Image Density Control in Toner Concentration Sensing
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Solution Overview
Problem
In image forming apparatuses using a two-component developer, variations in toner concentration due to temperature fluctuations lead to inaccurate sensing by toner concentration sensors, resulting in unintended toner feeding and a drop in image density, necessitating costly multiple temperature sensors for correction.
Innovation Solution
An image forming apparatus with an image forming portion, developing voltage power supply, control portion, and image density sensor, which adjusts developing voltage based on sensed image density to correct toner concentration discrepancies, performing recalibration when the toner concentration difference exceeds a threshold, thereby maintaining image density without relying on multiple temperature sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature correction is applied to toner concentration sensor output, then measurement precision is improved, but device complexity increases due to requiring multiple temperature sensors
Solution Approach 1:
The patent extracts the temperature correction function from a separate hardware component (temperature sensors) and integrates it into the existing toner concentration sensor. The toner concentration sensor is made capable of self-correcting its output based on detected temperature, eliminating the need for dedicated temperature sensors while maintaining measurement accuracy.
Solution Approach 2:
The toner concentration sensor is designed to perform multiple functions: it detects both toner concentration and temperature. By making the sensor multi-functional, the patent eliminates the need for separate temperature sensing components, thereby reducing device complexity while maintaining the ability to perform temperature-based corrections.
2Stability of the object's composition
If toner concentration is maintained at reference value, then image density stability is improved, but productivity decreases due to frequent toner feeding operations
Solution Approach 1:
The patent performs preliminary action by pre-heating the developing device before toner feeding operations. This preliminary heating ensures that the temperature is already at the optimal level when toner is fed, preventing temperature fluctuations that would otherwise cause image density variations and trigger frequent recalibration cycles.
Solution Approach 2:
The patent implements periodic action through scheduled calibration cycles that are triggered based on printing volume thresholds. Instead of continuous monitoring and adjustment, the system performs calibration at predetermined intervals, reducing the frequency of interventions while maintaining adequate image density stability.
3Manufacturing precision
If calibration is performed frequently, then image density accuracy is improved, but loss of time increases due to calibration interruptions
Solution Approach 1:
The patent performs preliminary heating of the developing device before calibration operations. This ensures that the temperature is already stabilized when calibration begins, allowing calibration to complete more quickly and accurately without requiring repeated adjustments due to temperature drift during the calibration process.
Solution Approach 2:
The patent uses test images as copies to verify calibration accuracy. By forming test toner images and measuring their density, the system can quickly assess whether calibration was successful without requiring extensive manual verification, thereby reducing the time lost during calibration interruptions.
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 solution effectively stabilizes image density by dynamically adjusting developing voltage and toner feeding, minimizing the impact of toner concentration variations and reducing the need for multiple temperature sensors, thus enhancing printing performance and reducing costs.
Implementation Method 1
a charging device which electrostatically charges the surface of the image carrying member
Implementation Method 2
an exposing device which exposes the surface of the image carrying member electrostatically charged by the charging device to light to form an electrostatic latent image
Implementation Method 3
a developing device that uses two-component developer containing magnetic carrier and toner... a magnetic brush formed of magnetic carrier and toner
Implementation Method 4
a toner concentration sensor which senses the toner concentration in the two-component developer inside the developer container
Data Source
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AI summary
An image forming apparatus (100) includes: an image forming portion (Pa-Pd) having an image carrying member (1a-1d), a charging device (2a-2d), an exposing device (5), and a developing device (3a-3d); a developing voltage power supply (43); a control portion (80); and an image density sensor (40). The developing device (3a-3d) has a developer carrying member (30) that carries two-component developer and a toner concentration sensor (31). The control portion (80) senses toner concentration during calibration or during first image formation after calibration for correcting image density based on the sensing result from the image density sensor (40). If the difference Vtarget - V between the output value V of the toner concentration sensor (31) actually sensed and a target value Vtarget of the toner concentration sensor (31) to be observed when the toner concentration equals a reference concentration is equal to or larger than a predetermined value, the control portion (80) performs calibration again when the amount of toner consumed after calibration reaches a predetermined threshold value.