LPI 차량의 燃料壓力 레귤레이터 性形解釋 關한 硏究

Abstract

Die casting which is extensively known as a necessary technology for lightweight spare parts of automobiles has three central elements of casting equipment, casting technology and die and has had much attention as a technology with the highest coefficient of expansion with increased need of high-quality and high-precision. However, technological aspect of advanced spare parts of automobiles is insignificant in comparison with that of advanced countries. For die casting, as automation rate and speed of production is high, mass-production with high-quality is possible thanks to reduced cost, precision, smooth casting surface and light-weight and thin casting and the technology is extensively used for spare parts of manufacturing machinery and automobile accessories. In die casting, filling is the most important. Flow style of molten metal while filling affects temperature inside the cast and temperature distribution affects the process of solidification of the molten metal. Molten metal may be solidified while being filled and the solidified part may be remelted by the filled molten metal. Thus, as the flowing molten metal is filled through an interaction with the process of solidification, the filling process is a physical phenomenon to be analysed foremost. (1～2) Several failures occurring during filling can be predicted through analyses of filling: incomplete filling of casting, adulteration of air or gas by filling of surface turbulent and so forth. To predict such failures, flow analysis and heat transfer analysis are important in filling of casting. However, national casting industries depend on experiences and intuition of well-trained technicians for design of casting or gating system rather than engineering analyses. Though experiences are important for casting design, understanding of casting process through casting filling and heat transfer analysis can give more physical insight to experienced technicians and standards of design to non-experienced ones. More importantly, it helps to curtail the time and process from design to manufacturing of casting, which contributes to less production cost. For optimal manufacturing of goods by casting, experiences technicians should make a model and a casting of a product, test their size or defects based on experiences of casting design, and correct them before the final products are manufactured. Such method requires much time, materials and energy. However, when computer-aided casting analysis is introduced, the manufacturing step of the model can be cut considerably, and time and cost can be saved. In general, as casting goods have complex configuration, it is hard to obtain solutions based on an analysis and as the phenomenon inside the casing can not be analysed with an approach of Bernoulli's equation, there have been many attempts to model casting process through numeric analyses through continuity equation, momentum and energy equation. Therefore, a regulator of LPI automobile receives high internal pressure and works as a central part of the basic fuel supply system according to quality of performance. To produce high-quality casting goods, we need to identify causes of defects and theoretical analyses on physical phenomena occurring in manufacturing. Through understanding of causes of defects, we have to predict defects in manufacturing, and change casting design or control processing variables to produce high-quality goods. Therefore, it is certain that this study is useful in manufacturing as it analyses such process through a computer-applied program. This study examined the casting analysis of fuel pressure regulator of LPI vehicles. We aims to predict all the phenomenon accompanied by flow and solidification in die casting, and maximize productivity and quality through optimal casting design and the following results are obtained: To produce light-weight and high-quality spare parts, this study looked at affecting factors of quality targeting test models and found that gate, overflow, casting speed and pressure are very important, which affect pores by gas, flow of molten metal and solidification. As a result of comparing Types A and B of casting design, it was found that the number of overflow affected flow, flow speed and solidification temperature. And there was a minute difference between solidification temperatures at thick section of the spare parts. Solidification began at temperatures of 624℃～630℃, but after the casting was completed, temperatures at the center of the parts were 600℃～614℃. Temperature of molten metal showed optimal flow at temperature of 680℃. It began to solidify around at 650℃, and to be cooled between 580℃～550℃ in high speed. When the process was analysed through a computer simulation, it was found that hardness of regulators manufactured through Type B of overflow was above HR60.