Surface Potential Estimation via Development Current in Image Forming Apparatus
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Solution Overview
Problem
Conventional surface potential sensors in electrographic image forming apparatuses are costly and inaccurate when toner scatters on the photosensitive drum, necessitating a method to estimate the surface potential without using such sensors.
Innovation Solution
An image forming apparatus that includes an image bearing member, a charger, a development device, a development power supply, an electric current measuring section, a calculating section, and an estimating section, which measures and calculates the surface potential based on development current and estimates the fogging toner amount to determine the optimal bias voltage for image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a surface potential sensor is used to detect the surface potential of the photosensitive drum, then the surface potential can be measured, but the cost increases and measurement accuracy deteriorates when scattered toner attaches to the drum
Solution Approach 1:
The patent introduces a development roller as an intermediary between the photosensitive drum and the measurement system. By measuring the development current flowing through the development roller instead of directly measuring the drum surface potential, the system avoids the problem of toner scattering affecting sensor accuracy. The development roller acts as a mediator that transfers the electrical characteristics of the drum surface to a measurable current signal.
Solution Approach 2:
The patent replaces the mechanical contact-based surface potential sensor with an electrical measurement system. Instead of physically contacting the drum surface with a sensor that can be contaminated by toner, the system uses electrical field interactions through the development roller to infer surface potential from development current measurements, eliminating the mechanical sensor that is vulnerable to toner contamination.
2Measurement precision
If a surface potential sensor is used to detect the surface potential of the photosensitive drum, then the surface potential can be measured, but the device cost increases
Solution Approach 1:
The patent replaces the expensive surface potential sensor with a cost-effective electrical measurement system using the existing development roller and current measuring circuitry. The development roller, which is already a necessary component in the electrophotographic system, serves dual purposes: image development and surface potential measurement, eliminating the need for additional expensive sensing components.
Solution Approach 2:
The patent makes the development roller multi-functional by using it both for its primary purpose of transferring toner to the drum and for measuring the surface potential through the development current. This eliminates the need for a separate dedicated surface potential sensor, reducing device complexity and cost while maintaining measurement capability.
3Manufacturing precision
If the development bias voltage is not optimized based on actual surface potential, then the image quality deteriorates, but using a sensor-based method increases cost and reduces reliability
Solution Approach 1:
The patent implements a feedback mechanism where the development current is measured and used to calculate the surface potential, which then informs the optimization of development bias voltage settings. This closed-loop feedback system ensures that the development parameters are continuously adjusted based on actual drum surface conditions, maintaining high image quality without relying on vulnerable sensor measurements.
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
Enables accurate estimation of the surface potential and optimal bias voltage application, reducing costs and improving image quality by eliminating the need for high-cost surface potential sensors and minimizing the impact of fogging toner.
Implementation Method 1
The charger charges the image bearing member
Implementation Method 2
The development device develops the electrostatic latent image formed on the image bearing member into a toner image by supplying a toner to the image bearing member
Implementation Method 3
The electric current measuring section measures a development current flowing in the development device
Implementation Method 4
The development power supply applies a bias voltage to the development device
Data Source
AI summary
An image forming apparatus includes: a development device which develops an electrostatic latent image formed on a photosensitive drum into a toner image; a charger which charges the photosensitive drum; a development power supply which applies a bias voltage to the development device; a calculating section which calculates a surface potential of the photosensitive drum based on a development current flowing in the development device; and an estimating section which estimates a fogging toner amount. The fogging toner amount is an amount of toner moved due to fogging. When the fogging toner amount estimated by the estimating section is less than a prescribed threshold, the calculating section calculates a value of the bias voltage at which the development current stops flowing as the surface potential.