JP2004125165A - Rolling bearing for fuel cell system, and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing for fuel cell system capable of providing increased durability by suppressing the internal start point peeling accompanying white texture change caused by hydrogen of the rolling bearing incorporated in a force-feeding machine for force-feeding various types of fluid to devices in a fuel cell system and the fuel cell system capable of stably generating power over a long period of time. <P>SOLUTION: This rolling bearing is incorporated in the force-feeding machine of the fuel cell system having at least a fuel cell stack and the force-feeding machine for transporting various types of fluid. A grease compound containing conductive substance of 0.1 to 10mass% or a grease compound substantially not containing sulphonate is sealed in the rolling bearing. The fuel cell system comprises the force-feeding machine having the rolling bearing for fuel cell system. <P>COPYRIGHT: (C)2004,JPO

Description

【００５１】
式中、Ｒ_１は炭素数７〜１２の芳香族環含有炭化水素基を示し、Ｒ_２は炭素数６〜１５の２価の芳香族環含有炭化水素基を示し、Ｒ_３はシクロヘキシル基または炭素数７〜１２のアルキルシクロヘキシル基を示す。特に、一般式（１）〜（３）で表されるジウレア化合物中の［Ｒ_１のモル数／（Ｒ_１のモル数＋Ｒ_３のモル数）］値が０〜０．５５であるジウレア化合物が好ましい。
【００５２】
尚、基油としてパーフルオロポリエーテル（ＰＦＰＥ）等のフッ素油を用いる場合は、増ちょう剤としてポリテトラフルオロエチレン（ＰＴＦＥ）等のフッ素樹脂を配合することが望ましい。
【００５３】
（含有量）
増ちょう剤のグリース組成物における含有量は、上記の基油とともにゲル構造を維持できる量であれば、特に制限されるものではない。但し、後述する導電性物質として好適なカーボンブラックはそれ自身増ちょう剤として機能するため、導電性物質としてカーボンブラックを選択した場合は、このカーボンブラックと増ちょう剤との合計量でグリース組成物全量に対して５〜４０質量％、好ましくは８〜３０質量％の範囲とする。尚、この場合も、カーボンブラックの添加量は、後述される導電性物質としての好適な範囲とする。
【００５４】
［導電性物質］
導電性物質は、導電性が良好な物質であれば特に制限されるものではなく、また液体であっても固体であっても良い。中でも、取り扱いや入手のし易さ、潤滑性を低下させない等の理由からカーボンブラックを用いることが好ましい。また、このカーボンブラックは、グリース組成物中での分散性や音響特性等を考慮すると、平均粒径で１０〜３００ｎｍ程度のものを選択することが好ましい。
【００５５】
また、導電性物質として、カーボンナノチューブも好適に使用することができる。このカーボンナノチューブは、図９に模式的に示されるように、主に炭素六員環の網目状構造が丸まって、両末端が閉口したチューブ状を呈する炭素多面体である。尚、異径のチューブ接合部や末端の閉口部においては、炭素５員環や炭素７員環となっている場合もある。また、カーボンナノチューブ類として球状構造を採るものがあり、例えばＣ_６０、Ｃ_７０はフラーレンとして知られているが、本発明においてはこのフラーレンも使用できる。これらカーボンナノチューブは、直径が０．５〜１５ｎｍで、長さ０．５〜５０μｍのものが特に好ましい。
【００５６】
（濃度）
導電性物質の添加量の好ましい添加量は、グリース組成物全量に対して０．１〜１０質量％である。添加量が０．１質量％より少ないと、十分な導電性が付与されずに白色組織変化に伴う内部起点剥離が起こりやすくなり、１０質量％より多く含有するとグリースが硬化し、焼付き寿命が低下するおそれがあるため好ましくない。導電性を確かにして前記剥離を起こさず、焼付き寿命も向上させるには、導電性物質をグリース組成物全量に対して０．５〜５質量％添加することが望ましい。また、導電性物質添加後のグリースちょう度が、ＮＬＧＩ　Ｎｏ．１〜３であることが、より望ましい。
【００５７】
［その他の添加剤］
潤滑性能をより一層高めるために、必要に応じて酸化防止剤、極圧剤、油性剤、防錆剤、金属不活性剤、粘度指数向上剤等種々の添加剤を単独で、もしくは適宜組み合わせてグリース組成物に添加することができる。これらは何れも公知のもので構わず、また添加量も特に制限されるものではないが、通常は合計でグリース組成物全量の２０質量％以下となるように添加される。
【００５８】
［製法］
上記グリース組成物を調製する方法には特に制約はない。しかし、一般的には基油中で増ちょう剤を反応させて得られる。導電性物質は、得られたグリース組成物に所定量を配合することが好ましい。但し、ニーダやロールミル等で導電性物質を添加した後に十分攪拌し、均一分散させる必要がある。この処理を行うときは、加熱するものも有効である。尚、上記製法において、酸化防止剤、防錆剤等のその他の添加剤は、導電性物質と同時に添加することが工程上好ましい。
【００５９】
（２）第２のグリース組成物
第２のグリース組成物は、水素脆性剥離の発生源となるスルフォン酸塩を実質的に含有しないことを特徴とする。尚、スルフォン酸塩はエプトン法で検出できることが知られており、本発明においてもこのエプトン法によりスルフォン酸塩の有無を確認する。
【００６０】
［基油及び増ちょう剤］
基油及び増ちょう剤として、第１のグリース組成物に使用される基油及び増ちょう剤を使用できる。但し、基油の４０℃における動粘度は、好ましくは５０〜６００ｍｍ^２／ｓｅｃ、より好ましくは７０〜５００ｍｍ^２／ｓｅｃ、更に好ましくは１００〜４５０ｍｍ^２／ｓｅｃである。また、増ちょう剤の含有量は、グリース全量中１０〜３５質量％とすることが好ましい。
【００６１】
［添加剤］
添加剤として、下記に示すナフテン酸塩やコハク酸誘導体を添加することが好ましい。
（ナフテン酸塩）
ナフテン核を有する飽和カルボン酸塩であればよく、特に制約はない。主に、飽和単環カルボン酸塩Ｃ_ｎＨ_２ｎ−１ＣＯＯＭ、飽和複環カルボン酸塩Ｃ_ｎＨ_２ｎ−３ＣＯＯＭ、脂肪族カルボン酸塩Ｃ_ｎＨ_２ｎ＋１ＣＯＯＭ、及びこれらの誘導体が挙げられる。例えば、単環のカルボン酸塩では、以下を挙げることができる。
【００６２】
【化２】

【００６３】
上式中、Ｒ_４は炭化水素基を示しており、アルキル基、アルケニル基、アリール基、アルカリール基、アラルキル基等が挙げられる。また、Ｍは金属元素を示しており、Ｃｏ，Ｍｎ，Ｚｎ，Ａｌ，Ｃａ，Ｂａ，Ｌｉ，Ｍｇ，Ｃｕ等である。これらのナフテン酸塩は、単独でも適宜組み合わせて使用してもよい。
【００６４】
（コハク酸誘導体）
コハク酸誘導体としては、具体的にそれぞれ以下の化合物を挙げることができる。例えば、コハク酸、アルキルコハク酸、アルキルコハク酸ハーフエステル、アルケニルコハク酸、アルケニルコハク酸ハーフエステル、コハク酸イミド等を挙げることができる。これらのコハク酸誘導体は、単独でも適宜組み合わせて使用してもよい。
【００６５】
上記のナフテン酸塩及びコハク酸誘導体は、それぞれ単独でもよいし、併用してもよい。単独使用及び併用の場合とも、その好ましい添加量は、グリース組成物全量に対して０．１〜１０質量％である。添加量がこれより少ないと、十分な防錆性を有することができず、これより多く含有するとグリースが軟化し、グリース漏れを発生させる恐れがあるため好ましくない。防錆性を確かにし、グリース漏れによる焼付き寿命を考慮するなら、グリース組成物全量に対して０．２５〜５質量％とすることが望ましい。
【００６６】
更に耐剥離性能を向上させるために、下記に示す有機金属塩を添加することがより望ましい。
【００６７】
（有機金属塩）
有機金属塩として、下記一般式（４）で示されるジアルキルジチオカルバミン酸（ＤＴＣ）系化合物や、下記一般式（５）で示されるジアルキルジチオリン酸（ＤＴＰ）系化合物を好適に使用することができる。
【００６８】
【化３】

【００６９】
式中、Ｍは金属種を示し、具体的には、Ｓｂ，Ｂｉ，Ｓｎ，Ｎｉ，Ｔｅ，Ｓｅ，Ｆｅ，Ｃｕ，Ｍｏ，Ｚｎが使用される。Ｒ_５、Ｒ_６は、同一基であっても、異なる基であってもよく、アルキル基、シクロアルキル基、アルケニル基、アリール基、アルキルアリール基、または、アリールアルキル基を示す。特に好ましい基としては、１，１，３，３−テトラメチルブチル基、１，１，３，３−テトラメチルヘキシル基、１，１，３−トリメチルヘキシル基、１，３−ジメチルブチル基、１−メチルウンデカン基、１−メチルヘキシル基、１−メチルペンチル基、２−エチルブチル基、２−エチルヘキシル基、２−メチルシクロヘキシル基、３−ヘプチル基、４−メチルシクロヘキシル基、ｎ−ブチル基、イソブチル基、イソプロピル基、イソヘプチル基，イソペンチル基、ウンデシル基、エイコシル基、エチル基、オクタデシル基、オクチル基、シクロオクチル基、シクロドデシル基、シクロペンチル基、ジメチルシクロヘキシル基、デシル基、テトラデシル基、ドコシル基、ドデシル基、トリデシル基、トリメチルシクロヘキシル基、ノニル基、プロピル基、ヘキサデシル基、ヘキシル基、ヘニコシル基、ヘプタデシル基、ヘプチル基、ペンタデシル基、ペンチル基、メチル基、第三ブチルシクロヘキシル基、第三ブチル基、２−ヘキセニル基、２−メタリル基、アリル基、ウンデセニル基、オレイル基、デセニル基、ビニル基、ブテニル基、ヘキセニル基、ヘプタデセニル基、トリル基、エチルフェニル基、イソプロピルフェニル基、第三ブチルフェニル基、第二ペンチルフェニル基、ｎ−ヘキシルフェニル基、第三オクチルフェニル基、イソノニルフェニル基、ｎ−ドデシルフェニル基、フェニル基、ベンジル基、１−フェニルメチル基、２−フェニルエチル基、３−フェニルプロピル基、１，１−ジメチルベンジル基、２−フェニルイソプロピル基、３−フェニルヘキシル基、ベンズヒドリル基、ビフェニル基等があり、またこれらの基はエーテル結合を有しても良い。
【００７０】
また、その他の有機金属塩として、下記一般式（６）〜（８）で示される有機亜鉛化合物も使用することができる。
【００７１】
【化４】

【００７２】
式中、Ｒ_７、Ｒ_８は、炭素数Ｃ_ｎがｎ＝１〜１８の炭化水素基または水素原子を示し、Ｒ_７、Ｒ_８は同一の基であっても異なる基であってもよい。特に、Ｒ_７、Ｒ_８が共に水素原子であるメチルカプトベンゾチアゾール亜鉛（一般式（６））、ベンゾアミドチオフェノール亜鉛（一般式（７））、及びメルカプトペンゾイミダゾール亜鉛（一般式（８））を好適に使用することができる。
【００７３】
更に、その他の有機金属塩として、下記一般式（９）で示されるアルキルキサントゲン酸亜鉛も使用することができる。
【００７４】
【化５】

【００７５】
式中、Ｒ_９は、炭素数Ｃ_ｎがｎ＝１〜１８の炭化水素基を示す。
【００７６】
尚、上記の一般式（４）〜（９）で表される有機金属塩は、各々単独で、または２種以上混合して使用することができるが、組合せについては特に限定されるものではない。また、有機金属塩は微小隙間に反応膜を形成して白色組織変化剥離を抑制する作用効果を有するが、添加量０．１質量％未満では十分な効果を発揮することができない。一方、添加量の上限は特に限定する必要は無いとも考えられるが、上述した有機金属塩は比較的高価であり、また過剰な添加は軸受材料との反応を異常に促進して、逆に焼付き性能を阻害するため、添加量を０．１〜１０質量％にすることが好ましい。より好ましくは、０．５〜１０質量％である。
【００７７】
また、上記したナフテン酸塩、コハク酸塩または有機金属塩は、第１のグリース組成物においてその他の添加剤として例示された添加剤と適宜併用することもできる。
【００７８】
［製法］
グリース組成物の調製方法は、第１のグリース組成物の調製方法に準ずることができ、基油中で増ちょう剤を反応させ、得られたグリース組成物に上記した添加剤を所定量配合し、必要に応じて加熱しながら、ニーダやロールミル等で十分攪拌して均一に分散させる。
【００７９】
【実施例】
以下に実施例及び比較例を挙げて本発明を更に説明するが、本発明はこれにより何ら制限されるものではない。
【００８０】
（実施例１）
ジイソシアネートを混合した基油（エーテル油；４０℃における動粘度１００ｍｍ^２／ｓｅｃ）に、アミンを混合した同一種の基油を反応させ、攪拌加熱して得られた半固体状物に、予め同一種の基油に溶解したアミン系酸化防止剤を加えて十分攪拌した。徐冷後、前記の半固形状物に、カーボンブラック（平均粒径３０ｎｍ）を、グリース全量に対して０．１〜１０質量％となるように添加量を変えて加え、ロールミルを通してカーボンブラックの添加量が異なる各種試験グリースを得た。
【００８１】
尚、上記において、カーボンブラックの添加量に応じて、増ちょう剤であるウレア化合物とカーボンブラックとの合計量がグリース全量に対して２０質量％で一定となるように調整した。また、試験グリースのちょう度をＮＬＧＩ　Ｎｏ．１〜３に調整した。
【００８２】
（比較例１、比較例２）
また、比較のために、何れもグリース全量に対して、ウレア化合物が１９．９５質量％で、カーボンブラックが０．０５質量％（比較例１）、ウレア化合物が８質量％で、カーボンブラックが１２質量％となるように、実施例１と同様の操作により試験グリースを調製した。
【００８３】
上記の各試験グリースを用い、以下の試験を行った。
（急加減速試験）
内径φ１７ｍｍ、外径φ４７ｍｍ、幅１４ｍｍの接触ゴムシール付き単列深溝玉軸受（図４参照）に、各試験グリースを２．３ｇ封入して試験軸受を作製し、図１０に示す試験装置を用いて剥離寿命を評価した。図示される試験装置において、一対の支持用軸受３７１，３７１で支持されたシャフト３７０の端部に試験軸受３７５の内輪を嵌合させ、更に外輪をホルダー３７２に固定し、プーリー３７３を介してエンジン（図示せず）からの回転を試験軸受３７５に伝達する。尚、符号３７４は外輪温度を測定するための温度計であり、符号３７６は外輪を加熱するためのヒータである。そして、軸受回転速度２４００〜１３３００ｍｉｎ^−１の繰り返し、室温雰囲気下、プーリー荷重１５６０Ｎの条件で軸受を連続回転させ、５００時間を目標に試験を行った。そして、試験軸受３７５の外輪転走面に剥離が生じて振動が発生したとき、あるいは剥離が発生しない場合には５００時間経過した時点で試験を終了した。試験は各１０回行い、下記式により剥離発生確率を算出した。
剥離発生確率＝（剥離発生回数／試験回数）×１００
【００８４】
（含水焼付き試験）
内径φ１７ｍｍ、外径φ４７ｍｍ、幅１４ｍｍの接触ゴムシール付き単列深溝玉軸受に試験グリースを１．０ｇ封入して試験軸受を作製し、図１１に示す試験装置を用いて焼付き寿命を評価した。図示される試験装置は、回転用シャフト３６０を一対の支持用軸受３６２，３６２で支持し、その中間部に試験軸受３６１を装着し、更に全体を所定温度に維持できるように恒温容器（図示せず）に収容する構成となっている。試験に際し、シャフト３６０を回転させて試験軸受３６１を内輪回転速度２０００ｍｉｎ^−１、軸受温度１２０℃、ラジアル荷重９８Ｎ、アキシアル荷重９８Ｎの条件で連続回転させた。また、２４時間毎に回転を止めて、注射器で０．３ｍｌの水を軸受内部に注入した。そして、焼付きが生じて軸受外輪温度が１３０℃以上に上昇したとき、試験を終了した。試験は各４回行い、その平均値を焼付き寿命時間とし、軸受外輪温度が１３０℃まで上昇するのに要した平均時間が２００時間以上を合格とした。
【００８５】
図１２に、上記の急加減速試験及び含水焼付き試験の結果をグラフにして示す。尚、白抜きの○及び△は、比較例１または比較例２の試験グリースによる結果を示している。図示されるように、本発明に従い導電性物質であるカーボンブラックを０．１〜１０質量％の範囲で添加した試験グリースを封入することにより、剥離発生確率が低く、かつ焼付き寿命にも優れる転がり軸受が得られることがわかる。これに対してカーボンブラックの添加量が０．１質量％未満では、剥離を起こしやすくなる。また、カーボンブラックの添加量が１０質量％を超える場合は、剥離が起こり難くなるもの、焼付き寿命に劣るようになる。
【００８６】
（実施例２）
カーボンブラックに代えてカーボンナノチューブ（直径０．７〜２ｎｍ、全長１０〜３０μｍ）を用いた以外は実施例１と同様にして、カーボンナノチューブ添加量が０．１〜１０質量％の範囲で異なる試験グリースを調製した。尚、ウレア化合物の配合量は、何れの添加量においてもウレア化合物とカーボンナノチューブとの合計量がグリース全量に対して２０質量％とした。
【００８７】
そして、上記と同様の急加減速試験及び含水焼付き試験を行ったところ、カーボンブラックの場合と同様に、カーボンナノチューブを０．１〜１０質量％の範囲で添加した試験グリースを封入することにより、カーボンブラックを用いた比較例１及び比較例２と比較して、剥離発生確率が低く、かつ焼付き寿命にも優れる転がり軸受が得られた。
【００８８】
（実施例３〜５、比較例３〜４）
表１に示す如く、ジイソシアネートを混合した基油（エーテル油；４０℃における動粘度２００ｍｍ^２／ｓｅｃ、またはポリα−オレフィン油（ＰＡＯ）：４０℃における動粘度１００ｍｍ^２／ｓｅｃ）に、アミンを混合した同一種の基油を反応させ、攪拌加熱して得られた半固体状物に、予め同一種の基油に溶解したアミン系酸化防止剤を加えて十分攪拌した。徐冷後、前記の半固形状物に、スルフォン酸バリウム、ナフテン酸亜鉛、コハク酸ハーフエステルまたはジチオカルバミン酸亜鉛を、グリース全量に対して表記される割合となるように添加量を変えて加え、ロールミルを通して各種試験グリースを得た。
【００８９】
【表１】

【００９０】
そして、内径φ１７ｍｍ、外径φ４７ｍｍ、幅１４ｍｍの接触ゴムシール付き単列深溝玉軸受に各試験グリースを２．３ｇ封入して試験軸受を作製し、図１０に示す試験装置を用いて上記と同様の急減速試験を行い、剥離寿命を評価した。尚、試験条件は軸受回転速度２４００〜１３３００ｍｉｎ^−１の繰り返し、室温雰囲気下、プーリー荷重１５６０Ｎとし、試験軸受７５の外輪転走面に剥離が生じて振動が発生するまでの時間（剥離寿命）を計測した。
【００９１】
図１３に、比較例３の試験軸受の寿命に対する相対値として実施例３及び実施例４の試験軸受のはくり寿命をグラフにして示すが、ナフテン酸亜鉛またはコハク酸ハーフエステルをグリース全量に対して０．１〜１０質量％含有するグリース組成物を封入することにより、転がり軸受の耐剥離性が向上して長寿命になることがわかる。また、図１４に、比較例３の試験軸受の寿命に対する相対値として実施例５及び比較例４の試験軸受の剥離寿命をグラフにして示すが、ジチオカルバミン酸亜鉛をグリース全量に対して０．１〜１０質量％含有するグリース組成物を封入することにより、転がり軸受の耐剥離性が向上して長寿命になることがわかる。
【００９２】
【発明の効果】
以上説明したように、本発明によれば、導電性物質を含有するグリース組成物またはスルフォン酸塩を実質的に含有しないグリース組成物を封入することにより、剥離が発生し難く、耐久性に優れた燃料電池システム用転がり軸受が得られ、更には長寿命の燃料電池システムが得られる。
【図面の簡単な説明】
【図１】本発明の燃料電池システムの一例（固体高分子電解質型燃料電池）の全体構成を示す図である。
【図２】本発明の燃料電池システムの他の例（水素タンク方式燃料電池）の全体構成を示す図である。
【図３】本発明の燃料電池システムに使用される圧送機の一例（インペラ式圧送機）を示す断面図である。
【図４】本発明の燃料電池システム用転がり軸受の一実施形態を示す断面図である。
【図５】本発明の燃料電池システムに使用される圧送機の他の例（スクロール式圧送機）を示す断面図である。
【図６】スクロール式圧送機の他の例を示す断面図である。
【図７】本発明の燃料電池システムに使用される圧送機の他の例（斜板式圧送機）を示す断面図である。
【図８】本発明の燃料電池システムに使用される圧送機の他の例（スクリュー式圧送機）を示す断面図である。
【図９】カーボンナノチューブを示す模式図である。
【図１０】急加減速試験に用いた試験装置を示す概略構成図である。
【図１１】含水焼付き試験に用いた試験装置を示す概略構成図である。
【図１２】実施例で得られた、カーボンブラックの添加量と焼付き寿命及び剥離発生確率との関係を示すグラフである。
【図１３】実施例で得られた、ナフテン酸亜鉛またはコハク酸ハーフエステルの添加量と剥離寿命比との関係を示すグラフである。
【図１４】実施例で得られた、ジチオカルバミン酸亜鉛の添加量と剥離寿命比との関係を示すグラフである。
【符号の説明】
１　固体高分子電解質膜
２　カソード
３　アノード
４　冷却部
５　改質器
６　熱交換器
７　シフトコンバータ
８　ＣＯ除去器
９　燃料タンク
１０　メタノール蒸発器
１１　メタノール供給ライン
１２　水タンク
１３　蒸気発生器
１４　水蒸気ライン
１５　加湿器
１６　ターボチャージャ
１７　コンプレッサ
１８　タービン
１９　燃焼器
２０　燃焼器
２１　冷却器
２２　カソード排ガスライン
２３　気水分離器
２４　アノード排ガスライン
２５　気水分離器
３１　回転軸
３２　インペラ
３３ａ，３３ｂ　転がり軸受
３４　水蒸気吸込み口
３５　ハウジング
３６　バックプレート
３７　加圧ボリュート
３８　水蒸気吐出口
３９　シーリング部材
４０　背面空間
４１　間隙
４２　バッフル
４３　ブッシュ
２５０　内輪
２５１　外輪
２５２　保持器
２５３　玉
２５４　シール[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides, as a fuel supply source, hydrogen as a fuel from a hydrogen storage means such as a hydrogen tank and a hydrogen storage alloy to a fuel cell stack, and a fuel cell system for generating power, or a hydrogen-containing compound such as methanol water. The present invention relates to a fuel cell system that takes out hydrogen with a reformer, removes impurities with an impurity removing device such as a CO removing device, supplies hydrogen to a fuel cell stack, and generates power. The present invention also relates to a rolling bearing for a fuel cell system used in a pump for pumping various fluids between devices in these fuel cell systems.
[0002]
[Prior art]
The use of fuel cells as power sources for automobiles, ships, spacecraft, etc. is being studied. However, solid polymer electrolyte fuel cells made from methanol can generate power at relatively low temperatures (100 ° C or lower). It is effective as a power source for vehicles such as automobiles because of its advantages such as high power density, low temperature operation, low deterioration of battery constituent materials, and easy start-up. .
[0003]
The basic structure of a solid polymer electrolyte fuel cell consists of two gas diffusion electrodes, a porous cathode (oxygen electrode) and an anode (fuel electrode), using a noble metal such as platinum as a catalyst on both sides of the solid polymer electrolyte membrane. The fuel cell stack is formed by stacking the stacked cells via a separator to form a fuel cell stack, gas passages are formed on both front and back surfaces of each separator, and an oxidizing gas is supplied and discharged to the gas passage on the cathode side, and the anode side In general, the fuel gas is supplied to and exhausted from the gas passage, and since the reaction of the fuel cell is an exothermic reaction, a configuration in which one cooling unit is provided in each of several cells is generally used.
[0004]
As a power generator using a solid polymer electrolyte fuel cell having such a configuration, for example, a power generator having a system configuration as shown in FIG. 1 is known. That is, a cell in which both surfaces of the solid polymer electrolyte membrane 1 are sandwiched between the gas diffusion electrodes of the cathode 2 and the anode 3 is laminated with a separator interposed therebetween to form a fuel cell stack, and cooling is performed one by one for several cells. A reformer 5, a heat exchanger 6, a shift converter 7, and a CO remover 8 are installed in order from the upstream side on the anode 3 inlet side of the solid polymer electrolyte fuel cell I including the unit 4, and the fuel tank 9 A methanol supply line 11 is provided so that the supplied methanol is introduced into the reformer 5 through a methanol evaporator 10, while steam from a part of water from a water tank 12 is turned into steam by a steam generator 13. The line 14 is connected to the methanol supply line 11 so that methanol and steam are introduced into the reformer 5 to perform steam reforming, and another part of water is exchanged for cooling. The fuel gas FG reformed in the reformer 5 is cooled by the cooling water from the water tank 12 in the heat exchanger 6 and then operated at 200 ° C. A shift reaction is performed in the shift converter 7 to reduce the concentration of carbon monoxide (CO), which is a catalyst poison of the solid polymer electrolyte fuel cell I, to a concentration (1% or less) that can be processed by the CO remover 8. To Further, the fuel gas FG which has been subjected to the CO removal treatment by the CO remover 8 operated at about 100 to 150 ° C. is supplied to the anode 3 of the solid polymer electrolyte fuel cell I via the humidifier 15.
[0005]
On the other hand, at the inlet side of the cathode 2 of the solid polymer electrolyte fuel cell I, air A as an oxidizing gas is compressed by the compressor 17 of the turbocharger 16 and supplied through the humidifier 15 and partially. Is branched into a CO remover 8 to be used for CO combustion, and the entire amount of the cathode exhaust gas CG discharged from the cathode 2 and a part of the anode exhaust gas AG discharged from the anode 3 After being burned in the combustor 19, it is introduced into the combustion chamber of the reformer 5, and the methanol in the reforming chamber of the reformer 5 absorbs heat to 250 ° C. in the presence of the reforming catalyst and reacts. Thus, the fuel gas FG is reformed.
[0006]
Further, the exhaust gas discharged from the combustion chamber of the reformer 5 is combusted in the combustor 20 together with a part of the anode exhaust gas AG discharged from the anode 3 and then guided to the turbine 18 to drive the compressor 17. The exhaust gas discharged from the turbine 18 is discharged as an exhaust gas through the steam generator 13 and the methanol evaporator 10. Further, a part of the cooling water from the water tank 12 is allowed to pass through the cooling unit 4 of the solid polymer electrolyte fuel cell I via the humidifier 15, and the cooling water passed through the cooling unit 4 Is cooled by the cooler 21 and put into the water tank 12, and is separated by the steam separator 23 in the cathode exhaust gas line 22 and the steam separator 25 in the anode exhaust gas line 24, respectively. The water is returned to the water tank 12 together with the water that has passed through the heat exchanger 6 and the CO remover 8.
[0007]
A hydrogen tank system is also known as a fuel cell, and for example, a system having a system configuration as shown in FIG. 2 is known. In the figure, reference numeral 51 denotes a fuel cell stack in which a fuel electrode 53 and an oxidant electrode 55 are arranged to face each other with a solid polymer electrolyte membrane interposed therebetween, and furthermore, a fuel cell stack is formed by stacking a plurality of layers with the separator interposed therebetween. is there. Reference numeral 57 denotes a humidifier, in which the fuel gas and the oxidizing gas are adjacent to the pure water via the semipermeable membrane, respectively, and the water molecules pass through the semipermeable membrane, so that the fuel gas and the oxidizing gas are separated from each other. Humidification.
[0008]
Hydrogen is stored in a hydrogen tank 59, and the hydrogen is regulated by a fuel pressure regulating valve 61, passes through an ejector pump 63, a supply-side water separator 65 and a humidifier 57, and is supplied to the fuel cell stack 51. The fuel is supplied from a fuel inlet 53a of the fuel electrode 53. The mixed gas of hydrogen and steam discharged from the fuel outlet 53b of the fuel electrode 53 passes through the discharge-side water separator 67, the flow path shutoff valve 69, and is mixed with the raw fuel gas by the ejector pumping machine 63, and this mixed gas Is circulated to the fuel electrode 53 of the fuel cell stack 51 via the supply-side water separator 65 and the humidifier 57.
[0009]
Further, a purge pipe 75 for purging hydrogen at a purge branch section 73 is branched and connected to a pipe 71 between the discharge-side water separator 67 and the flow path cutoff valve 69, and a purge gas cutoff valve is connected to the purge pipe 75. 77 and a purge gas catalyst 79 are provided respectively.
[0010]
The air as the oxidant is supplied from the oxidant inlet 55a to the oxidant electrode 55 of the fuel cell stack 1 through the humidifier 57 by the pump 81. The exhaust gas discharged from the oxidant outlet 55b of the oxidant electrode 55 contains water vapor and liquid water, and the liquid separator 83 separates liquid water. The water separator 83 is provided with an air purge pipe 85 for supplying air during hydrogen purging and a purge gas cutoff valve 87. At the time of hydrogen purging, air is supplied to the purge gas catalyst 79 and discharged to the outside. Further, an air discharge pipe 89 is branched and connected to the air purge pipe 85, and the air discharge pipe 89 is provided with an air pressure regulating valve 91.
[0011]
Further, the power generation state of the fuel cell stack 51 is detected by a sensor (not shown), and the hydrogen pressure and the air pressure are adjusted by the fuel pressure control valve 51 and the air pressure control valve 91 in response to the detection signal in response to the detection signal. In addition to performing feedback control, feedback control is performed so that the air flow rate is adjusted by the rotation speed of the compressor 81.
[0012]
Further, in the fuel cell system as described above, it is necessary to feed vaporized fuel, fuel gas, high-temperature fuel or compressed air between the devices, and various pumping devices such as a pumping pump and a turbocharger are used. Bearings are often incorporated into the pumps.
[0013]
For example, FIG. 3 is a cross-sectional view showing an example of such a pump (impeller type pump). As shown, an impeller 32 is attached to a rotating shaft 31, and the rotating shaft 31 is rolled. It is supported by bearings 33a and 33b. When the impeller 32 rotates at high speed with the high speed rotation of the rotating shaft 31, the steam sucked from the steam suction port 34 is pressurized by the centrifugal force of the impeller 32, and the steam formed by the housing 35 and the back plate 36 is formed. The water is pressure-fed from the water vapor discharge port 38 through the pressure volute 37. Further, in this pumping device, when the sealing property of the sealing member 39 is reduced, the steam flows from the back space 40 on the back of the impeller 32 through the gap 41 between the rotating shaft 31 and the sealing member 39, and the rolling bearings 33a, 33b , A baffle 42 and a bush 43 for preventing this are attached to the rotating shaft 31.
[0014]
For example, ball bearings as shown in FIG. 4 are used as the rolling bearings 33a and 33b. In the illustrated ball bearing, a plurality of balls 253, which are rolling elements, are rotatably held at substantially equal intervals via a retainer 252 between an inner ring 250 and an outer ring 251. A space S formed by the balls 253 is filled with a predetermined amount of grease (not shown) for lubrication, and sealed with a seal 254. Conventionally, as a grease, a lithium soap-mineral oil-based grease is generally used (for example, see Patent Document 1).
[Patent Document 1]
Japanese Patent Publication No. 3-26717
[0015]
[Problems to be solved by the invention]
However, in particular, a pump that pumps the fuel gas reformed by the reformer 5 to the fuel cell stack or a pump that pumps steam from the steam generator 13 to the reformer 5 is used under high-temperature steam. Therefore, water vapor may enter the rolling bearings 33a and 33b incorporated in the pump. When water or water vapor enters the inside of the rolling bearings 33a, 33b, a white structure peeling due to hydrogen often observed in automobile electric parts occurs in the bearing components, shortening the life of the pump and, consequently, the life of the entire system. It is possible to do it.
[0016]
Further, in order to suppress the generation of rust due to water or steam, a rust inhibitor is often added to the grease composition. However, sulfonates that are frequently used because of their excellent rust-preventive performance cause white-texture exfoliation due to hydrogen similar to the internal origin exfoliation described above, as described in Japanese Patent Publication No. 287849. easy.
[0017]
The ejector pump 63 also has the same problem in the hydrogen tank type fuel cell system.
[0018]
The present invention has been made in view of such circumstances, and in a fuel cell system, an internal structure accompanied by a white structure change caused by hydrogen of a rolling bearing incorporated in a pump for pumping various fluids between devices. An object of the present invention is to provide a rolling bearing for a fuel cell system in which starting point separation is suppressed and durability is improved, and a fuel cell system capable of performing stable power generation for a long time.
[0019]
[Means for Solving the Problems]
The present inventors have conducted intensive studies and found that, by enclosing a grease composition containing a conductive substance or a grease composition containing substantially no sulfonate, the white tissue exfoliation caused by hydrogen is effectively prevented. It was found that it was possible to suppress it.
[0020]
That is, in order to achieve the above object, the present invention provides a rolling bearing incorporated in at least a fuel cell stack and a fuel cell system including a pump for transporting various fluids, comprising: A grease composition containing a substance in a proportion of 0.1 to 10% by mass or a grease composition containing substantially no sulfonate; Provided is a fuel cell system including a pump having a rolling bearing for a fuel cell system.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0022]
In the present invention, the configuration of the fuel cell system itself is not limited, and a solid polymer electrolyte type fuel cell system as shown in FIG. 1 and a hydrogen tank type fuel cell system as shown in FIG. 2 are exemplified. Can be.
[0023]
Also, there is no limitation on the pumping machine. In addition to the impeller-type pumping machine as shown in FIG. 3, for example, a scroll-type, swash-plate-type or screw-type pumping machine shown below can be used.
[0024]
FIG. 5 is a side sectional view showing an example of the scroll-type pump. The illustrated scroll-type feeder 100 includes a compression mechanism unit 110 including a fixed scroll 111 and an orbiting scroll 112, and a crank mechanism unit that rotates the orbiting scroll 112 by a crankpin 122a provided eccentrically with respect to a motor main shaft 122. 130 and a drive motor unit 120 for rotating the motor main shaft 122.
[0025]
The crank mechanism 130 is provided with a rotation preventing mechanism 132 for preventing the orbiting scroll 112 from rotating. The anti-rotation mechanism 132 includes an Oldham coupling, a pin & ring coupling, and the like in addition to the ball coupling 134 shown in FIG. As the anti-rotation mechanism 132, a crank mechanism using a rolling bearing as disclosed in JP-A-2002-70762 is known, but any of the above-described anti-rotation mechanisms may be employed. .
[0026]
The fixed scroll 111 includes a fixed base 111a formed in a disc shape, a spiral swirling spiral part 111c standing upright from the fixed base 111a, and an outer peripheral wall 111b covering the swirling spiral part 111c. The orbiting scroll 112 includes a disc-shaped orbiting base 112b and a spiral orbiting spiral part 112a standing upright from the orbiting base 112b. At the center on the rear side of the swivel base 112b, there is provided a bottomed cylindrical concave portion 112c. A discharge port 114 for air or the like compressed between the fixed scroll 111 and the orbiting scroll 112 is provided substantially at the center of the fixed base 111a in the vertical direction in FIG.
[0027]
The needle roller bearing 133 is inserted into the inner peripheral side of the concave portion 112c using the concave portion 112c as a housing. The needle roller bearing 133 rotatably supports the orbiting scroll 112 around the crank pin 122a of the motor main shaft 122 as a rotation axis.
[0028]
In the drive motor unit 120, the drive motor 121 includes a rotor 123 fitted on a motor main shaft 122 and a stator 125 provided on the outer peripheral side of the rotor 123 and wound with a coil 124 in the motor housing 101.
[0029]
The motor main shaft 122 is rotatably supported by the motor housing 101 via the rolling bearing 102, and is rotatably supported at the rear end (right side in FIG. 5) by the rear housing 104 via the rolling bearing 103. ing. A seal 106 is interposed between the motor main shaft 122 and the motor housing 101 on the crankpin 122a side with respect to the rolling bearing 102, and between the motor housing 101 and the rear housing 104 on the rear side (right end in FIG. 5). Is provided with a seal 107. Further, the motor main shaft 122 is provided with a balance weight 122b, and the balance weight 122b cancels the moment of inertia generated when the orbiting scroll 112 turns, thereby reducing vibration.
[0030]
In the scroll-type pressure feeder 100 having the above-described configuration, when power is supplied to the drive motor 121, the motor main shaft 122 rotates, and the rotation is transmitted to the orbiting scroll 112 via the drive crank mechanism 130. The orbiting scroll 112 orbits while meshing with the fixed scroll 111 with the rotation of the motor main shaft 122, sucks air and the like between the fixed scroll 111 from a suction port (not shown), and compresses with the fixed scroll 111. Let it. Thereafter, compressed air or the like is discharged from the discharge port 114 to the electrode side of the fuel cell.
[0031]
Further, a scroll type pump having a configuration shown in FIG. 6 is also known. In the illustrated scroll-type feeder 140, the crank mechanism unit 150 includes a drive crank mechanism 151 that causes the orbiting scroll 112 to perform a turning motion, and a driven crank mechanism 152 that prevents the orbiting scroll 112 from rotating.
[0032]
The driven crank mechanism 152 includes a concave holding portion 112 c provided on the orbiting scroll 112, and a crank pin 153 a of the driven crank shaft 153 and a rolling bearing 154 that makes the crank pin 153 a rotatable with respect to the orbiting scroll 112. The driven crankshaft 153 is rotatably supported by the motor housing 101 via a rolling bearing 155 on the side opposite to the crankpin 153a.
[0033]
The driven crankshaft 153 is provided with a balance weight 153b similarly to the motor main shaft 122. The balance weight 153b cancels an inertia moment generated when the orbiting scroll 112 turns, thereby reducing vibration. . The other configurations and operations are the same as those of the scroll-type pumping machine 100 shown in FIG. 5, and the same parts are denoted by the same reference numerals.
[0034]
FIG. 7 is a side sectional view showing an example of the swash plate type pressure feeder. The illustrated swash plate type pump 160 includes a compression mechanism 170 that compresses a fluid such as air to be sent to an electrode of a fuel cell by reciprocation of a double-headed piston 172 accompanying rotation of a swash plate 171, and a motor spindle of a drive motor 181. A drive motor section 180 that drives the compression mechanism section 170 by the rotation of 182.
[0035]
In the compression mechanism 170, the double-headed piston 172 is provided in the crank chamber 163 of the cylinder block 161 so as to be able to reciprocate along the axial direction of the motor main shaft 182, and is connected to the swash plate 171 via the shoe 173. I have. The swash plate 171 is rotatably inserted into the outer peripheral surface of the motor main shaft 182 so as to be integrally rotatable with the motor main shaft 182, and is rotatably mounted on a support member 162 provided in the cylinder block 161 via a thrust bearing 174. Supported.
[0036]
In the drive motor section 180, the drive motor 181 includes a rotor 183 fitted on the motor main shaft 182 and a stator 185 provided on the outer peripheral side of the rotor 183 and wound with a coil 184 in a motor housing 186. Become.
[0037]
The motor main shaft 182 is rotatably supported by the motor housing 186 through a pair of left and right rolling bearings 187 in FIG. 7 from a substantially center in the axial direction, and a right side in FIG. 7, is rotatably supported by a support member 162 via a pair of left and right rolling bearings 175.
[0038]
In the swash plate type pressure feeder 160 configured as described above, when electric power is supplied to the drive motor 181, the motor main shaft 182 rotates, and the rotation is transmitted to the double-headed piston 172 via the swash plate 171 and the shoe 173. . The double-headed piston 172 reciprocates along the axial direction in the crank chamber 163 with the rotation of the motor main shaft 182, thereby sucking and compressing air and the like and discharging the air and the like to the electrode side of the fuel cell.
[0039]
FIG. 8 is a side sectional view showing an example of the screw type pumping machine. The illustrated screw type pump 190 includes a compression mechanism 200 that compresses a fluid such as air sent to the electrode of the fuel cell by rotating the main rotor 201 and the sub-rotor 202 by meshing with each other. And a drive motor unit 180 that drives the compression mechanism unit 200 by rotation of the motor main shaft 182. The drive motor unit 180 is the same as the swash plate type pressure feeder 160 shown in FIG. 6, and the same reference numerals are given and the description is omitted.
[0040]
In the compression mechanism 200, the main rotor 201 and the sub-rotor 202 are each formed in a corresponding spiral shape and are rotatable in cooperation with each other by meshing with each other. The main rotor 201 rotatably supports the left rotating shaft 201a in FIG. 8 by the housing 207 via a pair of left and right rolling bearings 203 in FIG. 8, and connects the right rotating shaft 201a to the rolling bearing 204 in FIG. The housing is rotatably supported by the housing. The sub-rotor 202 is rotatably supported by the housing 207 via a pair of left and right rolling bearings 205 in FIG. 8 so that the left rotating shaft 202a in FIG. 8 can be rotatably supported by the housing 207. It is rotatably supported by the housing 207 via 206.
[0041]
A seal 208 is interposed between the main shaft 201 and the housing 207 on the inner side in the axial direction with respect to the rolling bearings 203 and 204 of the rotating shafts 201a on both the left and right sides in FIG. A seal 209 is interposed between the rotation shafts 202a on the left and right sides of the sub-rotor 202 in FIG.
[0042]
The main rotor 201 and the sub-rotor 202 are linked via a connecting gear 210 provided on each of the left rotation shafts 201a and 202a in FIG. A driven gear 211 is provided at the left end of the rotating shaft 201 a on the left side of FIG. 7 of the main rotor 201, and the driven gear 211 is connected to a driving shaft 188 fitted to the motor main shaft 182 of the driving motor 181. It is meshed with the drive gear 189. Therefore, the main rotor 201 transmits the rotation of the motor main shaft 182 via the drive shaft 188, the drive gear 189, and the driven gear 211. The rotation of the main rotor 201 is transmitted to the sub-rotor 202 via the connection gear 210.
[0043]
The drive shaft 188 is rotatably supported by the housing 213 via a pair of left and right rolling bearings 212 in FIG. A seal 214 is interposed between the drive shaft 188 and the housing 213.
[0044]
In the screw pumping machine 190 configured as described above, when power is supplied to the drive motor 181, the motor main shaft 182 rotates, and the rotation is mainly performed via the drive shaft 188, the drive gear 189, and the driven gear 211. The power is transmitted to the rotation shaft 201a of the rotor 201. At the same time, the rotation is transmitted from the rotation shaft 201a of the main rotor 201 to the rotation shaft 202a of the sub-rotor 202 via the connection gear 210. The main rotor 201 and the sub-rotor 202 engage and rotate, thereby sucking / compressing air and the like and discharging the air and the like to the electrode side of the fuel cell.
[0045]
In the present invention, a first grease composition or a second grease composition described later is sealed in the rolling bearing of each of the above-described pumps. The amount of the grease composition to be filled is selected according to the use conditions in the range of 5 to 50% by volume of the bearing space volume as in the conventional case.
[0046]
(1) First grease composition
The first grease composition contains a base oil, a thickener, and a conductive substance. Hereinafter, each will be described in detail.
[0047]
(Base oil)
The base oil is not particularly limited, and any oil that is usually used as a base oil for a lubricating oil can be used. Preferably, the kinematic viscosity at 40 ° C. is preferably 30 to 600 mm in order to avoid generation of abnormal noise at low temperature startup due to insufficient low temperature fluidity and seizure caused by difficulty in forming an oil film at high temperature. ² / Sec, more preferably 50 to 500 mm ² / Sec, more preferably 70 to 250 mm ² / Sec is preferred.
[0048]
Specific examples include mineral oil-based, synthetic oil-based, and natural oil-based lubricating oils. As the mineral oil-based lubricating oil, a refined one obtained by appropriately combining mineral oil under reduced pressure distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining, and the like is used. it can. Examples of the synthetic oil-based lubricating base oil include a hydrocarbon-based oil, an aromatic-based oil, an ester-based oil, and an ether-based oil. Examples of the hydrocarbon oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as 1-decene and ethylene co-oligomer, and hydrides thereof. Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene, and polyalkylnaphthalene. Examples of the ester-based oil include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, diester oils such as methyl acetyl sinolate, and trioctyl trimellitate. , Tridecyl trimellitate, aromatic ester oils such as tetraoctyl pyromellitate, furthermore, trimethylolpropane caprylate, trimethylolpropaneperargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol belargonate, etc. Examples thereof include polyol ester oils, and complex ester oils which are oligoesters of a polyhydric alcohol and a mixed fatty acid of a dibasic acid / monobasic acid. Examples of the ether-based oil include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, and monoalkyl And phenyl ether oils such as tetraphenyl ether and dialkyltetraphenyl ether. Other synthetic lubricating base oils include tricresyl phosphate, silicone oil, perfluoroalkyl ether, perfluoropolyether (PFPE) and the like. Examples of the natural oil-based lubricating base oil include oils and fats such as beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and hydrides thereof. These base oils can be used alone or as a mixture, and are adjusted to the preferable kinematic viscosity described above.
[0049]
[Thickener]
There is no particular limitation as long as it has the ability to form a gel structure and retain the base oil in the gel structure. For example, non-soaps such as metal soaps such as Li, Na, etc., metal soaps such as composite metal soaps selected from Li, Na, Ba, Ca, etc., bentone, silica gel, urea compounds, urea / urethane compounds, urethane compounds, etc. The urea compound, urea / urethane compound, urethane compound, or a mixture thereof is preferable in consideration of the heat resistance of the grease composition. Specific examples of the urea compound, urea / urethane compound, and urethane compound include a diurea compound, a triurea compound, a tetraurea compound, a polyurea compound, a urea / urethane compound, a diurethane compound, and a mixture thereof. Urea-urethane compounds, diurethane compounds or mixtures thereof are more preferred. In consideration of heat resistance and acoustic properties, it is more preferable to mix a diurea compound. In order to further improve the high-temperature stability, a diurea compound represented by the following general formulas (1) to (3) is used.
[0050]
Embedded image

[0051]
Where R ₁ Represents an aromatic ring-containing hydrocarbon group having 7 to 12 carbon atoms; ₂ Represents a divalent aromatic ring-containing hydrocarbon group having 6 to 15 carbon atoms; ₃ Represents a cyclohexyl group or an alkylcyclohexyl group having 7 to 12 carbon atoms. In particular, [R] in the diurea compounds represented by the general formulas (1) to (3) ₁ Of moles / (R ₁ Number of moles + R ₃ Is a diurea compound having a value of 0 to 0.55.
[0052]
When a fluoro oil such as perfluoropolyether (PFPE) is used as the base oil, it is desirable to mix a fluororesin such as polytetrafluoroethylene (PTFE) as a thickener.
[0053]
(Content)
The content of the thickener in the grease composition is not particularly limited as long as the gel structure can be maintained together with the base oil. However, since carbon black suitable as a conductive substance described below functions as a thickener itself, when carbon black is selected as the conductive substance, the grease composition is determined by the total amount of the carbon black and the thickener. It is in the range of 5 to 40% by mass, preferably 8 to 30% by mass based on the total amount. In this case as well, the amount of carbon black to be added is in a suitable range as a conductive substance described later.
[0054]
[Conductive substance]
The conductive material is not particularly limited as long as it has good conductivity, and may be a liquid or a solid. Above all, it is preferable to use carbon black for reasons such as easy handling and availability, and a decrease in lubricity. In addition, it is preferable to select a carbon black having an average particle size of about 10 to 300 nm in consideration of dispersibility in a grease composition, acoustic characteristics, and the like.
[0055]
Further, carbon nanotubes can also be suitably used as the conductive substance. As schematically shown in FIG. 9, the carbon nanotube is a carbon polyhedron having a tubular shape in which a network structure of mainly a six-membered carbon ring is rounded and both ends are closed. In addition, the joint portion of the tube having a different diameter or the closed portion at the end may be formed as a 5-membered carbon ring or a 7-membered carbon ring. Some carbon nanotubes have a spherical structure. ₆₀ , C ₇₀ Is known as fullerene, but this fullerene can also be used in the present invention. It is particularly preferable that these carbon nanotubes have a diameter of 0.5 to 15 nm and a length of 0.5 to 50 μm.
[0056]
(concentration)
The preferable addition amount of the conductive substance is 0.1 to 10% by mass based on the total amount of the grease composition. If the addition amount is less than 0.1% by mass, sufficient conductivity is not provided, and the internal origin peeling due to the change in white structure is likely to occur. If the addition amount is more than 10% by mass, the grease is hardened and the seizure life is shortened. It is not preferable because it may decrease. In order to ensure conductivity and prevent the peeling and improve the seizure life, it is desirable to add a conductive substance in an amount of 0.5 to 5% by mass based on the total amount of the grease composition. In addition, the grease consistency after the addition of the conductive substance is NLGI No. More preferably, it is 1-3.
[0057]
[Other additives]
In order to further enhance the lubricating performance, various additives such as antioxidants, extreme pressure agents, oil agents, rust inhibitors, metal deactivators, and viscosity index improvers are used alone or in combination as necessary, if necessary. It can be added to the grease composition. Any of these may be known ones, and the amount of addition is not particularly limited, but is usually added so that the total amount is 20% by mass or less of the total amount of the grease composition.
[0058]
[Production method]
The method for preparing the grease composition is not particularly limited. However, it is generally obtained by reacting a thickener in a base oil. It is preferable to mix a predetermined amount of the conductive substance with the obtained grease composition. However, it is necessary to sufficiently stir and uniformly disperse after adding a conductive substance by a kneader or a roll mill. When performing this treatment, heating is also effective. In the above-mentioned production method, other additives such as an antioxidant and a rust preventive are preferably added at the same time as the conductive substance in the process.
[0059]
(2) Second grease composition
The second grease composition is characterized in that it does not substantially contain a sulfonate which causes hydrogen embrittlement peeling. It is known that the sulfonate can be detected by the Epton method. In the present invention, the presence or absence of the sulfonate is confirmed by the Epton method.
[0060]
[Base oil and thickener]
As the base oil and the thickener, the base oil and the thickener used in the first grease composition can be used. However, the kinematic viscosity at 40 ° C. of the base oil is preferably 50 to 600 mm. ² / Sec, more preferably 70 to 500 mm ² / Sec, more preferably 100 to 450 mm ² / Sec. The content of the thickener is preferably 10 to 35% by mass based on the total amount of the grease.
[0061]
[Additive]
It is preferable to add the following naphthenates and succinic acid derivatives as additives.
(Naphthenate)
Any saturated carboxylate having a naphthene nucleus may be used, and there is no particular limitation. Mainly, saturated monocyclic carboxylate C _n H _2n-1 COOM, saturated bicyclic carboxylate C _n H _2n-3 COOM, aliphatic carboxylate C _n H _{2n + 1} COOM, and derivatives thereof. For example, for a monocyclic carboxylate, the following can be mentioned.
[0062]
Embedded image

[0063]
In the above formula, R ₄ Represents a hydrocarbon group, and examples thereof include an alkyl group, an alkenyl group, an aryl group, an alkaryl group, and an aralkyl group. M represents a metal element, such as Co, Mn, Zn, Al, Ca, Ba, Li, Mg, and Cu. These naphthenates may be used alone or in appropriate combination.
[0064]
(Succinic acid derivative)
Specific examples of the succinic acid derivative include the following compounds. For example, succinic acid, alkyl succinic acid, alkyl succinic acid half ester, alkenyl succinic acid, alkenyl succinic acid half ester, succinimide and the like can be mentioned. These succinic acid derivatives may be used alone or in appropriate combination.
[0065]
The above naphthenate and succinic acid derivative may be used alone or in combination. When used alone or in combination, the preferable addition amount is 0.1 to 10% by mass based on the total amount of the grease composition. If the amount is less than this, sufficient rust-preventing properties cannot be obtained, and if the amount is more than that, the grease is softened, which may cause grease leakage. In order to ensure rust prevention and to consider the seizure life due to grease leakage, it is desirable that the content be 0.25 to 5% by mass based on the total amount of the grease composition.
[0066]
In order to further improve the peeling resistance, it is more desirable to add the following organic metal salts.
[0067]
(Organic metal salt)
As the organic metal salt, a dialkyldithiocarbamic acid (DTC) -based compound represented by the following general formula (4) and a dialkyldithiophosphoric acid (DTP) -based compound represented by the following general formula (5) can be suitably used.
[0068]
Embedded image

[0069]
In the formula, M represents a metal species, and specifically, Sb, Bi, Sn, Ni, Te, Se, Fe, Cu, Mo, and Zn are used. R ₅ , R ₆ May be the same or different, and represent an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, or an arylalkyl group. Particularly preferred groups include a 1,1,3,3-tetramethylbutyl group, a 1,1,3,3-tetramethylhexyl group, a 1,1,3-trimethylhexyl group, a 1,3-dimethylbutyl group, 1-methylundecane group, 1-methylhexyl group, 1-methylpentyl group, 2-ethylbutyl group, 2-ethylhexyl group, 2-methylcyclohexyl group, 3-heptyl group, 4-methylcyclohexyl group, n-butyl group, Isobutyl, isopropyl, isoheptyl, isopentyl, undecyl, eicosyl, ethyl, octadecyl, octyl, cyclooctyl, cyclododecyl, cyclopentyl, dimethylcyclohexyl, decyl, tetradecyl, docosyl , Dodecyl, tridecyl, trimethylcyclohexyl, nonyl Propyl, hexadecyl, hexyl, henicosyl, heptadecyl, heptyl, pentadecyl, pentyl, methyl, tert-butylcyclohexyl, tert-butyl, 2-hexenyl, 2-methallyl, allyl , Undecenyl, oleyl, decenyl, vinyl, butenyl, hexenyl, heptadecenyl, tolyl, ethylphenyl, isopropylphenyl, tert-butylphenyl, second pentylphenyl, n-hexylphenyl Tertiary octylphenyl group, isononylphenyl group, n-dodecylphenyl group, phenyl group, benzyl group, 1-phenylmethyl group, 2-phenylethyl group, 3-phenylpropyl group, 1,1-dimethylbenzyl group, 2-phenylisopropyl group, 3-phenylhexyl group, Nzuhidoriru group, there is a biphenyl group and the like, and these groups may have an ether bond.
[0070]
Further, as other organic metal salts, organic zinc compounds represented by the following general formulas (6) to (8) can also be used.
[0071]
Embedded image

[0072]
Where R ₇ , R ₈ Is the carbon number C _n Represents a hydrocarbon group or a hydrogen atom of n = 1 to 18, and R ₇ , R ₈ May be the same or different groups. In particular, R ₇ , R ₈ Are preferably hydrogen atoms, methylcaptobenzothiazole zinc (general formula (6)), benzamidothiophenol zinc (general formula (7)), and mercaptopopenzimidazole zinc (general formula (8)). be able to.
[0073]
Further, as other organic metal salts, zinc alkylxanthate represented by the following general formula (9) can also be used.
[0074]
Embedded image

[0075]
Where R ₉ Is the carbon number C _n Represents a hydrocarbon group of n = 1 to 18.
[0076]
The organic metal salts represented by the general formulas (4) to (9) can be used alone or in combination of two or more, but the combination is not particularly limited. . Further, the organometallic salt has a function of forming a reaction film in the minute gap to suppress the white structure change peeling, but if the added amount is less than 0.1% by mass, a sufficient effect cannot be exhibited. On the other hand, it is thought that the upper limit of the amount of addition does not need to be particularly limited. However, the above-mentioned organometallic salts are relatively expensive, and excessive addition abnormally promotes the reaction with the bearing material, and conversely, the sintering occurs. In order to inhibit the sticking performance, it is preferable to set the addition amount to 0.1 to 10% by mass. More preferably, it is 0.5 to 10% by mass.
[0077]
Further, the above-mentioned naphthenate, succinate or organometallic salt can be appropriately used in combination with the additives exemplified as other additives in the first grease composition.
[0078]
[Production method]
The method for preparing the grease composition can be in accordance with the method for preparing the first grease composition. The thickener is reacted in the base oil, and the obtained grease composition is mixed with a predetermined amount of the above additive. While heating as required, the mixture is sufficiently stirred with a kneader or a roll mill to uniformly disperse.
[0079]
【Example】
Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
[0080]
(Example 1)
Base oil mixed with diisocyanate (ether oil; kinematic viscosity at 40 ° C. 100 mm) ² / Sec) is reacted with the same type of base oil mixed with an amine, and the resulting mixture is heated under stirring to a semi-solid substance, to which an amine-based antioxidant previously dissolved in the same type of base oil is added and sufficiently stirred. did. After gradual cooling, carbon black (average particle size: 30 nm) was added to the semi-solid substance at an added amount of 0.1 to 10% by mass relative to the total amount of grease, and the carbon black was passed through a roll mill. Various test greases with different addition amounts were obtained.
[0081]
In the above, the total amount of the urea compound as a thickener and the carbon black was adjusted to be constant at 20% by mass based on the total amount of the grease in accordance with the amount of the carbon black added. In addition, the consistency of the test grease was set to NLGI No. Adjusted to 1-3.
[0082]
(Comparative Example 1, Comparative Example 2)
For comparison, the urea compound was 19.95% by mass, the carbon black was 0.05% by mass (Comparative Example 1), the urea compound was 8% by mass, and the carbon black was A test grease was prepared in the same manner as in Example 1 so that the concentration became 12% by mass.
[0083]
The following tests were performed using the above test greases.
(Sudden acceleration / deceleration test)
2.3 g of each test grease was sealed in a single-row deep groove ball bearing with a contact rubber seal having an inner diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm (see FIG. 4) to prepare a test bearing, and the test apparatus shown in FIG. 10 was used. The peel life was evaluated. In the illustrated test apparatus, the inner ring of the test bearing 375 is fitted to the end of the shaft 370 supported by the pair of support bearings 371, 371, the outer ring is further fixed to the holder 372, and the engine is connected via the pulley 373. The rotation from (not shown) is transmitted to the test bearing 375. Reference numeral 374 denotes a thermometer for measuring the temperature of the outer ring, and reference numeral 376 denotes a heater for heating the outer ring. And bearing rotation speed 2400-13300min ^-1 The bearing was continuously rotated under the conditions of a pulley load of 1560 N in an atmosphere at room temperature, and a test was performed with a target of 500 hours. The test was terminated when peeling occurred on the outer raceway contact surface of the test bearing 375 and vibration occurred, or when 500 hours had passed if peeling did not occur. The test was performed 10 times, and the peeling occurrence probability was calculated by the following equation.
Probability of peeling = (number of times of peeling / number of tests) × 100
[0084]
(Hydrous seizure test)
A test bearing was prepared by enclosing 1.0 g of test grease in a single-row deep groove ball bearing with a contact rubber seal having an inner diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm, and the seizure life was evaluated using a test device shown in FIG. The illustrated test apparatus supports a rotating shaft 360 with a pair of support bearings 362 and 362, mounts a test bearing 361 at an intermediate portion thereof, and further maintains a constant temperature vessel (not shown) so that the whole can be maintained at a predetermined temperature. ). During the test, the shaft 360 was rotated to rotate the test bearing 361 at the inner ring rotation speed of 2000 min. ^-1 The bearing was continuously rotated under the conditions of a bearing temperature of 120 ° C., a radial load of 98 N, and an axial load of 98 N. The rotation was stopped every 24 hours, and 0.3 ml of water was injected into the bearing with a syringe. The test was terminated when seizure occurred and the temperature of the bearing outer ring rose to 130 ° C. or higher. The test was performed four times each, and the average value was defined as the seizure life time, and the average time required for the temperature of the bearing outer ring to rise to 130 ° C. was determined to be 200 hours or more.
[0085]
FIG. 12 is a graph showing the results of the rapid acceleration / deceleration test and the seizure test containing water. The white circles and white circles indicate the results of the test grease of Comparative Example 1 or Comparative Example 2. As shown in the figure, by enclosing a test grease to which carbon black as a conductive substance is added in a range of 0.1 to 10% by mass in accordance with the present invention, the probability of occurrence of peeling is low and the seizure life is excellent. It can be seen that a rolling bearing is obtained. On the other hand, if the added amount of carbon black is less than 0.1% by mass, peeling tends to occur. On the other hand, if the amount of carbon black exceeds 10% by mass, peeling hardly occurs, but the seizure life becomes poor.
[0086]
(Example 2)
A test in which the addition amount of carbon nanotubes is different in the range of 0.1 to 10% by mass in the same manner as in Example 1 except that carbon nanotubes (diameter 0.7 to 2 nm, total length 10 to 30 μm) are used instead of carbon black. A grease was prepared. Regarding the blending amount of the urea compound, the total amount of the urea compound and the carbon nanotubes was set to 20% by mass with respect to the total amount of the grease at any of the added amounts.
[0087]
Then, the same rapid acceleration / deceleration test and water-containing seizure test as described above were performed. As in the case of carbon black, the test grease to which carbon nanotubes were added in the range of 0.1 to 10% by mass was filled. As compared with Comparative Examples 1 and 2 using carbon black, a rolling bearing having a lower probability of occurrence of peeling and an excellent seizure life was obtained.
[0088]
(Examples 3-5, Comparative Examples 3-4)
As shown in Table 1, a base oil mixed with diisocyanate (ether oil; kinematic viscosity at 40 ° C. 200 mm ² / Sec or poly-α-olefin oil (PAO): kinematic viscosity at 40 ° C. 100 mm ² / Sec) is reacted with the same type of base oil mixed with an amine, and the resulting mixture is heated under stirring to a semi-solid substance, to which an amine-based antioxidant previously dissolved in the same type of base oil is added and sufficiently stirred. did. After slow cooling, to the semi-solid, barium sulfonate, zinc naphthenate, succinic acid half ester or zinc dithiocarbamate was added by changing the addition amount so as to have a ratio represented by the total amount of grease, Various test greases were obtained through a roll mill.
[0089]
[Table 1]

[0090]
Then, 2.3 g of each test grease was sealed in a single-row deep groove ball bearing with a contact rubber seal having an inner diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm to prepare a test bearing, and the same as above using a test apparatus shown in FIG. A rapid deceleration test was performed to evaluate the peel life. The test conditions were as follows: bearing rotation speed 2400 to 13300 min ^-1 The pulling load was 1560 N in a room temperature atmosphere, and the time (separation life) from the occurrence of separation on the outer ring rolling surface of the test bearing 75 to the occurrence of vibration was measured.
[0091]
FIG. 13 is a graph showing the peeling life of the test bearings of Examples 3 and 4 as a relative value with respect to the life of the test bearing of Comparative Example 3. Zinc naphthenate or half succinic acid ester was used with respect to the total amount of grease. It can be seen that, by enclosing the grease composition containing 0.1 to 10% by mass, the peeling resistance of the rolling bearing is improved and the life is extended. FIG. 14 is a graph showing the peel life of the test bearings of Example 5 and Comparative Example 4 as a relative value with respect to the life of the test bearing of Comparative Example 3. Zinc dithiocarbamate was added to the total amount of grease by 0.1%. It can be seen that by enclosing the grease composition containing from 10 to 10% by mass, the peeling resistance of the rolling bearing is improved and the life is extended.
[0092]
【The invention's effect】
As described above, according to the present invention, by encapsulating a grease composition containing a conductive substance or a grease composition containing substantially no sulfonate, peeling does not easily occur and the durability is excellent. Thus, a rolling bearing for a fuel cell system can be obtained, and a long-life fuel cell system can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an example of a fuel cell system (a solid polymer electrolyte fuel cell) of the present invention.
FIG. 2 is a diagram showing the overall configuration of another example (hydrogen tank type fuel cell) of the fuel cell system of the present invention.
FIG. 3 is a cross-sectional view showing an example of a pump used in the fuel cell system of the present invention (impeller type pump).
FIG. 4 is a sectional view showing an embodiment of the rolling bearing for a fuel cell system of the present invention.
FIG. 5 is a sectional view showing another example (scroll type pump) used in the fuel cell system of the present invention.
FIG. 6 is a cross-sectional view showing another example of the scroll-type pump.
FIG. 7 is a cross-sectional view showing another example (swash plate type pump) used in the fuel cell system of the present invention.
FIG. 8 is a cross-sectional view showing another example (screw type pump) of the pump used in the fuel cell system of the present invention.
FIG. 9 is a schematic view showing a carbon nanotube.
FIG. 10 is a schematic configuration diagram showing a test device used for a rapid acceleration / deceleration test.
FIG. 11 is a schematic configuration diagram showing a test apparatus used for a water-containing seizure test.
FIG. 12 is a graph showing the relationship between the amount of carbon black added, the seizing life, and the probability of occurrence of peeling, obtained in the examples.
FIG. 13 is a graph showing the relationship between the amount of zinc naphthenate or succinic acid half ester obtained and the peel life ratio obtained in the examples.
FIG. 14 is a graph showing the relationship between the amount of zinc dithiocarbamate added and the peel life ratio obtained in the examples.
[Explanation of symbols]
1 solid polymer electrolyte membrane
2 cathode
3 Anode
4 Cooling unit
5 Reformer
6 heat exchanger
7 Shift converter
8 CO remover
9 Fuel tank
10 Methanol evaporator
11 Methanol supply line
12 water tank
13 Steam generator
14 Steam line
15 Humidifier
16 Turbocharger
17 Compressor
18 Turbine
19 Combustor
20 combustor
21 Cooler
22 Cathode exhaust gas line
23 Steam-water separator
24 Anode exhaust gas line
25 steam-water separator
31 Rotary axis
32 Impeller
33a, 33b rolling bearing
34 Water vapor inlet
35 Housing
36 Back plate
37 Pressurized volute
38 Steam outlet
39 Sealing material
40 Space behind
41 gap
42 Baffle
43 Bush
250 inner ring
251 Outer ring
252 cage
253 balls
254 seal

Claims (7)

At least a rolling bearing incorporated in the pump of the fuel cell system including a fuel cell stack and a pump for transporting various fluids,
A rolling bearing for a fuel cell system, wherein a grease composition containing a conductive substance at a ratio of 0.1 to 10% by mass or a grease composition containing substantially no sulfonate is sealed. 2. The rolling bearing for a fuel cell system according to claim 1, wherein the conductive substance is carbon black. 2. The rolling bearing for a fuel cell system according to claim 1, wherein the conductive material is a carbon nanotube. 4. The fuel cell system according to claim 1, wherein the amount of the thickener based on the total amount of the grease composition is 5 to 40% by mass in total including the carbon black. 5. Rolling bearing. The grease composition contains a thickener as a urea compound and contains at least one rust inhibitor selected from naphthenates and succinates in a ratio of 0.1 to 10% by mass based on the total amount of the grease. The rolling bearing for a fuel cell system according to any one of claims 1 to 4, wherein: The grease composition according to any one of claims 1 to 5, wherein the thickener is a urea compound, and the organic metal salt is contained in a ratio of 0.1 to 10% by mass based on the total amount of the grease. 13. The rolling bearing for a fuel cell system according to item 8. A fuel cell system comprising at least a fuel cell stack and a pump provided with the rolling bearing for a fuel cell system according to any one of claims 1 to 6.

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