Engine Ignition Timing Control for Starting Speed
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Solution Overview
Problem
Existing engine-operated working machines, such as cutters and chainsaws, face challenges in controlling engine speed during starting, leading to increased risk of spark plug fouling and excessive wear on brake mechanisms and centrifugal clutches, as existing solutions either compromise startability or fail to maintain optimal combustion.
Innovation Solution
An engine with a carburetor and ignition system that includes an engine-speed detecting unit, throttle-opening detecting unit, and control unit to intermittently adjust ignition timing from a general angle to a first and then a second angle, preventing excessive speed increases and maintaining optimal combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the throttle valve is fully opened for starting, then the startability of the engine is improved, but the engine speed suddenly increases causing the centrifugal clutch to engage and the front tool to rotate
Solution Approach 1:
The ignition timing is intermittently advanced from the first angle (extreme retardation) to a second angle (less retardation) at predetermined intervals during starting. This periodic adjustment allows the engine speed to be controlled in stages, preventing sudden increases while maintaining sufficient combustion to improve startability.
Solution Approach 2:
The ignition timing angle is changed from a general angle to a first angle (extreme retardation) when the throttle is opened for starting, and then intermittently adjusted to a second angle. This parameter change controls the combustion timing to regulate engine speed increases during starting.
2Speed
If the throttle valve is slightly opened for starting, then the engine speed increase is prevented, but the startability is reduced
Solution Approach 1:
The ignition timing is intermittently advanced at predetermined intervals during starting, providing periodic combustion boosts that improve startability without requiring the throttle to be fully opened, thus preventing excessive engine speed increases.
Solution Approach 2:
The ignition timing is changed from extreme retardation (first angle) to less retardation (second angle) at intervals, dynamically adjusting combustion timing to enhance startability while controlling engine speed increases.
3Ease of operation
If the brake mechanism is operated to prevent revolutions of the edge tool, then the front tool rotation is prevented, but the centrifugal clutch and clutch housing slide on each other generating heat and causing wear
Solution Approach 1:
The ignition timing is retarded to a first angle to prevent excessive engine speed increases at the beginning of starting, which preliminarily prevents the centrifugal clutch from engaging and the front tool from rotating, avoiding the need for brake operation and subsequent clutch wear.
Solution Approach 2:
The ignition timing is intermittently advanced during starting, providing controlled combustion that maintains engine operation without excessive speed increases, preventing centrifugal clutch engagement and eliminating the need for brake intervention.
4Speed
If the ignition timing is extremely retarded to control engine speed, then the engine speed increase is suppressed, but the spark plug may be fouled due to unburned gas causing the engine to stop
Solution Approach 1:
The ignition timing is intermittently advanced from the first angle (extreme retardation) to a second angle (less retardation) at predetermined intervals during starting. This periodic adjustment ensures that combustion occurs at appropriate timing, preventing unburned gas accumulation and spark plug fouling while maintaining control over engine speed increases.
Solution Approach 2:
The ignition timing angle is dynamically changed from extreme retardation (first angle) to less retardation (second angle) at intervals, adjusting combustion timing to prevent both excessive engine speed increases and spark plug fouling from unburned gas.
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 improves startability, prevents engine stoppages due to spark plug fouling, and reduces the burden on brake mechanisms and centrifugal clutches by controlling engine speed within predetermined limits during starting.
Implementation Method 1
an ignition device configured to ignite the air-fuel mixture in the cylinder
Data Source
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Figure 5~6
AI summary
To provide an engine-operated working machine capable of preventing an engine from stopping due to fouling on a spark plug while suppressing an increase in the speed of the engine during starting. The engine is configured such that, during the starting of the engine, when it is being detected that throttle opening has been set at a starting position, if it is detected that the engine speed has exceeded a predetermined speed slightly lower than a speed when a centrifugal clutch becomes an engaged state, a control unit retards the ignition timing from a general angle (for example, 25 degrees) to a first angle (-25 degrees) BTDC, and then advances the ignition timing to a second angle (+10 degrees) at predetermined intervals (for example, at intervals of 10 cycles), and holds the ignition timing at the second angle for a predetermined time period (for example, a time period corresponding to 1 cycle), thereby preventing the engine from stopping due to fouling on the spark plug while suppressing the engine speed at the speed when the centrifugal clutch becomes the engaged state, or less.