Abstract:
The invention relates to a method for mounting sensors ( 40 ), e.g. rpm sensors, on a support plate ( 10 ) of a control module. Said method comprises the following steps: a cylindrical sensor ( 40 ) is oriented and is inserted into a tubular sensor dome ( 18 ) of the support plate ( 10 ) in the mounting direction ( 56 ). An assembly dimension ( 88 ) for the sensor is then set as the distance between the face of the sensor and a top side ( 16 ) of the support plate ( 10 ). A positive connection between the sensor ( 40 ) and the sensor dome ( 18 ) is established by introducing a fixing material ( 68 ) into a hollow space ( 64 ), and a positive or a bonding sensor contact ( 76 ) between the sensor ( 40 ) and contacts ( 70 ) located at the support plate end is created when the sensor ( 40 ) is inserted into the sensor dome ( 18 ).

Description:
[0001]    The present invention relates to a rotation speed sensor that can be mounted in a vertically adjustable manner, which can in particular be used in transmission control modules in the automotive field as a rotation speed sensor for detecting the drive shaft speed or output shaft speed. 
       PRIOR ART 
       [0002]    DE 103 48 651 A1 has disclosed an installation unit for a motor vehicle, in particular intended for controlling a transmission of the motor vehicle. The installation unit includes a support piece, electrical and/or electronic components situated on the support piece, and electrical connecting elements that are situated on the support piece and are for electrically connecting the electrical and/or electronic components. The electrical connecting elements are embodied in the form of at least one FFC flexible flat cable that contains at least two metal band conductors extending parallel to each other. The metal band conductors extending parallel to each other are made of roller-pressed metal wires that are encased in a flat, strip-shaped insulation band. 
         [0003]    The at least one FFC flexible flat cable is mounted on the support piece by means of one-piece or multiple-piece plastic parts. The ends of the metal band conductors of the at least one FFC flexible flat cable protrude from the insulation casing of the FFC flexible flat cable on at least one end of a connecting section and are secured in a trough-shaped plastic part provided with a recess. The recess of the trough-shaped plastic part is filled with an insulating filling. The plastic part has at least one first plastic element that is fastened to the FFC flexible flat cable through extrusion coating of the FFC flexible flat cable with plastic. The plastic part also has at least one second plastic element that can be attached to the first plastic element and that is fastened to the support piece, preferably by means of stems provided on the plastic part, which are guided through openings in the support piece and then deformed in place. 
         [0004]    The installation unit includes at least one subassembly that is embodied as a multipoint connector with plug contacts. Transmission control modules currently in use in the automotive field have sensors of various lengths installed in them, for example for detecting the output shaft speed. Usually the sensors are pressed-fitted into a correspondingly configured sensor dome of a support plate, with the sensor centered in it. The fixing of the sensor occurs on the opposite end, at the sensor base, where the sensor is attached to the support plate by means of two hot caulks. The electrical contacting in relation to the transmission control module occurs by means of pressed screens that are attached to each other by means of laser welding. The disadvantage of the designs known from the prior art and the design according to DE 103 48 651 A1 is the fact that the required sensor elements, which are of various lengths, require the use of separate tool sets to manufacture the sensor, which increases the amount of technical production effort that must be expended. 
         [0005]    In the designs known from the prior art, care is taken to minimize the size of the air gap between the sensor head and a trigger wheel, for example. But this air gap is tolerance-encumbered, the overall tolerance being composed of the tolerance of the sensor position, the tolerance of the support plate, and an installation tolerance. Due to the above-outlined additive tolerance chain based on the desired air gap, occasionally a sensor head is situated an impermissibly large distance away from the trigger wheel, which has disadvantages from a technical signal detection standpoint. For this reason, efforts are made to minimize tolerances as much as possible in order to assure a well-defined air gap between a sensor head and the trigger wheel, for example, scanned by it. 
       DESCRIPTION OF THE INVENTION 
       [0006]    The present invention proposes producing the sensors of varying lengths, which are required depending on the type of transmission control module, by means of variable press-fitting and subsequent fixing of a modular sensor element. This achieves a simple, inexpensive manufacture of a transmission control module since it requires only one sensor tool set and only one assembly line for sensors. In addition, it enables implementation of an extremely simple sensor installation device in the module assembly. In particular, the use of a modular sensor element offers the possibility of a very precise adjustment of the installation height of the sensor module during installation in the transmission control module. The assembly precision is particularly advantageous with regard to a small air gap and is accompanied by functional advantages. In the design according to the invention, the assembly dimension can be adjusted very precisely during installation. In particular, it is possible to avoid the tolerance chain comprised of the support plate, sensor length, and installation tolerance so that the actual air gap between the sensor head and a trigger wheel, for example, of a motor vehicle transmission can be adjusted with a significantly greater degree of precision. From a technical signal detection standpoint, it is desirable to achieve the smallest possible air gap L between the circumference surface of the trigger wheel and the position of the sensor head of the sensor element. With the design according to the invention, the sensor assembly dimension that the method according to the invention achieves during installation is highly precise. It is also advantageous that the installation method according to the invention permits an infinitely variable installation of a sensor, which detects drive shaft speeds or output shaft speeds, in the sensor dome of a support plate, for example of a transmission control module. 
     
    
     
       DRAWINGS 
         [0007]    The invention will be described below in conjunction with the drawings. 
           [0008]      FIG. 1  shows a sensor attachment of a sensor element to a support plate of a transmission control module according to the prior art, 
           [0009]      FIG. 2  shows the tolerance chain resulting from the arrangement according to  FIG. 1 , 
           [0010]      FIG. 3  shows the modular sensor element according to the invention, with pressed screen extrusion coating and exposed regions of the pressed screens, 
           [0011]      FIG. 4  shows a sensor element mounted in a sensor dome of a support plate according to the depiction in  FIG. 3 , 
           [0012]      FIG. 5  shows a first exemplary embodiment of a contact between the support plate and the sensor element according to the depiction in  FIG. 4 , 
           [0013]      FIG. 6  another exemplary embodiment of a possible embodiment of a contact between the support plate and the sensor element according to  FIG. 4 , 
           [0014]      FIG. 7  shows a section through the contact according to the section line VII-VII from  FIG. 6 , 
           [0015]      FIG. 8  shows a section through the possible embodiment of a contact between the sensor element and support plate according to the section line VIII-VIII in  FIG. 6 , and 
           [0016]      FIG. 9  shows the tolerance chain resulting from the design according to the invention. 
       
    
    
     EXEMPLARY EMBODIMENTS 
       [0017]      FIG. 1  shows a sensor attachment of a sensor element to a support plate according to the prior art. 
         [0018]    A support plate  10  of a transmission control module for motor vehicle transmissions includes a multitude of recesses  14  that are separated from one another by intermediate pieces  12 . The support plate  10  contains a sensor dome  18  in which a sensor  20  is mounted. The symmetry axis of the sensor dome  18  is labeled with the reference numeral  30 . Centering lugs  24  serve to center the sensor  20  in the sensor dome  18 , which extends above the top surface  16  of the support plate  10 . At a sensor contact  26 , a contact is produced, for example by means of laser welding, between the sensor  20  situated on the sensor base  22  and the pressed screens extending inside the support plate  10 . The sensor  20  is mounted in position by means of a hot caulking, for example, at the sensor base  22 , as indicated by the reference numeral  28 . 
         [0019]      FIG. 2  shows the tolerance chain of a sensor arrangement known from the prior art. An air gap L by in which a sensor element situated on the end surface of the sensor  20  is spaced apart from the circumference of a trigger wheel  32 , is tolerance-encumbered. In the design shown in  FIG. 2 , the support plate  10  is encumbered with a tolerance  34 , as is also the case with the sensor length  36  of the sensor  20  and the installation tolerance  38  produced upon installation. This yields an overall tolerance  39  of the transmission control module that depends on at least three individual tolerances. Because of the unfavorably additive tolerances  34 ,  36 , and  38 , the sensor  20  can be spaced far enough away from the circumference of the trigger wheel  32  to impair the signal detection between the trigger wheel  32  and the sensor  20 . This must be structurally avoided as much as possible. The transmission-induced tolerances, which likewise influence the air gap L, are not considered in detail below. 
         [0020]      FIG. 3  shows the sensor module according to the invention, which can be used, for example, as a sensor for detecting the drive shaft speed or output shaft speed. 
         [0021]    The rotation speed sensor  40  shown in  FIG. 3  has a surface  42  on its head, at which the rotation speed sensor  40  can be grasped and oriented by an installation tool. The surface  42  is embodied on a sensor casing  44  of the rotation speed sensor  40  and, in a longer region extending in the axial direction, its circumference surface is provided with flutes  46 . The sensor casing  44  is provided with a filling  48  composed of a sealing compound. The sensor casing  44  is adjoined by pressed screens  52  that are embodied with a standardized excess length. The regions of the pressed screens  52  directly adjoining the sensor casing  44  are enclosed by a pressed screen extrusion coating  50 ; the pressed screens  52  are attached to the sensor casing  44  of the rotation speed sensor  40 , spaced apart from each other by a distance  54 . The pressed screens  52  also have a freely extending length labeled with the reference numeral  55 , which serves to produce an electrical contact with the support plate  10  of a transmission control module, for example. 
         [0022]      FIG. 4  shows a sensor module according to the depiction in  FIG. 3 , in the state in which it is mounted in a sensor dome of a support plate. 
         [0023]      FIG. 4  shows that the rotation speed sensor  40  according to  FIG. 3  is slid into the sensor dome  18  in the installation direction  56 . An insertion of the rotation speed sensor  40  into the sensor dome  18  occurs in accordance with a desired assembly dimension  88  of the rotation speed sensor  40 , which is measured between the top surface  16  of the support plate  10  and the end surface of the rotation speed sensor  40 . Between an inside  60  of the wall  58  of the sensor dome  18  and the circumference surface of the sensor casing  44  of the rotation speed sensor  40 , there is a slight press-fit that fixes the rotation speed sensor  40  in the sensor dome  18 . 
         [0024]    Before the insertion into the opening of the sensor dome  18 , the rotation speed sensor  40  is first oriented on the surface  42  so that the pressed screens  52  are not damaged upon insertion into openings  72  in the support plate  10 . 
         [0025]    The sensor dome  18  can be reinforced by rib-shaped supports  84  that can be injection-molded onto the support plate  10 . The sensor dome  18  is part of the support plate  10 , which is preferably manufactured as an injection-molded plastic component. After being press-fitted into the sensor dome  18 , the rotation speed sensor  40  is fixed in position by the press-fit produced between the circumference surface of the sensor casing  44  and the inside  60  of the wall  58 . The final fixing is produced by injecting a fixing compound such as adhesive, hot-melt glue, or easily flowing plastic injection-molding compound into an injection opening  66  that is provided in the wall  58  of the sensor dome  18 . During the injection process, the fixing compound  68  shown only on one side in the depiction in  FIG. 3  fills the cavity  64  delimited by the undercut  62  and flows between the flutes  46  embodied on the circumference surface of the sensor casing  44 . The undercut  62  in the sensor dome  18  makes it possible to implement a form-locked engagement of the rotation speed sensor  40  with the sensor dome  18 . The diameter of the undercut  62  is selected so that it can be pushed out of the injection mold by force. 
         [0026]    During insertion of the rotation speed sensor  40  in to the sensor dome  18 , the freely extending ends of the pressed screens  52  are first centered by insertion bevels  74  before the freely extending pressed screens  52  travel into the openings  72  of the support plate  10 . As soon as the freely extending ends of the pressed screens  52  have passed through the openings  72 , an electrical contact  76  is produced between the free ends of the pressed screens  72  and a pressed screen  70  that is injection-molded or inserted into the support plate  10 . The electrical contact  76  is shown in detail in  FIGS. 4 through 7 . 
         [0027]    Between the openings  72 , which can be provided in the support plate  10  of a transmission control module, for example, there is a rib-shaped dividing piece  90  that prevents short circuits between the contacts. 
         [0028]    It is clear from  FIG. 4  that after the production of the electrical contact  76  between the pressed screens  52  of the rotation speed sensor  40  and the support plate pressed screen  70 , an excess length  78  of pressed screen is left over on the freely extending ends of the pressed screen  52 . The excess length  78  of pressed screen in  FIG. 4  depends on the sensor assembly dimension  88 . The excess length  78  of pressed screen can be simply cut to length after the electrical contact  76  is produced. Then, the electrical contact  76  between the support plate pressed screen  70  and the freely protruding ends of the pressed screens  52  can optionally be covered by a covering plate  80  in order to protect the produced electrical contacts  76  from moisture, corrosion, and particulate deposits. 
         [0029]    For the sake of completeness, it should be mentioned that the support plate  10 , for example of a transmission control module, can be provided with several sensor domes  18  as well as with a number of fastening bushings  82  that are indicated in the depiction in  FIG. 3 . It is also clear from  FIG. 3  that depending on the respective individual sensor assembly dimension  88 , due to the excess length at the free ends of the pressed screens  52 , a protrusion dimension  86  of the rotation speed sensor  40  is produced, which is an indication of the installation variability with regard to the installation height of the rotation speed sensor  40  in the sensor dome  18 . In accordance with this dimension  86 , the circumference of the sensor casing  44  is provided with flutes  46  so that the rotation speed sensor  40  in the sensor dome  18  can be fixed in an integrally joined fashion or by means of a form-locked engagement at any installation height within the dimension  86  by injecting a fixing compound  68  through the injection opening  66 . 
         [0030]      FIG. 5  shows an insulation displacement contact between the free ends of the pressed screens and the support plate pressed screen. 
         [0031]    During insertion of the pressed screens  52 , the insertion bevels  74  provided at the top of the openings  72  in the support plate  10  center the freely extending ends of the pressed screens  52 . With further insertion of the pressed screens  52  during installation of the rotation speed sensor  40  in the sensor dome  18 , contact tabs  94 ,  96  on the support plate pressed screen  70  are spread apart and an insulation displacement contact  76  is produced. Because of the prestressing of the material of the pressed screen, the first and second contact tabs  94 ,  96  rest against the pressed screens  52 , as shown in the sectional depiction in  FIG. 7  according to the section line VII-VII in  FIG. 5 . After the contact  76  is produced—as shown in FIG.  7 —the pressed screen material to be cut to length (depicted with dashed lines in  FIG. 7 , see reference numeral  98 ) can be cut off and the cover  80  shown in  FIG. 4  can be attached to the underside of the support plate  10  so that it covers the above-described contacts  76  between the rotation speed sensor  40  and the support plate  10 . 
         [0032]      FIGS. 6 and 8  show another possible embodiment of an electrical contact  76  between the free ends of the pressed screens  52  and the pressed screen  70  mounted in the carrier plate  10 . 
         [0033]      FIG. 6  shows that the free ends of the pressed screens  52  are likewise centered by the insertion bevels  74  before insertion into the openings  72  of the support plate  10 . Further insertion of the free ends of the pressed screens  52  then occurs in such a way that they are slid in until the free ends of the pressed screens  52  are situated opposite an unbent end  102  of the support plate pressed screen  70 . The bent end  102  of the support plate pressed screen  70  is brought into congruence with the free end of the pressed screen  52  and an integrally joined connection  100  is then produced, for example by means of resistance welding or laser welding. 
         [0034]      FIG. 8  shows a sectional depiction of the integrally joined connection  100  according to the section line VIII-VIII in  FIG. 6 .  FIG. 7  also shows that after production of the integrally joined connection  100  between the bent end  102  of the support plate pressed screen  70  and the free end of the pressed screen  52  of the rotation speed sensor  40 , the pressed screen material  98  to be cut to length—depicted with dashed lines here—can be cut off below the integrally joined connection  100 . After the pressed screen material  98  to be cut to length is cut off, the electrical contact  76  can also be covered with the covering plate mounted to the underside of the support plate  10 , as shown in  FIG. 3 , and thus protected against corrosion, moisture, and particulate deposits. 
         [0035]    The sensor module according to the invention, which can be used, for example, as an output shaft rotation speed sensor  40  in a transmission control module, advantageously makes it possible to maintain individual sensor assembly dimensions  88 . The sensor casing  44  of the rotation speed sensor  40  in  FIGS. 3 and 4  has flutes  46  in a region of its circumference, which provide a corresponding variability  86  with regard to the installation height of the rotation speed sensor  40  in the sensor dome  18 . The final fixing of the rotation speed sensor  40  in the sensor dome  18  in terms of the protrusion dimension  86  can be achieved with infinite variation along the flutes  46  by injecting a fixing compound  68  through the injection opening  66 . The fact that the free ends of the pressed screens  52  are embodied with an excess length assures that an electrical contact  76  between the protruding ends of the pressed screens  52  and the support plate pressed screen  70  of the support plate  10  is always produced in accordance with the individual assembly dimension  88  of the rotation speed sensor  40 . The electrical contact  76  between the sensor element  40  and the support plate  10  can be an insulation displacement contact, as shown in  FIGS. 5 and 7 , and can also be an integrally joined connection  100  produced by means of laser welding or resistance welding, as shown in  FIGS. 6 and 8 . 
         [0036]      FIG. 9  shows a tolerance that can be achieved with the design according to the invention. 
         [0037]    By using the method according to the invention, it is possible to achieve an air gap L that is extremely precise in the installation of the rotation speed sensor  40 , whether this is intended for detecting the drive shaft speed or the output shaft speed. By contrast with the tolerance chain that is depicted in  FIG. 2  and is comprised of the tolerance  34 , the length of the sensor  36 , and the inevitable installation tolerance  38 , the design according to the invention achieves an overall tolerance  39  during the installation process that depends solely on the tolerance of the assembly dimension  88 . As a result, the air gap L between the rotation speed sensor  40  according to  FIG. 9  and the outer circumference of the trigger wheel  32  can be produced in a significantly more precise fashion. By virtue of the flutes  46  and the fixing compound  68  injected between the sensor dome  18  and the outer circumference of the sensor element  40 , the rotation speed sensor  40  can also be installed in the sensor dome  88  in an infinitely variable fashion. The sensor assembly dimension  88  can thus be selected so that an air gap L can be achieved, which is optimal with regard to the signal transmission between the trigger wheel  32  and the sensor element of the rotation speed sensor  40 .