Developing Roller Speed Control for Image Quality
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Solution Overview
Problem
In image forming apparatuses, developer accumulation on the upstream side of the developing gap between the developing roller and the photoconductor drum can lead to adhesion issues, resulting in substandard images with streaks and uneven image density, especially when the photoconductor drum is driven in conjunction with the developing roller during developer supply.
Innovation Solution
The solution involves controlling the driving of the developing roller and photoconductor drum such that the developing roller rotates at a lower speed than the photoconductor drum during the initial developer supply phase, preventing developer accumulation and adhesion by ensuring the developer enters the developing gap gradually, thereby inhibiting firm adhesion to the rollers or drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the photoconductor drum is driven in addition to the developing roller during developer supply, then the developer is distributed uniformly in the developing device in a relatively short time, but developer accumulates on the upstream side of the developing gap and surges into the developing gap causing firm adhesion to the developing roller or photoconductor drum
Solution Approach 1:
The patent applies preliminary action by driving the developing roller at a lower speed before the photoconductor drum is driven, allowing developer to be gradually supplied and distributed without accumulation. This preliminary controlled rotation prevents the harmful surge of developer into the developing gap that would occur if both components were driven at normal speed simultaneously, thereby avoiding firm adhesion while still achieving uniform distribution.
2Manufacturing precision
If the developing roller is driven at normal speed while the photoconductor drum is stationary during developer supply, then developer accumulation on the upstream side is reduced, but the developer supply process takes longer time
Solution Approach 1:
The patent applies dynamics by making the rotation speed of the developing roller variable rather than fixed. The controlling unit adjusts the developing roller's rotation speed based on the operational phase: lower speed during initial developer supply to prevent accumulation, and normal speed during uniform distribution. This dynamic speed adjustment resolves the contradiction between preventing adhesion and maintaining efficient supply time.
3Productivity
If the developing roller rotates at higher speed, then the developer is supplied faster into the developing device, but the developer accumulates on the upstream side of the developing gap and causes adhesion
Solution Approach 1:
The patent applies parameter changes by modifying the rotation speed parameter of the developing roller based on the supply phase. During initial developer supply, the rotation speed is set to a lower value to prevent accumulation and adhesion. Once uniform distribution is achieved, the speed is increased to normal operating levels. This parameter adjustment resolves the contradiction between supply speed and adhesion prevention.
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
An image forming apparatus (1) includes an image bearer (12), a first driver (61) to rotate the image bearer (12), a developing device (13) including a developing roller (13a), a second driver (62) to rotate the developing roller (13a), and a controller (60) to control the first driver (61) and the second driver (62) and set a linear speed ratio (X) of the developing roller (13a) relative to the image bearer (12). The controller (60) executes first driving in which the developing roller (13a) rotates with rotation of the image bearer (12) stopped in an idle time and executes second driving for a predetermined period (D2) subsequent to the first driving. The linear speed ratio (X) is set to a first ratio (X1) smaller than 1 in the second driving and to a second ratio (X2) equal to or greater than 1 in image formation.