Outboard Motor Controller Over-Revolution Backfire Prevention
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Solution Overview
Problem
In outboard motors, after fuel reduction to prevent over-revolution, a lean air-fuel ratio persists, leading to potential backfires as combustion continues into the intake stroke, causing unwanted combustion sounds.
Innovation Solution
A controller system that monitors engine speed, suspends fuel and ignition during over-revolution states and gradually reinstates them after the state is recovered, ensuring a stable air-fuel ratio by coordinating fuel injection and ignition timing across multiple cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel supply is suspended during over-revolution state, then engine speed is lowered and over-revolution is prevented, but a lean state persists after fuel supply is released causing backfire
Solution Approach 1:
The controller suspends ignition in advance before releasing fuel supply, preventing the lean mixture from causing backfire. By anticipating the potential harm of lean combustion and preemptively disabling ignition, the system avoids backfire while maintaining the benefit of over-revolution protection.
Solution Approach 2:
The controller applies preliminary anti-action by suspending ignition before fuel supply is restored. This counter-measure prevents the harmful effect (backfire) that would otherwise occur when lean mixture is ignited after fuel suspension, thereby neutralizing the potential harm before it can manifest.
2Productivity
If fuel supply is released immediately after over-revolution recovery, then engine returns to normal operation quickly, but combustion continues into intake stroke causing combustion sound
Solution Approach 1:
The controller suspends ignition in advance of releasing fuel supply, creating a buffer period that prevents immediate combustion of the lean mixture. This preliminary action allows the air-fuel ratio to stabilize before ignition resumes, eliminating combustion sounds while enabling quick engine recovery.
Solution Approach 2:
The controller skips the ignition phase temporarily after over-revolution recovery, rushing through the critical period where lean mixture would cause backfire. By skipping ignition for a predetermined number of cycles, the system quickly transitions to normal operation without the harmful effects of immediate re-ignition.
3Object-generated harmful factors
If ignition is suspended together with fuel supply during over-revolution, then backfire is prevented, but engine recovery is delayed
Solution Approach 1:
The controller suspends ignition in advance of releasing fuel supply, creating a protective buffer that prevents backfire. This preliminary suspension of ignition, followed by timely restoration, ensures both backfire prevention and efficient engine recovery without unnecessary delays.
Solution Approach 2:
The controller uses feedback from the over-revolution detection to control both fuel supply and ignition timing. By monitoring engine speed and coordinating the release of both fuel and ignition, the system optimizes the recovery process to prevent backfire while minimizing recovery time through synchronized control.
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
Prevents backfires by maintaining a stable air-fuel ratio during engine recovery, reducing the likelihood of combustion extending into the intake stroke and minimizing unwanted combustion sounds.
Implementation Method 1
the combustion device is connected to the combustion chamber
Data Source
AI summary
An outboard motor, including an engine having a cylinder containing a combustion chamber, an intake pathway connected to the combustion chamber, a piston disposed in the cylinder, a crankshaft connected to the piston, a fuel injection device connected to the intake pathway, and an ignition device connected to the combustion chamber. The outboard motor further includes a controller that is configured to receive a signal indicating an engine speed from a sensor, control the fuel injection device to suspend fuel supply and control the ignition device to suspend ignition, upon determining that the engine is in an over-revolution state, control the fuel injection device to release the suspension of the fuel supply upon determining that the engine has recovered from the over-revolution state, and control the ignition device to release the suspension of the ignition after lapse of a number of cycles of the engine since the release of the suspension of the fuel supply.