JP2006084877A

JP2006084877A - Image forming apparatus and image carrier discharging method

Info

Publication number: JP2006084877A
Application number: JP2004270453A
Authority: JP
Inventors: Masaru Ishikawa; 勝石川; Akihito Nishimura; 明仁西村; Tetsuya Fujita; 哲也藤田
Original assignee: Fuji Xerox Co Ltd
Current assignee: Fujifilm Business Innovation Corp
Priority date: 2004-09-16
Filing date: 2004-09-16
Publication date: 2006-03-30

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that prevents image failure caused by a transfer material stained with toner. <P>SOLUTION: The image forming apparatus includes: a scorotron charger 3 for charging the surface of a photoreceptor drum 2 to a prescribed potential; a transfer means for applying a transfer bias having the polarity opposite to the charging polarity of the scorotron charger 3, in order that a developed image on the surface of the photoreceptor drum 2 subjected to exposure and development is transferred to a transfer material; a discharging/charging device 5 by which an opposite transfer bias having the polarity opposite to that of the transfer bias is applied to the photoreceptor drum 2; and a control section 21 for controlling the output of the discharging/charging device 5 so that an area of the photoreceptor drum 2 charged by the transfer means to the polarity opposite to the charging polarity of the scorotron charger 3 has the polarity same as that of the charging polarity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、転写手段によって帯電した像担持体を除電する除電帯電器を備えた画像形成装置及び像担持体除電方法に関する。 The present invention relates to an image forming apparatus provided with a charge removing device for removing charge from an image carrier charged by a transfer unit, and an image carrier charge eliminating method.

感光体上に形成したトナー像を転写紙に直接転写するシステムの場合、帯電器によって感光体の表面を帯電させた極性とは逆の極性となるように転写手段によって帯電させる。ここでは、転写手段は、転写ローラや転写ベルトを指すものとする。例えば、トナー像は帯電器によってマイナスに帯電しているので、転写手段は感光体と転写紙にプラスの帯電をする。 In the case of a system in which a toner image formed on a photoconductor is directly transferred onto transfer paper, the toner image is charged by a transfer unit so that the polarity of the surface of the photoconductor is reversed by a charger. Here, the transfer means refers to a transfer roller or a transfer belt. For example, since the toner image is negatively charged by the charger, the transfer unit positively charges the photosensitive member and the transfer paper.

そのとき、感光体は転写紙を介して転写手段に接触している領域と、転写手段と直接接触している領域とができる。転写紙は抵抗の役割を果たすため、転写手段によって発生する転写電荷は転写紙を介していない、直接転写手段に接触している領域のほうに多く注入するように流れる。また、転写紙の幅が広くなり、直接転写手段が感光体に接触している領域が狭くなるほど、この直接接触領域への電荷注入量が増加する。 At that time, the photoconductor can have an area in contact with the transfer means via the transfer paper and an area in direct contact with the transfer means. Since the transfer paper plays a role of resistance, the transfer charge generated by the transfer means flows so as to be injected more into the area that is not directly in contact with the transfer means and does not pass through the transfer paper. Further, as the width of the transfer paper becomes wider and the area where the direct transfer means is in contact with the photosensitive member becomes narrower, the amount of charge injected into this direct contact area increases.

このため、従来はもっとも転写紙幅の大きいサイズに転写手段の感光体軸方向幅を合わせることによって、転写手段が直接感光体に接触している領域がないようにして、電荷注入が大きくならないようにしていた。また、転写紙が介在している感光体の領域内への電荷注入を除電できるよう除電出力を制御していた。 For this reason, conventionally, by adjusting the width of the transfer unit in the direction of the photosensitive member axis to the size of the largest transfer paper, there is no area where the transfer unit is in direct contact with the photosensitive member, so that charge injection does not increase. It was. Further, the charge removal output is controlled so that charge injection into the region of the photoreceptor where the transfer paper is interposed can be removed.

しかし、“Ａ３伸び用紙”といった非定形サイズの用紙の印刷を保証するため、通常使用されるＡ系サイズの転写紙幅に比較して転写手段の転写電荷注入領域が定形転写紙幅領域より両端部を広くするシステムにせざるを得なくなってきた。 However, in order to guarantee printing of non-standard size paper such as “A3 stretched paper”, the transfer charge injection area of the transfer means is located at both ends of the normal transfer paper width area compared to the A-size transfer paper width that is normally used. It has been forced to make the system wide.

そのため、通常の定形サイズの転写紙に印刷する場合、常に転写手段が直接感光体に接触している領域が狭い状態で存在する。この領域は、転写手段による逆極性電荷注入量が大きくなり、逆極に帯電するので、帯電器による帯電時には所定の帯電電位に達しない。このため直接転写領域は帯電電位が低下し、現像時に転写紙外領域にトナーかぶりが発生する。 For this reason, when printing on a normal standard size transfer paper, there is always a narrow area where the transfer means is in direct contact with the photoreceptor. In this region, the amount of reverse polarity charge injection by the transfer means increases and the opposite polarity is charged, so that the predetermined charging potential is not reached when charging by the charger. For this reason, the charged potential is lowered in the direct transfer area, and toner fog occurs in the area outside the transfer paper during development.

特許文献１〜３では、静電潜像の電位、転写紙の材質、厚さ、平滑度等の性状、記録材のサイズや種類に基づき、転写紙を介した領域内を基準にして徐電制御を行っている。 In Patent Documents 1 to 3, gradual charging is performed with reference to the area through the transfer paper based on the potential of the electrostatic latent image, transfer paper material, thickness, properties such as smoothness, and the size and type of the recording material. Control is in progress.

特開平６−０１１９３２号公報JP-A-6-011932 特開平６−０１９２６２号公報JP-A-6-019262 特開２０００−１６２８５１号公報JP 2000-162851 A

しかしながら、転写紙を基準にした制御では、転写紙内の領域の帯電電位低下は防止できるが、転写紙領域外の除電制御は不十分となる。このため、転写紙外ではかぶりトナーによる用紙端部の汚れや転写手段へかぶりトナーが転写され転写手段端部の汚れが発生し、定形サイズ用紙では用紙端部の汚れが、印刷サイズ用紙を走行したときには用紙裏面汚れになるという問題が生じる。 However, the control based on the transfer paper can prevent a decrease in the charged potential in the area in the transfer paper, but the charge removal control outside the transfer paper area is insufficient. For this reason, the edge of the paper due to the fog toner is transferred outside the transfer paper or the fog toner is transferred to the transfer means and the edge of the transfer means is generated. On the standard size paper, the dirt on the edge of the paper travels on the print size paper. When this happens, there is a problem that the back side of the paper becomes dirty.

さらに、近年感光体のロングライフ化を狙い感光層膜厚が厚くなってきている。有機系感光体では、感光層膜厚が厚いほど転写手段による逆極電荷注入が大きくなる。よって、常に直接転写手段が接触している領域を除電するには、除電帯電手段の出力は従来より倍以上の非常に高い出力が必要になってきている。 Furthermore, in recent years, the photosensitive layer thickness has been increased with the aim of extending the life of the photoreceptor. In the organic photoconductor, the reverse charge injection by the transfer means increases as the photosensitive layer thickness increases. Therefore, in order to neutralize the area where the direct transfer means is always in contact, the output of the static elimination charging means needs to be very high, more than double the conventional output.

コロトロン除電帯電装置の出力が大きいとオゾンや放電生成物もほぼ比例して多量に発生し、タルク含有紙による像流れや、連続稼動後に数時間放置すると発生する感光体の表面層が変質する帯電不良のレベルが大きく悪化する。さらに出力が高くなれば消費電力も高くなる。一方感光層膜厚が薄くなれば電荷注入は小さくなり、常に直接転写手段が接触している領域が狭い状態になっても、電荷注入により逆極化しなくなる。これまでの制御ではさらに感光体の膜厚が薄くなってきたときでも除電帯電の出力はそのままの出力のため、感光体膜厚が薄くなって大きな除電帯電装置の出力が必要なくなっても、出力は大きいまま制御することになり、放電生成物の低減化ができない。 When the output of the corotron static elimination charger is large, ozone and discharge products are also generated in large proportions, and the image flow due to talc-containing paper and the surface layer of the photoreceptor that changes when left standing for several hours after continuous operation are altered. The level of failure is greatly worsened. In addition, power consumption increases as the output increases. On the other hand, if the photosensitive layer thickness is reduced, the charge injection becomes smaller, and even if the area where the direct transfer means is always in contact is narrow, it is not reversed by charge injection. In the control so far, even if the film thickness of the photoconductor becomes thinner, the output of the static elimination charge remains as it is. Therefore, the discharge product is not reduced.

本発明は上記事情に鑑みてなされたものであり、転写材のトナー汚れによる画像不良を生じさせない画像形成装置及び像担持体除電方法を提供することを目的とする。 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus and an image carrier neutralizing method that do not cause image defects due to toner contamination of a transfer material.

かかる目的を達成するために本発明の画像形成装置は、像担持体の表面を所定電位に帯電する帯電手段と、露光、現像された前記像担持体表面の現像像を転写材に転写するため、前記帯電手段の帯電極性とは逆極性の転写バイアスを印加する転写手段と、前記転写バイアスとは逆極性のバイアスを前記像担持体に印加する除電帯電手段と、前記転写手段によって、前記帯電手段による前記帯電極性とは逆極性に帯電した前記像担持体の前記転写材を介さずに前記転写手段が直接接触する領域を、前記帯電極性と同極性となるように除電帯電手段の出力を制御する制御手段とを有する構成としている。このように帯電電極とは逆極性に帯電した像担持体の領域を、帯電極性と同極性となるように除電するので、かぶりトナーによって転写材や、転写手段の端部が汚れる、またこれによって転写ベルトで搬送中の転写材の裏面が汚れる等の不具合を防止し、転写材のトナー汚れによる画像不良を生じさせない。 In order to achieve such an object, the image forming apparatus of the present invention includes a charging means for charging the surface of the image carrier to a predetermined potential, and transferring the developed and developed image on the surface of the image carrier to a transfer material. A transfer means for applying a transfer bias having a reverse polarity to the charge polarity of the charging means; a charge eliminating charge means for applying a bias having a reverse polarity to the transfer bias to the image carrier; and the transfer means. The area of the image carrier that is charged to the opposite polarity to the charged polarity by the means is directly connected to the transfer means without going through the transfer material. And a control means for controlling. In this way, the area of the image carrier charged to the opposite polarity to the charging electrode is neutralized so as to have the same polarity as the charged polarity, so that the transfer material and the end of the transfer means are soiled by the fog toner. Problems such as contamination of the back surface of the transfer material being conveyed by the transfer belt are prevented, and image defects due to toner contamination of the transfer material are not caused.

上記画像形成装置において、前記像担持体の領域は、前記像担持体が、前記転写材を介さずに前記転写手段に直接接触する領域であるとよい。転写材を介さずに転写手段に直接接触する像担持体の領域は、転写電荷注入が多くなり逆極化すると、帯電器によって帯電しても正常な表面電位に戻らないことがある。この領域を帯電極性と同極性となるように除電しておくことで、現像時のかぶりトナーの発生を防止することができる。 In the image forming apparatus, the region of the image carrier may be a region where the image carrier directly contacts the transfer unit without passing through the transfer material. In the area of the image carrier that is in direct contact with the transfer means without passing through the transfer material, when transfer charge injection increases and the polarity is reversed, the surface potential may not return to the normal surface even when charged by a charger. By eliminating the charge in this region so as to have the same polarity as the charging polarity, it is possible to prevent the occurrence of fog toner during development.

上記画像形成装置において、前記像担持体の膜厚を測定する膜厚測定手段を有し、前記制御手段は、前記像担持体の膜厚に応じて前記除電帯電手段の出力を制御するように構成するとよい。像担持体の膜厚に応じて、逆極性の転写電荷注入量が変化する。このため、像担持体の膜厚に応じて除電帯電手段の出力を制御することで、精度よく像担持体の除電を行うことができる。また像担持体膜厚が薄くなれば、除電帯電手段を完全に停止させることも可能となるため、省エネルギー化を図ることができる。また、除電帯電手段の運転時間を抑えることで、オゾンや放電生成物の発生を抑えることが可能となり、タルク含有紙による像流れや、連続稼働後に数時間放置すると発生する、像担持体の表面層が変質する帯電不良を低減させることができる。 The image forming apparatus includes a film thickness measuring unit that measures a film thickness of the image carrier, and the control unit controls the output of the charge eliminating unit according to the film thickness of the image carrier. Configure. Depending on the film thickness of the image carrier, the transfer charge injection amount of reverse polarity changes. For this reason, by controlling the output of the charge eliminating means according to the film thickness of the image carrier, the image carrier can be accurately neutralized. Further, if the film thickness of the image carrier is reduced, it is possible to completely stop the charge eliminating and charging means, so that energy saving can be achieved. In addition, by suppressing the operation time of the static elimination charging means, it is possible to suppress the generation of ozone and discharge products, and the image flow caused by talc-containing paper and the surface of the image carrier that occurs when left for several hours after continuous operation. It is possible to reduce charging defects in which the layer is altered.

上記画像形成装置において、周囲の温度と湿度を計測する計測手段を有し、前記制御手段は、前記温度及び前記湿度と、前記転写材の種別とに基づいて前記除電帯電手段の出力を制御するように構成するとよい。温度と湿度によって転写材の含水率が変化すると転写材の抵抗値が変動し、転写材を介さずに転写手段に直接接触する像担持体の領域の転写電荷注入量が変動する。このため、温度及び湿度と、転写材の種別とに基づいて除電帯電手段の出力を制御することで、精度よく像担持体の除電を行うことができる。 The image forming apparatus includes a measuring unit that measures ambient temperature and humidity, and the control unit controls the output of the charge eliminating and charging unit based on the temperature and the humidity, and the type of the transfer material. It may be configured as follows. When the moisture content of the transfer material changes with temperature and humidity, the resistance value of the transfer material changes, and the transfer charge injection amount in the region of the image carrier that directly contacts the transfer means without using the transfer material changes. For this reason, by controlling the output of the charge eliminating and charging means based on the temperature and humidity and the type of the transfer material, the image carrier can be discharged with high accuracy.

上記画像形成装置において、前記制御手段は、前記転写材の前記像担持体軸方向サイズに応じて、前記除電帯電手段の出力を制御するように構成するとよい。転写材を介さずに転写手段に直接接触する像担持体の領域は、転写材の幅によって変わるため転写電荷注入量が変動するので、転写材の像担持体軸方向サイズに応じて除電帯電手段の出力を制御することで、精度よく像担持体の除電を行うことができる。 In the image forming apparatus, the control unit may be configured to control the output of the charge eliminating unit in accordance with the size of the transfer material in the axial direction of the image carrier. Since the area of the image carrier that is in direct contact with the transfer means without passing through the transfer material varies depending on the width of the transfer material, the transfer charge injection amount varies, so the charge eliminating means according to the size of the transfer material in the axial direction of the image carrier By controlling the output, the image carrier can be discharged with high accuracy.

上記画像形成装置において、前記転写手段は、前記転写バイアスを印加する転写ローラを含み、前記制御手段は、前記転写ローラの抵抗を測定する抵抗測定手段によって測定された抵抗値に基づいて、前記除電帯電手段の出力を制御するように構成するとよい。転写ローラの抵抗値に応じて、転写材を介さずに転写手段に直接接触する像担持体の領域の転写電荷注入量が変動する。このため、転写ローラの抵抗値に基づいて除電帯電手段の出力を制御することで、精度よく像担持体の除電を行うことができる。 In the image forming apparatus, the transfer unit includes a transfer roller that applies the transfer bias, and the control unit is configured to perform the charge removal based on a resistance value measured by a resistance measurement unit that measures a resistance of the transfer roller. It may be configured to control the output of the charging means. In accordance with the resistance value of the transfer roller, the transfer charge injection amount in the region of the image carrier that is in direct contact with the transfer means without using the transfer material varies. For this reason, by controlling the output of the charge removing means based on the resistance value of the transfer roller, the image carrier can be discharged with high accuracy.

上記画像形成装置において、前記転写手段は、前記転写バイアスを印加する転写ローラと前記転写ローラによって帯電された転写ベルトとを含み、前記制御手段は、前記転写ベルトの抵抗を測定する抵抗測定手段によって測定された抵抗値に基づいて、前記除電帯電手段の出力を制御するように構成するとよい。転写ベルトの抵抗値に応じて、転写材を介さずに転写手段に直接接触する像担持体の領域の転写電荷注入量が変動する。このため、転写ベルトの抵抗値に基づいて除電帯電手段の出力を制御することで、精度よく像担持体の除電を行うことができる。 In the image forming apparatus, the transfer unit includes a transfer roller that applies the transfer bias and a transfer belt that is charged by the transfer roller, and the control unit includes a resistance measurement unit that measures the resistance of the transfer belt. It is preferable that the output of the static elimination charging unit is controlled based on the measured resistance value. In accordance with the resistance value of the transfer belt, the transfer charge injection amount in the region of the image carrier that is in direct contact with the transfer means without using the transfer material varies. For this reason, by controlling the output of the charge eliminating means based on the resistance value of the transfer belt, the image carrier can be discharged with high accuracy.

上記画像形成装置において、前記転写手段は、前記転写バイアスを印加する転写ローラと前記転写ローラによって帯電された転写ベルトとを含み、前記制御手段は、前記転写ローラと前記転写ベルトの抵抗を測定する抵抗測定手段によって測定された抵抗値に基づいて、前記除電帯電手段の出力を制御するように構成するとよい。転写ローラと転写ベルトの抵抗値に応じて、転写材を介さずに転写手段に直接接触する像担持体の領域の転写電荷注入量が変動する。このため、転写ローラと転写ベルトの抵抗値に基づいて除電帯電手段の出力を制御することで、精度よく像担持体の除電を行うことができる。 In the image forming apparatus, the transfer unit includes a transfer roller for applying the transfer bias and a transfer belt charged by the transfer roller, and the control unit measures a resistance between the transfer roller and the transfer belt. It is preferable that the output of the charge eliminating unit is controlled based on the resistance value measured by the resistance measuring unit. Depending on the resistance values of the transfer roller and the transfer belt, the transfer charge injection amount in the region of the image carrier that directly contacts the transfer means without using the transfer material varies. For this reason, by controlling the output of the static elimination charging unit based on the resistance values of the transfer roller and the transfer belt, the image carrier can be accurately eliminated.

上記画像形成装置において、前記膜厚測定手段は、前記像担持体の回転数から前記膜厚を予測する手段であるとよい。また前記膜厚測定手段は、ワイヤとグリッドからなるスコロトロン帯電器のグリッド電圧と、前記スコロトロン帯電器によって帯電した前記像担持体の帯電表面電位との電位差から前記膜厚を予測する手段であってもよい。 In the image forming apparatus, the film thickness measurement unit may be a unit that predicts the film thickness from the number of rotations of the image carrier. The film thickness measuring means predicts the film thickness from a potential difference between a grid voltage of a scorotron charger composed of a wire and a grid and a charged surface potential of the image carrier charged by the scorotron charger. Also good.

上記画像形成装置において、前記抵抗測定手段は、前記転写ローラに定電流を流した時に測定される電圧値から抵抗を計測する手段、又は前記転写ベルトの抵抗値を前記転写ベルトの駆動時間から予測する手段であるとよい。 In the image forming apparatus, the resistance measuring unit predicts a resistance from a voltage value measured when a constant current is passed through the transfer roller, or predicts the resistance value of the transfer belt from the driving time of the transfer belt. It is good that it is means to do.

上記画像形成装置において、前記除電帯電手段は、コロトロン帯電器であり、前記制御手段によって定電流制御されるとよい。 In the image forming apparatus, the charge eliminating unit may be a corotron charger and may be controlled with a constant current by the control unit.

本発明の像担持体除電方法は、像担持体の表面を所定電位に帯電する帯電ステップと、露光、現像された前記像担持体表面の現像像を転写材に転写するため、前記帯電手段の帯電極性とは逆極性の転写バイアスを印加する転写バイアス印加ステップと、前記転写バイアスとは逆極性のバイアスを前記像担持体に印加し、前記像担持体表面の電荷を除電する除電ステップとを有し、前記除電ステップは、前記帯電ステップによって帯電した帯電極性とは逆極性に帯電した前記像担持体の前記転写材を介さずに前記転写手段が直接接触する領域が、前記帯電極性と同極性となるように除電するステップであるとよい。このように帯電電極とは逆極性に帯電した像担持体の領域を、帯電極性と同極性となるように除電するので、かぶりトナーによって転写材や、転写手段の端部が汚れる、またこれによって転写ベルトで搬送中の転写材の裏面が汚れる等の不具合を防止し、転写材のトナー汚れによる画像不良を生じさせない。 The image carrier neutralization method of the present invention comprises a charging step for charging the surface of the image carrier to a predetermined potential, and transferring the developed image of the exposed and developed surface of the image carrier to a transfer material. A transfer bias applying step for applying a transfer bias having a polarity opposite to the charging polarity, and a charge removing step for applying a bias having a polarity opposite to the transfer bias to the image carrier to remove charges on the surface of the image carrier. The charge removing step has the same area as the charged polarity in the area where the transfer means directly contacts without passing through the transfer material of the image carrier charged in the opposite polarity to the charged polarity charged in the charging step. It is good that it is a step of discharging so as to be polar. In this way, the area of the image carrier charged to the opposite polarity to the charging electrode is neutralized so as to have the same polarity as the charged polarity, so that the transfer material and the end of the transfer means are soiled by the fog toner. Problems such as contamination of the back surface of the transfer material being conveyed by the transfer belt are prevented, and image defects due to toner contamination of the transfer material are not caused.

本発明は、転写材のトナー汚れによる画像不良を生じさせない。 The present invention does not cause image defects due to toner contamination of the transfer material.

添付図面を参照しながら本発明の好適な実施例を説明する。 Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

まず、図１を参照しながら本実施例の構成を説明する。図１に電子写真方式の画像形成装置の構成を示す。図１に示す矢印方向に回転する感光体ドラム（像担持体）２の周囲に、感光体ドラム２を所定電位に帯電するスコロトロン帯電器３、感光体２上に静電潜像を書き込むレーザ走査装置（ＲＯＳ：ＲａｓｔｅｒＯｕｔｐｕｔＳｃａｎｎｅｒ）などの画像書込装置（本例では同装置からのレーザ光のみを示す）、感光体ドラム２上に形成された静電潜像をトナーにて可視像化する現像装置４、転写ベルト８、転写ローラ９等の転写手段から感光体ドラム２に注入された電荷を除電する除電帯電装置５、感光体ドラム２表面の未転写トナーをクリーニングするクリーニング装置６、感光体２表面の静電残像を除電するイレーズランプ７、転写材を搬送する転写ベルト８と現像装置４により現像された現像像を転写材に転写する転写ローラ９とからなる転写手段等を備えている。なお、除電帯電装置５として、コロトロン帯電器を用いることができ、後述する制御部２１によって定電流制御される。 First, the configuration of the present embodiment will be described with reference to FIG. FIG. 1 shows the configuration of an electrophotographic image forming apparatus. A scorotron charger 3 that charges the photosensitive drum 2 to a predetermined potential around a photosensitive drum (image carrier) 2 that rotates in the direction of the arrow shown in FIG. 1, and laser scanning that writes an electrostatic latent image on the photosensitive member 2 An image writing device such as a device (ROS: Raster Output Scanner) (in this example, only laser light from the device is shown), and the electrostatic latent image formed on the photosensitive drum 2 is visualized with toner. A developing device 4, a transfer belt 8, a transfer roller 9 and the like, a charge removing device 5 for removing charges injected from the transfer means such as the transfer roller 9, and a cleaning device 6 for cleaning untransferred toner on the surface of the photoconductor drum 2. From an erase lamp 7 for neutralizing the electrostatic residual image on the surface of the photosensitive member 2, a transfer belt 8 for conveying the transfer material, and a transfer roller 9 for transferring the developed image developed by the developing device 4 to the transfer material. Transfer means and the like. In addition, a corotron charger can be used as the static elimination charging device 5, and constant current control is performed by the control unit 21 described later.

画像形成装置の作像プロセスについて説明する。先ず、スコロトロン帯電器３にて感光体ドラム２を帯電した後、画像書込装置からのレーザ光にて感光体ドラム２上に静電潜像を書き込む。その後、現像装置４にて静電潜像をトナー像として可視像化し、所定のタイミングで転写部位へと移動させる。一方、転写材は、転写ベルト８にて所定のタイミングで転写部位へと搬送され、転写ローラ９と、帯電された転写ベルト８によって転写バイアスを印加されることで、感光体ドラム２上のトナー像が転写材に転写される。なお、転写ベルト８及び転写ローラ９とからなる転写手段は、スコロトロン帯電器３による帯電とは逆極性となるように転写電界をかける。 An image forming process of the image forming apparatus will be described. First, after the photosensitive drum 2 is charged by the scorotron charger 3, an electrostatic latent image is written on the photosensitive drum 2 by laser light from the image writing device. Thereafter, the electrostatic latent image is visualized as a toner image by the developing device 4 and moved to a transfer site at a predetermined timing. On the other hand, the transfer material is transported to a transfer site at a predetermined timing by the transfer belt 8, and a transfer bias is applied by the transfer roller 9 and the charged transfer belt 8, whereby the toner on the photoconductive drum 2. The image is transferred to a transfer material. The transfer means including the transfer belt 8 and the transfer roller 9 applies a transfer electric field so as to have a polarity opposite to that of charging by the scorotron charger 3.

図２に、感光体ドラム２と、転写手段の転写領域と、印刷サイズの対応幅との感光体ドラム２の軸方向での位置関係を示す。図２に示すように本実施例の画像形成装置は、感光体ドラム２の感光層領域が、Ａ系転写材幅領域より両端部が片側約1４ｍｍ程度広く、通常のＡ系サイズ用紙を使用した場合、常に感光体ドラム２が転写材を介さずに直接転写手段に接触する。このため、転写手段による転写バイアス印加時に、感光体は、転写紙を介して転写手段に接触している領域と、転写手段と直接接触している領域とで転写電荷注入量に差ができる。なお、これらの領域を以下では、転写材介在領域と、直接転写領域と呼ぶ。 FIG. 2 shows the positional relationship in the axial direction of the photosensitive drum 2 with respect to the photosensitive drum 2, the transfer area of the transfer means, and the corresponding width of the print size. As shown in FIG. 2, in the image forming apparatus of this embodiment, the photosensitive layer area of the photosensitive drum 2 is approximately 14 mm wider on both sides than the A-system transfer material width area, and ordinary A-size paper is used. In this case, the photosensitive drum 2 always comes into direct contact with the transfer means without using a transfer material. For this reason, when a transfer bias is applied by the transfer unit, the photoreceptor can make a difference in the transfer charge injection amount between the region in contact with the transfer unit via the transfer paper and the region in direct contact with the transfer unit. Hereinafter, these regions are referred to as a transfer material intervening region and a direct transfer region.

図３を参照しながら、測定部１０とコントローラ２０との構成を説明する。図３には、画像形成装置１の状態を測定する測定部１０と、画像形成装置の駆動を制御するコントローラ２０との構成が示されている。図３に示す測定部１０は、感光体膜厚測定部１１と、転写ローラ抵抗値計測部１２と、転写ベルト駆動時間測定部１３と、温度測定部１４と、湿度測定部１５とを備えている。またコントローラ２０は、制御部２１と、記憶部２２とを備えている。 The configuration of the measurement unit 10 and the controller 20 will be described with reference to FIG. FIG. 3 shows a configuration of a measurement unit 10 that measures the state of the image forming apparatus 1 and a controller 20 that controls driving of the image forming apparatus. The measurement unit 10 shown in FIG. 3 includes a photoreceptor film thickness measurement unit 11, a transfer roller resistance value measurement unit 12, a transfer belt drive time measurement unit 13, a temperature measurement unit 14, and a humidity measurement unit 15. Yes. The controller 20 includes a control unit 21 and a storage unit 22.

制御部２１は、感光体膜厚測定部１１によって測定された感光体ドラム２の膜厚に応じて、除電帯電装置５の出力を制御する。感光体ドラム２の膜厚の測定方法には種々の方法が考えられる。例えば、感光体ドラム２の総回転数から測定する方法がある。感光体ドラム２には、クリーニングブレートや、転写ベルト８などが当接しているので、感光体ドラム２の回転数に比例して膜厚が減っていく。従って、初期段階での感光体ドラム２の膜厚を測定しておき、感光体ドラム２の回転数に応じて膜厚を減らしていくことで、現在の膜厚を予測する。他の方法として、ワイヤとグリッドからなるスコロトロン帯電器３のグリッド電圧と、スコロトロン帯電器３によって帯電した感光体ドラム２の帯電表面電位との電位差から膜厚を測定することもできる。 The control unit 21 controls the output of the charge eliminating device 5 according to the film thickness of the photoconductor drum 2 measured by the photoconductor film thickness measuring unit 11. Various methods for measuring the film thickness of the photosensitive drum 2 are conceivable. For example, there is a method of measuring from the total number of rotations of the photosensitive drum 2. Since the cleaning drum and the transfer belt 8 are in contact with the photosensitive drum 2, the film thickness decreases in proportion to the rotational speed of the photosensitive drum 2. Therefore, the film thickness of the photosensitive drum 2 in the initial stage is measured, and the current film thickness is predicted by reducing the film thickness according to the number of rotations of the photosensitive drum 2. As another method, the film thickness can be measured from the potential difference between the grid voltage of the scorotron charger 3 composed of a wire and a grid and the charged surface potential of the photosensitive drum 2 charged by the scorotron charger 3.

感光体ドラム２をＯＰＣ感光体（ＯｒｇａｎｉｃＰｈｏｔｏ−Ｃｏｎｄｕｃｔｏｒ：有機光感光体）として、直接転写領域の転写電荷注入後の帯電後の帯電表面電位の低下量は、例えば標準環境で転写電流値が９０μＡ程度の場合、正常な帯電表面電位−７００Ｖに対して、膜厚３２μｍでは転写材介在領域では３５Ｖ低下の表面電位−６６５Ｖ程度であるが、直接転写領域では１３０Ｖ低下の表面電位−５７０Ｖ程度に低下量が増大する。 When the photosensitive drum 2 is an OPC photosensitive body (Organic Photo-Conductor: organic photoconductor), the amount of decrease in the charged surface potential after charging after transfer charge injection in the direct transfer region is, for example, 90 μA in a standard environment. When the film thickness is 32 μm, the surface potential is about −665 V, which is about 35 V lower than the normal charged surface potential of −700 V. In the direct transfer area, the surface potential is about −570 V, which is about 130 V lower. The amount increases.

これを定電流制御のコロトロン除電帯電器で除電するには、転写材領域は−２００μＡの出力程度でよいが、直接転写領域では−６００μＡ程度の出力が必要になる。 In order to neutralize this with a constant current control corotron neutralization charger, the transfer material region may have an output of about -200 μA, but the direct transfer region requires an output of about -600 μA.

また、膜厚２４μｍのとき、転写材介在領域では１５Ｖ低下の帯電電位−６８５Ｖ程度だが、直接転写領域では５０Ｖ低下の帯電電位−６５０Ｖ程度に電位低下量が増大する。これを除電帯電装置５で除電するには転写材領域は−１００μＡ程度、直接転写領域では−３００μＡ程度の出力が必要になる。 Further, when the film thickness is 24 μm, the charging potential decreases about 15V in the transfer material intervening region to about −685V, but the potential decreasing amount increases to about −650V charging potential in the direct transfer region. In order to eliminate the charge with the charge eliminating device 5, an output of about −100 μA is required for the transfer material region and about −300 μA for the direct transfer region.

また膜厚２０μｍの時には、転写材介在領域は０Ｖで電位低下は発生せず、直接転写領域では−２０Ｖ低下の帯電電位−６８０Ｖ程度になる。 When the film thickness is 20 μm, the transfer material intervening area is 0 V and no potential drop occurs, and in the direct transfer area, the charging potential is about −680 V, which is −20 V lower.

２０Ｖ程度の電位低下ならかぶりトナーは発生しないため、除電帯電の出力をオフにすることもできる。このように、感光体の膜厚が薄くなってくると、転写電荷注入による表面電位の低下量は小さくなり、膜厚に応じて除電帯電器の出力を低くでき、オフにすることもできる。 Since the fog toner is not generated when the potential is lowered by about 20 V, the charge removal charge can be turned off. As described above, when the film thickness of the photoconductor is reduced, the amount of decrease in the surface potential due to transfer charge injection is reduced, and the output of the charge eliminating charger can be lowered according to the film thickness, and can be turned off.

図４（Ａ）に記憶部２２に記録した管理テーブルを示す。制御部２１は、膜厚の初期値と、回転数から得られる目減り量とから図４（Ａ）に示す管理テーブルを参照し除電帯電装置５の出力を制御する。 FIG. 4A shows a management table recorded in the storage unit 22. The control unit 21 controls the output of the charge eliminating device 5 with reference to the management table shown in FIG. 4A from the initial value of the film thickness and the amount of reduction obtained from the rotation speed.

感光体ドラム２の膜厚に応じて除電帯電装置５の出力を制御することで、精度よく像担持体の除電を行うことができる。また感光体ドラム２の膜厚が薄くなれば、除電帯電装置５を完全に停止させることも可能となるため、省エネルギー化を図ることができる。また、除電帯電装置５の運転時間を抑えることで、オゾンや放電生成物の発生を抑えることが可能となり、タルク含有紙による像流れや、連続稼働後に数時間放置すると発生する、感光体ドラム２の表面層が変質する帯電不良を低減させることができる。 By controlling the output of the charge eliminating device 5 in accordance with the film thickness of the photosensitive drum 2, the image carrier can be discharged with high accuracy. Further, if the film thickness of the photosensitive drum 2 is reduced, the charge eliminating device 5 can be completely stopped, so that energy saving can be achieved. In addition, by suppressing the operation time of the static elimination charging device 5, it is possible to suppress the generation of ozone and discharge products, and the image drum caused by talc-containing paper or the photoconductive drum 2 generated when left for several hours after continuous operation. It is possible to reduce charging defects in which the surface layer of the material deteriorates.

また制御部２１は、転写ローラ９の抵抗値と転写ベルト８の抵抗値とに基づいて、除電帯電装置５の出力を制御する。転写ローラ９と転写ベルト８の抵抗値に応じて、直接転写領域の転写電荷注入量が変動する。転写手段の抵抗が小さい程、転写手段による直接転写領域への電荷注入量は少ない。このため、転写ローラ９の抵抗を転写ローラ抵抗値計測部１２で計測し、または、転写ベルト８の抵抗を転写ベルト駆動時間測定部１３で測定する。転写ローラ抵抗値計測部１２は、転写ローラ９に定電流を流した時に測定される電圧値から抵抗を計測する。また転写ベルト駆動時間測定部１３は、転写ベルト８の抵抗値を転写ベルト８の駆動時間から予測する。 Further, the control unit 21 controls the output of the charge eliminating device 5 based on the resistance value of the transfer roller 9 and the resistance value of the transfer belt 8. Depending on the resistance value of the transfer roller 9 and the transfer belt 8, the transfer charge injection amount in the direct transfer region varies. The smaller the resistance of the transfer means, the smaller the amount of charge injected into the direct transfer area by the transfer means. Therefore, the resistance of the transfer roller 9 is measured by the transfer roller resistance value measuring unit 12, or the resistance of the transfer belt 8 is measured by the transfer belt driving time measuring unit 13. The transfer roller resistance value measuring unit 12 measures resistance from a voltage value measured when a constant current is passed through the transfer roller 9. The transfer belt drive time measurement unit 13 predicts the resistance value of the transfer belt 8 from the drive time of the transfer belt 8.

図４（Ｂ）に記憶部２２に記憶した管理テーブルの構成を示す。制御部２１は、測定した転写ローラ９の抵抗と転写ベルト８の抵抗から図４（Ｂ）に示す管理テーブルを参照し、除電帯電装置５の出力を制御する。 FIG. 4B shows the configuration of the management table stored in the storage unit 22. The control unit 21 refers to the management table shown in FIG. 4B based on the measured resistance of the transfer roller 9 and the resistance of the transfer belt 8, and controls the output of the charge eliminating and charging device 5.

また制御部２１は、周囲の温度及び湿度と、転写材の種類と、転写材の感光体軸方向サイズに基づいて除電帯電装置５の出力を制御する。温度と湿度によって転写材の含水率が変化すると転写材の抵抗値が変動するため、直接転写領域の転写電荷注入量が変動する。転写材が乾燥するほど抵抗は高くなる。例えば、転写電流値が９０μＡ程度の場合、正常な帯電電位−７００Ｖに対して、直接転写領域の帯電後の表面電位の低下量は、標準環境の普通紙では、１３０Ｖなのが、低湿では２５０Ｖ程度になり、さらに厚紙になると、３５０Ｖも帯電電位が低下する。このため種類や温湿度で変わる転写材の抵抗によって除電帯電装置５の出力を制御する。また直接転写領域の範囲を転写材の感光体軸方向サイズを基に判定し、判定結果に応じて除電帯電装置５の出力を制御する。 Further, the control unit 21 controls the output of the charge removing device 5 based on the ambient temperature and humidity, the type of transfer material, and the size of the transfer material in the axial direction of the photoconductor. When the moisture content of the transfer material changes depending on the temperature and humidity, the resistance value of the transfer material changes, so that the transfer charge injection amount in the direct transfer region changes. The resistance increases as the transfer material dries. For example, when the transfer current value is about 90 μA, the amount of decrease in the surface potential after charging the direct transfer region is 130 V for normal paper in a standard environment and about 250 V for low humidity with respect to a normal charging potential of −700 V. When the paper becomes thicker, the charging potential decreases by 350V. For this reason, the output of the static elimination charging device 5 is controlled by the resistance of the transfer material that changes depending on the type and temperature and humidity. Further, the range of the direct transfer region is determined based on the size of the transfer material in the axial direction of the photosensitive member, and the output of the charge removing device 5 is controlled according to the determination result.

図４（Ｃ）に、記憶部２２に記憶した管理テーブルの構成を示す。制御部２１は、転写材の種類と、温度、湿度、転写材の感光体軸方向サイズとから図４（Ｃ）
に示す管理テーブルを参照し、除電帯電装置５の出力を制御する。 FIG. 4C shows the configuration of the management table stored in the storage unit 22. The control unit 21 determines the transfer material type, the temperature, the humidity, and the size of the transfer material in the direction of the photosensitive member axis as shown in FIG.
The output of the static elimination charging device 5 is controlled with reference to the management table shown in FIG.

上述した実施例は本発明の好適な実施の例である。但し、これに限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々変形実施可能である。例えば、上述した実施例では感光体ドラム２の膜厚と、温度、湿度と、転写手段の抵抗によってそれぞれ管理テーブルを設けているが、これらの測定値を一つにまとめた管理テーブルを作成し、全ての条件を満たすように除電帯電装置５の出力を制御することもできる。 The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the management table is provided according to the film thickness of the photosensitive drum 2, the temperature, the humidity, and the resistance of the transfer unit, but a management table in which these measured values are combined is created. The output of the static elimination charging device 5 can be controlled so as to satisfy all the conditions.

画像形成装置１の構成を示す図である。1 is a diagram illustrating a configuration of an image forming apparatus 1. FIG. 感光体ドラム２と、転写手段の転写領域と、印刷サイズの対応幅との感光体ドラム２の軸方向での位置関係を示す図である。FIG. 6 is a diagram illustrating a positional relationship in the axial direction of the photosensitive drum 2 with respect to the photosensitive drum 2, a transfer region of a transfer unit, and a corresponding width of a print size. 測定部１０とコントローラ部２０との構成を示すブロック図である。2 is a block diagram showing the configuration of a measurement unit 10 and a controller unit 20. FIG. 記憶部２２に記憶した管理テーブルの構成を示す図である。4 is a diagram illustrating a configuration of a management table stored in a storage unit 22. FIG.

符号の説明Explanation of symbols

１画像形成装置２感光体ドラム
３スコロトロン帯電器４現像装置
５除電帯電装置５６クリーニング装置
７イレーズランプ８転写ベルト
９転写ローラ１０測定部
１１感光体膜厚測定部１２転写ローラ抵抗値計測部
１３転写ベルト駆動時間測定部１４温度測定部
１５湿度測定部２０コントローラ
２１制御部２２記憶部
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 3 Scorotron charger 4 Developing apparatus 5 Static elimination charging apparatus 5 6 Cleaning apparatus 7 Erase lamp 8 Transfer belt 9 Transfer roller 10 Measuring part 11 Photoreceptor film thickness measuring part 12 Transfer roller resistance value measuring part 13 Transfer belt drive time measurement unit 14 Temperature measurement unit 15 Humidity measurement unit 20 Controller 21 Control unit 22 Storage unit

Claims

像担持体の表面を所定電位に帯電する帯電手段と、
露光、現像された前記像担持体表面の現像像を転写材に転写するため、前記帯電手段の帯電極性とは逆極性の転写バイアスを印加する転写手段と、
前記転写バイアスとは逆極性のバイアスを前記像担持体に印加する除電帯電手段と、
前記転写手段によって、前記帯電手段による前記帯電極性とは逆極性に帯電した前記像担持体の前記転写材を介さずに前記転写手段が直接接触する領域を、前記帯電極性と同極性となるように除電帯電手段の出力を制御する制御手段とを有することを特徴とする画像形成装置。 Charging means for charging the surface of the image carrier to a predetermined potential;
A transfer unit that applies a transfer bias having a polarity opposite to the charging polarity of the charging unit in order to transfer the developed and developed image on the surface of the image carrier to a transfer material;
Neutralizing and charging means for applying a bias having a polarity opposite to that of the transfer bias to the image carrier;
A region of the image carrier that is charged to a polarity opposite to the charging polarity by the charging unit by the transfer unit is made to have the same polarity as the charging polarity in a region where the transfer unit directly contacts without passing through the transfer material. And an image forming apparatus comprising: a control unit that controls the output of the charge eliminating and charging unit.

前記像担持体の膜厚を測定する膜厚測定手段を有し、
前記制御手段は、前記像担持体の膜厚に応じて前記除電帯電手段の出力を制御することを特徴とする請求項１記載の画像形成装置。 Having a film thickness measuring means for measuring the film thickness of the image carrier,
The image forming apparatus according to claim 1, wherein the control unit controls an output of the charge eliminating unit according to a film thickness of the image carrier.

周囲の温度と湿度を計測する計測手段を有し、
前記制御手段は、前記温度及び前記湿度と、前記転写材の種別とに基づいて前記除電帯電手段の出力を制御することを特徴とする請求項１又は２のいずれか一項記載の画像形成装置。 Has measuring means to measure ambient temperature and humidity,
The image forming apparatus according to claim 1, wherein the control unit controls an output of the charge eliminating unit based on the temperature, the humidity, and a type of the transfer material. .

前記制御手段は、前記転写材の前記像担持体軸方向サイズに応じて、前記除電帯電手段の出力を制御することを特徴とする請求項３記載の画像形成装置。 The image forming apparatus according to claim 3, wherein the control unit controls an output of the charge eliminating unit according to a size of the transfer material in an axial direction of the image carrier.

前記転写手段は、前記転写バイアスを印加する転写ローラを含み、
前記制御手段は、前記転写ローラの抵抗を測定する抵抗測定手段によって測定された抵抗値に基づいて、前記除電帯電手段の出力を制御することを特徴とする請求項１から４のいずれか一項記載の画像形成装置。 The transfer means includes a transfer roller for applying the transfer bias,
5. The control unit according to claim 1, wherein the control unit controls the output of the charge removing unit based on a resistance value measured by a resistance measuring unit that measures the resistance of the transfer roller. The image forming apparatus described.

前記転写手段は、前記転写バイアスを印加する転写ローラと前記転写ローラによって帯電される転写ベルトとを含み、
前記制御手段は、前記転写ベルトの抵抗を測定する抵抗測定手段によって測定された抵抗値に基づいて、前記除電帯電手段の出力を制御することを特徴とする請求項１から４のいずれか一項記載の画像形成装置。 The transfer means includes a transfer roller for applying the transfer bias and a transfer belt charged by the transfer roller,
5. The control unit according to claim 1, wherein the control unit controls the output of the charge eliminating unit based on a resistance value measured by a resistance measuring unit that measures the resistance of the transfer belt. The image forming apparatus described.

前記転写手段は、前記転写バイアスを印加する転写ローラと前記転写ローラによって帯電される転写ベルトとを含み、
前記制御手段は、前記転写ローラと前記転写ベルトの抵抗を測定する抵抗測定手段によって測定された抵抗値に基づいて、前記除電帯電手段の出力を制御することを特徴とする請求項１から４のいずれか一項記載の画像形成装置。 The transfer means includes a transfer roller for applying the transfer bias and a transfer belt charged by the transfer roller,
5. The control unit according to claim 1, wherein the control unit controls the output of the charge eliminating unit based on a resistance value measured by a resistance measuring unit that measures a resistance between the transfer roller and the transfer belt. The image forming apparatus according to claim 1.

前記膜厚測定手段は、前記像担持体の回転数から前記膜厚を測定する手段であることを特徴とする請求項２記載の画像形成装置。 The image forming apparatus according to claim 2, wherein the film thickness measuring unit is a unit that measures the film thickness from the number of rotations of the image carrier.

前記膜厚測定手段は、ワイヤとグリッドからなるスコロトロン帯電器のグリッド電圧と、前記スコロトロン帯電器によって帯電した前記像担持体の帯電電圧との差から前記膜厚を測定する手段であることを特徴とする請求項２記載の画像形成装置。 The film thickness measuring means is a means for measuring the film thickness from a difference between a grid voltage of a scorotron charger composed of a wire and a grid and a charging voltage of the image carrier charged by the scorotron charger. The image forming apparatus according to claim 2.

前記抵抗測定手段は、前記転写ローラに定電流を流した時に測定される電圧値から抵抗を測定する手段であることを特徴とする請求項５又は７記載の画像形成装置。 The image forming apparatus according to claim 5, wherein the resistance measuring unit is a unit that measures resistance from a voltage value measured when a constant current is passed through the transfer roller.

前記抵抗測定手段は、前記転写ベルトの抵抗値を前記転写ベルトの駆動時間から測定する手段であることを特徴とする請求項６又は７記載の画像形成装置。 The image forming apparatus according to claim 6, wherein the resistance measuring unit is a unit that measures a resistance value of the transfer belt from a driving time of the transfer belt.

前記除電帯電手段は、コロトロン帯電器であり、前記制御手段によって定電流制御されることを特徴とする請求項１から１１のいずれか一項記載の画像形成装置。 12. The image forming apparatus according to claim 1, wherein the charge eliminating unit is a corotron charger and is controlled at a constant current by the control unit.

像担持体の表面を所定電位に帯電する帯電ステップと、
露光、現像された前記像担持体表面の現像像を転写材に転写するため、前記帯電手段の帯電極性とは逆極性の転写バイアスを印加する転写バイアス印加ステップと、
前記転写バイアスとは逆極性のバイアスを前記像担持体に印加し、前記像担持体表面の電荷を除電する除電ステップとを有し、
前記除電ステップは、前記帯電ステップによって帯電した帯電極性とは逆極性に帯電した前記像担持体の前記転写材を介さずに前記転写手段が直接接触する領域が、前記帯電極性と同極性となるように除電するステップであることを特徴とする像担持体除電方法。
A charging step for charging the surface of the image carrier to a predetermined potential;
A transfer bias applying step of applying a transfer bias having a polarity opposite to the charging polarity of the charging means in order to transfer the developed and developed image on the surface of the image carrier to a transfer material;
Applying a bias having a polarity opposite to that of the transfer bias to the image carrier to neutralize charges on the surface of the image carrier,
In the static elimination step, a region of the image carrier that is charged to a polarity opposite to the charging polarity charged in the charging step is in the same polarity as the charging polarity in the region where the transfer unit directly contacts without passing through the transfer material. An image carrier neutralizing method, characterized by comprising the step of neutralizing as described above.