchanger 41, the main valve 24, and the outdoor heat exchanger 23 are switched. It is possible to perform a heating operation in which the refrigerant is circulated in this order.

<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 43 and the outdoor side control unit 28. That is, the control part 8 which performs operation control of the whole air conditioning apparatus 1 including heating operation etc. is comprised by the transmission line 7 which connects between the indoor side control part 43 and the outdoor side control part 28. FIG.

As shown in FIG. 2, the control unit 8 is connected so that it can receive detection signals from the various sensors 52 to 56, and various devices and

valves

21a, 22, 24 based on these detection signals. 25a, 27, 42a, etc. are connected so as to be controlled.

(2) Operation of Air Conditioner Next, the operation of the air conditioner 1 will be described with reference to FIGS. The air conditioner 1 can perform a cooling operation (see FIG. 3) and a heating operation (see FIG. 4). In addition, during the heating operation, it is also possible to perform a normal cycle defrosting operation (see FIGS. 5 and 6) for melting frost attached to the outdoor heat exchanger 23.

<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. 3). The overheat valve 27 of the discharge-suction bypass circuit 26 is closed.

In the refrigerant circuit 10, the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21 and is compressed until it reaches 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 the main valve 24.

The high-pressure liquid refrigerant sent to the main valve 24 is decompressed by the main valve 24 to the low pressure of the refrigeration cycle, and becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the main valve 24 is sent to the indoor heat exchanger 41 through 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 and the four-way switching valve 22.

Thus, in the refrigerant circuit 10 (here, the main refrigerant circuit 11), the cooling operation is performed in which the refrigerant is circulated in the order of the compressor 21, the outdoor heat exchanger 23, the main valve 24, and the indoor heat exchanger 41.

<Heating operation>
During the heating operation, the four-way switching valve 22 is switched to the heating cycle state (state indicated by the broken line in FIG. 4).

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 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 main valve 24 through the liquid refrigerant communication pipe 5.

The high-pressure liquid refrigerant sent to the main valve 24 is decompressed by the main valve 24 to the low pressure of the refrigeration cycle, and becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the main 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 by exchanging heat with outdoor air supplied as a heating source by the outdoor fan 25 in the outdoor heat exchanger 23. 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.

Thus, in the refrigerant circuit 10 (here, the main refrigerant circuit 11), the heating operation is performed in which the refrigerant is circulated in the order of the compressor 21, the indoor heat exchanger 41, the main valve 24, and the outdoor heat exchanger 23.

<Normal cycle defrosting operation>
-basic action-
During the heating operation described above, if frost formation in the outdoor heat exchanger 23 is detected due to the refrigerant temperature Txo in the outdoor heat exchanger 23 being lower than a predetermined temperature or the like, the refrigerant adheres to the outdoor heat exchanger 23. The defrosting operation in which the frost is melted is performed, and after the frost adhering to the outdoor heat exchanger 23 is melted, the heating operation is resumed. Here, detection of whether or not the frost attached to the outdoor heat exchanger 23 has melted is performed by the refrigerant temperature Txo in the outdoor heat exchanger 23 becoming higher than a predetermined temperature.

Here, the normal cycle defrosting operation is the same as in the heating operation, that is, in the heating cycle state in which the four-way switching valve 22 is indicated by the broken line in FIG. 21 is an operation for defrosting the outdoor heat exchanger 23 while circulating the refrigerant in the order of the indoor heat exchanger 41, the main valve 24, and the outdoor heat exchanger 23.

However, in the normal cycle defrosting operation, unlike the heating operation, the suction valve 21 sucks the compressor 21 from the discharge side of the compressor 21 through the discharge-suction bypass circuit 26 by opening the overheat valve 27 of the discharge-suction bypass circuit 26. The operation of bypassing the refrigerant to the side is performed.

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

A part of the high-pressure gas refrigerant discharged from the compressor 21 is bypassed to the suction side of the compressor 21 through the discharge-suction bypass circuit 26, and the remaining gas refrigerant is the four-way switching valve 22 and the gas refrigerant communication pipe 6. And sent to the indoor heat exchanger 41.

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. Thus, the room air is heated and then supplied indoors, so that the room is continuously heated even during defrosting.

The high-pressure refrigerant radiated by the indoor heat exchanger 41 is sent to the outdoor heat exchanger 23 through the liquid refrigerant communication tube 5 and the main valve 24.

In the outdoor heat exchanger 23, the refrigerant sent to the outdoor heat exchanger 23 exchanges heat with frost attached to the outdoor heat exchanger 23 to dissipate heat, and enters a gas-liquid two-phase state with a large amount of liquid refrigerant. Thereby, the frost adhering to the outdoor heat exchanger 23 is melted, and the outdoor heat exchanger 23 is defrosted.

The gas-liquid two-phase refrigerant of the liquid refrigerant radiated by the outdoor heat exchanger 23 is sent to the suction pipe 31 through the four-way switching valve 22 and is bypassed to the suction side of the compressor 21 through the discharge-suction bypass circuit 26. The gas refrigerant is combined with the gas refrigerant to be in a gas-liquid two-phase state or a gas state with a small amount of liquid refrigerant, and is sucked into the compressor 21 again.

In this manner, in the refrigerant circuit 10, the refrigerant is circulated in the order of the compressor 21, the indoor heat exchanger 41, the main valve 24, and the outdoor heat exchanger 23, and the overheat valve 27 is opened and compressed through the discharge-suction bypass circuit 26. A positive cycle defrosting operation is performed to bypass the refrigerant from the discharge side of the machine 21 to the suction side of the compressor 21.

-control-
During the normal cycle defrosting operation, the refrigerant sucked into the compressor 21 may be in an excessively overheated state. As a result, the compressor 21 may be burned or damaged, and as a result, the reliability of the compressor 21 may be impaired.

Therefore, here, the dehumidifying suction wetting control is performed to adjust the opening degree of the superheater valve 27 so that the refrigerant on the suction side of the compressor 21 becomes wet. Hereinafter, control of various devices including the forward cycle defrosting operation and the heating operation before and after the forward cycle defrosting operation will be described with reference to a time chart during the forward cycle defrosting operation and the heating operation before and after that.

First, during the heating operation before starting the normal cycle defrosting operation, the overheat valve 27 is fully closed as described above, and the main valve 24, the compressor 21, the outdoor fan 25, and the indoor fan. 42 is controlled so that the temperature Tra of the indoor air detected by the indoor temperature sensor 56 becomes the target indoor temperature, for example. Here, as the control of the main valve 24 during the heating operation, the heating main valve discharge temperature control for adjusting the opening of the main valve 24 based on the refrigerant temperature Td on the discharge side of the compressor 21 is performed. Specifically, control is performed to adjust the opening of the main valve 24 so that the refrigerant temperature Td on the discharge side of the compressor 21 becomes the target discharge temperature Tds. That is, when the refrigerant temperature Td is lower than the target discharge temperature Tds, control is performed to reduce the opening of the main valve 24. When the refrigerant temperature Td is higher than the target discharge temperature Tds, the main valve 24 is controlled. Control to increase the opening degree of is performed.

Next, when frost formation in the outdoor heat exchanger 23 is detected, the normal cycle defrosting operation is started. During the forward cycle defrosting operation, the operation of bypassing the refrigerant from the discharge side of the compressor 21 to the suction side of the compressor 21 through the discharge-suction bypass circuit 26 is performed by opening the overheat valve 27 as described above. Is called. And as said control of the superheat valve 27 at the time of a normal cycle defrost operation, said suction moisture control at the time of defrost is performed. Specifically, the suction dehumidification control at the time of defrosting obtains the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 from the temperature Td of the refrigerant on the discharge side of the compressor 21, and the refrigerant on the discharge side of the compressor 21 This is control for adjusting the opening degree of the superheater valve 27 so that the superheat degree TdSH of the engine becomes equal to or less than the target discharge superheat degree TdSHs. That is, when the superheat degree TdSH is higher than the target discharge superheat degree TdSHs, control to reduce the opening degree of the superheat valve 27 is performed. Here, the refrigerant temperature Td on the discharge side of the compressor 21 is obtained from the refrigerant temperature detected by the discharge temperature sensor 52 provided on the discharge side of the compressor 21. Further, the saturation temperature of the refrigerant on the discharge side of the compressor 21 is obtained from the refrigerant temperature Txi detected by the indoor heat exchanger temperature sensor 55 provided in the indoor heat exchanger 41. The superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 is determined by the temperature Td of the refrigerant on the discharge side of the compressor 21 detected by the discharge temperature sensor 52 and the temperature of the compressor 21 detected by the indoor heat exchanger temperature sensor 55. It is obtained from the saturation temperature (temperature Txi) of the refrigerant on the discharge side. That is, the degree of superheat TdSH is obtained by subtracting the refrigerant temperature Txi from the refrigerant temperature Td. Here, the target discharge superheat degree TdSHs is 15 deg. In consideration of the reliability of the compressor 21. Set to the following values: Further, as control of the main valve 24 during the normal cycle defrosting operation, control for setting the target opening for the normal cycle defrosting operation is performed instead of the heating main valve discharge temperature control. Further, the compressor 21 is operated at a defrost frequency that is a frequency for the positive cycle defrost operation. Here, the defrost frequency is set to a high frequency near the highest frequency. Moreover, the outdoor fan 25 is stopped. Further, the indoor fan 42 is operated at a defrosting rotational speed that is a rotational speed for a normal cycle defrosting operation. Here, the defrosting rotation speed is set to the minimum rotation speed or a low rotation speed near the minimum rotation speed.

Then, when it is detected that the frost attached to the outdoor heat exchanger 23 has melted, the normal cycle defrosting operation is terminated and the heating operation is resumed. Specifically, the overheat valve 26 is fully closed, the control of the main valve 24 is returned to the heating main valve discharge temperature control, and the control of the compressor 21, the outdoor fan 25 and the indoor fan 42 is changed to the control content during the heating operation. return.

In this way, in the refrigerant circuit 10 (here, the main refrigerant circuit 11), the refrigerant on the suction side of the compressor 21 is in a wet state during the forward cycle defrosting operation (specifically, the compressor 21 The dehumidification suction wetting control for adjusting the opening degree of the superheat valve 27 is performed so that the superheat degree TdSH of the refrigerant on the discharge side is equal to or less than the target discharge superheat degree TdSHs.

-Characteristic-
Here, as described above, during the forward cycle defrosting operation, the opening degree of the superheater valve 27 is adjusted so that the refrigerant on the suction side of the compressor 21 is in a wet state (intake dehumidification control during defrosting). Yes. For this reason, it is possible to appropriately manage the degree of overheating and wetness of the refrigerant sucked into the compressor 21 during the positive cycle defrosting operation. Thereby, here, the refrigerant sucked into the compressor 21 is suppressed from being excessively overheated, and the compressor 21 is also prevented from being burned or damaged. As a result, the reliability of the compressor 21 is ensured. can do.

Here, the degree of superheat and wetness of the refrigerant sucked into the compressor 21 tends to appear as the magnitude of the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21. Specifically, as the degree of superheating TdSH of the refrigerant on the discharge side of the compressor 21 increases, the degree of superheating of the refrigerant sucked into the compressor 21 tends to increase, and conversely, the degree of wetness tends to decrease. Become.

Therefore, here, as described above, as the dehumidification suction wetting control, the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 obtained from the temperature Td of the refrigerant on the discharge side of the compressor 21 is the target discharge superheat degree TdSHs. The control which adjusts the opening degree of the superheater valve 27 is adopted so that it may become below. Thereby, here, the target discharge superheat degree TdSHs is set to a value that takes into account the degree of superheat and wetness of the refrigerant sucked into the compressor 21, so that the refrigerant sucked into the compressor 21 is in an excessively overheated state. It can be suppressed reliably.

Here, as described above, since the saturation temperature of the refrigerant on the discharge side of the compressor 21 is obtained by the indoor heat exchanger temperature sensor 55, the pressure on the discharge side of the compressor 21 is detected and this pressure is detected. It is not necessary to obtain the saturation temperature of the refrigerant on the discharge side of the compressor 21 by converting the value into the saturation temperature. That is, in order to obtain the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21, it is not necessary to provide a pressure sensor on the discharge side of the compressor 21.

(3) Modification 1
In the above embodiment, only the opening degree of the superheater valve 27 is adjusted as the dehumidifying suction wetness control during the positive cycle defrosting operation. However, as shown in FIG. The opening degree of 24 may be adjusted. That is, dehumidification suction wetness control is performed in which the opening degree of the main valve 24 and the superheat valve 27 is adjusted so that the refrigerant on the suction side of the compressor 21 becomes wet.

Specifically, as in the above embodiment, control is performed to adjust the opening degree of the superheat valve 27 so that the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 is equal to or less than the target discharge superheat degree TdSHs. That is, when the superheat degree TdSH is higher than the target discharge superheat degree TdSHs, control to reduce the opening degree of the superheat valve 27 is performed. Moreover, here, unlike the above embodiment, the main valve 24 is also controlled to adjust the opening so that the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 is equal to or less than the target discharge superheat degree TdSHs. . That is, when the superheat degree TdSH is higher than the target discharge superheat degree TdSHs, control to increase the opening of the main valve 24 is performed. In addition, control of the other apparatuses (the compressor 21, the outdoor fan 25, and the indoor fan 42) at the time of a normal cycle defrost operation is the same as that of said embodiment.

Thus, in the present modification, as described above, the refrigerant on the suction side of the compressor 21 becomes wet during the normal cycle defrosting operation (specifically, the refrigerant on the discharge side of the compressor 21). The degree of opening of the main valve 24 and the superheat valve 27 is adjusted (intake dehumidification control during defrosting) so that the superheat degree TdSH becomes equal to or higher than the target discharge superheat degree TdSHs. Even in this case, the same effect as that of the above embodiment can be obtained. Moreover, in this modification, since the dehumidifying suction wetness control is performed for the two valves, the control range can be expanded.

(4) Modification 2
In the above-described embodiment and Modification 1, the opening degree of the superheater valve 27 is adjusted as the dehumidifying suction wetness control during the positive cycle defrosting operation. However, as shown in FIG. It is also possible to adjust only the opening degree. That is, the dehumidification suction wetness control is performed to adjust the opening of the main valve 24 so that the refrigerant on the suction side of the compressor 21 is in a wet state.

Specifically, as in the first modification, control is performed to adjust the opening so that the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 is equal to or less than the target discharge superheat degree TdSHs. That is, when the superheat degree TdSH is higher than the target discharge superheat degree TdSHs, control to increase the opening of the main valve 24 is performed. However, the overheat valve 27 is controlled to set the target opening for the normal cycle defrosting operation without performing the dehumidifying suction wetness control. In addition, control of the other apparatuses (the compressor 21, the outdoor fan 25, and the indoor fan 42) at the time of a normal cycle defrost operation is the same as that of said embodiment and the modification 1. FIG.

Thus, in the present modification, as described above, the refrigerant on the suction side of the compressor 21 becomes wet during the normal cycle defrosting operation (specifically, the refrigerant on the discharge side of the compressor 21). The degree of opening of the main valve 24 is adjusted (intake dehumidification control during defrosting) so that the superheat degree TdSH of the engine becomes equal to or higher than the target discharge superheat degree TdSHs. Even in this case, the same effects as those of the above-described embodiment and Modification 1 can be obtained. Moreover, in this modification, since the dehumidification suction wetness control which adjusts only the opening degree of the main valve 24 is adopted and the overheating valve 27 is set to the target opening degree, as shown in FIG. The overheat valve 27 is not a valve capable of opening control such as an electric expansion valve, but a valve capable of opening / closing control such as an electromagnetic valve can also be used.

(5) Modification 3
In the above embodiment and

Modifications

1 and 2, as the dehumidification suction wetting control during the positive cycle defrosting operation, the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 is set to be equal to or less than the target discharge superheat degree TdSHs. By adopting a control that adjusts the opening degree of the main valve 24 and / or the superheat valve 27, the refrigerant sucked into the compressor 21 is suppressed from being overheated, and the compressor 21 is burned or damaged. As a result, the reliability of the compressor 21 is ensured.

By the way, from the viewpoint of ensuring the reliability of the compressor 21, not only the refrigerant sucked into the compressor 21 is suppressed from being excessively heated, but also excessive liquid back to the compressor 21 is suppressed. It is preferable.

Therefore, here, as the dehumidifying suction wetness control during the positive cycle defrosting operation, the target discharge superheat degree TdSHs, the refrigerant on the suction side of the compressor 21 and the excessive liquid back to the compressor 21 can be suppressed. The value of the main valve 24 and / or the superheat valve 27 is adjusted so that the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 becomes the target discharge superheat degree TdSHs. Like to do.

Specifically, for example, as shown in FIG. 10, when performing defrosting suction wetting control by the overheat valve 27 and setting the main valve 24 to the target opening for the normal cycle defrost operation, the target discharge overheating is performed. The degree TdSHs is set to a value that allows the refrigerant on the suction side of the compressor 21 to be maintained in a wet state that can suppress excessive liquid back to the compressor 21. The opening degree of the superheater valve 27 is adjusted so that the superheat degree TdSH becomes the target discharge superheat degree TdSHs. That is, when the superheat degree TdSH is lower than the target discharge superheat degree TdSHs, control is performed to increase the opening degree of the superheat valve 27, and when the superheat degree TdSH is higher than the target discharge superheat degree TdSHs, the superheat valve 27 is controlled. Control to reduce the opening of. Here, the target discharge superheat degree TdSHs is 5 deg. ~ 15 deg. Set to a value of degree. In addition, control of the other apparatuses (the compressor 21, the outdoor fan 25, and the indoor fan 42) at the time of a normal cycle defrost operation is the same as that of said embodiment and the

modification

1,2.

Thus, in the present modification, as described above, as the dehumidifying suction wetness control during the positive cycle defrosting operation, both excessive overheating of the refrigerant sucked into the compressor 21 is suppressed, and The target discharge superheat degree TdSHs is set to a value that allows excessive liquid back to the compressor 21, and control is performed to adjust the opening degree of the superheater valve 27 so that the target discharge superheat degree TdSHs is reached. Yes. As a result, here, during the positive cycle defrosting operation, the refrigerant sucked into the compressor 21 becomes excessively overheated. The liquid back can also be suppressed.

Here, in the case where the dehumidification suction wetting control is performed by the superheat valve 27 as in the above embodiment, and the main valve 24 is set to the target opening for the normal cycle defrost operation, the target discharge superheat is set. Although the case where the control for adjusting the opening degree of the superheater valve 27 is employed so as to become the degree TdSHs is illustrated, the present invention is not limited to this. When wetting control is performed and the superheat valve 27 is set to the target opening for the normal cycle defrosting operation, or when the defrosting suction wetness control is performed by both the main valve 24 and the superheat valve 27 as in the first modification. Even in the case of performing the above, it is possible to employ the control for setting the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 to the target discharge superheat degree TdSHs.

(6) Modification 4
In the above-described embodiment and Modification 3, as the dehumidifying suction wetness control during the positive cycle defrosting operation, the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 is equal to or lower than the target discharge superheat degree TdSHs, or By adopting a control for adjusting the opening degree of the superheat valve 27 so that the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 becomes the target discharge superheat degree TdSHs, the refrigerant sucked into the compressor 21 is excessively increased. The reliability of the compressor 21 is ensured by suppressing the burning or breakage of the compressor 21 that occurs due to the overheating state.

In this case, as in the conventional case, if the target opening degree for the normal cycle defrosting operation of the main valve 24 is set to an opening degree near full open, the high pressure of the refrigeration cycle is not easily raised, and the compressor 21 The input power decreases, and as a result, the amount of heat that can be used for defrosting decreases, and as a result, the normal cycle defrosting operation may not be continued.

Therefore, here, during the positive cycle defrosting operation, the opening degree of the main valve 24 is adjusted so that the high pressure Ph of the refrigeration cycle in the main refrigerant circuit 11 becomes the target high pressure Phs along with the dehumidification suction wetness control by the overheat valve 27. The main valve high pressure control is performed during defrosting.

Specifically, for example, as shown in FIG. 11, the dehumidifying suction wetness that controls the opening degree of the superheater valve 27 so that the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 becomes the target discharge superheat degree TdSHs. In the case of performing the control, the main valve high pressure control at the time of defrosting is performed in which the opening degree of the main valve 24 is adjusted so that the high pressure Ph of the refrigeration cycle in the main refrigerant circuit 11 becomes the target high pressure Phs. Here, since the refrigerant temperature Txi detected by the indoor heat exchanger temperature sensor 55 corresponds to the saturation temperature of the refrigerant at the high pressure Ph of the refrigeration cycle, the refrigerant temperature Txi is used as the high pressure Ph of the refrigeration cycle. Control is performed to adjust the opening of the main valve 24 so that Ph becomes the target high pressure Phs. That is, when the high pressure Ph is lower than the target high pressure Phs, control is performed to reduce the opening of the main valve 24, and when the high pressure Ph is higher than the target high pressure Phs, the opening of the main valve 24 is increased. Take control. Here, the target high pressure Ph is set to a value near the upper limit value Phx of the high pressure Ph during the heating operation. The upper limit value Phx of the high pressure Ph is a value that is defined in consideration of the design pressure of the equipment constituting the refrigerant circuit 10, and a pressure value slightly lower than this value is set as the target high pressure Ph. In addition, control of the other apparatuses (the compressor 21, the outdoor fan 25, and the indoor fan 42) at the time of a normal cycle defrost operation is the same as that of said embodiment and the modification 3.

As described above, in the present modification, as described above, during the positive cycle defrosting operation, the dehumidifying suction wetness control is performed by the overheating valve 27, and the main valve is set so that the high pressure Ph of the refrigeration cycle becomes the target high pressure Phs. The opening degree of 24 is adjusted (main valve high pressure control during defrosting). For this reason, the high pressure Ph of the refrigeration cycle can be maintained near the desired target high pressure Phs while ensuring the reliability of the compressor 21 during the positive cycle defrosting operation. Thereby, here, the input power of the compressor 21 is increased, and as a result, the amount of heat that can be used for defrosting can be secured, and the normal cycle defrosting operation can be continued.

Here, the dehumidifying suction wetting control for controlling the opening degree of the superheater valve 27 is performed so that the superheat degree TdSH of the refrigerant on the discharge side of the compressor 21 becomes the target discharge superheat degree TdSHs as in the third modification. In this case, the case where the main valve high pressure control at the time of defrosting by the main valve 24 is illustrated is illustrated, but the present invention is not limited to this, and the refrigerant on the discharge side of the compressor 21 similar to the above embodiment is overheated. The defrost main valve high pressure control by the main valve 24 is adopted even when the defrost suction wetness control is performed to control the opening degree of the superheat valve 27 so that the degree TdSH becomes equal to or greater than the target discharge superheat degree TdSHs. be able to.

The present invention has a discharge-suction bypass circuit used during a positive cycle defrosting operation for defrosting the outdoor heat exchanger while circulating the refrigerant in the order of the compressor, the indoor heat exchanger, the main valve, and the outdoor heat exchanger. Widely applicable to air conditioners.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 11 Main refrigerant circuit 21 Compressor 23 Outdoor heat exchanger 24 Main valve 26 Discharge-suction bypass circuit 27 Overheat valve 41 Indoor heat exchanger 52 Discharge temperature sensor 55 Indoor heat exchanger temperature sensor

Japanese Patent Laid-Open No. 61-262560

Claims

A compressor (21), an indoor heat exchanger (41), a main valve (24), and an outdoor heat exchanger (23), the compressor, the indoor heat exchanger, the main valve, and the outdoor A main refrigerant circuit (11) capable of performing a heating operation in which the refrigerant is circulated in the order of the heat exchanger;
An overheat valve (27) is provided, and is connected to the main refrigerant circuit so that the refrigerant can be bypassed from the discharge side of the compressor to the suction side of the compressor during the heating operation. A discharge-suction bypass circuit (26);
With
During the positive cycle defrosting operation in which the outdoor heat exchanger is defrosted while circulating the refrigerant in the order of the compressor, the indoor heat exchanger, the main valve, and the outdoor heat exchanger, the superheat valve is opened and the discharge is performed. The refrigerant is bypassed from the discharge side of the compressor to the suction side of the compressor through the suction bypass circuit, and the main valve and / or the overheat valve is set so that the refrigerant on the suction side of the compressor becomes wet. Inhalation wetness control during defrost to adjust the opening,
Air conditioner (1).
In the dehumidification suction wetting control, the superheat degree of the refrigerant on the discharge side of the compressor is obtained from the temperature of the refrigerant on the discharge side of the compressor (21), and the superheat degree of the refrigerant on the discharge side of the compressor is determined. Control for adjusting the opening of the main valve (24) and / or the superheat valve (27) so as to be equal to or less than a target discharge superheat degree,
The air conditioner (1) according to claim 1.
Obtaining the temperature of the refrigerant on the discharge side of the compressor (21) from the temperature of the refrigerant detected by a discharge temperature sensor (52) provided on the discharge side of the compressor;
Obtaining the saturation temperature of the refrigerant on the discharge side of the compressor from the temperature of the refrigerant detected by the indoor heat exchanger temperature sensor (55) provided in the indoor heat exchanger,
The refrigerant on the discharge side of the compressor detected by the temperature of the refrigerant on the discharge side of the compressor detected by the discharge temperature sensor and the indoor heat exchanger temperature sensor is used to determine the degree of superheat of the refrigerant on the discharge side of the compressor. From the saturation temperature of the
The air conditioner (1) according to claim 2.