Adjusting Developing Roller Speed Ratio for Long Sheet Image Density
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Solution Overview
Problem
Image density variation in long sheets due to insufficient toner supply on the developing roller, leading to lowered image quality and shortened life cycle of image and developer bearing members.
Innovation Solution
An image forming apparatus that adjusts the circumferential speed ratio of the developing roller to the photosensitive drum and controls the developing bias based on the length of the recording material, increasing the speed ratio and residual toner amount for long sheets to maintain image density and extend the life cycle of the bearing members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the circumferential speed ratio of the developing roller to the photosensitive drum is increased to improve toner supply and stabilize image density on long sheets, then image density uniformity is improved, but the abrasion of the photosensitive drum or developing roller is increased, shortening their life cycle
Solution Approach 1:
The patent applies dynamics by making the circumferential speed ratio of the developing roller adjustable rather than fixed. The system dynamically changes the speed ratio based on the detected length of the recording material: using a first speed ratio for short sheets and a second, higher speed ratio for long sheets. This dynamic adjustment allows the system to optimize toner supply for long sheets (improving image density uniformity) while using lower speed ratios for short sheets (reducing unnecessary abrasion and extending component life cycle).
Solution Approach 2:
The patent implements parameter changes by modifying the circumferential speed ratio parameter according to the recording material length. The controller detects the material length and accordingly changes the speed ratio parameter between two predetermined values. This parameter change enables the system to adapt toner supply characteristics to match the specific requirements of different sheet lengths, resolving the contradiction between image quality and component durability.
2Manufacturing precision
If the developing efficiency by electric field is lowered to decrease toner consumption on the developing roller surface, then residual toner amount is increased and image density stability is improved, but the productivity or image formation speed is reduced
Solution Approach 1:
The patent applies dynamics by making the developing efficiency adjustable based on recording material length. The system dynamically switches between a first developing efficiency (higher productivity) for short sheets and a second developing efficiency (lower toner consumption, better density stability) for long sheets. This dynamic control allows optimization of both productivity and image quality according to the specific printing task.
Solution Approach 2:
The patent implements parameter changes by modifying the developing efficiency parameter according to the detected recording material length. The controller changes this parameter between two predetermined settings: one optimized for speed and another optimized for toner efficiency and density stability. This parameter adaptation resolves the contradiction between productivity and image density stability.
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
Stabilizes image density across the entire length of the long sheet and extends the life cycle of the image and developer bearing members by optimizing toner supply and reducing wear on the rollers.
Implementation Method 1
a bias applying portion configured to apply a developing bias to the developer bearing member
Data Source
AI summary
An image forming apparatus includes a controller to execute a first mode for forming a toner image on a recording medium, in which a maximum toner carrying amount per unit area is a first maximum toner carrying amount, and a second mode for forming a toner image on the recording medium, in which the maximum toner carrying amount per unit is a second maximum toner carrying amount larger than the first maximum toner carrying amount. In the first mode, the controller sets a circumferential speed ratio of the toner bearing member against an image bearing member at a first circumferential speed ratio, and in the second mode the controller sets the circumferential speed ratio at a second circumferential speed ratio higher than the first circumferential speed ratio. The controller executes the second mode upon an order of the second mode by an operator.