Patent Publication Number: US-7213575-B2

Title: Fuel manifold in thixotropic aluminum for the direct injection of fuel into an internal combustion engine

Description:
The present invention relates to a fuel manifold for the direct injection of fuel into an internal combustion engine. 
     The present invention can be used particularly advantageously for the production of a fuel manifold for the direct injection of fuel into a fuel-driven internal combustion engine to which the following description will explicitly refer without going into detail. 
     BACKGROUND OF THE INVENTION 
     In recent years, fuel-driven internal combustion engines, in which the fuel is injected directly into the cylinders, have come to the fore; in these engines, the fuel is supplied under pressure to a fuel manifold connected to a series of injectors (one for each cylinder of the engine), which are actuated cyclically to inject part of the fuel under pressure in the fuel manifold into a respective cylinder. 
     In known engines with indirect fuel injection, the fuel manifolds are currently made from plastic material (typically moulded technopolymers) and are secured to the intake manifold, which is also generally made from plastic material, by means of a series of screws. Plastic material is easy to process and extremely economic, but does not have good mechanical properties and is not therefore able to bear the relatively high pressures of the fuel used in direct fuel injection with the necessary safety margins. 
     In order to ensure the necessary mechanical strength, it has been proposed to use fuel manifolds made from steel in known direct fuel injection engines; these fuel manifolds are nevertheless costly because of the number of machining and welding operations to which they have to be subject. It has also been proposed to use fuel manifolds made from cast aluminum by means of gravity die casting; these fuel manifolds are also costly as gravity die casting is a relatively slow production method, requires a large number of machining operations once the component has been removed from the casting mould and imposes minimum component thicknesses of no less than 4–5 mm. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a fuel manifold for the direct injection of fuel into an internal combustion engine which is free from the drawbacks described above and is easy and economic to embody. 
     The present invention therefore relates to a fuel manifold for the direct injection of fuel into an internal combustion engine including a head provided with a plurality of cylinders and injectors, each of which is connected to the fuel manifold and adapted to directly inject fuel into the respective cylinder. An air intake manifold is connected to the head in order to supply fresh air to the cylinders. The fuel manifold is formed by a single monolithic body which is made of thixotropic aluminum by means of a pressure die casting process. The manifold includes a supply duct adapted to distribute the fuel under pressure to the injectors and a flange disposed laterally to the supply duct wherein the flange has a plurality of through holes in order to be secured to the head of the engine by respective screws and further comprises a plurality of coupling members, each of which is adapted to bringing a respective cylinder in communication with an intake manifold. The supply duct includes a main cylindrical tubular channel having two opposite open ends one of which is used to supply the fuel under pressure and the other is closed by a screw cap. In the vicinity of the end closed by the screw cap the main cylindrical tubular channel has a first opening adapted to receive a pressure regulator and a second opening adapted to receive a pressure sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the accompanying drawings, which show a non-limiting embodiment thereof, and in which: 
         FIG. 1  is a diagrammatic view of an internal combustion engine with direct fuel injection provided with a fuel manifold in accordance with the present invention; 
         FIG. 2  is a perspective view of a preferred embodiment of the fuel manifold of  FIG. 1 ; 
         FIG. 3  is a front view of the fuel manifold of  FIG. 2 ; 
         FIG. 4  is a view in section along the line IV—IV of the fuel manifold of  FIG. 2  coupled to the head of the engine of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1 , an internal combustion engine is shown overall by  1  and comprises a head  2  in which four cylinders  3  are provided (only one of which is shown in  FIG. 1 ), each of these cylinders  3  being connected to an intake manifold  4  by means of at least one respective intake valve  5  and to an exhaust manifold  6  by means of a respective exhaust valve  7 . The intake manifold  4  receives fresh air (i.e. ambient air from outside) by means of a butterfly valve  8  which can be adjusted between a closed position and a position of maximum opening; an exhaust duct  9  provided with one or more catalysts (not shown in detail) leads from the exhaust manifold  6  for the emission into the atmosphere of the gases generated by combustion in the cylinders  3 . 
     A low pressure pump (not shown in detail) supplies the fuel from a tank (not shown in detail) to a high pressure pump  10  which in turn supplies the fuel to a fuel manifold  11 ; a series of injectors  12  (one for each cylinder  3 ) is connected to the fuel manifold  11 , each of these injectors  12  being actuated cyclically to inject part of the fuel under pressure in the fuel manifold  11  into the respective cylinder  3 . The pressure value of the fuel in the fuel manifold  11  is maintained instant by instant at a desired value by means of a pressure regulator  13  which is coupled to the fuel manifold  11  and is adapted to discharge any surplus fuel to a recycling duct which returns this surplus fuel upstream of the low pressure pump (not shown). A sensor  14 , adapted to measure the pressure value of the fuel in the fuel manifold  11 , is also connected to the fuel manifold  11 . 
     As shown in  FIGS. 2 to 4 , the fuel manifold  11  is formed by a single monolithic body  15  which is made from thixotropic aluminum by means of a pressure die casting process and comprises a supply duct  16 , which is of substantially cylindrical shape, has a central axis of symmetry  17  and is adapted to distribute the fuel under pressure to the injectors  12 , and a flange  18  disposed laterally to the supply duct  16 . The flange  18  has a plurality of through holes  19  so that it can be secured by respective screws  20  to the head  2  of the engine  1  and comprises four coupling members  21 , each of which is adapted to bring a respective cylinder  3  into communication with the intake manifold  4 . 
     The flange  18  comprises a substantially plane plate  22  which extends laterally to the supply duct  16  from a median portion of this supply duct  16 ; each coupling member  21  comprises a tubular body  23  which rises from the plate  22  in a perpendicular manner with respect to the plane in which the plate  22  lies. Preferably, the end upper portion of each tubular body  23  is shaped to facilitate connection with a respective duct coming from the intake manifold  4 . A lower surface  24  of the plate  22 , i.e. the opposite surface with respect to the tubular bodies  23 , is plane and has a relatively very small surface roughness so that it can be coupled in a leak-tight manner (possibly with the interposition of a gasket) with a corresponding upper surface  25  of the head  2 . 
     A series of reinforcing ribs  26 , involving both the plate  22  and the supply duct  16 , are provided and are disposed perpendicularly with respect to the plane in which the plate  22  lies and with respect to the axis  17  of the supply duct  16 . The flange  18  has a series of raised zones  27 , via each of which a respective through hole  19  is provided for the passage of a connection screw  20  with the head  2  of the engine  1 . Part of the reinforcing ribs  26  starts from the raised zones  27 , while the remaining part of the reinforcing ribs  26  starts from the tubular bodies  23 . 
     As shown in  FIG. 4 , the supply duct  16  is formed by a main cylindrical tubular channel  28  from which a series of further secondary cylindrical tubular channels  29 , disposed perpendicularly with respect to the main cylindrical tubular channel  28 , leads; each secondary cylindrical tubular channel  29  is adapted to house a respective injector  12  in a leak-tight manner. The main cylindrical tubular channel  28  has two opposite open ends  30  and  31 , the end  30  being connected to the high pressure pump  10  in order to supply the fuel under pressure to the fuel manifold  11 , while the end  31  is closed by a relative screw cap  32 . The function of the end  31  is to enable the correct production of the main cylindrical tubular channel  28  during the pressure die casting process for the monolithic body  15 . In the vicinity of the end  31 , the main cylindrical tubular channel  28  has an opening  33  adapted to receive the pressure regulator  13  and an opening  34  adapted to receive the pressure sensor  14 . Preferably, the openings  33  and  34  are not formed during the pressure die casting process for the monolithic body  15 , but are produced subsequently by drilling of the monolithic body  15 .