Fixing Device Belt Tension and Thermal Conduction

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Solution Overview

Problem

The existing fixing devices in image forming apparatuses face issues with warm-up time, power consumption, and mechanical stability due to friction and uneven heating, leading to unstable rotation and potential jamming of recording media.

Innovation Solution

A fixing device incorporating a flexible endless belt-shaped fixing member, a cylindrical metal heat conductor, and a separator, where the metal heat conductor is heated internally and the belt is uniformly heated, with the separator ensuring proper alignment and preventing slackness to maintain consistent heat application and prevent jamming.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If a fixing film with smaller heat capacity is used instead of a fixing belt, then warm-up time is shortened and power consumption is reduced, but the fixing film may wear due to friction generated between the stationary ceramic heater and the rotating fixing film

Engineering Contradiction:

Improvewarm-up timeVSAvoidfixing film wear

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent replaces the ceramic heater (mechanical contact heating) with a heat conductor that allows the fixing film to rotate without direct frictional contact, substituting the mechanical heating system with a thermal conduction system that reduces wear on the fixing film while maintaining heating efficiency

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a heat conductor as an intermediary between the heat source and the fixing film, allowing thermal energy to be transferred without direct mechanical friction, thus reducing wear on the fixing film while maintaining effective heating

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the fixing film is heated only at the fixing nip, then the structure is simplified, but the fixing film is coolest when entering the fixing nip and may not reach desired fixing temperature at high rotation speeds

Engineering Contradiction:

Improveheating structureVSAvoidfixing film temperature at fixing nip

Core Design Contradiction:

Device complexityVSTemperature

Solution Approach 1:

The patent applies preliminary heating to the fixing film before it reaches the fixing nip by heating the heat conductor in advance, ensuring that the fixing film attains the desired temperature even at high rotation speeds, thereby preventing temperature deficiency at the critical fixing point

Inventive Principle:

Principle #10Preliminary action

3Reliability

If a fixing belt is used instead of a fixing film, then friction and wear are reduced, but the fixing belt may slacken at positions downstream from the fixing nip, causing hot offset and jamming

Engineering Contradiction:

Improvefriction stabilityVSAvoidfixing belt slackness

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent employs a tensioning mechanism that dynamically adjusts to maintain proper tension in the fixing belt throughout its rotation, preventing slackness downstream from the fixing nip while allowing the belt to accommodate thermal expansion and operational variations, thereby eliminating hot offset and jamming issues

Inventive Principle:

Principle #15Dynamics

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 reduces warm-up time, minimizes power consumption, stabilizes the fixing device operation, and prevents hot offset and jamming by ensuring consistent heat distribution and proper separation of the recording medium.

Implementation Method 1

a substantially cylindrical metal heat conductor which is provided inside the loop formed by the fixing member and which faces an inner circumferential surface of the fixing member

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a pressing member which presses the fixing member against the metal heat conductor to form a nip between the fixing member and the pressing member

Methodology Applied

Scientific EffectMechanical pressure: Compression

Implementation Method 3

a separator which presses the fixing member against the metal heat conductor and which contacts a recording medium discharged from the nip to separate the recording medium from the fixing member

Methodology Applied

Scientific EffectMechanical separation: Friction

Data Source

PatentUS8843043B2Fixing device and image forming apparatus incorporating same

Publication Date: 2014.09.23 RICOH CO LTD

AI summary

A fixing device includes a flexible, endless belt-shaped fixing member that rotates in a predetermined direction of rotation, a substantially cylindrical metal heat conductor provided inside a loop formed by the fixing member and facing an inner circumferential surface of the fixing member, a pressing member that presses the fixing member against the metal heat conductor to form a nip between the fixing member and the pressing member through which a recording medium bearing a toner image passes, and a separator that presses the fixing member against the metal heat conductor, provided downstream from the nip in the direction of rotation of the fixing member and contacting the recording medium discharged from the nip to separate the recording medium from the fixing member and guide the recording medium out of the fixing device.