Fuser Cover Structure for Water Vapor Control in Image Forming

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Solution Overview

Problem

Water vapor generated during the heating process in image forming apparatuses adheres to the print surface of the photosensitive member, leading to image defects.

Innovation Solution

A heating device with a cover structure comprising a first rotating member, a second rotating member forming a nip portion, a first cover along the outer peripheral surface of the first rotating member, and a second cover with a protruding portion that protrudes towards the first rotating member, where the length of the protruding portion is shorter than the first rotating member, to control airflow and prevent water vapor from reaching the photosensitive drum.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a cover is provided to cover the entire surface of the heating portion, then heat loss is reduced and heating efficiency is improved, but water vapor generated during heating adheres to the print surface of the photosensitive member causing image defects

Engineering Contradiction:

Improveheating efficiencyVSAvoidwater vapor adhesion to photosensitive member

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The cover is divided into two segments: a first cover that covers the heating portion, and a second cover with a protruding portion that extends toward the first rotating member. This segmentation allows the cover to both retain heat and prevent water vapor from reaching the photosensitive member surface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second cover with the protruding portion acts as an intermediary barrier between the water vapor generated during heating and the print surface of the photosensitive member. It intercepts and redirects the water vapor away from the photosensitive member, preventing adhesion and image defects.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If the cover completely surrounds the first rotating member, then heat retention is improved, but water vapor is trapped and flows onto the photosensitive member

Engineering Contradiction:

Improveheat retentionVSAvoidwater vapor flow toward photosensitive member

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The second cover has a localized protruding portion that specifically addresses the water vapor flow issue at the critical area near the first rotating member, while the rest of the cover maintains its heat retention function. This local modification allows simultaneous achievement of heat retention and water vapor control.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of allowing the cover to completely enclose the first rotating member, the second cover protrudes inward to create a barrier that redirects water vapor away from the photosensitive member. This inverted approach prevents water vapor accumulation while maintaining overall heat retention.

Inventive Principle:

Principle #13The other way round (Inversion)

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

The solution effectively suppresses the influence of water vapor, preventing image defects by directing airflow outward and reducing the likelihood of vapor adherence to the photosensitive drum, even in high-temperature, high-humidity environments.

Implementation Method 1

a first rotating member that is heated by a heat source

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

a second cover with a protruding portion that protrudes towards the first rotating member... directing airflow outward

Methodology Applied

Scientific EffectAirflow: Convection

Implementation Method 3

water vapor that flows then to the image forming portion, and adheres to a print surface

Methodology Applied

Scientific EffectCondensation: Condensation

Data Source

PatentUS12523953B2Heating device and image forming apparatus

Publication Date: 2026.01.13 CANON KK

AI summary

A heating device has a first rotating member that is heated by a heat source, and a second rotating member that forms a nip portion with the first rotating member, such that a recording material is heated up at the nip portion. The heating device further has: a first cover disposed along an outer peripheral surface of the first rotating member, so as to surround the first rotating member, and a second cover, disposed between the first cover and the first rotating member, and having a protruding portion that protrudes towards the first rotating member. In a longitudinal direction of the first rotating member, a length of the first rotating member is a first length, and a length of the protruding portion is a second length that is smaller than the first length.