Abstract:
A leak diagnostic strategy for an engine equipped with a high pressure common rail fuel system includes a plurality of separate leak lines. Each of the leak lines is constructed and positioned to capture fuel leaking from one of several different high pressure spaces associated with the fuel system. Once a leak is detected, the location of the leak can be diagnosed by opening different leak diagnostic ports until fuel is evacuated from the system. Each of the leak diagnostic ports is associated with one of the leak lines. The system allows for quick determination of a leak location without cumbersome testing or partial dismantlement of engine related subsystems and components.

Description:
TECHNICAL FIELD  
   The present invention relates generally to a strategy for diagnosing a leak location in a high pressure fuel system, and more particularly to a common rail fuel system with leak location diagnostic features. 
   BACKGROUND  
   Common rail fuel systems typically include at least one common rail that supplies high pressure fuel to a plurality of fuel injectors, and at least one high pressure pump that supplies high pressure fuel to the common rail(s). These high pressure spaces in an engine&#39;s fuel system are fluidly connected to one another through pipes that are located on the engine. Although leakage in these types of fuel systems is rare, it does occur. In order to contain any leak from the high pressure spaces, it is sometimes useful to contain these high pressure spaces within a low pressure envelope. For instance, a high pressure supply line might actually be a double walled tube with the inner tube containing high pressure fuel, and the outer tube enclosing the inner tube and being fluidly connected to drain in order to return any leaked fluid back to tank. For instance, U.S. Pat. No. 6,237,569 to Stelzer et al. teaches the formation of an internal leakage chamber that hermetically encloses lines and connections associated with a common rail fuel system. 
   In addition to containing leaks, there is an issue relating to detecting leaks. For instance, U.S. Pat. No. 5,685,268 to Wakeman teaches a fuel leakage detector system that issues an alert if the total amount of fuel leaving a high pressure area in the fuel system is less than the mass of fuel entering the same. Although Wakeman and others have taught methods of detecting a fuel leak in a high pressure common rail system, the problem of diagnosing a leak location in order to repair the same can remain elusive and problematic. In other words, detecting a leak is useful, but detection alone will not aid a technician in locating and repairing the leak. Thus, substantial down time and the associated expense can be involved in tracking down and repairing a leak. This can be further compounded in some engine applications where the various high pressure spaces in the fuel system are at different locations that are difficult to access. For instance, some high pressure spaces might require disassembly of other engine related components in order to gain access thereto. 
   The present invention is directed to one or more of the problems set forth above. 
   SUMMARY OF THE INVENTION  
   In one aspect, a leak diagnosis component includes a junction block with a plurality of inlets and at least one outlet that open through an external surface. The inlets are fluidly connected to the outlet via a plurality of leak paths disposed in the junction block. A separate leak collection cavity is fluidly connected to each of the leak paths, and is disposed in the junction block. A separate leak diagnostic port extends between each of the leak collection cavities and the external surface of the junction block. 
   In another aspect, a fuel system with leak diagnostic features includes a plurality of high pressure fuel spaces. A plurality of leak lines are operably positioned to capture fuel leaking from different ones of the high pressure spaces. A leak diagnostic port is fluidly connected to each of the leak lines and is operably positioned to evacuate fuel from different ones of said leak lines. 
   In still another aspect, a method of diagnosing a leak location in a fuel system for an engine includes a step of capturing fuel from a leak originating from one of a plurality of different high pressure spaces into one of a plurality of separate leak lines. Different leak diagnostic ports are opened until fuel is evacuated from one of the leak lines. The high pressure space that was the origin of the leak is identified by its associated leak line. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic illustration of an engine fuel system employing a leak diagnostic strategy according to the present invention; 
       FIG. 2  is an isometric view of a leak detection component for the fuel system of  FIG. 1 ; 
       FIG. 3  is a front sectioned view of the leak diagnostic component of  FIG. 2  as viewed along section lines  3 - 3 ; 
       FIG. 4  is a side sectioned view of the leak diagnostic component of  FIG. 2  as viewed along section lines  4 - 4 ; 
       FIG. 5  is an isometric view of a leak diagnostic component according to another aspect of the present invention; 
       FIG. 6  is a rear sectioned view of the leak diagnostic component of  FIG. 5  as viewed along section lines  6 - 6 ; 
       FIG. 7  is a front sectioned view of the leak diagnostic component of  FIG. 5  as viewed along section lines  7 - 7 ; and 
       FIG. 8  is a side sectioned view of the leak diagnostic component of  FIG. 5  as viewed along section lines  8 - 8 . 
   

   DETAILED DESCRIPTION  
   Referring to  FIG. 1 , an example fuel system  10  according to the present invention includes a right hand high pressure common rail  11  with eight associated fuel injectors  16 , and a left hand common rail (not shown) associated with eight other fuel injectors (also not shown). Fuel system  10  is used in relation to a  16  cylinder V-type diesel engine, and the left hand rail is not shown, but is identical to the right hand rail and associated fuel injectors. Although the present invention is illustrated in association with a common rail fuel system for a V-type diesel engine, the present invention could find potential application to virtually any fuel system that includes, or could be divided into, a plurality of high pressure spaces. Fuel system  10  includes a high pressure pump  12  that supplies high pressure fuel to right hand common rail  11  and the left hand common rail. Low pressure fuel is supplied to high pressure pump  12  from a fuel tank  14 . An electronic control module  18  controls the operation of fuel system  10  in a conventional manner. Fuel system  10  includes many features familiar to those skilled in the art but also includes a leak diagnostic component  50  that is fluidly positioned between leak lines associated with different high pressure spaces and fuel tank  14 . 
   Electronic control module  18  receives sensor inputs from a variety of typical sensors known in the art including an inlet pressure sensor  20 , an outlet pressure sensor  21  and a temperature sensor  22  that are associated with pressure regulator  35  and micron filter  34 . In addition, electronic control module  18  receives sensor input signals from a temperature sensor  23  and a pump outlet pressure sensor  24  associated with high pressure pump  12 . Electronic control module  18  also receives sensor input from a timing wheel sensor line  27  and a wet sensor  25 , which is operably positioned to detect a leak from any of several high pressure spaces associated with fuel system  10 . Wet sensor  25  is preferably included as a portion of leak diagnostic component  50 . 
   When in operation, low pressure fuel is drawn from tank  14  by either a priming pump  32  or a fuel transfer pump  33  along a fuel supply line  30 . Fuel in supply line  30  initially passes through a filter assembly  31 , which can include a water separator and possibly a water-in-fuel sensor. The low pressure fuel then arrives at pressure regulator  35 , which acts to maintain the fuel pressure in supply line  30  below some threshold pressure by returning excess fuel to tank via regulator return line  43 , if necessary. The fluid supply to high pressure pump  12  is controlled by the electronic control module  18  via a flow control valve  36 . Depending upon the position of flow control valve  36 , a portion of the fuel in supply line  30  is either directed to high pressure pump  12  or back to tank via flow valve return line  44 . The output from high pressure pump  12  enters a fuel discharge module  65  on its way to a high pressure supply line  61  via a pump outlet connection  60 . Fuel discharge module  65  can include a pressure relief valve and/or a manual drain valve that allows fuel to be returned to tank  14  via a pressure relief return line  45 . Any fuel returning to tank via either regulator return line  43 , flow valve return line  44  or pressure relief return line  45  pass through a return fuel manifold  38  and a cooler  39  before reentering tank  14 . 
   Since past experience has shown that a leak can occasionally occur at pump outlet connection  60 , it and high pressure supply line  61  constitute a high pressure space according to the present invention that is contained within a low pressure envelope in a conventional manner, such as by using a double walled tube. Any fuel that leaks from this high pressure space is captured in a pump output leak line  52  that is fluidly connected at its down stream end to an inlet  55  associated with leak diagnostic component  50 . Thus, in the rare occurrence where a leak exists at the high pressure connection  60 , that fuel will be captured and returned to tank via leak return line  52 . 
   High pressure supply line  61  is split into a right hand supply line  63  and a left hand supply line  64  at a T-Flange  62 . Supply line  63  and  64  are also preferably double walled tubes that create a low pressure envelope around the high pressure lines  63  and  64 . The right hand supply line  63  is fluidly connected to right hand common rail  11 , which together constitute another high pressure space of fuel system  10 . Likewise, left hand supply line  64  and the associated left hand common rail (not shown) constitute a third high pressure space for fuel system  10 . Any fuel that leaks from right hand rail  11  and/or supply line  63  is captured by the low pressure envelope and channeled to a right hand leakage connection  66 , where the fuel can be captured in right hand leak line  51  for return to tank  14 . Right hand leak line  51  is fluidly connected at its downstream end to an inlet  56  associated with leak diagnostic component  50 . Likewise, left hand supply line  64  and the left hand common rail constitute another high pressure space that is enclosed in a separate low pressure envelope that leads to left hand leakage connection  67 . Thus any fuel leakage that occurs in this high pressure space is captured in left hand leak line  53  that is fluidly connected at its downstream end to an inlet  54 , which is also associated with leak diagnostic component  50 . Any leakage that is captured by leak return lines  51 ,  52  or  53  passes through leak diagnostic component  50 , past wet sensor  25  and into a consolidated leak like  57 , which is fluidly connected to tank  14  via drain line  48 . In other words, an upstream end of consolidated leak line  57  is fluidly connected to an outlet  59  from leak diagnostic component  50 . 
   Fuel system  10  also includes several conventional return lines that are associated with fuel injectors  16 . For instance, any fuel returned via the normal operation of fuel injectors  16  from the right hand bank enter a right hand injector return manifold  37 , and is then channeled to drain line  48  via a right hand fuel injector return line  46 . Likewise, any fuel not used by the left hand fuel injectors is fluidly channeled to drain line  48  via a left hand injectors return line  47 . 
   Referring now to  FIGS. 2-4 , the structure of leak diagnostic component  50  is illustrated. In particular, leak diagnostic component  50  includes a metallic junction block  70  that is mounted at a suitable location on or adjacent the engine associated with fuel system  10 . Junction block  70  is formed to include inlets  54 ,  55 , and  56 , which are each fluidly connected to the separated leak lines  53 ,  52  and  51 , respectively, as shown in  FIG. 1 . Within junction block  70 , each of the leak lines  51 ,  52  and  53  has an associated leak collection cavity  75 ,  74  and  77 , respectively. Thus, any fuel traveling in leak return line  51  is initially channeled to leak collection cavity  75  before overflowing into consolidated leak line  57 . Likewise, any leakage in return line  51  first fills leak collection cavity  77  before overflowing into consolidated leak line  57 . Finally, any leakage that is captured in leak line  53  is first channeled to leak collection cavity  74  before overflowing into consolidated leak line  57 . Each of the leak collection cavities  74 ,  75  and  77  has an associated leak diagnostic port  72 ,  73  and  76 , respectively. The leak diagnostic port  72 ,  73  and  76  extend between the respective leak collection cavities and an outer surface of junction block  70 . Component  50  is preferably oriented such that gravity will maintain fuel, if any, in the respective leak diagnostic cavities. When installed in the fuel system  10  of  FIG. 1 , a separate plug is placed in each of the leak diagnostic ports  72 ,  73  and  76 . These plugs are preferably removable and can take on a wide variety of structures known in the art that allow for leak diagnostic ports  72 ,  73  and  76  to normally be maintained closed but allow each to be opened, preferably manually by a technician seeking to diagnose a leak location. 
   Junction block  70  is also formed to include a wet sensor port  71  within which is mounted a wet sensor  25  ( FIG. 1 ) so as to be in fluid contact with consolidated leak line  57 . Finally, Junction block  70  is machined to include an outlet  59  that allows component  50  to be fluidly connected to an external portion of consolidated leak line  57  as shown in  FIG. 1 . Thus, any fuel that leaks into one of the return lines is first collected in a separate leak collection cavity and then overflows into a consolidated leak line  57  where the leak is detected by the wet sensor  25 , which provides an alert to an operator in a conventional manner. For instance, the wet sensor can be operably connected to the electronic control module  18 , as shown in  FIG. 1 , where some suitable alert is provided to an operator by the electronic control module in a conventional manner. 
   Although the embodiment of  FIGS. 1-4  shows three separate leak lines, those skilled in the art will appreciate that the fuel system  10  can be subdivided into including any number of separate high pressure spaces with separate leak lines for a more sophisticated version of the present invention. For instance, in one extreme, each fuel injector could have a separate leak detection line. In any event, when applied to a specific fuel system and engine, it might be desirable to increase the number of leak lines in order to further isolate separate high pressure spaces of the fuel system in order to better enable a diagnosis of a leak location, should a leak occur. For instance,  FIGS. 5-8  show a leak diagnostic component  150  according to another aspect of the present invention that includes six separate leak inlets  151 - 156 , which would be fluidly connected to different high pressure spaces associated with a different engine. For instance, inlets  151  and  152  might be fluidly connected to different high pressure distribution blocks, inlets  153  and  154  could be fluidly connected to leak lines associated with two different high pressure pump connections, and inlets  155  and  156  could be fluidly connected to leak lines associated with two separate high pressure rails for the fuel system of an engine according to another application of the present invention. Each of the separate six leak inlets  151 - 156  has a separate leak collection cavity that is fluidly positioned between the inlet and a common outlet  159 . Thus, fuel entering one of the inlets  151 - 156  will first collect in a separate leak collection cavity before overflowing into a common leak return line fluidly connected to outlet  159 . Upstream of common outlet  159 , junction block  170  includes a wet sensor port  171  within which is mounted a wet sensor, which could be similar to wet sensor  25  identified in  FIG. 1 . Thus, before exiting junction block  170 , any leakage would be detected by the wet sensor before exiting at outlet  159 . Each of the leak collection cavities is fluidly connected to a leak diagnostic port that opens through an outer surface of junction block  170 . For instance, leak inlet  151  is fluidly connected to a leak collection cavity  172 , which is separated from the outer surface of junction block  170  by leak diagnostic port  181 . Several of the internal fluid connections are facilitated by unnumbered radial cross bores that have their openings plugged in the finished component. Leak inlet  154  is fluidly connected to a leak collection cavity  174  and a leak diagnostic port  182 . As in the previous embodiment, the leak diagnostic ports  181  are preferably plugged in a suitable manner during normal operation of the engine. Although not shown, each of the six inlets  151 - 156  has a separate leak collection cavity and a separate leak diagnostic port associated therewith. In order to consolidate different components and associated ports, junction block  170  also includes a fuel return manifold that includes fuel return inlets  140  and a return manifold outlet  141 . Those skilled in the art will appreciate that the return manifold inlets  140  would likely be fluidly connected to different fuel injector return lines, a pressure regulator return line, or any other return line known in the art. 
   INDUSTRIAL APPLICABILITY  
   Although the present invention has been illustrated in the context of a common rail fuel system for a diesel engine, the present invention could find potential application in any fuel system with two or more potential leak locations that can be fluidly isolated from one another via separate leak lines. Although the present invention is particularly well suited to common rail fuel systems, it could find potential application in other fuel systems that include even cyclic high pressure spaces, such as a pump and line fuel system. 
   When implementing the invention, engineers will normally have to arrive at a compromise as to how many leak lines to employ verses cost and how many different potential leak locations are likely. The invention is then implemented by separately enclosing each of the different high pressure spaces in a low pressure envelope, such as by using double walled tubes as supply lines and the like. Each of these low pressure envelopes is fluidly connected to a separate leak line. Each of the separate leak lines is fluidly connected to a different inlet in a leak diagnostic component according to the present invention. Any leakage that might occur in one of those leak lines is first captured by the leak line and then fills a leak diagnostic cavity before overflowing into a common leak line fluidly connected to tank. After an operator is alerted to the presence of a leak, which will occur due to a wet sensor in the consolidated leak line detecting the presence of fuel, the technician can open different leak diagnostic ports until fuel is evacuated from an associated leak collection cavity. By knowing which high pressure space is associated with that leak diagnostic port, the technician can quickly diagnose which high pressure space is leaking fuel, so as to more quickly implement a repair. 
   In the preferred embodiment of the present invention, the engine is preferably not running when the diagnostic procedure is preformed. In other words, after an operator is alerted to the presence of a leak, such as via the wet sensor described in relation to the fuel system of  FIG. 1 , the engine is shut down. Then, the technician sequentially opens different diagnostic ports until the one with fuel in its leak collection cavity is evacuated through the leak diagnostic port. The technician then associates that leak diagnostic port with a certain high pressure space of the fuel system. The technician then can proceed to repairing the leak in the high pressure space indicated by leak diagnostic cavity containing fuel. In order to further hasten the leak diagnostic procedure, all of the leak diagnostic ports are preferably located on a single surface of the leak diagnostic junction block, rather than scattered at different locations around the engine. 
   Although the present invention has been illustrated in the context of a leak diagnostic component with several inlets fluidly connected to separate leak lines, the present invention could also be implemented in another way. For instance, instead of the leak diagnostic junction block, the present invention could be employed by simply positioning an evacuation valve in each of the leak lines. With the engine running and a leak occurring, a technician could simply open different ones of the evacuation valves until fuel from one of the leak lines poured into a container held under the valve by the technician. The technician could then shut the engine down and proceed to repair the leak at the high pressure space associated with the leak line having the fuel therein. Thus, in that alternative, each of the valves would be considered a leak diagnostic port, and would normally be maintained in a closed position during normal operation of the engine, such as via a spring bias or the like. 
   Those skilled in the art will appreciate that the present invention can be implemented in various levels of sophistication depending upon the specific application. For instance, the invention is preferably implemented by dividing the high pressure spaces of a fuel system into separate places where leakage could occur. For instance, each fluid connection could be a potential leakage location and could be isolated with a separate leak line according to the present invention. In a more sophisticated version of the invention, which is not shown, each and every fuel injector could have a separate leak detection line associated with its high pressure fuel connections. However, those skilled in the art will appreciate that the number of separate leak lines should be balanced against cost and a likelihood of a leak occurring at that different location, as well as how difficult it is to access different leak locations for repairs and the like. The present invention is advantageous because is allows a leak location to be quickly diagnosed without having to employ more than one wet sensor for the entire fuel system. This advantage not only decreases the number of sensors on the engine by also can substantially reduce down time if a leak should occur, and reduce the expenses associated with a repair by allowing the technician to more quickly find and repair the leak. 
   It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. Thus, those skilled in the art will appreciate that other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.