Brakes – Internal-resistance motion retarder – Relative speed of thrust member or fluid flow
Reexamination Certificate
2000-02-25
2001-11-20
Schwartz, Christopher P. (Department: 3613)
Brakes
Internal-resistance motion retarder
Relative speed of thrust member or fluid flow
C188S322150, C188S317000, C188S282800, C188S322220
Reexamination Certificate
active
06318523
ABSTRACT:
TECHNICAL FIELD
This invention relates to fluid dampers for vehicles, and more specifically, to a blow-off valve for use in a mono-tube to provide digressive performance during operation of the damper.
BACKGROUND OF THE INVENTION
Fluid vehicle dampers, such as hydraulic shock absorbers and struts, provide a smooth ride by absorbing forces that are generated by an uneven road surface. Two common types of vehicle fluid dampers are mono-tube and twin tube shock absorbers, each of which have a cylinder and piston with a piston rod. The piston divides the shock absorber into compression and rebound fluid chambers and regulates the flow of fluid from one chamber to another thereby achieving particular ride handling characteristics. Typically, the piston has a compression and rebound valve assembly located on opposing surfaces that regulate fluid flow during the compression and rebound strokes. By modifying the valve assemblies, the ride handling characteristics may be calibrated.
It is desirable to have different rates of piston damping depending on vehicle ride conditions. For example, during vehicle cornering maneuvers in which the piston undergoes low speed compression, it is desirable to have a stiff ride handling characteristic, which manifests itself as a steep curve on a piston force v. piston velocity graph. Conversely, when the vehicle travels over pot holes at relatively high vehicle speeds in which the piston undergoes high speed compression, it is desirable to have a soft ride handling characteristic, which manifests itself as a flat curve on a piston force v. piston velocity graph. Further, it is desirable to have independent low and high speed damping rates that may be calibrated easily. One way to best achieve independent rates of damping is to provide a piston valve assembly having digressive performance, that is, a piston valve assembly which provides generally independent and distinct damping rates during low and high speed piston compression with very steep and very flat curves, respectively. Ease of calibration may be achieved when a wide range of damping rates may be attained by varying the valve assembly components. Prior art mono-tube designs have had very limited digressive performance with interdependent low and high speed damping rates thereby compromising versatility of ride handling characteristics at low and high vehicle speeds. Therefore, what is needed is a piston valve assembly that provides increased digressive performance.
SUMMARY OF THE INVENTION
The present invention provides a piston valve assembly for regulating the flow of fluid through a mono-tube fluid vehicle damper. The assembly includes a piston rod and a piston end having opposing first and second surfaces secured to the piston rod by a connector. A first outer annular seat is spaced radially from the piston rod and extends from the first surface. At least one first fluid passageway connects a first opening between the piston rod and the first outer annular seat and the second surface for providing fluid communication therebetween. A first blow-off valve has a hollow cylindrical portion with a first flange extending transversely from an end thereof with the first flange adjacent to the first outer annular seat when the first blow-off valve is in a closed position. The piston rod and connector secure the blow-off valve to the piston end. The first blow-off valve is movable to an open position away from the first surface. A first low speed bypass valve is interposed between the at least one first passageway and the second surface for permitting fluid to exit the at least one first fluid passageway past the first blow-off valve when the first blow-off valve is in the closed position. A first helical spring engages the first blow-off valve for biasing the first blow-off valve to the closed position. The blow-off valve provides digressive performance during operation of the damper.
Accordingly, the present invention provides a piston valve assembly that provides increased digressive performance.
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Khalkhali Hamed
Moradmand Jamshid Kargar
Delphi Technologies Inc.
Pezzlo Benjamin A.
Schwartz Christopher P.
Sigler Robert M.
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