Refrigeration cycle apparatus

Abstract

To secure comfort for a user and to improve energy-saving performance by performing an operation corresponding to a required capacity even when a non-azeotrope refrigerant having a large temperature gradient is used.SOLUTION: The indoor unit 2 includes the refrigerant circuit C in which the flammable refrigerant circulates, the indoor fan 22, and the refrigerant sensor 23 that detects the concentration of the refrigerant, and the controller 6 that controls the indoor unit 2. When the controller 6 determines that the concentration of the refrigerant detected by the refrigerant sensor is equal to or higher than the reference value, the controller 6 controls the indoor fan 22 to achieve the air volume Q [m3 / h] and performs the stirring operation. The air flow rate Q, the lower flammable limit concentration LFL, the assumed leakage rate W, and the assumed suction rate w satisfy the relationship Q> (W + w) / LFL, where LFL [kg / m3] is the lower flammable limit concentration of the refrigerant, W [kg / h] is the assumed leakage rate of the refrigerant, and w [kg / h] is the assumed suction rate of the refrigerant sucked into the indoor unit 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a refrigeration cycle device. [Background technology]

[0002] In recent years, as one of the measures against global warming, for example, conversion of refrigerants used in refrigeration cycle devices such as air conditioners and heat pump devices to refrigerants with low global warming potential (GWP: Global Warming Potential; hereinafter referred to as "GWP") has been considered. Refrigerants with low GWP include flammable refrigerants such as propane (R290), and measures must be taken to prevent the refrigerant from leaking into living spaces. Alternatively, measures must be prepared to ensure sufficient safety even if the refrigerant does leak into living spaces.

[0003] One safety measure to be taken in the event of a refrigerant leak from the indoor unit into the living space is to operate the indoor fan to perform a stirring operation, because if the leaked refrigerant accumulates in a specific location inside the indoor unit housing or in the living space, the risk of fire increases in the location where the refrigerant accumulates.

[0004] In the agitation operation, the indoor fan rotates to agitate the air in the indoor unit housing and the living space so that no area is formed in the living space where the refrigerant concentration exceeds the lower flammability limit (hereinafter referred to as "LFL"). By performing this agitation operation, the concentration of refrigerant that has leaked and accumulated in the living space is reduced.

[0005] Regarding the stirring operation, for example, Patent Document 1 below can be cited. The invention disclosed in Patent Document 1 specifies a minimum airflow rate of the indoor fan during stirring operation. Specifically, the indoor fan is controlled so that the airflow rate is greater than the refrigerant leakage rate divided by the LFL. By controlling the indoor fan in this manner, it is possible to keep the refrigerant concentration of the air blown into the living space below the LFL. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2017 / 187618 Summary of the Invention [Problem to be solved by the invention]

[0007] However, even if the agitation operation is performed as in the invention disclosed in the above-mentioned Patent Document 1, there may be cases where the refrigerant concentration in the blown air exceeds the LFL. That is, when the agitation operation is performed, the blown air containing the refrigerant is blown into the living space, and the blown air agitates the air in the living space. However, even if the air is agitated in this way, if the air present in the living space does not leave the living space, the refrigerant concentration in the living space will gradually increase.

[0008] That is, after a period of continuous stirring, the leaked refrigerant gradually mixes with the air suctioned by the indoor unit. This can increase the absolute amount of leaked refrigerant in the air blown out. This can result in areas inside the indoor unit and near the air outlet where the refrigerant concentration exceeds the LFL, resulting in a decrease in safety.

[0009] An object of the present invention is to provide a refrigeration cycle device that can ensure sufficient safety even when a flammable refrigerant is used as the refrigerant for an air conditioner. [Means for solving the problem]

[0010] A refrigeration cycle apparatus according to one aspect of the present invention includes a refrigerant circuit through which a flammable refrigerant circulates, an indoor unit that houses some of the equipment connected to the refrigerant circuit and has an indoor fan and a refrigerant sensor that detects the concentration of the refrigerant, and a control device that controls the indoor unit, wherein the control device compares the refrigerant concentration detected by the refrigerant sensor with a preset threshold value and, when it determines that the refrigerant concentration is equal to or greater than the threshold value, controls the indoor fan to operate at an airflow rate Q [m 3 / h], and the lower flammable limit of the refrigerant is controlled to LFL [kg / m 3 ], the assumed refrigerant leakage rate is W [kg / h], and the assumed suction rate of the refrigerant being drawn into the indoor unit is w [kg / h], the air volume Q, the lower flammable concentration LFL, the assumed leakage rate W, and the assumed suction rate w satisfy the relationship Q>(W+w) / LFL. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a refrigeration cycle device that can ensure sufficient safety even when a flammable refrigerant is used as the refrigerant for an air conditioner. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a refrigerant circuit diagram of a refrigeration cycle device according to an embodiment of the present invention. [Figure 2] 1 is a block diagram showing an internal configuration of a control device in a refrigeration cycle apparatus according to an embodiment of the present invention. [Figure 3] 1 is a schematic diagram showing an assumed leakage speed of a refrigerant and an assumed suction speed of a refrigerant in an indoor unit installed in a living space in a refrigeration cycle apparatus according to an embodiment of the present invention. FIG. [Figure 4] 1 is an explanatory diagram illustrating the results of comparison with Patent Document 1 in terms of combustible volume regarding control in a refrigeration cycle device according to an embodiment of the present invention. FIG. [Figure 5]1 is an explanatory diagram illustrating the results of comparison with Patent Document 1 in terms of risk reduction rate regarding control in a refrigeration cycle device according to an embodiment of the present invention. FIG. [Figure 6] 3 is a flowchart showing a control flow in the refrigeration cycle device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The structure of a refrigeration cycle apparatus S according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a refrigerant circuit diagram of the refrigeration cycle apparatus S according to an embodiment of the present invention. The refrigeration cycle apparatus S is used for cooling operation when an indoor heat exchanger 21 (described later) is used as an evaporator and an outdoor heat exchanger 41 is used as a condenser. On the other hand, when the indoor heat exchanger 21 is used as a condenser and the outdoor heat exchanger 41 is used as an evaporator, the refrigeration cycle apparatus S is used for heating operation.

[0014] The refrigeration cycle device S according to the embodiment of the present invention shown in Figure 1 has a refrigerant circuit C in which a compressor 1, an indoor heat exchanger 21, a pressure reduction mechanism 3, and an outdoor heat exchanger 41 are connected in sequence by refrigerant piping, and in which the refrigerant circulates.

[0015] Furthermore, a four-way valve 5 is provided between the compressor 1 and the indoor heat exchanger 21, and between the compressor 1 and the outdoor heat exchanger 41. The four-way valve 5 switches whether the refrigerant discharged from the compressor flows to the indoor heat exchanger 21 side or the outdoor heat exchanger 41 side.

[0016] The refrigerant circulating through the refrigerant circuit C of the refrigeration cycle apparatus S in this embodiment of the present invention is a flammable refrigerant such as R290 (propane). Flammable refrigerants include, for example, mildly flammable refrigerants such as R32, R1234yf, and R1234ze(E), as well as highly flammable refrigerants such as the above-mentioned R290 and R1270, but any flammable refrigerant may be used. The refrigerant may be a single refrigerant or a mixed refrigerant containing two or more refrigerants.

[0017] The compressor 1 draws in the refrigerant circulating in the refrigerant circuit C, compresses it, and discharges it into the refrigerant circuit C. The indoor unit 2 is installed in the living space L, and in the case of heating operation, for example, heat is exchanged between the refrigerant and the air flowing into the indoor unit 2, and the air heated by absorbing heat from the refrigerant is supplied to the living space L.

[0018] In the refrigeration cycle apparatus S according to the embodiment of the present invention, an indoor unit 2 is assumed that has the function of drawing in air from the living space L, exchanging heat therein, and then blowing the air out into the living space L. Specifically, for example, the indoor unit 2 is a wall-mounted type that is installed with its back surface fixed to the wall surface of the living space L. However, any other type of indoor unit may be used, such as a cassette type that is placed inside the ceiling, or a hanging type that is suspended from the ceiling.

[0019] The indoor unit 2 is equipped with an indoor heat exchanger 21, an indoor fan 22, and a refrigerant sensor 23 that detects the concentration of the refrigerant. The indoor heat exchanger 21 is connected to the refrigerant circuit C, and exchanges heat between the refrigerant flowing into the indoor heat exchanger 21 and the air in the living space L.

[0020] When the refrigeration cycle device S performs cooling operation, the indoor heat exchanger 21 functions as an evaporator and supplies cool air into the living space L. On the other hand, when the refrigeration cycle device S performs heating operation, the indoor heat exchanger 21 functions as a condenser and supplies warm air into the living space L.

[0021] The indoor fan 22 takes air from the living space L into the indoor unit 2, and supplies the air that has undergone heat exchange with the refrigerant in the indoor heat exchanger 21 into the living space L. Various types of fans, such as an axial fan or a centrifugal fan, can be used as the indoor fan 22 depending on the configuration of the indoor unit 2. In the refrigeration cycle apparatus S according to the embodiment of the present invention, for example, a cross-flow fan is used when the indoor unit 2 is a wall-mounted type.

[0022] Refrigerant sensor 23 detects the concentration of refrigerant in the air surrounding refrigerant sensor 23. Control device 6, which will be described later, determines whether or not there is a refrigerant leak based on the refrigerant concentration detected by refrigerant sensor 23. As refrigerant sensor 23, for example, a semiconductor gas sensor, an infrared gas sensor, or other gas sensor can be used.

[0023] Alternatively, an oxygen concentration meter or a temperature sensor such as a thermistor may be used as refrigerant sensor 23. When a temperature sensor is used as refrigerant sensor 23, refrigerant leakage is detected by detecting a decrease in temperature due to adiabatic expansion of the leaked refrigerant.

[0024] As described above, the presence or absence of a refrigerant leak is determined based on the refrigerant concentration detected by the refrigerant sensor 23, but possible causes of refrigerant leakage include, for example, a poor connection in the piping connecting the connecting piping to the indoor unit 2 or poor welding of the heat transfer tubes of the indoor heat exchanger 21. It is also possible that corrosion has occurred in the piping inside the indoor heat exchanger 21, causing refrigerant leakage.

[0025] Therefore, the refrigerant sensor 23 is disposed in a location where there are many piping connections in the indoor unit 2, such as to the side of the indoor heat exchanger 21, or in a space where piping is stored inside the indoor unit 2. Alternatively, the refrigerant sensor 23 is disposed near an air outlet through which air blown out from the indoor unit 2 into the living space L passes.

[0026] Refrigerant sensor 23 also constantly detects the refrigerant concentration. This is because if a refrigerant leak occurs and the refrigerant concentration in the air in the indoor space becomes flammable (hereinafter referred to as the "flammable concentration region"), the risk of fire increases. Note that "constantly" here includes not only continuous detection of the refrigerant concentration, but also detection of the refrigerant concentration intermittently at a predetermined interval.

[0027] The above-described indoor heat exchanger 21, indoor fan 22, and refrigerant sensor 23 are the only components provided in the indoor unit 2. However, this is merely a list of components necessary to explain the refrigeration cycle device S in the embodiment of the present invention, and therefore, other devices that the indoor unit 2 normally includes are of course also provided.

[0028] In the refrigerant circuit C, a pressure reducing mechanism 3 is provided between the indoor heat exchanger 21 and the outdoor heat exchanger 41. The pressure reducing mechanism 3 is, for example, an expansion valve, and reduces the pressure of the high-pressure refrigerant that has passed through the indoor heat exchanger 21 and the outdoor heat exchanger 41. The outdoor unit 4 is installed outside the living space L, and as shown by the dashed dotted line in FIG. 1 , the outdoor unit 4 contains therein a compressor 1, a pressure reducing mechanism 3, an outdoor heat exchanger 41, a four-way valve 5, an outdoor fan (not shown), and the like.

[0029] Here, the flow of refrigerant in the refrigerant circuit C when the refrigeration cycle apparatus S performs heating operation is as follows. When heating operation is performed, high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the indoor heat exchanger 21 via the four-way valve 5. The indoor heat exchanger 21 exchanges heat between the refrigerant and air in the living space L that is drawn into the indoor unit 2 by the indoor fan 22. The air that has been warmed by absorbing heat from the refrigerant is supplied into the living space L by the rotation of the indoor fan 22. The high-temperature, high-pressure gas refrigerant releases heat through heat exchange as it passes through the indoor heat exchanger 21, and becomes a high-pressure liquid refrigerant.

[0030] The high-pressure liquid refrigerant that flows out of the indoor heat exchanger 21 flows into the pressure reduction mechanism 3. The high-pressure liquid refrigerant is reduced in pressure as it passes through the pressure reduction mechanism 3, becoming a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant that flows out of the pressure reduction mechanism 3 then flows into the outdoor heat exchanger 41. In the outdoor heat exchanger 41, heat is exchanged with the outside air, causing the low-pressure two-phase refrigerant to absorb heat and become a low-pressure gas refrigerant, which is then drawn into the compressor 1 via the four-way valve 5.

[0031] On the other hand, when the refrigeration cycle apparatus S performs cooling operation, the flow of refrigerant in the refrigerant circuit C is as follows: When cooling operation is performed, high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 41 via the four-way valve 5. The refrigerant that has flowed into the outdoor heat exchanger 41 exchanges heat with the outside air, dissipates heat, and becomes high-pressure liquid refrigerant.

[0032] The high-pressure liquid refrigerant flowing out from the outdoor heat exchanger 41 flows into the pressure reducing mechanism 3, where it is reduced in pressure to become a low-pressure two-phase refrigerant. It then flows into the indoor heat exchanger 21, and while passing through the indoor heat exchanger 21, it exchanges heat with the air in the living space L, and the low-pressure two-phase refrigerant absorbs heat and becomes a gas refrigerant. The air cooled by exchanging heat with the refrigerant is then supplied into the living space L. The gas refrigerant flowing out from the indoor heat exchanger 21 is drawn into the compressor 1 via the four-way valve 5.

[0033] The control device 6 controls the compressor 1 and each device constituting the refrigeration cycle device S. The control device 6 also controls the rotation speed of the indoor fan 22 based on the control content described below. By the control device 6 controlling the indoor fan 22, even if a flammable refrigerant leaks into the living space L, an appropriate stirring operation can be performed, thereby taking sufficient safety measures to reduce the concentration of the refrigerant in the living space L.

[0034] However, in the following embodiments of the present invention, only the functions necessary for controlling the operation of the refrigeration cycle apparatus S using a flammable refrigerant will be described. Therefore, in the following Fig. 2, only the configuration necessary for executing the stirring operation in the control device 6 is shown.

[0035] Therefore, the control device 6 may have a configuration in which, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output interface are connected via a bus, which are not shown in Fig. 2. Furthermore, the input / output interface may be connected to the above-mentioned components as well as components such as a display unit, a communication control unit, or an input unit.

[0036] 2 is a block diagram showing the internal configuration of the control device 6 in the refrigeration cycle apparatus S according to the embodiment of the present invention. The control device 6 includes a refrigerant concentration information acquisition unit 61, a storage unit 62, a determination unit 63, and an indoor fan control unit 64.

[0037] The refrigerant concentration information acquisition unit 61 acquires information about the refrigerant concentration detected by the above-described refrigerant sensor 23. As described above, the refrigerant sensor 23 constantly detects the refrigerant concentration. Therefore, the refrigerant concentration information acquisition unit 61 also constantly acquires information about the refrigerant concentration detected by the refrigerant sensor 23.

[0038] The information regarding the refrigerant concentration may be acquired by the refrigerant concentration information acquisition unit 61 from the refrigerant sensor 23, or the refrigerant sensor 23 may transmit the information to the refrigerant concentration information acquisition unit 61.

[0039] The memory unit 62 stores, for example, information regarding the refrigerant concentration acquired by the refrigerant concentration information acquisition unit 61 and a threshold value used by the determination unit 63 when determining whether or not there is a refrigerant leak, as described below.

[0040] The threshold value described above is used by determination unit 63 to determine whether a refrigerant leak has occurred, and is set in advance. That is, the threshold value used here (hereinafter referred to as the "concentration threshold value") is set on the assumption that, when the refrigerant concentration indicates a value equal to or greater than the concentration threshold value, a flammable concentration region may be formed near the air outlet if refrigerant continues to leak. Specifically, the value is set within the range from the lower limit of the refrigerant concentration measurable by refrigerant sensor 23 to a concentration of ¼ of the LFL, for example.

[0041] Furthermore, the agitation operation is performed when the determination unit 63 determines that the refrigerant concentration is equal to or greater than the concentration threshold value. Therefore, the storage unit 62 also stores information regarding the rotation speed of the indoor fan 22 when the agitation operation is performed, an execution program for performing the agitation operation, and the like.

[0042] The stirring operation is performed to prevent the refrigerant concentration from becoming locally high and creating a flammable concentration region in the living space L. Therefore, after a preset time has elapsed since the stirring operation was started, the refrigerant concentration in the air in the living space L is generally averaged out and the refrigerant concentration decreases.

[0043] Therefore, for the agitation operation, whether or not the refrigerant concentration has increased is determined after a preset time has elapsed to determine whether or not to continue the agitation operation. The memory unit 62 also stores the preset time for starting this determination.

[0044] The storage unit 62 also stores a threshold value (increase threshold value) related to the increase in the refrigerant concentration, which is used to determine whether the refrigerant concentration has increased. For example, the increase threshold value is set to zero, and if the determination unit 63 determines that the change in the refrigerant concentration per unit time (increase) detected by the refrigerant sensor 23 is smaller than the increase threshold value, as will be described later, the refrigerant concentration has not increased, and the stirring operation is terminated.

[0045] The determination unit 63 determines whether or not to perform an agitation operation based on a refrigerant leak. Specifically, the determination unit 63 obtains information about the refrigerant concentration acquired by the refrigerant concentration information acquisition unit 61, and compares the information with the concentration threshold value that is set in advance and stored in the storage unit 62 to determine whether or not an agitation operation is necessary.

[0046] If the refrigerant concentration indicates a value equal to or greater than the concentration threshold value, the determination unit 63 determines that it is necessary to perform the agitation operation. When the determination unit 63 makes such a determination, the determination unit 63 accesses the storage unit 62 and acquires information related to the rotation speed of the indoor fan 22 required for the agitation operation, which information is stored in the storage unit 62. Then, the determination unit 63 instructs the indoor fan control unit 64 to drive the indoor fan 22 at the acquired rotation speed.

[0047] The rotation speed of the indoor fan 22 is a rotation speed that can supply the air volume required for the stirring operation described below to the living space L. When the stirring operation is performed, the indoor fan control unit 64 controls the driving of the indoor fan 22 so that a preset air volume is achieved.

[0048] On the other hand, if the determination unit 63 determines that the refrigerant concentration is lower than the concentration threshold value, the stirring operation is not necessary. Therefore, the stirring operation is not performed, and the determination unit 63 does not issue an instruction to the indoor fan control unit 64.

[0049] Here, when a stirring operation is required due to a refrigerant leak, the airflow rate Q [m 3 / h] is set as follows:

[0050] Q>(W+w) / LFL···(1)

[0051] where W [kg / h] is the assumed leakage rate of the refrigerant, w [kg / h] is the assumed suction rate of the refrigerant drawn into the indoor unit 2, and LFL [kg / m 3 ] indicates the lower flammable concentration of the refrigerant.

[0052] Looking at formula (1), it can be seen that not only the assumed refrigerant leakage rate W but also the assumed suction rate w is taken into consideration when setting the air volume Q. This point will be explained using Fig. 3. Fig. 3 is a schematic diagram showing the assumed refrigerant leakage rate W and the assumed refrigerant suction rate w in an indoor unit 2 installed in a living space L in a refrigeration cycle apparatus S according to an embodiment of the present invention.

[0053] The indoor unit 2 shown in Fig. 3 is an indoor unit of a type that is installed with its back surface fixed to the wall of the living space L in which it is installed. As described above, when the indoor fan 22 rotates, the indoor unit 2 blows out air that has exchanged heat with the refrigerant in the indoor heat exchanger 21 into the living space L. In Fig. 3, the air blown out from the indoor unit 2 is indicated by a long downward arrow M.

[0054] Naturally, with regard to the air that exchanges heat with the refrigerant in the indoor heat exchanger 21, the rotation of the indoor fan 22 causes the air in the living space L to be drawn into the indoor unit 2 from the ceiling side of the indoor unit 2. In Fig. 3, the air drawn into the indoor unit 2 is indicated by a short arrow N on the ceiling side of the living space L.

[0055] If refrigerant leaks in the indoor unit 2, the leaked refrigerant is blown out from the indoor unit 2 into the living space L together with the air drawn into the indoor unit 2, as shown by arrow M in Figure 3. Therefore, if refrigerant leaks inside the indoor unit 2 and the concentration of refrigerant inside the indoor unit 2 increases, a corresponding amount of refrigerant will be blown out together with the air. The refrigerant and air blown out from the indoor unit 2 are supplied to the living space L, so the concentration of refrigerant in the air in the living space L also gradually increases.

[0056] Therefore, the concentration of the refrigerant in the air drawn in for heat exchange with the refrigerant in the indoor unit 2 also gradually increases, as indicated by the arrow N in Fig. 3. The control in Patent Document 1 described above takes into account the refrigerant in the air that is blown out, but does not take into account the refrigerant in the air that is drawn in.

[0057] As described above, if refrigerant leaks, it is blown out together with air into the living space L, which may increase the absolute amount of leaked refrigerant in the blown air. Therefore, for example, there is a possibility that an area where the refrigerant concentration is equal to or higher than the LFL may be formed near the air outlet of the indoor unit.

[0058] Therefore, if the air volume during stirring operation is controlled without considering the refrigerant contained in the sucked air, as in the control described in Patent Document 1, a flammable concentration region may occur in the living space L. Therefore, when performing stirring operation in the refrigeration cycle device S in the embodiment of the present invention, not only the expected leakage rate W of the refrigerant but also the expected suction rate w is taken into consideration.

[0059] As described above, the air volume Q can be calculated from equation (1). The rotation speed of the indoor fan 22 when performing the stirring operation is set to a rotation speed at which air can be blown into the living space L at the set air volume Q. Here, the estimated leakage rate W, estimated suction rate w, and lower flammability limit concentration LFL of the refrigerant in equation (1) are values ​​that are set in advance. Therefore, the air volume Q can also be calculated in advance and is stored in the storage unit 62, for example.

[0060] Here, the assumed leak rate W is assumed to be, for example, "15 kg / h," "10 kg / h," or "7.5 kg / h." Of these, "15 kg / h" is a value that is an international standard defined by the International Electrotechnical Commission (IEC).

[0061] This value is the value adopted as a test condition for IEC leak simulation tests, and is the refrigerant leakage rate when 1 kg of flammable refrigerant R290 is charged into refrigerant circuit C and the entire amount leaks out in 4 minutes. In other words, the refrigerant leakage rate when the entire amount of 1 kg of refrigerant leaks out in 4 minutes is "15 kg / h."

[0062] Furthermore, the refrigerant leakage rate of "7.5 kg / h" is half the "15 kg / h" value used as the test condition for the IEC leakage simulation test mentioned above, and is the refrigerant leakage rate under the condition that 500 g of flammable refrigerant R290 is sealed in refrigerant circuit C and the entire amount of 500 g leaks out in 4 minutes.

[0063] The reason why we also considered the assumed leak rate W of "7.5 kg / h" is that not all air conditioners that use flammable refrigerants have 1 kg of R290 sealed in the refrigerant circuit. Smaller air conditioners are not filled with such an amount, so this is a more realistic assumed leak rate W for some indoor units.

[0064] In other words, the case where the assumed leak rate W is "15 kg / h" is the case where the risk is highest when a flammable refrigerant is filled into the refrigerant circuit C. Therefore, if the air volume Q can be set to correspond to this assumed leak rate W, it is thought that the formation of a flammable concentration region can be suppressed, and safety can be further improved.

[0065] In contrast, "10 kg / h" is a refrigerant leakage rate that was once adopted as an international standard. In the above-mentioned Cited Document 1, this value is adopted as the refrigerant leakage rate.

[0066] As such, the international standard requires that the entire amount of refrigerant leaks within four minutes as a test condition. Therefore, in the event of a refrigerant leak, the air volume Q is set taking into account not only the assumed leak rate W but also the assumed suction rate w to determine the air volume required to perform stirring operation in order to reduce the flammable concentration region or prevent its formation.

[0067] That is, based on the above international standards, the amount of leaked refrigerant is the largest when 4 minutes have elapsed since the refrigerant leakage, and it can be said that this is the most dangerous state after the refrigerant leakage. And the risk of ignition in the living space L at this time can be considered by "the volume of combustible gas (the volume of the combustible concentration region) [m 3 / the volume of the indoor space [m 3 ". Therefore, in order to ensure reliable safety at this time, in the refrigeration cycle device S in the embodiment of the present invention, control is performed so as to execute a stirring operation so that the region (combustible concentration region) that becomes LFL or more is the smallest at the time when 4 minutes have elapsed.

[0068] As described using FIG. 3, as the refrigerant concentration in the air of the living space L increases, the assumed suction speed w also increases accordingly. That is, if the assumed leakage speed W is large, the assumed suction speed w is also large, and if the assumed leakage speed W is small, the assumed suction speed w is also small. Therefore, the assumed suction speed w is determined based on the assumed leakage speed W.

[0069] The assumed suction speed w in the embodiment of the present invention is set so as to have a relationship of 0.35W < w < 0.75W based on the assumed leakage speed W. As can be seen from Equation (1), when the assumed suction speed w is set to "0.35W", the air volume Q becomes smaller than when the assumed suction speed w is set to "0.75W". Therefore, the assumed suction speed w is set depending on how much the risk when the flammable refrigerant leaks is estimated.

[0070] Therefore, regarding the control effect of the refrigeration cycle device S in the embodiment of the present invention, it will be described below using FIGS. 4 and 5 in comparison with the prior art documents. FIG. 4 is an explanatory diagram for explaining the comparison result with Patent Document 1 from the viewpoint of the combustible volume regarding the control in the refrigeration cycle device S according to the embodiment of the present invention. FIG. 5 is an explanatory diagram for explaining the comparison result with Patent Document 1 from the viewpoint of the risk reduction rate regarding the control in the refrigeration cycle device S according to the embodiment of the present invention.

[0071] First, we will explain Figure 4, which shows the simulation results for the flammable volume. In the explanatory diagram of Figure 4, the column direction is the air volume Q [m 3 / h], and the air volume gradually decreases from left to right. The maximum air volume is 700 [m 3 / h], and the minimum airflow is 200 [m 3 / h]".

[0072] The row direction indicates the assumed leakage speed W of the refrigerant (however, in the explanatory diagram of FIG. 4, it is simply indicated as "leak speed"). The assumed leakage speed W includes the three types of speeds as described above.

[0073] For example, in the above-mentioned prior art document, the required air volume Q is calculated when the refrigerant is R290, and in this case, the LFL is 0.038 [kg / m 3 ]. Also, as mentioned above, the assumed leakage rate W is "10 kg / h". In this case, the air volume Q is 263 [m 3 / h]. In the simulation results of Figure 4, the closest value of air volume Q is 265 [m 3 / h], and the flammable volume in this case is 0.0477 [m 3 ]".

[0074] In addition, when a simulation is performed based on the above assumptions for R290 in the prior art document, the air volume Q in the case of "15 kg / h" in the prior art document is approximately 395 m 3 / h], and the flammable volume in this case is 0.0474 [m 3 ]" is estimated to be

[0075] In addition, for the assumed leak rates W of "10 kg / h" and "15 kg / h" in the above-mentioned prior art documents, the margin of the explanatory diagram in Figure 4 indicates, for example, (prior art document_15 kg / h).

[0076] In this case, if 1 kg of R290 filled in the refrigerant circuit leaks out completely within 4 minutes, and the agitation operation is performed at the air volume Q indicated in the prior art document, the flammable volume will be 0.0474 [m 3 However, as mentioned above, the prior art documents take into account the assumed leakage rate W, but do not consider the assumed suction rate W at all. Therefore, the air volume Q in the case of "15 kg / h" in the above prior art documents is estimated to be approximately 395 [m 3 / h], it is unclear whether this will reliably prevent the occurrence of flammable concentration regions.

[0077] Thus, the air volume Q in the prior art document is 395 [m 3 / h], the flammable volume is 0.0474 [m 3 ]". As is clear from the explanatory diagram in Figure 4, the larger the air volume Q, the smaller the flammable volume. Assuming that the assumed leakage rate W is "15 kg / h", for example, when the air volume Q is 500 [m 3 / h], the flammable volume is 0.0187 [m 3 ]", 700[m 3 / h], the flammable volume is 0.0049 [m 3 Therefore, the larger the air volume Q, the smaller the flammable volume.

[0078] Next, the risk when such a flammable volume exists will be explained based on the explanatory diagram of FIG. 5. The explanatory diagram of FIG. 5 has the same contents shown in the column direction and row direction as the explanatory diagram of FIG. 4. In addition, when the air volume Q in the above-mentioned prior art document is 395 [m 3 / h], and the risk is set to "1" when the expected suction speed w is "15 kg / h," then let's look at what happens when the air volume Q increases.

[0079] For example, if the air volume Q is 500 m 3 / h], the flammable volume is 0.0187 [m 3 ]”, so the air volume Q is 395 [m 3 / h], the flammable volume is 0.0474 [m 3 ], its flammable volume is approximately 0.39 times smaller. Because the flammable volume is smaller, the risk is reduced accordingly. For this reason, the risk reduction rate is shown as 0.39 in the explanatory diagram in Figure 5.

[0080] Similarly, if the air volume Q is 600 [m 3 / h], the risk reduction rate is "0.22". Therefore, as mentioned above, if the air volume Q is 550 [m 3 / h], the air volume Q is 395 [m 3 / h], the risk reduction rate is roughly 3 / 10.

[0081] Furthermore, the air volume Q is 700 [m 3 / h], the risk reduction rate is "0.10", so the air volume Q is 395 [m 3 / h], the risk is reduced to 1 / 10.

[0082] In addition, in the prior art documents, the air volume Q is calculated on the assumption that the assumed leak rate W is 10 kg / h, as mentioned above. In other words, when the assumed leak rate W is 10 kg / h, the air volume Q is 265 m 3 / h], and the flammable volume in this case is "0.0477" [m 3 ]".

[0083] So, this air volume Q is 265 [m 3 / h], the risk reduction rate is set to "1", and the air volume Q is 550 [m 3 / h], the risk reduction rate can be estimated to be approximately 3 / 100, and the air volume Q is 700 [m 3 / h], the risk reduction rate is approximately 1 / 100.

[0084] Therefore, if the refrigerant leaks into the living space L, the fastest assumed leakage speed W is used as the standard, and the air volume Q is at least 550 m 3 / h] or more, and more preferably 700 [m 3 / h] or more, it is possible to achieve even better effects than those disclosed in the prior art documents.

[0085] Therefore, as explained above, when setting the air volume during stirring operation, not only the expected leakage speed but also the expected suction speed is taken into consideration, and by controlling the indoor fan to achieve the air volume as described above, greater safety can be ensured even if refrigerant leaks into the living space.

[0086] As explained above, the determination unit 63 starts the agitation operation when it determines that the refrigerant concentration detected by the refrigerant sensor 23 is equal to or greater than the concentration threshold. However, from the start of the agitation operation, the determination unit 63 starts the agitation operation when it determines that the refrigerant concentration detected by the refrigerant sensor 23 is equal to or greater than the concentration threshold. 3 / h] or more, and more preferably 700 [m 3 It is not necessary to control the rotation speed of the indoor fan 22 so that the rotation speed is equal to or greater than [rpm] / h.

[0087] That is, these preferable values ​​of air volume Q are set taking into consideration the flammable volume four minutes after the refrigerant leaks, which does not mean that the amount of refrigerant leaking will be the same as that four minutes after the initial leak.

[0088] Therefore, the indoor fan control unit 64 may control the air volume when blowing air from the indoor fan 22 to the living space L to gradually increase from the time when the refrigerant sensor 23 detects a refrigerant leak. This reduces the power consumption caused by driving the indoor fan 22. Various methods can be used to increase the air volume, such as gradually increasing the air volume every time a predetermined time elapses.

[0089] Furthermore, when the determination unit 63 determines that the refrigerant concentration detected by the refrigerant sensor 23 is equal to or greater than the concentration threshold, the stirring operation is started, but as a result of the stirring operation being performed, the refrigerant concentration does not increase from when the stirring operation started, or the refrigerant concentration in the living space L gradually decreases. If the living space L reaches this state, it can be considered that safety is ensured even if a refrigerant leak has occurred.

[0090] Therefore, the determination unit 63 performs the stirring operation for a preset time (for example, 10 minutes), and then determines the concentration of the refrigerant detected by the refrigerant sensor 23. The preset time here is the time stored in the storage unit 62 as described above.

[0091] The determination of the refrigerant concentration is a determination of whether or not an increase in the refrigerant concentration detected by refrigerant sensor 23 is recognized. Specifically, determination unit 63 first calculates the amount of increase per unit time of the refrigerant concentration detected by refrigerant sensor 23. Then, determination unit 63 compares the amount of increase with an increase amount threshold (for example, 0) stored in storage unit 62.

[0092] When the determination unit 63 compares the increase in the refrigerant amount with the increase threshold and finds that the former is greater than the latter, it can determine that the refrigerant concentration detected by the refrigerant sensor 23 is increasing. In such a case, the stirring operation continues.

[0093] On the other hand, when the determination unit 63 compares the increase in the refrigerant amount with the increase threshold and the former value is equal to or less than the latter value, it can be determined that the refrigerant leakage has ended. In this case, since no increase in the refrigerant concentration is recognized, the determination unit 63 instructs the indoor fan control unit 64 to stop the stirring operation.

[0094] When the determination unit 63 determines to stop the execution of the agitation operation, the indoor fan control unit 64 can also immediately stop the indoor fan 22. Alternatively, the indoor fan control unit 64 can perform intermittent operation in which the indoor fan 22 is alternately driven and stopped after performing the agitation operation for a preset time period until the execution of the agitation operation is stopped.

[0095] When the stirring operation is performed intermittently, the determination of the refrigerant concentration by the determination unit 63 is performed while the indoor fan 22 is stopped. That is, the determination is made based on the refrigerant concentration detected by the refrigerant sensor 23 while the indoor fan 22 is stopped.

[0096] This is because the indoor fan 22 is driven while the stirring operation is being performed, and indoor air is constantly being taken into the indoor unit 2. Therefore, it may not be possible to accurately determine whether or not the refrigerant leakage is continuing from the detection value (amount of increase in concentration) of the refrigerant sensor 23.

[0097] [Operation] Next, the flow of the agitation operation in the event of the above-mentioned flammable refrigerant leak will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the flow of control of the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0098] Determination unit 63 determines whether or not a refrigerant leaks (ST1). More specifically, as described above, refrigerant sensor 23 constantly detects the concentration of the refrigerant. Information about the concentration of the refrigerant detected by refrigerant sensor 23 is acquired by refrigerant concentration information acquisition unit 61.

[0099] The determination unit 63 acquires information about the refrigerant concentration from the refrigerant concentration information acquisition unit 61, and also acquires a concentration threshold value used to determine whether or not to perform the stirring operation from the storage unit 62. Then, it determines whether or not a refrigerant leak has occurred (ST2). Specifically, the obtained information about the refrigerant concentration is compared with the concentration threshold value.

[0100] If the determination unit 63 determines that the refrigerant concentration is smaller than the concentration threshold value as a result of the comparison, it determines that there is no refrigerant leakage (NO in ST2). Therefore, in this case, the determination as to whether there is a refrigerant leakage continues.

[0101] On the other hand, if the determination unit 63 determines that the refrigerant concentration is equal to or greater than the concentration threshold value as a result of the comparison, it determines that refrigerant is leaking (YES in ST2), and therefore starts processing to perform the stirring operation.

[0102] That is, the determination unit 63 controls the indoor fan control unit 64 to control the indoor fan to a preset air volume Q, and starts the stirring operation (ST3). As described above, the air volume Q is set in advance and stored in the storage unit 62 in association with the rotation speed of the indoor fan 22. Therefore, the determination unit 63 transmits information about the air volume Q to the indoor fan control unit 64. The indoor fan control unit 64 controls the rotation speed of the indoor fan 22 to a rotation speed associated with the air volume Q.

[0103] Thereafter, the determination unit 63 determines whether a preset time has elapsed (ST4). In Fig. 6, the "preset time" is represented as a "predetermined time." If the predetermined time has not elapsed (NO in ST4), the stirring operation continues.

[0104] On the other hand, if determination unit 63 determines that the predetermined time has elapsed (YES in ST4), determination unit 63 further determines whether the refrigerant concentration is increasing (ST5). Specifically, as described above, determination unit 63 acquires information about the refrigerant concentration detected by refrigerant sensor 23 via refrigerant concentration information acquisition unit 61. Then, determination unit 63 calculates the amount of increase per unit time of the detected refrigerant concentration and compares this amount of increase with an increase amount threshold stored in storage unit 62. As a result, if determination unit 63 determines that the amount of increase in the refrigerant concentration is higher than the increase amount threshold (YES in ST5), the stirring operation continues.

[0105] On the other hand, when the determination unit 63 determines that there is no increase in the refrigerant concentration as a result of comparing the increase in the refrigerant concentration with the increase threshold value (NO in ST5), the determination unit 63 instructs the indoor fan control unit 64 to end the stirring operation. Then, the indoor fan control unit 64 stops the rotation of the indoor fan 22, thereby ending the stirring operation (ST6).

[0106] At this time, as described above, after the stirring operation is performed for a predetermined period of time, it is also possible to perform intermittent operation in which the indoor fan 22 is alternately driven and stopped until the stirring operation is stopped.

[0107] As explained above, when setting the airflow rate during agitation operation, a more appropriate airflow rate can be set by taking into consideration not only the expected leakage rate but also the expected suction rate. Therefore, sufficient safety can be ensured even when a flammable refrigerant is used as the refrigerant for the air conditioner.

[0108] It should be noted that the present invention is not limited to the above-described embodiment, but is merely an example of the present invention. In the implementation stage, the components can be modified and embodied without departing from the spirit of the invention, and various changes and improvements can be made to the above-described embodiment. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiment.

[0109] For example, some components may be deleted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be combined as appropriate, and such modified or improved forms may also be included in the present invention. Such embodiments and their modifications are included in the scope and spirit of the inventions, and are also included in the scope of the inventions and their equivalents as defined in the claims.

[0110] In the above description, the determination of the presence or absence of refrigerant leakage as a determination of whether to start the stirring operation is based on the premise that the refrigeration cycle apparatus S is in operation. However, this determination may be performed not only when the refrigeration cycle apparatus S is in operation, but also when the operation is stopped.

[0111] In this way, while operation is stopped, the judgment unit 63 judges whether or not there is a refrigerant leak, and if it is determined that there is a leak, the indoor fan control unit 64 controls the indoor fan 22 to operate at a rotation speed that results in an air volume Q.

[0112] On the other hand, if a leak is detected during operation of the refrigeration cycle device S, the indoor fan control unit 64 controls the rotation speed of the indoor fan 22, which has been driven up until then, to a rotation speed that will result in the air volume Q.

[0113] The techniques described in the embodiments of the present invention may also be configured as follows. (1) a refrigerant circuit in which a flammable refrigerant circulates; an indoor unit that houses some of the equipment connected to the refrigerant circuit and has an indoor fan and a refrigerant sensor that detects the concentration of the refrigerant; a control device that controls the indoor unit, The control device When the refrigerant concentration detected by the refrigerant sensor is compared with a preset threshold value and it is determined that the refrigerant concentration is equal to or higher than the threshold value, the indoor fan is controlled to have an airflow rate Q [m 3 / h] and stirring is performed. The lower flammable limit of the refrigerant is defined as LFL [kg / m 3 ], the assumed leakage rate of the refrigerant is W [kg / h], and the assumed suction rate of the refrigerant drawn into the indoor unit is w [kg / h], The air volume Q, the lower flammability limit concentration LFL, the assumed leak rate W, and the assumed suction rate w are Q>(W+w) / LFL A refrigeration cycle device characterized by satisfying the following relationship. (2) The assumed suction speed w has a relationship of 0.35W < w < 0.75W with the assumed leakage speed W, and the refrigeration cycle device according to (1) above is characterized by this. (3) The refrigerant is R290, and the air volume Q satisfies the relationship of Q > 550 [m 3 / h], and the refrigeration cycle device according to (2) above is characterized by this. (4) The refrigerant is R290, and the air volume Q satisfies the relationship of Q > 700 [m 3 / h], and the refrigeration cycle device according to (2) above is characterized by this. (5) When executing the stirring operation, the control device controls the air volume from the indoor fan to gradually increase from when the refrigerant sensor detects the leakage of the refrigerant, and the refrigeration cycle device according to any one of (1) to (4) above is characterized by this. (6) After the control device executes the stirring operation for a preset time, it determines the concentration of the refrigerant detected by the refrigerant sensor. When it is determined that no increase in the concentration of the refrigerant is recognized, the execution of the stirring operation is stopped, and the refrigeration cycle device according to any one of (1) to (5) above is characterized by this. (7) After the control device executes the stirring operation for a preset time, until the execution of the stirring operation is stopped, it performs an intermittent operation of alternately driving and stopping the indoor fan, and the refrigeration cycle device according to (7) above is characterized by this.

Explanation of symbols

[0114] 1 ··· Compressor, 2 ··· Indoor unit, 21 ··· Indoor heat exchanger, 22 ··· Indoor fan, 23 ··· Refrigerant sensor, 3 ··· Pressure reducing mechanism, 4 ··· Outdoor unit, 5 ··· Four-way valve, C ··· Refrigerant circuit, L ··· Refrigeration cycle device, S ··· Refrigeration cycle device

Claims

1. a refrigerant circuit in which a flammable refrigerant circulates; an indoor unit that houses some of the equipment connected to the refrigerant circuit and has an indoor fan and a refrigerant sensor that detects the concentration of the refrigerant; a control device that controls the indoor unit, The control device When the concentration of the refrigerant detected by the refrigerant sensor is compared with a preset threshold value and it is determined that the concentration of the refrigerant is equal to or higher than the threshold value, the indoor fan is controlled to an airflow rate Q [m ３ / h] to carry out the stirring operation, The lower flammable limit concentration of the refrigerant is expressed as LFL [kg / m ３ ], the assumed leakage rate of the refrigerant is W [kg / h], and the assumed suction rate of the refrigerant drawn into the indoor unit is w [kg / h], The air volume Q, the lower flammability limit concentration LFL, the assumed leak rate W, and the assumed suction rate w are expressed as follows: Q>(W+w) / LFL A refrigeration cycle device characterized by satisfying the following relationship.

2. 2. The refrigeration cycle device according to claim 1, wherein the assumed suction speed w has a relationship with the assumed leakage speed W such that 0.35W<w<0.75W.

3. The refrigerant is R290, and the air volume Q is Q>550 [m ３ 3. The refrigeration cycle device according to claim 2, wherein the relationship of [times] / h is satisfied.

4. The refrigerant is R290, and the air volume Q is Q>700 [m ３ 3. The refrigeration cycle device according to claim 2, wherein the relationship of [times] / h is satisfied.

5. 2. The refrigeration cycle apparatus according to claim 1, wherein, when performing the stirring operation, the control device controls the air volume from the indoor fan to gradually increase from when the refrigerant sensor detects the refrigerant leakage.

6. 2. The refrigeration cycle device according to claim 1, wherein the control device performs the stirring operation for a predetermined time, then determines the concentration of the refrigerant detected by the refrigerant sensor, and stops the stirring operation if it determines that an increase in the concentration of the refrigerant is not observed.

7. 7. The refrigeration cycle apparatus according to claim 6, wherein the control device performs an intermittent operation in which the indoor fan is alternately driven and stopped after the stirring operation has been performed for a predetermined time period until the stirring operation is stopped.

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