Piston Ring Land Geometry for Stable Second Land Pressure

Solution Overview

Problem

Internal combustion engines face issues such as load-induced rapid combustion, higher emissions from oil burning, higher oil consumption, and increased piston deposits due to the wear of piston rings, which existing piston designs fail to adequately address, particularly in terms of reduced maintenance and consistent land pressure.

Innovation Solution

The piston design features an annular body with a crown portion, circumferential annular wall, and skirt, including grooves and lands with chamfered blends that reduce the variation in effective gap area, leading to more consistent second land pressure and improved engine performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If piston rings are used in compression ignition engines, then engine power and efficiency are improved, but load-induced rapid combustion, higher emissions from oil burning, higher oil consumption, and increased piston deposits occur due to ring wear and pressure variation

Engineering Contradiction:

Improveengine powerVSAvoidload-induced rapid combustion and emissions

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by modifying only the second land area between the first and second piston ring grooves, specifically by removing material to create a reduced cross-sectional area. This localized modification affects only the pressure distribution in the second land region, reducing second land pressures that cause load-induced rapid combustion, while leaving the rest of the piston structure unchanged to maintain overall engine power and performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the geometric parameter of the second land by reducing its cross-sectional area through material removal. This parameter change directly affects the pressure distribution characteristics in the second land region, lowering the peak pressures that lead to harmful combustion phenomena, oil consumption, and deposits, while maintaining the functional integrity of the piston ring system.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If conventional piston design with uniform land areas is used, then manufacturing is simple, but second land pressure variation is high causing increased maintenance needs

Engineering Contradiction:

Improvepiston manufacturing simplicityVSAvoidmaintenance interval

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by modifying only the second land area between the first and second piston ring grooves, specifically by removing material to create a reduced cross-sectional area. This localized modification affects only the pressure distribution in the second land region, reducing second land pressures that cause load-induced rapid combustion, while leaving the rest of the piston structure unchanged to maintain overall engine power and performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the geometric parameter of the second land by reducing its cross-sectional area through material removal. This parameter change directly affects the pressure distribution characteristics in the second land region, lowering the peak pressures that lead to harmful combustion phenomena, oil consumption, and deposits, while maintaining the functional integrity of the piston ring system.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11306678B1Piston design feature to minimize periodic second land pressure variation

Publication Date: 2022.04.19 CATERPILLAR INC

AI summary

A piston includes an annular body including a crown portion defining a longitudinal axis, a radial direction perpendicular to the longitudinal axis, and a circumferential direction. The crown portion includes a top squish surface, and a circumferential annular wall extending downwardly axially from the top squish surface as well as a skirt. A first piston ring receiving groove is spaced away from the top squish surface, an upper land and a lower land extend from the first piston ring receiving groove, and a bottom blend connects the lower land to the first piston ring receiving groove.