Abstract:
A vehicle steering wheel comprises a steering wheel skeleton, a longitudinal axis, at least two components movable relative to each other, and a horn contact switch, which has two electrical contact elements which are brought in contact with each other by means of a relative movement of the two components to each other for a horn actuation. The electrical contact elements are contact wires.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a vehicle steering wheel.  
       BACKGROUND OF THE INVENTION  
       [0002]     A vehicle steering wheel known from the German Utility Model 200 17 527 comprises a gas bag module connected with the steering wheel skeleton and mounted so that it is displaceable in the direction of the longitudinal axis for actuation of the horn. The electric contact elements comprise an electrically conductive detent hook projecting on the gas bag module on the rear side, which on actuation of the horn is brought in contact with a likewise conductive spring wire. In addition, it is known to construct the contact elements as metallic punched parts which are arranged on movable parts of the vehicle steering wheel and which come into contact with each other on actuation of the horn.  
         [0003]     The existing solutions from the prior art always require a particular overall height and frequently also particular parts which are to be manufactured by punching and/or bending, the manufacture of which is cost-intensive and the installation of which is complicated.  
         [0004]     Proceeding form these disadvantages, the invention is based on the problem of avoiding these disadvantages at least partially and providing a particularly favourably priced horn contact switch.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     According to the invention, this problem is solved by a vehicle steering wheel comprising a steering wheel skeleton, a longitudinal axis, at least two components movable relative to each other, and a horn contact switch, which has two electrical contact elements which are brought in contact with each other by means of a relative movement of the two components to each other for a horn actuation. The electrical contact elements are contact wires.  
         [0006]     Thereby, particular punched parts or special parts are no longer necessary. Rather, only two wires which are provided in any case have to be partially insulated, which are brought into contact with each other through the relative movement of two components of the vehicle steering wheel. The wires forming horn contacts are part of the known horn current circuit. The horn contacts and the horn current circuit are designed so that with a contact of the wires, the horn sounds.  
         [0007]     The two contact wires, preferably intersecting, viewed in the longitudinal axis, can be provided, uncoupled from each other, on two components, for example one on the underside of the intermediate plate of a gas bag module and the other on the corresponding site on the upper side of the hub of the skeleton.  
         [0008]     The horn contact switch according to the invention is particularly compact and simple to install when the two contact wires are provided coupled to a common component. For example, the contact wires can be arranged running parallel to each other in a recess, a first contact wire being spaced apart from the second contact wire, which is provided with a U-shaped curvature. For actuation of the horn, the elastic second contact wire is acted upon by force in the curved region and twisted, and also pressed onto the first contact wire, in order to close the horn current circuit After the horn actuation, the second contact wire moves independently into the unactuated initial position.  
         [0009]     Finally, the contact wires could be arranged in a common switch element with its own housing. This switch element, provided with plugs, can be fastened on installation simply onto the corresponding site, a corresponding coupling ensuring the necessary fixing of the plug, so that no further fixing means are necessary.  
         [0010]     The common arrangement of the two contact wires to a component involves the further advantage that the elastic contact wire can undertake the function of the restoring spring inside the vehicle steering wheel. Through corresponding dimensioning of the elastic contact wire, it is therefore no longer necessary to provide additional restoring springs for the gas bag module alongside the electric contact element or, if no gas bag is to be provided, for the component (e.g. steering wheel hub cap) which is to be moved by the driver. Thereby, a particularly compact and low overall height can be realized.  
         [0011]     In order to ensure a good contact between the contact wires on actuation of the horn, on one of the components carrying out the relative movement an actuating element can be provided, which presses one contact wire onto the other on actuation of the horn. This actuating element can be constructed either as an additional component which is to be installed or can be formed in one piece on a component, e.g. by injecting on a plastic part. This is particularly advantageous, because a plastic element is electrically insulating and does not have an effect on the mode of operation of the horn contact. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  shows a diagrammatic cross-sectional view through a first embodiment of the vehicle steering wheel according to the invention;  
         [0013]      FIG. 2   a  shows an enlarged view of the detail II of the vehicle steering wheel according to  FIG. 1  with the horn not actuated;  
         [0014]      FIG. 2   b  shows an enlarged view of the detail II of the vehicle steering wheel according to  FIG. 1  with the horn actuated;  
         [0015]      FIG. 3  shows a diagrammatic cross-sectional view through a second embodiment of the vehicle steering wheel according to the invention; and  
         [0016]      FIG. 4  shows an enlarged perspective view of the detail IV of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]     According to  FIG. 1 , a vehicle steering wheel has a steering wheel skeleton  10  and a gas bag module  12 . The longitudinal axis A of the steering wheel is represented by a dot-and-dash line. The steering wheel skeleton  10  has a steering wheel rim, surrounded by foam, not illustrated, which is connected by means of spokes  14  with a cup-shaped steering wheel hub  16 . In the region of the longitudinal axis A of the vehicle steering wheel, the hub  16  has a mounting opening  18  to receive a steering column.  
         [0018]     The gas bag module  12 , constructed as a “floating horn” is illustrated by way of example and has a cup-shaped module housing  20  with a base  22 , which at the same time forms the carrier for a gas generator  24 . The module housing  20  is closed towards the vehicle interior with a covering  26 , which covers a gas bag  28  folded inside the module housing  22 .  
         [0019]     On the underside of the base  22 , several detent hooks  30 , constructed in a known manner, are formed for fastening the module housing  20  on the hub  16 . The fastening takes place by means of arresting means which are secured to the skeleton. The arresting means consist here of components which are securely mounted in the skeleton but displaceable laterally by a certain amount (e.g. wires  32 ), which lock the detent hooks  30  in the installed position. This connection is designed so that a movement of the module housing  22  is made possible in the direction of the longitudinal axis A inside the steering wheel, without the detent connection  30 ,  32  being released.  
         [0020]     Between the module housing  20  and the skeleton  10 , compression springs  34  are arranged in a manner known per se. These compression springs  34  exert a restoring force onto the module housing  20  acting contrary to the actuating force for the horn. They are also designated as restoring springs.  
         [0021]     On the underside of the base  22  of the module housing  20 , a first contact wire  50  partially extends between two cross-pieces  52  on the base  22  of the module housing  20 . The cross-pieces  52  can be of plastic or metal. The contact wire  50  can be insulated (in metal cross-pieces  52 , it is compulsorily insulated); between the cross-pieces  52  it is in every case non-insulated. This first contact wire  50  represents the first of two contact wires of the horn contact switch. The second contact wire  54  of the horn contact switch extends running in the direction of viewing of  FIGS. 1 and 2   b  and thereby transversely to the longitudinal axis of the first contact wire  50  over a particular section on the upper side of the hub  16  between two cross-pieces  56 , which are provided for example in the foam surrounding the skeleton. The second contact wire  54  is also not insulated in the section between the cross-pieces  56 . The arrangement of the contact wires  50 ,  54  is constructed so that the first contact wire  50  in the installed position crosses the second contact wire  54  viewed in the direction of the longitudinal axis A, but is spaced apart from it. On actuation of the horn, the first contact wire  50  is pressed onto the second contact wire  54 ; this closes the horn contact switch. At least one of the two contact wires  50 ,  54  is mounted so as to be elastically flexible e.g. like a bending beam, so that it performs a stroke on actuation of the horn. The restoring movement of the module  10  can support the stroking contact wire  50 ,  54 .  
         [0022]     The second embodiment, illustrated in  FIGS. 3 and 4 , differs from the one previously described in that the two intersecting contact wires of the horn contact switch are provided coupled to a common component of the vehicle steering wheel. The corresponding components of the second embodiment in FIGS.  1  to  2   b  are marked by reference numbers increased by 100. The essential difference in this embodiment lies in that the intersecting contact wires  150  and  154  are not uncoupled, as in the first embodiment, but rather are arranged coupled to the steering wheel hub  116 , i.e. to the same component. For this purpose, in the upper side of the steering wheel hub  116  a trough-shaped recess  180  is provided, in which the insulated contact wires  150  and  154 , running through the skeleton  10 , extend approximately parallel to each other. In the region of the recess  180 , the contact wires  150 ,  154  are not insulated. The first contact wire  150  is arranged staggered slightly upwards and to the side from the second contact wire  154  in the recess  180 . It has, in addition, a U-shaped or arc-shaped curvature  150 a which crosses the second contact wire  154  in the initial position in the direction of longitudinal axis A, but spaced apart from it. The first contact wire  150  is constructed as a torsion spring and has a sufficient elastic force in order to undertake the function of the restoring- or compression springs  34 . With the horn actuation, the module housing  120  presses with an actuating element protruding on the rear side in the form of a projection  158  against the first contact wire  150  in the region of the curvature  150   a  and twists it against the elastic force of the first contact wire  150 , until the contact wires  150 ,  154  touch each other, and thus closes the horn contact switch.  
         [0023]     Alternatively to this, the contact wires  150 ,  154  can of course also be housed in the surrounding foam of the skeleton  10 , which does not have to be additionally illustrated.  
         [0024]     Spring bronze, for example, can be selected as material for the contact wires  50 ,  54 ,  150 ,  154 .  
         [0025]     Preferably, of course, several horn contact switches are provided between module and skeleton  10 ,  110 , which all together are formed only by the contact wires  50 ,  54 ,  150 ,  154 , which run in a loop shape between module and skeleton.  
         [0026]     Owing to the coupled arrangement of the contact wires  150 ,  154  in the recess  180 , in particular in the second embodiment the vehicle steering wheel has a flatter overall height than the prior art. In addition, in this embodiment, no additional compression springs are necessary for restoring the horn; the horn contact therefore undertakes the restoring function. All the embodiments have in common the fact that few separate components are required, and the contact wires are part of the conductors carrying signal current which are in any case provided. It is to be clearly understood that the construction according to the invention is not limited those vehicle steering wheels which have a gas bag module.