【特許請求の範囲】
【請求項１】 像担持体表面に接触配置された帯電部材により前記像担持体表面を一様に帯電する帯電手段と、帯電後の前記像担持体表面を画像情報に応じて露光して静電潜像を形成する露光手段と、前記静電潜像のうちの露光部分に帯電極性と同極性のトナーを付着させてトナー像として現像する現像手段と、前記像担持体上のトナー像を転写材上に転写する転写手段とを備え、転写時に前記転写材に転写されないで前記像担持体上の残ったトナーを前記帯電部材を通過させて前記現像手段で回収する画像形成装置において、
前記帯電部材に前記トナーの帯電極性と同極性および反対極性のバイアスを選択的に印加可能な帯電バイアス電源と、
前記帯電バイアス電源が前記帯電部材に印加するバイアスの極性、大きさ、印加タイミングを制御する制御手段と、を備え、
前記制御手段は、非画像形成時において、前記帯電バイアス電源を制御し、前記トナーの帯電極性と逆極性のバイアスを前記帯電部材に印加することにより前記帯電部材と前記像担持体との間に放電電界を形成した後、
前記トナーの帯電極性と同極性のバイアスであり、かつ、放電閾値以下のバイアスを前記帯電部材に印加する、
ことを特徴とする画像形成装置。
【請求項２】 前記非画像形成時は、画像形成を行う前の準備前回転時、画像形成を行った後の後回転時、先行する画像形成と後続の画像形成との間の準備回転時のうちの少なくとも１つである、
ことを特徴とする請求項１に記載の画像形成装置。
【請求項３】 前記放電電界を形成する際に、前記帯電部材に印加される前記トナーの帯電極性と逆極性のバイアスは、定電流制御により前記帯電部材に印加される、
ことを特徴とする請求項１または２に記載の画像形成装置。
【請求項４】 前記現像手段は、前記像担持体表面に接触配置された現像剤担持体を有し、前記トナーの帯電極性と同極性のバイアスが前記帯電部材に印加されたときに前記像担持体上に転移したトナーを、前記現像剤担持体に印加したバイアスによって回収する、
ことを特徴とする請求項１、２、または３に記載の画像形成装置。
[Claims]
1. A charging means for uniformly charging the surface of the image carrier by a charging member contact-arranged on the surface of the image carrier, and static electricity by exposing the surface of the image carrier after charging according to image information. An exposure means for forming an electro-latent image, a developing means for developing a toner image by adhering toner having the same polarity as the charging polarity to an exposed portion of the electrostatic latent image, and a toner image on the image carrier. In an image forming apparatus provided with a transfer means for transferring onto a transfer material, the toner remaining on the image carrier without being transferred to the transfer material at the time of transfer is passed through the charging member and collected by the developing means.
A charging bias power supply capable of selectively applying a bias having the same polarity as or opposite the charging polarity of the toner to the charging member,
The charging bias power supply includes a control means for controlling the polarity, magnitude, and application timing of the bias applied to the charging member.
The control means controls the charging bias power supply at the time of non-image formation, and applies a bias having a polarity opposite to the charging polarity of the toner to the charging member, thereby between the charging member and the image carrier. After forming the discharge electric field
A bias having the same polarity as the charging polarity of the toner and equal to or less than the discharge threshold is applied to the charging member.
An image forming apparatus characterized in that.
2. The non-image formation is during pre-preparation rotation before image formation, post-rotation after image formation, and pre-rotation between preceding image formation and subsequent image formation. At least one of
The image forming apparatus according to claim 1.
3. A bias having a polarity opposite to the charging polarity of the toner applied to the charging member when the discharge electric field is formed is applied to the charging member by constant current control.
The image forming apparatus according to claim 1 or 2.
4. The developing means has a developer carrier which is contact-arranged on the surface of the image carrier, and when a bias having the same polarity as the charging polarity of the toner is applied to the charging member, the image. The toner transferred onto the carrier is recovered by a bias applied to the developer carrier.
The image forming apparatus according to claim 1, 2, or 3.
請求項２に係る本発明は、請求項１の画像形成装置において、前記非画像形成時は、画像形成を行う前の準備前回転時、画像形成を行った後の後回転時、先行する画像形成と後続の画像形成との間の準備回転時のうちの少なくとも１つである、ことを特徴とする。
According to the second aspect of the present invention, in the image forming apparatus of the first aspect, the non-image forming is performed during the pre-preparation rotation before image formation, the post-rotation after image formation, and the preceding image. It is characterized in that it is at least one of the preparatory rotations between the formation and the subsequent image formation.
請求項４に係る本発明は、請求項１、２、または３の画像形成装置において、前記現像手段は、前記像担持体表面に接触配置された現像剤担持体を有し、前記トナーの帯電極性と同極性のバイアスが前記帯電部材に印加されたときに前記像担持体上に転移したトナーを、前記現像剤担持体に印加したバイアスによって回収する、ことを特徴とする。
According to the fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the developing means has a developing agent carrier which is contact-arranged on the surface of the image carrier, and the toner is charged. When a bias having the same polarity as that of the polarity is applied to the charged member, the toner transferred onto the image carrier is recovered by the bias applied to the developer carrier.