Ceramic Glow Plug Heater with Folded Resistor for Thermal Stress Reduction

Solution Overview

Problem

Ceramic heaters face challenges in maintaining reliability due to thermal stress and potential cracking caused by rapid temperature changes, which affects their durability and long-term performance.

Innovation Solution

A heater design featuring a silicon nitride ceramic body with a heating resistor and leads, incorporating a fold-back portion and projections to disperse heat evenly, reducing thermal stress and enhancing durability, along with a metal tube and brazing material for improved bonding and electrical connectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a ceramic heater is used for rapid heating, then heating efficiency is improved, but thermal stress and cracking increase reducing reliability

Engineering Contradiction:

Improveheating efficiencyVSAvoidreliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies local quality by creating a folded portion with projections in the heating resistor that specifically targets the high thermal stress region. This localized structural modification allows the folded portion to disperse heat more effectively in the critical area where thermal stress concentrates, without changing the entire heater structure. The projections extend from the folded portion to increase surface area and improve heat distribution locally, resolving the contradiction between rapid heating and thermal stress resistance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs dimensionality change by folding the heating resistor to create a three-dimensional folded portion with projections extending in multiple directions. This transforms a simple linear heating element into a complex spatial structure that occupies multiple dimensions within the ceramic body. The folded structure with projections radiating outward increases the effective heat dispersal pathways in different spatial directions, enabling rapid heating while reducing thermal stress concentration through enhanced multi-dimensional heat distribution.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Strength

If heating resistor is embedded in ceramic body, then structural support is improved, but thermal stress concentration increases causing cracking

Engineering Contradiction:

Improvestructural supportVSAvoidthermal stress concentration

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a folded portion with projections in the heating resistor that specifically targets the high thermal stress region. This localized structural modification allows the folded portion to disperse heat more effectively in the critical area where thermal stress concentrates, without changing the entire heater structure. The projections extend from the folded portion to increase surface area and improve heat distribution locally, resolving the contradiction between rapid heating and thermal stress resistance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the harmful thermal stress concentration into a beneficial effect by designing the folded portion with projections that actively utilize the thermal energy. Instead of allowing thermal stress to concentrate and cause cracking, the folded structure with its increased surface area and multi-dimensional configuration transforms the thermal energy into distributed heat radiation throughout the ceramic body. The projections act as heat dispersal elements that convert potential damage into effective heating, turning the harmful thermal stress into a beneficial heat distribution mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The design improves the heater's reliability by reducing thermal stress and the likelihood of cracking, leading to enhanced durability and performance under rapid temperature changes.

Implementation Method 1

a heating resistor 3

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a ceramic body 2... dispersing heat evenly, reducing thermal stress

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP3461228B1Heater and glow plug equipped with same

Publication Date: 2020.12.30 KYOCERA CORP

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AI summary

A heater of the present disclosure includes a ceramic body having a rod shape, and a heating resistor provided in an interior of the ceramic body. The heating resistor includes a fold-back portion and a projection having a wire shape and extending across an entirety of an outer periphery of the fold-back portion in a folding-back direction.