In the case of small size of planetary gear trains, the sun gear shaft is designed as foating sun gear which does not have bearings. In such case, the position of the sun gear shaft is determined on the balance of the three forces from the planetary gears and the sun gear weight This mechanism is called Self-centering process and is well-known, but the mechanism does not have examined in detail. Because a planetary gear trains have some back lash between gears, the sun gear causes various kinds of vibration. The vibration phenomena are so complicated that the theoretical analysis has not carried out.
In this paper, the vibrations of the sun gear shaft when the rotational speed increases with the relatively small load torque are investigated with experimental method Based on the results, mechanism of the vibration is examined and simulation programs for the vibration in the planetary gear trains are proposed and the calculated results are examined.
As the conclusion ;
(1) The movable area of the sun gear can be calculated with the magnitude of the backlash.
(2) Self-centering process can be explained as the alternation of the meshing surface of the gears. The meshing surface can be known by the magnitude of the load torque and self-centering locus can be obtained from the calculation.
(3) A simulation method for the vibration is proposed, and the calculated results are compared with the experimental results. Calculated results have a good accordance with the experimental ones.
(4) The designer can simulate the vibration before the production to change the parameter of the vibration system in the proposed program.