JP3740178B2 - SCREW ROTOR, SCREW COMPRESSOR, AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

【００２０】
酸化が発生すると、図１に示すようにコーティング層内のＭｏＳ₂が三酸化モリブデン（ＭｏＯ₃）に変質し、硫黄分は酸化してガス化し腐食の原因となると考えられる。これと共に、ＭｏＯ₃はバインダーとの結合力が弱くなって脱落し、膜厚の減少、剥離が発生し、コーティング本来の目的を発揮できなくなるものと考えられる。
【００２１】
一方、本発明の適用対象であるオイルフリースクリュウ式圧縮機の運転中のロータ表面の温度は、ロータの吸入側で５０〜１００℃、中間部で１２０〜１５０℃、吐出側で２２０〜３００℃程度である。さらに吐出温度保護リレーが作動する寸前においては最高３２０〜３５０℃程度まで上昇すると考えられる。◆
したがってスクリュウ式圧縮機では耐熱性の向上と共にＭｏＳ₂の酸化を防止することがコーティング技術の最も重要な課題である。
【００２２】
本発明の目的は、高温に曝されても潤滑性や耐久性を失わない耐熱性良好なコーティング材を被覆したスクリュウロータおよびそのスクリュウロータを適用した信頼性の高いスクリュウ式圧縮機並びにスクリュウロータの製法を提供することにある。
【００２３】
【課題を解決するための手段】
上記目的のスクリュウロータに関しては、以下の手段を備えることにより達成される。
【００２７】
（１）軸方向の外表面に螺旋状の歯形を形成してなるスクリュウロータにおいて、スクリュウロータは表面にＰＡＩからなる層を備え、その層の上にバインダーをＰＡＩとし、ピグメントとしてＭｏＳ2、Ｓｂ2Ｏ3及びＣを分散させた固体潤滑材被膜を備える。
【００２９】
（２）上記（１）において、Ｓｂ2Ｏ3、ＭｏＳ2及びＣは粒子として固体潤滑材被膜に備える。
【００３０】
（３）上記（１）において、固体潤滑材被膜は、ＰＡＩが１２乃至１８重量部、ＭｏＳ2が５乃至７重量部、Ｓｂ2Ｏ3が３乃至５重量部、Ｃが０．７乃至０．９重量部の範囲から選択した配合からなる。
【００３１】
また、上記目的のスクリュウ式圧縮機に関しては、以下の手段を備えることにより達成される。
【００３２】
（４）ケーシング内に互いに噛み合うオスロータとメスロータを少なくとも一対備えるスクリュウ式圧縮機において、ロータの両方若しくはいずれか一方に、上記（１）乃至（３）のいずれかのスクリュウロータを備える。
【００３３】
（５）ケーシング内に互いに噛み合うオスロータとメスロータを少なくとも一対備えるスクリュウ式圧縮機において、ロータのいずれか一方に上記（１）乃至（３）のいずれかのスクリュウロータを備え、他方のロータの表面にニッケル−リンめっき被膜を備える。
【００３４】
（６）ケーシング内に互いに噛み合うオスロータとメスロータを少なくとも一対備えるスクリュウ式圧縮機において、ロータのいずれか一方に上記（１）乃至（３）のいずれかのスクリュウロータを備え、他方のロータの表面に被膜内にＰＴＦＥを分散させたニッケル−リンめっき被膜を備える。
【００３６】
（７）ケーシング内に互いに噛み合うオスロータとメスロータを少なくとも一対備えるスクリュウ式圧縮機において、ケーシングのオスロータとメスロータが相対する表面にバインダーをＰＡＩとし、ピグメントとしてＭｏＳ 2 、Ｓｂ 2 Ｏ 3 及びＣを分散させた固体潤滑材被膜を備え、かつ前記固体潤滑材被膜は、ＰＡＩが１２乃至１８重量部、ＭｏＳ2が５乃至７重量部、Ｓｂ2Ｏ3が３乃至５重量部、Ｃが０．７乃至０．９重量部の範囲から選択した配合からなる。
【００３７】
さらに、上記目的のスクリュウロータの製法に関しては、以下の手段を備えることにより達成される。
【００４０】
（８）軸方向の外表面に螺旋状の歯形を形成してなるスクリュウロータの製法において、螺旋状の歯形を形成したスクリュウロータの表面に、ＰＡＩを塗布した後、その表面にＳｂ2Ｏ3を分散させた固体潤滑材を塗布し、加熱することにより固体潤滑材被膜を形成する。
【００４１】
（９）軸方向の外表面に螺旋状の歯形を形成してなるスクリュウロータの製法において、螺旋状の歯形を形成したスクリュウロータの表面に、ＰＡＩを塗布し、加熱した後、その表面にバインダーをＰＡＩとし、ピグメントにＭｏＳ2、Ｓｂ2Ｏ3及びＣを分散させた固体潤滑材を塗布し、加熱することにより固体潤滑材被膜を形成する。
【００４２】
【作用】
ＭｏＳ₂とＣを含むコーティング材にＳｂ₂Ｏ₃を添加すると、コーティング被膜中のＭｏＳ₂，Ｃなどの潤滑性粒子の酸化を防ぐ作用をする。すなわち被膜中にＳｂ₂Ｏ₃が存在することにより、被膜内に侵入してきた空気中の酸素を選択的に捕捉し、Ｓｂ₂Ｏ₃自身が先に酸化することにより、ＭｏＳ₂やＣの酸化を防止する。従ってコーティング材の潤滑性は長期間維持される。
【００４３】
またＳｂ₂Ｏ₃は、それ自体、ＭｏＳ₂ほどではないが若干の潤滑性をもっており、また展伸性も良いので、Ｓｂ₂Ｏ₃の存在自体もコーティング材皮膜の潤滑性維持に寄与する。◆
バインダーとして、耐熱性の高いＰＡＩを用い、その割合を１２ないし１８％とすることによって、空気中の酸素や水分、及び停止時の凝縮水がコーティング膜中に侵入することを阻止する。従って、ロータ表面の腐食を防止すると共にピグメント中のＭｏＳ₂およびＣを効果的に被覆することにより、その酸化、劣化を防いで潤滑性を長期間維持する。
【００４４】
ＰＡＩは、本来熱可塑性樹脂の一種であるが、イミド基を含むため熱硬化性の機能も併せ持つ樹脂である。したがって、塗布後の焼き付き温度と時間を適宜選択することにより、アミド酸がイミド環に変化するため熱硬化特性が顕著になり熱変形温度が上昇し、塗膜の耐熱性が向上する。また、ＰＡＩは溶剤により容易に液状化するため、塗布に際して潤滑剤粒子及び添加粒子との混合分散が確実に行える。なお溶剤は、ジメチルアセトアミドなどを用いると良い。
【００４５】
さらに、オスロータまたはメスロータのどちらか一方のロータの表面にＰＡＩを粘結剤としたＭｏＳ₂，Ｓｂ₂Ｏ₃及びＣを潤滑粒子としたコーティング材（以下コーティング材 No.５ と称する）を塗布した表面層を形成し、他方のロータを金属で形成するか、若しくは両ロータの表面をコーティング材 No.５ で被覆する。上記いずれの場合においても、両ロータはタイミングギヤで同期回転させる構造とするか、前記に加えロータの歯形そのものに転がり接触点の存在しない歯形を使用することにより、コーティング膜としてのコーティング材の相互すり合わせ（共ずり）によって、オス・メス両ロータのクリアランスを可能な限りゼロに近づけ、圧縮性能の飛躍的向上を図ることができる。具体的方法としては、オスロータにコーティング材 No.５ を塗布しメスロータには、この種の潤滑コーティング膜を施さず硬質表面のままとする。ここで硬質表面とは、金属ロータをコーティング膜なしか、或いは硬質金属メッキを施した、いわゆる硬質表面を指す。
【００４６】
基礎実験として行ったアムスラ摩擦摩耗試験（以下アムスラ試験と略す）によれば、ＭｏＳ₂などを主成分とするコーティング膜同士の組合せでは、長時間（例えば６時間）の試験において試験片に塗布したコーティング膜はほとんど剥落する。◆
しかしながら片方のロータ、例えばオスロータの表面が硬質の場合、メスロータに塗布されたコーティング膜の被覆が摩耗し始める時間は、両ロータ表面がコーティング材で塗布されている場合に比べて２倍もの長時間を要する。また摩耗開始後においてもその減少率は徐々の変化をみせるのみならず摩耗し始めて部分的に剥げ落ちて金属素地がみられても、すぐに剥落部にその近傍の健全部のコーティング膜が徐々に移動してその欠陥部を埋める。
【００４７】
即ち本発明のコーティング膜を用いた上記組合せによれば、コーティング膜が自己修復性を有するという被膜の長寿命化に好適な現象が認められた。◆
さらには自分修復が完了したあとのコーティング膜は、その後の長時間試験に於いても摩耗減少は殆ど見られなくなり今回の実験条件においては当初のコーティング膜の約２０〜３０％の厚さはそのまま極めて長時間維持される。
【００４８】
【実施例】
スクリュウロータへの適用に先立ち、まずコーティング被膜の検討結果について述べる。◆
検討は表２に示す耐熱性を向上できると思われる各種のコーティング材について行った。
【００４９】
【表２】

【００５０】
表の中で、比較の基準となる従来のコーティング材としてNo.１のＭｏＳ₂を検討した。No.２のＣは、No.１のＭｏＳ₂に対し耐熱性の向上を期待したものである。
【００５１】
また、No.３はＭｏＳ₂と三酸化アンチモン（Ｓｂ₂Ｏ₃）とを混合したものであり、Ｓｂ₂Ｏ₃によるＭｏＳ₂の酸化防止効果による耐熱性向上を期待したものである。No.４は、No.３の固形分を増量したもの、No.５はNo.４に更にＣを添加し耐熱性の改良を図ったものである。なお、No.１からNo.５まではバインダとしてＰＡＩを用いた。
【００５２】
No.６はバインダーを無機系の珪酸塩としコーティング材を窒化ほう素（ＢＮ）として４００℃以上の高温耐熱性を目的としたものである。◆
No.７は２層からなり、下層にＰＡＩを約３μｍ、上層にNo.５を配置したものである。◆
以上７種類のコーティング材について耐熱性、耐食性等のスクリーニングテストを行った。検討した各試料の被膜厚さは約２０μｍとした。表３に、以下に示す結果をまとめて示す。表中の評価は、▲印が実用上問題あり、△印が若干問題あり、○印が問題なし、二重丸印が全く問題なしとした。
【００５３】
【表３】

【００５４】
テストピースにはφ３０×５ｔのステンレス鋼（SUS420）を用い、サンドブラスト処理の後、所定のコーティング材を約２０μｍの厚さに塗布して２００℃で１時間焼き付けたものを用いた。
【００５５】
(1) 耐熱性試験◆
耐熱性は粘着テープによるコーティング膜の剥離試験で判定した。◆
上記のテストピースを、３８０℃で２０時間加熱した後、加熱のみによる被膜の剥離すなわちピーリングの発生の有無を調べた。次にテストピース中央部に粘着テープを貼付し１ｋｇｆ／ｃｍ²で加圧した後、ゆっくりテープをはがし、被膜の剥離状態を観察し耐熱性を判定した。
【００５６】
その結果、No.２は、No.１のＭｏＳ₂より耐熱性の優れたＣが主成分であるにもかかわらず剥離程度はNo.１より大でありピーリングも発生した。◆
ＭｏＳ₂にＳｂ₂Ｏ₃を加えたNo.３とNo.４は、No.１に比べて程度の差はあるものの、剥離の度合いが小さかった。また、No.５とNo.７は剥離がほとんどなく良好であり、No.６は剥離が全くなく最も良好であった。
【００５７】
(2) 耐食性試験◆
各種のコーティング材を塗布した上述のテストピースを、３６０℃で２０時間加熱後、温度６０℃、湿度９０％ＲＨの恒温恒湿槽中に１００時間保持の後表面の発銹状況を観察した。◆
その結果、No.２には全く腐食が見られず、ＭｏＳ₂＋Ｓｂ₂Ｏ₃を基本にしたNo.３、No.４、No.５はＭｏＳ₂のみのNo.１に比べて、同等もしくはやや良好であった。しかし、No.６は他のものに比べ銹の発生が多く認められた。
【００５８】
(3)潤滑性試験◆
各種コーティング材を塗布後のテストピースを、３６０℃で２０時間加熱し、その後上述の湿潤試験（６０℃×９０％ＲＨ×１００時間）を行った後、回転円盤に球形ボールを押し付けるピンオンディスク試験により、摩擦係数が０．３になるまでの総回転数を試料No.１の値を基準に相対回転数比により比較し潤滑耐久性を評価した。試験結果を図２に示す。
【００５９】
No.１と無機系のNo.６は他のものに比べ潤滑耐久性は良くない。◆
これに対し、No.４、No.３、No.７、No.２、No.５の順に潤滑性が向上している。特にNo.５はNo.１の約９倍の結果となり耐久性の高いことが判明した。
【００６０】
以上の検討結果をまとめた表３から明らかなように、それぞれに一長一短があるが、No.１と比較して、耐食性や潤滑性を低下させること無く、耐熱性を大幅向上させるという観点からは、ＰＡＩをバインダーとしＭｏＳ₂を主成分としてこれにＳｂ₂Ｏ₃、Ｃを加えたNo.５が最も良好であることが判明した。
【００６１】
つぎに、このNo.５の配合の最適配合範囲を検討した。◆
コーティング材は、溶剤と、バインダーとしての樹脂、および潤滑材粉末（以下ピグメントと称する）より成る。◆
溶剤の量は、使用条件によって適宜設定するが、乾燥時に蒸発するため乾燥後のコーテング膜中には通常溶剤は存在しないため、一定値（７５重量部）とし、またバインダーも１５重量部とし、ピグメントについて以下の配合の検討を行うことした。配合の割合は表４に示す。
【００６２】
ＭｏＳ₂は主たるコーティング材であり、ドライ下での潤滑作用は、このＭｏＳ₂の存在が大きい。しかし、前述したように、高温下においては空気中の酸素との間に酸化が促進され、２ＭｏＳ₂＋３Ｏ₂→２ＭｏＯ₃＋２Ｓ₂（ガス）の反応が進行し、その結果生成されたＭｏＯ₃は、剥離しやすい。また、かりに皮膜内に残留したとしても、潤滑性が低いため固体潤滑材の機能を全体として低下させる。
【００６３】
そこで、まず表４に示す配合１乃至配合５のように、Ｓｂ₂Ｏ₃とＣを一定としＭｏＳ₂の割合を変え、また配合６乃至配合１０のように、ＭｏＳ₂とＣを一定としＳｂ₂Ｏ₃の割合を変えて検討を行った。
【００６４】
【表４】

【００６５】
その結果、Ｓｂ₂Ｏ₃によるＭｏＳ₂の酸化防止効果は、Ｓｂ₂Ｏ₃の増加につれて向上するが、ＭｏＳ₂に比べてＳｂ₂Ｏ₃の比率が大きすぎると、潤滑性が低下してしまうことがわかった。その理由は相対的にバインダーとしてのＰＡＩの量が不足するためと考えられる。◆
従って、適正なＭｏＳ₂／Ｓｂ₂Ｏ₃の比は１．２〜２．０であり、さらに１．５が最適値であることが判明した。
【００６６】
次に、ＭｏＳ₂／Ｓｂ₂Ｏ₃の値を１．５一定とし、バインダーとしてのＰＡＩの割合を５乃至３０重量部の範囲内で変えて検討した。その結果、耐熱性、潤滑性および耐摩耗性のいずれもＰＡＩの割合によって影響を受けることが判明し、耐熱性はＰＡＩの割合が多い方が良好である傾向が明らかとなった。
【００６７】
しかし、潤滑性は、ＰＡＩが１４重量部付近にピークが認められ、また、耐摩耗性は、ピークがやや高い方に移り、約１６重量部付近であり、総合的にはＰＡＩの配合は１２乃至１８重量部の範囲が適正であることが判明した。
【００６８】
次に、Ｃの最適配合量の検討を行った。表４の配合１１乃至配合１５に示すように他の因子を固定し、Ｃのみ０．６乃至１．０重量部の範囲で変化させた。この結果、Ｃは０.７〜０.９重量部の範囲が良好であり、０．８重量部が最適値であることがわかった。◆
以上の検討結果から、コーティング材の構成は表５に示す割合が良好であることが明らかとなった。
【００６９】
次に、コーティング膜の焼き付け温度について検討した。上述した検討には２００℃で１時間焼き付け処理した試料を用いたが、温度のみを２００乃至４４０℃の間で２０℃ごとに変えた試料を用い、ピンオンディスク試験により潤滑性、耐摩耗性の評価を行った。検討した試料は表５の配合割合のものであり、表２のNo.５のものを用いた。なお溶剤は、ジメチルアセトアミドなどを用いると良い。
【００７０】
【表５】

【００７１】
潤滑性の試験結果を、図３に示す。図は試料の摩擦係数が０．３になるまでの回転数を、表２に示す従来品No.１の値を基準として求めたNo.５の相対回転数比を示す。図に明らかなように従来品の結果に対し、２００℃において、すでに寿命が約１０倍ある結果が示されているが、焼き付け温度の上昇に従って徐々に寿命が延び３２０℃を越えると急激に寿命が増加し、３６０℃から４４０℃の範囲では従来のものに比べ６０乃至８０倍の寿命増加を示した。また、焼き付け処理後に６０℃×９０％R/H×１００時間の湿潤条件下においた試料のピンオンディスク試験結果でもほぼ同様の潤滑性の向上がみられた。
【００７２】
次に、耐摩耗性の検討結果について述べる。◆
耐摩耗性の評価は、アムスラ試験機を用いて行った。試験は４０ｍｍ径で長さ１０ｍｍのリング状試料２ケを１０ｋｇｆで押し付け、１９０ｒｐｍで、相対滑りを１０％発生させて摺動する方法により行う。試料の内の一方はステンレス鋼ＳＵＳ４２０材を用いた。
【００７３】
No.５のコーティング膜を施した試料の焼き付け温度とアムスラ試験による摩耗粉が発生し始めるまでの時間の関係を求めた。図４にその結果を示す。図から明らかなように２０５℃以下では、従来のコーティング膜No.１の方が良好な結果となった。しかしこの温度を境として高温側ではNo.５が良好な耐摩耗性を示すようになり、３００℃で焼き付けたものでは摩耗粉の発生し始める時間はNo.１の約１８０倍となった。また温度が上昇すると摩耗粉発生までの時間が短くなるNo.１に対してNo.５は加熱温度の上昇とともに摩耗粉発生までの時間が長くなり、さきに述べた潤滑性能試験の結果と合わせ、従来の有機系バインダーとＭｏＳ₂を用いた固体潤滑剤に比べ高温特性が格段に向上した。
【００７４】
以下、上述の検討結果に基づいて明らかになった耐熱性が最も良好だった上記No.５のコーティング材を実際の装置に適用した。◆
本発明の一実施例を図５により説明する。図５は、本実施例に関するスクリュウ式圧縮機の構造を示す断面図である。オスロータ１は、一方の軸端に配設したピニオンギヤ３で駆動され、他方の軸端に配設されたタイミングギヤ４でメスロータ２を同期回転させる。オス・メスロータ間には冷却用の油は噴射されず、ロータの噛み合いによって吸入口Ａから吸入された空気は、高圧、高温となって吐出口Ｂから吐出される。オスロータとメスロータは、ステンレス鋼（ＳＵＳ４２０）を用いた。
【００７５】
オス・メスロータは転がり軸受５で支持され、ケーシング６内で回転する。軸受と各ロータ歯部の間には軸封部８が配設され、軸受５を浸した油が、圧縮室Ｃ内へ侵入するのを防止している。◆
図６は、オスロータとメスロータの噛み合わせ状態を示す図５のＫ−Ｋ部分の断面図、図７はオスロータとメスロータへの被膜の被覆状態を説明する概略断面図である。オスロータとメスロータは、互いに接触する摺動面に上記No.５のコーティング材を被覆し２５０℃で１．５ｈｒ焼き付け処理を施し、２０μｍの被膜を形成した。被膜の具体的配合は、溶剤７５：重量部、バインダー：１５重量部、ＭｏＳ₂：６重量部、Ｓｂ₂Ｏ₃：４重量部、Ｃ：０．８重量部とした。
【００７６】
なお、コーティング膜は歯形部及び軸方向の端面部にも被覆した。◆
圧縮機の運転条件は、回転数２４０００ｒｐｍ、吐出圧力７ｋｇｆ／ｃｍ²とし、起動後５分間運転して停止し、再起動する行程を３００００回繰り返した後、被膜を目視及び顕微鏡観察した。まず、目視観察では互いのロータの接触部分はコーティング膜が薄く削りとられた痕跡が認められるが、膜の変色はなく、前述した粘着テープによる剥離試験でも剥離は生じなかった。
【００７７】
比較に行った従来のコーティング膜No.１（ピグメントの主成分はＭｏＳ₂）の表面は、高温となる吐出側に変色部が発生していた。◆
次に、ロータを切断しコーティング膜の断面観察を行なった。コーティング膜の断面は、図８に示すようにバインダーであるＰＡＩ５１の中に粒状のピグメントが分散配置しており、Ｘ線分析の結果、それらはＭｏＳ₂粒子５２、Ｓｂ₂Ｏ₃粒子５３及びＣ粒子５４であることが分かった。比較に行った従来のコーティング膜No.１（ピグメントはＭｏＳ₂のみ）を観察した結果では、Ｍｏは残留しているが顕在化しておらず、Ｓが大幅に減少しＭｏは酸化が進行したＭｏＯ₃の形で、且つ形状も不明確な状態で残っていることが判明した。このＭｏＯ₃は、潤滑性がなく摺動部のコーティング膜としては不十分な状態に変質していることが判明した。
【００７８】
No.５のコーティング材の耐熱性が良い理由は、Ｓｂ₂Ｏ₃が膜中に侵入した酸素と選択的に反応しＭｏＳ₂の酸化を防いでいると考えられる。◆
以上の結果から、ＰＡＩをバインダーとし、ピグメントとしてＭｏＳ₂、Ｓｂ₂Ｏ₃及びＣの粒子を混合したコーティング膜は、熱による変色が無く膜の性状も大きく変化しておらずスクリュウ式圧縮機のロータの耐熱性潤滑被膜として好適であることが判明した。
【００７９】
本発明の他の実施例を、図９により説明する。◆
図９は、本実施例のロータの部分断面を示す概略断面図である。◆
オスロータ１は炭素鋼で製作し、その表面に上記のNo.５のコーティング材によりＭｏＳ₂：７重量部、Ｓｂ₂Ｏ₃：５重量部、Ｃ：０.９重量部及びバインダーとしてのＰＡＩ：１８重量部よりなるコーティング膜１０を設けた。被膜の焼き付け処理条件は３００℃×１ｈｒで行った。一方、メスロータ２もオスロータと同種の素材で製作し、その表面に無電解Ｎi−Ｐメッキ被膜１２を設けた。
【００８０】
オスロータ１とメスロータ２の周速は異なっているため、表面部には相対すべりを生じる。これによってオスロータ１とメスロータ２の干渉する部分では、メスロータ２側のＮi−Ｐメッキ被膜１２が軟質層であるオスロータ１のコーティング膜１０を研削する。すなわちメスロータ２表面上の高硬度層であるＮi−Ｐメッキ被膜１２によって、オスロータ１表面の軟質層が研削され、オスロータ形状に相応したメスロータの表面形状が創出される。研削された軟質層の粉末は、空気の流れと共に機外へと排出される。
【００８１】
これによって従来、運転中のロータ歯形部の温度分布を事前に想定し、ロータ歯形部の形状を室温時の形状に置き換えて高精度に加工していたが、実際の個々の圧縮機の各歯形部位置における膨張状態に相応して相手歯形が創出され、予め、運転状態に両ロータが干渉する寸法、即ち研削代を残しておくことにより、極小かつ最適のロータ間ギャップが確保できる。またメスロータ２は、第５図に示すタイミングギヤ４によって駆動されているためにオスロータ１の運転により、メスロータ２の歯形を回転創成仕上げを行った後には、接触は発生しなくなり、それ以上メスロータ２の表面層を減肉させることはなく、良好な接触状態を保持して運転させることができる。◆
なお本実施例では、メスロータに硬質な表面被膜を設けたが、オスロータとメスロータの被膜を換えても同様の結果が得られた。
【００８２】
本発明の他の実施例を、図９及び図１０により説明する。本実施例に用いたオスロータ１は、前記実施例のものと同様のものを用いた。前述の実施例とは、図９のメスロータ２の表面の無電解Ｎi−Ｐメッキ被膜１２中に、図１０に示すようにＰＴＦＥの粒子９を分散させた点が異なる。また、オスロータ及びメスロータを収納するケーシングを鋳鉄製とした。
【００８３】
本実施例の構造では、メスロータは上述したコーティング被膜No.５と接触し、コーティング被膜No.５の干渉部分を必要な部分だけ削り落す。また、鋳鉄製のケーシングの内側との接触部において、ケーシング内壁との干渉部分を削り取り、さらにＰＴＦＥが摺動面に付着しロータとケーシングと摩擦係数を低減しかじりや、焼付き等の現象の発生を防止する。なお本実施例においても、前述の実施例同様メスロータに硬質な表面被膜を設け、オスロータに上述のコーティング材No.５の被膜を設けたが、オスロータとメスロータの被膜を換えても同様の結果が得られた。
【００８４】
本発明の他の実施例を図１１により説明する。◆
本実施例のオスロータ１は、図１１に示す断面構造から明らかなようにその表面にＰＡＩのみの層１６を形成し、その上に上述のコーティング材No.５の被膜を設けた２層構造からなるコーティング膜を備えている。メスロータ２は、その表面にＮi−Ｐメッキ被膜１２を設けた。この組合せのスクリュウロータをスクリュウ式圧縮機に組込んで長期連続運転した後に、その表面を観察したところ上記実施例と同様にコーティング材No.５の被膜は変色部も剥離部もなく良好であった。本実施例によるとロータとコーティング材No.５の被膜は、コーティング材No.５のバインダＰＡＩにより結合され、ロータ側のＰＡＩのみの層はピグメントが混合していないためロータとの接着強度が増すとともに、耐食性が増す。
【００８５】
本発明の他の実施例を図１２により説明する。◆
本実施例のスクリュウロータは、メスロータの表面に上述のコーティング材No.５の被膜を設け、オスロータの表面にＮi−Ｐメッキ被膜を設けたものを用いている。
【００８６】
熱膨張による干渉によって相手側ロータの創成仕上げをより円滑に行うために、歯形を図１２に示すようにオスロータ１の転がりピッチ円径dpmをオスロータの歯底径dimより小さく、同時にメスロータ２の転がりピッチ円径dpfをメスロータ２の歯先径dofより大きく取る。これにより各々のロータのかみ合い回転時に、転がり接触を行う歯形部分がなくなり、即ち相対すべり速度が全ての部分に存在するため、オスロータ１表面に設けた高硬度層がメスロータ表面へ接触した際、必ず相手側のロータ表面が仕上げられる。
【００８７】
特にオイルフリースクリュウ式圧縮機において、圧縮効率を向上させるためにはロータ間のギャップを小さくする必要があるが、実際の運転状態での熱膨張状態の歯形を全ての断面で予測することは困難でありロータの接触を防止するために、ある程度の安全を見込み、予測より大きめのギャップを設定しているが、本発明によれば、接触により相手の歯形の干渉部を最終仕上し、かつロータ間のかじり付きを起さぬため、圧縮機の空気漏洩による損失を低減でき、信頼性を損なうことが無い。
【００８８】
尚、最終歯形への仕上げは、予め予想する運転最高温度に少しづつ運転温度を上げながら接触部の研削を徐々に行わせて行くのが良い。さらに、本実施例のオスロータ及びメスロータのコーティング膜を逆にしても、またオスロータの表面に被膜を被覆しない場合にも同様の結果が得られた。さらに、両ロータの表面に異なる硬さのコーティング膜を塗布しても同様の結果が得られた。
【００８９】
本発明の他の実施例を、図１３により説明する。図１３は、前述の図６に相当する両ロータの噛み合わせ状況及びケーシングとの関係を示す概略断面図である。
【００９０】
オスロータ１の表面に厚さ約２０μｍのＰＴＦＥ１０％入りの複合Ｎi−Ｐメッキ層を設けた。またメスロータ２の表面にはＭｏＳ₂：５重量部、Ｓｂ₂Ｏ₃：３重量部、Ｃ：０．７重量部及びバインダとしてのＰＡＩ：１２重量部よりなるコーティング膜１２を約２０μｍの厚さに設けた。両ロータともに、夫々の被膜は軸方向の端面部分にも被覆した。
【００９１】
ケーシング３には、オスロータ１及びメスロータ２と相対する部分と両ロータの軸方向の端面と相対する部分に上記メスロータ２の表面に施した被膜１５を約４０μｍの厚さに設けた。ケーシング３の被膜厚さがロータに比べて厚いのは、ロータは回転しているため軸方向に直角な断面では温度分布がほぼ一様になるが、ケーシングは回転せず吐出部付近が高温となり、吐出部付近において不均一な膨張が生じるため、膨張による変形を吸収するためである。
【００９２】
このような被膜をロータ及びケーシングの摺動面に形成してスクリュ圧縮機を連続運転した結果、性能の大幅向上が実現でき、且つ従来の被膜に比べメンテナンス期間を４倍まで延長させることができた。試験後の内面を観察したところ、ロータ及びケーシングの各摺動部分は共ずりの痕跡が認められ、それぞれの摺動部分の隙間が圧縮空気の漏洩を最小限にすることができたと考えられる。
【００９３】
本実施例では、ロータの端面部にも被膜を被覆したがケーシング側のロータ端面との対応部に被膜を被覆しているため、ロータ側の端面部分は除去しても同様の効果が得られる。
【００９４】
また、本実施例におけるオスロータとメスロータの被膜を逆に設けても同様の結果が得られた。
【００９５】
なお、上記の各実施例では、オスロータとメスロータが一対のもについて説明したが、本発明はオスロータとメスロータが一対以上で構成されるスクリュウ式圧縮機にも同様に適用できる。
【００９６】
【発明の効果】
以上、本発明によれば、ドライスクリュウ式圧縮機に用いるロータ及びケーシング表面に、ポリイミドアミド樹脂をバインダーとし、ＭｏＳ₂、Ｓｂ₂Ｏ₃及びＣをピグメントとしたコーティング材を塗布し、高温度で焼き付けることにより、ロータの吐出側に生ずる高温加熱化現象に対しても耐熱性があり、且つ耐摩耗性の高いコーティング被膜を形成できる。
【００９７】
また、共ずりによってロータ相互間及びロータとケーシング間の隙間を極少化することにより圧縮性能の大幅な向上ができるとともに、加工精度を高精度にする必要がないため、加工工数の低減をすることができる。
【００９８】
また、耐熱性及び耐摩耗性が向上したため、従来に比べメンテナンス期間を大幅に延長することができる。
【図面の簡単な説明】
【図１】コーティング被膜の剥離メカニズムを説明する図である。
【図２】表２に示すコーティング膜の潤滑性試験結果である。
【図３】ピンオンディスク試験による被膜の焼き付け温度と潤滑性との関係図である。
【図４】アムスラ試験による被膜の焼き付け温度と潤滑性との関係図である。
【図５】本発明の一実施例に係わるスクリュウ式圧縮機の断面図である。
【図６】本発明の一実施例に係わるオスロータとメスロータとの噛み合い状態を示す概略断面図である。
【図７】オスロータとメスロータの被膜の被覆状態を示す概略断面図である。
【図８】本発明の一実施例に係わるコーティング膜の断面図である。
【図９】本発明の一実施例に係わるロータの被膜の被覆状態を示す概略断面図である。
【図１０】本発明の一実施例に係わるコーティング膜の断面図である。
【図１１】本発明の一実施例に係わるオスロータとメスロータとの噛み合い状態を示す概略断面図である。
【図１２】本発明の一実施例に係わるオス・メス両ロータの噛み合わせ状況の説明図である。
【図１３】本発明の一実施例に係わるオスロータとメスロータとの噛み合い状態を示す概略断面図である。
【符号の説明】
１…オスロータ、２…メスメータ、３…ピニオンギヤ、４…タイミングギヤ、５…軸受、６…ケーシング、８…軸封部、１０，１２…コーティング被膜。[0001]
[Industrial application fields]
The present invention relates to a screw-type rotary machine used for a compressor, a blower, a vacuum pump, and the like and a rotor surface treatment method of the rotary machine, and in particular, a screw-type screw that enables maintenance-free, high-performance, and is suitable for a dry method. The present invention relates to a compressor and a surface treatment method for a rotor used in the compressor.
[0002]
[Prior art]
Friction and wear phenomena occur at the interface where the machine parts come into contact with each other and slide. Therefore, countermeasures are usually taken to place some lubricant on the sliding surface. ◆
These lubricants are roughly classified into liquid lubricants such as oil and water, ethylene tetrafluoride resin (hereinafter referred to as PTFE), molybdenum disulfide (hereinafter referred to as MoS).₂And solid lubricants (hereinafter referred to as coating materials) such as graphite (hereinafter referred to as C).
[0003]
The former has a long history and its usage is simple, but in recent years, problems that cannot be ignored, such as product contamination due to oil splashes and the effect on the environment, are also being revealed. ◆
The latter has a relatively new history and various technical difficulties, but its cleanliness is welcomed, and in recent years it has been applied to a dry solid lubrication system.
[0004]
As an example of adopting the solid lubrication method, a screw type compressor according to the present invention will be taken and described below. ◆
In a screw-type fluid machine, a male rotor and a female rotor rotate in a casing while meshing with each other, and a space formed by the casing and both rotors is reduced while moving in the axial direction to compress the fluid in the space. ing.
[0005]
Further, in the screw type fluid machine, as a lubrication method of the sliding part, a so-called oil cooling type in which oil is supplied into the casing together with the fluid to cool the oil between the rotors and between the rotors and the casing, and the casing There is a so-called dry method in which no oil is supplied.
[0006]
Among the above, in the former oil-cooled type, since the male rotor and the female rotor are in contact with each other through an oil film, when the male rotor is rotated by a motor connected through a drive gear, the female rotor is also rotated by the rotation of the male rotor. Therefore, it is not necessary to install a rotary drive mechanism in the female rotor, and the configuration can be simplified.
[0007]
In addition, the oil-cooled type can cool the frictional heat generated by the rotation of both rotors with oil, so that both rotors can be prevented from seizing. ◆
On the other hand, the oil-cooled type has a problem that the fluid is contaminated by oil droplets and oil vapor, so that it cannot be applied to a field requiring a clean fluid such as the food industry and the high-tech industry.
[0008]
On the other hand, the dry type has a feature that it becomes a clean fluid because no oil is mixed into the compressed fluid. ◆
On the other hand, since the dry type rotates with both rotors in non-contact state, both rotors cannot rotate synchronously, and it is necessary to install a synchronous gear at the shaft end of both rotors. And the structure becomes complicated. ◆
Further, since both rotors are not in contact with each other, there is a problem that fluid leakage is likely to occur and compression efficiency is lowered.
[0009]
As described above, the oil-cooled type and the dry type have advantages and disadvantages, respectively. However, the dry method is a method with great merit by minimizing fluid leakage.
[0010]
The rotor of the dry screw compressor is exposed to a high temperature of 300 to 350 ° C. on the discharge side. In addition, when the operation is stopped, the temperature of the high-temperature air around the rotor decreases, so that moisture in the air condenses and adheres to the rotor surface, which promotes corrosion of the rotor material.
[0011]
Therefore, the coating material applied to the rotor is required to have heat resistance and corrosion resistance in addition to good lubricity. Conventional coating materials have good lubricity, but are rarely used on the premise that they are used at high temperatures (for example, 250 to 350 ° C.). Therefore, development of materials having good heat resistance and corrosion resistance is not always required. It was not enough. The reason seems to be that there was almost no object of the use condition like a screw type compressor.
[0012]
That is, most of the conventional screw type compressors are oil type, and since oil is a lubricant, there is no need to use a coating material. However, in recent years, high-tech industries such as food, pharmaceuticals, and semiconductor manufacturing have come to require particularly clean compressed air, so the demand for dry screw compressors has increased rapidly. The situation will continue.
[0013]
That is, in such an oil-free (dry) compressor, in order to improve performance such as volumetric efficiency, it is necessary to reduce the gap between the male rotor and the female rotor and the gap between each rotor and the casing as much as possible. ◆
However, in order to reduce these gaps, it is necessary to extremely increase the machining accuracy such as grinding for both the male and female rotors and the casing. Also, when machining accuracy is increased and the gap is made as close as possible, it is caused by contact between male and female rotors due to thermal distortion of the rotor, timing gear backlash and rotor bearings, or contact between the rotor and casing. Failures such as seizure and damage occur.
[0014]
Therefore, various proposals have been made for the purpose of minimizing the gap between the male and female rotors. For example, (1) optimization of the tooth profile, and (2) the rotor surface is coated with a synthetic resin, and unnecessary coating film is removed by initial blending to reduce the gap.
[0015]
Regarding the latter, JP-A-58-48792 and JP-A-61-197794 disclose that PTFE or the like is applied to the surface of the rotor. ◆
Japanese Patent Application Laid-Open No. Hei 2-201072 mainly uses a polymer plastic as a binder for the surfaces of the male rotor and the female meter, and MoS.₂A non-metallic substance mixed with the above is coated to form a film thickness of 0.1 to 2 mm.
[0016]
[Problems to be solved by the invention]
In the example using the PTFE, when both the male and female rotors are brought into contact with each other, the PTFE coating is likely to be welded, peeled off, or worn, leading to a cause of failure.
[0017]
MoS₂Is superior in solid lubricity, but the conventional blending composition tends to gradually oxidize at a high temperature for a long time, and the lubricity tends to gradually decrease. Further, since the film thickness is 0.1 to 2 mm, for example, in order to cause the above-described co-shear phenomenon, the coating layer is too thick to contact the male rotor and the female rotor, and the film is easily peeled off. Further, since the film is thick, there is a problem that the performance is lowered as the gap is increased and the discharge air temperature is likely to rise excessively.
[0018]
Conventionally used MoS as the main component of the rotor coating material₂The oxidation temperature is said to be 400 ° C. or higher. However, this temperature is considered to be the temperature at which the oxidation is accelerated, and as shown in Table 1 (Solid Lubrication Handbook, page 93, Yukishobo), oxidation occurs at a low speed even at a temperature of 300 ° C. or lower. MoS coated on the rotor surface with severe temperature conditions₂It is a very strict condition for us.
[0019]
[Table 1]

[0020]
When oxidation occurs, MoS in the coating layer is formed as shown in FIG.₂Molybdenum trioxide (MoO_ThreeIt is thought that the sulfur content is oxidized and gasified to cause corrosion. Along with this, MoO_ThreeIs considered to be unable to exhibit the original purpose of the coating because the bonding strength with the binder becomes weak and falls off, resulting in a decrease in film thickness and peeling.
[0021]
On the other hand, the temperature of the rotor surface during operation of the oil-free screw compressor, to which the present invention is applied, is 50 to 100 ° C. on the suction side of the rotor, 120 to 150 ° C. on the intermediate portion, and 220 to 300 ° C. on the discharge side. Degree. Furthermore, it is considered that the temperature rises to about 320 to 350 ° C. immediately before the discharge temperature protection relay operates. ◆
Therefore, in screw type compressors, MoS is improved with improved heat resistance.₂Prevention of oxidation is the most important issue in coating technology.
[0022]
An object of the present invention is to provide a screw rotor coated with a coating material with good heat resistance that does not lose lubricity and durability even when exposed to high temperatures, a highly reliable screw compressor using the screw rotor, and a screw rotor. To provide a manufacturing method.
[0023]
[Means for Solving the Problems]
The screw rotor for the above object is achieved by providing the following means.
[0027]
  (1) In a screw rotor formed by forming a helical tooth profile on the outer surface in the axial direction, the screw rotor is provided with a layer made of PAI on the surface, the binder is PAI on the layer, and MoS2, Sb2O3 and C are used as pigments. A dispersed solid lubricant coating is provided.
[0029]
  (2)the above(1), Sb2O3, MoS2 and C are provided as particles in the solid lubricant film.
[0030]
  (3)the above(1)The solid lubricant coating is composed of a blend selected from the range of 12 to 18 parts by weight of PAI, 5 to 7 parts by weight of MoS2, 3 to 5 parts by weight of Sb2O3, and 0.7 to 0.9 parts by weight of C. Become.
[0031]
The screw compressor of the above object is achieved by including the following means.
[0032]
  (4) In a screw compressor including at least a pair of a male rotor and a female rotor meshing with each other in the casing, both or any one of the rotors may include the above (1) to (3A screw rotor is provided.
[0033]
  (5) In a screw type compressor having at least one pair of a male rotor and a female rotor meshing with each other in the casing, the above (1) to (1)3And a nickel-phosphorous plating film on the surface of the other rotor.
[0034]
  (6) In a screw type compressor having at least one pair of a male rotor and a female rotor meshing with each other in the casing, the above (1) to (1)3) And a nickel-phosphorous plating film in which PTFE is dispersed in the film on the surface of the other rotor..
[0036]
  (7)In a screw compressor including at least a pair of a male rotor and a female rotor meshing with each other in a casing, a binder is PAI on the surface of the casing facing the male rotor and the female rotor, and MoS is used as a pigment. 2 , Sb 2 O Three And a solid lubricant film in which C is dispersed, andThe solid lubricant coating has a composition selected from the range of 12 to 18 parts by weight of PAI, 5 to 7 parts by weight of MoS2, 3 to 5 parts by weight of Sb2O3, and 0.7 to 0.9 parts by weight of C.
[0037]
Furthermore, the manufacturing method of the above-described screw rotor is achieved by providing the following means.
[0040]
  (8) In a screw rotor manufacturing method in which a helical tooth profile is formed on the outer surface in the axial direction, PAI is applied to the surface of the screw rotor having the helical tooth profile, and then Sb2O3 is dispersed on the surface. A lubricant is applied and heated to form a solid lubricant film.
[0041]
  (9) In a screw rotor manufacturing method in which a helical tooth form is formed on the outer surface in the axial direction, PAI is applied to the surface of the screw rotor having the helical tooth form, heated, and then a binder is applied to the surface. The solid lubricant film in which MoS2, Sb2O3 and C are dispersed is applied to the pigment and heated to form a solid lubricant film.
[0042]
[Action]
MoS₂And Sb coating material₂O_ThreeIs added, MoS in the coating film₂, C and the like to prevent oxidation of lubricating particles. That is, Sb in the coating₂O_ThreeThe presence of oxygen selectively captures oxygen in the air that has entered the coating, and Sb₂O_ThreeAs it oxidizes first, MoS₂Prevents oxidation of C and C. Therefore, the lubricity of the coating material is maintained for a long time.
[0043]
Sb₂O_ThreeAs such, MoS₂Although it is not so moderate, it has some lubricity and also has good stretchability.₂O_ThreeThe presence itself contributes to maintaining the lubricity of the coating film. ◆
As the binder, PAI having high heat resistance is used, and the ratio is set to 12 to 18%, thereby preventing oxygen and moisture in the air and condensed water at the stoppage from entering the coating film. Accordingly, corrosion of the rotor surface is prevented and MoS in the pigment is prevented.₂By effectively coating C and C, the oxidation and deterioration are prevented and the lubricity is maintained for a long time.
[0044]
PAI is originally a kind of thermoplastic resin, but it also has a thermosetting function because it contains an imide group. Therefore, by appropriately selecting the baking temperature and time after application, the amic acid changes to an imide ring, so that the thermosetting characteristics become remarkable, the heat distortion temperature rises, and the heat resistance of the coating film is improved. In addition, since PAI is easily liquefied with a solvent, it can be reliably mixed and dispersed with lubricant particles and additive particles during coating. Note that dimethylacetamide or the like is preferably used as the solvent.
[0045]
Furthermore, MoS using PAI as a binder on the surface of either the male rotor or the female rotor.₂, Sb₂O_ThreeAnd a coating layer (hereinafter referred to as “coating material No. 5”) coated with C as lubricating particles, and the other rotor is formed of metal, or the surfaces of both rotors are coated with coating material No. 5 Cover. In any of the above cases, both rotors are structured to rotate synchronously with timing gears, or in addition to the above, the tooth profile of the rotor itself uses a tooth profile that does not have a rolling contact point, so that the coating material as a coating film can be mutually By sliding (co-spinning), the clearance between the male and female rotors can be made as close to zero as possible, and the compression performance can be dramatically improved. As a specific method, coating material No. 5 is applied to the male rotor, and this kind of lubricating coating film is not applied to the female rotor, and the hard surface is left as it is. Here, the hard surface refers to a so-called hard surface in which the metal rotor has no coating film or is subjected to hard metal plating.
[0046]
According to the Amsura friction and wear test (hereinafter abbreviated as Amsla test) conducted as a basic experiment, MoS₂In the case of a combination of coating films containing as a main component, the coating film applied to the test piece is peeled off in a long-time test (for example, 6 hours). ◆
However, when the surface of one rotor, for example, a male rotor, is hard, the coating film coating applied to the female rotor begins to wear out twice as long as when both rotor surfaces are coated with a coating material. Cost. In addition, even after the start of wear, the rate of decrease not only shows a gradual change, but even if it begins to wear and partially peels off and a metal substrate is seen, the coating film of the healthy part in the vicinity immediately becomes gradually peeled off. To fill in the defective part.
[0047]
That is, according to the above combination using the coating film of the present invention, a phenomenon suitable for prolonging the life of the coating film was observed that the coating film has self-repairing properties. ◆
Furthermore, the coating film after self-repair is completed, and wear reduction is hardly seen even in the subsequent long-term test, and the thickness of about 20 to 30% of the original coating film remains as it is under the present experimental conditions. It is maintained for a very long time.
[0048]
【Example】
Prior to the application to the screw rotor, the results of studying the coating film will be described first. ◆
The examination was conducted on various coating materials that are considered to be able to improve the heat resistance shown in Table 2.
[0049]
[Table 2]

[0050]
No.1 MoS as the conventional coating material in the table as a reference for comparison₂It was investigated. No.2 C is No.1 MoS₂In contrast, it is expected to improve heat resistance.
[0051]
No. 3 is MoS₂And antimony trioxide (Sb₂O_Three) And Sb₂O_ThreeMoS by₂This is expected to improve the heat resistance due to the antioxidant effect. No. 4 is obtained by increasing the solid content of No. 3, and No. 5 is obtained by further adding C to No. 4 to improve heat resistance. For No. 1 to No. 5, PAI was used as the binder.
[0052]
No. 6 is intended to have high temperature heat resistance of 400 ° C. or higher with an inorganic silicate binder and boron nitride (BN) as a coating material. ◆
No. 7 consists of two layers, with PAI about 3 μm in the lower layer and No. 5 in the upper layer. ◆
The above seven types of coating materials were subjected to screening tests such as heat resistance and corrosion resistance. The film thickness of each examined sample was about 20 μm. Table 3 summarizes the results shown below. Evaluations in the table are as follows: ▲ indicates a practical problem, △ indicates a slight problem, ○ indicates no problem, and double circle indicates no problem.
[0053]
[Table 3]

[0054]
As the test piece, φ30 × 5t stainless steel (SUS420) was used, and after sandblasting, a predetermined coating material was applied to a thickness of about 20 μm and baked at 200 ° C. for 1 hour.
[0055]
(1) Heat resistance test ◆
The heat resistance was judged by a coating film peeling test using an adhesive tape. ◆
After the test piece was heated at 380 ° C. for 20 hours, the presence or absence of peeling or peeling of the film only by heating was examined. Next, apply adhesive tape to the center of the test piece and apply 1kgf / cm.²After pressurizing, the tape was slowly peeled off, and the peeled state of the film was observed to determine the heat resistance.
[0056]
As a result, No. 2 is No. 1 MoS.₂Despite the fact that C, which has better heat resistance, is the main component, the degree of peeling was greater than No. 1 and peeling occurred. ◆
MoS₂Sb₂O_ThreeNo. 3 and No. 4 to which No. 1 was added had a small degree of peeling compared to No. 1, although there was a difference in degree. No. 5 and No. 7 were good with almost no peeling, and No. 6 was best with no peeling at all.
[0057]
(2) Corrosion resistance test ◆
The above-mentioned test piece coated with various coating materials was heated at 360 ° C. for 20 hours and then kept in a constant temperature and humidity chamber at a temperature of 60 ° C. and a humidity of 90% RH for 100 hours. ◆
As a result, no corrosion was observed in No. 2, and MoS₂+ Sb₂O_ThreeNo.3, No.4, and No.5 are based on MoS₂Compared to No. 1 only, it was equivalent or slightly better. However, No. 6 had more wrinkles than the others.
[0058]
(3) Lubricity test ◆
A pin-on-disk that presses a spherical ball against a rotating disk after heating the test piece after applying various coating materials at 360 ° C. for 20 hours and then performing the above-described wet test (60 ° C. × 90% RH × 100 hours). By the test, the total number of revolutions until the friction coefficient became 0.3 was compared with the relative revolution number ratio based on the value of Sample No. 1 to evaluate the lubrication durability. The test results are shown in FIG.
[0059]
No. 1 and inorganic No. 6 have poor lubrication durability compared to other types. ◆
On the other hand, the lubricity is improved in the order of No. 4, No. 3, No. 7, No. 2, and No. 5. In particular, No. 5 was about 9 times as high as No. 1 and was found to be highly durable.
[0060]
As is clear from Table 3 that summarizes the above examination results, each has advantages and disadvantages, but from the viewpoint of greatly improving heat resistance without deteriorating corrosion resistance and lubricity compared to No. 1. MoS with PAI as binder₂Sb as the main component₂O_ThreeNo. 5 to which C was added was found to be the best.
[0061]
Next, the optimum blending range of this No. 5 blend was examined. ◆
The coating material comprises a solvent, a resin as a binder, and a lubricant powder (hereinafter referred to as pigment). ◆
The amount of the solvent is appropriately set depending on the use conditions, but since it evaporates at the time of drying, there is usually no solvent in the coating film after drying, so it is a constant value (75 parts by weight), and the binder is also 15 parts by weight. The following formulation was examined for the pigment. Table 4 shows the blending ratio.
[0062]
MoS₂Is the main coating material, and the lubrication under dry condition is the MoS₂The presence of is great. However, as described above, oxidation is promoted between oxygen in the air and 2MoS at high temperatures.₂+ 3O₂→ 2MoO_Three+ 2S₂(Gas) reaction proceeds and the resulting MoO_ThreeIs easy to peel off. Moreover, even if it remains in the film, the function of the solid lubricant is lowered as a whole because the lubricity is low.
[0063]
Therefore, first, as in Formulation 1 to Formulation 5 shown in Table 4, Sb₂O_ThreeAnd C constant and MoS₂The ratio of MoS is changed, and as in Formulation 6 to Formulation 10, MoS₂And C are constant and Sb₂O_ThreeThe ratio was changed and examined.
[0064]
[Table 4]

[0065]
As a result, Sb₂O_ThreeMoS by₂The antioxidant effect of Sb₂O_ThreeAs MoS increases, MoS₂Compared to Sb₂O_ThreeIt has been found that if the ratio is too large, the lubricity is lowered. The reason is considered that the amount of PAI as a binder is relatively insufficient. ◆
Therefore, proper MoS₂/ Sb₂O_ThreeThe ratio was 1.2 to 2.0, and 1.5 was found to be an optimum value.
[0066]
Next, MoS₂/ Sb₂O_ThreeAnd the ratio of PAI as the binder was changed within the range of 5 to 30 parts by weight. As a result, it was found that all of heat resistance, lubricity and wear resistance were affected by the ratio of PAI, and it became clear that the heat resistance tends to be better when the ratio of PAI is larger.
[0067]
However, as for the lubricity, a peak is observed at around 14 parts by weight of PAI, and the wear resistance shifts to a slightly higher peak and is around 16 parts by weight. A range of 18 to 18 parts by weight was found to be appropriate.
[0068]
Next, the optimum blending amount of C was examined. Other factors were fixed as shown in Formulation 11 to Formulation 15 in Table 4, and only C was changed in the range of 0.6 to 1.0 parts by weight. As a result, it was found that C was in the range of 0.7 to 0.9 parts by weight, and 0.8 part by weight was the optimum value. ◆
From the above examination results, it has been clarified that the composition shown in Table 5 is good in the composition of the coating material.
[0069]
Next, the baking temperature of the coating film was examined. In the above examination, a sample baked at 200 ° C. for 1 hour was used, but a sample in which only the temperature was changed between 200 ° C. and 440 ° C. every 20 ° C. was used, and lubricity and wear resistance were determined by a pin-on-disk test. Was evaluated. Samples examined were those with the blending ratios shown in Table 5, and No. 5 in Table 2 was used. Note that dimethylacetamide or the like is preferably used as the solvent.
[0070]
[Table 5]

[0071]
The results of the lubricity test are shown in FIG. The figure shows the relative rotational speed ratio of No. 5 obtained by using the value of the conventional product No. 1 shown in Table 2 as a reference for the rotational speed until the friction coefficient of the sample reaches 0.3. As is apparent from the figure, the result is about 10 times longer at 200 ° C than the result of the conventional product, but the life gradually increases as the baking temperature rises, and when the temperature exceeds 320 ° C, the life sharply increases. In the range from 360 ° C. to 440 ° C., the lifetime increased 60 to 80 times compared to the conventional one. In addition, almost the same improvement in lubricity was observed in the pin-on-disk test results of the samples that were subjected to a wet condition of 60 ° C. × 90% R / H × 100 hours after baking.
[0072]
Next, the examination result of wear resistance will be described. ◆
The abrasion resistance was evaluated using an Amsura tester. The test is carried out by a method in which two ring-shaped samples having a diameter of 40 mm and a length of 10 mm are pressed with 10 kgf and slid by generating 10% relative slip at 190 rpm. One of the samples used stainless steel SUS420 material.
[0073]
The relationship between the baking temperature of the sample to which the coating film of No. 5 was applied and the time until the start of generation of abrasion powder by the Amsla test was determined. FIG. 4 shows the result. As is apparent from the figure, the conventional coating film No. 1 gave better results at 205 ° C. or lower. However, at this temperature, No. 5 showed good wear resistance on the high temperature side, and when it was baked at 300 ° C., the time at which abrasion powder started to be generated was about 180 times that of No. 1. When the temperature rises, the time until the generation of wear powder is shortened, whereas No. 5 increases the time until the wear powder is generated as the heating temperature rises. , Conventional organic binder and MoS₂Compared with solid lubricants using JIS, the high-temperature characteristics were significantly improved.
[0074]
Hereinafter, the coating material of No. 5 having the best heat resistance, which was clarified based on the above examination results, was applied to an actual apparatus. ◆
An embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view showing the structure of the screw compressor according to this embodiment. The male rotor 1 is driven by a pinion gear 3 disposed at one shaft end, and the female rotor 2 is synchronously rotated by a timing gear 4 disposed at the other shaft end. No cooling oil is injected between the male and female rotors, and the air sucked from the suction port A due to the meshing of the rotor is discharged from the discharge port B at a high pressure and a high temperature. Stainless steel (SUS420) was used for the male rotor and the female rotor.
[0075]
The male / female rotor is supported by the rolling bearing 5 and rotates in the casing 6. A shaft seal portion 8 is disposed between the bearing and each rotor tooth portion to prevent the oil immersed in the bearing 5 from entering the compression chamber C. ◆
FIG. 6 is a cross-sectional view of a portion KK in FIG. 5 showing a meshed state of the male rotor and the female rotor, and FIG. 7 is a schematic cross-sectional view illustrating a coating state of the male rotor and the female rotor. The male rotor and the female rotor were coated with the above No. 5 coating material on the sliding surfaces in contact with each other, and baked at 250 ° C. for 1.5 hr to form a 20 μm film. The specific composition of the film is as follows: solvent 75 parts by weight, binder 15 parts by weight, MoS₂: 6 parts by weight, Sb₂O_Three: 4 parts by weight, C: 0.8 parts by weight.
[0076]
The coating film was also coated on the tooth profile and the axial end face. ◆
The operating conditions of the compressor are as follows: rotational speed 24000 rpm, discharge pressure 7 kgf / cm²After starting, the operation was stopped for 5 minutes, stopped, and the process of restarting was repeated 30000 times, and then the film was visually and microscopically observed. First, in the visual observation, traces of the coating film being thinly scraped off at the contact portions of the rotors were observed, but there was no discoloration of the film, and no peeling occurred in the peeling test using the adhesive tape described above.
[0077]
Conventional coating film No. 1 used for comparison (the main component of the pigment is MoS₂) Had a discolored portion on the discharge side where the temperature was high. ◆
Next, the rotor was cut and the cross section of the coating film was observed. As shown in FIG. 8, the coating film has a cross-section in which granular pigments are dispersed in PAI51, which is a binder, as a result of X-ray analysis.₂Particle 52, Sb₂O_ThreeIt was found to be particles 53 and C particles 54. Conventional coating film No. 1 used for comparison (Pigment is MoS₂As a result of observing only Mo), Mo remains, but does not become apparent, S decreases significantly, and Mo is oxidized by MoO._ThreeAnd the shape remains unclear. This MoO_ThreeWas found to be in a state of insufficient lubricity and insufficient as a coating film for the sliding portion.
[0078]
The reason why the heat resistance of the coating material No.5 is good is Sb₂O_ThreeReacts selectively with oxygen that has penetrated into the film and MoS₂It is thought that the oxidation of the is prevented. ◆
From the above results, PAI is used as a binder, and MoS is used as a pigment.₂, Sb₂O_ThreeThe coating film in which the particles of C and C are mixed does not discolor due to heat and the properties of the film are not greatly changed. It has been found that the coating film is suitable as a heat-resistant lubricating film for the rotor of the screw compressor.
[0079]
Another embodiment of the present invention will be described with reference to FIG. ◆
FIG. 9 is a schematic cross-sectional view showing a partial cross section of the rotor of this embodiment. ◆
The male rotor 1 is made of carbon steel, and MoS is coated on the surface with the above No. 5 coating material.₂: 7 parts by weight, Sb₂O_ThreeA coating film 10 comprising: 5 parts by weight, C: 0.9 parts by weight, and PAI as a binder: 18 parts by weight was provided. The baking treatment conditions for the coating were 300 ° C. × 1 hr. On the other hand, the female rotor 2 was also made of the same material as the male rotor, and an electroless Ni-P plating film 12 was provided on the surface thereof.
[0080]
Since the peripheral speeds of the male rotor 1 and the female rotor 2 are different, relative slip occurs on the surface portion. As a result, in the part where the male rotor 1 and the female rotor 2 interfere with each other, the Ni-P plating film 12 on the female rotor 2 side grinds the coating film 10 of the male rotor 1 which is a soft layer. That is, the soft layer on the surface of the male rotor 1 is ground by the Ni-P plating film 12 which is a high hardness layer on the surface of the female rotor 2, and the surface shape of the female rotor corresponding to the male rotor shape is created. The ground soft layer powder is discharged out of the machine along with the air flow.
[0081]
In the past, the temperature distribution of the rotor tooth profile during operation was assumed in advance, and the shape of the rotor tooth profile was replaced with the shape at room temperature, which was processed with high precision. A mating tooth shape is created corresponding to the expanded state at the part position, and a minimum and optimum rotor gap can be ensured by leaving a dimension in which the two rotors interfere with the operating state, that is, a grinding allowance in advance. Further, since the female rotor 2 is driven by the timing gear 4 shown in FIG. 5, the contact of the female rotor 2 is not generated after the tooth profile of the female rotor 2 is rotationally generated by the operation of the male rotor 1, and the female rotor 2 is no longer generated. The surface layer is not thinned, and can be operated while maintaining a good contact state. ◆
In this example, a hard surface coating was provided on the female rotor, but similar results were obtained even when the male rotor and female rotor coatings were changed.
[0082]
Another embodiment of the present invention will be described with reference to FIGS. The male rotor 1 used in the present example was the same as that of the above example. This embodiment differs from the above-described embodiment in that PTFE particles 9 are dispersed in the electroless Ni-P plating film 12 on the surface of the female rotor 2 in FIG. 9 as shown in FIG. Moreover, the casing which accommodates a male rotor and a female rotor was made from cast iron.
[0083]
In the structure of the present embodiment, the female rotor contacts the above-described coating film No. 5, and scrapes off only the necessary part of the interference part of the coating film No. 5. In addition, at the contact portion with the inside of the cast iron casing, the interference with the inner wall of the casing is scraped off, and PTFE adheres to the sliding surface, reducing the friction coefficient between the rotor and the casing, and causing phenomena such as galling and seizure. Prevent occurrence. Also in this example, the female rotor was provided with a hard surface coating, and the male rotor was provided with the coating material No. 5 described above, but similar results were obtained even when the male rotor and female rotor coatings were changed. Obtained.
[0084]
Another embodiment of the present invention will be described with reference to FIG. ◆
The male rotor 1 of the present embodiment has a two-layer structure in which the PAI-only layer 16 is formed on the surface and the above-described coating material No. 5 is provided thereon, as is apparent from the cross-sectional structure shown in FIG. A coating film is provided. The female rotor 2 was provided with a Ni-P plating film 12 on the surface thereof. After the screw rotor of this combination was incorporated into a screw compressor and continuously operated for a long period of time, the surface was observed. As in the above example, the coating of coating material No. 5 was good with no discoloration or peeling. It was. According to this embodiment, the coating film of the rotor and the coating material No. 5 is bonded by the binder PAI of the coating material No. 5, and the PAI-only layer on the rotor side is not mixed with the pigment, so that the adhesive strength with the rotor is increased. At the same time, the corrosion resistance increases.
[0085]
Another embodiment of the present invention will be described with reference to FIG. ◆
The screw rotor of this example uses a coating of the coating material No. 5 described above on the surface of the female rotor and a Ni-P plating coating on the surface of the male rotor.
[0086]
In order to perform the finish creation of the mating rotor more smoothly due to interference due to thermal expansion, the rolling pitch circle diameter dpm of the male rotor 1 is smaller than the root diameter dim of the male rotor 1 as shown in FIG. The pitch circle diameter dpf is set larger than the tooth tip diameter dof of the female rotor 2. As a result, there is no tooth profile part that makes rolling contact during the meshing rotation of each rotor, that is, since the relative sliding speed exists in all parts, the high hardness layer provided on the surface of the male rotor 1 always comes into contact with the female rotor surface. The mating rotor surface is finished.
[0087]
Especially in oil-free screw compressors, it is necessary to reduce the gap between the rotors in order to improve the compression efficiency, but it is difficult to predict the tooth profile of the thermal expansion state in the actual operation state in all sections. In order to prevent contact with the rotor, a certain degree of safety is expected, and a gap larger than predicted is set. However, according to the present invention, the interference portion of the other tooth profile is finally finished by contact, and the rotor Since no galling occurs, loss due to air leakage of the compressor can be reduced, and reliability is not impaired.
[0088]
For finishing to the final tooth profile, it is preferable to gradually grind the contact portion while increasing the operating temperature little by little to the maximum operating temperature expected in advance. Furthermore, the same result was obtained even when the coating film of the male rotor and the female rotor of this example was reversed, and when the film was not coated on the surface of the male rotor. Furthermore, similar results were obtained even when coatings with different hardnesses were applied to the surfaces of both rotors.
[0089]
Another embodiment of the present invention will be described with reference to FIG. FIG. 13 is a schematic cross-sectional view showing the meshing state of both rotors corresponding to FIG. 6 described above and the relationship with the casing.
[0090]
A composite Ni-P plating layer containing 10% PTFE having a thickness of about 20 μm was provided on the surface of the male rotor 1. The surface of the female rotor 2 is MoS.₂: 5 parts by weight, Sb₂O_ThreeThe coating film 12 comprising: 3 parts by weight, C: 0.7 parts by weight, and PAI as a binder: 12 parts by weight was provided in a thickness of about 20 μm. In both rotors, the respective coatings were also coated on the end faces in the axial direction.
[0091]
The casing 3 was provided with a coating 15 applied to the surface of the female rotor 2 on a portion facing the male rotor 1 and the female rotor 2 and a portion facing the axial end surfaces of the two rotors to a thickness of about 40 μm. The film thickness of the casing 3 is thicker than that of the rotor. Since the rotor is rotating, the temperature distribution is almost uniform in the cross section perpendicular to the axial direction, but the casing does not rotate and the vicinity of the discharge part becomes high. This is because non-uniform expansion occurs in the vicinity of the discharge portion, and the deformation due to expansion is absorbed.
[0092]
As a result of forming such a coating on the sliding surfaces of the rotor and casing and continuously operating the screw compressor, the performance can be greatly improved, and the maintenance period can be extended up to 4 times compared to the conventional coating. It was. When the inner surface after the test was observed, the sliding portions of the rotor and the casing were found to have a joint trace, and it is considered that the gap between the sliding portions was able to minimize leakage of compressed air.
[0093]
In this embodiment, the end face of the rotor is coated with the coating, but the coating is coated on the portion corresponding to the rotor end surface on the casing side, so that the same effect can be obtained even if the end surface portion on the rotor side is removed. .
[0094]
Moreover, the same result was obtained even if it provided the film | membrane of the male rotor and the female rotor in a present Example reversely.
[0095]
In each of the above-described embodiments, a pair of male rotor and female rotor has been described. However, the present invention can be similarly applied to a screw type compressor in which a male rotor and a female rotor are composed of a pair or more.
[0096]
【The invention's effect】
As described above, according to the present invention, the rotor and casing surface used in the dry screw compressor have polyimide amide resin as a binder, and MoS.₂, Sb₂O_ThreeBy applying a coating material containing C and C as pigments and baking at a high temperature, it is possible to form a coating film having high heat resistance and high wear resistance against a high temperature heating phenomenon occurring on the discharge side of the rotor.
[0097]
Also, by reducing the gap between the rotors and between the rotor and the casing by co-rotation, the compression performance can be greatly improved, and it is not necessary to increase the processing accuracy, thus reducing the number of processing steps. Can do.
[0098]
In addition, since the heat resistance and wear resistance are improved, the maintenance period can be greatly extended compared to the conventional case.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a peeling mechanism of a coating film.
FIG. 2 is a result of a lubricity test of the coating film shown in Table 2.
FIG. 3 is a graph showing the relationship between the baking temperature and the lubricity of a film by a pin-on-disk test.
FIG. 4 is a graph showing the relationship between the baking temperature of the coating film and the lubricity obtained by an Amsla test.
FIG. 5 is a cross-sectional view of a screw compressor according to an embodiment of the present invention.
FIG. 6 is a schematic cross-sectional view showing a meshed state of a male rotor and a female rotor according to an embodiment of the present invention.
FIG. 7 is a schematic cross-sectional view showing a coating state of a coating film of a male rotor and a female rotor.
FIG. 8 is a cross-sectional view of a coating film according to an embodiment of the present invention.
FIG. 9 is a schematic cross-sectional view showing a coating state of a rotor coating according to an embodiment of the present invention.
FIG. 10 is a cross-sectional view of a coating film according to an embodiment of the present invention.
FIG. 11 is a schematic cross-sectional view showing a meshed state of a male rotor and a female rotor according to an embodiment of the present invention.
FIG. 12 is an explanatory view of a meshing state of both male and female rotors according to an embodiment of the present invention.
FIG. 13 is a schematic cross-sectional view showing a meshed state of a male rotor and a female rotor according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Male rotor, 2 ... Female meter, 3 ... Pinion gear, 4 ... Timing gear, 5 ... Bearing, 6 ... Casing, 8 ... Shaft seal part, 10, 12 ... Coating film.

Claims (9)

In the screw rotor formed by forming a helical tooth profile on the outer surface in the axial direction, the screw rotor is provided with a layer made of polyamideimide resin (PAI) on the surface, the binder is PAI on the layer, and two pigments are used as pigments. A screw rotor comprising a solid lubricant film in which molybdenum sulfide (MoS 2 ) , antimony trioxide (Sb 2 O 3 ), and graphite (C) are dispersed. 2. A screw rotor according to claim 1 , wherein said Sb2O3, MoS2 and C are provided as particles in said solid lubricant coating. 2. The solid lubricant film according to claim 1 , wherein the PAI is 12 to 18 parts by weight, MoS2 is 5 to 7 parts by weight, Sb2O3 is 3 to 5 parts by weight, and C is 0.7 to 0.9 parts by weight. A screw rotor comprising a composition selected from A screw compressor comprising at least a pair of a male rotor and a female rotor meshing with each other in a casing, wherein the screw rotor according to any one of claims 1 to 3 is provided on both or any one of the rotors. Machine. A screw compressor comprising at least a pair of a male rotor and a female rotor meshing with each other in a casing, wherein the screw rotor according to any one of claims 1 to 3 is provided on one of the rotors, and a nickel-phosphorous plating film is provided on the surface of the other rotor. A screw type compressor characterized by comprising. A screw compressor comprising at least a pair of a male rotor and a female rotor meshing with each other in a casing, wherein either one of the rotors is provided with the screw rotor according to any one of claims 1 to 3 , and a tetrafluoride film is formed on a surface of the other rotor. A screw compressor comprising a nickel-phosphorous plating film in which ethylene resin (PTFE) is dispersed. A screw compressor comprising at least a pair of a male rotor and a female rotor meshing with each other in a casing. A solid in which MoS 2 , Sb 2 O 3 and C are dispersed as pigments on a surface of the casing where the male rotor and female rotor face each other with PAI as a binder. The solid lubricant film comprises a lubricant film , and the PAI is 12 to 18 parts by weight, MoS2 is 5 to 7 parts by weight, Sb2O3 is 3 to 5 parts by weight, and C is 0.7 to 0.9 parts. A screw-type compressor comprising a composition selected from the range of parts by weight.   In the manufacturing method of a screw rotor in which a helical tooth profile is formed on the outer surface in the axial direction, PAI is applied to the surface of the screw rotor on which the helical tooth profile is formed, and then Sb2O3 is dispersed on the surface. A method for producing a screw rotor, comprising applying a lubricant and heating to form a solid lubricant film.   In the manufacturing method of a screw rotor in which a helical tooth form is formed on the outer surface in the axial direction, PAI is applied to the surface of the screw rotor on which the helical tooth form is formed, and after heating, a binder is applied to the surface of the screw rotor. And a solid lubricant film in which MoS2, Sb2O3 and C are dispersed as a pigment is applied and heated to form a solid lubricant film.

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