Abnormal discharge detection circuit for corona chargers

Patent metadata

Field	Value
Publication number	US-10691040-B2
Application number	US-201815936523-A
Country	US
Kind code	B2
Filing date	Mar 27, 2018
Priority date	Jun 30, 2017
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

An image forming apparatus has a photosensitive member, a plurality of corona chargers configured to charge the photosensitive member by corona discharge, a plurality of charge output circuits configured to output a charging voltage being applied to each of the corona chargers, a plurality of abnormal discharge detection circuits configured to output an abnormal discharge detection signal according to abnormal discharge occurring in each of the corona chargers, and a controller configured to have a common input port connected to the abnormal discharge detection circuits wherein the abnormal discharge detection signal output from each of the abnormal discharge detection circuits is input to the controller through the common input port. Each of the abnormal discharge detection circuits is connected to a corresponding one circuit out of the charge output circuits.

First claim

What is claimed is:

1. An image forming apparatus comprising:
a plurality of photosensitive members;
a plurality of corona chargers configured to charge the plurality of photosensitive members by corona discharge, each of the corona chargers including a charging wire and a grid which is disposed between one of the plurality of photosensitive members and the charging wire;
a plurality of charge output circuits connected to a plurality of the charging wires and configured to output a wire voltage, which is applied to each of the charging wires;
a plurality of abnormal discharge detection circuits configured to output an abnormal discharge detection signal according to abnormal discharge occurring in each of the corona chargers; and
a controller configured to have a common input port connected to the abnormal discharge detection circuits wherein the abnormal discharge detection signal output from each of the abnormal discharge detection circuits is input to the controller through the common input port,
wherein each of the abnormal discharge detection circuits is connected to a corresponding one of the charge output circuits connected to the charging wires.

2. The image forming apparatus according to claim 1 ,
wherein the plurality of charge output circuits includes a first charge output circuit having a high-load of a path for outputting the wire voltage, and a second charge output circuit having a lower load than the high-load of the path for outputting the wire voltage, and
wherein a sensitivity of detecting abnormal discharge by a first abnormal discharge detection circuit connected to the first charge output circuit is lower than a sensitivity of detecting abnormal discharge by a second abnormal discharge detection circuit connected to the second charge output circuit.

3. The image forming apparatus according to claim 2 ,
wherein the first abnormal discharge detection circuit connected to the first charge output circuit has the same circuit configuration as the second abnormal discharge detection circuit connected to the second charge output circuit, and
wherein circuit constants of the first and second abnormal discharge detection circuits are set such that the sensitivity of the first abnormal discharge detection circuit is lower than the sensitivity of the second abnormal discharge detection circuit.

4. The image forming apparatus according to claim 2 ,
wherein the second abnormal discharge detection circuit includes at least one circuit of an amplifier circuit configured to amplify the abnormal discharge detection signal and a comparison circuit configured to compare a voltage caused by the abnormal discharge and a reference voltage to output the abnormal discharge detection signal.

5. The image forming apparatus according to claim 2 ,
wherein a number of the corona chargers connected to the first charge output circuit is larger than the number of the corona chargers connected to the second charge output circuit.

6. The image forming apparatus according to claim 2 ,
wherein each of the corona chargers is provided corresponding to each of the photosensitive members,
wherein the photosensitive members include a photosensitive member configured to carry a developer of black, and
wherein the second charge output circuit is connected to the charging wire of the corona charger that charges the photosensitive member configured to carry the developer of black, and
outputs the wire voltage.

7. The image forming apparatus according to claim 2 ,
wherein each of the corona chargers is provided corresponding to each of the photosensitive members, and
wherein the first and second abnormal discharge detection circuits are connected to different power supplies, and outputs the abnormal discharge detection signals having signal levels different from each other.

Assignees

• Brother Ind Ltd

Inventors

• Katoh Hiroki

Classifications

• G03G15/0291

  corona discharge devices, e.g. wires, pointed electrodes, means for cleaning the corona discharge device · CPC title

• G03G15/0258

  provided with means for the maintenance of the charging apparatus, e.g. cleaning devices, ozone removing devices G03G15/0225, G03G15/0291 takes precedence · CPC title

• G03G2221/1609

  protective arrangements for preventing damage · CPC title

• G03G15/5004

  Power supply control, e.g. power-saving mode, automatic power turn-off · CPC title

• G03G15/0266 Primary

  Arrangements for controlling the amount of charge · CPC title