Fixing Heater Element Layout for Thermal Expansion Control

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Solution Overview

Problem

Existing fixing devices face issues with substrate damage due to opposing thermal expansion forces between resistance heating elements, which are arranged in a stepped manner to ensure insulation but can exceed safe displacement limits.

Innovation Solution

The arrangement of resistance heating elements on the substrate includes a first element with a second element displaced in the conveyance direction, maintaining an insulation distance and setting the displacement amount between them to 0.1 mm to 4.5 mm, reducing opposing thermal expansion forces and preventing substrate damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If resistance heating elements are arranged in a stepped manner with larger displacement to ensure insulation distance, then the heating body becomes more compact and insulation is improved, but the substrate becomes more prone to damage due to excessive opposing thermal expansion forces

Engineering Contradiction:
Improveinsulation distanceVSAvoidsubstrate strength
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent optimizes the displacement parameter between adjacent resistance heating elements, setting it within a specific range (0.1-4.5mm) to balance thermal expansion forces. This parameter optimization prevents substrate damage while maintaining adequate insulation, resolving the contradiction between insulation distance and substrate strength.

Inventive Principle:
Principle #35Parameter changes

2Strength

If resistance heating elements are arranged in a stepped manner with smaller displacement to reduce thermal expansion forces, then substrate damage is reduced, but the insulation distance may be insufficient

Engineering Contradiction:
Improvesubstrate strengthVSAvoidinsulation distance
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent establishes an optimal displacement range (0.1-4.5mm) for adjacent resistance heating elements that simultaneously satisfies both substrate strength requirements and insulation distance requirements. This parameter optimization resolves the contradiction by finding the balanced point where thermal expansion forces are manageable while insulation is adequate.

Inventive Principle:
Principle #35Parameter changes

3Volume of moving object

If the displacement between resistance heating elements is increased to make the heating body compact, then device size is reduced, but opposing thermal expansion forces increase and may damage the substrate

Engineering Contradiction:
Improveheating body sizeVSAvoidsubstrate strength
Core Design Contradiction:
Volume of moving objectVSStrength

Solution Approach 1:

The patent optimizes the displacement parameter between resistance heating elements within a specific range (0.1-4.5mm) to achieve compact heating body design while preventing substrate damage from excessive thermal expansion forces.

Inventive Principle:
Principle #35Parameter changes

4Strength

If the displacement between resistance heating elements is decreased to reduce thermal expansion forces, then substrate strength is maintained, but the heating body becomes less compact

Engineering Contradiction:
Improvesubstrate strengthVSAvoidheating body size
Core Design Contradiction:
StrengthVSVolume of moving object

Solution Approach 1:

The patent establishes an optimal displacement range (0.1-4.5mm) that balances substrate strength protection with heating body compactness, resolving the contradiction between these two 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 minimizes substrate damage by managing thermal expansion forces, ensuring efficient and durable operation of the fixing device.

Implementation Method 1

The heater includes a plurality of resistance heating elements formed on one surface of a substrate

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Implementation Method 2

heats the fixing belt

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

when the resistance heating elements are thermally expanded by being powered, forces opposite to each other are exerted between the adjacent resistance heating elements

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP4703806A1Fixing device and image forming apparatus
Publication Date: 2026.03.04 KYOCERA DOCUMENT SOLUTIONS INC
  • EP4703806A1 patent drawingFigure 1
  • EP4703806A1 patent drawingFigure 2
  • EP4703806A1 patent drawingFigure 3

AI summary

A fixing device (7) includes a fixing belt (20), a pressure member (21), and a heater (22). The heater (22) includes a plurality of resistance heating elements (31, 32) formed on one surface of a substrate at intervals in the axial direction. The resistance heating elements (31, 32) contain at least one first resistance heating element (31), and at least one second resistance heating element (32) formed at a position displaced from the first resistance heating element (31) on an upstream side or on a downstream side of the first resistance heating element (31) in a medium conveyance direction orthogonal to the axial direction. A displacement amount between the first resistance heating element (31) and the second resistance heating element (32) is less than a dimension of the pressure region in the conveyance direction, and is set in a range of 0.1 mm or larger to less than 4.5 mm.