Land vehicles – Wheeled – Running gear
Reexamination Certificate
2002-04-04
2004-08-17
Dunn, David (Department: 3616)
Land vehicles
Wheeled
Running gear
C280S124138
Reexamination Certificate
active
06776426
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to chassis systems for vehicles, more particularly to suspension devices for vehicles, and still more particularly to suspension devices which allow wheel camber control substantially independently of the vertical oscillations of the wheel.
2. The Related Art
Vehicular suspension devices have two main functions which must be fulfilled simultaneously at any moment during operation. One of these functions is that of suspending the vehicle, that is to say, permitting substantially vertical oscillations of each wheel in accordance with the load applied to the wheel. The other function of these devices is that of guiding the wheel, that is to say, controlling the angular position of the wheel plane.
The term “wheel plane” refers to the plane, associated with the wheel, which is perpendicular to the axis of the wheel and which passes through the center of the contact area with the ground. The angular position of the wheel plane with respect to the body of the vehicle is defined by two angles, the camber angle and the steering angle. The camber angle of a wheel is the angle separating, in a transverse plane perpendicular to the ground, the wheel plane from the mid-plane of the vehicle. This angle is positive when the upper part of the wheel deviates from the mid-plane towards the outside of the vehicle, this being commonly termed “camber” or “positive camber”. Conversely, when this angle is negative, the term used is “counter-camber” or “negative camber”. The steering angle of a wheel is the angle separating, in a horizontal plane parallel to the ground, the wheel plane from the mid-plane of the vehicle.
On most vehicles, the camber angle (“camber” or “camber angle” will be used without distinction hereinbelow) is fixed for a particular position of the suspension and the steering; that is to say, theoretically it cannot vary independently of the suspension deflection or the steering. However, it undergoes variations induced by the deformations of the elements constituting the suspension device caused by the forces exerted on the wheel by the ground. These variations may be considerable. For example, an ordinary passenger car experiences camber variations of several degrees under the transverse forces developed on the tire on a curve, irrespective of the contribution of the roll of the vehicle body (which generally tilts in the same direction under the effect of centrifugal force). This “elastic” variation of the camber causes the camber to increase (the camber tends towards positive values) for the outer wheel on the curve. Conversely, the camber decreases (it tends towards negative values) for the inner wheel on the curve. For a long time, these predictable variations have been incorporated into the design and adjustment compromises of the suspension devices for such ordinary vehicles in order to limit the harmful effects which they have on the functioning of the chassis system.
The camber has a great influence on the behavior of the vehicle and the performance of the chassis system. In particular, the performance of a tire is very variable depending on the configuration of its area of contact with the ground, and this configuration depends largely on the camber. The choice of the static camber angle is based mainly on these variations. Thus, for example, a large negative static camber is generally introduced on a racing vehicle in order to compensate for the variations due to the deformations of the tire under transverse force, as well as the suspension elements, even though they are much more rigid than on passenger cars, and due to the roll of the body. This configuration is both useful and acceptable in racing, since the criteria of grip on cornering are a major concern here. In contrast, on a passenger car, since the wear of the tires and the straight-line stability have more weight in the compromise being sought, a very slightly negative initial static camber is generally chosen. It is necessary to accept reduced slip thrusts, mainly on curves, when the effects of deformations of the tire and the elements of the ground contact system under the lateral forces on the positioning of the wheel plane are added to the effects of the roll of the vehicle.
In order to optimize the camber, in particular during transverse accelerations, suspension devices whose camber varies in accordance with the vertical deflection of the wheel have been designed. In this way, the roll experienced by the body of the vehicle can induce a useful variation of the camber which partly or totally compensates for the inclination of the body of the vehicle and the deformations described above. This is the case of the so-called “multi-link” systems. These devices require a specific design and vehicle architecture, which cannot be implemented on most current vehicles, for reasons of space requirements and cost. These systems react only to the consequence (deflection, rolling) of a transverse acceleration and not to the forces which cause it, thereby, on the one hand, delaying the effect of the correction. Moreover, to permit a sufficient variation of the camber, the kinematics of these systems require displacements of the position of the contact area with respect to the vehicle, called “track changes”, and these variations can also create difficulty. The range of camber corrections made possible by such systems is therefore relatively limited when the compromise necessary for correct functioning of the other load cases, such as travelling on a bumpy road, unilateral or in contrast simultaneous bouncing, is to be observed.
From the point of view of kinematics, in terms of degrees of freedom, suspension devices generally have only one degree of freedom (of the wheel or wheel carrier with respect to the vehicle). This degree of freedom permits vertical suspension movements which, as explained above, can be combined with limited camber variations.
Systems are known, however, in which the control of the camber is active; that is to say, the geometry modifications are controlled by movements of actuating cylinders, as described, for example, in the patent documents U.S. Pat. No. 4,515,390, U.S. Pat. No. 4,700,972 and DE 19717418. In these systems, at least a certain degree of additional freedom controlled by actuators has been permitted. These systems are very specific, since they cannot be used in most ordinary vehicles, in particular because of their space requirement, the considerable power necessary for the actuators and for costs reasons.
SUMMARY OF THE INVENTION
An object of the invention is to provide a suspension device of simple construction, which allows control of the camber substantially independently of the vertical oscillations of the suspension device and, more generally, of the movements of the body of the vehicle.
The foregoing and other objects of the invention are attained by a suspension device intended to connect a wheel carrier to a body of a vehicle, such device having means conferring to the wheel carrier, with respect to the body, a degree of camber freedom and a degree of suspension deflection freedom independent of one another. The means includes an intermediate support linking the wheel carrier to the body, the intermediate support being, on the one hand, articulated with respect to the body along a substantially vertical first axis and, on the other hand, articulated to the wheel carrier along a second axis, so that a rotation of the intermediate support about the first axis permits the degree of camber freedom. The suspension device of the invention has two degrees of freedom permitting independent suspension and camber movements. The camber movement is effected in a simple manner by virtue of the rotation of the intermediate support about a substantially vertical first axis. “Substantially vertical” means in this context that the axis of rotation can be inclined, for example up to an inclination of 30° from vertical as will be seen from the detailed description of the drawings.
Preferably, with
Dunn David
Fitzpatrick ,Cella, Harper & Scinto
Michelin & Recherche et Technique S.A.
LandOfFree
Suspension device permitting camber does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Suspension device permitting camber, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Suspension device permitting camber will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3344464