DE3844803C2 - Vehicular active suspension with controllable under or over-steer - Google Patents

Abstract

Displacement sensors (2) associated with the wheels or their suspensions provide input signals for a calculator (5) of average values of ground clearance, yaw and pitch angles. These averages are compared with predetermined or adjustable desired values for purposes of correction of the forces exerted by the hydraulic suspension units (10).Oil is pumped (8) from a reservoir (7) through a valve (11) to each suspension unit (10) so that the forces serving to balance out the yaw movements are distributed correctly between the front and rear wheels.The calculator (5) is programmable for any desired deg. of understeer, oversteer or neutral behaviour

Description

The invention relates to an active suspension system for Motor vehicles or the like associated with the wheels Actual value transmitters, each one the distance between Generate vehicle body and wheel reproducing signal and feed a computer, as well as assigned with the wheels Neten spring or support units, their support forces and / or counteracting the lifting movements of the wheels Resistors are controlled by the computer, the Calculator each from the signals of the actual value transmitter Actual value of the averaged ground clearance, an actual value of the averaged roll angle and an actual value of the averaged Pitch angle of the vehicle body determined and the spring or Support units depending on the deviations from these Actual values from predefined or predefinable setpoints controls.

The value depends on conventional passive suspension systems of motor vehicles of the support forces only from the stroke positions of the Wheels off, d. H. the support generated by a spring unit force grows as the distance between the respective wheel and the structure of the vehicle. Additionally effective from the effect of vibration dampers Resistance to lifting movements of the wheels in relation to the vehicle body are a function of the speed of these strokes. Despite the passive suspension systems remain at a high level of development it is inevitable that compromises were made in the vote  have to be walked. For example, the suspension in With regard to a high level of comfort, it is softly coordinated compares the vehicle body when cornering fast incline strongly towards the outside of the curve. When cornering so larger roll angles occur. There is a possibility speed, the roll angle by arranging stabilizers reduce which corresponds to the deflection of a wheel wheel on the other side of the vehicle Seek direction of compression to push so that the spring aggregates on the inside of the bend to support the wheels on the outside of the curve. Such Stabilizers, however, affect suspension comfort, if the vehicle has only the wheels of one side of the vehicle drives over uneven floors or when driving at an angle bumps running in the direction are run over.

DE 34 08 292 A1 now shows an active suspension system, which takes advantage of the fact that every movement of the vehicle body a combination of a pure Stroke movement relative to a reference plane and one Rotation around the vehicle's longitudinal axis (roll movement) and one Rotation around the vehicle's transverse axis (pitching movement). According to DE 34 08 292 A1, these movement components analyzed separately, which provides the opportunity the support or spring units when the To control the stroke positions of the wheels differently, each after whether the changes in the wheel position by a pure roll movement or a pure pitch movement or one pure lifting movement of the body or by different Combinations of these movement components was effected.  

This also offers the opportunity with different types of movement of the vehicle body different by means of the spring or support units counteract. In particular, it is, for example possible to achieve lifting movements of the vehicle body a good comfort to cushion relatively softly, during roll and pitch movements with respect to a safe driving behavior counteracted much more becomes. In this way it can be achieved that the vehicle, despite the soft adjustment of the suspension compared to the lifting movement only a little to the outside of the curve when cornering tends. Because the vehicle's pitch and roll movements can be largely prevented, occur only small Pitch and roll angles on, d. H. of each available standing suspension travel of a wheel is hardly due to inclined positions of the vehicle body with respect to the level of the road impaired. This provides the opportunity to Suspension very comfortable compared to lifting movements agree because the available travel through The vehicle's pitch or roll movements are only insignificant can be restricted. Furthermore, the advantage achieved that the wheel suspensions practically only movements run close to their optimal position and therefore no through the Deflection kinematics causes self-steering behavior of the Vehicle can occur.

DE 34 08 292 A1 also shows that that a to be set on the support units Supporting force vector representing a component has, which - with independent specification of the damping characteristic - determines the damping of the wheel movements.  

An optimal one in terms of comfort and driving safety Damping concept is not shown.

The object of the invention is now this advantageous per se Suspension system in terms of comfort as well as the floor liability of the wheels and thus also with regard to driving safety to improve even further.

This object is achieved in that the Computer continues from the signals of the actual position sensor wheel positions or wheel movements in which the one front wheel as well as the diagonally opposite rear wheel at the same time deflect while the other front wheel and this diagonally opposite other rear wheel at the same time rebound, and the spring or support units in mind a damping controls, the value of these wheel positions or wheel movements as long as they have no influence on the mean values of the ground clearance, the roll angle and the Pitch angles are.

The invention makes it particularly convenient Achieve suspension system coordination. For this, the Insight used that with an active suspension system, at which the pitching, rolling and lifting movements of the vehicle body can be determined for yourself, basically also the It is possible, in general, to also separately separate such wheel movements capture which neither the roll or Pitch angle compared to the stroke position of the vehicle body change the road surface.

The invention now makes this possible speed, such wheel movements that hit the ground  liability of the wheels - e.g. B. in the range of the natural suspension frequency in connection with unbalance or geometric irregularities of the wheel - can severely affect, selectively on individual wheel suspensions counteract and so the ground contact forces of the wheels as a whole moderate. This allows the suspension to be tuned systems remain comfort-oriented.

Accordingly, in the invention with a particular safe and manageable driving behavior also in Extreme situations can be expected.

The mean value of the Clearances of all wheels in relation to the vehicle body or a correlated variable can be used. As a mean The pitch angle can be the difference between the mean the distances of the front wheels from the vehicle body and the Average of the distances of the rear wheels from the vehicle body or serve a variable correlated with this difference. The difference between is the mean roll angle the average of the distances of the right wheels from the vehicle construction and the average of the distances of the left wheels from Vehicle body or a correlated with this difference Suitable size.

Become the averages listed above used, the position of the vehicle is relative to one Determines the reference plane, which is parallel to two straight lines, from which the one the wheel contact patches of the right front wheel as well as the left rear wheel and the other the wheel contact areas of the left front wheel and the right Interspersed rear wheel.

Otherwise, the preferred features of Invention on the dependent claim and the following Description of a preferred embodiment using the Drawing referenced.  

It shows

Fig. 1 is a schematic representation of a passenger car with the suspension system according to the invention and

Fig. 2 is a sectional view of a spring or support unit.

The wheels of the vehicle are supported against the vehicle body by means of hydraulic spring and support assemblies 10 , which are designed as piston-cylinder assemblies. The hydraulic pressure source used is a pump 8 driven by the vehicle engine, which is connected on the suction side to a reservoir 7 for hydraulic oil and is connected on the pressure side to a distributor 9 , from which pressure lines lead to the spring and support assemblies 10 , which also lead to relief lines the reservoir 7 are connected. The supply of hydraulic medium in the spring and support assemblies and the discharge of hydraulic medium from these assemblies is controlled via valve assemblies 11 arranged on the spring and support assemblies 10 , which in turn are actuated by means of a computer or microprocessor 5 , which on the input side the wheels of the driving tool associated encoder 2 is connected. The displacement sensors 2 generate signals which reflect the respective lifting position of the wheels relative to the vehicle body. Furthermore, the computer or microprocessor 5 can be connected on the input side to wheel acceleration sensors 1 and / or body acceleration sensors 3 . In addition, a manually operable command transmitter 6 can also be provided to enable the driver to intervene in the control of the suspension system. The control commands of the computer or microprocessor 5 for the valve arrangements 11 or the signals to be supplied to the computer or microprocessor 5 from the transmitters 1 to 3 are passed on via a data network which at least partially has data bus lines 4 .

The support units 10 and the valve arrangements 11 are shown in a somewhat more constructive manner in FIG. 2.

Each wheel 12 can be assigned a support assembly 10 configured as a piston-cylinder unit, each of which has a chamber 14 arranged above the piston 13 and a chamber 15 arranged below the piston 13 . The pressure in the chamber 14 attempts to push the piston 13 downward in FIG. 2, while the pressure in the chamber 15 acts in the opposite direction. With equal pressure in the chambers 14 and 15 of the piston 13 is urged downwardly, as a result of the piston rod 16 which is acted upon by pressure in the chamber 15 face of the piston 13 is smaller than the acted upon by the pressure in the chamber 14 face of the piston. 13 The chambers 14 and 15 are connected to one another via a line 17 , in which, if appropriate, a check valve which opens in the direction of flow in the chamber 15 can be arranged. To the line 17 a to the pressure side of the pump 8 and the distributor 9 (see. Fig. 1) the pressure line 18 is connected is connected (namely, between the, where appropriate in the line 17, check valve disposed and the chamber 14). In addition, a relief line 19 branches off from line 17 (specifically between the check valve which may be arranged therein and chamber 15 ). The supply of pressure medium via the pressure line 18 and the discharge of pressure medium via the relief line 19 are controlled by valves 20 and 21 of the valve arrangement 11 . These valves are preferably designed as throttle valves with continuously variable throttle resistance.

By appropriately controlling the valves 20 and 21 , the pressure in the chambers 14 and 15 can be varied within structurally predetermined limits. In this context, it should be noted that high values of the pressure in the chambers 14 and 15, in particular when the respective wheel 12 is trying to spring, by briefly closing the valves 20 and 21 or by closing the valve 20 and strong throttling of the valve 21 can be adjusted.

The system shown works in the following way:

The signals of the displacement sensor 2 are a measure of the distance of the wheels or the wheel axles from the vehicle body and accordingly also a measure of the distance of the vehicle body from the ground in the area of the respective wheel. From the signals of the displacement sensors 2 , the computer or microprocessor 5 can now determine an average ground clearance, for example by forming the average of the ground clearance measured by the displacement sensors 2 on the four wheels of the vehicle. Changes in the average ground clearance thus indicate that the vehicle is lifting in one direction or the other relative to the ground.

Furthermore, an average pitch angle can be determined from the signals of the displacement sensors 2 , for example by first determining the mean value of the ground clearances on the front wheels and the mean value of the ground clearances on the rear wheels and then determining the difference between these mean values. Changes over time of this difference then indicate that the vehicle body carries out pitching vibrations relative to the ground, ie rotary movements about the vehicle transverse axis in one direction or the other.

Furthermore, an average value of the roll angle can be determined from the signals of the displacement sensors 2 . For this purpose, the mean value of the ground clearances of the vehicle body is formed on the wheels on the right side and the mean value of the ground clearances on the wheels on the left side of the vehicle, and the difference between these mean values is then determined. Changes over time in this difference indicate that the vehicle is rolling, that is, rotations about the longitudinal axis of the vehicle in one direction or the other.

That have pitch and roll angles determined in this way at the same time the value zero when the vehicle body is about is aligned parallel to a plane, which in turn parallel to one of the wheel contact points of the right front straight line connecting the wheel and the left rear wheel and parallel to one of the wheel contact points of the left Straight front wheel and right rear wheel connecting Line is.

The computer or microprocessor 5 now registers the mean ground clearance, the mean roll angle and the mean pitch angle or the time change of these variables. This is equivalent to the fact that the computer or microprocessor breaks down every movement of the vehicle body relative to the ground into a lifting movement, a rolling movement and a pitching movement. This creates the possibility of counteracting the different types of movement of the vehicle body in different ways, ie in particular with different levels of progressiveness.

For example, it is possible to achieve a soft suspension behavior with respect to stroke movements, while the suspension behavior with respect to pitching and rolling movements is set significantly harder, ie with a higher spring stiffness. If there are deviations between the actual value of the average ground clearance and the respective target value, the support forces of the support units 10 can be changed relatively slightly - at least within a central range of the suspension strokes - in order to achieve a suspension that is particularly comfortable. In the case of deviations between the mean values of roll angle or pitch angle and the respective target values, on the other hand, stronger changes in the support forces of the support units 10 can be undertaken in order to ensure safe driving behavior, in particular at higher speeds.

The support force of a support unit is therefore not primarily depending on the particular Stroke position of the wheel determined, rather is for that The dimensioning of the support forces is decisive to what extent the Vehicle body to achieve a desired target position a pure lifting movement relative to the ground and / or one Rotation around the vehicle's longitudinal axis (change in roll angle) and / or a rotation about the vehicle transverse axis (change of the Pitch angle) must perform.  

The changes or corrections of the support forces of the support units 10 , which are separately calculated for correcting the respective stroke position and for correcting the respective roll angle and for correcting the respective pitch angle, can simply be additively linked to one another, ie the change in the support force actually carried out on each support unit corresponds in each case the sum of the individual corrections that were calculated for a desired change in the stroke position or the roll angle or the pitch angle.

In extreme cases, the calculated total correction may lie outside the design options of the support units. In such a case, the constructively achievable limit value is set on the respective support assembly 10 .

Accelerometers 1 and 3 , in particular wheel accelerometers 1 , enable the computer or microprocessor to know certain driving conditions particularly early on. For example, in the event of a sudden strong steering deflection, a noticeable lateral acceleration of the wheels or the vehicle body occurs before the vehicle body tries to incline towards the outside of the curve, ie before the respective driving state leads to a roll angle that can be registered by the displacement sensor 2 . The same applies in the case of strong decelerations or accelerations of the vehicle. Here too, the vehicle body only reacts with a pitching movement after a certain delay time, which can be determined by the displacement sensor 2 . By arranging the accelerometers 1 and 3 , the possibility is therefore created that the computer or microprocessor 5 is "prepared" in good time for anticipated roll or pitching movements of the vehicle body and that the support units 10 are already activated to generate corresponding counterforces before the pitching and / or roll movements actually occur. Pitch and / or roll movements are practically completely avoided.

Basically, there is the possibility that wheel movements occur which do not cause roll or pitch or lift movements of the vehicle body. For example, the one front wheel and the diagonally opposite rear wheel can simultaneously deflect, while the other front wheel and the diagonally opposite other rear wheel rebound simultaneously. If the compression strokes and the rebound strokes are all the same size, the mean values of the ground clearance, the roll angle and the pitch angle do not change. Nevertheless, such wheel movements are undesirable because the grip of the wheels can be lost. It is therefore provided that the stroke movements of the wheels, in particular when deflecting, are always opposed to a certain damping resistance, which can be generated, for example, by the valve 21 (see FIG. 2) being throttled accordingly during the deflection stroke (the valve 20 is during the Deflection stroke usually closed). In addition, there is the possibility that the computer or microprocessor 5 determines from the signals of the displacement sensor 2 whether or to what extent wheel movements of the last specified type occur. Then the support units 10 or their valve arrangements 11 can be used in the sense of a more or less strong damping of these wheel movements can be controlled. Since such movements of the wheels are relatively rarely stimulated, it is desirable in terms of comfort if the damper forces required to prevent these movements are only effective when necessary. This is made possible by the invention without sacrificing security.

Claims (2)

1. Active suspension system for motor vehicles or the like. With the wheel-assigned actual value transmitters, each of which generates a signal that represents the distance between the vehicle body and the wheel and feed it to a computer, and with the wheel-associated spring or support units, their support forces and / or resistances counteracting the lifting movements of the wheels are controlled by the computer, the computer determining from the signals of the actual value transmitters an actual value of the averaged ground clearance, an actual value of the averaged roll angle and an actual value of the averaged pitch angle of the vehicle body, and the spring or support assemblies as a function of this driven by the deviations of these actual values from predetermined or predeterminable target values, characterized in that the computer ( 5 ) further determines wheel positions or wheel movements from the signals of the actual value transmitter ( 2 ), in which the one front wheel and the diagonally opposite rear wheel deflect simultaneously, while the other front wheel and the diagonally opposite other rear wheel rebound at the same time, and actuate the spring or support units ( 10 ) in the sense of damping, the value of which depends on these wheel positions or wheel movements, as long as these movements have no effect are the mean values of the ground clearance, the roll angle and the pitch angle. 2. Active suspension system according to claim 1, characterized in that the damping of the said wheel movements is carried out by controlled throttling of valves ( 21 ).