Air Cleaner Inlet Design for Two-Stroke Engine Blowback Prevention

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Solution Overview

Problem

Two-stroke internal combustion engines face contamination of air cleaners due to blow-back of fuel from the air and air-fuel mixture passages, particularly during acceleration, deceleration, or at half-throttle conditions, leading to element contamination.

Innovation Solution

An air cleaner design with separate inlets for air and air-fuel mixture passages, where a passage forming member surrounds the inlets to create a blown-back fuel diffusion preventing region, preventing the diffusion of blow-back fuel into the cleaner element by directing it through extended passages and reflective walls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single air passage is used in the air cleaner, then the structure is simple, but fuel blow-back contaminates the cleaner element during acceleration, deceleration, or half-throttle operation

Engineering Contradiction:

Improveair cleaner structureVSAvoidelement contamination

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The air cleaner is divided into separate air passage and air-fuel mixture passage sections with independent inlets. The partition wall creates distinct flow paths that prevent fuel blow-back from contaminating the cleaner element, while maintaining relatively simple overall structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A partition wall acts as an intermediary barrier between the air passage and air-fuel mixture passage. This partition wall with its specific opening configuration prevents harmful fuel blow-back from reaching the cleaner element while still allowing necessary air flow.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If separate air passage and air-fuel mixture passage are used, then element contamination is prevented, but the device complexity increases

Engineering Contradiction:

Improveelement contaminationVSAvoidintake system structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The air cleaner integrates both the air passage and air-fuel mixture passage within a single housing structure. The partition wall and openings are formed as integral parts of the air cleaner body, combining multiple functions in one component rather than using separate assemblies.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The partition wall serves multiple functions: it separates the air passages, creates the opening for air-fuel mixture flow, and prevents fuel blow-back contamination. The single air cleaner housing accommodates both air intake paths and the element, providing universal protection and flow management.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Object-affected harmful factors

If the partition wall has no opening, then fuel blow-back is completely blocked, but air-fuel mixture flow is restricted during high-speed operation

Engineering Contradiction:

Improvefuel blow-back preventionVSAvoidair-fuel mixture flow

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The partition wall has different properties in different locations: it is closed in most areas to prevent fuel blow-back, but has a specific opening in the lower portion to allow air-fuel mixture flow during high-speed operation. This local variation in partition wall configuration optimizes both protection and flow.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The opening in the partition wall changes the flow parameters by allowing air-fuel mixture to pass through during high-speed operation while blocking fuel blow-back during low-speed or transient conditions. The opening acts as a flow regulator that adapts to different operating conditions.

Inventive Principle:

Principle #35Parameter changes

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

Effectively prevents contamination of the cleaner element by containing blow-back fuel and air-fuel mixture, maintaining the cleanliness and efficiency of the air cleaner during engine operation.

Implementation Method 1

an element member (206) provided with a cleaner element (64) filtering air

Methodology Applied

Scientific EffectFiltration: Filter (physical)

Data Source

PatentUS10113517B2Air cleaner for stratified scavenging two-stroke internal combustion engine

Publication Date: 2018.10.30 YAMABIKO CORP

AI summary

To improve the effect of preventing contamination of an element in an air cleaner. An air cleaner includes a first inlet (60) through which air is fed to an intake system air passage and a second inlet (62) through which air is fed to an intake system air-fuel mixture passage. An extended passage (72) leads to the second inlet (62), for example. A passage forming member (70, 204) forming the extended passage (72) is shaped to surround a periphery of the first inlet (60). The passage forming member (70, 204) forms a blown-back fuel diffusion preventing region (74) leading to the first inlet (60).