Piston Top Ring Groove Anodizing for Heat Insulation and Sealing
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Solution Overview
Problem
High Cu content in aluminum alloy pistons for internal combustion engines leads to reduced thermal insulation performance, causing the base material to soften and deteriorate the smoothness of the top ring groove, resulting in poor sealing and increased oil combustion, which violates environmental regulations.
Innovation Solution
A method involving a masking step, mixed acid immersion treatment to elute Cu from the top ring groove, and an anodizing treatment to form a heat insulation layer with a lower Cu content, followed by an anodized film formation, improving heat insulation and maintaining surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aluminum alloy with high Cu content is used to improve mechanical strength, then fatigue strength and tensile strength are improved, but thermal insulation performance deteriorates
Solution Approach 1:
The invention applies different material compositions to different regions of the piston. The base material uses high-Cu aluminum alloy for overall strength, while the top ring groove region undergoes mixed acid immersion treatment to create a localized low-Cu heat insulation layer. This local differentiation resolves the contradiction by providing both high strength (base material) and thermal insulation (top ring groove region) simultaneously.
2Strength
If high-Cu aluminum alloy is used as base material, then mechanical characteristics are improved, but the top ring groove smoothness deteriorates due to softening
Solution Approach 1:
The invention creates a localized low-Cu concentration region specifically in the top ring groove area through mixed acid immersion treatment. This local modification maintains the high strength of the base material while preventing softening and smoothness deterioration in the critical top ring groove region, thereby resolving the contradiction between strength and manufacturing precision.
3Temperature
If the base material temperature increases, then the base material softens, but sealing property deteriorates
Solution Approach 1:
The invention introduces a heat insulation layer with low Cu content as an intermediary between the high-Cu base material and the combustion chamber environment. This intermediate layer acts as a thermal barrier, reducing heat transfer to the base material and preventing softening that would compromise sealing properties, thus resolving the contradiction between temperature and reliability.
4Reliability
If oil flows into the combustion chamber due to poor sealing, then lubrication function is compromised, but harmful emissions increase
Solution Approach 1:
The heat insulation layer serves as a protective intermediary that maintains base material strength and surface integrity at the top ring groove. By preventing softening and maintaining smoothness, this intermediate layer ensures proper sealing, thereby simultaneously improving reliability and reducing harmful emissions from oil combustion.
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 approach enhances heat insulation performance, prevents base material softening, maintains sealing properties, and reduces the generation of environmentally harmful substances like PM and PN by ensuring the top ring groove remains smooth and effective.
Implementation Method 1
immersing the masked main body of the piston in aqueous mixed acid solution, and eluting Cu in a region with a depth from the inner surface of the exposed top ring groove
Implementation Method 2
an anodizing treatment step for forming the anodized film with the expected thickness on the inner surface of the top ring groove of the main body of the piston taken from the aqueous mixed acid solution
Data Source
Figure 1~2C
Figure 3~4
Figure 5~6B
AI summary
[Problem to be Solved] To provide a piston for an internal combustion engine and a method for manufacturing the same, ensuring improved heat insulation performance in a top ring groove irrespective of a base material made of an aluminum alloy with greater Cu content compared with a conventional case, and to maintain sealing property with a piston ring by maintaining smoothness of an inner surface of the top ring groove. [Solution] In a method for manufacturing a piston for an internal combustion engine according to the present invention, a masking step is performed on a main body of the piston made of an aluminum alloy as the base material 10, which contains Si at 5.0 to 20.0%, and Cu at 1.3% to 5.0% to expose the inner surface of the top ring groove. The main body of the piston is immersed in an aqueous mixed acid solution for eluting Cu in a region 27a with a depth corresponding to 1/2 or more of a thickness of an anodized film to be formed from the inner surface of the top ring groove so that the anodized film is formed. The piston for an internal combustion engine is provided with a heat insulation layer 27b between the base material 10 and the anodized film 20, which has a Cu content less than that of the base material.