JP2004037057A

JP2004037057A - Ejector cycle

Info

Publication number: JP2004037057A
Application number: JP2002198884A
Authority: JP
Inventors: Hirotsugu Takeuchi; 武内　裕嗣; Hiroshi Oshitani; 押谷　洋; Mika Saito; 齋藤　美歌
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2002-07-08
Filing date: 2002-07-08
Publication date: 2004-02-05
Anticipated expiration: 2022-07-08
Also published as: JP4078901B2

Abstract

<P>PROBLEM TO BE SOLVED: To prevent stagnation of a large quantity of the refrigerator oil in an evaporator. <P>SOLUTION: A check valve 81 is provided in a second oil return passage 80 for connecting a coolant outlet side of the evaporator 30 to a coolant suction side of a compressor 10, and the check valve 81 is set to be opened when the pressure of the coolant outlet side of the evaporator 30 becomes larger than the pressure of the coolant suction side of the compressor 10 and a pressure difference between them becomes the predetermined pressure difference or more. With this structure, when the refrigerator oil inside of the evaporator 30 is reduced, the check valve 81 is closed to automatically transfer operation mode from the oil return mode to the normal operation mode. Inversely, when a large quantity of the refrigerator oil inside of the evaporator 30 stays, the check valve 81 is opened to automatically transfer operation mode from the normal operation mode to the oil return mode, and the refrigerator oil staying in the evaporator 30 can be controlled to the predetermined rate or less to return a sufficient quantity of the refrigerator oil to the compressor 10. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、エジェクタサイクルに関するものである。
【０００２】
【従来の技術及び発明が解決しようとする課題】
エジェクタサイクルとは、例えば特開平５−１４９６５２号公報に記載のごとく、エジェクタにて冷媒を減圧膨張させて蒸発器にて蒸発した気相冷媒を吸引するとともに、膨張エネルギーを圧力エネルギーに変換して圧縮機の吸入圧を上昇させる蒸気圧縮式冷凍機である。
【０００３】
ところで、膨張弁等の減圧手段により等エンタルピ的に冷媒を減圧する蒸気圧縮式冷凍機（以下、膨張弁サイクルと呼ぶ。）では、膨張弁を流出した冷媒が蒸発器に流れ込むのに対して、エジェクタサイクルでは、エジェクタを流出した冷媒は気液分離器に流入し、気液分離器にて分離された液相冷媒が蒸発器に供給され、気液分離器にて分離された気相冷媒が圧縮機に吸入される。
【０００４】
つまり、膨張弁サイクルでは、冷媒が圧縮機→放熱器→膨張弁→蒸発器→圧縮機の順に循環する１つの冷媒流れとなるのに対して、エジェクタサイクルでは、圧縮機→放熱器→エジェクタ→気液分離器→圧縮機の順に循環する冷媒流れ（以下、駆動流と呼ぶ。）と、気液分離器→蒸発器→エジェクタ→気液分離器の順に循環する冷媒流れ（吸引流と呼ぶ。）とが存在する。
【０００５】
しかも、駆動流は圧縮機により直接的に循環させられるのに対して、吸引流は圧縮機にて圧縮された高圧冷媒の有するエネルギーを利用したエジェクタのポンプ作用（ＪＩＳ　Ｚ　８１２６　番号２．１．２．３等参照）により循環させられる。
【０００６】
このため、エジェクタのポンプ作用が低下すると、吸引流の流量が低下し、冷媒に混合された冷凍機油が蒸発器内に滞留してしまうので、蒸発器の吸熱能力が低下するとともに、圧縮機に戻ってくる冷凍機油が減少して圧縮機の潤滑不足を招くおそれが高い。
【０００７】
因みに、冷凍機油とは、圧縮機の摺動部を潤滑する潤滑油であり、一般的な蒸気圧縮式冷凍機では、冷媒に冷凍機油を混合することにより圧縮機内の摺動部を潤滑する。
【０００８】
本発明は、上記点に鑑み、第１には、従来と異なる新規なエジェクタサイクルを提供し、第２には、多量の冷凍機油が蒸発器内に滞留してしまうを防止することを目的とする。
【０００９】
【課題を解決するための手段】
本発明は、上記目的を達成するために、請求項１に記載の発明では、低温側の熱を高温側に移動させる蒸気圧縮式のエジェクタサイクルであって、圧縮機（１０）から吐出した高圧冷媒の熱を放熱する高圧側熱交換器（２０）と、低圧冷媒を蒸発させる低圧側熱交換器（３０）と、高圧冷媒を等エントロピ的に減圧膨張させるノズル（４１）を有し、ノズル（４１）から噴射する高い速度の冷媒流により低圧側熱交換器（３０）にて蒸発した気相冷媒を吸引するとともに、膨張エネルギーを圧力エネルギーに変換して圧縮機（１０）の吸入圧を上昇させるエジェクタ（４０）と、エジェクタ（４０）から流出した冷媒を気相冷媒と液相冷媒とに分離し、気相冷媒用出口が圧縮機（１０）の吸引側に接続され、液相冷媒用出口が低圧側熱交換器（３０）に接続された気液分離手段（５０）と、低圧側熱交換器（３０）の冷媒出口側と圧縮機（１０）の冷媒吸入側とを繋ぐ冷媒通路（８０）を構成する配管手段と、冷媒通路（８０）に冷媒を流す場合と流さない場合とを切り換えるバルブ（８１）とを具備し、冷媒通路（８０）に冷媒を流すことにより低圧側熱交換器（３０）内に滞留した冷凍機油を圧縮機（１０）に戻すオイル戻しモードを備えることを特徴とする。
【００１０】
これにより、低圧側熱交換器（３０）内に滞留する冷凍機油を所定量以下に制御して圧縮機（１０）に十分な量の冷凍機油を戻すことができるとともに、従来と異なる新規なエジェクタサイクルを得ることができる。
【００１１】
請求項２に記載の発明では、バルブ（８１）は、低圧側熱交換器（３０）の冷媒出口側の圧力が圧縮機（１０）の冷媒吸入側の圧力より大きくなり、かつ、その圧力差が所定圧力差以上となったときに、冷媒通路（８０）に冷媒を流すように構成されていることを特徴とするものである。
【００１２】
請求項３に記載の発明では、バルブ（８１）は、弁口を開閉する弁体（８１ａ）、及び弁体（８１ａ）に弁口を閉じる向きの弾性力を作用させるバネ手段（８１ｂ）を有して構成されていることを特徴とするものである。
【００１３】
請求項４に記載の発明では、バルブ（９１）は、エジェクタ（４０）の効率が所定値以下となったときに、冷媒通路（８０）に冷媒を流すように構成されていることを特徴とするものである。
【００１４】
請求項５に記載の発明では、低温側の熱を高温側に移動させる蒸気圧縮式のエジェクタサイクルであって、圧縮機（１０）から吐出した高圧冷媒の熱を放熱する高圧側熱交換器（２０）と、低圧冷媒を蒸発させる低圧側熱交換器（３０）と、高圧冷媒を等エントロピ的に減圧膨張させるノズル（４１）を有し、ノズル（４１）から噴射する高い速度の冷媒流により低圧側熱交換器（３０）にて蒸発した気相冷媒を吸引するとともに、膨張エネルギーを圧力エネルギーに変換して圧縮機（１０）の吸入圧を上昇させるエジェクタ（４０）と、エジェクタ（４０）から流出した冷媒を気相冷媒と液相冷媒とに分離し、気相冷媒用出口が圧縮機（１０）の吸引側に接続され、液相冷媒用出口が低圧側熱交換器（３０）に接続された気液分離手段（５０）と、圧縮機（１０）から吐出した冷媒をノズル（４１）を迂回させて低圧側熱交換器（３０）に導く冷媒通路（９０）を構成する配管手段と、冷媒通路（９０）に冷媒を流す場合と流さない場合とを切り換えるバルブ（９１）とを具備し、冷媒通路（８０）に冷媒を流すことにより低圧側熱交換器（３０）内に滞留した冷凍機油を圧縮機（１０）に戻すオイル戻しモードを備えることを特徴とする。
【００１５】
これにより、低圧側熱交換器（３０）内に滞留する冷凍機油を所定量以下に制御して圧縮機（１０）に十分な量の冷凍機油を戻すことができるとともに、従来と異なる新規なエジェクタサイクルを得ることができる。
【００１６】
請求項６に記載の発明では、冷媒通路（９０）には、冷媒を等エンタルピ的に減圧膨脹させる減圧手段（９３）が設けられていることを特徴とするものである。
【００１７】
請求項７に記載の発明では、冷媒として二酸化炭素が用いられていることを特徴とするものである。
【００１８】
請求項８に記載の発明では、冷媒として炭化水素が用いられていることを特徴とするものである。
【００１９】
請求項９に記載の発明では、冷媒としてフロンが用いられていることを特徴とするものである。
【００２０】
因みに、上記各手段の括弧内の符号は、後述する実施形態に記載の具体的手段との対応関係を示す一例である。
【００２１】
【発明の実施の形態】
（第１実施形態）
本実施形態は、本発明に係るエジェクタサイクルを、食品を冷蔵・冷凍保存するショーケース用の蒸気圧縮式冷凍機に適用したものであって、図１はエジェクタサイクルの模式図である。
【００２２】
圧縮機１０は冷媒を吸入圧縮する電動式の圧縮機であり、放熱器２０は圧縮機１０から吐出した高温・高圧の冷媒と室外空気とを熱交換して冷媒を冷却する高圧側熱交換器である。
【００２３】
また、蒸発器３０は、ショーケース内に吹き出す空気と低圧冷媒とを熱交換させて液相冷媒を蒸発させることにより冷凍能力を発揮する低圧側熱交換器であり、エジェクタ４０は放熱器２０から流出する冷媒を減圧膨張させて蒸発器３０にて蒸発した気相冷媒を吸引するとともに、膨張エネルギーを圧力エネルギーに変換して圧縮機１０の吸入圧を上昇させるエジェクタである。
【００２４】
そして、エジェクタ４０は、図２に示すように、流入する高圧冷媒の圧力エネルギーを速度エネルギーに変換して冷媒を等エントロピ的に減圧膨張させるノズル４１、ノズル４１から噴射する高い速度の冷媒流の巻き込み作用により蒸発器３０にて蒸発した気相冷媒を吸引しながら、ノズル４１から噴射する冷媒流とを混合する混合部４２、及びノズル４１から噴射する冷媒と蒸発器３０から吸引した冷媒とを混合させながら速度エネルギーを圧力エネルギーに変換して冷媒の圧力を昇圧させるディフューザ４３等からなるものである。
【００２５】
このとき、混合部４２においては、駆動流の運動量と吸引流の運動量との和が保存されるように駆動流と吸引流とが混合するので、混合部４２においても冷媒の圧力が（静圧）が上昇する。
【００２６】
一方、ディフューザ４３においては、通路断面積を徐々に拡大することにより、冷媒の速度エネルギ（動圧）を圧力エネルギ（静圧）に変換するので、エジェクタ４０においては、混合部４２及びディフューザ４３の両者にて冷媒圧力を昇圧する。そこで、以下、混合部４２とディフューザ４３とを総称して昇圧部と呼ぶ。
【００２７】
因みに、本実施形態では、ノズル４１から噴出する冷媒の速度を音速以上まで加速するために、通路途中に通路面積が最も縮小した喉部４１ａを有するラバールノズル（流体工学（東京大学出版会）参照）を採用しているが、勿論、先細ノズルを採用してもよいことは言うまでもない。
【００２８】
また、図１中、気液分離器５０はエジェクタ４０から流出した冷媒が流入するとともに、その流入した冷媒を気相冷媒と液相冷媒とに分離して冷媒を蓄える気液分離手段であり、気液分離器５０の気相冷媒流出口は圧縮機１０の吸引側に接続され、液相冷媒流出口は蒸発器３０側に接続されている。
【００２９】
絞り６０は気液分離器５０から流出した液相冷媒を減圧する減圧手段であり、第１オイル戻し通路７０は気液分離器５０にて分離された冷凍機油を圧縮機１０の吸入側に戻すものである。
【００３０】
第２オイル戻し通路８０は、蒸発器３０の冷媒出口側と圧縮機１０の冷媒吸入側とを繋ぐ冷媒通路であり、第２オイル戻し通路８０には、冷媒が蒸発器３０の冷媒出口側から圧縮機１０の冷媒吸入側に向かって流れることのみを許容する逆止弁８１が設けられており、この逆止弁８１が開閉することにより第２オイル戻し通路８０に冷媒を流す場合と流さない場合とが制御される。
【００３１】
ここで、逆止弁８１は、弁口を開閉する弁体８１ａ、及び弁体８１ａに弁口を閉じる向きの弾性力を作用させるバネ８１ｂを有して構成されたもので、弁体８１ａ及びバネ８１ｂは、蒸発器３０の冷媒出口側の圧力が圧縮機１０の冷媒吸入側の圧力より大きくなり、かつ、その圧力差が所定圧力差以上となったときに第２オイル戻し通路８０を開くように設定されている。
【００３２】
なお、図１の逆止弁８１は、ＪＩＳ　Ｂ　０１２５に従った逆止弁の記号であり、図１に示された弁体８１ａ及びバネ８１ｂの形状は、必ずしも実際の形状を示すものではない。
【００３３】
また、本実施形態では、冷媒を二酸化炭素とするとともに、図３に示すように、圧縮機１０にてノズル４１に流入する高圧冷媒を冷媒の臨界圧力以上まで昇圧している。因みに、図３の●で示される符号は、図１に示す●で示される符号位置における冷媒の状態を示すものである。
【００３４】
次に、本実施形態に係るサイクルの作動及び特徴点を述べる。
【００３５】
１．通常運転モード（図３参照）
圧縮機１０から吐出した冷媒を放熱器２０側に循環させる。これにより、放熱器２０にて冷却された冷媒は、エジェクタ４０のノズル４１にて等エントロピ的に減圧膨張して、音速以上の速度で混合部４２内に流入する。
【００３６】
そして、混合部４２に流入した高速冷媒の巻き込み作用に伴うポンプ作用により、蒸発器３０内で蒸発した冷媒が混合部４２内に吸引されるため、低圧側の冷媒が気液分離器５０→絞り６０→蒸発器３０→エジェクタ４０（昇圧部）→気液分離器５０の順に循環する。
【００３７】
一方、蒸発器３０から吸引された冷媒（吸引流）とノズル４１から吹き出す冷媒（駆動流）とは、混合部４２にて混合しながらディフューザ４３にてその動圧が静圧に変換されて気液分離器５０に戻る。
【００３８】
２．オイル戻しモード
本モードは、冷媒に混合された状態でエジェクタサイクル内を循環する冷凍機油が蒸発器３０内に所定量以上滞留した場合や外気温度が低下した場合等のエジェクタ効率ηｅが低下した場合又はエジェクタ４０のポンプ作用が低下した場合に自動的に実行されるモードである。
【００３９】
因みに、エジェクタ効率ηｅとは、放熱器２０を流通する冷媒の質量流量Ｇｎとノズル４１の出入口のエンタルピ差Δｉｅとの積を分母とし、分子には、圧縮機１０の仕事としてエネルギがどの程度回収されたかを示す冷媒流量Ｇｎと蒸発器３０を流通する冷媒の質量流量Ｇｅとの和とエジェクタ４０での圧力回復ΔＰを置いて定義したものである。具体的には、エジェクタ４０に吸引される前の吸引冷媒の速度エネルギを考慮して、以下の数式１で定義した。
【００４０】
【数１】

すなわち、エジェクタ４０のポンプ作用が十分に大きいときには、エジェクタ４０での圧力回復ΔＰ、つまりエジェクタ４０での昇圧量ΔＰが大きいため、図４に示すように、逆止弁８１を挟んで圧縮機１０の冷媒吸入側の圧力Ｐ３が相対的に蒸発器３０の冷媒出口側の圧力Ｐ１より大きくなり、第２オイル戻し通路８０は逆止弁８１により閉じられ、第２オイル戻し通路８０に冷媒は流れない。
【００４１】
しかし、エジェクタ４０のポンプ作用が小さくなると、逆止弁８１を挟んで蒸発器３０の冷媒出口側の圧力Ｐ１が相対的に圧縮機１０の冷媒吸入側の圧力Ｐ３より大きくなるため、図５に示すように、逆止弁８１が開き、第２オイル戻し通路８０に冷媒が流れる。
【００４２】
したがって、蒸発器３０の冷媒出口側が直接的に圧縮機１０の吸入側と連通するので、エジェクタ４０のポンプ作用が小さくても、蒸発器３０内に滞留していた冷凍機油が圧縮機１０に向かって流れ、冷凍機油の滞留が解消される。
【００４３】
そして、蒸発器３０内の冷凍機油が減少すると、蒸発器３０での冷凍能力が増大して吸引流及び駆動流の流量が増大するため、エジェクタ４０のポンプ作用が大きくなり、逆止弁８１を挟んで圧縮機１０の冷媒吸入側の圧力Ｐ３が相対的に蒸発器３０の冷媒出口側の圧力Ｐ１より大きくなる。
【００４４】
つまり、蒸発器３０内の冷凍機油が減少すると、逆止弁８１が閉じて自動的にオイル戻しモードから通常運転モードに移行し、逆に、蒸発器３０内の多量の冷凍機油が滞留すると、逆止弁８１が開いて自動的に通常運転モードからオイル戻しモードに移行する。
【００４５】
以上に述べたように、本実施形態では、蒸発器３０内に滞留する冷凍機油を所定量以下に制御して圧縮機１０に十分な量の冷凍機油を戻すことができる。
【００４６】
なお、図６は本実施形態に係るエジェクタサイクルにおける圧縮機１０内の冷凍機油量の変化、並びに第２オイル戻し通路８０及び逆止弁８１を有していない通常のエジェクタサイクルにおける圧縮機１０内の冷凍機油量の変化を示す試験結果であり、この結果からも明らかなように、本実施形態では、蒸発器３０内に滞留する冷凍機油を所定量以下に制御して圧縮機１０に十分な量の冷凍機油を戻すことができることが解る。
【００４７】
因みに、図７はエジェクタ効率ηｅを約４０％としたときの、外気温度とエジェクタ４０での昇圧量ΔＰとの関係を示すグラフ（数値シミレーション結果）である。
【００４８】
（第２実施形態）
第１実施形態では、機械式バルブをなす逆止弁８１により第２オイル戻し通路８０を開閉したが、本実施形態は、図８に示すように、逆止弁８１に代えて電磁弁８２とするとともに、圧力センサ８３ａ、８３ｂによりエジェクタ４０での昇圧量ΔＰを検出し、エジェクタ４０での昇圧量ΔＰが所定値以下となったときに電磁弁８２を開き、エジェクタ４０での昇圧量ΔＰが所定値を超えたときに電磁弁８２を閉じるようにしたものである。
【００４９】
なお、本実施形態は、電磁弁８２を閉じる時の所定値と電磁弁８３を閉じる時の所定値とを相違させても実施することができる。
【００５０】
また、本実施形態では、エジェクタ４０での昇圧量ΔＰをパラメータとして電磁弁８２の開閉制御を行ったが、本実施形態はこれに限定されるものではなく、例えば圧縮機１０の回転数、冷媒温度及び冷媒圧力等からエジェクタ効率ηｅを算出し、エジェクタ効率ηｅが所定値以下となったときに電磁弁８２を開き、エジェクタ効率ηｅが所定値を超えたときに電磁弁８２を閉じるようにしてもよい。この際、電磁弁８２を閉じる時のエジェクタ効率ηｅの所定値と電磁弁８３を閉じる時のエジェクタ効率ηｅの所定値とを相違させてもよいことは言うまでもない。
【００５１】
（第３実施形態）
本実施形態は、図９〜１２に示すように、第２オイル戻し通路８０を廃止し、圧縮機１０から吐出した冷媒をノズル４１を迂回させて蒸発器３０に導くバイパス通路９０を設けるとともに、バイパス通路９０と高圧冷媒通路との分岐部にバイパス通路９０に冷媒を流す場合と流さない場合とを切り換える三方弁９１を設け、バイパス通路９０に冷媒を等エントロピ的に減圧膨脹させる膨脹弁９３を設けたものである。
【００５２】
そして、エジェクタ４０での昇圧量ΔＰが所定値以下となったとき又はエジェクタ効率ηｅが所定値以下となったときにバイパス通路９０に冷媒を流してオイル戻しモードを実施し、エジェクタ４０での昇圧量ΔＰが所定値を超えたとき又はエジェクタ効率ηｅが所定値を超えたときにバイパス通路９０側を閉じて通常運転モードを行うもである。
【００５３】
因みに、膨脹弁９３は、蒸発器３０の冷媒出口側における冷媒過熱度が所定値となるように絞り開度を制御する機械式又は電気式の減圧器であるが、キャピラリーチューブやオリフィス等の固定絞りとしてもよい。
【００５４】
なお、図９、１１に示すエジェクタサイクルでは、オイル戻しモード時には、高圧冷媒がノズル４１に流入せず高圧冷媒の全量が膨脹弁９３に流れるので、オイル戻しモード時には、あたかも、膨脹弁サイクルと同様な冷媒流れとなる。
【００５５】
（第４実施形態）
本実施形態は、第３実施形態の変形例である。具体的には、図１３に示すように、膨脹弁９３を全閉可能なバルブとすることにより三方弁９１を廃止したものである。
【００５６】
すなわち、通常運転モード時には膨脹弁９３を全閉とし、オイル戻しモード時には、膨脹弁９３を開くことによりバイパス通路９０に冷媒を流すものである。
【００５７】
なお、図１３は第３実施形態の図９に対して本実施形態を適用したものであるが、図１０〜１２に対しても本実施形態を適用することができることは言うまでもない。
【００５８】
（その他の実施形態）
上述の実施形態では、二酸化炭素を冷媒としたが、本発明はこれに限定されるものではなく、例えば冷媒として炭化水素やフロン等を用いてもよい。
【００５９】
また、上述の実施形態では、高圧側冷媒圧力を臨界圧力以上としたが、本発明はこれに限定されるものではない。
【００６０】
また、上述の実施形態では、本発明に係るエジェクタサイクルを、食品を冷蔵・冷凍保存するショーケース用の蒸気圧縮式冷凍機に適用したが、本発明の適用はこれに限定されるものではなく、例えば空調装置にも適用することができる。
【００６１】
また、本発明は、オイル戻しモード時に、圧縮機１０により蒸発器３０内の冷凍機油を直接的に吸引する、又は圧縮機１０の吐出圧により直接的に蒸発器３０内の冷凍機油を押し出すものであるから、上述の実施形態に限定されるものではない。
【００６２】
また、ノズル４１の入口側に蒸発器３０の冷媒出口側における冷媒過熱度が所定値となるように絞り開度を制御するバルブを設けてもよい。
【００６３】
また、放熱器２０から流出した高圧冷媒と圧縮機１０に吸入される低圧冷媒とを熱交換する内部熱交換器を設けてもよい。
【図面の簡単な説明】
【図１】本発明の第１実施形態に係るエジェクタサイクルの模式図である。
【図２】本発明の実施形態に係るエジェクタの模式図である。
【図３】ｐ−ｈ線図である。
【図４】本発明の第１実施形態に係るエジェクタサイクルの作動説明図である。
【図５】本発明の第１実施形態に係るエジェクタサイクルの作動説明図である。
【図６】オイル戻し効果を示すグラフである。
【図７】エジェクタの性能低下を示すグラフである。
【図８】本発明の第２実施形態に係るエジェクタサイクルの模式図である。
【図９】本発明の第３実施形態に係るエジェクタサイクルの模式図である。
【図１０】本発明の第３実施形態に係るエジェクタサイクルの模式図である。
【図１１】本発明の第３実施形態に係るエジェクタサイクルの模式図である。
【図１２】本発明の第３実施形態に係るエジェクタサイクルの模式図である。
【図１３】本発明の第４実施形態に係るエジェクタサイクルの模式図である。
【符号の説明】
１０…圧縮機、２０…放熱器、３０…蒸発器、４０…エジェクタ、５０…気液分離器、６０…絞り、８０…第２オイル戻し通路、８１…逆止弁。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ejector cycle.
[0002]
Problems to be solved by the prior art and the invention
The ejector cycle is, for example, as described in JP-A-5-149652, in which the refrigerant is decompressed and expanded by the ejector, the vapor-phase refrigerant evaporated by the evaporator is sucked, and the expansion energy is converted into pressure energy. This is a vapor compression refrigerator that raises the suction pressure of the compressor.
[0003]
By the way, in a vapor compression refrigerator (hereinafter, referred to as an expansion valve cycle) in which the refrigerant is isenthalpically depressurized by a decompression means such as an expansion valve, the refrigerant flowing out of the expansion valve flows into an evaporator. In the ejector cycle, the refrigerant flowing out of the ejector flows into the gas-liquid separator, the liquid-phase refrigerant separated by the gas-liquid separator is supplied to the evaporator, and the gas-phase refrigerant separated by the gas-liquid separator is It is sucked into the compressor.
[0004]
That is, in the expansion valve cycle, the refrigerant becomes one refrigerant flow circulating in the order of compressor → radiator → expansion valve → evaporator → compressor, whereas in the ejector cycle, the refrigerant → compressor → radiator → ejector → A refrigerant flow circulating in the order of gas-liquid separator → compressor (hereinafter, referred to as a driving flow) and a refrigerant flow circulating in the order of gas-liquid separator → evaporator → ejector → gas-liquid separator (referred to as suction flow). ) And exists.
[0005]
In addition, the driving flow is directly circulated by the compressor, whereas the suction flow is a pumping action of the ejector utilizing the energy of the high-pressure refrigerant compressed by the compressor (JIS Z 8126 No. 2.1. (See 2.3 etc.).
[0006]
For this reason, when the pumping action of the ejector decreases, the flow rate of the suction flow decreases, and the refrigerating machine oil mixed with the refrigerant stays in the evaporator. There is a high possibility that the amount of returned refrigerating machine oil will decrease, resulting in insufficient lubrication of the compressor.
[0007]
Incidentally, the refrigerating machine oil is lubricating oil for lubricating a sliding part of the compressor. In a general vapor compression type refrigerating machine, a sliding part in the compressor is lubricated by mixing refrigerating machine oil with a refrigerant.
[0008]
The present invention has been made in view of the above circumstances, and has as its first object to provide a new ejector cycle different from the conventional one, and secondly to prevent a large amount of refrigerating machine oil from remaining in an evaporator. I do.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, there is provided a vapor compression type ejector cycle for transferring heat on a low-temperature side to a high-temperature side, the high-pressure ejector cycle being discharged from a compressor (10). A nozzle having a high-pressure side heat exchanger for releasing heat of the refrigerant (20), a low-pressure side heat exchanger for evaporating the low-pressure refrigerant (30), and a nozzle (41) for isoentropically decompressing and expanding the high-pressure refrigerant; The high-pressure refrigerant flow injected from (41) sucks the vapor-phase refrigerant evaporated in the low-pressure side heat exchanger (30) and converts expansion energy into pressure energy to reduce the suction pressure of the compressor (10). The ejector (40) to be raised and the refrigerant flowing out of the ejector (40) are separated into a gas-phase refrigerant and a liquid-phase refrigerant, and an outlet for the gas-phase refrigerant is connected to the suction side of the compressor (10). The outlet is a low-pressure side heat exchanger A gas-liquid separation means (50) connected to the refrigerant pipe (30) and a refrigerant passage (80) connecting the refrigerant outlet side of the low-pressure side heat exchanger (30) and the refrigerant suction side of the compressor (10); And a valve (81) for switching between a case where the refrigerant flows through the refrigerant passage (80) and a case where the refrigerant does not flow therethrough. The refrigerant flows through the refrigerant passage (80) and stays in the low-pressure side heat exchanger (30). An oil return mode for returning the refrigerating machine oil to the compressor (10).
[0010]
Thereby, the refrigerating machine oil staying in the low-pressure side heat exchanger (30) can be controlled to a predetermined amount or less to return a sufficient amount of the refrigerating machine oil to the compressor (10), and a new ejector different from the conventional one can be provided. You can get a cycle.
[0011]
According to the second aspect of the present invention, the valve (81) is configured such that the pressure at the refrigerant outlet side of the low-pressure side heat exchanger (30) is higher than the pressure at the refrigerant suction side of the compressor (10), and the pressure difference between the two. Is configured to flow the refrigerant into the refrigerant passage (80) when the pressure difference becomes equal to or more than a predetermined pressure difference.
[0012]
According to the third aspect of the present invention, the valve (81) includes a valve element (81a) for opening and closing the valve port and a spring means (81b) for applying an elastic force to the valve element (81a) in a direction to close the valve port. It is characterized by having such a configuration.
[0013]
According to a fourth aspect of the present invention, the valve (91) is configured to flow the refrigerant into the refrigerant passage (80) when the efficiency of the ejector (40) becomes equal to or less than a predetermined value. Is what you do.
[0014]
According to a fifth aspect of the present invention, there is provided a vapor compression type ejector cycle for transferring heat on a low temperature side to a high temperature side, wherein the high pressure side heat exchanger () radiates heat of the high pressure refrigerant discharged from the compressor (10). 20), a low-pressure side heat exchanger (30) for evaporating the low-pressure refrigerant, and a nozzle (41) for isoentropically decompressing and expanding the high-pressure refrigerant. An ejector (40) for sucking the vapor-phase refrigerant evaporated in the low-pressure side heat exchanger (30) and converting expansion energy into pressure energy to increase the suction pressure of the compressor (10); Is separated into a gaseous refrigerant and a liquid-phase refrigerant, an outlet for the gas-phase refrigerant is connected to the suction side of the compressor (10), and an outlet for the liquid-phase refrigerant is connected to the low-pressure side heat exchanger (30). Connected gas-liquid separation means (5 ), Piping means constituting a refrigerant passage (90) for guiding the refrigerant discharged from the compressor (10) to the low-pressure side heat exchanger (30) by bypassing the nozzle (41), and refrigerant in the refrigerant passage (90). A valve (91) for switching between flowing and non-flowing the refrigerant, and allowing the refrigerant flowing through the refrigerant passage (80) to flow the refrigerant oil retained in the low-pressure side heat exchanger (30) to the compressor (10). It is characterized by having an oil return mode for returning to oil.
[0015]
Thereby, the refrigerating machine oil staying in the low-pressure side heat exchanger (30) can be controlled to a predetermined amount or less to return a sufficient amount of the refrigerating machine oil to the compressor (10), and a new ejector different from the conventional one can be provided. You can get a cycle.
[0016]
The invention according to claim 6 is characterized in that the refrigerant passage (90) is provided with a decompression means (93) for decompressing and expanding the refrigerant in an isenthalpic manner.
[0017]
The seventh aspect of the present invention is characterized in that carbon dioxide is used as the refrigerant.
[0018]
The invention according to claim 8 is characterized in that a hydrocarbon is used as the refrigerant.
[0019]
The invention according to claim 9 is characterized in that chlorofluorocarbon is used as the refrigerant.
[0020]
Incidentally, the reference numerals in parentheses of the respective means are examples showing the correspondence with specific means described in the embodiments described later.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
In the present embodiment, the ejector cycle according to the present invention is applied to a vapor compression refrigerator for a showcase which refrigerates and freezes food, and FIG. 1 is a schematic diagram of the ejector cycle.
[0022]
The compressor 10 is an electric compressor that sucks and compresses refrigerant, and the radiator 20 exchanges heat between high-temperature and high-pressure refrigerant discharged from the compressor 10 and outdoor air to cool the refrigerant. It is.
[0023]
Further, the evaporator 30 is a low-pressure side heat exchanger that exhibits a refrigerating capacity by exchanging heat between the air blown into the showcase and the low-pressure refrigerant to evaporate the liquid-phase refrigerant. This is an ejector that decompresses and expands the outflowing refrigerant to suck the vapor-phase refrigerant evaporated in the evaporator 30, and converts the expansion energy into pressure energy to increase the suction pressure of the compressor 10.
[0024]
Then, as shown in FIG. 2, the ejector 40 converts the pressure energy of the inflowing high-pressure refrigerant into velocity energy and decompresses and expands the refrigerant in a isentropic manner. A mixing unit 42 that mixes the refrigerant flow ejected from the nozzle 41 while sucking the gas-phase refrigerant evaporated in the evaporator 30 by the entanglement effect, and a refrigerant ejected from the nozzle 41 and the refrigerant sucked from the evaporator 30. It is composed of a diffuser 43 or the like for converting velocity energy into pressure energy while mixing, and increasing the pressure of the refrigerant.
[0025]
At this time, in the mixing section 42, the driving flow and the suction flow are mixed so that the sum of the momentum of the driving flow and the momentum of the suction flow is preserved. ) Rises.
[0026]
On the other hand, in the diffuser 43, the velocity energy (dynamic pressure) of the refrigerant is converted into pressure energy (static pressure) by gradually increasing the cross-sectional area of the passage, so that in the ejector 40, the mixing section 42 and the diffuser 43 Both increase the refrigerant pressure. Therefore, hereinafter, the mixing unit 42 and the diffuser 43 are collectively referred to as a boosting unit.
[0027]
Incidentally, in the present embodiment, in order to accelerate the speed of the refrigerant ejected from the nozzle 41 to the speed of sound or more, a Laval nozzle having a throat portion 41a having the smallest passage area in the middle of the passage (see Fluid Engineering (Tokyo University Press)) However, it goes without saying that a tapered nozzle may be employed.
[0028]
In FIG. 1, the gas-liquid separator 50 is a gas-liquid separation unit that stores therein the refrigerant that flows out of the ejector 40 and separates the refrigerant that has flowed into a gas-phase refrigerant and a liquid-phase refrigerant. The gas-phase refrigerant outlet of the gas-liquid separator 50 is connected to the suction side of the compressor 10, and the liquid-phase refrigerant outlet is connected to the evaporator 30.
[0029]
The throttle 60 is a pressure reducing means for reducing the pressure of the liquid-phase refrigerant flowing out of the gas-liquid separator 50. The first oil return passage 70 returns the refrigerating machine oil separated by the gas-liquid separator 50 to the suction side of the compressor 10. Things.
[0030]
The second oil return passage 80 is a refrigerant passage connecting the refrigerant outlet side of the evaporator 30 and the refrigerant suction side of the compressor 10, and the refrigerant flows from the refrigerant outlet side of the evaporator 30 to the second oil return passage 80. A check valve 81 that allows only the refrigerant to flow toward the refrigerant suction side of the compressor 10 is provided. When the check valve 81 opens and closes, the refrigerant flows into and out of the second oil return passage 80. Is controlled.
[0031]
Here, the check valve 81 includes a valve body 81a that opens and closes a valve port, and a spring 81b that exerts an elastic force on the valve element 81a in a direction to close the valve port. The spring 81b opens the second oil return passage 80 when the pressure on the refrigerant outlet side of the evaporator 30 becomes larger than the pressure on the refrigerant suction side of the compressor 10 and the pressure difference becomes equal to or larger than a predetermined pressure difference. It is set as follows.
[0032]
Note that the check valve 81 in FIG. 1 is a symbol of a check valve according to JIS B 0125, and the shapes of the valve body 81a and the spring 81b shown in FIG. 1 do not necessarily indicate actual shapes. .
[0033]
In this embodiment, the refrigerant is carbon dioxide, and the high-pressure refrigerant flowing into the nozzle 41 in the compressor 10 is pressurized to a pressure higher than the critical pressure of the refrigerant as shown in FIG. Incidentally, the symbol indicated by ● in FIG. 3 indicates the state of the refrigerant at the symbol position indicated by ● in FIG.
[0034]
Next, the operation and features of the cycle according to the present embodiment will be described.
[0035]
1. Normal operation mode (see Fig. 3)
The refrigerant discharged from the compressor 10 is circulated to the radiator 20 side. Thus, the refrigerant cooled by the radiator 20 isentropically decompressed and expanded at the nozzle 41 of the ejector 40 and flows into the mixing section 42 at a speed higher than the speed of sound.
[0036]
Then, the refrigerant evaporated in the evaporator 30 is sucked into the mixing section 42 by the pumping action accompanying the entraining action of the high-speed refrigerant flowing into the mixing section 42, so that the low-pressure side refrigerant is removed from the gas-liquid separator 50 → throttle. The circulation is performed in the order of 60 → evaporator 30 → ejector 40 (pressure booster) → gas-liquid separator 50.
[0037]
On the other hand, while the refrigerant sucked from the evaporator 30 (suction flow) and the refrigerant blown out from the nozzle 41 (drive flow) are mixed in the mixing section 42, the dynamic pressure thereof is converted to static pressure in the diffuser 43, and Return to the liquid separator 50.
[0038]
2. Oil return mode This mode is used when the refrigerating machine oil circulating in the ejector cycle while being mixed with the refrigerant stays in the evaporator 30 for a predetermined amount or more, or when the ejector efficiency ηe decreases when the outside air temperature decreases. Alternatively, the mode is automatically executed when the pump action of the ejector 40 is reduced.
[0039]
Incidentally, the ejector efficiency ηe is defined as the product of the mass flow rate Gn of the refrigerant flowing through the radiator 20 and the enthalpy difference Δie between the inlet and the outlet of the nozzle 41, and how much energy is recovered as a work of the compressor 10 in the numerator. This is defined by adding the sum of the refrigerant flow rate Gn indicating whether the flow has been performed and the mass flow rate Ge of the refrigerant flowing through the evaporator 30, and the pressure recovery ΔP at the ejector 40. Specifically, it is defined by the following equation 1 in consideration of the velocity energy of the suction refrigerant before being sucked by the ejector 40.
[0040]
(Equation 1)

That is, when the pumping action of the ejector 40 is sufficiently large, the pressure recovery ΔP at the ejector 40, that is, the pressure increase amount ΔP at the ejector 40 is large, and therefore, as shown in FIG. , The pressure P3 on the refrigerant suction side becomes relatively higher than the pressure P1 on the refrigerant outlet side of the evaporator 30, the second oil return passage 80 is closed by the check valve 81, and the refrigerant flows through the second oil return passage 80. Absent.
[0041]
However, when the pump action of the ejector 40 is reduced, the pressure P1 on the refrigerant outlet side of the evaporator 30 with the check valve 81 interposed therebetween becomes relatively larger than the pressure P3 on the refrigerant suction side of the compressor 10, and FIG. As shown, the check valve 81 opens, and the refrigerant flows through the second oil return passage 80.
[0042]
Therefore, since the refrigerant outlet side of the evaporator 30 communicates directly with the suction side of the compressor 10, even if the pumping action of the ejector 40 is small, the refrigerating machine oil retained in the evaporator 30 is directed to the compressor 10. And the stagnation of the refrigerating machine oil is eliminated.
[0043]
When the refrigerating machine oil in the evaporator 30 decreases, the refrigerating capacity in the evaporator 30 increases, and the flow rates of the suction flow and the driving flow increase. Therefore, the pump action of the ejector 40 increases, and The pressure P3 on the refrigerant suction side of the compressor 10 becomes relatively higher than the pressure P1 on the refrigerant outlet side of the evaporator 30 with the sandwiched therebetween.
[0044]
That is, when the refrigerating machine oil in the evaporator 30 decreases, the check valve 81 closes and automatically shifts from the oil return mode to the normal operation mode. Conversely, when a large amount of refrigerating machine oil in the evaporator 30 accumulates, The check valve 81 opens and automatically shifts from the normal operation mode to the oil return mode.
[0045]
As described above, in the present embodiment, a sufficient amount of the refrigerating machine oil can be returned to the compressor 10 by controlling the refrigerating machine oil remaining in the evaporator 30 to a predetermined amount or less.
[0046]
FIG. 6 shows a change in the refrigerating machine oil amount in the compressor 10 in the ejector cycle according to the present embodiment, and a change in the compressor 10 in a normal ejector cycle without the second oil return passage 80 and the check valve 81. It is a test result showing a change in the amount of the refrigerating machine oil, and as is clear from the results, in the present embodiment, the refrigerating machine oil staying in the evaporator 30 is controlled to a predetermined amount or less, and the compressor 10 has a sufficient amount. It can be seen that the amount of refrigerator oil can be returned.
[0047]
FIG. 7 is a graph (a numerical simulation result) showing the relationship between the outside air temperature and the boost amount ΔP in the ejector 40 when the ejector efficiency ηe is set to about 40%.
[0048]
(2nd Embodiment)
In the first embodiment, the second oil return passage 80 is opened and closed by a check valve 81 which is a mechanical valve. However, in the present embodiment, as shown in FIG. At the same time, the

pressure sensors

83a and 83b detect the pressure increase amount ΔP at the ejector 40, and when the pressure increase amount ΔP at the ejector 40 becomes a predetermined value or less, the electromagnetic valve 82 is opened, and the pressure increase amount ΔP at the ejector 40 is The electromagnetic valve 82 is closed when a predetermined value is exceeded.
[0049]
Note that the present embodiment can be implemented even if the predetermined value when the electromagnetic valve 82 is closed is different from the predetermined value when the electromagnetic valve 83 is closed.
[0050]
Further, in the present embodiment, the opening / closing control of the electromagnetic valve 82 is performed using the pressure increase amount ΔP in the ejector 40 as a parameter. However, the present embodiment is not limited to this. The ejector efficiency ηe is calculated from the temperature, the refrigerant pressure, and the like. When the ejector efficiency ηe becomes equal to or less than a predetermined value, the electromagnetic valve 82 is opened, and when the ejector efficiency ηe exceeds the predetermined value, the electromagnetic valve 82 is closed. Is also good. At this time, it goes without saying that the predetermined value of the ejector efficiency ηe when the electromagnetic valve 82 is closed may be made different from the predetermined value of the ejector efficiency ηe when the electromagnetic valve 83 is closed.
[0051]
(Third embodiment)
In the present embodiment, as shown in FIGS. 9 to 12, the second oil return passage 80 is eliminated, and a bypass passage 90 that guides the refrigerant discharged from the compressor 10 to the evaporator 30 by bypassing the nozzle 41 is provided. A three-way valve 91 is provided at a branch between the bypass passage 90 and the high-pressure refrigerant passage to switch between a case where the refrigerant flows through the bypass passage 90 and a case where the refrigerant does not flow, and an expansion valve 93 that decompresses and expands the refrigerant isometrically in the bypass passage 90. It is provided.
[0052]
When the pressure increase amount ΔP in the ejector 40 becomes equal to or less than a predetermined value or when the ejector efficiency ηe becomes equal to or less than a predetermined value, the refrigerant is caused to flow through the bypass passage 90 to perform the oil return mode, and the pressure in the ejector 40 is increased. When the amount ΔP exceeds a predetermined value or when the ejector efficiency ηe exceeds a predetermined value, the bypass passage 90 side is closed to perform the normal operation mode.
[0053]
Incidentally, the expansion valve 93 is a mechanical or electric decompressor that controls the opening degree of the throttle so that the refrigerant superheat degree at the refrigerant outlet side of the evaporator 30 becomes a predetermined value. However, the expansion valve 93 is fixed to a capillary tube, an orifice, or the like. It may be an aperture.
[0054]
In the ejector cycle shown in FIGS. 9 and 11, in the oil return mode, the high-pressure refrigerant does not flow into the nozzle 41 and the entire amount of the high-pressure refrigerant flows through the expansion valve 93. Therefore, in the oil return mode, it is as if the expansion valve cycle. Refrigerant flow.
[0055]
(Fourth embodiment)
This embodiment is a modification of the third embodiment. Specifically, as shown in FIG. 13, the three-way valve 91 is eliminated by making the expansion valve 93 a fully-closable valve.
[0056]
That is, in the normal operation mode, the expansion valve 93 is fully closed, and in the oil return mode, the expansion valve 93 is opened to flow the refrigerant through the bypass passage 90.
[0057]
Although FIG. 13 shows the third embodiment in which the present embodiment is applied to FIG. 9, it is needless to say that the present embodiment can be applied to FIGS.
[0058]
(Other embodiments)
In the above embodiment, carbon dioxide is used as the refrigerant, but the present invention is not limited to this. For example, hydrocarbons, chlorofluorocarbons, or the like may be used as the refrigerant.
[0059]
In the above-described embodiment, the high-pressure side refrigerant pressure is equal to or higher than the critical pressure, but the present invention is not limited to this.
[0060]
In the above-described embodiment, the ejector cycle according to the present invention is applied to a vapor compression refrigerator for a showcase that refrigerates and freezes food, but the application of the present invention is not limited to this. For example, the present invention can be applied to an air conditioner.
[0061]
In the present invention, the refrigerating machine oil in the evaporator 30 is directly sucked by the compressor 10 or the refrigerating machine oil in the evaporator 30 is directly extruded by the discharge pressure of the compressor 10 in the oil return mode. Therefore, the present invention is not limited to the above embodiment.
[0062]
Further, a valve may be provided at the inlet side of the nozzle 41 to control the throttle opening degree so that the refrigerant superheat degree at the refrigerant outlet side of the evaporator 30 becomes a predetermined value.
[0063]
Further, an internal heat exchanger for exchanging heat between the high-pressure refrigerant flowing out of the radiator 20 and the low-pressure refrigerant drawn into the compressor 10 may be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an ejector cycle according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram of an ejector according to an embodiment of the present invention.
FIG. 3 is a ph diagram.
FIG. 4 is an operation explanatory view of an ejector cycle according to the first embodiment of the present invention.
FIG. 5 is an operation explanatory view of an ejector cycle according to the first embodiment of the present invention.
FIG. 6 is a graph showing an oil return effect.
FIG. 7 is a graph showing a decrease in ejector performance.
FIG. 8 is a schematic view of an ejector cycle according to a second embodiment of the present invention.
FIG. 9 is a schematic view of an ejector cycle according to a third embodiment of the present invention.
FIG. 10 is a schematic view of an ejector cycle according to a third embodiment of the present invention.
FIG. 11 is a schematic view of an ejector cycle according to a third embodiment of the present invention.
FIG. 12 is a schematic view of an ejector cycle according to a third embodiment of the present invention.
FIG. 13 is a schematic view of an ejector cycle according to a fourth embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 10: compressor, 20: radiator, 30: evaporator, 40: ejector, 50: gas-liquid separator, 60: throttle, 80: second oil return passage, 81: check valve.

Claims

A vapor compression type ejector cycle for transferring low-temperature heat to a high-temperature side,
A high-pressure side heat exchanger (20) for radiating heat of the high-pressure refrigerant discharged from the compressor (10);
A low pressure side heat exchanger (30) for evaporating the low pressure refrigerant,
It has a nozzle (41) for isoentropically decompressing and expanding a high-pressure refrigerant, and sucks a vapor-phase refrigerant evaporated in the low-pressure side heat exchanger (30) by a high-speed refrigerant flow injected from the nozzle (41). An ejector (40) for converting expansion energy into pressure energy to increase the suction pressure of the compressor (10);
The refrigerant flowing out of the ejector (40) is separated into a gas-phase refrigerant and a liquid-phase refrigerant, an outlet for the gas-phase refrigerant is connected to a suction side of the compressor (10), and an outlet for the liquid-phase refrigerant is connected to the low-pressure side. Gas-liquid separation means (50) connected to the heat exchanger (30);
Piping means for forming a refrigerant passage (80) connecting the refrigerant outlet side of the low-pressure side heat exchanger (30) and the refrigerant suction side of the compressor (10);
A valve (81, 91) for switching between a case where the refrigerant flows and a case where the refrigerant does not flow in the refrigerant passage (80),
An ejector cycle comprising: an oil return mode in which refrigeration oil retained in the low-pressure side heat exchanger (30) is returned to the compressor (10) by flowing a refrigerant through the refrigerant passage (80).

The valve (81) is configured such that the pressure at the refrigerant outlet side of the low-pressure side heat exchanger (30) is higher than the pressure at the refrigerant suction side of the compressor (10), and the pressure difference is greater than or equal to a predetermined pressure difference. 2. The ejector cycle according to claim 1, wherein the ejector cycle is configured to cause a coolant to flow through the coolant passage (80) at the time of becoming.

The valve (81) includes a valve element (81a) for opening and closing a valve port, and a spring means (81b) for applying an elastic force to the valve element (81a) in a direction to close the valve port. The ejector cycle according to claim 2, wherein the ejector cycle is provided.

The said valve (91) is comprised so that a refrigerant | coolant may flow into the said refrigerant | coolant channel | path (80), when the efficiency of the said ejector (40) becomes below a predetermined value. Ejector cycle.

A vapor compression type ejector cycle for transferring low-temperature heat to a high-temperature side,
A high-pressure side heat exchanger (20) for radiating heat of the high-pressure refrigerant discharged from the compressor (10);
A low pressure side heat exchanger (30) for evaporating the low pressure refrigerant,
It has a nozzle (41) for isoentropically decompressing and expanding a high-pressure refrigerant, and sucks a vapor-phase refrigerant evaporated in the low-pressure side heat exchanger (30) by a high-speed refrigerant flow injected from the nozzle (41). An ejector (40) for converting expansion energy into pressure energy to increase the suction pressure of the compressor (10);
The refrigerant flowing out of the ejector (40) is separated into a gas-phase refrigerant and a liquid-phase refrigerant, an outlet for the gas-phase refrigerant is connected to a suction side of the compressor (10), and an outlet for the liquid-phase refrigerant is connected to the low-pressure side. Gas-liquid separation means (50) connected to the heat exchanger (30);
Piping means for forming a refrigerant passage (90) for guiding the refrigerant discharged from the compressor (10) to the low pressure side heat exchanger (30) by bypassing the nozzle (41);
A valve (91) for switching between a case where the refrigerant flows and a case where the refrigerant does not flow in the refrigerant passage (90),
An ejector cycle comprising: an oil return mode in which refrigeration oil retained in the low-pressure side heat exchanger (30) is returned to the compressor (10) by flowing a refrigerant through the refrigerant passage (80).

The ejector cycle according to claim 5, wherein the refrigerant passage (90) is provided with decompression means (93) for decompressing and expanding the refrigerant in an isenthalpic manner.

The ejector cycle according to any one of claims 1 to 6, wherein carbon dioxide is used as the refrigerant.

The ejector cycle according to any one of claims 1 to 6, wherein a hydrocarbon is used as the refrigerant.

The ejector cycle according to any one of claims 1 to 6, wherein chlorofluorocarbon is used as the refrigerant.