JP7229057B2 - Cooling system - Google Patents

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JP7229057B2
JP7229057B2 JP2019055738A JP2019055738A JP7229057B2 JP 7229057 B2 JP7229057 B2 JP 7229057B2 JP 2019055738 A JP2019055738 A JP 2019055738A JP 2019055738 A JP2019055738 A JP 2019055738A JP 7229057 B2 JP7229057 B2 JP 7229057B2
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彌 永田
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Sanden Retail Systems Corp
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Description

本発明は、例えば、冷凍ショーケースに適用される冷却装置に関するものである。 TECHNICAL FIELD The present invention relates to a cooling device applied, for example, to a freezer showcase.

従来、この種の冷却装置としては、低段側圧縮部及び高段側圧縮部を有する圧縮機、放熱器、低圧膨張弁、蒸発器が順に接続された主冷媒流路と、主冷媒流路における放熱器と低圧膨張弁との間から分岐して高段側圧縮部の冷媒吸入側に接続される中圧冷媒流路と、主冷媒流路における放熱器と低圧膨張弁との間を流通する冷媒と中圧冷媒流路を流通する冷媒とを熱交換する過冷却熱交換器と、中圧冷媒流路における過冷却熱交換器よりも冷媒流通方向上流側に設けられた中圧膨張弁と、を備えたものが知られている（例えば、特許文献１参照）。 Conventionally, this type of cooling device includes a main refrigerant flow path in which a compressor having a low-stage compression section and a high-stage compression section, a radiator, a low-pressure expansion valve, and an evaporator are connected in order, and a main refrigerant flow path. circulates between the intermediate-pressure refrigerant flow path branched from between the radiator and the low-pressure expansion valve in the main refrigerant flow path and connected to the refrigerant suction side of the high-stage compression unit, and the radiator and the low-pressure expansion valve in the main refrigerant flow path A supercooling heat exchanger that exchanges heat between the refrigerant that flows through the medium-pressure refrigerant passage and the refrigerant that flows through the medium-pressure refrigerant passage, and a medium-pressure expansion valve provided on the upstream side in the refrigerant flow direction of the supercooling heat exchanger in the medium-pressure refrigerant passage. and are known (see, for example, Patent Document 1).

前記冷却装置は、高段側圧縮部から吐出される冷媒の温度の上昇を抑制するため、高段側圧縮部に吸入される冷媒の過熱度が目標として設定された目標過熱度となるように、中圧膨張弁の弁開度を制御している。また、前記冷却装置は、低段側圧縮部における液圧縮及び低段側圧縮部から吐出される冷媒の温度の上昇を抑制するため、低段側圧縮部に吸入される冷媒の過熱度が目標として設定された目標過熱度となるように、低圧膨張弁の弁開度を制御している。 In order to suppress an increase in the temperature of the refrigerant discharged from the high-stage compression section, the cooling device controls the degree of superheat of the refrigerant sucked into the high-stage compression section to a target degree of superheat set as a target. , which controls the opening of the intermediate pressure expansion valve. In addition, the cooling device suppresses liquid compression in the low-stage compression section and temperature rise of the refrigerant discharged from the low-stage compression section. The valve opening degree of the low-pressure expansion valve is controlled so as to achieve the target degree of superheat set as .

特開２００９－１９２１６４号公報JP 2009-192164 A

前記冷却装置は、圧縮機を停止している状態から起動した後しばらくの間、冷媒回路における冷媒の温度や圧力等の冷媒の状態が不安定となる。冷媒回路における冷媒の状態が不安定な場合には、中圧膨張弁の弁開度及び低圧膨張弁の弁開度を同時に制御すると、主冷媒流路の低圧側及び中圧冷媒流路の一方の冷媒流量が多くなり、他方の冷媒流量が少なくなる状態が生じ得る。この場合に、冷却装置は、異常な状態での運転と判断して安全装置によって運転が停止される可能性がある。 In the cooling device, the state of the refrigerant such as the temperature and pressure of the refrigerant in the refrigerant circuit becomes unstable for a while after the compressor is started from a stopped state. When the state of the refrigerant in the refrigerant circuit is unstable, if the valve opening degree of the intermediate pressure expansion valve and the valve opening degree of the low pressure expansion valve are controlled simultaneously, the low pressure side of the main refrigerant channel and one of the intermediate pressure refrigerant channels A situation can occur in which the refrigerant flow rate of one increases and the refrigerant flow rate of the other decreases. In this case, the cooling device may be judged to be operating in an abnormal state and be stopped by the safety device.

本発明の目的とするところは、圧縮機の起動時、外乱変動時または外気や負荷変動など外乱の影響下において冷凍サイクル及び冷凍能力の安定化を図ることのできる冷却装置を提供することにある。 SUMMARY OF THE INVENTION An object of the present invention is to provide a cooling system capable of stabilizing the refrigerating cycle and refrigerating capacity when the compressor is started, during disturbance fluctuations, or under the influence of external disturbances such as outside air and load fluctuations. .

本発明の冷却装置は、前記目的を達成するために、低段側圧縮部及び高段側圧縮部を有する圧縮機、放熱器、低圧膨張弁、蒸発器が順に接続された主冷媒流路と、前記主冷媒流路における前記放熱器と前記低圧膨張弁との間から分岐して前記高段側圧縮部の冷媒吸入側に接続される中圧冷媒流路と、前記主冷媒流路における前記放熱器と前記低圧膨張弁との間を流通する冷媒と前記中圧冷媒流路を流通する冷媒とを熱交換する過冷却熱交換器と、前記中圧冷媒流路における前記過冷却熱交換器よりも冷媒流通方向の上流側に設けられ、前記中圧冷媒流路における冷媒の流量を制御する流量制御部と、前記主冷媒流路における高圧側の圧力を検出する圧力検出部と、前記放熱器の冷媒流出側の冷媒の温度を検出する放熱器出口温度検出部と、前記圧力検出部の検出圧力及び前記放熱器出口温度検出部の検出温度に基づいて冷媒の状態を取得し、取得した冷媒の状態が臨界圧力未満において液冷媒でない場合または臨界圧力以上における所定の密度以下となる場合に前記流量制御部によって前記中圧冷媒流路における冷媒の流れを遮断し、取得した冷媒の状態が臨界圧力未満における液冷媒となる場合または臨界圧力以上における前記所定の密度よりも大きい場合に前記流量制御部により前記中圧冷媒流路における冷媒の流れを調節する中圧冷媒流路開閉制御部と、を備えている。 In order to achieve the above object, the cooling device of the present invention includes a main refrigerant flow path in which a compressor having a low-stage compression section and a high-stage compression section, a radiator, a low-pressure expansion valve, and an evaporator are connected in this order. a medium-pressure refrigerant flow path branched from between the radiator and the low-pressure expansion valve in the main refrigerant flow path and connected to the refrigerant suction side of the high-stage compression section; a supercooling heat exchanger that exchanges heat between a refrigerant flowing between a radiator and the low-pressure expansion valve and a refrigerant flowing through the intermediate-pressure refrigerant channel; and the supercooling heat exchanger in the intermediate-pressure refrigerant channel. A flow control unit provided on the upstream side in the refrigerant flow direction of the intermediate-pressure refrigerant flow path for controlling the flow rate of the refrigerant in the medium-pressure refrigerant flow path, a pressure detection unit for detecting pressure on the high-pressure side in the main refrigerant flow path, and the heat dissipation A radiator outlet temperature detector that detects the temperature of the refrigerant on the refrigerant outflow side of the device, and acquires and acquires the state of the refrigerant based on the detected pressure of the pressure detector and the detected temperature of the radiator outlet temperature detector. When the state of the refrigerant is not a liquid refrigerant at less than the critical pressure, or when the density is less than a predetermined density at the critical pressure or higher, the flow rate control unit cuts off the flow of the refrigerant in the medium-pressure refrigerant flow path, and the obtained state of the refrigerant is a medium-pressure refrigerant flow path opening/closing control unit that adjusts the flow of the refrigerant in the medium-pressure refrigerant flow path by the flow control unit when the refrigerant becomes a liquid refrigerant at a pressure less than the critical pressure or when the refrigerant has a density greater than the predetermined density at a pressure equal to or higher than the critical pressure; , is equipped with

本発明によれば、冷媒回路を流通する冷媒の状態が不安定な場合に、中圧冷媒流路への冷媒の流通を規制して主冷媒流路の低圧側に冷媒を流通させることによって、冷媒回路における冷媒の不安定な状態を解消することができる。 According to the present invention, when the state of the refrigerant flowing through the refrigerant circuit is unstable, by regulating the flow of the refrigerant to the medium-pressure refrigerant flow path and allowing the refrigerant to flow to the low-pressure side of the main refrigerant flow path, The unstable state of the refrigerant in the refrigerant circuit can be eliminated.

本発明の一実施形態を示す冷却装置の概略構成図である。1 is a schematic configuration diagram of a cooling device showing an embodiment of the present invention; FIG. 制御系を示すブロック図である。3 is a block diagram showing a control system; FIG. 低圧膨張弁開度調整処理を示すフローチャートである。4 is a flowchart showing a low-pressure expansion valve opening adjustment process; 中圧冷媒流量調整処理を示すフローチャートである。4 is a flowchart showing medium-pressure refrigerant flow rate adjustment processing. 電磁弁の開閉の条件を示すｐ－ｈ線図である。4 is a ph diagram showing conditions for opening and closing a solenoid valve; FIG.

図１乃至図５は、本発明の一実施形態を示すものである。 1 to 5 show one embodiment of the invention.

本発明の冷却装置１は、例えば、コンビニエンスストアの店舗内に設置される冷凍ショーケースに適用されるものである。この冷却装置１は、図１に示すように、所謂二段圧縮一段膨張サイクルを構成する冷媒回路１０を備え、後述する蒸発器によってショーケースの商品収納部を冷却するものである。 The cooling device 1 of the present invention is applied, for example, to a freezer showcase installed in a convenience store. As shown in FIG. 1, the cooling device 1 includes a refrigerant circuit 10 that constitutes a so-called two-stage compression and one-stage expansion cycle, and cools a product storage section of a showcase by an evaporator, which will be described later.

冷媒回路１０は、圧縮機１１、放熱器１２、過冷却熱交換器１３、低圧膨張弁１４、蒸発器１５、流量制御部としての中圧膨張弁１６、流量制御部としての電磁弁１７をステンレス管や銅管によって接続することで構成されている。冷媒回路１０を流通する冷媒としては、高圧側が超臨界状態となる冷媒が用いられる。本実施形態で用いられる冷媒は、例えば、二酸化炭素である。 The refrigerant circuit 10 includes a compressor 11, a radiator 12, a supercooling heat exchanger 13, a low-pressure expansion valve 14, an evaporator 15, a medium-pressure expansion valve 16 as a flow rate control section, and an electromagnetic valve 17 as a flow rate control section. It consists of connecting by pipes or copper pipes. As the refrigerant that flows through the refrigerant circuit 10, a refrigerant that is in a supercritical state on the high pressure side is used. The refrigerant used in this embodiment is, for example, carbon dioxide.

圧縮機１１は、低段側圧縮部１１ａ及び高段側圧縮部１１ｂを有する二段圧縮機である。圧縮機１１は、吸入した冷媒を低段側圧縮部１１ａにおいて圧縮して吐出し、低段側圧縮部１１ａから吐出された冷媒を高段側圧縮部１１ｂにおいて圧縮して吐出する。 The compressor 11 is a two-stage compressor having a low-stage compression section 11a and a high-stage compression section 11b. The compressor 11 compresses the sucked refrigerant in the low-stage compression portion 11a and discharges it, and compresses the refrigerant discharged from the low-stage compression portion 11a in the high-stage compression portion 11b and discharges the refrigerant.

放熱器１２は、一対の冷媒流路が設けられた、例えば、フィンチューブ式の熱交換器である。放熱器１２は、圧縮機１１の低段側圧縮部１１ａから吐出された中圧冷媒が流通する中圧冷媒流路と、高段側圧縮部１１ｂから吐出された高圧冷媒が流通する高圧冷媒流路と、を有している。また、放熱器１２の近傍には、放熱器を流通する冷媒と熱交換する空気を流通させるための放熱器用送風機１２ａが設けられている。 The radiator 12 is, for example, a fin-tube heat exchanger provided with a pair of refrigerant flow paths. The radiator 12 has an intermediate-pressure refrigerant flow path through which the intermediate-pressure refrigerant discharged from the low-stage compression portion 11a of the compressor 11 flows, and a high-pressure refrigerant flow through which the high-pressure refrigerant discharged from the high-stage compression portion 11b flows. It has a road and In the vicinity of the radiator 12, a radiator blower 12a is provided for circulating air that exchanges heat with the refrigerant flowing through the radiator.

蒸発器１５は、ショーケースの商品収納部に供給する空気が流通する空気流通路に設けられている。蒸発器１５の近傍には、蒸発器１５を流通する冷媒と熱交換する空気を流通させるための蒸発器用送風機１５ａが設けられている。 The evaporator 15 is provided in the air flow path through which the air supplied to the commodity storage section of the showcase circulates. An evaporator blower 15a is provided in the vicinity of the evaporator 15 for circulating air that exchanges heat with the refrigerant flowing through the evaporator 15 .

冷媒回路１０の回路構成を具体的に説明すると、圧縮機１１の低段側圧縮部１１ａの冷媒吐出側には、放熱器１２の中圧冷媒流路の冷媒流入側を接続することにより冷媒流通路１０ａが形成されている。放熱器１２の中圧冷媒流路の冷媒流出側には、圧縮機１１の高段側圧縮部１１ｂの冷媒吸入側を接続することにより冷媒流通路１０ｂが接続されている。圧縮機１１の高段側圧縮部１１ｂの冷媒吐出側には、放熱器１２の高圧冷媒流路の冷媒流入側を接続することにより冷媒流通路１０ｃが形成されている。放熱器１２の高圧冷媒流路の冷媒流出側には、過冷却熱交換器１３の高圧冷媒流路の冷媒流入側を接続することにより冷媒流通路１０ｄが形成されている。過冷却熱交換器１３の高圧冷媒流路の冷媒流出側には、蒸発器１５の冷媒流入側を接続することにより冷媒流通路１０ｅが形成されている。冷媒流通路１０ｅには、低圧膨張弁１４が設けられている。蒸発器１５の冷媒流出側には、圧縮機１１の低段側圧縮部１１ａの冷媒吸入側を接続することにより冷媒流通路１０ｆが形成されている。冷媒回路１０においては、冷媒流通路１０ａ，１０ｂ，１０ｃ、１０ｄ，１０ｅ，１０ｆによって、圧縮機１１、放熱器１２、過冷却熱交換器１３の高圧冷媒流路、低圧膨張弁１４及び蒸発器１５を接続することによって主冷媒流路が構成される。 Specifically, the circuit configuration of the refrigerant circuit 10 will be described. A path 10a is formed. A refrigerant flow path 10b is connected to the refrigerant outlet side of the intermediate-pressure refrigerant flow path of the radiator 12 by connecting the refrigerant suction side of the high-stage compression portion 11b of the compressor 11 . A refrigerant flow path 10 c is formed by connecting the refrigerant inflow side of the high-pressure refrigerant flow path of the radiator 12 to the refrigerant discharge side of the high-stage compression portion 11 b of the compressor 11 . A refrigerant flow path 10 d is formed by connecting the refrigerant inflow side of the high pressure refrigerant flow path of the subcooling heat exchanger 13 to the refrigerant outflow side of the high pressure refrigerant flow path of the radiator 12 . A refrigerant flow path 10 e is formed by connecting the refrigerant inflow side of the evaporator 15 to the refrigerant outflow side of the high-pressure refrigerant flow path of the subcooling heat exchanger 13 . A low-pressure expansion valve 14 is provided in the refrigerant flow passage 10e. A refrigerant flow passage 10 f is formed on the refrigerant outflow side of the evaporator 15 by connecting the refrigerant suction side of the low-stage compression portion 11 a of the compressor 11 . In the refrigerant circuit 10, the refrigerant passages 10a, 10b, 10c, 10d, 10e, and 10f connect the compressor 11, the radiator 12, the high-pressure refrigerant passage of the subcooling heat exchanger 13, the low-pressure expansion valve 14, and the evaporator 15. A main refrigerant flow path is configured by connecting the .

また、放熱器１２の高圧冷媒流路の冷媒流出側には、冷媒流通路１０ｄから分岐して過冷却熱交換器１３の中圧冷媒流路の冷媒流入側を接続することにより冷媒流通路１０ｇが形成されている。冷媒流通路１０ｇには、冷媒流通路１０ｄ側から順に、中圧膨張弁１６、流路開閉弁としての電磁弁１７が向けられている。過冷却熱交換器１３の中圧冷媒流路の冷媒流出側には、圧縮機１１の高段側圧縮部１１ｂの冷媒吸入側を接続することにより冷媒流通路１０ｈが形成されている。冷媒回路１０においては、冷媒流通路１０ｇ，１０ｈによって、中圧膨張弁１６、電磁弁１７、過冷却熱交換器１３を接続することによって中圧冷媒流路が構成される。 Further, the refrigerant flow path 10g is branched from the refrigerant flow path 10d and connected to the refrigerant inflow side of the medium-pressure refrigerant flow path of the subcooling heat exchanger 13 to the refrigerant flow out side of the high pressure refrigerant flow path of the radiator 12. is formed. A medium-pressure expansion valve 16 and an electromagnetic valve 17 as a flow path opening/closing valve are directed to the refrigerant flow path 10g in this order from the refrigerant flow path 10d side. A refrigerant flow passage 10h is formed by connecting the refrigerant suction side of the high-stage compression portion 11b of the compressor 11 to the refrigerant outflow side of the medium-pressure refrigerant passage of the subcooling heat exchanger 13 . In the refrigerant circuit 10, a medium-pressure refrigerant flow path is configured by connecting the medium-pressure expansion valve 16, the electromagnetic valve 17, and the subcooling heat exchanger 13 with the refrigerant flow paths 10g and 10h.

また、冷却装置１は、冷媒回路１０の動作を制御するためのコントローラ２０を備えている。 The cooling device 1 also includes a controller 20 for controlling the operation of the refrigerant circuit 10 .

コントローラ２０は、ＣＰＵ、ＲＯＭ，ＲＡＭを有している。コントローラ２０は、入力側に接続された装置からの入力信号を受信すると、ＣＰＵが、入力信号に基づいてＲＯＭに記憶されたプログラムを読み出すとともに、入力信号によって検出された状態をＲＡＭに記憶したり、出力側に接続された装置に出力信号を送信したりする。 The controller 20 has a CPU, ROM, and RAM. When the controller 20 receives an input signal from a device connected to the input side, the CPU reads the program stored in the ROM based on the input signal, and stores the state detected by the input signal in the RAM. , and send an output signal to a device connected to the output side.

コントローラ２０の入力側には、図２に示すように、圧縮機１１と、放熱器１２の高圧冷媒流路の冷媒吐出側の圧力を検出するための圧力検出部としての圧力センサ２１と、高段側圧縮部１１ｂの冷媒吐出側の冷媒温度を検出するための吐出温度検出部としての第１温度センサ２２と、放熱器１２の高圧冷媒流路の冷媒吐出側の冷媒温度を検出するための放熱器出口温度検出部としての第２温度センサ２３と、過冷却熱交換器１３の高圧冷媒流路の冷媒流出側の冷媒温度を検出するための第３温度センサ２４と、蒸発器１５の冷媒流入側の冷媒温度を検出するための第４温度センサ２５と、蒸発器１５の冷媒流出側の冷媒温度を検出するための第５温度センサ２６と、過冷却熱交換器１３の中圧冷媒流路の冷媒流入側の温度を検出するための第６温度センサ２７と、高段側圧縮部１１ｂに吸入される冷媒の温度を検出するための第７温度センサ２８と、が接続されている。 On the input side of the controller 20, as shown in FIG. A first temperature sensor 22 as a discharge temperature detection section for detecting the refrigerant temperature on the refrigerant discharge side of the stage-side compression section 11b, and a refrigerant temperature on the refrigerant discharge side of the high-pressure refrigerant flow path of the radiator 12 A second temperature sensor 23 as a radiator outlet temperature detection unit, a third temperature sensor 24 for detecting the refrigerant temperature on the refrigerant outflow side of the high-pressure refrigerant flow path of the subcooling heat exchanger 13, and the refrigerant in the evaporator 15 A fourth temperature sensor 25 for detecting the refrigerant temperature on the inflow side, a fifth temperature sensor 26 for detecting the refrigerant temperature on the refrigerant outflow side of the evaporator 15, and a medium pressure refrigerant flow of the subcooling heat exchanger 13 A sixth temperature sensor 27 for detecting the temperature on the refrigerant inflow side of the passage and a seventh temperature sensor 28 for detecting the temperature of the refrigerant sucked into the high-stage compression portion 11b are connected.

また、コントローラ２０の出力側には、圧縮機１１、低圧膨張弁１４、中圧膨張弁１６及び電磁弁１７が接続されている。 Further, the compressor 11 , the low pressure expansion valve 14 , the medium pressure expansion valve 16 and the electromagnetic valve 17 are connected to the output side of the controller 20 .

以上のように構成された冷却装置１の冷媒回路１０において、圧縮機１１の低段側圧縮部１１ａから吐出された冷媒は、放熱器１２の中圧冷媒流路、高段側圧縮部１１ｂ、放熱器１２の高圧冷媒流路、の順に流通する。放熱器１２の高圧冷媒流路から流出した冷媒の一部は、過冷却熱交換器１３の高圧冷媒流路、低圧膨張弁１４、蒸発器１５、の順に流通して圧縮機１１の低段側圧縮部１１ａに吸入される。また、放熱器１２の高圧冷媒流路から流出したその他の冷媒は、中圧膨張弁１６、過冷却熱交換器１３の中圧冷媒流路、の順に流通して圧縮機１１の高段側圧縮部１１ｂに吸入される。 In the refrigerant circuit 10 of the cooling device 1 configured as described above, the refrigerant discharged from the low-stage compression portion 11a of the compressor 11 flows through the medium-pressure refrigerant flow path of the radiator 12, the high-stage compression portion 11b, , the high-pressure refrigerant flow path of the radiator 12 . A part of the refrigerant that has flowed out from the high-pressure refrigerant flow path of the radiator 12 flows through the high-pressure refrigerant flow path of the subcooling heat exchanger 13, the low-pressure expansion valve 14, and the evaporator 15 in that order, and flows to the low-stage side of the compressor 11. It is sucked into the compression section 11a. Further, the other refrigerant that has flowed out of the high-pressure refrigerant flow path of the radiator 12 flows through the medium-pressure expansion valve 16 and the medium-pressure refrigerant flow path of the supercooling heat exchanger 13 in this order, and is compressed by the compressor 11 on the high-stage side. It is sucked into the portion 11b.

これにより、放熱器１２の高圧冷媒流路から流出した冷媒の一部は、過冷却熱交換器１３において放熱し、低圧膨張弁１４において減圧されて蒸発器１５において吸熱する。また、放熱器１２の高圧冷媒流路から流出したその他の冷媒は、中圧膨張弁１６において減圧されて過冷却熱交換器１３において吸熱する。 As a result, part of the refrigerant that has flowed out of the high-pressure refrigerant channel of the radiator 12 radiates heat in the subcooling heat exchanger 13 , is decompressed in the low-pressure expansion valve 14 , and absorbs heat in the evaporator 15 . Further, the rest of the refrigerant that has flowed out of the high-pressure refrigerant channel of the radiator 12 is decompressed by the intermediate-pressure expansion valve 16 and absorbs heat in the supercooling heat exchanger 13 .

また、蒸発器１５では、冷媒が吸熱することによって、空気が冷媒と熱交換して冷却される。ショーケースの商品収納部内は、蒸発器１５において冷却された空気によって冷却される。 In addition, in the evaporator 15, the air is cooled by exchanging heat with the refrigerant as the refrigerant absorbs heat. The inside of the product storage portion of the showcase is cooled by the air cooled by the evaporator 15 .

さらに、冷媒回路１０では、低圧膨張弁１４の弁開度を調整することによって、圧縮機１１の低段側圧縮部１１ａに吸入される冷媒の過熱度を制御することで、圧縮機１１の低段側圧縮部１１ａにおける液圧縮や低段側圧縮部１１ａから吐出される冷媒の温度の異常な温度の上昇を抑制している。 Furthermore, in the refrigerant circuit 10, the degree of superheat of the refrigerant sucked into the low-stage compression section 11a of the compressor 11 is controlled by adjusting the valve opening degree of the low-pressure expansion valve 14, thereby This suppresses an abnormal temperature rise of the liquid compression in the stage-side compression section 11a and the temperature of the refrigerant discharged from the low-stage-side compression section 11a.

また、冷媒回路１０では、中圧膨張弁１６の弁開度を調整することによって、過冷却熱交換器１３の高圧冷媒流路から流出する冷媒の過冷却度を制御し、冷却装置１の成績係数の向上を図っている。さらに、冷媒回路１０では、中圧膨張弁１６の弁開度を調整することによって、圧縮機１１の高段側圧縮部１１ｂに吸入される冷媒の過熱度を制御し、高段側圧縮部１１ｂにおける液圧縮や高段側圧縮部１１ｂから吐出される冷媒の温度の異常な温度の上昇を抑制している。 Further, in the refrigerant circuit 10, by adjusting the valve opening degree of the intermediate pressure expansion valve 16, the degree of supercooling of the refrigerant flowing out from the high pressure refrigerant flow path of the supercooling heat exchanger 13 is controlled, and the performance of the cooling device 1 is improved. We are trying to improve the coefficient. Further, in the refrigerant circuit 10, the degree of superheat of the refrigerant sucked into the high-stage compression portion 11b of the compressor 11 is controlled by adjusting the valve opening degree of the intermediate-pressure expansion valve 16. This suppresses an abnormal temperature rise of the liquid compression in and the temperature of the refrigerant discharged from the high-stage compression portion 11b.

コントローラ２０は、低圧膨張弁開度制御部として、低段側圧縮部１１ａに吸入される冷媒の過熱度を制御するとともに、高段側圧縮部１１ｂから吐出される冷媒の異常な温度の上昇を抑制するために、低圧膨張弁１４の弁開度を調整する低圧膨張弁開度調整処理を行う。このときのコントローラ２０の動作を図３のフローチャートを用いて説明する。 The controller 20, as a low-pressure expansion valve opening control section, controls the degree of superheat of the refrigerant sucked into the low-stage compression section 11a, and prevents an abnormal temperature rise of the refrigerant discharged from the high-stage compression section 11b. In order to suppress this, low-pressure expansion valve opening degree adjustment processing is performed to adjust the valve opening degree of the low-pressure expansion valve 14 . The operation of the controller 20 at this time will be described with reference to the flowchart of FIG.

（ステップＳ１）
ステップＳ１においてＣＰＵは、圧縮機１１が起動されたか否かを判定する。圧縮機１１が起動されたと判定した場合にはステップＳ２に処理を移し、圧縮機１１が起動されたと判定しなかった場合にはステップＳ１の処理を繰り返す。 (Step S1)
In step S1, the CPU determines whether or not the compressor 11 has been started. If it is determined that the compressor 11 has been started, the process proceeds to step S2, and if it is not determined that the compressor 11 has been started, the process of step S1 is repeated.

（ステップＳ２）
ステップＳ１において圧縮機１１が起動されたと判定した場合に、ステップＳ２においてＣＰＵは、圧縮機１１の低段側圧縮部１１ａに吸入される冷媒の過熱度を制御する低段側過熱度制御を実行し、ステップＳ３に処理を移す。 (Step S2)
When it is determined in step S1 that the compressor 11 has been started, in step S2 the CPU executes low-stage superheat degree control for controlling the degree of superheat of the refrigerant sucked into the low-stage compression section 11a of the compressor 11. Then, the process moves to step S3.

ここで、低段側過熱度制御は、第４温度センサ２５の検出温度Ｔ４及び第５温度センサ２６の検出温度Ｔ５に基づいて低圧膨張弁１４の弁開度を調整する。具体的には、第４温度センサ２５の検出温度Ｔ４と第５温度センサ２６の検出温度Ｔ５との温度差（Ｔ５－Ｔ４）が所定温度差となるように、低圧膨張弁１４の弁開度を調整する。 Here, the low-stage superheat degree control adjusts the valve opening degree of the low-pressure expansion valve 14 based on the detected temperature T4 of the fourth temperature sensor 25 and the detected temperature T5 of the fifth temperature sensor 26 . Specifically, the opening degree of the low-pressure expansion valve 14 is adjusted so that the temperature difference (T5-T4) between the temperature T4 detected by the fourth temperature sensor 25 and the temperature T5 detected by the fifth temperature sensor 26 becomes a predetermined temperature difference. to adjust.

（ステップＳ３）
ステップＳ３においてＣＰＵは、圧力センサ２１の検出圧力ＰｓＨが所定の圧力Ｐｓ１以上か否かを判定する。圧力センサ２１の検出圧力ＰｓＨが所定の圧力Ｐｓ１以上と判定した場合にはステップＳ４に処理を移し、圧力センサ２１の検出圧力ＰｓＨが所定の圧力Ｐｓ１以上と判定しなかった場合にはステップＳ２に処理を移す。 (Step S3)
In step S3, the CPU determines whether or not the pressure PsH detected by the pressure sensor 21 is greater than or equal to a predetermined pressure Ps1. If it is determined that the pressure PsH detected by the pressure sensor 21 is equal to or higher than the predetermined pressure Ps1, the process proceeds to step S4, and if it is determined that the pressure PsH detected by the pressure sensor 21 is not equal to or higher than the predetermined pressure Ps1, the process proceeds to step S2. transfer processing.

（ステップＳ４）
ステップＳ４においてＣＰＵは、低圧膨張弁１４の弁開度を所定開度開いて固定し、ステップＳ５に処理を移す。 (Step S4)
In step S4, the CPU fixes the valve opening degree of the low-pressure expansion valve 14 at a predetermined opening degree, and shifts the process to step S5.

（ステップＳ５）
ステップＳ５においてＣＰＵは、低圧膨張弁１４の弁開度を維持し、ステップＳ６に処理を移す。 (Step S5)
In step S5, the CPU maintains the valve opening degree of the low-pressure expansion valve 14, and shifts the process to step S6.

（ステップＳ６）
ステップＳ５において低圧膨張弁１４の弁開度を維持した後、ステップＳ６においてＣＰＵは、圧力センサ２１の検出圧力ＰｓＨが所定の圧力Ｐｓ２（Ｐｓ２＜Ｐｓ１）以下か否かを判定する。圧力センサ２１の検出圧力ＰｓＨが所定の圧力Ｐｓ２以下と判定した場合にはステップＳ２に処理を移し、圧力センサ２１の検出圧力ＰｓＨが所定の圧力Ｐｓ２以下と判定しなかった場合にはステップＳ５に処理を移す。 (Step S6)
After maintaining the valve opening degree of the low-pressure expansion valve 14 in step S5, the CPU determines whether or not the pressure PsH detected by the pressure sensor 21 is equal to or lower than a predetermined pressure Ps2 (Ps2<Ps1) in step S6. If it is determined that the pressure PsH detected by the pressure sensor 21 is equal to or less than the predetermined pressure Ps2, the process proceeds to step S2, and if it is determined that the pressure PsH detected by the pressure sensor 21 is not equal to or less than the predetermined pressure Ps2, the process proceeds to step S5. transfer processing.

また、コントローラ２０は、中圧冷媒流路開閉制御部及び中圧膨張弁開度制御部として、圧縮機１１の起動時における冷媒の不安定さを回避するために中圧冷媒流路の開閉を切り替える制御、過冷却熱交換器１３の高圧冷媒流路の冷媒吐出側の冷媒の過冷却度の制御、及び、圧縮機１１の高段側圧縮部１１ｂに吸入される冷媒の過熱度の制御、を切り替えて実行する中圧冷媒流量調整処理を行う。このときのコントローラ２０の動作を図４のフローチャートを用いて説明する。 In addition, the controller 20 functions as a medium-pressure refrigerant flow path opening/closing control unit and a medium-pressure expansion valve opening degree control unit to open and close the medium-pressure refrigerant flow path to avoid instability of the refrigerant when the compressor 11 is started. Switching control, control of the degree of supercooling of the refrigerant on the refrigerant discharge side of the high-pressure refrigerant flow path of the supercooling heat exchanger 13, and control of the degree of superheat of the refrigerant sucked into the high-stage compression portion 11b of the compressor 11, medium-pressure refrigerant flow rate adjustment processing that is executed by switching between . The operation of the controller 20 at this time will be described with reference to the flowchart of FIG.

（ステップＳ１１）
ステップＳ１１においてＣＰＵは、圧縮機１１が起動されたか否かを判定する。圧縮機１１が起動されたと判定した場合にはステップＳ１２に処理を移し、圧縮機１１が起動されたと判定しなかった場合にはステップＳ１１の処理を繰り返す。 (Step S11)
In step S11, the CPU determines whether or not the compressor 11 has been started. When it is determined that the compressor 11 has been started, the process proceeds to step S12, and when it is not determined that the compressor 11 has been started, the process of step S11 is repeated.

（ステップＳ１２）
ステップＳ１２においてＣＰＵは、電磁弁１７を閉鎖し、ステップＳ１３に処理を移す。 (Step S12)
In step S12, the CPU closes the solenoid valve 17 and shifts the process to step S13.

（ステップＳ１３）
ステップＳ１３においてＣＰＵは、電磁弁１７を開放するための条件が成立したか否かを判定する。電磁弁１７を開放するための条件が成立したと判定した場合にはステップＳ１４に処理を移し、電磁弁１７を開放するための条件が成立したと判定しなかった場合にはステップＳ１２に処理を移す。 (Step S13)
In step S13, the CPU determines whether or not the conditions for opening the solenoid valve 17 are satisfied. If it is determined that the condition for opening the solenoid valve 17 is satisfied, the process proceeds to step S14, and if it is not determined that the condition for opening the solenoid valve 17 is satisfied, the process proceeds to step S12. Move.

ここで、電磁弁１７を開放するための条件とは、圧力センサ２１の検出圧力ＰｓＨ及び第２温度センサ２３の検出温度Ｔ２から取得される放熱器１２の高圧冷媒流路の冷媒吐出側における冷媒の状態が、所定の状態となって所定時間継続した場合である。具体的に説明すると、コントローラ２０は、図５に示すように、記憶領域に二酸化炭素のｐ－ｈ線図（圧力－比エンタルピ線図）に関するテーブルを備えており、入力された圧力及び温度のデータに対応する冷媒の状態に関するデータを出力する。図５のｐ－ｈ線図における符号ａは、等温線を示す。また、図５のｐ－ｈ線図における符号ｂは、それぞれ、等密度線であり、右側から順に、３００ｋｇ／ｍ３、４００ｋｇ／ｍ３、４８０ｋｇ／ｍ３、７３０ｋｇ／ｍ３の等密度線を示す。電磁弁１７を開放するための条件の一つである冷媒の所定の状態とは、臨界圧力未満における液冷媒となる場合または臨界圧力以上における所定の密度よりも大きい場合である（図５における線Ｌよりも左側）。ここで、所定の密度は、３００ｋｇ／ｍ３以上７３０ｋｇ／ｍ３以下の範囲内であることが好ましく、４００ｋｇ／ｍ３以上４８０ｋｇ／ｍ３以下の範囲内であることがより好ましい。 Here, the condition for opening the solenoid valve 17 is the refrigerant on the refrigerant discharge side of the high-pressure refrigerant flow path of the radiator 12 obtained from the detected pressure PsH of the pressure sensor 21 and the detected temperature T2 of the second temperature sensor 23. is a predetermined state and continues for a predetermined period of time. Specifically, as shown in FIG. 5, the controller 20 has a table on the ph diagram (pressure-specific enthalpy diagram) of carbon dioxide in the storage area, and the input pressure and temperature Output data about the state of the refrigerant corresponding to the data. Symbol a in the ph diagram of FIG. 5 indicates an isothermal line. In addition, the symbols b in the ph diagram of FIG. 5 are contour lines, and the contour lines of 300 kg/m 3 , 400 kg/m 3 , 480 kg/m 3 and 730 kg/m 3 in order from the right side. indicates The predetermined state of the refrigerant, which is one of the conditions for opening the solenoid valve 17, is when the refrigerant becomes a liquid refrigerant below the critical pressure or when the density is greater than a predetermined value above the critical pressure (the line in FIG. left of L). Here, the predetermined density is preferably within the range of 300 kg/m 3 or more and 730 kg/m 3 or less, more preferably within the range of 400 kg/m 3 or more and 480 kg/m 3 or less.

（ステップＳ１４）
ステップＳ１３において電磁弁１７を開放するための条件が成立したと判定した場合に、ステップＳ１４においてＣＰＵは、電磁弁１７を開放してステップＳ１５に処理を移す。 (Step S14)
When it is determined in step S13 that the condition for opening the solenoid valve 17 is satisfied, the CPU opens the solenoid valve 17 in step S14 and shifts the process to step S15.

（ステップＳ１５）
ステップＳ１５においてＣＰＵは、過冷却熱交換器１３の高圧冷媒流路の冷媒吐出側の冷媒の過冷却度を制御する過冷却度制御を実行し、ステップＳ１６に処理を移す。 (Step S15)
In step S15, the CPU executes degree-of-supercooling control for controlling the degree of supercooling of the refrigerant on the refrigerant discharge side of the high-pressure refrigerant flow path of the supercooling heat exchanger 13, and shifts the process to step S16.

ここで、過冷却度制御は、第２温度センサ２３の検出温度Ｔ２及び第３温度センサ２４の検出温度Ｔ３に基づいて中圧膨張弁１６の弁開度を制御する。具体的には、第２温度センサ２３の検出温度Ｔ２と第３温度センサの検出温度Ｔ３との温度差（Ｔ３－Ｔ２）が目標として設定された温度差となるように、中圧膨張弁１６の弁開度を調整する。 Here, the degree of supercooling control controls the valve opening degree of the intermediate pressure expansion valve 16 based on the detected temperature T2 of the second temperature sensor 23 and the detected temperature T3 of the third temperature sensor 24 . Specifically, the medium-pressure expansion valve 16 is adjusted so that the temperature difference (T3-T2) between the detected temperature T2 of the second temperature sensor 23 and the detected temperature T3 of the third temperature sensor becomes the target temperature difference. Adjust the opening of the valve.

（ステップＳ１６）
ステップＳ１６においてＣＰＵは、電磁弁１７を閉鎖するための条件が成立したか否かを判定する。電磁弁１７を閉鎖するための条件が成立したと判定した場合にはステップＳ１２に処理を移し、電磁弁１７を開放するための条件が成立したと判定しなかった場合にはステップＳ１７に処理を移す。 (Step S16)
In step S16, the CPU determines whether or not the conditions for closing the solenoid valve 17 are satisfied. If it is determined that the condition for closing the electromagnetic valve 17 is satisfied, the process proceeds to step S12, and if it is not determined that the condition for opening the electromagnetic valve 17 is satisfied, the process proceeds to step S17. Move.

ここで、電磁弁１７を閉鎖するための条件とは、圧力センサ２１の検出圧力ＰｓＨ及び第２温度センサ２３の検出温度Ｔ２から取得される放熱器１２の高圧冷媒流路の冷媒吐出側における冷媒の状態が、所定の状態となって所定時間継続した場合である。電磁弁１７を閉鎖するための条件の一つである冷媒の所定の状態とは、臨界圧力未満において液冷媒でない場合または臨界圧力以上における所定の密度（３００ｋｇ／ｍ３以上７３０ｋｇ／ｍ３以下の範囲内、より好ましくは、４００ｋｇ／ｍ３以上４８０ｋｇ／ｍ３以下の範囲内）以下となる場合である（図５における線Ｌを含む右側）。 Here, the condition for closing the solenoid valve 17 is the refrigerant on the refrigerant discharge side of the high-pressure refrigerant flow path of the radiator 12 obtained from the detected pressure PsH of the pressure sensor 21 and the detected temperature T2 of the second temperature sensor 23. is a predetermined state and continues for a predetermined period of time. The predetermined state of the refrigerant, which is one of the conditions for closing the solenoid valve 17, is when the refrigerant is not liquid at a pressure less than the critical pressure or at a predetermined density (300 kg/m 3 or more and 730 kg/m 3 or less) at the critical pressure or higher. within the range, more preferably within the range of 400 kg/m 3 or more and 480 kg/m 3 or less (the right side including the line L in FIG. 5).

（ステップＳ１７）
ステップＳ１６において電磁弁１７を開放するための条件が成立したと判定しなかった場合に、ステップＳ１７においてＣＰＵは、第１温度センサ２２の検出温度Ｔ１が第１所定温度Ｔｓ１以上であるか否かを判定する。第１温度センサ２２の検出温度Ｔ１が第１所定温度Ｔｓ１以上であると判定した場合にはステップＳ１８に処理を移し、第１温度センサ２２の検出温度Ｔ１が第１所定温度Ｔｓ１以上であると判定しなかった場合にはステップＳ１５に処理を移す。 (Step S17)
If it is not determined in step S16 that the condition for opening the solenoid valve 17 is satisfied, in step S17 the CPU determines whether the temperature T1 detected by the first temperature sensor 22 is equal to or higher than the first predetermined temperature Ts1. judge. When it is determined that the detected temperature T1 of the first temperature sensor 22 is equal to or higher than the first predetermined temperature Ts1, the process proceeds to step S18, and it is determined that the detected temperature T1 of the first temperature sensor 22 is equal to or higher than the first predetermined temperature Ts1. If not determined, the process proceeds to step S15.

ここで、第１温度センサ２２の検出温度Ｔ１が第１所定温度Ｔｓ１以上である状態は、ステップＳ１５において過冷却度制御を行った結果、過冷却熱交換器１３の中圧冷媒流路を流通する冷媒の吸熱量が増加し、高段側圧縮部１１ｂに吸入される冷媒の過熱度が高くなった状態である。 Here, when the detected temperature T1 of the first temperature sensor 22 is equal to or higher than the first predetermined temperature Ts1, as a result of the supercooling degree control in step S15, In this state, the amount of heat absorbed by the refrigerant is increased, and the degree of superheat of the refrigerant sucked into the high-stage compression portion 11b is increased.

（ステップＳ１８）
ステップＳ１８においてＣＰＵは、圧縮機１１の高段側圧縮部１１ｂに吸入される冷媒の過熱度を制御する高段側過熱度制御を実行し、ステップＳ１９に処理を移す。 (Step S18)
In step S18, the CPU executes high-stage superheat degree control for controlling the degree of superheat of the refrigerant sucked into the high-stage compression section 11b of the compressor 11, and shifts the process to step S19.

ここで、高段側過熱度制御は、第６温度センサ２７の検出温度Ｔ６及び第７温度センサ２８の検出温度Ｔ７に基づいて中圧膨張弁１６の弁開度を調整する。具体的には、第６温度センサ２７の検出温度Ｔ６と第７温度センサ２８の検出温度Ｔ７との温度差（Ｔ６－Ｔ７）が目標として設定された温度差となるように、中圧膨張弁１６の弁開度を調整する。 Here, the high stage side superheat degree control adjusts the valve opening degree of the intermediate pressure expansion valve 16 based on the detected temperature T6 of the sixth temperature sensor 27 and the detected temperature T7 of the seventh temperature sensor 28 . Specifically, the intermediate-pressure expansion valve is adjusted so that the temperature difference (T6-T7) between the detected temperature T6 of the sixth temperature sensor 27 and the detected temperature T7 of the seventh temperature sensor 28 becomes the target temperature difference. 16 valve openings are adjusted.

（ステップＳ１９）
ステップＳ１９においてＣＰＵは、第１温度センサ２２の検出温度Ｔ１が第２所定温度Ｔｓ２（Ｔｓ２＜Ｔｓ１）未満であるか否かを判定する。第１温度センサ２２の検出温度Ｔ１が第２所定温度Ｔｓ２未満であると判定した場合にはステップＳ１５に処理を移し、第１温度センサ２２の検出温度Ｔ１が第２所定温度Ｔｓ２未満であると判定しなかった場合にはステップＳ１８に処理を移す。 (Step S19)
In step S19, the CPU determines whether or not the temperature T1 detected by the first temperature sensor 22 is lower than the second predetermined temperature Ts2 (Ts2<Ts1). When it is determined that the detected temperature T1 of the first temperature sensor 22 is less than the second predetermined temperature Ts2, the process proceeds to step S15, and it is determined that the detected temperature T1 of the first temperature sensor 22 is less than the second predetermined temperature Ts2. If not determined, the process proceeds to step S18.

ここで、第１温度センサ２２の検出温度Ｔ１が第２所定温度Ｔｓ２未満である状態は、高段側過熱度制御によって、高段側圧縮部１１ｂに吸入される冷媒の過熱度が適正な過熱度となった状態である。 Here, the state in which the detected temperature T1 of the first temperature sensor 22 is lower than the second predetermined temperature Ts2 means that the degree of superheat of the refrigerant sucked into the high stage side compression portion 11b is appropriate due to the high stage side superheat degree control. It is in a state of

このように、本実施形態の冷却装置１によれば、コントローラ２０は、圧力センサ２１の検出圧力ＰｓＨ及び第２温度センサ２３の検出温度Ｔ２に基づいて冷媒の状態を取得し、取得した冷媒の状態が臨界圧力未満において液冷媒でない場合または臨界圧力以上における所定の密度以下となる場合に電磁弁１７を閉鎖して中圧冷媒流路における冷媒の流通を遮断し、取得した冷媒の状態が臨界圧力未満における液冷媒となる場合または臨界圧力以上における所定の密度よりも大きい場合に電磁弁１７を開放して中圧冷媒流路における冷媒の流通を調節する。 Thus, according to the cooling device 1 of the present embodiment, the controller 20 acquires the state of the refrigerant based on the detected pressure PsH of the pressure sensor 21 and the detected temperature T2 of the second temperature sensor 23, If the state is not a liquid refrigerant at less than the critical pressure, or if the density is less than a predetermined value at the critical pressure or higher, the electromagnetic valve 17 is closed to block the flow of the refrigerant in the intermediate pressure refrigerant flow path, and the obtained state of the refrigerant is critical. When the refrigerant becomes a liquid refrigerant below the pressure or when the density is greater than a predetermined value above the critical pressure, the electromagnetic valve 17 is opened to adjust the flow of the refrigerant in the intermediate pressure refrigerant passage.

これにより、冷媒回路１０を流通する冷媒の状態が不安定な場合に、中圧冷媒流路への冷媒の流通を規制して主冷媒流路の低圧側に冷媒を流通させることによって、冷媒回路１０における冷媒の不安定な状態を解消することができる。よって、冷凍サイクルの冷凍能力が急激に低下するような状態を解消することができる。 As a result, when the state of the refrigerant flowing through the refrigerant circuit 10 is unstable, by regulating the flow of the refrigerant to the medium-pressure refrigerant flow path and allowing the refrigerant to flow to the low-pressure side of the main refrigerant flow path, the refrigerant circuit Refrigerant instability at 10 can be eliminated. Therefore, it is possible to eliminate a state in which the refrigerating capacity of the refrigerating cycle is rapidly lowered.

また、冷媒回路１０を流通する冷媒は、二酸化炭素であり、臨界圧力以上における所定の密度は、３００ｋｇ／ｍ３以上７３０ｋｇ／ｍ３以下の範囲内、より好ましくは、４００ｋｇ／ｍ３以上４８０ｋｇ／ｍ３以下の範囲内である。 Further, the refrigerant flowing through the refrigerant circuit 10 is carbon dioxide, and the predetermined density at the critical pressure or higher is in the range of 300 kg/ m3 or more and 730 kg/m3 or less, more preferably 400 kg/m3 or more and 480 kg/m3 or less. is within the range of

これにより、臨界圧力以上における３００ｋｇ／ｍ３以上７３０ｋｇ／ｍ３以下の範囲内、より好ましくは、４００ｋｇ／ｍ３以上４８０ｋｇ／ｍ３以下の範囲内の冷媒の密度を基準として電磁弁１７の開閉を切り替えることによって、冷媒回路１０を流通する冷媒の状態が不安定となる状態を確実に抑制することが可能となる。 As a result, the opening and closing of the electromagnetic valve 17 can be switched based on the density of the refrigerant within the range of 300 kg/ m3 or more and 730 kg/m3 or less, more preferably, within the range of 400 kg/m3 or more and 480 kg/m3 or less at the critical pressure or higher. Thus, it is possible to reliably prevent the state of the refrigerant flowing through the refrigerant circuit 10 from becoming unstable.

また、コントローラ２０は、電磁弁１７を開放した状態において、過冷却熱交換器１３の高圧冷媒流路の冷媒流出側の冷媒の過冷却度が目標として設定した目標過冷却度となるように前記中圧膨張弁１６の弁開度を制御する。 In addition, the controller 20 controls the degree of supercooling of the refrigerant on the refrigerant outflow side of the high-pressure refrigerant flow path of the supercooling heat exchanger 13 in a state in which the electromagnetic valve 17 is open so that the degree of supercooling reaches the target degree of supercooling set as a target. Controls the degree of valve opening of the intermediate pressure expansion valve 16 .

これにより、過冷却熱交換器１３の高圧冷媒流路の冷媒流出側の冷媒の過冷却度を目標過冷却度とすることによって、成績係数（ＣＯＰ）の高い運転を行って運転効率の向上を図ることが可能となる。 As a result, by setting the degree of supercooling of the refrigerant on the refrigerant outflow side of the high-pressure refrigerant flow path of the supercooling heat exchanger 13 to the target degree of supercooling, operation with a high coefficient of performance (COP) is performed to improve operating efficiency. It is possible to plan

また、コントローラ２０は、過冷却熱交換器１３の高圧冷媒流路の冷媒流出側の冷媒の過冷却度が目標過冷却度となるように中圧膨張弁１６の弁開度を制御している状態で、第１温度センサ２２によって第１所定温度Ｔｓ１以上の温度が検出されると、過冷却熱交換器１３の中圧冷媒流路の冷媒流出側の冷媒の過熱度が目標として設定された目標過熱度となるように中圧膨張弁１６の弁開度を制御する。 Further, the controller 20 controls the degree of opening of the medium-pressure expansion valve 16 so that the degree of supercooling of the refrigerant on the refrigerant outflow side of the high-pressure refrigerant flow path of the supercooling heat exchanger 13 reaches the target degree of supercooling. In this state, when the first temperature sensor 22 detects a temperature equal to or higher than the first predetermined temperature Ts1, the degree of superheat of the refrigerant on the refrigerant outflow side of the medium-pressure refrigerant passage of the subcooling heat exchanger 13 is set as a target. The degree of valve opening of the intermediate pressure expansion valve 16 is controlled so as to achieve the target degree of superheat.

これにより、過冷却熱交換器１３の中圧冷媒流路の冷媒流出側の冷媒の過熱度を目標過熱度とすることによって、圧縮機１１の高段側圧縮部１１ｂから吐出される冷媒の温度の上昇を抑制することが可能となる。 As a result, by setting the degree of superheat of the refrigerant on the refrigerant outflow side of the medium-pressure refrigerant passage of the subcooling heat exchanger 13 to the target degree of superheat, the temperature of the refrigerant discharged from the high-stage compression portion 11b of the compressor 11 It is possible to suppress the increase in

また、コントローラ２０は、過冷却熱交換器１３の中圧冷媒流路の冷媒流出側の冷媒の過熱度が目標過熱度となるように前記中圧膨張弁の弁開度を制御している状態で、第１温度センサ２２によって第２所定温度Ｔｓ２未満の温度が検出されると、過冷却熱交換器１３の高圧冷媒流路の冷媒流出側の冷媒の過冷却度が目標過冷却度となるように中圧膨張弁１６の弁開度を制御する。 Further, the controller 20 controls the degree of opening of the medium-pressure expansion valve so that the degree of superheat of the refrigerant on the refrigerant outflow side of the medium-pressure refrigerant flow path of the subcooling heat exchanger 13 reaches the target degree of superheat. Then, when a temperature lower than the second predetermined temperature Ts2 is detected by the first temperature sensor 22, the degree of subcooling of the refrigerant on the refrigerant outflow side of the high-pressure refrigerant flow path of the subcooling heat exchanger 13 reaches the target degree of supercooling. The valve opening degree of the intermediate pressure expansion valve 16 is controlled as follows.

これにより、圧縮機１１の高段側圧縮部１１ｂから吐出される冷媒の温度の上昇を抑制することによって圧縮機１１における異常な温度上昇を回避しながら、高効率な運転を継続することが可能となる。 As a result, it is possible to continue highly efficient operation while avoiding an abnormal temperature rise in the compressor 11 by suppressing the temperature rise of the refrigerant discharged from the high stage compression portion 11b of the compressor 11. becomes.

また、コントローラ２０は、圧力センサ２１によって所定より大きい圧力Ｐｓ１が検出されると、低圧膨張弁１４の弁開度を全開とする。 Further, when the pressure sensor 21 detects a pressure Ps1 higher than a predetermined value, the controller 20 fully opens the low-pressure expansion valve 14 .

これにより、圧縮機１１の低段側圧縮部１１ａに吸入される冷媒の過熱度を低下させることが可能となり、圧縮機１１における異常な温度上昇を回避することが可能となる。 As a result, the degree of superheat of the refrigerant sucked into the low-stage compression portion 11a of the compressor 11 can be reduced, and an abnormal temperature rise in the compressor 11 can be avoided.

尚、前記実施形態では、冷却装置１としてショーケースの商品収納部を冷却するものを示したが、これに限られるものではない。本発明の冷却装置は、ショーケース以外の冷凍庫や冷蔵庫に適用可能である。 In the above-described embodiment, the cooling device 1 is shown to cool the product storage section of the showcase, but the cooling device 1 is not limited to this. The cooling device of the present invention can be applied to freezers and refrigerators other than showcases.

また、前記実施形態では、電磁弁１７の開閉によって中圧冷媒流路の開閉を切り替えるようにしたものを示したが、これに限られるものではない。例えば、全閉と全開との間で開度の調整が可能なパイロット電磁弁を中圧膨張弁として用いることによって、電磁弁１７を用いることなく中圧冷媒流路の開閉を切り替えることが可能となる。 Further, in the above-described embodiment, switching between opening and closing of the medium-pressure refrigerant flow path is performed by opening and closing the electromagnetic valve 17, but the present invention is not limited to this. For example, by using a pilot solenoid valve whose opening degree can be adjusted between fully closed and fully opened as a medium pressure expansion valve, it is possible to switch between opening and closing of the medium pressure refrigerant flow path without using the solenoid valve 17. Become.

１…冷却装置、１０…冷媒回路、１１…圧縮機、１１ａ…低段側圧縮部、１１ｂ…高段側圧縮部、１２…放熱器、１３…過冷却熱交換器、１４…低圧膨張弁、１５…蒸発器、１６…中圧膨張弁、１７…電磁弁、２０…コントローラ、２１…圧力センサ、２２…第１温度センサ、２３…第２温度センサ、２４…第３温度センサ、２５…第４温度センサ、２６…第５温度センサ、２７…第６温度センサ、２８…第７温度センサ。 DESCRIPTION OF SYMBOLS 1... Cooling device, 10... Refrigerant circuit, 11... Compressor, 11a... Low stage side compression part, 11b... High stage side compression part, 12... Radiator, 13... Supercooling heat exchanger, 14... Low-pressure expansion valve, 15... Evaporator, 16... Intermediate pressure expansion valve, 17... Solenoid valve, 20... Controller, 21... Pressure sensor, 22... First temperature sensor, 23... Second temperature sensor, 24... Third temperature sensor, 25... Third temperature sensor 4 temperature sensors, 26... fifth temperature sensor, 27... sixth temperature sensor, 28... seventh temperature sensor.

Claims (7)

低段側圧縮部及び高段側圧縮部を有する圧縮機、放熱器、低圧膨張弁、蒸発器が順に接続された主冷媒流路と、
前記主冷媒流路における前記放熱器と前記低圧膨張弁との間から分岐して前記高段側圧縮部の冷媒吸入側に接続される中圧冷媒流路と、
前記主冷媒流路における前記放熱器と前記低圧膨張弁との間を流通する冷媒と前記中圧冷媒流路を流通する冷媒とを熱交換する過冷却熱交換器と、
前記中圧冷媒流路における前記過冷却熱交換器よりも冷媒流通方向の上流側に設けられ、前記中圧冷媒流路における冷媒の流量を制御する流量制御部と、
前記主冷媒流路における高圧側の圧力を検出する圧力検出部と、
前記放熱器の冷媒流出側の冷媒の温度を検出する放熱器出口温度検出部と、
前記圧力検出部の検出圧力及び前記放熱器出口温度検出部の検出温度に基づいて冷媒の状態を取得し、取得した冷媒の状態が臨界圧力未満において液冷媒でない場合または臨界圧力以上における所定の密度以下となる場合に前記流量制御部によって前記中圧冷媒流路における冷媒の流れを遮断し、取得した冷媒の状態が臨界圧力未満における液冷媒となる場合または臨界圧力以上における前記所定の密度よりも大きい場合に前記流量制御部により前記中圧冷媒流路における冷媒の流れを調節する中圧冷媒流路開閉制御部と、を備えた
冷却装置。 a main refrigerant flow path in which a compressor having a low-stage compression section and a high-stage compression section, a radiator, a low-pressure expansion valve, and an evaporator are connected in this order;
a medium-pressure refrigerant flow path branched from between the radiator and the low-pressure expansion valve in the main refrigerant flow path and connected to the refrigerant suction side of the high-stage compression section;
a supercooling heat exchanger that exchanges heat between refrigerant flowing between the radiator and the low-pressure expansion valve in the main refrigerant flow path and refrigerant flowing through the intermediate-pressure refrigerant flow path;
a flow control unit provided upstream in the refrigerant flow direction of the subcooling heat exchanger in the medium-pressure refrigerant flow path and controlling the flow rate of refrigerant in the medium-pressure refrigerant flow path;
a pressure detection unit that detects the pressure on the high pressure side in the main refrigerant channel;
a radiator outlet temperature detection unit that detects the temperature of the refrigerant on the refrigerant outflow side of the radiator;
The state of the refrigerant is acquired based on the pressure detected by the pressure detection unit and the temperature detected by the radiator outlet temperature detection unit, and if the obtained state of the refrigerant is not a liquid refrigerant at a pressure below the critical pressure or a predetermined density at a pressure above the critical pressure In the following cases, the flow rate control unit cuts off the flow of the refrigerant in the medium-pressure refrigerant flow path, and the obtained refrigerant state becomes a liquid refrigerant at a pressure less than the critical pressure, or the density is higher than the predetermined density at a pressure equal to or higher than the critical pressure. a medium-pressure refrigerant flow path opening/closing control section that adjusts the flow of refrigerant in the medium-pressure refrigerant flow path by the flow rate control section when the flow rate is large. 前記主冷媒流路及び前記中圧冷媒流路を流通する冷媒は、二酸化炭素であり、
前記所定の密度は、３００ｋｇ／ｍ３以上７３０ｋｇ／ｍ３以下の範囲内である
請求項１に記載の冷却装置。 the refrigerant flowing through the main refrigerant channel and the medium-pressure refrigerant channel is carbon dioxide;
The cooling device according to claim 1, wherein the predetermined density is within a range of 300 kg/ m3 or more and 730 kg/m3 or less. 前記中圧冷媒流路開閉制御部は、前記中圧冷媒流路における冷媒の流れを許容する状態において、前記主冷媒流路における前記過冷却熱交換器の冷媒流出側の冷媒の過冷却度が目標として設定した目標過冷却度となるように前記流量制御部によって前記中圧冷媒流路における冷媒の流量を制御する
請求項１または２に記載の冷却装置。 The intermediate-pressure refrigerant channel opening/closing control unit is configured to control the degree of subcooling of the refrigerant on the refrigerant outflow side of the supercooling heat exchanger in the main refrigerant channel in a state in which the flow of refrigerant in the intermediate-pressure refrigerant channel is permitted. The cooling device according to claim 1 or 2, wherein the flow control unit controls the flow rate of the refrigerant in the medium-pressure refrigerant flow path so as to achieve a target subcooling degree set as a target. 前記高段側圧縮部の吐出側の冷媒の温度を検出する吐出温度検出部を備え、
前記中圧冷媒流路開閉制御部は、前記過冷却度が目標過冷却度となるように前記流量制御部によって前記中圧冷媒流路における冷媒の流量を制御している状態で、前記吐出温度検出部によって第１所定温度以上の温度が検出されると、前記中圧冷媒流路における前記過冷却熱交換器の冷媒流出側の冷媒の過熱度が目標として設定された目標過熱度となるように前記流量制御部によって前記中圧冷媒流路における冷媒の流量を制御する
請求項３に記載の冷却装置。 a discharge temperature detection unit that detects the temperature of the refrigerant on the discharge side of the high-stage compression unit;
The intermediate-pressure refrigerant flow channel opening/closing control unit controls the flow rate of the refrigerant in the intermediate-pressure refrigerant flow channel by the flow control unit so that the degree of subcooling becomes a target degree of subcooling, and the discharge temperature When a temperature equal to or higher than the first predetermined temperature is detected by the detection unit, the degree of superheat of the refrigerant on the refrigerant outflow side of the subcooling heat exchanger in the medium-pressure refrigerant flow path is controlled so as to reach a target degree of superheat set as a target. 4 . The cooling device according to claim 3 , wherein the flow rate control unit controls the flow rate of the refrigerant in the medium-pressure refrigerant flow path. 前記中圧冷媒流路開閉制御部は、前記過熱度が目標過熱度となるように前記流量制御部によって前記中圧冷媒流路における冷媒の流量を制御している状態で、前記吐出温度検出部によって第２所定温度未満の温度が検出されると、前記過冷却度が目標過冷却度となるように前記流量制御部によって前記中圧冷媒流路における冷媒の流量を制御する
請求項４に記載の冷却装置。 The intermediate-pressure refrigerant flow path opening/closing control unit controls the flow rate of the refrigerant in the intermediate-pressure refrigerant flow path by the flow control unit so that the degree of superheat becomes a target degree of superheat, and the discharge temperature detection unit When a temperature lower than a second predetermined temperature is detected by cooling system. 前記蒸発器の冷媒流出側における冷媒の過熱度を制御するために前記低圧膨張弁の弁開度を調整している状態で、前記圧力検出部によって第１所定圧力以上の圧力が検出されると、前記低圧膨張弁の弁開度を所定開度まで開放する低圧膨張弁開度制御部を備えた
請求項１乃至５のいずれかに記載の冷却装置。 When the pressure detection unit detects a pressure equal to or higher than a first predetermined pressure in a state in which the valve opening degree of the low-pressure expansion valve is adjusted in order to control the degree of superheat of the refrigerant on the refrigerant outflow side of the evaporator, 6. The cooling device according to any one of claims 1 to 5, further comprising a low-pressure expansion valve opening degree control section for opening the valve opening degree of the low-pressure expansion valve to a predetermined opening degree. 前記低圧膨張弁開度制御部は、前記圧力検出部によって第２所定圧力以下の圧力が検出されると、前記蒸発器の冷媒流出側における冷媒の過熱度を制御するために前記低圧膨張弁の弁開度を調整する
請求項６に記載の冷却装置。 The low-pressure expansion valve opening controller controls the degree of superheat of the refrigerant on the refrigerant outflow side of the evaporator when the pressure detector detects a pressure equal to or lower than a second predetermined pressure. The cooling device according to claim 6, wherein the valve opening degree is adjusted.
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