JPWO2016113899A1 - Refrigeration cycle equipment - Google Patents

Abstract

The compressor 1, the condenser 3, the main expansion valve 4, and the evaporator 5 are connected in an annular shape, and a main circuit 30 in which a refrigerant having a higher boiling point than R407C circulates, and a part of the refrigerant discharged from the compressor 1 And a bypass circuit 40 (discharge gas bypass circuit 6 and suction bypass circuit 8) that joins the refrigerant flowing out of the condenser 3 and flows into the suction side of the compressor 1, and a negative pressure adjustment that adjusts the flow rate of the bypass circuit 40 And a negative pressure prevention control means 20a for performing a negative pressure prevention operation for controlling the negative pressure adjusting valve 7 to prevent the suction pressure of the compressor 1 from becoming negative pressure. Is.

Description

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

  As a conventional refrigeration cycle device, for example, “HFO-1234yf is used as a refrigerant, and at least a compressor, a condenser, a throttling device, and an evaporator are sequentially connected to form an annular refrigerant circuit, and a four-way valve is provided. The direction of refrigerant flow is changed, and during the cooling operation, the indoor heat exchanger acts as an evaporator and the outdoor heat exchanger as a condenser, and during the heating operation, the indoor heat exchanger serves as a condenser and the outdoor heat exchanger evaporates. "It has been made to act as a vessel" has been proposed. (For example, see Patent Document 1)

JP 2011-252638 A

  HFO-1234yf used in the technique of Patent Document 1 is a refrigerant having a higher boiling point than refrigerants such as R407C and R410A that have been conventionally used. For this reason, there is a characteristic that the compressor suction pressure is lowered. Therefore, particularly when the heating operation is performed under a low outside air temperature condition, the compressor is operated in a negative pressure state in which the suction pressure of the compressor is lower than the atmospheric pressure, causing problems such as malfunction due to air suction.

  The present invention has been made to solve the above-described problems. Even when a refrigerant having a higher boiling point than that of the R407C refrigerant is used, the compressor suction pressure is reduced to an atmospheric pressure or lower under low outside air conditions. The present invention provides a refrigeration cycle apparatus capable of preventing and improving reliability.

  In the refrigeration cycle apparatus according to the present invention, a compressor, a condenser, a main expansion valve, and an evaporator are connected in a ring shape, a main circuit in which a refrigerant having a higher boiling point than R407C circulates, and refrigerant discharged from the compressor A bypass circuit that joins a part of the refrigerant and the refrigerant that has flown out of the condenser to flow into the suction side of the compressor, a negative pressure adjustment valve that adjusts the flow rate of the bypass circuit, and a compressor that controls the negative pressure adjustment valve And a negative pressure prevention control means for performing a negative pressure prevention operation for preventing the suction pressure from becoming negative.

  According to the present invention, even when a refrigerant having a higher boiling point than that of the R407C refrigerant is used, the refrigeration capable of preventing the compressor suction pressure from being reduced to an atmospheric pressure or lower under low outside air conditions and improving the reliability. A cycle device can be obtained.

It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 1 of the present invention. It is the graph which compared the relationship between the saturation temperature of various refrigerant | coolants, and saturated vapor pressure. It is a Ph diagram which shows the operation state of the negative pressure prevention driving | operation in the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention. 1 is a system configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. It is a flowchart which shows the control procedure of the negative pressure prevention driving | operation in the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention. It is a system configuration figure of the refrigerating cycle device concerning Embodiment 2 of the present invention. It is a flowchart which shows the control procedure of the negative pressure prevention driving | operation in the refrigerating-cycle apparatus which concerns on Embodiment 2 of this invention. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 3 of the present invention. It is the schematic of the ejector of FIG. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 4 of the present invention. It is a refrigerant circuit figure of the refrigerating cycle device which shows modification 1 of the refrigerating cycle device concerning Embodiment 4 of the present invention. It is a refrigerant circuit figure of the refrigerating cycle device which shows modification 2 of the refrigerating cycle device concerning Embodiment 4 of the present invention. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 5 of the present invention. It is a Ph diagram which shows the operation state of the driving | operation of FIG. It is a system block diagram of the refrigerating-cycle apparatus which concerns on Embodiment 5 of this invention. It is a flowchart which shows the control procedure of the negative pressure prevention driving | operation in the refrigerating-cycle apparatus which concerns on Embodiment 5 of this invention. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 6 of the present invention. It is a refrigerant circuit figure of the modification 1 of the refrigerating-cycle apparatus which concerns on Embodiment 6 of this invention. It is a refrigerant circuit figure of the modification 2 of the refrigerating-cycle apparatus which concerns on Embodiment 6 of this invention.

  Hereinafter, a refrigeration cycle apparatus according to an embodiment of the present invention will be described with reference to the drawings. Here, in FIG. 1 and the following drawings, the same reference numerals denote the same or corresponding parts, and are common to the whole text of the embodiments described below. And the form of the component represented by the whole specification is an illustration to the last, Comprising: It does not limit to the form described in the specification. In particular, the combination of the components is not limited to the combination in each embodiment, and the components described in the other embodiments can be applied to another embodiment. The level of temperature, pressure, etc. is not particularly determined in relation to absolute values, but is relatively determined in the state, operation, etc. of the system, apparatus, and the like.

  Moreover, below, this Embodiment is demonstrated to the case where the refrigeration cycle apparatus is applied to a heat pump type hot water heater as an example.

Embodiment 1 FIG.
FIG. 1 is a refrigerant circuit diagram of the refrigeration cycle apparatus according to Embodiment 1 of the present invention, and shows a state when a heating operation (hot water supply operation) for increasing the temperature of water on the load side is performed. .

  In the refrigeration cycle apparatus of the first embodiment, a compressor 1, a four-way valve 2, a condenser 3, a main expansion valve 4, and an evaporator 5 are connected in an annular shape, and a main circuit 30 in which refrigerant circulates, and a bypass circuit 40. And a discharge gas bypass valve 7 as a negative pressure adjusting valve for adjusting the flow rate of the bypass circuit 40.

The compressor 1 is composed of, for example, a capacity-controllable inverter compressor or the like, and sucks low-temperature low-pressure gas refrigerant, compresses it, and discharges it as a high-temperature high-pressure gas refrigerant.
The four-way valve 2 switches the flow direction of the high-temperature high-pressure gas refrigerant discharged from the compressor 1 to the condenser 3 or the evaporator 5.
The condenser 3 is configured by a plate heat exchanger, and heat is exchanged between the refrigerant flowing through the main circuit 30 and a heat exchange medium supplied from a cooling load (not shown) to dissipate heat.
The main expansion valve 4 depressurizes the high-pressure refrigerant into a low-pressure two-phase refrigerant.
The evaporator 5 is composed of, for example, a plate fin heat exchanger or the like, and evaporates the refrigerant by exchanging heat with air.

  The bypass circuit 40 includes a discharge gas bypass circuit 6 and a suction bypass circuit 8, and a part of the refrigerant discharged from the compressor 1 and the refrigerant flowing out of the condenser 3 are joined to the suction side of the compressor 1. It is a circuit that flows in.

  The discharge gas bypass circuit 6 bypasses a part of the refrigerant discharged from the compressor 1 to the suction side of the compressor 1. The discharge gas bypass valve 7 is provided in the discharge gas bypass circuit 6 and adjusts the bypass amount of the discharge gas flowing through the discharge gas bypass circuit 6. When the opening degree of the discharge gas bypass valve 7 is increased, the refrigerant flow rate returning to the suction side of the compressor 1 through the discharge gas bypass circuit 6 is increased, and the compressor suction pressure is increased. On the other hand, when the opening degree of the discharge gas bypass valve 7 is reduced, the refrigerant flow rate returning to the suction side of the compressor 1 through the discharge gas bypass circuit 6 is reduced, and the compressor suction pressure is lowered.

  The suction bypass circuit 8 joins the high-pressure refrigerant at the outlet of the condenser 3 to 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 refrigerant flowing through the suction bypass circuit 8. When the opening degree of the suction bypass valve 9 is increased, the flow rate of the high-pressure refrigerant flowing into the suction side of the compressor 1 through the suction bypass circuit 8 increases, and the compressor suction superheat degree decreases. On the other hand, if the opening degree of the suction bypass valve 9 is reduced, the flow rate of the high-pressure refrigerant flowing from the suction bypass circuit 8 to the suction side of the compressor 1 is reduced, so that the compressor suction superheat degree is increased.

  Here, in this Embodiment 1, the refrigerant | coolant containing a HFO-1234yf refrigerant | coolant or a HFO-1234ze refrigerant | coolant is used as a refrigerant | coolant. 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. In the case of using a mixed refrigerant, for example, R32 can be used. These HFO-1234yf refrigerant or HFO-1234ze refrigerant have a global warming potential (GWP) of “4”, which is lower than the conventional R410A refrigerant “2090” and the R407C refrigerant “1770”, and has an effect on the global environment. Is a small refrigerant.

  Next, the operation of the refrigeration cycle of the refrigeration cycle apparatus according to Embodiment 1 will be described with reference to FIG.

First, a normal hot water supply operation will be described.
During normal hot water supply operation, the discharge gas bypass valve 7 and the suction bypass valve 9 are fully closed, and there is no refrigerant flow in the discharge gas bypass circuit 6 and the suction bypass circuit 8. In a normal hot water supply operation, a low-temperature and low-pressure gaseous refrigerant is sucked into the compressor 1 and compressed to be discharged as a high-temperature and high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 flows into the condenser 3 via the four-way valve 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 radiates heat to the heat exchange medium, and becomes high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed out of the condenser 3 flows into the main expansion valve 4 and is decompressed and expanded to become a low-temperature and low-pressure gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant that has flowed out of the main expansion valve 4 flows into the evaporator 5, cools the air that is the heat exchange medium, and evaporates to become a low-temperature and low-pressure gas refrigerant. The low-temperature and low-pressure gas refrigerant that has flowed out of the evaporator 5 passes through the four-way valve 2 again, and is again sucked into the compressor 1.

  Here, the relationship between the saturation temperature and the saturation vapor pressure will be described for each of the conventionally used R410A refrigerant and R407C refrigerant and the HFO-1234yf refrigerant and HFO-1234ze used in the first embodiment.

FIG. 2 is a graph comparing the relationship between the saturation temperature and saturation vapor pressure of various refrigerants. Here, R410A refrigerant, R407C refrigerant, HFO-1234yf refrigerant, and HFO-1234ze are shown as various refrigerants. In FIG. 2, the horizontal axis indicates the saturation temperature [° C.], and the vertical axis indicates the saturation vapor pressure [MPa (abs)].
According to FIG. 2, the HFO-1234yf refrigerant used in the first embodiment has a lower saturated vapor pressure than the conventionally used R410A refrigerant and R407C refrigerant. For this reason, when the hot water supply operation is performed in an extremely cold region where the outside air is, for example, −25 ° C. or less, the evaporation temperature falls below −29.5 ° C., which is the saturated vapor temperature at atmospheric pressure, and the compressor suction pressure is less than atmospheric pressure. It is expected that this will be a negative pressure operation. When the compressor suction pressure becomes negative, air is sucked into the refrigeration cycle, causing problems such as malfunction of the refrigeration cycle.

  Therefore, the refrigeration cycle apparatus according to the first embodiment performs the negative pressure prevention operation in which the hot water supply operation is continued while the compressor suction pressure is maintained at a negative pressure or higher even under a low outside air condition.

  Next, the refrigeration cycle operation in the negative pressure prevention operation will be described using the refrigerant circuit diagram of FIG. 1 and the Ph diagram of FIG.

  FIG. 3 is a Ph diagram illustrating the operating state of the negative pressure prevention operation in the refrigeration cycle apparatus according to Embodiment 1 of the present invention. [1] to [5] in FIG. 3 indicate refrigerant states at positions [1] to [5] in FIG. During the negative pressure prevention operation, the opening of the main expansion valve 4 is substantially closed. This “substantially closed” includes not only a completely closed state but also a very small opening that does not adversely affect the prevention of negative pressure. In other words, “substantially closed” corresponds to a fully closed position or an opening degree close to a fully closed position. If the main expansion valve 4 is open during the heating operation under the low outside air temperature condition, the refrigerant flows into the evaporator 5 and causes a reduction in the compressor suction pressure. For this reason, the main expansion valve 4 is closed during the negative pressure prevention operation so that the refrigerant does not flow into the evaporator 5.

  In the negative pressure prevention operation in the refrigeration cycle apparatus according to the first embodiment, the refrigerant ([1]) in the low-temperature and low-pressure gas state is sucked into the compressor 1, compressed, and discharged as high-temperature and high-pressure gas. The high-temperature and high-pressure refrigerant ([2]) discharged from the compressor 1 is branched into two, one of which flows into the discharge gas bypass circuit 6 and is decompressed by the discharge gas bypass valve 7 to be high-temperature and low-pressure gas refrigerant ([3]). And is bypassed to the suction side of the compressor 1. The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3 via the four-way valve 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 ([4]).

  The high-pressure liquid refrigerant that has flowed out of the condenser 3 flows into the suction bypass circuit 8, is decompressed and expanded by the suction bypass valve 9, and becomes a low-temperature and low-pressure gas-liquid two-phase refrigerant ([5]). The high-temperature and low-pressure gas ([3]) decompressed by the discharge gas bypass valve 7 and the low-temperature and low-pressure gas-liquid two-phase refrigerant ([5]) decompressed and expanded by the suction bypass valve 9 merge to form a low-temperature and low-pressure Gas refrigerant ([1]) and is sucked into the compressor 1 again. During the negative pressure prevention operation, the main expansion valve 4 is substantially closed, so that the low-pressure two-phase refrigerant hardly flows through the evaporator 5, and the refrigerant is not evaporated by heat exchange with the outside air. .

Here, an outline of the negative pressure prevention operation will be described.
The negative pressure prevention operation is started when the compressor suction pressure is in an operation state close to negative pressure. Almost no refrigerant flows through the evaporator 5 and most of the high-pressure refrigerant flowing out of the condenser 3 is sucked into the suction bypass circuit 8. It is the driving | running | working made to flow in. The discharge gas bypass valve 7 is controlled so that the compressor suction pressure is higher than the negative pressure, thereby preventing negative pressure. Further, in the first embodiment, in addition to the control of the discharge gas bypass valve 7, the suction bypass valve 9 is further controlled so that the compressor suction superheat degree is in an appropriate state.

  FIG. 4 is a system configuration diagram of the refrigeration cycle apparatus according to Embodiment 1 of the present invention. FIG. 5 is a flowchart showing a control procedure of the negative pressure prevention operation in the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 4, the refrigeration cycle apparatus according to the first embodiment includes a control device 20, a compressor suction pressure sensor 21, and a compressor suction temperature sensor 22. Other components are the same as those in FIG.

  The control device 20 controls the entire refrigeration cycle device. The control device 20 is constituted by a microcomputer, for example, and includes a CPU, a RAM, a ROM, and the like. The ROM stores a control program and a program corresponding to the flowchart of FIG.

  Each sensor is connected to the control device 20 so as to receive detection signals from the compressor suction pressure sensor 21 and the compressor suction temperature sensor 22. The control device 20 performs the opening degree control of the main expansion valve 4, the opening degree control of the discharge gas bypass valve 7, the opening degree control of the suction bypass valve 9, and the like based on these detection signals and the like. The control device 20 performs various operation controls including a negative pressure prevention operation based on detection signals from the sensors 21 and 22 and the like.

  Next, a functional configuration of the control device 20 will be described. The control device 20 includes negative pressure prevention control means 20a and superheat degree control means 20b. The negative pressure prevention control means 20a performs a negative pressure prevention operation for controlling the discharge gas bypass valve 7 to prevent the suction pressure of the compressor 1 from becoming negative. The superheat degree control means 20b adjusts the opening degree of the suction bypass valve 9 so that the superheat degree of the suction gas of the compressor 1 becomes a preset set value. The negative pressure prevention control means 20a and the superheat degree control means 20b are functionally constituted by a CPU and a control program.

  Next, the control operation of the negative pressure prevention operation of the refrigeration cycle apparatus according to the first embodiment will be described with reference to FIGS. 4 and 5.

  The control device 20 acquires the compressor suction pressure Ps detected by the compressor suction pressure sensor 21 (S1). The control device 20 sets the compressor suction pressure Ps and a preset value 1 (for example, 0.01 MPa (G), which is an upper limit pressure for starting the negative pressure prevention operation). (S2). While the compressor suction pressure Ps is equal to or higher than the set value 1, the control device 20 returns to step S1 and continues the normal hot water supply operation. On the other hand, when the compressor suction pressure Ps falls below the set value 1, the control device 20 determines that the outside air temperature is low and the compressor suction pressure is close to negative pressure, and starts negative pressure prevention operation ( S3).

  In the negative pressure operation, first, the control device 20 substantially closes the main expansion valve 4 (smallly closes or closes to an opening degree close to full closing) (S4). Next, the controller 20 sets a preset value 2 (for example, 0.02 MPa (G), at least a positive pressure) as a target value for the compressor suction pressure, and the compressor suction pressure Ps. Compare (S5). When the compressor suction pressure Ps is lower than the set value 2 (> set value 1), the control device 20 increases the opening of the discharge gas bypass valve 7 (S6). As a result, the compressor suction pressure Ps increases and approaches the set value 2. On the other hand, when the compressor suction pressure Ps is higher than the set value 2, the opening degree of the discharge gas bypass valve 7 is reduced (S7). As a result, the compressor suction pressure Ps decreases and approaches the set value 2. Although not shown in FIG. 5, when the compressor suction pressure Ps matches the set value 2, the opening degree of the discharge gas bypass valve 7 may be maintained as it is.

  Next, the control device 20 acquires the compressor suction temperature Ts detected by the compressor suction temperature sensor 22. Then, the control device 20 calculates the compressor suction superheat degree SHs using the acquired compressor suction temperature Ts (S9). That is, the control device 20 calculates the saturation temperature f (Ps) of the compressor suction pressure Ps, and subtracts the saturation temperature f (Ps) of the compressor suction pressure Ps from the compressor suction temperature Ts, so that the compressor suction overheat is performed. The degree SHs is calculated.

  Then, the control device 20 compares the calculated compressor suction superheat degree SHs with a set value 3 (for example, 5K) set in advance as a target value of the compressor suction superheat degree (S10). When the compressor suction superheat degree SHs is smaller than the set value 3, the control device 20 decreases the opening degree of the suction bypass valve 9 (S11). As a result, the compressor intake superheat degree SHs increases and approaches the set value 3. On the other hand, when the compressor suction superheat degree SHs is larger than the set value 3, the opening degree of the suction bypass valve 9 is increased (S12). Thereby, the compressor suction superheat degree SHs decreases and approaches the set value 3. Although not shown in FIG. 5, when the compressor intake superheat degree SHs matches the set value 3, the opening degree of the intake bypass valve 9 may be maintained as it is. Then, after the processing of S11 or S12, the control device 20 returns to S5, and repeats the control to match the compressor suction pressure Ps and the compressor suction superheat degree SHs with the corresponding set value 2 and set value 3, respectively.

  As described above, in the refrigeration cycle apparatus according to Embodiment 1, when the outside air temperature is low and the compressor suction pressure is close to a negative pressure, the main expansion valve 4 is fully closed and the refrigerant in the evaporator 5 is closed. Continue hot water supply operation without evaporating the water. The compressor suction pressure is controlled by the opening degree of the discharge gas bypass valve 7, and the compressor suction superheat degree is controlled by the opening degree of the suction bypass valve 9. For this reason, the hot water supply operation can be continued without causing the compressor suction pressure to become negative and with the compressor suction superheat degree being appropriate. Therefore, inconveniences such as malfunction due to air suction can be avoided even if the outside air decreases. Furthermore, since it is not necessary to stop the hot water supply operation for raising the temperature of the water even in a low outside air condition in the water heater, it is possible to prevent water piping from being frozen.

Embodiment 2. FIG.
The second embodiment further includes a two-way valve in the configuration of the first embodiment shown in FIG. Other components are the same as those in FIG. In the following, the second embodiment will be described focusing on the differences from the first embodiment.

  FIG. 6 is a system configuration diagram of the refrigeration cycle apparatus according to Embodiment 2 of the present invention. FIG. 7 is a flowchart showing a control procedure of negative pressure prevention operation in the refrigeration cycle apparatus according to Embodiment 2 of the present invention.

  As shown in FIG. 6, the refrigeration cycle apparatus according to the second embodiment further includes a two-way valve 10 in the configuration of the first embodiment.

  The two-way valve 10 is disposed between the four-way valve 2 and the evaporator 5, and shuts off the refrigerant flow between the four-way valve 2 and the evaporator 5 by closing the two-way valve 10.

  Next, the control operation of the refrigeration cycle apparatus according to Embodiment 2 will be described with reference to FIGS. Note that the normal hot water supply operation is the same as that of the first embodiment, and is omitted, and only the negative pressure prevention operation will be described.

  The negative pressure prevention operation in the refrigeration cycle apparatus according to the second embodiment is that the first embodiment shown in the flowchart of the first embodiment shown in FIG. 5 further includes a step (S21) of closing the two-way valve 10. Otherwise, the rest is the same. The process of closing the two-way valve 10 may be between step S3 and step S5.

  As described above, the refrigeration cycle apparatus according to the second embodiment can obtain the same effects as those of the first embodiment and the following effects. That is, in order to close the two-way valve 10 during the negative pressure prevention operation, the low-pressure and high-temperature refrigerant (refrigerant indicated by the dotted arrow in FIG. 6) that has flowed out of the discharge gas bypass valve 7 passes through the four-way valve 2 and has a low temperature. It can be prevented from flowing into the evaporator 5 and condensing and staying. For this reason, the negative pressure prevention operation can be continued without the refrigerant circulating through the discharge gas bypass circuit 6 and the suction bypass circuit 8 becoming insufficient.

Embodiment 3 FIG.
In the third embodiment, an ejector and a suction pipe are further provided in the configuration of the first embodiment shown in FIG. Other components are the same as those in FIG. In the following, the third embodiment will be described focusing on the differences from the first embodiment.

FIG. 8 is a refrigerant circuit diagram of the refrigeration cycle apparatus according to Embodiment 3 of the present invention.
The ejector 11 is disposed downstream of the discharge gas bypass valve 7 of the discharge gas bypass circuit 6 and sucks the refrigerant on the evaporator 5 side through the suction pipe 12.

FIG. 9 is a schematic view of the ejector of FIG.
The ejector 11 is composed of three parts, a nozzle 11a, a constricting part 11b, and a diffuser 11c. The main flow that flows from the inlet is constricted by the nozzle 11a, and the restricting part 11b has a higher flow velocity than the inlet. When the refrigerant pressure at the inlet is P1, the flow velocity is v1, the density is ρ1, the refrigerant pressure at the throttle portion 11b is P2, the flow velocity is v2, and the density is ρ2, the following relationship is established by Bernoulli's equation.

  Here, since the flow velocity v2 of the throttle portion 11b> the flow velocity v1 at the inlet, the pressure becomes P2 <P1, and the refrigerant suction portion 11d generates the differential pressure P1-P2, and the refrigerant is sucked.

  Next, the operation of the refrigeration cycle in the refrigeration cycle apparatus according to Embodiment 3 will be described with reference to FIG. Note that the operation of the refrigeration cycle in the normal hot water supply operation is the same as that in the first embodiment, and is therefore omitted. In the negative pressure prevention operation, the point that the main expansion valve 4 is substantially closed is the same as in the first embodiment.

  In the negative pressure prevention operation in the refrigeration cycle apparatus according to Embodiment 3, low-temperature and low-pressure gaseous refrigerant is sucked into the compressor 1, compressed, and discharged as high-temperature and high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 branches into two, one flows into the discharge gas bypass circuit 6, is decompressed by the discharge gas bypass valve 7, becomes a high-temperature and low-pressure gas refrigerant, and flows into the ejector 11. Inside the ejector 11, the refrigerant pressure decreases as the refrigerant flow rate increases, and the refrigerant on the evaporator 5 side is sucked through the suction pipe 12 connected to the refrigerant suction part 11d.

  The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3 via the four-way valve 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 radiates heat to the heat exchange medium, and becomes high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed 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 and low-pressure gas-liquid two-phase refrigerant. The high-temperature and low-pressure gas decompressed by the discharge gas bypass valve 7 and passed through the ejector 11 and the low-temperature and low-pressure gas-liquid two-phase refrigerant decompressed and expanded by the suction bypass valve 9 merge to become a low-temperature and low-pressure gas refrigerant, It is sucked into the compressor 1 again.

  As described above, the refrigeration cycle apparatus according to the third embodiment can obtain the same effects as those of the first embodiment and the following effects. That is, even if the low-pressure high-temperature refrigerant that has flowed out of the discharge gas bypass valve 7 during the negative pressure prevention operation flows into the low-temperature evaporator 5 via the four-way valve 2, the refrigerant that has flowed into the evaporator 5 side is sucked by the ejector 11. It can be pulled back to the discharge gas bypass circuit 6. Therefore, it is possible to prevent the refrigerant flowing out of the discharge gas bypass valve 7 and flowing into the evaporator 5 from condensing and staying in the evaporator 5. For this reason, the negative pressure prevention operation can be continued without the refrigerant circulating through the discharge gas bypass circuit 6 and the suction bypass circuit 8 becoming insufficient.

Embodiment 4 FIG.
In the fourth embodiment, a receiver is further provided in the configuration of the first embodiment shown in FIG. Other components are the same as those in FIG. Hereinafter, the difference between the fourth embodiment and the first embodiment will be mainly described.

FIG. 10 is a refrigerant circuit diagram of the refrigeration cycle apparatus according to Embodiment 4 of the present invention.
The receiver 13 is disposed in a pipe connecting the condenser 3 and the suction bypass valve 9 and stores surplus refrigerant generated during operation.

  Next, the operation of the refrigeration cycle according to Embodiment 4 will be described with reference to FIG. Note that the normal hot water supply operation is the same as that of the first embodiment, and is omitted, and only the negative pressure prevention operation will be described. In the negative pressure prevention operation, the point that the main expansion valve 4 is substantially closed is the same as in the first embodiment.

  In the negative pressure prevention operation in the refrigeration cycle apparatus according to Embodiment 4, low-temperature and low-pressure gaseous refrigerant is sucked into the compressor 1, compressed, and discharged as high-temperature and high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 is branched into two, one of which flows into the discharge gas bypass circuit 6 and is decompressed by the discharge gas bypass valve 7 to become a high-temperature and low-pressure gas refrigerant, and is bypassed to the suction side of the compressor 1. Is done. The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3 via the four-way valve 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 radiates heat to the heat exchange medium, and becomes high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed out of the condenser 3 flows into the suction bypass circuit 8 via the receiver 13 and is decompressed and expanded by the suction bypass valve 9 to become a low-temperature and low-pressure gas-liquid two-phase refrigerant. The high-temperature and low-pressure gas decompressed by the discharge gas bypass valve 7 and the low-temperature and low-pressure gas-liquid two-phase refrigerant decompressed and expanded by the suction bypass valve 9 merge to become a low-temperature and low-pressure gas refrigerant, and are returned to the compressor 1 again. Sucked.

  During the negative pressure prevention operation, the main expansion valve 4 is substantially closed, so that the low-pressure two-phase refrigerant hardly flows through the evaporator 5, and the refrigerant is not evaporated by heat exchange with the outside air. . Thus, since the evaporator 5 is not used in the negative pressure prevention operation, the required amount of refrigerant is smaller than that in the normal hot water supply operation. For this reason, surplus refrigerant is generated in the negative pressure prevention operation, but in the fourth embodiment, the surplus refrigerant can be stored in the receiver 13.

  As described above, the refrigeration cycle apparatus according to the fourth embodiment can obtain the same effects as those of the first embodiment and the following effects. In other words, since the excess refrigerant can be stored in the receiver 13 during the negative pressure prevention operation, the liquid back operation to the suction side of the compressor 1 can be prevented, and the highly reliable negative pressure prevention operation can be continued.

  The fourth embodiment has a configuration including a refrigerant storage container (here, receiver 13), but the arrangement of the refrigerant storage container is not limited to the arrangement shown in FIG. It can be modified as described above.

<Modification 1>
FIG. 11 is a refrigerant circuit diagram of the refrigeration cycle apparatus showing Modification 1 of the refrigeration cycle apparatus according to Embodiment 4 of the present invention.

  As shown in FIG. 11, the refrigerant circuit of Modification 1 of the refrigeration cycle apparatus according to Embodiment 4 is provided with a receiver 13 a and a check valve 14 instead of the receiver 13 of FIG. 10. Other components are the same as those in FIG.

  The receiver 13a is a refrigerant storage container that stores excess refrigerant generated during operation. The receiver 13 a is provided in parallel with the main circuit 30 on the outlet side of the condenser 3. In other words, the receiver 13 a is provided in parallel to the pipe between the junction between the upstream end of the suction bypass circuit 8 and the main circuit 30 and the outlet of the condenser 3.

  The check valve 14 prevents the refrigerant from flowing into the receiver 13a from the main expansion valve 4 side. During the hot water supply operation, the evaporator 5 may be frosted. In this case, the reverse defrost operation is performed. The reverse defrost operation is an operation in which the four-way valve 2 is switched in the dotted line direction of FIG. 11 and the high-temperature high-pressure gas refrigerant discharged from the compressor 1 is supplied to the evaporator 5 to remove frost attached to the evaporator 5. The check valve 14 prevents the refrigerant from flowing into the receiver 13a during the reverse defrost operation.

  Next, the refrigeration cycle operation of Modification 1 of the refrigeration cycle apparatus according to Embodiment 4 will be described with reference to FIG. Since the normal hot water supply operation is the same as that of the first embodiment, only the negative pressure prevention operation will be described. The point that the main expansion valve 4 is substantially closed during the negative pressure prevention operation is the same as in the first embodiment.

  In the negative pressure prevention operation of the first modified example, the refrigerant in a low-temperature and low-pressure gas state is sucked into the compressor 1 and compressed to be discharged as a high-temperature and high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 is branched into two, one of which flows into the discharge gas bypass circuit 6 and is decompressed by the discharge gas bypass valve 7 to become a high-temperature and low-pressure gas refrigerant, and is bypassed to the suction side of the compressor 1. Is done. The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3 via the four-way valve 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 radiates heat to the heat exchange medium, and becomes high-pressure liquid refrigerant.

  The high-pressure refrigerant that has flowed out of the condenser 3 is branched into two, one flows through the main circuit 30 to the suction bypass circuit 8, and the other is condensed and stored in the receiver 13a. 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 and low-pressure gas-liquid two-phase refrigerant. The high-temperature and low-pressure gas decompressed by the discharge gas bypass valve 7 and the low-temperature and low-pressure gas-liquid two-phase refrigerant decompressed and expanded by the suction bypass valve 9 merge to become a low-temperature and low-pressure gas refrigerant, and are returned to the compressor 1 again. Sucked.

  During the negative pressure prevention operation, the main expansion valve 4 is substantially closed, so that the low-pressure two-phase refrigerant hardly flows through the evaporator 5, and the refrigerant is not evaporated by heat exchange with the outside air. . In the negative pressure prevention operation, since the evaporator 5 is not used, the amount of refrigerant required is smaller than that in the normal hot water supply operation, and surplus refrigerant is generated. However, in the first modification, the surplus refrigerant can be stored in the receiver 13a. .

  As described above, in Modification 1 of the refrigeration cycle apparatus according to Embodiment 4, the receiver 13 a is provided in parallel with the main circuit 30 on the outlet side of the condenser 3. For this reason, even if the outlet of the condenser 3 is in the state of a two-phase refrigerant, it is possible to store surplus refrigerant in the receiver 13a. Therefore, during the negative pressure prevention operation in which surplus refrigerant is generated, the liquid back operation to the suction side of the compressor 1 can be prevented, and the highly reliable negative pressure prevention operation can be continued.

<Modification 2>
FIG. 12 is a refrigerant circuit diagram of the refrigeration cycle apparatus showing Modification 2 of the refrigeration cycle apparatus according to Embodiment 4 of the present invention.

  As shown in FIG. 12, the refrigerant circuit of Modification 2 of the refrigeration cycle apparatus according to Embodiment 4 is provided with an accumulator 15 instead of the receiver 13 of FIG. Other components are the same as those in FIG.

  The accumulator 15 is provided on the suction side of the compressor 1 and is a refrigerant storage container that stores excess refrigerant generated during operation.

  Next, the refrigeration cycle operation of Modification 2 of the refrigeration cycle apparatus according to Embodiment 4 will be described with reference to FIG. Since the normal hot water supply operation is the same as that of the first embodiment, only the negative pressure prevention operation will be described.

  In the negative pressure prevention operation of the modified example 2, the low-temperature and low-pressure gaseous refrigerant is sucked into the compressor 1, compressed, and discharged as high-temperature and high-pressure gas. The high-temperature and high-pressure refrigerant discharged from the compressor 1 is branched into two, one of which flows into the discharge gas bypass circuit 6 and is decompressed by the discharge gas bypass valve 7 to become a high-temperature and low-pressure gas refrigerant, and is bypassed to the suction side of the compressor 1. Is done. The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3 via the four-way valve 2. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 radiates heat to the heat exchange medium, and becomes high-pressure liquid refrigerant.

  The high-pressure refrigerant that has flowed out of the condenser 3 flows into the suction bypass circuit 8, and the high-pressure refrigerant that flows into the suction bypass circuit 8 is decompressed and expanded by the suction bypass valve 9 to become a low-temperature and low-pressure gas-liquid two-phase refrigerant. The high-temperature and low-pressure gas decompressed by the discharge gas bypass valve 7 and the low-temperature and low-pressure gas-liquid two-phase refrigerant decompressed and expanded by the suction bypass valve 9 merge to become a low-temperature and low-pressure refrigerant, and are compressed via the accumulator 15. It is sucked into the machine 1 again.

  During the negative pressure prevention operation, the main expansion valve 4 is substantially closed, so that the low-pressure two-phase refrigerant hardly flows through the evaporator 5, and the refrigerant is not evaporated by heat exchange with the outside air. . In the negative pressure prevention operation, since the evaporator 5 is not used, the amount of refrigerant required is smaller than that in the normal hot water supply operation, and surplus refrigerant is generated. However, in the second modification, the surplus refrigerant can be stored in the accumulator 15. .

  As described above, in Modification 2 of the refrigeration cycle apparatus according to Embodiment 4, since the accumulator 15 is provided on the suction side of the compressor 1, the excess refrigerant is supplied to the accumulator 15 during the negative pressure prevention operation in which excess refrigerant is generated. Can be stored. For this reason, the liquid back operation to the suction side of the compressor 1 can be prevented, and the highly reliable negative pressure prevention operation can be continued.

Embodiment 5. FIG.
In the first to fourth embodiments, a part of the refrigerant discharged from the compressor 1 and directed to the condenser 3 is branched into the discharge gas bypass circuit 6 to branch from the main circuit 30, and the branched refrigerant is supplied to the compressor 1. It is configured to return to the suction side. When returning the branch refrigerant to the suction side of the compressor 1, the branch refrigerant is combined with the refrigerant flowing through the suction bypass circuit 8 and downstream of the suction bypass valve 9 and returned. In contrast, in the fifth embodiment, when returning the branched refrigerant branched from the main circuit 30 to the suction side of the compressor 1, the branched refrigerant is divided into the refrigerant flowing through the suction bypass circuit 8 and the upstream side of the suction bypass valve 9. It is configured to be returned after being merged.

  FIG. 13 is a refrigerant circuit diagram of the refrigeration cycle apparatus according to Embodiment 5 of the present invention, and shows a state when a hot water supply operation for raising the temperature of water on the load side is being performed. FIG. 14 is a Ph diagram showing the operation state of the operation of FIG.

  In the fifth embodiment, the discharge gas bypass circuit 6 and the discharge gas bypass valve 7 are eliminated from the configuration of the first embodiment shown in FIG. 1, while the condenser bypass circuit 16 and the condenser bypass circuit 16 that bypass the condenser 3 are condensed. And a condenser bypass valve 17 for adjusting the flow rate of the condenser bypass circuit 16. The bypass circuit 41 according to the fifth embodiment includes a condenser bypass circuit 16 and a suction bypass circuit 8, and refrigerant (a part of the refrigerant discharged from the compressor 1) that has flowed out of the condenser bypass circuit 16 and the condenser. 3 is a circuit that merges the refrigerant that has flowed out of the refrigerant flow into the suction side of the compressor 1 via the suction bypass circuit 8. In this bypass circuit 41, the suction bypass valve 9 constitutes a negative pressure adjusting valve according to the present invention.

The condenser bypass circuit 16 bypasses a part of the refrigerant discharged from the compressor 1 to the outlet side of the condenser 3.
The condenser bypass valve 17 adjusts the bypass amount of the discharge gas that flows to the condenser bypass circuit 16.

  Next, the operation of the refrigeration cycle of the refrigeration cycle apparatus according to Embodiment 5 will be described with reference to FIG. During normal hot water supply operation, the condenser bypass valve 17 and the suction bypass valve 9 are fully closed, and there is no refrigerant flow in the condenser bypass circuit 16 and the suction bypass circuit 8. Therefore, the operation of the refrigeration cycle during normal hot water supply in Embodiment 5 is the same as that in Embodiment 1. Therefore, only the negative pressure prevention operation will be described. The point that the main expansion valve 4 is substantially closed during the negative pressure prevention operation is the same as in the first embodiment.

  Next, the operation of the negative pressure prevention operation will be described using the refrigerant circuit diagram of FIG. 13 and the Ph diagram of FIG. [1] to [5] in FIG. 14 indicate refrigerant states at positions [1] to [5] in FIG.

  In the negative pressure prevention operation in the refrigeration cycle apparatus according to Embodiment 5, the refrigerant ([1]) in the low-temperature and low-pressure gas state is sucked into the compressor 1 and compressed to become the high-temperature and high-pressure gas ([2]). Discharged. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the four-way valve 2 and branches into two branches, one of which flows into the condenser bypass circuit 16 and is decompressed by the condenser bypass valve 17 ([3] ) And flows out of the condenser bypass circuit 16. The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3. 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 ([4]).

  The high-temperature high-pressure gas refrigerant that has flowed out of the condenser bypass circuit 16 and the high-pressure liquid refrigerant that has flowed out of the condenser 3 merge to form a two-phase refrigerant ([5]) having a high pressure and high dryness. The two-phase refrigerant flows into the suction bypass circuit 8, is decompressed and expanded by the suction bypass valve 9, becomes a low-temperature and low-pressure gas refrigerant ([1]), and is sucked into the compressor 1 again. During the negative pressure prevention operation, the main expansion valve 4 is substantially closed, so that the low-pressure two-phase refrigerant hardly flows through the evaporator 5, and the refrigerant is not evaporated by heat exchange with the outside air. .

  In the first to fourth embodiments, the compressor suction pressure is controlled by the discharge gas bypass valve 7. In contrast, in the fifth embodiment, the refrigerant flows into the refrigerant flowing out of the condenser bypass circuit 16 ([3]) and the refrigerant flowing out of the condenser 3 ([4 ]) And the combined refrigerant is decompressed by the suction bypass valve 9 and sucked into the compressor 1. For this reason, in the fifth embodiment, the suction pressure of the compressor is controlled by the suction bypass valve 9.

FIG. 15 is a system configuration diagram of a refrigeration cycle apparatus according to Embodiment 5 of the present invention.
As shown in FIG. 15, in the refrigeration cycle apparatus according to the fifth embodiment, in the system configuration of the first embodiment shown in FIG. 4, the control device 20 replaces the discharge gas bypass valve 7 with a condenser bypass. The point from which the valve 17 is connected so that control is possible differs from FIG. As a functional configuration of the control device 20, the control device 20 includes a negative pressure prevention control unit 20A and a superheat degree control unit 20B. The negative pressure prevention control means 20A performs a negative pressure prevention operation for controlling the opening of the suction bypass valve 9 to prevent the suction pressure of the compressor 1 from becoming negative. The superheat degree control means 20B adjusts the opening degree of the condenser bypass valve 17 so that the superheat degree of the intake gas of the compressor 1 becomes a preset set value. The negative pressure prevention control means 20A and the superheat degree control means 20B are functionally constituted by a CPU and a control program. The other configuration is the same as that of FIG.

  FIG. 16 is a flowchart showing the control procedure of the negative pressure prevention operation in the refrigeration cycle apparatus according to Embodiment 5 of the present invention. The flowchart of the fifth embodiment shown in FIG. 16 differs from the flowchart of the first embodiment shown in FIG. 5 in the following points. That is, the opening degree control of the discharge gas bypass valve 7 in steps S6 and S7 in FIG. 5 is replaced with the opening degree control of the suction bypass valve 9 in steps S6a and S7a in FIG. Further, the opening degree control of the suction bypass valve 9 in step S11 and step S12 in FIG. 5 is replaced with the opening degree control of the condenser bypass valve 17 in FIG. The rest is the same as the control flowchart of FIG. Hereinafter, the control of the negative pressure prevention operation in the fifth embodiment will be described with a focus on the differences from the first embodiment.

  In the fifth embodiment, when the compressor suction pressure Ps is lower than the set value 2 as a result of comparing the compressor suction pressure Ps with the preset set value 2 in step S5, the opening degree of the suction bypass valve 9 is set. It is enlarged (S6a). As a result, the compressor suction pressure Ps increases and approaches the set value 2. On the other hand, when the compressor suction pressure Ps is higher than the set value 2, the opening degree of the suction bypass valve 9 is decreased (S7a). As a result, the compressor suction pressure Ps decreases and approaches the set value 2.

  Further, in the fifth embodiment, as a result of comparing the compressor suction superheat degree SHs with the set value 3 set in advance as the target value of the compressor suction superheat degree in step S10, the compressor suction superheat degree SHs is set to the set value 3. If smaller, the control device 20 increases the opening of the condenser bypass valve 17 (S11a). As a result, the compressor intake superheat degree SHs increases and approaches the set value 3. On the other hand, when the compressor suction superheat degree SHs is larger than the set value 3, the opening degree of the condenser bypass valve 17 is reduced (S12a). Thereby, the compressor suction superheat degree SHs decreases and approaches the set value 3. Then, after the processing of S11a or S12a, the control device 20 returns to S5, and repeats the control to match the compressor suction pressure Ps and the compressor suction superheat degree SHs with the corresponding set value 2 and set value 3, respectively.

  As described above, the refrigeration cycle apparatus according to the fifth embodiment has the same effects as those of the first embodiment although the bypass valve to be controlled is different in controlling the compressor suction pressure and the compressor suction superheat degree. Can be obtained. That is, when the outside air temperature is low and the compressor suction pressure is close to a negative pressure, the hot water supply operation is continued without fully evaporating the refrigerant in the evaporator 5 with the main expansion valve 4 fully closed. The compressor suction pressure is controlled by the opening degree of the suction bypass valve 9, and the suction superheat degree of the compressor 1 is controlled by the opening degree of the condenser bypass valve 17. For this reason, the hot water supply operation can be continued without causing the compressor suction pressure to become negative and with the compressor suction superheat degree being appropriate. Therefore, inconveniences such as malfunction due to air suction can be avoided even if the outside air decreases. Furthermore, since it is not necessary to stop the hot water supply operation for raising the temperature of the water even in a low outside air condition in the water heater, it is possible to prevent water piping from being frozen.

Embodiment 6 FIG.
In other words, the sixth embodiment corresponds to a configuration in which the fifth embodiment is combined with the fourth embodiment that includes the receiver 13. Hereinafter, the difference between the sixth embodiment and the fifth embodiment will be mainly described.

FIG. 17 is a refrigerant circuit diagram of the refrigeration cycle apparatus according to Embodiment 6 of the present invention.
As shown in FIG. 17, the system configuration diagram of the refrigeration cycle apparatus according to Embodiment 6 is provided with a receiver 13. Other components are the same as those in the fifth embodiment shown in FIG.

  The receiver 13 is disposed in a pipe connecting the condenser 3 and the suction bypass valve 9 and stores excess refrigerant generated during operation.

  Next, the operation of the refrigeration cycle according to Embodiment 6 will be described with reference to FIG. Note that the normal hot water supply operation is the same as that of the first embodiment, and is omitted, and only the negative pressure prevention operation will be described.

  A refrigerant in a low-temperature and low-pressure gas state is sucked into the compressor 1, compressed, and discharged as a high-temperature and high-pressure gas. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the four-way valve 2 and branches into two branches. One of the refrigerant flows into the condenser bypass circuit 16 and is depressurized by the condenser bypass valve 17. The circuit 16 flows out. The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3. 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 high-pressure liquid refrigerant and flows into the receiver 13. The high-temperature and high-pressure gas refrigerant that has flowed out of the condenser bypass circuit 16 and the high-pressure liquid refrigerant that has flowed out of the receiver 13 merge to form a two-phase refrigerant with high pressure and high dryness, and flow into the suction bypass circuit 8. The two-phase refrigerant that has flowed into the suction bypass circuit 8 is decompressed and expanded by the suction bypass valve 9 to become a low-temperature and low-pressure gas refrigerant, and is sucked into the compressor 1 again.

  During the negative pressure prevention operation, the main expansion valve 4 is substantially closed, so that the low-pressure two-phase refrigerant hardly flows through the evaporator 5, and the refrigerant is not evaporated by heat exchange with the outside air. . In the negative pressure prevention operation, since the evaporator 5 is not used, the amount of refrigerant required is smaller than in the normal hot water supply operation, and surplus refrigerant is generated. However, in the sixth embodiment, surplus refrigerant is stored in the receiver 13.

  As described above, the refrigeration cycle apparatus according to the sixth embodiment can obtain the same effects as those of the fifth embodiment and the following effects. In other words, since the excess refrigerant can be stored in the receiver 13 during the negative pressure prevention operation, the liquid back operation to the suction side of the compressor 1 can be prevented, and the highly reliable negative pressure prevention operation can be continued.

  The sixth embodiment has a configuration including a refrigerant storage container (here, receiver 13), but the arrangement of the refrigerant storage container is not limited to the arrangement shown in FIG. It can be modified as described above.

<Modification 1>
FIG. 18 is a refrigerant circuit diagram of Modification 1 of the refrigeration cycle apparatus according to Embodiment 6 of the present invention.

  As shown in FIG. 18, the refrigerant circuit of Modification 1 of the refrigeration cycle apparatus according to Embodiment 6 is provided with a receiver 13 a and a check valve 14 instead of the receiver 13 of FIG. 17. Other components are the same as those in FIG.

  The receiver 13a is a refrigerant storage container that stores excess refrigerant generated during operation. The receiver 13 a is provided in parallel with the main circuit 30 on the outlet side of the condenser 3. In other words, the receiver 13 a is provided in parallel to the pipe between the junction between the upstream end of the condenser bypass circuit 16 and the main circuit 30 and the outlet of the condenser 3.

  The check valve 14 prevents the refrigerant from flowing into the receiver 13a from the main expansion valve 4 side. During the hot water supply operation, the evaporator 5 may be frosted. In this case, the reverse defrost operation is performed. The reverse defrost operation is an operation in which the four-way valve 2 is switched in the direction of the dotted line in FIG. 18 and the high-temperature high-pressure gas refrigerant discharged from the compressor 1 is supplied to the evaporator 5 to remove frost attached to the evaporator 5. The check valve 14 prevents the refrigerant from flowing in during the reverse defrost operation.

  Next, the refrigeration cycle operation of Modification 1 of the refrigeration cycle apparatus according to Embodiment 6 will be described with reference to FIG. In addition, since it is the same as that of Embodiment 5 about normal hot water supply operation, it abbreviate | omits and demonstrates only negative pressure prevention operation. The point that the main expansion valve 4 is substantially closed during the negative pressure prevention operation is the same as in the fifth embodiment.

  In the negative pressure prevention operation of the first modified example, the refrigerant in a low-temperature and low-pressure gas state is sucked into the compressor 1 and compressed to be discharged as a high-temperature and high-pressure gas. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the four-way valve 2 and branches into two branches. One of the refrigerant flows into the condenser bypass circuit 16 and is depressurized by the condenser bypass valve 17. The circuit 16 flows out. The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 radiates heat to the heat exchange medium, and becomes high-pressure liquid refrigerant.

  The high-pressure refrigerant that has flowed out of the condenser 3 is branched into two, one flows into the main circuit 30 and the other is condensed and stored in the receiver 13a. The high-pressure refrigerant that has flowed to the main circuit 30 merges with the high-temperature and high-pressure gas refrigerant that has flowed out of the condenser bypass circuit 16, and becomes a high-pressure two-phase refrigerant with high dryness. This two-phase refrigerant flows into the suction bypass circuit 8, is decompressed and expanded by the suction bypass valve 9, becomes a low-temperature and low-pressure gas refrigerant, and is sucked into the compressor 1 again.

  During the negative pressure prevention operation, the main expansion valve 4 is substantially closed, so that the low-pressure two-phase refrigerant hardly flows through the evaporator 5, and the refrigerant is not evaporated by heat exchange with the outside air. . In the negative pressure prevention operation, since the evaporator 5 is not used, the amount of refrigerant required is smaller than in the normal hot water supply operation, and surplus refrigerant is generated. However, in Embodiment 6, the surplus refrigerant is stored in the receiver 13a.

  As described above, in Modification 1 of the refrigeration cycle apparatus according to Embodiment 6, the receiver 13a is provided in parallel with the main circuit 30 on the outlet side of the condenser 3. For this reason, even if the outlet of the condenser 3 is in the state of a two-phase refrigerant, it is possible to store surplus refrigerant in the receiver 13a. Therefore, during the negative pressure prevention operation in which surplus refrigerant is generated, the liquid back operation to the suction side of the compressor 1 can be prevented, and the highly reliable negative pressure prevention operation can be continued.

<Modification 2>
FIG. 19 is a refrigerant circuit diagram of Modification 2 of the refrigeration cycle apparatus according to Embodiment 6 of the present invention.

  As shown in FIG. 19, the refrigerant circuit of Modification 1 of the refrigeration cycle apparatus according to Embodiment 6 is provided with an accumulator 15 instead of the receiver 13 of FIG. 17. Other components are the same as those in FIG.

  The accumulator 15 is provided on the suction side of the compressor 1 and stores excess refrigerant generated during operation.

  Next, the operation of Modification 2 of the refrigeration cycle apparatus according to Embodiment 6 will be described with reference to FIG. Note that the normal hot water supply operation is the same as that of the first embodiment, and is omitted, and only the negative pressure prevention operation will be described.

  In the negative pressure prevention operation of the modified example 2, the low-temperature and low-pressure gaseous refrigerant is sucked into the compressor 1, compressed, and discharged as high-temperature and high-pressure gas. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the four-way valve 2 and branches into two branches. One of the refrigerant flows into the condenser bypass circuit 16 and is depressurized by the condenser bypass valve 17. The circuit 16 flows out. The other branched high-temperature high-pressure gas refrigerant flows into the condenser 3. The high-temperature high-pressure gas refrigerant that has flowed into the condenser 3 radiates heat to the heat exchange medium, and becomes high-pressure liquid refrigerant. The high-temperature and high-pressure gas refrigerant that has flowed out of the condenser bypass circuit 16 and the high-pressure liquid refrigerant that has flowed out of the condenser 3 merge to form a two-phase refrigerant with high pressure and high dryness, and flow into the suction bypass circuit 8. The two-phase refrigerant that has flowed into the suction bypass circuit 8 is decompressed and expanded by the suction bypass valve 9 to become a low-temperature and low-pressure refrigerant, and is sucked into the compressor 1 again via the accumulator 15.

  During the negative pressure prevention operation, the main expansion valve 4 is substantially closed, so that the low-pressure two-phase refrigerant hardly flows through the evaporator 5, and the refrigerant is not evaporated by heat exchange with the outside air. .

  As described above, in the second modification of the refrigeration cycle apparatus according to the sixth embodiment, since the accumulator 15 is provided on the suction side of the compressor 1, the excess refrigerant is supplied to the accumulator 15 during the negative pressure prevention operation in which excess refrigerant is generated. Can be stored. For this reason, the liquid back operation to the suction side of the compressor 1 can be prevented, and the highly reliable negative pressure prevention operation can be continued.

  In each of the above embodiments and modifications, a single refrigerant of HFO-1234yf, a single refrigerant of HFO-1234ze, a mixed refrigerant of HFO-1234yf or HFO-1234ze and R32 is used as the refrigerant. In addition, the refrigerant | coolant should just be a refrigerant | coolant with a high boiling point compared with R407C. In addition, the refrigerant is preferably a refrigerant having a lower global warming potential than R407C.

  In each of the above embodiments, the case where the refrigeration cycle apparatus is applied to a heat pump type hot water heater has been described, but the present invention can also be applied to an air conditioner or the like.

  1 Compressor, 2 Four way valve, 3 Condenser, 4 Main expansion valve, 5 Evaporator, 6 Discharge gas bypass circuit, 7 Discharge gas bypass valve, 8 Suction bypass circuit, 9 Suction bypass valve, 10 Two way valve, 11 Ejector , 11a Nozzle, 11b Throttle part, 11c Diffuser, 11d Refrigerant suction part, 12 Suction pipe, 13 Receiver, 13a Receiver, 14 Check valve, 15 Accumulator, 16 Condenser bypass circuit, 17 Condenser bypass valve, 20 Control device, 20A Negative pressure prevention control means, 20B Superheat degree control means, 20a Negative pressure prevention control means, 20b Superheat degree control means, 21 Compressor intake pressure sensor, 22 Compressor intake temperature sensor, 30 Main circuit, 40 Bypass circuit, 41 Bypass circuit.

In the refrigeration cycle apparatus according to the present invention, a compressor, a condenser, a main expansion valve, and an evaporator are connected in a ring shape, a main circuit in which a refrigerant having a higher boiling point than R407C circulates, and refrigerant discharged from the compressor A bypass circuit that joins a part of the refrigerant and the refrigerant that has flown out of the condenser to flow into the suction side of the compressor, a negative pressure adjustment valve that adjusts the flow rate of the bypass circuit, and a compressor that controls the negative pressure adjustment valve And a negative pressure prevention control means for performing a negative pressure prevention operation for preventing the suction pressure from becoming negative . The negative pressure prevention control means closes the main expansion valve during the negative pressure prevention operation .

Claims (23)

A main circuit in which a compressor, a condenser, a main expansion valve, and an evaporator are annularly connected, and a refrigerant having a higher boiling point than R407C circulates;
A bypass circuit for joining a part of the refrigerant discharged from the compressor and the refrigerant flowing out of the condenser to flow into the suction side of the compressor;
A negative pressure adjusting valve for adjusting the flow rate of the bypass circuit;
A refrigeration cycle apparatus comprising negative pressure prevention control means for performing a negative pressure prevention operation for controlling the negative pressure regulating valve to prevent the suction pressure of the compressor from becoming negative. The bypass circuit is:
A discharge gas bypass circuit that bypasses a part of the refrigerant discharged from the compressor to the suction side, and a suction that causes the refrigerant that flows out of the condenser to join the discharge gas bypass circuit and flow into the suction side of the compressor A bypass circuit,
The refrigeration cycle apparatus according to claim 1, wherein the negative pressure adjusting valve is a discharge gas bypass valve that adjusts a flow rate of the discharge gas bypass circuit. A pressure sensor for detecting the suction pressure of the compressor;
The negative pressure prevention control means starts the negative pressure prevention operation to control the discharge gas bypass valve when the suction pressure detected by the pressure sensor is lower than a first preset value. 2. The refrigeration cycle apparatus according to 2.   The negative pressure prevention control means closes the main expansion valve during the negative pressure prevention operation and adjusts the opening of the discharge gas bypass valve so that the suction pressure becomes a second preset value. The refrigeration cycle apparatus according to claim 2 or claim 3.   The refrigeration cycle apparatus according to any one of claims 2 to 4, further comprising a suction bypass valve that adjusts a flow rate of the suction bypass circuit to control a degree of superheat of the suction gas of the compressor.   6. The refrigeration cycle according to claim 5, further comprising a superheat degree control means for adjusting an opening degree of the suction bypass valve so that a superheat degree of the suction gas of the compressor becomes a preset third set value. apparatus.   The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein the main circuit further includes a four-way valve that switches a flow direction of the refrigerant discharged from the compressor.   The refrigeration cycle apparatus according to claim 7, further comprising a two-way valve between the four-way valve and the evaporator.   9. The refrigeration cycle apparatus according to claim 8, wherein the negative pressure prevention control means closes the two-way valve during the negative pressure prevention operation. In the bypass circuit, an ejector provided in a discharge gas bypass circuit that bypasses a part of the refrigerant discharged from the compressor to the suction side;
The refrigeration cycle apparatus according to claim 7, further comprising a suction circuit that sucks a refrigerant between the evaporator and the four-way valve into a suction portion of the ejector.   The refrigeration cycle apparatus according to any one of claims 1 to 9, further comprising a receiver on an outlet side of the condenser.   The refrigeration cycle apparatus according to any one of claims 1 to 9, further comprising a receiver in parallel with the main circuit on an outlet side of the condenser.   The refrigeration cycle apparatus according to any one of claims 1 to 9, further comprising an accumulator on the compressor suction side. The bypass circuit is:
A condenser bypass circuit that bypasses a part of the refrigerant discharged from the compressor to the outlet side of the condenser, and a refrigerant that flows out of the condenser bypass circuit and the condenser and joins the suction side of the compressor A suction bypass circuit for bypassing
The refrigeration cycle apparatus according to claim 1, wherein the negative pressure adjusting valve is a suction bypass valve that adjusts a flow rate of the suction bypass circuit. A pressure sensor for detecting the suction pressure of the compressor;
The negative pressure prevention control means starts the negative pressure prevention operation and controls the suction bypass valve when the suction pressure detected by the pressure sensor is lower than a first preset value. The refrigeration cycle apparatus described.   The negative pressure prevention control means closes the main expansion valve during the negative pressure prevention operation and adjusts the opening of the suction bypass valve so that the suction pressure becomes a second preset value. The refrigeration cycle apparatus according to claim 14 or claim 15.   The refrigeration cycle apparatus according to any one of claims 14 to 16, further comprising a condenser bypass valve that adjusts a flow rate of the condenser bypass circuit to control a degree of superheat of the suction gas of the compressor.   18. The refrigeration cycle according to claim 17, further comprising a superheat degree control means for adjusting an opening degree of the condenser bypass valve so that a superheat degree of the suction gas of the compressor becomes a preset third set value. apparatus.   The refrigeration cycle apparatus according to any one of claims 14 to 18, wherein the main circuit further includes a four-way valve that switches a flow direction of the refrigerant discharged from the compressor.   The refrigeration cycle apparatus according to any one of claims 14 to 19, further comprising a receiver on an outlet side of the condenser.   The refrigeration cycle apparatus according to any one of claims 14 to 19, further comprising a receiver in parallel with the main circuit on an outlet side of the condenser.   The refrigeration cycle apparatus according to any one of claims 14 to 19, further comprising an accumulator on the compressor suction side.   The refrigeration according to any one of claims 1 to 22, wherein the refrigerant is any one of a single refrigerant of HFO-1234yf, a single refrigerant of HFO-1234ze, and a mixed refrigerant containing HFO-1234yf or HFO-1234ze. Cycle equipment.

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