Heater Width Variation for Thermal Stress Suppression

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Solution Overview

Problem

In fixing apparatuses, thermal stress is created due to temperature differences caused by power shut-off members, leading to fixing irregularities and potential failures, especially when the heater enters an uncontrolled state.

Innovation Solution

A fixing apparatus with a heater having first and second heat generating resistors and a power shut-off member positioned between them, where the first portion of the heat generating resistor is narrower and positioned closer to the power shut-off member than the second portion, to ensure uniform heat distribution and reduce thermal stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a power shut-off member is provided in contact with the heater to prevent malfunction, then safety is improved, but temperature uniformity deteriorates causing fixing irregularities

Engineering Contradiction:

ImprovesafetyVSAvoidtemperature uniformity

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The heat generating resistor is designed with non-uniform width where it contacts the power shut-off member. Specifically, the width is reduced in the region corresponding to the contact area with the power shut-off member, creating localized high heat generation that compensates for heat loss to the shut-off member and maintains temperature uniformity across the heater surface.

Inventive Principle:

Principle #3Local quality

2Productivity

If high power is supplied to the heater for quick start, then productivity is improved, but thermal stress increases causing potential failure

Engineering Contradiction:

Improvequick start capabilityVSAvoidthermal stress

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The heat generating resistor features localized width variation with narrower sections at both ends and a wider central section. This non-uniform geometry creates corresponding localized heat generation patterns that compensate for heat loss at the ends while controlling central temperature, thereby reducing thermal gradients and thermal stress during high-power operation for quick start.

Inventive Principle:

Principle #3Local quality

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 thermal stress and ensures consistent fixability of toner images, preventing fixing failures even when the heater is in an uncontrolled state by maintaining a more uniform temperature distribution.

Implementation Method 1

a heat generating resistor formed on the substrate... the heater generates heat by electric power supplied thereto

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a power shut-off member that is operated by heat of the heater... the power shut-off member being in contact with the heater

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS10429783B2Fixing apparatus and heater used in the same that suppresses thermal stress from being created in the heater

Publication Date: 2019.10.01 CANON KK

AI summary

In a fixing apparatus, a width of a first portion of a first heat generating resistor is narrower than a width of a second portion, at least a portion of an outline of the first portion on the near side with respect to a power shut-off member is provided at a position closer to the power shut-off member than an outline of the second portion on the near side with respect to the power shut-off member, and at least a portion of an outline of the first portion on the far side with respect to the power shut-off member is provided at a position closer to the power shut-off member than an outline of the second portion on the far side with respect to the power shut-off member.