Fixing Device Pressure Roller Elastic Layer Thermal Expansion
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Solution Overview
Problem
Existing fixing devices in image forming apparatuses face challenges in maintaining consistent pressure distribution at the fixing nip due to thermal expansion of the elastic layer on the pressure roller, leading to potential damage of the fixing belt and sheet jamming issues.
Innovation Solution
The fixing device incorporates a deformable elastic layer on the pressure roller with a fixing pad that is biased by a biasing member and restricted by a stopper, ensuring a constant pressing force is maintained despite thermal expansion, and the fixing pad is designed to press against the elastic layer over its axial span to maintain consistent pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a deformable elastic layer is used on the pressure roller to maintain pressure distribution, then the fixing pressure is improved, but thermal expansion causes the elastic layer to deform and lose pressing force
Solution Approach 1:
The patent applies thermal expansion compensation by designing the elastic layer with specific material properties and structural characteristics that allow it to expand uniformly when heated, maintaining constant pressing force despite temperature increases. The elastic layer is formulated to have thermal expansion characteristics that counteract the natural contraction that would occur from heating, thereby stabilizing the pressing force against the fixing belt throughout the heating cycle.
2Stability of the object's composition
If the fixing pad is biased against the pressure roller to maintain contact, then the fixing nip stability is improved, but the fixing belt may skew due to uneven pressure distribution
Solution Approach 1:
The patent applies local quality by creating a pressure distribution pattern where the elastic layer provides different pressing forces at different locations. Specifically, the elastic layer is designed to exert greater pressing force at the edges of the fixing nip compared to the center, which compensates for the natural tendency of the fixing belt to skew under uniform pressure. This non-uniform pressure distribution maintains fixing nip stability while preventing fixing belt misalignment.
3Force
If thermal expansion of the elastic layer is allowed to occur, then the pressing force is maintained, but the fixing nip length becomes unstable
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the material properties of the elastic layer, including its elasticity modulus, density, and thermal expansion coefficient. By adjusting these parameters, the system achieves an optimal balance where the elastic layer expands thermally to maintain pressing force while the overall dimensional changes remain within acceptable limits, keeping the fixing nip length stable enough for proper image fixation.
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 stabilizes the fixing nip length and tension, preventing the fixing belt from skewing and reducing the likelihood of sheet jamming, thereby extending the life of the fixing belt and ensuring consistent image fixation.
Implementation Method 1
thermal expansion of the elastic layer on the pressure roller
Implementation Method 2
a biasing member biases the fixing pad and the fixing belt against the pressure roller
Data Source
AI summary
A fixing device includes a fixing belt formed into a loop rotatable in a predetermined direction of rotation and a pressure roller disposed opposite the fixing belt. The pressure roller includes a shaft fixedly positioned and a deformable elastic layer. A fixing pad is disposed inside the loop formed by the fixing belt and separably pressed against the pressure roller via the fixing belt to form a fixing nip between the fixing belt and the pressure roller, through which a recording medium bearing a toner image is conveyed. A biasing member biases the fixing pad and the fixing belt against the pressure roller. A stopper restricts motion of the fixing pad biased by the biasing member. The stopper contacts the fixing pad while the recording medium bearing the toner image is conveyed through the fixing nip.