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In automobile development, steering vibrations caused by engine excitation force and suspension vibration input from the road surface are a problem. The conventional method of reducing vibrations and thereby securing marketability has been to dispose a dynamic damper inside the steering wheel. The resonance frequency of a steering system varies for each vehicle developed (as a result of the vehicle size, the arrangement of the stiff members of the vehicle body, and the like). As a result, the individual values of dynamic dampers that are used with vehicles must be adjusted for each developed vehicle type. To address this problem, we have developed a new structure in which, rather than using a conventional dynamic damper, we disposed a floating bush on the Supplemental Restraint System (SRS) module attachment section and used the SRS module itself as the weight for the dynamic damper.

Generally, pass-by noise levels measured outdoors vary according to the influence of weather conditions, background noise and the driver’s skill. Manufactures, therefore, are trying to reproduce proving ground driving conditions on a chassis dynamometer. The tire noise that occurs on actual road surfaces, however, is difficult to reproduce in indoor tests. In 2016, new pass-by noise regulations (UN R51-03) will take effect in Europe, Japan and other countries. Furthermore, stricter regulations (2dB) will take effect in 2020. In addition to the acceleration runs required under current regulations, UN R51-03 will require constant speed runs. Therefore, an efficient measurement methods are necessary for vehicle development. To solve the above mentioned issues, an indoor evaluation system capable of reproducing the tire noise that occurs on road surfaces has been developed.

Crank rumble is an amplitude-modulation of engine noise perceived inside a car. It is common under full load acceleration but not under part load acceleration, so could cause concern. Honda and Ricardo carried out a program of work to research methods to reduce the perceived (subjective) level of crank rumble inside a vehicle under part load acceleration. Transfer Path Analysis (TPA) is a method of predicting vehicle interior noise by separating sources (the engine) and transfer paths (the vehicle body). TPA was applied in the time domain to allow subjective assessment of the different contributors to the interior sound quality. Subjective assessment was performed by a panel of listeners, to avoid bias caused by individual opinions. This approach identified key contributors to the perceived crank rumble, and allowed targets to be set. Computer Aided Engineering (CAE) was used to study a range of modifications to the engine.

In order to efficiently enhance engine sound quality under acceleration, the authors have developed an evaluation method for primary judgment of the sound quality of engine combustion noise at the stage of advanced engine development before the prototype vehicle is built. This method is an application of an existing method for evaluating the sound quality of engine combustion noise in vehicle interiors to the evaluation of noise and vibration at an engine acoustic test bench. In this method, it is necessary to consider the air-borne and the structure-borne components separately. The analysis procedure for the air-borne component is as follows. First, the sound pressure at a point 1 m away from the engine and the in-cylinder pressure of each cylinder are measured simultaneously in a semi-anechoic engine dynamometer test chamber. Next, the signal correlated with engine combustion is extracted from the measured sound pressure using the time domain combustion noise separation method.

This paper summarizes the piston pin noise mechanism and show the way to reduce noise level of semi-floating system. A mechanism of piston pin noise of semi-floating system was clarified by measurement of piston and piston pin behavior and visualization of engine oil mist around piston and piston pin. Piston and piston pin behavior was measured by accelerometer and eddy current type gap sensor with linkage system at the actual engine running condition. Engine oil behavior was visualized and measured its flow vector by Particle Tracking Velocimetry (PTV). For PTV, engine oil mist particle image was taken by high speed camera with fiber scope attached to linkage system. From themeasurement, it was cleared that engine oil doesn't reach to piston hole from undersurface of piston land and come rushing out from piston broach via groove. The result shows that lacking of engine oil between piston and piston pin makes noise larger.

This paper discussed the sound quality which assumed important factor in the development of outboard engines in the 183 to 257 kW class in the future. Many kinds of industrial product development dealt with sound quality, and there were many examples using sound quality index adapted customer requirements or products usage. In case of outboard engine development, there were examples of noise reduction and compliance with noise regulations, but there was almost no example of sound quality development. This research proceeded a questionnaire survey of 90 boat owners who were listening to several cruising engine sounds in main market, US. From this result, authors discussed customer trend and extracted 3 sound quality indexes, luxury, deep and sporty, which were demanded in our target class. Next step was that authors made simulation sounds referring 3 sound quality indexes to verify customer’s trend.