Piston Cooling Recesses for Thermal Management

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Solution Overview

Problem

Internal combustion engine pistons face severe thermal loads due to increased combustion temperatures and pressures, leading to material strength loss and dimensional instability, which existing cooling methods struggle to effectively address, especially in thermally stressed zones.

Innovation Solution

The introduction of conically widening recesses in the piston upper part to expand the cooling space, allowing for enhanced coolant flow and increased cooling efficiency, while maintaining structural integrity and compatibility with existing piston designs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If an annular cooling channel is used to cool the piston, then cooling is achieved, but the cooling effectiveness is insufficient in thermally stressed zones

Engineering Contradiction:

Improvepiston temperatureVSAvoidcooling effectiveness

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The cooling channel is segmented into multiple separate recesses distributed across the piston upper part, allowing coolant to be delivered to multiple thermally stressed zones simultaneously. Each recess acts as an independent cooling unit, improving overall cooling effectiveness while maintaining manageable individual channel sizes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Cooling is concentrated in specific local areas through the recesses positioned in thermally stressed zones of the piston upper part. The recesses are strategically located where heat generation is highest, providing localized intensive cooling rather than uniform distributed cooling, thereby improving cooling effectiveness where it is most needed.

Inventive Principle:

Principle #3Local quality

2Volume of stationary object

If cooling slots with parallel walls are introduced to enlarge cooling space, then cooling area increases, but manufacturing complexity increases

Engineering Contradiction:

Improvecooling space volumeVSAvoidmanufacturing ease

Core Design Contradiction:

Volume of stationary objectVSEase of manufacture

Solution Approach 1:

The recesses are designed with conically widening walls that converge to a rounded bottom, replacing the complex parallel-walled slots. This curved geometry simplifies manufacturing through standard drilling and reaming operations while effectively enlarging the cooling space volume through the conical expansion.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The cooling channel transitions from a two-dimensional annular groove to three-dimensional recesses with significant depth and conical expansion. By utilizing the vertical dimension and conical geometry, the cooling space volume is enlarged without requiring complex lateral slot structures, thereby simplifying manufacturing.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If the recesses are made deeper to increase cooling space, then cooling effectiveness improves, but structural strength decreases

Engineering Contradiction:

Improvecooling effectivenessVSAvoidpiston structural strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The recesses utilize conical wall geometry that changes the cross-sectional area parameter along their depth. The walls widen conically from the opening toward the bottom, maximizing the cooling space volume while maintaining adequate wall thickness in the piston body. This parameter variation allows deep recesses without compromising structural strength.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The conical curvature of the recess walls provides structural efficiency by distributing stresses more evenly compared to sharp corners or flat walls. The rounded bottom and sloped sides reduce stress concentrations, allowing deeper recesses to be accommodated while maintaining the structural integrity of the piston upper part.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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

This solution effectively reduces piston temperature below the flame point of conventional cooling oils, preventing coking and thermal deformation, enabling higher combustion temperatures and pressures, and meeting stringent emissions requirements while maintaining structural strength and reducing weight.

Implementation Method 1

The coolant flowing through the cooling channel acts to dissipate heat

Methodology Applied

Scientific EffectHeat dissipation: Convection

Implementation Method 2

the coolant flowing through the cooling channel and then exits

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8973548B2Piston upper part of an assembled or welded piston with extended cooling spaces

Publication Date: 2015.03.10 KS KOLBENSCHMIDT GMBH

AI summary

A liquid cooled piston of an internal combustion engine includes a piston lower part and piston upper part which has a combustion chamber recess. These piston components are supported via joining lands which are spaced apart radially and together form a dividing plane, and are joined together with a material-to-material fit. In order to receive piston rings, the piston upper part has a ring area and includes an annular cooling channel which extends into the piston lower part and is connected to an inner cooling space via connecting channels. The cooling channel is adjoined by recesses which are oriented in the direction of a piston head, are configured as a blind hole and widen conically starting from the cooling channel as far as a recess bottom. The recess bottom can be of a pronounced undulating enlarged surface or a finely undulating configuration.