Secondary Transfer Voltage Control for Duplex Print Contamination

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Solution Overview

Problem

In image forming apparatuses with double side print continuation processes, toner contamination on the back side of sheets occurs due to toner adherence to secondary transfer rollers, which can decrease productivity if cleaning is performed, and existing methods to suppress this contamination also reduce productivity.

Innovation Solution

An image forming apparatus with controlled voltage application to the secondary transfer portion, maintaining a potential difference below a discharging threshold during continuation processes to prevent toner adherence while ensuring productivity is maintained.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If the double side print continuation process is performed, then sheet waste is prevented, but back side contamination occurs due to toner adhering to the secondary transfer roller

Engineering Contradiction:

Improvesheet wasteVSAvoidback side contamination

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent applies a preliminary reverse polarity voltage to the secondary transfer roller before the toner image passes through, creating an electrostatic barrier that prevents toner adhesion in advance. This anti-action occurs during the sheet interval period, before the harmful toner transfer can occur, thereby preventing back side contamination while maintaining the continuation process benefit

Inventive Principle:

Principle #9Preliminary anti-action

2Object-affected harmful factors

If cleaning of the secondary transfer roller is performed to suppress back side contamination, then contamination is reduced, but productivity decreases due to extended sheet intervals

Engineering Contradiction:

Improveback side contaminationVSAvoidprint productivity

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The patent replaces the mechanical cleaning system (which requires stopping the machine and physically cleaning the roller) with an electrostatic control system. By applying reverse polarity voltage, the system achieves contamination prevention through electrical fields rather than mechanical intervention, eliminating the need to extend sheet intervals and maintaining continuous operation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If voltage is applied to prevent toner adhesion, then back side contamination is suppressed, but energy consumption increases

Engineering Contradiction:

Improveback side contaminationVSAvoidenergy consumption

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent applies the reverse polarity voltage only during the sheet interval period when no sheet is passing through the secondary transfer portion, rather than continuously. This periodic application limits energy consumption to only when necessary for prevention, while maintaining productivity by not interrupting the printing process

Inventive Principle:

Principle #19Periodic action

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

Effectively suppresses back side contamination without reducing productivity by applying controlled voltages during double side print continuation processes.

Implementation Method 1

by applying a voltage of opposite polarity to that applied during the transfer of the toner image onto the sheet to the secondary transfer roller

Methodology Applied

Scientific EffectElectrostatic repulsion: Electrostatics

Implementation Method 2

a predetermined voltage, which makes the outer roller be at a potential of the predetermined polarity side to the inner roller and makes an absolute value of a potential difference between the inner roller and the outer roller be less than a discharging threshold value

Methodology Applied

Scientific EffectElectrostatic induction: Electrostatic Induction

Data Source

PatentUS20260016779A1Image forming apparatus

Publication Date: 2026.01.15 CANON KK

AI summary

An image forming apparatus includes a controller which performs a continuation process in which a toner image is secondarily transferred to a back side of a sheet conveyed from a double side conveyance portion, when performing a double side print in a case in which a sheet of a feeding portion is not conveyed to a secondary transfer portion. The controller controls so that in a case of performing the continuation process, while an image formation area of the intermediary transfer belt passes through the secondary transfer portion, a predetermined voltage, which makes an outer roller be at a potential of a normal charge polarity side to an inner roller and makes an absolute value of the potential difference between the inner roller and the outer roller be less than a discharging threshold value, is applied to the secondary transfer portion.