Land vehicles – Suspension modification enacted during travel – Suspension geometry
Reexamination Certificate
1999-03-11
2001-07-31
Boehler, Anne Marie (Department: 3618)
Land vehicles
Suspension modification enacted during travel
Suspension geometry
C280S086751, C280S124106
Reexamination Certificate
active
06267387
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an independent suspension system for vehicles including wheel uprights which move in differing directions relative to the chassis when negotiating curves. The system automatically adjusts the wheel camber based on the forces effective on the vehicle when negotiating curves. Means are provided for registering the relative movement with respect to the chassis of the parts of the wheel suspension having mutually different movements when negotiating curves and for controlling the wheel camber angle and/or the steering angle of the wheels with the aid of actuating means.
In the case of vehicles having independent suspension systems, it is impossible to avoid changes in suspension geometry when negotiating curves (rolling movement of the chassis) or in the event of jounce and heave of the chassis (up and down movement of the vehicle).
The wheel camber angle is particularly adversely affected when negotiating curves. Inappropriate wheel camber angles have a negative effect on the driving characteristics of the vehicle, i.e. in the case of an optimally adjusted wheel camber for driving in a straight line, the driving characteristics, e.g. safety and speed, will suffer due to the above-mentioned changes in the geometry, since the maximum possible surface contact of the tires cannot be achieved or the maximum possible cornering force is not reached.
In the past, various attempts have been made to overcome the effects of the rolling movement of the chassis upon the wheel camber.
In order to get around the above-mentioned disadvantages when negotiating curves, it has been proposed for example that the wheel camber be set in a negative range for straight line driving, this then producing improved driving conditions or improved settings of the wheel camber when negotiating curves.
Here, however, it is disadvantageous that the tire will heat up very unevenly across the tire width when driving in a straight line due to the surface of the tire being raised at one side, thereby reducing the driving characteristics i.e. the maximum cornering force transmissible by the tire, especially in curves.
Furthermore, attempts have been made to reduce the above-mentioned disadvantages by means of special configurations of the suspension arms. For example, changes of wheel camber when the chassis is rolling are counteracted by means of non-parallel, unequally long suspension arms. Here, however, the virtually unavoidable alteration in the wheel camber during jounce and heave of the chassis has a disadvantageous effect upon the driving characteristics.
This solution can thus only be considered as being an unsatisfactory compromise.
It was proposed in the publication “Design of racing sports cars” by Colin Cambell, published by Chapman & Hall Ltd., London EC4P 4EE in 1973, that the wheel camber be adjusted or optimized in accordance with the rolling movement of the chassis or the effects of centrifugal force, this being referred to as “Trebron DRC” (double roll center suspension).
In this design, it is necessary to provide a sub-chassis which is pivotal about a center point located above the center of gravity of the vehicle with the aid of curved grooves on guide pins fixed to the chassis. The spring/damping elements and also the lower suspension arms engage this sub-chassis. The upper suspension arms are coupled via levers which, for their part, are pivotal about the guide pins at the chassis end of the arrangement. The sub-chassis is operatively coupled to the pivoted lever by means of a bearing pin.
One substantial disadvantage here is the space needed for the sub-chassis which makes it impossible to install or, at least, considerably increases the difficulty of installing certain parts of the vehicle or the engine/transmission, etc. The relatively large number of mechanical parts (sliding link guides, etc.), which are problematic as regards absence of play and accessibility, also stand in the way of the wanted precision in the control function.
SUMMARY OF THE INVENTION
In accordance with the invention, provision is made, for example, that hydraulic master cylinders be arranged between the chassis and the oscillating or swinging wheel uprights or suspension elements (suspension arms), the working spaces of these cylinders being mutually cross-coupled and the cylinders controlling slave cylinders on the upper suspension arms thereby producing a compensating effect for any alteration in the wheel camber in dependence on the rolling movement of the chassis.
REFERENCES:
patent: 2678830 (1954-05-01), Cigan et al.
patent: 2907578 (1959-10-01), Taber
patent: 3711113 (1973-01-01), Stammreich
patent: 4546997 (1985-10-01), Smyers
patent: 4700972 (1987-10-01), Young
patent: 5284353 (1994-02-01), Shinji et al.
patent: 5324056 (1994-06-01), Orton
patent: 41 13 736 A1 (1991-10-01), None
patent: 0 378 028 A1 (1990-07-01), None
patent: 0 378 028 B1 (1993-01-01), None
patent: 1 526 970 (1978-10-01), None
patent: 2 243 349 A (1991-10-01), None
Hamy, Norbert, “The Trebron DRC Racing Chassis”,Motor, Dec. 21, 1968, pp. 20-24.
Boehler Anne Marie
Townsend and Townsend / and Crew LLP
Winner Tony
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