System for limiting engine torque in dependence upon steering an

Details System for limiting engine torque in dependence upon steering an System for limiting engine torque in dependence upon steering an

1991-03-26

1993-11-02

Black, Thomas G.

Boots, shoes, and leggings

180197, B60T 858

Patent

active

052589145

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a drive control system which limits the engine torque when the driven wheels have a tendency to spin.
U.S. Pat. No. 4,779,202, discloses such a system including a longitudinal vehicle acceleration sensor, a steering angle sensor, and a circuit for computing a reference speed corresponding to the vehicle speed. There, when a tendency to spin commences, the vehicle acceleration is measured and the associated permissible value of transverse acceleration is determined. Then the cornering limit speed is determined from the maximum permissible transverse acceleration and the steering angle. If this limit speed is reached by the vehicle, the engine torque is reduced.


SUMMARY OF THE INVENTION

According to the invention, the engine torque is reduced when a steering angle limit value dependent on the vehicle speed is reached. If the steering angle limit value is reached and there is drive slip, the reference speed is kept at least approximately constant, as a result of which the vehicle speed is fixed around the reference speed. If the steering angle limit value is not reached or there is no drive slip, the reference speed is allowed to increase to the speed of the slowest turning wheel.
As compared to the prior art, the inventive system achieves a distinct improvement in handling when negotiating corners.


BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a diagram of the system.
FIG. 2 is a graph of the calculated coefficient of friction, which is used to calculate the critical steering angle, versus time.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, wheel speed sensors 1 and 2 are assigned to the non-driven wheels and wheel speed sensors 3 and 4 are assigned to the driven wheels. In a sub-block 5a of the computer 5, a reference speed V.sub.Ref approximated to the vehicle speed is obtained from the speed signals of the non-driven wheels by averaging. This reference speed and the wheel speeds of the driven wheels are fed to a further sub-block 5b for slip control. If strong drive slip occurs, a final control element 6 is operated, which here adjusts a throttle valve 7 in the sense of a reduction of the engine torque. It is insignificant for the invention whether the brakes of the driven wheels are also included in the drive slip control.
In order to improve handling on a corner, a steering angle sensor 8 is additionally provided. The steering angle limit value LW.sub.Krit is calculated in a computer 10. For this purpose, the computer 10 is fed the reference speed V.sub.Ref from the sub-block 5a and the friction coefficient .mu. is determined in a block 11 by the following procedure: a basic value for .mu..sub.B of, for example, 0.3 is specified. If the longitudinal vehicle acceleration a.sub.L which the longitudinal acceleration sensor 9 measures, exceeds an acceleration value which corresponds to the specified basic value .mu..sub.B or a value .mu. other than the latter which happens to exist at the time, the basic value or the existing value is raised by a corresponding value. In particular when a drive slip control or an anti-blocking control commences, the existing value for .mu. corresponding to the acceleration or retardation achieved, which the longitudinal acceleration sensor 9 measures, is raised or lowered. The new value is taken back to the basic value via a ramp with gentle slope over time. This is shown in FIG. 2. The ramp slopes vary in steepness (as shown). The approximation value for .mu. thus determined is fed to the computer 10, which calculates the steering angle limit value LW.sub.Krit according to the following relation; .mu./V.sub.Ref.sup.2
In addition, signals which are dependent on the temperature and whether the roadway is wet or dry and which vary the basic value .mu..sub.B, for example according to the following table, are also entered in the computer 10 via terminals 10a


______________________________________ Roadway wet dry ______________________________________ Temp. > 3.degree. .mu..sub..beta. = 0.25 0.

REFERENCES:
patent: 4704541 (1987-11-01), Leiber
patent: 4763262 (1988-08-01), Leiber
patent: 4763263 (1988-08-01), Leiber
patent: 4779202 (1988-10-01), Leiber
patent: 4794538 (1988-12-01), Cao et al.
patent: 4794539 (1988-12-01), Wallentowitz et al.
patent: 4849891 (1989-07-01), Krohn et al.
patent: 4984165 (1991-01-01), Muller et al.
patent: 4999778 (1991-03-01), Ruhl et al.

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