Oxygen Sensor Grain Size Distribution for Accuracy
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Solution Overview
Problem
Resistance-type oxygen sensors face challenges in achieving high detection accuracy for oxygen concentration in exhaust gases, particularly due to limitations in grain size distribution of oxide semiconductor particles, which affect the sensor's response and accuracy.
Innovation Solution
The oxygen sensor employs an oxide semiconductor layer with a grain size distribution having a first peak below 1 µm and a second peak exceeding 1 µm, combined with cerium and zirconium, to enhance the sensor's oxygen partial pressure dependence and detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the grain size of oxide semiconductor particles is reduced to improve response speed, then the response speed improves, but the detection accuracy deteriorates
Solution Approach 1:
The patent applies local quality by creating a grain size distribution with different regions having different grain sizes. Specifically, it contains fine particles (0.1-1 μm) that provide high response speed and coarse particles (1-10 μm) that provide high detection accuracy. This spatial distribution of different grain sizes within the same oxide semiconductor layer allows simultaneous optimization of both response speed and detection accuracy.
Solution Approach 2:
The patent uses composite materials by combining oxide semiconductor particles with different grain sizes within the same layer. The composite structure consists of fine particles (0.1-1 μm) and coarse particles (1-10 μm) distributed together, creating a material that exhibits both fast response characteristics of fine particles and high accuracy characteristics of coarse particles.
2Reliability
If zirconium is added to improve electron conduction rate, then the electron conduction rate improves, but the resistivity control becomes difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the zirconium addition amount within a specific range (0.01-0.5 mass%). This parameter control allows optimization of electron conduction rate while maintaining manufacturable resistivity. The fine-tuned zirconium content provides sufficient electron conduction improvement without excessive reduction in resistivity that would be difficult to control during manufacturing.
3Speed
If cerium oxide microparticles with small grain size are used to improve response, then the response improves, but the detection accuracy deteriorates
Solution Approach 1:
The patent applies local quality by creating a grain size distribution with different regions having different grain sizes. Specifically, it contains fine particles (0.1-1 μm) that provide high response speed and coarse particles (1-10 μm) that provide high detection accuracy. This spatial distribution of different grain sizes within the same oxide semiconductor layer allows simultaneous optimization of both response speed and detection accuracy.
Solution Approach 2:
The patent uses composite materials by combining oxide semiconductor particles with different grain sizes within the same layer. The composite structure consists of fine particles (0.1-1 μm) and coarse particles (1-10 μm) distributed together, creating a material that exhibits both fast response characteristics of fine particles and high accuracy characteristics of coarse particles.
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 grain size distribution significantly reduces resistivity in fuel-rich conditions, improving the sensor's output dependence on oxygen partial pressure, thereby enhancing detection accuracy and facilitating better air-fuel ratio control in internal combustion engines.
Implementation Method 1
a resistance-type oxygen sensor detects changes in the resistivity of an oxide semiconductor layer which is provided so as to be in contact with exhaust gas. When the oxygen partial pressure within the exhaust gas changes, the oxygen vacancy concentration in the oxide semiconductor layer fluctuates, thus causing a change in the resistivity of the oxide semiconductor layer.
Data Source
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AI summary
An oxygen sensor according to the present invention is an oxygen sensor of a resistance-type including: an oxide semiconductor layer (11); and detection electrodes (12) for detecting a resistivity of the oxide semiconductor layer. The oxide semiconductor layer includes oxide semiconductor particles (11a) composed of an oxide containing cerium. The oxide semiconductor particles have a grain size distribution with a first peak existing in a grain size range of less than 1 µm and a second peak existing in a grain size range exceeding 1 µm.