Fixing Device Variable Rotational Drive Sheet Separation
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Solution Overview
Problem
Existing fixing devices for electrophotography image forming apparatuses face challenges in improving sheet separability and gloss memory, particularly with thin paper, due to complex driving control systems and unsatisfactory separability results.
Innovation Solution
A fixing device with first and second rotating bodies that periodically change the velocity of the rotational drive of the first rotating body at a frequency shorter than the sheet's passage through the nip portion, using a control unit that adjusts the phase and frequency of the rotational speed changes based on the sheet's friction coefficient, basis weight, process speed, and fixing temperature, to optimize shearing forces for effective separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper pressure roller is rotationally driven to maintain a velocity difference between the upper pressure roller and the lower pressure roller, then sheet separability is improved, but the driving control system becomes complex and manufacturing cost increases
Solution Approach 1:
The patent applies periodic action by making the upper pressure roller rotate intermittently with a period shorter than the sheet passage time through the nip portion. This periodic rotation creates velocity differences that generate shearing forces for sheet separation, while avoiding continuous rotation that would complicate the control system. The intermittent rotation is controlled to occur only during specific intervals when sheets are passing through, simplifying the overall control requirements.
Solution Approach 2:
The patent applies dynamics by changing the rotational state of the upper pressure roller from static or continuously rotating to intermittently rotating. This dynamic adjustment allows the system to create necessary velocity differences for sheet separation only when needed, rather than maintaining continuous motion. The dynamic control adapts the roller's rotational behavior to the actual sheet processing requirements, reducing unnecessary control complexity.
2Reliability
If the upper pressure roller is rotationally driven to maintain a velocity difference, then sheet separability is improved, but manufacturing cost increases
Solution Approach 1:
The periodic intermittent rotation reduces manufacturing cost by eliminating the need for complex continuous control systems. The control mechanism only needs to activate the upper pressure roller during specific periodic intervals rather than maintaining continuous rotation, simplifying the control hardware and software requirements. This reduces manufacturing complexity and associated costs while maintaining effective sheet separation functionality.
3Reliability
If the velocity of the upper pressure roller is increased to improve sheet separation, then separability improves, but the risk of sheet sliding or damage increases
Solution Approach 1:
The periodic intermittent rotation applies velocity differences in short bursts rather than continuously, creating shearing forces for separation while limiting the total duration of high-velocity contact. This reduces the cumulative harmful effects on sheets while maintaining separation effectiveness during the active rotation intervals.
Solution Approach 2:
The patent applies partial action by using intermittent rotation rather than continuous rotation. The velocity difference is applied only during the periodic intervals when rotation occurs, which is sufficient to generate the necessary shearing forces for separation. This partial application of velocity difference reduces the overall stress and sliding risk on sheets compared to continuous high-velocity contact.
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 approach enhances sheet separability and gloss memory without complicating the driving control system, ensuring efficient separation and image quality by applying controlled shearing forces during the sheet's passage through the nip portion.
Implementation Method 1
a sheet is separated from a fixing belt by shearing force which occurs between a toner image on the sheet and a surface layer of the fixing belt
Implementation Method 2
each of the first and the second rotating bodies includes a core metal, and a viscoelastic layer which is formed on an outer circumference of the core metal
Implementation Method 3
a viscoelastic layer which is formed on an outer circumference of the core metal
Data Source
AI summary
A fixing device is equipped with a lower pressure roller, an upper pressure roller and a fixing belt which fix a toner image onto a sheet, by holding and conveying the sheet by a nip portion, and a control unit which controls rotation of the lower pressure roller. The control unit periodically changes a velocity of rotational drive of the lower pressure roller, at a frequency of which a period is shorter than a time needed for the sheet to pass through the nip portion, when the sheet passes through the nip portion.