Method for controlling an electric motor for a belt buckle of a safety belt device of a motor vehicle

Abstract

The present invention relates to a method for controlling an electric motor (6) for a belt buckle of a safety belt device of a motor vehicle, comprising the following steps in the following order: -activation of the electric motor (6) to extend the belt buckle from a target position into a presentation position when an open vehicle door and / or an occupant sitting on a vehicle seat is detected by a suitable first sensor device (3), -activation of the electric motor (6) for retracting the belt buckle from the presentation position to the desired position when a suitable second sensor device (4) detects the locking of a belt tongue locked in the belt buckle or no locking of the belt tongue in the belt buckle within a predetermined period of time, -activation of the electric motor (6) to retract the belt buckle from the target position into a tightened position when a suitable third sensor device (5) detects either a critical pre-accident driving situation or an early phase of an unavoidable accident situation, whereby -the electric motor (6) is activated to retract the belt buckle from the desired position into a retracted comfort position when an open vehicle door and / or an occupant entering the vehicle is detected by the first sensor device (3).

Description

The invention relates to a method for controlling an electric motor for a belt buckle of a seat belt device of a motor vehicle.Buckles in seat belt devices may be provided with drive means for various reasons. For example, for comfort reasons it may be desirable to move the belt buckle from an ergonomically unfavorable desired position into a pre-sting position that is favorable for grip, in order to facilitate the buckling for the occupant. Furthermore, it may be expedient to retract the belt buckle abruptly from the desired position in an incident phase or an early phase of the accident for pulling out existing belt slack from the seat belt and to tighten the seat belt. The setpoint position is the position in which the belt buckle is located when the occupant is tightened and no particular driving situation occurs, or when no belt tongue is locked in the belt buckle and no occupant is seated on the associated vehicle seat.Both functions can ideally be realized with the aid of an electric motor, wherein the belt buckle is then either extended or retracted from a desired position depending on the direction of rotation of the electric motor.The document DE 10 2007 015 187 A1 discloses a vehicle occupant restraint system in which a belt buckle is moved into different positions by means of a positioning mechanism depending on the situation, wherein the positions can be adapted by the vehicle occupant.Furthermore, the publication US 2004 / 0 217 583 A1 discloses a cam follower with a locking mechanism which is designed as a force limiter.It is an object of the invention to provide a method for controlling the electric motor, with which method the power of the electric motor can be optimally utilized both for the comfort function and for the tensioning function.According to claim 1, a method for controlling an electric motor for a belt buckle of a seat belt device of a motor vehicle is proposed for achieving the object, having the following steps in the following sequence:activating the electric motor for extending the belt buckle into a present position when an occupant sitting on a vehicle seat is detected via a suitable first sensor device,activating the electric motor for retracting the belt buckle from the present position into a desired position if the locking of a belt tongue locked in the belt buckle or no locking of the belt tongue in the belt buckle is detected within a predetermined time period via a suitable second sensor device,activating the electric motor for retracting the belt buckle from the desired position into a tightened position if either a critical incident driving situation or an early phase of an unavoidable accident situation is detected via a suitable third sensor device and the belt buckle is in the desired position, wherein the electric motor is activated before the activation for extending the belt buckle into the present position for retracting the belt buckle from the desired position into a retracted comfort position if an occupant entering via the first sensor device is detected and the belt buckle is in the desired position.The solution according to the invention makes it possible to make optimum use of the power of the electric motor, since the belt buckle is only retracted into the tensioning position when the preceding comfort function has been carried out completely to the end, and the belt buckle is in the desired position. In any case, this makes it possible to prevent the electric motor from carrying out the tensioning movement incorrectly even when the belt buckle is still in the present position, and the tensioning length would thereby be shortened by the extension path of the belt buckle into the present position. Furthermore, the proposed solution prevents the electric motor from being activated for carrying out the tensioning movement even if no belt tongue is locked in the belt buckle. In addition, the solution according to the invention prevents the belt buckle from remaining stationary in the present position when the belt tongue is not locked, i.e. when the fastening process is not completed, and thus obstructs other occupants during a movement over the free seat surface.By activating the electric motor for retracting the belt buckle from the desired position into a retracted comfort position, when an open vehicle door and / or an occupant entering the seat are detected via the first sensor device, the belt buckle is retracted into a deeper comfort position, by which the entering of the occupants in particular into the rear seats is facilitated. The belt buckle is preferably retracted to such an extent that it does not project beyond the seat surface. As a result, the occupants can slide over the seat surface during boarding without being hindered by the belt buckle otherwise protruding over the seat surface in the desired position. The belt buckle is then only extended into the present position when the occupant or all occupants have assumed their seated positions.It is also proposed that the electric motor, after locking or unlocking the belt tongue in the belt buckle, is only activated after a predetermined time period of 1-2 seconds for retracting the belt buckle from the present position into the desired position. The proposed time period until the electric motor is activated intentionally creates a time period in which the occupant can retract his hand after locking or unlocking the belt tongue before the belt buckle is retracted. Thereby, possible injuries to the occupant or hindrance of the retracting movement of the buckle by generous clothes on the arm of the occupant can be avoided.According to a further preferred development of the proposed method, the following method steps are proposed which follow the method steps of claim 1 or 2:activating the electric motor for extending the belt buckle from the desired position into the present position when a drive device of the motor vehicle is deactivated,activating the electric motor for retracting the belt buckle from the present position into the target position if unlocking of the belt tongue and / or unlocking of the belt tongue is sensed within a predetermined time period via the second sensor device.The proposed method steps cause the belt buckle to be moved for unbuckling the seat belt into a present position in which the belt buckle and in particular the pushbutton for unlocking the belt tongue can be reached more easily. Further, after the lowering, the buckle is retracted even if the tongue is not unlocked after a predetermined period of time and the occupant remains fastened. Thus, the belt buckle is in any case retracted from the present position into the desired position after the extension.It is further proposed that the electric motor is not activated and the belt buckle is not extended from the desired position into the present position when the belt tongue is manually unlocked or locked by an occupant seated on the vehicle seat in the desired position of the belt buckle. The occupant can practically bridge the process of extending the belt buckle by manually locking or unlocking the belt tongue, if he can locate and reach the belt buckle even without extending into the present position, whereby the locking and unbuckling process can be correspondingly simplified and carried out more quickly.According to a further preferred development of the proposed method, it is proposed that the activation of the electric motor is interrupted when a current consumption of the electric motor is sensed which exceeds a predefined limit value. Due to the excessive current consumption of the electric motor, it is possible to indirectly infer a malfunction of the electric motor, the drive device or the movable belt buckle, which may be caused, for example, by a clamping of the belt buckle or a clamped threaded sleeve or the like. This disturbance makes the belt buckle correspondingly difficult to extend or retract, which then leads to increased current consumption. In order that the electric motor, the drive device or the belt buckle is not damaged in this case, the activation of the electric motor is interrupted for the sake of caution.Furthermore, it is proposed in this case that the electric motor is activated for a short time after the interruption of the activation to a rotational movement opposite to the preceding rotational direction before the interrupted rotational movement is continued. The proposed temporary reversal of the direction of rotation of the electric motor makes it possible to eliminate the fault under favourable circumstances, for example by releasing the clamped threaded sleeve or by cancelling any other blockage of the system.It is further proposed that the current consumption of the electric motor is sensed during the continuation of the interrupted rotational movement and the activation of the electric motor is repeatedly interrupted if the current consumption exceeds a predefined limit value, wherein the activation of the electric motor again takes place according to claims 1 to 3 if the current consumption of the electric motor during the repeated activation lies below the predefined limit value. Alternatively, the electric motor is deactivated and a warning message for requesting a workshop visit is displayed on a display if the power consumption of the electric motor is not below the predetermined limit value even during a predetermined number of repetition processes.The invention is explained below with reference to preferred embodiments with reference to the attached figures. The following shows: FIG. 1 : shows a drive device with an electric motor for a belt buckle; FIG. 2 : shows a schematic illustration of a control unit with the electric motor and three different sensor devices; and FIG. 3 : shows a schematic illustration of the method according to the invention with the individual method steps.FIG. 1 shows a drive device 2 for a belt buckle, not shown, of a seat belt device for a motor vehicle having an electric motor 6 and a control unit 1. The drive device 2 comprises a threaded spindle 7 which can be driven in rotation by the electric motor 6 and the rotational movement of which is converted into a linear movement via a threaded sleeve 8 which is guided in a rotationally fixed, linear manner. The threaded sleeve 8 is connected to the belt buckle via a pull cable, not shown, which is designed and guided in such a way that, in addition to the pull forces, it can also transmit compressive forces for extending the belt buckle into a present position. When the electric motor 6 is activated, the threaded sleeve 8 is then linearly displaced in the direction of the electric motor 6 or away from the electric motor 6 depending on the direction of rotation of the electric motor 6, and the belt buckle is either extended from the desired position into a present position or retracted into a tightened position. The tensioning position is not to be understood as a fixed predefined position, but instead a position of the belt buckle, which results from the equilibrium of forces of the tensioning electric motor and the counterforce exerted via the seat belt. The counterforce exerted by the seat belt is dependent on the condition of the clothing of the occupant restrained by the seat belt, the friction present in the seat belt device and the system as such. The present position, on the other hand, can be regarded as a position of the belt buckle independent of the seat belt at least during the fastening process, since the belt buckle is moved into the present position without a belt tongue being locked in the belt buckle. Since no significant force is exerted by the belt tongue on the belt buckle even when the seat belt is unbuckled, the present position of the belt buckle can also be regarded in this case as independent of the seat belt system. However, the control of the extension and retraction movement of the belt buckle can be improved by a suitable sensor device which senses the position of the belt buckle in the present position and / or in the reversible taut position. In this case, the increasing current consumption of the electric motor 6 when reaching the present position or the taut position can also be used as a representative signal.FIG. 2 shows the schematically illustrated control unit 1 which is connected by signal technology to the electric motor 6. The control unit 1 is further connected by signal technology to a first sensor device 3, a second sensor device 4, a third sensor device 5 and a fourth sensor device 9. The first sensor device 3 is formed, for example, by a sensor sensing the opening state of a door or by a sensor detecting an occupant seated on a vehicle seat and serves to sense a state or an action by which a subsequent belt-fastening operation can be concluded(s). The first sensor device 3 can be formed by a door sensor, an occupant detection or also by a belt strap extension sensor; it is only important that the action triggering the signal is directly related to the occupant getting in or a subsequent belting-in process and enables a conclusion to be drawn about an imminent locking process of the belt tongue. The second sensor device 4 is formed, for example, by a belt buckle sensor which senses the locking of a belt tongue locked in the belt buckle. The third sensor device 3 serves to sense driving state-specific characteristic variables, such as the longitudinal acceleration of the motor vehicle, which make it possible to draw conclusions about a critical driving situation or an accident that cannot be avoided. For this purpose, the sensor system can also be used as third sensor device 3, which delivers the signals to a driving dynamics controller or to a slip control system. The fourth sensor device 9 serves to sense the deactivation of the drive device of the motor vehicle. This can be, for example, a sensor assigned to the ignition lock or the start stop button. Alternatively, the signal of the ignition lock or the start stop button itself can also be used.FIG. 3 describes the sequence of the proposed method with reference to boxes with symbols. The boxes represent positions of the belt buckle, movements of the belt buckle caused by actuation of the electric motor 6 or other actions such as displaying warning messages. The boxes are formed in the method sequence by program-related states or program sequences stored in a memory unit of the control unit 1, which are called up and executed in the provided sequence and by sensing corresponding characteristic variables by the sensor devices 3, 4, 5 and 9.First, the fastening process can be seen with reference to boxes A to E. In the initial position A, the belt buckle is in the desired position. This is the case, for example, when the vehicle door is closed and no occupant is seated on the vehicle seat. If the opening of the vehicle door or an occupant seated in the vehicle seat is sensed by means of the first sensor device 3 in this position, the electric motor 6 is activated and the belt buckle is moved in the direction of the present position. This movement sequence is symbolized by box B. In the event that during the movement of the belt buckle into the present position, a current consumption exceeding a predetermined limit value of the current consumption is sensed, the electric motor 6 is deactivated and a corresponding warning message is displayed on a display of the motor vehicle. This process is indicated by box N in the illustration. If no excessive current consumption is sensed, the belt buckle is extended until the present position is reached, which is represented by the box C. The belt buckle is easier to find and reach in the present position for the occupant, so that it can be easily fastened. If the occupant in this position of the belt buckle inserts the belt tongue into the belt buckle until the latter is locked, the locked state is detected via a second sensor device 4 and the electric motor 6 is activated repeatedly in order to retract the belt buckle from the present position into the desired position. This action of retracting the buckle is represented by box D. If the second sensor device 4 does not sense a locking of the belt tongue after a predetermined time period of, for example, 2 minutes, as is represented by the box K, the belt buckle is also retracted into the desired position after this time period. In the event that during the retraction of the belt buckle a current consumption exceeding a predetermined value of the current consumption is again sensed, the process of retracting the belt buckle into the desired position is interrupted and a corresponding warning signal is displayed on a display, which is represented by the box N. The reaching of the desired position of the belt buckle is finally represented in the illustration by the box E. This position corresponds to the position of the buckle when the occupant is tightened and the occupant starts and starts the motor vehicle. If, in this position of the belt buckle, a critical accident situation is subsequently sensed via a third sensor device 5, which situation does not necessarily have to lead to an accident, the belt buckle is pulled back from the desired position into a tightened position by activation of the electric motor 6. This movement sequence is characterized by the box PP1. If the current consumption of the electric motor 6 exceeds a predetermined limit value during the retraction of the belt buckle into the tensioning position, the movement process is interrupted and, after the box N, a corresponding warning message is displayed on a display. By retracting the belt buckle, the occupant is warned and additionally existing belt slacks are pulled out of the seat belt. If the critical accident situation changes over to an accident which cannot be avoided, the method procedure changes directly from the box PP1 to the box PP2. The belt buckle can be pulled back further into a second tensioning position for pulling out further belt slacks. In the event that the critical driving situation is ended without going over to an accident, the belt buckle is moved back from the tensioning position back into the desired position according to the movement sequence of the box D until the desired position corresponding to the box E is reached again. If an accident which cannot be avoided is sensed in the desired position corresponding to the box E, the belt buckle is likewise pulled back from the desired position into a tensioning position, which is represented by the box PP2. The airbag is then triggered, so that the motor vehicle must then necessarily be brought into a workshop in which the belt buckle with the drive device 2, the electric motor 6 and the control unit 1 must also be checked for further usability and replaced if necessary. This process is indicated by box M.The reverse unbuckling operation can be seen with reference to boxes E to I. First, the occupant is tightened and the buckle is in the target position (position box E). If, in this position, the ignition key is pulled out of the ignition lock or the drive device of the motor vehicle is otherwise switched off, this process is sensed by the fourth sensor device 9 and the unbuckling process is initiated. Alternatively, the unbuckling process can also be initiated or prepared when the speed of the motor vehicle is below a predefined limit value of, for example, 20 km / h and the occupant actuates a further button which directly initiates the unbuckling process or serves to prepare the exit from the motor vehicle or the actuation of which is directly associated with the exit. This can be, for example, a start stop button of the motor vehicle. The belt buckle is then extended from the desired position into the present position by activating the electric motor 6 according to the box F after one of the conditions mentioned. If an increased current consumption is sensed during this process, the extension of the belt buckle into the present position is interrupted and a corresponding warning message is displayed again on a display, which is represented by the box N. In the event that the current consumption lies within the predefined limit values and the electric motor 6 or the drive device 2 are functional, the belt buckle is extended until the present position is reached. This position is represented by the box G. After reaching the present position, the belt buckle is pulled back into the desired position by detecting the unlocking of the belt tongue after the movement sequence indicated by the box H. The same operation of retracting the buckle after the box H is initiated even if the tongue is not unlocked after a predetermined time period of, for example, 2 minutes, as illustrated by the connection of the box G to the box H via the box L. If, during the retraction of the belt buckle into the desired position, a current consumption exceeding a predetermined value of the current consumption is sensed, the movement process is interrupted and, after the box N, a warning message is displayed again on a display. If this is not the case, the belt buckle is properly retracted into the desired position until it is reached, which is indicated by the box I. If the vehicle door is subsequently opened, the method sequence is set via the state "the occupant gets off", which is identified by the box X, back to the initial state, which is identified by the box A. If the occupant instead actuates a corresponding activation button which initiates a repeated belt-fastening operation, the method sequence is set back to the box B and the belt buckle is extended again into the present position.Both the process sequence of unbuckling from the boxes E to I and the process sequence of unbuckling from the boxes A to E can be bridged by the occupant immediately unbuckling after unbuckling in the position of the box E of the process sequence by actuating an actuating button releasing the locking of the belt buckle or by locking the belt tongue in the position of the process sequence according to the box I. Bridging of the process flow is illustrated by the direct connection of box I to box E and by the direct connection of box E to box A. In both cases, the belt buckle is in the desired position both before and after the belt buckle. The bending and unbuckling process is thus carried out without the belt buckle being extended into the present position, in accordance with a conventional belt system, during which the occupant is still seated on the vehicle seat.In the event that the movement sequences of boxes B, D, PP1, F or H have been interrupted due to an increased current consumption and the warning message has been displayed after box N, electric motor 6 is first rotated back slightly relative to the preceding direction of rotation after a predefined time period of, for example, 5 seconds, i.e., actuated in the opposite direction, and is then activated again in the original direction of the movement sequences of the respective box B, D, PP1, F or H, which have been interrupted. This process is represented by box O. If the electric motor 6 is then actuated with a current consumption lying below the predefined limit value, which is represented by the box Y, the interrupted movement sequence is completed and the method steps are then continued according to the provided sequence at the location of the originally interrupted method sequence.If this process does not lead to the electric motor 6 being able to perform the intended movement sequence with a current consumption below the intended limit value, the process is repeated several times. If, after a predetermined number of tests (e.g. 10 tests), no actuation of the electric motor 6 with a current consumption lying below the predetermined limit value is possible, a second warning message is displayed, which prompts the occupant to visit a workshop. This process is represented by box S.The boxes A, E and I correspond to the state in which the belt buckle is in the desired position, respectively, wherein the belt tongue is locked in the belt buckle in the state of the box E and is not locked in the states of the boxes A and I. The cases C and G correspond to the states in which the buckle is extended to the present position, the tongue is not yet locked in the buckle in the state of the case C and locked in the buckle in the state of the case G. Furthermore, the method sequence can basically be divided into three different blocks. The first block of the method sequence is the method steps of boxes A to E, which represent the fastening process using the presenter function. The second block of the method sequence is the method steps of boxes E to I, which likewise represent the unbuckling process using the presenter function. The third block of the process sequence is formed by the tightening functions of boxes PP1 and PP2.In addition to the described sensor devices 3, 4, 5 and 9, additional sensor devices can be provided for sensing the position of the belt buckle. These sensors can sense either directly the position of the belt buckle or a part firmly connected to it. Alternatively, the position of the belt buckle can also be derived indirectly from the position of the threaded sleeve 8 or the rotational angle position or the rotations of the electric motor 6. Since the threaded sleeve 8 can in principle only be displaced between two stops, it would be possible to sense the position of the respective end position of the threaded sleeve 8 by sensors assigned to the stops.

Claims

Method for actuating an electric motor (6) for a belt buckle of a seat belt device of a motor vehicle, having the following steps in the following sequence: - activation of the electric motor (6) for extending the belt buckle into a present position if an occupant sitting on a vehicle seat is detected via a suitable first sensor device (3), - activation of the electric motor (6) for retracting the belt buckle from the present position into a desired position if locking of a belt tongue locked in the belt buckle or no locking of the belt tongue in the belt buckle is detected within a predetermined period of time via a suitable second sensor device (4), - activation of the electric motor (6) for retracting the belt buckle from the desired position into a taut position, if either a critical accident situation or an early phase of an unavoidable accident situation is detected via a suitable third sensor device (5) and the belt buckle is in the desired position, characterized in that - the electric motor (6) is activated before the activation for extending the belt buckle into the present position for retracting the belt buckle from the desired position into a retracted comfort position if an occupant entering via the first sensor device (3) is detected and the belt buckle is in the desired position.Method according to Claim 1, characterized in that, after locking or unlocking the belt tongue in the belt buckle, the electric motor (6) is only activated after a predefined time period of 1-2 seconds for retracting the belt buckle from the present position into the desired position.Method, characterized bythe following steps following the method steps of claim 1 or 2: - activation of the electric motor (6) for extending the belt buckle from the desired position into the present position, if a drive device of the motor vehicle is deactivated or if the speed of the motor vehicle is below a predetermined limit value and the occupant actuates a further button which directly initiates the unbuckling process or serves for preparing the exit from the motor vehicle or the actuation of which is directly associated with the exit, and - activation of the electric motor (6) for retracting the belt buckle from the present position into the desired position, if unlocking of the belt tongue and / or no unlocking of the belt tongue is sensed within a predetermined time period via the second sensor device (4).Method according to one of the preceding claims, characterized in that - the electric motor (6) is not activated and the belt buckle is not extended from the desired position into the present position when the belt tongue is manually unlocked or locked by an occupant seated on the vehicle seat in the desired position of the belt buckle.Method according to one of the preceding claims, characterized in that the activation of the electric motor (6) is interrupted if a current consumption of the electric motor (6) is sensed which exceeds a predefined limit value.Method according to Claim 5, characterized in that - after the interruption of the activation, the electric motor (6) is activated for a short time to a rotary movement which is opposite to the preceding direction of rotation, before the interrupted rotary movement is continued.Method according to Claim 6, characterized in that - the current consumption of the electric motor (6) is sensed during the continuation of the interrupted rotational movement and the activation of the electric motor (6) is repeatedly interrupted if the current consumption exceeds a predefined limit value.Method according to Claim 7, characterized in that - the activation of the electric motor (6) takes place again according to Claims 1 to 3 if the current consumption of the electric motor (6) during the repeated activation is below the predefined limit value.Method according to Claim 7, characterized in that - the electric motor (6) is deactivated and a warning message for requesting a workshop visit is displayed on a display if the power consumption of the electric motor (6) is not below the predetermined limit value even during a predetermined number of repetition processes.

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