Assembled Piston Upper Part Grooved Contact Surfaces
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Solution Overview
Problem
High ignition pressures in newer engines increase contact pressure and relative movements between the surfaces of assembled pistons, leading to excessive frictional wear and material detachment due to the high cost of wear-resistant coatings like tungsten carbide-cobalt plating or copper-nickel-indium alloy.
Innovation Solution
Implementing a groove-shaped profile on the contact surfaces of the upper piston part with a roughness of 10 to 25 μm, produced easily and inexpensively by turning or laser processing, to reduce wear without the need for expensive coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expensive wear-resistant coatings like tungsten carbide-cobalt plating or copper-nickel-indium alloy are applied using detonation spraying, then frictional wear of contact surfaces is reduced, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive, durable wear-resistant coatings with a cheaper alternative: a groove-shaped profile structure. This profile is created through relatively inexpensive turning or laser processing and provides wear protection through its geometric design rather than through expensive material coatings, thus reducing manufacturing cost while maintaining adequate wear resistance.
Solution Approach 2:
The patent changes the surface geometry parameter by introducing a groove-shaped profile with specific dimensions (groove depth of 10 to 500 μm, groove spacing of 300 to 1200 μm). This geometric modification alters the contact mechanics and reduces wear through the profile structure itself, eliminating the need for expensive material-based wear resistance solutions.
2Power
If high ignition pressures are used to increase engine performance, then power output improves, but contact pressure and relative movements between piston surfaces increase leading to excessive frictional wear
Solution Approach 1:
The patent applies a groove-shaped profile specifically to the contact surfaces of the piston upper part that are subject to wear. This local geometric modification concentrates the wear protection where it is most needed - at the contact interfaces experiencing high pressure and relative movement - without requiring expensive coatings over the entire piston surface.
Solution Approach 2:
The groove-shaped profile introduces curved geometric features (concave grooves) to the contact surfaces. These curved profiles help distribute contact pressures more favorably and reduce stress concentrations compared to flat surfaces, thereby reducing frictional wear under high ignition pressures.
Data Source
Figure 1~2
AI summary
An upper part (1) of an assembled piston is disclosed, comprising a radially directed inner contact surface (2) arranged on the underside of an annular rib (15) and a radially directed outer contact surface (3) arranged on the underside of an annular wall (25), the outer (3) and the inner contact surface (2) each having a grooved profile in the form of concentric grooves with an average depth between Rz 10 and Rz 30. The wear on the contacting surfaces of the upper piece and the lower piece of the assembled piston is thus reduced.