Charging Potential Control in Electrophotographic Apparatus

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Solution Overview

Problem

Existing electrophotographic apparatuses face challenges in accurately and quickly controlling the charging potential of electrophotographic photosensitive members due to increased size and cost with potentiometer-based methods, and inefficiencies in time and accuracy with discharge start voltage estimation methods.

Innovation Solution

An electrophotographic apparatus that includes a voltage application unit, a charge transfer amount detection unit, and a charging potential control unit, using specific procedures to define V1 and V2 voltages and equations to control the charging potential based on charge transfer amounts and residual potentials, allowing for high accuracy and short control times.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a potentiometer is mounted in the electrophotographic apparatus to directly detect the charging potential, then the charging potential can be accurately controlled to a desired value, but the apparatus size increases and cost increases

Engineering Contradiction:

Improvecharging potential measurement accuracyVSAvoidapparatus size and cost

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical potentiometer-based direct measurement system with an electrical field-based indirect measurement system. By detecting discharge current between the charging member and photosensitive member at different voltages, the system calculates charging potential without requiring physical contact or mechanical components, thereby reducing apparatus size and cost while maintaining measurement accuracy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces discharge current detection as an intermediary measurement method. Instead of directly measuring charging potential with a potentiometer, the system measures the discharge current that occurs when voltage is applied between the charging member and photosensitive member, then calculates the charging potential from this intermediate measurement, avoiding the need for direct potential measurement hardware

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the absolute value of voltage is gradually increased from a voltage at which discharge does not occur to the discharge start voltage, then the discharge start voltage can be estimated with high accuracy, but the control time becomes excessively long

Engineering Contradiction:

Improvedischarge start voltage estimation accuracyVSAvoidcontrol time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-establishing the relationship between discharge current and charging potential through measurement at multiple voltage points before actual image formation. This calibration data is stored and reused for subsequent charging potential control, eliminating the need to perform time-consuming gradual voltage increase and discharge detection during each image formation operation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses partial action by measuring discharge current at only several specific voltage points (e.g., 700V, 800V, 900V, 1000V) rather than gradually increasing voltage from zero to the discharge start voltage. This selective measurement at key voltage points provides sufficient accuracy for charging potential control while dramatically reducing the time required compared to continuous gradual voltage increase

Inventive Principle:

Principle #16Partial or excessive action

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

Enables precise and rapid control of the charging potential of electrophotographic photosensitive members, improving accuracy and reducing downtime while maintaining a compact and cost-effective apparatus design.

Implementation Method 1

a voltage application unit configured to cause discharge from an electroconductive member to the electrophotographic photosensitive member

Methodology Applied

Scientific EffectElectrostatic Discharge: Electrostatic Discharge

Implementation Method 2

a charge transfer amount detection unit configured to detect a charge transfer amount per unit time resulting from the discharge from the electroconductive member to the electrophotographic photosensitive member

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Data Source

PatentUS11947275B2Electrophotographic apparatus

Publication Date: 2024.04.02 CANON KK

AI summary

Provided is an electrophotographic apparatus including: an electrophotographic photosensitive member; a voltage application unit configured to cause discharge from an electroconductive member to the electrophotographic photosensitive member; a charge transfer amount detection unit configured to detect a charge transfer amount per unit time resulting from the discharge from the electroconductive member to the electrophotographic photosensitive member; and a charging potential control unit, wherein V1 and V2 defined by specific procedures for the electrophotographic photosensitive member satisfy a relationship represented by the following expression (E-4): 100V1<V2−V1 (E-4), and wherein the charging potential control unit is configured to control the charging potential of the electrophotographic photosensitive member at the time of image formation.