Clatter and rattle are an increasing challenge in developing low-noise automotive transmissions. Efforts to reduce consumption and emissions of combustion engines combined with reduction of idling speed result in ever greater cyclic irregularities in the drivelines of today's motor vehicles, which in turn lead to increased rattle and clatter in automotive transmissions. Loose parts that are not under load, such as idler gears, are responsible for this noise, as they are excited within their functional backlash by the irregular rotational speed pattern to vibrate, and consequently impact against fixed gears. With the aid of the EKM Calculation Method involving simulation and approximation, it is possible to investigate the rattle- and clatter-proneness of automotive transmissions at the development stage, and of existing transmissions on the basis of existing parameters. Numerous external and internal measures have already been developed to reduce rattle and rattle- and clatter-proneness, but only very few have been used in mass production. The use of these measures depends not only on the degree of noise reduction achieved, but also on the production engineering and economic parameters. The wear characteristics and the level of power loss and the intrinsic noise involved must also be taken into account. Each transmission system and each driveline system must be individually adapted from the large number of various possible solutions. Systematic measurement of rattle and clatter in automotive transmissions using knowledge derived from experience has been compiled in the form of an engineering design catalogue for low rattle and clatter automotive transmissions. This provides both rapid access to information and ease of use due to clear representation with schematic diagrams, and expandability of the principles and measures listed.
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