FR2712551A1 - Vehicle steering wheel able to contain air bag - Google Patents

Abstract

Steering wheel comprises a central body (7), a covering material (6) and an outer skin (8). The central body and covering layer are made from a relatively rigid thermoplastic material, while the outer skin is of a relatively supple thermoplastic material, e.g. polyurethane foam. The central body can be hollow and contain an air bag (10) or an impact absorber with flat deformable elements or a block of a cellular material. The steering wheel has peripheral (1,2) and central (3,5) reinforcing elements, the latter comprising a hub (3) and radial branches (5) connected to the backs of radial branches (2) of the peripheral elements. It is also equipped with a rear shell (19) with a lateral access port for an assembly/adjustment tool.

Description

 The invention relates to steering wheels for motor vehicles.

 It aims for a steering wheel that is simple, convenient and economical, both in manufacturing and in assembly, including in the case where it must integrate additional equipment such as an air bag module.

To this end, it offers a steering wheel for motor vehicles, characterized in that it comprises
- A central body having a front face, integral at the periphery with the coating of the rim and the branches; and
- An outer layer which continuously covers said front face of the central body and said coating.

 According to preferred characteristics - said central body and said coating are made of relatively rigid thermoplastic, and said outer layer of relatively flexible thermoplastic, - said coating and said central body are made of relatively rigid thermoplastic, and said outer layer of polyurethane foam, - it comprises an air bag module carried by said hollow body, - it comprises a head shock module carried by said hollow body, - said head shock module comprises an energy absorbing means formed by deformable flat elements, - said shock module -head comprises an energy absorbing means formed by a block of cellular material, - it comprises at least one electrical contactor carried by said hollow body, - it comprises a peripheral armature disposed in said coating and a central armature having a hub and branches secured at the rear to the branches of the peripheral reinforcement, - it has a rear shell, - the said rear shell comprises a lateral access hatch allowing the installation of a mounting part making it possible to subject the steering wheel hub to a steering column, - said rear shell comprises access hatches allowing the installation a mounting element making it possible to subject a module carried by said central body to said branches, - the central body adheres at the periphery to the coating of the rim and the branches, - the central body is molded at the periphery by the coating of the rim and the arms, - the central body and the coating of the rim and the arms are molded in one piece.

 In a second aspect, the invention relates to a mounting part adapted to be positioned laterally to secure the hub of a steering wheel as previously exposed to a steering column, comprising a ring whose inner contour follows two portions of a circle of different diameters, and a screw opposite the part with the smallest diameter.

 In a third aspect, the invention relates to a steering column adapted to receive a steering wheel as previously exposed, this steering wheel being secured by the previously exposed mounting part, this column having an end having, after the section intended to be surrounded by the hub, a section of smaller diameter, a groove being formed at the base of the section of smaller diameter, the inner contour of said mounting part having its largest portion of circle which is the diameter of said section of small diameter, and its portion of the circle smaller than the diameter of said groove.

In a fourth aspect, the invention relates to a method for molding said central body and said outer layer of a steering wheel in which the central body adheres at the periphery to the coating of the rim and of the branches, in which - the rim is placed and the branches previously coated, in a mold suitable for obtaining said central body in a first material, and for obtaining a lower portion of the outer layer, located under the joint plane, in a second material
- said first and second materials are injected into said mold
- the upper half-mold is changed by another suitable upper half-mold, in cooperation with the lower half-mold in which the assembly previously obtained remains, in obtaining in said second material the remainder of said outer layer, located at- above the parting line and
- Said second material is injected.

Objects, characteristics and advantages of the invention appear from the following description, given by way of nonlimiting example, with reference to the appended drawings in which
- Figure 1 is a partial schematic section of a steering wheel according to the invention
- Figure 2 is a perspective of a mounting part for securing the hub of the steering wheel to the steering column
- Figure 3 is a plan view showing how the mounting part cooperates with the steering column
- Figure 4 is a plan view of the peripheral metal frame of this steering wheel
- Figure 5 shows this frame embedded in a coating of thermoplastic material
- Figure 6 is a sectional elevation view of this coated frame on which adheres the lower portion of the outer layer and the central body of the steering wheel, the section being taken along a plane corresponding to that shown in AA in Figure 5
- Figure 7 is a similar view, but with the outer layer supplemented by its upper portion
- Figures 8 and 9 show similarly the following steps of the steering wheel assembly, in a variant where the attachment of the air-bag module is more complete
- Figure 10 shows in a similar way the central metal frame and the rear shell of the pre-assembled steering wheel, in a variant where the steering wheel is designed to be fixed on a conventional steering column
- Figures 11 and 12 are elevation-section views of the coated peripheral reinforcement, showing alternative embodiments of its coating, the section being taken along a plane corresponding to that marked in AA in Figure 5
- Figure 13 is a plan view of another alternative embodiment where the coating of the peripheral frame and the central body of the steering wheel are molded in one piece
- Figure 14 is the sectional elevation view taken along the plane marked in XIV-XIV in Figure 13
- Figure 15 is a similar view, but for a variant where the central body is molded on the periphery by the coating
- Figure 16 shows the assembly of Figure 15 coated with an outer layer of polyurethane foam molded in one piece; and
- Figures 17 and 18 are views similar to Figure 8, but in variants where the air bag module is replaced by a head-shock module.

 The steering wheel illustrated in FIG. 1 is provided with a metal frame divided into a peripheral frame and a central frame.

 The peripheral reinforcement (see also FIG. 4) comprises a rim 1 formed by an annular metal tube, for example made of steel, and short branches 2, for example made of welded steel or molded in aluminum.

 The central frame comprises a hub 3 for mounting on the steering column 4, and branches 5 for connecting the hub 3 to each of the branches 2.

 The peripheral reinforcement is embedded in a coating 6 (see also FIG. 5) in relatively rigid injected thermoplastic, this coating being secured to a central body 7 also in relatively rigid injected thermoplastic, the coating 6 and the body 7 being covered externally by a uniform and continuous surface layer 8, also made of injected thermoplastic, but more flexible, for example with a hardness of 24 shore A.

 An air bag module is provided inside the steering wheel, in its center, the metal box 9 containing the gas generator being fixed to the arms 5 and to the body 7, the folded air bag 10 being installed between the box 9 and a wall which comprises the body 7 in its center, points of weakness 11 (only one of which is shown in the drawing) being provided in this wall so that the association of this and of the surface layer 8 which covers it forms for the bag 10 a cover capable of opening in the desired manner to allow the bag to pass when the latter inflates suddenly following the ignition of the gas generator contained in the housing 9 in response to an electrical signal emitted by a shock detector and transmitted by the cable 13.

 In the example illustrated, the body 7 comprises around the central wall which forms the air bag cover, a flange 14 transverse to this wall, and the base of which has a lip where a bead 15 of the housing can be snapped into place 9, this snap-fastening providing the fixing between the housing 9 and the body 7; and the branches 5 have a shoulder on which the periphery of the base of the housing 9 is supported, screws 16 being provided for securing the housing 9 to the branches 5.

 In addition to the air bag module, the body 7 carries an electrical contactor 18, for example for the horn, the button of which can be pressed by simple pressure on the surface layer 8 at the corresponding location.

 At the rear of the steering wheel, between the hub 3 and the coating 6, an attached shell 19 is provided, fixed here by means of the screws 20 which serve to secure the arms 5 and the arms 2, that is to say the 'central frame and peripheral frame. The rear shell 19 is made of injected thermoplastic, with a relatively rigid internal layer 21, such as the coating 6 and the body 7, and a more flexible external layer 22, such as the layer 8.

 In general, the outer layers 8 and 22 provide a feel for the steering wheel which is more comfortable than if one were in direct contact with a rigid material, the elastic nature of the flexible thermoplastic being useful for providing the deformations allowing actuate the contactors such as 18, and so that the central part forming the air-bag cover has the desired behavior during opening, the fact that the outer thermoplastic layer is applied to an element itself of thermoplastic ensuring a perfect adhesion between them.

 To allow the mounting of the steering wheel on the column 4, there is provided in the shell 19 a hatch 28 (see FIG. 9) which provides lateral access to the top of the hub 3 to set up the element 23 which is used for the subject to column 4.

 In the example illustrated, the top of the latter is configured with a conical base and conventional grooves, the end not being threaded but having, after the section 24 intended to be surrounded by the hub, a section 25 of smaller size. diameter, a groove being formed at the base of the section 25.

 The mounting part 23 (see FIGS. 2 and 3) comprises a ring 26 whose inner contour follows two portions of a circle, the largest of which is the diameter of the section 25 of the column 4, and the smallest the diameter of the groove located at the junction between the sections 24 and 25. The part 23 also comprises, opposite the part having the smallest diameter, a clamping screw 27.

 The part 23 is put in place by sliding its internal part with a larger diameter along the section 25, until it rests on top of the section 24, the part 23 is then made to slide parallel to itself. so that its smaller diameter part enters the groove at the foot of the section 25, and then tightens the screw 27 which comes to bear against a dish provided in the groove 25, until the part 23 is securely held in position. Of course, as shown in FIG. 1, the underside of the part 23 bears on the top of the hub 3 while the top of the part 23 bears on the upper wall of the groove formed at the foot of the section 25.

 To allow tightening along the axis of column 4, a slight slope can be provided on the top and / or bottom of the part 23.

 To facilitate the mounting of the part 23, it can be supplied with a screw 27 connected by a breakable zone to a coaxial rod, this rod making it possible to set up the part 23 as indicated above, including for tighten the screw 27, after which the rod is removed by breaking the breakable zone.

 We will now describe in support of FIGS. 4 to 9 a method for obtaining the flywheel shown in FIG. 1.

 After having prepared the peripheral reinforcement, that is to say the rim 1 associated with the branches 2, it is overmolded to obtain the coating 6, as shown in FIG. 5. The assembly obtained is then placed in a mold suitable for obtaining the body 7 in a relatively hard thermoplastic, and for obtaining the lower portion of the outer layer 8, that is to say of the portion located under the joint plane shown by the symbol 29 in Figures 6 and 7, in a relatively flexible thermoplastic.

The two kinds of thermoplastic are then injected into this mold, and the assembly shown in FIG. 6 is thus obtained, the various thermoplastics which form the coating 6, the central body 7 and the lower portion of the outer layer 8 being chosen so that there is perfect adhesion between the periphery of the body 7 and the coating 6, and between the latter and the layer 8.

 While keeping the assembly shown in FIG. 6 in the lower half-mold (the one which is under the joint plane), the upper half-mold is changed to another which is suitable, in cooperation with the lower half-mold. , when the rest of the outer layer 8 is obtained, and the latter is then injected into the same flexible thermoplastic as its lower part.

 The contactor (s) 18 (s) 18 and the air bag module are then put in place in the body 7, these positioning being effected by simple snap-fastening in the example illustrated in FIGS. 1, 6 and 7.

 In the variant shown in FIG. 8, reinforcement brackets 30 are also put in place between the housing 9 and the base of the flange 14 in which a groove is made for this purpose.

 We then mount the central metal frame (hub 3 and arms 5) on the housing 9 using the screws 16 (embodiment of Figure 1) or the nuts 31 cooperating with the screws 32 (embodiment of Figures 8 and 9), then the rear shell 19 is put in place and the screws 20 are tightened, which completes the assembly of the steering wheel.

 The rear shell 19 may comprise, for each screw 20, in order to mask it, a cover molded at the same time as the layer 22, and connected to the rest of the shell 19 by a part forming a hinge. The shell 19 may also include a similar cover but of larger dimensions to close the side access hatch 28 provided for mounting the steering wheel on the steering column.

 As a variant, in the case where it is desired to mount the steering wheel according to the invention on a conventional steering column, that is to say with a thread where a nut is placed which bears on top of the hub 3 , the assembly shown in FIG. 10 is put in place, which comprises the central metal frame secured by the screws 20 to a rear shell 19 ', similar to the shell 19, but where the hatch 28 is replaced by hatches 33 each located at the base of the hole 34 formed in the branches 5 for the passage of the screw 16 or 32, and the assembly of the steering wheel is completed by positioning on this assembly, which forms the lower part of the steering wheel, the assembly shown in FIG. 8, which forms the upper part of the steering wheel, the screws 20 which are put in place in the branches 2 are tightened, and thanks to the hatches 33, the nuts 31 or the screws 16 are put in place.

 In each of the two mounting possibilities of the steering wheel described above, provision is preferably made for indexing means between the branches 2 and 5, and also between these latter branches and the rear shell, to guarantee that the assembled steering wheel is centered in all directions.

 In variants not shown of the metal frame of the steering wheel, the rim is produced in a solid profile rather than in a tube, this profile being of steel or of light alloy, the branches 2 possibly being of steel and linked to the rim by a aluminum overmolding, and it is also possible to provide that the whole of the peripheral frame 1, 2 is made of cast aluminum.

 Many variants are also possible for the coating 6, it can in particular be produced with gas injection in order to save material and lighten the steering wheel, like the coating 6 ′ shown in FIG. 11, or be produced in a material other than a thermoplastic, for example a cellular material such as expanded polyurethane foam, or else be produced by two half-shells 6A and 6B manufactured separately and then assembled together by sandwiching the peripheral reinforcement, the half-shells being able to be in cellular thermoplastic, in expanded thermoplastic or in expanded polyurethane foam.

 In the variant shown in FIGS. 13 and 14, the coating 6 and the central body 7 are made of relatively rigid thermoplastic and are obtained in the same injection operation, that is to say that they are molded from one piece.

 In the variant shown on the. FIG. 15, the central body 7 is pre-existing, and has a T-shaped periphery which is overmolded by the coating 6.

 Many other variants are possible to make the coating 6 and the periphery of the body 7 integral, that is to say assembled by construction, permanently (cannot be dismantled).

 In the variant shown in Figure 16, the outer layer 8 'is molded in one piece, and is made of a polyurethane foam adapted to adhere to the relatively rigid thermoplastic with which the central body 7 and the coating are made. 6.

 In the variant shown in FIG. 17, the air-bag module is replaced by a head-shock module 35 which is assembled by riveting on the flange 14. The module 35 comprises a reaction plate 36 which cooperates with the branches 5 of a similar manner to the housing 9 of the air-bag module, and an energy absorbing means, formed by deformable flat elements, here an element 37 of M section whose base is riveted on the plate 36 and the top secured to a energy distribution plate 38 which is located under the central part of the front wall of the body 7.

 In module 35, the plates 36 and 38 as well as the element 37 are made of metal. Alternatively, similar plastic elements can be used, and these flat elements can be given other shapes suitable for absorbing energy.

 In the variant shown in FIG. 18, the head-shock module 39 comprises, above the reaction plate 36, a simple block 40 of cellular material, in this case expanded polyurethane foam.

 It is seen that the fixing of the internal module to the steering wheel, respectively with respect to the central body 7 and with respect to the frame of the steering wheel, can be done in many ways. Thus, the assembly between the module and the central body 7 is done by simple snap-fastening in the embodiment shown in FIG. 1, additional reinforcing elements 30 are provided in the embodiment of FIGS. 8 and 9, while in the variants of FIGS. 17 and 18, the module is fixed to the central body 7 by riveting, and it is also possible, depending on the circumstances, to use bolts or other fixing means. With regard to the attachment of the module to the metal frame of the steering wheel, provision has been made in each of the examples illustrated to rest on a shoulder of the branches 5 and to perfect the attachment with screws, but instead of providing that the base of the module is directly supported on a shoulder of the frame, it is possible to complete the latter with intermediate pieces (in English: brackets) arranged between the branches, and on which the module bears, these pieces being able to be shaped so that the module can be fixed with fewer screws than the steering wheel has branches, which makes assembly of the steering wheel faster.

 It is also possible to provide a module comprising rear fixing lugs which extend to the junction point between the branches 2 and 5, so that the screws 20 are also used for fixing the module to the metal frame of the steering wheel.

 In the examples illustrated, the contactor 18 is carried by the central body 7, but it is also possible to have it carried by the metal frame of the steering wheel, for example by means of a connecting piece integral with the branches 5. The contactors that the 'provided in the steering wheel according to the invention can be used not only to activate the horn, but also a cruise control or a car radio.

 It is also possible to fix the rear shell 19 or 19 ′ in a different manner, for example by riveting or by simple snap-fastening. We can also use the rear shell to make it carry electrical components, including wiring, fittings, or the rotary switch illustrated at its base in the drawings, which is of the spring type of watch.

 In the case where the module installed in the steering wheel is an air bag, the part of the central body 7 which overhangs it, and which will therefore open when the balloon 10 is inflated, can be reinforced if necessary by a net or by straps.

 In other variants, the air bag module is replaced by any other module that it may be useful to have inside the steering wheel, or else no module is provided in its place.

 In the latter case, the internal frame 3, 5 and the rear shell 19 are directly assembled with the screws 20 after the contactors 18 have been fitted, in the case where the steering wheel has them.

 It will be recalled that the invention is not limited to the examples described and shown.

Claims (18)

 1. Steering wheel for motor vehicles characterized in that it comprises  - A central body (7) having a front face, integral at the periphery with the coating (6; 6 '; 6A, 6B) of the rim (1) and of the branches (2); and  - an outer layer (8; 8 ') which continuously covers said front face of the central body (7) and said coating (6).  2. Steering wheel according to claim 1, characterized in that said central body (7) and said coating (6; 6 '; 6A, 6B) are made of relatively rigid thermoplastic, and said outer layer (8) of relatively flexible thermoplastic.  3. Steering wheel according to claim 1, characterized in that said coating (6; 6 '; 6A, 6B) and said central body (7) are made of relatively rigid thermoplastic, and said outer layer (8') is made of polyurethane foam.  4. Steering wheel according to any one of claims 1 or 3, characterized in that it comprises an airbag module (9, 10) carried by said hollow body (7).  5. Steering wheel according to any one of claims 1 to 3, characterized in that it comprises a shock module (35; 39) carried by said hollow body (7).  6. Steering wheel according to claim 5, characterized in that said head-shock module (35) comprises an energy absorbing means formed by deformable flat elements (37, 38).  7. Steering wheel according to claim 5, characterized in that said head-shock module (39) comprises an energy absorbing means formed by a block (40) of cellular material.  8. Steering wheel according to any one of claims 1 to 7, characterized in that it comprises at least one electrical contactor (18) carried by said hollow body (7).  9. Steering wheel according to any one of claims 1 to 8, characterized in that it comprises a peripheral frame (1, 2) disposed in said coating and a central frame (3, 5) having a hub (3) and branches (5) secured from the rear to the branches (2) of one peripheral frame.  10. Steering wheel according to any one of claims 1 to 9, characterized in that it comprises a rear shell (19, 19 ').  11. Steering wheel according to claim 10, characterized in that said rear shell (19) comprises a lateral access hatch (28) allowing the installation of a mounting part (23) making it possible to secure the hub (3 ) from the steering wheel to a steering column (4).  12. Steering wheel according to claim 10, characterized in that said rear shell (19 ') comprises access hatches (33) allowing the installation of a mounting element for securing a module (9, 10; 35; 39) carried by said central body (7) to said branches (5).  13. Steering wheel according to any one of claims 1 to 12, characterized in that the central body (7) adheres at the periphery to the coating (6) of the rim and the branches.  14. Steering wheel according to any one of claims 1 to 12, characterized in that the central body (7) is molded at the periphery by the coating (6) of the rim and the branches.  15. Steering wheel according to any one of claims 1 to 12, characterized in that the central body (7) and the coating (6) of the rim and the branches are molded in one piece.  16. A mounting part adapted to be positioned laterally to secure the hub (3) of a steering wheel according to any one of claims 1 to 15 to a steering column (4), comprising a ring (26), the inner contour follows two portions of a circle of different diameter, and a screw (27) opposite the portion having the smallest diameter.  17. Steering column adapted to receive a steering wheel according to any one of claims 1 to 15, this steering wheel being secured by the mounting piece according to claim 16, comprising an end having, after the section (24) provided to be surrounded by the hub (3), a section (25) of smaller diameter, a groove being formed at the base of the section of smaller diameter, the inner contour of said mounting piece (23) having its largest portion of a circle which is at the diameter of said section (25) of small diameter, and its portion of the circle the smallest at the diameter of said groove.  18. A method of molding said central body (7) and said outer layer (8) of a flywheel according to claim 13, characterized in that  - placing the rim (1) and the branches (2) previously coated, in a mold suitable for obtaining said central body (7) in a first material, and for obtaining a lower portion of the outer layer (6), located under the joint plane (29), in a second material;  - said first and second materials are injected into said mold  the upper half-mold is changed by another suitable upper half-mold, in cooperation with the lower half-mold in which the assembly previously obtained remains, in obtaining in said second material the remainder of said external layer (8), located above the joint plane (29); and  - Said second material is injected.