JP6797262B2 - Refrigeration cycle equipment - Google Patents

Description

The present invention relates to a refrigeration cycle device such as a heat pump type water heater.

As a conventional refrigeration cycle device, for example, one in which at least a compressor, a condenser, a throttle device, and an evaporator are sequentially connected to form a refrigerant circuit and HFO-1234yf is used as a refrigerant has been proposed (for example, a patent). Reference 1).

Japanese Unexamined Patent Publication No. 2011-252638

The refrigerant used in Patent Document 1 is, for example, a refrigerant having a higher boiling point than a refrigerant such as R407C or R410A. Therefore, it is necessary to lower the evaporation temperature of the refrigerant, and when the evaporation temperature is lowered, the suction pressure of the compressor is lowered. In particular, when the heating operation is performed under a low outside air temperature condition, the suction pressure of the compressor is operated in a negative pressure state lower than the atmospheric pressure. As a result, the compressor may malfunction due to the suction of air.

The present invention has been made to solve the above problems, and provides a refrigeration cycle device for preventing malfunction due to air suction of a compressor.

The refrigeration cycle apparatus according to the present invention includes a circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected to circulate a refrigerant, a discharge gas bypass circuit in which a discharge side and a suction side of the compressor are connected, and the like. A suction bypass circuit that connects the outlet side of the condenser and the expansion valve, the suction side of the compressor, and the discharge side of the compressor, and the outlet side of the expansion valve and the evaporator are connected. The starting setting is the refrigerant discharge bypass circuit, the refrigerant discharge valve that opens and closes in the refrigerant discharge bypass circuit, the suction pressure sensor that detects the suction pressure of the compressor, and the suction pressure that is detected by the suction pressure sensor. A control device that starts a negative pressure prevention operation to prevent the suction pressure of the compressor from becoming negative under conditions including less than pressure and controls the operation of the refrigerant discharge valve, and an outside air temperature sensor that detects the outside air temperature. And an evaporator outlet temperature sensor that detects the temperature of the refrigerant flowing out of the evaporator as the outlet temperature, and the control device measures the outside air temperature detected by the outside air temperature sensor from the outlet temperature detected by the compressor outlet temperature sensor. Under conditions including that the subtracted value is lower than the first set temperature of the discharge valve, the refrigerant discharge valve is opened and the outside air temperature detected by the outside air temperature sensor is subtracted from the outlet temperature detected by the compressor outlet temperature sensor. The refrigerant discharge valve is provided with a valve control means for closing the refrigerant discharge valve under conditions including a value higher than the first set temperature of the discharge valve.

In the refrigeration cycle apparatus of the present invention, the gas refrigerant flowing through the discharge gas bypass circuit and the gas refrigerant flowing through the suction bypass circuit are merged to raise the temperature on the suction side of the compressor so that the suction pressure of the compressor becomes a negative pressure. By preventing this, it is possible to avoid malfunction of the compressor.

It is a figure which shows the refrigerant circuit and the system configuration of the refrigerating cycle apparatus which concerns on Embodiment 1 of this invention. It is a graph comparing the relationship between the saturation temperature of various refrigerants and the saturated vapor pressure. It is a flowchart which shows the control procedure of the negative pressure prevention operation of the refrigeration cycle apparatus which concerns on Embodiment 1 of this invention. It is a Ph diagram which shows the operation state of the negative pressure prevention operation in the refrigeration cycle apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the refrigerant circuit and the system configuration of the refrigerating cycle apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows the control procedure of the refrigerant discharge valve during the negative pressure prevention operation of the refrigeration cycle apparatus which concerns on Embodiment 2 of this invention. It is a flowchart of the modification 1 which shows the control procedure of the refrigerant discharge valve during the negative pressure prevention operation of the refrigeration cycle apparatus which concerns on Embodiment 2 of this invention. It is a flowchart of the modification 2 which shows the control procedure of the refrigerant discharge valve during the negative pressure prevention operation of the refrigeration cycle apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the refrigerant circuit and the system configuration of the refrigerating cycle apparatus which concerns on Embodiment 3 of this invention. It is a flowchart which shows the control procedure of the air mixture detection in the refrigerant circuit of the refrigerating cycle apparatus which concerns on Embodiment 3 of this invention. It is a figure which shows the refrigerant circuit and the system structure of the modification 1 of the refrigerating cycle apparatus which concerns on Embodiment 3 of this invention. It is a figure which shows the refrigerant circuit and the system structure of the modification 2 of the refrigerating cycle apparatus which concerns on Embodiment 3 of this invention. It is a flowchart of the modification 2 which shows the control procedure of the air mixture detection in the refrigerant circuit of the refrigerating cycle apparatus which concerns on Embodiment 3 of this invention.

Embodiment 1.
FIG. 1 is a diagram showing a refrigerant circuit and a system configuration of the refrigeration cycle device according to the first embodiment of the present invention. FIG. 1 shows a state when a heating operation (hot water supply operation) for raising the temperature of water on the load side is performed.

The refrigerating cycle device 100 includes a refrigerant circuit 30 in which a compressor 1, a condenser 3, an expansion valve 4, and an evaporator 5 are connected and a refrigerant circulates. In FIG. 1, the refrigerating cycle device 100 includes a flow path switch 2 in the refrigerant circuit 30, but the installation of the flow path switch 2 is optional.

The compressor 1 is composed of, for example, a rotary type, scroll type, or vane type compressor whose capacity is controllably controlled by an inverter, and sucks and compresses a low temperature low pressure gas refrigerant into a state of a high temperature high pressure gas refrigerant. Is discharged. The flow path switch 2 is composed of, for example, a four-way valve, and switches the direction between the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 and the low-temperature and low-pressure gas refrigerant sucked into the compressor 1. The condenser 3 is composed of, for example, a plate heat exchanger, and dissipates heat by exchanging heat between the refrigerant flowing through the refrigerant circuit 30 and the heat exchange medium supplied from the cooling load (not shown). .. The expansion valve 4 decompresses the high-pressure refrigerant into a low-pressure two-phase refrigerant. The evaporator 5 is composed of, for example, a plate fin type heat exchanger or the like, and evaporates the refrigerant by heat exchange with air.

The refrigeration cycle device 100 connects a discharge gas bypass circuit 6 that connects the discharge side and the suction side of the compressor 1, between the outlet side of the condenser 3 and the expansion valve 4, and the suction side of the compressor 1. It includes a suction bypass circuit 8 to be connected, and a refrigerant discharge bypass circuit 10 to connect the discharge side of the compressor 1 and the outlet side of the expansion valve 4 and the evaporator 5. The refrigeration cycle device 100 is further arranged in the refrigerant discharge bypass circuit 10, and the refrigerant discharge valve 11 that opens and closes, the discharge gas bypass valve 7 that adjusts the flow rate of the refrigerant flowing through the discharge gas bypass circuit 6, and the suction bypass circuit 8 A suction bypass valve 9 for adjusting the flow rate of the refrigerant flowing into the water is provided.

The discharge gas bypass circuit 6 connects the discharge side and the suction side of the compressor 1. The discharge gas bypass circuit 6 bypasses a part of the discharge refrigerant of the high-temperature and high-pressure gas discharged from the compressor 1 to the suction side of the compressor 1. At this time, the gas refrigerant flowing through the discharge gas bypass circuit 6 and the gas refrigerant returned from the flow path switch 2 are merged. The discharge gas bypass valve 7 is provided in the discharge gas bypass circuit 6 and adjusts the bypass amount of the discharge refrigerant flowing through the discharge gas bypass circuit 6. When the opening degree of the discharge gas bypass valve 7 is increased, the pressure is reduced, and the flow rate of the high-temperature low-pressure gas returning to the suction side of the compressor 1 through the discharge gas bypass circuit 6 increases, so that the temperature of the suction side of the compressor 1 rises. On the other hand, if the opening degree of the discharge gas bypass valve 7 is reduced, the flow rate of the high-temperature low-pressure gas returning to the suction side of the compressor 1 through the discharge gas bypass circuit 6 decreases, so that the temperature change on the suction side of the compressor 1 changes. Less.

The suction bypass circuit 8 connects the outlet side of the condenser 3 and the expansion valve 4 and the suction side of the compressor 1. The suction bypass circuit 8 merges with the discharge gas bypass circuit 6, merges the high-pressure refrigerant at the outlet of the condenser 3 with the high-temperature low-pressure gas refrigerant of the discharge gas bypass circuit 6, and flows into the suction side of the compressor 1. .. The suction bypass valve 9 is provided in the suction bypass circuit 8 and adjusts the flow rate of the refrigerant flowing through the suction bypass circuit 8 to control the degree of superheat of the suction gas of the compressor 1. When the opening degree of the suction bypass valve 9 is increased, the pressure is reduced and expanded, and the flow rate of the low-temperature low-pressure gas-liquid two-phase refrigerant flowing into the suction side of the compressor 1 through the suction bypass circuit 8 increases, so that the suction superheat degree of the compressor increases. Goes down. On the other hand, if the opening degree of the suction bypass valve 9 is reduced, the flow rate of the low-temperature low-pressure gas-liquid two-phase refrigerant flowing from the suction bypass circuit 8 to the suction side of the compressor 1 decreases, so that the suction superheat degree of the compressor 1 increases. Go up.

The refrigerant discharge bypass circuit 10 connects the discharge side of the compressor 1 with the outlet side of the expansion valve 4 and the evaporator 5. The refrigerant discharge bypass circuit 10 bypasses a part of the discharged refrigerant discharged from the compressor 1 to the refrigerant circuit 30 between the evaporator 5 and the expansion valve 4. The refrigerant discharge valve 11 is an on-off valve provided in the refrigerant discharge bypass circuit 10. By closing the expansion valve 4 and opening the refrigerant discharge valve 11, the refrigerant gas flows through the refrigerant discharge bypass circuit 10 and the liquid refrigerant in the evaporator 5 can be pushed out. The capacitance coefficient Cv value of the refrigerant discharge valve is smaller than the capacitance coefficient Cv value of the discharge gas bypass valve.

As shown in FIG. 1, the refrigeration cycle device 100 detects the temperature of the control device 15, the compressor suction pressure sensor 16 that detects the pressure on the suction side of the compressor 1, and the piping on the suction side of the compressor 1. A compressor suction temperature sensor 17 and an outside air temperature sensor 22 are provided.

The control device 15 controls the refrigeration cycle device 100. The control device 15 is composed of, for example, a microcomputer and includes a CPU, RAM, ROM, and the like. The control program and the program corresponding to the flowchart of FIG. 3 are stored in the ROM.

The control device 15 is connected to each sensor so that the signals detected by the compressor suction pressure sensor 16, the compressor suction temperature sensor 17, and the outside air temperature sensor 22 can be received. The control device 15 includes a valve control means 15a that opens and closes the expansion valve 4 and the refrigerant discharge valve 11 based on these detection signals to control the opening degree of the discharge gas bypass valve 7 and the suction bypass valve 9. The valve control means 15a controls the opening degree of the discharge gas bypass valve 7 for adjusting the bypass amount of the discharge refrigerant flowing through the discharge gas bypass circuit 6. Further, the valve control means 15a controls the opening and closing of the expansion valve 4 so as to open during normal hot water supply operation and close during negative pressure prevention operation. Further, the valve control means 15a controls the opening and closing of the refrigerant discharge valve 11 so as to push out the liquid refrigerant in the evaporator 5 during the negative pressure prevention operation. Further, the valve control means 15a controls the opening degree of the suction bypass valve 9 for adjusting the flow rate of the refrigerant flowing through the suction bypass circuit 8 so that the degree of superheat of the suction gas of the compressor 1 becomes a preset set value. To do. The valve control means 15a is functionally configured by a CPU and a control program.

The refrigeration cycle device 100 uses a refrigerant containing HFO-1234yf refrigerant or HFO-1234ze refrigerant as the refrigerant. The refrigerant may be a single refrigerant of HFO-1234yf, a single refrigerant of HFO-1234ze, or a mixed refrigerant containing HFO-1234yf or HFO-1234ze. These HFO-1234yf refrigerants or HFO-1234ze refrigerants have a global warming potential (GWP) of "4", which is lower than that of the conventional R410A refrigerant "2090" and R407C refrigerant "1770", and have an impact on the global environment. Is a small refrigerant. Here, the relationship between the saturation temperature and the saturated vapor pressure will be described for the conventionally used R410A refrigerant and R407C refrigerant, and the HFO-1234yf refrigerant and the HFO-1234ze refrigerant.

FIG. 2 is a graph comparing the relationship between the saturation temperature of various refrigerants and the saturated vapor pressure. FIG. 2 shows R410A refrigerant, R407C refrigerant, HFO-1234yf refrigerant, and HFO-1234ze refrigerant as various refrigerants. According to FIG. 2, for example, the HFO-1234yf refrigerant has a lower saturated vapor pressure than the conventionally used R410A refrigerant and R407C refrigerant. Therefore, when hot water supply operation is performed in an extremely cold region where the outside air is, for example, -25 ° C or lower, the evaporation temperature falls below the saturated steam temperature of −29.5 ° C at atmospheric pressure, and the suction pressure of the compressor 1 is large. It is expected that the operation will be negative pressure below the atmospheric pressure. When the suction pressure of the compressor 1 becomes negative, air is sucked into the refrigeration cycle, which may cause a malfunction of the refrigeration cycle. Therefore, the refrigeration cycle device 100 carries out a negative pressure prevention operation in which the hot water supply operation is continued so that the suction pressure of the compressor 1 does not become a negative pressure.

Next, the operation of the refrigeration cycle of the refrigeration cycle apparatus 100 will be described with reference to FIG. First, a normal hot water supply operation in the refrigeration cycle device 100 will be described.

The low-temperature low-pressure gas-state refrigerant is sucked into the compressor 1, compressed, and discharged as high-temperature high-pressure gas. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the condenser 3 via the flow path switch 2. The high-temperature and high-pressure gas refrigerant that has flowed into the condenser 3 dissipates heat to water, which is a heat exchange medium, and becomes a high-pressure liquid refrigerant. The high-pressure liquid refrigerant flowing out of the condenser 3 flows into the expansion valve 4 and is expanded under reduced pressure to become a low-temperature low-pressure gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant flowing out of the expansion valve 4 flows into the evaporator 5, cools the air which is the heat exchange medium, and evaporates to become a low-temperature low-pressure gas refrigerant. The low-temperature low-pressure gas refrigerant that has flowed out of the evaporator 5 passes through the flow path switch 2 again and is sucked into the compressor 1 again. During normal hot water supply operation, the discharge gas bypass valve 7, the suction bypass valve 9 and the refrigerant discharge valve 11 are fully closed, and the flow of the refrigerant in the discharge gas bypass circuit 6, the suction bypass circuit 8 and the refrigerant discharge bypass circuit 10 is Absent.

FIG. 3 is a flowchart showing a control procedure for negative pressure prevention operation of the refrigeration cycle apparatus according to the first embodiment of the present invention. Next, the operation of controlling the negative pressure prevention operation of the refrigeration cycle device 100 will be described with reference to FIGS. 1 and 3.

The control device 15 acquires the compressor suction pressure Ps detected by the compressor suction pressure sensor 16 (step S1). The control device 15 compares the compressor suction pressure Ps with the start set pressure SET1 (for example, 0.12 Mpa (abs)) which is the upper limit pressure for starting the negative pressure prevention operation (step S2). The control device 15 returns to step S1 and continues the normal hot water supply operation while the compressor suction pressure Ps is equal to or higher than the start set pressure SET1. On the other hand, when the compressor suction pressure Ps becomes less than the start set pressure SET1, the control device 15 determines that the compressor suction pressure is in an operating state close to the negative pressure, and starts the negative pressure prevention operation (step S3). ..

When the negative pressure prevention operation is started, the valve control means 15a opens the refrigerant discharge valve 11 (step S4). Next, the valve control means 15a reduces the expansion valve 4 to a fully closed or near-fully closed opening (step S5). Next, the control device 15 compares the compressor suction pressure Ps with the discharge valve set pressure SET2 (for example, 0.15 Mpa (abs)) set as the target value of the compressor suction pressure (step S6). Then, when the compressor suction pressure Ps is lower than the discharge valve set pressure SET2, the valve control means 15a increases the opening degree of the discharge gas bypass valve 7 by the set increase (step S7). On the other hand, when the compressor suction pressure Ps is higher than the discharge valve set pressure SET2, the valve control means 15a reduces the opening degree of the discharge gas bypass valve 7 by the set decrease (step S8). Although not shown in FIG. 3, when the compressor suction pressure Ps matches the discharge valve set pressure SET2, the opening degree of the discharge gas bypass valve 7 may be maintained as it is.

Next, the control device 15 acquires the compressor suction temperature Ts detected by the compressor suction temperature sensor 17 (step S9). Then, the control device 15 calculates the suction saturation temperature f (Ps) from the compressor suction pressure Ps, subtracts the suction saturation temperature f (Ps) from the compressor suction temperature Ts, and calculates the compressor suction superheat degree SHs. (Step S10). The control device 15 compares the calculated compressor suction superheat degree SHs with the suction valve set temperature SET3 (for example, 3 ° C.) set as the target value of the compressor suction superheat degree (step S11). When the compressor suction superheat degree SHs is smaller than the suction valve set temperature SET3, the valve control means 15a reduces the opening degree by the set reduction of the suction bypass valve 9 (step S12). When the compressor suction superheat degree SHs is larger than the suction valve set temperature SET3, the valve control means 15a increases the opening degree of the suction bypass valve 9 by the set increase (step S13). Although not shown in FIG. 3, when the compressor suction superheat degree SHs matches the suction valve set temperature SET3, the opening degree of the suction bypass valve 9 may be maintained as it is. Then, after the processing of step S12 or step S13, the control device 15 sets the compressor suction pressure Ps and the discharge valve set pressure SET9 (for example, 0.18 Mpa (abs)) set as the target value of the compressor suction pressure. Compare. Alternatively, the control device 15 compares the outside air temperature detected by the outside air temperature sensor 22 with the set outside air temperature SET 10 (for example, −15 ° C.) (step S14). When the compressor suction pressure Ps is lower than the discharge valve set pressure SET9, or when the outside air temperature is lower than the set outside air temperature SET10, the control device 15 returns to step S4, and the valve control means 15a discharges the refrigerant. Open valve 11. When the compressor suction pressure Ps is higher than the discharge valve set pressure SET9, or when the outside air temperature is higher than the set outside air temperature SET10, the control device 15 ends the negative pressure prevention operation and performs the normal hot water supply operation. Start (step S15).

FIG. 4 is a Ph diagram showing an operating state of negative pressure prevention operation in the refrigeration cycle apparatus according to the first embodiment of the present invention. Next, the operation of the negative pressure prevention operation in the refrigeration cycle apparatus 100 will be described with reference to the refrigerant circuit diagram of FIG. 1 and the Ph diagram of FIG. [A] to [E] in FIG. 4 indicate the refrigerant state at each position of [A] to [E] in FIG. During the negative pressure prevention operation, the opening degree of the expansion valve 4 is closed to a very small opening degree that is fully closed or substantially close to fully closed.

The low-temperature low-pressure gas-state refrigerant ([A]) is sucked into the compressor 1, compressed, and discharged as high-temperature high-pressure gas. The high-temperature and high-pressure refrigerant ([B]) discharged from the compressor 1 is branched into three, and in the first branch, the high-temperature and high-pressure refrigerant ([B]) flows into the discharge gas bypass circuit 6 to bypass the discharge gas. The pressure is reduced by the valve 7 to become a high-temperature low-pressure gas refrigerant ([C]), which is bypassed to the suction side of the compressor 1. In the second branch, the high-temperature and high-pressure refrigerant ([B]) flows into the condenser 3 via the flow path switch 2. The high-temperature high-pressure gas refrigerant flowing into the condenser 3 dissipates heat to water, which is a heat exchange medium, and becomes a high-pressure liquid refrigerant ([D]).

The high-pressure liquid refrigerant flowing out of the condenser 3 flows into the suction bypass circuit 8 and is decompressed and expanded by the suction bypass valve 9 to become a low-temperature low-pressure gas-liquid two-phase refrigerant ([E]). The high-temperature low-pressure gas ([C]) decompressed by the discharge gas bypass valve 7 and the low-temperature low-pressure gas-liquid two-phase refrigerant ([E]) decompressed and expanded by the suction bypass valve 9 merge to form a low-temperature low-pressure gas. It becomes the gas refrigerant ([A]) of No. 1 and is sucked into the compressor 1 again.

Further, during the negative pressure prevention operation, the opening degree of the expansion valve 4 is fully closed or the opening degree is extremely small, so that the low-pressure two-phase refrigerant hardly flows into the evaporator 5 through the expansion valve 4. However, heat exchange with the outside air and the high-temperature low-pressure refrigerant flowing out of the discharge gas bypass valve 7 flow into the low-temperature evaporator 5 via the flow path switch 2, so that the liquid refrigerant accumulates in the evaporator 5. I will go. As a result, the refrigerant may be insufficient during the negative pressure prevention operation, or the liquid refrigerant accumulated in the evaporator 5 at the time of switching to the normal operation may flow into the compressor 1 at once, resulting in liquid backing. Therefore, during the negative pressure prevention operation, the refrigerant discharge valve 11 is opened in the third branch, and the refrigerant discharged from the compressor 1 is allowed to flow to the evaporator 5 through the refrigerant discharge bypass circuit 10. By flowing the discharged refrigerant through the evaporator 5, the liquid refrigerant in the evaporator 5 can be pushed out, and the liquid refrigerant in the evaporator 5 can be prevented from staying.

As described above, the refrigeration cycle device 100 merges the gas refrigerant flowing through the discharge gas bypass circuit 6 and the gas refrigerant flowing through the suction bypass circuit 8 to raise the temperature on the suction side of the compressor 1 to raise the temperature of the compressor 1 of the compressor 1. By preventing the suction pressure from becoming a negative pressure and setting the suction pressure to be equal to or higher than the atmospheric pressure, it is possible to avoid malfunction of the compressor 1.

Further, when the outside air temperature is low and the suction pressure of the compressor 1 becomes close to the negative pressure, the expansion valve 4 is fully closed and the hot water supply operation is continued without evaporating the refrigerant in the evaporator 5. Then, the suction pressure of the compressor 1 is controlled by the opening degree of the discharge gas bypass valve 7. Therefore, it is possible to prevent the suction pressure of the compressor 1 from becoming a negative pressure. Further, the suction superheat degree of the compressor 1 is controlled by the opening degree of the suction bypass valve 9. Therefore, the hot water supply operation can be continued with the suction superheat degree of the compressor 1 in an appropriate state. Therefore, even if the outside air is lowered, inconveniences such as malfunction due to air suction can be avoided. Further, since it is not necessary to stop the hot water supply operation of the water heater to raise the temperature of the water even under low outside air conditions, it is possible to prevent the water pipe from freezing.

Further, by controlling the opening and closing of the refrigerant discharge valve 11 and flowing the discharged refrigerant from the compressor 1 to the evaporator 5 through the refrigerant discharge bypass circuit 10, the liquid refrigerant in the evaporator 5 can be pushed out, and the evaporator 5 can be pushed out. It is possible to prevent the liquid refrigerant inside from staying.

Further, the heating capacity during the negative pressure prevention operation is equal to or less than the input of the compressor 1 because the expansion valve 4 is closed and the evaporator 5 does not exchange heat. Therefore, it is possible to operate below the minimum heating capacity during normal operation, and the control range of the heating capacity can be expanded. In the normal operation alone, the compressor 1 can be continuously operated even at a low load in which the heating capacity is lowered by repeating the operation and the stop, and the power loss due to the start / stop operation of the compressor 1 can be reduced.

Further, since the refrigerant discharge valve 11 can be opened and the high-temperature and low-pressure refrigerant can be heated while flowing through the evaporator 5, the heating operation can be performed while defrosting the evaporator 5. Therefore, it is possible to reduce the time during which the heating operation cannot be performed during defrosting.

Embodiment 2.
FIG. 5 is a diagram showing a refrigerant circuit and a system configuration of the refrigeration cycle device according to the second embodiment of the present invention. Parts having the same configuration as the refrigeration cycle apparatus of FIGS. 1 to 4 are designated by the same reference numerals, and the description thereof will be omitted. The refrigerating cycle device 110 according to the second embodiment is different from the first embodiment in that it further includes an opening / closing step of the refrigerant discharge valve 11, and is the same except for the first embodiment.

Next, the operation of the refrigeration cycle according to the second embodiment will be described with reference to FIG. Since the normal hot water supply operation is the same as that of the first embodiment, it will be omitted, and only the negative pressure prevention operation will be described.

In the negative pressure prevention operation in the refrigeration cycle device 110 according to the second embodiment, the refrigerant in a low-temperature low-pressure gas state is sucked into the compressor 1, compressed, and discharged as a high-temperature high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 is branched into three, and in the first branch, the high-temperature and high-pressure refrigerant flows into the discharge gas bypass circuit 6 and is decompressed by the discharge gas bypass valve 7, and the high-temperature and low-pressure gas refrigerant is decompressed. And bypassed to the suction side of the compressor 1. In the second branch, the high temperature and high pressure refrigerant flows into the condenser 3 via the flow path switch 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 dissipates heat to water, which is a heat exchange medium, and becomes a high-pressure liquid refrigerant.

The high-pressure liquid refrigerant flowing out of the condenser 3 flows into the suction bypass circuit 8 and is decompressed and expanded by the suction bypass valve 9 to become a low-temperature low-pressure gas-liquid two-phase refrigerant. The high-temperature low-pressure gas decompressed by the discharge gas bypass valve 7 and the low-temperature low-pressure gas-liquid two-phase refrigerant decompressed and expanded by the suction bypass valve 9 merge to form a low-temperature low-pressure gas refrigerant, and are returned to the compressor 1. Be sucked.

Further, during the negative pressure prevention operation, the opening degree of the expansion valve 4 is fully closed or the opening degree is extremely small, so that the low-pressure two-phase refrigerant hardly flows into the evaporator 5 through the expansion valve 4. However, heat exchange with the outside air and the low-pressure high-temperature refrigerant flowing out of the discharge gas bypass valve 7 flow into the low-temperature evaporator 5 via the flow path switch 2, so that the liquid refrigerant accumulates in the evaporator 5. I will go. As a result, the refrigerant may be insufficient during the negative pressure prevention operation, or the liquid refrigerant accumulated in the evaporator 5 at the time of switching to the normal operation may flow into the compressor 1 at once, resulting in liquid backing. Therefore, during the negative pressure prevention operation, the refrigerant discharge valve 11 is controlled to open and close in the third branch, and the refrigerant discharged from the compressor 1 flows to the evaporator 5 through the refrigerant discharge bypass circuit 10. By flowing the discharged refrigerant through the evaporator 5, the liquid refrigerant in the evaporator 5 can be pushed out, and the liquid refrigerant in the evaporator 5 can be prevented from staying.

As shown in FIG. 5, the refrigeration cycle device 110 includes a control device 115, a compressor suction pressure sensor 16, a compressor suction temperature sensor 17, an evaporator outlet temperature sensor 18, and an outside air temperature sensor 22. ing.

The control device 115 controls the refrigeration cycle device 110. The control device 115 is composed of, for example, a microcomputer and includes a CPU, RAM, ROM, and the like. The control program and the program corresponding to the flowchart of FIG. 6, FIG. 7 or FIG. 8 are stored in the ROM.

The control device 115 is connected to each sensor so that the signals detected by the compressor suction pressure sensor 16, the compressor suction temperature sensor 17, the evaporator outlet temperature sensor 18, and the outside air temperature sensor 22 can be received. .. The control device 115 includes a valve control means 115a that controls the opening and closing of the expansion valve 4, the discharge gas bypass valve 7, and the suction bypass valve 9 and the opening / closing control of the refrigerant discharge valve 11 based on these detection signals. The valve control means 115a controls the opening degree of the discharge gas bypass valve 7 for adjusting the bypass amount of the discharge refrigerant flowing through the discharge gas bypass circuit 6. Further, the valve control means 115a controls the opening and closing of the expansion valve 4 so as to open during normal hot water supply operation and close during negative pressure prevention operation. Further, the valve control means 115a controls the opening and closing of the refrigerant discharge valve 11 so as to push out the liquid refrigerant in the evaporator 5 during the negative pressure prevention operation. Further, the valve control means 115a controls the opening degree of the suction bypass valve 9 for adjusting the flow rate of the refrigerant flowing through the suction bypass circuit 8 so that the degree of superheat of the suction gas of the compressor 1 becomes a preset set value. To do. The valve control means 115a is functionally configured by a CPU and a control program.

FIG. 6 is a flowchart showing a control procedure of the refrigerant discharge valve during the negative pressure prevention operation of the refrigeration cycle apparatus according to the second embodiment of the present invention. Next, the operation of the control of the refrigerant discharge valve 11 in step S4 during the negative pressure prevention operation of the refrigeration cycle device 110 will be described with reference to FIGS. 5 and 6. The negative pressure prevention operation in the refrigeration cycle device 110 is different from that of the first embodiment in that the flowchart of the first embodiment shown in FIG. 3 is further provided with an opening / closing step of the refrigerant discharge valve 11, and is the same except for the first embodiment. Is. The opening / closing step of the refrigerant discharge valve 11 may be between steps S3 and S5.

When the negative pressure prevention operation is started (step S3), the control device 115 subtracts the value obtained by subtracting the outside air temperature detected by the outside air temperature sensor 22 from the evaporator outlet temperature Tv detected by the evaporator outlet temperature sensor 18, and discharges the refrigerant. A comparison is made with the discharge valve first set temperature SET4 (for example, 3 ° C.) set as a target value for controlling the opening and closing of the valve 11 (step S4-1a). Then, when the value obtained by subtracting the outside air temperature from the evaporator outlet temperature Tv is lower than the discharge valve first set temperature SET4, the valve control means 115a opens the refrigerant discharge valve 11 (step S4-2a). On the other hand, when the value obtained by subtracting the outside air temperature from the evaporator outlet temperature Tv is higher than the discharge valve first set temperature SET4, the valve control means 115a closes the refrigerant discharge valve 11 (step S4-3a). Although not shown in FIG. 6, when the value obtained by subtracting the outside air temperature from the evaporator outlet temperature Tv matches the discharge valve first set temperature SET4, the opening and closing of the refrigerant discharge valve may be maintained as it is. ..

As described above, the refrigerating cycle device 110 discharges the refrigerant by utilizing the fact that the amount of the refrigerant accumulated in the evaporator 5 increases, so that the refrigerant temperature at the outlet of the evaporator decreases and the difference from the outside air temperature becomes small. The valve 11 is opened and closed. As a result, the amount of refrigerant flowing to the evaporator 5 for discharging the refrigerant can be minimized, and the heating loss in the evaporator 5 is reduced as compared with the case where the refrigerant discharge valve 11 is always opened, which is more efficient. You can drive. Further, the hot water supply operation can be continued without the compressor suction pressure becoming a negative pressure.

Modification example 1.
FIG. 7 is a flowchart of a modified example 1 showing a control procedure of the refrigerant discharge valve during the negative pressure prevention operation of the refrigeration cycle device according to the second embodiment of the present invention. Parts having the same configuration as the refrigeration cycle apparatus of FIGS. 1 to 6 are designated by the same reference numerals, and the description thereof will be omitted. Next, the operation of the control of the refrigerant discharge valve 11 in step S4 during the negative pressure prevention operation of the refrigeration cycle device 110 will be described with reference to FIGS. 5 and 7.

When the negative pressure prevention operation is started (step S3), the control device 115 sets the evaporator outlet temperature Tv detected by the evaporator outlet temperature sensor 18 and the discharge valve set as a target value for opening / closing the refrigerant discharge valve 11. Compare with the second set temperature SET5 (for example, −20 ° C.) (step S4-1b). Then, when the evaporator outlet temperature Tv is lower than the discharge valve second set temperature SET5, the valve control means 115a opens the refrigerant discharge valve 11 (step S4-2b). On the other hand, when the evaporator outlet temperature Tv is higher than the discharge valve second set temperature SET5, the valve control means 115a closes the refrigerant discharge valve 11 (step S4-3b). Although not shown in FIG. 7, when the evaporator outlet temperature Tv matches the discharge valve second set temperature SET5, the opening and closing of the refrigerant discharge valve may be maintained as it is.

As described above, the refrigerating cycle device 110 discharges the refrigerant by utilizing the fact that the amount of the refrigerant accumulated in the evaporator 5 increases, so that the refrigerant temperature at the outlet of the evaporator decreases and the difference from the outside air temperature becomes small. The valve 11 is opened and closed. As a result, the amount of refrigerant flowing to the evaporator 5 for discharging the refrigerant can be minimized, and the heating loss in the evaporator 5 is reduced as compared with the case where the refrigerant discharge valve 11 is always opened, which is more efficient. You can drive. Further, the hot water supply operation can be continued without the compressor suction pressure becoming a negative pressure.

Modification example 2.
FIG. 8 is a flowchart of Modification 2 showing a control procedure of the refrigerant discharge valve during the negative pressure prevention operation of the refrigeration cycle apparatus according to the second embodiment of the present invention. Parts having the same configuration as the refrigeration cycle apparatus of FIGS. 1 to 7 are designated by the same reference numerals, and the description thereof will be omitted. Next, the operation of the control of the refrigerant discharge valve 11 in step S4 during the negative pressure prevention operation of the refrigeration cycle device 110 will be described with reference to FIGS. 5 and 8.

When the negative pressure prevention operation is started (step S3), the control device 115 sets the compressor suction pressure Ps detected by the compressor suction pressure sensor 16 and the discharge valve set pressure set as target values of the compressor suction pressure Ps. Compare with SET6 (eg 0.15Mpa (abs)) (step S4-1c). Then, when the compressor suction pressure Ps is lower than the discharge valve set pressure SET6, the valve control means 115a opens the refrigerant discharge valve 11 (step S4-2c). On the other hand, when the compressor suction pressure Ps is higher than the discharge valve set pressure SET6, the valve control means 115a closes the refrigerant discharge valve 11 (step S4-3c). Although not shown in FIG. 8, when the compressor suction pressure Ps matches the discharge valve set pressure SET6, the opening and closing of the refrigerant discharge valve may be maintained as it is.

As described above, the refrigerant discharge valve 11 is opened and closed by utilizing the fact that the compressor suction pressure Ps detected by the compressor suction pressure sensor 16 decreases as the amount of the refrigerant accumulated in the evaporator 5 increases. As a result, the amount of refrigerant flowing to the evaporator 5 for discharging the refrigerant can be minimized, and the heating loss in the evaporator 5 is reduced as compared with the case where the refrigerant discharge valve 11 is always opened, which is more efficient. You can drive. Further, the hot water supply operation can be continued without the compressor suction pressure becoming a negative pressure.

Embodiment 3.
FIG. 9 is a diagram showing a refrigerant circuit and a system configuration of the refrigeration cycle device according to the third embodiment of the present invention. Parts having the same configuration as the refrigeration cycle apparatus of FIGS. 1 to 8 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 9, the refrigeration cycle device 120 of the third embodiment is the refrigeration cycle device 100 of the first embodiment provided with the receiver 12. The other components are the same as those in FIG.

The receiver 12 is arranged in a pipe connecting the condenser 3 and the suction bypass valve 9, and stores excess refrigerant generated during operation.

As shown in FIG. 9, the refrigeration cycle device 120 includes a control device 125, a compressor discharge pressure sensor 19 that detects the pressure on the discharge side of the compressor 1, and a receiver temperature that detects the pipe temperature at the inlet of the receiver 12. It includes a sensor 20 and an outside air temperature sensor 22. Although the receiver temperature sensor 20 is installed in the pipe at the inlet of the receiver 12 in FIG. 9, it may be installed in the pipe at the outlet of the receiver 12.

The control device 125 controls the refrigeration cycle device 120. The control device 125 is composed of, for example, a microcomputer and includes a CPU, RAM, ROM, and the like. The control program and the program corresponding to the flowchart of FIG. 10 or 13 are stored in the ROM.

The control device 125 is connected to each sensor so that the signals detected by the compressor discharge pressure sensor 19, the receiver temperature sensor 20, and the outside air temperature sensor 22 can be received. The control device 125 includes a compressor control means 125b that controls the output of the compressor 1 based on these detection signals. The compressor control means 125b adjusts the frequency of the compressor 1 to control the output of the compressor. The compressor control means 125b is functionally configured by a CPU and a control program. The control device 125 also includes a valve control means 15a.

Next, the operation of the refrigeration cycle according to the third embodiment will be described with reference to FIG. Since the normal hot water supply operation is the same as that of the first embodiment, it will be omitted, and only the negative pressure prevention operation will be described.

In the negative pressure prevention operation in the refrigeration cycle device 120 according to the third embodiment, the refrigerant in a low-temperature low-pressure gas state is sucked into the compressor 1, compressed, and discharged as a high-temperature high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 branches into three, and in the first branch, the high-temperature and high-pressure refrigerant flows into the discharge gas bypass circuit 6 and is decompressed by the discharge gas bypass valve 7, and the high-temperature and low-pressure gas refrigerant is decompressed. And bypassed to the suction side of the compressor 1. In the second branch, the high temperature and high pressure refrigerant flows into the condenser 3 via the flow path switch 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 dissipates heat to water, which is a heat exchange medium, and becomes a high-pressure liquid refrigerant.

The high-pressure liquid refrigerant flowing out of the condenser 3 flows into the suction bypass circuit 8 via the receiver 12, is decompressed and expanded by the suction bypass valve 9, and becomes a low-temperature low-pressure gas-liquid two-phase refrigerant. The high-temperature low-pressure gas decompressed by the discharge gas bypass valve 7 and the low-temperature low-pressure gas-liquid two-phase refrigerant decompressed and expanded by the suction bypass valve 9 merge to form a low-temperature low-pressure gas refrigerant, and are returned to the compressor 1. Be sucked.

Further, during the negative pressure prevention operation, the opening degree of the expansion valve 4 is fully closed or the opening degree is extremely small, so that the low-pressure two-phase refrigerant hardly flows into the evaporator 5 through the expansion valve 4. However, heat exchange with the outside air and the low-pressure high-temperature refrigerant flowing out of the discharge gas bypass valve 7 flow into the low-temperature evaporator 5 via the flow path switch 2, so that the liquid refrigerant accumulates in the evaporator 5. I will go. As a result, the refrigerant may be insufficient during the negative pressure prevention operation, or the liquid refrigerant accumulated in the evaporator 5 at the time of switching to the normal operation may flow into the compressor 1 at once, resulting in liquid backing. Therefore, during the negative pressure prevention operation, the refrigerant discharge valve 11 is opened in the third branch, and the refrigerant discharged from the compressor 1 is allowed to flow to the evaporator 5 through the refrigerant discharge bypass circuit 10. By flowing the discharged refrigerant through the evaporator 5, the liquid refrigerant in the evaporator 5 can be pushed out, and the liquid refrigerant in the evaporator 5 can be prevented from staying. Since the evaporator 5 is not used in the negative pressure prevention operation, the amount of refrigerant required is smaller than that in the normal hot water supply operation. Therefore, the excess refrigerant is generated in the negative pressure prevention operation, but in the refrigeration cycle device 120 of the third embodiment, the excess refrigerant can be stored in the receiver 12.

FIG. 10 is a flowchart showing a control procedure for detecting air contamination in the refrigerant circuit of the refrigeration cycle apparatus according to the third embodiment of the present invention. Next, with reference to FIGS. 9 and 10, the operation of the control for detecting the mixing of air into the refrigerant circuit during the operation including the negative pressure prevention operation of the refrigeration cycle device 120 will be described.

The control device 125 acquires the compressor discharge pressure Pd of the refrigeration cycle detected by the compressor discharge pressure sensor 19 (step ST1). Further, the control device 125 acquires the receiver temperature Tr detected by the receiver temperature sensor 20 (step ST2). Next, the control device 125 calculates the discharge saturation temperature f (Pd) from the compressor discharge pressure Pd, subtracts the receiver temperature Tr from the discharge saturation temperature f (Pd), and the target value of the compressor discharge pressure Pd. Compare with the compressor first set temperature SET7 (for example, 3 ° C.) set as (step ST3). Next, the compressor control means 125b continuously operates the compressor 1 when the value obtained by subtracting the receiver temperature Tr from the discharge saturation temperature f (Pd) is smaller than the compressor first set temperature SET7 (step). ST4). On the other hand, the compressor control means 125b stops the operation of the compressor 1 when the value obtained by subtracting the receiver temperature Tr from the discharge saturation temperature f (Pd) is equal to or higher than the compressor first set temperature SET7 (step ST5). ).

As described above, the refrigerating cycle device 120 detects the mixing of air into the refrigerant circuit by utilizing the change in the physical property value of the refrigerant due to the mixing of air in the refrigerant circuit. Specifically, during the operation including the negative pressure prevention operation, the receiver temperature Tr and the discharge saturation temperature f (Pd) of the compressor discharge pressure Pd are almost the same value. However, when air is mixed in the refrigerant circuit, the physical property value of the refrigerant changes, so that a temperature difference occurs between the receiver temperature Tr and the discharge saturation temperature f (Pd) of the compressor discharge pressure Pd. The compressor control means 125b determines that air is mixed in the refrigerant circuit when the temperature difference becomes large, and stops the operation of the compressor 1. Therefore, when air is mixed into the refrigerant circuit, it is possible to avoid malfunction of the compressor 1 due to suction of air.

Further, since the refrigeration cycle device 120 can store excess refrigerant in the receiver 12 during the negative pressure prevention operation, it prevents the liquid back operation to the suction side of the compressor 1 and performs a highly reliable negative pressure prevention operation. You can continue. Further, the refrigeration cycle device 120 can continue the hot water supply operation without the compressor suction pressure becoming a negative pressure.

The third embodiment is configured to include a refrigerant storage container (receiver 12 in this case), but the arrangement of the refrigerant storage containers is not limited to the arrangement shown in FIG. 9, and the following modifications 1 and 2 are arranged. It is possible to carry out as such.

Modification example 1.
FIG. 11 is a diagram showing a refrigerant circuit and a system configuration of a modification 1 of the refrigeration cycle device according to the third embodiment of the present invention. Parts having the same configuration as the refrigeration cycle apparatus of FIGS. 1 to 10 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 11, the refrigeration cycle device 130 includes a receiver 12a and a check valve 13. The other components are the same as those in FIG.

The receiver 12a is a refrigerant storage container that is arranged in parallel with a pipe connecting the outlet of the condenser 3 and the suction bypass valve 9 and stores excess refrigerant generated during operation. The check valve 13 is installed in a pipe on the outlet side of the receiver 12a to prevent the refrigerant from flowing into the receiver 12a from the expansion valve 4 side. During the hot water supply operation, frost may form on the evaporator 5, and a reverse defrost operation is performed to remove the frost. The reverse defrost operation is an operation of switching the direction of the flow path switch 2 and supplying the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 to the evaporator 5 to remove the frost adhering to the evaporator 5. is there. The check valve 13 prevents the refrigerant from flowing into the receiver 12a when the reverse defrost operation is performed.

Next, the operation of the refrigeration cycle device 130 will be described with reference to FIG. Since the normal hot water supply operation is the same as that of the first embodiment, it will be omitted, and only the negative pressure prevention operation will be described.

In the negative pressure prevention operation in the refrigeration cycle device 130 according to the third embodiment, the refrigerant in a low-temperature low-pressure gas state is sucked into the compressor 1, compressed, and discharged as a high-temperature high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 is branched into three, and in the first branch, the high-temperature and high-pressure refrigerant flows into the discharge gas bypass circuit 6 and is decompressed by the discharge gas bypass valve 7, and the high-temperature and low-pressure gas refrigerant is decompressed. And bypassed to the suction side of the compressor 1. In the second branch, the high temperature and high pressure refrigerant flows into the condenser 3 via the flow path switch 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 dissipates heat to water, which is a heat exchange medium, and becomes a high-pressure liquid refrigerant.

The high-pressure refrigerant flowing out of the condenser 3 is branched into two, one flows to the suction bypass circuit 8 and the other is condensed and stored in the receiver 12a. The high-pressure refrigerant flowing into the suction bypass circuit 8 is decompressed and expanded by the suction bypass valve 9 to become a low-temperature low-pressure gas-liquid two-phase refrigerant. The high-temperature low-pressure gas decompressed by the discharge gas bypass valve 7 and the low-temperature low-pressure gas-liquid two-phase refrigerant decompressed and expanded by the suction bypass valve 9 merge to form a low-temperature low-pressure gas refrigerant, which is sucked into the compressor 1 again. Will be done.

Further, during the negative pressure prevention operation, the opening degree of the expansion valve 4 is fully closed or the opening degree is extremely small, so that the low-pressure two-phase refrigerant hardly flows into the evaporator 5 through the expansion valve 4. However, heat exchange with the outside air and the low-pressure high-temperature refrigerant flowing out of the discharge gas bypass valve 7 flow into the low-temperature evaporator 5 via the flow path switch 2, so that the liquid refrigerant accumulates in the evaporator 5. I will go. As a result, there is a possibility that the refrigerant becomes insufficient during the negative pressure prevention operation, or the liquid refrigerant accumulated in the evaporator 5 at the time of switching to the normal operation flows into the compressor 1 at once, resulting in liquid backing. Therefore, during the negative pressure prevention operation, the refrigerant discharge valve 11 is opened in the third branch, and the refrigerant discharged from the compressor 1 is allowed to flow to the evaporator 5 through the refrigerant discharge bypass circuit 10. By flowing the discharged refrigerant through the evaporator 5, the liquid refrigerant in the evaporator 5 can be pushed out, and the liquid refrigerant in the evaporator 5 can be prevented from staying. Since the evaporator 5 is not used in the negative pressure prevention operation, the amount of refrigerant required is smaller than that in the normal hot water supply operation. Therefore, the excess refrigerant is generated in the negative pressure prevention operation, but in the refrigeration cycle device 130 of the third embodiment, the excess refrigerant can be stored in the receiver 12a.

As described above, in the refrigeration cycle device 130, the receiver 12a is provided in parallel with the pipe connecting the outlet of the condenser 3 and the suction bypass valve 9. Therefore, even if the outlet of the condenser 3 is in the state of a two-phase refrigerant, the surplus refrigerant can be stored in the receiver 12a. As a result, during the negative pressure prevention operation in which excess refrigerant is generated, the liquid back operation of the compressor 1 to the suction side can be prevented, and the highly reliable negative pressure prevention operation can be continued.

Modification example 2.
FIG. 12 is a diagram showing a refrigerant circuit and a system configuration of a modification 2 of the refrigeration cycle device according to the third embodiment of the present invention. Parts having the same configuration as the refrigeration cycle apparatus of FIGS. 1 to 11 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 12, the refrigeration cycle device 140 includes an accumulator 14. The other components are the same as those in FIG.

The accumulator 14 is provided on the suction side of the compressor 1 and is a refrigerant storage container for storing excess refrigerant generated during operation.

As shown in FIG. 12, the refrigeration cycle device 140 includes a control device 125, a compressor suction pressure sensor 16, an accumulator temperature sensor 21 for detecting the pipe temperature at the outlet of the accumulator 14, and an outside air temperature sensor 22. ing. In FIG. 12, the accumulator temperature sensor 21 is installed in the pipe at the outlet of the accumulator 14, but it may be installed in the pipe at the outlet of the accumulator 14.

The control device 125 is connected to each sensor so that the signals detected by the compressor suction pressure sensor 16, the accumulator temperature sensor 21, and the outside air temperature sensor 22 can be received. The control device 125 includes a compressor control means 125b that controls the output of the compressor 1 based on these detection signals.

Next, the operation of the refrigeration cycle device 140 will be described with reference to FIG. Since the normal hot water supply operation is the same as that of the first embodiment, it will be omitted, and only the negative pressure prevention operation will be described.

In the negative pressure prevention operation in the refrigeration cycle device 140 according to the third embodiment, the low-temperature low-pressure gas-state refrigerant is sucked into the compressor 1, compressed, and discharged as high-temperature high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 is branched into three, and in the first branch, the high-temperature and high-pressure refrigerant flows into the discharge gas bypass circuit 6 and is decompressed by the discharge gas bypass valve 7, and the high-temperature and low-pressure gas refrigerant is decompressed. And bypassed to the suction side of the compressor 1. In the second branch, the high temperature and high pressure refrigerant flows into the condenser 3 via the flow path switch 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 dissipates heat to water, which is a heat exchange medium, and becomes a high-pressure liquid refrigerant.

The high-pressure refrigerant flowing out of the condenser 3 flows into the suction bypass circuit 8, and the high-pressure refrigerant flowing into the suction bypass circuit 8 is decompressed and expanded by the suction bypass valve 9 to become a low-temperature low-pressure gas-liquid two-phase refrigerant. The high-temperature low-pressure gas decompressed by the discharge gas bypass valve 7 and the low-temperature low-pressure gas-liquid two-phase refrigerant decompressed and expanded by the suction bypass valve 9 merge to form a low-temperature low-pressure refrigerant. The low-temperature low-pressure refrigerant is sucked into the compressor 1 again via the accumulator 14.

Further, during the negative pressure prevention operation, the opening degree of the expansion valve 4 is fully closed or the opening degree is extremely small, so that the low-pressure two-phase refrigerant hardly flows into the evaporator 5 through the expansion valve 4. However, heat exchange with the outside air and the low-pressure high-temperature refrigerant flowing out of the discharge gas bypass valve 7 flow into the low-temperature evaporator 5 via the flow path switch 2, so that the liquid refrigerant accumulates in the evaporator 5. I will go. As a result, there is a possibility that the refrigerant becomes insufficient during the negative pressure prevention operation, or the liquid refrigerant accumulated in the evaporator 5 at the time of switching to the normal operation flows into the compressor 1 at once, resulting in liquid backing. Therefore, during the negative pressure prevention operation, the refrigerant discharge valve 11 is opened in the third branch, and the refrigerant discharged from the compressor 1 is allowed to flow to the evaporator 5 through the refrigerant discharge bypass circuit 10. By flowing the discharged refrigerant through the evaporator 5, the liquid refrigerant in the evaporator 5 can be pushed out, and the liquid refrigerant in the evaporator 5 can be prevented from staying. Since the evaporator 5 is not used in the negative pressure prevention operation, the amount of refrigerant required is smaller than that in the normal hot water supply operation. Therefore, the excess refrigerant is generated in the negative pressure prevention operation, but in the refrigeration cycle device 140 of the third embodiment, the excess refrigerant can be stored in the accumulator 14.

FIG. 13 is a flowchart of Modification 2 showing a control procedure for detecting air contamination in the refrigerant circuit of the refrigeration cycle apparatus according to the third embodiment of the present invention. Next, with reference to FIGS. 12 and 13, the operation of controlling the detection of air contamination in the refrigerant circuit during the operation including the negative pressure prevention operation of the refrigeration cycle device 140 will be described.

The control device 125 acquires the compressor suction pressure Ps of the refrigeration cycle detected by the compressor suction pressure sensor 16 (step ST21). Further, the control device 125 acquires the accumulator temperature Ta detected by the accumulator temperature sensor 21 (step ST22). Next, the control device 125 calculates the suction saturation temperature f (Ps) from the compressor suction pressure Ps, subtracts the accumulator temperature Ta from the suction saturation temperature f (Ps), and the target value of the compressor suction pressure Ps. Compare with the compressor second set temperature SET8 (for example, 3 ° C.) set as (step ST23). Next, the compressor control means 125b continuously operates the compressor 1 when the value obtained by subtracting the accumulator temperature Ta from the suction saturation temperature f (Ps) is smaller than the compressor second set temperature SET8 (step). ST24). On the other hand, the compressor control means 125b stops the operation of the compressor 1 when the value obtained by subtracting the accumulator temperature Ta from the suction saturation temperature f (Ps) is equal to or higher than the compressor second set temperature SET8 (step ST25). ).

As described above, the refrigerating cycle device 140 detects the mixing of air into the refrigerant circuit by utilizing the change in the physical property value of the refrigerant due to the mixing of air in the refrigerant circuit. Specifically, during the operation including the negative pressure prevention operation, the accumulator temperature Ta and the suction saturation temperature f (Ps) of the compressor suction pressure Ps are almost the same value. However, when air is mixed in the refrigerant circuit, the physical property value of the refrigerant changes, so that a temperature difference occurs between the accumulator temperature Ta and the suction saturation temperature f (Ps) of the compressor suction pressure Ps. The compressor control means 125b determines that air is mixed in the refrigerant circuit when the temperature difference becomes large, and stops the operation of the compressor. Therefore, when air is mixed into the refrigerant circuit, it is possible to avoid malfunction of the compressor due to suction of air.

Further, since the refrigeration cycle device 140 can store excess refrigerant in the accumulator 14 during the negative pressure prevention operation, it prevents the liquid back operation to the suction side of the compressor 1 and performs a highly reliable negative pressure prevention operation. You can continue. Further, the refrigeration cycle device 140 can continue the hot water supply operation without the compressor suction pressure becoming a negative pressure.

The embodiment of the present invention is not limited to the above-described first to third embodiments, and various modifications can be made. For example, although the condenser 3 is composed of a plate type heat exchanger, it may be composed of a plate fin type heat exchanger or the like to exchange heat with air for the refrigerant.

1 Compressor, 2 Flow path switcher, 3 Condenser, 4 Expansion valve, 5 Evaporator, 6 Discharge gas bypass circuit, 7 Discharge gas bypass valve, 8 Suction bypass circuit, 9 Suction bypass valve, 10 Refrigerant discharge bypass circuit, 11 Refrigerant discharge valve, 12 receiver, 12a receiver, 13 check valve, 14 accumulator, 15 controller, 15a valve control means, 16 compressor suction pressure sensor, 17 compressor suction temperature sensor, 18 evaporator outlet temperature sensor, 19 Compressor discharge pressure sensor, 20 receiver temperature sensor, 21 accumulator temperature sensor, 22 outside air temperature sensor, 30 refrigerant circuit, 100 refrigeration cycle device, 110 refrigeration cycle device, 115 control device, 115a valve control means, 120 refrigeration cycle device, 125 Control device, 125b compressor control means, 130 refrigeration cycle device, 140 refrigeration cycle device.

Claims (11)

A circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected and a refrigerant circulates,
A discharge gas bypass circuit that connects the discharge side and the suction side of the compressor,
A suction bypass circuit that connects the outlet side of the condenser, the expansion valve, and the suction side of the compressor.
A refrigerant discharge bypass circuit that connects the discharge side of the compressor, the outlet side of the expansion valve, and the evaporator.
A refrigerant discharge valve that is arranged in the refrigerant discharge bypass circuit and operates to open and close,
An suction pressure sensor that detects the suction pressure of the compressor,
Under the condition that the suction pressure detected by the suction pressure sensor is less than the start set pressure, the negative pressure prevention operation for preventing the suction pressure of the compressor from becoming a negative pressure is started to discharge the refrigerant. A control device that controls the operation of the valve and
An outside air temperature sensor that detects the outside air temperature,
An evaporator outlet temperature sensor that detects the temperature of the refrigerant flowing out of the evaporator as the outlet temperature, and
With
The control device
Under the condition that the value obtained by subtracting the outside air temperature detected by the outside air temperature sensor from the outlet temperature detected by the evaporator outlet temperature sensor is lower than the first set temperature of the discharge valve, the refrigerant discharge valve Under the condition that the value obtained by subtracting the outside air temperature detected by the outside air temperature sensor from the outlet temperature detected by the evaporator outlet temperature sensor is higher than the first set temperature of the discharge valve. , A refrigeration cycle device having a valve control means for closing the refrigerant discharge valve. A circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected and a refrigerant circulates,
A discharge gas bypass circuit that connects the discharge side and the suction side of the compressor,
A suction bypass circuit that connects the outlet side of the condenser, the expansion valve, and the suction side of the compressor.
A refrigerant discharge bypass circuit that connects the discharge side of the compressor, the outlet side of the expansion valve, and the evaporator.
A refrigerant discharge valve that is arranged in the refrigerant discharge bypass circuit and operates to open and close,
An suction pressure sensor that detects the suction pressure of the compressor,
Under the condition that the suction pressure detected by the suction pressure sensor is less than the start set pressure, the negative pressure prevention operation for preventing the suction pressure of the compressor from becoming a negative pressure is started to discharge the refrigerant. A control device that controls the operation of the valve and
An outside air temperature sensor that detects the outside air temperature,
An evaporator outlet temperature sensor that detects the temperature of the refrigerant flowing out of the evaporator as the outlet temperature, and
With
The control device
Under the condition that the outlet temperature detected by the evaporator outlet temperature sensor is lower than the discharge valve second set temperature, the refrigerant discharge valve is opened and the outlet temperature is set to the discharge valve second set temperature. A refrigeration cycle apparatus having a valve control means for closing the refrigerant discharge valve under conditions including a temperature higher than the temperature. A circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected and a refrigerant circulates,
A discharge gas bypass circuit that connects the discharge side and the suction side of the compressor,
A suction bypass circuit that connects the outlet side of the condenser, the expansion valve, and the suction side of the compressor.
A refrigerant discharge bypass circuit that connects the discharge side of the compressor, the outlet side of the expansion valve, and the evaporator.
A refrigerant discharge valve that is arranged in the refrigerant discharge bypass circuit and operates to open and close,
An suction pressure sensor that detects the suction pressure of the compressor,
Under the condition that the suction pressure detected by the suction pressure sensor is less than the start set pressure, the negative pressure prevention operation for preventing the suction pressure of the compressor from becoming a negative pressure is started to discharge the refrigerant. A control device that controls the operation of the valve and
An outside air temperature sensor that detects the outside air temperature,
An evaporator outlet temperature sensor that detects the temperature of the refrigerant flowing out of the evaporator as the outlet temperature, and
With
The control device
Under the condition that the suction pressure detected by the suction pressure sensor is lower than the discharge valve set pressure, the refrigerant discharge valve is opened and the suction pressure is higher than the discharge valve set pressure. A refrigeration cycle device having a valve control means for closing the refrigerant discharge valve under the conditions including. A suction bypass valve that adjusts the flow rate of the refrigerant flowing through the suction bypass circuit,
A receiver installed in a pipe connecting the outlet of the condenser and the suction bypass valve,
The refrigeration cycle apparatus according to any one of claims 1 to 3. A suction bypass valve that adjusts the flow rate of the refrigerant flowing through the suction bypass circuit,
The refrigeration cycle apparatus according to any one of claims 1 to 3, further comprising a receiver installed in parallel with a pipe connecting the outlet of the condenser and the suction bypass valve. The refrigeration cycle apparatus according to any one of claims 1 to 5, further comprising an accumulator installed on the suction side of the compressor. It further has a receiver temperature sensor that detects the temperature of the refrigerant at the inlet or outlet of the receiver, and a discharge pressure sensor that detects the discharge pressure of the compressor.
The control device
The discharge saturation temperature is calculated from the discharge pressure detected by the discharge pressure sensor, and the value obtained by subtracting the temperature of the refrigerant detected by the receiver temperature sensor from the discharge saturation temperature is calculated.
The valve control means
Under the condition that the value obtained by subtracting the temperature of the refrigerant detected by the receiver temperature sensor from the discharge saturation temperature becomes equal to or higher than the first set temperature of the compressor, the operation of the compressor is stopped and the discharge is performed. Claim 4 or 5 to continue the operation of the compressor under the condition that the value obtained by subtracting the temperature of the refrigerant detected by the receiver temperature sensor from the saturation temperature is lower than the first set temperature of the compressor. The refrigeration cycle device according to. Further having an accumulator temperature sensor for detecting the temperature of the refrigerant at the inlet or outlet of the accumulator.
The control device
The suction saturation temperature is calculated from the suction pressure detected by the suction pressure sensor, and a value obtained by subtracting the temperature of the refrigerant detected by the accumulator temperature sensor from the suction saturation temperature is calculated.
The valve control means
Under the condition that the value obtained by subtracting the temperature of the refrigerant detected by the accumulator temperature sensor from the suction saturation temperature becomes equal to or higher than the second set temperature of the compressor, the operation of the compressor is stopped and the operation is stopped. 6. The operation of the compressor is continued under the condition that the value obtained by subtracting the temperature of the refrigerant detected by the accumulator temperature sensor from the suction saturation temperature is lower than the second set temperature of the compressor. The refrigeration cycle device according to. A discharge gas bypass valve for adjusting the flow rate of the refrigerant flowing through the discharge gas bypass circuit is further provided.
The valve control means
Under the condition that the suction pressure detected by the suction pressure sensor includes the start set pressure or more, the refrigerant discharge valve, the discharge gas bypass valve, and the suction bypass valve are closed, and the expansion valve is closed. The refrigerating cycle apparatus according to claim 4 or 5, wherein the hot water supply operation is performed by controlling the gas to be open. The refrigeration cycle apparatus according to claim 9, wherein the capacitance coefficient Cv value of the refrigerant discharge valve is smaller than the capacitance coefficient Cv value of the discharge gas bypass valve. The refrigeration cycle apparatus according to any one of claims 1 to 10, wherein the refrigerant is any of a single refrigerant of HFO-1234yf, a single refrigerant of HFO-1234ze, and a mixed refrigerant containing HFO-1234yf or HFO-1234ze. ..

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