Photosensitive Drum Diameter and Transfer Roller Pressure in Image Forming

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Solution Overview

Problem

Tandem-type image forming apparatuses face issues with surface wear and image defects due to friction and contact pressure between intermediate transfer members and photosensitive members, especially when using larger-diameter photosensitive drums, leading to uneven toner transfer and shortened component lifetimes.

Innovation Solution

The apparatus employs a configuration with a first and second photosensitive drum of different diameters, where the larger-diameter drum is used for the black image forming unit, and a movable intermediate transfer belt with strategically positioned and urged transfer rollers to manage toner transfer, ensuring optimal contact and reduced wear by adjusting the shift amount and urging force of the transfer rollers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If a larger-diameter photosensitive drum is used for the black image forming unit, then the lifetime of the photosensitive drum is extended, but image defectiveness occurs due to abnormal discharge and deterioration in transfer property

Engineering Contradiction:

Improvelifetime of photosensitive drumVSAvoidtransfer property

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The patent changes the diameter parameter of the photosensitive drum for the black image forming unit to be larger than other color drums. This parameter change extends the lifetime of the black photosensitive drum while requiring compensation through adjusted transfer roller positioning and urging force to maintain reliable transfer properties

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different diameters to different photosensitive drums based on their specific functional requirements. The black photosensitive drum has a larger diameter optimized for its high-frequency use, while other color drums maintain standard diameters, creating localized optimization that balances lifetime extension with transfer reliability

Inventive Principle:

Principle #3Local quality

2Productivity

If the photosensitive member is forced to contact the intermediate transfer member in black monochrome mode, then the image forming operation can be performed, but the photosensitive member experiences unnecessary wear and shortened life

Engineering Contradiction:

Improveimage forming operationVSAvoidlifetime of photosensitive member

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The patent makes the intermediate transfer belt movable relative to the photosensitive drums, allowing the system to dynamically adjust contact configurations. In black monochrome mode, the intermediate transfer belt can be positioned to contact only the black photosensitive drum, enabling image forming operation while preventing unnecessary wear on other color photosensitive members

Inventive Principle:

Principle #15Dynamics

3Productivity

If the conveyance speed of the photosensitive member is different from that of the intermediate transfer member, then the image forming operation can proceed, but the abrasion amount of the surface layer excessively increases

Engineering Contradiction:

Improveimage forming operationVSAvoidabrasion of surface layer

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent employs a movable intermediate transfer belt that can dynamically adjust its position and contact configuration with different photosensitive drums. This dynamic adjustment allows the system to accommodate different conveyance speeds between photosensitive members and the intermediate transfer belt, enabling image forming operations while minimizing excessive abrasion through optimized contact management

Inventive Principle:

Principle #15Dynamics

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 enhances transfer efficiency, reduces image defects by stabilizing the nip formation and maintaining optimal contact pressure, thereby extending the life of photosensitive drums and improving image quality.

Implementation Method 1

a first transfer roller configured to be urged toward the first photosensitive drum across the intermediate transfer belt and configured to electrostatically transfer the toner image from the first photosensitive drum to the intermediate transfer belt

Methodology Applied

Scientific EffectElectrostatic transfer: Electrostatics

Data Source

PatentUS9389548B2Image forming apparatus having photosensitive drums

Publication Date: 2016.07.12 CANON KK

AI summary

An image forming apparatus includes a first photosensitive member, having a first outer diameter, a toner image being formed on the first photosensitive member, and a second photosensitive member, having a second outer diameter, a toner image being formed on the second photosensitive member, the second outer diameter being greater than the first outer diameter. A second transfer roller in relation to the second photosensitive member is disposed on a downstream side of a first transfer roller in relation to the first photosensitive member in a conveyance direction of an intermediate transfer belt. A pressing force of the second transfer roller applied to the second photosensitive member is set to be greater than a pressing force of the first transfer roller applied to the first photosensitive member.