Wideband Oxygen Sensor With Shared Electrode
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Solution Overview
Problem
Existing oxygen sensors for internal combustion engines face challenges in accurately determining the air:fuel ratio, particularly in small engines where size constraints limit the effectiveness of traditional sensors, and there is a need for alternative methods and systems to control combustion processes based on oxygen levels.
Innovation Solution
A wideband oxygen sensor system that includes both n-type and p-type sensing circuits sharing a common electrode, with a constant current source and a heater portion, allowing for the determination of the air:fuel ratio across a range of values in both rich and lean modes by calculating the ratio of currents in the n-type and p-type circuits and temperature, enabling precise control of the combustion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional oxygen sensors are used in small internal combustion engines, then the sensor can provide oxygen level data, but the size constraints of small engines present difficulties in identifying suitable oxygen sensors and achieving accurate wideband sensing
Solution Approach 1:
The oxygen sensor is divided into two separate sensing circuits: an n-type sensing circuit and a p-type sensing circuit. Each circuit uses a different semiconductor type that responds differently to oxygen levels, allowing the sensor to accurately measure air:fuel ratios across both rich and lean conditions without requiring a single large sensor element.
Solution Approach 2:
The sensor system achieves universal applicability across different engine types and operating conditions by combining both n-type and p-type sensing circuits. This dual-circuit configuration enables the sensor to function accurately in both rich (λ<1) and lean (λ>1) modes, making it suitable for various small engine applications including motorcycles, ATVs, and unmanned air vehicles.
2Adaptability or versatility
If a single-type oxygen sensor (n-type or p-type) is used, then the sensor structure is simpler, but the sensor cannot accurately determine air:fuel ratio across both rich and lean regions
Solution Approach 1:
The sensing function is segmented into two specialized circuits: n-type for rich region detection and p-type for lean region detection. Each circuit is optimized for its specific operating range, and the combination provides comprehensive coverage across the entire air:fuel ratio spectrum.
Solution Approach 2:
The n-type and p-type sensing circuits are merged into a single sensor assembly that shares common components including the heating element, substrate, and signal processing electronics. This integration achieves wideband sensing capability while minimizing the increase in device complexity through shared infrastructure.
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
Enables accurate determination of the air:fuel ratio across a wide range, allowing for improved engine management, enhanced fuel economy, and reduced emissions by precisely controlling the combustion process in both rich and lean modes.
Implementation Method 1
The oxygen sensor has an n-type sensing circuit and a p-type sensing circuit that share a common electrode. The sensing current is a sum of a first current in the n-type sensing circuit and a second current in the p-type sensing circuit.
Implementation Method 2
The determining the temperature value may comprise sensing a heater resistance of a heater portion of the oxygen sensor. The sensing the heater resistance may comprise sensing a current through, and an applied voltage of, a heater circuit that includes the heater portion.
Data Source
AI summary
An oxygen sensor that has both an n-type oxygen sensing portion comprising an n-type semiconductor layer and a p-type oxygen sensing portion comprising an p-type semiconductor layer. The n-type sensing portion and the p-type sensing portion share the common electrode. The n-type semiconductor layer and the p-type semiconductor layer attach directly to the common electrode, but are not in physical contact with each other such that a lateral gap exists between the n-type semiconductor layer and the p-type semiconductor layer. The air:fuel ratio for a combustion process may be determined, using the same oxygen sensor, across a range of air:fuel values in both the rich and lean regions; as such, the oxygen sensor may act as a wideband oxygen sensor.