Curved Separating Pad for Uniform Pressure in Fixing Nip

Solution Overview

Problem

Existing fixing devices in image forming apparatuses face issues with sheet separation, particularly at the central portion, leading to wrinkles and paper jams due to uneven pressure distribution across the sheet, especially when the sheet has high image density or moisture content.

Innovation Solution

A fixing device with a separating pad portion that has a curved pressing surface, where the upstream and downstream end portions protrude towards the central portion in the rotation axis direction, ensuring consistent pressure distribution and reducing the likelihood of sheet separation failures by maintaining equal pressure across the sheet.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional separating pad portion with a flat pressing surface is used, then the structure is simple, but uneven pressure distribution occurs at the central portion of the sheet causing wrinkles and paper jams

Engineering Contradiction:

Improvesheet separation performanceVSAvoidseparating pad structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The separating pad portion is designed with a curved pressing surface that protrudes toward the fixing member at the central portion in the rotation axis direction. This curvature compensates for the natural gap that forms at the center of the fixing nip, ensuring uniform pressure distribution across the entire sheet width and preventing wrinkles and paper jams.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The pressing surface of the separating pad portion has non-uniform geometry, with the central portion protruding more than the end portions. This local variation in shape is specifically designed to compensate for the non-uniform pressure distribution that occurs in the fixing nip, applying greater pressure where needed at the central region.

Inventive Principle:

Principle #3Local quality

2Reliability

If the separating pad portion presses uniformly across the sheet, then sheet separation is improved, but the fixing member cannot accommodate natural gap formation at the central portion

Engineering Contradiction:

Improvesheet separation performanceVSAvoidpressing surface geometry

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The separating pad portion is designed with a curved pressing surface that protrudes toward the fixing member at the central portion in the rotation axis direction. This curvature compensates for the natural gap that forms at the center of the fixing nip, ensuring uniform pressure distribution across the entire sheet width and preventing wrinkles and paper jams.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Reliability

If the pressing surface is flat, then manufacturing is easier, but pressure distribution becomes uneven leading to sheet separation failures

Engineering Contradiction:

Improvesheet separation performanceVSAvoidseparating pad fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The separating pad portion is designed with a curved pressing surface that protrudes toward the fixing member at the central portion in the rotation axis direction. This curvature compensates for the natural gap that forms at the center of the fixing nip, ensuring uniform pressure distribution across the entire sheet width and preventing wrinkles and paper jams.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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

The curved design of the separating pad portion enhances sheet separation performance, reducing wrinkles and paper jams, regardless of sheet size, image density, or moisture content, by ensuring consistent pressure distribution across the sheet.

Implementation Method 1

a separating pad portion that is disposed on an inner periphery of the belt member and includes a pressing surface which presses the fixing member

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the pressing surface of the separating pad portion curves so as to protrude toward the fixing member as it approaches a central portion thereof, ensuring consistent pressure distribution

Methodology Applied

Scientific EffectPressure distribution: Pressure Increase

Data Source

PatentUS9791811B2Fixing device and image forming apparatus

Publication Date: 2017.10.17 FUJIFILM BUSINESS INNOVATION CORP

AI summary

A fixing device includes a belt member, a fixing member facing an outer peripheral surface of the belt member and forming a fixing nip portion between the belt member, and a separating pad portion disposed inside the belt member, including a pressing surface for pressing the fixing member at downstream of the fixing nip portion in a moving direction of the belt member and separating a recording material from the fixing member. The pressing surface of the separating pad portion curves so as to protrude toward the fixing member as approaching a central portion thereof in a rotation axis direction of the fixing member. An upstream end portion and a downstream end portion of the pressing surface curve so as to protrude toward an upstream side in the moving direction as they approach the central portion in the rotation axis direction.