JP2004325018A

JP2004325018A - Refrigerating cycle

Info

Publication number: JP2004325018A
Application number: JP2003123117A
Authority: JP
Inventors: Kazuto Higa; 一人比嘉; Hirokatsu Kosokabe; 弘勝香曽我部; Kazuhiro Endo; 和広遠藤; Kenji Tojo; 健司東條
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2003-04-28
Filing date: 2003-04-28
Publication date: 2004-11-18
Anticipated expiration: 2023-04-28
Also published as: JP3998249B2

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a device with an efficient structure, reducing the cost, and improving COP (coefficient of performance) by utilizing the conversion of expansion energy of the working fluid into mechanical energy. <P>SOLUTION: An expander 5 for converting expansion energy of the working fluid into mechanical energy, and a sub-compressor 6 driven by the expander are accommodated in one sealed container 4. The refrigerant discharged from a main compressor 2 is partially branched to flow into the container 4, and the pressure in the sealed container is kept at high pressure same as the discharge pressure. Whereby the viscosity of the lubricant is lowered, the sufficient amount of lubricant can be supplied to a sliding part of the expander and the sub-compressor by pressure difference, and the sealing performance can be improved. Further the sealed container 4 can be also used as a receiver tank for storing the liquid refrigerant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、冷媒を圧縮膨張させる蒸気圧縮式の冷凍サイクルに関し、特に冷媒の膨張エネルギを機械（回転）エネルギに変換する膨張機を有する冷凍サイクルに関する。
【０００２】
【従来の技術】
従来の冷凍サイクルにおいて、膨張エネルギを回収できる圧縮・膨張システムとしては、特許文献１や特許文献２に記載のものが知られている。
【０００３】
この特許文献１記載のものは、主圧縮機と膨張機を分離し、膨張機で発生した膨張エネルギを回収する副圧縮機を備えた冷凍サイクルが記載されており、冷凍サイクルの主流回路を流れる主流冷媒を膨張機で膨張させ、そのときの主流冷媒の膨張エネルギを機械エネルギに変換しながら主流冷媒を減圧している。膨張機で発生した機械エネルギにより副圧縮機は駆動される。
【０００４】
特許文献２のものは、冷媒を圧縮する圧縮機構部と、冷媒を膨張させる膨張機構部を電動機を介して接続した軸直結構造とし、圧縮機構部の吸込み側が蒸発器に、吐出側がガスクーラに連通する一方、膨張機構部の吸込み側がガスクーラに、吐出側が蒸発器に連通するようにして冷凍サイクルが構成されている。
【特許文献１】特開２０００−３２９４１６号公報
【特許文献２】特開２００１−１０７８８１号公報
【発明が解決しようとする課題】
特許文献１においては、主圧縮機、副圧縮機、膨張機を定常的に潤滑する必要があるが、それぞれがサイクル中に別々に存在しているため、圧縮機と膨張機間で油が偏在する可能性があった。また、膨張機の周囲圧力に比べて膨張機の内圧が大きくなり、膨張機内部からのガス漏洩が発生し易い。さらに、周囲圧力が低圧であるために潤滑油への冷媒の溶け込み量が少なく、また低温であるため潤滑油の粘度が大きくなり、高粘度の潤滑油が電動機や圧縮機、膨張機の負荷になってしまう問題があった。また、膨張機や副圧縮機を用いるため、コスト上昇や設置スペースが大きくなる課題もある。
【０００５】
特許文献２においては、特許文献１のような圧縮機、膨張機間の油偏在の問題は改善されるが、主圧縮機と膨張機が近接した配置になるため、室内ユニットと室外ユニットに別れたセパレートタイプの冷凍空調機器とした場合、配管が長くなり、コスト上昇や配管の圧力損失による性能低下の問題がある。また、比較的低温で動作する膨張機が、ガス圧縮作用により高温となった圧縮機及び電動機からの熱影響を受けて加熱されるため、膨張過程のエンタルピ差が減少して膨張機での動力回収が少なくなり、膨張機効率を低下させる課題があった。
【０００６】
本発明の目的は、必要な部品を効率よく配置して装置の小型化、低コスト化を図ることのできる冷凍サイクルを得ることにある。
【０００７】
本発明の他の目的は、作動流体の膨張過程のエネルギを機械エネルギに効率よく変換して利用できる膨張／圧縮システムを構成することにより、ＣＯＰ（成績係数）を向上し、汎用性の高い冷凍サイクルを得ることにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、本発明は、主圧縮機で圧縮された冷媒を冷却する放熱器、この放熱器からの冷媒を膨張させる膨張手段と、該膨張手段で膨張された冷媒を蒸発させる蒸発器を有する冷凍サイクルにおいて、前記放熱器から流出した冷媒を分岐させ、その一方の冷媒を減圧膨張させると共にそのときの膨張エネルギを機械エネルギに変換する膨張機と、前記放熱器下流で分岐された他方の冷媒を減圧膨張させる膨張弁と、前記膨張機下流側と前記膨張弁下流側を合流させ、前記蒸発器に接続される流路と、前記膨張機の吸入圧力を制御する前段膨張弁と、前記膨張機により駆動され、前記蒸発器で蒸発した冷媒を圧縮して前記主圧縮機に供給する副圧縮機と、前記膨張機と前記副圧縮機を収納すると共に内部に潤滑油を貯溜した密閉容器とを備え、該密閉容器内を前記主圧縮機の吐出圧力と同一またはほぼ同一の圧力に保つことを特徴とする。
【０００９】
前記主圧縮機から吐出した冷媒の一部、或いは前記放熱器から流出した冷媒の一部を分岐させ、前記膨張機と副圧縮機を収納している前記密閉容器内に流通させることで、前記密閉容器内を主圧縮機の吐出圧力に保つようにしても良い。
【００１０】
前記放熱器から流出した冷媒を分岐させ、前記膨張機と前記副圧縮機を収納している密閉容器内に導入して貯留すると共に、この密閉容器の上部側から冷媒を流出させて前記膨張機に導き、該膨張機により前記冷媒を減圧膨張させるように構成すれば、前記膨張／圧縮システムの密閉容器を液冷媒或いは液冷媒と混合している潤滑油を溜めるレシーバタンクとしての機能を持たせることができる。
【００１１】
また、前記主圧縮機を、内部が該主圧縮機吸い込み圧力に保たれた密閉容器内に収納すると共に、該密閉容器内部には潤滑油を貯溜し、この潤滑油の油面上部に前記主圧縮機の吸入口を設けることもできる。
【００１２】
さらに、前記主圧縮機とそのモータを収納して内部に潤滑油を貯留した密閉容器を備え、この主圧縮機密閉容器内を該主圧縮機の吐出圧力に保つと共に、主圧縮機の吐出口を前記モータ下方の前記密閉容器側面に設けるようにすることもできる。
【００１３】
前記主圧縮機と前記放熱器の間に油分離器を設け、該油分離器で分離された油を、前記膨張機と副圧縮機を収納した前記密閉容器に戻すようにしても良い。
【００１４】
本発明の他の特徴は、主圧縮機、放熱器、膨張手段、蒸発器を順次接続して構成された冷凍サイクルにおいて、前記放熱器から流出した冷媒を分岐させその分岐された冷媒を減圧膨張させると共に膨張エネルギを回転エネルギに変換する膨張機と、前記放熱器下流で分岐された他方の冷媒を減圧膨張させる膨張弁と、
前記膨張機下流側と前記膨張弁下流側を合流させ、前記蒸発器に接続される流路と、前記膨張機の吸入圧力を制御する前段膨張弁と、前記膨張機により駆動され前記蒸発器で蒸発した冷媒を圧縮して前記主圧縮機側に供給するための副圧縮機と、前記膨張機と前記副圧縮機を収納すると共に内部に潤滑油を貯溜しかつ前記主圧縮機の吐出圧力と同一またはほぼ同一の圧力に保持される密閉容器とを備えたことにある。
【００１５】
上記において、前記放熱器下流で分岐された他方の冷媒を減圧膨張させる膨張弁は、放熱器からの高圧冷媒を、前記膨張機で減圧膨張されて吐出された冷媒の圧力と同程度の圧力まで減圧するように制御される構成にすると良い。
【００１６】
前記膨張機と副圧縮機を収納した密閉容器内を高圧・低温に保つことで、前記膨張機、副圧縮機の摺動部に潤滑油を供給するための差圧を大きくできるから、摺動部への油供給量が増加し、シール性能を向上させることが可能となる。また、前記密閉容器内が高圧となることにより、潤滑油への冷媒の溶け込み量が増加するため、潤滑油の粘度が低下し、膨張機及び副圧縮機の粘性摩擦損失を低減することもできる。
【００１７】
また、膨張機と副圧縮機を収納した前記密閉容器に、レシーバタンクの役割を兼ねさせることが可能となるから、レシーバタンクを不要にできる。
主圧縮機を密閉容器に収納し、この密閉容器内を主圧縮機吸入圧力に保り、主圧縮機吸入口をモータ下方で油面の上部に設ける構成としたものでは、副圧縮機から吐出された潤滑油が、吸入口付近まで上昇すると、冷媒の流れと共に主圧縮機容器から吐出され、放熱器を通過後、副圧縮機を収容した密閉容器に供給されるので、膨張／圧縮システムと主圧縮機間での潤滑油の偏在を防止できる。
【００１８】
主圧縮機密閉容器内を主圧縮機吐出圧力に保つ場合も同様に、主圧縮機吐出口をモータ下方の容器側面に設けるようにしているから、潤滑油が吐出口付近まで上昇すると、冷媒の流れと共に主圧縮機容器から吐出され、放熱器通過後、副圧縮機密閉容器に供給されるから、膨張／圧縮システムと主圧縮機間での潤滑油の偏在を防止することが可能となる。
【００１９】
【発明の実施の形態】
以下、本発明の実施例を図面に基づいて詳細に説明する。
図１は本発明の第１実施例を示す冷凍サイクルの模式図、図２は冷凍サイクルの作動流体として自然冷媒である二酸化炭素（Ｒ７４４）を使用した場合のモリエル線図、図３はＲ７４４を使用した冷凍サイクルに使用される潤滑油の粘度特性を示す線図である。なお、冷媒としての二酸化炭素は、地球温暖化係数（ＧＷＰ）がフロン系冷媒の数千分の一と小さく地球環境保全の点で優れている。反面、高圧冷媒であり、モリエル線図上の理論的ＣＯＰ（成績係数）が低いという欠点がある。しかし、Ｒ７４４は膨張過程のエネルギ損失がフロン系冷媒に比べて大きいことから、この膨張過程の動力を回収することによりＣＯＰの大幅な改善をできる可能性があり、高効率で信頼性の高い膨張機を備えた冷凍サイクルの開発が冷媒Ｒ７４４システムの実用化の鍵を握ると考えられている。フロン系冷媒のシステムでも改善比率は小さくなるが、ＣＯＰの向上を図ることができる。ここでは、冷媒Ｒ７４４を使用した冷凍サイクルの例を説明する。
【００２０】
図１において、３は電動機（モータ）（Ｍ）、２は主圧縮機（ＭＣ）、５は膨張機（膨張手段）（ＥＸ）、６は副圧縮機（ＳＣ）である。主圧縮機２で圧縮された高温・高圧冷媒（図２モリエル線図上の点Ｃの状態）は、主圧縮機２と電動機３を収納した密閉容器１に吐出され、吐出パイプ１１から放熱器（ガスクーラ）７に供給され、ここで放熱し温度低下（図２の点Ｄ）した後、流入パイプ１２を通って、膨張機５及び副圧縮機６を収容した膨張／圧縮システムの密閉容器４に入り、この容器４内を低温、高圧に保つ。この膨張／圧縮システム密閉容器４から流出パイプ１３を通って吐出された冷媒は、前段膨張弁９を通過して膨張機５の設計圧力比に合うように予膨張される。その後、冷媒は膨張機５に流入パイプ１４を通って入り、膨張動作を行って膨張エネルギを機械エネルギに変換し、流出パイプ１５から低温・低圧の気液二相冷媒（図２の点Ｅ）となって吐出される。膨張機５から吐出された冷媒は、放熱器７下流側で前記流入パイプ１２側から分岐され、膨張弁（膨張手段）１０を通って減圧膨張された冷媒と合流し、蒸発器８に入って吸熱ガス化し、吸入パイプ２６を通って副圧縮機６に吸い込まれ（図２の点Ａ）、この副圧縮機６内で若干昇圧されて吐出パイプ１６から吐出される（図２の点Ｂ）。副圧縮機６から吐出されたガス冷媒は主圧縮機２に戻り再び圧縮されて高温・高圧のガス冷媒となる。以上のサイクルが繰り返されて冷凍作用を行なう。
【００２１】
なお、前記膨張弁１０は、膨張機５をバイパスする回路に取り付けられ、冷凍サイクルの運転条件変化時の流量（圧力）調整等を行う。本実施例では、主圧縮機２で圧縮された高圧の冷媒を膨張／圧縮システム密閉容器４に流通させて密閉容器４内部を高圧に保つことで、潤滑油２９への冷媒の溶け込み量を増加させ、その結果潤滑油２９の粘度を低下させ（図３参照）、膨張機５と副圧縮機６にかかる負荷を低減させることが可能となる。また、密閉容器４には、放熱器７で放熱された冷媒を流通させることにより、主圧縮機側から比較的低温で動作する膨張機５への熱侵入を極力抑えることが可能となる。
【００２２】
図４は図１に示す膨張／圧縮システム密閉容器４内の詳細構造を説明する図、図５は図４に示す膨張機５の動作説明図で、クランク軸回転角ごとの作動流体の流入過程を説明した図である。
【００２３】
膨張／圧縮システムは、冷凍サイクルにおける作動流体の膨張エネルギを機械エネルギに変換する膨張機５と、この変換された機械エネルギにより仕事をする副圧縮機６から構成され、膨張機５と副圧縮機６は積層して配置され、クランク軸１７を介して連結されて、密閉容器４内に収納されている。
【００２４】
膨張機５は、クランク軸１７の軸受を兼ねた下ベア１８と中間仕切り板１９により、シリンダ２０の両端開口部が閉塞されている。シリンダ２０には中央部に円筒状内周面２０ａが形成されている。クランク軸１７にはシリンダ２０の円筒状内周面２０ａにあたる部分に偏心部１７ａが形成されており、この偏心部１７ａは、揺動ピストン２１のローラ部２１ａに圧入された軸受メタル２１ｂ円筒状内周面を摺動回転できるようになっている。
【００２５】
ローラ部２１ａの円筒状外周面には板状のベーン部２１ｃが一体で形成されている。シリンダ２０の円筒状内周面２０ａの外側にはその中心軸と平行な中心軸を持つ円筒孔部２０ｂが形成されており、円筒孔部２０ｂの外側には逃げ孔部２０ｃが形成されている。前記円筒孔部２０ｂは、シリンダ２０の円筒状内周面２０ａと、前記逃げ孔部２０ｃにそれぞれ連通している。揺動ピストン２１のベーン部２１ｃは円筒孔部２０ｂと逃げ孔部２０ｃとに挿入されている。ベーン部２１ｃと円筒孔部２０ｂとの間には、ベーン部２１ｃの平面部に摺動可能に当接する平面部と、円筒孔部２０ｂの円筒面部に摺動可能に当接する円筒面部とを有するシュー２２がベーン部２１ｃを挟み込む形で組込まれている。この結果、ベーン部２１ｃは円筒孔部２０ｂの中心軸を通る往復運動と中心軸廻りの揺動運動を行い、シュー２２は円筒孔部２０ｂ中心軸廻りの揺動運動を行う。ベーン部２１ｃの先端部は逃げ孔部２０ｃの中で運動し、シリンダ２０と干渉することはない。密閉容器４に取り付けられる流入パイプは、シリンダ２０の円筒孔部２０ｂに開口する流入通路２０ｄと接続される。
【００２６】
図５は、クランク軸の回転角が９０°毎のシリンダ２０内における揺動ピストン２１の位置関係を示したもので、揺動ピストン２１のベーン部２１ｃが上死点位置（ベーン部が最もシリンダ２０の外周部に突き出した状態）を回転角θの０°とし、クランク軸１７は時計廻りに回転する。
【００２７】
まず、回転角０°の状態では、（イ）図に示すように、シリンダ２０の流入通路２０ｄとシュー２２の流入孔２２ａとは一部連通しており、シュー２２の流入孔２２ａと揺動ピストン２１のベーン部２１ｃに形成された流入溝２１ｄも連通しているが、この流入溝２１ｄのシリンダ円筒状内周面２０ａ側端部ａはシュー２２により塞がれているため、蒸気圧縮冷凍サイクルの膨張過程入口にある高圧の作動流体はシリンダ２０内への流入を遮断された状態にある。一方、シリンダ２０の流出通路２０ｅはシリンダ２０内に連通しているため、作動流体は膨張過程出口にあたる低圧の圧力状態になっている。
【００２８】
この状態からクランク軸１７が時計廻りに回転すると、（ロ）図に示すように、ベーン部２１ｃがシリンダ２０内に突き出して流入溝２１ｄがシリンダ内との連通を開始するため、高圧の作動流体がシリンダ２０内に流入しはじめ、シリンダ２０内の圧力差によりピストン２１を介してクランク軸１７を時計廻りに回転させ、機械エネルギが発生する。（ロ）図に示す回転角９０°の状態では、シュー２２の揺動によりシリンダ流入通路２０ｄとシュー流入孔２２ａの接続部ｂの流路面積も拡大するため作動流体の流入が促進される。
【００２９】
さらに９０°回転した回転角１８０°の状態（（ハ）図参照）では、シリンダの流入通路２０ｄとシューの流入孔２２ａとは回転角０°の状態と同様に一部連通しているが、ベーン部２１ｃのシリンダ内周面２０ａ側への往復運動により、シュー流入孔２２ａとベーン流入溝２１ｄとは連通が遮断されている。このため、高圧の作動流体の流入が遮断された状態で作動室容積が拡大することから、作動流体は膨張してクランク軸を回転させ、機械エネルギに変換される。
【００３０】
（ニ）図に示す回転角２７０°の状態では、シュー流入孔２２ａとベーン流入溝２１ｄとは連通しはじめるが、シュー２２が回転角９０°の状態とは反対方向に揺動運動するため、シリンダの流入通路２０ｄとシューの流入孔２２ａとは連通が遮断され、このため作動流体はさらに膨張して機械エネルギに変換され続ける。
【００３１】
さらに回転が進むと、シリンダの流出通路２０ｅはシリンダ２０内に連通し、最初の回転角０°の状態になる。以上の動作を繰り返すことにより、作動流体の持つ膨張エネルギが機械エネルギに変換されることになる。
【００３２】
一方、副圧縮機６は、クランク軸１７の軸受を兼ねた上ベア２７と中間仕切り板１９によりシリンダ２３の両端開口部が閉塞されている。シリンダ２３には中央部に円筒状内周面２３ａが形成されている。クランク軸１７には、シリンダ内周面２３ａにあたる部分にもう一方の偏心部１７ｂが形成されており（この偏心部１７ｂは、膨張機５側の偏心部１７ａとは回転位相が１８０°ずれている）、偏心部１７ｂは円筒状ローラ２４の内周面に装着されたころ軸受内に回転可能に挿入されている。ローラ２４の円筒状外周面には板状のベーン２５がベーンスプリング２５ａにより押圧されている。シリンダ内周面２３ａより外側のシリンダ２３には、前記ベーン２５が往復摺動するためのベーン溝、ベーン２５がシリンダ２３と干渉しないように形成された逃げ孔部２３ｂ、及びベーンスプリング２５ａの他端部を装着するスプリング孔部２３ｃが形成されている。
【００３３】
密閉容器４に取り付けられた吸入パイプ２６は、シリンダ２３の吸入通路と接続しており、吸入パイプ２６から吸い込まれた冷媒ガスは、吸入通路を通ってシリンダ２３内に入る。クランク軸１７の回転によって、ローラ２４がシリンダ内周面２３ａに沿って偏心回転運動して移動し、シリンダ内周面２３ａの一部を切り欠く形に形成された吐出切り欠き２３ｅを通り、上ベア２７に形成された吐出ポート２７ａから吐出パイプ１６に吐き出され、外部の冷凍サイクルに流出する。
【００３４】
密閉容器４の底部には、潤滑油２９が貯溜されており、軸受摺動部（クランク軸１７の各軸受部）に強制的に潤滑油を給油するため、クランク軸１７の下端部に給油ピース２８を装着し、クランク軸１７内に形成した給油通路１７ｃを通してクランク軸１７の回転による遠心ポンプ作用で各軸受摺動部に潤滑油を供給するようになっている。本発明では、膨張機５及び副圧縮機６の大部分がこの潤滑油２９中に侵漬された状態とし、主圧縮機２で圧縮された高圧の冷媒を膨張／圧縮システム密閉容器４に流通させ、内部を高圧に保つことで、膨張機５の揺動ピストン２１及び副圧縮機６のローラ２４の両端面から、各摺動部に容易に潤滑油を供給することが可能となる。
【００３５】
次に、主圧縮機及び膨張／圧縮システムでの冷媒と潤滑油の状態について、図１と図６に基づいて説明する。図６の（ａ）図は主圧縮機密閉容器内を主圧縮機吸入圧力に保つ場合の例を、（ｂ）図は主圧縮機密閉容器内を主圧縮機吐出圧力に保つ場合の例を、（ｃ）図は膨張／圧縮システム密閉容器内の冷媒と潤滑油の状態をそれぞれ示したものである。
【００３６】
ガスクーラ７で液化された冷媒を分岐し、流入パイプ１２から膨張／圧縮システム密閉容器４に流入させると、液冷媒３１は潤滑油２９に比べて密度が小さく、混合することなく上部に蓄積する。本実施例では、流出パイプ１３の端を潤滑油２９の油面２９ａの上部に設けることにより、液冷媒３１のみを流出することができる。冷凍サイクルでは、条件によってサイクル中の必要な冷媒量が変化するが、膨張／圧縮システム密閉容器４の液冷媒３１の蓄積量を変化させるため、その液面３１ａを上下させることで、サイクルでの必要な冷媒量を容易に調節することが可能となる。即ち、密閉容器４はレシーバタンクとしての役割を兼ねるため、装置全体としての小型・低コスト化を実現できる。
【００３７】
また、膨張機５の揺動ピストン２１の両端面から差圧によって各摺動部に供給された潤滑油は、冷媒の流れと共に吐出パイプ１５から流出して副圧縮機６に供給され、その潤滑油と、副圧縮機６のローラ２４の両端面から差圧によって供給された潤滑油は吐出パイプ１６から吐き出される。さらに、この潤滑油は吐出パイプ１６から主圧縮機２へ供給され、主圧縮機密閉容器１内に吐出されて蓄積する。以上の過程から、膨張／圧縮システム密閉容器４内に貯溜された潤滑油２９は、次第に主圧縮機密閉容器１内に移動して蓄積され、主圧縮機密閉容器１と膨張／圧縮システム密閉容器４の間で潤滑油が偏在する。特に、膨張／圧縮システム密閉容器４では、潤滑油２９の油面２９ａが上下することに伴い、流出パイプ１３から液冷媒３１と共に、潤滑油２９やガス冷媒が流出してしまう可能性があった。しかし、本実施例では、図６（ａ）に示すように、主圧縮機密閉容器１の内部を主圧縮機２の吸入圧力に保つ場合、密閉容器１と４間で潤滑油の偏在が無い状態での油面３０ａを基準として、その油面３０ａのすぐ上に、主圧縮機の吸入口３２を設置する。これにより、油面３０ａが吸入口３２以上の高さに上昇すると、油は冷媒と共に該吸入口３２から主圧縮機２に吸い込まれ、吐出パイプ１１から流出される。
【００３８】
また、図６（ｂ）に示すように、主圧縮機密閉容器１の内部を主圧縮機２の吐出圧力に保つ場合、密閉容器１と４間で潤滑油の偏在が無い状態での油面３０ａを基準として、その油面３０ａのすぐ上の密閉容器１側面に、吐出パイプ１１を設置する。これにより、油面３０ｂがそれ以上に上昇すると、油は冷媒と共に吐出パイプ１１から流出される。
【００３９】
吐出パイプ１１から流出させた潤滑油は、ガスクーラ７で放熱させた後、流入パイプ１２から再び膨張／圧縮システム密閉容器４に戻される。この結果、密閉容器１，４間での潤滑油の偏在が防止され、膨張／圧縮システム密閉容器４内の潤滑油２９の油面２９ａが上下することも防止でき、密閉容器４のレシーバタンクとしての信頼性を向上することができる。なお、密閉容器１内の潤滑油３０の油面３０ａ，３０ｂを電動機３よりも下方に設定することにより、潤滑油３０による電動機３への負荷を防止できる。
【００４０】
【発明の効果】
本発明によれば、作動流体の膨張過程のエネルギを機械エネルギに効率よく変換して利用できる膨張／圧縮システムを実現できると共に、膨張／圧縮システム密閉容器内を、主圧縮機の吐出圧力と同一またはほぼ同一の高圧力に保つようにしたから、潤滑油の粘度を低下させて膨張機と副圧縮機の摩擦損失を低減することができ、冷凍サイクルのＣＯＰ（成績係数）向上を図れる効果がある。この結果、自然冷媒である二酸化炭素を用いた冷凍空調システム等の実現が可能となる。
【００４１】
また、膨張／圧縮システム密閉容器内に液冷媒を蓄積させてレシーバタンクとしての役割も兼ねさせることにより、小型・低コスト化も実現できる。
【００４２】
さらに、膨張／圧縮システム密閉容器内を高圧に保つことにより、膨張機と副圧縮機のシリンダ内各摺動部に差圧により容易に潤滑油を供給することも可能になる。
【００４３】
また、主圧縮機密閉容器の潤滑油を膨張／圧縮システム密閉容器に戻す構成にすることにより、密閉容器間での均油が可能となり、信頼性を向上できる。
【図面の簡単な説明】
【図１】本発明の第１実施例を示す冷凍サイクルの模式図である。
【図２】冷凍サイクルの作動流体として二酸化炭素を使用した場合ののモリエル線図である。
【図３】二酸化炭素を使用した冷凍サイクルに使用される潤滑油の粘度特性を示す線図である。
【図４】図１に示す膨張／圧縮システム密閉容器内の詳細構造を説明する縦断面図である。
【図５】図４に示す膨張機の動作説明図である。
【図６】主圧縮機密閉容器、及び膨張／圧縮システム密閉容器内の冷媒と潤滑油の状態を説明する模式図である。
【符号の説明】
１…主圧縮機密閉容器、２…主圧縮機、３…電動機（モータ）、４…膨張／圧縮システム密閉容器、５…膨張機、６…副圧縮機、７…放熱器（ガスクーラ）、８…蒸発器、９…膨張機前段膨張弁、１０…流量調整用膨張弁、１１…吐出パイプ、１２…流入パイプ、１３…流出パイプ、１４…膨張機の流入パイプ、１５…膨張機の吐出パイプ、１６…副圧縮機の吐出パイプ、１７…クランク軸、１７ａ，１７ｂ…偏心部、１７ｃ…給油通路、１８…下ベア、１９…中間仕切り板、２０…膨張機のシリンダ、２０ａ…円筒状内周面（シリンダ内周面）、２０ｂ…円筒孔部、２０ｃ…逃げ孔部、２０ｄ…流入通路、２０ｅ…流出通路、２１…揺動ピストン、２１ａ…ローラ部、２１ｂ…軸受メタル、２１ｃ…ベーン部、２１ｄ…流入溝、２２…シュー、２２ａ…流入孔、２３…副圧縮機のシリンダ、２３ａ…円筒状内周面（シリンダ内周面）、２３ｂ…逃げ孔部、２３ｃ…スプリング孔部、２３ｅ…吐出切り欠き、２４…ローラ、２５…ベーン、２５ａ…ベーンスプリング、２６…副圧縮機の吸入パイプ、２７…上ベア、２８…給油ピース、２９，３０…潤滑油、２９ａ，３０ａ，３０ｂ…油面、３１…液冷媒、３１ａ…液面、３２…主圧縮機の吸入口。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vapor compression refrigeration cycle for compressing and expanding a refrigerant, and more particularly to a refrigeration cycle having an expander for converting expansion energy of the refrigerant into mechanical (rotational) energy.
[0002]
[Prior art]
As a compression / expansion system capable of recovering expansion energy in a conventional refrigeration cycle, those described in Patent Documents 1 and 2 are known.
[0003]
This patent document 1 describes a refrigeration cycle including a sub-compressor that separates a main compressor and an expander and recovers expansion energy generated by the expander, and flows through a mainstream circuit of the refrigeration cycle. The mainstream refrigerant is expanded by the expander, and the mainstream refrigerant is decompressed while converting the expansion energy of the mainstream refrigerant into mechanical energy at that time. The sub-compressor is driven by mechanical energy generated by the expander.
[0004]
Japanese Patent Application Laid-Open No. H11-163,197 discloses a structure in which a compression mechanism for compressing a refrigerant and an expansion mechanism for expanding the refrigerant are directly connected to a shaft via an electric motor. The suction side of the compression mechanism communicates with an evaporator, and the discharge side communicates with a gas cooler. On the other hand, the refrigeration cycle is configured such that the suction side of the expansion mechanism communicates with the gas cooler and the discharge side communicates with the evaporator.
[Patent Document 1] JP-A-2000-329416 [Patent Document 2] JP-A-2001-107881 [Problems to be Solved by the Invention]
In Patent Literature 1, the main compressor, the sub-compressor, and the expander need to be constantly lubricated, but since each exists separately in the cycle, oil is unevenly distributed between the compressor and the expander. Could be. Further, the internal pressure of the expander becomes larger than the ambient pressure of the expander, and gas leakage from inside the expander is likely to occur. In addition, the low ambient pressure reduces the amount of refrigerant that dissolves into the lubricating oil, and the low temperature increases the viscosity of the lubricating oil, causing the high-viscosity lubricating oil to load the motor, compressor, and expander. There was a problem. In addition, since an expander and a sub-compressor are used, there are also problems that the cost increases and the installation space increases.
[0005]
In Patent Literature 2, the problem of uneven distribution of oil between the compressor and the expander as in Patent Literature 1 is improved, but since the main compressor and the expander are arranged close to each other, they are divided into an indoor unit and an outdoor unit. In the case of a separate type refrigeration and air-conditioning device, the piping becomes long, and there is a problem that the cost increases and the performance decreases due to pressure loss of the piping. In addition, since the expander that operates at a relatively low temperature is heated under the influence of heat from the compressor and the electric motor that have become hot due to the gas compression action, the enthalpy difference in the expansion process is reduced, and the power generated by the expander is reduced. There was a problem that the recovery was reduced and the efficiency of the expander was reduced.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a refrigeration cycle that can efficiently arrange necessary components and reduce the size and cost of an apparatus.
[0007]
Another object of the present invention is to improve the COP (coefficient of performance) and increase the versatility of a refrigeration system by configuring an expansion / compression system capable of efficiently converting the energy of the expansion process of a working fluid into mechanical energy and using the same. Is to get the cycle.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a radiator for cooling a refrigerant compressed by a main compressor, expansion means for expanding the refrigerant from the radiator, and evaporating the refrigerant expanded by the expansion means. In a refrigeration cycle having an evaporator, a refrigerant flowing out of the radiator is branched, and one of the refrigerants is decompressed and expanded, and an expander that converts expansion energy at that time into mechanical energy is branched off downstream of the radiator. An expansion valve for decompressing and expanding the other refrigerant, a flow path connected to the evaporator for joining the downstream side of the expander and the downstream side of the expansion valve, and a pre-stage expansion valve for controlling a suction pressure of the expander. A sub-compressor driven by the expander to compress the refrigerant evaporated by the evaporator and supply the compressed refrigerant to the main compressor; and a housing for storing the expander and the sub-compressor and for storing lubricating oil therein. Made dense And a container, characterized by keeping the closed vessel to the discharge pressure and the same or substantially the same pressure of the main compressor.
[0009]
By branching a part of the refrigerant discharged from the main compressor or a part of the refrigerant flowing out of the radiator, and allowing the refrigerant to flow in the closed container containing the expander and the sub-compressor, The inside of the closed container may be maintained at the discharge pressure of the main compressor.
[0010]
The refrigerant flowing out of the radiator is branched, introduced and stored in a sealed container containing the expander and the sub-compressor, and the refrigerant is discharged from the upper side of the sealed container to expand the compressor. If the refrigerant is decompressed and expanded by the expander, the sealed container of the expansion / compression system can function as a receiver tank for storing liquid refrigerant or lubricating oil mixed with liquid refrigerant. be able to.
[0011]
Further, the main compressor is housed in a sealed container whose inside is kept at the suction pressure of the main compressor, and a lubricating oil is stored in the sealed container. A compressor inlet can also be provided.
[0012]
Further, the main compressor and its motor are housed therein and a hermetically sealed container containing lubricating oil therein is provided. The inside of the main compressor hermetic container is maintained at the discharge pressure of the main compressor, and the discharge port of the main compressor is maintained. May be provided on the side surface of the closed container below the motor.
[0013]
An oil separator may be provided between the main compressor and the radiator, and the oil separated by the oil separator may be returned to the closed container containing the expander and the sub-compressor.
[0014]
Another feature of the present invention is that, in a refrigeration cycle configured by sequentially connecting a main compressor, a radiator, expansion means, and an evaporator, the refrigerant flowing out of the radiator is branched, and the branched refrigerant is decompressed and expanded. An expander that converts expansion energy into rotational energy and an expansion valve that decompresses and expands the other refrigerant branched downstream of the radiator,
The downstream side of the expander and the downstream side of the expansion valve are joined, a flow path connected to the evaporator, a pre-stage expansion valve for controlling the suction pressure of the expander, and the evaporator driven by the expander A sub-compressor for compressing the evaporated refrigerant and supplying it to the main compressor side, storing the expander and the sub-compressor, storing lubricating oil therein and discharging pressure of the main compressor; And a closed container maintained at the same or almost the same pressure.
[0015]
In the above, the expansion valve that decompresses and expands the other refrigerant that is branched downstream of the radiator is configured to reduce the pressure of the high-pressure refrigerant from the radiator to approximately the same pressure as the pressure of the refrigerant that has been decompressed and expanded by the expander and discharged. It is preferable that the pressure be reduced.
[0016]
By maintaining the inside of the sealed container containing the expander and the sub-compressor at high pressure and low temperature, the differential pressure for supplying lubricating oil to the sliding portion of the expander and the sub-compressor can be increased. The amount of oil supply to the section increases, and the sealing performance can be improved. Further, when the pressure in the closed container becomes high, the amount of the refrigerant dissolved into the lubricating oil increases, so that the viscosity of the lubricating oil decreases, and the viscous friction loss of the expander and the sub-compressor can be reduced. .
[0017]
In addition, since the sealed container containing the expander and the sub-compressor can also serve as a receiver tank, the receiver tank can be omitted.
In the case where the main compressor is housed in an airtight container and the inside of the airtight container is maintained at the main compressor suction pressure, and the main compressor suction port is provided below the motor and above the oil level, the main compressor is discharged from the sub compressor. When the lubricating oil reaches the vicinity of the suction port, it is discharged from the main compressor container together with the flow of the refrigerant, and after passing through the radiator, is supplied to the closed container containing the sub-compressor. The uneven distribution of the lubricating oil between the main compressors can be prevented.
[0018]
Similarly, in the case where the inside of the main compressor closed container is maintained at the main compressor discharge pressure, the main compressor discharge port is provided on the side of the container below the motor. Since the oil is discharged from the main compressor container along with the flow and is supplied to the sub-compressor closed container after passing through the radiator, it is possible to prevent uneven distribution of the lubricating oil between the expansion / compression system and the main compressor.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram of a refrigeration cycle showing a first embodiment of the present invention, FIG. 2 is a Mollier diagram when carbon dioxide (R744), which is a natural refrigerant, is used as a working fluid of the refrigeration cycle, and FIG. It is a diagram which shows the viscosity characteristic of the lubricating oil used for the used refrigeration cycle. In addition, carbon dioxide as a refrigerant has a global warming potential (GWP) as small as several thousandths of a chlorofluorocarbon-based refrigerant, and is excellent in preserving the global environment. On the other hand, it is a high-pressure refrigerant and has a disadvantage that the theoretical COP (coefficient of performance) on the Mollier diagram is low. However, since the energy loss of R744 in the expansion process is larger than that of the chlorofluorocarbon-based refrigerant, there is a possibility that the COP can be significantly improved by recovering the power in the expansion process. The development of a refrigeration cycle equipped with a refrigerator is considered to be the key to the practical application of the refrigerant R744 system. Although the improvement ratio becomes smaller even in a system using a chlorofluorocarbon-based refrigerant, the COP can be improved. Here, an example of a refrigeration cycle using the refrigerant R744 will be described.
[0020]
In FIG. 1, 3 is an electric motor (motor) (M), 2 is a main compressor (MC), 5 is an expander (expansion means) (EX), and 6 is a sub-compressor (SC). The high-temperature and high-pressure refrigerant (state at point C on the Mollier diagram in FIG. 2) compressed by the main compressor 2 is discharged to the hermetically sealed container 1 containing the main compressor 2 and the electric motor 3, and the radiator is discharged from the discharge pipe 11. (Gas cooler) 7, where the heat is radiated and the temperature is lowered (point D in FIG. 2), and then, through an inflow pipe 12, a sealed container 4 of the expansion / compression system containing the expander 5 and the sub-compressor 6. And the inside of the container 4 is kept at a low temperature and a high pressure. The refrigerant discharged from the expansion / compression system closed vessel 4 through the outflow pipe 13 passes through the pre-stage expansion valve 9 and is pre-expanded to match the design pressure ratio of the expander 5. Thereafter, the refrigerant enters the expander 5 through the inflow pipe 14, performs expansion operation, converts expansion energy into mechanical energy, and flows out of the outflow pipe 15 at a low-temperature and low-pressure gas-liquid two-phase refrigerant (point E in FIG. 2). And discharged. The refrigerant discharged from the expander 5 is branched off from the inflow pipe 12 downstream of the radiator 7, merges with the refrigerant decompressed and expanded through an expansion valve (expansion means) 10, and enters the evaporator 8. The gas is absorbed by the sub-compressor 6 through the suction pipe 26 (point A in FIG. 2), is slightly pressurized in the sub-compressor 6, and is discharged from the discharge pipe 16 (point B in FIG. 2). . The gas refrigerant discharged from the sub-compressor 6 returns to the main compressor 2 and is compressed again to become a high-temperature and high-pressure gas refrigerant. The above cycle is repeated to perform the refrigeration operation.
[0021]
The expansion valve 10 is attached to a circuit that bypasses the expander 5, and adjusts the flow rate (pressure) when the operating condition of the refrigeration cycle changes. In the present embodiment, the high-pressure refrigerant compressed by the main compressor 2 is circulated through the expansion / compression system closed container 4 to maintain the inside of the closed container 4 at a high pressure, thereby increasing the amount of the refrigerant dissolved into the lubricating oil 29. As a result, the viscosity of the lubricating oil 29 is reduced (see FIG. 3), and the load on the expander 5 and the sub-compressor 6 can be reduced. In addition, by allowing the refrigerant radiated by the radiator 7 to flow through the closed casing 4, it is possible to minimize heat intrusion from the main compressor into the expander 5 that operates at a relatively low temperature.
[0022]
FIG. 4 is a view for explaining the detailed structure of the expansion / compression system closed vessel 4 shown in FIG. 1, and FIG. 5 is a view for explaining the operation of the expander 5 shown in FIG. FIG.
[0023]
The expansion / compression system includes an expander 5 that converts expansion energy of a working fluid in a refrigeration cycle into mechanical energy, and a sub-compressor 6 that performs work by using the converted mechanical energy. The expander 5 and the sub-compressor 6 are stacked and connected via a crankshaft 17 and housed in a closed container 4.
[0024]
In the expander 5, openings at both ends of a cylinder 20 are closed by a lower bear 18 also serving as a bearing of a crankshaft 17 and an intermediate partition plate 19. The cylinder 20 has a cylindrical inner peripheral surface 20a formed at the center. An eccentric portion 17a is formed on the crankshaft 17 at a portion corresponding to a cylindrical inner peripheral surface 20a of the cylinder 20, and the eccentric portion 17a is formed inside a cylindrical bearing metal 21b pressed into a roller portion 21a of a swing piston 21. The peripheral surface can be slid and rotated.
[0025]
A plate-shaped vane portion 21c is integrally formed on the cylindrical outer peripheral surface of the roller portion 21a. A cylindrical hole 20b having a central axis parallel to the central axis is formed outside the cylindrical inner peripheral surface 20a of the cylinder 20, and a relief hole 20c is formed outside the cylindrical hole 20b. . The cylindrical hole 20b communicates with the cylindrical inner peripheral surface 20a of the cylinder 20 and the relief hole 20c. The vane portion 21c of the swing piston 21 is inserted into the cylindrical hole portion 20b and the escape hole portion 20c. Between the vane portion 21c and the cylindrical hole portion 20b, there is a flat portion slidably in contact with the flat portion of the vane portion 21c and a cylindrical surface portion slidably in contact with the cylindrical surface portion of the cylindrical hole portion 20b. The shoe 22 is incorporated so as to sandwich the vane portion 21c. As a result, the vane portion 21c performs a reciprocating motion passing through the central axis of the cylindrical hole portion 20b and a swinging motion around the central axis, and the shoe 22 performs a swinging motion around the central axis of the cylindrical hole portion 20b. The tip of the vane portion 21c moves in the escape hole portion 20c and does not interfere with the cylinder 20. The inflow pipe attached to the closed container 4 is connected to an inflow passage 20 d that opens into the cylindrical hole 20 b of the cylinder 20.
[0026]
FIG. 5 shows the positional relationship of the oscillating piston 21 in the cylinder 20 at every 90 ° rotation angle of the crankshaft. The vane portion 21c of the oscillating piston 21 is at the top dead center position (the 20 (a state protruding to the outer peripheral portion of 20) is set to a rotation angle θ of 0 °, and the crankshaft 17 rotates clockwise.
[0027]
First, when the rotation angle is 0 °, the inflow passage 20d of the cylinder 20 and the inflow hole 22a of the shoe 22 partially communicate with each other, as shown in FIG. Although the inflow groove 21d formed in the vane portion 21c of the piston 21 is also in communication, the end a of the inflow groove 21d on the cylinder inner peripheral surface 20a side is closed by the shoe 22, so that the vapor compression refrigeration is performed. The high-pressure working fluid at the inlet of the expansion process of the cycle is blocked from flowing into the cylinder 20. On the other hand, since the outflow passage 20e of the cylinder 20 communicates with the inside of the cylinder 20, the working fluid is in a low pressure state corresponding to the expansion process outlet.
[0028]
When the crankshaft 17 rotates clockwise from this state, the vane portion 21c protrudes into the cylinder 20 and the inflow groove 21d starts communicating with the inside of the cylinder as shown in FIG. Begins to flow into the cylinder 20, and the pressure difference in the cylinder 20 causes the crankshaft 17 to rotate clockwise through the piston 21 to generate mechanical energy. (B) When the rotation angle is 90 ° as shown in the drawing, the flow area of the connection portion b between the cylinder inflow passage 20d and the shoe inflow hole 22a is increased by the swing of the shoe 22, so that the inflow of the working fluid is promoted.
[0029]
Further, in a state of a rotation angle of 180 ° rotated by 90 ° (see FIG. 3C), the inflow passage 20d of the cylinder and the inflow hole 22a of the shoe partially communicate with each other as in the state of the rotation angle of 0 °. Due to the reciprocating motion of the vane portion 21c toward the cylinder inner peripheral surface 20a, the communication between the shoe inflow hole 22a and the vane inflow groove 21d is interrupted. For this reason, since the volume of the working chamber is expanded in a state where the inflow of the high-pressure working fluid is cut off, the working fluid expands, rotates the crankshaft, and is converted into mechanical energy.
[0030]
(D) In the state of a rotation angle of 270 ° shown in the figure, the shoe inflow hole 22a and the vane inflow groove 21d start to communicate with each other, but since the shoe 22 swings in the opposite direction to the state of the rotation angle of 90 °, The communication between the inflow passage 20d of the cylinder and the inflow hole 22a of the shoe is cut off, so that the working fluid further expands and is continuously converted into mechanical energy.
[0031]
When the rotation further proceeds, the outflow passage 20e of the cylinder communicates with the inside of the cylinder 20, and the state of the initial rotation angle is 0 °. By repeating the above operation, the expansion energy of the working fluid is converted into mechanical energy.
[0032]
On the other hand, in the sub-compressor 6, both ends of the cylinder 23 are closed by the upper bear 27 also serving as a bearing of the crankshaft 17 and the intermediate partition plate 19. The cylinder 23 has a cylindrical inner peripheral surface 23a formed at the center. The crankshaft 17 has another eccentric portion 17b formed in a portion corresponding to the cylinder inner peripheral surface 23a (the eccentric portion 17b is 180 ° out of rotation with the eccentric portion 17a on the expander 5 side). ), The eccentric portion 17b is rotatably inserted into a roller bearing mounted on the inner peripheral surface of the cylindrical roller 24. A plate-shaped vane 25 is pressed against a cylindrical outer peripheral surface of the roller 24 by a vane spring 25a. In the cylinder 23 outside the cylinder inner peripheral surface 23a, there are provided a vane groove for the vane 25 to reciprocate, a relief hole 23b formed so that the vane 25 does not interfere with the cylinder 23, and a vane spring 25a. A spring hole 23c for mounting the end is formed.
[0033]
The suction pipe 26 attached to the closed container 4 is connected to a suction passage of the cylinder 23, and the refrigerant gas sucked from the suction pipe 26 enters the cylinder 23 through the suction passage. Due to the rotation of the crankshaft 17, the roller 24 moves eccentrically and rotationally along the cylinder inner peripheral surface 23a, and passes through the discharge notch 23e formed by cutting out a part of the cylinder inner peripheral surface 23a. It is discharged from the discharge port 27a formed in the bear 27 to the discharge pipe 16, and flows out to an external refrigeration cycle.
[0034]
A lubricating oil 29 is stored at the bottom of the sealed container 4. The lubricating oil is forcibly supplied to the bearing sliding portion (each bearing of the crankshaft 17). The lubricating oil is supplied to each sliding portion of the bearing by a centrifugal pump action by rotation of the crankshaft 17 through an oil supply passage 17c formed in the crankshaft 17. In the present invention, most of the expander 5 and the sub-compressor 6 are immersed in the lubricating oil 29, and the high-pressure refrigerant compressed by the main compressor 2 flows to the expansion / compression system closed container 4. By keeping the inside at a high pressure, lubricating oil can be easily supplied to each sliding portion from both end surfaces of the oscillating piston 21 of the expander 5 and the roller 24 of the sub-compressor 6.
[0035]
Next, the state of the refrigerant and the lubricating oil in the main compressor and the expansion / compression system will be described with reference to FIGS. FIG. 6 (a) shows an example in which the inside of the main compressor closed vessel is maintained at the main compressor suction pressure, and FIG. 6 (b) shows an example in which the main compressor closed vessel is maintained at the main compressor discharge pressure. (C) shows the state of the refrigerant and the lubricating oil in the expansion / compression system closed container, respectively.
[0036]
When the refrigerant liquefied by the gas cooler 7 is branched and flows into the expansion / compression system closed container 4 from the inflow pipe 12, the liquid refrigerant 31 has a lower density than the lubricating oil 29 and accumulates at the upper portion without being mixed. In this embodiment, by providing the end of the outflow pipe 13 above the oil level 29a of the lubricating oil 29, only the liquid refrigerant 31 can flow out. In the refrigeration cycle, the required amount of refrigerant in the cycle changes depending on conditions. However, in order to change the amount of liquid refrigerant 31 stored in the expansion / compression system closed container 4, the liquid level 31a is raised and lowered to increase the amount of refrigerant in the cycle. The required amount of refrigerant can be easily adjusted. That is, since the sealed container 4 also serves as a receiver tank, the size and cost of the entire apparatus can be reduced.
[0037]
Further, the lubricating oil supplied to each sliding portion by the differential pressure from both end surfaces of the oscillating piston 21 of the expander 5 flows out of the discharge pipe 15 together with the flow of the refrigerant, and is supplied to the sub-compressor 6. Oil and lubricating oil supplied by differential pressure from both end surfaces of the roller 24 of the sub-compressor 6 are discharged from the discharge pipe 16. Further, the lubricating oil is supplied from the discharge pipe 16 to the main compressor 2 and discharged into the main compressor closed vessel 1 to accumulate. From the above process, the lubricating oil 29 stored in the expansion / compression system closed container 4 gradually moves and accumulates in the main compressor closed container 1 and the main compressor closed container 1 and the expansion / compression system closed container. 4, the lubricating oil is unevenly distributed. In particular, in the expansion / compression system closed container 4, the lubricating oil 29 and the gas refrigerant may flow out from the outflow pipe 13 together with the liquid refrigerant 31 as the oil level 29 a of the lubricating oil 29 rises and falls. . However, in this embodiment, as shown in FIG. 6A, when the inside of the main compressor closed container 1 is kept at the suction pressure of the main compressor 2, there is no uneven distribution of the lubricating oil between the closed containers 1 and 4. With the oil level 30a in the state as a reference, the suction port 32 of the main compressor is installed immediately above the oil level 30a. As a result, when the oil level 30a rises to a height equal to or higher than the suction port 32, the oil is sucked into the main compressor 2 from the suction port 32 together with the refrigerant, and flows out from the discharge pipe 11.
[0038]
As shown in FIG. 6 (b), when the inside of the main compressor closed vessel 1 is kept at the discharge pressure of the main compressor 2, the oil level between the closed vessels 1 and 4 in a state where the lubricating oil is not unevenly distributed. With reference to 30a, the discharge pipe 11 is installed on the side of the closed container 1 immediately above the oil level 30a. Thus, when the oil level 30b rises further, the oil flows out of the discharge pipe 11 together with the refrigerant.
[0039]
After the lubricating oil discharged from the discharge pipe 11 is radiated by the gas cooler 7, the lubricating oil is returned from the inflow pipe 12 to the expansion / compression system closed container 4 again. As a result, the uneven distribution of the lubricating oil between the closed containers 1 and 4 can be prevented, and the oil level 29a of the lubricating oil 29 in the expansion / compression system closed container 4 can be prevented from going up and down. Reliability can be improved. By setting the oil levels 30a and 30b of the lubricating oil 30 in the closed container 1 below the electric motor 3, a load on the electric motor 3 by the lubricating oil 30 can be prevented.
[0040]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, while being able to implement | achieve the expansion / compression system which can convert the energy of the expansion process of a working fluid into mechanical energy efficiently, and can utilize it, the inside of an expansion / compression system closed container is equal to the discharge pressure of a main compressor. Alternatively, since the same high pressure is maintained, the viscosity of the lubricating oil can be reduced to reduce the friction loss between the expander and the sub-compressor, thereby improving the COP (coefficient of performance) of the refrigeration cycle. is there. As a result, a refrigeration / air-conditioning system using carbon dioxide, which is a natural refrigerant, can be realized.
[0041]
In addition, by accumulating the liquid refrigerant in the expansion / compression system closed container and also serving as a receiver tank, downsizing and cost reduction can be realized.
[0042]
Further, by maintaining the inside of the expansion / compression system closed vessel at a high pressure, lubricating oil can be easily supplied to each sliding portion in the cylinder of the expander and the sub-compressor by differential pressure.
[0043]
Further, by employing a configuration in which the lubricating oil in the main compressor closed container is returned to the expansion / compression system closed container, the oil can be equalized between the closed containers, and the reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view of a refrigeration cycle showing a first embodiment of the present invention.
FIG. 2 is a Mollier diagram when carbon dioxide is used as a working fluid of a refrigeration cycle.
FIG. 3 is a diagram showing a viscosity characteristic of a lubricating oil used in a refrigeration cycle using carbon dioxide.
FIG. 4 is a longitudinal sectional view illustrating a detailed structure inside the expansion / compression system closed container shown in FIG. 1;
FIG. 5 is an operation explanatory view of the expander shown in FIG. 4;
FIG. 6 is a schematic diagram illustrating a state of a refrigerant and a lubricating oil in a main compressor closed container and an expansion / compression system closed container.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Main compressor closed container, 2 ... Main compressor, 3 ... Electric motor (motor), 4 ... Expansion / compression system closed container, 5 ... Expander, 6 ... Subcompressor, 7 ... Radiator (gas cooler), 8 ... Evaporator, 9 ... Expansion machine pre-stage expansion valve, 10 ... Flow rate adjustment expansion valve, 11 ... Discharge pipe, 12 ... Inflow pipe, 13 ... Outflow pipe, 14 ... Expansion machine inflow pipe, 15 ... Expansion machine discharge pipe , 16: Discharge pipe of sub-compressor, 17: Crank shaft, 17a, 17b: Eccentric part, 17c: Oil supply passage, 18: Lower bear, 19: Intermediate partition plate, 20: Cylinder of expander, 20a: Inside cylindrical shape Peripheral surface (cylinder inner peripheral surface), 20b: cylindrical hole, 20c: relief hole, 20d: inflow passage, 20e: outflow passage, 21: swing piston, 21a: roller portion, 21b: bearing metal, 21c: vane Part, 21d ... inflow groove, 22 ... sh , 22a ... inflow hole, 23 ... cylinder of sub-compressor, 23a ... cylindrical inner peripheral surface (cylinder inner peripheral surface), 23b ... escape hole, 23c ... spring hole, 23e ... discharge notch, 24 ... roller, Reference numeral 25: vane, 25a: vane spring, 26: suction pipe of the sub-compressor, 27: upper bear, 28: oil supply piece, 29, 30: lubricating oil, 29a, 30a, 30b: oil surface, 31: liquid refrigerant, 31a ... Liquid level, 32 ... Suction port of main compressor.

Claims

A radiator that cools the refrigerant compressed by the main compressor, an expansion unit that expands the refrigerant from the radiator, and a refrigeration cycle having an evaporator that evaporates the refrigerant expanded by the expansion unit.
An expander that branches the refrigerant flowing out of the radiator, decompresses and expands one of the refrigerants, and converts expansion energy at that time into mechanical energy.
An expansion valve for decompressing and expanding the other refrigerant branched downstream of the radiator,
Merging the expander downstream and the expansion valve downstream, a flow path connected to the evaporator,
A pre-stage expansion valve for controlling the suction pressure of the expander;
A sub-compressor driven by the expander and compressing the refrigerant evaporated by the evaporator and supplying the compressed refrigerant to the main compressor,
A sealed container containing the expander and the sub-compressor and storing lubricating oil therein,
A refrigeration cycle, wherein the inside of the closed vessel is maintained at the same or substantially the same pressure as the discharge pressure of the main compressor.

2. The refrigeration cycle according to claim 1, wherein a part of the refrigerant discharged from the main compressor is branched and circulated in a closed vessel containing the expander and the sub-compressor.

2. The refrigeration cycle according to claim 1, wherein the refrigerant that has flowed out of the radiator is branched and circulated in one closed container containing the expander and the sub-compressor.

2. The refrigerant according to claim 1, wherein the refrigerant flowing out of the radiator is branched, introduced and stored in a closed container containing the expander and the sub-compressor, and the refrigerant flows out from an upper side of the closed container. The refrigerant is led to the expander, and the refrigerant is decompressed and expanded by the expander.

5. The main compressor according to claim 1, wherein the main compressor is housed in a closed container whose inside is maintained at the suction pressure of the main compressor, and a lubricating oil is stored inside the closed container. A refrigeration cycle, wherein an inlet of the main compressor is provided above an oil level of the oil.

5. A sealed container in which the main compressor and its motor are housed and lubricating oil is stored therein according to any one of claims 1 to 4, wherein the inside of the main compressor sealed container is maintained at the discharge pressure of the main compressor. A refrigerating cycle, wherein a discharge port of a main compressor is provided on a side surface of the closed container below the motor.

An oil separator according to any one of claims 1 to 6, wherein an oil separator is provided between the main compressor and the radiator, and the oil separated by the oil separator is sealed in the expansion device and the sub-compressor. A refrigeration cycle characterized by returning to a container.

In the refrigeration cycle configured by sequentially connecting the main compressor, radiator, expansion means, and evaporator,
An expander that branches the refrigerant flowing out of the radiator, decompresses and expands the branched refrigerant, and converts expansion energy into rotational energy;
An expansion valve for decompressing and expanding the other refrigerant branched downstream of the radiator,
Merging the expander downstream and the expansion valve downstream, a flow path connected to the evaporator,
A pre-stage expansion valve for controlling the suction pressure of the expander;
A sub-compressor for compressing the refrigerant driven by the expander and evaporating in the evaporator and supplying the compressed refrigerant to the main compressor side;
A refrigerating machine, comprising: a closed container that houses the expander and the sub-compressor, stores lubricating oil therein, and is maintained at the same or substantially the same pressure as the discharge pressure of the main compressor. cycle.

The expansion valve according to any one of claims 1 to 8, wherein the expansion valve for decompressing and expanding the other refrigerant branched downstream of the radiator is configured to reduce a pressure of a high-pressure refrigerant from the radiator and a refrigerant discharged after being decompressed and expanded by the expander. A refrigeration cycle controlled to reduce the pressure to a pressure approximately equal to the pressure.