Fixing Device Sheet Conveyance Timing Control

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Solution Overview

Problem

Image forming apparatuses experience image streak defects due to separation discharge between the fixing member and the trailing edge of sheets, leading to potential contact with unfixed toner images, causing streak-like defects in subsequent sheets.

Innovation Solution

An image forming apparatus with a fixing device featuring a fluororesin surface layer and a controller that adjusts the sheet conveyance timing to prevent the portion of the fixing device's surface layer, which experiences separation discharge, from contacting the image area of subsequent sheets, instead bringing it into contact with the margin area, thereby preventing image streaks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the sheet conveyance period is shortened to improve productivity, then the output per unit time increases, but the separation discharge area of the fixing device may contact the image area of subsequent sheets causing image streaks

Engineering Contradiction:

Improveoutput per unit timeVSAvoidimage quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The controller preliminarily determines the conveyance period based on sheet size and conveys the next sheet only after the separation discharge area has rotated to a position that will contact the margin area rather than the image area. This preliminary timing adjustment prevents image streaks before they can occur.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The solution distinguishes between different areas of the sheet (image area vs. margin area) and ensures the separation discharge area contacts only the margin area. This local differentiation allows the problematic discharge area to be isolated from the critical image formation zone.

Inventive Principle:

Principle #3Local quality

2Reliability

If the sheet conveyance period is lengthened to prevent image streaks, then image quality is maintained, but productivity decreases

Engineering Contradiction:

Improveimage qualityVSAvoidoutput per unit time

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The controller dynamically adjusts the conveyance period based on real-time conditions including sheet size and the rotational position of the separation discharge area. This dynamic adaptation allows optimization of the timing to prevent image streaks while minimizing the impact on productivity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the conveyance period parameter according to sheet size and discharge area position. By adjusting this temporal parameter dynamically, the system maintains image quality while optimizing productivity for different operating conditions.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If continuous image formation processing is performed without adjusting conveyance timing, then productivity is maximized, but separation discharge causes image streaks on subsequent sheets

Engineering Contradiction:

Improvecontinuous processing speedVSAvoidimage streaks

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The controller monitors the position of the separation discharge area and provides feedback to adjust the conveyance timing of subsequent sheets. This feedback mechanism ensures that even during continuous processing, the timing is optimized to prevent image streaks while maintaining high productivity.

Inventive Principle:

Principle #23Feedback

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

Effectively prevents image streaks by ensuring the separation discharge area of the fixing device contacts the margin area of subsequent sheets, maintaining image quality while minimizing productivity reduction.

Implementation Method 1

separation discharge may occur between a fixing member (e.g., the fixing film) and a trailing edge of the sheet

Methodology Applied

Scientific EffectSeparation discharge: Electrostatic Discharge

Implementation Method 2

a nip portion formed by a fixing film heated by a heater and a pressing roller and fixes an unfixed toner image onto the sheet by heat from the heater

Methodology Applied

Scientific EffectHeat: Heating

Data Source

PatentUS10114329B2Image forming apparatus which controls period between trailing edge of preceding sheet and leading edge of next sheet

Publication Date: 2018.10.30 CANON KK

AI summary

An image forming apparatus includes an image forming device, a fixing device including a first rotary member of which a surface layer containing a fluororesin is brought into contact with a sheet surface having an unfixed toner image formed by the image forming device, and a controller. In a case that image formation processing for continuously forming a toner image on a plurality of predetermined sheets is executed, the controller can control conveyance of a sheet so that a portion of the surface layer of the first rotary member which is brought into contact with a trailing edge of a preceding sheet is brought into contact with a margin area on a leading edge side on a next sheet.