Magneto-Rheological Grease and its Application to Variable Damper

Magneto-rheological (MR) grease whose rheological properties can be controlled by the applied magnetic field strength was developed, and a variable damper was designed as an application of MR grease. MR fluid has attracted much attention due to similar properties and it is well known that MR suspension system and MR engine mount system for automobiles have already been equipped on several models produced in Europe as well as USA. Though these MR fluid systems can be adapted according to driving conditions, the sedimentation of magnetic particles dispersed in the fluid may take place frequently. In order to overcome this difficulty, we propose to use grease as a vehicle of magnetic particles. Three-dimensional fibrous structure of grease may preserve particles. As a result, no sedimentation may be expected in MR grease. In this paper, the typical properties of MR grease which were measured by a rotational viscometer are shown. Furthermore, MR grease was introduced into a cylindrical damper, and its performance as a variable damper was investigated.