In recent years attainment of high automotive sound quality has become a major effort in automotive vehicle refinement programs. Low frequency vibration phenomena, such as idle shake and transmission rattle, have emerged as major issues in the efforts to minimize undesirable sound qualities. Low gear rattle noise is often touted to differentiate automobile quality.
Transmission rattle is caused by engine excitation and backlash in geared transaxles. Backlash yields piecewise nonlinear characteristics in gear mesh stiffness. Despite intensive research efforts in the past, it is known that numerical difficulties in handling the nonlinearity have prohibited the development of general criteria of design of transmissions to eliminate the rattle noise.
This paper describes an analysis technique for investigation of the rattle dynamics in geared transmissions. A new and powerful technique based on the finite element method in the time domain (FET) is employed for steady-state motion analysis. In this approach, periodic response is sought via a set of algebraic equations in a fashion similar to the spatial finite element analysis used in solid mechanics. This approach offers several potential advantages over conventional numerical methods. It is shown to be particularly effective for obtaining parametric solutions of gear motions.