Undulated Pressure Roller for Belt Fixing Device
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Solution Overview
Problem
Belt-type fixing devices face issues with cracks in the resin layer and uneven pressure distribution due to the transformation of the elastic layer under pressure, leading to image defects and reduced durability, especially when a low-hardness solid rubber pressure roller is used.
Innovation Solution
Forming undulations on the outer circumferential surface of the pressure roller to distribute pressure evenly and prevent cracks, with the undulations designed to match the elongation characteristics of the elastic layer, ensuring the resin layer is not subjected to excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a low-hardness solid rubber elastic layer is used in the pressure roller, then the nip width and separation curvature are improved, but the rubber transforms under pressure causing cracks in the resin layer and uneven pressure distribution
Solution Approach 1:
The pressure roller surface is segmented into multiple undulated portions rather than a smooth surface. This segmentation allows each undulation to independently manage the transformation under pressure, preventing stress concentration that would cause cracks in the resin layer while maintaining overall pressure uniformity.
Solution Approach 2:
The elastic layer is designed with varying local properties through undulations of different heights, wavelengths, and densities in different regions. This allows the pressure roller to provide locally adapted pressure distribution, accommodating the transformation of low-hardness rubber under pressure while maintaining image quality.
2Productivity
If the elastic layer is made softer to increase nip width, then fixing speed is improved, but the rubber transformation causes cracks and durability deterioration
Solution Approach 1:
The undulated surface segments the continuous elastic layer into multiple zones that can independently deform. This prevents the propagation of cracks through the entire layer, thereby maintaining durability even when using softer rubber for higher fixing speed.
Solution Approach 2:
The undulations are designed in advance to anticipate and accommodate the transformation of the elastic layer under pressure. By pre-configuring the surface geometry, the design cushions against stress concentration that would otherwise lead to crack formation and durability loss.
3Stress or pressure
If a smooth pressure roller surface is used, then uniform pressure is achieved, but the fixing belt cannot slide easily causing abnormal noises and wrinkles
Solution Approach 1:
The pressure roller surface features local variations in the form of undulations rather than being uniformly smooth or rough. These localized features provide discrete contact points that maintain overall pressure uniformity while creating micro-gaps that facilitate sliding between the fixing belt and pressure roller.
Solution Approach 2:
The undulations introduce curved surfaces at the peaks and valleys of the wave patterns. These curved surfaces reduce the contact area and facilitate sliding by distributing the friction forces, preventing the fixing belt from sticking while maintaining pressure uniformity across the image area.
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 undulations on the pressure roller prevent cracks in both the resin and elastic layers, maintaining consistent pressure distribution and improving the durability and image quality by reducing the likelihood of uneven gloss and fixing troubles.
Implementation Method 1
Forming undulations on the outer circumferential surface of the pressure roller to distribute pressure evenly and prevent cracks
Implementation Method 2
a solid rubber layer is squeezed by high load, and a surface of the solid rubber shrinks once before entering the nip portion, and then is extended gradually as the pressure in the nip portion increases
Implementation Method 3
the elastic layer is made of solid rubber, and the elastic layer is covered by a resin layer
Data Source
AI summary
A belt-type fixing device having therein an endless fixing belt, a pressure roller arranged inside the aforesaid fixing belt and a pressure member that presses the fixing belt against the pressure roller, wherein a toner image on a recording material is fixed in a nip portion formed between the fixing belt and the pressure member, and wherein the pressure roller has an elastic layer made of solid rubber, and the elastic layer is covered by a resin layer, and further plural undulations are formed in the circumferential direction of the outer circumferential surface of the pressure roller.