Charge Roller Hard Filler Particles Static Contact Defects

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Solution Overview

Problem

Charge rollers in electrophotographic devices are prone to defects from prolonged static contact with photoconductor drums, especially at high temperatures and humidity, leading to chemical and mechanical issues that result in print defects, and existing solutions like non-contact rollers are costly and require tight tolerance control.

Innovation Solution

A charge roller with a cylindrical core and an outermost coating layer containing hard, large filler particles that absorb pressure and act as a bridge to prevent mechanical defects, featuring a coating material with a lower glass transition temperature than the filler particles, which are harder and larger than the coating layer thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a charge roller uses a coating layer to prevent chemical defects, then chemical resistance is improved, but mechanical defects from high contact pressure still occur

Engineering Contradiction:

Improvechemical resistanceVSAvoidmechanical resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The charge roller employs a composite coating structure consisting of a base coating layer and an outermost coating layer containing hard filler particles (such as silica or glass beads). This composite structure combines the chemical resistance of the polymer coating material with the mechanical strength and pressure absorption capability of the hard filler particles, thereby simultaneously improving both chemical and mechanical resistance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The outermost coating layer is designed with locally concentrated hard filler particles that have different properties from the base coating layer. These filler particles create regions of high mechanical strength and pressure distribution capability at the surface, while the underlying coating material maintains chemical resistance. This local differentiation allows the coating to perform both chemical protection and mechanical defect prevention.

Inventive Principle:

Principle #3Local quality

2Strength

If a non-contact charge roller is used to avoid mechanical defects, then mechanical resistance is improved, but cost and manufacturing complexity increase

Engineering Contradiction:

Improvemechanical resistanceVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

Instead of implementing a complex non-contact charging mechanism with precise gap control, the patent uses a simple, cost-effective coating layer with hard filler particles that can be applied using conventional coating techniques. This disposable-like approach (where the coating protects the underlying structure) provides mechanical defect resistance without requiring complex mechanical systems, tight tolerance control, or additional actuators.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Productivity

If a charge roller operates during prolonged static contact at high temperature and humidity, then productivity is maintained, but mechanical defects increase

Engineering Contradiction:

Improvecontinuous operation capabilityVSAvoiddefect resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The outermost coating layer with hard filler particles serves as a pre-established protective barrier that cushions the charge roller against mechanical defects before they can occur. The filler particles absorb and distribute contact pressure during prolonged static contact periods, preventing the formation of dents or flat spots even under high temperature and humidity conditions, thereby maintaining reliability during continuous operation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

The charge roller effectively resists mechanical defects and maintains printing quality even after extended periods of nonuse, as demonstrated by reduced print defects in testing under high temperature and humidity conditions.

Implementation Method 1

The filler particles absorb the pressure applied by a photoconductor drum upon contact with the charge roller

Methodology Applied

Scientific EffectPressure absorption: Absorption (physical)

Implementation Method 2

The filler particles are harder and have a higher glass transition temperature than the coating material

Methodology Applied

Scientific EffectGlass transition:

Data Source

PatentUS8750763B2Charge roller for an image forming apparatus using hard filler particles

Publication Date: 2014.06.10 LEXMARK INTERNATIONAL INC

AI summary

An image forming apparatus includes a charge roller with improved resistance to defects from prolonged periods of nonuse. The charge roller includes an outermost coating layer including a coating material and filler particles. The filler particles have an average particle size larger than an average thickness of the outermost coating layer in a portion without the filler particles. Furthermore, the filler particles are harder and have a higher glass transition temperature than the coating material.