US3816756A - Automatic bias control - Google Patents

Automatic bias control Download PDF

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Publication number
US3816756A
US3816756A US00307911A US30791172A US3816756A US 3816756 A US3816756 A US 3816756A US 00307911 A US00307911 A US 00307911A US 30791172 A US30791172 A US 30791172A US 3816756 A US3816756 A US 3816756A
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United States
Prior art keywords
voltage
resistor
resistivity
output
bias voltage
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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
US00307911A
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English (en)
Inventor
H Bresnick
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.)
Xerox Corp
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Xerox Corp
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Publication date
Application filed by Xerox Corp filed Critical Xerox Corp
Priority to US00307911A priority Critical patent/US3816756A/en
Priority to NL7315037A priority patent/NL7315037A/xx
Application granted granted Critical
Publication of US3816756A publication Critical patent/US3816756A/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/065—Arrangements for controlling the potential of the developing electrode

Definitions

  • PATENTE JUN 1 3 m4 SHEET 3 BF 4 Bias Vol/age Voltage Divider 1 AUTOMATIC BIAS CONTROL BACKGROUND OF THE INVENTION Thisinvention relates to electrostatographic process recording apparatus and, more particularly, to apparatus for maintaining image quality constant as environmental conditions vary.
  • circuitry is advantageously provided for controlling the bias voltage of a developing member in order to achieve the effect of a constant resistivity paper.
  • the resistivity of the paper is sensed and, as humidity affects the resistivity, control signals are generated which adjust the bias voltage level which is applied to the developing member.
  • FIG. 1 schematically depicts a typical paper path and the supply rollers therefor
  • FIG. 2(a) graphically depicts the surface resistivity as a function of the relative humidity for a typical paper
  • FIG. 2(b) graphically depicts the optimum process bias voltage as a function of the relative humidity
  • FIG. 3 depicts a block diagram of an illustrative control apparatus responsive to the resistivity of the paper for controlling the bias voltage level
  • FIG. 4 is a more detailed schematic diagram of an illustrative circuit embodiment of the block diagram of FIG. 3.
  • FIG. I depicted therein is a schematic representation of the paper path in an electrostatographic process recorder.
  • the paper travels from supply spool l to take-up spool 2 past imaging station 6 and development station 3.
  • the dotted lines represent the resistance R,I of the paper which may be sensed across conducting rollers 4 and which are used in transporting the paper.
  • FIG. 2(a) graphically depicts the surface resistivity of a typical coated paper as a function of relative humidity.
  • a typical coated paper may be, for example, coated with conductive polymer 261 manufactured by Calgon Corp. in the amount of two pounds per ream (1,300 square feet).
  • FIG. 2(b) graphically depicts the desired process bias voltage as a function of the relative humidity for 2 the paper whose characteristics are depicted in FIG. 2(a).
  • FIG. 3 depicts a block diagram of an illustrative control system in accordance with the principles of this invention.
  • the resistance R, of the paper is sensed across rollers 4 and 5 connected to a bridge circuit 31.
  • An output from bridge circuit 31 is fed to a preamplifier 33 whose output is one input to an operational amplifier 35.
  • the output of operational amplifier 35 is then transmitted to voltage divider 37 where it acts as a control signal to control the generation of the required bias voltage.
  • Voltage divider 37 sends a feedback signal to operational amplifier 35 to complete the control loop.
  • FIG. 4 depicted therein is a detailed schematic diagram of an illustrative circuit embodiment of the block diagram depicted in FIG. 3.
  • Resistors 41, 42, 43 and the paper resistance R, form a wheatstone bridge, to which is applied a supply voltage V
  • Resistors 41, 42 and 43 and voltage V l are selected so that the bridge output voltage V on line 45 is always positive over the range of paper resistivity as depicted in FIG. 2(a), and are also chosen so that V decreases as R,, decreases, a monotonic function.
  • Line 45 is connected to field effect transistor 47, connected in a follower configuration as a preamplifier to operational amplifier 35 for impedance matching purposes.
  • Resistors 50, 52 and transistor 55 comprise voltage divider 37 (FIG. 3).
  • the feedback loop from voltage divider 37 to operational amplifier 35 comprises resistors and 61 in a voltage divider configuration. This feedback loop samples the output bias voltage at output terminal 57 and feeds back a small amount of this voltage (V to operational amplifier 35.
  • an electrostatographic process recorder apparatus for controlling development process bias voltage in order to achieve the effect of constant paper resistivity, said apparatus comprising means for sensing the resistivity of the paper,
  • output means including a control element for providing said bias voltage
  • control means responsive to said voltage signal and said bias voltage for controlling said control element to vary said bias voltage so as to achieve the effect of constant paper resistivity.
  • said supplying means includes a plurality of resistors connected in a Wheatstone bridge configuration, one arm of said bridge being connected to said sensing means.
  • control element comprises a transistor having its collector connected to said output terminal and said first resistor and its emitter connected to said second resistor.
  • control means includes an operational amplifier having a first input connected to said supplying means, a second input connected to said output means, and an output connected to the base of said transistor.
  • control means further includes feedback means connected between said output terminal and said second input of said operational amplifier.
  • said feedback means comprises a plurality of resistors connected in a voltage divider configuration.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Or Security For Electrophotography (AREA)
US00307911A 1972-11-20 1972-11-20 Automatic bias control Expired - Lifetime US3816756A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US00307911A US3816756A (en) 1972-11-20 1972-11-20 Automatic bias control
NL7315037A NL7315037A (enExample) 1972-11-20 1973-11-01

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00307911A US3816756A (en) 1972-11-20 1972-11-20 Automatic bias control

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US3816756A true US3816756A (en) 1974-06-11

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US00307911A Expired - Lifetime US3816756A (en) 1972-11-20 1972-11-20 Automatic bias control

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US (1) US3816756A (enExample)
NL (1) NL7315037A (enExample)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4134147A (en) * 1976-11-02 1979-01-09 Rank Xerox Limited Transfer humidity control device
US4314755A (en) * 1978-10-31 1982-02-09 Sharp Kabushiki Kaisha Bias voltage controlled developing system in an electrophotographic copying machine
US4395112A (en) * 1980-09-19 1983-07-26 Mita Industrial Co., Ltd. Latent electrostatic image developing device
US4610530A (en) * 1984-12-21 1986-09-09 Xerox Corporation Capacitive paper property sensor for copying apparatus
US5036360A (en) * 1990-02-21 1991-07-30 Eastman Kodak Company Moisture compensation for electrostatographic apparatus
US5646717A (en) * 1991-06-28 1997-07-08 Canon Kabushiki Kaisha Image forming apparatus having charging member
GB2345467A (en) * 1999-01-11 2000-07-12 Samsung Electronics Co Ltd Modification of transfer voltage in printer to take account of variation of paper resistance

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3463934A (en) * 1966-10-14 1969-08-26 Hellige & Co Gmbh F Measuring circuit
US3586908A (en) * 1969-02-28 1971-06-22 Robert E Vosteen Automatic potential control system for electrophotography apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3463934A (en) * 1966-10-14 1969-08-26 Hellige & Co Gmbh F Measuring circuit
US3586908A (en) * 1969-02-28 1971-06-22 Robert E Vosteen Automatic potential control system for electrophotography apparatus

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4134147A (en) * 1976-11-02 1979-01-09 Rank Xerox Limited Transfer humidity control device
US4314755A (en) * 1978-10-31 1982-02-09 Sharp Kabushiki Kaisha Bias voltage controlled developing system in an electrophotographic copying machine
US4395112A (en) * 1980-09-19 1983-07-26 Mita Industrial Co., Ltd. Latent electrostatic image developing device
US4610530A (en) * 1984-12-21 1986-09-09 Xerox Corporation Capacitive paper property sensor for copying apparatus
US5036360A (en) * 1990-02-21 1991-07-30 Eastman Kodak Company Moisture compensation for electrostatographic apparatus
US5646717A (en) * 1991-06-28 1997-07-08 Canon Kabushiki Kaisha Image forming apparatus having charging member
GB2345467A (en) * 1999-01-11 2000-07-12 Samsung Electronics Co Ltd Modification of transfer voltage in printer to take account of variation of paper resistance
US6111594A (en) * 1999-01-11 2000-08-29 Samsung Electronics Co., Ltd. Method of and apparatus for controlling transfer voltage based on specific resistance of paper in laser beam printer
GB2345467B (en) * 1999-01-11 2001-03-28 Samsung Electronics Co Ltd Control of transfer voltage in printer

Also Published As

Publication number Publication date
NL7315037A (enExample) 1974-05-22

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