Gasbag module with outflow opening with adjustable gas permeability and a method for controlling the outflow of such a gasbag

Abstract

Gasbag module (1) for a vehicle occupant restraint device (2), comprising a gasbag (5) and at least one outlet opening (6) having adjustable gas permeability, through which gas can escape from the gasbag (5), wherein the at least one outlet opening (6) is formed by a region (8) of the gasbag (5) which has a gas permeability that can be changed due to the action of an electric voltage and / or an electric field, characterized in that the region (8) of the at least one outlet opening (6) is designed as a coating (11) on a gas-permeable carrier fabric (7) and that the gas permeability is adjustable proportionally to the strength of the applied electric voltage or electric field, wherein the adjustable region (8) comprises an array of polymer chains (13, 14) formed on the coating (11) from a polymeric material, which consist of different polymers,whose differing properties can be manipulated differently by applying an electrical voltage, such that in one functional position a first group of polymer chains (13) assumes a largely extended orientation, while the polymer chains (14) in a second group simultaneously contract and assume a coiled position, achieving a high degree of gas impermeability, and in another functional position the second group of polymer chains (14) assumes the extended orientation, while at the same time the first group of polymer chains (13) contracts and assumes a coiled position, achieving a high degree of gas permeability, so that the gas flow can pass through this area (8) almost unhindered.

Description

[0001] The invention relates to a gasbag module for a vehicle occupant restraint device, comprising a gasbag formed from a gasbag fabric and at least one outlet opening having adjustable gas permeability, through which gas generated by a gas generator can escape from the gasbag, wherein the outlet opening is formed by a region of the gasbag that has a gas permeability that can be changed by the action of an electric voltage or an electric field. Furthermore, the invention relates to a method for controlling the outflow of a volume of gas filling a gasbag of a vehicle occupant restraint device through an outlet opening of the gasbag.

[0002] DE 20 2005 001 000 U1 relates to a gasbag module for a vehicle occupant restraint device, comprising a gasbag made from a piece of fabric. Metal memory wires are woven into the fabric, which is either slightly gas-permeable or gas-tight below its material-specific transformation temperature. Upon heating above this temperature, the fabric returns to a pre-defined initial shape, enlarging an area through which gas can escape. This allows the effective cross-section of the outflow opening to be controlled. The fabric can be woven directly into the gasbag wall or designed as a cover positioned over an outflow opening formed in the gasbag wall. Heating can be achieved by passing an electric current through the metal wires.

[0003] German patent DE 10 2012 001 180 A1 relates to an airbag with a ventilation opening that is closed by a locking element. A melting or heating element connected to a voltage source releases the locking element. To allow the ventilation opening to be easily and reliably opened when needed, a coiled thread serves as the locking element, which is melted by applying a voltage, thus breaking the fabric's cohesion.

[0004] From EP 1 731 382 A1, a gas bag intended for a vehicle occupant restraint device is known, comprising an outflow device for releasing and / or modifying an outflow opening through which gas can escape from the gas bag, and an electrochemo-mechanical actuator with an active layer of polymers that change their volume depending on an electric field or electrochemical potential. This makes it possible to selectively influence the outflow behavior of a gas bag module.

[0005] A gasbag module is also known from WO 2003 / 006276 A2. To keep the exhaust opening of such an adaptive exhaust opening closed before and during inflation of the gasbag, and to allow the exhaust opening to be released only at a specific time, a retaining strap is provided in the known gasbag module. One end of the retaining strap is attached to the gasbag fabric in the area of ​​the adaptive exhaust opening. In its initial or installed position, the fabric completely covers and closes the exhaust opening. The other end of the retaining strap is secured to a module-side retaining device in such a way that the respective end of the retaining strap is released when the retaining device is triggered.

[0006] The retaining strap is dimensioned such that it completely covers the exhaust opening. After activation of the holding device by releasing the attached end of the retaining strap, the strap releases the fabric area containing the exhaust opening, allowing the area of ​​the gas bag defined by the retaining strap to fully unfold and the adaptive exhaust opening to fully open due to the stretching of the gas bag fabric.

[0007] In EP 2 421 727 B1, the adaptive outflow opening is formed by a slit cut into the gasbag fabric, with a retaining strap extending over the adaptive outflow opening being fixed to a vehicle-mounted part on the inside of the gasbag.

[0008] A disadvantage here is that the arrangement of the retaining strap, in terms of dimensions and attachment, must be matched to the respective size of the adaptive exhaust opening. Furthermore, the installation of the gas bag, including the attached retaining strap, is complex.

[0009] A gasbag module in which a venting area in the gasbag wall can be opened when a reduction in the internal gasbag pressure is desired is also known, for example, from WO 2004 / 045919 A1. A pyrotechnic charge in the form of an explosive cord is attached directly to the venting area, so that the venting area burns through or is mechanically ruptured after ignition of the explosive cord.

[0010] The gasbag module shown in WO 2003 / 097407 A2 includes an explosive bolt to release a tube-shaped outflow area of ​​the gasbag.

[0011] EP 1 279 574 A1 describes a gas bag module in which a slide is moved to open the vents in a holding part so that the bores formed in it align with the vents. The hot gas flowing into the gas bag melts the area of ​​the gas bag located between the bores of the slide and the vents in the holding part, so that some of the gas escapes from the gas bag during inflation.

[0012] US Patent 6,547,274 B2 discloses a gasbag module in which the opening cross-section of an exhaust opening in a carrier plate can be released by means of piezoelectrically controlled flaps. The current supply to the piezoelectric elements is controlled, for example, depending on the posture or body type of the vehicle occupant or the vehicle speed.

[0013] In EP 1 731 382 A1, the outflow device comprises at least one element made of an electrically controllable polymer actuator, which changes its volume depending on an electric field. This allows the composite to bend in response to voltage changes, similar to a bimetallic strip, thereby achieving large deflections to control the effective cross-section of the outflow opening. Preferably, the polymer actuator is integrated into the gasbag wall, in particular woven into the fabric of the gasbag wall, or connected to the gasbag fabric by sewing or gluing. Particularly preferably, the electrochemically inert fabric material can serve as a carrier layer for the active layer of the polymer actuator. When a voltage is applied to the polymer actuator, the gasbag fabric is deformed, thereby creating, enlarging, or reducing the size of the outflow area in the gasbag wall.

[0014] EP 1 683 685 A2 relates to a gas bag for a vehicle occupant restraint device, with a control device having a memory metal in order to selectively influence the outflow behavior of a gas bag module by controlling the effective cross-section of the outflow opening.

[0015] Furthermore, JP 2008-168176A refers to a separation membrane that uses a conductive polymer. Applying a voltage to the conductive polymer causes molecular shrinkage or expansion, thereby changing the pore size of the separation membrane.

[0016] In practice, the design effort associated with modifying such vent openings proves to be a disadvantage. For example, tear strips that open a seam to allow gas to escape require at least a release mechanism to open the strip as needed. Elements where the actual mechanical actuators of the vent opening are located on the textile gas bag are considerably more complex, as any risk of injury to the vehicle occupant from components of the actuator must be avoided. Furthermore, individual adjustments for specific vehicle occupants often require multiple adjustable vent openings, further increasing the complexity.

[0017] Against this background, the invention aims to design a gasbag module of the type mentioned above in such a way that it allows for a simple and rapid change in the outflow of the gas filling the gasbag. In particular, it should enable an individually adapted gas outflow to the respective vehicle occupant in order to adjust to the required filling pressure of the gasbag. Furthermore, a suitable control system for such a gasbag module should be provided.

[0018] The first problem is solved with a gasbag module according to the features of claim 1. The dependent claims relate to particularly advantageous further developments of the invention.

[0019] According to the invention, a gasbag module is provided in which the area of ​​the at least one outflow opening is designed as a coating on a gas-permeable carrier fabric and the gas permeability is adjustable proportionally to the strength of the applied electrical voltage or electric field, wherein the adjustable area comprises an array of polymer chains formed on the coating made of a polymeric material, which consist of different polymers whose differing properties can be manipulated differently by applying an electrical voltage, such that in one functional position a first group of polymer chains assumes a largely stretched orientation, while at the same time the polymer chains in a second group contract and assume a coiled position, achieving a high degree of gas impermeability.and in another functional position, the second group of polymer chains assumes the stretched orientation, while at the same time the first group of polymer chains contracts and assumes a coiled position, achieving a high degree of gas permeability so that the gas flow can pass through this area almost unhindered.

[0020] This enables, for the first time, continuously adjustable gas permeability of the area through which the filling gas can escape from the airbag, thus altering the gas pressure and the shape of the airbag and optimally adapting it to the individual vehicle occupants. Not only the amount of gas permeability, but also its rate of change over time can be adjusted accordingly. In particular, a phase with reduced gas permeability can be implemented after an increase in gas permeability. Because the gas permeability operates without mechanical components, especially without actuators or tear strips, it can be easily implemented with minimal effort and without structural modifications to existing vehicle occupant restraint systems.Furthermore, this allows for the creation of a multitude of different, and in particular, separately controllable areas that can have virtually any shape, thus enabling not only the desired airflow behavior but also variations in the shape of the airbag. For example, in the case of vehicle occupants of below-average height, the center of the airbag or the effective impact area can be shifted to a lower area of ​​the vehicle interior by selectively adjusting the gas permeability, thereby providing optimal support for the occupant's body.

[0021] By attaching the outflow opening as a layer and / or a coating on a gas-permeable carrier fabric, whereby the areas adjoining the outflow opening or the areas excluded by the layer are essentially gas-impermeable, the gas escape can be effectively limited to certain areas of the gas bag.

[0022] Since the gas permeability is proportional to the strength of the applied electrical voltage or electric field, it can be continuously varied. For example, by setting different gas permeability profiles in different areas during the outflow phase, it is even possible to position the vehicle occupant in a specific, biomechanically advantageous position for restraint during forward movement.

[0023] For this purpose, it has already proven promising to have several zones extending over a large portion, or nearly the entire, of the airbag's surface, and it is also possible to equip the entire airbag with an adjustable gas permeability. This significantly improves the effectiveness of the vehicle occupant restraint system, as the pressure exerted by the vehicle occupant upon impact can be dissipated very quickly after the airbag is fully inflated, either before or at least upon impact.

[0024] The control of the zones can be carried out according to specific procedures stored in a control unit. A particularly advantageous embodiment of the invention can also be achieved by allowing the gas permeability to be varied based on measured values ​​acquired by a control unit, especially personal measurements of the vehicle occupant, so that, for example, the body weight or height of the vehicle occupant can be taken into account when controlling the zone. Due to the very short reaction time, the gas permeability can also be changed during the activation of a gas generator of the airbag module. The occupant restraint process can thus be controlled.

[0025] For this purpose, according to a preferred embodiment, the gasbag module has a control unit that is connected to the outflow opening by an electrical conductor. By applying an electrical voltage to the respective area of ​​the gasbag, it is activated accordingly and the gas permeability is changed accordingly. Preferably, the electrical conductor is integrated into the gasbag, in particular woven in, so that the assembly effort is considerably reduced because the required electrical contact does not require any additional routing of electrical conductors.

[0026] To adapt to different vehicle occupants, the driver can adjust the gasbag module using a manually operated control unit.

[0027] In contrast, it is particularly advantageous if the gas permeability can be adjusted based on measurements taken by the control unit, for example, regarding the body weight and / or height of the vehicle occupant. This prevents incorrect presets by ensuring that the necessary parameters are detected by appropriate sensors. For this purpose, at least one sensor is installed at or assigned to each vehicle seat equipped with a gas airbag, for example, if it is a camera.

[0028] Furthermore, it is particularly promising if the area has a coating with a significant material component of a polymer whose gas permeability can be adjusted due to electrical influence.

[0029] The area preferably features a multitude of adjacent, brush-like fibers whose orientation can be changed by applying an electric voltage or electric field. Due to the application of the electric voltage, at least a proportion of the fibers are deformed or displaced into an extended orientation, thereby allowing for adjustable gas permeability. In an extended orientation, the fibers have a spacing that achieves the desired gas permeability. If no or only a very low electric voltage is applied, the fibers contract, assuming a coiled, compressed state that simultaneously provides a high degree of sealing and thus very low gas permeability. This effect is based on phase separation effects in multi-component polymer brushes.For this purpose, a coating consisting preferably of two components is applied to a flat surface, the components exhibiting hydrophilic and hydrophobic properties, respectively. The mutual collapse of the components leads to phase separation and is triggered by the application of an electric voltage or electric field. This results in a reversible change in the surface properties that can be repeated as often as desired.

[0030] The gas permeability as a function of the applied electrical voltage or electric field depends on the design of the area. It is particularly advantageous, however, if at least one operating state can be set without the influence of the electrical voltage or electric field, in which the gas permeability is very low or prevented, and if at least one further operating state can be set in which the gas permeability is high or the gas can flow out almost unhindered. The folding bag module can be designed in such a way that the uncontrolled area has very low gas permeability, so that in the event of damage to or interruption of the electrical connection, only minimal gas escape occurs.This ensures good protection, especially for vehicle occupants with above-average body weight, by providing a sufficient volume of gas in the gas bag.

[0031] Preferably, at least one outlet opening is arranged in an area of ​​the gasbag not facing the vehicle occupant, so that the gas volume can escape, particularly laterally. This effectively prevents any undesirable effect of the gas flow on a vehicle occupant.

[0032] Although the effectiveness of the invention does not depend on the type and design of the gas bag, it has already proven advantageous if the area is formed by a woven, knitted and / or crocheted fabric, so that the area provides an optimal basis for electrically activatable fibers to be arranged on it.

[0033] The second problem, namely to provide a method for controlling the outflow of a gas volume filling a gas bag of a vehicle occupant restraint device through the at least one outflow opening of the gas bag, is solved according to the invention by adjusting the gas permeability by changing the electrical voltage or the electric field, in particular personal data or measured values.

[0034] The invention allows for numerous embodiments. To further illustrate its basic principle, one of these is shown in the drawing and described below. This shows a schematic representation in each case. Fig. 1 a vehicle after impacting an obstacle with a filled gasbag of a gasbag module; Fig. 2 the in Fig. 1 Vehicle shown, in which the filling volume of the gas bag is reduced by gas outflow; Fig. 3 individual components of the gasbag module in an enlarged view; Fig. 4. The operating principle when setting a low gas permeability of the gas bag; Fig. 5. The operating principle when setting a high gas permeability of the gas bag.

[0035] The gasbag module 1 of a vehicle occupant restraint device 2 according to the invention is described below with reference to the Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5 explained in more detail. For the passive safety of the vehicle occupants 3 of a motor vehicle 4 shown here only in outline, the optimal deployment of the gas bag 5, also commonly referred to as an airbag, is of crucial importance in the event of an accident.

[0036] The inventive approach to improving vehicle occupant safety is based on the acquisition of essential personal measurements and parameters and the resulting individual control of the airbag 5. This means that parameters such as body weight, height, seating position, the position of the respective vehicle occupant 3, and the severity of the accident can be detected, and the filling of the airbag 5 can be varied accordingly. The airbag 5 can be triggered earlier or later and filled with different volumes of gas.

[0037] The basic operating principle of the invention will first be explained below with reference to the Fig. 1 and Fig. Figure 2 shows the effect of an adjustable outflow opening 6 of the gas bag 5 with respect to its gas permeability.

[0038] In its initial state, the outflow opening 6 has a very low gas permeability, so that the gas bag 5 is as in Fig. 1. It is recognizable that the gas bag 5 fully fills with gas. The outlet opening 6 can be switched to increase gas permeability either during the filling process or only after reaching the maximum filling volume.

[0039] The trigger for adjusting the altered gas permeability, starting from a first operating position with a very low gas permeability of the corresponding, here by a in Fig. The coating 11 on a gas-permeable carrier fabric 7 in the area 8 is achieved by applying an electrical voltage. For this purpose, an electrical conductor 9 is integrated into the carrier fabric 7, which runs through the gas bag 5 to a control unit 10.

[0040] In Fig. Figure 2 shows a second operating position with a significantly higher gas permeability, which leads to a flow of part of the gas volume contained in the gas bag 5 through the laterally arranged areas 8. The gas bag 5 is opened by means of the control unit 10, which also serves for the adaptive control of the gas bag module 1, by triggering a [function / action / etc.]. Fig. The gas generator 12 shown in Figure 3 is activated. In the next step, the gas pressure within the gas bag 5 is adaptively adjusted to the vehicle occupant parameters and the severity of the accident by appropriately controlling the corresponding area 8. For this purpose, area 8 is controlled in such a way that it has a high gas permeability. In this way, the gas pressure and thus the degree of hardness can be individually adjusted to the respective vehicle occupant 3, but also to the type, extent, or degree of accident-related deformation of the vehicle 4, by allowing a portion of the filling gas to flow out.

[0041] The adjustable area 8 for outflow comprises an array formed on the coating 11 from a polymeric material in the Fig. 4 and Fig. The polymer chains 13, 14 shown in Figure 5, which are also referred to as polymer brushes, have the property that, when densely arranged, they are oriented perpendicular to the carrier fabric 7 of the gas bag 5 and are only attached to the carrier fabric 7 at points. In the illustrated embodiment, the polymer chains 13, 14 consist of different polymers whose differing properties can be manipulated differently by applying an electrical voltage.

[0042] In the Fig. 4 and Fig. Figure 5 shows the two functional positions of the polymer chains 13 and 14 in the controllable area 8 of the outflow opening 6. When area 8 is activated, a first group of polymer chains 13 assumes a largely extended orientation, while the polymer chains 14 simultaneously contract in a second group and assume a coiled position. In this functional position, a high degree of gas impermeability is achieved, so that gas flow is effectively retained.

[0043] In the second, in Fig.In the functional position shown in Figure 5, the second group of polymer chains 14 assumes an extended orientation, while at the same time the first group of polymer chains 13 contracts and assumes a coiled position. Due to the different properties of this first group, this functional position results in a high degree of gas permeability, so that the gas flow can pass through this region 8 almost unimpeded. This effect is achieved by the contrasting properties of the polymers used.

[0044] These two operating positions can be continuously varied and changed at any time, even during the gas flow. This ensures, for example, that a minimum internal pressure is maintained in the gas bag 5 during the accident-related displacement of the vehicle occupant 3.

[0045] Furthermore, the control signal can also be pulsed, for example, to generate different identifiers, so that the control of the zones 8 can be adapted to the respective vehicle occupants 3. Thus, a continuous or constant voltage can be applied to the zones 8, or the voltage can be applied in the form of pulses. These pulses can be varied in time so that a larger or smaller volume flow of the filling gas can escape through the outlet 6. The gas outflow can begin even before the gas bag 5 is completely filled, thus enabling regulation of the gas flow during the containment phase. The gas permeability is continuously adjustable.

[0046] The inventive design of the gas bag module 1 results in a simple construction in which only individual areas 8 are provided with a correspondingly controllable coating 11. The response time for controlling the areas 8 is extremely short and can occur at any stage of the filling process, particularly before reaching certain fill levels. The space requirements as well as the other elements of the gas bag module 1 remain unchanged, and malfunctions are virtually eliminated. Reference symbol list 1 gasbag module 2 Restraint device 3 vehicle occupants 4 Motor vehicle 5 Gasbag 6. Outflow opening 7 Carrier tissues Area 8 9 Management 10 Control unit 11 Coating 12 Gas generator 13 Polymer chain 14 Polymer chain

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