PROBLEM TO BE SOLVED: To perform an effective restriction of vibration under a large inertia mass by integrating an inertia body with a rotary shaft member to increase a rotation moment against a specified vibration added to an object to be controlled in vibration.SOLUTION: An axial relative motion between a casing 2 and a sleeve 3 is converted into a rotation motion of a rotary shaft member 6 made of soft magnetic material by a ball screw 4 and a ball nut 5. A tight-sealed area 13 is formed between it and an outer periphery of the rotary shaft member 6 and an inertia body 7 made of soft magnetic material is coaxially supported with the rotary shaft member 6 in the casing 2. Electromagnets 8 forming a magnetic field M crossing a tight-sealed area 13 while the rotary shaft member 6 and the inertia body 7 are being applied as a part of a magnetic circuit are stored in the inertia body 7 and they are connected to an external DC power supply through a commutator 9 and a brush 10. A magnetic field by the electromagnets 8 is applied in a first tight-sealed area 13 to cause viscous hardness of magnetic viscous fluid 14 to be increased, the inertia body 7 to be integrally rotated with the rotary shaft member 6 and its rotation moment to be increased and requisite inertia mass required for restriction of vibration can be attained.SELECTED DRAWING: Figure 1
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