Lambda Probe Signal Analysis for Online Injector Diagnosis
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Solution Overview
Problem
Current diagnostic methods for vehicle engines, such as OSC diagnosis and injector tests, are primarily offline and can disturb the vehicle's operation, failing to detect high-pressure injection system malfunctions across various operating points, and are not perceivable by the driver during online diagnosis.
Innovation Solution
An online diagnosis method using pre-catalyst and post-catalyst lambda probes to monitor sensor signals and determine the oxygen storage capacity and residual oxygen content, allowing for a plausibility check and quantitative calculation of fuel-specific indicators, enabling preventive diagnosis without driver disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offline diagnostic methods (OSC diagnosis, injector tests) are used, then catalyst oxygen storage capacity can be determined and injector defects can be detected, but the vehicle operation is disturbed and driver perception occurs
Solution Approach 1:
The system performs preliminary assessment of diagnostic data during normal operation, preparing diagnostic information in advance without requiring active driver intervention or disturbing vehicle operation. Lambda probe signals are continuously monitored and evaluated to detect injector issues before they become critical problems.
2Speed
If active diagnosis during vehicle operation is implemented, then real-time detection is possible, but driver disturbance and irritation occur
Solution Approach 1:
The diagnostic system operates autonomously using existing lambda probe signals already present in the vehicle's exhaust gas monitoring system. No additional active testing or driver actions are required - the system self-evaluates injector performance by analyzing the temporal characteristics of lambda probe signals during normal vehicle operation.
3Device complexity
If limited operating point diagnosis is used, then diagnostic complexity is reduced, but high-pressure injection system malfunctions dependent on operating point cannot be detected
Solution Approach 1:
The diagnostic method utilizes the existing lambda probes (both pre-catalyst and post-catalyst) that are already installed for emission monitoring purposes. By analyzing the temporal duration of lambda probe signal transitions during fuel injection events, the system achieves multi-functionality - the same sensors serve both emission monitoring and injector diagnostics across various operating conditions without requiring additional specialized sensors.
4Measurement precision
If online diagnosis with plausibility checks is implemented, then sensor signal reliability is verified and fuel-specific key indicators are calculated, but computational requirements increase
Solution Approach 1:
The system employs feedback by comparing the measured temporal duration between pre-catalyst and post-catalyst lambda probe signals with expected values. This feedback mechanism enables plausibility checks of sensor signals and detection of deviations indicating injector defects, while utilizing the existing control unit's processing capabilities without requiring excessive computational resources.
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 timely detection of injector issues and ensures the functionality of lambda probes, allowing for quantitative determination of the stoichiometric fuel-air ratio and fuel-specific key indicators during vehicle operation, preventing component failures and maintaining engine performance.
Implementation Method 1
the oxygen storage capacity (OSC), thus the capability of converting harmful exhaust gases, is determined
Implementation Method 2
Both lambda probes emit corresponding sensor signals
Implementation Method 3
a catalytic converter and a lambda-controlled internal combustion engine
Implementation Method 4
the capability of converting harmful exhaust gases
Implementation Method 5
a lambda-controlled internal combustion engine
Data Source
AI summary
A method for the onboard diagnosis in a vehicle having a catalytic convertor and a lambda-controlled internal combustion engine in the running operation of the vehicle, includes determining the currently maximum possible oxygen storage capacity of the catalytic convertor as well as a measured temporal duration between the lean spike of the pre-catalyst lambda probe and the post-catalyst lambda probe takes place by means of an OSC diagnosis. The method also includes determining a theoretical residual oxygen content and determining a theoretical temporal duration. When the quotient between the measured temporal duration (Δt) and the theoretical temporal duration (Δttheo) lies within a predefined range delimited by a first and a second threshold value (SW1; SW2), thus:SW1≤ΔtΔttheo≤SW2,it is determined that the pre-catalyst lambda probe and the post-catalyst lambda probe operate without flaw.