Developing Device Conductive Roller Biasing for Toner Scattering
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Solution Overview
Problem
Existing developing devices using a two-component developer face issues with toner scattering due to increased pressure, which can lead to contamination and image defects.
Innovation Solution
The image forming apparatus incorporates a developing device with a shielding roller positioned between the developing and supplying rollers, rotated in the same direction as the developing roller, and applies a bias voltage to the shielding roller with the same polarity as the toner to suppress scattering by generating an electric field and drawing air to discharge toner externally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a first toner shielding member and a second toner shielding member are provided between the wall portion and the developing roller, then toner scattering to the outside of the developing device is suppressed, but the pressure inside the developing device increases causing floating toner to scatter through gaps
Solution Approach 1:
A conductive roller is introduced as an intermediary component between the supplying roller and the developing roller. This conductive roller serves as a mediator that can be biased to create an electric field, which actively suppresses toner scattering without requiring additional shielding members that would increase internal pressure. The conductive roller acts as a controllable barrier using electrical fields rather than purely mechanical shielding.
Solution Approach 2:
The invention changes the state of the conductive roller by applying a bias voltage during image formation. The bias polarity is dynamically set to be the same as the normal charge polarity of the toner, creating an electric field that repels floating toner particles. This parameter change (applying bias) allows the system to suppress toner scattering actively without increasing mechanical pressure inside the developing device.
2Object-affected harmful factors
If multiple toner shielding members are added to suppress toner scattering, then device complexity increases
Solution Approach 1:
The conductive roller performs multiple functions: it serves as a structural component of the developing device, acts as an electrode for generating the electric field, and functions as a toner suppression barrier. By making the conductive roller multi-functional, the invention eliminates the need for separate first and second toner shielding members, thereby reducing device complexity while still suppressing toner scattering effectively.
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 configuration effectively reduces toner scattering, maintains internal pressure, and prevents image defects by ensuring toner is retained within the device, enhancing the quality of the printed images.
Implementation Method 1
a first magnet provided non-rotationally and fixedly inside the developing roller and including a first magnetic pole, and a second magnet provided non-rotationally and fixedly inside the supplying roller and including a second magnetic pole
Implementation Method 2
a bias applying portion configured to apply a bias to each of the supplying roller, the developing roller, and the conductive roller, wherein during image formation, the bias is applied to each of the supplying roller, the developing roller, and the conductive roller
Data Source
AI summary
An image forming apparatus includes a developing device including a developing roller, a supply roller, and a conductive roller. During image formation, a bias is applied to each of the supplying roller, the developing roller, and the conductive roller in a state in which each of the supplying roller, the developing roller, and the conductive roller is rotationally driven. During the image formation, a polarity of a first potential obtained by subtracting a DC potential of the developing roller from a DC potential of the supplying roller is the same as a normal charge polarity of the toner, and a polarity of a second potential obtained by subtracting the DC potential of the developing roller from a DC potential of the conductive roller is the same as the normal charge polarity of the toner.