Supercharged diesel engine with a common-rail injection system

A supercharged diesel engine having at least one charged air conduit for distributing charged air and having a first chamber for conveying the charged air. Air inlet openings of the cylinder head are connected to the first chamber in a gastight manner. The charged air conduit has at least one second chamber, which is separate from the first chamber and has a removable lid. The fuel reservoir is secured in the second chamber, which is provided with a first passage allowing the high pressure fuel line and the fuel reservoir to communicate with one another. The second chamber has at least one second passage, facing the cylinder head, allowing the fuel injection lines and fuel connections on the cylinder head to communicate with one another. With the lid in place, the second chamber encloses the fuel reservoir, the fuel injection lines and the fuel connections such that in the event of leakage at any of them, leaking fuel flows into the second chamber.

The instant application should be granted the priority date of Dec. 3, 2004, the filing date of the corresponding German patent application 10 2004 058 350.1.

BACKGROUND OF THE INVENTION

The invention concerns a supercharged diesel engine with a Common-Rail injection system.

Common-Rail injection systems are increasingly used for better fuel efficiency and optimization of pollutant emissions of diesel engines. The system pressure obtainable in such fuel injection systems is very high. It does not depend on load and engine speed and allows optimal control of the injection process. In combination with an appropriate characterization of the charging, the result is an optimization of the combustion in all load ranges.

Besides the advantages described above, Common-Rail injection systems also have a disadvantage. The very high injection pressures that range from 1500 bar to 2000 bar today and will be even higher in future systems have to be controlled. This implies an extraordinarily high material stress, especially in areas of high fuel pressure such as the high-pressure fuel reservoir and the fuel injection lines of the injection system. In case of a breakage or leakage in such a high-pressure section of the injection system, fuel might leak out in the form of fine mist. To prevent ignition and hence explosive combustion, it is essential for leaking fuel to be collected safely and without reaching the surroundings, especially if engines with such injection systems are used in safety relevant locations.

In order to meet the mentioned safety requirements, it is known from DE 197 16 513 C2 to provide a casing for the fuel reservoir and the injection lines. The casing is realized in such a manner that the high-pressure fuel reservoir is integrated into a duct or channel, which is at least partly formed of the walls of the crankcase. This arrangement allows a safe casing of the endangered areas of the injection system, yet it has significant disadvantages in practical use. The crankcase has to be constructed a certain way if the casing is to be placed in it or next to it. Changes to the structure of the crankcase are a disadvantage, because it is a complex and very expensive component that often doesn't change throughout several engine generations or is used for various different engine types with different types of injection systems. Especially if a mass-produced engine was to be retrofitted with a casing, this would mean an expensive modification of the crankcase. In addition to that, the location of the crankcase is a highly unsuitable place for the high-pressure fuel reservoir because the large masses moved in the crankcase result in an increased vibration stress for the high-pressure fuel reservoir and the connected injection lines. Since the material stress is high anyway, increased vibration stress is to be avoided. Furthermore, the arrangement described above makes it complicated to collect, drain off and detect leaking fuel for there are different places where leaking fuel might accumulate.

Another fuel injection system is known from EP 0 690 221 A1. In this system, a high-pressure fuel reservoir supplied by a high-pressure fuel pump is integrated into the wall of a cylinder head cap of a diesel engine. Injection lines lead from the high-pressure fuel reservoir to fuel injection valves located in the cylinder head. This system is supposed to be advantageous because the high-pressure fuel reservoir is protected from vibration and damage. But placing the high-pressure fuel reservoir as described above has a significant disadvantage. Every time the cylinder head cap is demounted, which has to happen frequently for maintenance purposes, all connections from the high-pressure fuel reservoir to the fuel injection lines and to the high-pressure fuel pump have to be detached. Detaching of those sensitive connections, though, has to be avoided, both because screwing on and fastening of the fuel lines causes states of stress in them and because the system has to be kept extremely clean. Besides, a complete casing of the fuel injection lines is impossible because they have to be installed after the cylinder head cap has been mounted. Therefore, mounting openings are indispensable. Another disadvantage of the arrangement described above is that it cannot be used on individual cylinder heads, which are often part of diesel engines.

Another system known from DE 75 15 413 U1 shows an internal combustion engine on which all linesnecessary for fuel supply are placed in an extrusion, running parallel to one another. The extrusion can be integrated into an engine cowling or into a cooling air guidance means. Supposedly, the advantage of this arrangement lies in a grouping of the fuel lines that is easily understandable, safe to operate, easy to install and space saving. Meanwhile, it is a disadvantage that all fuel lines connected to the engine have to be detached when the engine cowling is demounted for maintenance purposes. Detaching of the fuel lines and especially of the high-pressure connections of Common-Rail injection systems has to be avoided for the reasons explained above. Besides, it is impossible to use this arrangement in combination with individual cylinder heads. Finally, an extrusion is not suited for a high-pressure fuel reservoir. The strength factors of such an extrusion are by far not enough regarding the pressures that need to be controlled.

Proceeding from this state of the art, it is an object of this invention to develop a diesel engine with a Common-Rail injection system in such manner, that the high-pressure section of the injection system is securely cased and well positioned concerning vibration. In addition to that, it is of importance that the position and casing of the high pressure reservoir and the fuel injection lines not require structural modifications of the crankcase or of the cylinder head and that the mounted casing not have negative effects on maintenance or repairing of the diesel engine.

SUMMARY OF THE INVENTION

The supercharged diesel engine of the present application has a Common-Rail injection system, which utilizes at least one high pressure fuel reservoir that is connected with a high pressure fuel pump via a high pressure fuel line. The engine has at least one bank of cylinders having the cylinders thereof disposed in a row, wherein at least one cylinder head is associated with the bank of cylinders. At least one of the cylinders is associated with the cylinder head, which is provided with air inlet openings. A plurality of the cylinders are associated with the high pressure fuel reservoir, which is connected via fuel injection lines to respective fuel connections, disposed on the cylinder head, of individual ones of the cylinders. The engine furthermore has at least one charged air conduit for distribution of charged air and having a first chamber for conveying the charged air. The air inlet openings of the cylinder head are connected to the first chamber in a gastight manner, wherein the charged air conduit has at least one second chamber, which is separate from the first chamber and has a removable lid. Mounting means are provided in the second chamber, and the high pressure fuel reservoir is adapted to be secured in the second chamber via the mounting means. The second chamber is provided with a first passage via which the high pressure fuel line and the high pressure fuel reservoir are adapted to communicate with one another. The second chamber is also provided with at least one second passage, facing the cylinder head, via which the fuel injection lines and the fuel connections of the cylinder head are adapted to communicate with one another. When the lid is in place, the second chamber encloses the high pressure fuel reservoir, the fuel injection lines and the fuel connections such that in the event of leakage at any of these, leaking fuel is adapted to flow into the second chamber.

The invention is based on the following considerations. Placing the high-pressure fuel reservoir on or inside the crankcase or on or inside the cylinder head requires structural modifications of the crankcase and/or cylinder head. It is therefore not an option, especially if the crankcase and/or cylinder head are meant to be used in various different types of engines with different types of fuel injection systems. Structural modification of the crankcase and/or cylinder head is also not an option if engine concepts used throughout several engine generations are to be retrofitted without changing those components. Based on the considerations specified above, it was found that placing the high pressure fuel reservoir inside an additional chamber which is formed on to the charge air conduit induces several advantages. Primarily, any modifications of the crankcase or the cylinder head can be avoided, solely the charge air conduit, a relatively inexpensive attaching part, has to be modified. Furthermore, the charge air conduit is comparatively low in vibration, for it is structurally separated from the heavily vibrating parts of the diesel engine. In addition to that, it is possible to make the fuel injection lines very short and therefore avoid high vibrational amplitudes by placing the charge air conduit on the cold side of the diesel engine, next to the intake air openings of the cylinder head. On the diesel engine, the charge air conduit is one of the parts least affected by maintenance and repairing. Unnecessary detaching of high-pressure fuel reservoir and fuel injection lines can therefore be avoided. Provided that the cylinder head is continuous, it could be demounted without having to detach the high-pressure fuel reservoir or the fuel injection lines first. The charge air conduit, the high pressure fuel reservoir and the fuel injection lines form a structural unit that can be pre-assembled and can therefore reduce the expenditure during the final assembly of the diesel engine. By providing a removable lid, which seals the second chamber of the charge air conduit, the high-pressure fuel reservoir and the fuel injection lines are completely accessible, so that maintenance and repairing can take place unimpeded. A particular advantage is that the arrangement according to this invention can be used both on in-line engines and on V-enginges, each either with individual or continuous cylinder heads. In other words, it can be used on various types of engines, and retrofitting of mass produced engines is possible without modifications of the engine block.

By placing the high-pressure fuel reservoir into the second chamber of the charge air conduit, that chamber can be configured and sealed in such a way that certain parts of the high-pressure fuel reservoir are excluded from the casing. Excluded may be parts with low risk of breakage or parts that should be accessible even with the lid of the second chamber put on.

To avoid that possibly leaking fuel can accumulate in different places, the second chamber is configured in a simple and therefore advantageous way. For all applications occurring during normal operation of the diesel engine, possibly leaking fuel will accumulate in the geodetically lowest point of the second chamber.

Providing the second chamber with a discharge opening, which is most conveniently placed at the geodetically lowest point of that chamber, allows for leaked fuel to be drained off safely. This can be of particular importance if the diesel engine, for example on a ship, has to be kept running due to safety reasons, even though e.g. a fuel injection line has broken.

Providing the second chamber with a fuel sensor, which is most conveniently placed at the geodetically lowest point of that chamber, allows even for small amounts of leaked fuel to be detected reliably and makes it possible to raise an alarm in case of such an event.

The second chamber of the charge air conduit contains areas and openings through which, during all anticipated operating situations of the diesel engine, leaking or already leaked fuel could escape uncontrollably. Those areas and openings of the second chamber are sealed with regard to the surroundings to prevent leakage.

For a better understanding of the arrangement according to this invention,FIG. 1gives an overview of the spatial arrangement of the individual components. The diesel engine1represented inFIG. 1with its crankcase2and, next to that, the cylinder head3is an in-line engine with a continuous cylinder head. The engine is shown parallel to its longitudinal axis. As mentioned above, the arrangement according to this invention is not restricted to that type of engine. It could also be used on a V-engine, and instead of the continuous cylinder head shown in the example, separate cylinder heads or cylinder heads containing more than one cylinder could be placed on the crankcase. According toFIG. 1, a charge air conduit4is placed on the cylinder head3and next to the cylinder head cap3a.The charge air conduit4comprises a first chamber5, which conveys the charge air, and a second chamber6. A high-pressure fuel reservoir7with the connected fuel injection lines8is placed inside the chamber6. The fuel injection lines8connect the high-pressure fuel reservoir7to the fuel connections9on the cylinder head3. The chamber5, which conveys the charge air, extends parallel to the longitudinal axis of the diesel engine and, via the transversely extending intake ducts intakes10, is connected to corresponding intake openings (not represented in the drawing) in the cylinder head3. A coolant conduit11runs parallel to the longitudinal axis of the charge air conduit4with parts of its walls directly next to the charge air conduit4. The coolant conduit11is connected to coolant ducts (not represented in the drawing) in the cylinder head3. In order to facilitate access to the second chamber6of the charge air conduit4, that chamber has a lid12, placed on the long side facing away from the cylinder head3. The feed of charge air to the chamber5is realized through a charge air connection13shown inFIG. 2. The charge air connection13is connected to a supercharging device (not represented in the drawing) of the diesel engine1.

FIG. 1shows a schematic representation of the charge air conduit4. InFIG. 2, the same charge air conduit4is shown more detailed in top plan view, at right angle to its longitudinal direction, with direction of view onto the side with the lid12. In the representation shown inFIG. 2, the lid12is removed. The positions of the cylinder head3and, next to it, the cylinder head cap3a,are indicated schematically by a dash-and-dot line.

The upper part ofFIG. 2shows the first chamber5of the charge air conduit4with its charge air connection13. From the chamber5, the intake ducts10curve downwardly and backwards and connect to the cylinder head3, which, inFIG. 2, lies behind the charge air conduit4. The charge air conduit4is mounted on the cylinder head3, equivalent to conventional charge air conduits. Boltholes14are drilled into the wall of the charge air conduit4that is next to the cylinder head3. The boltholes14correspond to tap holes (not represented) in the cylinder head3. The bolts that mount the charge air conduit4on the cylinder head3are not shown in the drawing. For clarity reasons, only some of the bolt holes14and intake ducts10are provided with reference symbols.

Located below the first chamber5and easily distinguishable due to the circumferential sealing collar or gasket15is the second chamber6of the charge air conduit4. The high-pressure fuel reservoir7is located in the lower part of the second chamber6. The second chamber6is configured in a way that certain parts of the high-pressure fuel reservoir7jut out higher than the sealing collar15. Those parts are accessible from the outside, even after the lid has been put on. The places where the high-pressure fuel reservoir protrudes through the wall of the second chamber6can be provided with sealing devices. The high-pressure fuel reservoir7is attached to the lower part of the second chamber6through mounting straps16, which are formed on the high-pressure fuel reservoir7. The mounting straps16are provided with boltholes17and are held by fixing bolts18, which are screwed into tap holes (not represented in the drawing) in the charge air conduit4.

To connect the high-pressure fuel reservoir7with the cylinder head3, the high-pressure fuel reservoir7is provided with connecting couplings19that reach into the free space of the second chamber6. The fuel injection lines8,8aconnect the connecting couplings19on the high-pressure fuel reservoir7to the fuel connections9on the cylinder head3. For clarity reasons, only two of the total six fuel injection lines are represented inFIG. 2. Openings20are located in the wall of the second chamber6that is facing the cylinder head3. Through those openings20, the fuel connections9on the cylinder head3are accessible. The openings20are sealed by those parts of the cylinder head3that lie behind them and, if required, by sealing means extending around the edges of the openings20(not represented).

For structural reasons, it is not always practicable that the second chamber6encloses all fuel connections9. Such a case is represented in the left part ofFIG. 2. The fuel connection9a,located on the cylinder head3, lies outside of the second chamber6of the charge air conduit4. It is connected to the high-pressure fuel reservoir7by means of the double-walled fuel injection line8aand through one of the connecting couplings19. In the double-walled fuel injection line8a,an inner, actual fuel injection line is separated from a surrounding outer line by an interspace. The interspace is connected to the second chamber6of the charge air conduit4through a connection21, asFIG. 2indicates in a simplified manner. Fuel that might leak into the interspace is conducted into the second chamber6. Double-walled fuel injection lines and their connections are well known in motor vehicle technology. For this reason, the simplified representation inFIG. 2does not have to be specified.

As mentioned above, the high-pressure fuel reservoir7is placed into the second chamber6of the charge air conduit4in such a way that certain parts of the high-pressure fuel reservoir7are situated outside of the chamber6. The pertaining parts are the excess-pressure valve22and, connected to that, the discharge connector23, both represented on the right side ofFIG. 2, and the high pressure connection24of the high pressure fuel reservoir7, shown on the left side ofFIG. 2. The discharge connector23of the excess-pressure valve22is connected to the drain reservoir26through the connecting line25. The drain reservoir26collects fuel returning from the fuel injection system. Through a high-pressure fuel line27, the high-pressure connection24is connected to a high-pressure fuel pump28. The high-pressure fuel pump28is responsible for generating the high fuel pressure. AsFIG. 2indicates in a simplified way, the high-pressure fuel line27is a double-walled line. The interspace between the actual high-pressure line and the surrounding outer line is connected to the second chamber6of the charge air conduit4. InFIG. 2, that connection is indicated by the arrow labeled with number29. A pressure sensor31can be installed on the high-pressure fuel reservoir7in order to determine the pressure conditions inside. The electrical connections (not represented) of the pressure sensor31can be run through the wall of the second chamber6in an appropriate place. Depending on its position, such a connection may require sealing.

The tap or threaded holes30in the second chamber6serve to attach the lid12, which is not represented inFIG. 2. The tap holes30correspond to bolt holes (not represented) in the lid12. By means of bolts (not represented), the lid12can be screwed onto the charge air conduit, sealing the second chamber6along its sealing collar15. Between the lid12and the sealing collar15, soft sealing material (not represented) may be applied.

In conjunction withFIG. 3, the following description explains the controlled drainage of fuel that flowed into the second chamber6of the charge air conduit4after leaking from the high-pressure section of the fuel injection system.FIG. 3shows a side view, with direction of view from the right side, of the arrangement according toFIG. 2. The lid12is put on, and in the area of the lid, the arrangement is represented in a fractionized way.

FIG. 3shows that a discharge connecotr32is located on the lid12. The connector32is connected to the drain reservoir26through a return line33. In case of fuel leaking from the high-pressure system of the fuel injection system, that fuel drains into the drain reservoir26. In this example, the drain reservoir26mentioned above is the same reservoir that serves to collect fuel regularly draining out of the fuel injection system. Unlike the example presented here, there can be two separate drain reservoirs. The discharge connector32is placed in the geodetically lowest point of the second chamber6. Therefore, no fuel can accumulate in the second chamber6. For the sake of completeness it is mentioned that the inner relief of the second chamber6is naturally configured in a way that it descends steadily towards the discharge connector32. It is assumed, that if the diesel engine is in a horizontal position, the charge air conduit4or at least its second chamber6is also horizontal. If the permissible and actual operating positions of the diesel engine differ significantly from the horizontal position, the inner walls of the second chamber6have to be configured in a way that they form a funnel, narrowing towards the discharge connector32. Examples for such conditions are if the diesel engine is installed in a vessel or in a motor vehicle used in extreme terrain, such as a tracked vehicle, e.g., a snowmobile.

To detect fuel that is leaking from the high-pressure section of the fuel injection system, a fuel sensor34is placed in the discharge connector32. Line35connects the fuel sensor34with an analyzing circuit36, which can be part of an engine-controlling device. The analyzing circuit36acts on the alarm system37, which raises an alarm if fuel is leaking from the high-pressure section of the fuel injection system. If permissible, an emergency turn off of the diesel engine can of course be performed by the analyzing circuit36.

As mentioned above, double walled lines like the fuel injection line8aand the high-pressure fuel line27have an interspace between the actual high-pressure line and the outer, surrounding line. Unlike the example described above, instead of being connected to the second chamber6of the charge air conduit4, that interspace can be connected to the return line33. In that case, the fuel sensor has to be placed downstream of that connection. Likewise, it is possible to provide the fuel injection line8aand the high-pressure fuel line27or rather their interspaces or subsequently added lines with separate fuel sensors and to directly connect the interspaces with the drain reservoir26.

Furthermore, the embodiment described in conjunction with the drawings can be varied in order to save material, weight and space. Parts of the walls of the second chamber6can therefore be formed by contiguous components. Eligible is e.g. that area of the second chamber6located right next to the coolant conduit11. In that area, the wall of the chamber6can be omitted and replaced by the wall of the coolant conduit11. Since the wall of the coolant conduit11seals the second chamber6towards the top, additional sealing is not required.

With the knowledge of one skilled in the art, the embodiments described above can naturally be configured in a great variety of ways without moving away from the basic idea of this invention. Therefore, the embodiments described above are to be seen only as examples.

The specification incorporates by reference the disclosure of German priority document 10 2004 058 350.1 filed Dec. 3, 2004.