GB2579641A

GB2579641A - Assembly of a common rail in an internal combustion engine

Info

Publication number: GB2579641A
Application number: GB1820040.2A
Authority: GB
Inventors: Akin Levent; Altinol Cuneyt
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-12-10
Filing date: 2018-12-10
Publication date: 2020-07-01
Anticipated expiration: 2038-12-10
Also published as: GB201820040D0; GB2579641B

Abstract

An assembly of a common rail in an internal combustion engine comprises a common rail (12, fig.1) having an elongate tubular body 20 extending along a longitudinal axis (22, fig.2) with an inner longitudinal bore 23 for containing pressurized fuel. The body 20 includes a plurality of transversally protruding connecting pieces 28, each connecting piece comprising a branch bore 30 in communication with the longitudinal bore. Two or more mounting supports 16 are provided as parts of engine component(s) of the internal combustion engine, for assembling the common rail (12) to the engine. The mounting supports 16 include a through hole 18. At least two of the connecting pieces 282 (and 284, fig.2) are also referred to as carrier pieces, and perform an additional mounting function, and are engaged in the holes 18 of the mounting supports, respectively, and are locked therein by a respective locking elements 50.

Description

ASSEMBLY OF A COMMON RAIL IN AN INTERNAL COMBUSTION ENGINE

Technical field

The present invention generally relates to the field of internal combustion engines and in particular to the assembly of a common rail of a fuel injection system in such engine.

Background of the Invention

Current diesel internal combustion engines generally comprise a high pressure pump feeding high pressure fuel to a reservoir referred to as common rail. The common rail, which acts as pressure accumulator, in turn provides the fuel to a plurality of solenoid actuated fuel injectors which are cyclically driven to inject fuel into a respective cylinder.

In order to withstand the very high pressure (above 2000 bars) of the fuel from the high pressure pump, the common rail is heavily built. It is typically made from a forged steel blank and comprises an elongated cylindrical body with a through bore along its longitudinal axis defining the inner volume that will, in use, receive high pressure fuel. The common rail typically comprises cylindrical cavities machined at each extremity of the body for receiving a pressure regulator device, such as a passive valve or an electromagnetic controlled valve, and a pressure sensor. An inlet port and a plurality of tubular connection pieces forming outlet ports protrude from the cylindrical surface of the body. The outlet ports are commonly formed as cylindrical sleeves extending in a direction perpendicular to the longitudinal axis of the common rail.

The mounting location of the common rail in the engine is usually chosen in order to attach the common rail to a surface that is sufficiently rigid to support it and withstand the vibrations generated by the engine. The common rail fixing features must also be able to resist the mechanical stresses induced by the fuel pipes delivering the fuel to the injectors and by the supply pipes connecting the common rail to the high pressure pump.

The common rail is thus generally mounted to a rigid engine component such as e.g. cylinder head or cylinder block.

For example, a known common rail has two or more extensions named "mounting pads" protruding transversally from the rail body for fixing the rail to an engine component (cylinder block).

These mounting pads are designed as flat plates with a through hole for passing a screw that further engages in a corresponding threaded bore in a wall of the engine component.

Although the use of such mounting pads is extremely common, it must be observed that it requires additional material on the rail body, increasing its weight. The forged body is also more complex, leading to increased manufacturing costs and reducing robustness.

This observation is not in line with the constant aim of the automotive field, which strives to reduce component mass and costs, optimising packaging and robustness, decreasing parts variety, and simplifying process requirements. There is therefore a need for a simpler way of assembling the common rail to the engine.

A further fastening arrangement for a common rail is disclosed in document EP 2 640 956. Mounting features are attached to the engine and comprise a circular clamp that surrounds the tubular body of the common rail. The clamp consists of two detachable semi-circular portions.

Object of the invention An object of the present invention is to provide a simple and efficient way of assembling a common rail to an internal combustion engine.

General Description of the Invention

The above-mentioned object is solved by the present invention, which proposes an assembly of a common rail in an internal combustion engine comprising: a common rail having an elongate tubular body extending along a longitudinal axis with an inner longitudinal bore for, in use, containing pressurized fuel, wherein the body comprises a plurality of transversally protruding connecting pieces, each connecting piece comprising a branch bore in communication with the longitudinal bore; and two or more mounting supports as parts of engine component(s) of the internal combustion engine, for assembling the common rail to the engine.

According to the invention, the mounting supports include a through hole; and at least two of the connecting pieces, referred to as carrier pieces, are to engaged in the holes of the mounting supports, respectively, and locked therein by a respective locking element.

In the present invention, some of the usual connecting pieces -that typically serve as inlet/outlet ports for the accumulator body-are assigned an additional mounting function. At least two of the connecting pieces are used to assemble the common rail and hence referred to as carrier pieces.

On the engine side, there is a corresponding number of mounting supports. The function of the locking element is to block the carrier piece so that it remains in engagement in the orifice of the mounting support, ensuring a stable and safe attachment to the engine.

As will be discussed below, the implementation of the invention actually requires only few design modifications of the common rail, as compared to conventional connecting pieces. Mainly, the carrier pieces have an increased length, in order to incorporate the mounting function to the carrier piece. Assembling the common rail to the engine then simply involves engaging the carrier pieces in the holes of the corresponding mounting supports and locking the assembly by means of the locking elements.

In general, the connecting pieces, including said carrier pieces, comprise an end thread that permits connection to a fuel line or an accessory (e.g. pressure sensor) mounted to the rail body. For connection to fuel lines, the end section of the connecting pieces are provided with a threaded section on their outer surface, herein referred to as end male thread. A fuel line typically includes a pipe or duct, ending on the common rail side by a nut, referred to as union nut, that is traversed by the pipe and threadedly engaged on the end male thread.

In embodiments, the carrier pieces are configured to include a profiled outer section and the locking element is designed to cooperate with the profiled outer section to secure the carrier pieces on the respective mounting supports. This can be done by any appropriate designs and shapes, e.g. by form-fitting or form combination, suitable to block the carrier piece in the hole of the mounting support. As a further example, the profiled outer section may be an annular groove surrounding the carrier piece and the locking element is a retainer ring that is inserted into the groove.

The profiled outer section may be conveniently located between the end male thread and the tubular body, but separated from the body by the mounting support.

In a very practical embodiment, the profiled outer section is a second male thread, and the locking element is a nut, referred to as fastening nut, threadedly engaged onto the second male thread and bearing against the mounting support. This is a very efficient embodiment where it suffices to design the carrier pieces with an additional length to integrate the threaded section for the fastening nut, as compared to the other connecting pieces that only include the end male thread. The end male thread and second male thread may be continuous along the length of the carrier piece, and of same diameter. In this case, it is preferred that there is an axial gap between the fastening nut and the union nut of the fuel line that is engaged on the end male thread. Alternatively the section of the carrier piece bearing the second male thread can be of larger diameter.

In another embodiment, the locking element is a union nut traversed by a fuel line in communication with the branch bore of the carrier piece. For this embodiment it is sufficient that the connecting piece used as carrier piece has a length long enough to traverse the mounting support. The union nut is here used to fix the fuel line and lock the fuel rail in engagement in the mounting support. In such embodiment, it is preferred to interpose a spring member between the union nut and the mounting support, to be preloaded therebetween. This spring gives the desired play to allow screwing the union nut as required on the carrier piece to ensure a proper sealing.

The mounting supports may be formed integrally with, or fixed to, the engine component they are associated with. The through holes are preferably circular with an inner diameter adapted (matching with mouting play) to the outer diameter of the connecting pieces. The mounting supports are preferably associated with a same engine component, e.g. cylinder head or cylinder block, but they could be on different engine components. The mounting supports are normally made of a rigid material, e.g. a metal, in particular steel. When they are formed intergally with the engine component they are made from the same material. Conveniently, the mounting supports are formed as flat tabs protruding from a same engine component.

Brief Description of the Drawings

Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawings, wherein: Fig. 1 is a perspective view of the assembly of a common rail in an engine according to an embodiment of the invention; Fig. 2 is a perspective view of the common rail of Fig. 1; Fig. 3 is a cross-section view of the assembly of Fig.1 through a plane passing through a mounting tab and a carrier piece.

Description of Preferred Embodiments

Fig.1 shows a common rail 12 mounted in an internal combustion engine 10, whereas the common rail 12 is shown alone in Fig. 2. The engine components and operation will not be detailed herein as it is not the focus of the invention, but the common rail 12 and its assembly to the engine 10 will be described below.

In the present embodiment, the common rail 12, or also simply rail, is mounted to a component of the engine 10, namely the cylinder block 14 of the engine (partially shown). The common rail 12 may alternatively be attached to another engine interface, i.e. another component, for example to the cylinder head, crankcase, or to the intake manifold, or any engine part having sufficient rigidity.

For the purpose of assembling and fixedly mounting the common rail 12 to the engine 10, here to the cylinder block 14, the latter is provided with a pair of mounting supports, which in this embodiment take the form of mounting tabs 16 provided with a through hole 18.

The common rail 12 is designed as a high-pressure fuel accumulator for a diesel engine fuel injection system, i.e. it is a high-pressure reservoir that stores high pressure fuel and distributes it to a number of fuel injectors. As best seen in Fig. 2, the rail 12 comprises an elongated tubular body 20 extending along a main longitudinal axis 22, which is made from metal, conventionally steel. The body 20 comprises an internal longitudinal bore 23, partly represented by dotted lines in Fig.2, that extends parallel to the longitudinal axis 22 for receiving, in use, high pressure fuel. To withstand the high-pressure, the body 20 typically has a relatively thick wall thickness. In the present variant, the longitudinal bore 22 is a through bore extending between two cavities, one at each extremity of the body. The cavities accommodate respectively a control valve 24 and a pressure sensor 26.

The rail 12 is provided with a plurality of tubular-shaped protrusions, designated generally 28, but individually differentiated on the drawings by a subscript index (281 to 286), and referred to as connecting pieces. The connecting pieces 28 extend transversally to the longitudinal axis 22, in particular radially, and protrude from the lateral surface of the body 20. The connecting pieces 28 are distributed along the length of the body 20. Each connecting piece 28 comprises an internal passage or branch bore 30, in communication with the longitudinal bore 23 and opening in the end face of the connecting piece 28. The branch bore 30 is typically centred in the connecting piece 28 and extends radially. As can be seen, the connecting piece 28 is generally shaped as a cylindrical sleeve extending radially from the body 20 and defining the branch bore 30, with a terminal orifice 32. At the basis of the sleeve 28, opposite the end face, there is a radially extending annular shoulder 34.

As it is known in the art, the rail 12 comprises a plurality of such connecting pieces 28, which are used for supplying fuel to or from the rail.

It may be noted that the rail may, in other applications, also have a simpler or a more complex design. The rail may for example further comprise a radial sensor connection port, or may not comprise a control valve or a pressure sensor port. Also, the connecting pieces 28 can be differently oriented and positioned.

In the present embodiment, the rail 12 comprises a total of 6 connecting pieces, amongst which there are: four high pressure outlet ports 281 to 284 for supplying fuel injectors, not shown, with high pressure fuel; one high pressure inlet port 285 for receiving fuel from a high pressure pump, not shown, and one low pressure outlet port 28e associated with the pressure control valve 24 to regulate the pressure inside the common rail 12.

All of these connecting pieces 28 are generally in fluid communication with other components of the injection system by means of fluid lines / ducts fixed onto their ends. Therefore, the connecting pieces 28 are typically provided with a threaded section next at their free end. Specifically, the end section of the sleeve 28, i.e. next to the end face, is provided with an external thread 36. This allows screwing thereon fluid lines with a terminal union nut, as shown in Fig. 1.

According to an important feature, two connecting pieces 282 and 284 are configured and used for fixing the rail 12 to the engine /cylinder block 14 and are therefore referred to as carrier pieces. In the present case, the carrier pieces 282 and 284 are two high pressure outlets.

It will be appreciated that the carrier pieces 282 and 284 have a double function, namely to supply high pressure fuel to the fuel injectors and to permit mounting the rail 12 to the engine interface.

As shown in Fig.1, the carrier pieces 282 and 284 cooperate with the mounting tabs 16 and are actually engaged in the through hole 18 of a respective mounting tab 16. Turning to Fig.3, one will recognise the fuel rail body 20 and carrier piece 282. Reference sign 16 designates one of the mounting tabs with circular through hole 18, which extends from the cylinder block 14 (and is integral therewith). Carrier piece 16 is engaged into hole 18 of tab 16. The rail body 20 is in contact with the tab 16 and in fact rests against the lower side 161 of the tab 16 with the annular shoulder 34 located at the basis of the carrier piece/sleeve 28. Most of the length of the connecting piece 28, resp. of the sleeve, hence protrudes upwardly beyond the upper side 162 of tab 16. The sleeve 28 and hole 18 have matching diameters so that the connecting piece 28 can be introduced into the hole 18 with mounting play that also allows for dilatation.

The carrier piece 282 is connected to a high pressure fuel duct 38 by a union nut 40 threadedly engaged onto the end male thread 36 of the sleeve 28. The union nut 40 has an end cover 42 traversed by the fuel duct 38, the extremity of which is applied on chamfered orifice 44 of the branch bore 30 extending through the sleeve 28 down to the longitudinal bore 23. The duct 38 has an outwardly protruding annular bulge 46 that has a larger diameter than an aperture 48 through which it crosses the union nut 40, whereby it can be biased towards the connecting piece 282.

Reference sign 50 designates a fastening nut that forms a locking element that blocks the carrier piece 282 in engagement in the mounting tab 16 and thus allows for a secure mounting of the common rail 12 to the engine 10. The nut 50 is threadedly engaged onto a second male thread 52 provided on the carrier piece 282, i.e. on its sleeve, and located before the end male thread 36. Specifically, the second male tread 52 is positioned between the end male thread 36 and the body 12, but on the opposite side of the shoulder 34 with respect to the tab 16. Accordingly, the fastening nut 50 can be screwed tightly to bear against the upper side 162 of mounting tab 16.

It goes without saying that in practice, upon engagement of the carrier piece 282 into the hole 18 of the mounting tab 16, fastening nut 50 is screwed first, and then the pipe with union nut 40 is put in place.

As can be observed, in the present embodiment since the carrier piece 282 is formed by a straight cylindrical sleeve, the end thread 36 and second thread 52 have the same diameter and thus can be formed as a continuous thread.

In this embodiment, the carrier pieces 282 and 284 have a greater length than the other connecting pieces 281 and 283 serving as high pressure outlets. Indeed, the sleeve is of greater length since it is passes through the tab 16 and includes an additional length of threaded section, namely the second threaded section 52.

Functionally, one can distinguish four sections along the sleeve of carrier piece 282, as illustrated on Fig.3. At the basis of the sleeve, at the junction with annular shoulder 34 is the tab section 56, i.e. a length of the sleeve that crosses the tab hole 18. Next to the tab section is the second male thread 52 that receives the fastening nut 50. The threaded section here extends continuously from the second threaded section 52 up to the end face of the sleeve, where the end male thread 36 is provided.

Reference sign 56 designates an annular clearance or gap between the two nuts 50 and 40. It is provided as a safety measure to avoid contact between the two nuts, in particular to avoid potential screwing problems of the union nut 40 that may compromise a fluid tight sealing.

As it will be understood, the number, orientation and axial positioning of the connecting pieces depend on the design and type of application and may thus vary from what has been shown above. For some applications there may be more or less than four connecting pieces provided as high pressure outlets. In diesel engines there is typically one high pressure outlet per cylinder. Also, the number of connecting pieces to be used as carrier piece may be greater than two. They can be selected based on their position on the rail in consideration of the ease of mounting and distribution of mechanical forces. The number of mounting supports is adapted to the number of carrier pieces.

The diameter of the sleeves will also depend on the application, and is adapted to desired flow rates in the fuel pipes 38. Common sleeves are designed with standard diameters M8, M16, M20 etc. The mounting supports, i.e. tabs 16, are advantageously integral with the engine component they are associated with. They can be manufactured in one piece with the component, e.g. through casting and/or machining of the component body. Alternatively, the tabs can be welded or mechanically fixed to the component. The tabs are typically metallic, in particular steel. The length of the tabs is preferably such that the rail can be mounted spaced away from the component, to avoid direct contact.

Although the mounting supports are here presented as two separate tabs 16, other shapes are possible. Also, the mounting supports can be unified, e.g. a large tab can extend parallel to the rail and comprise two holes for receiving two carrier pieces.

In other embodiments not shown, the diameters may vary along the sleeve of the carrier ports 282 and 284. For example, the diameter at the second thread 52 may be increased in order to improve the robustness of the connection.

LIST OF REFERENCE SIGNS: engine 12 common rail 14 cylinder block 16 mounting tabs/support 18 through hole tubular body 22 longitudinal axis 23 longitudinal bore 24 control valve 26 pressure sensor 28, 28; connecting piece branch bore 32 terminal orifice 34 shoulder 36 end thread 38 fuel duct union nut 42 end cover zo 44 orifice 46 annular bulge 48 aperture fastening nut 52 thread 56 tab section

Claims

Claims: Assembly of a common rail in an internal combustion engine, comprising: a common rail (12) having an elongate tubular body (20) extending along a longitudinal axis (22) with an inner longitudinal bore (23) for, in use, containing pressurized fuel, wherein said body (20) comprises a plurality of transversally protruding connecting pieces (28), each connecting piece comprising a branch bore (30) in communication with said longitudinal bore; two or more mounting supports (16) as parts of engine component(s) of said internal combustion engine, for assembling said common rail (12) to the engine; wherein said mounting supports (16) include a through hole (18); at least two of said connecting pieces (282, 284), referred to as carrier pieces, are engaged in said holes (18) of said mounting supports, respectively, and locked therein by a respective locking element (50).
2. The assembly according to claim 1, wherein said connecting pieces (28), including said carrier pieces (282, 284), comprise an end male thread (36) for connection in particular to a fuel line (38).
3. The assembly according to claim 2, wherein said carrier pieces (282, 284) include a profiled outer section and said locking element is configured to cooperate with said profiled outer section to secure said carrier pieces in the respective mounting supports.
4. The assembly according to claim 3, wherein said profiled outer section is located between said end male thread (36) and said tubular body (20), but separated from said body by said mounting support (16).
5. The assembly according to claim 3 or 4, wherein said profiled outer section is a second male thread (52), and said locking element is a nut (50) threadedly engaged onto said second male thread (52) and bearing against said mounting support (16).
6. The assembly according to claim 3 or 4, wherein said locking element form-s fittingly engages said profiled outer section.
7. The assembly according to claim 3 or 4, wherein said profiled outer section is an annular groove and said locking element is a retainer ring engaged therein.
8. The assembly according to claim 2, wherein said locking element is a nut traversed by a fuel line in communication with the branch bore of the carrier piece.
9. The assembly according to claim 8, wherein a spring member is preloaded between said nut and said mounting support.
10. The assembly according to any one of the preceding claims, wherein said body (20) is in abutment with said mounting support (16) via an annular shoulder (34) surrounding the basis of said connecting piece (28).
11. The assembly according to any one of the preceding claims, wherein said carrier pieces (282, 284) are used as outlet ports and have a greater length than the other connecting pieces (281, 283) used as outlet ports.
12. The assembly according to any one of the preceding claims, wherein said mounting supports (16) are integral or fixed to the engine component, and said through holes (18) are preferably circular with an inner diameter adapted to the outer diameter of said connecting pieces.
13. The assembly according to any one of the preceding claims, wherein said mounting supports (16) are formed as flat tabs protruding from a same engine component.
14. The assembly according to any one of the preceding claims, wherein said engine component is a cylinder head or cylinder block (14).