Two-Stroke Piston Structure for Weight and Emissions Balance
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Solution Overview
Problem
Two-stroke engines face challenges in reducing piston weight while maintaining structural strength and rigidity, as well as minimizing unburned hydrocarbon emissions, due to the addition of stratified scavenging channels which increase weight and vibration.
Innovation Solution
A two-stroke engine piston design featuring a weight reduction space with a larger axial extent radially inside the mantle surface, allowing for significant weight reduction without compromising structural strength or increasing emissions, by isolating the weight reduction space from gas transferring channels and incorporating a stratified scavenging channel for reduced hydrocarbon emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a stratified scavenging channel is added to the piston, then hydrocarbon emissions are reduced, but piston weight increases
Solution Approach 1:
The patent extracts material from the piston body to create a weight reduction space, removing unnecessary mass while preserving the stratified scavenging channel structure. This allows the piston to maintain its emission-reducing functionality while compensating for the weight added by the channel walls through selective material removal from non-critical areas.
Solution Approach 2:
The weight reduction space is strategically positioned and shaped to remove material only from areas where structural integrity is not compromised. The varying axial extent (greater radially inside than at the mantle surface) creates local density variations that optimize the balance between weight reduction and maintaining sufficient strength in critical regions.
2Weight of moving object
If piston weight is reduced, then vibrations and engine weight are decreased, but structural strength and rigidity may be compromised
Solution Approach 1:
The weight reduction space employs non-uniform material distribution with greater axial extent radially inside the mantle surface than at the mantle surface itself. This creates locally optimized density variations that preserve strength in critical load-bearing regions while removing mass from less critical areas, achieving weight reduction without compromising overall structural integrity.
Solution Approach 2:
The invention addresses the strength-weight tradeoff by transitioning from uniform two-dimensional cross-sectional thickness to a three-dimensional weight reduction space with varying axial extent in different radial directions. This dimensional approach allows selective mass removal while maintaining structural rigidity through strategic material distribution throughout the piston volume.
3Weight of moving object
If the weight reduction space has large axial extent at the mantle surface, then weight is reduced, but structural strength is compromised
Solution Approach 1:
The weight reduction space is designed with differential axial extent: greater radially inside the mantle surface and smaller at the mantle surface itself. This local quality variation ensures that material is removed preferentially from the interior where weight reduction provides the most benefit, while preserving the mantle surface material that is critical for structural strength and sealing functions.
Data Source
AI summary
A two-stroke engine piston (1) is disclosed comprising a piston top (3), a mantle surface (5), a stratified scavenging channel (7) in the mantle surface (5), and a weight reduction space (9) arranged between the piston top (3) and the stratified scavenging channel (7). The weight reduction space (9) has a largest first axial extent (a1) at the mantle surface (5) and a second axial extent (a2) radially inside the mantle surface (5), and wherein the second axial extent (a2) is greater than the largest first axial extent (a1). The present disclosure further relates to an engine (30), a hand-held tool (40), and a method of manufacturing an engine piston (1).