Fixing Device Curved Pad Reduces Belt Distortion

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Solution Overview

Problem

Conventional fixing devices in image forming apparatuses face challenges in uniformly fixing toner images onto sheets due to uneven curvature of the sliding surface, leading to distortion and potential smearing or blurriness, especially when the sliding surface has a single curvature.

Innovation Solution

The fixing device incorporates a pad member with a sliding surface divided into upstream and downstream regions, each with distinct curved surfaces, where the upstream region has a larger average curvature than the downstream region, and a pressure roller that rotates to press the endless belt, reducing distortion and slippage by managing thermal expansion and contraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the sliding surface has a single curvature, then the structure is simple and easy to manufacture, but the belt experiences uneven curvature leading to distortion and image defects

Engineering Contradiction:

Improvesliding surface structureVSAvoidimage fixing quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The sliding surface is segmented into multiple regions with different curvatures. The upstream region has a first curvature while the downstream region has a second curvature, allowing each region to handle specific functional requirements independently. This segmentation resolves the contradiction by enabling complex curvature patterns while maintaining manufacturing feasibility through modular design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the sliding surface are given different local curvatures optimized for their specific functions. The upstream region with larger curvature handles belt engagement and initial positioning, while the downstream region with smaller curvature maintains belt tension and stability. This local differentiation improves image fixing quality without requiring complete redesign of the entire surface.

Inventive Principle:

Principle #3Local quality

2Reliability

If the sliding surface has large curvature, then the belt is better constrained, but thermal expansion and contraction cause distortion and slippage

Engineering Contradiction:

Improvebelt constraintVSAvoidthermal distortion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The curvature parameter of the sliding surface is varied across different regions rather than maintaining a uniform value. By changing the curvature parameter from the first curvature in the upstream region to the second curvature in the downstream region, the system accommodates thermal expansion and contraction while maintaining reliable belt constraint throughout the heating process.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If the upstream region has larger curvature than downstream region, then belt positioning is improved, but the sliding surface becomes more complex

Engineering Contradiction:

Improvebelt positioningVSAvoidsliding surface geometry

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The sliding surface utilizes spherical or curved geometric forms with different radii in different regions. The first curvature and second curvature are implemented as concentric or adjacent curved surfaces that can be manufactured using standard machining techniques. This approach achieves precise belt positioning through geometric design rather than complex mechanical mechanisms.

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

This configuration minimizes the amplitude of distortion, reducing defects such as creases and smearing, while simplifying the manufacturing process and maintaining the shape of the sliding surface, thereby enhancing the quality of fixed images.

Implementation Method 1

a heating source that heats the belt

Methodology Applied

Scientific EffectThermal energy transfer: Conduction (thermal)

Implementation Method 2

reducing distortion and slippage by managing thermal expansion and contraction

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8934825B2Fixing device and image forming apparatus

Publication Date: 2015.01.13 FUJIFILM BUSINESS INNOVATION CORP

AI summary

A fixing device includes a rotatable endless belt, a heating source that heats the belt, a pad member having a sliding surface abutting on an inner surface of the belt, and a pressure roller that presses an outer surface of the belt toward the sliding surface and rotates to rotate the belt. The pressure roller works together with the belt to fix an unfixed toner image onto a medium that bears the unfixed toner image by allowing the medium to enter between the roller and the belt. Assuming that the sliding surface is divided into upstream and downstream regions in a moving direction of the belt, the upstream and downstream regions both have recessed curved surfaces in the moving direction. A first curved surface corresponding to the upstream region has an average curvature that is larger than that of a second curved surface corresponding to the downstream region.