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The paper presents development work of dual mode crank dampers implemented on 3.0L V6 engines. The history and the theoretic background of the crank dampers are reviewed. The development starts with measurement of crank bending by modal testing on static condition and by optical decode system on a running engine. Modal analysis theory is also described in the Appendix to explain how the test boundary conditions may greatly affect the measured damper frequencies and a recommended method is presented. The damper frequencies are defined by using transmissibility ratio to simplify the test process and eliminate effects of boundary conditions. To verify the effectiveness of the damper, engine dyno and vehicle road tests are conducted. The results show that the dual mode dampers cannot substantially reduce airborne noise, however they can make engine mount vibrations lower (about 30% in high RPM range) and therefore reduce the structure-borne noise.

Asymmetric sidebands of gear noise are frequently observed with a planetary gear set, and are different from typical sidebands that are symmetrical around the gear mesh order (or mesh frequency). The asymmetric sidebands are found to be caused by phase differences between the different mesh points. The sidebands' locations can be calculated with knowledge of the gear set parameters. In this paper, a numerical simulation is used to predict the sidebands in a 4-speed automatic transmission. An experimental test verifies the theoretical prediction. Finally an application is described to show how to use the theory for gear noise reduction on the planetary gear set.