JP7282258B2 - Outdoor unit and refrigeration cycle equipment - Google Patents

Description

The present disclosure relates to an outdoor unit and a refrigerating cycle device.

Japanese Patent Application Laid-Open No. 2014-119221 (Patent Document 1) describes a circulation flow path (main refrigerant circuit) in which refrigerant circulates through a compressor, a condenser, an expansion valve, and an evaporator, and an injection flow branching from the circulation flow path. A refrigeration system is disclosed that includes a channel. In this refrigeration system, part of the refrigerant flowing from the condenser toward the expansion valve joins the intermediate-pressure refrigerant in the compressor using the injection passage, thereby reducing the discharge temperature of the compressor. . Further, this refrigeration system is provided with a liquid receiver in the middle of the injection flow path, and is configured such that the amount of refrigerant stored in the liquid receiver can be adjusted by an expansion valve of the outdoor unit.

Further, this refrigeration system includes an economizer (heat exchanger) that exchanges heat between the refrigerant flowing through the circulation passage from the condenser toward the expansion valve and the refrigerant flowing through the injection passage. As a result, since the refrigerant flowing from the condenser toward the expansion valve is cooled by the refrigerant flowing through the injection passage, supercooling is ensured.

JP 2014-119221 A

As described above, in a refrigeration cycle apparatus having an injection flow path provided with a liquid receiver and the above-described heat exchanger (economizer), the amount of refrigerant gas and the amount of refrigerant liquid supplied from the liquid receiver to the economizer are Some exist with regulating flow control valves.

In the refrigeration cycle apparatus provided with the above flow rate control valve, the amount of refrigerant flowing from the injection flow path to the circulation flow path can be adjusted by adjusting the degree of opening of the flow rate control valve. Furthermore, in the refrigeration cycle apparatus equipped with the above flow control valve, if the temperature efficiency (heat exchange amount) of the above heat exchanger is low despite the fact that the opening degree of the flow control valve is large, circulation It can be determined that the refrigerant with which the entire refrigerant circuit including the flow path and the injection flow path is filled is insufficient.

However, when a refrigerant capable of reaching a supercritical state is used, the refrigerant may be operated in a supercritical state. When operating in a supercritical state, the relationship between the saturation temperature and the outside air temperature changes, so it is difficult to determine whether there is a shortage of refrigerant using the temperature efficiency of the heat exchanger.

The present disclosure has been made to solve the above-described problems, and an object thereof is to provide a refrigeration cycle apparatus in which a refrigerant capable of entering a supercritical state is used, and a refrigerant in a refrigerant circuit even under operating conditions in a supercritical state. It is to make it possible to determine the presence or absence of shortage.

An outdoor unit according to the present disclosure is a refrigeration cycle apparatus outdoor unit configured to be connected to a load device including a first expansion valve and an evaporator. This outdoor unit has a compressor having a suction port, a discharge port and an intermediate pressure port, a condenser, a first passage and a second passage, and a refrigerant flowing through the first passage and a refrigerant flowing through the second passage. A heat exchanger for exchanging heat therebetween and a second expansion valve. A flow path from the compressor to the condenser, the first passage of the heat exchanger, and the second expansion valve forms a circulation flow path in which the refrigerant circulates together with the load device. The outdoor unit further includes an injection channel that causes refrigerant to flow from the branch between the outlet of the condenser and the inlet of the first passage in the circulation channel to the compressor. The injection passage includes a first refrigerant passage through which the refrigerant flows from the branch portion to the inlet of the second passage, and a second refrigerant passage through which the refrigerant flows from the outlet of the second passage to the suction port or the intermediate pressure port of the compressor. , a liquid receiver arranged in the first refrigerant flow path, a third expansion valve arranged in a portion between the branch portion in the first refrigerant flow path and the inlet of the liquid receiver, and A flow control valve is provided that is positioned between the outlet of the receiver and the inlet of the second passageway. The outdoor unit further includes a controller that controls the compressor, the second expansion valve, the third expansion valve, and the flow control valve, and a notification device that notifies the user of information from the controller. When the discharge pressure of the compressor is in a supercritical state exceeding the critical pressure of the refrigerant, the control device determines whether the refrigerant contained in the circulation flow path and the injection flow path is insufficient based on the degree of opening of the flow control valve. determine whether

Advantageous Effects of Invention According to the present disclosure, in a refrigeration cycle device using a refrigerant that can be in a supercritical state, it is possible to determine whether there is a shortage of refrigerant in a refrigerant circuit even under operating conditions that are in a supercritical state.

1 is an overall configuration diagram of a refrigeration cycle device; FIG. It is the figure which showed the various sensors and control apparatus which are arrange|positioned at the refrigerating-cycle apparatus. FIG. 4 is a Mollier diagram schematically showing how refrigerant changes in a normal state; FIG. 2 is a Mollier diagram schematically showing how refrigerant changes in a supercritical state. 4 is a flowchart showing an example of a processing procedure when a control device performs refrigerant amount adjustment and refrigerant shortage detection;

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. A plurality of embodiments will be described below, but appropriate combinations of the configurations described in the respective embodiments have been planned since the filing of the application. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

(Configuration of refrigeration cycle device)
FIG. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to an embodiment. Note that FIG. 1 functionally shows the connection relationship and arrangement configuration of each device in the refrigeration cycle apparatus, and does not necessarily show the arrangement in a physical space.

Referring to FIG. 1 , refrigeration cycle device 1 includes an outdoor unit 2 , a load device 3 , and extension pipes 84 and 88 .

The outdoor unit 2 is an outdoor unit of the refrigeration cycle device 1 configured to be connected to the load device 3 . The outdoor unit 2 includes a compressor 10 having an intake port G1, a discharge port G2, and an intermediate pressure port G3, a condenser 20, a fan 22, a heat exchanger (economizer) 30, a second expansion valve 40, and piping. 80 to 83 and 89. The heat exchanger 30 has a first passage H1 and a second passage H2, and is configured to exchange heat between the refrigerant flowing through the first passage H1 and the refrigerant flowing through the second passage H2.

Load device 3 includes first expansion valve 50 , evaporator 60 , and pipes 85 , 86 , 87 . Evaporator 60 exchanges heat between the air and the refrigerant. In the refrigeration cycle device 1, the evaporator 60 evaporates the refrigerant by absorbing heat from the air in the space to be cooled. The first expansion valve 50 is an electronic expansion valve that can reduce the pressure of the refrigerant. Note that the first expansion valve 50 may be, for example, a temperature expansion valve that is controlled independently of the outdoor unit 2 .

Compressor 10 compresses the refrigerant sucked from pipes 89 and 96 and discharges it to pipe 80 . Compressor 10 can arbitrarily change the driving frequency by inverter control. Further, the compressor 10 is provided with an intermediate pressure port G3, and the refrigerant from the intermediate pressure port G3 can flow into the intermediate portion of the compression process. Compressor 10 is configured to adjust its rotational speed according to a control signal from control device 100 (see FIG. 2). By adjusting the rotational speed of the compressor 10, the circulation amount of the refrigerant is adjusted, and the capacity of the refrigeration cycle device 1 can be adjusted. Various types can be adopted for the compressor 10, for example, a scroll type, a rotary type, a screw type, and the like can be adopted.

Condenser 20 is configured such that the high-temperature, high-pressure gas refrigerant discharged from compressor 10 exchanges heat (radiates heat) with the outside air. This heat exchange causes the refrigerant to condense and change to a liquid phase. The refrigerant discharged from the compressor 10 to the pipe 80 is condensed and liquefied in the condenser 20 and flows out to the pipe 81 . A fan 22 is attached to the condenser 20 to send outside air to increase the efficiency of heat exchange. The fan 22 supplies outside air to the condenser 20 with which the refrigerant exchanges heat in the condenser 20 . By adjusting the rotation speed of the fan 22, the refrigerant pressure (high-pressure side pressure) on the discharge side of the compressor 10 can be adjusted. The second expansion valve 40 is an electronic expansion valve that can reduce the pressure of the refrigerant coming out of the condenser 20 .

The flow path from the compressor 10 to the condenser 20, the first passage H1 of the heat exchanger 30, and the second expansion valve 40 is the flow path in which the first expansion valve 50 and the evaporator 60 of the load device 3 are arranged. , form a circulation flow path through which the coolant circulates. Hereinafter, this circulation flow path is also referred to as the "main refrigerant circuit" of the refrigeration cycle.

The outdoor unit 2 further includes an "injection flow path 101" that branches off from the main refrigerant circuit and feeds the refrigerant to the compressor 10 via the second passage H2. The injection flow path 101 includes a "first refrigerant flow path" (pipes 91 to 94) for flowing the refrigerant from the pipe 81, which is a high-pressure part of the main refrigerant circuit, to the inlet of the second passage H2, and an outlet of the second passage H2. and a “second refrigerant flow path” (pipe 96 ) that flows the refrigerant from to the intermediate pressure port G<b>3 of the compressor 10 .

An on-off valve 75 is arranged in the second refrigerant channel (pipe 96 ) of the injection channel 101 . Whether or not the refrigerant is supplied to the intermediate pressure port G3 of the compressor 10 can be adjusted by the on-off valve 75 . Although not shown in FIG. 1, either one of the suction port G1 and the intermediate pressure port G3, which is disposed in the second refrigerant passage (pipe 96) and flows out from the outlet of the second passage H2, is the destination. A selectable channel switching device may be further provided.

A liquid receiver (receiver) 73 that stores refrigerant and a third expansion valve 71 are arranged in the first refrigerant flow path of the injection flow path 101 . The inlet of the liquid receiver 73 is connected by pipes 91 and 92 to the pipe 81 (that is, the portion of the circulation flow path between the outlet of the condenser 20 and the inlet of the first passage H1). The third expansion valve 71 is arranged in the middle of the pipes 91 and 92 .

A flow control valve 72 and a gas release passage 95 are further arranged in the first refrigerant flow path of the injection flow path 101 . The flow control valve 72 is an expansion valve arranged between a pipe 93 at the outlet of the liquid receiver 73 and a pipe 94 leading to the second passage H2. The gas vent passage 95 connects the gas discharge port of the liquid receiver 73 and the second passage H2, and discharges the refrigerant gas inside the liquid receiver 73 .

A pipe 91 is a pipe that branches off from the pipe 81 , which is the high-pressure portion of the main refrigerant circuit, and allows the refrigerant to flow into the liquid receiver 73 . The third expansion valve 71 is an electronic expansion valve that can reduce the pressure of the refrigerant in the pipe 81, which is the high-pressure portion of the main refrigerant circuit, to an intermediate pressure. The liquid receiver 73 is a container that separates the pressure-reduced two-phase refrigerant into gas and liquid in the container, stores the refrigerant, and adjusts the amount of refrigerant in the main refrigerant circuit. A gas venting passage 95 connected to the upper part of the liquid receiver 73 and a pipe 93 connected to the lower part of the liquid receiver 73 separate the gas refrigerant and the liquid refrigerant in the liquid receiver 73 in a state of separation. It is a pipe for taking out. The flow control valve 72 can adjust the amount of refrigerant in the liquid receiver 73 by adjusting the amount of liquid refrigerant discharged from the pipe 93 .

By providing the liquid receiver 73 in the injection flow path 101 in this way, it becomes easy to ensure the degree of supercooling in the pipes 82 and 83, which are the liquid pipes of the main refrigerant circuit. Since the liquid receiver 73 generally contains a gaseous refrigerant, the temperature of the refrigerant in the liquid receiver 73 reaches the saturation temperature. This is because the temperature of the refrigerant inside becomes less likely to fall below the saturation temperature, and the degree of supercooling cannot be ensured.

The heat exchanger 30 exchanges heat between the refrigerant flowing through the first passage H<b>1 that is part of the main refrigerant circuit and the refrigerant flowing through the second passage H<b>2 that is part of the injection passage 101 .

If the liquid receiver 73 is provided in the pipes 81 and 91, which are high-pressure portions of the main refrigerant circuit, when the pressure in the pipes 81 and 91 is high and the refrigerant in the pipes 81 and 91 is in a supercritical state, the liquid receiver The liquid refrigerant cannot be stored in 73, and the function of the liquid receiver 73 to buffer the excess refrigerant is lost. On the other hand, in the present embodiment, by providing the liquid receiver 73 in the pipe 92, which is the intermediate pressure portion where the pressure is lowered to the intermediate pressure by the third expansion valve 71, the amount of refrigerant is can be adjusted.

FIG. 2 is a diagram showing various sensors and the control device 100 arranged in the refrigeration cycle apparatus 1 shown in FIG. Referring to FIG. 2, outdoor unit 2 further includes pressure sensors 110-113, temperature sensors 120-125, notification device 150, and control device 100. As shown in FIG.

Pressure sensor 110 detects pressure PL at the suction port of compressor 10 and outputs the detected value to control device 100 . Pressure sensor 111 detects the discharge pressure PH of compressor 10 and outputs the detected value to control device 100 . Pressure sensor 112 detects pressure P<b>1 in pipe 83 at the outlet of second expansion valve 40 and outputs the detected value to control device 100 . Also, the pressure sensor 113 detects the intermediate pressure PM of the pipe 92 after the third expansion valve 71 and outputs the detected value to the control device 100 .

By providing the second expansion valve 40 in the liquid pipe, the outdoor unit 2 can reduce the pressure of the refrigerant below the design pressure of the load device 3 (for example, 4 MPa) before sending the refrigerant to the load device 3 . As a result, even if a supercritical refrigerant such as CO ₂ is used, a general-purpose product having the same design pressure as the conventional one can be used as the load device 3 .

Temperature sensor 120 detects a discharge temperature TH of compressor 10 and outputs the detected value to control device 100 . Temperature sensor 121 detects refrigerant temperature T<b>1 in piping 81 at the outlet of condenser 20 and outputs the detected value to control device 100 . Temperature sensor 122 detects the refrigerant temperature at the outlet of first passage H1 on the cooled side of heat exchanger 30 as outlet temperature T2 of heat exchanger 30 and outputs the detected value to control device 100 .

Temperature sensor 123 detects the ambient temperature of outdoor unit 2 as outside air temperature TA, and outputs the detected value to control device 100 . Temperature sensor 125 detects the temperature at the outlet of second passage H2 of heat exchanger 30 and outputs the detected value to control device 100 . Temperature sensor 124 detects temperature TL of the suction pipe of compressor 10 and outputs the detected value to control device 100 .

Notification device 150 is configured to notify the user of various information in response to a request from control device 100 . Notification device 150 may include at least one of a display device (eg, touch panel display), a speaker (eg, smart speaker), and a warning light.

The control device 100 includes a CPU (Central Processing Unit) 102, a memory 104 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown) for inputting and outputting various signals, and the like. Consists of The CPU 102 expands a program stored in the ROM into the RAM or the like and executes it. The program stored in the ROM is a program in which processing procedures of the control device 100 are described. The control device 100 controls each device in the outdoor unit 2 according to these programs. This control is not limited to processing by software, and processing by dedicated hardware (electronic circuit) is also possible.

In the present embodiment, CO ₂ is used as the refrigerant used in the refrigerant circuit of the refrigeration cycle device 1 . When _CO2 is used as the refrigerant, depending on the operating conditions, the pressure of the refrigerant may be below the critical pressure (hereinafter also referred to as "normal state"), or the pressure of the refrigerant may exceed the critical pressure (hereinafter " (also called "supercritical state").

FIG. 3 is a Mollier diagram schematically showing how the refrigerant changes in a normal state. FIG. 4 is a Mollier diagram schematically showing how the refrigerant changes in a supercritical state. 3 and 4, the horizontal axis indicates the enthalpy (the amount of heat of the refrigerant), and the vertical axis indicates the pressure of the refrigerant. Curve L1 indicates a saturated liquid line, and curve L2 indicates a saturated vapor line.

As shown in FIG. 3, in a normal state, the refrigerant pressure is less than the critical pressure, so when the enthalpy is lowered in the condenser 20, the refrigerant state straddles the saturated liquid line L1. Therefore, supercooling can be defined.

On the other hand, as shown in FIG. 4, since the refrigerant pressure exceeds the critical pressure in the supercritical state, the refrigerant state does not straddle the saturated liquid line L1 when the enthalpy is lowered in the condenser 20 . In this case, supercooling cannot be defined. In this specification, for ease of explanation, the degree of supercooling is also referred to as the amount of decrease in the temperature of the refrigerant in the supercritical state from the reference temperature.

[Pressure control in load device 3]
As described above, when CO ₂ is used as the refrigerant, the supercritical region of the refrigerant may be used depending on the operating conditions. Control device 100 controls compressor 10 and second expansion valve 40 so that the refrigerant pressure in load device 3 does not exceed the design pressure of load device 3 even when the supercritical region of the refrigerant is used. At this time, the control device 100 reduces the pressure by the second expansion valve 40 so that the load device 3 can be used in common with a device that uses a normal refrigerant. Specifically, the control device 100 controls the second expansion valve 40 as follows.

The control device 100 feedback-controls the second expansion valve 40 so that the pressure P1 of the pipe 83 at the outlet of the second expansion valve 40 matches the target pressure. Specifically, when the pressure P1 is higher than the target pressure, the control device 100 reduces the degree of opening of the second expansion valve 40 . As a result, the amount of pressure reduction by the second expansion valve 40 increases, so the pressure P1 decreases. On the other hand, when the pressure P1 is lower than the target pressure, the controller 100 increases the degree of opening of the second expansion valve 40 . As a result, the amount of pressure reduction by the second expansion valve 40 is reduced, so the pressure P1 increases. If the pressure P1 is the target pressure, the control device 100 maintains the current opening of the second expansion valve 40 .

Since the pressure P1 is controlled in this way, the refrigerant pressure in the load device 3 can be made below the design pressure of a conventional refrigeration system using a normal refrigerant (for example, R410A) that does not use a supercritical region, and the normal refrigerant can be shared with conventional load devices using

[Control of Third Expansion Valve 71 and Flow Control Valve 72]
In the refrigeration cycle apparatus 1 according to the present embodiment, by providing the injection flow path 101 branching from the main refrigerant circuit, the discharge temperature TH of the compressor 10 in the main refrigerant circuit is controlled, supercooling of the main refrigerant circuit is ensured, and the amount of refrigerant in the main refrigerant circuit can be adjusted. That is, the discharge temperature TH of the compressor 10 can be controlled by depressurizing the refrigerant in the pipe 81 through the injection passage 101 and causing the two-phase refrigerant to flow into the compressor 10 . Further, by making a part of the injection passage 101 the second passage H2 of the heat exchanger 30, supercooling of the refrigerant in the main refrigerant circuit can be ensured. Furthermore, the amount of refrigerant in the main refrigerant circuit can be adjusted by the liquid receiver 73 installed on the injection flow path 101 .

The control device 100 according to the present embodiment controls the discharge temperature TH in the main refrigerant circuit, ensures subcooling of the main refrigerant circuit, and adjusts the amount of refrigerant in the main refrigerant circuit. The third expansion valve 71 and the flow control valve 72 are controlled so as to be exhibited under the conditions.

(Control of discharge temperature TH)
The control device 100 feedback-controls the degree of opening of the third expansion valve 71 so that the discharge temperature TH of the compressor 10 matches the target temperature. Specifically, the control device 100 increases the degree of opening of the third expansion valve 71 when the discharge temperature TH of the compressor 10 is higher than the target temperature. As a result, the amount of refrigerant flowing into the intermediate pressure port G3 via the liquid receiver 73 increases, so the discharge temperature TH decreases.

On the other hand, when the discharge temperature TH of the compressor 10 is lower than the target temperature, the controller 100 reduces the degree of opening of the third expansion valve 71 . As a result, the amount of refrigerant flowing into the intermediate pressure port G3 via the liquid receiver 73 is reduced, and the discharge temperature TH rises.

When the discharge temperature TH is the target temperature, the control device 100 maintains the current opening of the third expansion valve 71 .

In this manner, the control device 100 controls the degree of opening of the third expansion valve 71 so that the discharge temperature TH of the compressor 10 approaches the target temperature.

(Refrigerant amount adjustment and refrigerant shortage detection under normal conditions)
The control device 100 controls the flow control valve 72 in accordance with the temperature efficiency ε of the heat exchanger 30 in order to ensure supercooling under the operating conditions of the normal state. In this embodiment, the temperature efficiency ε of the heat exchanger 30 is the temperature difference between the inlet and outlet of the first passage H1 of the heat exchanger 30 with respect to the degree of superheat of the second passage H2 of the heat exchanger 30 ( =T1-T2).

Specifically, the control device 100 calculates the temperature efficiency ε of the heat exchanger 30 from the difference between the refrigerant temperature T1 at the outlet of the condenser 20 and the outlet temperature T2 of the heat exchanger 30 . If the calculated temperature efficiency ε is greater than the target value, it is considered that the amount of refrigerant in the main refrigerant circuit is excessive. As a result, the amount of liquid refrigerant passing through the liquid receiver 73 decreases and the amount of liquid refrigerant in the liquid receiver 73 increases, so the amount of refrigerant circulating in the main refrigerant circuit decreases. On the other hand, when the calculated temperature efficiency ε is smaller than the target value, it is considered that the excess refrigerant is stored in the liquid receiver 73 and the amount of refrigerant in the main refrigerant circuit is insufficient. , to increase the opening of the flow control valve 72 . As a result, the amount of liquid refrigerant in the liquid receiver 73 decreases, so the amount of refrigerant circulating in the main refrigerant circuit increases. When the temperature efficiency ε is the target value, the control device 100 maintains the current opening of the flow control valve 72 .

In this way, the control device 100 feedback-controls the opening degree of the flow control valve 72 so that the temperature efficiency ε of the heat exchanger 30 becomes the target value under the operating condition of the normal state. Thereby, the temperature efficiency ε of the heat exchanger 30 is maintained at the target value, and the cooling of the refrigerant by the heat exchanger 30 is efficiently performed. This ensures supercooling.

Instead of feedback-controlling the flow regulating valve 72 so that the temperature efficiency ε of the heat exchanger 30 becomes the target value, may be feedback-controlled. In this case, the target temperature of the refrigerant temperature T1 may be set to the temperature of the refrigerant temperature T1 when the temperature efficiency ε of the heat exchanger 30 becomes the target value.

As described above, under the operating conditions of the normal state, the control device 100 increases the degree of opening of the flow control valve 72 so that By increasing the amount of refrigerant flowing through the main refrigerant circuit, the temperature efficiency ε is brought closer to the target value.

However, if the amount of refrigerant in the entire refrigerant circuit, including the main refrigerant circuit and injection passage 101, is insufficient in the first place, even if the opening degree of flow control valve 72 is increased, a sufficient amount of refrigerant will be supplied to the main refrigerant circuit. does not circulate, it is assumed that the temperature efficiency ε does not approach the target value and falls below the target value.

In view of this point, the control device 100 determines that the refrigerant in the entire refrigerant circuit is insufficient when the temperature efficiency ε of the heat exchanger 30 falls below the lower limit value lower than the target value, and outputs the determination result. The notification device 150 is controlled to notify the user.

(Refrigerant amount adjustment and refrigerant shortage detection in supercritical state)
Refrigerant amount adjustment and refrigerant shortage determination using temperature efficiency ε, which is performed in a normal state, has high determination accuracy and good followability. However, under the operating conditions of the supercritical state, it is not possible to define the saturation temperature and ensure supercooling. Judging is difficult.

In view of this point, the control device 100 performs refrigerant amount adjustment and refrigerant shortage determination in a method different from that in the normal state, that is, in a method that does not use the temperature efficiency ε, under the operating condition of the supercritical state. Specifically, under the supercritical operating condition, the controller 100 controls the temperature difference between the outside air temperature TA detected by the temperature sensor 123 and the refrigerant temperature T1 at the outlet of the condenser 20 detected by the temperature sensor 121. ΔT1 is used to control the opening of the flow control valve 72 . By using the temperature difference ΔT1, it is possible to adjust the amount of refrigerant with respect to the limit temperature of heat exchange by the condenser 20 (air heat exchanger) by utilizing the density change due to the change in refrigerant temperature. For example, when the temperature difference ΔT1 is large, it can be considered that the excess refrigerant is stored in the liquid receiver 73 and the amount of refrigerant in the main refrigerant circuit is insufficient. Accordingly, the opening degree of the flow control valve 72 is increased. As a result, the amount of liquid refrigerant flowing from the liquid receiver 73 to the main refrigerant circuit is increased.

Furthermore, under the operating condition of the supercritical state, the control device 100 determines whether or not there is a shortage of refrigerant based on the "opening degree of the flow control valve 72" feedback-controlled according to the temperature difference ΔT1 as described above. .

For example, when the temperature difference ΔT1 is large, the degree of opening of the flow control valve 72 is increased according to the size of the temperature difference ΔT1 by the feedback control for adjusting the amount of refrigerant described above. As a result, the amount of liquid refrigerant flowing from the liquid receiver 73 to the main refrigerant circuit is increased.

However, if the amount of refrigerant in the entire refrigerant circuit including the main refrigerant circuit and the injection flow path 101 is insufficient in the first place, even if the opening of the flow control valve 72 is increased to the upper limit opening, the main refrigerant circuit It is assumed that a sufficient amount of refrigerant does not circulate and the temperature difference ΔT1 does not change (do not decrease).

In view of this point, if the temperature difference ΔT1 does not change even if the state in which the opening degree of the flow control valve 72 reaches the upper limit opening degree continues for a certain period of time, the control device 100 includes the main refrigerant circuit and the injection circuit. It determines that the amount of refrigerant in the entire refrigerant circuit is insufficient, and controls the notification device 150 to notify the user of the determination result.

The method of determining the refrigerant shortage based on the "opening degree of the flow control valve 72" that is feedback-controlled according to the temperature difference ΔT1 may have poorer followability than the method using the temperature efficiency ε. By switching the determination method to , it becomes possible to determine the presence or absence of refrigerant shortage in all operating ranges including the normal state and the supercritical state.

(Adjustment of refrigerant charging amount)
Hereinafter, the adjustment of the amount of refrigerant charged when the refrigerant is charged into the refrigerant circuit will be described. Conventionally, when the refrigerant is first charged into the refrigerant circuit in which the refrigerant is not filled, for example, a sight glass is provided in the pipe 83, and the refrigerant in the pipe 83 is adjusted by checking whether flash gas exists in the refrigerant. rice field.

However, in the refrigerant circuit according to the present embodiment, in order to reduce the pressure in the load device 3, in addition to the expansion by the first expansion valve 50 in the load device 3, the expansion by the second expansion valve 40 in the outdoor unit 2 is performed. When expansion is performed by the second expansion valve 40, the relationship between the amount of refrigerant and the supercooling in the pipe 83 does not hold. Therefore, the amount of refrigerant charged is adjusted using the result of the determination that the amount of refrigerant is insufficient. Specifically, the charging of the refrigerant is continued while it is determined that there is a shortage of the refrigerant, and when it is no longer determined that there is a shortage of the refrigerant, it is determined that an appropriate amount of the refrigerant has been charged and charging of the refrigerant is stopped.

The refrigerant may be charged manually by the user of the outdoor unit 2 (including the contractor who installs the outdoor unit 2), or automatically by the controller 100. FIG. An example in which the control device 100 automatically performs the initial encapsulation will be described below.

At the time of initial filling, the control device 100 first fills the refrigerant into the refrigerant circuit while the compressor 10 is stopped until the discharge pressure PH of the compressor 10 detected by the pressure sensor 111 reaches a threshold value. After that, the control device 100 operates the compressor 10 to continue charging the refrigerant. At this time, since the discharge pressure PH of the compressor 10 is not supercritical, refrigerant shortage detection (refrigerant shortage detection in a normal state) is performed using the temperature efficiency ε. The control device 100 continues charging the refrigerant while it is determined that there is a shortage of refrigerant by refrigerant shortage detection using the temperature efficiency ε (detection of refrigerant shortage in a normal state).

After that, when the rotation speed of the compressor 10 increases and the discharge pressure PH of the compressor 10 exceeds the critical pressure, the "opening degree of the flow control valve 72" that is feedback-controlled according to the temperature difference ΔT1 is used. Refrigerant shortage detection (refrigerant shortage detection in a supercritical state) is performed. After the discharge pressure PH of the compressor 10 exceeds the critical pressure, if the opening degree of the flow control valve 72 does not reach the upper limit opening degree, it is not determined that the refrigerant shortage is detected. Therefore, after the discharge pressure PH of the compressor 10 becomes supercritical, the control device 100 determines that an appropriate amount of refrigerant has been charged and stops charging the refrigerant when it is not determined that the refrigerant shortage is detected. As a result, it is possible to ensure the accuracy and followability of charging the refrigerant even at the time of initial charging when the amount of refrigerant changes drastically.

(Overflow determination)
A case where the refrigerant circuit is excessively filled with refrigerant will be described. In this case, the discharge pressure PH of the compressor 10 detected by the pressure sensor 111 rises to exceed the critical pressure and enter a supercritical state. At this time, the flow regulating valve 72 is lowered to the lower limit opening degree by feedback control for adjusting the amount of refrigerant described above. If the discharge pressure PH of the compressor 10 does not change (does not decrease) even after a certain period of time has elapsed while the flow rate adjustment valve 72 is at the lower limit opening, the control device 100 determines that the refrigerant circuit is in an overcharged state. , the notification device 150 is controlled to notify the user of the determination result.

After determining the overfilled state, the control device 100 determines whether or not the rate of decrease in the discharge temperature TH of the compressor 10 detected by the temperature sensor 120 is greater than a reference value. Then, when the rate of decrease of the discharge temperature TH is larger than the reference value, that is, when the discharge temperature TH is rapidly decreased, the control device 100 controls the overflow state in which the liquid receiver 73 is filled with the liquid refrigerant. It is determined that the condition is present, and the notification device 150 is controlled to notify the user of the determination result.

After the overflow state is determined, the controller 100 determines whether the discharge superheat, which is the difference between the discharge temperature TH of the compressor 10 and the saturation temperature at the discharge pressure PH, is within the specification range of the compressor 10. If the degree of discharge superheat is not within the specification range of the compressor 10, the compressor 10 is stopped.

(Control Flow for Refrigerant Amount Adjustment and Refrigerant Insufficiency Detection)
FIG. 5 is a flowchart showing an example of a processing procedure when the control device 100 performs refrigerant amount adjustment and refrigerant shortage detection.

The control device 100 determines whether or not the discharge pressure PH of the compressor 10 exceeds the critical pressure (step S10). When the discharge pressure PH of the compressor 10 is in a supercritical state exceeding the critical pressure (YES in step S10), the control device 100 controls the outside air temperature TA and the refrigerant temperature T1 at the outlet of the condenser 20 as described above. The degree of opening of the flow control valve 72 is controlled using the temperature difference ΔT1 between the temperature and the temperature (step S11). For example, when the temperature difference ΔT1 is large, the control device 100 increases the degree of opening of the flow control valve 72 according to the magnitude of the temperature difference ΔT1.

Next, the control device 100 determines whether or not the degree of opening of the flow regulating valve 72 is the upper limit degree of opening (step S12). If the degree of opening of flow regulating valve 72 is not the upper limit degree of opening (NO in step S12), control device 100 shifts the process to step S22.

On the other hand, if the opening degree of the flow rate regulating valve 72 is the upper limit opening degree (YES in step S12), the control device 100 determines whether the state in which the opening degree of the flow rate regulating valve 72 is the upper limit opening has continued for a certain period of time. is determined (step S14). If the state in which the degree of opening of flow regulating valve 72 is at the upper limit degree of opening has not continued for a certain period of time (NO in step S14), control device 100 skips the subsequent processing and shifts the processing to return.

When the state in which the degree of opening of flow regulating valve 72 is at the upper limit degree of opening continues for a certain period of time (YES in step S14), control device 100 determines that the refrigerant in the entire refrigerant circuit is insufficient, and uses the determination result. The notification device 150 is controlled to notify the person (step S16).

On the other hand, when the discharge pressure PH of the compressor 10 is in the normal state not exceeding the critical pressure (NO in step S10), the control device 100 exchanges heat with the refrigerant temperature T1 at the outlet of the condenser 20, as described above. The temperature efficiency ε of the heat exchanger 30 is calculated from the difference in the outlet temperature T2 of the vessel 30, and the flow control valve 72 is controlled according to the calculated temperature efficiency ε (step S20).

Next, the control device 100 determines whether or not the calculated temperature efficiency ε is less than the lower limit (step S21). When the temperature efficiency ε is less than the lower limit value (YES in step S21), control device 100 determines that the refrigerant in the entire refrigerant circuit is insufficient, and controls notification device 150 to notify the user of the determination result. control (step S40).

On the other hand, if temperature efficiency ε is not less than the lower limit value (NO in step S21), control device 100 shifts the process to step S22.

In step S22, the control device 100 determines whether or not the degree of opening of the flow regulating valve 72 is the lower limit degree of opening. If the degree of opening of flow regulating valve 72 is not the lower limit degree of opening (NO in step S22), control device 100 skips the subsequent processing and shifts the processing to RETURN.

If the opening degree of flow rate regulating valve 72 is the lower limit opening degree (YES in step S22), control device 100 controls the compressor 100 even after the state in which the opening degree of flow rate regulating valve 72 is at the lower limit opening continues for a certain period of time. It is determined whether or not the discharge pressure PH of No. 10 is greater than the threshold value (step S24). The "threshold" used in step S24 is set to a value lower than the critical pressure, for example. When the state in which the opening degree of the flow rate adjustment valve 72 is at the lower limit opening degree has not continued for a certain period of time, or when the discharge pressure PH of the compressor 10 is less than the threshold value (NO in step S24), the control device 100 Skip the rest of the process and move to return.

If the discharge pressure PH of the compressor 10 is greater than the threshold even after the state in which the opening degree of the flow regulating valve 72 is at the lower limit opening degree continues for a certain period of time (YES in step S24), the control device 100 causes the refrigerant circuit to open. It is determined that the tank is overfilled, and the notification device 150 is controlled to notify the user of the determination result (step S26).

After the overfilled state is determined, the control device 100 determines whether or not the discharge temperature TH of the compressor 10 is rapidly decreasing. It is determined whether or not it is greater than the reference value (step S28). Then, when the rate of decrease of the discharge temperature TH is larger than the reference value, that is, when the discharge temperature TH is rapidly decreased, the control device 100 controls the overflow state in which the liquid receiver 73 is filled with the liquid refrigerant. It is determined that the condition is present, and the notification device 150 is controlled to notify the user of the determination result (step S30).

After the overflow state is determined, the controller 100 determines whether the discharge superheat, which is the difference between the discharge temperature TH of the compressor 10 and the saturation temperature at the discharge pressure PH of the compressor 10, is within the specification range of the compressor 10. It is determined whether or not it fits (step S32). If the degree of discharge superheat is within the specification range of compressor 10 (NO in step S32), control device 100 skips the subsequent processing and shifts the processing to RETURN. On the other hand, if the degree of discharge superheat is not within the specification range of compressor 10 (YES in step S32), control device 100 stops compressor 10 (step S34).

As described above, control device 100 according to the present embodiment determines whether or not there is a shortage of refrigerant using the temperature efficiency ε of heat exchanger 30 under the operating conditions of the normal state. On the other hand, under the operating condition of the supercritical state, the control device 100 does not use the temperature efficiency ε of the heat exchanger 30, but the temperature difference ΔT1 between the outside air temperature TA and the refrigerant temperature T1 at the outlet of the condenser 20. The presence or absence of refrigerant shortage is determined using the "opening degree of the flow rate adjustment valve 72" that is feedback-controlled. By switching the refrigerant shortage determination method in this way, it is possible to appropriately determine whether or not there is a refrigerant shortage in the refrigerant circuit even under operating conditions that are in a supercritical state. As a result, in the refrigeration cycle device 1 using a refrigerant that can be in a supercritical state, it becomes possible to determine whether or not there is a shortage of refrigerant in all operating ranges including the normal state and the supercritical state.

In addition, although the refrigerator provided with the refrigeration cycle device 1 was illustrated and demonstrated in the above-mentioned embodiment, the refrigeration cycle device 1 may be utilized for air conditioners.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of claims rather than the above description, and is intended to include all changes within the meaning and scope of equivalence to the scope of claims.

1 Refrigeration cycle device 2 Outdoor unit 3 Load device 10 Compressor 20 Condenser 22 Fan 30 Heat exchanger 40 Second expansion valve 50 First expansion valve 60 Evaporator 71 Third expansion valve , 72 flow control valve, 73 liquid receiver, 75 on-off valve, 80, 81 to 83, 85, 89, 91 to 94, 96 piping, 84, 88 extension piping, 95 degassing passage, 100 control device, 101 injection flow 102 CPU 104 memory 110-113 pressure sensor 120-125 temperature sensor 150 alarm device G1 intake port G2 discharge port G3 intermediate pressure port H1 first passage.

Claims (9)

An outdoor unit of a refrigeration cycle apparatus configured to be connected to a load device including a first expansion valve and an evaporator,
a compressor having a suction port, a discharge port and an intermediate pressure port;
a condenser;
a heat exchanger having a first passage and a second passage, and performing heat exchange between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage;
A flow path from the compressor to the condenser and the first passage of the heat exchanger forms a circulation flow path in which refrigerant circulates together with the load device,
further comprising an injection flow path for flowing a refrigerant to the compressor from a branch portion between the outlet of the condenser and the inlet of the first passage in the circulation flow path,
In the injection channel,
a first coolant channel that flows coolant from the branch portion to an inlet of the second channel;
a second refrigerant passage for flowing refrigerant from the outlet of the second passage to the suction port or the intermediate pressure port of the compressor;
a liquid receiver arranged in the first refrigerant flow path;
a third expansion valve arranged in a portion between the branch portion of the first refrigerant flow path and an inlet of the liquid receiver;
a flow control valve disposed in a portion of the first refrigerant flow path between the outlet of the liquid receiver and the inlet of the second passage,
a control device that controls the compressor , the third expansion valve, and the flow control valve;
Further comprising a notification device for notifying the user of information from the control device,
When the discharge pressure of the compressor is in a supercritical state exceeding the critical pressure of the refrigerant, the control device controls, based on the degree of opening of the flow control valve, the refrigerant contained in the circulation flow path and the injection flow path. An outdoor unit that determines whether or not there is a shortage of In the supercritical state, the control device increases the degree of opening of the flow control valve as the difference between the discharge temperature of the compressor and the outside air temperature increases, so that the flow rate from the liquid receiver to the circulation flow path increases. increase the amount of refrigerant flowing to
When the control device is in the supercritical state and the state in which the opening degree of the flow control valve is the upper limit opening degree continues for a certain period of time, the refrigerant contained in the circulation flow path and the injection flow path 2. The outdoor unit according to claim 1, wherein it is determined that the is insufficient. The control device determines that the refrigerant contained in the circulation flow path and the injection flow path is insufficient when the supercritical state is not present and the temperature efficiency of the heat exchanger is less than the lower limit value. The outdoor unit according to claim 2, wherein In the non-supercritical state, the control device reduces the amount of refrigerant flowing from the liquid receiver to the circulation flow path by decreasing the degree of opening of the flow control valve as the temperature efficiency of the heat exchanger increases. let
When the state is not the supercritical state and the state in which the opening degree of the flow control valve is at the lower limit opening degree continues for a certain period of time, the control device controls that the refrigerant contained in the circulation flow path and the injection flow path is The outdoor unit according to claim 2 or 3, which is determined to be excessive. 5. The outdoor unit according to claim 3, wherein said control device calculates the temperature efficiency of said heat exchanger from a difference between an inlet temperature and an outlet temperature of said heat exchanger. The controller determines that the liquid receiver is filled with liquid refrigerant and stops the compressor when the rate of decrease in the discharge temperature of the compressor is greater than a reference value. , The outdoor unit according to any one of claims 1 to 5. The outdoor unit according to any one of claims 1 to 6, further comprising a second expansion valve arranged between said first passage of said heat exchanger and said load device in said circulation passage. 8. The outdoor unit according to claim 7 , wherein the control device adjusts the degree of opening of the second expansion valve so that the outlet pressure of the second expansion valve in the circulation passage does not exceed the design pressure of the load device. . A refrigeration cycle apparatus comprising the outdoor unit according to any one of claims 1 to 8 and the load device.

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