Piston Box Wall Asymmetry for Load Capacity
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Solution Overview
Problem
Current pistons for internal combustion engines face challenges in achieving a balance between reduced weight and increased load capacity, while maintaining seizure resistance, low skirt friction, and smooth running, particularly at highly stressed points like the piston crown and pressure-side box walls, to support CO2 reduction through downsizing.
Innovation Solution
The structural arrangement of individual partial wall sections of box walls is optimized, with offset longitudinal centerlines of these sections within the box walls, enhancing strength and elasticity, and allowing for a flexible positioning of spray nozzles, thereby increasing load capacity and reducing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If lightweight piston design is used to reduce oscillating mass and CO2 emissions, then weight is reduced, but load capacity and resistance to cracking at highly stressed points deteriorates
Solution Approach 1:
The box wall is divided into two distinct partial wall sections: a first partial wall section extending between the pin boss and the pressure-side skirt wall, and a second partial wall section extending between the pin boss and the counter-pressure side skirt wall. This segmentation allows each section to be optimized independently for strength and weight
Solution Approach 2:
The longitudinal center line of the first partial wall section is offset from the longitudinal center line of the second partial wall section, creating an asymmetric configuration. The two center lines intersect outside the piston, forming a non-symmetric stress distribution pattern that enhances load capacity while maintaining reduced weight
2Strength
If box wall structure is optimized for increased strength, then load capacity improves, but elasticity and seizure resistance may worsen
Solution Approach 1:
Different regions of the box wall are given different structural characteristics through the offset center line configuration. The first partial wall section can be optimized for strength in the direction of the pressure-side skirt wall, while the second partial wall section maintains elasticity for seizure resistance, allowing each region to have locally optimized properties
3Strength
If first partial wall sections run towards each other to increase strength, then load capacity improves, but spray nozzle positioning flexibility deteriorates
Solution Approach 1:
The offset center line configuration creates three-dimensional spatial arrangement that provides multiple possible orientations for the partial wall sections. This allows the design to accommodate different spray nozzle positions by adjusting the offset magnitude and direction, rather than being constrained to a single planar configuration
Data Source
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AI summary
The present invention relates to a piston (1) for an internal combustion engine, with a piston crown (2) and a piston skirt (3) adjoining thereto, which has two skirt walls (6, 7) arranged on the thrust-side (DS) and the anti-thrust-side (GDS), and two relief section walls (8, 9) connecting these skirt walls (6, 7), pin hubs (10) being arranged in the relief section walls (8, 9). The essential aspect of the invention is that each relief section wall (8, 9) has two wall subsections (11, 12) in the area between the pin hub (10) and the piston crown (2), the first wall subsection (11) of which runs between the pin hub (10) and the thrust-side skirt wall (6), and the second wall subsection (12) runs between the pin hub (10) and the anti-thrust-side skirt wall (7), that a longitudinal center line (13) of the first wall subsection (11) is arranged offset from a longitudinal center line (14) of the second wall subsection (12), and that the two longitudinal center lines (13, 14) of the two wall subsections (11, 12) intersect outside the piston (1).