JPWO2016139783A1 - Refrigeration cycle equipment - Google Patents

Abstract

Provided is a refrigeration cycle apparatus that suppresses liquid back operation to a compressor during a hot gas reverse type defrosting operation. The refrigeration cycle apparatus (1) according to the present invention includes a compressor (21), a flow path switching valve (29), a heat source side heat exchanger (22), a main expansion valve (24), and a use side heat exchanger (25). Has a refrigerant circuit (2) configured by being connected by a refrigerant pipe, and performs a defrosting operation by a hot gas reverse method. The refrigeration cycle apparatus (1) controls a pressure sensor (3) for measuring the pressure on the high pressure side in the refrigerant circuit, the compressor (21), the flow path switching valve (29), and the main expansion valve (24). And a control device (4). A series circuit in which a sub expansion valve (26) capable of adjusting the opening, a refrigerant tank (27) for accumulating excess refrigerant, and a solenoid valve (28) are connected in series is a heat source side heat exchanger (22). Is connected in parallel to the main expansion valve (24) which is connected between the heat exchanger (25) and the use side heat exchanger (25). The control device (4) controls the opening degree of the sub expansion valve (26) and the opening / closing of the electromagnetic valve (28) based on the pressure measured by the pressure sensor (3).

Description

  The present invention relates to a refrigeration cycle apparatus, and particularly to liquid back suppression during a defrosting operation.

There is known an air conditioner or the like that cools or heats water using a refrigeration cycle device and uses cold water or hot water obtained thereby for air conditioning. For example, an air-cooled heat pump chiller corresponds to these refrigeration cycle apparatuses.
When the refrigeration cycle apparatus is heated in low-temperature outside air, that is, an air heat exchanger (outdoor heat exchanger) that exchanges heat between outside air and refrigerant is used as an evaporator, and a water heat exchanger (room When the inner heat exchanger is used as a condenser (for example, when hot water used for heating is manufactured), the air heat exchanger may be frosted. The frost attached to the air heat exchanger inhibits heat exchange between the outside air and the refrigerant, and reduces the ability to heat water on the water heat exchanger side. Therefore, it is necessary to quickly remove the frost that has arrived at the air heat exchanger (defrosting). Defrosting methods include, for example, a hot gas reverse method that operates an air heat exchanger as a condenser, an off-cycle defrost method that stops the refrigeration cycle apparatus, and a heater defrost method that heats by a heater installed near the heat exchanger Etc. In particular, an air-cooled heat pump chiller performs a defrosting operation by a hot gas reverse method.

  In the air-cooled heat pump chiller, the refrigerant circuit is configured by connecting, for example, a compressor, an air heat exchanger, an expansion valve, a water heat exchanger, a refrigerant tank, and a four-way valve through refrigerant piping. An expansion valve between the air heat exchanger and the water heat exchanger is connected in series with the circuit. The refrigerant tank is installed between the expansion valve and the water heat exchanger, and is connected in parallel to the refrigerant pipe connecting the expansion valve and the water exchanger. The four-way valve is connected to the compressor inlet side and outlet side, so that when one connection destination is an air heat exchanger, the other connection destination is a water heat exchanger. And vice versa, the connection destination can be switched. In this refrigerant circuit, during heating operation, the four-way valve is switched so that the refrigerant circulates in the order of the compressor, the water heat exchanger, the expansion valve, and the air heat exchanger, and hot water is produced in the water heat exchanger. During the cooling operation, the four-way valve is switched so that the refrigerant circulates in the order of the compressor, the air heat exchanger, the expansion valve, and the water heat exchanger, and cold water is produced in the water heat exchanger.

  In such a refrigerant circuit, frost may be formed on the air heat exchanger serving as an evaporator during the heating operation, and therefore, a hot gas reverse defrosting operation is performed. The hot gas reverse defrosting operation is a defrosting method in which a high-temperature refrigerant gas (hot gas) discharged from a compressor is sent to a frosted air heat exchanger and the frost is melted by the heat. At the start of defrosting, the liquid refrigerant accumulated in the refrigerant tank installed between the expansion valve and the water heat exchanger flows to the compressor through the water heat exchanger and enters the compressor inlet. . That is, a liquid back to the compressor occurs. Similarly, when the defrosting operation is finished and the heating operation is started, the liquid refrigerant accumulated in the air heat exchanger enters the suction port of the compressor. That is, a liquid back to the compressor occurs. Therefore, in the prior art, an accumulator is installed in order to suppress liquid back, and protection is performed so that there is no liquid back to the compressor. However, the accumulator has a large capacity and requires a large space in the machine room. Therefore, in order to take measures against liquid back in a small space, a method of adjusting the amount of refrigerant flowing in the refrigerant circuit by using a flow rate adjusting device by providing a refrigerant tank has been studied.

  In Patent Document 1, a refrigerant circuit in which a compressor, a condenser, a throttle device, and an evaporator are connected by a refrigerant pipe is configured, and a flow rate adjusting device and a receiver that accumulates excess refrigerant in the refrigerant circuit are connected in series. A refrigerant circuit is disclosed in which the above circuit is provided in parallel with the expansion device.

  In Patent Document 2, the compressor discharge unit and the low pressure after the solenoid valve are connected by a hot gas bypass, the refrigerant circuit is divided into a low pressure unit and a high pressure unit, and a defrosting operation is performed. An accumulator is provided on the suction side of the compressor. A connected refrigeration cycle apparatus is disclosed.

  In Patent Document 3, when the pressure on the high-pressure side of the operating refrigerant circuit rises by connecting the compressor suction portion and the rear of the solenoid valve and sandwiching the refrigerant tank therebetween, the refrigerant is caused to flow into the refrigerant tank. A technique for reducing the pressure on the high-pressure side in the circuit is disclosed.

JP 2014-119153 A Japanese Examined Patent Publication No. 7-52052 Japanese Patent Laid-Open No. 5-288427

  The technique disclosed in Patent Document 1 configures a refrigerant circuit that adjusts the refrigerant flow rate according to the required refrigerant amount, and performs control to open the flow rate adjustment device and return the refrigerant accumulated in the receiver to the refrigerant circuit during a power failure. However, it was not intended for control during the defrosting operation.

  The technology disclosed in Patent Document 2 is provided with a hot gas bypass connecting the solenoid valve to the compressor discharge side and connecting from the solenoid valve to the evaporator, and is installed downstream of the condenser during the defrosting operation. The valve is closed and defrosting is performed by a circuit connecting the high-pressure side of the compressor and the evaporator. In this configuration, a liquid back to the compressor is prevented by an accumulator provided between the evaporator and the suction port of the compressor, and a space for installing the accumulator is required. A hot gas bypass is provided for defrosting. Therefore, the subject that the space in the machine room of a refrigerating cycle device had to be taken up occurred.

  Patent Document 3 is a refrigerant circuit that connects a suction port of an compressor and an expansion valve and sandwiches a refrigerant tank therebetween, and stores the refrigerant in the refrigerant tank when the refrigerant circulation amount becomes excessive and the high pressure rises. It has become. In this configuration, when the pressure on the high pressure side of the refrigerant circuit is higher than the specified value, the solenoid valve is opened and the refrigerant is stored in the refrigerant tank. It was not configured to prevent liquid back into the compressor.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to enable liquid back suppression during a defrosting operation of a refrigerant circuit in a refrigerant circuit including a refrigerant tank (high-pressure receiver). It is what.

  A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit configured by connecting a compressor, a flow path switching valve, a heat source side heat exchanger, a main expansion valve, and a use side heat exchanger by a refrigerant pipe, and a hot gas In the refrigeration cycle apparatus that performs the defrosting operation by the reverse method, a pressure sensor that measures the pressure on the high-pressure side in the refrigerant circuit, and a control device that controls the compressor, the flow path switching valve, and the main expansion valve, respectively A series circuit in which a sub expansion valve capable of adjusting the opening, a refrigerant tank for storing excess refrigerant, and a solenoid valve are connected in series, the heat source side heat exchanger and the use side heat exchanger The control device controls the opening degree of the sub expansion valve and the opening / closing of the electromagnetic valve based on the pressure measured by the pressure sensor.

  According to the present invention, by controlling the sub expansion valve and the electromagnetic valve at the start of the defrosting operation, the refrigerant amount in the refrigerant tank is adjusted, and the refrigerant amount necessary for the defrosting operation is output to the refrigerant circuit. The liquid back to the compressor that has occurred during the defrosting operation can be suppressed.

1 is a schematic diagram of a refrigerant circuit of a refrigeration cycle apparatus in a first embodiment. It is the schematic of the refrigerant circuit of the refrigerating-cycle apparatus of a prior art (comparative example). FIG. 3 is a control flow diagram of the refrigeration cycle apparatus in the first embodiment. It is explanatory drawing which showed the relationship between the high pressure side pressure with respect to the time passage at the time of the defrost operation of a refrigerant circuit, and the motion of the solenoid valve accompanying it. 6 is a control flow diagram of a refrigeration cycle apparatus in Embodiment 2. FIG.

Embodiment 1 FIG.
Hereinafter, the refrigeration cycle apparatus 1 according to the present embodiment will be described with reference to the drawings.
FIG. 1 is a schematic diagram of a refrigerant circuit 2 of a refrigeration cycle apparatus 1 in the present embodiment. The refrigeration cycle apparatus 1 according to the present embodiment is an air conditioner that uses, for example, cold water or hot water obtained by cooling or heating water for air conditioning. The refrigeration cycle apparatus 1 corresponds to, for example, an air-cooled heat pump chiller.

  The refrigerant circuit 2 of the refrigeration cycle apparatus 1 includes a compressor 21, an air heat exchanger 22 (corresponding to a heat source side heat exchanger of the present invention), a main expansion valve 24, and a water heat exchanger 25 (utilization side heat of the present invention). The sub expansion valve 26, the refrigerant tank 27, the electromagnetic valve 28, and the four-way valve 29 (corresponding to the flow path switching valve of the present invention) are connected by refrigerant piping. The sub expansion valve 26, the refrigerant tank 27, and the electromagnetic valve 28 are connected in series in the refrigerant circuit. The connected sub expansion valve 26, refrigerant tank 27, and electromagnetic valve 28 are connected in parallel to the main expansion valve 24 between the air heat exchanger 22 and the water heat exchanger 25.

  The four-way valve 29 is connected to the suction port side and the discharge port side of the compressor 21, and when one connection destination is the air heat exchanger 22, the other connection destination is the water heat exchanger 25. And vice versa. The switching of the connection destination is not limited to the four-way valve 29, and other flow paths can be used as long as the refrigerant circulation direction of the refrigerant circuit 2 can be reversed by switching the connection destinations on the suction port side and the discharge port side of the compressor 21. A switching valve may be used. The main expansion valve 24 functions as a pressure reducing device in the refrigerant circuit 2. The sub-expansion valve 26 can change the opening degree to a fully opened, fully closed, or throttled state, and when fully opened, the refrigerant can be passed without reducing pressure or with little reduced pressure, and when fully closed, the refrigerant flow is blocked. be able to. When the sub expansion valve 26 is in the throttle state, it functions as a pressure reducing device in the refrigerant circuit 2 in the same manner as the main expansion valve 24. The solenoid valve 28 can be opened and closed. When opened, the refrigerant can be passed without depressurizing or with a reduced pressure, and when closed, the refrigerant flow can be blocked.

  The refrigeration cycle apparatus 1 is provided with a pressure sensor 3 and measures the pressure on the high pressure side of the refrigerant circuit 2. The refrigeration cycle apparatus 1 is provided with a control device 4. The control device 4 controls the operations of the compressor 21, the four-way valve 29, and the main expansion valve 24, and performs opening / closing control of the sub expansion valve 26 and the electromagnetic valve 28 based on the measured value of the pressure sensor 3. The control device 4 is constituted by, for example, a microcomputer. The relationship between the pressure on the high pressure side of the refrigerant circuit 2 and the opening control of the sub expansion valve 26 and the opening / closing control of the electromagnetic valve 28 will be described later.

  The air heat exchanger 22 is provided with a fan 23, and the fan 23 sends air outside the refrigeration cycle apparatus 1 (outside air) to the air heat exchanger 22 to exchange heat between the refrigerant and the outside air. It is. If frost formation occurs in the air heat exchanger 22 during the heating operation, the air sent from the fan 23 to the air heat exchanger 22 becomes difficult to pass, and the efficiency of heat exchange decreases.

(Movement of the refrigeration cycle apparatus 1 during heating operation)
The flow of the refrigerant in the refrigerant circuit 2 of the refrigeration cycle apparatus 1 and the function of each element in the refrigerant circuit at the time of heating operation (when hot water is produced by the water heat exchanger 25) will be described.
The refrigerant flowing in the piping of the refrigerant circuit 2 is compressed by the compressor 21, is made high temperature and high pressure, and enters the four-way valve 29. During the heating operation, the four-way valve 29 is switched as indicated by the dotted line in FIG. 1, and the high-temperature and high-pressure refrigerant that has come out from the discharge port of the compressor 21 flows into the water heat exchanger 25. The water heat exchanger 25 becomes a condenser during heating operation, and heat exchange is performed between water and the refrigerant. The high-temperature and high-pressure refrigerant dissipates heat to water in the water heat exchanger 25 and condenses to become liquid refrigerant.
The liquid refrigerant flowing out of the water heat exchanger 25 is depressurized through the main expansion valve 24 to be a low-temperature low-pressure gas-liquid two-phase refrigerant. In the heating operation, the solenoid valve 28 is normally opened, and the refrigerant that has exited the water heat exchanger 25 also flows to the refrigerant tank 27. The refrigerant tank has a function of accumulating excess refrigerant during heating operation. Further, the sub expansion valve 26 connected to the refrigerant tank 27 is in a throttle state, and functions as a refrigerant decompression device.

  The refrigerant that has been made into the gas-liquid two-phase by the main expansion valve 24 and the sub expansion valve 26 flows into the air heat exchanger 22. The air heat exchanger 22 becomes an evaporator during heating operation, and heat exchange is performed between the outside air and the refrigerant. The low-temperature low-pressure gas-liquid two-phase refrigerant receives heat from the outside air in the air heat exchanger 22 and becomes superheated gas. The refrigerant that has become superheated gas flows into the suction port of the compressor 21 through the four-way valve 29. After that, the same route is circulated again.

(Motion of refrigeration cycle apparatus 1 during defrosting operation)
The flow of the refrigerant in the refrigerant circuit 2 of the refrigeration cycle apparatus 1 during the defrosting operation and the function of each element in the refrigerant circuit will be described.
When the refrigeration cycle apparatus 1 is operated for heating in low-temperature outside air, that is, when the air heat exchanger 22 that performs heat exchange between the outside air and the refrigerant is used as an evaporator and the water heat exchanger 25 is used as a condenser. The air heat exchanger 22 may be frosted (for example, when producing hot water used for heating). When the air heat exchanger 22 is frosted, heat exchange between the outside air and the refrigerant in the air heat exchanger 22 is hindered, and the ability to heat water on the water heat exchanger 25 side is reduced. The frost that has arrived at the air heat exchanger 22 is removed by the frost operation.

  In the refrigeration cycle apparatus 1 of the present embodiment, defrosting is performed by a hot gas reverse method. When the defrosting operation is started, the four-way valve 29 is switched as shown by the solid line in FIG. The high-temperature and high-pressure gas refrigerant that has exited from the discharge port of the compressor 21 flows into the frosted air heat exchanger 22. Thereby, the frost which arrived at the air heat exchanger 22 is melted and defrosted.

(Refrigeration cycle device in comparative example)
FIG. 2 is a schematic diagram of the refrigerant circuit 102 of the refrigeration cycle apparatus 101 of the prior art (comparative example). The refrigerant circuit 102 of the refrigeration cycle apparatus 101 is configured by connecting a compressor 11, an air heat exchanger 12, a main expansion valve 14, a water heat exchanger 15, a refrigerant tank 17, and a four-way valve 19 by refrigerant piping. The refrigerant tank 17 is connected in parallel to the main expansion valve 14 between the air heat exchanger 12 and the water heat exchanger 15. The four-way valve 19 is connected to the suction port side and the discharge port side of the compressor 11. When one connection destination is the air heat exchanger 12, the other connection destination is the water heat exchanger 15. And vice versa. The air heat exchanger 12 is provided with a fan 13, and the fan 13 sends air outside the refrigeration cycle apparatus 101 (outside air) to the air heat exchanger 12 to exchange heat between the refrigerant and the outside air. It is.

Generally, in the refrigerant circuit 102 such as the refrigeration cycle apparatus 101, the internal volume of the air heat exchanger is larger than that of the water heat exchanger. During the heating operation, since the air heat exchanger 12 having a relatively small internal volume serves as a condenser, the amount of necessary refrigerant is less than that during the cooling operation, and surplus refrigerant is generated. Therefore, the refrigerant is stored in the refrigerant tank 17 during the heating operation. The same applies to the refrigeration cycle apparatus 1 of the present embodiment.
At the time of the defrosting operation, the refrigerant accumulated in the refrigerant tank 17 is connected to the air heat exchanger 12 on the discharge side of the compressor 11 and the water heat exchanger 15 on the suction side to reverse the circulation of the refrigerant with respect to the heating operation. All flow out onto the main refrigerant circuit. However, if all excess refrigerant flows out of the refrigerant tank 17, the amount of refrigerant is larger than the amount of refrigerant required during the defrosting operation, and the liquid refrigerant that has accumulated in the refrigerant tank 17 passes through the water heat exchanger 15 and flows into the compressor 11. It flows into the suction side and a liquid back occurs. Therefore, some countermeasures against liquid back are necessary in the refrigeration cycle apparatus 101 of the comparative example.

(Control of refrigeration cycle apparatus 1 in Embodiment 1)
FIG. 3 is a control flow diagram of the refrigeration cycle apparatus 1 in the present embodiment.
In the refrigeration cycle apparatus 101 of the comparative example, since countermeasures against liquid back are necessary, in the present embodiment, a refrigerant circuit 2 like the refrigeration cycle apparatus 1 is configured to prevent liquid back by the control described below. ing.

  When the defrosting operation is started, the control device 4 installed in the refrigeration cycle apparatus 1 causes the pressure on the high-pressure side in the refrigerant circuit 2 (for example, the refrigerant pipe between the discharge port of the compressor 21 and the four-way valve 29). The pressure of the pressure sensor 3 measuring the pressure of the refrigerant circuit 2 is detected and a change with respect to time of the pressure on the high pressure side of the refrigerant circuit 2 is detected to determine whether it is equal to or higher than the determination high pressure (corresponding to the specified value of the present invention). It is determined whether it is lower (control step S1). When the high-pressure side pressure is lower than the determination high pressure, the control device 4 closes the electromagnetic valve 28 (control step S2), fully opens the sub expansion valve 26 (control step S3), and removes the refrigerant in the refrigerant tank 27 from the main circuit 5. Put it in. The main circuit 5 is a part of a circuit in which the refrigerant is circulated by connecting the compressor 21, the four-way valve 29, the air heat exchanger 22, the main expansion valve 24, and the water heat exchanger 25 with refrigerant piping. By discharging the refrigerant in the refrigerant tank 27 to the main circuit 5, the shortage of the refrigerant amount in the main circuit 5 is solved, and an effect of avoiding problems such as overheating operation of the compressor 21 can be obtained.

  When the high-pressure side pressure is equal to or higher than the determination high pressure, the control device 4 opens the solenoid valve 28 (control step S4), fully closes the sub expansion valve 26 (control step S5), and removes the refrigerant in the main circuit 5 from the solenoid valve. It puts into the refrigerant tank 27 from 28 side. As a result, an amount of refrigerant necessary for defrosting can be output to the main circuit 5, and an effect of avoiding problems such as liquid back to the compressor 21 caused by excessive refrigerant in the main circuit 5 can be obtained.

  After the control step S2-S3 or the control step S4-S5 is performed, the control device 4 determines whether the defrosting operation end condition is satisfied (control step S6). When the defrosting operation end condition is not satisfied, the process returns to the control step S1 again. When the defrosting operation end condition is satisfied, the control during the defrosting operation is ended. The defrosting operation end condition is, for example, when the temperature of the air heat exchanger 22 is equal to or higher than a specified value, or when the elapsed time from the start of the defrosting operation is equal to or higher than a specified value, or when both are satisfied. It is determined by the conditions such as.

FIG. 4 is an explanatory diagram showing the relationship between the high-pressure side pressure with respect to the passage of time during the defrosting operation of the refrigerant circuit 2 and the movement of the electromagnetic valve 28 associated therewith.
The pressure in FIG. 4 is the pressure on the high pressure side in the refrigerant circuit 2. Specifically, the pressure of the refrigerant on the discharge side of the compressor 21 and between the compressor 21 and the four-way valve 29 is measured. When the refrigeration cycle apparatus 1 is switched to the defrosting operation, the pressure in the refrigerant circuit 2 increases with time. When the rate of increase in the pressure in the refrigerant circuit 2 with respect to the passage of time is larger than the standard (that is, the slope of the straight line in FIG. 4 is larger than the standard), the control device 4 determines that the pressure is high. When the rate of increase in the pressure in the refrigerant circuit 2 with respect to the passage of time is smaller than the standard (that is, the slope of the straight line in FIG. 4 is smaller than the standard), the control device 4 determines that the pressure is low. In accordance with this determination, the control device 4 controls the opening and closing of the sub expansion valve 26 and the electromagnetic valve 28 as described above.

  When the high-pressure side pressure is lower than the determination high pressure, the control device 4 can also close the electromagnetic valve 28 and control the sub expansion valve 26 to the throttle state. In the control for fully opening the sub-expansion valve 26, the pressure in the main circuit 5 may increase immediately. When the high-pressure side pressure exceeds the determination high pressure, the sub-expansion valve 26 is fully closed again and the solenoid valve 28 is closed. Will be controlled to open. Then, it is necessary to frequently perform opening / closing control of the sub expansion valve 26 and the electromagnetic valve 28, and the operation is not stable. However, by restricting the opening of the sub expansion valve 26, the amount of outflow from the refrigerant tank 27 to the main circuit 5 can be controlled, and the fluctuation in the pressure of the main circuit 5 can be moderated. Thereby, the frequency of opening and closing of the sub expansion valve 26 and the electromagnetic valve 28 can be reduced, and the defrosting operation of the refrigeration cycle apparatus 1 can be performed stably.

Embodiment 2.
In the present embodiment, control steps for the sub expansion valve 26 and the electromagnetic valve 28 are added to the refrigerant circuit 2 and its control in the first embodiment after the start of the defrosting operation and before the end of the defrosting operation. . Here, the description will focus on points that are different from the first embodiment.
FIG. 5 is a control flow diagram of the refrigeration cycle apparatus 1 in the present embodiment.
The refrigeration cycle apparatus 1 according to the present embodiment performs heating operation with the sub expansion valve 26 throttled and the electromagnetic valve 28 opened. At the start of the defrosting operation, the refrigeration cycle apparatus 1 switches the four-way valve 29 to change the circulation direction of the refrigerant. Thereafter, the control device 4 fully opens the sub expansion valve 26 and closes the electromagnetic valve 28 (control step S0). Thereafter, the process proceeds to the control step S1, and the control device 4 detects a change in the pressure on the high pressure side of the refrigerant circuit 2 with respect to time, and determines whether it is equal to or higher than a determination high pressure (corresponding to a specified value of the present invention) judge. That is, the same control steps S1-S6 as in the first embodiment are performed.

Immediately after the start of the defrosting operation, that is, in the control step S0, since the pressure on the high pressure side of the refrigerant circuit 2 is low, the refrigerant stored in the refrigerant tank 27 flows out to the main circuit 5 through the sub expansion valve 26. When a sufficient amount of refrigerant flows into the main circuit 5, the pressure on the high pressure side of the refrigerant circuit 2 increases. When the rate of increase in the pressure in the refrigerant circuit 2 with respect to the passage of time becomes larger than the specified value due to the increase in pressure (that is, the slope of the straight line in FIG. 4 becomes larger than the specified value), the control device 4 The valve 28 is opened, and the sub expansion valve 26 is closed. That is, the control steps S4-S5 are controlled through the control step S1. In this case, the refrigerant in the refrigerant circuit 2 flows into the refrigerant tank 27 through the electromagnetic valve 28. Thereby, the quantity of the refrigerant | coolant in the refrigerant circuit 2 used as the high pressure reduces, and the pressure in the refrigerant circuit 2 falls.
If the pressure on the high pressure side of the refrigerant circuit 2 is lower than the specified value even when the refrigerant flows out to the main circuit 5, the control device 4 opens the sub expansion valve 26 and closes the electromagnetic valve 28.

When control step S6 is reached by the same control as in the first embodiment, control device 4 determines whether or not the defrosting operation end condition is satisfied. When the defrosting operation end condition is not satisfied, the process returns to the control step S1 again. When the defrosting operation end condition is satisfied, the control device 4 performs control to fully open the sub expansion valve 26 and close the electromagnetic valve 28 (control step S7). Thereafter, the four-way valve 29 is switched and the heating operation is resumed. During the heating operation, the air heat exchanger 22 side of the refrigerant circuit 2 is on the low pressure side, but immediately after the heating operation is started, liquid refrigerant is present in the air heat exchanger 22 due to the defrosting operation. However, when the sub expansion valve 26 is fully opened and the electromagnetic valve 28 is closed, the refrigerant in the main circuit 5 flows into the refrigerant tank 27, so that the liquid refrigerant present in the air heat exchanger 22 goes to the compressor 21. Disappears.
In addition, the timing which transfers to control step S7 should just set the predetermined time before completion | finish of a defrost operation (before restarting heating operation) according to the specification of the refrigerating cycle apparatus 1, for example. In this case, the control step S7 ends when a predetermined time has elapsed, and the defrosting control ends. Thereafter, the heating operation is resumed. Further, for example, a pressure change in the refrigerant circuit 2 is detected, and when the pressure satisfies a predetermined condition, the process proceeds to the control step S7. When the pressure falls to a specified value, the control step S7 is terminated, and the defrosting is performed. Control ends.

  By performing the above control, the amount of refrigerant in the main circuit 5 is maintained appropriately, and the pressure is also maintained at an appropriate value. Thereby, when switching from heating operation to defrosting operation and when switching from defrosting operation to heating operation, it can suppress that the liquid back to compressor 21 arises.

  DESCRIPTION OF SYMBOLS 1 Refrigeration cycle apparatus, 2 Refrigerant circuit, 3 Pressure sensor, 4 Control apparatus, 5 Main circuit, 11 Compressor, 12 Air heat exchanger, 13 Fan, 14 Main expansion valve, 15 Water heat exchanger, 17 Refrigerant tank, 18 Solenoid valve, 19 Four-way valve, 21 Compressor, 22 Air heat exchanger, 23 Fan, 24 Main expansion valve, 25 Water heat exchanger, 26 Sub expansion valve, 27 Refrigerant tank, 28 Solenoid valve, 29 Four-way valve, 101 Refrigeration Cycle device, 102 Refrigerant circuit.

A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit configured by connecting a compressor, a flow path switching valve, a heat source side heat exchanger, a main expansion valve, and a use side heat exchanger by a refrigerant pipe, and a hot gas In the refrigeration cycle apparatus that performs the defrosting operation by the reverse method, a pressure sensor that measures the pressure on the high-pressure side in the refrigerant circuit, and a control device that controls the compressor, the flow path switching valve, and the main expansion valve, respectively the provided, sub-expansion valve capable of adjusting the refrigerant tank, the opening is arranged on the heat source side heat exchanger side with respect to the refrigerant tank for storing the surplus refrigerant, and the use-side with respect to the refrigerant tank a series circuit connecting a solenoid valve arranged in the heat exchanger-side in series, are connected in parallel with the main expansion valve connected between said utilization side heat exchanger and the heat source-side heat exchanger, the control Location, based on the pressure measurement of the pressure sensor, controls the opening and closing of the opening and the solenoid valve of the sub-expansion valve.

Claims (5)

Refrigeration having a refrigerant circuit configured by connecting a compressor, a flow path switching valve, a heat source side heat exchanger, a main expansion valve, and a use side heat exchanger by refrigerant piping and performing a defrosting operation by a hot gas reverse method In cycle equipment,
A pressure sensor for measuring the pressure on the high pressure side in the refrigerant circuit;
A control device for controlling the compressor, the flow path switching valve and the main expansion valve, respectively,
A series circuit in which a sub expansion valve capable of adjusting the opening, a refrigerant tank for storing excess refrigerant, and an electromagnetic valve are connected in series is provided between the heat source side heat exchanger and the use side heat exchanger. Connected in parallel to the connected main expansion valve,
The controller is
A refrigeration cycle apparatus that controls the opening of the sub expansion valve and the opening and closing of the electromagnetic valve based on the pressure measured by the pressure sensor.   When the pressure is higher than a specified value, the sub expansion valve is opened and the solenoid valve is closed. When the pressure is lower than a specified value, the sub expansion valve is fully closed, and the solenoid valve is The refrigeration cycle apparatus according to claim 1, which is opened.   When the pressure is higher than a specified value, the opening of the sub expansion valve is throttled and the electromagnetic valve is closed, and when the pressure is lower than a specified value, the sub expansion valve is fully closed, and The refrigeration cycle apparatus according to claim 1, wherein the solenoid valve is opened.   The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the sub expansion valve is fully opened and the electromagnetic valve is closed until the pressure reaches a specified value after the start of the defrosting operation. .   The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein the sub-expansion valve is fully opened and the electromagnetic valve is closed for a predetermined time before the defrosting operation is completed.

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