Rotary Carburetor Rotor Groove Pockets for Idling Stability
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Solution Overview
Problem
Conventional two-bore rotary carburetors for stratified scavenging engines face challenges in maintaining a lean air-fuel ratio during idling, as the structural features cause the rotor to displace, leading to inconsistent air and fuel supply, making it difficult to achieve an optimal air-fuel ratio.
Innovation Solution
A rotor valve with a vertically formed, bottomed cylindrical rotor valve port, featuring a semicircular air supply-side bore and a fuel supply-side bore, with minimal groove pockets at the aperture edges, allows for controlled air and fuel supply during idling and throttle opening, ensuring stable air-fuel ratio by facilitating rapid emulsion formation and minimizing air variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a partition is placed into the same bore to simplify structure and minimize height, then the carburetor becomes more compact, but it becomes difficult to maintain a lean air-fuel ratio at idling because the rotor displaces downward
Solution Approach 1:
The patent applies local quality by creating groove pockets at specific locations (aperture edges) of the rotor valve bores. These localized structural modifications change the flow characteristics specifically at the bore apertures without altering the overall rotor structure, enabling precise control of air-fuel mixture at idling while maintaining the compact single-bore design.
Solution Approach 2:
The groove pockets are pre-formed at the aperture edges of the bores to anticipate and compensate for the rotor's downward displacement during operation. This preliminary structural feature ensures that even when the rotor moves down, the groove pockets maintain proper fuel-air mixing characteristics, preventing the air-fuel ratio from becoming too rich during idle operation.
2Ease of operation
If the bore on the fuel supply side is made symmetrically larger to make it open first during idling, then the fuel supply opens first, but the air-fuel ratio varies greatly when the air supply bore starts to open in a partial state
Solution Approach 1:
Instead of uniformly enlarging the fuel supply bore, the patent applies local quality by adding groove pockets specifically at the aperture edges. This localized modification allows the fuel bore to open first during idle while controlling the rate of fuel flow, preventing excessive fuel delivery and maintaining stable air-fuel ratio even as the air bore begins to open in partial states.
Solution Approach 2:
The groove pockets change the flow parameters (flow rate, pressure distribution) at the bore apertures. By modifying the effective flow area and velocity distribution through the groove geometry, the system achieves controlled fuel delivery that maintains stable air-fuel ratio across different throttle positions, preventing the large variations that occur with simple bore enlargement.
3Device complexity
If a single rotor structure is used with two bores, then the device complexity is reduced, but it becomes difficult to control the air-fuel ratio precisely during idle and partial throttle operations
Solution Approach 1:
The patent resolves the contradiction between simple structure and precise control by applying local quality - adding groove pockets only at the critical aperture edge locations of the bores. This minimal local modification to the simple single-rotor structure provides the necessary flow control characteristics for precise air-fuel ratio management during idle and partial throttle operations, without requiring complex multi-rotor or adjustable mechanisms.
Data Source
AI summary
The present invention provides an internal shape of a rotor for a two-bore rotary carburetor used in a stratified scavenging engine whereby an engine for a power saw, lawn mower, or the like can be stabilized in the course of a complete change in orientation during idling. A groove pocket (10) in communication with a fuel supply-side bore (8) is formed at the aperture edge of each of the upstream end and the downstream end of a carburetor rotor valve (6) toward an accelerated rotation direction in the fuel supply-side bore (8) of the rotor valve (6). The groove pocket (10) is shaped so as to gradually rise and decrease in cross-sectional surface area toward the accelerated rotation direction along a peripheral surface of the rotor valve (6). The resulting structure is one in which the groove pocket (10) is initially superposed with the mixing channel during horizontal rotation of the rotor valve (6), the fuel supply-side bore (8) and the mixing channel are in communication with each other, and the fuel supply-side bore (8) opens before the air supply-side bore (7) does.