Hollow Valve Stem Geometry for Better Internal Cooling
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Solution Overview
Problem
Existing methods for producing hollow valves with optimized interior stem geometry are costly and require numerous process steps, often involving expensive machining and spot welds at critical points, which can lead to inefficiencies in material utilization and cooling efficiency.
Innovation Solution
A method involving flow forming over a structuring mandrel with a surface structure to enlarge the tubular wall, followed by swaging or drawing to reduce the outer diameter, enhancing the interior stem geometry for improved heat transfer and cooling, while minimizing process steps and avoiding costly machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If turning or milling the cavity is used to produce hollow valves, then the interior stem geometry can be created, but the production cost increases significantly
Solution Approach 1:
The patent replaces expensive mechanical machining processes (turning, milling) with a flow forming process that uses plastic deformation to create the interior stem geometry. This substitution eliminates the need for costly CNC machining operations while achieving the same geometric precision through forming rather than material removal.
Solution Approach 2:
The invention changes the manufacturing approach from subtractive machining to additive/deformative flow forming. By altering the fundamental manufacturing parameter from cutting to flowing material over a mandrel, the process achieves complex interior geometries without the high costs associated with precision machining.
2Ease of manufacture
If multiple process steps including welding are used to produce hollow valves, then the valve can be manufactured, but the number of process steps and production time increase
Solution Approach 1:
The patent combines multiple separate manufacturing operations into a single integrated flow forming process. The preform is directly formed into the final hollow valve geometry with interior stem structure in one continuous operation, eliminating the need for separate machining, assembly, and welding steps that would otherwise be required.
Solution Approach 2:
The invention performs the interior stem geometry creation during the initial flow forming stage rather than requiring subsequent machining operations. The preform is pre-shaped with the correct interior geometry through the flow forming process itself, eliminating later corrective or finishing operations.
3Ease of manufacture
If a smooth interior stem surface is used, then the manufacturing process is simpler, but the heat transfer efficiency between the valve wall and cooling medium decreases
Solution Approach 1:
The patent applies a structured surface pattern to the interior stem area while keeping the exterior surface smooth. This local differentiation provides enhanced heat transfer surfaces in the critical interior region where cooling occurs, without compromising the overall manufacturing simplicity of the flow forming process.
Solution Approach 2:
The invention uses a mandrel with a specifically designed surface structure that creates optimized curvature patterns on the interior stem surface. These curved and textured surfaces increase the effective heat transfer area and improve thermal contact with the cooling medium compared to a simple smooth cylindrical surface.
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 achieves optimized interior stem geometry with enhanced heat transfer and cooling efficiency, reducing material waste and process complexity, resulting in a more productive and cost-effective hollow valve production process.
Implementation Method 1
flow forming the tubular wall over a flow-forming mandrel, which is inserted into the cavity to enlarge a length of the tubular wall; and reducing an outer diameter of the tubular wall by swaging or drawing and ironing
Implementation Method 2
optimising the interior stem geometry by means of a structure to increase the heat transfer both within the cavity, i.e. by means of a cooling medium located within it, as well as between the valve wall and the cooling medium
Data Source
AI summary
A method for producing a valve body of a hollow valve with optimised interior stem geometry includes a preform with a valve plate and a tubular wall surrounding a cavity. Flow forming the tubular wall over a flow-forming mandrel, which is inserted into the cavity to enlarge a length of the tubular wall. An interior area of the tubular wall is embossed with a structure either due to the fact that the flow-forming mandrel is a structuring mandrel having a surface structure, or alternatively, because the method includes a further step of reducing an outer diameter of the tubular wall by swaging or drawing and ironing over a structuring mandrel. Furthermore, a hollow valve is produced by this method.