A FUEL RAIL AND A SIMPLE METHOD FOR PREPARATION OF THE SAME

Technical Field of the Invention

The present invention relates to fuel rails and methods of preparation thereof. In particular, the present invention relates to an improvement in sealing of the forged fuel rails.

Background of the Invention

Fuel rails are used in automotive industry for arranging distribution of fuel into a plurality of fuel injectors in a controlled manner. The fuel provided into a tube is communicated into fuel injectors through injector cups that have a respective inner volume that is in fluid flow communication with the tube hole of such tube.

When preparing the fuel rail that is formed by forging, constitution of such fluid flow communication is challenging if axial projections of the tube hole and injector cups do not overlap with each other. In such cases, the fluid flow communication can be constituted with a plurality of drilling steps, to form a T-shaped cross bore that connects the injector cup to the tube hole. Such multi-step drilling results in an opening on a front face of the injector cup, and the opening must be properly sealed for avoiding leakage of the fuel therethrough. It is important to arrange an efficient sealing of the opening with minimized costs.

Brief Description of the Invention

Primary object of the present invention is to propose a fuel rail with a simple yet efficient sealing. Another object of the present invention is to propose a low cost and simple solution for sealing of cross bores in fuel rails, in particular, in forged fuel rails.

The present application proposes fuel rail that comprises a tube with a tube hole and a plurality of injector cups in fluid flow communication with the tube hole via a respective plurality of T-shaped cross bores that include a first bore and a second bore. The first bore extends from the tube hole towards a front face of a respective injector cup, said front face being distal to the tube hole with regard to a central axis of the first bore. The second bore is arranged to provide fluid flow communication from the first bore to an inner volume of the injector cup. The first bore is provided with a plug at a distal end of the first bore with regard to the tube hole. A distal end of the first bore is provided with a plug housing such that, radial to a plug axis, the plug housing has a greater diameter when compared to a diameter of the first bore.

The plug housing is provided with a wedge that is arranged for pushing and biasing the plug towards the tube hole. The plug housing is further provided with a couple of wedge bores for receiving and hosting the wedge across the plug axis.

Hence, sealing of the first bore can be achieved mechanically, even without necessitating a welding operation. As a result, the context proposed in the present application allows a simplified, low-cost process in sealing of the cross bore. Accordingly, a simplified and low-cost fuel rail is rendered available with the teaching of the present application.

In a possible embodiment, the wedge can include an inclined side that is arranged for facing the plug and for transferring a gradually increasing a mechanical force applied by the wedge onto the plug towards the first bore during the placement of the wedge at assembling of the fuel rail. This measure enables an easy pre-placement of the wedge to the wedge bores, and the axial mechanical force exerted by the wedge onto the plug is increased gradually.

In a possible embodiment, the plug is arranged with a flexible material to be in mechanical contact with the plug housing and/or with the first bore around the plug axis. The flexible material enables the sealing without necessitating a high extent of force to be exerted by the wedge onto the plug.

In a possible embodiment, the plug can include a substantially conical centering face, that at least partially extends into the first bore. This measure facilitates the placement and alignment of the plug at assembling the fuel rail.

In a further possible embodiment, the flexible material can be in the form of a coating, sheet or ring provided on or around the centering face. In a possible embodiment, the flexible material can include rubber.

Brief Description of Figures

The figures, whose brief explanations are herewith provided, are solely intended for providing a better understanding of the present invention and are as such not intended to define the scope of protection or the context in which the scope is to be interpreted in the absence of the description. Fig.1 is a perspective view of an exemplary forged fuel rail according to the present application prior to sealing, wherein fuel injectors and sensor are omitted.

Fig.2 is perspective view of the exemplary forged fuel rail shown in Fig.l after the sealing, wherein fuel injectors and sensor are omitted.

Fig.3 is a side view of the fuel rail shown in Fig.l.

Fig.4 is a side view of the fuel rail shown in Fig.2.

Fig.5 is the A-A section taken from Fig.3.

Fig.6 is the B-B section taken from Fig.4.

Fig.7 is the D-D section taken from Fig.4.

Fig.8 is the detail E taken from Fig.7.

Fig.9a is a top view of an exemplary wedge for use in the fuel rail according to the present application.

Fig.9b is a side view of the wedge shown in Fig.9a.

Fig.9c is a front view of the wedge shown in Fig.9a.

Fig.lOa is perspective view of an exemplary plug for use in the fuel rail according to the present application.

Fig.lOb is a side view of the plug shown in Fig.lOa.

Detailed Description of the Embodiments

Referring to the figures described above, the present application proposes an improved fuel rail (1000). A fuel rail (1000) can comprise several design elements that include a tube (10) with a tube hole (11) (i.e., an inner volume of the tube 10) along a tube axis (At). The design elements further include a plurality of injector cups (20) in fluid flow communication with the tube hole (11). The injector cups (20) can be considered to be arranged for being coupled with a respective plurality of fuel injectors to be mounted onto the fuel rail (1000).

The design elements can be considered to further include the following: a plurality of mounting brackets designated to the respective plurality of the injector cups (20); one or more fuel inlet fittings arranged for fuel supply into the tube hole (11); and one or more sensor fittings (50).

A process for formation of the fuel rail (1000) can include brazing or forging. In the former version, the design elements can be manufactured separately by pre-machining, to be brought together later by brazing. On the other hand, forging can include formation of the design elements from a single piece of metal, by hot pressing to a predetermined shape in a die system. Said die system can include, for instance, a couple of dies for formation of the fuel rail (1000) therebetween. When compared with brazing, the advantages of forging include minimization of the of material and labor costs.

After the forging, the fluid flow communication between the tube hole (11) and an inner volume (21) of the injector cup (20) can be constituted by bore formation between the tube hole (11) and said inner volume (21) by a drilling step. The drilling step is performed by introduction of a drill bit from the inner volume (21) towards the tube hole (11).

In the following case, the drilling step bears the risk of being subjected to a side-contact (that is, a mechanical contact by the injector cup (20), oblique to a rotational axis of the drill bit): if the tube hole (11) and the inner volume (21) of the injector cup (20) are offset with respect to each other (in other words, if respective axial projections of the tube hole (11) and said inner volume (21) do not at least partially overlap); and the inner volume (21) of the injector cup (20) have a geometry (e.g., a length/diameter value and/or depth along an injector cup axis (Ac)) that does not allow the drill to aim the tube hole (11) when inserted into the inner volume (21) of the injector cup (20).

So, the vertical distance (offset) of the tube axis (At) to the injector cup axis (Ac) affects the possibility of one-step formation of the fluid flow communication between the tube hole (11) and the inner volume (21) of the injector cup (20) (See: Fig.6). At higher extents of the vertical distance, said fluid flow communication cannot be constituted with a one-step drilling operation without damaging either or both of the injector cup (20) and the drill bit. In such case, the drill bit is inevitably subjected to transversal forces due to said mechanical contact. As a result, the drill bit loses its functionality and the drilling process is interrupted. Even more importantly, the injector cup (20) can undergo a deformation by threaded side surfaces of the drill bit. The latter phenomenon results in damage of the whole fuel rail (1000). To eliminate the above-mentioned risk, the following measure is taken: a first bore (Bl) is drilled to connect the tube hole (11) to a front face (22) (that is, a side of the injector cup (20) distal to the tube hole (11)); a second bore (B2) is drilled to connect the inner volume (21) of the injector cup (20), to the first bore (Bl); thereby achieving a T-shaped cross-bore and a plug (60) is provided to seal the first bore (Bl) at a front face side end thereof (i.e., at a distal end with regard to the tube hole (11)), thus sealing the front face (22).

To secure said sealing under pressure conditions at operating the fuel rail (1000), the plug (60) can be fixed by a fixing method that can include press fitting, screwing or welding. The welding can include laser welding or capacitor discharge welding. Laser welding and capacitor discharge welding are highly complex processes that require expensive manufacturing equipment. The present application overcomes these problems by means of the features that constitute the annexed independent claims.

Within the context of the present application, sealing of the first bore (Bl) can be achieved mechanically, thus even without necessitating a welding operation. Upon placing of the plug (60) to cover the end of the first bore (Bl) distal to the tube hole (11), a wedge (70) can be arranged for pushing and biasing the plug (60) towards the tube hole (11). The plug (60) can be placed into a plug housing (61) that has a greater diameter when compared to the diameter of the first bore (Bl); here, said diameters correspond to respective radial widths of the plug housing (61) and first bore (Bl) around a plug axis (Ap).

Fig.l shows a perspective view of an exemplary forged fuel rail (1000) according to the present application prior to sealing, wherein fuel injectors and sensor are omitted. Fig.2 shows a sealed state of the exemplary forged fuel rail (1000) shown in Fig.l; that is, after the provision of a plug (60) and wedge (70) within the context of the present application.

Hence, the plug hole (61) can be provided with a wedge (70) that is arranged for pushing and biasing the plug (60) towards the tube hole (11). To this end, the plug hole (61) can be provided with a couple of wedge bores (71) for receiving and hosting the wedge (70) across the plug axis (Ap), at multiple portions of the wedge (70).

The wedge bores (71) can be disposed across the plug axis (Ap). The wedge bores (71) can be considered as a couple of openings opposing each other at two sides radial to the plug axis (Ap). The openings can be radially formed around the plug axis (Ap), at an axial distance from the centering face (62) that allows the wedge (70) to axially press the plug (60) towards/into the first bore (Bl), and to keep the plug (60) in mechanical contact with the first bore (Bl) for circumferentially sealing the same.

The wedge (70) can include an inclined side (72) arranged for facing the plug (60) and for transferring a gradually increasing a mechanical force applied by the wedge (70) onto the plug (60) towards the first bore (Bl) during the placement of the wedge (70) at assembling of the fuel rail (1000). By the presence of such inclined side (72), distal ends of the wedge (70) have different widths. Such that a first end having the inclined side (72) has a lower width when compared to a second end that is distal to the first end. At assembling, the first end can be introduced first into the plug housing (61) through the wedge bores (71), and after the first end enters the opposite side of the wedge bores (71), the placement of the wedge (70) orthogonal to the plug axis (Ap) is secured. Then, upon further advancing the position of the wedge (70), the force exerted by the wedge (70) onto the plug (60) gradually increases by means of the inclined side (72).

The plug (60) can include a substantially conical centering face (62) arranged for being at least partially introduced into the first bore (Bl) at assembly. The centering face (62) facilitates the alignment of the plug (60) for securing the circumferential sealing of the first bore (Bl).

In a possible embodiment, the plug (60) can be provided with a flexible material to be in mechanical contact with the plug housing (61) and/or with the first bore (Bl) around the plug axis (Ap). The presence of the flexible material enables a sufficient extent of sealing with a minimized extent of axial force exerted by the wedge (70) towards the first bore (Bl) (or towards the tube hole 11). The flexible material can be in the form of a coating, sheet or ring provided on or around the centering face (62). An exemplary flexible material for this effect can include rubber. Selection of the flexible material can include measures for avoiding dissolution or swelling of the flexible material in a fuel for which the fuel rail (1000) is intended.

It can be considered that the plug (60) and plug housing (61) have cylindrical geometries with respective heights along the central axis of the first bore (Bl), and the height of the plug (60) is smaller than the height of the plug housing (61). This measure allows the formation of the wedge bores (71) and placement of the wedge (70) behind the plug (60) regarding from the first bore (Bl) along the plug axis (Ap). Said central axis of the first bore (Bl) can be considered to correspond to the plug axis (Ap). Reference signs:

10 tube

11 tube hole

20 injector cup

21 inner volume, of the injector cup

22 front face

50 sensor fitting

60 plug

61 plug housing

62 centering face

70 wedge

71 wedge bore

72 inclined side

1000 fuel rail

Ac injector cup axis

Ap plug axis

At tube axis

Bl first bore

B2 second bore