Minolta Company, Ltd.

Toshifumi Watanabe

Masaki Tanaka

Yukihiko Okuno

Atsushi Kawai

Tetsuya Sakai

Kentaro Katori

Katsuyuki Hirata

Hironobu Nakata

Naoyoshi Kinoshita

Yasuyuki Inada

Kuniya Matsuura

Hiroshi Nishikawa

Futoshi Hamada

Hiroshi Sakakibara

A tandem-type image forming apparatus forms a color image by transferring images formed by a plurality of image forming units set along a transfer belt onto a recording sheet transported by the transfer belt. The tandem-type image forming apparatus includes a plurality of detecting units, each detecting a toner image formed by a corresponding image forming unit to obtain the amount of toner in the toner image, a standard pattern formation controlling unit for controlling one of the image forming units to form a standard pattern to be detected by the detecting units, a sensitivity obtaining unit for obtaining a value as an evaluation value that is outputted by each of the detecting units on detecting the standard pattern, and an detection output adjusting unit for adjusting a value outputted by the detecting unit in accordance with the evaluation value. An image forming condition is set for each of the image forming units in accordance with the adjusted value, and image formation is performed under the image forming conditions.

Image forming apparatus having function for automatically adjusting image forming condition

The object of the present invention is to reduce the burden with regard to cleaning of the test toner pattern formed during AIDC in an electrophotographic image forming apparatus. In order to attain said object, the present invention is an electrophotographic copying machine that transfers a toner image formed on a photoreceptor drum onto a sheet of paper conveyed on a conveyor belt, wherein where the toner density of the test toner pattern formed on the photoreceptor drum under prescribed image formation parameters is optically detected by a sensor, the transfer charger output is set to be lower than it is in image formation mode, and a portion of the test toner pattern is transferred onto the conveyor belt and then wiped off by a cleaner.

Image forming apparatus that reduces test toner cleaning

A digital copying machine develops an electrostatic latent image formed on a photosensitive drum with toner, and transfers the developed image onto a sheet. In forming images on the photosensitive drum successively, three types of test patterns are formed in order in intro-image areas between image forming areas, and AIDC is made. The first test pattern is a low-density pattern, the second test pattern is an intermediate-density pattern, and the third test pattern is a high-density pattern.

Image forming apparatus

Using an image forming apparatus, toner images are respectively formed on photosensitive drums of image forming units set along a transport belt, and the toner images are transferred onto the transport belt or a recording sheet transported on the transport belt to form a color image. The image forming apparatus is composed of a first density detecting sensor for detecting a density of a toner image formed on the recording sheet or the transport belt at the upstream side of each transfer position of at least one image forming unit which is located at the downstream side of a first image forming unit in a transport direction of the transport belt and which is selected as a subject of an image forming condition determination, a second density detecting sensor for detecting a density of the toner image formed on the recording sheet or the transport belt at the downstream side of the transfer position, and an image forming condition determining unit for comparing a detection value given by the first density detecting sensor with a detection value given by the second density detecting sensor and for determining an image forming condition in accordance with the comparison result for an image formation performed by the image forming unit selected as the subject.

Tandem-type image forming apparatus and image forming condition

A device for measuring toner concentration of developer housed in a developing system, which developer comprising toner and carrier. The device has a transparent detection window facing the interior of the developing system, which transparent detection window comprising a first transparent plate member and a second transparent plate member being in contact with the first transparent plate member. The first transparent plate member is made of a material which becomes charged, through its contact with the second transparent plate member, with the opposite polarity from the charge polarity of the toner and the second transparent plate member is made of a material which becomes charged, through its contact with the carrier, with the same polarity from the charge polarity of the toner, so that the second transparent plate member strongly repels the toner having the same polarity charge and adherence of the toner to the second transparent plate member is reliably prevented.

Device for measuring toner concentration in developer comprising toner

An image forming apparatus is provided which is immune to characteristic variations of a photoconductor and a developer material, which can detect the amount of toner adhering to a test toner image accurately, and which can always form a favorable image using an optimal image forming parameter. A predetermined test toner image is formed on the photoconductor using developing devices. The amount of toner adhering to the formed test toner image is detected by an AIDC sensor. A printer control unit determines grid potential Vg of a corona charger and development bias potential Vb of each developing device based on the detected amount of adhering toner. A predetermined image is formed using the determined grid potential and development bias potential. The printer control unit changes the image forming condition for the next test toner image based on the detected amount of adhering toner so that the amount of toner adhering to the next test toner image can be detected in a range of high detection sensitivity of the AIDC sensor.

Digital image forming apparatus with test image optimization

An image formation apparatus for forming a full color image in the four colors of cyan, magenta, yellow and black has a optical ATDC sensor attached in a cyan developing device to control the toner density under optical ATDC. A black developing device has the toner density controlled by AIDC. A standard develop efficiency .eta.STD of the cyan developing device obtained as a result of the AIDC is compared with a develop efficiency .eta. of black toner. The toner supply amount of the black developing device is determined according to the comparison result to supply the toner. Thus, an image formation apparatus is provided that can detect at favorable accuracy the toner density of a developing device incorporating a developer of which the toner density cannot be detected using optical ATDC to supply a required amount of toner.

Image formation apparatus that can maintain appropriately toner density

A printer control unit carries out a predetermined calculation based on the amount of adhering toner detected by an AIDC sensor and the surface potential of a photoconductor detected by a V sensor to correct the light emission intensity of a light source to prepare light emission characteristic data for .gamma. correction to obtain an optimal image. A .gamma. correcting unit corrects an image signal output from an image signal processing unit using the calculated light emission characteristic data for .gamma. correction to control the light source to emit light based on the corrected data. More specifically, since the .gamma. correction data is obtained by calculation, optimal .gamma. correction can always be carried out without a memory of a large capacity.

Digital image forming apparatus which specifies a sensitivity

A copying machine wherein a developing device is provided with a first sensor for detecting the toner density in a developer and a second sensor which is provided around a photosensitive drum for detecting the amount of deposited toner on a test pattern. The toner supply is controlled according to a result detected by the second sensor. When the toner density is judged high from a result detected by the first sensor, a developing bias voltage is set high by a computer, and when the toner density is judged low, the developing bias voltage is set low.

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Toyohashi, Japan

Toshifumi Watanabe