Development of Dual Mode Engine Crank Damper

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. In addition to improving modulation noise that causes sound quality problems, the dual mode damper reduces overall noise at driver's right ear by 2- 3 dB(A) and reduces vibrations at steering wheel and seat track.