Monolithic Steel Piston Cooling via Direct Oil Impingement
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Solution Overview
Problem
Existing piston constructions face challenges in achieving increased compression loads and operating temperatures while maintaining structural integrity and reducing weight, cost, and heat loss, particularly due to the presence of annular cooling galleries which increase manufacturing costs and limit piston size and mass reduction.
Innovation Solution
A monolithic steel piston design without an annular cooling gallery, featuring an openly exposed undercrown surface and peripherally enclosed through channels, which enhances cooling, reduces weight, and allows direct oil application for improved lubrication and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an annular cooling gallery is included in the piston construction, then the operating temperature of the piston can be maintained within workable limits, but the piston size, mass, and compression height increase, and manufacturing cost increases
Solution Approach 1:
The invention extracts and eliminates the annular cooling gallery from the piston construction, removing the source of the problem. The piston is designed as a monolithic structure without the traditional annular gallery, thereby reducing piston mass and compression height while maintaining cooling effectiveness through alternative means such as direct oil spray to the crown and improved heat transfer pathways.
Solution Approach 2:
The invention changes the cooling approach from internal annular gallery circulation to external direct oil spray application on the piston crown and sides. This parameter change in the cooling method allows elimination of the gallery structure, reducing piston weight and volume while achieving the required temperature control.
2Temperature
If an annular cooling gallery is included in the piston construction, then the operating temperature of the piston can be maintained within workable limits, but the manufacturing cost increases due to joining and finish machining processes
Solution Approach 1:
The invention extracts and eliminates the annular cooling gallery from the piston construction, removing the source of the problem. The piston is designed as a monolithic structure without the traditional annular gallery, thereby reducing piston mass and compression height while maintaining cooling effectiveness through alternative means such as direct oil spray to the crown and improved heat transfer pathways.
Solution Approach 2:
The invention merges the piston into a single monolithic structure, eliminating the need for separate upper and lower parts that would require joining processes. This consolidation into one piece removes the associated manufacturing steps and costs while simplifying the overall construction.
3Weight of moving object
If the piston compression height is decreased to reduce piston size and weight, then the piston becomes more compact and lightweight, but the structural integrity and temperature control become difficult to maintain
Solution Approach 1:
The invention changes the cooling approach from internal annular gallery circulation to external direct oil spray application on the piston crown and sides. This parameter change in the cooling method allows elimination of the gallery structure, reducing piston weight and volume while achieving the required temperature control.
Solution Approach 2:
The piston design allows direct oil spray to contact the crown and side surfaces, enabling the piston to cool itself through direct impingement cooling. This self-service cooling mechanism eliminates the need for internal galleries while maintaining temperature control in the reduced-compression-height design.
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 solution results in a robust, lightweight piston that is more compact, fuel-efficient, with reduced unit loading and deformation, leading to optimal piston ring performance and extended engine life, while minimizing manufacturing costs and heat loss.
Implementation Method 1
a monolithic steel piston body extending along a central longitudinal axis... enhanced strength and durability to withstand increased compression loads and temperatures... ability to direct oil directly from oil nozzles of the engine directly onto and against an undercrown surface... constant, fresh supply of oil being directed against the openly exposed undercrown region immediately adjacent the ring belt region, further enhancing the ability of the piston rings to perform
Implementation Method 2
an ability to direct oil directly from oil nozzles of the engine directly onto and against an undercrown surface... constant, fresh supply of oil being directed against the openly exposed undercrown region... enhancing the ability of the piston rings to perform as intended over an extended useful life
Data Source
AI summary
A piston for an internal combustion engine and method of construction is provided. The piston has a robust, lightweight monolithic piston body including an upper wall forming a combustion bowl depending radially inwardly from an annular, uppermost combustion surface. An undercrown surface is formed on an underside of the combustion bowl, with at least a portion of the undercrown surface being bounded by diametrically opposite skirt portions, pin bosses and strut portions connecting the skirt portions to the pin bosses. The bounded undercrown surface has an openly exposed surface area, as viewed looking along a central longitudinal axis along which the piston reciprocates, providing an expansive area against which oil being splashed or sprayed can come into direct contact with to enhance cooling the piston while in use. Through channels extending over upper regions of the pin bosses can be provided to further reduce weight and facilitate cooling.