EP0545639A2 - Gerät und Verfahren zur Korrektur eines Spannungsfühlers - Google Patents

Gerät und Verfahren zur Korrektur eines Spannungsfühlers Download PDF

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Publication number
EP0545639A2
EP0545639A2 EP19920310853 EP92310853A EP0545639A2 EP 0545639 A2 EP0545639 A2 EP 0545639A2 EP 19920310853 EP19920310853 EP 19920310853 EP 92310853 A EP92310853 A EP 92310853A EP 0545639 A2 EP0545639 A2 EP 0545639A2
Authority
EP
European Patent Office
Prior art keywords
potential sensor
potential
photoreceptor drum
reference bias
straight line
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.)
Withdrawn
Application number
EP19920310853
Other languages
English (en)
French (fr)
Inventor
Kensuke Room 105 Sumiyoshipakumanshon Fujihara
Hideyuki Tanaka
Yoshinobu Takemura
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.)
Kyocera Mita Industrial Co Ltd
Original Assignee
Mita Industrial Co Ltd
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 Mita Industrial Co Ltd filed Critical Mita Industrial Co Ltd
Publication of EP0545639A2 publication Critical patent/EP0545639A2/de
Withdrawn legal-status Critical Current

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    • 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
    • G03G15/5037—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 the characteristics being an electrical parameter, e.g. voltage
    • 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
    • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
    • G03G15/0266—Arrangements for controlling the amount of charge

Definitions

  • the present invention relates to apparatus for and method of correcting the output of a potential sensor for detecting the electric charge potential of a photoreceptor.
  • an image forming apparatus having a photoreceptor there is generally known an electrophotographic copying apparatus, a laser printer, an electrophotographic facsimile or the like.
  • a laser printer has a photoreceptor in the form of a drum (hereinafter referred to a photoreceptor drum).
  • a photoreceptor drum is generally made of an aluminium tube and provided at the surface thereof with a photosensitive semiconductor layer.
  • the laser printer is arranged such that, during image formation, the photosensitive semiconductor layer on the surface of the photoreceptor drum is electrically charged to have a uniform potential by corona discharge of a charger, and the photosensitive semiconductor layer thus charged is then exposed to laser light to eliminate the electric charge in the light-exposed area thereof, where an electrostatic latent image will be formed.
  • the output of the potential sensor is required to be corrected for the following two reasons.
  • a predetermined high voltage is applied directly to the photoreceptor drum, the output of the potential sensor at that time is read out, and a correction value is determined based on the output of the potential sensor supplied at the time when the high voltage is applied to the photoreceptor drum.
  • an image forming apparatus arranged such that, to correct the output of a potential sensor, a connector connected to a developing bias circuit is exchanged with a connector connected to a photoreceptor drum, a predetermined high voltage is applied from a high voltage generating circuit to the photoreceptor drum, and the output of the potential sensor at that time is read out to correct the output of the potential sensor.
  • the correcting method above-mentioned uses a high voltage and can therefore be applied only at the time of production of the image forming apparatus or at a time of maintenance carried out by a professional service engineer.
  • the applicant of the present invention has already proposed an image forming apparatus which incorporates a potential sensor for detecting the surface potential of a photoreceptor drum, a high voltage generating circuit and a switching circuit, and which is arranged such that, when the switching circuit is operated to apply a high voltage to the photoreceptor drum, the surface potential of the photoreceptor drum is measured by the potential sensor, and provision is made such that the potential sensor for measuring the surface potential of the photoreceptor drum supplies an output always equal to a proper corrected value, thereby to electrically charge the photoreceptor drum with a desired potential at all times (US Patent No. 4,939,542).
  • a plurality of different reference bias voltages are applied to a photoreceptor, the surface potentials of the photoreceptor are detected, and there is determined a first straight line which represents the relationship between the detected voltages and output characteristics of the potential sensor, based on the outputs of the potential sensor supplied at the time when the reference bias voltages are applied to the photoreceptor. Then, there is obtained a second straight line having the same inclination as that of the first straight line and passing through the origin. Based on the second straight line thus obtained, the output of the potential sensor is corrected.
  • the output of the potential sensor is corrected based on the second straight line having the same inclination as that of the first straight line and passing through the origin, so that the output of the potential sensor can be accurately corrected without any influence exerted by a residual potential.
  • Fig. 1 is a schematic view illustrating the arrangement of an image forming unit of an image forming apparatus.
  • Fig. 1 there are disposed, around a photoreceptor drum 1, charge eliminating lamps 2, a main corona discharger 3, a potential sensor 4, a developing device 6, a transferring corona discharger 7, a separating corona discharger 8 and a cleaner 9 in this order along the rotation direction of the photoreceptor drum 1.
  • an exposure position Ex is set between the main corona discharger 3 and the potential sensor 4, and light from an optical system 10 is adapted to be irradiated to the exposure position Ex.
  • the optical system 10 has a camera element (hereinafter referred to as CCD) 11 for converting document image information into an electric signal, a laser scan unit (hereinafter referred to as LSU) 12 for irradiating laser light to the photoreceptor drum 1 based on an output signal from the CCD 11, so that the photoreceptor drum 1 is exposed to the laser light, and a polygon mirror 13 for reflecting and guiding the laser light from the LSU 12 to the exposure position Ex of the photoreceptor drum 1.
  • CCD camera element
  • LSU laser scan unit
  • the photoreceptor drum 1 is rotated at a constant speed in the direction of the arrow in Fig.1 and residual charge at the surface of the photoreceptor drum 1 is removed by the charge eliminating lamps 2, and the surface of the photoreceptor drum 1 is then electrically charged to a fixed potential by the main corona discharger 3.
  • laser light of the LSU 12 irradiated based on the output signal of the CCD 11 is applied to the exposure position Ex of the photoreceptor drum 1.
  • Such light exposure eliminates the electric charge at the area which has been exposed to the light, and an electrostatic latent image is then formed on the surface of the photoreceptor drum 1.
  • the developing device 6 supplies toner to the surface of the photoreceptor drum 1, so that the electrostatic latent image is developed by the toner.
  • the toner is supplied to the surface of the photoreceptor drum 1 by a developing roller (not shown) incorporated in the developing device 6.
  • a developing bias voltage having the same potential as that at the surface of the photoreceptor drum 1 is applied to the developing roller in order to prevent excessive toner from sticking to the surface of the photoreceptor drum 1.
  • a paper sheet is fed by a paper feeding unit (not shown) and the toner image on the surface of the photoreceptor drum 1 is transferred to the paper sheet.
  • the paper sheet to which the toner image has been transferred is separated from the surface of the photoreceptor drum 1 by the separating corona discharger 8 and then sent to a fixing unit (not shown), where the transferred image is fixed.
  • this embodiment is arranged as follows. At the initial stage of the image forming operation, two reference bias voltages are applied to the photoreceptor drum 1, and the surface potentials of the photoreceptor drum 1 are measured by the potential sensor 4. The measured values are fed back to a potential sensor correcting apparatus, to be discussed later, which is adapted to control the main corona discharger 3.
  • the potential sensor correcting apparatus is adapted to correct the output of the potential sensor 4 such that the values measured by the potential sensor 4 always present an accurate relationship with respect to the surface potentials of the photoreceptor drum 1.
  • the correcting apparatus has a main high voltage unit 20 for supplying a high voltage to the main corona discharger 3 to carry out corona discharge to the surface of the photoreceptor drum 1, causing the photosensitive semiconductor layer at the surface of the photoreceptor drum 1 to be electrically charged; a low reference bias unit 21 for applying a low reference bias voltage VA (for example, 200V) directly to the photoreceptor drum 1; a high reference bias unit 22 for applying a high reference bias voltage VB (for example, 600V) directly to the photoreceptor drum 1; and a control unit 23 for controlling the drives of the units 20, 21, 22. It is known that, when the reference bias voltage VA or VB is applied directly to the photoreceptor drum 1 with no residual charge remaining thereon, the surface of the photoreceptor drum 1 is generally electrically charged at the potential VA or VB.
  • the control unit 23 has a memory 23a adapted to store values Y A and Y B measured by the potential sensor 4 at the time when the two reference bias voltages VA and VB are applied to the photoreceptor drum 1. As shown in Fig. 3, from the values Y A and Y B which have been measured by the potential sensor 4 at the time of application of the two reference bias voltages VA, VB, and which have been stored in the memory 23a, the control unit 23 determines a first straight line Y1 which represents the relationship between the detected voltages and outputs of the potential sensor 4, on the assumption that the same residual potential C remains on the surface of the photoreceptor drum 1 when the two reference bias voltages VA, VB are applied.
  • control unit 23 has both a calculating function for obtaining a second straight line Y2 which has the same inclination as that of the first straight line Y1 thus determined and which passes through the origin, and a correcting function for correcting the output of the potential sensor 4 based on the second straight line Y2.
  • a changeover switch 24 controls the energization between the photoreceptor drum 1 and each of the low and high reference bias units 21, 22. More specifically, at the time of correction, when the changeover switch 24 is connected to a contact a , the low reference bias unit 21 is electrically connected to the photoreceptor drum 1, and when the changeover switch 24 is connected to a contact b , the high reference bias unit 22 is electrically connected to the photoreceptor drum 1. Normally, the changeover switch 24 is connected to a contact c to prevent the two bias voltages VA, VB from being applied to the photoreceptor drum 1.
  • a drive motor 25 for driving the photoreceptor drum 1 and other image forming mechanisms, and the charge eliminating lamps 2.
  • the control unit 23 turns on the charge eliminating lamps 2 at Step 1 to eliminate the electric charge of the photoreceptor drum 1 such that the surface potential thereof drops to a certain extent to prevent the potential from being changed in a moment due to dark-attenuation or the like.
  • the changeover switch 24 is thrown to the side of the contact a (See Fig. 2) of the low reference bias unit 21 at Step 2, thereby to connect the low reference bias unit 21 to the photoreceptor drum 1, so that the low reference bias voltage VA (for example, 200V) is applied to the photoreceptor drum 1.
  • the low reference bias voltage VA for example, 200V
  • the output Y A of the potential sensor 4 with the low reference bias voltage VA applied to the photoreceptor drum 1.
  • the value Y A is stored in the memory 23a of the control unit 23.
  • the changeover switch 24 is thrown to the side of the contact b (See Fig. 2) of the high reference bias unit 22 to connect the high reference bias unit 22 to the photoreceptor drum 1, so that the high reference bias voltage VB (for example, 600V) is applied to the photoreceptor drum 1.
  • the high reference bias voltage VB for example, 600V
  • the output Y B of the potential sensor 4 with the high reference bias voltage VB applied to the photoreceptor drum 1.
  • the value Y B is stored in the memory 23a of the control unit 23.
  • the first straight line Y1 representing the relationship between the detected voltages and output characteristics of the potential sensor 4 is determined, as shown in Fig. 3, based on the measured values Y A and Y B of the potential sensor 4 stored in the memory 23a. Then, there is obtained the second straight line Y2 which has the same inclination as that of the first straight line Y1 thus determined and which passes through the origin. More specifically, even though the electric charge of the photoreceptor drum 1 has been eliminated at Step 1, it is difficult to perfectly eliminate the residual charge of the photoreceptor drum 1, and any amount of residual charge still remains. Accordingly, attention is placed on a method of correcting the output of the potential sensor 4 in recognition of the presence of the residual charge.
  • the second straight line Y2 represented by the equation (4) is stored, as the correction characteristics of the potential sensor 4, in the memory 23a.
  • the main high voltage unit 20 is driven at Step 10 so that the surface of the photoreceptor drum 1 is electrically charged with a high voltage by the main corona discharger 3.
  • the main corona discharger 3 is driven by a high voltage required for the desired potential which is 800V for example.
  • the potential of actual electric charge at the surface of the photoreceptor drum 1 is measured by the potential sensor 4. It is now supposed that the output of the potential sensor 4 at this time is Y X .
  • the surface potential of the photoreceptor drum 1 which corresponds to the measured value Y X of the potential sensor 4 is calculated by applying the value Y X to the correction characteristics stored at Step 9, i.e., to the equation (4). It is then judged whether or not the surface potential thus calculated (for example, 780V) is in a predetermined error range with respect to the desired potential of 800V.
  • the LSU 12 irradiates laser light to the exposure position Ex of the photoreceptor drum 1 at Step 13, thereby to expose the photoreceptor drum 1 to light.
  • the exposure potential of the photoreceptor drum 1 is measured by the potential sensor 4.
  • Step 15 When it is judged at Step 15 that the surface potential calculated by applying the measured value of the potential sensor 4 to the correction characteristics in the equation (4), is in the predetermined error range with respect to the desired exposure potential, the sequence is returned.
  • Step 12 When it is judged at Step 12 that the calculated surface potential deviates from the predetermined error range with respect to the desired potential, the control voltage of the main corona discharger 3 is changed at Step 16, based on the judging result at Step 12, and the sequence is returned back to Step 10, where the photoreceptor drum 1 will be again electrically charged with a high voltage.
  • Step 15 When it is judged at Step 15 that the calculated surface potential deviates from the predetermined error range with respect to the desired exposure potential, the laser output of the LSU 12 is changed at Step 17, based on the judging result at Step 15, and the sequence is returned back to Step 13 where the photoreceptor drum 1 will be again exposed to light.
  • Steps 1 to 9 of correcting the potential sensor 4 may be carried out at the time when the image forming apparatus is started. Further, a potential sensor correcting switch may be disposed and a professional service engineer or the like may carry out the correction by operating such a potential sensor correcting switch at the time of maintenance of the image forming apparatus. In short, by correcting the potential sensor 4 at predetermined time intervals, a proper electric charge can be measured at all times, enabling a clear image to be formed.
  • the electric charge at the surface of the photoreceptor drum 1 is first eliminated such that the surface potential thereof drops to a certain extent to prevent the potential from being greatly changed due to dark-attenuation or the like, and the output of the potential sensor 4 is then corrected.
  • the first straight line Y1 representing the relationship between the detected voltages and outputs of the potential sensor 4 is determined on the assumption that the same residual potential C still remains on the surface of the photoreceptor drum 1 when the two reference bias voltages VA, VB are applied thereto, and there is obtained the second straight line Y2 which has the same inclination as that of the first straight line Y1 thus determined and which passes through the origin.
  • the output of the potential sensor 4 is corrected. Accordingly, even though the output of the potential sensor 4 is corrected with residual charge still remaining on the surface of the photoreceptor drum 1 immediately after the completion of image formation or the like, the output of the potential sensor 4 can be corrected without any influence exerted by the residual potential.
  • two reference bias voltages are applied to the photoreceptor drum 1 and the surface potentials of the photoreceptor drum 1 are measured by the potential sensor 4.
  • three or more reference bias voltages VA, VB, VC, VD.... may be applied and surface potentials YA, YB, YC, YD.... of the photoreceptor drum 1 may be measured, so that the first straight line Y1 may be determined with the use of a least squares method.
  • the second straight line Y2 which has the same inclination as that of the first straight line Y1 thus determined and which passes through the origin.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Control Or Security For Electrophotography (AREA)
  • Fax Reproducing Arrangements (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
EP19920310853 1991-11-29 1992-11-27 Gerät und Verfahren zur Korrektur eines Spannungsfühlers Withdrawn EP0545639A2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP316904/91 1991-11-29
JP3316904A JPH05150580A (ja) 1991-11-29 1991-11-29 電位センサの補正装置

Publications (1)

Publication Number Publication Date
EP0545639A2 true EP0545639A2 (de) 1993-06-09

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EP19920310853 Withdrawn EP0545639A2 (de) 1991-11-29 1992-11-27 Gerät und Verfahren zur Korrektur eines Spannungsfühlers

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JP (1) JPH05150580A (de)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6156372A (ja) * 1984-08-28 1986-03-22 Fuji Xerox Co Ltd 電子複写機用表面電位計較正装置

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