Opposing Roller Speed Control for Image Scaling Stability

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Solution Overview

Problem

Existing image reading apparatuses experience reading failures due to temporary variations in sheet conveyance speed, leading to partial expansion or reduction of read images.

Innovation Solution

The image reading apparatus includes a first conveyance roller, first and second transparent members, first and second reading units, and first and second opposing rollers. The driving unit controls the first opposing roller to have a faster circumferential speed than the second conveyance roller, stabilizing the image scaling ratio and reducing reading failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the opposing roller is arranged at a fixed position to stabilize the distance between sheet and reading unit, then the reading position stability is improved, but the sheet conveyance speed varies causing partial expansion or reduction of read image

Engineering Contradiction:

Improvereading position stabilityVSAvoidimage scaling accuracy

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The opposing roller is made rotatable with adjustable speed, transitioning from a fixed static position to a dynamic controllable one. The driving mechanism enables the opposing roller to rotate at speeds synchronized with the conveyance roller, allowing active compensation for sheet speed variations while maintaining stable reading position distance.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The rotational speed parameter of the opposing roller is changed to match the conveyance speed. By controlling the rotational speed of the opposing roller to be substantially equal to the conveyance roller speed, the system compensates for sheet speed variations and maintains both reading position stability and image scaling accuracy.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the opposing roller rotates at the same speed as the conveyance roller, then the image scaling ratio is stabilized, but the trailing edge of the sheet may still experience speed variation

Engineering Contradiction:

Improveimage scaling accuracyVSAvoidconveyance speed stability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The system establishes a feedback control mechanism where the rotational speed of the opposing roller is continuously adjusted based on the conveyance roller speed. This feedback loop ensures that any variations in sheet conveyance speed are immediately compensated by corresponding adjustments to the opposing roller speed, maintaining both image scaling accuracy and conveyance stability.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12219106B2Image reading apparatus and image forming system

Publication Date: 2025.02.04 CANON KK

AI summary

An image reading apparatus includes first and second first conveyance rollers, transparent members, reading units, and opposing rollers, and includes a driving unit. The first reading unit reads an image on a sheet first surface through the first transparent member at a first reading position. The first opposing roller is opposed to the first transparent member at the first reading position. The second reading unit reads an image on a sheet second surface through the second transparent member at a second reading position. The second opposing roller is opposed to the second transparent member at the second reading position. The second conveyance roller is arranged where a sheet trailing edge passes through the first reading position while the second conveyance roller conveys the sheet. The driving unit drives the first opposing roller so that a first opposing roller circumferential speed is faster than a second conveyance roller circumferential speed.