Search Results

In motorcycles, the exposed mechanical parts play important roles in the styling design. The bolts that fasten these parts a good appearance in addition to the fastening function. Since many parts of a motorcycle are designed so as to appeal the mechanical and metallic beauty, needs are higher for silver-color bolts. Motorcycle bolts are exposed to the external environment, so they are required to have also cosmetic durability. Though there is a surface treatment having a higher cosmetic durability such as the chromium plating, due to its metallic gloss like a mirror, chrome-plated bolts are applicable only to specific models and parts. In this study, we developed a surface treatment that enhance the appearance and cosmetic durability required of bolts for motorcycles. The layer of developed surface treatment is dip coating with thin film polyorganosiloxane material on zinc plating.

A black surface treatment without using hexavalent chromium and applicable to bolts of motorcycles has been developed. The surface treatment also satisfies the requirements of bolts for motorcycles such as fastening performance, corrosion resistance, weather resistance and appearance of outer finish. There is a method of coating a black chemical conversion film using trivalent chromium on the zinc-plated surface as one of the surface treatments that do not use the hexavalent chromium. Such a black film, however, is thinner than the film using hexavalent chromium, and unable to ensure satisfactory black appearance. Meanwhile, although the dip-coating using a black paint can provide a sufficient black color, it is necessary to apply coating two times to eliminate an irregular color. As a result, thick paint films are formed on the roots of thread, making it difficult to fit into the internal thread. To simultaneously solve the above-mentioned two issues, two measures were executed.

Catalyst specifications and converter layouts were studied to identify the high conversion performance under various in-use driving conditions, high mileage intervals and extended life cycle. The effects of volumes, configuration, selection and loading distribution of precious metals, additive components and substrate type for catalyst were studied on engine dynamometers and vehicle tests to optimize a catalyst converter system. Moreover, model gas experiments were conducted to analyze deterioration mechanisms and conversion characteristics of catalysts. As a result, the concept of a divided catalyst converter system, which provides separate functions for a close-coupled and an under-floor catalyst, was found to be effective for the future exhaust system. For reducing HC emissions, the close-coupled catalyst should warm up quickly and resist a high temperature. The under-floor catalyst, located at a rather low temperature position, is durable and maintains high NOx conversion.

The exhaust valves of 21-4N or 21-2N generally have hardfaced heads for heavy-duty engines. Hardfacing alloys contain a large amount of cobalt (Co), which sometimes becomes very scarce and outrageously expensive. Therefore, some automakers have adopted nickel (Ni)-base superalloys as unfaced exhaust valves, but continued to search for less expensive heat resisting alloy. THE authors had succeeded in developing an iron (Fe)-base superalloy, RS 914, containing 40% Ni, 19% Cr, 2.8% Ti and 0.7% Al. The mechanical and chemical properties of this alloy had proved to be comparable with those of Ni-base Inconel 751. And unfaced exhaust valves of RS 914 passed endurance tests in turbo-charged diesel engines with minimal damage. This alloy is relatively low cost and easy to fabricate, so that it can be applied for unfaced exhaust valves substituting for Ni-base superalloys.