VEHICLE OCCUPANT PROTECTION SYSTEM AND METHOD FOR PROTECTING A VEHICLE OCCUPANT

Abstract

In a vehicle occupant protection system a first tether is permanently fastened to a front panel of the airbag and is detachably fixed to an actuator unit on the module side. A second tether is arranged on the module side and is connected to the first tether, wherein in an extension of the second tether there is provided a decoupling arrangement which is located in the flow of forces between the second tether and the first tether only when the actuator unit is activated. In order to protect the vehicle occupant, when a vehicle seat is in a first sitting position, an airbag of the airbag module is filled with a first smaller volume and, in response to a height of the vehicle occupant sitting in the vehicle seat, a venting device is opened or closed. When the vehicle seat is in a second sitting position, the airbag is filled with a second larger volume and the venting device is opened.

Claims

1. A vehicle occupant protection system comprising an airbag module which includes an airbag having first and second tethers extending in an interior of the airbag and an actuator unit fixed to the module, wherein the first tether is permanently fastened to an airbag-side fastening point on a front panel of the airbag and is detachably fixed to the actuator unit on the module side at a first module-side fastening point, and the second tether is arranged on the module side at a second module-side fastening point and is connected to the first tether at a tether connecting point, wherein in the extension of the second tether between the second module-side fastening point and the tether connecting point there is provided a decoupling arrangement which triggers when a predetermined force threshold is exceeded, wherein activation of the actuator unit releases the first tether on the module side and wherein the decoupling arrangement is located in the flow of forces between the second module-side fastening point of the second tether and the airbag-side fastening point of the first tether only when the actuator unit is activated.

2. The vehicle occupant protection system according to claim 1, wherein an extension of the tether from the second module-side fastening point of the second tether via the tether connecting point and the first module-side fastening point of the first tether on the actuator unit to the airbag-side fastening point of the first tether, when viewed in the direction of the airbag-side fastening point of the first tether, the first module-side fastening point of the first tether is located behind the tether connecting point and the second module-side fastening point of the second tether.

3. The vehicle occupant protection system according to claim 1, wherein the force threshold is selected so that, with the actuator unit being activated, during an initial phase or a middle phase of filling of the airbag the first tether exerts a force on the decoupling arrangement which is above the force threshold, while in a final phase of the filling a force exerted by the first tether on the decoupling arrangement constantly remains below the force threshold.

4. The vehicle occupant protection system according to claim 1, wherein the first tether is permanently fastened to the airbag-side fastening point on the front panel at a first end and at a second end on the airbag panel, especially on the front panel, and the first module-side fastening point and the tether connecting point are located between the two ends of the first tether.

5. The vehicle occupant protection system according to claim 1, wherein the decoupling arrangement is arranged at the second module-side fastening point of the second tether, at the tether connecting point or therebetween.

6. The vehicle occupant protection system according to claim 1, wherein there is provided a venting device on which a venting tether extending in the interior of the airbag and being detachably connected to the actuator unit will act.

7. The vehicle occupant protection system according to claim 6, wherein the venting device is designed such that the venting device is opened only when the venting tether is released by the actuator unit.

8. The vehicle occupant protection system according to claim 1, wherein a vehicle seat is provided which can adopt a first position and a second position, wherein in the second position the vehicle seat is further distant from the airbag module by a factor of about 1.5 to 2 than in the first position, and in that in the first position of the vehicle seat the airbag in the filled state adopts a first smaller volume and in the second position of the vehicle seat in the filled state adopts a second larger volume.

9. A method for protecting a vehicle occupant, especially comprising a vehicle occupant protection system according to claim 1, wherein there is provided a vehicle seat which can adopt a first position and a second position and which is provided for receiving a vehicle occupant, wherein the vehicle seat in the second position has a larger distance from an airbag module than in the first position, and wherein in a situation of restraint that occurs when the vehicle seat is in the first position, an airbag of the airbag module is filled with a first smaller volume and, in response to a height of the vehicle occupant sitting in the vehicle seat, a venting device of the airbag is opened or closed, and in a situation of restraint that occurs when the vehicle seat is in the second position, the airbag is filled with a second larger volume and the venting device is opened.

10. The method according to claim 9, wherein in a restraint situation in which the vehicle seat is in the first sitting position, the actuator unit always is not activated or is activated only in a final phase of the filling of the airbag and the decoupling arrangement does not trigger, and in a situation of restraint in which the vehicle seat is in the second sitting position, the actuator unit always is activated and the decoupling arrangement triggers.

11. The method according to claim 10, wherein there is provided a venting device on which a venting tether extending in the interior of the airbag and being detachably connected to the actuator unit will act, and in that in the first sitting position, in response to a first, taller body height and a second smaller body height of a vehicle occupant in the vehicle seat, the actuator unit is activated in a final phase of the filling of the airbag when the vehicle occupant has the second smaller body height, and the actuator unit is not activated when the vehicle occupant has the first taller body height.

12. The vehicle occupant protection system according to claim 2, wherein the force threshold is selected so that, with the actuator unit being activated, during an initial phase or a middle phase of filling of the airbag the first tether exerts a force on the decoupling arrangement which is above the force threshold, while in a final phase of the filling a force exerted by the first tether on the decoupling arrangement constantly remains below the force threshold.

13. The vehicle occupant protection system according to claim 12, wherein the first tether is permanently fastened to the airbag-side fastening point on the front panel at a first end and at a second end on the airbag panel, especially on the front panel, and the first module-side fastening point and the tether connecting point are located between the two ends of the first tether.

14. The vehicle occupant protection system according to claim 13, wherein the decoupling arrangement is arranged at the second module-side fastening point of the second tether, at the tether connecting point or therebetween.

15. The vehicle occupant protection system according to claim 14, wherein there is provided a venting device on which a venting tether extending in the interior of the airbag and being detachably connected to the actuator unit will act.

16. The vehicle occupant protection system according to claim 15, wherein the venting device is designed such that the venting device is opened only when the venting tether is released by the actuator unit.

17. The vehicle occupant protection system according to claim 15, wherein a vehicle seat is provided which can adopt a first position and a second position, wherein in the second position the vehicle seat is further distant from the airbag module by a factor of about 1.5 to 2 than in the first position, and in that in the first position of the vehicle seat the airbag in the filled state adopts a first smaller volume and in the second position of the vehicle seat in the filled state adopts a second larger volume.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0049] Hereinafter, the disclosure shall be described in detail by way of an example arrangement with reference to the attached figures, wherein in the drawings:

[0050] FIG. 1 shows a schematic representation of a vehicle occupant protection system according to the disclosure for carrying out a method according to the disclosure, comprising a vehicle seat which is in a first forward position and an airbag being which is filled up to a first smaller volume in a first situation of restraint, an actuator unit being not activated;

[0051] FIG. 2 shows the vehicle occupant protection system of FIG. 1 in a second situation of restraint, the actuator unit being activated;

[0052] FIG. 3 shows the vehicle occupant protection system of FIG. 1 in a third situation of restraint, wherein the vehicle seat is in a second rearward position of the vehicle seat and the airbag is filled up to a second larger volume, the actuator unit being activated;

[0053] FIG. 4 shows a schematic view of the vehicle occupant protection system of FIG. 1 in a first exemplary arrangement, with the airbag being illustrated during filling;

[0054] FIG. 4a shows an enlarged cutout from FIG. 4;

[0055] FIG. 5 shows a variant of the vehicle occupant protection system of FIG. 4;

[0056] FIG. 6 shows a schematic view of the vehicle occupant protection system of FIG. 1 in a second exemplary arrangement, with the airbag being illustrated during filling;

[0057] FIGS. 7 to 9 show the vehicle occupant protection system of FIG. 4 during the filling of the airbag in the first restraint situation;

[0058] FIGS. 10 to 13 show the vehicle occupant protection system of FIG. 4 during the filling of the airbag in the second restraint situation; and

[0059] FIGS. 14 to 16 show the vehicle occupant protection system of FIG. 4 during the filling of the airbag in the third restraint situation.

DETAILED DESCRIPTION

[0060] FIGS. 1 to 3 illustrate a vehicle occupant protection system 10 in three different restraint situations, FIG. 1 representing a first restraint situation, FIG. 2 representing a second restraint situation and FIG. 3 representing a third restraint situation.

[0061] The vehicle occupant protection system 10 comprises an airbag 12 which in a situation of restraint fills with filling gas. The airbag 12 is part of an airbag module 14 not shown in detail which also comprises a gas generator (not shown) which supplies the filling gas for the airbag 12 in a known way.

[0062] In the example shown here the airbag module 14 is accommodated in a steering wheel 16 of a vehicle so that the airbag 12 is designed as a driver airbag.

[0063] FIG. 6 shows an exemplary arrangement in which the airbag module 14 is arranged in an instrument panel 18 of the vehicle, with the airbag 12 being designed as a passenger airbag.

[0064] The general structure of the vehicle occupant protection system 10 as well as the behavior thereof in the different situations of restraint and thus also the method carried out by the vehicle occupant protection system 10 are identical for both exemplary arrangements, however.

[0065] A vehicle occupant 20 in a vehicle seat 22 which is assigned to the airbag module 14 is caught in a restraint situation by the filled airbag 12, wherein the vehicle occupant immerses into a baffle provided on a front panel 24 of the airbag 12.

[0066] The vehicle seat 22 and thus the vehicle occupant 20 may be at different distances d from the airbag module 14, as the vehicle seat 22 is adjustable along a longitudinal direction of the vehicle. In the method for protecting a vehicle occupant 20 described here, two distances d.sub.1, d.sub.2 are of interest, wherein each of the distances d.sub.1, d.sub.2 can stand for a distance range comprising e.g. 20 to 50 cm.

[0067] The distance d.sub.1 describes a seat distance at which the vehicle seat 22 is placed relatively close to the airbag module 14, i.e. relatively close to the steering wheel 16 or to the instrument panel 18. Such seat distance is adopted in a driving situation, for example, in which the hands of the vehicle occupant 20 are lying on the steering wheel 16. When the vehicle seat 22 is provided at a seat distance d.sub.1, this is also referred to as the first tor front sitting position or else as driving position here.

[0068] The distance d.sub.2 describes a seat distance at which the vehicle seat 22 is significantly further distant from the steering wheel 16 or the instrument panel 18 than at the distance d.sub.1. This position of the vehicle seat, here also referred to as second or rear sitting position or as comfort position, is adopted e.g. in a comfort situation in which the vehicle drives autonomously and the vehicle occupant 20 is not busy driving the vehicle. It is also imaginable that in the second sitting position a backrest 26 of the vehicle seat 22 is folded back. Here, it would also be possible that the vehicle seat 22 is closer to the vehicle module 14 than the distance d.sub.2, as a torso of the vehicle occupant 20 is further distant from the airbag module 14 by the leaned-back position. Hence it is imaginable that in the comfort position only the torso of the vehicle occupant 20 is located at a distance d.sub.2 from the airbag module 14.

[0069] It is possible that especially the distance d.sub.1 may slightly vary, as a taller vehicle occupant 20 possibly adjusts the vehicle seat 22 at a somewhat larger distance from the vehicle front end than a smaller vehicle occupant 20. However, this variation should not reach the distance d.sub.2 in the second rearward sitting position.

[0070] The filling behavior of the airbag 12 is different in response to the sitting position.

[0071] In the first sitting position, upon activation of the airbag module 14 in a restraint situation the airbag 12 is always filled only up to a first smaller volume V.sub.1 (see FIGS. 1 and 2), while in the second sitting position upon activation of the airbag module 14 the airbag 12 is always filled up to a second larger volume V.sub.2 so as to take the larger distance of the vehicle occupant 20 from the airbag module 14 into account (see FIG. 3).

[0072] The airbag 12 here has a venting device 28 that can adopt a closed state and an opened state, wherein in the opened state (also referred to as opened venting device 28) gas can escape from the interior 30 of the airbag 12 to the environment.

[0073] When the vehicle seat 22 is in the first sitting position, the venting device 28 is opened in response to a body height K.sub.1, K.sub.2 of the vehicle occupant 20 in the vehicle seat 22.

[0074] When the vehicle occupant 20 has a first body height K.sub.1 which is larger than a predetermined limit, the venting device 28 remains closed in the situation of restraint. As a result, the airbag 12 has such great hardness that it can safely catch the tall vehicle occupant 20.

[0075] When the vehicle occupant 20, on the other hand, has a second body height K.sub.2 which is smaller than the predetermined limit and thus is smaller than the first body height K.sub.1, the venting device 28 is opened in the restraint situation so that the airbag 12 becomes softer and the forces are reduced during immersion.

[0076] For determining the limit value of the body height, for example the values of a 50% dummy and a 95% dummy or the values of a 5% dummy and a 50% dummy are considered.

[0077] In the interior 30 of the airbag 12, a first tether 32 is arranged which is permanently fixed to the inside of the front panel 24 of the airbag 12 at an airbag-side fastening point 33 and which is fastened on the module side at a first module-side fastening point 34 on an actuator unit 36 fixed to the module so that it detaches on the module side when the actuator unit 36 is activated.

[0078] The actuator unit 36 is, for example, a tether activation unit (TAU) known per se that may comprise an explosive stud which is activated by a control signal transmitted by a control unit (not shown) and which then releases the first module-side fastening point 34 of the first tether 32. When the actuator unit 36 is not actuated, the first tether 32 remains fixed to its first module-side fastening point 34 in a manner fixed to the module and thus fixed to the vehicle.

[0079] Here, a fastening fixed to the module is understood to be a fastening fixed to the vehicle in the area of the airbag module 14, for example on a housing of the airbag module 14 or on the gas generator of the airbag module 14.

[0080] Moreover, a second tether 38 which is fixed to a second module-side fastening point 40 on the module side and which is connected to the first tether 32 at a tether connecting point 42 is arranged in the interior 30 of the airbag 12.

[0081] In the extension of the second tether 38 a decoupling arrangement 44 is arranged which triggers, when a predetermined force threshold is exceeded, and then interrupts the extension of the tether along the second tether 38.

[0082] The decoupling arrangement 44 can be designed in any way. In the present example it is realized by a tear seam which is provided either at the second module-side fastening point 40 of the second tether 38 (see FIG. 4a) or at the tether connecting point 42 (see FIG. 5) for fastening the second tether 38. Upon exceeding the predetermined force threshold, the tear seam comes undone and the second tether 38 is released at the respective fastening point. It would be equally imaginable to arrange a tear seam or perforation between the second module-side fastening point 40 and the tether connecting point 42. It would also be possible to completely replace the second tether 38 with a suitable decoupling arrangement 44.

[0083] In an extension of the tether from the second module-side fastening point 40 of the second tether 38 to the airbag-side fastening point 33 of the first tether 32, the second module-side fastening point 40 of the second tether 38, the tether connecting point 42, the first module-side fastening point 34 of the first tether 32 and the airbag-side fastening point 33 of the first tether 32 are located successively in the force path. This means that a force F which, usually starting from the front panel 24 of the airbag 12, acts on the first tether 32 is introduced to the vehicle through the first module-side fastening point 34 of the first tether 32 and the actuator unit 36, as long as the actuator unit 36 is not activated. In this case, the decoupling arrangement 44 is so-to-speak bridged.

[0084] Only when the actuator unit 36 is activated and thus the first module-side fastening point 34 of the first tether 32 is freely suspended in the interior 30 of the airbag 12, forces acting on the first tether 32 are transmitted via the tether connecting point 42 to the second tether 38 and thus to the decoupling arrangement 44.

[0085] In the interior 30 of the airbag 12, here moreover a venting tether 46 is provided which is connected to the venting device 28 and, on the module side, to the actuator unit 36, When the actuator unit 36 is activated, also the venting tether 46 is always released. As a result, the venting device 28 is opened and gas may escape from the interior 30 of the airbag.

[0086] Here, the venting device 28 is realized by a venting hole 48 in the panel of the airbag 12 and a flap 50 connected to the venting tether 46 (see FIG. 4a). In the shown exemplary arrangements, the venting device 28 is configured so that the flap 50 closes the venting opening 48, as long as the venting tether 46 is tensioned and the flap 50 releases the venting hole and thus opens the venting device 28, when the venting tether 46 is released by the actuator unit 36.

[0087] When the actuator unit 36 is not activated, also the venting device 28 remains closed. When the actuator unit 36 is activated, the venting device 28 is always opened.

[0088] So that the tether connecting point 42 interconnecting the first tether 32 and the second tether 38 can be located in the tether extension ahead of the first module-side fastening point 34 of the first tether 32 on the actuator unit 36, the first tether 32 must extend at least somewhat beyond the first module-side fastening point 34.

[0089] In the examples shown here, the first tether 32 is configured to be so long that its second end 52 extends beyond the tether connecting point 42 to the front panel 24 of the airbag 12, where it is permanently fixed to the front panel 24 in a further airbag-side fastening point 54. The first end 56 is fastened to the front panel 24 at the airbag-side fastening point 33.

[0090] The tether connecting point 42 and the first module-side fastening point 34 are located between the ends 52, 56 and, in this example, approximately in the middle of the extension of the first tether 32 so that the first tether 32 extends in V-shape in the interior 30 of the airbag 12, when the actuator unit 36 is not activated and the airbag 12 is filled. When the actuator unit 36 is not activated, therefore a tensile force also acts on the portion of the first tether 32 that extends between the first module-side fastening point 34 and the airbag-side fastening point 54 on the front panel 24.

[0091] The second tether 38 is longer, however, than the length of the first tether 32 between the tether connecting point 42 and the first module-side fastening point 34, and the second module-side fastening point 40 of the second tether 38 is positioned on the module side so that loading of the second tether 38 is suppressed, when the actuator unit 36 is not activated.

[0092] When the actuator unit 36 is not activated, the ends 54, 56 of the first tether 32 fixed to the front panel 24 of the airbag 12 exert tensile force on the front panel 24 and prevent the airbag 12 from expanding to a volume exceeding a first volume V (see also FIGS. 1 and 2 as well as FIGS. 7 to 13).

[0093] Only when the actuator unit 36 is activated and releases the first module-side fastening point 34 of the first tether 32 and additionally triggers the decoupling arrangement 44, can the first module-side fastening point 34 of the first tether 32 move freely into the interior 30 of the airbag 12 and thus exerts no more tensile force on the front panel 24 of the airbag 12. The latter then fills up to its second larger volume V.sub.2 (see FIG. 3 as well as FIGS. 14 to 16).

[0094] FIGS. 4 and 5 illustrate the airbag module 14 designed for being mounted in the steering wheel 16. The only difference between the shown variants resides in the fact that the decoupling arrangement 44 in FIG. 4 is formed by a tear seam at the second module-side fastening point 40 of the second tether 38, while in FIG. 5 the decoupling arrangement 44 is realized by a tear seam at the tether connecting point 42.

[0095] The venting device 28 is arranged at an upper panel portion of the airbag 12 facing the windscreen of the vehicle.

[0096] FIG. 6 illustrates the airbag module 14 designed for being mounted in the instrument panel 18. The principle of functioning is identical. The decoupling arrangement 44 is designed as in the variants of FIGS. 4 and 5 (not shown in greater detail).

[0097] Here, the venting device 28 is arranged in a laterally directed panel portion of the airbag 12 so that the shape of the flap 50 closing the venting hole 48 as long as the venting tether 46 is fixed to the actuator unit 36 is visible.

[0098] In FIGS. 4, 5 and 6, respectively, the actuator unit 36 is not triggered.

[0099] FIGS. 7 to 16 illustrate the method for protecting a vehicle occupant by an afore-described vehicle occupant protection system 10 in the three different restraint situations in greater detail.

[0100] The first restraint situation shown in FIGS. 7 to 9 describes the behavior of the vehicle occupant protection system 10 in a situation of restraint in which a tall vehicle occupant 20 of a first body height K.sub.1 is sitting at the first forward sitting position at the distance d.sub.1 from the airbag module 14.

[0101] In this case, the airbag 12 is to be filled with the first smaller volume V.sub.1 but with sufficient hardness for catching a tall vehicle occupant 20.

[0102] FIG. 7 illustrates the airbag 12 in the initial phase of filling just after the start of filling. The actuator unit 36 is not triggered so that both the first tether 32 and the venting tether 46 remain fixed tightly to the actuator unit 36 and thus in a manner fixed to the module.

[0103] FIG. 8 illustrates the airbag 12 in a middle phase during filling, the airbag 12 already having adopted almost its final shape.

[0104] FIG. 9 finally shows the airbag 12 after the final phase of filling in the completely filled state with the first smaller volume V.sub.1. The actuator unit 36 is still has not been activated so that even in the completely filled state the front panel 24 is retained by the intact first tether 32, which is still fixed on the module side by its first module-side fastening point 34 on the actuator unit 36, at its desired distance from the airbag module 14. The venting tether 46 is equally still fixed on the actuator unit 36 in a way fixed to the module so that the venting device 28 remains closed.

[0105] All forces acting on the first tether 32 are transferred into the vehicle via the actuator unit 36 and the first module-side fastening point 34 of the first tether 32. Therefore, the decoupling arrangement 44 remains always unloaded so that it is not adapted to trigger.

[0106] FIGS. 10 to 13 illustrate the behavior of the vehicle occupant protection system 10 in a second situation of restraint in which a smaller vehicle occupant 20 of a second body height K.sub.2 is sitting at a distance d.sub.1 the first forward sitting position, while the situation of restraint occurs.

[0107] FIG. 10 shows an initial phase of the filling of the airbag 12.

[0108] The actuator unit 36 is not activated so that both the first tether 32 and the venting tether 46 remain held on the actuator unit 36 in a manner fixed to the module. Since no force can act on the decoupling arrangement 44, the latter mill not trigger.

[0109] FIG. 11 illustrates a middle phase of the filling of the airbag 12 during which the front panel 24 moves toward the vehicle seat 22.

[0110] FIG. 12 shows a final phase of filling in which the front panel 24 has substantially come to rest and the airbag 12 has substantially adopted its first smaller volume V.sub.1.

[0111] On the tether 32 there are no longer acting the dynamic forces which have occurred while the front panel 24 has moved outwardly but there are merely acting the static forces which are caused by the internal pressure of the airbag 12, with the internal pressure already having reached substantially its maximum value.

[0112] At this point in time, now the actuator unit 36 is activated and both the first tether 32 at its first module-side fastening point 34 and the module-side end of the venting tether 46 is detached from the airbag module.

[0113] FIG. 13 illustrates the final state. Although the second tether 38 and also the decoupling arrangement 44 now are located in the flow of forces between the airbag-side fastening point 33 of the first tether 32 and the second module-side fastening point 40 of the second tether 38, the force acting on the decoupling arrangement 44 remains below the predetermined force threshold and is not sufficient to trigger the decoupling arrangement.

[0114] The force threshold from which the decoupling arrangement 44 triggers is generally selected such that purely static forces acting on the first tether 32 after the filling of the airbag 12 are not sufficient to exceed the force threshold. Forces that are high enough to trigger the decoupling arrangement 44 are reached only during the dynamic initial and middle filling phases, especially during a quick upward movement of the front panel 24. Hence, when the actuator unit 36 is activated in the final phase of the filling of the airbag 12 in which the airbag has already substantially adopted its position in the vehicle interior and has substantially reached the first volume V.sub.1, the forces acting on the first tether 32 are no longer sufficient to release the decoupling arrangement 44.

[0115] As a consequence, the second tether 38 remains fastened both to the second module-side fastening point 40 and to the tether connecting point 42, and the module-side fastening of the first tether 32 is maintained via the second tether 38.

[0116] The length of the second tether 38 is selected to be so short that the volume of the airbag 12 achieved in this state still corresponds to the first volume V.sub.1 for all practical needs.

[0117] In contrast to the afore-described first situation of restraint, however, the venting device 28 is opened by activating the actuator unit, as the venting tether 46 is released on the module side. Thus, gas can escape from the interior 30 of the airbag 12, thereby enabling the smaller vehicle occupant 20 to be caught more softly.

[0118] FIGS. 14 to 16 illustrate the behavior of the vehicle occupant protection system 10 in a third situation of restraint.

[0119] In this case, a vehicle occupant 20 of any body height K.sub.1, K.sub.2 is sitting in the vehicle seat 22 at the second rearward sitting position at a distance d.sub.2 from the airbag module 14.

[0120] FIG. 14 illustrates the vehicle occupant protection system 10 in the initial phase of the filling of the airbag 12. Already in this phase, where necessary already while activating the gas generator of the airbag module 14, the actuator unit 36 is activated so that the first module-side fastening point 34 of the first tether 32 and the module-side fastening of the venting tether 46 are released and are detached from the airbag module 14.

[0121] A point in time shortly after activation of the actuator unit 36 is illustrated in FIG. 15. Since the decoupling arrangement 44 now is located in the flow of forces between the front panel 24 of the airbag 12, the first tether 32 and the second module-side fastening point 40 of the second tether 38, the forces occurring during deployment of the airbag 12 which are caused by the front panel 24 moving away quickly from the airbag module 14, will act on the decoupling arrangement 44 via the first tether 32. Said forces are above the predetermined force threshold so that the decoupling arrangement 44 triggers and the connection of the first tether 32 fixed to the module is suspended.

[0122] As described above, this may take place, for example, by the fact that the connection of the second tether 38 to the first tether 32 at the tether connecting point 42 or the connection of the second tether to the airbag module 14 at the second module-side fastening point 40 is released. In the example illustrated here, the decoupling arrangement 44 is provided at the tether connecting point 42.

[0123] FIG. 16 illustrates the final phase of the filling of the airbag 12 in which the airbag adopts its completely filled state. Since neither the actuator unit 36 nor the second tether 38 withholds the first tether 32 at the airbag module 14 in a way fixed to the module, the front panel 24 can move further in the direction of the vehicle seat 22 than in the first two situations of restraint. Therefore, the airbag 12 fills up to its second larder volume V.sub.2.

[0124] Both ends 52, 56 of the first tether 32 remain tightly connected to the front panel 24 of the airbag 12, but the tether connecting point 42 is located freely in the interior 30 of the airbag 12.

[0125] Since also the venting tether 46 has been released by the actuator unit 36, the venting device 28 opens, just as in the second situation of restraint, so that gas may escape from the interior 30 of the airbag 12 and the airbag 12 becomes softer.

[0126] For an airbag module 14 which is arranged in the instrument panel 18 the three restraint situations as described are run analogously. The principle of the disclosure can also be realized for airbag modules 14 at other positions of any vehicle, as a matter of course.