Abstract:
A ventilation device ( 1 ) for a fuel container ( 2 ) with a liquid trap ( 3 ) and a suction jet pump ( 8 ) which is provided for emptying the liquid trap ( 3 ) has a filling-level limit switch ( 11 ) for detecting the filling level of fuel in the liquid trap ( 3 ). A valve ( 10 ) which is connected to the filling-level limit switch ( 11 ) is connected upstream of the suction jet pump ( 8 ). The suction jet pump ( 8 ) is first activated by means of the valve ( 10 ) when the intended filling level of fuel in the liquid trap ( 3 ) is exceeded.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. national stage application of International Application No. PCT/EP2006/066142 filed Sep. 7, 2006, which designates the United States of America, and claims priority to German application number 10 2005 043 888.1 filed Sep. 14, 2005, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a ventilation device for a fuel container, with a liquid trap connected to at least one ventilation line and with a suction jet pump, arranged in the liquid trap, for the conveyance of fuel out of the liquid trap into the fuel container. 
       BACKGROUND 
       [0003]    Such ventilation devices are often used for ventilating the fuel container during refueling and during operation and are therefore known. Mostly, in present-day ventilation devices, ventilation lines lead from a bubbling container designed as a liquid trap to various sides of the fuel container and, if appropriate, to an activated charcoal filter. The suction jet pump is connected to a fuel pump arranged in the fuel container and sucks away fuel accumulated in the liquid trap and conveys it back into the fuel container. However, the constant connection of the suction jet pump to the fuel pump means that, even when the liquid trap is empty, the suction jet pump is in operation and fuel is conveyed unnecessarily through the suction jet pump. This contributes to a disturbing formation of foam in the fuel container and to an unnecessary energy consumption of the fuel pump. 
       SUMMARY 
       [0004]    A ventilation device of the type initially mentioned may be configured such that it avoids an unnecessary energy consumption for the suction jet pump and an unnecessary formation of foam in the fuel container. According to an embodiment, a ventilation device for a fuel container, may comprise a liquid trap connected to at least one ventilation line, a suction jet pump, arranged in the liquid trap, for the conveyance of fuel out of the liquid trap into the fuel container, and a valve connected to the suction jet pump, wherein the valve is switched as a function of the filling level of fuel in the liquid trap. 
         [0005]    According to a further embodiment, a filling-level limit switch for switching the valve can be arranged in the liquid trap. According to a further embodiment, the filling-level limit switch may have a float. According to a further embodiment, the valve may be switched electrically. According to a further embodiment, the valve may have an electric actuator and a valve body movable against a valve seat is connected to the actuator. According to a further embodiment, the electric actuator may have an electromagnet or a piezo-element. According to a further embodiment, the filling-level limit switch may have an electrical contact. According to a further embodiment, the electrical contact of the filling-level limit switch may be arranged in series with the electric actuator of the valve. According to a further embodiment, the electrical contact of the filling-level limit switch and the electric actuator of the valve may be connected to a common electronic control unit. According to a further embodiment, a baffle provided for mounting in the fuel container may have an electromotive fuel pump, a conveying line of the fuel pump is connected to the suction jet pump, and the baffle may form with the liquid trap a structural unit. According to a further embodiment, the valve body of the valve can be guided movably toward a nozzle of the suction jet pump. According to a further embodiment, the valve can be arranged in the conveying line. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]    The invention permits numerous embodiments. To make its basic principal even clearer, one of these is illustrated in the drawing and is described below. In the drawing: 
           [0007]      FIG. 1  shows diagrammatically a first embodiment of the ventilation device, 
           [0008]      FIG. 2  shows diagrammatically a further embodiment of the ventilation device with an electronic control unit, 
           [0009]      FIGS. 3 ,  4  show two embodiments of a valve of the ventilation device from  FIG. 1  or  2  with a piezo-element, 
           [0010]      FIGS. 5 ,  6  show two embodiments of the valve of the ventilation device from  FIG. 1  or  2  with an electromagnet, 
           [0011]      FIGS. 7 ,  8  show two embodiments of a completely mechanical valve of the ventilation device. 
       
    
    
     DETAILED DESCRIPTION  
       [0012]    According to various embodiments, the suction jet pump may be connected to a valve, and the valve can be switched as a function of the filling level of fuel in the liquid trap. 
         [0013]    By virtue of this configuration, the suction jet pump can be switched off via the valve when no fuel has accumulated in the liquid trap. Only above a filling level provided can the valve be opened and the suction jet pump be supplied with fuel. It is thereby possible in a particularly simple way to avoid the situation where the suction jet pump is kept in operation when the liquid trap is empty. According to various embodiments, switching off the suction jet pump when the liquid trap is empty prevents an unnecessary energy consumption and an unnecessary formation of foam in the fuel container. 
         [0014]    As a rule, it is sufficient to carry out the sucking away of the fuel from the liquid trap only when a filling level provided is reached. In this case, the ventilation device according to an embodiment has a particularly simple structural configuration when a filling-level limit switch for switching the valve is arranged in the liquid trap. 
         [0015]    According to another embodiment, the filling-level limit switch has a particularly simple structural configuration when the filling-level limit switch has a float. 
         [0016]    The control of the valve could, for example, take place completely mechanically, in that a valve body movable against a valve seat is connected to the float. However, according to another embodiment, the suction jet pump can be activated particularly reliably when the valve is switched electrically. 
         [0017]    The valve can be manufactured particularly cost-effectively when the valve has an electric actuator and a valve body movable against a valve seat is connected to the actuator. 
         [0018]    The electrically switched valve has a particularly simple structural configuration when the electric actuator has an electromagnet or a piezo-element. 
         [0019]    According to another embodiment, the control of the electrically switched valve is particularly simple when the filling-level limit switch has an electrical contact. The electrical contact can open and close as a function of the filling level in the liquid trap. 
         [0020]    According to another embodiment, the control outlay for switching the valve can be kept particularly low when the electrical contact to the filling-level limit switch is arranged in series with the electric actuator of the valve. 
         [0021]    The ventilation device according to an embodiment allows a particularly versatile activation of the valve when the electrical contact to the filling-level limit switch and the electric actuator of the valve are connected to a common electronic control unit. In this case, for example, the activation of the valve may be absent at particularly low temperatures or when the internal combustion engine of the motor vehicle is started. In these cases, mostly, the entire fuel conveyed by the fuel pump is required for the internal combustion engine. The closing of the valve, which is possible by means of the electronic control unit, consequently prevents the situation where fuel is branched off to the suction jet pump of the liquid trap at low temperatures or when the internal combustion engine is started. 
         [0022]    The mounting of the ventilation device according to an embodiment is particularly simple when a baffle provided for mounting in the fuel container has an electromotive fuel pump, when a conveying line of the fuel pump is connected to the suction jet pump, and when the baffle forms with the liquid trap a structural unit. Preferably, the baffle is fastened to the liquid trap. 
         [0023]    According to another embodiment, the valve and the suction jet pump can be assembled to form a particularly compact unit when the valve body of the valve is guided movably toward a nozzle of the suction jet pump. It thereby becomes possible for the valve to close or open the suction jet pump directly. 
         [0024]    According to another embodiment, a disturbance in the conveyance of the suction jet pump by the valve body arranged near the nozzle can be avoided in a simple way when the valve is arranged in the conveying line. 
         [0025]      FIG. 1  shows a ventilation device  1  for a fuel container  2  of a motor vehicle, with a liquid trap  3  arranged in the upper region. Ventilation lines  4  lead from the liquid trap  3  to lateral regions of the fuel container  2 . Furthermore, a baffle  5  with an electromotive fuel pump  6  is arranged on the bottom of the fuel container  2 . The fuel pump  6  sucks in fuel from the baffle  5  and conveys it via a forward-flow line  7  to an internal combustion engine, not illustrated, of the motor vehicle. Arranged in the liquid trap  3  is a suction jet pump  8  which is connected via a conveying line  9  to the forward-flow line  7  of the fuel pump  6 . Arranged in the conveying line  9  is an electrically switchable valve  10  which is connected via an electrical line  12  to a liquid-level limit switch  11  arranged in the liquid trap  3 . The filling-level limit switch  11 , the electrically switchable valve  10  and the fuel pump  6  are likewise connected via electrical lines  13 ,  14  to a power supply  15  of the motor vehicle. The filling-level limit switch  11  has an electrical contact  17  switchable by a float  16 . 
         [0026]    When a fuel filling level provided is overshot in the liquid trap  3 , the float  16  is deflected and closes the electrical contact  17  of the filling-level limit switch  11 . Consequently, the electrically switchable valve  10  is connected to the power supply  15 , opens and releases the conveying line  9 . The fuel pump  6  consequently conveys fuel as a propellant to the suction jet pump  8 . The suction jet pump  8  subsequently sucks in accumulated fuel from the liquid trap  3  and conveys it via a discharge line  18  into the fuel container  2 . Conversely, below the fuel filling level provided in the liquid trap  3 , the electrically switchable valve  10  is not connected to the power supply  15 , so that the suction jet pump  8  receives no fuel as a propellant and the entire fuel conveyed by the fuel pump  6  enters the forward-flow line  7 . 
         [0027]      FIG. 2  shows a further embodiment of the ventilation device  1  which differs from that of  FIG. 1  only in that the filling-level limit switch  11  arranged in the liquid trap  3  and the electrically switchable valve  10  are connected in each case to an electronic control unit  19 . The electronic control unit  19  activates the electronically switchable valve  10 , as described with regard to  FIG. 1 . Furthermore, with an appropriate control program, the electronic control unit  19  can, for example, prevent an opening of the valve  10  when, in operating states provided, the entire fuel conveyed by the fuel pump  6  is to be conveyed into the forward-flow line  7 . Such operating states prevail, for example, when the internal combustion engine is started and at low temperatures. A time-controlled opening of the valve  10  is likewise possible, thus ensuring that the liquid trap  3  is emptied reliably whenever the valve  10  is switched. 
         [0028]      FIGS. 1 and 2  illustrate diagrammatically the valve  10  outside the liquid trap  3 . The valve  10  may, of course, also be arranged inside the liquid trap  3  and form with the suction jet pump  8  and/or the filling-level limit switch  11  a structural unit. In the case of a purely mechanical activation of the valve  10 , moreover, in an alternative embodiment, not illustrated, no electrical lines  12 ,  14  for connecting the valve  10  and the filling-level limit switch  11  to the power supply  15  are required. 
         [0029]      FIG. 3  shows a structural unit consisting of a nozzle  20  of the section jet pump  8  and of the electrically switchable valve  10 . The electrically switchable valve  10  has an actuator  21  with a piezo-element  22 . When current is applied to the piezo-element  22 , a valve body  23  is moved away from the nozzle  20  of the section jet pump  8  and releases the connection of the suction jet pump  8  to the conveying line  9 . Electrical contacts  24  serve for connecting the actuator  21  to the electrical lines  12  illustrated in  FIGS. 1 and 2 . 
         [0030]      FIG. 4  shows a further embodiment of the structural unit consisting of a nozzle  20  of the suction jet pump  8  with the electrically switchable valve  10 . As in the embodiment according to  FIG. 3 , the valve  10  has an actuator  25  with a piezo-element  26 . The piezo-element  26  controls the movement of the valve body  23  via a lever  27 . 
         [0031]      FIG. 5  shows a further embodiment of the structural unit consisting of a nozzle  20  of the suction jet pump  8  with the electrically switchable valve  10 . In contrast to the embodiments according to  FIGS. 3 and 4 , the valve  10  has an actuator  28  with an electromagnet  29 . The electromagnet  29  moves a magnet  30  connected to the valve body  23 . When current is applied appropriately, therefore, the valve body  23  is moved toward the nozzle  20  of the suction jet pump  8  or away from this. 
         [0032]      FIG. 6  shows a further embodiment of the structural unit consisting of a nozzle  20  of the suction jet pump  8  with the electrically switchable valve  10 , in which the valve  10  has an actuator  31  with an electromagnet  32 . When current is applied appropriately, a closing cylinder  33  with a magnet  34  can be moved into the conveying line  9  and consequently interrupt the conveyance of fuel to the nozzle  20  of the suction jet pump  8 . 
         [0033]      FIG. 7  shows a further embodiment of the ventilation device  1 , in which the valve  10  is arranged in the conveying line  9  leading to the suction jet pump  8  and forms a structural unit with a filling-level limit switch  11 . In contrast to the preceding embodiments, the valve  10  is connected to the float  16  and consequently has a purely mechanical function. The float  16  carries a magnet  35  which is mounted so as to be movable toward a wall of the conveying line  9 . The valve  10  has a closing cylinder  36  guided longitudinally movably and having a magnet  37 . When the float  16  lies on the wall, the closing cylinder  36  is pulled up and closes the conveying line  9 . The position of the float  16  lying on the wall of the conveying line  9  is illustrated by dashes and dots in  FIG. 7 . Of course, that portion of the conveying line  9  which has the filling-level limit switch  11  must be arranged at the location provided in the liquid trap  3  illustrated in  FIGS. 1 and 2 . 
         [0034]      FIG. 8  shows a further embodiment of the ventilation device  1 , in which the valve  10  forms a structural unit with the nozzle  20  of the suction jet pump  8  and with the filling-level limit switch  11 . The float  16  of the filling-level limit switch  11  is connected via a lever  38  to the valve body  23  movable longitudinally displaceably toward the nozzle  20 . As in the embodiment according to  FIG. 7 , hereto, the float  16  and the valve  10  must be arranged inside the liquid trap  3 .