EP0519710B1 - Bilderzeugungsgerät mit der Einstellvorrichtung für die Bilderzeugungsbedingungen ansprechend auf ein Testmusterbild - Google Patents

Bilderzeugungsgerät mit der Einstellvorrichtung für die Bilderzeugungsbedingungen ansprechend auf ein Testmusterbild Download PDF

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Publication number
EP0519710B1
EP0519710B1 EP19920305567 EP92305567A EP0519710B1 EP 0519710 B1 EP0519710 B1 EP 0519710B1 EP 19920305567 EP19920305567 EP 19920305567 EP 92305567 A EP92305567 A EP 92305567A EP 0519710 B1 EP0519710 B1 EP 0519710B1
Authority
EP
European Patent Office
Prior art keywords
image
transfer
image forming
bearing member
toner
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19920305567
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English (en)
French (fr)
Other versions
EP0519710A2 (de
EP0519710A3 (en
Inventor
Masami C/O Canon Kabushiki Kaisha Izumizaki
Yoshihiro c/o Canon Kabushiki Kaisha Murasawa
Yoshinori c/o Canon Kabushiki Kaisha Nagao
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
Original Assignee
Canon Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
Publication of EP0519710A2 publication Critical patent/EP0519710A2/de
Publication of EP0519710A3 publication Critical patent/EP0519710A3/en
Application granted granted Critical
Publication of EP0519710B1 publication Critical patent/EP0519710B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/50—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control
    • G03G15/5054—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control by measuring the characteristics of an intermediate image carrying member or the characteristics of an image on an intermediate image carrying member, e.g. intermediate transfer belt or drum, conveyor belt
    • G03G15/5058—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control by measuring the characteristics of an intermediate image carrying member or the characteristics of an image on an intermediate image carrying member, e.g. intermediate transfer belt or drum, conveyor belt using a test patch
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
    • G03G15/16—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
    • G03G15/163—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using the force produced by an electrostatic transfer field formed between the second base and the electrographic recording member, e.g. transfer through an air gap
    • G03G15/1635—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using the force produced by an electrostatic transfer field formed between the second base and the electrographic recording member, e.g. transfer through an air gap the field being produced by laying down an electrostatic charge behind the base or the recording member, e.g. by a corona device
    • G03G15/1645—Arrangements for controlling the amount of charge
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/50—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control
    • G03G15/5033—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control by measuring the photoconductor characteristics, e.g. temperature, or the characteristics of an image on the photoconductor
    • G03G15/5041—Detecting a toner image, e.g. density, toner coverage, using a test patch
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/00025—Machine control, e.g. regulating different parts of the machine
    • G03G2215/00029—Image density detection
    • G03G2215/00033—Image density detection on recording member
    • G03G2215/00037—Toner image detection
    • G03G2215/00042—Optical detection
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/00025—Machine control, e.g. regulating different parts of the machine
    • G03G2215/0013—Machine control, e.g. regulating different parts of the machine for producing copies with MICR

Definitions

  • the present invention relates to an image forming apparatus having an image forming condition controller responsive to a test pattern image, more particularly to an image forming apparatus in which a test pattern is formed on an image bearing member such as an electrophotographic photosensitive member, and an image forming condition is controlled in accordance with detection of the test pattern.
  • image bearing member such as an electrophotographic photosensitive member
  • image forming condition is controlled in accordance with detection of the test pattern.
  • full-color image forming machines including an electrophotographic type, an ink jet recording type or a thermal transfer recording type.
  • the electrophotographic type is advantageous in the high speed printing and availability of the plain paper, and therefore, the developments thereof are promoted.
  • toner is supplied into the developing device to compensate for the consumption of the toner and In order to accomplish this, a developer content detector and a control device are used to maintain the toner content.
  • FIG. 2 shows an example of such an image forming apparatus.
  • the image forming apparatus comprises a bi-directional emission type LED 1, a photodiode 2, a developing sleeve 3 and an image bearing member in the form of a photosensitive drum 4.
  • a developing device 9 is disposed faced to the photosensitive drum 4 and includes a developer chamber 11 and a stirring chamber 12 which are partitioned by a partition wall 10 extending in the direction perpendicular to the sheet of the drawing of Figure 2. The portion above the partition wall 10 is opened so as to allow the developer to be returned from the developer chamber 11 to the stirring chamber by a screw.
  • the developer chamber and the stirring chamber 12 contain the two component developer comprising the toner and carrier particles.
  • the LED 1 illuminates a test pattern image (patch) 20 which is an area toner image formed on the image bearing member prior to a regular image forming operation.
  • the light reflected by the patch 20 is received by a photodiode 2, which produces an electrical output, which is in turn compared with a reference level. In response to the difference between the output and the reference level, the toner is supplied to the upstream side of the screw of the stirring chamber.
  • the developer chamber 11 of the developing device 9 is provided with an opening at a position corresponding to a developing zone.
  • a developing sleeve 3 is disposed in the opening 14 and is partly exposed to the photosensitive drum 4 in the developing zone.
  • the developing sleeve 3 is made of non-magnetic material such as stainless steel or aluminum. During the developing operation, it rotates in the direction indicated by an arrow, and a magnet 13 is stationarily disposed therein to function as a magnetic field generating means.
  • the developing sleeve 3 is supplied with an AC biased DC voltage from a voltage source 15, so that the toner is transferred onto the photosensitive drum 4 from the developing sleeve 3 by the electric field of the electrostatic latent image.
  • the toner images of different colors are transferred from the photosensitive drum 4 onto the same transfer material carried on the transfer drum 16 by the electric potential produced by the transfer charger 17. After each of the transfer operations, the toner remaining on the drum is cleaned and removed by the cleaning means 18.
  • a reference density pattern or patch 20 is formed on the photosensitive drum 4, and the patch 20 is developed under a predetermined developing condition.
  • the reflection image density of the developed patch is detected by the photodiode 2, and the detection is used to control the toner content.
  • the sensor comprising the LED 1 and the photodiode 2 are easily contaminated by the toner scattered from the developing device 9 with the result of erroneous image density detection and therefore erroneous toner content control.
  • U.S. Patent Specification No. 4,797,705 discloses electrophotographic image forming apparatus which includes a sensor for detecting the amount of toner adhering to the photosensitive member so as to detect malfunctions.
  • Japanese Patent Abstract No. 61-55675 discloses a transfer-type printer which can obtain the difference between toner density before and after transfer of toner so as to detect malfunctions.
  • Figure 1 is a sectional view of an image forming apparatus according to an embodiment of the present invention.
  • Figure 2 is a sectional view of a conventional image forming apparatus.
  • Figure 4 illustrates a part of an image forming apparatus according to a fourth embodiment of the present invention.
  • Figure 5 is a sectional view of the image forming apparatus according to the fourth embodiment of the present invention.
  • Figure 7 is a block diagram of a control system for the apparatus according to the fourth embodiment.
  • FIG 1 there is shown an image forming apparatus according to a first embodiment of the present invention.
  • the elements 1 - 4, 9 - 18 and 20 are similar to those in Figure 2, and the detailed description thereof are omitted for simplicity.
  • the apparatus of Figure 1 includes a pushing means 21, a CPU 22 and a cleaning means 25 for cleaning the transfer drum.
  • the discrimination is made as to whether the image is the patch pattern or the usual image. If it is the patch, the transfer current to the transfer charger 17 is stopped or reduced at step S104 so as to prevent the patch image from being transferred onto the transfer sheet on the transfer drum 16.
  • the patch image is illuminated by the LED 1, and the light reflected thereby is detected by the photodiode 2.
  • the output of the photodiode 2 is compared with a reference level. In accordance with the difference from the reference level, the toner is supplied.
  • step S106 the toner image of the patch is removed by the cleaning means 18.
  • the patch reading sensor comprising the LED 1 and the photodiode 2 is disposed downstream of the transfer drum 16 with respect to the movement direction of the periphery of the image bearing member.
  • the charge of the transfer drum 16 is removed, or it is charged to the polarity which is the same as the toner charge, when the patch 20 passes on the transfer drum 16.
  • the patch image is stably read without contamination of the sensor surfaces.
  • the pushing means 21 in the form of a sheet made of polyethylene or a rod pushes the transfer material supporting sheet of the transfer drum 16 to provide the proper nip pressure.
  • the pushing means 21 is released when the patch 20 passes by the transfer drum to prevent the transfer of the patch image to the transfer drum or the transfer material thereon. For the purpose of this release, the pushing means 21 is rotated or moved.
  • the voltage applied to the transfer charger during rotation of the photosensitive drum is opposite when the usual image is at the transfer position from that when the patch image 20 is at the transfer position.
  • the used toner is charged to the negative polarity, and therefore, the potential of the transfer drum is positive when the usual toner image is to be transferred onto the transfer material.
  • the negative potential is produced.
  • Embodiment 3 may be combined with Embodiment 2.
  • the sensor comprises an LED 1 and a photodiode 2 which are disposed at the opposite side of the developing device 9 from the transfer drum 16.
  • the density detecting patch includes 16 tone gradation levels formed at predetermined timing and is used as information for controlling image forming conditions. On the basis of the detection a relation between an input pulse and output density is determined. Then, a tone gradation correcting function (LUT ... look-up table) is determined. Using the correction function LUT, the image forming condition or conditions are changed. Examples of the image forming conditions include the degree of charging, the exposure amount, the level of developing bias, the transfer bias and a combination of them.
  • the transfer bias voltage application is changed so as to prevent the toner image during the patch detecting operation, when the transfer drum is used. Therefore, the transfer drum is also prevented from contamination.
  • the present invention is effective when the transfer drum is replaced with an intermediate image transfer material or a transfer material conveying belt.
  • the number of image forming stations corresponds to the number of colors.
  • the toner image on the photosensitive drum formed at each of the image forming stations is transferred onto the transfer drum conveyed on a transfer belt 31a to face the transfer material to the photosensitive drums sequentially.
  • the image forming stations Pm, Pc, Py and Pk are for magenta, cyan, yellow and black colors, respectively, and are provided with the photosensitive drums 26M, 26C, 26Y and 26K, respectively.
  • the photosensitive drums are rotated in the direction indicated by arrows (clockwise direction).
  • a primary (corona) charger 27M, 27C, 27Y or 27K there are a primary (corona) charger 27M, 27C, 27Y or 27K, optical scanning means 28M, 28C, 28Y or 28K, a developing device 29M, 29C, 29Y or 29K, and a cleaning device 30M, 30C, 30Y or 30K.
  • An image transfer means 31 constituting image forming means comprises a transfer belt 31a common to all of the image forming stations, transfer chargers 31M, 31C, 31Y and 31K for the respective transfer stations.
  • the transfer material P conveyed in the predetermined direction on the transfer drum 31a receives sequentially the toner images of the different colors from the photosensitive drum.
  • Polyethylene sheets 41M, 41C, 41Y and 41K are disposed below the photosensitive drums 26M, 26C, 26Y and 26K, respectively to provide the proper nip pressure between the photosensitive drum and the transfer belt 31a, that is, the transfer belt 31a is pushed upwardly by the sheets.
  • the sheets are rotatable to take contact and non-contact positions, thus permitting contact and non-contact between the photosensitive drum and the transfer belt.
  • the material of the transfer belt 31a may be polyurethane material, polycarbonate material, PVdF (polyvinylidene fluoride) or the like.
  • the toner has an average particle size of 3 - 20 microns and comprises polyester resin and coloring pigments dispersed therein.
  • the toner powder contains silica particles.
  • the materials may be styrene-acryl resin material, and the coloring material may be carbon black, benzene yellow pigment, anthraquinone dye, copper phthalocyanine pigment.
  • the transfer efficiency is determined on the basis of the density of the test patch pattern 47, and on the basis of the determination, the image density is stabilised.
  • the test patch latent image is formed on each of the photosensitive drums 26M, 26C, 26Y and 26K.
  • the test patch comprises 8 bit linear density levels from 00 (white) to FF (black), and therefore, the test patch latent image is expressed as FFH.
  • the latent images are visualised by the developing devices 29M, 29C, 29Y and 29K, respectively.
  • the pushing films 41M, 41C, 41Y and 41K are placed at a non-contact position relative to the transfer belt 31a, so that the transfer belt 31a is spaced from the photosensitive drum.
  • the image density of the test patch pattern is optically detected and converted to an electric signal by the patch image density sensor 43.
  • the photosensitive drum is cleaned so that the residual toner is removed.
  • the pre-transfer density Da determined at step S104 and the post-transfer density Db determined at S109 are subjected to the transfer efficiency calculation.
  • the image forming condition or conditions are controlled on the basis of the transfer efficiency thus obtained.
  • the discrimination is made as to whether the toner content T/(T+C) (wt. %) is deviated from the reference density or not, on the basis of the output of the developer density sensor 44. If it is not deviated, the following transfer current control is carried out.
  • the results of the detections by the patch image density sensor 43, the potential sensor 42 and the developer density sensor 44 are discriminated by the controller 46. If the transfer efficiency is deviated from 85 ⁇ 5 %, the controller 46 produces instruction to the transfer current control circuit 48 in accordance with the deviation so as to provide the proper transfer efficiency.
  • step S101 the latent images of the test patches FFH are formed on the photosensitive drums 26M, 26C, 26Y and 26K.
  • step S102 the latent images are visualized by the developing devices 29M, 29C, 29Y and 29K.
  • step S103 the pushing films 41M, 41C, 41Y and 41K are spaced away from the belt 31a to bring the transfer belt 31a out of contact with the drum, so that the test patch 47 passes through the image transfer station while being out of contact with the transfer belt 31a.
  • the test patch 47 becomes faced to the patch image density sensor 43M, 43C, 43Y or 43K, the image density is detected (step S104). Then, the photosensitive drum 26M, 26C, 26Y or 26K is stopped.
  • the photosensitive drums 26M, 26C, 26Y and 26K are rotated in the opposite direction, and at step S106, the photosensitive drums are then stopped when the test images are at the positions between the transfer belt 31a and the associated developing devices 29M, 29C, 29Y and 29K.
  • the films 41M, 41C, 41Y and 41K are contacted to the belt 31a.
  • the photosensitive drums are rotated in the forward direction, again.
  • the test patches 47 passes through the transfer position (transfer belt 31a)
  • the image transfer current is supplied to the transfer chargers 31M, 31C, 31Y and 31K, so that the transfer voltages are applied, and therefore, the test patches 47 are transferred onto the transfer belt.
  • the image densities of the test patches 43a remaining on the associated photosensitive drums 26M, 26C, 26Y and 26K are detected at step S109 by the patch density sensors 43M, 43C, 43Y and 43K. Thereafter, the images are removed by the cleaning means at step S110. Similarly to the fifth embodiment, the transfer efficiency is calculated at step S111.
  • the pre-transfer and post-transfer image densities can be detected through one test patch image formation.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Control Or Security For Electrophotography (AREA)
  • Dry Development In Electrophotography (AREA)

Claims (7)

  1. Bilderzeugungsgerät mit
    einem photoleitfähigen Bildhalteteil (4, 26) zum Halten eines elektrischen Bildes,
    einer Entwicklungseinrichtung (9, 29) zur Entwicklung des elektrischen Bildes auf dem Bildhalteteil mittels Toner in ein Tonerbild,
    einem drehbaren Übertragungsteil (16, 31A) zum Fördern eines Bildträgerteils zur Übertragung des Tonerbildes an einer Bildübertragungsposition von dem Bildhalteteil auf das Bildträgerteil,
    Testbild-Ausbildungseinrichtungen zum Ausbilden eines Testbildes auf dem Bildhalteteil, und
    Erfassungseinrichtungen (1, 2, 43) zur Erfassung der Dichte eines Testbildes, das die Bildübertragungsposition durchlaufen hat,
    gekennzeichnet durch
    eine steuerbare Andruckeinrichtung (21, 41), um die Oberfläche des Übertragungsteils entweder zu dem Bildhalteteil hin oder von dem Bildhalteteil weg zu bewegen, und
    eine Steuereinrichtung (22) zur Steuerung der Andruckeinrichtung derart, daß die Oberfläche des Übertragungsteils von dem Bildhalteteil weg bewegt wird, wenn ein Testbild auf dem Bildhalteteil die Bildübertragungsposition durchläuft.
  2. Gerät nach Anspruch 1,
    gekennzeichnet durch
    eine Einrichtung (17, 31) zur Erzeugung eines elektrischen Übertragungs-Feldes zwischen dem Bildhalteteil und dem drehbaren Übertragungsteil, wobei die Steuereinrichtung im Betrieb die Einrichtung zur Erzeugung des elektrischen ÜbertragungsFeldes abschaltet, wenn ein auf dem Bildhalteteil ausgebildeter Testbildausschnitt die Bildübertragungsposition durchläuft.
  3. Gerät nach Anspruch 1 oder 2,
    dadurch gekennzeichnet, daß die Erfassungseinrichtung eine Lichtquelle (1) und einen Photoempfänger (2) enthält.
  4. Gerät nach einem der vorangehenden Ansprüche,
    gekennzeichnet durch
    eine Bildausbildungsbedingungs-Steuereinrichtung (46) zur Steuerung der Bedingungen, unter denen ein Bild auf einen Aufzeichnungsträger übertragen wird, beruhend auf dem Ausgangssignal der Erfassungseinrichtung (1, 2, 43).
  5. Gerät nach Anspruch 4,
    dadurch gekennzeichnet, daß
    die Bildausbildungsbedingungs-Steuereinrichtung (46) zur Steuerung der Feldstärke eines elektrischen Feldes zwischen dem Bildhalteteil und dem Übertragungsteil (16, 31A) geeignet ist.
  6. Gerät nach Anspruch 4 oder 5,
    dadurch gekennzeichnet, daß
    die Bildausbildungsbedingungs-Steuereinrichtung (46) das bei der Erzeugung eines Bildes auf dem Bildhalteteil vorliegende Potential steuert.
  7. Gerät nach Anspruch 4, 5 oder 6,
    dadurch gekennzeichnet, daß
    die Bildausbildungsbedingungs-Steuereinrichtung (46) zur Steuerung der Entwicklungseinrichtung (9, 29) geeignet ist.
EP19920305567 1991-06-18 1992-06-17 Bilderzeugungsgerät mit der Einstellvorrichtung für die Bilderzeugungsbedingungen ansprechend auf ein Testmusterbild Expired - Lifetime EP0519710B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP146200/91 1991-06-18
JP14620091 1991-06-18
JP19892991 1991-07-12
JP198929/91 1991-07-12

Publications (3)

Publication Number Publication Date
EP0519710A2 EP0519710A2 (de) 1992-12-23
EP0519710A3 EP0519710A3 (en) 1993-02-24
EP0519710B1 true EP0519710B1 (de) 1996-08-21

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EP19920305567 Expired - Lifetime EP0519710B1 (de) 1991-06-18 1992-06-17 Bilderzeugungsgerät mit der Einstellvorrichtung für die Bilderzeugungsbedingungen ansprechend auf ein Testmusterbild

Country Status (2)

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EP (1) EP0519710B1 (de)
DE (1) DE69212915T2 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8121498B2 (en) 2007-10-23 2012-02-21 Ricoh Company, Limited Image forming apparatus and developer supply method therefor

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3126611B2 (ja) * 1993-12-28 2001-01-22 キヤノン株式会社 画像形成装置
DE69629146T2 (de) * 1995-04-28 2004-05-27 Canon K.K. Trägerelement für Übertragungsmaterialien
US5937229A (en) * 1997-12-29 1999-08-10 Eastman Kodak Company Image forming apparatus and method with control of electrostatic transfer using constant current
JP2008049671A (ja) 2006-08-28 2008-03-06 Fujifilm Corp 画像形成装置および画像形成方法
JP4355002B2 (ja) * 2007-03-06 2009-10-28 シャープ株式会社 画像形成装置

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57202569A (en) * 1981-06-08 1982-12-11 Minolta Camera Co Ltd Electrophotographic copier
JPS59123857A (ja) * 1982-12-29 1984-07-17 Canon Inc 画像再生制御装置
JPS6155675A (ja) * 1984-08-27 1986-03-20 Fujitsu Ltd 転写形印刷装置
JPH0789250B2 (ja) * 1986-02-04 1995-09-27 ミノルタ株式会社 画像記録装置
GB2212419B (en) * 1987-12-25 1991-12-04 Ricoh Kk Image density control method and color image forming apparatus
CN1038277C (zh) * 1987-12-28 1998-05-06 佳能公司 成象设备

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8121498B2 (en) 2007-10-23 2012-02-21 Ricoh Company, Limited Image forming apparatus and developer supply method therefor

Also Published As

Publication number Publication date
DE69212915T2 (de) 1997-01-02
EP0519710A2 (de) 1992-12-23
EP0519710A3 (en) 1993-02-24
DE69212915D1 (de) 1996-09-26

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