Minolta Camera Kabushiki Kaisha

Yasuhiro Kusuda

Takafumi Tottori

Hiroshi Okamoto

Masahide Ueda

Tadafumi Shimizu

Takashi Onishi

Masaru Komura

Chujiro Yokoyama

Moriyoshi Matsushiro

An image forming apparatus provides for the scanning of an original document when placed on a document table. The scanning operation moves from a predetermined position along a predetermined scanning direction. A specifying arrangement for specifying an original document area is provided which is movable along one side of the document table along with a second specifying arrangement for specifying a copy area which is also movable in parallel with the side of the document table. Both specifying arrangements include magnetic members. A detector is incorporated with the scanner so as to detect positions of the specifying arrangements. Signals are generated when the detector detects the magnetic members of the specifying arrangements during the scanning operation. A copy ratio is then computed based on a comparison of the signals which have been detected so that an image is formed which corresponds to the document and the computed copy ratio.

Copy ratio setting apparatus

A developing apparatus comprising: a developing device for contacting an electrostatic image-bearing member with a development mix of toner and carrier particles; a first transporting member for transporting the mix to the developing device, a second transporting member for transporting the mix to the first transporting member; a third transporting member for transporting the mix to the second transporting member such that first and second circulations of the mix are, respectively, formed between the first and second transporting members and between the second and third transporting members; a sensor for producing a concentration signal having a value indicative of the ratio of toner in the mix of the first circulation, which is disposed in the first circulation of the mix; and a toner replenishing device for replenishing toner to the second circulation of the mix in response to the concentration signal such that the toner is replenished from an area except for the area corresponding to the second transporting member in the second circulation of the mix.

Developing apparatus for determining decreased concentration of toner

An image forming apparatus which detects the cause of the image unevenness in the image formation of an electrostatic recording system used for a copying machine, laser beam printer or the like, and automatically takes measures responding thereto. This image forming apparatus includes a surface potential sensor for detecting charge unevenness after charging a photoconductive drum by a charger and a toner density sensor for detecting toner adhesion unevenness after developing by a developing unit, and based on the results of detections of these sensors, when charge unevenness exits, the apparatus judges that the cause of the image unevenness is an abnormal state of the charger, and cleans a charge wire, and when no charge unevenness exists and density unevenness exists, the apparatus judges that the developing unit is abnormal, and displays this abnormality and inhibits the operation of the apparatus. The apparatus further includes a toner sensor for detecting density unevenness after transfer, and when density unevenness is detected by this sensor, it is judged that the cause of the image unevenness is an abnormal state of a transferring charger, and displays this abnormality and inhibits the operation of the apparatus.

Abnormal charge and toner density detecting system and method for use in

In a multi-color copying apparatus including a plurality of developing units containing developers in different colors, respectively, the improvement comprising: said developing units each including a magnet roller, a rotatable sleeve roller and a changeover means for changing over each of said developing units between a developing state and a nondeveloping state; in at least one of said developing units disposed downstream of the remaining ones of said developing units in a direction of displacement of a photosensitive member, said changeover means including a first means for effecting angular displacement of said magnet roller between developing and nondeveloping positions at which one of magnetic poles of said magnet roller confronts and does not confront said photosensitive member, respectively, and a second means for turning on said sleeve roller for its rotational drive such that at the time of changeover of said one of said developing units from the nondeveloping state to the developing state, said second means is actuated upon lapse of a predetermined time period after actuation of said first means.

Multi-color image forming apparatus incorporating selectively operable

An image forming apparatus arranged to develop an electrostatic latent image formed on an electrostatic latent image holding member, and including a developing sleeve rotatably provided to confront the electrostatic latent image holding member, a sleeve driving device for rotating the developing sleeve, a magnet roller provided within the developing sleeve and having a plurality of magnetic poles, a magnet roller driving device for rotating the magnet roller through a predetermined angle, with the magnet roller driving device being arranged to rotate the magnet roller between a first state where its magnetic pole confronts the electrostatic latent image holding member and a second state where an intermediate portion between neighboring magnetic poles confronts the electrostatic latent image holding member, and a control unit for controlling the sleeve driving device and the magnet roller driving device in such a manner as to rotate the magnetic poles of the magnet roller from the first state to the second state after stopping rotation of the developing sleeve when the developing function is to be completed. A bias voltage is applied to the developing sleeve such that the amount of bias voltage applied to the developing sleeve is change from a first value to a second value upon stopping rotation of the developing sleeve or following rotation of the magnet roller, the first value being closer to zero than the second value.

Image forming apparatus capable of preventing simultaneous rotation of

A multi-colored image forming apparatus is capable of forming a copy image of an original document with different colors in designated edit areas. The apparatus has first and second developing devices each containing a developer material of different color and a control section for controlling the first and second developing devices in response to a developing switch signal generated with scanning of designated edit areas of the document. The developing devices have a sleeve to be rotated in a predetermined direction, a multi-pole magnetic roller disposed in the sleeve to be rotated in the same direction as the sleeve, a scraper member for scraping off developer material from the sleeves peripheral face and a feed device for feeding developer material to an upstream side of the scraper member relative to the rotational direction of the sleeve. The control section is operable to stop the rotation of the first actuated developing device's magnetic roller while maintaining the rotation of its sleeve in response to a developing switch signal. Thereafter, the second actuated developing device's magnetic roller is energized. By causing the sleeves of the developing devices to be rotated at different rates, the different color areas may be made to overlap or, alternatively, such overlapping may be minimized or avoided.

Multi-colored image forming apparatus

A multi-color image forming apparatus including an original platform, a photoreceptor, a scanning device, an image forming device for forming an electrostatic latent image on the photoreceptor, first and second developing device for developing the latent image in different colors, respectively, a movable designating device, an input device for giving a command for starting copying, a starting device for starting operation of the scanning device, the image forming device and the first developing device in response to the command from the input device, an output device for outputting a changeover signal for effecting changeover between the first and second developing devices and a control device for, in response to the changeover signal from the output device, stopping operation of the first developing device and starting operation of the second developing device.

Multi-color image forming apparatus

A multiple color image forming apparatus using a plurality of developing devices selectively during one image forming process to reproduce a plurality of designated areas respectively in designated color, whereby color mixing and non-developing of the reproduced image can be freely performed by setting the start and end points of the designated area responsive to a plurality of the developing devices and controlling them in response to such setting.

Growing community of inventors

Osaka, Japan

Yasuhiro Kusuda