Image Forming Apparatus Developing Contrast Control
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Solution Overview
Problem
Existing image forming apparatuses face challenges in maintaining high development efficiency and preventing low image density toner images due to changes in toner charge state caused by environmental factors, leading to increased ratios of small particle size toners and decreased developing properties.
Innovation Solution
An image forming apparatus with a rotatable image bearing member, charging means, exposure portion, developer carrying member, voltage applying means, cleaning means, and current detecting means, which sets the developing contrast based on detected current values to maintain optimal toner charge and particle size distribution, ensuring high development efficiency and preventing low image density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a charger is added to adjust toner charge amount, then development efficiency is improved, but device complexity increases and space requirements increase
Solution Approach 1:
The system uses the existing cleaning means to serve a dual purpose: both cleaning residual toner from the developer carrying member and detecting toner charge state through current measurement. This eliminates the need for a separate charger while maintaining development efficiency.
Solution Approach 2:
The cleaning means is designed to perform multiple functions: mechanical cleaning of toner residue and electrical detection of toner charge state. By making the cleaning means multi-functional, the patent avoids adding extra components like a charger, thereby maintaining simple device structure while achieving high development efficiency.
2Productivity
If toner charge amount increases, then development efficiency is improved, but small particle size toners are preferentially used leading to low image density
Solution Approach 1:
The system continuously monitors the current flowing between the developer carrying member and cleaning means, which reflects the toner charge state. Based on this feedback, the control unit adjusts the developing voltage to maintain optimal development efficiency while preventing excessive use of small particle size toners that would lead to low image density.
Solution Approach 2:
The system dynamically adjusts the developing voltage parameter based on detected toner charge state and particle size distribution. By changing the developing voltage in response to detected conditions, the system maintains high development efficiency while ensuring proper image density through controlled toner deposition.
3Reliability
If developing voltage is increased to improve development efficiency, then image density is improved, but toner charge amount requirements change due to environmental factors
Solution Approach 1:
The system detects toner charge state through current measurement during the cleaning process and uses this feedback to adjust developing voltage. This closed-loop control enables the system to adapt to environmental changes (temperature, humidity) that affect toner charge, maintaining consistent image density without manual intervention.
Solution Approach 2:
The developing voltage is not fixed but dynamically adjusted based on real-time detection of toner charge state and particle size distribution. This dynamic adjustment allows the system to adapt to changing environmental conditions and maintain optimal development efficiency and image density across various operating conditions.
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
The apparatus effectively maintains high development efficiency and prevents low image density by adjusting the developing contrast, allowing for the efficient use of toners of various particle sizes and prolonging the liquid developer's exchange cycle.
Implementation Method 1
a charging means for electrically charging a surface of the image bearing member to a second potential
Implementation Method 2
an exposure portion for exposing the charged image bearing member to light to form an electrostatic latent image
Implementation Method 3
Such development of the electrostatic latent image into the toner image is carried out by movement of the charged toner in a liquid layer of the liquid developer formed between the developing roller and the photosensitive drum (so-called electrophoresis)
Implementation Method 4
a current detecting means for detecting a current flowing between the developer carrying member and the cleaning means
Data Source
AI summary
An image forming apparatus detects a current flowing between a developer carrying member and a cleaning member is detected for each of a plurality of toner images when a region on the developer carrying member passes through the cleaning member, and a potential difference to be used during image formation between the developing voltage and an image portion potential is set on the basis of a value of the detected current for each of the plurality of toner images. An absolute value of the potential difference to be used during image formation is larger than the potential difference between the developing voltage and the image portion potential whose absolute value is smallest among potential differences between the developing voltage and the image portion potential to be used for developing a toner image of which the value of the current detected is in a predetermined range among the plurality of toner images.