Developing Roller Magnetic Pole Arrangement for Developer Separation
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Solution Overview
Problem
Conventional developing rollers in image forming apparatuses face challenges in reliably separating developer from the roller due to magnetic attracting forces, leading to issues like developer re-adhesion and density irregularities in the formed images.
Innovation Solution
The developing roller features a specific magnetic pole arrangement with a S1-pole and S2-pole having different magnetic forces, creating a flat area with a minimal horizontal magnetic force component between them, ensuring reliable developer separation and allowing the S2-pole to function as both a draw-up and regulating magnetic pole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional magnetic pole arrangements are used in the developing roller, then developer can be carried on the sleeve, but developer separation becomes unreliable due to magnetic attracting forces causing re-adhesion
Solution Approach 1:
The stationary magnet is divided into multiple magnetic poles (first magnetic pole and second magnetic pole) with alternating polarities arranged in the circumferential direction. This segmentation creates distinct magnetic zones that control developer distribution and separation, preventing re-adhesion by ensuring like poles are positioned to generate repelling fields in the separation region.
Solution Approach 2:
Different regions of the stationary magnet are designed with different magnetic pole polarities to create localized magnetic field characteristics. The first magnetic pole and second magnetic pole have opposite polarities, creating a magnetic field distribution where the inter-pole region provides repelling forces for developer separation while other regions provide attracting forces for developer carry.
2Reliability
If magnetic poles are arranged to separate developer, then developer separation improves, but magnetic field uniformity deteriorates causing density irregularities
Solution Approach 1:
The magnetic pole arrangement uses asymmetric positioning of the first and second magnetic poles with different polarities. The inter-pole region is designed with specific angular spacing to create an asymmetric magnetic field pattern that provides both separation functionality and uniform toner distribution, avoiding density irregularities.
Solution Approach 2:
The magnetic field control extends into the angular dimension by strategically positioning magnetic poles at specific circumferential locations. The inter-pole region spans a defined angular range that incorporates both separation and uniformity requirements, adding dimensional control to the magnetic field distribution.
3Productivity
If strong magnetic forces are used to carry developer, then developer conveyance improves, but developer separation becomes difficult due to strong magnetic attraction
Solution Approach 1:
The stationary magnet creates a periodic magnetic field pattern as the sleeve rotates, with alternating regions of strong magnetic attraction (for developer carry) and repulsion (for developer separation). This periodic magnetic action ensures continuous developer conveyance followed by reliable separation at the inter-pole region.
Solution Approach 2:
The magnetic attraction force that initially causes developer re-adhesion is converted into a benefit by strategically positioning like poles to create repelling fields in the separation region. The same magnetic pole arrangement that provides strong carry forces also creates the inter-pole region with repelling forces for reliable separation.
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 enhances developer separation, preventing re-adhesion and density irregularities, leading to improved image quality by ensuring consistent toner distribution and effective developer conveyance.
Implementation Method 1
The stationary magnet includes a first magnetic pole lying downstream of the developing position in the rotational direction and having a specific polarity, and a second magnetic pole lying downstream of the first magnetic pole in the rotational direction and having the same polarity as the first magnetic pole, the second magnetic pole producing a magnetic field that allows the sleeve to receive developer supplied by the developer stirring member.
Implementation Method 2
The developing roller includes a stationary magnet having a plurality of magnetic poles arranged in a circumferential direction
Implementation Method 3
In an entire inter-pole region (IE) between a maximum vertical component position of a magnetic force of the first magnetic pole and a maximum vertical component position of a magnetic force of the second magnetic pole, the stationary magnet produces a magnetic force including a horizontal component that keeps the specific polarity and has a value greater than zero (mT).
Data Source
AI summary
A developing device includes a housing, a developing roller, a developer stirring member, and a layer thickness regulating member. The developing roller includes a stationary magnet and a sleeve. The stationary magnet includes a first magnetic pole having a specific polarity, and a second magnetic pole lying downstream of the first magnetic pole and having the same polarity as the first magnetic pole. In an entire inter-pole region between the first magnetic pole and the second magnetic pole, the stationary magnet produces a magnetic force including a horizontal component that keeps the specific polarity and has a value greater than zero (mT). The inter-pole region includes a flat area where a horizontal magnetic force component having a minimum absolute value exits and the horizontal magnetic force component changes within a range of 0.5 (mT) or less, the flat area extending over a range of 10 degrees or more.