Gas Sensor Electrode Geometry for Noble Metal Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing gas sensors require significant amounts of expensive and rare noble metals, and they cannot achieve stable output until the solid electrolyte reaches a predetermined activation temperature, necessitating a heater to rapidly raise the temperature.
Innovation Solution
A gas sensor design with a bottomed cylindrical solid electrolyte base body, featuring a heater with a heating resistor pattern within the same axial range as the gas contact inner region, where the inner electrode's sensing portion is formed only on the heat-facing area, and the outer sensing portion is thicker to ensure rapid heating and reduce noble metal usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inner electrode is formed on the whole inner surface of the base body, then the sensor output stability is improved, but the amount of noble metal used increases
Solution Approach 1:
The inner electrode is selectively formed only on the heat-facing area of the gas contact inner region, which is the specific zone where stable sensing output is most critical. This localized electrode formation maintains reliability where needed while reducing noble metal consumption in non-critical areas.
Solution Approach 2:
The inner surface of the base body is divided into different functional regions: the heat-facing area where the inner electrode is formed for stable sensing, and other areas where no electrode is formed. This segmentation allows differential treatment of surface areas based on their functional requirements.
2Loss of time
If the heater is energized to rapidly raise the temperature of the solid electrolyte base body to activation temperature, then the sensor output stabilization time is reduced, but the energy consumption increases
Solution Approach 1:
The heating resistor pattern is applied only to the heat-facing area region rather than the entire base body. This localized heating approach concentrates energy where it is most needed for rapid activation, reducing overall energy consumption while achieving quick sensor output stabilization.
Solution Approach 2:
The heat-facing area is pre-positioned and pre-heated by the heater before gas contact occurs. This preliminary heating action ensures that the critical sensing region reaches activation temperature quickly, reducing the time needed for stable sensor output without requiring the entire base body to be heated.
3Reliability
If the outer sensing portion thickness is increased, then the durability is improved, but the noble metal usage increases
Solution Approach 1:
The outer sensing portion is made thicker specifically in the gas contact region where durability is most critical for withstanding exhaust gas exposure. The thickness is optimized locally rather than uniformly throughout, providing enhanced durability where needed while minimizing overall noble metal consumption.
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 design allows for quick stabilization of sensor output by efficiently heating the solid electrolyte to activation temperature while minimizing noble metal usage, enhancing durability and reducing the risk of premature deterioration of the inner sensing portion.
Implementation Method 1
a heater having a heating portion arranged in a cylindrical inner space of the base body... energization of the heater... rapidly raising the temperature of the solid electrolyte base body to the activation temperature
Implementation Method 2
an inner electrode formed of noble metal (such as platinum) on an inner surface of the base body... for detecting the concentration of oxygen in exhaust gas
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Provided is a gas sensor capable of obtaining a stable sensor output quickly upon energization of a heater while reducing the amount of noble metal used on an inner surface of a base body. A gas sensor 30 includes an inner electrode 21 having an inner sensing portion 21g formed in a gas contact inner region 1kg such that the inner sensing portion 21g is located on the whole of a heat-facing area 1kt of the gas contact inner region 1kg facing a heating resistor pattern of a heating portion 33c in a radial direction of a base body 1, a terminal contact portion 21t formed in a rear end region 1kc such that the terminal contact portion 21t is located in at least a part of the rear end region 1kc in a circumferential direction of the base body 1 and a lead portion 21s formed only on a part of an inner surface 1k of the base body 1 in the circumferential direction of the base body 1 so as to connect the inner sensing portion 21g and the terminal contact portion 21t to each other.