Two-Stroke Engine Mixture Inlet Timing for Acceleration Stalling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Two-stroke engines in hand-held power tools often stall during acceleration from idle due to insufficient fuel supply caused by the reversal of mixture supply through divided intake passages, leading to underfueling of the combustion chamber.
Innovation Solution
The mixture inlet is connected to the crankcase before the air passage in the upward piston stroke, creating underpressure in the mixture passage and ensuring fuel is sucked in, preventing the deficiency in fuel supply by opening only a portion of the mixture inlet's width before the air passage connects with the transfer passage, thus maintaining fuel supply during acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the air passage and mixture passage are both open during piston upward stroke, then fuel supply is maintained through both passages, but fuel supply reversal causes engine stalling during acceleration
Solution Approach 1:
The mixture inlet is opened before the air passage connects to the transfer passage during piston upward stroke. This preliminary action ensures that the mixture passage is activated first, preventing fuel supply reversal and engine stalling during acceleration from idle.
Solution Approach 2:
The piston-controlled mixture inlet dynamically opens and closes at specific positions during piston stroke. By controlling the timing of mixture inlet opening relative to air passage connection, the system adapts fuel supply to match engine operating conditions, preventing stalling during acceleration while maintaining efficient operation at full load.
2Reliability
If the mixture inlet is opened fully before air passage connects, then fuel supply is ensured during acceleration, but inefficient fuel supply occurs at full load
Solution Approach 1:
The mixture inlet is designed to open fully only after the air passage connects to the transfer passage. This dynamic timing ensures that at full load conditions, fuel is supplied efficiently through the air passage while preventing unnecessary fuel supply through the mixture passage, thereby optimizing fuel efficiency.
Solution Approach 2:
The opening position and duration of the mixture inlet are precisely controlled parameters. By optimizing these parameters, the system achieves the minimum necessary opening time to prevent stalling during acceleration while minimizing fuel supply through the mixture passage at full load, thus reducing energy loss.
3Productivity
If the throttle valve is kept open for acceleration, then fuel supply is maintained, but the engine stalls due to improper mixture supply timing
Solution Approach 1:
The mixture inlet is opened preliminarily before the air passage connects to the transfer passage during piston upward stroke. This timing ensures that when the throttle valve opens for acceleration, the mixture passage is already active, preventing fuel supply reversal and engine stalling.
Solution Approach 2:
The piston position controls the timing of mixture inlet opening and air passage connection, creating a feedback mechanism that adapts fuel supply to engine operating conditions. This ensures stable engine operation during acceleration by synchronizing fuel supply with piston movement and throttle valve position.
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 configuration prevents engine stalling by ensuring consistent fuel supply to the combustion chamber, even at low throttle positions, and maintains efficient operation under full load by controlling the sequence of passage openings.
Implementation Method 1
upon upward stroke of the piston first underpressure is applied to the air passage and only subsequently to the mixture passage
Implementation Method 2
fuel from the mixture passage is sucked through the connection of the passages into the air passage
Data Source
AI summary
A hand-held power tool has a two-stroke engine with a cylinder with combustion chamber and a piston disposed therein that drives a crankshaft supported in a crankcase. In at least one piston position, crankcase and combustion chamber are connected by a transfer passage. An air passage supplies in at least one piston position combustion air to the transfer passage. A mixture passage for fuel/air mixture is provided. Air and mixture passages in operation are at least partially connected to each other. Part of the mixture passage is formed in a carburetor where a fuel port opens into the mixture passage. The mixture passage opens into the crankcase with a piston-controlled mixture inlet having a width in circumferential direction of the cylinder. Upon upward piston stroke the mixture inlet is connected to the crankcase with a portion of the width before a connection of air passage and transfer passage is established.