Knee gasbag module

Abstract

Knee airbag module of a vehicle occupant restraint system, comprising an outer housing (14; 114) in which an airbag (20; 120) folded into an airbag pack (18) before its deployment and a gas generator (16; 116) are accommodated, which generates filling gas for filling the airbag (20; 120), wherein an outlet opening (22; 122) oriented downwards in the installed position is formed in the outer housing (14; 114), through which the airbag (20; 120) leaves the outer housing (14; 114) when deployed, and wherein the airbag (20; 120) is divided into several chambers (28a - 28f; 128a - 128f) arranged in series and in flow communication, characterized in that the chamber (28a; 128a) closest to the gas generator is separated from an adjacent chamber (28b; 128b) is separated by a wall (32; 132) which extends in the inflated gas bag (20; 120) substantially in the area of ​​the outlet opening (22; 122) along the outlet opening (22; 122), wherein the chamber nearest to the gas generator (28a;128a) is arranged in the folded gas bag package (18) such that, after activation of the gas generator (16; 116), the chamber closest to the gas generator (28a; 128a) fills first, while the rest of the gas bag package (18) remains essentially folded, so that the rest of the gas bag package (18) is positioned exactly below the outlet opening (22; 122) before further chambers (28b-28f, 128b-128e) of the gas bag (20; 120) unfold along an instrument panel (12).

Description

[0001] The invention relates to a knee airbag module of a vehicle occupant restraint system.

[0002] Knee airbag modules protect the knee and shin area of ​​a vehicle occupant and are located in a lower section of the instrument panel or in the footwell adjacent to the instrument panel. The airbag of the knee airbag module is concealed behind the instrument panel or a footwell cover until it is deployed. When the knee airbag module is activated, the airbag enters the vehicle interior and deploys along the instrument panel towards the vehicle occupant.

[0003] In so-called "low-mounted" modules, the knee airbag module is mounted on the underside of the instrument panel above the footwell. To deploy, the airbag must first be moved downwards out of its housing, and then upwards in a movement directed towards the occupant. This arrangement and deployment sequence distinguishes these "low-mounted" modules from so-called "mid-mounted" modules, which are located in the center of the instrument panel and have an opening facing the occupant. The airbag exits through this opening in a largely horizontal direction and then deploys in front of the occupant's shins or knees.

[0004] Such a “mit-mounted” module, which is located in the central area of ​​the instrument panel and has an opening directed towards the occupant, and which immediately deploys the gas bag in the direction of the occupant’s shins, is shown, for example, in US 2002 / 0 171 232 A1.

[0005] Furthermore, US 8 998 249 B2 shows a “low-mounted” module that has an outer housing with a downward-facing outlet opening in the installed position, through which the gas bag leaves the outer housing when deployed, and a gas bag that is divided into several chambers arranged in series and connected by flow.

[0006] The object of the invention is to improve the exit and deployment behavior of the gas bag when the “low-mounted” knee gas bag module is activated.

[0007] This task is accomplished with a knee airbag module of a vehicle occupant restraint system, which has an outer housing containing an airbag that is folded into a gasbag pack before deployment, as well as a gas generator that produces the filling gas for inflating the airbag. The outer housing has a downward-facing outlet opening in its installed position, through which the airbag exits the housing during deployment. The airbag is divided into several chambers arranged in series and connected by airflow. The chamber closest to the gas generator is separated from an adjacent chamber by a wall that extends, in the inflated airbag, essentially in the area of ​​the outlet opening and along its length. In its installed position, the chamber closest to the gas generator is located above the adjacent chamber.

[0008] The chamber closest to the gas generator is filled immediately after activation of the knee airbag module. Advantageously, the inflow of filling gas and the filling of this chamber constitute the first inflation step after activation. The pressure generated by the volume increase allows the outlet opening to be released by opening a flap that previously covered it downwards and towards the vehicle interior. Furthermore, as the chamber closest to the gas generator is filled, the remaining, still-folded airbag package can be moved as a compact unit from the outer housing through the outlet opening into the vehicle interior, in front of the instrument panel or footwell cover.The chamber closest to the gas generator can thus be used advantageously to move the remaining folded gas bag package from the outer casing into the vehicle interior and to position it at a location below the outer casing that is favorable for further unfolding.

[0009] The chamber closest to the gas generator, when filled, ends in the area of ​​the outlet opening and preferably in the plane of the outlet opening, so that, according to the invention, the remaining gas bag assembly is positioned precisely below the outlet opening before the remaining chambers of the gas bag unfold along the instrument panel. In this way, the gas bag is safely moved around the edge of the outlet opening without any unwanted force being exerted on the edge of the instrument panel.

[0010] To achieve this, the chamber closest to the gas generator can be positioned within the outer casing in such a way that it at least partially fills and generates a force directed outwards from the outer casing onto the remaining gas bag assembly. For example, the chamber closest to the gas generator can be located between the remaining gas bag assembly and the rear wall of the outer casing to exert a defined force on the remaining gas bag assembly during inflation.

[0011] According to the invention, the chamber closest to the gas generator in the folded gas bag package is arranged such that, after activation of the gas generator in a first activation step, the chamber closest to the gas generator is filled first, while the rest of the gas bag package remains essentially in its folded state.

[0012] The force generated by the filling gas and the volume increase of the chamber nearest the gas generator is preferably directed essentially perpendicular to the plane of the outlet opening. This direction can coincide with the vertical if the knee airbag module is located at the lower end of the instrument panel in the vehicle and the plane of the outlet opening is essentially horizontal. In this activation step, the airbag pack is then moved essentially perpendicular to the outlet opening without any transverse components being generated along the instrument panel.

[0013] The wall bounding the chamber closest to the gas generator is designed to allow a flow connection between this chamber and the adjacent chamber, whereby the entire gas flow should occur exclusively from the gas generator into the chamber closest to the gas generator and from there into the directly adjacent chamber. The initially filled volume is limited by the wall of the chamber closest to the gas generator and / or by the way the remaining gas bag package is folded.

[0014] The gas bag package is preferably folded and the chamber closest to the gas generator is arranged such that the filling gas produced by the gas generator flows directly and completely into the chamber closest to the gas generator first. This direct flow can be facilitated by ensuring that the flow path within the chamber closest to the gas generator is not crossed by a fold in the gas bag, a partition, or a retaining strap inside the gas bag.

[0015] The shape and volume of the chamber closest to the gas generator can be designed such that, when inflated, it essentially fills the entire space within the outer casing. It has been found that this method reliably generates a force directed perpendicular to the outlet opening across the entire surface of the remaining gas bag assembly.

[0016] In order to place the folded gas bag package directly in front of the outlet opening in the vehicle interior, it is advantageous if the wall separating the chamber nearest the gas generator from the rest of the gas bag package lies in the plane or substantially parallel to the plane of the outlet opening when the gas bag is inflated.

[0017] In a first preferred embodiment, the wall is formed by a constriction or a partition wall connected with at least one flow-through opening between the chamber closest to the gas generator and an adjacent second chamber. The constriction can be created, for example, by the shape of the blanks of the chamber closest to the gas generator and the directly adjacent second chamber. Another simple method for manufacturing the wall is to insert a partition wall with flow-through openings between the chamber closest to the gas generator and the adjoining chamber.

[0018] In a second preferred embodiment, the wall is formed by at least one retaining band running inside the gas bag, which connects two opposing outer wall sections of the gas bag and limits a maximum distance between the outer wall sections.

[0019] The retaining strap preferably runs in the plane of the exit opening in order to achieve a defined positioning of the remaining gas bag package directly in front of the exit opening during the initial activation phase.

[0020] In each embodiment, the wall can be designed to resist the inflowing filling gas, so that the chamber closest to the gas generator is filled first, while the rest of the gas bag package remains essentially folded. It is also conceivable to supplement the wall during the initial unfolding phase with a fold in the gas bag package, arranged so that further gas flow into the remaining chambers is only possible after the chamber closest to the gas generator has more or less completely unfolded. For this purpose, for example, a section of the outer wall of the gas bag could be positioned over a flow opening between the chamber closest to the gas generator and the chamber adjoining it.

[0021] The gasbag, for example, has at least three chambers arranged one behind the other, with the chamber closest to the gas generator adjacent to a second chamber, and the second chamber adjacent to a third chamber, such that the gasbag as a whole has a curved shape when inflated. This allows the gasbag to follow the curve of the instrument panel and position itself between the instrument panel and the knee-shin area of ​​the vehicle occupant.

[0022] The chamber closest to the gas generator, the second chamber, and the third chamber preferably enclose each other at approximately a 90° angle, with the second chamber being flush with the interior of the outer casing. This design ensures that, after the remaining folded gas bag package has been pushed through the chamber closest to the gas generator in front of the outlet opening, the gas bag can unfold along the instrument panel without the panel obstructing its unfolding.

[0023] To support the curvature of the gasbag along the instrument panel, for example the second chamber can be separated from the third chamber by a partition wall provided with at least one flow opening, the partition wall running at an angle of about 0° - 30° to the vertical when the gasbag is inflated.

[0024] The chamber closest to the gas generator preferably has a smaller volume than the subsequent second chamber when the gas bag is inflated, since the chamber closest to the gas generator serves only to selectively push the remaining gas bag out of the outer casing during the initial activation phase of the knee gas bag module, while the subsequent second chamber can also have a retaining effect.

[0025] The invention is described in more detail below with reference to two exemplary embodiments and the accompanying drawings. The drawings show: -Fig. 1 a schematic sectional view of a knee gasbag module according to a first embodiment according to the invention, before activation; - Fig. 2 the knee airbag module from Fig. 1 in a first activation step; - Fig. 3 the knee airbag module from Fig. 1 in a second activation step; - Fig. 4 the knee airbag module Fig. 1, with the gasbag fully deployed; and - Fig. 5 a schematic sectional view of a knee gasbag module according to a second embodiment according to the invention, with the knee gasbag in a fully unfolded state.

[0026] The Fig. Figures 1 to 4 show a knee airbag module 10 of a vehicle occupant restraint system not shown in detail, according to a first embodiment.

[0027] The knee airbag module 10 is arranged in an opening of an instrument panel 12 or adjacent to a lower end of the instrument panel 12. The knee airbag module 10 has an outer housing 14 in which a gas generator 16 and a gasbag 20, folded into a gasbag pack 18 before deployment, are accommodated. An outlet opening 22 of the outer housing 14 for the gasbag 20 is closed by a cover 24 before the knee airbag module 10 is activated. The cover 24 extends in line with the instrument panel 12 and abuts an edge 26 of the instrument panel 12, which can form either a lower end of the instrument panel 12 or an upper end of a recess in the instrument panel 12.

[0028] The gasbag 20 is divided into several serially arranged chambers 28a - 28f (see Fig. 4) The chamber 28a closest to the gas generator, also referred to as the first chamber 28a, connects directly to the gas generator 16 and, as the first chamber of the gas bag 20, receives the filling gas flowing out of the gas generator 16.

[0029] In the folded gas bag package 18, the chamber 28a closest to the gas generator is arranged such that the filling gas from the gas generator 16 can flow directly into it, immediately leading to an increase in the volume of chamber 28a. In this example, chamber 28a is not folded in on itself and is placed directly between a rear side 30 of the outer casing 14 and the rest of the gas bag package 18.

[0030] Fig. Figure 1 shows the state of the knee airbag module 10 before activation. The cover 24 closes the outlet opening 22, and the airbag package 18 is fully folded and enclosed in the outer housing 14.

[0031] When activating the knee airbag module 10, a first activation step, as described in Fig. As shown in Figure 2, initially only the chamber 28a of the gas bag 20 closest to the gas generator is filled. In the example shown here, this chamber quickly reaches its maximum volume, which corresponds approximately to the dimensions of the interior of the outer casing 14.

[0032] This increase in volume generates a force F directed perpendicular to the outlet opening 22 and the cover 24. The force F acts on the entire surface of the gas bag pack 18, which extends parallel to the outlet opening 22, and initially presses the still-folded gas bag pack 18 against the cover 24. The cover yields at predetermined weakening zones 36, thus releasing the outlet opening 22. Subsequently, the force F, generated by the inflating first chamber 28a nearest the gas generator, presses against the gas bag pack 18 and pushes it perpendicular to the plane of the outlet opening 22 into the vehicle interior 38. The gas bag pack 18 now lies below the edge 26 of the instrument panel 12. This state is in Fig. 2 shown.

[0033] The wall 32, which separates the chamber 28a closest to the gas generator from the adjoining second chamber 28b, is formed in this example by a constriction 34 between chamber 28a and chamber 28b resulting from the shape of the individual cut-out parts of the gas bag 20. However, the wall 32 could also be realized, for example, by a fabric part inserted into the gas bag 20 with one or more flow openings that separate chambers 28a and 28b from each other.

[0034] When the chamber 28a closest to the gas generator is fully inflated, wall 32 lies in the plane of the outlet opening and extends along the outlet opening 22.

[0035] In this example, the wall 32 opposes the gas flow from the gas generator 16 with a flow resistance, which leads to the complete inflation of the chamber 28a before the rest of the gas bag package 18 begins to expand substantially.

[0036] It is also conceivable that flow openings in the wall 32 are closed off by the rest of the gas bag package 18 in the first activation step, so that essentially no gas can yet flow into the rest of the gas bag 20 outside the chamber 28 closest to the gas generator.

[0037] In a second activation step, which takes place in Fig. As shown in Figure 3, the filling gas produced by the gas generator 16 now flows through the chamber 28a closest to the gas generator into the second chamber 28b and inflates it. From there, the gas flows further into the remaining chambers 28c to 28f, so that the gas bag 20 unfolds along the instrument panel 12 and inflates to its final shape. This is shown in Fig. 4 shown.

[0038] The volume of the inflated chamber 28a closest to the gas generator is significantly smaller than that of the adjacent second chamber 28b.

[0039] The second chamber 28b is located here in the inflated state directly below the chamber 28a closest to the gas generator and is in line with the interior of the outer casing 14.

[0040] Overall, the gasbag 20, when inflated, describes a curved shape. This is due, among other things, to the first three chambers 28a, 28b, 28c, which are arranged at approximately a 90° angle.

[0041] All chambers 28a to 28f are linearly interconnected by flow, whereby the gas supplied by gas generator 16 can only flow from one chamber to the directly adjacent next, and all gas initially flows into chamber 28a closest to the gas generator. This is in Fig. 4 illustrated by arrows.

[0042] The gasbag 20 unfolds along the instrument panel 12 into its final position, protecting the knee / shin area of ​​the vehicle occupant, only after the gasbag package 18, with its still folded chambers 28b to 28f responsible for protecting the vehicle occupant, has already left the outer housing 14. This initial positioning of the still largely folded gasbag package 18 within the vehicle interior 38 is achieved exclusively by the inflating chamber 28a closest to the gas generator.

[0043] The partition 40 between the second chamber 28b and the third chamber 28c is positioned here in the fully inflated gas bag 20 at an angle of approximately 0° to 30° to the vertical.

[0044] The separation of the individual chambers 28a to 28f from one another can be achieved, as between the chamber 28a closest to the gas generator and the adjacent second chamber 28b, by a constriction or a partition with flow openings, but also by retaining straps. This is left to the discretion of the person skilled in the art.

[0045] Fig. Figure 5 shows a knee gasbag module 100 according to a second embodiment.

[0046] The gasbag 120 is shown here only in its fully inflated form. However, just as in the first embodiment, it is folded into a gasbag package and placed inside the outer housing 114, together with a gas generator 116, before the knee gasbag module 100 is activated.

[0047] However, in contrast to the first embodiment, the wall 132 between the first chamber 128a closest to the gas generator and the adjacent chamber 128b is formed here by one or more retaining bands which are arranged in the plane of the outlet opening 122 of the outer housing 114.

[0048] The at least one retaining band that forms the wall 132 connects two opposing outer wall sections 150, 152 of the gasbag 120 and limits their distance to the width of the exit opening 122.

[0049] Furthermore, the wall 132 offers a certain flow resistance, which ensures that the first chamber 128a is inflated first and pushes the still folded, remaining gasbag package ahead of it with a force perpendicular to the outlet opening 122 through the outlet opening 122 into the vehicle interior 38. There, the remaining gasbag 120 unfolds into the Fig.Figure 5 shows the curved, inflated shape in which it lies between the instrument panel 12 and the (not shown) knee / shin area of ​​the vehicle occupant. The subdivision provided by the wall 132 at the level of the outlet opening 122 tapers the area of ​​the gas bag 120 near the gas generator in the plane of the outlet opening 122, which additionally generates a force directed perpendicular to the outlet opening 122.

[0050] In this example, chambers 128a and 128b can be formed by common outer wall sections. The subdivision into the individual chambers 128a and 128b can be achieved entirely by the retaining strip(s) forming wall 132.

[0051] However, even in this embodiment, the wall 132 is gas-permeable, so that the filling gas supplied by the gas generator 116 can flow serially through all chambers 128a to 128f. The retaining band forming the wall 132 can, for example, have one or more flow openings, but can also be arranged inside the gas bag 120 in such a way that the gas can flow past the sides of the retaining band into the adjacent chamber 128b.

[0052] In this embodiment as well, the partition wall 140 between the second chamber 128b and the third chamber 128c is inclined at approximately 0° to 30° relative to the vertical.

[0053] Otherwise, the essential features of the knee gasbag module 100 are identical to those of the knee gasbag module 10 of the first embodiment.

[0054] In the example shown, the retaining strap forming wall 132 is formed integrally with a section of the partition wall 140 between the second chamber 128b and the third chamber 128c. At the transition from wall 132 to partition wall 140, the retaining strap is sewn to the gasbag wall.

[0055] The features of the individual embodiments can of course be combined or exchanged at the discretion of the person skilled in the art.

Claims

[1] Knee airbag module of a vehicle occupant restraint system, comprising an outer housing (14; 114) in which an airbag (20; 120) folded into an airbag pack (18) before its deployment is received, as well as a gas generator (16; 116) which generates filling gas for filling the airbag (20; 120), wherein an outlet opening (22; 122) oriented downwards in the installed position is formed in the outer housing (14; 114), through which the airbag (20; 120) leaves the outer housing (14; 114) when deployed, and wherein the airbag (20; 120) is divided into several chambers (28a - 28f; 128a - 128f) arranged in series and in flow communication, characterized by, that the chamber nearest to the gas generator (28a; 128a) is separated from an adjacent chamber (28b; 128b) by a wall (32; 132) which extends along the outlet opening (22; 122) in the inflated gas bag (20; 120) substantially in the region of the outlet opening (22; 122), wherein the chamber nearest to the gas generator (28a; 128a) is arranged in the folded gas bag package (18) such that, after activation of the gas generator (16; 116), the chamber nearest to the gas generator (28a; 128a) fills first, while the rest of the gas bag package (18) remains substantially folded, so that the rest of the gas bag package (18) is positioned exactly below the outlet opening (22; 122) before further chambers (28b-28f, 128b-128e) unfold the gasbag (20; 120) along an instrument panel (12). [2] Knee gasbag module according to claim 1, characterized by, that the chamber nearest to the gas generator (28a; 128a) is arranged within the outer casing (14; 114) in such a way that it fills at least partially and generates a force (F) directed out of the outer casing (14; 114) on the remaining gas bag package (18). [3] Knee gasbag module according to one of the preceding claims, characterized by , that the gas bag package (18) is folded and the chamber nearest to the gas generator (28a; 128a) is arranged such that the filling gas produced by the gas generator (16; 116) flows directly and completely first into the chamber nearest to the gas generator (28a; 128a). [4] Knee gasbag module according to one of the preceding claims, characterized by , that the chamber nearest to the gas generator (28a; 128a) in the inflated state substantially fills the space inside the outer casing (14; 114). [5] Knee gasbag module according to one of the preceding claims, characterized by, that the wall (32; 132) separating the chamber (28a; 128a) nearest to the gas generator from the rest of the gas bag package (18) lies in the plane or substantially parallel to the plane of the outlet opening (22; 122) when the gas bag (20; 120) is inflated. [6] Knee gasbag module according to one of the preceding claims, characterized by , that the wall (32) is formed by a constriction (34) or a partition wall connected with at least one flow opening between the chamber (28a) nearest the gas generator and an adjacent second chamber (28b). [7] Knee gasbag module according to any one of claims 1 to 5, characterized by , that the wall (132) is formed by at least one retaining band running inside the gasbag (120), which connects two opposing outer wall sections (150, 152) of the gasbag (120) and limits a maximum distance between the outer wall sections (150, 152). [8] Knee gasbag module according to one of the preceding claims, characterized by , that the gas bag (20; 120) has at least three chambers (28a - 28f; 128a - 128f) arranged one behind the other, wherein the chamber closest to the gas generator (28a; 128a) adjoins a second chamber (28b; 128b) in such a way and the second chamber (28b; 128b) adjoins a third chamber (28c; 128c) in such a way that the gas bag (20; 120) as a whole has a curved shape when inflated. [9] Knee gasbag module according to claim 8, characterized by , that the chamber nearest to the gas generator (28a; 128a), the second chamber (28b; 128b) and the third chamber (28c; 128c) describe an angle of approximately 90°, with the second chamber (28b; 128b) being in line with the interior of the outer casing (14; 114). [10] Knee gasbag module according to one of claims 8 and 9, characterized by, that the second chamber (28b; 128b) is separated from the third chamber (28c; 128c) by a partition (40; 140) having at least one flow opening, which runs at an angle of 0 to 30° to the vertical when the gas bag (20; 120) is inflated. [11] Knee gasbag module according to one of the preceding claims, characterized by , that the chamber nearest to the gas generator (28a; 128a) has a smaller volume than the subsequent second chamber (28b; 128b) when the gas bag (20; 120) is inflated.

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