JP4196450B2

JP4196450B2 - Supercritical refrigeration cycle

Info

Publication number: JP4196450B2
Application number: JP31371798A
Authority: JP
Inventors: 泰孝黒田; 伸西田
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 1997-11-06
Filing date: 1998-11-04
Publication date: 2008-12-17
Anticipated expiration: 2018-11-04
Also published as: JPH11201568A

Description

【０００１】
【発明の属する技術分野】
本発明は、放熱器内の圧力が冷媒の臨界圧力を超える蒸気圧縮機式冷凍サイクル（超臨界冷凍サイクル）に関するもので、二酸化炭素（以下、ＣＯ₂と記す。）を冷媒とする超臨界冷凍サイクル（以下、ＣＯ₂サイクルと呼ぶ。）に適用して有効である。
【０００２】
【従来の技術】
ＣＯ₂サイクルの作動は、原理的には、フロンを使用した従来の蒸気圧縮式冷凍サイクルの作動と同じである。すなわち、図２３（ＣＯ₂モリエル線図）のＡ−Ｂ−Ｃ−Ｄ−Ａで示されるように、圧縮機１で気相状態のＣＯ₂を圧縮し（Ａ−Ｂ）、この高温高圧の超臨界状態のＣＯ₂を放熱器２にて冷却する（Ｂ−Ｃ）。
【０００３】
そして、圧力制御弁３により減圧して（Ｃ−Ｄ）、気液２相状態となったＣＯ₂を蒸発させて（Ｄ−Ａ）、蒸発潜熱を空気等の外部流体から奪って外部流体を冷却する。なお、ＣＯ₂は、圧力が飽和液圧力（線分ＣＤと飽和液線ＳＬとの交点の圧力）を下まわるときから、気液２相状態に相変化するので、Ｃの状態からＤの状態へとゆっくり変化する場合には、ＣＯ₂は超臨界状態から液相状態を経て気液２相状態に変化する。
【０００４】
因みに、超臨界状態とは、密度が液密度と略同等でありながら、ＣＯ₂分子が気相状態のように運動する状態をいう。
しかし、ＣＯ₂の臨界温度は約３１℃と従来のフロンの臨界温度（例えば、Ｒ１２では１１２℃）と比べて低いので、夏場等では放熱器側でのＣＯ₂温度がＣＯ₂の臨界点温度より高くなってしまう。つまり、放熱器出口側においてもＣＯ₂は凝縮しない（線分ＢＣが飽和液線と交差しない）。
【０００５】
また、放熱器出口側（Ｃ点）の状態は、圧縮機の吐出圧力と放熱器出口側でのＣＯ₂温度とによって決定され、放熱器出口側でのＣＯ₂温度は、放熱器の放熱能力と外気温度とによって決定する。そして、外気温度は制御することができないので、放熱器出口側でのＣＯ₂温度は、実質的に制御することができない。
したがって、放熱器出口側（Ｃ点）の状態は、圧縮機の吐出圧力（放熱器出口側圧力）を制御することによって制御可能となる。つまり、夏場等の外気温度が高い場合に、十分な冷却能力（エンタルピ差）を確保するためには、図１４のＥ−Ｆ−Ｇ−Ｈ−Ｅで示されるように、放熱器出口側圧力を高くする必要がある。
【０００６】
しかし、放熱器出口側圧力を高くするには、前述のように圧縮機の吐出圧力を高くしなければならないので、圧縮機１の圧縮仕事（圧縮過程のエンタルピ変化量ΔＬ）が増加する。したがって、蒸発過程（Ｄ−Ａ）のエンタルピ変化量Δｉの増加量より圧縮過程（Ａ−Ｂ）のエンタルピ変化量ΔＬの増加量が大きい場合には、ＣＯ₂サイクルの成績係数（ＣＯＰ＝Δｉ／ΔＬ）が悪化する。
【０００７】
そこで、例えば放熱器２出口側でのＣＯ₂温度を４０℃として、放熱器２出口側でのＣＯ₂圧力と成績係数と関係を図２３を用いて試算すれば、図２４の実線に示すように、圧力Ｐ₁（約１０ＭＰａ）において成績係数が最大となる。同様に、放熱器出口側でのＣＯ₂温度を３５℃とした場合には、図２４の破線で示すように、圧力Ｐ₂（約９．０ＭＰａ）において成績係数が最大となる。
【０００８】
以上のようにして、放熱器出口側のＣＯ₂温度と成績係数が最大となる圧力とを算出し、この結果を図２３上に描けば、図２３の太い実線η_max（以下、最適制御線と呼ぶ。）に示すようになる。したがって、上記ＣＯ₂サイクルを効率良く運転するには、放熱器出口側圧力と放熱器出口側のＣＯ₂温度とを、最適制御線η_maxで示されるように制御する必要がある。
【０００９】
因みに、上記最適制御線η_maxは、蒸発器側の圧力を約３．５ＭＰａ（蒸発器温度０℃相当）とし、凝縮域（臨界圧力以下の領域）での過冷却度（サブクール）が約３℃となるように試算したものである。また、図２５は、放熱器出口側のＣＯ₂温度および放熱器出口側の圧力を変数とするデカルト座標に、最適制御線η_maxを描いたものであり、この図から明らかなように、放熱器出口側のＣＯ₂温度が上昇に応じて放熱器出口側の圧力を上昇させる必要がある。
【００１０】
そこで、ＣＯ₂サイクルの放熱器２出口側圧力を制御する圧力制御装置として、発明者等は既に特願平８−１１２４８号を出願している。
【００１１】
【発明が解決しようとする課題】
ところで、発明者等は、蒸発器から流出したＣＯ₂（以下、このＣＯ₂を低圧ＣＯ₂と呼ぶ。）と放熱器から流出したＣＯ₂（以下、このＣＯ₂を高圧ＣＯ₂と呼ぶ。）とを熱交換して蒸発器入口側のＣＯ₂のエンタルピを低下させて、蒸発器入口と出口とのエンタルピ差を拡大してＣＯ₂サイクルの冷凍能力を向上させるＣＯ₂サイクル（図２６のＡ’−Ｂ’−Ｃ−Ｄ参照）を検討していたところ、以下に述べる問題が発生する可能性があることを発見した。
【００１２】
すなわち、上記ＣＯ₂サイクルでは、低圧ＣＯ₂と高圧ＣＯ₂とを熱交換するので、両ＣＯ₂間で熱交換をしないＣＯ₂サイクル（図２６のＡ−Ｂ−Ｃ−Ｄ参照）と異なり、低圧ＣＯ₂は０℃以上の所定の加熱度を有することとなる。
一方、圧力制御装置は、放熱器出口側のＣＯ₂温度に基づいて放熱器出口側の圧力を制御するので、圧力制御装置は、蒸発器での熱負荷が小さくなり、蒸発器内圧力の低下とともに低圧ＣＯ₂温度が低下しても、これに連動して直ちに放熱器出口側の圧力を低下させず、その時の放熱器出口側のＣＯ₂温度に基づいて放熱器出口側の圧力を制御する。
【００１３】
このため、仮に放熱器出口側のＣＯ₂温度が変化しなければ、放熱器出口側の圧力も変化しないので、図２６に示されるように、蒸発器での熱負荷が小さくなると、圧縮機の吸入側から吐出側に至るＣＯ₂の通路においてＣＯ₂温度が上昇してしまう。そして、ＣＯ₂温度が上昇すると、圧縮機の摺動部において油膜切れを誘発するので、圧縮機が破損するという問題が発生してしまう。
【００１４】
因みに、放熱器入口側のＣＯ₂温度が上昇すれば、放熱器出口側のＣＯ₂温度も上昇するので、圧力制御装置が低圧ＣＯ₂温度に直ちに連動して作動しないということを考慮すれば、蒸発器での熱負荷が小さくなると、圧力制御装置は放熱器出口側の圧力を上昇させる。したがって、蒸発器での熱負荷の低下と共にＣＯ₂温度が上昇していく可能性がある。
【００１５】
本発明は、上記点に鑑み、放熱器出口側の温度に基づいて放熱器出口側の圧力を制御する圧力制御装置を有する超臨界冷凍サイクルにおいて、圧縮機の破損を防止することをことを目的とする。
【００１６】
【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、以下の技術的手段を用いる。請求項１〜３に記載の発明では、圧力制御弁（３００）は、閉弁することにより放熱器（２００）の出口側圧力を所定の圧力まで昇圧させた後、開弁して冷媒を減圧することで、放熱器（２００）出口側の冷媒圧力を制御するように構成され、前記所定の圧力は、放熱器（２００）出口側の冷媒温度に基づいて変化する圧力であり、放熱器（２００）出口側の冷媒温度の上昇に応じて前記所定の圧力が上昇し、放熱器（２００）出口側の冷媒温度の低下に応じて前記所定の圧力が低下し、放熱器（２００）出口側の冷媒温度が一定であれば前記所定の圧力も一定になり、さらに、放熱器（２００）出口側の冷媒温度の上昇に応じて圧力制御弁（３００）が閉弁状態で放熱器（２００）出口側の冷媒圧力を上昇させようとする状況下において、蒸発器（４００）の流入側から放熱器（２００）の入口側に至る冷媒通路の所定位置における冷媒温度が所定温度以上となったときに、気液分離装置（５００）から流出した冷媒を熱交換器（６００）を迂回させて圧縮機（１００）に流通させる冷媒バイパス手段（７００）を備えることを特徴とする。
【００１７】
これにより、熱交換器（６００）を経由して圧縮機（１００）に吸入される場合に比べて、圧縮機（１００）吸入側の冷媒温度を低下させることができるので、圧縮機（１００）の吸入側から吐出側に至る冷媒通路において冷媒温度を低下させることができ、圧縮機（１００）の破損を未然に防止することができる。請求項４に記載の発明では、圧力制御弁（３００）は、閉弁することにより放熱器（２００）の出口側圧力を所定の圧力まで昇圧させた後、開弁して冷媒を減圧することで、放熱器（２００）出口側の冷媒圧力を制御するように構成され、前記所定の圧力は、放熱器（２００）出口側の冷媒温度に基づいて変化する圧力であり、放熱器（２００）出口側の冷媒温度の上昇に応じて前記所定の圧力が上昇し、放熱器（２００）出口側の冷媒温度の低下に応じて前記所定の圧力が低下し、放熱器（２００）出口側の冷媒温度が一定であれば前記所定の圧力も一定になり、さらに、放熱器（２００）出口側の冷媒温度の上昇に応じて圧力制御弁（３００）が閉弁状態で放熱器（２００）出口側の冷媒圧力を上昇させようとする状況下において、圧縮機（１００）の吐出側から圧力制御弁（３００）の流入側圧力に至る冷媒通路の所定位置における冷媒温度が所定温度以上となったときに、前記熱交換器（６００）における熱交換を停止させることを特徴とする。
【００１８】
これにより、請求項１に記載の発明と同様に、圧縮機（１００）吸入側の冷媒温度を低下させることができるので、圧縮機（１００）の吸入側から吐出側に至る冷媒通路において冷媒温度を低下させることができ、圧縮機（１００）の破損を未然に防止することができる。請求項５に記載の発明では、圧力制御弁（３００）は、閉弁することにより放熱器（２００）の出口側圧力を所定の圧力まで昇圧させた後、開弁して冷媒を減圧することで、放熱器（２００）出口側の冷媒圧力を制御するように構成され、前記所定の圧力は、放熱器（２００）出口側の冷媒温度に基づいて変化する圧力であり、放熱器（２００）出口側の冷媒温度の上昇に応じて前記所定の圧力が上昇し、放熱器（２００）出口側の冷媒温度の低下に応じて前記所定の圧力が低下し、放熱器（２００）出口側の冷媒温度が一定であれば前記所定の圧力も一定になり、さらに、放熱器（２００）出口側の冷媒温度の上昇に応じて圧力制御弁（３００）が閉弁状態で放熱器（２００）出口側の冷媒圧力を上昇させようとする状況下において、圧力制御弁（３００）の出口側から圧縮機（１００）の吸入側に至る冷媒通路の所定位置における冷媒温度が所定温度以下となったときに、熱交換器（６００）における熱交換を停止させることを特徴とする。
【００１９】
これにより、請求項１に記載の発明と同様に、圧縮機（１００）吸入側の冷媒温度を低下させることができるので、圧縮機（１００）の吸入側から吐出側に至る冷媒通路において冷媒温度を低下させることができ、圧縮機（１００）の破損を未然に防止することができる。
請求項６に記載の発明では、圧縮機（１００）の吐出側から圧力制御装置（３００）の流入側に至る冷媒通路の所定位置における冷媒圧力と、圧力制御装置（３００）の出口側から圧縮機（１００）の吸入側に至る冷媒通路の所定位置における冷媒圧力との差圧が、所定差圧以上となったときに、熱交換器（６００）における熱交換を停止させることを特徴とする。
【００２０】
これにより、請求項１に記載の発明と同様に、圧縮機（１００）吸入側の冷媒温度を低下させることができるので、圧縮機（１００）の吸入側から吐出側に至る冷媒通路において冷媒温度を低下させることができ、圧縮機（１００）の破損を未然に防止することができる。請求項７に記載の発明では、圧力制御弁（３００）は、閉弁することにより放熱器（２００）の出口側圧力を所定の圧力まで昇圧させた後、開弁して冷媒を減圧することで、放熱器（２００）出口側の冷媒圧力を制御するように構成され、前記所定の圧力は、放熱器（２００）出口側の冷媒温度に基づいて変化する圧力であり、放熱器（２００）出口側の冷媒温度の上昇に応じて前記所定の圧力が上昇し、放熱器（２００）出口側の冷媒温度の低下に応じて前記所定の圧力が低下し、放熱器（２００）出口側の冷媒温度が一定であれば前記所定の圧力も一定になり、さらに、放熱器（２００）出口側の冷媒温度の上昇に応じて圧力制御弁（３００）が閉弁状態で放熱器（２００）出口側の冷媒圧力を上昇させようとする状況下において、圧力制御弁（３００）の出口側から圧縮機（１００）の吸入側に至る冷媒通路の所定位置における冷媒圧力が、所定圧力以下となったときに、熱交換器（６００）における熱交換を停止させることを特徴とする。
【００２１】
これにより、請求項１に記載の発明と同様に、圧縮機（１００）吸入側の冷媒温度を低下させることができるので、圧縮機（１００）の吸入側から吐出側に至る冷媒通路において冷媒温度を低下させることができ、圧縮機（１００）の破損を未然に防止することができる。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。
【００２２】
【発明の実施の形態】
（第１実施形態）
図１は本実施形態に係るＣＯ₂サイクルを車両用空調装置に適用したものであり、１００は車両走行用エンジンから駆動力を得て気相状態のＣＯ₂を圧縮する圧縮機である。２００は圧縮機１００で圧縮されたＣＯ₂を外気等との間で熱交換して冷却する放熱器（ガスクーラ）であり、３００は放熱器２出口側でのＣＯ₂温度に応じて放熱器２００出口側圧力を制御する圧力制御弁（圧力制御装置）である。なお、圧力制御弁３００は、放熱器２００出口側圧力を制御するとともに減圧器を兼ねており、ＣＯ₂は、この圧力制御弁３００にて減圧されて低温低圧の気液２相状態のＣＯ₂となる。
【００２３】
４００は、車室内の空気冷却手段をなす蒸発器（吸熱器）で、気液２相状態のＣＯ₂は蒸発器４００内で気化（蒸発）する際に、車室内空気から蒸発潜熱を奪って車室内空気を冷却する。５００は、気相状態のＣＯ₂と液相状態のＣＯ₂とを分離して気相冷媒を圧縮機１００の吸入側に向けて流出させるとともに、液相状態のＣＯ₂を一時的に蓄えるアキュムレータ（気液分離装置）である。
【００２４】
６００は、アキュムレータ５００から流出して圧縮機１００に吸入されるＣＯ₂と、放熱器２００から流出したＣＯ₂との間で熱交換を行う内部熱交換器であり、７１０はアキュムレータ５００から流出したＣＯ₂を内部熱交換器６００を迂回させて圧縮機１００に流通させるバイパス通路７２０を開閉する電磁弁（弁手段）である。
【００２５】
なお、内部熱交換器６００は、図２示すように、渦巻き状のＣＯ₂流路を対抗して設けたものであり、６０１が放熱器２００側に接続される高圧流入口であり、６０２が圧力制御弁３００側に接続される高圧流出口であり、６０３はアキュムレータ５００側に接続される低圧流入口であり、６０４は圧縮機１００側に接続される低圧流出口である。
【００２６】
７１１は圧縮機１００の吐出側のＣＯ₂温度を検出するサーミスタ式の温度センサ（温度検出器）であり、この温度センサ７１１の検出信号は、比較装置７１２に入力される。この比較装置７１２は、温度センサ７１１の検出信号に対応するＣＯ₂温度が所定温度Ｔ（本実施形態では１２０℃）以上であると判定したときに、電磁弁７１０の開閉を制御する制御装置７１３に信号を発するものである。
【００２７】
そして、制御装置７１３は、比較装置７１２からの信号が入力されたときに電磁弁７１０を開き、信号が入力されないときには電磁弁７１０を閉じる。以下、７１０〜７１３、７２０を総称して、冷媒バイパス手段と呼ぶ。
なお、所定温度Ｔは、１２０℃に限定されるものではなく、圧縮機１００の耐摩耗性および潤滑油の耐熱性を考慮して適宜選定されるべきものである。
【００２８】
因みに、８００は、圧力制御弁３００の故障等により、放熱器２００出口側の圧力が異常上昇したときに、圧力制御弁３００を迂回してＣＯ₂を流通させるリリーフ弁である。
次に、圧力制御弁３００の構造について図３を用いて述べる。
３０１は放熱器２から蒸発器４００に至るＣＯ₂流路６ａの一部を形成するととに、後述するエレメントケース３１５を収納するケーシングであり、３０１ａは放熱器２側に接続される流入口３０１ｂを有する上蓋であり、３０１ｃは蒸発器４側に接続される流出口３０１ｄを有するケーシング本体である。
【００２９】
また、ケーシング３０１には、ＣＯ₂流路６ａを上流側空間３０１ｅと下流側空間３０１ｆとに仕切る隔壁部３０２が配設されており、この隔壁部３０２には、上流側空間３０１ｅと下流側空間３０１ｆとを連通させる弁口３０３が形成されている。
そして、弁口３０３は、針状のニードル弁体（以下、弁体と略す。）３０４により開閉され、この弁体３０３および後述するダイヤフラム３０６は、ダイヤフラム３０６の変位に連動して、ダイヤフラム３０６が中立状態から弁体３０３側（ダイヤフラム３０６の厚み方向他端側）に向けて変位したときに弁口３０３を閉じ、厚み方向一端側に向けて変位したときに弁口３０３の開度（弁口３０３を閉じた状態を基準とする弁体３０４の変位量）が最大となるように構成されている。
【００３０】
また、上流側空間３０１ｅには、密閉空間（ガス封入室）３０５が形成されており、この密閉空間３０５は、密閉空間３０５内外の圧力差に応じて変形変位する、ステンレス材からなる薄膜状のダイヤフラム（変位部材）３０６、およびダイヤフラム３０６の厚み方向一端側に配設されたダイヤフラム上側支持部材（形成部材）３０７から形成されている。
【００３１】
一方、ダイヤフラム３０６の厚み方向他端側には、ダイヤフラム上側支持部材（以下、上側支持部材と略す。）３０７と共にダイヤフラム３０６を保持固定するダイヤフラム下側支持部材（保持部材）３０８が配設されており、このダイヤフラム下側支持部材（以下、下側支持部材と略す。）３０８のうち、ダイヤフラム３０６に形成された変形促進部（変位部材変形部）３０６ａに対応する部位には、図４、５に示すように、変形促進部３０６ａに沿う形状に形成された凹部（保持部材変形部）３０８ａが形成されている。
【００３２】
なお、変形促進部３０６ａとは、ダイヤフラム３０６の径外方側の一部を波状に変形させたもので、ダイヤフラム３０６が密閉空間３０５内外の圧力差に略比例して変形変位するようにするためのものである。
また、下側支持部材３０８のうちダイヤフラム３０６に面する部位には、弁口３０３が弁体３０４により閉じられた状態において、弁体３０４のうちダイヤフラム３０６に接触する面３０４ａに対して略同一面となる下側平面部（保持部材平面部）３０８ｂが形成されている。
【００３３】
また、ダイヤフラム３０６の厚み方向一端側（密閉空間３０５内）には、図３に示すように、ダイヤフラム３０６を介して弁体３０４に対して弁口３０３を閉じる向きの弾性力を作用させる第１コイルばね（第１弾性部材）３０９が配設されており、一方、ダイヤフラム３０６の厚み方向他端側には、弁体３０４に対して弁口３０３を開く向きの弾性力を作用させる第２コイルバネ（第２弾性部材）３１０が配設されている。
【００３４】
また、３１１は第１コイルばね３０９のばね座を兼ねるプレート（剛体）であり、このプレート３１１は、ダイヤフラム３０６より剛性が高くなるように所定の厚みを有して金属にて構成されている。そして、プレート３１１は、図４、５に示すように、上側支持部材３０７に形成された段付き部（ストッパ部）３０７ａに接触することにより、ダイヤフラム３０６が、その厚み方向一端側（密閉空間３０５側）に向けて所定値以上に変位することを規制している。
【００３５】
そして、上側支持部材３０７には、プレート３１１と段付き部３０７ａとが接触したときに、プレート３１１のうちダイヤフラム３０６に接触する面３１１ａに対して略同一面となる上側平面部（形成部材平面部）３０７ｂが形成されている。因みに、上側支持部材３０７の円筒部３０７ｃの内壁は、第１コイルばね３０９の案内部をも兼ねている。
【００３６】
なお、プレート３１１および弁体３０４は、両コイルばね３０９、３１０により互いにダイヤフラム３０６に向けて押し付けられているので、プレート３１１、弁体３０４およびダイヤフラム３０６は互いに接触した状態で一体的に変位（稼働）する。
ところで、図３中、３１２は第２コイルばね３１０が弁体３０４に対して作用させる弾性力を調節するとともに、第２コイルばね３１０のプレートを兼ねる調節ネジ（弾性力調節機構）であり、この調節ネジ３１２は、隔壁部３０２に形成された雌ねじ３０２ａにネジ結合している。因みに、両コイルバネ３０９、３１０による初期荷重（弁口３０３を閉じた状態での弾性力）は、ダイヤフラム３０６での圧力換算で約１ＭＰａである。
【００３７】
また、３１３は密閉空間３０５内外に渡って上側支持部材３０７を貫通し、密閉空間３０５内にＣＯ₂を封入するための封入管（貫通部材）であり、この封入管３１３は、ステンレス製の上側支持部材３０７より熱伝導率の大きい銅等の材料から構成されている。なお、下側支持部材３０８もステンレス製である。
そして、封入管３１３は、弁口３０３が閉じられた状態における密閉空間３０５内体積に対して約６００ｋｇ／ｍ³の密度で封入した後、その端部を溶接等の接合手段により閉塞される。
【００３８】
なお、３１４は、隔壁部３０２〜封入管３１３からなるエレメントケース３１５をケーシング本体３０１ｃ内に固定する円錐ばねであり、３１６はエレメントケース３１５（隔壁部３０２）とケーシング本体３０１ｃとの隙間を密閉するＯリングである。
因みに、図６の（ａ）はエレメントケース３１５のＡ矢視図であり、図６の（ｂ）は（ａ）のＢ矢視図であり、図６から明らかなように、弁口３０３は隔壁部３０２の側面側にて上流側空間３０１ｅに連通している。
【００３９】
次に、本実施形態に係る圧力制御弁３００の作動を述べる。
密閉空間３０５内には、約６００ｋｇ／ｍ³でＣＯ₂が封入されているので、密閉空間３０５内圧と温度とは、図７に示される６００ｋｇ／ｍ³の等密度線に沿って変化する。したがって、例えば密閉空間３０５内温度が２０℃の場合には、その内圧は約５．８ＭＰａである。また、弁体３０４には、密閉空間３０５の内圧と両コイルばね３０９、３１０による初期荷重とが同時に作用しているので、その作用圧力は約６．８ＭＰａである。
【００４０】
したがって、放熱器２側である上流側空間３０１ｅの圧力が６．８ＭＰａ以下の場合には、弁口３０３は弁体３０４によって閉止され、また、上流側空間３０１ｅの圧力が６．８ＭＰａを越えると、弁口３０３は開弁する。同様に、例えば密閉空間１２内温度が４０℃の場合には、密閉空間３０５の内圧は図７より約９．７ＭＰａであり、弁体３０４に作用する作用力は約１０．７ＭＰａである。したがって、上流側空間３０１ｅの圧力が１０．７ＭＰａ以下の場合には、弁口３０３は弁体３０４によって閉止され、また、上流側空間３０１ｅの圧力が１０．７ＭＰａを越えると、弁口３０３は開弁する。
【００４１】
次に、ＣＯ₂サイクルの作動を図７を用いて説明する。
ここで、例えば放熱器２００の出口側温度が４０℃、かつ、放熱器２００出口圧力が１０．７ＭＰａ以下のときは、前述のように、圧力制御弁３００は閉じているので、圧縮機１００は、アキュムレータ５００内に蓄えられたＣＯ₂を吸引して放熱器２００へ向けて吐出する。これにより、放熱器２００の出口側圧力が上昇していく（ｂ’−ｃ’→ｂ”−ｃ”）。
【００４２】
そして遂に、放熱器２００の出口側圧力が１０．７ＭＰａを越える（Ｂ−Ｃ）と圧力制御弁３００が開弁するので、ＣＯ₂は減圧しながら気相状態から気液２相状態に相変化して（Ｃ−Ｄ）蒸発器４００内に流れ込む。そして、蒸発器４００内で蒸発して（Ｄ−Ａ）空気を冷却した後、再びアキュムレータ５００に還流する。このとき、放熱器２００の出口側圧力が再び低下するので、圧力制御弁３００は再び閉じる。
【００４３】
すなわち、このＣＯ₂サイクルは、圧力制御弁３００を閉じることにより、放熱器２００の出口側圧力を所定の圧力まで昇圧させた後、ＣＯ₂を減圧、蒸発させて空気を冷却するものである。
次に、本実施形態の特徴を述べる。
本実施形態に係るＣＯ₂サイクルは、冷媒バイパス手段７００を有しているので、圧縮機１００の吐出側（放熱器２００の入口側）ＣＯ₂温度が所定温度Ｔ以上となったときに、アキュムレータ５００から流出したＣＯ₂を内部熱交換器６００を迂回させるので、低圧ＣＯ₂と高圧ＣＯ₂との間で熱交換が行われず、圧縮機１００の吸入側のＣＯ₂（低圧ＣＯ₂）加熱度が０℃となる。したがって、内部熱交換器６００を経由して圧縮機１００に吸入される場合に比べて低圧ＣＯ₂温度を低下させることができるので、圧縮機１００の吸入側から吐出側に至るＣＯ₂の通路においてＣＯ₂温度を低下させることができ、圧縮機１００の破損を未然に防止することができる。
【００４４】
また、アキュムレータ５００を備えているので、圧縮機１００に液相ＣＯ₂が吸入されることを防止できる。延いては、液圧縮より圧縮機１００が破損することを防止できる。
（第２実施形態）
上述の実施形態では、冷媒バイパス手段７００を電磁弁７１０および温度センサ７３０などの電気的な機器によって構成したが、本実施形態は、図８、９に示すように、冷媒バイパス手段７００を機械的に構成したものである。
【００４５】
すなわち、図９に示すように、バイパス通路７２０を開閉する弁体７３１の一方側に、バイパス通路７２０を閉じる向きに弾性力を弁体７３１に作用させるバネ（弾性体）７３２を配設するととともに、他方側にイソブタンなどの流体を所定密度で封入した感温筒部７３３を設け、バイパス通路７２０を開く向きの圧力を弁体７３１に作用させる。
【００４６】
したがって、圧縮機１００吐出側のＣＯ₂温度の上昇とともに感温筒部７３３内の圧力が上昇すると、その圧力により弁体７３１が稼動してバイパス通路７２０が開かれる。一方、圧縮機１００吐出側のＣＯ₂温度の低下とともに感温筒部７３３内の圧力が低下すると、バネ７３２の弾性力によりバイパス通路７２０が閉じられる。
【００４７】
（第３実施形態）
上述の実施形態では、ＣＯ₂温度を電気的または機械的に検出してバイパス通路７２０の開閉を行ったが、本実施形態は、「発明が解決しようとする課題」の欄で述べたように、低圧ＣＯ₂の圧力が低圧ＣＯ₂の温度（圧縮機１００吐出側のＣＯ₂温度）に連動して変化することに着目してなされたものである。
【００４８】
すなわち、図１０に示すように、蒸発器４００の流出側と圧縮機１００の吸入側との間に低圧ＣＯ₂の圧力を検出する圧力センサ（圧力検出手段）７４１、および圧力センサ７４１の検出圧力が所定圧力Ｐ以下となったときに、制御装置７１３に信号を発する比較装置７４２を設けたものである。
なお、所定圧力Ｐは、第１、２実施形態における所定温度Ｔに対応する圧力であって、本実施形態では約６ＭＰａである。
【００４９】
これにより、低圧ＣＯ₂の圧力が所定圧力Ｐ以下となったときに、第１、２実施形態と同様に、アキュムレータ５００から流出したＣＯ₂を内部熱交換器６００を迂回させるので、圧縮機１００の吸入側のＣＯ₂（低圧ＣＯ₂）加熱度が０℃となる。したがって、内部熱交換器６００を経由して圧縮機１００に吸入される場合に比べて低圧ＣＯ₂温度を低下させることができるので、圧縮機１００の吸入側から吐出側に至るＣＯ₂の通路においてＣＯ₂温度を低下させることができ、圧縮機１００の破損を未然に防止することができる。
【００５０】
（第４実施形態）
第３実施形態では、圧縮機１００の吸入側の圧力を圧力センサ７４１にて電気的に検出して冷媒バイパス手段７００を構成したが、本実施形態は、図１１、１２に示すように、圧縮機１００の吸入側の圧力に対して機械的作動する冷媒バイパス手段７００を採用したものである。
【００５１】
すなわち、図１２に示すように、バイパス通路７２０を開閉する弁体７５１の一方側に、バイパス通路７２０を開く向きの弾性力を弁体７５１に作用させるバネ（弾性体）７５２を配設するととともに、他方側に、バイパス通路７２０を閉じる向きの力を弁体７５１に作用させるべく、圧縮機１００の吸入側圧力を導く。
【００５２】
これにより、熱負荷の低下とともに圧縮機１００の吸入側の圧力が低下すると、バネ７５２の弾性力により弁体７５１が稼動してバイパス通路７２０が開かれ、一方、圧縮機１００の吸入側の圧力が上昇すると、その圧力よりバイパス通路７２０が閉じられる。
（第５実施形態）
上述の実施形態では、アキュムレータ５００から流出したＣＯ₂を内部熱交換器６００を迂回させて圧縮機１００に流通させるバイパス通路７２０を開閉することにより、低圧ＣＯ₂と高圧ＣＯ₂との間で熱交換をするか否かを制御していたが、本実施形態は、図１４に示すように、放熱器２００から流出したＣＯ₂を内部熱交換器６００を迂回させて圧力制御弁３００に流通させるバイパス通路７４０を電磁弁７５０にて開閉することにより、低圧ＣＯ₂と高圧ＣＯ₂との間で熱交換をするか否かを制御するように構成したものである。
【００５３】
すなわち、第１実施形態と同様に、圧縮機１００の吐出側（放熱器２００の入口側）ＣＯ₂温度が所定温度Ｔ以上となったときに、電磁弁７５０を開いて放熱器２００から流出したＣＯ₂を内部熱交換器６００を迂回させて圧力制御弁３００に流通させて低圧ＣＯ₂と高圧ＣＯ₂との間の熱交換を停止させる。
これにより、低圧ＣＯ₂温度を低下させることができるので、圧縮機１００の吸入側から吐出側に至るＣＯ₂の通路においてＣＯ₂温度を低下させることができ、圧縮機１００の破損を未然に防止することができる。
【００５４】
（第６実施形態）
本実施形態は、圧縮機１００の吸入側から吐出側に至るＣＯ₂の通路においてＣＯ₂温度が上昇するときとは、例えばクールダウン（急速冷房運転）時のごとく、低圧ＣＯ₂の圧力が高く、低圧ＣＯ₂と高圧ＣＯ₂との圧力差が小さいときであることに着目してなされたものである（図７のＡ−Ｂ−Ｃ−Ｄ参照）。なお、クールダウン（急速冷房運転）時では、一般的に外気温度が略一定と見なせるので、高圧ＣＯ₂の圧力も略一定であると見なすことができる。
【００５５】
そして、クールダウン時では、大きな冷凍能力を必要とするので、内部熱交換器６００にて低圧ＣＯ₂と高圧ＣＯ₂とを熱交換させた方がよい。一方、車室内温度が低下してきて低圧ＣＯ₂の圧力が低下し、低圧ＣＯ₂と高圧ＣＯ₂との圧力差が大きくなってきたときには、大きな冷凍能力を必要としないことに加えて、圧縮機１００の吐出冷媒温度がクールダウン時に比べて上昇するので（図７のＥ−Ｆ−Ｇ参照）、低圧ＣＯ₂と高圧ＣＯ₂との熱交換を停止させた方がよい。
【００５６】
そこで、本実施形態では、図１５に示すように、圧縮機１００の吐出側圧力（＝高圧ＣＯ₂の圧力）と圧縮機１００の吸入側圧力（＝低圧ＣＯ₂の圧力）との差圧により、バイパス通路７２０を機械的に開閉するバイパス手段７６０を設けている。
ここで、バイパス手段７６０は、図１６に示すように、バイパス通路７２０を開閉する弁体７６１の一方側に、バイパス通路７２０を閉じる向きの弾性力を弁体７６１に作用させるバネ（弾性体）７６２を配設するととともに、アキュムレータ５００の流出側圧力（圧縮機１００の吸入側圧力）を作用させ、他方側に、バイパス通路７２０を開く向きの力を弁体７６１に作用させるべく、圧縮機１００の吐出側圧力を導いている。
【００５７】
このとき、バネ７６２は、圧縮機１００の吐出側圧力（＝高圧ＣＯ₂の圧力）と圧縮機１００の吸入側圧力（＝低圧ＣＯ₂の圧力）との差圧が６ＭＰａ以上となったときにバイパス通路７２０を開くように設定されている。
これにより、圧縮機１００の吸入側から吐出側に至るＣＯ₂の通路においてＣＯ₂温度を低下させることができ、圧縮機１００の破損を未然に防止することができる。
【００５８】
（第７実施形態）
本実施形態も第６実施形態と同様に、低圧ＣＯ₂と高圧ＣＯ₂との圧力差に基づいて両ＣＯ₂を熱交換するか否か制御するように構成したものである。
すなわち、本実施形態では、図１７に示すように、圧力制御弁３００のＣＯ₂入口側の圧力（＝高圧ＣＯ₂の圧力）と圧力制御弁３００のＣＯ₂出口側の圧力（＝低圧ＣＯ₂の圧力）との差圧により、バイパス通路７４０を機械的に開閉するバイパス手段７８０を設けている。
【００５９】
ここで、バイパス手段７８０は、図１８に示すように、バイパス通路７２０を開閉する弁体７８１の一方側に、バイパス通路７２０を閉じる向きの弾性力を弁体７８１に作用させるバネ（弾性体）７８２を配設するととともに、圧力制御弁３００のＣＯ₂出口側の圧力（＝低圧ＣＯ₂の圧力）を作用させ、他方側に、バイパス通路７２０を開く向きの力を弁体７７１に作用させるべく、圧縮機１００の吐出側圧力を導いている。
【００６０】
このとき、バネ７６２は、圧力制御弁３００のＣＯ₂入口側の圧力（＝高圧ＣＯ₂の圧力）と圧力制御弁３００のＣＯ₂出口側の圧力（＝低圧ＣＯ₂の圧力）との差圧との差圧が６ＭＰａ以上となったときにバイパス通路７２０を開くように設定されている。
（第８実施形態）
本実施形態は、第６実施形態の冒頭で述べたように、クールダウン時等では、低圧ＣＯ₂の圧力が、車室内温度が低下してきたときに比べて高いことを利用してなされたものである。
【００６１】
すなわち、本実施形態では、図１９に示すように、バイパス通路７２０を開閉するバイパス手段７８０の弁体７８１の一方側に、バイパス通路７２０を開く向きの弾性力を弁体７８１に作用させるバネ（弾性体）７８２を配設するととともに、他方側に、バイパス通路７２０を閉じる向きの力を弁体７８１に作用させるべく、アキュムレータ５００の流出側圧力を導くようにしたものである。
【００６２】
ここで、バネ７８２は、アキュムレータ５００の流出側圧力（低圧ＣＯ₂の圧力）が所定圧力（本実施形態では４ＭＰａ）以下となったときにバイパス通路７２０を開くように設定されている。
（第９実施形態）
本実施形態は、第８実施形態と同様に、クールダウン時等では、低圧ＣＯ₂の圧力が、車室内温度が低下してきたときに比べて高いことを利用してなされたものである。
【００６３】
すなわち、本実施形態では、図２１に示すように、バイパス通路７４０を開閉するバイパス手段７９０の弁体７９１の一方側に、バイパス通路７４０を開く向きの弾性力を弁体７９１に作用させるバネ（弾性体）７９２を配設するととともに、他方側に、バイパス通路７４０を閉じる向きの力を弁体７９１に作用させるべく、圧力制御装置３００の流出側圧力を導くようにしたものである。
【００６４】
ここで、バネ７９２は、圧力制御装置３００の流出側圧力（低圧ＣＯ₂の圧力）が所定圧力（本実施形態では４ＭＰａ）以下となったときにバイパス通路７４０を開くように設定されている。
ところで、本発明は、ＣＯ₂を使用した超臨界冷凍サイクルに使用が限定されるものではなく、例えば、エチレン、エタン、酸化窒素等の超臨界域で使用する冷媒を用いた蒸気圧縮式冷凍サイクルにも適用することができる。
【００６５】
また、上述の実施形態では、圧力制御弁３００を機械的に構成したが、圧力センサおよび電気式の開閉弁などにて電気的な圧力制御弁を構成してもよい。
また、内部熱交換器６００の構造は、図２に示すように、渦巻き状に限定されるものではなく、図１３に示すように、２重円筒状に構成してもよい。
また、第１、２実施形態では、圧縮機１００の吐出側のＣＯ₂温度に基づいて電磁弁などの弁手段を開閉したが、ＣＯ₂温度を検出する位置はこれに限定されるものではなく、蒸発器４００の流入側から放熱器２００の入口側に至る冷媒通路の所定位置であればどこでもよい。但し、所定温度は、その検出位置に応じて適宜設定する必要がある。
【００６６】
また、第８、９実施形態は、低圧ＣＯ₂の圧力に基づいて低圧ＣＯ₂と高圧ＣＯ₂とを熱交換するか否か制御したが、ＣＯ₂圧力は、ＣＯ₂温度と相関関係があることから、低圧ＣＯ₂の温度が所定温度（例えば４ＭＰａのＣＯ₂に対応するＣＯ₂温度）以下となったときに、低圧ＣＯ₂と高圧ＣＯ₂との熱交換を停止させてもよい。
【図面の簡単な説明】
【図１】第１実施形態に係る超臨界冷凍サイクルの模式図である。
【図２】内部熱交換器の説明図である。
【図３】圧力制御弁の断面図である。
【図４】開弁状態を示すダイヤフラム部分の拡大図である。
【図５】閉弁状態を示すダイヤフラム部分の拡大図である。
【図６】（ａ）は図３のＡ矢視図であり、（ｂ）は（ａ）のＢ矢視図である。
【図７】ＣＯ₂のモリエル線図である。
【図８】第２実施形態に係る超臨界冷凍サイクルの模式図である。
【図９】第２実施形態に係る圧力制御弁の模式図である。
【図１０】第３実施形態に係る超臨界冷凍サイクルの模式図である。
【図１１】第３実施形態に係る超臨界冷凍サイクルの模式図である。
【図１２】第４実施形態に係る圧力制御弁の模式図である。
【図１３】内部熱交換器の変形例を示す図面である。
【図１４】第５実施形態に係る超臨界冷凍サイクルの模式図である。
【図１５】第６実施形態に係る超臨界冷凍サイクルの模式図である。
【図１６】第６実施形態２係るバイパス手段の拡大図である。
【図１７】第７実施形態に係る超臨界冷凍サイクルの模式図である。
【図１８】第７実施形態２係るバイパス手段の拡大図である。
【図１９】第８実施形態に係る超臨界冷凍サイクルの模式図である。
【図２０】第８実施形態２係るバイパス手段の拡大図である。
【図２１】第９実施形態に係る超臨界冷凍サイクルの模式図である。
【図２２】第９実施形態２係るバイパス手段の拡大図である。
【図２３】ＣＯ₂のモリエル線図である。
【図２４】放熱器出口側圧力と成績係数（ＣＯＰ）との関係を示すグラフである。
【図２５】放熱器出口側のＣＯ₂温度と目標放熱器出口側圧力との関係を示すグラフである。
【図２６】ＣＯ₂のモリエル線図である。
【符号の説明】
１００…圧縮機、２００…放熱器、３００…圧力制御弁（圧力制御装置）
４００…蒸発器、５００…アキュムレータ（気液分離装置）、
６００…内部熱交換器、７００…冷媒バイパス手段。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vapor compressor refrigeration cycle (supercritical refrigeration cycle) in which the pressure in the radiator exceeds the critical pressure of the refrigerant. ₂ . ) As a refrigerant supercritical refrigeration cycle (CO ₂ Call a cycle. It is effective when applied to).
[0002]
[Prior art]
CO ₂ The operation of the cycle is in principle the same as the operation of a conventional vapor compression refrigeration cycle using Freon. That is, FIG. 23 (CO ₂ As shown by A-B-C-D-A of the Mollier diagram) ₂ (A-B), and this high-temperature and high-pressure supercritical state CO ₂ Is cooled by the radiator 2 (BC).
[0003]
Then, the pressure is reduced by the pressure control valve 3 (C−D), and the CO that has become a gas-liquid two-phase state ₂ Is evaporated (D-A), latent heat of vaporization is taken away from the external fluid such as air, and the external fluid is cooled. CO ₂ Since the phase changes to the gas-liquid two-phase state from when the pressure falls below the saturated liquid pressure (pressure at the intersection of the line segment CD and the saturated liquid line SL), it slowly changes from the C state to the D state. If you do, CO ₂ Changes from a supercritical state through a liquid phase state to a gas-liquid two phase state.
[0004]
Incidentally, the supercritical state means that the density is approximately equal to the liquid density, ₂ A state in which molecules move like a gas phase.
But CO ₂ Is about 31 ° C, which is lower than the critical temperature of conventional chlorofluorocarbons (for example, 112 ° C for R12). ₂ The temperature is CO ₂ It becomes higher than the critical point temperature. In other words, CO also on the radiator outlet side ₂ Does not condense (the line segment BC does not intersect the saturated liquid line).
[0005]
Also, the state of the radiator outlet side (C point) is the discharge pressure of the compressor and the CO at the radiator outlet side. ₂ The CO at the outlet side of the radiator ₂ The temperature is determined by the heat dissipation capability of the radiator and the outside air temperature. And since the outside air temperature cannot be controlled, CO at the radiator outlet side ₂ The temperature cannot be substantially controlled.
Therefore, the state of the radiator outlet side (point C) can be controlled by controlling the discharge pressure (radiator outlet side pressure) of the compressor. That is, in order to ensure a sufficient cooling capacity (enthalpy difference) when the outside air temperature is high such as in summer, as shown by E-F-G-H-E in FIG. Need to be high.
[0006]
However, since the discharge pressure of the compressor has to be increased as described above in order to increase the radiator outlet side pressure, the compression work of the compressor 1 (the enthalpy change amount ΔL in the compression process) increases. Accordingly, when the increase amount of the enthalpy change amount ΔL in the compression process (AB) is larger than the increase amount of the enthalpy change amount Δi in the evaporation process (DA), CO ₂ The coefficient of performance of the cycle (COP = Δi / ΔL) deteriorates.
[0007]
Therefore, for example, CO at the outlet side of the radiator 2 ₂ CO at the outlet side of radiator 2 with temperature of 40 ° C ₂ If the relationship between the pressure and the coefficient of performance is calculated using FIG. 23, as shown by the solid line in FIG. ₁ The coefficient of performance becomes maximum at (about 10 MPa). Similarly, CO at the radiator outlet side ₂ When the temperature is set to 35 ° C., as shown by the broken line in FIG. ₂ The coefficient of performance becomes maximum at (about 9.0 MPa).
[0008]
As described above, the CO at the outlet side of the radiator ₂ If the temperature and the pressure at which the coefficient of performance is maximized are calculated and this result is drawn on FIG. 23, the thick solid line η in FIG. _max (Hereinafter referred to as the optimal control line). Therefore, the CO ₂ To operate the cycle efficiently, the pressure on the outlet side of the radiator and the CO on the outlet side of the radiator ₂ Temperature and the optimal control line η _max Need to be controlled as shown in.
[0009]
Incidentally, the optimum control line η _max Is a trial calculation so that the pressure on the evaporator side is about 3.5 MPa (evaporator temperature equivalent to 0 ° C) and the degree of supercooling (subcool) in the condensation zone (region below the critical pressure) is about 3 ° C. It is. FIG. 25 shows CO at the outlet side of the radiator. ₂ The Cartesian coordinates with the temperature and the pressure at the outlet side of the radiator as variables are _max As is apparent from this figure, the CO at the outlet side of the radiator ₂ It is necessary to increase the pressure on the radiator outlet side as the temperature rises.
[0010]
So CO ₂ The inventors have already filed Japanese Patent Application No. 8-11248 as a pressure control device for controlling the pressure on the outlet side of the radiator 2 of the cycle.
[0011]
[Problems to be solved by the invention]
By the way, the inventors have reported that CO that has flowed out of the evaporator. ₂ (Hereafter, this CO ₂ Low pressure CO ₂ Call it. ) And CO flowing out of the radiator ₂ (Hereafter, this CO ₂ High pressure CO ₂ Call it. ) To exchange CO on the evaporator inlet side ₂ The enthalpy of the evaporator is reduced, and the difference in enthalpy between the evaporator inlet and outlet is expanded. ₂ CO to improve cycle refrigeration capacity ₂ While examining the cycle (see A′-B′-C-D in FIG. 26), it was discovered that the following problems may occur.
[0012]
That is, the CO ₂ In the cycle, low pressure CO ₂ And high pressure CO ₂ Heat exchange with the two CO ₂ CO without heat exchange between ₂ Unlike the cycle (see ABCD in FIG. 26), the low pressure CO ₂ Has a predetermined heating degree of 0 ° C. or higher.
On the other hand, the pressure control device uses CO on the outlet side of the radiator. ₂ Since the pressure on the outlet side of the radiator is controlled based on the temperature, the pressure control device reduces the heat load in the evaporator and reduces the low pressure CO as the evaporator internal pressure decreases. ₂ Even if the temperature drops, the pressure at the outlet side of the radiator is not immediately reduced in conjunction with this, but the CO at the outlet side of the radiator at that time ₂ The pressure on the outlet side of the radiator is controlled based on the temperature.
[0013]
For this reason, the CO on the radiator outlet side ₂ If the temperature does not change, the pressure on the radiator outlet side also does not change. Therefore, as shown in FIG. 26, when the heat load on the evaporator becomes small, the CO from the compressor suction side to the discharge side is reduced. ₂ CO in the passage ₂ The temperature will rise. And CO ₂ When the temperature rises, oil film breakage is induced in the sliding portion of the compressor, which causes a problem that the compressor is damaged.
[0014]
By the way, the CO at the inlet side of the radiator ₂ If the temperature rises, CO on the radiator outlet side ₂ Since the temperature also rises, the pressure control device ₂ Considering that it does not operate immediately in conjunction with temperature, the pressure control device increases the pressure on the radiator outlet side when the heat load on the evaporator is reduced. Therefore, CO decreases with decreasing heat load in the evaporator. ₂ The temperature may increase.
[0015]
In view of the above points, the present invention aims to prevent damage to a compressor in a supercritical refrigeration cycle having a pressure control device that controls the pressure on the radiator outlet side based on the temperature on the radiator outlet side. And
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the present invention uses the following technical means. In invention of Claims 1-3, The pressure control valve (300) is closed to increase the outlet side pressure of the radiator (200) to a predetermined pressure, and then opens the valve to decompress the refrigerant, thereby releasing the radiator (200) outlet side. The predetermined pressure is a pressure that changes based on the refrigerant temperature on the outlet side of the radiator (200), and corresponds to an increase in the refrigerant temperature on the outlet side of the radiator (200). If the predetermined pressure rises and the predetermined pressure decreases in accordance with a decrease in refrigerant temperature on the outlet side of the radiator (200), and the refrigerant temperature on the outlet side of the radiator (200) is constant, the predetermined pressure The pressure also becomes constant, and further, the pressure control valve (300) tries to increase the refrigerant pressure on the outlet side of the radiator (200) when the pressure control valve (300) is closed according to the increase in the refrigerant temperature on the outlet side of the radiator (200). Under circumstances, When the refrigerant temperature at a predetermined position in the refrigerant passage extending from the inlet side of the evaporator (400) to the inlet side of the radiator (200) becomes equal to or higher than a predetermined temperature, the refrigerant flowing out of the gas-liquid separator (500) is heated. Refrigerant bypass means (700) for bypassing the exchanger (600) and flowing to the compressor (100) is provided.
[0017]
As a result, the refrigerant temperature on the suction side of the compressor (100) can be reduced as compared with the case where the refrigerant is sucked into the compressor (100) via the heat exchanger (600). The refrigerant temperature can be lowered in the refrigerant passage extending from the suction side to the discharge side, and damage to the compressor (100) can be prevented. In the invention according to claim 4, The pressure control valve (300) is closed to increase the outlet side pressure of the radiator (200) to a predetermined pressure, and then opens the valve to decompress the refrigerant, thereby releasing the radiator (200) outlet side. The predetermined pressure is a pressure that changes based on the refrigerant temperature on the outlet side of the radiator (200), and corresponds to an increase in the refrigerant temperature on the outlet side of the radiator (200). If the predetermined pressure rises and the predetermined pressure decreases in accordance with a decrease in refrigerant temperature on the outlet side of the radiator (200), and the refrigerant temperature on the outlet side of the radiator (200) is constant, the predetermined pressure The pressure also becomes constant, and further, the pressure control valve (300) tries to increase the refrigerant pressure on the outlet side of the radiator (200) when the pressure control valve (300) is closed according to the increase in the refrigerant temperature on the outlet side of the radiator (200). Under circumstances, Pressure control from the discharge side of the compressor (100) valve The heat exchange in the heat exchanger (600) is stopped when the refrigerant temperature at a predetermined position of the refrigerant passage reaching the inflow side pressure of (300) becomes equal to or higher than a predetermined temperature.
[0018]
Accordingly, the refrigerant temperature on the suction side of the compressor (100) can be lowered as in the invention described in claim 1, and therefore, the refrigerant temperature in the refrigerant passage from the suction side to the discharge side of the compressor (100). And the compressor (100) can be prevented from being damaged. In the invention according to claim 5, The pressure control valve (300) is closed to increase the outlet side pressure of the radiator (200) to a predetermined pressure, and then opens the valve to decompress the refrigerant, thereby releasing the radiator (200) outlet side. The predetermined pressure is a pressure that changes based on the refrigerant temperature on the outlet side of the radiator (200), and corresponds to an increase in the refrigerant temperature on the outlet side of the radiator (200). If the predetermined pressure rises and the predetermined pressure decreases in accordance with a decrease in refrigerant temperature on the outlet side of the radiator (200), and the refrigerant temperature on the outlet side of the radiator (200) is constant, the predetermined pressure The pressure also becomes constant, and further, the pressure control valve (300) tries to increase the refrigerant pressure on the outlet side of the radiator (200) when the pressure control valve (300) is closed according to the increase in the refrigerant temperature on the outlet side of the radiator (200). Under circumstances, Pressure control valve The heat exchange in the heat exchanger (600) is stopped when the refrigerant temperature at a predetermined position in the refrigerant passage extending from the outlet side of (300) to the suction side of the compressor (100) becomes equal to or lower than a predetermined temperature. And
[0019]
Accordingly, the refrigerant temperature on the suction side of the compressor (100) can be lowered as in the invention described in claim 1, and therefore, the refrigerant temperature in the refrigerant passage from the suction side to the discharge side of the compressor (100). And the compressor (100) can be prevented from being damaged.
According to the sixth aspect of the present invention, the refrigerant pressure at a predetermined position in the refrigerant passage from the discharge side of the compressor (100) to the inflow side of the pressure control device (300) and the compression from the outlet side of the pressure control device (300). The heat exchange in the heat exchanger (600) is stopped when the differential pressure from the refrigerant pressure at a predetermined position in the refrigerant passage leading to the suction side of the machine (100) becomes equal to or higher than the predetermined differential pressure. .
[0020]
Accordingly, the refrigerant temperature on the suction side of the compressor (100) can be lowered as in the invention described in claim 1, and therefore, the refrigerant temperature in the refrigerant passage from the suction side to the discharge side of the compressor (100). And the compressor (100) can be prevented from being damaged. In invention of Claim 7, The pressure control valve (300) is closed to increase the outlet side pressure of the radiator (200) to a predetermined pressure, and then opens the valve to decompress the refrigerant, thereby releasing the radiator (200) outlet side. The predetermined pressure is a pressure that changes based on the refrigerant temperature on the outlet side of the radiator (200), and corresponds to an increase in the refrigerant temperature on the outlet side of the radiator (200). If the predetermined pressure rises and the predetermined pressure decreases in accordance with a decrease in refrigerant temperature on the outlet side of the radiator (200), and the refrigerant temperature on the outlet side of the radiator (200) is constant, the predetermined pressure The pressure also becomes constant, and further, the pressure control valve (300) tries to increase the refrigerant pressure on the outlet side of the radiator (200) when the pressure control valve (300) is closed according to the increase in the refrigerant temperature on the outlet side of the radiator (200). Under circumstances, Pressure control valve Stopping the heat exchange in the heat exchanger (600) when the refrigerant pressure at a predetermined position of the refrigerant passage extending from the outlet side of (300) to the suction side of the compressor (100) becomes equal to or lower than the predetermined pressure. Features.
[0021]
Accordingly, the refrigerant temperature on the suction side of the compressor (100) can be lowered as in the invention described in claim 1, and therefore, the refrigerant temperature in the refrigerant passage from the suction side to the discharge side of the compressor (100). And the compressor (100) can be prevented from being damaged. Incidentally, the reference numerals in parentheses of the above means are the embodiments described later. In It is an example which shows the correspondence with the specific means of description.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows a CO according to this embodiment. ₂ The cycle is applied to a vehicle air conditioner, and 100 is a gas phase CO 2 obtained by obtaining driving force from a vehicle travel engine. ₂ It is a compressor that compresses. 200 represents CO compressed by the compressor 100. ₂ Is a radiator (gas cooler) that exchanges heat with the outside air and cools it, and 300 is a CO 2 at the outlet side of the radiator 2. ₂ This is a pressure control valve (pressure control device) that controls the pressure on the outlet side of the radiator 200 in accordance with the temperature. The pressure control valve 300 controls the pressure on the outlet side of the radiator 200 and also serves as a decompressor. ₂ Is reduced in pressure by the pressure control valve 300 and is in a low-temperature low-pressure gas-liquid two-phase state. ₂ It becomes.
[0023]
Reference numeral 400 denotes an evaporator (heat absorber) that serves as an air cooling means in the passenger compartment. ₂ When vaporizing (evaporating) in the evaporator 400, the vehicle interior air is deprived of the latent heat of vaporization and the vehicle interior air is cooled. 500 is the gas phase CO ₂ And liquid phase CO ₂ And the gas-phase refrigerant flows out toward the suction side of the compressor 100, and the liquid-phase CO ₂ Is an accumulator (gas-liquid separator) that temporarily stores.
[0024]
600 represents CO that flows out of the accumulator 500 and is sucked into the compressor 100. ₂ And CO flowing out of the radiator 200 ₂ 710 is an internal heat exchanger that exchanges heat with the CO. ₂ Is a solenoid valve (valve means) that opens and closes a bypass passage 720 that bypasses the internal heat exchanger 600 and flows to the compressor 100.
[0025]
As shown in FIG. 2, the internal heat exchanger 600 has a spiral CO 2 ₂ 601 is a high-pressure inlet connected to the radiator 200 side, 602 is a high-pressure outlet connected to the pressure control valve 300 side, and 603 is the accumulator 500 side. 604 is a low-pressure outlet connected to the compressor 100 side.
[0026]
Reference numeral 711 denotes CO on the discharge side of the compressor 100. ₂ This is a thermistor type temperature sensor (temperature detector) that detects the temperature, and the detection signal of this temperature sensor 711 is input to the comparison device 712. The comparison device 712 includes a CO corresponding to the detection signal of the temperature sensor 711. ₂ When it is determined that the temperature is equal to or higher than the predetermined temperature T (120 ° C. in the present embodiment), a signal is sent to the control device 713 that controls the opening / closing of the electromagnetic valve 710.
[0027]
The control device 713 opens the electromagnetic valve 710 when the signal from the comparison device 712 is input, and closes the electromagnetic valve 710 when the signal is not input. Hereinafter, 710 to 713 and 720 are collectively referred to as refrigerant bypass means.
The predetermined temperature T is not limited to 120 ° C., and should be appropriately selected in consideration of the wear resistance of the compressor 100 and the heat resistance of the lubricating oil.
[0028]
Incidentally, when the pressure on the outlet side of the radiator 200 rises abnormally due to a failure of the pressure control valve 300, 800 bypasses the pressure control valve 300 and ₂ It is a relief valve that circulates.
Next, the structure of the pressure control valve 300 will be described with reference to FIG.
301 is the CO from the radiator 2 to the evaporator 400. ₂ A part of the flow path 6a is formed and a casing for accommodating an element case 315 to be described later. 301a is an upper lid having an inflow port 301b connected to the radiator 2 side, and 301c is on the evaporator 4 side. It is a casing main body which has the outflow port 301d connected.
[0029]
Also, the casing 301 has a CO ₂ A partition wall 302 that divides the flow path 6a into an upstream space 301e and a downstream space 301f is provided. The partition wall 302 has a valve port 303 that allows the upstream space 301e and the downstream space 301f to communicate with each other. Is formed.
The valve port 303 is opened and closed by a needle-like needle valve body (hereinafter abbreviated as a valve body) 304, and the valve body 303 and a diaphragm 306, which will be described later, are linked with the displacement of the diaphragm 306. When the valve body 303 is displaced from the neutral state toward the valve body 303 (the other end in the thickness direction of the diaphragm 306), the valve port 303 is closed, and when the valve body 303 is displaced toward the one end in the thickness direction, The displacement amount of the valve body 304 with reference to the state in which 303 is closed is maximized.
[0030]
Further, a sealed space (gas filled chamber) 305 is formed in the upstream space 301e, and this sealed space 305 is a thin film-like material made of stainless steel that is deformed and displaced in accordance with the pressure difference inside and outside the sealed space 305. A diaphragm (displacement member) 306 and a diaphragm upper support member (formation member) 307 disposed on one end in the thickness direction of the diaphragm 306 are formed.
[0031]
On the other hand, a diaphragm lower support member (holding member) 308 that holds and fixes the diaphragm 306 together with a diaphragm upper support member (hereinafter, abbreviated as an upper support member) 307 is disposed on the other end in the thickness direction of the diaphragm 306. Of the diaphragm lower support member (hereinafter, abbreviated as the lower support member) 308, a portion corresponding to the deformation promoting portion (displacement member deforming portion) 306a formed in the diaphragm 306 is shown in FIGS. As shown, a recess (holding member deforming portion) 308a formed in a shape along the deformation promoting portion 306a is formed.
[0032]
The deformation promoting part 306a is a part of the outer side of the diaphragm 306 deformed in a wave shape so that the diaphragm 306 is deformed and displaced approximately in proportion to the pressure difference inside and outside the sealed space 305. belongs to.
Further, the portion of the lower support member 308 that faces the diaphragm 306 is substantially flush with the surface 304a of the valve body 304 that contacts the diaphragm 306 when the valve port 303 is closed by the valve body 304. A lower flat portion (holding member flat portion) 308b is formed.
[0033]
Further, as shown in FIG. 3, a first elastic force is applied to one end side in the thickness direction of the diaphragm 306 (in the sealed space 305) so as to close the valve port 303 with respect to the valve body 304 via the diaphragm 306. A coil spring (first elastic member) 309 is disposed. On the other hand, a second coil spring that applies an elastic force in the direction of opening the valve port 303 to the valve body 304 is applied to the other end in the thickness direction of the diaphragm 306. (Second elastic member) 310 is provided.
[0034]
Reference numeral 311 denotes a plate (rigid body) that also serves as a spring seat for the first coil spring 309. The plate 311 is made of metal having a predetermined thickness so as to be more rigid than the diaphragm 306. 4 and 5, when the plate 311 comes into contact with a stepped portion (stopper portion) 307a formed on the upper support member 307, the diaphragm 306 has one end in the thickness direction (sealed space 305). The displacement to a predetermined value or more toward the side) is regulated.
[0035]
When the plate 311 and the stepped portion 307a are in contact with the upper support member 307, the upper plane portion (formation member plane portion) that is substantially flush with the surface 311a of the plate 311 that contacts the diaphragm 306 ) 307b is formed. Incidentally, the inner wall of the cylindrical portion 307 c of the upper support member 307 also serves as a guide portion for the first coil spring 309.
[0036]
Since the plate 311 and the valve body 304 are pressed against the diaphragm 306 by the coil springs 309 and 310, the plate 311, the valve body 304, and the diaphragm 306 are integrally displaced (operated) while being in contact with each other. )
In FIG. 3, reference numeral 312 denotes an adjusting screw (elastic force adjusting mechanism) that adjusts the elastic force that the second coil spring 310 acts on the valve body 304 and also serves as a plate of the second coil spring 310. The adjustment screw 312 is screwed to a female screw 302 a formed in the partition wall 302. Incidentally, the initial load (elastic force with the valve port 303 closed) by the coil springs 309 and 310 is about 1 MPa in terms of pressure in the diaphragm 306.
[0037]
Further, 313 penetrates the upper support member 307 across the inside and outside of the sealed space 305, and CO inside the sealed space 305. ₂ This sealing tube 313 is made of a material such as copper having a higher thermal conductivity than the upper support member 307 made of stainless steel. The lower support member 308 is also made of stainless steel.
The sealed tube 313 is about 600 kg / m with respect to the volume in the sealed space 305 when the valve port 303 is closed. ^Three Then, the end portion is closed by a joining means such as welding.
[0038]
Reference numeral 314 denotes a conical spring for fixing the element case 315 including the partition wall 302 to the enclosure tube 313 in the casing main body 301c, and 316 seals a gap between the element case 315 (partition wall 302) and the casing main body 301c. O-ring.
Incidentally, FIG. 6A is a view from the arrow A of the element case 315, FIG. 6B is a view from the arrow B of FIG. 6A, and as is clear from FIG. It communicates with the upstream space 301e on the side surface side of the partition wall 302.
[0039]
Next, the operation of the pressure control valve 300 according to this embodiment will be described.
In the sealed space 305, about 600 kg / m ^Three In CO ₂ Is enclosed, so that the internal pressure and temperature of the sealed space 305 are 600 kg / m shown in FIG. ^Three Varies along the isodensity line. Therefore, for example, when the temperature in the sealed space 305 is 20 ° C., the internal pressure is about 5.8 MPa. Further, since the internal pressure of the sealed space 305 and the initial load by the two coil springs 309 and 310 are simultaneously acting on the valve body 304, the working pressure is about 6.8 MPa.
[0040]
Therefore, when the pressure in the upstream space 301e on the radiator 2 side is 6.8 MPa or less, the valve port 303 is closed by the valve body 304, and when the pressure in the upstream space 301e exceeds 6.8 MPa. The valve port 303 is opened. Similarly, for example, when the temperature in the sealed space 12 is 40 ° C., the internal pressure of the sealed space 305 is about 9.7 MPa from FIG. 7, and the acting force acting on the valve body 304 is about 10.7 MPa. Therefore, when the pressure in the upstream space 301e is 10.7 MPa or less, the valve port 303 is a valve body When closed by 304 and the pressure in the upstream space 301e exceeds 10.7 MPa, the valve port 303 is opened.
[0041]
Next, CO ₂ The operation of the cycle will be described with reference to FIG.
Here, for example, when the outlet side temperature of the radiator 200 is 40 ° C. and the outlet pressure of the radiator 200 is 10.7 MPa or less, the pressure control valve 300 is closed as described above. , CO stored in accumulator 500 ₂ Is sucked and discharged toward the radiator 200. Thereby, the outlet side pressure of the radiator 200 increases (b′−c ′ → b ″ −c ″).
[0042]
Finally, when the pressure on the outlet side of the radiator 200 exceeds 10.7 MPa (BC), the pressure control valve 300 is opened. ₂ Changes from a gas phase to a gas-liquid two-phase state while reducing the pressure (CD) and flows into the evaporator 400. And after evaporating in the evaporator 400 (DA) and cooling air, it recirculates to the accumulator 500 again. At this time, since the outlet side pressure of the radiator 200 decreases again, the pressure control valve 300 is closed again.
[0043]
That is, this CO ₂ In the cycle, the pressure on the outlet side of the radiator 200 is increased to a predetermined pressure by closing the pressure control valve 300, and then the CO 2 ₂ Is cooled and evaporated to cool the air.
Next, features of the present embodiment will be described.
CO according to this embodiment ₂ Since the cycle includes the refrigerant bypass means 700, the discharge side of the compressor 100 (the inlet side of the radiator 200) CO ₂ CO flowing out of accumulator 500 when temperature exceeds predetermined temperature T ₂ Bypasses the internal heat exchanger 600, so low pressure CO ₂ And high pressure CO ₂ Heat exchange between the compressor 100 and the CO on the suction side of the compressor 100 ₂ (Low pressure CO ₂ ) The heating degree becomes 0 ° C. Therefore, compared with the case where it is sucked into the compressor 100 via the internal heat exchanger 600, the low pressure CO ₂ Since the temperature can be lowered, the CO from the suction side to the discharge side of the compressor 100 ₂ CO in the passage ₂ The temperature can be lowered and the compressor 100 can be prevented from being damaged.
[0044]
In addition, since the accumulator 500 is provided, the compressor 100 includes a liquid phase CO. ₂ Can be prevented from being inhaled. As a result, it is possible to prevent the compressor 100 from being damaged by liquid compression.
(Second Embodiment)
In the above-described embodiment, the refrigerant bypass means 700 is configured by electrical devices such as the electromagnetic valve 710 and the temperature sensor 730. However, in the present embodiment, as shown in FIGS. It is configured.
[0045]
That is, as shown in FIG. 9, a spring (elastic body) 732 that applies an elastic force to the valve body 731 in a direction to close the bypass passage 720 is disposed on one side of the valve body 731 that opens and closes the bypass passage 720. On the other side, a temperature sensing cylinder portion 733 in which a fluid such as isobutane is sealed at a predetermined density is provided, and pressure that opens the bypass passage 720 is applied to the valve body 731.
[0046]
Therefore, the CO on the discharge side of the compressor 100 ₂ When the pressure in the temperature sensing cylinder portion 733 rises as the temperature rises, the valve body 731 is operated by the pressure and the bypass passage 720 is opened. On the other hand, the CO on the discharge side of the compressor 100 ₂ When the pressure in the temperature sensing cylinder portion 733 decreases as the temperature decreases, the bypass passage 720 is closed by the elastic force of the spring 732.
[0047]
(Third embodiment)
In the above embodiment, CO ₂ The bypass passage 720 is opened and closed by detecting the temperature electrically or mechanically. As described in the section “Problems to be solved by the invention”, this embodiment is a low-pressure CO. ₂ Pressure is low pressure CO ₂ Temperature (CO on the discharge side of the compressor 100 ₂ It was made by paying attention to the fact that it changes in conjunction with (temperature).
[0048]
That is, as shown in FIG. 10, a low pressure CO is provided between the outflow side of the evaporator 400 and the suction side of the compressor 100. ₂ A pressure sensor (pressure detection means) 741 for detecting the pressure of the pressure sensor 741 and a comparison device 742 that issues a signal to the control device 713 when the detected pressure of the pressure sensor 741 becomes a predetermined pressure P or less.
The predetermined pressure P is a pressure corresponding to the predetermined temperature T in the first and second embodiments, and is about 6 MPa in the present embodiment.
[0049]
This allows low pressure CO ₂ When the pressure of the gas becomes equal to or lower than the predetermined pressure P, the CO that has flowed out of the accumulator 500 is the same as in the first and second embodiments. ₂ To bypass the internal heat exchanger 600, the CO on the suction side of the compressor 100 ₂ (Low pressure CO ₂ ) The heating degree becomes 0 ° C. Therefore, compared with the case where it is sucked into the compressor 100 via the internal heat exchanger 600, the low pressure CO ₂ Since the temperature can be lowered, the CO from the suction side to the discharge side of the compressor 100 ₂ CO in the passage ₂ The temperature can be lowered and the compressor 100 can be prevented from being damaged.
[0050]
(Fourth embodiment)
In the third embodiment, the refrigerant bypass means 700 is configured by electrically detecting the pressure on the suction side of the compressor 100 by the pressure sensor 741, but in this embodiment, as shown in FIGS. The refrigerant bypass means 700 that mechanically operates with respect to the pressure on the suction side of the machine 100 is employed.
[0051]
That is, as shown in FIG. 12, a spring (elastic body) 752 for applying an elastic force to the valve body 751 to open the bypass passage 720 to one side of the valve body 751 that opens and closes the bypass passage 720 is provided. On the other side, the suction side pressure of the compressor 100 is introduced so that a force in the direction of closing the bypass passage 720 acts on the valve body 751.
[0052]
As a result, when the pressure on the suction side of the compressor 100 decreases as the thermal load decreases, the valve body 751 is operated by the elastic force of the spring 752 to open the bypass passage 720, while the pressure on the suction side of the compressor 100 is Rises, the bypass passage 720 is closed by the pressure.
(Fifth embodiment)
In the above-described embodiment, the CO that has flowed out of the accumulator 500. ₂ By opening and closing a bypass passage 720 that bypasses the internal heat exchanger 600 and flows to the compressor 100, low pressure CO ₂ And high pressure CO ₂ In the present embodiment, as shown in FIG. 14, CO 2 flowing out of the radiator 200 is controlled. ₂ By opening and closing the bypass passage 740 that bypasses the internal heat exchanger 600 and flows to the pressure control valve 300 with the electromagnetic valve 750, low pressure CO ₂ And high pressure CO ₂ It is comprised so that it may control whether it heat-exchanges between.
[0053]
That is, as in the first embodiment, the discharge side of the compressor 100 (the inlet side of the radiator 200) CO ₂ When the temperature exceeds a predetermined temperature T, the solenoid valve 750 is opened and the CO that has flowed out of the radiator 200 ₂ Is bypassed through the internal heat exchanger 600 and circulated through the pressure control valve 300 to provide low pressure CO. ₂ And high pressure CO ₂ The heat exchange with is stopped.
This allows low pressure CO ₂ Since the temperature can be lowered, the CO from the suction side to the discharge side of the compressor 100 ₂ CO in the passage ₂ The temperature can be lowered and the compressor 100 can be prevented from being damaged.
[0054]
(Sixth embodiment)
In the present embodiment, the CO from the suction side to the discharge side of the compressor 100 ₂ CO in the passage ₂ When the temperature rises, for example, during a cool-down (rapid cooling operation), low-pressure CO ₂ High pressure, low pressure CO ₂ And high pressure CO ₂ Is made when paying attention to the fact that the pressure difference is small (see A-B-C-D in FIG. 7). During cool-down (rapid cooling operation), the outside air temperature can generally be regarded as substantially constant, so high-pressure CO ₂ It can be considered that the pressure of is substantially constant.
[0055]
And at the time of cool-down, since a large refrigerating capacity is required, the internal heat exchanger 600 uses a low pressure CO. ₂ And high pressure CO ₂ It is better to exchange heat with. On the other hand, the temperature in the passenger compartment has dropped and low pressure CO ₂ Pressure decreases, low pressure CO ₂ And high pressure CO ₂ In addition to not requiring a large refrigeration capacity, the discharge refrigerant temperature of the compressor 100 rises compared to the time of cool-down (see EFG in FIG. 7). , Low pressure CO ₂ And high pressure CO ₂ It is better to stop the heat exchange with.
[0056]
Therefore, in the present embodiment, as shown in FIG. 15, the discharge side pressure (= high pressure CO) of the compressor 100. ₂ Pressure) and suction side pressure of the compressor 100 (= low pressure CO) ₂ The bypass means 760 is provided for mechanically opening and closing the bypass passage 720 by a pressure difference between the pressure and the pressure.
Here, as shown in FIG. 16, the bypass means 760 is a spring (elastic body) that acts on the valve body 761 with an elastic force in a direction to close the bypass passage 720 on one side of the valve body 761 that opens and closes the bypass passage 720. Compressor 100 is arranged so that the outlet side pressure of accumulator 500 (the suction side pressure of compressor 100) is applied and the force that opens bypass passage 720 is applied to valve body 761 on the other side. The discharge side pressure is guided.
[0057]
At this time, the spring 762 causes the discharge side pressure of the compressor 100 (= high pressure CO). ₂ Pressure) and suction side pressure of the compressor 100 (= low pressure CO) ₂ The bypass passage 720 is set to be opened when the differential pressure with respect to the pressure of 6) is 6 MPa or more.
Thereby, the CO from the suction side to the discharge side of the compressor 100 ₂ CO in the passage ₂ The temperature can be lowered and the compressor 100 can be prevented from being damaged.
[0058]
(Seventh embodiment)
In the present embodiment, as in the sixth embodiment, the low pressure CO ₂ And high pressure CO ₂ Both CO based on the pressure difference between ₂ Is configured to control whether or not to exchange heat.
That is, in this embodiment, as shown in FIG. ₂ Pressure on the inlet side (= high pressure CO ₂ Pressure) and CO of the pressure control valve 300 ₂ Outlet pressure (= low pressure CO ₂ The bypass means 780 is provided for mechanically opening and closing the bypass passage 740 by a pressure difference between the pressure and the pressure.
[0059]
Here, as shown in FIG. 18, the bypass means 780 is a spring (elastic body) that applies an elastic force to the valve body 781 to close the bypass passage 720 on one side of the valve body 781 that opens and closes the bypass passage 720. 782 is provided, and the CO of the pressure control valve 300 is ₂ Outlet pressure (= low pressure CO ₂ The pressure on the discharge side of the compressor 100 is introduced to the valve body 771 so that the force in the direction of opening the bypass passage 720 is applied to the valve body 771.
[0060]
At this time, the spring 762 causes the CO of the pressure control valve 300 to move. ₂ Pressure on the inlet side (= high pressure CO ₂ Pressure) and CO of the pressure control valve 300 ₂ Outlet pressure (= low pressure CO ₂ The bypass passage 720 is set to open when the pressure difference between the pressure and the pressure difference becomes 6 MPa or more.
(Eighth embodiment)
In the present embodiment, as described at the beginning of the sixth embodiment, the low-pressure CO is used during cool-down. ₂ This is made by utilizing the fact that the pressure in the vehicle is higher than when the temperature in the passenger compartment decreases.
[0061]
That is, in the present embodiment, as shown in FIG. 19, on the one side of the valve body 781 of the bypass means 780 that opens and closes the bypass passage 720, the spring ( The elastic body) 782 is disposed, and the pressure on the outlet side of the accumulator 500 is guided to the valve body 781 on the other side so that a force in the direction of closing the bypass passage 720 is applied to the valve body 781.
[0062]
Here, the spring 782 has a pressure on the outflow side of the accumulator 500 (low pressure CO ₂ Is set to open the bypass passage 720 when the pressure becomes equal to or lower than a predetermined pressure (4 MPa in the present embodiment).
(Ninth embodiment)
As in the eighth embodiment, this embodiment is a low-pressure CO during cool-down. ₂ This is made by utilizing the fact that the pressure in the vehicle is higher than when the temperature in the passenger compartment decreases.
[0063]
That is, in this embodiment, as shown in FIG. 21, a spring (on the one side of the valve body 791 of the bypass means 790 that opens and closes the bypass passage 740 acts to act on the valve body 791 in the direction in which the bypass passage 740 is opened). The elastic body) 792 is disposed, and the pressure on the outlet side of the pressure control device 300 is guided to the valve body 791 on the other side so that the force in the direction of closing the bypass passage 740 is applied to the valve body 791.
[0064]
Here, the spring 792 is a pressure on the outflow side of the pressure control device 300 (low pressure CO ₂ Is set to open the bypass passage 740 when the pressure is equal to or lower than a predetermined pressure (4 MPa in the present embodiment).
By the way, the present invention relates to CO. ₂ The use is not limited to the supercritical refrigeration cycle using the above, and for example, it can be applied to a vapor compression refrigeration cycle using a refrigerant used in a supercritical region such as ethylene, ethane, or nitric oxide.
[0065]
In the above-described embodiment, the pressure control valve 300 is mechanically configured. However, an electrical pressure control valve may be configured by a pressure sensor and an electric on-off valve.
Further, the structure of the internal heat exchanger 600 is not limited to a spiral shape as shown in FIG. 2, but may be configured in a double cylindrical shape as shown in FIG.
In the first and second embodiments, the CO on the discharge side of the compressor 100 ₂ Valve means such as solenoid valves were opened and closed based on temperature, but CO ₂ The position for detecting the temperature is not limited to this, and may be any predetermined position in the refrigerant path from the inlet side of the evaporator 400 to the inlet side of the radiator 200. However, the predetermined temperature needs to be appropriately set according to the detection position.
[0066]
In addition, the eighth and ninth embodiments have a low-pressure CO ₂ Low pressure CO based on the pressure of ₂ And high pressure CO ₂ Whether or not to exchange heat with ₂ The pressure is CO ₂ Low pressure CO due to correlation with temperature ₂ Is a predetermined temperature (for example, 4 MPa of CO ₂ CO corresponding to ₂ Low temperature CO when ₂ And high pressure CO ₂ The heat exchange with may be stopped.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a supercritical refrigeration cycle according to a first embodiment.
FIG. 2 is an explanatory diagram of an internal heat exchanger.
FIG. 3 is a cross-sectional view of a pressure control valve.
FIG. 4 is an enlarged view of a diaphragm portion showing a valve open state.
FIG. 5 is an enlarged view of a diaphragm portion showing a valve closed state.
6A is a view taken in the direction of an arrow A in FIG. 3, and FIG. 6B is a view taken in the direction of an arrow B in FIG.
FIG. 7 CO ₂ It is a Mollier diagram.
FIG. 8 is a schematic diagram of a supercritical refrigeration cycle according to a second embodiment.
FIG. 9 is a schematic diagram of a pressure control valve according to a second embodiment.
FIG. 10 is a schematic diagram of a supercritical refrigeration cycle according to a third embodiment.
FIG. 11 is a schematic diagram of a supercritical refrigeration cycle according to a third embodiment.
FIG. 12 is a schematic diagram of a pressure control valve according to a fourth embodiment.
FIG. 13 is a view showing a modified example of the internal heat exchanger.
FIG. 14 is a schematic diagram of a supercritical refrigeration cycle according to a fifth embodiment.
FIG. 15 is a schematic diagram of a supercritical refrigeration cycle according to a sixth embodiment.
FIG. 16 is an enlarged view of bypass means according to a sixth embodiment.
FIG. 17 is a schematic diagram of a supercritical refrigeration cycle according to a seventh embodiment.
FIG. 18 is an enlarged view of the bypass means according to the seventh embodiment.
FIG. 19 is a schematic diagram of a supercritical refrigeration cycle according to an eighth embodiment.
FIG. 20 is an enlarged view of bypass means according to an eighth embodiment.
FIG. 21 is a schematic diagram of a supercritical refrigeration cycle according to a ninth embodiment.
FIG. 22 is an enlarged view of bypass means according to the ninth embodiment.
FIG. 23 CO ₂ It is a Mollier diagram.
FIG. 24 is a graph showing the relationship between the radiator outlet-side pressure and the coefficient of performance (COP).
FIG. 25: CO at the radiator outlet side ₂ It is a graph which shows the relationship between temperature and a target radiator outlet side pressure.
FIG. 26 CO ₂ It is a Mollier diagram.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Compressor, 200 ... Radiator, 300 ... Pressure control valve (pressure control device)
400 ... evaporator, 500 ... accumulator (gas-liquid separator),
600 ... Internal heat exchanger, 700 ... Refrigerant bypass means.

Claims

A compressor (100) for compressing the refrigerant;
A radiator (200) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant;
A pressure control valve (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure on the outlet side of the radiator (200) based on the refrigerant temperature on the outlet side of the radiator (200); ,
An evaporator (400) for evaporating the refrigerant depressurized by the pressure control valve (300);
A gas-liquid separator (500) that separates the refrigerant flowing out of the evaporator (400) into a gas-phase refrigerant and a liquid-phase refrigerant, and causes the gas-phase refrigerant to flow out toward the suction side of the compressor (100);
A heat exchanger (600) for exchanging heat between the refrigerant flowing out of the gas-liquid separator (500) and sucked into the compressor (100) and the refrigerant flowing out of the radiator (200); With
The pressure control valve (300) is closed to increase the outlet-side pressure of the radiator (200) to a predetermined pressure, and then opened to decompress the refrigerant, thereby reducing the radiator (200). ) Configured to control the outlet side refrigerant pressure,
The predetermined pressure is a pressure that changes based on the refrigerant temperature on the outlet side of the radiator (200), and the predetermined pressure increases in accordance with an increase in the refrigerant temperature on the outlet side of the radiator (200), The predetermined pressure decreases in accordance with a decrease in refrigerant temperature on the outlet side of the radiator (200), and the predetermined pressure becomes constant if the refrigerant temperature on the outlet side of the radiator (200) is constant,
Further, in a situation where the pressure control valve (300) is closed to increase the refrigerant pressure on the radiator (200) outlet side in response to an increase in the refrigerant temperature on the outlet side of the radiator (200). When the refrigerant temperature at a predetermined position in the refrigerant passage extending from the inlet side of the evaporator (400) to the inlet side of the radiator (200) becomes equal to or higher than a predetermined temperature, it flows out of the gas-liquid separator (500). A supercritical refrigeration cycle comprising refrigerant bypass means (700) for bypassing the heat-reduced refrigerant through the heat exchanger (600) and flowing to the compressor (100).

The refrigerant bypass means (700)
A bypass passage (720) for allowing the refrigerant flowing out of the gas-liquid separator (500) to bypass the heat exchanger (600) and to flow to the compressor (100);
Valve means (710) for opening and closing the bypass passage (720);
Valve control means (711 to 713) for detecting the temperature of the refrigerant discharged from the compressor (100) and opening the valve means (710) when the detected temperature is equal to or higher than a predetermined temperature. The supercritical refrigeration cycle according to claim 1, wherein the supercritical refrigeration cycle is configured.

The refrigerant bypass means (700)
A bypass passage (720) for allowing the refrigerant flowing out of the gas-liquid separator (500) to bypass the heat exchanger (600) and to flow to the compressor (100);
Valve means (710) for opening and closing the bypass passage (720);
Valve control means (741 to 743) for detecting the pressure of the refrigerant sucked into the compressor (100) and opening the valve means (710) when the detected pressure becomes a predetermined pressure or less. The supercritical refrigeration cycle according to claim 1, wherein the supercritical refrigeration cycle is configured.

A compressor (100) for compressing the refrigerant;
A radiator (200) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant;
A pressure control valve (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure on the outlet side of the radiator (200) based on the refrigerant temperature on the outlet side of the radiator (200); ,
An evaporator (400) for evaporating the refrigerant depressurized by the pressure control valve (300);
A gas-liquid separator (500) that separates the refrigerant flowing out of the evaporator (400) into a gas-phase refrigerant and a liquid-phase refrigerant, and causes the gas-phase refrigerant to flow out toward the suction side of the compressor (100);
A heat exchanger (600) for exchanging heat between the refrigerant flowing out of the gas-liquid separator (500) and sucked into the compressor (100) and the refrigerant flowing out of the radiator (200); With
After the pressure control valve (300) is closed, the pressure on the outlet side of the radiator (200) is increased to a predetermined pressure that changes based on the refrigerant temperature on the outlet side of the radiator (200). The refrigerant pressure on the outlet side of the radiator (200) is controlled by opening the valve to depressurize the refrigerant,
The predetermined pressure increases as the refrigerant temperature on the outlet side of the radiator (200) increases, decreases as the refrigerant temperature decreases on the outlet side of the radiator (200), and the radiator (200). If the refrigerant temperature at the outlet side is constant, the pressure becomes constant,
Further, in a situation where the pressure control valve (300) is closed to increase the refrigerant pressure on the radiator (200) outlet side in response to an increase in the refrigerant temperature on the outlet side of the radiator (200). When the refrigerant temperature at a predetermined position in the refrigerant passage extending from the discharge side of the compressor (100) to the inflow side of the pressure control valve (300) becomes equal to or higher than a predetermined temperature, the heat in the heat exchanger (600) A supercritical refrigeration cycle characterized by stopping the exchange.

A compressor (100) for compressing the refrigerant;
A radiator (200) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant;
A pressure control valve (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure on the outlet side of the radiator (200) based on the refrigerant temperature on the outlet side of the radiator (200); ,
An evaporator (400) for evaporating the refrigerant depressurized by the pressure control valve (300);
A gas-liquid separator (500) that separates the refrigerant flowing out of the evaporator (400) into a gas-phase refrigerant and a liquid-phase refrigerant, and causes the gas-phase refrigerant to flow out toward the suction side of the compressor (100);
A heat exchanger (600) for exchanging heat between the refrigerant flowing out of the gas-liquid separator (500) and sucked into the compressor (100) and the refrigerant flowing out of the radiator (200); With
After the pressure control valve (300) is closed, the pressure on the outlet side of the radiator (200) is increased to a predetermined pressure that changes based on the refrigerant temperature on the outlet side of the radiator (200). The refrigerant pressure on the outlet side of the radiator (200) is controlled by opening the valve to depressurize the refrigerant,
The predetermined pressure increases as the refrigerant temperature on the outlet side of the radiator (200) increases, decreases as the refrigerant temperature decreases on the outlet side of the radiator (200), and the radiator (200). If the refrigerant temperature at the outlet side is constant, the pressure becomes constant,
Further, in a situation where the pressure control valve (300) is closed to increase the refrigerant pressure on the radiator (200) outlet side in response to an increase in the refrigerant temperature on the outlet side of the radiator (200). When the refrigerant temperature at a predetermined position in the refrigerant passage extending from the outlet side of the pressure control valve (300) to the suction side of the compressor (100) becomes equal to or lower than a predetermined temperature, the heat in the heat exchanger (600) A supercritical refrigeration cycle characterized by stopping the exchange.

A compressor (100) for compressing the refrigerant;
A radiator (200) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant;
A pressure control device (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure on the outlet side of the radiator (200) based on the refrigerant temperature on the outlet side of the radiator (200); ,
An evaporator (400) for evaporating the refrigerant decompressed by the pressure control device (300);
A gas-liquid separator (500) that separates the refrigerant flowing out of the evaporator (400) into a gas-phase refrigerant and a liquid-phase refrigerant, and causes the gas-phase refrigerant to flow out toward the suction side of the compressor (100);
A heat exchanger (600) for exchanging heat between the refrigerant flowing out of the gas-liquid separator (500) and sucked into the compressor (100) and the refrigerant flowing out of the radiator (200); With
The refrigerant pressure at a predetermined position in the refrigerant passage extending from the discharge side of the compressor (100) to the inflow side of the pressure control device (300), and from the outlet side of the pressure control device (300) of the compressor (100) A supercritical refrigeration cycle characterized in that heat exchange in the heat exchanger (600) is stopped when a differential pressure with a refrigerant pressure at a predetermined position of the refrigerant passage leading to the suction side becomes equal to or higher than a predetermined differential pressure. .

A compressor (100) for compressing the refrigerant;
A radiator (200) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant;
A pressure control valve (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure on the outlet side of the radiator (200) based on the refrigerant temperature on the outlet side of the radiator (200); ,
An evaporator (400) for evaporating the refrigerant depressurized by the pressure control valve (300);
A gas-liquid separator (500) that separates the refrigerant flowing out of the evaporator (400) into a gas-phase refrigerant and a liquid-phase refrigerant, and causes the gas-phase refrigerant to flow out toward the suction side of the compressor (100);
A heat exchanger (600) for exchanging heat between the refrigerant flowing out of the gas-liquid separator (500) and sucked into the compressor (100) and the refrigerant flowing out of the radiator (200); With
After the pressure control valve (300) is closed, the pressure on the outlet side of the radiator (200) is increased to a predetermined pressure that changes based on the refrigerant temperature on the outlet side of the radiator (200). The refrigerant pressure on the outlet side of the radiator (200) is controlled by opening the valve to depressurize the refrigerant,
The predetermined pressure increases as the refrigerant temperature on the outlet side of the radiator (200) increases, decreases as the refrigerant temperature decreases on the outlet side of the radiator (200), and the radiator (200). If the refrigerant temperature at the outlet side is constant, the pressure becomes constant,
Further, in a situation where the pressure control valve (300) is closed to increase the refrigerant pressure on the radiator (200) outlet side in response to an increase in the refrigerant temperature on the outlet side of the radiator (200). When the refrigerant pressure at a predetermined position in the refrigerant passage from the outlet side of the pressure control valve (300) to the suction side of the compressor (100) becomes equal to or lower than a predetermined pressure, the heat exchanger (600) A supercritical refrigeration cycle characterized by stopping heat exchange.