Fixing Device Non-Contact Heating Offset Prevention
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Solution Overview
Problem
In wet electrophotographic image forming devices, excessive carrier liquid in the toner layer leads to offset issues where toner is transferred to the fixing roller instead of the sheet, and existing non-contact heating solutions do not adequately reduce this offset due to insufficient penetration of the carrier liquid into the sheet before the toner image reaches the fixing roller.
Innovation Solution
A fixing device with a non-contact heating portion and a pressurizing and heating unit is configured such that the toner image is heated to a melting temperature, and the carrier liquid penetrates into the sheet before the image enters the pressurizing and heating unit, ensuring a toner-to-carrier liquid weight ratio of 70% or more, which effectively reduces offset by enhancing internal cohesion and facilitating carrier liquid volatilization and penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a non-contact heating portion is provided to melt toner and push out carrier liquid, then the amount of carrier liquid in the toner layer is reduced, but the penetration of carrier liquid into the sheet is insufficient before the toner image reaches the fixing roller
Solution Approach 1:
The patent applies preliminary action by providing a non-contact heating portion upstream of the fixing roller that melts the toner and pushes carrier liquid into the sheet before the toner image reaches the fixing roller. This preliminary penetration action ensures that when the toner later contacts the fixing roller, sufficient carrier liquid has already penetrated the sheet, preventing offset. The heating portion performs the carrier liquid penetration action in advance, before the critical fixing stage.
2Productivity
If the toner image enters the pressurizing and heating unit quickly, then productivity is improved, but the carrier liquid penetration becomes insufficient and offset occurs
Solution Approach 1:
The patent performs carrier liquid penetration as a preliminary action in the non-contact heating portion before the toner image reaches the pressurizing and heating unit. This allows the system to maintain high printing speeds while ensuring offset prevention, because the carrier liquid penetration is completed in advance during the heating stage, so no additional time is needed during the high-speed fixing stage.
3Productivity
If the amount of carrier liquid in the toner layer is excessively large, then the wet developer can be used for high-speed printing, but the adhesive force between toner and fixing roller becomes greater than internal cohesion causing offset
Solution Approach 1:
The patent uses preliminary carrier liquid penetration into the sheet during the non-contact heating stage to reduce the amount of carrier liquid remaining in the toner layer before fixing. This allows the system to maintain high printing speeds with wet developer while preventing offset, because the excessive carrier liquid is removed in advance through penetration, restoring the balance between adhesive force and internal cohesion.
Solution Approach 2:
The patent changes the physical state and distribution of carrier liquid by heating the toner image to melt the toner and facilitate carrier liquid penetration into the sheet. This parameter change (from liquid carrier dispersed in toner to penetrated carrier in sheet) reduces the harmful effects of excessive carrier liquid while maintaining the benefits of wet developer for high-speed printing.
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 configuration significantly reduces offset by ensuring sufficient penetration of the carrier liquid into the sheet, improving the fixing quality and maintaining the toner image on the sheet, particularly on coated paper, by maintaining a toner ratio of 70% or more before the image enters the pressurizing and heating unit.
Implementation Method 1
a non-contact heating portion that includes at least one non-contact heating unit which heats the toner image on the sheet in a non-contact manner
Implementation Method 2
a pressurizing and heating unit that is provided on a downstream side in a sheet transport direction with respect to the non-contact heating portion and that pressurizes and heats the toner image on the sheet
Data Source
AI summary
A fixing device includes: a non-contact heating portion that includes at least one non-contact heating unit which heats a toner image on a sheet; and a pressurizing and heating unit that is provided downstream in a sheet transport direction with respect to the non-contact heating portion and that pressurizes and heats the toner image. A time from a first point of time when the toner image reaches a toner melting temperature by heating of the non-contact heating portion to a second point of time when the toner image enters the pressurizing and heating unit is set equal to or more than a predetermined time. The predetermined time is a time when a ratio between the weight of the toner in the toner image before the entrance and the sum of the weight of the toner and the weight of the carrier liquid is equal to or more than 70%.