Forged Piston Cooling Oil Injection via Oblique Borehole
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Solution Overview
Problem
Existing piston manufacturing methods struggle to efficiently introduce cooling oil into complex cooling duct geometries, particularly in cast pistons, due to the need for expensive cores and casting molds, and in assembled pistons, the oil often rebounds due to blind hole drilling and welding beads.
Innovation Solution
A method involving a forged piston lower part with a closed supply inlet funnel formed by a forging tool, allowing for an oblique borehole that improves cooling oil retention and eliminates the need for clamping, enabling better cooling oil flow and integration with laser-welded steel pistons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blind hole is drilled from below to introduce cooling oil into the cooling duct, then the cooling oil can be supplied into the cooling duct, but the cooling oil rebounds due to the welding bead and does not flow efficiently into the cooling duct
Solution Approach 1:
Instead of drilling the borehole from below (shaft side) as in conventional methods, the invention drills the borehole from above (cooling duct side). This inversion allows the borehole to be drilled at an angle that directs cooling oil away from the welding bead, preventing rebound and improving flow efficiency into the cooling duct.
2Reliability
If a funnel element is positioned in the cooling duct cover to increase cooling oil retention, then cooling oil retention degree increases, but a complicated fastening is required to prevent it from falling out or twisting
Solution Approach 1:
The invention integrates the funnel function directly into the piston structure by forming a closed supply inlet funnel as an integral part of the piston lower part through forging. This merging eliminates the need for separate funnel elements and their complicated fastening structures, while maintaining the cooling oil retention function.
Solution Approach 2:
The piston lower part serves multiple functions: it provides structural support, contains the cooling duct, and includes the integrated closed supply inlet funnel for oil retention. This multi-functionality eliminates the need for separate components and simplifies the overall structure.
3Ease of manufacture
If the piston is made as a cast one-piece structure, then manufacturing is simpler, but complex cooling duct geometries cannot be reproduced or require very expensive cores and casting moulds
Solution Approach 1:
The invention divides the piston into two parts: a piston lower part (forged with cooling duct and funnel) and a piston upper part (cast or forged). This segmentation allows the complex cooling duct geometry to be precisely formed in the forged lower part while keeping the overall manufacturing process feasible and cost-effective.
Solution Approach 2:
The invention changes the manufacturing method for the piston lower part from casting to forging. This parameter change enables precise reproduction of complex cooling duct geometries and the integrated funnel structure, while the piston upper part can still be manufactured by casting or forging, maintaining manufacturing simplicity.
4Reliability
If the coordinate of the injection nozzle is predetermined close to the ring part, then the injection position is fixed, but a blind hole must be drilled which is restricted by the welding bead causing unfavorable oil rebound
Solution Approach 1:
Instead of drilling from below (which is restricted by the predetermined injection nozzle position and welding bead), the invention drills from above (cooling duct side) at an angle. This allows the borehole to be formed without interference from the welding bead, eliminating oil rebound while maintaining accurate injection positioning near the ring part.
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
This method enhances cooling oil retention and flow into the cooling duct, preventing oil rebound and allowing for efficient cooling, while simplifying the manufacturing process and enabling effective assembly of complex geometries without the need for costly cores.
Implementation Method 1
a closed supply inlet funnel is forged in the piston lower part into a cooling duct by means of a corresponding forging tool
Implementation Method 2
it is possible to form an oblique borehole at a distance from the ring part whereby an improved injection behaviour of the cooling oil can be reached
Implementation Method 3
The piston lower part and the piston upper part are then still welded to one another in a known way
Data Source
AI summary
A method for manufacturing a piston of an internal combustion engine from a piston upper part and a piston lower part may include producing at least the piston lower part as a forged steel part. A partial cross section of a cooling duct may be provided in the piston lower part. A closed supply inlet funnel may be forged within the piston lower part. The closed supply inlet funnel may be bored into the piston lower part from the cooling duct. A borehole may be introduced into the piston lower part obliquely to a piston axis. The piston lower part and the piston upper part may be welded to one another.