Minolta Camera Kabushiki Kaisha

Kunio Toda

Tomoaki Yokoyama

Tateki Oka

Taisuke Nagao

Naoki Toyoshi

Mineyuki Sako

Yasuyuki Hiromoto

An image forming apparatus is provided with an optical system for forming a first electrostatic latent image and a second electrostatic latent image on a rotatable photosensitive member, a first developing device accommodating a first developer for developing the first electrostatic latent image, and a second developing device accommodating a second developer for developing the second electrostatic latent image. The second developing device is located downstream from the first developing device in a direction of rotation of the photosensitive member and is provided with a developing roller having a magnetic force. The second developer differs in color from the first developer and has a magnetism greater than the first developer. The second developer is transported to the second electrostatic latent image along a periphery of the developing roller. The image forming apparatus is further provided with a collector provided in the second developing device and having a collecting member confronting the developing roller. The first developer mixed in the second developer is moved toward and collected by the collecting member under the influence of an electric field formed between the collecting member and developing roller. Alternatively, the photosensitive member can act as a collector for collecting first developer mixed in the second developer.

Image forming apparatus having a plurality of developing devices

An image forming apparatus includes an image support member; a first electrostatic latent image forming device for forming a first electrostatic latent image on the image support member; a first developing device for developing the first electrostatic latent image with first toner; a second electrostatic latent image forming device for forming a second electrostatic latent image on the image support member; and a second developing device for developing the second electrostatic latent image with second toner; the second toner having a color different from that of the first toner and having charging characteristics relative to carrier, identical with those of the first toner; the second toner having an average particle diameter larger than that of the first toner.

Image forming apparatus having developing devices which use different

An image forming apparatus having plural developing devices, comprising: a photosensitive member arranged rotatably in one direction and holding an electrostatic latent image corresponding to an original image; a developing sleeve rotatably arranged in each developing device at a position confronting said photosensitive member to transport a developer; a device for simultaneously driving for rotation of each of said developing sleeves in said developing devices; and an adjusting mechanism for adjusting operation of said developing devices so that in a region where said developing sleeves confront with said photosensitive member, a developer packaged density (F) in said developing device arranged at an upstream side in a rotational direction of said member is larger than that of said developing device arranged at a downstream side in the rotational direction of said member, which is

Image forming apparatus having plural magnetic brush developing devices

An image forming apparatus includes a photosensitive member rotatably supported; an upstream developing device, in a rotary direction of the member, for developing an electrostatic latent image corresponding to a solid image and/or a literal image with an accommodated developer therein; a downstream developing device, in the direction thereof, for developing an electrostatic latent image corresponding to a line image with an accommodated developer in the same color as that in the upstream developing device; a cleaning device for collecting the developer remained on the surface of the member; and a developer transporting device for transporting the developer collected by the cleaning device to the upstream developing device. The apparatus further includes a charging device for charging a specified zone of the surface of the member; an image forming device for forming the latent image on the charged specified zone thereof; a voltage changing device for selecting one of a first developing bias voltage and a second developing bias voltage which is higher than the first developing bias voltage; and a control device for controlling the voltage changing device. By the control device, the first developing bias voltage is applied to the upstream developing device while the latent image on the specified zone of the member passes through a developing region of the upstream developing device and the second developing bias voltage is applied thereto while the specified zone passes therethrough again after the latent image passes therethrough.

Image forming apparatus

An image forming apparatus wherein a photosensitive layer arranged to rotate in one direction is charged by a charger, and a negative electrostatic latent image is formed thereon by an exposure unit and then is subjected to reversal development by a developing device so that a positive noticeable image can be attained. The apparatus has a scorotoron charger for charging the negative latent image which has just been formed by the exposure unit with the opposite polarity thereof. A grid of the scorotoron charger is constituted to be impressed with a voltage with the same polarity as the latent image and a value lower than that of the surface potential, and by the scorotoron charger, the potential of the non-imaged portions of the latent image is lowered around the grid voltage. Further, the developing device is constituted to be impressed with a developing bias voltage with the same polarity as the latent image and a value lower than that of the surface potential but higher than a developing threshold value, whereby toner charged with the same polarity as that charged by the charger sticks to the imaged portions with potential lower than the developing bias voltage, resulting in a positive toner image with sharp line widths.

Electrophotographic image forming apparatus

A toner supply device including a hopper for containing the toner; a toner supply roller rotatably disposed below the hopper so as to fill an opening formed in a lower section of the hopper; a charging blade which is disposed so as to be in close contact under pressure with the toner supply roller to electrically charge the toner which is transported on the toner supply roller; a toner scraping mechanism having a toner scraping blade arranged at a position located downstream to the charging blade with respect to a rotational direction of the toner supply; a sensor for detecting the toner density; and a control unit for controlling the toner scraping mechanism depending on signals from the sensor so as to make the toner scraping blade move to one of a first position at which it comes in close contact under pressure with the toner supply roller and a second position at which the blade stands apart from the toner supply roller. When the toner supply roller is driven, a charged toner layer is formed on the peripheral surface of the roller by the charging blade. And the toner scraping blade is positioned at the first position by the control unit in the case of a low density of the toner, so that the charged toner layer thereon may be scraped off to be supplied to the developing device.

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Osaka, Japan

Kunio Toda