Galleryless Steel Piston Cooling via Undercrown Oil Splash
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Solution Overview
Problem
Internal combustion engine pistons face challenges in achieving increased compression loads and operating temperatures while maintaining a workable piston temperature, which limits the reduction of piston size and weight, and increases manufacturing costs due to the need for steel construction and closed cooling galleries.
Innovation Solution
A 'galleryless' piston design without a cooling gallery, constructed from a single piece of steel using machining, forging, or casting, featuring an undercrown surface with a significant exposed area for enhanced cooling, minimizing weight and compression height, and utilizing an annular ring belt and pin bosses for lateral pin bores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a closed or partially closed cooling gallery is added to reduce piston operating temperature, then the piston temperature is controlled within workable limits, but the manufacturing cost increases due to the joining process and the piston weight increases requiring steel construction
Solution Approach 1:
The invention extracts and eliminates the cooling gallery structure from the piston design. By removing this unnecessary component, the piston weight is reduced and manufacturing complexity is decreased, while cooling is achieved through alternative means (oil splash cooling on the undercrown surface) that do not require additional structural elements.
Solution Approach 2:
The invention applies local quality by creating a specifically designed undercrown surface with enhanced oil splash cooling capability. Instead of a uniform cooling approach throughout the piston, the cooling function is localized to the undercrown surface where oil splash is most effective, allowing for weight reduction in other areas.
2Temperature
If a closed or partially closed cooling gallery is added to reduce piston operating temperature, then the piston temperature is controlled within workable limits, but the manufacturing cost increases due to the joining process
Solution Approach 1:
The invention extracts and eliminates the cooling gallery structure from the piston design. By removing this unnecessary component, the piston weight is reduced and manufacturing complexity is decreased, while cooling is achieved through alternative means (oil splash cooling on the undercrown surface) that do not require additional structural elements.
Solution Approach 2:
The invention merges the cooling function into the existing piston structure by utilizing the undercrown surface as the primary cooling interface. This eliminates the need for separate cooling gallery components and their associated joining processes, thereby reducing manufacturing cost while maintaining cooling effectiveness.
3Weight of moving object
If the piston compression height is decreased to reduce overall piston size and weight, then the piston becomes more compact and lighter, but the ability to withstand increased mechanical and thermal loads is compromised
Solution Approach 1:
The invention applies local quality by concentrating structural reinforcement and cooling functionality at the undercrown surface. This allows the piston compression height to be reduced overall while maintaining or enhancing strength and thermal management at the critical load-bearing and heat-exposure zones.
Solution Approach 2:
The invention utilizes parameter changes by optimizing the undercrown surface geometry and material properties to enhance cooling efficiency and load-bearing capacity. By changing the surface area, curvature, and material characteristics of the undercrown region, the piston can withstand higher loads with reduced compression height.
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
The design achieves reduced weight and cost while maintaining effective cooling, allowing for increased compression loads and temperatures, and preventing oil buildup, thus enhancing engine efficiency and performance.
Implementation Method 1
The undercrown surface has an exposed 2-dimensional surface area, as viewed looking along the central longitudinal axis, ranging from 25 to 60 percent of a cross-sectional area defined by a maximum outer diameter of the piston body
Data Source
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Figure 3
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AI summary
A galleryless steell piston for an internal combustion engine is provided. The piston has a monolithic piston body including an upper wall forming an upper combustion surface with first and second portions. The first portion extends annularly along an outer periphery of the upper wall and the second portion defines a combustion bowl. The piston further includes undercrovvn surface located directly opposite the combustion bowl with an exposed 2-dimensional surface area allowing for contact of cooling oil. The exposed 2-dimensional surface area ranges from 25 to 60 percent of a cross-sectional area defined by a maximum outer diameter of the piston body. To further enhance cooling, a portion of the undercrown surface is concave or convex, such that oil is channeled during reciprocation of the piston from one side to the opposite side of the piston.