Two-Stroke Engine Cylinder Layout for Compact Power Tools
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Solution Overview
Problem
Existing two-stroke engines for power tools have a bulky configuration due to the relative positioning of the mixture intake and exhaust port, which limits the piston's height and overall tool size.
Innovation Solution
The mixture intake and exhaust port are arranged on the same side of a transverse plane within the cylinder, allowing for a compact design by enabling a shorter piston configuration and optimizing the air passage layout for efficient scavenging air filling, reducing flow resistance and tool size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mixture intake and exhaust port are arranged on opposite sides of the transverse plane, then the piston can be made tall to prevent piston recess from connecting exhaust port and air intake, but the power tool becomes bulky and large in size
Solution Approach 1:
The patent inverts the conventional arrangement by placing the mixture intake and exhaust port on the same side of the transverse plane instead of opposite sides. This inversion allows the piston recess to effectively control both openings while enabling a shorter piston configuration, thus reducing the overall tool size without compromising the prevention of unwanted connections.
Solution Approach 2:
The patent utilizes the radial dimension of the piston by designing the piston recess to extend radially inward from the piston perimeter. This dimensional approach allows the recess to control both the exhaust port and mixture intake openings effectively, enabling compact piston design while maintaining proper sealing and control functions.
2Ease of operation
If the piston is made tall to prevent piston recess from opening toward exhaust port, then the exhaust port and mixture intake can be controlled separately, but the overall height and size of the engine increases
Solution Approach 1:
The patent segments the piston structure into an outer peripheral region and an inner region with the piston recess. The piston recess is positioned to control the mixture intake opening while the piston perimeter controls the exhaust port opening. This segmentation allows both openings to be controlled separately despite the compact piston height.
Solution Approach 2:
The piston recess is nested within the piston structure, creating a multi-level configuration where the recess controls the mixture intake while the piston perimeter controls the exhaust port. This nested arrangement enables separate control of both openings without requiring increased piston height.
3Productivity
If the air passage is divided into several branches to supply scavenging air, then the air can be distributed to multiple transfer passages, but the flow resistance increases and the piston recess must be smaller
Solution Approach 1:
The patent merges the air passage configuration into a single dominant passage that supplies scavenging air to multiple transfer passages through the piston recess. This merging approach minimizes flow resistance by avoiding multiple branching paths while still achieving effective distribution of air to all necessary transfer passages.
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 configuration results in a more compact power tool with improved air passage filling and reduced flow resistance, facilitating easier handling and weight distribution, while maintaining efficient engine operation.
Implementation Method 1
The piston controls with its upper edge the exhaust port and with its lower edge the mixture intake
Implementation Method 2
the crankcase is in flow communication with the combustion chamber by means of a transfer passage
Implementation Method 3
the two-stroke engine has an air passage that supplies combustion air and opens with its air intake into the cylinder
Data Source
AI summary
A power tool is driven by a two-stroke engine. The two-stroke engine has a cylinder and a piston reciprocating within the cylinder. The cylinder has a combustion chamber delimited by the piston. The two-stroke engine has a crankcase and a crankshaft rotatably supported in the crankcase and driven by the piston with a connecting rod. The two-stroke engine has one or more transfer passages connecting the crankcase to the combustion chamber in at least one position of the piston. The two-stroke engine has a mixture passage that is connected to a piston-controlled mixture intake provided at the cylinder and supplies a fuel/air mixture. The combustion chamber has an exhaust port provided within the cylinder. The two-stroke engine has a transverse plane dividing the cylinder parallel to and along the longitudinal cylinder axis. The exhaust port and the mixture intake are arranged on the same side of the transverse plane.