Ignition Timing Control for Engine Speed Overshoot
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Solution Overview
Problem
In internal combustion engines without a battery as a power supply, a delay in activating the stepping motor during engine start can cause engine speed to overshoot the connecting rotation speed of the centrifugal clutch, leading to potential engine stall due to connection shock.
Innovation Solution
A control apparatus that includes a generator with both a main and auxiliary coil, where the ignition timing control means detects engine speed and retards ignition timing when it exceeds a predetermined threshold, using the auxiliary coil pulses to measure time, thereby stabilizing engine speed at idling without exceeding the centrifugal clutch's rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a generator without a battery is used as the power supply, then the device complexity is reduced, but the stepping motor activation is delayed causing engine speed to overshoot the centrifugal clutch connecting rotation speed
Solution Approach 1:
The system performs preliminary action by detecting engine speed and retarding ignition timing before the throttle valve closing action occurs. This proactive speed control prevents overshooting of the centrifugal clutch connecting rotation speed, compensating for the delayed stepping motor activation in batteryless generator-powered engines.
2Speed
If the stepping motor is activated immediately to close the throttle valve, then the engine speed can be controlled, but the engine may stall due to connection shock from centrifugal clutch
Solution Approach 1:
The system applies preliminary anti-action by retarding ignition timing to suppress engine speed increase before the throttle valve closing action occurs. This counteracts the potential for engine speed overshoot and prevents connection shock that would cause engine stall, ensuring reliable operation.
3Speed
If ignition timing is retarded to suppress engine speed increase, then the engine speed overshooting is prevented, but the ignition timing must be restored after a predetermined time
Solution Approach 1:
The system implements periodic action by temporarily retarding ignition timing for a predetermined period after engine start, then restoring it to normal timing. This time-limited control approach effectively manages engine speed during the critical startup phase while avoiding permanent modification of the ignition system.
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
Effectively suppresses engine speed overshooting and stabilizes the engine at idling speed, preventing stall and ensuring smooth operation by retarding ignition timing and restoring it after a predetermined time.
Implementation Method 1
a generator (45) as a power supply of the engine, the generator including a main generator coil (45a) for supplying power to the stepping motor, and an auxiliary generator coil (45b) for supplying power to an ignition device of the engine
Implementation Method 2
an output shaft connected via a centrifugal clutch to a load device
Data Source
AI summary
In a control apparatus for a general-purpose internal combustion engine including a generator as a power supply, the generator includes a main generator coil supplying power to the stepping motor, and an auxiliary generator coil supplying power to an ignition device of the engine. The apparatus includes ignition timing controller for, when starting the engine by a manual starter, detecting that an engine speed reaches or exceeds a predetermined engine speed not exceeding a connecting rotation speed of a centrifugal clutch to retard an ignition timing of the engine, thereby suppressing increase in the engine speed to less than the connecting rotation speed, and for restoring the ignition timing to its normal timing after a predetermined time elapses from start of retarding the ignition timing. Accordingly, it suppresses overshooting of an engine speed above the connecting rotation speed even if a delay occurs in closing a throttle valve by a delay in activating the motor.