Photosensitive Drum Potential Management for Carrier Adhesion

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Solution Overview

Problem

In image forming apparatuses with two-phase developing devices, the carrier adheres to the photosensitive medium due to potential difference when the main motor is turned off, causing surface wear and blade abrasion, and existing methods to prevent this are complex.

Innovation Solution

An image forming apparatus with a controller that removes the potential from the photosensitive drum using an eraser unit while the drum rotates due to inertial force after the main motor stops, and a method that compares the average voltage of the toner during rotation with the stationary voltage to determine when to turn off the eraser unit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the main motor is turned off to stop the photosensitive drum, then the drum stops rotating, but the carrier adheres to the drum surface due to potential difference

Engineering Contradiction:

Improveprevention of carrier adhesionVSAvoidcomplexity of preventing carrier adhesion

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The eraser unit is activated before the main motor stops to remove the potential difference on the photosensitive drum surface. This preliminary action prevents carrier adhesion from occurring in the first place, rather than addressing it after the problem arises.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The eraser unit serves as an intermediary device between the main motor and the carrier adhesion problem. By removing the potential difference through the eraser unit, the harmful effect of carrier adhesion is prevented without directly interfering with the motor's operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the eraser unit is activated continuously to prevent carrier adhesion, then carrier adhesion is prevented, but energy is wasted when the drum has already stopped

Engineering Contradiction:

Improveprevention of carrier adhesionVSAvoidenergy waste from continuous eraser operation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The controller monitors the rotation state of the photosensitive drum and activates the eraser unit only when the drum is still rotating. This feedback mechanism ensures the eraser unit operates only when necessary to prevent carrier adhesion, avoiding energy waste when the drum has stopped.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The eraser unit's operation is made dynamic rather than static. It is activated only during the rotation period when the drum has inertial motion, and turned off when the drum stops, adapting the eraser's operation to the actual need at different times.

Inventive Principle:

Principle #15Dynamics

3Reliability

If the cleaning blade removes carrier particles from the drum surface, then carrier adhesion is removed, but the cleaning blade abrasion increases

Engineering Contradiction:

Improveremoval of carrier adhesionVSAvoidlifetime of cleaning unit

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The invention converts the harmful potential difference that causes carrier adhesion into a beneficial effect. By using the eraser unit to remove the potential difference, the problem of carrier adhesion is solved without needing the cleaning blade to physically remove carrier particles, thereby protecting the cleaning blade from abrasion.

Inventive Principle:

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

Solution Approach 2:

The mechanical cleaning blade system is replaced with an electrical field-based eraser unit. Instead of using mechanical force to scrape off carrier particles, the eraser unit uses electrical field to remove the potential difference, preventing carrier adhesion in the first place and eliminating the need for mechanical removal.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Prevents carrier adhesion to the photosensitive medium, reducing surface wear and improving the lifetime of the cleaning unit by effectively managing the potential difference during motor shutdown.

Implementation Method 1

an eraser unit to remove a potential charged on the photosensitive drum

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Implementation Method 2

the photosensitive medium still rotates for a dwell period of time due to an inertial force

Methodology Applied

Scientific EffectInertial force: Inertia

Data Source

PatentUS7574159B2Image forming apparatus and method of preventing carrier from adhering to photo receptor

Publication Date: 2009.08.11 HEWLETT PACKARD DEVELOPMENT COMPANY LP

AI summary

An image forming apparatus and a method of preventing a carrier from adhering to a photosensitive drum are provided. The image forming apparatus includes a photosensitive drum on which an electrostatic latent image is formed by an exposure unit, a main motor which rotates the photosensitive drum, an eraser unit which removes a potential charged on the photosensitive drum, and a controller which controls the eraser unit to remove a potential of the photosensitive drum while the photosensitive drum rotates due to an inertial force after the main motor stops rotating.