Developing Bias Calibration for Image Density Stability
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Solution Overview
Problem
Existing image forming apparatuses using the two-component development method face challenges in accurately setting the developing bias conditions, particularly with the AC bias, leading to instability in image density due to difficulties in measuring high image densities and predicting toner charge amounts based on developing current alone.
Innovation Solution
The image forming apparatus incorporates a developing bias calibration system that determines appropriate inter-peak voltages for both DC and AC biases by analyzing the developing current and image density, allowing for timely adjustments based on toner charge changes, ensuring stable image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If developing bias conditions are set using conventional methods, then image formation can proceed, but image density becomes unstable due to inability to accurately measure high densities and predict toner charge amounts
Solution Approach 1:
The patent introduces developing current as an intermediary parameter to indirectly assess toner charge amount and image density conditions. Instead of directly measuring difficult-to-obtain high density values, the system uses the developing current (which is easier to measure accurately) as a mediator to infer the state of the image density and toner charge, thereby resolving the measurement precision limitation.
Solution Approach 2:
The system implements a feedback mechanism where the measured developing current is continuously monitored and used to adjust the developing bias conditions. By establishing a relationship between developing current and image density/toner charge state, the system can dynamically feedback control the developing process to maintain stable image density even when direct measurement becomes unreliable at high densities.
2Ease of operation
If AC bias is applied to the developing roller, then toner image formation is enabled, but accurate setting of inter-peak voltage becomes difficult leading to image density instability
Solution Approach 1:
The system uses developing current measurement as feedback to automatically determine optimal AC bias inter-peak voltage settings. By monitoring how the developing current responds to different AC bias conditions, the system can automatically adjust the inter-peak voltage to achieve stable image density, eliminating the need for manual trial-and-error setting and improving both ease of operation and reliability.
Solution Approach 2:
The patent dynamically adjusts the AC bias inter-peak voltage parameter based on measured developing current characteristics. By changing the inter-peak voltage parameter in response to developing current feedback, the system optimizes the developing conditions for different toner charge states and image density requirements, resolving the contradiction between ease of setting and image density stability.
3Loss of information
If developing current is used to predict toner charge amount, then toner charge can be estimated, but prediction accuracy is insufficient for precise image density control
Solution Approach 1:
The system changes the approach from using developing current alone to using a combination of parameters including developing current, developing bias voltage, and their relationships. By analyzing multiple parameters together and their interrelationships, the system improves the accuracy of toner charge prediction beyond what single-parameter measurement can achieve, reducing information loss while maintaining measurement simplicity.
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 the setting of optimal developing bias conditions, stabilizing image density and improving image quality by accurately responding to changes in toner charge and environmental conditions.
Implementation Method 1
The charging device charges the image carrier to a specific charging potential
Implementation Method 2
The exposure device is disposed on a downstream side in a rotation direction of the image carrier with respect to the charging device, and forms an electrostatic latent image by exposing a surface of the image carrier that is charged to the charging potential in accordance with specific image information
Implementation Method 3
The developing device includes a developing roller that includes a peripheral surface rotated and carrying a developer including toner and carrier, and forms the toner image by supplying toner to the image carrier
Implementation Method 4
The transferer transfers the toner image carried on the image carrier to a sheet
Data Source
AI summary
A bias condition determiner executes a direct current voltage determination mode (DC calibration) for determining a reference direct current voltage that is a reference for a direct current voltage of a developing bias applied to a developing roller in an image forming operation and an inter-peak voltage determination mode (AC calibration) for determining a reference inter-peak voltage that is a reference for an inter-peak voltage of an alternating current voltage of the developing bias applied to the developing roller in the image forming operation. A calibration executor determines whether the inter-peak voltage determination mode needs to be executed in accordance with a value of the reference direct current voltage.