Abstract:
The invention relates to a switching device for a vehicle horn of a vehicle having an actuation element by means of which the vehicle horn is triggered when pressure is applied by an operator. In order to make the switching device particularly user-friendly, the invention provides for the actuation element to be mounted on a pantograph device in such a way that the actuation element can move exclusively in a direction which is predefined by the pantograph device.

Description:
INCORPORATION BY REFERENCE  
         [0001]    German Patent Application No. 102 41 048.8-42 filed on Aug. 30, 2002 is incorporated herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    The invention relates to a switching device for a vehicle horn having the features in accordance with the preamble of claim  1 .  
         BACKGROUND OF THE INVENTION  
         [0003]    Such a switching device is known from the German laid-open application 197 32 022 A1. In the previously known switching device, a cover cap of an airbag which is integrated into the steering device or steering wheel structure of a vehicle forms an actuation device for the vehicle horn. The cover cap of the airbag is attached in a sprung fashion to the steering wheel structure via two spring elements. In order to guide the cover cap laterally with respect to the steering wheel structure, two pins which are inserted into drilled holes in the steering wheel structure which match them are provided in the cover cap. In each case an electrical switching contact is provided on the cover cap and on the steering wheel structure; by pressing on the spring-mounted cover cap, the two switching contacts are closed and the horn is triggered or activated.  
         SUMMARY OF THE INVENTION  
         [0004]    The invention is based on the object of specifying a switching device for a vehicle horn which can be operated in a particularly user-friendly way. For example, it is considered user-friendly if the horn is always triggered with the same actuation force or actuation pressure.  
           [0005]    This object is achieved according to the invention by means of the characterizing features of claim  1 , taking a switching device of the type specified at the beginning as the basis. Advantageous refinements of the switching device according to the invention are described in the subclaims.  
           [0006]    Accordingly, there is provision for the switching device to have an actuation element which is mounted on a pantograph device. The actuation element is provided with bearings which are such that the actuation element can move exclusively in a direction which is predefined by the pantograph device. An essential advantage of the switching device according to the invention is that when pressure is applied the actuation element cannot execute a “tilting movement”. Owing to the precisely predefined direction, the actuation path which is required to trigger the vehicle horn and the required actuation force are always of the same size, specifically irrespective of whether the actuation element is activated, or force is applied to it, in its centre or at its edge region. In contrast, for example, to the previously known switching devices without a pantograph device, with the switching device according to the invention it is therefore impossible that the force for actuating the horn or the necessary actuation travel when the actuation element is depressed depends on the location at which the actuation element is pressed on its surface. Actuation elements for switching devices for vehicle horns are in fact generally very large in area in order to ensure that in an emergency situation a driver of a vehicle can readily trigger the vehicle horn by pressing on the external surface of the actuation element. If, as is the case for example in the previously known switching device, the actuation element is spring-mounted, it may be the case that when the actuation element is activated in the central region a relatively large force is necessary to trigger the vehicle horn because in fact all the spring elements of the switching device have to be compressed, while on the other hand if the actuation element is depressed in its edge region it is possible, under certain circumstances, that exclusively the spring force of a single spring device will have to be overcome, which leads to a situation in which the horn is triggered with a relatively small expenditure of force. As a result, with switching devices of the previously known art without a pantograph device it is possible for the expenditure of force which is necessary to trigger the horn to depend on the location at which the horn is depressed; this is avoided with the switching device according to the invention.  
           [0007]    The pantograph device in the switching device according to the invention can be formed particularly easily, and thus advantageously, with at least two pantograph elements which are connected by means of at least one rotary bearing.  
           [0008]    In order to permit the pantograph device to be installed particularly easily in the switching device of the vehicle, it is considered advantageous if the pantograph elements are of mirror-symmetrical design. The at least one rotary bearing is then to be advantageously arranged in the region of the mirror axis of the pantograph elements.  
           [0009]    With respect to the integration of the pantograph device in the switching device, it is considered advantageous if the one end of each of the pantograph elements is in contact with the actuation element, and the respective other end, opposite the one end, is in contact with a basic unit of the switching device, the two pantograph elements having the at least one rotary bearing in the central region between their two ends.  
           [0010]    The pantograph device can be advantageously attached by centering the pantograph device on four support points in guide bearings in such a way that when they are actuated the pantograph elements can move freely in a floating fashion over the four support points.  
           [0011]    In order to support the pantograph elements in the guide bearings, it is considered advantageous if the pantograph elements are mounted in the bearing region on plastic having good surface slip because plastic having good surface slip has a particularly low coefficient of friction.  
           [0012]    It is also considered advantageous if the actuation element of the switching device is spring-mounted; this can be advantageously achieved in particular by virtue of the fact that the pantograph device is prestressed with a pressure spring or flat spring whose spring force has to be overcome when the actuation element is actuated.  
           [0013]    It is also considered advantageous if the basic unit of the switching device is formed by the steering device or the steering wheel structure of the vehicle.  
           [0014]    If the switching device has an electrical switching element which is closed by the actuation element, it is considered advantageous if the pantograph element is electrically insulated, and at least one electrical switching contact of the switching element is arranged on the pantograph device.  
           [0015]    The switching device according to the invention can be integrated particularly easily and advantageously in a steering wheel of a vehicle by virtue of the fact that the actuation element of the switching device is formed by a cover cap of the steering wheel and the pantograph device is arranged between the cover cap and the steering device. If the steering wheel has an airbag device integrated into it, it is considered advantageous if the actuation element is formed by means of a cover cap of the airbag device, and the pantograph device is arranged between the airbag device and the steering wheel structure.  
           [0016]    Furthermore, one of the switching contacts can also be attached to the steering device, and its corresponding contact to an airbag of the vehicle.  
           [0017]    Furthermore, it is considered advantageous if the pantograph device is embodied as a single, self-bearing prefabricated structural unit which is added to the steering device or to an airbag unit while the switching device is being mounted. Alternatively, the pantograph device can advantageously also be mounted in the switching device as individual parts in such a way that its stability is formed by the steering device or the airbag unit.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 shows an exemplary embodiment of a switching device according to the invention in a side view;  
         [0019]    [0019]FIG. 2 shows the airbag unit of the exemplary embodiment according to FIG. 1 in a plan view;  
         [0020]    [0020]FIG. 3 shows the pantograph device according to the exemplary embodiment in accordance with FIG. 1 in detail;  
         [0021]    [0021]FIG. 4 shows a second exemplary embodiment of a pantograph device;  
         [0022]    [0022]FIG. 5 shows an exemplary embodiment of a rotary bearing for a pantograph device;  
         [0023]    [0023]FIG. 6 shows an exemplary embodiment of a pantograph device with a spring device;  
         [0024]    [0024]FIG. 7 shows an exemplary embodiment of a pantograph device with a spring device and with electrical contacts;  
         [0025]    [0025]FIG. 8 shows a further exemplary embodiment of a switching device according to the invention in a side view;  
         [0026]    [0026]FIG. 9 shows the further exemplary embodiment according to FIG. 8 in a plan view;  
         [0027]    [0027]FIG. 10 shows a further embodiment of a switching device according to the invention in a side view; and  
         [0028]    [0028]FIG. 11 shows the pantograph device of FIG. 10 in detail.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    [0029]FIG. 1 shows an airbag unit  10  which is attached to a steering device  40  via a spring device  20  and a pantograph device  30 . A first switching contact  50 , which is connected to a second switching contact  60  on a contact carrier plate  65  of the steering device  40  and can be brought into electrical contact with it, is attached to the airbag unit  10 . The second switching contact  60  therefore acts as a corresponding contact and is arranged on the steering device  40 . Specifically, an electrical connection is formed between the first switching contact  50  and the second switching contact  60  when the airbag unit  10  is depressed in the direction of the steering device  40  counter to the spring force of the spring device  20 .  
         [0030]    The movement of the airbag unit  10  in the direction of the steering device  40  is defined here by means of the pantograph device  30 . The pantograph device  30  has the effect specifically of enabling the airbag unit  10  to be moved exclusively perpendicularly, i.e. in the direction predefined by the arrow  70 —downwards. It is therefore not possible to tilt the airbag unit  10 , specifically irrespective of how the cover cap  100  of the airbag unit  10  is depressed.  
         [0031]    This is clearly illustrated by means of the arrows  120 ,  130  and  140  in FIG. 1: irrespective of the location at which pressure is exerted on the airbag  10  and the direction of force with which pressure is exerted on the airbag  10 , said airbag moves in the direction  70  which is predefined by the pantograph device  30 . In the exemplary embodiment according to FIG. 1, the airbag unit  10  can therefore only move in parallel with the direction predefined by the arrow  70 .  
         [0032]    Furthermore, FIG. 1 shows that the ends  150  of the pantograph elements of the pantograph device  30  are mounted in guide bearings  200  which are preferably formed by means of plastic having good surface slip. These plastic bearings permit low-friction movement of the pantograph device  30 .  
         [0033]    [0033]FIG. 2 shows the airbag unit  10  according to FIG. 1 in a plan view. It is apparent that the airbag unit  10  is mounted on the pantograph device  30 . The pantograph device  30  is illustrated by dashed lines in FIG. 2 and formed by means of two rectangular frames which are connected to one another by means of two rotary bearings  310  and  320 .  
         [0034]    [0034]FIG. 3 shows the pantograph device according to the exemplary embodiment in accordance with FIGS. 1 and 2, once more in detail. It is possible to see the pantograph device  30  with the two rotary bearings  310  and  320  which connect two U-shaped frame parts  340  and  350  to one another. The two U-shaped frame parts form the pantograph elements of the pantograph device and are oriented in opposite directions, the smaller frame part  350  being partly surrounded by the larger frame part  340 .  
         [0035]    [0035]FIG. 4 shows a second exemplary embodiment of a pantograph device for the switching device according to the invention. It is possible to see an external pantograph element  400  which surrounds an internal pantograph element  410  and is connected to it via a single rotary bearing  420 .  
         [0036]    [0036]FIG. 5 shows in detail how the rotary bearing  420  can be configured in detail in accordance with FIG. 4, or the two rotary bearings  310  and  320  in accordance with FIG. 3.  
         [0037]    [0037]FIG. 6 shows a pantograph device  500  with a spring device  510  which is attached to the external end of two pantograph elements of the pantograph device. When the pantograph device  500  in accordance with FIG. 6 is used in the exemplary embodiment in accordance with FIG. 1, the pantograph device  500  would not only replace the pantograph device  30  but also the spring device  20 .  
         [0038]    [0038]FIG. 7 shows a pantograph device  600  which is equipped with a spring device  510  as well as with two electrical switching contact  610  and  620 . The horn of the vehicle can be electrically triggered using the two electrical switching contacts  610  and  620 . When the pantograph device  600  according to FIG. 7 is used in the exemplary embodiment in accordance with FIG. 1, the pantograph device  600  would not only replace the pantograph device  30  but also the spring device  20  and the switching contacts  50  and  60 .  
         [0039]    [0039]FIGS. 8 and 9 show a further exemplary embodiment of a switching device according to the invention. The further exemplary embodiment according to FIGS. 8 and 9 differs from the first exemplary embodiment according to FIGS. 1 and 2 in that the pantograph device is integrated in the “steering wheel” between contact plates (cover plate and contact carrier plate), whereas in the exemplary embodiment according to FIGS. 1 and 2 it is arranged between the airbag  10  and the contact carrier plate  65  of the steering wheel  40 .  
         [0040]    [0040]FIG. 8 shows a steering wheel  800  with a steering wheel hub  810 , a body  820  and steering wheel spokes  830 . A cover plate  840  rests on a pantograph device  850  and is attached to the steering wheel  800  by means of collar screws  860 . An electrical contact  870 , which interacts with a corresponding contact  880  on a contact carrier plate  885 , is arranged at the lower part of the cover plate.  
         [0041]    In addition, a spring device  890  which exerts a spring force on the pantograph device  850  is shown. In addition, or instead, the spring force can also be generated by means of helical springs which are attached to the screw collars  860 . This is not illustrated in FIG. 8 for the sake of clarity.  
         [0042]    [0042]FIG. 9 shows the exemplary embodiment according to FIG. 8 in a plan view. It is possible to see the pantograph device  850  which is covered by the cover plate  840 . The cover plate  840  is screwed to the steering wheel  800  via three collar screws  860 . Furthermore, FIG. 9 shows the steering wheel spokes  830 .  
         [0043]    Further, another representative embodiment of the present invention comprising a switching device  901 , and airbag unit  910  and a steering wheel  900  is described in detail in reference to FIGS. 10 and 11. According to this embodiment, the airbag unit  910  is provided on the cover plate  980 . While the airbag unit  910  includes a cover cap  912 , an inflator  911  and an airbag inflated by the inflator  911 , only the cover cap  912  and the inflator  911  are shown in FIG. 10 and the airbag itself is not particularly shown for the sake of convenience.  
         [0044]    The cover plate  980  (also referred to as “retainer”) onto which the airbag unit  910  is mounted is connected to the carrier plate  965  (also referred to as “horn plate”) by means of a pantograph device  930 . In other words, the pantograph device  930  is disposed between the cover plate  980  and the carrier plate  965 . The pantograph device  930  includes a pair of pantograph elements  930   a,    930   b.  The pantograph elements  930   a,    930   b  intersects to each other to form “X”. The pantograph device  930  functions to keep the pressing force exerted onto the cover cap  912  as constant without respect to the cover cap region where the operator presses. In this respect, the pantograph device  930  serves as a stabilizer to equalize the pressing force of the operator and may embrace any types of pantograph structure that can stabilize the pressing force exerted onto the cover cap  912  even when the operator presses the cover cap  912  at different regions of the cover cap  912  to activate the vehicle horn.  
         [0045]    [0045]FIG. 11 shows the pantograph device  930  to be fastened to the cover plate  980  and the carrier plate  965 . Both ends of respective pantograph elements  930   a,    930   b  include bearings  932  made of resin by means of pantograph rotation holder  931 . Each of the pantograph elements  930   a,    930   b  is allowed to relatively rotate with respect to the respective bearings  932  by way of the rotation holder  931 . In this embodiment, a clip  933  made of resin is coupled to each bearing  932 . Clips  933  can be inserted to clip insertions holes  980   a,    965   a  provided respectively in the cover plate  980  and in the carrier plate  965  (see FIG. 10). Thus, each bearing  932  is fastened to the cover plate  980  and to the carrier plate  965  such that any unintended detachment of each bearing  932  from the cover plate  980  and the carrier plate  965  can be prevented. That is, clips  933  can be secured to the plates  980  and  965  only by pushing clips  933  into the clip insertion holes  980   a,    965   a,  respectively. As a result, the pantograph device  930  can be easily connected to the cover plate  980  and to the carrier plate  965  in a one-touch or single step manner. Further, the pantograph device  930  may be easily detached from the plates  980 ,  965  by way of the detaching operation of the clip  933 . Each of the bearings  932  and each of the clips  933  may be provided by utilizing any materials other than resin. For example, hard rubber or metal may preferably be utilized for the bearings  932  and for the clips  933 . Further each clip  933  may be integrally manufactured together with the bearing  932 . Otherwise, each clip  933  may be detachably or fixedly coupled to the bearing  932  after being manufactured. As well, each bearing  932  may be integrally manufactured together with the pantograph elements  930   a,    930   b.  Otherwise, each bearing  932  may be detachably or fixedly coupled to the pantograph elements  930   a,    930   b  after being manufactured.  
         [0046]    Further, as shown in FIG. 10, a spring device  920  is provided between both ends of the pantograph element  930   a,    930   b.  The spring device  920  exerts biasing force so as to move the pantograph elements  930   a,    930   b  away from each other.  
         [0047]    The cover plate  980  is connected to a moveable plate  982  via a connecting plate  981 . Further, the carrier plate  965  is connected to a stationary plate  969  via a connecting plate  968 . The movable plate  982  and the stationary plate  969  are disposed so as to face to each other. A guide bolt  971  is provided via an insulator  972  on the surface of the stationary plate  969  that faces to the movable plate  982 . The guide bolt  971  penetrates the moveable plate  982 . The guide bolt  971  includes a cover plate movement controlling device  973  on the opposite side of the moveable plate  982 . The controlling device  973  has larger diameter than the diameter of the guide bolt  971  in order to prevent the moveable plate  982  from moving away from the stationary plate  969  beyond a predetermined distance. Further, a spring  974  is provided around the guide bolt  971  between the moveable plate  982  and the stationary plate  969 . The spring  974  exerts biasing force so as to move the moveable plate  982  away from the stationary plate  969 . As a result, the movable plate  982  is biased by the spring  974  to move away from the stationary plate  969 , while the removing distance from the stationary plate  969  is controlled by means of the controlling device  973 . When the operator moves the moveable plate  982  too close to the stationary plate  969  against the biasing force of the spring  974 , the moveable plate  982  can be securely guided by the guide bolt  971  so as to be prevented from moving laterally according to FIG. 10.  
         [0048]    Further, first switching contact  950  and second switching contact  960  are provided on the respective surface of the moveable plate  982  and the stationary plate  969  facing to each other so as to form a switch device  901 . Switching contact  950 ,  960  are connected to each other when the moveable plate  982  closes to the stationary plate  969 . As a result, the vehicle horn device can be activated.  
         [0049]    A fastening plate  966  is provided on the bottom surface of the carrier plate  965 . A fastening bolt  967  can be engaged with the fastening plate  966 . By utilizing the fastening plate  966  and the fastening bolt  967 , the carrier plate  965  can be detachably fastened to the steering wheel body  982  of the steering wheel  900 .  
         [0050]    According to this embodiment, the airbag unit  910 , the cover plate  980 , the pantograph device  930 , the carrier plate  965  and the switching device  901  are integrally preassembled before being mounted to the steering wheel  900 . At this stage, the pantograph device  930  can be easily coupled to the cover plate  980  and to the carrier plate  965  by utilizing the clip  933  in one-touched manner. Thus, the forming of the preassembled body including the airbag unit  910 , the pantograph device  930  and the switching device  901  can be easily accomplished. Then, the preassembled body can be easily fastened to the steering wheel  900  by utilizing fastening plate  966  and the fastening bolt  967 .  
         [0051]    While there have been illustrated and described particular embodiments of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.  
         [0052]    List of Reference Numerals  
         [0053]    [0053] 10  Airbag unit  
         [0054]    [0054] 20  Spring device  
         [0055]    [0055] 30  Pantograph device  
         [0056]    [0056] 40  Steering device  
         [0057]    [0057] 50  First switching contact  
         [0058]    [0058] 60  Second switching contact  
         [0059]    [0059] 65  Contact carrier plate  
         [0060]    [0060] 70  Arrow  
         [0061]    [0061] 100  Cover cap  
         [0062]    [0062] 120 ,  130 ,  140  Arrows  
         [0063]    [0063] 150  Pantograph elements  
         [0064]    [0064] 200  Guide bearings  
         [0065]    [0065] 310 ,  320  Rotary bearings  
         [0066]    [0066] 340 ,  350  Frame parts  
         [0067]    [0067] 400  External pantograph element  
         [0068]    [0068] 410  Internal pantograph element  
         [0069]    [0069] 420  Rotary bearing  
         [0070]    [0070] 500  Pantograph device  
         [0071]    [0071] 510  Spring device  
         [0072]    [0072] 600  Pantograph device  
         [0073]    [0073] 610 ,  620  Electrical switching contacts  
         [0074]    [0074] 800  Steering wheel  
         [0075]    [0075] 810  Steering wheel hub  
         [0076]    [0076] 820  Body  
         [0077]    [0077] 830  Steering wheel spokes  
         [0078]    [0078] 840  Cover plate  
         [0079]    [0079] 850  Pantograph device  
         [0080]    [0080] 860  Collar screws  
         [0081]    [0081] 870  Electrical contact  
         [0082]    [0082] 880  Corresponding contact  
         [0083]    [0083] 885  Contact carrier plate  
         [0084]    [0084] 890  Spring device