DE102014223467A1 - Method for adjusting a crawl of a vehicle with an automated clutch system - Google Patents

Abstract

The invention relates to a method for adjusting a creep of a vehicle with an automated clutch system, wherein the creep behavior is determined in dependence on a creep pitch of the vehicle. In a method where the creep process is reproducibly adjustable, a creep threshold (Kmax) is determined at which the creep operation is executable under all operating conditions of the vehicle and an actual creep slope (K) of the vehicle is determined to set the creep and with the determined creep slope threshold (Kmax) is compared, wherein when falling below the Kriechsteigungsschwellwertes (Kmax) by the current creep slope (K) of the creep process is performed, while exceeding the Kriechsteigungsschwellwertes (Kmax) of the creep process is inhibited.

Description

The invention relates to a method for adjusting a creep of a vehicle with an automated clutch system, wherein the creep behavior is determined in dependence on a creep pitch of the vehicle.

Vehicles with automated clutch systems include a creep strategy, wherein a maximum achievable slope in a crawl of the vehicle is significantly influenced by the defined maximum drive torque of the vehicle during creep. The drive torque is a variable whose accuracy can sometimes fluctuate greatly, since it is based either on the engine torque of the internal combustion engine of the vehicle or on a clutch torque of the clutch of the vehicle. The clutch torque, in turn, is learned from the engine torque of the vehicle's drive motor. Both engine torque and clutch torque can be misjudged. Reasons for this are often in imprecise engine torque models. For example, in such engine torque models, a cold start behavior of the vehicle or consumer, such as the air conditioning system, is displayed inadequately. These fluctuations in the estimated drive torque may cause the maximum creep slope to also fluctuate. For the end user, this means that the vehicle crawls once in one place and not another time. Thus, incorrectly estimated drive torques ensure poorly reproducible creep behavior on gradients.

From the DE 10 2007 056 884 A1 a method for controlling a clutch is known, in which a creep torque is determined, which is dependent on vehicle speed signals and other control variables, such as a force acting on the vehicle downgrade force or a mass of the vehicle, wherein the mass under the entire load of the vehicle including fuel and driver is understood. The determination of these, depending on the slope force or the mass of the vehicle control signals is very complex and requires a predetermined computing time to determine the appropriate control variables for the creep process.

The invention is thus based on the object of specifying a method for adjusting a creeping process of a vehicle, in which a reproducible creep behavior on slopes can be determined by simple means.

According to the invention, the object is achieved in that a creep slope threshold is determined at which the creep operation is executable under all operating conditions of the vehicle, wherein a current creep pitch of the vehicle is determined and compared with the determined creep threshold, wherein falls below the creep slope threshold by the current creep slope of the Creep is performed while exceeding the Kriechsteigungsschwellwertes the creep is prevented. By determining the creep threshold at which vehicle crawl can be realized in most vehicle operating conditions, a sufficiently small value is used to ensure that non-reproducible situations in which the vehicle once crawls and the next Not once, be stopped. Due to such a creep threshold, it is ensured that the creeping process can be reproduced. Such a reproducible creep behavior on slopes represents a quality feature of an automated drive train, since such a constant creep behavior on the part of the end user is desired.

Advantageously, the creep slope threshold is determined as a function of a predetermined loading of the vehicle in an application process. The creep slope threshold is selected once so that the creep process can be realized at the calibrated creep threshold in the loaded and unloaded states.

In one embodiment, the creep slope threshold is determined as a function of a maximum permissible creep torque and conversion tolerances of the vehicle in the application process. Since this drive torque depends on the engine torque or the clutch torque of the vehicle and in particular the engine torque is determined by means of engine torque models, a misjudged engine and clutch torque can lead to a variation of the drive torque of the vehicle.

In one variant, a drive torque of the vehicle is achieved at the determined creep threshold, which is always smaller than the maximum allowable creep torque. This embodiment prevents a misconduct of the vehicle, in which an exceeding of the maximum permissible creeping torque is prevented. This increases the safety of the vehicle during operation.

In order to ensure the reproducible vehicle behavior, the creep slope threshold value applies to a tilt angle of the vehicle, which is determined during the application process, which is determined by setting the predetermined load, the maximum allowable creep torque and the environmental tolerances of the vehicle.

Advantageously, an inclination angle of the vehicle is determined by means of an inclination sensor present in the vehicle. Such inclination angle sensors are present, for example, in ESP systems of the motor vehicle, so that the signals supplied by the sensors can additionally be used in their creep control.

In one embodiment, the creep slope threshold is reduced or the maximum drive torque of the vehicle is raised at a predetermined inclination angle of the vehicle to realize a reproducible creep of the vehicle. This ensures that the vehicle always crawls up to the defined creep threshold. Above the defined creep threshold, the creep process is terminated or not initiated. The invention allows numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing.

Show it:

1 Determination of the creep threshold value as a function of a load state of the vehicle,

2 : Determination of the creep threshold as a function of an accuracy of a maximum drive torque.

In 1 is an inclination angle K of the vehicle via a drive torque M _A shown. It documents the 1a the state of the art, while 1b an embodiment of the inventive solution shows. The inclination angle K of the vehicle changes linearly with the drive torque M _A. In this case, the curve I shows the unloaded vehicle, while the curve II represents a vehicle which is slightly loaded. At the same time, the two diagrams 1a, 1b are subdivided into regions, wherein in the region A, the vehicle always creeps when the predetermined curves I and II, which run in the region A, increase. In the area B, however, the slopes of the curves I and II are so high that a creeping process is never carried out here.

In 1a is formed between the two areas A and B, a region C, in which the vehicle has a slope at which the vehicle crawls depending on the load. This means that in a heavy load of the vehicle no creep is performed, while at a weak load of the vehicle of the creeping process is still running. Such irregularities are prevented by the inventive solution.

How out 1b can be seen, this area C is completely eliminated if a creep slope threshold K _max is selected so that it is independent of the load of the vehicle. To ensure this, the creep slope threshold K _{max is} chosen to be sufficiently small, so that it is ensured that the vehicle in the in 1b shown slopes of the curves I, II within the range A is always in creep. In the area B adjoining the area A, a creeping process is never carried out or a creeping process which has already begun per se is discontinued when the slope changes.

The vehicle inclination is measured by means of a tilt angle sensor, for example, the ESP system of the vehicle, and taken as a basis for deciding whether the vehicle performs the crawl or not. Due to the independence of the maximum creep threshold K _max of the load of the vehicle, the vehicle behaves reproducible in terms of creep. If the reproducibility is to be improved at a given angle of inclination, either the maximum creep slope threshold K _{max can be selected} lower or the maximum drive torque M _{A max} can be raised.

In this arrangement, it is ensured at the same time that the drive torque M _A always remains limited. In 2 the maximum creep slope is shown as a function of the accuracy of the maximum drive torque M _{A max} . It represents the 2a The prior art is where the creep slope of the accuracy of the maximum drive torque M _{A max} depends. Here, too, there is an area C between the areas A and B, where as a result of the driving torque M _{A max of} the vehicle, which is estimated with different accuracy, it may happen that the vehicle crawls once or does not crawl once at the same location. The real maximum drive torque M _{AR max} for creep may have tolerances due to model inaccuracies and be in the band D. There, as in 2 B is shown, the reproducibility of the maximum creep pitch is independent of the accuracy of the maximum drive torque M _{A max} , it can not happen that the vehicle crawls once at the same place and not once.

By setting a reproducible creep process by selecting the creep slope threshold K _max , a reproducible vehicle behavior is ensured. It is decided by means of a precise tilt angle signal, whether the creeping process is executed or not. The reproducibility is guaranteed up to a defined Kriechwinkelschwellwert K _max .

Bezugszeichenlistew

• K _max

  Kriechsteigungsschwellwert

  M _A

  drive torque

  M _{A max}

  maximum drive torque

  M _{AR max}

  real maximum drive torque

  K

  tilt angle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007056884 A1 [0003]

Claims (7)

Method for adjusting a crawl of a vehicle with an automated clutch system, wherein the creep behavior is determined depending on a creep pitch of the vehicle, characterized in that a creep slope threshold (K _max ) is determined, in which the creep operation is executable in all operating conditions of the vehicle, and to set the creep process, a current creep slope (K) of the vehicle is determined and compared with the determined creep threshold (K _max ), which falls below the creep threshold (K _max ) by the current creep (K) of the creep is performed while exceeding the Creep slope threshold (K _max ) creep is prevented. A method according to claim 1, characterized in that in an application process, the creep slope threshold (K _max ) is determined in dependence on a predetermined load of the vehicle. A method according to claim 1 or 2, characterized in that the Kriechsteigungsschwellwert (K _max ) is determined in dependence on a maximum allowable creep torque and conversion tolerances of the vehicle. A method according to claim 3, characterized in that at the determined creep slope threshold (K _max ) a drive torque (M _A ) of the vehicle is achieved, which is always smaller than that, for the creep maximum drive torque (M _{A max} ). Method according to at least one of the preceding claims, characterized in that the Kriechsteigungsschwellwert (K _max ) applies to a determined during the application process inclination angle of the vehicle, which is determined by setting the predetermined load, the maximum permissible creep torque and the environmental tolerances of the vehicle. A method according to claim 5, characterized in that the inclination angle of the vehicle is determined by means of a, in itself present in the vehicle inclination angle sensor. Method according to at least one of the preceding claims, characterized in that at a predetermined angle of inclination of the vehicle to realize a reproducible creep of the vehicle, the creep slope threshold (K _max ) is reduced or the maximum permissible for the creep drive torque (M _{A max} ) of the vehicle is raised.

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