Airbag module for a motor vehicle

An airbag module for a motor vehicle includes an airbag that may be inflated for restraining a person, at least one outlet opening for releasing gas out of the module and originating at least partially from the inflated airbag, and a reservoir containing coolant for cooling the gas released from the module through the outlet opening. The reservoir includes a wall that sealingly encloses the coolant and is opened to bring the coolant into direct contact with the released gas to cool the released gas.

BACKGROUND

The present invention relates generally to an airbag module for a motor vehicle. The invention relates more specifically to an in airbag module in which outflowing gas is cooled when leaving the module.

An airbag module typically comprises an airbag that may be inflated to aid in restraining a person in a vehicle. The module typically also includes at least one outlet opening through which gas originating at least partially from the inflated airbag is able to be released out of the module. The module also may include and a reservoir with a coolant that is used for cooling the outflowing gas.

In the event of an accident, the airbag may be inflated with gas released from a gas generator and have a high temperature when a hot gas generator is used. The subsequent release of hot gas from the airbag module (in particular from the airbag) may be associated with a risk of injury for people who may come into contact with the gas. Moreover, parts of the vehicle interior fittings may be damaged by hot gas. The gas may be cooled, however the cooled gas generally conducts considerably more easily into an at least partially enclosed space (e.g., the airbag) due to the lower volume of gas required and the airbag may not completely inflate or more gas may be required to inflate the airbag.

SUMMARY

One embodiment of the invention relates to an airbag module for a motor vehicle. The air bag module includes an airbag that may be inflated for restraining a person, at least one outlet opening for releasing gas out of the module and originating at least partially from the inflated airbag, and a reservoir containing coolant for cooling the gas released from the module through the outlet opening. The reservoir includes a wall that sealingly encloses the coolant and is opened to bring the coolant into direct contact with the released gas to cool the released gas.

DETAILED DESCRIPTION

European patent application EP 0 620 140 A1, which is herein incorporated by reference in its entirety, discloses an airbag module for conducting gas flowing out of an airbag over steel wool or aluminum wool, for example to cool the gas by heating the metal wool according to one exemplary embodiment.

German patent application DE 196 02 695 C2, which is herein incorporated by reference in its entirety, discloses a gas generator for filling an airbag with gas that may be cooled by direct contact with a liquid according to an exemplary embodiment. A cooling element formed from non-heat-resistant material is filled with a coolant and with foamed silicone rubber. When the hot gas comes into contact with the material of the cooling element, the material is damaged and the coolant released. The foamed silicone rubber may increase the available surface area of the coolant.

Other exemplary embodiments of the invention may allow rapid and effective cooling of gas when releasing the gas from an airbag module even when the gas has been previously used for inflating the airbag.

The released gas from the airbag module may flow to a reservoir which is filled with a coolant. A wall of the reservoir sealingly encloses the coolant on all sides so that a reduced amount of coolant is able to escape from the reservoir provided that the wall of the reservoir is intact and sealed. The wall may be opened in order to allow direct contact between the coolant and the gas to be cooled.

The temperature of the gas flowing out of the airbag may be rapidly reduced by the direct contact of the gas with the coolant and may be efficiently reduced by the relatively low requirement for coolant.

In a preferred exemplary embodiment of the invention, the outlet openings through which the gas is released are located in the gas generator carrier. Alternatively, said outlet openings may be located on the bottom face of the airbag module. A guide plate with a large opening that encloses the outlet openings in the airbag module in a frame-like manner may be fastened to the bottom face. The guide plate may not directly serve as a gas generator carrier but may, for example, be used in a passenger airbag module—similar to the gas generator carrier in a driver airbag module—to guide specific elements of the airbag module (e.g., a valve slide) and to receive openings for releasing gas. The guide plate may also be a device for fastening a pyrotechnic element or thread for fastening further elements to the guide plate. The guide plate is typically attached to the housing of the airbag module.

According to a preferred exemplary embodiment, the coolant reservoir is located in the flow path of the released gas and thus upstream of the outlet openings of the airbag module. Alternatively, the coolant reservoir may be arranged in the flow path of the released gas downstream of the outlet openings of the airbag module.

According to another preferred embodiment, the wall of the coolant reservoir encloses a hollow space or a plurality of hollow spaces, in which the coolant is located. The wall of the coolant reservoir is preferably made from a plastic material.

In another preferred embodiment, the coolant reservoir has a planar basic shape, for example that of a disk-shaped ring or cuboid. The term “planar” is intended to be understood in this case that the expansions of the reservoir are greater in length and width than the expansion in height, while the length and width of the reservoir extend substantially in one plane.

Various exemplary embodiments may include a solid or a liquid coolant. By using various coolants (e.g., water), the cooling of gases may be possible at a wide range of temperatures. As the reservoir only has to be filled with coolant, a more simple and less complicated reservoir may be used.

In a preferred embodiment, the coolant has a sublimation point, evaporation point, or other phase transition point in a temperature range of the gas to be cooled. As a result, direct or indirect contact of the gas to be cooled with the reservoir filled with coolant leads to a higher absorption of energy by the coolant in the course of its phase transition. The high evaporation point, sublimation point or other phase transition enthalpy of the coolant, which is applied to the detriment of the temperature of the gas, leads to an effective cooling of the gas. In comparison with a coolant that has no phase transition in the corresponding temperature range, by utilizing the phase transition enthalpy of the coolant considerably less coolant may be used to achieve a comparable cooling of the airbag gas and increase the efficiency of the cooling process.

The phase transition of the coolant is preferably a transition into the gaseous phase to achieve a volume increase of the coolant that is as large as possible. The alteration to the volume accompanying the phase transition of the coolant may lead to a high increase in pressure inside the reservoir. Preferably, this leads solely, or in combination with the pressure exerted by the outflowing gas on the reservoir and/or with the thermal loading of the reservoir by the hot gas, to an opening of the wall of the reservoir. As a result, coolant is released both in its original state and also in its new state. The direct contact of the gas to be cooled with the released coolant leads to an even more effective energy transmission from the gas to the coolant than was possible by indirect contact as the contact surface area is significantly increased between the gas and the coolant.

According to various exemplary embodiments, the reservoir may not be primarily opened by the internal pressure produced by the evaporating coolant or sublimating coolant, but may be opened by the pressure exerted by the outflowing gas on the reservoir and allow a direct contact between the gas and coolant.

According to other exemplary embodiments, a pyrotechnic unit (which may be separate and associated specifically with the coolant reservoir) is located sealingly on the coolant reservoir. After activation of the pyrotechnic unit by the applied pressure (possibly indirectly via a force transmission element activated by the pyrotechnic unit), an opening is formed in the wall of the coolant reservoir.

Preferably, the wall of the reservoir reacts to overpressure and acts on the wall either from the inside, the outside, in combination with thermal loading by rupturing or splitting open, and/or by a comparable process that damages the wall of the reservoir. The wall may have at least one predetermined rupture point that leads to easier rupture of the wall at that point. The predetermined rupture point may be, for example, a perforation, a score line, and/or a comparable weakened portion.

According to various exemplary embodiments, the outlet openings of the module may be permanently open to allow a continuous outflow of gas from the airbag and/or the module. According to the pressure conditions of the airbag and surroundings and even during the filling of the airbag, one portion of the airbag gas may flow out of the airbag and/or the module and come into contact with the coolant reservoir.

According to other exemplary embodiments, the outflow of gas from the module may be controlled by at least one controllable valve. The control may be carried out by a closure element, for example by a valve slide, as disclosed in DE 103 61 887 A1, which is herein incorporated by reference in its entirety. An annular adjusting disk may be displaced as the closure element in a limited rotational movement by the pressure applied by a pyrotechnic element. In an initial position the outlet openings of the adjusting disk, which may be similar in shape and number to those of the valve main body located above the adjusting disk, are not aligned with said outlet openings of the valve main body and the closure element is closed. By the limited rotational movement, the adjusting disk is moved into a position where the outlet openings are aligned with those of the valve main body and the closure element is open. Such an arrangement may be used when the airbag module is intended to be accommodated in a steering wheel or is intended to have a cylindrical shape. Such a control of the gas flow may, however, also be used when the airbag module is intended to have a generally prismatic or cuboid shape, for example to be used on the passenger side of a vehicle. In this case, an equivalent valve slide carries out a comparable limited translatory movement relative to a guide plate. The energy required for this movement may be provided by a pyrotechnic element in a manner similar to the rotational movement.

According to other exemplary embodiments, the closure element may include projections on the side facing the coolant reservoir. In the defined rotational or translatory movement of the closure element for opening the outflow openings of the airbag module, the projections may come into contact with the wall of the coolant reservoir. This contact may either create a predetermined rupture point in the wall (e.g., in the form of a score or a perforation) or directly tear open the coolant reservoir by damaging the wall. The gas flowing out of the airbag may come even more rapidly into direct contact with the coolant and the time period that the gas requires for flowing out of the airbag module may be shortened.

Alternatively, by the overpressure from inside or outside the wall of the reservoir, an opening device, for example a valve or a flap, is reversibly opened and releases the coolant so that it leads to direct contact between the coolant and the gas. The wall of the coolant reservoir may not be damaged when opening the reservoir but is still intact after closing the opening device.

Preferably, the gas flowing out of the module may flow into a partially or entirely enclosed container. Due to the low temperature of the gas, the gas may have a relatively smaller volume than a gas that has not been cooled. The use of a partially or entirely enclosed container may additionally reduce the risk of injury. Damage to the vehicle interior fittings may also be reduced or eliminated by the lower gas temperature and the use of the container.

In a preferred embodiment, the coolant reservoir is provided with a carrier (for example in the form of a carrier plate) and is attached by fastening elements (e.g., screws) to an airbag device so that the carrier and reservoir are fixedly connected to one another and fixedly connected to a suitable receiving part in the airbag module. The carrier and reservoir may, for example, be fixed between the gas generator carrier and the flange of the gas generator. Both the carrier and the coolant reservoir have circular recesses that are aligned with one another and are generally congruent with the threads in the gas generator carrier into which the screws are fastened. Alternatively or additionally to screwing, the carrier and coolant reservoir may be fastened to the airbag module by clamping, bonding, welding, or similar methods for fastening. The carrier and coolant reservoir may also be connected to one another by clamping, bonding, welding or similar methods for fastening. The carrier may stabilize the coolant reservoir and allow for a larger range of materials from which the coolant reservoir may be made. The carrier itself is preferably produced from a plastic material. The carrier and the coolant reservoir may form a cooling unit as a result of their connection.

The carrier and the coolant reservoir may respectively have a shape such that they may be fitted into differently shaped airbag modules. The carrier and reservoir, for example, may have an annular basic shape to be integrated into an airbag module designed for use in a steering wheel or a similarly shaped housing. The coolant reservoir may, for example, also have the shape of an open ring while the carrier has a general shape of a closed ring with a recess in the region of the opening of the coolant reservoir. These interruptions to the fully closed rings may allow the carrier and coolant reservoir to be incorporated into airbag modules equipped with a pyrotechnic unit for generating pressure for the movement of a valve slide. The carrier plate and coolant reservoir may have a prismatic or cuboid shape and may be incorporated into an airbag module designed for use in a passenger seat in a motor vehicle or for use in any other prismatic or cuboid housing.

When the carrier is arranged between the outlet openings of the gas generator carrier or the valve main body and the coolant reservoir, the released gas from the module flows through the outlet openings of the generator carrier or the valve main body and then through the apertures of the carrier to come into contact with the coolant reservoir. When using a passenger airbag module in which the outlet openings of the module are not in the gas generator carrier but on the bottom face of the airbag module, the same position of the carrier plate and coolant reservoir may result in the released gas from the module flowing out of the airbag and coming into contact with the coolant reservoir first and then flowing through the apertures of the carrier plate and the outlet openings of the airbag module.

Preferably, the carrier has at least one aperture so that the airbag gases are able to escape from the airbag module. The shape and number of apertures are generally similar to the apertures of the outlet openings of the airbag module (e.g., the apertures of the gas generator carrier and/or the valve main body, the apertures of the outlet openings incorporated in the bottom face of the airbag module, etc.). Preferably, the aperture and/or apertures of the carrier are congruent with the outlet opening and/or the outlet openings of the airbag module so that the gas outflow from the module is not hindered by the carrier.

When using a generally cylindrical airbag module, an adapter plate may be fastened to the module by suitable fastening elements, for example screws. The adapter plate may stabilize the coolant reservoir and carrier plate on the respective radial outer faces thereof by clamping. Thus the adapter plate may be an optional component of the cooling unit. The adapter plate may provide and/or allow the incorporation of the airbag module into a steering wheel or a further receiver space in a motor vehicle.

FIG. 1shows a cylindrical airbag module1(e.g., a driver and/or pot-shaped airbag module) comprising a module cover2, an inflatable airbag3, a gas generator carrier4and a gas generator flange5. A gas generator (e.g., a hot gas generator) provides the gas for filling the airbag by a chemical process, is located in the interior of the module1, and is fixedly connected via the gas generator flange5to the gas generator carrier4by fastening screws7. The module1has four generally permanently open outlet openings6incorporated in the gas generator carrier4. Gas that has previously been located in the airbag3may continuously flow out of the module1through the outlet openings6. A planar annular carrier plate8includes four generally evenly distributed apertures10and circular openings11. A planar annular coolant reservoir9includes a wall16enclosing a hollow space and four circular openings12. The carrier plate8and reservoir9are fastened between the gas generator flange5and the gas generator carrier4by the screws7so that the carrier plate8is located on the side of the gas generator carrier4and the coolant reservoir9is on the side of the gas generator flange5. The circular openings11in the carrier plate8may also allow for screws7to passing through and screw into threads in the gas generator carrier4. The four apertures10of the carrier plate8are aligned with the outlet openings6of the gas generator carrier4, so that the gas flowing out of the module1may come into contact with the coolant reservoir9unhindered. An adapter plate13includes a large circular opening and a radius that is smaller than the external radius of the carrier plate8and the coolant reservoir9so that after fastening with the screws14in corresponding threads15an effective clamping in the radial outer region of the carrier plate8and coolant reservoir9is produced. The entire airbag module1with the integral carrier plate8and integral coolant reservoir9may be fastened in a steering wheel configured to receive an airbag module.

According to one exemplary embodiment, the mode of operation of the cooling of the hot gas when flowing out of the airbag is to be described briefly hereinafter with reference toFIG. 1. The gas escaping through the outlet openings6and the apertures10comes into contact with the coolant reservoir9, which includes a wall16enclosing a hollow space and is filled in its interior with coolant (e.g., water). The hot gas heats the coolant and changes the coolant into the gaseous state increasing the pressure in the interior of the coolant reservoir9. The coolant reservoir9is configured so its wall16ruptures as a result of the increased pressure and releases the coolant to direct contact between the gas and coolant. For example, the rupture of the coolant reservoir9may occur at a single point or, as shown inFIG. 2, the rupture point may be configured as a score line or perforation160. The effectiveness of the cooling process may be significantly increased by direct contact between the gas and coolant.

FIG. 2shows an enlarged view of the planar annular carrier plate8and the planar annular coolant reservoir9ofFIG. 1. In the outer annular region16aand in the internal annular region16bof the wall16of the coolant reservoir9, two plastics layers of the wall16are directly superimposed without forming a hollow space. A hollow space may be formed in the central annular region16cof the wall16and filled with coolant. The circular openings11in the carrier plate8may be apertures for fastening screws. The four outlet openings10in the carrier plate8allow a flow of gas from the airbag module to the coolant reservoir9. The openings10may be configured in the same manner as the outlet openings6of the gas generator carrier4ofFIG. 1and are aligned after mounting the carrier plate8and coolant reservoir9(seeFIG. 1). As a result, the carrier plate8may exert no additional resistance to the gas flow from the airbag3in the module1.

FIG. 3shows a cylindrical airbag module21(e.g., a driver and/or pot-shaped airbag module) with a module cover22, an inflatable airbag23, a valve main body24and a gas generator flange25. A gas generator is located inside the module21and is connected to the main valve body24by the gas generator flange25and fastening screws30. The valve main body24may be a gas generator carrier or represents a special type of gas generator carrier. The valve main body24has a plurality of closable outlet openings26athat when opened allow gas from the airbag23is to flow out of the module21. It is noted that inFIG. 2, only two of the outlet openings26ahave been identified and are representative of each outlet opening. The initially closed outlet openings26amay be opened by a pyrotechnic element27fastened by a union nut28to a projection of the valve main body24. An external signal may activate the pyrotechnic element27to move in a limited rotational manner by a pressure increase in a pressure chamber of the valve main body24. A planar annular adjusting disk29is located between the valve main body24and the airbag23and has the same number and shape of outlet openings26bas the outlet openings26aof the valve main body24. It is noted that only two of the outlet openings26bhave been identified and are representative of each outlet openings. By the limited rotational movement of the adjusting disk29, the outlet openings26bare moved into a position where they are aligned with the outlet openings26aof the valve main body24(as shown inFIG. 3) and provide an opening through the outlet openings26a.

A planar carrier plate31has the basic shape of a closed ring but has a recess34projecting from the outer edge of the plate towards the inside and encompasses less than the complete width of the carrier plate31so that the annular basic shape of the carrier plate31is not entirely interrupted. The carrier plate31and a planar coolant reservoir32(with the basic shape of an open ring) are fastened between the gas generator flange25and the valve main body24by screws30such that the carrier plate31is located on the side of the valve main body24and the coolant reservoir32is on the side of the gas generator flange25. The annular opening of the coolant reservoir32is positioned over the recess34of the carrier plate31so the pyrotechnic element27is in contact neither with the carrier plate31nor with the coolant reservoir32. The carrier plate31generally has the same number, shape, and arrangement of apertures33as the valve main body has outlet openings26aand the adjusting disk29has outlet openings26b. InFIG. 3and by way of example, an aperture33is identified as being representative of the other apertures. The carrier plate31is fastened to the valve main body24so the apertures33are aligned with the outlet openings26a. As a result, the gas flowing out of the module is able to come into contact with the coolant reservoir32generally unhindered, provided that the outlet openings26aare congruent or at least similar to the outlet openings26band not closed by the adjusting disk29. The carrier plate31defines circular openings35, which are apertures for the fastening screws30and coolant reservoir32defines circular openings36. Only one of each of the circular openings35,36is identified as being representative of the other openings shaped in a similar manner.

The coolant reservoir32has a wall38enclosing a hollow space. As in the exemplary embodiments described with reference toFIG. 2, the hollow space is located in the central region38aof the open ring and is filled with a coolant. The coolant reservoir32differs from the coolant reservoir9ofFIGS. 1 and 2only in that it does not have the shape of a closed ring but that of an open ring.

An adapter plate39defines a large circular opening with a radius smaller than the external radius of the carrier plate31and the coolant reservoir32. When the adapter plate39is fastened with screws37in corresponding threads40in the module21, it produces an effective clamping in the radial outer region of the carrier plate31and the coolant reservoir32. The entire airbag module21together with integral carrier plate31and integral coolant reservoir32may be fastened in a steering wheel designed for receiving an airbag module.

The general cooling mechanism of the arrangement shown inFIG. 3, generally does not differ from the mechanism of the arrangement shown inFIG. 1. The difference between the two arrangements is that the flow of gas out of the module1inFIG. 1is carried out continuously while the gas may be released by the adjusting disk29(depending on various parameters) with the module21inFIG. 3.

FIG. 4shows a generally prismatic or cuboid airbag module50(e.g., a passenger airbag module) that comprises a module housing51on a bottom face with a plurality of outlet openings and a frame-like guide plate52surrounding the outlet openings that defines a large central opening and a plurality of threads61. It is noted that only one thread61is identified and is representative of each thread. The outlet openings in the bottom face of the module housing51are not visible inFIG. 4, but are covered by projections54of a movable valve slide that is attached between the outlet openings and the guide plate52. If the projections54of the valve slide (as shown inFIG. 4) are located over the outlet openings in the bottom face of the module housing51, the outlet openings are closed. The outlet openings may be opened by a pyrotechnic element55which is fastened by a union nut56to a projection of the guide plate52. The pyrotechnic element55is activated by an external signal and may move the valve slide in a limited translatory manner by a pressure increase in a pressure chamber. As a result, the projections54of the valve slide move into a position where they no longer cover the outlet openings and thus the outlet openings are opened. A carrier plate57has a cuboid basic shape with inwardly rounded corners as well as circular recesses60and is described in detail with reference toFIG. 5. A coolant reservoir58includes a wall that encloses a plurality of hollow spaces62filled with coolant. The carrier plate57and the reservoir58are fixedly connected to one another, for example bonded or welded. The coolant reservoir58and the carrier plate57are fixedly connected to the guide plate52by screws59and recesses60(a penetration point for the screws59) via threads61in the guide plate52. Only individual examples of screws59, circular recesses60in the carrier plate57, threads61in the guide plate52, and hollow spaces62in the coolant reservoir58are identified in the Figure and are example representatives of each component. A gas generator63generates gas by to fill an airbag (not shown) and is attached in front of the coolant reservoir58and the carrier plate59and fastened by screws65in threads66to the module housing51. The gas generator is fixed by a support unit67of annular design that is attached to the module housing51. The support unit67also introduces the gases escaping from the gas generator into the airbag.

In an exemplary embodiment according toFIG. 4, gas that is intended to flow out of the module housing51and the airbag comes into contact with the coolant reservoir58and heats the coolant located in the hollow spaces62. The heating changes the coolant into the gaseous phase and causes the wall of the coolant reservoir58to burst. A hollow space62of the reservoir58filled with coolant is associated with each outlet opening in the bottom face of the module housing51. The direct contact between the gas and coolant may lead to efficient cooling of the gas flowing out of the airbag and airbag module through the opened outlet openings in the bottom face of the module housing51.

FIG. 5andFIG. 6show an exploded view (FIG. 5) and a perspective view (FIG. 6) of a generally prismatic or cuboid cooling unit that may be used in a passenger airbag module such as illustrated inFIG. 4. The cooling unit includes a cuboid coolant reservoir72that comprises a wall74enclosing a hollow space. The cooling unit also includes a cuboid carrier plate57that serves to stabilize and fasten the coolant reservoir72to the guide plate52shown inFIG. 4. The coolant reservoir72defines two recesses75on one of its narrow sides and that are located in the region of two openings60for fastening the carrier plate57to the guide plate52ofFIG. 4. The coolant reservoir72and the carrier plate57have inwardly rounded corners76and/or77that are aligned with one another when the coolant reservoir72and the carrier plate57are connected fixedly to one another. The wall74of the reservoir72encloses a continuous hollow space that is filled in the interior with a coolant (e.g., water) that evaporates in the temperature range of the airbag gases. The volume increase of the coolant caused by the evaporation leads to an increasing pressure in the reservoir72and that may cause the wall74of the reservoir72to burst, leading to a direct contact between the airbag gases and the coolant located in the coolant reservoir72. In contrast to the coolant reservoir58shown inFIG. 4, the coolant reservoir72shown inFIGS. 5 and 6does not have individual chambers and/or hollow spaces separated from one another but has a single continuous hollow space that is filled with the coolant. Both a coolant reservoir58with hollow spaces62separated from one another (seeFIG. 4) and a reservoir72with a continuous hollow space may be used in the airbag module illustrated inFIG. 4.

The carrier plate57has a plurality of outlet openings73, of which one is identified inFIG. 5as being representative of each outlet opening. The outlet openings73are identical or at least similar in number and shape to the outlet openings in the bottom face of the module housing51inFIG. 4. The outlet openings73are aligned (after assembling the carrier plate57on the guide plate52) by using the circular openings60, which receive screws59(seeFIG. 4). When used in an airbag module, the carrier plate57and the coolant reservoir72are fixedly connected to one another (for example by bonding or welding) as shown inFIG. 6. Thus it may not be necessary to provide the coolant reservoir72with circular openings for passing through screws or other fastening elements.

The priority application, German patent application no. 202005016457.7, filed Oct. 17, 2005 including the specification, drawings, claims and abstract, is incorporated herein by reference in its entirety.