Counter Roller Elastic Layer Thickness Gradient for Fixing Nip Shift Force
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Solution Overview
Problem
In image forming apparatuses using an electrophotographic system, the side-end reference conveyance method can cause a shift force to be generated in the fixing device, leading to wear, damage, and reduced life of the heating unit. Additionally, increasing the thickness of the fixing film to enhance life may decrease thermal conductivity, slowing down the fixing process.
Innovation Solution
The fixing device incorporates a counter roller with an elastic layer of varying thickness across its width, and an urging unit that applies different urging forces at each end portion of the counter roller. This configuration ensures that one end portion of the sheet passes through a predetermined position of the fixing nip regardless of sheet size, while minimizing the shift force on the fixing film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the thickness of the fixing film is increased to increase the life, then the life is improved, but the thermal conductivity decreases and fixing processing is slowed down
Solution Approach 1:
The elastic layer of the counter roller is designed with non-uniform thickness, being thinner at the first end portion and thicker at the second end portion. This local variation in thickness creates corresponding variations in urging force distribution, which compensates for the shift force generated by temperature differences in side-end reference conveyance, thereby preventing fixing film displacement without requiring increased overall thickness that would harm thermal conductivity.
2Ease of operation
If the side-end reference conveyance method is applied, then the positional reference is simplified, but a shift force is generated that causes wear and damage to the fixing film
Solution Approach 1:
The counter roller is designed with pre-calculated non-uniform elastic layer thickness to create compensating urging forces that counteract the shift force generated by side-end reference conveyance. By proactively designing this force compensation mechanism, the fixing film is protected from displacement and wear before the harmful effects can occur, maintaining reliability while preserving the simplicity of side-end reference conveyance.
3Force
If the thickness of the elastic layer is varied to reduce shift force, then the shift force is minimized, but the complexity of the counter roller increases
Solution Approach 1:
The counter roller's elastic layer thickness is varied continuously from the first end portion to the second end portion, creating a gradient profile that optimally distributes urging force. This parameter change approach allows for smooth force compensation without requiring complex mechanical assemblies, multiple components, or adjustment mechanisms, thereby minimizing structural complexity while effectively reducing shift force.
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 solution effectively reduces the shift force on the fixing film, preventing wear and damage, and allowing for increased speed and life of the fixing device without compromising thermal conductivity or fixing performance.
Implementation Method 1
a counter roller (61) that faces the heating unit (60) and forms a fixing nip together with the heating unit (60)... the counter roller (61) includes a roller portion (26) including a base portion (261) and an elastic layer (262) provided around the base portion (261) and having elasticity
Implementation Method 2
a heating unit (60) that heats a sheet... configured to fix a toner image borne on the sheet to the sheet by applying heat and pressure at the fixing nip
Data Source
AI summary
A fixing device includes a heating unit configured to heat a sheet, and a counter roller facing the heating unit and forming a fixing nip together with the heating unit. The counter roller includes a roller portion including an elastic layer. When a side on which a predetermined position is positioned with respect to a central portion of the roller portion in a width direction is defined as a first side, and a side opposite to the first side is defined as a second side, the roller portion has a first end portion which is an end portion on the first side in the width direction, and a second end portion which is an end portion on the second side in the width direction. A thickness of the elastic layer at the second end portion is smaller than a thickness of the elastic layer at the first end portion.