JP4546018B2 - Fuel cells and electrical equipment - Google Patents

Description

【００５９】
ただし、
【００６０】
【数２】

である。
【００６１】
ここで、Ｅはヤング率、ｍはポアッソン比（^-1）、Ｐは圧力である。ダイヤフラム半径を１［ｍｍ］、厚さを０．１［ｍｍ］とすると、シリコーンゴムのヤング率４．９５［ＭＰａ］、ｍ^-1＝０．４５より、ダイヤフラムに差圧が０．０１ＭＰａ（約０．１［ａｔｍ］）かかった場合の中心部のたわみは、０．３［ｍｍ］程度となる。従って、ダイヤフラムのばね定数ｋ＝Ｐ×πｒ² ／ω＝１０３．９［Ｎ／ｍ］となる。
【００６２】
また、シリコーンゴムの密度は１．２［ｇ／ｃｍ³ ］程度であることから、ダイヤフラム質量は０．３８［ｍｇ］となる。従って、ダイヤフラムの固有振動数ｆは１６．６［ｋＨｚ］程度となる。
【００６３】
軸の長さを調節することにより、バルブが開く時の燃料極室の圧力Ｐ₂₀を変えることができる。差圧検出機構からバルブまでの距離と軸の長さとの差をｘ₀ とすると、バルブは燃料極室の圧力が、
【００６４】
【数３】

となった時に開くようになる。
【００６５】
バルブ軸と軸穴との摩擦を低減するために、軸及び軸穴の表面にテフロン（登録商標）など摩擦を低減する性質を持つ材料でコーティングしたり、軸と軸穴の間を通る燃料の流れを利用して気体軸受けとして用いることも可能である。気体軸受けについては、通常のバルブ、軸穴、軸の構成であっても、効果は期待できるが、図８（ａ）〜図８（ｃ）のような構造を用いれば更に軸受けの効果が高まる。
【００６６】
また、燃料極室の圧力が過剰に上がってしまった場合に、ダイヤフラムおよびバルブの破損を防ぐために、ダイヤフラムの酸化剤極室側にストッパー機構２６を備えることも可能である。ストッパー機構によって、ダイヤフラムに酸化剤極室（外気）の圧力が伝わらなくなることと防ぐために、ストッパー機構は多孔質材料からなるか通気口を有する。また、該ストッパー機構は燃料電池の発電セル同士が接することを防ぐ支持部材と兼ねることも可能である。
【００６７】
一方、酸化剤極室の圧力が燃料極室の圧力に対して過剰である場合にも、ストッパー機構を設けることが可能である。ストッパー機構２６は図１９（ａ）に示すように、ダイヤフラム２３の燃料極室側にダイヤフラムの動きを止めるように設置することができる。また、図１９（ｂ）に示すように燃料流路壁を利用することも可能である。また、図１９（ｃ）に示すように、マイクロバルブ１８の動きを止めるように設置することも可能である。
【００６８】
材料の強度について以下に述べる。燃料タンクはタンク内圧力が０．５ＭＰａ（約５気圧）とし、安全率を５として計算すると、材料がステンレスの場合は１ｍｍ程度、チタンの場合は０．８ｍｍ程度まで薄くすることが可能である。バルブの軸穴を有する板部材に関しては０．５ｍｍ程度の厚さで十分である。さらに、穴板に補強部材２９をつければ、穴板自体の厚さはステンレスを用いた場合で、０．２［ｍｍ］まで薄くすることが可能である。
【００６９】
燃料電池での水素消費量は以下の通りである。燃料極での反応がＨ₂ →２Ｈ⁺ ＋２ｅ^- である。従って、１［Ａ］の電流を流した場合の水素消費量は、５．１×１０^-6 ［ｍｏｌ／ｓ］、すなわち標準状態で、１１４［ｍｍ³ ／ｓ］である。一方、タンクにＬａＮｉ₅ を充填し、容積が５．１５［ｃｍ³ ］の場合の各温度における水素放出速度は下記の表１に示す通りである。従って、本燃料電池においては、水素消費量に比べて十分速くタンクから水素を供給できる。
【００７０】
【表１】

【００７１】
本実施例では、燃料電池セル間の燃料極室体積は、燃料電池全体が非常に小さくかつ薄いため、７５０［ｍｍ³ ］程度であり、発電に伴う水素流量に比べて小さい。そこで、燃料電池のセルに、燃料極室には燃料流量の急激な変化を和らげるためのバッファー機構をもうけることもできる。例えば発電セルと燃料タンクとの間にバッファーとして、８×２８×３．６［ｍｍ］の領域を設けると、バッファー領域の体積は８０５［ｍｍ³ ］となり、燃料極室全体の体積を２倍にまで広げることができる。
【００７２】
また、燃料極室で燃料圧が急激に増加した場合に、圧力を下げるための機構を設けることが可能である。減圧には、リリーフバルブを設ける方法や、余分に発電を行い、燃料を消費する方法が有効である。
【００７３】
ＬａＮｉ₅ の温度による解離圧の変化を下記の表２に示す。この表２から、本発明の燃料電池をデジタルカメラなどの小型電気機器に搭載して用いる場合、燃料タンクの圧力は０．１〜０．４ＭＰａ程度である。
【００７４】
【表２】

【００７５】
図９に示すように、外気の圧力をＰ₀ 、燃料タンクの圧力をＰ₁ 、燃料極室の圧力をＰ₂ とし、バルブの底面の面積をＳ₁ 、ダイヤフラム面積をＳ₂ とすると、圧力の釣り合いから、バルブが開く条件は、Ｐ₀を０．１ＭＰａ（約１［ａｔｍ］）、（Ｐ₁ −Ｐ₂ ）Ｓ₁ ＜（Ｐ₀ −Ｐ₂ ）Ｓ₂ となる。従って、Ｓ₁ およびＳ₂ を決定することにより、バルブが開くときの燃料極室の圧力Ｐ₂₀を最適に設計することができる。例えば、Ｓ₁ ：Ｓ₂ ＝１：１６にしたときの、様々なＰ₁ でのＰ₂₀を表にすると、下記の表３に示すようになる。この場合、Ｐ₁ が０．４ＭＰａ（約４［ａｔｍ］）以下程度であれば、バルブは適切に動作し、一方、過剰な加熱などにより、Ｐ₁ が著しく高くなった場合には、バルブが開かなくなり、発電が停止するので、バルブが安全装置として働く。
【００７６】
【表３】

【００７７】
バルブの形状には様々なものが考えられる。例えば、バルブの絞り形状を図１０のようにオリフィスにすることも可能である。燃料を比圧縮流体と仮定した場合、バルブの通過流量ＱとＰ₁ とＰ₂ の差圧ΔＰとの関係は次式で表される。
【００７８】
【数４】

【００７９】
ただし、Ａは絞り面積、Ｃ_d は流量係数、ρは流体の密度である。Ｃ_d ＝０．７、ρ＝０．０８９９［ｋｇ／ｍ³ ］（水素標準状態）としたときのＡとＱとΔＰの関係を示したのが下記の表４である。十分な発電を行うための流量を得るためには、オリフィス径は１０［μｍ］程度であることが分かる。
【００８０】
【表４】

【００８１】
また、オリフィスの形状の一つとして、バルブ形状を図１１に示すように、球形にすることも可能である。
さらに大きな減圧効果を得るために、バルブの絞り形状を図１２に示すようにチョーク絞りにすることも可能である。この場合、バルブでの流量と圧力との関係は以下のように表される。
【００８２】
【数５】

【００８３】
ここで、μは粘性係数、ΔＰは絞り前後の圧力差、Ｄは絞り穴径、Ｌは絞り部の長さである。μ＝８．８×１０^-6［Ｐａ／ｓ］、Ｌ＝０．５［ｍｍ］とすると、様々な穴径での流量と絞り部での差圧（Ｐ₁ とＰ₂ の圧力差）は下記の表５に示すようになる。従って、適当な穴径は２５〜７５μｍ程度となる。
【００８４】
【表５】

【００８５】
チョーク絞りの形状３２は、必要な絞りの抵抗に合わせて、軸に対して平行な溝３３を１つ以上設ける方法（図１３（ａ））や、軸穴の中心にバルブ軸が通り、その隙間３４を流路として用いる方法（図１３（ｂ））、軸に対して垂直に凸凹溝３５を設ける方法（図１３（ｃ））や、軸にスクリュー状の溝３６を設ける方法（図１３（ｄ））や、軸に多孔質材料３７からなる部分を設ける方法（図１３（ｅ））を用いることも可能である。例えば、図１３（ａ）の場合、穴径ｄの小流路がｎ個あるとすると、流量と差圧との関係は以下のように表される。
【００８６】
【数６】

【００８７】
また、図１３（ｂ）の場合、円形流路の幅をｈ、半径をｒとすると流量と差圧との関係は以下のように表される。
【００８８】
【数７】

【００８９】
しかしながら、これらのバルブ機構だけでは、絞り部での抵抗が変化しないため、燃料の流量を段階的に制御することが難しく、燃料の流量が多すぎて、頻繁にバルブを閉じなければならなかったり、十分な流量を得ることが難しかったりという問題が生じる。そこで、本発明のバルブは、燃料極室の圧力と酸化剤極室または外気の圧力の差圧および燃料タンクの圧力に応じて、燃料タンクからの燃料の流量を制御するバルブの開度が変化することで、燃料の流量を制御し、燃料の供給量が燃料の消費量に等しくなるように制御される。本機能が実現される仕組みを以下に詳細に説明する。
【００９０】
本発明のバルブはバルブが開くに従って、バルブ部分での流路抵抗が小さくなるようになっている。これは通常のオリフィス、チョーク弁でも弁体の抵抗により有る程度は実現は可能であるが、例えば、図１４（ａ）に示すように、弁体２１およびバルブ軸穴２４がテーパーを有して接している方法を用いればより効果的である。この場合、バルブが開くに従って、流路幅が広くなるので、流量が増加する。その他にバルブが開くに従って、バルブ部分での流路抵抗が小さくなるような機構としては、図１４（ｂ）のように、バルブ軸径がテーパー状に変化するする方法がある。この場合、テーパー構造を有する溝を複数設けてもよい。また、図１４（ｃ）のように、バルブの径が途中で変化する段差を設ける方法もある。また、図１４（ｄ）のようにバルブの一部にのみ、絞り効果を持たせる機構を持たせることもできる。その他にも絞り効果の異なる形状を複数組み合わせることによっても可能である。
【００９１】
これらの機構は以下のように動作する。燃料極室と酸化剤極室（外気）との差圧が大きくなるか燃料タンクの圧力が低下すると、ダイヤフラムのたわみ量も大きくなり、それに従って、バルブも大きく移動する。バルブが開くに従って、バルブ部分での流路抵抗が小さくなるため、より流量が多くなる。バルブは、燃料極室と酸化剤極室（外気）との差圧とダイヤフラムのたわみによりバネの力が釣り合う位置、すなわち、発電による燃料の消費量と燃料タンクからの燃料の流量が等しくなる位置で安定に静止する。従って、本バルブは、燃料電池が発電を開始すると、バルブを開き、燃料消費量と等しい量の燃料を燃料タンクから燃料極室へ供給する位置で釣り合って静止し、発電を停止すると閉じる。このため、発電の最中に頻繁にバルブの開閉を繰り返したり、発電量が多くなったときに、燃料の供給が不足したりということなく、燃料を供給することが可能である。
【００９２】
図１５のように弁体およびバルブ軸がテーパーを有して接している場合のダイヤフラムの変位と流量の関係を具体的に述べる。バルブでの流量Ｑとバルブの変位ｘとの関係は以下のように表される。ここで、ｋはダイヤフラムのばね定数、ｒは流路穴半径、φはバルブテーパー角度、Ｌ₁ はテーパー部高さである。
【００９３】
【数８】

【００９４】
一方、弁が開くときの圧力Ｐ₂₀は以下のように表される。
【００９５】
【数９】

また、
【００９６】
【数１０】

従って、
【００９７】
【数１１】

となる。
【００９８】
上式をもとに、具体的な絞り形状の大きさを示す。
Ｐ₀ ＝０．１［Ｍｐａ］（約１ａｔｍ）、μ＝８．８×１０^-6［Ｐａ／ｓ］、ｋ＝１０４［Ｎ／ｍ］、Ｓ₁ ＝０．１９６［ｍｍ² ］（直径５００［μｍ］）、Ｓ₂ ＝３．１４［ｍｍ² ］（直径２［ｍｍ］）、Ｄ＝３００［μｍ］（ｒ＝２００［μｍ］）、Ｌ＝５００［ｍ］、Ｌ₁ ＝１００［μｍ］＝４５°とすると（図１６）、
バルブが最も小さく変位する場合（Ｐ₁ ＝０．４［ＭＰａ］（約４ａｔｍ）、Ｑ＝２２．８［ｍｍ³ ］（１［Ｗ］発電））で、Ｐ₂₀＝０．０８１［ＭＰａ］（約０．８ａｔｍ）、ｘ＝０．９３［μｍ］となる。
【００９９】
また、バルブが最も大きく変位する場合（Ｐ₁ ＝０．１５［ＭＰａ］（約１．５ａｔｍ）、Ｑ＝２２８［ｍｍ³ ］（１０［Ｗ］発電））で、Ｐ₂₀＝０．０９７［ＭＰａ］（約０．９７ａｔｍ）、ｘ＝４．９５［μｍ］となる。
【０１００】
また、Ｐ₀ ＝０．１［Ｍｐａ］（約１ａｔｍ）、μ＝８．８×１０^-6［Ｐａ／ｓ］、ｋ＝１０４［Ｎ／ｍ］、Ｓ₁ ＝０．１９６［ｍｍ² ］（直径５００［μｍ］）、Ｓ₂ ＝３．１４［ｍｍ² ］（直径２［ｍｍ］）、Ｄ＝２００［μｍ］（ｒ＝１７５［μｍ］）、Ｌ＝５００［ｍ］、Ｌ₁ ＝１００［μｍ］＝６０°とすると（図１７）、
バルブが最も小さく変位する場合（Ｐ₁ ＝０．４［ＭＰａ］（約４ａｔｍ）、Ｑ＝２２．８［ｍｍ³ ］（１［Ｗ］発電））で、Ｐ₂₀＝０．０８１［ＭＰａ］（約０．８ａｔｍ）、ｘ＝１．０２［μｍ］となる。
【０１０１】
また、バルブが最も大きく変位する場合（Ｐ₁ ＝０．１５［ＭＰａ］（約１．５ａｔｍ）、Ｑ＝２２８［ｍｍ³ ］（１０［Ｗ］発電））で、Ｐ₂₀＝０．０９７［ＭＰａ］（約０．９７ａｔｍ）、ｘ＝５．４４［μｍ］となる。
【０１０２】
バルブが開く圧力と閉じる圧力とに差を持たせるために、バルブにヒステリシス機構を備えることも可能である。具体的な方法には図１８（ａ）に示すように、バルブの弁体に隣接した燃料タンク側に電磁石または永久磁石４１を設置し、またバルブの弁体に永久磁石、または鉄、ニッケル、コバルトなどの磁性体からなる部分４０を設けたり、図１８（ｂ）に示すように、バルブの弁体および弁体に隣接した燃料タンク側に両方ともエレクトレットからなる部分４２、または片方が誘電体からなる部分を設けることにより、バルブが開いた際に両者が引き合い、バルブがとじにくくなる。
【０１０３】
本発明の燃料電池は、デジタルカメラ、デジタルビデオカメラ、小型プロジェクタ、小型プリンタ、ノート型パソコンなどの持ち運び可能な小型電気機器に特に好適に用いられることができる。
【０１０４】
【発明の効果】
以上説明した様に、本発明の燃料電池によれば、小型燃料電池に搭載可能な、非常に小型に製作したバルブである小型減圧弁を使用し、減圧弁の微小な圧力変化による振動を抑制し、発電電力を安定して供給することが可能になる。
【０１０５】
特に、持ち運んで使用できる小型電気機器に搭載可能でかつ大容量、高出力の燃料電池において、制御及び駆動に電気を使用せずに、燃料タンクからの圧力を最適に減圧して燃料電池セルに供給することができるようになり、燃料電池セルを大きな差圧による破断から防ぎ、発電の起動、停止および安定した電力が提供できるようになる。
【図面の簡単な説明】
【図１】本発明の燃料電池を示す斜視図である。
【図２】本発明の燃料電池のシステムを示す概要図である。
【図３】図１の本発明の燃料電池の平面図である。
【図４】図１の本発明の燃料電池の正面図である。
【図５】本発明に用いられるバルブ（減圧弁）の概要図である。
【図６】本発明に用いられるバルブの動作図である。
【図７】本発明に用いられるダイヤフラムの概略図である。
【図８】本発明に用いられるラジアル気体軸受けの概略図である。
【図９】本発明に用いられるバルブの概略図である。
【図１０】本発明に用いられるオリフィス絞りを有するバルブの概略図である。
【図１１】本発明における球形弁体を有するバルブの概略図である。
【図１２】本発明におけるチョーク絞りを有するバルブの概略図である。
【図１３】本発明における複数の流路溝を有するチョーク絞りの構造を示す概略図である。
【図１４】本発明におけるバルブの弁体と軸穴の関係を示す概略図である。
【図１５】本発明におけるバルブの弁体と軸穴がテーパーを有して接しているチョーク弁を示す概略図である。
【図１６】本発明におけるバルブの弁体と軸穴がテーパーを有して接しているチョーク弁を示す概略図である。
【図１７】本発明におけるバルブの弁体と軸穴がテーパーを有して接しているチョーク弁を示す概略図である。
【図１８】本発明におけるバルブの弁体およびタンク側に磁石または磁性体の部分を設けたヒステリシス機構を示す概略図である。
【図１９】本発明における酸化剤極室圧が燃料極室圧に対して過剰な場合のストッパー例を示す概略図である。
【図２０】本発明の燃料電池にデジタルカメラに搭載する場合の概要図である。
【符号の説明】
１１ 燃料電池セル
１１１ 酸化剤極
１１２ 高分子電解質膜
１１３ 燃料極
１２ 電極
１３ 通気孔
１４ 保水部
１５ 燃料供給部
１６ 燃料タンク
１６１ 燃料注入口
１７ 差圧検出機構
１８ マイクロバルブ
２１ 弁体
２２ バルブ軸（弁軸）
２３ ダイヤフラム
２４ 軸穴
２５ シール部材
２６ ストッパー機構
２７ 燃料極室
２８ 酸化剤極室
２９ 補強部材
３０ 燃料流路
３１ ベローズ
３２ チョーク絞りの形状
３３ 溝
３４ 隙間
３５ 凸凹溝
３６ スクリュー状の溝
３７ 多孔質材料
５０ 燃料電池
５１ デジタルカメラ[0001]
BACKGROUND OF THE INVENTION
  The present inventionFor fuel cellsIn particular, it relates to pressure control valves in small fuel cells, and the amount of power generation that can be mounted on portable small electric devices such as digital cameras, digital video cameras, small projectors, small printers, notebook computers, etc. is from several milliwatts. It is effective for polymer electrolyte fuel cells up to several hundred watts.
[0002]
[Prior art]
Conventionally, various primary batteries and secondary batteries have been used to carry and use small electric devices. However, with the recent high performance of small electrical devices, power consumption has increased, and primary batteries are small and light and cannot supply sufficient energy. On the other hand, although the secondary battery has an advantage that it can be repeatedly charged and used, the energy that can be used in one charge is much less than that of the primary battery. In the future, as electric devices become increasingly smaller and lighter, and the wireless network environment is in place, the tendency to carry and use devices will increase. Conventional primary and secondary batteries are sufficient to drive devices. It is difficult to supply a large amount of energy.
[0003]
As a solution to such a problem, a small fuel cell has attracted attention. Conventionally, fuel cells have been developed as a drive source for large generators and automobiles. This is mainly because the fuel cell has higher power generation efficiency and clean waste than the conventional power generation system. On the other hand, the reason why fuel cells are useful as a drive source for small electric devices is that the amount of energy that can be supplied per volume and per weight is several to ten times that of conventional batteries.
[0004]
Although various types of fuel cells have been invented, solid polymer fuel cells are suitable for small electric devices, especially devices that are carried and used.
This is because it can be used at a temperature close to room temperature, and since the electrolyte is a solid rather than a liquid, it has the advantage of being safe to carry.
[0005]
Conventionally, methanol has been studied as a fuel for fuel cells for small electrical devices. This was mainly due to the fact that methanol is a fuel that is easy to store and obtain, although its output is small.
[0006]
For a fuel cell for obtaining a large output, it is optimal to use hydrogen as a fuel. However, hydrogen is a gas at room temperature, and a technique for storing hydrogen at high density in a small fuel tank is required. The first method is a method of compressing hydrogen and storing it as a high-pressure gas. Even if the pressure of the gas is increased to 200 atm, the volume hydrogen density is 18 mg / cm 2.^Three Degree. Moreover, in order to handle a high-pressure gas tank safely, it is necessary to increase the thickness of the tank, which is not suitable for downsizing.
[0007]
The second method is a method in which hydrogen is stored at a low temperature as a liquid. In this method, high-density storage is possible. However, in order to liquefy hydrogen, a large amount of energy is required, and liquid hydrogen naturally vaporizes and leaks.
[0008]
The third method is a method of storing hydrogen using a hydrogen storage alloy. In this method, since the specific gravity of the hydrogen storage alloy is large, only about 2 wt% of hydrogen can be stored on a weight basis, and the fuel tank becomes heavy, but the storage amount on a volume basis is large. It is effective for miniaturization.
[0009]
In the fourth method, there is a method in which methanol, gasoline, or the like is loaded into a fuel tank, reformed and converted to hydrogen, and the reforming reaction is performed at a high temperature of 100 ° C. or higher, and a reformer is required. Therefore, it is not suitable for small electrical equipment. Compared with these methods, carbon-based materials such as carbon nanotubes, graphite nanofibers, and carbon nanohorns have attracted attention in order to store fuel at high density. These carbon-based materials are said to be able to occlude about 10 wt% of hydrogen per weight.
[0010]
Similarly, there is a method using chemical hydride as a method for storing hydrogen at high density. Chemical hydride is a compound that absorbs and releases hydrogen using chemical reaction, and it can be broadly classified into organic and inorganic materials. An inorganic chemical hydride is borohydride. Organic chemical hydrides include cyclohexane and decalin. These compounds can occlude about 5 to 10 wt% of hydrogen.
[0011]
Thus, for example, when used as a power source for a digital camera, it is possible to shoot about 3 to 5 times as compared with the case of using a conventional lithium ion battery.
However, the hydrogen storage system using carbon-based materials and chemical hydrides has a high hydrogen storage capacity per weight, but the storage material itself has a low density, so a hydrogen storage alloy is suitable for a small fuel tank.
[0012]
On the other hand, power generation of the polymer electrolyte fuel cell is performed as follows. A perfluorosulfonic acid cation exchange resin is often used for the polymer electrolyte membrane. For example, Nafyon manufactured by DuPont is well known as such a film.
A pair of porous electrodes carrying a catalyst such as platinum, that is, a membrane electrode assembly sandwiched between a fuel electrode and an oxidizer electrode, serves as a power generation cell. By supplying an oxidant to the oxidant electrode and a fuel to the fuel electrode, protons move through the polymer electrolyte membrane to generate electricity.
[0013]
The polymer electrolyte membrane usually has a thickness of about 50 to 100 μm in order to maintain mechanical strength and prevent the fuel gas from permeating. The strength of these solid polymer electrolyte membranes is about 0.3 to 0.5 MPa. Therefore, in order to prevent the membrane from being broken due to the differential pressure, the differential pressure between the oxidant electrode chamber and the fuel electrode chamber of the fuel cell should be controlled to be 0.05 MPa in normal times and 0.1 MPa or less even in an emergency. Is preferred.
[0014]
When the pressure difference between the fuel tank pressure and the oxidant electrode chamber is smaller than the above pressure, the fuel tank and the fuel electrode chamber are directly connected, and there is no need for depressurization, but the oxidant electrode chamber is open to the atmosphere. In addition, when the fuel is filled at a higher density, it is necessary to reduce the pressure in the process of supplying the fuel from the fuel tank to the fuel electrode chamber. In addition, the above mechanism is necessary for starting / stopping power generation and stabilizing the generated power.
Normally, in large fuel cell systems such as power plants, household power generation systems, and onboard fuel cells, pressure sensors are provided in the fuel electrode chamber and the oxidizer electrode chamber, and the pressure in the fuel supply path is based on these signals. The valve was controlled.
[0015]
However, providing these sensors and wirings in a miniaturized fuel cell system has caused the system to become large and complicated. Therefore, there is an attempt to eliminate these sensors and realize a small fuel flow rate control mechanism. In Japanese Patent Laid-Open No. 2002-33112, a layered body of proton conductors is made movable so that the layered body and the valve can move together, and the proton conductor film is bent by the differential pressure between the fuel electrode chamber and the oxidant electrode chamber. Is used to drive the valve. In another embodiment of the invention, the heater coil is wound around the valve, and the opening / closing member constituted by the bimetal is deformed by a current flowing through the heater coil in accordance with the amount of power generated by the fuel cell. I am trying to control the fuel flow rate.
[0016]
[Problems to be solved by the invention]
However, the valves used in conventional fuel cells are large, and it has been difficult to realize a small fuel cell system that can be mounted on a small electric device that can be carried and used. In addition to the valve, a pressure sensor that sends a control signal is required, which hinders downsizing and simplification of the system.
[0017]
Furthermore, although the fuel cell is a power generation engine, electric power is required to drive valves and sensors and to transmit signals, reducing the amount of power generation that can be taken out.
[0018]
In addition, for diaphragm-driven small pressure reducing valves due to differential pressure, valve vibration due to minute pressure changes near the set pressure occurs, and the amount of fuel consumed by power generation by the flow rate at the valve Therefore, it is necessary to frequently turn on and off the valve, which not only significantly reduces the life of the valve but also makes stable power generation difficult.
[0019]
In the invention using a fuel cell as a diaphragm of a pressure reducing valve (Japanese Patent Application Laid-Open No. 2002-33112), the membrane is formed when a large force is applied that damages the fuel cell because the fuel cell vibrates. The fuel cell itself has a three-layer structure because it does not withstand the pressure of the tank because there is no structural member that supports the fuel cell, and fuel leaks from the joint as the valve opens and closes. The problem is that power generation efficiency is reduced because a part of the fuel cell is used as a valve support, the process is complicated and the cost is high, and it cannot be applied when a plurality of cells are stacked. Had.
[0020]
The present invention has been made in view of such a conventional technique, and uses a small pressure reducing valve, which is a very small valve that can be mounted on a small fuel cell, and uses a small pressure change of the pressure reducing valve. An object of the present invention is to provide a fuel cell that can suppress vibration and stably supply generated power.
[0021]
  In addition, the present invention can optimally reduce the pressure from the fuel tank and supply it to the fuel cell, prevent the fuel cell from being broken by a large differential pressure, and provide start and stop of power generation and stable power Intended to provide a fuel cellIt is.
[0022]
[Means for Solving the Problems]
  That is, the present inventionAn oxidant electrode chamber; a fuel electrode chamber; a fuel tank containing fuel to be supplied to the fuel electrode chamber; a fuel flow path connecting the fuel electrode chamber and the fuel tank; A pressure difference between the pressure of the fuel tank and the pressure of the anode chamber;The pressure in the anode chamberAboveUtilizing the pressure difference between the oxidant electrode chamber and the outside air,AboveFrom the fuel tankTo the fuel electrode chamberA fuel cell comprising a control mechanism for controlling the amount of fuel supplied, the control mechanism for controlling the amount of fuel supplied,The pressure in the fuel electrode chamber and the pressure in the oxidant electrode chamber or outside airA differential pressure detection mechanism comprising a diaphragm or bellows for detecting a differential pressure, a valve having a throttle mechanism for controlling a fuel flow rate, and a shaft of the valve for connecting the differential pressure detection mechanism and the valve. A fuel cell comprising a coupling mechanism.
[0023]
  It is preferable that the oxidant electrode chamber is open to the outside air.
  A differential pressure detection mechanism for detecting a differential pressure between the pressure in the fuel electrode chamber and the oxidant electrode chamber or the outside air is a diaphragm or a bellows. One side of the diaphragm or bellows is the fuel electrode chamber, and the other surface is oxidized. It is preferable to be in contact with the agent electrode chamber or the outside air.
[0024]
The diaphragm or bellows is a metal selected from stainless steel, beryllium, hastelloy, cantal, brass, aluminum, phosphor bronze, a non-metallic material selected from silicone rubber, fluororubber, NBR, EPT, urethane rubber, or a semiconductor material made of silicon. It is preferable to consist of these materials.
The surface of the diaphragm preferably has a corrugated shape.
Stopper mechanism that protects the differential pressure detection mechanism that detects the differential pressure between the pressure of the fuel electrode chamber and the pressure of the oxidant electrode chamber or the outside air when the pressure of the fuel electrode chamber is excessive with respect to the pressure of the fuel electrode chamber It is preferable to have.
[0025]
It is preferable that the stopper mechanism is disposed on the side in contact with the oxidant electrode chamber or the outside air of the differential pressure detection mechanism that detects the differential pressure between the pressure of the fuel electrode chamber and the pressure of the oxidant electrode chamber or the outside air.
The stopper mechanism is preferably a porous body or a structure having a vent hole.
It has a stopper mechanism that protects the differential pressure detection mechanism that detects the differential pressure between the pressure in the fuel electrode chamber and the pressure in the oxidizer electrode chamber or outside air when the pressure of the outside air becomes excessive with respect to the pressure in the fuel electrode chamber. Is preferred.
[0026]
It is preferable that the stopper mechanism is disposed on the side in contact with the fuel flow path of the differential pressure detection mechanism that detects the differential pressure between the pressure in the fuel electrode chamber and the pressure in the oxidant electrode chamber or outside air.
It is preferable that the stopper mechanism is an inner wall of the fuel flow path.
It is preferable that the stopper mechanism operates by contacting a valve that controls the fuel flow rate.
[0027]
A differential pressure detection mechanism that detects the differential pressure between the pressure in the fuel electrode chamber and the pressure in the oxidizer electrode chamber or outside air, and a connecting mechanism that connects a valve that controls the flow rate of fuel from the fuel tank are made up of shafts. The valve body is preferably driven by the displacement of the detection mechanism.
Depending on the length of the shaft of the connecting mechanism that connects the differential pressure detection mechanism that detects the differential pressure between the pressure in the fuel electrode chamber and the pressure in the oxidizer electrode chamber or outside air, and the valve that controls the fuel flow rate from the fuel tank. It is preferable to adjust the pressure at which the valve opens.
It is preferable to have a mechanism for reducing friction between the valve shaft and the shaft hole for controlling the fuel flow rate.
[0028]
The mechanism for reducing friction between the valve shaft and the shaft hole is preferably formed by coating a material having a property of reducing friction on at least one surface of the shaft and the shaft hole.
It is preferable that the mechanism for reducing the friction between the valve shaft and the shaft hole is a gas bearing using a flow of fuel passing between the shaft and the shaft hole.
It is preferable to have a throttle mechanism in the flow path having a valve for controlling the fuel flow rate.
[0029]
It is preferable that the throttle mechanism for controlling the fuel flow rate of the valve has an orifice structure.
The valve body of the valve having the orifice structure is preferably substantially spherical.
The throttle mechanism for controlling the fuel flow rate of the valve preferably has a choke structure.
[0030]
The choke structure preferably has one or more grooves parallel to the valve axis.
It is preferable that the choke structure has an uneven groove perpendicular to the valve axis.
The choke structure preferably has a screw-like groove on the valve shaft.
The choke structure preferably has a portion made of a porous material on the valve shaft.
[0031]
The flow rate of the fuel is changed by changing the opening of the valve that controls the flow rate of the fuel from the fuel tank in accordance with the differential pressure between the pressure in the fuel electrode chamber and the pressure in the oxidant electrode chamber or outside air and the pressure in the fuel tank. It is preferable to provide a control mechanism that controls the fuel supply amount so that the fuel supply amount becomes equal to the fuel consumption amount.
As the mechanism in which the valve has a choke structure and the flow rate changes depending on the opening degree of the valve, the valve body and the shaft hole are preferably tapered.
The valve shaft preferably has a choke structure, and the valve shaft is preferably tapered as a mechanism for changing the flow rate according to the opening degree of the valve.
[0032]
It is preferable that the valve has a choke structure and has one or more tapered grooves as a mechanism for changing the flow rate according to the opening degree of the valve.
The valve preferably has a choke structure, and as a mechanism for changing the flow rate depending on the opening degree of the valve, it is preferable that the valve has a step where the diameter of the valve changes midway.
It is preferable that the valve has a choke structure, and a mechanism in which the flow rate is changed depending on the opening degree of the valve is a combination of a plurality of the throttle structure mechanisms described above.
[0033]
In the part where the valve blocks the fuel flow path, at least one surface of the valve or flow path is made of a material having a property of reducing fuel leakage selected from silicone rubber, fluorine rubber, NBR, EPT, and urethane rubber. It is preferable to become.
It is preferable to have a taper at the portion of the shaft hole that contacts the valve body.
It is preferable to have a fuel buffer for temporarily storing fuel in the anode chamber.
A filter for preventing clogging of the valve is preferably provided between the fuel tank and the valve.
It is preferable to have a pressure reducing mechanism for reducing the fuel pressure between the fuel tank and the valve.
[0034]
It is preferable that the pressure reducing mechanism is made of a fuel resistance film.
It is preferable that the pressure reducing mechanism has a throttle shape.
It is preferable to have a relief valve in the fuel tank.
It is preferable to have a mechanism for reducing excess fuel in the anode chamber.
It is preferable to have a relief valve as a mechanism for reducing excess fuel in the anode chamber.
As a mechanism for reducing excess fuel in the anode chamber, it is preferable to generate power from the fuel cell.
[0035]
It is preferable that the valve for controlling the flow rate of fuel from the fuel tank has hysteresis.
As a mechanism for opening and closing the valve that controls the flow rate of fuel from the fuel tank, there is an electromagnet or permanent magnet on the fuel tank side adjacent to the valve body, and the valve body is made of iron, nickel, It is preferably made of a magnetic material selected from cobalt or a permanent magnet.
[0036]
As a mechanism for opening and closing the valve that controls the flow rate of fuel from the fuel tank, there is an electret material on the fuel tank side adjacent to the valve body of the valve or one of the valve bodies, and the other electret material Alternatively, it is preferably made of a dielectric.
[0037]
The present invention also relates to an electric device using the above fuel cell.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
The fuel cell according to the present invention includes a control mechanism that controls the amount of fuel supplied from the fuel tank using a pressure difference between the pressure in the fuel electrode chamber and the pressure in the oxidant electrode chamber or outside air.
[0039]
In the present invention, by providing the small valve between the fuel tank and the fuel battery cell according to the above configuration, the fuel battery cell is prevented from being broken due to a large pressure difference, and the start / stop of power generation is controlled to stabilize the generated power. Can be kept in.
[0040]
In particular, in the present invention, a diaphragm is used at the boundary between the fuel supply path and the oxidant supply path, and it is directly connected to the valve so that it is driven by the differential pressure between the fuel supply path and the oxidant supply path without using electricity. Thus, a pressure reducing valve that optimally controls the fuel pressure supplied to the fuel cell is realized.
[0041]
Further, the present invention minimizes the drive of the valve by controlling the flow rate of the fuel optimally by changing the flow resistance of the valve in accordance with the fuel tank pressure and the fuel consumption accompanying power generation. be able to.
Further, the present invention can optimally design the size, thickness, material, flow path width, valve size, etc. of the fuel film, and can suppress the vibration of the valve due to a small pressure difference.
[0042]
【Example】
A fuel cell equipped with the microvalve of the present invention will be described.
FIG. 1 is a perspective view showing an overview of the fuel cell of the present invention. FIG. 2 is a schematic diagram of the fuel cell system of the present invention. FIG. 3 is a plan view of the fuel cell of the present invention, and FIG. 4 is a front view of the fuel cell of the present invention. The outer dimension of the fuel cell is 50 mm × 30 mm × 10 mm, which is almost the same as the size of a lithium ion battery usually used in a compact digital camera.
[0043]
FIG. 20 is a schematic diagram when the fuel cell 50 of the present invention is mounted on a digital camera 51. Thus, since the digital camera of the present invention is small and integrated, it has a shape that can be easily incorporated into a portable device.
[0044]
The fuel cell of the present invention has vent holes 13 for taking in the outside air on the upper and lower surfaces and the side surfaces in order to take in oxygen used for the reaction as an oxidant from the outside air. The vent hole 13 also serves to release the generated water as water vapor and to release the heat generated by the reaction to the outside. On one side, there is an electrode 12 for taking out electricity. Inside, the polymer electrolyte membrane 112, the oxidant electrode 111 of the cell electrode, the fuel electrode 113, the fuel battery cell 11 comprising the catalyst, the fuel tank 16 for storing the fuel, the fuel tank and the fuel electrode of each cell are connected, The fuel supply unit 15 controls the flow rate of the fuel. The fuel supply unit 15 includes a differential pressure detection mechanism 17 that measures a pressure difference between a fuel electrode chamber 27 that supplies fuel to the fuel electrode and an oxidant electrode chamber 28 that supplies oxidant to the oxidant electrode, and supplies fuel in the fuel flow path. It is comprised by the micro valve 18 which controls. Moreover, when there is much water produced | generated with electric power generation, it may have the water holding part 14 which stores the produced | generated water.
[0045]
The fuel cell of the present invention has an electromotive force of 0.8 V and a current density of 300 mA / cm.² The unit cell size is 1.2 cm × 2 cm. By connecting eight fuel cells in series, the output of the entire battery is 4.6 W at 6.4 V and 720 mA.
[0046]
The fuel tank 16 will be described. The inside of the tank is filled with a hydrogen storage alloy capable of storing hydrogen. Since the pressure resistance of the polymer electrolyte membrane used in the fuel cell is 0.3 to 0.5 MPa, it is necessary to use the pressure difference with the outside air within a range of 0.1 MPa.
[0047]
As a hydrogen storage alloy, for example, LaNi_Five Etc., the release pressure of hydrogen is about 0.2 MPa at room temperature. If the volume of the fuel tank is half that of the entire fuel cell, the tank thickness is 1 mm, and the tank material is titanium, then the weight of the fuel tank is about 50 g, and the fuel tank volume is 5.2 cm.^Three become. LaNi_Five Can absorb and desorb 1.1 wt% of hydrogen per weight, so the amount of hydrogen stored in the fuel tank is 0.4 g, and the energy that can be generated is about 11.3 [W · hr]. It is about 4 times that of lithium ion batteries. In addition, a relief valve can be provided in the fuel tank in order to prevent the fuel pressure from excessively increasing due to a temperature change or the like.
[0048]
On the other hand, when a hydrogen storage material having a hydrogen release pressure exceeding 0.2 MPa at room temperature is used, it is necessary to provide a microvalve 18 for pressure reduction between the fuel tank and the fuel electrode.
[0049]
The hydrogen stored in the tank is supplied to the fuel electrode 113 through the fuel supply unit 15. Outside air is supplied to the oxidizer electrode 111 from the vent hole 13. Electricity generated by the fuel cell is supplied from the electrode 12 to a small electric device.
[0050]
FIG. 5 is a sectional view showing a pressure reducing valve as an example of a valve used in the present invention. The pressure reducing valve includes a diaphragm 23, a valve body 21, a valve shaft 22 directly connecting the valve body and the diaphragm, and a shaft hole 24 through which the valve shaft passes and fuel passes. Bellows may be used in place of the diaphragm. The diaphragm has one surface in contact with the fuel electrode chamber 27 and the other surface in contact with the oxidant electrode chamber (outside air). The valve body 21 is attached so as to block the fuel flow path 30 from the fuel tank 16 to the fuel electrode chamber 27. The overall size of the valve is within 1 cm square, and the size of the valve element is within 1 mm square. By realizing such a small valve mechanism, it is possible to incorporate a fuel flow rate control mechanism into a small fuel cell.
[0051]
In order to suppress leakage (leakage), a seal member 25 is coated on a portion where the valve body and the flow path are in contact with each other. An elastic body such as silicone rubber is effective for the seal member. The seal member may be attached to one or both of the flow path and the valve body.
[0052]
The valve opening / closing operation associated with the power generation of the fuel cell will be described below. During power generation stop, the valve is closed as shown in FIG. When power generation starts, the fuel in the anode chamber is consumed, and the fuel pressure in the anode chamber decreases. The diaphragm bends toward the fuel electrode chamber from the pressure difference between the external pressure and the pressure in the fuel electrode chamber (downward in the figure). Thereby, the valve directly connected to the diaphragm by the valve shaft is pushed down, and the valve is opened (FIG. 6A). As a result, fuel is supplied from the fuel tank to the anode chamber. When the pressure in the anode chamber is restored, the diaphragm is pushed up and the valve is closed at the same time.
[0053]
Since the valve will not open unless the pressure in the anode chamber is lower than the external pressure, the anode chamber will be damaged and fuel will leak, or even if the valve is broken, the valve will be closed and the fuel will leak from the tank. Can be prevented.
[0054]
A diaphragm or a bellows can be used for the differential pressure detection portion. The bellows 31 has a characteristic that a large displacement can be obtained with a small pressure difference in the structure shown in FIG. Examples of bellows materials include stainless steel, phosphor bronze, and beryllium.
[0055]
On the other hand, the diaphragm 23 has a simple structure and is easy to manufacture. Diaphragms are largely divided into non-metallic diaphragms FIG. 7 (a) and metallic diaphragms FIG. 7 (b) depending on materials and structures. Non-metallic material diaphragms use elastic materials such as rubber and have a very simple structure. However, metal diaphragms are more difficult in terms of strength and resistance to leakage at joints with support members. Are better. In addition, the metal diaphragm is superior in strength at the joint with the valve shaft. Metal diaphragms are often shaped into corrugations to obtain greater displacement. Non-metallic material diaphragm materials include silicone rubber, fluororubber, NBR, EPT, urethane rubber, and the like. Metal diaphragm materials include stainless steel, beryllium, hastelloy, cantal, and brass.
[0056]
When the radius of the diaphragm is 1 [mm], the thickness is about 0.6 [μm] when the material is silicone rubber, and the thickness is 0.06 [μm] or more when the material is aluminum. It has sufficient strength. These materials can be appropriately selected according to the design guidelines, shapes, and manufacturing methods described below.
[0057]
The characteristics of the differential pressure detection mechanism will be described using a silicone rubber diaphragm as an example. The displacement ω at the center when a uniform pressure is applied to a peripheral fixed disk having a radius r and a thickness h is expressed by the following equation.
[0058]
[Expression 1]

[0059]
However,
[0060]
[Expression 2]

It is.
[0061]
Where E is Young's modulus and m is Poisson's ratio (^-1), P is pressure. When the diaphragm radius is 1 [mm] and the thickness is 0.1 [mm], the Young's modulus of the silicone rubber is 4.95 [MPa], m^-1= 0.45, the deflection of the central portion when the differential pressure is applied to the diaphragm is 0.01 MPa (about 0.1 [atm]) is about 0.3 [mm]. Therefore, the diaphragm spring constant k = P × πr² /Ω=103.9 [N / m].
[0062]
The density of the silicone rubber is 1.2 [g / cm.^Three ], The diaphragm mass is 0.38 [mg]. Therefore, the natural frequency f of the diaphragm is about 16.6 [kHz].
[0063]
By adjusting the length of the shaft, the pressure P of the anode chamber when the valve opens₂₀Can be changed. The difference between the distance from the differential pressure detection mechanism to the valve and the shaft length is x₀ Then, the valve has a pressure in the anode chamber,
[0064]
[Equation 3]

It will open when it becomes.
[0065]
In order to reduce the friction between the valve shaft and the shaft hole, the surface of the shaft and the shaft hole is coated with a material having a friction reducing property such as Teflon (registered trademark), or the fuel passing between the shaft and the shaft hole It is also possible to use it as a gas bearing using the flow. As for the gas bearing, the effect can be expected even with a normal valve, shaft hole, and shaft configuration, but if the structure as shown in FIGS. 8A to 8C is used, the effect of the bearing is further enhanced. .
[0066]
Further, when the pressure in the fuel electrode chamber is excessively increased, a stopper mechanism 26 can be provided on the oxidant electrode chamber side of the diaphragm in order to prevent damage to the diaphragm and the valve. In order to prevent the pressure of the oxidant electrode chamber (outside air) from being transmitted to the diaphragm by the stopper mechanism, the stopper mechanism is made of a porous material or has a vent hole. The stopper mechanism can also serve as a support member that prevents the power generation cells of the fuel cell from contacting each other.
[0067]
On the other hand, even when the pressure in the oxidant electrode chamber is excessive with respect to the pressure in the fuel electrode chamber, a stopper mechanism can be provided. As shown in FIG. 19A, the stopper mechanism 26 can be installed on the fuel electrode chamber side of the diaphragm 23 so as to stop the movement of the diaphragm. Further, as shown in FIG. 19B, it is possible to use a fuel flow path wall. Moreover, as shown in FIG.19 (c), it is also possible to install so that the movement of the microvalve 18 may be stopped.
[0068]
The strength of the material will be described below. The fuel tank can be thinned to about 1 mm when the material is stainless steel and about 0.8 mm when the material is stainless steel when the tank internal pressure is 0.5 MPa (about 5 atm) and the safety factor is 5. . A thickness of about 0.5 mm is sufficient for a plate member having a valve shaft hole. Furthermore, if the reinforcing member 29 is attached to the hole plate, the thickness of the hole plate itself can be reduced to 0.2 [mm] when stainless steel is used.
[0069]
The hydrogen consumption in the fuel cell is as follows. Reaction at the fuel electrode is H₂ → 2H⁺ + 2e^- It is. Accordingly, the hydrogen consumption when a current of 1 [A] is passed is 5.1 × 10 5.^-6  [Mol / s], that is, 114 [mm in the standard state^Three / S]. On the other hand, LaNi in the tank_Five And the volume is 5.15 [cm^Three ], The hydrogen release rate at each temperature is as shown in Table 1 below. Therefore, in this fuel cell, hydrogen can be supplied from the tank sufficiently faster than the hydrogen consumption.
[0070]
[Table 1]

[0071]
In this example, the volume of the anode chamber between the fuel cells is 750 [mm because the entire fuel cell is very small and thin.^Three It is small compared to the hydrogen flow rate accompanying power generation. Therefore, a buffer mechanism for mitigating a rapid change in the fuel flow rate can be provided in the fuel electrode cell in the fuel cell. For example, if an area of 8 × 28 × 3.6 [mm] is provided as a buffer between the power generation cell and the fuel tank, the volume of the buffer area is 805 [mm]^Three Thus, the volume of the entire fuel electrode chamber can be expanded to twice.
[0072]
Further, it is possible to provide a mechanism for lowering the pressure when the fuel pressure suddenly increases in the fuel electrode chamber. For reducing the pressure, a method of providing a relief valve or a method of generating power excessively and consuming fuel are effective.
[0073]
LaNi_Five The change in dissociation pressure with temperature is shown in Table 2 below. From Table 2, when the fuel cell of the present invention is mounted on a small electric device such as a digital camera, the pressure of the fuel tank is about 0.1 to 0.4 MPa.
[0074]
[Table 2]

[0075]
As shown in FIG.₀ , P for fuel tank pressure₁ , P₂ And the area of the bottom of the valve is S₁ , Diaphragm area S₂ Then, from the balance of pressure, the condition for opening the valve is P₀0.1 MPa (about 1 [atm]), (P₁ -P₂ ) S₁ <(P₀ -P₂ ) S₂ It becomes. Therefore, S₁ And S₂ By determining the pressure P of the anode chamber when the valve opens.₂₀Can be designed optimally. For example, S₁ : S₂ = 1: 16, various P₁ P in₂₀Is shown in Table 3 below. In this case, P₁ Is about 0.4 MPa (about 4 [atm]) or less, the valve operates properly.₁ When the value becomes extremely high, the valve does not open and power generation stops, so that the valve functions as a safety device.
[0076]
[Table 3]

[0077]
Various valve shapes are possible. For example, the throttle shape of the valve can be an orifice as shown in FIG. Assuming that the fuel is a specific compression fluid, the flow rates Q and P through the valve₁ And P₂ Is expressed by the following equation.
[0078]
[Expression 4]

[0079]
Where A is the aperture area and C_d Is the flow coefficient and ρ is the density of the fluid. C_d = 0.7, ρ = 0.0899 [kg / m^Three Table 4 below shows the relationship between A, Q, and ΔP when hydrogen is in the hydrogen standard state. It can be seen that the orifice diameter is about 10 [μm] in order to obtain a sufficient flow rate for power generation.
[0080]
[Table 4]

[0081]
Further, as one of the orifice shapes, the valve shape may be a sphere as shown in FIG.
In order to obtain a larger pressure reducing effect, the throttle shape of the valve can be a choke throttle as shown in FIG. In this case, the relationship between the flow rate and pressure at the valve is expressed as follows.
[0082]
[Equation 5]

[0083]
Here, μ is a viscosity coefficient, ΔP is a pressure difference before and after throttling, D is a throttling hole diameter, and L is a length of the throttling portion. μ = 8.8 × 10^-6When [Pa / s] and L = 0.5 [mm], the flow rate at various hole diameters and the differential pressure (P₁ And P₂ The pressure difference is as shown in Table 5 below. Accordingly, an appropriate hole diameter is about 25 to 75 μm.
[0084]
[Table 5]

[0085]
The shape 32 of the choke diaphragm can be obtained by a method in which one or more grooves 33 parallel to the shaft are provided in accordance with the required resistance of the diaphragm (FIG. 13A), or the valve shaft passes through the center of the shaft hole. A method of using the gap 34 as a flow path (FIG. 13B), a method of providing an uneven groove 35 perpendicular to the shaft (FIG. 13C), and a method of providing a screw-like groove 36 on the shaft (FIG. 13). (D)) and a method of providing a portion made of the porous material 37 on the shaft (FIG. 13E) can also be used. For example, in the case of FIG. 13A, assuming that there are n small channels having a hole diameter d, the relationship between the flow rate and the differential pressure is expressed as follows.
[0086]
[Formula 6]

[0087]
In the case of FIG. 13B, when the width of the circular flow path is h and the radius is r, the relationship between the flow rate and the differential pressure is expressed as follows.
[0088]
[Expression 7]

[0089]
However, with these valve mechanisms alone, the resistance at the throttle portion does not change, so it is difficult to control the fuel flow rate step by step, the fuel flow rate is too high, and the valve must be closed frequently. There arises a problem that it is difficult to obtain a sufficient flow rate. Therefore, the valve of the present invention changes the opening degree of the valve that controls the flow rate of the fuel from the fuel tank according to the differential pressure between the pressure in the fuel electrode chamber and the oxidant electrode chamber or the outside air and the pressure in the fuel tank. By doing so, the flow rate of the fuel is controlled, and the supply amount of the fuel is controlled to be equal to the consumption amount of the fuel. The mechanism for realizing this function will be described in detail below.
[0090]
In the valve of the present invention, the flow path resistance at the valve portion decreases as the valve opens. This can be achieved to the extent that the resistance of the valve body can be achieved even with a normal orifice or choke valve. For example, as shown in FIG. 14A, the valve body 21 and the valve shaft hole 24 have a taper. It is more effective to use the touching method. In this case, as the valve is opened, the flow path width is increased, so that the flow rate is increased. As another mechanism for reducing the flow path resistance at the valve portion as the valve opens, there is a method in which the valve shaft diameter changes in a tapered shape as shown in FIG. In this case, a plurality of grooves having a tapered structure may be provided. Further, as shown in FIG. 14C, there is a method of providing a step where the diameter of the valve changes midway. Further, as shown in FIG. 14D, only a part of the valve can be provided with a mechanism for providing a throttling effect. In addition, it is possible to combine a plurality of shapes having different aperture effects.
[0091]
These mechanisms operate as follows. When the pressure difference between the fuel electrode chamber and the oxidant electrode chamber (outside air) increases or the pressure of the fuel tank decreases, the amount of deflection of the diaphragm increases, and the valve moves accordingly. As the valve opens, the flow resistance at the valve portion decreases, so the flow rate increases. The valve is a position where the spring force is balanced by the differential pressure between the fuel electrode chamber and the oxidant electrode chamber (outside air) and the deflection of the diaphragm, that is, the position where the amount of fuel consumed by power generation is equal to the flow rate of fuel from the fuel tank. It will rest stably. Therefore, this valve opens when the fuel cell starts power generation, and stops at the position where fuel equal to the fuel consumption is supplied from the fuel tank to the anode chamber, and closes when power generation is stopped. For this reason, it is possible to supply the fuel without repeating the opening and closing of the valve frequently during the power generation, or without the shortage of the fuel supply when the power generation amount increases.
[0092]
The relationship between the displacement of the diaphragm and the flow rate when the valve body and the valve shaft are in contact with each other as shown in FIG. 15 will be specifically described. The relationship between the flow rate Q at the valve and the displacement x of the valve is expressed as follows. Where k is the diaphragm spring constant, r is the channel hole radius, φ is the valve taper angle, L₁ Is the height of the tapered portion.
[0093]
[Equation 8]

[0094]
On the other hand, the pressure P when the valve opens₂₀Is expressed as follows.
[0095]
[Equation 9]

Also,
[0096]
[Expression 10]

Therefore,
[0097]
## EQU11 ##

It becomes.
[0098]
Based on the above formula, the size of the specific aperture shape is shown.
P₀ = 0.1 [Mpa] (about 1 atm), μ = 8.8 × 10^-6[Pa / s], k = 104 [N / m], S₁ = 0.196 [mm² ] (Diameter 500 [μm]), S₂ = 3.14 [mm² ] (Diameter 2 [mm]), D = 300 [μm] (r = 200 [μm]), L = 500 [m], L₁ = 100 [μm] = 45 ° (FIG. 16),
When the valve is displaced the smallest (P₁ = 0.4 [MPa] (about 4 atm), Q = 22.8 [mm^Three ] (1 [W] power generation)), P₂₀= 0.081 [MPa] (about 0.8 atm) and x = 0.93 [μm].
[0099]
If the valve is displaced the most (P₁ = 0.15 [MPa] (about 1.5 atm), Q = 228 [mm^Three ] (10 [W] power generation))₂₀= 0.097 [MPa] (about 0.97 atm), x = 4.95 [[mu] m].
[0100]
P₀ = 0.1 [Mpa] (about 1 atm), μ = 8.8 × 10^-6[Pa / s], k = 104 [N / m], S₁ = 0.196 [mm² ] (Diameter 500 [μm]), S₂ = 3.14 [mm² ] (Diameter 2 [mm]), D = 200 [μm] (r = 175 [μm]), L = 500 [m], L₁ = 100 [μm] = 60 ° (FIG. 17),
When the valve is displaced the smallest (P₁ = 0.4 [MPa] (about 4 atm), Q = 22.8 [mm^Three ] (1 [W] power generation)), P₂₀= 0.081 [MPa] (about 0.8 atm) and x = 1.02 [μm].
[0101]
If the valve is displaced the most (P₁ = 0.15 [MPa] (about 1.5 atm), Q = 228 [mm^Three ] (10 [W] power generation))₂₀= 0.097 [MPa] (about 0.97 atm) and x = 5.44 [μm].
[0102]
In order to provide a difference between the pressure at which the valve opens and the pressure at which it closes, the valve can be provided with a hysteresis mechanism. Specifically, as shown in FIG. 18 (a), an electromagnet or permanent magnet 41 is installed on the fuel tank side adjacent to the valve body of the valve, and the permanent magnet, iron, nickel, A portion 40 made of a magnetic material such as cobalt is provided. As shown in FIG. 18B, both the valve body of the valve and the portion 42 made of electret on the fuel tank side adjacent to the valve body, or one of them is a dielectric. By providing the portion consisting of the two, when the valve is opened, they are attracted to each other, and the valve is difficult to close.
[0103]
The fuel cell of the present invention can be particularly suitably used for portable small electric devices such as digital cameras, digital video cameras, small projectors, small printers, and notebook computers.
[0104]
【The invention's effect】
As described above, according to the fuel cell of the present invention, a small pressure reducing valve that is a very small valve that can be mounted on a small fuel cell is used to suppress vibration caused by a minute pressure change of the pressure reducing valve. In addition, the generated power can be supplied stably.
[0105]
In particular, in a large-capacity, high-power fuel cell that can be mounted on a small electric device that can be carried and used, the pressure from the fuel tank is optimally reduced to a fuel cell without using electricity for control and drive. As a result, the fuel cell can be prevented from being broken by a large differential pressure, and power generation can be started and stopped, and stable power can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a fuel cell of the present invention.
FIG. 2 is a schematic view showing a fuel cell system of the present invention.
FIG. 3 is a plan view of the fuel cell of the present invention of FIG.
4 is a front view of the fuel cell of the present invention shown in FIG. 1. FIG.
FIG. 5 is a schematic view of a valve (pressure reducing valve) used in the present invention.
FIG. 6 is an operation diagram of a valve used in the present invention.
FIG. 7 is a schematic view of a diaphragm used in the present invention.
FIG. 8 is a schematic view of a radial gas bearing used in the present invention.
FIG. 9 is a schematic view of a valve used in the present invention.
FIG. 10 is a schematic view of a valve having an orifice restriction used in the present invention.
FIG. 11 is a schematic view of a valve having a spherical valve body according to the present invention.
FIG. 12 is a schematic view of a valve having a choke stop in the present invention.
FIG. 13 is a schematic view showing the structure of a choke stop having a plurality of flow channel grooves in the present invention.
FIG. 14 is a schematic view showing a relationship between a valve body and a shaft hole of a valve in the present invention.
FIG. 15 is a schematic view showing a choke valve in which a valve body and a shaft hole of the valve according to the present invention are in contact with each other with a taper.
FIG. 16 is a schematic view showing a choke valve in which a valve body and a shaft hole of the valve according to the present invention are in contact with each other with a taper.
FIG. 17 is a schematic view showing a choke valve in which a valve body and a shaft hole of the valve according to the present invention are in contact with each other with a taper.
FIG. 18 is a schematic view showing a hysteresis mechanism in which a magnet or a magnetic part is provided on the valve body and tank side of the valve in the present invention.
FIG. 19 is a schematic view showing an example of a stopper when the oxidant electrode chamber pressure is excessive with respect to the fuel electrode chamber pressure in the present invention.
FIG. 20 is a schematic diagram when the fuel cell of the present invention is mounted on a digital camera.
[Explanation of symbols]
11 Fuel cell
111 Oxidant electrode
112 Polymer electrolyte membrane
113 Fuel electrode
12 electrodes
13 Vent
14 Water retention department
15 Fuel supply section
16 Fuel tank
161 Fuel inlet
17 Differential pressure detection mechanism
18 Micro valve
21 Disc
22 Valve shaft (valve shaft)
23 Diaphragm
24 Shaft hole
25 Seal member
26 Stopper mechanism
27 Fuel electrode chamber
28 Oxidant electrode chamber
29 Reinforcing member
30 Fuel flow path
31 Bellows
32 Shape of choke diaphragm
33 groove
34 Clearance
35 Uneven groove
36 Screw-shaped groove
37 Porous material
50 Fuel cell
51 digital camera

Claims (13)

An oxidant electrode chamber; a fuel electrode chamber; a fuel tank containing fuel to be supplied to the fuel electrode chamber; a fuel flow path connecting the fuel electrode chamber and the fuel tank; the road, by using the differential pressure between the pressure of the fuel electrode chamber and the pressure of the fuel tank, the pressure difference between the pressure and the oxidizing agent electrode chamber or outside air pressure of the fuel electrode chamber, from the fuel tank A fuel cell comprising a control mechanism for controlling the amount of fuel supplied to the fuel electrode chamber , wherein the control mechanism for controlling the amount of fuel supplied comprises the pressure in the fuel electrode chamber and the oxidant electrode chamber or outside air. A differential pressure detection mechanism comprising a diaphragm or a bellows for detecting a differential pressure with respect to the pressure of the fuel, a valve having a throttle mechanism for controlling a fuel flow rate, and the valve for connecting the differential pressure detection mechanism and the valve Consisting of a connecting mechanism consisting of Fuel cell and features.   2. The fuel cell according to claim 1, wherein the throttle mechanism for controlling the flow rate of the fuel in the valve has an orifice structure.   The fuel cell according to claim 2, wherein a valve body of the valve having the orifice structure is substantially spherical.   2. The fuel cell according to claim 1, wherein the throttle mechanism for controlling the flow rate of fuel in the valve has a choke structure.   5. The fuel cell according to claim 4, wherein the choke structure has one or more grooves parallel to the valve axis.   The fuel cell according to claim 4, wherein the choke structure has an uneven groove perpendicular to the axis of the valve.   The fuel cell according to claim 4, wherein the choke structure has a screw-like groove on a shaft of the valve.   The fuel cell according to claim 4, wherein the choke structure has a portion made of a porous material on a shaft of the valve. Differential pressure between the pressure and the pressure of the fuel electrode chamber of the fuel tank, according to a differential pressure between the pressure and the oxidizing agent electrode chamber or outside air pressure of the fuel electrode chamber, the flow rate of fuel from the fuel tank 9. A control mechanism comprising a control mechanism for controlling a flow rate of fuel by changing an opening degree of a valve to be controlled so that a fuel supply amount becomes equal to a fuel consumption amount. The fuel cell according to any one of the above.   10. The fuel cell according to claim 9, wherein the valve has a choke structure, and the valve body and the shaft hole are tapered as a mechanism for changing a flow rate according to an opening degree of the valve.   10. The fuel cell according to claim 9, wherein the valve has a choke structure, and the valve shaft is tapered as a mechanism for changing a flow rate according to an opening degree of the valve.   10. The fuel cell according to claim 9, wherein the valve has a choke structure, and has one or more tapered grooves as a mechanism for changing a flow rate according to an opening degree of the valve.   10. The fuel cell according to claim 9, wherein the valve has a choke structure, and the mechanism in which the flow rate changes according to the opening of the valve has a step in which the diameter of the valve changes midway.

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