EP2204573A1

EP2204573A1 - Fuel supply system

Info

Publication number: EP2204573A1
Application number: EP08022495A
Authority: EP
Inventors: Edoardo Giorgetti; Giandomenico Serra
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive GmbH
Priority date: 2008-12-29
Filing date: 2008-12-29
Publication date: 2010-07-07

Abstract

Fuel supply system (50) of a combustion engine (22). The fuel supply system (50) comprises a fuel rail (18) having a main body (25) with a central longitudinal axis (L) and an inner cavity (26), a cylinder head (24), a coupling recess (27) penetrating the inner cavity (26) and the main body (25) of the fuel rail (18) and having an axis (A) extending substantially perpendicular to the central longitudinal axis (L), a tube (28) being arranged in the coupling recess (27) of the fuel rail (18) in the direction of the axis (A) and being fixedly coupled to the main body (25) of the fuel rail (18) in a fluid-tight manner, and a fixing element (34). The fixing element (34) has a head portion (36), the fuel rail (18) is arranged between the head portion (36) and the cylinder head (24), and the fixing element (34) extends through the tube (28) and is in engagement with the cylinder head (24) in a manner that the fuel rail (18) is fixedly coupled to the cylinder head (24).

Description

Fuel supply system

The invention relates to a fuel supply system for providing a combustion engine with fuel.
Fuel supply systems are in widespread use, in particular for internal combustion engines.
In order to keep pressure fluctuations during the operation of the internal combustion engine at a very low level, internal combustion engines are supplied with a fuel accumulator to which fuel injectors are connected and which has a relatively large volume. Such a fuel accumulator is often referred to as a common rail or a fuel rail.
Fuel rails often comprise a hollow body with recesses, wherein the fuel injectors are arranged. Fuel can be supplied to the internal combustion engine by the fuel supply system through the fuel injector. The fuel rail can be coupled to a cylinder head of the internal combustion engine in different manners.
The object of the invention is to create a fuel supply system for providing a combustion engine with fuel which is simply to be manufactured and which facilitates a reliable and precise connection between the fuel rail and the cylinder head.
The objects are achieved by the features of the independent claim. Advantageous embodiments of the invention are given in the sub-claims.
The invention is distinguished by a fuel supply system of a combustion engine. The fuel supply system comprises a fuel rail having a main body with a central longitudinal axis and an inner cavity, a cylinder head, a coupling recess penetrating the inner cavity and the main body of the fuel rail and having an axis extending substantially perpendicular to the central longitudinal axis, a tube being arranged in the coupling recess of the fuel rail in the direction of the axis and being fixedly coupled to the main body of the fuel rail in a fluid-tight manner, and a fixing element. The fixing element has a head portion, and the fuel rail is arranged between the head portion and the cylinder head. The fixing element extends through the tube and is in engagement with the cylinder head in a manner that the fuel rail is fixedly coupled to the cylinder head.
This has the advantage that a compact construction of the fuel supply system with a low requirement of space is possible. Furthermore, a low mass of the fuel supply system is possible. Additionally, a direct transmission of forces from the fixing element to the fuel rail and the cylinder head is possible.
In an advantageous embodiment the fixing element is a screw element with a male thread portion. The male thread portion is in engagement with a female thread portion which is arranged in the cylinder head. By this, a simple and secure coupling between the fixing element and the fuel rail as well as between the fixing element and the cylinder head is possible.
In a further advantageous embodiment a deformation element is arranged between the head portion of the fixing element and the fuel rail. This has the advantage that the deformation element can absorb forces which occur between the head portion and the fuel rail. Consequently, the fuel rail can be kept free from forces due to the fixing of the fixing element to the cylinder head.
In a further advantageous embodiment the deformation element is a bended sheet element. By this, a low mass of the deformation element in combination with a high potential of deformation is possible.
In a further advantageous embodiment a distance element is arranged between the fuel rail and the cylinder head. This has the advantage that a defined distance between the fuel rail and the cylinder head can be kept. Furthermore, a transmission of forces from the head portion of the fixing element via the fuel rail and the distance element to the cylinder head is possible.
In a further advantageous embodiment the distance element comprises a tube and the fixing element extends through the distance element. By this, a direct transmission of forces from the head portion of the fixing element via the fuel rail and the distance element to the cylinder head is possible.
Exemplary embodiments of the invention are explained in the following with the aid of schematic drawings. These are as follows:

Figure 1: an internal combustion engine in a schematic view,
Figure 2: a fuel supply system in a longitudinal section view,
Figure 3: the fuel supply system in a further longitudinal section view along the line III-III' of figure 2.

Elements of the same design and function that occur in different illustrations are identified by the same reference character.
Figure 1 shows a fuel feed device which is assigned to an internal combustion engine 22 which can be a diesel engine or a gasoline engine. A fuel tank 12 is connected to a fuel pump 14 via a first fuel line. The output of the fuel pump 14 is connected to a fuel inlet 16 of a fuel rail 18. In the fuel rail 18, the fuel is stored for example under a pressure of about 200 bar in the case of a gasoline engine or of about 2,000 bar in the case of a diesel engine. Fuel injectors 20 are connected to the fuel rail 18 and the fuel is fed to the fuel injectors 20 via the fuel rail 18. The fuel injectors 20 are arranged in a cylinder head 24 of the internal combustion engine 22.
Figures 2 and 3 show a fuel supply system 50. The fuel rail 18 is mechanically coupled of to the cylinder head 24 of the internal combustion engine 22.
Figure 2 shows a longitudinal section through the fuel supply system 50. The fuel rail 18 has a cylindrical main body 25 with an inner cavity 26 which forms an inner surface of the main body 25. The cross section of the main body 25 can be of any shape, in particular of a square shape or a circular shape as shown in Figure 3. The main body 25 has a central longitudinal axis L and is designed to contain fuel.
A coupling recess 27 penetrates the inner cavity 26 and the main body 25 of the fuel rail 18. The coupling recess 27 has a longitudinal axis A which extends basically perpendicular to the central longitudinal axis L of the main body 25 of the fuel rail 18. The coupling recess 27 comprises two openings in the main body 25 of the fuel rail 18 being arranged at the axial ends of the coupling recess 27.
The fuel supply system 50 comprises a tube 28 which is arranged in the coupling recess 27. That means that the tube 28 extends through the inner cavity 26 of the fuel rail 18. Thus, the tube 28 is arranged basically perpendicular to the central longitudinal axis L of the main body 25 of the fuel rail 18 in direction of the longitudinal axis A of the coupling recess 27. The length of the tube 28 in direction of the axis A is approximately equal to the diameter of the main body 25 of the fuel rail 18. Advantageously, collars 31 are arranged at the axial ends of the tube 28. The collars 31 are fixedly coupled to the main body 25 of the fuel rail 18, preferably by welding or brazing. This enables a fluid-proof connection between the tube 28 and the fuel rail 18.
A fuel injector cup 30 is mechanically and hydraulically coupled to the fuel rail 18. Furthermore, the fuel injector cup 30 is in engagement with a fuel inlet portion of the fuel injector 20. A sealing ring is arranged between the fuel injector cup 30 and the fuel injector 20 to sealingly couple the fuel injector 20 to the fuel injector cup 30.
Between the fuel rail 18 and the cylinder head 24 a distance element 32 is arranged. Preferably, the distance element 32 has the shape of hollow cylinder and takes up portions of the main body 25 of the fuel rail 18, as can be seen in Figure 3. Consequently, a defined distance between the fuel rail 18 and the cylinder head 24 can be obtained.
The fuel supply system 50 further comprises a fixing element 34 which has a head portion 36 and a pin-shaped portion.
Preferably, the fixing element 34 is a screw element with the head portion 36 and a male thread portion 38. The fixing element 34 extends through the tube 28 and engages the cylinder head 24. The head portion 36 is arranged at a part of an outer surface of the main body 25 facing away from the cylinder head 24. This means that the main body 25 of the fuel rail 18 is arranged between the head portion 36 and the cylinder head 24.
The cylinder head 24 has a recess 40 with a female thread portion 42. The male thread portion 38 of the fixing element 34 is in engagement with the female thread portion 42 arranged in the cylinder head 24. By this the fuel rail 18 can be fixedly coupled to the cylinder head 24.
Between the head portion 36 of the fixing element 34 and the fuel rail 18 a deformation element 48 is arranged. The deformation element 48 absorbs forces which appear between the head portion 36 and the fuel rail 18. For example, forces which appear due to the tightening torque on the fixing element 34 to screw the male thread portion 38 into the female thread portion 42 in the cylinder head 24 can be kept away from the fuel rail 18. Preferably, the deformation element 48 is formed as a bended sheet element, so that a low mass of the deformation element 48 can be obtained. Furthermore, a bended sheet element can have a high potential of deformation.
The fuel supply system 50 as described allows a compact construction of the assembly of the fuel rail 18 and the cylinder head 24. Therefore, only little space is required for these components. Furthermore, the fuel supply system 50 can have a little mass. Finally, a direct transmission of forces from the fixing element 34 to the fuel rail 18 and the cylinder head 24 can be obtained.
In the following the assembly of the fuel supply system 50 will be described:
The tube 28 is inserted into the coupling recess 27 of the fuel rail 18 and the collars 31 of the tube 28 are brazed to the main body 25 of the fuel rail 18. By this the tube 28 can be fixedly coupled to the main body 25 of the fuel rail 18 in a manner that the fuel is contained in a proof manner in the inner cavity 26 of the fuel rail 18.
In a further step, the distance element 32 is fixedly coupled to the main body 25 of the fuel rail 18. Preferably this is carried out be brazing or welding. In the following, the fuel rail 18 and the distance element 32 are arranged on the cylinder head 24 in a manner that the tube 28, the distance element 32 and the recess 40 in the cylinder head 24 are aligned on the common longitudinal axis A.
In a following step, the deformation element 48 is arranged on the main body 25, and the fixing element 34 is passed through the deformation element 48 and inserted into the tube 28 and the distance element 32. Then the fixing element 34 is screwed into the recess 40 in the cylinder head 24. Due to the tightening torque acting on the head portion 36 of the fixing element 34 the deformation element 48 can be deformed. Thereby the forces caused by the tightening torque are distributed and the stress acting on the main body 25 of the fuel rail 18 and/or the tube 28 can be kept very small.

Claims

Fuel supply system (50) of a combustion engine (22), the fuel supply system (50) comprising
- a fuel rail (18) having a main body (25) with a central longitudinal axis (L) and an inner cavity (26),

- a cylinder head (24),

- a coupling recess (27) penetrating the inner cavity (26) and the main body (25) of the fuel rail (18) and having an axis (A) extending substantially perpendicular to the central longitudinal axis (L),

- a tube (28) being arranged in the coupling recess (27) of the fuel rail (18) in the direction of the axis (A) and being fixedly coupled to the main body (25) of the fuel rail (18) in a fluid-tight manner, and

- a fixing element (34) having a head portion (36), the fuel rail (18) being arranged between the head portion (36) and the cylinder head (24), and the fixing element (34) extending through the tube (28) and being in engagement with the cylinder head (24) in a manner that the fuel rail (18) is fixedly coupled to the cylinder head (24).
Fuel supply system (50) in accordance with claim 1, wherein the fixing element (34) is a screw element with a male thread portion (38), the male thread portion (38) being in engagement with a female thread portion (42) arranged in the cylinder head (24).
Fuel supply system (50) in accordance with claim 1 or 2, with a deformation element (48) being arranged between the head portion (36) of the fixing element (34) and the fuel rail (18).
Fuel supply system (50) in accordance with claim 3, with the deformation element (48) being a bended sheet element.
Fuel supply system (50) in accordance with one of the preceding claims, with a distance element (32) being arranged between the fuel rail (18) and the cylinder head (24).
Fuel supply system (50) in accordance with claim 5, with the distance element (32) comprising a tube and the fixing element (34) extending through the distance element (32).