Abstract:
A windshield wiping device, in particular for cleaning a windshield of the motor vehicle, includes at least one wiper and a control device. The at least one wiper is driven by an electrical drive motor and displaceable between two end positions. The control device processes a current wiper position and switching signals of a manually operated switching element via input variables. The control device controls a supply voltage of the electrical drive motor and a wiper velocity via an output variable. The at least one wiper moves from end position to end position. In a first switch position of the switching element, the at least one wiper has a first velocity. In a second switch position of the switching element, the at least one wiper has a second velocity, which is greater than the first velocity. The at least one wiper in the second switch position moves at the first velocity each time it is in the vicinity of an upper and lower end position. An electrical drive motor has a contact disk system, rotating synchronously with revolutions of the electrical motor for the periodic switchover between the second velocity and the first velocity.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a windshield wiping device for cleaning motor vehicle windshields. 
     BACKGROUND INFORMATION 
     Windshield wiping devices for cleaning motor vehicle windshields are conventional. Conventional devices of this type usually have two switch positions for different wiper speeds, as well as a position for intermittent operation. Depending on the degree to which the windshield is wetted, the wiper arm moving over the windshield, due to frictional forces, experiences different levels of resistance. The frictional forces operating on the rubber lips of the wiper are the smallest at the second, more rapid velocity level, and on a wet windshield. The geometric design of the windshield wiping device, with respect to the maximum possible wiping field, must therefore take this operating state into account. 
     On the other hand, at the usually roughly 30% slower first velocity level, the result, in the turning points, is a smaller wiping field, and therefore also a smaller vision field, because the momentum of the wiping device, as a result of the moments of inertia of the moving parts, and particularly so on a dry windshield, is significantly less than on a wet windshield at the rapid level. A corresponding enlargement of the wiping field at the first level, at the second level on a wet windshield, would lead to a deflection of the windshield wiper beyond the windshield and therefore to faulty functioning or damage to the wiper. 
     To render the end positions of the wiper arms as congruent as possible at the two velocity levels, there are conventional measures, shortly before the wiper arm reaches the upper or the lower end position, to switch the electrical drive motor of the windshield wiping device to the slower velocity level and, as a result, to maintain the inertial forces, and thus the lag of the windshield wiping device, at as constant a value as possible. 
     Thus, WO PCT Publications No. 96/09944 describes a windshield wiping device having a supplemental switching device, which, shortly before the turning points, switches from a more rapid velocity level to a slower level. For this purpose, an electrical switch is mechanically coupled to the rotor of the electrical drive motor. The switch has a plurality of concentric cams for the periodic control of contact tags. Disadvantageous in the system is the relatively complex and bulky design of the switch, which, in addition, cannot be realized using conventional switches as they are usually employed in motor vehicles. Also, no provision is made for an integrated control of a park position. 
     SUMMARY OF THE INVENTION 
     The windshield wiping device according to the present invention has the particular advantage, as a result of simple mechanical components, of achieving a maximum possible wiping field on the windshield of a motor vehicle. This is essentially achieved as a result of the fact that at the second velocity level, which is higher than a first velocity level of the electrical drive motor of the windshield wiping device, shortly before the at least one wiper arrives at the upper or the lower end position (the turnaround point), a switchover takes place to the first, i.e., slower velocity level, and, shortly after leaving the upper or lower end position, a return to the second velocity level is carried out. This switchover occurs in a simple manner through the use of a contact disk system rotating in concert with the motor revolutions. The contact disk system, for example, is able to periodically change the motor velocity through three contact tags sliding on partially interrupted pathways and acting as switching contacts. In the same manner, the precise resting position of the windshield wiper can also be assured in the lower end position after switchoff. For this purpose, it is advantageous to arrange two contact disk systems so as to be coaxial in relation to each other, so that a fixed assignment of the angle positions of the contact disks is made possible with regard to the position of the windshield wiper on the windshield. 
     It is particularly advantageous that the contact disk systems have a simple interface with regard to a steering column switch. The steering column switch has a very simple and proven design and function. 
     In an advantageous embodiment, the contact disk has connected to it not the entire engine voltage but rather a small control voltage, which can then drive a power transistor or thyristor. 
     Another advantageous embodiment of the present invention can provide for electronic detection of the wiper position, for example using a rotating perforated disk for driving a photo-electric reader or a Hall sensor. Its signals can be used by a downstream evaluating circuit for the precise maintenance of a maximum wiping field. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a basic circuit diagram for variable velocity control of a windshield wiping device according to the present invention. 
     FIG. 2 a  shows a basic circuit diagram of a first switch position. 
     FIG. 2 b  shows a basic circuit diagram of a second switch position. 
     FIG. 2 c  shows a basic circuit diagram of a third switch position. 
     FIG. 2 d  shows a basic circuit diagram of a fourth switch position. 
     FIG. 3 a  shows a first switch position having corresponding representations of current flow. 
     FIG. 3 b  shows a second switch position having corresponding representations of current flow. 
     FIG. 3 c  shows a third switch position having corresponding representations of current flow. 
     FIG. 3 d  shows a fourth switch position having corresponding representations of current flow. 
     FIG. 3 e  shows a fifth switch position having corresponding representations of current flow. 
     FIG. 3 f  shows a sixth switch position having corresponding representations of current flow. 
     FIG. 4 a  shows a first change of a switch position in response to turning a contact disk. 
     FIG. 4 b  shows a second change of a switch position in response to turning a contact disk. 
     FIG. 4 c  shows a third change of a switch position in response to turning a contact disk. 
     FIG. 5 shows a schematic representation of a contact disk. 
     FIG. 6 shows a basic circuit diagram for variable velocity control of a windshield wiping device in an altered configuration. 
     FIG. 7 shows an overall schematic representation of an electrical drive motor having contact disk systems. 
     FIG. 8 shows a systematic representation of a wiper system. 
     FIG. 9 shows an embodiment of an arrangement for determining a current wiper position. 
     FIG. 10 shows another embodiment of an arrangement for determining a current wiper position. 
    
    
     DETAILED DESCRIPTION 
     Description of the Exemplary Embodiments 
     FIG. 1, in a basic circuit diagram, shows a changeable control of the velocity of a windshield wiping drive for cleaning a windshield of a motor vehicle. Using this device, the windshield wiper may, at each wiper velocity selected by a driver, reach, in each case, approximately the same upper and lower end position, as result of which the kinematic design can optimally be aimed at a maximum wiping field. 
     An electrical drive motor  2 , indicated only schematically, can be recognized, which has three electrical connections. A grounded connection leads to a clamp  31  and thus to a negative pole of an undepicted vehicle battery or to a vehicle ground. A clamp  53 , via a steering column switch (FIG. 3) that is undepicted in FIG. 1, is routed to a positive pole of the vehicle battery, if the drive motor is to run at a first, i.e., slower level I. If drive motor  2  is to be operated at a more rapid, second level II, then, additionally, a shunt winding of drive motor  2  is connected to a clamp  53   b.    
     Drive motor  2 , furthermore, is coupled to two contact disk systems  10 ,  20 , which permanently rotate at a fixed transmission ratio with respect to a rotor  40  of drive motor  2 . First contact disk system  10  is responsible for the park position run and is described further below. Second contact disk system  20  is responsible for switching back from more rapid level II to slower level I of drive motor  2 , if the at least one wiper is positioned shortly before the upper or lower end position. 
     For this purpose, and shortly before one of the end positions, a switchover is carried out via contact disk system  20  from clamp  53   b  to clamp  53 , which is connected via a reversed-polarity damping diode  6  to a drive motor  2  and for a short time switches over the latter to the slower operating level. Upon leaving the end position, clamp  53   b  is switched back to shunt  53   b  of drive motor  2  via contact disk system  20 , as result of which drive motor  2  again runs at the more rapid operating level, until it has reached its other end position. These processes are carried out periodically, each time one of the end positions of the wipers is reached. Furthermore, there is provided an arrangement  101  for detecting the current wiper position. 
     FIGS. 2 a-d  depict, in four basic circuit diagrams, one complete motor revolution at more rapid operating level II. It is illustrated how contact disk system  20  provides for a switchover from more rapid operating level II to slower operating level I, in each case shortly before an end position of the windshield wiper is reached. Identical parts of FIG. 1 are designated using identical reference numerals and are not described again. In all representations of FIG. 2, steering column switch  4  is disposed in position II for more rapid level II. 
     Contact disk system  20  has a rotating, planar, electrically conductive contact disk  21  (FIG.  5 ), on which a fixed collector brush  28  slidingly engages three contact tags. Each of these contact tags slides on one of three paths of contact disk  21  that are concentrically arranged with respect to each other and electrically connected. A central path  24  is configured so as to be continuous and is connected, via the central contact tag of collector brush  28 , to clamp  53   b  on steering column switch  4  and, via the latter, can be connected to the positive pole of the vehicle battery. An interior path  22  and an exterior path  26  both have segment sections disposed at 180° and having insulating coatings. As result of the rotation of contact disk  21 , the interior or the exterior contact tag of collector brush  28  slides, interchangeably, on an insulating or a conductive coating of interior path  22  or exterior path  26  and thus functions as a simple switchover device. Therefore, clamp  53   b  can be connected either to the corresponding clamp of the shunt winding on drive motor  2  or, via a reversed-polarity damping diode  6 , to the main winding. 
     FIG. 2 a  depicts a first rotor position, in which central path  24  connects collector brush  28  to interior path  22  and thus to clamp  53   b  of the shunt winding of drive motor  2 . Drive motor  2  in this switch position, operates at more rapid operating level II. Right-hand contact disk system  10  is responsible for the park position run when the windshield wipers are turned off, in or shortly before reaching the park position of the windshield wiper, and for the moment will not be described in greater detail. 
     FIG. 2 b  depicts rotor  40  shortly before reaching the upper end position of the wiper. In this context, collector brush  28  is connected simultaneously to central path  24  and exterior path  26 , the interior contact tag encountering an insulating coating of interior path  22 . The exterior contact tag is connected, via reversed-polarity damping diode  6 , to clamp  53  of drive motor  2 , which as a result runs at slower operating level I and therefore can assure a constant location of the end position of the windshield wiper. 
     FIG. 2 c  depicts a further position of rotor  40  of drive motor  2  during a downward movement of the wiper. In this context, the central contact tag of collector brush  28  is connected, via central path  24  and interior path  22 , to the interior contact tag, i.e., clamp  53   b  of drive motor  2  is connected. Drive motor  2  in turn runs at its more rapid operating level II. 
     FIG. 2 d , finally, depicts an operating position shortly before the windshield wiper reaches the lower end position. Here too, collector brush  28  is connected to central path  24  and exterior path  26  of contact disk  21 , as a result of which clamp  53  is connected to the positive pole of the battery, and drive motor  2  runs at its slower operating level I. 
     FIGS. 3 a - 3   f  illustrate the functions of the park position operation, which is essentially to ensure a reliable and precise placing of the wiper in the park position, the same parts shown in the preceding Figures being provided with the same reference numerals. 
     FIG. 3 a  depicts drive motor  2  at its first slower operating level I. In this context, steering column switch  4  is at first switching level I, and the positive pole of the battery is connected to clamp  53  of drive motor  2 . Clamp  31  on drive motor  2  is connected to the negative pole of the vehicle battery. 
     FIG. 3 b  depicts steering column switch  4  at the second level, in which drive motor  2  rotates at more rapid velocity level II. Clamp  53   b  of drive motor  2 , in this context, is connected to the positive pole of the vehicle battery, whereas clamp  53  is not connected. 
     FIG. 3 c  illustrates the switching off of the windshield wiper after operation. Steering column switch  4  is in a zero position. Since the wipers are not yet in their end position, drive motor  2  must continue to run until the park position of the wipers has been reached. For this purpose, drive motor  2  is provided with contact disk system  10 , which, in all rotor positions except the end position, makes possible a current flow from clamp  31   b  to clamp  53   a  and thus, via a contact bridge in steering column switch  4 , makes an electrical connection from the positive pole of the vehicle battery to connection  53  of drive motor  2  possible. 
     FIG. 3 d  depicts the approach of the wiper to its park position. The current flow between connection  53   a  and connection  31   b , in this context, is already interrupted, but drive motor  2  continues to run due to its inertia. 
     FIG. 3 e  depicts the park position, now definitely reached. In this context, drive motor  2  is short-circuited via contact disk system  10  through a connection of  31  to  31   b  or  53 . The motor is thus actively braked. 
     FIG. 3 f , finally, depicts an intermittent operation of drive motor  2 . The control takes place via a relay, and a start-up can be achieved by a direct flow of current corresponding to FIG. 3 a , or by a park position run, corresponding to FIGS. 3 c ,  3   d , and  3   e.    
     FIGS. 4 a  through  4   c  depict in three schematic illustrations a motion sequence of contact disk system  10 , when at least one windshield wiper reaches the park position. In this context, it can be seen how, through the rotation of contact disk  11 , the switchover takes place from the connection of clamps  31   b  and  53   a  (FIG. 4 a ) to a connection of clamps  31  to  31   b  (FIG. 4 c ), and thus drive motor  2  is short-circuited. 
     FIG. 5 shows contact disk  21  of contact disk system  20 , which is provided for switching velocities. Recognizable here are continuous central path  24  as well as interior path  22  and exterior path  26 , each interrupted twice and provided at these interrupted locations with an insulating coating. Collector brush  28  that has its three contact tags running on the contact disk, in this context, is only sketched in. Also only sketched in, in this illustration, is support disk  42 , on which both contact disks  11  and  21  are secured, above and below, and which is provided on the exterior with gear teeth  44  for engaging with a worm gear  46  connected to rotor  40  of electrical drive motor  2 . 
     FIG. 6, furthermore, depicts an alternative drive of electrical drive motor  2 . Instead of connecting the full operating current directly via contact disk system  20 , the latter functions solely to drive an electrical switch  38 , for example a thyristor or a power transistors which is then able to put through the full power current to drive motor  2  and thus is able to assure a better wear resistance of the contact tags of collector brush  28  of contact disk system  20 . The remaining design is analogous to that in FIG.  1  and will not be described here once again. 
     FIG. 7 depicts a schematic overall representation of an electrical drive motor  2  that has contact disk systems  10  and  20  built into a transmission housing of the worm gear driven by a motor drive shaft. Axes of rotation  3  and  5  of drive motor  2  and of contact disk systems  10 ,  20 , that are arranged so as to be coaxial with respect to each other and are installed in a common housing  7 , are situated so as to be perpendicular with respect to each other. Contact disks  11 ,  21  are mounted on a common support disk  42  (FIG.  5 ), which has external gear teeth  44  (FIG. 5) and which engages, permanently and with virtually no play, with a worm gear mounted on rotor  40  of electrical drive motor  2 . Rotor  40  and the worm gear are not depicted in detail. They are located in a housing  9  of drive motor  2 , housing  9  and housing  7  being able to be configured in one piece. The transmission ratio of these gear teeth  44  must be selected  50  that a switching sequence is assured that is synchronous with the turning motions of the windshield wiper. In FIG. 7, furthermore, connecting lines  11  can be seen which connect the contacts rubbing on the contact disk to the corresponding clamps. 
     In FIG. 8, a schematic view of a windshield wiping device is shown. In this context, a windshield  70  of a motor vehicle has assigned to it a windshield wiping device, which has at least one wiper arm  72 . In accordance with the varying specific embodiments of the wiping devices, there may be only one or more than two wiper arms  72 . The latter can be placed into an oscillating motion about a chassis-fixed rotational axes  74 . In accordance with a drive rod  76 , arranged between drive motor  2  and rotational axis  74 , in this context, the rotational motion of a rotor of drive motor  2  is translated into the oscillating motion, wiper arm  72  sweeping over a wiping field  82  between an upper end position  78  and a lower end position  80 . Drive motor  2  can be actuated via steering column switch  4  in a conventional manner. In addition, contact disk system  10 ,  20 , configured together with drive motor  2 , is schematically sketched. The control of wiper arm  72 , explained on the basis of the preceding Figures, is carried out by the contact disk system  10 ,  20 . The park position, which is approached via the contact disk system, is located, for example, somewhat beneath lower end position  80 . 
     As shown in FIGS. 1 and 2 a - 2   d , the contact disk systems  10  and  20  may be provided with an arrangement  101  for detecting the current wiper position. FIG. 9 shows an exemplary embodiment of the arrangement  101  for detecting the current wiper position for the optical detecting of the current wiper position using perforated disks  102 , photo-electric readers  103 , and a downstream evaluation circuit  104 . FIG. 10 shows another embodiment of the arrangement  101  for detecting the current wiper position using perforated disks  105 , Hall sensors  106 , and a downstream evaluation circuit  104 .