Two-Stroke Engine Ignition Control for Overspeed Prevention
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Solution Overview
Problem
In two-stroke internal combustion engines mounted on handheld working machines, excessive rotational speed can lead to self-ignition and uncontrollable engine operation due to advanced ignition timing, potentially causing engine damage.
Innovation Solution
The ignition timing is advanced to a specific BTDC angle to prevent self-ignition, and a misfire stroke is introduced after proper combustion to reduce the force given to the piston, thereby preventing continuous rotational speed increase and maintaining control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the ignition timing is advanced from the top dead center position to increase rotational speed, then the engine acceleration improves, but self-ignition occurs causing loss of control
Solution Approach 1:
The ignition timing is made dynamically adjustable based on rotational speed conditions. The control device switches between a first ignition timing (larger advanced angle) for normal operation and a second ignition timing (smaller advanced angle) when rotational speed exceeds the predetermined value, allowing the system to adapt to changing conditions and prevent self-ignition while maintaining acceleration capability
Solution Approach 2:
The ignition control device monitors rotational speed and uses this feedback to determine ignition timing. When the rotational speed exceeds the predetermined value, the control device automatically selects the second ignition timing with smaller advance angle, creating a closed-loop control system that prevents self-ignition while maintaining engine performance
2Reliability
If the ignition timing is retarded to near top dead center to prevent continuous speed increase, then rotational speed control improves, but engine power decreases
Solution Approach 1:
The ignition timing is made dynamically adjustable based on rotational speed conditions. The control device switches between a first ignition timing (larger advanced angle) for normal operation and a second ignition timing (smaller advanced angle) when rotational speed exceeds the predetermined value, allowing the system to adapt to changing conditions and prevent self-ignition while maintaining acceleration capability
Solution Approach 2:
The ignition timing parameter is changed based on rotational speed conditions. By switching between two distinct ignition timing values (first and second ignition timings with different advanced angles), the system optimizes engine performance across different operating conditions, maintaining power when needed and preventing overspeed when necessary
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 solution effectively prevents the engine from over-speeding and maintains control by ensuring proper combustion and reducing the risk of engine damage from self-ignition, ensuring stable operation.
Implementation Method 1
an ignition plug disposed in an upper portion of the cylinder; and an ignition control device activating the ignition plug
Implementation Method 2
Effective activation of the ignition plug ignites fuel-air mixture in the cylinder to combust it
Implementation Method 3
inflation of the combusted air gives a force to the piston so as to move the piston from a top dead center position to a bottom dead center position
Data Source
AI summary
An internal combustion engine according to the present invention has an ignition control device. When a rotational speed of the internal combustion engine increases beyond a predetermined rotational over speed, the ignition control device advances an ignition timing of the ignition plug to a first BTDC angle where proper combustion is performed. Further, the ignition control device performs a misfire stroke or strokes of the ignition plug in one rotation or rotations of the crankshaft after the proper combustion is performed by activating the ignition plug at the first BTDC angle.