Multi-Cylinder Engine Oxygen Sensing for Catalyst Diagnostics
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Solution Overview
Problem
Existing multi-cylinder engines face challenges in detecting catalyst deterioration and cylinder-to-cylinder imbalance in air-fuel ratio without using an air-fuel ratio sensor, especially when the air supply to cylinders varies.
Innovation Solution
The engine unit employs a pre-catalyst oxygen sensor group and a post-catalyst oxygen sensor to detect oxygen percentages in the exhaust gas, allowing the control device to determine cylinder-to-cylinder air-fuel ratio imbalance and catalyst deterioration without an air-fuel ratio sensor, using individual oxygen sensors in some or all exhaust pipes and a pre-catalyst oxygen sensor in the manifold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pre-catalyst oxygen sensor group and post-catalyst oxygen sensor are used to detect oxygen percentages, then catalyst deterioration and cylinder-to-cylinder air-fuel ratio imbalance can be detected, but an air-fuel ratio sensor cannot be used
Solution Approach 1:
The oxygen sensing function is segmented into multiple individual oxygen sensors, with each sensor monitoring a specific exhaust pipe. This segmentation allows the system to detect air-fuel ratio conditions in individual cylinders while using simpler oxygen sensors instead of complex air-fuel ratio sensors.
Solution Approach 2:
The oxygen sensors serve multiple functions: they detect oxygen percentage in exhaust gases, enable catalyst deterioration detection, identify cylinder-to-cylinder air-fuel ratio imbalance, and provide data for fuel injection control. This multi-functionality replaces the need for dedicated air-fuel ratio sensors.
2Measurement precision
If individual oxygen sensors are provided in some or all exhaust pipes, then cylinder-to-cylinder air-fuel ratio imbalance can be detected, but the number of sensors increases
Solution Approach 1:
Individual oxygen sensors are selectively placed in specific exhaust pipes based on the need to monitor particular cylinders. The system can configure sensors in all exhaust pipes for complete monitoring or in selected pipes for specific diagnostic needs, allowing flexible adaptation to different detection requirements.
Solution Approach 2:
The pre-catalyst oxygen sensor group combines multiple individual oxygen sensors into a unified monitoring system. The control device integrates data from these sensors to comprehensively detect catalyst deterioration and air-fuel ratio imbalance, reducing the need for separate dedicated sensors for each function.
3Productivity
If oxygen levels are monitored to detect catalyst deterioration and air-fuel ratio imbalance, then precise fuel control is enabled, but the system must process multiple sensor signals
Solution Approach 1:
The control device continuously receives oxygen percentage signals from individual oxygen sensors and the post-catalyst oxygen sensor, processes this feedback information to detect catalyst deterioration and air-fuel ratio conditions, and adjusts fuel injection amounts accordingly. This closed-loop feedback enables precise fuel control while systematically managing the processing of multiple sensor signals.
Solution Approach 2:
The system performs preliminary detection of oxygen percentages and air-fuel ratio conditions before making fuel control adjustments. The control device analyzes sensor data to identify catalyst deterioration or cylinder imbalance conditions in advance, allowing proactive fuel injection corrections to maintain optimal engine performance.
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
Accurately detects catalyst deterioration and cylinder-to-cylinder air-fuel ratio imbalance by monitoring oxygen levels, enabling precise fuel control and notification of deviations, thus maintaining optimal engine performance.
Implementation Method 1
a pre-catalyst oxygen sensor group for detecting a percentage of oxygen in the exhaust gas
Implementation Method 2
a post-catalyst oxygen sensor for detecting a percentage of oxygen in the exhaust gas having passed through the catalyst
Implementation Method 3
the catalyst being disposed downstream of the merge portion in a flow direction of the exhaust gas
Data Source
AI summary
An engine unit, including: a plurality of cylinders respectively cooperating with a plurality of pistons; a plurality of individual exhaust pipes configured to allow exhaust gases from the plurality of cylinders to respectively flow therethrough; an exhaust manifold, including a merge portion into which the individual exhaust pipes merge, and a catalyst disposed downstream thereof; a group of pre-catalyst oxygen sensors disposed between the cylinders and the catalyst for all paths of the exhaust gases flowing into the catalyst from the plurality of cylinders; a post-catalyst oxygen sensor disposed in the exhaust manifold, downstream of the catalyst in the flow direction of the exhaust gas; and a control device configured to detect a cylinder-to-cylinder imbalance in air-fuel ratio between the plurality of cylinders, and a deterioration of the catalyst, using detection results of pre-catalyst and post-catalyst oxygen sensors without using an air-fuel ratio sensor.