SE525232C2 - Method and apparatus for influencing a driving relationship - Google Patents

Abstract

As a component in an acceleration slip regulation (ASR) brake controller (506), a subtraction block (501) receives front (DELTAvkardsollVA) and rear (DELTAvkardsollHA) axle input quantities, where DELTAvkardsollVA is a quantity that is produced as a difference in a target cardan speed assigned to a front axle and an actual cardan speed assigned to the front axle. An Independent claim is also included for a device for affecting a motor vehicle's performance.

Description

525 252 2 Vehicles with drive on all wheels generally have a longitudinal locking regulator for distributing the engine torque between the front and rear axles. Via this length lock controller, the speed difference is adjustable without any major effort. According to the invention, the driver has the opportunity to adapt the vehicle's driving characteristics to the current situation by means of, for example, a steering wheel or a stepped switch.

An advantageous embodiment is characterized in that the difference speed is dependent on the speed of the setpoint and the vehicle in the longitudinal direction. In particular, the speed of the vehicle in the longitudinal direction is a quantity already available to almost every vehicle.

A further embodiment is characterized in that, depending on the predetermined stocking diameter and the speed of the vehicle in the longitudinal direction, a braking effect is carried out for the effect on the driving characteristics either on the wheels of the front axle or on the wheels of the rear axle. Braking action can easily be performed by a well control or brake control device.

An advantageous embodiment is characterized in that the braking effect takes place symmetrically in that both wheels of one axle are braked equally (or approximately equally).

That is, both wheels on one axle are braked with equal intensity or equal braking mMoCDÉ.

A further advantageous embodiment is characterized in that - for setting understeer driving characteristics the difference speed is selected so that the speed variable characteristic of the wheels of the front axle is greater than the speed variable characteristic of the wheels of the rear axle, - for setting overriding driving characteristics the difference the speed variable characteristic of the front axle is less than the speed variable characteristic of the wheels of the rear axle, - for setting neutral driving characteristics the difference speed is chosen so that the speed variable characteristic of the front axle wheels is approximately equal to the speed variable characteristic of the rear axle wheels. Yet another advantageous embodiment comprises that the brush slide difference (A1ambda_bör) refers to a brush slide difference between the wheels of the rear axle and the wheels of the front axle. Yet another advantageous embodiment is characterized in that the effect on the driving characteristics takes place through the influence of a longitudinal locking regulator. The length lock adjuster is already standard in many vehicles with drive on all wheels as standard.

In addition, it is advantageous if the characteristic speed quantities, for both the wheels of the rear axle and the wheels of the front axle, each relate to an average value of the wheel speeds of the two wheels on the respective axle.

A device according to the entry for the effect on the driving characteristics of a vehicle regarding understeer, neutral steering or oversteer, - which vehicle has drive on all wheels and - which device has a means of influencing the driving characteristics by setting a difference speed for the difference between one characteristic of the wheels of the rear axle speed variable and a speed variable characteristic of the front axle wheels and is characterized by, - that the actuators are activatable and deactivatable by the driver - and that the intensity of overriding or understeer driving properties by the actuators is actuated by the driver either continuously or at least in two steps at least two steps regarding understeer.

The drawing The drawing consists of fi g. 1 to 3.

Fig. 1 shows the construction of the device according to the invention. Fig. 2 shows the use of the device according to the invention or the method according to the invention for influencing the driving characteristics.

Fig. 3 shows the principal course of the method according to the invention.

Design example By means of a transverse differential (= equalization gear), the driving torque of the motor is distributed uniformly to the two wheels on one axle. This has both advantages and disadvantages.

Advantage: When accelerating (even on a one-sided slippery road surface), no ginomene affecting the vehicle occurs. This is based on the fact that the insignificant drive torque delivered to the slippery carriageway side of the roadway is also delivered on the side of the roadway that has good grip.

Disadvantage: The propulsive force acting on the vehicle is determined by the wheel having the lower coefficient of friction or the lower coefficient of adhesion.

A remedy for this is the use of a blocking differential. This prevents the slimming of a wheel by deflecting the excess (in this case not releasable to the road surface) torque to the wheel having the higher adhesion potential. Admittedly, for it now a ginnoment affecting the vehicle may appear.

Mechanically lockable differentials are clearly more expensive compared to open, non-lockable differentials.

However, it is possible, through a driver-independent braking process of the sliding wheel, to achieve the function of a differential lock electronically and thereby avoid the use of a mechanically lockable differential.

This possibility exists both for transverse differentials (which regulate the wheel speed of the two wheels on one axle) and also for longitudinal differentials (which regulate the speeds coordinated with the separate axles). In the present invention, the effect on a longitudinal differential with electronic longitudinal locking is considered.

A longitudinal differential for distributing the engine torque between the front and rear axles is present in vehicles with drive on all wheels. There is a weighted torque distribution to the drive shafts.

I fi g. 1 shows the relationship between the gimbal speeds and the wheel speeds of a vehicle. In this case, block 100 characterizes the engine of the vehicle, which is in interaction with the motor control device 110. The motor 100 is connected via the cardan shaft to the longitudinal locking regulator L (block 101). The PTO shaft rotates with the PTO speed vkard_är. The length lock regulator transmits via two additional cardan shafts the speed vkard_är_VA to the transverse locking regulator 102 for the front axle and the speed vkard_är_HA to the transverse locking regulator 103 for the rear axle.

The left front wheel 104 rotates with the wheel speed vL_är_VA, the right front wheel 105 rotates with the wheel speed vR_är_VA, both are connected to the transverse locking regulator 102. The left rear wheel 106 rotates with the wheel speed vL_är_HA, the right rear wheel speed is rotated with vR_är_VA. transverse locking regulator 103.

Due to the effect of the longitudinal lock, it is possible to change the driving characteristics of the vehicle depending on the current situation. By increasing the drive wheel slip on the front axle, understeer driving characteristics can be achieved. An increase in the drive wheel grinding on the rear axle contributes to overridden driving characteristics.

This is explained using fi g. 2.

The subtraction block 501 is a component included in the ASR brake regulator 506. The input quantities Avkard_bör_VA and Avkard_bör_HA are fed to block 501. 525 232 6 In this case, Avkard_bör_VA is a quantity, which is obtained as the difference between a should-cardan speed coordinated with the front axle vkard_bör_VA and a is-cardan speed coordinated with the fi-axis is vkard_är_VA. Thereby, vkard__bör__VA = (vR_bör_VA + vL_bör_VA) / 2 and vkard_âr_VA = (vR_är_VA + vL_är_VA) / 2.

In these forms, the following quantities occur: vR_bör_VA = set speed for the right front wheel, vL__bör_VA = set speed for the left front wheel, vR_är_VA = actual speed of the right front wheel, vL_är_VA = actual speed for the left front wheel.

Thus obtained for the front axle Avkard__bör_VA = vkard_bör_VA - vkard_âr_VA.

Analogous conditions apply to the rear axle, where the quantity is determined Avkard__bör__HA. In the interconnection block 501, the difference Avkard_bör_VA - Avkard_bör_HA is determined. This difference is fed to the additional interconnection block 502. An additional quantity is added to this difference (Alambda_bör * vf).

Alambda_bör is a setpoint for a desired slimming difference between the wheels on the rear axle and the front axle, vf is the vehicle's longitudinal speed. To determine the Alambda_shall, for example, the mean value of the stock gluing of the rear axle wheels can be subtracted from the average value of the stock exchange gluing of the front axle wheels. The product Alambda_bör * vf describes the exchange difference in peripheral speed between the wheels of the front axle (for example, the average value of the two peripheral speeds of the front axle wheels) and the wheels of the rear axle (for example, the average of the two peripheral speeds of the rear axle wheels).

The output signal from block 502 is forwarded to the length lock controller 503. The length lock controller performs a realization of the electronic longitudinal lock, as long as the value of the input signal does not exceed a predeterminable limit value, symmetrical brake engagement on the wheels of a shaft can also be a hysteresis, ie for exceeding and falling below different limit values apply).

By means of the inserted co-coupling block 502, the difference formed in block 501 is superimposed on an offset value Alambda_bör * vf. This overlay means that the difference Avkard_bör_VA - Avkard_bör_HA by means of the longitudinal locking regulator is no longer adjusted with the value zero, since this is actually arranged for the electronic length lock.

This is conditioned by the fact that the longitudinal blocking regulator regulates the difference Avkard__bör_VA - Avkard_bör_HA on the value -Alambda_bör * vf (because exactly then the output signal from block 502 and thus the input signal to the longitudinal blocking regulator is zero).

The output signal is forwarded to blocks 504 and 505. Block 504 performs symmetrical brake engagement on the wheels of the fi-axis, block 505 performs symmetrical well engagement on the wheels of the rear axle. The term "symmetrical braking engagement" is thus to be understood as meaning that the left and right wheels of each axle are braked equally.

Through this device and this procedure, the driving characteristics can be continuously affected in the entire area between oversteer and understeer. This is done in the exemplary embodiment by specifying a setpoint speed difference and a setpoint difference between the front and rear axles, respectively. Thus, according to the invention, an equalization of the wheel speeds between the axles, as it is arranged by the electronic length lock, is deliberately prevented, in order thereby to affect the driving characteristics.

If the sign for Alambda_should is so chosen that the drive wheel slip increases on the front axle wheels or is greater than the drive wheel slip on the rear axle wheels, understeered driving characteristics are thereby achieved. If, on the other hand, the signs for Alambda__ should be selected in such a way that the drive wheel slip increases on the rear axle wheels or is greater than the drive wheel slip on the front axle wheels, overridden driving characteristics are thereby achieved.

If, on the other hand, Alambda_be = 0 is selected, the longitudinal beam distributes the torque delivered to the roadway on both axles in such a way that maximum neutral driving characteristics are achieved.

By means of this interface 502 between the vehicle regulator 506 (eg ASR brake regulator) and the length lock regulator 503, the distribution of the drive wheel slimming between the two axles can be influenced and thus the driving characteristics. As a result, the effect of vehicle control (eg actuation of a driving dynamics control system) in the event of oversteer and understeer can not only take place on wheels, but also by means of symmetrical braking on both wheels of one axle. This results in a clear comfort increase during driving.

Furthermore, it is possible to permanently influence the driving characteristics. Certain driving conditions (eg an understeered driving condition) can be set by calculating and adding the corresponding setpoint difference speed Alambda_bör * vf and the corresponding setpoint difference gluing Alambda_be to the corresponding length locking deviation.

This can be done, for example, by a step-up, driver-activatable and deactivable switch, by means of which the "understeer", "override" and "neutral" states can be set. The first two of these states can of course also be further subdivided, e.g. "slightly understeer" and "strongly understeer".

The process of the process according to the invention is shown in fi g. 3. When starting in block 301, a difference speed is then determined in block 302 between a speed variable characteristic of the wheels of the rear axle and a speed variable characteristic of the wheels of the front axle. Then, in block 303, for the effect of the driving characteristics, either a braking action on the wheels of the fi-arnaxehi or a braking action on the wheels of the rear axle is performed.

Claims (9)

20 25 30 525 252 q. A method for influencing the driving characteristics of a vehicle regarding understeer, neutral steering or oversteer, which vehicle has drive on all wheels and the effect on the driving characteristics is by setting a difference speed for the difference between a speed variable characteristic of the wheels of the rear axle ( v_kard_bör_HA) and a speed variable characteristic of the front axle wheels (v_kard_bör_VA), characterized in that the effect on the driving characteristics is activatable and deactivatable by the driver and that the intensity of overriding or understeering driving characteristics can be influenced by the driver either continuously or at least in two steps or at least two steps regarding understeer. Method according to Claim 1, characterized in that the difference speed is dependent on a setpoint slip difference (Alambda_shot) and on the vehicle speed (vf) in the longitudinal direction. Method according to Claim 2, characterized in that a braking effect is carried out either on the wheels of the front axle or on the wheels of the rear axle, depending on the predetermined brush-slip difference (Alambda_should) and the speed of the vehicle in the longitudinal direction (vf). Method according to Claim 3, characterized in that the braking action takes place symmetrically, i.e. that both wheels of one axle are braked equally. Method according to one of Claims 1 to 4, characterized in that - for setting the understeer driving characteristics, the differential speed (Av_card_should) should be chosen so that the speed variable characteristic of the wheels of the front axle (Av_kard_bör_VA) is greater than that of the wheels of the rear axle for the setting of overriding driving characteristics, the differential speed (Av_card_shot_shop) is selected so that the speed characteristic of the wheels of the front axle (Av_kard_bör_VA) is less than that of the characteristic of the rear axle of the wheels. (Off_card_should_HA), - for setting neutral driving characteristics, the difference speed (Av¿card_should) is selected so that the speed variable characteristic of the wheels of the front axle (Av__kard_bör_VA) is approximately equal to the speed variable characteristic of the wheels of the rear axle (Av_). Method according to Claim 1, characterized in that the effect on the driving characteristics is effected by the action of a longitudinal locking regulator. Method according to claim 1, characterized in that the characteristic speed variables, for both the wheels of the rear axle and the wheels of the front axle, each refer to an average value of the wheel speeds of the two wheels on the respective axle. Method according to Claim 2, characterized in that the load-bearing slip difference (Alambda_share) refers to a brush-slip difference between the wheels of the rear axle and the wheels of the front axle. Device for influencing the driving characteristics of a vehicle with regard to understeer, neutral steering or oversteering, - which vehicle has drive on all wheels and - the device has actuating means (502) for influencing the driving characteristics by setting a difference speed between a speed variable characteristic of the rear axle wheels (v_kard_bör_HA) and a speed variable characteristic of the wheels of the front axle (v_kard_bör_VA), characterized in that the actuating means (502) are activatable and deactivatable by the driver and that the intensity of overriding or understeer driving characteristics by the actuating means (502) is continuously actuated by the driver. two steps for oversteering or at least two steps for understeer.