Cylindrical Light Guide with Inclined End for Uniform Charge Removal

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Solution Overview

Problem

In image forming apparatuses using electrophotographic methods, residual charge on the photosensitive drum can lead to nonuniform surface potential, causing 'drum ghost' defects due to light leakage at the end portions of light guides, which existing configurations attempt to address by increasing light source output or adding components, resulting in increased power consumption and apparatus size.

Innovation Solution

A pre-exposure unit with a cylindrical light guide having one end for light input and another end with an inclined surface to reflect light towards the central axis, ensuring uniform light distribution along the photosensitive drum and preventing light leakage, thus maintaining surface potential uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a light guide is used in a pre-exposure unit to remove charge from the photosensitive drum, then charge removal effectiveness is improved, but light amount becomes nonuniform at the end portion due to light leakage

Engineering Contradiction:

Improvecharge removal effectivenessVSAvoidlight amount uniformity

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The light guide is designed with different end portions: one end has a light incident surface for introducing light from the LED, while the other end has a light emitting surface with an inclined surface that reflects light toward the central axis. This local differentiation ensures uniform light distribution along the photosensitive drum, preventing light leakage at the end portion while maintaining effective charge removal throughout the entire drum surface.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If the output of the light source is increased to suppress light amount decline at the end portion, then light amount uniformity is improved, but power consumption increases

Engineering Contradiction:

Improvelight amount uniformityVSAvoidpower consumption

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The inclined surface at the light emitting end portion is designed to reflect light that would otherwise be lost toward the central axis of the light guide. This converts the potentially harmful light leakage into a beneficial effect, redistributing light uniformly along the drum surface without requiring increased light source output, thereby avoiding additional power consumption.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Illumination intensity

If a casing or cover member is provided at the end portion to suppress light amount decline, then light amount uniformity is improved, but device complexity and apparatus size increase

Engineering Contradiction:

Improvelight amount uniformityVSAvoidnumber of components

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The light guide itself is designed to perform the function of light reflection and distribution without requiring separate casings or cover members. The inclined surface at the light emitting end portion is integrated directly into the light guide structure, combining the light guiding and light reflecting functions into a single component, thereby reducing device complexity and apparatus size while maintaining light amount uniformity.

Inventive Principle:

Principle #5Merging (Combining)

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 configuration effectively suppresses light amount decline at the end portions, preventing drum ghost defects while reducing power consumption and apparatus size by ensuring efficient light reflection and distribution.

Implementation Method 1

a light guide that is configured to guide the light to irradiate the surface of the image bearing member with the light

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

the another end portion includes an inclined surface inclining in a direction from the one end portion to the another end portion, toward a central axis of a circumference of the light guide

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS11513463B2Image forming apparatus and cartridge that include light guide that guides light

Publication Date: 2022.11.29 CANON KK

AI summary

A charge removing unit emits light onto a surface of an image bearing member for removing charge on the surface. The charge removing unit includes a light source configured to emit the light, and a light guide that is configured to guide the light to irradiate the surface of the image bearing member with the light and has a cylindrical shape extending in an axial direction of the image bearing member. At both ends in a longitudinal direction of the light guide, one end portion and another end portion are respectively provided. The light is introduced to the one end portion. The another end portion includes an inclined surface inclining in a direction from the one end portion to the another end portion, toward a central axis of a circumference of the light guide.