Abstract:
A sensor for optical detection of foreign bodies, in particular raindrops, on a window, in particular on the windshield of a motor vehicle, having a sensor element that is coupled to the inside of the window and having a fastening device, which is glued to the window, wherein the housing part has a fastening part pivotably attached to it, which can be brought into engagement with the fastening device by the clamping tension.

Description:
BACKGROUND OF THE INVENTION 
     The invention is based on a sensor DE 44 10 217 A1 has already disclosed a sensor with a number of housing parts. In this sensor, a fastening device is glued to a window. Two sliders, which are guided in an outer housing part and function as a fastening means, allow the outer housing part to engage with the fastening device. The sensor elements are affixed to an inner housing part, which is pressed against the window by means of a spring force acting on the outer housing part. This type of fastening, however, is complex, expensive, malfunction-prone, and therefore connected with high costs. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a sensor is proposed, for a sensor for optical detection of foreign bodies, in particular raindrops, on a window, in particular on the windshield of a motor vehicle, having a sensor element that can be coupled to the inside of the window, having at least one fastening device to be fastened, to the window, and having a housing part that contains at least the sensor element, where the sensor element can be coupled to the window by means of spring force, characterized in that the housing part has at least one fastening part attached to it, which can be brought into engagement with the fastening device by means of clamping tension. 
     The sensor according to the invention has the advantage that the fastening device is comprised of an easy-to-produce stamped and bent part and the spring elements are affixed to the housing in a predefined manner. As a result, no separate parts need to be installed and a single housing part suffices, which is pressed as a whole against the window. If the sensor element is firmly affixed to this housing part, then the number of moving parts of the sensor is reduced, which prevents a loss of adjustment due to vibrations of the window. 
     Advantageous modifications of the sensor unit according to the main claim are possible by means of the steps taken in the dependent claims. 
     The contact force of the sensor against the window surface can be kept uniform by means of two fastening parts disposed opposite each other. 
     If the fastening device has pins for engaging the fastening part, this makes it possible to simply remove the sensor at any time. It the fastening part is attached to the housing in a pivotable fashion and has elastic properties, then the contact force can be precisely adapted to the requirements. During installation, the fastening part is subjected to a continuous increase in force, which is further intensified when, during the rotation of the spring, the force is generated by an oblique plane on which the pins of the fastening device slide. Thus a greater contact force can be produced without complicating the installation. 
     Recesses in the fastening part for receiving the pins in the installed position assure a very high vibration resistance. 
     Advantageously, the fastening part has an oblong protrusion on its exterior. This stiffens the fastening part and achieves a better transmission of force during installation. 
     The manufacture of the fastening part as a stamped and bent part or as an injection molded plastic part is extremely simple and reduces costs. 
     In addition, if the fastening device is embodied is being of one piece, then particular spacing dimensions are of no concern when the fastening device is glued to the window, which results in a not insignificant time savings. A collar on the fastening device for receiving the sensor housing assures a rapid and simple installation. 
     An additional advantage is achieved through a modular design of the sensor that is comprised of 3 modules. The housing and the fastening parts constitute the first module, the printed circuit board with the plug connector or socket and the transmitters and receivers constitute the second module, and the optical body, coupling medium, and for example external light baffle constitute the third module. In addition to a precise and rapid assembly of the reciprocally matched components, this design also permits an uncomplicated replacement of individual components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is shown in the drawings and will be explained in detail in the subsequent description. 
         FIG. 1  is an oblique view of a sensor unit in a housing, with a fastening device before a fastening procedure, 
         FIG. 2  is an enlarged oblique view of a fastening part, 
         FIG. 3  is an oblique view of a sensor unit in a housing, with a fastening device, during a fastening procedure, and 
         FIG. 4  is an oblique view of a sensor unit in a housing, with a fastening device, after a fastening procedure, 
         FIG. 5  shows a section through a sensor unit before a fastening procedure, and 
         FIGS. 6 and 7  show respective embodiments for the fastening part and the housing part of the sensor. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a sensor  10  according to the invention, including a housing part  12 , two fastening parts  14 , and a fastening device  16 . 
     The fastening device  16  is embodied as a plate-shaped part with a recess in the center so that it can receive the housing part  12  in a collar-like fashion. On the side, the fastening device  16  has tabs  19  on which pins  20  are provided, which extend latterly outward. The tabs  19  extend essentially perpendicular to the window  18 , as a result of which the pins  20  extend approximately parallel to the window  18 . The fastening device  16  is embodied of one piece and is glued to the inside of a window  18 . 
     The housing part  12  is comprised of a shell-shaped plastic part whose sides are provided with pocket-like formations  23 , which extend parallel to the window  18  and can receive the fastening parts  14 . Likewise, the housing part  12  has a socket  22 , which serves as a communications interface of a sensor element  21  ( FIG. 5 ) with a set of evaluation electronics  40 . 
       FIG. 2  shows the fastening part  14  also shown in FIG.  1 . The fastening part  14  is an essentially T-shaped stamped sheet metal part comprised of a base part  14   a  and a top part  14   b . The base part  14   a  is comprised of 3 sections, a curved elastic region  27  as the first section, which is adjoined by a flat region  27   a  as a second section. The subsequent third section is comprised of a semi-tubular bend  25 . The elastic region  27  of the first section curves in the opposite direction from the bend  25  of the third section. The top part  14   b , which adjoins the elastic region  27  of the first section of the base part  14   a , constitutes a retaining bracket  30  that also has three regions. The first, central region is comprised of a flat piece, the middle of which is provided with an oblong protrusion  24 . This section is adjoined on both sides by a second region that is curved toward the bend  25 . The ends of the top part  14   b  are formed by two trapezoidal bracket tabs  26  and thus constitute the third section of the retaining bracket  30 . Each of these bracket tabs  26  has a recess  29  at its end oriented toward the second region. The trapezoidal form of the bracket tabs  26  constitute an oblique plane  28  that is disposed on the side oriented away from the window  18  in the installed position. 
       FIG. 5  shows a sectional view of the housing part  12 , with the fastening parts  14  and the sensor element  21 . The pocket-like formation  23  is constituted by a clamp-like overhang of  33  embodied at the top of the housing part  12 , oriented away from the window  18 . The overhang  33  terminates in a cylindrical formation  31  into which the bend  25  of the fastening part  14  can be movably inserted. 
     The cooperation of the fastening device  16 , the housing part  12 , and the fastening part  14  is shown in FIG.  3  and will be explained in detail below. 
     The fastening device  16  is glued to the window  18 . The thickness  17  of the fastening device  16  produces a collar into which the housing part  12  is inserted. If the retaining brackets  30 , which are fastened so that they can pivot by means of the bend  25  in the pocket-like formations  23  of the housing  12 , are pressed toward the window  18 , then the bracket tabs  26  slide along the pins  20 . The pins  20  therefore slide in relation to the bracket tabs  26  along an oblique plane  28  produced by the trapezoidal form of the bracket tabs  26 , as a result of which the curvature of the elastic region  27  is enlarged. Because the elastic fastening parts  14  strive to keep the curvature in the elastic region  27  constant, the housing part  12 , together with the sensor element  21 , is pressed toward the fastening device  16  and therefore toward the window  18  since the fastening device  16  receives the housing part  12  in a collar-like fashion. The ratio between the cylindrical formations  31  and the semi-tubular bend  25  here is dimensioned so that the dynamic effect does not occur between the overhang  33  and the fastening device  16 , but rather between a contact face  32  and the fastening device  16 . 
     In the end position, as shown in  FIG. 4 , the pins  20  engage in detent fashion in the recesses  29  of the fastening part  14 . 
     During installation, a force in the direction of the window  18  is required in order to cause the pins  20  to slide along the oblique plane  28 . The oblong protrusions  24  stiffen the fastening part  14  and effectively prevent the installation tool from sliding off in the direction of the window  18 . 
     In a variant of the exemplary embodiment, the fastening device  16  can also be comprised of a number of parts. It is also possible for the fastening device  16  to be attached to the window  18  in a manner other than a glued connection. 
     The fastening parts  14  can, for example, also be coated in order to improve grip during installation. The clamping force of the elastic region  27  can be precisely adjusted by means of a central recess  36  in the base part of the fastening part  14 . 
     As shown in  FIG. 6 , the base part  14   a  of the fastening part  14  can also be provided with projections  35  that lock the fastening parts  14  in a definite position on the housing part  12  in the installed position. To that end, the housing part  12  has securing struts  34 , as shown in FIG.  7 . 
     For example, the sensor element  21  can also be screwed into the sensor housing  12  or elastically fastened in the sensor housing  12 . Likewise, the socket  22  can be fastened to the sensor element  21  and connected by means of a recess in the housing part  12 .