JP2006235328A - Developing device and electrostatic recording apparatus using the same - Google Patents

Developing device and electrostatic recording apparatus using the same Download PDF

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JP2006235328A
JP2006235328A JP2005051007A JP2005051007A JP2006235328A JP 2006235328 A JP2006235328 A JP 2006235328A JP 2005051007 A JP2005051007 A JP 2005051007A JP 2005051007 A JP2005051007 A JP 2005051007A JP 2006235328 A JP2006235328 A JP 2006235328A
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developing
electrostatic image
developing roller
carrier
image carrier
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Hiroyuki Mabuchi
裕之 馬淵
Masayoshi Nakayama
政義 中山
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Ricoh Printing Systems Ltd
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Ricoh Printing Systems Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device without lowering printing density or causing carrier scattering even in the case of printing a high quality image at high printing speed, and to provide an electrostatic recording apparatus using the developing device. <P>SOLUTION: The developing device has such configuration that: magnetic powder in a two-component developer has ≤65 μm average particle size and ≥60 emu/g saturation magnetization; a developing roller placed in an upstream side in the traveling direction of an electrostatic image carrier is rotated in the opposite direction to the traveling direction of the electrostatic image carrier; a developing roller placed in a downstream side in the traveling direction of the electrostatic image carrying body is rotated in the same direction as the traveling direction of the electrostatic carrier; and the voltage applied on the developing roller in the upstream side is nearer to the charging voltage of the electrostatic image carrier than the voltage applied on the developing roller in the downstream side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は電子写真方式のプリンタや複写機等の現像装置及びそれを用いた静電気録装置に係り、特に、トナーと磁性粉体とからなる２成分現像剤を用いる現像装置及びそれを用いた静電気録装置に関する。   BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device such as an electrophotographic printer and a copying machine and an electrostatic recording device using the same, and more particularly, to a developing device using a two-component developer composed of toner and magnetic powder, and electrostatic using the same. Recording apparatus.

電子写真方式のプリンタや複写機等の静電気録装置は、感光体と称される静電像担持体を所定電位に帯電させた後、画像情報に応じて露光して静電潜像を形成し、この状態で現像装置からトナーを静電像担持体に供給することで可視像を形成し、その後、静電像担持体上の可視像を記録媒体に転写定着して印刷している。そして、前記現像装置内には、トナーと、このトナーを帯電させて搬送するキャリアと称される磁性粉体とを所定の混合比で混ぜ合わせた２成分現像剤を内臓している。   Electrostatic recording devices such as electrophotographic printers and copiers charge an electrostatic image carrier called a photoconductor to a predetermined potential and then expose it according to image information to form an electrostatic latent image. In this state, a visible image is formed by supplying toner from the developing device to the electrostatic image carrier, and then the visible image on the electrostatic image carrier is transferred and fixed onto a recording medium for printing. . In the developing device, a two-component developer in which toner and a magnetic powder called a carrier that is charged with the toner are mixed at a predetermined mixing ratio is incorporated.

上記現像装置を備えた静電記録装置においては、高画質化の要求に伴い、キャリアを小粒径化することが進められている。即ち、キャリアを小粒径化することにより、現像ローラに保持されて静電像担持体の表面を摺動する２成分現像剤の穂が緻密になるため、静電潜像をより忠実に現像することが可能となり、ざらつきのない良好な画像を得ることができるのである。   In the electrostatic recording apparatus provided with the developing device, the carrier is being made to have a smaller particle size in response to a demand for higher image quality. In other words, by reducing the particle size of the carrier, the ears of the two-component developer that is held on the developing roller and slides on the surface of the electrostatic image carrier become dense, so that the electrostatic latent image can be developed more faithfully. Therefore, it is possible to obtain a good image without roughness.

しかし、キャリアを小粒径化すると、現像ローラでのキャリアの磁気的保持力が弱くなるために、キャリア飛びが発生しやすくなると云う新たな問題が生じる。この小粒径キャリアのキャリア飛びを抑制するためには、磁気ブラシの長さを短くして磁気的保持力を磁気ブラシの先端部まで利かせる必要がある。そのためには、現像ローラと静電像担持体との対向間隔、云い代えれば現像隙間を狭くする必要がる。   However, when the carrier particle size is reduced, the magnetic holding force of the carrier at the developing roller is weakened, which causes a new problem that carrier jump is likely to occur. In order to suppress the carrier jump of the small particle size carrier, it is necessary to shorten the length of the magnetic brush and apply the magnetic holding force to the tip of the magnetic brush. For this purpose, it is necessary to narrow the gap between the developing roller and the electrostatic image carrier, in other words, the developing gap.

このような現像隙間を狭くする構成に対し、特許文献１に記載の現像装置は、現像剤の付着量を規制する現像剤規制部材（ドクタブレード）と現像ローラとの隙間、所謂ドクタギャップを狭くしている。しかしながら、ドクタギャップを狭くすると、部品の僅かな加工誤差や組立誤差が直ちにドクタギャップのばらつきとなって現れ、現像剤の搬送量を一定に調整することが困難となる。   In contrast to such a configuration in which the developing gap is narrowed, the developing device described in Patent Document 1 narrows the gap between the developer regulating member (doctor blade) that regulates the amount of developer adhering to the developing roller, the so-called doctor gap. is doing. However, if the doctor gap is narrowed, slight processing errors and assembly errors of parts immediately appear as variations in the doctor gap, making it difficult to adjust the developer transport amount to be constant.

また、現像ローラを構成するスリーブローラ上の現像剤吸着量が適正値を超える場合には、キャリアの磁気ブラシ先端部に行くにしたがい磁気的保持力が弱くなるので、現像の際、スリーブローラに磁気ブラシ先端部のキャリアを保持しきれずに、静電像担持体へキャリアが飛散して付着し易くなるほか、現像ローラ上の現像剤が静電像担持体と接触して現像を行う現像部での現像剤充填率が高くなるので、磁気ブラシによる機械的な掻き取り力が大きくなって静電像担持体上の画像にキャリアの掃き筋等が生じる。   In addition, when the developer adsorption amount on the sleeve roller constituting the developing roller exceeds an appropriate value, the magnetic holding force decreases as it goes to the tip of the magnetic brush of the carrier. The developing unit that does not hold the carrier at the tip of the magnetic brush and easily spreads and adheres to the electrostatic image carrier, and the developer on the developing roller contacts the electrostatic image carrier and develops it. Since the developer filling rate of the toner is increased, the mechanical scraping force by the magnetic brush is increased, and the image on the electrostatic image carrier has carrier scavenging stripes.

さらに、現像ローラを構成するスリーブローラ上の現像剤吸着量が適正値に満たない場合には、静電像担持体上の画像濃度が薄くなったり、不均一になったりすると云う問題があり、このために、小粒径キャリアを用いて狭い現像隙間で現像を行う静電気録装置においては、ドクタギャップの変動に対してスリーブローラ上の現像剤吸着量の変化を少なくする必要がある。   Furthermore, when the developer adsorption amount on the sleeve roller constituting the developing roller is less than an appropriate value, there is a problem that the image density on the electrostatic image bearing member becomes thin or non-uniform, For this reason, in an electrostatic recording apparatus that performs development in a narrow development gap using a small particle size carrier, it is necessary to reduce the change in the amount of developer adsorbed on the sleeve roller with respect to fluctuations in the doctor gap.

このほか、ドクタギャップを狭くすると、現像剤を通過させる際に、現像剤は圧縮されるので機械的負荷を付与され、これが長期に亘って画質を維持することを妨げるので、ドクタギャップでの現像剤への機械的負荷を小さくする必要がある。   In addition, if the doctor gap is narrowed, the developer is compressed when passing the developer, so that a mechanical load is applied, which prevents maintaining the image quality for a long time. It is necessary to reduce the mechanical load on the agent.

上記問題点を解消する手段として、特許文献２に記載の現像装置のように、現像ローラの磁石に対向する位置に現像剤規制部材（ドクタブレード）を配置する構成が存在する。このような構成とすることで、比較的広いドクタギャップでも現像剤の搬送量を少なくなるように規制することが可能となる。その結果、ドクタギャップのばらつきによる現像剤搬送量の変動を小さくでき、ドクタギャップを通過する現像剤に対する機械的負荷も小さくできるので、長期間安定して高画質の印刷を行うことができる。   As means for solving the above problems, there is a configuration in which a developer regulating member (doctor blade) is arranged at a position facing the magnet of the developing roller as in the developing device described in Patent Document 2. By adopting such a configuration, it is possible to regulate the developer conveyance amount to be reduced even with a relatively wide doctor gap. As a result, fluctuations in the developer conveyance amount due to variations in the doctor gap can be reduced, and the mechanical load on the developer passing through the doctor gap can be reduced, so that high-quality printing can be performed stably for a long period of time.

特開２０００−１１２２２６号公報JP 2000-112226 A 特開平２−７９８７８号公報Japanese Patent Laid-Open No. 2-79878

近年、印刷速度の速い装置でも高画質化の要求が高まっており、より小粒径のキャリアを使用できる現像装置の出現が望まれている。しかしながら、印刷速度を早くすると、当然ながら現像ローラの回転速度も早くする必要があるが、現像ローラの高速回転化によりキャリア飛び量が増加する問題が生じる。特に、カラー印刷を行う静電記録装置においては、印刷密度の高い印刷が行われるのでトナーの消費量が多くなるので、２成分現像剤中のトナー量が低下すると、印刷濃度の低下やキャリア飛びが発生しやすくなる。   In recent years, there has been an increasing demand for higher image quality even in an apparatus with a high printing speed, and the development of a developing apparatus that can use a carrier having a smaller particle diameter is desired. However, when the printing speed is increased, it is natural that the rotation speed of the developing roller needs to be increased, but there is a problem that the carrier jump amount increases due to the high speed rotation of the developing roller. In particular, in an electrostatic recording apparatus that performs color printing, since printing with high print density is performed, toner consumption increases. Therefore, when the toner amount in the two-component developer decreases, the print density decreases and the carrier skips. Is likely to occur.

このように、従来の現像装置においては、印刷速度が速く高画質の印刷を行うに際し、印刷濃度の低下やキャリア飛びが発生するので、その改善が望まれていた。   As described above, in the conventional developing device, when the printing speed is high and high-quality printing is performed, the print density is lowered and the carrier skip occurs, so that improvement has been desired.

本発明の目的は、印刷速度が速く高画質の印刷を行うに際しても、印刷濃度の低下やキャリア飛びの発生がない現像装置及びそれを用いた静電記録装置を提供することにある。   SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device that does not cause a decrease in print density and carrier skip even when printing with high printing speed and high image quality, and an electrostatic recording device using the same.

本発明は上記目的を達成するために、円周上に配置された複数の磁石とその外周部に回転可能に配置されたスリーブローラとを有し静電像担持体に対向して配置された少なくとも２つの現像ローラと、これら現像ローラの前記磁石に対向する位置に設置されトナーと磁性粉体とからなる２成分現像剤の前記現像ローラへの吸着量を規制する現像剤規制部材と、前記現像ローラ側に２成分現像剤を搬送する現像剤搬送手段と、この現像剤搬送手段にトナーを供給するトナー供給手段とを備え、かつ、前記現像ローラのうち、前記静電像担持体の移動方向の上流側に位置する現像ローラを静電像担持体の移動方向に対して逆方向に回転させると共に、前記静電像担持体の移動方向の下流側に位置する現像ローラを静電像担持体の移動方向に対して順方向に回転させるように構成した現像装置において、前記磁性粉体の体積平均粒径を６５μｍ以下とすると共に前記磁性粉体の飽和磁化を６０ｅｍｕ／ｇ以上とし、前記逆方向に回転する現像ローラへの印加電圧を、順方向に回転する現像ローラへの印加電圧よりも、前記静電像担持体の帯電電圧に接近する値に設定したのである。   In order to achieve the above object, the present invention has a plurality of magnets arranged on the circumference and a sleeve roller arranged rotatably on the outer periphery thereof, and is arranged to face the electrostatic image carrier. At least two developing rollers, a developer regulating member installed at a position facing the magnets of these developing rollers and regulating the amount of adsorption of the two-component developer composed of toner and magnetic powder to the developing roller; A developer conveying means for conveying the two-component developer to the developing roller side; and a toner supplying means for supplying toner to the developer conveying means; and the movement of the electrostatic image carrier among the developing rollers The developing roller located upstream in the direction is rotated in the direction opposite to the moving direction of the electrostatic image carrier, and the developing roller located downstream in the moving direction of the electrostatic image carrier is carried by the electrostatic image carrier. With respect to the direction of body movement In the developing device configured to rotate in the direction, the volume average particle size of the magnetic powder is set to 65 μm or less, the saturation magnetization of the magnetic powder is set to 60 emu / g or more, and the developing roller rotates in the reverse direction. Is set to a value closer to the charging voltage of the electrostatic image carrier than the voltage applied to the developing roller rotating in the forward direction.

以上説明したように本発明によれば、静電像担持体の移動方向の上流側に位置する現像ローラを静電像担持体の移動方向に対して逆方向に回転させると共に、前記静電像担持体の移動方向の下流側に位置する現像ローラを静電像担持体の移動方向に対して順方向に回転させるように構成し、２成分現像剤のキャリア粒径を６５μm以下とし、前記逆方向に回転する現像ローラの印加電圧を静電像担持体の帯電電圧に接近させ、さらに、現像ローラ側に２成分現像剤を搬送する現像在搬送手段に対してトナーを規定量供給するトナー供給手段とによって、印刷速度が速く高画質の印刷を行うに際しても、印刷濃度の低下を防止することができる。   As described above, according to the present invention, the developing roller positioned upstream in the moving direction of the electrostatic image carrier is rotated in the direction opposite to the moving direction of the electrostatic image carrier, and the electrostatic image is transferred. The developing roller located downstream in the moving direction of the carrier is configured to rotate in the forward direction with respect to the moving direction of the electrostatic image carrier, the carrier particle size of the two-component developer is 65 μm or less, and the reverse Toner supply for supplying a specified amount of toner to the developing and conveying means for conveying the two-component developer to the developing roller side by making the applied voltage of the developing roller rotating in the direction approach the charging voltage of the electrostatic image carrier Depending on the means, it is possible to prevent a decrease in print density even when printing is performed at a high printing speed and high image quality.

また、前記可逆回転する現像ローラと、飽和磁化が６０ｅｍｕ／ｇ以上のキャリアと、前記順方向に回転する下流側の現像ローラの印加電圧を静電像担持体の帯電電圧との電位差が大きくなるようにし、さらに、現像ローラ側に２成分現像剤を搬送する現像在搬送手段に対してトナーを規定量供給するトナー供給手段とによって、印刷速度が速く高画質の印刷を行うに際しても、キャリア飛びを防止することができる。   In addition, the potential difference between the reversibly rotating developing roller, the carrier having a saturation magnetization of 60 emu / g or more, and the applied voltage of the downstream developing roller rotating in the forward direction is different from the charging voltage of the electrostatic image carrier. Furthermore, the carrier skipping can be carried out even when high-quality printing is performed at a high printing speed by the toner supply means for supplying a specified amount of toner to the developing conveying means for conveying the two-component developer to the developing roller side. Can be prevented.

更に、特別な装置や部品を付属させる必要がないので、装置を大型化することなく、また価格を上昇させることもない。   Furthermore, since it is not necessary to attach special devices and parts, the size of the device is not increased and the price is not increased.

以下本発明による現像装置の実施の形態を図１及び図２に基づいて説明する。   Hereinafter, an embodiment of a developing device according to the present invention will be described with reference to FIGS.

現像装置１は、静電気録装置（図示せず）に設けられた感光体である静電像担持体２に対向して設けられている。そして現像装置１は、前記静電像担持体２に対向して軸支された２つの現像ローラ３，４を備えている。前記静電像担持体２の移動方向Ａの上流側に位置する現像ローラ３は、前記静電像担持体２の移動方向Ａに対して逆方向Ｂに静電像担持体２の周速の１．１〜２．０倍の周速で駆動され、前記静電像担持体２の移動方向Ａの下流側に位置する現像ローラ４は、前記静電像担持体２の移動方向Ａに対して順方向Ｃに静電像担持体２の周速の１．１〜２．０倍の周速で駆動されている。これら現像ローラ３，４は、夫々円周上に回転方向に倣ってＳ１極，Ｎ１極，Ｓ２極，Ｎ２極，Ｎ３極の順に着磁した磁石５と、その外周部に回転可能に支持されたスリーブローラ６とを備えている。前記磁石５のＮ１極は前記静電像担持体２に対向させて位置させており、このＮ１極は対向するスリーブローラ６表面の飽和磁束密度が０．０７テスラの磁力を有するように着磁されている。一方、残る磁極は、対向するスリーブローラ６表面の飽和磁束密度が０．０４〜０．０６テスラとなるように着磁されている。尚、本実施の形態においては、２つの現像ローラ３，４を備えた現像装置１であるが、例えば現像ローラ３の上流側及び／又は現像ローラ４の下流側に複数本の現像ローラを備えてもよい。   The developing device 1 is provided to face an electrostatic image carrier 2 that is a photosensitive member provided in an electrostatic recording device (not shown). The developing device 1 includes two developing rollers 3 and 4 that are pivotally supported to face the electrostatic image carrier 2. The developing roller 3 located on the upstream side in the moving direction A of the electrostatic image carrier 2 has a circumferential speed of the electrostatic image carrier 2 in a direction B opposite to the moving direction A of the electrostatic image carrier 2. The developing roller 4 that is driven at a peripheral speed of 1.1 to 2.0 times and is located on the downstream side in the moving direction A of the electrostatic image carrier 2 is in relation to the moving direction A of the electrostatic image carrier 2. In the forward direction C, the electrostatic image carrier 2 is driven at a peripheral speed 1.1 to 2.0 times the peripheral speed. These developing rollers 3 and 4 are rotatably supported on the outer periphery of the magnet 5 magnetized in the order of S1, N1, S2, N2, and N3 in the order of rotation on the circumference. Sleeve roller 6. The N1 pole of the magnet 5 is positioned to face the electrostatic image carrier 2, and the N1 pole is magnetized so that the saturation magnetic flux density on the surface of the facing sleeve roller 6 has a magnetic force of 0.07 Tesla. Has been. On the other hand, the remaining magnetic poles are magnetized so that the saturation magnetic flux density on the surface of the facing sleeve roller 6 is 0.04 to 0.06 Tesla. In the present embodiment, the developing device 1 includes two developing rollers 3 and 4. For example, a plurality of developing rollers are provided on the upstream side of the developing roller 3 and / or the downstream side of the developing roller 4. May be.

前記現像ローラ３，４の間には、現像ローラ３，４と所定間隔Ｇ１，Ｇ２をもって対向するドクタブレード７（現像剤規制部材）が配置されており、現像ローラ３，４に吸着される２成分現像剤８の吸着量を規制している。   Between the developing rollers 3 and 4, a doctor blade 7 (developer regulating member) facing the developing rollers 3 and 4 with a predetermined gap G 1 and G 2 is disposed and is adsorbed by the developing rollers 3 and 2. The adsorption amount of the component developer 8 is regulated.

また、静電像担持体２の移動方向最下流側の現像ローラ４に接近した位置には、２成分現像剤８を規定量保持し、そこから現像ローラ３，４側に２成分現像剤８を汲み上げる汲み上げパドル９が設けられている。この汲み上げパドル９は、前記現像ローラ３，４と平行に軸支されており、矢印Ｆ方向に回転駆動されることで周辺に保持された２成分現像剤８を現像ローラ３，４側に汲み上げるものである。ところで、２成分現像剤８は、トナーとこのトナーを帯電させて搬送するキャリアと称される磁性粉体とを所定の混合比で汲み上げパドル９部で撹拌されて混ぜ合わせたものであり、トナーは２成分現像剤８の全重量の２〜１０％の重量比で混合されている。   A predetermined amount of the two-component developer 8 is held at a position close to the developing roller 4 on the most downstream side in the moving direction of the electrostatic image carrier 2, and the two-component developer 8 is then moved to the developing rollers 3 and 4 side. A pumping paddle 9 is provided for pumping up the water. This pump-up paddle 9 is supported in parallel with the developing rollers 3 and 4 and is driven to rotate in the direction of arrow F to pump up the two-component developer 8 held in the vicinity to the developing rollers 3 and 4 side. Is. By the way, the two-component developer 8 is obtained by pumping toner and a magnetic powder called a carrier that is charged with the toner and transporting the toner at a predetermined mixing ratio, and stirring and mixing them in 9 parts of the paddle. Are mixed in a weight ratio of 2 to 10% of the total weight of the two-component developer 8.

前記２成分現像剤８を構成するキャリアは回収されるが、トナーは、現像ローラ３，４を介して静電像担持体２へ転写されて消費されるので重量比が減少する。このトナー量の減少を補充するために、汲み上げパドル９側へ規定量のトナー８Ｔを供給するトナー供給装置１０が設けられている。そして、トナー供給装置１０と汲み上げパドル９との間には、供給された規定量のトナー８Ｔを汲み上げパドル９に搬送してキャリアと混合させるための搬送部材（現像剤搬送手段）１１，１２が設置されている。これら搬送部材１１，１２は、前記現像ローラ３，４の軸方向と同方向に延在する互いに逆回転するスクリュー構成をしており、搬送部材１１は矢印D方向に回転することでトナー８Tを紙面奥側から手前側に搬送し、搬送部材１２は矢印Ｅ方向に回転することでトナー８Tを紙面手前側から奥側に搬送して汲み上げパドル９側のキャリアと撹拌混合している。これによってトナー８Tは、キャリアと摩擦して−１０〜−３０μｃ／ｇに帯電される。このように所定のトナー重量比及び帯電量に調整された２成分現像剤８は、前記現像ローラ３，４の近傍の汲み上げパドル９に導かれる。   The carrier constituting the two-component developer 8 is collected, but the toner is transferred to the electrostatic image carrier 2 through the developing rollers 3 and 4 and consumed, so the weight ratio decreases. In order to replenish this decrease in the toner amount, a toner supply device 10 for supplying a specified amount of toner 8T to the pumping paddle 9 is provided. Further, between the toner supply device 10 and the pumping paddle 9, there are transport members (developer transporting means) 11 and 12 for transporting the supplied specified amount of toner 8T to the pumping paddle 9 and mixing it with the carrier. is set up. These conveying members 11 and 12 have a screw structure that extends in the same direction as the axial direction of the developing rollers 3 and 4 and rotates in the opposite directions, and the conveying member 11 rotates in the direction of arrow D, thereby supplying the toner 8T. The toner is transported from the back side to the near side, and the transport member 12 rotates in the direction of arrow E, so that the toner 8T is transported from the near side to the far side and is mixed with the carrier on the pumping paddle 9 side. As a result, the toner 8T is rubbed with the carrier and charged to −10 to −30 μc / g. The two-component developer 8 adjusted to a predetermined toner weight ratio and charge amount as described above is guided to the pumping paddle 9 in the vicinity of the developing rollers 3 and 4.

ところで、２成分現像剤８のキャリアの粒径は、図３に示すように、印刷画像のざらつき感に関係し、キャリアを小粒径にするほど、静電像担持体２の表面を摺動する２成分現像剤８の穂が緻密になって静電潜像をより忠実に現像できる。キャリアの小粒径化によるざらつき感の改善効果は、６５μｍ以下の粒径で大きく、６５μｍ以上の粒径では改善効果が小さくなる。したがって、本実施の形態で用いるキャリア粒径は、６５μｍ以下の粒径のキャリアを用いている。   Incidentally, the particle size of the carrier of the two-component developer 8 is related to the rough feeling of the printed image as shown in FIG. 3, and the surface of the electrostatic image carrier 2 slides as the carrier becomes smaller in particle size. Thus, the ears of the two-component developer 8 become dense, and the electrostatic latent image can be developed more faithfully. The effect of improving the rough feeling by reducing the particle size of the carrier is large when the particle size is 65 μm or less, and the improvement effect is small when the particle size is 65 μm or more. Therefore, the carrier particle size used in this embodiment is a carrier having a particle size of 65 μm or less.

また、互いに逆方向に回転する２本の現像ローラ３，４に、同一の電圧を印加した際のキャリア粒径とキャリア飛びの関係を見ると、図４に示す関係になる。尚、図４中、破線Ｌａは飽和磁化が約６０ｅｍｕ／ｇのキャリアを示し、実線Ｌｂは飽和磁化が約８０６０ｅｍｕ／ｇのキャリアを示している。この線図から明らかなように、キャリアを小粒径にするほど、キャリア飛びが多くなる傾向にある。しかし、飽和磁化が高いキャリア（実線Ｌｂ）は、小粒径にしてもキャリア飛びが抑えられている。これは、飽和磁化が高いキャリアのほうが、現像部での磁気的保持力が強くなるので、キャリア飛びが少なくなるものと考えられる。ただ、磁気的保持力が強くなると、現像の際に画像を擦る力が強くなるので、キャリアによる掃き筋が目立つと云う新たな問題が生じるので、即、飽和磁化が約８０６０ｅｍｕ／ｇのキャリアを用いることはできない。   4 shows the relationship between the carrier particle diameter and the carrier jump when the same voltage is applied to the two developing rollers 3 and 4 rotating in opposite directions. In FIG. 4, a broken line La indicates a carrier having a saturation magnetization of about 60 emu / g, and a solid line Lb indicates a carrier having a saturation magnetization of about 8060 emu / g. As is apparent from this diagram, the carrier skip tends to increase as the carrier has a smaller particle diameter. However, even if the carrier having high saturation magnetization (solid line Lb) has a small particle size, carrier jump is suppressed. This is presumably because the carrier with higher saturation magnetization has a stronger magnetic holding force at the developing portion, so that the carrier jump is reduced. However, if the magnetic holding force is increased, the force for rubbing the image during development is increased, which causes a new problem that the scavenging lines by the carrier are conspicuous. Therefore, a carrier having a saturation magnetization of about 8060 emu / g is immediately applied. Cannot be used.

そこで、互いに逆方向に回転する２本の現像ローラ３，４を用いた現像装置１で、飽和磁化の小さい小粒径のキャリアを用いた場合の画像へのキャリアの付着状態を検討したところ、特に問題となったのは、先に現像を行う、云い代えれば静電像担持体２の移動方向の上流側となる現像ローラ３において、２成分現像剤８が画像を現像した後に背景電位部である静電像担持体２へ接触する状況での付着であることが確認された。これは、先に現像を行う現像ローラ３において、トナー濃度の低下した２成分現像剤、云い代えればキャリア表面のトナーが少なくなってキャリアが静電像担持体２へ直接接触し易くなった状態で、現像ロータ３とトナーを付着させない背景部電位（静電像担持体２の帯電電位）とで形成される強い電場に曝されるために、キャリアが静電像担持体２に付着するものと予想される。   Therefore, when the developing device 1 using the two developing rollers 3 and 4 rotating in the opposite directions to each other and examining the carrier adhesion state on the image when using a carrier having a small particle diameter with small saturation magnetization, A particular problem is that the development is performed first, in other words, in the developing roller 3 on the upstream side in the moving direction of the electrostatic image carrier 2, the background potential portion after the two-component developer 8 develops the image. It was confirmed that the adhesion was in the state of contact with the electrostatic image carrier 2. This is because, in the developing roller 3 that performs the development first, the two-component developer having a lowered toner concentration, in other words, the amount of toner on the surface of the carrier is reduced, and the carrier is easily in direct contact with the electrostatic image carrier 2. The carrier adheres to the electrostatic image carrier 2 because it is exposed to a strong electric field formed by the developing rotor 3 and the background portion potential (charging potential of the electrostatic image carrier 2) that does not cause the toner to adhere. It is expected to be.

以上から、互いに逆方向に回転する２本の現像ローラ３，４を用いた現像装置１においては、先に現像を行う現像ローラ３の電位と静電像担持体２の帯電電位との電位差を小さくすることで、飽和磁化の低い（図４の実線Ｌｂ）小粒径のキャリアを使用しても、キャリア飛びを少なくすることができる。   From the above, in the developing device 1 using the two developing rollers 3 and 4 rotating in opposite directions, the potential difference between the potential of the developing roller 3 that performs the development first and the charging potential of the electrostatic image carrier 2 is calculated. By making it small, even if a carrier having a small particle diameter with a low saturation magnetization (solid line Lb in FIG. 4) is used, carrier jump can be reduced.

ところで、現像ローラ３の電位を静電像担持体２の帯電電位に接近させると、通常被りが増加して画質の低下を招く。しかし、本願発明者らの検討の結果、互いに逆方向に回転する２本の現像ローラ３，４を近接配置した現像装置１において、先に現像を行う現像ローラ３が静電像担持体２に接触した２成分現像剤８を静電像担持体２の移動方向とは逆方向に回転させることと、現像ローラ３の電位を後に現像を行う現像ローラ４よりも静電像担持体２の帯電電位に接近させることで、先に現像を行う現像ローラ３による静電像担持体２へのキャリア付着を低減でき、かつ、後に現像を行う現像ローラ４で静電像担持体２へ付着した被りトナーを掃き取ることができ、結果として、飽和磁化が低く小粒径のキャリアを用いても、キャリア付着量を低減して静電像担持体２へのトナーの被りを抑制できることが確認された。   By the way, when the potential of the developing roller 3 is brought close to the charging potential of the electrostatic image carrier 2, the normal covering increases and the image quality is degraded. However, as a result of the study by the inventors of the present application, in the developing device 1 in which the two developing rollers 3 and 4 rotating in opposite directions are arranged close to each other, the developing roller 3 that performs the development first becomes the electrostatic image carrier 2. The contacted two-component developer 8 is rotated in the direction opposite to the moving direction of the electrostatic image carrier 2, and the electrostatic image carrier 2 is charged more than the developing roller 4 that develops the potential of the developing roller 3 later. By approaching the potential, carrier adhesion to the electrostatic image carrier 2 by the developing roller 3 that performs development first can be reduced, and the covering that adheres to the electrostatic image carrier 2 by the development roller 4 that performs development later. As a result, it was confirmed that even when a carrier having a low saturation magnetization and a small particle diameter is used, it is possible to reduce the carrier adhesion amount and suppress the toner covering on the electrostatic image carrier 2. .

上記２成分現像剤８を用いて静電気録装置（図示せず）を作動させると、現像装置１の現像ローラ４の近傍にある２成分現像剤８は、現像ローラ４のマグネット５の磁極Ｎ３によってスリーブローラ６の表面に吸着され、スリーブローラ６の回転に伴ってドクタブレード７に対向した磁極Ｓ１まで搬送される。搬送された２成分現像剤８は、磁極Ｎ１における現像部の容積に対して２０〜４０％の容積比となるように、ドクタブレード７とスリーブローラ６との間隔Ｇ２で、搬送量が規制される。このとき、ドクタブレード７での規制により余剰となった２成分現像剤８は、現像ローラ３のマグネット５の磁極Ｓ１によってスリーブ６の表面に吸着され、スリーブ６の回転に伴って、ドクタブレード７とスリーブローラ６との間隔Ｇ１で規制された後、現像ローラ３の現像部である磁極Ｎ１に導かれる。   When an electrostatic recording device (not shown) is operated using the two-component developer 8, the two-component developer 8 in the vicinity of the developing roller 4 of the developing device 1 is moved by the magnetic pole N 3 of the magnet 5 of the developing roller 4. It is attracted to the surface of the sleeve roller 6 and is conveyed to the magnetic pole S1 facing the doctor blade 7 as the sleeve roller 6 rotates. The transport amount of the transported two-component developer 8 is regulated by the gap G2 between the doctor blade 7 and the sleeve roller 6 so that the volume ratio is 20 to 40% with respect to the volume of the developing portion in the magnetic pole N1. The At this time, the surplus two-component developer 8 due to restriction by the doctor blade 7 is attracted to the surface of the sleeve 6 by the magnetic pole S1 of the magnet 5 of the developing roller 3, and the doctor blade 7 is rotated as the sleeve 6 rotates. After being regulated by a gap G 1 between the sleeve roller 6 and the sleeve roller 6, it is guided to a magnetic pole N 1 that is a developing portion of the developing roller 3.

現像ローラ３，４の現像部で２成分現像剤８は磁極Ｎ１によって穂立ちをし、静電像担持体２の表面と摺動する。現像ローラ３，４には、上述のように、異なる電圧設定で現像バイアス電圧が印加される。因みに、本実施の形態においては、現像ローラ３には−４００Ｖ、現像ローラ４には−３００Ｖの電圧を印加している。   In the developing portions of the developing rollers 3 and 4, the two-component developer 8 rises by the magnetic pole N 1 and slides on the surface of the electrostatic image carrier 2. As described above, a developing bias voltage is applied to the developing rollers 3 and 4 with different voltage settings. Incidentally, in the present embodiment, a voltage of −400 V is applied to the developing roller 3, and a voltage of −300 V is applied to the developing roller 4.

その後、現像ローラ３，４に吸着された２成分現像剤８のトナーが静電像担持体２の表面の静電潜像に転写され、トナーによる可視画像が形成される。   Thereafter, the toner of the two-component developer 8 adsorbed by the developing rollers 3 and 4 is transferred to the electrostatic latent image on the surface of the electrostatic image carrier 2 to form a visible image with the toner.

現像部である静電像担持体２と現像ローラ３，４との対向部を通過した２成分現像剤８は、夫々磁極Ｎ２，Ｎ３間の反発磁界によって現像ローラ３，４から剥離され、再び汲み上げパドル９に戻って同様な動作を繰り返す。   The two-component developer 8 that has passed through the facing portion between the electrostatic image carrier 2 and the developing rollers 3 and 4 as the developing portion is peeled off from the developing rollers 3 and 4 by the repulsive magnetic field between the magnetic poles N2 and N3, respectively. Returning to the pumping paddle 9, the same operation is repeated.

尚、静電像担持体２の表面に形成された可視画像は、図示しない転写部によって記録用紙（図示せず）に転写印刷された後、図示しない定着部で記録用紙上に定着される。   The visible image formed on the surface of the electrostatic image carrier 2 is transferred and printed on a recording paper (not shown) by a transfer unit (not shown), and then fixed on the recording paper by a fixing unit (not shown).

以上説明した本発明による実施形態の現像装置１と、比較例として同方向に回転する複数本の現像ローラの上流側現像ローラで現像に用いた２成分現像剤を下流側現像ローラに受け渡して用いる現像装置とを比較実験をしたところ、本発明による実施形態の現像装置の方が約３０％高い現像性能を得ることができた。   As described above, the two-component developer used for development by the developing device 1 according to the embodiment of the present invention and the upstream developing roller of a plurality of developing rollers rotating in the same direction as a comparative example is transferred to the downstream developing roller and used. As a result of a comparative experiment with the developing device, the developing device according to the embodiment of the present invention was able to obtain a developing performance that was approximately 30% higher.

また、本実施の形態によれば、静電像担持体２に対して２本の現像ローラ３，４が互いに逆方向に回転して摺動するので、摺動方向に起因する画像の方向性（先端欠け又は後端欠け）がない良好な画像を得ることができた。   Further, according to the present embodiment, since the two developing rollers 3 and 4 rotate and slide in the opposite directions with respect to the electrostatic image carrier 2, the directionality of the image caused by the sliding direction. A good image with no (tip missing or trailing edge missing) could be obtained.

さらに、現像ローラ３に印加される電圧を、静電像担持体２の帯電電圧、即ち、現像を行わない背景電圧に接近させたことにより、現像でトナーを消費したキャリアが画像後端部を通過する際の背景電位差が小さく、しかもキャリアに作用する静電気力が弱くなるためにキャリア付着の発生を抑制することができた。   Further, by bringing the voltage applied to the developing roller 3 close to the charging voltage of the electrostatic image carrier 2, that is, the background voltage at which development is not performed, the carrier that has consumed toner during development causes the trailing edge of the image to move. Since the background potential difference at the time of passing is small and the electrostatic force acting on the carrier is weakened, the occurrence of carrier adhesion can be suppressed.

さらにまた、現像ローラ４に印加される電圧を、現像ローラ３に印加される電圧よりも多きくしているので、現像ローラ３での現像時に発生したトナー被りを清掃することができ、現像ローラ４を通過した後の画像は２本の現像ローラに同一の電圧を印加した場合の画像と同等にすることができた。   Furthermore, since the voltage applied to the developing roller 4 is higher than the voltage applied to the developing roller 3, the toner covering generated during the development with the developing roller 3 can be cleaned, and the developing roller 4 The image after passing through can be made equivalent to the image when the same voltage is applied to the two developing rollers.

ところで、現像速度が３００mm／ｓ程度では、現像ローラが１本の現像装置でも所望の現像性能を得ることができると共に、画像の方向性も許容レベルの画像を得ることができる。しかし、３００mm／ｓを超える現像速度では、現像ローラが１本では所望の現像性能を得ることは難しくなる。そこで、３００mm／ｓを超える現像速度で現像ローラが１本でも所望の現像性能を得るには、静電像担持体の移動速度に対して現像ローラの周速の比率を高くすることが考えられるが、周速の比率を高くすると、２成分現像剤の穂による静電像担持体表面への擦りが強くなって良好な画像を得ることが困難になる。しかし、本発明による実施の形態によれば、互いに逆方向に回転する２本の現像ローラ３，４を用いることで、３００mm／ｓを超える現像速度でも良好な画質を得ることができた。   By the way, when the developing speed is about 300 mm / s, it is possible to obtain a desired developing performance even with a developing device having one developing roller and to obtain an image with an acceptable level of image orientation. However, at a developing speed exceeding 300 mm / s, it is difficult to obtain a desired developing performance with a single developing roller. Therefore, in order to obtain a desired developing performance even with one developing roller at a developing speed exceeding 300 mm / s, it is conceivable to increase the ratio of the peripheral speed of the developing roller to the moving speed of the electrostatic image carrier. However, when the ratio of the peripheral speed is increased, rubbing of the two-component developer ears on the surface of the electrostatic image bearing member becomes strong, and it becomes difficult to obtain a good image. However, according to the embodiment of the present invention, by using the two developing rollers 3 and 4 rotating in opposite directions, a good image quality can be obtained even at a developing speed exceeding 300 mm / s.

また、現像速度が速いと、現像時のトナー消費が早くなるので、印刷開始時点で高画質印刷が行えても、連続印刷しているとトナー濃度が低下して印刷濃度の低下やキャリア飛びが発生することがある。特に、フルカラー機のように高密度の印刷を多頁連続して印刷を行う装置では不都合が発生しやすい。これは、印刷によるトナー消費量に対し、現像剤搬送手段から現像ローラに供給されるトナー量が少なかったり、不均一になったりすることが原因である。   In addition, if the development speed is fast, toner consumption during development is accelerated, so even if high-quality printing can be performed at the start of printing, if continuous printing is performed, the toner density decreases, causing a decrease in print density and carrier skipping. May occur. In particular, an inconvenience is likely to occur in an apparatus that continuously prints multiple pages at a high density, such as a full-color machine. This is because the amount of toner supplied from the developer conveying means to the developing roller is small or non-uniform with respect to the amount of toner consumed by printing.

しかし、本実施の形態のように、搬送部材１１，１２で軸方向に２成分現像剤８を撹拌した後、現像剤搬送手段９によって現像ローラ３，４に供給するようにした現像装置１では、印刷速度（静電像担持体の移動速度）をＶ（cm／ｓ）、前記現像ローラで２成分現像剤が搬送されるローラ幅方向寸法をＬ（cm）、前記静電像担持体のトナー量をＭ（ｇ／cm２）としたとき、現像剤搬送手段９で搬送される２成分現像剤８に混入されるトナー８Ｔの軸方向の流量Ｗ（ｇ／ｃ）を、
１０・Ｖ・Ｌ・Ｍ＜Ｗ
とすること、つまり、印刷時に単位時間当たりに消費されるトナー量の１０倍以上のトナーを供給することで解決できることが判明した。 However, in the developing apparatus 1 in which the two-component developer 8 is stirred in the axial direction by the conveying members 11 and 12 and then supplied to the developing rollers 3 and 4 by the developer conveying means 9 as in the present embodiment. , The printing speed (moving speed of the electrostatic image carrier) is V (cm / s), the dimension in the roller width direction in which the two-component developer is conveyed by the developing roller is L (cm), and the electrostatic image carrier is When the toner amount is M (g / cm 2 ), the axial flow rate W (g / c) of the toner 8T mixed into the two-component developer 8 conveyed by the developer conveying means 9 is
10 ・ V ・ L ・ M <W
In other words, it has been found that the problem can be solved by supplying toner that is 10 times or more the amount of toner consumed per unit time during printing.

ただ、トナーの供給量が単位時間当たりのトナー消費量の４０倍を超えると、搬送するトナーの帯電量が適正範囲から外れてしまってトナー被りなどの画質上の不具合が発生したり、２成分現像剤の劣化が早まって長期的に画質を維持することが困難となったりするので、トナー８Ｔの現像剤搬送手段９による軸方向の流量Ｗ（ｇ／ｃ）は、
１０・Ｖ・Ｌ・Ｍ＜W＜４０・Ｖ・Ｌ・Ｍ
の範囲が好ましいことがわかった。 However, if the amount of toner supplied exceeds 40 times the amount of toner consumed per unit time, the charge amount of the toner to be transported will deviate from the proper range, causing problems in image quality such as toner covering, Since the deterioration of the developer is accelerated and it is difficult to maintain the image quality in the long term, the axial flow rate W (g / c) of the toner 8T by the developer conveying means 9 is
10 ・ V ・ L ・ M <W <40 ・ V ・ L ・ M
The range of was found to be preferable.

尚、本実施の形態において、印刷速度が７００mm／ｓの記録装置でも、高画質の印刷が行え、キャリア飛びなどの不具合もなく、長期的に安定した画像が得られることを確認している。   In this embodiment, it has been confirmed that even a recording apparatus having a printing speed of 700 mm / s can perform high-quality printing and can obtain a stable image for a long period of time without defects such as carrier skipping.

また、前記２成分現像剤のキャリアとして、マグネタイト、Ｍｎ−Ｍｇフェライト、Ｍｇフェライト、Ｃｕ−Ｚｎフェライト等のキャリア心材の表面を絶縁性樹脂により均一な厚さに被覆し、表面の絶縁性樹脂にトナーとの適正な摩擦帯電特性を持たせたものも使用することができる。   Further, as the carrier of the two-component developer, the surface of the carrier core material such as magnetite, Mn-Mg ferrite, Mg ferrite, Cu-Zn ferrite or the like is coated with an insulating resin to a uniform thickness, and the surface insulating resin is used. Those having appropriate triboelectric charging characteristics with the toner can also be used.

本発明による現像装置の一実施の形態を示す概略縦断面図。1 is a schematic longitudinal sectional view showing an embodiment of a developing device according to the present invention. 図１の現像ローラ近傍の拡大図。FIG. 2 is an enlarged view of the vicinity of a developing roller in FIG. 1. キャリアの平均粒径と印刷物のざらつき感との関係を示す線図。The diagram which shows the relationship between the average particle diameter of a carrier, and the rough feeling of printed matter. キャリアの平均粒径とキャリア飛びとの関係を示す線図。The diagram which shows the relationship between the average particle diameter of a carrier, and carrier jump.

符号の説明Explanation of symbols

１…印刷装置、２…静電像担持体、３，４…現像ローラ、５…磁石、６…スリーブローラ、７…ドクタブレード、８…２成分現像剤、８Ｔ…トナー、９…汲み上げパドル、１０…トナー供給装置、１１，１２…搬送部材。   DESCRIPTION OF SYMBOLS 1 ... Printing apparatus, 2 ... Electrostatic image carrier, 3, 4 ... Developing roller, 5 ... Magnet, 6 ... Sleeve roller, 7 ... Doctor blade, 8 ... Two-component developer, 8T ... Toner, 9 ... Pumping paddle, 10: Toner supply device, 11, 12 ... Conveying member.

Claims (4)

円周上に配置された磁石とその外周部に回転可能に配置されたスリーブローラとを有し静電像担持体に対向して配置された少なくとも２つの現像ローラと、これら現像ローラの前記磁石に対向する位置に設置されトナーと磁性粉体とからなる２成分現像剤の前記現像ローラへの吸着量を規制する現像剤規制部材と、前記現像ローラ側に２成分現像剤を搬送する現像剤搬送手段と、この現像剤搬送手段に規定量のトナーを供給するトナー供給手段とを備え、かつ、前記現像ローラのうち、前記静電像担持体の移動方向の上流側に位置する現像ローラを静電像担持体の移動方向に対して逆方向に回転させると共に、前記静電像担持体の移動方向の下流側に位置する現像ローラを静電像担持体の移動方向に対して順方向に回転させるように構成した現像装置において、前記磁性粉体の平均粒径を６５μｍ以下とすると共に前記磁性粉体の飽和磁化を６０ｅｍｕ／ｇ以上とし、前記逆方向に回転する現像ローラへの印加電圧を、順方向に回転する現像ローラへの印加電圧よりも、前記静電像担持体の帯電電圧に接近する値にしたことを特徴とする現像装置。   At least two developing rollers having a magnet disposed on the circumference and a sleeve roller rotatably disposed on the outer periphery thereof, and disposed opposite to the electrostatic image carrier, and the magnets of these developing rollers And a developer regulating member that regulates the amount of adsorption of the two-component developer made of toner and magnetic powder to the developing roller, and a developer that conveys the two-component developer to the developing roller side. A developing roller located on the upstream side in the moving direction of the electrostatic image bearing member, of the developing roller, and a toner supplying unit that supplies a predetermined amount of toner to the developer conveying unit; The developer roller is rotated in the opposite direction to the moving direction of the electrostatic image carrier, and the developing roller located downstream in the moving direction of the electrostatic image carrier is moved in the forward direction with respect to the moving direction of the electrostatic image carrier. Configured to rotate In the image apparatus, the average particle size of the magnetic powder is 65 μm or less, the saturation magnetization of the magnetic powder is 60 emu / g or more, and the applied voltage to the developing roller rotating in the reverse direction is rotated in the forward direction. The developing device is characterized in that it is set to a value closer to the charging voltage of the electrostatic image carrier than the voltage applied to the developing roller. 前記現像ローラの少なくとも一つの磁石の最大磁束密度を、０．０７テスラ以上としたことを特徴とする請求項１記載の現像装置。   2. The developing device according to claim 1, wherein the maximum magnetic flux density of at least one magnet of the developing roller is 0.07 Tesla or more. 前記静電像担持体の移動速度をＶ（cm／ｓ）、前記現像ローラで２成分現像剤が搬送されるローラ幅方向寸法をＬ（cm）、前記静電像担持体のトナー量をＭ（ｇ／cm２）としたとき、前記現像剤搬送手段でのトナー流量Ｗ（g／s）を、
１０・Ｖ・Ｌ・Ｍ＜W＜４０・Ｖ・Ｌ・Ｍ
としたことを特徴とする請求項１又は２記載の現像装置。 The moving speed of the electrostatic image carrier is V (cm / s), the dimension in the width direction of the roller where the two-component developer is conveyed by the developing roller is L (cm), and the toner amount of the electrostatic image carrier is M. (G / cm 2 ), the toner flow rate W (g / s) in the developer conveying means is
10 ・ V ・ L ・ M <W <40 ・ V ・ L ・ M
The developing device according to claim 1 or 2, wherein 請求項１，２又は３記載の現像装置を用いたことを特徴とする静電気録装置。   An electrostatic recording apparatus using the developing device according to claim 1, 2 or 3.
JP2005051007A 2005-02-25 2005-02-25 Developing device and electrostatic recording apparatus using the same Pending JP2006235328A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010008934A (en) * 2008-06-30 2010-01-14 Sharp Corp Developing device and image forming apparatus
CN102854777A (en) * 2011-06-29 2013-01-02 株式会社理光 Developing device, image forming apparatus, and process cartridge
EP3043212A1 (en) 2015-01-09 2016-07-13 Ricoh Company, Ltd. Developing device, process cartridge, and image forming apparatus including same

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010008934A (en) * 2008-06-30 2010-01-14 Sharp Corp Developing device and image forming apparatus
JP4613228B2 (en) * 2008-06-30 2011-01-12 シャープ株式会社 Developing device and image forming apparatus
CN102854777A (en) * 2011-06-29 2013-01-02 株式会社理光 Developing device, image forming apparatus, and process cartridge
US8787804B2 (en) 2011-06-29 2014-07-22 Ricoh Company, Ltd. Developing device including a developer container with toner particles and magnetic carrier particles (Rz=0.5−3.0 gm) and a developer bearing member (Rz=10−30 gm), and an image forming apparatus and process cartridge containing the same
CN102854777B (en) * 2011-06-29 2015-03-25 株式会社理光 Developing device, image forming apparatus, and process cartridge
EP3043212A1 (en) 2015-01-09 2016-07-13 Ricoh Company, Ltd. Developing device, process cartridge, and image forming apparatus including same
US9529297B2 (en) 2015-01-09 2016-12-27 Ricoh Company, Ltd. Developing device, process cartridge, and image forming apparatus including same

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