Photosensitive Drum Surface Potential Control via Measurement Roller
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Solution Overview
Problem
Existing image forming apparatuses in electrophotographic systems face challenges in accurately controlling the surface potential of photosensitive drums, leading to potential differences that can result in image defects like fogging, due to reliance on voltage calculations based on the use state rather than the drum's potential and errors in potential measurement using transfer rollers.
Innovation Solution
An image forming apparatus that includes a measurement member to calculate the surface potential of the photosensitive drum based on discharge start voltage, allowing for correction of the surface potential and adjustment of charging voltage and exposure amount to achieve target values, thereby improving accuracy and reducing image defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the voltage applied to the charging roller is calculated on the basis of a use state of the photosensitive drum, then the control process is simplified, but the surface potential measurement precision deteriorates
Solution Approach 1:
The patent introduces a dedicated measurement roller as an intermediary component to measure the surface potential of the photosensitive drum. This measurement roller is equipped with a discharge detector that measures discharge current when brought into contact with the drum surface, providing direct and accurate potential measurements without relying on use state calculations.
Solution Approach 2:
The patent replaces the indirect mechanical estimation method (calculating potential based on use state) with a direct electrical measurement method. The discharge current measurement between the measurement roller and photosensitive drum surface provides direct electrical data about the surface potential, substituting the need for mechanical wear-based calculations.
2Productivity
If the surface potential is measured using the transfer roller, then the measurement can be performed, but errors occur due to individual differences between transfer rollers
Solution Approach 1:
The patent replaces the transfer roller as the measurement intermediary with a dedicated measurement roller. This new intermediary is specifically designed for potential measurement with a discharge detector, eliminating the measurement errors that occurred when using transfer rollers with individual manufacturing variations.
Solution Approach 2:
The patent creates a specialized measurement function by introducing a measurement roller that copies the essential contact measurement capability but with optimized measurement-specific characteristics. The discharge detector on the measurement roller provides accurate potential readings without the individual difference errors present in transfer rollers.
3Adaptability or versatility
If the voltage to the charging roller is adjusted based on use state, then the system adapts to deterioration, but the surface potential does not reach target values due to measurement errors
Solution Approach 1:
The patent implements a feedback control system where the discharge current measured by the measurement roller is used to calculate the actual surface potential. This measured potential is then fed back to adjust the charging roller voltage, creating a closed-loop control that ensures the surface potential reaches target values despite drum deterioration.
Solution Approach 2:
The patent replaces the open-loop use-state-based voltage adjustment with a closed-loop electrical measurement and control system. The discharge current measurement and subsequent voltage adjustment based on actual measured potential provides precise control that ensures target values are reached, substituting the inaccurate mechanical wear estimation.
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 enables high-accuracy measurement and control of the surface potential, reducing the occurrence of image defects such as fogging by directly addressing the potential differences and ensuring the surface potential reaches desired values.
Implementation Method 1
calculating as a measurement value the surface potential of the image bearing member on the basis of a discharge start voltage between the measurement member and the image bearing member
Data Source
AI summary
A control portion executes: a step of calculating a surface potential of an image bearing member charged by a charging member, to which a predetermined voltage is applied, and exposed to light by a predetermined exposure amount on the basis of a discharge start voltage between a measurement member and the image bearing member and calculating a correction value from a difference between a target value and calculated surface potential of the image bearing member; a step of correcting calculated surface potential of the image bearing member on the basis of the correction value; and a step of controlling at least one of the voltage applied to the charging member and an exposure amount of the exposure apparatus on the basis of the corrected surface potential of the image bearing member so that the surface potential of the image bearing member reaches the target value.