DE102009028914A1 - Method for recognizing trapping case of closing device, involves determining variable of state, which indicates force for movement of closing element in closing direction - Google Patents

Abstract

The method involves determining a variable of state, which indicates a force for movement of a closing element (2) in closing direction and determining temporal gradients of the variable of state as variable of state gradients. A temporal change of the variable of state gradients is determined and a variable of state threshold value is determined, if the change variable of state gradients exceeds a given gradient threshold value. Independent claims are also included for the following: (1) a device for recognizing trapping case of a closing device; and (2) a computer program product, which has a computer program.

Description

Technical area

The invention relates to a closing device, in particular in or on a motor vehicle, such as an electrically operated window, an electrically actuated sunroof and the like. The invention further relates to a method for detecting a Einklemmfalls when closing the locking device.

State of the art

In closing devices on a motor vehicle, such as power windows, electric sunroofs and the like, it is necessary to ensure that during a closing operation between the closing element (window pane, sunroof) and a stop edge (window frame, roof recess) no objects or body parts are damaged or can be injured. In order to avoid such a case, an algorithm which detects a resistance during a closing operation of the closing element is implemented in a control unit which activates a servomotor coupled to the closing element of the closing device. In this case, the closing process is interrupted or carried out a reversal, in which the closing element at least briefly performs an opening movement.

In order to detect a jamming case, the position of the closing element and the closing force which must act on the closing element to perform the closing operation are constantly checked and the speed of the closing movement is reduced and / or the closing force required for maintaining the closing movement is increased closed to a pinch.

In the realization of Einklemmerkennung must be ensured that it is determined if there is an increase in force during the closing process, which is due to pinching. In this case, react immediately and stop the movement of the closing element or reopen it in an opening movement (reversing). An erroneous determination in the detection of a trapping by the algorithm can lead to a permanent pinching of an object or a body part on the one hand or cause a faulty reversal of the closing element in an error detection. This affects comfort.

A common solution for detecting a reduction in the speed of the closing movement based on an evaluation of the speed curve of the servomotor. For example, to the servomotor have a ring magnet and a Hall sensor. The engine speed can thereby be easily detected by an evaluation of square wave signals generated by the passage of the magnet past the Hall sensor. The frequency of the square-wave signals represents an indication of the rotational speed. From the signal detected in this way, the force for performing a closing movement can be derived and the actuating motor can be controlled accordingly.

An alternative method determines the speed of the servo motor by means of an evaluation of the motor current. The motor current usually has current ripple, which correspond to an image of the armature rotation of the servomotor. From the frequency of the current ripple, the speed of the servomotor can be derived.

Instead of the speed change, the load change of the servomotor can also be derived directly from the stream, since upon impingement of the closing element on an object, the motor current increases. For example, the publication discloses DE 44 42 171 a method for detecting an electrical window jam case by deriving a reference current profile from one or more pre-recorded current profiles, comparing it to a current current profile, and assuming a jamming case in a difference. Once taught in, the current profile is assumed to be preset. An adaptation to changes in the behavior of the closing element in the closing device, for example due to changed friction due to aging, changed ambient temperatures and the like, as well as changing parameters of the closing element driving servomotor, usually does not take place.

When monitoring the motor current or another state signal of the closing device which reflects a load change, the load change can usually only be detected with a delay in a change of the state signals. This delay means a loss of time in detecting a trapping case, which reduces the time window in which to respond to the trapping case. Thereby, the robustness of detecting a jamming case based on a change of state signals can be reduced.

It is therefore an object of the present invention to provide an improved method and a device with which a trapping case of a closing device can be detected.

Disclosure of the invention

This object is achieved by the method for detecting a trapping case of a locking device according to claim 1 and by the device according to the independent claim.

Further advantageous embodiments are specified in the dependent claims.

• – Erfassen einer Zustandsgröße, die eine Kraft zur Bewegung eines Schließelements in Schließrichtung angibt;
• – Ermitteln eines zeitlichen Gradienten der Zustandsgröße als Zustandsgrößen-Gradienten;
• – Ermitteln einer zeitlichen Änderung des Zustandsgrößen-Gradienten;
• – Festlegen eines Zustandsgrößen-Schwellenwerts, wenn die Änderung des Zustandsgrößen-Gradienten einen vorgegebenen Gradienten-Schwellenwert übersteigt;
• – Erkennen des Einklemmfalls, wenn die Zustandsgröße nach dem Festlegen des Zustandsgrößen-Schwellenwerts den Zustandsgrößen-Schwellenwert übersteigt.

According to a first aspect, a method for detecting a trapping case of a locking device is provided. The method comprises the following steps:

• - detecting a state quantity indicative of a force for moving a closing element in the closing direction;
• Determining a temporal gradient of the state variable as state variable gradient;
• Determining a temporal change of the state variable gradient;
• - determining a state quantity threshold if the change in the state quantity gradient exceeds a predetermined gradient threshold;
• Detecting the pinch case when the state quantity after setting the state quantity threshold exceeds the state size threshold.

An idea of the present invention is to detect a state quantity of the closing device, which reflects a load in the closing device for closing the closing element, in particular a load of the drive motor. The state variable is evaluated by continuously determining a temporal gradient of the state variable and, depending on a specific course of the state variable gradient, determining the state variable threshold value. With the current state variable and the state variable threshold value, a threshold value comparison is carried out, the result of which indicates a trapping case. That is to say, as a rule, if the state variable exceeds the state variable threshold dependent on the state variable present at the specific instant, a pinch-in is detected.

The above method has the advantage that it can robustly detect a trapping case regardless of changes in friction conditions, load profiles or aging-related operating parameters of the drive motor. For example, the above method for detecting a trapping case can properly recognize a trapping case even if the friction in the movement of the shutter member in a guide greatly changes due to a temperature change. Further, because of the variable state quantity threshold, the above method is robust against erroneous detection of an entrapment case upon occurrence of external acceleration forces such as in a motor vehicle when driving on a rough road.

Furthermore, the state quantity gradients can be determined by averaging a plurality of differences between successively detected state variables or by determining a difference between two average values of a plurality of state variables in successive time windows spaced apart from one another by a specific time duration.

In particular, the determination of the state variable threshold value can be carried out by determining an entrapment time as the point in time of a potential trapping case when the predetermined gradient threshold value is exceeded by the change of the state variable gradient, wherein the state variable threshold value is determined as a function of the value of the state variable which was at the time of pinching.

It can be provided that the pinching time is determined as the time of the change of the state variable gradient by a retroactive calculation, wherein the retrograde calculation a calculation of an intersection of a first straight line, by the state size gradient at a time before the detected increase of State variable gradient, and a second straight line defined by the current state quantity gradient, the intersection point indicating the pinch point.

According to an embodiment, setting the state quantity threshold may be performed by adding an absolute or relative state quantity offset to the value of the state variable that existed at the pinch point.

The state quantity threshold may be cleared and the jamming case detection may not be performed if the state quantity threshold is not exceeded within a time window after the jam time.

Further, the state quantity threshold value can be cleared and the jamming case detection can not be performed when the average slope of the state quantity since the pinching time exits a predetermined gradient range.

In particular, the state quantity threshold may be added by adding an absolute or relative state quantity offset to the value of State variable, which was present at the pinching time, are performed, wherein the state quantity offset is increased when the average since the pinching time slope of the state variable falls below a predetermined gradient range defined by the lower gradient threshold.

According to an embodiment, the state quantity may correspond to a motor current of a drive motor for driving the closing element.

• – eine Zustandsgröße zu erfassen, die eine Kraft zur Bewegung eines Schließelements in Schließrichtung angibt;
• – einen zeitlichen Gradienten der Zustandsgröße als Zustandsgrößen-Gradienten zu ermitteln;
• – eine zeitlichen Änderung des Zustandsgrößen-Gradienten zu ermitteln;
• – einen Zustandsgrößen-Schwellenwert festzulegen, wenn die Änderung des Zustandsgrößen-Gradienten einen vorgegebenen Gradienten-Schwellenwert übersteigt;
• – den Einklemmfall zu erkennen, wenn die Zustandsgröße nach dem Festlegen des Zustandsgrößen-Schwellenwerts den Zustandsgrößen-Schwellenwert übersteigt.

According to a further aspect, an apparatus for detecting a trapping case of a closing device is provided, which is designed

• To detect a state quantity indicative of a force for moving a closing element in the closing direction;
• To determine a temporal gradient of the state variable as state variable gradient;
• To determine a temporal change of the state variable gradient;
• - set a state quantity threshold if the change in the state quantity gradient exceeds a predetermined gradient threshold;
• To detect the pinch case when the state quantity exceeds the state size threshold after the state variable threshold is set.

According to a further aspect, a use of the above device for a power window system of a motor vehicle is provided.

In another aspect, a computer program product is provided that includes a computer program that, when executed on a computing device, performs the above method.

Brief description of the drawings

Preferred embodiments will be explained in more detail with reference to the accompanying drawings. Show it:

1 a schematic representation of an electric power window system for a motor vehicle;

2 a flowchart illustrating the sequence of the method according to the invention for detecting a pinching case;

3 Diagrams to illustrate the time course of the motor current and the clamping force in a Einklemmfall;

4 a diagram illustrating the timing of the motor current and illustrating the operations for the detection of a trapping case;

5 a diagram illustrating the time course of the motor current for operating an electric window of a motor vehicle that runs on uneven roads.

Description of embodiments

In 1 is a vehicle door 1 a motor vehicle shown. The vehicle door 1 comprises an electric power window system (closing device) with a window pane 2 as a closing element in a window frame 3 slidably arranged. The window glass 2 is powered by a servomotor 5 about a mechanics 6 driven. The servomotor 5 and the mechanics 6 form a drive unit for the closing element.

The servomotor 5 is preferably designed as a rotary DC motor. The mechanic 6 serves to a rotational movement of the servomotor 5 to transform it into a transverse movement around the windowpane 2 in the window frame 3 to move. The window glass 2 can through the mechanics 6 and the servomotor 5 be moved in the direction of an open position and in the direction of a closed position. When moving in the direction of the closed position, an edge of the window pane moves 2 towards an edge 4 of the window frame 3 while moving the windowpane 3 in the direction of the open position, the gap between the edge 4 of the window frame 3 and the windowpane 2 increased.

The servomotor 5 is from a control unit 7 driven. The control unit 7 is with a control switch 8th coupled. With the help of the control switch 8th For example, a driver of the motor vehicle can instruct the power window system, the windowpane 2 to move to the window of the vehicle door 1 close. That is, the driver operates the control switch 8th so generates the control unit 7 a control variable for the servomotor 5 so that it is put into a rotary motion and the windowpane 2 about the mechanics 6 towards the top edge 4 of the window frame 3 emotional. Usually, the control of the servo motor takes place 5 with the help of a DC voltage.

By the closing movement of the windowpane 2 towards the edge 4 of the window frame 3 Can be objects or body parts that are between an edge of the windowpane 2 and the edge 4 of the window frame 3 be trapped and thereby damaged or injured. Because of this, is in the control unit 7 in usually implemented a anti-trap function, which tries to detect such a pinching case on a monitoring of a state variable of the locking device and the closing movement regardless of the driver's request by the operating switch 8th cancel. Furthermore, reversing is often provided, which reverses the movement in the direction of the closed position into a movement in the direction of the open position, in order to release the clamped object or the clamped body part.

In the control unit 7 (or externally) is a current measuring unit 9 provided as a state quantity, which represents a force to be applied for the closing movement, that of the servomotor 5 recorded motor current I to measure. The motor current I depends directly on the engine load, which in turn depends directly on the applied force for the closing movement. In other words, the motor current I increases with increasing engine load and drops with decreasing engine load. Therefore, the detection of the motor current I is in principle suitable to determine a load increase.

The current detection is carried out by known methods, for example by means of a measuring resistor (not shown) which is in one of the control units 7 and the servomotor 5 connecting connecting lines is provided. The voltage drop across the measuring resistor becomes an indication of the current in the servomotor 5 used. Of course, other known methods for current detection are possible.

The method for detecting a trapping case in the power window system of 1 will now be in conjunction with the flow chart of 2 explained in more detail.

After the start of the method, it is checked in a step S1 whether the operating switch 8th has been pressed to the windowpane 2 to move in a movement in the direction of the closed position. If this is the case (alternative: yes), then in a step S2, first a certain period of time is waited, after which it is ensured that a start-up current pulse has decayed during a start-up phase. The starting current pulse represents an increased motor current I, which is used to accelerate the servomotor 5 and to overcome the stiction of the windowpane 2 in the window frame 3 as well as the static friction in mechanics 6 and in the servomotor 5 necessary is.

Upon completion of the waiting of the step S2 during this start-up phase, a continuous current detection by means of the current detector 9 performed in step S3. In current detection, motor currents are detected and motor current gradient motor current gradients are determined by determining a difference between a current value of the motor current and a previous value of the motor current regardless of the number of elapsed cycles between the current values. To ensure the robustness of the gradient is z. For example, the motor current gradient is determined as the difference of a first motor current average of a number of values of the motor current I within a current first time window and a second motor current average of a number of values of the motor current I within a preceding (preferably not overlapping with the first time window) second time window to influences due to measurement tolerances, noise and mechanically short-term increases in resistance of the window pane 2 in the window frame 3 to reduce.

Furthermore, alternatively, a motor current gradient can also be robustly determined by averaging a plurality of current differences, determined in succession in a time window, from two values of the motor current I detected at different times. Since historical data is necessary in this way for determining the motor current gradient, a change in the motor current gradient to a preceding motor current gradient is determined to be delayed. In step S3, it is also provided to store a history of the values of the motor currents I and the values of the motor current gradients.

In 3 is an example of the time course of the motor current I during a movement of the window 2 shown in the direction of the closed position. It can be seen a relatively constant course of the motor current I up to a pinching time t _E , from which the motor current gradient increases. The rising motor current gradient, however, can only be detected at a detection time t _D due to the way in which the motor current gradient is determined. If the motor current gradient detected at the detection time t _D exceeds a predetermined gradient threshold, an increase in the motor current I is detected and a recalculation to the time of the pinching time t _{E takes place} , ie a recalculation of the time at which the motor current gradient has changed. This is done in step S4.

In step S4, the current motor current gradient information provided by the process of step S3 is compared with a motor current gradient at a previous time window. Between the current motor current gradient and the motor current gradient at the preceding time or window, a predetermined fixed or variable time period may be provided. Is the instantaneous motor current gradient with respect to the motor current gradient at the previous time or time window increased by more than a predetermined gradient threshold, a possible Einklemmfall is detected (alternative: Yes). If this is not the case, the method returns to step S3 (alternative: no). The size of the time windows and their temporal distance to each other

If a possible trapping case is detected, the trapping time A is determined by recalculation in a step S5. This can be done, for example, by determining an intersection of the straight line defined by the motor current gradient at the detection time t _D , the value of the motor current at the detection time t _D and the detection time t _D , and the current through the motor current gradient. Time t _R , the value of the motor current at the reference time t _R and the reference time t _R defined lines are performed. The reference time t _R is a time which is a fixed period of time before the detection time t _D , wherein the fixed time period is selected so that the time is safe before the Einklemm-time t _{E of} a possible Einklemmfalls. The determination of the pinching time t _E by the calculation of the timing at which the above straight lines intersect is well known in the art, and therefore will not be discussed in detail herein.

In step S6, the motor current I which has occurred at this point in time is determined from the pinpointing time t _E determined in step S5 from the values of the motor current I stored in step S3. Depending on the motor current I at the pinching time t _E , a motor current threshold value S is defined, which is determined, for example, by applying the value of the motor current I to the pinching time t _E with an absolute or relative motor current offset MO. If the current motor current I exceeds the motor current threshold value S (step S7) in the further course after the recognition of a possible pinching case, then an actual jamming case is detected (alternative: yes). This can in step S8 to an immediate interruption of the movement of the window 2 in the direction of the closed position and optionally lead to a reversal of the movement in the direction of the open position. Alternatively or additionally, the trapping case can be signaled acoustically, optically and / or haptically. If the current motor current does not exceed the motor current threshold value S (alternative: No), then the system jumps back to step S3.

In this way it is possible, regardless of the movement of the windowpane 2 currently (from the position of the windowpane 2 dependent) load to define a motor current threshold S, with the aid of a pinching case can be detected.

• – Ändert sich der Motorstrom-Gradient erneut in negativer Richtung um einen bestimmten weiteren vorgegebenen Gradienten-Schwellenwert, d. h. der in Schritt S3 ermittelte Motorstrom-Gradient wird flacher oder sogar negativ, so wird der Motorstrom-Schwellenwert S gelöscht und erst – wie oben beschrieben- bei einer erneuten Änderung des Motorstrom-Gradienten in positiver Richtung um mehr als den Gradienten-Schwellenwert erneut in oben beschriebener Weise ermittelt.
• – Der Motorstrom-Schwellenwert S kann auch gelöscht werden, wenn der Wert des Motorstroms innerhalb eines vorgegebenen Zeitfensters ab dem Einklemm-Zeitpunkt A den Motorstrom-Schwellenwert S nicht erreicht hat.
• – Weiterhin kann vorgesehen sein, abhängig von dem ermittelten Einklemm-Zeitpunkt t_E eines möglichen Einklemmfalls einen ersten Gradientenschwelle GS1 und/oder eine zweite Gradientenschwelle GS2 zu definieren. Die Gradientenschwellen GS1, GS2 definieren gemeinsam mit dem Wert des Motorstroms zu dem Einklemm-Zeitpunkt t_E sowie dem Einklemm-Zeitpunkt t_E Geraden, die zu jedem Zeitpunkt nach dem Einklemm-Zeitpunkt t_E eine obere und untere Grenze für den Motorstrom I vorgeben. Innerhalb des durch die obere und untere Grenze für den Motorstrom I definierten Motorstrombereichs müssen die Werte des Motorstroms nach dem Einklemm-Zeitpunkt t_E verlaufen, wenn ein Einklemmfall vorliegt. Verlässt der Wert des Motorstroms I den jeweiligen zu dem bestimmten Zeitpunkt vorliegenden Motorstrombereich, so wird der Motorstrom-Schwellenwert S gelöscht und es wird zu Schritt S3 zurückgesprungen.

Once the motor current threshold value S has been determined, it remains valid as long as no jamming case is detected in step S7 or one or more of the following conditions exist which lead to the deletion of the motor current threshold value S:

• If the motor current gradient changes again in the negative direction by a certain further predetermined gradient threshold value, ie the motor current gradient ascertained in step S3 becomes flatter or even negative, the motor current threshold value S is cleared and, as described above, in a new change of the motor current gradient in the positive direction by more than the gradient threshold again determined in the manner described above.
• The motor current threshold value S can also be erased if the value of the motor current has not reached the motor current threshold value S within a predetermined time window from the pinch-in point A.
• Furthermore, it can be provided to define a first gradient threshold GS1 and / or a second gradient threshold GS2 depending on the determined pinching time t _{E of} a possible trapping case. The gradient thresholds GS1, GS2, together with the value of the motor current at the pinching time t _E and the pinching time t _E , define straight lines which specify an upper and lower limit for the motor current I at each time after the pinching time t _E. Within the motor current range defined by the upper and lower limits for the motor current I, the values of the motor current must pass after the pinching time point t _E when there is a pinching-in case. If the value of the motor current I leaves the respective motor current range present at the given instant, the motor current threshold value S is cleared and the method returns to step S3.

The motor current range is in 4 shown in more detail. It can be seen that in the present case the course of the motor current I runs within the area of the triangle until the value of the motor current I reaches the motor current threshold value S. Then a trapping case is detected. However, if the motor current I increases faster starting from the pinching time t _E than predetermined with the aid of the first gradient threshold GS 1 or slower than with the aid of the second gradient threshold GS 2, the detection of a trapping case is aborted and the motor current threshold value S cleared. In this case, the procedure for detecting a trapping case is restarted. In other words, it is detected whether the course of the motor current I by the of the Einklemm-time t _E outgoing straight line with the slope of the first gradient threshold GS1 defined current values exceeds or falls below the outgoing by the pinching time A straight line with the slope of the second gradient threshold GS1. If this is not the case and exceeds the value of the motor current I at a certain time t _S of the motor current threshold value S, a jamming situation is determined at this time.

The method described above can be performed in parallel several times. Ie. An entrapment time t _E is always determined when a defined change in the motor current gradient occurs over two consecutive time windows that is greater than a specific, predetermined gradient threshold value. This can be z. B. also within the in 4 be illustrated, so that multiple motor current thresholds S and / or gradient thresholds GS1, GS2 can be defined parallel to each other.

If the course of the current values before reaching the motor current threshold value S intersects the straight line defined by the second gradient threshold GS2, then external influences on the window regulator system can occur 1 getting closed. For example, such external influences may be caused due to an uneven road surface over which the vehicle travels. In such a case, when determining the motor current threshold value S, different motor current offsets MO can be predefined on the basis of the motor current I _E prevailing at the pinching time t _E. After the first cutting of the straight line defined by the second gradient threshold GS2, for example, the motor current offset MO can be increased, for. B. be doubled. Generally, the increase of the motor current offset MO may be by an absolute offset amount or relative. In this way, starting from a value of the motor current I _E at a next determined pinching time t _E for a possible trapping case, the motor current threshold S as current value I _E at the next determined pinching time t _E plus the increased motor current offset MO be determined. This is for example in 5 shown.

In 5 one recognizes a case in which the vehicle drives, for example, over an uneven road and thus fluctuations in the load in the servomotor 5 but do not cause the motor current threshold S to be exceeded. Rather, after detecting the state of driving over an uneven road surface, the motor current offset MO for determining the motor current threshold value S is increased. A reduction in the motor current offset MO can take place, for example, if no pinching time t _{E has} been detected for a possible jamming case for a certain period of time, ie no significant, gradient gradient exceeding, positive change in the motor current gradient has occurred. Further, the motor current offset MO for detecting the motor current threshold value S may be reset after detecting a pinching case to a reference value which may be initially assumed.

In principle, it is proposed to define a motor current range based on a value of the motor current I _E at a pinching time t _E , which is determined on the basis of a result of a threshold comparison of a gradient change of the course of the current value. If an upper limit defined by the motor current range is exceeded by the value of the motor current, a trapping case is detected. If the motor current range is exceeded at its lateral limits before the upper limit of the motor current range is exceeded, then the previously defined motor current range is deleted and the detection of a trapping case is restarted, ie a trapping time is again determined as a function of the result of the threshold comparison of the gradient change of the motor current , The lateral limits of the motor current range defined by the gradient thresholds GS1, GS2 are assumed to be linear in the above-described examples, but these may also include other characteristics, eg. B. by curved gradients or curves. Furthermore, the course of the motor current threshold value S can also be defined by any other function instead of by a straight line.

According to an alternative embodiment it can be provided that the previously defined motor current range is only cleared when leaving at one or both lateral limits (in the direction of the time axis, ie at too high or too low average motor current gradient) when the motor current I the upper limit is not up to a detection end time t _DE (see 4 ) defined by the upper limit and the second gradient threshold GS2. Ie. the detection end time t _DE is defined as the time at which the straight line defined by the second gradient threshold exceeds the motor current threshold value S. If the gradient threshold value is exceeded by the motor current gradient before reaching the detection end time point, a new motor current range is defined in parallel to the already defined motor current range and maintained until the relevant detection end time point is reached.

In the above example, the detection of the pinching case is based on the course of the value of the Motor current in the servomotor 5 been explained. As an alternative to the motor current, other state variables indicative of the respective load torque of the motor can likewise be used for the above method. For example, the load of the servomotor 5 with a corresponding load receiver directly to the servomotor 5 be measured.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 4442171 [0007]

Claims (12)

Method for detecting a trapping case of a closing device, comprising the following steps: - detecting a state variable (I) which has a force for moving a closing element ( 2 indicating in the closing direction; - Determining a temporal gradient of the state variable (I) as a state variable gradient; Determining a temporal change of the state variable gradient; - determining a state quantity threshold value (S) if the change of the state variable gradient exceeds a predetermined gradient threshold value; Detecting the pinching case when the state quantity (I) exceeds the state quantity threshold value (S) after the state variable threshold value (S) has been determined. The method of claim 1, wherein the state quantity gradients are determined by averaging a plurality of differences between successively detected state quantities (I) or by determining a difference between two average values of a plurality of state variables (I) in successive time slots spaced apart by a certain period of time becomes. The method of claim 1 or 2, wherein the setting of the state variable threshold value (S) is performed by a pinching time (t _E ) is determined as the time of a possible Einklemmfalls when exceeding the predetermined gradient threshold by the change of the state variable gradient in which the state quantity threshold value (S) is determined as a function of the value of the state variable (I) that was present at the pinching time point (t _E ). The method of claim 3, wherein the pinching time (t _E ) is determined as a time of change of the state variable gradient by a retroactive calculation, wherein the retrograde calculation is a calculation of an intersection of a first straight line passing through the state quantity gradient at a time before entering the defined increase of the state quantity gradient is defined, and a second straight line, which is defined by the current state variable gradient, wherein the intersection of the pinching time (t _E ) indicates. A method according to claim 3 or 4, wherein determining the state quantity threshold (S) by adding an absolute or relative state quantity offset (MO) to the value of the state quantity (I) that existed at the pinch point (t _E ) , is carried out. Method according to one of claims 3 to 5, wherein the state quantity threshold value (S) is deleted and the detection of the pinching case is not performed if the state quantity threshold value (S) is not exceeded within a time window after the pinching time point (t _E ) becomes. Method according to one of claims 3 to 6, wherein the state variable threshold value (S) is deleted and the detection of the Einklemmfalls is not performed when the since the pinching time (t _E ) average slope of the state variable (I) leaves a predetermined gradient range , The method of claim 7, wherein the state quantity threshold value (S) is performed by adding an absolute or relative state quantity offset (MO) to the value of the state quantity (I) present at the pinching time point (t _E ), wherein the state variable offset (MO) is increased if the average slope of the state variable since the pinch-in point in time (t _E ) falls below a lower gradient threshold defined by the predetermined gradient range. Method according to one of claims 1 to 8, wherein the state variable (I) a motor current of a drive motor for driving the closing element ( 2 ) corresponds. Device for detecting a trapping case of a closing device, which is designed to detect a state quantity (I) which has a force for moving a closing element ( 2 indicating in the closing direction; To determine a temporal gradient of the state variable (I) as a state variable gradient; To determine a temporal change of the state variable gradient; - set a state quantity threshold (S) if the change in the state quantity gradient exceeds a predetermined gradient threshold; To detect the pinching case when the state quantity (I) exceeds the state quantity threshold value (S) after the state variable threshold value (S) has been established. Use of the device according to claim 10 for a window lift system of a motor vehicle. A computer program product containing a computer program which, when executed on a data processing unit, performs a method according to any one of claims 1 to 8.

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