JPWO2018163422A1 - Refrigeration cycle equipment - Google Patents

Abstract

The refrigeration cycle apparatus (1) according to the present invention includes an on-off valve (16) and a control device (17). The on-off valve (16) is connected in parallel with the compressor (11) between the discharge port and the suction port of the compressor (11). The control device (17) controls opening and closing of the on-off valve (16) and switches the operation mode. The operation mode includes a heating mode, a defrost mode, and a pressure equalization mode. In the pressure equalization mode, the on-off valve (16) is opened. In the pressure equalization mode, the flow path resistance of the open on-off valve (16) is larger than the flow path resistance of the four-way valve (15). A control apparatus (17) switches an operation mode in order of heating mode, pressure equalization mode, and defrost mode.

Description

  The present invention relates to a refrigeration cycle apparatus that performs defrosting of a heat exchanger by switching a refrigerant circulation direction and causing a heat exchanger functioning as an evaporator in a heating mode to function as a condenser.

  Conventionally, there is known a refrigeration cycle apparatus that performs defrosting of a heat exchanger by switching a refrigerant circulation direction and causing a heat exchanger that functions as an evaporator in a heating mode to function as a condenser. . For example, in Japanese Patent Application Laid-Open No. 2011-174661 (Patent Document 1), after performing a pump-down operation for collecting refrigerant in a receiver, the refrigerant circuit is switched from a heating cycle to a cooling cycle by a four-way valve to start a defrost operation. An air heat source heat pump hot water supply / air conditioner is disclosed.

JP 2011-174661 A

  When the circulation direction of the refrigerant in the heating mode is switched by a flow path switching device such as a four-way valve in order to start the defrosting mode, it is connected to the discharge port of the compressor in the heating mode and functions as a condenser. One heat exchanger is connected to the inlet of the compressor. On the other hand, the second heat exchanger connected to the compressor inlet in the heating mode and functioning as an evaporator is connected to the compressor outlet in the defrost mode. In the heating mode, the pressure of the first heat exchanger connected to the discharge port (high pressure side) of the compressor is that of the second heat exchanger connected to the suction port (low pressure side) of the compressor. Higher than pressure. Immediately after the refrigerant circulation direction is switched by the four-way valve to start the defrosting mode, the differential pressure in the heating mode remains between the first heat exchanger and the second heat exchanger. When the defrost mode is started and the compressor is operated with the differential pressure remaining, a large amount of refrigerant can move from the first heat exchanger to the second heat exchanger.

  When the amount of refrigerant remaining in the first heat exchanger decreases, the pressure and temperature of the first heat exchanger decrease. When the temperature of the first heat exchanger decreases, for example, condensation in the refrigeration cycle apparatus, or pipe breakage due to solidification of a heat medium such as water that exchanges heat with the refrigerant in the first heat exchanger and conveys heat to the heating terminal. Can occur. As a result, stable operation of the refrigeration cycle apparatus can be difficult.

  The present invention has been made to solve the above-described problems, and its object is to suppress a temperature drop at the start of the defrosting mode in a heat exchanger functioning as a condenser in the heating mode. That is.

  The refrigeration cycle apparatus according to the present invention includes a heating mode and a defrosting mode as operation modes. In the heating mode, the refrigerant circulates in the order of the compressor, the flow path switching device, the first heat exchanger, the expansion valve, and the second heat exchanger. In the defrost mode, the refrigerant circulates in the order of the compressor, the flow path switching device, the second heat exchanger, the expansion valve, and the first heat exchanger. The refrigeration cycle apparatus includes a flow control valve and a control device. The flow control valve is connected in parallel with the compressor between the discharge port of the compressor and the suction port of the compressor. The control device controls the opening degree of the flow control valve. The control device switches the operation mode. The operation mode further includes a pressure equalization mode. In the pressure equalization mode, the flow control valve is open. In the pressure equalization mode, the flow resistance of the flow control valve corresponding to the opening of the flow control valve is larger than the flow resistance of the flow switching device. The control device switches the operation mode in the order of the heating mode, the pressure equalization mode, and the defrosting mode.

  In the refrigeration cycle apparatus according to the present invention, when the operation mode is switched from the heating mode to the defrosting mode, the heating mode, the pressure equalization mode, and the defrosting mode are executed in this order. In the pressure equalization mode, since the flow control valve is open, the high-pressure side refrigerant moves to the low-pressure side via the flow control valve. The differential pressure between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant at the end of the pressure equalization mode (at the start of the defrost mode) is the difference at the time of the pressure equalization mode start (at the end of the heating mode). It becomes smaller than the pressure. Moreover, the flow path resistance corresponding to the opening degree of the flow regulating valve in the pressure equalization mode is larger than the flow path resistance of the flow path switching device. Therefore, the refrigerant quantity flowing out from the first heat exchanger in the pressure equalization mode can be suppressed. In the pressure equalization mode, the pressure difference at the start of the defrost mode between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant is set to the end of the heating mode while suppressing the amount of refrigerant flowing out of the first heat exchanger. It can be made smaller than the differential pressure at the time. In addition, the pressure equalization mode is executed before the defrosting mode, and the differential pressure at the start of the defrosting mode between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant is calculated as the differential pressure at the end of the heating mode. By making it smaller than this, the amount of refrigerant flowing out from the first heat exchanger at the start of the defrosting mode can be suppressed. Therefore, the temperature fall of the 1st heat exchanger at the time of defrost mode start can be controlled. As a result, the refrigeration cycle apparatus can be stably operated.

It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus which concerns on Embodiment 1, and the flow of the refrigerant | coolant in heating mode. It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus of FIG. 1, and the flow of the refrigerant | coolant in a defrost mode. It is a flowchart for demonstrating the flow of the process performed by the control apparatus of FIG. 1 when the defrost start conditions are satisfied in heating mode. It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus of FIG. 1, and the flow of the refrigerant | coolant in pressure equalization mode. It is a flowchart which shows the flow of the process performed by the control apparatus of FIG. 1 in pressure equalization mode. It is a flowchart which shows the flow of the process performed by the control apparatus of FIG. 1 in a defrost mode. FIG. 5 is an enlarged view of the vicinity of a connection portion between a flow path connecting the suction port of the compressor and the four-way valve in FIG. 4 and a flow path through which refrigerant from the on-off valve passes. It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus which concerns on Embodiment 2, and the flow of the refrigerant | coolant at the time of defrost mode start. It is a flowchart which shows the flow of the process performed by the control apparatus of FIG. 8 in a defrost mode. 10 is a flowchart showing a flow of processing performed by the control device of the refrigeration cycle apparatus according to Embodiment 3 when the defrosting start condition is satisfied in the heating mode. It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus which concerns on Embodiment 3, and the flow of the refrigerant | coolant in pump down mode. It is a flowchart which shows the flow of the process performed by the control apparatus of FIG. 11 in pump down mode. It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus which concerns on the modification 1 of Embodiment 3, and the flow of the refrigerant | coolant in pump down mode. 10 is a flowchart illustrating an example of processing performed when a defrost start condition is satisfied in a refrigeration cycle apparatus according to Modification 2 of Embodiment 3. 10 is a flowchart illustrating another example of processing performed when a defrost start condition is satisfied in the refrigeration cycle apparatus according to Modification 2 of Embodiment 3. It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus which concerns on Embodiment 4, and the flow of the refrigerant | coolant in pressure equalization mode. It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus which concerns on the modification of Embodiment 4, and the flow of the refrigerant | coolant in pressure equalization mode. It is a figure which shows collectively the function structure of the refrigerating-cycle apparatus which concerns on Embodiment 5, and the flow of the refrigerant | coolant in pressure equalization mode.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a functional configuration of the refrigeration cycle apparatus 1 according to Embodiment 1 and a refrigerant flow in the heating mode. The operation mode of the refrigeration cycle apparatus 1 includes a heating mode and a defrosting mode. As shown in FIG. 1, the refrigeration cycle apparatus 1 includes a compressor 11, a heat exchanger 12, an expansion valve 13, a heat exchanger 14, a four-way valve 15, an on-off valve 16, and a control device 17. Is provided. In the heating mode, the refrigerant circulates in the order of the compressor 11, the four-way valve 15, the heat exchanger 12, the expansion valve 13, and the heat exchanger 14. The on-off valve 16 corresponds to the flow control valve of the present invention.

  The compressor 11 adiabatically compresses a low-pressure gaseous refrigerant (gas refrigerant) and discharges the high-pressure gas refrigerant.

  The four-way valve 15 connects the discharge port of the compressor 11 and the heat exchanger 12 in the heating mode, and connects the heat exchanger 14 and the suction port of the compressor 11. In the heating mode, the four-way valve 15 forms a flow path so that the refrigerant circulates in the order of the compressor 11, the four-way valve 15, the heat exchanger 12, the expansion valve 13, and the heat exchanger 14.

  The heat exchanger 12 functions as a condenser in the heating mode. The gas refrigerant from the compressor 11 releases the condensation heat in the heat exchanger 12 and condenses to become a liquid refrigerant (liquid refrigerant). In the heat exchanger 12, heat exchange is performed between the refrigerant and the heat medium that conveys heat to the heating terminal 100. Examples of the heat medium include water and brine (brine).

  The expansion valve 13 adiabatically expands and depressurizes the liquid refrigerant, and flows it out as wet vapor in a gas-liquid two-phase state. As the expansion valve 13, for example, an electronically controlled expansion valve (LEV) can be used.

  The heat exchanger 14 is disposed outdoors and functions as an evaporator in the heating mode. The wet steam from the expansion valve 13 is vaporized by absorbing the heat of vaporization from outside air in the heat exchanger 14.

  The on-off valve 16 is connected in parallel with the compressor 11 between the discharge port and the suction port of the compressor 11. The channel resistance of the on-off valve 16 is larger than the channel resistance of the four-way valve 15. Note that the flow path resistance of the on-off valve is the flow path resistance when the on-off valve is open (the opening degree is fully open). That is, the Cv value of the on-off valve 16 when the on-off valve 16 is open is smaller than the Cv value of the four-way valve 15. The on-off valve 16 is closed in the heating mode.

  The control device 17 switches the operation mode of the refrigeration cycle apparatus 1. The control device 17 controls the driving frequency of the compressor 11 to control the amount of refrigerant discharged from the compressor 11 per unit time. The control device 17 controls the four-way valve 15 to switch the circulation direction of the refrigerant. The control device 17 controls the opening degree of the expansion valve 13. The control device 17 controls the opening / closing of the on-off valve 16. The control device 17 obtains the refrigerant pressure (suction pressure) at the suction port of the compressor 11 and the pressure (discharge pressure) of the refrigerant at the discharge port from the pressure sensors S1 and S2, respectively, and the differential pressure between the discharge pressure and the suction pressure. Is calculated.

  In the heating mode, frost may be generated in the heat exchanger 14 that is arranged outdoors and functions as an evaporator. When frost is generated in the heat exchanger 14, the heat exchange efficiency of the heat exchanger 14 functioning as an evaporator is lowered, and the performance of the refrigeration cycle apparatus 1 is lowered. In the refrigeration cycle apparatus 1, when frost is generated in the heat exchanger 14, the heating mode is interrupted, and a defrosting mode for removing the frost generated in the heat exchanger 14 is performed.

  FIG. 2 is a diagram illustrating the functional configuration of the refrigeration cycle apparatus 1 of FIG. 1 and the refrigerant flow in the defrosting mode. As shown in FIG. 2, in the defrost mode, the four-way valve 15 connects the discharge port of the compressor 11 and the heat exchanger 14, and connects the heat exchanger 12 and the suction port of the compressor 11. In the defrost mode, the four-way valve 15 forms a flow path so that the refrigerant circulates in the order of the compressor 11, the four-way valve 15, the heat exchanger 14, the expansion valve 13, and the heat exchanger 12. The heat exchanger 14 functions as a condenser in the defrosting mode. In the heat exchanger 14, the frost generated in the heat exchanger 14 is dissolved and removed by the condensation heat released when the refrigerant is liquefied.

  In the defrost mode, the heat exchanger 12 connected to the high pressure side in the heating mode is connected to the low pressure side. On the other hand, the heat exchanger 14 connected to the low pressure side in the heating mode is connected to the high pressure side. In the heating mode, the pressure of the heat exchanger 12 connected to the high pressure side is higher than the pressure of the heat exchanger 14 connected to the low pressure side. Immediately after starting the defrosting mode, the differential pressure in the heating mode remains between the heat exchanger 12 and the heat exchanger 14. When the defrost mode is started and the compressor 11 is operated in a state where the differential pressure remains, a large amount of refrigerant can move from the heat exchanger 12 to the heat exchanger 14.

  When the amount of refrigerant remaining in the heat exchanger 12 decreases, the pressure and temperature of the heat exchanger 12 decrease. When the temperature of the heat exchanger 12 decreases, for example, condensation in the refrigeration cycle apparatus 1 or damage to piping due to solidification of a heat medium such as water may occur. As a result, stable operation of the refrigeration cycle apparatus 1 can be difficult.

  Therefore, in the refrigeration cycle apparatus 1, when the defrosting start condition is satisfied in the heating mode, the operation mode is switched in the order of the heating mode, the pressure equalization mode, and the defrosting mode. In the pressure equalization mode, the connection state in the heating mode is maintained and the on-off valve 16 is opened, and the differential pressure at the start of the defrosting mode between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant is the heating mode. The pressure difference is made smaller than the differential pressure at the end of. Since the flow path resistance of the on-off valve 16 is larger than the flow path resistance of the four-way valve 15, the amount of refrigerant flowing out of the heat exchanger 12 in the pressure equalization mode can be suppressed. In the pressure equalization mode, the pressure difference at the start of the defrost mode between the high-pressure side pressure and the low-pressure side pressure is set to the differential pressure at the end of the heating mode while suppressing the amount of refrigerant flowing out of the heat exchanger 12. Can be made smaller. Further, the pressure equalization mode is executed before the defrosting mode, and the differential pressure between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant at the start of the defrosting mode is set to the differential pressure at the end of the heating mode. By making it smaller than this, the amount of refrigerant flowing out of the heat exchanger 12 at the start of the defrosting mode can be suppressed. Therefore, the temperature drop of the heat exchanger 12 at the start of the defrosting mode can be suppressed. As a result, the refrigeration cycle apparatus 1 can be stably operated.

  FIG. 3 is a flowchart showing a flow of processing in which the control device 17 in FIG. 1 switches the operation mode of the refrigeration cycle apparatus 1. Hereinafter, the step is simply referred to as S. The processing shown in FIG. 3 is executed by a main routine (not shown) that performs comprehensive control of the refrigeration cycle apparatus 1.

  As shown in FIG. 3, the control device 17 determines whether or not the termination condition of the refrigeration cycle apparatus 1 is satisfied in S <b> 10. Examples of the end condition of the refrigeration cycle apparatus 1 include a condition that the end operation is performed by the user, or a condition that the end time set by the user has arrived. If the end condition is satisfied (YES in S10), control device 17 returns the process to the main routine. If the end condition is not satisfied (NO in S10), control device 17 advances the process to S20. The control device 17 executes the heating mode in S20. When the defrosting start condition is satisfied in the heating mode, the control device 17 advances the process to S200. Examples of the defrosting start condition include a condition that the temperature of the heat exchanger 14 is lower than the reference temperature, or a condition that the amount of frost (frosting amount) generated in the heat exchanger 14 exceeds the reference amount. it can. The amount of frost formation can be calculated from the temperature of the heat exchanger 14 and the humidity around the heat exchanger 14.

  After executing the pressure equalization mode in S200, the control device 17 advances the process to S300. The control apparatus 17 returns a process to S10, after performing defrost mode in S300. The control device 17 switches the operation mode in the order of the heating mode (S20), the pressure equalization mode (S200), and the defrosting mode (S300).

  FIG. 4 is a diagram illustrating the functional configuration of the refrigeration cycle apparatus 1 of FIG. 1 and the refrigerant flow in the pressure equalization mode. As shown in FIG. 4, in the pressure equalization mode, the control device 17 stops the compressor 11, closes the expansion valve 13, and opens the on-off valve 16. In the pressure equalization mode, the four-way valve 15 maintains the connection between the discharge port of the compressor 11 and the heat exchanger 12 and the connection between the heat exchanger 14 and the suction port of the compressor 11 in the heating mode. Since the expansion valve 13 is closed, the refrigerant is prevented from moving from the heat exchanger 12 having a high refrigerant pressure to the heat exchanger 14 having a low refrigerant pressure via the expansion valve 13.

  Since the on-off valve 16 is open, the refrigerant flows from the heat exchanger 12 to the heat exchanger 14 via the on-off valve 16. The channel resistance of the on-off valve 16 is larger than the channel resistance of the four-way valve 15. Therefore, the refrigerant amount flowing out of the heat exchanger 12 in the pressure equalization mode is smaller than the refrigerant amount flowing out of the heat exchanger 12 when the defrosting mode is started without performing the pressure equalization mode. In the pressure equalization mode, the pressure difference at the start of the defrost mode between the high-pressure side pressure and the low-pressure side pressure is determined from the differential pressure at the end of the heating mode while suppressing the amount of refrigerant flowing out of the heat exchanger 12. Can also be reduced. As a result, the temperature drop of the heat exchanger 12 can be suppressed at the start of the defrost mode performed after the pressure equalization mode.

  FIG. 5 is a flowchart showing a flow of processing performed by the control device 17 of FIG. 1 in the pressure equalization mode. The process shown in FIG. 5 is a process performed in S200 of FIG.

  As shown in FIG. 5, the control device 17 stops the compressor 11 in S201 and advances the process to S202. The control device 17 closes the expansion valve 13 in S202 and advances the process to S203. The control device 17 opens the on-off valve 16 in S203 and advances the process to S204. In S204, the control device 17 determines whether or not the differential pressure between the discharge pressure and the suction pressure is smaller than the reference differential pressure. When the differential pressure between the discharge pressure and the suction pressure is smaller than the reference differential pressure (YES in S204), the controller 17 has sufficiently reduced the differential pressure between the high-pressure side refrigerant pressure and the low-pressure side refrigerant pressure. The process is returned to the main routine. When the differential pressure between the discharge pressure and the suction pressure is equal to or higher than the reference differential pressure (NO in S204), the control device 17 advances the process to S205. The control device 17 determines whether or not a reference time has elapsed since the opening / closing valve 16 was opened in S205. When the reference time has elapsed since opening of the on-off valve 16 (YES in S205), the control device 17 determines that the high pressure side refrigerant and the low pressure side refrigerant are sufficiently equalized, and performs processing. Return to main routine. If the reference time has not elapsed since opening of the on-off valve 16 (NO in S205), the control device 17 waits for a certain time in S206, and then returns the process to S204. The reference differential pressure in S204 and the reference time in S205 can be appropriately calculated through actual machine experiments or simulations.

  FIG. 6 is a flowchart showing a flow of processing performed by the control device 17 of FIG. 1 in the defrosting mode. The process shown in FIG. 6 is a process performed in S300 of FIG.

  As shown in FIG. 6, the control device 17 switches the four-way valve 15 in S301 and advances the process to S302. The control device 17 closes the on-off valve 16 in S302 and advances the process to S303. The control device 17 opens the expansion valve 13 to an appropriate opening degree in S303, and advances the process to S304. The control device 17 activates the compressor 11 in S304 and advances the process to S305. The control device 17 determines whether or not the defrost termination condition is satisfied in S305. When the defrost termination condition is satisfied (YES in S305), control device 17 returns the process to the main routine. When the defrost termination condition is not satisfied (NO in S305), the control device 17 waits for a certain time in S306, and then returns the process to S305. The defrosting termination condition includes, for example, a condition that the temperature of the heat exchanger 14 is equal to or higher than a reference temperature, or a condition that a reference time has elapsed since the start of the defrosting mode.

  Referring to FIG. 4 again, in the refrigeration cycle apparatus 1, the height of the heat exchanger 12 is lower than the height of the four-way valve 15. The height of the connecting portion J10 between the flow path connecting the suction port of the compressor 11 and the four-way valve 15 and the flow path through which the refrigerant from the on-off valve 16 passes is lower than the height of the four-way valve 15. Therefore, it becomes difficult for the refrigerant to move from the heat exchanger 12 to the four-way valve 15. Moreover, it becomes difficult for a refrigerant | coolant to move to the four-way valve 15 from the connection part J10. As a result, the amount of refrigerant flowing out of the heat exchanger 12 in the pressure equalization mode can be further suppressed.

  FIG. 7 is an enlarged view of the vicinity of the connection portion J10 between the flow path RP1 connecting the suction port of the compressor 11 and the four-way valve 15 in FIG. 4 and the flow path RP2 through which the refrigerant from the on-off valve 16 passes. As shown in FIG. 7, in the refrigeration cycle apparatus 1, the angle α1 formed by the flow paths RP1 and RP2 is larger than 0 degree and smaller than 180 degrees. Therefore, the refrigerant flowing through the flow path RP2 collides with the inner wall of the flow path RP1 at the connection portion J10 between the flow paths RP1 and RP2. Since the refrigerant from the on-off valve 16 is less likely to join the flow path RP1, the amount of refrigerant per unit time that passes through the on-off valve 16 in the pressure equalization mode decreases. As a result, the amount of refrigerant flowing out of the heat exchanger 12 can be further suppressed in the pressure equalization mode.

  Further, in the refrigeration cycle apparatus 1, the flow path RP2 is narrower than the flow path RP1, as shown in FIG. That is, the area of the passage portion of the refrigerant in the cross section of the flow path RP2 orthogonal to the traveling direction of the refrigerant moving in the flow path RP2 is the refrigerant in the cross section of the flow path RP1 orthogonal to the traveling direction of the refrigerant moving in the flow path RP1. It is smaller than the area of the passing part. Compared with the case where the thickness of the flow path RP2 is the same as the thickness of the flow path RP1, the amount of refrigerant per unit time passing through the on-off valve 16 in the pressure equalization mode can be reduced. As a result, the amount of refrigerant flowing out of the heat exchanger 12 can be further suppressed. Moreover, the manufacturing cost of the refrigeration cycle apparatus 1 can be suppressed as compared with the case where the thickness of the flow path RP2 is the same as the thickness of the flow path RP1.

  As mentioned above, according to the refrigerating cycle device concerning Embodiment 1, by performing pressure equalization mode before defrost mode, at the time of defrost mode start of the heat exchanger which was functioning as a condenser in heating mode Temperature drop can be suppressed. As a result, the refrigeration cycle apparatus can be stably operated.

Embodiment 2. FIG.
In Embodiment 1, the case where the on-off valve opened in the pressure equalization mode is closed before the compressor is started in the defrost mode has been described. In the second embodiment, a case where the on-off valve is closed after starting the compressor in the defrosting mode will be described.

  In the second embodiment, the compressor is operated with the on-off valve opened for a while from the start of the defrosting mode. While the release valve is open, a part of the refrigerant discharged from the compressor is returned to the compressor inlet via the on-off valve. The refrigerant from the heat exchanger functioning as the condenser in the heating mode is less likely to be sucked into the compressor by the amount of the refrigerant returned to the compressor inlet through the on-off valve. As a result, the amount of refrigerant flowing out from the heat exchanger at the start of the defrost mode can be further suppressed.

  The difference between the second embodiment and the first embodiment is the process flow in the defrosting mode. The other points are the same as in the first embodiment. That is, FIGS. 2 and 6 of the first embodiment are replaced with FIGS. 8 and 9 of the second embodiment, respectively. Since the configuration other than these is the same, the description will not be repeated.

  FIG. 8 is a diagram illustrating the functional configuration of the refrigeration cycle apparatus 2 according to Embodiment 2 and the refrigerant flow at the start of the defrosting mode. As shown in FIG. 8, the opening / closing valve 16 is opened at the start of the defrosting mode of the refrigeration cycle apparatus 2. While the on-off valve is open, a part of the refrigerant discharged from the compressor 11 is returned to the suction port of the compressor 11 through the on-off valve 16.

  FIG. 9 is a flowchart showing a flow of processing performed by the control device 17 of FIG. 8 in the defrosting mode. As shown in FIG. 8, after switching the four-way valve 15 in S <b> 311, the control device 17 advances the process to S <b> 312. The control device 17 opens the expansion valve 13 to an appropriate opening degree in S312, and advances the process to S313. The control device 17 activates the compressor 11 in S313 and advances the process to S314. The control device 17 determines whether or not the defrost termination condition is satisfied in S314. When the defrost termination condition is satisfied (YES in S314), control device 17 causes the process to proceed to S315. The controller 17 determines whether or not the on-off valve 16 is open in S315. When on-off valve 16 is closed (NO in S315), control device 17 returns the process to the main routine. If the on-off valve 16 is open (YES in S315), the control device 17 closes the on-off valve 16 in S316, and then returns the process to the main routine.

  When the defrost termination condition is not satisfied (NO in S314), control device 17 causes the process to proceed to S317. In S317, the control device 17 determines whether or not the suction pressure exceeds the reference pressure. If the suction pressure exceeds the reference pressure (YES in S317), the controller 17 determines that the suction pressure has increased sufficiently, closes the on-off valve 16 in S319, waits for a certain time in S320, and then performs the process in S314. Return to. If the suction pressure is equal to or lower than the reference pressure (NO in S317), control device 17 advances the process to S318. The control device 17 determines whether or not a reference time has elapsed since the compressor 11 was started in S318. If the reference time has elapsed since the start of the compressor 11 (YES in S318), it is determined that a sufficient time has passed to increase the suction pressure, and the on-off valve 16 is closed in S319, and the predetermined time is determined in S320. After waiting, the process returns to S314. If the reference time has not elapsed since the compressor 11 was started (NO in S318), the control device returns the process to S314. The reference pressure in S317 and the reference time in S318 can be appropriately calculated by actual machine experiments or simulations.

  As described above, even in the refrigeration cycle apparatus according to Embodiment 2, the temperature at the start of the defrosting mode of the heat exchanger functioning as a condenser in the heating mode by executing the pressure equalization mode before the defrosting mode. The decrease can be suppressed. As a result, the refrigeration cycle apparatus can be stably operated.

  In the second embodiment, the defrost mode start of the heat exchanger functioning as a condenser in the heating mode is started by operating the compressor with the on-off valve opened for a while from the start of the defrost mode. The temperature drop at the time can be further suppressed. As a result, the refrigeration cycle apparatus can be operated more stably.

Embodiment 3 FIG.
In Embodiment 1, the case where the pressure equalization mode is performed next to the heating mode when the defrosting start condition is satisfied has been described. In the third embodiment, a description will be given of a case where the pump down mode is performed next to the heating mode and the pressure equalization mode is performed next to the pump down mode when the defrosting start condition is satisfied. In the pump down mode, the amount of refrigerant in the heat exchanger functioning as a condenser in the heating mode is increased. By executing the pump down mode before the pressure equalization mode, the amount of refrigerant in the heat exchanger at the start of the pressure equalization mode is increased as compared to the first embodiment. Therefore, the temperature fall at the time of the defrost mode start of the said heat exchanger can further be suppressed. As a result, the refrigeration cycle apparatus can be operated more stably.

  The difference between the third embodiment and the first embodiment is that a pump down mode is added to the operation mode. That is, FIG. 3 of the first embodiment is replaced with FIG. 10 of the second embodiment. Since it is the same about other points, description is not repeated.

  FIG. 10 is a flowchart showing a flow of processing in which the control device of the refrigeration cycle apparatus according to Embodiment 3 switches the operation mode of the refrigeration cycle apparatus. As shown in FIG. 10, when the defrost start condition is satisfied in the heating mode (S20), the control device executes the pump down mode in S100. Thereafter, as in the first embodiment, the control device executes the pressure equalization mode in S200 and executes the defrosting mode in S300. When the defrosting start condition is satisfied, the control device switches the operation mode in the order of the heating mode, the pump down mode, the pressure equalization mode, and the defrosting mode.

  FIG. 11 is a diagram illustrating a functional configuration of the refrigeration cycle apparatus 3 according to Embodiment 3 and a refrigerant flow in the pump down mode. As shown in FIG. 11, in the pump down mode, the control device 17 operates the compressor 11, closes the expansion valve 13, and closes the on-off valve 16. In the pump down mode, the four-way valve 15 maintains the connection between the discharge port of the compressor 11 and the heat exchanger 12 and the connection between the heat exchanger 14 and the suction port of the compressor 11. Since the compressor 11 is operating and the expansion valve 13 is closed, the refrigerant discharged from the compressor 11 is stored in the heat exchanger 12. While the pump-down mode is performed, the amount of refrigerant in the heat exchanger 12 increases. The refrigerant amount in the heat exchanger 12 at the start of the pressure equalization mode is increased as compared with the first embodiment in which the pump down mode is not performed. At the start of the defrosting mode performed after the pressure equalization mode, the amount of refrigerant remaining in the heat exchanger 12 is increased from that in the first embodiment. Therefore, the temperature drop of the heat exchanger 12 is reduced from that in the first embodiment. Can also be suppressed.

  FIG. 12 is a flowchart showing a flow of processing performed by the control device 17 of FIG. 11 in the pump down mode. The process shown in FIG. 12 is a process performed in S100 of FIG.

  As shown in FIG. 12, the control device 17 closes the expansion valve 13 in S101, and advances the process to S102. In S102, the control device 17 determines whether or not the suction pressure is smaller than the reference pressure. When the suction pressure is smaller than the reference pressure (YES in S102), the controller 17 determines that the amount of refrigerant sucked into the compressor 11 has decreased due to a sufficient amount of refrigerant stored in the heat exchanger 12. Return processing to the main routine. If the suction pressure is equal to or higher than the reference pressure (NO in S102), control device 17 advances the process to S103. The control device 17 determines whether or not a reference time has elapsed since the expansion valve 13 was closed in S103. If the reference time has elapsed since the expansion valve 13 was closed (YES in S103), the control device 17 determines that a sufficient time has elapsed to increase the amount of refrigerant in the heat exchanger 12, and performs processing. Return to main routine. If the reference time has not elapsed since the expansion valve 13 was closed (NO in S103), the control device 17 waits for a certain time in S104, and then returns the process to S102.

Modification 1 of Embodiment 3
It is assumed that the amount of refrigerant flowing into the heat exchanger 12 in the pump down mode exceeds the capacity of the heat exchanger 12. In preparation for such a case, it is desirable that a refrigerant reservoir 30 is connected between the heat exchanger 12 and the expansion valve 13 as in the refrigeration cycle apparatus 3A shown in FIG. When the amount of refrigerant flowing into the heat exchanger 12 exceeds the capacity of the heat exchanger 12, the refrigerant flowing out of the heat exchanger 12 is stored in the refrigerant reservoir 30. Therefore, the refrigerant amount existing on the high pressure side at the end of the pump down mode can be increased as compared with the third embodiment. As a result, the temperature drop at the start of the defrosting mode of the heat exchanger 12 can be further suppressed.

Modification 2 of Embodiment 3
The heat capacity of the heat exchanger in the defrosting mode increases as the amount of frost (frosting amount) generated in the heat exchanger functioning as an evaporator in the heating mode increases. As the heat capacity of the heat exchanger to be defrosted increases, the amount of refrigerant flowing into the heat exchanger at the start of the defrost mode increases. Therefore, as the amount of frost formation increases, the amount of refrigerant flowing out at the start of the defrost mode from the heat exchanger functioning as a condenser in the heating mode increases. Conversely, when the amount of frost formation is small, the amount of refrigerant flowing out at the start of the defrosting mode from the heat exchanger functioning as a condenser in the heating mode decreases. When the amount of frost formation is small, it is desirable to shorten the time during which the pump down mode is performed in order to shorten the interruption time of the heating mode. For example, when the amount of frost formation is smaller than the reference amount (YES in S30) as in the process shown in FIG. 14, the reference time in S103 of FIG. 12 may be shortened by a predetermined ratio (S40). By performing the process as shown in FIG. 14, the time during which the pump-down mode (S200) is performed can be shortened. Since the time until the defrost mode is completed after the defrost start condition is satisfied can be shortened, the interruption time of the heating mode can be shortened.

  Or you may determine whether pump down mode is performed according to the amount of frost formation. For example, when the frost formation amount is smaller than the reference amount (YES in S30) as in the process shown in FIG. 15, the pressure equalization mode (S200) may be executed without performing the pump down mode. By performing the processing as shown in FIG. 15, an unnecessary pump-down mode can be avoided. As a result, the interruption time of the heating mode can be shortened.

  As described above, also in the refrigeration cycle apparatus according to Embodiment 3, Modification 1 and Modification 2, by performing the pressure equalization mode before the defrost mode, as a condenser in the heating mode at the start of the defrost mode. It is possible to suppress the temperature drop of the functioning heat exchanger. As a result, the refrigeration cycle apparatus can be stably operated.

  In the refrigeration cycle apparatus according to Embodiment 3, Modification 1 and Modification 2, by performing the pump-down mode before the pressure equalization mode, the inside of the heat exchanger functioning as a condenser in the heating mode The pressure equalization mode is executed after increasing the refrigerant amount. Therefore, the temperature fall at the time of the defrost mode start of the said heat exchanger can further be suppressed. As a result, the refrigeration cycle apparatus can be operated more stably.

Embodiment 4 FIG.
In a flow path switching device such as a four-way valve, the connection state of the refrigeration cycle apparatus cannot be switched unless the differential pressure between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant is equal to or higher than a reference differential pressure. is there. In the fourth embodiment, a case will be described in which the differential pressure is maintained at a reference differential pressure or higher in order to guarantee the operation of the flow path switching device.

  The difference between the fourth embodiment and the first embodiment is that the four-way valve is different in the fourth embodiment when the differential pressure between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant is equal to or higher than the reference differential pressure. It is operable and has a constant differential pressure valve that keeps the differential pressure at or above the reference differential pressure. Since it is the same about other structures, description is not repeated.

  FIG. 16 is a diagram illustrating the functional configuration of the refrigeration cycle apparatus 4 according to Embodiment 4 and the refrigerant flow in the pressure equalization mode. As shown in FIG. 16, in the refrigeration cycle apparatus 4, the four-way valve 15 of the refrigeration cycle apparatus 1 shown in FIG. 4 is replaced with a four-way valve 154. The four-way valve 154 is operable when the differential pressure between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant is equal to or higher than the reference differential pressure. The refrigeration cycle apparatus 4 further includes a constant differential pressure valve 40 in addition to the configuration of the refrigeration cycle apparatus 1 shown in FIG. The constant differential pressure valve 40 is connected in series with the on-off valve 16 between the discharge port and the suction port of the compressor 11. The constant differential pressure valve 40 is a mechanical valve that keeps the pressure difference between both ends of the constant differential pressure valve 40 at or above the reference differential pressure.

  In the refrigeration cycle apparatus 4, the differential pressure between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant is maintained at or above the reference differential pressure by the constant differential pressure valve 40. Therefore, it is possible to prevent a situation in which the four-way valve 154 does not operate because the differential pressure is smaller than the reference differential pressure.

Modified example of the fourth embodiment.
The configuration that can make the differential pressure between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant equal to or higher than the reference differential pressure is not limited to the constant differential pressure valve. For example, as in the refrigeration cycle apparatus 4A shown in FIG. 17, a valve 41 capable of stepwise adjustment of the opening degree in the open state is used instead of the on-off valve 16, and the pressure of the high-pressure side refrigerant and the low-pressure side refrigerant The opening degree of the valve 41 may be adjusted by the control device 17 so that the pressure difference with the reference pressure becomes equal to or higher than the reference pressure difference.

  As described above, also by the refrigeration cycle apparatus according to the fourth embodiment and the modification, the heat exchange functioning as the condenser in the heating mode at the start of the defrost mode is performed by executing the pressure equalization mode before the defrost mode. The temperature drop of the vessel can be suppressed. As a result, the refrigeration cycle apparatus can be stably operated.

  According to the refrigeration cycle apparatus according to the fourth embodiment and the modification, the flow path switching device can operate when the differential pressure between the pressure of the high-pressure side refrigerant and the pressure of the low-pressure side refrigerant is smaller than the reference differential pressure. It is possible to prevent the situation of being unable to do so. As a result, the refrigeration cycle apparatus can be operated more stably.

Embodiment 5 FIG.
In the fifth embodiment, a case where a gas-liquid separator is connected between the on-off valve and the suction port of the compressor will be described. The refrigerant flowing out in the pressure equalization mode from the heat exchanger functioning as a condenser in the heating mode is stored in the gas-liquid separator in the pressure equalization mode. At the start of the defrosting mode, in addition to the refrigerant from the heat exchanger that functioned as a condenser in the heating mode, the refrigerant from the gas-liquid separator is also added, so the outflow from the heat exchanger at the start of the defrosting mode The amount of refrigerant to be performed can be suppressed as compared with the first embodiment.

  Even when the flow path resistance of the on-off valve is made smaller than that in the first embodiment and the amount of refrigerant flowing out from the heat exchanger functioning as a condenser in the heating mode is increased, the heat exchanger in the pressure equalizing mode The refrigerant from is stored in the gas-liquid separator. Since the refrigerant from the gas-liquid separator is also added to the refrigerant sucked into the compressor at the start of the defrosting mode, the temperature drop of the heat exchanger functioning as a condenser in the heating mode is reduced to the same level as in the first embodiment. Can be suppressed. The time required for the pressure equalization mode can be reduced as compared with the first embodiment by making the flow path resistance of the on-off valve smaller than that of the first embodiment. As a result, the interruption time of the heating operation can be shortened.

  FIG. 18 is a diagram illustrating the functional configuration of the refrigeration cycle apparatus 5 according to Embodiment 5 and the refrigerant flow in the pressure equalization mode. As shown in FIG. 18, in the refrigeration cycle apparatus 5, the on-off valve 16 of the refrigeration cycle apparatus 1 shown in FIG. 4 is replaced with an on-off valve 165. The channel resistance of the on-off valve 165 when the on-off valve 165 is open is larger than the channel resistance of the four-way valve 15 and smaller than the channel resistance of the on-off valve 16 when the on-off valve 16 is open. The refrigeration cycle apparatus 5 further includes a gas-liquid separator 50 in addition to the configuration of the refrigeration cycle apparatus 1 shown in FIG. The gas-liquid separator 50 is connected between the on-off valve 16 and the suction port of the compressor 11. The gas-liquid separator 50 includes a discharge port LS1 for discharging the stored liquid refrigerant. The discharge port LS1 is connected to a junction J2 of a flow path connecting the suction port of the compressor 11 and the four-way valve 15. The height of the discharge port LS1 is lower than the height of the junction J2.

  The refrigerant that has flowed out of the heat exchanger 12 in the pressure equalization mode passes through the on-off valve 16 and is then stored in the gas-liquid separator 50. The liquid refrigerant stored in the gas-liquid separator 50 is discharged from the discharge port LS1, and merges with the refrigerant toward the heat exchanger 14 at the junction J2.

  In the pressure equalization mode, the refrigerant from the heat exchanger 12 passes through the on-off valve 16 and is stored in the gas-liquid separator 50. Since the refrigerant from the gas-liquid separator 50 is added in addition to the refrigerant from the heat exchanger 12 at the start of the defrost mode, the amount of refrigerant flowing out from the heat exchanger 12 at the start of the defrost mode is suppressed. Can do. Further, since the flow path resistance of the on-off valve 165 is smaller than the flow path resistance of the on-off valve 16 of the first embodiment, the time required for the pressure equalization mode can be shortened compared to the first embodiment. Furthermore, since the height of the discharge port LS1 is lower than the height of the junction J2, the amount of refrigerant discharged from the gas-liquid separator 50 can be suppressed. As a result, the amount of refrigerant that moves from the high pressure side to the low pressure side can be further suppressed.

  As described above, also by the refrigeration cycle apparatus according to Embodiment 5, the temperature at the start of the defrosting mode of the heat exchanger functioning as a condenser in the heating mode by executing the pressure equalization mode before the defrosting mode. The decrease can be suppressed. As a result, the refrigeration cycle apparatus can be stably operated.

  According to the refrigeration cycle apparatus according to Embodiment 5, the refrigerant from the heat exchanger that has functioned as a condenser in the heating mode is stored in the gas-liquid separator, thereby functioning as a condenser in the heating mode. The amount of refrigerant flowing out from the heat exchanger at the start of the defrosting mode can be suppressed. Further, since the flow path resistance of the on-off valve can be made smaller than that in the first embodiment, the time required for the pressure equalization mode can be made smaller than that in the first embodiment.

  Each embodiment disclosed this time is also planned to be implemented in appropriate combination within a consistent range. The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 2, 3A, 4, 4A, 5 Refrigeration cycle device, 11 Compressor, 12, 14 Heat exchanger, 13 Expansion valve, 15, 154 Four-way valve, 16, 165 On-off valve, 17 Control device, 30 Refrigerant reservoir 40, differential pressure valve, 41 valve, 50 gas-liquid separator, 100 heating terminal, LS1 discharge port, RP1, RP2 flow path, S1, S2 pressure sensor.

Claims (15)

The operation mode includes a heating mode and a defrosting mode. In the heating mode, the refrigerant circulates in the order of a compressor, a flow path switching device, a first heat exchanger, an expansion valve, and a second heat exchanger, and the defrosting is performed. In the mode, the refrigerant circulates in the order of the compressor, the flow path switching device, the second heat exchanger, the expansion valve, and the first heat exchanger,
A flow control valve connected in parallel with the compressor between a discharge port of the compressor and a suction port of the compressor;
A control device configured to control the opening of the flow control valve and to switch the operation mode,
The operation mode further includes a pressure equalization mode,
In the pressure equalization mode, the flow control valve is opened, and the flow resistance of the flow control valve corresponding to the opening is greater than the flow resistance of the flow switching device,
The said control apparatus is a refrigerating-cycle apparatus comprised so that the said operation mode may be switched in order of the said heating mode, the said pressure equalization mode, and the said defrost mode. The flow path switching device is configured to switch the connection state of the refrigeration cycle device between a first connection state and a second connection state,
The controller is
In the heating mode, the connection state is set to the first connection state, the compressor is operated, the expansion valve is opened, the flow control valve is closed,
In the pressure equalization mode, the connection state is maintained in the first connection state, the compressor is stopped, the expansion valve is closed, and the opening degree is increased.
The defrosting mode is configured to set the connection state to the second connection state, operate the compressor, open the expansion valve, and close the flow control valve. The refrigeration cycle apparatus according to 1.   The refrigeration cycle apparatus according to claim 2, wherein the control device is configured to close the flow control valve before the compressor is started in the defrosting mode.   The refrigeration cycle apparatus according to claim 2, wherein the control device is configured to close the flow control valve after the compressor is started in the defrosting mode. The operation mode further includes a pump down mode for increasing the amount of the refrigerant in the first heat exchanger,
The control device switches the operation mode in the order of the heating mode, the pump down mode, the pressure equalization mode, and the defrost mode,
The pump down mode is configured to maintain the connection state in the first connection state, operate the compressor, close the expansion valve, and close the flow control valve. The refrigeration cycle apparatus according to any one of claims 2 to 4.   The refrigeration cycle apparatus according to claim 5, wherein the control device is configured to adjust an operation time of the pump-down mode according to a frost formation amount of the second heat exchanger in the heating mode. The operation mode further includes a pump down mode for increasing the amount of the refrigerant in the first heat exchanger,
The controller is
When the frosting amount of the second heat exchanger in the heating mode is larger than a reference amount, the operation mode is switched in the order of the heating mode, the pump down mode, the pressure equalization mode, and the defrosting mode,
When the amount of frost formation in the heating mode is smaller than the reference amount, the operation mode is switched in the order of the heating mode, the pressure equalization mode, and the defrosting mode,
The pump down mode is configured to maintain the connection state in the first connection state, operate the compressor, close the expansion valve, and close the flow control valve. The refrigeration cycle apparatus according to any one of claims 2 to 4.   The refrigeration cycle apparatus according to any one of claims 5 to 7, further comprising a refrigerant storage section connected between the first heat exchanger and the expansion valve. The flow path switching device is configured to connect the connection when a pressure difference between the pressure of the refrigerant from the discharge port to the expansion valve and a pressure of the refrigerant from the expansion valve to the suction port is equal to or higher than a reference differential pressure. The state can be switched,
A constant differential pressure valve connected in series with the flow control valve between the discharge port and the suction port;
The refrigeration cycle apparatus according to any one of claims 2 to 8, wherein the constant differential pressure valve maintains the differential pressure to be equal to or higher than the reference differential pressure. The flow path switching device is configured to connect the connection when a pressure difference between the pressure of the refrigerant from the discharge port to the expansion valve and a pressure of the refrigerant from the expansion valve to the suction port is equal to or higher than a reference differential pressure. The state can be switched,
The said control apparatus is comprised so that the said opening may be adjusted so that the said differential pressure may become more than the said reference differential pressure in the said pressure equalization mode, The any one of Claims 2-8. The refrigeration cycle apparatus described. A gas-liquid separator connected between the flow control valve and the suction port;
The gas-liquid separator includes a liquid discharge port for discharging the stored liquid of the refrigerant,
The refrigeration cycle apparatus according to any one of claims 1 to 10, wherein the liquid discharge port is connected to a flow path that connects the suction port and the flow path switching device.   The refrigeration cycle apparatus according to claim 11, wherein a height of the liquid discharge port is lower than a height of a junction where the liquid from the liquid discharge port merges with the flow path. The height of the first heat exchanger is lower than the height of the flow path switching device,
Height of a connection portion between the first flow path connecting the suction port and the flow path switching device and the second flow path through which the refrigerant from the flow control valve passes and connects to the first flow path Is a refrigeration cycle apparatus according to claim 1, which is lower than a height of the flow path switching device.   In a connection portion between the first flow path connecting the suction port and the flow path switching device, and the second flow path through which the refrigerant from the flow control valve passes and connects to the first flow path, The refrigeration cycle apparatus according to claim 1, wherein an angle formed by the first flow path and the second flow path is greater than 0 degrees and smaller than 180 degrees.   The area of the passage portion of the refrigerant in the cross section of the first flow path orthogonal to the traveling direction of the refrigerant moving through the first flow path connected to the flow control valve is the second flow connected to the suction port. 2. The refrigeration cycle apparatus according to claim 1, wherein the refrigeration cycle apparatus is smaller than an area of a passage portion of the refrigerant in a cross section of the second flow path orthogonal to a traveling direction of the refrigerant moving along a path.