Glow Plug Heater Thermal Stress Reduction
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Solution Overview
Problem
Heaters used in high-temperature environments, such as automobile engines, face increased thermal stress due to heat cycles, leading to reduced durability and reliability.
Innovation Solution
A heater design featuring an insulating ceramic base with buried resistors and leads containing electrical conductors and ceramic particles, where the ceramic particles in the resistor are smaller than those in the leads, reducing thermal stress through matched thermal expansion coefficients and improved heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heater is used in a high-temperature environment, then the heating function is effective, but thermal stress increases leading to reduced durability
Solution Approach 1:
The patent changes the material parameters of the lead and resistor by incorporating ceramic particles with specific size distributions. The resistor contains finer ceramic particles (0.1-10 μm) while the lead contains coarser ceramic particles (1-50 μm), creating different thermal expansion coefficients that compensate for thermal stress during heat cycles, thereby improving durability in high-temperature environments
Solution Approach 2:
The patent uses composite materials consisting of electrical conductors combined with ceramic particles in both the lead and resistor. This composite structure provides both electrical conductivity and thermal stress compensation, allowing the heater to maintain reliability under high-temperature operating conditions
2Reliability
If ceramic particles are added to reduce thermal stress, then durability improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by using different ceramic particle size distributions in different components. The resistor uses finer ceramic particles (0.1-10 μm) to control thermal expansion in the heat-generating area, while the lead uses coarser ceramic particles (1-50 μm) to manage thermal stress in the conductive area, optimizing each component for its specific function
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 enhances the heater's durability and reliability in high-temperature environments by minimizing thermal stress and microcrack formation, while allowing for efficient heat generation and resistance adjustment.
Implementation Method 1
The heater for use in a glow plug of an automobile engine or the like contains a resistor having a heat-generating portion, a lead, and an insulating base
Implementation Method 2
both the resistor and the leads contain electrical conductors and ceramic particles dispersed in the electrical conductors, and the insulating ceramic particles contained in the resistor are smaller than the insulating ceramic particles contained in the leads
Data Source
AI summary
A heater of this invention includes an insulating base made of a ceramic, a resistor buried in the insulating base, and leads connected to end portions of the resistor, in which both the resistor and the leads contain electrical conductors and insulating ceramic particles dispersed in the electrical conductors and the insulating ceramic particles contained in the resistor are smaller than the insulating ceramic particles contained in the leads.