Diesel Exhaust Fluid Injector Temperature Estimation via Solenoid Resistance
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Solution Overview
Problem
Diesel Exhaust Fluid (DEF) injectors in SCR systems are exposed to high temperatures, leading to potential damage and operational issues due to the lack of temperature monitoring and protection mechanisms.
Innovation Solution
An electronic control unit (ECU) is configured to estimate the temperature of the DEF injector by calculating electric resistance values from voltage and current measurements, and corrects for thermal contributions from exhaust gases, ambient air, and DEF, allowing for proactive cooling measures to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DEF injector is placed in direct contact with exhaust gases for injection, then the injection function is achieved, but the injector is heated to very high temperatures causing damage
Solution Approach 1:
The patent introduces an intermediary substance (DEF - Diesel Exhaust Fluid) that acts as a buffer between the hot exhaust gases and the injector components. The DEF is injected into the exhaust stream, absorbing thermal energy and creating a protective thermal barrier that reduces the temperature exposure of the injector needle and nozzle while maintaining the necessary injection function.
2Reliability
If a temperature sensor is added to monitor injector temperature, then temperature protection is achieved, but device complexity increases
Solution Approach 1:
The patent implements a self-service temperature monitoring approach where the ECU (Electronic Control Unit) calculates injector temperature indirectly using electrical parameters (voltage, current, resistance) already present in the injector's solenoid circuit. This eliminates the need for separate temperature sensors, as the existing electrical system serves the dual purpose of actuation and temperature monitoring.
Solution Approach 2:
The patent replaces the mechanical/physical temperature sensing approach (using temperature sensors) with an electrical measurement approach. By measuring the electrical resistance of the solenoid coil, which varies with temperature, the system substitutes direct thermal measurement with electrical property measurement, simplifying the hardware while achieving temperature monitoring.
3Reliability
If cooling measures are implemented to protect the injector, then thermal damage is prevented, but device complexity and cost increase
Solution Approach 1:
The patent converts the harmful high-temperature exhaust gases into a beneficial cooling agent. By injecting DEF into the exhaust stream, the endothermic decomposition of urea and the evaporation process absorb excessive heat from the exhaust gases, thereby cooling the injector components. The harmful thermal energy is transformed into a cooling mechanism that protects the injector without requiring external cooling systems.
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
The solution effectively protects the DEF injector from thermal damage by accurately estimating its temperature and activating cooling phases when necessary, reducing the risk of malfunctions and extending the injector's lifespan without requiring complex cooling systems.
Implementation Method 1
a solenoid (e.g. electric coil) that can be energized to generate a magnetic field that moves the needle to open the nozzle
Implementation Method 2
Since a correlation exists between the electric resistance of the injector solenoid and its own temperature
Data Source
AI summary
A control apparatus is disclosed for a diesel exhaust fluid injector located in an exhaust pipe of a diesel internal combustion engine. The control apparatus includes an electronic control unit configured to: energize a solenoid of the injector to perform a diesel exhaust fluid injection; determine an electric voltage value indicative of the electric voltage applied to the injector solenoid during the diesel exhaust fluid injection; determine an electric current value indicative of the electric current flowing through the injector solenoid during the diesel exhaust fluid injection; calculate an electric resistance value of the injector solenoid as a function of the determined electric voltage value and the electric current value; and estimate an injector temperature value as a function of the calculated electric resistance value.