JP3794090B2 - Image carrier unit - Google Patents

Description

Ｌｉ：ｉ番目の部材の長さ
αｉ：ｉ番目の線膨張率
△Ｔ：温度差
となるように構成されているので、使用環境や輸送環境で温度が変化しても、像担持体ユニットの内部には、その軸線方向における熱歪が発生しないか、発生したとしても許容応力以下のものとなる。
【００５９】
したがって、薄肉円筒状の像担持体の大きな歪み、永久変形が防止され、振れの発生も防止されるので、現像ローラ等の各プロセス部材との間隔が温度環境によって大きく変動せず、確実で安定した接触状態、あるいはギャップ管理が可能となり、帯電むら、現像不良、転写不良等のない良好な画像を得ることができる。
【００６０】
また、像担持体が熱歪で座屈し、あるいは破断してしまうということがなくなり、構成部品の固定部が熱応力で破損してしまうということもなくなるので、機械的信頼性が向上する。
【００６１】
すなわち、この請求項３記載の像担持体ユニットによれば、使用環境や輸送環境で温度が変化しても破損等を生じることなく、硬質ローラ等の当接部材との確実で安定した接触状態を得ることが可能であるとともに、製造が簡単であるという効果が得られる。
【００６２】
請求項４記載の像担持体ユニットによれば、請求項１，２，または３記載の像担持体ユニットにおいて、前記像担持体は、その内周面と前記円筒部材の外周面との間に、像担持体の許容変形量より小さな間隔を隔てて前記固定部材で支持されているので、例えば像担持体ユニットの交換作業時等にオペレータが誤って像担持体の中央部を強く押圧したとしても、像担持体は破損にいたる前に円筒部材によって支持されることとなるため破損しない。したがって、この像担持体ユニットは、前述した特開昭５８−８６５５０号公報に開示されたドラム状像担持体部材（図１６参照）に比べて取扱い性に優れている。
【００６３】
しかも、像担持体を強く押圧してもこれが破損しないから、当接部材を強く当接させることができる。
【００６４】
すなわち、この請求項４記載の像担持体ユニットによれば、使用環境や輸送環境で温度が変化しても破損等を生じることなく、硬質ローラ等の当接部材との確実で安定した接触状態を得ることが可能であるとともに、製造が簡単でしかも取扱い性に優れているという効果が得られる。
【００６５】
請求項５記載の像担持体ユニットによれば、請求項１，２，３，または４記載の像担持体ユニットにおいて、前記円筒部材および固定部材は、導電性を有しているので、画像形成に必要な像担持体に対する電気的導通をこれら円筒部材および固定部材を通じて得ることができる。したがって、別途導通手段を設ける必要がなくなる。
【００６６】
【発明の実施の形態】
以下、本発明の実施の形態について図面を参照して説明する。
【００６７】
＜第１の実施の形態＞
図１は本発明に係る像担持体ユニットの第１の実施の形態を用いた画像形成装置の要部を示す模式図、図２は図１におけるＩＩ−ＩＩ断面図で、主として像担持体ユニットを示す図である。
【００６８】
これらの図において、１００は像担持体ユニットであり、この実施の形態においては、電子写真方式の画像形成装置に用いられる感光体ユニットとして構成してある。
【００６９】
この感光体ユニット１００は、図示しない適宜の駆動手段によって図１の矢印方向（時計方向）に回転駆動されるようになっている。
【００７０】
感光体ユニット１００は、像担持体１１０と、この像担持体１１０の両端部１１１，１１１を支持する一対の支持部材１２０，１２０と、像担持体１１０の内方に配置された円筒部材１４０とを備えている。
【００７１】
像担持体１１０は、可撓性を有する薄肉円筒状に形成されており、可撓性を有する基材の表面（外周面）に感光層を形成することにより構成されている。例えば、基材としては、電鋳法にて作製したニッケルシームレス管を用いることができる。感光層は、いわゆるＯＰＣ（有機感光体）をディッピング法で形成することができる。このような像担持体１１０の可撓性すなわち柔軟さは、基材の厚みと径とを調整することにより決定することが可能であるから、使用される画像形成装置に応じて適宜設定することが可能である。例えば、基材厚み２０〜２００μｍ、基材直径１０〜３００ｍｍの範囲で、後述する許容変形量δ２が２０〜５００μｍ程度となるように適宜設定する。なお、ＯＰＣは主として樹脂からなるので、可撓性の面では優れるが、基材との密着性を確保し、レーザー光の干渉対策を施すために、基材とＯＰＣとの間に下引き層を形成することが望ましい。下引き層としては、酸化亜鉛、酸化チタン等のレーザー光を吸収可能な粒子をナイロン樹脂等の樹脂に分散させた層が好適である。
【００７２】
支持部材１２０は、像担持体１１０の端縁部１１１ａよりも多少中央側に位置しており、固定部材としての固着部材１２１と、スペーサ１３０とを備えている。
【００７３】
固着部材１２１は、それ自体の熱膨張を無視し得る短い長さで、像担持体１１０と円筒部材１４０とを、その両端部付近で支持し、連結している。ここで、図２に示すように、像担持体１１０における固着部材１２１との連結部間の軸線方向長さをＬ１、円筒部材１４０における固着部材１２１との連結部間の長さをＬ３とすると、Ｌ１＝Ｌ３となる。
【００７４】
したがって、感光体ユニット１００をとりまく温度が変化して温度差が発生した場合でも、後述するように、像担持体１１０と円筒部材１４０とを、その線膨張率を略等しく構成し、あるいは同種の材料で構成することによって、Ｌ１，Ｌ３の長さの変化を略同じとし、像担持体１１０に生じる歪や変形を小さくし、良好な機械精度を保持することができる。
【００７５】
上記固着部材１２１，スペーサ１３０は円筒部材１４０の外周面に円環状に配置され、円筒部材１４０と像担持体１１０との間に介装されている。
【００７６】
この実施の形態において、固着部材１２１は導電性接着剤、例えば、エポキシ系、シアノ系、アクリル系の樹脂接着剤に導電性粒子を分散させた導電性接着剤で構成されている。なお、導電性粒子としては、金属（銀、アルミ等）、カーボン等を用いることができる。
【００７７】
図３は主としてスペーサ１３０の一例を示す模式図で、図（ａ１）は像担持体１１０が装着される前の状態を示す正断面図、図（ａ２）は図（ａ１）の部分左側面図、図（ａ３）は作用説明図、図（ｂ１）は像担持体１１０が装着された後の状態を示す正断面図、図（ｂ２）は図（ｂ１）の部分左側面図、図（ｃ）は像担持体１１０が装着された後の状態を示す左側面である。
【００７８】
これらの図に示すように、この実施の形態におけるスペーサ１３０は、円筒部材１４０の外周面１４５に固着される薄リング状の基部１３１と、この基部１３１の外周面に突設された弾性部としての弾性突起１３２とを備えている。基部１３１は、例えば金属または合成樹脂で構成され、弾性突起１３２は、例えばシリコンゴムで構成されている。弾性突起１３２は、図（ｃ）に示すように、基部１３１の円周方向に等間隔で複数（図では１２個）設けられている。図（ａ２）に示すように、基部１３１の外径Ｒｆは像担持体１１０の内径Ｒａよりも小さく設定されており、像担持体１１０が装着される前の弾性突起１３２の先端を結んだ円の半径（像担持体１１０の中心から弾性突起１３２の先端までの距離）Ｒｅは像担持体１１０の内径Ｒａよりも大きく設定されている。なお、基部１３１の厚さは１００μｍ程度、弾性突起１３２の高さは、図（ｂ１）（ｂ２）に示すように像担持体１１０が装着された状態で同じく１００μｍ程度である。弾性突起１３２は、例えば、シリコン系ゴム塗料を基部１３１の表面に印刷することにより形成することが可能である。
【００７９】
像担持体１１０は、これを円筒部材１４０にかぶせた後（円筒部材１４０を像担持体１１０に挿入した後）、その両端部１１１と円筒部材１４０の外周面との間に接着剤１２１を注入することによって円筒部材１４０上に固着される。
【００８０】
この際、スペーサ１３０は、次のように作用する。
【００８１】
像担持体１１０を図（ａ１）に矢印Ｘ１で示すように円筒部材１４０にかぶせる（円筒部材１４０を像担持体１１０に挿入する）過程で、スペーサ１３０の先端は像担持体１１０の内面と接触して矢印Ｘ１方向に押され、図（ａ３）に示すように一時的に矢印Ｘ１方向に変形する。
【００８２】
その後、円筒部材１４０が像担持体１１０に完全に挿入され、矢印Ｘ１方向に作用する外力がなくなると、スペーサ１３０は、それ自身の弾性力（復原力）によって像担持体１１０を図（ｂ１）に示すように矢印Ｘ２方向に多少押し戻しつつ同図に示すように押しつぶされた状態となり、それ自身の弾性によって内方から像担持体１１０を支持することとなる。
【００８３】
ここで、弾性突起１３２は、図（ｃ）に示すように、基部１３１の円周方向に等間隔で複数設けられているので、弾性突起１３２の弾性力（復原力）ｆｃが像担持体１１０に対してほぼ均一に作用することとなり、結果として、図（ｂ２）に示すように、像担持体１１０は、円筒部材１４０との間隔Ｓがほぼ均一となる状態（すなわちほぼ真円状態）で円筒部材１４０上に装着されることとなる。このような状態で像担持体１１０の両端部１１１と円筒部材１４０の外周面との間に接着剤１２１（図２参照）が注入されて像担持体１１０が円筒部材１４０上に固着される。
【００８４】
円筒部材１４０の外周面１４５と像担持体１１０の内周面１１３との間の間隔Ｓは、像担持体１１０の許容変形量、すなわち像担持体１１０を内方に変形させたときに破壊にいたる変形量δ２（図２参照）よりも小さく設定されている。
【００８５】
図２に示すように、円筒部材１４０は、その両端部１４１，１４１が、それぞれ円板状の側板１４２，１４３に固定されている。円筒部材１４０および側板１４２，１４３は、極めて変形しにくい金属あるいは合成樹脂等の高剛性材で構成されている。合成樹脂で構成する場合には、これにアルミニウム、ニッケル、銅等の金属を蒸着し、あるいはメッキ等で導電層を形成するか、または、樹脂中に、カーボン等の導電材を入れて導電性を付与する。
【００８６】
円筒部材１４０と側板１４２，１４３との固定は適宜の手段、例えば接着、圧入、圧着等によって行なうことができる。側板１４２，１４３には、軸１４２ａ，１４３ａが一体的に設けられており、一方の軸１４３ａには歯車１４４が固定されている。
【００８７】
以上のような像担持体ユニット１００は、次の（１）（２）のいずれかによって構成する。
【００８８】
（１）像担持体１１０の線膨張率と円筒部材１４０の線膨張率とが、略等しくなるように構成する。
【００８９】
例えば、像担持体１１０の基材をニッケルシームレス管（線膨張率は１２．８×１０^-6／゜Ｃ〜１３．４×１０^-6／゜Ｃである）とした場合には、筒状部材１４０をガラス繊維または雲母等の無機質（ミネラル）入りのＰＥＴ（ポリエチレンテレフタレート）で構成する。ガラス含有率を５５％（重量比）とすることによって、線膨張率を１１．０×１０^-6／゜Ｃ〜１４．０×１０^-6／゜Ｃとすることができる。
【００９０】
（２）像担持体１１０と円筒部材１４０とを同種の材料で構成する。
【００９１】
例えば、像担持体１１０の基材をニッケルシームレス管とした場合には、筒状部材１４０をニッケルあるいはステンレスで構成する。
【００９２】
次に、画像形成装置の一例について説明すると、以上のような像担持体ユニット１００は、例えば図２に示すように、軸１４２ａ，１４３ａが装置のフレームＦに回転可能に支持される。１４６，１４６はベアリングである。歯車１４４とベアリング１４６との間には、ガタつき防止のための圧縮バネ１４７が設けられている。
【００９３】
このようにして、感光体ユニット１００はフレームＦに回転可能に支持されており、図示しない適宜の駆動手段によって図１矢印方向（時計方向）に回転駆動される。
【００９４】
図１に示すように、感光体ユニット１００の回りには、その回転方向に沿って、帯電手段２１０、露光手段２２０、現像手段２３０、転写手段２４０、クリーニング手段２５０、および除電手段２６０が配置されている。
【００９５】
帯電手段２１０は、像担持体１１０の外周面に当接して回転する、硬質の高抵抗樹脂ローラ、または、表面に高抵抗層をもつ金属ローラで構成されており、感光体ユニット１００の像担持体１１０の外周面を一様に帯電させるようになっている。
【００９６】
露光手段２２０は、レーザー光Ｌで像担持体１１０の外周面を走査することにより、像担持体１１０上に静電潜像を形成するようになっている。
【００９７】
現像手段２３０は、像担持体１１０の外周面に当接して回転し、像担持体１１０の外周面にトナーを付着させてトナー像を形成する硬質の現像ローラ２３１と、この現像ローラ２３１に供給されるトナーが収容されたトナー貯留室２３２とを備えている。現像ローラ２３１は、表面を粗面化した金属ローラ、または、硬質の樹脂ローラで構成されている。
【００９８】
転写手段２４０は、硬質の高抵抗樹脂ローラ、または、表面に高抵抗層をもつ金属ローラで構成されており、像担持体１１０上のトナー像を転写媒体（用紙等の記録媒体あるいは中間転写ベルト）Ｔに転写させるようになっている。
【００９９】
クリーニング手段２５０は、像担持体１１０の外周面に当接し、転写手段２４０によりトナー像が転写された後に像担持体１１０の外周面に残存している残留トナーを掻き落として除去するクリーニング部材としてのクリーニングブレード２５１と、このブレード２５１によって掻き落とされたトナーを回収するトナー回収室２５２とを有している。
【０１００】
除電手段２６０は除電ランプで構成されており、像担持体１１０の表面に一様に光を照射することにより、その表面の除電を行なうようになっている。
【０１０１】
以上のような各手段のうち、帯電ローラ２１０、および転写ローラ２４０は、いずれも、像担持体１１０と接触して像担持体１１０の内周面１１３が円筒部材１４０の外周面１４５と当接するまで像担持体１１０を内方に撓ませ、かつ像担持体１１０の周速と同一の周速度で回転するようになっている。このように帯電位置および転写位置においては、像担持体１１０の内周面１１３と円筒部材１４０の外周面１４５とが接触するから、両者間の摩擦係数は、できるだけ小さくしておくことが望ましい。帯電ローラ２１０は、図１に示すようにモータ２１２で（直接または歯車等を介して）駆動されて像担持体１１０の周速と同一の周速度で回転し、転写ローラ２４０は、像担持体１１０との接触により（転写媒体Ｔがある場合には転写媒体Ｔを介した接触により）、像担持体１１０に従動して像担持体１１０の周速と同一の周速度で回転するようになっている。なお、帯電ローラ２１０は、その軸２１１が図示しない一対の軸受部材で回転可能に支持され、かつ図示しない公知の付勢手段（例えばバネ）で円筒部材１４０に向けて付勢されている。転写ローラ２４０の支持構造および付勢構造も同様である。
【０１０２】
現像ローラ２３１は、像担持体１１０の内周面１１３が円筒部材１４０の外周面１４５に当接しないように像担持体１１０を内方に撓ませて像担持体１１０に接触している。ローラ当接部位における像担持体１１０の内側に撓んだ内周面１１３と円筒部材１４０の外周面１４５との間隙をＳ１で示してある。現像ローラ２３１の軸２３３は、一対の軸受部材２３４，２３４で回転可能に支持されており、この軸受部材２３４が、像担持体１１０の両側において円筒部材１４０の外周面１４５に回転可能に当接していることによって、現像ローラ２３１と円筒部材１４０との間隔が規制されている。なお、現像ローラ２３１は、その軸２３３が図示しない付勢手段により円筒部材１４０に向けて付勢されている。また、現像ローラ２３１は、軸２３３が図示しない駆動手段で駆動されることにより、回転駆動されるようになっている。現像ローラ２３１の回転速度は、その周速が像担持体１１０の周速と同一となるようにしても良いし、異なるように（通常は増速）しても良い。
【０１０３】
クリーニング手段２５０のクリーニングブレード２５１は、像担持体１１０の内周面１１３が円筒部材１４０の外周面１４５に当接するまで像担持体１１０を押圧してその外周面のトナーを除去するようになっている。このクリーニング位置においては、像担持体１１０の内周面１１３と円筒部材１４０の外周面１４５とが接触するから、両者間の摩擦係数は、できるだけ小さくしておくことが望ましい。
【０１０４】
以上のような画像形成装置による画像形成動作は次の通りである。
【０１０５】
図示しない駆動手段によって感光体ユニット１００が回転駆動され、これによって像担持体１１０も回転駆動される。
【０１０６】
その過程において、像担持体１１０は、先ず除電手段２６０によって除電された後、帯電手段２１０によって一様に帯電させられる。
【０１０７】
次いで、露光手段２２０によりレーザー光Ｌが照射されることで像担持体１１０上に静電潜像が形成され、この静電潜像は現像手段２３０で現像されてトナー像となる。
【０１０８】
このトナー像は、転写ローラ２４０と像担持体１１０との間に供給される転写媒体Ｔに転写ローラ２４０によって転写される。
【０１０９】
この際、完全に転写されることなく像担持体１１０の表面に残留したトナーは、クリーニング手段２５０のクリーニングブレード２５１によって掻き落とされる。
【０１１０】
その後、像担持体１１０は、再び除電手段２６０によって除電され、次の画像形成がなされる。
【０１１１】
以上のような像担持体ユニット１００によれば、次のような作用効果が得られる。
【０１１２】
（ａ）像担持体１１０は、可撓性を有する薄肉円筒状であり、その両端部１１１が一対の支持部材１２０，１２０によって支持された構成となっているので、像担持体１１０は、支持部材１２０によって支持されていない中央部分１１４が内方に変形可能である。
【０１１３】
したがって、この像担持体１１０の中央部分１１４は、いわば疑似軟質材として利用することが可能であるため、これに当接される帯電手段等が硬質ローラであっても、確実で安定した接触状態を得ることができ、確実に像担持体１１０上に像を形成し、あるいは像を担持させることができる。
【０１１４】
この点について、図４〜図７を参照して詳しく説明する。
【０１１５】
図４は、像担持体１１０に対して硬質ローラ２００を軽く当接させた状態を示している。なお、説明を分かりやすくするために、完全に円柱形とはなっていない硬質ローラの例として、逆クラウン形状のローラ２００を用いている。
【０１１６】
像担持体１１０は、その両端部１１１が前述した一対の支持部材１２０，１２０によって支持されているが、図の煩雑を避けるために図示していない。
【０１１７】
図４に示すように、硬質ローラ２００を軽く当接させただけでは、その両端２０１，２０１のみが像担持体１１０に接触するだけであり、中央部２０２は接触しない。したがって、このような状態では、良好な帯電状態、現像状態、転写状態等は得られない。
【０１１８】
図５は、硬質ローラ２００を、図４に示した状態からさらに像担持体１１０に向けて、硬質ローラのクラウン量δ３（図４参照）よりも大きな量δ４だけ押圧した場合の像担持体１１０の変形状態を有限要素法にて解析し、像担持体の変形量を倍率５０倍にして示したワイヤーフレームの斜視図である。像担持体１１０は軸対称変形するので、図の煩雑を避けるために半分だけ示してある。
【０１１９】
図６は、図５における矢印Ｘ方向からみた図である。図７は図６におけるａ断面、ｂ断面、ｃ断面、およびｄ断面における像担持体１１０の外周面を図５における矢印Ｚ方向から見て重ね合わせて示した図で、図中実線ａはａ断面、破線ｂはｂ断面、一点鎖線ｃはｃ断面、二点鎖線ｄはｄ断面における像担持体１１０の外周面をそれぞれ示している。
【０１２０】
図５〜図７から明らかなように、クラウン量δ３の硬質ローラ２００を像担持体１１０に向けて、クラウン量δ３よりも大きな量δ４で押圧すると、その押圧部（いわゆるニップ部）Ｎにおいて、像担持体１１０は硬質ローラ２００の形状に忠実に沿って変形し、ニップ部Ｎ全域に亙って硬質ローラ２００に確実に接触することとなる。
【０１２１】
これは、像担持体１１０が可撓性を有する薄肉円筒状であることによる作用である。薄肉円筒状である像担持体１１０は、軸方向に直交する平面方向に非常に大きな可撓性を有しており、逆クラウン形状の硬質ローラ表面に追従するようにして軸方向に連続的に変形形状を変えて行く。薄肉円筒の軸方向にも金属の弾性範囲内で極微小な変形は発生するが、軸方向の剛性は直交する断面方向の剛性に比べて非常に高く、可撓性にはあまり大きく貢献しない。したがって、像担持体の変形は、軸に直交する断面方向の可撓性によるところが非常に大きい。これは薄肉円筒特有の変形モードであり、この変形を利用して像担持体を変形させることにより、硬質なローラの凹凸に追従させ、安定した接触を確保することができる。
【０１２２】
図６および図７を参照し、像担持体の変形状態について、より詳しく説明すると、図６におけるａ部（像担持体の両端部分（支持部材１２０で支持されている部分））では、図７に実線ａで示すように、像担持体１１０は基本的に真円状態に保持されている。
【０１２３】
ｂ部（ローラ２００の端部直近）では、図７に破線ｂで示すように、最大変形量であるδ４だけ内方に変形しているが、円周方向におけるｂ点（ニップ部）近くのｂ１点では大きく外側に膨らむように変形している。
【０１２４】
ｄ部はローラ２００の中央部であり、像担持体はδ４−δ３だけ変形しているが、円周方向におけるｄ点近くのｄ１点では外側に膨らむように変形している。逆に、このｄ１点から多少離れたｄ２点では内側にやや凹むように変形している。
【０１２５】
ｂ部からｄ部に至る部分ではｂ部における変形状態からｄ部における変形状態へと連続的に変化して行く。その一例としてｃ部での変形状態を一点鎖線ｃで示す。ｃ１点はｄ１点よりもｂ１点寄りで膨らんでおり、ｃ２点の凹み量はｄ２点の凹み量よりも小さい。
【０１２６】
以上からも明らかなように、薄肉円筒状である像担持体１１０は、軸方向に直交する平面方向に非常に大きな可撓性を有していて、逆クラウン形状の硬質ローラの表面に追従するようにして軸方向に連続的に変形形状を変えて行く。
【０１２７】
なお、以上の説明では、説明を分かりやすくするために、完全には円柱形とはなっていない硬質ローラの例として、逆クラウン形状のローラ２００を用いて説明したが、多少の凹凸のあるローラは逆クラウン形状のローラを複数本連続させたものと同等であり、また多少のテーパがついたローラは逆クラウン形状（またはクラウン形状）のローラの一部と同等であるから、像担持体１１０は、完全には円柱形とはなっていない硬質ローラ（製造誤差程度の凹凸やテーパを有するローラ）に対しても良好に確実かつ安定した状態で接触することとなる。
【０１２８】
上述した画像形成装置では、帯電手段２１０、転写手段２４０が、像担持体１１０と接触して像担持体１１０の内周面１１３が円筒部材１４０の外周面１４５と当接するまで像担持体１１０を内方に撓ませる硬質ローラで構成されているので、帯電位置および転写位置においては、像担持体１１０とこれら硬質ローラ２１０，２４０とを確実かつ安定した状態で接触させることができ、確実に像担持体１１０を帯電させ、あるいは像を転写させることができる。
【０１２９】
硬質ローラが、像担持体１１０と接触してその内周面１１３が円筒部材１４０の外周面１４５と当接するまで像担持体１１０を内方に撓ませると、像担持体１１０は、硬質ローラと円筒部材１４０との間に挟まれた状態となる。このような状態においては、像担持体１１０が硬質ローラに対して適度な圧接力で良好に確実かつ安定した状態で接触することとなる。
【０１３０】
（ｂ） この像担持体ユニット１００は、像担持体１１０の内方に円筒部材１４０を配置するようにして、像担持体１１０の両端部１１１を一対の支持部材１２０で支持することにより製造することができ、前述した特公平４−６９３８３号公報記載の感光体ドラム１（図１３〜図１５参照）のように弾性材料層を充填する必要がないから、簡単に製造することが可能である。
【０１３１】
（ｃ） 像担持体ユニット１００は、上記（１）（２）のいずれかの構成となっているので、使用環境や輸送環境で温度が変化しても、像担持体ユニット１００の内部には熱膨張差による熱歪が発生しないか、発生したとしても微小なものとなる。
【０１３２】
したがって、薄肉円筒状の像担持体１１０の歪み、変形が防止され、振れの発生も防止されるので、現像ローラ２３１等の各プロセス部材との間隔が温度環境によって変動せず、確実で安定した接触状態、あるいはギャップ管理が可能となり、帯電むら、現像不良、転写不良等のない良好な画像を得ることができる。
【０１３３】
また、像担持体１１０が熱歪で座屈し、破断し、あるいは永久変形してしまうということがなくなり、構成部品の固定部が熱応力で破損してしまうということもなくなるので、機械的信頼性が向上する。
【０１３４】
（ｄ） 支持部材１２０は、像担持体１１０をその内方から弾性的かつ均一に支持する弾性部を有するスペーサ１３０と、このスペーサ１３０で支持された像担持体１１０と円筒部材１４０とを固着する固着部材１２１とを備えているから、特開昭５８−８６５５０号のドラム状像担持体部材（図１６）に比べて製造が容易であると共に、スペーサ１３０で支持された像担持体１１０は円筒部材１４０に対してその間隔Ｓが円周方向において等間隔すなわちほぼ真円状態で支持された状態で固着部材１２１で固着されることとなる。したがって、像担持体１１０の軸線方向への変位や振れが極めて少ない安定した回転状態が得られることとなる。
【０１３５】
（ｅ） 像担持体１１０の内方には、剛性の円筒部材１４０が、その外周面１４５と像担持体１１０の内周面１１３との間に像担持体１１０の許容変形量δ２より小さな間隔Ｓを隔てて配置されているから、例えば像担持体ユニット１００の交換作業時等にオペレータが誤って像担持体１１０の中央部を強く押圧したとしても、像担持体１１０は破損にいたる前に円筒部材１４０によって支持されることとなるため破損しない。したがって、この像担持体ユニット１００は、前述した特開昭５８−８６５５０号公報に開示されたドラム状像担持体部材（図１６参照）に比べて取扱い性に優れている。
【０１３６】
（ｆ） 像担持体１１０を強く押圧してもこれが破損しないから、硬質ローラやクリーニングブレード等の当接部材を強く当接させることができる。
【０１３７】
（ｇ） スペーサ１３０は、円筒部材１４０が像担持体１１０の内方に配置されたときに、円筒部材１４０と像担持体１１０とで圧縮されることにより像担持体１１０を弾性的に支持する構成であるから、このスペーサ１３０を円筒部材１４０（または像担持体１１０）に予め装着しておくことにより、より一層簡単に像担持体ユニットを製造することができる。
【０１３８】
（ｈ） スペーサ１３０が、像担持体１１０をその内方からその円周方向において複数箇所かつ等間隔で弾性的に支持する構成となっているので、スペーサ１３０による弾性力が像担持体１１０の円周方向全体に亙って良好に分散され、像担持体１１０が円筒部材１４０に対してより均一に支持されることとなる。
【０１３９】
（ｉ） 円筒部材１４０および支持部材１２０が導電性を有しているので、画像形成に必要な像担持体１１０に対する電気的導通をこれら円筒部材１４０および支持部材１２０を通じて得ることができる。したがって、別途導通手段を設ける必要がなくなる。
【０１４０】
（ｊ） 支持部材１２０は、像担持体１１０の端縁部１１１ａよりも多少中央側に位置しているので、像担持体１１０が円筒部材１４０に対してより一層均一に支持されることとなり、より一層振れ精度の向上が図られる。
【０１４１】
詳しく説明すると、像担持体１１０を電鋳法で構成した場合、その端縁部１１１ａには、カッティングによるカエリやバリが生じることとなる。仮に、このバリ等を除去することなく、支持部材１２０で像担持体１１０の端縁部１１１ａを支持する構成とすると、バリ等による影響で、像担持体１１０の円筒部材１４０に対する間隔Ｓが不均一になってしまうおそれがある。一方、上記バリ等を除去しようとすると、薄肉円筒状である像担持体１１０に新たな歪を加えたり、いたずらに変形を増やすばかりでなく、非常に工数が掛かるという問題も生じる。
【０１４２】
これに対し、この実施の形態の像担持体ユニットによれば、支持部材１２０が像担持体１１０の端縁部１１１ａよりも多少中央側に位置しているので、像担持体１１０に上記バリ等があってもその影響を受けることなく、像担持体１１０を円筒部材１４０に対して均一に支持することができ、一層振れ精度の向上を図ることができる。
【０１４３】
（ｋ）上述した画像形成装置においては、硬質ローラである帯電ローラ２１０，転写ローラ２４０が、像担持体１１０の周速と同一の周速度で回転するので、帯電ローラ２１０，転写ローラ２４０と像担持体１１０との接触部すなわち帯電位置および転写位置においては像担持体と各ローラとの間に相対速度差が生じない。したがって、接触部における摩擦が発生せず、これによる振動挙動も生じないため、安定した接触回転が得られることとなり、安定した帯電動作および転写動作が得られることとなる。
【０１４４】
また、上記振動挙動による像担持体１１０の破損も生じ難くなり、信頼性が向上する。
【０１４５】
なお、現像ローラ２３１の回転速度を、その周速が像担持体１１０の周速と異なるようにした場合、像担持体１１０は現像ローラ２３１との接触部において、現像ローラ２３１から摩擦力を受けることとなるが、両者の当接は、像担持体１１０の内周面１１３と円筒部材１４０の外周面１４５との間に間隔Ｓ１が形成される程度の当接であるから、像担持体１１０と現像ローラ２３１との当接力は小さい。このため、両者間の摩擦力も小さく、したがって、その変動による振動挙動も小さくなり、現像ローラ２３１と像担持体１１０とは、比較的安定した状態で接触し、回転することとなる。
【０１４６】
＜第２の実施の形態＞
図８は本発明に係る像担持体ユニットの第２の実施の形態の要部を示す模式図で、（ａ）は円筒部材およびスペーサを示す上半分の側面図、（ｂ）は部分斜視図である。
【０１４７】
この第２の実施の形態が、前述した第１の実施の形態と異なる点は、スペーサの構造にあり、その他の点に変わりはない。
【０１４８】
この第２の実施の形態におけるスペーサ１３３は、円筒部材１４０の外周面１４５に固着される薄リング状の基部１３３ａと、この基部１３３ａの外周面に突設された弾性部としての弾性突条１３３ｂとを備えており、前述した第１の実施の形態におけるスペーサ１３０の弾性部がいわば点状の１２個の突起１３２であったのに対し、弾性部が軸線方向に一定の長さを有する２４個の弾性突条１３３ｂとなっている点でのみ第１の実施の形態と異なっている。
【０１４９】
弾性部がこのような突条１３３ｂであると、像担持体１１０がより安定した状態で支持されることとなる。
【０１５０】
また、個数が多いことによって、弾性部の復原力が像担持体１１０に対して、より一層均一に作用することとなり、結果として、像担持体１１０と円筒部材１４０との間隔Ｓがより一層均一となる。
【０１５１】
＜第３の実施の形態＞
図９は本発明に係る像担持体ユニットの第３の実施の形態の要部を示す模式図で、（ａ）は円筒部材およびスペーサを示す上半分の側面図、（ｂ）は部分斜視図、（ｃ）は図（ａ）の部分拡大図、（ｄ）は作用説明図である。
【０１５２】
この第３の実施の形態が、前述した第１の実施の形態と異なる点は、スペーサの構造にあり、その他の点に変わりはない。
【０１５３】
この第３の実施の形態におけるスペーサ１３４は、円筒部材１４０の外周面１４５に固着される金属テープにエンボス加工を施すことにより、それ自身が弾性部として構成されている。なお、エンボス加工により形成される弾性突条１３４ｂの数は２４個である。
【０１５４】
このようなスペーサ１３４は、図（ｄ）に示すように像担持体１１０が装着されると、弾性突条１３４ｂが押圧された状態となり、それ自身の弾性によって内方から像担持体１１０を支持することとなる。
【０１５５】
このようなスペーサ１３４は、金属テープにエンボス加工を施すことにより簡単に作成することができる。
【０１５６】
また、スペーサ１３４によって像担持体１１０と円筒部材１４０との導通がとられるので、この実施の形態においては、接着剤１２１に必ずしも導電性を持たせる必要がなくなる。
【０１５７】
＜第４の実施の形態＞
図１０は本発明に係る像担持体ユニットの第４の実施の形態の要部を示す模式図で、（ａ）は円筒部材およびスペーサを示す上半分の部分斜視図、（ｂ）は断面図、（ｃ）は作用説明図である。
【０１５８】
この第４の実施の形態が、前述した第１の実施の形態と異なる点は、スペーサの構造にあり、その他の点に変わりはない。
【０１５９】
この第４の実施の形態におけるスペーサ１３５は、全体として截頭円錐筒形状をなしており、円筒部材１４０の外周面１４５に固着される薄リング状の基部１３５ａと、この基部１３５ａから一体的に放射状に形成された弾性部としての２４枚の可撓片１３５ｂとを備えている。なお、円筒部材１４０にはスペーサ１３５の基部１３５ａの固着を確実にするために、円環状の凹部１４０ａを設けることが望ましい。
【０１６０】
このようなスペーサ１３５は、像担持体１１０を図（ｂ）に矢印Ｘ１で示すように円筒部材１４０にかぶせると（円筒部材１４０を像担持体１１０に挿入すると）、可撓片１３５ｂが矢印Ｙ方向に撓み、それ自身の復原力によって図（ｃ）に示すように内方から像担持体１１０を支持することとなる。
【０１６１】
このようなスペーサ１３５は薄肉金属または合成樹脂を截頭円錐筒形状に成形し、これにスリット１３５ｃを形成することにより簡単に作成することができる。
【０１６２】
また、スペーサ１３５を金属で作成した場合には、これによって像担持体１１０と円筒部材１４０との導通がとられるので、接着剤１２１に必ずしも導電性を持たせる必要がなくなる。
【０１６３】
＜第５の実施の形態＞
図１１は本発明に係る像担持体ユニットの第５の実施の形態の要部を示す模式図で、上半分の断面を示した図である。下半分は上半分と対称である。
【０１６４】
この第５の実施の形態が、前述した第１の実施の形態と異なる点は、像担持体１１０の両端部１１１の固定構造にあり、その他の点に変わりはない。
【０１６５】
この第５の実施の形態において、円筒部材１４０上に像担持体１１０の両端部１１１を固定する固定部材１５１，１５２は、それぞれ像担持体１１０と円筒部材１４０との間に円環状に設けられており、像担持体１１０との連結部（例えば接着等による接合部）１５１ａ，１５２ａと、円筒部材１４０との連結部１５１ｂ，１５２ｂとを有している。
【０１６６】
そして、像担持体１１０における固定部材１５１，１５２との連結部１５１ａ，１５２ａ間の軸線方向長さおよび線膨張率がＬ１およびα１，円筒部材１４０における固定部材１５１，１５２との連結部１５１ｂ，１５２ｂ間の長さおよび線膨張率がＬ３およびα３，固定部材１５２，１５１の像担持体１１０および円筒部材１４０との連結部間、すなわち１５２ａ，１５２ｂ間、１５１ａ，１５１ｂ間の軸線方向長さがＬ２，Ｌ４、線膨張率がα２，α４であり、
像担持体１１０のヤング率をＥ１，許容応力をσａとしたとき、

Ｌｉ：ｉ番目の部材の長さ
αｉ：ｉ番目の線膨張率
△Ｔ：温度差
ｎ：連結された部材の総数（この場合ｎ＝４）
ｉ：連結された部材の順番（この場合ｉは１からｎ）
となるように構成してある。なお、具体例については、後述する実施例の欄に記載してある。
【０１６７】
ここで、先ず、上式に関する定義について図１２（ａ）を参照して説明する。
【０１６８】
図１２（ａ）（ｂ）は、長さおよび熱膨張率がそれぞれ異なる部材を連結した構造体において発生する熱膨張を説明するための図である。
【０１６９】
図１２において、部材１，２，３，４は、それぞれ、
長さが、Ｌ１，Ｌ２，Ｌ３，Ｌ４
熱膨張率が、α１，α２，α３，α４である。
【０１７０】
なお、ここでの長さは、部材同士の連結部（接合部）間の長さである。
【０１７１】
ここで熱膨張を考えるとき、長さについては、その正負を次のようにして定義する。
【０１７２】
先ず、連結した構造体のある連結点を起点および終点とする。図１２（ａ）では、最左端の連結点における部材１側の連結点ア点を起点とし、部材４側の連結点イを終点とする。
【０１７３】
次に、起点アに対して最も離れた連結点を決める。図１２（ａ）では、最右端に位置するウ点が、起点アに対して最も離れた連結点である。
【０１７４】
そして、起点ア→点ウ→終点イという時計回りの閉ループを考えたときに、
起点アからウ点に向かう方向を正（図中右方向）、ウ点から終点イに向かう方向を負（図中左方向）とする。
【０１７５】
すなわち、起点アから、順次連結点を追ってゆくとき、ある連結点に対して次の連結点が有る方向（ある連結点から次の連結点に向かう方向）によって上記のように正負を決定する。
【０１７６】
したがって、部材１，２，３，４の長さの正負は、Ｌ１，Ｌ２は＋、Ｌ３，Ｌ４は−となる。
【０１７７】
次に、上式の意義について図１２（ｂ）を参照して説明する。
【０１７８】
ア点とイ点とを連結した時点（すなわち構造体を作成した時点）から、構造体をとりまく環境温度が変化し、温度差△Ｔ（△Ｔは、温度が上昇した場合を＋、低下した場合を−とする）が生じたとする。ここで、仮にア点とイ点とが連結されていないとすると、温度変化によって伸縮した各部材１，２，３，４の長さＬ１’，Ｌ２’，Ｌ３’，Ｌ４’は、
Ｌ１’＝Ｌ１×（１＋α１×△Ｔ）
Ｌ２’＝Ｌ２×（１＋α２×△Ｔ）
Ｌ３’＝Ｌ３×（１＋α３×△Ｔ）
Ｌ４’＝Ｌ４×（１＋α４×△Ｔ）
となる。
【０１７９】
ここで、これらの総和が０でないとすると、図１２（ｂ）に示すようにア点とイ点とはずれることとなり、そのずれ量Ｌｔは、

となる。
【０１８０】
なお、Ｌｔの値が正であれば、図１２（ｂ）に示すように、イ点はア点より正側（右側）にずれ、負であれば負側（左側）にずれることとなる。
【０１８１】
しかしながら、実際には、ア点とイ点とは連結されているから、上記ずれは生じず、その分、構造体内に熱歪ないし熱応力が生じることとなる。
【０１８２】
この熱歪ないし熱応力は、構造体内の最も弱い部材に対して作用し、その部材の許容応力を越える熱応力が生じると、その部材が破壊し、あるいは永久変形することとなる。
【０１８３】
この実施の形態では、可撓性を有する薄肉円筒状の像担持体１１０が最も弱い部材であるから、温度変化があった場合、熱応力は像担持体１１０に作用することとなる。
【０１８４】
しかしながら、この実施の形態では、上述したように、像担持体１１０における固定部材１５１，１５２との連結部１５１ａ，１５２ａ間の軸線方向長さおよび線膨張率がＬ１およびα１，円筒部材１４０における固定部材１５１，１５２との連結部１５１ｂ，１５２ｂ間の長さおよび線膨張率がＬ３およびα３，固定部材１５２，１５１の像担持体１１０および円筒部材１４０との連結部間、すなわち１５２ａ，１５２ｂ間、１５１ａ，１５１ｂ間の軸線方向長さがＬ２，Ｌ４、線膨張率がα２，α４であり、
像担持体１１０のヤング率をＥ１，許容応力をσａとしたとき、

となるように構成されているので、使用環境や輸送環境で温度が変化し、像担持体ユニットの内部に、その軸線方向における熱歪が発生したとしてもその熱応力は許容応力以下のものとなる。
【０１８５】
したがって、薄肉円筒状の像担持体１１０の大きな歪み、永久変形が防止され、振れの発生も防止されるので、現像ローラ等の各プロセス部材との間隔が温度環境によって大きく変動せず、確実で安定した接触状態、あるいはギャップ管理が可能となり、帯電むら、現像不良、転写不良等のない良好な画像を得ることができる。
【０１８６】
また、像担持体１１０が熱歪で座屈し、あるいは破断してしまうということがなくなり、構成部品の固定部が熱応力で破損してしまうということもなくなるので、機械的信頼性が向上する。
【０１８７】
なお、上式におけるσａとしては、永久変形を問題とする場合には比例限度または耐力（０．２％耐力等）を採用し、破壊を問題とする場合には、引っ張り強さを採用する。
【０１８８】
また、図１１に示したこの実施の形態における部材と、図１２に示した各部材との対応関係について、念のために説明すると、
像担持体１１０は、図１２の部材１に、
固定部材１５２は、図１２の部材２に、
円筒部材１４０は、図１２の部材３に、
固定部材１５１は、図１２の部材４に、
連結部１５１ａは、図１２のア点およびイ点に、
連結部１５２ａは、図１２のウ点に、
それぞれ対応している。
【０１８９】
【実施例】
以下、具体的な実施例について説明する。
【０１９０】
なお、実施例１〜５は前述した構成（２）の実施例であり、実施例６〜７は前述した構成（１）の実施例であり、実施例８は前述した第５の実施の形態の実施例である。
【０１９１】
｛実施例１｝
＜像担持体１１０＞
像担持体１１０の基材は、厚さ５０μｍ、内径８５．３６ｍｍ、長さ４００ｍｍのニッケル電鋳管とした。
【０１９２】
感光層は、上記基材に下引き層を形成し、厚さ２０μｍのＯＰＣ（有機感光層）をディッピングにて形成した。
【０１９３】
＜円筒部材１４０＞
パイプ状の円筒部材として、直径８４．９１ｍｍ、長さ４４０ｍｍ、厚さ２ｍｍのステンレス製中空円筒を用いた。
【０１９４】
円板状の側板１４２，１４３は、ステンレス製の切削部品で構成した。
【０１９５】
なお、円筒部材１４０および側板１４２，１４３は、その全体を切削加工により成形することもできる。
【０１９６】
＜支持部材１２０＞
スペーサ１３０は、その基部１３１として金属テープを用い、この金属テープの外周面に、弾性印刷にて弾性突起１３２を形成した。
【０１９７】
固着部材１２１としては、導電性接着剤を用いた。
【０１９８】
円筒部材１４０の外周面１４５と像担持体１１０の内周面１１３との間の間隔Ｓは０．２２５ｍｍとした。
【０１９９】
＜硬質ローラ＞
硬質ローラは具体的には次のようにして構成することができる。
【０２００】
すなわち、硬質のローラ状基体の表面に抵抗層を設けることによって構成する。
【０２０１】
ローラ状基体としては、アルミニウム、アルミニウム合金、鉄、銅等の金属を、切削、研磨等で、振れ精度、表面精度を良好に加工する。表面はバフ加工、ポリッシュ加工、スーパーフィニッシュ加工、ダイヤモンド研削、センタレス研磨等で鏡面仕上げを施す。
【０２０２】
または、合成樹脂例えば、ポリエステル、ポリエチレンテレフタレート（ＰＥＴ）、ポリカーボネート（ＰＣ）、ポリイミド（ＰＩ）、ポリアミド（ＰＡ）、ポリフェニレンサルファイド（ＰＰＳ）、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリスチレン（ＰＳ）、ナイロン（ＮＹ）、等をローラ状に成形し、これにアルミニウム、ニッケル、銅等の金属を蒸着、メッキ等で導電層を形成するか、または、樹脂中に、カーボン等の導電材を入れ、導電性樹脂として導電性を付与すれば良い。
【０２０３】
抵抗層は、体積抵抗１０⁸〜１０¹⁴Ωｃｍの抵抗性樹脂を厚さ２μｍ〜１ｍｍ位に形成し中高抵抗の表面層を形成する。抵抗性樹脂としては、ナイロン、ポリウレタン、ポリエチレン等の薄膜樹脂に、カーボン、アルミニウム、ニッケル等の導電性粒子を分散したものを採用することができる。また、ポリビニールアニリン等の導電性樹脂やイオン導電性樹脂を用いても良い。
【０２０４】
以上のような硬質ローラは、ローラ状基体が硬質なため、鏡面仕上げが可能であり、これに形成された薄膜の樹脂の表面も極めて平滑である。
【０２０５】
また、表面が薄膜の樹脂であるため、硬度のバラツキや導電性のバラツキも少ない。
【０２０６】
＜像担持体の変形状態を有限要素法にて解析するために用いた各部材等＞
図５および図７に示した像担持体の変形状態を有限要素法にて解析するために用いた各部材等の諸元は次の通りである。
【０２０７】

｛実施例２｝
像担持体１１０の基材および、円筒部材１４０を両者ともステンレスで構成した。その他は実施例１と同じである。
【０２０８】
｛実施例３｝
像担持体１１０の基材および、円筒部材１４０を両者ともポリエチレンテレフタレート（ＰＥＴ）で構成した。像担持体１１０の基材および円筒部材１４０には、これにアルミニウム、ニッケル、銅等の金属を蒸着し、あるいはメッキ等で導電層を形成し、または、樹脂中に、カーボン等の導電材を入れて導電性を付与した。
【０２０９】
その他は実施例１と同じである。
【０２１０】
｛実施例４｝
像担持体１１０の基材、円筒部材１４０を、アルミ、ジュラルミン、マグナリウムのいずれかで構成した。
【０２１１】
その他は実施例１と同じである。
【０２１２】
｛実施例５｝
像担持体１１０の基材、円筒部材１４０を、黄銅、銅、りん青銅のいずれかで構成した。
【０２１３】
その他は実施例１と同じである。
【０２１４】
｛実施例６｝
筒状部材１４０をガラス繊維含有率５５％（重量比）のＰＥＴ（ポリエチレンテレフタレート）で構成した。円筒部材１４０には、これにアルミニウム、ニッケル、銅等の金属を蒸着し、あるいはメッキ等で導電層を形成し、または、樹脂中に、カーボン等の導電材を入れて導電性を付与した。
【０２１５】
その他は実施例１と同じである。
【０２１６】
｛実施例７｝
像担持体１１０の基材をアルミニウム管（線膨張率は２３．１×１０^-6／゜Ｃである）で構成し、筒状部材１４０をガラス繊維または雲母等の無機質（ミネラル）入りのＰＥＴ（ポリエチレンテレフタレート）で構成したる。ガラス含有率を４５％（重量比）とすることによって、線膨張率を２３．０×１０^-6／゜Ｃとした。円筒部材１４０には、これにアルミニウム、ニッケル、銅等の金属を蒸着し、あるいはメッキ等で導電層を形成し、または、樹脂中に、カーボン等の導電材を入れて導電性を付与した。
【０２１７】
その他は実施例１と同じである。
【０２１８】
｛実施例８｝
像担持体１１０の基材はニッケル電鋳管で構成し、その長さは、Ｌ１＝３００ｍｍとした。熱膨張率はα１＝１３．４×１０^-6／゜Ｃ、ヤング率はＥ１＝２００００ｋｇ／ｍｍ²である。許容応力としては０．２％耐力を採用した。すなわち、
σａ＝５０ｋｇ／ｍｍ²である。
【０２１９】
左右の固定部材１５１，１５２としては、ナイロン６１０を用い、その長さは、
Ｌ２＝Ｌ４＝５ｍｍとした。熱膨張率はα２＝α４＝９０×１０^-6／゜Ｃである。
【０２２０】
円筒部材１４０は炭素鋼で構成し、その長さは、Ｌ３＝２９０ｍｍとした。熱膨張率はα３＝１０．７×１０^-6／゜Ｃである。
【０２２１】
そして、通常、像担持体ユニット１００の組立は室温（およそ２０〜２５゜Ｃ）の環境下で行なわれ、実際に使用される（あるいは輸送中における）環境温度は、通常、０〜４５゜Ｃ位であるので、温度差としては△Ｔ＝２０゜Ｃを採用した。
【０２２２】
以上のような条件で前述したずれ量Ｌｔを計算すると、
Ｌｔ＝０．０００３４ｍｍとなる。
【０２２３】
したがって、像担持体１１０の熱歪εｔは、
εｔ＝Ｌｔ／Ｌ１＝１．１３×１０^-6
熱応力σｔは
σｔ＝Ｅ１×εｔ＝０．０２２６７ｋｇ／ｍｍ²
となり、許容応力σａ＝５０ｋｇ／ｍｍ²でに比べて極めて小さな値となる。
【０２２４】
したがって、熱膨張による像担持体１１０の歪、振れ等が増加することなく、組立時の状態が維持され、極めて高精度な像担持体ユニット１００が得られる。
【０２２５】
以上、本発明の実施の形態および実施例について説明したが、本発明は上記の実施の形態または実施例に限定されるものではなく、本発明の要旨の範囲内において適宜変形実施可能である。
【０２２６】
例えば、
（１）上記実施の形態では像担持体ユニットを感光体ユニットとして説明したが、本発明の像担持体ユニットは、これに限らず、中間転写媒体ユニットとしても構成することができる。この場合、像担持体は薄肉円筒状の中間転写体で構成される。
【０２２７】
（２）支持部材１２０は、固定部材としての固着部材１２１と、スペーサ１３０とを備えている構成としたが、固定部材だけで構成することもできる。
【０２２８】
【発明の効果】
請求項１〜３記載のいずれの像担持体ユニットによっても、使用環境や輸送環境で温度が変化しても破損等を生じることなく、硬質ローラ等の当接部材との確実で安定した接触状態を得ることが可能であるとともに、製造が簡単であるという効果が得られる。
【０２２９】
さらに、請求項２記載の像担持体ユニットによれば、取扱い性に優れているという効果が得られ、請求項３記載の像担持体ユニットによれば、別途導通手段を設ける必要がなくなるという効果が得られる。
【０２３０】
【図面の簡単な説明】
【図１】本発明に係る像担持体ユニットの第１の実施の形態を用いた画像形成装置の要部を示す模式図。
【図２】図１におけるＩＩ−ＩＩ断面図で、主として像担持体ユニットを示す図。
【図３】主としてスペーサの一例を示す模式図で、図（ａ１）は像担持体１１０が装着される前の状態を示す正断面図、図（ａ２）は図（ａ１）の部分左側面図、図（ａ３）は作用説明図、図（ｂ１）は像担持体１１０が装着された後の状態を示す正断面図、図（ｂ２）は図（ｂ１）の部分左側面図、図（ｃ）は像担持体１１０が装着された後の状態を示す左側面。
【図４】作用説明図。
【図５】作用説明図。
【図６】作用説明図。
【図７】作用説明図。
【図８】本発明に係る像担持体ユニットの第２の実施の形態の要部を示す模式図で、（ａ）は円筒部材およびスペーサを示す上半分の側面図、（ｂ）は部分斜視図。
【図９】本発明に係る像担持体ユニットの第３の実施の形態の要部を示す模式図で、（ａ）は円筒部材およびスペーサを示す上半分の側面図、（ｂ）は部分斜視図、（ｃ）は図（ａ）の部分拡大図、（ｄ）は作用説明図。
【図１０】本発明に係る像担持体ユニットの第４の実施の形態の要部を示す模式図で、（ａ）は円筒部材およびスペーサを示す上半分の部分斜視図、（ｂ）は断面図、（ｃ）は作用説明図。
【図１１】本発明に係る像担持体ユニットの第５の実施の形態の要部を示す模式図で、上半分の断面を示した図。
【図１２】（ａ）（ｂ）は、長さおよび熱膨張率がそれぞれ異なる部材を連結した構造体において発生する熱膨張を説明するための図。
【図１３】従来技術の説明図。
【図１４】従来技術の説明図。
【図１５】従来技術の説明図。
【図１６】従来技術の説明図。
【符号の説明】
１００ 感光体ユニット
１１０ 像担持体
１１１ 両端部
１１１ａ 端縁部
１１３ 内周面
１２０ 支持部材
１２１ 固着部材（固定部材）
１３０ スペーサ
１４０ 円筒部材
１４５ 外周面
１５１，１５２ 固定部材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image carrier unit used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine that forms an image by electrophotographic technology.
[0002]
[Prior art]
In general, an image forming apparatus using an electrophotographic technique has a photosensitive member having a photosensitive layer on an outer peripheral surface, a charging unit that uniformly charges the outer peripheral surface of the photosensitive member, and a charging unit that is uniformly charged by the charging unit. An exposure unit that selectively exposes the outer peripheral surface to form an electrostatic latent image, and a toner that is a developer is applied to the electrostatic latent image formed by the exposure unit to form a visible image (toner image). Developing means for transferring, and transfer means for transferring the toner image developed by the developing means to a transfer medium such as paper.
[0003]
As the photosensitive member, a hard photosensitive drum having a photosensitive layer formed on the outer peripheral surface and a flexible photosensitive belt having a photosensitive layer formed on the surface are generally known.
[0004]
Further, as the charging unit, the developing unit, and the transfer unit, there are known roller-like ones that are brought into contact with the surface of the photoreceptor, and the rollers include those made of hard and soft rubber. Are known.
[0005]
When a hard photosensitive drum is used as the photosensitive member, and a hard roller is used as a roller for contacting the photosensitive drum, there is a limit to manufacturing the photosensitive drum and the hard roller with high accuracy. As a result, it is difficult to bring them into uniform contact. If the two do not come into contact with each other, there will be a problem that gaps are locally generated and charging unevenness, development unevenness, transfer unevenness, etc., or the photosensitive drum and the hard roller are damaged by being pressed more strongly than necessary.
[0006]
Therefore, it is not usually done to make both the photoconductor and the roller to be in contact with the hard body. When a hard photoconductor drum is used as the photoconductor, the roller is made of soft rubber. When a hard roller is used, a flexible photosensitive belt is used as the photosensitive member.
[0007]
However, when the roller brought into contact with the photosensitive member is made of soft rubber, there is the following problem (Japanese Patent Laid-Open No. 3-33768).
[0008]
When the charging roller or the like that is brought into contact with the photosensitive member is a rubber roller, conductive particles such as carbon are dispersed in order to impart conductivity to the charging roller. As a result, the rubber hardness changes, and the hardness on the roller surface varies, so that there is a problem that a good adhesion state to the photoreceptor cannot be obtained.
[0009]
On the other hand, if the amount of carbon dispersion is reduced in order to obtain a good adhesion to the photoreceptor, there is a problem in that the conductivity varies and uneven charging occurs.
[0010]
Also, if a plasticizer is added as a compounding agent in order to increase flexibility, the plasticizer may ooze out on the surface depending on the long-term use or usage environment. There is a problem that the photoconductive material in the photoconductor is denatured by being attached to the surface of the photoconductor, or the photoconductor is stuck to the roller and the surface of the photoconductor is peeled off.
[0011]
Such a problem can be solved by using a hard roller as the roller and using a flexible photosensitive belt as the photosensitive member.
[0012]
However, when a photoconductor belt is used as the photoconductor, at least two support rollers are required to support the photoconductor belt, so that not only the structure becomes complicated but also the apparatus becomes large. there were.
[0013]
Conventionally, a photoconductor drum described in Japanese Patent Publication No. 4-69383 (Japanese Patent Laid-Open No. 59-192260) has been known as an attempt to solve all of the above problems.
[0014]
The photoreceptor drum described in Japanese Patent Publication No. 4-69383 is shown in FIGS.
[0015]
The photosensitive drum 1 includes a rotating shaft 2, an elastic material layer 3 that is supported by the rotating shaft 2 and has a cylindrical shape in a free state, and an outer surface that is mounted around the elastic material layer 3. Layer 4. The outer layer 4 includes a photosensitive support layer 5 that can be elastically deformed, and a photosensitive layer 6 that is supported on the surface of the support layer 5. The elastic material layer 3 is filled between the rotating shaft 2 and the outer layer 4 without substantially forming a gap.
[0016]
Since the photosensitive drum 1 has the outer layer 4 and the elastic material layer 3 that can be elastically deformed, the surface can be elastically deformed when an external force is applied to the surface.
[0017]
In FIG. 13, 7 is a charging charger, 10 is a developing roller, and 13 is a transfer charger.
[0018]
At the time of image formation, the photosensitive drum 1 is rotated in the clockwise direction in FIG. 13, and the photosensitive layer 6 of the drum 1 is charged to a predetermined polarity by the charging charger 7. By irradiating the charged portion with light 8, an electrostatic latent image is formed on the drum 1. This latent image is developed with the toner carried on the developing roller 10 rotating in the direction of the arrow in the drawing to be visualized, and transferred to the transfer paper 12 by the transfer charger 13.
[0019]
In FIG. 13, 14 is a separation charger, 15 is a cleaning blade, and 16 is a static elimination charger.
[0020]
According to the above configuration, since the surface of the photosensitive drum 1 can be elastically deformed, the developing roller 10 can be pressed against the photosensitive drum 1 and the surface of the photosensitive drum 1 can be elastically deformed in the radial direction. For this reason, the peripheral surfaces of the photosensitive drum 1 and the developing roller 10 are slightly decentered with respect to the central axis thereof, or the outer diameters thereof are slightly different in manufacturing, and at least the surface of the developing roller 10 is made of a rigid body. However, the toner on the developing roller 10 can be brought into contact with the photosensitive drum 1 in a more reliable and stable state than before without causing the inconvenience of scratching the drum surface and the developing roller. It is possible to suppress deterioration in the image quality of the visible image due to a large gap between the toner on the upper surface and the surface of the drum 1.
[0021]
That is, according to the photosensitive drum 1, even if a hard developing roller is used, the photosensitive drum and the developing roller are not damaged, and an increase in the size of the apparatus can be prevented.
[0022]
A photosensitive drum similar to this photosensitive drum is also disclosed in Japanese Patent Application Laid-Open No. 58-90655.
[0023]
On the other hand, in Japanese Patent Laid-Open No. 58-86550, for the purpose of reducing the weight and preventing the generation of induced eddy currents, as shown in FIG. An endless belt made of metal (Cu, Al, W, Mo, etc.) is used as a drum base 31, an image bearing layer (photoconductive material layer) 32 is formed on the drum base 31, and both ends of the drum base 31 are circular. A drum-shaped image carrier member fixed to a steel shaft 34 with a plate-shaped end plate 33 is disclosed.
[0024]
[Problems to be solved by the invention]
The photosensitive drum 1 described in Japanese Patent Publication No. 4-69383 described above (see FIGS. 13 to 15) substantially forms a gap between the rotating material 2 and the outer layer 4 with the elastic material layer 3 therebetween. Since the structure is filled without any problems, it has the following problems.
[0025]
Since the photosensitive layer 6 is formed on the elastic material layer 3, the photosensitive layer 6 is displaced in the axial direction with a minute force. Since the photosensitive layer 6 is provided with a pressure contact member such as a developing roller 10 and a cleaning blade 15 that are in pressure contact with the photosensitive layer 6, the rotational axis of the photosensitive layer 6 and the axis of the pressure contact member are inclined, or the pressure contact force is axial. If the photosensitive layer 6 is not uniform, the photosensitive layer 6 receives a thrust force in the axial direction, and is displaced in the axial direction by the thrust force. Since this thrust force fluctuates, the image formed on the photosensitive layer 6 is also displaced in the axial direction. As a result, there is a problem that the positional accuracy of the image in the axial direction is deteriorated. In particular, when multi-color superposition is performed, there is a problem that deterioration of color superposition accuracy causes a hue shift and the image is remarkably deteriorated.
[0026]
In addition, as a method of manufacturing such a photosensitive drum 1,
(1) First, the outer layer 4 in which the photosensitive layer 6 is formed on the photosensitive layer support layer 5 is produced, and then the shaft 2 and the outer layer 4 are arranged at a predetermined interval, and the shaft 2 and the outer layer 4 are arranged. And manufacturing the elastic material layer 3 by pouring a heated elastic material into the space
(2) First, the shaft 2 and the photosensitive member support layer 5 are arranged at a predetermined interval, and a heated elastic material is poured into the space between the shaft 2 and the photosensitive member support layer 5 to form the elastic material layer 3. Method of manufacturing by forming and then forming photosensitive layer 6 on photosensitive layer support layer 5
(3) A cylindrical elastic member having an outer diameter slightly larger than the inner diameter of the outer layer 4 is produced, and the cylindrical elastic member is inserted into the outer layer 4 in a state of being compressed in the radial direction, whereby an elastic material layer Method for manufacturing by forming 3
Can be considered.
[0027]
However, in the above method (1), the operation of pouring a heated elastic material into the outer layer 4 with the photosensitive layer 6 formed on the surface of the outer layer 4 is performed. There is a problem that the characteristics of the photosensitive member deteriorate due to the above. Further, the surface of the photosensitive layer 6 may be scratched or foreign matter (foreign matter such as an elastic material) may be attached.
[0028]
In the method (2), since the photosensitive layer 6 is formed after the elastic material layer 3 is formed, the elastic material layer 3 is swollen and dissolved by a cleaning solution or a coating solution when the photosensitive layer is applied. Or hardening may arise, As a result, there exists a possibility that the function as an elastic material layer may fall.
[0029]
Therefore, it is very difficult to obtain the desired photosensitive drum 1 by the methods (1) and (2).
[0030]
In the method (3), the tubular elastic member is likely to expand unevenly in the process of being released from the compressed state and expanding toward the outer layer 4. For this reason, the coaxiality between the shaft 2 and the outer layer 4 is impaired, and there is a possibility that the shake when the photosensitive drum 1 rotates becomes very large. In the image forming apparatus, contact members such as a charging unit, a developing unit, a transfer unit, and a cleaning unit that are in contact with the photosensitive member are disposed around the photosensitive member. There is a problem that the contact state with the contact member becomes unstable and image unevenness occurs.
[0031]
On the other hand, if the drum-shaped image carrier member (see FIG. 16) described in JP-A-58-86550 is configured so that the drum base 31 can be easily bent inward, this drum The base 31 can be used as a pseudo soft material, and it can be expected that the problem in the photosensitive drum 1 (see FIGS. 13 to 15) described in Japanese Patent Publication No. 4-69383 is solved.
[0032]
However, the drum-shaped image carrier member (see FIG. 16) has a structure in which both ends of a drum base 31 made of Cu, Al, W, Mo, or the like are fixed to a steel shaft 34 with disc-shaped end plates 33. Therefore, there are the following problems.
[0033]
That is, since the drum base 31 is fixed to the end plate 33 fixed to the shaft 34, and the shaft 34 and the drum base 31 are made of the above-mentioned different materials, the temperature is increased in the use environment and the transport environment. When it changes, a large thermal strain is generated inside the drum-shaped image carrier member.
[0034]
For this reason, the thin cylindrical drum base 31 is distorted and deformed to generate vibration, and the distance from each process member such as the developing roller varies depending on the temperature environment, so that a reliable and stable contact state or gap Management becomes impossible, and there is a risk of image defects due to uneven charging, development failure, transfer failure, and the like.
[0035]
Further, the thin cylindrical drum base 31 may buckle due to thermal strain, break, or be permanently deformed.
[0036]
Furthermore, there is a possibility that the fixed part of the component is damaged by thermal stress.
[0037]
Further, when the drum base 31 is configured so as to be easily bent inward, there is a problem that if the operator presses the center portion by mistake, the drum base 31 is damaged. Since this type of image carrier is usually a replacement part, if there is a risk of damage due to its handling, the replacement work becomes extremely difficult.
[0038]
The present invention is intended to solve the above-described problems. The first object of the present invention is to provide a contact member such as a hard roller without causing damage or the like even if the temperature changes in the use environment or the transport environment. It is an object of the present invention to provide an image carrier unit that can obtain a reliable and stable contact state and can be easily manufactured.
[0039]
In addition, a second object is to provide an image carrier unit having excellent handling properties.
[0042]
[Means for Solving the Problems]
  In order to achieve the first object, an image carrier unit according to claim 1 has a flexible thin-walled cylindrical image carrier and an outer diameter smaller than the inner diameter of the image carrier, A rigid cylindrical member disposed inward of the image carrier, and a fixing member for fixing both ends of the image carrier on the cylindrical member, and between the connecting portions of the image carrier with the fixing member The length in the axial direction and the linear expansion coefficient are L1 and α1, and the length and linear expansion coefficient between the connecting portions of the cylindrical member and the fixed member are L3 and α3. The image carrier of the fixed member and the cylindrical member The axial length between the connecting portions is L2, L4, the linear expansion coefficient is α2, α4,
  Regarding the length in the axial direction, in the structure having the connected image carrier, the cylindrical member, and the fixing member, a certain connecting point of the connecting portions is set as a starting point and an ending point, and from this starting point, from the starting point. When considering a closed loop from the most distant connection point toward the end point toward the other end point, the direction from the start point to the farthest connection point is positive, and the most distant connection point The direction from to the end point is negative, and
  When the Young's modulus of the image carrier is E1, and the allowable stress is σa,
                  n
    σa> E1 × ΣLi × (1 + αi · ΔT) / L1
                 i = 1
  Li: length of the i-th member
  αi: i-th linear expansion coefficient
  ΔT: ΔT = 20 ° C
It is characterized by being.
[0043]
  Claim2The image carrier unit described in claim1In the image carrier unit described above, the image carrier is supported by the fixing member with an interval smaller than an allowable deformation amount of the image carrier between an inner peripheral surface thereof and an outer peripheral surface of the cylindrical member. It is characterized by being.
[0044]
  Claim3The image carrier unit described above is the image carrier unit according to claim 1, 2, 3, or 4, wherein the cylindrical member and the fixing member have electrical conductivity.
[0045]
[Function and effect]
In the image carrier unit according to claim 1, both ends of the flexible thin cylindrical image carrier are fixed by a fixing member on a cylindrical member having an outer diameter smaller than the inner diameter of the image carrier. Since it is configured, the image bearing member can be deformed inward at the central portion that is not fixed by the fixing member.
[0046]
Therefore, since the central portion of the image carrier can be used as a so-called pseudo-soft material, even if the member abutting on it is hard (for example, a hard roller), it is reliable and stable. The contact state can be obtained, and an image can be reliably formed on the image carrier or the image can be carried.
[0047]
Further, this image carrier unit can be manufactured by disposing a cylindrical member inside the image carrier and fixing both ends of the image carrier with fixing members. Since it is not necessary to fill the elastic material layer as in the photosensitive drum 1 (see FIGS. 13 to 15) described in Japanese Patent No. 693693, it can be easily manufactured.
[0048]
Since the linear expansion coefficient of the image carrier and the linear expansion coefficient of the cylindrical member are substantially equal, even if the temperature changes in the use environment or the transportation environment, the thermal expansion is not performed inside the image carrier unit. Thermal distortion due to the difference does not occur or even if it occurs.
[0049]
Therefore, the thin cylindrical image carrier is prevented from being distorted and deformed, and the occurrence of shake is prevented, so that the distance from each process member such as the developing roller does not vary depending on the temperature environment, and the contact state is reliable and stable. Alternatively, gap management becomes possible, and a good image free from uneven charging, development failure, transfer failure and the like can be obtained.
[0050]
In addition, the image carrier is not buckled, broken or permanently deformed by thermal strain, and the fixed part of the component is not damaged by thermal stress. improves.
[0051]
That is, according to the image carrier unit of the first aspect, a reliable and stable contact state with the contact member such as the hard roller without causing damage or the like even if the temperature changes in the use environment or the transport environment. It is possible to obtain the effect that the manufacturing is simple.
[0052]
According to the image carrier unit of the second aspect, similar to the image carrier unit of the first aspect, both ends of the flexible thin cylindrical image carrier have outer sides smaller than the inner diameter of the image carrier. Since it is configured to be fixed on a cylindrical member having a diameter by a fixing member, even if the member abutting on the member is hard (for example, a hard roller), a reliable and stable contact state is obtained. Therefore, it is possible to reliably form an image on the image carrier or to carry the image, and it is possible to easily manufacture the image.
[0053]
Since the image carrier and the cylindrical member are made of the same material, thermal distortion due to the difference in thermal expansion occurs inside the image carrier unit even if the temperature changes in the environment of use or transportation. Even if it occurs, it becomes minute.
[0054]
Therefore, the thin cylindrical image carrier is prevented from being distorted and deformed, and the occurrence of shake is prevented, so that the distance from each process member such as the developing roller does not vary depending on the temperature environment, and the contact state is reliable and stable. Alternatively, gap management becomes possible, and a good image free from uneven charging, development failure, transfer failure and the like can be obtained.
[0055]
In addition, the image carrier is not buckled, broken, or permanently deformed due to thermal strain, and the fixed part of the component is not damaged by thermal stress. improves.
[0056]
That is, according to the image carrier unit according to claim 2, a reliable and stable contact state with the abutting member such as a hard roller without causing damage or the like even if the temperature changes in the use environment or the transport environment. It is possible to obtain the effect that the manufacturing is simple.
[0057]
According to the image carrier unit of the third aspect, similar to the image carrier unit of the first aspect, both ends of the flexible thin cylindrical image carrier have outer sides smaller than the inner diameter of the image carrier. Since it is configured to be fixed on a cylindrical member having a diameter by a fixing member, even if the member abutting on the member is hard (for example, a hard roller), a reliable and stable contact state is obtained. Therefore, it is possible to reliably form an image on the image carrier or to carry the image, and it is possible to easily manufacture the image.
[0058]
The axial length and the linear expansion coefficient between the connecting portions of the image carrier with the fixing member are L1 and α1, and the length and the linear expansion coefficient between the connecting portions of the cylindrical member and the fixing member are L3 and α3. , The axial length between the connecting parts of the fixing member to the image carrier and the cylindrical member is L2, L4, and the linear expansion coefficient is α2, α4,
When the Young's modulus of the image carrier is E1, and the allowable stress is σa,

Li: length of the i-th member
αi: i-th linear expansion coefficient
ΔT: temperature difference
Therefore, even if the temperature changes in the usage environment or transport environment, thermal distortion in the axial direction does not occur inside the image carrier unit, or even if it occurs, it is below the allowable stress Will be.
[0059]
Therefore, large distortion and permanent deformation of the thin cylindrical image carrier are prevented, and occurrence of shake is prevented, so that the distance from each process member such as the developing roller does not vary greatly depending on the temperature environment, and is reliable and stable. The contact state or the gap can be managed, and a good image free from uneven charging, development failure, transfer failure, etc. can be obtained.
[0060]
Further, the image carrier is not buckled or broken due to thermal strain, and the fixing part of the component is not damaged due to thermal stress, so that the mechanical reliability is improved.
[0061]
That is, according to the image carrier unit of claim 3, a reliable and stable contact state with the abutting member such as the hard roller without causing damage or the like even if the temperature changes in the use environment or the transport environment. It is possible to obtain the effect that the manufacturing is simple.
[0062]
According to an image carrier unit of claim 4, in the image carrier unit of claim 1, 2, or 3, the image carrier is between an inner peripheral surface thereof and an outer peripheral surface of the cylindrical member. Since the image bearing member is supported by the fixing member at an interval smaller than the allowable deformation amount of the image carrier, for example, when the operator mistakenly presses the central portion of the image carrier accidentally when the image carrier unit is replaced. However, the image carrier is not damaged because it is supported by the cylindrical member before being damaged. Therefore, this image carrier unit is superior in handleability compared to the drum-like image carrier member (see FIG. 16) disclosed in Japanese Patent Laid-Open No. 58-86550 described above.
[0063]
In addition, even if the image carrier is strongly pressed, it does not break, so that the contact member can be strongly contacted.
[0064]
That is, according to the image carrier unit of claim 4, a reliable and stable contact state with the abutting member such as the hard roller without causing damage or the like even if the temperature changes in the use environment or the transport environment. As well as easy manufacturing and excellent handling properties.
[0065]
According to the image carrier unit of claim 5, in the image carrier unit of claim 1, 2, 3, or 4, the cylindrical member and the fixing member have conductivity, so that image formation is performed. The electrical conduction to the image carrier necessary for this can be obtained through the cylindrical member and the fixing member. Therefore, it is not necessary to provide a separate conduction means.
[0066]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0067]
<First Embodiment>
FIG. 1 is a schematic view showing a main part of an image forming apparatus using the first embodiment of an image carrier unit according to the present invention. FIG. 2 is a sectional view taken along line II-II in FIG. FIG.
[0068]
In these drawings, reference numeral 100 denotes an image carrier unit. In this embodiment, the image carrier unit is configured as a photosensitive unit used in an electrophotographic image forming apparatus.
[0069]
The photosensitive unit 100 is rotationally driven in the direction of the arrow (clockwise) in FIG. 1 by an appropriate driving unit (not shown).
[0070]
The photoreceptor unit 100 includes an image carrier 110, a pair of support members 120 and 120 that support both ends 111 and 111 of the image carrier 110, and a cylindrical member 140 that is disposed inside the image carrier 110. It has.
[0071]
The image carrier 110 is formed in a thin cylindrical shape having flexibility, and is configured by forming a photosensitive layer on the surface (outer peripheral surface) of a flexible substrate. For example, a nickel seamless tube produced by electroforming can be used as the base material. The photosensitive layer can be formed by so-called OPC (organic photoreceptor) by dipping. Such flexibility, that is, softness of the image carrier 110 can be determined by adjusting the thickness and the diameter of the base material, and therefore is appropriately set according to the image forming apparatus used. Is possible. For example, the allowable deformation amount δ2 (described later) is appropriately set within a range of a base material thickness of 20 to 200 μm and a base material diameter of 10 to 300 mm. Since OPC is mainly made of resin, it is excellent in flexibility. However, in order to ensure adhesion with the base material and to take measures against interference of laser light, an undercoat layer is provided between the base material and the OPC. It is desirable to form. As the undercoat layer, a layer in which particles capable of absorbing laser light such as zinc oxide and titanium oxide are dispersed in a resin such as nylon resin is preferable.
[0072]
The support member 120 is located slightly closer to the center than the edge portion 111 a of the image carrier 110, and includes a fixing member 121 as a fixing member and a spacer 130.
[0073]
The fixing member 121 has a short length that can ignore its own thermal expansion, and supports and connects the image carrier 110 and the cylindrical member 140 in the vicinity of both ends thereof. Here, as shown in FIG. 2, when the length in the axial direction between the connecting portions of the image carrier 110 and the fixing member 121 is L1, and the length between the connecting portions of the cylindrical member 140 and the fixing member 121 is L3. , L1 = L3.
[0074]
Therefore, even when the temperature surrounding the photoconductor unit 100 changes and a temperature difference occurs, the image carrier 110 and the cylindrical member 140 are configured to have substantially the same linear expansion coefficient or the same kind as described later. By using the material, it is possible to make the changes in the lengths of L1 and L3 substantially the same, reduce distortion and deformation generated in the image carrier 110, and maintain good mechanical accuracy.
[0075]
The fixing member 121 and the spacer 130 are arranged in an annular shape on the outer peripheral surface of the cylindrical member 140, and are interposed between the cylindrical member 140 and the image carrier 110.
[0076]
In this embodiment, the fixing member 121 is made of a conductive adhesive, for example, a conductive adhesive in which conductive particles are dispersed in an epoxy, cyano, or acrylic resin adhesive. As the conductive particles, metal (silver, aluminum, etc.), carbon, or the like can be used.
[0077]
FIG. 3 is a schematic diagram mainly showing an example of the spacer 130. FIG. (A1) is a front sectional view showing a state before the image carrier 110 is mounted, and FIG. (A2) is a partial left side view of FIG. Fig. (A3) is a diagram for explaining the operation, Fig. (B1) is a front sectional view showing the state after the image carrier 110 is mounted, Fig. (B2) is a partial left side view of Fig. (B1), and Fig. (C) ) Is a left side view showing a state after the image carrier 110 is mounted.
[0078]
As shown in these drawings, the spacer 130 in this embodiment includes a thin ring-shaped base 131 fixed to the outer peripheral surface 145 of the cylindrical member 140 and an elastic portion protruding from the outer peripheral surface of the base 131. The elastic projection 132 is provided. The base 131 is made of, for example, metal or synthetic resin, and the elastic protrusion 132 is made of, for example, silicon rubber. As shown in FIG. 2C, a plurality of elastic protrusions 132 (12 pieces in the figure) are provided at equal intervals in the circumferential direction of the base 131. As shown in the diagram (a2), the outer diameter Rf of the base 131 is set smaller than the inner diameter Ra of the image carrier 110, and a circle connecting the tips of the elastic protrusions 132 before the image carrier 110 is mounted. The radius (the distance from the center of the image carrier 110 to the tip of the elastic projection 132) Re is set to be larger than the inner diameter Ra of the image carrier 110. The base 131 has a thickness of about 100 μm, and the elastic protrusion 132 has a height of about 100 μm in the state where the image carrier 110 is mounted as shown in FIGS. The elastic protrusion 132 can be formed, for example, by printing a silicone rubber paint on the surface of the base 131.
[0079]
After the image carrier 110 is placed on the cylindrical member 140 (after the cylindrical member 140 is inserted into the image carrier 110), the adhesive 121 is injected between the both end portions 111 and the outer peripheral surface of the cylindrical member 140. By doing so, it is fixed on the cylindrical member 140.
[0080]
At this time, the spacer 130 acts as follows.
[0081]
In the process of covering the image carrier 110 with the cylindrical member 140 as shown by the arrow X1 in the drawing (a1) (inserting the cylindrical member 140 into the image carrier 110), the tip of the spacer 130 contacts the inner surface of the image carrier 110. Then, it is pushed in the direction of the arrow X1, and temporarily deformed in the direction of the arrow X1 as shown in FIG.
[0082]
After that, when the cylindrical member 140 is completely inserted into the image carrier 110 and the external force acting in the direction of the arrow X1 disappears, the spacer 130 moves the image carrier 110 into the figure (b1) by its own elastic force (restoring force). As shown in FIG. 4, the image carrier 110 is crushed as shown in the figure while being pushed back slightly in the direction of the arrow X2, and the image carrier 110 is supported from the inside by its own elasticity.
[0083]
Here, a plurality of elastic protrusions 132 are provided at equal intervals in the circumferential direction of the base 131 as shown in FIG. 3C, so that the elastic force (restoring force) fc of the elastic protrusions 132 is the image carrier 110. As a result, as shown in FIG. 2 (b2), the image carrier 110 is in a state where the distance S between the cylindrical member 140 and the cylindrical member 140 is substantially uniform (that is, a substantially circular state). It will be mounted on the cylindrical member 140. In this state, an adhesive 121 (see FIG. 2) is injected between both end portions 111 of the image carrier 110 and the outer peripheral surface of the cylindrical member 140, and the image carrier 110 is fixed onto the cylindrical member 140.
[0084]
The distance S between the outer peripheral surface 145 of the cylindrical member 140 and the inner peripheral surface 113 of the image carrier 110 is an allowable deformation amount of the image carrier 110, that is, when the image carrier 110 is deformed inward, it is destroyed. It is set to be smaller than the amount of deformation δ2 (see FIG. 2).
[0085]
As shown in FIG. 2, both ends 141 and 141 of the cylindrical member 140 are fixed to disk-shaped side plates 142 and 143, respectively. The cylindrical member 140 and the side plates 142 and 143 are made of a highly rigid material such as a metal or a synthetic resin that is extremely difficult to deform. When it is made of synthetic resin, a metal such as aluminum, nickel, or copper is deposited on it, or a conductive layer is formed by plating, or a conductive material such as carbon is placed in the resin to make it conductive. Is granted.
[0086]
The cylindrical member 140 and the side plates 142 and 143 can be fixed by an appropriate means such as adhesion, press-fitting, and pressure bonding. The side plates 142 and 143 are integrally provided with shafts 142a and 143a, and a gear 144 is fixed to one of the shafts 143a.
[0087]
The image carrier unit 100 as described above is configured by one of the following (1) and (2).
[0088]
(1) The linear expansion coefficient of the image carrier 110 and the linear expansion coefficient of the cylindrical member 140 are configured to be substantially equal.
[0089]
For example, the base material of the image carrier 110 is a nickel seamless tube (linear expansion coefficient is 12.8 × 10^-6/°C~13.4×10^-6/ ° C.), the cylindrical member 140 is made of PET (polyethylene terephthalate) containing mineral (mineral) such as glass fiber or mica. By setting the glass content to 55% (weight ratio), the linear expansion coefficient is 11.0 × 10^-6/°C~14.0×10^-6/ ° C.
[0090]
(2) The image carrier 110 and the cylindrical member 140 are made of the same kind of material.
[0091]
For example, when the base material of the image carrier 110 is a nickel seamless tube, the cylindrical member 140 is made of nickel or stainless steel.
[0092]
Next, an example of the image forming apparatus will be described. In the image carrier unit 100 as described above, for example, as shown in FIG. 2, shafts 142a and 143a are rotatably supported by a frame F of the apparatus. Reference numerals 146 and 146 denote bearings. A compression spring 147 is provided between the gear 144 and the bearing 146 to prevent rattling.
[0093]
In this way, the photoconductor unit 100 is rotatably supported by the frame F and is rotationally driven in the arrow direction (clockwise) in FIG. 1 by an appropriate driving means (not shown).
[0094]
As shown in FIG. 1, a charging unit 210, an exposure unit 220, a developing unit 230, a transfer unit 240, a cleaning unit 250, and a charge eliminating unit 260 are arranged around the photosensitive unit 100 along the rotation direction. ing.
[0095]
The charging unit 210 is composed of a hard high-resistance resin roller rotating in contact with the outer peripheral surface of the image carrier 110 or a metal roller having a high-resistance layer on the surface. The outer peripheral surface of the body 110 is uniformly charged.
[0096]
The exposure unit 220 forms an electrostatic latent image on the image carrier 110 by scanning the outer peripheral surface of the image carrier 110 with the laser light L.
[0097]
The developing unit 230 rotates in contact with the outer peripheral surface of the image carrier 110, and a hard developing roller 231 that forms a toner image by attaching toner to the outer peripheral surface of the image carrier 110, and is supplied to the developing roller 231. And a toner storage chamber 232 in which the toner to be stored is stored. The developing roller 231 is composed of a metal roller whose surface is roughened or a hard resin roller.
[0098]
The transfer means 240 is composed of a hard high resistance resin roller or a metal roller having a high resistance layer on the surface, and transfers the toner image on the image carrier 110 to a transfer medium (recording medium such as paper or an intermediate transfer belt). ) Transfer to T.
[0099]
The cleaning unit 250 is a cleaning member that comes into contact with the outer peripheral surface of the image carrier 110 and scrapes and removes residual toner remaining on the outer peripheral surface of the image carrier 110 after the toner image is transferred by the transfer unit 240. Cleaning blade 251, and a toner collection chamber 252 for collecting the toner scraped off by the blade 251.
[0100]
The neutralization means 260 is constituted by a neutralization lamp, and the surface of the image carrier 110 is uniformly irradiated with light to neutralize the surface.
[0101]
Among the above means, the charging roller 210 and the transfer roller 240 are both in contact with the image carrier 110 and the inner peripheral surface 113 of the image carrier 110 abuts on the outer peripheral surface 145 of the cylindrical member 140. The image carrier 110 is bent inward and rotated at the same peripheral speed as that of the image carrier 110. Thus, since the inner peripheral surface 113 of the image carrier 110 and the outer peripheral surface 145 of the cylindrical member 140 are in contact with each other at the charging position and the transfer position, it is desirable that the friction coefficient between them is as small as possible. As shown in FIG. 1, the charging roller 210 is driven by a motor 212 (directly or via a gear or the like) and rotates at the same peripheral speed as the peripheral speed of the image carrier 110, and the transfer roller 240 is By contact with 110 (by contact via transfer medium T when there is transfer medium T), the image carrier 110 is driven to rotate at the same peripheral speed as the peripheral speed of image carrier 110. ing. The charging roller 210 has a shaft 211 rotatably supported by a pair of bearing members (not shown), and is urged toward the cylindrical member 140 by known urging means (for example, a spring) (not shown). The support structure and urging structure of the transfer roller 240 are the same.
[0102]
The developing roller 231 is in contact with the image carrier 110 by bending the image carrier 110 inward so that the inner peripheral surface 113 of the image carrier 110 does not contact the outer peripheral surface 145 of the cylindrical member 140. A gap between the inner peripheral surface 113 bent inward of the image carrier 110 and the outer peripheral surface 145 of the cylindrical member 140 at the roller contact portion is indicated by S1. The shaft 233 of the developing roller 231 is rotatably supported by a pair of bearing members 234 and 234, and the bearing members 234 abut against the outer peripheral surface 145 of the cylindrical member 140 on both sides of the image carrier 110. As a result, the distance between the developing roller 231 and the cylindrical member 140 is regulated. The developing roller 231 has a shaft 233 biased toward the cylindrical member 140 by a biasing means (not shown). The developing roller 231 is driven to rotate when the shaft 233 is driven by a driving means (not shown). The rotational speed of the developing roller 231 may be the same as the peripheral speed of the image carrier 110 or may be different (usually increased).
[0103]
The cleaning blade 251 of the cleaning unit 250 presses the image carrier 110 until the inner peripheral surface 113 of the image carrier 110 abuts on the outer peripheral surface 145 of the cylindrical member 140 to remove toner on the outer peripheral surface. Yes. In this cleaning position, the inner peripheral surface 113 of the image carrier 110 and the outer peripheral surface 145 of the cylindrical member 140 are in contact with each other, and therefore it is desirable that the friction coefficient between the two is as small as possible.
[0104]
The image forming operation by the image forming apparatus as described above is as follows.
[0105]
The photosensitive unit 100 is driven to rotate by a driving unit (not shown), and the image carrier 110 is also driven to rotate.
[0106]
In the process, the image carrier 110 is first charged by the discharging unit 260 and then uniformly charged by the charging unit 210.
[0107]
Next, an electrostatic latent image is formed on the image carrier 110 by irradiating the exposure unit 220 with laser light L, and the electrostatic latent image is developed by the developing unit 230 to become a toner image.
[0108]
This toner image is transferred by the transfer roller 240 to the transfer medium T supplied between the transfer roller 240 and the image carrier 110.
[0109]
At this time, toner remaining on the surface of the image carrier 110 without being completely transferred is scraped off by the cleaning blade 251 of the cleaning means 250.
[0110]
Thereafter, the image carrier 110 is discharged again by the discharging unit 260, and the next image formation is performed.
[0111]
According to the image carrier unit 100 as described above, the following operational effects can be obtained.
[0112]
(A) Since the image carrier 110 has a thin cylindrical shape having flexibility and both end portions 111 are supported by a pair of support members 120 and 120, the image carrier 110 is supported. The central portion 114 not supported by the member 120 is deformable inward.
[0113]
Therefore, since the central portion 114 of the image carrier 110 can be used as a so-called pseudo soft material, even if the charging means that comes into contact with this is a hard roller, a reliable and stable contact state is achieved. Thus, it is possible to reliably form an image on the image carrier 110 or to carry the image.
[0114]
This point will be described in detail with reference to FIGS.
[0115]
FIG. 4 shows a state in which the hard roller 200 is slightly in contact with the image carrier 110. For easy understanding, the reverse crown-shaped roller 200 is used as an example of a hard roller that is not completely cylindrical.
[0116]
The image carrier 110 is supported at both ends 111 by the pair of support members 120 and 120 described above, but is not shown in order to avoid complication of the drawing.
[0117]
As shown in FIG. 4, if the hard roller 200 is lightly contacted, only both ends 201 and 201 are in contact with the image carrier 110, and the central portion 202 is not in contact. Therefore, in such a state, a good charged state, a developed state, a transferred state, etc. cannot be obtained.
[0118]
FIG. 5 shows the image carrier 110 when the hard roller 200 is further pressed toward the image carrier 110 from the state shown in FIG. 4 by an amount δ4 larger than the crown amount δ3 of the hard roller (see FIG. 4). FIG. 6 is a perspective view of a wire frame in which the deformation state is analyzed by a finite element method and the deformation amount of the image carrier is set to 50 times. Since the image carrier 110 is axisymmetrically deformed, only half of the image carrier 110 is shown in order to avoid complication of the drawing.
[0119]
6 is a diagram viewed from the direction of the arrow X in FIG. 7 is a diagram showing the outer peripheral surface of the image carrier 110 in the a section, b section, c section, and d section in FIG. 6 as viewed from the direction of the arrow Z in FIG. The cross section, the broken line b is the b cross section, the alternate long and short dash line c is the c cross section, and the alternate long and two short dashes line d is the outer peripheral surface of the image carrier 110 in the d cross section.
[0120]
As is apparent from FIGS. 5 to 7, when the hard roller 200 having the crown amount δ3 is pressed toward the image carrier 110 by the amount δ4 larger than the crown amount δ3, in the pressing portion (so-called nip portion) N, The image carrier 110 is deformed along the shape of the hard roller 200 faithfully, and reliably comes into contact with the hard roller 200 over the entire nip portion N.
[0121]
This is due to the fact that the image carrier 110 has a flexible thin cylindrical shape. The image carrier 110 having a thin cylindrical shape has a very large flexibility in a plane direction orthogonal to the axial direction, and continuously follows the surface of the reverse crown-shaped hard roller in the axial direction. Change the deformed shape. Even in the axial direction of the thin-walled cylinder, a very small deformation occurs within the elastic range of the metal, but the rigidity in the axial direction is much higher than the rigidity in the cross-sectional direction orthogonal to each other, and does not contribute much to flexibility. Therefore, the deformation of the image carrier is very large due to the flexibility in the cross-sectional direction orthogonal to the axis. This is a deformation mode peculiar to a thin cylinder. By deforming the image carrier using this deformation, it is possible to follow the unevenness of a hard roller and to ensure stable contact.
[0122]
The deformation state of the image carrier will be described in more detail with reference to FIG. 6 and FIG. 7. FIG. 7 shows a portion (both ends of the image carrier (portions supported by the support member 120)) in FIG. As shown by a solid line a, the image carrier 110 is basically held in a perfect circle state.
[0123]
In the portion b (near the end of the roller 200), as shown by a broken line b in FIG. 7, the inner portion is deformed inward by the maximum deformation amount δ4, but near the point b (nip portion) in the circumferential direction. The point b1 is deformed so as to bulge outward.
[0124]
The portion d is the central portion of the roller 200, and the image carrier is deformed by δ4-δ3, but is deformed so as to bulge outward at a point d1 near the point d in the circumferential direction. On the other hand, it is deformed so as to be slightly recessed inward at a point d2 that is slightly apart from the point d1.
[0125]
In the part from b part to d part, it changes continuously from the deformation state in b part to the deformation state in d part. As an example, a deformed state at the portion c is indicated by a one-dot chain line c. The point c1 swells closer to the point b1 than the point d1, and the amount of depression at the point c2 is smaller than the amount of depression at the point d2.
[0126]
As is clear from the above, the image carrier 110 having a thin cylindrical shape has very large flexibility in the plane direction orthogonal to the axial direction, and follows the surface of the hard roller having an inverted crown shape. In this way, the deformation shape is continuously changed in the axial direction.
[0127]
In the above description, in order to make the description easy to understand, the reverse crown-shaped roller 200 has been described as an example of a hard roller that is not completely cylindrical, but a roller with some unevenness. Is equivalent to a series of a plurality of reverse crown-shaped rollers, and a roller with a slight taper is equivalent to a part of the reverse crown-shaped (or crown-shaped) roller. Will be in good and reliable contact with a hard roller that is not perfectly cylindrical (roller with irregularities or taper that is about the manufacturing error).
[0128]
In the above-described image forming apparatus, the charging unit 210 and the transfer unit 240 contact the image carrier 110, and the image carrier 110 is held until the inner peripheral surface 113 of the image carrier 110 abuts the outer peripheral surface 145 of the cylindrical member 140. Since it is composed of a hard roller that bends inward, the image carrier 110 and these hard rollers 210 and 240 can be brought into contact with each other in a reliable and stable manner at the charging position and transfer position. The carrier 110 can be charged or an image can be transferred.
[0129]
When the image bearing member 110 is bent inward until the hard roller comes into contact with the image bearing member 110 and the inner peripheral surface 113 of the hard roller contacts the outer peripheral surface 145 of the cylindrical member 140, the image bearing member 110 becomes a hard roller. The state is sandwiched between the cylindrical member 140. In such a state, the image carrier 110 contacts the hard roller in a favorable and stable state with an appropriate pressure contact force.
[0130]
(B) The image carrier unit 100 is manufactured by supporting the both ends 111 of the image carrier 110 with a pair of support members 120 such that the cylindrical member 140 is disposed inside the image carrier 110. Since it is not necessary to fill the elastic material layer unlike the photosensitive drum 1 described in Japanese Patent Publication No. 4-69383 (see FIGS. 13 to 15), it can be easily manufactured. .
[0131]
(C) Since the image carrier unit 100 has any one of the constitutions (1) and (2), even if the temperature changes in the use environment or the transportation environment, Thermal strain due to thermal expansion difference does not occur or even if it occurs.
[0132]
Accordingly, the thin cylindrical image carrier 110 is prevented from being distorted and deformed, and the occurrence of shake is also prevented, so that the distance from each process member such as the developing roller 231 does not vary depending on the temperature environment, and is reliable and stable. The contact state or gap management becomes possible, and a good image free from uneven charging, development failure, transfer failure and the like can be obtained.
[0133]
Further, the image carrier 110 is not buckled, broken or permanently deformed due to thermal strain, and the fixed part of the component is not damaged by thermal stress. Will improve.
[0134]
(D) The support member 120 fixes the spacer 130 having an elastic portion that elastically and uniformly supports the image carrier 110 from the inside thereof, and fixes the image carrier 110 and the cylindrical member 140 supported by the spacer 130. Therefore, the image carrier 110 supported by the spacer 130 is easier to manufacture than the drum-like image carrier member (FIG. 16) disclosed in JP-A-58-86550. The cylindrical member 140 is fixed by the fixing member 121 in a state in which the interval S is supported at equal intervals in the circumferential direction, that is, in a substantially circular state. Therefore, a stable rotation state in which the displacement or shake of the image carrier 110 in the axial direction is extremely small can be obtained.
[0135]
(E) On the inner side of the image carrier 110, the rigid cylindrical member 140 is spaced between the outer peripheral surface 145 and the inner peripheral surface 113 of the image carrier 110 by a distance smaller than the allowable deformation amount δ 2 of the image carrier 110. Since the S is arranged at a distance, even if the operator mistakenly presses the central portion of the image carrier 110 accidentally when the image carrier unit 100 is replaced, for example, the image carrier 110 is not damaged. Since it will be supported by the cylindrical member 140, it will not be damaged. Therefore, this image carrier unit 100 is superior in handleability compared to the drum-like image carrier member (see FIG. 16) disclosed in Japanese Patent Laid-Open No. 58-86550 described above.
[0136]
(F) Since the image carrier 110 is not damaged even if it is strongly pressed, a contact member such as a hard roller or a cleaning blade can be strongly contacted.
[0137]
(G) The spacer 130 elastically supports the image carrier 110 by being compressed by the cylindrical member 140 and the image carrier 110 when the cylindrical member 140 is disposed inside the image carrier 110. Since the configuration is such that the spacer 130 is attached to the cylindrical member 140 (or the image carrier 110) in advance, the image carrier unit can be manufactured more easily.
[0138]
(H) Since the spacer 130 elastically supports the image carrier 110 from the inside in the circumferential direction at a plurality of positions and at equal intervals, the elastic force of the spacer 130 is applied to the image carrier 110. The image carrier 110 is well dispersed over the entire circumferential direction, and the image carrier 110 is more uniformly supported by the cylindrical member 140.
[0139]
(I) Since the cylindrical member 140 and the support member 120 have conductivity, electrical conduction to the image carrier 110 necessary for image formation can be obtained through the cylindrical member 140 and the support member 120. Therefore, it is not necessary to provide a separate conduction means.
[0140]
(J) Since the support member 120 is located slightly on the center side with respect to the edge portion 111a of the image carrier 110, the image carrier 110 is supported more uniformly with respect to the cylindrical member 140. The shake accuracy can be further improved.
[0141]
More specifically, when the image carrier 110 is configured by electroforming, burrs and burrs due to cutting are generated at the edge 111a. If the support member 120 supports the edge 111a of the image carrier 110 without removing the burrs or the like, the spacing S between the image carrier 110 and the cylindrical member 140 is not effective due to the influence of burrs or the like. There is a risk of becoming uniform. On the other hand, removing the burrs and the like not only adds new distortion to the image carrier 110 having a thin cylindrical shape, but also undesirably increases the deformation, and also increases the number of steps.
[0142]
On the other hand, according to the image carrier unit of this embodiment, since the support member 120 is located slightly on the center side with respect to the end edge portion 111a of the image carrier 110, the above-mentioned burrs and the like are formed on the image carrier 110. Even if there is, the image carrier 110 can be supported uniformly with respect to the cylindrical member 140 without being affected by this, and the shake accuracy can be further improved.
[0143]
(K) In the image forming apparatus described above, the charging roller 210 and the transfer roller 240, which are hard rollers, rotate at the same peripheral speed as the peripheral speed of the image carrier 110. There is no relative speed difference between the image carrier and each roller at the contact portion with the carrier 110, that is, at the charging position and the transfer position. Therefore, no friction occurs at the contact portion, and no vibration behavior is caused by this, so that stable contact rotation can be obtained, and stable charging operation and transfer operation can be obtained.
[0144]
Further, the image carrier 110 is not easily damaged due to the vibration behavior, and the reliability is improved.
[0145]
When the rotational speed of the developing roller 231 is different from the peripheral speed of the image carrier 110, the image carrier 110 receives a frictional force from the developing roller 231 at the contact portion with the developing roller 231. However, the abutment between the two is an abutment such that a space S1 is formed between the inner peripheral surface 113 of the image carrier 110 and the outer peripheral surface 145 of the cylindrical member 140. And the developing roller 231 have a small contact force. For this reason, the frictional force between the two is also small, and hence the vibration behavior due to the fluctuation is also small, and the developing roller 231 and the image carrier 110 are in a relatively stable state and rotate.
[0146]
<Second Embodiment>
8A and 8B are schematic views showing the main part of the second embodiment of the image carrier unit according to the present invention. FIG. 8A is a side view of the upper half showing a cylindrical member and a spacer, and FIG. 8B is a partial perspective view. It is.
[0147]
The second embodiment is different from the first embodiment described above in the structure of the spacer, and the other points are not changed.
[0148]
The spacer 133 in the second embodiment includes a thin ring-shaped base portion 133a fixed to the outer peripheral surface 145 of the cylindrical member 140, and an elastic protrusion 133b as an elastic portion protruding from the outer peripheral surface of the base portion 133a. The elastic portion of the spacer 130 in the first embodiment is 12 point-like projections 132, whereas the elastic portion has a certain length in the axial direction. It differs from the first embodiment only in that it is a single elastic protrusion 133b.
[0149]
When the elastic portion is such a protrusion 133b, the image carrier 110 is supported in a more stable state.
[0150]
Further, since the number of the elastic members increases, the restoring force of the elastic portion acts on the image carrier 110 more uniformly. As a result, the distance S between the image carrier 110 and the cylindrical member 140 becomes even more uniform. It becomes.
[0151]
<Third Embodiment>
9A and 9B are schematic views showing the main part of the third embodiment of the image carrier unit according to the present invention. FIG. 9A is a side view of the upper half showing a cylindrical member and a spacer, and FIG. 9B is a partial perspective view. (C) is the elements on larger scale of Drawing (a), (d) is an operation explanatory view.
[0152]
The third embodiment differs from the first embodiment described above in the structure of the spacer, and the other points are not changed.
[0153]
The spacer 134 according to the third embodiment is configured as an elastic portion by embossing a metal tape fixed to the outer peripheral surface 145 of the cylindrical member 140. Note that the number of elastic protrusions 134b formed by embossing is 24.
[0154]
When the image carrier 110 is mounted as shown in FIG. 4D, the spacer 134 is in a state where the elastic protrusion 134b is pressed and supports the image carrier 110 from the inside by its own elasticity. Will be.
[0155]
Such a spacer 134 can be easily formed by embossing a metal tape.
[0156]
Further, since the image carrier 110 and the cylindrical member 140 are electrically connected by the spacer 134, in this embodiment, the adhesive 121 does not necessarily need to have conductivity.
[0157]
<Fourth embodiment>
10A and 10B are schematic views showing the main part of the fourth embodiment of the image carrier unit according to the present invention. FIG. 10A is a partial perspective view of the upper half showing a cylindrical member and a spacer, and FIG. (C) is an operation explanatory view.
[0158]
The fourth embodiment is different from the first embodiment described above in the structure of the spacer, and the other points are not changed.
[0159]
The spacer 135 in the fourth embodiment has a truncated conical cylindrical shape as a whole, and a thin ring-shaped base portion 135a fixed to the outer peripheral surface 145 of the cylindrical member 140, and the base portion 135a integrally. And 24 flexible pieces 135b as elastic portions formed radially. The cylindrical member 140 is preferably provided with an annular recess 140a in order to secure the base portion 135a of the spacer 135.
[0160]
When the image bearing member 110 is placed on the cylindrical member 140 as shown by the arrow X1 in FIG. 7B (when the cylindrical member 140 is inserted into the image bearing member 110), such a spacer 135 causes the flexible piece 135b to move to the arrow Y. The image carrier 110 is supported from the inside as shown in FIG.
[0161]
Such a spacer 135 can be easily formed by forming a thin metal or a synthetic resin into a truncated conical cylinder shape and forming a slit 135c therein.
[0162]
In addition, when the spacer 135 is made of metal, the image carrier 110 and the cylindrical member 140 are electrically connected to each other, so that the adhesive 121 does not necessarily need to have conductivity.
[0163]
<Fifth embodiment>
FIG. 11 is a schematic diagram showing the main part of the fifth embodiment of the image carrier unit according to the present invention, and shows a cross section of the upper half. The lower half is symmetric with the upper half.
[0164]
The fifth embodiment is different from the first embodiment described above in the fixing structure of both end portions 111 of the image carrier 110, and the other points are not changed.
[0165]
In the fifth embodiment, fixing members 151 and 152 for fixing both end portions 111 of the image carrier 110 on the cylindrical member 140 are provided in an annular shape between the image carrier 110 and the cylindrical member 140, respectively. And connecting portions 151a and 152a (for example, joint portions by bonding or the like) with the image carrier 110 and connecting portions 151b and 152b with the cylindrical member 140.
[0166]
The axial length between the connecting portions 151a and 152a with the fixing members 151 and 152 in the image carrier 110 and the linear expansion coefficient are L1 and α1, and the connecting portions 151b and 152b with the fixing members 151 and 152 in the cylindrical member 140. The length and linear expansion coefficient between them are L3 and α3, and the axial length between the connecting parts of the fixing members 152 and 151 to the image carrier 110 and the cylindrical member 140, that is, between 152a and 152b and between 151a and 151b is L2. , L4, the linear expansion coefficient is α2, α4,
When the Young's modulus of the image carrier 110 is E1, and the allowable stress is σa,

Li: length of the i-th member
αi: i-th linear expansion coefficient
ΔT: temperature difference
n: Total number of connected members (in this case n = 4)
i: Order of connected members (in this case, i is 1 to n)
It is comprised so that it may become. Note that specific examples are described in the column of Examples described later.
[0167]
Here, first, the definition relating to the above formula will be described with reference to FIG.
[0168]
FIGS. 12A and 12B are diagrams for explaining thermal expansion that occurs in a structure in which members having different lengths and thermal expansion coefficients are connected.
[0169]
In FIG. 12, members 1, 2, 3, and 4 are respectively
Length is L1, L2, L3, L4
The thermal expansion coefficient is α1, α2, α3, α4.
[0170]
In addition, the length here is the length between the connection parts (joining part) of members.
[0171]
Here, when considering thermal expansion, the length is defined as follows.
[0172]
First, let a connection point with a connected structure be a starting point and an end point. In FIG. 12A, the connection point a on the member 1 side at the leftmost connection point is the starting point, and the connection point a on the member 4 side is the end point.
[0173]
Next, the connection point farthest from the starting point a is determined. In FIG. 12A, the point C located at the rightmost end is the connection point farthest from the starting point A.
[0174]
And when considering the clockwise closed loop of starting point a → point u → end point i,
The direction from the starting point A to the point U is positive (right direction in the figure), and the direction from the point C to the end point A is negative (left direction in the figure).
[0175]
That is, when following the connecting point sequentially from the starting point a, the positive / negative is determined as described above depending on the direction in which the next connecting point is located with respect to a certain connecting point (the direction from one connecting point to the next connecting point).
[0176]
Therefore, the lengths of the members 1, 2, 3 and 4 are positive for L1 and L2, and negative for L3 and L4.
[0177]
Next, the significance of the above equation will be described with reference to FIG.
[0178]
The environmental temperature surrounding the structure has changed since the point A and point B were connected (ie, when the structure was created), and the temperature difference ΔT (ΔT was + or decreased when the temperature increased) Suppose that-) occurs. Here, if the points A and B are not connected, the lengths L1 ', L2', L3 ', L4' of the members 1, 2, 3, 4 expanded and contracted by the temperature change are
L1 ′ = L1 × (1 + α1 × ΔT)
L2 '= L2 × (1 + α2 × ΔT)
L3 ′ = L3 × (1 + α3 × ΔT)
L4 '= L4 × (1 + α4 × ΔT)
It becomes.
[0179]
Here, if the sum of these is not 0, the points a and i will deviate from each other as shown in FIG.

It becomes.
[0180]
If the value of Lt is positive, the point a shifts to the positive side (right side) from the point a, and if it is negative, the point a shifts to the negative side (left side).
[0181]
However, since the points A and B are actually connected, the above-described deviation does not occur, and thermal strain or thermal stress is generated in the structure accordingly.
[0182]
The thermal strain or thermal stress acts on the weakest member in the structure, and when a thermal stress exceeding the allowable stress of the member is generated, the member is broken or permanently deformed.
[0183]
In this embodiment, the flexible thin-walled cylindrical image carrier 110 is the weakest member. Therefore, when there is a temperature change, the thermal stress acts on the image carrier 110.
[0184]
However, in this embodiment, as described above, the axial length and the linear expansion coefficient between the connecting portions 151a and 152a of the image carrier 110 with the fixing members 151 and 152 are L1 and α1, and the cylindrical member 140 is fixed. The length between the connecting portions 151b and 152b with the members 151 and 152 and the linear expansion coefficient are L3 and α3, between the connecting portions of the fixing members 152 and 151 with the image carrier 110 and the cylindrical member 140, that is, between 152a and 152b. The axial length between 151a and 151b is L2 and L4, the linear expansion coefficient is α2 and α4,
When the Young's modulus of the image carrier 110 is E1, and the allowable stress is σa,

Therefore, even if thermal distortion occurs in the axial direction inside the image carrier unit, the thermal stress is less than the allowable stress. Become.
[0185]
Accordingly, large distortion and permanent deformation of the thin-walled cylindrical image carrier 110 are prevented, and occurrence of shake is prevented, so that the distance from each process member such as the developing roller does not vary greatly depending on the temperature environment, and is reliable. A stable contact state or gap management becomes possible, and a good image free from uneven charging, development failure, transfer failure and the like can be obtained.
[0186]
Further, the image carrier 110 is not buckled or broken due to thermal strain, and the fixing part of the component is not damaged due to thermal stress, so that the mechanical reliability is improved.
[0187]
As σa in the above equation, a proportional limit or yield strength (0.2% yield strength, etc.) is adopted when permanent deformation is a problem, and tensile strength is adopted when destruction is a problem.
[0188]
Also, the correspondence between the members in this embodiment shown in FIG. 11 and the members shown in FIG.
The image carrier 110 is attached to the member 1 in FIG.
The fixing member 152 is added to the member 2 in FIG.
The cylindrical member 140 is the same as the member 3 in FIG.
The fixing member 151 is added to the member 4 in FIG.
The connecting portion 151a is provided at points a and i in FIG.
The connecting portion 152a is located at the point C in FIG.
Each corresponds.
[0189]
【Example】
Specific examples will be described below.
[0190]
Examples 1 to 5 are examples of the configuration (2) described above, Examples 6 to 7 are examples of the configuration (1) described above, and Example 8 is the fifth embodiment described above. This is an example.
[0191]
{Example 1}
<Image carrier 110>
The base material of the image carrier 110 was a nickel electroformed tube having a thickness of 50 μm, an inner diameter of 85.36 mm, and a length of 400 mm.
[0192]
The photosensitive layer was formed by forming an undercoat layer on the substrate and dipping an OPC (organic photosensitive layer) having a thickness of 20 μm.
[0193]
<Cylindrical member 140>
A stainless steel hollow cylinder having a diameter of 84.91 mm, a length of 440 mm, and a thickness of 2 mm was used as the pipe-shaped cylindrical member.
[0194]
The disk-shaped side plates 142 and 143 were made of stainless steel cutting parts.
[0195]
The entire cylindrical member 140 and side plates 142 and 143 can be formed by cutting.
[0196]
<Support member 120>
The spacer 130 uses a metal tape as its base 131, and elastic protrusions 132 are formed on the outer peripheral surface of the metal tape by elastic printing.
[0197]
As the fixing member 121, a conductive adhesive was used.
[0198]
The distance S between the outer peripheral surface 145 of the cylindrical member 140 and the inner peripheral surface 113 of the image carrier 110 was 0.225 mm.
[0199]
<Hard roller>
Specifically, the hard roller can be configured as follows.
[0200]
That is, it is configured by providing a resistance layer on the surface of a hard roller base.
[0201]
As the roller-shaped substrate, a metal such as aluminum, an aluminum alloy, iron, or copper is processed with good runout accuracy and surface accuracy by cutting, polishing, or the like. The surface is mirror finished by buffing, polishing, super-finishing, diamond grinding, centerless polishing, etc.
[0202]
Or synthetic resins such as polyester, polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyamide (PA), polyphenylene sulfide (PPS), polyethylene (PE), polypropylene (PP), polystyrene (PS), Nylon (NY) or the like is formed into a roller shape, and a conductive layer is formed by vapor deposition, plating, or the like of a metal such as aluminum, nickel, or copper, or a conductive material such as carbon is put in the resin. What is necessary is just to provide electroconductivity as a conductive resin.
[0203]
The resistance layer has a volume resistance of 10⁸-10¹⁴A resistive resin of Ωcm is formed to a thickness of about 2 μm to 1 mm to form a surface layer with medium to high resistance. As the resistive resin, it is possible to employ a resin in which conductive particles such as carbon, aluminum and nickel are dispersed in a thin film resin such as nylon, polyurethane and polyethylene. Further, a conductive resin such as polyvinyl aniline or an ion conductive resin may be used.
[0204]
The hard roller as described above can be mirror-finished because the roller-like substrate is hard, and the surface of the thin film resin formed thereon is also very smooth.
[0205]
In addition, since the surface is a thin resin, there is little variation in hardness and variation in conductivity.
[0206]
<Each member used to analyze the deformation state of the image carrier by the finite element method>
Specifications of the members used for analyzing the deformation state of the image carrier shown in FIGS. 5 and 7 by the finite element method are as follows.
[0207]

{Example 2}
Both the base material of the image carrier 110 and the cylindrical member 140 were made of stainless steel. Others are the same as in the first embodiment.
[0208]
{Example 3}
Both the base material of the image carrier 110 and the cylindrical member 140 were made of polyethylene terephthalate (PET). The base material of the image carrier 110 and the cylindrical member 140 are formed by depositing a metal such as aluminum, nickel, copper or the like, or forming a conductive layer by plating or the like, or a conductive material such as carbon in the resin. In order to impart conductivity.
[0209]
Others are the same as in the first embodiment.
[0210]
{Example 4}
The base material of the image carrier 110 and the cylindrical member 140 were made of aluminum, duralumin, or magnalium.
[0211]
Others are the same as in the first embodiment.
[0212]
{Example 5}
The base material of the image carrier 110 and the cylindrical member 140 were made of brass, copper, or phosphor bronze.
[0213]
Others are the same as in the first embodiment.
[0214]
{Example 6}
The cylindrical member 140 was made of PET (polyethylene terephthalate) having a glass fiber content of 55% (weight ratio). The cylindrical member 140 was provided with conductivity by depositing a metal such as aluminum, nickel, copper, or the like, or forming a conductive layer by plating or the like, or putting a conductive material such as carbon in the resin.
[0215]
Others are the same as the first embodiment.
[0216]
{Example 7}
The base material of the image carrier 110 is an aluminum tube (linear expansion coefficient is 23.1 × 10^-6The cylindrical member 140 is made of PET (polyethylene terephthalate) containing inorganic (mineral) such as glass fiber or mica. By setting the glass content to 45% (weight ratio), the linear expansion coefficient is 23.0 × 10^-6/ ° C. The cylindrical member 140 was provided with conductivity by depositing a metal such as aluminum, nickel, copper or the like, or forming a conductive layer by plating or the like, or putting a conductive material such as carbon in the resin.
[0217]
Others are the same as the first embodiment.
[0218]
{Example 8}
The base material of the image carrier 110 is composed of a nickel electroformed tube, and its length is L1 = 300 mm. The coefficient of thermal expansion is α1 = 13.4 × 10^-6/ ° C, Young's modulus is E1 = 20000 kg / mm²It is. As the allowable stress, 0.2% proof stress was adopted. That is,
σa = 50 kg / mm²It is.
[0219]
Nylon 610 is used as the left and right fixing members 151 and 152, and the length is
L2 = L4 = 5 mm. The coefficient of thermal expansion is α2 = α4 = 90 × 10^-6/ ° C.
[0220]
The cylindrical member 140 was made of carbon steel, and its length was L3 = 290 mm. The coefficient of thermal expansion is α3 = 10.7 × 10^-6/ ° C.
[0221]
Normally, the image carrier unit 100 is assembled in an environment of room temperature (approximately 20 to 25 ° C.), and the ambient temperature actually used (or in transit) is usually 0 to 45 ° C. Therefore, ΔT = 20 ° C. was adopted as the temperature difference.
[0222]
When the above-described deviation Lt is calculated under the above conditions,
Lt = 0.00034 mm.
[0223]
Therefore, the thermal strain εt of the image carrier 110 is
εt = Lt / L1 = 1.13 × 10^-6
Thermal stress σt is
σt = E1 × εt = 0.02267 kg / mm²
The allowable stress σa = 50 kg / mm²The value is extremely small compared to.
[0224]
Therefore, the state at the time of assembly is maintained without increasing distortion, shake, and the like of the image carrier 110 due to thermal expansion, and the image carrier unit 100 with extremely high accuracy can be obtained.
[0225]
Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments or examples, and can be appropriately modified within the scope of the gist of the present invention.
[0226]
For example,
(1) In the above embodiment, the image carrier unit is described as the photosensitive unit. However, the image carrier unit of the present invention is not limited to this, and can also be configured as an intermediate transfer medium unit. In this case, the image carrier is constituted by a thin cylindrical intermediate transfer member.
[0227]
(2) Although the support member 120 is configured to include the fixing member 121 as the fixing member and the spacer 130, the supporting member 120 may be configured with only the fixing member.
[0228]
【The invention's effect】
The image carrier unit according to any one of claims 1 to 3, wherein a reliable and stable contact state with a contact member such as a hard roller without causing damage or the like even if the temperature changes in a use environment or a transport environment. It is possible to obtain the effect that the manufacturing is simple.
[0229]
  And claims2According to the image carrier unit described above, an effect that the handleability is excellent is obtained.3According to the described image carrier unit, there is an effect that it is not necessary to separately provide a conduction means.
[0230]
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a main part of an image forming apparatus using a first embodiment of an image carrier unit according to the present invention.
2 is a cross-sectional view taken along the line II-II in FIG. 1, mainly showing an image carrier unit.
FIG. 3 is a schematic diagram mainly showing an example of a spacer, in which FIG. (A1) is a front sectional view showing a state before the image carrier 110 is mounted, and FIG. (A2) is a partial left side view of FIG. (A1). Fig. (A3) is a diagram for explaining the operation, Fig. (B1) is a front sectional view showing the state after the image carrier 110 is mounted, Fig. (B2) is a partial left side view of Fig. (B1), and Fig. (C) ) Is a left side view showing a state after the image carrier 110 is mounted.
FIG. 4 is an explanatory diagram of operation.
FIG. 5 is an operation explanatory diagram.
FIG. 6 is an explanatory diagram of operation.
FIG. 7 is an explanatory diagram of operation.
FIGS. 8A and 8B are schematic views showing a main part of a second embodiment of an image carrier unit according to the present invention, in which FIG. 8A is a side view of an upper half showing a cylindrical member and a spacer, and FIG. Figure.
FIGS. 9A and 9B are schematic views showing a main part of a third embodiment of an image carrier unit according to the present invention, in which FIG. 9A is a side view of an upper half showing a cylindrical member and a spacer, and FIG. FIG. 4C is a partially enlarged view of FIG. 1A, and FIG.
FIGS. 10A and 10B are schematic views showing a main part of a fourth embodiment of an image carrier unit according to the present invention, in which FIG. 10A is a partial perspective view of an upper half showing a cylindrical member and a spacer, and FIG. FIG. 4C is a diagram for explaining the operation.
FIG. 11 is a schematic diagram showing the main part of a fifth embodiment of an image carrier unit according to the present invention, and showing a cross section of the upper half.
FIGS. 12A and 12B are views for explaining thermal expansion that occurs in a structure in which members having different lengths and thermal expansion coefficients are connected to each other.
FIG. 13 is an explanatory diagram of the prior art.
FIG. 14 is an explanatory diagram of a conventional technique.
FIG. 15 is an explanatory diagram of the prior art.
FIG. 16 is an explanatory diagram of the prior art.
[Explanation of symbols]
100 photoconductor unit
110 Image carrier
111 Both ends
111a edge
113 Inner surface
120 Support member
121 Fixing member (fixing member)
130 Spacer
140 Cylindrical member
145 outer peripheral surface
151,152 Fixing member

Claims (3)

A thin cylindrical image carrier having flexibility, a rigid cylindrical member having an outer diameter smaller than the inner diameter of the image carrier, and disposed on the inner side of the image carrier; and on the cylindrical member A fixing member that fixes both ends of the image carrier, and the axial length and linear expansion coefficient between the connecting portions of the image carrier and the fixing member are L1 and α1, and the fixing member of the cylindrical member. The length between the connecting portions and the linear expansion coefficient are L3 and α3, the axial length between the connecting portions of the fixing member to the image carrier and the cylindrical member is L2 and L4, and the linear expansion coefficients are α2 and α4. Yes,
Regarding the length in the axial direction, in the structure having the connected image carrier, the cylindrical member, and the fixing member, a certain connecting point of the connecting portions is set as a starting point and an ending point, and from this starting point, from the starting point. When considering a closed loop from the most distant connection point toward the end point toward the other end point, the direction from the start point to the farthest connection point is positive, and the most distant connection point The direction from to the end point is negative, and
When the Young's modulus of the image carrier is E1, and the allowable stress is σa,
n
σa> E1 × ΣLi × (1 + αi · ΔT) / L1
i = 1
Li: length of i-th member αi: i-th linear expansion coefficient ΔT: ΔT = 20 ° C.
An image carrier unit characterized in that   The image bearing member is supported by the fixing member between an inner circumferential surface of the image bearing member and an outer circumferential surface of the cylindrical member at a distance smaller than an allowable deformation amount of the image bearing member. 2. The image carrier unit according to 1.   3. The image carrier unit according to claim 1, wherein the cylindrical member and the fixing member have conductivity.

Images