1. Field of the Invention
The present invention relates generally to shock absorbers which create an anti-roll system for a vehicle. More particularly, the present invention relates to shock absorbers having a passive damping system for providing variable damping in response to lateral forces placed upon the vehicle.
2. Description of the Related Art
Various types of shock absorbers are used in connection with motor vehicle suspension systems to absorb unwanted vibrations which occur during various driving conditions. To dampen the unwanted vibrations, shock absorbers are generally connected between the sprung portion (i.e., the vehicle body) and the unsprung (i.e., the suspension) of the vehicle. A piston assembly is located within the working chamber of the shock absorber and is connected to the body of the motor vehicle through a piston rod. Generally, the piston assembly includes a primary valving arrangement that is able to limit the flow of damping fluid within the working chamber when the shock absorber is compressed or extended. As such, the shock absorber is able to generate a damping force which "smooths" or "dampens" the vibrations transmitted from the suspension to the vehicle body. Typically, these vibrations occur from forces generated in a vertical direction between the vehicle body and the driving surface.
The greater the degree to which the flow of damping fluid within the working chamber is restricted across the piston assembly, the greater the damping forces which are generated by the shock absorber. It is also possible to implement a primary valving arrangement which produces one magnitude of damping on the compression stroke, and a second magnitude of damping on the rebound stroke. However, these different damping rates are typically constant because they are produced by varying the sizes of the compression and rebound bypass orifices.
While these shock absorbers produce ride comfort levels ranging from "soft" to "firm," few, if any, of the known shock absorbers produce varying degrees of damping in a passive manner. The shock absorber systems known within the art which are capable of producing varying degrees of damping force, typically achieve this through the use of active control systems. However, these systems generally react to the vertically generated forces placed upon the vehicle suspension.
Accordingly, it is desirable to provide a shock absorber which includes a primary damping mechanism for counteracting the vertical forces placed upon the vehicle, and a secondary damping mechanism which is capable of providing varying damping in response to horizontal and lateral forces which are placed upon the vehicle suspension. Further, it is desirable that this secondary and variable damping be provided in proportion to the lateral force encountered by a passive control or valving arrangement. Such a system could be used to implement a passive anti-roll system for enhancing the control to the vehicle provided by the vehicle suspension. Such a passive damping system also eliminates the need for complicated and expensive control systems which actively provide the varying degrees of damping.
An example of the lateral forces placed upon the vehicle suspension are the lateral forces generated during high-speed cornering. As these lateral forces are counteracted by the vehicle's suspension and tires, a rolling action on the vehicle body is produced. When these rolling forces exceed the limit for the vehicle, a rollover condition may be created where the vehicle is literally flipped over on its side. Accordingly, it is desirable to provide a shock absorber which provides increased damping in response to these lateral and horizontal forces for counteracting or at least minimizing these rolling forces.