Endless Belt End Surface Geometry for Stress Distribution
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Solution Overview
Problem
The existing film-heating-type fixing devices in image forming apparatuses face challenges with deviation forces affecting the longevity of the fixing film, particularly due to differences in parallelism and pressing force between the pressure roller and the fixing film, leading to stress concentration and potential damage.
Innovation Solution
The image heating apparatus incorporates an endless belt with a base layer made of a metal material, featuring a plane and curved surface region on its end surface, with a flatness ratio of 50% to 90%, to distribute stress evenly and prevent damage from deviation forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thick metal sleeve is used as the base layer of the fixing film to improve heat transfer efficiency, then heat transfer efficiency is improved, but deviation force increases due to stress concentration at the film end
Solution Approach 1:
The end surface of the base layer is designed with non-uniform thickness, creating a curved surface region with smaller thickness at the edges and a plane region with larger thickness in the center. This local variation in thickness distributes stress more evenly across the end surface, preventing stress concentration at the edges while maintaining the overall structural integrity and heat transfer efficiency of the thick metal sleeve base layer.
2Reliability
If pressing force is increased to ensure fixing property, then fixing property is improved, but deviation force increases due to unevenness in the elastic layer
Solution Approach 1:
The non-uniform thickness distribution at the end surface of the base layer creates a stress-distributing structure that compensates for the increased deviation forces resulting from higher pressing forces. The curved surface region with reduced thickness at the edges acts as a stress-relief zone, preventing crack initiation while allowing the increased pressing force to be applied effectively for reliable fixing.
3Strength
If the parallelism between pressure roller and fixing film is improved, then deviation force is reduced, but manufacturing complexity increases
Solution Approach 1:
Instead of requiring high manufacturing precision for the entire base layer, the invention applies the complex geometry only to the end surface where stress concentration occurs. The curved surface region with its varying thickness is localized to the end surface, while the main body of the base layer can be manufactured with standard precision, thus reducing overall manufacturing complexity while still achieving the goal of reducing deviation forces.
4Strength
If the flatness ratio H is increased to distribute stress evenly, then film durability is improved, but contact area with the regulating surface decreases
Solution Approach 1:
The end surface design creates a balanced stress distribution through its non-uniform thickness profile. The curved surface region with reduced thickness at the edges prevents stress concentration, while the plane region in the center maintains sufficient contact area with the regulating surface. This local differentiation in thickness allows the structure to achieve both stress distribution and adequate contact area simultaneously.
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 design enhances the durability of the fixing film by dispersing stress across a larger contact area, reducing the likelihood of damage and ensuring reliable operation even at increased process speeds and extended lifespan.
Implementation Method 1
a heater that contacts with an inner surface of the endless belt
Implementation Method 2
a backup member that forms a nip portion together with the heater through the endless belt. The image formed on the recording medium is heated while being pinched and conveyed in the nip portion
Data Source
AI summary
The image heating apparatus for heating an image formed on a recording medium has an endless belt with a base layer made of a metal material; a heater that contacts with an inner surface of the endless belt; and a backup member that forms a nip portion together with the heater through the endless belt. The image formed on the recording medium is heated while being pinched and conveyed in the nip portion. An end surface of the base layer includes a plane region and a curved surface region. When the thickness of the base layer is t, the width of the plane region in a thickness direction of the base layer is h, and the flatness ratio H of the end surface of the base layer is defined as h/t, the flatness ratio H satisfies 50%≦H≦90%.