Rotary damper with magnetic seals

Brakes – Internal-resistance motion retarder – Magnetic fluid or material

Reexamination Certificate

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Details

C188S290000, C188S276000, C192S208000

Reexamination Certificate

active

06318522

ABSTRACT:

TECHNICAL FIELD
The present invention relates to shock absorbers, and more particularly, to rotary dampers sufficiently rugged to be used in vehicle shock absorbing systems.
BACKGROUND OF THE INVENTION
Shock absorbers are used with automobiles and other vehicles to absorb shock forces sustained by the vehicle wheels. One type of shock absorber used in such applications is the conventional, linear-style shock absorber. Linear-style shock absorbers typically include a pair of telescoping cylindrical sleeves oriented generally vertically in the vehicle. A piston associated with one of the sleeves travels in a fluid-filled cylinder associated with the other sleeve. One end of the shock absorber is coupled to a wheel support structure and the other end is fixed to the body or frame of the vehicle. When a shock force displaces one of the vehicle wheels, the force drives the piston along the cylinder, thereby driving fluid through an orifice in the piston. The piston resists such motion with a force proportional to the shock force. Such linear shock absorbers must be oriented substantially vertically within the vehicle body and must be positioned adjacent the associated vehicle wheel.
Rotary shock absorbers, also known as rotary dampers, have been developed to replace linear-style shock absorbers. Rotary shock absorbers operate by converting shock forces into rotary motion, and then damping the rotary motion. Rotary shock absorbers have several advantages over conventional linear-style shock absorbers. For example, rotary shock absorbers do not need to be mounted adjacent to the vehicle wheel, as do linear-type shock absorbers, nor do they need to be mounted in any particular orientation. Rotary dampers may be oriented generally horizontally, and thereby extend underneath the body of the vehicle.
Rotary dampers typically include a shaft which transmits shock forces from the wheel to one or more rotors encased in a cylindrical housing. Each rotor preferably includes two or more lobes and the housing includes ported guide plates between the lobes. The housing contains fluid in the gap between the lobes and guide plates. When the rotor is rotated, the fluid is compressed by the rotor against the guide plates and is forced through the ports in the guide plates. Typically, there arc seals between the rotor and the housing and the rotor and the guide plates which restrict the flow of damping fluid around the rotor, and such seals require close tolerances to be effective. However, repeated oscillations of the rotor wear the mechanical seals and eventually require replacement of the damper. Accordingly, there is a need for a rotary damper which has effective, durable, and inexpensive flow-restricting seals between the rotor and the housing and guide plates.
SUMMARY OF THE INVENTION
The present invention is a rotary damper, suitable for use in a vehicle shock absorbing system, which provides an effective, durable and inexpensive flow-restricting seal between the rotor and the housing, and between the rotor and the guide plates. The damper uses magnetorheological fluid to damp the motion of the rotor, and permanent magnets to restrict the flow of fluid between the rotor and the housing and between the rotor and the guide plates. Because the magnetorheological fluid increases in viscosity in the presence of a magnetic field, the magnets effectively act as seals to minimize the flow of magnetorheological fluid between the rotor and the guide plates and the housing.
In a preferred embodiment of the invention, the damper includes a housing having an inner surface defining a chamber, and a rotor mounted in the chamber for oscillatory movement. The rotor has a pair of opposing lobes positioned between ported guide plates fixed to the housing. The space in the chamber between the lobes and the guide plates is filled with magnetorheological fluid. The rotor is attached to a shaft which, in turn, is connected to the wheel suspension assembly, and the housing is mounted on the vehicle frame. Oscillatory movement of the rotor in the chamber in response to the pivoting movement of the shaft forces the magnetorheological fluid through orifices in the guide plates and damps the movement of the rotor. Each lobe of the rotor includes a magnet positioned at the interface with the inner surface of the housing, which increases the viscosity of the fluid and hence reduces the ability of the magnetorheological fluid to flow between the lobe and the housing inner surface. The guide plates each include a permanent magnet adjacent to the rotor to provide a seal at that interface.
Accordingly, it is an object of the present invention to provide a rotary damper which is sufficiently rugged and durable to be used in motor vehicle applications; a rotary damper which utilizes magnetorheological fluid properties to effect a restrictive seal; and a rotary damper which is easy to fabricate and install.
Other objects and advantages of the present invention will be apparent from the following description, the accompanying drawings and the appended claims.


REFERENCES:
patent: 3613842 (1971-10-01), Buciak
patent: 4716996 (1988-01-01), Hummel
patent: 5081882 (1992-01-01), Kogure et al.
patent: 5305858 (1994-04-01), Haga et al.
patent: 5816372 (1998-10-01), Carlson et al.
patent: 5845752 (1998-12-01), Gopalswamy et al.
patent: 5848678 (1998-12-01), Johnston et al.
patent: 5947238 (1999-09-01), Jolly et al.
patent: 5988336 (1999-11-01), Wendt et al.

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