Patent Publication Number: US-7222609-B2

Title: Fuel supply system

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a fuel supply system for supplying an internal combustion engine of a motor vehicle, having two feed means, which are arranged in a fuel tank, for feeding fuel, and having a connecting piece for guiding the fuel fed by the feed means from two inlets, which are each connected to the feed means, to an outlet. 
   Fuel supply systems of this type are used, for example, for motor vehicles having a high power consumption and narrow fuel tanks, in which an individual feed means is frequently insufficient in terms of power, and are known in practice. Furthermore, fuel supply systems of this type are used in what are referred to as saddle tanks, in which the fuel tank has two chambers, with suction jet pumps which feed fuel into one or two baffles additionally being arranged in the individual chambers. The connecting pieces combine a flow from two lines, for example from the feed units, into one fuel line leading to the internal combustion engine or to one or two suction jet pumps. The connecting pieces of the known fuel supply system are conventional T-pieces. 
   A disadvantage of the known fuel supply system is that, for example, if one of two feed means is in operation, fuel may overflow from one of the feed means to the feed means which has been switched off. This results in an unnecessary circulation of the fuel and to energy losses in the feeding of the fuel to the internal combustion engine. In order to avoid this problem, a practical remedy is to use a respective nonreturn valve between the inlets and the feed means. However, this results in a very large structural outlay on the fuel supply system. 
   The invention is based on the problem of developing a fuel supply system of the type mentioned at the beginning in such a manner that an unnecessary overflowing of the fuel via the connecting piece is avoided and that the fuel supply system is constructed in a particularly simple manner. 
   BRIEF DESCRIPTION OF THE INVENTION 
   This problem is solved according to the invention by the connecting piece having a mixer valve and by, when there is a difference in pressure between the inlets, the mixer valve closing the inlet with the low pressure. 
   This design makes it possible for the mixer valve to prevent fuel from being able to overflow from one inlet to the other inlet. In the case of two feed units which are connected to the inlets but only one of which is in operation, fuel can therefore be prevented from overflowing to the feed unit which has been switched off. Furthermore, the fuel supply system according to the invention does not require any additional nonreturn valves in the lines leading from the feed units to the connecting piece. The fuel supply system according to the invention is therefore composed of particularly few components which are to be assembled, and is therefore constructed in a particularly simple manner. Of course, by connecting a plurality of mixer valves one behind another, more than two feed means can be connected to a single outlet for the connection of a single fuel line. According to one advantageous development of the invention, the connection of the fuel flows fed by the feed means is structurally particularly simple if the inlets each have a valve seat, and if between the valve seats a valve body is guided moveably by the pressure in the inlets, and if the distance between the valve seats is greater than the width of the valve body. To avoid periodically occurring pressure fluctuations, the movement of the valve body may of course also be damped. 
   When there is approximately identical pressure in the inlets, the consumer can be supplied with fuel, according to one advantageous development of the invention, via the two feed means if in a central position of the valve body between the valve seats the two inlets are connected to the outlet. This ensures that, when the internal combustion engine requires a large quantity of fuel, both feed units can feed fuel jointly. 
   According to another advantageous development of the invention, a forward flow line leading to the internal combustion engine can be prevented from running dry if a nonreturn valve is arranged between the mixer valve and the outlet. 
   During a supplying of suction jet pumps with fuel, a pipette effect can be avoided, according to another advantageous development of the invention, if a control valve is arranged between the mixer valve and the outlet, which control valve, in the unpressurized state, connects the outlet to an opening leading into the fuel tank and, in the pressurized state, closes the opening. By means of this design, when the feed means are feeding, the opening is closed and fuel flows from the mixer valve of the connecting piece to the outlet and therefore to the suction jet pumps. However, when the feed means are switched off, the control valve prevents fuel from being sucked up via the outlet. 
   The installation of the fuel supply system according to the invention becomes particularly simple if the mixer valve together with the control valve or the nonreturn valve is designed as a structural unit. This makes it possible to preassemble the mixer valve together with the control valve or together with the nonreturn valve outside the fuel tank to form the structural unit and subsequently to insert it with little outlay into the fuel tank. 
   The fuel supply system according to the invention is manufactured particularly cost-effectively if the mixer valve and the control valve or the nonreturn valve have a common housing. 
   The manufacturing costs of the fuel supply system according to the invention are further reduced if the mixer valve and/or the control valve and/or the nonreturn valve have straight channels for receiving the valve body, and if the channels are closed by a closure means. The closure means is preferably designed as a cap or stopper connected to the housing in a form-fitting manner. 
   According to another advantageous development of the invention, the mixer valve becomes structurally particularly simple if one of the valve seats of the mixer valve is arranged in the closure means and the other of the valve seats is arranged in the housing. 
   If the feed means are divided into a basic-load feed means and a peak-load feed means, one of the inlets can easily be closed in the basic position if the valve body of the mixer valve is prestressed into a designated position. 
   According to another advantageous development of the invention, the guiding of the valve body between the two valve seats requires a particularly low outlay if the valve body of the mixer valve is designed as a ball. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention permits numerous embodiments. To further clarify its basic principle, a number of embodiments are illustrated in the drawing and are described below. In the drawing 
       FIG. 1  shows diagrammatically a fuel supply system according to the invention with two feed units, 
       FIG. 2  shows a sectional illustration through a first valve of the fuel supply system from  FIG. 1 , 
       FIG. 3  shows a sectional illustration through a second valve of the fuel supply system from  FIG. 1 , 
       FIG. 4  shows a mixer valve in a further embodiment of the first or second valve from  FIG. 1 , 
       FIG. 5  shows the mixer valve in a further embodiment of the first or second valve from  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a fuel tank  1  for a motor vehicle with a fuel supply system for supplying an internal combustion engine  2  with fuel. The fuel tank  1  is designed as a saddle tank with two chambers  3 ,  3 ′ and has a filler neck  4 . The fuel supply system has two feed units  5 ,  5 ′ each having a baffle  6 ,  6 ′. Directly above the feed units  5 ,  5 ′, the fuel tank  1  has installation flanges  7 ,  7 ′. A forward flow line  8  routed from the feed units  5 ,  5 ′ to the internal combustion engine  2  is guided through one of the installation flanges  7 ′. The system here is what is referred to as a fuel supply system without a return flow, in which fuel which is not consumed by the internal combustion engine  2  is not returned to the fuel tank  1 . 
   The feed units  5 ,  5 ′ are in each case electrically driven and in each case have a preliminary stage  9  and a main stage  10 . The main stages  10  feed fuel from the baffles  6 ,  6 ′ via a first connecting piece  11  to the internal combustion engine  2 . The preliminary stages  9  feed fuel from the baffles  6 ,  6 ′ via a second connecting piece  12  to suction jet pumps  13 ,  13 ′ arranged in the chambers  3 ,  3 ′. The suction jet pumps  13 ,  13 ′ are thereby supplied with fuel as motive agent and feed fuel from the chambers  3 ,  3 ′ into the baffles  6 ,  6 ′. Furthermore, the baffles  6 ,  6 ′ each have a bottom valve  14  via which fuel flows from the fuel tank  1  into the baffles  3 ,  3 ′. Filters  15  of the main stages  10  are arranged in the baffles  6 ,  6 ′. The feed units  5 ,  5 ′ can be operated individually or together in accordance with the requirements of the internal combustion engine  2 . If the internal combustion engine  2  requires a low amount of fuel, one of the feed units  5 ,  5 ′ is therefore switched off. 
     FIG. 2  shows the first connecting piece  11  of the fuel supply system from  FIG. 1  in a sectional illustration. It can be seen here that the connecting piece  11  has two inlets  16 ,  16 ′ which are each connected to the main stages  10  of the feed units  5 ,  5 ′ from  FIG. 1 . Furthermore, the connecting piece  11  has an outlet  17  to which the forward flow line  8 , which is illustrated in  FIG. 1  and leads to the internal combustion engine  2 , can be connected. The connecting piece  11  has a nonreturn valve  18  and a mixer valve  19 . The nonreturn valve  18  has a valve body  22  which is prestressed against a valve seat  21  by a spring element  20 . If neither of the feed units  5 ,  5 ′ illustrated in  FIG. 1  is feeding fuel, the spring element  20  presses the valve body  22  against the valve seat  21  and closes the outlet  17 . This prevents the forward flow line  8  from running dry. If at least one of the feed units  5 ,  5 ′ is feeding, the valve body  22  of the nonreturn valve  18  is pressed away from the valve seat  21  and fuel flows to the outlet  17  of the first connecting piece  11  and therefore into the forward flow line  8 . The mixer valve  19  has a valve body  24  which is guided moveably between two valve seats  23 ,  23 ′ and is designed as a ball. If only one of the feed units  5 ,  5 ′ from  FIG. 1  is feeding, the valve body  24  is pressed against one of the valve seats  23 ,  23 ′ and therefore closes the inlet  16 ,  16 ′ of the other feed unit  5 ,  5 ′. This prevents fuel which is fed by the one feed unit  5 ,  5 ′ from being fed back into the fuel tank  1  by the other feed unit  5 ,  5 ′ which has been switched off. If both feed units  5 ,  5 ′ illustrated in  FIG. 1  are feeding fuel, the pressure at the valve body  24  of the mixer valve  19  is in equilibrium, as a result of which the valve body  24 , as illustrated in  FIG. 2 , is held between the valve seats  23 ,  23 ′. Neither of the inlets  16 ,  16 ′ is therefore blocked, and both feed units  5 ,  5 ′ feed fuel through the nonreturn valve  18  to the outlet  17  leading to the internal combustion engine  2 . The first connecting piece  11  has a common housing  25  for the mixer valve  19  and the nonreturn valve  18 . The mixer valve  19  and the nonreturn valve  18  are in each case tightly closed by a cap  26 ,  27 . 
     FIG. 3  shows the second connecting piece  12  of the fuel supply system from  FIG. 1 , with two inlets  28 ,  28 ′ for connecting the preliminary stages  9  of the feed units  5 ,  5 ′ from  FIG. 1  and an outlet  29  to which the two suction jet pumps  13 ,  13 ′ can be connected. The second connecting piece  12  has a mixer valve  30  which is constructed in the manner of the mixer valve  19  of the first valve  11  from  FIG. 2 . Furthermore, the second connecting piece  12  has behind the mixer valve  30 , as seen in the direction of flow, a control valve  31  with a valve body  33  which is kept away from a valve seat  32  by gravity. As seen from the valve body  33 , the control valve  31  has behind the valve seat  32  an opening  34  leading into the fuel tank  1 . When at least one of the feed units  5 ,  5 ′ of the fuel supply system from  FIG. 1  is feeding, the valve body  33  is pressed against the valve seat  32  and closes the opening  34 . Fuel is therefore fed via the outlet  29  to the suction jet pumps  13 ,  13 ′ illustrated in  FIG. 1 . If both feed units  5 ,  5 ′ are switched off, the valve body  33  of the control valve  31  is pressed by gravity from the valve seat  32  into the position illustrated. The outlet  29  is thereby connected to the opening  34  leading into the fuel tank  1 . Air therefore passes into the lines leading to the suction jet pumps  13 ,  13 ′. A pipette effect which would lead to fuel being sucked up by the preliminary stages  9  of the feed units  5 ,  5 ′ is therefore prevented. 
     FIG. 4  shows a further embodiment of the mixer valve  19 ,  30  of the first or second connecting piece  11 ,  12  which differs from that from  FIGS. 2 and 3  only by the fact that a valve body  35  guided between two valve seats  36 ,  36 ′ is of disk-shaped design. Furthermore, in an embodiment which is not illustrated, the valve body  35  may also be prestressed by a spring element into the central position, for example. If the feed units  5 ,  5 ′ from  FIG. 1  are divided into a basic-load feed unit  5 ,  5 ′ and a peak-load feed unit  5 ,  5 ′, the valve body  33  can alternatively also be prestressed against the valve seat  36 ,  36 ′ leading to the peak-load feed unit  5 ,  5 ′. An inlet  37 ,  37 ′ leading to the peak-load feed unit  5 ,  5 ′ is therefore always closed if the internal combustion engine  2  from  FIG. 1  does not require an increased amount of fuel. 
     FIG. 5  shows a further embodiment of the mixer valve  19 ,  30  for the first or second valve  11 ,  12  from  FIG. 1 , with two inlets  38 ,  38 ′, in which a channel  39  leading to the control valve  31  from  FIG. 3  or to the nonreturn valve  18  from  FIG. 2  is guided under one of the inlets  38 . As in the embodiments of the mixer valve  19 ,  30  from  FIGS. 2 and 3 , a valve body  40  is guided moveably between two valve seats  41 ,  41 ′.