Diagnostic Circuit for SCR Injector Voltage Suppressor
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Solution Overview
Problem
Existing diagnostic circuits for fluid injectors, particularly selective catalytic reduction (SCR) dosing injectors, lack reliable compatibility with various engine control units (ECUs) due to energy dissipation issues during coil discharge, leading to potential ECU overheating and reliability problems.
Innovation Solution
A diagnostic circuit and method that measure and compare voltage or current characteristics in the drive circuit of a fluid injector to determine the functionality of a PN junction voltage suppressor, allowing for reliable discharge of stored energy without overloading ECUs, and utilizing a shared cooling system to maintain the voltage suppressor within a safe operating temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage suppressor is used to discharge stored energy in the coil, then the reliability of the injector is improved, but the temperature of the voltage suppressor increases causing potential failure
Solution Approach 1:
A diagnostic circuit is introduced as an intermediary component to monitor the voltage across the PN junction of the voltage suppressor. This diagnostic circuit detects whether the voltage exceeds a predetermined threshold, indicating that the voltage suppressor is actively discharging stored energy and generating excessive heat. By providing this intermediate detection layer, the system can identify overheating conditions before they cause failure, resolving the contradiction between maintaining reliability through energy discharge and preventing thermal damage.
2Reliability
If the PN junction discharges all stored energy quickly, then the reliability check is improved, but the voltage suppressor may overheat and fail
Solution Approach 1:
The diagnostic circuit provides feedback by continuously monitoring the voltage across the PN junction and comparing it against a predetermined threshold. When the voltage exceeds the threshold, indicating excessive energy discharge and potential overheating, the system receives feedback about this condition. This feedback mechanism allows the system to detect problematic discharge events and can trigger appropriate responses (such as warning signals or operational adjustments) to prevent cumulative thermal damage, thus preserving the operational lifespan of the voltage suppressor while maintaining reliability monitoring.
3Reliability
If a diagnostic circuit is added to monitor PN junction functionality, then the reliability monitoring is improved, but the device complexity increases
Solution Approach 1:
The diagnostic circuit is designed with multi-functionality to minimize added complexity. It serves multiple purposes: monitoring the voltage across the PN junction, comparing it against a predetermined threshold, detecting discharge events, and providing diagnostic information about voltage suppressor health. By consolidating these functions into a single integrated diagnostic module rather than separate components, the circuit achieves comprehensive reliability monitoring while limiting the increase in overall device complexity.
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
Enhances the reliability of SCR dosing injectors by ensuring compatible operation with a broader range of ECUs, reducing the risk of ECU overheating and increasing engine reliability through efficient energy dissipation and shared cooling.
Implementation Method 1
determine whether a PN junction is working to discharge electrical energy stored in the coil of the fluid injector
Implementation Method 2
utilizing a shared cooling system to maintain the voltage suppressor within a safe operating temperature
Data Source
Figure 1
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Figure 4
AI summary
A diagnostic circuit arranged to measure an electrical characteristic (334, 430) in a drive circuit (300) of a coil (110) of a fluid injector and compare the measured electrical characteristic with another electrical characteristic to determine whether a PN junction (130) is working to discharge electrical energy in the coil (110) of the fluid injector, in particular a selective catalytic reduction dosing injector.