Abstract:
A contact-disk system is described having a rotatable contact disk and a plurality of contact elements, the contact disk having a plurality of paths and each contact element being assigned to one path. Two selected contact elements of the plurality of contact elements are always at the same electrical potential and glide on the same path. A windshield-wiper motor and a method for controlling a windshield-wiper motor are also described.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a contact-disk system having a rotatable contact disk and a plurality of contact elements, the contact disk having a plurality of paths and each contact element being assigned to one path. The present invention also relates to a method for controlling a windshield-wiper motor using a contact-disk system having a rotatable contact disk and a plurality of contact elements, the contact disk having a plurality of paths and each contact element being assigned to one path. Furthermore, the present invention relates to a windshield-wiper motor which comprises a contact-disk system having a rotatable contact disk and a plurality of contact elements, the contact disk having a plurality of paths and each contact element being assigned to one path. 
     BACKGROUND INFORMATION 
     Conventional windshield-wiper devices may include contact-disk systems as well as methods for controlling windshield-wiper motors for cleaning of motor vehicle windshields. The windshield-wiper devices may be operated by a switch which may be located in the vehicle interior, the switch being implemented, for example, as a steering-column switch. By operating the steering-column switch, the windshield-wiper device may be shifted from a switched-off state to at least one operating state. The operating states may be implemented by a plurality of windshield-wiper speeds and an intermittent control. 
     To ensure that the windshield wipers do not come to rest in an intermediate position when the windshield wiper is switched off by the steering column switch, but instead are properly guided back to park position, contact-disk systems may be used. Such contact-disk systems may maintain a closed circuit, in which the windshield-wiper motor operates, until the windshield wipers have reached the park position. 
     FIG. 1 shows a contact disk  110  which may be used in a conventional contact-disk system. A contact disk  110  of this kind may be installed in generic windshield-wiper motors in such a manner that it rotates in synchronism with the windshield-wiper motor. Contact disk  110  establishes contact with three contact elements, which in each case glide on one path of contact disk  110 . A first contact element glides on outer path  120 , which has a gap. A second contact element glides on inner path  122 , which is implemented as a short path, and a third contact element glides on a center path  121 , which is continuous. Such a construction may maintain a current flow in all motor settings, except for the end position and in an area approaching the end position. This may be achieved by a contact element, which is connected to the positive pole of the battery, gliding on outer path  120 . A contact element gliding on center path  121  is connected to the wiper motor. Therefore, a current flow from the positive pole of the battery to the wiper motor is maintainable as long as the first contact element glides on a conductive region of outer path  120 . The current flow may only be interrupted when contact disk  110  has rotated to the point where the contact element is located in the gap in outer path  120 . Due to the inertia of the motor, the contact disk continues to rotate despite the interrupted current flow. However, this further rotation may come to an end when the conductive region of short, inner path  122  connects with a contact element. This contact element is switched such that the motor is short-circuited and may be actively braked in this manner. 
     Due to the three paths of a conventional contact disk, it may have a certain minimum size. However, in the case of windshield-wiper motors it is desirable to achieve an overall size that is as small as possible, and, therefore, in particular also a small size of the contact disk. A small size of the contact disk may also be desirable in the production of windshield-wiper motors, in particular in rear-wiper motors with oscillating gears, where the contact disk may be required to be arranged with the contacting on the opposite side with respect to the oscillating gear. For this reason, the windshield-wiper motor may be required at present to be rotated on the assembly line during production, which may make the production process expensive. 
     SUMMARY OF THE INVENTION 
     The present invention builds on the conventional contact-disk system in that the contact disk may have two paths and in that two selected contact elements of the plurality of contact elements may always be at the same electrical potential and glide on the same path. In this manner, an electric current flow may be maintained, with a two-path contact disk, until the park position of the windshield wiper is reached or until shortly before the park position has been reached. Because the contact disk may require no more than two paths it may have a smaller size and a smaller radial overall width, which may be desirable with respect to the mentioned overall size of the windshield-wiper motor and in view of the manufacturing process. 
     The selected contact elements may glide on a first path, which may have an electrically conductive and an electrically insulating area, and at least one contact element of the selected contact elements is connected to the electrically conductive area. If the windshield-wiper motor is switched off by operating the steering-column switch, an electrical connection to the wiper motor may be maintained at least via one of the selected contact elements, since at least one of the selected contact elements may always be in contact with the electrically conductive area of the first path. 
     The electrically insulating area of the first path may be implemented by a gap in a conductive path, and the selected contact elements may have a spacing that is larger than the gap of the first path. Therefore, given a circular contact disk, the electrically insulating area may be realized by a cut-out with radially extending boundaries. If the opening angle of this gap is less than the clearance angle of the selected contact elements, it may be assured in this manner that one of the selected contact elements is always in contact with the electrically conductive area of the first path. 
     A first, additional contact element may glide on the first path. This first additional contact element may be used to maintain an electrical connection between the contact disk and the positive pole of the vehicle battery. Therefore, even when the steering-column switch is in the off-position, an electrical connection mat be maintained between the positive pole of the battery and the motor via the first additional contact element and at least one of the selected contact elements. Only when the first additional contact element leaves the electrically conductive area of the first path and is located in the insulating area of the first path, may the current flow be interrupted. 
     A second path may have an electrically insulating area and an electrically conductive area. A second additional contact element may glide on the second path. This contact element may be used to realize an electrical short-circuit of the motor and to actively brake the motor in this manner once the park position has been reached. 
     The gap in the first path, the electrically conductive area of the second path, the first additional contact element and the second additional contact element may be arranged with respect to one another in such a manner that a state exists in which neither the first additional contact element nor the second additional contact element are connected to an electrically conductive area of the first path and the second path, respectively. Although the current flow in the electrical circuit of the windshield-wiper motor may already be interrupted, the motor and the contact disk may still continue to rotate, due to their inertia. During this phase the motor speed may be reduced, and an active braking of the motor may only occur, due to the electrical short-circuit, when the second additional contact element makes contact with the electrically conductive area of the second path. 
     The angular range, which may be covered by the electrically conductive area of the second path, may be less than the angular range that is covered by the electrically insulating area of the first path. As a result, the first additional contact element may have already left the conductive area of the first path due to the rotation of the contact disk, while the second additional contact element may have not yet reached the conductive area of the second path. Therefore, the motor may be neither actuated nor actively braked in this intermediate state. The motor may continue to rotate due to its inertia, with the rotational speed decreasing, however. Only when the electrically conductive area of the second path makes contact with the second additional contact element, may the motor be finally braked. 
     These contact elements may be contact springs. In this manner, a reliable contact between the contact disk and the contact elements may be established. 
     The present invention may build on a conventional method in that a contact-disk system according to the present invention may be used to control a windshield-wiper motor. In this manner, a contact-disk system according to the present invention may be implemented by a control method. 
     In an exemplary method according to the present invention it may be desirable if a switch connected to the contact-disk system is operated and if a rotation of the contact disk is maintained until the second additional contact element is connected to the electrically conductive area of the second path. Thus, the control method may allow the windshield wipers to be guided from one operating position to a park position in a reliable manner. 
     In this context, prior to connecting the second additional contact element to the electrically conductive area of the second path, the connection of the first additional contact element to the electrically conductive area of the first path may be interrupted. Although the electrical connection of the motor and the battery may already be interrupted during this created intermediate state, rotation may still occur nevertheless, due to the inertia of the involved components, although the rotational speed of the motor may decrease. Only when the second additional contact element contacts the electrically conductive area of the second path may an active braking of the motor occur. 
     The present invention may build on a conventional windshield-wiper motor in that it may have a contact disk according to the present invention. As a result, the windshield-wiper motor may implement desired features of a contact disk according to the present invention and an exemplary method according to the present invention. A windshield-wiper motor may be manufactured that has a reduced size. 
     The present invention may be based on a recognition that, by an appropriate arrangement of contact elements and a suitable geometric design of a contact disk, the functions of a three-path contact disk may be realized, as it may be used in conventional windshield-wiper motors, or by two-path contact disks. Therefore, windshield-wiper motors according to the present invention may also be produced in smaller sizes. The manufacturing process, in particular, may be simplified since a rotation of the motor on the workpiece-carrier of the assembly line may no longer be required. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a conventional contact disk. 
     FIG. 2 shows a contact-disk system according to an exemplary embodiment of the present invention. 
     FIG. 3 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in switched-on state. 
     FIG. 4 shows a substitute circuit diagram of the circuit according to FIG.  3 . 
     FIG. 5 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a first intermediate state. 
     FIG. 6 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a second intermediate state. 
     FIG. 7 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a third intermediate state. 
     FIG. 8 shows a substitute circuit diagram of the circuits according to FIGS. 5 through 7. 
     FIG. 9 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a fourth intermediate state. 
     FIG. 10 shows a substitute circuit diagram of the circuit according to FIG.  9 . 
     FIG. 11 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a switched-off state. 
     FIG. 12 shows a substitute circuit diagram of the circuit according to FIG.  11 . 
    
    
     DETAILED DESCRIPTION 
     In the following description of the drawings, identical elements have been provided with the same reference numerals. 
     FIG. 2 shows a contact-disk system according to an exemplary embodiment of the present invention in a top view. The contact-disk system includes a contact disk  10  and a plurality of contact elements  12 ,  14 ,  16 ,  18 . Contact elements  12 ,  14 ,  16 ,  18  are in the form of contact springs. Contact disk  10  has two paths  20 ,  22 . First path  20  has a relatively long electrically conductive area  24  and a comparatively short electrically insulating area  26 , which is realized by a gap in path  20 . First path  20  is located in the radial direction outside of second path  22 . This second path  22  has a relatively long electrically insulating area  28  and a comparatively short electrically conductive area  30 . The electrically conductive area  30  is implemented as a short connecting piece to the electrically conductive area  24  of first path  20 . Two contact elements  12 ,  14  of the plurality of contact elements  12 ,  14 ,  16 ,  18 , which are referred to as selected contact elements  12 ,  14 , have a clearance angle with respect to their contact areas  36 ,  38  that is greater than gap  26  in first path  20 . In this manner, at least one of contact elements  12 ,  14  is always in contact with the electrically conductive area  24  of first path  20 . First additional contact element  16  slides on first path  20 . Second additional contact element  18  slides on second path  22 . The angular range, which is covered by gap  26  in first path  20 , is larger than the angular range that is covered by electrically conductive area  30  of the second path. Contact point  40  of first additional contact element  16  and contact point  42  of second additional contact element  18  as well as gap  26  in first path  20  and electrically conductive area  30  of second path  22  are arranged in such a manner with respect to each other that there exists a state in which neither first additional contact element  16  nor second additional contact element  18  is in contact by their respective paths. Also, the arrangement of first additional contact element  16  and second additional contact element  18  is and gap  26  in first path  20  and of electrically conductive area  30  of second path  22  are selected such that a state exists in which second additional contact element  18  is in contact with electrically conductive area  30  of second path  22 , while first additional contact element  16  is located in electrically insulating area  26  of first path  20  and thus does not have any electrical contact to contact disk  10 . 
     FIG. 3 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a switched-on state. A switch  34 , which may be in the form of a steering-column switch, establishes a connection between terminal  53  and the positive pole of the vehicle battery. In this manner, the positive potential is applied to motor  32  via terminal  53 , a polarity-reversal damping diode  44  and a coil  46 . This is independent of the position of contact disk  10  with regard to contact elements  12 ,  14 ,  16 ,  18 , an arbitrary instantaneous survey of contact disk  10  rotating synchronously with motor  32  being depicted in the present case. 
     FIG. 4 shows a substitute circuit diagram according to FIG.  3 . It is shown that terminal  53  may always be at a positive potential via switch  34 . Contact disk  10 , which is symbolized by a switch activated by motor  32 , alternates between several switching states; at certain times an additional connection of motor  32  to the positive pole exists via terminal  53   a . This is symbolized by the solid line in the symbolic depiction of contact disk  10 . At other times, an additional connection of motor  32  to terminal  53  is provided. This is symbolized by the dashed line to the right of the symbolic depiction of contact disk  10 . There is also a state in which contact disk does not establish any further connection of motor  32  to one of the terminals  53 ,  53   a , which is represented by the center dashed line of the symbolically represented contact disk  10 . Regardless of the switching states of disk  10 , a positive potential may be given at motor  32  via coil  46  in switched-on state, i.e. the state in which switch  34  creates a connection to the positive pole. 
     FIG. 5 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a first intermediate state. Switch  34  has been switched to turn the window wiper off, so that a connection to the negative pole of the battery is now given by switch  34 . However, motor  32  is still provided with the positive potential via terminal  53   a , contact element  16 , contact disk  10  and contact element  12 . In the instantaneous survey represented in FIG. 5, contact element  14  is locate in the electrically insulating area of first path  20  of contact disk  10 . Since the space between the selected contact elements  12 ,  14  is larger than gap  26  in first path  20  of contact element  10 , contact disk  10  may always maintain a connection to motor  32 . Second additional contact element  18 , which is at a negative potential via terminal  53 , is not in contact with the contact disk, since it is located in the electrically insulating area of second path  22 . 
     FIG. 6 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a second intermediate state. This second intermediate state corresponds to the first intermediate state according to FIG. 5, with the exception that the contact of the positive pole is now provided via the other selected contact element  14 . 
     FIG. 7 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a third intermediate state. This third intermediate state also corresponds to the first intermediate state according to FIG.  5  and the second intermediate state according to FIG. 6, with the exception that the connection between the positive pole and motor  32  is maintained by both selected contact elements  12 ,  14  in the instantaneous survey according to FIG. 7 . 
     FIG. 8 shows a substitute circuit diagram of the circuits according to FIGS. 5 through 7. In all states, the positive pole is connected to the motor via terminal  53   a , so that its operation may be maintained. 
     FIG. 9 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a fourth intermediate state. This fourth intermediate state electrically differs from the first intermediate state, the second intermediate state and the third intermediate state. In the fourth intermediate state according to FIG. 9, the first additional contact element  16  is located in electrically insulating area  26  of first path  20 . Therefore, the positive potential is no longer at the selected contacted elements  12 ,  14 , so that there is also no longer any voltage at motor  32 . Second additional contact element  18  is located in the electrically insulating area of second path  22 , but just before contacting the electrically conductive area. Starting from the state according to FIG. 9, a further rotation of the contact disk may occur due to the inertia of the involved components. 
     FIG. 10 shows a substitute circuit diagram of the circuit according to FIG.  9 . It is shown that neither terminal  53   a  nor terminal  53  is connected to the motor. This indicates that there is neither a positive potential for the normal operation of motor  32 , nor is there a negative potential at motor  32 , which would short-circuit motor  32 . 
     FIG. 11 shows an electrical circuit including a contact-disk system according to an exemplary embodiment of the present invention in a switched-off state. In accordance to FIG. 9, here, too, contact element  16  is located in electrically insulating area  26  of path  20 . In contrast to FIG. 9, however, in the instantaneous survey according to FIG. 11, contact element  18  is in electrically conductive area  30  of second path  22 . Thus, a connection exists between the negative pole and the motor via terminal  53  and contact element  18 . Motor  32  is short-circuited and thereby actively braked. The windshield-wiper is in park position. 
     FIG. 12 shows a substitute circuit of diagram of the circuit according to FIG.  11 . It may be seen that the switch, which symbolizes contact disk  10 , connects motor  32  to the negative pole, so that it is short-circuited. 
     The preceding description of exemplary embodiments according to the present invention may be for illustrative purposes only, and is not mean to restrict the invention. Various changes and modifications may be possible within the framework of the present invention, without leaving the scope of the present invention and its equivalents.