Two-Stroke Engine Ignition Timing Control for Kickback Prevention
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Solution Overview
Problem
Two-stroke engines often stall at low engine speeds due to advanced ignition timing causing kickback, which is influenced by both ignition timing and combustion strength, and the effectiveness of combustion chamber scavenging.
Innovation Solution
The ignition timing is set based on engine speed and the number of engine cycles since the last combustion, with different ignition timings for different operating states and speed ranges to prevent kickback, using an ignition map with characteristic lines that adjust ignition timing to avoid early ignition and ensure optimal combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If ignition timing is advanced to improve combustion efficiency, then power output increases, but kickback occurs causing engine stalling
Solution Approach 1:
The ignition timing is made dynamic by selecting from multiple characteristic lines based on the number of engine cycles since last combustion. This allows the ignition timing to adapt automatically to changing combustion conditions, advancing timing when scavenging is effective (higher power) and retarding it when kickback risk increases (maintaining stability).
Solution Approach 2:
The patent changes the ignition timing parameter based on the engine cycle history and scavenging effectiveness. By monitoring the number of cycles since last combustion and selecting appropriate characteristic lines, the system optimizes ignition timing to balance power output and prevent kickback-induced stalling.
2Device complexity
If simple ignition timing control is used to reduce device complexity, then control system simplicity increases, but engine stalling occurs at low speeds
Solution Approach 1:
The control system uses information already available from the engine operation (engine cycles since last combustion, current operating state) to automatically select the appropriate ignition timing characteristic line. No additional sensors or complex control mechanisms are needed - the system serves itself by utilizing existing operational data.
Solution Approach 2:
The ignition timing control is segmented into multiple characteristic lines, each optimized for specific combustion conditions. The control unit selects the appropriate segment (characteristic line) based on the number of cycles since last combustion, providing simple yet effective adaptation without increasing overall system complexity.
3Productivity
If ignition timing is advanced at low engine speeds to improve combustion, then combustion efficiency increases, but kickback probability increases causing stalling
Solution Approach 1:
The system uses feedback from engine operation (number of cycles since last combustion as an indicator of scavenging effectiveness) to adjust ignition timing. When feedback indicates good scavenging, timing is advanced for efficient combustion; when feedback suggests poor scavenging, timing is retarded to prevent kickback.
Solution Approach 2:
The control unit preliminarily determines the appropriate characteristic line based on the number of engine cycles since last combustion before setting the actual ignition timing. This preliminary selection ensures that the ignition timing is pre-adjusted to match current combustion conditions, preventing kickback before it occurs.
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 stabilizes engine operation by optimizing ignition timing, preventing kickback and ensuring stable engine running at low speeds without requiring additional sensors, by considering both engine speed and the number of engine cycles since the last combustion.
Implementation Method 1
A spark plug projects into the combustion chamber and ignites a fuel/air mixture in the combustion chamber
Implementation Method 2
The piston drives in rotation a crankshaft
Data Source
AI summary
A two-stroke engine has a cylinder with a combustion chamber delimited by a reciprocating piston, wherein the piston drives in rotation a crankshaft, and wherein a spark plug projects into the combustion chamber and ignites a fuel/air mixture. The two-stroke engine further has devices for supplying fuel and combustion air to the combustion chamber and a control unit that determines the ignition timing based on an ignition map. The ignition map indicates the ignition timing as a function of the engine speed for at least one first and one second operating states and for at least one first and one second engine speed ranges. The engine is controlled in that for an engine cycle the ignition timing is set in the second operating state at least within the first engine speed range based on the engine speed and on the number of engine cycles since the last combustion.