Gas bag module

A Gas bag module for use in a vehicle occupant restraint device has a plastic generator support. On the generator support a printed circuit is formed by metal deposition. For activating an electrical function element, the printed circuit cooperates with a switching element that is arranged on a section of the generator support.

TECHNICAL FIELD

The present invention relates to a gas bag module for use in a vehicle occupant restraint device having a plastic generator support.

BACKGROUND OF THE INVENTION

Gas bag modules are a component part of vehicle occupant restraint systems and can be arranged in the steering wheel, for example, for the protection of the driver. However, due to the space requirements for the gas bag module, problems arise with respect to the spatial arrangement of the cabling and contacts for activating electrical function elements such as an electrical horn. In addition, operating elements and switches for controlling the vehicle functions need to be easily accessible for the driver on or in the steering wheel, and if possible they should be configured as multifunctional elements. However, in this way the number of cables for connecting the operating elements to the vehicle electronics grows, along with the space requirements.

In accordance with the so-called “floating horn” principle, gas bag modules are arranged on the steering wheel in such a way that the horn signal can be activated by pressure exerted by the driver on the gas bag module. In this context, one contact is arranged on the gas bag module and one on the steering wheel, the gas bag module being connected to the steering wheel by elastic distancing elements. Thus the contacts can be closed when pressure is exerted on the gas bag module by a motion of the gas bag module towards the steering wheel, and in this way the horn or other electrical function element can be activated.

From DE 199 27 032 A1, an assembly is known that operates in accordance with this principle and that has a steering wheel and a gas bag module. The gas bag module includes a plastic generator support, which is manufactured in an injection molding process and into which a wire element is injected. The wire element has hoop-shaped segments, which are provided with plastic sleeves for electrical insulation and which engage in latching hooks that are arranged on the steering wheel for the purpose of attaching the gas bag module. The generator support also has one or more recesses, in which the wire element is accessible and is not electrically insulated. In these recesses, the wire element constitutes a contact that activates the horn and that cooperates with an electrically conductive opposite contact on the steering wheel. When the contact and the opposite contact are closed through pressure being exerted on the gas bag module in the direction of the steering wheel, the electrical horn is activated.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a gas bag module that is simply designed and that permits the integration of multifunctional elements and switches without requiring additional components and cable leads. According to the invention, the gas bag module for use in a vehicle occupant restraint device comprises a plastic generator support. On the generator support a printed circuit formed by metal deposition is provided. For activating an electrical function element, the printed circuit cooperates with a switching element that is arranged on a section of the generator support.

The generator support of the gas bag module according to the present invention can therefore be configured in a simple manner as a three-dimensional, injection-molded circuit substrate or molded interconnected device. Thus a multiplicity of familiar and cost-effective manufacturing methods are available. The conducting tracks of the printed circuit formed on the generator support take on the function of the conventional cabling. Therefore, on the one hand, weight can be reduced and, on the other hand, installation space for the usual cable leads and plug connectors is saved. In order that the printed circuit that is applied to the generator support be connected to the vehicle electronics, only a single plug-in circuit board is required, as a result of which the placement of cables in the steering wheel is made significantly simpler. Various switching elements for activating electrical function elements via the vehicle electronics can be connected to the printed circuit on the generator support, the switching elements being comfortably accessible to the driver as a result of the arrangement of the switching elements in the steering wheel.

Finally, the present invention makes it possible to additionally simplify the design of the multifunctional switches that are integrated in the steering wheel, because the generator support that must be there in any case can be used as a base for the switching elements. In this way, a simple and cost-effective design of a multifunctional switch that is integrated in the steering wheel is achieved.

A separate panel can be used as a cover for the multifunctional switch or for the switching element that is arranged on the section of the generator support that has the printed circuit. However, it is especially advantageous if at least one opening or through hole is introduced in the cover of the gas bag module, in which an actuating section of the switching element is accommodated. Then the cover of the gas bag module at the same time constitutes the cover of the multifunctional switch, advantageously making a further component unnecessary. In a familiar manner, the switching element itself can be configured as a silicone switching mat. Furthermore, the switching element can include a conventional circuit board that is connected to the printed circuit.

For activating an electrical function element, for example an electrical horn, the switching element is preferably brought into contact with a contact section on the printed circuit. The contact section can advantageously be formed by two sections of the printed circuit that are adjacent to each other and electrically insulated from each other and that are bridged by the switching element for activating the electrical function element, thus forming a closed electrical circuit.

In one variant of the gas bag module according to the present invention, a printed circuit formed by metal deposition is provided on the plastic generator support, the printed circuit for activating an electrical function element, for example an electrical horn, cooperating with a switching element that is arranged at a predetermined distance from a contact section of the printed circuit. In this context, it is especially preferable, in accordance with the “floating horn” principle, if the gas bag module has elastic distancing elements, which maintain a defined distance between the section of the printed circuit and the switching element, which is formed, in a simple manner, as an opposite contact. As a result of a pressure being exerted on the cover of the gas bag module, the contact section, which is preferably formed by two conducting tracks that are adjacent to each other and electrically insulated from each other, is bridged by the opposite contact, which is configured, for example, as a metallized surface, and the circuit is closed, so that the electrical function element, i.e. the horn, is activated.

The printed circuit and therefore the various multifunctional switches that are connected to the printed circuit can be connected to the vehicle electronics via a simple, soldered plug connection. In this way, the cabling of the individual switching elements to the vehicle electronics is significantly simplified.

The generator support can be manufactured as a so-called “MID” component, i.e., a molded interconnected device or an injection-molded circuit substrate, in accordance with various methods. Preferably, the generator support is produced in a one-component injection molding process from a thermoplastic plastic matrix, which has a metal complex that is embedded in the plastic matrix. The thermoplastic plastic matrix can be more particularly selected from the group consisting of polyamide, polyethylene terephthalate, polybutylene terephthalate, acrylonitrile butadiene styrene, polypropylene, polycarbonate, and polyether imide. The generator support that is produced in this way in an injection-molding process is then pretreated in a first step through patterned irradiation with a laser. In a predetermined area, the laser treatment generates a surface roughness and therewith undercuts for the cramping of the metal layer to be deposited later. The laser treatment also leads to a decomposition of the metal complex embedded in the plastic matrix while producing metallizable nuclei or seeds. The generator support that is pretreated in this way is then in a familiar manner subjected to an electroless plating. For this purpose, the generator support is dipped into a bath of a metal salt solution, for example, a nickel or copper salt, and a reducing agent. In this manner, on the sections of the generator support that have been pretreated by the laser patterning, a conductive metal layer is formed, whereas the untreated sections of the generator support surface remain free of metal and therefore electrically insulating. The metal layer that is so formed can then be reinforced by an electroplating process in a galvanic cell so as to produce the printed circuit. Just as in the case of manufacturing conventional printed circuit boards, it is also possible using this method to form metallized through holes in the printed circuit on the generator support.

In place of the method of direct laser patterning described here, it is also possible to use other methods for generating patterned surfaces, such as a chemical etching or plasma etching. Finally, conventional silk-screen or tampon printing methods for manufacturing printed circuits can also be used. The generator support can then be produced as a one- or two-component part using any desired injection molding process.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1depicts generator support12of a gas bag module (not shown here) which is designed for installation in the steering wheel of a motor vehicle. Generator support12is made of plastic in an injection molding process. It has a generally pot-shaped design, having a base14and a circumferential side wall16that proceeds from base14. Base14has a central opening18for accommodating a gas generator (not shown). In addition, further openings20are introduced in the base, serving, for example, to attach the gas generator to generator support12.

On two opposite positions of side wall16, a respective plate-shaped section22is integrally formed, projecting outwardly. On base14, a printed circuit24having conducting tracks26is applied by metal deposition, the printed circuit extending as far as to plate-shaped section22.

As is depicted inFIG. 2in a detail view, plate-shaped section22having conducting tracks26of printed circuit24, applied thereon, functions as the base for a switching element28, which is preferably configured as a silicone switching mat having actuating sections34that are positioned thereon. After switching element28is placed onto plate-shaped section22, it cooperates with conducting tracks26of printed circuit24on section22for activating an electrical function element (not shown here). In particular, conducting tracks26can include contact sections30that are adjacent to each other and electrically insulated from each other and that can be bridged for activating the electrical function element through pressure being applied to actuating sections34of switching element28.

In the embodiment depicted inFIG. 3, gas bag module10includes pot-shaped generator support12having essentially planar base14and circumferential side wall16. At the free end of side wall16, plate-shaped section22is integrally formed, projecting outwardly. On generator support12and plate-shaped section22, printed circuit24having conducting tracks26is formed by deposition of metal. Conducting tracks26cooperate with switching element28, which is placed on plate-shaped section22. Switching element28is fixed in position on plate-shaped section22by a panel32, which is clipped onto switching element28. Actuating sections34of switching element28are quite accessible to the driver by corresponding openings in the panel32. Switching element28, panel32, and plate-shaped section22of generator support12therefore constitute a simply designed multifunctional switch that is easily accessible to the driver through its being integrated in the steering wheel.

In addition, gas bag module10includes a cover36that is elastically connected to generator support12. For this purpose, base14of generator support12has an essentially tubular extension piece38, which extends inward into gas bag module10and onto which a spiral spring40is placed. At its opposite end, spiral spring40encompasses a cup-shaped extension42in the base of gas bag module10. In this manner, spiral spring40, as an elastic distancing element, defines a predetermined distance between base14and cup-shaped extension42.

In the area of tubular extension piece38, contact sections30of printed circuit24, which are adjacent to each other and electrically insulated from each other, are formed on base14. Situated opposite contact sections30is cup-shaped extension42, which functions as a switching element and can either be made of metal or have a metallized contact surface44. This contact surface44constitutes an opposite contact to contact sections30of printed circuit24. Through pressure applied to cover36in the direction of the steering wheel, spiral spring40is compressed and metallized contact surface44comes into electrical contact with conducting tracks26. The latter are bridged, a circuit is closed, and thus the electrical function element, for example a horn, is activated.

InFIG. 4, the cover36of a gas bag module is shown, in which edge sections46are provided with openings48. These openings48can accommodate actuating sections34of switching element28, which is depicted inFIG. 2. Cover36therefore also replaces panel32of the embodiment depicted inFIG. 3. In this way, a further reduction in the switching components can be achieved.

Finally, inFIG. 5, it is shown that the lower side of generator support12, as described above, can also be provided with a printed circuit24. Printed circuit24is attached to a plug connector50, which can provide a connection to the vehicle electronics in a simple manner. Printed circuit24takes on the task of cable leads, for example to horn contacts52, the cable leads including contact sections30of conducting tracks26that are adjacent to each other and electrically insulated from each other. Furthermore, conducting tracks26extend toward plate-shaped sections22, where they cooperate with switching element(s)28(FIG. 2). Plate-shaped sections22can be further reinforced mechanically using bars or ribs54that are arranged on their lower side.