Photosensitive Member Potential Difference Detection for Image Density Control
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Solution Overview
Problem
Existing image forming apparatuses using the electrophotographic process face challenges in stabilizing image density and tone reproduction due to fluctuations in surface potential of the photosensitive member, which affects latent image contrast and toner adhesion, leading to inefficiencies in color gamut enlargement and potential transfer or fixing failures.
Innovation Solution
An image forming apparatus that detects the difference in potential between unexposed and exposed portions of the photosensitive member using a voltage applying member and a detecting unit, allowing for real-time adjustment of image forming conditions without the need for multiple power supplies, thereby simplifying the configuration and reducing downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage having positive polarity and a voltage having negative polarity are applied to a charging member to calculate discharge start voltages, then information concerning latent image contrast can be acquired, but the apparatus size, cost, and control time increase due to requiring both positive and negative polarity power supplies
Solution Approach 1:
The patent extracts only the essential measurement function by applying voltage having the same polarity as the charging member polarity. This eliminates the need for dual polarity power supplies while still acquiring latent image contrast information through current detection at different voltage levels.
Solution Approach 2:
The charging member's existing power supply is made multi-functional by using it for both normal charging operations and latent image contrast measurements. The same polarity voltage source serves dual purposes, eliminating the need for separate measurement power supplies.
2Adaptability or versatility
If the output of the exposure device is increased to enlarge color gamut, then latent image contrast increases and toner adhesion improves, but the relationship between output increase and latent image contrast change fluctuates according to photosensitive member characteristics and atmospheric environment
Solution Approach 1:
The patent implements feedback control by measuring latent image contrast through current detection and using this information to adjust the exposure device output. This closed-loop system compensates for fluctuations in photosensitive member characteristics and atmospheric conditions, ensuring reliable toner adhesion while maintaining color gamut enlargement.
Solution Approach 2:
The patent dynamically adjusts exposure output based on measured latent image contrast values. By changing the exposure parameter (light amount) according to actual measurements rather than using fixed values, the system adapts to varying photosensitive member characteristics and environmental conditions.
3Manufacturing precision
If surface potential of the photosensitive member is controlled to stabilize image density and tone reproduction, then image quality improves, but additional measurement and control mechanisms are required increasing apparatus complexity
Solution Approach 1:
The patent makes the existing charging member and power supply multi-functional, using them for both charging operations and surface potential measurements. This eliminates the need for separate measurement electrodes or power supplies, reducing apparatus complexity while maintaining image density control capability.
Solution Approach 2:
The charging member serves itself by performing both charging and measurement functions. The same component that charges the photosensitive member also measures the surface potential through current detection, eliminating the need for dedicated measurement infrastructure.
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 stable acquisition of latent image contrast information and control of image forming conditions, ensuring consistent image density and tone reproduction, thereby preventing inefficiencies in color gamut enlargement and reducing the risk of transfer or fixing failures.
Implementation Method 1
a detecting unit configured to detect a value of a current flowing to the photosensitive member when a voltage is supplied to the voltage applying member
Implementation Method 2
a charging member configured to charge the photosensitive member to form an unexposed portion on the photosensitive member
Implementation Method 3
exposes the uniformly charged surface of the photosensitive member according to image information to form an electrostatic image on the photosensitive member
Data Source
AI summary
An image forming apparatus includes a detecting unit detecting a value of a current flowing to a photosensitive member when a voltage is supplied to a voltage applying member or a value of a voltage applied to the photosensitive member when a current is supplied to the voltage applying member, an acquiring unit acquiring information concerning a difference between potentials of the unexposed portion and the exposed portion, based on detection results of the detecting unit at times when the voltage is applied by the voltage applying member to each of an unexposed portion formed in a region chargeable by a charging member in a rotation axis direction of the photosensitive member and an exposed portion formed in a region exposable by the exposure device in the rotation axis direction of the photosensitive member, and a control unit controlling an image forming condition based on the information concerning the difference.