Development of Manufacturing Technology for Precision Compressor Wheel Castings for Turbochargers

An aluminum alloy cast compressor wheel, also known as a compressor impeller, is the main component of a turbocharger. Since 1965 we have manufactured compressor wheels at our casting plant at Oyama, Tochigi Prefecture, delivering high-quality products that meet the needs of our customers. Figure 1 shows a cross section of a typical turbocharger, comprising a compressor wheel, a turbine and a housing, with the compressor wheel and the turbine coupled to a single shaft. Exhaust gas from the engine turns the turbine, causing the compressor wheel mounted at the engine intake also to turn and supply compressed air to the engine. Because their exhaust is black, diesel vehicles have tended in Japan to be saddled with the image of having an adverse effect on the environment, but in Europe and other countries the many advantages in terms of economy, including the cost of fuel, and low levels of CO2 emission have led to steady growth in the demand for diesel vehicles, as shown in Figure 2 1). In addition, with stricter environmental regulations, it has become necessary for diesel vehicles to be fitted with turbochargers, leading to a strong increase in demand for them. On the other hand, as turbocharger performance has improved, customer expectations in terms of levels of quality have risen enormously. Because they turn at speeds in excess of 150,000 rpm, there is a need not only for high durability, but also for high dimensional accuracy, and particularly for product coaxiality, also known as initial balance. To address these user needs, Furukawa Sky-Aluminum Recently, the demand for turbo chargers for automobiles is increasing worldwide because of the emission regulations in Europe and the expansion of the Asian car market. The compressor wheel is the main unit of a turbo charger, and not only high durability, but also high dimensional accuracy, is required of it by customers. The most important property required is the initial balance (i.e., coaxiality). We have developed a new manufacturing technology at our casting plant to improve the initial balance. ABSTRACT