Exhaust Sensor Mating Terminal Clad Alloy Oxidation Resistance
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Solution Overview
Problem
Conventional exhaust sensors face challenges with oxide layer formation at the interface between electrical contacts and terminals due to high temperatures and abrasive ceramic substrates, leading to compromised electrical connections and increased costs for gold plating or using oxidation-resistant materials that are difficult to form into complex geometries.
Innovation Solution
An exhaust sensor with a mating terminal made from a base material, such as stainless steel, clad with an alloy comprising less than 20% iron, greater than 40% nickel, and greater than 13% chromium, which provides resistance to oxide layer formation and maintains a robust electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gold plating is applied to the electrical terminal to prevent oxide layer formation, then oxidation resistance is improved, but manufacturing cost increases and the gold plating can be scratched off during assembly
Solution Approach 1:
The patent applies composite materials by combining a base material (stainless steel) with a clad material (nickel-chromium alloy) to create a terminal structure that exhibits properties superior to either material alone. The clad layer provides oxidation resistance while the base material provides structural integrity and formability, resolving the contradiction between reliability and ease of manufacture.
Solution Approach 2:
The patent applies local quality by providing oxidation-resistant clad material only on the portions of the terminal that contact the ceramic substrate and are susceptible to oxidation, rather than plating the entire terminal. This localized approach reduces material cost while maintaining protection where needed, and reduces the likelihood of plating damage during assembly.
2Reliability
If gold plating is applied to prevent oxide layer formation, then oxidation resistance is improved, but the gold plating can be scratched off during assembly due to high normal force and abrasive ceramic substrate
Solution Approach 1:
The composite structure of base material plus clad material provides both oxidation resistance (from the clad) and abrasion resistance (from the combination of materials). The clad layer is designed to withstand the abrasive action of the ceramic substrate while maintaining its protective function, preventing both oxidation and plating damage.
Solution Approach 2:
The patent changes the material parameters by selecting specific alloy compositions for the clad material (nickel-chromium alloy with controlled percentages of various elements) to optimize both oxidation resistance and abrasion resistance. This parameter optimization ensures the clad layer survives the assembly process and provides long-term protection.
3Reliability
If highly oxidation resistant materials such as stainless steel high in nickel and chromium are used, then oxidation resistance is improved, but the ability to form complex geometries deteriorates
Solution Approach 1:
The composite structure separates the functions of formability and oxidation resistance into different materials. The base material (stainless steel) is selected for its formability and ability to be formed into complex geometries, while the clad material is applied subsequently to provide oxidation resistance. This resolves the contradiction by allowing each material to excel at its primary function.
Solution Approach 2:
The patent applies preliminary action by forming the terminal geometry first using the formable base material, and then applying the oxidation-resistant clad material in a subsequent step. This sequence allows complex geometries to be created without compromising oxidation resistance, as the clad is applied after forming is complete.
4Volume of moving object
If the exhaust sensor is made smaller, then device size is reduced, but the temperature at the interface between electrical contacts and terminals increases
Solution Approach 1:
The use of oxidation-resistant clad material on the terminal allows the sensor to be miniaturized without compromising the thermal stability of the electrical interface. The clad material maintains its protective function at elevated temperatures, enabling compact design while managing the increased interface temperature through material selection rather than increased spacing.
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 solution effectively prevents oxide layer formation, ensuring a reliable and robust electrical connection while allowing for complex terminal geometries and withstanding high temperatures and abrasion, thus addressing the limitations of conventional materials.
Implementation Method 1
the clad material is located between the sensing element terminal and the base material, thereby providing the electrical communication... effectively prevents oxide layer formation
Data Source
AI summary
An exhaust sensor includes a sensing element with a ceramic sensing element substrate and a sensing element terminal which is electrically conductive and which is supported by the ceramic sensing element substrate such that the sensing element is configured to sense constituents of exhaust gases when exposed thereto. The exhaust sensor also includes a mating terminal which is electrically conductive and which is in electrical communication with the sensing element terminal. The mating terminal has a base material and a clad material bonded to the base material such that the clad material contacts the sensing element terminal and such that the clad material is located between the sensing element terminal and the base material, thereby providing the electrical communication. The clad material is an alloy which is less than or equal to 20% iron, greater than or equal to 40% nickel, and greater than or equal to 13% chromium.