Photosensitive Drum Back Contrast Control for Reverse Fogging

Solution Overview

Problem

Existing image forming apparatuses face issues with toner remaining on the photosensitive drum due to reverse fogging, which diminishes the charging performance of the charging unit and affects image quality.

Innovation Solution

The image forming apparatus includes a control unit that adjusts the back contrast in specific areas to enhance developer collection, reducing reverse fogging by controlling the charging, developing, and transfer voltages, and utilizes an image information acquiring unit to manage toner density and collection based on acquired toner image data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If developer collection is performed with high back contrast to improve residual toner removal, then collection efficiency is improved, but reverse fogging increases and charging performance deteriorates

Engineering Contradiction:

Improvedeveloper collection efficiencyVSAvoidcharging unit performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The photosensitive drum surface is divided into multiple regions (image formation region and non-image formation region) with different back contrast values. The control unit sets a first back contrast value in the image formation region and a second back contrast value (higher than the first) in the non-image formation region, enabling differentiated toner collection strategies across different areas.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different back contrast values are applied to different regions of the photosensitive drum based on local needs. The non-image formation region receives a higher back contrast to enhance residual toner removal, while the image formation region maintains a lower back contrast to prevent reverse fogging and preserve charging performance.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If uniform high back contrast is applied across the entire photosensitive drum to maximize toner collection, then residual toner removal is improved, but reverse fogging occurs and image quality deteriorates

Engineering Contradiction:

Improvetoner collection uniformityVSAvoidreverse fogging

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The photosensitive drum surface is divided into multiple regions (image formation region and non-image formation region) with different back contrast values. The control unit sets a first back contrast value in the image formation region and a second back contrast value (higher than the first) in the non-image formation region, enabling differentiated toner collection strategies across different areas.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different back contrast values are applied to different regions of the photosensitive drum based on local needs. The non-image formation region receives a higher back contrast to enhance residual toner removal, while the image formation region maintains a lower back contrast to prevent reverse fogging and preserve charging performance.

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 reduces reverse fogging, maintaining charging unit performance and improving image quality by efficiently collecting residual toner, thereby enhancing the overall operation of the image forming process.

Implementation Method 1

a charging unit for charging the image bearing member

Methodology Applied

Scientific EffectElectrostatic charging: Electrostatics

Implementation Method 2

an exposing unit for exposing the image bearing member and forming an electrostatic latent image

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 3

the residual toner on the photosensitive drum is collected by a developing roller (called 'developer collection') using the potential difference between surface potential Vd on the photosensitive drum and developing roller potential Vdc

Methodology Applied

Scientific EffectElectrostatic attraction: Electrostatics

Implementation Method 4

a transfer unit for transferring the toner image formed on the image bearing member to a transferred member

Methodology Applied

Scientific EffectElectrostatic transfer: Electrostatics

Data Source

PatentUS20260093203A1Image forming apparatus

Publication Date: 2026.04.02 CANON KK

AI summary

Provided is an image forming apparatus that forms a toner image by developing an electrostatic latent image which is formed by charging and exposing an image bearing member, and transfers the toner image onto a transferred member. The image forming apparatus can perform developer collection to return a toner image on the image bearing member to developing unit. The image forming apparatus sets a first area in accordance with the toner density and a second area in which density is higher than the first area, along a rotating shaft direction in a collected area which is a target of developer collection, and performs control so that a second back contrast in the second area is higher than a first back contrast in the first area in a case of the developer collection.