Method for reducing drive slip of a vehicle

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Details

36443107, 180197, 303142, B60K 2816

Patent

active

056966830

DESCRIPTION:

BRIEF SUMMARY
PRIOR ART

It is known to reduce the engine torque in a traction slip controller (TSC) when a tendency of the wheels to spin occurs (see e.g. DE 34 17 089 A1, to which U.S. Pat. No. 4,771,849 corresponds). The engine torque is reduced starting from the moment when a specific wheel slip and/or a specific wheel acceleration of a driven wheel or the driven wheels is reached or by means of some other criterion for the spinning of the wheel or wheels. In order to control the traction slip the fuel supply can be reduced (throttle valve adjustment or control of the quantity injected). It is also possible to influence the ignition (control of spark failure or adjustment of ignition time). In the prior art the engine torque is changed along a slope until it drops below the instability criterion again.


SUMMARY OF THE INVENTION

In the inventive design of the TSC, when a drive instability occurs the engine torque is reduced to that drive torque which is sufficient for the given moment taking into account the interfering influences such as gradient, towed weight and/or payload (torque demand), and at which spinning cannot occur. The torque demand is calculated continuously so that when required it is available immediately for the control.
It is possible (if the mass of the vehicle, the mass inertia moments, air resistance and rolling resistance are known) to assign the speed and acceleration to be achieved to a specific drive torque MA for driving on the level.
Deviations from this are caused by additional torque demand, that is to say e.g. by gradient, payload or towed weight. (It is not known to detect the values of these interfering variables without additional sensors).
In order to detect the values of these interfering variables it has proven advantageous to select the equivalent mass as auxiliary variable, which equivalent mass is equal, without the interfering torques, to the prescribed vehicle mass, but is increased or even decreased when interfering torques occur.
The increased torque demand is assigned to the rolling resistance and the acceleration as a result of increased mass (equivalent mass). In the case of vehicle acceleration on the level the following applies: MWR+acceleration resistance MWB+rotational acceleration resistance MWBR the vehicle mass, a being the acceleration and k1 to k3 being vehicle-specific constants. ##EQU1## In the case of instability, the drive torque is reduced to the actual torque demand on the basis of the learnt equivalent mass. An increased torque demand, for example, as a result of payload, gradient or towed weight is thus taken into account during the calculation of the level of the torque demand, as is a reduced torque demand for example as a result of a negative gradient.
Additional sensors for determining the road resistance are not required.
The reduction drive torque (torque demand) MAR is obtained from the following derivation. It applies for an accelerating vehicle: factor F in order to influence propulsion or comfort. It will be near to 1.
In order to suppress negative influences, the speed of increase of the equivalent mass is limited, e.g. to 12.00 kg/s.
In order to obtain the correlation of the equivalent mass and drive torque (and acceleration) it is appropriate to filter the signal with a PT1 filter.
The drive torque MA can be calculated from the output engine torque MMOT ##EQU2## iGES being the overall transmission ratio, .eta. being the degree of efficiency and .mu. being the converter transmission ratio. The gear can be calculated from the ratio of the speed of revolution of the engine to that of the drive axle or determined in some other way.
In automatic vehicles the gear information is obtained for example from the gearbox control.
The output engine torque MMOT can either be determined by means of a characteristic diagram MMOT=f (nMot, .alpha.) (nMot engine speed, .alpha. throttle valve angle) or by means of a load signal generated by a digital engine control.


BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a block diagram of the exemplary embodiment.

REFERENCES:
patent: 4771849 (1988-09-01), Leiber et al.
patent: 5103928 (1992-04-01), Danner et al.
patent: 5132906 (1992-07-01), Sol et al.
patent: 5137105 (1992-08-01), Suzuki et al.
patent: 5245542 (1993-09-01), Itoh et al.
patent: 5539643 (1996-07-01), Yamamoto et al.

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