JP2021071225A - Refrigeration cycle device - Google Patents

Abstract

To provide a refrigeration cycle device that can detect shortage of an amount of refrigerant sucked into a compressor without a suction pressure sensor.SOLUTION: An air conditioning device includes a refrigerant circuit, a first sensor and a controller. The refrigerant circuit includes a compressor, a condenser, an expansion valve and an evaporator. The first sensor detects condensation temperature or condensation pressure of a refrigeration cycle in the refrigerant circuit. The controller controls the refrigeration cycle in the refrigerant circuit. The controller performs first control of increasing evaporation pressure of the refrigeration cycle in the refrigerant circuit when a first condition is met. The first condition represents a state where a refrigerant overcooling degree at an outlet of the condenser in the refrigerant circuit increases and the condensation temperature or condensation pressure detected by the first sensor decreases.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a refrigeration cycle device.

For example, as in Patent Document 1 (Japanese Unexamined Patent Publication No. 2001-141290), when various sensors are provided in the refrigerant circuit of the vapor compression refrigerating cycle apparatus for the purpose of monitoring the operating state of the refrigerating cycle apparatus and controlling the operation. There is.

For example, as disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. 2001-141290), if an suction pressure sensor for measuring the suction pressure is provided in the refrigerant circuit and a decrease in the suction pressure is detected, the refrigerant is sucked into the compressor. It is possible to grasp the shortage of the amount of refrigerant.

However, in order to reduce costs, the refrigeration cycle device may not be provided with an suction pressure sensor. In a refrigeration cycle device that does not have an suction pressure sensor, it may be difficult to detect a decrease in suction pressure, grasp the shortage of the amount of refrigerant sucked into the compressor, and perform control corresponding to this.

The refrigeration cycle device of the first aspect includes a refrigerant circuit, a first sensor, and a control unit. Refrigerant circuits include compressors, condensers, expansion valves and evaporators. The first sensor detects the condensation temperature or the condensation pressure of the refrigeration cycle in the refrigerant circuit. The control unit controls the refrigeration cycle in the refrigerant circuit. The control unit performs the first control for increasing the evaporation pressure of the refrigeration cycle in the refrigerant circuit when the first condition is satisfied. The first condition is that the degree of supercooling of the refrigerant at the outlet of the condenser of the refrigerant circuit has increased, and the condensation temperature or the condensation pressure detected by the first sensor has decreased.

When the degree of supercooling of the refrigerant at the outlet of the condenser increases in the refrigeration cycle apparatus, the condensation temperature and the condensation pressure usually increase. In the refrigeration cycle device, if the condensation temperature and the condensation pressure are decreasing even though the degree of supercooling is increasing, the amount of refrigerant sucked into the compressor may be insufficient.

In the refrigeration cycle apparatus of the first aspect, control is performed to increase the evaporation pressure of the refrigeration cycle when the degree of supercooling is increased and the condensation temperature or the condensation pressure is decreased. Therefore, in the refrigeration cycle device of the first aspect, the operation of the refrigeration cycle device can be continued while suppressing damage to the compressor due to insufficient amount of the sucked refrigerant.

The refrigeration cycle device of the second aspect is the refrigeration cycle device of the first aspect, and the control unit opens the expansion valve so that the supercooling degree approaches the target supercooling degree when the first control is not performed. The second control for adjusting is performed.

The refrigeration cycle apparatus according to the second aspect performs the second control for adjusting the degree of supercooling at the outlet of the condenser to the target value when the first control is not performed. In other words, the refrigeration cycle apparatus of the second aspect performs supercooling degree control when the evaporation pressure of the refrigeration cycle is not lowered. By performing such a second control, it is possible to operate the refrigeration cycle device efficiently.

The refrigeration cycle apparatus of the third aspect is the refrigeration cycle apparatus of the second aspect, and the control unit performs at least one of the following (a) to (c) in the second control after the first condition is satisfied. Do.
(A) Decrease the target supercooling degree.
(B) Reduce the amount of reduction in the opening degree of the expansion valve per unit time.
(C) Increase the minimum opening of the expansion valve.

If the first condition is satisfied when the second control is executed and the second control is subsequently performed with the same control content, the amount of refrigerant sucked into the compressor may be insufficient again.

In the refrigeration cycle apparatus of the third viewpoint, when the first condition is satisfied, the control content of the second control is changed to a control content in which the first condition is difficult to be satisfied, so that the occurrence of a situation where the first control is required is suppressed. it can.

The refrigeration cycle device of the fourth aspect is any of the refrigeration cycle devices of any of the first to third aspects, and the control unit controls the opening degree of the expansion valve as the first control when the first condition is satisfied. Control is performed so that it is larger than the opening degree of the expansion valve.

In the refrigeration cycle apparatus of the fourth aspect, the evaporation pressure in the refrigeration cycle can be increased.

The refrigeration cycle device of the fifth viewpoint is any of the refrigeration cycle devices of any of the first to fourth viewpoints, and the control unit controls the number of revolutions of the compressor as the first control when the first condition is satisfied. Controls to lower the number of revolutions of the compressor.

In the refrigeration cycle apparatus of the fifth aspect, the evaporation pressure in the refrigeration cycle can be increased.

The refrigeration cycle device of the sixth aspect is any of the refrigeration cycle devices of the first to fifth aspects, and further includes a fan for supplying air to the evaporator. As the first control, the control unit controls the fan rotation speed to be higher than the fan rotation speed when the first condition is satisfied.

In the refrigeration cycle apparatus of the sixth aspect, the evaporation pressure in the refrigeration cycle can be increased.

The refrigeration cycle device of the seventh aspect is any of the refrigeration cycle devices of the first to sixth aspects, and further includes a second sensor and a third sensor. The second sensor measures the temperature of the refrigerant flowing through the evaporator. The third sensor measures the temperature of the refrigerant sucked into the compressor. After the start of the first control, the control unit increases the condensed pressure in the refrigeration cycle of the refrigerant circuit to a predetermined pressure, or the value obtained by subtracting the measured value of the second sensor from the measured value of the third sensor to a predetermined value. Then, the first control is terminated.

In the refrigeration cycle device of the seventh aspect, an increase in the evaporation pressure of the refrigeration cycle is detected based on an increase in the condensation pressure and an increase in the temperature difference between the temperature of the refrigerant sucked into the compressor and the temperature of the refrigerant flowing through the evaporator. Then, the first control can be stopped and the normal refrigeration cycle apparatus can be returned to operation.

The refrigeration cycle apparatus according to the eighth aspect is any refrigeration cycle apparatus from the first aspect to the seventh aspect, and when the first condition is satisfied when the rotation speed of the compressor does not change for a predetermined time, the control unit becomes the first. 1 Control is performed.

In the refrigeration cycle apparatus of the eighth aspect, the state where the condensation temperature and the condensation pressure are lowered due to the decrease in the rotation speed of the compressor is determined to be the state where the evaporation pressure of the refrigeration cycle is lowered, and the first control is performed. Can be suppressed from being executed.

It is a schematic block diagram of the air conditioner which concerns on one Embodiment of a refrigeration cycle apparatus. It is a control block diagram of the air conditioner of FIG. It is a flowchart explaining the 1st control of the controller of FIG. 2 and the process related to the 1st control. It is a schematic block diagram of the air conditioner which concerns on modification B.

An embodiment of the refrigeration cycle apparatus will be described with reference to the drawings.

(1) Overall Configuration The overall configuration of the air conditioner 1 according to the embodiment of the refrigeration cycle apparatus will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of the air conditioner 1.

The air conditioner 1 is a device that cools and heats an air-conditioned space by using a vapor compression refrigeration cycle. However, the air conditioner 1 is not limited to a device capable of performing both cooling and heating, and may be, for example, a dedicated cooling device capable of performing only cooling. Further, the refrigeration cycle device of the present disclosure is not limited to an air conditioner. The refrigeration cycle device may be another type of device that utilizes a vapor compression refrigeration cycle, for example, a hot water supply device, a refrigerating device, or the like.

Although the type of the refrigerant is not limited, in the present embodiment, the refrigerant used by the air conditioner 1 is, for example, a fluorocarbon-based refrigerant such as R32.

As shown in FIG. 1, the air conditioner 1 mainly includes a heat source unit 2, a utilization unit 3, and refrigerant connecting pipes 41 and 42. In the present embodiment, the air conditioner 1 has only one utilization unit 3, but the air conditioner 1 may have a plurality of utilization units 3 connected in parallel to each other. The refrigerant connecting pipes 41 and 42 include a liquid refrigerant connecting pipe 41 and a gas refrigerant connecting pipe 42. The refrigerant communication pipes 41 and 42 are pipes that connect the heat source unit 2 and the utilization unit 3. The refrigerant connecting pipes 41 and 42 are pipes installed at the installation site when the air conditioner 1 is installed.

The refrigerant circuit 10 of the air conditioner 1 is configured by connecting the heat source unit 2 and the utilization unit 3 via the liquid refrigerant connecting pipe 41 and the gas refrigerant connecting pipe 42. The refrigerant circuit 10 mainly includes a compressor 21 of the heat source unit 2, a flow direction switching mechanism 22, a heat source heat exchanger 23, an expansion valve 24, and a heat exchanger 31 of the utilization unit 3.

(2) Detailed Configuration The detailed configuration of the air conditioner 1 will be described with reference to FIG. FIG. 2 is a control block diagram of the air conditioner 1.

(2-1) Utilization unit The utilization unit 3 is installed in, for example, an air-conditioned space. For example, the utilization unit 3 is a ceiling-embedded unit installed on the ceiling of the air-conditioned space. However, the utilization unit 3 is not limited to the ceiling-embedded unit, and may be a ceiling-hung type unit, a wall-mounted unit, or a floor-standing type unit. The utilization unit 3 may be arranged in a space different from the air conditioning target space, and the air cooled or heated by the utilization unit 3 may be supplied to the air conditioning target space by a duct or the like.

As shown in FIG. 1, the utilization unit 3 mainly includes a utilization heat exchanger 31, a first fan 32, and a first control unit 62. Further, as shown in FIG. 1, the utilization unit 3 includes a liquid refrigerant pipe 33 connecting the liquid side end of the utilization heat exchanger 31 and the liquid refrigerant connecting pipe 41, and the gas side end of the utilization heat exchanger 31 and the gas refrigerant. It has a gas refrigerant pipe 34 for connecting to the connecting pipe 42.

The structure of the utilization heat exchanger 31 is not limited, but for example, a cross-fin type fin-and-tube heat exchanger composed of a heat transfer tube (not shown) and a large number of fins (not shown). Is. In the utilization heat exchanger 31, heat exchange is performed between the refrigerant flowing through the utilization heat exchanger 31 and the air in the air-conditioned space.

The utilization heat exchanger 31 functions as an evaporator during the cooling operation. The utilization heat exchanger 31 functions as a condenser (radiator) during the heating operation.

The utilization heat exchanger 31 is provided with a utilization heat exchange temperature sensor 75 that measures the temperature of the refrigerant flowing through the utilization heat exchanger 31. For example, the utilization heat exchange temperature sensor 75 measures the temperature of the refrigerant flowing in the intermediate position of the utilization heat exchanger 31 in the refrigerant flow direction. The used heat exchange temperature sensor 75 is, for example, a thermistor. The utilization heat exchange temperature sensor 75 measures the temperature of the refrigerant flowing through the evaporator during the cooling operation of the air conditioner 1. The utilization heat exchange temperature sensor 75 measures the temperature of the refrigerant flowing through the condenser during the heating operation of the air conditioner 1. In other words, the utilization heat exchange temperature sensor 75 measures the condensation temperature in the refrigeration cycle during the heating operation of the air conditioner 1.

The first fan 32 sucks air into the utilization unit 3 and supplies it to the utilization heat exchanger 31, and supplies the air that has exchanged heat with the refrigerant in the utilization heat exchanger 31 to the air conditioning target space. The first fan 32 supplies air to the heat exchanger 31 used as an evaporator during the cooling operation of the air conditioner 1. The first fan 32 supplies air to the heat exchanger 31 used as a condenser during the heating operation of the air conditioner 1.

The first fan 32 is a centrifugal fan such as a turbo fan or a sirocco fan. However, the type of the first fan 32 is not limited to the centrifugal fan, and may be appropriately selected. The first fan 32 is driven by the fan motor 32a. The rotation speed of the fan motor 32a can be controlled by an inverter.

The first control unit 62 controls the operation of each unit constituting the utilization unit 3.

The first control unit 62 is electrically connected to a device such as a fan motor 32a included in the utilization unit 3. Further, the first control unit 62 is communicably connected to various sensors provided in the utilization unit 3. Various sensors provided in the utilization unit 3 include a utilization heat exchange temperature sensor 75 and a temperature sensor (not shown) for measuring the temperature of the air-conditioned space. The first control unit 62 includes a microprocessor including a CPU and a memory, an input / output device, and the like (not shown). The first control unit 62 controls the operation of each unit constituting the utilization unit 3 by the CPU executing a program stored in the memory. The first control unit 62 does not have to realize all the control by software, and may realize some or all control by hardware using various control circuits.

The first control unit 62 is configured to be able to receive various control signals including an operation signal and a stop signal of the air conditioner 1 transmitted from a remote controller for operating the air conditioner 1 (not shown). Further, the first control unit 62 exchanges various signals and the like with the second control unit 61 of the heat source unit 2 via the communication line. The first control unit 62 and the second control unit 61 cooperate with each other to function as the controller 60. The function of the controller 60 will be described later.

(2-2) Heat Source Unit The heat source unit 2 is not limited to the installation location, but is installed, for example, on the rooftop of the building where the air conditioner 1 is installed, the machine room, or the periphery of the building.

As shown in FIG. 1, the heat source unit 2 includes a compressor 21, a flow direction switching mechanism 22, a heat source heat exchanger 23, an expansion valve 24, an accumulator 25, a second fan 26, a liquid shutoff valve 27, and the like. It mainly has a gas shutoff valve 28 and a second control unit 61. Further, the heat source unit 2 has various sensors including a suction temperature sensor 71, a discharge temperature sensor 72, a heat source heat exchange temperature sensor 73, and a liquid tube temperature sensor 74.

As shown in FIG. 1, the heat source unit 2 includes a suction pipe 10a, a discharge pipe 10b, a first gas refrigerant pipe 10c, a liquid refrigerant pipe 10d, and a second gas refrigerant pipe 10e. The suction pipe 10a connects the flow direction switching mechanism 22 and the suction end of the compressor 21. The suction pipe 10a is provided with a suction temperature sensor 71. The discharge pipe 10b connects the discharge end of the compressor 21 and the flow direction switching mechanism 22. The discharge pipe 10b is provided with a discharge temperature sensor 72. The first gas refrigerant pipe 10c connects the flow direction switching mechanism 22 and the gas side end of the heat source heat exchanger 23. The liquid refrigerant pipe 10d connects the liquid side end of the heat source heat exchanger 23 and the liquid refrigerant connecting pipe 41. A liquid closing valve 27 is provided at a connection portion of the liquid refrigerant pipe 10d with the liquid refrigerant connecting pipe 41. The liquid refrigerant pipe 10d is provided with an expansion valve 24. A liquid pipe temperature sensor 74 is provided between the expansion valve 24 and the liquid closing valve 27 of the liquid refrigerant pipe 10d. The second gas refrigerant pipe 10e connects the flow direction switching mechanism 22 and the gas refrigerant connecting pipe 42. A gas closing valve 28 is provided at a connection portion of the second gas refrigerant pipe 10e with the gas refrigerant connecting pipe 42. The liquid shutoff valve 27 and the gas shutoff valve 28 are valves that are manually opened and closed.

The configuration of the heat source unit 2 will be further described below.

(2-2-1) Compressor The compressor 21 is a device that compresses and discharges the refrigerant by the compression mechanism 21a. The compressor 21 pressurizes the low pressure refrigerant in the refrigeration cycle to the high pressure in the refrigeration cycle. The type of the compressor 21 is not limited, but is, for example, a rotary type or scroll type positive displacement compressor. The compression mechanism 21a of the compressor 21 is driven by the compressor motor 21b (see FIG. 1). The rotation speed of the compressor motor 21b can be controlled by an inverter. The compression mechanism 21a of the compressor 21 may be driven by a prime mover (for example, an internal combustion engine) other than the motor.

(2-2-2) Flow direction switching mechanism The flow direction switching mechanism 22 is a mechanism for switching the flow direction of the refrigerant discharged by the compressor 21. In other words, the flow direction switching mechanism 22 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 10. In the present embodiment, the flow direction switching mechanism 22 is a four-way switching valve. However, instead of the four-way switching valve, a plurality of solenoid valves and a refrigerant pipe may be combined to realize a flow direction switching mechanism 22 capable of switching the flow direction of the refrigerant as described below.

The air conditioner 1 switches between the cooling operation of the air conditioner 1 and the heating operation of the air conditioner 1 by switching the flow direction of the refrigerant by the flow direction switching mechanism 22.

During the cooling operation, the flow direction switching mechanism 22 communicates the suction pipe 10a with the second gas refrigerant pipe 10e and connects the discharge pipe 10b with the first gas refrigerant as shown by the solid line in the flow direction switching mechanism 22 in FIG. Communicate with tube 10c. As a result of the flow direction switching mechanism 22 connecting the refrigerant pipes in this way, the refrigerant discharged from the compressor 21 during the cooling operation has the heat source heat exchanger 23, the expansion valve 24, and the utilization heat exchanger in the refrigerant circuit 10. It flows in the order of 31, and returns to the suction end of the compressor 21. During the cooling operation, the heat source heat exchanger 23 functions as a condenser, and the utilization heat exchanger 31 functions as an evaporator.

During the heating operation, the flow direction switching mechanism 22 communicates the suction pipe 10a with the first gas refrigerant pipe 10c and the discharge pipe 10b with the second gas refrigerant as shown by the broken line in the flow direction switching mechanism 22 in FIG. Communicate with the tube 10e. As a result of the flow direction switching mechanism 22 connecting the refrigerant pipes in this way, the refrigerant discharged from the compressor 21 during the heating operation uses the heat exchanger 31, the expansion valve 24, and the heat source heat exchanger in the refrigerant circuit 10. It flows in the order of 23, and returns to the suction end of the compressor 21. During the heating operation, the utilization heat exchanger 31 functions as a condenser, and the heat source heat exchanger 23 functions as an evaporator.

(2-2-3) Heat Source Heat Exchanger The structure of the heat source heat exchanger 23 is not limited, but for example, a cross fin composed of a heat transfer tube (not shown) and a large number of fins (not shown). This is a fin-and-tube heat exchanger of the type. In the heat source heat exchanger 23, heat exchange is performed between the refrigerant flowing through the heat source heat exchanger 23 and the heat source air.

The heat source heat exchanger 23 functions as a condenser (radiator) during the cooling operation. The heat source heat exchanger 23 functions as an evaporator during the heating operation.

(2-2-4) Expansion valve The expansion valve 24 is an electronic expansion valve whose opening degree can be adjusted, which is used for adjusting the flow rate of the refrigerant and the like.

The expansion valve 24 is provided in the liquid refrigerant pipe 10d. The expansion valve 24 decompresses the refrigerant flowing from the heat source heat exchanger 23 toward the utilization heat exchanger 31 or the refrigerant flowing from the utilization heat exchanger 31 toward the heat source heat exchanger 23.

(2-2-5) Accumulator The accumulator 25 is a container having a gas-liquid separation function that separates an inflowing refrigerant into a gas refrigerant and a liquid refrigerant. The accumulator 25 is provided in the suction pipe 10a as shown in FIG. In other words, the accumulator 25 is arranged on the upstream side of the compressor 21 in the flow direction of the refrigerant as shown in FIG. The refrigerant flowing into the accumulator 25 is divided into a gas refrigerant and a liquid refrigerant, and the gas refrigerant gathering in the upper space flows into the compressor 21.

(2-2-6) Second fan The second fan 26 sucks heat source air into the heat source unit 2 and supplies it to the heat source heat exchanger 23, and heat exchanges air with the refrigerant in the heat source heat exchanger 23 as a heat source. It is a fan that discharges to the outside of the unit 2. The second fan 26 supplies air to the heat source heat exchanger 23 as a condenser during the cooling operation of the air conditioner 1. The second fan 26 supplies air to the heat source heat exchanger 23 as an evaporator during the heating operation of the air conditioner 1.

The second fan 26 is an axial fan such as a propeller fan. However, the type of the second fan 26 is not limited to the axial flow fan, and may be appropriately selected. The second fan 26 is driven by the fan motor 26a. The rotation speed of the fan motor 26a can be controlled by an inverter.

(2-2-7) Sensor The heat source unit 2 has various sensors including a suction temperature sensor 71, a discharge temperature sensor 72, a heat source heat exchange temperature sensor 73, and a liquid tube temperature sensor 74. The heat source unit 2 does not have a suction pressure sensor for cost control and the like.

The suction temperature sensor 71, the discharge temperature sensor 72, the heat source heat exchange temperature sensor 73, and the liquid tube temperature sensor 74 are, for example, a thermistor.

The suction temperature sensor 71 measures the temperature (suction temperature) of the refrigerant sucked into the compressor 21. The suction temperature sensor 71 is an example of the third sensor.

The discharge temperature sensor 72 measures the temperature (discharge temperature) of the refrigerant discharged by the compressor 21.

The heat source heat exchange temperature sensor 73 is provided in the heat source heat exchanger 23. The heat source heat exchange temperature sensor 73 measures the temperature of the refrigerant flowing through the heat source heat exchanger 23. For example, the temperature of the refrigerant flowing in the intermediate position of the heat source heat exchanger 23 in the refrigerant flow direction is measured. The heat source heat exchange temperature sensor 73 measures the temperature of the refrigerant flowing through the condenser during the cooling operation of the air conditioner 1. In other words, the heat source heat exchange temperature sensor 73 measures the condensation temperature in the refrigeration cycle during the cooling operation of the air conditioner 1. On the other hand, the heat source heat exchange temperature sensor 73 measures the temperature of the refrigerant flowing through the evaporator during the heating operation of the air conditioner 1.

The liquid pipe temperature sensor 74 measures the temperature of the refrigerant flowing through the liquid refrigerant pipe 10d.

(2-2-8) Second Control Unit The second control unit 61 controls the operation of each unit constituting the heat source unit 2.

The second control unit 61 is electrically connected to various devices included in the heat source unit 2, including the compressor motor 21b, the flow direction switching mechanism 22, the expansion valve 24, and the fan motor 26a. Further, the second control unit 61 is communicably connected to various sensors provided in the heat source unit 2. Various sensors provided in the heat source unit 2 include temperature sensors 71 to 74. The second control unit 61 includes a microprocessor including a CPU and a memory, an input / output device, and the like (not shown). The second control unit 61 controls the operation of each unit constituting the heat source unit 2 by the CPU executing a program stored in the memory. The second control unit 61 does not have to realize all the control by software, and may realize some or all control by hardware using various control circuits.

The second control unit 61 exchanges various signals and the like with the first control unit 62 of the utilization unit 3 via a communication line. The second control unit 61 and the first control unit 62 cooperate with each other to function as the controller 60. The function of the controller 60 will be described later.

(2-3) Controller In the present embodiment, the controller 60 that controls the operation of the air conditioner 1 by the cooperation of the second control unit 61 of the heat source unit 2 and the first control unit 62 of the utilization unit 3. Functions as. For example, the CPU of the second control unit 61 executes the control program of the air conditioner 1, and the CPU of the first control unit 62 executes the control program of the air conditioner 1, so that the controller 60 is the air conditioner. Control the operation of 1. However, some or all of the functions of the controller 60 may be realized by hardware such as a control circuit.

In addition to the second control unit 61 and the first control unit 62, the air conditioner 1 may have a control device (not shown) that realizes a part or all of the functions described below. Further, the air conditioner 1 may have a control device (not shown) that realizes all the functions described below in place of the second control unit 61 and the first control unit 62. The control device here is a device provided separately from the heat source unit 2 and the utilization unit 3.

As shown in FIG. 2, the controller 60 is communicably connected to the suction temperature sensor 71, the discharge temperature sensor 72, the heat source heat exchange temperature sensor 73, the liquid pipe temperature sensor 74, and the utilization heat exchange temperature sensor 75. ing. The controller 60 receives the measurement signals transmitted by these temperature sensors 71 to 75. The controller 60 is electrically connected to the compressor motor 21b, the flow direction switching mechanism 22, the expansion valve 24, the fan motor 26a, and the fan motor 32a. The controller 60 includes a compressor motor 21b, a flow direction switching mechanism 22, an expansion valve 24, and a fan motor 26a based on a control signal transmitted by a control remote controller of the air conditioner 1 and a measurement signal of a sensor including temperature sensors 71 to 75. And controls the operation of the equipment of the air conditioner 1 including the fan motor 32a. The controller 60 controls the refrigeration cycle in the refrigerant circuit 10 by controlling the operation of the air conditioner 1.

The controller 60 controls various devices of the air conditioner 1 to cause the air conditioner 1 to perform a cooling operation or a heating operation.

When the air conditioner 1 starts the cooling operation or the heating operation, the controller 60 first performs activation control. In the start control, the rotation speed of the compressor motor 21b of the compressor 21 is gradually increased from a predetermined minimum rotation speed to the target rotation speed, and the expansion valve 24 adjusts to the increase in the rotation speed of the compressor motor 21b. This is a control that gradually increases the opening degree. Start control usually ends in a few minutes. After the start control is completed, the controller 60 performs normal control.

At the time of normal control, the controller 60 constantly controls the compressor motor 21b of the compressor 21 when there is no change in the operating capacity (the change is equal to or less than a predetermined amount). In addition, the controller 60 performs supercooling degree control, which is an example of the second control, during normal control. The supercooling degree control is a control for adjusting the opening degree of the expansion valve 24 so that the supercooling degree of the refrigerant at the outlet of the condenser approaches a predetermined target supercooling degree.

Further, the controller 60 performs the first control when the first condition is satisfied during the normal control. Specifically, the controller 60 performs the first control when it is determined that the first condition is satisfied. The first condition, the first control, and the end condition of the first control will be described below.

(2-3-1) First Condition When the controller 60 determines that both the following first item and the second item are satisfied, it determines that the first condition is satisfied.

(A) First item The controller 60 determines that the first item is satisfied when the degree of supercooling of the refrigerant at the outlet of the condenser of the refrigerant circuit 10 is increased. In other words, during the cooling operation, the controller 60 determines that the first item is satisfied when the degree of supercooling of the refrigerant at the outlet of the heat source heat exchanger 23 is increasing. Further, during the heating operation, the controller 60 determines that the first item is satisfied when the degree of supercooling of the refrigerant at the outlet of the utilization heat exchanger 31 is increasing.

In the state where the degree of supercooling of the refrigerant is increasing, the value of the degree of supercooling calculated by using the measured values of the heat source heat exchange temperature sensor 73 and the liquid pipe temperature sensor 74 during the cooling operation is used. Including the rising state. At this time, the value of the degree of supercooling is calculated by subtracting the measured value of the liquid pipe temperature sensor 74 from the measured value of the heat source heat exchange temperature sensor 73. Further, when the degree of supercooling of the refrigerant is increasing, the value of the degree of supercooling calculated by using the measured values of the heat exchange temperature sensor 75 and the liquid pipe temperature sensor 74 during the heating operation is used. Including the rising state. At this time, the value of the degree of supercooling is calculated by subtracting the measured value of the liquid pipe temperature sensor 74 from the measured value of the used heat exchange temperature sensor 75.

For example, when the calculated supercooling degree is larger than the previously calculated supercooling degree by a predetermined value or more, the controller 60 determines that the supercooling degree has increased. For example, the controller 60 determines that the supercooling degree is increased when the calculated supercooling degree is larger than a predetermined value or more than the supercooling degree calculated 30 seconds ago.

Further, the controller 60 may determine whether or not the degree of supercooling of the refrigerant has increased based on the results of a plurality of measurements. For example, specifically, the controller 60 calculates the degree of supercooling based on the measured value of the sensor once every few seconds (for example, once every 5 seconds). Then, the controller 60 may determine that the supercooling degree of the refrigerant is increasing when the value of the supercooling degree calculated continuously a plurality of times (for example, 5 times) is increasing.

(B) Second item The controller 60 determines that the second item is satisfied when the condensation temperature detected by the first sensor that measures the condensation temperature of the refrigeration cycle in the refrigerant circuit 10 is lowered. For example, in the cooling operation, the controller 60 determines that the second item is satisfied when the value of the measured value of the heat source heat exchange temperature sensor 73 as the first sensor is low. During the heating operation, the controller 60 determines that the second item is satisfied when the value of the measured value of the heat exchange temperature sensor 75 used as the first sensor is low.

For example, when the temperature measured by the first sensor is lower than the temperature measured by the first sensor last time by a predetermined value or more, the controller 60 determines that the condensation temperature detected by the first sensor has decreased. For example, when the temperature measured by the first sensor is lower than the temperature measured by the first sensor 30 seconds ago by a predetermined value or more, the controller 60 determines that the condensation temperature detected by the first sensor has decreased. To do.

Further, the controller 60 may determine that the condensation temperature detected by the first sensor has decreased based on the results of a plurality of measurements. For example, the measured value of the first sensor is measured once every few seconds (for example, once every 5 seconds). Then, the controller 60 may determine that the condensation temperature detected by the first sensor has decreased when the measured value of the first sensor has decreased a plurality of times (for example, five times) in succession. ..

(2-3-2) First control The first control executed by the controller 60 is a control for increasing the evaporation pressure of the refrigeration cycle in the refrigerant circuit 10. In other words, the first control executed by the controller 60 is a control that increases the region in which the gas-liquid two-phase refrigerant flows in the evaporator.

When the first condition is satisfied, the controller 60 executes at least one of the following control contents (i) to (iii) as the first control.
(I) The opening degree of the expansion valve 24 is made larger than the opening degree of the expansion valve 24 when the first condition is satisfied.
(Ii) The rotation speed of the compressor motor 21b of the compressor 21 is lower than that of the compressor motor 21b of the compressor 21 when the first condition is satisfied.
(Iii) The rotation speed of the fan motor of the fan that supplies air to the evaporator is increased higher than the rotation speed of the fan motor of the fan when the first condition is satisfied. In the cooling operation, when the first condition is satisfied, the rotation speed of the fan motor 32a of the first fan 32 is increased to be higher than the rotation speed of the fan motor 32a when the first condition is satisfied. In the case of heating operation, when the first condition is satisfied, the rotation speed of the fan motor 26a of the second fan 26 is increased to be higher than the rotation speed of the fan motor 26a when the first condition is satisfied.

(2-3-3) Termination Condition of First Control The controller 60 terminates the first control when either of the following two termination conditions is satisfied. Each of the following two termination conditions is a condition for determining that the shortage of the amount of refrigerant sucked into the compressor 21 has been improved.

(A) First termination condition The controller 60 determines that the first termination condition is satisfied when the condensing pressure in the refrigerating cycle of the refrigerant circuit 10 rises to a predetermined pressure. For example, the controller 60 determines that the first end condition is satisfied when the condensation pressure in the refrigeration cycle of the refrigerant circuit 10 rises by a predetermined value or more with respect to the condensation pressure at the time when the first condition is satisfied.

In this embodiment, the refrigerant circuit 10 is not provided with a pressure sensor for measuring the condensing pressure. Therefore, the controller 60 uses the measured value of the first sensor that measures the condensation temperature of the refrigeration cycle that correlates with the condensation pressure to determine whether the condensation pressure has risen to a predetermined pressure. In the controller 60, for example, based on the measured value of the first sensor that measures the condensation temperature of the refrigerating cycle that correlates with the condensing pressure, the condensing pressure in the refrigerating cycle of the refrigerant circuit 10 is set with respect to the condensing pressure at the time when the first condition is satisfied. It is judged that the value has risen above the specified value. During the cooling operation, the controller 60 determines whether or not the first end condition is satisfied based on the measured value of the heat source heat exchange temperature sensor 73 as the first sensor. During the heating operation, the controller 60 determines whether or not the first end condition is satisfied based on the measured value of the heat exchange temperature sensor 75 used as the first sensor.

In the controller 60, the condensation pressure in the refrigeration cycle of the refrigerant circuit 10 is the condensation pressure when the first condition is satisfied, based on the measured value of the discharge temperature sensor 72 that measures the discharge temperature of the compressor 21 that correlates with the condensation pressure. On the other hand, it may be determined that the value has increased by a predetermined value or more.

(B) Second termination condition The controller 60 obtains the measured value of the second sensor for measuring the temperature of the refrigerant flowing through the evaporator from the measured value of the suction temperature sensor 71 for measuring the temperature of the refrigerant sucked into the compressor 21. When the deducted value increases to a predetermined value, it is determined that the second end condition is satisfied. More specifically, the controller 60 measures the temperature of the refrigerant flowing through the heat exchanger 31 used as an evaporator from the measured value of the suction temperature sensor 71 during the cooling operation. When the value obtained by subtracting is increased to a predetermined value, it is determined that the second end condition is satisfied. Further, the controller 60 subtracts the measured value of the heat source heat exchange temperature sensor 73 for measuring the temperature of the refrigerant flowing through the heat source heat exchanger 23 as an evaporator from the measured value of the suction temperature sensor 71 during the heating operation. When the value increases to a predetermined value, it is determined that the second end condition is satisfied.

The reason why the second termination condition is a condition for determining that the shortage state of the refrigerant sucked into the compressor 21 is improved will be described.

First, the second sensor is usually a sensor provided with the intention of measuring the temperature of the refrigerant in the gas-liquid two-layer state. In other words, the second sensor is a sensor that measures the evaporation temperature (saturation temperature) in the refrigeration cycle.

However, in a situation where the amount of refrigerant sucked into the compressor 21 is insufficient, since the amount of refrigerant flowing into the evaporator is small, there is a possibility that all the refrigerants are already in a gas state near the refrigerant inlet of the evaporator. is there. Therefore, the temperature of the refrigerant measured by the second sensor may be the temperature of the refrigerant in a superheated state, depending on which part of the evaporator the temperature of the refrigerant flowing through is measured by the second sensor. .. In this state, the measured value of the second sensor may be substantially the same as the measured value of the suction temperature sensor 71 that measures the temperature of the refrigerant sucked into the compressor 21. In other words, the value obtained by subtracting the measured value of the second sensor from the measured value of the suction temperature sensor 71 may become almost zero even though the refrigerant sucked into the compressor 21 is overheated. In other words, even though the degree of heating of the refrigerant sucked into the compressor 21 is attached, there is a possibility that it will be erroneously detected if the degree of overheating is not attached.

On the other hand, when the first control is performed and the shortage of the amount of the refrigerant sucked into the compressor 21 is improved, the measured value of the second sensor becomes the measured value of the temperature of the refrigerant in the gas-liquid two-layer state. .. As a result, the value obtained by subtracting the measured value of the second sensor (the temperature of the refrigerant having two layers of gas and liquid) from the measured value of the suction temperature sensor 71 (the temperature of the refrigerant having a degree of superheat) becomes a positive value. Therefore, it is possible to detect that the state of insufficient refrigerant sucked into the compressor 21 is improved by using the value obtained by subtracting the measured value of the second sensor from the measured value of the suction temperature sensor 71.

(3) Control of the air conditioner by the controller For the normal control of the air conditioner 1 during the cooling operation by the controller 60, the normal control of the air conditioner 1 during the heating operation by the controller 60, and the first control and the first control by the controller 60. The process executed by the controller 60 will be described in relation to this.

(3-1) Normal control during cooling operation When an instruction for cooling operation is given by an instruction from the remote controller or the like of the air conditioner 1, the controller 60 is in a state in which the flow direction switching mechanism 22 is shown by the solid line in FIG. The flow direction switching mechanism 22 is controlled in this way. Then, the controller 60 starts the normal control after the start control.

In normal control, the controller 60 controls the rotation speed of the compressor motor 21b of the compressor 21 to a predetermined rotation speed according to the air conditioning load. When there is no change in the air conditioning load (the amount of change is equal to or less than a predetermined amount), the controller 60 constantly controls the rotation speed of the compressor motor 21b of the compressor 21. Further, the controller 60 controls the operation of the expansion valve 24 so that the value (supercooling degree) obtained by subtracting the measured value measured by the liquid pipe temperature sensor 74 from the measured value of the heat source heat exchange temperature sensor 73 approaches the target temperature. (Supercooling degree control).

The flow of the refrigerant in the refrigerant circuit 10 during the cooling operation will be described.

During the cooling operation, the low-pressure gas refrigerant in the refrigerant circuit 10 is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant. The gas refrigerant compressed by the compressor 21 is sent to the heat source heat exchanger 23 through the flow direction switching mechanism 22. The high-pressure gas refrigerant sent to the heat source heat exchanger 23 exchanges heat with the outdoor air supplied by the second fan 26 in the heat source heat exchanger 23 that functions as a condenser, is cooled, condensed, and has a high pressure. It becomes the liquid refrigerant of. The liquid refrigerant condensed by the heat source heat exchanger 23 is decompressed by the expansion valve 24 to expand, and is sent to the utilization unit 3 through the liquid closing valve 27 and the liquid refrigerant connecting pipe 41. The refrigerant sent to the utilization unit 3 is sent to the utilization heat exchanger 31. The refrigerant sent to the utilization heat exchanger 31 evaporates by being heated by exchanging heat with the indoor air supplied by the first fan 32 in the utilization heat exchanger 31 that functions as an evaporator, and is low pressure. It becomes a gas refrigerant. The low-pressure gas refrigerant is sent from the utilization unit 3 to the heat source unit 2 through the gas refrigerant connecting pipe 42. The low-pressure gas refrigerant sent to the heat source unit 2 is sucked into the compressor 21 again through the gas closing valve 28 and the flow direction switching mechanism 22.

(3-2) Normal control during heating operation When an instruction for heating operation is given by an instruction from the remote controller or the like of the air conditioner 1, the controller 60 is in the state in which the flow direction switching mechanism 22 is shown by the broken line in FIG. The flow direction switching mechanism 22 is controlled in this way. Then, the controller 60 starts the normal control after the start control.

In normal control, the controller 60 controls the rotation speed of the compressor motor 21b of the compressor 21 to a predetermined rotation speed according to the air conditioning load. When there is no change in the air conditioning load (the amount of change is equal to or less than a predetermined amount), the controller 60 constantly controls the rotation speed of the compressor motor 21b of the compressor 21. Further, the controller 60 controls the operation of the expansion valve 24 so that the value (supercooling degree) obtained by subtracting the measured value measured by the liquid pipe temperature sensor 74 from the measured value of the used heat exchange temperature sensor 75 approaches the target temperature. (Supercooling degree control).

The flow of the refrigerant in the refrigerant circuit 10 during the heating operation will be described.

During the heating operation, the low-pressure gas refrigerant in the refrigerant circuit 10 is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant. The gas refrigerant compressed by the compressor 21 is sent from the heat source unit 2 to the utilization unit 3 through the flow direction switching mechanism 22, the gas closing valve 28, and the gas refrigerant connecting pipe 42. The high-pressure gas refrigerant sent to the utilization unit 3 is sent to the utilization heat exchanger 31. The high-pressure gas refrigerant sent to the utilization heat exchanger 31 is cooled by exchanging heat with the indoor air supplied by the first fan 32 in the utilization heat exchanger 31 that functions as a condenser (radiator). It condenses and becomes a high-pressure liquid refrigerant. The high-pressure liquid refrigerant is sent from the utilization unit 3 to the heat source unit 2 through the liquid refrigerant connecting pipe 41. The refrigerant sent to the heat source unit 2 is sent to the expansion valve 24, decompressed by the expansion valve 24, and sent to the heat source heat exchanger 23. The refrigerant sent to the heat source heat exchanger 23 evaporates by being heated by exchanging heat with the outdoor air supplied by the second fan 26 in the heat source heat exchanger 23 that functions as an evaporator, and has a low pressure. It becomes the gas refrigerant of. The low-pressure gas refrigerant is sucked into the compressor 21 again through the flow direction switching mechanism 22.

(3-3) First control and processing related to the first control The first control executed by the controller 60 and the processing executed by the controller 60 related to the first control will be described with reference to FIG. .. FIG. 3 is a flowchart illustrating the first control of the controller 60 and the processing related to the first control.

Here, the first control executed by the controller 60 during the cooling operation and the process executed by the controller 60 in connection with the first control will be described. During the heating operation, the utilization heat exchanger 31 becomes a condenser, and the heat source heat exchanger 23 becomes an evaporator. Therefore, in the process executed by the controller 60 in relation to the first control during the heating operation, the sensors functioning as the first sensor and the second sensor are different from those during the cooling operation. However, the process executed by the controller 60 in relation to the first control during the heating operation is almost the same as the process executed by the controller 60 in relation to the first control during the cooling operation, except that the sensors used are different. Therefore, detailed description thereof will be omitted.

First, the controller 60 performs activation control as described above when the air conditioner 1 that has been stopped in response to an instruction from the remote controller or the like of the air conditioner 1 starts the cooling operation (step S1). The controller 60 gradually increases the rotation speed of the compressor motor 21b of the compressor 21 from a predetermined minimum rotation speed to the target rotation speed, and adjusts the rotation speed of the compressor motor 21b to the increase of the rotation speed of the expansion valve 24. Gradually increase the opening.

When the start control is completed, the controller 60 starts normal control (step S2). Specifically, the controller 60 constantly controls the compressor motor 21b of the compressor 21 when there is no change in the operating capacity (the change is equal to or less than a predetermined amount). Further, the controller 60 performs a second control (supercooling degree control) for adjusting the opening degree of the expansion valve 24 so that the supercooling degree at the outlet of the condenser approaches a predetermined target supercooling degree at the time of normal control.

During the supercooling degree control, the controller 60 supercools the value obtained by subtracting the measured value of the liquid pipe temperature sensor 74 from the measured value of the heat source heat exchange temperature sensor 73 at predetermined time intervals (for example, every 5 seconds). It is calculated as a degree. The calculated value of the degree of supercooling is stored in the storage unit 60a of the controller 60 as operation information. Further, the controller 60 grasps the elapsed time from setting the rotation speed of the compressor motor 21b of the compressor 21 to a certain value during normal control.

The controller 60 determines whether the time for maintaining the rotation speed of the compressor motor 21b of the compressor 21 at a constant value exceeds a predetermined time (for example, 30 seconds) during normal control (step S3). In other words, the controller 60 determines whether the time during which the rotation speed of the compressor motor 21b of the compressor 21 does not change exceeds a predetermined time. When the controller 60 determines that the time during which the rotation speed of the compressor motor 21b of the compressor 21 does not change exceeds a predetermined time, the process proceeds to step S4. The controller 60 repeats the process of step S3 until it is determined that the time during which the rotation speed of the compressor motor 21b of the compressor 21 does not change exceeds a predetermined time.

In step S4, the controller 60 determines whether or not the first item of the first conditions is satisfied. In other words, in step S4, the controller 60 determines whether or not the degree of supercooling of the refrigerant at the outlet of the condenser of the refrigerant circuit 10 has increased. Since the method for determining whether or not the first item is satisfied has already been described, the description thereof will be omitted here. When the controller 60 determines that the first item is satisfied, the process proceeds to step S5. When the controller 60 determines that the first item is not satisfied, the process returns to step S3.

In step S5, the controller 60 determines whether or not the second item of the first conditions is satisfied. In other words, in step S5, the controller 60 determines whether or not the measured value of the first sensor has decreased. The first sensor is a sensor that measures the condensation temperature of the refrigeration cycle in the refrigerant circuit 10. For example, the controller 60 determines whether or not the temperature measured by the heat source heat exchange temperature sensor 73 has decreased. Since the method of determining whether or not the second item is satisfied has already been described, the description thereof will be omitted here. When the controller 60 determines that the second item is satisfied, the process proceeds to step S6. When the controller 60 determines that the second item is not satisfied, the process returns to step S3.

In step S6, the controller 60 determines that the first condition is satisfied because the determinations in steps S4 and S5 are both “Yes”. At this time, the controller 60 stores various operating parameters (measured values of various sensors, rotation speeds of the motors 21b, 26a, 32a, opening degree of the expansion valve 24, etc.) in the storage unit 60a. Further, when the controller 60 determines that the first condition is satisfied, the controller 60 interrupts the supercooling degree control. In other words, the controller 60 interrupts the control of adjusting the opening degree of the expansion valve 24 so that the supercooling degree at the outlet of the condenser approaches the target supercooling degree.

After that, the controller 60 starts the first control. The controller 60 executes at least one of the above-mentioned control contents (i) to (iii) as the first control. For example, when the controller 60 executes the control content (i), the controller 60 makes the opening degree of the expansion valve 24 larger than the opening degree of the expansion valve 24 when the first condition is satisfied. When the controller 60 executes the control content (ii), the controller 60 sets the rotation speed of the compressor motor 21b of the compressor 21 to be higher than that of the compressor motor 21b of the compressor 21 when the first condition is satisfied. Lower. When the controller 60 executes the control content (iii), the controller 60 raises the rotation speed of the fan motor 32a of the first fan 32 to be higher than the rotation speed of the fan motor 32a when the first condition is satisfied.

When the controller 60 starts the first control, it determines whether or not either the first end condition or the second end condition is satisfied (see step S7).

The controller 60 determines whether or not the first termination condition has been completed, for example, as follows. The controller 60 reads the measured value (condensation temperature) of the heat source heat exchange temperature sensor 73 into the value of the condensation pressure using a table or a mathematical formula stored in the storage unit 60a. Then, the controller 60 determines whether the condensation pressure in the refrigeration cycle of the refrigerant circuit 10 is higher than a predetermined value or more than the pressure at the time when the first condition is satisfied (condensation pressure calculated from the condensation temperature), and determines a predetermined value. If the temperature rises above that level, it is determined that the first termination condition is satisfied.

The controller 60 determines whether or not the second termination condition has been completed, for example, as follows. The controller 60 has a predetermined value (for example, 0.) obtained by subtracting the measured value of the used heat exchange temperature sensor 75 for measuring the temperature of the refrigerant flowing through the used heat exchanger 31 as an evaporator from the measured value of the suction temperature sensor 71. When it increases to 5 degrees), it is judged that the second termination condition is satisfied.

Since the method of determining whether or not the first end condition and the second end condition are satisfied has already been described, further detailed description will be omitted.

When the controller 60 determines that the first termination condition or the second termination condition is satisfied, the process proceeds to step S8.

Here, the controller 60 determines that both the first end condition and the second end condition are satisfied, and if it is determined that either one is satisfied, the process proceeds to step S8. However, the present invention is not limited to such an embodiment, and the controller 60 determines the establishment of only one of the first termination condition and the second termination condition, and when the termination condition is satisfied. , May be configured to proceed to the process of step S8.

In step S8, it is preferable that the controller 60 executes at least one of the following setting changes (a) to (c) with respect to the supercooling degree control during normal control before the first condition is satisfied. The purpose of executing the process of step S8 is to prevent the amount of refrigerant sucked into the compressor 21 from becoming insufficient during normal control.

(A) Target of supercooling degree control Decrease the supercooling degree. For example, if the target supercooling degree before the first condition is satisfied is 5 ° C., the target supercooling degree is lowered by 1 ° C. to 4 ° C. in step S8.

(B) The amount of reduction in the opening degree of the expansion valve 24 per unit time during supercooling control is reduced. Details will be described below.

The controller 60 controls to increase the degree of supercooling and reduce the opening degree of the expansion valve 24 when the degree of supercooling approaches the target degree of supercooling. For example, when the controller 60 controls to reduce the opening degree of the expansion valve 24, the number of pulses is set to a predetermined amount A1 per control at a predetermined time interval ΔT1 before the first condition is satisfied. It is assumed that the control is performed to reduce the size. On the other hand, when the first condition is satisfied, the controller 60 changes the time interval for changing the opening degree of the expansion valve 24 from ΔT1 to ΔT2 larger than ΔT1. In addition to or instead of this, when the first condition is satisfied, the controller 60 changes the number of pulses to be changed per control of the expansion valve 24 from the quantity A1 to the quantity A2 smaller than the quantity A1. To do. In this way, the controller 60 reduces the amount of reduction in the opening degree of the expansion valve 24 per unit time when controlling the degree of supercooling.

(C) Increase the minimum opening of the expansion valve 24. For example, before the first condition is satisfied, the controller 60 is allowed to reduce the opening degree (number of pulses) of the expansion valve 24 to the minimum value B1 when controlling the degree of supercooling. On the other hand, in step S8, the controller 60 changes the minimum value of the opening degree of the expansion valve 24 allowed in the supercooling degree control from B1 to B2 which is larger than B1.

After the execution of step S8, the controller 60 ends the first control (step S9) and returns to the normal control (step S2). After returning to the normal control, the controller 60 controls the degree of supercooling by using the setting changed in step S8.

As described above, here, the process executed by the controller 60 in relation to the first control is described based on the flowchart of FIG. However, the contents of the processing and the order of the processing described here are merely examples, and may be appropriately changed within a consistent range. For example, the order of determination in steps S3 to S5 may be changed as appropriate within a consistent range, and the processes in steps S3 to S5 may be executed in parallel. Further, for example, the process of step S8 does not need to be executed when the end condition of the first control is satisfied, and may be executed immediately when it is determined that the first condition is satisfied.

(4) Features of the air conditioner The features of the air conditioner 1 will be described.

The following description of the features of the air conditioner 1 describes the condenser as the heat source heat exchanger 23, the evaporator as the heat exchanger 31, the first sensor as the heat source heat exchange temperature sensor 73, and the second sensor as the second sensor. The heat exchange temperature sensor 75 and the fan may be read as the first fan 32. Further, the following description of the features of the air conditioner 1 will be described by using a condenser for a heat exchanger 31, an evaporator for a heat source heat exchanger 23, and a first sensor for a heat exchange temperature sensor 75 and a second sensor during heating operation. The sensor may be read as a heat source heat exchange temperature sensor 73, and the fan may be read as a second fan 26.

(4-1)
The air conditioner 1 as an example of the refrigeration cycle device includes a refrigerant circuit 10, a first sensor, and a controller 60 as an example of a control unit. The refrigerant circuit 10 includes a compressor 21, a condenser, an expansion valve 24, and an evaporator. The first sensor detects the condensation temperature of the refrigeration cycle in the refrigerant circuit 10. The controller 60 controls the refrigeration cycle in the refrigerant circuit 10. When the first condition is satisfied, the controller 60 performs the first control for increasing the evaporation pressure of the refrigerating cycle in the refrigerant circuit 10. The first condition is that the degree of supercooling of the refrigerant at the outlet of the condenser of the refrigerant circuit 10 has increased, and the condensation temperature detected by the first sensor has decreased.

When the degree of supercooling of the refrigerant at the outlet of the condenser in the air conditioner 1 increases, the condensation temperature usually rises. In the air conditioner 1, if the condensation temperature is lowered even though the degree of supercooling is rising, there is a possibility that the amount of refrigerant sucked into the compressor 21 is insufficient.

In the air conditioner 1 of the present embodiment, control is performed to increase the evaporation pressure of the refrigeration cycle when the degree of supercooling is increasing and the condensation temperature is decreasing. Therefore, in the air conditioner 1, the operation of the air conditioner 1 can be continued while suppressing damage to the compressor 21 due to insufficient amount of the sucked refrigerant.

(4-2)
In the air conditioner 1 of the present embodiment, as an example of the second control, the controller 60 adjusts the opening degree of the expansion valve 24 so that the supercooling degree approaches the target supercooling degree when the first control is not performed. Controls the degree of supercooling.

Since the air conditioner 1 of the present embodiment performs supercooling control that adjusts the supercooling degree at the outlet of the condenser to a target value when the first control is not performed, the air conditioner 1 is operated efficiently. Is possible.

(4-3)
In the air conditioner 1 of the present embodiment, the controller 60 performs at least one of the following (a) to (c) in the supercooling degree control after the first condition is satisfied.
(A) Decrease the target supercooling degree.
(B) The amount of reduction in the opening degree of the expansion valve 24 per unit time is reduced.
(C) Increase the minimum opening of the expansion valve 24.

If the first condition is satisfied while the supercooling degree control is being executed, and if the supercooling degree control is subsequently performed with the same control content, the amount of refrigerant sucked into the compressor 21 may be insufficient again.

In the air conditioner 1 of the present embodiment, when the first condition is satisfied, the control content of the supercooling degree control is changed to a control content in which the first condition is difficult to be satisfied. Can be suppressed.

(4-4)
In the air conditioner 1 of the present embodiment, the controller 60 executes at least one of the following control contents (i) to (iii) as the first control.
(I) The opening degree of the expansion valve 24 is made larger than the opening degree of the expansion valve 24 when the first condition is satisfied.
(Ii) The rotation speed of the compressor 21 is lowered from the rotation speed of the compressor 21 when the first condition is satisfied.
(Iii) The rotation speed of the fan that supplies air to the evaporator is increased from the rotation speed of the fan when the first condition is satisfied.

In the air conditioner 1 of the present embodiment, the evaporation pressure in the refrigeration cycle can be increased by performing such a first control.

(4-5)
The air conditioner 1 of the present embodiment includes a second sensor and a suction temperature sensor 71 as an example of the third sensor. The second sensor measures the temperature of the refrigerant flowing through the evaporator. The suction temperature sensor 71 measures the temperature of the refrigerant sucked into the compressor 21. After the start of the first control, the controller 60 has a predetermined value when the condensation pressure in the refrigeration cycle of the refrigerant circuit 10 rises to a predetermined pressure, or a value obtained by subtracting the measured value of the second sensor from the measured value of the suction temperature sensor 71. When it increases to, the first control is terminated.

In the air conditioner 1 of the present embodiment, the evaporation pressure of the refrigeration cycle is increased based on the increase of the condensation pressure and the increase of the temperature difference between the temperature of the refrigerant sucked into the compressor 21 and the temperature of the refrigerant flowing through the evaporator. It is possible to detect and stop the first control and return to the normal operation of the air conditioner 1.

(4-6)
In the air conditioner 1 of the present embodiment, the controller 60 performs the first control when the first condition is satisfied when the rotation speed of the compressor motor 21b of the compressor 21 does not change for a predetermined time.

In the present embodiment, the state in which the condensation temperature is lowered due to the decrease in the rotation speed of the compressor 21 is determined to be the state in which the condensation temperature in the refrigeration cycle is lowered, and the first control is executed. Can be suppressed.

(5) Modification Example A modification of the above embodiment is shown below. Each of the following modifications may be appropriately combined with a part or all of the configurations of the above-described embodiment and other modifications within a range that does not contradict each other.

(5-1) Modification A
In the above embodiment, the controller 60 determines that the degree of supercooling of the refrigerant at the outlet of the condenser of the refrigerant circuit 10 is increasing by using the measured value of the sensor.

However, the controller 60 may determine whether or not the degree of supercooling of the refrigerant is increasing without using the measured value of the sensor. For example, the controller 60 is in a state where other operating conditions are not changed (for example, a state in which the rotation speed of the compressor motor 21b is not changed), and controls are performed to reduce the opening degree of the expansion valve 24. In that case, it may be determined that the degree of supercooling of the refrigerant is increasing.

(5-2) Modification B
As shown in FIG. 4, the refrigerant circuit 10 may be provided with a discharge pressure sensor 76 in the discharge pipe 10b. When the discharge pressure sensor 76 is provided in the refrigerant circuit 10, the controller 60 determines that the measured value of the discharge pressure sensor 76 is a predetermined value with respect to the measured value of the discharge pressure sensor 76 when the first condition is satisfied. When the pressure rises above this level, the condensation pressure in the refrigeration cycle of the refrigerant circuit 10 rises to a predetermined pressure, and it may be determined that the first termination condition is satisfied.

Further, in the above embodiment, the controller 60 has a degree of supercooling based on the difference between the value measured by the temperature sensor of the temperature of the refrigerant flowing through the condenser and the value measured by the temperature sensor of the temperature of the refrigerant at the outlet of the condenser. Is calculated. However, when the discharge pressure sensor 76 is provided in the refrigerant circuit 10, the controller 60 determines the degree of supercooling with the condensation temperature calculated from the discharge pressure (condensation pressure) measured by the discharge pressure sensor 76 and the condensation. The degree of supercooling may be calculated based on the difference between the temperature of the refrigerant at the outlet of the vessel and the value measured by the temperature sensor.

(5-3) Modification C
In the above embodiment, the controller 60 performs the first control when the first condition is satisfied when the rotation speed of the compressor motor 21b of the compressor 21 does not change for a predetermined time. However, the controller 60 determines whether the above-mentioned first item and the second item are satisfied when the rotation speed of the compressor motor 21b of the compressor 21 is changing, and the first condition is satisfied. You may decide whether or not. For example, the controller 60 may perform the first control even when the first condition is satisfied when the rotation speed of the compressor motor 21b of the compressor 21 is increasing.

<Additional notes>
Although the embodiments and modifications of the present disclosure have been described above, it is understood that various modifications of the forms and details are possible without departing from the purpose and scope of the present disclosure described in the claims. Will.

The present disclosure is widely applicable and useful for refrigeration cycle equipment.

1 Air conditioner (refrigeration cycle device)
10 Refrigerant circuit 21 Compressor 23 Heat source Heat exchanger (condenser, evaporator)
24 Expansion valve 26 2nd fan (evaporator fan)
31 Utilization heat exchanger (evaporator, condenser)
32 1st fan (evaporator fan)
60 controller (control unit)
71 Inhalation temperature sensor (3rd sensor)
73 Heat source heat exchange temperature sensor (1st sensor, 2nd sensor)
75 Utilization heat exchange temperature sensor (2nd sensor, 1st sensor)
76 Discharge pressure sensor (first sensor)

Japanese Unexamined Patent Publication No. 2001-141290

Claims (8)

A refrigerant circuit (10) including a compressor (21), a condenser (23, 31), an expansion valve (24) and an evaporator (31, 23).
The first sensor (73,75,76) that detects the condensation temperature or condensation pressure of the refrigeration cycle in the refrigerant circuit, and
A control unit (60) that controls the refrigeration cycle in the refrigerant circuit, and
With
The control unit satisfies the first condition that the degree of supercooling of the refrigerant at the outlet of the condenser of the refrigerant circuit increases and the condensation temperature or the condensation pressure detected by the first sensor decreases. If so, the first control for increasing the evaporation pressure of the refrigeration cycle in the refrigerant circuit is performed.
Refrigeration cycle device (1). When the first control is not performed, the control unit performs a second control for adjusting the opening degree of the expansion valve so that the supercooling degree approaches the target supercooling degree.
The refrigeration cycle apparatus according to claim 1. In the second control after the first condition is satisfied, the control unit
Lower the target supercooling degree,
Decrease the amount of reduction in the opening degree of the expansion valve per unit time, and increase the minimum opening degree of the expansion valve.
Do at least one of
The refrigeration cycle apparatus according to claim 2. As the first control, the control unit controls the opening degree of the expansion valve to be larger than the opening degree of the expansion valve when the first condition is satisfied.
The refrigeration cycle apparatus according to any one of claims 1 to 3. As the first control, the control unit controls the rotation speed of the compressor to be lower than the rotation speed of the compressor when the first condition is satisfied.
The refrigeration cycle apparatus according to any one of claims 1 to 4. A fan (32, 26) for supplying air to the evaporator is further provided.
As the first control, the control unit controls the rotation speed of the fan to be higher than the rotation speed of the fan when the first condition is satisfied.
The refrigeration cycle apparatus according to any one of claims 1 to 5. Second sensors (75,73) that measure the temperature of the refrigerant flowing through the evaporator,
A third sensor (71) that measures the temperature of the refrigerant sucked into the compressor, and
Further prepare
In the control unit, after the start of the first control, when the condensation pressure in the refrigeration cycle of the refrigerant circuit rises to a predetermined pressure, or a value obtained by subtracting the measurement value of the second sensor from the measurement value of the third sensor. When increases to a predetermined value, the first control is terminated.
The refrigeration cycle apparatus according to any one of claims 1 to 6. When the first condition is satisfied when the rotation speed of the compressor does not change for a predetermined time, the control unit performs the first control.
The refrigeration cycle apparatus according to any one of claims 1 to 7.

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