Transfer Voltage Control for Image Density Uniformity

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Solution Overview

Problem

Conventional image forming apparatuses using electrophotographic technology face challenges in maintaining proper image density due to fluctuations in transfer voltage, leading to issues like poor image density and white voids, especially at the leading end of the recording material, where limiter control is not timely and results in density non-uniformity and improper transfer.

Innovation Solution

An image forming apparatus with a controller that adjusts the transfer voltage based on real-time current detection, allowing a larger voltage change at the leading end of the recording material compared to the central portion, ensuring the transfer current remains within a predetermined range, thus preventing density non-uniformity and improper transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If limiter control is applied to adjust transfer voltage based on current detection, then transfer current can be kept within predetermined range, but response time is insufficient at leading end portion causing improper transfer

Engineering Contradiction:

Improvetransfer current control stabilityVSAvoidresponse time at leading end

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The controller increases the voltage change amount when the leading end portion of the recording material passes through the transfer portion, allowing the transfer voltage to reach the appropriate level faster and reducing the time lag before proper transfer current control is established

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The voltage change amount is dynamically adjusted based on the position of the recording material (leading end vs. central portion), being larger at the leading end and smaller at the central portion, allowing adaptive response to different operational conditions

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If transfer voltage is increased to improve image density, then transfer efficiency improves, but electric discharge occurs causing white voids

Engineering Contradiction:

Improveimage densityVSAvoidelectric discharge

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The controller detects the transfer current and adjusts the transfer voltage based on the detection result, creating a closed-loop control system that maintains transfer current within a predetermined range, preventing both insufficient transfer and electric discharge

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The transfer voltage is dynamically adjusted by changing the voltage change amount based on the position of the recording material and current detection results, allowing optimization of transfer conditions without causing electric discharge

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If transfer voltage is decreased to prevent electric discharge, then safety improves, but image density becomes insufficient

Engineering Contradiction:

Improveelectric discharge preventionVSAvoidimage density

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The controller continuously detects transfer current and adjusts voltage accordingly, ensuring the transfer current remains within the predetermined range that prevents electric discharge while maintaining sufficient image density

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The voltage control is dynamic rather than static, with the voltage change amount being larger at the leading end and smaller at the central portion, allowing optimization of both safety and image quality at different positions

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 approach effectively suppresses density non-uniformity near the central portion of the recording material while preventing improper transfer at the leading end, ensuring consistent image quality by dynamically adjusting the transfer voltage in response to current fluctuations.

Implementation Method 1

a toner image is electrostatically transferred from a photosensitive member or an intermediary transfer belt as an image bearing member onto a recording material such as paper

Methodology Applied

Scientific EffectElectrostatic transfer: Electrostatics

Implementation Method 2

a current value is detected, so that a voltage value at which a predetermined target current is obtained

Methodology Applied

Scientific EffectElectrical current detection: Electrical Resistance

Data Source

PatentUS11099504B2Image forming apparatus

Publication Date: 2021.08.24 CANON KK

AI summary

An image forming apparatus includes an image bearing member, a transfer member, a voltage source, a current detecting portion, and a controller. When the recording material passes through the transfer portion, the controller is capable of changing the predetermined voltage on the basis of a detection result of said current detecting portion so that the detection result of the current detecting portion falls within a predetermined range. A maximum changeable amount per once of the predetermined voltage is larger when a leading end portion of the recording material with respect to a recording material feeding direction passes through the transfer portion than when a central portion of the recording material with respect to the recording material feeding direction passes through the transfer portion.