DE102019132589A1 - Method for performing a gear change in a motor vehicle with an automatic transmission when upshifting in full load operation - Google Patents

Abstract

The invention relates to a method for performing a gear change in a motor vehicle with an automatic transmission when upshifting in full load operation, a shift from a current gear (m) to the next gear (m + 1) being triggered after a predetermined shift criterion has been reached, with the shift criterion for When the switching process is triggered, a stored switching speed (nu) is used that is lower than a maximum speed (nmax) provided by a speed limiter.

Description

The invention relates to a method for performing a gear change in a motor vehicle with an automatic transmission when upshifting in full load operation according to the type specified in claim 1.

Motor vehicles with a dual clutch transmission as an automatic transmission are sufficiently known from the prior art. Reference is made to the Audi R8 or the Lamborghini Huracan by way of example only. If such motor vehicles are operated in "sport mode", the upshift takes place in "full load operation", i.e. the shift process should be initiated as late as possible, namely when a maximum speed specified by a speed limiter is reached. To ensure this, it is customary to apply a lead time for each gear by which the shifting process must be started so that the latest possible shifting time, namely when the specified maximum speed is reached, can be ensured. This hold-back time applies to an ideal transmission oil temperature (ideal viscosity). If there are other boundary conditions, e.g. lower transmission oil temperature (lower viscosity), this means that - in order to ensure the latest possible switching point - the hold-back time must be correspondingly longer, i.e. the switching process must be started earlier. Since a gearshift only works if the engine speed gradient remains the same, other boundary conditions, such as sudden ASR intervention on a wet road, also have an influence on the timing of the gearshift. This means that upshifting at the latest possible switching time can only be ensured by adding data to various sub-functions. However, in the event of the smallest changes to the engine or ESP, the data must be checked and adjusted if necessary. This can result in the motor “hanging” in the speed limiter for approx. 200 - 500 ms because the switching process was triggered too late.

Various methods for controlling automatic transmissions are known from the prior art. The DE 10 2012 219 454 A1 and DE 10 2015 220 933 A1 referenced. Further information on the problem of upshifting in full load operation cannot be found in the above publications.

The invention is based on the object of specifying a method for performing a gear change in a motor vehicle with an automatic transmission when upshifting in full-load operation, by means of which a reduction in the shifting time is made possible.

This object is achieved by the features of claim 1.

The dependent claims 2 and 3 form advantageous developments of the invention.

According to the method, it is provided that the shifting process for changing gears from the currently engaged gear to the next higher gear is triggered in full load operation when a predetermined shift criterion is reached. According to the invention, only a stored changeover speed is used as the switching criterion for triggering the shifting process, the stored changeover speed being less than a maximum speed provided by a speed limiter.

The method according to the invention now ensures that when the stored changeover speed is reached, a “forced upshift” is triggered and carried out. This means that, according to the method according to the invention, the switching process is carried out without a lead time and without the need to input data for various sub-functions. This has the consequence that the gear change takes place much faster, so that the driver has a particularly sporty vehicle handling.

The automatic transmission is preferably designed as a double clutch transmission in which the current gear is positively connected to an engine of the motor vehicle via a first sub-transmission of the double clutch transmission and the following gear is already engaged in a second sub-transmission of the double clutch transmission. According to the method, it is now provided that when the changeover speed is reached and the shifting process is triggered, an engine torque intervention is carried out which causes the speed of the engine to be reduced from the changeover speed to a target speed of the next gear, and when the target speed is present, a the first clutch assigned to the first sub-transmission of the dual clutch transmission is opened or disengaged and a second clutch assigned to the second sub-transmission is closed or engaged so that the next gear is positively connected to the engine.

Since an engine-torque intervention is now carried out when the gearshift is triggered, the engine already runs at the desired target speed when changing gears, i.e. the engine "gets stuck" in the speed limiter for approx. 200 - 500 ms is thereby successfully avoided. Another advantage is that, since the shifting process is carried out essentially parallel to the engine torque intervention, a particularly fast upshift and thus sporty driving behavior is made possible.

It is preferably provided that, based on that of a speed limiter The intended maximum speed nmax for the changeover speed n _u applies: $$0.98\le {\text{n}}_{\text{u}}/{\text{n}}_{\text{Max}}\le \mathrm{0.99.}$$

This ensures that the shifting process is triggered and carried out almost when the maximum permissible engine speed is present, so that during the acceleration process the gears are "extended" to almost the maximum permissible engine speed.

Further advantages and possible applications of the present invention emerge from the following description in conjunction with the exemplary embodiment shown in the drawing.

• 1 ein erstes Diagramm, in dem Drehzahl n über Zeit t aufgetragen ist und ein zweites Diagramm, in dem Drehmoment M über Zeit t aufgetragen ist, zur Darstellung des Drehzahl- bzw. Drehmomentenverlaufs beim Gangwechsel unter Volllast eines Kraftfahrzeugs mit Doppelkupplungsgetriebe beim Hochschalten nach dem Stand der Technik, und
• 2 die Diagramme aus 1, wobei der Gangwechsel nach dem erfindungsgemäßen Verfahren durchgeführt wird.

In the drawing means:

• 1 a first diagram in which speed n is plotted against time t and a second diagram in which torque M is plotted against time t, to illustrate the speed or torque curve when changing gear under full load of a motor vehicle with dual clutch transmission when upshifting according to the state of the Technology, and
• 2 the charts 1 , wherein the gear change is carried out according to the method according to the invention.

In the upper diagram of 1 and 2 the speed n (y-axis) is plotted against time t (x-axis). While with the curve 10 the speed curve of the engine is shown, show the curves K1 and K2 the speed curve of the first and second clutch of the dual clutch transmission, namely K1 the first clutch and K2 the second clutch.

In the lower diagram of 1 and 2 the torque M (y-axis) is plotted against time t (x-axis); accordingly is with 10 ' the torque curve of the motor and with K1 ' , K2 ' denotes the torque curve of the two clutches of the dual clutch transmission.

Like the top diagram of 1 As can be seen, when the engine is to change gear, the speed initially rises continuously up to a maximum speed nmax - provided by a speed limiter - and then due to the applied lead time, briefly, for approx. 200 to 500 ms, all at once Δtv designated time interval to hang.

The associated torque curve 10 ' of the motor as well as the torque curve K1 ' and K2 ' the couplings is from the lower diagram of 1 evident. As from the lower diagram of 1 can be seen, the opening or decoupling and the closing or coupling of the two clutches takes place K1 , K2 in the above time interval Δtv . The gear change time is thus made up of two time intervals, namely the time interval Δtv and an adjoining with Δtz designated time interval, which reflects the length of time until the engine torque has reached its initial value again.

In order to reduce the gear change time, it is now provided according to the invention that a forced upshift into the next gear is carried out when a predetermined changeover speed nu is reached. This means that the switching process is triggered when the switching speed nu is reached. When the shifting process is triggered, engine torque intervention is carried out, by means of which the speed of the engine is reduced to the target speed of the next gear and the first clutch, which is still non-positively connected to the engine, becomes K1 open / disengaged and the second clutch K2 is closed / engaged.

As from the diagram above and below from 2 can be seen, this has the effect that the gear change time - due to the elimination of the applied lead time and thus elimination of the time interval Δtv - on the duration Δtz shortened.

That means that a "hanging" perceived as annoying of approx. 200 - 500 ms in a speed range no longer occurs, so that a sportier driving behavior is possible.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 102012219454 A1 [0003]
• DE 102015220933 A1 [0003]

Claims (3)

Method for carrying out a gear change in a motor vehicle with an automatic transmission when upshifting in full load operation, a shift from a current gear (m) to the next gear (m + 1) being triggered after a specified shift criterion has been reached stored changeover _{speed (n u} ) is used, which is less than a maximum speed (n _max ) provided by a speed limiter. Procedure according to Claim 1 The automatic transmission is designed as a double clutch transmission in which the current gear (m) is positively connected to an engine of the motor vehicle via a first sub-transmission of the double clutch transmission and the following gear (m + 1) is already engaged in a second sub-transmission of the double clutch transmission, characterized in that when the switching process is triggered, an engine torque intervention is carried out, which causes a reduction in the speed of the engine from the switching speed (n _u ) to a target speed of the next gear (m + 1), and that when the target speed is present a first clutch (K1) assigned to the first sub-transmission of the double clutch transmission is decoupled and a second clutch (K2) assigned to the second sub-transmission is engaged, so that the next gear (m + 1) is positively connected to the engine. Procedure according to Claim 1 or 2 , characterized in that based on the maximum speed (nmax) provided by a speed limiter for the switching speed (n _u ): $$0.98\le {\text{n}}_{\text{u}}/{\text{n}}_{\text{Max}}\le \mathrm{0.99.}$$

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