Piston Crown Pent-Roof Ridge Line Positioning for Intake Flow
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Solution Overview
Problem
In four-valve four-stroke internal combustion engines, the offset ridge line between intake and exhaust valve recesses restricts intake air flow, limiting intake efficiency and ignitability when intake and exhaust valves are opened simultaneously.
Innovation Solution
A piston structure with a pent-roof shaped piston crown, where the exhaust-side inclined flat surface extends into the intake valve recesses and the ridge line is positioned on the intake side, allowing unobstructed flow of intake air to both sides, and tangent lines at the exhaust-side end portions of the intake valve recesses direct air flow around the ridge line, enhancing intake efficiency and ignitability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the ridge line is offset to the exhaust side to separate intake and exhaust surfaces, then the piston structure can match the combustion chamber ceiling, but intake air flow is blocked and intake efficiency deteriorates
Solution Approach 1:
The patent applies asymmetry by positioning the ridge line offset to the intake side rather than the exhaust side, creating asymmetric intake and exhaust surfaces with different areas. This asymmetric configuration allows intake air to flow freely across the piston crown to both intake and exhaust sides, resolving the blocking issue while maintaining the pent-roof shape that matches the combustion chamber ceiling geometry
2Ease of operation
If the intake valve recesses are made larger to accommodate larger intake valves, then the intake valve head fits properly, but the intake-side inclined flat surfaces become larger and push the ridge line to the exhaust side, blocking air flow
Solution Approach 1:
The patent inverts the conventional ridge line positioning by placing it on the intake side rather than the exhaust side. This inversion allows the larger intake valve recesses to be accommodated while preventing the ridge line from blocking intake air flow, as the ridge line now sits on the opposite side from where the air flow restriction would occur
Data Source
AI summary
A piston structure for a four-stroke internal combustion engine is provided, enabling an increase in the intake efficiency and a favorable ignitability to improve the performance of the internal combustion engine. In a piston structure for a four-valve four-stroke internal combustion engine, a piston crown includes: an intake-side inclined flat surface formed in a single plane by bottom surfaces of a pair of intake valve recesses and an intake-side common flat surface; and an exhaust-side inclined flat surface formed in a single plane by bottom surfaces of a pair of exhaust valve recesses and an exhaust-side common flat surface. The intake-side inclined flat surface and the exhaust-side inclined flat surface are formed into a pent-roof shape with a ridge line at an intersection therebetween. The exhaust-side inclined flat surface extends into the intake valve recesses, and the ridge line is located on a side of the intake valve recesses.