Abstract:
The invention is based on a hitching device with a stabilizer for avoiding and/or damping rolling motions between a traction vehicle and a trailer coupled to it. The stabilizer is equipped with a friction clutch, which affects the friction conditions between a trailer hitch on the end toward the traction vehicle and a coupling element on the end toward the trailer. According to the invention, the stabilizer is provided with an externally triggerable electric motor and a gear acted upon by the electric motor be used for actuating the fiction clutch. The gear is self-locking in the release direction of the stabilizer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on German Patent Application No. 10 2007 059 900.7 filed on Dec. 12, 2007, upon which priority is claimed. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention is based on a hitching device with a stabilizer for avoiding and/or damping rolling motions between a traction vehicle and a trailer coupled to this traction device. 
         [0004]    2. Description of the Prior Art 
         [0005]    One such hitching device with a stabilizer is already known from German Utility Model DE 20316698 U1, for example. This stabilizer is secured to a tow bar of a trailer. It has a pair of friction brake linings, which in the coupled state of the trailer are pressed against a trailer hitch on the end toward the traction vehicle. The tightening force at any given time is brought to bear mechanically or by hydraulic pressure. Because of the adjustability of the tightening force, the friction conditions between the traction vehicle and the trailer can be defined once and for all upon hitching. 
         [0006]    German Patent Disclosure DE 3702699 A1 likewise discloses mechanical, pneumatic or hydraulic means for exerting the tightening force and moreover suggests adjusting these tightening forces as a function of the travel speed of the traction vehicle and/or of the total weight of the trailer load. 
         [0007]    However, stabilizers acted upon hydraulically and pneumatically have the disadvantage that to maintain the tightening forces during travel, system pressure must be constantly available, so that accordingly such systems are dependent on a permanent supply of energy. Moreover, stabilizers acted upon hydraulically or pneumatically can be economically used only with trailers that are already equipped with a hydraulic or pneumatic trailer brake. However, since a majority of trailers are equipped with mechanical trailer brake systems, these trailers are not readily suited for the use of stabilizers that are actuatable hydraulically or pneumatically. 
         [0008]    Mechanically actuated stabilizers, by comparison, have the advantage of a more-economical construction. However, for the driver, manipulating them involves physical exertion and is therefore perceived as uncomfortable. In stabilizer systems that operate mechanically, only unsatisfactory adaptation of the tightening forces to the travel conditions at that time has been possible, until now. 
       OBJECT AND SUMMARY OF THE INVENTION 
       [0009]    By comparison, a hitching device with a stabilizer according to the invention has the advantage that actuating the stabilizer is done by an electric motor having a downstream gear. The gear has self-locking in the release direction of the stabilizer. Thus energy has to be exerted only to close the stabilizer, or in other words to increase the tightening force, but not for maintaining the tightening force once established. Unintentional release of the stabilizer is avoided by the self-locking. 
         [0010]    Stabilizers actuatable by electric motor can be operated without expending physical force, by a manually actuatable user control element. Hence the comfort of hitching a trailer to a traction vehicle can be improved, making even persons with relatively little physical strength also capable of performing the hitching operation. 
         [0011]    In addition, stabilizers that can be actuated by an electric motor can be incorporated relatively simply into an electronic control or regulating circuit. From sensors known per se, parameters that describe the travel state of a group comprising a traction vehicle and a trailer are simply ascertained and delivered to an electronic control unit. Without extensive sensors, a conclusion can be drawn as to the tightening force of the stabilizer prevailing at that time, based on the current flowing to the electric motor. By use of the electronic control unit, from its signals, trigger signals can be generated that permit an adaptation of the tightening force of a stabilizer to the travel states of a group during ongoing travel. 
         [0012]    Moreover, stabilizers actuated by electric motor are suitable for retrofitting trailers that until now had no stabilizer at all. There are no limitations on the type of trailer brake system, since all mass-produced trailers are already connectable to the electric power supply of the traction vehicle, for instance for operating their lighting system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings, in which: 
           [0014]      FIG. 1  is a schematically highly simplified side view, showing a hitching device with an electromechanical stabilizer; and 
           [0015]      FIG. 2  shows a top view of a first embodiment of gears for actuating the electromechanical stabilizers according to the invention. 
           [0016]      FIG. 3  shows a top view of a second embodiment of gears for actuating the electromechanical stabilizers according to the invention. 
           [0017]      FIG. 4  shows a top view of a third embodiment of gears for actuating the electromechanical stabilizers according to the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]      FIG. 1  shows the back end of a traction vehicle  10 , with a trailer hitch  12  anchored to it. This trailer hitch  12  is designed in conventional form and on its free end has a ball head  14 . A coupling element  18 , attached to a tow bar  16  of a trailer, not shown, cooperates with this ball head  14 . The coupling element  18  is embodied in simplified form as a ball-shaped dome that is open at the bottom and to the sides and that from above fits over onto the ball head  14  of the trailer hitch  12  of the vehicle. The trailer hitch  12  and the coupling element  18  together form a hitching device  20 , which according to the invention is equipped with a stabilizer  30  that can be actuated by an electric motor. The stabilizer includes a friction clutch with friction brake linings  32  that act on the ball head  14  of the trailer hitch  12 . An electric motor  34  is provided for adjusting the tightening force with which the friction brake linings  32  are pressed against the ball head  14 . The electric motor  34  actuates the friction brake linings  32  via a downstream gear  36 . 
         [0019]      FIG. 2  shows a stabilizer  30  according to a first embodiment of the invention, which is actuated by an electric motor  34  and whose friction clutch has friction brake linings  32  that are secured to two parallel, horizontally extending brake levers  38 . The brake levers  38  are disposed on diametrically opposed sides of the ball head  14  and extend in the travel direction F of the traction vehicle  10 . On their first ends, oriented toward the traction vehicle  10 , the two brake levers  38  are connected in articulated fashion to a cross-arm  40 . This cross-arm is located between the traction vehicle  10  and the ball head  14  and extends transversely to the travel direction F. The gear  36  of the stabilizer  30  furthermore includes a threaded spindle  42  that can be driven by the electric motor  34 . The brake levers  38 , coupled to one another via the cross-arm  40 , can be spread apart or clamped as a function of the direction of rotation of this threaded spindle  42 . For that purpose, the threaded spindle  42  is disposed on the side of the ball head  14  diametrically opposite the cross-arm  40  and are likewise oriented transversely to the travel direction F of the vehicle  10 . The operative connection between the brake levers  38  and the threaded spindle  42  can be attained for instance by way of a threaded set of teeth with different pitch directions or can also be attained by means of a rotatable positional fixation of the threaded spindle  42  to one of the brake levers  38 , in combination with a threaded set of teeth between the threaded spindle  42  and the respective other brake lever  38 . The tooth geometry is designed such that the gear  36  has self-locking in the release direction. 
         [0020]    In the second exemplary embodiment of  FIG. 3 , the stabilizer  30  that is actuated by electric motor has a threaded spindle  42 , which is driven by an electric motor  34  and is oriented in the travel direction F of the vehicle  10 . This threaded spindle  42  now actuates a gear  36 , in the form of a scissors drive  50  comprising a total of four joints  51 ,  52  and four scissor blades  54 . Each of the scissor blades  54  connects two joints  51 ,  52  movably relative to one another. The two joints  51  are disposed in stationary fashion at diametrically opposed points of two brake levers  38  that have function brake linings  32 , while the other two joints  52  are disposed axially movably on the threaded spindle  42 , for instance by means of threaded bushes. The threaded bushes of the joints  52  cooperate with the threaded spindle  42  for instance via sets of threaded teeth with different pitch directions, and as a result can move toward or away from one another as a function of the direction of rotation of the threaded spindle  42 . Upon a motion of the joints  52  on the threaded spindle  42 , the spacing between them changes, and the friction brake linings  32  are pressed against the ball head  14  with increasing or decreasing tightening force. 
         [0021]    The third exemplary embodiment of  FIG. 4  has a stabilizer  30 , actuated by electric motor, with a movably disposed floating frame  60 . This floating frame  60  is rectangular, for example, and in spaced-apart fashion surrounds the ball head  14  of a trailer hitch  12  on the end toward the traction vehicle. The electric motor  34  is solidly anchored to the floating frame  60 . The gear  36  driven by the electric motor  34  comprises a threaded spindle  42 , which is extended through an opening on one face end of the floating frame  60  and on which a first friction brake lining  32  is movably disposed. This friction brake lining  32  is guided laterally inside the floating frame  60 , so that the friction brake lining  32 , as a result of the rotary motion of the threaded spindle  42 , executes an axial translational motion in or counter to the travel direction F of a vehicle  10 . The direction of motion is effected as a function of the direction of rotation of the threaded spindle  42 . As soon as the first friction brake lining  32  meets the ball head  14  of the trailer hitch  12 , the floating frame  60 , because of the reaction force, executes an axial motion counter to the travel direction F. This axial motion ends as soon as a second friction brake lining  32 , diametrically opposite the first friction brake lining  32 , also meets the ball head  14 . With this gear construction, the electric motor  34 , threaded spindle  42  and friction brake linings  32  are oriented coaxially to one another in the travel direction F of the vehicle  10 . 
         [0022]    All the stabilizers  30  described function in such a way that upon a change in the direction of rotation of the electric motor  34 , the stabilizer  30  can be tightened or released. In the tightening direction, friction brake linings  32  are pressed with increasing tightening force against the ball head  14  of a trailer hitch  12 , and the forces of friction between this trailer hitch  12  and a coupling element  18  are thus increased. Conversely, these fiction conditions can be lessened by driving the stabilizer  30  in the release direction. 
         [0023]    The invention is not limited to the threaded spindle drives described. Other constructions of gears can equally be imagined, such as worm gears or gear wheel/rack drives. All these types of gears can be designed, in a manner known to one skilled in the art, by the selection of their toothing geometries, in such a way that they have self-locking in the release direction. As a result, the function conditions, once established, cannot vary automatically, or in other words not without the electrical triggering of the electric motor  34 . 
         [0024]    For furnishing a trigger signal for the electric motor  34 , a user control element  70  that is actuatable manually by the driver can be provided, for instance in the form of an electromechanical key or switch. Thus the stabilizer  30 , when a trailer is being hitched, can be actuated comfortably without the expenditure of force. For showing the established state of tightening of the stabilizer  30 , a display instrument  72  may additionally be provided. 
         [0025]    In a dismantling step, it is possible to control the stabilizer  30  as a function of parameters, or in other words to vary the tightening force of the stabilizer  30  as a function of the varying group speed during travel. For that purpose, an electronic control unit  80  would have to be provided that detects signals  82  which represent the group speed and which evaluates these arriving signals  82  for trigger signals  84  for the electric motor  34  of the stabilizer  30 . 
         [0026]    It is also possible, for instance by detecting transverse accelerations or yawing moments occurring at the traction vehicle  10  and/or at the trailer, by the electronic control unit  80  during travel to design the described stabilizer  30  as an automatic group stabilizing system, in which the established tightening forces are regulated in accordance with these measured parameters. A conclusion about the friction conditions at that time between a trailer hitch  12  and a coupling element  18  can easily be drawn by way of the current consumed by the electric motor  34 . 
         [0027]    It is understood that refinements or additions to the exemplary embodiments described are conceivable without departing from the fundamental concept of the invention. 
         [0028]    Stabilizers  30  actuatable by electric motor for instance also allow direct monitoring of the friction conditions between a trailer hitch  12  and a coupling element  18  and can be controlled or regulated as a function of the values ascertained. The prevailing friction conditions can for instance be ascertained by force sensors, which detect the incident shear forces between the brake levers  38  and the brake linings  32  secured to them, and send signals to the electronic control unit  80  to be evaluated. Temperature fluctuations can also be compensated for on the basis of temperature models stored in memory in the electronic control unit  80 . 
         [0029]    The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.