Image Forming Apparatus Reverse Polarity Cleaning Bias

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Solution Overview

Problem

During the decoloring operation of decolorable toner in image forming apparatuses, non-decolorable toner can cause dirt on sheets, leading to reduced reuse frequency due to 'fogging' issues, especially when both types of toner are present, as the intermediate belt rotation deteriorates toner charge and causes adhesion to transfer rollers.

Innovation Solution

The image forming apparatus operates in two modes: a first mode for image formation with a transfer bias matching toner polarity and a second mode for decoloring, where a cleaning bias with reverse polarity is applied to prevent toner adhesion, using a control unit to manage biases and ensure effective cleaning of the intermediate transfer belt and secondary transfer roller.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the intermediate belt is rotated to transport the sheet during decoloring operation, then the sheet can pass through the transfer unit, but the toner charge amount decreases and toner deposits on the secondary transfer roller causing fogging

Engineering Contradiction:

Improvedecoloring operation efficiencyVSAvoidfogging on sheet

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The invention applies a cleaning bias with reverse polarity to the intermediate transfer belt before the sheet passes through the transfer unit during decoloring operation. This preliminary action prevents toner adhesion to the belt surface, thereby avoiding subsequent fogging on the sheet while maintaining the necessary belt rotation for sheet transport

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The invention changes the electrical parameter (bias polarity) of the intermediate transfer belt from the normal transfer bias polarity to a reverse polarity cleaning bias during decoloring operation. This parameter change prevents toner adhesion to the belt while allowing the belt to continue rotating for sheet transport

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the auger is rotated to agitate the developer during decoloring operation, then the developer is mixed, but the toner surface separates and charge amount decreases

Engineering Contradiction:

Improvedeveloper uniformityVSAvoidtoner charge stability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The invention extracts the auger rotation function from the decoloring operation. By stopping the auger rotation during decoloring, the invention prevents toner surface separation and charge degradation while still allowing the developer to be sufficiently mixed from previous operations, thus maintaining developer uniformity without compromising toner reliability

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If the transfer bias is applied during decoloring operation, then the sheet passes through the transfer unit, but non-decolorable toner adheres to the sheet causing dirt

Engineering Contradiction:

Improvedecoloring process simplicityVSAvoidsheet dirt from non-decolorable toner

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The invention inverts the bias polarity applied to the intermediate transfer belt during decoloring operation. Instead of applying a transfer bias with the same polarity as toner charge, a cleaning bias with reverse polarity is applied. This inverted approach prevents non-decolorable toner adhesion to the sheet while maintaining simple decoloring process operation

Inventive Principle:

Principle #13The other way round (Inversion)

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 solution effectively prevents dirt from non-decolorable toner during decoloring operations, maintaining sheet reuse frequency and reducing toner adhesion, thereby extending the life and cleanliness of sheets.

Implementation Method 1

when the sheet passes through a transfer unit, a cleaning bias having a reverse polarity to that of the transfer bias is applied to a transfer member

Methodology Applied

Scientific EffectElectrostatic attraction/repulsion: Electrostatics

Data Source

PatentUS9977377B1Image forming apparatus

Publication Date: 2018.05.22 KK TOSHIBA

AI summary

An embodiment provides an image forming apparatus that has a first operation mode and a second operation mode. The first operation mode forms an image on a sheet with toner. The second operation mode decolorizes the toner on the sheet on which the image is formed with a decolorable toner having a decoloring function. In the first operation mode, when the sheet passes through a transfer unit, a transfer bias having the same polarity as that of a charge of the toner is applied to the transfer member and a toner image formed on a surface of the transfer member is transferred to the sheet. In the second operation mode, when the sheet passes through the transfer unit, a cleaning bias having a reverse polarity to that of the transfer bias is applied to the transfer member.