Toner Charge Prediction via Developing Current Feedback
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Solution Overview
Problem
Existing image forming apparatuses face challenges in accurately predicting the charge amount of toner, leading to issues like decreased image density, toner fogging, and increased toner scattering due to variations in conditions such as the number of sheets printed, environmental changes, and image formation mode.
Innovation Solution
The apparatus includes a charger, exposure device, developing device with a rotatable developing roller, density detecting section, developing current measuring section, and a control system that forms measurement toner images with different toner amounts to accurately acquire the toner charge amount based on image density and developing current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the charge amount of toner is predicted by combining predictions under individual conditions (number of sheets, environmental changes, image formation mode, coverage rate), then the prediction can be made based on available data, but the prediction accuracy is insufficient when multiple conditions change simultaneously
Solution Approach 1:
The system measures the actual charge amount of toner using a current sensor during the development process, then feeds this information back to adjust the developing bias voltage. This closed-loop feedback mechanism continuously corrects prediction errors and maintains accurate charge amount control even when multiple conditions change simultaneously.
Solution Approach 2:
The patent replaces complex multi-parameter prediction algorithms with direct electrical measurement of toner charge amount through current sensing. By substituting computational prediction with physical measurement, the system achieves higher accuracy without requiring sophisticated software models.
2Measurement precision
If surface potential sensors or current measurements are used to accurately measure toner charge amount, then prediction accuracy improves, but device complexity and cost increase
Solution Approach 1:
The developing roller itself serves as the measurement tool by generating the developing bias voltage and simultaneously sensing the resulting current. This self-service approach eliminates the need for separate surface potential sensors or complex measurement systems, as the existing development components perform both development and measurement functions.
Solution Approach 2:
The developing bias applying section serves dual purposes: it applies the necessary bias voltage for toner development while simultaneously functioning as a measurement device by monitoring the current flow. This multi-functionality reduces overall system complexity by combining development and measurement capabilities in a single component.
3Productivity
If the developer is used for extended periods without adjustment, then productivity is maintained, but image quality deteriorates due to toner charge amount changes from environmental factors and usage
Solution Approach 1:
The system continuously monitors the current during development and adjusts the developing bias voltage in real-time to compensate for toner charge changes. This feedback mechanism ensures consistent image quality over extended operation periods by dynamically adapting to environmental changes and usage conditions.
Solution Approach 2:
The system performs periodic measurement and adjustment cycles during operation, where the charge amount is measured at intervals and the developing bias is recalibrated accordingly. This periodic action maintains image quality stability throughout continuous operation without requiring frequent manual intervention.
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 allows for precise prediction of the toner charge amount without the need for surface potential sensors or current measurements, stabilizing image quality by adjusting toner density and developing bias, thus improving image density and reducing toner scattering.
Implementation Method 1
a charger charging the image bearing member with a predetermined charge potential
Implementation Method 2
an exposure device that exposes the surface of the image bearing member charged with the predetermined charge potential to light according to predetermined image information to form the electrostatic latent image
Implementation Method 3
a developing bias applying section that applies a developing bias including an AC voltage superposed on an DC voltage to the developing roller
Implementation Method 4
a density detecting section that detects a density of the toner image
Implementation Method 5
a developing current measuring section that measures a DC component of a developing current flowing between the developing roller and the developing bias applying section
Data Source
AI summary
A mode controller outputs a characteristic value according to a DC component of a developing current measured by an ammeter at a predetermined measurement timing. The measurement timing is defined as a timing at which a non-image forming region of a surface of a photosensitive drum is located opposite to a developing roller in the entirety of an axial direction and an electric field in a direction in which a toner moves from the photosensitive drum toward the developing roller by a potential difference between a surface potential of the photosensitive drum and the DC component of a developing bias is formed in a developing nip part. A determining section determines an execution timing for a charge amount acquisition operation according to the characteristic value output by the mode controller.