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Understanding of the oil film formation mechanism around a piston skirt is very important to reduce the friction loss at piston skirt. We have investigated lubricant oil film behavior around piston skirt which is affected by piston slap under motoring condition. In this study, a cylinder liner of a commercial engine is displaced with a quartz cylinder. Photographic observations of oil film behavior between the cylinder liner and the piston skirt were performed with two kinds of methods; direct monochromatic photography and LIF (Laser Induced Fluorescence) image using a high speed camera. The oil film distributions were determined from oil boundary observed by the direct photography, and oil film thickness was estimated from the LIF intensity. Differences of the oil film distributions and the oil film thickness depending on piston shapes were investigated for four types of pistons.

The objective of the present investigation is to develop a suitable simulation method for dynamic analysis of rotary engines using Finite Element Method (FEM) and for flexible multi-body dynamics using AVL EXCITE. The engine analyzed is the current MAZDA gasoline engine with two rotors. The general approach and the tools applied are well established for reciprocating combustion engines, but the requirements concerning the simulation of rotary engines are very different due to the higher bearing loads, rotor guidance in the housing by a gear and the special requirements for axial movement of the rotor relative to the housing to ensure sealing. Detailed investigations are made for the simulation of the complex dynamics of the moving engine parts with respect to the interaction between flexible models of rotors, eccentric shaft and housing using axial contact between rotors and housing as well as detailed elasto-hydrodynamic bearing models (EHD) for the rotor bearings.

The effort of gear noise reduction has traditionally focused on minimizing transmission error. On the other hand, gears vibration characteristics are also known to influence gear noise strongly. With the thin helical gears, therefore, the entire gear noise mechanism is clarified quantitatively by experimental analysis, and a dominant factor is specified. The analysis has shown that meshing force is the most significant factor. Thus, innovative gear structure has been devised, which aggressively controls meshing force characteristics like a dynamic vibration reducer. Redesigned gears have successfully improved gear noise. These experimental technologies and design methods can be applied to general gear noise problem in order to conduct optimization.

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.