Brakes – Internal-resistance motion retarder – Resistance alters relative to direction of thrust member
Reexamination Certificate
2001-12-20
2003-12-02
Lavinder, Jack (Department: 3683)
Brakes
Internal-resistance motion retarder
Resistance alters relative to direction of thrust member
C188S322150
Reexamination Certificate
active
06655512
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to a damper adapted for use in a vehicle suspension system, and more particularly to a vehicle damper providing digressive force versus velocity performance at low damper velocities.
BACKGROUND OF THE INVENTION
A hydraulic damper used in a vehicle suspension system, such as a shock absorber or a MacPherson strut, must be capable of reacting to and dissipating energy under all types of driving conditions and road obstacles that the vehicle may encounter. The vehicle damper must be capable of handling low velocity inputs, such as chassis sway, encountered during normal maneuvering of the vehicle, and high velocity inputs when the wheels of the vehicle encounter bumps or potholes in the road surface.
In order to accommodate both low and high velocity movements of the suspension, vehicle dampers often include one or more valves having a notched orifice disk, of the type illustrated in FIG.
1
. Under low velocity input conditions, the orifice disk is clamped against a valve seat to close off flow apertures within the damper that allow passage of fluid through the internal components of the damper. When a high velocity input to the damper is encountered, fluid in the flow apertures reaches a pressure that is high enough to force all or a portion of the orifice disk off of the valve seat, thereby allowing the internal components of the damper to move through the fluid and provide high velocity damping of the suspension. The orifice disk may be part of a blow-off valve assembly, where the orifice disk is held against the valve seat by a spring, until the pressure in the flow apertures increases to an opening pressure at which force, generated by the fluid pressure in the flow apertures acting against the orifice disk, compresses the spring, and the entire orifice disk lifts off of the valve seat to provide a large effective orifice area for the passage of fluid during dissipation of the high velocity input by the damper. Alternatively, the orifice disk may be part of a deflecting disk valve, where the central portion of the disk remains clamped to the valve seat, and the outer periphery of the orifice disk flexes away from the valve seat to allow passage of fluid during high velocity inputs to the damper, when the fluid pressure in the flow apertures acting on the orifice disk reaches a pressure high enough to cause the disk to deflect.
During low velocity input conditions, the orifice disk remains clamped against the valve seat, and fluid in the flow apertures is allowed to bleed through the notches in the outer periphery of the orifice disk. The low speed performance of the damper can be tuned fairly accurately by judicious selection of the size and number of notches in the orifice disk, and the thickness of the orifice disk.
Valves having notched orifice disks, as described above, provide a fixed area effective orifice during low velocity operation of the damper. Such a fixed area orifice allows fluid to flow through the notches during low speed operation of the damper in such a manner that the force generated by the damper is a generally parabolic function of velocity of the input, as depicted in the low velocity portion ‘A’ of the operating curve illustrated in FIG.
2
. When the opening pressure ‘B’ of the valve is reached, the orifice disk blows off or deflects away from the valve seat, thereby increasing the effective orifice area significantly, and the operating characteristic of the damper changes to a linear or much flatter partially parabolic relationship during high velocity operation, as shown by the high velocity portion ‘C’ of the operating curve illustrated in FIG.
2
.
The parabolic shaped, low velocity operating characteristic provided by valves having fixed area orifice disks is not ideal for all suspension systems, however. In some suspension systems, it is desirable to have a vehicle damper that provides a force versus velocity operating characteristic during low velocity inputs that digresses, as shown in
FIG. 3
, from the parabolic shape provided by fixed area orifice plates of the type used in prior vehicle dampers, and described above.
What is needed, therefore, is an improved valve assembly and vehicle damper that provides a digressive operating characteristic for damping low velocity inputs to the damper. Preferably, the improved valve assembly can be configured alternatively in the form of a blow-off valve, a clamped deflecting disk valve, or in a valve combining both deflecting disk and blow-off functions. It is also desirable that the improved valve be capable of use in various forms as a compression or a rebound valve on the piston of a vehicle damper, or as a base valve in a dual tube vehicle damper.
SUMMARY OF THE INVENTION
Our invention provides such an improved valve and vehicle damper through the use of an imperforate and deflectable, variable orifice disk, having an outer periphery that is only partially clamped against a valve seat, during low velocity operation of the damper, by a variable orifice support disk that has an outer periphery which is not coextensive with the outer periphery of the variable orifice disk. The portion of the outer periphery of the variable orifice disk that is not clamped against the valve seat deflects away from the valve seat during low velocity operation of the damper, in response to force on the variable orifice plate generated by pressure of fluid in flow apertures closed off by the variable orifice plate, to provide a variable orifice for fluid flow through the valve and digressive performance of the damper.
Our invention may take the form of a compression or rebound valve on the piston of a vehicle damper, or a base valve in a dual tube damper. Our invention may take the form of a blow-off valve, a deflecting disk valve, a combination blow-off deflecting disk valve, or as part of other types of valves suited for use in vehicle dampers. A damper according to our invention may include one or more valves according to our invention in combination with other valves of conventional construction.
In one form of our invention, a valve assembly for a vehicle damper includes a valve seat, and orifice disk means. The valve seat defines a flow aperture adapted for receiving a fluid and directing a flow of the fluid through the valve seat. The orifice disk means are adapted for sealing engagement with the valve seat to block the flow of fluid through the flow aperture until the fluid in the flow aperture reaches an opening pressure of the valve, with the orifice disk means providing a variable orifice area for a flow of fluid through the valve prior to the fluid in the flow aperture reaching the opening pressure of the valve. The variable orifice area of the valve allows a flow of fluid through the valve, prior to the fluid in the flow aperture reaching the opening pressure of the valve, that digresses from a parabolic force versus flow characteristic of the type produced by a constant area bleed orifice.
The orifice disk means may include a variable area orifice disk that is partly deflectable away from the valve seat by fluid pressure in the flow aperture acting against the orifice disk when it is in sealing engagement with the valve seat. The deflected disk forms a flow area through the valve that varies in accordance with the pressure of the fluid in the flow apertures prior to the fluid in the flow aperture reaching the opening pressure of the valve.
The flexible orifice disk may have an outer periphery adapted for clamped engagement against the valve seat, and for blocking the flow aperture when the outer periphery of the flexible orifice disk is not deflected away from the valve seat, with the support disk being adapted for clamping less than the entire outer periphery of the flexible orifice against the valve seat. The support disk is shaped for providing only partial clamping and support of the flexible orifice disk against the valve seat, such that fluid pressure within the flow aperture causes localized deflection in a direction away from the valve seat of
Knapczyk Marcin
Moradmand Jamshid K.
Neal Robert A.
Delphi Technologies Inc.
Lavinder Jack
McBain Scott A.
Pezzlo Benjamin A
LandOfFree
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