Spark Plug Soot Detection via Sense Resistor Voltage Monitoring
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Solution Overview
Problem
Existing methods for determining soot accumulation on spark plugs in spark ignited engines often result in engine misfires, leading to increased hydrocarbon emissions, and do not allow for soot removal before a misfire occurs.
Innovation Solution
A system that monitors the voltage across a sense resistor during the ignition dwell period to detect carbonaceous soot on the spark plug center electrode, allowing for early detection and removal of soot before a misfire occurs, using a controller to adjust engine operation and increase temperature and pressure in the cylinder to oxidize the soot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If additional fuel is injected to vaporize in the cylinder for cold starting, then the air-fuel mixture can be ignited, but soot or conductive deposits form on the spark plug center electrode, shunting the spark gap and reducing spark possibility
Solution Approach 1:
The system performs preliminary detection of soot accumulation on the spark plug by monitoring voltage across a sense resistor during the ignition dwell period. When soot is detected before it causes misfire, the controller activates a soot removal mode by enriching the air-fuel mixture and increasing cylinder temperature, thereby removing soot proactively before it compromises spark reliability
Solution Approach 2:
The system continuously monitors the voltage signal from the sense resistor during ignition dwell to detect changes indicative of soot accumulation. This feedback loop allows the controller to detect soot formation early and activate removal operations before the soot reaches levels that would cause misfire or spark failure
2Measurement precision
If engine misfire is used to detect soot accumulation on spark plugs, then soot detection is possible, but engine emissions degrade with increased hydrocarbon emissions
Solution Approach 1:
The system detects soot accumulation by monitoring voltage changes during the ignition dwell period before misfire occurs. By identifying soot presence early through the sense resistor voltage signal, the controller can activate soot removal mode proactively, preventing misfire and the associated hydrocarbon emissions that would result from incomplete combustion
Solution Approach 2:
The system converts the potentially harmful effect of soot accumulation (which would cause misfire and emissions) into a beneficial early warning signal. The voltage change across the sense resistor during ignition dwell serves as an early indicator of soot presence, allowing the system to take corrective action before emissions deteriorate
3Loss of time
If voltage across sense resistor is monitored during ignition dwell period, then soot accumulation can be detected early, but system complexity increases
Solution Approach 1:
The sense resistor serves multiple functions: it limits current during normal operation and simultaneously acts as a detection element for soot accumulation. By monitoring the voltage across this existing component during the ignition dwell period, the system achieves early soot detection without adding separate sensing hardware, thereby minimizing system complexity
Solution Approach 2:
The ignition system's own electrical characteristics during the dwell period are used for detection. The voltage signal naturally present across the sense resistor during normal ignition operation contains information about soot accumulation, eliminating the need for separate active sensing mechanisms and reducing overall system 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
This approach allows for the detection and removal of soot without causing engine misfires, improving engine emissions by reducing hydrocarbon emissions and providing an indication of spark duration to prevent misfires.
Implementation Method 1
monitoring voltage or current of a sense resistor during an ignition dwell period, it may be possible to determine an amount of carbonaceous soot or other conductive deposits that may be present on the center electrode ceramic of a spark plug
Implementation Method 2
an ignition coil including primary and secondary coils
Implementation Method 3
a spark plug in electrical communication with the secondary coil
Implementation Method 4
The system attempts to remove the carbonaceous soot from the spark plug electrode by increasing temperature and pressure in the cylinder in which the spark plug supplies spark
Data Source
AI summary
A system for monitoring and cleaning a spark plug is disclosed. In one example, an amount of carbonaceous soot at the center electrode ceramic of the spark plug is determined in response to a voltage of a sense resistor that is in electrical communication with the spark plug. The system may institute spark plug cleaning after carbonaceous soot is detected so that the possibility of engine misfire may be reduced.