Module cap for an airbag module

Abstract

Disclosed is a module cap (24) for an airbag module (10), having a predetermined breaking path (26) which is formed by a groove (28) on a rear side of the module cap (24). In addition, the module cap (24) comprises a rib (32) which extends at least partially along the predetermined breaking path (26) and protrudes from the rear side of the module cap (24).

Description

[0001] Module cap for a gas bag module

[0002] The invention relates to a module cap for a gas bag module with a predetermined predetermined breaking point.

[0003] Gas bag modules are used in vehicle occupant restraint systems and provide a protective function for one or more vehicle occupants.

[0004] Such a gas bag module with a gas bag comprises a module cap, which represents a frontal plastic cover and tears open in the event of restraint. The module cap has a predefined exit opening for the gas bag. To precisely define the exit opening and, above all, to enable the module cap to be torn open with predetermined forces, the module cap typically has a predetermined breaking line, i.e., a groove in the rear of the module cap that defines the predetermined breaking path.

[0005] In order for the module cap to break along the predetermined breaking line, a certain internal pressure is required, which is applied by the gas bag.

[0006] The weakened material of the module cap along the predetermined breaking line must be designed to be sufficiently thin to ensure the fastest possible deployment of the gas bag. On the other hand, the material must not be too thin at this point, otherwise the groove will be visible on the front.

[0007] Accordingly, it is an object of the invention to provide a module cap for an airbag module that is easier to manufacture and has a very precise tear path. Furthermore, the airbag module should be able to deploy at the lowest possible pressure to ensure the best possible safety for the vehicle occupants.

[0008] This object is achieved according to the invention by a module cap for an airbag module with a predetermined predetermined breaking point, which is formed by a groove on a rear side of the module cap. In addition, the module cap comprises a rib that extends at least partially along the predetermined breaking point and protrudes from the rear side of the module cap. In other words, the module cap is reinforced on at least one side of the groove, whereby the cap becomes stiffer in this area. The rib is a material thickening that serves to stiffen the cap. This means that the rib merges integrally into the rest of the module cap.

[0009] By providing a rib along at least part of the predetermined breaking line, stress is concentrated in this area of ​​the groove, causing the module cap to fracture earlier, i.e., at a lower pressure load, along the predetermined breaking line. Accordingly, the gas bag of the gas bag module can deploy more quickly, and surrounding module components are subjected to less stress. In addition, the module cap can be made thicker in the area of ​​the groove if necessary, simplifying production by reducing the likelihood of the module cap accidentally breaking during the manufacturing process.

[0010] Preferably, the rib is provided in the central area of ​​the front wall of the module cap to allow at least partial deployment of the gas bag while the rest of the module cap is breaking open. This allows for even faster gas bag deployment.

[0011] The rib may taper towards its end, i.e. towards its edge remote from the back, in particular have a trapezoidal cross-section, which simplifies the manufacture of the rib.

[0012] According to one embodiment, the predetermined breaking line defines at least one flap-like section on the module cap. The rib is provided either only on or only outside the flap-like section.

[0013] Alternatively, it is conceivable to provide at least one rib on the flap-like section as well as at least one rib outside the flap-like section, wherein the ribs then preferably have different cross-sections, in particular different rib heights.

[0014] The provision of a flap-like section ensures that the module cap remains attached to the airbag module on at least one side and does not detach from the airbag module in an uncontrolled manner due to the pressure exerted by the airbag. By reinforcing the edge of the resulting outlet opening, it is ensured that the stress concentration takes place in the desired area or at the desired location in the groove, thus ensuring that the module cap opens as quickly as possible. If there is a rib both on the flap-like section and a rib outside the flap-like section, in other words if ribs are provided on both sides of the groove, these ribs are preferably different, in particular with different rib heights.It has been found that the desired effect of stress concentration in the groove and the resulting premature opening of the module cap is particularly pronounced in rib designs that are asymmetrical with respect to the groove. Therefore, the design variant in which a rib is provided only on one side of the groove is particularly simple and preferred.

[0015] According to a further embodiment, the predetermined breaking line is H-shaped. The predetermined breaking line defines two flap-like sections on the module cap, separated by an intermediate web of the H. The rib is provided on only one of the flap-like sections, in the area of ​​the intermediate web of the H.

[0016] Alternatively, a rib is provided on each of the flap-like sections in the region of the intermediate web of the H, wherein the ribs then preferably have different cross-sections, in particular different rib heights.

[0017] If two flap-like sections are provided, the module cap opens on two sides, which enables faster airbag deployment because each of the flap-like sections has to expose a smaller area. The arrangement of the rib or ribs along the intermediate web means that the module cap can tear open here first. The module cap then tears open at the side webs. If there is a rib on each of the flap-like sections, in other words if ribs are provided on both sides of the groove, these ribs are preferably designed differently, in particular with different rib heights. It has been found that the desired effect of stress concentration in the groove and a resulting, premature opening of the module cap is particularly pronounced with rib designs that are asymmetrical with respect to the groove.The design variant in which a rib is provided only on one side of the groove in the area of ​​the intermediate web of the H-shaped predetermined breaking line is therefore particularly simple and preferred.

[0018] Preferably, the rib has a width of 1 mm to 3 mm and a height of 2 mm to 15 mm in the area of ​​its free end. A rib with dimensions in these ranges provides sufficient stiffening of the module cap along the predetermined breaking point, thus achieving optimal stress concentration.

[0019] To simplify the manufacturing process while still ensuring reliable tearing, the groove preferably has a width of 0.5 mm to 1 mm, in particular 0.1 mm to 0.5 mm, at its deepest point. The module cap can have a thickness of 0.5 mm to 1 mm, in particular 0.1 mm to 0.5 mm, at the deepest point of the groove.

[0020] In contrast, the module cap has a thickness of 1 mm to 4 mm in the area outside the rib and outside the groove in order to ensure a certain basic stability for the gas bag module and the module cap without unnecessarily increasing the installation space and the weight of the gas bag module.

[0021] On the side leading to the rib, the groove can run obliquely from the deepest point, in particular continuously and without a step, in the direction of the rib, which on the one hand simplifies the manufacture of the module cap in the area of ​​the groove and on the other hand transfers the stresses to the deepest point of the groove.

[0022] The rib can run along the groove with or without a gap, in particular a constant gap, from the groove, meaning the rib does not have to be directly adjacent to the groove. Optionally, the gap is a maximum of 10 mm, in particular a maximum of the largest width of the rib.

[0023] The module cap described above can be used for the airbag module of a vehicle steering wheel. Of course, the module cap can also be used for any other vehicle airbag module. In principle, the module cap could also be used in other areas, as long as a predetermined breaking point is provided to allow the opening or unfolding of an object covered by the module cap.

[0024] Emblems are commonly located centrally on module caps for steering wheels or passenger airbags. In this case, the groove and rib extend in an arc around a central emblem section, so the emblem is not subjected to stress. Especially in such arced areas, the rib offers advantages in terms of stress concentration.

[0025] Further features and advantages of the invention will become apparent from the following description and the accompanying drawings, to which reference is made. In the drawings:

[0026] Figure 1 is a schematic representation of a gas bag module,

[0027] Figure 2 shows a cross section through the gas bag module from Figure 1 with a module cap according to the invention;

[0028] Figure 3 is a perspective view of a vehicle steering wheel with a module cap according to the invention;

[0029] Figure 4 is a schematic representation of a rear side of the module cap according to the invention, which can be seen in Figure 3;

[0030] Figure 5 shows a detailed view of the predetermined breaking point from Figure 4; and

[0031] Figure 6 is a schematic representation of a cross-section of the module cap in the area of ​​the groove defining the predetermined breaking line.

[0032] Figure 1 shows a gas bag module 10 of a vehicle occupant restraint system of a motor vehicle.

[0033] The gas bag module 10 has a gas bag 12 with an inflatable chamber 14 and a gas bag wall 16 that encloses the chamber 14.

[0034] In the present embodiment, the gas bag 12 is a front gas bag which is arranged in a vehicle steering wheel 18 of the motor vehicle.

[0035] In principle, the gas bag 12 can be any gas bag and / or be attached to any element of the motor vehicle. In particular, however, it is a front gas bag that provides protection in the event of a frontal impact.

[0036] The gas bag module 10 further comprises a gas generator 20, by means of which the gas bag 12 can be inflated in a restraint case in order to provide a protective effect for one or more vehicle occupants.

[0037] The gas generator 20 is preferably arranged in the chamber 14. In an alternative embodiment, the gas generator 20 can also be provided separately from the airbag module 10 and / or arranged at any location in the motor vehicle or in the airbag module 10. It is only important that the gas generator 20 is connected to the chamber 14 so that the gas generated by the gas generator 20 in the restraint situation flows into the chamber 14 to inflate the airbag 12.

[0038] The gas bag 12 unfolds in a main deployment direction H.

[0039] The gas bag module 10 also comprises a module housing 22, in which at least the gas bag 12, and preferably also the gas generator 20, is arranged. The module housing 22 is closed at the front by a module cap 24, which is made of plastic.

[0040] Accordingly, the production of the module cap 24 is inexpensive and quick, since it can be produced, for example, by an injection molding process.

[0041] While Figure 1 shows the gas bag module 10 with an activated gas bag 12, Figure 2 shows a cross-section of the gas bag module 10 before the gas bag 12 is activated.

[0042] In order for the gas bag 12 to be able to unfold in the event of restraint, the module cap 24 has a predetermined breaking line which defines a predetermined breaking path 26 along which the module cap 24 breaks open in the event of restraint.

[0043] This predetermined breaking line 26 can be seen in Figure 3 by an H-shaped line on the module cap 24.

[0044] The predetermined breaking line 26 is achieved by a material weakening on the rear side of the module cap 24, in particular by a groove 28 formed on a rear side 30 of the module cap 24. The rear side 30 is the side of the module cap 24 that faces toward the gas bag 12 and away from the vehicle occupants.

[0045] In addition to the predetermined breaking line 26, the module cap 24 has an elongated rib 32 (see Figure 4) which is integrally formed on the module cap 24 and extends at least partially along the predetermined breaking line 26 and protrudes from the rear side 30 of the module cap 24.

[0046] In contrast to the predetermined breaking line 26, the rib 32 is a material thickening which provides local stiffening of the module cap 24.

[0047] Due to the rib 32, the residual material thickness of the module cap 24 in the region of the deepest point of the groove 28 can be greater than if no rib 32 is provided, which can simplify the manufacturing process.

[0048] In addition, the stiffening by means of the rib 32 along the groove 28 results in a stress concentration in the corresponding area of ​​the groove 28, that is, in the deepest section of the groove 28, which defines the predetermined breaking line 26.

[0049] The rib 32 is provided in particular in the central area of ​​the module cap 24, i.e. in the area in which it is intended to tear open first.

[0050] Figures 4 and 5 show the rear side 30 of the module cap 24. It can be seen that, in the embodiment shown, the rib 32 is arranged in a central region of the module cap 24; more precisely, the groove 28 and rib 32 extend in an arc around an emblem section 33. An emblem is then applied to the outside of the module cap, which emblem, for example, has rear-side pins that extend to the rear side of the module cap 24 and are deformed there, for example, to form holding devices.

[0051] The groove 28 and thus the predetermined breaking line 26 have an H-shape, clearly visible in Figure 3, with an intermediate web 35, in the center of which are provided the curved section of the groove 28 and the rib 32. The intermediate web 35 connects two side webs 37. The H-shape results in a first flap-like section 34 and an adjacent second flap-like section 36, which are separated from each other by the intermediate web 35.

[0052] Alternatively, only a single flap-like section can be provided, which would then be defined by a U-shaped groove.

[0053] As can be seen in particular in Figures 4 and 5, in the exemplary embodiment shown here the rib 32 is located only on one of the two flap-like sections 34, 36, in particular on the second flap-like section 36, more precisely in the region of the intermediate web 35. Likewise, the rib 32 can also be provided exclusively on the first flap-like section 34.

[0054] Alternatively, it is also conceivable that a rib is provided on each of the first flap-like portion 34 and the second flap-like portion 36. In this case, the ribs are preferably not identical, but rather designed differently, e.g., in particular, with different rib heights. The desired effect of stress concentration in the groove 28 and a resulting premature opening of the module cap 24 is particularly pronounced in rib designs that are asymmetrical with respect to the groove 28. The embodiment shown in Figures 4 and 5, in which a rib 32 is provided only on one side of the groove 28, is therefore particularly simple and preferred.

[0055] In Figures 4 and 5, it can be seen that the groove 28, on the side 38 leading to the rib 32, runs obliquely and without a step from its deepest point to the rib 32 and merges directly into it. In the slightly modified variant according to Figure 6, the rib 32 is not arranged directly next to the groove 28, but runs parallel to the groove 28 at a minimal distance A via a step 40. The distance A is preferably smaller than the width of the rib 32, whereby the desired effect of stress concentration in the groove 28 is still achieved up to a maximum distance of 10 mm.

[0056] The rib 32 tapers conically toward its free end 42 and preferably has a trapezoidal cross-section, viewed transversely to the longitudinal extent of the rib 32. The width B1 of the rib 32 at its free end 42 is preferably only 1 to 3 mm.

[0057] The module cap 24 has a thickness S1 of 2 to 15 mm in the area of ​​the rib 32, whereas outside the groove 28 and the emblem section 33 it has a predominantly uniform thickness S2 in the range between 1 to 4 mm.

[0058] At its deepest point, the groove 28 has a width B2 of 0.05 to 1 mm, in particular 0.1 to 0.5 mm and the module cap 24 has a thickness S3 of 0.05 to 1 mm, in particular 0.1 to 0.5 mm.

[0059] According to an alternative embodiment already indicated above, which is not shown in the figures, only a first flap-like section on the module cap 24 is defined by the predetermined breaking line. The rib can be provided either only on the first flap-like section or only outside the first flap-like section.

[0060] Alternatively, both a rib on the first flap-like section and a rib outside the first flap-like section can be provided. As already mentioned above, however, the two ribs on opposite sides of the groove should not be identical, but rather different, so that a pronounced stress concentration in the groove 28 in the area of ​​the ribs continues to occur.

[0061] If a restraint event occurs, the gas generator 20 is activated and fills the chamber 14 of the gas bag 12 with gas. This causes the gas bag 12 to deploy, exerting pressure from the inside on the module cap 24. Accordingly, the module cap 24 is under tension, with the rib 32, which extends at least partially along the predetermined breaking line 26, ensuring a stress concentration in the corresponding area of ​​the groove 28, so that the module cap 24 breaks sooner or more quickly. In other words, the pressure required to break the module cap 24 is reduced by the provision of the rib 32.

[0062] By breaking the module cap 24 earlier, the airbag 12 can deploy faster and more effectively, so that the full protective effect for the vehicle occupants can be provided sooner. Furthermore, the stress concentration in the area of ​​the groove 28 ensures that surrounding module components of the airbag module 10 are subjected to less stress, so that the entire activation process of the airbag module 10 can take place in a more controlled manner.

Claims

Patent claims 1. Module cap (24) for a gas bag module (10) with a predetermined predetermined breaking course (26) which is formed by a groove (28) on a rear side (30) of the module cap (24), and a rib (32) which extends at least partially along the predetermined breaking course (26) and protrudes from the rear side (30) of the module cap (24).

2. Module cap (24) according to claim 1, characterized in that the rib (32) is provided in the central region of the module cap (24).

3. Module cap (24) according to claim 1 or 2, characterized in that the rib (32) tapers conically in cross section towards its end (42), in particular has a trapezoidal cross section.

4. Module cap (24) according to one of the preceding claims, characterized in that the predetermined breaking line (26) defines at least one flap-like section (34, 36) on the module cap (24) and the rib (32) is provided only on the flap-like section (34, 36) or only outside the flap-like section (34, 36).

5. Module cap (24) according to one of claims 1 to 3, characterized in that the predetermined breaking course (26) defines at least one flap-like section (34, 36) on the module cap (24) and at least one rib (32) on the flap-like section (34, 36) as well as at least one rib (32) outside the flap-like section (34, 36) is provided.

6. Module cap (24) according to one of claims 1 to 3, characterized in that the predetermined breaking course (26) is H-shaped and defines two flap-like sections (34, 36) on the module cap (24) which are separated by an intermediate web (35) of the H, wherein the rib (32) is provided only on one of the flap-like sections (34, 36) in the region of the intermediate web (35) of the H.

7. Module cap (24) according to one of claims 1 to 3, characterized in that the predetermined breaking line (26) is H-shaped and has two flap-like sections (34, 36) are defined on the module cap (24), which are separated by an intermediate web (35) of the H, wherein a rib (32) is provided on each of the two flap-like sections (34, 36) in the region of the intermediate web (35) of the H and the ribs (32) extend along the intermediate web (35).

8. Module cap (24) according to one of the preceding claims, characterized in that the rib (32) in the region of its free end has a width (B1) of 1 mm to 3 mm, and the module cap (24) in the region of the rib (32) has a thickness (S1) of 2 mm to 15 mm.

9. Module cap (24) according to one of the preceding claims, characterized in that the groove (28) has a width (B2) at its deepest point and / or the module cap (24) has a thickness (S3) of 0.05 mm to 1 mm, in particular of 0.1 mm to 0.5 mm, at the deepest point of the groove (28).

10. Module cap (24) according to one of the preceding claims, characterized in that the module cap (24) has a thickness (S2) of 1 mm to 4 mm in the region outside the rib (32) and outside the groove (28).

11. Module cap (24) according to one of the preceding claims, characterized in that the groove (28) on its side (38) which leads to the rib (32) runs obliquely, in particular without a step, from the deepest point in the direction of the rib (32).

12. Module cap (24) according to one of the preceding claims, characterized in that the rib (32) runs along the groove (28) without or with a distance (A) from the groove (28).

13. Module cap (24) according to one of the preceding claims, characterized in that the module cap (24) is a module cap (24) of a gas bag module (10) of a vehicle steering wheel (18).

14. Module cap (24) according to one of the preceding claims, characterized in that the groove (28) and the rib (32) extend in an arc around a central emblem section (33).

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