METHOD FOR DETECTING MISUSE OF A SAFETY BELT AND SAFETY BELT SYSTEM

Abstract

In a method for identifying misuse of a seat belt in a vehicle, vehicle data are detected and, based on said data, a plausibility check is performed for determining whether the seat belt is fastened as intended. Signals of at least one belt buckle sensor and of at least one webbing extension sensor are detected and a plausibility check for misuse is performed by taking the time course of the signals and/or the point in time of input of the signals into account so as to make a comparison with stored reference data. A seat belt system in a vehicle for carrying out said method comprises at least one belt buckle sensor and at least one webbing extension sensor as well as at least one seat occupation sensor, one door sensor, one vehicle acceleration sensor and/or one vehicle speedometer as well as a control unit in which the signals of the sensors are stored and evaluated.

Claims

1. A method of identifying misuse of a seat belt in a vehicle in which vehicle data are detected and by said data a plausibility check is performed for determining whether the seat belt is fastened as intended, wherein signals of at least one belt buckle sensor (20) and at least one webbing extension sensor (24) are detected and a plausibility check for misuse is performed by considering the time course of the signals and/or the point in time of input of the signals so as to make a comparison with stored reference data.

2. The method according to claim 1, wherein the vehicle data comprise: signals of at least one seat occupation sensor (28) and signals of at least one door sensor (14) and the vehicle acceleration and/or the vehicle speed.

3. The method according to claim 1, wherein the plausibility check of whether the seat belt is fastened as intended comprises checking whether a plug-in tongue of the seat belt is correctly inserted in an assigned belt buckle (18) and whether the webbing is guided as intended.

4. The method according to claim 1, wherein the stored sensor signals are assigned to events.

5. The method according to claim 4, wherein based on the point in time of signal input a time order of events is established and/or time intervals between the events are determined.

6. The method according to claim 4, wherein values supplied by sensors are entered into the plausibility check as parameters linked with events.

7. The method according to claim 4, wherein the plausibility check of whether the seat belt is fastened as intended a time order of events is evaluated and compared to a reference order, and/or parameters concerning events are evaluated and compared to reference parameter values.

8. The method according to claim 4, wherein only events are taken into account which are located before a predetermined event or a combination of events, especially a combination of a signal of the belt buckle sensor (20) outputting insertion of the plug-in tongue and a signal of a speedometer (32) indicating an exceeding of the limit speed.

9. The method according to claim 4, wherein a misuse is concluded when the time order of the events deviates from the order of “door opened”, “webbing extension”, “plug-in tongue inserted”.

10. The method according to claim 1, wherein a misuse is concluded when no or only small webbing extension is determined upon determining transverse vehicle acceleration and/or vehicle deceleration.

11. The method according to claim 1, wherein a misuse is concluded when during a speed other than zero over a predetermined period of time the webbing movements which do not correlate with vehicle acceleration events deviate from a reference value.

12. A seat belt system in a vehicle for carrying out a method according to claim 1, comprising at least one belt buckle sensor (20) and at least one webbing extension sensor (24) as well as at least one seat occupation sensor (23), one door sensor (14), one vehicle acceleration sensor (30) and/or one vehicle speedometer (32) as well as a control unit (16) in which the signals of the sensors are stored and evaluated.

13. The seat belt system according to claim 12, wherein a coding which is adjusted to exactly one belt buckle (18) of the system is provided on at least one plug-in tongue.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Hereinafter the invention shall be described in detail by way of plural embodiments with reference to the enclosed drawings, wherein:

[0030] FIG. 1 is a schematic representation of a seat belt system according to the invention for carrying out a method of identifying misuse of a seat belt in a vehicle according to the invention;

[0031] FIG. 2 is a schematic representation of the assessment of vehicle data for identifying misuse;

[0032] FIG. 3 shows a first example of an identification of misuse;

[0033] FIG. 4 shows a second example of an identification of misuse; and

[0034] FIG. 5 shows a third example of an identification of misuse.

DESCRIPTION

[0035] FIG. 1 schematically illustrates a seat belt system 10 in which a plurality of vehicle components is connected to sensors adapted to detect a movement a condition or a parameter of the vehicle component.

[0036] In this example, inter alia a vehicle door 12 is provided which is connected to a door sensor 14, wherein the door look sensor 14 is capable of detecting opening and closing of the vehicle door 12 and reports the same by a respective signal to a control unit 16.

[0037] In the control unit 16 all incoming sensor signals are stored, wherein moreover the point in time of signal input is always stored. An evaluation in which each specific sensor signal is considered to be a separate event is carried out.

[0038] The seat belt system 10 further includes plural belt buckles 18 each having a belt buckle sensor 20 (for reasons of representation only one belt buckle is shown). The belt buckle sensor 20 detects insertion and release of a plug-in tongue and reports said signal to the control unit 16. Such “plug-in tongue inserted” signal is output by the belt buckle sensor 20 only when the plug-in tongue is correctly locked in the belt buckle 18.

[0039] Furthermore, a belt retractor 22 comprising a webbing extension sensor 24 is provided. The webbing extension sensor 24 records webbing movements, namely both in the positive and in the negative direction of extension. The direction of movement and the length of the respective webbing extension are equally reported to the control unit 16 where they are stored, or appropriate signals are transmitted to the control unit 16 which then determines the direction of movement and the length of the webbing extension effected.

[0040] In this example, moreover a vehicle seat 26 comprising a seat occupation sensor 28 is provided, wherein the seat occupation sensor 28 reports to the control unit 16 when the vehicle seat 26 is loaded by a load exceeding a predetermined limit. This, too, is stored in the control unit 16 together with the signal input time. A seat occupation sensor 28 is provided especially for a passenger seat, but it may also be provided for other seats in the vehicle.

[0041] Moreover, data from acceleration sensors 30 as well as from a speedometer 32 are detected and are equally reported to the control unit 16. Acceleration signals are noted in the control unit together with the time of signal input. It is possible to take only accelerations above a predetermined limit into account.

[0042] The vehicle speed may be continuously detected and recorded, but also in this case it is possible to restrict detection to particular limits. It is especially important to detect exceeding of a limit speed from which fastening of the seat belt is obligatory and from which control instances within the vehicle not shown in detail output a seat belt warning signal. Exceeding of said limit speed is equally stored in the control unit 16 together with the time of signal input.

[0043] The control unit 16 is connected to an SBI system 34 which is adapted to inhibit, upon misuse of the seat belt use and movement of the vehicle in total or outputs at least a warning which cannot be switched off.

[0044] For detecting misuse, a plausibility check is carried out in the control unit. This means that not merely the sensor signals are considered, especially the signals of the belt buckle sensor 20 as well as of the webbing extension sensor 24, to determine whether the seat belt is fastened as intended, but that further data for estimating whether it is plausible that the seat belt is fastened as intended are taken into account.

[0045] In this way, on the one hand, based on the stored point in time of signal input an order of events is calculated illustrating in which time sequence the individual sensor signals have been received and, consequently, in which time sequence the individual events have occurred. Moreover, the time interval between the events can be determined and used for evaluation. Finally, parameters of the individual events, especially a length of webbing extension and acceleration values, may be included in the evaluation.

[0046] Checking a misuse comprises two generally different ways. On the one hand, it has to be assessed whether the correct plug-in tongue was inserted in the matching belt buckle and, on the other hand, it has to be assessed whether the webbing is fastened as intended and, resp., guided as intended.

[0047] In order to find out whether the correct plug-in tongue was inserted into the matching belt buckle 18, in this case mechanically and/or electronically coded plug-in tongues are used which only fit into one single belt buckle 18 in the vehicle. Only when said plug-in tongue is inserted in the respective belt buckle 18, does the belt buckle sensor 20 report the “plug-in tongue inserted” signal which is then stored in the control unit 16.

[0048] The coding is realized, for example, by a specific geometry on the plug-in tongue which is designed so that only this specific plug-in tongue can be locked in the belt buckle 18. Other types of coding may also be used, of course.

[0049] For assuming that the matching plug-in tongue was correctly inserted it is further checked whether the belt belonging to said plug-in tongue is in fact used. It is checked, for example, whether webbing is extended at all, or furthermore, whether a webbing extension is followed at most by a small webbing retraction but not by a webbing retraction back to the parking position of the seat belt.

[0050] If both conditions are met, it can be concluded therefrom that the correct belt including the attached plug-in tongue was fixed in the correct belt buckle (see FIG. 2).

[0051] For identifying whether the webbing is fastened and guided as intended, further vehicle data are taken into account. This branch is illustrated on the right side in FIG. 2. The driving dynamics data listed there constitute a sub-group of the general vehicle data.

[0052] Here especially the evaluation of the webbing movement is incorporated, i.e. of the webbing extension and the webbing retraction over time. Accordingly, it is checked, on the one hand, whether the webbing movements are matching the detected vehicle accelerations. Moreover, it is checked by way of reference profiles established before and stored in the control unit 16 whether the measured webbing movements are plausible to an occupant movement in the absence of vehicle accelerations. Hereby operating the car radio or the navigation system, reaching into the glove compartment, shifting in the case of manual gearshift or reaching to the mirror as well as loosening a piece of clothing, for example, are understood. Those movements statistically take place at a certain frequency and entail a respective characteristic webbing extension. When considering the webbing movements which are not correlated with a vehicle acceleration over a particular time, for example several minutes up to one hour, it can thus be detected whether there is a natural webbing movement from which it can be concluded that in fact an occupant has fastened the seat belt or whether there is virtually no or definitely no webbing movement from which it can be concluded that the bolt is not fastened around the upper body part.

[0053] There may also be established typical reference profiles for unmoved objects or child safety seats which are fastened on the passenger or back seat and which naturally differ from living persons as to webbing movements that are not correlated with a vehicle acceleration.

[0054] Moreover, based on the sensor signals an event order is established by evaluating the signal input time which may equally be used to identify whether a belt has in fact been fastened or whether fastening of a seat belt was merely pretended.

[0055] FIG. 2 illustrates that both ways are combined in the plausibility check for identifying misuse, if misuse is identified, this is transmitted to the SBI system 34 and, where necessary, movement of the vehicle is inhibited or a signal is output to the driver.

[0056] When checking whether the seat belt is correctly buckled, it is also checked whether the plug-in tongue is connected to the webbing or is used as a cheating tongue. While the insertion of a plug-in tongue connected to the webbing is preceded by a webbing extension and possibly a small webbing retraction is following, both steps do not occur when a cheating tongue is inserted. An evaluation of the webbing movement before and after insertion thus is indicative of whether or not the respective webbing is connected to the plug-in tongue.

[0057] The webbing extension length, too, can be checked for plausibility. For example, an unused seat belt in its so-called parking position exhibits zero extension length, however this is not compatible, of course, with a signal of the belt buckle sensor indicating that the plug-in tongue is inserted.

[0058] When during traveling there are no further webbing movements, this is also indicative of the fact that a cheating tongue is used and the webbing is not connected to the plug-in tongue or that the occupant sits on the extended belt.

[0059] The course of action of the vehicle occupant and thus the order of events of the incoming sensor signals normally differ, when the belt is correctly fastened, from the course of action in the case of misuse.

[0060] Normal buckling is carried out after unlocking the vehicle, opening the door, taking a seal, by a webbing extension followed by inserting the plug-in tongue into the belt buckle.

[0061] When inserting the plug-in tongue without buckling of the occupant, the plug-in tongue normally remains permanently in the belt buckle, similarly to the use of a cheating tongue, and thus permanently generates the belt buckle sensor signal “plug-in tongue inserted”, irrespective of the driving condition. This, too, can be considered for identifying misuse. For example, in the case of intended use the plug-in tongue is not yet inserted when the door is opened. If thus signal times of “open door” and “plug-in tongue inserted” coincide or are falling within a very short period of time, this is indicative of misuse.

[0062] When a seat occupation sensor is used, it can be identified whether the seat belt was fastened as intended by checking whether an occupant sits down although a plug-in tongue has already been inserted into the belt buckle. This is not compatible with the correct signal order of the occupant first sitting down and then fastening the seat belt.

[0063] A complete check of all combinations requires a lot of time and computing capacity. Therefore, only a limited number of sensor signals is used hare for taking a decision. Only sensor signals in a time interval before meeting a specific condition are evaluated and are considered in the plausibility check. This condition is, for example, the combination of the events of “plug-in tongue inserted” and exceeding the limit speed from which the seat belt has to be fastened as supplied by the vehicle speed indicator.

[0064] FIGS. 3 to 5 illustrate examples of inquiry schemes for identifying misuse.

[0065] FIGS. 3 and 4 especially illustrate examples of identifying whether the webbing was correctly fastened, i.e. a correct belt fastening operation was carried out.

[0066] On the one hand, it is checked whether the actual event order established from the input time of the sensor signals and vehicle data corresponds to a predetermined reference order. The reference order here is: “open door” and, resp., “close door” signal of the door sensor 14, webbing extension signal of webbing extension sensor 24, belt buckle sensor signal “plug-in tongue inserted”.

[0067] Moreover, the webbing extension sensor 24 should report at most a small webbing movement directly following the belt buckle sensor signal. A large movement indicates a misuse, whereas a small movement is plausible when the webbing tightly contacts the body immediately after buckling. In addition, it may be checked whether the webbing extension is plausible, i.e. for example whether a sufficient amount of webbing has been extended for buckling a vehicle occupant.

[0068] Even if the belt buckle sensor signal reporting an inserted plug-in tongue is provided already together with the door sensor signal for opening or closing the door, a misuse can be concluded therefrom.

[0069] It may be additionally checked for the passenger seat, as shown in FIG. 4, whether the seat occupation sensor 28 has output a seat occupation before the input of a belt buckle sensor signal or whether allegedly first the plug-in tongue was inserted before the occupant sat down on the seat 26.

[0070] Intended guiding of the webbing can be checked, for example, by the inquiry scheme of FIG. 5.

[0071] In this case, in addition to checking for a belt buckle sensor signal for an inserted plug-in tongue and to checking whether the reported webbing extension is plausible, over a certain period of time in the traveling vehicle the transverse acceleration of the vehicle is correlated with the output sensor signals of the webbing extension sensor and the webbing movements occurring in transverse acceleration are measured and stored. This is also done for longitudinal accelerations of the vehicle, wherein both webbing output in vehicle decelerations and webbing retraction in positive vehicle accelerations are detected.

[0072] It is expected in both cases that an acceleration above a specific limit entails a webbing movement when inertia forces act on the vehicle occupant and the latter has guided the belt around the upper body part. In contrast, if the vehicle occupant sits on the belt or if the belt is not inserted at all and a cheating tongue is used, small webbing movements are expected at the very most. By comparing the webbing movements collected over a certain period of time or when checking for each individual acceleration event to reference values established before it can be checked during traveling whether the seat belt is correctly fastened.

[0073] Moreover, it is checked in this case whether the webbing movement is plausible to the vehicle occupant's own movements. Accordingly, webbing movements not correlated with vehicle accelerations are evaluated. A vehicle occupant is expected to move in the course of time, for example for operating the car radio, the shift lever or for opening the glove compartment, whereby webbing movements are taking place. In this example, too, a comparison is made with stored reference values established before. If the entire webbing movement is smaller than this limit, a misuse can be concluded.