PURPOSE: To secure safety at the time of occurrence of unexpected vibration such as an earthquake etc. by providing a fixing device that cramps a movable housing in which bearings for supporting a revolving shaft in an abnormal time.
CONSTITUTION: A revolving shaft 5 having a bowl 7 in the lower part is supported by bearings 3, 4 and a housing 21 that contains the bearings 3, 4. As the housing 21 side forms a spherical seat 22, pendulum motion around a point A is possible. The displacement of the revolving shaft 5 is observed using a non contact type displacement meter 33, and when the displacement becomes above allowable value, the housing 21 is pressed from above by plural hydraulic cylinders 31 attached to a frame to fix the housing 21 that moves with whirling of the revolving shaft. When abnormal vibration ceases, the hydraulic cylinder driving device 32 releases locking according to the signal from the displacement meter.