GB2578747A

GB2578747A - A unitary element for a rail body of a fuel injection system

Info

Publication number: GB2578747A
Application number: GB1818099.2A
Authority: GB
Inventors: Sert Nihat; Aktekin Necati; Güsav Pihava Ernur
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-11-06
Filing date: 2018-11-06
Publication date: 2020-05-27
Also published as: GB201818099D0

Abstract

A unitary element 12 for a rail body of a fuel injection equipment of an internal combustion engine, said unitary element 12 comprising a body provided with a through bore 22 extending in a longitudinal direction L of the body and with a radial bore 24 extending from an external surface 28 of the body to the through bore 22. The unitary elements 12 may be joined by welding to produce a rail body module, and allows for a relatively long common rail with a straight longitudinal bore.

Description

A UNITARY ELEMENT FOR A RAIL BODY OF A FUEL INJECTION SYSTEM

TECHNICAL FIELD

The present invention relates a unitary element for a rail body of a fuel injection equipment of an internal combustion engine.

BACKGROUND OF THE INVENTION

A common rail is a direct fuel injection system for diesel or gasoline engines that delivers high pressure fuel to the engine injectors. Known common rails include radial bores, each bore being connected to a respective injector, and a longitudinal bore providing fuel to the radial bores Depending on the required design of the common rail, the manufacturing process might be very complex and it is not rare that the obtained common rail presents defects leading to a malfunctioning of the engine.

In particular, a truck common rail may have a length of more than a meter, and it is not easy to drill a straight longitudinal bore of this length

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problem in providing a unitary element for a rail body of a fuel injection equipment of an internal combustion engine, said unitary element comprising a body provided with a through bore extending in a longitudinal direction of the body and with a radial bore extending from an external surface of the body to the through bore.

Thanks to the present invention, it is possible to manufacture various shapes of common rails depending on the chosen length and design of each unitary element.

Additionally, given the small dimensions of a unitary element, its manufacturing process is much simpler and more reliable than the manufacturing process of the common rails known from the prior art.

The external surface may comprise a bulging region around the radial bore A top surface of the bulging region may be flat around the radial bore.

The radial bore may comprise a constriction.

An end of the through bore may define a shoulder.

The invention also relates to a rail body for a fuel injection equipment of an internal combustion engine, comprising at least two unitary elements as already described, said at least two unitary elements being fixed one to another.

The unitary elements may be fixed together by their ends.

The ends of the unitary elements may be fixed together by welding The rail body may comprise at least one fixation pad The rail body may be straight shaped, the through bores of all the unitary elements being aligned.

The rail body may be an angled shaped, two successive unitary elements forming an elbow.

The invention also relates to a process for manufacturing a rail body as already described, comprising a step of welding the unitary elements one to another to obtain a rail body module and then a step of surfacing the external surface of said rail body module

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a unitary element for a rail body according to the present invention Figure 2 is a longitudinal view of another unitary element for a rail body according to the present invention Figure 3 is a perspective view of a part of a rail body according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown on the figures, the invention relates to unitary elements as well as a rail body comprising at least two unitary elements.

The rail body 10 is illustrated in figure 3 and comprises central unitary elements 12 and an end unitary element 14 (a second end unitary element is not drawn). A central unitary element 12 is illustrated in figure 1 while a end unitary element 14 is illustrated in figure 2.

As can be seen from figures 1 and 2, each unitary element 12, 14 comprises a body 16 extending longitudinally along a direction L from a first end 18 to a second end 20.

Each unitary element 12, 14 comprises a through bore 22 extending along the longitudinal direction L from the first end 18 to the second end 20. In other words, the through bore 20 is a longitudinal bore As can also be seen from figures 1 and 2, each unitary element 12, 14 comprises a unique radial bore 24 extending from an opening 26 of an external surface 28 of the body 16 to the through bore 22. The radial bore 24 is positioned sensibly orthogonally to the direction L. The radial bore 24 is arranged to be connected to an injector of the engine. As shown on figure 2, the radial bore 24 has a general shape of a cone extending through the opening 26 to a constriction 30. The cone 24 forms a sealing seat for mounting an HP tube while the constriction 30 is a throttle configuredto control the flow pressure of the fuel in the inj ector.

As shown on the figures, the external surface 28 comprises a bulging region 32 around the radial bore 24. The bulging region 32 is mostly of a spherical shape with a flat top surface 34 formed around the opening 26. Preferably, the top surface 34 is flat to ensure a simple connection of the bore 24 to the associated injector.

On figures 1 and 2, a bottom portion 34 of the bulging region 32 is rounded while on figure 3 the bottom portion 34 is flat.

The unitary element 12, 14 also comprises two aligned first and second arms 36, 38 disposed on both sides of the bulging region 32. The first arm 36 extends from the bulging region 32 to the first end 18 while the second arm 38 extends from the bulging region 32 to the second end 20.

As can be seen from figure 1, the first and second arms 36, 38 of the central unitary element 12 are preferably identical.

As can be seen from figure 2, the second end 20 of the through bore 22 of the end unitary element 14 defines a shoulder 40 in the second arm 36. The shoulder 40 is aimed at connecting the rail body 10 to a pressure sensor 42 and a dump valve, said valve being arranged to open when a value of the fluid pressure that is measured by the pressure sensor is higher than a given threshold.

The opposed end (not illustrated) of the rail body is configured to be connected to an HP pump of the engine so as to provide fuelto the injectors via the rail body..

The rail body 10 is now described in relation with figure 3.

On this figure are illustrated three central unitary elements 12 and an end unitary element 14.

The unitary elements 12, 14 are positioned aligned one after the other along the longitudinal direction L in position such that the through bores 24 are aligned. The unitary elements are fixed one to another by their ends, preferably by welding, as will be detailed later.

As can be seen from figure 3, the rail body 10 also comprises pads 44 to firmly attach the rail body 10 to another element of the vehicle. Each fixation pad is a lug provided with three holes 46, each hole receiving a screw 48.

On the illustrated embodiment, the rail body 10 is straight shaped, but the invention is not limited to this arrangement and the form given to the rail body is to fit its environment in the engine. In particular, its shape can be chosen according to the dimension and form of the space that should be occupied in the vehicle. For instance, the rail body the rail body 10 may be angled shaped, two successive unitary elements forming an elbow.

Finite element analysis (PEA) results show that -900 MPa compressive stresses are obtained along a gun-drill axis. Maximum compressive stresses (1027 MPa) are obtained at sub-surface (under of micro hole surface). These results are similar to stress distribution with prior art common rail designs.

Due to ABS maximum principle theory, -1027 MPa compressive stresses prevent tensile stresses obtained on micro-hole surface.

As shown on the following table, results are comparable for the present invention and a prior art common rail design: Maximum Principle (Tensile) Stress Minimum Principle / MPa (Compressive Residual) Stress /MPa LS3 LS2 AS LS2

Prior art 220,5 -22,5 243 -944

Design Invention 280.72 -64.406 345.126 -1027 The invention also relates to a method for manufacturing the rail body 10. Said method comprises a step of welding the unitary elements one to another to obtain a rail body module and then a step of surfacing the external surface of the rail body module. Possible welding types are frictional welding, butt welding, or laser welding. Gas melted arc welding is not to be used. Therefore, during welding operation, no gases or smoke are generated, and porosity or slag inclusions are prevented from being generated. Also, since no additional material is to be used during welding, the material body resistance increases.

Preferably, the process also comprises a step of forming each unitary element 12, 14, by cold forging for instance. Cold forging metal allows the grain structure to be minimized and increases fatigue reliability of the material.

After welding operation, gun-drill and cone machining are done. Female thread is preferably used in order to prevent misalignment problem.

As already explained, the present invention has numerous advantages compared to the prior art common rails. In particular, thanks to the modular rail body of the present invention, various shapes and lengths of the rail body can be chosen and its manufacturing process is easier and more reliable.

LIST OF REFERENCES

longitudinal direction of the unitary elements rail body 12 central unitary element 14 end unitary 16 body 18 first end of body second end of body 22 longitudinal through bore 24 radial bore 26 opening 28 external surface constriction 32 bulging region 34 top surface 36 first arm 38 second arm shoulder 42 valve 44 fixation pad 46 hole 48 screw

Claims

CLAIMS: 1. A unitary element for a rail body of a fuel injection equipment of an internal combustion engine, said unitary element (12, 14) comprising a body (16) provided with a through bore (22) extending in a longitudinal direction of the body (L) and with a radial bore (24) extending from an external surface (28) of the body (16) to the through bore (22).
2. A unitary element as claimed in claim 2, wherein the external surface (28) comprises a bulging region (30) around the radial bore (24).
3. A unitary element as claimed in the preceding claim, wherein a top surface (34) of the bulging region (30) is flat around the radial bore (24)
4. A unitary element as claimed in any of the preceding claims, wherein the radial bore (24) comprises a constriction (30).
5. A unitary element as claimed in any of the preceding claims, wherein an end (20) of the through bore (22) defines a shoulder (40).
6. A rail body for a fuel injection equipment of an internal combustion engine, comprising at least two unitary elements as claimed in any of the preceding claims, said at least two unitary elements being fixed one to another.
7. A rail body as claimed in the preceding claim, wherein the unitary elements (12, 14) are fixed together by their ends.
8. A rail body as claimed in the preceding claim, wherein the ends of the unitary elements (12, 14) are fixed together by welding.
9. A rail body as claimed in claims 6-8, comprising at least one fixation pad (44).
10. A rail body as claimed in claims 6-9, wherein the rail body has a straight shape, the through bores (22) of all the unitary elements (12, 14) being aligned.
11. A rail body as claimed in claims 6-9, wherein the rail body has an angled shape, two successive unitary elements (12, 14) forming an elbow.
12. A method for manufacturing a rail body as claimed in any of claims 6-11, comprising a step of welding the unitary elements one to another to obtain a rail body module and then a step of surfacing the external surface of said rail body 10 module.