JP3972789B2

JP3972789B2 - Charge amount adjustment device for battery pack

Info

Publication number: JP3972789B2
Application number: JP2002297187A
Authority: JP
Inventors: 孝昭安部; 修嶋村
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2002-10-10
Filing date: 2002-10-10
Publication date: 2007-09-05
Anticipated expiration: 2022-10-10
Also published as: JP2004135424A

Description

【０００１】
【発明の属する技術分野】
本発明は、組電池の単電池（セル）間の充電量を調整する装置に関する。
【０００２】
【従来の技術】
複数のセルが直列に接続された組電池では、セルの充電量にバラツキがあると出力電圧や放電容量が低下する。そこで、スイッチと抵抗とが直列に接続されたバイパス回路を各セルに並列に接続するとともに、各セルの両端電圧を検出し、検出したセル電圧に基づいて各セルの充電量のバラツキを算出し、各セルのバイパス回路を選択的に作動させて各セルの充電量が均一になるように調整する組電池の充電量調整装置が知られている（例えば特許文献１参照）。
【０００３】
この出願の発明に関連する先行技術文献としては次のものがある。
【特許文献１】
特開２００２−１０１５６５号公報（第５−９頁、図１）
【０００４】
【発明が解決しようとする課題】
しかしながら、上述した従来の組電池の充電量調整装置では、各セルの電圧を検出し、各セルの検出電圧に基づいて各セルの充電量のバラツキを算出しているので、各セルの電圧を検出する電圧検出回路と、各セルごとの検出結果をコントローラーへ送信する信号回路とが必要となり、装置のコストがかかるという問題がある。
【０００５】
本発明の目的は、組電池の充電量調整装置のコストを低減することにある。
【０００６】
【課題を解決するための手段】
本発明は、単電池（セル）を複数個直列に接続した組電池、または複数のセルを並列に接続したセル並列回路を複数組直列に接続した組電池の充電量を調整する装置において、セルの温度を検出し、セル温度検出値に基づいてセルまたはセル並列回路の充電量のバラツキを推定し、充電量バラツキの推定結果が所定値を超えたら、組電池の目標充電量をツェナーダイオードのツェナー電圧に相当する充電量よりもわずかに高い値に設定し、組電池の充電量が目標充電量となるように組電池の充電制御を行う。
【０００７】
【発明の効果】
本発明によれば、装置のコストを低減できる。
【０００８】
【発明の実施の形態】
本発明をパラレルハイブリッド車両に適用した一実施の形態を説明する。なお、本発明はパラレルハイブリッド車両に好適であるが、パラレルハイブリッド車両に限定されず、例えばシリーズハイブリッド車両や電気自動車などの組電池を用いたあらゆる装置に適用することができる。
【０００９】
図１は一実施の形態の全体構成を示す。一実施の形態のパラレルハイブリッド車両はエンジン１の出力軸に交流モーター２の回転軸が直結されており、エンジン１と交流モーター２のいずれか一方または両方の制駆動力により走行する。エンジン１および／またはモーター２の制駆動力は変速機３および減速機４を介して駆動輪５ａ、５ｂへ伝達される。バッテリー６はインバーター７を介してモーター２へ駆動電力を供給するとともに、インバーター７を介してモーター２から回生電力を受け入れる。車両コントローラー８は、エンジン１、バッテリー６およびインバーター７を制御する。
【００１０】
図２は、一実施の形態のパラレルハイブリッド車両のバッテリーと車両コントローラーの詳細を示す。一実施の形態のバッテリー６は、２個のセル（単電池）を並列に接続した並列回路をｎ組直列に接続した組電池である。図２に示すように、セルＣ１１とＣ１２の並列回路からセルＣｎ１とＣｎ２の並列回路までｎ組のセル並列回路を直列に接続して構成する。
【００１１】
バッテリー６のセル並列回路にはそれぞれ、抵抗器ＲとツェナーダイオードＺの直列回路を並列に接続する。例えばセルＣ１１とＣ１２の並列回路には、抵抗器Ｒ１とツェナーダイオードＺ１の直列回路を並列に接続する。他のセル並列回路にも同様に、抵抗器ＲとツェナーダイオードＺの直列回路を並列に接続する。
【００１２】
これらの抵抗器ＲとツェナーダイオードＺの直列回路は、各セル並列回路のセルの充電量を調整し、すべてのセル並列回路の充電量を均一にする回路である。例えばセルＣ１１とＣ１２の並列回路の充電量の増加にともなってこのセル並列回路の端子電圧が上昇し、ツェナーダイオードＺ１のツェナー電圧Ｖｚを超えると、充電電流は並列回路のセルＣ１１、Ｃ１２を流れず、抵抗器Ｒ１とツェナーダイオードＺ１の直列回路を流れるようになる。したがって、セル並列回路の端子電圧はツェナー電圧Ｖｚ以上には上昇しない。
【００１３】
通常の使用状態において、セル並列回路の端子電圧はセルＣ１１とＣ１２の充電量にほぼ比例しており、セル並列回路の端子電圧をツェナー電圧Ｖｚで制限すれば、セル並列回路の充電量をツェナー電圧Ｖｚに応じた充電量に制限することができる。したがって、すべてのツェナーダイオードＺのツェナー電圧Ｖｚをほぼ同一の値に揃えておけば、バッテリー６の各セル並列回路の充電量を均一に調整することができる。この抵抗器ＲとツェナーダイオードＺの直列回路を充電電流バイパス回路と呼ぶ。
【００１４】
バイパス回路のツェナーダイオードＺの代わりにトランジスターやＦＥＴなどのスイッチ素子を用いるとともに、セル並列回路ごとに両端電圧を検出する電圧センサーを設け、セル並列回路の両端電圧が所定電圧に達したらバイパス回路のスイッチ素子を閉路して充電電流をバイパスし、セル並列回路の充電量を調整する方法がある。このような充電量調整装置では、セル並列回路ごとに電圧センサーを設置し、検出電圧に基づいてコントローラーによりバイパス回路のスイッチ素子を開閉制御しなければならないため、制御が複雑になる上に装置のコストがかかる欠点がある。この一実施の形態のバイパス回路では、各バイパス回路のツェナーダイオードＺのツェナー電圧Ｖｚを揃えるだけで、各セル並列回路の充電量を均一に調整することができ、制御を簡略化できる上に、各セル並列回路に電圧センサーを設ける必要がなく、装置のコストを低減することができる。
【００１５】
バッテリー６の両端には電圧センサーＶ１を接続し、バッテリー６の端子電圧（以下、総電圧という）ＶＢを検出する。車両コントローラー８は、バッテリー６の総電圧ＶＢに基づいてバッテリー６の充電状態ＳＯＣ[％]を求める。
【００１６】
車両コントローラー８はＣＰＵ８ａ、ＲＯＭ８ｂ、ＲＡＭ８ｃ、Ａ／Ｄコンバーター８ｄなどの備え、バッテリー６の各セル並列回路の充電量を調整する。この車両コントローラー８には、温度センサーＴ１１〜Ｔ１４、Ｔ２１〜Ｔ２４と、メインスイッチ９を接続する。温度センサーＴ１１〜Ｔ１４、Ｔ２１〜Ｔ２４は、バッテリー６のセル温度を検出するためのセンサーである。これらの温度センサーにはサーミスタなどの感温素子を用いることができる。また、メインスイッチ９は従来のエンジン車両のイグニッションスイッチに相当するものである。
【００１７】
図３はバッテリー内部の構造を示す。一実施の形態のバッテリー６は、セル並列回路を６列、４段に積層した例を示す。各段の間には間隙を設け、これらの間隙に送風機（不図示）により冷却空気を送ってバッテリーセルを冷却する。冷却風が図３に示すようにバッテリー６の左側から右側へ流れる場合には、温度センサーＴ１１〜Ｔ１４を冷却風上流端のセル近傍に配置するとともに、温度センサーＴ２１〜Ｔ２４を冷却風下流端のセル近傍に配置する。つまり、温度センサーＴ１１〜Ｔ１４により冷却風上流端の最も温度の低いセルの温度ｔｈ１１〜ｔｈ１４を検出し、温度センサーＴ２１〜Ｔ２４により冷却風下流端の最も温度の高いセルの温度ｔｈ２１〜ｔｈ２４を検出する。
【００１８】
なお、バッテリーの内部構造はこの一実施の形態の構造に限定されるものではないが、どのような構造のバッテリーに対しても冷却風上流端のセル温度と冷却風下流端のセル温度を検出するのが望ましい。これにより、すべてのセルに温度センサーを設置して最高と最低のセル温度を選ぶのに比べ、使用する温度センサーの数が少なくなって装置のコストを低減することができる。
【００１９】
この一実施の形態では抵抗器ＲとツェナーダイオードＺを直列に接続したバイパス回路を用い、セル並列回路の充電量を調整する。セル並列回路に流れていた充電電流がバイパス回路に流れ始めるセル並列回路の電圧は、ツェナーダイオードＺのツェナー電圧Ｖｚであり、ツェナー電圧Ｖｚを変えることによってセル並列回路の電圧、すなわち充電量を変えることができる。つまり、ツェナー電圧Ｖｚの低いツェナーダイオードＺを用いれば、セル並列回路の電圧が低い状態、すなわち充電量が少ない状態ですべてのセル並列回路の充電量均一化を実施することができる。逆に、ツェナー電圧Ｖｚの高いツェナーダイオードＺを用いれば、セル並列回路の電圧が高い状態、すなわち充電量が多い状態ですべてのセル並列回路の充電量均一化を実施することができる。
【００２０】
ところが、ツェナー電圧Ｖｚの低いツェナーダイオードＺを用い、充電量が少ないときにバイパス回路へ充電電流を流して充電量の調整を行うと、充電電流がバイパス回路へ流れる頻度が多くなって電力を無駄に捨てることになる。逆に、ツェナー電圧Ｖｚの高いツェナーダイオードＺを用い、充電量が多いときにバイパス回路へ充電電流を流して充電量の調整を行うと、充電電流がバイパス回路へ流れる頻度が少なくなって電力を無駄に捨てることはなくなるが、充電量を調整する機会が少なくなり、すべてのセル並列回路の充電量を均一にすることが困難になる。
【００２１】
特に、パラレルハイブリッド車両では、通常、バッテリーの充電状態ＳＯＣが３０〜７０％の目標範囲内になるようにバッテリーの充放電制御が行われるので、バッテリーがＳＯＣ７０％を超える充電量になる機会が少ない。
【００２２】
そこで、バッテリーが満充電に近い状態にあるときに充電量の調整が実施されるツェナー電圧Ｖｚを選択するとともに、定期的にバッテリーの目標充電状態ＳＯＣを１００％にして満充電状態まで充電を行う必要がある。しかし、定期的に満充電状態までの充電を行う方法では、セルまたはセル並列回路の充電量のバラツキが少なくても満充電が実施されることになり、やはり無駄な電力を消費することになる。
【００２３】
この一実施の形態では、無駄な電力消費を防止して充電量のバラツキを調整するために、バッテリーが満充電またはそれに近い状態にあるときに充電量の調整が実施されるツェナー電圧Ｖｚを選択するとともに、バッテリー６のセル並列回路の充電量のバラツキを推定し、充電量バラツキの推定値が所定値以上になったらバッテリー６の満充電を実施する。
【００２４】
上述したように、セル並列回路ごとに電圧センサーを設置し、各セル並列回路の端子電圧を計測してセル並列回路の充電量のバラツキを検出する従来の方法では、制御が複雑になる上に装置のコストがかかる欠点がある。この一実施の形態では、各セル並列回路に電圧センサーを設けずに、後述する方法によりセル並列回路の充電量のバラツキを推定する。
【００２５】
図４は、単電池の温度と充電状態ＳＯＣに対する自己放電速度の関係を示す。一般に、組電池のセル（単電池）は温度に応じて自己放電速度が異なるため、温度が異なる環境下に長時間置かれるとセルごとの充電量にバラツキが発生する。図４は、マンガン系リチウムイオン電池の温度と充電状態ＳＯＣに対する自己放電速度dＳＯＣ/dtの特性を表す。この特性図から明らかなように、セル温度が高いほど自己放電速度が速く、またセルの充電状態ＳＯＣが高いほど自己放電速度が速い。
【００２６】
そこで、充電量の調整を行う組電池のセル温度と充電状態ＳＯＣに対する自己放電速度の特性を計測し、自己放電速度データマップとして記憶しておく。そして、使用中の組電池のセル温度を計測し、最高のセル温度と最低のセル温度を求めるとともに、組電池の総電圧を計測して組電池の充電状態ＳＯＣを検出する。次に、上述した自己放電速度データマップを参照し、最低セル温度に対応する自己放電速度ＳＶ１と最高セル温度に対応する自己放電速度ＳＶ２を表引き演算し、次式により組電池の現在の充電量バラツキＳＢを演算により推定する。
【数１】
ＳＢ＝ＳＢold＋（ＳＶ２−ＳＶ１）・Δｔ
数式１において、ＳＢoldは前回の演算時の充電量バラツキ、Δｔは充電量バラツキの演算実行時間間隔である。
【００２７】
組電池の推定充電量バラツキＳＢが所定値以上になったら、組電池の目標充電状態ＳＯＣを少なくともツェナー電圧Ｖｚに相当する充電状態ＳＯＣよりもわずかに高いＳＯＣに設定し、組電池の充電制御を行って充電量のバラツキを調整する。
【００２８】
ここで、ツェナーダイオード電圧Ｖｚに相当する充電状態ＳＯＣよりもはるかに高いＳＯＣ、例えばＳＯＣ１００％を設定すると、充電量のバラツキがなくなっているのにバラツキ調整が続けられることになり、無駄な電力を消費することになるから、少なくともツェナー電圧Ｖｚに相当する充電状態ＳＯＣよりもわずかに高い目標ＳＯＣを設定する。
【００２９】
図５は、一実施の形態の充電量調整プログラムを示すフローチャートである。車両コントローラー８のＣＰＵ８ａは、メインスイッチ９がオン状態にある間、この充電量調整プログラムを繰り返し実行する。
【００３０】
ステップ１において、バッテリー６の充電状態ＳＯＣが目標範囲３０〜７０％内に収まるように充放電を制御する、通常の充電量制御を行う。続くステップ２で、図６に示すサブルーチンを実行して充電量バラツキＳＢを演算する。
【００３１】
図６のステップ２１において、電圧センサーＶ１によりバッテリー総電圧ＶＢを計測する。ステップ２２では、バッテリー総電圧ＶＢに基づいてバッテリー６の充電状態ＳＯＣを演算する。具体的には、予めバッテリー６の総電圧ＶＢに対する充電状態ＳＯＣを計測し、ＳＯＣデータマップとして記憶しておき、計測したバッテリー総電圧ＶＢに対応する充電状態ＳＯＣを表引き演算により求める。
【００３２】
次に、ステップ２３で、冷却風上流端のセル近傍に設置した温度センサーＴ１１〜Ｔ１４によりセル温度ｔｈ１１〜ｔｈ１４を計測するとともに、冷却風下流端のセル近傍に設置した温度センサーＴ２１〜Ｔ２４によりセル温度ｔｈ２１〜ｔｈ２４を計測する。図３に示すように、バッテリー６のセルの中で冷却風上流端のセルの温度が最も低く、冷却風下流端のセルの温度が最も高いから、温度センサーＴ１１〜Ｔ１４により最低のセル温度ｔｈ１１〜ｔｈ１４を計測し、温度センサーＴ２１〜Ｔ２４により最高のセル温度ｔｈ２１〜ｔｈ２４を計測することになる。
【００３３】
ステップ２４において、冷却風上流端のセル温度ｔｈ１１〜ｔｈ１４の平均値を求め、予め記憶しておいた図４に示す自己放電速度データマップから、セル温度ｔｈ１１〜ｔｈ１４の平均値とステップ２２で求めたバッテリー充電量ＳＯＣとに対応する自己放電速度ＳＶ１を表引き演算する。続くステップ２５でも同様に、冷却風下流端のセル温度ｔｈ２１〜ｔｈ２４の平均値を求め、上記自己放電速度データマップからセル温度ｔｈ２１〜ｔｈ２４の平均値とバッテリー充電量ＳＯＣに対応する自己放電速度ＳＶ２を表引き演算する。
【００３４】
ステップ２６では、前回の充電量バラツキ演算時の充電量バラツキＳＢoldと、冷却風上流端セルの自己放電速度ＳＶ１と、冷却風下流端セルの自己放電速度ＳＶ２と、充電量バラツキ演算時間間隔Δｔとに基づいて、上記数式１により今回の充電量バラツキＳＢを演算により推定する。演算後、今回の充電量バラツキＳＢにより前回の充電量バラツキＳＢoldを更新し、図５のステップ３へリターンする。
【００３５】
リターン後の図５のステップ３において、推定充電量バラツキＳＢが所定値Ｋ以上か否かを判定し、所定値Ｋ未満の場合はステップ１へ戻って通常充電量制御を継続する。一方、推定充電量バラツキＳＢが所定値Ｋ以上の場合はステップ４へ進み、高充電量制御を行う。具体的には、バッテリー６の目標充電状態ＳＯＣを、少なくともツェナー電圧Ｖｚに相当する充電状態ＳＯＣよりもわずかに高いＳＯＣに設定し、バッテリー６の充放電を制御して充電量のバラツキを調整する。
【００３６】
ステップ５では充電量のバラツキ調整が終了したか否かを判定する。バッテリー６のセルの内、冷却風下流端に配置されたセルは最も温度が高く、最も自己放電速度が速い。したがって、冷却風下流端のセルは最も充電量が少ない。そこで、バッテリー６の充放電電流を積算して冷却風下流端のセルの充電量を求め、冷却風下流端のセルの充電量が目標充電量ＳＯＣに達したかどうかを判定する。冷却風下流端の最も温度の高いセルの充電量が目標充電量ＳＯＣに達したら、充電量のバラツキ調整が終了したとする。
【００３７】
セル並列回路の充電量のバラツキ調整が終了していない場合はステップ４へ戻り、高充電量制御を継続して充電量のバラツキを調整する。一方、充電量のバラツキが終了した場合はステップ６へ進み、今回の充電量バラツキＳＢと前回演算時の充電量バラツキＳＢoldを０にリセットし、ステップ１へ戻って上述した通常の充電量制御を実行する。
【００３８】
このように、一実施の形態では、複数のセルを並列に接続したセル並列回路を複数組直列に接続した組電池の充電量を調整する装置において、セルの温度を検出し、セル温度検出値に基づいてセル並列回路の充電量のバラツキを推定し、この推定結果により充電量調整を実施するようにした。セル並列回路を複数組直列に接続した組電池において、従来の充電量調整装置のようにセル並列回路ごとに電圧センサーを設けると、組電池側の高圧回路と電圧センサー側の低圧回路とを絶縁する必要があるため、信号回路が複雑になり、コストがかかる。この一実施の形態によれば、各セル並列回路に電圧センサーを設ける必要がなく、また、温度センサーは組電池側高圧回路との絶縁が容易に取れるので、装置のコストを低減することができる。
【００３９】
また、この一実施の形態では、抵抗器とツェナーダイオードとを直列に接続した回路であって、セル並列回路に流れる充電電流をバイパスする回路をセル並列回路ごとに設け、充電量バラツキの推定結果が所定値を超えたら、バイパス回路が作動するように組電池の充電制御を行うようにした。これにより、トランジスターやＦＥＴなどのスイッチ素子と抵抗器とを直列に接続した従来のバイパス回路のようにスイッチ素子を制御する必要がなく、制御を簡略化できる上に、無駄な電力を消費することなくセル並列回路の充電量を均一にすることができる。
【００４０】
さらに、この一実施の形態では、組電池の冷却風上流端に配置されたセルと冷却風下流端に配置されたセルの温度を検出し、冷却風上流端のセル温度検出値と冷却風下流端のセル温度検出値とに基づいてセル並列回路の充電量のバラツキを推定するようにしたので、すべてのセルに温度センサーを設置して最高と最低のセル温度を選ぶのに比べ、使用する温度センサーの数が少なくなって装置のコストをさらに低減することができる。
【００４１】
この一実施の形態ではまた、組電池の充電状態ＳＯＣを検出し、セル温度検出値とＳＯＣ検出値とに基づいてセル並列回路の充電量のバラツキを推定するようにした。パラレルハイブリッド車両では、通常、組電池のＳＯＣが３０〜７０％の目標範囲に収まるように充放電制御が行われるため、セル温度検出値のみに基づいてセル並列回路の充電量のバラツキを推定しても十分な推定結果を得ることができる。しかし、セル温度検出値とＳＯＣ検出値とに基づいてセル並列回路の充電量のバラツキを推定することによって、さらに正確な推定結果を得ることができる。
【００４２】
特許請求の範囲の構成要素と一実施の形態の構成要素との対応関係は次の通りである。すなわち、温度センサーＴ１１〜Ｔ１４、Ｔ２１〜Ｔ２４がセル温度検出手段を、車両コントローラー８が充電量バラツキ推定手段および制御手段をそれぞれ構成する。なお、本発明の特徴的な機能を損なわない限り、各構成要素は上記構成に限定されるものではない。
【００４３】
なお、上述した一実施の形態では、２個のセルを並列に接続したセル並列回路をｎ組直列に接続した組電池を例に上げて説明したが、本願発明はこの一実施の形態の組電池に限定されるものではない。単一のセルを複数個直列に接続した組電池、あるいは３個以上のセルを並列に接続した並列回路を複数組直列に接続した組電池に対して本願発明を適用することができる。単一のセルを複数個直列に接続した組電池に対して本願発明を適用する場合には、上述した一実施の形態のセル並列回路を単一のセルと置き換えて考えればよい。
【００４４】
また、本願発明は、セル（単電池）の種類についても特に限定されるものではなく、例えばマンガン系、コバルト系、ニッケル系のリチウムイオン電池や、各種のニッケル水素電池など、あらゆる種類のセルに対して本願発明を適用することができる。
【図面の簡単な説明】
【図１】一実施の形態の全体構成を示す図である。
【図２】一実施の形態のパラレルハイブリッド車両のバッテリーと車両コントローラーの詳細を示す図である。
【図３】バッテリー内部の構造を示す図である。
【図４】単電池の温度と充電状態ＳＯＣに対する自己放電速度の関係を示す図である。
【図５】一実施の形態の充電量調整プログラムを示すフローチャートである。
【図６】一実施の形態の充電量バラツキ演算サブルーチンを示すフローチャートである。
【符号の説明】
１エンジン
２モーター
３変速機
４減速機
５ａ、５ｂ駆動輪
６バッテリー
７インバーター
８車両コントローラー
８ａＣＰＵ
８ｂＲＯＭ
８ｃＲＡＭ
８ｃＡ／Ｄコンバーター
９メインスイッチ
Ｃ１１、Ｃ１２、Ｃ２１、Ｃ２２、Ｃ３１、Ｃ３２、Ｃｎ１、Ｃｎ２セル（単電池）
Ｒ１、Ｒ２、Ｒ３、Ｒｎ抵抗器
Ｚ１、Ｚ２、Ｚ３、Ｚｎツェナーダイオード
Ｖ１電圧センサー
Ｔ１１〜Ｔ１３、Ｔ２１〜Ｔ２４温度センサー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for adjusting the amount of charge between single cells (cells) of an assembled battery.
[0002]
[Prior art]
In an assembled battery in which a plurality of cells are connected in series, the output voltage and the discharge capacity are reduced when there is a variation in the charge amount of the cells. Therefore, a bypass circuit in which a switch and a resistor are connected in series is connected in parallel to each cell, the voltage across each cell is detected, and the variation in the charge amount of each cell is calculated based on the detected cell voltage. A battery pack charge amount adjusting device is known that selectively operates a bypass circuit of each cell to adjust the charge amount of each cell to be uniform (see, for example, Patent Document 1).
[0003]
Prior art documents related to the invention of this application include the following.
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-101565 (page 5-9, FIG. 1)
[0004]
[Problems to be solved by the invention]
However, the above-described conventional battery pack charge amount adjustment device detects the voltage of each cell and calculates the variation in the charge amount of each cell based on the detected voltage of each cell. A voltage detection circuit for detection and a signal circuit for transmitting a detection result for each cell to the controller are required, which causes a problem that the cost of the apparatus is increased.
[0005]
The objective of this invention is reducing the cost of the charge amount adjustment apparatus of an assembled battery.
[0006]
[Means for Solving the Problems]
The present invention relates to an apparatus for adjusting the charge amount of an assembled battery in which a plurality of single cells (cells) are connected in series, or an assembled battery in which a plurality of cell parallel circuits in which a plurality of cells are connected in parallel are connected in series. , And the variation in the charge amount of the cell or the cell parallel circuit is estimated based on the detected cell temperature value.If the estimation result of the variation in the charge amount exceeds a predetermined value, the target charge amount of the assembled battery is set to the value of the Zener diode. The battery pack is controlled to be charged to a value slightly higher than the charge amount corresponding to the Zener voltage so that the charge amount of the battery pack becomes the target charge amount .
[0007]
【The invention's effect】
According to the present invention, the cost of the apparatus can be reduced.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the present invention is applied to a parallel hybrid vehicle will be described. The present invention is suitable for a parallel hybrid vehicle, but is not limited to a parallel hybrid vehicle, and can be applied to any device using a battery pack such as a series hybrid vehicle or an electric vehicle.
[0009]
FIG. 1 shows the overall configuration of an embodiment. In the parallel hybrid vehicle according to the embodiment, the rotating shaft of the AC motor 2 is directly connected to the output shaft of the engine 1, and the vehicle travels by the braking / driving force of one or both of the engine 1 and the AC motor 2. The braking / driving force of the engine 1 and / or the motor 2 is transmitted to the drive wheels 5a and 5b via the transmission 3 and the speed reducer 4. The battery 6 supplies driving power to the motor 2 via the inverter 7 and receives regenerative power from the motor 2 via the inverter 7. The vehicle controller 8 controls the engine 1, the battery 6 and the inverter 7.
[0010]
FIG. 2 shows details of the battery and the vehicle controller of the parallel hybrid vehicle according to the embodiment. The battery 6 according to one embodiment is an assembled battery in which n sets of parallel circuits in which two cells (unit cells) are connected in parallel are connected in series. As shown in FIG. 2, n sets of cell parallel circuits are connected in series from a parallel circuit of cells C11 and C12 to a parallel circuit of cells Cn1 and Cn2.
[0011]
A series circuit of a resistor R and a Zener diode Z is connected in parallel to each cell parallel circuit of the battery 6. For example, a series circuit of a resistor R1 and a Zener diode Z1 is connected in parallel to the parallel circuit of the cells C11 and C12. Similarly, the series circuit of the resistor R and the Zener diode Z is connected in parallel to other cell parallel circuits.
[0012]
The series circuit of the resistor R and the Zener diode Z is a circuit that adjusts the charge amount of the cells of each cell parallel circuit and makes the charge amounts of all the cell parallel circuits uniform. For example, when the charge amount of the parallel circuit of the cells C11 and C12 increases and the terminal voltage of the cell parallel circuit rises and exceeds the Zener voltage Vz of the Zener diode Z1, the charging current flows through the cells C11 and C12 of the parallel circuit. Instead, the current flows through a series circuit of the resistor R1 and the Zener diode Z1. Therefore, the terminal voltage of the cell parallel circuit does not rise above the Zener voltage Vz.
[0013]
In a normal use state, the terminal voltage of the cell parallel circuit is substantially proportional to the charge amount of the cells C11 and C12. If the terminal voltage of the cell parallel circuit is limited by the Zener voltage Vz, the charge amount of the cell parallel circuit is reduced. The amount of charge according to the voltage Vz can be limited. Therefore, if the Zener voltages Vz of all Zener diodes Z are set to substantially the same value, the charge amount of each cell parallel circuit of the battery 6 can be adjusted uniformly. A series circuit of the resistor R and the Zener diode Z is called a charging current bypass circuit.
[0014]
A switch element such as a transistor or FET is used in place of the zener diode Z of the bypass circuit, and a voltage sensor for detecting the voltage across each cell parallel circuit is provided. When the voltage across the cell parallel circuit reaches a predetermined voltage, the bypass circuit There is a method of adjusting the charge amount of the cell parallel circuit by closing the switch element to bypass the charging current. In such a charge amount adjustment device, a voltage sensor must be installed for each cell parallel circuit, and the switch element of the bypass circuit must be controlled to open and close by the controller based on the detected voltage. There is a drawback that costs. In the bypass circuit of this embodiment, the charge amount of each cell parallel circuit can be adjusted uniformly by simply aligning the Zener voltage Vz of the Zener diode Z of each bypass circuit, and the control can be simplified. It is not necessary to provide a voltage sensor in each cell parallel circuit, and the cost of the apparatus can be reduced.
[0015]
A voltage sensor V1 is connected to both ends of the battery 6, and a terminal voltage (hereinafter referred to as a total voltage) VB of the battery 6 is detected. The vehicle controller 8 obtains the state of charge SOC [%] of the battery 6 based on the total voltage VB of the battery 6.
[0016]
The vehicle controller 8 includes a CPU 8a, a ROM 8b, a RAM 8c, an A / D converter 8d, and the like, and adjusts the charge amount of each cell parallel circuit of the battery 6. Temperature sensors T11 to T14, T21 to T24, and a main switch 9 are connected to the vehicle controller 8. The temperature sensors T11 to T14 and T21 to T24 are sensors for detecting the cell temperature of the battery 6. A temperature sensitive element such as a thermistor can be used for these temperature sensors. The main switch 9 corresponds to an ignition switch for a conventional engine vehicle.
[0017]
FIG. 3 shows the internal structure of the battery. The battery 6 of one embodiment shows an example in which cell parallel circuits are stacked in six rows and four stages. Gaps are provided between the stages, and cooling air is sent to these gaps by a blower (not shown) to cool the battery cells. When the cooling air flows from the left side to the right side of the battery 6 as shown in FIG. 3, the temperature sensors T11 to T14 are arranged near the cell at the upstream end of the cooling air, and the temperature sensors T21 to T24 are arranged at the downstream end of the cooling air. Place near the cell. That is, the temperature th11 to th14 of the cell having the lowest temperature at the upstream end of the cooling air is detected by the temperature sensors T11 to T14, and the temperature th21 to th24 of the cell having the highest temperature at the downstream end of the cooling air is detected by the temperature sensors T21 to T24. To do.
[0018]
The internal structure of the battery is not limited to the structure of this embodiment, but the cell temperature at the upstream end of the cooling air and the cell temperature at the downstream end of the cooling air are detected for any battery structure. It is desirable to do. As a result, the number of temperature sensors to be used can be reduced and the cost of the apparatus can be reduced as compared with installing temperature sensors in all cells and selecting the highest and lowest cell temperatures.
[0019]
In this embodiment, a bypass circuit in which a resistor R and a Zener diode Z are connected in series is used to adjust the charge amount of the cell parallel circuit. The voltage of the cell parallel circuit where the charging current flowing in the cell parallel circuit starts to flow into the bypass circuit is the Zener voltage Vz of the Zener diode Z, and the voltage of the cell parallel circuit, that is, the charge amount is changed by changing the Zener voltage Vz. be able to. That is, if the Zener diode Z having a low Zener voltage Vz is used, the charge amounts of all the cell parallel circuits can be equalized in a state where the voltage of the cell parallel circuit is low, that is, in a state where the charge amount is small. On the contrary, if the Zener diode Z having a high Zener voltage Vz is used, the charge amounts of all the cell parallel circuits can be equalized in a state where the voltage of the cell parallel circuit is high, that is, in a state where the charge amount is large.
[0020]
However, if a Zener diode Z with a low Zener voltage Vz is used and the charge amount is adjusted by flowing the charge current to the bypass circuit when the charge amount is small, the charge current is frequently flowed to the bypass circuit and power is wasted. Will be thrown away. Conversely, if a Zener diode Z with a high Zener voltage Vz is used and the charge amount is adjusted by flowing a charge current to the bypass circuit when the charge amount is large, the frequency of the charge current flowing to the bypass circuit is reduced and power is reduced. Although it is not thrown away unnecessarily, there are fewer opportunities to adjust the charge amount, and it becomes difficult to make the charge amounts of all the cell parallel circuits uniform.
[0021]
In particular, in a parallel hybrid vehicle, the battery charge / discharge control is normally performed so that the state of charge SOC of the battery is within a target range of 30 to 70%, and therefore, there is little opportunity for the battery to have a charge amount exceeding SOC 70%. .
[0022]
Therefore, the Zener voltage Vz is selected so that the amount of charge is adjusted when the battery is nearly fully charged, and the battery is periodically charged to the fully charged state by setting the target charge state SOC of the battery to 100%. There is a need. However, in the method of periodically charging to a fully charged state, even if there is little variation in the amount of charge of the cell or the cell parallel circuit, full charging is performed, and wasteful power is still consumed. .
[0023]
In this embodiment, in order to prevent wasteful power consumption and adjust the variation in the charge amount, the Zener voltage Vz at which the charge amount is adjusted when the battery is fully charged or close to it is selected. At the same time, the variation in the charge amount of the cell parallel circuit of the battery 6 is estimated, and the battery 6 is fully charged when the estimated value of the charge amount variation exceeds a predetermined value.
[0024]
As described above, the conventional method of installing a voltage sensor for each cell parallel circuit and measuring the terminal voltage of each cell parallel circuit to detect the variation in the charge amount of the cell parallel circuit makes the control complicated. There is a disadvantage that the cost of the apparatus is high. In this embodiment, the variation in the charge amount of the cell parallel circuit is estimated by a method described later without providing a voltage sensor in each cell parallel circuit.
[0025]
FIG. 4 shows the relationship between the cell temperature and the self-discharge rate with respect to the state of charge SOC. In general, a battery (unit cell) of an assembled battery has a self-discharge rate that varies depending on the temperature. Therefore, when the cell is placed in an environment having a different temperature for a long time, the amount of charge for each cell varies. FIG. 4 shows the characteristics of the self-discharge rate dSOC / dt with respect to the temperature of the manganese-based lithium ion battery and the state of charge SOC. As is apparent from this characteristic diagram, the higher the cell temperature, the faster the self-discharge rate, and the higher the state of charge SOC of the cell, the faster the self-discharge rate.
[0026]
Therefore, the characteristics of the self-discharge rate with respect to the cell temperature and the state of charge SOC of the assembled battery whose charge is adjusted are measured and stored as a self-discharge rate data map. Then, the cell temperature of the assembled battery in use is measured to obtain the highest cell temperature and the lowest cell temperature, and the total voltage of the assembled battery is measured to detect the state of charge SOC of the assembled battery. Next, the self-discharge rate SV1 corresponding to the lowest cell temperature and the self-discharge rate SV2 corresponding to the highest cell temperature are calculated by referring to the above-described self-discharge rate data map, and the current charge of the assembled battery is calculated by the following equation: The amount variation SB is estimated by calculation.
[Expression 1]
SB = SBold + (SV2−SV1) · Δt
In Formula 1, SBold is a charge amount variation at the time of the previous calculation, and Δt is a calculation execution time interval of the charge amount variation.
[0027]
When the estimated charge amount variation SB of the assembled battery exceeds a predetermined value, the target charge state SOC of the assembled battery is set to an SOC that is slightly higher than the charged state SOC corresponding to at least the Zener voltage Vz, and the charge control of the assembled battery is performed. Go to adjust the variation in charge.
[0028]
Here, if a SOC much higher than the state of charge SOC corresponding to the Zener diode voltage Vz is set, for example, SOC 100%, the variation adjustment is continued even though the variation in the charge amount is eliminated, and wasteful power is consumed. Since it will be consumed, a target SOC slightly higher than the state of charge SOC corresponding to at least the Zener voltage Vz is set.
[0029]
FIG. 5 is a flowchart illustrating a charge amount adjustment program according to an embodiment. The CPU 8a of the vehicle controller 8 repeatedly executes this charge amount adjustment program while the main switch 9 is on.
[0030]
In step 1, normal charge amount control is performed to control charging / discharging so that the state of charge SOC of the battery 6 falls within the target range of 30 to 70%. In the subsequent step 2, the subroutine shown in FIG. 6 is executed to calculate the charge amount variation SB.
[0031]
In step 21 of FIG. 6, the battery total voltage VB is measured by the voltage sensor V1. In step 22, the state of charge SOC of the battery 6 is calculated based on the total battery voltage VB. Specifically, the state of charge SOC for the total voltage VB of the battery 6 is measured in advance and stored as an SOC data map, and the state of charge SOC corresponding to the measured battery total voltage VB is obtained by a table calculation.
[0032]
Next, at step 23, the cell temperatures th11 to th14 are measured by the temperature sensors T11 to T14 installed near the cells at the upstream end of the cooling air, and the cells are measured by the temperature sensors T21 to T24 installed near the cells at the downstream end of the cooling air. Temperatures th21 to th24 are measured. As shown in FIG. 3, since the temperature of the cell at the upstream end of the cooling air is the lowest among the cells of the battery 6 and the temperature of the cell at the downstream end of the cooling air is the highest, the lowest cell temperature th11 is detected by the temperature sensors T11 to T14. ~ Th14 is measured, and the highest cell temperatures th21 to th24 are measured by the temperature sensors T21 to T24.
[0033]
In step 24, the average value of the cell temperatures th11 to th14 at the upstream end of the cooling air is obtained, and the average value of the cell temperatures th11 to th14 is obtained in step 22 from the self-discharge rate data map shown in FIG. The self-discharge speed SV1 corresponding to the battery charge amount SOC is calculated. In the subsequent step 25 as well, the average value of the cell temperatures th21 to th24 at the downstream end of the cooling air is obtained, and the self discharge rate SV2 corresponding to the average value of the cell temperatures th21 to th24 and the battery charge SOC from the self discharge rate data map. Is calculated.
[0034]
In step 26, the charge amount variation SBold at the time of the previous charge amount variation calculation, the self-discharge rate SV1 of the cooling wind upstream end cell, the self-discharge rate SV2 of the cooling wind downstream end cell, and the charge amount variation calculation time interval Δt Based on the above, the current charge amount variation SB is estimated by calculation according to the above formula 1. After the calculation, the previous charge amount variation SBold is updated by the current charge amount variation SB, and the process returns to step 3 in FIG.
[0035]
In step 3 of FIG. 5 after the return, it is determined whether or not the estimated charge amount variation SB is equal to or greater than a predetermined value K. If the estimated charge amount variation SB is less than the predetermined value K, the process returns to step 1 to continue the normal charge amount control. On the other hand, when the estimated charge amount variation SB is equal to or greater than the predetermined value K, the process proceeds to step 4 and high charge amount control is performed. Specifically, the target charge state SOC of the battery 6 is set to an SOC slightly higher than the charge state SOC corresponding to at least the Zener voltage Vz, and the charge / discharge of the battery 6 is controlled to adjust the variation in the charge amount. .
[0036]
In step 5, it is determined whether or not the variation adjustment of the charge amount is completed. Among the cells of the battery 6, the cell disposed at the downstream end of the cooling air has the highest temperature and the highest self-discharge rate. Therefore, the cell at the downstream end of the cooling air has the least amount of charge. Therefore, the charge / discharge current of the battery 6 is integrated to determine the charge amount of the cell at the downstream end of the cooling air, and it is determined whether the charge amount of the cell at the downstream end of the cooling air has reached the target charge amount SOC. When the charge amount of the cell having the highest temperature at the downstream end of the cooling air reaches the target charge amount SOC, the charge amount variation adjustment is finished.
[0037]
If the variation adjustment of the charge amount of the cell parallel circuit is not completed, the process returns to step 4 and the high charge amount control is continued to adjust the variation of the charge amount. On the other hand, when the variation in the charge amount is completed, the process proceeds to step 6 to reset the current charge amount variation SB and the charge amount variation SBold at the previous calculation to 0, and return to step 1 to perform the above-described normal charge amount control. Execute.
[0038]
Thus, in one embodiment, in an apparatus for adjusting the charge amount of an assembled battery in which a plurality of cell parallel circuits in which a plurality of cells are connected in parallel are connected in series, the temperature of the cell is detected, and the cell temperature detection value Based on the above, the variation in the charge amount of the cell parallel circuit is estimated, and the charge amount adjustment is performed based on the estimation result. In a battery pack in which multiple sets of cell parallel circuits are connected in series, if a voltage sensor is provided for each cell parallel circuit as in the conventional charge adjustment device, the high voltage circuit on the battery pack side is insulated from the low voltage circuit on the voltage sensor side. Therefore, the signal circuit becomes complicated and expensive. According to this embodiment, it is not necessary to provide a voltage sensor in each cell parallel circuit, and the temperature sensor can be easily insulated from the assembled battery side high voltage circuit, so that the cost of the apparatus can be reduced. .
[0039]
Further, in this embodiment, a circuit in which a resistor and a Zener diode are connected in series, and a circuit that bypasses the charging current flowing in the cell parallel circuit is provided for each cell parallel circuit, and the estimation result of the charge amount variation When the battery voltage exceeds a predetermined value, the charging control of the assembled battery is performed so that the bypass circuit operates. This eliminates the need to control the switch element as in a conventional bypass circuit in which a switch element such as a transistor or FET and a resistor are connected in series, simplifying the control, and consuming unnecessary power. Therefore, the charge amount of the cell parallel circuit can be made uniform.
[0040]
Furthermore, in this embodiment, the temperature of the cell disposed at the upstream end of the cooling air and the cell disposed at the downstream end of the cooling air are detected, and the detected cell temperature at the upstream end of the cooling air and the downstream of the cooling air are detected. Since the variation in the charge amount of the cell parallel circuit is estimated based on the detected cell temperature at the end, it is used compared to installing temperature sensors in all cells and selecting the highest and lowest cell temperature The number of temperature sensors can be reduced and the cost of the apparatus can be further reduced.
[0041]
In this embodiment, the state of charge SOC of the assembled battery is detected, and the variation in the charge amount of the cell parallel circuit is estimated based on the cell temperature detection value and the SOC detection value. In a parallel hybrid vehicle, charge / discharge control is normally performed so that the SOC of the assembled battery is within a target range of 30 to 70%. Therefore, the variation in the charge amount of the cell parallel circuit is estimated based only on the detected cell temperature. However, a sufficient estimation result can be obtained. However, a more accurate estimation result can be obtained by estimating the variation in the charge amount of the cell parallel circuit based on the detected cell temperature value and the detected SOC value.
[0042]
The correspondence between the constituent elements of the claims and the constituent elements of the embodiment is as follows. That is, the temperature sensors T11 to T14, T21 to T24 constitute cell temperature detection means, and the vehicle controller 8 constitutes charge amount variation estimation means and control means. In addition, each component is not limited to the said structure, unless the characteristic function of this invention is impaired.
[0043]
In the above-described embodiment, an example of an assembled battery in which n sets of cell parallel circuits in which two cells are connected in parallel is connected in series has been described. However, the present invention is a set of this embodiment. It is not limited to batteries. The present invention can be applied to a battery pack in which a plurality of single cells are connected in series, or a battery pack in which a plurality of parallel circuits in which three or more cells are connected in parallel are connected in series. When the present invention is applied to an assembled battery in which a plurality of single cells are connected in series, the above-described cell parallel circuit of the embodiment may be replaced with a single cell.
[0044]
The invention of the present application is not particularly limited with respect to the type of cell (single cell). For example, the present invention can be applied to all types of cells such as manganese-based, cobalt-based, nickel-based lithium ion batteries, and various nickel-hydrogen batteries. The present invention can be applied to the present invention.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an embodiment.
FIG. 2 is a diagram showing details of a battery and a vehicle controller of the parallel hybrid vehicle according to the embodiment.
FIG. 3 is a diagram showing an internal structure of a battery.
FIG. 4 is a diagram showing the relationship between the temperature of the unit cell and the self-discharge rate with respect to the state of charge SOC.
FIG. 5 is a flowchart illustrating a charge amount adjustment program according to an embodiment.
FIG. 6 is a flowchart illustrating a charge amount variation calculation subroutine according to an embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 2 Motor 3 Transmission 4 Reducer 5a, 5b Drive wheel 6 Battery 7 Inverter 8 Vehicle controller 8a CPU
8b ROM
8c RAM
8c A / D converter 9 Main switch C11, C12, C21, C22, C31, C32, Cn1, Cn2 cell (single cell)
R1, R2, R3, Rn Resistors Z1, Z2, Z3, Zn Zener diode V1 Voltage sensors T11-T13, T21-T24 Temperature sensors

Claims

In an apparatus for adjusting the amount of charge of an assembled battery in which a plurality of single cells (hereinafter referred to as cells) are connected in series,
A circuit in which a resistor and a Zener diode are connected in series, and a circuit for bypassing a charging current flowing through the cell is provided for each cell.
Cell temperature detecting means for detecting the temperature of the cell;
A charge amount variation estimating means for estimating a variation in the charge amount of the cell based on the detected cell temperature;
Control means for performing charge amount adjustment according to the estimation result of the charge amount variation ,
When the estimation result of the charge amount variation exceeds a predetermined value, the control means sets the target charge amount of the assembled battery to a value slightly higher than the charge amount corresponding to the Zener voltage of the Zener diode, and A charge amount adjusting device that performs charge control of the assembled battery so that a charge amount of the battery becomes the target charge amount .

In the assembled battery charge amount adjusting device according to claim 1,
The cell temperature detection means detects the temperature of the cell disposed at the cooling wind upstream end of the assembled battery and the cell disposed at the cooling wind downstream end,
The charge amount variation estimating means estimates a variation in the charge amount of the cell based on a detected cell temperature value at the upstream end of the cooling air and a detected cell temperature value at the downstream end of the cooling air. Charge amount adjustment device.

In the assembled battery charge amount adjusting device according to claim 1 or 2,
Comprising a SOC detection means for detecting the assembled battery state of charge SOC (State Of Charge),
The charge amount adjustment device for an assembled battery, wherein the charge amount variation estimation unit estimates variation in the charge amount of the cell based on the cell temperature detection value and the SOC detection value .

In an apparatus for adjusting the amount of charge of an assembled battery in which a plurality of cell parallel circuits in which a plurality of cells are connected in parallel are connected in series,
A circuit in which a resistor and a Zener diode are connected in series, and a circuit that bypasses a charging current flowing through the cell parallel circuit is provided for each cell parallel circuit,
Cell temperature detecting means for detecting the temperature of the cell;
Charge amount variation estimation means for estimating variation in the charge amount of the cell parallel circuit based on the detected cell temperature;
Control means for performing charge amount adjustment according to the estimation result of the charge amount variation,
When the estimation result of the charge amount variation exceeds a predetermined value, the control means sets the target charge amount of the assembled battery to a value slightly higher than a charge amount corresponding to a Zener voltage of the Zener diode, and A charge amount adjusting apparatus that performs charge control of the assembled battery so that a charge amount of the battery becomes the target charge amount .

In the charge amount adjustment apparatus according to claim 4,
The cell temperature detection means detects the temperature of the cell disposed at the cooling wind upstream end of the assembled battery and the cell disposed at the cooling wind downstream end,
The charge amount variation estimating means estimates a variation in the charge amount of the cell parallel circuit based on a cell temperature detection value at the cooling air upstream end and a cell temperature detection value at the cooling air downstream end. Charge amount adjustment device for battery pack.

In the assembled battery charge amount adjustment device according to claim 4 or 5,
Comprising a SOC detection means for detecting the assembled battery state of charge SOC (State Of Charge),
The charge amount adjustment device for an assembled battery, wherein the charge amount variation estimation means estimates a variation in a charge amount of the cell parallel circuit based on the cell temperature detection value and the SOC detection value .