Thyristor Switching Timing for Fixation Quality in Image Heating
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Solution Overview
Problem
Conventional image heating apparatuses face issues with incomplete toner image fixation due to temporary reductions in heat generation when switching between heating elements, leading to insufficient heating and potential fixation failures.
Innovation Solution
An image heating apparatus with a thyristor and relay system that controls the switching of electrical power between first and second heat generating elements, ensuring a controlled temperature transition to prevent temperature drops during the switching process, thereby maintaining consistent heat delivery to the toner image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching between heat generating elements is performed during continuous sheet conveyance, then the throughput is maintained, but the toner image fixation quality deteriorates due to temporary temperature drops
Solution Approach 1:
The controller determines the switching timing in advance based on predicted sheet conveyance timing, and performs the switching operation during periods when no sheet is present in the nip. This preliminary planning ensures that temperature drops occur only when they will not affect fixation quality, while maintaining continuous operation for throughput.
Solution Approach 2:
The system uses sheet detection means to monitor the actual presence of sheets in the nip and compares it with predicted timing. Based on this feedback, the controller adjusts the switching timing dynamically to ensure switching occurs during idle periods, thereby maintaining both throughput and fixation quality.
2Device complexity
If the switching timing is not synchronized with sheet conveyance, then the device complexity is reduced, but the heating uniformity deteriorates causing insufficient toner image fixation
Solution Approach 1:
The controller calculates and determines the optimal switching timing in advance based on sheet conveyance speed and nip position, before actual switching occurs. This preliminary determination ensures precise synchronization with sheet conveyance cycles, maintaining heating uniformity without requiring complex real-time control systems.
Solution Approach 2:
The system utilizes the natural periodicity of sheet conveyance through the nip to automatically determine switching intervals. The sheet detection means and controller work together to create a self-regulating system that synchronizes switching with conveyance cycles, achieving precise heating control without external intervention or complex algorithms.
3Adaptability or versatility
If multiple heat generating elements are used with switching capability, then the adaptability to different sheet widths is improved, but the device complexity increases due to additional switching components
Solution Approach 1:
Multiple heat generating elements are designed with different heating ranges to cover various sheet widths. The switching mechanism allows a single fixing apparatus to handle different sheet sizes by selecting the appropriate heating element, providing universal functionality without requiring separate devices for each sheet size.
Solution Approach 2:
The controller determines in advance which heat generating element should be activated based on the detected sheet width and conveyance timing. This preliminary selection allows the system to switch between elements optimally, providing adaptability to different sheet sizes while maintaining simple control logic that reduces overall device complexity.
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
The solution effectively prevents the toner image from being unsatisfactorily heated during the switching process, ensuring reliable fixation by synchronizing the power switching with the sheet's movement through the nip, thus enhancing the image forming process's efficiency and reducing the risk of fixation failures.
Implementation Method 1
a first heat generating element configured to heat the nip, a second heat generating element configured to heat the nip
Implementation Method 2
a thyristor configured to control electrical power supplied to the first heat generating element and the second heat generating element
Implementation Method 3
a relay configured to switch a supply destination of the electrical power supply between the first heat generating element and the second heat generating element
Implementation Method 4
a film, a heater that is in contact with the inward surface of the film, and a pressure roller that forms a fixation nip between itself and film, with the film being sandwiched between the pressure roller and the heater
Data Source
AI summary
An image heating apparatus includes a first and second heat generating elements, a thyristor that controls electrical power supplied to the heat generating elements, and a relay that switches a supply destination of the electrical power supply between the heat generating elements. A controller switches the thyristor from on to off, and then actuates the relay to switch the supply destination from the first heat generating element to the second heat generating element, and, thereafter switches the thyristor from off to on. The controller sets a timing of switching of the thyristor from on to off to be in a period in which an image on a current recording material is in a nip, and sets timing of switching of the thyristor from off to on to be in a period in which an image on a current recording material or a subsequent recording material is not in the nip.