Vehicle occupant restraint system, and method for operating a vehicle occupant restraint system

Abstract

The invention relates to a vehicle occupant restraint system (10) comprising a side airbag (14) which is arranged on a vehicle seat (12) and with which two structurally independent gas generators (20, 22) for providing filling gas are associated, the side airbag (14) having a first inflatable chamber (16) and a second inflatable chamber (18) which are not fluidically connected to each other. Each of the two chambers (16, 18) is fluidically connected to precisely one of the gas generators (20, 22), and the first gas generator (20) is activated on the basis of a pre-crash signal (SP) from a pre-crash sensor (30) and inflates the first chamber (16), while the second gas generator (22) is activated on the basis of an impact signal (SA) from an impact sensor (32) of the vehicle and inflates the second chamber (18). The side airbag (14) has a venting device (52) for the first chamber (16), which venting device is activated during inflation of the second chamber (18) and vents the first chamber (16) while the second chamber (18) is being inflated.

Description

[0001] ZF Automotive Germany GmbH

[0002] Industriestraße 10

[0003] 73553 Alfdorf

[0004] Vehicle occupant restraint system and method for operating a vehicle occupant restraint system

[0005] The invention relates to a vehicle occupant restraint system with a side airbag arranged on a vehicle seat and to a method for operating a vehicle occupant restraint system.

[0006] It is often desirable to be able to vary the timing of the filling of a gas bag in a restraint situation, depending on parameters related to the restraint situation and vehicle occupants.

[0007] Multi-stage gas generators are known that contain several separately ignitable propellant charges for gas generation in a single housing. However, a disadvantage of this design is that the configuration of the propellant charges must be determined at the beginning of the gas generator's development. Furthermore, the time interval between the ignition of the individual propellant charges cannot be arbitrarily selected due to the design. A more flexible concept can be implemented with two independent, separate gas generators. To make the best possible use of the very limited installation space, for example, on the backrest of a vehicle seat, the arrangement of the gas generators is a factor to consider, as described in DE 10 2020 126 393 A1.

[0008] As developments in autonomous and piloted driving progress, an increasing number of sensors are becoming available for ferry operations to detect the current driving situation and potential hazards. This enables, in effect, the prediction of restraint situations through a sensor reading from a pre-crash sensor before an actual accident occurs. The object of the invention is to provide a vehicle occupant restraint system that takes such data into account.

[0009] This task is solved by a vehicle occupant restraint system with a side airbag arranged on a vehicle seat, to which two structurally separate gas generators for providing filling gas are assigned, wherein the side airbag has a first fillable chamber and a second fillable chamber which are not in flow communication with each other, wherein each of the two chambers is in flow communication with exactly one of the gas generators and the two gas generators are designed to be activatable at different times, wherein a control unit is provided which is designed to activate the first gas generator on the basis of a precrash signal from a precrash sensor and the second gas generator on the basis of an impact signal from an impact sensor of the vehicle, wherein the side airbag has a venting device for the first chamber.

[0010] Since each of the two chambers has its own dedicated gas generator, they can be filled with gas independently. The activation times of the two gas generators are also completely independent.

[0011] The use of the pre-crash signal makes it possible to inflate the first chamber of the side airbag by activating the first gas generator even before a restraint situation occurs, and to use this inflation to affect the vehicle occupant. This allows, for example, the vehicle occupant to be moved out of an immediate danger zone, particularly away from a side wall of the vehicle. If necessary, the vehicle occupant can also be moved into a position suitable for a restraint situation.

[0012] If an impact actually occurs after this point, the second gas generator is also activated to fill the second chamber of the side gas bag for restraining the vehicle occupant.

[0013] The first chamber is essentially a pre-crash chamber, which is filled in response to the pre-crash signal, while the second chamber is an in-crash chamber, which is only filled in response to the signal from an impact sensor and serves to actually catch the vehicle occupant.

[0014] Basically, the filling gas supplied by the respective gas generator builds up the internal pressure in its assigned chamber independently of the internal pressure of the other chamber. The venting device ensures that the internal pressure in the first chamber drops so quickly that it does not significantly affect the internal pressure in the second chamber.

[0015] After the vent is activated, the internal pressure of the second chamber is determined solely by the filling gas from the second gas generator. The filling gas still present in the first chamber, however, no longer has any significant influence on the internal pressure of the side airbag. Therefore, the thickness and internal pressure of the side airbag never exceed predetermined limits.

[0016] Since the internal pressures of the two chambers do not overlap, the internal pressure of each chamber can be set more precisely than before.

[0017] The filling gas still present in the first chamber when the venting device is activated is pushed out of the first chamber, particularly by the increase in volume of the second chamber as it is filled with the filling gas from the second gas generator. This allows the first chamber to be vented abruptly by the venting device when the second gas generator is activated.

[0018] The vent is preferably designed so that it is activated by filling the second chamber and vents the first chamber during the filling of the second chamber. In this way, a simple, cost-effective, purely mechanical vent can be implemented.

[0019] For example, the venting device includes a releaseable vent opening in an outer wall section of the first chamber, which is closed before the venting device is activated. The vent opening can be, for example, a cutout in the surface of the outer wall section of the first chamber or, alternatively, an open section of a circumferential seam of the first chamber. In any case, the vent opening must be large enough to allow the first chamber to be completely vented within a few milliseconds.

[0020] In a preferred embodiment, the venting device comprises a band that is fixed in the side gas bag by a tear seam before the second chamber is filled and keeps the vent opening closed as long as the second chamber is not filled, wherein the band is arranged such that when the second chamber is filled, the tear seam opens and releases the vent opening. For example, the band is sewn around the vent opening with the tear seam so that the vent opening is sufficiently gas-tight before it is opened.

[0021] The gas pressure of the filling gas flowing into the second chamber can be used to open the rupture seam. For this purpose, before the venting device is activated, a section of the second chamber wall can be folded over and surrounded by the tape. As the second chamber is filled, the filling gas flows into this folded-over section and exerts an opening force on the rupture seam. The venting device can thus be opened reliably and easily.

[0022] Preferably, the two chambers in the deployed side airbag are in similar positions. In particular, the two chambers in the fully deployed side airbag are arranged directly next to each other in a transverse direction and extend parallel to each other. The two chambers act on the vehicle occupant at approximately the same point and alternate in time, with the first chamber exerting a force on the vehicle occupant at an earlier time than the second chamber.

[0023] The wall of the second chamber preferably has an inner and an outer wall section that enclose the second chamber. The first chamber can be formed by an outer wall section placed on top of the inner outer wall section of the second chamber, such that the inner outer wall section also bounds the first chamber. In this case, the wall of the first chamber consists of the attached outer wall section and a portion of the inner outer wall section of the second chamber.

[0024] The two outer wall sections of the second chamber are advantageously made of a standard coated and nearly gas-tight gas bag fabric to provide sufficient service life for the second chamber to contain the vehicle occupant.

[0025] The two outer wall sections and the outer wall part are optionally attached to each other, at least partially, with the same circumferential seam, thus easily achieving a parallel arrangement of the first and second chambers. The circumferential seam can be manufactured in any suitable way, in particular by sewing, gluing, or welding.

[0026] The outer wall section that borders the first chamber can have a smaller area than the inner outer wall section of the second chamber.

[0027] Normally, the outer wall section of the first chamber does not contribute to the gas tightness of the second chamber. It is even possible that the outer wall section bounding the first chamber has a higher gas permeability than the material of the outer wall sections of the second chamber. This higher gas permeability can be achieved, for example, by using an uncoated, standard gasbag fabric.

[0028] In a preferred embodiment, the first chamber is located on the side of the side airbag facing the occupant, and the second chamber is located on the side facing away from the occupant. However, the arrangement could also be reversed.

[0029] The first chamber can have an inflatable protrusion that, when fully inflated, extends from the side airbag relative to the vehicle's vertical direction, forming a contact area for the occupant. For example, the inflatable protrusion is formed by an invertible pocket within the first chamber, specifically in the outer wall section of the first chamber. Thus, when inflated, the first chamber has a three-dimensional shape that differs from a simple cushion. The inflatable protrusion conforms to the occupant's position, establishing the earliest possible contact between the side airbag and the vehicle occupant in the seat.

[0030] The inflatable protrusion is designed to move the vehicle occupant slightly away from the immediate danger zone before an impact occurs. For example, the inflatable protrusion acts on the upper rib area of ​​the occupant under the arm to rotate the arm slightly upwards. Alternatively or additionally, the inflatable protrusion can act on the abdominal area, thereby moving the occupant sideways on the seat.

[0031] To simplify the construction of the vehicle occupant restraint system, the two gas generators are preferably arranged on a common support that is attached to the vehicle seat. For example, two structurally separate tubular gas generators are mounted on the support, each with its own electrical contact, allowing them to be easily activated at different times. The tubular gas generators can be easily mounted in parallel on the support to minimize the required installation space. In this case, it is also possible to combine the gas supply to both chambers at a central point, which simplifies, for example, sewing steps during the manufacture of the gas bag.

[0032] In one possible design, each gas generator protrudes into its assigned chamber with an outflowing end.

[0033] For example, both gas generators are primarily located in the second chamber, and the exhaust outlet of the first gas generator protrudes through a slot in the inner outer wall section of the second chamber into the first chamber. Optionally, the first gas generator can be surrounded at this point by a seal made of an elastic material to prevent the filling gas from escaping into the second chamber. However, it is also conceivable to omit a seal at this point.

[0034] For example, the gas generators can each be located primarily in their respective assigned chamber, with the exhaust outlet of the first gas generator protruding into the first chamber through a gas generator receptacle in the outer wall section of the first chamber, and the exhaust outlet of the second gas generator protruding into the second chamber through a gas generator receptacle in the outer wall section of the second chamber. The two gas generators can differ in their output capacity. For example, the first gas generator, which supplies the first chamber with filling gas, can be designed for a lower output than the second gas generator, which supplies the second chamber.

[0035] Of course, it is also conceivable to attach the two gas generators independently of each other in a structurally separate manner to the vehicle, for example to a vehicle seat.

[0036] The above-mentioned task is also solved using a method for operating a vehicle occupant restraint system, as described above. The following steps are performed:

[0037] Detecting a potentially imminent restraint situation and transmitting the pre-crash signal to the control unit,

[0038] - Activation of the first gas generator based on the precrash signal at a calculated first time prior to impact and filling of the first chamber of the side gas bag, and

[0039] Detecting an impact and activating the second gas generator based on the impact signal at a second time point after the first time point, and filling the second chamber of the side gas bag, and

[0040] - Activating the venting device during the filling of the second chamber and venting the first chamber while the second chamber is being filled.

[0041] The first gas generator is activated in response to the pre-crash signal at the first moment, even before the vehicle actually impacts an obstacle, when a potential restraint situation is detected. This means that the first chamber, through the inflowing filling gas supplied by the first gas generator, already acts on the vehicle occupant during the driving situation before an impending impact, moving them, in particular, out of a potentially dangerous area and / or into a more favorable position for a subsequent restraint situation that actually occurs.

[0042] The first chamber moves the occupant into a position favorable for restraint and out of an immediate danger zone, while the second chamber catches the occupant in the event of an actual impact.

[0043] The first chamber can be filled at a lower rate and / or to a lower internal pressure than the second chamber, as this has proven sufficient to move the vehicle occupant out of the immediate danger zone in time. A lower filling rate and / or lower internal pressure in the first chamber ensures that only a moderate force is exerted on the vehicle occupant and that they are moved as gently as possible.

[0044] The first chamber should be filled with a sufficiently high pressure and its volume should be large enough to move the vehicle occupant in the seat by a predetermined amount. This could involve shifting the occupant away from a side wall of the vehicle, for example by 5 to 10 cm, and / or applying a force that moves the occupant's arm and / or upper body into a position more favorable for capture by the second chamber.

[0045] The second gas generator is activated in response to the impact signal from the impact sensor at the second time point, for example with a time delay of approximately 150 ms compared to the activation of the first gas generator at the first time point.

[0046] If the pre-crash sensor fails to deliver a pre-crash signal, the second gas generator will only be activated upon an actual impact triggered by the impact sensor signal, and only the second chamber of the side airbag will be inflated. In such a case, the first gas generator remains deactivated, and the first chamber uninflated.

[0047] Preferably, after activation of the second gas generator, the expanding second chamber forces the remaining filling gas from the first chamber through the open vent. Thus, as a rule, both chambers are never completely filled simultaneously, and the internal pressure of the gas bag is always defined by the filling gas in only one of the two chambers. The invention is described in more detail below with reference to several exemplary embodiments and the accompanying figures. The figures show:

[0048] Figure 1 shows a schematic representation of a vehicle occupant restraint system according to the invention;

[0049] Figure 2 shows a side gas bag of the vehicle occupant restraint system from Figure 1 in a schematic sectional view along line 11 - 11 in Figure 1, with a fully filled first chamber and a second chamber that is just beginning to fill;

[0050] Figures 3 and 4 show the side gas bag from Figure 2 in a schematic representation during the activation of a venting device according to a first variant;

[0051] Figure 5 shows a schematic sectional view of the venting device from Figures 3 and 4;

[0052] Figures 6 and 7 are schematic representations of the seam shapes of the venting device from Figure 5; and

[0053] Figures 8 and 9 show the side gas bag from Figure 2 with a venting device according to a second variant.

[0054] For the sake of clarity, not all identical components are always labelled with reference symbols.

[0055] The same reference numerals (as well as numbers increased by 100) designate identical or essentially identical or equivalent components and parts in different embodiments.

[0056] Figure 1 shows a vehicle occupant restraint system 10 with a vehicle seat 12 and a side airbag 14 arranged on it.

[0057] The side gas bag 14 comprises a first fillable chamber 16 and a second fillable chamber 18. The two chambers 16, 18 are not in flow communication with each other.

[0058] Each of the two chambers 16, 18 is fluidically connected to its own gas generator 20, 22. The two gas generators 20, 22 are independent gas generators, structurally separated from each other, each with its own electrical contact for activation, and can be activated at independent times ti, t2.

[0059] In this example, both gas generators 20, 22 are designed as tubular gas generators and are fixed parallel to each other on a common support 24, which in turn is firmly connected to a seat frame 26 of the vehicle seat 12 (see e.g. figure 2).

[0060] The two gas generators 20, 22 are activated individually and at different times ti , t2 by a control unit 28.

[0061] The control unit 28 is connected to a pre-crash sensor 30 and to an impact sensor 32 of the vehicle in which the vehicle occupant restraint system 10 is installed.

[0062] In a potentially imminent restraint situation, the control unit receives a precrash signal SP from the precrash sensor 30.

[0063] The pre-crash sensor 30 does not have to be a separate physical sensor, but can be composed of various sensors and evaluation routines of a vehicle electronics system.

[0064] When the pre-crash sensor 30 is activated and the pre-crash signal SP is transmitted, the vehicle has not yet collided with an obstacle. An actual collision of this kind is detected separately by the impact sensor 32 and reported to the control unit 28 by an impact signal SA.

[0065] The control unit 28 is designed such that, upon receiving the pre-crash signal SP at the first time ti, only the first gas generator 20 is activated, and upon receiving the impact signal SA, only the second gas generator 22 is activated at the second time t2. There is a time difference t2 - h between the activation of the first gas generator 20 and that of the second gas generator 22, which is determined by the time interval between the sensor signals SP and SA and can also be adjusted by the control unit 28.

[0066] The side airbag 14 is arranged as is conventionally known on one side of the vehicle seat 12 and unfolds in a transverse direction Q of the vehicle between the vehicle seat 12 and a side wall 34 of the vehicle, for example a door panel.

[0067] The second chamber 18 consists of an outer wall section 36 and an inner wall section 38, which are joined together at a circumferential seam 40 in a suitable manner (for example, by sewing, gluing, or welding). The two wall sections 36 and 38 are essentially gas-tight. After a planned service life of the second chamber 18, the filling gas supplied by the second gas generator 22 can exit the second chamber 18 through an outlet opening (not shown).

[0068] The first chamber 16 is formed by placing an outer wall section 44 onto the inner outer wall section 38 of the second chamber 18 and firmly connecting it to the inner outer wall section 38 along its circumference. The outer wall section 44 rests flat against the inner outer wall section 38 of the second chamber 18. In this example, the outer wall section 44 has a smaller surface area than the inner outer wall section 38, so that at least part of the circumference of the outer wall section 44 is fixed to the surface of the inner outer wall section 38.

[0069] An outlet 46 of the second gas generator 22 protrudes here through a slot in the inner outer wall section 38 of the second chamber 18 into the second chamber 186 (indicated in Figure 1). Optionally, a seal is arranged at this point to prevent the overflow of filling gas from the first gas generator 20 into the second chamber 18.

[0070] The two chambers 16, 18 are arranged parallel to each other and next to each other in the transverse direction Q of the vehicle (see Figure 1).

[0071] In the variant shown here, the first chamber 16 is arranged on the side of the side airbag 14 facing the vehicle seat 12 and thus the vehicle occupant, while the second chamber 18 is facing away from the vehicle seat, i.e. towards the side wall 34.

[0072] When the control unit 28 receives the precrash signal SP from the precrash sensor 30, it activates the first gas generator 20 at the first time h. Filling gas flows from the first gas generator 20 into the first chamber 16 and fills it completely (see Figure 2). The second chamber 18 remains empty at this time, so that the inner outer wall section 38 and the outer outer wall section 36 are in contact.

[0073] During filling, the first chamber 16 acts on a vehicle occupant in the vehicle seat 12 and moves them away from the immediate danger zone and away from the side wall 34. The displacement of the vehicle occupant can be, for example, approximately 5 to 15 cm, in particular 5 to 10 cm.

[0074] In this example, the first chamber 16 is filled with a relatively low filling rate and a relatively low internal pressure, so that only moderate forces, which are well tolerated by the vehicle occupants, act upon them.

[0075] The first chamber 16 has an inflatable projection 48 (see Figure 2) which, when the first chamber 16 is filled, points towards the vehicle occupant on the vehicle seat 12.

[0076] The inflatable protrusion 48 is designed and positioned to act on the upper body of the vehicle occupant in the area of ​​the upper ribs and to rotate the arm of the vehicle occupant facing the side airbag 14 upwards. It can also act on an abdominal area of ​​the vehicle occupant, thus moving the vehicle occupant a short distance laterally away from the side wall 34.

[0077] Before filling the first chamber 16, the inflatable protrusion 48 is folded into a kind of pocket 50 inside the first chamber (see Figure 3).

[0078] If an impact occurs, the impact sensor 32 is triggered and sends the impact signal SA to the control unit 28. In this case, at the second time t2, the control unit 28 activates the second gas generator 22, whose filling gas flows into the second chamber 18. The second time point can be, for example, approximately 150 ms after the first time point h.

[0079] The side gas bag 14 has a venting device 52 for the first chamber 16. The venting device 52 comprises a vent opening 54 in the outer wall section 44 of the first chamber 16 and a band 56 covering the vent opening 54 before the second chamber 18 is filled. The band 56 is fixed to the outer wall section 44 by a tear seam 58. At its opposite end, the band 56 is permanently fixed to the second chamber 18, e.g., to the outer wall section 36.

[0080] The vent opening 54 is located in the immediate vicinity of a circumferential seam 60 of the outer wall part 44, with which it is attached to the surface of the inner outer wall section 38 of the second chamber 18, and is located here in the area of ​​the inflatable projection 48.

[0081] In the variant shown here, a section 62 of a wall 64 of the second chamber 18 formed by the inner outer wall section 38 and the outer outer wall section 36 is folded over immediately adjacent to the circumferential seam 40 of the second chamber 18 when the second chamber 18 is unfilled and fixed in this position by the band 56 (see Figure 5).

[0082] The tear seam 58 fixes the band 56 section by section around the vent opening 54 (see Figures 6 and 7).

[0083] When the first chamber 16 is filled, the tear seam 58 remains closed and the wall of the second chamber 18 is fixed in this position. Thus, the vent opening 54 also remains covered.

[0084] The venting device 52 is activated by filling the second chamber 18 with filling gas from the second gas generator 22.

[0085] When the filling gas from the second gas generator 22 flows into the second chamber 18, and thus between the outer outer wall section 36 and the inner outer wall section 38, it also enters the folded section 62 of the wall 64. Due to the increase in volume and the rise in internal pressure in the second chamber 18, section 62 expands, which tightens the band 56 and tears open the rupture seam 58. This releases the band 56 from the vent opening 54. As a result, the vent opening 54 is opened, and the filling gas still contained in the first chamber 16 is abruptly expelled through the vent opening 54. This forces the filling gas remaining in the first chamber 16 out, so that the inner outer wall section 38 and the outer wall section 44 now abut each other. Thus, during the filling of the second chamber 18, the first chamber 16 is completely vented.

[0086] The side gas bag 14 therefore has either a completely filled first chamber 16 or a completely filled second chamber 18. The side gas bag 14 thus does not have a state in which both the first chamber 16 and the second chamber 18 are simultaneously completely filled. The internal pressure of the side gas bag 14 is therefore defined either by the pressure in the first chamber 16 or by the pressure of the second chamber 18, but not by a combination of the internal pressures of both chambers 16 and 18.

[0087] Since the inner outer wall section 38 is part of the wall of both the first chamber 16 and the second chamber 18, the middle outer wall section 38 always shifts towards the opposite outer wall of the chamber 16, 18 which is not yet or no longer completely filled.

[0088] The occupant in vehicle seat 12 is contained exclusively by the second chamber 18 if the vehicle experiences an impact. At this point, the first chamber 16 is practically completely empty, so it plays no role in actually restraining the vehicle occupant.

[0089] Figures 6 and 7 show two possible forms for the tear seam 58 in the area of ​​the vent opening 54. In the example of Figure 6, the tear seam 58 is in two parts, with the two sections adjoining each other at a leading edge 66 of the vent opening 54 opposite to a tensile direction Rz and being sewn together there. In the example of Figure 7, the tear seam 58 is continuous in this area and is sewn away from the vent opening 54.

[0090] If the band 56 is pulled from the left side (as shown in Figures 6 and 7) to the right in the direction of tension Rz, the tear seam 58 is subjected to the greatest stress in the area of ​​the front edge 66 (at the leftmost point in Figures 6 and 7) and tears open there. From there, the tear seam 58 opens until the vent opening 54 is completely exposed. This state is shown in Figure 4. In this example, the tear seam 58 is designed as a seam, but it could also be, for example, an adhesive bond or a weld.

[0091] Figures 8 and 9 show a second variant of the ventilation device 152. All other features of the vehicle occupant restraint system 10 and the side airbag 14 correspond to those of the variant described above.

[0092] In contrast to the variant just described, the vent opening 154 is not formed by a flat opening in the outer wall section 44 of the first chamber 16, but by an unstitched section 168 in the circumferential seam 60, which fixes the outer wall section 44 to the inner outer wall section 38 of the second chamber 18. This section 168 is covered, as described in the first variant, with a corresponding band 156 and a tear seam 58 as long as the second chamber 18 is not filled.

[0093] To open the tear seam 58, as described above, a section 62 of the wall 64 of the second chamber 18 is folded over, so that the gas pressure of the incoming filling gas from the second gas generator 22 stretches this section 62 and opens the tear seam 58.

[0094] In the example of Figure 8, the tear seam 58 runs straight in extension of the circumferential seam 60. In the example of Figure 9, the tear seam 58 runs in the form of a point perpendicular to the circumferential seam 60. The functional principle is identical in both variants.

Claims

Patent claims 1. Vehicle occupant restraint system (10) with a side airbag (14) arranged on a vehicle seat (12), to which two structurally separate gas generators (20, 22) are assigned for providing filling gas, wherein the side airbag (14) has a first fillable chamber (16) and a second fillable chamber (18) which are not in flow communication with each other, wherein each of the two chambers (16, 18) is in flow communication with exactly one of the gas generators (20, 22) and the two gas generators (20, 22) are designed to be activated at different times (ti, t2), wherein a control unit (28) is provided which is designed to activate the first gas generator (20) on the basis of a precrash signal (SP) from a precrash sensor (30) and the second gas generator (22) on the basis of an impact signal (SA) from an impact sensor (32) of the to activate the vehiclewherein the side gas bag (14) has a venting device (52) for the first chamber (16).

2. Vehicle occupant restraint system (10) according to claim 1, wherein the venting device (52) is designed such that it is activated by filling the second chamber (18) and vents the first chamber (16) during the filling of the second chamber (18).

3. Vehicle occupant restraint system (10) according to one of the preceding claims, wherein the venting device (52) comprises a releaseable vent opening (54) in an outer wall part (44) of the first chamber (16) which is closed before activation of the venting device (52).

4. Vehicle occupant restraint system (10) according to claim 3, wherein the venting device (52) comprises a band (56) which is fixed in the side airbag (14) by a tear seam (58) prior to filling the second chamber (18) and keeps the vent opening (54) closed as long as the second chamber (18) is not filled, wherein the band (56) is arranged such that when the second chamber (18) is filled the tear seam (58) opens and releases the vent opening (54).

5. Vehicle occupant restraint system (10) according to claim 4, wherein, prior to the activation of the venting device (52), a region (62) of a wall (64) the second chamber (18) is folded over and surrounded by the band (56) and when the second chamber (18) is filled, filling gas flows into the folded area (62) and exerts an opening force on the tear seam (58).

6. Vehicle occupant restraint system (10) according to one of the preceding claims, wherein the two chambers (16, 18) in the fully unfolded side airbag (14) are arranged directly next to each other in a seat transverse direction (Q) and extend parallel to each other and a wall (64) of the second chamber (18) has an inner and an outer outer wall section (38, 36) which enclose the second chamber (18), and the first chamber (16) is formed by an outer wall part (44) placed on the inner outer wall section (38) of the second chamber (18), such that the inner outer wall section (38) also limits the first chamber (16).

7. Vehicle occupant restraint system (10) according to one of the preceding claims, wherein the first chamber (16) is arranged on an occupant-facing side and the second chamber (18) is arranged on an occupant-away side of the side airbag (14).

8. Vehicle occupant restraint system (10) according to claim 7, wherein the first chamber (16) has an inflatable projection (48) which, when the first chamber (16) is fully inflated, protrudes from the side airbag (14) with respect to a vehicle vertical direction (h) and forms a contact area for the occupant.

9. Method for operating a vehicle occupant restraint system (10) according to one of the preceding claims, comprising the steps: Detecting a potentially imminent restraint situation and transmitting the precrash signal (SP) to the control unit (28), - Activation of the first gas generator (20) based on the precrash signal (SP) at a calculated first time (ti) prior to an impact and filling of the first chamber (16) of the side gas bag (14), Detection of an impact and activation of the second gas generator (22) based on the impact signal (SA) AT a second time (t2) after the first time point (ti) and filling of the associated second chamber (18) of the side gas bag (14), and - Activating the venting device (52) during the filling of the second chamber (18) and venting the first chamber (16) while the second chamber (18) is being filled.

10. Method according to claim 9, wherein the filling second chamber (18) pushes the filling gas still located in the first chamber (16) out of it.

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