JP2016017713A - Cooling device and freezing vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling device capable of optimizing a return amount of refrigerating machine oil to a compressor.SOLUTION: A cooling device 30 built in a freezing vehicle 100 includes: a compressor 31; a condenser 33; an electronic expansion valve 34; an evaporator 35; a flow rate adjustment valve 39 capable of adjusting a return amount of refrigerating machine oil separated from refrigerant on the discharge side of the compressor 31 and returned to a suction part 31b of the compressor 31; and a control unit 61 controlling the opening of the flow rate adjustment valve 39 according to an operation load state based on an ambient temperature Ta to thereby adjust the return amount of the refrigerating machine oil.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cooling device and a refrigeration vehicle, and in particular, a cooling device including a refrigeration oil flow rate adjustment valve capable of adjusting a return amount of refrigeration oil separated from a refrigerant on the discharge side of the compressor and returned to the suction side of the compressor. And refrigeration vehicles.

  Conventionally, a cooling device including a refrigerating machine oil flow rate adjustment valve capable of adjusting the return amount of refrigerating machine oil separated from the refrigerant on the discharge side of the compressor and returned to the suction side of the compressor is known (for example, Patent Documents). 1).

  Patent Document 1 discloses a transport refrigeration apparatus (cooling apparatus) including a compressor, a condenser, an expansion valve, and an evaporator. In the transport refrigeration apparatus described in Patent Document 1, an oil separator that separates oil (refrigerant oil) in refrigerant gas is provided in a discharge pipe of a compressor, and an oil separator and a suction pipe of the compressor are provided. Are connected via an oil return pipe. The oil return pipe is provided with a flow rate adjusting means for adjusting the pressure and flow rate of the refrigeration oil returned to the compressor suction pipe.

JP 2009-216292 A

  However, the transport refrigeration apparatus described in Patent Document 1 describes that an expansion valve capable of increasing and decreasing the valve opening is applicable as an example of the flow rate adjusting means in the oil return pipe. There is no disclosure or suggestion of specific control contents when applying such a flow rate adjustment valve (refrigeration oil flow rate adjustment valve) for adjusting the return amount of the refrigeration oil. For this reason, when the opening degree control of the refrigerating machine oil flow rate adjustment valve is not properly performed, there is a problem that the return amount of the refrigerating machine oil returned to the compressor is not optimized.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a cooling device and a freezing vehicle capable of optimizing the return amount of the refrigerating machine oil to the compressor. Is to provide.

  In order to achieve the above object, a cooling device according to a first aspect of the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant, an expansion valve that expands the refrigerant condensed by the condenser, An evaporator for evaporating the refrigerant expanded by the expansion valve, a refrigerating machine oil flow rate adjustment valve capable of adjusting a return amount of the refrigerating machine oil separated from the refrigerant on the discharge side of the compressor and returned to the suction side of the compressor, And a control unit configured to adjust the return amount of the refrigerating machine oil by controlling the opening degree of the refrigerating machine oil flow rate adjusting valve according to the operating load state.

  In the cooling device according to the first aspect of the present invention, as described above, a refrigerating machine oil flow rate adjustment valve capable of adjusting the return amount of refrigerating machine oil separated from the refrigerant on the discharge side of the compressor and returned to the suction side of the compressor; And a control unit configured to adjust the return amount of the refrigerating machine oil by controlling the opening degree of the refrigerating machine oil flow rate adjusting valve in accordance with the operating load state. Thereby, the return amount of the refrigerating machine oil to the compressor in the operating (operating) cooling device can be optimized in consideration of the operating load state. That is, since the mixing ratio of the refrigerating machine oil to the suction refrigerant is optimized, the compressor can always be operated in an optimum state. As a result, a reduction in the refrigerating capacity when the refrigeration oil is returned excessively (a decrease in the refrigerant density accompanying an increase in the intake refrigerant temperature) and a failure of the compressor due to a shortage of the refrigeration oil are avoided. Can do.

  In the cooling device according to the first aspect described above, preferably, the operating load state includes at least one of an environmental temperature on the condenser side or a cooling temperature on the evaporator side, and the control unit is configured such that the environmental temperature on the condenser side or the evaporator. The return amount of the refrigerating machine oil is adjusted by controlling the opening degree of the refrigerating machine oil flow rate adjustment valve based on at least one of the cooling temperatures on the side. If comprised in this way, the cooling device in operation based on at least one of the environmental temperature condition on the high pressure side (condenser side) and the temperature condition on the low pressure side (evaporator side) (evaporation temperature condition of the refrigerant) in the refrigeration cycle It is possible to directly grasp the driving load state of Therefore, the opening degree control of the refrigerating machine oil flow rate adjustment valve according to the operating load state can be easily performed.

  In this case, preferably, the control unit adjusts the suction refrigerant temperature of the refrigerant sucked into the compressor to an intake refrigerant temperature range corresponding to at least one of the environmental temperature on the condenser side and the cooling temperature on the evaporator side. In addition, control is performed to adjust the return amount of the refrigerating machine oil by the refrigerating machine oil flow rate adjusting valve. According to this configuration, the refrigerant refrigerant sucked into the compressor is increased or decreased in the return amount of the refrigeration oil so that the operating load state of the cooling device (the ambient temperature on the condenser side or the cooling temperature on the evaporator side) is increased. The temperature can be adjusted to a temperature (intake refrigerant temperature range) in consideration of at least one of them. Therefore, since the compressor can be operated within an appropriate operating range according to the operating load state of the cooling device, the failure rate of the compressor can be reduced. In addition, since the compressor can be operated within an appropriate operating range according to the operating load state, the cooling capacity can be maximized and stable cooling performance can be exhibited in the cooling device.

  In the configuration in which the operating load state includes the environmental temperature on the condenser side, preferably, an environmental temperature detection unit for detecting the environmental temperature on the condenser side as the operating load state, and suction of refrigerant sucked into the compressor An intake refrigerant temperature detection unit that detects the refrigerant temperature, and the control unit presets the intake refrigerant temperature detected by the intake refrigerant temperature detection unit according to the environmental temperature detected by the environmental temperature detection unit First opening control for increasing the opening of the refrigerating machine oil flow rate adjustment valve when it is smaller than the predetermined threshold value, and opening degree of the refrigerating machine oil flow rate adjustment valve when the intake refrigerant temperature is larger than the predetermined threshold value It is comprised so that 2nd opening degree control which decreases may be performed. If comprised in this way, when 1st opening degree control is performed, since more refrigeration oil can be returned to a compressor with the increase in opening degree, the refrigeration oil shortage with respect to a compressor is ensured. It can be avoided. In addition, when the second opening degree control is performed, an excessive increase in the intake refrigerant temperature can be suppressed, so that it is possible to suppress the refrigerant density from decreasing and the refrigerating capacity from decreasing. As a result, the failure rate of the cooling device can be surely reduced, and the cooling device can be surely exerted the stable cooling performance by maximizing the cooling capacity.

  In this case, preferably, the apparatus further includes a table in which a relationship between the environmental temperature and the intake refrigerant temperature corresponding to the environmental temperature is defined in advance, and the control unit performs the first opening degree control and the second opening degree based on the table. It is configured to perform control. If configured in this way, the recommended value (target value) of the intake refrigerant temperature for the operating load state obtained based on the environmental temperature condition on the high pressure side (condenser side) in the refrigeration cycle can be easily grasped using a table. can do.

  A refrigeration vehicle according to a second aspect of the present invention includes a vehicle provided with a storage, and a cooling device mounted on the vehicle for cooling the inside of the storage, and the cooling device compresses the refrigerant. And a condenser for condensing the refrigerant, an expansion valve for expanding the refrigerant condensed by the condenser, an evaporator for evaporating the refrigerant expanded by the expansion valve, and being separated from the refrigerant on the discharge side of the compressor Refrigerator oil flow rate adjustment valve that can adjust the return amount of refrigeration oil returned to the suction side of the compressor, and the return amount of refrigeration oil adjusted by controlling the opening of the refrigeration oil flow rate adjustment valve according to the operating load state And a control unit configured to perform control.

  In the refrigerating vehicle according to the second aspect of the present invention, as described above, a refrigerating machine oil flow rate adjusting valve capable of adjusting a return amount of refrigerating machine oil separated from the refrigerant on the discharge side of the compressor and returned to the suction side of the compressor; The cooling device is provided with a control unit configured to adjust the return amount of the refrigerating machine oil by controlling the opening degree of the refrigerating machine oil flow rate adjusting valve according to the operating load state. Thereby, the return amount of the refrigerating machine oil to the compressor in the operating (operating) cooling device can be optimized in consideration of the operating load state. That is, since the mixing ratio of the refrigerating machine oil to the suction refrigerant is optimized, the compressor can always be operated in an optimum state. As a result, in the refrigeration vehicle of the present invention, the compressor is caused by a decrease in refrigeration capacity when the refrigeration oil is returned excessively (decrease in refrigerant density due to an increase in intake refrigerant temperature) or a shortage of refrigeration oil. A failure can be avoided.

  According to the present invention, as described above, it is possible to provide a cooling device and a refrigeration vehicle capable of optimizing the return amount of refrigeration oil to the compressor.

It is the figure which showed the schematic whole structure of the freezing vehicle by one Embodiment of this invention. It is the refrigerant circuit figure which showed the schematic structure of the cooling device mounted in the freezer truck by one Embodiment of this invention. It is the block diagram which showed the control structure of the cooling device mounted in the freezer truck by one Embodiment of this invention. It is the figure which showed the temperature table used for operation control of the cooling device mounted in the freezer truck by one Embodiment of this invention. It is the figure which showed the processing flow of the control part regarding the operation control of the cooling device mounted in the freezer truck by one Embodiment of this invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

  First, with reference to FIGS. 1-4, the structure of the refrigerator car 100 by one Embodiment of this invention is demonstrated.

  For example, the refrigerator 100 according to the embodiment of the present invention needs to manage temperature in the range of about −5 ° C. to 0 ° C. when transporting frozen food that needs to be maintained at a low temperature around −20 ° C. during transportation. This is a commercial truck capable of switching between transporting fresh food (chilled food) and transporting refrigerated food containing milk beverages that require temperature control around + 5 ° C. In addition, as shown in FIG. 1, the refrigerator car 100 includes a vehicle body 10, a freezer 20 as a freezer refrigerator, and a cooling device 30 that cools the inside of the freezer 20. The vehicle body 10 is an example of the “vehicle” in the present invention, and the freezer 20 is an example of the “storage” in the present invention.

  The vehicle body 10 is provided with a traveling engine 12 (shown by a broken line) on the front side (X1 side) of the chassis 11 and a cab 13 is provided so as to cover the engine 12. A battery 14 is mounted on the side of the chassis 11. The electric power of the battery 14 is used as electric power for a control operation when the cooling device 30 is operated. The battery 14 is charged during traveling by an alternator 12a that generates electric power using the driving force of the engine 12. The vehicle main body 10 is equipped with a control box 60 that controls the operation of the cooling device 30. The control box 60 is configured as a separate control device from the vehicle body side control unit (ECU) 12b that controls the engine 12 on the vehicle body 10 side. Note that a control unit (CPU) 61 for performing operation control of the cooling device 30 is provided in the control box 60.

  The freezer 20 is installed on the chassis 11 at the rear (X2 side) of the cab 13. Moreover, the freezer 20 is mainly comprised by the side wall part 21 perpendicular | vertical with respect to the road surface 1, the floor part 22 and the ceiling part 23 parallel to the road surface 1, and the opening-and-closing door 24 which can be opened and closed toward the outer side. ing. The side wall portion 21, the floor portion 22, the ceiling portion 23, and the open / close door 24 are made of heat-insulating members, and each member is assembled to a metal frame (frame), thereby forming a hollow box structure. The freezer 20 is formed. Further, the floor portion 22 has a flat floor surface, and the product 2 is loaded on the floor surface. In addition, in FIG. 1, the state (overall external shape of the goods 2) by which the several goods 2 packed in a box were piled up on the floor part 22 is shown using the dashed-two dotted line.

  Moreover, the cooling device 30 is configured to be able to form a predetermined refrigeration cycle, as shown in FIG. Specifically, the cooling device 30 includes a compressor 31, an oil separator (oil separator) 32, a condenser 33, an electronic expansion valve 34, an evaporator 35, and refrigerant pipes 36a to 36a that sequentially connect them. 36d. The cooling device 30 further includes an oil return circuit 37 that connects the oil separator 32 and the suction side of the compressor 31. The electronic expansion valve 34 is an example of the “expansion valve” in the present invention.

  Each functional component constituting the cooling device 30 will be briefly described. The compressor 31 has a role of compressing the sucked gas refrigerant (R134a) and discharging it to the refrigerant pipe (discharge pipe) 36a. Here, the compressor 31 is installed in the vicinity of the engine 12 (see FIG. 1), and is driven by the power of the engine 12 via an electromagnetic clutch (not shown). As the compressor 31, any of a reciprocating compressor, a rotary compressor, a scroll compressor, etc. may be used regardless of the control method (inverter control type or constant speed type).

  The oil separator 32 is disposed immediately after the discharge part 31a of the compressor 31, and the oil separator 32 converts the refrigerating machine oil contained in the refrigerant gas (high-temperature high-pressure gas) discharged from the compressor 31 from the refrigerant gas. Have a role to separate. The configuration of the oil return circuit 37 will be described later. Moreover, the condenser 33 which consists of an air heat exchanger has a function which cools the superheated gas state refrigerant | coolant which distribute | circulates an inside using the external air (air) ventilated by the air blower 51. FIG. The refrigerant condensed (liquefied) in the condenser 33 flows through the refrigerant pipe (liquid pipe) 36 b and flows into the electronic expansion valve 34.

  The electronic expansion valve 34 has a role of expanding the refrigerant cooled (liquefied) by the condenser 33 and supplying it to the evaporator 35. The electronic expansion valve 34 is driven to open and close using the driving force of a stepping motor driven by pulse control. Then, the flow rate of the refrigerant flowing into the evaporator 35 is controlled according to the opening degree of the electronic expansion valve 34. In addition, the liquid refrigerant expanded and contracted by the electronic expansion valve 34 flows into the evaporator 35 through the refrigerant pipe 36c in a gas-liquid two-phase state.

  The evaporator 35 composed of an air heat exchanger has a function of evaporating the gas-liquid two-phase refrigerant supplied from the electronic expansion valve 34. That is, heat is taken away from the air recirculated from the freezer 20 and passes through the outer surface of the evaporator 35, and the refrigerant circulating in the evaporator 35 evaporates by obtaining latent heat of evaporation. Further, the evaporated refrigerant becomes a gas state containing a large amount of gas phase, is circulated through the refrigerant pipe (suction pipe) 36d, and is returned to the compressor 31. Thus, in the cooling device 30, the refrigerant discharged from the compressor 31 circulates in the direction of the arrow A in the order of the oil separator 32, the condenser 33, the electronic expansion valve 34, and the evaporator 35, and returns to the compressor 31 again. Repeat the cycle to return.

  As shown in FIG. 1, the cooling device 30 is separated into a compressor 31 and a cooling unit 40 in which a portion other than the compressor 31 is housed, and is mounted on the vehicle body 10. The cooling unit 40 is attached to the outer surface of the side wall 21 of the freezer 20 above the cab 13 and behind the cab 13. The cooling unit 40 also includes a heat radiating part 41 (condenser 33 side) and a cooling part 42 (evaporator 35 side) housed inside the unit cover 43.

  Moreover, in the cooling unit 40, the housing 50 which comprises the cooling part 42 is attached to the side wall part 21 so that it may protrude ahead (arrow X1 direction) from the outer surface by the side of X1 of the side wall part 21. FIG. The evaporator 35 and the blower 52 are integrally accommodated in the housing 50 through a rectangular opening (not shown) provided in the side wall 21. Further, the heat radiating portion 41 is disposed on the front side (X1 side) of the cooling portion 42 with the housing 50 therebetween. Further, in the state where the evaporator 35 and the blower 52 are accommodated in the housing 50, the opening (not shown) of the side wall portion 21 blows out cold air (cold air) from the cooling unit 42 into the freezer 20. It is comprised so that it may be divided | segmented and arrange | positioned into 42a and the inlet 42b for sucking the air in the freezer 20 into the cooling part 42. FIG. The compressor 31 in the vicinity of the engine 12, the condenser 33 in the cooling unit 40, the electronic expansion valve 34, and the evaporator 35 are sequentially connected via refrigerant pipes 36a to 36d.

  In the heat radiating portion 41, the air outside the vehicle is sucked from the grill portion 43a by rotating the blower 51 by the driving force of the fan motor. And the air which cooled the condenser 33 is exhausted upwards (arrow Z1 direction) and downward (arrow Z2 direction) via the grill part 43b. In the cooling unit 42, the air in the freezer 20 is sucked into the evaporator 35 from the suction port 42b by rotating the blower 52 by the driving force of the fan motor. Then, the cold air cooled by the evaporator 35 is blown into the freezer 20 through the blower 52 through the blower outlet 42a.

  As shown in FIG. 1, an in-compartment temperature sensor 71 for detecting a cooling temperature (internal temperature) in the freezer 20 is attached in the vicinity of the ceiling 23 of the freezer 20. An outside air temperature sensor 72 that detects an outside air temperature Ta is attached to the door mirror 13a beside the cab 13. The outside air temperature sensor 72 is shown large for convenience. As shown in FIG. 2, a refrigerant temperature sensor 81 that detects the temperature of the refrigerant flowing out of the evaporator 35 is attached to a portion of the refrigerant pipe 36 d near the outlet of the evaporator 35. In addition, a suction temperature sensor 82 for detecting the suction refrigerant temperature Ts of the refrigerant sucked into the compressor 31 is attached to the refrigerant pipe 36 d of the suction portion 31 b of the compressor 31. The internal temperature sensor 71, the outside air temperature sensor 72, the refrigerant temperature sensor 81, and the suction temperature sensor 82 are electrically connected to the control box 60, and signals from the sensors (71 to 82) are controlled. It is comprised so that it may input into the part 61 (refer FIG. 3). Moreover, operation control of the cooling device 30 is performed when the control part 61 makes a predetermined judgment based on the input signal from each sensor (71-82). Thus, the refrigerator 100 is configured such that the inside of the freezer 20 is maintained at a desired temperature (low temperature) by the cold air cooled in the cooling unit 40. The outside air temperature sensor 72 is an example of the “environment temperature detector” in the present invention. The outside air temperature Ta is an example of the “condenser side environmental temperature” in the present invention. The suction temperature sensor 82 is an example of the “refrigerant temperature detection unit” in the present invention.

  Further, the oil return circuit 37 (see FIG. 2) has a role of refrigerating machine oil (oil) separated from the refrigerant gas by the oil separator 32 to the suction portion 31b of the compressor 31.

  Specifically, as shown in FIG. 2, the oil return circuit 37 includes an oil return pipe 38 and a flow rate control valve 39. The oil return pipe 38 is configured to connect the oil discharge part 32a of the oil separator 32 and the suction part 31b (merging part P1) of the compressor 31. The flow control valve 39 is provided in the middle of the oil return pipe 38. The flow control valve 39 opens and closes the valve mechanism using the driving force of the stepping motor driven by pulse control. Further, the return amount of the refrigerating machine oil discharged from the oil separator 32 is controlled according to the opening degree of the flow control valve 39. In addition to the refrigerating machine oil, some refrigerant gas also flows through the oil return circuit 37 and is returned to the compressor 31. The flow control valve 39 is an example of the “refrigeration machine oil flow rate adjustment valve” in the present invention.

  Here, in the present embodiment, the valve opening degree of the flow control valve 39 is controlled according to the operation load state of the cooling device 30 based on the command of the control unit 61. Further, along with the valve opening degree control of the flow rate control valve 39, the return amount of the refrigerating machine oil discharged from the oil separator 32 is adjusted. Further, by adjusting the opening degree of the flow rate control valve 39 and the return amount of the refrigeration oil, the intake refrigerant temperature Ts of the refrigerant sucked into the compressor 31 is set in a temperature range (described later) according to the operating load state. It is configured to be adjusted within the threshold value α).

  This point will be described in detail. During operation of the cooling device 30, the outside air temperature Ta in the outside environment to which the cooling device 30 (mainly the condenser 33) is exposed is detected by the outside air temperature sensor 72. Here, the outside air temperature Ta is acquired regardless of the running state of the refrigerator car 100. Then, based on the outside air temperature Ta detected by the outside air temperature sensor 72, the operation load state of the cooling device 30 is grasped by the control unit 61. For example, in the present embodiment, the cooling device 30 is operating under “low temperature conditions” where the outside air temperature Ta is less than about 0 ° C., or is operated under “standard conditions” where the outside air temperature Ta is between about 0 ° C. and about 35 ° C. The control unit 61 grasps whether the engine is in operation or is operating under an “overload condition” in which the outside air temperature Ta exceeds about 35 ° C. The opening amount of the flow control valve 39 is controlled in consideration of the operation load state (one of the low temperature condition, the standard condition, and the overload condition) grasped by the control unit 61, whereby the return amount of the refrigerator oil is reduced. It is configured to be adjusted.

  By performing the opening degree control of the flow rate control valve 39, the return amount of the refrigerating machine oil discharged from the oil separator 32 and returned to the suction portion 31b of the compressor 31 is adjusted. In the suction part 31b (merging part P1), the relatively low-temperature gas refrigerant returned from the evaporator 35 is mixed with the relatively high-temperature refrigerating machine oil returned from the oil separator 32. By adjusting the return amount of the refrigeration oil, which is the mixing amount of the refrigeration oil having a higher temperature with respect to the low-temperature gas refrigerant, the intake refrigerant temperature Ts of the refrigerant sucked into the compressor 31 is adjusted (increase or decrease). ) For example, when the return amount of the refrigerating machine oil is larger than the appropriate value, the mixing ratio of the refrigerating machine oil to the intake refrigerant increases, and further, the refrigerant density decreases as the intake refrigerant temperature Ts in the compressor 31 increases ( The cooling capacity (refrigeration capacity) of the evaporator 35 may be reduced as the refrigerant vapor becomes thinner. On the other hand, when the return amount of the refrigeration oil is less than the appropriate value, the compressor 31 may run out of oil, leading to failure. Therefore, the state of the refrigerating cycle of the cooling device 30 appropriately adjusts the refrigerating capacity by adjusting the sucked refrigerant temperature Ts within the suction refrigerant temperature range suitable for the operating load state of the cooling device 30 currently operating. It will be within the range that can be demonstrated. Further, the appropriate adjustment control of the intake refrigerant temperature Ts leads to the operation of the compressor 31 in an appropriate operation range, and in this sense, contributes to the operation protection of the compressor 31.

  As shown in FIG. 2, the intake refrigerant temperature Ts is configured to be detected by an intake temperature sensor 82. Therefore, the intake refrigerant temperature Ts, which is repeatedly adjusted every predetermined control period, is gradually brought closer to the target value by the opening degree control of the flow rate control valve 39. The opening degree control of the flow rate control valve 39 (valve opening / closing control) is performed as follows.

  In the cooling device 30, the target value (threshold value α) of the refrigerant temperature Ts of the refrigerant sucked into the compressor 31 is set in advance according to the outside air temperature Ta (operating load state) detected by the outside air temperature sensor 72. It has been established. Specifically, a temperature table 65 as shown in FIG. 4 is stored in the ROM 62 (see FIG. 3). In the temperature table 65, when the outside air temperature Ta detected by the outside air temperature sensor 72 is less than 0 ° C. (low temperature condition: Ta <0 ° C.), the intake refrigerant temperature Ts corresponds to “0 ° C ≦ Ts” corresponding to the low level. Correspondences that fall within the range of “≦ 30 ° C.” are defined. When the outside air temperature Ta is 0 ° C. or more and 35 ° C. or less (standard conditions), the suction refrigerant temperature Ts is within the range of “20 ° C. ≦ Ts ≦ 40 ° C.” corresponding to the intermediate level, and the outside air temperature Ta Is over 35 ° C. (overload condition: Ta> 35 ° C.), the intake refrigerant temperature Ts falls within the range of “30 ° C. ≦ Ts ≦ 60 ° C.” corresponding to the high level. It is prescribed. The temperature table 65 is an example of the “table” in the present invention.

  Regarding the temperature table 65, under low temperature conditions, the intake refrigerant temperature Ts is individually set within the range of 0 ° C. ≦ Ts ≦ 30 ° C. according to the detected outside air temperature Ta. Similarly, in the standard condition and the overload condition, the intake refrigerant temperature Ts is in the range of 20 ° C. ≦ Ts ≦ 40 ° C. or in the range of 30 ° C. ≦ Ts ≦ 60 ° C. depending on the detected outside air temperature Ta. Are set individually. Further, the intake refrigerant temperature Ts set individually in each operation load state is equal to the target value (threshold value α) of the intake refrigerant temperature Ts of the refrigerant drawn into the compressor 31. In other words, the threshold value α is individually set according to the outside air temperature Ta detected by the outside air temperature sensor 72 and stored as data. Therefore, the content defined in the temperature table 65 is preferably such that the cooling device 30 and the compressor 31 are operated in the state of the threshold value α (= intake refrigerant temperature Ts) individually set in each operation load state. Means that. In addition, since the specific numerical value of each threshold value (alpha) changes with specifications etc. of the compressor 31, the description is abbreviate | omitted. The threshold value α is an example of the “predetermined threshold value” in the present invention.

  In the present embodiment, the suction refrigerant temperature Ts of the refrigerant sucked into the compressor 31 detected by the suction temperature sensor 82 is set in accordance with the outside air temperature Ta detected by the outside air temperature sensor 72. When it is smaller than Ts (threshold value α), control for increasing the opening degree of the flow control valve 39 is performed. The intake refrigerant temperature Ts of the refrigerant sucked into the compressor 31 detected by the intake temperature sensor 82 is set according to the outside air temperature Ta detected by the outside air temperature sensor 72 (threshold α). Is greater than), the control for decreasing the opening degree of the flow control valve 39 is performed. The control for increasing the opening degree of the flow control valve 39 and the control for decreasing the opening degree of the flow control valve 39 are always performed based on the magnitude relationship between the intake refrigerant temperature Ts and the threshold value α. That is, the intake refrigerant temperature Ts acquired by the intake temperature sensor 82 is fed back to the control unit 61 at a predetermined control period and compared with the threshold value α. Based on the difference between the intake refrigerant temperature Ts and the threshold value α, the opening degree of the flow control valve 39 is increased, decreased, or maintained by a predetermined amount from the current value. The control for increasing the opening degree of the flow control valve 39 is an example of “first opening degree control” of the present invention, and the control for decreasing the opening degree of the flow control valve 39 is “second opening control” of the present invention. It is an example of “degree control”.

  The increment (decrease) in the opening of the flow control valve 39 in one opening control is set to a constant value regardless of the opening value (absolute opening size) of the flow control valve 39. May be. Alternatively, for example, the pulse control of the stepping motor is performed such that the amount of decrease in the opening per one opening control decreases as the opening of the flow control valve 39 decreases. You may comprise so that the pulse control of a stepping motor may be performed so that the increase amount of the opening degree per opening control may decrease, so that an opening degree becomes large. Further, the control content is configured such that the amount of increase (decrease) in the opening degree of the flow control valve 39 is determined in detail according to the change rate of the difference between the suction refrigerant temperature Ts and the threshold value α for each control cycle. It may be.

  Moreover, as a control structure of the cooling device 30, as shown in FIG. 3, in addition to the control part 61 which consists of CPU, ROM62 and RAM63 are provided. The controller 61 makes a predetermined determination based on input signals from the internal temperature sensor 71, the outside air temperature sensor 72, and the refrigerant temperature sensors 81 and 82, and the compressor 31, the electronic expansion valve 34, and the flow control valve 39. In addition, it is configured to appropriately control various functional components such as the fans 51 and 52. That is, in the cooling device 30, in addition to the opening degree control of the flow rate control valve 39, the capacity control of the cooling unit 42 (see FIG. 1) is simultaneously performed based on the internal temperature sensor 71 and the refrigerant temperature sensor 81. It is configured as follows.

  In addition to the control program executed by the control unit 61, the ROM 62 stores the temperature table 65 and the opening control table 66 used for opening control of the flow control valve 39 and the opening control of the electronic expansion valve 34. An opening control table 67 to be used, a frequency control table (not shown) relating to the rotation speed control of the compressor 31, and the like are stored.

  The opening degree control table 66 includes a flow rate control valve corresponding to the difference between the intake refrigerant temperature Ts calculated based on the detection value of the intake temperature sensor 82 and the target value (threshold value α) of the intake refrigerant temperature Ts. A change amount (number of pulses) of 39 is defined. Further, the opening degree control table 67 defines a change amount (number of pulses) of the valve opening degree according to the superheat degree value calculated (calculated) from the refrigerant temperature sensor 81. The RAM 63 is also used as a working memory that temporarily stores control parameters used when the control program is executed. The refrigeration vehicle 100 according to the present embodiment is configured as described above.

  Next, with reference to FIGS. 1-5, the operation control of the cooling device 30 mounted in the refrigerator car 100 (refer FIG. 1) by this embodiment is demonstrated. Hereinafter, the opening degree control of the flow rate control valve 39 (see FIG. 3) by the control unit 61 (see FIG. 3) when the freezer 20 (see FIG. 3) is cooled to a predetermined temperature by the cooling device 30 (see FIG. 3). The flow will be described.

  First, in step S1, as shown in FIG. 5, information on the operating load state of the operating cooling device 30 (see FIG. 3) is acquired based on a command from the control unit 61 (see FIG. 3). That is, by inputting a signal from the outside air temperature sensor 72 (see FIG. 3) to the control unit 61 at a predetermined control cycle interval, the outside air temperature Ta in the environment where the current cooling device 30 (heat radiating unit 41) is exposed. Is acquired by the control unit 61. For example, when it is detected that the current outside air temperature Ta is 20.6 ° C., the cooling device 30 is operating under standard conditions (when the outside air temperature Ta is 0 ° C. or more and 35 ° C. or less). Is grasped on the control unit 61 side.

  In step S2, the temperature table 65 (see FIG. 4) stored in the ROM 62 (see FIG. 3) is referred to based on the command from the control unit 61. Then, the target value of the intake refrigerant temperature Ts corresponding to the detected current outside air temperature Ta is grasped. Further, this target value is recognized as the threshold value α of the intake refrigerant temperature Ts in the operating load state.

  In step S3, the controller 61 determines whether or not the current intake refrigerant temperature Ts is close to the threshold value α (target value). That is, a signal from the suction temperature sensor 82 (see FIG. 3) is input to the control unit 61 at a predetermined control cycle interval, whereby the control unit 61 acquires the suction refrigerant temperature Ts of the refrigerant sucked into the compressor 31. Is done. Then, the current suction refrigerant temperature Ts and the threshold value α set in the temperature table 65 are compared. When the intake refrigerant temperature Ts is within a certain range with respect to the threshold value α (for example, ± 0.2 ° C. or the like, within the resolution range of the outside air temperature sensor 72), the intake refrigerant temperature Ts is the threshold value. It is determined that it is in the vicinity of α (target value) (Ts≈α). On the contrary, when the intake refrigerant temperature Ts exceeds or falls below a certain range (for example, within a range of ± 0.2 ° C.) with respect to the threshold value α, the intake refrigerant temperature Ts becomes the threshold value α (target value). ) (Ts <α or Ts> α).

  If it is determined in step S3 that the intake refrigerant temperature Ts is within a certain range with respect to the threshold value α (Ts≈α), the flow control valve 39 is opened based on a command from the control unit 61 in step S4. The degree is maintained at the current opening value. That is, the return amount of the refrigeration oil in the oil return circuit 37 (see FIG. 2) is not substantially changed. Thereby, this control flow is once complete | finished. After the end of the control flow, the control flow shown in FIG. 5 is executed again after a predetermined control cycle has elapsed.

  On the other hand, if it is determined in step S3 that the intake refrigerant temperature Ts is not within a certain range with respect to the threshold value α (Ts <α or Ts> α), the control flow proceeds to step S5.

  In step S5, when it is determined that the intake refrigerant temperature Ts is smaller than the threshold value α (Ts <α), the opening degree of the flow control valve 39 is set to the current opening based on the command of the control unit 61 in step S6. The degree value is increased by a predetermined amount. That is, the return amount of the refrigerating machine oil in the oil return circuit 37 (see FIG. 2) is increased by a predetermined amount. Thereby, this control flow is once complete | finished.

  Further, when it is determined in step S5 that the intake refrigerant temperature Ts is larger than the threshold value α (Ts> α), the opening degree of the flow control valve 39 is determined based on the command of the control unit 61 in step S7. The opening degree is reduced by a predetermined amount. The return amount of the refrigerating machine oil in the oil return circuit 37 (see FIG. 2) is reduced by a predetermined amount. Thereby, this control flow is once complete | finished. After the completion of the control flow through step S5 or step S7, the control flow shown in FIG. 5 is executed again after a predetermined control period has elapsed.

  Thus, in this embodiment, the opening degree of the flow control valve 39 is increased by a predetermined amount from the current value (step S6), decreased (step S7), or maintained (step) based on the determination results of steps S3 and S5. S4). As a result, the return amount of the refrigerating machine oil is adjusted by controlling the opening degree of the flow control valve 39 according to the operating load state of the cooling device 30 ascertained from the detected value of the outside air temperature Ta. In this way, the opening degree control of the flow rate control valve 39 by the control unit 61 is performed. In the cooling device 30, in addition to the opening degree control of the flow rate control valve 39, the cooling unit 42 (see FIG. 1) based on the internal temperature sensor 71 (see FIG. 2) and the refrigerant temperature sensor 81 (see FIG. 2). Capacity control is performed simultaneously.

  In the present embodiment, the following effects can be obtained.

  That is, in this embodiment, as described above, the flow rate control valve 39 that can adjust the return amount of the refrigeration oil separated in the oil separator 32 and returned to the suction portion 31b of the compressor 31, and the operating load state The cooling device 30 is provided with a control unit 61 configured to adjust the return amount of the refrigerating machine oil by controlling the opening degree of the flow control valve 39. Thereby, the return amount of the refrigerating machine oil to the compressor 31 in the operating (operating) cooling device 30 can be optimized in consideration of the operating load state based on the outside air temperature Ta. That is, since the mixing ratio of the refrigerating machine oil to the suction refrigerant is optimized, the compressor 31 can always be operated in an optimal state. This prevents the compressor 31 from failing due to a decrease in refrigerating capacity when the refrigerating machine oil is returned excessively (a decrease in refrigerant density due to an increase in the intake refrigerant temperature Ts) or a shortage of refrigerating machine oil. can do.

  Further, in the present embodiment, the control unit 61 is configured to adjust the return amount of the refrigerating machine oil by controlling the opening degree of the flow rate control valve 39 based on the outside air temperature Ta on the condenser 33 side to which the heat radiating unit 41 is exposed. Configure. Thereby, based on the environmental temperature conditions of the high pressure side (condenser 33 side) in a refrigerating cycle, the operating load state of the cooling device 30 in operation can be directly grasped. Therefore, the opening degree control of the flow control valve 39 according to the operating load state can be easily performed.

  Further, in the present embodiment, the flow rate adjustment valve 39 is adjusted so that the suction refrigerant temperature Ts of the refrigerant sucked into the compressor 31 is adjusted to a temperature (threshold value α) according to the outside air temperature Ta on the condenser 33 side. Thus, the control unit 61 is configured to perform control for adjusting the return amount of the refrigerating machine oil. As a result, the intake refrigerant temperature Ts of the refrigerant sucked into the compressor 31 is set to a temperature that takes into account the operating load state of the cooling device 30 (the outside air temperature Ta on the condenser 33 side) by increasing or decreasing the return amount of the refrigerator oil. The threshold value α) can be adjusted. Therefore, since the compressor 31 can be operated within an appropriate operating range according to the operating load state of the cooling device 30, the failure rate of the compressor 31 can be reduced. In addition, since the compressor 31 can be operated within an appropriate operating range according to the operating load state, the cooling capacity of the cooling unit 42 can be maximized, and the cooling device 30 can exhibit stable cooling performance. it can.

  Further, in the present embodiment, the outside air temperature sensor 72 for detecting the outside air temperature Ta on the condenser 33 side as the operating load state, and the suction temperature sensor for detecting the suction refrigerant temperature Ts of the refrigerant sucked into the compressor 31. 82. When the intake refrigerant temperature Ts detected by the intake temperature sensor 82 is smaller than a threshold value α set in advance according to the outside air temperature Ta detected by the outside air temperature sensor 72, the opening degree of the flow control valve 39 is increased. The controller 61 is configured to perform a first opening degree control for increasing the opening degree and a second opening degree control for reducing the opening degree of the flow control valve 39 when the intake refrigerant temperature Ts is larger than the threshold value α. . Thus, when the first opening degree control is performed, more refrigeration oil can be returned to the compressor 31 as the opening degree increases, so that a shortage of refrigeration oil with respect to the compressor 31 is reliably avoided. be able to. Further, when the second opening degree control is performed, an excessive increase in the intake refrigerant temperature Ts can be suppressed, so that it is possible to suppress a decrease in refrigerant density and a decrease in refrigeration capacity. As a result, the failure rate of the cooling device 30 can be reliably reduced, and the cooling device 30 can reliably exhibit stable cooling performance by maximizing the cooling capacity.

  In the present embodiment, a temperature table 65 is provided in which the relationship between the outside air temperature Ta and the intake refrigerant temperature Ts corresponding to the outside air temperature Ta is defined in advance. Then, based on the temperature table 65, control for increasing the opening of the flow control valve 39 (first opening control) and control for decreasing the opening of the flow control valve 39 (second opening control) are performed. The control unit 61 is configured. Accordingly, the recommended value (target value) of the intake refrigerant temperature Ts with respect to the operating load state grasped based on the environmental temperature condition on the high pressure side (condenser 33 side) in the refrigeration cycle can be easily grasped using the temperature table 65. can do.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above-described embodiment, the target value (individual threshold value α) of the intake refrigerant temperature Ts of the refrigerant sucked into the compressor 31 is defined in advance according to the outside air temperature Ta detected by the outside air temperature sensor 72. Although an example in which the opening degree of the flow control valve 39 is controlled using the temperature table 65 (see FIG. 4) has been shown, the present invention is not limited to this. For example, the opening degree of the flow control valve 39 is controlled using a pressure table that predefines the target value of the refrigerant pressure sucked into the compressor 31 according to the outside air temperature Ta detected by the outside air temperature sensor 72. You may comprise. In this case, when the suction refrigerant pressure of the refrigerant sucked into the compressor 31 is smaller than the suction refrigerant pressure (threshold value) set according to the outside air temperature Ta detected by the outside air temperature sensor 72, the flow rate control is performed. While performing the first opening degree control for increasing the opening degree of the valve 39, the suction refrigerant pressure is larger than the suction refrigerant pressure (threshold value) set according to the outside air temperature Ta detected by the outside air temperature sensor 72. In such a case, the second opening degree control for reducing the opening degree of the flow control valve 39 may be performed.

  Moreover, in the said embodiment, it comprised so that the return amount of refrigerating machine oil might be adjusted by controlling the opening degree of the flow control valve 39 based on the outdoor temperature Ta by the side of the condenser 33 to which the thermal radiation part 41 is exposed to external air. Although an example has been shown, the present invention is not limited to this. For example, the operating load state of the cooling device 30 (for example, one of the low temperature condition, the standard condition, and the overload condition) using both the outside air temperature Ta and the cooling temperature (refrigerant evaporation temperature condition) on the evaporator 35 side. You may comprise so that it may grasp | ascertain. Then, the return amount of the refrigerating machine oil is adjusted by controlling the opening degree of the flow rate control valve 39 based on the outside air temperature Ta on the condenser 33 side and the cooling temperature on the evaporator 35 side (evaporation temperature condition of the refrigerant). The control unit 61 may be configured.

  By configuring as in this modification, the operating load state of the cooling device 30 in operation is based on the temperature condition on the high pressure side (condenser 33 side) and the temperature condition on the low pressure side (evaporator 35 side) in the refrigeration cycle. Can be grasped directly. Therefore, the opening degree control of the flow control valve 39 according to the operating load state can be easily performed. Further, the internal temperature Ti of the freezer 20 detected by the internal temperature sensor 71 instead of the outside air temperature Ta on the condenser 33 side and the cooling temperature (refrigerant evaporation temperature condition) on the evaporator 35 side (see FIG. 1). May be used to grasp the operating load state of the cooling device 30. Alternatively, the operating load state of the cooling device 30 may be grasped using only the cooling temperature on the evaporator 35 side, or the operating load state of the cooling device 30 may be grasped only using the internal temperature Ti of the freezer 20. Also good. In any modification, it is preferable that a temperature table 65 corresponding to each modification is created.

  Moreover, although the said embodiment showed about the example which divided the driving | running load state into three conditions (low temperature conditions, standard conditions, and overload conditions) and comprised the temperature table 65, this invention is not limited to this. The classification according to the outside air temperature Ta may be classified other than the above three stages.

  In the above-described embodiment, the example in which the control for increasing the opening degree of the flow control valve 39 and the control for decreasing the opening degree of the flow rate control valve 39 based on the temperature table 65 has been described, but the present invention is not limited thereto. That is, you may comprise so that the opening degree of the flow control valve 39 may be controlled according to a driving | running load state, without using the temperature table 65. FIG. For example, the flow control valve 39 may be directly controlled to have a predetermined opening degree according to the outside air temperature Ta detected by the outside air temperature sensor 72. Also by this, it is possible to adjust the return amount of the refrigerating machine oil by controlling the opening degree of the flow control valve 39 according to the operating load state of the cooling device 30.

  Moreover, in the said embodiment, although the cooling device 30 provided with the compressor 31, the oil separator 32, the condenser 33, the electronic expansion valve 34, and the evaporator 35 was shown, this invention is not restricted to this. I can't. That is, the cooling device 30 may be configured by providing a subcooler (supercooler), a receiver (liquid receiver), a filter dryer, a sight glass, or the like between the condenser 33 and the electronic expansion valve 34. In addition, the cooling device 30 may be further configured by providing an accumulator between the evaporator 35 and the compressor 31.

  Further, in the above embodiment, the opening degree control of the flow rate control valve 39 is performed using the temperature table 65 in which the target value (threshold value α) of the intake refrigerant temperature Ts corresponding to the operating load state is stored as data. Although the configuration example is shown, the present invention is not limited to this. For example, the correspondence relationship between the operating load state and the target value (threshold value α) of the intake refrigerant temperature Ts may be defined using a predetermined function. Thereby, when using the temperature table 65, the data amount memorize | stored in ROM62 can be reduced significantly. Moreover, it is possible to easily cope with the opening degree control of the flow rate control valve 39 for each refrigerator truck 100 in which the cooling device 30 is mounted only by rewriting the function in the control program.

  Further, in the above-described embodiment, an example using the electronic expansion valve 34 in which the valve mechanism is driven by pulse control has been described, but the present invention is not limited to this. For example, either an external pressure equalizing type or an internal pressure equalizing type temperature type expansion valve provided with a temperature sensing cylinder may be used.

  Moreover, although the said embodiment showed about the example which attached the outside temperature sensor 72 which detects the outside temperature Ta to the door mirror part 13a beside the cab 13 was shown, this invention is not limited to this. For example, an outside air temperature sensor 72 for detecting the outside air temperature Ta may be attached in the vicinity of the roof portion of the cab 13, or the outside air temperature sensor 72 may be attached in the vicinity of the grill portion 43 a where air outside the vehicle is sucked.

  Moreover, in the said embodiment, although the example which provided the thermal radiation part 41 in the cooling unit 40 installed above the cab 13 was shown, this invention is not limited to this. For example, the cooling unit 40 installed above the cab 13 is configured only by the cooling unit 42 (the evaporator 35 and the blower 52), and the heat radiation unit 41 (the condenser 33 and the blower 51) is replaced with the chassis 11 in the vehicle main body 10. The refrigeration vehicle 100 may be configured by being disposed on the side portion of the refrigerator.

  Moreover, in the said embodiment, although the example which applied the cooling device 30 to the refrigerator car 100 was shown, this invention is not limited to this. That is, if it is a cooling device provided with the oil return circuit 37, cooling operations (cooling operation) other than the refrigerator car 100, such as a showcase, a commercial refrigerator, a household refrigerator, and an air conditioner (especially a computer room) are performed throughout the year. The present invention may be applied to a cooling device such as a required facility air conditioning system. In addition, the present invention may be applied to a refrigerator car having a freezer compartment divided into different cooling temperature zones. In addition, the “cooling device” of the present invention includes a heat pump device capable of switching between a cooling operation and a heating operation, and can be applied during operation of the compressor 31 in this case.

Moreover, in the said embodiment, although shown about the example which used R134a for the refrigerant | coolant, this invention is not limited to this. For example, the cooling device 30 may be configured by using a compressor 31 configured to compress a refrigerant such as HFO-1234yf having a small warming potential as an alternative refrigerant for R134a. Alternatively, carbon dioxide (CO ₂₎ may be configured cooling apparatus 30 with a compressor 31 that is configured to be able to compress such refrigerant or other natural refrigerants.

  Moreover, in the said embodiment, the control process regarding the opening degree control of the flow control valve 39 of the control part 61 was demonstrated using the flowchart of the "flow drive type" which processes in order along a process flow for convenience of explanation. However, the present invention is not limited to this. In the present invention, the process of the control unit 61 may be performed by an “event driven type (event driven type)” process that executes a process in units of events. In this case, it may be performed by a complete event drive type or a combination of event drive and flow drive.

10 Vehicle body (vehicle)
20 Freezer (storage)
DESCRIPTION OF SYMBOLS 30 Cooling device 31 Compressor 31a Discharge part 31b Suction part 32 Oil separator 33 Condenser 34 Electronic expansion valve (expansion valve)
35 Evaporator 36a-36d Refrigerant piping 37 Oil return circuit 38 Oil return piping 39 Flow control valve (refrigeration machine oil flow control valve)
40 Cooling unit 41 Heat radiation part 42 Cooling part 60 Control box 61 Control part 65 Temperature table (table)
72 Outside temperature sensor (environment temperature detector)
82 Refrigerant temperature sensor (refrigerant temperature detector)
100 freezer car

Claims (6)

A compressor for compressing the refrigerant;
A condenser that condenses the refrigerant;
An expansion valve for expanding the refrigerant condensed by the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
A refrigerating machine oil flow rate adjustment valve capable of adjusting the return amount of refrigerating machine oil separated from the refrigerant on the discharge side of the compressor and returned to the suction side of the compressor;
And a control unit configured to adjust a return amount of the refrigerating machine oil by controlling an opening degree of the refrigerating machine oil flow rate adjustment valve according to an operating load state. The operating load state includes at least one of an environmental temperature on the condenser side or a cooling temperature on the evaporator side,
The control unit adjusts the return amount of the refrigerating machine oil by controlling the opening of the refrigerating machine oil flow rate adjusting valve based on at least one of the environmental temperature on the condenser side or the cooling temperature on the evaporator side. The cooling device according to claim 1, which is configured as follows.   The control unit adjusts the suction refrigerant temperature of the refrigerant sucked into the compressor to an intake refrigerant temperature range corresponding to at least one of the condenser-side environmental temperature or the evaporator-side cooling temperature, The cooling device according to claim 2, configured to perform control for adjusting a return amount of the refrigerating machine oil by the refrigerating machine oil flow rate adjustment valve. An environmental temperature detection unit for detecting an environmental temperature on the condenser side as the operating load state, and an intake refrigerant temperature detection unit for detecting an intake refrigerant temperature of refrigerant sucked into the compressor,
When the intake refrigerant temperature detected by the intake refrigerant temperature detection unit is smaller than a predetermined threshold set in advance according to the environmental temperature detected by the environmental temperature detection unit A first opening degree control for increasing the opening degree of the refrigerating machine oil flow rate adjustment valve; and a second opening for reducing the opening degree of the refrigerating machine oil flow rate adjustment valve when the intake refrigerant temperature is larger than the predetermined threshold value. The cooling device according to claim 2, wherein the cooling device is configured to perform degree control. A table in which a relationship between the ambient temperature and the suction refrigerant temperature according to the ambient temperature is defined in advance;
The cooling device according to claim 4, wherein the control unit is configured to perform the first opening degree control and the second opening degree control based on the table. A vehicle with a storage;
A cooling device mounted on the vehicle for cooling the inside of the storage;
The cooling device is
A compressor for compressing the refrigerant;
A condenser that condenses the refrigerant;
An expansion valve for expanding the refrigerant condensed by the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
A refrigerating machine oil flow rate adjustment valve capable of adjusting the return amount of refrigerating machine oil separated from the refrigerant on the discharge side of the compressor and returned to the suction side of the compressor;
And a control unit configured to perform control for adjusting a return amount of the refrigerating machine oil by controlling an opening degree of the refrigerating machine oil flow rate adjusting valve according to an operating load state.

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