Abstract:
The invention relates to a windshield wiper drive ( 1 ) for a motor vehicle, in particular a windshield wiper drive ( 1 ), with a reverse-operating drive motor ( 3 ), for driving a wiper shaft ( 6 ) connected non-rotatably to a wiper arm ( 18 ), and with a fastening board ( 7 ) for attaching the windshield wiper drive ( 1 ) to a vehicle body or to a body-mounted component ( 29 ). The invention provides that a first end stop surface ( 22 ) for delimiting the rotary movement of the wiper shaft ( 6 ) in a first direction of rotation is provided on the fastening board ( 7 ) or on a component ( 29 ) affixed to the fastening board ( 7 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a windshield wiper drive for a motor. 
         [0002]    In windshield wiper drives used nowadays, an electric driving motor is connected to the wiper shaft via a crank assembly. A continuous rotational movement of the driving motor is converted by the crank assembly into an oscillating movement of the wiper shaft to and fro. Disadvantages of the known windshield wiper drives include the complex construction and the number of components required. 
         [0003]    “Windshield wiper direct drives” have therefore been developed, in which the provision of a crank assembly is omitted. In windshield wiper direct drives, either the motor shaft of a reverse-operable driving motor is connected in a rotationally fixed manner to the wiper shaft, or the motor shaft forms said wiper shaft, or a toothed gear mechanism is arranged between the motor shaft and the wiper shaft. A disadvantage of windshield wiper direct drives is that the wiper shaft is theoretically rotatable through 360° when large external displacement forces are applied. During journeys at a high speed, this may result in the wiper arm which is fixed to the wiper shaft being pivoted due to the forces in effect into a region outside the vehicle window, which constitutes a considerable safety risk. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention is based on the problem of proposing an optimized windshield wiper drive, in particular a windshield wiper direct drive, in which the maximum angular range through which the wiper shaft is rotatable is limited. 
         [0005]    The invention is based on the concept of providing a first stop surface for limiting the rotational movement of the wiper shaft in a first direction of rotation on a fastening plate for fixing the windshield wiper drive to a body or to a component mounted on the body. As an alternative, said first end stop surface may also be provided on a component fixed to the fastening plate. It is essential that the first end stop surface is arranged and designed in such a manner that it can limit the maximum angle of rotation of the wiper shaft in a first direction of rotation. For this purpose, in order to limit the rotational movement, the first end stop surface does not necessarily have to interact directly with the wiper shaft—an embodiment can also be realized, in which the first end stop surface of the fastening plate or of the component fixed to the fastening plate interacts directly with a component connected in a rotationally fixed manner to the wiper shaft, in particular with the wiper arm. By means of the provision of a first end stop surface for limiting the maximum rotational movement or the maximum angle of rotation of the wiper shaft, it is avoided that a maximum angle of rotation can be exceeded by the wiper shaft, and therefore the wiping region of the wiper arm on the window is not strayed from. An embodiment of the windshield wiper drive is particularly preferred, in which the end stop surface is not used during normal operation, i.e. the wiper shaft or a component fixed thereto does not strike against the first end stop surface during each pivoting movement in the first direction of rotation. It is preferable for the first end stop surface to form a type of emergency stop or emergency limit. During normal operation, the wiper shaft should be reversed prior to striking against the end stop surface by means of an appropriate design of the motor control system. It lies within the scope of the invention that the first end stop surface limits a lower parking position of the wiper shaft or of the wiper arm or an upper or lateral maximum end pivoted position. 
         [0006]    The window wiper drive designed in accordance with the concept of the invention is preferably a windshield wiper direct drive without a crank assembly, in which either the wiper shaft is connected in a rotationally fixed manner to the motor shaft, or is formed by the motor shaft, or in which the wiper shaft is connected directly to the wiper shaft in a torque-transmitting manner via a toothed gear mechanism and/or worm wheel gear mechanism, i.e. without the interconnection of a crank assembly. 
         [0007]    In a development of the invention, it is advantageously provided that a second end stop surface for limiting the rotational movement or the pivoting angle of the wiper shaft in a second direction of rotation opposed to the first direction of rotation is provided in addition to the first end stop surface for limiting the rotational movement or the pivoting angle of the wiper shaft in a first direction of rotation. In other words, the wiper shaft can be displaced at maximum in a region between the two end stop surfaces. By means of the provision of two end stop surfaces which are spaced apart from each other in the circumferential direction, the maximum rotational movement of the wiper shaft or the maximum pivoting movement of the wiper arm in both pivoting directions is therefore limited. 
         [0008]    In order to enable optimum fixing of the windshield wiper drive to the vehicle body, an embodiment is preferred in which the wiper shaft, which is designed as a single part or in multi-part form, is arranged such that it passes through the fastening plate. In other words, a preferably circumferentially closed through opening for receiving the wiper shaft is provided in the fastening plate. 
         [0009]    In order to obtain a particularly compact design, an embodiment is preferred, in which the first and/or the second end stop surface are/is formed by the inner contour of the through opening. It is also preferred in this embodiment if at least one of the two end stop surfaces, preferably both end stop surfaces, are/is formed directly on the fastening plate. However, an embodiment can also be realized, in which one or both end stop surfaces is/are arranged on a component fixed to the fastening plate. 
         [0010]    With regard to realizing the window wiper drive in a manner optimized in terms of costs, an embodiment is preferred, in which a first counterstop surface for interaction with the first end stop surface is formed on the wiper arm fixed to the wiper shaft. A second counterstop surface for interaction with the second end stop surface, which may optionally be provided, is preferably also provided on the wiper arm. Particularly preferably, the counterstop surfaces are located on an in particular circumferentially closed section of the wiper arm, which section surrounds the wiper shaft and projects in sections in the axial direction into a through opening in the fastening plate. At least that section of the wiper arm which has at least one counterstop surface for interaction with an end stop surface of the fastening plate or with an end stop surface on a component fixed to the fastening plate is particularly preferably an injection molded part made from plastic. 
         [0011]    In addition or as an alternative, an embodiment can be realized, in which the first counterstop surface and/or the second counterstop surface are/is arranged directly on the wiper shaft or on a component connected in a rotationally fixed manner to the wiper shaft. This component which has at least one counterstop surface is preferably a component which is pressed onto the wiper shaft. An embodiment is particularly preferred, in which the component is received between two shaft parts of the wiper shaft, as seen in the axial direction, wherein said shaft parts can preferably be plugged one into the other. 
         [0012]    A particularly compact design of the windshield wiper drive can be realized if the first and the second end stop surface are arranged on two sides facing away from each other of a radially inwardly directed radial section of the fastening plate. Said radial section preferably projects radially inward into the through opening for receiving the wiper shaft. As an alternative, the radial section together with the two end stop surfaces is not formed directly by the fastening plate but rather by a component fixed to the fastening plate. In order to ensure an exact course of pivoting of the wiper arm relative to the fastening plate and at the same time interaction of the end stop surfaces with corresponding counterstop surfaces, an embodiment is preferred, in which the radial section together with the two end stop surfaces projects in the radial direction into a guide slot formed on the wiper arm, wherein the guide slot preferably extends over an angular region of a wiper arm section directed in the axial direction and is limited by one counterstop surface on each of the two end sides which are opposite each other in the circumferential direction. 
         [0013]    In an alternative embodiment, the two counterstop surfaces are not arranged at the ends of a guide slot but rather are formed by two sides facing away from each other and spaced apart from each other in the circumferential direction of a radially outwardly directed radial section of the wiper shaft. As an alternative, the radial section is not formed directly by the wiper shaft but rather by a component fixed to the wiper shaft. The radial section together with the two counterstop surfaces which are spaced apart in the circumferential direction advantageously projects in the radial direction into a guide slot which is either arranged directly on the fastening plate or on a component fixed to the fastening plate, wherein the guide slot extends over an angular region in the circumferential direction and has an end stop surface on both end sides which are spaced apart from each other in the circumferential direction, wherein each end stop surface is designed and arranged for interaction with a respective counterstop surface provided on the radial section. 
         [0014]    In order to permit as defined and exact a positioning or fixing as possible of the windshield wiper drive on the vehicle body or on a component mounted on the vehicle body, the fastening plate preferably has three fastening openings which are spaced apart from one another in the circumferential direction and in each of which a fastening screw can be received. In addition or as an alternative, differently designed fastening means may be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Further advantages, features and details of the invention emerge from the description below of preferred exemplary embodiments and with reference to the drawings, in which: 
           [0016]      FIG. 1  shows a perspective view of a first exemplary embodiment of a windshield wiper drive, 
           [0017]      FIG. 2  shows an exploded illustration of the part of the windshield wiper drive according to  FIG. 1 , 
           [0018]      FIG. 3  shows a perspective view of a second, alternative exemplary embodiment of a windshield wiper drive, and 
           [0019]      FIG. 4  shows an exploded illustration of a part of the windshield wiper drive according to  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Identical components and components with the same function are identified by the same reference numbers in the figures. 
         [0021]      FIGS. 1 and 2  show a first exemplary embodiment of a windshield wiper drive  1  designed as a windshield wiper direct drive. 
         [0022]    The windshield wiper drive  1  comprises an electric driving motor  3  which is arranged in a motor housing  2  and can be reverse-operated by means of a motor control system (not shown). In the exemplary embodiment shown, the driving motor  3  is connected via a gear mechanism  5 , which is arranged in a gear mechanism housing  4  and has no crank rod, to a wiper shaft  6  in a torque-transmitting manner. An embodiment can also alternatively be realized, in which a gear mechanism  5  is omitted, and the motor shaft of the driving motor  3  forms the wiper shaft  6  or is connected in a rotationally fixed manner to a wiper shaft  6 . In the exemplary embodiment shown, the motor housing  2  which is designed as a deep-drawn part is flange-mounted laterally on the gear mechanism housing  4 . To fix the windshield wiper drive  1  to a vehicle body, the windshield wiper drive  1  comprises a metal fastening plate  7  with three fastening openings  8  spaced apart in the circumferential direction. 
         [0023]    The fastening plate  7  is fixed to the gear mechanism housing  4  with the aid of three fixing screws  9  which pass through respective fixing openings  10  in the fastening plate  7 . 
         [0024]    The fixing openings  10  are arranged around the edge of an elevation  11  which has a slightly obliquely rising circumferential wall  12  and an upper annular section  13  running substantially at right angles to the circumferential wall  12 . The annular section  13  delimits a through opening  14 , through which the wiper shaft  6  passes, radially on the outside. As is apparent from  FIG. 2 , the wiper shaft  6  is designed in two parts and consists of an upper shaft part  15  which can be inserted by a lower axial section  16  into a lower shaft part  17 . The wiper shaft  6  is connected by the upper shaft part  15  in a rotationally fixed manner to a wiper arm  18  or to an articulated section of a wiper arm  18 , to which a wiper blade (not shown) can be fixed. The two-part design of the wiper shaft  6  has the advantage that a cap to guard against water can be fitted in a simple manner. An external threaded section  19  is provided at the end of the upper shaft part  15 , said external threaded section serving to receive a fixing nut  20  by means of which the wiper arm  18  can be fixed in turn to the wiper shaft  6 . 
         [0025]    As emerges in particular from  FIG. 2 , the through opening  14  for receiving the wiper shaft  6  has a substantially circular contour. At one point, said circular contour is interrupted by a radial section  21  which projects inward in the radial direction into the through opening  14 . On the side which is on the left in the plane of the drawing, the radial section  21  is delimited by a first end stop surface  22  which, in the fitted state, interacts with a first counterstop surface  23  to limit the rotational movement of the wiper shaft  6 . On the side facing away from the first end stop surface  22  in the circumferential direction, the radial section  21  is delimited by a second end stop surface  24  which, in the fitted state, interacts with a second counterstop surface  25 . In this case, the two end stop surfaces  22 ,  24  project radially inward. 
         [0026]    The two counterstop surfaces  23 ,  25  delimit a guide slot  26  in the circumferential direction on a section  27  of the wiper arm  18 , which section extends in the axial direction. In this case, the guide slot  26  is designed as a recess extending in the circumferential direction in the circumferential wall of the section  27 . The outside diameter of the section  27  substantially corresponds to the diameter of the through opening  14  minus a small amount of play, and therefore the wiper arm  18  in the fitted state is guided on the inner circumference of the through opening  14 , in which case the maximum pivoting angle is limited by the relatively large circumferential extent of the guide slot  26 , the end sides of which, which is spaced apart in the circumferential direction, are formed, as mentioned, by counterstop surfaces  23 ,  25  which interact with the end stop surfaces  22 ,  24  on the radially inwardly pointing radial section  21 . 
         [0027]      FIGS. 3 and 4  show an alternative exemplary embodiment of a windshield wiper drive  1  which is designed as a windshield wiper direct drive, wherein the illustration of the driving motor and of the gear mechanism or gear mechanism housing has been omitted for reasons of clarity. Said features may be designed, for example, as in the exemplary embodiment according to  FIGS. 1 and 2 . To avoid repetitions, essentially only the differences over the exemplary embodiment according to  FIG. 1  are entered into below. With regard to the common features, reference is made to  FIGS. 1 and 2  and to the associated description of the figures. 
         [0028]      FIG. 3  shows the fastening plate  7  together with the fastening openings  8  therein for fixing the windshield wiper drive  1  to a vehicle body. As in the exemplary embodiment according to  FIG. 1 , the fastening plate  7  has a dome-like elevation  11  with an upper annular section  13  which delimits a through opening  14  which has a substantially circular ring contour. The through opening  14  merges in an angular region into a guide slot  26  which is designed as a recess in the fastening plate  7  and as a radial extension of the through opening  14 . The guide slot  26  extends in the shape of a circular arc in the circumferential direction and is delimited by one counterstop surface  23 ,  25  at each of the two end sides which are spaced apart from each other in the circumferential direction. The counterstop surfaces  23 ,  25  interact with the end stop surfaces  22 ,  24  which delimit a radial section  28 , which points outward in the radial direction, in the circumferential direction. The radial section  28  is arranged on a component  29  which has an annular section  30  (cf.  FIG. 4 ) through which the wiper shaft  6 , or more precisely the axial section  16  of the upper shaft part  15  of the wiper shaft  6 , passes. The component  29  is connected together with the annular section  30  thereof to the axial section  16  of the shaft  6  in a rotationally fixed manner. The outside diameter of the annular section  30  corresponds to the diameter of the through opening  14  in the fastening plate  7  minus an amount of play, and therefore the wiper shaft  6  is guided on the fastening plate  7  via the component  29 .