Abstract:
A fuel tank valve for connection to a degassing circuit ( 15 ), the valve comprising a moving closure member and means ( 11 ) capable of being controlled from outside the tank ( 2 ) to act on the closure member ( 10 ) to bring it into a predetermined position when the vehicle is in a predetermined state, the valve being characterized by the fact that the closure member is suitable for rising by floating on the surface of the fuel.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a valve for a motor vehicle fuel tank for connection to a degassing circuit through which air and fuel vapor contained in the tank escape while the tank is being filled. 
     The degassing circuit communicates with the atmosphere via an activated carbon filter, also known as a “cannister”, for the purpose of preventing fuel vapor being dumped into the atmosphere. 
     The valve needs to be opened while the tank is being filled so as to avoid impeding the flow of air and fuel vapor to the degassing circuit. 
     Nevertheless, it is desirable to prevent droplets of fuel being entrained into the degassing circuit while the vehicle is running since they might reach the activated carbon filter which would rapidly become saturated and thus lose its effectiveness. 
     German patent application DE-195 09 889 describes a motor vehicle tank degassing device for controlling the passage of fuel vapor to a cannister, the valve including a magnetizable element that can be moved under magnetic drive to open or to close the passage to the canister. 
     German patent application DE-40 12 368 describes a degassing device having a moving magnetizable element suitable for closing the passage to a cannister, with movement of the disk being controlled by means of an electromagnet and a spring. 
     Each of those two devices also includes a respective floating body that is separate from the magnetizable element and suitable for rising when the level of fuel in the tank rises, thereby closing the passage to the cannister at the end of tank filling. 
     The above-mentioned devices are relatively complex in structure, and in particular they comprise large numbers of parts. 
     SUMMARY OF THE INVENTION 
     A particular object of the present invention is to propose a novel valve which is capable firstly of providing effective ventilation of the tank while it is being filled and secondly of reducing the risk of liquid fuel reaching the degassing circuit while the vehicle is running. 
     Another object of the invention is to simplify the structure of the valve, in particular by reducing the number of its component parts. 
     The invention achieves this by the fact that the valve has a moving closure member and means that can be controlled from outside the tank to act on said closure member and bring it into a predetermined position when the vehicle is in a predetermined state, e.g. into a position in which the valve is completely or partially closed while the engine is running, the closure member being suitable for rising by floating on the surface of the fuel. 
     Advantageously, the means for acting on the closure member bring it into the open position while the tank is being filled. 
     The closure member can thus have a float function solely while the tank is being filled and the valve is open. 
     The means for acting on the closure member can advantageously include a coil that is excited by an electric current to exert an electromagnetic force on the closure member, the closure member then being magnetizable. 
     The coil can be excited electrically at the beginning of filling so as to create a magnetic field tending to cancel the effects of a permanent magnet. 
     Advantageously, in the absence of electrical excitation of the coil, the permanent magnet is suitable for holding the closure member in a high position for closing the valve. 
     In a particular embodiment, the closure member has a magnetizable metal part on top, e.g. a magnetizable metal ring, and the valve has a coil wound around a permanent magnet such that when the closure member is in the valve-closing position, the metal part is attracted by the permanent magnet sufficiently to hold the closure member in the closed position even though the coil is carrying no current. 
     The magnetic attraction of the metal part of the closure member to the permanent magnet can be interrupted when the coil is powered in such a manner as to create a magnetic field opposite to that of the permanent magnet, the closure member then returning under gravity to its open position. 
     The excitation of the coil which enables a magnetic field to be created that tends to cancel the effects of the permanent magnet at the time of filling can advantageously be caused to come into operation by removal of the filler cap from the tank. 
     In another implementation of the invention, the means for acting on the closure member make use of the energy of a fuel pump, which pump is advantageously the same as the pump used for delivering fuel to the injectors of the engine. 
     When the engine is running, the fuel pump delivers fuel at relatively high pressure and the energy thereof is advantageously used for bringing the closure member into the closed position. 
     When the engine is switched off, this energy ceases to be supplied and the closure member can return to an open position. 
     The valve can include a nozzle squirting a jet of fuel beneath the closure member, said jet tending to bring it into a valve closure position where it closes access to the degassing circuit. 
     In a variant, the means for acting on the closure member can comprise a diaphragm suitable for inflating under the effect of fuel being delivered under pressure. 
     In a preferred embodiment, the closure member is suitable for closing the degassing circuit in the event of the vehicle accidentally rolling over. 
     The invention also provides a motor vehicle fuel tank fitted with a valve as specified above. 
     Other characteristics and advantages of the present invention will appear on reading the following detailed description of three non-limiting embodiments of the invention, and on examining the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic view of a valve constituting a first embodiment of the invention, while the vehicle is at rest; 
     FIG. 2 shows the FIG. 1 valve while the engine is running; 
     FIG. 3 is a view on section line III—III of FIG. 2; 
     FIG. 4 is a diagrammatic view of a valve constituting a second embodiment of the invention, while the vehicle is at rest; 
     FIG. 5 shows the FIG. 4 valve while the engine is running; 
     FIG. 6 is a diagrammatic view of a valve forming a third embodiment of the invention, while the vehicle is at rest; 
     FIG. 7 shows the FIG. 6 valve while the engine is running; and 
     FIG. 8 is a highly diagrammatic fragmentary view of the permanent magnet and the coil of the valve of FIGS.  6  and  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 show a valve  1  constituting a first embodiment of the invention. 
     The valve  1  is fitted to a fuel tank  2  which is shown in part only in order to clarify the drawing. 
     A pump  3  shown highly diagrammatically is provided to take fuel from the tank  2  and deliver it to the injectors  7  of the vehicle engine. 
     A regulator  5  is connected to the pump  3  and to the injectors  7  via respective ducts  4  and  6 . 
     The regulator  5  returns the fuel that is not consumed by the injector  7  to the pump  3  via a duct  8 . 
     The pump  3  together with the regulator  5  and the ducts  4  and  8  constitutes a unit which is inserted as a single piece in the tank  2 , and this is represented by dashed lines in FIGS. 1 and 2. 
     The substantially tubular body of the valve  1  defines a housing  9  that is elongate on an axis X, and a closure member  10  is movable therein along said axis. 
     When the vehicle is at rest on a horizontal surface, the axis X is substantially vertical. 
     The closure member  10  is slidably guided by the side wall  27  of the body of the valve  1  by means of guide ribs that are not shown in the drawing. 
     These ribs co-operate with one another and with the side wall  27  to leave axial passages  29 . 
     A nozzle  11  centered on the axis X opens out substantially in the base of the housing  9  so as to squirt liquid fuel under pressure beneath the closure member  10 , which fuel is taken from the duct  8 . 
     The nozzle  11  can be integrally molded with the bottom wall of the body of the valve  1  or it can be implemented by fitting a separate piece. 
     The pipe connecting the nozzle  11  to the duct  8  is referenced  12  in the drawing. 
     The housing  9  communicates with the inside of the tank  2  via openings  13  made through the bottom wall of the body of the valve  1 , all around the nozzle  11 . 
     Supports  14  are formed level with the outlet orifice of the nozzle  11  to act as a seat for the closure member  10  in the absence of a fuel jet being emitted by the nozzle, as can be seen in FIG.  1 . 
     These supports  14  leave gaps  19  between one another, as can be seen in FIG.  3 . 
     A duct  15  of a conventional degassing circuit (not shown) penetrates in leakproof manner into the tank  2 . 
     This duct  15  communicates with the housing  9  via an orifice  16  centered on the axis X and made in the top wall of the body of the valve  1 . 
     When the vehicle engine is at rest, the pump  3  is not in operation and no jet of fuel leaves the nozzle  11 . 
     The closure member  10  then rests via its bottom face  17  on the supports  14 . 
     Air and fuel vapor present inside the tank can then leave the tank so as to be replaced by liquid fuel during filling, the air and vapor penetrating into the housing  9  of the valve  1  via the openings  13 , passing through the gaps  19 , and then traveling along the closure member  10  in the axial passages  29  and escaping via the duct  15 , which is represented in FIG. 1 by the arrows. 
     It will be observed that when the closure member  10  is resting on the supports  14 , the orifice  16  is thoroughly disengaged thus allowing gas to flow through the valve  1  at a relatively high rate without excessive head loss. 
     By way of example, the section of the orifice  16  can lie in the range 1.5 square centimeters (cm 2 ) to 2.5 cm 2 , thus enabling air to flow through the valve  1  at a rate of 6000 liters per minute (l/min) with head loss of less than 10 mbar. 
     At the end of filling, the closure member  10  can rise by floating on the surface of the fuel, thereby closing the orifice  16  and causing the filler nozzle to trip. 
     When the engine is running, the pump  3  feeds the duct  4  with fuel under pressure. 
     The regulator  5  sends a fraction to the injectors  7  and the fraction which is not consumed thereby is returned to the tank  2  via the duct  8 . 
     At least a fraction of the fuel under pressure traveling in the duct  8  leaves via the nozzle  11  to form an upwardly directed jet  18  of fuel on the axis X, which jet strikes the bottom face  17  of the closure member  10  and lifts it, as shown in FIG.  2 . 
     It will be observed that the bottom face  17  of the closure member  10  is in the form of a spherical cap so as to increase the lift effect of the fuel jet  18  delivered by the nozzle  11 . 
     The force of the jet  18  is sufficient to press the closure member  10  against the edge of the orifice  16  so as to close it. 
     The duct  15  is thus isolated from the inside of the tank  2  so any droplets of fuel that may be splashed by waves of fuel sloshing in the tank while the vehicle is running are prevented from penetrating into the degassing circuit. 
     The fuel squirted against the bottom face  17  of the closure member  10  returns to the tank through the gaps  19  and the openings  13 , as represented by arrows in FIG.  2 . 
     In the event of the tank being accidentally turned upside-down, the closure member  10  closes the orifice  16  under the effect of its own weight. 
     It will be understood that the invention makes it possible to act on the closure member  10  from outside the tank  2  by switching the pump  3  on and off. This ensures that a force is applied to the closure member only when the engine is running. 
     This result can be achieved by other means without going beyond the ambit of the invention, and another embodiment of the invention is described below with reference to FIGS. 4 and 5. 
     In these figures, the same reference numerals are used as in FIGS. 1 and 3 to designate the same component parts, and they are not described again. 
     The valve  20  shown in FIGS. 4 and 5 differs from the above-described valve  1  essentially by the means which are used for raising the closure member which is referenced  21 . 
     In this case, the closure member  21  is in the form of a cylinder having a hollow interior over a fraction of its height from its bottom face, and having portions in relief  22  on the outside. 
     When the vehicle is at rest, these portions in relief  22  rest on supports  23  that project into the housing  9 , and that leave gaps between one another like the above-described supports  14 . 
     The valve  20  makes use of the pressure of the fuel in the duct  8 , but the nozzle  11  of the above embodiment is replaced by a bag  26  whose top wall is constituted by a diaphragm  24  of deformable material. 
     The inside of the bag  26  communicates with the pipe  12  such that the diaphragm  24  tends to inflate under the pressure of the fuel returned via the duct  8  by the regulator  5  while the engine is running, as shown in FIG.  5 . 
     The bag  26  also co-operates with the side wall  27  of the valve  20  to leave passages (not shown) enabling fuel vapor and air that penetrates via the openings  13  to reach the top portion of the valve  20  by flowing along passages that exist between the side wall  27  of the body of the valve  20  and the closure member  21 . 
     The diaphragm  24  serves to modify the position of the closure member as a function of the state of the vehicle, i.e. in the example described as a function of whether or not the engine is running. 
     Openings  40  are made in the side wall  27 . 
     When the engine is at rest, the closure member  21  has its bottom face  28  resting on the diaphragm  24  which is then plane and the portions in relief  22  bear against the supports  23 . 
     The air and the fuel vapor present inside the tank can reach the inside of the valve  20  via the openings  13  and  40 , pass along the passages that exist between the side wall  27  of the body of the valve  20  and the bag  26  and then the passages between the closure member  21  and the side wall  27  so as to end up by reaching the duct  15 , as represented by arrows in FIG.  4 . 
     It will be observed in this figure that the closure member  21  is far enough away from the orifice  16  at the beginning of filling to enable the tank to be ventilated effectively until the end of tank filling, as in the embodiment described above. 
     When the diaphragm  24  inflates under the effect of the pressure of the fuel contained in the duct  8 , as shown in FIG. 5, the closure member  21  is pressed by the diaphragm  24  against the edge of the orifice  16  so as to close off access to the duct  15 . 
     Two embodiments are described above with reference to FIGS. 1 to  5  in which the energy that enables the closure member to be held in its high, closing position when the engine is running comes from the pressure in the return circuit of the pump  3 . 
     Naturally, it would not go beyond the ambit of the present invention to use the pressure in the go circuit  4  of the pump  3 . 
     FIGS. 6 and 7 show a valve  30  constituting a third embodiment of the invention. 
     The valve  30  differs from the above-described valves  1  and  20  by the fact that electromagnetic means are implemented to bring the closure member into its position for closing the valve. 
     The valve  30  comprises a substantially tubular body  31  defining a housing  32  with the degassing duct  15  opening out into the top thereof via an orifice  16 , like the embodiments described above. 
     The closure member that moves inside the body  31  is given reference  33  in this case. 
     The body  31  has openings  34  in its bottom portion and where appropriate in its side wall to allow the air contained in the tank to escape to the degassing duct when the valve is open. 
     At its top, the closure member  33  includes a magnetizable part constituted by a metal ring  36 . 
     An assembly  37  constituted by a permanent magnet  37   a  with a coil  37   b  wound around it is fixed to the top portion of the body  31 , as can be seen in FIGS. 6 to  8 . 
     In the absence of electrical excitation of the coil, the permanent magnet  37   a  is capable of holding the ring  36  by magnetic attraction and consequently of holding the closure member  33  in its high position where it closes the valve. 
     The coil  37   b  can be excited to create a magnetic field opposite to that created by the permanent magnet  37   a,  thereby causing the metal ring  36  to cease to be attracted by the assembly  37  so that the closure member  33  then falls under gravity to its low, open position. 
     The coil  37   b  of the assembly  37  is connected by an electric cable  38  to a source of electricity situated outside the tank, e.g. the vehicle battery, via a switch and a pulse control device (not shown). 
     The switch can be operated by taking the cap off the tank when filling, thereby exciting the coil  37   b  of the assembly  37 . 
     The length of time the coil  37   b  remains excited after the cap has been taken off the tank is controlled by the pulse control device and it can be relatively short, e.g. equal to 5 seconds. 
     All that is required is that this duration should enable the closure member  33  to separate from the permanent magnet  37   a.    
     Once the closure member  33  has dropped into its low, open position, before the cap is put back into place, and after the excitation current to the coil  37  has been stopped, the permanent magnet  37   a  again creates an attractive magnetic field. 
     As the closure member  33  rises due to filling, it reaches a point where it comes close enough to the permanent magnet  37   a  to be attracted by the magnet into its high, closed position. 
     Because the coil is excited during a brief period only, its electricity consumption is relatively modest and does not give rise to any heating that could be prejudicial to the safety of the assembly. 
     Naturally, the invention is not limited to the embodiments described above. 
     In particular, springs can be added to the valves as described above in order to compensate for a fraction of the weight of the closure members. 
     Such springs are useful for ensuring that the degassing duct is closed in the event of the vehicle rolling onto its side.