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김건회(Gunhoi Kim) 한국생산제조학회 2008 한국생산제조학회지 Vol.17 No.1
Currently existing high-accuracy and high-speed die sets used in reciprocal press create scratches at the surface of guide posts, steel balls, and bushes due to vertical movement of balls with point-contacts between inner surface of bushes and guide posts. Consequently, accuracy of the die set and the life span of the metal mold are reduced. However, those scratches could reduce the pre-load of the steel ball. This research designed and developed a groove-type die set which improves life span of the die set by eliminating point-contacts of steel balls with guide posts. The guide post consisted of a steel-ball retainer, a steel-ball retainer stopper, a guide bush, a guide pin, a snap ring, and a spring. The steel-ball retainer has 72 holes with 8 columns of 9 holes in each column. The inner surface of the guide bush was grinded(surface roughness: Ra = 0.2㎛, accuracy: 0 ~ -0.002㎜) after NC turning and heat treatment. Also, a line of small intermediate pocket was processed inside of the guide bush for lubrication and elimination of foreign materials. Guide grooves of steel balls were processed using a wire EDM(Electrical Discharge Machining) after heat treatment. With such a design of the guide post stated above, loads against steel balls could be dispersed greatly by the line contacts through the guide groove between the guide post and the guide bush, and the life span of the guide post could be expanded semi-permanently.
바이오디젤유를 적용한 CRDI 방식 상용 디젤기관의 내구특성 연구
김종열(Jonglyul Kim),최승훈(Seunghun Choi),오영택(Youngtaig Oh),김건회(Gunhoi Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
Our environment is faced with serious problems related to the air pollution from automobiles in these days. In particular. the exhaust emissions of diesel engine are recognized main cause which has influenced environment problem. In this study, a common rail diesel engine was fueled with 5% biodiesel fuel(BDF 5) in excess of 150 hours. Engine dynamometer testing was completed at regularly scheduled intervals to investigate the engine performance and exhaust emissions. The engine performance and exhaust emissions were sampled at 1 hour intervals for analysis. When CR야 diesel engine runs on BDF 5% for long time, power and energy consumption of the engine arc similar to the case using diesel fuel, though there is difference of calorific value of Biodiesel fuel. The smoke emission of biodiesel fuel 5vol-% was reduced in comparison with diesel fuel, that is, it was reduced approximately 15% at 4000rpm, load 90%, also CO and CO₂ were reduced. On the other hand, NOx emission of biodiesel fuel was slightly increased. but it was almost same as commercial diesel fuel.