LED Array Substrate Thermal Expansion Compensation

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Solution Overview

Problem

In electrophotographic image forming apparatuses, thermal expansion of LED arrays leads to image deviation among colors due to differing temperature rise amounts, causing width changes and resulting in poor image quality, with existing solutions either requiring complex mechanisms or increasing costs.

Innovation Solution

An image forming apparatus with a staggered arrangement of light emitting element array chips and a temperature detecting portion, where the controller corrects image data magnification based on substrate length fluctuations, allowing for precise image data arrangement and alignment to compensate for thermal expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If LED arrays are used for exposure, then image forming speed and resolution are improved, but thermal expansion causes image width variation and color deviation

Engineering Contradiction:

Improveimage forming speedVSAvoidimage width consistency

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by detecting temperature variations of the substrate and dynamically adjusting the light emission timing and duration of LEDs to compensate for thermal expansion. When temperature increases cause substrate expansion, the system reduces light emission parameters to maintain consistent image width across different colors.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback control by continuously monitoring substrate temperature with a temperature detection unit and using this information to adjust LED light emission in real-time. This closed-loop system ensures that image width remains consistent despite thermal effects during operation.

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If multiple light emitting chips are used for color images, then color image quality is improved, but temperature rise differences cause image deviation among colors

Engineering Contradiction:

Improvecolor image qualityVSAvoidimage alignment among colors

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The patent changes operational parameters by adjusting the light emission timing and duration of each color's LED array based on detected substrate temperature. This allows each color channel to compensate for differential thermal expansion, maintaining proper alignment and registration of multi-color images.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality control by independently managing the light emission parameters of each color's LED array based on its specific thermal characteristics. Each color channel can be optimized and adjusted separately to account for different temperature rise amounts, ensuring consistent color registration.

Inventive Principle:

Principle #3Local quality

3Temperature

If substrate length increases due to thermal expansion, then image width becomes longer, but this causes image deviation and reduces image quality

Engineering Contradiction:

Improvesubstrate temperatureVSAvoidimage width accuracy

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent compensates for thermal expansion effects by dynamically changing LED light emission parameters based on substrate temperature measurements. As temperature increases and substrate expands, the system adjusts light emission timing and duration to maintain accurate image width and position.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses feedback control where substrate temperature is continuously measured and this information feeds back to adjust light emission parameters. This closed-loop system counteracts the relationship between temperature increase and image width expansion, maintaining consistent image quality.

Inventive Principle:

Principle #23Feedback

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 solution effectively corrects image width variations due to thermal expansion, reducing image deviation among colors and maintaining image quality without the need for additional costly mechanisms, thus enhancing the output image while keeping costs in check.

Implementation Method 1

By the influence of this heat generation amount, thermal expansion of a substrate on which the LED arrays are mounted may occur, so that a length of the substrate with respect to a main scan direction of the substrate becomes long

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10795280B2Image forming apparatus

Publication Date: 2020.10.06 CANON KK

AI summary

An image forming apparatus includes a photosensitive drum; an exposure portion including light emitting elements; and a controller configured to control activation of the light emitting elements. The exposure portion includes array chips, each including the light emitting elements, a substrate on which the array chips are arranged in a staggered fashion in the rotational axis direction, and a substrate temperature detecting portion. The controller includes a correcting portion configured to correct magnification of the image data with respect to the rotational axis direction depending on a length fluctuation amount of the substrate calculated on the basis of the temperature detected by the temperature detecting portion, and a converting portion. Depending on magnification correction by the correcting portion, the image data is arranged by the converting portion on the basis of the mounting positions of the array chips.