US3912989A - Method and apparatus for charging by corona discharge - Google Patents

Method and apparatus for charging by corona discharge Download PDF

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Publication number
US3912989A
US3912989A US451008A US45100874A US3912989A US 3912989 A US3912989 A US 3912989A US 451008 A US451008 A US 451008A US 45100874 A US45100874 A US 45100874A US 3912989 A US3912989 A US 3912989A
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United States
Prior art keywords
corona discharge
current
rate
discharge device
charging
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Expired - Lifetime
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US451008A
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English (en)
Inventor
Masanori Watanabe
Takaaki Konuma
Hirokazu Asano
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Katsuragawa Electric Co Ltd
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Kip KK
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Assigned to KATSURAGAWA DENKI KABUSHIKI KAISHA reassignment KATSURAGAWA DENKI KABUSHIKI KAISHA MERGER (SEE DOCUMENT FOR DETAILS). Assignors: KABUSHIKI KAISHA KIP
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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
    • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
    • G03G15/0291—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices corona discharge devices, e.g. wires, pointed electrodes, means for cleaning the corona discharge device

Definitions

  • the corona discharge current is controlled to vary at a predetermined rate at the commencement and termination of corona discharge so as to ensure uniform deposition of electric charge on the surface of the element.
  • This invention relates to a method and apparatus for depositing electric charge on a surface of relatively large area by means of corona discharge, and more particularly to a method and apparatus for uniformly depositing electric charge in a short time on the surface of the photosensitive element of an electrophotographic apparatus on which an electrostatic latent image is to be formed.
  • the corona discharge device utilized in this method is usually constructed such that at least two corona discharge wires pass by respective points on the image forming surface during the corona discharge interval so as to prevent non-uniform distribution of the deposited charge and to prevent the formation of the shadows of the discharge wires, but where a large quantity of charge is to be deposited in a short time there is a defect in that non-uniform distribution of the deposited charge in the form of stripes parallel to the corona discharge wires often results. We have found that this defect is caused for the following reason.
  • a method of charging the surface of a body to be charged by corona discharge wherein the surface is charged by means of a corona discharge device substantially covering the entire surface of the body and by relatively moving the body and the corona discharge device, characterized in that the current flowing through the body is varied at a predetermined rate during the period of commencement of the corona discharge until a predetermined current value is reached and that the current is gradually decreased from the predtermined current value during the period of termination of the corona discharge.
  • apparatus for charging a body to be charged by means of corona discharge of the type comprising a corona discharge device substantially covering the surface of the body, a source of power for energizing the corona discharge device, and means for moving the corona discharge device relative to the body in a direction substantially parallel to the surface of the body, characterizedin that there is provided control means for controlling the corona discharge current of the corona discharge device, and that the control means includes means for varying the corona discharge current at a predetermined rate at the time of commencement of the corona discharge until a predetermined current value is reached and means for gradually decreasing the corona discharge current from the predetermined current value at the time of termination of the corona discharge.
  • the control means may be an electrical control circuit or a mechanical device.
  • FIG. 1 is a diagrammatic representation showing an arrangement of a conventional corona discharge device and a photosensitive element
  • FIG. 2 is a graph showing the waveform of the current flowing through the grounded plate of the corona discharge device shown in FIG. 1;
  • FIG. 3 is a graph showing the waveform of the current flowing through the photosensitive element shown in FIG. 1;
  • FIG. 4 is a block diagram showing one example of the control device utilized to carry out the invention.
  • FIG. 5 is a graph similar to FIG. 2 and shows the current waveform obtained by carrying out the method of this invention
  • FIGS. 6, 7, and 8 are graphs similar to FIG. 3 and show current waveforms of the current flowing through the photosensitive element when the method of this invention is applied.
  • FIG. 9 is a diagrammatic perspective view showing a modified embodiment of this invention.
  • the body to be charged by corona discharge shown therein comprises a photosensitive element 30 utilized in electrophotography and including an insulative layer 2, a photosensitive photoconductive layer 3 and a grounded electrode layer 1 which are bonded together into an integral structure.
  • the insulative layer 2 is used as an image forming surface and is deposited with electric charges by means of a corona discharge device 4 spaced apart a short distance from the insulative layer 2 and moved in parallel with the surface thereof.
  • the corona discharge device 4 has a size sufficient to cover the entire surface of the insulative layer 2 for the purpose of depositing charge in an extremely short time and includes a grounded conductive substrate 5, a plurality of equally spaced corona discharge wires 6 insulated from the substrate and a plurality of parallel conductive vanes 7 each interposed between adjacent discharge wires 6 and electrically connected to the substrate 5.
  • a light image is projected upon the photoconductive layer 3 through the corona discharge device 4 in which case the substrate 5 is made of a conductive glass plate such as Nesa Glass (registered trade mark) or takes the form of a rectangular frame.
  • a light image is projected through the electrode layer in which case the electrode layer 1 must be transparent to light.
  • the corona discharge wires 6 are connected to the negative or positive terminal of a DC source 9 via a switch 8 depending upon the conductivity type of the photosensitive element 30. The opposite terminal of the source 9 is grounded as shown.
  • the switch 8 is closed to create corona discharge between corona discharge wires 6 and vanes 7 and or substrate 5 while the corona discharge device 4 is being moved at a constant speed in parallel with the surface of the insulative layer 2 thereby depositing negative charge thereon.
  • switch 8 is opened and the movement of the corona discharge device 4 is stopped thus completing the deposition of the charge.
  • the current flowing through the grounded substrate 5 of the corona discharge device 4 during this interval is shown by the graph shown in FIG. 2 in which t represents an instant at which the corona discharge was commenced and t an instant at which the corona discharge was terminated.
  • the graph shown in FIG. 3 shows the variation in the current flowing through the photosensitive element during the interval between instants t and
  • a large charging current I flows through the photosensitive element 30 at the instant t when the corona discharge is initiated and the current gradually attenuates to a small value I, at the instant I at which the corona discharge is terminated. Thereafter, the current rapidly decreases to zero.
  • the reason that the current does not instantly decrease to zero at instant is caused by the fact that it takes a certain time for deionization.
  • the photosensitive photoconductive layer was omitted and a body to be charged was comprised by a polyester resin film having a thickness of 16 microns and an area of 300 X 300 mm and the electrode layer consisted of an aluminum layer vapour deposited on the rear surface of the polyester resin film.
  • Each corona discharge wire had a diameter of 0.06 mm, the spacing between the corona discharge wires and the polyester resin film was selected to be 7 mm.
  • the corona discharge device was moved at a speed of mm/sec, and operated for 0.5 sec. under an applied voltage of 4,60OV and a total current of 60 mA.
  • FIG. 4 shows a connection diagram of one example of a current control device that can be used in combination with the corona discharge device shown in FIG. 1.
  • This control device comprises a driving circuit 10 which operates to move the corona discharge device 4, FIG. 1, at a constant speed in parallel with the surface of the insulative layer 2 in response to an input signal.
  • the corona discharge device 4 operates a first microswitch, not shown, included in a synchronizing circuit 11 for energizing a current regulator 12 which is connected to a time controller 13 including a plurality of variable resistors R R and R Variable resistor R is used to control the build-up rate of the corona discharge current between an interval of I or the inclination angle 0, until a current of a definite value I (see FIG. 5) is reached at the commencement of the discharge.
  • Variable resistor R is used to maintain the current I at the constant value until an instant I is reached, whereas the variable resistor R is used to control the rate of build-down of the corona discharge current between an interval t.,, that is the inclination angle 6
  • the suitable adjustments of variable resistors R R and R it is possible to obtain any desired current waveforms as well as the discharge period.
  • the output from the current regulator 12 is applied to a source of high voltage 14 so as to apply a variable voltage to the corona discharge device 4 to deposit a charge of the desired polarity (in this case, negative) on the surface of the insulative layer.
  • the current flowing through the photosensitive element 30, or a body to be charged, is shown in FIG. 6, thus assuring uniform charge on the surface of the insulative layer as will be described later.
  • a signal is fed back from the output of current regulator 12 to synchronizing circuit 11, thereby deenergizing current regulator 12, high voltage source 14 and corona discharge device 4.
  • the corona discharge device 4 actuates a second micro-switch, not shown, for deenergizing the driving circuit 10 for the corona discharge device 4.
  • the parameters for the corona discharge device and of the body to be charged were selected to be the same as the experiment described above and angles 6 and 6 were varied variously by adjusting variable resistors R R and R
  • the time scale on the abscissa was selected to be 0.1 sec/cm
  • the current scale on the ordinate was 20 mA/crn
  • the interval between t and to be 0.08 sec was varied uniformly from zero to 60 mA.
  • the interval between and L was selected to be 0.3 sec.
  • the speed of the corona discharge device was set to l 50 mm/sec. and angles 6 and 0 were varied under the same conditions as the first mentioned experiment. With the same time and current scales as described above, no nonuniform charge distribution on the surface of the insulative layer was, noted where angle 0 was larger than about and angle 0 was smaller than 55. As can be noted from these experiments, it is possible to increase angle 0 where the speed of movement of the corona discharge device is increased.
  • control circuit was set to obtain an attenuation curve a shown in FIG. 7.
  • time and current scales described above it was confirmed that substantially uniform distribution of the charge deposited on the surface of the insulative layer can be obtained when the inclination angle 6 during current attenuation was adjusted to lie between about 45 and 50. Further, no nonuniform distribution of the deposited charge was noted when the control circuit was set to obtain an attenuation curve b shown in FIG. 7.
  • FIG. 9 diagrammatically shows the charging device utilized in this modified method.
  • opposite ends of a pair of stationary parallel shafts and 16 are pivotally connected to a corona discharge device 18 through parallel arms 17.
  • the corona discharge device 18 may have the same construction as that of device 4 shown in FIG. 1.
  • One end of a rope 19 is connected to one end of the corona discharge device .18 and the opposite end of the rope 19 is connected to a drum 21 rotated by a motor 20.
  • a spring 22 is interposed between the stationary portion of the copying machine and the opposite end of the corona discharge device 18 for biasing the same to the left as viewed in FIG. 9.
  • the corona discharge device was moved relative to the body to be charged, it will be clear that it is also possible to move the body to be charged relative to the corona discharge device as in the case of a rotary drum type electrophotographic copying machine. Further, although the body to be charged was shown as a three layered photosensitive element in one case and as an insulative layer in the other case it will be clear that the method and apparatus of this invention are applicable to any application requiring uniform charging by corona discharge.
  • the current control circuit shown in FIG. 4 may by replaced by a voltage control circuit for controlling the voltage of a high voltage source for the corona discharge device. As has been pointed out hereinabove, the polarity of the charge is not limited to being negative.
  • a method of charging the surface of a body to be charged by means of a corona discharge device including a plurality'of spaced corona discharge wires and substantially covering the entire surface of said body by relatively moving said body and said corona discharge device substantially parallel with each other, and wherein charging current tends to increase at a high rate through said body at the commencement of the corona discharge and tends to decrease at a high rate at the termination of the corona discharge the improvement which comprises the steps of controlling the rate of increase of said charging current to a rate lower than said high rate of increase at the time of commencement of the corona discharge until a predetermined current value is reached, and controlling the rate of decrease of said current from said predetermined current value to a rate lower than said high rate of decrease at the time of termination of the corona discharge so as to prevent non-uniform charging of said surface caused by said corona discharge wires.
  • apparatus for charging the surface of a body to be charged by means of corona discharge of the type comprising a corona discharge device including a plurality of spaced corona discharge wires and substantially covering the surface of said body, a source of power for energizing said corona discharge device, and means for moving said corona discharge device relative to said body in a direction substantially parallel to the surface of said body, and wherein charging current tends to increase at a high rate through said body at the commencement of the corona discharge and tends to decrease at a high rate at the termination of the corona discharge, the improvement which comprises control means for controlling the rate of increase of said charging current to a rate lower than said high rate of increase at the time of commencement of the corona discharge until a predetermined current value is reached and for controlling the rate of decrease of said corona discharge current from said predetermined current value to a rate lower than said high rate of decrease at the time of termination of the corona discharge so as to prevent nonuniform charging of said surface caused by said
  • control means further includes means for maintaining said predetermined current value for a predetermined interval before said decrease of the corona discharge current.
  • control means comprises an electric control circuit connected to said source of power, said electric control circuit including a plurality of variable resistors, a first one thereof determining the rate of increase of said corona discharge current, a second one determining the rate of decrease of said corona discharge current and a third one determining said predetermined current value.
  • control means comprises mechanical means for driving said corona discharge device toward the surface of said body during the period of commencement of the corona discharge and awayfrom said surface during the period of termination of the corona discharge while said corona discharge device is being moved relative to said body in a direction substantially parallel to the surface of said body.
  • said mechanical means comprises spaced parallel arms for suspending said corona discharge device.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
US451008A 1973-03-30 1974-03-14 Method and apparatus for charging by corona discharge Expired - Lifetime US3912989A (en)

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JP3629373A JPS5541430B2 (de) 1973-03-30 1973-03-30

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US (1) US3912989A (de)
JP (1) JPS5541430B2 (de)
CA (1) CA1015023A (de)
DE (1) DE2414907C3 (de)
FR (1) FR2223732B1 (de)
GB (1) GB1467972A (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4228480A (en) * 1979-02-12 1980-10-14 Eastman Kodak Company Electrophotographic apparatus with improved corona charging
US4245272A (en) * 1979-04-30 1981-01-13 Eastman Kodak Company Apparatus and method for low sensitivity corona charging of a moving photoconductor
US4260240A (en) * 1978-11-13 1981-04-07 Olympia Werke Ag Movable support for electrostatic corona discharge device
US4305651A (en) * 1979-02-25 1981-12-15 Konishiroku Photo Industry Co., Ltd. System for adjusting output current of discharge electrode for electrophotographic copying machines
US4333124A (en) * 1976-10-18 1982-06-01 Canon Kabushiki Kaisha Electrically discharging method and device
US4386834A (en) * 1981-07-06 1983-06-07 Kirlian Equipment Corporation Kirlian photography device
US4481557A (en) * 1982-09-27 1984-11-06 Ransburg Corporation Electrostatic coating system
US4558221A (en) * 1983-05-02 1985-12-10 Xerox Corporation Self limiting mini-corotron
US4890190A (en) * 1988-12-09 1989-12-26 Graco Inc. Method of selecting optimum series limiting resistance for high voltage control circuit
US5081476A (en) * 1990-04-04 1992-01-14 Xerox Corporation Ionographic printhead gating control for controlling charge density image defects due to surface velocity variations

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5480360U (de) * 1977-11-17 1979-06-07
JPS55120061A (en) * 1979-03-08 1980-09-16 Canon Inc Transfer device
US4496827A (en) * 1983-04-25 1985-01-29 Proctor-Silex, Inc. Enhanced heat and mass transfer apparatus

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3684364A (en) * 1971-06-24 1972-08-15 Xerox Corp Lift off electrode

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3684364A (en) * 1971-06-24 1972-08-15 Xerox Corp Lift off electrode

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4333124A (en) * 1976-10-18 1982-06-01 Canon Kabushiki Kaisha Electrically discharging method and device
US4260240A (en) * 1978-11-13 1981-04-07 Olympia Werke Ag Movable support for electrostatic corona discharge device
US4228480A (en) * 1979-02-12 1980-10-14 Eastman Kodak Company Electrophotographic apparatus with improved corona charging
US4305651A (en) * 1979-02-25 1981-12-15 Konishiroku Photo Industry Co., Ltd. System for adjusting output current of discharge electrode for electrophotographic copying machines
US4245272A (en) * 1979-04-30 1981-01-13 Eastman Kodak Company Apparatus and method for low sensitivity corona charging of a moving photoconductor
US4386834A (en) * 1981-07-06 1983-06-07 Kirlian Equipment Corporation Kirlian photography device
US4481557A (en) * 1982-09-27 1984-11-06 Ransburg Corporation Electrostatic coating system
US4558221A (en) * 1983-05-02 1985-12-10 Xerox Corporation Self limiting mini-corotron
US4890190A (en) * 1988-12-09 1989-12-26 Graco Inc. Method of selecting optimum series limiting resistance for high voltage control circuit
US5081476A (en) * 1990-04-04 1992-01-14 Xerox Corporation Ionographic printhead gating control for controlling charge density image defects due to surface velocity variations

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Publication number Publication date
DE2414907B2 (de) 1979-10-31
CA1015023A (en) 1977-08-02
GB1467972A (en) 1977-03-23
FR2223732A1 (de) 1974-10-25
JPS49123336A (de) 1974-11-26
DE2414907C3 (de) 1980-07-24
FR2223732B1 (de) 1978-06-02
JPS5541430B2 (de) 1980-10-24
DE2414907A1 (de) 1974-10-10

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Owner name: KATSURAGAWA DENKI KABUSHIKI KAISHA

Free format text: MERGER;ASSIGNOR:KABUSHIKI KAISHA KIP;REEL/FRAME:004772/0728

Effective date: 19870807