Fuel Shutoff System Using Ignition Coil Induction
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Solution Overview
Problem
Small internal combustion engines experience backfiring due to unburned fuel being forced into heated mufflers after the engine is shut off, causing noise and potential damage, and existing solutions require additional circuitry for fuel flow interruption.
Innovation Solution
A fuel control system that uses a movable control member and electromagnetic coil to restrict fuel flow to the carburetor, energized by induced current from the primary ignition coil when the kill switch is activated, with a capacitor and diode circuit to ensure positive voltage and maintain the control member in the extended position, preventing fuel flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a kill switch is used to interrupt spark plug operation, then engine operation is quickly stopped, but unburned fuel continues to be drawn into the cylinder and forced into the heated muffler causing backfiring
Solution Approach 1:
The fuel flow control device is activated immediately upon kill switch closure, before the engine has fully stopped rotating. The control member moves to the extended position to restrict fuel flow to the carburetor, preventing unburned fuel from being drawn into the cylinder and causing backfiring in the heated muffler.
2Reliability
If a storage capacitor or battery is used to power the fuel flow interrupt device, then fuel flow can be restricted, but additional circuitry such as alternators must be included to charge the battery
Solution Approach 1:
The system uses the existing induced current from the primary ignition coil during engine operation to charge the storage capacitor. When the kill switch is activated, the capacitor discharges to power the electromagnetic coil that moves the control member, eliminating the need for separate charging circuitry like alternators.
Solution Approach 2:
The storage capacitor serves multiple functions: it stores energy during normal engine operation from the induced current, and then discharges to power the fuel flow interruption mechanism when the kill switch is activated. This multi-functionality eliminates the need for separate charging and power supply systems.
3Object-generated harmful factors
If the control member is moved to restrict fuel flow, then backfiring is prevented, but the control member must be held in position requiring additional electromagnetic energy
Solution Approach 1:
The storage capacitor is charged in advance during normal engine operation using the induced current from the primary ignition coil. When fuel flow restriction is needed, the capacitor discharges to provide the electromagnetic energy to move and hold the control member, eliminating the need for continuous energy input during the restricted state.
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 prevents backfiring by immediately restricting fuel flow to the carburetor upon engine shutdown, utilizing existing energy and reducing the need for additional circuitry, thus protecting the muffler and improving engine shutdown efficiency.
Implementation Method 1
the rotating flywheel within the engine induces current within a primary ignition coil
Implementation Method 2
the induced current within the primary ignition coil induces a voltage across a secondary ignition coil
Data Source
AI summary
A fuel control system that has a fuel control device to control the flow of fuel to a carburetor of an internal combustion engine. The fuel control device includes a control member that is movable between a first position and a second position to control the flow of fuel into a carburetor. When a kill switch within the fuel control system is closed, induced current from a primary ignition coil within the internal combustion engine is fed through an electromagnetic coil, causing the fuel flow control device to interrupt the supply of fuel to the carburetor. Thus, when an operator desires to stop the internal combustion engine, the kill switch closes and the fuel control device interrupts the supply of fuel to the carburetor to prevent backfires.