Developing Device Magnet Configuration for Carrier Control
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Solution Overview
Problem
In high-speed image forming apparatuses, the carrier in the developer tends to fly from the supplying roller and deposit on the developing roller, leading to carrier deposition issues that affect image quality.
Innovation Solution
A developing device with a specific magnet configuration on the supplying and developing rollers, where the magnetic flux density is optimized to reduce carrier deposition, including a first magnet in the developing roller and multiple poles in the supplying roller with varying magnetic flux densities and angles to enhance magnetic attraction and control developer distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rotational speed of the supplying roller is increased to improve productivity, then image forming speed is improved, but carrier flies from the supplying roller and deposits on the developing roller
Solution Approach 1:
The magnet inside the supplying roller is divided into multiple poles (first pole, second pole, third pole) with different polarities arranged along the rotational direction. This segmentation creates multiple magnetic attraction zones that work together to control carrier movement, preventing carrier flight at high rotational speeds while maintaining productive operation.
Solution Approach 2:
Different regions of the supplying roller are equipped with magnets having different local properties (different polarities and magnetic flux densities). The first pole has stronger magnetic flux density than the second pole, creating localized magnetic fields that selectively attract and hold carriers at specific positions, preventing their deposition on the developing roller while allowing toner transfer.
2Object-generated harmful factors
If magnetic flux density is increased to suppress carrier deposition, then carrier control is improved, but toner transfer efficiency may be affected
Solution Approach 1:
The magnet is designed with non-uniform magnetic flux density distribution along the rotational direction, with the first pole having stronger flux density than the second pole. This local quality variation creates differentiated magnetic forces: the stronger first pole effectively suppresses carrier deposition, while the weaker second pole allows smooth toner transfer, thus resolving the contradiction between carrier control and toner transfer efficiency.
Solution Approach 2:
The magnet is segmented into multiple poles with different flux densities, allowing independent optimization of each pole's function. The first pole is optimized for carrier suppression with higher flux density, while the second pole is optimized for toner transfer with lower flux density, enabling both carrier control and productivity to be maintained simultaneously.
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 optimized magnet configuration effectively suppresses carrier deposition onto the developing roller, improving image quality by maintaining developer distribution and preventing dot image defects.
Implementation Method 1
a magnet disposed inside the supplying roller includes a main pole in a position opposing the developing roller
Implementation Method 2
a magnet provided inside the developing roller includes a receiving pole different in polarity from the main pole in a position opposing the supplying roller
Data Source
AI summary
A developing device includes a developing container, a developing roller, a supplying roller, a first magnet including a first magnetic pole, a second magnet including second to fifth magnetic poles, and a regulating member. A maximum magnetic flux density of the second magnetic pole is larger in absolute value than a maximum magnetic flux density of the third magnetic pole in a normal direction to the supplying roller, and a maximum magnetic flux density of the third magnetic pole is larger in absolute value than a maximum magnetic flux density of the fourth magnetic pole in the normal direction. With respect to a rotational direction of the supplying roller, an angle between maximum magnetic flux density positions of the second and third magnetic poles is smaller than an angle between maximum magnetic flux density positions of the third and fourth magnetic poles.