SCR Temperature Sensor Diagnosis via Controlled Heating Cycles
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Solution Overview
Problem
Temperature sensors in SCR exhaust-gas aftertreatment systems face challenges in diagnosing faults, particularly in identifying 'stuck' sensors due to low temperature dynamics and thermal insulation, which complicates the detection of errors in temperature readings.
Innovation Solution
A method involving the activation of the heating device outside normal temperature conditions to assess the temperature sensor's signal change, checking if the expected value is reached within a predefined time, and evaluating the temperature gradient after deactivation to distinguish between sensor and heating device faults, allowing for independent diagnosis without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thermal insulation is applied to the reducing agent tank to maintain temperature, then heat loss is reduced and energy efficiency is improved, but temperature dynamics are dampened and fault detection capability deteriorates
Solution Approach 1:
The diagnostic method activates the heating device in advance under controlled conditions (engine off, ambient temperature above freezing) to create a known thermal stimulus before attempting to detect sensor faults. This preliminary action establishes a baseline temperature change pattern that should be observed if the sensor is functioning correctly, enabling differentiation between insulation effects and sensor failures.
Solution Approach 2:
The system monitors the temperature signal from the sensor during and after heating device activation, comparing the observed temperature dynamics against expected patterns. This feedback mechanism allows the system to identify when the sensor fails to respond appropriately to thermal changes, indicating a fault condition, while accounting for the thermal insulation's damping effect on temperature fluctuations.
2Reliability
If the heating device is activated continuously to prevent freezing, then reliability of the reducing agent delivery is improved, but energy consumption increases
Solution Approach 1:
Instead of continuous heating, the system employs periodic diagnostic heating cycles where the heating device is activated for predetermined periods based on detected temperature conditions. The control method determines specific activation moments when the engine is off and ambient temperature is above freezing, creating periodic rather than continuous heating operation. This reduces overall energy consumption while maintaining reliability by ensuring the reducing agent remains liquid when needed.
Solution Approach 2:
The system changes operational parameters of the heating device based on detected temperature conditions and diagnostic results. Heating activation duration, intensity, and frequency are adjusted according to the actual thermal state of the reducing agent and environmental conditions. This parameter adaptation allows the system to maintain reliable reducing agent delivery while optimizing energy consumption by avoiding unnecessary heating when temperatures are already adequate.
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
This method enables reliable temperature sensor diagnosis, independent of external conditions and reducing agent fill level, and differentiates between faulty sensors and heating devices by analyzing temperature signal changes and drops, ensuring accurate system operation.
Implementation Method 1
heating systems which melt the frozen liquid in the tank and change said reagent into a liquid, that is to say flowable, state of aggregation
Implementation Method 2
the signal of the temperature sensor, proceeding from a start temperature, changes by a predefined expected value within a predefined time period upon activation of the heating device
Data Source
AI summary
The present disclosure describes a method for checking the signal of a temperature sensor in an exhaust-gas aftertreatment system for an internal combustion engine. The method may include: in an operating state which does not require heating of the reducing agent, activating the heating device for the purposes of checking the temperature sensor; determining whether the signal of the temperature sensor changes by a predefined expected value (ΔT) within a predefined time period (Δt2); provisionally identifying the temperature sensor as fault-free if it does; deactivating the heating device; determining whether the signal of the temperature sensor reaches the start temperature (T0) again within a time period (Δt3); and confirming the temperature sensor as fault-free if it does.