Electroconductive Member Offset Contact for Developing Roller Bias

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Solution Overview

Problem

Existing image forming apparatuses face challenges in stabilizing bias application to developing rollers, particularly due to residual protrusions on metal shafts and the need for separate urging members to prevent abrasion, which complicates maintenance and operation.

Innovation Solution

A cartridge design that uses an electroconductive member to apply bias to the metal shaft of a rotatable member, such as a developing roller, while an urging member provides longitudinal force, allowing for stable bias application without requiring protrusion removal machining, and utilizing the contact pressure for both bias application and urging, with the electroconductive member contacting the metal shaft at a location other than the rotation center.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a separate urging member is provided to prevent abrasion and stabilize bias application, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improvestability of bias applicationVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the urging member and electroconductive member into a single integrated component. The urging member is formed with an electroconductive layer on its surface, allowing it to serve both mechanical urging functions and electrical conduction functions simultaneously. This eliminates the need for separate urging members and electroconductive components, reducing structural complexity while maintaining reliable bias application stability.

Inventive Principle:

Principle #5Merging (Combining)

2Manufacturing precision

If protrusion removal machining is performed on the metal shaft, then manufacturing precision is improved, but productivity decreases

Engineering Contradiction:

Improvesurface quality of metal shaftVSAvoidmanufacturing efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent converts the harmful residual protrusions on the metal shaft into a beneficial feature. Instead of removing the protrusions through machining, the design allows the electroconductive member to contact the metal shaft at a position offset from the rotation center, where the protrusions do not interfere with electrical contact. This approach eliminates the need for time-consuming protrusion removal machining while maintaining stable electrical connection and bias application.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If the electroconductive member contacts the metal shaft at the rotation center, then ease of manufacture is improved, but reliability deteriorates due to protrusion interference

Engineering Contradiction:

Improveassembly simplicityVSAvoidstability of electrical contact

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by creating an offset contact configuration where the electroconductive member contacts the metal shaft at a specific position away from the rotation center. This localized contact position is strategically chosen to avoid interference from residual protrusions while maintaining stable electrical connection. The contact position is designed to be tolerant of manufacturing variations, ensuring reliable contact without requiring high-precision machining.

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

Enables stable and efficient bias application to the developing roller, reducing maintenance needs and operational complexity by utilizing contact pressure for both bias application and urging, even without removing residual protrusions on the metal shaft.

Implementation Method 1

an electroconductive member, supported movably in the axial direction of the metal shaft in contact to an end surface of the metal shaft in one end side of the metal shaft, for constituting at least a part of an electroconductive path for electrically connecting the metal shaft and a contact member provided in the main assembly

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

an urging portion for urging the metal shaft via the electroconductive member in a direction from the one end side to another end side of the metal shaft

Methodology Applied

Scientific EffectMechanical force: Mechanical Force

Data Source

PatentUS9188945B2Cartridge and image forming apparatus

Publication Date: 2015.11.17 CANON KK

AI summary

A cartridge includes: a rotatable member, including a metal shaft, supported movably in an axial direction of the metal shaft; an electroconductive member, supported movably in the axial direction in contact to an end surface of the metal shaft in one end side of the metal shaft, for constituting an electroconductive path for electrically connecting the metal shaft and a contact member provided in an image forming apparatus main assembly; an urging portion for urging the metal shaft via the electroconductive member in a direction from the one end side to another end side of the metal shaft; and an abutting portion for positioning the rotatable member by being abutted by the metal shaft. The electroconductive member includes a contact portion to the end surface of the metal shaft, at a portion other than a rotation center portion of the metal shaft at the end surface.