Spark-ignition engine valve clearance and stroke optimization
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Solution Overview
Problem
In spark-ignition internal combustion engines with high geometric compression ratios, increasing the combustion chamber height to delay flame collision leads to insufficient engine output power due to smaller intake valve diameters and reduced air charging, resulting in lower engine performance.
Innovation Solution
A spark-ignition internal combustion engine design with a geometric compression ratio of 14 or more, featuring specific clearances between the piston and valves, and a stroke length that satisfies the relationship S≦0.977×B+18.2, where B is the bore diameter, to ensure a larger intake valve opening area and adequate air charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the combustion chamber height is increased to delay flame collision, then flame collision is delayed and thermal efficiency is improved, but the stroke length becomes longer and the bore diameter becomes smaller, resulting in smaller intake valve opening area and insufficient air charging
Solution Approach 1:
The patent applies parameter changes by precisely controlling the stroke length B within the range of 75-95mm and the bore diameter S within the range of 85-105mm, with the specific relationship S≦0.977×B+18.2. These parameter optimizations allow the combustion chamber height to be increased for delayed flame collision while preventing excessive stroke lengthening that would reduce bore diameter and intake valve size, thereby maintaining sufficient intake air charge
Solution Approach 2:
The patent employs dynamics by making the combustion chamber height adjustable through the piston top surface design with a convex portion. The convex portion height H is controlled within 2-6mm to dynamically optimize the combustion chamber height, allowing delayed flame collision while compensating for the effects of increased stroke length on intake valve dimensions
2Length of stationary object
If the stroke length is increased to increase combustion chamber height, then flame collision is delayed, but the bore diameter becomes relatively smaller and the intake valve opening area becomes smaller
Solution Approach 1:
The patent applies parameter changes by establishing specific ranges for stroke length (75-95mm) and bore diameter (85-105mm), with the critical relationship S≦0.977×B+18.2. This mathematical relationship ensures that when stroke length increases to raise combustion chamber height, the bore diameter is maintained at sufficient levels to accommodate adequately sized intake valves with sufficient opening areas
Solution Approach 2:
The patent uses dynamics by designing the piston top surface with a convex portion of height H (2-6mm) that can be adjusted to optimize combustion chamber height. This dynamic adjustment allows the combustion chamber height to increase for delayed flame collision while the bore diameter and intake valve dimensions are maintained through the controlled parameter relationship
3Loss of energy
If the geometric compression ratio is set to a high value, then thermal efficiency is improved, but the combustion chamber height must be increased which leads to longer stroke length and smaller intake valve opening area
Solution Approach 1:
The patent applies parameter changes by setting the geometric compression ratio to a high value (13.0:1 or higher) while simultaneously controlling the stroke length B (75-95mm) and bore diameter S (85-105mm) with the relationship S≦0.977×B+18.2. This coordinated parameter optimization achieves high thermal efficiency through high compression ratio while preventing excessive stroke lengthening, thereby maintaining sufficient bore diameter and intake valve opening area for adequate air charging and engine output power
Solution Approach 2:
The patent employs dynamics by using the adjustable convex portion height H (2-6mm) on the piston top surface to optimize the combustion chamber height. This dynamic adjustment enables the combustion chamber height to be increased for high compression ratio and delayed flame collision, while the parameter relationship S≦0.977×B+18.2 ensures the bore diameter and intake valve dimensions remain sufficient for maintaining engine output power
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 achieves high engine output power while maintaining a high geometric compression ratio, enhancing thermal efficiency and fuel economy by ensuring sufficient air charge and preventing premature flame collision, thus optimizing engine performance.
Implementation Method 1
a spark plug provided in the cylinder head to face the combustion chamber
Implementation Method 2
a fuel injection valve provided in the cylinder head to face the combustion chamber
Implementation Method 3
a spark-ignition internal combustion engine
Implementation Method 4
a piston adapted to be reciprocatingly moved within the cylinder
Implementation Method 5
two intake valves provided in the cylinder head and each capable of shutting off an inflow of air into the cylinder
Implementation Method 6
two exhaust valves provided in the cylinder head and each capable of shutting off an outflow of exhaust gas from the cylinder
Data Source
AI summary
Provided is a spark-ignition internal combustion engine capable of ensuring engine output power while setting a geometric compression ratio of an engine body to a high value. In the spark-ignition internal combustion engine, each of a clearance between a top surface (3a) of a piston (3) located at a top dead center position and a lower surface (8a) of each of two intake valves (8) in a full-closed state, and a clearance between the top surface (3a) of the piston (3) located at the top dead center position and a lower surface (9a) of each of two exhaust valves (9) in a full-closed state, is set to 5 mm or more, and a stroke length S of the piston (3) is set to satisfy the following relation: S≦0.977×B+18.2, where B is a bore diameter of a cylinder.