Gradient Anodized Piston Crown for Thermal Shock Resistance
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Solution Overview
Problem
Internal combustion engine pistons with heat barrier films of varying thicknesses are prone to thermal fatigue, leading to cracks and peeling due to thermal shock, and existing methods for forming such films inevitably create steps that exacerbate these issues, compromising both heat shielding performance and gas temperature followability.
Innovation Solution
An internal combustion engine piston with an anodized film on the piston crown surface, where the film thickness and silicon particle size gradually increase from the intake side to the exhaust side, accompanied by a gradual increase in the proportion of acicular silicon, formed through laser irradiation and anodizing treatment, eliminating the step boundary and enhancing thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the film thickness of the heat barrier film is increased, then the heat shielding performance is improved, but the gas temperature followability deteriorates
Solution Approach 1:
The patent applies local quality by creating regions with different film thicknesses on the piston crown surface. The heat barrier film is made thinner in regions requiring good gas temperature followability (such as near the spark plug) and thicker in regions requiring superior heat shielding (such as near the exhaust port), thereby optimizing both contradictory requirements in different locations simultaneously
Solution Approach 2:
The patent introduces a gradient film thickness structure that dynamically adapts to different thermal conditions across the piston crown. The film thickness varies continuously or in steps from one region to another, allowing the heat barrier film to provide appropriate thermal resistance locally while maintaining overall system performance
2Temperature
If the film thickness of the heat barrier film is decreased, then the gas temperature followability is improved, but the heat shielding performance deteriorates
Solution Approach 1:
The patent applies local quality by creating regions with different film thicknesses on the piston crown surface. The heat barrier film is made thinner in regions requiring good gas temperature followability (such as near the spark plug) and thicker in regions requiring superior heat shielding (such as near the exhaust port), thereby optimizing both contradictory requirements in different locations simultaneously
3Reliability
If a heat barrier layer with different film thicknesses is provided on the piston crown surface, then the heat shielding performance and gas temperature followability are optimized, but cracks and peeling occur due to thermal fatigue
Solution Approach 1:
The patent introduces a gradient film thickness structure that dynamically adapts to different thermal conditions across the piston crown. The film thickness varies continuously or in steps from one region to another, allowing the heat barrier film to provide appropriate thermal resistance locally while maintaining overall system performance
Solution Approach 2:
The patent applies preliminary action by pre-heating the piston crown surface before forming the heat barrier film. This pre-heating treatment modifies the surface properties and reduces thermal stress during subsequent thermal cycling, thereby preventing cracks and peeling that would otherwise occur due to thermal fatigue
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 configuration achieves superior heat shielding performance and gas temperature followability while suppressing cracks and peeling under thermal shock, improving engine efficiency and reducing abnormal combustion.
Implementation Method 1
a heat barrier film is formed on the surface of the aluminum alloy... suppresses heat conduction to the base material of aluminum alloy
Implementation Method 2
the ability to follow changes in the ambient gas temperature depends on the heat capacity (= specific heat × density × volume) of the heat barrier film
Implementation Method 3
anodized film covering the piston crown surface and containing silicon particles... formed through laser irradiation and anodizing treatment
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
[Problem to be Solved] To provide a piston for an internal combustion engine that is excellent in both heat shielding performance and gas temperature followability, and can suppress cracks and peeling even in a situation in which a thermal shock is repeatedly applied to the piston during sudden acceleration or deceleration, and a method for manufacturing the piston. [Solution] A piston crown surface 11 of a piston body made of aluminum alloy is irradiated with a laser to gradually increase an average particle size of eutectic Si in a surface of the piston crown surface from an intake side 5 to an exhaust side 6 of the piston crown surface by changing an irradiation output of the laser, and thereafter anodizing treatment is carried out on the piston crown surface to form an anodized film 12. As a result, a piston is obtained in which the film thickness of the anodized film 12 gradually increases from the intake side 5 to the exhaust side 6, the average particle size of the Si particles in the anodized film 12 and the average particle size of the eutectic Si immediately below the film in the piston crown surface gradually increase, and the proportion of acicular Si in the eutectic Si immediately below the film in the piston crown surface gradually increases.