JP6276004B2 - refrigerator - Google Patents

Description

  The present invention is used to cool a large number of electronic devices such as servers and computers constituting an information technology device (hereinafter referred to as “IT device”) and an information communication technology device (hereinafter referred to as “ICT device”). The present invention relates to a refrigerator used.

  In the data center, a large number of electronic devices such as servers and computers constituting IT devices and ICT devices are arranged on the floor, and refrigerators, air conditioning systems, and the like for processing heat generated from these electronic devices are used. ing.

  Many of these air conditioning systems and the like that employ a vapor compression refrigeration cycle are used. The heat generated from the electronic device is large, and if the temperature rises too much, there is a risk that normal operation of the electronic device cannot be ensured. Therefore, when designing an air conditioning system or the like, it is common to design an air conditioning system that can cope with the assumed maximum heat generation load (also referred to as a design assumed cooling load).

  On the other hand, when the air conditioning system or the like is operated, the heat load applied by the air conditioning system or the like becomes smaller than the design assumed cooling load. In particular, at the beginning of operation, the tendency becomes strong, and air conditioning systems and the like are often operated with a low load. For example, in a medium-capacity or large-capacity air conditioning system equipped with two compressors, one compressor is stopped and only the remaining one compressor is operated in order to support low-load operation. It corresponds by doing.

  However, the compressor is designed to exhibit the rated cooling capacity. If the load is much smaller than the rated cooling capacity, the compressor will be out of the continuous operation range, making stable continuous operation difficult or impossible. Met. An air conditioning system using a gas injection cycle or the like has been proposed as one corresponding to such a partial load (see, for example, Patent Document 1). In the case of an air conditioning system or the like using such a gas injection cycle, the amount of refrigerant to be compressed by the compressor can be optimized, so that it is easy to cope with partial loads.

JP 2002-106995 A

  In a medium capacity or large capacity air conditioning system equipped with two compressors as described above, there is a limit to dealing with partial loads that do not satisfy the rated cooling capacity as described above. There is a problem that it is necessary to deal with "compressor start / stop" repeatedly. Due to the start and stop of the compressor, the air temperature of the air conditioning system also fluctuated, and the room temperature was not stable. Furthermore, since the compressor is started and stopped, there is a problem that the efficiency of the cooling operation is liable to be reduced and it is difficult to reduce the power consumption.

  Even in an air conditioning system or the like using the gas injection cycle described in Patent Document 1 described above, when the load decreases beyond a previously assumed range, the compressor must be started and stopped, and the load is low. There was a problem that stable cooling operation was not possible. In addition, due to the start / stop of the compressor, there is a problem in that it is difficult to reduce the power consumption because the efficiency of the cooling operation tends to decrease.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a refrigerator capable of reducing power consumption and realizing a stable cooling operation at a low load. .

In order to achieve the above object, the present invention provides the following means.
The refrigerator according to the present invention includes a high-pressure heat exchanger that cools a high-pressure refrigerant and a high-pressure refrigerant that is cooled by the high-pressure heat exchanger in a refrigeration apparatus that moves low-temperature heat to a high-temperature side. 1 decompression unit, a gas-liquid separator that separates the low-pressure refrigerant decompressed by the first decompression unit into a gas refrigerant and a refrigerant liquid, and a first decompression unit that further depressurizes the liquid refrigerant separated by the gas-liquid separator. 2 decompression sections, a low pressure heat exchanger that evaporates the refrigerant decompressed by the second decompression section, the gas refrigerant separated by the gas-liquid separator, and the refrigerant that has flowed out of the low pressure heat exchanger A first compression section that compresses at least one and discharges it between the first compression section and the high-pressure heat exchanger; and compresses refrigerant discharged from the low-pressure heat exchanger and discharges the refrigerant toward the high-pressure heat exchanger To be separated by the second compression unit and the gas-liquid separator A selection unit that selects one of the gas refrigerant and the refrigerant that has flowed out of the low-pressure heat exchanger and sucks it into the first compressor, and the operation of stopping the first compression unit and the second compression unit. And control of refrigerant selection by the selection unit, which operates the first compression unit and stops the second compression unit, operates the second compression unit, and operates the second compression unit. Medium load control for stopping the first compression section, operating both the first compression section and the second compression section, and sucking the gas refrigerant separated by the gas-liquid separator into the first compression section The injection control to be performed, and the first compression unit and the second compression unit are both operated, and at least high load control for sucking the refrigerant flowing out of the low-pressure heat exchanger is performed in the first compression unit. And a control unit, characterized in that is provided.

  According to the refrigerator of the present invention, the first compression unit is used not only as a compression unit that realizes an injection cycle during injection control, but also as a compression unit that contributes to heat exchange in the low-pressure heat exchanger during high load control. used. As described above, by using the first compression unit for realizing the injection cycle, the refrigerator of the present invention can be stably cooled even under a low load. Furthermore, since the first compression unit is used so as to contribute to cooling by the refrigerator of the present invention, the operation efficiency of the refrigerator can be improved and the power consumption can be reduced.

  In the above invention, the first compression unit has a smaller compression capacity of the refrigerant than the second compression unit, the second compression unit is stopped during the low load control, and the first compression unit Preferably it is operated.

  Thus, by making the compression capacity of the first compression part smaller than the compression capacity of the second compression part, it becomes easier to reduce the power consumption in the refrigerator, and realizes a stable cooling operation at a low load. It becomes easy. In general, the power consumed by the compression unit decreases as the compression capacity decreases. Therefore, it becomes easy to reduce the electric power consumed in low load control by reducing the compression capacity of the 1st compression part operated by low load control. Further, since the cooling capacity when the refrigerator is continuously operated in the low load control is further reduced, it is easy to continuously operate the refrigerator without starting and stopping even when the required cooling capacity is small. In addition, since the 1st compression part compresses the refrigerant | coolant (refrigerant which does not flow through a low voltage | pressure heat exchanger) which does not contribute to the cooling capacity of a refrigerator, when the low load control is not performed, it is 2nd compression part The compression capacity can be set small compared with.

  In the above invention, there are a plurality of the second compression sections, and the discharge capacity, which is the capacity per unit time of the refrigerant discharged from some of the second compression sections, is fixed or variably controlled by the control section. It is preferable that the discharge capacity discharged from the remaining second compression unit is variably controlled by the control unit.

  By providing a plurality of second compression units in this way, the amount of heat exchange (heat load) in the low-pressure heat exchanger can be increased, and higher cooling capacity can be exhibited. Furthermore, by making the discharge capacity fixed or variable for a part of the second compression section and making the discharge capacity variable for the rest, stable cooling operation can be realized even during high load control.

  In the above invention, when the controller performs the first control to increase the discharge capacity, which is the capacity per unit time, of the refrigerant discharged from the first compressor during the high load control, the second compression is performed. The first compression section when performing the second control for increasing the discharge capacity of the section, and when performing the third control for increasing the discharge capacity of the first compression section and the discharge capacity of the second compression section And the characteristics of the second compression unit are stored, and when the control unit increases the heat exchange capacity in the low pressure heat exchanger during the high load control, the first control, the second control, and It is preferable that the control with the lowest power consumption is selected from the third control based on the characteristics of the first compression section and the characteristics of the second compression section.

  Thus, by selecting the control with the lowest power consumption based on the characteristics of the first compression unit and the characteristics of the second compression unit from the first control, the second control, and the third control, the power consumption can be reduced. Can be achieved.

  In the above invention, the control unit obtains operation information of the first compressor and the second compressor, and stores the first compression unit in the first control, the second control, and the third control that are stored. It is preferable to update the characteristics of the second compression unit and the characteristics of the second compression unit at predetermined intervals based on the acquired operation information.

  In this way, the operation information of the first compression unit and the operation information of the second compression unit in the first control, the second control, and the third control are updated based on the operation information of the first compression unit and the second compression unit. As a result, the accuracy in selecting the control with the lowest power consumption becomes higher.

In the above invention, it is preferable that the acquired operation information of the first compressor and the second compressor is stored in a storage unit of the control unit.
By storing the operation information of the first compression unit and the operation information of the second compression unit in the storage unit in this way, the stored operation information can be used for controlling the first compression unit, the second compression unit, and the like. This makes it easier to reduce power consumption.

  In the said invention, the said control part operated the power consumption at the time of driving | running a said 1st compression part, and the said 2nd compression part, when increasing the heat exchange capability in the said low pressure heat exchanger at the time of the said low load control It is preferable to operate the compression unit with low power consumption by comparing with the power consumption at the time.

  Thus, by comparing the power consumption when operating the first compression unit with the power consumption when operating the second compression unit, and operating the compression unit with low power consumption, heat is reduced during low load control. Even when the exchange capacity is increased, the power consumption can be reduced.

  In the above invention, when the control unit determines that cooling operation is possible at the maximum frequency of the first compression unit when reducing the heat exchange capacity in the low pressure heat exchanger in the medium load control or injection control, It is preferable to compare the power consumption when the first compression unit is operated with the power consumption when the second compression unit is operated, and operate the compression unit with low power consumption.

  Thus, by comparing the power consumption when operating the first compression unit with the power consumption when operating the second compression unit, and operating the compression unit with low power consumption, heat is reduced during low load control. Even when the exchange capacity is increased, the power consumption can be reduced.

  In the above invention, the control unit executes the injection control when it is determined that the pressure ratio, which is the ratio of the suction side pressure and the discharge side pressure of the first compression unit, is equal to or greater than a predetermined pressure ratio. It is preferable to allow.

  As described above, by performing the injection control only when the pressure ratio of the first compression section is equal to or higher than the predetermined pressure ratio, the first compression section can be stably operated during the injection control. . In addition, as a predetermined pressure ratio, the minimum allowable pressure ratio which is a minimum pressure ratio in order to drive | operate a 1st compression part can be illustrated.

  According to the refrigerator of the present invention, the first compression unit is used not only as a compression unit that realizes an injection cycle during injection control, but also as a compression unit that contributes to heat exchange in a low-pressure heat exchanger during high load control. Therefore, the power consumption can be reduced and the stable cooling operation with a low load can be realized.

It is a mimetic diagram explaining the composition of the air-conditioning system concerning a 1st embodiment of the present invention. It is a block diagram explaining the structure of the control part in FIG. It is a schematic diagram explaining the driving | running state in low load control. It is a schematic diagram explaining the driving | running state in medium load control. It is a schematic diagram explaining the driving | running state in injection control. It is a schematic diagram explaining the driving | running state in high load control. It is a flowchart explaining the determination process performed when indoor temperature rises. It is a flowchart explaining the determination process performed when indoor temperature rises. It is a flowchart explaining the determination process performed when indoor temperature falls. It is a flowchart explaining the determination process performed when indoor temperature falls. It is a flowchart explaining the determination process performed when indoor temperature falls. It is a graph explaining the relationship between a load and the rotation speed of a compressor when 1st control is selected at the time of high load control. FIG. 13A is a graph for explaining the relationship between the load and the rotation speed of the compressor when the second control is selected during the high load control, and FIG. It is a graph explaining the relationship between a load and the rotation speed of a compressor when 3 control is selected. It is a flowchart explaining the 1st modification of the flowchart shown in FIG. It is a flowchart explaining the 2nd modification of the flowchart shown in FIG. It is a graph explaining the relationship between the load and the rotation speed of a compressor explaining the 3rd modification of 1st Embodiment, Fig.16 (a) is a case where 1st control is selected in high load control. FIG. 16B is a graph when the second control is selected in the high load control. It is a 3rd modification, Comprising: It is a graph when 3rd control is selected in high load control. It is a 3rd modification, Comprising: It is a graph when 3rd control is selected in high load control. It is a schematic diagram explaining the structure of the air conditioning system which concerns on the 2nd Embodiment of this invention. It is a block diagram explaining the structure of the control part in FIG. It is a schematic diagram explaining the driving | running state in low load control. It is a schematic diagram explaining the driving | running state in medium load control. It is a schematic diagram explaining the driving | running state in medium load injection control. It is a schematic diagram explaining the driving | running state in high load control. It is a schematic diagram explaining the driving | running state in high load injection control. It is a schematic diagram explaining the driving | running state in super load control. It is a flowchart explaining the determination process performed when indoor temperature rises. It is a flowchart explaining the determination process performed when indoor temperature rises. It is a flowchart explaining the determination process performed when indoor temperature rises. It is a flowchart explaining the determination process performed when indoor temperature falls. It is a flowchart explaining the determination process performed when indoor temperature falls. It is a flowchart explaining the determination process performed when indoor temperature falls. It is a graph explaining the relationship between a load and the rotation speed of a compressor when 1st control is selected at the time of high load control. It is a graph explaining the relationship between load and the rotation speed of a compressor when 2nd control is selected at the time of high load control. It is a graph explaining the relationship between a load and the rotation speed of a compressor when 3rd control is selected at the time of high load control. It is a graph explaining the other relationship of load and the rotation speed of a compressor when 1st control is selected at the time of high load control. It is a graph explaining the other relationship between load and the rotation speed of a compressor when 2nd control is selected at the time of high load control. It is a graph explaining the other relationship of load and the rotation speed of a compressor when 3rd control is selected at the time of high load control.

[First Embodiment]
Hereinafter, an air conditioning system (refrigerator) 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 18. The air conditioning system 1 of the present embodiment is used for air conditioning of a data center, and processes a large amount of heat generated from electronic devices such as servers and computers arranged on the floor of the data center.

  The outdoor unit 10 of the air conditioning system 1 is arranged outdoors, for example, in contact with outside air such as the roof of a data center, and the indoor unit 20 is arranged on a floor on which electronic devices such as servers are arranged, and indoor air on the floor It is arranged so that it can be cooled. In FIG. 1, for ease of explanation, an example in which one outdoor unit 10 and one indoor unit 20 are provided is described. However, a plurality of indoor units 20 are provided for one outdoor unit 10. It may be provided, and a plurality of indoor units 20 may be provided for a plurality of outdoor units 10, and the number of units is not particularly limited.

  As shown in FIG. 1, the air conditioning system 1 includes a condenser (high pressure heat exchanger) 11 disposed in the outdoor unit 10, a first expansion valve (first decompression unit) 21 disposed in the indoor unit 20, a first 1 gas-liquid separator (gas-liquid separator) 22, second expansion valve (second decompression unit) 23, evaporator (low-pressure heat exchanger) 24, second gas-liquid separator 25, first compressor (first Compressor) 26, second compressor (second compressor) 27, first control valve (selector) 28, second control valve (selector) 29, and controller 40. .

  The condenser 11 is a heat exchanger into which the high-temperature and high-pressure gaseous refrigerant discharged from at least one of the first compressor 26 and the second compressor 27 flows, and releases the heat of the flowing-in refrigerant to the outside to condense. Is. Outside air is guided to the condenser 11 by a blowing means (not shown) such as a fan provided in the outdoor unit 10. As the condenser 11, a known type of heat exchanger can be used, and the type is not particularly limited. Further, it may be an air-cooled heat exchanger that releases heat to the outside air guided as described above, or a liquid-cooled heat exchanger that releases heat to water supplied from the outside. Good.

  The first expansion valve 21 is disposed between the condenser 11 and the first gas-liquid separator 22. The first expansion valve 21 expands the refrigerant condensed by the condenser 11 to reduce the pressure thereof, and also controls the pressure on the suction side of the first compressor 26.

  The second expansion valve 23 is disposed between the first gas-liquid separator 22 and the evaporator 24. The second expansion valve 23 expands the liquid refrigerant supplied from the first gas-liquid separator 22 and further reduces the pressure thereof, and controls the pressure on the suction side of the evaporator 24 and the second compressor 27. It is.

  As the 1st expansion valve 21 and the 2nd expansion valve 23, a well-known expansion valve or a pressure-reduction mechanism can be used, The form etc. are not specifically limited. In the present embodiment, the first expansion valve 21 is described as being applied to the one that adjusts the suction pressure (injection pressure) of the first compressor 26, and the second expansion valve 23 is a refrigerant that flows out of the evaporator 24. However, description will be made by applying to a device having a mechanism for adjusting the degree of pressure reduction so as to have a desired superheat.

  The first gas-liquid separator 22 is a container disposed between the first expansion valve 21, the second expansion valve 23 and the first compressor 26, and the gas-liquid two decompressed by the first expansion valve 21. The refrigerant of the layer flows in and separates the gas refrigerant and the liquid refrigerant. A pipe connected from the first gas-liquid separator 22 to the second expansion valve 23 is connected to an area below the first gas-liquid separator 22 where liquid refrigerant is stored. On the other hand, the pipe connected from the first gas-liquid separator 22 to the first compressor 26 is connected to the area above the first gas-liquid separator 22 and where the gaseous refrigerant exists.

  The evaporator 24 is a heat exchanger disposed between the second expansion valve 23 and the second gas-liquid separator 25, and exchanges heat between the refrigerant decompressed by the second expansion valve 23 and room air. Is to do. The refrigerant that has flowed into the evaporator 24 is evaporated by absorbing the heat of the room air and becomes a gaseous refrigerant. On the other hand, the temperature of the indoor air is lowered because the heat is taken away by the refrigerant.

  Indoor air is guided to the evaporator 24 by a blowing means such as a blower fan provided in the indoor unit 20. Therefore, the indoor air that has increased in temperature by absorbing heat generated from the electronic devices that constitute the ICT device or the like is sucked into the indoor unit 20 and cooled by the evaporator 24. The cooled room air is blown out from the indoor unit 20 into the room.

  The second gas-liquid separator 25 is a container disposed between the evaporator 24 and the first compressor 26 and the second compressor 27, and is a gas refrigerant or a gas-liquid two-phase flow that flows out of the evaporator 24. The refrigerant flows in and separates the gas refrigerant and the liquid refrigerant. A pipe connected from the second gas-liquid separator 25 to the first compressor 26 and the second compressor 27 is connected to a region above the second gas-liquid separator 25 and where a gas refrigerant is present.

  The first compressor 26 is a compressor disposed between the first gas-liquid separator 22 and the second gas-liquid separator 25 and the condenser 11. Further, one of the gas refrigerant separated in the first gas-liquid separator 22 and the gas refrigerant separated in the second gas-liquid separator 25 is sucked and compressed, and the high-temperature and high-pressure refrigerant is directed to the condenser 11. To be discharged.

  The second compressor 27 is a compressor disposed between the evaporator 24 and the condenser 11. Further, the gas refrigerant flowing out of the evaporator 24 is sucked and compressed, and the high-temperature and high-pressure refrigerant is discharged toward the condenser 11. The compression volume for compressing the refrigerant of the first compressor 26 is smaller than the compression volume of the second compressor 27.

  On the discharge side of the first compressor 26, a check valve 26A for preventing the reverse flow of the refrigerant is arranged, and on the discharge side of the second compressor 27, a check valve 27A for preventing the reverse flow of the refrigerant is arranged. The check valve 26A prevents the refrigerant from flowing back to the first compressor 26 from the second compressor 27 or the condenser 11 when the first compressor 26 is stopped. Similarly, the check valve 27A prevents the refrigerant from flowing back from the first compressor 26 or the condenser 11 to the second compressor 27 when the second compressor 27 is stopped.

  In this embodiment, the first compressor 26 and the second compressor 27 will be described as applied to an example of a fixed capacity compressor driven by an electric motor whose rotation speed is controlled within a predetermined range by inverter control. . The first compressor 26 and the second compressor 27 are controlled based on a control signal output from the control unit 40 described later. More specifically, the operation of the first compressor 26 and the second compressor 27 is controlled by controlling the electric motor by inverter control based on the control signal. As the first compressor 26 and the second compressor 27, those of a known format can be used, and the format is not particularly limited.

  The first control valve 28 controls the inflow of refrigerant from the first gas-liquid separator 22 to the first compressor 26, and connects the first gas-liquid separator 22 and the suction portion of the first compressor 26. It is an on-off valve arranged in the connecting pipe. The second control valve 29 controls the inflow of refrigerant from the second gas / liquid separator 25 to the first compressor 26, and connects the second gas / liquid separator 25 and the suction portion of the first compressor 26. This is an open / close valve that is connected between a branch point where the pipe extending to the suction portion of the second compressor 27 branches and a junction point of the pipe where the first control valve 28 is arranged. .

  In the present embodiment, the opening and closing of the first control valve 28 and the second control valve 29 will be described as applied to an example in which the first control valve 28 and the second control valve 29 are controlled by actuator means such as a servo motor provided in each. The operation of this actuator means is controlled based on a control signal input from the control unit 40 described later.

  The control unit 40 controls the operating state of the air conditioning system 1 and is a microcomputer having a CPU (Central Processing Unit), ROM, RAM, input / output interface, and the like. For example, as shown in FIG. 1, the place where the control unit 40 is disposed may be inside the indoor unit 20 or may be a place other than the indoor unit 20, and is not particularly limited.

  As shown in the schematic diagram of FIG. 2, the control program stored in the ROM or the like causes the CPU to function as the calculation unit 41 and causes the ROM or the like to function as the storage unit 42. The control of the operation state by the control unit 40 can be exemplified by control using the temperature of room air performed in a conventional air conditioning system as a set temperature, control at low load, which is a feature of the present embodiment, and the like.

  The control unit 40 includes a suction temperature sensor 32 that measures the temperature of indoor air before heat exchange sucked into the indoor unit 20, and a blowout temperature sensor that measures the temperature of indoor air after heat exchange blown from the indoor unit 20. 33, a measurement signal indicating the temperature measured from is input. Furthermore, a first suction pressure sensor 34 that measures the pressure of the refrigerant sucked into the first compressor 26, a first discharge pressure sensor 35 that measures the pressure of the refrigerant discharged from the first compressor 26, and a second The pressure measured from the second suction pressure sensor 36 for measuring the pressure of the refrigerant sucked into the compressor 27 and the second discharge pressure sensor 37 for measuring the pressure of the refrigerant discharged from the second compressor 27 is shown. A measurement signal is input.

  From the control unit 40, a control signal for controlling the operating state of the first compressor 26 and the second compressor 27 and a control signal for controlling opening and closing of the first control valve 28 and the second control valve 29 are mainly used. It is output. The control unit 40 also outputs other control signals related to the control performed in the conventional air conditioning system.

  Next, the operation in the air conditioning system 1 having the above-described configuration will be described with reference to the circuit diagrams of FIGS. Specifically, the control in the case of a low load with the lowest heat load on the air conditioning system 1 (hereinafter referred to as “low load control”), and the control in the case of a medium load with the next smallest heat load (hereinafter, “Medium load control”), control in the case of an injection that can be operated in an injection cycle (hereinafter referred to as “injection control”), and the thermal load is the most. The operation in the control in the case of a high high load (hereinafter referred to as “high load control”) will be described.

  First, the operation in the low load control will be described with reference to FIG. In this case, the control unit 40 of the air conditioning system 1 outputs a control signal for closing the valve to the first control valve 28 and outputs a control signal for opening the valve to the second control valve 29. In the figure, black indicates a state where the valve is closed, and white indicates a state where the valve is opened.

  Further, the control unit 40 outputs a control signal for operating the first compressor 26 and outputs a control signal for stopping the second compressor 27. In the figure, the part indicated by the solid line indicates that the refrigerant flows, and the part indicated by the dotted line indicates a state where the refrigerant does not flow.

  The high-temperature and high-pressure gas refrigerant discharged from the first compressor 26 exchanges heat with the outside air in the condenser 11 to release heat. The refrigerant that has released the heat condenses into a liquid refrigerant, flows out of the condenser 11, and travels toward the first expansion valve 21. The high-pressure liquid refrigerant is decompressed by the first expansion valve 21 to become a gas-liquid two-phase refrigerant.

  The gas-liquid two-phase refrigerant flows into the first gas-liquid separator 22 and is separated into a gas refrigerant and a liquid refrigerant. The liquid refrigerant is further depressurized by the second expansion valve 23 from the first gas-liquid separator 22 and flows into the evaporator 24. Since the first control valve 28 is closed, the gas refrigerant in the first gas-liquid separator 22 is not sucked into the first compressor 26. In the figure, the piping connecting the first gas-liquid separator 22 and the first compressor 26 is represented by a dotted line, which indicates that no refrigerant is flowing.

  In the evaporator 24, the refrigerant absorbs the heat of the indoor air introduced by the indoor fan unit 31. The liquid refrigerant evaporates by the absorbed heat and becomes a gaseous refrigerant. On the other hand, indoor air is cooled by taking heat away and blown out to the floor by the indoor fan unit 31.

  The refrigerant that has flowed out of the evaporator 24 flows into the second gas-liquid separator 25 and is separated into a gaseous refrigerant and a liquid refrigerant. The gaseous refrigerant is sucked into the first compressor 26 through the second control valve 29 and compressed, and is discharged toward the condenser 11 as a high-temperature and high-pressure refrigerant whose pressure has been increased to a predetermined pressure.

  The control unit 40 compares the input set temperature of the room air with the temperature of the room air measured by the suction temperature sensor 32, and controls the air conditioning system 1 so that the temperature of the room air becomes the set temperature. . For example, when it is determined that the temperature of the room air is higher than the set temperature, control for increasing the cooling capacity of the air conditioning system 1 is performed. Specifically, the flow rate of the refrigerant circulating through the air conditioning system 1 by increasing the rotational frequency of the indoor fan in the indoor fan unit 31 to increase the flow rate of the indoor air to be heat-exchanged, and increasing the operating frequency of the first compressor 26. The control which increases is performed.

  Moreover, when it determines with the temperature of indoor air being lower than preset temperature, control which suppresses the cooling capability of the air conditioning system 1 is performed. Specifically, the flow rate of the refrigerant circulating through the air conditioning system 1 by reducing the rotation frequency of the indoor fan in the indoor fan unit 31 to reduce the flow rate of the indoor air to be heat-exchanged, and reducing the operating frequency of the first compressor 26. Control to reduce the amount is performed.

  Next, the operation in the medium load control will be described with reference to FIG. In this case, the control unit 40 of the air conditioning system 1 outputs a control signal for closing the valves to the first control valve 28 and the second control valve 29. In addition, a control signal for stopping the first compressor 26 is output, and a control signal for operating the second compressor 27 is output.

  The refrigerant discharged from the second compressor 27 is condensed in the condenser 11 to become a high-pressure liquid refrigerant, flows out of the condenser 11, and travels toward the first expansion valve 21. The high-pressure liquid refrigerant is decompressed by the first expansion valve 21 to become a gas-liquid two-phase refrigerant.

  The gas-liquid two-phase refrigerant is separated into gas refrigerant and liquid refrigerant in the first gas-liquid separator 22, and the liquid refrigerant is further decompressed by the second expansion valve 23 and flows into the evaporator 24. Since the first control valve 28 is closed, the gas refrigerant in the first gas-liquid separator 22 is not sucked into the first compressor 26.

  In the evaporator 24, the liquid refrigerant evaporates into a gaseous refrigerant. The refrigerant that has flowed out of the evaporator 24 flows into the second gas-liquid separator 25 and is separated into a gaseous refrigerant and a liquid refrigerant. The gaseous refrigerant is sucked into the second compressor 27 and compressed, and is discharged toward the condenser 11 as a high-temperature and high-pressure refrigerant whose pressure has been increased to a predetermined pressure. Since the second control valve 29 is closed and the first compressor 26 is not operated, the gas refrigerant in the second gas-liquid separator 25 is not sucked into the first compressor 26.

  Next, the operation in the injection control will be described with reference to FIG. In this case, the control unit 40 of the air conditioning system 1 outputs a control signal for opening the valve to the first control valve 28 and outputs a control signal for closing the valve to the second control valve 29. In addition, a control signal for operating the first compressor 26 and the second compressor 27 is output.

  The refrigerant discharged from the first compressor 26 and the second compressor 27 is condensed in the condenser 11 to become a high-pressure liquid refrigerant, flows out of the condenser 11, and travels toward the first expansion valve 21. The high-pressure liquid refrigerant is decompressed by the first expansion valve 21 to become a gas-liquid two-phase refrigerant.

  The gas-liquid two-phase refrigerant is separated into gas refrigerant and liquid refrigerant in the first gas-liquid separator 22, and the liquid refrigerant is further decompressed by the second expansion valve 23 and flows into the evaporator 24. On the other hand, the gaseous refrigerant is sucked into the first compressor 26 through the first control valve 28 and compressed, and is discharged toward the condenser 11 as a high-temperature and high-pressure refrigerant whose pressure has been increased to a predetermined pressure.

  In the evaporator 24, the liquid refrigerant evaporates into a gaseous refrigerant. The refrigerant that has flowed out of the evaporator 24 flows into the second gas-liquid separator 25 and is separated into a gaseous refrigerant and a liquid refrigerant. The gaseous refrigerant is sucked into the second compressor 27 and compressed, and is discharged toward the condenser 11 as a high-temperature and high-pressure refrigerant whose pressure has been increased to a predetermined pressure. Since the second control valve 29 is closed, the gas refrigerant in the second gas-liquid separator 25 is not sucked into the first compressor 26.

  Next, the operation in the high load control will be described with reference to FIG. In this case, the control unit 40 of the air conditioning system 1 outputs a control signal for closing the valve to the first control valve 28 and outputs a control signal for opening the valve to the second control valve 29. In addition, a control signal for operating the first compressor 26 and the second compressor 27 is output.

  The refrigerant discharged from the first compressor 26 and the second compressor 27 is condensed in the condenser 11 to become a high-pressure liquid refrigerant, flows out of the condenser 11, and travels toward the first expansion valve 21. The high-pressure liquid refrigerant is decompressed by the first expansion valve 21 to become a gas-liquid two-phase refrigerant.

  The gas-liquid two-phase refrigerant is separated into gas refrigerant and liquid refrigerant in the first gas-liquid separator 22, and the liquid refrigerant is further decompressed by the second expansion valve 23 and flows into the evaporator 24. Since the first control valve 28 is closed, the gas refrigerant in the first gas-liquid separator 22 is not sucked into the first compressor 26.

  In the evaporator 24, the liquid refrigerant evaporates into a gaseous refrigerant. The refrigerant that has flowed out of the evaporator 24 flows into the second gas-liquid separator 25 and is separated into a gaseous refrigerant and a liquid refrigerant. The gaseous refrigerant is sucked into the first compressor 26 and the second compressor 27 and compressed, and is discharged toward the condenser 11 as a high-temperature and high-pressure refrigerant whose pressure has been increased to a predetermined pressure.

  While the air conditioning system 1 is in operation, the control unit 40 repeatedly performs a process of determining which of low load control, medium load control, injection control, and control in the case of high load is to be executed. This determination is performed according to the flowcharts shown in FIGS. First, the determination process performed when the room temperature rises will be described with reference to FIGS.

  First, as shown in FIG. 7, the calculation unit 41 of the control unit 40 measures the temperature of the air blown from the indoor unit 20 (S11). Specifically, the measurement signal output from the blowing temperature sensor 33 is captured, and the temperature of the air blown out from the indoor unit 20 is obtained based on the measurement signal.

  Thereafter, the calculation unit 41 performs calculation processing for obtaining a blowing temperature difference which is a temperature difference between the measured value of the blowing temperature and a preset value of the blowing temperature (S12), and the blowing temperature difference is determined in advance. A determination process is performed as to whether or not the threshold value is greater than or equal to the threshold value (S13). When it is determined that the blowout temperature difference is less than the threshold value (in the case of NO), the calculation unit 41 returns to S11 and repeats the above-described processing.

  In the determination process of S13, when it is determined that the blowing temperature difference is equal to or greater than the threshold (in the case of YES), the calculation unit 41 operates the first compressor 26 and stops the second compressor 27. It is determined whether or not only the first compressor 26 is operating (S14). Specifically, it is determined whether or not the low load control is being performed and whether or not the refrigerant is circulating in the manner shown in FIG.

  When it is determined that only the first compressor 26 is operating (in the case of YES), the calculation unit 41 determines whether the first compressor 26 is operating at the maximum frequency as shown in FIG. Is determined (S15). When it is determined that the first compressor 26 is not operating at the maximum frequency (in the case of NO), the control unit 40 outputs a control signal for increasing the operating frequency to the first compressor 26 (S16). ).

In the determination process of S15, when it is determined that the first compressor 26 is operating at the maximum frequency (in the case of YES), the control unit 40 performs a control process for performing the cooling operation with the second compressor 27. Perform (S17) .

  Thereafter, the calculation unit 41 performs a determination process as to whether or not the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio (predetermined pressure ratio) (S18). Specifically, based on the measurement signals of the first suction pressure sensor 34 and the first discharge pressure sensor 35, a pressure ratio that is a ratio between the suction pressure and the discharge pressure of the first compressor 26 is obtained. It is determined whether the pressure ratio is equal to or higher than the minimum allowable pressure ratio, which is the minimum pressure ratio necessary for operating the first compressor 26. Examples of the minimum allowable pressure ratio include values such as 1.2, but are not limited to these values.

  When it is determined that the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio (in the case of YES), the control unit 40 performs the injection with the first compressor 26 and the second compressor A control process for performing operation 27 is performed (S19). Specifically, injection control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 5 is performed.

  When it is determined in S18 that the pressure ratio of the first compressor 26 is less than the minimum allowable pressure ratio (in the case of NO), the control unit 40 performs control for performing the cooling operation only by the second compressor 27. Processing is performed (S20). Specifically, medium load control is performed, and control processing for circulating the refrigerant in the manner shown in FIG. 4 is performed.

  On the other hand, in the determination of S14 shown in FIG. 7, when it is determined that only the first compressor 26 is not operating (in the case of NO), the calculation unit 41 operates only the second compressor 27. Whether the first compressor 26 is stopped and the second compressor 27 is in operation is determined (S21).

  When it is determined that only the second compressor 27 is operated (in the case of YES), the calculation unit 41 determines whether the second compressor 27 is operated at the maximum frequency as shown in FIG. Is determined (S22). When it is determined that the second compressor 27 is not operating at the maximum frequency (in the case of NO), the control unit 40 outputs a control signal for increasing the operating frequency to the second compressor 27 (S23). ). Thereafter, the calculation unit 41 performs the control processing after S18 described above.

  In the determination process of S22, when it is determined that the second compressor 27 is operating at the maximum frequency (in the case of YES), the control unit 40 operates the first compressor 26 and the second compressor 27. A control process is performed (S24). Specifically, high load control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 6 is performed.

  Thereafter, the calculation unit 41 performs a process of selecting any of the next first control, second control, and third control (S25). Here, the first control is control for increasing the operating frequency of the first compressor 26, the second control is control for increasing the operating frequency of the second compressor 27, and the third control is the first compressor 26. And control for increasing the operating frequency of the second compressor 27.

  The calculation unit 41 performs the second control and the power consumption when the first control is performed based on the characteristics of the first compressor 26 and the characteristics of the second compressor 27 stored in the storage unit 42. The control with the lowest power consumption is selected from the power consumption when the third control is performed and the power consumption when the third control is performed. Examples of the characteristics of the first compressor 26 and the second compressor 27 include data such as suction pressure and discharge pressure in the compressor, operation frequency, and power consumption. This characteristic is updated based on data periodically acquired during operation of the air conditioning system 1.

  On the other hand, as shown in FIG. 7, in the determination of S21, when it is determined that only the second compressor 27 is not operating (in the case of NO), is the calculation unit 41 operating in the injection cycle? A determination process of whether or not is performed (S26).

  When it is determined that the vehicle is operating in the injection cycle (in the case of YES), the calculation unit 41 performs a series of control processes after S22. On the other hand, if it is determined that the engine is operating in the injection cycle (NO), the control unit 40 outputs a control signal for increasing the operating frequency of the first compressor 26 (S27).

  After S16, S19, S20, S25, and S27, the control unit 40 performs control processing for acquiring the characteristics of the first compressor 26 and the second compressor 27, and storing and storing them in the storage unit 42 (S28). . When the process of accumulating the characteristics ends, the control unit 40 returns to S11 again and repeats the above process.

  Next, determination processing performed when the room temperature decreases will be described with reference to FIGS. 9 to 11. Here, the calculation part 41 of the control part 40 performs the determination process whether only the 1st compressor 26 is drive | operated from the place which measures the temperature of the air blown out from the indoor unit 20 (S11). However, the process up to (S14) is the same as the determination process (see FIG. 7) performed when the room temperature rises, so the flowchart is shown in FIG.

  When it is determined that only the first compressor 26 is operating (in the case of YES), the calculation unit 41 determines whether or not the first compressor 26 is operating at the minimum frequency as shown in FIG. Is determined (S31). When it is determined that the first compressor 26 is not operated at the minimum frequency (in the case of NO), the control unit 40 outputs a control signal for lowering the operation frequency to the first compressor 26 (S32). ). On the other hand, when it is determined that the first compressor 26 is operating at the minimum frequency (in the case of YES), the control unit 40 outputs a control signal for stopping the first compressor 26 (S33). ).

  On the other hand, in the determination of S14 shown in FIG. 9, when it is determined that only the first compressor 26 is not operated (in the case of NO), the calculation unit 41 operates only the second compressor 27. Whether the first compressor 26 is stopped and the second compressor 27 is in operation is determined (S21).

  When it is determined that only the second compressor 27 is operating (in the case of YES), the calculation unit 41 determines whether or not the second compressor 27 is operating at the minimum frequency as shown in FIG. Is determined (S34). When it is determined that the second compressor 27 is operating at the minimum frequency (in the case of YES), the control unit 40 operates the first compressor 26 and stops with the second compressor 27. A control signal is output (S35). Specifically, low load control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 3 is performed.

  When it is determined that the second compressor 27 is not operated at the minimum frequency (in the case of YES), the control unit 40 outputs a control signal for lowering the operation frequency to the second compressor 27 (S36). ). Thereafter, the calculation unit 41 determines whether or not the pressure ratio of the first compressor 26 is equal to or greater than the minimum allowable pressure ratio, similarly to S18 (S37).

  When it is determined that the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio (in the case of YES), the control unit 40 performs the injection with the first compressor 26 and the second compressor A control process for performing operation 27 is performed (S38). Specifically, injection control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 5 is performed.

  When it is determined in S37 that the pressure ratio of the first compressor 26 is less than the minimum allowable pressure ratio (in the case of NO), the control unit 40 performs control for performing the cooling operation only by the second compressor 27. Processing is performed (S39). Specifically, medium load control is performed, and control processing for circulating the refrigerant in the manner shown in FIG. 4 is performed.

  On the other hand, in the determination of S21 shown in FIG. 9, when it is determined that only the second compressor 27 is not operated (in the case of NO), the calculation unit 41 is operated in the injection cycle or not. The determination process is performed (S26).

  When it is determined that the vehicle is operating in the injection cycle (in the case of YES), the calculation unit 41 thereafter performs a series of control processes after S34. On the other hand, when it is determined that the engine is not operated in the injection cycle (in the case of NO), the control unit 40 performs a determination process as to whether or not the first control has been selected in S25 described above (S40). ). When it is determined that the first control has been selected (in the case of YES), the control unit 40 determines whether or not the first compressor 26 is operating at the minimum frequency as shown in FIG. (S41).

  When it is determined that the first compressor 26 is operating at the minimum frequency (in the case of YES), the control unit 40 outputs a control signal for stopping the first compressor 26 (S42). On the other hand, when it is determined that the first compressor 26 is not operated at the minimum frequency (in the case of NO), the control unit 40 sends a control signal for lowering the operation frequency to the first compressor 26. Output (S43).

  If it is determined in S40 that the first control is not selected (in the case of NO), the control unit 40 determines whether or not the second control is selected in S25. (S44). When it is determined that the second control has been selected (in the case of YES), the control unit 40 determines whether or not the second compressor 27 is operating at the minimum frequency as shown in FIG. (S45). Here, the minimum frequency of the second compressor 27 is a frequency when the second compressor 27 starts operation in the high load control.

  When it is determined in S45 that the second compressor 27 is operating at the lowest frequency (in the case of YES), the control unit 40 outputs a control signal for stopping the first compressor 26 ( S46). On the other hand, when it is determined that the second compressor 27 is not operated at the lowest frequency (in the case of NO), the control unit 40 outputs a control signal for reducing the operation frequency of the second compressor 27. (S47).

  If it is determined in S44 that the second control is not selected (in the case of NO), the third control is selected, and the control unit 40, as shown in FIG. Then, it is determined whether or not the first compressor 26 and the second compressor 27 are operating at the minimum frequency (S48). Here, the minimum frequency of the first compressor 26 is a frequency when the first compressor 26 starts operation in the high load control, and the same applies to the minimum frequency of the second compressor 27.

  When it is determined in S48 that the first compressor 26 and the second compressor 27 are operating at the minimum frequency (in the case of YES), the control unit 40 operates the first compressor 26. A control signal to be stopped is output (S49). On the other hand, when it is determined that the first compressor 26 and the second compressor 27 are not operating at the minimum frequency (in the case of NO), the control unit 40 performs the first compressor 26 and the second compression. A control signal for lowering the operating frequency of the machine 27 is output (S50).

  After S32, S33, S35, S38, S39, S42, S43, S46, S47, S49, and S50, as shown in FIG. 10, the control unit 40 changes the characteristics of the first compressor 26 and the second compressor 27. A control process for acquiring, storing and storing in the storage unit 42 is performed (S51). When the process of accumulating the characteristics ends, the control unit 40 returns to S11 in FIG. 9 again and repeats the above process.

  Next, the relationship between the load in the low load control, the medium load control, the injection control and the high load control and the rotation speed of the compressor will be described with reference to the graphs of FIGS. 12 (a) and 12 (b). . Here, an example in which the first control is selected in the high load control will be described. In the graphs of FIG. 12A and FIG. 12B, the vertical axis represents the rotation speed of the compressor (synonymous with the operating frequency), and the horizontal axis represents the load of the air conditioning system 1.

  Furthermore, from the low load area (left side of the figure) to the high load area (right side of the figure), it becomes a low load control area, a medium load control or injection control area, and a high load control area. Yes. In the graph, the line with the symbol A represents the first compressor 26, and the line with the symbol B represents the second compressor 27.

  First, a case where the load increases from a low load to a high load will be described with reference to FIG. In this case, since the first compressor 26 is operated and the second compressor 27 is stopped in the low load control region, only the second compressor 27 is continuously operated (indicated by a dotted line). Compared with, the minimum value of the load which the air-conditioning system 1 can respond is low.

  In the middle load control or injection control region, the rotational speed of the second compressor 27 is adjusted according to the load, and when the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio, a dotted line is used. As shown, the rotational speed of the first compressor 26 is adjusted according to the injection amount and pressure. In the high load control region, the second compressor 27 is operated at the maximum rotation speed regardless of the load, and the rotation speed of the first compressor 26 is adjusted according to the load.

  Next, a case where the load decreases from a high load to a low load will be described with reference to FIG. In this case, it is the same as in the case of FIG. 12A in that the rotation speed of the compressor is adjusted according to the load. The difference from FIG. 12A is that the load for switching from the middle load control or injection control region to the low load control region is different.

  That is, in the case of FIG. 12A where the load increases in the load region that can be handled by both the first compressor 26 and the second compressor 27, the operation of the first compressor 26 is used. On the other hand, in the case of FIG. 12B in which the load decreases, the difference is that the operation is performed by the operation of the second compressor 27.

  When the second control is selected during the high load control, it is shown in the graph of FIG. 13 (a), and when the third control is selected, it is shown in the graph of FIG. 13 (b).

  When the second control is selected, as shown in FIG. 13A, the first compressor 26 is operated at the maximum rotational speed over the entire high load control region, and the rotational speed of the second compressor 27 is It is controlled according to the load. When the third control is selected, as shown in FIG. 13B, the rotation speeds of the first compressor 26 and the second compressor 27 are controlled according to the load.

  FIG. 13B shows an example in which the ratio of the change in the rotational speed of the first compressor 26 with respect to the change in the load is larger than that in the second compressor 27. In addition, the ratio of this change may be larger in the 2nd compressor 27, may be the same, and is not specifically limited.

  According to the air conditioning system 1 configured as described above, the first compressor 26 is not only used as a compressor that realizes an injection cycle during injection control, but also contributes to heat exchange in the evaporator 24 during high load control. Also used as As described above, by using the first compressor 26 for realizing the injection cycle, the air conditioning system 1 can be stably cooled even under a low load. Furthermore, since the first compressor 26 is used so as to contribute to cooling by the air conditioning system 1, the operating efficiency of the air conditioning system 1 can be improved, and the power consumption can be reduced.

  By making the compression capacity of the first compressor 26 smaller than the compression capacity of the second compressor 27, it becomes easier to reduce the power consumption in the air conditioning system 1, and realize a stable cooling operation at a low load. It becomes easy. In general, the power consumed by a compressor decreases as its compression capacity decreases. In addition, the efficiency decreases as the load factor decreases. Therefore, it becomes easy to reduce the electric power consumed in low load control by making small the compression capacity of the 1st compressor 26 operated by low load control. Further, since the cooling capacity when the air-conditioning system 1 is continuously operated in the low load control is further reduced, it is easy to operate the air-conditioning system 1 continuously without starting and stopping even when the required cooling capacity is small. Become. Note that when the low load control is not performed, the first compressor 26 compresses the refrigerant that does not contribute to the cooling capacity of the air conditioning system 1 (the refrigerant that does not flow through the evaporator 24). Compared with the machine 27, the compression capacity can be set small.

  By selecting the control with the lowest power consumption based on the characteristics of the first compressor 26 and the characteristics of the second compressor 27 from the first control, the second control, and the third control, the power consumption can be reduced. Can be planned.

  Furthermore, the characteristics of the first compressor 26 and the characteristics of the second compressor 27 in the first control, the second control, and the third control are updated based on the operation information of the first compressor 26 and the second compressor 27. As a result, the accuracy in selecting the control with the lowest power consumption becomes higher.

  By storing the characteristics of the first compressor 26 and the characteristics of the second compressor 27 in the storage unit 42, the stored operation information can be used for controlling the first compressor 26, the second compressor 27, and the like. This makes it easier to reduce power consumption.

  In the above-described embodiment, as shown in FIG. 7 and FIG. 9, the temperature difference between the temperature of the air blown out from the indoor unit 20 and the preset value of the predetermined blow temperature is set in advance. Although it is applied to an example in which it is determined whether or not it is equal to or more than a predetermined threshold (S11 to S13), the temperature of the air sucked into the indoor unit 20 and a predetermined set value of the suction temperature It may be determined whether or not the difference in suction temperature, which is the difference, is greater than or equal to a predetermined threshold, and is not particularly limited.

  In addition, when the first control, the second control, and the third control are selected in S25 of FIG. 8, the characteristics of the first compressor 26 that are updated based on data that is periodically acquired when the air conditioning system 1 is operated. Although the description has been made by applying to an example in which selection is made based on the characteristics of the second compressor 27, the characteristics of the first compressor 26 and the characteristics of the second compressor 27 have predetermined characteristics. It may be left as it is (not updated), and is not particularly limited. If the characteristics are not updated, the characteristics accumulation processing in S28 and S51 may or may not be performed.

  Furthermore, the first control may be selected from the beginning in S25, and only when the first control is selected (YES) in S40 of FIG. By doing so, the amount of calculation processing in the control unit 40 can be reduced.

  In addition, although it applied and demonstrated to the example in which the control process which raises the operating frequency of the 1st compressor 26 equivalent to 1st control in S27 is performed, it is applied to the control process equivalent to 2nd control, or 3rd control Corresponding control processing may be performed and is not particularly limited.

  Further, the operation information stored in the storage unit 42 may be used for updating the characteristics of the first compressor 26 and the characteristics of the second compressor 27 as described above, or the temperature change of the blown air and the intake air It may be used for controlling the change width of the operating frequency of the first compressor 26 or the second compressor 27 according to the temperature change, and is not particularly limited. In this case, the driving information stored in the storage unit 42 also stores a difference that is a change amount from the previous storage time.

  When storing the difference of the operation information in the storage unit 42, the stored operation information or the like can also be used for prediction of the future control state according to the change state such as the blown air temperature. It is not limited.

[First Modification of First Embodiment]
Next, a first modification of the first embodiment of the present invention will be described with reference to FIG. The basic configuration of the air conditioning system of the present modification is the same as that of the first embodiment. However, only the first compressor is operated in the determination process performed when the room temperature rises. The contents of control after the determination is made (after YES in S14 in FIG. 7) are different.

In this modification, only the control content after it is determined that only the first compressor is operating will be described using FIG. 14, and description of other control content and the like will be omitted.
When the calculation unit 41 of the control unit 40 in the air conditioning system 1 of the present modification determines that only the first compressor 26 is operating (YES in S14 in FIG. 7), the second compression is performed as shown in FIG. A determination process is performed as to whether or not operation is possible even at the minimum frequency of the machine 27 (S60). That is, it is determined whether or not the cooling capacity when the second compressor 27 is operated at the minimum frequency is excessive with respect to the load required for the air conditioning system 1.

  When it is determined that the second compressor 27 can be operated even at the minimum frequency (in the case of YES), the calculation unit 41 compares the power consumption when the first compressor 26 is operated with the second compressor. A determination process is performed as to whether or not the power consumption when driving 27 is small (S61). That is, in the case where the operation of the first compressor 26 or the operation of the second compressor 27 is possible, a process is performed to determine which compressor is operated to reduce the power consumption.

  When it is determined that the power consumption when operating the second compressor 27 is small (in the case of YES), the control unit 40 outputs a control signal for operating the second compressor 27 and performing the cooling operation. (S62). Thereafter, the calculation unit 41 performs a determination process as to whether or not the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio, similarly to S18 (S63).

  When it is determined that the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio (in the case of YES), the control unit 40 performs the injection with the first compressor 26 and the second compressor A control process for performing operation 27 is performed (S64). On the other hand, when it is determined that the pressure ratio of the first compressor 26 is less than the minimum allowable pressure ratio (in the case of NO), the control unit 40 performs the cooling operation only with the second compressor 27. (S65).

  When it is determined in S60 that operation is not possible at the minimum frequency of the second compressor 27 (in the case of NO), and in the determination of S61, power consumption is not small when the second compressor 27 is operated. When it is determined that the power consumption is large (in the case of NO), the control unit 40 outputs a control signal for increasing the operating frequency to the first compressor 26 (S66).

  After S64, S65, and S66, the control unit 40 performs control processing for acquiring the characteristics of the first compressor 26 and the second compressor 27, storing them in the storage unit 42, and storing them (S28). When the process of accumulating the characteristics ends, the control unit 40 returns to S11 again (see FIG. 7) and repeats the above process.

  According to the air conditioning system 1 of the present modification, in the determination process that is performed when the indoor temperature rises, the compression that reduces power consumption in the region that can be operated by either the first compressor 26 or the second compressor 27. Operation using a machine can be performed. Therefore, the power consumption of the air conditioning system 1 can be further reduced.

[Second Modification of First Embodiment]
Next, a second modification of the first embodiment of the present invention will be described with reference to FIG. The basic configuration of the air conditioning system of the present modification is the same as that of the first embodiment, but only the second compressor is operated in the determination process that is performed when the room temperature decreases. The control contents after the determination that the operation in the injection cycle is performed (after YES in S26 in FIG. 9) are different.

  In this modification, only the control contents after it is determined that the operation in the injection cycle is performed after it is determined that only the second compressor 27 is operated using FIG. 15 will be described. Explanation of other control contents is omitted.

  When the calculation unit 41 of the control unit 40 in the air conditioning system 1 of the present modification determines that only the second compressor 27 is operating (YES in S21 in FIG. 9), or is operating in the injection cycle. If it determines (YES of S26 in FIG. 9), as shown in FIG. 15, the determination process of whether it can drive | operate also with the maximum frequency of the 1st compressor 26 is performed (S70). That is, it is determined whether or not the cooling capacity when the first compressor 26 is operated at the maximum frequency satisfies the load required for the air conditioning system 1.

  When it is determined that the first compressor 26 can be operated even at the minimum frequency (in the case of YES), the calculation unit 41 compares the power consumption when the second compressor 27 is operated with the first compressor. A determination process is performed as to whether or not the power consumption when driving the vehicle 26 is small (S71). That is, in the case where the operation of the first compressor 26 or the operation of the second compressor 27 is possible, a process is performed to determine which compressor is operated to reduce the power consumption.

  When it is determined in S70 that operation is not possible at the maximum frequency of the first compressor 26 (in the case of NO), and in the determination of S71, power consumption is not small when the first compressor 26 is operated. When it is determined that the power consumption is large (in the case of NO), the control unit 40 outputs a control signal for lowering the operating frequency to the second compressor 27 (S72).

  Thereafter, the calculation unit 41 performs a determination process as to whether or not the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio, similarly to S18 (S73). When it is determined that the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio (in the case of YES), the control unit 40 performs the injection with the first compressor 26 and the second compressor A control process for performing operation 27 is performed (S74). On the other hand, when it is determined that the pressure ratio of the first compressor 26 is less than the minimum allowable pressure ratio (in the case of NO), the control unit 40 performs the cooling operation only with the second compressor 27. (S75).

  On the other hand, in the determination of S71, when it is determined that the power consumption when the first compressor 26 is operated is small (in the case of YES), the control unit 40 stops the second compressor 27, A control signal for operating the first compressor 26 is output (S76).

  After S74, S75, and S76, the control unit 40 performs control processing for acquiring the characteristics of the first compressor 26 and the second compressor 27, storing them in the storage unit 42, and storing them (S51). When the process of accumulating the characteristics ends, the control unit 40 returns to S11 again (see FIG. 9) and repeats the above process.

  According to the air conditioning system 1 of the present modified example, in the determination process performed when the room temperature decreases, the compression that reduces the power consumption for the region that can be operated by either the first compressor 26 or the second compressor 27. Operation using a machine can be performed. Therefore, the power consumption of the air conditioning system 1 can be further reduced.

[Third Modification of First Embodiment]
Next, a third modification of the first embodiment of the present invention will be described with reference to FIGS. The basic configuration of the air conditioning system of the present modification is the same as that of the first embodiment, but is different from the first embodiment in the first compressor near the boundary with the medium load control or the injection control in the high load control. 26 and the control content for the second compressor 27 are different.

First, referring to FIG. 16 (a), the control of the rotational speed for the first compressor 26 and the second compressor 27 when the first control is selected in the high load control will be described.
In the air conditioning system 1 of the present modification, the control unit 40 reduces the rotational speed of the second compressor 27 by a predetermined amount from the maximum rotational speed when switching from the medium load control or the injection control to the high load control. The operation of the first compressor 26 is started at the rotational speed. Here, as the predetermined amount to be reduced, the flow rate of the refrigerant discharged from the second compressor 27 is decreased by a refrigerant flow rate equal to the refrigerant flow rate discharged when the first compressor 26 is operated at the minimum rotation speed. The change width of the number of rotations can be exemplified.

  Thereafter, the first compressor 26 is operated at the minimum rotational speed in a region where the rotational speed of the second compressor 27 increases as the load increases and reaches the maximum rotational speed. After the rotation speed of the second compressor 27 reaches the maximum rotation speed, the rotation speed of the first compressor 26 increases as the load increases.

  When the load decreases, the above description is reversed. That is, when the load is high, the rotation speed of the first compressor 26 decreases as the load decreases, and the second compressor 27 is operated at the maximum rotation speed. When the rotation speed of the first compressor 26 reaches the minimum rotation speed, the rotation speed of the second compressor 27 decreases according to the decrease in load. When the high load control is switched to the medium load control or the injection control, the rotation speed of the second compressor 27 increases to the maximum rotation speed, and then the rotation speed of the second compressor 27 decreases as the load decreases.

  By controlling the rotation speeds of the first compressor 26 and the second compressor 27 in this way, the refrigerant flow circulating in the air conditioning system 1 is prevented from greatly fluctuating (hunting) at the time of switching of control. Therefore, stable operation can be performed.

Next, with reference to FIG. 16B, the control of the rotational speed for the first compressor 26 and the second compressor 27 when the second control is selected in the high load control will be described.
In the air conditioning system 1 of the present modification, the control unit 40 operates the first compressor 26 at the maximum rotational speed and switches the rotational speed of the second compressor 27 when the medium load control or the injection control is switched to the high load control. Are operated at a rotational speed that is lower than the rotational speed at the start of operation in the first embodiment by a predetermined amount. The rotational speed of the second compressor 27 rapidly increases to the rotational speed in the first embodiment, and thereafter increases according to the increase in load as in the first embodiment.

When the load decreases, the above description is reversed.
By controlling the rotational speed of the second compressor 27 in this way, the refrigerant flow circulating in the air conditioning system 1 is prevented from greatly fluctuating (hunting) at the time of switching of control, and stable operation is achieved. It can be carried out.

Next, with reference to FIG. 17A to FIG. 18, the control of the rotational speed for the first compressor 26 and the second compressor 27 when the third control is selected in the high load control will be described.
In the air conditioning system 1 of the present modification, the control unit 40 performs any one of the three controls described below when switching from medium load control or injection control to high load control. The control unit 40 may select and perform one of these three controls in advance, or may select based on the characteristics of the compressor.

  First, as shown in FIG. 17A, the first compressor 26 is operated at a rotational speed that is lower by a predetermined amount than the rotational speed at the start of operation in the first embodiment. The rotation speed of the second compressor 27 is controlled in the same manner as in the first embodiment.

  Next, as shown in FIG. 17B, the second compressor 27 is operated at a rotational speed that is lower by a predetermined amount than the rotational speed at the start of operation in the first embodiment. The rotation speed of the first compressor 26 is controlled in the same manner as in the first embodiment.

  Finally, as shown in FIG. 18, the first compressor 26 is operated at a rotational speed that is lower by a predetermined amount than the rotational speed at the start of operation in the first embodiment, and the second The compressor 27 is operated at a rotational speed that is lower by a predetermined amount than the rotational speed at the start of operation in the first embodiment.

When the load decreases, the above description is reversed.
By controlling the rotation speeds of the first compressor 26 and the second compressor 27 in this way, the refrigerant flow circulating in the air conditioning system 1 is prevented from greatly fluctuating (hunting) at the time of switching of control. Therefore, stable operation can be performed.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. The basic configuration of the air conditioning system of this embodiment is the same as that of the first embodiment, but the number of compressors provided is different from that of the first embodiment.

  As shown in FIG. 19, the air conditioning system 101 of the present embodiment includes a condenser 11, a first expansion valve 21, a first gas-liquid separator 22, a second expansion valve 23, an evaporator 24, and a second gas-liquid. The separator 25, the first compressor 26, the second compressor 27, the third compressor (second compression unit) 127, the first control valve 28 and the second control valve 29, and the control unit 140 are mainly configured. Has been.

  Similarly to the second compressor 27, the third compressor 127 is a compressor disposed between the evaporator 24 and the condenser 11, and has a compression volume equal to that of the second compressor 27 for compressing the refrigerant. It is. Comparing the third compressor 127 and the second compressor 27, the operating frequency of the second compressor 27 is variably controlled by inverter control, whereas the operating frequency of the third compressor 127 is fixed. The point is different.

  In addition, a check valve 127 </ b> A for preventing the refrigerant from flowing backward is disposed on the discharge side of the third compressor 127. The check valve 127 </ b> A prevents the refrigerant from flowing back from the first compressor 26, the second compressor 27, and the condenser 11 to the third compressor 127 when the third compressor 127 is stopped. .

  The control unit 140 controls the operation state in the air conditioning system 101, and is a microcomputer having a CPU (Central Processing Unit), ROM, RAM, input / output interface, and the like. For example, as shown in FIG. 19, the place where the control unit 140 is disposed may be inside the indoor unit 20 or may be a place other than the indoor unit 20, and is not particularly limited.

  The control program stored in the ROM or the like causes the CPU to function as the arithmetic unit 41 and causes the ROM or the like to function as the storage unit 42 as shown in the schematic diagram of FIG. The control of the operation state by the control unit 140 can be exemplified by control in which the temperature of room air that is performed in a conventional air conditioning system is set as a set temperature, control at low load, which is a feature of the present embodiment, and the like.

  Compared with the control unit 40 of the first embodiment, the control unit 140 includes a third suction pressure sensor 136 that measures the pressure of the refrigerant sucked into the third compressor 127, and a discharge from the third compressor 127. The third discharge pressure sensor 137 that measures the pressure of the refrigerant that has been measured is different in that a measurement signal indicating the pressure measured from the third discharge pressure sensor 137 is further input. Further, the control unit 40 is different from the control unit 40 of the first embodiment in that a control signal for controlling the operation state of the third compressor 127 is output.

  Next, the operation in the air conditioning system 101 having the above-described configuration will be described with reference to the circuit diagrams of FIGS. Specifically, the control in the case of a low load with the lowest heat load on the air conditioning system 101 (hereinafter referred to as “low load control”), and the control in the case of a medium load with a small heat load (hereinafter, "Medium load control"), and control in the case of an injection that can be operated in an injection cycle (corresponding to the injection control in the claims, hereinafter referred to as "medium load injection control") Control in case of high load with high heat load (corresponding to medium load control in claims, hereinafter referred to as “high load control”), in case of high load and injection cycle Control in the case of injection that can be operated at the same time (corresponding to the injection control in the claims, hereinafter "high load injection control" Wherein for.), And the control in the case of the thermal load is highest high load (corresponds to a high load control in the claims, hereinafter referred to as "super-load control." For operation in) will be described.

  First, the operation in the low load control will be described with reference to FIG. In this case, the control unit 140 of the air conditioning system 101 outputs a control signal for closing the valve to the first control valve 28 and outputs a control signal for opening the valve to the second control valve 29.

  In addition, the control unit 140 outputs a control signal for operating the first compressor 26 and outputs a control signal for stopping the second compressor 27 and the third compressor 127. Since the flow of the refrigerant in this case is the same as that in the case of the low load control in the first embodiment, the description thereof is omitted.

  Next, the operation in the medium load control will be described with reference to FIG. In this case, the control unit 140 of the air conditioning system 101 outputs a control signal for closing the valves to the first control valve 28 and the second control valve 29. Further, a control signal for stopping the first compressor 26 and the third compressor 127 is output, and a control signal for operating the second compressor 27 is output. Since the refrigerant flow in this case is the same as that in the case of the medium load control in the first embodiment, the description thereof is omitted.

  Next, the operation in the medium load injection control will be described with reference to FIG. In this case, the control unit 140 of the air conditioning system 101 outputs a control signal for opening the valve to the first control valve 28 and outputs a control signal for closing the valve to the second control valve 29. In addition, a control signal for operating the first compressor 26 and the second compressor 27 is output, and a control signal for stopping the third compressor 127 is output. Since the flow of the refrigerant in this case is the same as in the case of the injection control in the first embodiment, the description thereof is omitted.

  Next, the operation in the high load control will be described with reference to FIG. In this case, the control unit 140 of the air conditioning system 101 outputs a control signal for closing the valves to the first control valve 28 and the second control valve 29. Moreover, while outputting the control signal which stops to the 1st compressor 26, the control signal which performs an operation | movement with respect to the 2nd compressor 27 and the 3rd compressor 127 is output.

  The refrigerant flow in this case is the same as in the case of the high load control in the first embodiment, except that the second compressor 27 and the third compressor 127 are operated and the first compressor 26 is stopped. Therefore, the description thereof is omitted.

  Next, the operation in the high load injection control will be described with reference to FIG. In this case, the control unit 140 of the air conditioning system 101 outputs a control signal for opening the valve to the first control valve 28 and outputs a control signal for closing the valve to the second control valve 29. In addition, a control signal for operating the first compressor 26, the second compressor 27, and the third compressor 127 is output.

  Since the refrigerant flow in this case is the same as that in the case of the injection control in the first embodiment except that the first compressor 26, the second compressor 27, and the third compressor 127 are operated, The description is omitted.

  Finally, the operation in the super load control will be described with reference to FIG. In this case, the control unit 140 of the air conditioning system 101 outputs a control signal for closing the valve to the first control valve 28 and outputs a control signal for opening the valve to the second control valve 29. In addition, a control signal for operating the first compressor 26, the second compressor 27, and the third compressor 127 is output.

  The refrigerant flow in this case is the same as that in the case of the high load control in the first embodiment except that the first compressor 26, the second compressor 27, and the third compressor 127 are operated. The description is omitted.

  While the air conditioning system 101 is in operation, the control unit 140 determines whether to execute low load control, medium load control, medium load injection control, high load control, high load injection control, or super load control. Repeatedly. This determination is performed according to the flowcharts shown in FIGS. First, a determination process performed when the room temperature rises will be described with reference to FIGS.

  From where the calculation unit 41 of the control unit 140 measures the temperature of the air blown out from the indoor unit 20 (S11) to when the control signal for raising the operating frequency is output to the second compressor 27 (S23). Since this is the same as the determination process (see FIGS. 7 and 8) performed in the first embodiment, the flowchart is shown in FIGS. 27 and 28 and the description thereof is omitted.

  In the determination process of S22, when it is determined that the second compressor 27 is operating at the maximum frequency (in the case of YES), the control unit 140 operates the second compressor 27 and the third compressor 127. A control process is performed (S124). Specifically, high load control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 24 is performed.

  Thereafter, the calculation unit 41 determines whether or not the pressure ratio of the first compressor 26 is equal to or greater than the minimum allowable pressure ratio, similarly to S18 (S125). When it is determined that the pressure ratio of the first compressor 26 is equal to or greater than the minimum allowable pressure ratio (in the case of YES), the control unit 140 performs injection with the first compressor 26 and the second compressor 27 and a control process for operating the third compressor 127 is performed (S126). Specifically, high-load injection control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 25 is performed.

  When it is determined in S125 that the pressure ratio of the first compressor 26 is less than the minimum allowable pressure ratio (in the case of NO), the control unit 140 includes only the second compressor 27 and the third compressor 127. Then, a control process for performing the cooling operation is performed (S127). Specifically, high load control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 24 is performed.

  On the other hand, in the determination of S21 shown in FIG. 27, when it is determined that only the second compressor 27 is not operating (in the case of NO), the calculation unit 41 causes the first compressor 26 to be in the injection cycle. It is determined whether or not the second compressor 27 is in operation (S128).

  When it is determined that the first compressor 26 is operated in the injection cycle and the second compressor 27 is operated (in the case of YES), the calculation unit 41 performs a series of control processes after S22. On the other hand, when it is determined that the first compressor 26 is operated in the injection cycle and the second compressor 27 is operated (in the case of NO), the calculation unit 41 includes the second compressor 27 and A determination process is performed to determine whether only the third compressor 127 is operating (S129).

  When it is determined that only the second compressor 27 and the third compressor 127 are operating (in the case of YES), the calculation unit 41 indicates that the second compressor 27 has the maximum frequency as shown in FIG. Whether or not the vehicle is being operated is determined (S130). When it is determined that the second compressor 27 is not operated at the maximum frequency (in the case of NO), the control unit 140 outputs a control signal for increasing the operation frequency to the second compressor 27 (S131). ). Thereafter, the control unit 140 performs the control processing after S125.

  When it is determined in S130 that the second compressor 27 is operating at the maximum frequency (in the case of YES), the control unit 140 controls the first compressor 26, the second compressor 27, and the third compressor. A control signal for operating the compressor 127 is output (S132). Specifically, super load control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 6 is performed. Thereafter, the calculation unit 41 performs a process of selecting any one of the first control, the second control, and the third control, similarly to S25 (S133).

  On the other hand, as shown in FIG. 27, when it is determined in S129 that only the second compressor 27 and the third compressor 127 are not operating (in the case of NO), the calculation unit 41 It is determined whether or not the first compressor 26 is operated in the injection cycle and the second compressor 27 and the third compressor 127 are operated (S134).

  When it is determined that the first compressor 26 is operated in the injection cycle and the second compressor 27 and the third compressor 127 are operated (in the case of YES), the calculation unit 41 performs the calculation after S130. Process. On the other hand, when it is determined that the first compressor 26 is operated in the injection cycle and the second compressor 27 and the third compressor 127 are not operated (in the case of NO), the control unit 140 A control signal for increasing the operating frequency of the first compressor 26 is output (S135).

  After S16, S19, S20, S126, S127, S133, and S135, the control unit 140 acquires the characteristics of the first compressor 26, the second compressor 27, and the third compressor 127 and stores them in the storage unit 42. Then, a control process for accumulating is performed (S136). When the process of accumulating the characteristics ends, the control unit 140 returns to S11 in FIG. 27 again and repeats the above process.

  Next, a determination process that is performed when the room temperature decreases will be described with reference to FIGS. 30 to 32. Here, since the calculation unit 41 of the control unit 140 measures the temperature of the air blown from the indoor unit 20 (S11), the control unit 140 performs a control process in which the cooling operation is performed only by the second compressor 27. Since it is the same as the control (refer FIG. 9 and FIG. 10) in 1st Embodiment until it performs (S39), the flowchart is shown to FIG. 30 and FIG. 31, and description is abbreviate | omitted.

  In the determination of S21 shown in FIG. 30, when it is determined that only the second compressor 27 is not operated (in the case of NO), the calculation unit 41 operates the injection cycle with the first compressor 26, A determination process is performed as to whether or not the second compressor 27 is performing a cooling operation (S128). When it is determined that the injection cycle is operated by the first compressor 26 and the cooling operation is performed by the second compressor 27 (in the case of YES), the calculation unit 41 thereafter performs a series of control processes after S34. I do.

  On the other hand, when it is determined that the injection cycle is operated by the first compressor 26 and the cooling operation is not performed by the second compressor 27 (in the case of NO), the computing unit 41 is configured to operate the first compressor. Whether or not only 26 and the second compressor 27 are in operation is determined (S129). When it is determined that only the first compressor 26 and the second compressor 27 are operating (in the case of YES), the calculation unit 41 indicates that the second compressor 27 has the minimum frequency as shown in FIG. Whether or not the vehicle is being operated is determined (S234).

  When it is determined that the second compressor 27 is operating at the minimum frequency (in the case of YES), the control unit 140 stops the third compressor 127 and outputs a control signal for operating the second compressor 27. It outputs (S235). Thereafter, the control unit 140 performs the control processing after S37 described above.

  When it is determined in S234 that the second compressor 27 is not operating at the adopted frequency (in the case of NO), the control unit 140 outputs a control signal for reducing the operating frequency of the second compressor 27. (S236). Thereafter, similarly to S18, the calculation unit 41 performs a determination process as to whether or not the pressure ratio of the first compressor 26 is equal to or greater than the minimum allowable pressure ratio (S237).

  When it is determined that the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio (in the case of YES), the first compressor 26 performs injection, and the second compressor 27 and the third compressor A control process for operating the machine 127 is performed (S238). Specifically, high-load injection control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 25 is performed.

  When it is determined in S237 that the pressure ratio of the first compressor 26 is less than the minimum allowable pressure ratio (in the case of NO), the control unit 140 includes only the second compressor 27 and the third compressor 127. Then, a control process for performing the cooling operation is performed (S239). Specifically, high load control is performed, and a control process for circulating the refrigerant in the manner shown in FIG. 24 is performed.

  On the other hand, in the determination of S129 shown in FIG. 30, when it is determined that only the second compressor 27 and the third compressor 127 are not operating (in the case of NO), the calculation unit 41 performs the first compression. It is determined whether or not the machine 26 is operated in the injection cycle and the second compressor 27 and the third compressor 127 are operated (S134). When it is determined that the first compressor 26 is operated in the injection cycle and the second compressor 27 and the third compressor 127 are operated (in the case of YES), the control unit 140 performs the above-described S234 and subsequent steps. Perform control processing.

  When it is determined that the first compressor 26 is operated in the injection cycle and the second compressor 27 and the third compressor 127 are not operated (in the case of NO), the control unit 140 determines in S133 described above. A determination process is performed to determine whether or not the first control has been selected (S240). When it is determined that the first control has been selected (in the case of YES), the control unit 140 determines whether or not the first compressor 26 is operating at the minimum frequency, as shown in FIG. (S241).

  When it is determined that the first compressor 26 is operating at the minimum frequency (in the case of YES), the control unit 140 outputs a control signal for stopping the first compressor 26 (S242). On the other hand, when it is determined that the first compressor 26 is not operated at the minimum frequency (in the case of NO), the control unit 140 sends a control signal for lowering the operation frequency to the first compressor 26. It outputs (S243).

  If it is determined in S240 that the first control is not selected (NO), the control unit 140 performs a determination process as to whether or not the second control is selected in S133. (S244). When it is determined that the second control has been selected (in the case of YES), the control unit 140 determines whether or not the second compressor 27 is operating at the minimum frequency as shown in FIG. (S245).

  When it is determined in S245 that the second compressor 27 is operating at the lowest frequency (in the case of YES), the control unit 140 outputs a control signal for stopping the first compressor 26 ( S246). On the other hand, when it is determined that the second compressor 27 is not operated at the lowest frequency (in the case of NO), the control unit 140 outputs a control signal for reducing the operation frequency of the second compressor 27. (S247).

  When it is determined in S244 that the second control is not selected (in the case of NO), the third control is selected, and the control unit 140, as shown in FIG. Then, it is determined whether or not the first compressor 26 and the second compressor 27 are operating at the minimum frequency (S248).

  When it is determined in S248 that the first compressor 26 and the second compressor 27 are operating at the minimum frequency (in the case of YES), the control unit 140 operates the first compressor 26. A control signal to be stopped is output (S249). On the other hand, when it is determined that the first compressor 26 and the second compressor 27 are not operated at the minimum frequency (in the case of NO), the control unit 140 performs the first compressor 26 and the second compression. A control signal for lowering the operating frequency of the machine 27 is output (S250).

  After S32, S33, S35, S38, S39, S238, S239, S242, S243, S246, S247, S249, S250, as shown in FIG. 31, the control unit 140 includes the first compressor 26 and the second compressor. The control process of acquiring 27 characteristics, storing them in the storage unit 42, and accumulating them is performed (S51). When the process of accumulating the characteristics ends, the control unit 140 returns to S11 in FIG. 30 again and repeats the above process.

  Next, the relationship between the load in the low load control, the medium load control, the medium load injection control, the high load control, the high load injection control, and the super load control and the rotation speed of the compressor is referred to the graph of FIG. explain. Here, an example in which the first control is selected in the super load control will be described. In the graph of FIG. 33, the vertical axis represents the rotation speed of the compressor (synonymous with the operating frequency), and the horizontal axis represents the load of the air conditioning system 1.

  Since the relationship with the rotation speed of the compressor in the low load control, medium load control, and medium load injection control regions is the same as that in the first embodiment, the description thereof is omitted. In the region of high load control and high load injection control, the third compressor 127 is operated at a constant rotational speed, and the rotational speed of the second compressor 27 is adjusted according to the load. When the pressure ratio of the first compressor 26 is equal to or higher than the minimum allowable pressure ratio, the rotation speed of the first compressor 26 is adjusted according to the load as indicated by the dotted line. In the super load control, the second compressor 27 and the third compressor 127 are operated at a constant rotation speed, and the rotation speed of the first compressor 26 is adjusted according to the load.

  When the second control is selected during the super load control, the graph of FIG. 34 is shown, and when the third control is selected, the graph of FIG. 35 is shown. As in the case of the first embodiment, when the second control is selected, as shown in FIG. 34, the first compressor 26 is operated at the maximum rotation speed over the entire superload control region, and the first control is performed. The rotational speed of the two compressors 27 is controlled according to the load. When the third control is selected, as shown in FIG. 35, the rotation speeds of the first compressor 26 and the second compressor 27 are controlled according to the load.

  According to the air conditioning system 101 having the above configuration, by providing the second compressor 27 and the third compressor 127, the amount of heat exchange (heat load) in the evaporator 24 can be increased, and higher cooling capacity is exhibited. Can be made. Furthermore, by setting the discharge capacity of the third compressor 127 to be fixed and making the discharge capacity of the second compressor 27 variable, it is possible to realize a stable cooling operation even during high load control or super load control.

  In the above-described embodiment, the third compressor 127 is described as being applied to an example in which the compressor is a compressor having a fixed discharge capacity that is rotationally driven at a constant speed. The compressor may be capable of variably controlling the operation frequency and controlling the discharge capacity. In this case, inverter control as shown in FIGS. 36 to 38 may be performed on the first compressor 26, the second compressor 27, and the third compressor 127.

  Moreover, about the air conditioning system 101 which concerns on this embodiment, the application from a 1st modification to a 3rd modification etc. is possible like the case of 1st Embodiment, and it is not limited only to this embodiment. .

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the description has been made assuming that a vapor compression refrigeration cycle using an alternative chlorofluorocarbon or the like is applied as an air conditioning system, but a supercritical cycle using carbon dioxide or the like may be applied. Good.

  DESCRIPTION OF SYMBOLS 1,101 ... Air-conditioning system (refrigerator), 11 ... Condenser (high pressure heat exchanger), 21 ... 1st expansion valve (1st pressure reduction part), 22 ... 1st gas-liquid separator (gas-liquid separator), 23 ... 2nd expansion valve (2nd pressure reduction part), 24 ... Evaporator (low pressure heat exchanger), 26 ... 1st compressor (1st compression part), 27 ... 2nd compressor (2nd compression part), 28 ... 1st control valve (selection part), 29 ... 2nd control valve (selection part), 40, 140 ... control part, 127 ... 3rd compressor (2nd compression part)

Claims (9)

In the refrigeration system that moves the heat on the low temperature side to the high temperature side,
A high-pressure heat exchanger that cools the high-pressure refrigerant;
A first decompression unit that decompresses the high-pressure refrigerant cooled in the high-pressure heat exchanger;
A gas-liquid separator that separates the low-pressure refrigerant decompressed by the first decompression unit into a gaseous refrigerant and a refrigerant liquid;
A second decompression unit for further decompressing the liquid refrigerant separated by the gas-liquid separator;
A low pressure heat exchanger for evaporating the refrigerant decompressed in the second decompression unit;
The gas refrigerant separated by the gas-liquid separator, and a first compression unit for ejecting before Symbol higher pressure heat exchanger by compressing at least one of the refrigerant flowing from the low pressure heat exchanger,
A second compression section that compresses the refrigerant flowing out of the low-pressure heat exchanger and discharges the refrigerant toward the high-pressure heat exchanger;
A selection unit that selects one of the gaseous refrigerant separated by the gas-liquid separator and the refrigerant that has flowed out of the low-pressure heat exchanger and sucks it into the first compression unit ;
Control of operation stop of the first compression unit and the second compression unit, and control of refrigerant selection by the selection unit,
Low load control for operating the first compression unit and stopping the second compression unit, middle load control for operating the second compression unit and stopping the first compression unit, the first compression unit and the first compression unit Both the two compression sections are operated, and the first compression section is configured to inject the gas refrigerant separated by the gas-liquid separator, and both the first compression section and the second compression section A control unit that performs at least a high load control for sucking the refrigerant that has flowed out of the low-pressure heat exchanger into the first compression unit,
Is provided ,
The control unit switches from the low load control to the medium load control or the injection control according to an increase in load, and switches from the medium load control or the injection control to the low load control according to a decrease in the load. And
Switching from the medium load control or the injection control to the low load control is performed at a lower load than when the low load control is switched to the medium load control or the injection control. refrigerator.   The first compression unit has a smaller compression capacity of the refrigerant than the second compression unit, and the second compression unit is stopped and the first compression unit is operated during the low load control. The refrigerator according to claim 1. The second compression unit is plural,
The discharge capacity, which is the capacity per unit time of the refrigerant discharged from some of the second compression units, is fixed or variably controlled by the control unit,
The refrigerator according to claim 1 or 2, wherein the discharge capacity discharged from the remaining second compression section is variably controlled by the control section. In the control unit, during the high load control,
When performing the first control to increase the discharge capacity that is the capacity per unit time of the refrigerant discharged from the first compression unit,
When performing the second control to increase the discharge capacity of the second compression unit, and
The characteristics of the first compression section and the characteristics of the second compression section when the third control for increasing the discharge capacity of the first compression section and the discharge capacity of the second compression section are stored.
When the control unit increases the heat exchange capacity of the low pressure heat exchanger during the high load control, the characteristics of the first compression unit are selected from the first control, the second control, and the third control. The refrigerator according to any one of claims 1 to 3, wherein the control with the lowest power consumption is selected based on characteristics of the second compression unit. The control unit acquires operation information of the first compression unit and the second compression unit ,
Based on the acquired operation information, the characteristics of the first compression unit and the characteristics of the second compression unit in the stored first control, second control, and third control are determined at predetermined intervals. The refrigerating machine according to claim 4, wherein the refrigerating machine is updated. 6. The refrigerator according to claim 5, wherein the obtained operation information of the first compression unit and the second compression unit is stored in a storage unit of the control unit. When the control unit increases the heat exchange capacity in the low pressure heat exchanger during the low load control,
The power consumption when the first compression unit is operated is compared with the power consumption when the second compression unit is operated, and the compression unit with low power consumption is operated. The refrigerator according to any one of 6. In the medium load control or the injection control, when the control unit determines that the cooling operation is possible at the maximum frequency of the first compression unit when reducing the heat exchange capacity in the low pressure heat exchanger,
The power consumption when the first compression unit is operated is compared with the power consumption when the second compression unit is operated, and the compression unit with low power consumption is operated. The refrigerator according to any one of 7.   The control unit permits execution of the injection control when it is determined that a pressure ratio, which is a ratio between the suction side pressure and the discharge side pressure of the first compression unit, is equal to or greater than a predetermined pressure ratio. The refrigerator according to any one of claims 1 to 8, wherein:

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