Piston Cooling Gallery Inlet Geometry to Prevent Oil Egress
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Solution Overview
Problem
Existing piston designs for internal combustion engines face challenges in maintaining effective oil circulation within the annular cooling galleries, leading to insufficient cooling and potential reduction in piston lifespan due to oil egress through the oil inlet, with existing solutions requiring additional manufacturing processes and costs.
Innovation Solution
A piston design featuring an upstanding toroid-shaped protrusion at the oil inlet and no protrusion at the oil outlet, formed as a monolithic extrusion from the lower crown, which inhibits reverse oil flow and enhances one-way circulation, allowing for improved cooling effectiveness while minimizing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate annular part is fixed to the piston to form a barrier about the oil inlet, then oil egress is inhibited, but manufacturing complexity and cost increase due to secondary attachment processes
Solution Approach 1:
The barrier is merged with the piston body by forming it as an integral feature of the lower crown during the same forging or casting process, eliminating the need for separate parts and secondary attachment processes while maintaining the oil circulation effectiveness
Solution Approach 2:
The lower crown serves multiple functions: it provides structural support, forms the cooling gallery, and creates the barrier feature to prevent oil egress, all in a single integrated component that simplifies manufacturing
2Reliability
If a barrier is formed in a casting operation, then oil egress is prevented, but manufacturing flexibility is reduced and special molds are required for each piston form
Solution Approach 1:
The barrier is formed as an integral feature of the lower crown during the same forging or casting process, eliminating the need for separate parts and secondary attachment processes while maintaining the oil circulation effectiveness
Solution Approach 2:
The barrier geometry is optimized by varying its height and position parameters within the lower crown, allowing adaptation to different piston designs without requiring fundamentally different manufacturing processes or special molds
3Ease of manufacture
If oil is allowed to exit through the oil inlet, then manufacturing is simpler, but cooling effectiveness is insufficient and piston life is diminished
Solution Approach 1:
Instead of using complex mechanisms to force oil through the cooling gallery, the design inverts the approach by creating a simple geometric barrier that naturally prevents oil from taking the easy exit path, relying on the oil pressure and gallery geometry to ensure proper circulation
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 ensures effective oil circulation and cooling within the annular gallery, preventing oil egress and promoting uniform cooling, thereby extending piston life and reducing manufacturing complexities and costs.
Implementation Method 1
The upstanding protrusion of the oil inlet extends upwardly from the floor into the cooling gallery, wherein the protrusion is formed as a monolithic extrusion from the material of the lower crown floor. The protrusion inhibits the reverse flow of oil outwardly from the cooling gallery through the oil inlet
Implementation Method 2
Pistons for internal combustion engines are known to include annular cooling galleries to facilitate maintaining the pistons within operable temperature limits. Once oil is delivered into the cooling gallery through an oil inlet, it is desirable to have the oil circulate to an opposite side of the piston
Implementation Method 3
the protrusion is formed as a monolithic extrusion from the material of the lower crown floor
Data Source
Figure 1~2A
Figure 2~3
AI summary
A piston and method of construction thereof are provided. The piston includes an upper crown having an upper combustion surface and a lower crown depending therefrom. The lower crown includes a pair of laterally spaced, axially aligned pin bores configured for receipt of a wrist pin. A substantially closed, annular outer cooling gallery is formed between the upper and lower crowns, wherein a bottom surface of the cooling gallery is formed by a floor of the lower crown. An oil inlet and an oil outlet extend through the floor. The oil inlet includes an upstanding toroid-shaped protrusion that extends upwardly from the floor into the cooling gallery, wherein the protrusion is formed as a monolithic extrusion from the material of the lower crown floor.