DE102014213701A1 - Method and device for operating a sail-operable motor vehicle - Google Patents

Abstract

The present invention relates to a method and an apparatus for operating a sailworthy motor vehicle, in which it is provided in particular that a prediction of a sufficiently long sail operating phase is performed, that at predicted sufficiently long sail operating phase is entered into the sailing operation (255), that in the Sail operation occurring speed reduction of the motor vehicle with a predetermined speed difference (260) is compared, and that the sailing operation depending on the result of the comparison is terminated (265).

Description

The invention relates to a method and a device for operating a sail-capable motor vehicle according to the preambles of the respective independent claims. Furthermore, the invention relates to a computer program, which executes all the steps of the inventive method when it runs on a computing device or a control device, and a computer program product with program code, which is stored on a machine-readable carrier, for carrying out the method according to the invention, when the program a computing device or a control device is executed.

State of the art

A known approach to reducing the fuel consumption of motor vehicles is the so-called "sailing operation" in which the drive train of a motor vehicle is at least temporarily opened to allow a free rolling operation of the motor vehicle. The initiation of such sailing operation takes place in the prior art only in the operating case in which the driver has completely left the pedals, in particular the accelerator and the brake pedal, with his feet. However, as long as the driver steps on one of the pedals, the sailing operation is prevented.

Disclosure of the invention

The invention proposes to operate a sailworthy motor vehicle, a predictive method for predicting a sufficiently long sail operating phase to allow an automatic transition to the sailing operation, and in particular independent of the operating state of the pedals of the motor vehicle. The prediction is based in particular on a previously determined desired speed of the driver. Thus, a corresponding operating strategy for the transition from normal operation to sailing operation enables the sailing operation to be actively initiated under certain conditions, even though the driver has e.g. the accelerator pedal presses. The predictive method allows a cyclically or periodically alternating normal operation and sailing operation.

The operating strategy according to the invention is preferably determined by evaluating various operating variables of the motor vehicle or of the internal combustion engine of the motor vehicle. Depending on the strategy, the sail operation is initiated even when the accelerator pedal is actuated, and the sailing operation is ended again when an empirically determined, maximum permissible speed difference is exceeded. As a result, even when the driver does not adapt the driving style, sailing operation is enabled and the driver, regardless of his personal driving style, is supported in terms of fuel economy. The said maximum permissible speed difference is preferably determined by the smallest possible influence of the speed fluctuations on the driving comfort. This minimal influence is expressed according to the invention in that a vibration intensity of the motor vehicle does not exceed a predetermined threshold value, in particular a threshold value of 0.4. The vibration intensity is determined according to VDI Guideline 2057 certainly.

Furthermore, during the transition to the sailing mode, an increase in the vehicle speed preferably takes place by a predetermined factor, for example by 4%. For example, a motor vehicle traveling at a speed of 50 km / h at the time of transition to sailing would be accelerated to a speed of 52 km / h.

In particular, in the case of a lower torque request on the part of the driver when leaving the sailing operation is preferably a load point shift of the internal combustion engine, which as a result, the fuel consumption of the internal combustion engine is significantly reduced.

Instead of an automatic transition to the sailing mode can be provided to assist the driver with regard to a possible use of the sailing function only, i. a possible sailing operation e.g. to display over the dashboard. This allows the driver to decide for himself whether he wants to use the sailing operation or not.

Based on the said desired speed and a determined driving resistance, a maximum sailing time can be calculated and only then transferred to the sailing operation or the driver to be informed about a possible sailing operation when the calculated sailing time is greater than a predetermined threshold. As a result, it can be avoided that the motor vehicle switches between normal operation and sailing operation for a relatively short time, as a result of which the stated advantages of fuel economy are not yet established, but the ride comfort is considerably reduced.

• – Der Wert der momentanen Fahrzeugbeschleunigung ist kleiner als ein vorgegebener erster Schwellenwert;
• – eine aktuelle Änderung des Fahrpedalwinkels ist kleiner als ein vorgegebener zweiter Schwellenwert;
• – innerhalb eines vorgegebenen Zeitfensters ist keine Bewegung des Schalthebels erfolgt;
• – der Antriebsstrang des Kraftfahrzeugs ist derzeit geschlossen.

The determination of the desired speed of the driver can be made by checking the fulfillment of at least one of the following operating conditions of the motor vehicle:

• The value of the instantaneous vehicle acceleration is less than a predetermined first threshold value;
• An actual change in the accelerator pedal angle is less than a predetermined second threshold value;
• - Within a predetermined time window, no movement of the shift lever has occurred;
• - The drive train of the motor vehicle is currently closed.

These operating conditions are e.g. by means of a control device arranged in the motor vehicle easily accessible, so that the implementation of the method according to the invention can be carried out inexpensively.

• – Die berechnete zeitliche Länge des möglichen Segelbetriebs ist größer als ein vorgegebener dritter Schwellenwert (235);
• – die im Segelbetrieb zu erwartende Beschleunigungsdifferenz ist kleiner als ein vorgegebener vierter Schwellenwert (240);
• – der momentane Lenkwinkel ist geringer als ein vorgegebener fünfter Schwellenwert (245);
• – eine zwischen zwei Segelbetriebsphasen einzuhaltende Mindestzeit wird eingehalten (250).

On the basis of a certain desired speed of the driver and said speed difference, the time length of a possible sailing operation can be determined and passed on satisfying at least one of the following further operating conditions in the sailing operation or informing the driver about a possible sailing operation:

• - The calculated time length of the possible sailing operation is greater than a predetermined third threshold ( 235 );
• - the acceleration difference expected during sailing is less than a given fourth threshold ( 240 );
• The instantaneous steering angle is less than a predetermined fifth threshold ( 245 );
• - a minimum time to be respected between two sailing operations is respected ( 250 ).

The other operating conditions are e.g. easily accessible by means of a control device arranged in the motor vehicle, so that the implementation of the corresponding method can be carried out inexpensively.

Said, to be observed between two sailing operating phases minimum time can be determined on the basis of following a sail operating phase acceleration phase, the minimum time must be sufficiently long to allow minimal loss of ride comfort. These minimal losses are inventively expressed in that a vibration intensity of the motor vehicle does not exceed a predetermined threshold value, in particular a threshold value of 0.4.

In a motor vehicle capable of operating a sail with a cruise control system, the method according to the invention can be designed such that a desired speed and a maximum permissible speed difference or a corresponding permissible speed tolerance band are specified by the vehicle driver at the cruise control system that sufficiently long sail operating phase predicted on the basis of the predetermined desired speed is transferred to the sailing operation or the driver is informed of a possible sailing operation, that the speeding decrease of the motor vehicle in the sailing operation is compared with the predetermined speed difference, and that the sailing operation is terminated depending on the result of the comparison.

In contrast to the previous exemplary embodiments, in the present case a recognition of the desired speed on the basis of said operating variables of the motor vehicle is not necessary. This operating strategy for operating such a motor vehicle makes it possible, in particular, to be able to use the aforementioned advantages of a sailing function even when the cruise control system is activated.

As an alternative to specifying the maximum permissible speed difference by the driver, it may also be provided that values of the speed difference dependent on the vehicle speed are stored in a control unit of the motor vehicle and thus, depending on the instantaneous vehicle speed, a specific value for the speed difference is automatically selected.

With the method according to the invention, the sailing operation can be initiated at cyclical time intervals in a moving motor vehicle and then the motor vehicle can be accelerated again, resulting in a total of a sawtooth-like speed profile. Alternatively it can be provided that depending on the driver's request a said Sägezahnfahrt is allowed or only a sailing operation in the case of an input at the cruise control speed reduction and / or downhill is possible. Likewise, the method according to the invention makes it possible to activate the cruise control system during a sailing phase without having to manually end the sailing operation beforehand.

To save fuel, a sailing operation can always be initiated when a set or desired speed set by the driver on the cruise control system is below a current vehicle speed. This operating strategy can be implemented by special adaptation of the cruise control system.

In the aforementioned prediction of a time sufficiently long sailing operation phase may additionally be provided that camera and / or radar-based data of a traffic monitoring consideration. Also, through collaboration with a navigation system, additional functionalities can be implemented, such as speed limits, city entrances and city exits, as well as altitude data, by means of which a named, automated sawtooth travel can be further optimized. As a result, the driving behavior of the driver as slight as possible influence is guaranteed. In addition, said speed difference can also be determined on the basis of such data.

The method according to the invention can be implemented in a particularly cost-effective manner in the form of a control program, e.g. in a control unit of the motor vehicle.

Alternatively, the method according to the invention can also be realized by means of a device according to the invention, wherein a bistable toggle switch for initiating the sail operation is provided for the corresponding operation of a sail-operable motor vehicle, with default values and / or conditions for the possible transition to the sail operation at a SET input of the toggle switch abutment and at a RESET input of the toggle switch provided by a calculation module provided RESET conditions.

The output values for the calculation module used can be the output values present at the output of the bistable toggle switch, wherein it is checked on the basis of the output values by means of at least one processing element if predetermined limit values for the accelerator pedal position and / or the predefined speed difference are exceeded and in the case of an ascertained excess a RESET bit is output, which terminates an existing sailing operation. The toggle switch according to the invention can also be realized inexpensively.

The invention can be used in any sail operable motor vehicle. In addition, an application in motor vehicles with an electronic clutch system for a manual transmission is possible.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

1 shows the schematic course of the present invention proposed function "predicated car sailing".

2 shows an embodiment of the inventive method for operating a sail operable motor vehicle.

3 shows an embodiment of an inventive device for operating a sail operable motor vehicle.

4 shows a further embodiment of the method according to the invention for use in a motor vehicle having a cruise control system.

Description of exemplary embodiments

The following are based on 1 described function "Predicated car sailing" (PAS), where the vehicle speed 100 in [km / h] (y direction) over time 105 (x-direction) is applied, is activated in particular when the accelerator pedal is actuated, and detects or evaluates different operating variables of the motor vehicle. The result of the evaluation is in particular a value of the desired speed 110 , The detection or evaluation is preferably carried out at regular intervals. Preferred quantities are easily accessible variables such as the instantaneous vehicle acceleration, but also calculable variables such as the vehicle acceleration predicted in the sailing mode and the predicted sailing time until the aforementioned, empirically determined maximum permissible speed difference is reached 115 ,

The function first determines a value of the probable desired speed from said operating data of the motor vehicle or other data such as current or recently recorded pedal data (eg accelerator pedal, brake pedal, clutch pedal) or the current or recently recorded operating data of the internal combustion engine such as the engine speed 110 the driver. Based on this desired speed 110 and the said driving resistance, the maximum achievable sailing time is calculated and, if the predicted sailing time is longer than a pre-empirically determined threshold, initiated the sailing operation 120 , Due to the driving resistance, the driving speed decreases in the sailing mode in the manner shown. When reaching the mentioned speed difference 115 the sailing operation is left again and there is a short acceleration phase 125 to the desired speed 110 reach again. Over a longer period this results in a periodically changing, eg sawtooth profile-like driving speed of the motor vehicle. On average, however, the sailing operation is approximately a constant trip.

It should be noted that the function described also initiates or recommends the sailing operation in the presence of a mountain pasture and also supports the driver in such a driving situation or intervenes to assist in the driving operation.

When accelerating 125 after the sailing phase 120 depending on the currently available maximum speed difference 115 , the requested engine torque increases accordingly. By this increase of the requested moment in the acceleration phases 125 It is possible to operate the internal combustion engine with a higher efficiency.

If the said function, especially the sawtooth driving operation 120 . 125 is used in a hybrid motor vehicle with an additional electric motor, the electric motor can be used at least supportive for holding the sail operating speed, thereby the sailing operation phase 120 extend as much as possible. In this embodiment, the vehicle speed, depending on the performance of the electric motor and / or the driving resistance of the motor vehicle, falls in the sailing phase of operation 120 not or only slightly.

• 1. Ist der Wert der momentanen Fahrzeugbeschleunigung kleiner als ein empirisch vorgegebener erster Schwellenwert, welcher bevorzugt nahe Null beträgt (Prüfschritt 210).
• 2. Ist eine aktuelle Änderung des Fahrpedalwinkels kleiner als ein empirisch vorgegebener zweiter Schwellenwert, welcher bevorzugt nahe Null beträgt (Prüfschritt 215).
• 3. Innerhalb eines empirisch vorgegebenen Zeitfensters ist keine Bewegung des Schalthebels erfolgt (Prüfschritt 220).
• 4. Der Antriebsstrang des Fahrzeugs ist derzeit geschlossen, d.h. die Kupplung des Fahrzeuggetriebes ist eingekuppelt (Prüfschritt 225).

This in 2 The method illustrated by a flow chart is based on a first block 200 on the determination or prediction of the desired speed of the driver, which is independent of driver assistance systems such as an Adaptive Cruise Control (ACC) or cruise control. To determine the desired speed, the fulfillment or non-fulfillment of all the following conditions is checked. If one of the conditions 1 to 4 is not fulfilled, the system jumps back to the beginning of the shown routine.

• 1. Is the value of the instantaneous vehicle acceleration less than an empirically predetermined first threshold, which is preferably close to zero (test step 210 ).
• 2. Is an actual change in the accelerator pedal angle smaller than an empirically predetermined second threshold value, which is preferably close to zero (test step 215 ).
• 3. Within an empirically predetermined time window no movement of the shift lever has taken place (test step 220 ).
• 4. The drive train of the vehicle is currently closed, ie the clutch of the vehicle transmission is engaged (test step 225 ).

If all conditions 1 to 4 are met, the current speed of the vehicle is assumed to be the desired speed (step 230 ), according to the equation v_wunsch: = v_momentan.

It is worth noting that when checking conditions 1 through 4 it does not affect the order of the test steps 210 - 225 arrives, so that, for example, the fulfillment of condition 4 are first checked, since this represents, so to speak, an exclusion criterion for the presence or absence of the required driving status. If all conditions 1 to 4 are met, the current vehicle speed is assumed to be the driver's desired speed.

• 5. Die prädizierte Segelbetriebslänge ist größer als ein empirisch vorgegebener dritter Schwellenwert (Prüfschritt 235). Dabei wird von der Wunschgeschwindigkeit ein vorgegebener Sicherheitswert v_delta abgezogen und über die vorliegenden Fahrwiderstände eine Segelbetriebslänge berechnet.
• 6. Die im Segelbetrieb zu erwartende Beschleunigungsdifferenz im Vergleich zum Normal(fahr)betrieb ist kleiner als ein empirisch vorgegebener vierter Schwellenwert (Prüfschritt 240).
• 7. Der momentane Lenkwinkel ist geringer als ein empirisch vorgegebener fünfter Schwellenwert (Prüfschritt 245), d.h. es liegt derzeit keine Kurvenfahrt vor.
• 8. Eine zwischen zwei Segelbetriebsphasen einzuhaltende Mindestzeit wird eingehalten (Prüfschritt 250). Diese Mindestzeit bestimmt sich bevorzugt dadurch, dass für die in 1 gezeigte Beschleunigungsphase 125 ausreichend Zeit vorhanden ist, damit auch die für den erfindungsgemäßen zyklischen Fahrbetrieb erforderliche Beschleunigung mit möglichst geringem Kraftstoffverbrauch und/oder möglichst minimalen Einbussen des Fahrkomforts erfolgen kann.

In the case of a recognized desired speed, the following are also in a second block 205 summarized conditions 5. to 8. (according to the further test steps 235 to 250 ), then the sailing operation is initiated 255 , For this purpose, a calculation or prediction (prediction) of the time length of the possible sailing operation is carried out in advance on the basis of the said empirically predetermined maximum permissible speed difference. Because we already at 1 described, the sailing operation is terminated upon reaching this speed difference.

• 5. The predicted sail operating length is greater than an empirically predetermined third threshold (test step 235 ). In this case, a predefined safety value v_delta is subtracted from the desired speed, and a sail operating length is calculated using the present driving resistances.
• 6. The expected in sailing operation acceleration difference compared to the normal (driving) operation is smaller than an empirically predetermined fourth threshold (test step 240 ).
• 7. The instantaneous steering angle is less than an empirically predetermined fifth threshold value (test step 245 ), ie there is currently no cornering.
• 8. A minimum time to be respected between two phases of sailing operation is maintained (test step 250 ). This minimum time is preferably determined by the fact that for the in 1 shown acceleration phase 125 Sufficient time is available so that the required for the cyclic driving according to the invention acceleration can be done with the lowest possible fuel consumption and / or minimal loss of ride comfort.

It should be emphasized that it is also in the testing of conditions 5. to 8. not on the order of the test steps 235 - 250 arrives.

After the sailing operation according to step 255 is initiated is being examined 260 whether the decrease in speed Δv_sailing, which takes place during sailing, is greater than or equal to the maximum permissible speed difference. If the speed difference has not yet been reached, the test step is carried out 260 again, if necessary after an empirically specified time delay. If the speed decrease is greater than the predetermined speed difference, then the sail operation is terminated 265 and returned to normal operation of the motor vehicle. Thereafter, the program jumps back to the beginning of the routine and the steps 210 to 265 as described, possibly re-executed.

In the 3 an embodiment of a device according to the invention is shown in the form of a block diagram. The device comprises a bistable toggle switch ("flip-flop") 300 which, depending on the output signal "Q" binary output signal either initiates the sailing operation or not 305 , At the "set" entrance 310 of the flip-flop 300 are default values or conditions 315 Sailing time, speed difference (between instantaneous speed and desired speed) and accelerator pedal position. At the reset input 320 of the flip-flop 300 are appropriate, from a calculation module 325 determined "reset" conditions. The desired speed is in the embodiment, as in 2 described, determined.

As input variables for the calculation module 325 serve the output values of the flip-flop 300 , On the basis of these initial values, by means of a first processing element 330 the current values of the accelerator pedal position and the current driving speed of the motor vehicle stored. By means of a second processing element 335 On the basis of the values thus stored, it is checked or monitored whether the maximum limits for accelerator pedal position and the speed difference have been exceeded. In case of such exceeding, the calculation module returns 325 a "reset" bit, which ends in the case of an existing sailing operation this.

Based on 4 an embodiment of the method according to the invention is described in which the motor vehicle has a cruise control system ("GRA" or "cruise control"), which automatically controls the speed of the internal combustion engine of the motor vehicle so that the motor vehicle complies with a desired speed specified by the driver as far as possible. The speed control in modern motor vehicles is known to be mostly electronic, the exact implementation depends in particular on whether the motor vehicle e-gas (pulses from the gas pedal are electrically transmitted to the throttle, drive-by-wire) or a Bowden cable between throttle or accelerator pedal and throttle has , When the hand or foot brake or the clutch is actuated (in some vehicles with a manual transmission), the control is deactivated. In the case of a mechanical vehicle clutch, such a motor vehicle has a drive train, in which the vehicle clutch can be controlled by a control unit. The operating strategy underlying this exemplary embodiment of the method according to the invention for operating a sail-capable motor vehicle affected here enables sailing operation even when the cruise control system is activated or switched on.

Before driving or during the journey, the driver gives a desired speed and a maximum permissible speed difference via an input device or user interface connected to the speed control system, e.g. an operating lever or an input display. On the basis of the desired speed specified in this way, a prediction as described above is carried out as to whether a sufficiently long sailing operating phase is possible. If the prediction that such a sailing operation is possible, is transferred to the sailing operation or the driver informed of a possible sailing operation, so that he can initiate the sailing itself. With the maximum permitted speed difference specified by the driver, the speed decrease of the motor vehicle occurring in the sailing mode is compared and the sailing mode is stopped, depending on the result of the comparison, if necessary,

The said operating strategy in an automatic cruise control leads to a cyclical acceleration or cyclic sailing of the motor vehicle.

In the 4 corresponding variants of this operating strategy are shown schematically (ie unitless). In the upper part of the 4 is a elevation (ie topographic) course of the road 400 ("H") shown, wherein the (not shown) motor vehicle according to the drawn arrow 403 moved from left to right. The road course shown as an example 400 includes for illustration purposes both flat track parts as well as climbs and gradients. In the lower part of the 4 is the current vehicle speed 405 ("V") over the distance s plotted. In addition, the maximum permissible speed difference specified by the driver is in the form of a tolerance band 410 located.

If the cruise control system, as assumed here, activated Motor vehicle in a first sailing condition 415 when the motor vehicle is in a downgrade or the desired speed is reduced via said input device or via the user interface in the current driving operation (not shown here) and thereby the conditions for minimum sail time described above are met. The first sailing condition 415 is terminated and in a short normal operating phase 420 passed. Thereafter, the vehicle is in the second sailing state shown 423 offset because the instantaneous vehicle speed is the upper limit of the tolerance band 410 has reached.

Is the motor vehicle in a flat route 425 or in slightly falling 430 or rising 435 Terrain, the vehicle can be cyclically accelerated or placed in the sailing condition, if the above conditions for the minimum sail time are met.

It should be emphasized that the abovementioned compliance with the minimum sail time is required in all embodiments, since a shortfall of the minimum sail time leads both to loss of comfort and to increased fuel consumption.

The method described can be realized either in the form of a control program in an existing control unit for controlling an internal combustion engine or an electronic transmission clutch or in the form of a corresponding control unit.

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 non-patent literature

• VDI Guideline 2057 [0004]

Claims (19)

A method for operating a sail-operable motor vehicle, characterized in that a prediction of a sufficiently long sail operating phase is carried out that is transferred at predicted sufficiently long sail operating phase in the sailing operation ( 255 ) or the vehicle driver is informed about a possible sailing operation, that the speed reduction of the motor vehicle taking place in the sailing mode with a predetermined speed difference ( 260 ) and that the sailing operation is ended depending on the result of the comparison ( 265 ). Method in particular according to claim 1, characterized in that at least one operating variable of the motor vehicle is determined and on the basis of the at least one determined operating variable a desired speed of the vehicle driver is determined ( 200 . 230 ) that in dependence on at least one further operating variable of the motor vehicle ( 205 ) is transferred to the sailing operation ( 255 ), that the speed reduction of the motor vehicle taking place in the sailing mode with a predetermined speed difference ( 260 ) and that the sailing operation is ended depending on the result of the comparison ( 265 ). Method in particular according to claim 1, characterized in that at least one operating variable of the motor vehicle is determined and on the basis of the at least one determined operating variable a desired speed of the vehicle driver is determined ( 200 . 230 ) and that in dependence on at least one further operating variable of the motor vehicle ( 205 ) the vehicle driver is informed about a possible sailing operation, wherein in the case of sail operation activated by the driver, the speed decrease of the motor vehicle taking place in the sailing mode with a predetermined speed difference ( 260 ) and the sailing operation is ended depending on the result of the comparison ( 265 ). Method according to claim 1 in a motor vehicle capable of sail operation with a cruise control system, characterized in that a desired speed and a maximum permissible speed difference at the cruise control system are specified by the vehicle operator that is switched to the sailing mode on the basis of the predefined desired speed predicted sufficiently long sail operating phase ( 255 ) or the vehicle driver is informed about a possible sailing operation, that the speed reduction of the motor vehicle taking place in the sailing mode with the predetermined speed difference ( 260 ) and that the sailing operation is ended depending on the result of the comparison ( 265 ) Method according to one of the preceding claims, characterized in that the speed difference ( 260 ) is determined on the basis of an influence of the transition into the sailing operation on the ride comfort of the motor vehicle, in which a vibration intensity of the motor vehicle does not exceed a predetermined threshold. Method according to one of the preceding claims, characterized in that on the basis of the determined desired speed ( 200 . 230 ) and a determined driving resistance a maximum sailing time is calculated and is transferred to the sailing operation ( 255 ) or the driver is informed of a possible sailing operation when the calculated sailing time is greater than a predetermined threshold. Method according to one of the preceding claims, characterized in that when leaving the sail operation, a load point shift of the motor vehicle engine takes place. Method according to one of the preceding claims, characterized in that for determining the desired speed of the vehicle driver ( 200 . 230 ) at least one of the following conditions is checked: the value of the instantaneous vehicle acceleration is less than a predetermined first threshold value ( 210 ); An actual change of the accelerator pedal angle is smaller than a predetermined second threshold value ( 215 ); - within a given time window no movement of the shift lever has occurred ( 220 ); The drive train of the motor vehicle is currently closed ( 225 ). A method according to claim 8, characterized in that on the basis of the determined desired speed of the driver ( 200 . 230 ) and the predetermined speed difference ( 260 ) the temporal length of a possible sailing operation is calculated and when fulfilling at least one of the following conditions is entered into sailing operation ( 255 ) or informs the driver about a possible sailing operation: - The calculated time length of the possible sailing operation is greater than a predetermined third threshold ( 235 ); - the acceleration difference expected during sailing is less than a given fourth threshold ( 240 ); The instantaneous steering angle is less than a predetermined fifth threshold ( 245 ); - a minimum time to be respected between two sailing operations is respected ( 250 ). Method according to Claim 9, characterized in that the minimum time to be observed between two phases of the sailing operation is determined on the basis of an acceleration phase following a sailing operation phase, wherein the minimum time must be sufficient so that a vibration intensity of the motor vehicle does not exceed a predetermined threshold value. Method according to one of the preceding claims, characterized in that dependent on the vehicle speed values of the speed difference are stored and, depending on the current vehicle speed, one of these values is selected for the speed difference. Method according to one of claims 4 to 11, characterized in that is transferred to the sailing operation when a desired speed set by the driver is below a current vehicle speed. Method according to one of the preceding claims, characterized in that camera and / or radio-based data of a traffic monitoring are taken into account in the prediction of a sufficiently long sailing operation phase. Method according to one of the preceding claims, characterized in that data of a navigation system are taken into account in the prediction of a sufficiently long sailing operation phase. Method according to claim 13 and / or 14, characterized in that the speed difference ( 260 ) is determined on the basis of said data. Device for operating a sail-operable motor vehicle according to the method according to one of the preceding claims, characterized by a bistable toggle switch ( 300 ) for initiating a sailing operation ( 305 ), whereby at a SET input ( 310 ) of the bistable toggle switch ( 300 ) Default values and / or conditions ( 315 ) for the possible transition into the sail mode and at a RESET input ( 320 ) of the bistable toggle switch ( 300 ) from a calculation module ( 325 ) provided RESET conditions. Apparatus according to claim 16, characterized in that as input variables for the calculation module ( 325 ) at the output of the bistable toggle switch ( 300 serve) based on the output values by means of at least one processing element ( 330 . 335 ), whether predetermined limit values for the accelerator pedal position and / or the predetermined speed difference ( 260 ) are exceeded and wherein in the case of a determined excess a RESET bit is output, which terminates an existing sailing operation. A computer program that performs all the steps of a method according to any one of claims 1 to 15 when executed on a computing device or a controller. Computer program product with program code, which is stored on a machine-readable carrier, for performing a method according to one of claims 1 to 15, when the program is executed on a computing device or a control device.

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