JP2004055220A

JP2004055220A - Separator of fuel cell

Info

Publication number: JP2004055220A
Application number: JP2002208394A
Authority: JP
Inventors: Katsuzo Konakawa; 粉川　勝蔵; Kazuhito Hado; 羽藤　一仁; Hiroki Kusakabe; 日下部　弘樹; Shinsuke Takeguchi; 竹口　伸介
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2002-07-17
Filing date: 2002-07-17
Publication date: 2004-02-19
Anticipated expiration: 2022-07-17
Also published as: JP4601893B2

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability of an electrolyte film and a gas-diffusion electrode as well as an electric conversion energy efficiency and a complete prevention of flooding, through prevention of reaction concentration at an entrance side flow channel groove part of a separator of a solid polymer electrolyte fuel cell. <P>SOLUTION: A flow channel groove 2 of the separator 1 consists of an entrance side flow channel groove part 13 located at an entrance side and an exit side flow channel groove part 14 located at an exit side, and is equipped with a bypass flow channel groove part 15 communicating from the entrance side flow channel groove part 13 to the exit side flow channel groove part 14. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、固体高分子電解質型燃料電池のセパレータに関する。
【０００２】
【従来の技術】
従来、この種の燃料電池は、イオン導電性が付与された固体高分子電解質膜の両面に触媒を担持したガス拡散電極を両面に重ね合わせて発電セルを構成している。そして、この発電セルは複数個を接続して所定の電圧を得る。このため、発電セル間にセパレータを介在させ発電セルを積層してスタック化する。そして、セパレータの両側にそれぞれ燃料ガス及び酸化ガスを供給してそれぞれのガス拡散電極に燃料ガス及び酸化ガスを供給すると、固体高分子膜でのイオン導電と各ガス拡散電極の電気化学反応が進行して一対のガス拡散電極間に電圧が発生し、集電電極の機能を持つ両端側の一対のセパレータを介して外部回路に給電する。この様な発電においては、供給ガスを出来るだけ均等にガス拡散電極の電極面に供給することがガス利用率を高め、発電効率と出力性能を良くする。
【０００３】
しかし、ガス拡散電極の全面に供給ガスが供給されるようにすると、セパレータとガス拡散電極との接触面積が無くなり、発生した電流の効率的な集電やガス拡散電極で発生する熱の除去が難しくなる。このため、セパレータとガス拡散電極の境界部分に、供給ガスの通流方向を規制する流路溝が設けられ、セパレータとガス拡散電極とをある割合に接触面積を保っている。セパレータ側に形成したこの流路溝部は、蛇行したサーペンタイン構成、あるいは複数本構成が特公昭５０−８７７７号公報、特開平７−２６３００３号公報等に記載されている。
そして、固体高分子電解質型燃料電池は、固体高分子電解質のイオン導電性を十分に発揮させて発電効率を高く維持するためには、供給するガスを加湿して供給ガス中の水蒸気濃度を高める必要があり、さらに、水素と酸素から水を生成する電気化学反応のエネルギーを電気量に変換するものであるため、カソード側において水が生成する。
【０００４】
このため、供給ガスの流路溝には、反応上生成される水が下流側、特に出口側に多量に含有し、気液二相状態となってガス流路溝を塞いでしまい（この現象をフラッディングという）終には、ガス流れが停止して発電を停止する。このフラッディングを防止する技術の従来例としては、特開平１０−１０６５９４号公報に記載されたものが知られている。図６は従来の固体高分子電解質型燃料電池の酸化ガスセパレータを示す。セパレータ１の溝部材２は、ガス拡散電極に対応した方形状でガス不透過性と導電性をして構成される。入口マニホールド３から酸化ガスが流入され、流路溝材２の溝を経た酸化ガスを出口マニホールド４より導出する。燃料ガスのセパレータ１も酸化ガスの入口マニホールド３および出口マニホールド４と互違いの位置に形成された入口マニホールド５及び出力マニホールド６より燃料ガスの流入と導出が行われる。流路溝材２の溝は、入口マニホールド３に直接に連通した入口側流路溝７Ａと、上記出口マニホールド４に直接に連通した出口側流路溝８Ｂと、上記入口側流路溝７Ａ及び出口側流路溝８Ｂとを連通した中間流路溝９とから構成されている。入口側流路溝７Ａと出口側流路溝８Ｂとは格子状に形成され、中間流路溝９は、複数回折返した曲折形態に形成され、複数本の直線状に延びる独立流路群９Ａ〜９Ｅと、折返し部に形成された格子状溝１０Ａ〜１０Ｄとから構成されている。すなわち、入口側流路溝７Ａと出口側流路溝８Ｂは、縦横に整列して形成された孤立突起ａ以外の領域がガス流路溝であり、独立流路群９Ａ〜９Ｅは長延突起ｂ以外の領域がガス流路溝である。また、折返し部の格子状溝１０Ａ〜１０Ｄは、孤立突起ｃ以外の領域がガス流路溝である。
【０００５】
反応生成水によるフラッディングにより供給ガスの停滞を防止するため、過去より種々のガス流路溝が工夫され、ガス流路が格子状となるタイプと、入口から出口まで１本の流路とするタイプがあるが、格子状タイプは、フラッディングに達するような水溜まりは生じないが、全体に均一となるガス拡散性能、一部が閉塞するなど排水性能に劣る。また、１本流路タイプは、拡散性が良いが、流れ抵抗が増えてガス供給装置側の元圧を高くする必要を生じ補機動力が増加してシステム効率が低下する。
【０００６】
そして、特開平１０−１０６５９４号公報に記載されたものは、供給ガスの入口側流路溝部及び出口側流路溝部が縦横に整列して形成された孤立突起ａ以外の領域がガス流路溝であり格子状をなすため、電極へのガスの接触面積が広くなると共に、ガスが自由に移動でき、時間的に速く電極と接触する。従って、入口側流路溝部では供給ガスと電極との接触効率（面積的に広く及び時間的に速く接触）が高く入口側におけるガス拡散性の損失を回避し得る。また、出口側流路溝部では、入口側と同様のガス拡散性の損失を回避し、かつ流路断面積が広くなるため排水性を確保してフラッディングを防止することができると記述してある。
【０００７】
【発明が解決しようとする課題】
しかしながらこの従来構成においては、入口側流路溝部ではガス拡散性を高め、この部分の反応を促進して全体の電気変換エネルギー効率を高めたため、入口側流路溝部での反応が集中し固体高分子電解質の膜やガス拡散電極の触媒層の劣化が進み耐久性に課題が残った。また、出口側流路溝部では、流路断面積が広くして排水性を確保してフラッディングを防止してあるが、流路断面積が広いためガスの流れが偏在し一様でなく、流速の遅い部分では生成水が流路溝の一部を閉塞した状態を発生し、この部分にはガスが供給できなく完全にフラッディングを防止できなかった。
【０００８】
本発明は、前記従来の課題を解決するもので、入り口から出口に至る反応量を均一化させて耐久信頼性の向上と全体の電気変換エネルギー効率を高め、かつフラッディングを防止して信頼性を高めた燃料電池のセパレータを提供することを目的とする。
【０００９】
【課題を解決するための手段】
前記従来の課題を解決するために、本発明の燃料電池のセパレータは、固体高分子電解質を挟持する一対のガス拡散電極と、前記ガス拡散電極のおのおのの面に燃料ガスと酸化ガスをそれぞれの入口側から出口側に導く流路溝を形成したセパレータより構成し、少なくとも一方の前記セパレータの前記流路溝は、前記入口側に位置する入口側流路溝部と前記出口側に位置する出口側流路溝部とからなり、前記入口側流路溝部から前記出口側流路溝部に連通するバイパス流路溝部を構成してある。
【００１０】
これによって、各々の入口側から入った燃料ガスおよび酸化ガスは、途中で水となり順次質量を減じながら出口側にいたる、そのため、入口側における燃料ガスおよび酸化ガスのガス量は、出口側に比較して大変多くなる。
【００１１】
前記入口側から前記出口側に連通するバイパス流路溝部を構成したことにより、入口側流路に入るガス量の一部は入口側流路部を通らずに直接出口側流路に流れる。そのため、流量の多い入口部でのガスの流速を小さく設計できるため拡散電極へのガス拡散を小さくでき、入口側部での過大な反応促進を低減できると共に、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部の流速が小さいため全体の損失抵抗を小さくすることが可能となる。
【００１２】
また、入口側と出口側の流速が近似でき電流密度の均一化と流れの損失抵抗の低減できる流路を構成できるものである。特に、負荷に合わせて、供給するガス流量を変化した場合も、この均一性が維持でき、耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００１３】
そして、出口側流路溝部では、ガスの流速を大きく設計できるため、内部で発生した生成水をガスの動圧により外部に排出できる。このため、流路が水により閉塞するフラッディングを防止することが可能となる。
【００１４】
【発明の実施の形態】
請求項１記載の発明は、固体高分子電解質を挟持する一対のガス拡散電極と、前記ガス拡散電極のおのおのの面に燃料ガスと酸化ガスをそれぞれの入口側から出口側に導く流路溝を形成したセパレータより構成し、少なくとも一方の前記セパレータの前記流路溝は、前記入口側に位置する入口側流路溝部と前記出口側に位置する出口側流路溝部とからなり、前記入口側流路溝部から前記出口側流路溝部に連通するバイパス流路溝部を構成してある。
【００１５】
これによって、前記入口側から前記出口側に連通するバイパス流路溝部を構成したことにより、入口側流路に入るガス量の一部は入口側流路部を通らずに直接出口側流路に流れる。そのため、流量の多い入口部でのガスの流速を小さく設計できるため拡散電極へのガス拡散を小さくでき、入口側部での過大な反応促進を低減できると共に、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部の流速が小さいため全体の損失抵抗を小さくすることが可能となる。
【００１６】
また、入口側と出口側の流速が近似でき電流密度の均一化と流れの損失抵抗の低減できる流路を構成できるものである。特に、負荷に合わせて、供給するガス流量を変化した場合も、この均一性が維持でき、耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００１７】
そして、出口側流路溝部では、ガスの流速を大きく設計できるため、内部で発生した生成水をガスの動圧により外部に排出できる。このため、流路が水により閉塞するフラッディングを防止することが可能となる。そして、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部の流速が小さいため全体の損失抵抗を小さくすることが可能となるため、送風機の動力も小さくて済み、補機の動力が低減できシステム全体の効率が向上できる。
【００１８】
請求項２記載の発明は、特に請求項１記載の燃料電池のセパレータに関し、供給ガスの出口側流路溝部の流路断面積は、入口側流路溝部とバイパス流路溝部の和の流路断面積よりも小さく構成してあるため、流量の少ない出口部でのガスの流速を大きく設計できるためガス拡散電極へのガス拡散を大きくでき、出口側部での反応促進を増大できる。このため、供給ガスの入口から出口に至る反応量を均一化させて各部分の電流密度を一定となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００１９】
請求項３記載の発明は、特に請求項１〜２の燃料電池のセパレータを入口側流路溝部の入口側から出口側流路溝部の入口側にバイパス流路溝部を連通して構成したことにより、流量の最も多い入口側流路溝部の入口側でのガスの流速を小さく設計しガス拡散電極へのガス拡散を小さくしながら、発電のためには必ず流す必要のある出口側流路溝部の入口側から全部のガスを流すことにより設計どおりの電気化学反応が可能となる。このため、電流密度を小さく均一となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００２０】
請求項４記載の発明は、特に請求項１〜３の燃料電池のセパレータを入口側流路溝部は少なくとも複数の流路で構成し、前記入口側流路溝部の少なくとも一部を合流後出口側流路溝部に連通したことにより、入口側流路溝部の流路パターンが同じでも、入口側流路溝部は出口側流路溝部に対して単位流路当りのガス拡散電極の面積を大幅に増加できるため、電流密度を小さく均一となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができ、流路の設計自由度が向上し、加工も容易で安価となる。
【００２１】
請求項５記載の発明は、特に請求項４の燃料電池のセパレータを入口側流路溝部の合流箇所を複数としたことにより、電流密度と電気化学反応により減少するガス流れの損失抵抗の分布に応じで最適な流路を構成できるものである。
【００２２】
請求項６記載の発明は、特に請求項１〜５の燃料電池のセパレータを少なくとも一部のバイパス流路部をガス拡散電極と隔離して構成したことにより、このバイパス流路部では、反応を生じることがなく、入口流路部と出口流路部で全ての反応を行う。このため、バイパス流路部の冷却や電流密度を考慮する必要がなく、電流密度を小さく均一となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができ、流路の設計自由度が向上し、加工も容易で安価となる。
【００２３】
請求項７記載の発明は、特に請求項１〜６の燃料電池のセパレータを入口側流路溝部の流路断面積を出口側流路溝部の流路断面積よりも大きく構成してある。
【００２４】
これによって、供給ガスの流量の多い入口側流路溝部でのガスの流速をより小さく設計できるため拡散電極へのガス拡散をさらに小さくでき、過大な反応促進を低減できると共に、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部の流速が小さいため全体の損失抵抗を小さくすることが可能となる。また、供給ガスの出口側流路溝部の流路断面積入口側流路溝部の流路断面積よりも小さく構成してあるため、流量の少ない出口部でのガスの流速をさらに大きく設計できるため拡散電極へのガス拡散を大きくでき、出口側部での反応促進を増大できる。このため、供給ガスの入口から出口に至る反応量をさらに均一化させて各部分の電流密度が一定となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００２５】
さらに、出口側流路溝部では、ガスの流速をさらに大きく設計できるため、内部で発生した生成水をガスの動圧により外部に排出できる。このため、流路が水により閉塞するフラッディングを防止することが可能となる。そして、供給ガス流量全体の損失抵抗を小さくすることが可能となるため、送風機の動力も小さくて済み、補機の動力が低減できシステム全体の効率が向上できる。
【００２６】
請求項８記載の発明は、特に請求項７の燃料電池のセパレータを入口側流路溝部の溝幅を出口側流路溝部の溝幅より大きく構成して、前記入口側流路溝部の流路断面積は前記出口側流路溝部の流路断面積よりも大きくしたことにより、流量の多い入口部でのガスの流速を小さく設計し拡散電極へのガス拡散を小さくしながら、かつ、流路幅を拡大して広い拡散電極で反応することが可能となる。このため、電流密度を小さく均一となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。また、セパレータはカーボン、または金属の薄板をプレス、射出成型等によりセパレータの一部の流路溝幅を大きく加工することは容易である。
【００２７】
請求項９記載の発明は、特に請求項７の燃料電池のセパレータを入口側流路溝部の溝深さを出口側流路溝部の溝深さより大きく構成して、前記入口側流路溝部の流路断面積は前記出口側流路溝部の流路断面積よりも大きくし、流路を大幅に大きくすることが可能であり、流量の多い入口部でのガスの流速を小さく設計し拡散電極へのガス拡散を小さくしながら、かつ、流路に対抗して主に反応する拡散電極面積を供給ガスの入口から出口に至るまで均一な面積とでき、各部分の電流密度を一定とし耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。また、セパレータはカーボン、または金属の薄板をプレス、射出成型等によりセパレータの一部の流路溝深さを大きく加工することは容易である。
【００２８】
請求項１０記載の発明は、特に請求項７〜９の燃料電池のセパレータを入口側流路溝部または出口側流路溝部の少なくとも一方の流路断面積を順次小さく構成したことにより、反応により減少するガス流量に応じて流路断面積を順次小さくして、流量の多い入口部から流量の最も少ない出口部まで、ガスの流速を一定に設計できる。このため、供給ガスの入口から出口に至る反応量を均一化させて各部分の電流密度を一定とし耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００２９】
また、流路内を流れるガスは２Ｈ_２＋Ｏ_２→２Ｈ_２Ｏの反応によりガス流量は、順次減少する。流路断面積を順次小さく構成したことにより、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部の流速が小さいため全体の損失抵抗を小さくすることが可能となる。そして、出口側流路溝部では、ガスの流速を大きく設計できるため、内部で発生した生成水をガスの動圧により外部に排出できるため、流路が水により閉塞するフラッディングを防止することができ、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部の流速が小さいため全体の損失抵抗を小さくすることが可能となるため、送風機の動力も小さくて済み、補機の動力が低減できシステム全体の効率が向上できる。
【００３０】
（実施例１）
図１は、本発明の第１の実施例における燃料電池のセパレータの全体構成図、図２は燃料電池全体の断面図を示す。図２において、固体高分子型の燃料電池は、イオン伝導性が付与された固体高分子電解質の膜１１の両面に触媒を担持したガス拡散電極１２を両面に重ね合わせて発電セルを構成している。そして、この発電セルは複数個を接続して所定の電圧を得る。このため、発電セル間にセパレータ１を介在させ発電セルを積層してスタック化する。そして、セパレータの両側にそれぞれ燃料ガス及び酸化ガスを供給してそれぞれのガス拡散電極１２に燃料ガス及び酸化ガスを供給すると、固体高分子膜１１でのイオン導電と各ガス拡散電極の電気化学反応が進行して一対のガス拡散電極１２間に電圧が発生し、集電電極の機能を持つ両端側の一対のセパレータ１を介して外部回路（図示せず）に給電する。この様な発電においては、供給ガスを出来るだけ均等にガス拡散電極１２の電極面に供給することがガス利用率を高め、発電効率と出力性能を良くする。
【００３１】
図１に示すセパレータ１は、セパレータ１の流路溝２は、ガス拡散電極１２に対応した形状としガス不透過性と導電性有するカーボン、表面処理をした金属を用いて構成する。入口マニホールド３から燃料または酸化ガスが流入され、流路溝２の溝を経た前記ガスを出口マニホールド４より流出する。他方酸化ガスまたは燃料ガスのセパレータ１はこのセパレータ１の背面側に同様の流れる構成を設け入口マニホールド５及び出力マニホールド６よりガスの流入と導出が行われる。これにより、固体高分子電解質の膜１１を挟持する一対のガス拡散電極１２のおのおのの面に燃料ガスと酸化ガスをそれぞれの入口側から出口側に導く流路溝２を形成したセパレータ１を構成している。
【００３２】
そして、流路溝材２の溝は、入口側の入口マニホールド３に直接に連通した入口側流路溝部１３と出口マニホールド４に直接に連通した出口側流路溝部１４と、入口側流路溝部１３から出口側流路溝部１４に連通するバイパス流路溝部１５を構成してある。入口側流路溝部１３は、複数の溝で構成し入口マニホールド３に直接に連通し蛇行しなからバイパス流路溝部１５との合流部１６に至る。出口側流路溝部１４も、複数の溝で構成し合流部１６に連通し蛇行しなから出口マニホールド４に至る。バイパス流路溝部１５は、複数の溝で構成し入口マニホールド３に直接に連通し出口側流路溝部１４との合流部１６に至る。
【００３３】
以上のように構成された燃料電池のセパレータについて、以下その動作、作用を説明する。
【００３４】
まず、入口マニホールド３から入口側流路溝部１３に入った燃料ガスおよび酸化ガスは、途中の入口側流路溝部１３と出口側流路溝部１４を流れる時、ガス拡散電極に拡散して電気化学反応を行い、燃料ガスは消費され、酸化ガスは水となり順次質量を減じながら出口側流路溝部１４に至り排出される。そのため、入口側における燃料ガスおよび酸化ガスのガス量は、出口側に比較して大変多くなる。
【００３５】
入口マニホールド３から入るガス量の一部は入口側流路部１３を流れ、残りのガスは入口側流路部１３を通らずにバイパス流路溝部１５を通って合流部１６に流れ、この合流部１６で入口側流路部１３を流れたガスとバイパス流路溝部１５を流れたガスが合流し、出口側流路溝部１４から出口マニホールド４に至り排出する。このため、流量の多い入口部の入口側流路部１３でのガスの流速を小さく設計できる。ガスのガス拡散電極１２へのガス拡散はガスの流速が早くなると増加する。このため、ガス拡散電極１２へのガス拡散を小さくでき、入口側の入口側流路部１３での過大な反応促進を低減できると共に、供給ガス流量が最も多く流れ抵抗が大きい入口側流路溝部１３の流速が小さいため全体の損失抵抗を小さくすることが可能となる。また、供給ガスの出口側流路溝部１４の流路断面積は、入口側流路溝部１３とバイパス流路溝部１５の和の流路断面積よりも小さく構成できるため、（最適値は０．５〜０．７）流量の少ない出口部の出口側流路溝部１４でのガスの流速を入口側と同じほど大きく設計できるためガス拡散電極１２へのガス拡散を大きくでき、出口側の出口側流路溝部１４での電気化学反応促進を増大できる。このため、供給ガスの入口から出口に至る電気化学反応量を均一化させて各部分の電流密度を一定となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００３６】
また、発電する電気量は、実使用実態に合わせて増減コントロールする必要がある。そのため、負荷に応じて燃料ガスおよび酸化ガスのガス量を増減して調整する必要がある。入口側の入口側流路溝部１３と出口側の出口側流路溝部１４の流速が近似でき電流密度の均一化と流れの損失抵抗の低減できる流路を構成できるものであり、特に、負荷に合わせて供給するガス流量を変化した場合も、この均一性は維持できるため、耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００３７】
そして、出口側流路溝部１４では、ガスの流速を大きく設計できるため、内部で発生した生成水をガスの動圧により外部に排出できる。このため、流路が水により閉塞するフラッディングを防止することが可能となり、良好な運転範囲が拡大し安定性が向上する。
【００３８】
そして、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部の流速が小さいため全体の損失抵抗を小さくすることが可能となるため、送風機の動力も小さくて済み、補機の動力が低減できシステム全体の効率が向上できる。
【００３９】
また、セパレータ１を入口側流路溝部１３の入口側である入口マニホールド３から出口側流路溝部１４の入口側である合流部１６にバイパス流路溝部１５をそれぞれ連通して構成したことにより、流量の最も多い入口側流路溝部１３の入口側でのガスの流速を最も小さく設計しガス拡散電極１２へのガス拡散を小さくしながら、発電のためには必ず流す必要のある出口側流路溝部１４の入口側から全部のガスが流すことができ設計どおりの電気化学反応が可能となる。このため、電流密度を小さく均一となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。
【００４０】
（実施例２）
図３は、本発明の第２の実施例における燃料電池のセパレータの全体構成を示す。実施例１と異なるところは、セパレータ１を入口側流路溝部１３は６流路１３ａ〜ｆの複数で構成し、入口側流路溝部１３の流路１３ａ〜ｆを合流部１６ａ１６ｂ１６ｃでおのおの合流して後、出口側流路溝部１４の流路１４ａ〜ｃに連通してある。このことにより、入口側流路溝部１３の流路パターンが同じでも、入口側流路溝部１３は出口側流路溝部１４に対して単位流路当りのガス拡散電極の面積を大幅に増加できる。このため、電流密度を小さく均一となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができ、流路の設計自由度が向上し、加工も容易で安価となる。また、電気変換エネルギー効率が高いことは、セパレータを小さくできコンパクト化が可能となる。
【００４１】
（実施例３）
図４は、本発明の第３の実施例における燃料電池のセパレータの全体構成を示す。実施例２と異なるところは、燃料電池のセパレータ１を入口側流路溝部１３の合流箇所を１６ｄ、１６ｅの２箇所と複数に構成してある。入口側流路溝部１３、出口側流路溝部１４のそれぞれの出口側のガス量は電気化学反応により入口側減少する。そのため、合流箇所１６ｄ、１６ｅを複数として、順次流速を調整したことにより、電流密度と電気化学反応により減少するガス流れの損失抵抗の分布に応じで最適な流路を構成できるものである。合流箇所は数を増やすほど性能は向上する。
【００４２】
（実施例４）
図５は、本発明の第４の実施例における燃料電池のセパレータの全体構成を示す。実施例１と異なるところは、燃料電池のセパレータ１のバイパス流路部１５を流れる燃料ガスまたは酸化ガスを拡散させるガス拡散電極１２と離し隔離して構成してある。具体的には、ガス拡散電極１２は、入口側流路溝部１３、出口側流路溝部１４と、合流箇所１５である流路部２に対向して構成し、、バイパス流路部１５はパッキン部材１７で片面を閉塞してある。このため、バイパス流路部１５では、ガス拡散せず電気化学反応を生じることがない。そのため、バイパス流路部１５の冷却や電流密度分布の均一化を考慮する必要がなく、電流密度を小さく均一となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができ、流路の設計自由度が向上し、加工も容易で安価となる。
【００４３】
また、セパレータ１のガスが流れる溝形状の断面積を順次小さくしてフラッディングを防止する方法は、特許第３２７２９８０号公報や特開平６−２６７５６４号公報に記載があるが、本発明の構成を加えることにより、電流密度の均一化とフラッディング抑制に対して効果がある。実施例１〜４において、セパレータ１を入口側流路溝部１３の流路断面積を出口側流路溝部１４の流路断面積よりも大きく構成することによって、供給ガスの流量の多い入口側流路溝部１３でのガスの流速をより小さく設計できるためガス拡散電極１２へのガス拡散をさらに小さくでき、過大な反応促進を低減できると共に、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部１３の流速が小さいため全体の損失抵抗を小さくすることが可能となる。また、供給ガスの出口側流路溝部１４の流路断面積を入口側流路溝部の流路断面積よりも小さく構成してあるため、流量の少ない出口部でのガスの流速をさらに大きく設計できるためガス拡散電極１２へのガス拡散を大きくでき、出口側部での反応促進を増大できる。このため、供給ガスの入口から出口に至る反応量をさらに均一化させて各部分の電流密度を一定となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。そして、出口側流路溝部１４では、ガスの流速をさらに大きく設計できるため、内部で発生した生成水をガスの動圧により外部に排出できる。このため、流路が水により閉塞するフラッディングを防止することが可能となる。そして、供給ガス流量全体の損失抵抗を小さくすることが可能となるため、送風機の動力も小さくて済み、補機の動力が低減できシステム全体の効率が向上できる。
【００４４】
さらに、セパレータ１を入口側流路溝部１３は出口側流路溝部１４より溝幅を大きく構成して、入口側流路溝部１３の流路断面積は出口側流路溝部１４の流路断面積よりも大きくしたことにより、流量の多い入口部でのガスの流速を小さく設計しガス拡散電極１２へのガス拡散を小さくしながら、かつ、流路幅を拡大して広い拡散電極で反応することが可能となる。このため、電流密度を小さく均一となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。また、セパレータ１はカーボン、または金属の薄板をプレス、射出成型等によりセパレータの一部の流路溝幅を大きく加工することは容易である。
【００４５】
また、セパレータ１を入口側流路溝部１３は出口側流路溝部１４の溝深さを大きく構成して、入口側流路溝部１３の流路断面積は出口側流路溝部１４の流路断面積よりも大きくし、流路を大幅に大きくすることが可能であり、流量の多い入口部でのガスの流速を小さく設計しガス拡散電極１２へのガス拡散を小さくしながら、かつ、流路に対抗して主に反応する拡散電極面積を供給ガスの入口から出口に至るまで均一な面積とでき、各部分の電流密度を一定とし耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。また、セパレータはカーボン、または金属の薄板をプレス、射出成型等によりセパレータの一部の流路溝深さを大きく加工することは容易である。
【００４６】
そして、セパレータ１を入口側流路溝部１３または出口側流路溝部１４の少なくとも一方の流路断面積を順次小さく構成したことにより、反応により減少するガス流量に応じて流路断面積を順次小さくして、流量の多い入口部から流量の最も少ない出口部まで、ガスの流速を一定に設計できる。このため、供給ガスの入口から出口に至る反応量を均一化させて各部分の電流密度を一定となり耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。そして、流路内を流れるガスは２Ｈ_２＋Ｏ_２→２Ｈ_２Ｏの反応によりガス流量は、順次減少する。流路断面積を順次小さく構成したことにより、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部１３の流速が小さいことにより全体の損失抵抗を小さくすることが可能となる。そして、出口側流路溝部１４では、ガスの流速を大きく設計できるため、内部で発生した生成水をガスの動圧により外部に排出できるため、流路が水により閉塞するフラッディングを防止することができ、供給ガス流量が最も多く流れ抵抗が大きい入口側流路部１３の流速が小さいため全体の損失抵抗を小さくすることが可能となるため、送風機の動力も小さくて済み、補機の動力が低減できシステム全体の効率が向上できる。
【００４７】
【発明の効果】
以上のように本発明によれば、流量の多い入口側部での過大な反応促進を低減できると共に、全体の損失抵抗を小さくすることが可能となる。また、流量の少ない出口部でのガスの流速を大きく設計できるため反応促進を増大でき、反応量を均一化させて電流密度を一定とし耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。そして、負荷に合わせてこの均一性が維持でき、耐久信頼性の向上と全体の電気変換エネルギー効率を高めることができる。また、出口側流路溝部では、ガスの流速を大きく設計できるため、内部で発生した生成水をガスの動圧により外部に排出できる。このため、流路が水により閉塞するフラッディングを防止することが可能となる。
【図面の簡単な説明】
【図１】本発明の第１の実施例における燃料電池のセパレータを示す全体構成図
【図２】本発明の第１の実施例における燃料電池全体の断面図
【図３】本発明の第２の実施例における燃料電池のセパレータを示す全体構成図
【図４】本発明の第３の実施例における燃料電池のセパレータを示す全体構成図
【図５】本発明の第４の実施例における燃料電池のセパレータを示す全体構成図
【図６】従来の燃料電池のセパレータを示す全体構成図
【符号の説明】
１　セパレータ
２　流路溝
３　入口マニホールド
４　出口マニホールド
１３　入口側流路溝部
１４　出口側流路溝部
１５　バスパス流路溝部
１６　合流部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a separator for a polymer electrolyte fuel cell.
[0002]
[Prior art]
Conventionally, this type of fuel cell has a power generation cell in which a gas diffusion electrode carrying a catalyst on both surfaces of a solid polymer electrolyte membrane provided with ionic conductivity is superposed on both surfaces. Then, a plurality of the power generation cells are connected to obtain a predetermined voltage. For this reason, a separator is interposed between the power generation cells, and the power generation cells are stacked and stacked. When the fuel gas and the oxidizing gas are supplied to both sides of the separator and the fuel gas and the oxidizing gas are supplied to the respective gas diffusion electrodes, the ionic conduction in the solid polymer membrane and the electrochemical reaction of each gas diffusion electrode progress. As a result, a voltage is generated between the pair of gas diffusion electrodes, and power is supplied to an external circuit via a pair of separators at both ends having a function of a current collecting electrode. In such power generation, supplying the supplied gas to the electrode surface of the gas diffusion electrode as evenly as possible increases the gas utilization rate and improves power generation efficiency and output performance.
[0003]
However, if the supply gas is supplied to the entire surface of the gas diffusion electrode, the contact area between the separator and the gas diffusion electrode is lost, so that the current generated efficiently and the heat generated in the gas diffusion electrode are removed. It becomes difficult. For this reason, a flow channel for regulating the flow direction of the supply gas is provided at the boundary between the separator and the gas diffusion electrode, and the contact area between the separator and the gas diffusion electrode is maintained at a certain ratio. The channel groove formed on the separator side has a meandering serpentine configuration or a plurality of this configuration described in Japanese Patent Publication No. 50-8777, Japanese Patent Application Laid-Open No. 7-263003, and the like.
In order to maintain the high power generation efficiency by sufficiently exhibiting the ionic conductivity of the solid polymer electrolyte, the solid polymer electrolyte fuel cell increases the water vapor concentration in the supplied gas by humidifying the supplied gas. It is necessary to convert the energy of an electrochemical reaction for generating water from hydrogen and oxygen into an electric quantity, so that water is generated on the cathode side.
[0004]
For this reason, a large amount of water generated during the reaction is contained in the flow path groove of the supply gas on the downstream side, particularly on the outlet side, and a gas-liquid two-phase state is formed to block the gas flow path groove (this phenomenon). At the end, the gas flow stops and power generation stops. As a conventional example of the technique for preventing the flooding, a technique disclosed in Japanese Patent Application Laid-Open No. 10-106594 is known. FIG. 6 shows an oxidizing gas separator of a conventional solid polymer electrolyte fuel cell. The groove member 2 of the separator 1 has a rectangular shape corresponding to the gas diffusion electrode and has gas impermeability and conductivity. The oxidizing gas flows from the inlet manifold 3, and the oxidizing gas having passed through the groove of the flow channel member 2 is led out from the outlet manifold 4. The fuel gas separator 1 also flows in and out of the fuel gas from an inlet manifold 5 and an output manifold 6 formed at positions different from the oxidizing gas inlet manifold 3 and the outlet manifold 4. The grooves of the flow channel material 2 include an inlet flow channel 7A that directly communicates with the inlet manifold 3, an outlet flow groove 8B that directly communicates with the outlet manifold 4, an inlet flow channel 7A, And an intermediate flow channel 9 communicating with the outlet flow channel 8B. The inlet-side channel groove 7A and the outlet-side channel groove 8B are formed in a lattice shape, and the intermediate channel groove 9 is formed in a bent shape obtained by turning a plurality of times, and a plurality of linear channels 9A extending linearly. To 9E, and lattice-shaped grooves 10A to 10D formed in the folded portion. That is, the inlet-side flow grooves 7A and the outlet-side flow grooves 8B are gas flow grooves in areas other than the isolated protrusions a formed in a matrix, and the independent flow path groups 9A to 9E are elongated protrusions b. The other area is the gas channel groove. In addition, in the lattice-shaped grooves 10A to 10D of the folded portions, regions other than the isolated protrusions c are gas flow grooves.
[0005]
Various gas flow grooves have been devised from the past to prevent stagnation of the supply gas due to flooding with the reaction product water, and the gas flow path has a lattice shape, and the gas flow path has a single flow path from the inlet to the outlet. However, the grid type does not cause water pools to reach flooding, but is inferior in gas diffusion performance that is uniform throughout and drainage performance such as partial blockage. In addition, the single flow channel type has good diffusivity, but increases the flow resistance, which necessitates a higher original pressure on the gas supply device side, increases the power of auxiliary equipment, and lowers the system efficiency.
[0006]
Japanese Unexamined Patent Publication No. 10-106594 discloses that a region other than an isolated projection a in which an inlet-side flow channel portion and an outlet-side flow channel portion of a supply gas are arranged vertically and horizontally is a gas flow channel. Therefore, since the contact area of the gas with the electrode is increased, the gas can move freely, and the electrode is quickly contacted with the electrode. Therefore, the contact efficiency between the supply gas and the electrode (the contact area is large and the contact time is fast) is high in the inlet-side channel groove, and loss of gas diffusibility on the inlet side can be avoided. In addition, it is described that in the outlet-side channel groove portion, the same loss of gas diffusivity as in the inlet side can be avoided, and since the cross-sectional area of the channel becomes wider, drainage can be secured and flooding can be prevented. .
[0007]
[Problems to be solved by the invention]
However, in this conventional configuration, gas diffusion is enhanced in the inlet-side channel groove, and the reaction in this portion is promoted to increase the overall electric conversion energy efficiency. Deterioration of the molecular electrolyte membrane and the catalyst layer of the gas diffusion electrode progressed, and there was a problem in durability. In addition, in the outlet-side channel groove, flooding is prevented by widening the channel cross-sectional area to ensure drainage.However, since the flow channel cross-sectional area is large, the gas flow is unevenly distributed, and the flow velocity is not uniform. In the slow part, the generated water blocked a part of the channel groove, and gas could not be supplied to this part, so that flooding could not be completely prevented.
[0008]
The present invention solves the above-mentioned conventional problems, in which the reaction amount from the entrance to the exit is made uniform, thereby improving the durability reliability and the overall electric conversion energy efficiency, and preventing flooding to improve the reliability. It is an object to provide an enhanced fuel cell separator.
[0009]
[Means for Solving the Problems]
In order to solve the conventional problem, the fuel cell separator of the present invention includes a pair of gas diffusion electrodes sandwiching a solid polymer electrolyte, and a fuel gas and an oxidizing gas on each surface of the gas diffusion electrodes. The separator is formed with a flow path groove leading from the inlet side to the outlet side, and the flow path groove of at least one of the separators is an inlet side flow groove portion located on the inlet side and an outlet side located on the outlet side. And a bypass channel groove communicating with the outlet-side channel groove from the inlet-side channel groove.
[0010]
As a result, the fuel gas and oxidizing gas entering from each inlet side turn into water on the way and gradually decrease in mass and reach the outlet side. Therefore, the amounts of the fuel gas and the oxidizing gas at the inlet side are compared with those at the outlet side. And very much.
[0011]
By forming the bypass flow passage groove portion communicating from the inlet side to the outlet side, a part of the gas amount entering the inlet flow passage flows directly to the outlet flow passage without passing through the inlet flow passage portion. Therefore, the gas flow rate at the inlet part where the flow rate is high can be designed to be small, so that the gas diffusion to the diffusion electrode can be reduced, and excessive reaction promotion at the inlet side part can be reduced. Since the flow velocity in the large inlet-side flow path is small, the overall loss resistance can be reduced.
[0012]
In addition, the flow paths on the inlet side and the outlet side can be approximated, and a flow path can be formed that can make the current density uniform and reduce the flow loss resistance. In particular, even when the supplied gas flow rate is changed in accordance with the load, this uniformity can be maintained, and the durability reliability can be improved and the overall electric conversion energy efficiency can be increased.
[0013]
In the outlet-side channel groove, the gas flow rate can be designed to be large, so that the generated water generated inside can be discharged to the outside by the dynamic pressure of the gas. For this reason, it is possible to prevent flooding in which the flow path is blocked by water.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
The invention according to claim 1 is characterized in that a pair of gas diffusion electrodes sandwiching the solid polymer electrolyte, and a flow channel for guiding the fuel gas and the oxidizing gas from the respective inlet sides to the respective outlet sides on the respective surfaces of the gas diffusion electrodes. The flow channel of at least one of the separators includes an inlet flow channel groove located on the inlet side and an outlet flow channel groove located on the outlet side. A bypass passage groove is formed to communicate from the passage groove to the outlet-side passage groove.
[0015]
With this, by configuring the bypass channel groove portion communicating from the inlet side to the outlet side, a part of the gas amount entering the inlet side channel directly passes through the inlet side channel portion to the outlet side channel portion without passing through the inlet side channel portion. Flows. Therefore, the gas flow rate at the inlet part where the flow rate is high can be designed to be small, so that the gas diffusion to the diffusion electrode can be reduced, and excessive reaction promotion at the inlet side part can be reduced. Since the flow velocity in the large inlet-side flow path is small, the overall loss resistance can be reduced.
[0016]
In addition, the flow paths on the inlet side and the outlet side can be approximated, and a flow path can be formed that can make the current density uniform and reduce the flow loss resistance. In particular, even when the supplied gas flow rate is changed in accordance with the load, this uniformity can be maintained, and the durability reliability can be improved and the overall electric conversion energy efficiency can be increased.
[0017]
In the outlet-side channel groove, the gas flow rate can be designed to be large, so that the generated water generated inside can be discharged to the outside by the dynamic pressure of the gas. For this reason, it is possible to prevent flooding in which the flow path is blocked by water. In addition, the flow rate of the inlet-side flow passage section where the flow rate of the supply gas is the largest and the flow resistance is large is small, so that the overall loss resistance can be reduced. Therefore, the power of the blower can be reduced and the power of the auxiliary equipment can be reduced. The efficiency of the entire system can be improved.
[0018]
The second aspect of the present invention relates to the fuel cell separator of the first aspect, wherein the flow path cross-sectional area of the supply gas outlet side flow path groove is a sum of the inlet side flow path groove section and the bypass flow path groove section. Since it is configured to be smaller than the cross-sectional area, it is possible to design the flow velocity of the gas at the outlet part where the flow rate is small, so that the gas diffusion to the gas diffusion electrode can be increased and the reaction promotion at the outlet side part can be increased. For this reason, the reaction amount from the inlet to the outlet of the supply gas is made uniform, the current density of each part becomes constant, and the durability reliability and the overall electric conversion energy efficiency can be improved.
[0019]
The invention according to claim 3 is that the separator of the fuel cell according to claim 1 or 2 is configured such that the bypass flow channel communicates from the inlet side of the inlet flow channel to the inlet side of the outlet flow channel. The gas flow rate on the inlet side of the inlet-side channel groove with the highest flow rate is designed to be small, and gas diffusion to the gas diffusion electrode is reduced. By flowing all the gas from the inlet side, an electrochemical reaction as designed becomes possible. For this reason, the current density is small and uniform, so that the durability reliability can be improved and the overall electric conversion energy efficiency can be increased.
[0020]
The invention according to claim 4 is a fuel cell separator according to claims 1 to 3, wherein the inlet-side channel groove is formed of at least a plurality of channels, and at least a part of the inlet-side channel groove is merged with the outlet side. Due to the communication with the flow channel, the flow channel pattern of the inlet flow channel is the same, but the inlet flow channel greatly increases the area of the gas diffusion electrode per unit flow channel compared to the outlet flow channel. As a result, the current density can be made small and uniform, the durability reliability can be improved and the overall electric conversion energy efficiency can be increased, the degree of freedom in designing the flow path can be improved, and the processing is easy and inexpensive.
[0021]
The invention according to claim 5 is particularly advantageous in that the fuel cell separator according to claim 4 has a plurality of converging points in the inlet-side flow channel portion, thereby reducing the current density and the loss resistance of the gas flow reduced by the electrochemical reaction. An optimal flow path can be configured according to the conditions.
[0022]
In the invention according to claim 6, the separator of the fuel cell according to any of claims 1 to 5 is configured so that at least a part of the bypass passage is separated from the gas diffusion electrode. All reactions take place in the inlet channel and the outlet channel without any occurrence. For this reason, there is no need to consider the cooling and current density of the bypass flow path portion, the current density is small and uniform, the durability reliability can be improved, and the overall electric conversion energy efficiency can be increased. It is easy to process and inexpensive.
[0023]
In the invention according to claim 7, the separator of the fuel cell according to any one of claims 1 to 6 is configured such that the cross-sectional area of the inlet-side flow groove is larger than the cross-sectional area of the outlet-side flow groove.
[0024]
As a result, the gas flow rate at the inlet-side channel groove portion where the flow rate of the supply gas is large can be designed to be smaller, so that the gas diffusion to the diffusion electrode can be further reduced, and excessive reaction promotion can be reduced. Since the flow velocity in the inlet-side flow passage portion having a large flow resistance is small, the overall loss resistance can be reduced. Also, since the cross-sectional area of the supply gas outlet-side channel groove is configured to be smaller than the flow-path cross-sectional area of the inlet-side channel groove, the gas flow rate at the outlet with a smaller flow rate can be designed to be even larger. The gas diffusion to the diffusion electrode can be increased, and the promotion of the reaction at the outlet side can be increased. For this reason, the reaction amount from the inlet to the outlet of the supply gas is made more uniform, the current density of each part becomes constant, the durability reliability can be improved, and the overall electric conversion energy efficiency can be increased.
[0025]
Furthermore, in the outlet-side channel groove, the flow velocity of the gas can be designed to be further increased, so that the generated water generated inside can be discharged to the outside by the dynamic pressure of the gas. For this reason, it is possible to prevent flooding in which the flow path is blocked by water. Since the loss resistance of the entire supply gas flow rate can be reduced, the power of the blower can be reduced, the power of the auxiliary equipment can be reduced, and the efficiency of the entire system can be improved.
[0026]
The invention according to claim 8 is that the fuel cell separator according to claim 7 is configured such that the width of the inlet-side flow groove is larger than the width of the outlet-side flow groove, and the flow path of the inlet-side flow groove is formed. The cross-sectional area is made larger than the cross-sectional area of the outlet-side channel groove, so that the gas flow rate at the inlet portion with a large flow rate is designed to be small to reduce gas diffusion to the diffusion electrode, and The width can be increased and the reaction can be performed with a wide diffusion electrode. For this reason, the current density is small and uniform, so that the durability reliability can be improved and the overall electric conversion energy efficiency can be increased. In addition, it is easy to press a thin plate made of carbon or metal by press molding, injection molding, or the like to increase the width of a part of the flow channel groove of the separator.
[0027]
According to a ninth aspect of the present invention, in particular, the fuel cell separator of the seventh aspect is configured such that the depth of the inlet-side flow groove is larger than the depth of the outlet-side flow groove, and the flow rate of the inlet-side flow groove is increased. The cross-sectional area of the passage is larger than the cross-sectional area of the outlet-side channel groove, and the flow path can be significantly increased. The diffusion electrode area that reacts mainly against the flow path can be made uniform from the inlet to the outlet of the supply gas while reducing the gas diffusion of the gas, and the current density of each part is constant and the durability is high. And the overall electric conversion energy efficiency can be increased. Further, it is easy to increase the depth of the channel groove of a part of the separator by pressing, injection molding, or the like a thin plate made of carbon or metal.
[0028]
The invention according to claim 10 is particularly advantageous in that the separator of the fuel cell according to claims 7 to 9 is configured so that at least one of the inlet-side channel groove and the outlet-side channel groove is configured to have a smaller cross-sectional area, thereby reducing the reaction. The cross-sectional area of the flow passage is gradually reduced in accordance with the gas flow rate, and the gas flow rate can be designed to be constant from the inlet with the highest flow rate to the outlet with the lowest flow rate. For this reason, the reaction amount from the inlet to the outlet of the supply gas can be made uniform, the current density of each part can be made constant, the durability reliability can be improved, and the overall electric conversion energy efficiency can be increased.
[0029]
The gas flowing in the flow path is 2H ₂ + O ₂ → 2H ₂ Due to the reaction of O, the gas flow rate gradually decreases. By sequentially reducing the cross-sectional area of the flow path, the flow loss in the inlet-side flow path section having the largest supply gas flow rate and the highest flow resistance is small, so that the overall loss resistance can be reduced. In the outlet-side channel groove, the flow velocity of the gas can be designed to be large, so that the generated water generated inside can be discharged to the outside by the dynamic pressure of the gas, so that flooding in which the channel is blocked by water can be prevented. Since the flow rate at the inlet side flow passage section where the supply gas flow rate is the largest and the flow resistance is large is small, it is possible to reduce the overall loss resistance, so the power of the blower can be reduced and the power of the auxiliary equipment can be reduced. The efficiency of the entire system can be improved.
[0030]
(Example 1)
FIG. 1 is an overall configuration diagram of a fuel cell separator according to a first embodiment of the present invention, and FIG. 2 is a sectional view of the entire fuel cell. In FIG. 2, a solid polymer type fuel cell comprises a power generation cell in which a gas diffusion electrode 12 carrying a catalyst on both surfaces of a solid polymer electrolyte membrane 11 provided with ion conductivity is superposed on both surfaces. I have. Then, a plurality of the power generation cells are connected to obtain a predetermined voltage. For this reason, the separators 1 are interposed between the power generation cells, and the power generation cells are stacked and stacked. When the fuel gas and the oxidizing gas are supplied to both sides of the separator and the fuel gas and the oxidizing gas are supplied to the respective gas diffusion electrodes 12, the ionic conduction in the solid polymer membrane 11 and the electrochemical reaction of each gas diffusion electrode are performed. Progresses, a voltage is generated between the pair of gas diffusion electrodes 12, and power is supplied to an external circuit (not shown) via the pair of separators 1 on both ends having a function of a current collecting electrode. In such power generation, supplying the supplied gas to the electrode surface of the gas diffusion electrode 12 as evenly as possible increases the gas utilization rate and improves the power generation efficiency and output performance.
[0031]
In the separator 1 shown in FIG. 1, the flow channel 2 of the separator 1 has a shape corresponding to the gas diffusion electrode 12 and is made of carbon having gas impermeability and conductivity, and surface-treated metal. Fuel or oxidizing gas flows from the inlet manifold 3, and flows out of the outlet manifold 4 through the gas of the flow channel 2. On the other hand, the oxidizing gas or fuel gas separator 1 is provided with a similar flow structure on the back side of the separator 1, and gas is introduced and discharged from the inlet manifold 5 and the output manifold 6. Thereby, the separator 1 is formed in which the flow grooves 2 for guiding the fuel gas and the oxidizing gas from the respective inlet sides to the respective outlet sides are formed on the respective surfaces of the pair of gas diffusion electrodes 12 sandwiching the solid polymer electrolyte membrane 11. are doing.
[0032]
The grooves of the flow channel material 2 include an inlet flow groove 13 directly communicating with the inlet manifold 3 on the inlet side, an outlet flow groove 14 directly communicating with the outlet manifold 4, and an inlet flow groove. A bypass channel groove 15 communicating from the outlet 13 to the outlet channel groove 14 is formed. The inlet-side channel groove portion 13 is constituted by a plurality of grooves, directly communicates with the inlet manifold 3, and reaches a junction 16 with the bypass channel groove portion 15 while meandering. The outlet-side channel groove portion 14 also includes a plurality of grooves, communicates with the merging portion 16, and reaches the outlet manifold 4 while meandering. The bypass channel groove 15 is composed of a plurality of grooves, communicates directly with the inlet manifold 3, and reaches a junction 16 with the outlet channel groove 14.
[0033]
The operation and operation of the fuel cell separator configured as described above will be described below.
[0034]
First, when the fuel gas and the oxidizing gas which have entered the inlet-side channel groove 13 from the inlet manifold 3 flow through the inlet-side channel groove 13 and the outlet-side channel groove 14 on the way, the fuel gas and the oxidizing gas diffuse into the gas diffusion electrode and electrochemically diffuse. The reaction is performed, the fuel gas is consumed, and the oxidizing gas becomes water, and is discharged to the outlet-side channel groove portion 14 while sequentially reducing the mass. Therefore, the amounts of the fuel gas and the oxidizing gas on the inlet side are much larger than those on the outlet side.
[0035]
Part of the amount of gas entering from the inlet manifold 3 flows through the inlet-side flow path 13, and the remaining gas flows through the bypass flow-path groove 15 to the junction 16 without passing through the inlet-side flow path 13. In the section 16, the gas flowing in the inlet side flow path section 13 and the gas flowing in the bypass flow path groove section 15 merge, and reach the outlet manifold 4 from the outlet side flow path groove section 14 and are discharged. For this reason, it is possible to design the flow velocity of the gas in the inlet-side flow path section 13 of the inlet section having a large flow rate to be small. The gas diffusion to the gas diffusion electrode 12 increases as the gas flow rate increases. For this reason, the gas diffusion to the gas diffusion electrode 12 can be reduced, and excessive reaction promotion in the inlet-side inlet channel section 13 can be reduced, and the inlet-side channel groove section having the largest supply gas flow rate and the largest flow resistance. Since the flow velocity of the flow path 13 is small, the overall loss resistance can be reduced. In addition, since the cross-sectional area of the supply-side flow channel groove portion 14 of the supply gas can be configured to be smaller than the sum of the flow-path cross-sectional area of the inlet-side flow channel groove portion 13 and the bypass flow channel groove portion 15 (the optimal value is set to 0. 5 to 0.7) Since the flow rate of gas in the outlet side flow channel portion 14 of the outlet portion with a small flow rate can be designed to be as large as the inlet side, gas diffusion to the gas diffusion electrode 12 can be increased, and the outlet side of the outlet side The promotion of the electrochemical reaction in the channel groove 14 can be increased. For this reason, the amount of electrochemical reaction from the inlet to the outlet of the supply gas is made uniform, the current density of each part becomes constant, and the durability reliability can be improved and the overall electric conversion energy efficiency can be increased.
[0036]
In addition, it is necessary to control the amount of generated electricity to increase or decrease according to the actual usage. Therefore, it is necessary to increase or decrease the amounts of the fuel gas and the oxidizing gas in accordance with the load. The flow path of the inlet-side flow channel groove 13 on the inlet side and the outlet-side flow channel groove 14 on the outlet side can be approximated to form a flow path capable of equalizing current density and reducing flow loss resistance. This uniformity can be maintained even when the flow rate of the supplied gas is changed, so that the durability reliability can be improved and the overall electric conversion energy efficiency can be improved.
[0037]
In the outlet-side channel groove portion 14, the flow velocity of the gas can be designed to be large, so that the generated water generated inside can be discharged to the outside by the dynamic pressure of the gas. For this reason, it becomes possible to prevent flooding in which the flow path is blocked by water, and a favorable operation range is expanded and stability is improved.
[0038]
In addition, the flow rate of the inlet-side flow passage section where the flow rate of the supply gas is the largest and the flow resistance is large is small, so that the overall loss resistance can be reduced. Therefore, the power of the blower can be reduced and the power of the auxiliary equipment can be reduced. The efficiency of the entire system can be improved.
[0039]
Further, the separator 1 is configured such that the bypass channel grooves 15 are respectively communicated from the inlet manifold 3 on the inlet side of the inlet-side channel grooves 13 to the junction 16 on the inlet side of the outlet-side channel grooves 14. An outlet-side flow channel that must be flowed for power generation while designing the gas flow velocity at the inlet side of the inlet-side flow channel groove 13 having the largest flow rate to be the smallest and reducing gas diffusion to the gas diffusion electrode 12. All of the gas can flow from the inlet side of the groove 14, and the electrochemical reaction as designed becomes possible. For this reason, the current density is small and uniform, so that the durability reliability can be improved and the overall electric conversion energy efficiency can be increased.
[0040]
(Example 2)
FIG. 3 shows an overall configuration of a fuel cell separator according to a second embodiment of the present invention. The difference from the first embodiment is that the separator 1 has the inlet-side channel groove 13 composed of a plurality of six channels 13a to 13f, and the channels 13a to 13f of the inlet-side channel groove 13 join at the junctions 16a16b16c. After that, it communicates with the flow paths 14a to 14c of the outlet side flow path groove 14. Accordingly, even if the flow pattern of the inlet-side flow channel portion 13 is the same, the area of the gas diffusion electrode per unit flow channel of the inlet-side flow channel portion 13 can be significantly increased with respect to the outlet-side flow channel groove 14. For this reason, the current density is small and uniform, so that the durability reliability can be improved and the overall electric conversion energy efficiency can be increased, the degree of freedom in designing the flow path is improved, and the processing is easy and inexpensive. In addition, the high electric conversion energy efficiency allows the separator to be made smaller and compact.
[0041]
(Example 3)
FIG. 4 shows an overall configuration of a fuel cell separator according to a third embodiment of the present invention. The difference from the second embodiment is that the separator 1 of the fuel cell is configured such that the converging point of the inlet-side flow channel portion 13 is a plurality of 16d and 16e. The gas amount on the outlet side of each of the inlet-side channel groove portion 13 and the outlet-side channel groove portion 14 decreases on the inlet side due to an electrochemical reaction. Therefore, by adjusting the flow velocity sequentially with a plurality of junctions 16d and 16e, an optimal flow path can be formed according to the current density and the distribution of the loss resistance of the gas flow reduced by the electrochemical reaction. The performance increases as the number of junctions increases.
[0042]
(Example 4)
FIG. 5 shows an overall configuration of a fuel cell separator according to a fourth embodiment of the present invention. The difference from the first embodiment is that the fuel cell and the gas diffusion electrode 12 for diffusing the fuel gas or the oxidizing gas flowing through the bypass channel portion 15 of the separator 1 of the fuel cell are separated from each other. Specifically, the gas diffusion electrode 12 is configured to face the inlet-side flow channel groove 13, the outlet-side flow channel groove 14, and the flow channel 2 that is the merging point 15, and the bypass flow channel 15 is formed by packing. One side is closed by a member 17. For this reason, in the bypass flow path part 15, gas diffusion does not occur and an electrochemical reaction does not occur. Therefore, there is no need to consider the cooling of the bypass flow passage portion 15 and the uniformity of the current density distribution, and the current density can be reduced and uniform, and the durability reliability can be improved and the overall electric conversion energy efficiency can be increased. The degree of freedom in design is improved, and processing is easy and inexpensive.
[0043]
Further, a method of preventing the flooding by sequentially reducing the cross-sectional area of the groove shape through which the gas of the separator 1 flows is described in Japanese Patent No. 3272980 and Japanese Patent Application Laid-Open No. 6-267564, but the configuration of the present invention is added. This is effective in making the current density uniform and suppressing flooding. In the first to fourth embodiments, the separator 1 is configured such that the cross-sectional area of the inlet-side channel groove 13 is larger than the cross-sectional area of the outlet-side channel groove 14, so that the inlet-side flow having a large flow rate of the supply gas is provided. Since the gas flow velocity in the channel groove portion 13 can be designed to be smaller, gas diffusion to the gas diffusion electrode 12 can be further reduced, excessive reaction promotion can be reduced, and the inlet-side flow passage having the largest supply gas flow rate and the largest flow resistance. Since the flow velocity of the portion 13 is small, the overall loss resistance can be reduced. In addition, since the cross-sectional area of the supply gas outlet-side channel groove portion 14 is configured to be smaller than the flow-path cross-sectional area of the inlet-side channel groove portion, the flow velocity of the gas at the outlet portion where the flow rate is small is further increased. Therefore, gas diffusion to the gas diffusion electrode 12 can be increased, and the promotion of reaction at the outlet side can be increased. For this reason, the reaction amount from the inlet to the outlet of the supply gas is made more uniform, the current density of each part becomes constant, and the durability reliability and the overall electric conversion energy efficiency can be improved. In the outlet-side channel groove portion 14, the flow rate of the gas can be designed to be further increased, so that the generated water generated inside can be discharged to the outside by the dynamic pressure of the gas. For this reason, it is possible to prevent flooding in which the flow path is blocked by water. Since the loss resistance of the entire supply gas flow rate can be reduced, the power of the blower can be reduced, the power of the auxiliary equipment can be reduced, and the efficiency of the entire system can be improved.
[0044]
Further, the separator 1 is configured such that the inlet-side channel groove 13 has a larger groove width than the outlet-side channel groove 14, and the cross-sectional area of the inlet-side channel groove 13 is larger than that of the outlet-side channel groove 14. As a result, the gas flow rate at the inlet portion where the flow rate is large is designed to be small, and gas diffusion to the gas diffusion electrode 12 is reduced, and at the same time, the reaction is performed with a wide diffusion electrode by enlarging the flow path width. Becomes possible. For this reason, the current density is small and uniform, so that the durability reliability can be improved and the overall electric conversion energy efficiency can be increased. In addition, it is easy to press the thin plate made of carbon or metal into the separator 1 by pressing, injection molding or the like, and to process a part of the separator so as to increase the width of the channel groove.
[0045]
In addition, the separator 1 is configured such that the inlet-side channel groove 13 has a larger groove depth of the outlet-side channel groove 14, and the cross-sectional area of the inlet-side channel groove 13 is smaller than that of the outlet-side channel groove 14. It is possible to increase the flow rate of the gas at the inlet portion where the flow rate is large and to reduce the gas diffusion to the gas diffusion electrode 12 while reducing the gas flow to the gas diffusion electrode 12. The area of the diffusion electrode, which reacts mainly against the gas, can be made uniform from the inlet to the outlet of the supply gas, keeping the current density of each part constant, improving durability reliability and increasing the overall electrical conversion energy efficiency. Can be. Further, it is easy to increase the depth of the channel groove of a part of the separator by pressing, injection molding, or the like a thin plate made of carbon or metal.
[0046]
The separator 1 is configured such that at least one of the inlet-side channel groove portion 13 and the outlet-side channel groove portion 14 has a smaller channel cross-sectional area, so that the channel cross-sectional area is gradually reduced according to the gas flow rate reduced by the reaction. Thus, the flow velocity of the gas can be designed to be constant from the inlet part where the flow rate is high to the outlet part where the flow rate is the lowest. For this reason, the reaction amount from the inlet to the outlet of the supply gas is made uniform, the current density of each part becomes constant, and the durability reliability and the overall electric conversion energy efficiency can be improved. The gas flowing in the flow path is 2H ₂ + O ₂ → 2H ₂ Due to the reaction of O, the gas flow rate gradually decreases. By sequentially reducing the cross-sectional area of the flow path, the overall flow resistance can be reduced by reducing the flow velocity of the inlet-side flow path section 13 having the largest supply gas flow rate and the highest flow resistance. In the outlet-side channel groove portion 14, the flow rate of the gas can be designed to be large, and the generated water generated inside can be discharged to the outside by the dynamic pressure of the gas. Therefore, flooding in which the channel is blocked by water can be prevented. Since the flow rate of the inlet-side flow path 13 where the supply gas flow rate is the largest and the flow resistance is large is small, it is possible to reduce the overall loss resistance, so that the power of the blower is small and the power of the auxiliary machine is small. It can be reduced and efficiency of the whole system can be improved.
[0047]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce excessive reaction promotion at the inlet side where the flow rate is large and to reduce the overall loss resistance. In addition, since the flow rate of gas at the outlet with a small flow rate can be designed to be large, the promotion of reaction can be increased, the reaction amount is made uniform, the current density is made constant, the durability reliability is improved, and the overall electric conversion energy efficiency is increased. Can be. This uniformity can be maintained according to the load, and the durability reliability can be improved and the entire electric conversion energy efficiency can be increased. In the outlet-side channel groove, the flow velocity of the gas can be designed to be large, so that the generated water generated inside can be discharged to the outside by the dynamic pressure of the gas. For this reason, it is possible to prevent flooding in which the flow path is blocked by water.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a fuel cell separator according to a first embodiment of the present invention.
FIG. 2 is a sectional view of the entire fuel cell according to the first embodiment of the present invention.
FIG. 3 is an overall configuration diagram showing a fuel cell separator according to a second embodiment of the present invention.
FIG. 4 is an overall configuration diagram showing a fuel cell separator according to a third embodiment of the present invention.
FIG. 5 is an overall configuration diagram showing a fuel cell separator according to a fourth embodiment of the present invention.
FIG. 6 is an overall configuration diagram showing a conventional fuel cell separator.
[Explanation of symbols]
1 separator
2 Channel groove
3 Inlet manifold
4 Exit manifold
13 Inlet-side channel groove
14 Outlet side channel groove
15 Bus path channel groove
16 junction

Claims

A pair of gas diffusion electrodes sandwiching the solid polymer electrolyte, and a separator having a flow channel formed on each surface of the gas diffusion electrodes to guide the fuel gas and the oxidizing gas from the respective inlet side to the outlet side, at least. The flow channel of one of the separators includes an inlet flow channel located on the inlet side and an outlet flow channel located on the outlet side, and the outlet flow channel extends from the inlet flow channel. A separator for a fuel cell, wherein a bypass passage groove portion communicating with the groove portion is formed.

2. The fuel cell separator according to claim 1, wherein a flow path cross-sectional area of the outlet-side flow groove is smaller than a total flow cross-sectional area of the inlet-side groove and the bypass flow path groove.

3. The fuel cell separator according to claim 1, wherein a bypass passage groove is configured to communicate from an inlet side of the inlet-side passage groove to an inlet side of the outlet-side passage groove. 4.

The inlet-side channel groove portion is constituted by at least a plurality of channels, and at least a part of the inlet-side channel groove portion is connected to the outlet-side channel groove portion after merging. Item 14. The fuel cell separator according to Item 1.

5. The fuel cell separator according to claim 4, wherein a plurality of junctions of the inlet-side channel groove are provided.

The fuel cell separator according to any one of claims 1 to 5, wherein at least a part of the bypass channel portion is configured to be separated from the gas diffusion electrode.

The fuel cell separator according to any one of claims 1 to 6, wherein a flow path cross-sectional area of the inlet flow path groove is configured to be larger than a flow path cross-sectional area of the outlet flow path groove.

The inlet-side channel groove has a groove width larger than that of the outlet-side channel groove, and the cross-sectional area of the inlet-side channel groove is larger than that of the outlet-side channel groove. The fuel cell separator according to claim 7, wherein:

The inlet-side channel groove is configured such that the groove depth is greater than the groove depth of the outlet-side channel groove, and the channel cross-sectional area of the inlet-side channel groove is larger than the channel cross-sectional area of the outlet-side channel groove. The fuel cell separator according to claim 7, wherein:

The fuel cell separator according to any one of claims 7 to 9, wherein at least one of the inlet-side channel groove and the outlet-side channel groove has a channel cross-sectional area that is sequentially reduced.