Heating Device Non-Uniform Pressing Force for Image Fixing

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Solution Overview

Problem

Existing heating devices in image forming apparatuses face challenges in maintaining uniform temperature distribution and fixing properties due to variations in heat generation along the heater's longitudinal direction, leading to uneven image glossiness and fixing quality.

Innovation Solution

The implementation of a heating device with a laminated heater and pressing devices that adjust pressing forces based on temperature distribution, ensuring uniform pressure conditions to counteract heat generation disparities, thereby maintaining consistent image quality across the heater's length.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a uniform heater is used along the longitudinal direction, then the structure is simple and manufacturing is easy, but the temperature distribution becomes uneven due to heat generation variations

Engineering Contradiction:

Improvetemperature distribution uniformityVSAvoidheater structure complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The heater is designed with non-uniform heat generation characteristics, where different longitudinal portions generate different amounts of heat. Specifically, the heat generation amount is adjusted to be higher at portions where more pressing force is applied, creating a local quality distribution that compensates for the uneven pressing force and achieves uniform temperature distribution across the heated object.

Inventive Principle:

Principle #3Local quality

2Reliability

If pressing force is increased uniformly across the heater, then fixing properties improve, but the temperature distribution becomes more uneven due to heat generation variations

Engineering Contradiction:

Improvefixing property consistencyVSAvoidtemperature uniformity

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The pressing devices are configured to apply different pressing forces at different longitudinal portions. The pressing force is adjusted to be inversely proportional to the heat generation amount, so that portions with higher heat generation receive lower pressing force and portions with lower heat generation receive higher pressing force, achieving uniform temperature and consistent fixing properties.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The pressing force parameter is varied along the longitudinal direction of the heater. By changing the pressing force parameter according to the heat generation distribution, the system compensates for thermal non-uniformity and maintains consistent fixing properties across different regions.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If pressing force is decreased at high heat generation portions, then temperature uniformity improves, but fixing properties deteriorate at those portions

Engineering Contradiction:

Improvetemperature distribution uniformityVSAvoidfixing property consistency

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The system applies different pressing forces at different longitudinal portions based on local heat generation characteristics. High heat generation portions receive lower pressing force while low heat generation portions receive higher pressing force, creating a localized compensation mechanism that maintains both temperature uniformity and fixing property consistency across the entire heated region.

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 solution ensures consistent image fixing properties and reduced unevenness in glossiness by dynamically adjusting pressing forces to match heat generation variations, enhancing the overall performance and reliability of the image forming process.

Implementation Method 1

a heater (22) that heats the fixing belt (20), wherein the heater (22) includes a first portion and a second portion, and the second portion generates a smaller amount of heat than the first portion

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a plurality of pressing devices that are arranged in a longitudinal direction of the heater (22) and each configured to press at least one of the fixing belt (20) and the pressure roller (21) and cause the fixing belt (20) and the pressure roller (21) to press each other

Methodology Applied

Scientific EffectMechanical force: Mechanical Force

Implementation Method 3

a fixing device that fixes a toner image on a recording medium under heat

Methodology Applied

Scientific EffectThermal fixing: Heating

Data Source

PatentUS11378904B2Image forming apparatus and heating device comprising plural pressing devices configured to generate different pressing forces

Publication Date: 2022.07.05 RICOH CO LTD

AI summary

A heating device includes a rotator, an opposed rotator configured to contact the rotator to form a nip, a heater configured to heat the rotator, and a plurality of pressing devices. The heater includes a first portion and a second portion. The second portion of the heater generates a smaller amount of heat than the first portion of the heater. The pressing devices are arranged in a longitudinal direction of the heater and each configured to press at least one of the rotator and the opposed rotator and cause the rotator and the opposed rotator to press each other. The pressing devices include a first pressing device corresponding to the first portion of the heater and a second pressing device corresponding to the second portion of the heater, and the first pressing device generates a smaller pressing force than the second pressing device.