WO2008071663A1

WO2008071663A1 - Suspension device and automotive vehicle fitted with such device

Info

Publication number: WO2008071663A1
Application number: PCT/EP2007/063617
Authority: WO
Inventors: Flavien De Bonnevie; Eric Debernard; Jean-Guillaume Meyrignac; Christophe Portaz
Original assignee: Renault S.A.S
Priority date: 2006-12-11
Filing date: 2007-12-10
Publication date: 2008-06-19
Also published as: FR2909590B1; FR2909590A1

Abstract

The invention relates to a suspension device for an automotive vehicle, wherein said device includes suspension actuators acting individually on the wheels of said vehicle, said vehicle having given physical parameters and being provided with sensors for estimating rolling variables (?x, ?y, ?, h1, h2, h0, l1, l2) and driving requests (a, PF, PA), the device being characterised in that it comprises sensors for measuring the ground vertical force (Fz11, Fz12, Fz21, Fz22) applied on each of said wheels, and control means for calculating, according to said parameters, variables and/or requests, and outputting instructions towards at least one of said actuators in order to increase the ground vertical force (Fz11, Fz12, Fz21, Fz22) applied on one of said wheels.

Description

SUSPENSION DEVICE AND MOTOR VEHICLE EQUIPPED WITH SUCH DEVICE FIELD OF THE INVENTION

The present invention relates to a suspension device for a vehicle comprising suspension actuators, sensors measuring the vertical force of the ground exerted on the wheels of the vehicle as well as the control means of these suspension actuators so as to increase these downward vertical forces. depending on the needs.

Furthermore, the present invention relates to a control method of the suspension actuators of a vehicle, and a vehicle equipped with such a device.

PRIOR STATE OF THE ART

In a known manner, a suspension device equipping a vehicle must fulfill a function of comfort for the occupants of this vehicle as well as a safety function of maintaining the stability of the vehicle as it rolls. The comfort of the passengers of the vehicle depends on the capacity of the suspension device to filter the shocks and vibrations due to the irregularities that the road presents. Current vehicles generally implement three levels of filtering of these irregularities.

First of all, it is possible to filter these vibrations directly between the ground and the wheel, that is to say at the level of the tires. Insofar as the tire is a device that transmits the guiding forces of the vehicle to the road, it also transmits the vertical excitations of shocks and vibrations due to the road.

The second level of filtering is operated between the wheels and the chassis of the vehicle. To treat the forces exerted or undergone by the vehicle chassis in the vertical direction, the chassis is suspended above the wheels by means of a suspension device. The elements carried by this suspension are conventionally called "suspended masses". Such a device thus makes it possible to filter the vibrations and jolts due to the irregularities of the road. In the longitudinal direction and in the lateral direction, the filtering of the forces and vibrations is ensured by the trains or half-trains connecting the wheels to their rotary drive member. The half-trains are thus designed to control the plane of the wheels and they contribute substantially to the stability of the vehicle and the comfort of these occupants.

In addition, there is a third level of filtering of the irregularities of the road which intervenes between the chassis and the body of the occupants of the vehicle. Indeed, the seats of a vehicle are provided to minimize the transmission of chassis vibrations for the occupants. This level of filtering is not directly related to the object of the present invention.

In addition to the comfort of the occupants of the vehicle, a suspension device plays a major role in the stability, therefore the safety, of the vehicle that it equips. Indeed, it contributes to the handling of the vehicle, especially when the latter is stressed significantly in acceleration, braking or cornering by its driver. For this, the suspension device comprises suspension actuators capable of exerting on each of the wheels the moments and the forces to prevent the detachment of the wheels and ensure their follow-up closer to the profile of the road.

In addition, the suspension device of a vehicle can dampen the jolts, percussion and other rebounds of wheels by damping the vibrations generated by the profile of the road. In particular, when the vehicle is traveling on a degraded road surface, on a paved road or on projecting obstacles such as potholes or speed bumps, the suspension actuators have the function of keeping the tires of the vehicle in contact with each other. with the road. In terms of safety, this allows in particular to limit the braking distance of the vehicle to the stop.

There are different methods of controlling the suspension device of a vehicle depending on the road profile, driving conditions and / or requests expressed by the driver in terms of braking, acceleration or cornering. In all cases, these various processes are designed to improve the stability of the vehicle and the comfort of these occupants by controlling the variations of the vertical forces exerted on each wheel or tire.

The vehicles of the prior art are equipped with suspension devices using different measurements and information to fulfill the functions of comfort, that is to say to filter the vibrations generated by the irregularities of the road, and safety, that is to say essentially to keep the wheels in contact with the road. These measurements and information actually represent driving variables and driving requests evaluated by sensors fitted to the vehicle.

Among the driving variables used by the current suspension devices, mention may be made of the speed of the vehicle, its lateral acceleration, its longitudinal acceleration, the height of vertical displacement of each wheel and the speed of this vertical deflection. Among the driving requests include the angle of the steering wheel chosen by the driver, the pressure it exerts on the brake pedals and accelerator. Other variables may also be evaluated to inform the suspension device and allow it to calculate the instructions it must issue to the suspension actuators to perform its functions. Thus, the suspension device can be informed of the intensity of the current flowing in a particular suspension actuator or braking actuator.

Thus, all of this information and measurements collected by the suspension device allow it to estimate the vertical force exerted on each wheel to determine the instructions to be transmitted to the suspension actuators.

However, several difficulties are likely to distort the estimation of these vertical forces and thus limit the effectiveness of the suspension of the vehicle.

Firstly, when the vehicle is traveling in a quasi-steady state, the estimate of the vertical forces is based on an estimate of the vehicle mass, the location of its center of gravity and its longitudinal and lateral accelerations. However, the mass of the vehicle can vary according to the number of passengers and / or the payload transported, so that the location of the center of gravity can also vary according to the distribution of its mass, while the signals representing the accelerations can be noisy.

In addition, a vehicle with four wheels is a hyperstatic mechanism of degree one. The information and measures previously listed are therefore insufficient to precisely determine the vertical force exerted on each wheel of the vehicle. The suspension device must then know precisely the stiffnesses and the damping coefficients specific to each subset of suspension. front-rear-right-left. However, these magnitudes depend on the position of each wheel, the elements of the suspension exhibiting a parasitic stiffness, and thus interdependent contributions from the actuators and the passive elements of the suspension device.

On the other hand, the vertical forces obviously vary according to the dynamic stresses on the chassis and on the wheels. When the vehicle is traveling at a regime that is not quasi-stationary, it must therefore take into account the transient movements of the chassis and the inertia it has locally, which can be difficult.

Similarly, when the wheel undergoes a vertical deflection generated by the obstacles of the road, the energy of such deflections is absorbed by the chassis elements such as tires, articulation components (ball joints, gimbals), dampers etc. . However, this energy absorption prevents to know precisely the intensity of the vertical forces exerted on each wheel of the vehicle.

Therefore, the suspension devices of the prior art are not really able to evaluate such vertical forces. As a result, these suspension devices can not optimally regulate the suspension actuators that distribute the vertical forces on each wheel to ensure the comfort and stability of the vehicle.

The object of the present invention therefore relates to a suspension device for a motor vehicle whose evaluation of the vertical forces to the wheels is not approximate or disturbed.

SUMMARY OF THE INVENTION

The present invention relates to a suspension device for a motor vehicle capable of efficiently regulating the vertical forces exerted on the wheels of the vehicle in order to keep each wheel in contact with the road.

The present invention firstly relates to a suspension device for a motor vehicle, which comprises suspension actuators acting individually on wheels of the vehicle. This vehicle has physical parameters and is equipped sensors capable of evaluating driving variables and driving requests. According to the invention, this device comprises sensors capable of measuring the vertical force of the ground exerted on each of the wheels, as well as control means for, depending on these parameters, variables and / or requests, calculating and issuing instructions. to at least one of these suspension actuators, so as to increase the vertical force of the ground exerted on one of the wheels.

In other words, the suspension device object herein is able to accurately measure the vertical forces on the wheels of the vehicle and to regulate accordingly the suspension actuators to keep these wheels in contact with the road.

In practice, each of these sensors may consist of strain gauges housed in a bearing of one of these wheels.

These sensors then indirectly measure the vertical forces on each wheel, since a strain gauge generally measures an elongation via the variation of the electric current flowing through it. Such stress sensors represent a minimum space requirement and they are positioned at locations where the vertical forces to be measured actually operate.

According to a practical embodiment of the invention, these means can calculate and issue instructions to at least one of the suspension actuators acting on the inner rear wheel at a turn followed by the vehicle.

Such a device avoids the detachment of the inner rear wheel when the vehicle approaches a turn in difficult driving conditions.

Conveniently, each of the suspension actuators can act on at least one of the wheels through the front and rear half-shafts on which these wheels are mounted.

Such suspension actuators are therefore able to generate a vertical force on each of the wheels of the vehicle, namely at the front, rear, right and left.

According to an advantageous embodiment of the invention, the suspension actuators may comprise at least one anti-roll bar associated with a jack rotary capable of applying a torque on each of the half-shafts.

Such a suspension actuator generates an anti-roll torque, which implies the realization of a vertical force down on one and / or the other wheels mounted on these half-shafts.

According to another advantageous embodiment of the invention, the suspension actuators may comprise at least one linear jack capable of exerting a force on each of the half-shafts.

Such a suspension actuator can therefore exert a vertical force on each wheel through the corresponding half-shaft.

According to an alternative embodiment of the invention, the suspension actuators may comprise at least one controlled suspension.

In practice :

the physical parameters may include the wheelbase, the front and rear tracks, the mass of the vehicle, the stiffness of the suspension actuators; the rolling variables may comprise the longitudinal and lateral accelerations, the roll angle, the ground height of the front and rear roll centers, the vertical distance separating the roll axis from the inertia center of the suspended masses, the longitudinal distances separating respectively the front wheels and the rear wheels from the center of inertia, the travel and the vertical travel speed of each wheel;

- driving requests include the steering wheel angle, the pressure exerted on the brake pedal, the pressure exerted on the accelerator pedal.

Thus, the knowledge of all these physical parameters, driving variable and driving request allows to completely determine the hyperstatic system of degree one that represents the vehicle suspended above four wheels.

On the other hand, the present invention relates to a motor vehicle equipped with a device according to the invention. BRIEF DESCRIPTION OF THE FIGURES

The way in which the invention can be realized and the advantages which result therefrom will also emerge from the following exemplary embodiments, given by way of indication and without limitation, in support of the appended figures among which:

Figure 1 is a three-dimensional schematic representation illustrating the parameters and variables to be taken into account to establish the balance of the forces exerted on the components of a vehicle according to the present invention. FIG. 2a represents a flowchart illustrating the regulation of a suspension device according to the invention.

Figure 2b shows a flowchart illustrating the control of a suspension device object of the present invention.

FIG. 3 is a comparative diagram illustrating the measurement of the vertical force exerted on the inner rear wheel as a function of the position of a vehicle in a turn, the continuous line curve corresponds to a vehicle according to the present invention, while that the curve in dashed lines corresponds to a vehicle of the prior art.

MODES FOR CARRYING OUT THE INVENTION

Figure 1 illustrates all the forces, forces and moments that are exerted on the chassis of the vehicle, that is to say between the wheels and the chassis through the suspension actuators. In addition, Figure 1 illustrates the forces due to accelerations that are exerted on the vehicle at its center of gravity. FIG. 1 also shows the geometrical parameters that make up the characteristic physical parameters of the vehicle, as well as the driving variables that characterize the instantaneous conditions in which the vehicle rolls.

In general, the notation of the parameters shown in FIG. 1 makes it possible to distinguish the quantities of the same type as a function of their location on the chassis.

Indeed, the first numerical index affixed to a quantity characterizes the longitudinal location of this quantity, that is to say its position at the front or rear of the vehicle. The index 1 represents the front of the vehicle, while the index 2 represents the rear of the vehicle. In addition, the second numerical index possibly affixed to a magnitude of Figure 1 represents the lateral or transverse location of this magnitude on the frame.

Thus, the index 1 designates the left side, while the index 2 designates the right side. By Therefore, the vertical forces F ^ - exerted by each of the wheels on the chassis are respectively noted F _Λ1 , F ^ ₂ , F _22I and F ₂₂₂ TO designate the forces to the front-right wheels, front-left, rear-right and rear -Left of the vehicle. Indices are also used to differentiate the other quantities shown in Figure 1.

Among the anti-roll couples illustrated in FIG. 1, the "passive" anti-roll torques C _M are distinguished. θ and Ck ₂ -G "active" anti-roll pairs C _a i and C _a2 . Indeed, the "passive" anti-roll couples C _M .Θ and c ^ .θ are due to the inertia of the suspension springs and front and rear axles that are modeled by their angular stiffness noted C _M and Ck ₂ . On the other hand, the "active" anti-roll couples C _a i and C a ₂ are due to the anti-roll suspension actuators which are associated with driving members, such as a rotary jack or a linear jack, so that the values of these "active" pairs C _a i and C a ₂ can be controlled.

The physical parameters characterizing the vehicle are noted: m: mass of the vehicle

Vi: front track

V ₂ : rear track

E: wheelbase C _M : angular stiffness modeling the front suspension actuators

Ck ₂ : angular stiffness modeling the rear suspension actuators

In this figure, the rolling variables are noted as follows:

G: center of inertia of the suspended masses A _r : roll axis of the vehicle h ₀ : vertical distance separating the center of inertia G of the roll axis A _r γ _x : longitudinal acceleration γ _y : lateral acceleration θ: angle of roll hi: height on the ground of the center of roll before h ₂ : height on the ground of the center of rear roll

Li: longitudinal distance separating the front axle from the center of inertia G

L ₂ : longitudinal distance separating the rear axle from the center of inertia G

C _a i: torque delivered by the front actuator C _a2 : torque delivered by the rear actuator

FIG. 1 therefore makes it possible to establish a balance of the forces exerted on the chassis of the vehicle and thereby determine the intensity of the variable forces by writing the equilibrium equations. FIG. 1 shows the forces F _XJ , F _Y i and F _Z i exerted by the chassis on the front axle in response to the forces Fχi, F _Y i and F _Z i exerted by this train on the chassis. We did the same for the rear axle (with index 2).

Thus, the equilibrium equations of the front axle are written:

Similarly, the equilibrium equations of the rear axle of the vehicle are written:

[VIII] - ^ F ₂₂ I + hi (Fχ2i + Fx ₂₂ ) + C _a2 + c _k2 θ = - ^ F ₂₂₂

The equilibrium equations of the chassis of the vehicle body are written:

[XII] LiF ₂₁ + mγχho = L ₂ F ₂₂

[XIII] L ₁ Fx ₁ + mγ _x h0. = L ₂ F _X2 [XIV] C _al + C _a2 + (c _k1 + c _k2 ) θ = rngho.θ + mγ _x ho

From equation [XIV], we deduce the roll angle:

[XV] θ = mγ _x ho - (C _s + C _a2) / (c + c _kl _k2 - mgho)

Then, by replacing in the equations [IX], [X] and [XI] the forces F by their expressions resulting from equilibrium equations of the front and rear trains ([I] to [VIII]), then subtracting two to two intermediate equations obtained, we obtain the expressions of the vertical forces F _zij - following: r _vΛ , _τπ I ₂ 1 1 1 Ji ₁ L ₂ 1 Jφ Ji ₀

[XVI] F _{zl l} = ^ ⁱⁱ -g - - C _al - - ç _kl θ - - -T ^{my '(} 2 V [^ ¹ ***

[XVIII] - (I ₊ M) I _n ,,

[X, X] _Fz22 = i _{mg +} ± c, ₂ - J-C ₁₂ Θ ₊ -L M. m ,, - (I - £) £ - *

IE V ₁ V ₂ V ₂ E 2 V ₂ E

However, the equations [XVI] to [XIX] make it possible to precisely determine the vertical forces F _ZIJ - exerted by each wheel on the frame regulating the values of the "active" anti-roll pairs C _a i and C _a 2 while measuring real-time rolling variables contained in equations [XVI] to [XIX], such as longitudinal and lateral accelerations or roll angle. The vehicle object of the invention is indeed equipped with sensors capable of evaluating such driving variables and / or driving requests.

The suspension device of the present invention thus makes it possible to drive the anti-roll suspension actuators located on the front and rear axles so as to distribute the vertical forces of the ground exerted on each wheel. Indeed, insofar as these anti-roll suspension actuators are capable of generating anti-roll torque, they are capable of inducing a vertical charge transfer on one or the other of the wheels of the vehicle. It is also possible to vary the front or rear anti-roll stiffness Cki Ck2 to modulate the F _z , insofar as it is parameters specific to the chassis.

As the suspension device object of the present invention is equipped with sensors measuring the vertical force of the soil exerted on each wheel of the vehicle, it is possible to set up control loops. According to the invention, each wheel of the vehicle can thus comprise a sensor constituted by strain gauges housed in one of the bearings of this wheel. In general, the strain gauge allows the force to be indirectly measured by elongating elastically. However, such elongation varies the electrical resistance of the gauge. One can know the force by circulating a current through the gauge.

Therefore, a suspension device according to the present invention makes it possible to establish a control loop so as to achieve precisely the values of the desired vertical _forces . Thus, when it is desired to increase the vertical force of the ground on one or more wheel (s), in order to maintain the comfort and / or stability of the vehicle for driving variables and requests for driving data. FIG. 2a illustrates such a control loop in which the desired vertical forces F _ZIJ are first determined, then the actual vertical forces Fzi _{j are} measured and the "active" anti-roll pairs C _a i and C _{Ά 2 are adjusted in} order to minimize the difference ΔF _Z = F _ZIJ - desired - F _ZIJ - real.

According to a particular embodiment of the invention, the suspension device makes it possible to maintain the inner rear wheel at the turn approached by the vehicle in contact with the ground, that is to say to avoid the detachment of this wheel. Indeed, as explained above, the detachment of the inner rear wheel significantly degrades the stability and handling of the vehicle and its stopping distance.

FIG. 2b thus illustrates a control loop making it possible to guarantee a minimum vertical force of the ground F _22J , thus guaranteeing contact between the inner rear wheel and the ground. For this, when the suspension device measures a significant lateral acceleration γ _y , which means that the vehicle is in a relatively tight bend. A computer of the suspension device according to the invention then determines the desired minimum downward vertical force F _22J , then regulates the active anti-roll pairs C _a i and C _a 2 to minimize the difference ΔF _Z 2 between the downward vertical force F _Z 2 _j desired and the vertical force of the soil F _Z 2 _j real.

Thus, a vehicle according to the invention is therefore equipped with a suspension device according to the invention which makes it possible to avoid the gradual detachment of the inner rear wheel, as shown in the diagram of FIG. can thus observe the shedding of the rear wheel inside the turn, as shown between the instants t _v and t _D.

In this figure, there is shown the vertical force of the ground F _Z2j - exerted on the inner rear wheel at the turn as a function of time. Until time t _v, which represents the beginning of the turning of the vehicle, the vertical force of the ground exerted on the inner rear wheel F _Z2j - is relatively large and passes through a maximum value F _Zmax .

In the turn, the increase in γ _y continuously decreases the vertical force F _Z2j - exerted on the rear inner wheel at the turn, which is represented in the diagram of Figure 3 by the slope that curves present.

In the case of a vehicle of the prior art (dashed lines), whose device for suspension is not able to measure nor to influence the vertical force of the ground exerted on the inner rear wheel, this wheel takes off from the roadway from the instant t _v where the vertical force of the ground F _Z 2 _j becomes no.

On the other hand, the curve in solid lines representing the behavior of a vehicle according to the present invention shows that the vertical force of the ground F _Z2j exerted on the rear inner wheel at the turn has a minimum threshold F _Zm in, so that this wheel does not take off from the roadway. Thus, the safety and comfort of passengers are preserved by the suspension device object of the present invention.

Other embodiments are possible without departing from the scope of the present invention.

Claims

1. Suspension device for a motor vehicle, said device comprising suspension actuators acting individually on wheels of said vehicle, said vehicle having physical parameters and being equipped with sensors capable of evaluating rolling variables (γ _x , γ _y , θ , hi, h ₂ , ho, Li, L ₂ ) and driving requests (α, P _F , P _A ), characterized in that it comprises sensors able to measure the vertical force of the ground (F _z π, F _z i ₂ , F _z ₂ i, F _z ₂₂ ) exerted on each of said wheels, as well as control means for, depending on said parameters, variables and / or requests, calculating and sending instructions to at least one of said actuators so as to increase the vertical force of the ground (F _z π, F _z i ₂ , F _z2 i, F _z22 ) exerted on one of said wheels.

2. Device according to claim 1, characterized in that each of said sensors is constituted by strain gauges housed in a bearing of one of said wheels.

3. Device according to one of the preceding claims, characterized in that said means calculate and issue instructions to at least one of said actuators acting on the inner rear wheel at a turn followed by said vehicle (G).

4. Device according to one of the preceding claims, characterized in that each of said actuators acts on at least one of said wheels through the front and rear half shafts on which said wheels are mounted.

5. Device according to claim 4, characterized in that said actuators comprise at least one anti-roll bar associated with a rotary jack adapted to apply a torque on each of said half-shafts.

6. Device according to claim 4, characterized in that said actuators comprise at least one linear jack adapted to exert a force on each of said half-shafts.

7. Device according to claim 4, characterized in that said actuators comprise at least one controlled suspension.

8. Device according to one of the preceding claims, characterized in that:

said physical parameters include the wheelbase (E), the front (Vi) and rear (V ₂ ) tracks, the mass of the said vehicle (m), the stiffnesses (c _k i, C _k2 ) of the suspension actuators;

said rolling variables comprise the longitudinal (γ _x ) and lateral (γ _y ) accelerations, the roll angle (θ), the ground height of the front (hi) and rear roll centers (h ₂ ), the distance vertically (ho) separating the roll axis from the center of inertia (G) of the suspended masses, the longitudinal distances (Ii and I ₂ ) respectively separating the front wheels and the rear wheels from said center of inertia (G), the travel and vertical travel speed of each wheel;

- The said driving requests include the steering wheel angle (α), the pressure exerted on the brake pedal (P _F ), the pressure exerted on the accelerator pedal (P _A ).

9. Motor vehicle (G) having physical parameters and being equipped with sensors capable of evaluating rolling variables (γ _x , γ _y , θ, hi, h ₂ , ho, Li, L ₂ ) and driving requests ( α, P _F , P _A ), characterized in that it comprises a device according to one of claims 1 to 8.