Fixing Device Pressure Distribution for Image Quality
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Solution Overview
Problem
The existing fixing devices for color image-forming machines face issues with defective images due to excessive heating, paper curling, and surface contamination, which are exacerbated by increased nipping width and wear on the thermally fixing roller, especially when using an endless belt mechanism.
Innovation Solution
A fixing device with a thermally fixing roller and an endless belt, where the belt is pushed onto the roller to create a pressure distribution with maximum pressures at the upstream and downstream ends and a lower pressure in the intermediate region, combined with a parting member to manage paper separation, optimizing nipping time and parting time to prevent excessive heating and surface damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the nipping width between the belt and thermally fixing roller is increased to improve fixing property, then fixing property is improved, but the paper is excessively heated causing defective images (white spots)
Solution Approach 1:
The patent applies local quality by creating a non-uniform pressure distribution across the nipping region. The pushing means is configured to generate higher pressure at the upstream end and lower pressure at the downstream end, allowing different regions of the nipping zone to serve different functions: the upstream region provides strong pressure for effective toner fixation, while the downstream region reduces pressure to prevent excessive heating and paper damage.
2Ease of operation
If peeling pawls are arranged to part the paper from the thermally fixing roller, then paper parting is improved, but wear increases on the roller surface causing scars and shortened device life
Solution Approach 1:
The patent extracts the harmful peeling pawls from the system and replaces them with a belt-based parting mechanism. The endless belt, through its elastic deformation and pressure distribution, naturally parts the paper from the thermally fixing roller without requiring direct contact between hard peeling components and the roller surface, thereby eliminating wear and scar formation.
Solution Approach 2:
The patent changes the operational parameters by using the elastic properties of the belt and the pressure distribution characteristics to achieve paper parting. Instead of relying on mechanical peeling action, the system uses the belt's ability to deform and release paper through controlled pressure variations, avoiding direct contact wear.
3Ease of operation
If peeling pawls are used to part the paper, then paper parting is improved, but toner and paper dust contaminate the paper surface
Solution Approach 1:
The patent removes the peeling pawls that cause contamination and replaces the parting function with the belt mechanism. The belt, being in continuous contact with the paper through the nipping region, parts the paper cleanly without introducing additional contaminants, thus eliminating the harmful effect of toner and dust deposition on the paper surface.
4Loss of energy
If the thickness of the elastic layer on the thermally fixing roller is decreased to save energy and reduce warming-up time, then energy consumption is reduced, but the nipping width decreases and fixing property is spoiled
Solution Approach 1:
The patent merges the functions of the thermally fixing roller and the pressing belt into a cooperative system. The belt, with its own elastic layer, works in conjunction with the thermally fixing roller to provide the necessary nipping width and pressure. This combination allows the roller's elastic layer to be thinner while maintaining overall fixing performance, as the belt compensates for the reduced roller elasticity.
Solution Approach 2:
The patent changes the system configuration by introducing a belt-based pressing mechanism with adjustable pressure characteristics. This allows optimization of the roller's elastic layer thickness for energy efficiency while the belt's pressure distribution compensates to maintain adequate nipping width and fixing property.
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 maintains good fixing properties, prevents defective images, reduces paper curling, and minimizes surface contamination and wear on the thermally fixing roller, while ensuring effective paper parting and extended device lifespan.
Implementation Method 1
increasing the thickness of the elastic layer provided on the thermally fixing roller and/or on the pressing roller, such as increasing the thickness of the elastic layer of the pressing roller
Implementation Method 2
a thermally fixing roller that is heated by a source of heat
Data Source
AI summary
A fixing device comprises a thermally fixing roller, a belt, and pushing means which pushes the belt toward the thermally fixing roller. A nipping region is formed between the belt and the thermally fixing roller. A maximum pressure is produced in an upstream end region of the thermally fixing roller in the direction of rotation in the nipping region, another maximum pressure is produced in a downstream end region thereof in the direction of rotation in the nipping region, and a pressure is produced in an intermediate region, which pressure being not higher than the maximum pressure in the upstream end region and not higher than the another maximum pressure in the downstream end region.