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Valve train motion was investigated with computer simulation technique. The application of a 5-mass model was found to accurately predict the valve train behavior. It was identified that valve train stiffness and close-side characteristics of valve lift curve have significant effects on bounce occurrence. A valve train with high stiffness tends to develop bounce after jump, while on one with low stiffness, bounce starts in the absence of jump. These findings allowed to develop a new cam form with use of harmonic curves for elevating the revolution limit of the valve train.

Substantial amount of fuel energy input is lost by heat transfer through combustion chamber walls in the internal combustion engines. Thus, these heat losses account for reduced thermal efficiency, in that spray-wall impingement plays a crucial role in Direct Injection diesel engines. The objective of this study is to investigate the mechanism of the heat transfer from the spray/flame to the impinging wall under small diesel engine-like condition and how the spray characteristics are affected with regards to effect of injection pressure, nozzle hole diameter and impingement distance. The experiment results showed that injection pressure was predominant factor on spray-wall heat transfer.

Heat loss is more critical for the thermal efficiency improvement in small size diesel engines than large-size diesel engines. More than half of total heat energy in the internal-combustion engine is lost by cooling through the cylinder walls to the atmosphere and the exhaust gas. Therefore, the new combustion concept is needed to reduce losses in the cylinder wall. In a Direct Injection (DI) diesel engine, the spray behavior, including spray-wall impingement has an important role in the combustion development to reduce heat loss. The aim of this study is to understand the mechanism of the heat transfer from the spray and flame to the impinging wall. Experiments were performed in a constant volume vessel (CVV) at high pressures and high temperatures. Fuel was injected using a single-hole injector with a 0.133 mm diameter nozzle. Under these conditions, spray evaporates, then burns near the wall. Spray/flame behavior was investigated with a high-speed video camera.

Reduction of transmission error by gear tooth profile optimization and tuning of gear resonance modes are known as effective methods for gear noise reduction. This paper concentrates on structuring a process for reducing gear noise using the latter method. The procedure comprises a study of gear noise mechanism from transmission error to radiation noise, an application of Steyer's method in gear frequency analysis and implementation of an invented device called “noise reduction ring”. This inexpensive and practical ring reduces gear noise drastically by 10dB, which is predicted by the simulation and verified by the experiment.

In order to minimize power train length, it is required for transmission components to layout compact. The requirement results in thinner and larger transfer gears, which are disadvantageous for gear noise. On the other hand, improvement of gear accuracy and/or vehicle interior noise increases sensitivity to manufacturing variation. It tends to appear noisiness by transmission unit variation. To prevent such gear noise problem, we made detailed investigation by both several tests and simulation, i.e. noise measurement, shaker test, running gear vibration measurement and FE Model analysis. This paper describes the experimental analysis of gear noise generation mechanism of transmission with thin and large diameter gear and its prediction method. It was found that gear web out-of-plane vibration modes are closely related to vibration transfer to the mission case. Planarly non-symmetric modes have dominant effect for case dynamic excitation by gear engagement.

The fuel economy of recent small size DI diesel engines has become more and more efficient. However, heat loss is still one of the major factors contributing to a substantial amount of energy loss in engines. In order to a full understanding of the heat loss mechanism from combustion gas to cylinder wall, the effect of hole size and rail pressure at similar injection rate condition on transient heat flux to the wall were investigated. Using a constant volume vessel with a fixed impingement wall, the study measured the surface heat flux of the wall at the locations of spray flame impingement using three thin-film thermocouple heat-flux sensors. The results showed that the transferred heat was similar under similar injection rate profiles. However, in case of flame luminosity, temperature distribution, characteristic of local heat flux and soot distribution was also similar except the smaller nozzle hole size with higher injection pressure.