To avoid the engagement failure of the gear of an epicyclic gear mechanism resulted from the deflection change of a crank shaft by fixing a bracket for supporting and fixing the planetary gear of the epicyclic gear mechanism to an engine side member through a vibration isolating material.

A planetary gear carrier 13 is connected and fixed to the inside of a bracket 16 supported on a shaft 15 by a bearing 17. The arm part 16a of the bracket 16 is fixed to a front cover 8 which is an engine side member through a vibration isolating material 22. Although a crank shaft 1 tends to be whirled by the deflection change by combustion pressure or the deflection change in a specified vibration mode, the whirling motion of an internal gear 11 can be absorbed by the elastic deformation of the vibration isolating material 22. Consequently, the engagement failure of the gear of an epicyclic gear mechanism 10 can be avoided, and the rolling vibration reducing effect of an engine body can be improved.