Refrigeration cycle, air conditioner, refrigerator and method

Abstract

To provide a refrigeration cycle, an air conditioner, a refrigerator and a method capable of suppressing generation of autolysis reaction.SOLUTION: A refrigeration cycle comprises an accumulator 106, a compressor 107, expansion valves 101, 201, an evaporator, and a condenser, and is filled with a refrigerant. The refrigeration cycle includes: a refrigerant shortage determination unit 520 that determines whether or not an amount of refrigerant circulating through the refrigeration cycle is insufficient relative to a predetermined threshold; and a refrigeration cycle control unit 540 that controls a level of superheat of the accumulator 106 when the refrigerant shortage determination unit 520 determines that the amount of circulating refrigerant is insufficient. The refrigerant is a non-azeotropic refrigerant mixture containing a first refrigerant that has property of undergoing a self-decomposition reaction and a second refrigerant that does not have the property of undergoing a self-decomposition reaction.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a refrigeration cycle, an air conditioner, a refrigerator, and a method for suppressing the occurrence of an autodecomposition reaction. [Background technology]

[0002] From the perspective of reducing the burden on the environment, It has been proposed to use a refrigerant with a low warming potential (GWP) in a refrigeration cycle. Examples of low-GWP refrigerants include ethene-based refrigerants such as R1123, R1132(E), and R1132a.

[0003] However, when used alone, these refrigerants can undergo an explosive self-decomposition reaction called a disproportionation reaction under high-temperature and high-pressure conditions. Therefore, they are often used in combination with a refrigerant with a higher boiling point, such as R1234yf. In the refrigeration cycle configuration, a potential ignition source that can cause a self-decomposition reaction is, for example, a high-pressure chamber compressor.

[0004] In this regard, Japanese Patent Laid-Open Publication No. 2020-34249 (Patent Document 1) discloses a configuration in which, in order to suppress the occurrence of autodecomposition reactions, the diameter of an oil return hole in an accumulator that returns refrigerant to the compressor is increased, thereby making the ratio of HFO-1123 refrigerant to the total amount of non-azeotropic refrigerant inside the compressor lower than the ratio that causes disproportionation reactions. According to Patent Document 1, it is possible to suppress the occurrence of disproportionation reactions in a non-azeotropic refrigerant mixture formed by mixing HFO-1123 refrigerant and a high-boiling point refrigerant inside the compressor.

[0005] However, Patent Document 1 does not take into consideration the amount of oil in the accumulator. Therefore, for example, if the amount of refrigeration oil in the accumulator increases and the amount of refrigerant dissolved in the oil increases, the refrigerant will accumulate in the accumulator container. In this case, the ratio of high-boiling-point refrigerant in the oil will be relatively high, and the ratio of high-boiling-point refrigerant circulating in the refrigeration cycle will be relatively low. In other words, the ratio of typical refrigerant circulating in the refrigeration cycle will be relatively high, increasing the possibility of autolysis.

[0006] Therefore, there is a need for further technology to suppress the occurrence of the self-decomposition reaction. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-34249 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the problems in the prior art described above, and has an object to provide a refrigeration cycle, an air conditioner, a refrigerator, and a method for suppressing the occurrence of a self-decomposition reaction. [Means for solving the problem]

[0009] That is, according to the present invention, A refrigeration cycle including an accumulator, a compressor, an expansion valve, an evaporator, and a condenser, and containing a refrigerant, a determination means for determining whether the amount of refrigerant circulating in the refrigeration cycle is insufficient relative to a predetermined threshold; a control means for controlling the degree of superheat of the accumulator when the determination means determines that the amount of the circulating refrigerant is insufficient; and Including, The refrigerant is a non-azeotropic refrigerant mixture containing a first refrigerant having a property of undergoing a self-decomposition reaction and a second refrigerant having a property of not undergoing a self-decomposition reaction. A refrigeration cycle is provided. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a refrigeration cycle, an air conditioner, a refrigerator, and a method for suppressing the occurrence of an autolysis reaction. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing a schematic configuration of an air conditioning apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the configuration of an accumulator according to the present embodiment. [Figure 3] FIG. 4 is a diagram illustrating the ratio of a mixed refrigerant in the present embodiment. [Figure 4] FIG. 2 is a diagram showing the hardware configuration included in the air conditioning apparatus of the present embodiment. [Figure 5] FIG. 2 is a software block diagram included in the air conditioning apparatus of the present embodiment. [Figure 6] 4 is a flowchart showing a process for suppressing the occurrence of an autolysis reaction in the present embodiment. [Figure 7] FIG. 3 is a diagram illustrating the solubility of a refrigerant in a refrigerating machine oil in the present embodiment. [Figure 8] FIG. 3 is a Mollier diagram illustrating the injection operation of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments described below. In the drawings referred to below, the same reference numerals will be used for common elements, and their description will be omitted as appropriate.

[0013] In the following description of the embodiment, an air conditioner is used as an example of an apparatus equipped with a refrigeration cycle, but this is not intended to limit the embodiment. Therefore, the refrigeration cycle of the present embodiment may be provided in an apparatus other than an air conditioner, such as a refrigerator.

[0014] FIG. 1 is a diagram showing the schematic configuration of an air conditioner 10 according to the present embodiment. As shown in FIG. 1, the air conditioner 10 according to the present embodiment is mainly composed of an outdoor unit 100 and an indoor unit 200. Also, as shown in FIG. 1, the air conditioner 10 may be composed of multiple indoor units 200a, 200b. The number of indoor units 200 included in the air conditioner 10 is not limited to that shown in FIG. 1, and the air conditioner 10 according to the present embodiment may be equipped with any number of indoor units. In FIG. 1, the arrows shown by solid lines indicate the direction of refrigerant flow when the air conditioner 10 is in cooling operation, and the arrows shown by dashed lines indicate the direction of refrigerant flow when the air conditioner 10 is in heating operation.

[0015] The outdoor unit 100 of this embodiment includes an outdoor expansion valve 101, an outdoor heat exchanger 102, an outdoor fan 103, a four-way valve 104, a suction pressure sensor 105, an accumulator 106, a compressor 107, a discharge temperature sensor 108, a discharge pressure sensor 109, and an injection circuit expansion valve 110. The indoor unit 200 includes an indoor expansion valve 201, an indoor heat exchanger 202, and an indoor fan 203.

[0016] Here, the refrigeration cycle of the air conditioner 10 of this embodiment will be described using cooling operation as an example. The compressor 107 compresses low-temperature, low-pressure gas refrigerant and discharges it as high-temperature, high-pressure gas refrigerant. The gas refrigerant discharged from the compressor 107 passes through the four-way valve 104 and flows into the outdoor heat exchanger 102. Note that the solid lines of the four-way valve 104 in FIG. 1 illustrate the connection of the refrigerant path during cooling operation. Therefore, when the air conditioner 10 is performing heating operation, the refrigerant passes through the path of the four-way valve 104 indicated by the dashed lines.

[0017] In the outdoor heat exchanger 102, heat is exchanged between the refrigerant flowing therethrough and the outside air sent in from the outdoor fan 103. During cooling operation, the outdoor heat exchanger 102 functions as a condenser, and discharges the refrigerant as a high-pressure liquid refrigerant through heat exchange. During heating operation, the outdoor heat exchanger 102 functions as an evaporator.

[0018] The refrigerant discharged from the outdoor heat exchanger 102 flows into the indoor unit 200.

[0019] The low-temperature refrigerant that flows into the indoor unit 200 is decompressed by the indoor expansion valve 201, and its volume expands, lowering its temperature. The low-temperature refrigerant flows into the indoor heat exchanger 202. The indoor heat exchanger 202 operates as an evaporator during cooling operation, and exchanges heat between the low-temperature, low-pressure liquid refrigerant and the air blown by the indoor fan 203. The indoor unit 200 can lower the temperature of the indoor space by discharging the air that has undergone heat exchange. The refrigerant that has undergone heat exchange and flows out of the indoor heat exchanger 202 is a low-pressure gas refrigerant, and flows to the outdoor unit 100 through a refrigerant pipe.

[0020] The refrigerant that has returned to the outdoor unit 100 flows into the accumulator 106 via the four-way valve 104. The accumulator 106 is installed on the suction side of the compressor 107, and separates the refrigerant into gas and liquid. By providing the accumulator 106, liquid compression in the compressor 107 is prevented, and the dryness of the refrigerant drawn into the compressor 107 is appropriately adjusted. The refrigerant then flows out of the accumulator 106, is drawn into the compressor 107, and is compressed. The refrigerant then circulates through the refrigeration cycle by repeating the above process.

[0021] In this embodiment, an injection circuit may be provided to properly eliminate the high-temperature, high-pressure state of the refrigerant, as shown in Fig. 1. The injection circuit in Fig. 1 bypasses part of the liquid refrigerant in the liquid pipe, reduces the pressure in the injection circuit expansion valve 110, and exchanges heat with the mainstream liquid refrigerant, and then enters the compression process of the compressor 107 to cool the discharged gas refrigerant. Alternatively, a configuration may be adopted in which the heat exchange circuit as shown in Fig. 1 is not provided, and part of the liquid refrigerant is reduced in pressure and directly entered into the compression process of the compressor 107.

[0022] The suction pressure sensor 105, the discharge temperature sensor 108, and the discharge pressure sensor 109 constitute a detection means in this embodiment. The suction pressure sensor 105 measures the pressure of the refrigerant drawn into the compressor 107. The suction pressure sensor 105 may be installed between the four-way valve 104 and the accumulator 106 to measure the pressure, or may be installed between the accumulator 106 and the compressor 107 to measure the pressure. The discharge temperature sensor 108 measures the temperature of the refrigerant discharged from the compressor 107. The discharge temperature sensor 108 may measure the temperature of the refrigerant by measuring the temperature of the piping on the discharge side of the compressor 107, or by measuring the surface temperature of the compressor 107. In this embodiment, the surface temperature of the compressor 107 is measured from the perspective of temperature responsiveness to suppress autolysis reactions. The discharge pressure sensor 109 measures the pressure of the refrigerant discharged from the compressor 107. The discharge pressure sensor 109 can be installed in the piping on the discharge side of the compressor 107 to measure the pressure.

[0023] The air conditioner 10 can perform air conditioning using a refrigeration cycle in which a refrigerant circulates as shown in FIG. 1. The refrigerant filled in the refrigeration cycle of this embodiment can be a non-azeotropic refrigerant mixture of an ethene-based refrigerant and a refrigerant with a boiling point higher than that of the ethene-based refrigerant (hereinafter referred to as a "high-boiling-point refrigerant"). While ethene-based refrigerants have a low GWP and high refrigerant performance, they may undergo autodecomposition under high-temperature and high-pressure conditions. Examples of ethene-based refrigerants include R1123, R1132(E), and R1132a. Because high-boiling-point refrigerants do not undergo autodecomposition, mixing them with an ethene-based refrigerant can reduce the likelihood of autodecomposition in non-azeotropic refrigerant mixtures. Examples of high-boiling-point refrigerants include R1234yf. The ethene-based refrigerants and high-boiling-point refrigerants listed above are merely examples and do not limit the scope of the present invention. Refrigerants other than the listed refrigerants may also be used to form the refrigerant mixture.

[0024] Here, a non-azeotropic refrigerant mixture refers to a mixture of multiple refrigerants, each with its own dew point and boiling point separated across the entire composition range, and thus possessing the properties of a simple mixture of the individual refrigerants. When a non-azeotropic refrigerant mixture is used in a refrigeration cycle, the composition may fluctuate within the refrigeration cycle. For example, the composition ratio of a certain refrigerant may be high at one location in the refrigeration cycle and low at another location. Therefore, it is preferable to lower the composition of refrigerants that may cause a self-decomposition reaction (disproportionation reaction) near an energy source that may trigger the self-decomposition reaction.

[0025] Note that Fig. 1 illustrates an example of a refrigeration cycle in the air conditioner 10, and in the case of a refrigeration cycle included in another device, the configuration in Fig. 1 may be changed as appropriate. For example, when the refrigeration cycle is used in a refrigerator, the four-way valve 104 may be omitted from the configuration in Fig. 1, and one indoor unit 200 may be used.

[0026] 2 is a diagram showing the configuration of the accumulator 106 of this embodiment. As shown in FIG. 2, the accumulator 106 receives the refrigerant from the four-way valve 104 and sends the refrigerant to the compressor 107.

[0027] Not only liquid refrigerant but also refrigerant oil is stored inside the accumulator 106. The refrigerant oil is a lubricant for lubricating the compressor 107. In the case of the accumulator 106 using a U-shaped tube, a hole (liquid return hole 106a) for returning liquid to the compressor 107 is provided at the bottom of the U-shaped tube. Liquid and oil accumulate at a position lower than the liquid return hole 106a. Some U-shaped tubes have a second liquid return hole 106a at an even higher position, and the liquid level is adjusted so that it does not rise above this position. The amount of refrigerant oil that accumulates in the accumulator 106 is also related to the position of the liquid return hole 106a. The refrigerant sealed in the refrigeration cycle of this embodiment (hereinafter referred to as the "sealed refrigerant") can be one that circulates within the refrigeration cycle (hereinafter referred to as the "circulating refrigerant") or one that dissolves in the refrigerant oil (hereinafter referred to as the "oil-in-oil refrigerant"). In this embodiment, in order to suppress the autodecomposition reaction, control is performed to reduce the ratio of refrigerant that has a property of easily causing the autodecomposition reaction in the circulating refrigerant.

[0028] The refrigerant ratio will now be described with reference to Fig. 3. Fig. 3 is a diagram illustrating the ratio of the mixed refrigerant in this embodiment. The horizontal axis of Fig. 3 indicates the ratio of the oil-in-oil refrigerant to the refrigerant sealed in the refrigeration cycle. The vertical axis of Fig. 3 indicates the ratio of the ethene-based refrigerant to the high-boiling-point refrigerant in the circulating refrigerant or the oil-in-oil refrigerant. In Fig. 3, the dark-colored area indicates the high-boiling-point refrigerant, and the hatched area indicates the ethene-based refrigerant.

[0029] When the degree of superheat is not high, high-boiling-point refrigerants are more soluble in oil than ethene-based refrigerants. Therefore, as the refrigerant-in-oil ratio increases, the ratio of high-boiling-point refrigerants in the oil also increases. Meanwhile, the ratio of ethene-based refrigerants in the circulating refrigerant also increases. Here, a relatively high ratio of refrigerants refers to a ratio higher than the mixture ratio of the refrigerants charged in the refrigeration cycle.

[0030] For example, when the refrigerant ratio in oil is 0%, that is, all of the enclosed refrigerant is circulating refrigerant. In this case, the ratio of the ethene-based refrigerant to the high-boiling-point refrigerant in FIG. 3 corresponds to the mixing ratio of the mixed refrigerant. Here, consider the case where the refrigerant ratio in oil is 50% in FIG. 3. In this case, as shown in FIG. 3, the ratio of the ethene-based refrigerant in the circulating refrigerant is higher than when the refrigerant ratio in oil is 0%.

[0031] If the ratio of ethene-based refrigerant in the circulating refrigerant is high, an energy source such as a short circuit in the compressor 107 may trigger a self-decomposition reaction when the circulating refrigerant is drawn into the compressor 107. Although the amount of charged refrigerant in a refrigeration cycle is generally greater than the amount of refrigeration oil, a shortage of circulating refrigerant may occur during refrigerant charging, restarting a stopped refrigeration cycle, or refrigerant leakage. If the total amount of circulating refrigerant is insufficient, the ratio of ethene-based refrigerant in the circulating refrigerant increases, potentially causing a self-decomposition reaction. Therefore, in this embodiment, the occurrence of a self-decomposition reaction is suppressed by reducing the ratio of ethene-based refrigerant in the circulating refrigerant. Details regarding superheat and refrigerant dissolving in refrigeration oil will be described later.

[0032] Next, we will explain the hardware configuration of the air conditioning apparatus 10. Figure 4 is a diagram showing the hardware configuration included in the air conditioning apparatus 10 of this embodiment. The air conditioning apparatus 10 of this embodiment is configured to include a CPU 410, RAM 420, ROM 430, sensor I / F 440, and operation I / F 450, and each piece of hardware is connected via a bus.

[0033] The CPU 410 is a device that executes programs that control the operation of the air conditioning apparatus 10 and performs predetermined processing. The RAM 420 is a volatile storage device that provides an execution space for the programs executed by the CPU 410, and is used for storing and expanding programs and data. The ROM 430 is a non-volatile storage device that stores programs executed by the CPU 410, firmware, etc.

[0034] The sensor I / F 440 is an interface for connecting to various sensors. The sensor I / F 440 in this embodiment is connected to, for example, the suction pressure sensor 105, the discharge temperature sensor 108, and the discharge pressure sensor 109, and can acquire values ​​measured by each sensor and output them to the CPU 410, etc.

[0035] The operation I / F 450 is an interface for connecting to a device for operating the air conditioner 10. The operation I / F 450 of this embodiment can be connected to, for example, an infrared receiving device that receives signals from a remote control, or an operation button provided on the air conditioner 10. A signal related to an operation received via the operation I / F 450 is output to the CPU 410 or the like.

[0036] So far, we have explained the refrigeration cycle that constitutes the air conditioner 10 of this embodiment, and the hardware configuration included in the air conditioner 10. Next, we will explain the functional means executed by each piece of hardware in this embodiment with reference to Figure 5. Figure 5 is a software block diagram included in the air conditioner 10 of this embodiment.

[0037] The air conditioner 10 is configured to include the following functional means: a refrigerant state detection unit 510, a refrigerant shortage determination unit 520, an alarm output unit 530, and a refrigeration cycle control unit 540. Each functional means will be described in detail below.

[0038] Refrigerant state detection unit 510 is a means for detecting the state of the refrigerant included in the refrigeration cycle. Refrigerant state detection unit 510 constitutes the detection means in this embodiment. Refrigerant state detection unit 510 in this embodiment can detect the state of the refrigerant based on values ​​measured by various sensors such as suction pressure sensor 105, discharge temperature sensor 108, and discharge pressure sensor 109. Here, the state of the refrigerant detected by refrigerant state detection unit 510 includes various states such as the amount of refrigerant charged in the refrigeration cycle, the refrigerant pressure, the refrigerant temperature, and the degree of subcooling.

[0039] The refrigerant shortage determination unit 520 is a means for determining whether the amount of refrigerant charged in the refrigeration cycle is insufficient. The refrigerant shortage determination unit 520 constitutes the determination means in this embodiment. The refrigerant shortage determination unit 520 in this embodiment determines that there is a refrigerant shortage when the amount of circulating refrigerant is less than a predetermined threshold. The refrigerant shortage determination unit 520 can determine the amount of refrigerant based on, for example, the degree of subcooling of the condenser, the operating pressure, the expansion valve opening, etc.

[0040] The alarm output unit 530 is a means for outputting an alarm indicating that the refrigerant is insufficient. The alarm output unit 530 constitutes the output means in this embodiment. The alarm output unit 530 in this embodiment outputs an alarm when the refrigerant shortage determination unit 520 determines that the refrigerant is insufficient. The form of the alarm is not particularly limited, and the alarm output unit 530 can output the alarm by any method. Therefore, the alarm output unit 530 may output the alarm by voice, or by an LED, a display device, or the like, for example.

[0041] The refrigeration cycle control unit 540 is a means for controlling the operation of various components that make up the refrigeration cycle of the air conditioner 10. The refrigeration cycle control unit 540 constitutes the control means in this embodiment. The refrigeration cycle control unit 540 in this embodiment can control, for example, the rotation speed of the compressor 107, the opening degrees of the outdoor expansion valve 101 and the indoor expansion valve 201, the rotation speeds of the outdoor fan 103 and the indoor fan 203, etc.

[0042] The software blocks described above correspond to functional means realized by causing each piece of hardware to function by executing the program of this embodiment with the CPU 410. The functional means shown in each embodiment may be realized entirely by software, or some or all of them may be implemented as hardware that provides equivalent functions.

[0043] Next, the processing executed by each of the above-mentioned functional means will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the processing for suppressing the occurrence of an autolysis reaction in this embodiment.

[0044] The air conditioning apparatus 10 starts processing from step S1000. In the following step S1001, the refrigerant state detection unit 510 detects the state of the refrigerant based on values ​​measured by various sensors.

[0045] In step S1002, the process branches depending on whether or not there is a refrigerant shortage. The determination in step S1002 can be made by refrigerant shortage determination unit 520. If refrigerant shortage determination unit 520 determines in step S1002 that there is no refrigerant shortage (NO), the process returns to step S1001, and the state of the refrigerant is detected again.

[0046] A shortage of refrigerant may occur, for example, due to a refrigerant leak or the shutdown of the air conditioner 10. If the air conditioner 10 is shut down for an extended period of time, the temperature of the accumulator 106 drops, and the refrigerant that flows from the evaporator to the piping on the intake side of the compressor 107 tends to accumulate in the accumulator 106. In such a case, if the air conditioner 10 is restarted, the refrigerant will likely be insufficient until the liquid refrigerant in the accumulator is depleted.

[0047] Furthermore, when a refrigeration cycle is used in a refrigerator, the refrigerant is charged at the site where the refrigerator is installed. In this case, the refrigerant may be charged while the refrigerator is running. However, the amount of refrigerant in the refrigeration cycle may be insufficient at the start of the charging operation, resulting in a refrigerant shortage. This increases the proportion of high-boiling-point refrigerant dissolved in the refrigeration oil and the proportion of ethene-based refrigerant in the circulating refrigerant, making autolysis more likely. Therefore, it is preferable to warn the person charging the refrigerant into the refrigerator's refrigeration cycle, measure the refrigerant discharge temperature and discharge pressure during the charging operation, and control the refrigeration cycle so that the refrigerant does not become high in temperature and high in pressure.

[0048] In step S1002, if refrigerant shortage determination unit 520 determines that there is a shortage of refrigerant (YES), the process proceeds to step S1003. In step S1003, warning output unit 530 outputs a warning that there is a shortage of refrigerant. If there is a shortage of refrigerant in the refrigeration cycle, an autodecomposition reaction may occur, so by outputting a warning to that effect, the user can be prompted to take action.

[0049] Thereafter, in step S1004, the refrigeration cycle control unit 540 controls the superheat degree of the accumulator 106. The refrigeration cycle control unit 540 can control the superheat degree of the accumulator 106 by controlling the aperture of the expansion valve on the evaporator side. In step S1004, the refrigeration cycle control unit 540 preferably ensures a sufficient superheat degree of the accumulator 106 in order to eliminate the refrigerant shortage (for example, a superheat degree of 10 Kelvin or more is achieved in consideration of the temperature gradient of the mixed refrigerant). In particular, in the case of a refrigeration cycle with a large pressure ratio such as a refrigerator, or in the case of a refrigeration cycle including an accumulator 106 configured to supply a small amount of liquid refrigerant to the compressor 107, the possibility of an autodecomposition reaction occurring can be reduced by ensuring the superheat degree of the accumulator 106 by reducing the aperture of the expansion valve on the evaporator side.

[0050] Although the method of step S1004 has been described as an example of a method for dealing with a refrigerant shortage, this is not intended to limit the present embodiment. Therefore, the refrigerant shortage may be resolved by a method other than controlling the degree of superheat of the accumulator 106. For example, the refrigerant shortage may be resolved by adding refrigerant to be charged. In particular, when a refrigeration cycle is used in a refrigerator, refrigerant is charged when the refrigerator is installed. Therefore, even if a refrigerant shortage is detected, the refrigerant shortage can be resolved by charging the refrigerant.

[0051] Next, in step S1005, the process branches depending on whether the refrigerant shortage has been resolved. The determination in step S1005 can be made by refrigerant shortage determination unit 520, similar to step S1002. If refrigerant shortage determination unit 520 determines in step S1005 that the refrigerant shortage has been resolved, the process proceeds to step S1007, where the process ends.

[0052] On the other hand, if the refrigerant shortage determination unit 520 determines in step S1005 that the refrigerant shortage has not been resolved, the process proceeds to step S1006. In step S1006, the refrigeration cycle control unit 540 performs control to resolve the high-temperature, high-pressure state of the refrigerant in order to prevent the occurrence of an autodecomposition reaction. If there is a refrigerant shortage, that is, if the ratio of ethene-based refrigerant in the circulating refrigerant is high, there is a possibility that an autodecomposition reaction will occur when high-temperature, high-pressure refrigerant is drawn into the compressor 107. Therefore, in step S1006, the refrigeration cycle control unit 540 controls the operation of the components that make up the refrigeration cycle so that the high-temperature, high-pressure state of the refrigerant is resolved.

[0053] In step S1006, the refrigeration cycle control unit 540 can eliminate the high temperature and high pressure state of the refrigerant by various methods.

[0054] For example, in step S1006, the refrigeration cycle control unit 540 can perform control to reduce the rotation speed of the compressor 107. When the rotation speed of the compressor 107 is reduced, the pressure of the refrigerant decreases, and the temperature also decreases. Furthermore, by stopping the compressor 107, the high temperature and high pressure are eliminated, and the compressor 107 no longer operates as an energy source that may trigger an autolysis reaction, thereby further improving safety.

[0055] In step S1006, the refrigeration cycle control unit 540 can perform control to increase the opening of the expansion valve installed at the inlet of the evaporator. By increasing the opening of the expansion valve, the refrigerant remaining in the condenser decreases, and the refrigerant pressure decreases. In addition, the refrigerant that cannot evaporate returns to the compressor 107 from the outlet of the evaporator, and the discharge temperature decreases.

[0056] Furthermore, in step S1006, the refrigeration cycle control unit 540 can perform control to increase the rotation speed of the fan on the condenser side. Increasing the airflow rate of the fan on the condenser side improves condensation performance and reduces the discharge temperature. For example, when the air conditioner 10 is in cooling operation, the outdoor heat exchanger 102 functions as a condenser, so the rotation speed of the outdoor fan 103 is increased. Also, for example, when the air conditioner 10 is in heating operation, the indoor heat exchanger 202 functions as a condenser, so the rotation speed of the indoor fan 203 is increased.

[0057] In step S1006, the refrigeration cycle control unit 540 can perform control to introduce the refrigerant from the injection circuit expansion valve 110 to the compressor 107 (for example, control to open or close the injection circuit expansion valve 110). The injection circuit can cool the discharge gas by introducing the liquid refrigerant from the liquid pipe into the compression process of the compressor 107, and can lower the temperature of the refrigerant.

[0058] In step S1006, the refrigeration cycle control unit 540 performs one or more of the various controls described above to eliminate the high-temperature, high-pressure state of the refrigerant. Note that the control performed by the refrigeration cycle control unit 540 in step S1006 is not limited to the above-described controls, and other controls may be performed. After performing control to eliminate the high-temperature, high-pressure state in step S1006, the process proceeds to step S1007. In step S1007, the process ends.

[0059] By the process shown in FIG. 6, the air conditioner 10 of this embodiment can suppress the self-decomposition reaction of the refrigerant.

[0060] Here, the refrigerant dissolving in refrigerating machine oil will be described with reference to Fig. 7. Fig. 7 is a diagram illustrating the solubility of refrigerant in refrigerating machine oil in this embodiment. The horizontal axis of Fig. 7 represents the solubility of the refrigerant, and the vertical axis represents the pressure of the refrigerant. Fig. 7 also shows a solubility curve for each temperature of the refrigerating machine oil, and Fig. 7 shows examples where the temperatures of the refrigerating machine oil are T°C, T+10°C, and T+20°C.

[0061] Generally, when the refrigerant pressure is the same, the solubility of the refrigerant tends to decrease as the temperature of the refrigerant oil increases. For example, there are some refrigerant oils whose solubility of the refrigerant becomes less than 40 wt% when the refrigerant oil is superheated to 10 Kelvin or more.

[0062] A refrigerant with a solubility of 100 wt% exists as a liquid refrigerant, and the pressure at this point corresponds to the saturation pressure of the refrigerant at that temperature. If the temperature of the refrigerating machine oil is increased, the refrigerant dissolved in the refrigerating machine oil gasifies, reducing the solubility. For example, as shown in Figure 7, consider a state in which the solubility is 100 wt% when the refrigerating machine oil temperature is T°C. The pressure at this point, i.e., the saturation pressure, is indicated by the dashed-dotted line in Figure 7. If the refrigerating machine oil temperature is increased while maintaining the pressure in this state, the solubility decreases, as shown by the solubility curves at T+10°C and T+20°C in Figure 7. For example, at T+10°C in Figure 7, the solubility decreases to approximately 35%, and at T+20°C in Figure 7, the solubility decreases to approximately 20%. In other words, by raising the temperature of the refrigeration oil by about 10°C (in other words, by superheating the refrigeration oil by about 10 Kelvin), the solubility of the refrigerant can be reduced to a level where the self-decomposition reaction is less likely to occur.

[0063] In this embodiment, the introduction of refrigerant through an injection circuit is one example of control for lowering the temperature of high-temperature, high-pressure refrigerant. Fig. 8 is a Mollier diagram illustrating the operation of the injection circuit of this embodiment. In Fig. 8, the solid line indicated by ABCDEFGH shows an example of a refrigeration cycle with an injection circuit, and the dashed line indicated by abcd shows an example of a refrigeration cycle without an injection circuit.

[0064] In a refrigeration cycle without an injection circuit, at point a in section ab, the refrigerant is in a gas-liquid two-phase state and liquid refrigerant accumulates in the accumulator 106. On the other hand, at point A in section ABCD, the refrigerant is in a superheated state and no liquid refrigerant accumulates in the accumulator 106. Furthermore, the temperature of the gas refrigerant discharged from the compressor 107 is lower when there is an injection circuit (point D) than when there is no injection circuit (point b). Here, the EHC section when there is an injection circuit indicates the cycle of the path through which the refrigerant enters the compressor 107 from the injection circuit.

[0065] 8, by providing an injection circuit in the refrigeration cycle, the temperature of the refrigerant in a high temperature state can be lowered, and the occurrence of an autolysis reaction of the refrigerant can be suppressed. Note that the degree of superheat of accumulator 106 may be calculated from the difference between the measurement value of a temperature sensor attached to accumulator 106 and the saturation temperature calculated from the suction pressure, or may be determined based on the suction pressure, discharge pressure, and the state of the injection circuit, depending on whether the discharge temperature is appropriate.

[0066] According to the embodiments of the present invention described above, it is possible to provide a refrigeration cycle, an air conditioner, a refrigerator, and a method for suppressing the occurrence of a self-decomposition reaction.

[0067] Each function of the above-described embodiments of the present invention can be realized by a device-executable program written in C, C++, C#, Java (registered trademark), etc., and the program of this embodiment can be stored and distributed on a device-readable recording medium such as a hard disk drive, CD-ROM, MO, DVD, flexible disk, EEPROM (registered trademark), EPROM, etc., and can also be transmitted over a network in a format that can be used by other devices.

[0068] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above-described embodiments, and any embodiment that can be conceived by a person skilled in the art is included in the scope of the present invention as long as it exhibits the functions and effects of the present invention. [Explanation of symbols]

[0069] 10...Air conditioning equipment, 100...Outdoor unit, 101...Outdoor expansion valve, 102...Outdoor heat exchanger, 103...Outdoor fan, 104...Four-way valve, 105...suction pressure sensor, 106...accumulator, 106a...liquid return hole, 107...Compressor, 108...Discharge temperature sensor, 109...Discharge pressure sensor, 110...injection circuit expansion valve, 200...Indoor unit, 201... Indoor expansion valve, 202...Indoor heat exchanger, 203...Indoor fan, 410...CPU, 420…RAM, 430...ROM, 440...Sensor I / F, 450...Operation I / F, 510...refrigerant state detection unit, 520...Refrigerant shortage determination unit, 530...alarm output unit, 540...Refrigeration cycle control unit

Claims

1. A refrigeration cycle including an accumulator, a compressor, an expansion valve, an evaporator, and a condenser, and containing a refrigerant, a determination means for determining whether the amount of refrigerant circulating in the refrigeration cycle is insufficient relative to a predetermined threshold; a control means for controlling the degree of superheat of the accumulator when the determination means determines that the amount of the circulating refrigerant is insufficient; and Including, The refrigerant is a non-azeotropic refrigerant mixture containing a first refrigerant having a property of undergoing a self-decomposition reaction and a second refrigerant having a property of not undergoing a self-decomposition reaction. Refrigeration cycle.

2. The control means adjusts the degree of superheat by controlling the opening degree of the expansion valve. The refrigeration cycle according to claim 1.

3. the control means controls the expansion valve so that the degree of superheat is 10 Kelvin or more. The refrigeration cycle according to claim 2.

4. The determination means further determines whether or not the shortage of the amount of circulating refrigerant has been resolved by the control of the degree of superheat by the control means, When the determination means determines that the shortage of the amount of circulating refrigerant has not been resolved, the control means performs control to reduce the pressure or temperature of the circulating refrigerant. The refrigeration cycle according to claim 1.

5. The control means performs control to reduce the rotation speed of the compressor. The refrigeration cycle according to claim 4.

6. the control means performs control to increase the opening degree of the expansion valve provided at the refrigerant inlet of the evaporator. The refrigeration cycle according to claim 4.

7. the control means performs control to increase the rotation speed of the fan on the condenser side. The refrigeration cycle according to claim 4.

8. Further comprising injection, The control means controls the introduction of the refrigerant from the injection to the compressor. The refrigeration cycle according to claim 4.

9. an output means for outputting an alarm when the determining means determines that the amount of circulating refrigerant is insufficient; The refrigeration cycle of claim 1 further comprising:

10. An air conditioner comprising the refrigeration cycle according to any one of claims 1 to 9.

11. A refrigerator comprising the refrigeration cycle according to any one of claims 1 to 9.

12. A method for controlling a refrigeration cycle including an accumulator, a compressor, an expansion valve, an evaporator, and a condenser, and containing a refrigerant, comprising: determining whether the amount of refrigerant circulating in the refrigeration cycle is insufficient with respect to a predetermined threshold; a step of controlling a degree of superheat of the accumulator when it is determined in the determining step that the amount of the circulating refrigerant is insufficient; Including, The refrigerant is a non-azeotropic refrigerant mixture containing a first refrigerant having a property of undergoing a self-decomposition reaction and a second refrigerant having a property of not undergoing a self-decomposition reaction. method.

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