Trapezoid Ring Groove Machining for Piston Height Reduction
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Solution Overview
Problem
Existing trapezoid ring grooves for pistons are not suitable for receiving trapezoid rings with small axial overall height, leading to increased piston height and wear issues, particularly in series production due to limitations in tool steel machining capabilities.
Innovation Solution
A two-step method for producing a trapezoid annular groove using a tool steel with a trapezoid profile and parallel surfaces at the inward-facing end, where the groove is initially plunge cut and then finish-machined to achieve a small overall height, allowing for the reception of trapezoid rings with reduced axial dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-step plunge cutting method is used to machine the trapezoid groove, then the manufacturing process is simple and fast, but the tool steel cannot achieve the required small internal dimension with maximum height of 1 mm
Solution Approach 1:
The machining process is divided into two distinct steps: first, a preliminary groove is cut with a tool steel having a trapezoid profile to establish the basic geometry; second, the groove flanks are finish-machined to achieve the precise small dimensions (maximum height ≤ 1 mm) and parallel surfaces. This segmentation allows each step to be optimized for its specific function, resolving the contradiction between simplicity and precision.
Solution Approach 2:
The preliminary groove cutting step creates a pre-formed groove structure that prepares the workpiece for the subsequent precision machining. By performing this preliminary action first, the tool steel can remove larger amounts of material efficiently, and the second step can then focus on achieving the precise final dimensions without the complexity of attempting to do everything in one step.
2Length of moving object
If the groove base height is reduced to less than 1 mm, then the piston overall height is reduced, but the tool life decreases and wear increases
Solution Approach 1:
The tool steel is designed with different local geometries: the inward-facing end has two mutually parallel flanks for the groove base to ensure proper reception of the trapezoid ring and distribute loads evenly, while the outer portion has a trapezoid profile for the preliminary groove cutting. This local differentiation allows the groove base to have the required small height (≤ 1 mm) for reduced piston height while the parallel flank design maintains tool life by reducing wear through better load distribution.
3Duration of action of moving object
If the groove flanks are made parallel, then the tool life is significantly increased, but the trapezoid ring reception geometry is compromised
Solution Approach 1:
The tool steel incorporates two distinct local geometries: parallel flanks at the inward-facing end for the groove base that maximize tool life through reduced wear, and trapezoid profile flanks in the outer portion that facilitate proper trapezoid ring reception. This local differentiation resolves the contradiction by assigning different geometric qualities to different regions of the tool, allowing each function to be optimized independently.
Data Source
AI summary
A method for producing a piston for internal combustion engines, where the piston includes a circumferential trapezoid annular groove for receiving trapezoid rings with small axial dimensions the groove having a groove base with adjoining surfaces and groove flanks. The groove base with adjoining surfaces is created in a first method step by machining using a cutting steel tool and the groove flanks are created in a further method step. Also disclosed are a piston produced according to the method and a cutting steel tool.