Conductive Sheet Guide for Image Forming Apparatus

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Solution Overview

Problem

Existing image forming apparatuses using electro-photographic recording systems face issues with defective toner transfer due to excessive current flow from the transfer member to the metal plate, leading to poor image quality, and there is a need for a more cost-effective solution to manage this issue.

Innovation Solution

Incorporating a sheet guide portion with a resin member and a conductive portion, where the conductive portion has lower volume resistivity than the resin member, to control current flow and prevent toner image defects during the transfer process, eliminating the need for a variable resistor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a metal plate is used to guide the sheet to the transfer nip portion, then the sheet can be guided effectively, but excessive current flows from the transfer member to the metal plate through the sheet, causing defective transfer of the toner

Engineering Contradiction:

Improvesheet guidanceVSAvoidtoner transfer quality

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The invention changes the electrical parameter (volume resistivity) of the sheet guide portion from high conductivity (metal plate) to controlled conductivity (resin member with specific volume resistivity of 1×10^10 to 1×10^14 Ω·cm). This parameter change prevents excessive current flow while maintaining sheet guidance functionality, thereby resolving the contradiction between ease of operation and reliability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite structure consisting of a resin member with specific volume resistivity and a conductive portion (metal plate or conductive resin) with lower volume resistivity. This composite material approach combines the guidance effectiveness of conductive materials with the current-limiting properties of resistive materials, achieving both good sheet guidance and prevention of excessive current flow.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a variable resistor is interposed in the grounding wire to restrain current flow, then defective transfer of toner is prevented, but the apparatus cost increases

Engineering Contradiction:

Improvetoner transfer qualityVSAvoidapparatus cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention extracts and eliminates the variable resistor from the grounding wire configuration. Instead of using an external variable resistor component, the current-limiting function is integrated into the sheet guide portion itself through the use of a resin member with specific volume resistivity. This extraction simplifies the apparatus structure, reduces cost, and maintains reliable toner transfer.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The sheet guide portion itself provides the current-limiting function through its inherent volume resistivity, eliminating the need for separate current-control components. The resin member with controlled electrical resistance serves dual purposes: guiding the sheet and restraining current flow, making the system self-sufficient and reducing overall apparatus complexity and cost.

Inventive Principle:

Principle #25Self-service

3Weight of moving object

If a resin member with conductive portion is used instead of a variable resistor, then apparatus weight is reduced, but the volume resistivity must be precisely controlled to prevent excessive current

Engineering Contradiction:

Improveapparatus weightVSAvoidvolume resistivity control

Core Design Contradiction:

Weight of moving objectVSManufacturing precision

Solution Approach 1:

The invention specifies a precise range for volume resistivity (1×10^10 to 1×10^14 Ω·cm) of the resin member to achieve the desired balance between current limitation and sheet guidance. This parameter specification ensures that the resin member provides sufficient electrical resistance to prevent excessive current flow while maintaining the necessary guidance function, resolving the contradiction between weight reduction and manufacturing precision requirements.

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

This configuration effectively suppresses uneven charge distribution and prevents defective toner transfer, enhancing image quality while reducing costs and apparatus weight, making it suitable for compact and cost-effective image forming devices.

Implementation Method 1

a conductive portion provided to be in contact with the sheet to which the toner image is being transferred by the transfer portion and on the resin member so as to be earthed through the resin member

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

a transfer portion transferring a toner image to a sheet

Methodology Applied

Scientific EffectElectro-photographic transfer:

Data Source

PatentUS9557688B2Image forming apparatus having conductive sheet guide

Publication Date: 2017.01.31 CANON KK

AI summary

An image forming apparatus includes a transfer portion transferring a toner image to a sheet, and a sheet guide portion guiding the sheet to the transfer portion. The sheet guide portion includes a resin member and a conductive member. The conductive member is provided to be in contact with the sheet to which the toner image is being transferred by the transfer portion and on a surface of the resin member so as to be grounded through the resin member, and has a volume resistivity which is lower than that of the resin member.