DE10255467A1 - Vehicle roll prevention method for preventing a motor vehicle from rolling backwards switches a brake system into a mode for delaying reduction in brake pressure after the vehicle comes to a stop - Google Patents

Abstract

When a vehicle is stationary, a brake system is switched into a mode for delaying reduction in brake pressure. A first pedal value (dp/dt) that characterizes the speed of brake pedal release is detected if the vehicle comes to a stop. The mode for delaying reduction in brake pressure is deactivated by relying on the first pedal value. An Independent claim is also included for a device for preventing a motor vehicle from rolling backwards.

Description

State of technology

The invention is based on a Method for preventing a vehicle from rolling away when starting up according to the preamble of the main claim.

The Hillholder is about a system that allows the driver to start the operation of the driver Handbrake released. By "locking in" the driver applied Braking pressure will roll back of the vehicle between the time of release of the brake pedal and the Time of actual startup prevented.

Many Hillholder systems do not have one Sensor with which the pitch angle the roadway can be measured. This can be missing if there is one Sensor can not be distinguished, whether the driver uphill or downhill would like to drive. Therefore, the Hillholder both in a mountain drive, at a Downhill and activated in the plane. This has a disadvantageous effect when the driver wants to roll the vehicle downhill, especially when he wants to park downhill.

To eliminate this disadvantage it is possible, that the hillholder is only activated when the driver is fast from the brake pedal, i. if a big negative pressure gradient is present. In this case it is assumed that a fast Pedal change will follow a starting process. Is the negative pressure gradient on the other hand rather low, then one can assume that the driver wants to let the vehicle roll.

• – Erfassen wenigstens einer charakteristischen Pedalbetätigung eines Bremspedals bei Stillstand des Fahrzeugs;
• – Aktivieren eines Betriebsbremssteuerdrucks dann, wenn die charakteristische Betätigungsgröße wenigstens ein vorgegebenes Kriterium erfüllt;
• – Zeitverzögertes Deaktivieren des Betriebsbremssteuerdrucks, nachdem das Bremspedal gelöst wurde.

From the DE 199 50 162 A1 For example, there is known a method of preventing the vehicle from rolling back during startup. This is characterized by the following steps:

• - detecting at least one characteristic pedal operation of a brake pedal when the vehicle is at a standstill;
• - Activating a service brake control pressure when the characteristic operation amount meets at least a predetermined criterion;
• Time-delayed deactivation of the service brake control pressure after the brake pedal has been released.

The features of the preambles of the independent claims are based on DE 199 50 162 A1 out.

• – das Bremssystem bei Stillstand des Fahrzeugs in einen Bremsdruckabbauverzögerungsmodus (= Hillholder) geschaltet wird und
• – wenigstens eine die Bremspedalentlastungsgeschwindigkeit charakterisierende erste Pedalgröße bei Stillstand des Fahrzeugs erfasst wird, Weiterhin beinhaltet das Verfahren,
• – dass abhängig von der ersten Pedalgröße der Bremsdruckabbauverzögerungsmodus deaktiviert wird.

The invention relates to a method for preventing the rolling back of a vehicle, in which

• - The braking system is switched at standstill of the vehicle in a brake pressure release delay mode (= Hillholder) and
• At least one first pedal size characterizing the brake pedal unloading speed is detected when the vehicle is at a standstill.
• - That the brake pressure release delay mode is deactivated depending on the first pedal size.

Through this "preventive activation" of the Hillholder will be a high level Safety and reliability reached, i. The Hillholder can also be activated after a successful "weak" braking process become.

An advantageous embodiment of The invention is characterized in that it is the pedal unloading speed characterizing speed (= first pedal size) around the change of the form per unit time. This size is without significant effort detectable, since a form sensor in modern braking systems already is included as a standard component.

• – unabhängig von der ersten Pedalgröße
• – sowie unabhängig von einer eine Bremspedalbetätigungsgeschwindigkeit charakterisierenden zweiten Pedalgröße

erfolgt.A further advantageous embodiment is characterized. that activation of the brake pressure release delay mode

• - regardless of the first pedal size
• - And regardless of a brake pedal operating speed characterizing second pedal size

he follows.

• – der Betrag der ersten Pedalgröße einen vorgebbaren und/oder vorgegebenen Schwellenwert unterschreitet
• – und/oder wenigstens eine weitere Bedingung erfüllt ist.

A further advantageous embodiment is characterized in that the brake pressure release delay mode is deactivated when

• - The amount of the first pedal size falls below a predetermined and / or predetermined threshold
• - And / or at least one further condition is met.

The first of these two conditions is checked with what speed the driver takes his foot off the brake pedal. The second of these conditions prevented by an additional Security query that mistakenly the preventive activated Hillholder is deactivated.

• – der Betrag der ersten Pedalgröße den Schwellenwert über ein Zeitintervall vorgebbarer Länge hinweg stets unterschreiten muss und/oder
• – der Vordruck während der Überprüfung, ob der Betrag der ersten Pedalgröße einen vorgebbaren Schwellenwert unterschreitet, größer als ein vorgebbarer Schwellenwert ist,

Hier handelt es sich um zusätzliche Sicherheitsabfragen.An advantageous embodiment is characterized in that as a further condition

• - The amount of the first pedal size must always fall below the threshold over a time interval of predeterminable length and / or
• - the form during the check whether the amount of the first pedal size falls below a predefinable threshold, is greater than a predefinable threshold,

These are additional security queries.

A beneficial additional Security query contains also the embodiment, which is characterized in that the check whether the amount of the first pedal size one falls below a predetermined threshold, only then occurs when since switching the brake system to the brake pressure release delay mode a time interval of predeterminable length elapsed is.

An advantageous embodiment of Invention is characterized in that at the same time as the deactivation the brake pressure release delay mode a lock mode is activated, which is a re-activation the brake pressure release delay mode prevented. This is a "vibration behavior" of Hillholdermodus, i.e. a rapid change of activation processes and deactivation processes avoided.

• – wenn eine eine Bremspedalbetätigungsgeschwindigkeit charakterisierende Größe einen vorgebbaren Schwellenwert überschreitet oder
• – wenn keine Bremsbetätigung durch den Fahrer erfolgt und kein Fahrzeugstillstand mehr vorliegt.

An advantageous embodiment is characterized in that the blocking mode is then deactivated again,

• If a variable characterizing a brake pedal actuation speed exceeds a predefinable threshold value, or
• - if no braking operation by the driver and no vehicle standstill is present.

In these cases there is a renewed driver braking or a successful starting by the driver. Therefore it now makes sense to deactivate the lock mode. It is here on it indicated that the deactivation of the lock mode no activation Hillholder means: Disabling lock mode means only that Hillholder can now be activated again.

A further advantageous embodiment is characterized in that at least depending on the first pedal size, the brake pressure release delay mode is deactivated prematurely. With the Hillholder, the brake pressure usually becomes while maintained a time interval of predetermined length. The length of this Time interval is typically on the order of up to several Seconds. Under the "premature Deactivation "will thereby understood a deactivation before the expiration of this time interval.

• – Hillholderaktivierungsmittel, mit denen das Bremssystem bei Stillstand des Fahrzeugs in einen Bremsdruckabbauverzögerungsmodus geschaltet wird sowie
• – Sensormittel, mit denen wenigstens eine die Bremspedalentlastungsgeschwindigkeit charakterisierende erste Pedalgröße bei Stillstand des Fahrzeugs erfasst wird. Weiterhin sind in der Vorrichtung
• – Hillholderdeaktivierungsmittel enthalten, mit denen abhängig von der ersten Pedalgröße der Bremsdruckabbauverzögerungsmodus deaktiviert wird.

The device for preventing the rolling back of a vehicle contains

• - Hillholderaktivierungsmittel with which the brake system is switched when the vehicle is in a brake pressure release delay mode and
• Sensor means for detecting at least one first pedal size characterizing the brake pedal release speed when the vehicle is at a standstill. Furthermore, in the device
• - Include Hillholderdeaktivierungsmittel with which, depending on the first pedal size of the brake pressure release delay mode is deactivated.

• – der Betrag der die ersten Pedalgröße einen vorgebbaren und/oder vorgegebenen Schwellenwert unterschreitet und/oder
• – wenigstens eine weitere Bedingung erfüllt ist.

An advantageous embodiment of the device is characterized in that the brake pressure release delay mode is deactivated when

• - The amount of the first pedal size falls below a predetermined and / or predetermined threshold and / or
• - At least one other condition is met.

Further advantageous embodiments The invention can be found in the dependent claims. The described embodiments of the procedure Of course also to corresponding embodiments the device and vice versa.

drawing

An embodiment of the invention is shown in the following drawings 1 to 6.

1 shows an embodiment of the deactivation of the hillholder.

2 shows an embodiment of the reset of the lock.

3 Illustratively illustrates the various "bands" (which may also be referred to as print areas or print bands) of the invention.

4 shows the operation of the invention using measured signals.

5 shows the sequence of the method according to the invention.

6 shows the structure of the device according to the invention.

embodiments

• 1. das Fahrzeug befindet sich im Stillstand,
• 2. der Fahrer betätigt die Bremse, dies wird durch einen aktivierten Bremslichtschalter erkannt,
• 3. der Vordruck im Bremskreis überschreitet einen vorgegebenen Schwellenwert und
• 4. es ist ein Gang eingelegt.

The present invention relates to an improved activation or deactivation of the hillholder. For this purpose, the hillholder is activated when the motor vehicle stops when the following conditions are met:

• 1. the vehicle is at a standstill,
• 2. the driver actuates the brake, this is detected by an activated brake light switch,
• 3. the pressure in the brake circuit exceeds a predetermined threshold and
• 4. there is a gear engaged.

The second and third of these conditions can also by an or-link be linked i.e. the fulfillment at least one of these two conditions is sufficient.

• – ob der Hillholder weiter aktiv bleibt, d.h. ob nach dem Loslassen des Bremspedals noch über eine gewisse Zeit Druck in den Radbremszylindern verbleibt (der Druck wird „eingesperrt" und erst zeitverzögert abgebaut) oder
• – ob der Hillholder deaktiviert wird, d.h. ob nach dem Loslassen des Bremspedals kein Druck mehr in den Radbremszylindern eingesperrt bleibt.

When releasing the brake pedal by the driver (which is associated with a negative pressure gradient), the decision is made

• - whether the hillholder remains active, that is, whether after releasing the brake pedal for a certain time pressure in the wheel brake cylinders remains (the pressure is "locked" and reduced until a time delay) or
• - Whether the hill holder is deactivated, ie whether after releasing the brake pedal no pressure remains trapped in the wheel brake cylinders.

The pressure gradient is in this case, for example, the gradient or the temporal change of the form. The form is at the brake circuit side output of Master cylinder measured by a pressure sensor.

In particular, the Hillholder remains then active, if the amount of pressure gradient is a large value has, i. if the amount of the pressure gradient is a predefinable Threshold exceeds. This clearly means that the driver with his foot the brake pedal quickly dissolves, this indicates a start-up process (e.g., uphill or uphill the level).

This decision about a Deactivation of the hill holder is done by considering the brake pressure gradient and at least one additional condition:

• – wenn der Betrag des Druckgradienten einen kleinen Wert hat, d.h. wenn der Betrag des Druckgradienten einen vorgebbaren Schwellenwert unterschreitet. Das bedeutet anschaulich, dass der Fahrer mit seinem Fuß das Bremspedal langsam löst und
• – wenigstens eine weitere Zusatzbedingung erfüllt ist.

The hillholder is then deactivated

• - When the amount of the pressure gradient has a small value, that is, when the amount of the pressure gradient falls below a predetermined threshold. This clearly shows that the driver slowly releases the brake pedal with his foot and
• - At least one additional condition is met.

The typical driver releases the brake pedal especially slowly, if you let the vehicle roll downhill would like to or during a parking operation on a longitudinally inclined roadway.

The term "amount" is the amount value ("| ... |") in mathematical Meaning to understand.

Here are, for example, the following Additional conditions conceivable:

Condition 1:

The pressure gradient must be within certain limits within a time window of predefinable length. These are in 1 plotted two time profiles of the pressure gradient. The abscissa is plotted along the time t and a time window of length ΔT, along the ordinate is the pressure gradient dp / dt and the two example values
-5 bar / s and -70 bar / s applied. Next are in 1 two in the example assumed as linear pressure gradient curves 100 and 101 applied. The pressure gradient course 100 leads to a deactivation of the hillholder, since during the entire time window ΔT the value of dp / dt is between the limits -5 bar / s and -70 bar / s. The pressure gradient course 101 on the other hand does not lead to a deactivation of the Hillholder, since within the time window ΔT the limit of -70 bar / s is exceeded in terms of amount. For ΔT, a time interval of 250 ms has proven suitable.

In 1 is in addition the deadband 102 This is valid for the pressure gradient values -5 bar / s ≤ dp / dt ≤ 0.

With the deadband is prevented that random slight fluctuations of the pressure gradient to a deactivation lead the Hillholders.

Condition 2:

The form must be larger than be a threshold. This depends together with that in the presence of very small pressures also generally their gradients accept only small values. Thus, in particular the following case is intercepted, whose temporal Sequence is shown in the following steps:

• - of the Driver leaves the brake pedal very quickly
• - as a result of the initial great negative pressure gradient finds no deactivation of the hillholder instead of.
• m In the final stages of pressure reduction (after the pressure is very fast decayed to small values) occur only small pressure gradients.
• - By the requirement for a threshold for the form is ensured, that these small pressures do not turn off the hillholder to lead.

Condition 3:

The evaluation of the pressure gradient takes place at the earliest then, if after hillholder activation a time interval of predefinable length has passed. This will produce effects such as a momentary overshoot the output signal of the pressure sensor hidden.

After deactivating the hillholder as a result of a low and plausible pressure gradient a renewed activation of the hillholder only after fulfillment of certain conditions again possible his. Until then, a lock is set, which is a re-activation the Hillholder does not allow it.

• 1. Der Vordrucks steigt erneut an, d.h. es liegt ein positiver Vordruckgradient vor. Dieser Fall liegt vor, wenn der Fahrer nach einem kurzen Loslassen des Bremspedals erneut bremst („Nachtreten des Fahrers"}.
• 2. Der Hillholder ist nicht aktiviert, es liegt keine Bremsbetätigung und kein Fahrzeugstillstand vor.
• 3. der Druckgradient muss innerhalb eines Zeitfensters vorgebbarer Länge einen vorgebbaren Schwellenwert überschreiten.

Possible conditions for resetting the lock so as to allow the hillholder to be activated again may be:

• 1. The form increases again, ie it is on positive admission pressure gradient. This is the case if the driver brakes again after a brief release of the brake pedal ("Driver's Rise"}.
• 2. The hillholder is not activated, there is no brake application and no vehicle standstill.
• 3. the pressure gradient must exceed a predefinable threshold within a time window of predeterminable length.

There are also other conditions possible, the arbitrarily linked can be.

In 2 is shown as an example how the suspension of the hillholder can be lifted. Along the abscissa of 2 is the time t and along the ordinate the pressure gradient dp / dt (ie the time change of the pressure) is plotted. Further, a lower threshold of 15 bar / s is given as examples, of course, other numerical values are conceivable and possible. Next are in 2 two possible time courses 200 and 201 drawn the pressure gradient. The history 200 exceeds the threshold value of 15 bar / s during the entire time interval ΔT (the value ΔT = 100 ms has proven suitable, of course other values are conceivable and possible). Therefore the pressure course leads 200 to reset the suspension of the hillholder. The suspension of the hillholder's suspension does not mean that the hillholder is now activated. The reset simply means that the Hillholder is now activated again. During the course 201 However, the limit of 15 bar / s is not exceeded during the entire time window ΔT. Therefore, in this case, the suspension of the hillholder is not canceled.

The course of the two bands is in an illustrative manner again in 3 summarized. The ordinate shows the pressure gradient dp / dt.

• – kennzeichnet 301 das Totband,
• – 302 kennzeichnet den Gradientenbereich, in dem eine Deaktivierung des Hillholders erfolgen kann und
• – 303 kennzeichnet den Gradientenbereich, in dem der Hillholder nach einer Sperrung erneut aktiviert werden kann (d.h. Rücknahme der Sperre). Dabei kann es sich beim Band 303 um ein nach oben offenes Band handeln.

there

• - indicates 301 the deadband,
• - 302 indicates the gradient range in which deactivation of the hillholder can take place and
• - 303 indicates the gradient range in which the hillholder can be reactivated after a lock (ie, the lock is withdrawn). It may be the band 303 to be an open-topped band.

The operation of the invention is based on measured waveforms in 4 shown.

In 4 the time t is plotted in the abscissa direction, different signals are plotted in the ordinate direction.

• Signal 1: Dieses mit BLS gekennzeichnete Signal kennzeichnet den Zustand des Bremslichtschalters. Nimmt dieses binäre Signal den „high"-Wert an, dann ist der Bremslichtschalter aktiviert.
• Signal 2: Dieses mit HHC bezeichnet Signal kennzeichnet den Betriebszustand des Hillholders. Nimmt dieses binäre Signal den „high"-Wert an, dann ist der Hillholder aktiviert.
• Signal 3: Dieses mit „lock" gekennzeichnete Signal kennzeichnet den Status der Sperre. Nimmt dieses binäre Signal den „high"-Wert an, dann ist der Sperre aktiviert, d.h. der Hillholder ist nicht aktivierbar.
• Signal 4: Dieses mit dp/dt gekennzeichnete Signal kennzeichnet den Gradienten des Vordrucks, d.h. dessen Änderung pro Zeiteinheit.
• Signal 5: Dieses mit pvor gekennzeichnete Signal kennzeichnet den zeitlichen Verlauf des Vordrucks.
• Signal 6: Dieses mit p_rad gekennzeichnete Signal kennzeichnet den Bremsdruck in einem ausgewählten Radbremszylinder, welcher repräsentativ für alle an einem Bremsvorgang beteiligten Radbremszylinder steht. Der Bremsdruck kann dabei entweder geschätzt oder gemessen sein.

These signals are first explained in order from top to bottom:

• Signal 1: This signal marked BLS indicates the status of the brake light switch. If this binary signal assumes the "high" value, then the brake light switch is activated.
• Signal 2: This HHC signal indicates the operating status of the Hillholder. If this binary signal assumes the "high" value, then the hillholder is activated.
• Signal 3: This signal marked with "lock" indicates the status of the lock If this binary signal assumes the "high" value, then the lock is activated, ie the hillholder can not be activated.
• Signal 4: This signal marked dp / dt indicates the gradient of the form, ie its change per unit of time.
• Signal 5: This signal marked with pvor indicates the time course of the form.
• Signal 6: This signal marked p_rad identifies the brake pressure in a selected wheel brake cylinder which is representative of all the wheel brake cylinders involved in a braking operation. The brake pressure can either be estimated or measured.

• – es findet ein Vordruckaufbau (Signal 5) und ein Druckaufbau im Radbremszylinder (Signal 6) statt,
• – es tritt ein Vordruckgradient dp/dt auf (Signal 4),
• – der Bremslichtschalter (Signal 1) wird aktiviert und
• – der Hillholder wird (Signal 2) aktiviert.

At a time 401 the driver presses the brake pedal. This has the following effects based on 4 :

• - there is a pre-pressure build-up (signal 5) and a build-up of pressure in the wheel brake cylinder (signal 6),
• - there is a pre-pressure gradient dp / dt (signal 4),
• - the brake light switch (signal 1) is activated and
• - The Hillholder is activated (Signal 2).

• - der Vordruck pvor absinkt (weil der Fahrer das Bremspedal entlastet hat),
• - aber der Radbremsdruck p_rad konstant bleibt (weil der Hillholder aktiviert ist).

Since the brake pedal is then released very quickly by the driver, a very large negative gradient dp / dt occurs (see 403). This large gradient causes the hillholder to remain activated (see 404). This expresses itself at the time 402 in that

• - the pre-pressure pvor drops (because the driver has relieved the brake pedal),
• - But the wheel brake pressure p_rad remains constant (because the hillholder is activated).

At the time 405 is the activation period of Hillholder expired, the brake pressure p_rad in the wheel brake cylinder decreases.

At the time 406 a new braking process takes place by the driver. This time, the driver takes the brake pedal only very slowly (see 407 ), the evaluation of dp / dt during the time window 408 shows a small gradient.

• – der Hillholder deaktiviert und
• – die Sperre („lock") aktiviert.

That's why at the time 409

• - the Hillholder disabled and
• - the lock is activated.

The sequence of an embodiment of the method according to the invention is in 5 shown.

The start of the procedure is in block 500 , Subsequently, in block 501 the brake system is switched to a brake pressure release delay mode when the vehicle is stationary, ie the hill holder is activated. After that, in block 502 a characterizing the brake pedal relief speed, for example, the (negative) gradient of the form, evaluated.

In block 503 is then checked whether the amount of brake pedal relief speed falls below a predetermined threshold. If this is not the case ("n"), then it becomes block 500 branches back. Is the query condition in block 503 however fulfilled ("y"), then finds in block 504 a new query instead. In block 504 For example, it is checked whether the undershooting takes place over a given time window of predefinable length. If this is not the case then it becomes block 500 branches back. If this is the case ("y"), then it will be in block 505 the brake pressure release delay mode is prematurely deactivated and a lock mode is activated which prevents a renewed activation of the brake pressure release delay mode.

• – ob eine eine Bremspedalbetätigungsgeschwindigkeit charakterisierenden Größe einen vorgebbaren Schwellenwert überschreitet oder
• – ob keine Bremsbetätigung durch den Fahrer erfolgt und kein Fahrzeugstillstand mehr vorliegt.

After that, in block 506 asked if

• Whether a variable characterizing a brake pedal actuation speed exceeds a predefinable threshold value, or
• - If no braking operation by the driver and no vehicle standstill is present.

If the answer is no ("n"), then find in block 507 a time increment takes place and then becomes block 506 branches back. The time increment means vividly that the query 506 takes place again at a later date. In contrast, at least one of the in block 506 queried conditions met ("y"), then in block 508 the lock is deactivated again. Thereafter, the Hillholder is ready for activation again and it will start the process in block 500 branches back.

The structure of the device according to the invention is in 6 shown. It contains block 601 first sensor means, which detect a stoppage of the vehicle. These sensor means are, for example, wheel speed sensors. The output signals of these first sensor means become the Hillholder activating means 602 fed. Depending on the signals recorded with the sensor means (eg a detected vehicle standstill), the hillholder is activated. Furthermore, the device contains second sensor means 604 with which at least one of the Bremspedalentlastungsgeschwindigkeit characterizing size is detected at standstill of the vehicle. The output signals of the blocks 602 and 604 become the Hillholder deactivator 603 supplied with which depending on the Bremspedalentlastungsgeschwindigkeit characterizing size and at least one further condition of the brake pressure release delay mode is prematurely deactivated.

block 605 includes the brake system and in particular its brake actuators. This will be the outputs of the blocks 602 and 603 supplied and depending on the components contained in the brake system for the purpose of maintaining the Hillholder braking or discontinuation of Hillholder braking are driven.

Claims (11)

A method for preventing the rolling back of a vehicle, in which - the braking system is switched to a braking pressure reduction delay mode when the vehicle is stationary ( 501 ), - at least one brake pedal relief speed characterizing first pedal size (dp / dt) is detected when the vehicle has substantially come to a standstill ( 502 ), characterized in that - at least depending on the first pedal size (dp / dt) the brake pressure release delay mode is deactivated ( 505 ). Method according to claim 1, characterized in that that the first pedal size is the change of the preprint (pvor) per unit of time (dp / dt). Method according to claim 1, characterized in that that activation of the brake pressure release delay mode - independent of the first pedal size (dp / dt) - such as independently from a brake pedal actuation speed characterizing second pedal size is done. Method according to claim 1, characterized in that that is the brake pressure release delay mode then deactivated if - the amount of the first Pedal size one predetermined and / or predetermined threshold falls below and / or - at least fulfilled another condition is. Method according to claim 4, characterized in that that as another condition The amount of the first pedal size exceeds the threshold above Time interval of predefinable length (ΔT) always falls below and / or - the form (pvor) during the check to see if the Amount of the first pedal size one falls below a predefined threshold, greater than a predefinable threshold is. Method according to Claim 4, characterized in that the check as to whether the amount of the first pedal size falls below a predefinable threshold value takes place only when, since then Activation of the brake pressure reduction delay mode a time interval of predeterminable length has elapsed. Method according to claim 1, characterized in that that with the deactivation of the brake pressure release delay mode a lock mode is activated, which is a re-activation the brake pressure release delay mode prevented. A method according to claim 8, characterized in that the lock mode is then deactivated again - when a brake pedal actuation speed characterizing variable exceeds a predefinable threshold value or - if no brake actuation by the driver and no vehicle standstill is present ( 506 ). A method according to claim 1, characterized in that - at least depending on the first pedal size (dp / dt), the brake pressure release delay mode is prematurely deactivated ( 505 ). Device for preventing the rolling back of a vehicle, which - Hillholderaktivierungsmittel ( 602 ), with which the brake system is switched to a brake pressure reduction delay mode when the vehicle is at a standstill, and - sensor means ( 604 ), with which at least one first pedal size (dp / dt) characterizing the brake pedal unloading speed is detected when the vehicle has essentially come to a standstill, characterized in that - hillholder deactivating means ( 603 ) are included with which, depending on the first pedal size (dp / dt), the brake pressure release delay mode is deactivated. Device according to claim 10, characterized in that that is the brake pressure release delay mode then deactivated if - the amount of the first Pedal size one predetermined and / or predetermined threshold falls below and / or - at least fulfilled another condition is.