Kabushiki Kaisha Toshiba

Kabushiki Kaisha Tec

Chinobu Sakai

Takahito Kabai

Seiji Arai

Michihisa Iguchi

Satoshi Katagata

Tetsuya Nakamura

Yoshiaki Okano

Hiroshi Hashizume

Hirotaka Fukuyama

Kouichirou Satou

Takashi Ishikawa

Masaaki Ishikawa

An image forming apparatus including an image forming unit to form a developer image on an image carrier, a conveying member to convey an image receiving member toward the image carrier, a transfer charger to transfer the developer image formed on the image carrier on the image receiving member by giving a transfer charge to the image receiving member conveyed by the conveying member, a guide member provided between the conveying member and the transfer charger to guide the image receiving member conveyed by the conveying member toward the transfer position and a separation charger arranged at the downstream side of the transfer charger along the transfer direction of the image receiving member to separate the image receiving member with the developer image transferred thereon by the transfer charger. A bias voltage having the same polarity as the transfer charge is applied to the guide member. When the developer image is transferred on the image receiving member by the transfer charger, this bias voltage is controlled so that it is set at a first bias voltage before the image receiving member comes near the separation charger and at a second bias voltage that is larger than the first bias voltage when the image receiving member comes near the separation charger.

Image forming apparatus for forming a more uniform image

At start of rotation of a photosensitive drum, rotation of a developing roller caused by a developing/register rollers driver is kept stopped until a time required for a predetermined point on the photosensitive member, which was located at a charging position when charging thereof by a charging device was started, to reach a development position elapses, and thereafter the developing roller is rotated by the developing/register rollers driver. When the predetermined point on the photosensitive member, which was located at the developing position when at least rotation of the photosensitive member was started, passes the transfer position, a roller cleaning voltage having the same polarity as the charge polarity of toner is applied to a transfer roller.

Electrophotographic apparatus that prevents toner from attaching to a

A developing device used in an electrophotographic apparatus has seal members fixedly disposed between both end portions of a developing roller and those portions of inner walls of a device casing which correspond to both end portions of the developing roller. The seal members are made of a material which can be charged by friction with the developing roller to have the same polarity as charged toner. The toner is blocked by the seal members and presented from entering end portions of the developing roller.

Electrophotographic apparatus having cleaning device and developing

In a developing device for developing an electrostatic latent image formed on a photosensitive member in an electrophotographic apparatus, a developing roller and a developing blade are formed such that the hardness of the surface of the developing blade is higher than the hardness of the surface of the developing roller by 30 degrees or more in JIS-A hardness. The developing blade deforms and bites into the developing roller. Accordingly, the developing roller can be brought into tight contact with the developing blade, and a great frictional force is applied to the toner passing between the developing roller and blade to fully charge the toner.

Developing device for electrophotographic apparatus

A transfer device of a contact transfer method wherein a transfer power supply applies a predetermined transfer voltage to a transfer roller contacting the rear surface of a printing sheet, so that an electric field for causing the toner to be attracted by the transfer roller is generated. A lumped constant resistor is electrically inserted between the transfer roller and the transfer power supply. The lumped constant resistor has an electric resistance smaller than an equivalent electric resistance obtained when the whole transfer roller is regarded as one electric resistor. When the electric resistance of the printing sheet changes in accordance with a change in ambient environment, the voltage drop across the lumped constant resistor is changed to compensate for the change in electric resistance of the printing sheet.

Transfer roller and toner for electrophotographic apparatus

A developing device used in an electrophotographic apparatus has seal members fixedly disposed between both end portions of a developing roller and those portions of inner walls of a device casing which correspond to both end portions of the developing roller. The seal members are made of a material which can be charged by friction with the developing roller to have the same polarity as charged toner. The toner is blocked by the seal members and prevented from entering end portions of the developing roller.

Electrophotographic apparatus having developing device with seals for

In an electrophotographic device, a main body is divided into a lower body and a swingable upper body. A process unit formed of at least a toner holder, a charger, and a developer is detachably mounted in the lower body. The position of the process unit (particularly, the photosensitive member) relative to the lower body (particularly, a member driving gear) is controlled by placing a shaft of the member through a groove in a side wall of the lower body at one end of the member, and by bringing a lower end of the side wall of the process unit supporting the member into contact with an upper end of a support member supporting the member driving gear. An exposure unit mounted in the upper body is positioned to the photosensitive member with a predetermined distance therebetween by bringing a contact portion of the exposure head into contact with the side wall of the lower body supporting the member.

Detachable process unit for an electrophotographic device

A developing device includes an agitator rotated in a toner hopper. The agitator has a rod portion. A first coil spring portion is wound around the first portion of the rod portion in a first direction. A second coil spring portion is wound around the second portion of the rod portion in a second direction. The first direction is opposite to the second direction.

Developing device and image forming apparatus including an agitator

A toner pack for use in an electrophotographic apparatus is formed of a polypropylene resin containing 30 to 50 wt % calcium carbonate filler. This resin has a high deformability, and generates a small amount of heat at the time of incineration thereof. Thus, the used toner pack can be disposed of together with flammable products made of paper and/or wood. Further, at the time of disposal, it is possible to fold the used toner pack to reduce its size.

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Tokyo, Japan

Chinobu Sakai