Carburetor Fuel Supply Control for Engine Start-Up
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Solution Overview
Problem
Existing carburetor systems face challenges in effectively controlling fuel supply during engine start-up, particularly in reducing the risk of flooding and ensuring adequate fuel delivery, with existing solutions being either inadequate, costly, or complex.
Innovation Solution
A method that sets the fuel supply system in either lean or rich mode based on engine parameter evaluations, using a bistable valve to optimize fuel supply during start-up, with the fuel supply system being set in lean mode after a successful run to minimize flooding risks and in rich mode when additional fuel is needed, such as during cold starts or if ignition is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the choke valve is closed and throttle valve is set in start gas position to deliver air and fuel mixture to crankcase, then the engine can be started, but the engine may be flooded with too much fuel if the operator misses the first ignition
Solution Approach 1:
The patent applies dynamics by making the fuel supply system adaptive and changeable during start-up operations. The system dynamically switches between different fuel supply modes (first mode with choke closed, second mode with choke open) based on operational conditions. This allows the fuel supply to be optimized in real-time, providing rich mixture when needed for starting while preventing flooding by transitioning to leaner mixture after successful ignition detection, thereby resolving the contradiction between reliable start-up and avoiding fuel flooding
Solution Approach 2:
The patent implements parameter changes by varying the fuel-air mixture composition and choke valve position based on detected engine conditions. The system changes the fuel supply parameters (from rich to lean mixture) and choke valve state (closed to open) depending on whether the engine is in start-up mode or running mode. This parameter adaptation allows the system to provide adequate fuel for starting while automatically reducing fuel supply to prevent flooding after ignition, thus resolving the technical contradiction
2Device complexity
If a conventional carburetor with single fuel path is used, then the structure is simple, but the fuel supply control at start-up is inadequate
Solution Approach 1:
The patent applies segmentation by dividing the fuel supply system into distinct operational modes and pathways. The system is segmented into a first fuel supply mode (with choke valve closed) and a second fuel supply mode (with choke valve open), each with specific fuel delivery characteristics. This segmentation allows independent optimization of fuel supply for different operational phases, providing adequate control during start-up while maintaining structural simplicity through shared hardware components, thus resolving the contradiction between simplicity and control adequacy
Solution Approach 2:
The patent implements universality by designing a fuel supply system that performs multiple functions using the same physical components. The choke valve and fuel injection system serve dual purposes: they control both the start-up phase (with restricted airflow and specific fuel mixing) and the running phase (with open choke and different fuel requirements). This multi-functionality allows adequate fuel supply control during start-up without adding separate dedicated components, thereby resolving the contradiction between structural simplicity and control reliability
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 approach optimizes fuel supply at start-up, reducing the risk of engine flooding and ensuring efficient fuel delivery by dynamically adjusting the fuel mode based on engine conditions, thereby improving start-up reliability and efficiency.
Implementation Method 1
The depression created by the passing air in the carburetor venturi draws fuel into the engine
Implementation Method 2
the fuel metering chamber is generally separated from atmosphere by a diaphragm that adjusts the fuel pressure to a constant pressure
Data Source
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AI summary
The invention concerns a method for controlling the fuel supply to an internal combustion engine at start-up. The fuel supply system can be set in at least two start modes, a lean mode and a rich mode, and the selection of mode is based on an evaluation of a previous start attempt or successful run. The invention also concerns a carburettor (10) having a fuel supply system including a main fuel path (13) with an actively controlled fuel valve (26) and an idling fuel path (14) branching off from the main fuel path (13) downstream of the valve (26). The fuel supply system further includes a start fuel line (23, 423) starting upstream (figure 1 ) or downstream (figure 4) of the fuel valve (26) and ending in at least one start fuel outlet near and downstream of a choke valve.