Image Forming Apparatus Backside Soil Prevention via AC Bias Control

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Solution Overview

Problem

Conventional image forming apparatuses face issues with backside soil on transfer materials due to toner deposition on non-image areas, which is not effectively addressed by existing solutions, particularly when no cleaning device is used on the secondary transfer roller.

Innovation Solution

The apparatus employs a configuration where DC and AC bias voltages are applied to the developing device, with the AC bias voltage being reduced or turned off in non-image areas to prevent toner deposition on the transfer roller surface, thereby avoiding backside soil without the need for a cleaning mechanism on the secondary transfer roller.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a cleaning device such as a blade or brush is provided on the secondary transfer roller, then toner deposition on the roller surface is removed, but the structure becomes more complex and requires increased pressure or speed difference which increases torque and may require an exclusive driving apparatus

Engineering Contradiction:

Improvebackside soil on transfer materialVSAvoidsecondary transfer unit structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The invention removes the cleaning device (blade or brush) from the secondary transfer roller, extracting the harmful factor removal function from the mechanical cleaning system. Instead, it uses electrical field control to prevent toner deposition in the first place, thereby simplifying the structure while maintaining effectiveness.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention applies preliminary anti-action by controlling the AC bias voltage in the non-image area to prevent toner deposition before it occurs. By applying a reduced or zero AC bias voltage in non-image areas, the electrical field prevents toner from adhering to the roller surface in the first place, eliminating the need for subsequent cleaning operations.

Inventive Principle:

Principle #9Preliminary anti-action

2Productivity

If the photoreceptor is stopped independently of the photoreceptor, then the developing device can be stopped, but toner or carrier may deposit on the photoreceptor depending on the potential

Engineering Contradiction:

Improveindependent stopping capabilityVSAvoidtoner or carrier deposition on photoreceptor

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #9Preliminary anti-action

3Productivity

If the developing function is constantly working, then image formation is continuous, but toner is transferred also in the non-image area between image areas causing image fog

Engineering Contradiction:

Improvecontinuous developing functionVSAvoidimage quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The invention applies local quality by differentiating the AC bias voltage application between image areas and non-image areas. In image areas, normal AC bias voltage is applied for proper toner development, while in non-image areas, the AC bias voltage is reduced or set to zero to prevent toner deposition. This spatial differentiation allows continuous developing operation while preventing image fog in non-image areas.

Inventive Principle:

Principle #3Local quality

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 approach effectively prevents backside soil on transfer materials throughout the 200,000-copy durability test, reduces toner consumption, and avoids photoreceptor damage from carrier deposition, while simplifying the secondary transfer unit structure and eliminating the need for a cleaning mechanism.

Implementation Method 1

DC bias voltage and AC bias voltage are applied to the development roller of the developing device

Methodology Applied

Scientific EffectElectrostatic deposition: Electrostatic Deposition

Implementation Method 2

transfer is carried out by contact electrification without a cleaning device

Methodology Applied

Scientific EffectContact electrification: Triboelectric Effect

Data Source

PatentUS7639961B2Image forming apparatus with means of preventing backside soil of transfer material

Publication Date: 2009.12.29 KONICA MINOLTA BUSINESS TECH INC

AI summary

An image forming apparatus, includes: a photoreceptor on which a toner image is formed by a charging device, an image exposure device and a developing device; and a transfer section for transferring the toner image on the photoreceptor. DC bias and AC bias voltage is applied to a development roller of the developing device, and the DC bias and AC bias voltage is set to regular value for an image area on the photoreceptor, and only the AC bias voltage is changed for a non-image area on the photoreceptor.