Fixing Belt Heat Equalizing Structure for Uniform Toner Heating

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Solution Overview

Problem

In existing image heating devices, the heat conduction member thermally expands in the longitudinal direction, causing uneven temperature distribution and image defects due to biased heating of the toner on the recording material.

Innovation Solution

A fixing device with a cylindrical fixing belt, a pressure member, a heater, a heat equalizing member, and a positioning structure, where the heat equalizing member absorbs heat from the heater and transfers it uniformly along the axial direction, supported by a positioning structure that allows thermal expansion while maintaining alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a heat conduction member is used to conduct heat from the heating member, then heat transmission efficiency is improved, but thermal expansion of the heat conduction member causes uneven temperature distribution and image defects

Engineering Contradiction:

Improveheat transmission efficiencyVSAvoidtemperature distribution uniformity

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The heat conduction member is divided into multiple independent heat conduction portions arranged in the longitudinal direction. Each portion independently conducts heat from the heating member to the fixing belt, preventing the thermal expansion problem of a single long member while maintaining efficient heat transmission. The segmentation allows each portion to be shorter and less prone to differential expansion that would cause temperature bias.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A positioning structure is introduced as an intermediary between the heat conduction member and the holder. This positioning structure includes positioning holes and positioning recesses that align and secure the heat conduction portions, preventing their movement due to thermal expansion. The intermediary positioning structure absorbs the dimensional changes from thermal expansion while maintaining the precise positioning needed for uniform temperature distribution.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the heat conduction member is engaged with the holder via a regulating part, then movement regulation is improved, but thermal expansion still causes the heat conduction member to shift relative to the heating member

Engineering Contradiction:

Improvemovement regulationVSAvoidpositioning accuracy

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The heat conduction member is segmented into multiple portions, each with its own positioning. This segmentation allows each portion to be independently positioned and regulated, preventing the cumulative positioning errors and thermal expansion shifts that occur in a single continuous member with regulating parts.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The positioning structure utilizes the thermal expansion itself by providing positioning holes and recesses that allow controlled movement while maintaining alignment. The heat conduction portions are positioned to protrude through the holder with specific clearance, allowing them to self-adjust during thermal expansion while the positioning structure prevents excessive movement that would cause misalignment.

Inventive Principle:

Principle #25Self-service

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

Uniform temperature distribution across the fixing belt is achieved, preventing excessive temperature rise and reducing image defects by ensuring consistent toner heating.

Implementation Method 1

The heat equalizing member extends in the axial direction so as to be less than or equal to a dimension of the heater in the axial direction, comes into contact with one surface of the heater on an opposite side to the fixing belt, absorbs heat emitted from the heater and moves it in the axial direction

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

the heat conduction member thermally expands (extends) mainly to the other side in the longitudinal direction which is opposite to the regulating part

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20260064049A1Fixing device and image forming apparatus

Publication Date: 2026.03.05 KYOCERA DOCUMENT SOLUTIONS INC

AI summary

A fixing device includes a fixing belt, a pressure member, a heater, a heat equalizing member, a support member, and a positioning structure. The support member comes into contact with one surface of the heat equalizing member on an opposite side to the heater, and supports the heat equalizing member. The positioning structure positions the heat equalizing member with respect to the support member. The positioning structure includes a positioning hole, a positioning recess, and a positioning member. The positioning hole penetrates in a thickness direction a center region of the heat equalizing member in the axial direction. The positioning recess is recessed in a center region of the support member in the axial direction, where coincides with the positioning hole. The positioning member is fitted into a positioning space formed by the positioning hole and the positioning recess while in contact with one surface of the heater.