JP2015148727A - image forming apparatus - Google Patents
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Abstract
Description
本発明は、複写機、レーザプリンタ等の画像形成装置に関するものである。 The present invention relates to an image forming apparatus such as a copying machine or a laser printer.
従来、例えば電子写真方式の画像形成装置として、感光体に形成されたトナー像を中間転写体に１次転写した後に、紙などの転写材に２次転写する中間転写方式を採用したものがある。中間転写方式を採用した画像形成装置において、電源数の削減によるコストダウンや装置本体の小型化を目的として、２次転写部から中間転写体の周方向に電流を流して１次転写と２次転写の両方を行うものが提案されている。特許文献１には、中間転写体として周方向に電流を流すことが可能な導電性を有する無端状のベルトを用い、このベルトの張架ローラをツェナーダイオードやバリスタなどを介して接地し、２次転写部材に電圧を印加してベルトに電流を流す構成が開示されている。 2. Description of the Related Art Conventionally, for example, an electrophotographic image forming apparatus employs an intermediate transfer method in which a toner image formed on a photosensitive member is primarily transferred to an intermediate transfer member and then secondarily transferred to a transfer material such as paper. . In an image forming apparatus that employs an intermediate transfer method, primary transfer and secondary transfer are performed by passing a current from the secondary transfer portion in the circumferential direction of the intermediate transfer body in order to reduce costs by reducing the number of power supplies and to reduce the size of the apparatus body. Some have been proposed to do both transcriptions. In Patent Document 1, a conductive endless belt capable of flowing a current in the circumferential direction is used as an intermediate transfer member, and a tension roller of the belt is grounded via a Zener diode, a varistor, or the like. A configuration is disclosed in which a voltage is applied to the next transfer member to pass a current through the belt.
中間転写体を用いた画像形成装置では、トナー像を中間転写体から転写材に２次転写した時に、中間転写体上に一部のトナーが残ることがある。このトナーを残トナーと呼ぶ。この残トナーは中間転写体が一周した時に、転写材に転写されて残像のような画像不良を発生させる恐れがある。この画像不良を防ぐために、中間転写体を清掃して残トナーを除去する必要がある。特許文献２では、中間転写体の清掃方法として帯電クリーニング方式が提案されている。この方式では、像担持体上のトナーが中間転写体に一次転写されるのと同時に、帯電部材によって帯電された残トナーが中間転写体から像担持体へ逆転写される。この方式により、中間転写体を清掃するために連続印刷を停止する期間を設けることなく、中間転写体から残トナーを除去することが可能である。 In an image forming apparatus using an intermediate transfer member, when a toner image is secondarily transferred from the intermediate transfer member to a transfer material, some toner may remain on the intermediate transfer member. This toner is called residual toner. The residual toner may be transferred to a transfer material when the intermediate transfer member makes a round and may cause an image defect such as a residual image. In order to prevent this image defect, it is necessary to clean the intermediate transfer member and remove the residual toner. Patent Document 2 proposes a charging cleaning method as a method for cleaning the intermediate transfer member. In this method, the toner on the image carrier is primarily transferred to the intermediate transfer member, and at the same time, the residual toner charged by the charging member is reversely transferred from the intermediate transfer member to the image carrier. With this method, it is possible to remove the residual toner from the intermediate transfer member without providing a period for stopping continuous printing in order to clean the intermediate transfer member.
しかしながら、特許文献１に開示されているような構成では、２次転写部材に印加される電圧によって１次転写部に生成される電位の極性が制御される。そのため、１次転写部と２次転写部とに生成する電位の極性をそれぞれ独立して制御することができない。そのため、特許文献１に開示されているような構成で帯電クリーニング方式を採用する場合は、残トナーを各画像形成部に振り分けて回収することが難しい。 However, in the configuration as disclosed in Patent Document 1, the polarity of the potential generated in the primary transfer portion is controlled by the voltage applied to the secondary transfer member. Therefore, the polarity of the potential generated at the primary transfer portion and the secondary transfer portion cannot be controlled independently. For this reason, when the electrification cleaning method is adopted with the configuration disclosed in Patent Document 1, it is difficult to distribute and collect the remaining toner to each image forming unit.
したがって、本発明の目的は、１次転写部と２次転写部とに生成する電位の極性を独立して制御できない構成において、残トナーの振り分け回収が可能な画像形成装置を提供することである。 Accordingly, an object of the present invention is to provide an image forming apparatus capable of sorting and collecting residual toner in a configuration in which the polarity of the potential generated at the primary transfer portion and the secondary transfer portion cannot be controlled independently. .
上記課題を解決するため本発明は、静電潜像が形成される感光体と、前記感光体に形成された感光体を現像する現像手段と、前記感光体上からトナーを除去する清掃手段と、を各々が備えた複数の画像形成部と、各画像形成部の前記感光体に露光する露光手段と、回転可能で無端状であり、前記複数の画像形成部の各感光体と形成する１次転写部で前記感光体からトナー像が１次転写される導電性の中間転写ベルトと、前記中間転写ベルトと２次転写部を形成し前記２次転写部で前記中間転写ベルトから転写材にトナー像を２次転写する２次転写手段と、転写材に転写されず前記中間転写ベルト上に残留した残トナーを帯電する帯電手段と、を有し、前記帯電手段によって帯電された残トナーを前記複数の画像形成部の各感光体に前記中間転写ベルトから移動させることが可能であり、前記２次転写手段から前記中間転写ベルトに供給される電流によって前記中間転写ベルトの周方向にわたって電位が変更される画像形成装置において、転写材の後端が前記２次転写部を通過した後の前記中間転写ベルトの電位は、前記感光体の露光部と非露光部の表面電位の間の電位であることを特徴とする。 In order to solve the above problems, the present invention provides a photoconductor on which an electrostatic latent image is formed, a developing unit that develops the photoconductor formed on the photoconductor, and a cleaning unit that removes toner from the photoconductor. , A plurality of image forming units each having a plurality of image forming units, an exposure unit that exposes the photoconductors of the image forming units, and a rotatable and endless one that is formed with the photoconductors of the plurality of image forming units. A conductive intermediate transfer belt on which a toner image is primarily transferred from the photosensitive member at a secondary transfer portion, and a secondary transfer portion and the intermediate transfer belt are formed, and the intermediate transfer belt is transferred from the intermediate transfer belt to a transfer material at the secondary transfer portion. A secondary transfer unit that secondary-transfers the toner image; and a charging unit that charges the residual toner that is not transferred to the transfer material and remains on the intermediate transfer belt. The residual toner charged by the charging unit The intermediate transfer is applied to each photoconductor of the plurality of image forming units. In the image forming apparatus that can be moved from the belt, and the potential is changed in the circumferential direction of the intermediate transfer belt by the current supplied from the secondary transfer unit to the intermediate transfer belt, the trailing edge of the transfer material is The potential of the intermediate transfer belt after passing through the secondary transfer portion is a potential between the surface potential of the exposed portion and the non-exposed portion of the photoreceptor.
本発明によれば、感光体の露光部と非露光部の表面電位の間の電位に中間転写体の電位を維持することで、１次転写部と２次転写部とに生成する電位の極性を独立制御できない構成であっても、残トナーの振り分け回収が可能である。 According to the present invention, the polarity of the potential generated at the primary transfer portion and the secondary transfer portion is maintained by maintaining the potential of the intermediate transfer member at a potential between the surface potential of the exposed portion and the non-exposed portion of the photoreceptor. Even in a configuration in which the toner cannot be independently controlled, the remaining toner can be sorted and collected.
以下、図面を参照して、本発明の好適な実施形態を例示的に詳しく説明する。ただし、以下の実施形態に記載されている構成部品の寸法、材質、形状、それらの相対配置などは、本発明が適用される装置の構成や各種条件により適宜変更されるべきものである。従って、特に特定的な記載がない限りは、本発明の範囲をそれらのみに限定する趣旨のものではない。 Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.
（実施形態１）
（画像形成装置の構成と動作）
画像形成装置の動作全体について説明する。図１は、本実施形態１の画像形成装置を示す概略構成図である。４つの画像形成部１ａ、１ｂ、１ｃ、１ｄが中間転写体の移動方向に沿って配置されている。複数の画像形成部１ａ、１ｂ、１ｃ、１ｄは、それぞれ、イエロー色、マゼンタ色、シアン色、ブラック色のトナー像を形成する。本実施形態では、４つの画像形成部１ａ、１ｂ、１ｃ、１ｄの構成および動作は使用するトナーの色と動作タイミングが異なることを除いて同じである。以下では、各色用の要素であることを示す添え字ａ、ｂ、ｃ、ｄは省略して一括で説明する。画像形成部１の像担持体２、帯電手段３、現像手段４、像担持体清掃手段６は色毎に一体として交換可能なカートリッジとして構成されている。
(Embodiment 1)
(Configuration and operation of image forming apparatus)
The overall operation of the image forming apparatus will be described. FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to the first embodiment. Four image forming units 1a, 1b, 1c, and 1d are arranged along the moving direction of the intermediate transfer member. The plurality of image forming units 1a, 1b, 1c, and 1d form yellow, magenta, cyan, and black toner images, respectively. In the present embodiment, the configuration and operation of the four image forming units 1a, 1b, 1c, and 1d are the same except that the color of toner used and the operation timing are different. Hereinafter, the subscripts a, b, c, and d indicating elements for each color will be omitted and will be described collectively. The image carrier 2, the charging unit 3, the developing unit 4, and the image carrier cleaning unit 6 of the image forming unit 1 are configured as a cartridge that can be replaced as a unit for each color.
像担持体２は直径３０ｍｍのアルミ円筒の表面に正孔阻止層と電荷発生層を塗工した上に、２０μｍの電荷移動層を塗工した感光体２である。また、アルミ円筒は接地している。感光体２は、ドラム状の感光ドラム２であり、表面速度２５０ｍｍ／ｓｅｃで時計方向へ回転させる。感光ドラム２に接して帯電手段３として帯電ローラを配置している。帯電ローラ３の金属軸には−１１００Ｖの電圧を印加している。この帯電ローラ３を接触させて感光ドラム２を回転させると、帯電ローラと感光ドラム２の間の放電により感光ドラム２が帯電される。トレック社製の表面電位計Ｍｏｄｅｌ３４４で感光ドラム２の表面電位を測定すると、−５００Ｖ程度であった。 The image carrier 2 is a photoreceptor 2 in which a hole blocking layer and a charge generation layer are coated on the surface of an aluminum cylinder having a diameter of 30 mm, and a charge transfer layer of 20 μm is coated. The aluminum cylinder is grounded. The photosensitive member 2 is a drum-shaped photosensitive drum 2 and is rotated clockwise at a surface speed of 250 mm / sec. A charging roller is disposed as the charging unit 3 in contact with the photosensitive drum 2. A voltage of −1100 V is applied to the metal shaft of the charging roller 3. When the photosensitive drum 2 is rotated by contacting the charging roller 3, the photosensitive drum 2 is charged by the discharge between the charging roller and the photosensitive drum 2. When the surface potential of the photosensitive drum 2 was measured with a surface potential meter Model 344 manufactured by Trek, it was about -500V.
帯電した感光ドラム２に、レーザとポリゴンミラーとレンズからなる露光手段７から放射されるレーザを照射する。レーザは回転するポリゴンミラーにより、感光ドラム２の表面を像担持体の軸方向に２１５ｍｍ走査する。レーザが１走査する間に感光ドラム２が１画素分回転することで感光ドラム２の表面を隙間なく走査する。このとき、画像データに基づいてレーザの光量を制御することで、感光ドラム２上に静電潜像が形成される。最大光量を受けた部分の表面電位は−１００Ｖ程度に低下する。 The charged photosensitive drum 2 is irradiated with a laser emitted from an exposure means 7 comprising a laser, a polygon mirror and a lens. The laser scans the surface of the photosensitive drum 2 by 215 mm in the axial direction of the image carrier by a rotating polygon mirror. The surface of the photosensitive drum 2 is scanned without a gap by rotating the photosensitive drum 2 by one pixel while the laser scans one time. At this time, an electrostatic latent image is formed on the photosensitive drum 2 by controlling the amount of laser light based on the image data. The surface potential of the portion that has received the maximum light amount decreases to about -100V.
現像手段４は現像剤担持体１６に単位質量あたりのトナーの帯電量は−４０μＣ／ｇ程度で、単位面積当たりのトナー量は、０．４ｍｇ／ｃｍ２程度の均一なトナー層を形成していている。ここで、単位質量あたりのトナーの帯電量と単位面積当たりのトナー量は、現像剤担持体１６上のトナーを内部にフィルタをもつ吸引式ファラデーゲージで吸引捕集して、ファラデーゲージで測定された電荷と、トナーの捕集面積、フィルタの質量増加から求めた。つまり、単位質量あたりのトナーの帯電量は、ファラデーゲージで測定された電荷をフィルタの質量増加で除して求め、単位面積当たりのトナー量はフィルタの質量増加を捕集面積で除して求めた。また、現像手段４は停止時には現像剤担持体１６を感光ドラム２から離間させているが、画像形成時は現像剤担持体１６を感光ドラム２当接させる機構を備えている。 The developing unit 4 forms a uniform toner layer on the developer carrier 16 with a toner charge amount per unit mass of about −40 μC / g and a toner amount per unit area of about 0.4 mg / cm 2. Yes. Here, the charge amount of the toner per unit mass and the toner amount per unit area are measured by the Faraday gauge after the toner on the developer carrier 16 is sucked and collected by a suction type Faraday gauge having a filter inside. The charge was obtained from the toner charge collection area and the filter mass increase. In other words, the toner charge amount per unit mass is obtained by dividing the charge measured by the Faraday gauge by the filter mass increase, and the toner amount per unit area is obtained by dividing the filter mass increase by the collection area. It was. In addition, the developing unit 4 separates the developer carrier 16 from the photosensitive drum 2 when stopped, but includes a mechanism for bringing the developer carrier 16 into contact with the photosensitive drum 2 during image formation.
トナーは、懸濁重合法で製造した樹脂粒子である。帯電の正規極性は負で、体積平均粒径が６．５μｍ程度である。表面性を改質するために、２０ｎｍ程度の酸化ケイ素粒子をトナー重量の１．５％程度の量を表面に均一に付着させている。ここで、トナーの平均粒径はベックマン・コールター株式会社製のレーザ回折式粒度分布測定器ＬＳ−２３０で測定した体積平均粒径である。 The toner is resin particles produced by a suspension polymerization method. The normal polarity of charging is negative and the volume average particle diameter is about 6.5 μm. In order to modify the surface property, silicon oxide particles of about 20 nm are uniformly attached to the surface in an amount of about 1.5% of the toner weight. Here, the average particle diameter of the toner is a volume average particle diameter measured with a laser diffraction particle size distribution analyzer LS-230 manufactured by Beckman Coulter, Inc.
感光ドラム２は現像手段４である−３００Ｖの電圧の印加された現像装置４の現像剤担持体１６に接触する。静電潜像のうちレーザの最大光量を受けた部分の表面電位は−１００Ｖでトナーが像担持体に引き付けられる方向に電界が生じ、一方、レーザの露光を受けなかった部分の表面電位は−５００Ｖでトナーが感光ドラム２と反発する方向に電界が生じる。この静電気力により感光ドラム２の静電潜像の露光部のみにトナーが付着することで、静電潜像が現像されて、トナー像になる。 The photosensitive drum 2 comes into contact with the developer carrying member 16 of the developing device 4 to which a voltage of −300 V is applied as the developing means 4. The surface potential of the portion of the electrostatic latent image that has received the maximum amount of laser light is −100 V, and an electric field is generated in the direction in which the toner is attracted to the image carrier, while the surface potential of the portion that has not been exposed to the laser is − An electric field is generated in the direction in which the toner repels the photosensitive drum 2 at 500V. By this electrostatic force, the toner adheres only to the exposed portion of the electrostatic latent image on the photosensitive drum 2, whereby the electrostatic latent image is developed and becomes a toner image.
次に、感光ドラム２上（感光体上）のトナー像は、回転可能な中間転写体８と接触する。中間転写体８は厚み１００μｍのポリフェニレンサルファイド（ＰＰＳ）樹脂にカーボンブラックを分散させた無端状のベルトで、抵抗は１１０ｋΩである。表面（像担持体に接する面）には、厚み０．５〜３μｍで高抵抗のアクリル樹脂の表層を設けている。以下、中間転写ベルト８とする。 Next, the toner image on the photosensitive drum 2 (on the photosensitive member) comes into contact with the rotatable intermediate transfer member 8. The intermediate transfer member 8 is an endless belt in which carbon black is dispersed in a polyphenylene sulfide (PPS) resin having a thickness of 100 μm, and the resistance is 110 kΩ. A surface layer of acrylic resin having a thickness of 0.5 to 3 μm and a high resistance is provided on the surface (the surface in contact with the image carrier). Hereinafter, the intermediate transfer belt 8 is used.
中間転写ベルト８の抵抗は株式会社三菱化学アナリテック製の抵抗率計ハイレスタＵＰにハイレスタＵＰ専用プローブＵＲＳプローブ接続して印加電圧１００Ｖで測定しようと試みたが、抵抗が低くレンジ外であった。そのために、本実施形態で使用した画像形成装置を用いて図２のように測定した。 The resistance of the intermediate transfer belt 8 was measured by connecting a Hiresta UP dedicated probe URS probe to a resistivity meter Hiresta UP manufactured by Mitsubishi Chemical Analytech Co., Ltd., but the resistance was low and out of range. Therefore, measurement was performed as shown in FIG. 2 using the image forming apparatus used in this embodiment.
図２（ａ）、（ｂ）は、本実施形態に用いられる中間転写ベルト８の抵抗を測定するための方法を説明するための概略図である。図２（ａ）では、２次転写ローラ１５の代わりに２次転写ローラ１５と同径の金属２次転写ローラ１５Ｍを配置し、画像形成部１ｄに感光ドラム２ｄの代わりに、電荷移動層などを塗工していないアルミ円筒２ｄＭを配置した。金属ローラ１５Ｍに高圧電源１９を接続して、アルミ円筒は電流計Ａを経由して接地した。そして、高圧電源１９で１００Ｖを印加したときに流れる電流を測定した。このときの印加電圧１００Ｖを測定された電流で割った値を中間転写ベルト８の抵抗とする。 2A and 2B are schematic diagrams for explaining a method for measuring the resistance of the intermediate transfer belt 8 used in the present embodiment. In FIG. 2A, a metal secondary transfer roller 15M having the same diameter as the secondary transfer roller 15 is arranged instead of the secondary transfer roller 15, and a charge transfer layer or the like is used instead of the photosensitive drum 2d in the image forming unit 1d. An aluminum cylinder 2dM that was not coated was placed. A high voltage power source 19 was connected to the metal roller 15M, and the aluminum cylinder was grounded via an ammeter A. And the electric current which flows when 100V is applied with the high voltage power supply 19 was measured. A value obtained by dividing the applied voltage 100 V at this time by the measured current is defined as the resistance of the intermediate transfer belt 8.
中間転写ベルト８の表面の移動方向に対してアルミ円筒２ｄＭから２次転写部２ｄＭまでの距離は３７０ｍｍ、反対側は４２０ｍｍであった。この方法で測定した中間転写ベルト８の抵抗（以下、周方向の抵抗）は、１．１×１０５Ωである。また、図２（ｂ）のようにアルミ円筒２ｄＭを設置する位置を変えて、中間転写ベルト８の抵抗を測定した場合も抵抗の値はほぼ同じ結果になった。中間転写ベルト８の表面の移動方向に対してアルミ円筒２ｄＭから２次転写ローラ１５までの距離は７１０ｍｍ、反対側は８０ｍｍであった。本実施形態では、周方向の抵抗が１．０×１０５Ω〜１．０×１０９Ωのものを導電性ベルトとしている。 The distance from the aluminum cylinder 2dM to the secondary transfer portion 2dM with respect to the moving direction of the surface of the intermediate transfer belt 8 was 370 mm, and the opposite side was 420 mm. The resistance (hereinafter referred to as circumferential resistance) of the intermediate transfer belt 8 measured by this method is 1.1 × 10 5 Ω. Further, when the resistance of the intermediate transfer belt 8 was measured by changing the position where the aluminum cylinder 2dM was installed as shown in FIG. 2B, the resistance value was almost the same. The distance from the aluminum cylinder 2dM to the secondary transfer roller 15 with respect to the moving direction of the surface of the intermediate transfer belt 8 was 710 mm, and the opposite side was 80 mm. In this embodiment, a conductive belt having a circumferential resistance of 1.0 × 10 5 Ω to 1.0 × 10 9 Ω is used.
図１に示すように、この導電性ベルトである中間転写ベルト８は駆動ローラ１１と２次転写対向ローラ１２とテンションローラ１３の３本のローラ（３本合わせて、「張架ローラ」と称する）で、内周面が張架されている。駆動ローラ１１の表層は高摩擦で体積抵抗１０５Ωｃｍ以下の導電性ゴム層を設けている。駆動ローラ１１は駆動モータ（不図示）により駆動されて、中間転写ベルト８を感光ドラム２と同じ表面速度２５０ｍｍ／ｓｅｃで反時計方向に回転させる。２次転写対向ローラ１２は、２次転写部である２次転写ニップ部を形成するために表面にゴム層を設けた。表層のゴム層は体積抵抗１０５Ωｃｍ以下の導電性のものを用いた。２次転写対向ローラ１２は、中間転写ベルト８に従動して回転する。テンションローラ１３は、金属ローラからなり、総圧約６０Ｎの張力を中間転写ベルト８に付与し、中間転写ベルト８に従動して回転する。駆動ローラ１１、２次転写対向ローラ１２、テンションローラ１３は一括して、直列に接続した降伏電圧３００Ｖのツェナーダイオード１４ａと逆方向に降伏電圧２００Ｖのツェナーダイオード１４ｂを介して接地している。ここでツェナーダイオード１４ａとツェナーダイオード１４ｂは、それぞれ、各張架ローラを所定電位に維持するための電圧維持素子である。 As shown in FIG. 1, the intermediate transfer belt 8, which is a conductive belt, is composed of three rollers of a driving roller 11, a secondary transfer counter roller 12, and a tension roller 13 (the three are collectively called “stretching roller”). ), The inner surface is stretched. The surface layer of the drive roller 11 is provided with a conductive rubber layer having a high friction and a volume resistance of 10 5 Ωcm or less. The drive roller 11 is driven by a drive motor (not shown) to rotate the intermediate transfer belt 8 counterclockwise at the same surface speed as the photosensitive drum 2 at 250 mm / sec. The secondary transfer counter roller 12 was provided with a rubber layer on the surface in order to form a secondary transfer nip portion as a secondary transfer portion. As the surface rubber layer, a conductive layer having a volume resistance of 10 5 Ωcm or less was used. The secondary transfer counter roller 12 rotates following the intermediate transfer belt 8. The tension roller 13 is made of a metal roller, applies a tension of a total pressure of about 60 N to the intermediate transfer belt 8, and rotates following the intermediate transfer belt 8. The driving roller 11, the secondary transfer counter roller 12 and the tension roller 13 are collectively grounded via a Zener diode 14b having a breakdown voltage 200V in the opposite direction to the Zener diode 14a having a breakdown voltage 300V connected in series. Here, the Zener diode 14a and the Zener diode 14b are voltage maintaining elements for maintaining each tension roller at a predetermined potential.
押圧ローラ５は金属芯金に弾性層を被覆している。高分子計器株式会社製のアスカーゴム硬度計Ｃ型で１ｋｇ重（９．８Ｎ）の加重で測定したゴム硬度が３０度で、体積抵抗は１０５〜１０９Ωｃｍである。押圧ローラ５は感光ドラム２に対向して中間転写ベルト８に総圧約９．８Ｎで当接して１次転写部を形成している。押圧ローラ５は、中間転写ベルト８の回転に伴い従動して回転する。押圧ローラ５は電気的にフロートである。 The pressure roller 5 has a metal core covered with an elastic layer. The rubber hardness measured by a weight of 1 kg weight (9.8 N) with an Asker rubber hardness meter C type manufactured by Kobunshi Keiki Co., Ltd. is 30 degrees, and the volume resistance is 10 5 to 10 9 Ωcm. The pressure roller 5 faces the photosensitive drum 2 and abuts against the intermediate transfer belt 8 with a total pressure of about 9.8 N to form a primary transfer portion. The pressure roller 5 is driven to rotate as the intermediate transfer belt 8 rotates. The pressing roller 5 is electrically floated.
２次転写ローラは２次転写対向ローラ１２に対向して中間転写ベルト８に総圧約３９．２Ｎで当接して２次転写ニップ部を形成している。２次転写ローラ１５は金属芯金にＥＰＤＭ発泡体からなる弾性層を被覆している。高分子計器株式会社製のアスカーゴム硬度計Ｃ型で１ｋｇ重（９．８Ｎ）の加重で測定したゴム硬度が３０度で、体積抵抗率が１０７〜１０９Ωｃｍである。 The secondary transfer roller faces the secondary transfer counter roller 12 and contacts the intermediate transfer belt 8 with a total pressure of about 39.2 N to form a secondary transfer nip portion. The secondary transfer roller 15 has a metal core covered with an elastic layer made of EPDM foam. The rubber hardness is 30 degrees and the volume resistivity is 10 7 to 10 9 Ωcm, measured by a weight of 1 kg weight (9.8 N) using an Asker rubber hardness meter C type manufactured by Kobunshi Keiki Co., Ltd.
２次転写用電源１９から２次転写ローラ１５に２０００Ｖの電圧を印加すると、２次転写ローラ１５から２次転写ニップ部の接触を介して中間転写ベルト８の周方向に電流が流れる。また、同時に２次転写対向ローラ１２を介してツェナーダイオード１４ａに電流が流れ、所定以上の電流が流れることで接続された各張架ローラを所定電位以上に維持する。それぞれの１次転写部でトレック社製の表面電位計Ｍｏｄｅｌ３４４で中間転写ベルト８の表面電位を測定したところ、いずれの位置においても表面電位は２００Ｖであった。 When a voltage of 2000 V is applied from the secondary transfer power source 19 to the secondary transfer roller 15, a current flows in the circumferential direction of the intermediate transfer belt 8 from the secondary transfer roller 15 through contact with the secondary transfer nip portion. At the same time, a current flows through the Zener diode 14a through the secondary transfer counter roller 12, and the connected tension rollers are maintained at a predetermined potential or higher by flowing a current of a predetermined level or higher. When the surface potential of the intermediate transfer belt 8 was measured with a surface potential meter Model 344 manufactured by Trek Co. at each primary transfer portion, the surface potential was 200 V at any position.
１次転写部では感光ドラム２の表面電位（非露光部は−５００Ｖ、露光部−１００Ｖ）と中間転写ベルト８の表面電位（２００Ｖ）の差により電界が形成される。電界の向きは感光ドラム２の露光部と非露光部にかかわらず、トナーの正規極性（本実施形態では負極性）に帯電しているトナーを感光ドラム２から中間転写ベルト８に転写する方向である。この電界により感光ドラム２上のトナー像は中間転写ベルト８に移動する。中間転写ベルト８が駆動ローラ１１により表面速度２５０ｍｍ／ｓｅｃで反時計方向に回転することで、４つの画像形成部１ａ、１ｂ、１ｃ、１ｄで順次イエロー色、マゼンタ色、シアン色、ブラック色のトナー像が転写される。その結果、中間転写ベルト８上にカラー画像のトナー像が形成される。１次転写されずに感光ドラム２に残った１次転写残トナーは、感光ドラム２に当接したゴムブレードからなる清掃部材６で感光ドラム２上から除去されて回収トナー容器１０に回収される。 In the primary transfer portion, an electric field is formed by the difference between the surface potential of the photosensitive drum 2 (-500 V for the non-exposed portion and -100 V for the exposed portion) and the surface potential (200 V) of the intermediate transfer belt 8. The direction of the electric field is a direction in which the toner charged to the normal polarity (negative polarity in this embodiment) of the toner is transferred from the photosensitive drum 2 to the intermediate transfer belt 8 regardless of the exposed portion and the non-exposed portion of the photosensitive drum 2. is there. The toner image on the photosensitive drum 2 moves to the intermediate transfer belt 8 by this electric field. The intermediate transfer belt 8 is rotated counterclockwise by the driving roller 11 at a surface speed of 250 mm / sec, so that yellow, magenta, cyan, and black colors are sequentially generated in the four image forming units 1a, 1b, 1c, and 1d. The toner image is transferred. As a result, a color toner image is formed on the intermediate transfer belt 8. The primary transfer residual toner remaining on the photosensitive drum 2 without being subjected to the primary transfer is removed from the photosensitive drum 2 by the cleaning member 6 formed of a rubber blade in contact with the photosensitive drum 2 and collected in the collected toner container 10. .
中間転写ベルト８上のトナー像は中間転写ベルト８の回転で運ばれて２次転写部に移動する。２次転写部では中間転写ベルト８の表面電位（２００Ｖ）と２次転写ローラに印加された電圧（２０００Ｖ）との差により、トナー像が中間転写ベルト８から２次転写ローラ１５に向かう電界が形成される。 The toner image on the intermediate transfer belt 8 is carried by the rotation of the intermediate transfer belt 8 and moves to the secondary transfer portion. In the secondary transfer portion, the electric field of the toner image from the intermediate transfer belt 8 to the secondary transfer roller 15 is caused by the difference between the surface potential (200 V) of the intermediate transfer belt 8 and the voltage (2000 V) applied to the secondary transfer roller. It is formed.
転写材格納カセット（不図示）に収納された転写材Ｐは、中間転写ベルト８上のトナー像に対して印刷位置が合うタイミングで２次転写ニップ部を通過する。転写材Ｐが２次転写ニップ部を通過する時に、中間転写ベルト８上のトナー像は２次転写ニップ部に形成された電界により転写材Ｐに移動する。ここで転写材として上質紙（坪量７５ｇ／ｍ２）を用いた。 The transfer material P stored in a transfer material storage cassette (not shown) passes through the secondary transfer nip portion at a timing when the printing position matches the toner image on the intermediate transfer belt 8. When the transfer material P passes through the secondary transfer nip portion, the toner image on the intermediate transfer belt 8 moves to the transfer material P by an electric field formed in the secondary transfer nip portion. Here, high-quality paper (basis weight 75 g / m 2) was used as a transfer material.
２次転写されずに中間転写ベルト８上に残留した残トナーは中間転写ベルト８付着したまま清掃手段７５に向かう。図３を用いて、清掃手段について説明する。清掃手段７５は、帯電ブラシ７１と、それに電圧を供給する電源７２からなる。帯電ブラシ７１は１０６〜１０９Ωｃｍの導電性を有するナイロン製の繊維が略密となるように構成されたブラシである。帯電ブラシ７１の先端位置は、中間転写ベルト８の表面に対して１ｍｍ進入させて配置されて帯電ニップ部を形成している。帯電ブラシ７１の長手方向（中間転写ベルト８の表面の移動方向と直交する方向）の幅は、同方向の画像形成可能領域の幅と略同じである。 Residual toner remaining on the intermediate transfer belt 8 without being subjected to the secondary transfer is directed to the cleaning means 75 with the intermediate transfer belt 8 attached thereto. The cleaning means will be described with reference to FIG. The cleaning unit 75 includes a charging brush 71 and a power source 72 that supplies a voltage to the charging brush 71. The charging brush 71 is a brush configured such that nylon fibers having conductivity of 10 6 to 10 9 Ωcm are substantially dense. The front end position of the charging brush 71 is arranged 1 mm into the surface of the intermediate transfer belt 8 to form a charging nip portion. The width of the charging brush 71 in the longitudinal direction (the direction perpendicular to the moving direction of the surface of the intermediate transfer belt 8) is substantially the same as the width of the image formable area in the same direction.
電源７２は帯電ブラシ７１から接地に向かう方向を正として１５μＡの定電流制御で、帯電ブラシ７１に電圧を印加している。このとき帯電ニップ部では帯電ブラシ７１と中間転写ベルト８との間で放電が生じている。 The power source 72 applies a voltage to the charging brush 71 with a constant current control of 15 μA with the direction from the charging brush 71 toward the ground being positive. At this time, discharge occurs between the charging brush 71 and the intermediate transfer belt 8 in the charging nip portion.
残トナーは帯電ニップ部を通過すると、放電によりトナーの正規極性に対して逆極性（本実施形態では、正極性）に帯電される。正極性に帯電された残トナーは中間転写ベルト８の回転で運ばれて画像形成部１ａに向かって移動する。画像形成部１ａの１次転写部において、負極性に帯電した感光ドラム２上のトナーが中間転写ベルト８に転写すると同時に、正極性に帯電された残トナーが中間転写ベルト８から感光ドラム２へと逆転写される。これによって、中間転写ベルト８上の残トナーが除去される。感光ドラム２ａに逆転写された残トナーは１次転写残トナーと一緒に清掃部材６で感光ドラム２上から除去されて回収トナー容器１０に回収される。 When the remaining toner passes through the charging nip portion, it is charged to a reverse polarity (positive polarity in this embodiment) with respect to the normal polarity of the toner by discharge. The residual toner charged to the positive polarity is conveyed by the rotation of the intermediate transfer belt 8 and moves toward the image forming unit 1a. In the primary transfer portion of the image forming portion 1a, toner on the photosensitive drum 2 charged to negative polarity is transferred to the intermediate transfer belt 8, and at the same time, residual toner charged to positive polarity is transferred from the intermediate transfer belt 8 to the photosensitive drum 2. And reverse transcribed. As a result, the residual toner on the intermediate transfer belt 8 is removed. The residual toner reversely transferred to the photosensitive drum 2 a is removed from the photosensitive drum 2 together with the primary transfer residual toner by the cleaning member 6 and collected in the collected toner container 10.
転写材Ｐ上のトナー像は定着ローラ１７ａと加圧ローラ１７ｂを有する定着装置１７で加熱及び加圧されて転写材Ｐ上に定着される。画像が形成された転写材Ｐは、排紙トレイ（不図示）へ排出されて画像形成工程が終了する。 The toner image on the transfer material P is heated and pressed by a fixing device 17 having a fixing roller 17a and a pressure roller 17b to be fixed on the transfer material P. The transfer material P on which the image is formed is discharged to a paper discharge tray (not shown), and the image forming process ends.
（振り分け回収動作）
次に、残トナーを振り分け回収する動作について詳細に説明する。図４は、Ａ４サイズの転写材に４枚連続印刷した後に、残トナーを画像形成部１ｂ、１ｃ、１ｄに振り分けて回収する動作を表すタイミングチャートである。この説明においては、残トナーを画像形成部１ｂ、１ｃ、１ｄに振り分けて回収したが、残トナーをどの画像形成部に振り分けて回収するかは自由に決めることが出来る。それぞれの画像形成部での残トナーの回収量を決めるために、回収トナー容器１０の回収トナー量を検知した結果や、現像手段４に残ったトナー量を検知した結果を利用することも可能である。
(Distribution collection operation)
Next, the operation for distributing and collecting the remaining toner will be described in detail. FIG. 4 is a timing chart showing an operation of distributing and collecting the remaining toner to the image forming units 1b, 1c, and 1d after continuously printing four sheets on an A4 size transfer material. In this description, the residual toner is distributed and collected to the image forming units 1b, 1c, and 1d, but it can be freely determined to which image forming unit the residual toner is distributed and collected. In order to determine the amount of remaining toner collected in each image forming unit, the result of detecting the amount of toner collected in the collected toner container 10 or the result of detecting the amount of toner remaining in the developing unit 4 can be used. is there.
このタイミングチャートにおいて、横軸は時間で、それぞれの画像形成部１の１次転写部での感光ドラム２の表面電位と、２次転写ローラ１５の印加電圧と、帯電ブラシ７１の印加電圧と、中間転写体８の表面電位を記載している。 In this timing chart, the horizontal axis represents time, the surface potential of the photosensitive drum 2 at the primary transfer unit of each image forming unit 1, the applied voltage of the secondary transfer roller 15, the applied voltage of the charging brush 71, The surface potential of the intermediate transfer member 8 is described.
ここで、感光ドラム２の電位は画像形成タイミングには−１００Ｖになると表示しているが、これは画像形成のタイミングを表すためで、実際には出力する画像に合わせて−１００Ｖ（露光部）と−５００Ｖ（非露光部）の間の値をとる。また、それぞれの画像形成部１の１次転写部と、２次転写ニップ部、帯電ニップ部をトナー像が通過するするタイミングを記載している。トナー像の通過タイミングの表示において、ブロックはトナー像を表し、右上４５度に向かうハッチングされたブロックは正極性に帯電させた残トナー、右下４５度に向かうハッチングされたブロックは負極性に帯電させた残トナーを表す。また、番号は印刷ページ番号を表す。 Here, the potential of the photosensitive drum 2 is displayed as -100V at the image forming timing, but this is for representing the image forming timing, and actually, it is -100V (exposure section) in accordance with the output image. And a value between −500 V (non-exposed area). In addition, the timing at which the toner image passes through the primary transfer portion, the secondary transfer nip portion, and the charging nip portion of each image forming portion 1 is described. In the toner image passage timing display, the block represents the toner image, the block hatched toward the upper right 45 degrees is the remaining toner charged to the positive polarity, and the block hatched toward the lower right 45 degrees is charged to the negative polarity Represents the remaining toner. The number represents a print page number.
初めに、画像形成部１ａ、１ｂ、１ｃ、１ｄの像担持体を−５００Ｖに帯電するとともに、現像手段４を感光ドラム２に当接させて画像形成の準備を行う。そして、２次転写用電源１９から２次転写ローラに２０００Ｖを印加し、帯電ブラシ７１に電源７２から接地に向かう方向を正として１５μＡの定電流制御で電圧を印加する。中間転写ベルト８はツェナーダイオード１４ａで接地されているので、２次転写ローラ１５と帯電ブラシ７１からの電流供給で中間転写ベルト８の表面電位が２００Ｖになる。 First, the image bearing members of the image forming units 1a, 1b, 1c, and 1d are charged to −500 V, and the developing unit 4 is brought into contact with the photosensitive drum 2 to prepare for image formation. Then, 2000 V is applied from the secondary transfer power source 19 to the secondary transfer roller, and a voltage is applied to the charging brush 71 with a constant current control of 15 μA with the direction from the power source 72 to the ground being positive. Since the intermediate transfer belt 8 is grounded by the Zener diode 14a, the surface potential of the intermediate transfer belt 8 becomes 200V by supplying current from the secondary transfer roller 15 and the charging brush 71.
続いて、それぞれの画像形成部１ａ、１ｂ、１ｃ、１ｄで順次画像を形成していく。１枚目の１次転写が終了すると引き続き２枚目の画像が中間転写ベルト８に転写されはじめる。画像形成部１ａで３枚目の１次転写が行われている頃に中間転写ベルト８が一周する。すると、帯電ブラシ７１で正極性に帯電された１ページ目の残トナーが画像形成部１ａに到着する。このとき、中間転写ベルト８と感光ドラム２の電位は図５（ａ）のようになっている。そのために、画像形成部１ａで３枚目の負極性に帯電したトナー像が感光ドラム２ａから中間転写ベルト８に１次転写されると同時に、１ページ目の正極性に帯電された残トナーが中間転写ベルト８から感光ドラム２ａに逆転写される。 Subsequently, images are sequentially formed by the respective image forming units 1a, 1b, 1c, and 1d. When the first primary transfer is completed, the second image starts to be transferred to the intermediate transfer belt 8. The intermediate transfer belt 8 makes a round when the third primary transfer is performed in the image forming unit 1a. Then, the remaining toner on the first page charged to the positive polarity by the charging brush 71 arrives at the image forming unit 1a. At this time, the potentials of the intermediate transfer belt 8 and the photosensitive drum 2 are as shown in FIG. For this reason, the third negatively charged toner image is primarily transferred from the photosensitive drum 2a to the intermediate transfer belt 8 in the image forming unit 1a, and at the same time, the remaining toner charged to the positive polarity of the first page is transferred. Reverse transfer is performed from the intermediate transfer belt 8 to the photosensitive drum 2a.
逆転写された感光ドラム２ａ上の残トナーは清掃部材６により除去されて回収トナー容器１０に回収される。以後、画像形成部１ｄの１次転写が終了するまで同様に画像形成が行われる。この間、残トナーは回収トナー容器１０ａに回収される。画像形成部１ｄの１次転写が終了すると、現像手段４の現像剤担持体１６を感光ドラム２から離間する。 The reversely transferred residual toner on the photosensitive drum 2 a is removed by the cleaning member 6 and collected in the collected toner container 10. Thereafter, image formation is similarly performed until the primary transfer of the image forming unit 1d is completed. During this time, the remaining toner is collected in the collected toner container 10a. When the primary transfer of the image forming unit 1d is completed, the developer carrier 16 of the developing unit 4 is separated from the photosensitive drum 2.
ここで２次転写を行いながら、電源７２の設定電流を１５μＡから−１０μＡに変更する。すると、中間転写ベルト８の電位が２００Ｖから０Ｖに変化する。変更後は、帯電ニップ部を通過した残トナーが負極性に帯電する。変更するタイミングは、後に行う２次転写用電源１９の設定電圧の変更時に画像形成部１ｄの転写ニップを通過する中間転写ベルト８上の点が、その直前に帯電ニップ部を通過する時である。このとき、中間転写ベルト８と感光ドラム２の電位は図５（ｂ）のようになっている。そのために中間転写ベルト８上の残トナーは、画像形成部の１次転写部を通過することが可能である。 Here, the set current of the power source 72 is changed from 15 μA to −10 μA while performing the secondary transfer. Then, the potential of the intermediate transfer belt 8 changes from 200V to 0V. After the change, the residual toner that has passed through the charging nip is charged negatively. The timing of the change is when a point on the intermediate transfer belt 8 that passes through the transfer nip of the image forming unit 1d passes through the charging nip immediately before the change of the set voltage of the secondary transfer power source 19 to be performed later. . At this time, the potentials of the intermediate transfer belt 8 and the photosensitive drum 2 are as shown in FIG. Therefore, the residual toner on the intermediate transfer belt 8 can pass through the primary transfer portion of the image forming portion.
次に、４枚目の２次転写が終了した時点で２次転写用電圧１９の設定電圧を２０００Ｖから−２０００Ｖに変更する。中間転写ベルト８はツェナーダイオード１４ｂで接地されているので、２次転写ローラ１５とブラシ部材７１からの電圧供給で中間転写ベルト８の表面電位が０Ｖから−３００Ｖに変化する。このとき、図５（ｄ）に示すように中間転写ベルト８の電位は感光ドラム２の露光部と非露光部の表面電位の間になる。この電位になった中間転写ベルト８上にある負極性のトナーは、通過する画像形成部１の感光ドラム２の表面電位が非露光部の電位である−５００Ｖの場合は回収されずに通過して、露光部の電位である−１００Ｖの場合には回収される。そこで、感光ドラム２ｂ、２ｃ、２ｄの一部を露光して、４枚目の残トナーを回収トナー容器１０ｂ、１０ｃ、１０ｄに振り分けて回収することが可能である。 Next, when the secondary transfer of the fourth sheet is completed, the set voltage of the secondary transfer voltage 19 is changed from 2000V to -2000V. Since the intermediate transfer belt 8 is grounded by the Zener diode 14b, the surface potential of the intermediate transfer belt 8 changes from 0V to −300V by the voltage supply from the secondary transfer roller 15 and the brush member 71. At this time, as shown in FIG. 5D, the potential of the intermediate transfer belt 8 is between the surface potential of the exposed portion and the non-exposed portion of the photosensitive drum 2. The negative polarity toner on the intermediate transfer belt 8 at this potential passes through without being recovered when the surface potential of the photosensitive drum 2 of the image forming unit 1 that passes through is −500 V that is the potential of the non-exposed portion. In the case of −100 V which is the potential of the exposed portion, it is recovered. Therefore, it is possible to expose a part of the photosensitive drums 2b, 2c, and 2d and distribute the remaining toner of the fourth sheet to the collected toner containers 10b, 10c, and 10d.
（電源７２の切り替えタイミング）
電源７２の設定電流を変更するタイミングとしては以下の５つのタイミングが考えられる。
（１）画像形成部１ａの１次転写が終了する時に、画像形成部１ａの１次転写ニップを通過する中間転写ベルト８上の領域がその直前に帯電ニップ部を通過する時間より前。
（２）（１）以降で、画像形成部１ｄの１次転写が終了する前。
（３）（２）以降で、２次転写が終了する時に画像形成部１ｄを通過する中間転写体上８の点がその直前に帯電ニップ部を通過する時間より前。
（４）（３）以降で、２次転写終了がする時間より前。
（５）２次転写終了後。
(Power supply 72 switching timing)
The following five timings can be considered as the timing for changing the set current of the power source 72.
(1) Before the time at which the region on the intermediate transfer belt 8 passing through the primary transfer nip of the image forming unit 1a passes through the charging nip immediately before the primary transfer of the image forming unit 1a is completed.
(2) Before (1) and before the primary transfer of the image forming unit 1d is completed.
(3) Before (2) and before the time at which the point on the intermediate transfer member 8 passing through the image forming portion 1d passes through the charging nip immediately before the secondary transfer is completed.
(4) Before (3) and before the time when the secondary transfer ends.
(5) After completion of secondary transfer.
ここで、２次転写終了とは、転写材の後端が２次転写部を通過したタイミングのことである。ここで、画像形成部１ａは、中間転写ベルト８の回転方向における最上流に位置する画像形成部である。 Here, the end of the secondary transfer is the timing when the trailing edge of the transfer material has passed through the secondary transfer portion. Here, the image forming unit 1 a is an image forming unit located at the uppermost stream in the rotation direction of the intermediate transfer belt 8.
表１に各タイミングにおける画像不良の有無と、１次転写性への影響と、２次転写性への影響と、振り分け回収可能な最大の画像量と、２次転写終了した時点から残トナーの回収が終わるまでの最大の回収時間を表す。ここの表中において、○は画像不良または転写への影響が無いことを、×は画像不良もしくは転写性が低下する部分があることを、−は評価できないことを示す。振り分け回収可能な画像量は、残トナーを振り分け回収できる中間転写ベルト８の領域の周方向長さで評価した。回収時間は２次転写が終了してから残トナーが回収されるまでに必要な中間転写ベルト８の回転時間で評価した。 Table 1 shows the presence / absence of image defects at each timing, the influence on the primary transferability, the influence on the secondary transferability, the maximum image amount that can be sorted and collected, and the remaining toner from the end of the secondary transfer. Represents the maximum collection time until collection ends. In the table, “◯” indicates that there is no image defect or no influence on transfer, and “x” indicates that there is a portion where the image defect or transferability deteriorates, and − indicates that it cannot be evaluated. The image amount that can be sorted and collected was evaluated by the circumferential length of the area of the intermediate transfer belt 8 that can sort and collect the remaining toner. The collection time was evaluated by the rotation time of the intermediate transfer belt 8 necessary from the end of the secondary transfer to the collection of the residual toner.
（１）の場合は、中間転写ベルト８上で負極性の残トナーの上に負極性のトナー像が重なる。このために、残トナーが画像中に残像のように現れる画像不良を生じる。 In the case of (1), the negative toner image is superimposed on the negative residual toner on the intermediate transfer belt 8. For this reason, an image defect occurs in which the residual toner appears like an afterimage in the image.
（２）の場合は、１次転写途中に電源７２の設定電流を変更する。これにより中間転写ベルト８の電位が２００Ｖから０Ｖに低下してしまう。図６に中間転写ベルト８の電位と１次転写残トナー濃度の測定結果を示す。中間転写ベルト８の電位が２００Ｖから０Ｖに低下すると１次転写性が低下していることがわかる。ここで、１次転写残濃度は次のように測定した。画像形成部１ｃで１次転写が行われている途中で画像形成装置を停止する。そこで、像担持体上の１次転写後の部分に残った１次転写残トナーをポリエステルテープで採取して上質紙に貼り付けた。また、参照としてポリエステルテープを上質紙上に貼り付けて、これらをグレタグマクベス社製の分光濃度計Ｘ−Ｒｉｔｅ５０４でシアン色の濃度測定を実行した。そして、２つの測定の差を１次転写残トナー量として評価の対象にした。 In the case of (2), the set current of the power source 72 is changed during the primary transfer. As a result, the potential of the intermediate transfer belt 8 decreases from 200V to 0V. FIG. 6 shows the measurement results of the potential of the intermediate transfer belt 8 and the primary transfer residual toner density. It can be seen that when the potential of the intermediate transfer belt 8 is lowered from 200 V to 0 V, the primary transfer property is lowered. Here, the primary transfer residual density was measured as follows. The image forming apparatus is stopped while the primary transfer is being performed in the image forming unit 1c. Therefore, the primary transfer residual toner remaining in the portion after the primary transfer on the image carrier was collected with a polyester tape and attached to a high quality paper. Moreover, polyester tape was affixed on high-quality paper as a reference, and the density measurement of cyan color was performed using a spectral densitometer X-Rite 504 manufactured by Gretag Macbeth. The difference between the two measurements was used as the evaluation target as the primary transfer residual toner amount.
（３）の場合は、２次転写が終了して２次転写用電源１９の設定電圧を２０００Ｖから−２０００Ｖに変更して振り分け回収を開始した時に、中間転写ベルト８上に最下流の画像形成装置１ｄを通過している残トナーが存在する。これを回収するためには、中間転写ベルト８を１周させる必要があるので回収時間が３．２秒に増加してしまう。 In the case of (3), when secondary transfer is completed and the set voltage of the secondary transfer power source 19 is changed from 2000 V to −2000 V and sorting and collection are started, the most downstream image formation on the intermediate transfer belt 8 is performed. There is residual toner passing through the device 1d. In order to collect this, it is necessary to make the intermediate transfer belt 8 make one revolution, and thus the collection time increases to 3.2 seconds.
（５）の場合は、２次転写が終了しているので２次転写用電源１９の設定電圧を変更可能である。そのために、電源７２の設定電流を変更させずに２次転写用電源１９の設定電圧を変更させることで振り分けられる画像量と同じ効果しか得られない。この場合は、２次転写終了するまでに画像形成部１ａの１次転写部を通過する残トナーは回収トナー容器１０ａに回収される。そのために、振り分け回収が可能な残トナーは中間転写ベルト８の移動方向に沿って２次転写ニップから画像形成部１ａの１次転写部までの距離である８２ｍｍ分になる。この残トナーを回収するためには、トナーが正極性に帯電しているので、図５（ｃ）のような中間転写ベルト８と感光ドラム２の表面電位の関係にして回収する。 In the case of (5), since the secondary transfer is completed, the set voltage of the secondary transfer power source 19 can be changed. For this reason, only the same effect as the image amount to be distributed can be obtained by changing the setting voltage of the secondary transfer power supply 19 without changing the setting current of the power supply 72. In this case, the remaining toner that passes through the primary transfer portion of the image forming portion 1a before the end of the secondary transfer is collected in the collected toner container 10a. Therefore, the remaining toner that can be sorted and collected is 82 mm, which is the distance from the secondary transfer nip to the primary transfer portion of the image forming portion 1 a along the moving direction of the intermediate transfer belt 8. In order to collect the remaining toner, since the toner is positively charged, the toner is collected in the relationship between the surface potential of the intermediate transfer belt 8 and the photosensitive drum 2 as shown in FIG.
２次転写性については、いずれのタイミングにおいても低下することがなかった。これは、２次転写途中に電源７２の設定電流を変更して中間転写ベルト８の電位が２００Ｖから０Ｖに低下してしまっても、２次転写用電源１９の設定電圧の２０００Ｖに対して中間転写ベルト８の電位変動が小さいためだと考えられる。そのため、２次転写ニップ部の電界変化が許容範囲内になる。 Secondary transferability did not decrease at any timing. Even if the set current of the power supply 72 is changed during the secondary transfer and the potential of the intermediate transfer belt 8 is lowered from 200V to 0V, it is intermediate to the set voltage of 2000V of the secondary transfer power supply 19. This is considered to be because the potential fluctuation of the transfer belt 8 is small. Therefore, the electric field change in the secondary transfer nip portion is within the allowable range.
以上から、（４）のタイミングが、画像不良、１次転写性の低下、２次転写性の低下を生じることなしに、回収時間を延ばすことなく振り分け回収可能な画像量を大きくすることが可能なタイミングである。 From the above, it is possible to increase the amount of images that can be sorted and collected without extending the collection time, without causing the timing of (4) to cause image failure, primary transferability degradation, and secondary transferability degradation. Is the right timing.
（振り分け回収の回収性能の評価）
シアン色の画像形成部１ｃの全面単色画像１枚を印刷して、残トナーを画像形成部１ｂに振り分けて回収する設定で印刷した。そして、振り分け回収動作中の画像形成装置を強制停止して残トナーをサンプリングした。サンプリングは２次転写ニップ通過後、帯電ニップ部通過後、画像形成部１ａの１次転写ニップ通過後、画像形成部１ｂの１次転写ニップ通過後で行った。サンプリング方法は、中間転写体上に付着した残トナーをポリエステルテープで採取して上質紙に貼り付けた。また、参照としてポリエステルテープを上質紙上に貼り付けて、これらを東京電色工業株式会社の白色度計ＴＣ−６ＤＳにトナー色の補色フィルタを通して測定した。そして、２つの測定の差をカブリ量として評価の対象にした。それぞれの状態でのカブリ量は表２のようになった。
(Evaluation of sorting collection performance)
A single monochrome image was printed on the entire surface of the cyan image forming unit 1c, and the remaining toner was printed on the image forming unit 1b. The image forming apparatus during the sorting and collecting operation was forcibly stopped to sample the remaining toner. Sampling was performed after passing through the secondary transfer nip, after passing through the charging nip, after passing through the primary transfer nip of the image forming unit 1a, and after passing through the primary transfer nip of the image forming unit 1b. In the sampling method, the residual toner adhering to the intermediate transfer member was collected with a polyester tape and attached to a high-quality paper. For reference, polyester tape was affixed on high-quality paper, and these were measured through a toner color complementary color filter through a whiteness meter TC-6DS of Tokyo Denshoku Industries Co., Ltd. And the difference of two measurement was made into the object of evaluation as fogging amount. The fog amount in each state is as shown in Table 2.
表２に示したように、残トナーはブラシ部材７１であるブラシで一部が停止される。そして、画像形成部１ａでは一部は回収されるがほとんどの残トナーは通過する。画像形成部１ｂでほとんどの残トナーが回収される。画像形成部１ｂ通過後に中間転写ベルト８に残った残トナーのカブリ量は０．５程度で目視確認できないレベルであった。 As shown in Table 2, a part of the remaining toner is stopped by the brush which is the brush member 71. In the image forming unit 1a, a part of the toner is collected but most of the remaining toner passes. Most of the remaining toner is collected in the image forming unit 1b. The fog amount of the residual toner remaining on the intermediate transfer belt 8 after passing through the image forming portion 1b is about 0.5, which is a level that cannot be visually confirmed.
（実施形態２）
実施形態１では、ブラシ部材７１に印加する電圧を変更するタイミングが（４）である場合について説明した。これに対し、本実施形態では、変更するタイミングが（２）であり、印加する電圧設定を変更する。なお、その他の構成については実施形態１の画像形成装置と同様であるので、同様の部分については同様の符号を付して説明する。
(Embodiment 2)
In Embodiment 1, the case where the timing which changes the voltage applied to the brush member 71 is (4) was demonstrated. On the other hand, in this embodiment, the change timing is (2), and the voltage setting to be applied is changed. Since other configurations are the same as those of the image forming apparatus according to the first embodiment, the same portions are denoted by the same reference numerals and described.
図７は、本実施形態の動作を表すタイミングチャートである。（２）のタイミングチャートにおいて、実施形態１と同じ２次転写用電源の設定電圧が２０００Ｖの場合は、１次転写途中にトナー帯電電圧が変更されるために１次転写性の低下が発生する可能性がある。そこで、本実施形態においては、２次転写用電源の設定電圧を、２５００Ｖにしている。これによりトナー帯電電圧を１５μＡから−１０μＡに変更したときも中間転写ベルト８の表面電位を２００Ｖに維持できた。それにより１次転写性の低下を抑制し、回収時間が長くなるが多くの残トナーを振り分け回収を可能とする。 FIG. 7 is a timing chart showing the operation of the present embodiment. In the timing chart of (2), when the set voltage of the secondary transfer power source, which is the same as that of the first embodiment, is 2000 V, the toner charge voltage is changed during the primary transfer, so that the primary transfer property is deteriorated. there is a possibility. Therefore, in the present embodiment, the set voltage of the secondary transfer power supply is set to 2500V. Thereby, even when the toner charging voltage was changed from 15 μA to −10 μA, the surface potential of the intermediate transfer belt 8 could be maintained at 200V. As a result, the primary transferability is prevented from being lowered, and the collection time becomes long, but a large amount of residual toner can be distributed and collected.
（その他の実施形態）
本実施形態においては中間転写ベルト８のブラシ部材７１としてブラシを用いたがこれに限定されるものではなく、残トナーを所望の極性に帯電できるものであればローラ、ブラシとローラの組合せなどでもよい。
(Other embodiments)
In the present embodiment, a brush is used as the brush member 71 of the intermediate transfer belt 8. However, the present invention is not limited to this, and a roller, a combination of a brush and a roller, or the like may be used as long as the remaining toner can be charged to a desired polarity. Good.
さらに、中間転写ベルト８は、ＰＰＳにカーボンを添加して導電性を持たせているが、これに限るものではなく、他の樹脂や金属等でも本例と同等の導電性があれば同様の効果を期待することができる。また、単層および２層の中間転写ベルトを用いたが、弾性層を設けるなどした３層以上のベルトでも前記周方向抵抗であれば、同様の効果を期待することができる。 Furthermore, although the intermediate transfer belt 8 is made conductive by adding carbon to PPS, the invention is not limited to this, and other resins, metals, and the like may have the same conductivity as in this example. The effect can be expected. Further, although a single-layer and two-layer intermediate transfer belt is used, a similar effect can be expected even with a belt having three or more layers, such as an elastic layer, provided that the circumferential resistance is used.
２層の中間転写ベルトは、基層を成形したあとコートすることで製造しているが、一体成型する等、抵抗値が前述の条件を満たしていれば製造方法はこれに限るものではない。 The two-layer intermediate transfer belt is manufactured by coating after forming the base layer. However, the manufacturing method is not limited to this as long as the resistance value satisfies the above-described conditions such as integral molding.
１ａ〜１ｄ 画像形成部
２ａ〜２ｄ 感光ドラム（感光体）
８ 中間転写ベルト
１５ ２次転写ローラ
１９ 電圧電源
７５ ベルトクリーニング装置
７１ ブラシ部材
1a to 1d Image forming portions 2a to 2d Photosensitive drum (photosensitive member)
8 Intermediate transfer belt 15 Secondary transfer roller 19 Voltage power supply 75 Belt cleaning device 71 Brush member
Claims (8)
転写材の後端が前記２次転写部を通過した後の前記中間転写ベルトの電位は、前記感光体の露光部と非露光部の表面電位の間の電位であることを特徴とする画像形成装置。 A plurality of image forming units each including a photoconductor on which an electrostatic latent image is formed, a developing unit that develops the photoconductor formed on the photoconductor, and a cleaning unit that removes toner from the photoconductor Toner from the photoconductor in a primary transfer unit formed with the image forming unit, an exposure unit that exposes the photoconductor in each image forming unit, and a rotatable and endless photoconductor in each of the plurality of image forming units A secondary intermediate image forming apparatus includes a conductive intermediate transfer belt on which an image is primarily transferred, a secondary transfer portion formed with the intermediate transfer belt, and a secondary transfer portion that secondarily transfers a toner image from the intermediate transfer belt to a transfer material. A transfer unit; and a charging unit that charges residual toner that has not been transferred to the transfer material and remains on the intermediate transfer belt. The residual toner charged by the charging unit is exposed to each of the plurality of image forming units. Can be moved from the intermediate transfer belt to the body , And the image forming apparatus in which the potential is varied over the circumferential direction of the intermediate transfer belt by a current supplied to the intermediate transfer belt from the secondary transfer unit,
Image formation wherein the potential of the intermediate transfer belt after the trailing edge of the transfer material has passed through the secondary transfer portion is a potential between the surface potential of the exposed portion and the non-exposed portion of the photoreceptor. apparatus.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2014021708A JP2015148727A (en) | 2014-02-06 | 2014-02-06 | image forming apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2014021708A JP2015148727A (en) | 2014-02-06 | 2014-02-06 | image forming apparatus |
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| Publication Number | Publication Date |
|---|---|
| JP2015148727A true JP2015148727A (en) | 2015-08-20 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2014021708A Pending JP2015148727A (en) | 2014-02-06 | 2014-02-06 | image forming apparatus |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017219570A (en) * | 2016-06-02 | 2017-12-14 | キヤノン株式会社 | Image forming apparatus |
| JP2018072362A (en) * | 2016-10-24 | 2018-05-10 | 株式会社沖データ | Image forming apparatus |
-
2014
- 2014-02-06 JP JP2014021708A patent/JP2015148727A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017219570A (en) * | 2016-06-02 | 2017-12-14 | キヤノン株式会社 | Image forming apparatus |
| JP2018072362A (en) * | 2016-10-24 | 2018-05-10 | 株式会社沖データ | Image forming apparatus |
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