Press Member Positioning to Prevent Belt Deflection in Transfer Nip

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Solution Overview

Problem

In image forming apparatuses using an electro-photographic system, vibrations in the intermediate transfer belt can cause gaps between the toner image carrying surface and the recording medium, leading to abnormal discharges and defective images due to the generation of intense electric fields at the transfer nip portion, even with the use of press members to suppress vibrations.

Innovation Solution

An image forming apparatus is designed with an inner and outer roller configuration, where the outer roller is offset upstream in the rotation direction to form a transfer nip portion, and a press member is positioned upstream of the inner roller to press the image carrying belt, ensuring the length of the press member's contact area is shorter than the recording medium's end margin, thereby minimizing the generation of gaps and abnormal discharges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a press member is provided to press the intermediate transfer belt from the back surface to suppress vibration, then the vibration suppression effect is improved, but the recording medium may push up the belt at the end portion causing gap generation and defective images

Engineering Contradiction:

Improvevibration suppressionVSAvoidgap generation at end portion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The press member is designed with non-uniform pressure distribution where the pressing force is stronger at the center portion and weaker at the end portion. This local differentiation allows effective vibration suppression at the center while minimizing gap generation at the end portion where the recording medium's end may push up the belt.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The press member is positioned upstream of the transfer nip portion to preemptively press the intermediate transfer belt before the recording medium reaches the critical area. This preliminary action ensures the belt is held firmly in place before any potential gap generation can occur during the transfer process.

Inventive Principle:

Principle #10Preliminary action

2Stability of the object's composition

If the press member contact length is increased to improve vibration suppression, then the belt stability is improved, but the recording medium end margin is reduced possibly causing gap generation

Engineering Contradiction:

Improvebelt stabilityVSAvoidrecording medium end margin

Core Design Contradiction:

Stability of the object's compositionVSLength of moving object

Solution Approach 1:

The press member's contact length is precisely controlled to be shorter than the recording medium's end margin. This parameter optimization ensures that the press member provides sufficient belt stabilization while leaving adequate margin at the end portion to prevent gap generation when the recording medium's end pushes up the belt.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If high voltage is applied to the transfer rotating body to create intense electric field for toner transfer, then the transfer efficiency is improved, but abnormal discharge occurs when gap is generated causing defective images

Engineering Contradiction:

Improvetransfer efficiencyVSAvoidabnormal discharge

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention accepts that some gap generation may occur at the end portion but converts this potential harmful factor into a beneficial design feature by positioning the press member upstream. This allows the intense electric field to be applied effectively during transfer while the upstream press member prevents the gap from forming in the critical transfer zone.

Inventive Principle:

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

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 configuration effectively reduces the occurrence of defective images by maintaining contact between the intermediate transfer belt and the recording medium, preventing abnormal discharges and ensuring consistent image transfer without voids, as demonstrated by experimental results where voids were not conspicuous when the press member's contact length was within the rear end margin of the recording medium.

Implementation Method 1

a power supply applying voltage between the inner and outer rollers to transfer the toner image from the image carrying belt to the recording medium conveyed through the transfer nip portion

Methodology Applied

Scientific EffectElectrostatic transfer: Electrostatics

Implementation Method 2

a press member provided upstream, in the rotation direction of the image carrying belt, of the inner roller and pressing the image carrying belt from the inner circumferential side of the belt

Methodology Applied

Scientific EffectMechanical pressure: Mechanical Force

Data Source

PatentUS9348266B2Image forming apparatus using press member to prevent deflection of belt

Publication Date: 2016.05.24 CANON KK

AI summary

An outer roller is provided at a position offset upstream, in a rotation direction of an image carrying belt, of an inner roller. The inner and outer rollers are provided across the image carrying belt and form a transfer nip portion nipping and conveying a recording medium. A press member presses the image carrying belt from an inner circumferential side at upstream of the inner roller. The press member is provided such that a length along a belt surface of the image carrying belt between a downstream end of a part thereof in contact with the image carrying belt and an upstream end of the transfer nip portion is shorter than a length of an end margin formed on an upstream end area of the recording medium.