JPS55133067A - Developing bias voltage control unit of electrophotographic copier - Google Patents

Developing bias voltage control unit of electrophotographic copier

Info

Publication number
JPS55133067A
JPS55133067A JP4026679A JP4026679A JPS55133067A JP S55133067 A JPS55133067 A JP S55133067A JP 4026679 A JP4026679 A JP 4026679A JP 4026679 A JP4026679 A JP 4026679A JP S55133067 A JPS55133067 A JP S55133067A
Authority
JP
Japan
Prior art keywords
voltage
bias voltage
latent image
capacitor
image
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.)
Pending
Application number
JP4026679A
Other languages
Japanese (ja)
Inventor
Yuichi Kobayashi
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.)
Ricoh Co Ltd
Original Assignee
Ricoh 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 Ricoh Co Ltd filed Critical Ricoh Co Ltd
Priority to JP4026679A priority Critical patent/JPS55133067A/en
Publication of JPS55133067A publication Critical patent/JPS55133067A/en
Pending legal-status Critical Current

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  • Developing For Electrophotography (AREA)
  • Control Or Security For Electrophotography (AREA)

Abstract

PURPOSE: To perform bias voltage controlling according to the actual ground potential and make possible the constant-density and sharp copying irrespective of image ratios by regarding the minimum voltage of the latent image potentials detected by boosting and dropping means as ground potential.
CONSTITUTION: When the switch RS3 connecting to a boosting resistance R14 is closed for a fixed time before a sensor 11 opposes to the latent image of a photosensitive drum 13, a capacitor C4 is charged up to the voltage by which the maximum bias voltage is applied to a main electrode 13. Thence, when the latent image of the drum 13 and the sensor 11 oppose, the latent image potential detected is impedance-converted by an FETQ1 and is applied to the negative side terminal of a voltage-dropping diode. If the pontential is below the voltage of the capacitor C4, the voltage of the capacitor C4 corresponds to the minimum surface potential through discharging. With the voltage which is regarded as a ground potential as a reference, the bias voltage is controlled by way of a transistor Q4, Zener diode ZD6, etc. Thereby the sharp copy of a fixed density whose image density does not decrease is made irrespective of the large and small of the image ratios.
COPYRIGHT: (C)1980,JPO&Japio
JP4026679A 1979-04-05 1979-04-05 Developing bias voltage control unit of electrophotographic copier Pending JPS55133067A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP4026679A JPS55133067A (en) 1979-04-05 1979-04-05 Developing bias voltage control unit of electrophotographic copier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP4026679A JPS55133067A (en) 1979-04-05 1979-04-05 Developing bias voltage control unit of electrophotographic copier

Publications (1)

Publication Number Publication Date
JPS55133067A true JPS55133067A (en) 1980-10-16

Family

ID=12575840

Family Applications (1)

Application Number Title Priority Date Filing Date
JP4026679A Pending JPS55133067A (en) 1979-04-05 1979-04-05 Developing bias voltage control unit of electrophotographic copier

Country Status (1)

Country Link
JP (1) JPS55133067A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4669859A (en) * 1982-03-23 1987-06-02 Ricoh Company, Ltd. Developing device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4669859A (en) * 1982-03-23 1987-06-02 Ricoh Company, Ltd. Developing device

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