Fuel Injector Diagnostics Using Single Oxygen Sensor
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Solution Overview
Problem
Undetected failures in fuel injectors can lead to the malfunction or non-compliance of aftertreatment systems in internal combustion engines, as existing technologies lack effective methods for diagnosing fuel injector issues in real-time.
Innovation Solution
A system utilizing a single oxygen sensor and a processing subsystem to determine fuel injector faults by measuring air-fuel ratio changes and injection rate variations, with a controller commanding fuel injection rate changes and determining fault values based on thresholds and engine operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single oxygen sensor is used for fuel injector diagnostics, then device complexity is reduced, but measurement precision may be insufficient to detect fuel injector failures
Solution Approach 1:
The diagnostic process is segmented into multiple phases: baseline air-fuel ratio measurement, fuel injector activation, and post-activation measurement. This temporal segmentation allows a single oxygen sensor to effectively detect fuel injector failures by comparing AFR values before and after injector activation, resolving the contradiction between using few sensors and achieving high detection accuracy.
Solution Approach 2:
The system performs preliminary measurement of the baseline air-fuel ratio before activating the fuel injector. This preliminary action establishes a reference value that enables accurate detection of fuel injector failures through comparison, allowing a single sensor to achieve precision that would otherwise require multiple sensors.
2Measurement precision
If air-fuel ratio measurements are used to detect fuel injector failures, then measurement capability is improved, but reliability is reduced due to interference from aftertreatment components
Solution Approach 1:
The system dynamically adjusts the diagnostic timing to perform measurements during transient conditions immediately after fuel injector activation, before aftertreatment components like oxidation catalysts have time to significantly alter exhaust composition. This dynamic approach maintains measurement reliability while utilizing air-fuel ratio data.
Solution Approach 2:
The system performs preliminary baseline measurements of air-fuel ratio before aftertreatment effects become significant, establishing reference values that are less susceptible to interference from aftertreatment components during the diagnostic comparison process.
3Productivity
If the diagnostic procedure is performed quickly, then productivity is improved, but measurement precision deteriorates due to thermal response time limitations
Solution Approach 1:
The system performs a simplified diagnostic that captures the essential failure detection capability within a shorter time frame. By focusing on the most critical measurement comparisons (baseline vs. post-activation AFR) and accepting that the diagnostic may not capture all nuanced injector conditions, the system achieves acceptable precision while significantly improving diagnostic productivity.
Solution Approach 2:
The diagnostic procedure skips waiting for full thermal equilibrium of aftertreatment components by performing measurements during the transient phase immediately after fuel injector activation. This rushing through the diagnostic process before thermal effects fully develop maintains sufficient measurement precision while dramatically reducing diagnostic time and improving productivity.
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 early detection of fuel injector failures, preventing system malfunctions and ensuring compliance by accurately determining fault values through air-fuel ratio and injection rate analysis.
Implementation Method 1
an oxygen sensor disposed in the exhaust flow at a location downstream of the fuel injector
Data Source
AI summary
A method includes providing a system having a fluid flow, a fuel injector and an oxygen sensor disposed in the fluid flow, where the oxygen sensor is downstream of the fuel injector. The method includes determining a first air fuel ratio, changing an injection rate of the fuel injector and determining a second air fuel ratio, and determining a fault value for the fuel injector from the first air fuel ratio and the second air fuel ratio. The method further includes determining the fault value for the fuel injector by determining a difference between the first air fuel ratio and the second air fuel ratio, and by determining that the fault value is positive in response to the difference being lower than a passing threshold value. The method includes changing injection rates of the fuel injector for specified periods of time short enough to significant disruption of system temperatures.