Coated Piston Ring Geometry for Lower Piston Groove Wear
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Solution Overview
Problem
Conventional piston rings for internal combustion engines cause significant wear in the piston grooves due to mechanisms like step wear, trumpet wear, and flat wear, and improving piston groove material strength through laser hardening is expensive and unfeasible.
Innovation Solution
A piston ring design featuring an annular base body with specific geometric features and protective coatings, including DLC and ceramic materials, to reduce wear and adhesive wear, with chamfers and texturing to minimize mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If piston groove material strength is improved through laser hardening, then wear resistance is improved, but manufacturing cost and process complexity increase significantly
Solution Approach 1:
The piston ring is designed with a non-uniform cross-section where the radially outer surface section has a limited extension (at most 0.3 mm) and merges into a radially inner surface section at an obtuse angle. This creates localized stress distribution that protects the piston groove without requiring expensive laser hardening of the entire piston groove material.
Solution Approach 2:
The piston ring employs a composite structure combining different material properties in specific geometric configurations. The base body material (stainless steel with 10-17% chromium) is combined with specific geometric features (chamfers, obtuse angle transitions) to achieve wear resistance without expensive surface hardening processes.
2Duration of action of stationary object
If piston ring geometry is optimized to reduce wear, then piston groove durability is improved, but manufacturing precision requirements increase
Solution Approach 1:
Chamfers are provided at the edges formed between the joint flanks and the axial end face, with axial extent of at most 0.16 mm (preferably 0.06 mm). These preliminary geometric features prevent stress concentration and edge damage before the piston ring is installed, reducing wear without requiring extremely tight manufacturing tolerances on the main body.
Solution Approach 2:
The radially outer surface section merges radially inward into the radially inner surface section at an obtuse angle, creating a smooth curved transition rather than a sharp corner. This geometric rounding prevents stress concentration and reduces manufacturing precision requirements while improving durability.
3Reliability
If protective coatings are applied to the piston ring, then wear and adhesive wear are reduced, but manufacturing complexity and cost increase
Solution Approach 1:
A protective coating is applied to the axial end face of the piston ring to serve as an intermediary layer between the metal piston ring and the piston groove. This coating (polymer, Cr electroplating, or DLC film) reduces direct metal-to-metal contact and adhesive wear, while the base geometric design (obtuse angle transitions, limited outer surface extension) provides mechanical protection, allowing for a balanced coating application process.
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
Significantly reduces piston groove wear and extends the life of the piston ring by minimizing abrasive and adhesive wear, enhancing durability and performance.
Implementation Method 1
a protective coating arranged on an outer circumference of the annular base body... Particularly expediently, the protective coating comprises or is a DLC coating
Implementation Method 2
a coating material of the protective coating may comprise or consist of a ceramic material, in particular a PVD ceramic coating based on nitrides
Implementation Method 3
The base material can comprise 10 to 17% of chromium
Data Source
AI summary
A piston ring for an internal combustion engine may include an annular base body and a protective coating arranged on an outer circumference of the base body. The base body may include a first joint flank, a second joint flank, an interruption along the circumferential direction, an axial end face, and an edge formed between the first joint flank and the end face. The interruption may form a joint bounded along a circumferential direction of the base body via the first joint flank and the second joint flank. The axial end face may include a radially outer surface section extending perpendicularly to a central longitudinal axis of the base body and merging radially inwards into a radially inner surface section extending at an obtuse angle to the central longitudinal axis. The edge may include a chamfer.