Piston Cooling Gallery Tilt for Mass Reduction
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Solution Overview
Problem
Aluminum pistons for internal combustion engines face challenges in reducing stress and mass while maintaining performance, particularly when an iron insert is used in the top ring groove, leading to increased mass due to the need for additional aluminum material.
Innovation Solution
A piston design featuring a tilted cooling gallery with an inner side wall tilted away from the center axis and an outer side wall tilted toward it, allowing for a larger cooling gallery and reduced mass by removing aluminum material adjacent the ring belt, and incorporating an iron insert in the top ring groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the cooling gallery is tilted 10 to 20 degrees to reduce stress in aluminum pistons, then stress is reduced, but mass increases due to additional aluminum material required
Solution Approach 1:
The patent removes aluminum material from non-structural areas, specifically extracting material from the region below the cooling gallery and around the iron insert. This extraction eliminates the mass increase that would normally result from tilting the cooling gallery, while preserving the stress-reducing benefits of the tilt.
Solution Approach 2:
The patent applies different material densities strategically: using iron (higher density) for the insert in the top ring groove where strength is needed, and aluminum (lower density) for the piston body. This local differentiation of material quality allows stress reduction through gallery tilting without proportionally increasing overall mass.
2Strength
If an iron insert is used in the top ring groove to enhance strength, then structural strength is improved, but mass increases due to additional material required
Solution Approach 1:
The iron insert is placed locally in the top ring groove where maximum strength is required, while the rest of the piston body uses lighter aluminum material. This localized application of high-strength material provides the necessary strength support without uniformly increasing the piston's overall mass.
Solution Approach 2:
The patent uses a composite construction combining iron insert and aluminum piston body. This composite approach allows the piston to benefit from the high strength of iron in critical areas while maintaining the low weight advantage of aluminum in non-critical areas, achieving an optimal strength-to-weight ratio.
3Weight of moving object
If aluminum material is removed to reduce mass, then piston mass is reduced, but structural strength may be compromised
Solution Approach 1:
Material removal is selectively applied only to non-structural areas of the piston, such as regions below the cooling gallery and areas not required for structural support. Critical load-bearing regions retain their material integrity, ensuring that strength is maintained while achieving mass reduction in permissible areas.
Solution Approach 2:
The piston is segmented into different functional zones: structural regions that require material for strength and non-structural regions where material can be removed for mass reduction. This segmentation allows differential material distribution, maintaining strength where needed while reducing mass where permissible.
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 mass and stress, enhancing engine performance by maintaining structural strength while minimizing non-structural mass, typically reducing the piston's mass by 5 to 8 grams compared to conventional designs.
Implementation Method 1
The cooling gallery of the body portion includes an inner side wall and an outer side, the inner side wall is tilted away from the center axis of the body portion, and the outer side wall is tilted toward the center axis of the body portion
Implementation Method 2
To reduce stress in aluminum pistons, the cooling gallery can be tilted 10 to 20 degrees
Data Source
AI summary
An aluminum piston including a cooling gallery with titled inner and outer side walls is provided. The piston comprises a ring belt with a ring grooves, and an iron insert is disposed in a top one of the ring grooves. To reduce stress and mass of the piston, material located under the iron insert is removed, so that the outer side wall of the cooling gallery is tilted toward the center axis. The inner side wall of the cooling gallery is tilted away from the center axis.