Fixing Member Rotation Detection via Thermal Rate

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Solution Overview

Problem

In electrophotographic image forming apparatuses, the durability of fixing members is compromised, and image defects occur due to deformation when power transmission to the fixing member fails, leading to non-rotation and increased temperature.

Innovation Solution

A fixing device with a controller that detects the rotational state of the fixing member by monitoring temperature changes after stopping electrical power to the heat generating member, allowing for discrimination between rotation and non-rotation based on temperature lowering rates, thus preventing thermal deformation and image defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an electroconductive portion and a non-electroconductive portion are provided in mixture along a circumferential direction of the fixing member to detect rotation, then the rotational state can be discriminated, but the durability of the fixing member deteriorates and image defects occur due to deformation

Engineering Contradiction:

Improverotation detection accuracyVSAvoidfixing member durability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical/electrical detection method (electroconductive and non-electroconductive portions) with a thermal detection method. A temperature detecting member monitors temperature changes of the heat generating member during motor operation. When the fixing member fails to rotate, temperature continues to rise; when rotation occurs, temperature stabilizes or decreases, enabling rotation detection without mechanical processing of the fixing member.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a temperature detecting member as an intermediary between the heat generating member and the control system. This intermediary indirectly detects the rotational state by monitoring temperature changes, avoiding direct contact or processing of the fixing member that would compromise its durability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the fixing member is processed to discriminate rotation or non-rotation, then the rotational state can be detected, but the durability of the fixing member is lowered

Engineering Contradiction:

Improverotation detection capabilityVSAvoidfixing member service life

Core Design Contradiction:

Measurement precisionVSDuration of action of stationary object

Solution Approach 1:

The patent substitutes mechanical processing of the fixing member with a thermal field-based detection method. By monitoring temperature changes in the heat generating member during motor operation, the system can determine rotational state without any mechanical intervention, marking, or processing of the fixing member, thereby preserving its service life.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes temperature as a parameter to detect rotational state. During motor operation, if the fixing member rotates normally, heat is dissipated and temperature remains stable or decreases. If rotation fails, temperature continuously rises. This parameter change provides a non-intrusive detection method that does not affect the fixing member's durability.

Inventive Principle:

Principle #35Parameter changes

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 method effectively suppresses the deterioration of the fixing member's durability and prevents image defects by accurately determining the rotational state of the fixing member, ensuring reliable operation even when power transmission is compromised.

Implementation Method 1

a heat generating member configured to heat the first rotatable member

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a temperature detecting member configured to detect a temperature of the heat generating member

Methodology Applied

Scientific EffectTemperature detection: Thermistor

Data Source

PatentUS10444682B2Fixing device that detects a rotational state of a rotatable member based on a temperature lowering rate of a detected temperature of a temperature detecting member

Publication Date: 2019.10.15 CANON KK

AI summary

A fixing device includes a first rotatable member, a second rotatable member, a heat generating member that heats the first rotatable member, and a temperature detecting member that detects a temperature of the heat generating member. A motor drives one of the first rotatable member and the second rotatable member. In addition, a controller controls the fixing device by causing the motor to rotate in a state in which a predetermined amount of electrical power is supplied to the heat generating member, and then, supply of the electrical power to the heat generating member is stopped. On the basis of a temperature lowering rate of a detected temperature of the temperature detecting member during rotation of said motor, the controller detects, after stopping supply of the electrical power to the heat generating member, a rotational state of the one of the first rotatable member and the second rotatable member.