Alternating Bias Control for Charging Roller Electrostatic Cleaning

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Solution Overview

Problem

The discharge of a photosensitive drum in image forming apparatuses leads to a decrease in surface potential, causing contaminants to adhere to the charging roller, which is difficult to remove without increasing costs, especially when using traditional cleaning methods that may enter minute unevenness on the roller surface.

Innovation Solution

An image forming apparatus with a control circuit that alternately turns off and on the charging roller and transfer roller to apply biases of predetermined polarities, effectively enhancing electrostatic cleaning by alternating the bias phases between the two rollers, thereby improving cleaning performance without the need for additional cleaning members.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a cleaning member such as a bristle brush is used to contact the charging roller to remove contaminant, then the contaminant can be removed from the charging roller, but the contaminant may enter minute unevenness on the surface of the charging roller and additional cleaning members are required which leads to cost increase

Engineering Contradiction:

Improvecharging roller cleanlinessVSAvoidcleaning member requirement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical cleaning system (bristle brush) with an electrostatic cleaning system. A cleaning roller with opposite polarity to the contaminant is used to attract and remove contaminants from the charging roller through electrostatic attraction, eliminating the need for mechanical contact and additional cleaning members.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the electrical parameter (bias polarity) of the cleaning roller dynamically. By switching the bias polarity of the cleaning roller between positive and negative states, the system creates alternating electrostatic attraction and release cycles that effectively remove contaminants without mechanical contact.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the photosensitive drum is driven and rotated when surface potential is low, then the drum can be operated, but contaminant on the photosensitive drum may pass through cleaning blade and adhere to charging roller causing contamination

Engineering Contradiction:

Improvedrum operation capabilityVSAvoidcharging roller contamination

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary electrostatic cleaning to the charging roller before the photosensitive drum is rotated and before contaminants can transfer from the drum to the charging roller. By pre-charging the cleaning roller with appropriate polarity, contaminants are removed in advance, preventing subsequent contamination during drum operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful effect of low surface potential (which causes contaminant adhesion) into a beneficial cleaning mechanism. The low surface potential state is used as an opportunity to apply electrostatic cleaning to the charging roller, transforming the problematic condition into a preventive maintenance opportunity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method enhances the electrostatic cleaning effect, reducing contamination on the charging roller and preventing white stripe images, allowing for significantly more sheets to be passed before contamination occurs, thus improving cleaning performance while reducing costs.

Implementation Method 1

The charging roller is configured to charge the photosensitive drum

Methodology Applied

Scientific EffectElectrostatic charging: Electrostatics

Implementation Method 2

The transfer roller is configured to receive a toner image formed on the photosensitive drum

Methodology Applied

Scientific EffectElectrostatic attraction: Ion Repulsion/Attraction

Implementation Method 3

controls the charging roller to alternately turn off and on to a first bias of a predetermined polarity and the transfer roller to alternately turn off and on to a second bias of the predetermined polarity

Methodology Applied

Scientific EffectElectrostatic cleaning: Electrostatics

Data Source

PatentUS10976681B1Alternate bias control of charging roller and transfer roller in image forming apparatus

Publication Date: 2021.04.13 TOSHIBA TEC KK

AI summary

An image forming apparatus includes a photosensitive drum, a charging roller, a transfer roller, and a control circuit. The control circuit is configured to perform an alternating bias control. During the alternating bias control, the control circuit causes the charging roller and the transfer roller to rotate in accordance with a rotation of the photosensitive drum, and controls the charging roller to alternately turn off and on to a first bias of a predetermined polarity and the transfer roller to alternately turn off and on to a second bias of the predetermined polarity, such that at least a part of a region of the photosensitive drum biased by the first bias is not biased by the second bias, and that at least a part of a region of the photosensitive drum biased by the second bias is not biased by the first bias.