Hydraulic mount with magnetorheological fluid

A hydraulic mount (10, 110) for automotive engine and powertrain applications includes an elastomer body (12, 112), a base (30, 130) and a partition (24, 124) interposed the body and the base to form a fluid-pumping chamber (22, 122) and a reservoir (37, 137). Circumferentially spaced axial extending holes (52) or slots (53) or an annular orifice track (151) are formed in the partition together with a magnetic coil (54, 154) operable to impose a magnetic field on the holes, slots or orifice track to control the shear properties of a magnetorheological (MR) fluid in the pumping chamber and reservoir. An elastomeric decoupler member (46, 146) is in communication with at least one of the pumping chamber and the reservoir to reduce the mount dynamic stiffness for isolating low-displacement relatively high-frequency vibrations. Vibrations of multiple frequencies may be isolated by tuning the mount with a controller (58, 158).