Urea Injector Blockage Detection via Coil Inductance Measurement
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Solution Overview
Problem
Existing methods for detecting a blocked urea injector in SCR systems are inadequate as they do not allow for rapid malfunction detection before the system is started up, leading to potential ammonia leaks and excessive NOx emissions.
Innovation Solution
A method that involves measuring the intensity of current through a measurement resistance over time to determine the inductance of the solenoid coil, allowing for differentiation between blocked open and closed positions of the injector, using a microcontroller to compute and compare the inductance to threshold values, enabling early detection and appropriate action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a NOx sensor is positioned downstream of the SCR catalyst to detect injector malfunction, then the nitrogen oxide level can be measured, but the detection is delayed due to catalyst saturation and chemical reaction inertia
Solution Approach 1:
The patent applies preliminary action by measuring the voltage at the injector terminals before activating the SCR system to detect potential blockages. This early detection prevents the need to wait for catalyst saturation and chemical reactions, eliminating the time delay inherent in downstream NOx sensor methods. The voltage measurement is performed in advance, allowing the system to identify injector failures before they impact SCR performance.
2Reliability
If the SCR system is activated multiple times to test injector function, then diagnosis can be performed, but ammonia leaks and excessive NOx emissions occur during the testing period
Solution Approach 1:
The patent replaces the mechanical/chemical testing method (activating the SCR system multiple times with urea injection) with an electrical measurement method. By measuring the voltage at the injector terminals, the system can diagnose injector blockages without physically activating the SCR process, thereby eliminating ammonia leaks and NOx emissions that would otherwise occur during diagnostic testing.
3Reliability
If voltage measurement at injector terminals is performed using prior art methods, then blocked injectors can be detected, but the method cannot distinguish between blocked open and blocked closed positions
Solution Approach 1:
The patent uses feedback by continuously monitoring the voltage signal at the injector terminals during activation and analyzing its characteristics. The voltage waveform provides feedback about the injector's operational state, allowing the system to distinguish between blocked open and blocked closed positions based on the specific voltage patterns observed during the activation cycle.
Solution Approach 2:
The patent metaphorically applies the principle of detecting state changes through signal characteristics. Just as color changes indicate different states, the voltage signal characteristics (magnitude, waveform, timing) change to indicate different blockage positions. By analyzing these electrical signal variations, the system can determine whether the injector is blocked open or blocked closed.
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 rapid determination of injector blockage before system startup, preventing ammonia leaks and excessive NOx emissions, and allowing for timely intervention to resolve blockages without system activation.
Implementation Method 1
an electromagnetic solenoid with a coil having a resistance and an inductance, passed through by a power supply current of maximum intensity
Implementation Method 2
Measurement by the microcontroller of the intensity of the current passing through the measurement resistance
Data Source
AI summary
A method for determining if an injector (10) is in a blocked state, the injector including a coil of resistance R and of inductance L, passed through by a power supply current of maximum intensity (Imax), and powered by a voltage E, the method includes:controlling the opening of the injector,measuring the intensity I passing through a measurement resistance r as a function of time t,determining a necessary duration τ to reach a predetermined intensity value (Ipred), lower than the maximum intensity (Imax),computing the inductance L as a function of the necessary duration,if L≧Lth, then the injector is blocked in the closed position, otherwiseif L<Lth, the injector is blocked in the open position, with Lth being a threshold value of the inductance.