JPS55133067A - Developing bias voltage control unit of electrophotographic copier - Google Patents
Developing bias voltage control unit of electrophotographic copierInfo
- 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
Links
Landscapes
- 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
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)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4669859A (en) * | 1982-03-23 | 1987-06-02 | Ricoh Company, Ltd. | Developing device |
-
1979
- 1979-04-05 JP JP4026679A patent/JPS55133067A/en active Pending
Cited By (1)
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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