Transfer Device with Offset Drum Axis for Compact Image Formation

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Solution Overview

Problem

Conventional color image forming apparatuses face challenges in switching between monochrome and full-color modes due to large distances required for detaching and attaching primary transfer rollers, leading to increased setup time and varying image quality caused by changes in the contact width of the intermediate transfer belt with photosensitive drums.

Innovation Solution

A transfer device where the rotation axis of the first image-carrier rotating member is positioned closer to the transfer belt and displaced from the line of other image-carrier rotating members, with bias-applying rotating members positioned downstream and orthogonal to the moving direction of the transfer belt, ensuring consistent contact angles and image quality across modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If all photosensitive drums are arranged in a row on a single plane, then the structure is simple and easy to manufacture, but the distance required for detaching primary transfer rollers becomes large

Engineering Contradiction:

Improvestructural simplicityVSAvoiddetachment distance

Core Design Contradiction:

Ease of manufactureVSLength of moving object

Solution Approach 1:

The invention changes the arrangement from a single-plane linear configuration to a multi-dimensional configuration where the first photosensitive drum's rotation axis is displaced from the line of other drums' axes, enabling compact spatial arrangement that reduces detachment distance while maintaining manufacturing simplicity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Length of moving object

If the first photosensitive drum is positioned closer to the transfer belt, then the detachment distance is reduced, but the contact width of the intermediate transfer belt with the photosensitive drum changes between modes

Engineering Contradiction:

Improvedetachment distanceVSAvoidcontact width consistency

Core Design Contradiction:

Length of moving objectVSStability of the object's composition

Solution Approach 1:

The invention makes the contact width dynamic by positioning the first photosensitive drum closer to the transfer belt, allowing the contact area to vary between monochrome and full-color modes. This dynamic adjustment enables shorter detachment distance while accepting variable contact characteristics as part of the operational flexibility

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention applies different operational characteristics to different operational modes: in monochrome mode the first drum operates with a specific contact width optimized for single-color transfer, while in full-color mode the contact width adjusts to accommodate multiple drums. Each mode has its own optimized local characteristics

Inventive Principle:

Principle #3Local quality

3Reliability

If primary transfer rollers are detached from the intermediate transfer belt in monochrome mode, then the photosensitive drums are protected from mechanical wear, but the setup time for mode switching increases

Engineering Contradiction:

Improvedrum protectionVSAvoidmode switching time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The invention performs preliminary positioning by arranging the first photosensitive drum closer to the transfer belt and displacing its axis, so that when monochrome mode is selected, the primary transfer roller is already in a position requiring minimal movement for detachment. This preliminary spatial configuration reduces the time needed for mode switching while maintaining drum protection

Inventive Principle:

Principle #10Preliminary action

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 reduces the distance required for primary transfer roller detachment, maintains consistent image quality by maintaining constant contact angles, and enhances the gripping force of the driving roller and cleaning unit's contact area, facilitating smooth image transfer and improved cleaning efficiency.

Implementation Method 1

a transfer device that transfers a toner image formed on an image-carrier rotating member onto transfer medium via an intermediate transfer belt

Methodology Applied

Scientific EffectElectrostatic transfer: Electrostatics

Data Source

PatentUS7643781B2Transfer device and image forming apparatus

Publication Date: 2010.01.05 RICOH CO LTD

AI summary

A transfer device transfers an image formed on each of image-carrier rotating members onto a transfer belt by applying a bias voltage to the image-carrier rotating members. A rotation axis of one of image-carrier rotating member located the most upstream is positioned closer to the transfer belt than those of the other image-carrier rotating members. Each of the bias-applying rotating members is displaced downstream of the corresponding image-carrier rotating member, and a line on which a rotation axis of the bias-applying rotating member and that of the corresponding image-carrier rotating member fall is orthogonal to a moving direction of the transfer belt.