JP2009156524A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device capable of surely preventing depletion of an oil of a compressor caused by an operating state of the compressor by performing an operation with suppression of oil discharge amount from the compressor. <P>SOLUTION: This refrigerating cycle device includes: an oil level detecting means (oil level sensor 66) for detecting an oil level of the compressor (compressor 37 for cooling); a valve device (oil supply valve 65) disposed in an oil returning circuit 64 and deciding whether the oil is returned to the compressor from an oil separator 31 or not, and a control means (outdoor-side cooling controller 32) for controlling an operational frequency of the compressor and opening/closing of the valve device. The control means opens the valve device, and limits the operational frequency of the compressor, when the oil level of the compressor is lower than a prescribed lower limit value on the basis of the output of the oil level detecting means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus including a compressor, an oil separator provided on the refrigerant discharge side of the compressor, and an oil return circuit for returning oil from the oil separator to the compressor.

  Conventionally, air conditioners installed in stores such as convenience stores and supermarkets, and refrigeration cycle devices that make up refrigeration cycles such as open showcases and walk-in showcases are installed indoor units installed in stores and outside the stores. The outdoor unit is installed, and a refrigerant circuit is piped between them. The refrigerant circuit performs an air-conditioning cycle in the store by a heat exchanger installed in the indoor unit, a heat exchanger installed in the outdoor unit and a compressor including a sealed container, and an open showcase. It was intended to cool and refrigerate the interior of the store and walk-in showcases.

  In order to return the oil discharged from the compressor together with the refrigerant into the sealed container (inside the compressor), a tank is provided on the downstream side of the refrigerant discharge pipe provided in the sealed container, and an oil separator is attached in the tank. It was. An oil return pipe is attached to the oil separator, and the other end of the oil return pipe is attached to the sealed container so that the oil separator communicates with the sealed container. And the oil discharged with the refrigerant | coolant from the compressor was isolate | separated by the oil separator, and the isolate | separated oil was returned in the airtight container from the oil return pipe | tube (refer patent document 1).

On the other hand, if the amount of oil returning from the oil return pipe to the sealed container is large, the oil in the oil separator is exhausted. When the oil in the oil separator is exhausted, the refrigerant gas discharged from the compressor into the oil separator returns to the hermetic container, and the refrigeration efficiency of the refrigeration cycle apparatus is significantly reduced. Therefore, a float (oil level sensor) is provided in the sealed container, and a valve device is provided in the oil return pipe. When the oil level sensor detects that the oil in the compressor has dropped to a predetermined value, the valve device is released. The oil in the oil separator was returned to the sealed container (see Patent Document 2).
JP 2004-239204 A JP 2005-214435 A

  However, the amount of refrigerant gas discharged from the compressor varies depending on the operating frequency of the compressor. That is, when the compressor is operated at a low operating frequency or when the compressor is operated at a high operating frequency, the amount of oil discharged from the compressor increases. In this case, the oil that cannot be completely separated by the oil separator circulates in the refrigerant circuit together with the refrigerant. In particular, when the piping length of the refrigerant circuit is long, the oil is difficult to return to the compressor because it accumulates in a heat exchanger or the like in the refrigerant circuit.

  In such a state, when the oil level in the compressor is lowered to a predetermined value as in the prior art, if the oil is simply returned from the oil separator into the sealed container, it will come out of the compressor depending on the operating state. The amount returned to the oil amount will not be in time, and the oil in the compressor will be exhausted. For this reason, there existed a problem that lubrication of a sliding part, sealing performance, etc. will fall.

  The present invention has been made to solve the problems of the related art, and by performing an operation of suppressing the amount of oil discharged from the compressor, the oil in the compressor is depleted depending on the operating state of the compressor. An object of the present invention is to provide a refrigeration cycle apparatus that can reliably prevent the occurrence of refrigeration.

  That is, the refrigeration cycle apparatus of the present invention comprises a compressor, an oil separator provided on the refrigerant discharge side of the compressor, and an oil return circuit for returning oil from the oil separator to the compressor. An oil level detecting means for detecting the oil level of the compressor, a valve device provided in the oil return circuit for controlling whether or not the oil is returned from the oil separator to the compressor, the operating frequency and valve of the compressor Control means for controlling opening and closing of the device, the control means, based on the output of the oil level detection means, when the oil level of the compressor is below a predetermined lower limit value, the valve device is opened, and the compressor The operation frequency is limited.

  Further, in the refrigeration cycle apparatus according to the second aspect of the present invention, in the above, the control means opens the valve device when the oil level of the compressor falls below a predetermined upper limit value higher than the lower limit value, and in that state the oil When the level falls below the lower limit, the operating frequency of the compressor is limited.

  The refrigeration cycle apparatus according to claim 3 is the refrigeration cycle apparatus according to claim 1 or 2, wherein the control means sets the operation frequency of the compressor to a predetermined specified value when the oil level falls below a lower limit value. It is fixed.

  According to a fourth aspect of the present invention, there is provided a refrigeration cycle apparatus according to any one of the first to third aspects, further comprising a low pressure side pressure detecting means for detecting a low pressure side pressure of the refrigerant circuit, and the control means has a lower oil level. When the pressure falls below the value, the compressor is stopped based on the output of the low pressure side pressure detection means when the low pressure side pressure is below a predetermined threshold value.

  As described above in detail, according to the present invention, a compressor, an oil separator provided on the refrigerant discharge side of the compressor, and an oil return circuit for returning oil from the oil separator to the compressor are provided. An oil level detecting means for detecting the oil level of the compressor, a valve device provided in the oil return circuit for controlling whether or not to return the oil from the oil separator to the compressor, and the operating frequency of the compressor Control means for controlling opening and closing of the valve device, the control means, based on the output of the oil level detection means, when the oil level of the compressor is below a predetermined lower limit value, the valve device is opened and the compression Since the operating frequency of the compressor is limited, in addition to returning the oil from the oil separator, the operating frequency of the compressor is also limited. Therefore, the amount of oil discharged from the compressor is reduced, and the oil in the compressor is depleted. It can be effectively prevented. As a result, it is possible to reliably prevent the inconvenience that the compressor oil is depleted depending on the operating state of the compressor.

  According to the invention of claim 2, in the above, the control means opens the valve device when the oil level of the compressor falls below a predetermined upper limit value higher than the lower limit value, and the oil level is in that state. If it falls below the lower limit, the operating frequency of the compressor is limited, so after starting the oil return, the operating frequency of the compressor is limited in a situation where the oil level still decreases. The adverse effect on the cooling effect due to the fact that it does not rise can be suppressed to a minimum.

  According to a third aspect of the present invention, in the first or second aspect, the control means fixes the operating frequency of the compressor to a predetermined specified value when the oil level falls below a lower limit value. Therefore, the oil accumulated in the refrigerant circuit can be returned smoothly.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the low pressure side pressure detecting means for detecting the low pressure side pressure of the refrigerant circuit is provided, and the control means has an oil level equal to or lower than a lower limit value. When the low pressure side pressure is equal to or lower than a predetermined threshold value based on the output of the low pressure side pressure detection means, the compressor is stopped, so that, for example, the refrigerant circuit that is in a state where the object to be cooled is sufficiently cooled When the pressure on the low pressure side is low, the compressor is stopped, the refrigerant (oil) is stopped, and natural oil return can be promoted. Thereby, since the oil naturally returns to the suction side of the compressor through the refrigerant circuit, it can be sufficiently ensured that the oil in the compressor is not exhausted. Therefore, it is possible to reliably prevent inconveniences such as a decrease in lubrication and sealing performance of the sliding portion.

  The main feature of the present invention is to prevent the oil in the compressor from being exhausted depending on the operating state of the compressor by performing an operation that suppresses the oil discharge amount from the compressor. The purpose of preventing the compressor oil from being exhausted is realized by simple control that limits the operating frequency of the compressor when the oil level of the compressor drops below a predetermined lower limit.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a system configuration including a refrigerant circuit of a refrigeration cycle apparatus 1 according to an embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The refrigeration cycle apparatus 1 shown in FIG. 1 performs, for example, indoor air conditioning by an air conditioning indoor unit 29 installed in a store 2 of a convenience store, and cooling of the refrigerator case 3 and the freezing case 4 installed therein. It is realized. The refrigerated case 3 includes an open showcase whose front and upper surfaces are open, and a walk-in showcase whose opening is opened and closed freely with a transparent glass door. ~ + 10 ° C), and beverages and refrigerated foods are displayed. The freezer case 4 has a refrigerator that is cooled to a freezing temperature (−10 ° C. to −20 ° C.) to display frozen foods, frozen desserts, and the like.

  The refrigeration cycle apparatus 1 includes an air conditioning system 6 that performs air conditioning in the store 2, and a refrigeration system 8 that cools the refrigeration case 3 and the refrigeration case 4. The air conditioning system 6 includes an indoor unit 11 installed on the ceiling of the store 2 and an outdoor unit 12 installed outside the store. An air conditioning refrigerant circuit 7 is provided between the indoor unit 11 and the outdoor unit 12. This air conditioning refrigerant circuit 7 includes a use side heat exchanger 27 housed in the indoor unit 11, a heat source side heat exchanger 16 installed in the outdoor unit 12, and an air conditioning compressor 13 </ b> A as the compression unit 13, The cooling and heating cycle is performed by 13B.

  The air conditioning compressor 13A is a compressor for inverter control, and the air conditioning compressor 13B is a compressor for constant speed operation. These air conditioning compressors 13A and 13B are connected in parallel, the discharge sides of the air conditioning compressors 13A and 13B are joined via check valves 5A and 5B, and one inlet of the four-way valve 14 via the oil separator 10. Connected to. One outlet of the four-way valve 14 is connected to the inlet of the heat source side heat exchanger 16. The heat source side heat exchanger 16 includes an inlet side 16A having a relatively small flow resistance composed of a large number of parallel pipes and an outlet side 16B in which these are aggregated into a small number of parallel pipes or a single pipe. The outlet on the outlet side 16B of the heat source side heat exchanger 16 is connected to the inlet of the expansion valve 18 via the check valve 5C and the expansion valve 17 connected in parallel. The outlet of the expansion valve 18 is an indoor unit. 11 is connected to the entrance of the use side heat exchanger 27.

  The outlet of the use side heat exchanger 27 is connected to the other inlet of the four-way valve 14 across the outdoor unit 12. The other outlet of the four-way valve 14 is connected to the inlet of the accumulator 23 via a check valve 5D, and the outlet of the accumulator 23 is connected to the suction side of the air-conditioning compressors 13A and 13B. The check valve 5D has a forward direction on the accumulator 23 side.

  In the air conditioning refrigerant circuit 7, the refrigerant pipe between the expansion valve 17 and the expansion valve 18 is branched, and this branch pipe is connected to the cascade heat exchanger 21 via the expansion valve 19. The cascade heat exchanger 21 is formed by stacking a plurality of heat transfer plates, and alternately forming an air conditioning side passage 21A and a case side passage 21B through which two kinds of refrigerants flow in each heat transfer plate tube. A plate heat exchanger is used in which heat exchange is performed via a heat transfer plate while two types of refrigerant flow through the case side passage 21B adjacent to 21A. The cascade heat exchanger 21 thermally connects the low-pressure side of the air-conditioning refrigerant circuit 7 and the high-pressure side of the cooling refrigerant circuit 9 (corresponding to the refrigerant circuit of the present invention) that is operated after the refrigeration system 8.

  In the cascade heat exchanger 21, the inlet of the air conditioning side passage 21A is connected to the expansion valve 19, and the outlet located on the opposite side of the air conditioning side passage 21A is connected to the suction side of the air conditioning compressors 13A and 13B via the accumulator 23. Has been. As a result, the refrigerant whose pressure has been reduced by the expansion valve 19 is supplied to the cascade heat exchanger 21 and then returned to the air conditioning compressors 13A and 13B. That is, in the refrigeration cycle apparatus 1, a path α that passes through the use side heat exchanger 27 and a path β that passes through the cascade heat exchanger 21 are formed as the refrigerant circulation paths.

  The outdoor unit 12 is provided with an outdoor air conditioning controller 26. The outdoor air conditioning controller 26 is composed of a general-purpose microcomputer, and the equipment of the air conditioning system 6 on the outdoor unit 12 side based on the outside air temperature and the refrigerant pressure. Is to control. The indoor air conditioning controller 28 is configured by a general-purpose microcomputer, and controls the equipment on the indoor unit 11 side based on a user instruction input via a remote controller (not shown) or the outdoor air conditioning controller 26. And data communication according to user instructions. The blower 24 of the heat source side heat exchanger 16 is a blower that blows outside air to the heat source side heat exchanger 16, and the blower 15 of the use side heat exchanger 27 sends indoor air to the use side heat exchanger 27. It is a blower to send.

  On the other hand, the refrigeration system 8 includes the refrigeration case 3 and the refrigeration case 4 and the cooling refrigerant circuit 9 provided between the outdoor unit 12. The cooling refrigerant circuit 9 includes a refrigeration evaporator 43 provided in the refrigeration case 3, a refrigeration evaporator 49 provided in the refrigeration case 4, and a condenser (heat exchanger) 38 installed in the outdoor unit 12. In addition, the refrigeration cycle is performed by the cooling compressor 37 (corresponding to the compressor of the present invention) and the pressurizing compressor 54 configured in a sealed container. A predetermined number of refrigeration evaporators 43 and refrigeration evaporators 49 are installed in supermarkets, convenience stores, and the like according to the scale of the store, but in FIG. 1 refrigeration evaporators 43 and refrigeration evaporators 49 are provided. Only two of these are shown.

  The cooling compressor 37 has a main role of refrigerant circulation. The outlet side 37B (discharge side) of the cooling compressor 37 is connected to the oil separator 31 via a discharge side pipe 40 (shown in FIG. 3). The pipe 31 </ b> A connected to the outlet side of the oil separator 31 is connected to one inlet of the four-way valve 39, and one outlet of the four-way valve 39 is connected to the inlet of the condenser 38. The condenser 38 includes an inlet side 38A having a relatively small flow resistance composed of a large number of parallel pipes, and an outlet side 38B in which these are aggregated into a small number of parallel pipes or a single pipe. The outlet on the outlet side 38B of the condenser 38 is connected to the inlet of the receiver tank 36, and the outlet of the receiver tank 36 is connected to one inlet of the four-way valve 41. That is, the receiver tank 36 is connected to the refrigerant downstream side of the condenser 38.

  One outlet of the four-way valve 41 is connected to the inlet of the case side passage 21 </ b> B of the cascade heat exchanger 21. Further, the outlet of the case side passage 21B of the cascade heat exchanger 21 is connected to the other inlet of the four-way valve 39, and the other outlet of the four-way valve 39 is connected to the other inlet of the four-way valve 41. . The other outlet of the four-way valve 41 exits from the outdoor unit 12 and branches into the store 2 (store). One branched pipe is connected to the inlet of the refrigeration evaporator 43 of the refrigeration case 3 through the electromagnetic valve 46 and the expansion valve 44. The other branched pipe is connected to the inlet of the freezing evaporator 49 of the freezing case 4 via the electromagnetic valve 52 and the expansion valve 51.

  The outlet of the freezing evaporator 49 is connected to the suction side of the boosting compressor 54 via the check valve 30. The pressurizing compressor 54 is for increasing the pressure of the refrigerant that has passed through the refrigeration case 4 to the refrigerant pressure that has passed through the refrigeration case 3, and is a compressor having a smaller output than the cooling compressor 37. The discharge side of the pressurizing compressor 54 is connected to one inlet of the four-way valve 42 via the oil separator 45, and one outlet of the four-way valve 42 is the outlet side of the refrigeration evaporator 43 and the cooling compressor 37. Is connected to a suction side pipe 34 (shown in FIG. 3) connected to the suction side. That is, the boosting compressor 54 and the cooling compressor 37 are connected in series on the refrigerant circuit. The other inlet of the four-way valve 42 is connected to a pipe line on the inlet side of the pressurizing compressor 54, and the other outlet of the four-way valve 42 is connected to the case of the cascade heat exchanger 21 via a check valve 61. It is connected to the pipe line on the inlet side of the side passage 21B. The check valve 61 has a forward direction on the cascade heat exchanger 21 side. In addition, oil for ensuring lubrication and sealing performance in the cooling compressor 37 is dissolved in the refrigerant sealed in the refrigerant circuit 9 for cooling, and each of the oil separators 10, 31, 45 is in the refrigerant circuit. The refrigerant and the oil are separated, and the separated oil is returned to the compressors 13A, 13B, 37, and 54.

  In the above configuration, among the components of the refrigeration system 8, the boosting compressor 54, the check valve 30, the oil separator 45, and the four-way valve 42 are separate units from the outdoor unit 12 that houses the cooling compressor 37. It is stored in the booster unit 22. The four-way valve 42 accommodated in the booster unit 22 switches the refrigerant from the refrigeration evaporator 43 and the refrigeration evaporator 49 (cooling refrigerant) to each compressor (cooling refrigerant) of the refrigeration system 8 by switching them. The bypass passage leading to the inlet of the cascade heat exchanger 21 can be formed without going through the compressor 37 for boosting or the compressor for boosting 54). According to this, when one of the cooling compressor 37 and the boosting compressor 54 fails, the refrigerant flowing out of the refrigeration evaporator 43 and the refrigeration evaporator 49 breaks down by switching the four-way valve 42. It can be led to the inlet of the cascade heat exchanger 21 via the compressor on the non-side.

  The outdoor side cooling controller 32 (corresponding to the control means of the present invention) provided in the refrigeration cycle apparatus 1 is composed of a general-purpose microcomputer, and controls the equipment of the refrigeration system 8 on the outdoor unit 12 side based on the outside air temperature and the refrigerant pressure. It is something to control. The outdoor cooling controller 32 is connected to an alarm device 33 that issues an alarm when an oil amount of a cooling compressor 37 described later is insufficient. The refrigeration case controller 50 is constituted by a general-purpose microcomputer, and controls devices in the refrigeration system 8 based on the internal temperature of the refrigeration case 3. The refrigeration case controller 55 is composed of a general-purpose microcomputer, and controls devices in the refrigeration system 8 based on the internal temperature of the refrigeration case 4. The blower 35 is a blower that blows outside air to the condenser 38, the blower 20 is a blower that sends the air in the refrigerator case 3 to the condenser 38, and the blower 25 is frozen to the freezing evaporator 49. This is a blower for sending the air in the case 4.

  The refrigeration cycle apparatus 1 has a main controller 56. The main controller 56 is composed of a general-purpose microcomputer, and performs data communication with the outdoor side air conditioning controller 26, the indoor side air conditioning controller 28, the outdoor side cooling controller 32, the refrigeration case controller 50, and the freezing case controller 55. In the refrigeration cycle apparatus 1, different refrigerants are used in the air conditioning refrigerant circuit 7 and the cooling refrigerant circuit 9. For example, R410A is used in the air conditioning refrigerant circuit 7, and the cooling refrigerant circuit 9 includes R404A having a higher boiling point than R410A is used. As described above, the refrigeration cycle apparatus 1 can use the optimum refrigerant for each refrigerant circuit, so that the degree of freedom in circuit design can be increased.

  On the other hand, the oil separator 31 is provided with an oil return circuit 64 for returning the oil in the oil separator 31 to the cooling compressor 37. The oil return circuit 64 includes an oil return pipe 62 and an oil supply valve 65 (corresponding to the valve device of the present invention). One end of the oil return pipe 62 is connected to the oil return outlet side 31 </ b> B provided at the lower part of the oil separator 31, and the other end is connected to the oil return inlet side 37 </ b> C of the cooling compressor 37. The oil return pipe 62 communicates the oil separator 31 and the cooling compressor 37 with an oil return circuit 64. The oil supply valve 65 is controlled to be opened and closed by the outdoor side cooling controller 32 and controls whether or not oil is returned from the oil separator 31 to the cooling compressor 37. The oil return circuit 64 will be described in detail later.

  The cooling compressor 37 has an oil level sensor 66 (corresponding to the oil level detecting means of the present invention) for detecting the amount of oil in the cooling compressor 37, and the cooling compressor 37 has a suction side ( A pressure sensor 67 (corresponding to the low pressure side pressure detecting means of the present invention) for detecting the pressure on the inlet side 37A = shown in FIG. 3 is provided, and the outdoor cooling controller 32 includes the oil level sensor 66 and the pressure sensor 67. Detect output from. The oil level sensor 66 is composed of two oil level sensors 66A and 66B. The two oil level sensors 66A and 66B are used to set an upper limit value and a lower limit value of oil in the cooling compressor 37. Can be detected (shown in FIG. 3). The cooling compressor 37 is provided with a pressure sensor 68 that detects the pressure on the discharge side 37B and stops the cooling compressor 37 when a predetermined high pressure is reached.

  One of the two oil level sensors 66A and 66B (for example, the oil level sensor 66A or 66B) is long, and the other (for example, the oil level sensor 66B or 66A) is short. It is inserted upward from the lower part of the hermetic container (cooling compressor 37). Then, a high oil level value, which will be described later, is detected at the tip of the longer oil level sensor 66A (66B), and a low oil level value is detected at the tip of the shorter oil level sensor 66B (66A). The sensor 66 is referred to as detecting a high oil level value and a low oil level value. An oil level sensor 66 is attached from the side of the cooling compressor 37, and either one of the lower oil level sensors 66B (66A) has a low oil level value and the top of the upper oil level sensor 66A (66B). It does not matter if a high oil level value is detected.

  Next, the operation of the refrigeration cycle apparatus 1 will be described.

  In this refrigeration cycle apparatus 1, the air conditioning system 6 includes a set temperature instructed by the outdoor air conditioning controller 26 and the indoor air conditioning controller 28 via a remote controller (not shown), and a temperature sensor provided in the indoor unit 11. The cooling operation or the heating operation is performed according to the deviation from the temperature (room temperature) in the store 2 detected by the above, and the room temperature is air-conditioned to the set temperature. In addition, the refrigeration system 8 sets the internal temperature of the refrigeration case 3 to a preset refrigeration temperature under the control of the outdoor side cooling controller 32, the refrigeration case controller 50, and the refrigeration case controller 55. The internal temperature is set to a preset freezing temperature.

  More specifically, in this refrigeration cycle apparatus 1, the main controller 56 receives data related to the current operating state of the air conditioning system 6 and the refrigeration system 8 by performing data communication with the controllers 26, 28, 32, 50, 55. Then, based on the received data, an optimum operation pattern at that time point to be described later is determined, and data relating to this optimum operation pattern and operation data of each device are transmitted to each controller 26, 28, 32, 50, 55. Each controller 26, 28, 32, 50, 55 executes a control operation to be described later based on the data received from the main controller 56.

Next, the cooling operation of the air conditioning system unit of the refrigeration cycle apparatus 1 and the heating operation of the air conditioning system unit will be described.
(1) Cooling operation of air-conditioning system section First, when the outdoor air-conditioning controller 26 determines that the cooling operation of the air-conditioning system 6 is optimal, the outdoor-side air conditioning controller 26 is predetermined to the indoor-side air conditioning controller 28 and the main controller 56 to perform the cooling operation. The main controller 56 that has received the data transmits these data to the outdoor side cooling controller 32, the refrigeration case controller 50, and the freezing case controller 55.

  As shown in FIG. 1, the outdoor air conditioning controller 26 communicates one inlet (a connection port with the oil separator 10) of the four-way valve 14 to one outlet (a connection port with the heat source side heat exchanger 16), The other inlet (connection port with the use side heat exchanger 27) is communicated with the other outlet (connection port with the accumulator 23). Further, the expansion valve 17 is fully opened, and the air conditioning compressors 13A and 13B are operated. The outdoor air-conditioning controller 26 performs capacity control by controlling the operation frequency of the air-conditioning compressor 13A by inverter.

  When the air-conditioning compressors 13A and 13B are operated, the high-temperature and high-pressure gas refrigerant discharged from the discharge side of the air-conditioning compressors 13A and 13B passes from the oil separator 10 through the four-way valve 14 as shown by arrows in FIG. It enters the inlet side 16 </ b> A of the heat source side heat exchanger 16. Outside air is ventilated by the air blower 24 to the heat source side heat exchanger 16, and the refrigerant dissipates heat here to be condensed and liquefied. That is, in this case, the heat source side heat exchanger 16 functions as a condenser. The liquid refrigerant is branched after passing through the expansion valve 17 via the heat source side heat exchanger 16. One of the branched branches reaches the expansion valve 18, where it is throttled to a low pressure (decompression), and then flows into the use side heat exchanger 27 where it evaporates. Indoor air (air in the store 2) is ventilated by the blower 15 to the use side heat exchanger 27, and the indoor air is cooled by an endothermic action due to evaporation of the refrigerant. Thereby, the inside of the store 2 (indoor) is cooled. The low-temperature gas refrigerant exiting from the use-side heat exchanger 27 repeats circulation supplied to the suction side of the air-conditioning compressors 13A and 13B through the four-way valve 14, the check valve 5D, and the accumulator 23 in order.

  Further, the other refrigerant branched after passing through the expansion valve 17 reaches the expansion valve 19 where it is throttled to a low pressure (decompression) and then flows into the air conditioning side passage 21A of the cascade heat exchanger 21 where it evaporates. To do. The cascade heat exchanger 21 is cooled by the heat absorption effect of the refrigerant evaporation of the air conditioning refrigerant circuit 7 and becomes a low temperature. The low-temperature gas refrigerant exiting the cascade heat exchanger 21 repeats circulation supplied to the suction side of the air-conditioning compressors 13A and 13B via the accumulator 23.

  The indoor side air conditioning controller 28 uses the use side heat so that the temperature of the room (store 2) is set to a preset temperature based on the air temperature of the store 2 detected via a temperature sensor (not shown). The blower 15 that ventilates the exchanger 27 is controlled. Information of the indoor air conditioning controller 28 is transmitted to the outdoor air conditioning controller 26, and the outdoor air conditioning controller 26 controls the operation of the air conditioning compressors 13A and 13B based on this information.

  The outdoor air conditioning controller 26 detects the refrigerant temperature at the entrance / exit of the use side heat exchanger 27 or the temperature of the use side heat exchanger 27 detected through a temperature sensor (not shown) and the entrance / exit of the cascade heat exchanger 21. Based on the refrigerant temperature or the temperature of the cascade heat exchanger 21, the valve openings of the expansion valves 18 and 19 are adjusted so as to achieve an appropriate degree of superheat.

  On the other hand, the outdoor side cooling controller 32 supplies one inlet of the four-way valve 39 of the refrigeration system 8 (cooling refrigerant circuit 9) to supply the high-temperature and high-pressure gas refrigerant discharged from the cooling compressor 37 to the condenser 38. (The connection port with the oil separator 31) communicates with one outlet (the connection port with the condenser 38), and the other inlet (the connection port with the cascade heat exchanger 21) communicates with the other outlet (the four-way valve 41). Connect to the connection port. The outdoor cooling controller 32 controls the capacity of the cooling compressor 37 by inverter-controlling the operation frequency.

  In addition, the outdoor side cooling controller 32 uses one inlet (a connection port with the four-way valve 39) of the four-way valve 41 as one outlet (refrigeration) in order to supply the gas refrigerant that has passed through the condenser 38 to the cascade heat exchanger 21. Communication with the evaporator 43 and the refrigeration evaporator 49 (connection ports with the electromagnetic valves 46, 47, 52), and the other inlet (connection port with the receiver tank 36) is connected with the other outlet (cascade heat exchanger 21). Communication port). Then, the cooling compressor 37 and the boosting compressor 54 are operated.

  Thus, the high-temperature and high-pressure gas refrigerant discharged from the cooling compressor 37 is separated by the oil separator 31 and then enters the inlet side 38A of the condenser 38 through the four-way valve 39. Outside air is passed through the condenser 38 by the blower 35, and the refrigerant flowing into the condenser 38 dissipates heat and condenses. The refrigerant discharged from the condenser 38 enters the receiver tank 36 and is temporarily stored therein to separate the gas / liquid. The separated liquid refrigerant exits from the receiver tank 36 and passes through the four-way valve 41, and then enters the case side passage 21B of the cascade heat exchanger 21. The refrigerant in the cooling refrigerant circuit 9 supplied to the cascade heat exchanger 21 is cooled by the cascade heat exchanger 21 that is at a low temperature due to evaporation of the refrigerant in the air conditioning refrigerant circuit 7 as described above, and further subcooled. The Since the receiver tank 36 is disposed immediately after the condenser 38 as described above, heat loss during supercooling can be eliminated and the amount of refrigerant can be adjusted.

  The refrigerant supercooled in the cascade heat exchanger 21 is branched after sequentially passing through the four-way valves 39 and 41, and one of the refrigerant passes through the electromagnetic valve 46 and reaches the expansion valve 44. ), Flows into the refrigeration evaporator 43 and evaporates there. In the refrigerator 43 for refrigeration, the air in the refrigerator case 3 is ventilated and circulated by the blower 20, and the air in the refrigerator is cooled by an endothermic action due to evaporation of the refrigerant. Thereby, the inside cooling of the refrigeration case 3 is performed. Then, the low-temperature gas refrigerant exiting the refrigeration evaporator 43 reaches the outlet side of the oil separator 45 (four-way valve 42) of the pressurizing compressor 54.

  The other refrigerant that is subcooled and branched in the cascade heat exchanger 21 passes through the electromagnetic valve 52 to reach the expansion valve 51, where it is throttled (decompression) and then supplied to the refrigeration evaporator 49. Where it evaporates. The refrigeration evaporator 49 is circulated and circulated with the air in the refrigeration case 4 by the blower 25, and the refrigeration evaporator 49 is cooled by the endothermic effect of the evaporation of the refrigerant. Thereby, the inside cooling of the freezing case 4 is performed.

  The low-temperature gas refrigerant that has exited the freezing evaporator 49 is branched, and one of the refrigerant passes through the check valve 30 and reaches the pressurizing compressor 54 where it is compressed and pressure on the outlet side of the refrigerating evaporator 43 (refrigeration system). After the pressure is raised to the low pressure side pressure), the oil is discharged from the pressure boosting compressor 54 and separated by the oil separator 45, and then merges with the refrigerant from the refrigeration evaporator 43 via the four-way valve 42. The merged refrigerant repeats circulation that is sucked into the suction side of the cooling compressor 37.

  The refrigeration case controller 50 detects the temperature inside the refrigeration case 3 detected via a temperature sensor (not shown), the cold air temperature discharged through the refrigeration evaporator 43, or the cold air temperature sucked into the refrigeration evaporator 43, and the refrigeration case controller 50. The valve opening degree of the expansion valve 44 is controlled based on the refrigerant temperature on the outlet side of the evaporator 43 or the temperature of the refrigeration evaporator 43. Thereby, it is set as the appropriate superheat degree (constant superheat degree), maintaining the inside of the refrigerator | coolant case 3 cooling at the refrigeration temperature mentioned above. Further, the refrigeration case controller 55 is configured such that the internal temperature of the refrigeration case 4, the cold air temperature discharged through the refrigeration evaporator 49, the cold air temperature sucked into the refrigeration evaporator 49, and the refrigerant temperature on the outlet side of the refrigeration evaporator 49. Alternatively, the valve opening degree of the expansion valve 51 is controlled based on the temperature of the refrigeration evaporator 49. As a result, while maintaining the inside of the freezing case 4 to be cooled to the above-described freezing temperature, an appropriate degree of superheat (constant superheat) is obtained.

Next, the heating operation of the air conditioning system unit of the refrigeration cycle apparatus 1 will be described with reference to FIG.
(2) Heating operation of the air conditioning system section First, when the outdoor air conditioning controller 26 determines that the heating operation of the air conditioning system 6 is optimal, the outdoor air conditioning controller 26 is predetermined to the indoor air conditioning controller 28 and the main controller 56 to perform the heating operation. The main controller 56 that has received the data transmits these data to the outdoor side cooling controller 32, the refrigeration case controller 50, and the freezing case controller 55.

  The outdoor air-conditioning controller 26 connects one inlet (connection port with the oil separator 10) of the four-way valve 14 to one outlet (connection with the use-side heat exchanger 27) in order to reverse the refrigerant flow to that during the cooling operation. The other inlet (connection port with the accumulator 23) is communicated with the other outlet (connection port with the heat source side heat exchanger 16). Further, the expansion valve 17 is fully closed and the expansion valve 18 is fully opened, and the air conditioning compressors 13A and 13B are operated.

  When the air-conditioning compressors 13A and 13B are operated, the high-temperature and high-pressure gas refrigerant discharged from the discharge side of the air-conditioning compressors 13A and 13B passes through the oil separator 10 and the four-way valve 14 as shown by arrows in FIG. It is supplied to the use side heat exchanger 27. The use side heat exchanger 27 is ventilated with room air by the blower 15, and the refrigerant dissipates heat here and heats the room air while condensing. Thereby, the room (in-store 2) is heated.

  The refrigerant liquefied by the use side heat exchanger 27 is reduced in pressure through the expansion valve 18 and the expansion valve 19 in order (decompression), and then flows into the air conditioning side passage 21A of the cascade heat exchanger 21 and evaporates there. After the heat is absorbed, the circulation supplied to the suction side of the air-conditioning compressors 13A and 13B through the accumulator 23 is repeated.

  The outdoor side air conditioning controller 26 adjusts the valve opening degree of the expansion valves 18 and 19 so as to achieve an appropriate degree of superheat based on the refrigerant temperature at the entrance and exit of the cascade heat exchanger 21 or the temperature of the cascade heat exchanger 21. . Further, the indoor side air conditioning controller 28 uses the use side heat so that the temperature of the room (in the store 2) is set to a preset temperature based on the temperature of the use side heat exchanger 27 and the air temperature sucked into the use side heat exchanger 27. The blower 15 that ventilates the exchanger 27 is controlled.

  On the other hand, the outdoor side cooling controller 32 communicates one inlet (a connection port with the oil separator 31) of the four-way valve 39 of the cooling refrigerant circuit 9 of the refrigeration system 8 to one outlet (a connection port with the four-way valve 41). The other inlet (connection port with the cascade heat exchanger 21) is communicated with the other outlet (connection port with the condenser 38). Further, the outdoor side cooling controller 32 uses one inlet (a connection port with the receiver tank 36) of the four-way valve 41 as one outlet (a refrigeration evaporator 43 and a freezing evaporator 49 (solenoid valves 46, 47, 52)). And the other inlet (the connection port with the four-way valve 39) is communicated with the other outlet (the connection port with the cascade heat exchanger 21). Then, the cooling compressor 37 and the boosting compressor 54 are operated.

  Accordingly, the high-temperature and high-pressure gas refrigerant discharged from the cooling compressor 37 is supplied to the case side passage 21 </ b> B of the cascade heat exchanger 21 through the four-way valves 39 and 41. That is, the high-temperature and high-pressure gas refrigerant discharged from the cooling compressor 37 is supplied to the cascade heat exchanger 21 after passing through the condenser 38 in the cooling operation, whereas it is cascaded before going to the condenser 38. It is supplied to the heat exchanger 21.

  The refrigerant in the cooling refrigerant circuit 9 supplied to the cascade heat exchanger 21 is cooled by the cascade heat exchanger 21 that is at a low temperature due to evaporation of the refrigerant in the air conditioning refrigerant circuit 7 as described above, and further subcooled. The In other words, the refrigerant in the air conditioning refrigerant circuit 7 can pump up heat from the refrigerant in the cooling refrigerant circuit 9.

  The refrigerant that has passed through the case side passage 21 </ b> B of the cascade heat exchanger 21 enters the inlet side 38 </ b> A of the condenser 38 through the four-way valve 39. Outside air is passed through the condenser 38 by the blower 35, and the refrigerant flowing into the condenser 38 dissipates heat and condenses.

  The refrigerant discharged from the condenser 38 enters the receiver tank 36 and is temporarily stored therein to separate the gas / liquid. The separated liquid refrigerant exits from the receiver tank 36, passes through the four-way valve 41, and is branched, and goes to the electromagnetic valves 46 and 52 in the same manner as described above.

  By the above operation, even during the heating operation of the air conditioning refrigerant circuit 7, the low-pressure side refrigerant flowing through the air-conditioning refrigerant circuit 7 is supplied to the cascade heat exchanger 21, and the high-pressure side refrigerant flowing through the cooling refrigerant circuit 9 is excessively passed. By cooling, the cooling capacity of the refrigeration evaporator 43 and the refrigeration evaporator 49 of the refrigeration case 3 and the refrigeration case 4 and the operation efficiency of the refrigeration system 8 are improved.

  Furthermore, during the heating operation, the refrigerant in the air conditioning refrigerant circuit 7 pumps heat from the refrigerant in the cooling refrigerant circuit 9 in the cascade heat exchanger 21, so that the heating capacity of the air conditioning system 6 can be improved, The efficiency of the entire refrigeration cycle apparatus 1 that performs air conditioning and cooling of the refrigeration case 3 and the refrigeration case 4 is improved to save energy.

  Here, in a supermarket, a convenience store, etc., a predetermined number of refrigeration evaporators 43 and refrigeration evaporators 49 are installed according to the scale of the store as described above. When a large number of refrigeration and refrigeration cases 4 are cooled and frozen to a predetermined temperature and the respective evaporators 43, 49... Are cooled and stopped, the cooling compressor 37 cannot suck the refrigerant. The low pressure side (inlet side 37A) of the cooling compressor 37 is low pressure. Conversely, when all the evaporators 43, 49,... Are in cooling and freezing operation, the refrigerant flows through the cooling refrigerant circuit 9, so that the cooling compressor 37 can suck the refrigerant and the pressure on the inlet side 37A. Becomes a pressure higher than that at the time of low pressure (normal pressure).

  When any one of the expansion valves 44, 51... Is open, the outdoor side cooling controller 32 (pressure on the suction side (inlet side) of the cooling compressor 37 (low pressure of the cooling refrigerant circuit 9). ) To control the operating frequency of the cooling compressor 37. In this case, in the state in which the interiors of the refrigerated case 3 and the refrigerated case 4 are sufficiently cooled, the outdoor side cooling controller 32 rotates the operating frequency of the cooling compressor 37 at a low speed and hardly cools the interior. 3 and the outdoor case cooling controller 32 perform control for rapidly cooling the inside of the refrigerator by rotating the operating frequency of the cooling compressor 37 at a high speed. That is, the outdoor side cooling controller 32 controls and operates the operating frequency of the cooling compressor 37 in the range of low speed (25 Hz) to high speed (80 Hz), for example, by the pressure on the inlet side 37 </ b> A of the cooling compressor 37.

  In this case, the pressure sensor 67 detects the pressure on the inlet side 37A of the cooling compressor 37, and the pressure on the inlet side 37A is equal to or lower than a predetermined threshold value (each expansion valve 44, 51... All are fully closed), the outdoor side cooling controller 32 stops the operation of the cooling compressor 37 (the booster unit 22 is also stopped) or operates at a low operating frequency. Further, when the pressure sensor 67 detects the pressure on the inlet side 37A of the cooling compressor 37 and the pressure on the inlet side 37A is equal to or higher than a preset threshold value (the expansion valves 44, 51... Are all fully opened). ), The outdoor side cooling controller 32 operates the operating frequency of the cooling compressor 37 at a high frequency. In the outdoor cooling controller 32, the pressure sensor 67 detects the pressure on the inlet side 37A of the cooling compressor 37, and the pressure on the inlet side 37A is preset between a predetermined high pressure and a low pressure. In this case, an operation is performed in which the operation frequency of the cooling compressor 37 is controlled between a low speed (25 Hz) and a high speed (80 Hz) based on the pressure.

  Here, the operation frequency control of the oil return circuit 64 and the cooling compressor 37 will be described with reference to the flowchart of FIG. When the operation frequency of the cooling compressor 37 is low (for example, 25 Hz to 35 Hz) or when the operation frequency is high (for example, 70 Hz to 80 Hz), the oil in the cooling compressor 37 is maintained. The amount may decrease. Therefore, in the present invention, the level of the oil amount in the cooling compressor 37 is divided into three stages, and the range where the oil amount sufficient for the operation of the cooling compressor 37 is defined as the upper oil level range Hi, and the cooling compressor. The range of the amount that may interfere with the engine 37 is the lower oil level range Lo, and the range between the upper oil level range Hi and the lower oil level range Lo is the middle oil level range M.

  If the oil level sensors 66B and 66A cannot detect the oil, the lower oil level range Lo is detected. If the oil is detected, the oil level sensor 66A (66B), whichever is shorter, When the longer oil level sensor 66A (66B) cannot detect oil, the middle oil level range M is reached. The upper oil level range Hi, the lower oil level range Lo, and the middle oil level range M are set to have a division ratio depending on the operating state of the cooling compressor 37. In addition, the inlet side 37A of the cooling compressor 37 is divided into a high pressure zone where the pressure is high, a low pressure zone where the pressure is low, and an intermediate zone where the pressure is intermediate.

  The oil level detected by the oil level sensor 66 (oil level SW in the figure) is a high oil level value (corresponding to the upper limit value of the present invention) between the upper oil level range Hi and the middle oil level range M, A low oil level value (corresponding to the lower limit value of the present invention) is set between the middle oil level range M and the lower oil level range Lo. When the oil level detected by the oil level sensor 66 is lower than the high oil level value (when it is lower than the upper oil level range Hi), the outdoor side cooling controller 32 opens the oil supply valve 65 to return the oil return circuit 33. The oil is returned to the cooling compressor 37, and when the oil level is lower than the low oil level value (lower oil level range Lo), the operating frequency of the cooling compressor 37 is controlled to a low frequency. Yes. The oil level in the cooling compressor 37 is detected by the oil level sensor 66 when the oil level SW is turned ON.

  That is, in step S1, the outdoor cooling controller 32 proceeds to step S2 when the oil level detected by the oil level sensor 66 is equal to or lower than the high oil level value in the cooling compressor 37 (medium oil level range M). The fuel supply valve 65 is opened (ON in the figure), and the fuel supply lamp is turned on. As a result, the oil stored in the oil separator 31 is returned from the oil return circuit 64 into the cooling compressor 37. The oil supply valve 65 is closed without being opened except when it passes through step S2.

  In step S3, the outdoor cooling controller 32 detects that the oil level in the cooling compressor 37 detected by the oil level sensor 66 is not less than the low oil level value and not more than the high oil level value (in this case, the middle oil level range M). In this case, the process waits for the oil level in the cooling compressor 37 to be higher than the high oil level value (upper oil level range Hi) or lower than the low oil level value (lower oil level range Lo). When the outdoor level cooling controller 32 detects that the oil level in the cooling compressor 37 is equal to or lower than the low oil level value (lower oil level range Lo) by the oil level sensor 66, the process proceeds to step S4.

  At this time, when the cooling compressor 37 is operated at an operating frequency higher than 50 Hz, the outdoor side cooling controller 32 proceeds to step S5 and operates the operating frequency of the cooling compressor 37 at 50 Hz. That is, based on the output of the oil level sensor 66, the outdoor side cooling controller 32 switches the oil supply valve 65 when the oil level of the cooling compressor 37 falls below a predetermined low oil level value (lower oil level range Lo). It opens and the operation frequency of the compressor 37 for cooling is fixedly operated at a low frequency (50 Hz). And the outdoor side cooling controller 32 progresses to step S7, when the oil in the compressor 37 for cooling increases to the middle oil level range M in the middle of driving | operating by 50 Hz of operation frequency by step S6, there, After the cooling compressor 37 is operated for 1 minute, the process proceeds to step S8, the cooling compressor 37 is normally operated in response to a request from the refrigeration case 3, the refrigeration case 4, and the like, and the process returns to step S1.

  In step S4, the outdoor side cooling controller 32 proceeds to step S9 when the cooling compressor 37 has an operating frequency lower than 50 Hz. Therefore, the outdoor cooling controller 32 determines that the pressure on the inlet side 37A of the cooling compressor 37 detected by the pressure sensor 67 is equal to or lower than a predetermined threshold (the inlet side 37A of the cooling compressor 37 is set in advance). In the case of a predetermined low pressure zone), the process proceeds to step S10. Therefore, the outdoor-side cooling controller 32 stops the operation of the cooling compressor 37 for 3 minutes, and then proceeds to step S5 to control the rotation frequency of the cooling compressor 37 to 50 Hz. In this case, when the oil level of the cooling compressor 37 drops below a predetermined high oil level value that is higher than the low oil level value (in the middle oil level range M), the outdoor side cooling controller 32 determines the oil supply valve 65. When the oil level falls below the low oil level value in this state (when the oil level falls within the lower oil level range Lo), the operating frequency of the cooling compressor 37 is controlled to a low frequency (50 Hz). .

  Specifically, the outdoor cooling controller 32 is configured so that each refrigeration case 3, the refrigeration case 4,... Is sufficiently cooled, the pressure on the inlet side 37A of the cooling compressor 37 is below a predetermined threshold value, and the oil level is low. In the level range Lo, the cooling compressor 37 is stopped for about 3 minutes. In this case, when the pressure on the inlet side 37A of the cooling compressor 37 naturally returns to the predetermined threshold by stopping the cooling compressor 37 for about 3 minutes, the process proceeds to step S5 and the cooling compressor 37 is reached. The operation frequency is controlled to 50 Hz (corresponding to fixing the operation frequency of the cooling compressor 37 of the present invention to a predetermined specified value), and steps S6 to S8 and steps S1 to S5 are repeated.

  In step S6, the outdoor cooling controller 32 operates the cooling compressor 37 at an operation frequency of 50 Hz, and the oil level in the cooling compressor 37 detected by the oil level sensor 66 is a predetermined low oil level value. When it falls below (when the oil level is in the lower oil level range Lo), the process proceeds to step S11. Therefore, the outdoor cooling controller 32 repeats step S6 and step S11, and the oil level in the cooling compressor 37 is predetermined even when the operation of the cooling compressor 37 (frequency operation at 50 Hz) has elapsed for 10 minutes or more. If the oil level is less than the low oil level value, the process proceeds to step S12 to activate the alarm device 33 (preliminary alarm).

  That is, when the cooling compressor 37 is in the lower oil level range Lo in step S11 and the 50 Hz frequency operation has continued for 10 minutes or longer, the outdoor side cooling controller 32 proceeds to step S12 and sets the alarm device 33. To issue a preliminary warning. Note that as the preliminary alarm, for example, an LED provided on the base of the outdoor cooling controller 32 is blinked or a notification is sent to the administrator through communication.

  In step S13, the outdoor cooling controller 32 does not increase the oil level during operation of the cooling compressor 37 at a frequency of 50 Hz, and the oil level in the cooling compressor 37 detected by the oil level sensor 66 is low. If the value is less than or equal to the value, the process proceeds to step S14. Therefore, the outdoor cooling controller 32 repeats Steps S13 and S14, and the oil level in the cooling compressor 37 is maintained even if the operation of the cooling compressor 37 (50 Hz frequency operation) is continued for more than 20 minutes. If it is equal to or lower than the predetermined low oil level value, the process proceeds to step S15. Therefore, after stopping the operation of the cooling compressor 37, the outdoor side cooling controller 32 issues a main alarm from the alarm device (this alarm is issued in the figure) in step S16, and returns to step S13.

  Specifically, when the oil level in the cooling compressor 37 detected by the oil level sensor 66 is the lower oil level range Lo and the cooling compressor 37 is continuously operated at an operation frequency of 50 Hz for 20 minutes or more, outdoor cooling is performed. Based on the output of the pressure sensor 67, the controller 32 stops the operation of the cooling compressor 37 and prevents the oil in the cooling compressor 37 from being exhausted when the low-pressure side pressure is equal to or lower than a predetermined threshold value. The outdoor cooling controller 32 stops the operation of the cooling compressor 37 and then issues a main alarm in step S16. As the main alarm, it reports to the store 2 (reports such as sounding a buzzer), and reports to the manager and service company (the oil level in the compressor 37 for cooling is at a lower oil level range Lo at an operating frequency of 50 Hz) Notification that the cooling compressor 37 has been continuously operated for 20 minutes or more). As a result, the oil in the cooling compressor 37 is depleted and the inconveniences such as the lubrication and sealing performance of the sliding portion are prevented.

  In step S13, if the outdoor cooling controller 32 increases the amount of oil in the cooling compressor 37 while repeating steps S13 and S14, the process proceeds to step S7, and the cooling compressor 37 is operated for one minute as described above. After that, the process proceeds to step S8, the normal operation of the cooling compressor 37 is performed according to the request from the refrigeration case 3, the refrigeration case 4, etc., the process returns to step S1, and the subsequent steps are repeated. In addition, during operation of the cooling compressor 37 in step S1, step S3, step S6, and step S13, the oil level in the cooling compressor 37 is changed by the oil level sensor 66 and becomes the upper oil level range Hi. If detected, the process proceeds to step S8, and the subsequent steps are repeated.

  As described above, the outdoor cooling controller 32 determines that the oil level in the cooling compressor 37 is equal to or lower than the predetermined high oil level value (the middle oil level range M and the lower oil level range Lo) based on the output of the oil level sensor 66. If the oil supply valve 65 falls below the low oil level value, the operating frequency of the cooling compressor 37 is limited to a predetermined rotational speed. As a result, in addition to returning the oil from the oil separator 31 to the cooling compressor 37 via the oil return circuit 64, the operating frequency of the cooling compressor 37 is also limited, so the oil discharge amount from the cooling compressor 37 Thus, oil exhaustion in the cooling compressor 37 can be effectively prevented. Therefore, it is possible to reliably prevent the disadvantage that the oil in the cooling compressor 37 is depleted depending on the operating state of the cooling compressor 37 and the lubrication or sealing performance of the sliding portion is lowered.

  The outdoor cooling controller 32 opens the oil supply valve 65 when the oil level of the cooling compressor 37 is higher than the low oil level value and below a predetermined high oil level value (in the middle oil level range M). In this state, when the oil level falls below the low oil level value (in the case of the lower oil level range Lo), the operating frequency of the cooling compressor 37 is limited. Since the operating frequency of the cooling compressor 37 is limited under a decreasing condition, it is possible to minimize the adverse effect on the cooling effect due to the operating frequency of the cooling compressor 37 not increasing.

  Further, the outdoor cooling controller 32 determines the operating frequency of the cooling compressor 37 as described above when the oil level falls below a predetermined low oil level value (in the case of the lower oil level range Lo). Since the value (50 Hz) is fixed, the oil accumulated in the cooling refrigerant circuit 9 can be smoothly returned to the cooling compressor 37.

  Further, the outdoor side cooling controller 32 determines the low pressure side pressure based on the output of the pressure sensor 67 when the oil level detected by the oil level sensor 66 falls below the low oil level value (in the lower oil level range Lo). Is below a predetermined threshold value, the operation of the cooling compressor 37 is stopped. Therefore, for example, when the low-pressure side pressure of the refrigerant circuit in which the cooling target is sufficiently cooled is low, the cooling compressor 37 To stop refrigerant (oil) discharge. Accordingly, since natural oil return can be promoted, the oil naturally returns to the suction side of the cooling compressor 37 through the refrigerant circuit (cooling refrigerant circuit 9). Therefore, since the oil in the cooling compressor 37 is not exhausted, sufficient oil can be secured.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this. For example, in the above embodiment, the case where the present invention is applied to the refrigeration cycle apparatus 1 applied to a store such as a convenience store has been described. However, air conditioning and cooling of refrigeration cases other than the refrigeration case 3 and the refrigeration case 4 are performed. It can be widely applied to the refrigeration cycle apparatus to be performed. Furthermore, the piping configuration shown in the above embodiment is not limited thereto, and can be appropriately changed without departing from the gist of the present invention.

  Further, in claim 1, when the oil level in the cooling compressor 37 is equal to or lower than a predetermined lower limit value (lower oil level range Lo) based on the outputs of the outdoor cooling controller 32 and the oil level sensor 66, the oil supply valve 65, and the operating frequency of the cooling compressor 37 is limited. However, the oil level in the cooling compressor 37 is below a predetermined upper limit (the middle oil level range M and the lower oil level range Lo). The operating frequency of the cooling compressor 37 may be controlled. Thereby, in addition to the effects of the embodiment, fine operation control of the cooling compressor 37 can be performed, and the amount of oil in the cooling compressor 37 can be further secured. Further, if the amount of oil in the cooling compressor 37 is less than or equal to the high oil level value (including the middle oil level range M and the lower oil level range Lo), the operating frequency of the cooling compressor 37 is controlled at any position. Needless to say, there is no problem.

  In the present embodiment, the configuration in which the refrigeration cycle apparatus 1 is arranged in a convenience store has been described. However, even in a school or a supermarket, for example, air conditioning of a space having the refrigeration case 3 and cooling of the refrigeration case 3 are performed. When performing, the said refrigeration cycle apparatus 1 is applicable.

It is a figure which shows the system configuration | structure containing the refrigerant circuit of the refrigerating-cycle apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the heating operation of the air-conditioning system part of the refrigerating-cycle apparatus which concerns on embodiment of this invention. It is an enlarged view of the principal part of the refrigerating-cycle apparatus (FIG. 1, FIG. 2) which concerns on embodiment of this invention. It is a flowchart which shows the operating frequency control of the oil return circuit and cooling compressor of the refrigerating-cycle apparatus which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration cycle apparatus 6 Air conditioning system 7 Air conditioning refrigerant circuit 8 Refrigeration system 9 Cooling refrigerant circuit 11 Indoor unit 12 Outdoor unit 13 Compression unit 21 Cascade heat exchanger 31 Oil separator 32 Outdoor cooling controller 33 Alarm device 37 Cooling compressor 56 Main controller 64 Oil return circuit 65 Oil supply valve 66 Oil level sensor 67 Pressure sensor

Claims (4)

In a refrigeration cycle apparatus comprising a compressor, an oil separator provided on the refrigerant discharge side of the compressor, and an oil return circuit for returning oil from the oil separator to the compressor,
Oil level detection means for detecting the oil level of the compressor;
A valve device that is provided in the oil return circuit and controls whether oil is returned from the oil separator to the compressor;
Control means for controlling the operating frequency of the compressor and the opening and closing of the valve device,
The control means, based on the output of the oil level detection means, opens the valve device and limits the operating frequency of the compressor when the oil level of the compressor is below a predetermined upper limit value. A characteristic refrigeration cycle apparatus.   The control means opens the valve device when the oil level of the compressor falls below a predetermined upper limit value higher than the lower limit value, and when the oil level falls below the lower limit value in that state, The refrigeration cycle apparatus according to claim 1, wherein an operating frequency of the compressor is limited.   The refrigeration according to claim 1 or 2, wherein the control means fixes the operating frequency of the compressor to a predetermined specified value when the oil level falls below the lower limit value. Cycle equipment. Low pressure side pressure detecting means for detecting the low pressure side pressure of the refrigerant circuit,
The control means stops the compressor based on the output of the low-pressure side pressure detecting means when the oil level falls below the lower limit value, when the low-pressure side pressure is below a predetermined threshold value. The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein

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