Brakes – Internal-resistance motion retarder – Cylinder structure
Reexamination Certificate
1999-05-25
2001-11-27
Swann, J. J. (Department: 3611)
Brakes
Internal-resistance motion retarder
Cylinder structure
C188S299100, C188S313000, C280S005500, C280S005515, C701S037000, C701S048000
Reexamination Certificate
active
06321888
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to hydraulic dampers, and more particularly to a new and improved semi-active damper with an externally mounted valve assembly for selectively varying stiffness of the damper in compression and separately selectively varying stiffness of the damper in rebound.
2. Description of Related Art
Dampers are used in conjunction with automotive suspension systems to absorb unwanted vibrations which occur while driving a vehicle. In order to absorb unwanted vibrations, dampers are generally connected between the body and the suspension of an automobile. A piston is located within the damper which is connected to the body of the automobile through a piston rod. Furthermore, the damper body is connected to the suspension of the automobile. Because the piston is able to limit the flow of damping fluid within the working chamber of the damper as the damper is compressed extended, the damper is able to produce a damping force which counteracts suspension system vibration which wold otherwise be transmitted from the suspension to the body. By further restricting the flow of damping fluid within the working chamber of a damper, greater damping forces are generated by the damper.
In determining the optimal amount of damping that a damper should provide, three vehicle performance characteristics are often considered: ride comfort, vehicle handling and road holding ability. Ride comfort is typically a function of the spring constant of the vehicle's main springs, as well as the spring constant of the occupant's seat, the vehicle's tires the suspension geometry, and the damper. Vehicle handling is related to changes in the vehicle's attitude (i.e., pitch, yaw, and roll). To achieve optimum vehicle handling, relatively large damping forces are required to avoid excessively rapid variation in the vehicle's attitude during acceleration, deceleration, and cornering. Road holding ability is generally dependent on the amount of contact between the vehicle tires and the ground. In order to optimize a vehicle's road holding ability, large damping forces are required as a vehicle passes over irregular surfaces in order to prevent loss of contact between the wheels and ground for an excessive period of time.
Because different driving characteristics require differing amounts of damping force from the damper in order to optimize its performance, it is often desirable to have a damper which can be adjusted to increase or decrease the requisite damping forces. One method for selectively changing a damper's damping characteristics is described in U.S. Pat. No. 4,890,858. This reference discloses a rotary valve for use in controlling a damper. The damper comprises a first valve member which is disposed within the pressure cylinder for establishing a plurality of flow passages. Furthermore, the damper comprises a second valve member also disposed within the pressure cylinder for establishing a second plurality of flow passages. In addition, the damper includes an actuator for providing an accelerating and decelerating force to the second valve member. Finally, control means for controlling displacement of the second valve member are also disclosed.
Because dampers which provide adjustable damping generally use a single valve to control the flow of damping fluid during both compression and rebound, a sensor is generally required to determine whether the damper is in compression or rebound. Not only does this provide a degree of difficultly in terms of sensor placement, there are also disadvantages with respect to the electronics which are required to generate an output indicative of whether the damper is in compression or rebound from the output of the sensor. Accordingly, these systems tend to be somewhat expensive.
SUMMARY OF THE INVENTION
The present invention relates to a damper which includes a pressure cylinder and a piston which is reciprocally mounted in the cylinder so as to define a compression chamber and rebound chamber. The compression and rebound chambers are operable to store damping fluid and the piston is movable for reciprocally varying the volumes of the compression and rebound chambers. The damper further includes a valve for controlling the flow of fluid between the compression and rebound chambers, as well as a reservoir for receiving damping fluid. A compression transfer tube is provided which allows fluid communication between the compression chamber and the reservoir. The damper further includes a compression valve in communication with the transfer tube as well as a base valve in the pressure cylinder in communication with the pressure chamber and the reservoir. Finally, the damper includes a reservoir fluid aperture in the reservoir for establishing fluid flow from the reservoir to the rebound chamber.
Accordingly, the primary object of the present invention is to provide a semiactive damper for use in an automatic damping system of a vehicle which can be controlled by individually dedicated or shared electronic control modules. In this regard, a related object of the present invention is to provide a simplified and lower cost semiactively adjustable damper in which adaptive external valves allow for independent adjustable setting of the damper damping in rebound and compression.
A further object of the present invention is to provide a semi-active damper in which a pair of separate dedicated valving systems are utilized to soften damper damping in rebound and compression, which simplifies the damper while still providing an automatic damper system in which the rate of damping fluid flow between upper and lower portions of a working chamber may be controlled with a relatively high degree of accuracy. A related object of the present invention is to provide a semi-active damping system in which detection of rebound-compression transitions for each damper are not required which eliminates the need for a position sensor to sense the transition, yet still allows for achievement of separately tailored compression and rebound characteristics.
Further objects, features and advantages of this invention are to provide a damper which can be easily and readily adjusted automatically and semi-actively to optimize damping characteristics, with separate discrete or continuously variable external valves achieving separate damping settings in rebound and compression, and which has a long service life and is rugged, durable, reliable, of simplified design and of relatively economical manufacture and assembly.
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Reybrouck Koenraad G.
Schurmans Rudi J.
Divine David
Harness Dickey & Pierce PLC
Swann J. J.
Tenneco Automotive Inc.
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