Developer Bearing Region Positioning for Toner Collection

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Solution Overview

Problem

In electrophotographic image forming apparatuses, the contact charging member often becomes contaminated with toner remaining on the photosensitive drum after transfer, which can adversely affect image formation, especially in cleanerless systems where waste toner is not produced but residual toner can adhere to the contact charging member.

Innovation Solution

The design includes a developer bearing member with a developer bearing region that collects toner from the photosensitive drum after image transfer, and a transfer member with a transfer bias applicable region, where the end portions of the developer bearing region are located outside the transfer bias applicable region, preventing toner adhesion to the contact charging member by ensuring the toner is negatively charged and collected before reaching the charging roller.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If a contact charging member is used in a cleanerless image forming apparatus, then waste toner is eliminated and resources are used efficiently, but residual toner on the photosensitive drum adheres to the contact charging member causing contamination

Engineering Contradiction:

Improvewaste tonerVSAvoidcontamination of contact charging member

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the harmful function (toner adhesion) from the contact charging member by providing a protective layer on its surface. This protective layer prevents residual toner from adhering to the charging member while allowing the charging function to continue, thus eliminating waste toner without causing contamination

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a protective layer as an intermediary between the contact charging member and the residual toner. This intermediate layer acts as a barrier that prevents direct contact and adhesion between the charging member surface and the toner particles, resolving the contradiction between resource efficiency and contamination prevention

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the developer bearing region extends beyond the transfer bias applicable region, then toner collection is improved, but toner may adhere to the contact charging member

Engineering Contradiction:

Improvetoner collection efficiencyVSAvoidtoner adhesion to charging member

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different properties to different regions: the developer bearing region is optimized for toner collection while the contact charging member surface is protected by a protective layer. This local differentiation allows the developer bearing region to extend beyond the transfer bias applicable region for improved collection efficiency without causing toner adhesion to the charging member

Inventive Principle:

Principle #3Local quality

3Device complexity

If residual toner is not collected by the developing device, then the device complexity is reduced, but image quality deteriorates due to toner adhesion on the charging member

Engineering Contradiction:

Improvecleaning deviceVSAvoidimage quality

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent enables the developing device to perform dual functions: it both develops the image and collects residual toner from the photosensitive drum. This self-service capability eliminates the need for a separate cleaning device while maintaining image quality by preventing toner adhesion to the charging member through the protective layer

Inventive Principle:

Principle #25Self-service

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 configuration effectively reduces contamination of the contact charging member by ensuring that residual toner is collected and reused, maintaining image quality and reducing the risk of toner adhesion, even when the amount of fog toner is large or its polarity is not successfully changed to negative.

Implementation Method 1

a charging member configured to come into contact with the image carrying member and electrically charge a surface of the image carrying member

Methodology Applied

Scientific EffectContact charging: Conduction (electrical)

Implementation Method 2

a transfer member configured to transfer the developed image onto the recording material, wherein the transfer member has a transfer bias applicable region to which a transfer bias is applicable

Methodology Applied

Scientific EffectElectrostatic transfer: Electrostatics

Implementation Method 3

a developer bearing member configured to collect developer remaining on the image carrying member after a developed image formed on the image carrying member has been transferred onto a recording material

Methodology Applied

Scientific EffectElectrostatic collection: Electrostatics

Data Source

PatentUS9915892B2Developing device, process cartridge, and image forming apparatus

Publication Date: 2018.03.13 CANON KK

AI summary

What is provided is an image forming apparatus in which longitudinal end portions of a developer bearing region or longitudinal end portions of an opening are respectively located outside longitudinal end portions of a transfer bias applicable region.