Abstract: The piston for a magneto-rheological fluid system is manufactured from a piston skirt of a material having a high magnetic permeability and a piston plate which closes one end of the piston skirt having a low magnetic permeability and therefore must be made out of a material such as stainless steel. The piston is manufactured by placing the plate on one electrode and clamping another set of electrodes against the outer circumferential surface of the piston ring or skirt. The plate and ring are brought into contact with one another while applying a current through the piston ring and the piston plate, thereby heating interfering portions of the ring and plate and permitting the plate to be forced inside of the ring while at the same time allowing the softened or plastic portions of the ring and plate to intermingle with one another and thus form a solid state bond.

Abstract: The piston for a magneto-rheological fluid system is manufactured from a piston skirt of a material having a high magnetic permeability and a piston plate which closes one end of the piston skirt having a low magnetic permeability and therefore must be made out of a material such as stainless steel. The piston is manufactured by placing the plate on one electrode and clamping another set of electrodes against the outer circumferential surface of the piston ring or skirt. The plate and ring are brought into contact with one another while applying a current through the piston ring and the piston plate, thereby heating interfering portions of the ring and plate and permitting the plate to be forced inside of the ring while at the same time allowing the softened or plastic portions of the ring and plate to intermingle with one another and thus form a solid state bond.

Abstract: A magneto-rheological (“MR”) damper having a damper body tube containing an MR fluid. A piston assembly is disposed in the damper body tube and forms an annular flow gap between the piston assembly and the damper body tube. The piston assembly has a piston core containing ferrous material and an electromagnetic coil mounted on the piston core for generating a magnetic field. The damper further includes a ferromagnetic member positioned outside of the damper body tube substantially adjacent the piston assembly for providing at least a part of a magnetic flux return path for the magnetic field.

Abstract: The piston for a magneto-rheological fluid system is manufactured from a piston skirt of a material having a high magnetic permeability and a piston plate which closes one end of the piston skirt having a low magnetic permeability and therefore must be made out of a material such as stainless steel. The piston is manufactured by placing the plate on one electrode and clamping another set of electrodes against the outer circumferential surface of the piston ring or skirt. The plate and ring are brought into contact with one another while applying a current through the piston ring and the piston plate, thereby heating interfering portions of the ring and plate and permitting the plate to be forced inside of the ring while at the same time allowing the softened or plastic portions of the ring and plate to intermingle with one another and thus form a solid state bond.

Abstract: A piston rod for use in a magnetorheological dampening device having a surface finish that renders the device resistant to wear at the elastomeric seal/piston rod interface. The piston rod has a surface finish of Ra<0.065 &mgr;m and &Dgr;a≦1.4°, as measured using a Gaussian filter with a 0.08 mm cut-off length. There is further provided a method of achieving the surface finish, including rotating the piston rod while moving an abrasive tape against the outer surface of the rod.

Abstract: A piston rod for use in a magnetorheological dampening device having a surface finish that renders the device resistant to wear at the elastomeric seal/piston rod interface. The piston rod has a surface finish of Ra<0.065 &mgr;m and &Dgr;a≦1.4°, as measured using a Gaussian filter with a 0.08 mm cut-off length. There is further provided a method of achieving the surface finish, including rotating the piston rod while moving an abrasive tape against the outer surface of the rod.

Abstract: A damper body for a magnetorheological (MR) damper and associated methods of forming the damper body. The damper body is formed of a base material, such as a steel, and is coated with an abrasion-resistant layer comprising chromium. The layer of chromium provides a sliding wear surface for sliding contact with a reciprocating piston. To avoid high-stress abrasive wear over the expected service life of the magnetorheological damper, the layer of chromium has a minimum thickness greater than or equal to a minimum thickness of about 8 &mgr;m. In other embodiments, before applying the abrasion-resistant layer of chromium, the damper body is coated with a layer of a hard coating material having a hardness greater than the hardness of the base material. The effective hardness of the damper body is a composite of the respective hardnesses of the base material comprising the damper body and the layer of hard coating material.

Abstract: A magneto-rheological (“MR”) damper having a damper body tube containing an MR fluid. A piston assembly is disposed in the damper body tube and forms an annular flow gap between the piston assembly and the damper body tube. The piston assembly has a piston core containing ferrous material and an electromagnetic coil mounted on the piston core for generating a magnetic field. The damper further includes a ferromagnetic member positioned outside of the damper body tube substantially adjacent the piston assembly for providing at least a part of a magnetic flux return path for the magnetic field.

Abstract: A magneto-rheological (“MR”) damper having a gas cup that slidably moves within a damper body tube and isolates an MR fluid from a gas in one end of the damper body tube. The gas cup has a dynamic seal that comprises an MR fluid compatible O-ring located in a narrow O-ring groove disposed in an outer surface of the gas cup. The narrow O-ring groove is sized to reduce entrapment of abrasive magnetic particles in the MR fluid between the O-ring and an inner surface of the damper body tube. The O-ring groove has a free roll room of about less than 12%.

Abstract: A damper body for a magnetorheological (MR) damper and associated methods of forming the damper body. The damper body is formed of a base material, such as a steel, and is coated with an abrasion-resistant layer comprising chromium. The layer of chromium provides a sliding wear surface for sliding contact with a reciprocating piston. To avoid high-stress abrasive wear over the expected service life of the magnetorheological damper, the layer of chromium has a minimum thickness greater than or equal to a minimum thickness of about 8 &mgr;m. In other embodiments, be fore applying the abrasion-resistant layer of chromium, the damper body is coated with a layer of a hard coating material having a hardness greater than the hardness of the base material. The effective hardness of the damper body is a composite of the respective hardnesses of the base material comprising the damper body and the layer of hard coating material.

Abstract: The piston for a magneto-rheological fluid system is manufactured from a piston skirt of a material having a high magnetic permeability and a piston plate which closes one end of the piston skirt having a low magnetic permeability and therefore must be made out of a material such as stainless steel. The piston is manufactured by placing the plate on one electrode and clamping another set of electrodes against the outer circumferential surface of the piston ring or skirt. The plate and ring are brought into contact with one another while applying a current through the piston ring and the piston plate, thereby heating interfering portions of the ring and plate and permitting the plate to be forced inside of the ring while at the same time allowing the softened or plastic portions of the ring and plate to intermingle with one another and thus form a solid state bond.

Abstract: A monotube damper and suspension spring assembly for a motor vehicle includes a tubular housing defining a chamber filled with damping fluid. A piston and piston rod reciprocate within the chamber. In order to compensate for volumetric changes of the chamber due to extension and retraction of the piston rod within the chamber, either the upper seal cover or lower bottom ring assembly is slidable within the housing. A preload is applied either to the housing or to the seal cover to thereby bias these elements to compensate for volumetric changes in the chamber.

Abstract: An improved magnetorheological fluid damper is provided which effectively provides a smooth transition, without a sharp break in the damper force/velocity curve, between very low damping forces near zero damper velocity to higher damping forces at higher piston velocities while maintaining desirable maximum force levels. The damper includes a piston assembly, including a magnet assembly and a flow gap extending through the piston assembly to permit fluid flow between the chambers. The force/velocity optimization feature includes a groove or passage open to the flow gap, positioned in series with a part of the flow gap in a magnetic circuit generated by the magnet assembly and dimnensioned/sized to permit fluid flowing through the passage to experience a magnetorheological effect less than a magnetorheological effect experienced by fluid flowing through the flow gap but not through the groove. Preferably, the passage is formed in an inner annular surface of a flux ring positioned around a piston core.

Abstract: A novel and improved magnetorheological fluid damper is provided which effectively secures a flux ring to a piston core in a manner which prevents relative axial and radial movement between the flux ring and the core throughout operation while minimizing the size of the piston assembly yet providing effective damping. Several connector devices are disclosed for both axially and radially securing the flux ring relative to the piston core at one end of the piston assembly in a simple manner without increasing the length of the piston assembly. The connector device may include an outer portion brazed to the flux ring, an inner portion connected to the piston core, bridge portions extending between the outer and inner portions, flow passages formed between the bridge portions and an inlet cavity formed adjacent an annular flow gap to permit unimpeded, enhanced laminar flow through the flow gap by improving the damping effect.

Abstract: A magnetorheological fluid damper is provided which permits effective control of damping while minimizing assembly size and costs by including a thin-walled insert in a flow gap formed between a flux ring and a piston body. The insert may include a thin-walled tubular insert having a generally smooth cylindrical shape for increasing the shear surface area. Alternatively, a corrugated insert may be provided having corrugations formed by edges extending axially along the insert. The corrugations may be formed in a variety of locations, sizes, shapes and spacings along the axial extent of the insert and the circumference of the insert. The corrugations advantageously effectively align the insert within the flow gap and also function to securely connect the flux ring to the piston body without the use of other devices such as plates thereby reducing the size and cost of the assembly.

Abstract: A snap ring closure system is particularly useful in securing a rod guide in an end of a tube of a hydraulic damper. The snap ring closure system utilizes an end cap or rod guide having a double-lobed groove and a peripheral flange about its outer end. The double-lobed groove includes an outer lobe and an inner lobe of a lesser depth than the outer lobe. A groove is formed on the tube and is positioned to design with the doubled-lobed groove when the end cap is inserted in the tube. The end cap includes a first snap ring in the outer lobe which expands outwardly into the tube groove when the cap is first inserted. The cap is secured by engagement of the first snap ring with the inner more shallow lobe. A second snap ring is placed between the flange and the end of the tube to remove any play between the end cap and tube.

Abstract: A damper includes a piston that carries a relatively compact control valve for controlling fluid flow through the piston. The control valve provides a variable amount of damping by regulating damper fluid flow between the extension chamber and the compression chamber of the damper during extension and compression strokes. Pressure regulation across the piston is controlled through two alternate flow paths as determined by the control valve. Damping through the first flow path is relatively soft and is determined according to the deflective characteristics of a single bi-directional annular disc valve. Damping through the second flow path is relatively firm and is determined by the first bi-directional single annular disc and a second bi-directional single annular disc in series.

Abstract: A damper includes a piston that carries a relatively compact control valve for controlling fluid flow through the piston. The control valve provides a variable amount of damping by regulating damper fluid flow between the extension chamber and the compression chamber of the damper during extension and compression strokes. Pressure regulation across the piston is controlled through two alternate flow paths as determined by the control valve. Damping through the first flow path is relatively soft and is determined according to the deflective characteristics of first and second single bi-directional annular disc valves in parallel. Damping through the second flow path is relatively firm and is determined solely by the second bi-directional single annular disc.