Patent Publication Number: US-2003233994-A1

Title: Fuel injection system for an internal combustion engine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
     [0001] The present patent application claims the benefit of U.S. Provisional Patent Application No. 60/389,737 filed Jun. 19, 2002. 
    
    
     
       BACKGROUND OF INVENTION  
       [0002] 1. Technical Field  
       [0003] The present invention relates to a fuel system for an internal combustion engine that has, in association therewith, a fuel tank, a fuel pump and a fuel filter that is located in a flow duct between the fuel pump and the fuel consuming components of the engine. The flow duct includes a valve chamber, located downstream of the fuel filter, with a valve cone movably arranged in the chamber between an upper valve seat and a lower valve seat.  
       [0004] 2. Background of the Invention  
       [0005] Fuel systems for internal combustion engines are conventionally designed in such a way that exchanging a fuel filter involves emptying the fuel line between the outlet of the filter housing and the cylinder head. In this connection, the environmentally harmful substance (fuel) should be collected to avoid spillage. Exchanging a fuel filter is a common service action, especially on heavy diesel engines. It is usual for fuel systems of diesel engines to be provided with a bleed nipple and a hand pump that can be used when air bleeding and refilling of fuel is carried out. Before the engine is next started, however, a large number of strokes of the hand pump it typically required, and it is necessary to open one or more bleed nipples in order to remove the significant quantity of air that is present in the new filter. This involves expensive workshop time and also a risk of fuel spillage because the abovementioned nipples are generally not closed before the fuel flows.  
       [0006] There are fuel systems with devices for automating the procedure for removing air as disclosed in U.S. Pat. No. 5,534,161. Therein, a pump is described that can be driven in two directions by means of a microprocessor, and that can be used for removing water from a fuel system. This device, however, can only facilitate the procedure for bleeding air from the fuel system, and further actions are required in order to remove air from the high-pressure side of the system. Inclusion of this device therefore means that the number of components in the fuel system increases without fully solving the problem of facilitating the bleed procedure.  
       SUMMARY OF INVENTION  
       [0007] One objective of the invention is to provide a fuel system that enables automated removal of air, after filter exchange, without adding further complication or expense.  
       [0008] The fuel system design comprises (includes, but is not limited to) a fuel tank, a fuel pump and a fuel filter located in a flow duct between the fuel pump and the fuel consumers of the engine. An example of such fuel consumers is the piston and chamber arrangement which burns fuel. The flow duct includes a valve chamber, located downstream of the fuel filter, with a valve cone arranged movably therein between an upper valve seat and a lower valve seat. An upper part of the valve chamber has an outlet for bleeding to the fuel tank, and the valve cone is provided with an inner passage having a valve seat, that, under normal fuel pressure, interacts with a bleed cone which is movable in the passage. On the one hand, this design of the fuel system ensures that fuel spillage during filter exchange is minimized, and, on the other hand, the subsequent bleeding of the fuel system can take place automatically. 
     
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
     [0009] The invention will be described in greater detail below with reference to illustrative embodiments shown in the accompanying drawings, in which:  
     [0010]FIG. 1 is a diagrammatical view of an internal combustion engine with a fuel system configured according to the teachings of the present invention;  
     [0011]FIG. 2 is a more detailed view of a filter holder, forming part of the fuel system of FIG. 1, with an associated filter; and  
     [0012] FIGS.  3 - 5  are diagrammatical views, in further enlarged scale, of three different functional states of a valve chamber forming part of the disclosed fuel system. 
    
    
     DETAILED DESCRIPTION  
     [0013] The internal combustion engine  10  shown diagrammatically in FIG. 1 is a 6-cylinder diesel engine with a corresponding number of standard type injectors  11 . Exemplarily, the engine  10  can be used to power a heavy truck.  
     [0014] Diesel fuel is fed by a pump  12 , driven by the engine  10 , from a tank  13 , via a common feeder line  14 , to the injectors  11 . A combination valve  15  for pressure control and bleeding is mounted downstream of the injectors  11 . A return line  16  for uncombusted fuel is connected to the combination valve. A bleed line  17  is also connected to the combination valve, and which is in communication with the fuel tank  13 .  
     [0015] The fuel system also comprises a filter holder  18  with a fuel filter  19 . The filter holder  18  is shown in detail in FIG. 2 and is provided with a cylindrical valve chamber  20  located downstream of the fuel filter as illustrated in greater detail in FIGS.  3 - 5 . The lower end wall  20   a  of the chamber is provided with a central inlet  21  from the fuel filter  19 . Via a central outlet  22 , the upper end wall  20   b  communicates with the fuel tank  13  via the bleed line  17 . The valve chamber also communicates with the feeder line  14  via a laterally directed outlet  23  arranged in the lateral surface  20   c.    
     [0016] The valve chamber  20  accommodates a valve cone  24  which is provided with an inner passage  25  having a valve seat  25   a  and a bleed cone  26  which is movable in the passage  25 . The bleed cone  26  is arranged to interact with the lower valve seat  27  of the valve chamber at low fuel pressure as depicted in FIG. 3. As utilized herein, components that are described as being arranged to interact means the so-described components are adapted to sealingly engage when abutting one another. As the fuel pressure increases, the bleed cone, which is considerably more freely moving than the valve cone  24 , can remove itself from the valve seat  27 , air bubbles then being able to move past the bleed cone and out via the bleed port  22  as shown in the configuration of FIG. 4. When the fuel pressure (from below) is sufficiently high, the bleed cone  26  interacts with the valve seat  25   a  and the valve cone  24  is then moved from the valve seat  27  so that fuel can pass out through the outlet  23  to the feeder line  14 .  
     [0017] When the engine is started after an exchange of the fuel filter  19 , the fuel pump  12  sucks fuel from the tank  13  and fills the filter  19 . When pressure in the filter has become sufficiently great, the bleed cone  26  is lifted from the valve seat  27  and air can pass through the passage  25  past the bleed cone and on through the outlet  22 . When the fuel reaches the valve chamber  20 , the bleed cone will close the valve seat  25   a , the valve cone  24  then being displaced upward and air-free fuel starting to be pushed to the consumers  11  of the engine via the outlet  23  to the feeder line  14 .  
     [0018] The weight of the bleed cone  26  is adapted in such a way that air bubbles in the fuel easily cause it to lift from the lower valve seat  27 . The weight of the valve cone  24  is in turn adapted in such a way that only the fuel pressure is capable of causing it to lift from the lower valve seat  27 .  
     [0019] Since the bleed cone  26  serves as a non-return valve, and can rapidly close the inlet  21 , a large part of the positive pressure in the feeder line  14  can be retained during filter exchange. This positive pressure constitutes a prerequisite for the engine starting and continuing to run for the time it takes before all the air has passed out through the bleed port  22 , after which the incoming fuel pressure can rise to the normal level which is maintained by the combination valve  15 . The engine, therefore, runs even during the bleeding process because fuel still remains around the injectors  11  and in the fuel line  14  leading thereto. It should be pointed out that this assumes that the engine is running under low load; that is to say, with low fuel consumption thereby it possible for the pump to replace the air quantity present in the filter with fuel. Moreover, this bleeding process takes only about ten seconds.  
     [0020] The invention is not to be regarded as being limited to the illustrative embodiments described above, but a number of further variants and modifications are conceivable within the scope of the following patent claims. It is possible, for example, to use spring means which act in the closing direction as a supplement to the weight of the valve cone  24  and/or the bleed cone  26 .