JP2004086167A - Process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an abnormal noise made by an image carrier drum in an image forming apparatus in which the surface of the rotating image carrier is electrified by an electrifying device, the electrified surface is exposed to form an electrostatic latent image, then, the electrostatic latent image is developed as a toner image with low melting point toner, thereafter, the toner image is transferred to a recording medium, and the image carrier drum after the toner image is transferred is cleaned by a cleaning blade. <P>SOLUTION: A damping member 4 made of materials whose loss tangent tanδ is ≥ 0.5 is arranged inside the image carrier drum 2. The toner having an outflow start temperature of ≤ 102°C measured by a flow tester method is used. <P>COPYRIGHT: (C)2004,JPO

Description

【００３８】
表１中の「発生」は、画像形成装置の周辺の観測者が明らかに異音が発生していることを感知したことを示し、「未発生」は異音を感知しなかったことを示している。表１から判るように、低融点トナーを用いても、損失正接ｔａｎδが０．５の材料より成る制振部材４を像担持ドラム２内に設けると、異音の発生は認められなかった。同じトナーを使用し、損失正接ｔａｎδが０．５未満の制振部材４を用いた場合には、異音の発生が確認された。なお。像担持ドラム２内に制振部材を設けずに同じ試験を行なったところ、いずれのトナーを用いたときも、顕著な異音発生が認められた。
【００３９】
損失正接ｔａｎδが０．５よりも大きい物質、特に０．６以上、或いは０．８以上の物質によって制振部材４を構成すれば、像担持ドラム２に対する制振効果をより一層高めることができる。
【００４０】
また、画像形成装置のプロセスカートリッジにおいて使用されるトナーとして、高級脂肪酸金属塩、例えばステアリン酸亜鉛などを含むトナーを用いると、その一部が像担持ドラム２の表面に付着してクリーニングブレード３０との摩擦係数が低下するので、クリーニングブレード３０のエッジ部の滑りが良好となり、クリーニングブレード３０の振動を抑制でき、異音発生防止効果をより一層高めることができる。
【００４１】
図２に示した制振部材４は、中実な円柱状に形成され、図３に示した制振部材４は円筒状に形成されているが、図２に示した如き中実の制振部材４を用いると、その重量が大きくなり、当該制振部材と像担持ドラム２の全体の重量が増大する結果、耳障りな高周波の騒音を効果的に低減できる。逆に、図３に示した如き円筒状の制振部材４を用いると、制振部材の材料を減量でき、そのコストを低減できる。その際、必要な制振効果が得られるように、制振部材４の損失正接ｔａｎδや、その重量、その形態、特にその肉厚を設定すべきは当然である。円筒状に成形されている制振部材４を用いることもできるが、シート状の部材を丸めて円筒状の制振部材を構成することもできる。後者の方法によれば、安価なシート状部材により円筒状の制振部材４を得ることができるので、そのコストをより一層低減することが可能となる。
【００４２】
制振部材４を像担持ドラム２に装着する方法としては、像担持ドラム２に挿入する前の制振部材４の外径をｄ、像担持ドラム２の内径をＤＩとしたとき、ｄをＤＩよりも若干大きく設定した制振部材を像担持ドラム２に挿入して制振部材４を像担持ドラム２の内部に圧入する方法と、ｄをＤＩよりも若干小さく設定し、かかる制振部材４を像担持ドラム２の内部に挿入して該制振部材４を像担持ドラム２の内壁面に接着材によって接着する方法を採用することができる。制振部材４を、像担持ドラム２に圧入し、かつ接着剤によって像担持ドラム２の内面に固定することもできる。いずれの方法によっても充分な制振効果を得ることが可能であるが、制振部材４を像担持ドラム２に圧入する場合、ｄがＤＩよりも小さいと像担持ドラム２の内壁面と制振部材４との密着不良が発生し、制振効果が低下し、逆にｄがＤＩよりも大幅に大きい場合には、像担持ドラム２の内部に制振部材４を挿入する際、過大な力が必要となり、組付け性が低下するだけでなく、その組付け時に像担持ドラムを変形させてしまうので、ＤＩ≦ｄ≦ＤＩ＋１ｍｍとすることが好ましい。
【００４３】
制振部材を像担持ドラムに圧入して固定すると、その固定のために接着剤が不要であるため、固定に要するコストを低減でき、しかも制振部材４を像担持ドラム２から容易に取り外すことができ、リサイクル性を高めることができる。これに対し、制振部材４を像担持ドラム２に接着して固定すると、制振部材４を像担持ドラム２により強固に固定することができる。
【００４４】
図１に示した画像形成装置は、像担持ドラム２の表面に圧接してトナー像転写後の像担持ドラム表面を清掃するクリーニングブレード３０を有しているが、像担持ドラムを停止させる際に、その像担持ドラムをわずかな角度だけ逆転させると、クリーニングブレード３０と像担持ドラム２の表面との間に挟まった紙粉などの異物を除去することができる。像担持ドラム２にトナー像を形成しているときの像担持ドラム２の回転方向、すなわち正転方向とは逆方向に像担持ドラム２を回転させる逆転モードを設定するのであるが、このようにすると、クリーニングブレード３０の振動に基因する異音が像担持ドラムの正転時だけでなく、逆転時にも発生するおそれがある。従来の画像形成装置の場合、特に像担持ドラムが回転を停止する間際で異音が発生しやすく、像担持ドラム２が正転、停止、逆転、停止という動作を行うとき、２回連続して大きな異音が発生していた。ところが、前述の構成の制振部材４を像担持ドラム２の内部に設けることにより、像担持ドラム２が逆転動作を行うときも、大きな異音が発生することを阻止できる。
【００４５】
次に、制振部材４が装着される像担持ドラム２について説明する。電子写真方式において使用される像担持ドラムの感光層としてはセレンやアモルファスシリコン等の無機系半導体材料を使用したもの、有機系半導体材料を使用したもの、或いはその両者を組み合わせたもの等、種々知られている。近年では、コストの低さ、感光体設計の自由度の高さ、無公害性等から有機系感光層が広く利用されるようになってきているが、前述の制振部材はいずれの方式の感光層を有する像担持ドラムにも装着可能である。
【００４６】
有機系の電子写真感光層には、ポリビニルカルバゾール（ＰＶＫ）に代表される光導電性樹脂、ＰＶＫ−ＴＮＦ（２，４，７−トリニトロフルオレノン）に代表される電荷移動錯体型、フタロシアニン−バインダーに代表される顔料分散型、電荷発生物質と電荷輸送物質とを組み合わせて用いる機能分離型の感光層などが知られており、特に機能分離型の感光層が注目されている。この機能分離型の感光層における静電潜像形成のメカニズムは、感光層を帯電した後光照射すると、光は透明な電荷輸送層を通過し、電荷発生層中の電荷発生物質により吸収され、光を吸収した電荷発生物質は電荷担体を発生し、この電荷担体は電荷輸送層に注入され、帯電によって生じている電界にしたがって電荷輸送層中を移動し、感光層表面の電荷を中和することにより静電潜像を形成するものである。機能分離型感光層においては、主に紫外部に吸収を持つ電荷輸送物質と、主に可視部に吸収を持つ電荷発生物質とを組み合わせて用いることが知られており、かつ有用である。
【００４７】
一方、有機系の感光層の弱点として、機械的、化学的な耐久性に乏しいという点が知られている。即ち、電荷輸送物質は多くが低分子化合物として開発されているが、低分子化合物は単独で製膜性がないため、通常、不活性高分子に分散・混合して用いられる。しかるに、低分子電荷輸送物質と不活性高分子からなる電荷輸送層は一般に柔らかく、機械的耐久性に乏しく、電子写真プロセスにおいては繰り返し使用による種々接触部材（現像・転写紙・クリーニングブラシ・クリーニングブレード等）から受ける機械的な負荷により、膜削れを生じやすい。そこで、感光層の保護及び耐久性の向上の目的で、保護層を、表層として感光層の上に設けることもできる。この保護層に使用される材料としては、ＡＢＳ樹脂、ＡＣＳ樹脂、オレフィン−ビニルモノマー共重合体、塩素化ポリエーテル樹脂、アリル樹脂、フェノール樹脂、ポリアセタール樹脂、ポリアミド樹脂、ポリアミドイミド樹脂、ポリアクリレート樹脂、ポリアリルスルホン樹脂、ポリブチレン樹脂、ポリブチレンテレフタレート樹脂、ポリカーボネート樹脂、ポリエーテルスルホン樹脂、ポリエチン樹脂、ポリエチレンテレフタレート樹脂、ポリイミド樹脂、アクリル樹脂、ポリメチルペンテン樹脂、ポリプロピレン樹脂、ポリフェニレンオキシド樹脂、ポリスルホン樹脂、ＡＳ樹脂、ＡＢ樹脂、ＢＳ樹脂、ポリウレタン樹脂、ポリ塩化ビニル樹脂、ポリ塩化ビニリデン樹脂、エポキシ樹脂等の樹脂が挙げられる。保護層には、耐摩耗性を更に向上する目的でフィラーが添加されてもよい。このフィラーとしては、ポリテトラフルオロエチレンのような弗素樹脂、シリコーン樹脂、これら樹脂に酸化チタン、酸化スズ、チタン酸カリウム、シリカ、アルミナ等の無機材料を分散したもの等が挙げられる。保護層に添加されるフィラーの量は、重量基準で通常は、１０〜４０％、好ましくは、２０〜３０％である。フィラーの量が、１０％未満では、摩耗が大きく耐久性に劣り、４０％を越えると、露光時における明部電位の上昇が著しくなって、感度低下が無視できなくなるので望ましくない。さらに保護層には、フィラーの分散性を向上させるために分散助剤を添加することができる。添加される分散助剤は塗料等に使用されるものが適宜利用できその量は重量基準で通常は含有するフィラーの量に対して０．５〜４％、好ましくは、１〜２％である。また、保護層には、電荷輸送物質を添加することも有効であり、さらに酸化防止剤も必要に応じて添加することができる。保護層の形成法としては、スプレー法等通常の塗布法が採用される。保護層の厚さは、０．５〜１０μｍ、好ましくは４〜６μｍ程度が適当である。
【００４８】
感光層と保護層との間に中間層を設けることも可能である。中間層には、一般にバインダー樹脂を主成分として用いる。これら樹脂としては、ポリアミド、アルコール可溶性ナイロン、水溶性ポリビニルブチラール、ポリビニルブチラール、ポリビニルアルコールなどが挙げられる。中間層の形成法としては、前述のごとく通常の塗布法が採用される。なお、中間層の厚さは０．０５〜２μｍ程度が適当である。
【００４９】
上述のように像担持ドラムが表面に保護層を有していると、感光層の膜削れを抑制することができるので、より強い押圧力でクリーニングブレードを像担持ドラム表面に圧接させることができる。そのため、低融点トナー使用時に像担持ドラム上に付着するトナー中のワックス等もクリーニングすることでき、像担持ドラム表面の摩擦係数のバラツキが小さくなる。つまり、クリーニング性の向上と異音防止とを実現することができる。
【００５０】
さらに、保護層がフィラーを含有していると、感光層の膜削れをより確実に抑制することができ、保護層を設けた効果をより確実にすることができる。
【００５１】
また、保護層が電荷輸送物質を含有していると、感光層の膜削れをより確実に抑制することができ、保護層を設けた効果をより確実にすることができる。
【００５２】
ところで、図１に示した画像形成装置においては、前述のように像担持ドラム２と、その像担持ドラムにトナー像を形成するための複数の作像手段とが一体的なプロセスカートリッジ１８として構成されている。かかるプロセスカートリッジは、少なくとも像担持ドラムと、トナー像転写後の像担持ドラム表面を清掃するクリーニングブレード３０とを一体的に組み付けて構成することができるものであるが、その際、クリーニングブレード３０は、そのまわりの温度と湿度によって反発弾性やヤング率などの特性値が変化し、温湿度が高くなると振動しやすくなり、像担持ドラムから異音が発生しやすくなる。そこで、プロセスカートリッジ内の温度と湿度の少なくとも一方を所定の値以下に保つための環境制御手段を設けると有利である。より具体的な例を示すと、図１に示すようにプロセスカートリッジ１８の内部に温度又は湿度、或いはその両者を検知するセンサ３を設け、このセンサ３によってプロセスカートリッジ１８内の温度又は湿度、或いはその両者が所定値以上となったことが検知されたとき、画像形成装置本体内に設けられた図示していないファンが作動し、図１に矢印Ｅで示すように、プロセスカートリッジ１８内に空気を吹き込み、クリーニングブレード３０を冷却する。これにより異音発生をより一層効果的に抑制することができる。
【００５３】
図１に示した画像形成装置においては、帯電装置が像担持ドラム２に近接して配置された帯電ローラ２０により構成されているが、前述の制振部材を像担持ドラム２の内部に設ける構成は、図４乃至図６に示すような他の形式の帯電装置を有する画像形成装置にも適用できる。図４乃至図６に示した帯電装置は、矢印方向に回転する感光体ドラムよりなる像担持ドラム２の表面に接触して像担持ドラム２を帯電する接触式の帯電装置を示し、それぞれ帯電ローラ２０Ａ、ブラシローラ２０Ｂ及び磁気ブラシ装置２０Ｃによって帯電装置が構成されている。
【００５４】
図４に示した帯電ローラ２０Ａは、芯金３７ａと、その外周に固定された導電性のゴム層３７ｂにより構成され、芯金３７ａの両端が図示していない軸受部材などで回転自由に支持されている。この帯電ローラ２０Ａは図示していない加圧手段によって像担持ドラム２に所定の加圧力で押圧され、像担持ドラム２に従動して回転する。より具体的には、直径９ｍｍの芯金３７ａ上に、１×１０^５Ω・ｃｍ程度の中抵抗のゴム層３７ｂが被覆され、当該帯電ローラ２０Ａの直径が１６ｍｍとなっている。芯金３７ａは電源５０に接続され、電源５０から帯電ローラ２０Ａに対して所定のバイアスが印加される。これにより、像担持ドラム２の周面が所定の極性・電位に一様に帯電処理される。像担持ドラム２の内部には、前述のような制振部材が装着されている。この制振部材の作用により、帯電ローラ２０Ａに対して直流電圧に加えて交流電圧を重畳した帯電電圧を印加した場合でも、像担持ドラム２の騒音の発生が抑制される。
【００５５】
図５に示した例では、ブラシローラ２０Ｂのブラシ４７ｂが所定幅のニップをもって所定の押圧力で像担持ドラム２の表面に接触している。ブラシの材質としては、例えば、カーボン、硫化銅、金属、および金属酸化物により導電処理されたブラシを用い、これを金属や他の導電処理された芯金に巻き付けたり張り付けたりすることで帯電ローラ２０Ｂが構成される。より具体的に示すと、電極を兼ねる直径６ｍｍの金属製の芯金４７ａに、ブラシ４７ｂとしてユニチカ（株）製の導電性レーヨン繊維ＲＥＣ−Ｂをパイル地にしたテープをスパイラル状に巻き付けて、外径１４ｍｍ、軸方向長さ２５０ｍｍのブラシローラ２０Ｂを構成する。ブラシは３００デニール／５０フィラメント、１平方ミリメートル当たり１５５本の密度である。このブラシローラ２０Ｂを内径が１２ｍｍのパイプ内に一方向に回転させながらさし込み、ブラシと、パイプが同心となるように設定し、高温多湿雰囲気中に放置してクセ付けで斜毛させることもできる。ブラシローラ２０Ｂの抵抗値は印加電圧１００Ｖにおいて１×１０^５Ωである。この抵抗値は、金属製の直径３０ｍｍのドラムにブラシローラ２０Ｂをニップ幅３ｍｍで当接させ、芯金４７ａに１００Ｖの電圧を印加したときに流れる電流から換算した。ブラシローラの抵抗値は、被帯電体である像担持ドラム上にピンホール等の低耐圧欠陥部が生じた場合にもこの部分に過大なリーク電流が流れ込んで帯電ニップ部が帯電不良になる画像不良を防止するために１０^４Ω以上必要であり、像担持ドラム表面に十分に電荷を注入させるために１０^７Ω以下である必要がある。また、ブラシの材質としては、ユニチカ（株）製のＲＥＣ−Ｂ以外にも、ＲＥＣ−Ｃ、ＲＥＣ−Ｍ１、ＲＥＣ−Ｍ１０、さらに東レ（株）製のＳＡ−７、日本蚕毛（株）製のサンダーロン、カネボウ製のベルトロン、クラレ（株）のクラカーボ、レーヨンにカーボンを分散したもの、三菱レーヨン（株）製のローバル等が考えられる。ブラシは一本が３〜１０デニールで、１０〜１００フィラメント／束、８０〜６００本／ｍｍの密度が好ましい。毛足は１〜１０ｍｍが好ましい。本例のブラシローラ２０Ｂは像担持ドラム２の回転方向と逆方向（カウンター）に所定の周速度（表面の速度）をもって回転駆動され、像担持ドラム面に対して速度差を持って接触する。そしてこのブラシローラ２０Ｂに電源５０から所定の帯電電圧を印加することで、回転する像担持ドラムが所定の極性・電位に一様に接触帯電処理される。本例ではブラシローラ２０Ｂによる像担持ドラムの接触帯電は直接注入帯電が支配的となって行なわれ、像担持ドラム表面はブラシローラに対する印加帯電電圧とほぼ等しい電位に帯電される。図５に示した像担持ドラム２の内部にも、前述の制振部材が装着されている。この制振部材の作用により、ブラシローラ２０Ｂに直流電圧に加えて交流電圧を重畳した帯電電圧を印加した場合でも、像担持ドラム２の騒音の発生が抑制される。
【００５６】
図６に示した例では、磁気ブラシ方式による帯電装置が像担持ドラム２に隣接して設けられ、所定のニップ幅で磁気ブラシＭＢを像担持ドラム２の周面に接触させるよう構成されている。本例の磁気ブラシ装置２０Ｃは、磁気ブラシＭＢを支持するための非磁性スリーブ５７ａと、これに内蔵される不図示の磁石ローラ体によって構成されており、磁気ブラシを構成する粒子としては、例えばＺｎ−Ｃｕフェライト等、各種フェライト粒子を用いることができる。より具体的には、平均粒径：２５μｍのＺｎ−Ｃｕフェライト粒子と、平均粒径１０μｍのＺｎ−Ｃｕフェライト粒子を重量比１：０．０５で混合して、それぞれの平均粒径の位置にピークを有する、平均粒径２５μｍのフェライト粒子を、中抵抗樹脂層でコートした磁性粒子を用いて、その被覆磁性粒子をスリーブ５７ａ上に、厚さ１ｍｍでコートして、磁気ブラシとすることができる。磁性粒子は、スリーブ５７ａに内蔵される磁石ローラ体の磁力によってスリーブ上に担持される。このような磁気ブラシＭＢにより、像担持ドラム２との間に幅約５ｍｍ（回転方向の幅）の帯電ニップを形成し、該磁性粒子を保持するスリーブ５７ａと像担持ドラム２との間隙を約５００μｍとすることができる。また、非磁性スリーブ５７ａは、スリーブ表面が像担持ドラム表面の周速に対してその２倍の速さで像担持ドラム表面の移動方向とは逆方向に移動するように回転され、磁気ブラシを像担持ドラム表面に摺擦させ、像担持ドラムと磁気ブラシとを均一に接触させることが好ましい。スリーブ５７ａには電源５０から所定の帯電電圧が印加され、磁気ブラシＭＢを介して像担持ドラムが所定の極性・電位に一様に帯電処理される。図６に示した像担持ドラム２の内部にも、前述の制振部材が装着されている。この制振部材の作用により、本例の磁気ブラシ装置２０Ｃのような接触式帯電装置を使用し、これに直流電圧に加えて交流電圧を重畳した帯電電圧を印加した場合でも、像担持ドラム２の騒音の発生を抑制できる。
【００５７】
本発明は、複数の感光体ドラムより成る像担持ドラムを並設したカラー画像形成装置などにも適用でき、またプリンタ、ファクシミリ、複写機、その複合機などの各種画像形成装置に適用できるものである。
【００５８】
また、以上説明した画像形成装置は、像担持ドラム２の外周面に形成したトナー像を最終的な転写材としての記録媒体Ｐに直に転写して記録画像を得るように構成されているが、本発明は、像担持ドラムの外周面に形成したトナー像を無端ベルト又はドラム状に構成された中間転写体より成る転写材に転写し、そのトナー像を記録媒体に転写して記録画像を得る画像形成装置にも適用できるものである。図７は、かかる画像形成装置の一例を示す概略図である。ここに示した画像形成装置においては、矢印方向に回転する像担持ドラム２を帯電ローラ２０によって帯電し、その帯電面に図示していない露光装置から出射するレーザビームＬを照射して像担持ドラム２に第１の静電潜像を形成する。次いでその静電潜像を現像装置２２のイエロー現像器２２Ｙによりイエロートナー像として可視像化し、該トナー像を、転写材の一例である中間転写体５１に転写する。この中間転写体５１は矢印Ｆ方向に回転する無端ベルトより成るが、ドラム状の中間転写体を用いることもできる。イエロートナー像転写後の像担持ドラム表面はクリーニング装置２７により清掃される。
【００５９】
上述したところと全く同様にして、像担持ドラム２上に第２の静電潜像が形成され、その潜像が現像装置２２のマゼンタ現像器２２Ｍによりマゼンタトナー像として可視像化され、そのトナー像が、中間転写体５１上に、先に転写されたイエロートナー像に重ねて転写される。全く同様にして、像担持ドラム２上には、現像装置２２のシアン現像器２２Ｃ及びブラック現像器２２ＢＫによって、それぞれシアントナー像とブラックトナー像が形成され、これらのトナー像が中間転写体５１上に順次重ねて転写される。
【００６０】
このようにして、中間転写体５１上に転写された重ねトナー像は、給紙装置５２から給送された最終転写材としての記録媒体Ｐ上に転写され、その記録媒体が定着装置５３を通るとき、そのトナー像が記録媒体上に定着される。
【００６１】
上述した画像形成装置の像担持ドラム２にも、制振部材４が装着され、この制振部材４も先に説明したところと同じく、像担持ドラム２に挿入されている。図７に示した画像形成装置の場合には、像担持ドラム２と、その像担持ドラムにトナー像を形成するための少なくとも１つの作像手段を一体的に組み付けてプロセスカートリッジを構成できるほか、これらに中間転写体５１を一体的に組み付けてプロセスカートリッジ１８を構成することもできる。
【００６２】
上述したいずれの形式の画像形成装置も、像担持ドラムに形成したトナー像を、転写材（記録媒体又は中間転写体）に転写して記録画像を得るように構成されている。
【００６３】
以上、感光体ドラムより成る像担持ドラムの内部に制振部材を設ける例を説明したが、感光体からトナー像を転写される中間転写体が像担持ドラムより成る場合には、その像担持ドラムの内部に前述の制振部材を設けることにより、その像担持ドラムより成る中間転写体からの異音発生を効果的に抑制することができる。このように、前述の各構成は、像担持ドラムが感光体からトナー像を転写される中間転写体より成るときも適用できるものである。さらに、無端ベルト状の感光体や無端ベルト状の中間転写体を支持するローラの内部に前述の制振部材を配置しても、異音発生を抑制することができる。
【００６４】
【発明の効果】
本発明によれば、低融点トナーを用いても、異音の発生を効果的に抑制することができる。
【図面の簡単な説明】
【図１】画像形成装置の一部を示す概略断面図である。
【図２】内部に制振部材が配置された像担持ドラムの縦断面図である。
【図３】図２に示した制振部材とは形態の異なる制振部材を示す縦断面図である。
【図４】像担持ドラム表面に当接する帯電ローラを示す図である。
【図５】ブラシローラより成る帯電装置を示す図である。
【図６】磁気ブラシ装置より成る帯電装置を示す図である。
【図７】画像形成装置の他の例を示す概略断面図である。
【符号の説明】
２　像担持ドラム
４　制振部材
１８　プロセスカートリッジ
２２　現像装置
２７　クリーニング装置
３０　クリーニングブレード
Ｐ　記録媒体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a process cartridge in which an image bearing drum and at least one image forming means for forming a toner image on the image bearing drum are integrally assembled, a process cartridge for forming a toner image on the image bearing drum, The present invention relates to an image forming apparatus that transfers a toner image to a transfer material to obtain a recorded image.
[0002]
[Prior art]
2. Description of the Related Art An image forming apparatus of the above-described type configured as a copier, a printer, a facsimile or a multifunction peripheral thereof, and a process cartridge used in such an image forming apparatus have been conventionally known. The image bearing drum is configured as, for example, a photoconductor drum on which a toner image is formed on the surface by charging, exposure, and development, or an intermediate transfer drum on which a toner image is transferred from the photoconductor to form a toner image on the surface. . Such an image bearing drum vibrates due to an external vibration force applied thereto, so that abnormal noise is generated from the image bearing drum. For example, in the case of a photosensitive drum, an image forming unit such as a charging device and a cleaning device having a cleaning blade is provided around the photosensitive drum, but the charging member is affected by an AC voltage applied to the charging device. Vibrates, and the cleaning blade pressed against the surface of the image bearing drum vibrates by causing stick slip with the rotation of the image bearing drum, and these vibrations are transmitted to the image bearing drum, and the image bearing drum vibrates. This may cause abnormal noise and give the user discomfort. Therefore, conventionally, a vibration damping member is provided in the inside of the image bearing drum, thereby suppressing the vibration of the image bearing drum and taking measures to suppress the generation of abnormal noise (for example, see Patent Document 1).
[0003]
On the other hand, in order to save energy, an image forming apparatus has been put to practical use, which is configured to use a low melting point toner and to fix a toner image transferred to a recording medium as a final transfer material at a relatively low temperature. I have. However, it has been found that when such a low melting point toner is used, abnormal noise is likely to be generated as compared with a case where a toner having a high melting point is used, and the generation of the abnormal noise cannot be sufficiently suppressed by the conventional vibration damping member. . It is not clear why the use of low-melting toner causes abnormal noise, but additives such as wax in the toner tend to adhere to the surface of the image bearing drum, and the amount of adhesion becomes non-uniform depending on the image pattern. Therefore, it is considered that the movement of the member abutting on the surface of the image bearing drum, for example, the cleaning blade becomes uneven, and the image bearing drum generates a violent noise due to the vibration.
[0004]
[Patent Document 1]
JP-A-10-97158 (page 5, FIG. 4)
[0005]
[Problems to be solved by the invention]
The present invention has been made based on the above-described novel recognition. It is an object of the present invention to provide an image forming apparatus which can effectively suppress abnormal noise generation of an image bearing drum even when a low-melting toner is used. To provide a process cartridge.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a process cartridge in which an image bearing drum and at least one image forming means for forming a toner image on the image bearing drum are integrally assembled by a flow tester method. The toner image is formed with a toner having a measured outflow start temperature of 102 ° C. or less, and a vibration damping member made of a substance having a loss tangent tan δ of 0.5 or more is provided inside the image bearing drum. A process cartridge is proposed (claim 1).
[0007]
The process cartridge according to claim 1, wherein the charging device charges the image bearing drum, and the electrostatic latent image formed by exposing the charged image bearing drum is visualized as a toner image. A developing device, a transfer device for transferring the toner image formed on the image bearing drum onto a transfer material, and a cleaning device for cleaning the surface of the image bearing drum after the transfer of the toner image. It is advantageous that the image forming apparatus is configured to be detachably attached to the image forming apparatus main body (claim 2).
[0008]
Furthermore, in the process cartridge according to claim 1 or 2, it is advantageous that the toner contains a metal salt of a higher fatty acid (claim 3).
[0009]
In the process cartridge according to any one of the first to third aspects, it is advantageous that the vibration damping member is formed in a solid cylindrical shape (claim 4).
[0010]
Furthermore, in the process cartridge according to any one of claims 1 to 3, it is advantageous that the vibration damping member is formed in a cylindrical shape (claim 5).
[0011]
Further, in the process cartridge according to any one of the first to fifth aspects, it is advantageous that the vibration damping member is press-fitted inside the image bearing drum (claim 6).
[0012]
Further, in the process cartridge according to any one of claims 1 to 6, it is advantageous that the vibration damping member is adhered to an inner wall surface of the image bearing drum (claim 7).
[0013]
In order to achieve the above object, the present invention proposes an image forming apparatus including the process cartridge according to any one of claims 1 to 7 (claim 8).
[0014]
Further, in order to achieve the above object, the present invention measures a toner image by a flow tester method in an image forming apparatus for forming a toner image on a rotating image bearing drum and transferring the toner image to a transfer material to obtain a recorded image. An image forming method, wherein the toner image is formed with a toner having an outflow start temperature of 102 ° C. or less, and a damping member made of a substance having a loss tangent tan β of 0.5 or more is provided inside the image bearing drum. A device is proposed (claim 9).
[0015]
In the image forming apparatus according to the ninth aspect, it is advantageous that the toner contains a metal salt of a higher fatty acid (claim 10).
[0016]
Furthermore, in the image forming apparatus according to the ninth or tenth aspect, it is advantageous that the damping member is formed in a solid cylindrical shape (an eleventh aspect).
[0017]
In the image forming apparatus according to the ninth or tenth aspect, it is advantageous that the vibration damping member is formed in a cylindrical shape.
[0018]
Further, in the image forming apparatus according to any one of the ninth to twelfth aspects, it is advantageous that the vibration damping member is press-fitted inside the image bearing drum (claim 13).
[0019]
In the image forming apparatus according to any one of the ninth to thirteenth aspects, it is advantageous that the vibration damping member is adhered to an inner wall surface of the image bearing drum.
[0020]
The image forming apparatus according to any one of claims 9 to 14, further comprising a cleaning blade that presses against the surface of the image bearing drum to clean the surface of the image bearing drum after the transfer of the toner image. It is also possible to provide a reverse rotation mode for rotating the image bearing drum in a direction opposite to the rotation direction of the image bearing drum when a toner image is being formed on the image bearing drum. .
[0021]
In the image forming apparatus according to any one of the ninth to fifteenth aspects, it is advantageous that the image bearing drum has a protective layer on a surface (claim 16).
[0022]
Further, in the image forming apparatus according to claim 16, it is advantageous that the protective layer contains a filler (claim 17).
[0023]
In the image forming apparatus according to the present invention, it is advantageous that the protective layer contains a charge transport material (claim 18).
[0024]
19. The image forming apparatus according to claim 9, wherein at least the image bearing drum and a cleaning blade for cleaning a surface of the image bearing drum after the transfer of the toner image are integrally assembled. Advantageously, a cartridge is provided, and environmental control means for keeping at least one of the temperature and the humidity in the process cartridge at a predetermined value or less is provided (claim 19).
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0026]
FIG. 1 is a schematic sectional view showing an example of an image forming apparatus having a cylindrical image bearing drum 2. The image bearing drum 2 shown here is a cylindrical element tube made of a conductive metal such as aluminum. The photosensitive drum is provided with a photosensitive layer on the outer peripheral surface. In the example shown in FIG. 1, the process cartridge 18 is configured by integrally assembling the image bearing drum 2 and an image forming means for forming a toner image on the image bearing drum 2 as described later.
[0027]
The image bearing drum 2 is rotatably supported by a case 19 of the process cartridge 18 and is driven to rotate clockwise in FIG. 1 by a drive motor (not shown). At this time, a charging roller 20, which is an example of a charging device rotatably supported by a case 19, rotates, and a charging voltage is applied to the charging roller 20, so that the surface of the image bearing drum 2 has a predetermined polarity. Be charged. In the image forming apparatus of the present embodiment, a spacer made of a tape 1 is wound around each end of the charging roller 20 in the longitudinal direction, and these tapes 1 come into contact with the outer peripheral surface of the image bearing drum 2, whereby the charging roller 20 It is located with a minute gap from the surface of the image bearing drum 2.
[0028]
The charged surface of the image bearing drum 2 is irradiated with a modulated laser beam L emitted from an exposure device (not shown) provided separately from the process cartridge 18, whereby an electrostatic charge is applied to the image bearing drum 2. A latent image is formed. This electrostatic latent image is visualized as a toner image by the developing device 22, and the toner image is transferred to a recording medium P made of transfer paper or the like carried on the transfer belt 8 and conveyed in the direction of arrow A. The image is transferred by the operation of the transfer brush 9 as an example. The recording medium P constitutes an example of a transfer material on which a toner image is transferred from an image bearing drum. However, as described later, a transfer material formed of an intermediate transfer member may be used.
[0029]
When the recording medium P passes through a fixing device (not shown), the toner image transferred onto the recording medium P is fixed on the recording medium P by the action of heat and pressure. The paper is discharged to a paper discharge unit not shown. Further, the toner remaining on the image bearing drum after the transfer of the toner image is removed by the cooperation of the cleaning brush 29 of the cleaning device 27 and the cleaning blade 30.
[0030]
The developing device 22 has a developing case 23 constituted by a part of the case 19 of the process cartridge 18 and a developing roller 24 rotatably supported by the developing case 23. Have been. The developer D is carried and conveyed by the rotating developing roller 24, and the conveyed developer visualizes the electrostatic latent image. Here, a two-component developer having a toner and a carrier is used as the developer, and when a decrease in the toner concentration of the developer is detected, the toner is supplied from the toner container 33.
[0031]
The cleaning device 27 also has a cleaning case 28 constituted by a part of the case 19 of the process cartridge 18, and the cleaning brush 29 and the cleaning blade 30 described above are supported by the cleaning case 28.
[0032]
As described above, the process cartridge 18 of the present embodiment includes the image bearing drum 2 rotatably supported by the case 19 and the plurality of image forming means arranged around the drum. The cartridge can be configured to have at least one image forming unit. In other words, the process cartridge has an image bearing drum and at least one image forming means for forming a toner image on the image bearing drum, which are integrally assembled. More specifically, the process cartridge includes a charging device that charges the image bearing drum, and a developing device that visualizes an electrostatic latent image formed by exposing the charged image bearing drum as a toner image. The apparatus includes at least one of an image forming device, a transfer device that transfers a toner image formed on the image bearing drum to a transfer material, and a cleaning device that cleans the surface of the image bearing drum after the transfer of the toner image. The process cartridge is configured to be removably mounted on an image forming apparatus main body (not shown). When the process cartridge reaches the end of its life, it can be replaced with a new process cartridge.
[0033]
The image forming apparatus and the process cartridge 18 of the present embodiment form a toner image on the outer peripheral surface of the rotating image bearing drum 2 and transfer the toner image to a recording medium P, which is an example of a transfer material, to form a recorded image. Is used in the developing device 22 so that the toner image transferred to the recording medium P can be fixed in the fixing device at a relatively low surface temperature of the fixing roller, for example, about 145 ° C. Low melting point toner is used as the toner to be used. The toner is formed on the image bearing drum with a toner having an outflow start temperature measured by a flow tester method of 102 ° C. or less, preferably 99 ° C. to 102 ° C. For measuring the outflow starting temperature by the flow tester method, a Shimadzu flow tester model CFT500 manufactured by Shimadzu Corporation is used. This flow tester heats and melts the sample contained in the cylinder from the periphery of the cylinder, applies pressure with a constant load from the top of the cylinder with a piston, and applies the molten sample to the hole of the die placed at the bottom of the cylinder. And the temperature at which the sample flows out of the die hole is the outflow starting temperature. Load applied to piston is 10kg / cm ² A toner image having an outflow start temperature of 102 ° C. or less was used under the conditions of a temperature rising rate of 3.0 ° C./min, a die diameter of 0.5 mm, and a die length of 10.0 mm, and a toner image was formed on an image carrying drum. It forms. The flow tester method is described in JP-A-2001-147551 and JP-A-2001-75106.
[0034]
A charging roller 20 is arranged on the outer peripheral surface of the image bearing drum 2 shown in FIG. 1 and a cleaning blade 30 is in contact with the charging roller 20. A charging voltage obtained by superimposing a DC voltage and an AC voltage is applied to the charging roller 20. Then, the charging roller 20 vibrates due to the application of the AC voltage. In addition, when the image bearing drum 2 rotates, the cleaning blade 30 causes stick-slip, so that the blade 30 vibrates. These vibrations are transmitted to the image bearing drum 2, which causes the image bearing drum 2 to vibrate, which may cause abnormal noise. In particular, when the low-melting toner as described above is used, in the conventional image forming apparatus and its process cartridge, a loud noise is generated, and the user may be inconvenienced. For example, a thin aluminum cylinder having an outer diameter of 30 mm, an inner diameter of 28.5 mm, and a peripheral wall thickness of about 0.75 mm is used as the raw tube of the image bearing drum 2. In the conventional image forming apparatus using the image bearing drum 2 and the process cartridge thereof, abnormal noise is particularly likely to occur.
[0035]
Therefore, in the image forming apparatus and the process cartridge 18 of the present embodiment, as shown in FIGS. 1 and 2, the vibration damping member 4 is provided inside the image bearing drum 2. A damping member 4 having a form as shown in FIG. 3 can be used. Such a vibration damping member 4 is made of a substance having a loss tangent tan δ of 0.5 or more. The tangent of the phase angle of stress and strain in a material: δ (loss angle) is the loss tangent (tan δ), and the greater the value of the loss tangent tan δ, the greater the damping effect. In the image forming apparatus and the process cartridge 18 of the present embodiment, focusing on such material properties, the vibration damping member 4 made of a substance having a loss tangent tan δ of 0.5 or more is provided in the image bearing drum 2. Thereby, the rotating image bearing drum 2 is effectively damped, and even when the low melting point toner as described above is used, abnormal noise generated from the rotating image bearing drum 2 during image formation is kept extremely low. It was possible. As the substance having a loss tangent tan δ of 0.5 or more, for example, a rubber material such as butyl rubber and nitrile rubber can be used.
[0036]
The inventor of the present invention has proposed a damping member 4 having a loss tangent tan δ of 0.5 in a rubber material having a value of 0.5 and a damping member 4 made of ABS resin having a loss tangent tan δ of less than 0.5. Each was provided inside the image bearing drum 2 shown in FIG. 1 to perform an image forming operation, and it was examined whether or not people around the image forming apparatus felt abnormal noise. A charging voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging roller 20, and the toner is fixed at a temperature of about 145 ° C. with a toner whose outflow start temperature is 102 ° C. or less and a fixing roller surface temperature in an actual machine is about 145 ° C. And a high-melting toner capable of fixing a toner image at a temperature where the outflow start temperature is higher than 102 ° C. and the surface temperature of a fixing roller in an actual machine is about 175 ° C. The measurement of the loss tangent tan δ of the material of the damping member 4 was performed according to the non-resonant vibration method specified in JIS K7244-4. A test piece having a thickness of 2 mm, a width of 5 mm, and a length of 30 mm was measured at an applied frequency of 30 Hz. Table 1 shows the results.
[0037]
[Table 1]

[0038]
"Occurrence" in Table 1 indicates that an observer around the image forming apparatus clearly sensed that abnormal noise was generated, and "Not generated" indicates that no abnormal noise was detected. ing. As can be seen from Table 1, even when the low melting point toner was used, no abnormal noise was observed when the damping member 4 made of a material having a loss tangent tan δ of 0.5 was provided in the image bearing drum 2. When the same toner was used and the damping member 4 having a loss tangent tan δ of less than 0.5 was used, generation of abnormal noise was confirmed. In addition. When the same test was performed without providing a vibration damping member in the image bearing drum 2, remarkable noise generation was observed when any of the toners was used.
[0039]
If the damping member 4 is made of a substance having a loss tangent tan δ greater than 0.5, particularly 0.6 or 0.8 or more, the damping effect on the image bearing drum 2 can be further enhanced. .
[0040]
When a toner containing a metal salt of a higher fatty acid, such as zinc stearate, is used as the toner used in the process cartridge of the image forming apparatus, a part of the toner adheres to the surface of the image bearing drum 2 and , The sliding of the edge of the cleaning blade 30 is improved, the vibration of the cleaning blade 30 can be suppressed, and the effect of preventing abnormal noise can be further enhanced.
[0041]
The vibration damping member 4 shown in FIG. 2 is formed in a solid columnar shape, and the vibration damping member 4 shown in FIG. 3 is formed in a cylindrical shape. When the member 4 is used, its weight increases, and the overall weight of the damping member and the image bearing drum 2 increases. As a result, harsh high-frequency noise can be effectively reduced. Conversely, when the cylindrical vibration damping member 4 as shown in FIG. 3 is used, the amount of the material of the vibration damping member can be reduced, and the cost can be reduced. At this time, it is natural that the loss tangent tan δ of the damping member 4, its weight, its form, especially its thickness should be set so that the necessary damping effect can be obtained. Although a cylindrical vibration damping member 4 can be used, a sheet-shaped member can be rolled to form a cylindrical vibration damping member. According to the latter method, since the cylindrical vibration damping member 4 can be obtained from an inexpensive sheet-like member, the cost can be further reduced.
[0042]
As a method for mounting the damping member 4 on the image bearing drum 2, when the outer diameter of the damping member 4 before being inserted into the image bearing drum 2 is d and the inner diameter of the image bearing drum 2 is DI, d is DI A method in which a vibration damping member set slightly larger than the above is inserted into the image bearing drum 2 to press the vibration damping member 4 into the inside of the image bearing drum 2, and d is set slightly smaller than DI, and Is inserted into the image bearing drum 2 and the vibration damping member 4 is adhered to the inner wall surface of the image bearing drum 2 with an adhesive. The vibration damping member 4 may be pressed into the image bearing drum 2 and fixed to the inner surface of the image bearing drum 2 with an adhesive. Either method can provide a sufficient vibration damping effect. However, when the vibration damping member 4 is pressed into the image bearing drum 2, if d is smaller than DI, the vibration damping member 4 and the inner wall surface of the image bearing drum 2 may be vibrated. When the poor adhesion with the member 4 occurs and the damping effect is reduced, and when d is much larger than DI, excessive force is applied when the damping member 4 is inserted into the image bearing drum 2. Is required, and not only the assemblability is reduced but also the image carrying drum is deformed at the time of the assembling.
[0043]
When the vibration damping member is press-fitted into the image bearing drum and fixed, no adhesive is required for fixing the vibration damping member, so that the cost required for fixing can be reduced, and the vibration damping member 4 can be easily removed from the image bearing drum 2. And recyclability can be improved. On the other hand, when the damping member 4 is adhered and fixed to the image bearing drum 2, the damping member 4 can be firmly fixed by the image bearing drum 2.
[0044]
The image forming apparatus shown in FIG. 1 has a cleaning blade 30 that presses against the surface of the image bearing drum 2 and cleans the surface of the image bearing drum after transferring the toner image. When the image bearing drum is reversed by a slight angle, foreign matter such as paper dust sandwiched between the cleaning blade 30 and the surface of the image bearing drum 2 can be removed. The rotation direction of the image bearing drum 2 when a toner image is formed on the image bearing drum 2, that is, a reverse rotation mode in which the image bearing drum 2 is rotated in a direction opposite to the normal rotation direction is set. Then, an abnormal noise due to the vibration of the cleaning blade 30 may be generated not only when the image bearing drum rotates normally but also when the image bearing drum rotates reversely. In the case of the conventional image forming apparatus, abnormal noise is likely to be generated particularly just before the image bearing drum stops rotating, and when the image bearing drum 2 performs the operation of normal rotation, stop, reverse rotation, and stop, it is performed twice consecutively. A loud noise was occurring. However, by providing the vibration damping member 4 having the above-described configuration inside the image bearing drum 2, it is possible to prevent the generation of loud noise even when the image bearing drum 2 performs a reverse rotation operation.
[0045]
Next, the image bearing drum 2 on which the vibration damping member 4 is mounted will be described. As the photosensitive layer of the image bearing drum used in the electrophotographic system, various kinds of photosensitive layers such as those using inorganic semiconductor materials such as selenium and amorphous silicon, those using organic semiconductor materials, and those combining both are used. Have been. In recent years, organic photosensitive layers have been widely used due to low cost, high degree of freedom in photoconductor design, and no pollution. It can also be mounted on an image bearing drum having a photosensitive layer.
[0046]
The organic electrophotographic photosensitive layer includes a photoconductive resin represented by polyvinyl carbazole (PVK), a charge transfer complex type represented by PVK-TNF (2,4,7-trinitrofluorenone), and a phthalocyanine-binder. And a function-separated type photosensitive layer using a combination of a charge-generating substance and a charge-transporting substance, and a function-separated type photosensitive layer is particularly attracting attention. The mechanism of the formation of an electrostatic latent image in this function-separated type photosensitive layer is as follows: when the photosensitive layer is charged and irradiated with light, the light passes through the transparent charge transport layer and is absorbed by the charge generating substance in the charge generation layer, The light-absorbing charge generating substance generates charge carriers, which are injected into the charge transport layer, move in the charge transport layer according to the electric field generated by the charge, and neutralize the charge on the photosensitive layer surface. Thus, an electrostatic latent image is formed. In the function-separated type photosensitive layer, it is known and useful to use a charge transport material having absorption mainly in the ultraviolet region in combination with a charge generation material having absorption mainly in the visible region.
[0047]
On the other hand, as a weak point of an organic photosensitive layer, it is known that mechanical and chemical durability are poor. That is, although many charge transporting substances have been developed as low molecular weight compounds, since low molecular weight compounds alone do not have a film-forming property, they are usually used after being dispersed and mixed with an inert polymer. However, the charge transport layer composed of a low-molecular charge transport material and an inert polymer is generally soft and has poor mechanical durability. In an electrophotographic process, various contact members (development, transfer paper, cleaning brush, cleaning blade) are used repeatedly. Etc.), the film is likely to be scraped by the mechanical load. Therefore, a protective layer may be provided on the photosensitive layer as a surface layer for the purpose of protecting the photosensitive layer and improving the durability. Materials used for the protective layer include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether resin, allyl resin, phenol resin, polyacetal resin, polyamide resin, polyamideimide resin, and polyacrylate resin. , Polyallyl sulfone resin, polybutylene resin, polybutylene terephthalate resin, polycarbonate resin, polyether sulfone resin, polyethene resin, polyethylene terephthalate resin, polyimide resin, acrylic resin, polymethylpentene resin, polypropylene resin, polyphenylene oxide resin, polysulfone resin, Examples of the resin include an AS resin, an AB resin, a BS resin, a polyurethane resin, a polyvinyl chloride resin, a polyvinylidene chloride resin, and an epoxy resin. A filler may be added to the protective layer for the purpose of further improving abrasion resistance. Examples of the filler include a fluorine resin such as polytetrafluoroethylene, a silicone resin, and a resin in which an inorganic material such as titanium oxide, tin oxide, potassium titanate, silica, and alumina is dispersed. The amount of the filler added to the protective layer is usually 10 to 40%, preferably 20 to 30% on a weight basis. If the amount of the filler is less than 10%, the abrasion is large and the durability is inferior. If the amount exceeds 40%, the light-area potential at the time of exposure is significantly increased, and the decrease in sensitivity cannot be ignored. Further, a dispersing aid can be added to the protective layer in order to improve the dispersibility of the filler. The dispersing agent to be added may be appropriately used ones used in paints and the like, and the amount thereof is usually 0.5 to 4%, preferably 1 to 2% based on the weight of the filler contained. . It is also effective to add a charge transport material to the protective layer, and an antioxidant can be added as needed. As a method for forming the protective layer, a normal coating method such as a spray method is employed. The thickness of the protective layer is 0.5 to 10 μm, preferably about 4 to 6 μm.
[0048]
It is also possible to provide an intermediate layer between the photosensitive layer and the protective layer. The intermediate layer generally uses a binder resin as a main component. Examples of these resins include polyamide, alcohol-soluble nylon, water-soluble polyvinyl butyral, polyvinyl butyral, and polyvinyl alcohol. As a method for forming the intermediate layer, a normal coating method is employed as described above. The thickness of the intermediate layer is suitably about 0.05 to 2 μm.
[0049]
When the image bearing drum has a protective layer on the surface as described above, since the film of the photosensitive layer can be suppressed, the cleaning blade can be pressed against the surface of the image bearing drum with a stronger pressing force. . Therefore, the wax and the like in the toner that adheres to the image carrying drum when the low melting point toner is used can be cleaned, and the variation in the coefficient of friction of the surface of the image carrying drum becomes small. That is, improvement in cleaning performance and prevention of abnormal noise can be realized.
[0050]
Furthermore, if the protective layer contains a filler, the film removal of the photosensitive layer can be more reliably suppressed, and the effect of providing the protective layer can be more assured.
[0051]
Further, when the protective layer contains a charge transporting substance, the shaving of the photosensitive layer can be more reliably suppressed, and the effect of providing the protective layer can be further ensured.
[0052]
In the image forming apparatus shown in FIG. 1, the image bearing drum 2 and a plurality of image forming means for forming a toner image on the image bearing drum are formed as an integral process cartridge 18 as described above. Have been. Such a process cartridge can be constructed by integrally assembling at least an image bearing drum and a cleaning blade 30 for cleaning the surface of the image bearing drum after the transfer of the toner image. The characteristic values such as the rebound resilience and the Young's modulus change depending on the temperature and the humidity around it, and when the temperature and the humidity are high, the vibration is apt to occur, and the noise is easily generated from the image bearing drum. Therefore, it is advantageous to provide an environment control means for keeping at least one of the temperature and the humidity in the process cartridge at a predetermined value or less. More specifically, as shown in FIG. 1, a sensor 3 for detecting the temperature and / or humidity is provided inside the process cartridge 18 as shown in FIG. When it is detected that both of them become equal to or more than the predetermined value, a fan (not shown) provided in the image forming apparatus main body operates, and as shown by an arrow E in FIG. Is blown to cool the cleaning blade 30. Thereby, generation of abnormal noise can be more effectively suppressed.
[0053]
In the image forming apparatus shown in FIG. 1, the charging device is constituted by the charging roller 20 arranged close to the image bearing drum 2, but the above-described vibration damping member is provided inside the image bearing drum 2. Is applicable to an image forming apparatus having another type of charging device as shown in FIGS. The charging devices shown in FIGS. 4 to 6 are contact-type charging devices that charge the image bearing drum 2 by contacting the surface of the image bearing drum 2 composed of a photosensitive drum that rotates in the direction of the arrow. A charging device is constituted by 20A, the brush roller 20B, and the magnetic brush device 20C.
[0054]
The charging roller 20A shown in FIG. 4 includes a core bar 37a and a conductive rubber layer 37b fixed to the outer periphery thereof, and both ends of the core bar 37a are rotatably supported by bearing members (not shown) or the like. ing. The charging roller 20A is pressed against the image bearing drum 2 with a predetermined pressing force by a pressing means (not shown), and rotates following the image bearing drum 2. More specifically, 1 × 10 ⁵ A medium resistance rubber layer 37b of about Ω · cm is covered, and the diameter of the charging roller 20A is 16 mm. The metal core 37a is connected to a power supply 50, and a predetermined bias is applied from the power supply 50 to the charging roller 20A. As a result, the peripheral surface of the image bearing drum 2 is uniformly charged to a predetermined polarity and potential. The above-described damping member is mounted inside the image bearing drum 2. By the action of the vibration damping member, even when a charging voltage in which an AC voltage is superimposed on the charging roller 20 </ b> A in addition to the DC voltage is applied, generation of noise of the image bearing drum 2 is suppressed.
[0055]
In the example shown in FIG. 5, the brush 47b of the brush roller 20B is in contact with the surface of the image bearing drum 2 with a predetermined pressing force with a nip having a predetermined width. As a material of the brush, for example, a brush that has been conductively treated with carbon, copper sulfide, metal, and metal oxide is used, and the brush is wound or stuck on a metal or other conductively processed core metal, and the charging roller is thus obtained. 20B are configured. More specifically, a tape in which conductive rayon fiber REC-B manufactured by Unitika Ltd. is piled as a brush 47b is spirally wound around a metal core bar 47a having a diameter of 6 mm also serving as an electrode. The brush roller 20B has an outer diameter of 14 mm and an axial length of 250 mm. The brushes are 300 denier / 50 filaments, 155 densities per square millimeter. The brush roller 20B is inserted into a pipe having an inner diameter of 12 mm while rotating in one direction, the brush and the pipe are set to be concentric, and the brush and the pipe are left in a high-temperature and high-humidity atmosphere to be inclined by a habit. You can also. The resistance value of the brush roller 20B is 1 × 10 at an applied voltage of 100 V. ⁵ Ω. This resistance value was calculated from the current flowing when a brush roller 20B was brought into contact with a metal drum having a diameter of 30 mm with a nip width of 3 mm and a voltage of 100 V was applied to the metal core 47a. The resistance value of the brush roller is such that, even when a low-voltage defect such as a pinhole is formed on the image bearing drum, which is a member to be charged, an excessive leakage current flows into this portion and the charging nip portion becomes defectively charged. 10 to prevent defects ⁴ Ω or more, and 10 ⁷ Ω or less. In addition to REC-B manufactured by Unitika Ltd., REC-C, REC-M1, REC-M10, and SA-7 manufactured by Toray Industries, Inc. Sanderon manufactured by Kanebo Co., Ltd., Bertron manufactured by Kuraray Co., Ltd., Cracarbo manufactured by Kuraray Co., Ltd., dispersion of carbon in rayon, Robal manufactured by Mitsubishi Rayon Co., Ltd., etc. The brush preferably has a denier of 3 to 10 deniers, a density of 10 to 100 filaments / bundle, and a density of 80 to 600 brushes / mm. The hair foot is preferably 1 to 10 mm. The brush roller 20B of this embodiment is rotationally driven at a predetermined peripheral speed (surface speed) in a direction (counter) opposite to the rotation direction of the image bearing drum 2, and comes into contact with the image bearing drum surface with a speed difference. Then, by applying a predetermined charging voltage from the power supply 50 to the brush roller 20B, the rotating image bearing drum is uniformly contact-charged to a predetermined polarity and potential. In this example, the contact charging of the image bearing drum by the brush roller 20B is performed by direct injection charging being dominant, and the surface of the image bearing drum is charged to a potential substantially equal to the charging voltage applied to the brush roller. The above-described vibration damping member is also mounted inside the image bearing drum 2 shown in FIG. Due to the function of the vibration damping member, even when a charging voltage in which an AC voltage is superimposed on the brush roller 20B in addition to the DC voltage is applied, generation of noise of the image bearing drum 2 is suppressed.
[0056]
In the example shown in FIG. 6, a charging device of the magnetic brush type is provided adjacent to the image bearing drum 2 and is configured to contact the magnetic brush MB with the peripheral surface of the image bearing drum 2 with a predetermined nip width. . The magnetic brush device 20C of the present example includes a non-magnetic sleeve 57a for supporting the magnetic brush MB and a magnet roller body (not shown) incorporated therein, and particles constituting the magnetic brush include, for example, Various ferrite particles such as Zn-Cu ferrite can be used. More specifically, Zn-Cu ferrite particles having an average particle diameter of 25 μm and Zn-Cu ferrite particles having an average particle diameter of 10 μm are mixed at a weight ratio of 1: 0.05, and are mixed at the positions of the respective average particle diameters. Using magnetic particles coated with a ferrite particle having an average particle diameter of 25 μm having a peak and a medium resistance resin layer, the coated magnetic particles may be coated on the sleeve 57a with a thickness of 1 mm to form a magnetic brush. it can. The magnetic particles are carried on the sleeve by the magnetic force of the magnet roller body incorporated in the sleeve 57a. With such a magnetic brush MB, a charging nip having a width of about 5 mm (width in the rotating direction) is formed between the magnetic brush MB and the image bearing drum 2, and a gap between the sleeve 57 a holding the magnetic particles and the image bearing drum 2 is reduced. It can be 500 μm. The non-magnetic sleeve 57a is rotated so that the surface of the sleeve moves in a direction opposite to the moving direction of the surface of the image bearing drum at twice the speed of the peripheral speed of the surface of the image bearing drum. It is preferable that the surface of the image bearing drum be rubbed and the image bearing drum and the magnetic brush be uniformly contacted. A predetermined charging voltage is applied to the sleeve 57a from the power supply 50, and the image bearing drum is uniformly charged to a predetermined polarity and potential via the magnetic brush MB. The above-described vibration damping member is also mounted inside the image bearing drum 2 shown in FIG. Due to the action of the vibration damping member, even when a contact type charging device such as the magnetic brush device 20C of the present embodiment is used and a charging voltage obtained by superimposing an AC voltage in addition to a DC voltage is applied thereto, the image bearing drum 2 Noise can be suppressed.
[0057]
The present invention can be applied to a color image forming apparatus in which image bearing drums composed of a plurality of photosensitive drums are arranged side by side, and can be applied to various image forming apparatuses such as a printer, a facsimile, a copying machine, and a multifunction peripheral thereof. is there.
[0058]
The image forming apparatus described above is configured to directly transfer the toner image formed on the outer peripheral surface of the image bearing drum 2 to a recording medium P as a final transfer material to obtain a recorded image. According to the present invention, a toner image formed on an outer peripheral surface of an image bearing drum is transferred to a transfer material including an endless belt or an intermediate transfer body formed in a drum shape, and the toner image is transferred to a recording medium to print a recorded image. The present invention can also be applied to an obtained image forming apparatus. FIG. 7 is a schematic diagram illustrating an example of such an image forming apparatus. In the image forming apparatus shown here, the image bearing drum 2 rotating in the direction of the arrow is charged by a charging roller 20, and the charged surface thereof is irradiated with a laser beam L emitted from an exposure device (not shown) to form the image bearing drum 2. 2, a first electrostatic latent image is formed. Next, the electrostatic latent image is visualized as a yellow toner image by a yellow developing device 22Y of the developing device 22, and the toner image is transferred to an intermediate transfer member 51 which is an example of a transfer material. Although the intermediate transfer body 51 is formed of an endless belt rotating in the direction of arrow F, a drum-shaped intermediate transfer body may be used. The surface of the image bearing drum after the transfer of the yellow toner image is cleaned by the cleaning device 27.
[0059]
In exactly the same manner as described above, a second electrostatic latent image is formed on the image bearing drum 2, and the latent image is visualized as a magenta toner image by a magenta developing device 22 M of the developing device 22. The toner image is transferred onto the intermediate transfer body 51 so as to overlap the previously transferred yellow toner image. In exactly the same manner, a cyan toner image and a black toner image are formed on the image bearing drum 2 by the cyan developing device 22C and the black developing device 22BK of the developing device 22, respectively. Are sequentially superimposed and transferred.
[0060]
In this way, the superimposed toner image transferred onto the intermediate transfer body 51 is transferred onto a recording medium P as a final transfer material fed from a paper feeding device 52, and the recording medium passes through a fixing device 53. At that time, the toner image is fixed on the recording medium.
[0061]
The damping member 4 is also mounted on the image bearing drum 2 of the above-described image forming apparatus, and the damping member 4 is also inserted into the image bearing drum 2 as described above. In the case of the image forming apparatus shown in FIG. 7, the process cartridge can be constructed by integrally assembling the image bearing drum 2 and at least one image forming means for forming a toner image on the image bearing drum. The process cartridge 18 can also be configured by integrally assembling the intermediate transfer member 51 with them.
[0062]
Any of the above-described image forming apparatuses is configured to transfer a toner image formed on an image bearing drum to a transfer material (a recording medium or an intermediate transfer body) to obtain a recorded image.
[0063]
Although the example in which the vibration damping member is provided inside the image bearing drum composed of the photosensitive drum has been described above, when the intermediate transfer body onto which the toner image is transferred from the photosensitive drum is composed of the image bearing drum, the image bearing drum is provided. By providing the above-described vibration damping member in the inside, the generation of abnormal noise from the intermediate transfer body including the image bearing drum can be effectively suppressed. As described above, the above-described configurations can be applied to the case where the image bearing drum is formed of the intermediate transfer member on which the toner image is transferred from the photosensitive member. Further, even if the above-described vibration damping member is disposed inside a roller that supports an endless belt-shaped photoconductor or an endless belt-shaped intermediate transfer body, generation of abnormal noise can be suppressed.
[0064]
【The invention's effect】
According to the present invention, even when a low-melting-point toner is used, generation of abnormal noise can be effectively suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a part of an image forming apparatus.
FIG. 2 is a longitudinal sectional view of an image bearing drum in which a vibration damping member is disposed.
FIG. 3 is a longitudinal sectional view showing a damping member having a different form from the damping member shown in FIG. 2;
FIG. 4 is a diagram illustrating a charging roller that comes into contact with the surface of the image bearing drum.
FIG. 5 is a diagram illustrating a charging device including a brush roller.
FIG. 6 is a diagram illustrating a charging device including a magnetic brush device.
FIG. 7 is a schematic sectional view showing another example of the image forming apparatus.
[Explanation of symbols]
2 Image bearing drum
4 Damping members
18 Process cartridge
22 Developing device
27 Cleaning device
30 Cleaning blade
P Recording medium

Claims (19)

In a process cartridge in which an image bearing drum and at least one image forming means for forming a toner image on the image bearing drum are integrally assembled, a toner whose outflow start temperature measured by a flow tester method is 102 ° C. or less is used. And a damping member made of a substance having a loss tangent tan δ of 0.5 or more is provided inside the image bearing drum. A charging device for charging the image bearing drum, a developing device for visualizing an electrostatic latent image formed by exposing the charged image bearing drum as a toner image, and a toner formed on the image bearing drum The image forming apparatus includes at least one of a transfer device that transfers an image to a transfer material and a cleaning device that cleans the surface of the image bearing drum after the transfer of the toner image, and is detachably attached to the image forming apparatus main body. The process cartridge according to claim 1, wherein 3. The process cartridge according to claim 1, wherein the toner contains a metal salt of a higher fatty acid. The process cartridge according to claim 1, wherein the vibration damping member is formed in a solid cylindrical shape. The process cartridge according to claim 1, wherein the damping member is formed in a cylindrical shape. The process cartridge according to claim 1, wherein the vibration damping member is press-fitted inside the image bearing drum. 7. The process cartridge according to claim 1, wherein the vibration damping member is adhered to an inner wall surface of the image bearing drum. An image forming apparatus comprising the process cartridge according to claim 1. In an image forming apparatus for forming a toner image on a rotating image bearing drum and transferring the toner image to a transfer material to obtain a recorded image, the toner image having a flow start temperature of 102 ° C. or lower measured by a flow tester method is used. An image forming apparatus, wherein a damping member made of a substance having a loss tangent tan δ of 0.5 or more is provided inside the image bearing drum. The image forming apparatus according to claim 9, wherein the toner contains a metal salt of a higher fatty acid. The image forming apparatus according to claim 9, wherein the damping member is formed in a solid cylindrical shape. The image forming apparatus according to claim 9, wherein the vibration damping member is formed in a cylindrical shape. The image forming apparatus according to claim 9, wherein the vibration damping member is press-fitted inside the image bearing drum. The image forming apparatus according to claim 9, wherein the vibration damping member is adhered to an inner wall surface of the image bearing drum. A cleaning blade for cleaning the surface of the image bearing drum after the transfer of the toner image by pressing against the surface of the image bearing drum, and a cleaning blade for forming the toner image on the image bearing drum; 15. The image forming apparatus according to claim 9, further comprising a reverse rotation mode for rotating the image bearing drum in a direction opposite to a rotation direction. The image forming apparatus according to claim 9, wherein the image bearing drum has a protective layer on a surface. The image forming apparatus according to claim 16, wherein the protective layer contains a filler. The image forming apparatus according to claim 16, wherein the protective layer contains a charge transport material. At least the image bearing drum and a cleaning blade for cleaning the surface of the image bearing drum after the transfer of the toner image are integrally assembled to form a process cartridge, and at least one of the temperature and humidity in the process cartridge is adjusted to a predetermined value. The image forming apparatus according to any one of claims 9 to 18, further comprising an environment control unit for keeping the value at or below the value.

Images