Fixing Device Corona Charging Bias Adjustment
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Solution Overview
Problem
The offset phenomenon occurs in image forming apparatuses where toner adheres to the fixing member and transfers back to the medium, due to the insulating fixing member being charged with an opposite polarity to the toner, leading to inefficiencies in the fixing process.
Innovation Solution
A fixing device with a charger using corona discharge to charge the fixing member to the same polarity as the toner, and an adjusting part that increases the bias on the discharging electrode based on the cumulative number of printed media and printing rate, ensuring uniform charging and reducing offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fixing member is made of an electrically insulating material to prevent toner adhesion, then the fixing member can be charged by friction with the medium, but this causes the offset phenomenon where toner adheres to the fixing member and transfers back to the medium
Solution Approach 1:
The charger applies a preliminary charging action to the fixing member surface before the toner transfer process, creating an electrostatic field that prevents toner from adhering to the fixing member. By pre-charging the fixing member with the same polarity as the toner, the system counteracts the harmful friction charging that would otherwise cause offset.
Solution Approach 2:
The system changes the electrical parameter (surface charge polarity) of the fixing member from negative (friction-induced) to positive (charger-induced) to prevent toner adhesion. The charger modifies the surface charge density and polarity of the fixing member, transforming the electrostatic conditions to eliminate offset.
2Object-generated harmful factors
If a charger is used to charge the fixing member to prevent offset, then toner offset is reduced, but the charging uniformity deteriorates due to accumulated discharge products on the discharging electrode
Solution Approach 1:
The system dynamically adjusts the bias voltage applied to the discharging electrode based on the cumulative printing amount. As discharge products accumulate and affect charging uniformity, the bias is increased to maintain effective corona discharge. This dynamic adjustment compensates for the deteriorating charging uniformity over time.
Solution Approach 2:
The system implements feedback control by monitoring the cumulative printing amount and adjusting the bias voltage accordingly. The controller increases the bias in response to accumulated discharge products, creating a closed-loop system that maintains charging effectiveness despite electrode contamination.
3Object-generated harmful factors
If the bias on the discharging electrode is increased to maintain charging effectiveness, then offset prevention is improved, but the service life of the charger decreases due to accelerated discharge product accumulation
Solution Approach 1:
The bias voltage is dynamically adjusted based on actual printing conditions and cumulative usage rather than being fixed at a high value. This allows the system to use higher bias only when necessary (when discharge products accumulate), extending charger life while maintaining offset prevention effectiveness.
Solution Approach 2:
The system changes the bias parameter adaptively based on cumulative printing amount and printing rate. By correlating bias adjustment with actual usage patterns, the system optimizes the balance between offset prevention and charger durability, applying higher bias only when offset risk increases.
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 reduces toner offset by maintaining uniform charging of the fixing member, improving the fixing process efficiency and extending the service life of the charger.
Implementation Method 1
The charger uses a corona discharge that occurs in an electric field generated around a discharging electrode facing the fixing member so as to charge the fixing member to a same polarity of toner in the toner images
Data Source
AI summary
A fixing device includes a fixing member, a pressing member, a charger, and adjusting part. The fixing member heats toner images on media. The pressing member forms nips with the fixing member and presses the media. The charger uses a corona discharge that occurs in an electric field generated around a discharging electrode so as to charge the fixing member to a same polarity of toner in the toner images. The adjusting part increases a bias applied to the discharging electrode in accordance with increase of a cumulative number calculated by accumulating a number of the media on which the toner images are fixed or increase of a cumulative printing amount calculated by multiplying a printing rate that indicates a ratio of an area of the toner images to an area of the media by the cumulative number.