This application is a National Stage of International Application No. PCT/EP2007/005557, filed Jun. 23, 2007, which claims priority under 35 U.S.C. §119 to German Patent Application No. 10 2006 038 124.6, filed Aug. 14, 2006, the entire disclosure of which is herein expressly incorporated by reference.
The present invention relates to a restraint system for a motor vehicle.
It is well known for motor vehicles to protect occupants from injuries by inflating an air bag in a short period of time, to catch the occupant who is displaced in a forward direction. For this purpose, it is important that the air bag quickly reaches its effective volume, and it is therefore necessary to produce relative large amounts of gas (e.g., in a pyrotechnical manner) and to introduce them into the gas bag. Recently, for dimensioning the gas volume to be added, occupant/and or vehicle parameters have been evaluated, so as not to unfold the gas bag to its full size for example in the case of a so-called “out of position” of the occupant. However, the necessity for adjustment to all possible load conditions and the relatively cost-intensive control and regulation technique have made this feature problematic.
Intensified efforts have been made, therefore to develop so-called self-regulating systems which can adjust automatically to the corresponding load conditions. For example, venting apertures have been provided, which close automatically when the inner pressure of the gas bag becomes too large.
German patent document DE 2 302 737 discloses a restraint system comprising a two-layer gas bag, where the gas is guided only between the two layers, so that a complete gas cushion does not result; rather, a spherical annular supporting structure. The unfolding of the support structure thereby occurs in the transverse direction of the abutting gas cushions. On the other hand, European patent document EP 0589 059 B1 shows furthermore, that it is necessary during the unfolding of the two-layer gas bag, to suck ambient air into the interior so as to overcome the negative pressure.
Both of these systems have in common the feature that less gas volume is necessary to unfold the gas bag to its full size, due to the gas bag's being formed with two layers. The temperature and the pollution can thereby be reduced.
Finally, UK patent document GB 1 420 226 A discloses a restraint system for a motor vehicle, where a tubular supporting structure is provided in the interior of the two-layer gas cushion, the longitudinal extension of which exceeds the dimensions of the transverse extension in the inflated (that is, active) state. The supporting structure unfolds due to its particular geometry mainly in the direction of its longitudinal extension.
An automatic adjustment of the gas bag dependent on the respective load condition (e.g., dependent on the respective occupant or his or her position) is not described.
It is therefore an object of the present invention to improve the generic restraint system in such a manner that its size adjusts to the respective load condition.
This and other objects and advantages are achieved by the restraint system according to the invention, which when it impacts upon an obstacle during unfolding, does not achieve the stability it would have when fully unfolded and/or the final volume or the final extension, due to the particular geometric form of the supporting structure (that is, due to its longitudinal extension exceeding its cross section). The supporting structure has a different stability during unfolding, due to its longitudinal formation. While the supporting structure is initially rather unstable (that is, can be easily hindered during unfolding), the completely unfolded supporting structure achieves full stability (that is restraining force). This means that, if the supporting structure impacts upon an obstacle during the unfolding, as is the case for example with occupants leaning forward (out of position), unfolding can be stopped more easily or deflected due to the supporting structure which is still unstable. These small forces effect a low pressurization of the occupant.
As used herein, the term “supporting structure” refers to a structure which is similar to a skeleton (in contrast to a conventional spherical gas bubble—a gas bag), and which comprises a restraint effect in the fully unfolded state comparable to the conventional gas bag. The provision of a substantially more complex inflatable supporting structure according to the invention, for example a branched tree structure not only reduces the necessary gas volume, but also diminishes the force peaks acting on the occupant during unfolding, if he is effectively “in the way” of the unfolding supporting structure. In contrast, the gas amount in the conventional gas bubble is on a substantially higher level from the start of the activation until the full unfolding, so that obstacles in the unfolding path are put under more pressure independent of the unfolding state.
The supporting structure can preferably be filled with gas, and it is unimportant whether it is filled with gas generated in a pyrotechnical manner or with gas from a pressure vessel or the ambient air. The ambient air can be guided into the carrier volume enclosed by the supporting structure by suction through the negative pressure occurring during the unfolding. The gas volume can be reduced further in this manner.
If several supporting structures are provided, which are connected to one another or to the environment in a fluidic manner, a restraint system can be formed, which is constructed in a net-like, tree-like or supporting frame-like manner. Thus, supporting structures proceeding in the longitudinal direction of the vehicle can be connected to supporting structures proceeding transversely to the transverse direction of the vehicle. The unfolding of the transverse supporting structures thereby nevertheless takes place in the direction of the longitudinal extension of the respective supporting structure.
The supporting structures can be connected by flexible sheets, in particular flexible textile sheets. In this case, the flexible sheet can be fixed between two adjacent supporting structures.
If several supporting structures are connected to one another by a flexible sheet, the gas can be used for restraining action in the resulting enclosed carrier volume enclosed. The gas in the carrier volume serving to restrain occupants can be heated or supplemented by means of a heating device (e.g., an ignition tablet or a small gas generator step, which develops heat with a possibly very low gas volume). As a result, the gas volume or the inner pressure, and thus the restraint action, increases therewith correspondingly.
If a supporting structure impacts upon an obstacle during unfolding, the gas flowing into the supporting structure can be distributed to other adjacent supporting structures or into the environment, by gas redistribution components. The inner pressure generated by the flow in the supporting structure can also be reduced by increasing its cross section. This can take place in such a manner that tear seams break down at a certain pressure, so that the supporting structure can increase in its transverse direction. A pressure-relief valve can also be provided, which opens when an interior pressure is reached which is too high.
With conventional compact gas bags, it was previously necessary to refrain from directing venting apertures towards the occupant, because gas temperatures are reached which are too high. However, with the system according to the invention, as cold ambient air flows within the carrier volume, and not a pyrotechnically produced gas, and venting apertures can be directed towards the occupant by the reduced temperature. The air bag dampening can thus be adapted for various environmental conditions, by sealing a venting aperture cross section between occupant and air bag.
Thus, this contact surface and its sealing with persons having a higher volume (and usually a higher weight) is larger, so that a stronger restraint action is achieved hereby. With more severe accidents, the contact surface and thus the restraint action is also increased by a stronger immersion of the occupant into the air bag. This principle also permits a variable air bag dampening for belted and unbelted occupants, because in the unbelted state, the occupant will be immersed into the air bag with less force.
If the venting apertures are formed as perforations (that is, many small apertures), as for example with a textile net, a projection area corresponding to the measurements of the occupant can be closed. The reproducibility of the results increases on average with many small venting apertures.
In a preferred embodiment, at least one of the supporting structures extends at least partially in an overlap of a hard structure, as for example a supporting column. It is also possible to provide a structure which unfolds between the occupants as an interaction bag.
So as to be able to manufacture a complex supporting structure with its inflatable components and the flexible sheets, the one-piece woven technique is recommended. This technique distinguishes itself in that, on one and the same device, a double layer can be manufactured for the inflatable structures, and one layer for the flexible sheets, or a three-dimensional structure can be woven.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.