Air bag system for a motor vehicle

An air bag system, for example for a steering wheel, in which a surface of the cushioning arrangement facing the vehicle interior is at least partially covered by a thin-walled sheet metal unit. The sheet metal bar unit is fixedly connected with the surface of the cushioning arrangement. The sheet metal unit is provided with at least one turned-in edge toward the inside of the cushioning arrangement in the area of lateral edges of the cushioning arrangement as well as in the area of the at least one tear edge.

BACKGROUND AND SUMMARY OF THE INVENTION
 This application claims the priority of German patent 198 29 755.6, filed
 Jul. 3, 1998, the disclosure of which is expressly incorporated by
 reference herein.
 The invention relates to an air bag system for a motor vehicle,
 particularly in a steering wheel of a vehicle interior, having a
 cushioning arrangement, which extends at least over an outlet opening for
 an air bag unit, faces a vehicle interior and has at least one tear flap
 defined by a tear contour for exposing the outlet opening during an
 expansion of an air bag of the air bag unit.
 Such an air bag system is generally known for passenger cars. The air bag
 system is integrated particularly in a steering wheel of the passenger
 car. However, in the same manner, such an air bag system is provided also
 in a front passenger area of a passenger car. An outlet opening of an air
 bag unit of the air bag system is provided on an exterior side facing the
 vehicle interior with a cushioning arrangement which has at least one tear
 contour at the level of the outlet opening for an air bag. In the event of
 a sudden expansion of the air bag, the cushioning arrangement is destroyed
 along the tear contour and the outlet opening for the expansion of the air
 bag is exposed.
 It is an object of the invention to provide an air bag system of the
 initially mentioned type which, despite safety-related requirements, can
 be designed with an attractive appearance in the vehicle interior.
 This object is achieved in that a surface of the cushioning arrangement
 facing the vehicle interior is covered at least partially by a thin-walled
 sheet metal bar unit which is fixedly connected with the surface of the
 cushioning arrangement and which, in the area of side edges of the
 cushioning arrangement as well as in the area of the at least one tear
 contour, is provided with at least one turned-in edge formed to the inside
 toward the cushioning arrangement. Particularly when the air bag system is
 inserted in a steering wheel, it is possible by means of the solution
 according to the invention to achieve for the steering wheel the
 impression of a metal-spoke steering wheel, and to nevertheless meet the
 corresponding safety requirements for today's motor vehicles. However,
 corresponding design-related impressions can also be achieved for a front
 passenger side of a center console area of the vehicle interior in that
 the sheet metal bar unit covers a corresponding cushioning arrangement in
 the center console area at the level of a front passenger air bag unit.
 The inwardly formed turned-in edge of the cushioning arrangement ensures
 that the corresponding cut edges of the sheet metal bar unit are led away
 from the visible surface and can therefore represent no risks of injury to
 the vehicle occupants. This is particularly advantageous in the event of a
 head impact onto the steering wheel or onto the front-passenger-side
 center console area. The sheet metal bar unit may be designed in one piece
 or consist of several pieces, as a function of the surface area of the
 cushioning arrangement to be covered, which may also be divided in the
 tear area. The tear contours may be provided on the underside of the
 cushioning arrangement so that they are invisible in the direction of the
 surface. The inwardly formed turned-in edge is advantageously at least
 partially embedded in the cushioning arrangement.
 As a further development of the invention, the sheet metal bar unit is
 connected by way of at least one fastening link with a carrier arrangement
 for the air bag unit. This further improves the fastening of the sheet
 metal bar unit on the air bag system so that a tearing-off of the
 cushioning arrangement as well as of the sheet metal bar unit is reliably
 avoided during an expansion operation of the air bag system.
 In a further development of the invention, the sheet metal bar unit is
 flatly connected with the cushioning arrangement, particularly by welding,
 by a spraying process or by gluing. This reliably avoids a detachment of
 the sheet metal bar unit from the cushioning arrangement.
 In a further development of the invention, the at least one turned-in edge
 of the sheet metal bar unit reaches in the area of the side edges at least
 in sections in a form-locking manner around the side edges. This further
 improves the safety with respect to a detachment of the sheet metal bar
 unit from the cushioning arrangement.
 In a further development of the invention, the at least one tear flap is
 covered at least partially by a medal fixedly connected with the tear flap
 and/or the sheet metal bar unit. A manufacturer's emblem can be mounted on
 this medal. The medal is designed as a plate or disk and may preferably
 have a round, oval or polygonal shape.
 In a further development of the invention, the medal is dimensioned such
 that it covers the tear contour. As a result, the tear contour is arranged
 in an invisible manner, whereby the whole cushioning arrangement of the
 air bag system has an aesthetically attractive design.
 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.

DETAILED DESCRIPTION OF THE DRAWINGS
 A steering wheel 1 according to FIG. 1 has a steering wheel rim 2 in which
 an air bag system is arranged in a manner to be described in the
 following. The air bag system has a cushioning arrangement 4 which forms
 the top side and the externally visible surface of the air bag system and
 which is preferably designed as an injection-molded part of a
 thermoplastic elastomer. The cushioning arrangement 4 forms steering wheel
 spokes and is fastened on its underside in a form-locking manner to a
 pot-type carrier arrangement 8 which carries an air bag unit 7, 9. In a
 manner known per se, the carrier arrangement 8 is fastened inside the
 steering wheel. In the illustrated embodiment, the air bag unit 7, 9 is
 formed by a gas generator 7 fastened on the carrier arrangement 8 as well
 as by an air bag 9 which is only outlined and which is folded together in
 its uninflated condition inside the pot-type carrier arrangement 8.
 The cushioning arrangement 4 is provided with several tear edges A serving
 as tear contours which are situated below three slot-shaped sections 5a,
 which will be discussed in detail in the following. The tear edges A are
 in each case made as a slot-type groove from an underside into the
 cushioning arrangement 4. By means of the tear edges A, which extend in a
 star-shaped manner toward an emblem section 6 of the cushioning
 arrangement 4 carrying a medal 14 and partially in a surrounding manner
 flank the emblem section 6, three tear flap sections are formed, the
 emblem section 6 being assigned to an upper tear flap section.
 The cushioning arrangement 4 is covered in the area of its surface facing
 the vehicle interior by a sheet metal unit 3 designed as a one-piece bar,
 which represents a thin-walled aluminum sheet bar of a thickness of
 preferably between 0.5 mm and 0.7 mm. The sheet metal unit 3 flatly covers
 the cushioning arrangement 4 and is flatly connected with the surface of
 the cushioning arrangement 4, particularly glued, welded or back-sprayed.
 In the area of cut edges of the sheet metal unit 3, the 3, has turned-in
 edges 12, 13 which are bent toward the inside at approximately a right
 angle or are formed in a different manner. The turned-in edges 12 are
 designed in the area of the tear edges A such that T-shaped strip areas
 5a, 5b are formed which correspond approximately to the contours of the
 tear flap sections of the cushioning arrangement 4. In the area of these
 turned-in edges 12, the cut edges are bent toward the interior at a right
 angle and are embedded in the material of the cushioning arrangement 4. In
 the area of the outer edges of the cushioning arrangement 4, the turned-in
 edges 13 are formed toward the inside--preferably by deep-drawing or
 bending--and are additionally sealed in a form-locking manner with the
 cushioning arrangement 4 at points distributed along the circumference of
 the cushioning arrangement 4.
 The medal 14 is fastened on a section of the sheet metal unit 3 stepped in
 the area of the emblem section 6. In the illustrated embodiment, they are
 connected, even before the flat connection with the cushioning arrangement
 4, in an opening of the sheet metal unit 3, in a form-locking manner by
 back-spraying by means of an injection pin.
 In addition, the sheet metal unit 3 has several fastening links 11 which
 are distributed over its circumference and which are molded in one piece
 to the turned-in edges 13 and project toward the inside to the level of
 the carrier arrangement 8 of the air bag system. The fastening links 11
 are connected with the carrier arrangement 8 by means riveted joints 10 or
 other fastening devices in an undetachable and force-transmitting manner.
 In the plan view, almost only the sheet metal unit 3 and the medal 14,
 which also covers the emblem section 6, are visible in the spoke area of
 the steering wheel 1. The cushioning arrangement situated under the sheet
 metal unit 3 is visible only at the level of the strip areas 5a, 5b. The
 strip areas 5a, 5b are selected such that the sheet metal unit 3 covering
 the cushioning arrangement 4 does not hinder the tear flap function of the
 cushioning arrangement 4 in the event of a sudden expansion of the air bag
 9.
 The embodiments according to FIGS. 3 to 8 described in the following each
 have sheet metal unit 3a to 3c which, analogously to the above-described
 embodiment, are flatly connected with a cushioning arrangement 4a to 4c
 corresponding to the above-described cushioning arrangement 4. In the case
 of the steering wheels 1a to 1c described in the following, only the
 differences with respect to the embodiment according to FIGS. 1 and 2 will
 be described again in detail. In this case, the steering wheels 1a to 1c
 also have air bag systems which are constructed analogously to the air bag
 system according to FIGS. 1 and 2. Particularly the design and the linking
 of the sheet metal bar units 3a to 3c as well as the presence of a carrier
 arrangement for the air bag unit and the presence of the air bag system
 itself will not be described again in detail at this point. In this
 respect, reference is made to the above disclosure.
 The steering wheel 1a according to FIGS. 3 and 4 has a central disk-shaped
 medal 14a which, in the illustrated embodiment, consists of plastic and by
 means of at least one injection pin 15a is back-sprayed with the
 cushioning arrangement 4a; that is, flatly connected by means of an
 injection molding arrangement. The sheet metal bar arrangement 3a ends in
 the area of the emblem section of the cushioning arrangement defined by
 the medal 14a. The medal 14a covers a surrounding circular tear contour A.
 In the embodiments according to FIGS. 3 to 6, the reference number 17 in
 each case indicates an additional securing groove for a back-snapping for
 the air bag system, which is known per se.
 The tear flap which is formed by the surrounding tear contours A and is
 also disk-shaped and has a smaller diameter than the medal 14a, is
 connected by way of a hinge arrangement in the form of a hinge joint 16
 including the medal 14a with the outer areas of the cushioning arrangement
 4a. In this case, the flexible hinge arrangement 16 in the form of the
 hinge joint is embedded in the cushioning arrangement 4a so that, even in
 the event of a sudden bursting-open of the emblem section and of the medal
 14a, it cannot be removed from the cushioning arrangement 4a by the
 triggering of the air bag. The hinge joint 16 reaches in a form-locking
 manner around the injection pin 15a in the area of the emblem section of
 the cushioning arrangement 4a, whereby an additional securing of the medal
 14a and of the emblem section are achieved. As illustrated in FIG. 3, a
 narrow circular gap remains between the sheet metal unit 3a and the medal
 14a which shows the cushioning arrangement 4a.
 The steering wheel 1b according to FIGS. 5 and 6 also has a sheet metal
 unit 3b which encloses a tear area of the cushioning arrangement 4b.
 Concentric within the circular tear area of the cushioning arrangement 4b,
 a medal 14b is arranged. Analogously to the above-described embodiment,
 the medal 14b is form-lockingly connected via an injection pin 15b with
 the cushioning arrangement 4b by way of back-spraying. By means of
 corresponding tear contours A, the cushioning arrangement 4b forms a total
 of three circular ring sections. On the circular ring section which is on
 top in FIG. 5, an emblem section 6b is molded on in one piece which
 carries the medal 14b. The tear contour surrounds this emblem section 6b
 similarly to the embodiment shown in FIG. 1. The tear area of the
 cushioning arrangement 4b therefore forms three
 circular-ring-segment-shaped tear flaps which tear open with small
 swivelling radii. The upper tear flap, which carries the medal 14b by way
 of its emblem section 6b, is also connected via a flexible hinge joint 18
 with the cushioning arrangement 4b provided in the area of the sheet metal
 unit 3b, the hinge joint 18 being integrated in the cushioning arrangement
 4b and the emblem section 6b. The hinge joint 18 also reaches around the
 injection pin 15b of the medal 14b in a form-locking manner, in that it
 has a recess at this level.
 In the event that the air bag is triggered, the medal 14b, including the
 pertaining emblem section 6b, is therefore held on the steering wheel so
 that it cannot be lost, whereby injuries to the driver can be avoided.
 In the illustrated embodiment, the steering wheel 1c according to FIGS. 7
 and 8 has a three-spoke design. However, in the same manner, it may also
 be constructed with four spokes without any differences with respect to
 the characteristics described in the following. In the case of this
 steering wheel 1c, the sheet metal unit 3c covers almost the entire
 surface of the cushioning arrangement 4c. It ends in the area of a
 circular emblem section 6c which carries a medal 14c. By means of a
 surrounding tear contour A, which may have a circular, elliptical or
 polygonal design, the tear flap of the cushioning arrangement 4c is formed
 which, in the embodiment according to FIGS. 7 and 8, is identical with the
 emblem section 6c. In the embodiment according to FIGS. 7 and 8, the sheet
 metal unit 3c itself acts as the hinge arrangement, in that a strip
 section of the sheet metal bar unit 3c is continued into the emblem
 section 6c according to FIG. 8. The medal 14c reaches by way of a
 corresponding injection-molded nose 15c in a form-locking manner behind
 this strip section of the sheet metal unit 3c, the fastening of the medal
 14c on the sheet metal unit 3c corresponding to the arrangement according
 to FIG. 2. The medal 14c is constructed to be so large that it completely
 covers the tear flap and thus the emblem section 6c of the cushioning
 arrangement 4c. This is also illustrated by broken reference lines in FIG.
 7. A tear flap with a polygonal tear contour A is particularly
 advantageous for this embodiment if, in the area of the strip section of
 the sheet metal unit 3c, which forms the hinge arrangement, the tear
 contour A extends in a straight line A. As a result, a largely
 tension-free swivelling-open of the strip section and of the medal 14c is
 achieved. The strip section therefore has a web-shaped design.
 The foregoing disclosure has been set forth merely to illustrate the
 invention and is not intended to be limiting. Since modifications of the
 disclosed embodiments incorporating the spirit and substance of the
 invention may occur to persons skilled in the art, the invention should be
 construed to include everything within the scope of the appended claims
 and equivalents thereof.