Elliptical Piston With Rotation-Symmetric Ring Groove Machining
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Solution Overview
Problem
The production of pistons for internal combustion engines is complex and costly due to the need for multiple production steps to create an elliptical outer surface and a ring groove, which often results in burrs and increased mechanical loading, leading to wear and increased production effort.
Innovation Solution
Forming the ring groove region rotation-symmetrically, allowing for simplified machining and integration with the elliptical piston outer surface, reducing production steps and eliminating the need for separate production processes for the ring portion and piston body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piston outer surface is machined elliptically to account for different loads on pressure side and counter-pressure side, then the piston performance and durability are improved, but the production complexity and cost increase due to requiring superimposed oscillations on rotary movement during turning and specialized tools
Solution Approach 1:
The piston production process is segmented into two distinct phases: first, the blank is turned with a rotation-symmetrical outer surface using conventional rotary movement; second, the ring groove is introduced into the already-formed piston body. This segmentation allows each step to use simple, standard machinery without requiring complex superimposed oscillations, thereby reducing production complexity while maintaining the ability to produce the elliptical outer surface through subsequent machining of the ring groove region only
Solution Approach 2:
The blank is pre-formed with a rotation-symmetrical outer surface through conventional turning before the ring groove is introduced. This preliminary action with simple machinery establishes the basic piston shape, allowing the subsequent ring groove machining to be the only step requiring specialized tooling for the elliptical profile, thereby simplifying the overall production process
2Ease of manufacture
If the ring groove is introduced after machining the piston outer surface, then the production sequence is logical, but burrs are formed on the ring groove edges leading to increased wear and mechanical loading during operation
Solution Approach 1:
The conventional sequence is inverted: instead of machining the outer surface first and then introducing the ring groove (which creates burrs), the ring groove is introduced into the blank first, and then the outer surface is machined. This inversion allows the outer surface machining to simultaneously finish the ring groove edges, removing burrs and preventing the harmful effects of protruding material during operation
3Reliability
If the ring portion is moved radially to the inside to prevent contact of the harder ring carrier with the cylinder wall, then wear is reduced, but additional production steps are required to machine the radial recess
Solution Approach 1:
The machining of the radial recess for the ring portion and the introduction of the ring groove are merged into a single production step. The ring groove is introduced directly into the blank at the appropriate radial position, eliminating the need for a separate step to machine the radial recess. This combining of operations reduces the total number of production steps while achieving the same wear protection effect
Data Source
AI summary
A piston for an internal combustion engine may include a piston crown, a piston body, and a ring portion. The piston body may have a radially outermost piston outer surface, which may emanate from the piston crown and extend axially and in a circumferential direction. The ring portion may be disposed axially spaced apart from the piston crown. The ring portion may extend axially and in the circumferential direction. The ring portion may include a ring carrier with a ring groove configured to receive a piston ring. The ring portion may further include a radially outer ring portion outer surface that extends in the circumferential direction. The ring portion outer surface may be disposed radially to an inside relative to the piston outer surface. The piston outer surface may extend elliptically in the circumferential direction. The ring portion outer surface may extend rotation-symmetrically in the circumferential direction.