Dynamic Toner Scraping Control for Image Quality
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Solution Overview
Problem
In image forming apparatuses using the electrophotographic method, fluctuations in sheet interval during sheet feeding can cause overlapping of developing and scraping sections, leading to inadequate toner supply and image defects.
Innovation Solution
An image forming apparatus with a control system that dynamically adjusts the potential difference between the developing and supplying members based on detected sheet presence, allowing for timely switching between scraping and developing operations to maintain optimal toner transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scraping is performed at always the same non-developing section regardless of sheet feeding timing, then toner can be moved to the supplying roller side, but if the sheet interval narrows, the developing section and scraping section may overlap, resulting in inadequate toner supply and image defects
Solution Approach 1:
The patent applies dynamics by making the scraping section position variable rather than fixed. The control unit dynamically adjusts the scraping section position on the developing roller based on the detected sheet interval, allowing the system to adapt to fluctuations in sheet feeding timing and prevent overlap between developing and scraping sections.
Solution Approach 2:
The patent implements feedback by using a detection unit to measure the sheet interval and feeding timing, then using this information to control the position of the scraping section. This closed-loop feedback mechanism ensures that the scraping operation is properly coordinated with the variable sheet feeding rhythm.
2Productivity
If the sheet interval narrows, then sheet feeding speed increases, but the developing section and scraping section overlap, causing insufficient toner supply
Solution Approach 1:
The system dynamically repositions the scraping section based on the actual sheet interval. When sheet feeding speed increases and the interval narrows, the control unit adjusts the scraping section position to occur at a different rotational position of the developing roller, ensuring that scraping completes before the developing section arrives, thus maintaining image quality despite higher productivity.
3Device complexity
If scraping is performed in a fixed position, then the structure is simple, but it cannot adapt to variations in sheet feeding timing
Solution Approach 1:
The patent changes the parameter of scraping section position from a fixed value to a variable that depends on the detected sheet interval. The control unit calculates the appropriate scraping position based on feeding timing information, allowing the system to adapt to different operating conditions without requiring multiple physical scraping mechanisms.
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 approach ensures proper toner scraping and transfer even with fluctuating sheet intervals, preventing image defects and maintaining image quality.
Implementation Method 1
a detecting portion configured to detect information on presence or absence of the recording material in a conveyance passage
Implementation Method 2
a first potential difference is formed between the supplying member and the developing member, the first potential difference being a potential difference in a direction in which an electrostatic force in a direction toward the developing member from the supplying member is acted on the toner charged to the normal polarity
Data Source
AI summary
An image forming apparatus includes a controller. The controller controls to perform a first operation in which a first potential difference is formed between a supplying member and a developing member, the first potential difference being a potential difference in a direction in which an electrostatic force in a first direction toward the developing member from the supplying member is acted on toner charged to a normal polarity, and a second operation in which a second potential difference is formed between them and in a second direction opposite to the first direction. When an image forming operation is performed, the controller controls timing for changing from the first operation to the second operation based on information on presence or absence of a recording material in a conveyance passage toward a transferring portion in a non-image forming operation before the recording material is nipped and conveyed at the transferring portion.