Image Forming Apparatus Separation Failure Jam Detection

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Solution Overview

Problem

Conventional image forming apparatuses using intermediate transfer belts face issues with detection accuracy for separation failure jams, particularly with thin sheets, leading to paper jams and potential damage to the belt surface, and misdetection due to toner contamination.

Innovation Solution

The apparatus includes a registration roller pair upstream of the secondary transfer unit to synchronize sheet transport with toner image transfer, a detection sensor downstream to detect the sheet after transfer, and a control unit that stops the drive units based on elapsed time to prevent sheet entry into the image forming section in case of a jam, thereby improving detection accuracy and preventing belt damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a detection sensor is installed at a position facing the belt surface of the intermediate transfer belt, then separation failure jams can be detected, but the sensor surface gets contaminated with toner causing misdetection

Engineering Contradiction:

Improveseparation failure jam detectionVSAvoiddetection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

A reflective member is introduced as an intermediary between the detection sensor and the intermediate transfer belt. The reflective member reflects light from the detection sensor to detect belt surface displacement, preventing direct contact between the sensor and toner-contaminated belt surface while maintaining detection capability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct optical detection (sensor facing belt surface) with indirect optical detection using light reflection. The detection sensor detects belt surface displacement by measuring changes in reflected light from the reflective member, substituting a mechanical/optical intermediary system for direct sensing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If separation claws are installed to separate sheets from the belt surface, then separation failure jams can be prevented, but the belt surface gets damaged causing image defects

Engineering Contradiction:

Improveseparation failure preventionVSAvoidbelt surface integrity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent replaces mechanical separation claws with a control system that stops the intermediate transfer belt upon detecting separation failure jams. This substitution eliminates mechanical contact that could damage the belt surface while maintaining the ability to prevent and handle separation failures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses the detection sensor and control unit to automatically detect and respond to separation failure jams, eliminating the need for mechanical intervention. The belt system serves itself by stopping automatically when a problem is detected, rather than requiring external mechanical separation devices

Inventive Principle:

Principle #25Self-service

3Measurement precision

If the detection sensor is placed close to the intermediate transfer belt for detection, then detection capability is improved, but toner contamination of the sensor surface increases

Engineering Contradiction:

Improvedetection sensitivityVSAvoidtoner contamination

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The reflective member serves as a mediator that allows the detection sensor to be positioned close to the belt for sensitive detection while preventing direct exposure to toner. The reflective member captures light and reflects it to the sensor without the sensor contacting the toner-contaminated belt surface

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9581927B2Image forming apparatus having detection of separation failure jams

Publication Date: 2017.02.28 CANON KK

AI summary

An image forming apparatus includes a primary transfer unit, a secondary transfer unit, a registration roller pair placed upstream of the secondary transfer unit in a sheet transport direction, and a drive unit driving the registration roller pair. In addition, a detection sensor unit is placed on a sheet transport path downstream of the secondary transfer unit and detects a sheet transported after a toner image is secondary transferred by the secondary transfer unit, and a transport unit transports the sheet after the secondary transfer. A control unit stops the drive unit when it determines absence of the sheet on the sheet transport path based on a signal from the detection sensor unit when a predetermined time based on an interval of time, which is from when the control unit controls the drive unit and starts to transport the sheet by the registration roller pair to when a leading edge of the sheet reaches the detection sensor unit, has elapsed, or when an interval of time, which is taken from when the control unit controls the drive unit and starts to transport the sheet by the registration roller pair to when the leading edge of the sheet reaches the transport unit, has elapsed.