Image Forming Apparatus Developing Bias Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing image forming apparatuses experience inconsistency in density due to changes in temperature and humidity, which affect the times required to change transfer and developing biases, leading to inadequate toner distribution on the photosensitive drum.

Innovation Solution

An image forming apparatus with a control device that adjusts transfer and developing biases in response to detected temperature and humidity, changing the biases at specific rates to maintain consistent toner distribution across the photosensitive drum.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the transfer bias is turned off to reduce electrostatic discharge, then electrostatic discharge is reduced, but the absolute value of surface potential increases causing inconsistency in density

Engineering Contradiction:

Improveelectrostatic dischargeVSAvoiddensity consistency

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The developing bias is increased in advance when the trailing end portion of the sheet passes the transfer position, creating a compensatory effect that prevents the density inconsistency caused by the turned-off transfer bias. This preliminary anti-action ensures toner is supplied to areas with high surface potential before the inconsistency occurs.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The developing bias parameter is dynamically changed based on the sheet trailing end detection, switching from a normal value to a greater value to compensate for the turned-off transfer bias. This parameter change ensures consistent toner distribution despite the transfer bias being off.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the developing bias is increased to supply toner to high surface potential areas, then toner distribution improves, but the time for changing developing bias becomes mismatched with transfer bias change time under low temperature and humidity conditions

Engineering Contradiction:

Improvetoner distribution uniformityVSAvoidcontrol timing consistency

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The developing bias control system dynamically adjusts based on detected temperature and humidity conditions. Under low temperature and humidity, the developing bias is increased to match the extended time required for transfer bias changes, ensuring consistent toner distribution regardless of environmental conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Temperature and humidity sensors provide feedback to the control device, which then adjusts the developing bias accordingly. This feedback mechanism ensures the developing bias change timing remains synchronized with transfer bias change timing under varying environmental conditions.

Inventive Principle:

Principle #23Feedback

3Reliability

If the transfer bias change time is extended under low temperature and humidity, then the transfer bias can be properly applied, but the developing bias change time remains short causing timing mismatch

Engineering Contradiction:

Improvetransfer bias application reliabilityVSAvoiddeveloping bias change time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The developing bias parameter is changed based on environmental conditions. Under low temperature and humidity, the developing bias is increased and maintained for a longer duration to match the extended transfer bias change time, preventing timing mismatch and ensuring consistent image quality.

Inventive Principle:

Principle #35Parameter changes

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 solution reduces the likelihood of density inconsistency by synchronizing the times for changing transfer and developing biases with environmental conditions, ensuring adequate toner supply to areas with high surface potential.

Implementation Method 1

a transfer member configured to transfer a developer image formed on an image carrying member to a sheet

Methodology Applied

Scientific EffectElectrostatic attraction: Electrostatics

Implementation Method 2

reduce electrostatic discharge from occurring between a trailing end portion of a sheet and a photosensitive drum and reduce inconsistency in density due to a change in the surface potential of the photosensitive drum

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Data Source

PatentUS9482995B2Image forming apparatus that changes a developing bias or surface potential

Publication Date: 2016.11.01 BROTHER KOGYO KK

AI summary

An image forming apparatus includes an image carrying member, a developer carrying member configured to carry developer to be supplied to the image carrying member, a transfer member configured to transfer a developer image formed on the image carrying member to a sheet passing between the image carrying member and the transfer member, a detector configured to detect a temperature, and a control device. The control device is configured to change, in response to a sheet interval, a developing bias to be applied to the developer carrying member from a first developing bias to a second developing bias at a changing rate based on a temperature detected by the detector, the changing rate being an amount of change in the developing bias per unit time based on the temperature.