Fixing Device Sheet Interval Control for Small-Sheet Overheating

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Solution Overview

Problem

The temperature of non-passage regions in a fixing device of an image forming apparatus increases when smaller sheets pass through, potentially damaging support members and sheet sensors due to heat accumulation.

Innovation Solution

A controller is employed to control the sheet interval between sheets passing through the fixing device, ensuring the non-passage region temperature remains below a predetermined limit and the component temperature is managed to prevent overheating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the fixing device width is designed for maximum sheet size, then large sheets can pass through, but non-passage regions experience excessive temperature rise when smaller sheets are used

Engineering Contradiction:

Improvesheet size adaptabilityVSAvoidnon-passage region temperature

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The patent applies throughput-down control by introducing periodic intervals between sheets passing through the fixing device. When a small sheet is detected, the system periodically stops conveying sheets for a predetermined time, allowing the non-passage region temperature to decrease before the next sheet passes, thus preventing excessive temperature accumulation while maintaining sheet size adaptability

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the operational parameters of the fixing device by dynamically adjusting the sheet interval based on sheet size detection. The controller modifies the conveying timing parameter (throughput) to create appropriate gaps between sheets, thereby controlling the thermal accumulation in non-passage regions without changing the physical structure of the fixing device

Inventive Principle:

Principle #35Parameter changes

2Temperature

If throughput-down control is implemented to suppress temperature rise, then non-passage region temperature is controlled, but processing speed decreases

Engineering Contradiction:

Improvenon-passage region temperatureVSAvoidsheet processing speed

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The patent implements dynamic throughput control where the sheet interval is adjusted in real-time based on the detected sheet size. When a small sheet is detected, the system dynamically increases the interval (throughput-down control). When normal-sized sheets are detected, the system returns to normal throughput. This dynamic adjustment optimizes the balance between temperature control and processing speed

Inventive Principle:

Principle #15Dynamics

3Reliability

If sheet sensor is arranged outside the fixing device for jam detection, then jam detection capability is provided, but the sensor is exposed to heat from the fixing device

Engineering Contradiction:

Improvejam detection capabilityVSAvoidheat exposure to sensor

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies throughput-down control as a preliminary protective action before the sensor is exposed to excessive heat. By creating time intervals between sheets when small sheets pass through, the system proactively prevents heat accumulation that would otherwise damage the sheet sensor positioned near the fixing device, thereby protecting the sensor while maintaining its jam detection functionality

Inventive Principle:

Principle #10Preliminary action

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 approach effectively prevents overheating of non-passage regions and sheet sensors, maintaining device longevity and sensor functionality while optimizing throughput.

Implementation Method 1

A fixing device that fixes a toner image on a sheet using an electrophotographic process fixes the toner image onto the sheet by applying heat to the sheet and the toner image

Methodology Applied

Scientific EffectHeat: Heating

Implementation Method 2

a temperature of a non-passage region through which sheets do not pass in the fixing device is suppressed to a predetermined first limit temperature or less and a temperature of the component is suppressed to a predetermined second limit temperature or less

Methodology Applied

Scientific EffectHeat propagation: Conduction (thermal)

Data Source

PatentUS12535763B2Image forming apparatus that controls sheet interval

Publication Date: 2026.01.27 CANON KK

AI summary

An image forming apparatus includes a conveyance member to convey a sheet, an image forming unit, a fixing device, a component, and a controller. The image forming unit forms a toner image on the conveyed sheet conveyed. The fixing device fixes an unfixed toner image formed on the sheet, onto the sheet. Heat of the fixing device propagates to the component. The controller controls a passing sheet interval between a plurality of sheets passing through the fixing device. The controller executes throughput control for controlling a sheet interval, which is an interval between a preceding sheet and a subsequent sheet passing through the fixing device, such that a temperature of a non-passage region through which sheets do not pass in the fixing device is suppressed to a predetermined first limit temperature or less and a temperature of the component is suppressed to a predetermined second limit temperature or less.