Fuel system with leak location diagnostic features and component for same

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.

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'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.

DETAILED DESCRIPTION

Referring toFIG. 1, an example fuel system10according to the present invention includes a right hand high pressure common rail11with eight associated fuel injectors16, and a left hand common rail (not shown) associated with eight other fuel injectors (also not shown). Fuel system10is used in relation to a16cylinder 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 system10includes a high pressure pump12that supplies high pressure fuel to right hand common rail11and the left hand common rail. Low pressure fuel is supplied to high pressure pump12from a fuel tank14. An electronic control module18controls the operation of fuel system10in a conventional manner. Fuel system10includes many features familiar to those skilled in the art but also includes a leak diagnostic component50that is fluidly positioned between leak lines associated with different high pressure spaces and fuel tank14.

Electronic control module18receives sensor inputs from a variety of typical sensors known in the art including an inlet pressure sensor20, an outlet pressure sensor21and a temperature sensor22that are associated with pressure regulator35and micron filter34. In addition, electronic control module18receives sensor input signals from a temperature sensor23and a pump outlet pressure sensor24associated with high pressure pump12. Electronic control module18also receives sensor input from a timing wheel sensor line27and a wet sensor25, which is operably positioned to detect a leak from any of several high pressure spaces associated with fuel system10. Wet sensor25is preferably included as a portion of leak diagnostic component50.

When in operation, low pressure fuel is drawn from tank14by either a priming pump32or a fuel transfer pump33along a fuel supply line30. Fuel in supply line30initially passes through a filter assembly31, which can include a water separator and possibly a water-in-fuel sensor. The low pressure fuel then arrives at pressure regulator35, which acts to maintain the fuel pressure in supply line30below some threshold pressure by returning excess fuel to tank via regulator return line43, if necessary. The fluid supply to high pressure pump12is controlled by the electronic control module18via a flow control valve36. Depending upon the position of flow control valve36, a portion of the fuel in supply line30is either directed to high pressure pump12or back to tank via flow valve return line44. The output from high pressure pump12enters a fuel discharge module65on its way to a high pressure supply line61via a pump outlet connection60. Fuel discharge module65can include a pressure relief valve and/or a manual drain valve that allows fuel to be returned to tank14via a pressure relief return line45. Any fuel returning to tank via either regulator return line43, flow valve return line44or pressure relief return line45pass through a return fuel manifold38and a cooler39before reentering tank14.

Since past experience has shown that a leak can occasionally occur at pump outlet connection60, it and high pressure supply line61constitute 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 line52that is fluidly connected at its down stream end to an inlet55associated with leak diagnostic component50. Thus, in the rare occurrence where a leak exists at the high pressure connection60, that fuel will be captured and returned to tank via leak return line52.

High pressure supply line61is split into a right hand supply line63and a left hand supply line64at a T-Flange62. Supply line63and64are also preferably double walled tubes that create a low pressure envelope around the high pressure lines63and64. The right hand supply line63is fluidly connected to right hand common rail11, which together constitute another high pressure space of fuel system10. Likewise, left hand supply line64and the associated left hand common rail (not shown) constitute a third high pressure space for fuel system10. Any fuel that leaks from right hand rail11and/or supply line63is captured by the low pressure envelope and channeled to a right hand leakage connection66, where the fuel can be captured in right hand leak line51for return to tank14. Right hand leak line51is fluidly connected at its downstream end to an inlet56associated with leak diagnostic component50. Likewise, left hand supply line64and 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 connection67. Thus any fuel leakage that occurs in this high pressure space is captured in left hand leak line53that is fluidly connected at its downstream end to an inlet54, which is also associated with leak diagnostic component50. Any leakage that is captured by leak return lines51,52or53passes through leak diagnostic component50, past wet sensor25and into a consolidated leak like57, which is fluidly connected to tank14via drain line48. In other words, an upstream end of consolidated leak line57is fluidly connected to an outlet59from leak diagnostic component50.

Fuel system10also includes several conventional return lines that are associated with fuel injectors16. For instance, any fuel returned via the normal operation of fuel injectors16from the right hand bank enter a right hand injector return manifold37, and is then channeled to drain line48via a right hand fuel injector return line46. Likewise, any fuel not used by the left hand fuel injectors is fluidly channeled to drain line48via a left hand injectors return line47.

Referring now toFIGS. 2-4, the structure of leak diagnostic component50is illustrated. In particular, leak diagnostic component50includes a metallic junction block70that is mounted at a suitable location on or adjacent the engine associated with fuel system10. Junction block70is formed to include inlets54,55, and56, which are each fluidly connected to the separated leak lines53,52and51, respectively, as shown inFIG. 1. Within junction block70, each of the leak lines51,52and53has an associated leak collection cavity75,74and77, respectively. Thus, any fuel traveling in leak return line51is initially channeled to leak collection cavity75before overflowing into consolidated leak line57. Likewise, any leakage in return line51first fills leak collection cavity77before overflowing into consolidated leak line57. Finally, any leakage that is captured in leak line53is first channeled to leak collection cavity74before overflowing into consolidated leak line57. Each of the leak collection cavities74,75and77has an associated leak diagnostic port72,73and76, respectively. The leak diagnostic port72,73and76extend between the respective leak collection cavities and an outer surface of junction block70. Component50is preferably oriented such that gravity will maintain fuel, if any, in the respective leak diagnostic cavities. When installed in the fuel system10ofFIG. 1, a separate plug is placed in each of the leak diagnostic ports72,73and76. These plugs are preferably removable and can take on a wide variety of structures known in the art that allow for leak diagnostic ports72,73and76to normally be maintained closed but allow each to be opened, preferably manually by a technician seeking to diagnose a leak location.

Junction block70is also formed to include a wet sensor port71within which is mounted a wet sensor25(FIG. 1) so as to be in fluid contact with consolidated leak line57. Finally, Junction block70is machined to include an outlet59that allows component50to be fluidly connected to an external portion of consolidated leak line57as shown inFIG. 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 line57where the leak is detected by the wet sensor25, which provides an alert to an operator in a conventional manner. For instance, the wet sensor can be operably connected to the electronic control module18, as shown inFIG. 1, where some suitable alert is provided to an operator by the electronic control module in a conventional manner.

Although the embodiment ofFIGS. 1-4shows three separate leak lines, those skilled in the art will appreciate that the fuel system10can 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. 5-8show a leak diagnostic component150according to another aspect of the present invention that includes six separate leak inlets151-156, which would be fluidly connected to different high pressure spaces associated with a different engine. For instance, inlets151and152might be fluidly connected to different high pressure distribution blocks, inlets153and154could be fluidly connected to leak lines associated with two different high pressure pump connections, and inlets155and156could 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 inlets151-156has a separate leak collection cavity that is fluidly positioned between the inlet and a common outlet159. Thus, fuel entering one of the inlets151-156will first collect in a separate leak collection cavity before overflowing into a common leak return line fluidly connected to outlet159. Upstream of common outlet159, junction block170includes a wet sensor port171within which is mounted a wet sensor, which could be similar to wet sensor25identified inFIG. 1. Thus, before exiting junction block170, any leakage would be detected by the wet sensor before exiting at outlet159. Each of the leak collection cavities is fluidly connected to a leak diagnostic port that opens through an outer surface of junction block170. For instance, leak inlet151is fluidly connected to a leak collection cavity172, which is separated from the outer surface of junction block170by leak diagnostic port181. Several of the internal fluid connections are facilitated by unnumbered radial cross bores that have their openings plugged in the finished component. Leak inlet154is fluidly connected to a leak collection cavity174and a leak diagnostic port182. As in the previous embodiment, the leak diagnostic ports181are preferably plugged in a suitable manner during normal operation of the engine. Although not shown, each of the six inlets151-156has a separate leak collection cavity and a separate leak diagnostic port associated therewith. In order to consolidate different components and associated ports, junction block170also includes a fuel return manifold that includes fuel return inlets140and a return manifold outlet141. Those skilled in the art will appreciate that the return manifold inlets140would 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 ofFIG. 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.