JP4147930B2

JP4147930B2 - Vapor compression refrigerator

Info

Publication number: JP4147930B2
Application number: JP2002366793A
Authority: JP
Inventors: 誠司伊藤; 素弘山口
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2002-12-18
Filing date: 2002-12-18
Publication date: 2008-09-10
Anticipated expiration: 2022-12-18
Also published as: JP2004198027A

Description

【０００１】
【発明の属する技術分野】
本発明は、蒸気圧縮式冷凍機に関するもので、高圧（高温）側で発生する温熱を利用する空調装置や給湯器等に用いて有効である。
【０００２】
【従来の技術】
蒸気圧縮式冷凍機では、低温（低圧）側の熱交換器にて冷媒を蒸発させて吸熱して冷熱を生成し、高温（高圧）側の熱交換器にて低温側熱交換器にて吸熱した熱量、及びポンプ手段をなす圧縮機の圧縮仕事相当の熱量を放熱して温熱を生成している。
【０００３】
しかし、低温側熱交換器の温度は雰囲気温度より低いため、低温側熱交換器の表面に霜が発生（着霜）してしまう。
【０００４】
そこで、従来は、低温側熱交換器の雰囲気温度（雰囲気の乾球温度）と低温側熱交換器から流出する冷媒の温度とに基づいて低温側熱交換器の表面に霜が発生したか否かを判定し、霜が発生したことを判定したときには、圧縮機から吐出した高温の冷媒を低温側熱交換器に流入させることにより低温側熱交換器を内側から加熱して低温側熱交換器の表面に発生した霜を除去していた（例えば、特許文献１参照）。
【０００５】
【特許文献１】
特開２００２−１７４４７４号公報
【０００６】
【発明が解決しようとする課題】
ところで、低温側熱交換器の表面に発生する霜は、低温側熱交換器の表面に発生した凝縮水が凝固した（凍った）ものであるので、雰囲気温度が水の凝固点以下であっても、凝縮水が発生しなければ霜は発生しない。逆に、低温側熱交換器の表面に凝縮水が発生しても、雰囲気温度が凝固点より高いときには、霜は発生しない。
【０００７】
したがって、低温側熱交換器の雰囲気温度及び低温側熱交換器から流出する冷媒の温度のみから低温側熱交換器の表面に霜が発生し得るか否かを予測することはできない。このため、特許文献１に記載の検出方法にて着霜を判定したときには、既に低温側熱交換器の表面に多量の霜が着霜してしまっているおそれが高い。
【０００８】
本発明は、上記点に鑑み、第１には、従来と異なる新規な蒸気圧縮式冷凍機を提供し、第２には、低温側熱交換器の表面に多量の霜が着霜してしまう前に着霜を判定することを目的とする。
【０００９】
【課題を解決するための手段】
本発明は、上記目的を達成するために、請求項１に記載の発明では、低温側の熱を高温側に移動させる蒸気圧縮式冷凍機であって、低温側雰囲気である室外の空気中に配置され、冷媒と雰囲気とを熱交換させる低温側熱交換器（３）と、高温側に配置され、冷媒と水とを熱交換させる高温側熱交換器（２）と、低温側熱交換器（３）と高温側熱交換器（２）との間で冷媒を循環させるポンプ手段（１）と、低温側熱交換器（３）の表面に霜が発生し得る状況にあるか否か判定する着霜予測手段と、着霜予測手段により低温側熱交換器（３）の表面に霜が発生し得る状況にあると判定されたときに、ポンプ手段（１）の作動を制御する着霜判定時ポンプ制御手段とを備え、
高温側熱交換器（２）にて熱交換した水は、室内に吹き出す空気を加熱する熱源として用いられ、着霜予測手段は、低温側熱交換器（３）から流出する冷媒の温度（ＴＨＯ）が、室外空気の相対湿度および室外空気の温度から算出される室外空気の露点温度（Ｔｆ）未満であるときであって、かつ、低温側熱交換器（３）から流出する冷媒の温度（ＴＨＯ）が水の凝固点以下であるときに、低温側熱交換器（３）の表面に霜が発生し得る状況にあると判定し、
着霜予測手段により低温側熱交換器（３）の表面に霜が発生し得る状況にないと判定されたときには、ポンプ手段（１）の目標回転数（ＩＶＯ）は、高温側熱交換器（２）にて加熱された水の温度が目標吹出温度（ＴＡＯ）に基づいて算出された目標水温（ＴＷＯ）となるような値に決定され、目標吹出温度（ＴＡＯ）は、室外空気の温度、室内空気の温度、室内に注がれる日射量および室内の設定温度に基づいて算出されており、着霜予測手段により低温側熱交換器（３）の表面に霜が発生し得る状況にあると判定されたときには、着霜判定時ポンプ制御手段が、着霜予測手段により低温側熱交換器（３）の表面に霜が発生し得る状況にあると判定される前の目標回転数（ＩＶＯ）から予め定めた所定値（β）を減算した値に、目標回転数（ＩＶＯ）を変更することを特徴とする。
【００１０】
これにより、低温側熱交換器の雰囲気温度及び低温側熱交換器から流出する冷媒の温度のみから低温側熱交換器の表面に霜が発生し得るか否かを予測する手法に比べて、低温側熱交換器の表面に多量の霜が着霜してしまう前に着霜を判定することができ得る
【００１４】
さらに、吸熱効率が大きく低下することを抑制しながら、除霜運転が行われる頻度を低減することができるので、蒸気圧縮式冷凍機の運転効率を向上させることができる。
【００１５】
請求項２に記載の発明では、冷媒として二酸化炭素が用いられていることを特徴とするものである。
【００１６】
請求項３に記載の発明では、高圧側の冷媒圧力を冷媒の臨界圧力以上まで上昇させることを特徴とするものである。
【００２０】
因みに、上記各手段の括弧内の符号は、後述する実施形態に記載の具体的手段との対応関係を示す一例である。
【００２１】
【発明の実施の形態】
（第１実施形態）
本実施形態は、本発明に係る蒸気圧縮式冷凍機を、二酸化炭素を冷媒とする電気自動車用の空調装置に適用したものであって、図１は本実施形態に係る車両用空調装置の模式図である。
【００２２】
なお、本実施形態に係る電気自動車は、酸素と水素とを化学反応させることにより発電する燃料電池（ＦＣスタック）２０から走行用電動モータ（図示せず。）に電力を供給するものであり、ラジエータ２１は燃料電池２０を加熱又は冷却するための冷却水と外気とを熱交換して冷却水を冷却する熱交換器であり、ポンプ２２は冷却水を循環させる電動ポンプである。
【００２３】
圧縮機１は冷媒を吸入圧縮するポンプ手段であり、本実施形態では、インバータ制御方式の電動圧縮機を採用している。第１室外熱交換器２は圧縮機１から吐出した冷媒と燃料電池２０から流出した冷却水とを熱交換する熱交換器であり、第２室外熱交換器３は冷媒と室外空気とを熱交換する熱交換器である。
【００２４】
なお、図１では、第１室外熱交換器２において冷媒と冷却水とは並行流となっているが、実際の第１室外熱交換器２では、両者を対向流として熱交換効率を高めている。
【００２５】
室内熱交換器４は室内に吹き出す空気と冷媒とを熱交換する熱交換器であり、内部熱交換器５は圧縮機１に吸引される低圧冷媒と減圧される前の高圧冷媒とを熱交換する熱交換器である。
【００２６】
切替弁６は圧縮機１から吐出した減圧される前の高圧冷媒を第２室外熱交換器３側に循環させる場合と室内熱交換器４側に循環させる場合とを切り替えるバルブである。第１、２減圧器７、８は冷媒を減圧膨脹させる減圧手段であり、両減圧器７、８の絞り開度は、電子制御装置（図示せず。）により制御される。
【００２７】
そして、電子制御装置には、圧縮機１から吐出する冷媒の温度を検出する吐出冷媒温度センサ９ａ、圧縮機１から吐出する冷媒の圧力検出する吐出冷媒圧力センサ９ｂ、第１室外熱交換器２から流出する冷媒の温度を検出する第１室外熱交換器冷媒温度センサ９ｃ、第２室外熱交換器３から流出する冷媒の温度を検出する第２室外熱交換器冷媒温度センサ９ｄ、室内熱交換器４から流出した冷媒の圧力を検出する室内熱交換器冷媒圧力センサ９ｅ、室内熱交換器４から流出した冷媒の温度を検出する室内熱交換器冷媒温度センサ９ｆ、第１室外熱交換器２に流入する冷却水の温度を検出する水温センサ９ｇ、車室外空気温度を検出する外気温センサ９ｈ、車室外空気の相対湿度を検出する外気湿度センサ９ｊ、室内空気温度を検出する内気温センサ９ｋ、室内に注がれる日射を検出する日射センサ９ｍ、車室内空気の相対湿度を検出する内気湿度センサ９ｎ、及び室内熱交換器４を通過した直後の空気温度を検出する室内熱交換器空気温度センサ９ｐの検出値が入力されている。
【００２８】
なお、アキュムレータ１０は、冷媒を気相冷媒と液相冷媒とに分離して余剰冷媒を液相冷媒として蓄えるとともに、気相冷媒を圧縮機１の吸入側に供給するものである。
【００２９】
ところで、空調ケーシング１１は、室内熱交換器４を収納して室内に吹き出す空気の通路を構成するもので、この空調ケーシング１１内うち室内熱交換器４より空気流れ下流側には、冷却水を熱源として室内に吹き出す空気を加熱するヒータ１２が配置されている。
【００３０】
エアミックスドア１３は、室内熱交換器４を通過した空気のうちヒータ１２を通過して加熱される温風とヒータ１２を迂回して流れる冷風との風量割合を調節することにより室内に吹き出す空気の温度を調節するものである。
【００３１】
また、空調ケーシング１１の最上流側には、空調ケーシング１１内に導入する室内空気量と室外空気量と調節する内外気切換ユニット１４、及び室内に空気を送風する送風機１５が設けられ、空調ケーシング１１の最下流側には、空気を吹き出させる吹出口を選択開閉する吹出モード切換装置（図示せず。）が設けられている。
【００３２】
なお、圧縮機１の回転数、エアミックスドア１３、内外気切換ユニット１４、送風機１５及び吹出モード切換装置も電子制御装置にて制御されている。
【００３３】
次に、本実施形態の作動を述べる。
【００３４】
１．冷房運転（図２参照）
外気温センサ９ｈ、内気温センサ９ｋ及び日射センサ９ｍの検出値、並びに乗員が設定入力した希望室内温度（設定温度）等に基づいて算出された目標吹出温度ＴＡＯが所定温度以下のときに実行されるもので、エアミックスドア１３にてヒータ１２のコア面を閉じて室内に流れ込む温風量を０とした状態で、冷媒を、圧縮機１→第１室外熱交換器２→第２減圧器８→切替弁６→第２室外熱交換器３→内部熱交換器５→第１減圧器７→室内熱交換器４→アキュムレータ１０→内部熱交換器５→圧縮機１の順で循環させる。
【００３５】
このとき、第２減圧器８にて冷媒が減圧されないように第２減圧器８の絞り開度を全開とするとともに、吐出冷媒圧力センサ９ｂの検出圧力が第２室外熱交換器冷媒温度センサ９ｄによって決定される目標高圧圧力Ｐｏとなるように第１減圧器７の絞り開度を制御することにより、室内熱交換器４にて室内に吹き出す空気から吸熱して蒸発した冷媒の熱を第１室外熱交換器２及び第２室外熱交換器３にて放熱する。
【００３６】
なお、目標高圧圧力Ｐｏとは、蒸気圧縮式冷凍機の成績係数が略最大となる圧力であり、この目標高圧圧力Ｐｏは高圧側での放熱能力によって変化するため、冷房運転時では、第２室外熱交換器冷媒温度センサ９ｄの検出温度に基づいて決定する。
【００３７】
また、室内熱交換器空気温度センサ９ｐの検出温度が目標吹出温度ＴＡＯとなるように圧縮機１の回転数が制御される。
【００３８】
２．暖房運転（図３参照）
目標吹出温度ＴＡＯが所定温度以上であって、内気温センサ９ｋの検出温度が内気湿度センサ９ｎの検出湿度及び内気温センサ９ｋの検出温度から算出される露点温度より高いときに実行されるもので、エアミックスドア１３にてヒータ１２を迂回する空気通路を閉じた状態で、冷媒を、圧縮機１→第１室外熱交換器２→第２減圧器８→切替弁６→室内熱交換器４→第１減圧器７→内部熱交換器５→第２室外熱交換器３→切替弁６→アキュムレータ１０→圧縮機１の順に循環させる。
【００３９】
このとき、第２減圧器８にて冷媒が減圧されないように第２減圧器８の絞り開度を全開とするとともに、室内熱交換器冷媒圧力センサ９ｅの検出圧力が室内熱交換器冷媒温度センサ９ｆによって決定される目標高圧圧力Ｐｏとなるように第１減圧器７の絞り開度を制御することにより、第２室外熱交換器３にて室外空気から吸熱して蒸発した冷媒の熱を第１室外熱交換器２及び室内熱交換器４にて放熱する。このため、室内に吹き出す空気は室内熱交換器４及びヒータ１２にて加熱されて室内に吹き出される。
【００４０】
また、ヒータ１２に供給される冷却水（温水）は、燃料電池２０及び第１室外熱交換器２にて加熱されており、ヒータ１２に供給される冷却水の温度は第１室外熱交換器２の加熱能力で決定されることから、本実施形態では、ヒータ１２に供給される冷却水の温度が、目標吹出温度ＴＡＯにヒータ１２での熱交換効率γを乗じた目標水温ＴＷＯ（＝ＴＡＯ×γ）となるように圧縮機１の回転数を制御する。
【００４１】
具体的には、目標水温ＴＷＯと水温センサ９ｇの検出温度との温度差、及び温度差の変化率からファジー理論に基づいて圧縮機１の回転数変化量Δｆを決定するものである。
【００４２】
なお、内部熱交換器５の圧縮機１側及び第１減圧器７側には、共に減圧後の冷媒が流れるため、実質的に熱交換が行われない。
【００４３】
因みに、目標水温ＴＷＯと水温センサ９ｇの検出温度との温度差が所定温度以下のとき、又は水温センサ９ｇの検出温度が目標水温ＴＷＯ以上であるときには、圧縮機１を停止して蒸気圧縮式冷凍機による暖房補助、つまり蒸気圧縮式冷凍機によってヒータ１２に流入する冷却水を加熱することは行わない。
【００４４】
３．除湿暖房
目標吹出温度ＴＡＯが所定温度以上であって、内気温センサ９ｋの検出温度が内気湿度センサ９ｎの検出湿度及び内気温センサ９ｋの検出温度から算出される露点温度より高いときに実行されるもので、エアミックスドア１３にてヒータ１２を迂回する空気通路を閉じた状態で、冷媒を暖房運転時と同様な経路で循環させる。
【００４５】
具体的には、圧縮機１→第１室外熱交換器２→第２減圧器８→切替弁６→室内熱交換器４→第１減圧器７→内部熱交換器５→第２室外熱交換器３→切替弁６→アキュムレータ１０→圧縮機１の順である。
【００４６】
このとき、吐出冷媒圧力センサ９ｂの検出圧力が第１室外熱交換器冷媒温度センサ９ｃによって決定される目標高圧圧力Ｐｏとなるように第２減圧器８の絞り開度を制御することにより、第１室外熱交換器２にて冷却水を加熱して間接的に室内に吹き出す空気を加熱するとともに、室内熱交換器４にて冷媒を蒸発させて室内に吹き出す空気を冷却する。
【００４７】
このため、室内熱交換器４にて除湿冷却された空気がヒータ１２にて再加熱されるため、除湿しながら暖房を行うことができる。因みに、圧縮機１の制御は、暖房運転時と同じである。
【００４８】
なお、暖房運転時及び除湿暖房運転時においては、第２室外熱交換器３が特許請求の範囲に記載された低温側熱交換器となり、第１室外熱交換器２が特許請求の範囲に記載された高温側熱交換器となる。
【００４９】
ところで、図４は暖房運転時及び除湿暖房運転時における空調装置の特徴的作動を示すフローチャートであり、以下、このフローチャートについて述べる。
【００５０】
外気温センサ９ｈ、内気温センサ９ｋ及び日射センサ９ｍの検出値、並びに乗員が設定入力した希望室内温度（パネル入力）等に基づいて算出された目標吹出温度ＴＡＯを算出し（Ｓ１１０〜Ｓ１３０）、この目標吹出温度ＴＡＯから目標水温ＴＷＯを算出した後（Ｓ１４０）、目標水温ＴＷＯに基づいて圧縮機１の目標回転数ＩＶＯを算出する（Ｓ１６０）。
【００５１】
次に、外気湿度センサ９ｊ及び外気温センサ９ｈの検出温度（外気乾球温度）に基づいて、第２室外熱交換器３の雰囲気の露点温度Ｔｆを算出し、第２室外熱交換器冷媒温度センサ９ｄの検出温度ＴＨＯが露点温度Ｔｆ未満であるか否かを判定する（Ｓ１７０）。
【００５２】
そして、検出温度ＴＨＯが露点温度Ｔｆ未満であるときには、第２室外熱交換器３の表面に凝縮水が発生することから、検出温度ＴＨＯが所定温度α、つまり水の凝固点（０℃）以下か否かを判定する（Ｓ１８０）。
【００５３】
なお、露点温度Ｔｆは、周知ごとく、相対湿度及び乾球温度が解れば、湿り空気線図（図５参照）から求めることができる。
【００５４】
そして、検出温度ＴＨＯが所定温度α以下のときには、第２室外熱交換器３の表面に霜が発生するおそれが非常に高いことから、Ｓ１６０にて決定した目標回転数ＩＶＯより低い回転数を目標圧縮機回転数ＩＶＯとして、アクチュエータ、つまり圧縮機１及び減圧機等を実際に稼動させる（Ｓ１９０、Ｓ２００）。
【００５５】
換言すれば、第２室外熱交換器３の表面に霜が発生し得る状況にあると判定されたときには、第２室外熱交換器３の表面に霜が発生し得る状況にあると判定される前に比べて、循環させる冷媒流量を減少させて蒸気圧縮式冷凍機の吸熱能力及び加熱能力を低下（セーブ）する。
【００５６】
なお、検出温度ＴＨＯと外気温度との温度差が所定温度差（例えば、２０℃）以上となったときには、圧縮機１から吐出した高圧冷媒（ホットガス）を第２室外熱交換器３にに流入させることにより第２室外熱交換器３を内側から加熱して霜を除去する除霜を行う。
【００５７】
次に、本実施形態の作用効果を述べる。
【００５８】
本実施形態では、低温側雰囲気の温度及び相対湿度に基づいて露点温度を算出して低温側熱交換器をなす第２室外熱交換器３の表面に霜が発生し得る状況にあるか否か判定するので、低温側熱交換器の表面に多量の霜が着霜してしまう前に着霜を判定することができ得る。
【００５９】
また、第２室外熱交換器３の表面に霜が発生し得る状況にあると判定されたときには、循環させる冷媒流量を減少させて蒸気圧縮式冷凍機の吸熱能力及び加熱能力を低下（セーブ）するので、着霜の進行速度を小さくすることができる。
【００６０】
したがって、吸熱効率が大きく低下することを抑制しながら、除霜運転が行われる頻度を低減することができるので、蒸気圧縮式冷凍機の運転効率を向上させることができる。
【００６１】
（参考例）
上述の実施形態では、第２室外熱交換器３の表面に霜が発生し得る状況にあると判定されたときには、循環させる冷媒流量を減少させて蒸気圧縮式冷凍機の吸熱能力及び加熱能力を低下（セーブ）したが、参考例では、第２室外熱交換器３の表面に霜が発生し得る状況にあると判定されたときには、蒸気圧縮式冷凍機による暖房補助を行うか行わないかのしきい値をなす温度を下げるものである。
【００６２】
具体的には、図６のＳ１９５に示すように、第２室外熱交換器３の表面に霜が発生し得る状況にあると判定されたときには、目標水温ＴＷＯを低下させることにより蒸気圧縮式冷凍機による暖房補助を第１実施形態に比べて早めに停止させて、蒸気圧縮式冷凍機の吸熱能力及び加熱能力を低下（セーブ）させるものである。
【００６３】
なお、Ｓ１９５及び水温センサ９ｇの検出温度が所定温度（例えば、６０℃）以上となったときに除霜運転を行う点以外は第１実施形態と同じである。
【００６４】
ところで、図１では、燃料電池２０はラジエータ２１及び第２室外熱交換器３とは別の部位に配置されているが、実装状態では、車両前側から順に、第２室外熱交換器３、ラジエータ２１、燃料電池２０の順で配置されている。このため、車両の走行風は、第２室外熱交換器３及びラジエータ２１を通過して燃料電池２０に当たる。
【００６５】
これにより、本参考例では、第１実施形態に比べて第２室外熱交換器３の表面に多くの霜が発生するものの、第２室外熱交換器３の表面に多くの霜が発生すると、燃料電池２０に当たる走行風量が減少するので、第２室外熱交換器３に霜が発生する以前に比べて冷却水温度が上昇し、蒸気圧縮式冷凍機による暖房補助を停止しても、燃料電池２０にて加熱された冷却水のみにて室内に吹き出す空気を十分に加熱することができる。
【００６６】
延いては、蒸気圧縮式冷凍機の稼働率を低減することができるので、蒸気圧縮式冷凍機の運転効率を向上させることができる。
【００６７】
（その他の実施形態）
上述の実施形態では、運転時に発熱する車両機器として燃料電池２０を用いたが、本発明はこれに限定されるものではなく、運転時に発熱する車両機器として、例えば内燃機関としてもよい。
【００６８】
また、上述の実施形態では、高圧（高温）側で発生する温熱を利用する空調装置に本発明を適用したが、冷凍庫等の低温（低圧）側で発生する冷熱を利用する蒸気圧縮式冷凍機にも適用することができる。
【００６９】
また、上述の実施形態では、高圧側の冷媒圧力を冷媒の臨界圧力以上まで上昇させて必要な能力を得ていたが、本発明はこれに限定されるものではなく、例えば冷媒をフロンとして、高圧側の冷媒圧力を冷媒の臨界圧力未満としてもよい。
【図面の簡単な説明】
【図１】本発明の実施形態に係る空調装置の模式図である。
【図２】本発明の実施形態に係る空調装置の冷媒流れを示す模式図である。
【図３】本発明の実施形態に係る空調装置の冷媒流れを示す模式図である。
【図４】本発明の第１実施形態に係る空調装置の制御を示すフローチャートである。
【図５】湿り線図である。
【図６】参考例に係る空調装置の制御を示すフローチャートである。
【符号の説明】
１…圧縮機、２…第１室外熱交換器、３…第２室外熱交換器、
４…室内熱交換器、５…内部熱交換器、９ｈ…外気温センサ、
９ｊ…外気湿度センサ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vapor compression refrigerator, and is effective for use in an air conditioner, a water heater, or the like that uses the heat generated on the high pressure (high temperature) side.
[0002]
[Prior art]
In a vapor compression refrigerator, the refrigerant is evaporated in a low-temperature (low-pressure) side heat exchanger to absorb heat and generate cold, and the high-temperature (high-pressure) side heat exchanger absorbs heat in the low-temperature side heat exchanger. The generated heat amount and the heat amount corresponding to the compression work of the compressor constituting the pump means are radiated to generate warm heat.
[0003]
However, since the temperature of the low-temperature side heat exchanger is lower than the ambient temperature, frost is generated (frosted) on the surface of the low-temperature side heat exchanger.
[0004]
Therefore, conventionally, whether or not frost has occurred on the surface of the low temperature side heat exchanger based on the ambient temperature of the low temperature side heat exchanger (the dry bulb temperature of the atmosphere) and the temperature of the refrigerant flowing out of the low temperature side heat exchanger. When it is determined that frost has occurred, the low-temperature side heat exchanger is heated from the inside by allowing the high-temperature refrigerant discharged from the compressor to flow into the low-temperature side heat exchanger. The frost which generate | occur | produced on the surface of was removed (for example, refer patent document 1).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-174474
[Problems to be solved by the invention]
By the way, the frost generated on the surface of the low-temperature side heat exchanger is obtained by condensing (frozen) the condensed water generated on the surface of the low-temperature side heat exchanger, so even if the ambient temperature is below the freezing point of water. If no condensed water is generated, frost will not be generated. Conversely, even if condensed water is generated on the surface of the low temperature side heat exchanger, frost does not occur when the ambient temperature is higher than the freezing point.
[0007]
Therefore, it cannot be predicted whether or not frost can be generated on the surface of the low temperature side heat exchanger only from the ambient temperature of the low temperature side heat exchanger and the temperature of the refrigerant flowing out of the low temperature side heat exchanger. Therefore, when it is determined the frost by detecting method described in Patent Document 1 has a high possibility that already a large amount of frost on the surface of the low-temperature heat exchanger are waiting to frosted.
[0008]
In view of the above point, in the first, provides unconventional new vapor compression refrigerating machine, the second, a large amount of frost on the surface of the low-temperature heat exchanger is by frost The purpose is to determine frost formation before rolling.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a vapor compression refrigerator that moves the heat on the low temperature side to the high temperature side according to the invention described in claim 1, and is in outdoor air that is a low temperature side atmosphere. A low-temperature side heat exchanger (3) arranged to exchange heat between the refrigerant and the atmosphere, a high-temperature side heat exchanger (2) arranged on the high-temperature side to exchange heat between the refrigerant and water, and a low-temperature side heat exchanger It is determined whether frost can be generated on the surface of the pump means (1) for circulating the refrigerant between (3) and the high temperature side heat exchanger (2) and the low temperature side heat exchanger (3). Frost formation predicting means, and frost formation for controlling the operation of the pump means (1) when it is determined by the frost prediction means that the frost can be generated on the surface of the low temperature side heat exchanger (3). A pump control means for determination,
The water subjected to heat exchange in the high temperature side heat exchanger (2) is used as a heat source for heating the air blown into the room, and the frost prediction means determines the temperature of the refrigerant flowing out from the low temperature side heat exchanger (3) (THO). ) Is lower than the dew point temperature (Tf) of the outdoor air calculated from the relative humidity of the outdoor air and the temperature of the outdoor air, and the temperature of the refrigerant flowing out from the low temperature side heat exchanger (3) ( When (THO) is below the freezing point of water, it is determined that frost can be generated on the surface of the low temperature side heat exchanger (3) ,
When it is determined by the frost formation predicting means that there is no situation where frost can be generated on the surface of the low temperature side heat exchanger (3), the target rotational speed (IVO) of the pump means (1) is set to the high temperature side heat exchanger ( 2), the temperature of the water heated in step 2) is determined to be a target water temperature (TWO) calculated based on the target outlet temperature (TAO), and the target outlet temperature (TAO) is the outdoor air temperature, It is calculated on the basis of the temperature of the indoor air, the amount of solar radiation poured into the room, and the set temperature in the room, and when frost can be generated on the surface of the low temperature side heat exchanger (3) by the frost formation predicting means. When it is determined, the target rotational speed (IVO) before the frost determination determination pump control means determines that the frost prediction means determines that frost can be generated on the surface of the low temperature side heat exchanger (3). To the value obtained by subtracting a predetermined value (β) from And changes the IVO).
[0010]
As a result, compared with the method for predicting whether or not frost can be generated on the surface of the low-temperature side heat exchanger only from the ambient temperature of the low-temperature side heat exchanger and the temperature of the refrigerant flowing out of the low-temperature side heat exchanger, a large amount of frost on the surface of the side heat exchanger may be able to determine the frosting before Mau to frosted [0014]
Furthermore , since it is possible to reduce the frequency at which the defrosting operation is performed while suppressing a significant decrease in the endothermic efficiency, it is possible to improve the operating efficiency of the vapor compression refrigerator.
[0015]
The invention according to claim 2 is characterized in that carbon dioxide is used as the refrigerant.
[0016]
The invention according to claim 3 is characterized in that the refrigerant pressure on the high-pressure side is increased to a critical pressure or more of the refrigerant.
[0020]
Incidentally, the reference numerals in parentheses of each means described above are an example showing the correspondence with the specific means described in the embodiments described later.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
In the present embodiment, the vapor compression refrigerator according to the present invention is applied to an air conditioner for an electric vehicle using carbon dioxide as a refrigerant, and FIG. 1 is a schematic diagram of the vehicle air conditioner according to the present embodiment. FIG.
[0022]
The electric vehicle according to the present embodiment supplies electric power to a traveling electric motor (not shown) from a fuel cell (FC stack) 20 that generates electricity by chemically reacting oxygen and hydrogen. The radiator 21 is a heat exchanger that cools the cooling water by exchanging heat between the cooling water for heating or cooling the fuel cell 20 and the outside air, and the pump 22 is an electric pump that circulates the cooling water.
[0023]
The compressor 1 is a pump unit that sucks and compresses refrigerant. In this embodiment, an inverter-controlled electric compressor is employed. The first outdoor heat exchanger 2 is a heat exchanger that exchanges heat between the refrigerant discharged from the compressor 1 and the cooling water flowing out of the fuel cell 20, and the second outdoor heat exchanger 3 heats the refrigerant and outdoor air. It is a heat exchanger to exchange.
[0024]
In FIG. 1, the refrigerant and the cooling water are in parallel flow in the first outdoor heat exchanger 2. However, in the actual first outdoor heat exchanger 2, the heat exchange efficiency is improved by using both as a counterflow. Yes.
[0025]
The indoor heat exchanger 4 is a heat exchanger that exchanges heat between the air blown into the room and the refrigerant, and the internal heat exchanger 5 exchanges heat between the low-pressure refrigerant sucked into the compressor 1 and the high-pressure refrigerant before being decompressed. Heat exchanger.
[0026]
The switching valve 6 is a valve that switches between a case where the high pressure refrigerant discharged from the compressor 1 is circulated to the second outdoor heat exchanger 3 side and a case where it is circulated to the indoor heat exchanger 4 side. The first and second decompressors 7 and 8 are decompressing means for decompressing and expanding the refrigerant, and the throttle opening degree of both decompressors 7 and 8 is controlled by an electronic control device (not shown).
[0027]
The electronic control unit includes a discharge refrigerant temperature sensor 9a that detects the temperature of the refrigerant discharged from the compressor 1, a discharge refrigerant pressure sensor 9b that detects the pressure of the refrigerant discharged from the compressor 1, and the first outdoor heat exchanger 2. A first outdoor heat exchanger refrigerant temperature sensor 9c for detecting the temperature of the refrigerant flowing out of the second outdoor heat exchanger, a second outdoor heat exchanger refrigerant temperature sensor 9d for detecting the temperature of the refrigerant flowing out of the second outdoor heat exchanger 3, and an indoor heat exchange. An indoor heat exchanger refrigerant pressure sensor 9e for detecting the pressure of the refrigerant flowing out of the heat exchanger 4, an indoor heat exchanger refrigerant temperature sensor 9f for detecting the temperature of the refrigerant flowing out of the indoor heat exchanger 4, and the first outdoor heat exchanger 2 Water temperature sensor 9g for detecting the temperature of the cooling water flowing into the vehicle, outside air temperature sensor 9h for detecting the outside air temperature of the passenger compartment, outside air humidity sensor 9j for detecting the relative humidity of the outside air of the passenger compartment, and the inside air temperature for detecting the indoor air temperature. Sensor 9k, solar radiation sensor 9m for detecting solar radiation poured into the room, indoor air humidity sensor 9n for detecting the relative humidity of the air in the passenger compartment, and an indoor heat exchanger for detecting the air temperature immediately after passing through the indoor heat exchanger 4 The detection value of the air temperature sensor 9p is input.
[0028]
The accumulator 10 separates the refrigerant into a gas phase refrigerant and a liquid phase refrigerant, stores the surplus refrigerant as a liquid phase refrigerant, and supplies the gas phase refrigerant to the suction side of the compressor 1.
[0029]
By the way, the air conditioning casing 11 constitutes a passage of air that houses the indoor heat exchanger 4 and blows out into the room. Cooling water is supplied to the downstream side of the air flow from the indoor heat exchanger 4 in the air conditioning casing 11. A heater 12 for heating the air blown into the room as a heat source is arranged.
[0030]
The air mix door 13 is an air blown into the room by adjusting the air volume ratio between the warm air heated by passing through the heater 12 and the cool air flowing around the heater 12 out of the air that has passed through the indoor heat exchanger 4. The temperature is adjusted.
[0031]
Further, on the most upstream side of the air conditioning casing 11, an indoor / outdoor air switching unit 14 that adjusts the amount of indoor air introduced into the air conditioning casing 11 and the amount of outdoor air, and a blower 15 that blows air into the room are provided. 11 is provided with a blowing mode switching device (not shown) for selectively opening and closing a blow-out port for blowing air.
[0032]
The number of rotations of the compressor 1, the air mix door 13, the inside / outside air switching unit 14, the blower 15, and the blowing mode switching device are also controlled by the electronic control unit.
[0033]
Next, the operation of this embodiment will be described.
[0034]
1. Cooling operation (see Fig. 2)
This is executed when the target air temperature TAO calculated based on the detected values of the outside air temperature sensor 9h, the inside air temperature sensor 9k and the solar radiation sensor 9m, the desired room temperature (set temperature) set and input by the occupant, etc. is below a predetermined temperature. In the state where the core surface of the heater 12 is closed by the air mix door 13 and the amount of warm air flowing into the room is set to 0, the refrigerant is changed from the compressor 1 to the first outdoor heat exchanger 2 to the second decompressor 8. -> Switching valve 6-> second outdoor heat exchanger 3-> internal heat exchanger 5-> first decompressor 7-> indoor heat exchanger 4-> accumulator 10-> internal heat exchanger 5-> compressor 1 are circulated in this order.
[0035]
At this time, the throttle opening of the second pressure reducer 8 is fully opened so that the refrigerant is not depressurized by the second pressure reducer 8, and the detected pressure of the discharged refrigerant pressure sensor 9b is the second outdoor heat exchanger refrigerant temperature sensor 9d. By controlling the throttle opening of the first pressure reducer 7 so as to be the target high pressure Po determined by the above, the heat of the refrigerant that has absorbed heat and evaporated from the air blown into the room by the indoor heat exchanger 4 is the first. Heat is radiated by the outdoor heat exchanger 2 and the second outdoor heat exchanger 3.
[0036]
Note that the target high pressure Po is a pressure at which the coefficient of performance of the vapor compression refrigerator is substantially maximized, and this target high pressure Po changes depending on the heat dissipation capacity on the high pressure side. This is determined based on the temperature detected by the outdoor heat exchanger refrigerant temperature sensor 9d.
[0037]
Moreover, the rotation speed of the compressor 1 is controlled so that the detected temperature of the indoor heat exchanger air temperature sensor 9p becomes the target blowing temperature TAO.
[0038]
2. Heating operation (see Fig. 3)
This is executed when the target outlet temperature TAO is equal to or higher than a predetermined temperature and the detected temperature of the internal air temperature sensor 9k is higher than the dew point temperature calculated from the detected humidity of the internal air humidity sensor 9n and the detected temperature of the internal air temperature sensor 9k. In the state where the air passage that bypasses the heater 12 is closed by the air mix door 13, the refrigerant is changed to the compressor 1 → the first outdoor heat exchanger 2 → the second pressure reducer 8 → the switching valve 6 → the indoor heat exchanger 4. -> First decompressor 7-> internal heat exchanger 5-> second outdoor heat exchanger 3-> switching valve 6-> accumulator 10-> compressor 1
[0039]
At this time, the throttle opening of the second decompressor 8 is fully opened so that the refrigerant is not decompressed by the second decompressor 8, and the detected pressure of the indoor heat exchanger refrigerant pressure sensor 9e is the indoor heat exchanger refrigerant temperature sensor. By controlling the throttle opening of the first pressure reducer 7 so that the target high pressure Po determined by 9f is reached, the second outdoor heat exchanger 3 absorbs heat from the outdoor air and evaporates the heat of the refrigerant evaporated. Heat is radiated by the outdoor heat exchanger 2 and the indoor heat exchanger 4. For this reason, the air blown into the room is heated by the indoor heat exchanger 4 and the heater 12 and blown into the room.
[0040]
The cooling water (hot water) supplied to the heater 12 is heated by the fuel cell 20 and the first outdoor heat exchanger 2, and the temperature of the cooling water supplied to the heater 12 is the first outdoor heat exchanger. In this embodiment, the temperature of the cooling water supplied to the heater 12 is determined by multiplying the target blowing temperature TAO by the heat exchange efficiency γ in the heater 12 in this embodiment. The number of rotations of the compressor 1 is controlled so as to satisfy (× γ).
[0041]
Specifically, the rotational speed change amount Δf of the compressor 1 is determined based on the fuzzy theory from the temperature difference between the target water temperature TWO and the detected temperature of the water temperature sensor 9g and the change rate of the temperature difference.
[0042]
In addition, since the refrigerant | coolant after pressure reduction flows into the compressor 1 side and the 1st pressure reduction device 7 side of the internal heat exchanger 5 substantially, heat exchange is not performed.
[0043]
Incidentally, when the temperature difference between the target water temperature TWO and the detected temperature of the water temperature sensor 9g is equal to or lower than the predetermined temperature, or when the detected temperature of the water temperature sensor 9g is equal to or higher than the target water temperature TWO, the compressor 1 is stopped and the vapor compression refrigeration is performed. Heating assistance by the machine, that is, heating the cooling water flowing into the heater 12 by the vapor compression refrigerator is not performed.
[0044]
3. This is executed when the dehumidifying and heating target blowing temperature TAO is equal to or higher than a predetermined temperature and the detected temperature of the internal air temperature sensor 9k is higher than the dew point temperature calculated from the detected humidity of the internal air humidity sensor 9n and the detected temperature of the internal air temperature sensor 9k. Therefore, the refrigerant is circulated through the same route as in the heating operation with the air passage that bypasses the heater 12 closed by the air mix door 13.
[0045]
Specifically, the compressor 1 → the first outdoor heat exchanger 2 → the second pressure reducer 8 → the switching valve 6 → the indoor heat exchanger 4 → the first pressure reducer 7 → the internal heat exchanger 5 → the second outdoor heat exchange. The order of the unit 3 → the switching valve 6 → the accumulator 10 → the compressor 1 is obtained.
[0046]
At this time, by controlling the throttle opening of the second decompressor 8 so that the detected pressure of the discharged refrigerant pressure sensor 9b becomes the target high pressure Po determined by the first outdoor heat exchanger refrigerant temperature sensor 9c, The cooling water is heated by the outdoor heat exchanger 2 to heat the air indirectly blown into the room, and the refrigerant is evaporated by the indoor heat exchanger 4 to cool the air blown into the room.
[0047]
For this reason, since the air dehumidified and cooled by the indoor heat exchanger 4 is reheated by the heater 12, heating can be performed while dehumidifying. Incidentally, the control of the compressor 1 is the same as in the heating operation.
[0048]
In the heating operation and the dehumidifying heating operation, the second outdoor heat exchanger 3 serves as the low temperature side heat exchanger described in the claims, and the first outdoor heat exchanger 2 is described in the claims. It becomes the high temperature side heat exchanger made.
[0049]
FIG. 4 is a flowchart showing the characteristic operation of the air conditioner during heating operation and dehumidifying heating operation. This flowchart will be described below.
[0050]
The target air temperature TAO calculated based on the detected values of the outside air temperature sensor 9h, the inside air temperature sensor 9k and the solar radiation sensor 9m, the desired room temperature (panel input) set and input by the occupant, etc. is calculated (S110 to S130), After calculating the target water temperature TWO from the target outlet temperature TAO (S140), the target rotational speed IVO of the compressor 1 is calculated based on the target water temperature TWO (S160).
[0051]
Next, the dew point temperature Tf of the atmosphere of the second outdoor heat exchanger 3 is calculated based on the detected temperatures (outside air dry bulb temperature) of the outdoor air humidity sensor 9j and the outdoor air temperature sensor 9h, and the second outdoor heat exchanger refrigerant temperature is calculated. It is determined whether or not the detected temperature THO of the sensor 9d is lower than the dew point temperature Tf (S170).
[0052]
When the detected temperature THO is lower than the dew point temperature Tf, condensed water is generated on the surface of the second outdoor heat exchanger 3, so that the detected temperature THO is equal to or lower than the predetermined temperature α, that is, the freezing point (0 ° C.) of water. It is determined whether or not (S180).
[0053]
As is well known, the dew point temperature Tf can be obtained from a wet air diagram (see FIG. 5) if the relative humidity and the dry bulb temperature are known.
[0054]
When the detected temperature THO is equal to or lower than the predetermined temperature α, the possibility that frost is generated on the surface of the second outdoor heat exchanger 3 is very high. Therefore, the target rotational speed is lower than the target rotational speed IVO determined in S160. As the compressor rotation speed IVO, the actuator, that is, the compressor 1 and the decompressor are actually operated (S190, S200).
[0055]
In other words, when it is determined that frost can be generated on the surface of the second outdoor heat exchanger 3, it is determined that frost can be generated on the surface of the second outdoor heat exchanger 3. Compared to before, the refrigerant flow rate to be circulated is decreased to reduce (save) the heat absorption capability and heating capability of the vapor compression refrigerator.
[0056]
When the temperature difference between the detected temperature THO and the outside air temperature is equal to or greater than a predetermined temperature difference (for example, 20 ° C.), the high-pressure refrigerant (hot gas) discharged from the compressor 1 is transferred to the second outdoor heat exchanger 3. By making it flow in, the 2nd outdoor heat exchanger 3 is heated from the inside, and the defrost which removes frost is performed.
[0057]
Next, the function and effect of this embodiment will be described.
[0058]
In the present embodiment, whether or not the dew point temperature is calculated based on the temperature and the relative humidity of the low temperature side atmosphere and frost can be generated on the surface of the second outdoor heat exchanger 3 constituting the low temperature side heat exchanger. since the determination may be able to determine the frosting before Mau to frosted large amount of frost on the surface of the low-temperature heat exchanger.
[0059]
Further, when it is determined that frost can be generated on the surface of the second outdoor heat exchanger 3, the refrigerant flow rate to be circulated is decreased to reduce the heat absorption capacity and heating capacity of the vapor compression refrigerator (save). Therefore, the progress speed of frost formation can be reduced.
[0060]
Therefore, since it is possible to reduce the frequency at which the defrosting operation is performed while suppressing a significant decrease in the endothermic efficiency, it is possible to improve the operating efficiency of the vapor compression refrigerator.
[0061]
( Reference example )
In the above-described embodiment, when it is determined that frost can be generated on the surface of the second outdoor heat exchanger 3, the refrigerant flow rate to be circulated is decreased to increase the heat absorption capability and heating capability of the vapor compression refrigerator. In the reference example , when it is determined that frost can be generated on the surface of the second outdoor heat exchanger 3, in the reference example , whether or not heating assistance is performed by the vapor compression refrigerator The temperature that forms the threshold value is lowered.
[0062]
Specifically, as shown in S195 of FIG. 6, when it is determined that frost can be generated on the surface of the second outdoor heat exchanger 3, the vapor compression refrigeration is performed by reducing the target water temperature TWO. Heating assistance by the machine is stopped earlier than in the first embodiment, and the heat absorption capacity and heating capacity of the vapor compression refrigerator are reduced (saved).
[0063]
In addition, it is the same as 1st Embodiment except the point which performs a defrost operation when the detection temperature of S195 and the water temperature sensor 9g becomes more than predetermined temperature (for example, 60 degreeC).
[0064]
By the way, in FIG. 1, although the fuel cell 20 is arrange | positioned in the site | part different from the radiator 21 and the 2nd outdoor heat exchanger 3, in the mounting state, it is the 2nd outdoor heat exchanger 3 and the radiator sequentially from the vehicle front side. 21 and the fuel cell 20 are arranged in this order. For this reason, the traveling wind of the vehicle hits the fuel cell 20 through the second outdoor heat exchanger 3 and the radiator 21.
[0065]
Thereby, in this reference example , although many frost generate | occur | produces on the surface of the 2nd outdoor heat exchanger 3 compared with 1st Embodiment, when many frost generate | occur | produces on the surface of the 2nd outdoor heat exchanger 3, Since the traveling air volume hitting the fuel cell 20 decreases, the fuel cell temperature increases even when the cooling water temperature rises compared to before the frost is generated in the second outdoor heat exchanger 3 and the heating assistance by the vapor compression refrigerator is stopped. The air blown into the room can be sufficiently heated only by the cooling water heated at 20.
[0066]
As a result, since the operating rate of the vapor compression refrigerator can be reduced, the operation efficiency of the vapor compression refrigerator can be improved.
[0067]
(Other embodiments)
In the above embodiments, using a fuel cell 20 as the vehicle equipment that generates heat during operation, the present invention is rather to be limited thereto, as the vehicle appliance to heat during operation, for example, it may be an internal combustion engine.
[0068]
In the above-described embodiment, the present invention is applied to the air conditioner that uses the heat generated on the high pressure (high temperature) side. However, the vapor compression refrigerator that uses the cold generated on the low temperature (low pressure) side of a freezer or the like. It can also be applied to.
[0069]
Further, in the above-described embodiment, the required pressure is obtained by increasing the refrigerant pressure on the high-pressure side to the critical pressure of the refrigerant or more, but the present invention is not limited to this. For example, the refrigerant is flon, The refrigerant pressure on the high pressure side may be less than the critical pressure of the refrigerant.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an air conditioner according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a refrigerant flow of the air conditioner according to the embodiment of the present invention.
FIG. 3 is a schematic diagram showing a refrigerant flow of the air conditioner according to the embodiment of the present invention.
FIG. 4 is a flowchart showing control of the air conditioner according to the first embodiment of the present invention.
FIG. 5 is a wetting line diagram.
FIG. 6 is a flowchart showing control of an air conditioner according to a reference example .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... 1st outdoor heat exchanger, 3 ... 2nd outdoor heat exchanger,
4 ... Indoor heat exchanger, 5 ... Internal heat exchanger, 9h ... Outside air temperature sensor,
9j: Outside air humidity sensor.

Claims

A vapor compression refrigerator that moves the heat on the low temperature side to the high temperature side,
A low-temperature side heat exchanger (3) that is disposed in outdoor air that is a low-temperature side atmosphere and exchanges heat between the refrigerant and the atmosphere;
A high temperature side heat exchanger (2) disposed on the high temperature side for exchanging heat between the refrigerant and water ;
Pump means (1) for circulating refrigerant between the low temperature side heat exchanger (3) and the high temperature side heat exchanger (2);
Frost prediction means for determining whether or not frost can be generated on the surface of the low temperature side heat exchanger (3);
Pump control at the time of frost determination that controls the operation of the pump means (1) when it is determined by the frost prediction means that the frost can be generated on the surface of the low temperature side heat exchanger (3). Means and
The water subjected to heat exchange in the high temperature side heat exchanger (2) is used as a heat source for heating the air blown into the room,
The frost formation predicting means is configured such that the temperature (THO) of the refrigerant flowing out of the low temperature side heat exchanger (3) is calculated from the relative humidity of the outdoor air and the temperature of the outdoor air (dew point temperature of the outdoor air ( Tf) and when the temperature (THO) of the refrigerant flowing out of the low temperature side heat exchanger (3) is below the freezing point of water, the low temperature side heat exchanger (3) Judge that the surface can be frosty ,
When it is determined by the frost formation prediction means that there is no situation where frost can be generated on the surface of the low temperature side heat exchanger (3), the target rotational speed (IVO) of the pump means (1) is The temperature of the water heated in the heat exchanger (2) is determined to be a value such that it becomes the target water temperature (TWO) calculated based on the target outlet temperature (TAO),
The target blowing temperature (TAO) is calculated based on the temperature of the outdoor air, the temperature of the indoor air, the amount of solar radiation poured into the room, and the set temperature in the room,
When it is determined by the frost prediction unit that the frost can be generated on the surface of the low temperature side heat exchanger (3), the frost determination determination pump control unit uses the frost prediction unit to control the low temperature. The target rotational speed (β) is subtracted from a predetermined predetermined value (β) from the target rotational speed (IVO) before it is determined that the surface of the side heat exchanger (3) can generate frost. A vapor compression type refrigerator characterized by changing IVO) .

The vapor compression refrigerator according to claim 1 , wherein carbon dioxide is used as the refrigerant.

The vapor compression refrigerator according to claim 1 or 2 , wherein the refrigerant pressure on the high-pressure side is increased to a critical pressure or higher of the refrigerant.