Fixing Device Nip Width Control for Thermal Expansion
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Solution Overview
Problem
The existing fixing devices in electrophotographic apparatuses face issues with image defects due to fluctuations in nip pressure intersecting the recording medium transport direction, caused by changes in the pressure unit's profile during continuous transportation of recording media.
Innovation Solution
A fixing device with a heating unit, a pressure unit, and a moving unit that adjusts the nip state by controlling the movement of either the heating unit or the pressure unit to reduce the nip width between recording media, using a controller to manage the movement in a separation direction, thereby maintaining consistent nip pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressure unit maintains a fixed nip state during continuous transportation of recording media, then the structure is simple and operation is easy, but image defects occur due to fluctuations in nip pressure caused by thermal expansion of the pressure roller
Solution Approach 1:
The patent applies the dynamics principle by making the nip state of the pressure unit adjustable rather than fixed. The moving unit enables dynamic change of the nip width between the pressure unit and heating unit, allowing the system to adapt to thermal expansion of the pressure roller during continuous operation, thereby preventing image defects while maintaining operational simplicity
Solution Approach 2:
The patent implements parameter changes by varying the nip width parameter of the pressure unit based on operating conditions. The controller adjusts the nip state parameter dynamically - maintaining a larger nip width during continuous transportation to accommodate thermal expansion, and adjusting to appropriate nip width for single sheet processing, thus ensuring consistent image quality across different operating modes
2Manufacturing precision
If the nip width is reduced at recording medium intervals to prevent thermal expansion effects, then image quality is maintained, but the device requires complex control mechanisms
Solution Approach 1:
The patent applies periodic action by rhythmically adjusting the nip width in sync with the continuous transportation of recording media. The controller periodically reduces the nip width at recording medium intervals and maintains it during transportation, creating a cyclic control pattern that prevents thermal expansion-induced image defects without requiring complex real-time monitoring systems
Solution Approach 2:
The patent implements feedback control by using a controller that monitors the operating state and automatically adjusts the nip width accordingly. The controller receives information about continuous transportation mode and thermal expansion conditions, then provides feedback control signals to the moving unit to maintain optimal nip width, ensuring fixing uniformity through automated closed-loop control
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 prevents image defects by maintaining consistent nip pressure and reducing thermal expansion of the pressure roller, ensuring uniform fixing and preventing sheet wrinkles or uneven fixing during continuous printing.
Implementation Method 1
a heating unit configured to heat a toner on a recording medium
Implementation Method 2
a pressure unit configured to transport the recording medium while sandwiching the recording medium in a nip that the pressure unit and the heating unit form
Implementation Method 3
prevention of an image defect caused by a fluctuation in a nip pressure in a direction intersecting a recording medium transport direction due to a change in a profile of a pressure unit, as compared with a case where a nip state is not changed when recording media are continuously transported
Data Source
AI summary
A fixing device includes a heating unit, a pressure unit, a moving unit, and a controller. The heating unit is configured to heat a toner on a recording medium. The pressure unit is configured to transport the recording medium while sandwiching the recording medium in a nip that the pressure unit and the heating unit form. The moving unit is configured to change a nip state of the pressure unit with respect to the heating unit by moving the heating unit or the pressure unit. The controller is configured to, when plural recording media are transported continuously, control the moving unit so that the moving unit moves the heating unit or the pressure unit in a separation direction so as to reduce a nip width at a recording medium interval between the recording media.