Developing Sleeve Speed Control for Fog Reduction in Image Forming Apparatus
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Solution Overview
Problem
In image forming apparatuses using the electrophotographic printing method, reducing the peripheral speed of the photosensitive drum for modes like OHT and thick paper results in increased fog due to the proportional reduction in developing sleeve speed maintaining the same peripheral speed ratio, leading to inadequate toner charging and distribution.
Innovation Solution
The image forming apparatus independently controls the rotational speeds of the photosensitive drum and developing sleeve, allowing the developing sleeve speed to be within ±30% of its speed at normal mode when the photosensitive drum speed is reduced, thereby adjusting the peripheral speed ratio to suppress fog.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the peripheral speed of the photosensitive drum is reduced for OHT and thick paper modes, then the fixing time is extended and image quality is improved, but the peripheral speed of the developing sleeve is also reduced proportionally, resulting in increased fog and inadequate toner charging
Solution Approach 1:
The patent applies dynamics by making the peripheral speed ratio between the developing sleeve and photosensitive drum variable rather than fixed. The control unit dynamically adjusts the developing sleeve speed based on the photosensitive drum speed, allowing the speed ratio to change according to operating mode. This enables optimization of toner charging conditions at reduced drum speeds while preventing fog formation.
Solution Approach 2:
The patent changes the parameter of peripheral speed ratio between the developing sleeve and photosensitive drum. By controlling the developing sleeve speed to be within a specific range (±30%) of its normal mode speed even when the drum speed is reduced, the system maintains optimal toner charging parameters and prevents fog, thereby resolving the contradiction between reduced drum speed and fog control.
2Device complexity
If the peripheral speed ratio between developing sleeve and photosensitive drum is maintained constant, then the control system is simple, but toner charging becomes inadequate at reduced drum speeds, causing increased fog
Solution Approach 1:
The system transitions from a static constant speed ratio to a dynamic variable speed ratio. The control unit adjusts the developing sleeve speed based on the actual operating mode, making the speed ratio adaptive rather than fixed. This maintains relatively simple control while optimizing toner charging performance at different drum speeds.
Solution Approach 2:
The patent changes the speed ratio parameter from constant to variable. By defining that the developing sleeve speed should be within ±30% of its normal mode speed regardless of drum speed reduction, the system maintains optimal toner charging parameters through parameter adjustment, resolving the contradiction between control simplicity and charging adequacy.
3Device complexity
If the developing sleeve speed is reduced proportionally with the photosensitive drum speed, then the mechanical drive system remains simple, but the peripheral speed ratio becomes suboptimal, resulting in poor toner distribution and increased fog
Solution Approach 1:
The patent applies dynamics by making the developing sleeve speed independent of proportional reduction with drum speed. Instead of following the drum speed reduction proportionally, the developing sleeve speed is controlled to remain within ±30% of its normal mode value. This dynamic control maintains optimal speed ratio for toner distribution while keeping the drive system relatively simple.
Solution Approach 2:
The system changes the speed parameter relationship from proportional to fixed-range control. By controlling the developing sleeve speed to stay within a specific range (±30% of normal speed) regardless of drum speed, the system maintains optimal toner distribution parameters without complicating the drive system architecture.
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 adjustment ensures stable image quality by maintaining low fog levels and preventing developer deterioration, even at reduced photosensitive drum speeds, by optimizing toner charging and distribution.
Implementation Method 1
The developing sleeve is opposed to the photosensitive drum with a minute gap therebetween to thereby form a developing nip portion. The magnetic brush borne on the surface of the developing sleeve is brought into contact with or proximity to the photosensitive drum and further, an alternating electric field is continuously applied to the developing nip portion to thereby shift the toner on the surface of the developing sleeve onto the photosensitive drum.
Data Source
AI summary
An image forming apparatus includes a rotatable image bearing member bearing an electrostatic image; a rotatable developer carrying member carrying a developer to develop the electrostatic image; speed controlling means for switching a rotating speed of the image bearing member between a first speed and a second speed lower than the first speed, and performing an image forming operation at each speed; and developer carrying member speed controlling means for controlling a rotating speed of the developer carrying member so that a rotating speed of the developer carrying member when the image forming operation is performed by rotating the image bearing member at the second speed, which is less than 70% of the first speed so as to be within a range of ±30% of a rotating speed of the developer carrying member when the image forming operation is performed by rotating the image bearing member at the first speed.