Outboard-motor cylinder block and manufacturing method therefor
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Solution Overview
Problem
Outboard-motor cylinder blocks made of aluminum alloy are susceptible to corrosion when exposed to seawater, and existing methods for preventing corrosion do not adequately address the issue of corrosion resistance and sealing at the joining surface with a gasket.
Innovation Solution
A manufacturing method involving the formation of a sealed anodized film on the aluminum alloy surface, followed by a chemical conversion coating film, which includes pressing with elastic jigs to ensure uniform coverage and sealing of the anodized film pores, using chromium and/or zirconium as primary components in the sealing and coating processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If aluminum alloy is used for the cylinder block to reduce weight, then weight is reduced, but corrosion resistance deteriorates due to low natural electrical potential in seawater environment
Solution Approach 1:
The invention applies a multi-layer composite coating system on the aluminum alloy cylinder block surface, consisting of a phosphate conversion coating layer and an epoxy polyester paint layer. This composite material approach provides both weight reduction from aluminum alloy and corrosion protection through the layered coating structure that acts as barrier against seawater penetration.
Solution Approach 2:
The invention changes the surface parameters of the aluminum alloy by applying chemical conversion coating (phosphating) followed by organic paint coating. This transforms the naturally susceptible aluminum surface into a protected surface with improved corrosion resistance while maintaining the base material's lightweight property.
2Reliability
If existing anodizing and sealing treatment is applied to improve corrosion resistance, then corrosion resistance is improved, but sealing characteristics with gasket at joining surface deteriorate due to lack of smoothness
Solution Approach 1:
The invention segments the treatment into two distinct zones: the cylinder bore inner peripheral surface receives anodizing and sealing treatment for corrosion protection, while the joining surface is excluded from this treatment to maintain smoothness. This spatial segmentation allows each surface to have optimized properties for its specific function.
Solution Approach 2:
The invention applies different surface treatments to different locations: anodized film with sealing is applied locally to the cylinder bore area where corrosion resistance is critical, while the joining surface maintains its original smooth aluminum alloy surface quality to ensure proper gasket sealing. This local differentiation resolves the contradiction between corrosion protection and sealing performance.
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 method enhances corrosion resistance and sealing characteristics at the joining surface, preventing corrosion even under high-temperature and seawater exposure conditions, ensuring effective sealing with the gasket and maintaining smoothness.
Implementation Method 1
subjecting the cylinder block body to anodizing to form an anodized film on a surface part of the aluminum alloy
Implementation Method 2
forming an anodized film on a surface of an aluminum alloy part of the outboard-motor cylinder block body other than the cylinder bore by carrying out an anodizing treatment
Implementation Method 3
carrying out a sealing treatment to seal the pores of the anodized film, thereby forming the sealed anodized film
Implementation Method 4
forming a chemical conversion coating film on a surface of the anodized film covering an inner peripheral surface of the water jacket and on a surface of the aluminum alloy exposed on the joining surface
Data Source
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AI summary
After an anodized film is formed on the surface of an aluminum alloy part of an outboard-motor cylinder block body other than cylinder bores, sealing treatment is performed on the surface of the anodized film and finishing processing of removing the anodized film on a joining surface to expose the aluminum alloy is performed, and then a chemical conversion coating film is formed on the anodized film, which covers the inner peripheral surface of a water jacket, and the aluminum alloy on the joining surface. Accordingly, an outboard-motor cylinder block in which the aluminum alloy on the inner peripheral surface of the water jacket is covered with the sealed anodized film, the sealed anodized film is further covered with the chemical conversion coating film, and the aluminum alloy on the joining surface is covered with the chemical conversion coating film can be obtained.