Stratified Charge Carburetor Valve Overlap for Intake Separation

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Solution Overview

Problem

Existing carburetor designs for stratified charge two-stroke engines require separate separator plates or complex die casting to separate air-fuel and air intakes, which is inefficient and costly.

Innovation Solution

A carburetor with a specially shaped choke valve and matching venturi and throttle bore configuration allows for air-fuel mixture separation without a separator plate, utilizing an irregularly shaped butterfly type choke valve that overlaps with the throttle valve in the venturi during wide-open throttle operation, minimizing leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a separate separator plate or complex die casting is used to separate air-fuel and air intakes, then the separation function is achieved, but the device complexity and manufacturing cost increase

Engineering Contradiction:

Improveseparation functionVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The choke valve and throttle valve are integrated into a single carburetor body without requiring separate separator plates or complex die casting. The choke valve assembly combines the functions of air-fuel mixture separation and airflow control in one component, eliminating the need for additional separation structures.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The choke valve serves multiple functions: it acts as a flow control element, creates the air-fuel mixture, and provides the separation function between air intake and air-fuel mixture intake. This multi-functionality eliminates the need for separate dedicated components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a separate separator plate or complex die casting is used to separate air-fuel and air intakes, then the separation function is achieved, but the manufacturing cost increases

Engineering Contradiction:

Improveseparation functionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention uses simpler, more cost-effective valve components that can be manufactured using standard machining processes rather than complex die casting. The choke and throttle valves are designed as simpler parts that reduce manufacturing complexity and cost.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of operation

If the trailing edge of the choke valve and leading edge of the throttle valve overlap, then air-fuel and air intake passages are created, but leakage between passages may occur

Engineering Contradiction:

Improveintake passage separationVSAvoidleakage control

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The carburetor body is designed with different geometric characteristics in different regions. The venturi section has a specific curvature and cross-sectional area that creates favorable flow patterns, while the choke and throttle valve areas have optimized geometries to control flow separation and minimize leakage between the air and air-fuel mixture passages.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The venturi section features a curved, streamlined geometry that promotes smooth airflow and reduces turbulence. This curved design helps contain the air-fuel mixture flow within the lower passage while minimizing leakage into the upper air intake passage during wide-open throttle operation.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 design effectively separates air-fuel and air intakes during wide-open throttle operation without additional components, reducing leakage and operational complexity, and is more cost-effective than traditional methods.

Implementation Method 1

the carburetor body has a venturi extending from the choke bore

Methodology Applied

Scientific EffectVenturi effect: Venturi Effect

Data Source

PatentUS7523922B2Carburetor for stratified charge two-cycle engine

Publication Date: 2009.04.28 ZAMA JAPAN

AI summary

A carburetor for a stratified charge two cycle engine with a choke bore, venturi, and throttle bore configuration matching an irregularly shaped choke valve. The trailing and leading edges of the choke and throttle valves, respectively, preferably overlap during wide open throttle operation to separate a single intake passage bore into an air intake passage above the choke and throttle valves and an air/fuel intake passage below the choke and throttle valves. The choke valve is preferably bent to minimize operational rotation and limit fuel spit back.