Abstract:
In a window cleaning system for a motor vehicle, having a dual pump ( 2 ) and having a valve ( 7 ) which is switched by the dual pump ( 2 ), a pressure surge which is generated during the switching of the valve ( 7 ) is conducted into the dual pump ( 2 ). For this purpose, valve seats ( 22, 23 ) are connected to inlets ( 25, 26 ) of the valve ( 7 ). Conducting the pressure surge into the dual pump ( 2 ) prevents that, during the switching of the valve ( 7 ), washer fluid passes onto a window ( 15, 16 ) which is not to be sprayed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application No. 10 2007 052 644.1 filed Nov. 5, 2007, the contents of which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The invention relates to a window cleaning system for windows of a motor vehicle, having a dual pump which can be driven in two rotational directions and having a valve which has a valve body which can be moved between two valve seats, having two washer fluid lines which are connected to the valve and which lead to washer nozzles, with it being selectively possible as a function of the rotational direction of the dual pump for a first window to be sprayed with washer fluid via the one washer nozzle or for a second window to be sprayed with washer fluid via the other washer nozzle. 
       BACKGROUND 
       [0003]    Window cleaning systems of said type are often used in modern-day motor vehicles for independently cleaning two windows, for example a front window and a rear window, or headlamp lenses, and are known from practice. Non-return valves are often arranged directly upstream of the washer nozzles, which non-return valves prevent washer fluid lines which are arranged between the valve and the washer nozzles from running dry. By using the dual pump which can be switched in two rotational directions, it is possible to separately clean different windows using only a single pump and, aside from the valve, without further control means. In the known valve, the valve body is designed as a movable diaphragm and bears against one of the valve seats. If the one side of the diaphragm is acted on with pressure from the dual pump, the diaphragm is moved away from the first valve seat and is pressed against the second valve seat. 
         [0004]    A disadvantage of the known window cleaning system is however that the valve body, during its movement by the dual pump, displaces washer fluid before it is pressed against the second valve seat. Said washer fluid is fed in the form of a surge to the washer nozzle. Said pressure surge has an intensity which is sufficient to spray a splash of the washer fluid onto the window which is presently not to be supplied with washer fluid. 
       SUMMARY 
       [0005]    A window cleaning system of the type specified in the introduction can be refined in such a way as to prevent a splash on the window which is not to be supplied with washer fluid. 
         [0006]    According to an embodiment, a window cleaning system for windows of a motor vehicle, may comprise a dual pump which is operable to be driven in two rotational directions and having a valve which has a valve body which is operable to be moved between two valve seats, and two washer fluid lines which are connected to the valve and which lead to washer nozzles, wherein the window cleaning system is operable depending on a function of the rotational direction of the dual pump to select between a first window to be sprayed with washer fluid via the one washer nozzle and a second window to be sprayed with washer fluid via the other washer nozzle, and wherein an impulse, which is generated during the movement of the valve body within the washer fluid situated in the valve, is directed away from the outlet. 
         [0007]    According to a further embodiment, at least one of the valve seats can be arranged at an inlet which opens out from the dual pump into the valve. According to a further embodiment, the valve body can be arranged on the center of a diaphragm. According to a further embodiment, the inlets of the valve can be arranged so as to taper toward one another and can be directed at the center of the valve body. According to a further embodiment, at least one of the outlets of the valve can be connected to an annular calming duct and the calming duct surrounds the valve seat. According to a further embodiment, the valve body can be guided so as to be movable transversely with respect to the valve seat. According to a further embodiment, the valve seat may be arranged on a tube piece which projects into the valve and which has a closed base, and the valve body annularly surrounds the tube piece. According to a further embodiment, the valve body may tightly surround the tube piece and may be guided so as to be movable between a position in which the valve seat is opened and a position in which the valve seat is covered. According to a further embodiment, the tube piece which projects into the valve may have an encircling ramp as a valve seat. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The invention permits numerous embodiments. To further illustrate its basic principle, a plurality of said embodiments are illustrated in the drawing and are described below. In the drawing: 
           [0009]      FIG. 1  schematically shows a window cleaning system according to an embodiment for a motor vehicle, in partial section, 
           [0010]      FIG. 2  shows a section illustration through a valve for the window cleaning system according to the embodiment of  FIG. 1 , 
           [0011]      FIG. 3  shows a further embodiment of the valve for the window cleaning system according to the embodiment of  FIG. 1 , 
           [0012]      FIG. 4  shows the valve from  FIG. 3  with the valve body moved, 
           [0013]      FIG. 5  shows a further embodiment of the valve for the window cleaning system according to  FIG. 1 , 
           [0014]      FIG. 6  shows the valve from  FIG. 5  with the valve body moved. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    By means of the design according to various embodiments, a pressure impulse which is generated during the switching of the valve is conducted into a point which does not lead directly to the washer nozzle. It is thereby prevented that washer fluid is fed in the form of a surge to the washer nozzle which is presently not to be supplied with washer fluid. According to various embodiments, the generation of a splash on the window which is not to be supplied with washer fluid is thereby prevented. 
         [0016]    According to an embodiment, the pressure surge of washer fluid can be conducted into the inlet of the valve in a simple manner if at least one of the valve seats is arranged at an inlet which opens out from the dual pump into the valve. The valve body, during its movement, thereby presses washer fluid which is present upstream of the valve seat into the inlet and therefore in the direction of the dual pump. 
         [0017]    According to another embodiment, the valve is of particularly simple structural design if the valve body is arranged on the center of a diaphragm. 
         [0018]    An unintended delivery of washer fluid to the washer nozzles can, according to yet another embodiment, be kept particularly low if the inlets of the valve are arranged so as to taper toward one another and are directed at the center of the valve body. 
         [0019]    To further reduce the unintended delivery of washer fluid, according to yet another embodiment, it is conducive if at least one of the outlets of the valve is connected to an annular calming duct and if the calming duct surrounds the valve seat. The washer nozzles are thereby supplied with washer fluid from the calming duct. Pressure surges which are generated in the valve are substantially prevented from propagating in the direction of the washer nozzle as a result of the annular design of the calming duct. 
         [0020]    A pressure surge which is generated by the valve body is, according to another embodiment, reliably conducted past the valve seat if the valve body is guided so as to be movable transversely with respect to the valve seat. By means of said design, a flow of washer fluid generated by the dual pump is cut off by the movement of the valve body, which further reduces possible pressure surges in the washer fluid line which leads to the washer nozzle. 
         [0021]    According to another embodiment, the valve is of particularly simple structural design if the valve seat is arranged on a tube piece which projects into the valve and which has a closed base, and if the valve body annularly surrounds the tube piece. 
         [0022]    According to another embodiment, during the movement of the valve body, the delivery of the washer fluid to the washer nozzle is uniformly throttled if the valve body tightly surrounds the tube piece and is guided so as to be movable between a position in which the valve seat is opened and a position in which the valve seat is covered. 
         [0023]    According to another embodiment, to further reduce an impulse which is directed into the outlet of the valve, it is conducive if the tube piece which projects into the valve has an encircling ramp as a valve seat. 
         [0024]      FIG. 1  shows a window cleaning system for a motor vehicle, having a dual pump  2  which can be driven in two rotational directions by an electric motor  1 . The dual pump  2  has a rotor  3  with guide blades  4  and has two outlet ducts  5 ,  6  at which a valve  7  is arranged. A suction duct  8 , which is arranged centrally with respect to the rotor  3 , of the dual pump  2  is connected to a washer fluid line  10  which leads to a storage tank  9 . The valve  7  has two outlets  11 ,  12  at which in each case one washer nozzle  13 ,  14  is arranged. The washer nozzles  13 ,  14  are arranged in front of different windows  15 ,  16 , for example a front window and a rear window of the motor vehicle. Non-return valves  17 ,  18  are arranged directly upstream of the washer nozzles  13 ,  14 , which non-return valves  17 ,  18  prevent washer fluid lines  19 ,  20 , which connect the washer nozzles  13 ,  14  to the outlets  11 ,  12  of the valve  7 , from running dry. 
         [0025]    The valve  7  has a valve body  21  which is movable between a first valve seat  22  and a second valve seat  23 . In the event of the dual pump  2  being driven such that the rotor  3  rotates counterclockwise, the valve body  21  is pressed firmly against the first valve seat  22  and washer fluid is fed from the storage tank  9  through the second valve seat  23  to the one washer nozzle  14 . If the dual pump  2  is driven in the opposite direction, the valve body  21  is pressed against the second valve seat  23  and washer fluid is fed to the other washer nozzle  13 . 
         [0026]    However, during the movement of the valve body  21  as a result of a change in the rotational direction of the rotor  3  of the dual pump  2 , a pressure surge is generated which, as a result of the design of the valve  7 , is conducted into the dual pump  2 . The valve body  21  of the valve  7  is arranged in the center of a diaphragm  24 . The valve seats  22 ,  23  are arranged on inlets  25 ,  26 , which are connected to the outlet ducts  5 ,  6  of the dual pump  2 , of the valve. Therefore, during the switch of the valve  7  as a result of a change in rotational direction of the dual pump  2 , the greatest movement of the diaphragm  24  takes place at the valve body  21 , such that washer fluid displaced by the diaphragm  24  is conducted to the dual pump  2 . Outlets  11 ,  12 , which are provided for connecting the washer fluid lines  19 ,  20 , of the valve  7  are arranged in each case at annular calming ducts  27 ,  28 . The calming ducts  27 ,  28  surround the valve seats  22 ,  23 . 
         [0027]      FIG. 2  shows a further embodiment of the valve  7  which differs from that of  FIG. 1  in that a valve body  29  bears against a first valve seat  31  as a result of the internal tension of a diaphragm  30 . The valve body  29  is situated opposite a second valve seat  32  with a spacing. The second valve seat  32  is arranged at an inlet  33  which is connected to the dual pump  2 , while the other inlet  34  opens out upstream of the diaphragm  30 . The first valve seat  31  is arranged at a first outlet  35  which leads to a washer nozzle  13 , while the second outlet  36 , as in the valve from  FIG. 1 , is connected to an annular calming duct  37 . The second outlet  36  is preferably connected to a washer nozzle  14  which is arranged in front of the front window, and the first outlet  35  is preferably connected to a washer nozzle  13  which is arranged in front of the rear window of the motor vehicle. 
         [0028]      FIG. 3  shows a further embodiment of the valve  7  having a valve body  38  and a first valve seat  39  and a second valve seat  40 , in which valve  7  a valve body  38  is guided transversely with respect to the second valve seat  40 . The second valve seat  40  is arranged on the wall of a tube piece  41  which projects into the valve  7 . The tube piece  41  has a closed base  42  and is tightly surrounded by the valve body  38 . The valve seats  39 ,  40  are arranged at outlets  43 ,  44  which lead to the washer nozzles  13 ,  14 . During the movement of the valve body  38  as a result of the dual pump  2  from  FIG. 1  being driven, the valve body  38  is pushed over the tube piece  41  and closes off or opens the second valve seat  40 . 
         [0029]      FIG. 4  shows the valve  7  from  FIG. 3  in the position in which the second valve seat  40  is closed off. The left-hand side of the valve  7  is of the same construction as that from  FIG. 2 . The valve  7  may of course also be of symmetrical design. 
         [0030]      FIG. 5  shows a further embodiment of the valve  7  with a movable valve body  45 , a first valve seat  46  and a second valve seat  47 . The valve  7  differs from that from  FIG. 3  in that the second valve seat  47  is arranged on an encircling ramp  48 . The ramp  48  is arranged on a tube piece  49  which projects into the valve  7 . The tube piece  49  has a closed base  50 . The valve body  45  surrounds, with a spacing, that end of the tube piece  49  which projects into the valve  7 . During a movement of the valve body  45  as a result of the change in rotational direction of the dual pump  2 , the free end of the valve body  45  moves against the ramp  48 , as illustrated in  FIG. 6 . Two outlets  51 ,  52  of the valve  7  serve to connect the washer fluid lines  19 ,  20  illustrated in  FIG. 1 . The left-hand side of the valve  7  is of the same construction as that from  FIG. 2 . The valve  7  may of course also be of symmetrical design.