Fluid-filled vibration damping device and control method of the device used as engine mount

A control method of vibration damping characteristics of an automotive engine mount provided by a fluid-filled vibration damping device comprising:

• a first mounting member and a second mounting member linked by a main rubber elastic body;
• a partition member supported by the second mounting member and defining to one side of the partition member a pressure-receiving chamber whose wall is partially constituted by the main rubber elastic body, while defining to an other side of the partition member an equilibrium chamber whose wall is partially constituted by a flexible film, the pressure-receiving chamber and the equilibrium chamber being filled with a non-compressible fluid;
• and an orifice passage through which the pressure-receiving chamber and the equilibrium chamber communicate with one another, wherein the partition member comprises an outer orifice member having a tubular portion and an inner orifice member fitting inside the outer orifice member with the members relatively displaceable in an axial direction;
• an orifice-defining window is provided on either one of two mating faces of an inside peripheral face of the tubular portion of the outer orifice member and an outside peripheral face of the inner orifice member;
• the orifice passage is defined utilizing a covered zone of the orifice-defining window, the zone being produced through partial covering of the orifice-defining window by an other of the outer orifice member and the inner orifice member;
• the covered zone of the orifice-defining window changes through relative displacement of the inner orifice member in the axial direction with respect to the outer orifice member;
• a fluid path length along the orifice passage between an opening thereof at the pressure-receiving chamber end and an opening thereof at the equilibrium chamber end changes in association with change of the covered zone of the orifice-defining window;
• an actuator shaft attached at one end thereof to the inner orifice member passes through the flexible film and extends to an outside of the equilibrium chamber, while an other end of the actuator shaft is attached to an actuator that is situated outside the equilibrium chamber;
• an actuating force of the actuator is exerted on the inner orifice member through an agency of the actuator shaft to bring about relative displacement of the inner orifice member in the axial direction with respect to the outer orifice member;
• a fluid passage that connects the pressure-receiving chamber with the equilibrium chamber is formed in the partition member;
• and the tuning frequency of the fluid passage is set to a lower frequency than the orifice passage;
• and the orifice passage is blocked by bringing the inner orifice member to a specific position in the axial direction with respect to the outer orifice member, the control method being executed through actuation control of the actuator adapted to bring about relative displacement of the inner orifice member in the axial direction with respect to the outer orifice member, and comprising the steps of:
• determining by driving/idling determining means if an automobile is moving or idling while measuring by speed measuring means engine speed of the automobile;
• blocking the orifice passage to allow fluid flow through the fluid passage in an event of a decision by the driving/idling determining means that the automobile is moving;
• opening the orifice passage whereas in an event of a decision by the driving/idling determining means that the automobile is idling;
• and
• undergoing controlled modification of a relative position of the inner orifice member with respect to the outer orifice member in the axial direction depending on the engine speed that is measured by the speed measuring means, so as to shorten a passage length of the orifice passage in response to higher engine speed.