Piston Oil Control Ring Grooves and Coating

Solution Overview

Problem

Internal combustion engine pistons face challenges in balancing strength, durability, and reduced size and weight to improve engine efficiency, fuel economy, and reduce oil consumption, as existing designs struggle to optimize these competing demands.

Innovation Solution

A piston design featuring an improved oil control ring with a monolithic construction, annular grooves for oil collection and reduced contact area, through openings for fluid communication, tapered surfaces for reduced friction, and a chromium-based coating with nanodiamonds, which minimizes oil consumption and friction while reducing the number of components and material costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the piston is made robust to handle increased power demands, then strength and durability are improved, but the size and weight increase

Engineering Contradiction:

Improvepiston strengthVSAvoidpiston weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The piston is divided into functionally optimized zones: a robust crown section for strength and durability, and a reduced-mass skirt section. The crown features optimized thickness and reinforcement ribs specifically where structural integrity is needed, while the lower sections use thinner walls and optimized geometry to reduce weight. This segmentation allows the piston to be strong where required without unnecessary weight throughout the entire component.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the piston are given different structural qualities tailored to their specific functional requirements. The crown and combustion chamber area use thicker sections and reinforcement features for strength, while the skirt and lower sections use reduced thickness for weight savings. The oil control ring groove area incorporates specific local features that optimize both structural integrity and weight reduction in that localized region.

Inventive Principle:

Principle #3Local quality

2Reliability

If traditional oil control ring design is used, then oil control function is provided, but the ring occupies excessive axial space and increases piston compression height

Engineering Contradiction:

Improveoil control functionVSAvoidaxial space occupation

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

Multiple oil control functions are merged into a single integrated ring structure. The oil control ring incorporates both the oil scraping function and the oil distribution function within one component, eliminating the need for separate oil control and oil wiper rings. This merging reduces the total axial space occupied by oil control components while maintaining comprehensive oil management functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The oil control ring is designed as a multi-functional component that performs multiple tasks simultaneously: scraping excess oil from the cylinder wall, distributing oil uniformly across the piston surface, and controlling oil consumption. This universal design eliminates the need for multiple specialized rings, reducing axial space requirements while enhancing overall oil control reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If the number of piston rings is increased to improve sealing and oil control, then sealing and oil control performance are improved, but the piston compression height and complexity increase

Engineering Contradiction:

Improvesealing and oil control performanceVSAvoidpiston ring quantity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The oil control ring is designed as a multi-functional component that performs multiple tasks simultaneously: scraping excess oil from the cylinder wall, distributing oil uniformly across the piston surface, and controlling oil consumption. This universal design eliminates the need for multiple specialized rings, reducing axial space requirements while enhancing overall oil control reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Multiple oil control functions are merged into a single integrated ring structure. The oil control ring incorporates both the oil scraping function and the oil distribution function within one component, eliminating the need for separate oil control and oil wiper rings. This merging reduces the total axial space occupied by oil control components while maintaining comprehensive oil management functionality.

Inventive Principle:

Principle #5Merging (Combining)

4Loss of substance

If annular grooves are added to the oil control ring for oil collection, then oil consumption is reduced, but the contact area between ring and groove wall increases friction potential

Engineering Contradiction:

Improveoil consumptionVSAvoidfriction and stick condition

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The annular grooves act as intermediary oil collection channels that capture excess oil before it contributes to friction and sticking. By providing dedicated pathways for oil drainage, the grooves reduce the amount of oil that would otherwise accumulate in the ring groove and increase friction. The grooves mediate between the oil control function and the friction reduction requirement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The groove geometry is locally optimized to balance oil collection and friction reduction. The grooves are positioned and dimensioned to capture oil effectively while maintaining sufficient clearance and smooth transitions that minimize contact friction. The local groove design quality ensures that oil collection does not come at the expense of excessive friction or sticking potential.

Inventive Principle:

Principle #3Local quality

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

The improved piston design enhances engine efficiency, reduces friction and oil consumption, minimizes size and mass, and lowers manufacturing costs, achieving a balance between strength and weight reduction while maintaining durability.

Implementation Method 1

facilitate the collection of oil that is scraped from a cylinder wall, and further facilitate the return of the collected oil to a crank case sump

Methodology Applied

Scientific EffectGravity: Gravitation

Implementation Method 2

a chromium-based coating with nanodiamonds, which minimizes oil consumption and friction

Methodology Applied

Scientific EffectLubrication: Lubrication

Data Source

PatentEP3368800B1Piston, oil control ring therefor and method of construction thereof

Publication Date: 2020.02.12 TENNECO INC

Figure 1A~2
Figure 1B~3
Figure 4

AI summary

A piston for an internal combustion engine having an improved oil control ring is provided. The piston has a piston body providing an upper combustion surface and an annular outer wall depending therefrom. A ring belt region including a plurality of ring grooves is formed in the annular outer wall. A first compression ring is disposed in one of the ring grooves and the oil control ring is disposed in another of the ring grooves. The oil control ring has generally parallel, planar upper and lower surfaces, with the upper and lower surfaces having are annular groove recessed therein. A through opening can be formed to bring the annular grooves into fluid communication with one another. The annular grooves collect oil scraped from a cylinder wail and return oil to the crank sump and reduce the contact area between the oil control ring and the wall of the ring groove.