Fixing Unit Heater Power Path Switching for Mixed Sheet Sizes

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Solution Overview

Problem

Conventional image forming apparatuses with sheet-shaped ceramic heat generation members experience temperature rises in non-sheet-feeding regions when handling sheets of different sizes, leading to potential damage and reduced productivity due to the need for throughput control and switching times between heat generation members.

Innovation Solution

An image forming apparatus with a fixing unit featuring at least two heat generation members of different lengths, where a control unit dynamically switches the power supply based on the number of smaller-width sheets to be printed, ensuring optimal temperature management and minimizing wait times for edge portion heating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single heat generation member supporting maximum sheet width is used, then normal-size sheets can be processed, but non-sheet-feeding region temperature rise occurs with small size sheets causing damage to supporting members

Engineering Contradiction:

Improvesheet size adaptabilityVSAvoidmember damage risk

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The heat generation member is divided into multiple independent heating zones along the sheet width direction, allowing selective activation of only the regions needed for the current sheet size, thereby preventing temperature rise in non-sheet-feeding regions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically adjusts which heating zones are activated based on the detected sheet size, transitioning from static full-width heating to dynamic selective heating to match the actual sheet dimensions

Inventive Principle:

Principle #15Dynamics

2Reliability

If multiple heat generation members with different lengths are used, then non-sheet-feeding portion temperature rise is prevented, but switching time between members reduces productivity

Engineering Contradiction:

Improvetemperature control accuracyVSAvoidthroughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Multiple heating zones are integrated into a single heat generation member structure, eliminating the need for physical switching between separate members while maintaining the ability to selectively activate different regions based on sheet size

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If switch relay is used to change heat generation members, then appropriate heater selection is achieved, but relay switching time of about 200 msec reduces productivity

Engineering Contradiction:

Improveheat generation member selectionVSAvoidswitching time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The switching function is extracted from the heat generation member selection process - instead of physically switching members via relay, the system extracts and activates only the necessary heating zones within a single integrated member, eliminating relay switching time

Inventive Principle:

Principle #2Taking out (Extraction)

4Reliability

If heat generation member is switched from short width to long width, then fixing properties are improved, but edge portion temperature decrease requires wait time reducing productivity

Engineering Contradiction:

Improvefixing propertiesVSAvoidwait time for edge heating

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

When switching from small size sheet mode to normal size sheet mode, the system performs preliminary heating of the edge portions by activating all heating zones before the actual fixing process, ensuring edge portions reach required temperature without waiting

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 configuration prevents damage to the heat generation members, maintains high productivity by avoiding throughput reduction, and ensures consistent fixing properties across varying sheet sizes without extending sheet intervals, thereby enhancing overall print efficiency.

Implementation Method 1

a sheet-shaped ceramic heat generation member heater is used as a heat source

Methodology Applied

Scientific EffectResistive heating: Joule Heating

Data Source

PatentUS10928758B2Image forming apparatus controlling power supply path to heater

Publication Date: 2021.02.23 CANON KK

AI summary

The image forming apparatus includes a fixing apparatus including a heater that includes at least two heat generation members, the fixing unit configured to fix an unfixed toner image formed on a sheet by an image forming unit, a heat generation member switching device configured to switch a power supply path so that electric power can be supplied to one of the heat generation members, a CPU configured to control switching the power supply path by the heat generation member switching device based on a number of shorter width sheets in a longitudinal direction continuously printed in a case where a plurality of mixed sheets including longer width sheets and the shorter width sheets.