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Driveline clunk is perceived as disturbing metallic noise due to severe impact at driveline components such as gear pairs when the engine torque is suddenly applied and transmitted to the driveline system. In this work, experimental method detecting the most contributive gear pair to the clunk generation was investigated and applied to mini van vehicle of front-engine and rear-wheel-drive. Another experimental method, TPA (Transfer Path Analysis), was employed to identify transfer path of the clunk. And then, driveline clunk model was developed using commercial multi-body-dynamics program, ADAMS, in order to further investigate the critical clunk mechanism and potential clunk reduction solutions by performing parameter study.

This paper reflects an efficient and comprehensive approach for vehicle sound optimization integrated into the entire development process. It shows the benefits of early consideration of typical vehicle NVH features and of intensive interaction of P/T and vehicle responsibilities. The process presented here considers the typical restriction that acoustically representative prototypes of engines and vehicles are not available simultaneously at the early development phase. For process optimization at this stage, a method for vehicle interior noise estimation is developed, which bases on measurements from the P/T test bench only, while the vehicle transfer behavior for airborne and structure-borne noise is assumed to be similar to a favorable existing vehicle. This method enables to start with the pre- optimization of the pure P/T and its components by focusing on such approaches which are mainly relevant for the vehicle interior noise.

The noise of passenger cars has to be further decreased according to customer and legislative requirements. Both, a lower sound level and a better sound quality are the aims to achieve a noise more accepted by the passengers. Taking into account the transmission of structure-borne and air-borne noise primary measures on the engine as the dominant noise excitation source of a motor vehicle are most promising and effective to solve these problems. In the early design stage of an engine the fundamentals for an advantageous acoustical behavior have to be laid down. In this connection, the length of crankcase-skirts and the design in the main bearing area, i.e. the bottom end design, are important degrees of freedom concerning the acoustical optimization process of the engine block. In this report the influence of different bottom end designs on the acoustical behavior of two high-performance spark-ignition engines -' one with short and one with deep skirt crankcase - is described.

One major noise source of diesel engines are timing gear impacts. The structure vibration excitation mechanisms of the timing gears of different 3-cylinder diesel engines are investigated. To this end, the engine timing gears are equipped with acceleration sensors for simultaneous measurements of the rotary gear motion. The peripheral acceleration component shows impacts between the different gear pairs which are due to the alternating camshaft torque and alternating fuel injection pump torque. The dependence of these excitation mechanisms on e.g. engine speed, load, start of pump delivery and valve clearence will be described. Additional findings on the impact generation are obtained by analysing many consecutive cycles of the peripheral gear acceleration. By comparing the peripheral acceleration measurements taken on the rotating gears with the structure vibration measurements on the gear bearings, the impact transfer into the engine block structure is roughly quantified.