Piston Undercrown Coating for Hot Spot Mitigation
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Solution Overview
Problem
Internal combustion engine pistons face challenges in maintaining uniform temperature due to hot spots along the cooling gallery and undercrown regions, leading to oil degradation and reduced engine efficiency, as existing cooling methods require high oil flow and frequent oil changes.
Innovation Solution
A piston design with a coating of high thermal conductivity (45 to 429 W/m·K) applied to hotter areas of the undercrown surface, while omitting it from cooler areas, to create a more uniform temperature distribution and reduce hot spots, thereby minimizing oil degradation and improving engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a cooling gallery with oil cooling is used to moderate the temperature of the piston crown, then the temperature of the crown is controlled, but high oil flow must be constantly maintained which adds to parasitic losses and reduces engine fuel efficiency
Solution Approach 1:
The patent applies different thermal conductivity properties to different regions of the piston crown. High thermal conductivity material (e.g., copper or aluminum) is used in specific hot spot areas to enhance heat dissipation locally, while the rest of the piston body maintains its original material properties. This localized approach reduces the need for high oil flow rates while effectively controlling temperatures in critical regions.
Solution Approach 2:
The patent employs composite construction by combining materials with different thermal conductivities in the piston crown. The composite structure integrates high thermal conductivity material in strategic locations to create preferential heat pathways, allowing the piston to dissipate heat more efficiently with reduced cooling oil flow requirements.
2Temperature
If a high flow of cooling oil is maintained to control piston temperature, then the temperature control is effective, but oil degradation occurs over time due to high temperature and frequent oil changes are required
Solution Approach 1:
By concentrating high thermal conductivity material in hot spot regions, the patent locally enhances heat dissipation where it is most needed. This reduces the overall thermal stress on the cooling oil and decreases the rate of oil degradation, extending oil service life while maintaining effective temperature control in critical areas.
Solution Approach 2:
The patent converts the problematic hot spots into beneficial heat dissipation zones by applying high thermal conductivity material precisely where hot spots occur. This transforms the previously harmful localized overheating into controlled heat transfer pathways, reducing overall thermal load on the cooling system and decreasing oil degradation.
3Ease of manufacture
If the piston body material has lower thermal conductivity (such as 42CrMo4+Si with 25 to 30 W/m·K), then manufacturing and material selection is simplified, but hot spots become more prevalent along the cooling gallery and undercrown regions
Solution Approach 1:
The patent maintains the ease of manufacturing the piston body with standard materials while locally addressing hot spot issues by applying high thermal conductivity material only in specific regions. This selective approach preserves manufacturing simplicity while effectively eliminating hot spots in critical areas.
Solution Approach 2:
The patent creates a composite structure by combining the base piston material with high thermal conductivity material in strategic locations. This composite approach allows the use of easily manufactured base materials while introducing thermal management capabilities in specific regions where hot spots occur.
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 high thermal conductivity coating effectively dissipates heat from hot spots, reducing oil degradation and enhancing engine efficiency by maintaining a more uniform temperature, thus extending engine service life and improving fuel efficiency.
Implementation Method 1
A coating having a thermal conductivity ranging from 45 to 429 W/m·K is applied to at least one hotter area of at least one of the portions of the undercrown surface
Data Source
AI summary
A vehicle internal combustion piston and method of construction thereof are provided. The piston includes piston body extending along a central longitudinal axis, having an upper combustion wall forming an upper combustion surface and an undercrown surface opposite the upper combustion surface. An annular ring belt region depends from the upper combustion surface, a pair of skirt panels depend from the ring belt region, and a pair of pin bosses depend from the undercrown surface to provide laterally spaced pin bores aligned along a pin bore axis for receipt of a wrist pin. The undercrown surface forms a central undercrown region, and a portion of either an open outer cooling gallery, a sealed outer cooling gallery, or an outer galleryless region. A coating including copper is applied to hot spots along the undercrown surface to mitigate the hot spots provide a more uniform temperature along the undercrown surface during operation.