Land vehicles – Suspension modification enacted during travel – Lateral vehicle disposition
Reexamination Certificate
2001-10-11
2003-09-16
Dickson, Paul N. (Department: 3616)
Land vehicles
Suspension modification enacted during travel
Lateral vehicle disposition
C280S005506, C280S005507, C280S005508, C280S005515, C701S038000
Reexamination Certificate
active
06619672
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns the field of land-vehicle suspensions, and more precisely means used to resist body roll or body pitch. In a particular application, it relates to the suspension of passenger cars.
It is known that the suspension of a vehicle embodies constructional arrangements by means of which the displacement of a wheel or of wheels of an axle with respect to the body (or with respect to the chassis if the vehicle is provided with a chassis, or between body and chassis if appropriate) is guided, and it includes means controlling the deflection of each wheel (a wheel is a member belonging to non-suspended members) with respect to the body (any point situated on the body is referred to as a “suspended” point), in order to bear the load while maintaining a certain ground clearance of the vehicle (this is the function of a spring) and in order to prevent the maintenance of the oscillations arising between suspended and non-suspended points following a disturbance (this is the function of a damper).
It is known that the design of a suspension is characterised by the search for a compromise between objectives which have a reputation for being, at least to a large extent, contradictory: comfort and handling. Numerous efforts have been made to find increasingly favorable compromises. In the state of the art, suspension systems are known which are referred to as active or semi-active suspensions and whose control has now been made possible by progress in electronics. In such suspensions, commands are transmitted by electric or electrohydraulic means in order to modify the flexibility and/or damping characteristics of the suspension in real time. This leads to the addition of an electronic regulation stage, with its sensors and means for calculation, to conventional mechanical, pneumatic or hydraulic devices, as well as solenoid valves or servovalves, in order to transmit the commands for changing the characteristics to the mechanical members responsible for the functioning of the suspension as such. For example, a valve in a damper has to be opened or closed in order to modify the dissipation of energy which it brings about.
In the majority of suspension systems for passenger cars, trucks and passenger-transporting coaches, there also exist specific means for opposing the roll of the body (or chassis) under the effect of centrifugal forces. The tilting of the body about a horizontal axis contained in a longitudinal and vertical plane of symmetry of the vehicle is called “roll”. Excessive roll is detrimental to the comfort of the passengers and, depending on the wheel-guiding means used, may even be detrimental to the working of the tires when the camber of the tire with respect to the ground is influenced by the roll of the body. This is typically the case for a double-wishbone suspension, which is widely used in passenger cars. The roll then influences the stresses to which the said tire is subjected and the more or less favorable position in which it is situated for transmitting forces, in particular forces in the transverse direction. It is known that these forces are of prime importance for the guidance of the vehicle, and thus for safety.
The most commonly employed means for opposing this roll consists in using an anti-roll bar, in general one anti-roll bar per axle. Unfortunately, an anti-roll bar can only limit the roll by opposing the latter with a reaction torque. On principle, it cannot prevent the roll, and thus it cannot prevent the tilting of the wheels in a direction unfavorable to the correct functioning of the tires. In addition, it is known that an anti-roll bar needlessly stiffens the suspension in a straight line, since it opposes the non-identical suspension deflections of the wheels of an axle connected by such a bar. It is only in a pure vertical deflection that the anti-roll bar does not intervene.
From the patent application WO 99/67100, a proposal is already known which describes an active roll control, produced by means of an anti-roll bar comprising an electric motor intended to impose thereon a pre-tension in the desired direction. However, this solution is limited to the control of the roll.
The pitch of a vehicle (lift at the front on acceleration, diving on braking) poses problems comparable to those posed by roll. The pitch is generally opposed by suspension configurations adapted so that the longitudinal transfers of loads only partially stress the springs, but this is a palliative not without detrimental effects. The roll and pitch are both referred to hereinbelow as “trim variation ”. A trim variation embraces, in the present specification, a variation of the ground clearance and also any tilting with respect to the a reference plane linked to the non-suspended mass of the vehicle.
Also known are numerous proposals for active suspensions, such as those described in the patents or patent applications U.S. Pat. Nos. 5,060,959, 5,028,073, 5,066,041, 5,740,039 or EP 0 878 333, to mention only some of them. The diversity of the constructional arrangements and of the control laws proposed compared with the very small number of active suspensions on the market gives an idea of the difficulty of controlling the suspensions effectively. The state of the art comes up against the choice of control parameters, and the correct utilization of a multitude of signals which are thought to be needed for correctly capturing the attitude of a vehicle.
SUMMARY OF THE INVENTION
The aim of the invention is to obtain a high level of operational safety of the vehicles and great comfort.
The invention proposes a vehicle suspension device comprising at least two suspension systems each connecting a non-suspended mass comprising a wheel to a suspended mass with possible vertical deflection, each suspension system comprising a vertical suspension reacting to the variations of distance between the suspended mass and the non-suspended mass, the said vertical suspension comprising a spring and a reversible electric actuator acting in parallel with the spring, the device comprising means for evaluating a non-vertical stress applied to the suspended mass and likely to bring about a trim variation of the suspended mass, the said device comprising means for controlling the electric actuators of each of the said suspension systems so that they each develop a force consisting of the addition of two components: a damping component opposing the deflection speed and a trim correction component, the said trim correction components applying a trim correction to the suspended mass.
Thus, through the simple programming of the mere two components indicated above, one of which is a dissipative damping component, it is possible to control the force in the electric actuator so as to obtain a safe and relatively comfortable suspension. The present proposal does not have recourse to more complex means as proposed in the patent application EP 0 878 333, in which a road-contour-following control is proposed, accompanied in one embodiment by a detection of the occurrence of a resonance of the tire in order to introduce a damping.
An advantageous example of the use of the invention concerns a trim correction controlled by means for evaluating a non-vertical stress applied to the suspended mass and likely to bring about a trim variation of the suspended mass. The rest of the description concerns essentially roll, since this is sufficient to make the invention clear. The said at least two suspension systems form an axle and are mounted on either side of the median plane of symmetry of the vehicle, so that the said trim correction torque opposes the roll. However, this is not limiting. All that has been said in connection with roll may be developed in connection with pitch. The invention can be applied to a bicycle such as a motorcycle. The proposed means can be used to oppose either or both of these phenomena. The invention thus extends to the case in which the said at least two suspension systems comprise a front suspension system and a rear suspension system,
Charaudeau Jean-Jacques
Laurent Daniel
Linda Jean-Louis
Varenne Pierre
Conception et Development Michelin S.A.
Dickson Paul N.
Ilan Ruth
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