Piston Crown Recesses for Thermal Management
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Solution Overview
Problem
Internal combustion engines face knocking issues due to heat retention caused by anodized films on piston crown surfaces, which have high thermal conductivity and volume specific heat capacity, leading to durability and thermal efficiency challenges, especially under continuous operation.
Innovation Solution
A method involving laser irradiation to create recesses on the piston crown surface of an aluminum alloy piston, followed by an AC/DC superposed voltage anodizing treatment to form an anodized film that closes the recess openings, creating hollow spaces within the film, thereby reducing thermal conductivity and volume specific heat capacity while maintaining durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an anodized film is formed on the piston crown surface to improve heat insulating property, then thermal efficiency is improved, but heat retention occurs leading to knocking and reduced durability
Solution Approach 1:
The patent forms an anodized film with a porous structure containing numerous pores on the piston crown surface. This porous structure reduces the thermal conductivity and volume specific heat capacity of the film compared to conventional dense anodized films, allowing heat to pass through more effectively while maintaining the insulating function, thereby suppressing heat retention and knocking during continuous operation
Solution Approach 2:
The patent creates a composite structure by forming an anodized film (aluminum oxide layer) on the aluminum alloy piston surface. The composite consists of the base aluminum alloy piston body and the porous anodized film layer with controlled porosity (30-70%), combining the structural integrity of the metal with the thermal management properties of the porous oxide layer
2Temperature
If an anodized film is formed on the piston crown surface, then heat insulating property is improved, but thermal conductivity and volume specific heat capacity increase causing heat retention
Solution Approach 1:
The patent utilizes a porous anodized film structure where the pores occupy 30-70% of the film volume. These pores reduce the effective thermal conductivity and volume specific heat capacity of the film by replacing solid material with air-filled voids, which have lower thermal properties. This allows the film to provide heat insulation while minimizing heat retention, solving the contradiction between insulation and heat loss
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 approach results in an anodized film with low thermal conductivity and volume specific heat capacity, effectively suppressing heat retention even during continuous engine operation, enhancing durability and thermal efficiency by allowing better heat dissipation.
Implementation Method 1
irradiating a piston crown surface of a piston body made of aluminum alloy with laser light to form a recess in a part of the piston crown surface irradiated with the laser light
Implementation Method 2
forming an anodized film on the piston crown surface by an anodizing treatment
Implementation Method 3
forming an anodized film on the piston crown surface by an anodizing treatment to close an opening of the recess
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~5(e)
AI summary
[Problem to be Solved] The present invention provides a piston for an internal combustion engine in which an anodized film is formed on a piston crown surface, the anodized film having low thermal conductivity and volume specific heat capacity, excellent durability, and the ability to suppress heat retention even during a continuous run of an internal combustion engine. The present invention also provides a method for manufacturing the piston. [Solution] The method for manufacturing a piston for an internal combustion engine according to the present invention includes: irradiating a piston crown surface 2 of a piston body made of aluminum alloy with laser light to form a recess 10; and forming an anodized film 20 on the piston crown surface 2 by applying an AC/DC superposed voltage to close an opening 13 of the recess 10. The piston for an internal combustion engine according to the present invention has a plurality of the recesses 10 in the piston crown surface 2, of which the openings are closed with the anodized film 25, and has a hollow space 26 closed with the anodized film 20 inside each of the plurality of recesses 10.