Abstract:
An engine includes air-assisted fuel injection including fuel injectors supplying fuel through cylinder head-mounted air injectors. An internal air passage in the cylinder head connects with internal air pockets receiving the injectors and supplying them with air. Seals on the air injectors prevent air leakage from the air pockets. The air temperature in the head is affected by an adjacent coolant passage.

Description:
TECHNICAL FIELD 
     This invention relates to internal combustion engines and more particularly to an engine with air-assisted direct cylinder fuel injection. 
     BACKGROUND OF THE INVENTION 
     It is known in the art relating to spark-ignited internal combustion engines to provide for the direct injection of fuel into the combustion chambers, normally through the cylinder head of the engine. Air-assisted direct injection fuel systems have been developed for such engines which utilize a combination of solenoid-actuated fuel injectors which inject pressurized fuel into associated air injectors. The air injectors mix pressurized air with the fuel and inject the mixture of air and fuel directly into the engine combustion chambers. The air injectors are mounted in the engine cylinder head and the fuel injectors are mounted at the outer ends of the air injectors. Separate air and fuel rails are provided which respectively supply air to the air injectors and fuel to the fuel injectors. The arrangement is easily modified for application to various engine configurations but involves a large number of components to be mounted along the top of the cylinder head and having external fittings and connections. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved arrangement for an air-assisted fuel injection system mounted on an engine. The engine includes an internal air passage acting as an air manifold and preferably disposed in an engine cylinder head or other component defining a portion of an associated combustion chamber. Modified air injectors are provided which fit into stepped boars in the cylinder head and include seals at opposite ends of a central portion of the bore which defines annular air pockets. The air pockets are intersected by the internal air passage or manifold running longitudinally along the length of the cylinder head. The air passage or manifold is provided with pressurized air from an external source which is fed to the air pockets and enters each of the air injectors. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a transverse cross-sectional view of an engine cylinder head assembly showing mounting of the air injector and internal air supply in the engine cylinder head; 
     FIG. 2 is a pictorial view of a fuel injection assembly for installation in an engine with the location of the cylinder head internal air passage indicated but without the cylinder head structure being shown; and 
     FIG. 3 is a pictorial cross-sectional view of an alternative cylinder head assembly including air-assisted injection components in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1 of the drawings in detail, numeral  10  generally indicates an engine cylinder head assembly for use in an engine according to the invention. Assembly  10  includes a cylinder head  12  having a lower wall with a recess  14  defining a portion of a combustion chamber of an associated engine. The cylinder head includes an injector mounting opening  16 . Opening  16  is formed as a stepped bore including an enlarged inlet portion  18 , a smaller central portion  20  and a still smaller outlet portion  22 , opening to the combustion chamber recess  14 . The central portion  20  of the opening  16  defines an air pocket, one side of which is intersected by an air passage  24  that extends longitudinally through the cylinder head, connecting with other combustion chambers not shown defined by the cylinder head. The cylinder head also contains a coolant passage  26  extending adjacent to the air pockets in the central portions  20  of the openings  16 . 
     An air injector  28  is mounted in the injector mounting opening  16  and is stepped with three diameters corresponding to the mounting opening diameters. An upper seal  30  is mounted in an upper portion of the air injector engaging the inlet portion  18  of opening  16 . A lower seal  32  is mounted near the lower end of the central portion  20  of the injector  28 , engaging the wall of the central portion  20  or air pocket of the mounting opening  16 . The seals  30 ,  32  close off the upper and lower ends of the air pocket  20  to prevent the escape of air supplied to the air pocket through the intersecting air passage  24 . 
     In operation, pressurized air is continuously fed to the air injector from the passage  24  and pocket  20 . The fuel injector when actuated delivers fuel to the air injector to mix with the air. The air injector is then actuated to deliver the pressurized air-fuel mixture to the combustion chamber of the associated engine where it is ignited and burned to produce power. 
     The arrangement so far described reduces the external plumbing and fittings commonly utilized with air-assisted fuel injection systems by providing the internal air passage, intersecting air pockets in associated injector mounting openings which directly feed air to the air injectors mounted in the cylinder head. Placement of the air pockets  20  and passage  24  adjacent to coolant passages  26  in the cylinder head also has the advantage of helping to maintain the pressurized air at a controlled temperature. This reduces the possibility of water vapor condensing out of the air in liquid form and adversely affecting fuel mixture preparation. It also prevents freezing or icing, which can affect functioning of the injectors. 
     Referring now to FIG. 2 of the drawings, a fuel system assembly  34  is shown as mounted within a cylinder head  12 , not shown. Assembly  34  includes four air injectors  28  as mounted in a cylinder head  12 , not shown, and connected to the air passage  24  within the cylinder head through which pressurized air is supplied to the cylinder head air pockets  20 , not shown. The air injectors extend to lower ends which are connected with associated combustion chambers  14 , not shown, of the associated cylinder head. The air injectors further include attachment flanges  36 , secured by fasteners  38  to the cylinder head, and electrical connectors  40  for connection with a controller for controlling the opening and closing action of the air injectors. Each of the air injectors  28  is fed by a fuel injector  42  which mounts on the upper end of the air injector. The fuel injectors  42  are connected with a fuel rail  44 , extending above the cylinder head and connecting with upper ends of the individual fuel injectors. Electrical connectors  46  are provided, one for each of the fuel injectors, for providing external actuation of the fuel injectors as required. The fuel rail includes a fuel pressure regulator  48  at one end with associated fuel supply and return lines  50 ,  52 . 
     FIG. 3 shows a portion of a modified engine cylinder head assembly with a fuel system including features of the present invention. Cylinder head assembly  54  includes a fuel pressure regulator  56  actuated by air pressure supplied to an internal passage  58  that extends longitudinally within the cylinder head  60  to connect with air pockets  62  in which air injectors  64  are mounted. Injectors  64  extend downward into associated combustion chambers  66  defined in part below the cylinder head. Electric igniters  68  are mounted in the cylinder head and have lower tips adjacent the outlet ends of the air injectors for igniting the air-fuel mixture injected into the combustion chamber. A coolant passage  70  in the cylinder head lies adjacent to the air passage  58 , air pockets  62  and the air injectors  64  to help maintain the air at an elevated constant temperature and prevent condensation of moisture in the air. Fuel injectors  72  are mounted to the upper ends of the air injectors  64  and operated to provide fuel for mixing with the pressurized air in the manner previously described. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.